Light-emitting device and display device

Abstract

To provide a light-emitting device with excellent characteristics.SOLUTION: In a light-emitting device, an intermediate layer exists between a first electrode and a second electrode, a first light-emitting layer exists between the first electrode and the intermediate layer, a second light-emitting layer exists between the intermediate layer and the second electrode, the first light-emitting layer includes a first light-emitting center material and a first organic compound, the first organic compound includes deuterium, the second light-emitting layer includes a second light-emitting center material, the first light-emitting center material is a phosphorescence emitting material having an emission peak in a wavelength range of 440 nm or more and 500 nm or less, the difference between the maximum peak wavelength in the PL spectrum of the first light-emitting center material and the maximum peak wavelength in the PL spectrum of the second light-emitting center material is 30 nm or less, and the first light-emitting layer and the second light-emitting layer include a light-emitting layer that exhibits light in a color range different from that of the light-emitting layer included in at least one light-emitting device among a plurality of other light-emitting devices adjacent to the aforementioned light-emitting device.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] One embodiment of the present invention relates to a light-emitting device. Note that this embodiment of the present invention is not limited to the above technical field. The technical field of one embodiment of the invention disclosed in this specification etc. relates to an object, a method, or a manufacturing method. Alternatively, one embodiment of the present invention relates to a process, a machine, a manufacture, or a composition of matter. Therefore, more specifically, examples of the technical field of one embodiment of the present invention disclosed in this specification include semiconductor devices, display devices, liquid crystal display devices, light-emitting devices, lighting devices, power storage devices, memory devices, imaging devices, electronic devices, driving methods thereof, and manufacturing methods thereof. [Background technology]

[0002] In recent years, display devices are expected to be used in a variety of applications. For example, applications of large display devices include home television devices (also called televisions or television receivers), digital signage (electronic billboards), and public information displays (PIDs). In addition, development of mobile information terminals such as smartphones and tablet terminals equipped with touch panels is progressing.

[0003] There is also a demand for higher resolution display devices. Devices requiring high resolution display devices, such as those for virtual reality (VR), augmented reality (AR), substitutional reality (SR), and mixed reality (MR), are being actively developed.

[0004] As a display device, for example, a light-emitting device having a light-emitting device (also called a light-emitting element) has been developed. A light-emitting device (also called an EL device or an EL element) utilizing the electroluminescence (hereinafter referred to as EL) phenomenon has features such as being easily thin and lightweight, being capable of high-speed response to input signals, and being capable of being driven by a DC constant voltage power supply, and is therefore applied to a display device.

[0005] Tandem light-emitting devices in particular have attracted attention because they achieve high current efficiency, and Patent Documents 1 and 2 disclose tandem light-emitting devices using a separate coloring method. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-317548 [Patent Document 2] Japanese Patent Publication No. 2023-161850 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of one embodiment of the present invention is to provide a light-emitting device with good characteristics.An object of one embodiment of the present invention is to provide a light-emitting device with good emission efficiency.An object of one embodiment of the present invention is to provide a light-emitting device with good reliability.An object of one embodiment of the present invention is to provide a light-emitting device with low driving voltage.An object of one embodiment of the present invention is to provide a light-emitting device with good reliability and low driving voltage.

[0008] Another object of one embodiment of the present invention is to provide a light-emitting device that can provide a display device with good characteristics. Another object of one embodiment of the present invention is to provide a light-emitting device that can provide a display device with good emission efficiency. Another object of one embodiment of the present invention is to provide a light-emitting device that can provide a display device with good reliability. Another object of one embodiment of the present invention is to provide a light-emitting device that can provide a display device with low driving voltage. Another object of one embodiment of the present invention is to provide a light-emitting device that can provide a display device with low driving voltage and good reliability.

[0009] Another object is to provide any one of an organic semiconductor device, a light-emitting device, a light-receiving device, a display device, an electronic device, and a lighting device that consumes low power, or to provide any one of an electronic device and a lighting device that is highly reliable, or to provide any one of a novel organic semiconductor device, a light-emitting device, a light-receiving device, a display device, an electronic device, and a lighting device.

[0010] Note that the description of these problems does not preclude the existence of other problems. Note that one embodiment of the present invention does not necessarily solve all of these problems. Note that problems other than these will become apparent from the description of the specification, drawings, claims, etc., and it is possible to extract other problems from the description of the specification, drawings, claims, etc. [Means for solving the problem]

[0011] One embodiment of the present invention is a light-emitting device having a first electrode, a second electrode, an intermediate layer, a first light-emitting layer, and a second light-emitting layer, wherein the intermediate layer is located between the first electrode and the second electrode, the first light-emitting layer is located between the first electrode and the intermediate layer, and the second light-emitting layer is located between the intermediate layer and the second electrode, the first light-emitting layer has a first light-emitting center substance and a first organic compound, the first organic compound has deuterium, the second light-emitting layer has a second light-emitting center substance, and the first light-emitting center The material is a phosphorescent material having an emission peak in the wavelength region of 440 nm or more and 500 nm or less, the difference between the maximum peak wavelength in the PL spectrum of the first luminescent center substance and the maximum peak wavelength in the PL spectrum of the second luminescent center substance is 30 nm or less, and the first luminescent layer and the second luminescent layer are luminescent layers that exhibit emission in a color gamut different from that of the luminescent layer of at least one of a plurality of other luminescent devices adjacent to the luminescent device.

[0012] One embodiment of the present invention is a light-emitting device having a first electrode, a second electrode, an intermediate layer, a first light-emitting layer, and a second light-emitting layer, wherein the intermediate layer is located between the first electrode and the second electrode, the first light-emitting layer is located between the first electrode and the intermediate layer, and the second light-emitting layer is located between the intermediate layer and the second electrode, the first light-emitting layer has a first light-emitting center substance, a first organic compound, and a second organic compound, at least one of the first organic compound and the second organic compound has deuterium, and the second light-emitting layer has a second light-emitting center substance, a first organic compound, and a second organic compound. the first luminescent center substance is a phosphorescent material having an emission peak in the wavelength region of 440 nm or more and 500 nm or less, the difference between the maximum peak wavelength in the PL spectrum of the first luminescent center substance and the maximum peak wavelength in the PL spectrum of the second luminescent center substance is 30 nm or less, and the first and second luminescent layers have luminescent layers that emit light in a color gamut different from that of the luminescent layer of at least one of a plurality of other luminescent devices adjacent to the light-emitting device.

[0013] In the above invention, the light-emitting device is such that the first organic compound has a π-electron-deficient heteroaromatic ring, and the second organic compound has at least one of a π-electron-rich heteroaromatic ring or an aromatic amine skeleton.

[0014] In the above invention, the second light-emitting layer comprises a second luminescent center substance, a third organic compound, and a fourth organic compound, the third organic compound having a π-electron-deficient heteroaromatic ring, the fourth organic compound having at least one of a π-electron-rich heteroaromatic ring and an aromatic amine skeleton, at least one of the third organic compound and the fourth organic compound having deuterium, the first organic compound and the second organic compound being combined to form a first exciplex, the third organic compound and the fourth organic compound being combined to form a second exciplex, the emission edge on the short wavelength side in the PL spectrum of the first exciplex being positioned at a wavelength shorter than the absorption edge on the long wavelength side in the absorption spectrum of the first luminescent center substance, and the emission edge on the short wavelength side in the PL spectrum of the second exciplex being positioned at a wavelength shorter than the absorption edge on the long wavelength side in the absorption spectrum of the second luminescent center substance.

[0015] In the above invention, the difference between the lowest triplet excitation energy level of the first organic compound and the lowest triplet excitation energy level of the second organic compound is 0.20 eV or less, and the difference between the lowest triplet excitation energy level of the third organic compound and the lowest triplet excitation energy level of the fourth organic compound is 0.20 eV or less.

[0016] In the above invention, the light-emitting device has a phosphorescence lifetime or delayed fluorescence lifetime at 77 K of the first organic compound that is 1.20 times or more the phosphorescence lifetime or delayed fluorescence lifetime at 77 K of a fifth organic compound in which the deuterium in the first organic compound is hydrogen, and the phosphorescence lifetime or delayed fluorescence lifetime at 77 K of the second organic compound that is 1.05 times or more the phosphorescence lifetime or delayed fluorescence lifetime at 77 K of a sixth organic compound in which the deuterium in the second organic compound is hydrogen.

[0017] In the above light-emitting device, when the phosphorescence lifetime or delayed fluorescence lifetime of the first organic compound at 77 K is X times the phosphorescence lifetime or delayed fluorescence lifetime at 77 K of a fifth organic compound in which the deuterium in the first organic compound is hydrogen, and the phosphorescence lifetime or delayed fluorescence lifetime of the second organic compound is Y times the phosphorescence lifetime or delayed fluorescence lifetime at 77 K of a sixth organic compound in which the deuterium in the second organic compound is hydrogen, the value obtained by multiplying X and Y is 1.26 or more.

[0018] In the above invention, the first luminescent center substance and the second luminescent center substance are the same substance in the light-emitting device.

[0019] In the above invention, the first luminescent center substance is a platinum complex.

[0020] In the above invention, the light-emitting device has a first hole transport layer between the first electrode and the first light-emitting layer, and a second hole transport layer between the intermediate layer and the second light-emitting layer, the first hole transport layer or the second hole transport layer having a laminated structure including at least a first layer having a seventh organic compound and a second layer having an eighth organic compound, the second layer being in contact with the first light-emitting layer or the second light-emitting layer, the seventh organic compound including an amine skeleton and a polycyclic hydrocarbon, and the eighth organic compound including a π-electron-rich polycyclic heteroaromatic ring.

[0021] In the above invention, the light-emitting device has a first electron transport layer between the second light-emitting layer and the second electrode, the first electron transport layer has a layer having a ninth organic compound having a triazine skeleton, and the intermediate layer has a first mixed layer of a tenth organic compound having a phenanthroline skeleton and lithium or a lithium compound.

[0022] In the above invention, the first electron transport layer has a second mixed layer of an eleventh organic compound having a triazine skeleton and lithium or a lithium compound, and the second mixed layer is located between the layer having the ninth organic compound and the second electrode.

[0023] One embodiment of the present invention is a display device including a light-emitting device A and a light-emitting device B emitting light of a different color from that of the light-emitting device A. The light-emitting device A is a light-emitting device including a first electrode A, a second electrode A, an intermediate layer A, a first light-emitting layer A, and a second light-emitting layer A, wherein the intermediate layer A is located between the first electrode A and the second electrode A, the first light-emitting layer A is located between the first electrode A and the intermediate layer A, and the second light-emitting layer A is located between the intermediate layer A and the second electrode A, the first light-emitting layer A includes a first luminescent center substance A, a first organic compound A, and a second organic compound A, at least one of the first organic compound A and the second organic compound A contains deuterium, the second light-emitting layer A includes a second luminescent center substance A, and the first luminescent center substance A and the second luminescent center substance A are phosphorescent materials having an emission peak in a wavelength range of 440 nm to 500 nm, and the first luminescent center substance A The difference between the maximum peak wavelength in the PL spectrum of the second luminescent center substance A and the maximum peak wavelength in the PL spectrum of the second luminescent center substance A is 30 nm or less. The light-emitting device B is a light-emitting device having a first electrode B, a second electrode B, an intermediate layer B, a first luminescent layer B, and a second luminescent layer B, wherein the intermediate layer B is located between the first electrode B and the second electrode B, the first luminescent layer B is located between the first electrode B and the intermediate layer B, and the second luminescent layer B is located between the intermediate layer B and a second electrode B, the first light-emitting layer B has a first light-emitting center substance B, the second light-emitting layer B has a second light-emitting center substance B, the difference between the maximum peak wavelength in the PL spectrum of the first light-emitting center substance B and the maximum peak wavelength in the PL spectrum of the second light-emitting center substance B is 30 nm or less, and the first light-emitting layer A and the second light-emitting layer A emit light in a color gamut different from that of the first light-emitting layer B and the second light-emitting layer B.

[0024] In the above invention, the display device is such that the first light-emitting layer B contains a first organic compound B, and the first organic compound B contains deuterium.

[0025] One embodiment of the present invention is a display device having a light-emitting device A, a light-emitting device B having an emission color different from that of the light-emitting device A, and a light-emitting device C having an emission color different from that of the light-emitting device A and the light-emitting device B. The light-emitting device A has a first electrode A, a second electrode A, an intermediate layer A, a first light-emitting layer A, and a second light-emitting layer A, wherein the intermediate layer A is located between the first electrode A and the second electrode A, the first light-emitting layer A is located between the first electrode A and the intermediate layer A, and the second light-emitting layer A is located between the intermediate layer A and the second electrode A, and the first light-emitting layer A is The light-emitting device B comprises a first luminescent center substance A, a first organic compound A, and a second organic compound A, at least one of the first organic compound A and the second organic compound A containing deuterium; the second luminescent layer A comprises a second luminescent center substance A, and the first luminescent center substance A and the second luminescent center substance A are phosphorescent materials, and the difference between the maximum peak wavelength in the PL spectrum of the first luminescent center substance A and the maximum peak wavelength in the PL spectrum of the second luminescent center substance A is 30 nm or less; and the light-emitting device B comprises a first electrode B, a second electrode B, an intermediate layer B, a first luminescent layer B, and and a second emitting layer B, wherein the intermediate layer B is located between a first electrode B and a second electrode B, the first emitting layer B is located between the first electrode B and the intermediate layer B, and the second emitting layer B is located between the intermediate layer B and the second electrode B, the first emitting layer B has a first emitting center substance B, and the second emitting layer B has a second emitting center substance B, the first emitting center substance B and the second emitting center substance B are phosphorescent emitting substances, and the maximum peak wavelength in the PL spectrum of the first emitting center substance B and the maximum peak wavelength in the PL spectrum of the second emitting center substance B are phosphorescent emitting substances. the difference in peak wavelength between the first electrode C and the second electrode C is 30 nm or less; the light-emitting device C is a light-emitting device having a first electrode C, a second electrode C, an intermediate layer C, a first light-emitting layer C, and a second light-emitting layer C, wherein the intermediate layer C is located between the first electrode C and the second electrode C, the first light-emitting layer C is located between the first electrode C and the intermediate layer C, and the second light-emitting layer C is located between the intermediate layer C and the second electrode C, the first light-emitting layer C has a first luminescent center substance C, and the second light-emitting layer C has a second luminescent center substance C, and the first luminescent center substance C and the second luminescent center substance C are phosphorescent materials;The difference between the maximum peak wavelength in the PL spectrum of the first luminescent center substance C and the maximum peak wavelength in the PL spectrum of the second luminescent center substance C is 30 nm or less, and the first luminescent layer A and the second luminescent layer A emit light in a color gamut different from the first luminescent layer B and the second luminescent layer B and the first luminescent layer C and the second luminescent layer C.

[0026] In the above invention, the display device is such that the first light-emitting layer B contains a first organic compound B, and the first organic compound B contains deuterium, and the first light-emitting layer C contains a first organic compound C, and the first organic compound C contains deuterium.

[0027] Another embodiment of the present invention is a light-emitting device including the light-emitting device having any of the above structures and a transistor or a substrate.

[0028] Another embodiment of the present invention is an electronic device including a light-emitting device having any of the above structures and a detection unit, an input unit, or a communication unit.

[0029] In this specification, the term "light-emitting device" includes an image display device using a light-emitting device. The term "light-emitting device" may also include a module in which a connector, such as an anisotropic conductive film or TCP (Tape Carrier Package), is attached to a light-emitting device on a substrate, a module in which a printed wiring board is provided at the end of the TCP, or a module in which an IC (integrated circuit) is directly mounted on a light-emitting device using a COG (Chip On Glass) method. Furthermore, lighting fixtures and the like may include a light-emitting device. [Effects of the Invention]

[0030] According to one embodiment of the present invention, a light-emitting device with favorable characteristics can be provided. Alternatively, according to one embodiment of the present invention, a light-emitting device with favorable emission efficiency can be provided. Alternatively, according to one embodiment of the present invention, a light-emitting device with favorable reliability can be provided. Alternatively, according to one embodiment of the present invention, a light-emitting device with low driving voltage can be provided. Alternatively, according to one embodiment of the present invention, a light-emitting device with favorable reliability and low driving voltage can be provided.

[0031] Alternatively, one embodiment of the present invention can provide a light-emitting device that can provide a display device with good characteristics. Alternatively, one embodiment of the present invention can provide a light-emitting device that can provide a display device with good emission efficiency. Alternatively, one embodiment of the present invention can provide a light-emitting device that can provide a display device with good reliability. Alternatively, one embodiment of the present invention can provide a light-emitting device that can provide a display device with low driving voltage. Alternatively, one embodiment of the present invention can provide a light-emitting device that can provide a display device with low driving voltage and good reliability.

[0032] Alternatively, any one of an organic semiconductor device, a light-emitting device, a light-receiving device, a display device, an electronic device, and a lighting device with low power consumption can be provided. Alternatively, any one of an electronic device and a lighting device with high reliability can be provided. Alternatively, any one of a novel organic semiconductor device, a light-emitting device, a light-receiving device, a display device, an electronic device, and a lighting device can be provided.

[0033] Note that the description of these effects does not preclude the existence of other effects. One embodiment of the present invention does not necessarily have all of these effects. Effects other than these can be extracted from the description in the specification, drawings, and claims. [Brief explanation of the drawings]

[0034] [Figure 1] 1(A) and 1(B) are diagrams showing a light-emitting device. [Figure 2] FIG. 2 is a diagram illustrating a light-emitting device. [Figure 3] 3(A) and 3(B) are diagrams showing a light-emitting device. [Figure 4] FIG. 4 is a diagram illustrating a light-emitting device. [Figure 5] 5A and 5B illustrate a display device according to one embodiment of the present invention. [Figure 6] 6(A) and 6(B) are a top view and a cross-sectional view of the light emitting device. [Figure 7] 7A to 7E are cross-sectional views showing an example of a method for manufacturing a display device. [Figure 8] 8A and 8B are cross-sectional views showing an example of a method for manufacturing a display device. [Figure 9] 9A to 9D are cross-sectional views showing an example of a method for manufacturing a display device. [Figure 10] 10A to 10C are cross-sectional views showing an example of a method for manufacturing a display device. [Figure 11] 11A to 11C are cross-sectional views showing an example of a method for manufacturing a display device. [Figure 12] 12A to 12C are cross-sectional views showing an example of a method for manufacturing a display device. [Figure 13] 13A to 13G are top views showing examples of pixel configurations. [Figure 14] 14A to 14I are top views showing examples of pixel configurations. [Figure 15] 15(A) and 15(B) are perspective views showing configuration examples of a display module. [Figure 16] 16(A) and 16(B) are cross-sectional views showing examples of the configuration of a display device. [Figure 17] FIG. 17 is a perspective view showing an example of the configuration of a display device. [Figure 18] FIG. 18 is a cross-sectional view showing an example of the configuration of a display device. [Figure 19] FIG. 19 is a cross-sectional view showing an example of the configuration of a display device. [Figure 20] FIG. 20(A) is a cross-sectional view showing a configuration example of a display device, and FIG. 20(B) and FIG. 20(C) are top views showing the configuration example of a display device. [Figure 21] FIG. 21 is a cross-sectional view showing an example of the configuration of a display device. [Figure 22] FIG. 22(A) is a cross-sectional view showing a configuration example of a display device, and FIG. 22(B) and FIG. 22(C) are top views showing the configuration example of a display device. [Figure 23] 23A to 23D are diagrams showing examples of electronic devices. [Figure 24] 24(A) to 24(F) are diagrams showing examples of electronic devices. [Figure 25] 25(A) to 25(G) are diagrams showing examples of electronic devices. [Figure 26] FIG. 26 is a diagram illustrating the structure of the sample. [Figure 27] FIG. 27 is a diagram illustrating the structure of the sample. [Figure 28] 28(A) and 28(B) are diagrams illustrating the PL spectra of the organic compounds used as samples. [Figure 29] 29(A) and 29(B) are diagrams illustrating the PL spectra of the organic compounds used as samples. [Figure 30] FIG. 30 is a diagram illustrating the PL spectrum of the organic compound used as the sample. [Figure 31] FIG. 31 is a diagram illustrating the PL spectrum of the organic compound used as the sample. [Figure 32] 32(A) and 32(B) are diagrams illustrating the PL spectra of the organic compounds used in the samples. [Figure 33] 33(A) and 33(B) are diagrams illustrating the PL spectra of the organic compounds used in the samples. [Figure 34] FIG. 34 is a diagram illustrating the PL spectrum of the mixed film used as the sample. [Figure 35] FIG. 35 is a diagram illustrating the PL spectrum of the mixed film used as the sample. [Figure 36] FIG. 36 is a diagram illustrating the PL spectrum of the mixed film used as the sample. [Figure 37] FIG. 37 is a diagram illustrating the PL spectrum of the mixed film used as the sample. [Figure 38] FIG. 38 is a diagram illustrating the PL spectrum of the mixed film used as the sample. [Figure 39] FIG. 39 is a diagram illustrating the absorption spectrum and PL spectrum of the organic compound used as the sample. [Figure 40] FIG. 40 is a diagram illustrating the absorption spectrum and PL spectrum of the organic compound used as the sample. [Figure 41] FIG. 41 is a diagram illustrating the absorption spectrum and PL spectrum of the organic compound used as the sample. [Figure 42] FIG. 42 is a diagram illustrating the PL spectrum of the organic compound used as the sample. [Figure 43] FIG. 43 is a diagram illustrating the PL spectrum of the organic compound used as the sample. [Figure 44] FIG. 44 is a diagram illustrating the PL spectrum of the organic compound used as the sample. [Figure 45] FIG. 45 is a diagram illustrating the measurement of the phosphorescence lifetime of the organic compound used as the sample. [Figure 46] FIG. 46 is a diagram illustrating the measurement of the phosphorescence lifetime of the organic compound used as the sample. [Figure 47] FIG. 47 is a diagram illustrating the measurement of the phosphorescence lifetime of the organic compound used as the sample. [Figure 48] FIG. 48 is a diagram illustrating the measurement of the phosphorescence lifetime of the organic compound used as the sample. [Figure 49] FIG. 49 shows the luminance-current density characteristics of the sample. [Figure 50] FIG. 50 shows the luminance-voltage characteristics of the sample. [Figure 51] FIG. 51 is a graph showing the current efficiency-luminance characteristics of the sample. [Figure 52] FIG. 52 shows the current density-voltage characteristics of the sample. [Figure 53]FIG. 53 shows the electroluminescence spectrum of the sample. [Figure 54] FIG. 54 shows the blue index-current density characteristics of the sample. [Figure 55] FIG. 55 shows the luminance-current density characteristics of the sample. [Figure 56] FIG. 56 shows the luminance-voltage characteristics of the sample. [Figure 57] FIG. 57 shows the current efficiency-luminance characteristics of the sample. [Figure 58] FIG. 58 shows the current density-voltage characteristics of the sample. [Figure 59] FIG. 59 shows the electroluminescence spectrum of the sample. [Figure 60] FIG. 60 shows the blue index-current density characteristics of the sample. [Figure 61] FIG. 61 shows the luminance-current density characteristics of the sample. [Figure 62] FIG. 62 shows the luminance-voltage characteristics of the sample. [Figure 63] FIG. 63 shows the current efficiency-luminance characteristics of the sample. [Figure 64] FIG. 64 shows the current density-voltage characteristics of the sample. [Figure 65] FIG. 65 shows the electroluminescence spectrum of the sample. [Figure 66] FIG. 66 shows the blue index-current density characteristics of the sample. [Figure 67] FIG. 67 shows the luminance-current density characteristics of the sample. [Figure 68] FIG. 68 shows the luminance-voltage characteristics of the sample. [Figure 69] FIG. 69 shows the current efficiency-luminance characteristics of the sample. [Figure 70] FIG. 70 shows the current density-voltage characteristics of the sample. [Figure 71] FIG. 71 shows the electroluminescence spectrum of the sample. [Figure 72] FIG. 72 shows the luminance-current density characteristics of the sample. [Figure 73] FIG. 73 shows the luminance-voltage characteristics of the sample. [Figure 74] FIG. 74 shows the current efficiency-luminance characteristics of the sample. [Figure 75] FIG. 75 shows the current density-voltage characteristics of the sample. [Figure 76] FIG. 76 shows the electroluminescence spectrum of the sample. [Figure 77] FIG. 77 is a diagram illustrating the reliability characteristics of a light-emitting device. [Figure 78] FIG. 78 is a diagram illustrating the PL spectrum of the mixed film used as the sample. [Figure 79] FIG. 79 is a diagram illustrating the PL spectrum of the mixed film used as the sample. [Figure 80] FIG. 80 is a diagram illustrating the measurement of the phosphorescence lifetime of the organic compound used as the sample. [Figure 81] FIG. 81 is a diagram illustrating the measurement of the phosphorescence lifetime of the organic compound used as the sample. [Figure 82] FIG. 82 is a diagram illustrating the measurement of the phosphorescence lifetime of the organic compound used as the sample. [Figure 83] FIG. 83 is a diagram illustrating the measurement of the phosphorescence lifetime of the organic compound used as the sample. [Figure 84] FIG. 84 shows the luminance-current density characteristics of the sample. [Figure 85] FIG. 85 shows the luminance-voltage characteristics of the sample. [Figure 86] FIG. 86 shows the current efficiency-luminance characteristics of the sample. [Figure 87] FIG. 87 shows the current density-voltage characteristics of the sample. [Figure 88] FIG. 88 shows the electroluminescence spectrum of the sample. [Figure 89] FIG. 89 shows the luminance-current density characteristics of the sample. [Figure 90] FIG. 90 shows the luminance-voltage characteristics of the sample. [Figure 91] FIG. 91 is a graph showing the current efficiency-luminance characteristics of the sample. [Figure 92] FIG. 92 shows the current density-voltage characteristics of the sample. [Figure 93] FIG. 93 shows the electroluminescence spectrum of the sample. [Figure 94] FIG. 94 shows the luminance-current density characteristics of the sample. [Figure 95] FIG. 95 shows the luminance-voltage characteristics of the sample. [Figure 96] FIG. 96 is a graph showing the current efficiency-luminance characteristics of the sample. [Figure 97] FIG. 97 shows the current density-voltage characteristics of the sample. [Figure 98] FIG. 98 shows the electroluminescence spectrum of the sample. [Figure 99] FIG. 99 shows the luminance-current density characteristics of the sample. [Figure 100] FIG. 100 shows the luminance-voltage characteristics of the sample. [Figure 101] FIG. 101 is a graph showing the current efficiency-luminance characteristics of the sample. [Figure 102] FIG. 102 shows the current density-voltage characteristics of the sample. [Figure 103] FIG. 103 shows the electroluminescence spectrum of the sample. [Figure 104] FIG. 104 is a graph showing the luminance-current density characteristics of the sample. [Figure 105] FIG. 105 shows the luminance-voltage characteristics of the sample. [Figure 106] FIG. 106 is a graph showing the current efficiency-luminance characteristics of the sample. [Figure 107] FIG. 107 shows the current density-voltage characteristics of the sample. [Figure 108] FIG. 108 shows the electroluminescence spectrum of the sample. [Figure 109] FIG. 109 shows the blue index-current density characteristics of the sample. [Figure 110] FIG. 110 is a graph showing the luminance-current density characteristics of the sample. [Figure 111] FIG. 111 shows the luminance-voltage characteristics of the sample. [Figure 112] FIG. 112 shows the current efficiency-luminance characteristics of the sample. [Figure 113] FIG. 113 shows the current density-voltage characteristics of the sample. [Figure 114] FIG. 114 shows the electroluminescence spectrum of the sample. [Figure 115] FIG. 115 shows the blue index-current density characteristics of the sample. [Figure 116] FIG. 116 is a diagram illustrating the reliability characteristics of a light-emitting device. [Figure 117] FIG. 117 is a diagram illustrating the reliability characteristics of a light-emitting device. [Figure 118] FIG. 118 is a diagram illustrating the reliability characteristics of a light-emitting device. [Figure 119] FIG. 119 is a diagram illustrating the PL spectrum of the mixed film used as the sample. [Figure 120] FIG. 120 shows the luminance-current density characteristics of the sample. [Figure 121] FIG. 121 shows the luminance-voltage characteristics of the sample. [Figure 122] FIG. 122 shows the current efficiency-luminance characteristics of the sample. [Figure 123] FIG. 123 shows the current density-voltage characteristics of the sample. [Figure 124] FIG. 124 shows the electroluminescence spectrum of the sample. [Figure 125] FIG. 125 shows the luminance-current density characteristics of the sample. [Figure 126] FIG. 126 shows the luminance-voltage characteristics of the sample. [Figure 127] FIG. 127 shows the current efficiency-luminance characteristics of the sample. [Figure 128] FIG. 128 shows the current density-voltage characteristics of the sample. [Figure 129] FIG. 129 shows the electroluminescence spectrum of the sample. [Figure 130]FIG. 130 is a diagram illustrating the absorption spectrum and PL spectrum of the organic compound used as the sample. [Figure 131] FIG. 131 is a diagram illustrating the absorption spectrum and PL spectrum of the organic compound used as the sample. [Figure 132] FIG. 132 shows the luminance-current density characteristics of the sample. [Figure 133] FIG. 133 shows the luminance-voltage characteristics of the sample. [Figure 134] FIG. 134 shows the current efficiency-luminance characteristics of the sample. [Figure 135] FIG. 135 shows the current density-voltage characteristics of the sample. [Figure 136] FIG. 136 shows the electroluminescence spectrum of the sample. [Figure 137] FIG. 137 shows the blue index-current density characteristics of the sample. [Figure 138] FIG. 138 shows the luminance-current density characteristics of the sample. [Figure 139] FIG. 139 shows the luminance-voltage characteristics of the sample. [Figure 140] FIG. 140 shows the current efficiency-luminance characteristics of the sample. [Figure 141] FIG. 141 shows the current density-voltage characteristics of the sample. [Figure 142] FIG. 142 shows the electroluminescence spectrum of the sample. [Figure 143] FIG. 143 shows the luminance-current density characteristics of the sample. [Figure 144] FIG. 144 shows the luminance-voltage characteristics of the sample. [Figure 145] FIG. 145 is a graph showing the current efficiency-luminance characteristics of the sample. [Figure 146] FIG. 146 shows the current density-voltage characteristics of the sample. [Figure 147] FIG. 147 shows the electroluminescence spectrum of the sample. [Figure 148] FIG. 148 shows the luminance-current density characteristics of the sample. [Figure 149] FIG. 149 shows the luminance-voltage characteristics of the sample. [Figure 150] FIG. 150 is a graph showing the current efficiency-luminance characteristics of the sample. [Figure 151] FIG. 151 shows the current density-voltage characteristics of the sample. [Figure 152] FIG. 152 shows the electroluminescence spectrum of the sample. [Figure 153] FIG. 153 shows the blue index-current density characteristics of the sample. [Fig. 154] FIG. 154 shows the luminance-current density characteristics of the sample. [Figure 155] FIG. 155 shows the luminance-voltage characteristics of the sample. [Figure 156] FIG. 156 is a graph showing the current efficiency-luminance characteristics of the sample. [Figure 157] FIG. 157 shows the current density-voltage characteristics of the sample. [Figure 158] FIG. 158 shows the electroluminescence spectrum of the sample. [Figure 159] FIG. 159 shows the luminance-current density characteristics of the sample. [Figure 160] FIG. 160 shows the luminance-voltage characteristics of the sample. [Figure 161] FIG. 161 is a graph showing the current efficiency-luminance characteristics of the sample. [Figure 162] FIG. 162 shows the current density-voltage characteristics of the sample. [Figure 163] FIG. 163 shows the electroluminescence spectrum of the sample. DETAILED DESCRIPTION OF THE INVENTION

[0035] The embodiments will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and it will be readily understood by those skilled in the art that various changes can be made in form and detail without departing from the spirit and scope of the present invention. Therefore, the present invention should not be interpreted as being limited to the description of the embodiments shown below.

[0036] In the configuration of the invention described below, the same parts or parts having similar functions are denoted by the same reference numerals in different drawings, and repeated explanations thereof will be omitted. In addition, when referring to similar functions, the same hatch pattern may be used and no particular reference numeral may be assigned.

[0037] Furthermore, for ease of understanding, the position, size, range, etc. of each component shown in the drawings may not represent the actual position, size, range, etc. Therefore, the disclosed invention is not necessarily limited to the position, size, range, etc. disclosed in the drawings.

[0038] The terms "film" and "layer" can be interchangeable depending on the circumstances. For example, the term "conductive layer" can be changed to the term "conductive film." Or, for example, the term "insulating film" can be changed to the term "insulating layer."

[0039] As used herein, a "deuterated organic compound" refers to an organic compound in which, when focusing on hydrogen (including deuterium) present at a specific position in the organic compound, the proportion of the hydrogen (including deuterium) that is deuterium is greater than the natural abundance of deuterium. This proportion is preferably sufficiently greater than the natural abundance. In this case, "sufficiently" refers to, for example, 7.5% or more being deuterated. The deuteration of an organic compound can be confirmed by methods such as NMR and mass spectrometry.

[0040] In this specification, etc., a device fabricated using a metal mask or an FMM (fine metal mask, high-resolution metal mask) may be referred to as a device with an MM (metal mask) structure. In addition, in this specification, etc., a device fabricated without using a metal mask or an FMM may be referred to as a device with an MML (metal maskless) structure.

[0041] In this specification and the like, holes or electrons may be referred to as "carriers." Specifically, a hole injection layer or electron injection layer may be referred to as a "carrier injection layer," a hole transport layer or electron transport layer may be referred to as a "carrier transport layer," and a hole block layer or electron block layer may be referred to as a "carrier block layer." Note that the above-mentioned carrier injection layer, carrier transport layer, and carrier block layer may not be clearly distinguishable. Furthermore, one layer may have two or three functions among the carrier injection layer, carrier transport layer, and carrier block layer. Furthermore, the terms "injection layer," "transport layer," and "block layer" may be simply referred to as "layer." Similarly, other layers such as "light-emitting layer" and "intermediate layer" may also be referred to as "layer."

[0042] In this specification and the like, a light-emitting device (also referred to as a light-emitting element) has an EL layer between a pair of electrodes. The EL layer has at least a light-emitting layer. In this specification and the like, a light-receiving device (also referred to as a light-receiving element) has at least an active layer that functions as a photoelectric conversion layer between a pair of electrodes. In this specification and the like, one of the pair of electrodes may be referred to as a pixel electrode, and the other as a common electrode.

[0043] In this specification, a tapered shape refers to a shape in which at least a portion of the side surface of the structure is inclined with respect to the substrate surface. For example, it is preferable to have a region in which the angle (also called the taper angle) between the inclined side surface and the substrate surface is less than 90°. The side surface of the structure and the substrate surface do not necessarily need to be completely flat, and may be approximately planar with a slight curvature or approximately planar with minute irregularities.

[0044] In this specification, the term "light-emitting device" includes an image display device using an organic EL device. The term "light-emitting device" may also include a module in which a connector, such as an anisotropic conductive film or TCP (Tape Carrier Package), is attached to an organic EL device, a module in which a printed wiring board is provided at the end of the TCP, or a module in which an IC (integrated circuit) is directly mounted on an organic EL device using a COG (Chip On Glass) method. Furthermore, lighting fixtures and the like may include a light-emitting device.

[0045] (Embodiment 1) A tandem light-emitting device has a structure in which multiple light-emitting units are stacked between a pair of electrodes with an intermediate layer (charge-generating layer) sandwiched between them. Each of the multiple light-emitting units has a light-emitting layer, and light can be emitted from any of the light-emitting layers by passing a current through them. A tandem light-emitting device having such a configuration has significantly higher current efficiency than a non-tandem light-emitting device, and is therefore suitable for use in display devices that require high brightness or high reliability.

[0046] Tandem light-emitting devices have multiple light-emitting layers, making it easy to produce white light. Therefore, full-color display devices using tandem light-emitting devices often use a white color filter system. Color conversion systems using a blue-emitting light-emitting layer and a color conversion layer, typically a quantum dot, have also been put to practical use.

[0047] On the other hand, some display devices using tandem light-emitting devices that employ a color-coded method for full color have also been put to practical use. Color-coded light-emitting devices have little or no energy loss in the color filters or color conversion layers, making them more efficient than the two methods mentioned above.

[0048] Furthermore, it is preferable that the light-emitting layer of the tandem light-emitting device is separated from the light-emitting layer of at least one of the other adjacent light-emitting devices, or that the light-emitting layer of the tandem light-emitting device has a light-emitting layer different from the light-emitting layer of at least one of the other adjacent light-emitting devices, or that the color of light emitted by the tandem light-emitting device is different from the color of light emitted by at least one of the other adjacent light-emitting devices, or that the light-emitting center substance of the light-emitting layer of the tandem light-emitting device has a different structure from the light-emitting center substance of the light-emitting layer of at least one of the other adjacent light-emitting devices.

[0049] The light-emitting device of the present invention having the above structure can be a light-emitting device with high current efficiency, low energy loss, and favorable characteristics. A display device according to one embodiment of the present invention using such a light-emitting device can be a display device with low power consumption, high reliability, and high luminance and thus favorable visibility.

[0050] Next, a light-emitting device of one embodiment of the present invention will be described in detail with reference to the drawings. Figure 1A shows a light-emitting device 130 of one embodiment of the present invention. The light-emitting device of one embodiment of the present invention is a tandem light-emitting device including a first electrode 101 including an anode and a second electrode 102 including a cathode, and an organic compound layer 103 (also referred to as an EL layer) including a first light-emitting unit 501 including a first light-emitting layer 113_1, a second light-emitting unit 502 including a second light-emitting layer 113_2, and an intermediate layer 160.

[0051] Although the present embodiment describes an example of a light-emitting device having one intermediate layer 160 and two light-emitting units, the light-emitting device may have n (n is an integer of 1 or more) intermediate layers and n+1 light-emitting units. For example, the light-emitting device 130 shown in Fig. 1(B) is an example of a tandem light-emitting device in which n is 2 and the light-emitting device has a first light-emitting unit 501, a first intermediate layer 160_1, a second light-emitting unit 502, a second intermediate layer 160_2, and a third light-emitting unit 503.

[0052] It is preferable that the color gamut of the light emitted by the light-emitting layer in each light-emitting unit is the same.

[0053] In one embodiment of the present invention, a material that emits phosphorescence (hereinafter also referred to as a phosphorescent material) is used as the luminescent center substance contained in the first light-emitting layer 113_1 or the second light-emitting layer 113_2. In particular, it is preferable to use a phosphorescent material in a light-emitting device that emits blue light.

[0054] In current-excited organic EL devices, the generation probability of the singlet excited state and the triplet excited state is 1:3, and it is known that the theoretical limit of the internal quantum efficiency of light-emitting devices using fluorescent materials, which can only use the singlet excited state for emission, is 25%. On the other hand, phosphorescent materials can convert the singlet excited state to the triplet excited state through intersystem crossing, so light-emitting devices with a theoretical internal quantum efficiency of 100% can be realized, and light-emitting devices with higher luminous efficiency than fluorescent materials can be obtained.

[0055] When an organic compound exhibiting blue phosphorescence is used in the light-emitting layer, the host material preferably contains at least one of a compound having a heteroaromatic ring, a compound having a carbazole skeleton, or a compound having an aromatic amine skeleton. Furthermore, the host material particularly preferably contains deuterium. Specifically, the host material has a structure in which some or all of the hydrogen atoms contained in the host material are replaced with deuterium atoms. Compared to organic compounds containing only hydrogen atoms, organic compounds containing deuterium exhibit reduced material degradation when used in a light-emitting device, thereby improving the reliability of the light-emitting device.

[0056] A compound having a heteroaromatic ring functions as an electron-transporting host, and a compound having a carbazole skeleton or an aromatic amine skeleton functions as a hole-transporting host. The combination of an electron-transporting host and a hole-transporting host is preferred because it facilitates the formation of an exciplex (also called an exciplex). Thus, it is preferred to have multiple host materials, and in particular, a material containing deuterium can be used as at least one of the multiple host materials.

[0057] Furthermore, by incorporating a phosphorescent material and an exciplex into the light-emitting layer, the energy transfer from the exciplex to the light-emitting material, known as ExTET (Exciplex-Triplet Energy Transfer), can be efficiently performed, thereby improving the luminous efficiency. Furthermore, this configuration simultaneously achieves high efficiency, low-voltage operation, and a long life for the light-emitting device.

[0058] In particular, at least one of the light-emitting layers included in a tandem light-emitting device according to one embodiment of the present invention includes a light-emitting center substance, a first host material, and a second host material. The light-emitting center substance is preferably a phosphorescent light-emitting substance. The first host material and the second host material are both organic compounds that form an exciplex. The tandem light-emitting device according to one embodiment of the present invention has a structure in which the light-emitting center substance emits light upon energy transfer from the exciplex formed by the first host material and the second host material to the light-emitting center substance. This improves the efficiency of excitation energy transfer to the light-emitting center substance, resulting in a highly efficient and reliable light-emitting device. Furthermore, a reduction in driving voltage is also achieved.

[0059] As a combination of materials that efficiently form an exciplex, it is preferable that the HOMO level of the hole-transporting material be equal to or higher than the HOMO level of the electron-transporting material. It is also preferable that the LUMO level of the hole-transporting material be equal to or higher than the LUMO level of the electron-transporting material. It is also preferable that the difference between the HOMO level of the hole-transporting material and the HOMO level of the electron-transporting material be 0.2 eV or more. It is also preferable that the difference between the LUMO level of the hole-transporting material and the LUMO level of the electron-transporting material be 0.2 eV or more. This configuration is preferable because it facilitates the injection of holes into the hole-transporting material and electrons into the electron-transporting material. The LUMO level and HOMO level of a material can be derived from the electrochemical properties (reduction potential and oxidation potential) of the material measured by cyclic voltammetry (CV), or can also be derived by photoelectron spectroscopy, optical absorption spectroscopy, inverse photoelectron spectroscopy, etc. When comparing values ​​between different compounds, it is preferable to use values ​​estimated by the same measurement method.

[0060] Furthermore, it is preferable that the HOMO level of the phosphorescent material is lower than that of the material having hole-transporting properties, and that the LUMO level of the phosphorescent material is higher than that of the material having electron-transporting properties. That is, it is preferable that the energy difference between the LUMO level and the HOMO level of the phosphorescent material is larger than the energy difference between the LUMO level of the material having electron-transporting properties and the HOMO level of the material having hole-transporting properties. This can suppress the reaction that forms an exciplex between the phosphorescent material and the material having hole-transporting properties or the material having electron-transporting properties, thereby providing a light-emitting device that emits light efficiently.

[0061] Phosphorescent materials have the function of converting triplet excitation energy into light emission. Furthermore, the triplet excited state is stable because its energy is lower than that of the singlet excited state. Therefore, phosphorescent materials can emit light with an energy lower than the energy difference between the LUMO level and the HOMO level. Even when the energy difference between the LUMO level and the HOMO level of a phosphorescent material is larger than the energy difference between the LUMO level and the HOMO level of a material having electron-transporting properties and the HOMO level of a material having hole-transporting properties, if the emission energy of the phosphorescent material or the transition energy calculated from the absorption spectrum is equal to or smaller than the energy difference between the LUMO level and the HOMO level of the material having electron-transporting properties or the emission energy of an exciplex formed by the material having electron-transporting properties and the material having hole-transporting properties, the excitation energy can be transferred from the exciplex formed by the material having electron-transporting properties and the material having hole-transporting properties to the phosphorescent material, and efficient light emission can be obtained from the phosphorescent material.

[0062] Furthermore, in order for a phosphorescent material to emit light with high emission energy (short wavelength), it is preferable that the lowest triplet excitation energy level (T1 level) of the phosphorescent material is high. To this end, it is preferable to use a ligand with a high lowest triplet excitation energy level as the ligand coordinated to the heavy metal atom of the phosphorescent material, and it is preferable that the ligand has low electron-accepting property and a high LUMO level. A phosphorescent material having such a structure tends to have a molecular structure with a high LUMO level and a high HOMO level that easily accepts holes. When a phosphorescent material has a molecular structure that easily accepts holes, the HOMO level of the phosphorescent material may be higher than the HOMO level of a material having hole-transporting properties. However, even in such a case, if the energy difference between the LUMO level and the HOMO level of the phosphorescent material is larger than the energy difference between the LUMO level of the material having electron-transporting properties and the HOMO level of the material having hole-transporting properties, if the emission energy of the phosphorescent material or the transition energy calculated from the absorption spectrum is equal to or smaller than the energy difference between the LUMO level of the material having electron-transporting properties and the HOMO level of the material having hole-transporting properties, or if the transition energy is equal to or smaller than the emission energy of the exciplex formed by the material having electron-transporting properties and the material having hole-transporting properties, then excitation energy can be transferred from the exciplex formed by the material having electron-transporting properties and the material having hole-transporting properties to the phosphorescent material, and efficient emission from the phosphorescent material can be obtained.

[0063] The formation of exciplexes can be confirmed by, for example, comparing the PL spectra of a material with hole transport properties, a material with electron transport properties, and a mixed film of these materials and observing the phenomenon that the PL spectrum of the mixed film is shifted to longer wavelengths than the PL spectra of each material (or has a new peak at longer wavelengths). Alternatively, it can be confirmed by comparing the transient photoluminescence (transient PL) of a material with hole transport properties, the transient PL of a material with electron transport properties, and a mixed film of these materials and observing differences in transient response, such as the transient PL lifetime of the mixed film having a longer-lived component or a larger proportion of delayed components than the transient PL lifetimes of the individual materials. The above-mentioned transient PL can also be interpreted as transient electroluminescence (transient EL). In other words, the formation of exciplexes can also be confirmed by comparing the transient EL of a material with hole transport properties, the transient EL of a material with electron transport properties, and a mixed film of these materials and observing differences in transient response.

[0064] For example, when a first host material and a second host material form an exciplex, the short-wavelength emission edge of the photoluminescence (PL) spectrum of the exciplex is preferably positioned at a wavelength shorter than the long-wavelength absorption edge of the absorption spectrum of the luminescent center substance. Such a positional relationship between the PL spectrum of the exciplex and the absorption edge of the luminescent center substance enables efficient energy transfer.

[0065] Alternatively, the peak wavelength of the PL spectrum of the exciplex formed by the first host material and the second host material is preferably shorter than the peak wavelength of the PL spectrum of the luminescent center substance. Furthermore, the difference between the peak wavelength of the PL spectrum of the exciplex and the peak wavelength of the PL spectrum of the luminescent center substance is more preferably 30 nm or less. Such a relationship between the peak wavelength of the PL spectrum of the exciplex and the peak wavelength of the PL spectrum of the luminescent center substance enables efficient energy transfer.

[0066] Alternatively, the difference between the peak wavelength of the PL spectrum of the exciplex formed by the first host material and the second host material and the wavelength of the absorption edge on the long-wavelength side in the absorption spectrum of the luminescent center substance is preferably within 30 nm. Such a relationship between the peak wavelength of the PL spectrum of the exciplex and the wavelength of the absorption edge on the long-wavelength side in the absorption spectrum of the luminescent center substance enables efficient energy transfer.

[0067] Alternatively, the short-wavelength emission edge of the PL spectrum of the exciplex formed by the first host material and the second host material is preferably positioned at a wavelength shorter than the short-wavelength emission edge of the PL spectrum of the luminescent center substance. Furthermore, the difference between the short-wavelength emission edge of the PL spectrum of the exciplex and the short-wavelength emission edge of the PL spectrum of the luminescent center substance is more preferably within 0.3 eV. Such a relationship between the short-wavelength emission edge of the PL spectrum of the exciplex and the short-wavelength emission edge of the PL spectrum of the luminescent center substance enables efficient energy transfer.

[0068] The emission edge on the short wavelength side of the PL spectrum can be calculated by drawing a tangent at the value where the absolute value of the slope on the short wavelength side of the peak (or shoulder peak) observed at the shortest wavelength in the PL spectrum is maximum, and then calculating from the intersection of the tangent with the horizontal axis or the baseline. The absorption edge on the long wavelength side of the absorption spectrum can be calculated by drawing a tangent at the value where the absolute value of the slope on the long wavelength side of the peak (or shoulder peak) observed at the longest wavelength in the absorption spectrum is maximum, and then calculating from the intersection of the tangent with the horizontal axis or the baseline.

[0069] The PL spectrum of the exciplex is preferably measured using a co-evaporated film of the first host material and the second host material. The mixing ratio of the first host material to the second host material, either by weight, volume, or molar ratio, may be in the range of 1:19 to 19:1 (first host material:second host material), preferably 1:9 to 9:1, and more preferably 3:7 to 7:3. The PL spectrum of a mixed film of the first host material and the second host material may also be measured using the spectrum of a mixed film in which the first host material and the second host material are mixed at a ratio of 1:1 (first host material:second host material). When measuring the PL spectrum or absorption spectrum of the luminescent center substance, the sample may be in the form of a thin film or a solution. However, a solution is preferred from the viewpoint of examining the state of isolated molecules. The solvent for the solution is preferably a relatively low-polarity solvent, such as toluene or chloroform.

[0070] When a phosphorescent material is used in the light-emitting layer, the T1 levels of the first and second host materials are preferably higher than the T1 level of the phosphorescent material. The singlet excitation energy and triplet excitation energy of the first or second host material can be transferred from the S1 level and T1 level of the first or second host material to the T1 level of the phosphorescent material. As a result, the phosphorescent material enters a triplet excited state and emits phosphorescence.

[0071] The T1 level can be determined by measuring the phosphorescence component (phosphorescence spectrum) in the PL spectrum observed at low temperatures (for example, at temperatures between 4 K and 80 K). Specifically, for example, a 50 nm thin film of the sample is formed on a quartz substrate, and the PL spectrum (phosphorescence spectrum) is measured at a measurement temperature of 10 K. The energy at the emission edge on the short wavelength side can be regarded as the T1 level. The emission edge can be calculated by drawing a tangent at the point where the absolute value of the slope on the short wavelength side of the peak (or shoulder peak) observed at the shortest wavelength in the PL spectrum (phosphorescence spectrum) is maximum, and then finding the intersection of the tangent with the horizontal axis (wavelength) or the baseline.

[0072] Furthermore, the T1 level of a phosphorescent material can be determined by measuring the PL spectrum observed at low temperatures (for example, any temperature in the range of 4 K to 80 K) or room temperature (for example, any temperature in the range of 275 K to 305 K), and the energy at the emission edge on the short wavelength side can be regarded as the T1 level.

[0073] Furthermore, in the light-emitting device according to one embodiment of the present invention, when one or both of the first host material and the second host material contain deuterium, the energy transfer efficiency can be improved. This is because the phosphorescence lifetime or delayed fluorescence lifetime of a deuterated organic compound is longer than the phosphorescence lifetime or delayed fluorescence lifetime of a non-deuterated organic compound. That is, the intramolecular vibration in the lowest triplet excited state (T1 state) of a deuterated organic compound is suppressed more than the intramolecular vibration of a non-deuterated organic compound, thereby suppressing the non-radiative transition from the T1 state to a more stable state.

[0074] Energy transfer efficiency φ from an energy donor (in one embodiment of the present invention, an exciplex) to an energy acceptor (in one embodiment of the present invention, a substance capable of converting triplet excitation energy into luminescence) ET is expressed by the following formula (1): From this formula, the energy transfer efficiency φ ET To increase the energy transfer rate constant k h*→g becomes large, and other competing rate constants k r +k nr It turns out that it is good if (=1 / τ) becomes relatively small.

[0075] In addition, in formula (1), k r represents the rate constant of the luminescence process of the energy donor (fluorescence when discussing energy transfer from a singlet excited state, phosphorescence or delayed fluorescence when discussing energy transfer from a triplet excited state), and k nr represents the rate constant of the non-radiative process of the energy donor (thermal deactivation and intersystem crossing), and τ represents the measured lifetime of the excited state of the energy donor. h*→g represents the rate constant for energy transfer (Förster or Dexter mechanism).

[0076]

number

[0077] Energy transfer rate constant k h*→g is almost the same in deuterated and non-deuterated organic compounds because the atomic arrangement of the molecules, the spectral shape, etc. are almost the same (see the following formula (2) or formula (3)). Therefore, when comparing deuterated and non-deuterated organic compounds, the energy transfer rate constant k h*→g is significantly affected by the luminescence lifetime (phosphorescence lifetime or delayed fluorescence lifetime) τ. In other words, the energy transfer efficiency improves as the luminescence lifetime (phosphorescence lifetime or delayed fluorescence lifetime) increases.

[0078]

number

[0079]

number

[0080] Equation (2) is the rate constant k of the Förster mechanism. h*→g Equation (3) is the rate constant k h*→g is the formula.

[0081] In equation (2), ν represents the frequency, and f′ h (ν) represents the normalized emission spectrum of the host material (fluorescence spectrum when discussing energy transfer from a singlet excited state, and phosphorescence spectrum when discussing energy transfer from a triplet excited state), and ε g(ν) represents the molar absorption coefficient of the guest material, N represents Avogadro's number, n represents the refractive index of the medium, R represents the intermolecular distance between the host material and the guest material, τ represents the measured lifetime of the excited state (fluorescence lifetime, phosphorescence lifetime), φ represents the luminescence quantum yield (fluorescence quantum yield when discussing energy transfer from a singlet excited state, and phosphorescence quantum yield when discussing energy transfer from a triplet excited state), and K 2 is a coefficient (0 to 4) that represents the orientation of the transition dipole moments of the host material and guest material. In the case of random orientation, K 2 =2 / 3.

[0082] In equation (3), h is Planck's constant, K is a constant with the dimension of energy, ν is the frequency, and f′ h (ν) represents the normalized emission spectrum of the host material (fluorescence spectrum when discussing energy transfer from a singlet excited state, and phosphorescence spectrum when discussing energy transfer from a triplet excited state), and ε′ g (ν) represents the normalized absorption spectrum of the guest material, L represents the effective molecular radius, and R represents the intermolecular distance between the host material and the guest material.

[0083] As described above, in the energy transfer from the first host material and the second host material, the efficiency of energy transfer from each triplet excited state is important, and therefore the lifetime of the triplet excited state is important. That is, by deuterating one or both of the first host material and the second host material, the phosphorescence lifetime or delayed fluorescence lifetime is extended, thereby improving the energy transfer efficiency and suppressing deterioration of the deuterated organic compound. As a result, a light-emitting device having an energy donor using a deuterated organic compound can be made to have more suppressed deterioration of the organic compound than a light-emitting device having an energy donor that does not use a deuterated organic compound, resulting in a light-emitting device with good reliability.

[0084] The phosphorescence lifetime and delayed fluorescence lifetime are calculated by measuring transient PL through time-resolved measurements, in which the intensity of the decaying emission is measured at regular intervals after the excitation light is blocked with a shutter. In this case, fluorescent components may be mixed in at the beginning of the decay, and the graph may not form a straight line. In such cases, the starting point can be determined at the linear portion of the graph, and the time it takes for the intensity at the starting point to decay to 1 / e can be used as the phosphorescence lifetime or delayed fluorescence lifetime.

[0085] In a light-emitting device according to one embodiment of the present invention, an exciplex formed from a first host material and a second host material preferably serves as an energy donor. However, as described above, with respect to a triplet excited state, there may be a pathway for energy transfer from the triplet excited state of the exciplex via the triplet excited states of the first host material and the second host material. Therefore, the phosphorescence lifetime or delayed fluorescence lifetime of the first host material and the second host material constituting the exciplex is important. Here, it has been found that in a light-emitting device according to one embodiment of the present invention, the phosphorescence lifetime or delayed fluorescence lifetime is increased by a certain amount or more due to the presence of deuterium in one or, preferably, both, of the first host material and the second host material, and the reliability of the light-emitting device using the exciplex as an energy donor is significantly improved.

[0086] That is, the first host material is preferably an organic compound whose phosphorescence lifetime or delayed fluorescence lifetime is 1.20 times or more that of a first host material in which the deuterium of the first host material is hydrogen. The second host material is preferably an organic compound whose phosphorescence lifetime or delayed fluorescence lifetime is 1.05 times or more that of a second host material in which the deuterium of the second host material is hydrogen. When the phosphorescence lifetime or delayed fluorescence lifetime of the first host material is X times that of a first host material in which the deuterium of the first host material is hydrogen, and the phosphorescence lifetime or delayed fluorescence lifetime of the second host material is Y times that of a second host material in which the deuterium of the second host material is hydrogen, the product of X and Y is preferably 1.26 or more. In this case, it is preferable that the light emitted by the substance capable of converting triplet excitation energy into luminescence (the luminescent substance contained in the luminescent layer) is in the blue region, that is, the peak wavelength is typically 440 nm or more and 500 nm or less.

[0087] Furthermore, when the light emitted by the substance capable of converting triplet excitation energy into luminescence (the luminescent substance contained in the luminescent layer) is in the green region, i.e., when the peak wavelength is typically longer than 500 nm and shorter than 600 nm, the first host material is preferably an organic compound whose phosphorescence lifetime or delayed fluorescence lifetime is 1.50 times or more that of a first host material in which the deuterium in the first host material is hydrogen. Furthermore, the second host material is preferably an organic compound whose phosphorescence lifetime or delayed fluorescence lifetime is 3.00 times or more that of a second host material in which the deuterium in the second host material is hydrogen. Furthermore, when the phosphorescence lifetime or delayed fluorescence lifetime of the first host material is X times the phosphorescence lifetime or delayed fluorescence lifetime of the first host material in which deuterium is hydrogen, and the phosphorescence lifetime or delayed fluorescence lifetime of the second host material is Y times the phosphorescence lifetime or delayed fluorescence lifetime of the second host material in which deuterium is hydrogen, the value obtained by multiplying X and Y is preferably 4.50 or more.

[0088] As shown in Figure 81, the starting point was set to t=0 within the range where the graph is a straight line from the measurement data (left panel of Figure 81) (here, t=0 was set to the time when the light intensity reached 50% of the intensity at the start of measurement) (right panel of Figure 81). The time from there until the light intensity decays to 1 / e of the time at t=0 is the phosphorescence lifetime or delayed fluorescence lifetime. In Figure 81, the graph was created with the time when the measurement data reached 50% of the intensity at the start of measurement as time 0 s, and when the light intensity at 0 s is set to 1, the time when the light intensity reaches 1 / e is the phosphorescence lifetime or delayed fluorescence lifetime. Note that while it is easy to use an intensity of 50% of the intensity at the start of measurement as the starting point, other values ​​can also be used.

[0089] The phosphorescence lifetime can be measured at the liquid nitrogen temperature (77 K) by installing a liquid nitrogen cooling unit in a fluorometer such as the FP-8600 manufactured by JASCO Corporation. The material solution is prepared in a glove box, and the sample is dissolved in deoxygenated 2-MeTHF and stirred with a stirrer at room temperature for about 30 minutes (heating may also be used for materials that are difficult to dissolve). -4 A solution with a concentration of about M can be prepared and used.

[0090] Time-resolved measurements can be performed by irradiating the sample cell with excitation light for approximately 30 seconds, shutting off the excitation light with a shutter, and then measuring the decaying emission intensity at 10-ms intervals. The wavelength for phosphorescence lifetime measurements is preferably the peak wavelength of the phosphorescence spectrum. If there are multiple peaks in the phosphorescence spectrum, it is preferable to select the wavelength with the highest peak intensity. Accurate measurements may be hindered by the presence of mixed fluorescence spectra at certain wavelengths. In such cases, it is preferable to compare the PL spectrum (emission spectrum including phosphorescence) measured at low temperatures (e.g., 77 K) with the PL spectrum (emission spectrum containing fluorescence only, without phosphorescence) measured at room temperature and select a phosphorescence wavelength with minimal overlapping fluorescence. Alternatively, the longest peak wavelength of the phosphorescence spectrum can be selected. In the case of frozen solutions, emission from states other than the lowest triplet excited state may also be observed. In such cases, the longest peak wavelength should be selected.

[0091] The excitation wavelength can be selected appropriately within a wavelength range that is not affected by the solvent. If the material can be sufficiently excited, measurement at 330 nm is preferable because there is no solvent effect. The bandwidth of the excitation light and measurement light should be approximately 10 nm. Ideally, the emission decays according to a single exponential function, so the starting point is set in the linear portion of the graph, and the time it takes for the intensity at the starting point to decay to 1 / e can be defined as the phosphorescence lifetime or delayed fluorescence lifetime.

[0092] Fluorescence lifetime, phosphorescence lifetime, and delayed fluorescence lifetime can be distinguished by their lifetimes when time-resolved measurements are performed. The fluorescence lifetime is an emission lifetime of around n seconds, while the phosphorescence lifetime and delayed fluorescence lifetime are emission lifetimes of μs to msec or more.

[0093] In a light-emitting device according to one embodiment of the present invention, reliability is improved by extending the phosphorescence lifetime of the first and second host materials, i.e., the lifetime of triplet excitons. The extended lifetime of triplet excitons is due to the suppression of nonradiative deactivation of triplet excitation energy, which is caused by the suppression of vibrations due to deuteration. A small difference between the lowest triplet excitation energy level (T1 level) of the first host material and the T1 level of the second host material makes it difficult for excitation energy to be biased toward one of the organic compounds, preventing significant degradation of either of them, and thus improving the reliability of the light-emitting device. Specifically, the difference between the T1 levels of the first host material and the second host material is preferably 0.20 eV or less, preferably 0.15 eV or less, and more preferably 0.10 eV or less.

[0094] The lowest triplet excitation energy level (T1 level) can be calculated by measuring the PL spectrum (phosphorescence spectrum) at a temperature of 10 K using a 50 nm thin film of the sample deposited on a quartz substrate. Measurements can be performed using a microPL microscope, LabRAM HR-PL (Horiba, Ltd.), with a He-Cd laser (325 nm) as the excitation light. The emission edge can be calculated by drawing a tangent at the point where the absolute value of the slope on the short-wavelength side of the peak (or shoulder peak) observed at the shortest wavelength in the PL spectrum (phosphorescence spectrum) is maximum, and then calculating the emission edge from the intersection of this tangent with the horizontal axis (wavelength) or the baseline.

[0095] Alternatively, in one embodiment of the present invention, the sublimation temperatures of the first host material and the second host material are preferably close to each other. For example, the difference between the 5% weight loss temperature measured by thermogravimetry of the first host material and the 5% weight loss temperature measured by thermogravimetry of the second host material is preferably 60°C or less. It is more preferably 45°C or less, more preferably 20°C or less, and even more preferably 10°C or less. This allows vapor deposition to be performed using a mixture of the first host material and the second host material, thereby reducing the number of vapor deposition sources and enabling the provision of a light-emitting device with excellent characteristics at low cost.

[0096] The 5% weight loss temperature can be determined from the relationship between weight and temperature (thermogravimetry) by thermogravimetry-differential thermal analysis (TG-DTA). If the pressure at which vapor deposition is performed is predetermined, it is preferable to use the value measured under that pressure.

[0097] Note that a light-emitting device with better characteristics can be realized by combining the extension rates of the phosphorescence lifetime or delayed fluorescence lifetime due to deuteration of the first host material and the second host material, their product, the difference in T1 level, and the difference in sublimation temperature.

[0098] Furthermore, it is preferable that the photoluminescence (PL) spectrum of the exciplex formed from the first host material and the second host material overlaps with the PL spectrum of the light-emitting substance (a substance capable of converting triplet energy into light emission). This is because the excitation energy of the energy donor and that of the light-emitting substance are close to each other, thereby reducing the driving voltage of the light-emitting device. Therefore, it is preferable that the difference in the maximum peak wavelengths between them is 30 nm or less. Alternatively, a light-emitting device having a configuration in which the difference in wavelength between the short-wavelength emission edge in the PL spectrum of the exciplex and the short-wavelength emission edge in the PL spectrum of the light-emitting substance is 30 nm or less is preferable, as it can reduce the driving voltage.

[0099] The PL spectrum of an exciplex is preferably measured using a co-evaporated film of a first host material and a second host material. When measuring the PL spectrum of a light-emitting substance (a substance capable of converting triplet energy into luminescence), the sample may be in the form of a thin film or a solution, but a solution is preferred from the viewpoint of examining the state of isolated molecules. The solvent for the solution is not particularly limited as long as the same solvent is used for comparison, but a solvent with relatively low polarity, such as toluene or chloroform, is preferred.

[0100] When the light emitted by the substance capable of converting triplet excitation energy into light (the light-emitting substance contained in the light-emitting layer) is light in the blue region, that is, when the peak wavelength is typically 440 nm or more and 500 nm or less, the first host material is preferably an organic compound having an azine skeleton, and the second host material is preferably an organic compound having a carbazole skeleton.

[0101] Examples of azine skeletons that can be used as the host material include a pyridine ring, a pyrimidine ring, and a triazine ring. These can improve the electron transport property. It is preferable to use a compound in which a carbazole skeleton is bonded to the azine skeleton directly or via an arylene group, and it is preferable to have multiple carbazole skeletons. It is also preferable that multiple carbazole skeletons are not bonded to each other. Thus, the presence of a carbazole skeleton can adjust the electron transport property. The compound having a heteroaromatic ring may also have one or more elements such as silicon, boron, oxygen, and sulfur.

[0102] Furthermore, the compound having a carbazole skeleton preferably has multiple carbazole skeletons. It is preferable that the compound has at least one of the following structures: a structure in which the 3-position of one carbazole skeleton is bonded to the 9-position of another carbazole skeleton; a structure in which the 2-position of one carbazole skeleton is bonded to the 9-position of another carbazole skeleton; a structure in which the 4-position of one carbazole skeleton is bonded to the 9-position of another carbazole skeleton; a structure in which the 1-position of one carbazole skeleton is bonded to the 9-position of another carbazole skeleton; or a structure in which the 3-position of one carbazole skeleton is bonded to the 3-position of another carbazole skeleton. Because the 3- and 9-positions of the carbazole skeletons have excellent reactivity, compounds having a bonding position at the 3- or 9-position of the carbazole skeleton can easily improve yield or purity during the compound production process. Furthermore, compounds having a bonding position at the 1-position of the carbazole skeleton tend to require lower deposition temperatures, facilitating film formation. Furthermore, since the T1 level can be adjusted by the bonding position of the carbazole skeleton, it is preferable to design the molecule according to the desired properties of the organic compound. It is more preferable to have a plurality of these structures. Furthermore, the compound having a carbazole skeleton may contain one or more elements such as silicon, boron, oxygen, and sulfur.

[0103] When two compounds are used in combination as a host material, it is preferable that both the compound having a heteroaromatic ring and the compound having a carbazole skeleton have multiple carbazole skeletons. In this case, the number of carbazole skeletons contained in the compound having a carbazole skeleton is preferably equal to or greater than the number of carbazole skeletons contained in the compound having a heteroaromatic ring. By adjusting the number of carbazole skeletons in this manner, the electron transport property and hole transport property of the host material can be adjusted.

[0104] Furthermore, when the two compounds, the compound having a heteroaromatic ring and the compound having a carbazole skeleton, contain an element such as silicon, boron, oxygen, or sulfur, it is preferable that the two compounds contain the same element, because this can improve the characteristics of a light-emitting device using a phosphorescent material.

[0105] For example, organic compounds that can be used as the host material include 9,9'-{6-[3-(triphenylsilyl)phenyl]-1,3,5-triazine-2,4-diyl}bis(9H-carbazole) (abbreviation: SiTrzCz2) represented by structural formula (450), 2-phenyl-4,6-bis[3-(triphenylsilyl)phenyl]-1,3,5-triazine (abbreviation: mSiTrz) represented by structural formula (451), and 9-{4-phenyl-6-[3-(triphenylsilyl)phenyl]-1,3,5-triazin-2-yl}-9H-carbazole (abbreviation: SiCzTrz), 9-{4,6-bis[3-(triphenylsilyl)phenyl]-1,3,5-triazin-2-yl}-9H-carbazole (abbreviation: DSiCzTrz) represented by structural formula (453), 9-(biphenyl-4-yl)-3-(4-{[4'-( 4,6-diphenyl-1,3,5-triazin-2-yl)biphenyl-4-yl]diphenylsilyl}phenyl)-9H-carbazole (abbreviation: CzSiTzn), 3-{6-[3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]dibenzothiophen-4-yl}-9-phenyl-9H-carbazole (abbreviation: mPCDBtPTzn) represented by structural formula (455), 9-[3- Examples of such organic compounds include [4-(2,12-di-tert-butyl-5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracen-7-yl)phenyl]triphenylsilane represented by structural formula (457), and deuterated organic compounds represented by structural formula (458), structural formula (459), and structural formula (460).

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[0108] When the host material contains deuterium, the entire molecule may be deuterated or may be partially deuterated. In the case of partial deuteration, it is preferable that the group where the lowest triplet excitation energy level is localized is deuterated. A partially deuterated compound can be produced more inexpensively than a compound where the entire molecule is deuterated. In some cases, only the heteroaromatic ring is deuterated, only the carbazole skeleton is deuterated, or only the hydrocarbon group is deuterated. In addition, in a compound having a heteroaromatic ring and a hydrocarbon group, part of the heteroaromatic ring and part of the hydrocarbon group may be deuterated. The group where the lowest triplet excitation energy level is localized can be deuterated.

[0109] Specifically, a deuterated organic compound that can be used as a host material is 9,9'-{6-[3-(triphenylsilyl)phenyl]-1,3,5-triazine-2,4-diyl}bis(9H-carbazole-1,2,3,4,5,6,7,8,1',2',3',4',5',6',7',8'-d 16 )(Abbreviation: SiTrzCz2-d 16 ), or 9-[3-(triphenylsilyl)phenyl]-3,9'-(bi-9H-carbazole-d) represented by structural formula (475) 15 ) (Abbreviation: PSiCzCz-d 15 Organic compounds represented by the following structural formulas (461) to (483), such as 2-(2-methyl-2-phenylpropanol), can be used.

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[0114] Furthermore, when the light emitted by the substance capable of converting triplet excitation energy into light (the light-emitting substance contained in the light-emitting layer) is light in the green region (with a peak wavelength typically longer than 500 nm and shorter than 600 nm) or in the red region (with a peak wavelength typically longer than 600 nm and shorter than 700 nm), the first host material is preferably an organic compound having a diazine skeleton or a triazine skeleton, and the second host material is preferably an organic compound having a carbazole skeleton.

[0115] Specifically, 3-[9-(4,6-diphenyl-1,3,5-triazin-2-yl)-2-dibenzofuranyl]-9-phenyl-9H-carbazole (abbreviation: PCDBfTzn) represented by structural formula (600), bBCzDBfTzn represented by structural formula (601), 11-[4-(biphenyl-4-yl)-6-phenyl-1,3,5-triazin-2-yl]-11,12-dihydro-12-(biphenyl-3-yl)indolo[2,3-a]carbazole (abbreviation: BP-mBPIcz( II)Tzn), 2-(6-Benzo[b]naphtho[1,2-d]furan-3-yl-1-naphthalenyl)-4,6-diphenyl-1,3,5-triazine (abbreviation: Bnf(3)NTzn) represented by structural formula (603), 9-[4-phenyl-6-(9-phenyl-3-dibenzofuranyl)-1,3,5-triazin-2-yl]-9H-carbazole (abbreviation: PDBf-CzTzn) represented by structural formula (604), 2-[3'-(triphenylene 2-(biphenyl-4-yl)-4-phenyl-6-[3-(triphenylen-2-yl)phenyl]-1,3,5-triazine (abbreviation: mTpBPTzn) represented by structural formula (606), 2-(biphenyl-4-yl)-4-phenyl-6-[3-(triphenylen-2-yl)phenyl]-1,3,5-triazine (abbreviation: BP-mTpPTzn) represented by structural formula (607), an organic compound represented by structural formula (608), 9-(biphenyl-3-yl)-9'-(biphenyl-4-yl)-9H,9'H-3,3'-bicarbazole (abbreviation: mBPCCBP) represented by structural formula (608), ), 9,9'-bis(biphenyl-4-yl)-3,3'-bi-9H-carbazole (abbreviation: BisBPCz) represented by structural formula (609), N-(biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF) represented by structural formula (610), 9-(biphenyl-4-yl)-9'-phenyl-3,3'-bi-9H-carbazole (abbreviation: PCCzBP) represented by structural formula (611), and the like.

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[0118] In addition, examples of deuterated organic compounds that can be used as host materials include organic compounds represented by structural formulas (612) to (631), such as PCzC represented by structural formula (618), PCBA1BPIV represented by structural formula (619), 1Adm-mCP represented by structural formula (629), mCz2C-PCz represented by structural formula (630), and mFadPCz represented by structural formula (631).

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[0122] In addition, when a plurality of host materials are used, organic compounds represented by the following structural formulas (632) to (640) can be used in combination.

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[0125] Other examples of the first host material include 8-(1,1':4',1''-terphenyl-3-yl-2,4,5,6,2',3',5',6',2'',3'',4'',5'',6''-d13 )-4-[3-(dibenzothiophen-4-yl-1,2,3,6,7,8,9-d7)phenyl-2,4,6-d3]-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 8mpTP-4mDBtPBfpm-d 23 ), 8-(1,1':4',1''-terphenyl-3-yl-2,4,5,6,2',3',5',6',2'',3'',4'',5'',6''-d 13 )-4-[3-(dibenzothiophen-4-yl)phenyl]-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 8mpTP-4mDBtPBfpm-d 13 ), 11-[4-(biphenyl-4-yl-2,2',3,3',4',5,5',6,6'-d9)-6-(phenyl-2,3,4,5,6-d5)-1,3,5-triazin-2-yl]-11,12-dihydro-12-(biphenyl-3-yl)indolo[2,3-a]carbazole-1,2,3,4,5,6,7,8,9,10-d 10 Examples include:

[0126] As a second host material, 9-(2-naphthyl-1,3,4,5,6,7,8-d7)-9'-(phenyl-2,3,4,5,6-d5)-3,3'-bi-9H-carbazole-1,1',2,2',4,4',5,5',6,6',7,7',8,8'-d 14 (Abbreviation: βNCCP-d 26 ), 9-phenyl-9'-(phenyl-2,3,4,5,6-d5)-3,3'-bis(9H-carbazole) (abbreviation: PCCP-d5), etc.

[0127] By using the above host material for the phosphorescent material, a light-emitting device with high luminous efficiency can be provided.

[0128] For example, an organometallic complex can be used as a phosphorescent material that emits blue light. The organometallic complex can use a heavy metal, such as platinum (Pt), palladium (Pd), iridium (Ir), Ru (ruthenium), Re (rhenium), Au (gold), or Os (osmium), as the central metal. Furthermore, it is preferable for the complex to have a heterocycle coordinated to the central metal. Examples of the heterocycle include a six-membered ring, such as a pyridine ring, a pyrazine ring, a triazine ring, or a pyrimidine ring, and a five-membered ring, such as a pyrazole ring, an indole ring, or a triazole ring. A structure in which both a five-membered ring and a six-membered ring are coordinated to the central metal can also be used. Furthermore, it is preferable for the complex to have a nitrogen-containing heterocyclic carbene coordinated to the central metal. Furthermore, it is preferable for the heterocycle to have an alkyl group as a substituent. For example, when a pyridine ring is used as the heterocycle, it is preferable for the pyridine ring to have an alkyl group at the 4-position, and more preferably an alkyl group containing deuterium. Alternatively, the pyridine ring may have alkyl groups at positions 3 and 5, preferably an alkyl group containing deuterium, and may have a phenyl group at position 4, preferably a structure in which the phenyl group further has an alkyl group.

[0129] Because the dissociation energy of a carbon-deuterium bond is higher than that of a carbon-proton bond, in organometallic complexes containing a pyridine ring, the molecular structure can be stabilized by attaching a deuterium-containing alkyl group to the 3rd and 5th carbon atoms of the pyridine ring, where the spin density is high in the triplet excited state. This also suppresses bond dissociation in the excited state and improves the stability of the organometallic complex. Furthermore, by attaching a deuterium-containing alkyl group to the 3rd and 5th carbon atoms of the pyridine ring, where the LUMO distribution is concentrated, the stability of the organometallic complex in the state where an electron has been accepted by the LUMO, i.e., in the reduced state, can be improved.

[0130] Furthermore, in organometallic complexes having a pyridine ring, the addition of a deuterium-containing alkyl group creates a steric hindrance effect on the phenyl group bonded to the 4-position of the pyridine ring. This suppresses the rotation of the phenyl group, improving the thermal properties of the organometallic complex, such as sublimation. Furthermore, this suppresses the vibration of the organometallic complex, preventing thermal deactivation from an excited state.

[0131] In addition, by attaching a phenyl group to the 4-carbon atom adjacent to the 3- and 5-carbon atoms of the pyridine ring, where the LUMO distribution is concentrated, the LUMO distribution can be broadened, and the LUMO can be stabilized, improving the stability of the organometallic complex in a reduced state.

[0132] Furthermore, in an organometallic complex having a pyridine ring, bonding a phenyl group to the carbon atom at the 4th position of the pyridine ring can enhance the planarity of the organometallic complex. This induces stronger molecular orientation, making it easier to orient the organometallic complex horizontally relative to the substrate plane when the organometallic complex is used as an emission center substance in the light-emitting layer of a light-emitting device. Furthermore, when the organometallic complex emits light, the light is emitted in the direction perpendicular to the transition dipole moment associated with the organometallic complex's emission. Therefore, if the transition dipole moment of the organometallic complex is oriented parallel to the substrate plane, the organometallic complex emits more light in the direction perpendicular to the substrate plane, thereby improving the light extraction efficiency of the light-emitting device. Therefore, it is preferable to orient the organometallic complex so that the transition dipole moment associated with the organometallic complex's emission is parallel to the substrate plane.

[0133] Furthermore, when the phenyl group bonded to the 4-position of the pyridine ring has an alkyl group, intermolecular interactions can be suppressed. For example, by using an organometallic complex of one embodiment of the present invention as an emission center substance in an emission layer of a light-emitting device, interaction between the emission center substance and a host material (one or more host materials when multiple host materials are used) can be prevented, thereby improving the emission efficiency of the light-emitting device.

[0134] Therefore, for example, the above organometallic complex can be favorably used for the light-emitting layer of the light-emitting device of one embodiment of the present invention.

[0135] Specific examples of organic compounds that exhibit blue phosphorescence and have an emission peak in the wavelength range of 440 nm to 500 nm are shown below: (2-{3-[3-(3,5-di-tert-butylphenyl)benzimidazol-1-yl-2-ylidene-κC2]phenoxy-κC2}-9-[5-(methyl-d3)-4-phenyl-2-pyridinyl-κN]carbazole-2,1-diyl-κC)platinum(II) (abbreviation: Pt(mmtBubOcz5m4ppy-d3)) represented by structural formula (400), and (2-{3-[3-(3,5-di-tert-butylphenyl)benzimidazol-1-yl-2-ylidene-κC2]phenoxy-κC2}-9-[5-(methyl-d3)-4-phenyl-2-pyridinyl-κN]carbazole-2,1-diyl-κC)platinum(II) represented by structural formula (401). 2]phenoxy-κC2}-9-(4-tert-butyl-2-pyridinyl-κN)-6-(5-cyano-2-methylphenyl)carbazole-2,1-diyl-κC)platinum(II) (abbreviation: Pt(mmtBubOm5CPcztBupy)), represented by structural formula (402): {[9-(4-tert-butyl-2-pyridinyl-κN)-[3,9'-bi-9H-carbazole]-2,1-diyl-κC]oxy-9-(4-tert-butyl-2-pyridinyl-κN)carbazole-2,1-diyl-κC}platinum(II) (abbreviation: Pt(cztBucpyOtBucpy)), {[9-(4-tert-butyl-2-pyridinyl-κN)carbazole-2,1-diyl-κC]oxy-9-(4-tert-butyl-2-pyridinyl-κN)carbazole-2,1-diyl-κC}platinum(II) (abbreviation: Pt(tBucpy2O)) represented by structural formula (403), {[9-(2-pyridinyl-κN)carbazole-2,1-diyl-κC]oxy-9-(2-pyridinyl-κN)carbazole-2,1-diyl-κC} 2-{4-methyl-3-[3-(3,5-di-tert-butylphenyl)benzimidazol-1-yl-2-ylidene-κC]phenoxy-κC}-9-[3,5-di(methyl-d3)-4-phenyl-2-pyridinyl-κN]carbazole-2,1-diyl-κC}platinum(II) (abbreviation: PtNON), (2-{4-methyl-3-[3-(3,5-di-tert-butylphenyl)benzimidazol-1-yl-2-ylidene-κC]phenoxy-κC}-9-[3,5-di(methyl-d3)-4-phenyl-2-pyridinyl-κN]carbazole-2,1-diyl-κC)platinum(II) (abbreviation: Pt(Me-mmtBubOcz35dm4ppy-d6)) represented by structural formula (406), {[3-(3,5-di-tert-butylphenyl)-9-(4-tert-butyl-2-pyridinyl-κN)carbazole-2,1-diyl-κC]oxy-9-(4-tert-butyl-2-pyridinyl-κN)carbazole-2,1-diyl-κC}platinum(II) (abbreviation: Pt(mmtBuptBucpyOtBucpy)), represented by structural formula (407): (2-{3-[3-(3,5-di-tert-butylphenyl)benzimidazol-1-yl-2-ylidene-κC2]phenoxy-κC2}-9-[3,5-di(methyl-d3)-4-phenyl-2-pyridinyl-κN]carbazole-2,1-diyl-κC)platinum(II) (abbreviation: Pt(mmtBubOcz35dm4ppy, - d6)), (2-{5-tert-butyl-3-[3-(3,5-di-tert-butylphenyl)benzimidazol-1-yl-2-ylidene-κC2]phenoxy-κC2}-9-[3,5-di(methyl-d3)-4-phenyl-2-pyridinyl-κN]carbazole-2,1-diyl-κC)platinum(II) (abbreviation: Pt(tBu-mmtBubOcz3)) represented by structural formula (408). 5dm4ppy-d6)), {2-(3-{3-[2,6-di(phenyl-d5)phenyl]benzimidazol-1-yl-2-ylidene-κC2}phenoxy-κC2)-9-[3,5-di(methyl-d3)-4-phenyl-2-pyridinyl-κN]carbazole-2,1-diyl-κC1}platinum(II) (abbreviation: Pt(mTPbOcz35dm4ppy-d 16)), and (2-{3-[3-(3,5-di-tert-butylphenyl)benzimidazol-1-yl-2-ylidene-κC2]phenoxy-κC2}-9-[4-tert-butylphenyl-3,5-di(methyl-d3)-2-pyridinyl-κN]carbazole-2,1-diyl-κC)platinum(II) (abbreviation: Pt(mmtBubOcz35dm4tBuppy-d6)) represented by structural formula (410). In addition, PtON1 represented by structural formula (411), PtON7 represented by structural formula (412), PtON1-Me represented by structural formula (413), PtON1-tBu represented by structural formula (414), PtON1-NMe2 represented by structural formula (415), PtON6-tBu represented by structural formula (416), PtON7-dtb represented by structural formula (417), PtN1N represented by structural formula (418), P represented by structural formula (419) Examples include tN1pyCl, PtON7-tBu represented by structural formula (420), Pt(ppzOczpy) represented by structural formula (421), Pt(ppzOczpy-m) represented by structural formula (422), Pt(ppzOczpy-2m) represented by structural formula (423), PdN1N represented by structural formula (424), PdN1N-dm represented by structural formula (425), and PdN6N represented by structural formula (426).

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[0139] Other examples include organometallic iridium compounds with a 4H-triazole skeleton, such as tris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-κN2]phenyl-κC}iridium(III) (abbreviation: [Ir(mpptz-dmp)3]) and tris(5-methyl-3,4-diphenyl-4H-1,2,4-triazolato)iridium(III) (abbreviation: [Ir(Mptz)3]). complexes, organometallic iridium complexes with 1H-triazole skeletons such as tris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazolato]iridium(III) (abbreviation: [Ir(Mptz1-mp)3]), tris(1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazolato)iridium(III) (abbreviation: [Ir(Prptz1-Me)3]), fac-tris[1-(2,6 -diisopropylphenyl)-2-phenyl-1H-imidazole]iridium(III) (abbreviation: [Ir(iPrpim)3]), tris[3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-f]phenanthridinato]iridium(III) (abbreviation: [Ir(dmpimpt-Me)3]), tris(2-{1-[2,6-bis(1-methylethyl)phenyl]-1H-imidazol-2-yl-κN3}-4-cyano Organometallic iridium complexes with an imidazole skeleton, such as tris[(6-tert-butyl-3-phenyl-2H-imidazo[4,5-b]pyrazin-1-yl-κC2)phenyl-κC]iridium(III) (abbreviation: [Ir(cb)3]), and organometallic complexes with a benzimidazolidene skeleton, such as tris[(6-tert-butyl-3-phenyl-2H-imidazo[4,5-b]pyrazin-1-yl-κC2)phenyl-κC]iridium(III) (abbreviation: [Ir(cb)3]). 2’ ]iridium(III) tetrakis(1-pyrazolyl)borate (abbreviation: FIr6), bis[2-(4',6'-difluorophenyl)pyridinato-N,C 2’ ]iridium(III) picolinate (abbreviation: FIrpic), bis{2-[3',5'-bis(trifluoromethyl)phenyl]pyridinato-N,C 2’}iridium(III) picolinate (abbreviation: [Ir(CF3ppy)2(pic)]), bis[2-(4',6'-difluorophenyl)pyridinato-N,C 2’ ] Organometallic iridium complexes with phenylpyridine derivatives having electron-withdrawing groups as ligands, such as iridium(III) acetylacetonate (abbreviated as FIracac), and platinum complexes such as (2-{3-[3-(3,5-di-tert-butylphenyl)benzimidazol-1-yl-2-ylidene-κC2]phenoxy-κC2}-9-(4-tert-butyl-2-pyridinyl-κN)carbazole-2,1-diyl-κC1)platinum(II) (abbreviated as PtON-TBBI) can be used.

[0140] By using the phosphorescent material, a light-emitting device with high luminous efficiency can be provided.

[0141] Further, the first light-emitting unit 501 and the second light-emitting unit 502 may include other functional layers in addition to the light-emitting layers described above. In FIG. 1A, the first light-emitting unit 501 includes a first hole-transport layer 112_1, a hole-injection layer 111, and a first electron-transport layer 114_1 in addition to the first light-emitting layer 113_1, and the second light-emitting unit 502 includes a second hole-transport layer 112_2, a second electron-transport layer 114_2, and an electron-injection layer 115 in addition to the second light-emitting layer 113_2. However, the structure of the organic compound layer 103 in one embodiment of the present invention is not limited thereto, and any of the layers may be omitted, or other layers may be provided.

[0142] 1A, the first electron-transporting layer 114_1 and the second electron-transporting layer 114_2 are illustrated as single layers, but the first electron-transporting layer 114_1 and the second electron-transporting layer 114_2 may have a single layer or a stacked structure. In addition, the first electron-transporting layer 114_1 and the second electron-transporting layer 114_2 do not necessarily have the same structure.

[0143] For example, the first electron transport layer 114_1 may be a single layer, and the second electron transport layer 114_2 may be a laminated layer. Specifically, the electron transport layer included in the cathode-side light-emitting unit (for example, the second electron transport layer 114_2 in FIG. 1A) may be a laminated layer, and the electron transport layers included in the other light-emitting units (for example, the first electron transport layer 114_1 in FIG. 1A) may be a single layer.

[0144] In one embodiment of the present invention, the electron-transporting layer included in the cathode-side light-emitting unit preferably includes at least one layer made of an organic compound having a triazine skeleton. Alternatively, the electron-transporting layer may have a stacked structure using organic compounds having different triazine skeletons. In particular, the cathode-side layer of the stacked layers preferably includes an organic compound having a triazine skeleton and an alkali metal such as Li. This structure can improve electron injection properties.

[0145] The electron transport layer included in the light-emitting unit located closer to the anode than the light-emitting unit on the cathode side (hereinafter also referred to as the anode-side light-emitting unit) may use the same organic compound as that used in the electron transport layer included in the light-emitting unit on the cathode side, or may use a different organic compound. For example, the electron transport layer may use an organic compound including a triazine skeleton that is different from the organic compound including a triazine skeleton used in the electron transport layer included in the light-emitting unit on the cathode side.

[0146] In order to reduce power consumption, it is preferable that the electron transport layer included in the light-emitting unit on the anode side also contains an organic compound containing a triazine skeleton. In particular, using the same organic compound as that used in the electron transport layer included in the light-emitting unit on the cathode side is preferable because it prevents the manufacturing equipment from becoming complicated and is advantageous in terms of raw material procurement costs.

[0147] Furthermore, the electron transport layer included in the light-emitting unit on the anode side contains an organic compound that does not contain a triazine skeleton, which makes it easier to control carrier transport properties and allows for the provision of a light-emitting device with better characteristics. Organic compounds that do not contain a triazine skeleton are preferably organic compounds that contain a heteroaromatic ring having a pyridine skeleton or a heteroaromatic ring having a diazine (pyrimidine or pyrazine) skeleton. Therefore, the electron transport layer included in the light-emitting unit on the anode side can be an organic compound that contains a triazine skeleton, a pyrimidine skeleton, an imidazole skeleton, or an anthracene skeleton.

[0148] The electron transport layer included in the light-emitting unit on the anode side may have either a laminated structure or a single-layer structure, but the laminated structure provides high current efficiency, lower power consumption, and a light-emitting device with excellent characteristics. A single-layer structure is advantageous in terms of manufacturing costs because fewer film-forming chambers are required.

[0149] The organic compound containing the triazine skeleton, which can be used in the electron transport layer included in the light-emitting unit on the anode side and the electron transport layer included in the light-emitting unit on the cathode side, has an electron mobility of 1×10 at a square root of an electric field strength [V / cm] of 600. -7 cm 2 / Vs or more, preferably 1×10 -6 cm 2 It is preferable that the material has an electron mobility of 1 / Vs or more. Note that other materials can be used as long as they have a higher electron transporting property than holes.

[0150] The organic compound containing a triazine skeleton is preferably a compound containing a triazine skeleton and an aromatic ring. The aromatic ring may be a monocyclic aromatic ring, a polycyclic aromatic ring, an aromatic ring having an alkyl group as a substituent, an aromatic ring having a fluoro group as a substituent, or an aromatic ring having a cyano group as a substituent. The triazine skeleton may have a substituent other than the aromatic ring, and the aromatic ring may have a substituent other than the fluoro group, cyano group, or alkyl group. The triazine skeleton is also called a triazine ring, and the skeleton of other skeletons can also be referred to as a ring.

[0151] Examples of the monocyclic aromatic ring include aromatic hydrocarbon rings such as a benzene ring, and heteroaromatic rings such as a pyrrole ring, a pyridine ring, a pyrimidine ring, a triazine ring, etc. Having an aromatic ring as a substituent improves heat resistance, specifically, has the effect of improving the glass transition temperature (Tg) and the effect of improving electron transport properties.

[0152] Examples of polycyclic aromatic rings include aromatic hydrocarbon rings such as naphthalene rings, phenanthrene rings, chrysene rings, triphenylene rings, fluorene rings, and spirobifluorene rings, as well as heteroaromatic rings such as carbazole rings, dibenzofuran rings, dibenzothiophene rings, xanthene rings, indolocarbazole rings, and indenocarbazole rings. Compounds having polycyclic aromatic rings as substituents are preferred because they can improve heat resistance compared to compounds having benzene rings. Furthermore, compounds having a ring in which an aromatic ring (such as a benzene ring, a naphthalene ring, or a pyridine ring) is fused to these polycyclic aromatic rings as a substituent can further improve heat resistance. Examples of rings in which an aromatic ring is fused to a polycyclic aromatic ring include a benzofluorene ring, a benzonaphthofuran ring, a benzoxanthene ring, and a benzonaphthothiophene ring. By providing a layer containing a highly heat-resistant compound near the cathode, damage to the device due to heat can be suppressed when high-temperature treatment such as a patterning step is performed after forming the layer or the cathode.

[0153] Examples of alkyl groups include methyl, ethyl, propyl, tertiary butyl, cyclohexyl, and adamantyl groups. A layer using a compound having an alkyl group as a substituent can lower the refractive index. Therefore, total reflection at the interface between the layer and other layers can be reduced, improving light extraction efficiency. Furthermore, using a compound having these substituents in the hole transport layer can also lower the refractive index. In particular, using a compound having a triazine skeleton and an alkyl group in the electron transport layer and a compound having an aromatic amine skeleton and an alkyl group in the hole transport layer can synergistically enhance the light extraction efficiency improvement effect. Furthermore, the alkyl group can be made to have multiple carbon atoms, preferably 3 or more, more preferably 4 or more, and even more preferably 5 or more, to enhance the effect. A layer using a compound having a fluoro group as a substituent is also preferred because it can lower the refractive index. In particular, having multiple fluoro groups can enhance the refractive index improvement effect. It is also effective to use a compound having a fluoro group in both the electron transport layer and the hole transport layer.

[0154] In addition, a compound having a cyano group as a substituent is preferable because it can improve the electron transport property.

[0155] It is also preferable to combine a polycyclic aromatic ring, an alkyl group, a fluoro group, or a cyano group as a substituent. For example, when a polycyclic aromatic ring and a cyano group are used as a substituent, both heat resistance and electron transport properties can be improved. Furthermore, when a polycyclic aromatic ring and an alkyl group are used as a substituent, both heat resistance and light extraction efficiency can be improved. In this way, a combination of substituents can be used depending on the desired function.

[0156] Furthermore, the heat resistance can be further improved by including a plurality of polycyclic aromatic rings as substituents. In this case, it is preferable that the aromatic hydrocarbon ring and the heteroaromatic ring are included.

[0157] Specific examples of organic compounds containing a triazine skeleton include 2-(biphenyl-4-yl)-4-phenyl-6-(9,9'-spirobi[9H-fluoren]-2-yl)-1,3,5-triazine (abbreviation: BP-SFTzn), 2-{3-[3-(benzo[b]naphtho[1,2-d]furan-8-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mBnfBPTzn), and 2-{3-[3-(benzo[b]naphtho[1,2-d]furan-6-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mBnfBPTzn). azine (abbreviation: mBnfBPTzn-02), 2-{4-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: PCCzPTzn), 9-[3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]-9'-phenyl-2,3'-bi-9H-carbazole (abbreviation: mPCCzPTzn-02), 2-[3'-(9,9-dimethyl-9H-fluoren-2-yl)biphenyl-3-yl]-4,6-diphenyl-1,3,5- triazine (abbreviation: mFBPTzn), 5-[3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]-7,7-dimethyl-5H,7H-indeno[2,1-b]carbazole (abbreviation: mINc(II)PTzn), 2-{3-[3-(dibenzothiophen-4-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mDBtBPTzn), 2,4,6-tris[3'-(pyridin-3-yl)biphenyl-3-yl]-1,3,5-triazine (abbreviation: TmPPPyTz), 2-[3-(2,6 -dimethyl-3-pyridinyl)-5-(9-phenanthryl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mPn-mDMePyPTzn), 11-[4-(biphenyl-4-yl)-6-phenyl-1,3,5-triazin-2-yl]-11,12-dihydro-12-phenylindolo[2,3-a]carbazole (abbreviation: BP-Icz(II)Tzn), 2-[3'-(triphenylen-2-yl)biphenyl-3-yl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mTpBPTzn), 3-[9-(4,6-diphenyl-1,3,5-triazin-2-yl)-2-dibenzofuranyl]-9-phenyl-9H-carbazole (abbreviation: PCDBfTzn), 2-(biphenyl-3-yl)-4-phenyl-6-{8-[(1,1':4',1''-terphenyl)-4-yl]-1-dibenzofuranyl}-1,3,5-triazine (abbreviation: mBP-TPDBfTzn), 2-[4-(2-naphthyl)phenyl]-4-phenyl-6-spiro[9H-fluorene-9,9'-[9H]xanthene]-4-yl-1,3,5-triazine (abbreviation: βN P-SFx(4)Tzn), 9,9'-{6-[3-(triphenylsilyl)phenyl]-1,3,5-triazine-2,4-diyl}bis(9H-carbazole) (abbreviated as SiTrzCz2), 2-phenyl-4,6-bis[3-(triphenylsilyl)phenyl]-1,3,5-triazine (abbreviated as mSiTrz), 11-[4-(biphenyl-4-yl)-6-phenyl-1,3,5-triazin-2-yl]-11,12-dihydro-12-(biphenyl-3-yl)indolo[2,3-a]carbazole (abbreviated as BP-mBPIcz (II)Tzn), 3-{3-[9-(4,6-diphenyl-1,3,5-triazin-2-yl)-2-dibenzofuranyl]phenyl}-9-phenyl-9H-carbazole (abbreviated as mPCPDBfTzn), 9,9'-[6-(biphenyl-4-yl)-2-phenyl-1,3,5-triazine-4,3''-diyl]bis(9H-carbazole) (abbreviated as Cz-pmCzBPTzn), 3-phenyl-9-[4-phenyl-6-(9-phenyl-3-dibenzofuranyl)-1,3,5-triazin-2-yl]-9H-carbazole ( abbreviation: PDBf-PCzTzn), 9-[4-(4,6-diphenyl-1,3,5-triazin-2-yl)-2-dibenzothienyl]-2-phenyl-9H-carbazole (abbreviation: PCzDBtTzn), 2,4-diphenyl-6-[3'-(spiro[7H-benzo[c]fluorene-7,9'-[9H]xanthene]-2'-yl)biphenyl-3-yl]-1,3,5-triazine (abbreviation: mSbfxBPTzn), 3'-[4-phenyl-6-(spiro[9H-fluorene-9,9'-[9H]xanthene]-2'-yl)-1,3,Organic compounds containing heteroaromatic rings with a triazine skeleton, such as [5-triazin-2-yl]biphenyl-4-carbonitrile (abbreviation: mpCNBP-SFxTzn) and 2,2'-(1,2-naphthalenediyldi-4,1-phenylene)bis[4,6-diphenyl-1,3,5-triazine] (abbreviation: TznP2N), can be used. Particularly preferred are TznP2N represented by the structural formula (500), mSbfxBPTzn represented by the structural formula (501), mpCNBP-SFxTzn represented by the structural formula (502), CNBPNPTzn represented by the structural formula (503), βNP-SFx(4)Tzn represented by the structural formula (504), mmtBuBP-mDMePyPTzn represented by the structural formula (505), and mBnfBPTzn represented by the structural formula (506).

[0158] [ka]

[0159] In addition, materials that can be used for the electron transport layer included in the light-emitting unit on the anode side are those having an electron mobility of 1×10 at a square root of an electric field strength [V / cm] of 600 or less. -7 cm 2 / Vs or more, preferably 1×10 -6 cm 2 A substance having an electron mobility of 1 / Vs or more is preferred. Note that other substances can be used as long as they have a higher electron transport property than holes. Note that the organic compound is preferably an organic compound having a π-electron-deficient heteroaromatic ring. Examples of the organic compound having a π-electron-deficient heteroaromatic ring include, for example, one or more of an organic compound having a heteroaromatic ring with an azole skeleton, an organic compound having a heteroaromatic ring with a pyridine skeleton, an organic compound having a heteroaromatic ring with a diazine skeleton, and an organic compound having a heteroaromatic ring with a triazine skeleton. An organic compound having a heteroaromatic ring with a triazine skeleton is particularly preferred. Note that organic compounds obtained by appropriately deuterating the above-listed organic compounds can also be used.

[0160] As an organic compound having electron transport properties that can be used in the electron transport layer included in the light-emitting unit on the anode side, the electron transport materials described below can be used. In particular, organic compounds containing a heteroaromatic ring having a diazine skeleton, organic compounds containing a heteroaromatic ring having a pyridine skeleton, and organic compounds containing a heteroaromatic ring having a triazine skeleton are preferred because of their high reliability. In particular, organic compounds containing a heteroaromatic ring having a diazine (pyrimidine or pyrazine) skeleton and organic compounds containing a heteroaromatic ring having a triazine skeleton have high electron transport properties and can reduce driving voltage.

[0161] In addition, in one embodiment of the present invention, in the tandem light-emitting device, the intermediate layer 160 preferably contains an organic compound containing a phenanthroline skeleton.

[0162] The organic compound containing the phenanthroline skeleton has an electron mobility of 1×10 at a square root of an electric field strength [V / cm] of 600. -7 cm 2 / Vs or more, preferably 1×10 -6 cm 2 It is preferable that the material has an electron mobility of 1 / Vs or more. Note that other materials can be used as long as they have a higher electron transporting property than holes.

[0163] The organic compound containing a phenanthroline skeleton is preferably a compound containing a phenanthroline skeleton and an aromatic ring, and the aromatic ring may be a monocyclic aromatic ring or a polycyclic aromatic ring.

[0164] Examples of monocyclic aromatic rings include a benzene ring, a pyrrole ring, a pyridine ring, and a pyrimidine ring. Furthermore, polycyclic aromatic rings preferably include aromatic hydrocarbon rings such as a naphthalene ring, a phenanthrene ring, a chrysene ring, a triphenylene ring, and a fluorene ring, and heteroaromatic rings such as a phenanthroline ring and a pyrrole ring. In particular, containing a plurality of these polycyclic aromatic rings is preferable because it can improve heat resistance or electron transport properties.

[0165] Examples of organic compounds containing a phenanthroline skeleton include bathophenanthroline (abbreviation: Bphen), bathocuproine (abbreviation: BCP), 2,9-di(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline (abbreviation: NBphen), 2,2'-(1,3-phenylene)bis(9-phenyl-1,10-phenanthroline) (abbreviation: mPPhen2P), 2-[3-(2-triphenylenyl)phenyl]-1,10-phenanthroline (abbreviation: mTpPPhen), and 2-phenyl-9-(2

[0043] Organic compounds containing a heteroaromatic ring having a phenanthroline skeleton, such as 2-[4-(9-phenanthryl)-1-naphthyl]-1,10-phenanthroline (abbreviation: Ph-TpPhen), 2-[4-(9-phenanthryl)-1-naphthyl]-1,10-phenanthroline (abbreviation: PnNPhen), and 2-[4-(2-triphenylenyl)phenyl]-1,10-phenanthroline (abbreviation: pTpPPhen), can be used. However, PnNPhen shown in the following structural formula (200) or mPPhen2P shown in structural formula (201) is particularly preferred.

[0166] [ka]

[0167] In the light-emitting device of one embodiment of the present invention, the intermediate layer may have any structure as long as it contains an organic compound having a phenanthroline skeleton and can inject electrons into the light-emitting unit on the anode side and holes into the light-emitting unit on the cathode side, both of which are in contact with the intermediate layer, by applying a voltage between the first electrode and the second electrode. However, as shown in Figure 1(A), the intermediate layer 160 preferably has a stacked structure including a first layer 161 containing an organic compound and a second layer 162 located closer to the cathode than the first layer.

[0168] The first layer preferably contains a metal or a metal compound in addition to an organic compound. The metal or metal in the metal compound is preferably an alkali metal (Group 1 element) such as Li, an alkaline earth metal (Group 2 element) such as Mg or Ca, a Group 3 element including a lanthanide such as Y, Eu, or Yb, a Group 11 element such as Cu, Ag, or Au, a Group 12 element such as Zn, or an earth metal (Group 13 element) such as Al or In.

[0169] The first layer may have a stacked structure of a layer containing an organic compound and a layer containing a metal or metal compound located closer to the cathode than the layer containing the organic compound. Alternatively, the first layer may be a mixed layer of an organic compound and a metal or metal compound. The mixed layer is preferable for the first layer because it requires fewer deposition chambers, reduces manufacturing costs, and also contributes to improving the stability of the light-emitting device.

[0170] When an organic compound and a metal or metal compound are mixed, the distribution of the organic compound and the distribution of the metal or metal compound show roughly the same tendency when the first layer is analyzed in the film thickness direction. That is, when the distribution of the organic compound is constant, the distribution of the metal or metal compound is also roughly constant. In the case of a laminated structure of a layer containing an organic compound and a layer having a metal or metal compound, the metal or metal compound may be detected in areas other than the layer having the metal or metal compound due to diffusion from the layer having the metal or metal compound, but since the distribution shows a different distribution from the distribution of the organic compound, the analysis results can be distinguished between diffusion and mixing.

[0171] Furthermore, when the first layer is analyzed in the film thickness direction, if there is a region in which a metal or metal compound is detected that is 10 nm or more, preferably 15 nm or more, and more preferably 20 nm or more, the first layer can be considered to have a mixed layer in which an organic compound and a metal or metal compound are mixed.

[0172] In particular, the metal in the metal or metal compound is preferably a substance that exhibits donor properties toward an organic compound having a phenanthroline skeleton. Examples of substances that exhibit donor properties toward an organic compound having a phenanthroline skeleton include metals of Group 1 and Group 2, with lithium or a lithium compound being particularly preferred. Specifically, Li, lithium fluoride (LiF), lithium oxide (LiO), and 8-quinolinolato-lithium (abbreviation: Liq) are preferred. When the first layer contains an organic compound having a phenanthroline skeleton and a substance that exhibits donor properties toward the organic compound having a phenanthroline skeleton, electrons are generated by charge separation. When a voltage is applied between the first electrode and the second electrode, the electrons are injected into the light-emitting unit on the anode side via the organic compound having a phenanthroline skeleton. This allows the light-emitting device of one embodiment of the present invention to have a low driving voltage.

[0173] In addition to the organic compounds described above, preferred organic compounds containing a phenanthroline skeleton include those containing a phenanthroline skeleton with an electron-donating substituent. The phenanthroline skeleton is a skeleton that easily interacts with metals, etc., and when such an organic compound containing a phenanthroline skeleton further contains an electron-donating group, the electron density of the phenanthroline skeleton increases, making it more likely to interact with metals or metal compounds. In particular, when a metal belonging to Groups 3, 11, 12, or 13 is used as the metal or the metal in the metal compound, an increase in driving voltage can be suppressed, and a tandem light-emitting device with excellent characteristics can be provided.

[0174] Specific examples of the electron-donating group include an alkyl group, an alkoxy group, an aryloxy group, an alkylamino group, an arylamino group, and a heterocyclic amino group. However, the electron-donating group that is preferably introduced into the phenanthroline ring is not limited to these. Any group that can increase the electron density of the phenanthroline ring by introducing it into the phenanthroline ring can be used as the electron-donating group. In addition, the electron-donating group may be introduced into the phenanthroline ring via an arylene group such as a phenylene group, and the arylene group is preferably a p-phenylene group.

[0175] Specific examples of organic compounds containing a phenanthroline skeleton having an electron-donating substituent are shown in structural formulas (203) to (213).

[0176] [ka]

[0177] Note that a configuration in which the first layer contains an element of Group 1 or Group 2, particularly lithium or a lithium compound, and an organic compound containing a phenanthroline skeleton with an electron-donating substituent is preferable because it can provide a tandem light-emitting device with lower drive voltage and better reliability. Furthermore, a configuration in which the first layer contains an element of Group 1 or Group 2, particularly lithium or a lithium compound, and an organic compound containing a phenanthroline skeleton with an electron-donating substituent is preferable because it can suppress an increase in drive voltage when processing the organic compound layer of the light-emitting device by photolithography.

[0178] In an intermediate layer having the above-described configuration, organic compounds containing a phenanthroline skeleton, particularly organic compounds containing a 1,10-phenanthroline skeleton, are preferred because the two nitrogen atoms contained therein can coordinate to a metal, and therefore interaction with a metal or metal compound is likely to occur.

[0179] When an electron-donating group is introduced into the 1,10-phenanthroline skeleton, the electron-donating group is preferably substituted at positions 4 and 7 of the 1,10-phenanthroline skeleton. By introducing the electron-donating group into positions 4 and 7 of the 1,10-phenanthroline skeleton, the electron density of the nitrogen atoms at positions 1 and 10 can be increased, making it easier for the 1,10-phenanthroline skeleton to interact with a metal or metal compound.

[0180] The first layer may further contain an organic compound different from the organic compound containing a phenanthroline skeleton. The organic compound is preferably an organic compound having electron transport properties. In particular, the organic compound preferably has two or more heteroaromatic rings bonded or condensed to each other, and the two or more heteroaromatic rings preferably have a total of three or more heteroatoms. By including such an organic compound in the first layer, improvements in heat resistance and electron transport properties can be achieved.

[0181] The second layer 162 preferably contains an organic compound having a hole-transporting property. The second layer 162 preferably further contains a substance exhibiting an accepting property, and the substance exhibiting an accepting property is preferably an organic compound exhibiting an accepting property to an organic compound having a hole-transporting property. As the substance exhibiting an accepting property, an organic compound having at least one of a halogen group and a cyano group is particularly preferable, and an organic compound having at least one of a fluorine group and a cyano group is more preferable. It is more preferable that the organic compound contains four or more halogen groups (fluorine) and cyano groups in total.

[0182] When the second layer 162 contains an organic compound having a hole-transporting property and a substance that accepts the organic compound having a hole-transporting property, holes are generated by charge separation, and when a voltage is applied between the first electrode and the second electrode, the holes are injected into the light-emitting unit on the cathode side through the organic compound having a hole-transporting property. This allows the light-emitting device of one embodiment of the present invention to have a low driving voltage.

[0183] The intermediate layer may have a third layer 163 between the first layer 161 and the second layer 162 .

[0184] The third layer contains a substance having an electron transporting property and has functions such as reducing the driving voltage by smoothing the transfer of electrons between the first layer 161 and the second layer 162, and improving reliability by reducing the interaction between the first layer 161 and the second layer 162.

[0185] The thickness of the third layer 163 is preferably 1 nm or more and 10 nm or less, more preferably 2 nm or more and 5 nm or less, in order to suppress an increase in the driving voltage.

[0186] The light-emitting device of the present invention having the above-described structure can be a light-emitting device with high current efficiency, low energy loss, and favorable characteristics. In addition, a display device according to one embodiment of the present invention using such a light-emitting device can be a display device with low power consumption, high reliability, and high luminance and thus favorable visibility.

[0187] In one embodiment of the present invention, in a tandem light-emitting device, the first hole-transport layer 112_1 and the second hole-transport layer 112_2 are preferably formed using an organic compound having an amine skeleton and a polycyclic hydrocarbon, more preferably an organic compound having an amine skeleton and a polycyclic aromatic hydrocarbon, or even more preferably an organic compound having an amine skeleton and a fluorene skeleton. Organic compounds having an amine skeleton and a fluorene skeleton have good reliability and can enhance hole-transport properties. Use of such organic compounds can reduce the power consumption of the tandem light-emitting device.

[0188] The first hole-transport layer 112_1 and the second hole-transport layer 112_2 may have a stacked structure. Specifically, a material having excellent hole-transport properties, poor electron-transport properties, and a high lowest unoccupied molecular orbital (LUMO) level is used as the hole-transport layer in contact with the first light-emitting layer 113_1 or the second light-emitting layer 113_2. In particular, the hole-transport layer may be formed using a material having a LUMO level higher than the LUMO level of the material constituting the light-emitting layer (at least the host material, preferably a host material having electron-transport properties, the material with the largest composition ratio among the materials constituting the light-emitting layer, or the material with the highest LUMO level among the materials constituting the light-emitting layer), preferably 0.30 eV or more, more preferably 0.5 eV or more higher. Organic compounds having a π-electron-rich polycyclic heteroaromatic ring, particularly organic compounds having a carbazole skeleton or a bicarbazole skeleton, are stable and reliable, and therefore suitable for the first hole transport layer 112_1 and the second hole transport layer 112_2.

[0189] By forming the first hole-transport layer 112_1 as a stacked structure and using a material having a LUMO level higher than that of the material constituting the light-emitting layer for a layer in contact with the first light-emitting layer 113_1, it is possible to prevent electrons from passing through from the first light-emitting layer 113_1 to the first electrode 101. Similarly, by forming the second hole-transport layer 112_2 as a stacked structure and using a material having a LUMO level higher than that of the material constituting the light-emitting layer for a layer in contact with the second light-emitting layer 113_2, it is possible to prevent electrons from passing through from the second light-emitting layer 113_2 to the intermediate layer 160, and therefore it is possible to manufacture a highly efficient and long-life display device.

[0190] Furthermore, when a red or green phosphorescent material is used in the light-emitting layer, the T1 level of the organic compound used in the first hole-transport layer 112_1 and the second hole-transport layer 112_2 is preferably higher than the T1 level of the phosphorescent material. In particular, by using such a structure for the hole-transport layer in contact with the light-emitting layer, the excitation energy of excitons generated by carrier recombination in the light-emitting layer can be prevented from diffusing to the layer in contact with the light-emitting layer, resulting in a light-emitting device with high luminous efficiency. On the other hand, when a blue phosphorescent material is used in the light-emitting layer, a stable and reliable light-emitting device can be obtained by using an organic compound having a T1 level lower than the T1 level of the phosphorescent material in the layer in contact with the light-emitting layer. Furthermore, by making the T1 level of the organic compound used in one of the layers in contact with the anode side and the cathode side of the light-emitting layer higher than the T1 level of the phosphorescent material and by making the T1 level of the organic compound used in the other layer lower than the T1 level of the phosphorescent material, a light-emitting device with high luminous efficiency and high stability and reliability can be obtained. However, since the use of an organic compound with a significantly lower T1 level in the layer in contact with the light-emitting layer tends to reduce the luminous efficiency, by making the energy difference between the T1 level of the phosphorescent material and the T1 level of the organic compound used in the layer in contact with the light-emitting layer 0.1 eV or more, preferably 0.2 eV or more and 1.0 eV or less, preferably 0.5 eV or less, the reduction in luminous efficiency can be avoided and a light-emitting device with high stability and reliability can be obtained.

[0191] In other words, by forming the first hole transport layer 112_1 and the second hole transport layer 112_2 into a stacked structure in which organic compounds having different polycyclic aromatic rings and different properties are combined, the design freedom of the display device can be improved.

[0192] Specifically, organic compounds containing either or both of an aromatic amine skeleton and a π-electron-rich heteroaromatic ring are preferably used as organic compounds that can be used for the first hole-transport layer 112_1 and the second hole-transport layer 112_2. Examples of aromatic rings contained in organic compounds containing an aromatic amine skeleton include monocyclic aromatic rings and polycyclic aromatic rings. These aromatic rings may also have an alkyl group as a substituent.

[0193] Examples of monocyclic aromatic rings include aromatic hydrocarbon rings such as benzene rings and heteroaromatic rings such as pyrrole rings and furan rings. Having an aromatic ring as a substituent improves heat resistance and increases the glass transition temperature (Tg). Having an aromatic ring as a substituent also has the effect of adjusting the transportability of carriers such as holes or electrons. Having multiple monocyclic aromatic rings can further increase Tg, and for example, a biphenyl structure or a terphenyl structure is preferred. The compound may have a paraphenylene structure, a metaphenylene structure, or an orthophenylene structure. Having at least one metaphenylene structure or an orthophenylene structure can improve the solubility of the compound, facilitate production, and also reduce the refractive index. In addition, when a compound has three or more benzene rings, such as a terphenyl structure, having an aromatic ring containing at least two of a paraphenylene structure, a metaphenylene structure, and an orthophenylene structure is preferred because it can adjust the solubility and refractive index as well as the carrier transportability.

[0194] In addition, when a benzene ring is used as a linking group, it is usually called a phenylene group, but to avoid complicating the explanation, it may also be called a phenyl group when used as a linking group. Similarly, when other aromatic rings are used as linking rings, they may be called an aryl group instead of an arylene group, or a heteroaryl group instead of a heteroarylene group. Furthermore, the term benzene ring may be referred to as a benzene structure or a benzene skeleton, and such terminology applies to other substituents (such as aromatic rings).

[0195] Examples of polycyclic aromatic rings include aromatic hydrocarbon rings such as naphthalene rings, phenanthrene rings, chrysene rings, triphenylene rings, fluorene rings, and spirobifluorene rings, as well as heteroaromatic rings such as carbazole rings, dibenzofuran rings, dibenzothiophene rings, and xanthene rings. Compounds having polycyclic aromatic rings as substituents are preferred because they can improve heat resistance compared to compounds having monocyclic aromatic rings. It is also preferred to have multiple of these polycyclic aromatic rings. When multiple polycyclic aromatic rings are present, they may be the same or different. When the rings are the same, examples include structures having multiple aromatic hydrocarbon rings, structures having multiple heteroaromatic rings, and structures having one or more aromatic hydrocarbon rings and one or more heteroaromatic rings. When the rings are the same, reduction in raw material costs and simplification of the synthesis process can be expected. When different aromatic rings are used, the transport properties of carriers such as holes or electrons, or the Tg, can be adjusted depending on the type of aromatic ring used. Examples of polycyclic aromatic rings include a structure having a carbazole ring and a dibenzofuran ring, a structure having two, three, or four or more carbazole rings, and a structure having two, three, or four or more fluorene rings.

[0196] Furthermore, in the case of a compound having a ring in which an aromatic ring (such as the monocyclic aromatic ring described above) is further fused to the polycyclic aromatic ring as a substituent, the heat resistance can be further improved. Examples of the ring in which an aromatic ring is further fused to the polycyclic aromatic ring include a benzofluorene ring, a benzonaphthofuran ring, a benzoxanthene ring, and a benzonaphthothiophene ring.

[0197] The monocyclic aromatic ring and the polycyclic aromatic ring can be used as substituents. Examples include a structure in which a monocyclic aromatic ring is used as a linking group between the nitrogen in the amine skeleton and the polycyclic aromatic ring. Examples include a structure in which a phenylene group is used between the nitrogen and the fluorene ring, a structure in which a phenylene group is used between the nitrogen and the carbazole ring, or a structure in which a phenylene group is used between the nitrogen and the dibenzofluorene ring. A structure in which multiple polycyclic aromatic rings are bonded to one phenylene group used as a linking group is also effective. The multiple polycyclic aromatic rings may be the same or different aromatic rings. For example, a compound in which both a carbazole ring and a dibenzofluorene ring are bonded to one phenylene group can improve Tg and obtain the functions of both the carbazole ring and the dibenzofluorene ring.

[0198] Examples of alkyl groups include methyl, ethyl, propyl, tertiary butyl, cyclohexyl, and adamantyl groups. A layer using a compound having an alkyl group as a substituent can lower the refractive index. Therefore, total reflection at the interface between the layer and other layers can be reduced, improving light extraction efficiency. Furthermore, using a compound having such a substituent in the hole transport layer can also reduce the refractive index. In particular, using a compound having an aromatic amine skeleton and an alkyl group in the hole transport layer can synergistically enhance the effect of improving light extraction efficiency. Furthermore, the effect can be enhanced when the alkyl group has multiple carbon atoms, preferably 3 or more, more preferably 4 or more, and even more preferably 5 or more. Furthermore, multiple alkyl groups bonded to one aromatic ring are preferred because they can further reduce the refractive index. In this case, the multiple alkyl groups may be the same or different. For example, two or three tertiary butyl groups may be bonded to one benzene ring. Furthermore, when multiple aromatic rings are present, alkyl groups bonded to two or more aromatic rings can reduce the refractive index. Furthermore, the refractive index can be adjusted by including alkyl groups on some of the multiple aromatic rings. For example, when there are three aromatic rings, there may be a structure in which two of the aromatic rings have alkyl groups and the remaining aromatic ring does not have an alkyl group.

[0199] Specific examples of organic compounds containing an aromatic amine skeleton are shown as the following structural formulas (300) to (330). In particular, BBASF (4) shown in structural formula (300), oBBASF shown in structural formula (301), BBAFLP (4) shown in structural formula (302), oFBiSF (2) shown in structural formula (303), FBiSF (4) shown in structural formula (304), oFBiSF shown in structural formula (305), FBimFLP shown in structural formula (306), and FBimMemFL shown in structural formula (307). P, SF(4)FAF represented by structural formula (308), FrBBiFLP represented by structural formula (309), tBu-oFBiSF(2) represented by structural formula (310), FBiFLPB represented by structural formula (311), DBfBBFLP(2) represented by structural formula (312), FLP2oBP represented by structural formula (313), PCAFLP(2)-02 represented by structural formula (314), and tBu2FoFBi represented by structural formula (316), oFrTPPnox represented by structural formula (317), mPDBfBNBN represented by structural formula (317), BBAaBnf(7) represented by structural formula (318), DBfBB1TP represented by structural formula (319), BOx3Am represented by structural formula (320), BBA2BP represented by structural formula (321), PCBBi1BP represented by structural formula (322), structural formula (323) YGBBiBP-02 represented by the structural formula (324), YGBBiBP represented by the structural formula (324), PCBBiTP represented by the structural formula (325), YGBBiPDBf represented by the structural formula (326), BPPCA represented by the structural formula (327), PCBBiF represented by the structural formula (328), DBf-YGBBiBP represented by the structural formula (329), and YGTPDBfB represented by the structural formula (330) are preferred.

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[0204] For example, it is preferable to use an organic compound having an amine skeleton and a polycyclic heteroaromatic ring among the organic compounds represented by structural formulas (300) to (330) for the first hole-transport layer 112_1 and the second hole-transport layer 112_2.

[0205] In addition, it is preferable that the layer in contact with the light-emitting layer out of the first hole-transporting layer 112_1 and the second hole-transporting layer 112_2 does not have an amine skeleton and an organic compound having a π-electron-rich polycyclic heteroaromatic ring.Specific examples of organic compounds used in the first hole transport layer 112_1 and the second hole transport layer 112_2, which are in contact with the light-emitting layer, include 9-[3-(triphenylsilyl)phenyl]-3,9'-bi-9H-carbazole (abbreviation: PSiCzCz) represented by structural formula (350), 9'-[3-(triphenylsilyl)phenyl]-9'H-9,3':6',9''-terecarbazole (abbreviation: PSiCzGI) represented by structural formula (351), and 9,9''-(1,3-phenylene)bis(3,9'-bi-9H-carbazole) (abbreviation: mCzCz2P), 1,3-bis(N-carbazolyl)benzene (abbreviation: mCP) represented by structural formula (353), 9,9''-[3,3'-(diphenylsilyl)diphenyl]bis(3,9'-bi-9H-carbazole) (abbreviation: mCzCz2PSi) represented by structural formula (354), 3,3'-9H-carbazol-9-yl-biphenyl (abbreviation: mCBP) represented by structural formula (359), 9'-phenyl-9'H-9,3':6',9''-tercarbazole (abbreviation: PhCzGI) represented by structural formula (360), 12-[3-(9H -carbazol-9-yl)phenyl]-5,12-dihydro-5-phenyl-indolo[3,2-a]carbazole (abbreviation: mCzPICz), 5,12-bis[3-(9H-carbazol-9-yl)phenyl]-5,12-dihydro-indolo[3,2-a]carbazole (abbreviation: mCzP2ICz) represented by structural formula (362), 5-[3-(9H-carbazol-9-yl)phenyl]-5,12-dihydro-12-phenyl-indolo[3,2-a]carbazole (abbreviation: mCzPICz-02) represented by structural formula (3 Examples of such compounds include 12,12'-(1,4-phenylene)bis(5,12-dihydro-5-phenyl-indolo[3,2-a]carbazole) (abbreviation: ICz2P) represented by structural formula (64), 12,12'-(1,3-phenylene)bis(5,12-dihydro-5-phenyl-indolo[3,2-a]carbazole) (abbreviation: mICz2P) represented by structural formula (365), and 5,5'-(1,3-phenylene)bis(5,12-dihydro-12-phenyl-indolo[3,2-a]carbazole) (abbreviation: mICz2P-02) represented by structural formula (366).Further, organic compounds represented by structural formulas (355) to (358) can be used. When the organic compounds represented by structural formulas (350) to (366) are used in a blue light-emitting device, for example, they can be used in the first hole-transport layer 112_1 and the second hole-transport layer 112_2, which are in contact with the light-emitting layer. Further, the organic compounds represented by structural formulas (350) to (366) can also be used as host materials for the light-emitting layer of a blue light-emitting device, for example.

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[0208] Furthermore, when the first hole-transport layer 112_1 and the second hole-transport layer 112_2 have a stacked structure, the layer in contact with the light-emitting layer may be made of an organic compound having a LUMO level and a T1 level higher than those of the material constituting the light-emitting layer (at least the host material, preferably the material constituting the light-emitting layer). Specifically, an organic compound having a π-electron-rich heteroaromatic ring or a polycyclic heteroaromatic ring may be used. A specific example of a π-electron-rich heteroaromatic ring or a polycyclic heteroaromatic ring is a carbazole skeleton. The carbazole skeleton is preferred because of its stability and reliability. More preferably, an organic compound having two or more carbazole skeletons may be used. A bicarbazole skeleton is preferred because of its stability and reliability. A bicarbazole skeleton in which two carbazolyl groups are bonded to each other at any of the 2- to 4-positions is particularly preferred because of its high donor property. Examples of the bicarbazole skeleton include 2,2'-bi-9H-carbazole, 3,3'-bi-9H-carbazole, 4,4'-bi-9H-carbazole, 2,3'-bi-9H-carbazole, 2,4'-bi-9H-carbazole, and 3,4'-bi-9H-carbazole. Furthermore, a bicarbazole skeleton in which two carbazolyl groups are bonded to each other at any one of the 2- to 4-positions and the 9-position has a large band gap and a high excitation energy level, making it suitable for blue-light-emitting devices. Examples of the bicarbazole skeleton include 2,9'-bi-9H-carbazole, 3,9'-bi-9H-carbazole, and 4,9'-bi-9H-carbazole. Specific examples include 9-[3-(triphenylsilyl)phenyl]-3,9'-bi-9H-carbazole (abbreviation: PSiCzCz), 9'-phenyl-9'H-9,3':6',9''-tercarbazole (abbreviation: PhCzGI), 12-[3-(9H-carbazol-9-yl)phenyl]-5,12-dihydro-5-phenyl-indolo[3,2-a]carbazole (abbreviation: mCzPICz), and 3,3'-bis(9-phenyl-9H-carbazole) (abbreviation: PCCP).

[0209] Here, among the multiple layers (e.g., hole transport layer, intermediate layer, light-emitting layer, electron transport layer, capping layer, etc.) that the light-emitting device has, the compound used in one layer and the compound used in another layer may be different compounds and may contain the same aromatic ring (monocyclic aromatic ring or polycyclic aromatic ring) as a substituent. By containing the same aromatic ring even if the compounds are different, it is expected that the cost of raw materials when producing the compound will be reduced or the number of synthesis steps will be shortened.

[0210] Aromatic rings that can be used in these different compounds include fused rings (also called fused structures) such as naphthalene, fluorene, benzofluorene, triphenylene, benzonaphthofuran, xanthene, benzoxanthene, spirofluorenexanthene (also called SFx), spirobenzofluorenexanthene (also called Sbfx), carbazole, benzocarbazole, dibenzofuran, dibenzothiophene, and benzonaphthothiophene. These structures are shown below. When the aromatic ring shown below has a substituent, any one of the carbon atoms or nitrogen atoms is a bond.

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[0212] Furthermore, these fused rings can adjust the carrier transport property or Tg depending on the position at which they are bonded to other groups (also referred to as the bonding position), and therefore can be used as skeletons contained in materials constituting various layers. For example, it is preferable to use a material containing a naphthalene ring with a bonding position at the 1-position as the electron transport layer material and a material containing a naphthalene ring with a bonding position at the 2-position as the hole transport layer material. It is also preferable to use a material containing a naphthalene ring with a bonding position at the 2-position as the host material for the light-emitting layer and a material containing a naphthalene ring with a bonding position at the 1-position as the hole transport layer material. When a naphthalene ring is used as a linking group, it is preferable to use a material containing a naphthalene ring with bonding positions at the 1- and 2-positions as the electron transport layer material and a material containing a naphthalene ring with bonding positions at the 1- and 6-positions as the host material for the light-emitting layer. In this way, it is preferable to use the same fused ring with different bonding positions in a compound used in one layer and a compound used in another layer.

[0213] Furthermore, when the same fused ring is used in multiple layers, it is preferable to use different substituents, such as using a fused ring with a cyano group bonded (e.g., a naphthalene ring) as the material for the electron transport layer and a fused ring with an alkyl group bonded (e.g., a naphthalene ring) as the material for the hole transport layer, making it possible to provide materials suited to the properties required for each layer.

[0214] Furthermore, when aromatic rings are used in multiple layers, they are not limited to the same aromatic ring, and aromatic rings with structural isomerism may also be used. Using aromatic rings with structural isomerism may also allow for production using the same raw materials, as described above, which can reduce raw material costs or shorten the synthesis steps. For example, structural isomers of benzonaphthofuran rings include three condensed structures, depending on the condensed position of the benzene ring: benzo[b]naphtho[2,1-d]furan ring (also referred to as aBnf skeleton), benzo[b]naphtho[2,3-d]furan ring (also referred to as Bnf(II) skeleton), and benzo[b]naphtho[1,2-d]furan ring (also referred to as Bnf skeleton). Specific structures of these skeletons are shown below. When the benzonaphthofuran ring below has a substituent, one of the carbons or nitrogen atoms is a bond.

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[0216] When aromatic rings having structural isomerism are used, a material having the aBnf skeleton can be used as the material for the electron transport layer, a material having the Bnf(II) skeleton can be used as the host material for the light-emitting layer, and a material having the Bnf skeleton can be used as the material for the hole transport layer. Materials using aromatic rings having structural isomerism have different properties (carrier transport properties, HOMO, LUMO, etc.), so by using an aromatic ring appropriate for the properties required for each layer, it is possible to adjust the Tg, reduce raw material costs, shorten the synthesis steps, and also improve properties.

[0217] It is also preferable that each host material in each light-emitting layer of the red, green, and blue light-emitting devices contains aromatic rings that are structurally isomeric. When different materials are used for the hole transport layer materials of each color, aromatic rings that are structurally isomeric may be contained. When multiple electron transport layers are used, it is also preferable that the multiple layers contain aromatic rings that are structurally isomeric. The same applies to when multiple hole transport layers are used. Thus, it is preferable that multiple materials used in the light-emitting device contain aromatic rings that are structurally isomeric. When structurally isomeric aromatic rings contain a fused ring structure, they can also be referred to as aromatic rings with the same molecular weight but different fused positions. This is true not only for benzonaphthofuran rings, but also for the other aromatic rings mentioned above (e.g., benzofluorene rings, benzoxanthene rings, spirobenzofluorenexanthene rings, benzocarbazole rings, and benzonaphthothiophene rings). As described above, the term "benzonaphthofuran ring" includes structural isomers such as aBnf, Bnf(II), and Bnf, and similarly includes structural isomers of other fused rings.

[0218] Each fused ring in the structural formula may have a substituent. Different compounds may have the same substituent or different substituents.

[0219] The first light-emitting unit 501 and the second light-emitting unit 502 may include other functional layers in addition to the above-described light-emitting layer, hole-transport layer, electron-transport layer, etc. The structure is not limited to that shown in Figure 1(A), and any of the layers may be omitted, or other layers may be provided. Representative examples of such other layers include a carrier block layer and an exciton block layer.

[0220] When a red or green phosphorescent material is used, the T1 level of the organic compound used in the carrier blocking layer is preferably higher than the T1 level of the phosphorescent material. This configuration can prevent the excitation energy of excitons generated by carrier recombination in the light-emitting layer from diffusing to the carrier blocking layer, resulting in a light-emitting device with high luminous efficiency. On the other hand, when a blue phosphorescent material is used in the light-emitting layer, a stable and reliable light-emitting device can be achieved by using an organic compound having a T1 level lower than the T1 level of the phosphorescent material in the carrier blocking layer. Furthermore, by using an organic compound in one of the carrier blocking layers in contact with the anode and cathode of the light-emitting layer that has a T1 level higher than the T1 level of the phosphorescent material and an organic compound in the other layer that has a T1 level lower than the T1 level of the phosphorescent material, a light-emitting device with high luminous efficiency, stability, and reliability can be achieved. However, when an organic compound with a significantly low T1 level is used in the carrier blocking layer, the luminous efficiency is likely to decrease. Therefore, by making the energy difference between the T1 level of the phosphorescent material and the T1 level of the organic compound used in the carrier blocking layer 0.1 eV or more, preferably 0.2 eV or more and 1.0 eV or less, preferably 0.5 eV or less, it is possible to avoid a decrease in luminous efficiency and to obtain a stable and reliable light-emitting device.

[0221] The first electrode 101 is an electrode including an anode. The first electrode 101 may have a stacked structure, in which case the layer in contact with the organic compound layer 103 functions as the anode. The anode is preferably formed using a metal, alloy, conductive compound, or mixture thereof having a large work function (specifically, 4.0 eV or more). Specific examples include indium tin oxide (ITO), indium tin oxide containing silicon or silicon oxide, indium zinc oxide, and indium oxide containing tungsten oxide and zinc oxide (IWZO). These conductive metal oxide films are usually formed by sputtering, but may also be formed by applying a sol-gel method or the like. For example, indium zinc oxide may be formed by sputtering using a target in which 1 to 20 wt % of zinc oxide is added to indium oxide. Indium oxide containing tungsten oxide and zinc oxide (IWZO) can also be formed by sputtering using a target containing 0.5 to 5 wt % tungsten oxide and 0.1 to 1 wt % zinc oxide relative to indium oxide. Other materials that can be used for the anode include gold (Au), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), and nitrides of metal materials (e.g., titanium nitride). Graphene can also be used for the anode. Note that using the composite material constituting the first layer 161 (also referred to as a P-type layer) in the intermediate layer 160 as a layer in contact with the anode (typically a hole injection layer) allows for the selection of an electrode material regardless of the work function.

[0222] The hole injection layer 111 is provided in contact with the anode and has the function of facilitating injection of holes into the organic compound layer 103 (first light-emitting unit 501). The hole injection layer 111 can be formed of a phthalocyanine-based compound or complex compound such as phthalocyanine (abbreviation: HPc) or copper phthalocyanine (abbreviation: CuPc), an aromatic amine compound such as 4,4'-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation: DPAB) or 4,4'-bis(N-{4-[N'-(3-methylphenyl)-N'-phenylamino]phenyl}-N-phenylamino)biphenyl (abbreviation: DNTPD), or a polymer such as poly(3,4-ethylenedioxythiophene) / polystyrenesulfonic acid (abbreviation: PEDOT / PSS).

[0223] Alternatively, the hole injection layer 111 may be formed of a substance having electron acceptor properties. Examples of the substance having acceptor properties include organic compounds having an electron-withdrawing group (such as a halogen group or a cyano group), such as 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation: F4-TCNQ), chloranil, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviation: HAT-CN), 1,3,4,5,7,8-hexafluorotetracyano-naphthoquinodimethane (abbreviation: F6-TCNNQ), and 2-(7-dicyanomethylene-1,3,4,5,6,8,9,10-octafluoro-7H-pyren-2-ylidene)malononitrile. In particular, compounds in which an electron-withdrawing group is bonded to a fused aromatic ring having multiple heteroatoms, such as HAT-CN, are preferred because of their thermal stability. Radialene derivatives having electron-withdrawing groups (especially halogen groups such as fluoro groups, cyano groups, etc.) are also preferred because of their extremely high electron-accepting properties. Specific examples include α,α',α''-1,2,3-cyclopropanetriylidenetris[4-cyano-2,3,5,6-tetrafluorobenzeneacetonitrile], α,α',α''-1,2,3-cyclopropanetriylidenetris[2,6-dichloro-3,5-difluoro-4-(trifluoromethyl)benzeneacetonitrile], and α,α',α''-1,2,3-cyclopropanetriylidenetris[2,3,4,5,6-pentafluorobenzeneacetonitrile]. As the substance having acceptor properties, in addition to the organic compounds described above, transition metal oxides such as molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, and manganese oxide can be used.Alternatively, the hole injection layer 111 can be formed using a phthalocyanine compound or complex compound such as phthalocyanine (abbreviation: HPc) or copper phthalocyanine (abbreviation: CuPc), an aromatic amine compound such as 4,4'-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation: DPAB) or 4,4'-bis(N-{4-[N'-(3-methylphenyl)-N'-phenylamino]phenyl}-N-phenylamino)biphenyl (abbreviation: DNTPD), or a polymer such as poly(3,4-ethylenedioxythiophene) / polystyrene sulfonic acid (abbreviation: PEDOT / PSS). Acceptor materials can extract electrons from an adjacent hole transport layer (or hole transport material) when an electric field is applied.

[0224] The hole-injecting layer 111 is preferably formed using a composite material containing the above-mentioned material having an acceptor property and a substance having a hole-transport property.

[0225] As a substance having hole transport properties used in a composite material, various organic compounds such as aromatic amine compounds, heteroaromatic compounds, aromatic hydrocarbons, and polymer compounds (oligomers, dendrimers, polymers, etc.) can be used. Note that as a substance having hole transport properties used in a composite material, a 1×10 -6 cm 2 Preferably, the compound has a hole mobility of 1 / Vs or more. The hole-transporting substance used in the composite material is preferably a compound having a fused aromatic hydrocarbon ring or a π-electron-rich heteroaromatic ring. As the fused aromatic hydrocarbon ring, an anthracene ring, a naphthalene ring, or the like is preferred. As the π-electron-rich heteroaromatic ring, a fused aromatic ring containing at least one of a pyrrole skeleton, a furan skeleton, and a thiophene skeleton is preferred. Specifically, a carbazole ring, a dibenzothiophene ring, or a ring in which an aromatic ring or a heteroaromatic ring is further fused to the above ring is preferred.

[0226] Such hole-transporting substances preferably have one or more of a carbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton, and an anthracene skeleton. In particular, aromatic amines having a substituent containing a dibenzofuran ring or a dibenzothiophene ring, aromatic monoamines having a naphthalene ring, or aromatic monoamines in which a 9-fluorenyl group is bonded to the nitrogen of the amine via an arylene group may be used. Note that these hole-transporting substances preferably have an N,N-bis(4-biphenyl)amino group, because they can fabricate light-emitting devices with long lifetimes. Organic compounds having a carbazole skeleton and a dibenzofuran skeleton are also preferred because they can improve heat resistance and adjust the hole-transporting properties. Furthermore, the use of a dibenzothiophene skeleton in addition to the carbazole skeleton and the dibenzofuran skeleton can further adjust the hole-transporting properties. By using two or more of the above skeletons in consideration of the desired device properties and compatibility with other layers (light-emitting layer and electron-transporting layer), improved physical properties and device characteristics can be expected.

[0227] Specific examples of the substance having the hole transporting property as described above include N-(4-biphenyl)-6,N-diphenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BnfABP), N,N-bis(4-biphenyl)-6-phenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BBABnf), 4,4'-bis(6-phenylbenzo[b]naphtho[1,2-d]furan-8-yl)-4''-phenyltriphenylamine (abbreviation: BnfBB1BP), N,N-bis(4-biphenyl)benzo[b]naphtho[1,2-d]furan-8-yl, [b]naphtho[1,2-d]furan-6-amine (abbreviation: BBABnf(6)), N,N-bis(4-biphenyl)benzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BBABnf(8)), N,N-bis(4-biphenyl)benzo[b]naphtho[2,3-d]furan-4-amine (abbreviation: BBABnf(II)(4)), N,N-bis[4-(dibenzofuran-4-yl)phenyl]-4-amino-p-terphenyl (abbreviation: DBfBB1TP), N-[4-(dibenzothiophen-4-yl)phenyl]- N-phenyl-4-biphenylamine (abbreviation: ThBA1BP), 4-(2-naphthyl)-4',4''-diphenyltriphenylamine (abbreviation: BBAβNB), 4-[4-(2-naphthyl)phenyl]-4',4''-diphenyltriphenylamine (abbreviation: BBAβNBi), 4,4'-diphenyl-4''-(6;1'-binaphthyl-2-yl)triphenylamine (abbreviation: BBAαNβNB), 4,4'-diphenyl-4''-(7;1'-binaphthyl-2-yl)triphenylamine (abbreviation: BBAαNβN B-03), 4,4'-diphenyl-4''-(7-phenyl)naphthyl-2-yltriphenylamine (abbreviated as BBAPβNB-03), 4,4'-diphenyl-4''-(6;2'-binaphthyl-2-yl)triphenylamine (abbreviated as BBA(βN2)B), 4,4'-diphenyl-4''-(7;2'-binaphthyl-2-yl)triphenylamine (abbreviated as BBA(βN2)B-03), 4,4'-diphenyl-4''-(4;2'-binaphthyl-1-yl)triphenylamine (abbreviated as BBAβNαNB), 4,4'-Diphenyl-4''-(5;2'-binaphthyl-1-yl)triphenylamine (abbreviation: BBAβNαNB-02), 4-(4-biphenylyl)-4'-(2-naphthyl)-4''-phenyltriphenylamine (abbreviation: TPBiAβNB), 4-(3-biphenylyl)-4'-[4-(2-naphthyl)phenyl]-4''-phenyltriphenylamine (abbreviation: mTPBiAβNBi), 4-(4-biphenylyl)-4'-[4-(2-naphthyl)phenyl] 4'-[4'-(3-phenyl-9H-carbazol-9-yl)biphenyl-4-yl]-4''-phenyltriphenylamine (abbreviated as TPBiAβNBi), 4-phenyl-4'-(1-naphthyl)triphenylamine (abbreviated as αNBA1BP), 4,4'-bis(1-naphthyl)triphenylamine (abbreviated as αNBB1BP), 4,4'-diphenyl-4''-[4'-(carbazol-9-yl)biphenyl-4-yl]triphenylamine (abbreviated as YGTBi1BP), 4'-[4-(3-phenyl-9H-carbazol-9-yl)furan N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-N-[4-(1-naphthyl)phenyl]-9,9'-spirobi[9H-fluorene]-2-amine (abbreviation: PCBNBSF), N,N- Bis(biphenyl-4-yl)-9,9'-spirobi[9H-fluorene]-2-amine (abbreviation: BBASF), N,N-bis(biphenyl-4-yl)-9,9'-spirobi[9H-fluorene]-4-amine (abbreviation: BBASF(4)), N-(biphenyl-2-yl)-N-(9,9-dimethyl-9H-fluoren-2-yl)-9,9'-spirobi[9H-fluorene]-4-amine (abbreviation: oFBiSF), N-(biphenyl-4-yl)-N-(9,9-dimethyl-9H-fluoren-2-yl)dibenzofuran-4-amine (abbreviation: FrBiF), N-[4-(1-naphthyl)phenyl]-N-[3-(6-phenyldibenzofuran-4-yl)phenyl]-1-naphthylamine (abbreviation: mPDBfBNBN), 4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP), 4-phenyl-3'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: mBPAFLP), 4-phenyl-4'-[4-(9-phenylfluoren-9-yl)triphenylamine] 4,4'-diphenyl-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviated as BPAFLBi), 4-phenyl-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviated as PCBA1BP), 4,4'-diphenyl-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviated as PCBBi1BP), 4-(1-naphthyl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviated as PCBANB), 4,4'-di(1-naphthyl)-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine Triphenylamine (abbreviation: PCBNBB), N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9'-spirobi[9H-fluorene]-2-amine (abbreviation: PCBASF), N-(biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF), N,N-bis(9,9-dimethyl-9H-fluoren-2-yl)-9,9'-spirobi-9H-fluoren-4-amine, N,N-bis( 9,9-dimethyl-9H-fluoren-2-yl)-9,9'-spirobi-9H-fluoren-3-amine, N,N-bis(9,9-dimethyl-9H-fluoren-2-yl)-9,9'-spirobi-9H-fluoren-2-amine, N,N-bis(9,9-dimethyl-9H-fluoren-2-yl)-9,9'-spirobi-9H-fluoren-1-amine, 9-[3-(triphenylsilyl)phenyl]-3,9'-bi-9H-carbazole (abbreviation: PSiCzCz), 9'-[3-(triphenylsilyl)phenyl]-9'H-9,3':6',Examples include 9''-terecarbazole (abbreviation: PSiCzGI).

[0228] Other aromatic amine compounds that can be used as hole-transporting substances include N,N'-di(p-tolyl)-N,N'-diphenyl-p-phenylenediamine (abbreviation: DTDPPA), 4,4'-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation: DPAB), 4,4'-bis(N-{4-[N'-(3-methylphenyl)-N'-phenylamino]phenyl}-N-phenylamino)biphenyl (abbreviation: DNTPD), and 1,3,5-tris[N-(4-diphenylaminophenyl)-N-phenylamino]benzene (abbreviation: DPA3B).

[0229] By forming the hole injection layer 111, the hole injection property becomes good, and a light emitting device with a low driving voltage can be obtained.

[0230] Among substances having acceptor properties, organic compounds having acceptor properties are easy to use because they can be easily vapor-deposited and formed into a film.

[0231] The hole transport layers (the first hole transport layer 112_1 and the second hole transport layer 112_2) are formed by containing an organic compound having a hole transport property. -6 cm 2 In addition to the organic compounds having an amine skeleton and a fluorene skeleton described above, organic compounds having a hole transport property can be used as needed.

[0232] Examples of the hole-transporting substance include 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB), N,N'-diphenyl-N,N'-bis(3-methylphenyl)-4,4'-diaminobiphenyl (abbreviation: TPD), N,N'-bis(9,9'-spirobi[9H-fluoren]-2-yl)-N,N'-diphenyl-4,4'-diaminobiphenyl (abbreviation: BSPB), 4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP), 4-phenyl-3-methylphenyl-4,4'-diaminobiphenyl (abbreviation: 4,4'-bis(9H-fluoren-2-yl)triphenylamine) ... '-(9-Phenylfluoren-9-yl)triphenylamine (abbreviated as mBPAFLP), 4-phenyl-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviated as PCBA1BP), 4,4'-diphenyl-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviated as PCBBi1BP), 4-(1-naphthyl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviated as PCBANB), 4,4'-di(1-naphthyl)-4''-(9-phenyl) Compounds with an aromatic amine skeleton, such as 9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]fluoren-2-amine (abbreviation: PCBAF), and N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9'-spirobi[9H-fluorene]-2-amine (abbreviation: PCBASF), 1,3-bis(N-carbazolyl)benzene (abbreviation: mCP), 4,4'-di( N-carbazolyl)biphenyl (abbreviation: CBP), 3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviation: CzTP), 3,3'-bis(9-phenyl-9H-carbazole) (abbreviation: PCCP), 9,9'-bis(biphenyl-4-yl)-3,3'-bi-9H-carbazole (abbreviation: BisBPCz), 9,9'-bis(biphenyl-3-yl)-3,3'-bi-9H-carbazole (abbreviation: BismBPCz), 9-(biphenyl-3-yl)-9'-(biphenyl-4-yl)-9H,9'H-3,3'-Bicarbazole (abbreviation: mBPCCBP), 9-(2-naphthyl)-9'-phenyl-3,3'-bi-9H-carbazole (abbreviation: βNCCP), 9-(3-biphenyl)-9'-(2-naphthyl)-3,3'-bi-9H-carbazole (abbreviation: βNCCmBP), 9-(4-biphenyl)-9'-(2-naphthyl)-3,3'-bi-9H-carbazole (abbreviation: βNCCBP), 9,9'-di-2-naphthyl-3,3'-9H,9'H-bicarbazole (abbreviation: BisβNCz), 9-(2-naphthyl)-9'-[1,1' :4',1"-terphenyl]-3-yl-3,3'-9H,9'H-bicarbazole, 9-(2-naphthyl)-9'-[1,1':3',1"-terphenyl]-3-yl-3,3'-9H,9'H-bicarbazole, 9-(2-naphthyl)-9'-[1,1':3',1"-terphenyl]-5'-yl-3,3'-9H,9'H-bicarbazole, 9-(2-naphthyl)-9'-[1,1':4',1"-terphenyl]-4-yl-3,3'-9H,9'H-bicarbazole, 9-(2-naphthyl)-9'-[1,1':3' ,1"-terphenyl]-4-yl-3,3'-9H,9'H-bicarbazole, 9-(2-naphthyl)-9'-(triphenylen-2-yl)-3,3'-9H,9'H-bicarbazole, 9-phenyl-9'-(triphenylen-2-yl)-3,3'-9H,9'H-bicarbazole (abbreviation: PCCzTp), 9,9'-bis(triphenylen-2-yl)-3,3'-9H,9'H-bicarbazole, 9-(4-biphenyl)-9'-(triphenylen-2-yl)-3,3'-9H,9'H-bicarbazole, 9-(triphenylen-2-yl)-3,3'-9H,9'H-bicarbazole, Compounds with a carbazole skeleton such as N,N-bis(9,9-dimethyl-9H-fluoren-2-yl)-9'-[1,1':3',1"-terphenyl]-4-yl-3,3'-9H,9'H-bicarbazole, N,N-bis(9,9-dimethyl-9H-fluoren-2-yl)-9,9'-spirobi-9H-fluoren-1-amine, and 9-[3-(triphenylsilyl)phenyl]-3,9'-bi-9H-carbazole (abbreviation: PSiCzCz), 4,4',4''-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation: DBT3P-II), 2,Examples of suitable materials include compounds having a thiophene skeleton, such as 8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene (abbreviation: DBTFLP-III) and 4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviation: DBTFLP-IV), and compounds having a furan skeleton, such as 4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation: DBF3P-II) and 4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran (abbreviation: mmDBFFLBi-II). Among the above, compounds having an aromatic amine skeleton and compounds having a carbazole skeleton are preferred because they have good reliability, high hole transport properties, and contribute to reduced driving voltage. Furthermore, compounds having both an aromatic amine skeleton and a carbazole skeleton are expected to further improve reliability and reduce driving voltage. Furthermore, a compound having an aromatic amine skeleton, a carbazole skeleton, and a dibenzofuran skeleton is more preferable because it can improve heat resistance. Furthermore, the organic compounds listed as the hole-transporting substances used in the composite material of the hole injection layer 111 can also be suitably used as materials for forming the hole transport layer 112 (the first hole transport layer 112_1 and the second hole transport layer 112_2).

[0233] Note that the first hole transport layer 112_1 and the second hole transport layer 112_2 preferably contain an organic compound having the same skeleton, and more preferably contain the same compound.

[0234] The light-emitting layers (first light-emitting layer 113_1, second light-emitting layer 113_2) preferably contain a light-emitting center substance and a host material. The light-emitting layers may also contain other materials. At least one of the light-emitting layers uses a phosphorescent material as the light-emitting center substance. In particular, it is preferable to use the above-mentioned phosphorescent material that emits blue light as the light-emitting center substance.

[0235] Furthermore, the first light-emitting layer 113_1 and the second light-emitting layer 113_2 are preferably light-emitting layers that emit light of similar colors. For example, red, green, and blue pixels are often used in display devices to express full colors. In a light-emitting device used for a red pixel, both the first light-emitting layer 113_1 and the second light-emitting layer 113_2 are light-emitting layers that emit red light. In a light-emitting device used for a green pixel, both the two light-emitting layers are light-emitting layers that emit green light. In a light-emitting device used for a blue pixel, both the first light-emitting layer 113_1 and the second light-emitting layer 113_2 emit blue light. In this case, the light-emitting center substance contained in the first light-emitting layer 113_1 and the light-emitting center substance contained in the second light-emitting layer 113_2 are preferably compounds whose difference in maximum peak wavelength in their PL spectra is 30 nm or less, more preferably 20 nm or less, and even more preferably 10 nm or less. It is more preferable that the light-emitting center substance contained in the first light-emitting layer 113_1 and the light-emitting center substance contained in the second light-emitting layer 113_2 are the same.

[0236] The luminescent center substance may be a fluorescent substance, a phosphorescent substance, a substance exhibiting thermally activated delayed fluorescence (TADF), or any other luminescent substance.

[0237] Examples of fluorescent substances that can be used as the luminescent center substance in the light-emitting layer include the following: In addition, fluorescent substances other than these can also be used.

[0238] 5,6-bis[4-(10-phenyl-9-anthryl)phenyl]-2,2'-bipyridine (abbreviation: PAP2BPy), 5,6-bis[4'-(10-phenyl-9-anthryl)biphenyl-4-yl]-2,2'-bipyridine (abbreviation: PAPP2BPy), N,N'-diphenyl-N,N'-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine (abbreviation: 1,6FLPAPrn), N,N'-bis(3-methylphenyl)-N,N'-bis[3-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine )phenyl]pyrene-1,6-diamine (abbreviation: 1,6mMemFLPAPrn), N,N'-bis[4-(9H-carbazol-9-yl)phenyl]-N,N'-diphenylstilbene-4,4'-diamine (abbreviation: YGA2S), 4-(9H-carbazol-9-yl)-4'-(10-phenyl-9-anthryl)triphenylamine (abbreviation: YGAPA), 4-(9H-carbazol-9-yl)-4'-(9,10-diphenyl-2-anthryl)triphenylamine (abbreviation: 2YGAPPA), N,9-diphenyl-N-[4-( 10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine (abbreviation: PCAPA), perylene, 2,5,8,11-tetra-tert-butylperylene (abbreviation: TBP), 4-(10-phenyl-9-anthryl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBAPA), N,N''-(2-tert-butylanthracene-9,10-diyldi-4,1-phenylene)bis(N,N',N'-triphenyl-1,4-phenylenediamine) (abbreviation: DPABPA), N,9 -diphenyl-N-[4-(9,10-diphenyl-2-anthryl)phenyl]-9H-carbazol-3-amine (abbreviated as 2PCAPPA), N-[4-(9,10-diphenyl-2-anthryl)phenyl]-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviated as 2DPAPPA), N,N,N',N',N'',N'',N''',N'''-octaphenyldibenzo[g,p]chrysene-2,7,10,15-tetraamine (abbreviated as DBC1), Coumarin 30, N-(9,10-diphenyl-2-anthryl)-N,9-Diphenyl-9H-carbazol-3-amine (abbreviation: 2PCAPA), N-[9,10-bis(biphenyl-2-yl)-2-anthryl]-N,9-diphenyl-9H-carbazol-3-amine (abbreviation: 2PCABPhA), N-(9,10-diphenyl-2-anthryl)-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPA), N-[9,10-bis(biphenyl-2-yl)-2-anthryl]-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviation: 2DPABPhA) , 9,10-bis(biphenyl-2-yl)-N-[4-(9H-carbazol-9-yl)phenyl]-N-phenylanthracen-2-amine (abbreviation: 2YGABPhA), N,N,9-triphenylanthracen-9-amine (abbreviation: DPhAPhA), Coumarin 545T, N,N'-diphenylquinacridone (abbreviation: DPQd), rubrene, 5,12-bis(biphenyl-4-yl)-6,11-diphenyltetracene (abbreviation: BPT), 2-(2-{2-[4-(dimethylamino)phenyl]ethenyl}-6-methyl-4H-pyra N,N,N',N'-tetrakis(4-methylphenyl)acenaphtho[1,2-a]fluoranthene-3,10-diamine (abbreviation: p-mPhTD), 2-{2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCM1), 2-{2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCM2), N,N,N',N'-tetrakis(4-methylphenyl)tetracene-5,11-diamine (abbreviation: p-mPhTD), 7,14-diphenyl-N,N,N',N'-tetrakis(4-methylphenyl)acenaphtho[1,2-a]fluoranthene-3,10-diamine (abbreviation: p-mPhTD), Name: p-mPhAFD), 2-{2-isopropyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCJTI), 2-{2-tert-butyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCJTB),6-Bis{2-[4-(dimethylamino)phenyl]ethenyl}-4H-pyran-4-ylidene)propanedinitrile (abbreviation: BisDCM), 2-{2,6-bis[2-(8-methoxy-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: BisDCJTM), N,N'-diphenyl-N,N'-(1,6-pyren-diyl)bis[(6-phenylbenzo[b]naphtho]] Examples include N,N'-diphenyl-N,N'-bis(9-phenyl-9H-carbazol-2-yl)naphtho[2,3-b;6,7-b']bisbenzofuran-3,10-diamine (abbreviated as 3,10PCA2Nbf(IV)-02), and 3,10-bis[N-(dibenzofuran-3-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviated as 3,10FrA2Nbf(IV)-02). In particular, condensed aromatic diamine compounds, such as pyrenediamine compounds 1,6FLPAPrn, 1,6mMemFLPAPrn, and 1,6BnfAPrn-03, are preferred due to their high hole-trapping properties and excellent luminous efficiency and reliability.

[0239] In the light-emitting layer, as the phosphorescent material that can be used as the luminescent center material, in addition to the above-mentioned blue-emitting phosphorescent material, a material that emits green or red light can also be used.

[0240] For example, when red, green, and blue pixels are used to express full color in a display device, a light-emitting device with high luminous efficiency can be obtained by using a phosphorescent material in all of the red, green, and blue pixels.

[0241] For example, tris(4-methyl-6-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(mppm)3]), tris(4-t-butyl-6-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(tBuppm)3]), (acetylacetonato)bis(6-methyl-4-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(mppm)2(acac)]), (acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(tBuppm)2(acac)]), (acetylacetonato)bis[6-(2-norbornyl)-4-phenylpyrimidinato]iridium(III) (abbreviation: [Ir(nbppm)2(acac)]), (acetylacetonato)bis[5-methyl-6 Organometallic iridium complexes with a pyrimidine skeleton, such as -(2-methylphenyl)-4-phenylpyrimidinato]iridium(III) (abbreviation: [Ir(mpmppm)2(acac)]) and (acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III) (abbreviation: [Ir(dppm)2(acac)]), organometallic iridium complexes with a pyrazine skeleton, such as (acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazinato)iridium(III) (abbreviation: [Ir(mppr-Me)2(acac)]) and (acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinato)iridium(III) (abbreviation: [Ir(mppr-iPr)2(acac)]), and tris(2-phenylpyridinato-N,C 2’ ) Iridium(III) (abbreviation: [Ir(ppy)3]), bis(2-phenylpyridinato-N,C 2’ ) Iridium(III) acetylacetonate (abbreviation: [Ir(ppy)2(acac)]), bis(benzo[h]quinolinato)iridium(III) acetylacetonate (abbreviation: [Ir(bzq)2(acac)]), tris(benzo[h]quinolinato)iridium(III) (abbreviation: [Ir(bzq)3]), tris(2-phenylquinolinato-N,C 2’ ) Iridium(III) (abbreviation: [Ir(pq)3]), bis(2-phenylquinolinato-N,C 2’) iridium(III) acetylacetonate (abbreviation: [Ir(pq)2(acac)]), [2-d3-methyl-8-(2-pyridinyl-κN)benzofuro[2,3-b]pyridine-κC]bis[2-(5-d3-methyl-2-pyridinyl-κN2)phenyl-κC]iridium(III) (abbreviation: Ir(5mppy-d3)2(mbfpypy-d3)), {2- (Methyl-d3)-8-[4-(1-methylethyl-1-d)-2-pyridinyl-κN]benzofuro[2,3-b]pyridin-7-yl-κC}bis{5-(methyl-d3)-2-[5-(methyl-d3)-2-pyridinyl-κN]phenyl-κC}iridium(III) (abbreviation: Ir(5mtpy-d6)2(mbfpypy-iPr-d4)), [2-d3-methyl Ir(ppy)2(mbfpypy-d3) and Ir(ppy)2(mbfpypy-d3) are bis[2-(4-methyl-5-phenyl-2-pyridinyl-κN)phenyl-κC]iridium(III) compounds. ) (abbreviation: Ir(ppy)2(mdppy)), [2-(4-d3-methyl-5-phenyl-2-pyridinyl-κN2)phenyl-κC]bis[2-(5-d3-methyl-2-pyridinyl-κN2)phenyl-κC]iridium(III) (abbreviation: [Ir(5mppy-d3)2(mdppy-d3)]), [2-methyl-(2-pyridinyl-κN)benzofuro[2,Organometallic iridium complexes with a pyridine skeleton, such as [2-(2-pyridinyl-κN)phenyl-κC]iridium(III) (abbreviated as [Ir(ppy)2(mbfpypy)]), [2-(4-methyl-5-phenyl-2-pyridinyl-κN)phenyl-κC]bis[2-(2-pyridinyl-κN)phenyl-κC]iridium (abbreviated as [Ir(ppy)2(mdppy)]), and tris{2-[5-(methyl-d3)-4-phenyl-2-pyridinyl-κN]phenyl-κC}iridium(III) (abbreviated as Ir(5m4dppy-d3)3), as well as (2-{1-(5-tert-butylbiphenyl-2-yl)-4-[3-tert-butyl-5-(4-phenyl-2-pyridinyl- Examples of platinum complexes include [2-(4-(3,5-di-tert-butylphenyl)-6-{3-[4-(5'-tert-butyl[1,1':3',1''-terphenyl]-2'-yl)-2-pyridinyl-κN]phenyl-κC2}-2-pyridinyl-κN)phenolato-κO]platinum(II) (abbreviation: Pt(tBudppymmtBubiz-tBubp)), [2-(4-(3,5-di-tert-butylphenyl)-6-{3-[4-(5'-tert-butyl[1,1':3',1''-terphenyl]-2'-yl)-2-pyridinyl-κN]phenyl-κC2}-2-pyridinyl-κN)phenolato-κO]platinum(II) (abbreviation: Pt(4tButpppypyp-mmtBup)), and rare earth metal complexes such as tris(acetylacetonato)(monophenanthroline)terbium(III) (abbreviation: [Tb(acac)3(Phen)]). These compounds primarily exhibit green phosphorescence, with emission peaks in the wavelength range of more than 500 nm to 600 nm. Organometallic iridium complexes with a pyrimidine skeleton are particularly preferred because they are remarkably superior in reliability and luminous efficiency. Compounds in which some of the hydrogen atoms in these compounds are replaced with deuterium atoms can also be used.

[0242] and organometallic iridium complexes having a pyrimidine skeleton, such as (diisobutyrylmethanato)bis[4,6-bis(3-methylphenyl)pyrimidinato]iridium(III) (abbreviation: [Ir(5mdppm)2(dibm)]), bis[4,6-bis(3-methylphenyl)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: [Ir(5mdppm)2(dpm)]), and bis[4,6-di(naphthalen-1-yl)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: [Ir(d1npm)2(dpm)]). Organometallic iridium complexes with a pyrazine skeleton, such as (acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III) (abbreviation: [Ir(tppr)2(acac)]), bis(2,3,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III) (abbreviation: [Ir(tppr)2(dpm)]), and (acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III) (abbreviation: [Ir(Fdpq)2(acac)]), tris(1-phenylisoquinolinato-N,C 2’ ) Iridium(III) (abbreviation: [Ir(piq)3]), bis(1-phenylisoquinolinato-N,C 2’) iridium(III) acetylacetonate (abbreviated as [Ir(piq)2(acac)]), (3,7-diethyl-4,6-nonanedionato-κO4,κO6)bis[2,4-dimethyl-6-[7-(1-methylethyl)-1-isoquinolinyl-κN]phenyl-κC]iridium(III), and (3,7-diethyl-4,6-nonanedionato-κO4,κO6)bis[2,4-dimethyl-6-[5-(1-methylethyl)-2-quinolinyl-κN]phenyl-κC]iridium(III). In addition to iridium complexes, platinum complexes such as 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin platinum(II) (abbreviation: PtOEP) and rare earth metal complexes such as tris(1,3-diphenyl-1,3-propanedionato)(monophenanthroline)europium(III) (abbreviation: [Eu(DBM)3(Phen)]) and tris[1-(2-thenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(III) (abbreviation: [Eu(TTA)3(Phen)]) are examples of iridium complexes. These compounds exhibit red phosphorescence, with peak emission in the wavelength range from 600 to 700 nm. Organometallic iridium complexes with a pyrazine skeleton also exhibit excellent chromaticity in red light. Compounds in which some of the hydrogen atoms in these compounds are replaced with deuterium atoms can also be used.

[0243] In one embodiment of the present invention, the use of a deuterated compound as the luminescent center substance improves luminous efficiency, and therefore the luminescent center substance is preferably a deuterated material.

[0244] In addition to the phosphorescent compounds described above, known phosphorescent compounds may be selected and used.

[0245] TADF materials include fullerene and its derivatives, acridine and its derivatives, eosin derivatives, etc. Also available are metal-containing porphyrins containing magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), or palladium (Pd). Examples of the metal-containing porphyrin include protoporphyrin-tin fluoride complex (SnF2(Proto IX)), mesoporphyrin-tin fluoride complex (SnF2(Meso IX)), hematoporphyrin-tin fluoride complex (SnF2(Hemato IX)), coproporphyrin tetramethyl ester-tin fluoride complex (SnF2(Copro III-4Me)), octaethylporphyrin-tin fluoride complex (SnF2(OEP)), etioporphyrin-tin fluoride complex (SnF2(Etio I)), and octaethylporphyrin-platinum chloride complex (PtCl2OEP), all of which are shown in the following structural formulas.

[0246] [ka]

[0247] In addition, 2-(biphenyl-4-yl)-4,6-bis(12-phenylindolo[2,3-a]carbazol-11-yl)-1,3,5-triazine (abbreviation: PIC-TRZ), 9-(4,6-diphenyl-1,3,5-triazin-2-yl)-9'-phenyl-9H,9'H-3,3'-bicarbazole (abbreviation: PCCzTzn), 2-{4-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: PCCzPTzn), 2-[4-(10H-phenoxazin-10-yl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: PCCzPTzn), and Heterocyclic compounds having one or both of a π-electron-rich heteroaromatic ring and a π-electron-deficient heteroaromatic ring, such as 3-[4-(5-phenyl-5,10-dihydrophenazin-10-yl)phenyl]-4,5-diphenyl-1,2,4-triazole (abbreviation: PPZ-3TPT), 3-(9,9-dimethyl-9H-acridin-10-yl)-9H-xanthen-9-one (abbreviation: ACRXTN), bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone (abbreviation: DMAC-DPS), and 10-phenyl-10H,10'H-spiro[acridin-9,9'-anthracene]-10'-one (abbreviation: ACRSA), can also be used. The heterocyclic compound has a π-electron-rich heteroaromatic ring and a π-electron-deficient heteroaromatic ring, and therefore has high electron transport and hole transport properties, and is therefore preferred. Among the skeletons having a π-electron-deficient heteroaromatic ring, pyridine skeleton, diazine skeleton (pyrimidine skeleton, pyrazine skeleton, pyridazine skeleton), and triazine skeleton are preferred because they are stable and reliable. In particular, benzofuropyrimidine skeleton, benzothienopyrimidine skeleton, benzofuropyrazine skeleton, and benzothienopyrazine skeleton are preferred because they have high acceptor properties and good reliability. Furthermore, among the skeletons having a π-electron-rich heteroaromatic ring, acridine skeleton, phenoxazine skeleton, phenothiazine skeleton, furan skeleton, thiophene skeleton, and pyrrole skeleton are preferred because they are stable and reliable.The furan skeleton is preferably a dibenzofuran skeleton, and the thiophene skeleton is preferably a dibenzothiophene skeleton. The pyrrole skeleton is particularly preferably an indole skeleton, a carbazole skeleton, an indolocarbazole skeleton, a bicarbazole skeleton, or a 3-(9-phenyl-9H-carbazol-3-yl)-9H-carbazole skeleton. Substances in which a π-electron-rich heteroaromatic ring and a π-electron-deficient heteroaromatic ring are directly bonded are particularly preferred because the electron-donating ability of the π-electron-rich heteroaromatic ring and the electron-accepting ability of the π-electron-deficient heteroaromatic ring are both enhanced, thereby reducing the energy difference between the S1 level and the T1 level, thereby enabling efficient thermally activated delayed fluorescence. Instead of the π-electron-deficient heteroaromatic ring, an aromatic ring bonded to an electron-withdrawing group such as a cyano group may be used. The π-electron-rich skeleton may be, for example, an aromatic amine skeleton or a phenazine skeleton. Examples of usable π-electron-deficient skeletons include a xanthene skeleton, a thioxanthene dioxide skeleton, an oxadiazole skeleton, a triazole skeleton, an imidazole skeleton, an anthraquinone skeleton, a boron-containing skeleton such as phenylborane or boranthrene, an aromatic ring having a nitrile group or a cyano group such as benzonitrile or cyanobenzene, a heteroaromatic ring, a carbonyl skeleton such as benzophenone, a phosphine oxide skeleton, a sulfone skeleton, etc. In this way, a π-electron-deficient skeleton and a π-electron-rich skeleton can be used in place of at least one of a π-electron-deficient heteroaromatic ring and a π-electron-rich heteroaromatic ring.

[0248] [ka]

[0249] In addition, TADF materials that are in thermal equilibrium between the singlet excited state and the triplet excited state may also be used. Such TADF materials have a shorter emission lifetime (excitation lifetime), which can suppress efficiency decline in the high brightness range of light-emitting devices. Specific examples include materials with the molecular structure shown below.

[0250] [ka]

[0251] TADF materials are materials with a small difference between the S1 and T1 levels, and have the ability to convert triplet excitation energy to singlet excitation energy through reverse intersystem crossing. Therefore, triplet excitation energy can be upconverted to singlet excitation energy (reverse intersystem crossing) using a small amount of thermal energy, allowing for efficient generation of a singlet excited state. Triplet excitation energy can also be converted into light emission.

[0252] Furthermore, exciplexes that form excited states with two types of substances have an extremely small difference between the S1 and T1 levels, and function as TADF materials that can convert triplet excitation energy into singlet excitation energy.

[0253] Note that the T1 level can be measured using a phosphorescence spectrum observed at low temperatures (for example, 77 K to 10 K). For a TADF material, when a tangent line is drawn at the base of the fluorescence spectrum on the short wavelength side and the energy of the wavelength of the extrapolated line is taken as the S1 level, and a tangent line is drawn at the base of the phosphorescence spectrum on the short wavelength side and the energy of the wavelength of the extrapolated line is taken as the T1 level, the difference between S1 and T1 is preferably 0.3 eV or less, and more preferably 0.2 eV or less.

[0254] When a TADF material is used as a light-emitting material, the S1 level of the host material is preferably higher than the S1 level of the TADF material, and the T1 level of the host material is preferably higher than the T1 level of the TADF material.

[0255] As the host material of the light-emitting layer, in addition to the organic compounds described above, various carrier transport materials such as materials having electron transport properties and / or materials having hole transport properties, and the TADF materials described above can be used.

[0256] The material having hole transport properties is preferably an organic compound having an amine skeleton, a π-electron-rich heteroaromatic ring skeleton, etc. The π-electron-rich heteroaromatic ring is preferably a fused aromatic ring containing at least one of an acridine skeleton, a phenoxazine skeleton, a phenothiazine skeleton, a furan skeleton, a thiophene skeleton, and a pyrrole skeleton, and specifically preferably a carbazole ring, a dibenzothiophene ring, or a ring in which an aromatic ring or a heteroaromatic ring is further fused to the carbazole ring, a dibenzothiophene ring, or the ring in which the π-electron-rich heteroaromatic ring is further fused to the carbazole ring, a dibenzothiophene ring, or the ring in which ... a dibenzothiophene ring, or the ring in which the carbazole ring, a dibenzothiophene ring, a dibenzothiophene ring, or the ring in which the carbazole ring, a dibenzothiophene ring, a dibenzothiophene ring, a dibenzothiophene ring, or the ring in which the carbazole ring, a dibenzothiophene ring, a dibenzothiophene ring, a dibenzothiophene ring, a dibenzothiophene ring, a

[0257] Such a substance having hole-transporting properties preferably has a carbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton, or an anthracene skeleton. In particular, the substance may be an aromatic amine having a substituent containing a dibenzofuran ring or a dibenzothiophene ring, an aromatic monoamine having a naphthalene ring, or an aromatic monoamine in which a 9-fluorenyl group is bonded to the nitrogen of the amine via an arylene group. It is preferable that the substance having hole-transporting properties is an organic compound having an N,N-bis(4-biphenyl)amino group, since this allows the fabrication of a light-emitting device with a long lifetime.

[0258] As such an organic compound, for example, the following organic compounds are preferable: 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB), N,N'-diphenyl-N,N'-bis(3-methylphenyl)-4,4'-diaminobiphenyl (abbreviation: TPD), N,N'-bis(9,9'-spirobi[9H-fluoren]-2-yl)-N,N'-diphenyl-4,4'-diaminobiphenyl (abbreviation: BSPB), 4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP), 4-phenyl-3 ... mBPAFLP), 4-phenyl-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviated as PCBA1BP), 4,4'-diphenyl-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviated as PCBBi1BP), 4-(1-naphthyl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviated as PCBANB), 4,4'-di(1-naphthyl)-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviated as PCBANB), )triphenylamine (abbreviation: PCBNBB), 9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]fluoren-2-amine (abbreviation: PCBAF), N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9'-spirobi[9H-fluorene]-2-amine (abbreviation: PCBASF), compounds with an aromatic amine skeleton such as 1,3-bis(N-carbazolyl)benzene (abbreviation: mCP), 4,4'-di(N-carbazolyl)biphenyl ( abbreviation: CBP), 3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviation: CzTP), 3,3'-bis(9-phenyl-9H-carbazole) (abbreviation: PCCP), 3,9-bis(9-phenyl-9H-carbazole-3-yl)-9H-carbazole (abbreviation: PCCzPC), 9-(biphenyl-4-yl)-9'-phenyl-3,3'-bi-9H-carbazole (abbreviation: PCCzBP), 9,9'-bis(biphenyl-4-yl)-3,3'-bi-9H-carbazole (abbreviation: BisBPCz), 9,9'-Bis(biphenyl-3-yl)-3,3'-bi-9H-carbazole (abbreviation: BismBPCz), 9-(biphenyl-3-yl)-9'-(biphenyl-4-yl)-9H,9'H-3,3'-bicarbazole (abbreviation: mBPCCBP), 9-(2-naphthyl)-9'-phenyl-3,3'-bi-9H-carbazole (abbreviation: βNCCP), 9-(3-biphenyl)-9'-(2-naphthyl)-3,3'-bi-9H-carbazole (abbreviation: βNCCmBP), 9-(4-biphenyl)-9'-(2-naphthyl)-3, 3'-Bi-9H-carbazole (abbreviation: βNCCBP), 9,9'-di-2-naphthyl-3,3'-9H,9'H-bicarbazole (abbreviation: BisβNCz), 9-(2-naphthyl)-9'-[1,1':4',1"-terphenyl]-3-yl-3,3'-9H,9'H-bicarbazole, 9-(2-naphthyl)-9'-[1,1':3',1"-terphenyl]-3-yl-3,3'-9H,9'H-bicarbazole, 9-(2-naphthyl)-9'-[1,1':3',1"-terphenyl]-5'-yl-3,3'-9H ,9'H-bicarbazole, 9-(2-naphthyl)-9'-[1,1':4',1"-terphenyl]-4-yl-3,3'-9H,9'H-bicarbazole, 9-(2-naphthyl)-9'-[1,1':3',1"-terphenyl]-4-yl-3,3'-9H,9'H-bicarbazole, 9-(2-naphthyl)-9'-(triphenylen-2-yl)-3,3'-9H,9'H-bicarbazole, 9-phenyl-9'-(triphenylen-2-yl)-3,3'-9H,9'H-bicarbazole (abbreviation: PCCzTp), 9,9'-Bis(triphenylen-2-yl)-3,3'-9H,9'H-bicarbazole, 9-(4-biphenyl)-9'-(triphenylen-2-yl)-3,3'-9H,9'H-bicarbazole, 9-(triphenylen-2-yl)-9'-[1,1':3',1"-terphenyl]-4-yl-3,3'-9H,9'H-bicarbazole, N,N-bis(9,9-dimethyl-9H-fluoren-2-yl)-9,9'-spirobi-9H-fluoren-1-amine, 9-[3-(triphenylsilyl)phenyl]-3,Compounds with a carbazole skeleton, such as 9'-bi-9H-carbazole (abbreviation: PSiCzCz) and 9'-[3-(triphenylsilyl)phenyl]-9'H-9,3':6',9''-tercarbazole (abbreviation: PSiCzGI), 4,4',4''-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation: DBT3P-II), and 2,8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene (abbreviation: DBTFLP-I) Examples of suitable compounds include compounds having a thiophene skeleton, such as 4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviation: DBTFLP-IV), and compounds having a furan skeleton, such as 4,4',4''-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation: DBF3P-II) and 4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran (abbreviation: mmDBFFLBi-II). Among the above, compounds having an aromatic amine skeleton or a carbazole skeleton are preferred because they have good reliability, high hole transport properties, and contribute to reducing driving voltage. The organic compounds listed as examples of materials having hole transport properties for the hole transport layer can also be used.

[0259] The electron-transporting material is preferably an organic compound having a π-electron-deficient heteroaromatic ring. Examples of the organic compound having a π-electron-deficient heteroaromatic ring skeleton include an organic compound having a heteroaromatic ring with an azole skeleton, an organic compound having a heteroaromatic ring with a pyridine skeleton, an organic compound having a heteroaromatic ring with a diazine skeleton, and an organic compound having a heteroaromatic ring with a triazine skeleton.

[0260] Among these, organic compounds containing a heteroaromatic ring having a diazine skeleton (pyrimidine skeleton, pyrazine skeleton, pyridazine skeleton), organic compounds containing a heteroaromatic ring having a pyridine skeleton, and organic compounds containing a heteroaromatic ring having a triazine skeleton are preferred because of their high reliability. In particular, organic compounds containing a heteroaromatic ring having a diazine (pyrimidine or pyrazine) skeleton and organic compounds containing a heteroaromatic ring having a triazine skeleton have high electron transport properties and contribute to reduced driving voltage. In addition, benzofuropyrimidine skeletons, benzothienopyrimidine skeletons, benzofuropyrazine skeletons, and benzothienopyrazine skeletons are preferred because of their high acceptor properties and high reliability.

[0261] As the organic compound having a π-electron-deficient heteroaromatic ring skeleton, for example, the following organic compounds are preferable: 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: TAZ), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene (abbreviation: OXD-7), 9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole (abbreviation: :CO11), 2,2',2''-(1,3,5-benzenetriyl)tris(1-phenyl-1H-benzimidazole) (abbreviation: TPBI), 2-[3-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole (abbreviation: mDBTBIm-II), 4,4'-bis(5-methylbenzoxazol-2-yl)stilbene (abbreviation: BzOs), and other organic compounds with an azole skeleton, such as 3,5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine (abbreviation: 35DCzPPy), 1,3,5-tri[3-(3-pyridyl)phenyl]benzene (abbreviation: TmPyPB), bathophenanthroline (abbreviation: Bphen), bathocuproine (abbreviation: BCP), 2,9-di(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline (abbreviation: NBphen), 2,2'-(1,3-phenylene)bis(9-phenyl-1,10-phenanthroline) (abbreviation: mPPhen2P), 2-[3-(2-triphenylenyl)phenyl]-1,10-phenane Organic compounds containing heteroaromatic rings with a pyridine skeleton, such as 2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTPDBq-II), 2-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTBPDBq-II), 2-[3'-(9H-carbazol-9-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mCzBPDBq), 2-[4'-(9-phenyl-9H-carbazol-3-yl)-3,1'-biphenyl-1-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mpPCBPDBq), 2-[4-(3,6-diphenyl phenyl-9H-carbazol-9-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviated as 2CzPDBq-III), 7-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviated as 7mDBTPDBq-II), and 6-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviated as 6mDBTPDBq-II), 9-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]naphtho[1',2':4,5]furo[2,3-b]pyrazine (abbreviated as 9mDBtBPNf pr), 9-[3'-(dibenzothiophen-4-yl)biphenyl-4-yl]naphtho[1',2':4,5]furo[2,3-b]pyrazine (abbreviated as 9pmDBtBPNfpr), 4,6-bis[3-(phenanthrene-9-yl)phenyl]pyrimidine (abbreviated as 4,6mPnP2Pm), 4,6-bis[3-(dibenzothiophen-4-yl)phenyl]pyrimidine (abbreviated as 4,6mDBTP2Pm-II), 4,6-bis[3-(9H-carbazol-9-yl)phenyl]pyrimidine (abbreviated as 4,6mCzP2Pm), 9,9'-[pyrimidinyl benzofuro[3,2-d]pyrimidine (abbreviated as 8BP-4mDBtPBfpm), 3,8-bis[3-(dibenzothiophen-4-yl)phenyl]benzofuro[2,3-b]pyrazine (abbreviated as 3,8mDBtP2Bfpr), 4,8-bis[3-(dibenzothiophen-4-yl)phenyl]benzofuro[3,2-d]pyrimidine (abbreviation: 4,8mDBtP2Bfpm), 8-[3'-(dibenzothiophen-4-yl)(1,1'-biphenyl-3-yl)]naphtho[1',2':4,5]furo[3,2-d]pyrimidine (abbreviation: 8mDBtBPNfpm), 8-[(2,2'-binaphthalen)-6-yl]-4-[3-(dibenzothiophen-4-yl)phenyl]-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 8(βN2)-4mDBtPBfpm), 2,2'-(pyridine-2,6-diyl)bis(4-phenylbenzo[h ]quinazoline) (abbreviation: 2,6(P-Bqn)2Py), 2,2'-(pyridine-2,6-diyl)bis{4-[4-(2-naphthyl)phenyl]-6-phenylpyrimidine} (abbreviation: 2,6(NP-PPm)2Py), 6-(biphenyl-3-yl)-4-[3,5-bis(9H-carbazol-9-yl)phenyl]-2-phenylpyrimidine (abbreviation: 6mBP-4Cz2PPm), 2,6-bis(4-naphthalen-1-ylphenyl)-4-[4-(3-pyridyl)phenyl]pyrimidine (abbreviation: 2,4NP-6PyPPm), 4-[3,5-bis(9H-carbazol-9-yl)phenyl]-2-phenyl-6-(biphenyl-4-yl)pyrimidine (abbreviation: 6BP-4Cz2PPm), 7-[4-(9-phenyl-9H-carbazol-2-yl)quinazolin-2-yl]-7H-dibenzo[c,g]carbazole (abbreviation: PC-cgDBCzQz), 8-(1,1':4',1''-terphenyl-3-yl)-4-[3-(dibenzothiophen-4-yl)phenyl]-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 8mpTP-4mDBtP organic compounds with a diazine skeleton such as 2-(biphenyl-4-yl)-4-phenyl-6-(9,9'-spirobi[9H-fluoren]-2-yl)-1,3,5-triazine (abbreviation: BP-SFTzn), 2-{3-[3-(benzo[b]naphtho[1,2-d]furan-8-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mBnfBPTzn), and 2-{3-[3-(benzo[b]naphtho[1,2-d]furan-6-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mBnfBPTzn-02), 2-{4-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: PCCzPTzn), 9-[3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]-9'-phenyl-2,3'-bi-9H-carbazole (abbreviation: mPCCzPTzn-02), 2-[3'-(9,9-dimethyl-9H-fluoren-2-yl)biphenyl-3-yl]-4,6-diphenyl Indeno[2,1-b]carbazole (abbreviation: mINc(II)PTzn), 5-[3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]-7,7-dimethyl-5H,7H-indeno[2,1-b]carbazole (abbreviation: mINc(II)PTzn), 2-{3-[3-(dibenzothiophen-4-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mDBtBPTzn), 2,4,6-tris[3'-(pyridin-3-yl)biphenyl-3-yl]-1,3,5-triazine (abbreviation: TmPPPyTzn) ), 2-[3-(2,6-dimethyl-3-pyridinyl)-5-(9-phenanthryl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mPn-mDMePyPTzn), 11-[4-(biphenyl-4-yl)-6-phenyl-1,3,5-triazin-2-yl]-11,12-dihydro-12-phenylindolo[2,3-a]carbazole (abbreviation: BP-Icz(II)Tzn), 2-[3'-(triphenylen-2-yl)biphenyl-3-yl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mTp BPTzn), 3-[9-(4,6-diphenyl-1,3,5-triazin-2-yl)-2-dibenzofuranyl]-9-phenyl-9H-carbazole (abbreviated as PCDBfTzn), 2-(biphenyl-3-yl)-4-phenyl-6-{8-[(1,1':4',1''-terphenyl)-4-yl]-1-dibenzofuranyl}-1,3,5-triazine (abbreviated as mBP-TPDBfTzn), 2-[4-(2-naphthyl)phenyl]-4-phenyl-6-spiro[9H-fluorene-9,9'-[9H]xanthene]-4-yl-1,3,5-Triazine (abbreviation: βNP-SFx(4)Tzn), 9,9'-{6-[3-(triphenylsilyl)phenyl]-1,3,5-triazine-2,4-diyl}bis(9H-carbazole) (abbreviation: SiTrzCz2), 2-phenyl-4,6-bis[3-(triphenylsilyl)phenyl]-1,3,5-triazine (abbreviation: mSiTrz), 11-[4-(biphenyl-4-yl)-6-phenyl-1,3,5-triazin-2-yl]-11,12-dihydro-12-(biphenyl-3-yl)indolo[2,3-a]carbazole (abbreviation: BP-mBPIcz(II)Tzn), 3-{3-[9-(4,6-diphenyl-1,3,5-triazin-2-yl)-2-dibenzofuranyl ]phenyl}-9-phenyl-9H-carbazole (abbreviation: mPCPDBfTzn), 9,9'-[6-(biphenyl-4-yl)-2-phenyl-1,3,5-triazine-4,3''-diyl]bis(9H-carbazole) (abbreviation: Cz-pmCzBPTzn), 3-phenyl-9-[4-phenyl-6-(9-phenyl-3-dibenzofuranyl)-1,3,5-triazin-2-yl]-9H-carbazole (abbreviation: PDBf-PCzTzn), and 9-[4-(4,6-diphenyl-1,3,5-triazin-2-yl)-2-dibenzothienyl]-2-phenyl-9H-carbazole (abbreviation: PCzDBtTzn) are examples of organic compounds containing a heteroaromatic ring with a triazine skeleton. In addition, organic compounds containing a heteroaromatic ring having a diazine skeleton, organic compounds containing a heteroaromatic ring having a pyridine skeleton, and organic compounds containing a heteroaromatic ring having a triazine skeleton are preferred because of their high reliability. In particular, organic compounds containing a heteroaromatic ring having a diazine (pyrimidine or pyrazine) skeleton and organic compounds containing a heteroaromatic ring having a triazine skeleton have high electron transport properties and contribute to reducing driving voltage.

[0262] TADF materials that can be used as host materials can be the same as those listed above as TADF materials that can be used as emissive center materials. When a TADF material is used as a host material, the triplet excitation energy generated in the TADF material is converted to singlet excitation energy through reverse intersystem crossing, and the energy is then transferred to the emissive material, thereby improving the luminous efficiency of the light-emitting device. In this case, the TADF material functions as an energy donor, and the emissive material functions as an energy acceptor.

[0263] This is very effective when the luminescent material is a fluorescent luminescent material. In this case, in order to obtain high luminous efficiency, the S1 level of the TADF material is preferably higher than the S1 level of the fluorescent luminescent material. In addition, the T1 level of the TADF material is preferably higher than the S1 level of the fluorescent luminescent material. Therefore, the T1 level of the TADF material is preferably higher than the T1 level of the fluorescent luminescent material.

[0264] It is also preferable to use a TADF material that emits light that overlaps with the wavelength of the lowest-energy absorption band of the fluorescent material, as this allows for smooth transfer of excitation energy from the TADF material to the fluorescent material, resulting in efficient light emission.

[0265] Furthermore, to efficiently generate singlet excitation energy from triplet excitation energy through reverse intersystem crossing, carrier recombination is preferred in the TADF material. Furthermore, it is preferable that the triplet excitation energy generated in the TADF material does not transfer to triplet excitation energy in the fluorescent material. To achieve this, the fluorescent material preferably has a protecting group around the luminophore (the skeleton responsible for light emission) of the fluorescent material. The protecting group is preferably a substituent without a π bond, and is preferably a saturated hydrocarbon. Specific examples include alkyl groups with 3 to 10 carbon atoms, substituted or unsubstituted cycloalkyl groups with 3 to 10 carbon atoms, and trialkylsilyl groups with 3 to 10 carbon atoms. Multiple protecting groups are even more preferred. Substituents without a π bond have poor carrier transport properties, allowing for increased distance between the TADF material and the luminophore of the fluorescent material without significantly affecting carrier transport or carrier recombination. Here, the term "luminophore" refers to the atomic group (skeleton) responsible for light emission in the fluorescent material. The luminophore preferably has a skeleton having a π bond, preferably contains an aromatic ring, and preferably has a fused aromatic ring or a fused heteroaromatic ring. Examples of such luminophores include a phenanthrene skeleton, a stilbene skeleton, an acridone skeleton, a phenoxazine skeleton, a phenothiazine skeleton, a naphthalene skeleton, an anthracene skeleton, a fluorene skeleton, a chrysene skeleton, a triphenylene skeleton, a tetracene skeleton, a pyrene skeleton, a perylene skeleton, a coumarin skeleton, a quinacridone skeleton, and a naphthobisbenzofuran skeleton. In particular, fluorescent materials having a naphthalene skeleton, an anthracene skeleton, a fluorene skeleton, a chrysene skeleton, a triphenylene skeleton, a tetracene skeleton, a pyrene skeleton, a perylene skeleton, a coumarin skeleton, a quinacridone skeleton, or a naphthobisbenzofuran skeleton are preferred because of their high fluorescence quantum yield.

[0266] When a fluorescent substance is used as the emission center substance, a material having an anthracene skeleton is suitable as the host material. Using a substance having an anthracene skeleton as a host material for a fluorescent substance makes it possible to realize an emission layer with both excellent luminous efficiency and durability. As a substance having an anthracene skeleton to be used as a host material, a diphenylanthracene skeleton, particularly a 9,10-diphenylanthracene skeleton, is preferred due to its chemical stability. Furthermore, host materials having a carbazole skeleton are preferred because of their enhanced hole injection and transport properties. However, host materials containing a benzocarbazole skeleton, in which a benzene ring is further condensed to the carbazole skeleton, are even more preferred because their HOMO is approximately 0.1 eV higher than that of host materials having a carbazole skeleton, facilitating hole insertion. In particular, host materials containing a dibenzocarbazole skeleton are preferred because their HOMO is approximately 0.1 eV higher than that of host materials having a carbazole skeleton, facilitating hole insertion, and also exhibiting excellent hole transport properties and high heat resistance. Therefore, a more preferable host material is a substance having both a 9,10-diphenylanthracene skeleton and a carbazole skeleton (or a benzocarbazole skeleton or a dibenzocarbazole skeleton). Note that, from the viewpoint of the hole injection / transport property, a benzofluorene skeleton or a dibenzofluorene skeleton may be used instead of the carbazole skeleton.Examples of such substances include 9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: PCzPA), 3-[4-(1-naphthyl)phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPN), 9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: CzPA), 7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole (abbreviation: cgDBCzPA), 6-[3-(9,10-diphenyl-2-anthryl)phenyl]benzo[b]naphtho[1,2-d]furan (abbreviation: 2mBnfPPA), 9-phenyl-10-[4-(9-phenyl-9H-fluoren-9-yl)biphenyl-4' -yl]anthracene (abbreviation: FLPPA), 9-(1-naphthyl)-10-[4-(2-naphthyl)phenyl]anthracene (abbreviation: αN-βNPAnth), 9-(1-naphthyl)-10-(2-naphthyl)anthracene (abbreviation: α,βADN), 2-(10-phenylanthracen-9-yl)dibenzofuran, 2-(10-phenyl-9-anthryl)benzo Examples include zo[b]naphtho[2,3-d]furan (abbreviation: Bnf(II)PhA), 9-(2-naphthyl)-10-[3-(2-naphthyl)phenyl]anthracene (abbreviation: βN-mβNPAnth), 1-{4-[10-(biphenyl-4-yl)-9-anthryl]phenyl}-2-ethyl-1H-benzimidazole (abbreviation: EtBImPBPhA), etc. In particular, CzPA, cgDBCzPA, 2mBnfPPA, and PCzPA are preferred choices because they exhibit very good properties.

[0267] The host material may be a mixture of multiple substances. When a mixture of host materials is used, it is preferable to mix a material having electron-transporting properties with a material having hole-transporting properties. By mixing a material having electron-transporting properties with a material having hole-transporting properties, the transport properties of the light-emitting layer 113 can be easily adjusted, and the recombination region can also be easily controlled. The weight ratio of the content of the material having hole-transporting properties to the material having electron-transporting properties is preferably 1:19 to 19:1, more preferably 1:9 to 9:1, and even more preferably 3:7 to 7:3.

[0268] A phosphorescent material can be used as part of the mixed material. The phosphorescent material can be used as an energy donor that provides excitation energy to a fluorescent material when the fluorescent material is used as a light-emitting material.

[0269] Furthermore, these mixed materials may form an exciplex. It is preferable to select a combination that forms an exciplex that emits light that overlaps with the wavelength of the lowest-energy absorption band of the light-emitting material, because this allows for smooth energy transfer and efficient light emission. Furthermore, using this structure is also preferable because it reduces the driving voltage.

[0270] At least one of the materials forming the exciplex may be a phosphorescent material, which allows triplet excitation energy to be efficiently converted into singlet excitation energy by reverse intersystem crossing.

[0271] The first electron-transporting layer 114_1 is a layer containing a substance having an electron-transporting property. The material having an electron-transporting property is a material having an electron mobility of 1×10 at a square root of an electric field strength [V / cm] of 600. -7 cm 2 / Vs or more, preferably 1×10 -6 cm 2A substance having an electron mobility of 1 / Vs or more is preferred. Note that other substances can be used as long as they have a higher electron transport property than holes. Note that the organic compound is preferably an organic compound having a π-electron-deficient heteroaromatic ring. As the organic compound having a π-electron-deficient heteroaromatic ring, for example, one or more of an organic compound having a heteroaromatic ring with an azole skeleton, an organic compound having a heteroaromatic ring with a pyridine skeleton, an organic compound having a heteroaromatic ring with a diazine skeleton, and an organic compound having a heteroaromatic ring with a triazine skeleton are preferred, and an organic compound having a heteroaromatic ring with a triazine skeleton is particularly preferred.

[0272] The organic compounds having electron transport properties that can be used in the first electron-transport layer 114_1 can be the same as the organic compounds that can be used as the organic compounds having electron transport properties of the host materials in the first light-emitting layer 113_1 and the second light-emitting layer 113_2. Among them, organic compounds containing a heteroaromatic ring with a diazine skeleton, an organic compound containing a heteroaromatic ring with a pyridine skeleton, and an organic compound containing a heteroaromatic ring with a triazine skeleton are preferred because of their high reliability. In particular, organic compounds containing a heteroaromatic ring with a diazine (pyrimidine or pyrazine) skeleton and an organic compound containing a heteroaromatic ring with a triazine skeleton have high electron transport properties and contribute to reducing driving voltage.

[0273] As described above, the second electron-transporting layer 114_2 is a layer including an organic compound having a triazine skeleton, and the details thereof have already been described, so they will not be described again.

[0274] Note that the first electron-transport layer 114_1 preferably contains an organic compound having a triazine skeleton in order to reduce power consumption. In particular, it is preferable that the first electron-transport layer 114_1 contains the same organic compound having a triazine skeleton as the organic compound having a triazine skeleton contained in the second electron-transport layer 114_2, because this prevents the manufacturing equipment from becoming complicated and is advantageous in terms of raw material procurement costs.

[0275] Furthermore, since the first electron-transporting layer 114_1 contains an organic compound that does not contain a triazine skeleton, it becomes easier to control the carrier transport property, and it becomes possible to provide a light-emitting device with better characteristics. As the organic compound that does not contain a triazine skeleton, an organic compound that contains a heteroaromatic ring having a pyridine skeleton, or an organic compound that contains a heteroaromatic ring having a diazine (pyrimidine or pyrazine) skeleton is preferable.

[0276] The intermediate layer 160 is a layer containing an organic compound having a phenanthroline skeleton. As shown in FIG. 1A, the intermediate layer 160 preferably includes a first layer 161 containing an organic compound having a phenanthroline skeleton. The intermediate layer 160 also preferably includes a second layer 162 containing a compound having hole-transporting properties and a substance having acceptor properties. The second layer 162 is located closer to the second electrode 102 than the first layer 161. The intermediate layer 160 may also include a third layer 163 between the first layer 161 and the second layer 162.

[0277] The details of the first layer have been described above, so a repeated description will be omitted.

[0278] The first layer 161 may further include an organic compound having electron-transporting properties. Examples of organic compounds having electron-transporting properties that can be used for the organic compound include those that can be used as the organic compounds having electron-transporting properties of the host materials in the first light-emitting layer 113_1 and the second light-emitting layer 113_2. Furthermore, it is preferable to use an organic compound having two or more heteroaromatic rings bonded to or condensed with each other, and the two or more heteroaromatic rings having three or more heteroatoms in total, because this improves the resistance to photolithography and suppresses an increase in driving voltage.

[0279] The first layer 161 may have a stacked structure of a layer containing an organic compound and a layer having a metal or metal compound located closer to the cathode than the layer containing the organic compound, or may be a mixed layer of an organic compound and a metal or metal compound. A mixed layer is preferable because it requires fewer deposition chambers and reduces manufacturing costs, and also contributes to improving the stability of the light-emitting device.

[0280] When an organic compound and a metal or metal compound are mixed, the distribution of the organic compound and the distribution of the metal or metal compound show roughly the same tendency when the first layer 161 is analyzed in the film thickness direction. That is, when the distribution of the organic compound is constant, the distribution of the metal or metal compound is also roughly constant. In the case of a laminated structure of a layer containing an organic compound and a layer having a metal or metal compound, the metal or metal compound may be detected in regions other than the layer having the metal or metal compound due to diffusion from the layer having the metal or metal compound, but since the distribution shows a different distribution from the distribution of the organic compound, the analysis results can be distinguished between diffusion and mixing.

[0281] The second layer 162 preferably contains an organic compound having a hole-transporting property. The second layer 162 preferably further contains a substance exhibiting an acceptor property, and the substance exhibiting an acceptor property is preferably an organic compound exhibiting an acceptor property to the organic compound having a hole-transporting property.

[0282] When the second layer 162 contains an organic compound having a hole-transport property and a substance that accepts the organic compound having a hole-transport property, holes are generated by charge separation, and when a voltage is applied between the first electrode 101 and the second electrode 102, the holes are injected into the first light-emitting unit 501 on the cathode side through the organic compound having a hole-transport property. Thus, the light-emitting device 130 of one embodiment of the present invention can be a light-emitting device with low driving voltage.

[0283] As the organic compound having hole transport properties, various organic compounds can be used, such as aromatic amine compounds, heteroaromatic compounds, aromatic hydrocarbons, and polymer compounds (oligomers, dendrimers, polymers, etc.). -6 cm 2 Preferably, the organic compound has a hole mobility of 1 / Vs or more. Furthermore, the organic compound having hole transport properties is preferably a compound having a fused aromatic hydrocarbon ring or a π-electron-rich heteroaromatic ring. The fused aromatic hydrocarbon ring is preferably an anthracene ring, a naphthalene ring, or the like. Furthermore, the π-electron-rich heteroaromatic ring is preferably a fused aromatic ring containing at least one of a pyrrole skeleton, a furan skeleton, and a thiophene skeleton, and specifically, a carbazole ring, a dibenzothiophene ring, or a ring in which an aromatic ring or a heteroaromatic ring is further fused to the above ring.

[0284] Such organic compounds having hole-transporting properties preferably have a carbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton, or an anthracene skeleton. In particular, aromatic amines having a substituent containing a dibenzofuran ring or a dibenzothiophene ring, aromatic monoamines having a naphthalene ring, or aromatic monoamines in which a 9-fluorenyl group is bonded to the nitrogen of the amine via an arylene group may be used. It is preferable that these organic compounds having hole-transporting properties are substances having an N,N-bis(4-biphenyl)amino group, since this allows the fabrication of light-emitting devices with long lifetimes.

[0285] Specifically, as the organic compound having the hole-transporting property as described above, the organic compounds listed as the organic compounds having the hole-transporting property that can be used in the hole injection layer 111 can be similarly used.

[0286] As the substance having acceptor properties, for example, the substances exemplified as organic compounds having acceptor properties that can be used in the hole-injection layer 111 can be similarly used. In particular, organic compounds having at least one of a halogen group and a cyano group are preferred, and organic compounds having at least one of a fluorine group and a cyano group are more preferred. It is more preferred that the organic compound contains four or more halogen groups (fluorine) and cyano groups in total. Examples of organic compounds having at least one of a halogen group and a cyano group include α,α',α''-1,2,3-cyclopropane triylidene tris[4-cyano-2,3,5,6-tetrafluorobenzeneacetonitrile], α,α',α''-1,2,3-cyclopropane triylidene tris[2,6-dichloro-3,5-difluoro-4-(trifluoromethyl)benzeneacetonitrile], and α,α',α''-1,2,3-cyclopropane triylidene tris[2,3,4,5,6-pentafluorobenzeneacetonitrile].

[0287] It is preferable that the material having acceptor properties has electron-accepting properties for the organic compound having hole-transporting properties. When the material having acceptor properties has electron-accepting properties for the organic compound having hole-transporting properties, charge separation occurs, and the second layer 162 can function as a charge-generating layer and as a tandem intermediate layer. It is also preferable that the second layer 162 exhibits a signal observed by electron spin resonance. For example, the spin density resulting from a signal observed around a g-value of 2.00 is 1×10 17 spins / cm 3 More than 1×10 is preferable. 18 spins / cm 3 More than 1×10 is preferable. 19 spins / cm 3 The above is even more preferable.

[0288] The third layer 163 contains a substance having an electron transporting property, and has functions such as preventing interaction between the first layer 161 and the second layer 162, smoothing the transfer of electrons to reduce the driving voltage, and reducing the interaction between the first layer 161 and the second layer 162 to improve reliability.

[0289] The LUMO level of the substance having electron-transporting properties contained in the third layer 163 is preferably between the LUMO level of the substance having acceptor properties in the second layer 162 and the LUMO level of the organic compound contained in the layer in contact with the first layer 161 in the light-emitting unit on the anode side (the first electron-transporting layer 114_1 in the first light-emitting unit 501 in FIG. 1(A)).

[0290] The specific energy level of the LUMO level of the substance having an electron-transporting property used in the third layer 163 is preferably −5.0 eV or higher, preferably −5.0 eV or higher to −3.0 eV or lower, more preferably −4.30 eV or higher to −3.00 eV or lower, and still more preferably −4.30 eV or higher to −3.30 eV or lower, in order to suppress an increase in driving voltage. Note that the substance having an electron-transporting property used in the third layer 163 is preferably a phthalocyanine-based material or a metal complex having a metal-oxygen bond and an aromatic ligand.

[0291] Specific examples of the substance having an electron transport property that can be used for the third layer 163 include diquinoxalino[2,3-a:2′,3′-c]phenazine (abbreviation: HATNA), 2,3,8,9,14,15-hexafluorodiquinoxalino[2,3-a:2′,3′-c]phenazine (abbreviation: HATNA-F6), perylene tetracarboxylic acid derivatives such as 3,4,9,10-perylene tetracarboxylic diimide (abbreviation: PTCDI) and 3,4,9,10-perylene tetracarboxylic-bis-benzimidazole (abbreviation: PTCBI), (C60-Ih)[5,6]fullerene (abbreviation: C60), and (C70-D5h)[5,6]fullerene (abbreviation: C70). Compounds having a heterophane skeleton, which is a cyclophane skeleton containing a heterocycle, can also be used, including phthalocyanine compounds such as phthalocyanine (abbreviated as HPc). Metal phthalocyanines containing copper, zinc, cobalt, iron, chromium, nickel, etc., such as copper phthalocyanine (abbreviated as CuPc), zinc phthalocyanine (abbreviated as ZnPc), cobalt phthalocyanine (abbreviated as CoPc), iron phthalocyanine (abbreviated as FePc), tin phthalocyanine (abbreviated as SnPc), tin oxide phthalocyanine (abbreviated as SnOPc), titanium oxide phthalocyanine (abbreviated as TiOPc), and vanadium oxide phthalocyanine (abbreviated as VOPc), as well as derivatives thereof, can also be used. Also preferred are metal complexes of the phthalocyanine series, such as copper phthalocyanine or zinc phthalocyanine, or 2,3,8,9,14,15-hexafluorodiquinoxalino[2,3-a:2',3'-c]phenazine.

[0292] The thickness of the third layer 163 is preferably 1 nm or more and 10 nm or less, and more preferably 2 nm or more and 5 nm or less.

[0293] Since the second layer 162 in the intermediate layer 160 functions as a hole injection layer, the second light-emitting unit 502 does not have a hole injection layer, but the second light-emitting unit 502 may have a hole injection layer.

[0294] The second electrode 102 is an electrode including a cathode. The second electrode 102 may have a laminated structure, in which case the layer in contact with the organic compound layer 103 functions as the cathode. Materials that form the cathode include metals, alloys, electrically conductive compounds, and mixtures thereof, each having a low work function (specifically, 3.8 eV or less). Specific examples of such cathode materials include alkali metals such as lithium (Li) or cesium (Cs), elements belonging to Group 1 or Group 2 of the periodic table such as magnesium (Mg), calcium (Ca), and strontium (Sr), alloys containing these elements (MgAg, AlLi), rare earth metals such as europium (Eu) and ytterbium (Yb), and alloys containing these elements. Specific examples include alkali metals, alkaline earth metals, rare earth metals, such as lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF2), 8-quinolinolato-lithium (abbreviated as Liq), and ytterbium (Yb), as well as compounds or complexes thereof, and electrides. Examples of electrides include a substance in which a high concentration of electrons is added to a mixed oxide of calcium and aluminum. Two or more of these may be mixed and used. When the second electrode 102 has a layered structure, materials with good conductivity can be used for the components other than the cathode, regardless of their work function.

[0295] Note that the second electron-transport layer 114_2 is preferably in contact with the second electrode 102. When the second electron-transport layer 114_2 is in contact with the second electrode 102, a light-emitting device having excellent electron injection and electron transport properties, low driving voltage, and low power consumption can be provided.

[0296] When the second electrode 102 is formed using a material that is transparent to visible light, a light-emitting device that emits light from the second electrode 102 side can be obtained.

[0297] These conductive materials can be formed into films by dry methods such as vacuum deposition or sputtering, inkjet methods, spin coating, etc. Alternatively, they may be formed by a wet method using a sol-gel method, or by a wet method using a paste of a metal material.

[0298] In addition, various methods, whether dry or wet, can be used to form the organic compound layer 103. For example, vacuum deposition, gravure printing, offset printing, screen printing, inkjet printing, spin coating, or the like may be used.

[0299] Furthermore, the above-mentioned electrodes or layers may be formed using different film formation methods.

[0300] FIG. 2 shows two adjacent light-emitting devices (light-emitting device 130a and light-emitting device 130b) included in a display device according to one embodiment of the present invention.

[0301] The light-emitting device 130a has an organic compound layer 103a between a first electrode 101a and a second electrode 102 on an insulating layer 175. The organic compound layer 103a has a configuration in which a first light-emitting unit 501a and a second light-emitting unit 502a are stacked with an intermediate layer 160a sandwiched therebetween. While FIG. 2 shows an example in which two light-emitting units are stacked, a configuration in which three or more light-emitting units are stacked may also be used. The first light-emitting unit 501a has a hole injection layer 111a, a first hole transport layer 112a_1, a first light-emitting layer 113a_1, and a first electron transport layer 114a_1. The intermediate layer 160a has a second layer 162a, a third layer 163a, and a first layer 161a. The third layer 163a is optional. The second light-emitting unit 502a includes a second hole-transporting layer 112a_2, a second light-emitting layer 113a_2, and a second electron-transporting layer 114a_2.

[0302] The light-emitting device 130b has an organic compound layer 103b between a first electrode 101b and a second electrode 102 on an insulating layer 175. The organic compound layer 103b has a configuration in which a first light-emitting unit 501b and a second light-emitting unit 502b are stacked with an intermediate layer 160b sandwiched therebetween. Note that while FIG. 2 shows an example in which two light-emitting units are stacked, a configuration in which three or more light-emitting units are stacked may also be used. The first light-emitting unit 501b has a hole injection layer 111b, a first hole transport layer 112b_1, a first light-emitting layer 113b_1, and a first electron transport layer 114b_1. The intermediate layer 160b has a second layer 162b, a third layer 163b, and a first layer 161b. The third layer 163b is optional. The second light-emitting unit 502b includes a second hole-transporting layer 112b_2, a second light-emitting layer 113b_2, and a second electron-transporting layer 114b_2.

[0303] The first hole transport layer 112a_1 and the second hole transport layer 112a_2 have a laminated structure, and the layer in contact with the light-emitting layer is formed using a material whose LUMO level is higher than the LUMO level of the material constituting the light-emitting layer (at least the host material, preferably the material constituting the light-emitting layer, the material with the largest composition ratio among the materials constituting the light-emitting layer, or the material with the highest LUMO level among the materials constituting the light-emitting layer).

[0304] The second electron-transporting layer 114a_2 and the second electron-transporting layer 114b_2 are layers containing an organic compound having a triazine skeleton. The first layer 161a and the first layer 161b are layers containing an organic compound having a phenanthroline skeleton.

[0305] The first light-emitting layer 113a_1 and the second light-emitting layer 113a_2 are preferably light-emitting layers that emit light of similar colors. Furthermore, the luminescent center substances contained in each layer are preferably compounds whose PL spectra have a difference in maximum peak wavelength of 30 nm or less, more preferably compounds whose PL spectra have a difference in maximum peak wavelength of 20 nm or less, and even more preferably compounds whose PL spectra have a difference in maximum peak wavelength of 10 nm or less, and even more preferably compounds whose PL spectra have a difference in maximum peak wavelength of 30 nm or less, more preferably compounds whose PL spectra have a difference in maximum peak wavelength of 20 nm or less, and even more preferably compounds whose PL spectra have a difference in maximum peak wavelength of 10 nm or less, and even more preferably compounds whose PL spectra have a difference in maximum peak wavelength of 10 nm or less.

[0306] Preferably, the first light-emitting layer 113a_1 and the first light-emitting layer 113b_1 are separated, and the second light-emitting layer 113a_2 and the second light-emitting layer 113b_2 are separated. Preferably, the emission colors of the first light-emitting layer 113a_1 and the second light-emitting layer 113a_2 are different from the emission colors of the first light-emitting layer 113b_1 and the second light-emitting layer 113b_2. Preferably, the luminescent center substance contained in the first light-emitting layer 113a_1 is different from the luminescent center substance contained in the first light-emitting layer 113b_1, and the luminescent center substance contained in the second light-emitting layer 113a_2 is different from the luminescent center substance contained in the second light-emitting layer 113b_2.

[0307] The hole injection layer 111a and the hole injection layer 111b, the first hole transport layer 112a_1 and the first hole transport layer 112b_1, the first electron transport layer 114a_1 and the first electron transport layer 114b_1, the intermediate layer 160a and the intermediate layer 160b (the second layer 162a and the second layer 162b, the third layer 163a and the third layer 163b, and the first layer 161a and the first layer 161b), the second hole transport layer 112a_2 and the second hole transport layer 112b_2, and the second electron transport layer 114a_2 and the second electron transport layer 114b_2 may be continuous layers or may be separate layers in the light-emitting device 130a and the light-emitting device 130b. Being continuous layers improves productivity and enables light-emitting devices to be fabricated inexpensively. The separate layers for each light-emitting device allow the use of materials suited to the emission color, thereby enabling the manufacture of light-emitting devices or display devices with excellent characteristics. In particular, the second electron-transporting layer 114a_2 and the second electron-transporting layer 114b_2 are preferably continuous layers, since this allows both the light-emitting device 130a and the light-emitting device 130b to have excellent characteristics.

[0308] Being a continuous layer means that the second electron transport layer 114a_2 and the second electron transport layer 114b_2 are layers made of the same material. That is, when the second electron transport layer 114a_2 and the second electron transport layer 114b_2 are layers made of the same material, both the light-emitting device 130a and the light-emitting device 130b can be light-emitting devices with excellent characteristics. Furthermore, it is more preferable that the second electron transport layer 114a_2 and the second electron transport layer 114b_2 are layers having similar structures, and it is even more preferable that they are layers having the same structure.

[0309] Furthermore, when the luminescent center substance contained in the first light-emitting layer 113a_1 is a different substance from the luminescent center substance contained in the first light-emitting layer 113b_1, and when the luminescent center substance contained in the second light-emitting layer 113a_2 is a different substance from the luminescent center substance contained in the second light-emitting layer 113b_2 (for example, when the first light-emitting layer 113a_1 and the second light-emitting layer 113a_2 are blue fluorescent light-emitting layers and the first light-emitting layer 113b_1 and the second light-emitting layer 113b_2 are green phosphorescent light-emitting layers, or When the first and second light-emitting layers 113a_1 and 113a_2 are blue fluorescent light-emitting layers and the first and second light-emitting layers 113b_1 and 113b_2 are red phosphorescent light-emitting layers, or when the first and second light-emitting layers 113a_1 and 113a_2 are green phosphorescent light-emitting layers and the first and second light-emitting layers 113b_1 and 113b_2 are red phosphorescent light-emitting layers, the carrier balances of the light-emitting layers of the light-emitting devices 130a and 130b are different. Therefore, to maximize the performance of each of the light-emitting devices 130a and 130b, appropriate intermediate layers and electron-transporting layers must be selected and changed. However, by using layers containing an organic compound having a triazine skeleton for the second electron transport layer 114a_2 and the second electron transport layer 114b_2 and using layers containing an organic compound having a phenanthroline skeleton for the first layer 161a and the first layer 161b, it is possible to obtain the performance of both the light-emitting device 130a and the light-emitting device 130b even if the second electron transport layer 114a_2 and the second electron transport layer 114b_2 have the same structure. In other words, it is possible to achieve both improved productivity and improved performance. Note that the first layer 161a and the first layer 161b may have the same structure.

[0310] The continuous layer is a so-called common layer that is formed across both the light-emitting device 130a and the light-emitting device 130b.

[0311] FIG. 3(A) is a modified example of FIG. 2. Light-emitting device 130a and light-emitting device 130b emit light of different colors, and therefore have different optical path lengths between electrodes that can amplify light emission using a microcavity structure. Therefore, in light-emitting device 130b1, the distance between the electrodes can be adjusted by increasing the thickness of light-emitting layers such as light-emitting layer 113b_11 and light-emitting layer 113b_21. Alternatively, the optical path length can be changed by thickening or adding a functional layer, such as hole-transport layer 112b_21.

[0312] FIG. 3B illustrates three adjacent light-emitting devices (light-emitting device 130a, light-emitting device 130b1, and light-emitting device 130c) included in a display device of one embodiment of the present invention.

[0313] The light-emitting device 130c includes an organic compound layer 103c between a first electrode 101c and a second electrode 102 on an insulating layer 175. The organic compound layer 103c includes a first light-emitting unit 501c and a second light-emitting unit 502c stacked with an intermediate layer 160c sandwiched therebetween. While FIG. 3B shows an example in which two light-emitting units are stacked, a stack of three or more light-emitting units may also be used. The first light-emitting unit 501c includes a hole injection layer 111c, a first hole transport layer 112c_1, a first light-emitting layer 113c_1, and a first electron transport layer 114c_1. The intermediate layer 160c includes a second layer 162c, a third layer 163c, and a first layer 161c. The third layer 163c is optional. The second light-emitting unit 502c includes a second hole-transporting layer 112c_2, a second light-emitting layer 113c_2, and a second electron-transporting layer 114c_2.

[0314] The light emitted from the light-emitting device 130c is assumed to have a shorter wavelength than the light-emitting devices 130a and 130b1. The inter-electrode distance of the light-emitting device 130c is adjusted by making the film thicknesses of the first light-emitting layer 113c_1 and the second light-emitting layer 113c_2 thinner than those of the other two light-emitting devices.

[0315] The second electron-transporting layer 114c_2 is a layer containing an organic compound having a triazine skeleton, and the first layer 161c is a layer containing an organic compound having a phenanthroline skeleton.

[0316] The first light-emitting layer 113c_1 and the second light-emitting layer 113c_2 preferably emit light of similar colors, and the luminescent center substances contained therein are preferably compounds whose PL spectra have a maximum peak wavelength difference of 30 nm or less, more preferably 20 nm or less, and even more preferably 10 nm or less, and it is even more preferable that the luminescent center substances contained therein are the same.

[0317] Preferably, the first light-emitting layer 113a_1 and the first light-emitting layer 113c_1 are separated, and the second light-emitting layer 113a_2 and the second light-emitting layer 113c_2 are separated. Preferably, the emission colors of the first light-emitting layer 113a_1 and the second light-emitting layer 113a_2 are different from the emission colors of the first light-emitting layer 113c_1 and the second light-emitting layer 113c_2. Preferably, the luminescent center substance contained in the first light-emitting layer 113a_1 is different from the luminescent center substance contained in the first light-emitting layer 113c_1, and the luminescent center substance contained in the second light-emitting layer 113a_2 is different from the luminescent center substance contained in the second light-emitting layer 113c_2.

[0318] In the above example, hole injection layer 111a and hole injection layer 111c, first hole transport layer 112a_1 and first hole transport layer 112c_1, first electron transport layer 114a_1 and first electron transport layer 114c_1, intermediate layer 160a and intermediate layer 160c (second layer 162a and second layer 162c, third layer 163a and third layer 163c, first layer 161a and first layer 161c), and second hole transport layer 112a_2 and second hole transport layer 112c_2 are each independently separated between light-emitting device 130a and light-emitting device 130c, while second electron transport layer 114a_2 and second electron transport layer 114c_2 are a continuous layer. In this way, a single light-emitting device may include both continuous and separated layers. This allows a light-emitting device or display device with a good balance between productivity and performance to be manufactured. In particular, the second electron-transporting layer 114a_2 and the second electron-transporting layer 114c_2 are preferably formed as a continuous layer, which allows both the light-emitting device 130a and the light-emitting device 130c to have good performance.

[0319] For example, in a three-color light-emitting device having two light-emitting devices with fluorescent luminescent center substances and one light-emitting device with phosphorescent luminescent center substances, it is preferable that the carrier transport layer in the light-emitting device with fluorescent luminescent center substances be formed as a continuous layer, and that the carrier transport layer in the light-emitting device with phosphorescent luminescent center substances be formed as a layer separated from the light-emitting devices emitting other luminescent colors. Alternatively, in a three-color light-emitting device having two light-emitting devices with phosphorescent luminescent center substances and one light-emitting device with fluorescent luminescent center substances, it is preferable that the carrier transport layer in the light-emitting device with phosphorescent luminescent center substances be formed as a continuous layer, and that the carrier transport layer in the light-emitting device with fluorescent luminescent center substances be formed as a layer separated from the light-emitting devices emitting other luminescent colors.

[0320] A light-emitting device according to one embodiment of the present invention will be described with reference to Fig. 4. Fig. 4 is a schematic diagram of a light-emitting device 130a and a light-emitting device 130b, which are two adjacent light-emitting devices formed on the same insulating surface and which are included in a light-emitting device, and which are modifications of the light-emitting devices described with reference to Figs.

[0321] The light-emitting device 130a is located on the insulating layer 175 and includes a first electrode 101a including an anode, a second electrode 102 including a cathode, and an organic compound layer 103a. The organic compound layer 103a is located between the first electrode 101a and the second electrode 102. The organic compound layer 103a has a configuration in which a first light-emitting unit 501a and a second light-emitting unit 502a are stacked with an intermediate layer 160a sandwiched therebetween.

[0322] The first light-emitting unit 501a includes a first hole-transport layer 112a_1 (hole-transport layer 112a_1a and hole-transport layer 112a_1b), a first light-emitting layer 113a_1, and a first electron-transport layer 114a_1. The intermediate layer 160a includes a first layer 161a and a second layer 162a. The second light-emitting unit 502a includes a second hole-transport layer 112a_2 (hole-transport layer 112a_2a and hole-transport layer 112a_2b), a second light-emitting layer 113a_2, a second electron-transport layer 114a_2, and an electron-injection layer 115. Therefore, it can be said that the intermediate layer 160a is located between the first light-emitting layer 113a_1 and the second light-emitting layer 113a_2.

[0323] In the light-emitting device 130a, the first light-emitting unit 501a preferably includes a hole-injection layer 111a. The intermediate layer 160a may include a third layer 163a between the first layer 161a and the second layer 162a. When the anode-side surface of the light-emitting unit is in contact with the intermediate layer 160a, as in the case of the second light-emitting unit 502a, the second layer 162a of the intermediate layer 160a located on the cathode side can also function as the hole-injection layer for the second light-emitting unit 502a. Therefore, the hole-injection layer 111 may not be provided in the second light-emitting unit. In other words, the hole-injection layer 111 may be provided as needed to achieve the desired performance of the light-emitting device.

[0324] Here, the light-emitting device 130b may have a different structure from the light-emitting device 130a. For example, the light-emitting device 130b shown in FIG. 4 has a different structure from the light-emitting device 130a in the first hole transport layer 112a_1 and the second hole transport layer 112a_2. When different light-emitting materials are used for the light-emitting layers of the light-emitting device 130a and the light-emitting device 130b, it is preferable to prepare an appropriate layer structure according to each light-emitting material. By separately preparing a structure for each light-emitting device so as to obtain optimal characteristics, the characteristics of the light-emitting device as a whole can be improved.

[0325] The light-emitting device 130b is located on the insulating layer 175 and includes a first electrode 101b including an anode, a second electrode 102 including a cathode, and an organic compound layer 103b. The organic compound layer 103b is located between the first electrode 101b and the second electrode 102. The organic compound layer 103b has a structure in which a first light-emitting unit 501b and a second light-emitting unit 502b are stacked with an intermediate layer 160b sandwiched therebetween.

[0326] The first light-emitting unit 501b includes a first light-emitting layer 113b_1. The intermediate layer 160b includes a first layer 161b and a second layer 162b. The second light-emitting unit 502b includes a second light-emitting layer 113b_2 and an electron injection layer 115. In other words, the intermediate layer 160b is located between the first light-emitting layer 113b_1 and the second light-emitting layer 113b_2.

[0327] In the light-emitting device 130b, the first light-emitting unit 501b preferably includes a hole-injection layer 111b, a first hole-transport layer 112b_1, and a first electron-transport layer 114b_1 in addition to the first light-emitting layer 113b_1. The second light-emitting unit 502b preferably includes a second hole-transport layer 112b_2 and a second electron-transport layer 114b_2 in addition to the second light-emitting layer 113b_2 and the electron-injection layer 115. The intermediate layer 160b may include a third layer 163b between the first layer 161b and the second layer 162b. In addition, when the anode-side surface of the light-emitting unit is in contact with the intermediate layer 160b, as in the second light-emitting unit 502b, the second layer 162b of the intermediate layer 160b located on the cathode side can also serve as the hole-injection layer for the second light-emitting unit 502b, and therefore the light-emitting unit may not be provided with the hole-injection layer 111. In other words, the hole-injection layer 111 may be provided as needed to achieve the desired performance of the light-emitting device.

[0328] Note that the light-emitting device according to one embodiment of the present invention does not necessarily have to include a light-emitting device having the configuration shown in light-emitting device 130b, and may include a plurality of light-emitting devices having the configuration shown in light-emitting device 130a. When the configuration of the light-emitting devices is unified in the light-emitting device, the complexity of the manufacturing equipment can be reduced.

[0329] Although Figure 4 shows an example in which each organic compound layer contains two light-emitting units, one embodiment of the present invention is not limited to this. Each organic compound layer may contain three or more light-emitting units. By stacking multiple light-emitting units between a pair of electrodes with an intermediate layer sandwiched therebetween, a highly reliable light-emitting device can be realized, which can emit light with high luminance while maintaining a low current density. Furthermore, a light-emitting device with low power consumption can be realized.

[0330] Furthermore, the light-emitting device 130, the light-emitting device 130a, or the light-emitting device 130b may be a light-emitting device fabricated using, for example, a lithography method. That is, the light-emitting device 130, the light-emitting device 130a, and the light-emitting device 130b can each be fabricated by processing a part of the organic compound layer using a lithography method. In the case of a light-emitting device fabricated using a lithography method, at least the first light-emitting layer 113_1 or the second light-emitting layer 113_2 and the organic compound layer provided closer to the first electrode 101 than the first light-emitting layer 113_1 or the second light-emitting layer 113_2 are processed simultaneously, so that their edges are roughly aligned in the vertical direction.

[0331] A light-emitting device of the present invention having such a structure can be a light-emitting device with high current efficiency, low energy loss, and favorable characteristics. A display device according to one embodiment of the present invention using such a light-emitting device can be a display device with low power consumption, high reliability, and high luminance, and thus has favorable visibility. This embodiment can be freely combined with other embodiments.

[0332] The above structure provides particularly significant benefits when used in a multi-layered tandem light-emitting device according to one embodiment of the present application. As described below, multi-layered tandem light-emitting devices have different layer structures for the red, green, and blue light-emitting devices, and because these devices are stacked, the types and amounts of materials used are increased. Therefore, by using the same fused rings, the same fused rings bonded at different positions, or fused rings that are structural isomers in multiple layers, as described above, it is possible to achieve manufacturing benefits such as reduced raw material costs and simplified synthesis steps, as well as physical property benefits such as adjustment of Tg and carrier transport properties. Furthermore, by using such materials in a multi-layered tandem light-emitting device according to one embodiment of the present application, a light-emitting device suitable for mass production can be realized.

[0333] (Embodiment 2) In this embodiment, a display device manufactured using the light-emitting device described in Embodiment 1 will be described with reference to FIG. 5. FIG. 5A is a top view showing the display device, and FIG. 5B is a cross-sectional view taken along lines AB and CD in FIG. 5A. This display device includes a driver circuit section (source line driver circuit) 601, a pixel section 602, and a driver circuit section (gate line driver circuit) 603, all of which are shown by dotted lines, to control light emission from the light-emitting device. 604 is a sealing substrate, 605 is a sealant, and the inside surrounded by the sealant 605 is a space 607.

[0334] The routing wiring 608 is wiring for transmitting signals input to the source line driver circuit 601 and the gate line driver circuit 603, and receives video signals, clock signals, start signals, reset signals, etc. from an FPC (flexible print circuit) 609, which serves as an external input terminal. Although only the FPC is shown here, a printed wiring board (PWB) may be attached to this FPC. In this specification, the display device includes not only the display device itself, but also a state in which an FPC or PWB is attached to it.

[0335] Next, the cross-sectional structure will be described with reference to Fig. 5(B) . A driver circuit portion and a pixel portion are formed on an element substrate 610, but here, a source line driver circuit 601, which is the driver circuit portion, and one pixel in a pixel portion 602 are shown.

[0336] The element substrate 610 may be made of a substrate made of glass, quartz, organic resin, metal, alloy, semiconductor, or a plastic substrate made of FRP (Fiber Reinforced Plastics), PVF (Polyvinyl Fluoride), polyester, acrylic resin, or the like.

[0337] The structure of the transistors used in the pixels and the driver circuits is not particularly limited. For example, they may be inverted staggered transistors or staggered transistors. Furthermore, they may be top-gate or bottom-gate transistors. The semiconductor material used for the transistors is not particularly limited, and examples thereof include silicon, germanium, silicon carbide, and gallium nitride. Alternatively, an oxide semiconductor containing at least one of indium, gallium, and zinc, such as an In-Ga-Zn-based metal oxide, may be used.

[0338] The crystallinity of a semiconductor material used for a transistor is not particularly limited, and any of an amorphous semiconductor and a crystalline semiconductor (a microcrystalline semiconductor, a polycrystalline semiconductor, a single crystal semiconductor, or a semiconductor having a crystalline region in part) may be used. The use of a crystalline semiconductor is preferable because it can suppress deterioration of transistor characteristics.

[0339] Here, it is preferable to use an oxide semiconductor for the transistors provided in the pixel and the driver circuit, as well as for semiconductor devices such as transistors used in touch sensors, which will be described later. In particular, it is preferable to use an oxide semiconductor having a wider band gap than silicon. By using an oxide semiconductor having a wider band gap than silicon, the current in the off state of the transistor can be reduced.

[0340] The oxide semiconductor preferably contains at least indium (In) or zinc (Zn), and more preferably contains an oxide represented by In-M-Zn oxide (M is a metal such as Al, Ti, Ga, Ge, Y, Zr, Sn, La, Ce, or Hf).

[0341] In particular, it is preferable to use an oxide semiconductor film as the semiconductor layer, which has a plurality of crystal parts whose c-axes are oriented perpendicular to the surface on which the semiconductor layer is formed or the top surface of the semiconductor layer, and in which no grain boundaries can be found between adjacent crystal parts.

[0342] By using such a material for the semiconductor layer, fluctuations in electrical characteristics are suppressed, and a highly reliable transistor can be realized.

[0343] Furthermore, a transistor having the above-described semiconductor layer can retain charge accumulated in a capacitor through the transistor for a long period of time due to its low off-state current. By applying such a transistor to a pixel, it is possible to stop a driver circuit while maintaining the gray level of each pixel. As a result, an electronic device with extremely low power consumption can be realized.

[0344] To stabilize the characteristics of the transistor, it is preferable to provide an underlayer film. The underlayer film can be formed as a single layer or a multilayer using an inorganic insulating film such as a silicon oxide film, a silicon nitride film, a silicon oxynitride film, or a silicon nitride oxide film. The underlayer film can be formed by a sputtering method, a CVD (Chemical Vapor Deposition) method (such as a plasma CVD method, a thermal CVD method, or a MOCVD (Metal Organic CVD) method), an ALD (Atomic Layer Deposition) method, a coating method, a printing method, or the like. Note that the underlayer film need not be provided if it is not necessary.

[0345] Note that FET 623 represents one of the transistors formed in the source line driver circuit 601. The driver circuit may be formed of various CMOS circuits, PMOS circuits, or NMOS circuits. In addition, although this embodiment shows a driver-integrated type in which the driver circuit is formed on a substrate, this is not necessarily required, and the driver circuit may also be formed externally rather than on the substrate.

[0346] Furthermore, the pixel portion 602 is formed by a plurality of pixels each including a switching FET 611, a current control FET 612, and a first electrode 613 electrically connected to the drain of the FET, but is not limited to this, and the pixel portion may be formed by combining three or more FETs and a capacitive element.

[0347] An insulator 614 is formed to cover an end portion of the first electrode 613. Here, the insulator 614 can be formed using a positive photosensitive acrylic resin film.

[0348] Furthermore, in order to improve the coverage of an organic compound layer or the like to be formed later, a curved surface having a curvature is formed at the upper or lower end of the insulator 614. For example, when a positive photosensitive acrylic resin is used as the material for the insulator 614, it is preferable that only the upper end of the insulator 614 has a curved surface having a curvature radius (0.2 μm to 3 μm). Furthermore, either a negative photosensitive resin or a positive photosensitive resin can be used as the insulator 614.

[0349] An organic compound layer 616 and a second electrode 617 are formed on the first electrode 613. The first electrode 613, which functions as an anode, is preferably made of a material with a large work function. For example, a single-layer film such as an ITO film, an indium tin oxide film containing silicon, an indium oxide film containing 2 to 20 wt % zinc oxide, a titanium nitride film, a chromium film, a tungsten film, a Zn film, or a Pt film can be used. It is also possible to use a laminated structure of a titanium nitride film and a film mainly composed of aluminum, or a three-layer structure of a titanium nitride film, a film mainly composed of aluminum, and a titanium nitride film. The laminated structure provides low wiring resistance, good ohmic contact, and the first electrode 613 can function as an anode.

[0350] The organic compound layer 616 is formed by various methods such as a vapor deposition method using a vapor deposition mask, an inkjet method, or a spin coating method. The organic compound layer 616 includes the structure described in Embodiment 1. Other materials constituting the organic compound layer 616 may be low-molecular-weight compounds or high-molecular-weight compounds (including oligomers and dendrimers).

[0351] Furthermore, the second electrode 617, which is formed on the organic compound layer 616 and functions as a cathode, is preferably made of a material with a small work function (such as Al, Mg, Li, or Ca, or alloys and compounds thereof (MgAg, MgIn, AlLi, etc.)). When light generated in the organic compound layer 616 is to be transmitted through the second electrode 617, the second electrode 617 is preferably made of a laminate of a thin metal thin film and a transparent conductive film (such as ITO, indium oxide containing 2 to 20 wt % zinc oxide, indium tin oxide containing silicon, or zinc oxide (ZnO)).

[0352] Note that a light-emitting device is formed with the first electrode 613, the organic compound layer 616, and the second electrode 617. The light-emitting device is the light-emitting device described in Embodiment 1. Note that a pixel portion is formed with a plurality of light-emitting devices, but the display device in this embodiment may include both the light-emitting device described in Embodiment 1 and light-emitting devices having other structures.

[0353] Furthermore, by bonding the sealing substrate 604 to the element substrate 610 with a sealant 605, a structure is formed in which a light-emitting device 618 is provided in a space 607 surrounded by the element substrate 610, the sealing substrate 604, and the sealant 605. The space 607 is filled with a filler, which may be filled with an inert gas (nitrogen, argon, etc.) or a sealant. A recess is formed in the sealing substrate and a desiccant is provided therein, which is a preferable configuration because it can suppress deterioration due to the influence of moisture.

[0354] It is preferable to use epoxy resin or glass frit for the sealing material 605. It is also desirable that these materials are as moisture and oxygen impermeable as possible. In addition, materials that can be used for the sealing substrate 604 include glass substrates, quartz substrates, and plastic substrates made of FRP (Fiber Reinforced Plastics), PVF (Polyvinyl Fluoride), polyester, acrylic resin, etc.

[0355] Although not shown in Fig. 5, a protective film may be provided on the second electrode. The protective film may be formed of an organic resin film or an inorganic insulating film. The protective film may also be formed so as to cover the exposed portion of the sealing material 605. The protective film may also be provided so as to cover the surfaces and side surfaces of the pair of substrates, the exposed side surfaces of the sealing layer, the insulating layer, etc.

[0356] The protective film can be made of a material that is impermeable to impurities such as water, and therefore can effectively prevent impurities such as water from diffusing from the outside to the inside.

[0357] The protective film may be made of an oxide, nitride, fluoride, sulfide, ternary compound, metal, polymer, or the like. For example, a material containing aluminum oxide, hafnium oxide, hafnium silicate, lanthanum oxide, silicon oxide, strontium titanate, tantalum oxide, titanium oxide, zinc oxide, niobium oxide, zirconium oxide, tin oxide, yttrium oxide, cerium oxide, scandium oxide, erbium oxide, vanadium oxide, indium oxide, or the like; a material containing aluminum nitride, hafnium nitride, silicon nitride, tantalum nitride, titanium nitride, niobium nitride, molybdenum nitride, zirconium nitride, or gallium nitride, or the like; a nitride containing titanium and aluminum, an oxide containing titanium and aluminum, an oxide containing aluminum and zinc, a sulfide containing manganese and zinc, a sulfide containing cerium and strontium, an oxide containing erbium and aluminum, or an oxide containing yttrium and zirconium, or the like.

[0358] The protective film is preferably formed using a film formation method that provides good step coverage. One such method is atomic layer deposition (ALD). It is preferable to use a material that can be formed using the ALD method for the protective film. By using the ALD method, it is possible to form a dense protective film with reduced defects such as cracks and pinholes, or with a uniform thickness. In addition, it is possible to reduce damage to the workpiece when forming the protective film.

[0359] For example, by forming a protective film using the ALD method, it is possible to form a uniform protective film with few defects on surfaces with complex uneven shapes, including the top, side, and back surfaces of a touch panel.

[0360] In this manner, a display device manufactured using the light-emitting device described in Embodiment 1 can be obtained.

[0361] The display device in this embodiment uses the light-emitting device described in Embodiment 1, and therefore, a display device with favorable characteristics can be obtained. Specifically, the light-emitting device described in Embodiment 1 has high emission efficiency, and therefore, a display device with low power consumption can be obtained. Furthermore, the light-emitting device described in Embodiment 1 has favorable reliability, and therefore, a display device with favorable reliability can be obtained. In addition, the light-emitting device described in Embodiment 1 can be a light-emitting device with favorable chromaticity and color purity, and therefore, a display device with favorable display quality can be obtained.

[0362] This embodiment mode can be freely combined with other embodiment modes.

[0363] (Embodiment 3) 6A and 6B, a plurality of light-emitting devices 130 are formed over an insulating layer 175 to form a display device. In this embodiment, a display device according to one embodiment of the present invention will be described in detail.

[0364] The display device 100 has a pixel section 177 in which a plurality of pixels 178 are arranged in a matrix. The pixel 178 has a sub-pixel 110R, a sub-pixel 110G, and a sub-pixel 110B.

[0365] In this specification and the like, when describing matters common to, for example, the subpixels 110R, 110G, and 110B, they may be referred to as the subpixels 110. When describing matters common to other components distinguished by alphabets, they may also be described using symbols without the alphabets.

[0366] The sub-pixel 110R emits red light, the sub-pixel 110G emits green light, and the sub-pixel 110B emits blue light. This allows an image to be displayed in the pixel unit 177. In this embodiment, sub-pixels of three colors, red (R), green (G), and blue (B), are described as an example, but combinations of sub-pixels of other colors may also be used. The number of sub-pixels is not limited to three, and may be four or more. Examples of four sub-pixels include sub-pixels of four colors: R, G, B, and white (W); sub-pixels of four colors: R, G, B, and yellow (Y); and sub-pixels of R, G, B, and infrared (IR).

[0367] In this specification, the row direction may be referred to as the X direction, and the column direction may be referred to as the Y direction. The X direction and the Y direction intersect, for example, perpendicularly.

[0368] 6A shows an example in which sub-pixels of different colors are arranged side by side in the X direction, and sub-pixels of the same color are arranged side by side in the Y direction. Note that sub-pixels of different colors may also be arranged side by side in the Y direction, and sub-pixels of the same color may also be arranged side by side in the X direction.

[0369] A connection portion 140 may be provided outside the pixel portion 177, and a region 141 may be provided. The region 141 is provided between the pixel portion 177 and the connection portion 140. The region 141 is provided with an organic compound layer 103. Furthermore, the connection portion 140 is provided with a conductive layer 151C.

[0370] 6(A) shows an example in which the region 141 and the connection portion 140 are located on the right side of the pixel portion 177, but the positions of the region 141 and the connection portion 140 are not particularly limited. The region 141 and the connection portion 140 may be singular or plural.

[0371] Fig. 6(B) is an example of a cross-sectional view taken along dashed line A1-A2 in Fig. 6(A). As shown in Fig. 6(B), the display device 100 includes an insulating layer 171, a conductive layer 172 on the insulating layer 171, an insulating layer 173 on the insulating layer 171 and on the conductive layer 172, an insulating layer 174 on the insulating layer 173, and an insulating layer 175 on the insulating layer 174. The insulating layer 171 is provided on a substrate (not shown). The insulating layer 175, the insulating layer 174, and the insulating layer 173 have openings that reach the conductive layer 172, and a plug 176 is provided to fill the opening.

[0372] In the pixel section 177, the light-emitting device 130 is provided on the insulating layer 175 and the plug 176. A protective layer 131 is provided to cover the light-emitting device 130. The substrate 120 is bonded to the protective layer 131 by a resin layer 122. Preferably, an inorganic insulating layer 125 and an insulating layer 127 on the inorganic insulating layer 125 are provided between adjacent light-emitting devices 130.

[0373] 6B shows multiple cross sections of the inorganic insulating layer 125 and the insulating layer 127, it is preferable that the inorganic insulating layer 125 and the insulating layer 127 are connected to one another when the display device 100 is viewed from above. That is, it is preferable that the inorganic insulating layer 125 and the insulating layer 127 are insulating layers having openings above the first electrodes.

[0374] 6(B) shows light emitting device 130R, light emitting device 130G, and light emitting device 130B. Light emitting device 130R, light emitting device 130G, and light emitting device 130B emit light of different colors. For example, light emitting device 130R can emit red light, light emitting device 130G can emit green light, and light emitting device 130B can emit blue light. Furthermore, light emitting device 130R, light emitting device 130G, or light emitting device 130B may emit other visible light or infrared light.

[0375] The display device of one embodiment of the present invention can be, for example, a top-emission type that emits light in a direction opposite to a substrate on which a light-emitting device is formed. Note that the display device of one embodiment of the present invention may also be a bottom-emission type.

[0376] Examples of the light-emitting material contained in the light-emitting device 130 include organic compounds or organometallic complexes such as fluorescent materials, phosphorescent materials, and thermally activated delayed fluorescence (TADF) materials. Furthermore, the light-emitting material may also be an inorganic compound such as quantum dots.

[0377] The light-emitting device 130R has the configuration described in Embodiment 1. It includes a first electrode (pixel electrode) composed of a conductive layer 151R and a conductive layer 152R, an organic compound layer 103R on the first electrode, a common layer 104 on the organic compound layer 103R, and a second electrode (common electrode) 102 on the common layer 104. The common layer 104 may or may not be provided, but is preferably provided because it can reduce damage to the organic compound layer 103R during processing. When the common layer 104 is provided, it is preferably an electron injection layer. When the common layer 104 is provided, the stacked structure of the organic compound layer 103R and the common layer 104 corresponds to the organic compound layer 103.

[0378] The light-emitting device 130G has the same configuration as that described in Embodiment 1. It includes a first electrode (pixel electrode) composed of a conductive layer 151G and a conductive layer 152G, an organic compound layer 103G on the first electrode, a common layer 104 on the organic compound layer 103G, and a second electrode (common electrode) 102 on the common layer 104. The common layer 104 may or may not be provided, but is preferably provided because it can reduce damage to the organic compound layer 103G during processing. When the common layer 104 is provided, it is preferably an electron injection layer. When the common layer 104 is provided, the stacked structure of the organic compound layer 103G and the common layer 104 corresponds to the organic compound layer 103.

[0379] The light-emitting device 130B has the same configuration as that described in Embodiment 1. It includes a first electrode (pixel electrode) composed of a conductive layer 151B and a conductive layer 152B, an organic compound layer 103B on the first electrode, a common layer 104 on the organic compound layer 103B, and a second electrode (common electrode) 102 on the common layer 104. The common layer 104 may or may not be provided, but is preferably provided because it can reduce damage to the organic compound layer 103B during processing. When the common layer 104 is provided, it is preferably an electron injection layer. When the common layer 104 is provided, the laminated structure of the organic compound layer 103B and the common layer 104 corresponds to the organic compound layer 103.

[0380] One of the pixel electrode and the common electrode of the light-emitting device functions as an anode and the other functions as a cathode. In the following description, unless otherwise specified, the pixel electrode functions as an anode and the common electrode functions as a cathode.

[0381] The organic compound layer 103R, the organic compound layer 103G, and the organic compound layer 103B are independent and island-shaped for each light-emitting device. By providing the organic compound layer 103 in an island shape for each light-emitting device 130, leakage current between adjacent light-emitting devices 130 can be suppressed even in a high-resolution display device. This makes it possible to prevent crosstalk and realize a display device with extremely high contrast. In particular, a display device with high current efficiency at low brightness can be realized.

[0382] The island-shaped organic compound layer 103 is formed by depositing an EL film and processing the EL film using a lithography method.

[0383] In the display device of one embodiment of the present invention, the first electrode (pixel electrode) of the light-emitting device preferably has a stacked structure. For example, in the example shown in FIG. 6B, the first electrode of the light-emitting device 130 has a stacked structure of a conductive layer 151 (conductive layer 151R, conductive layer 151G, and conductive layer 151B) and a conductive layer 152 (conductive layer 152R, conductive layer 152G, and conductive layer 152B). For example, when the display device 100 is a top-emission type and the pixel electrode of the light-emitting device 130 functions as an anode, it is preferable that the conductive layer 151 has high reflectivity for visible light and the conductive layer 152 has transparency to visible light and a high work function. When the display device 100 is a top-emission type, the higher the reflectivity of the pixel electrode for visible light, the higher the extraction efficiency of light emitted from the organic compound layer 103. When the pixel electrode functions as an anode, the higher the work function of the pixel electrode, the easier it is to inject holes into the organic compound layer 103. As described above, by forming the pixel electrode of the light-emitting device 130 into a laminated structure of the conductive layer 151 having a high reflectivity for visible light and the conductive layer 152 having a high work function, the light-emitting device 130 can be made into a light-emitting device with high light extraction efficiency and low driving voltage.

[0384] When the conductive layer 151 is a layer having high reflectance to visible light, the reflectance of the conductive layer 151 to visible light is preferably, for example, 40% to 100%, or 70% to 100%. When the conductive layer 152 is an electrode that is transparent to visible light, the transmittance of the conductive layer 152 to visible light is preferably, for example, 40% or more.

[0385] For example, a metal material can be used for the conductive layer 151. Specifically, metals such as aluminum (Al), titanium (Ti), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), gallium (Ga), zinc (Zn), indium (In), tin (Sn), molybdenum (Mo), tantalum (Ta), tungsten (W), palladium (Pd), gold (Au), platinum (Pt), silver (Ag), yttrium (Y), neodymium (Nd), etc., and alloys containing appropriate combinations of these metals can also be used.

[0386] The conductive layer 152 can be formed using an oxide containing one or more selected from indium, tin, zinc, gallium, titanium, aluminum, and silicon. For example, it is preferable to use a conductive oxide containing one or more of indium oxide, indium tin oxide, indium zinc oxide, zinc oxide, zinc oxide containing gallium, titanium oxide, indium zinc oxide containing gallium, indium zinc oxide containing aluminum, indium tin oxide containing silicon, and indium zinc oxide containing silicon. In particular, indium tin oxide containing silicon has a large work function, for example, a work function of 4.0 eV or more, and therefore can be suitably used for the conductive layer 152.

[0387] The conductive layer 151 or the conductive layer 152 may have a stacked structure of multiple layers containing different materials. In this case, the conductive layer 151 may include a layer using a material that can be used for the conductive layer 152, such as a conductive oxide, or the conductive layer 152 may include a layer using a material that can be used for the conductive layer 151, such as a metal material. For example, when the conductive layer 151 has a stacked structure of two or more layers, a layer in contact with the conductive layer 152 can be a layer using a material that can be used for the conductive layer 152.

[0388] The side surfaces of the conductive layer 151 or the conductive layer 152 preferably have a tapered shape. Specifically, the side surfaces of the conductive layer 151 or the conductive layer 152 preferably have a tapered shape with a taper angle of less than 90°. The end surfaces of the insulating layer 156 (insulating layer 156R, insulating layer 156G, and insulating layer 156B) may also have a tapered shape. Specifically, when the end surfaces of the insulating layer 156 have a tapered shape with a taper angle of less than 90°, the coverage of structures provided along the side surfaces of the insulating layer 156 can be improved.

[0389] The conductive layer 151 may also have a stacked structure of three or more layers. When the conductive layer 151 has a stacked structure of multiple layers, the reflectivity of at least one of the layers constituting the conductive layer 151 to visible light may be higher than the reflectivity of the conductive layer 152 to visible light. When the conductive layer 151 has a structure of three or more layers, it is preferable that the outermost conductive layer be made of a material that is less susceptible to deterioration than the conductive layers used in the middle. For example, the layer in contact with the insulating layer 175 can be made of a material that is less susceptible to migration than the materials used in the other layers. The layer in contact with the insulating layer 175 can be made of a material that is less susceptible to oxidation and has an oxide with lower electrical resistivity than the oxides of the materials used in the other layers.

[0390] As described above, it is possible to widen the range of material choices for the conductive layer 151. Therefore, by using aluminum or an alloy containing aluminum as the material for the conductive layer 151, the layer can have high reflectance for visible light. Furthermore, aluminum may be combined with titanium, which has a lower reflectance for visible light than aluminum but is less likely to cause migration than aluminum even when in contact with the insulating layer 175.

[0391] Alternatively, silver or an alloy containing silver may be used for the conductive layer 151. Silver has a characteristic that its reflectance to visible light is higher than that of titanium. Furthermore, silver is less susceptible to oxidation than aluminum, and the electrical resistivity of silver oxide is lower than that of aluminum oxide. As described above, when silver or an alloy containing silver is used for the conductive layer 151, the reflectance of the conductive layer 151 to visible light can be suitably increased while suppressing an increase in the electrical resistance of the pixel electrode due to oxidation. Here, an alloy containing silver can be, for example, an alloy of silver, palladium, and copper (Ag-Pd-Cu, also referred to as APC).

[0392] For example, when a microcavity structure is applied to the light-emitting device 130, the conductive layer 151 can be made of silver or an alloy containing silver, which is a material with high reflectivity for visible light, to suitably improve the light extraction efficiency of the display device 100.

[0393] Furthermore, when the conductive layer 152 has a laminated structure, by making the laminated structure such that the reflectance for visible light (for example, the reflectance for light of a predetermined wavelength in the range of 400 nm or more and less than 750 nm) is different from the reflectance for visible light of the conductive layer 151, it is possible to form a microcavity structure in combination with the conductive layer 151.

[0394] As described above, the characteristics of the display device can be improved by forming the conductive layer 151 or the conductive layer 152 into a stacked structure of multiple layers. For example, the display device 100 can have high light extraction efficiency and high reliability.

[0395] Note that the conductive layer 151 can be formed by a lithography method. Specifically, first, a conductive film to be the conductive layer 151 is formed. Next, a resist mask is formed over the conductive film to be the conductive layer 151. After that, the conductive film in a region that does not overlap with the resist mask is removed by, for example, an etching method. Here, compared to when the conductive layer 151 is formed so that the side surfaces are not tapered, that is, so that the side surfaces are vertical, the conductive film is processed under conditions that make it easy for the resist mask to recede (shrink), whereby the side surfaces of the conductive layer 151 can be tapered.

[0396] The conductive layer 152 may be processed by lithography simultaneously with the conductive layer 151. In this case, the side surface of the conductive layer 152 can also be formed into a tapered shape.

[0397] Here, if the conductive film is processed under conditions that make it easy for the resist mask to recede (shrink), the conductive film may be easily processed in the horizontal direction, which may result in higher isotropy of etching than when the conductive layer 151 is formed so that the side surfaces are vertical.

[0398] Furthermore, when the conductive layer 151 has a laminated structure of a plurality of layers made of different materials, the ease of processing in the horizontal direction may differ between the plurality of layers.

[0399] 6B, the insulating layer 156 can prevent corrosion of the conductive layer 151. Therefore, the display device 100 can be manufactured with a high yield. Furthermore, the occurrence of defects can be prevented, and the display device 100 can be a highly reliable display device.

[0400] 6(B), the insulating layer 156 preferably has a curved surface. This can prevent discontinuities in the conductive layer 152 covering the insulating layer 156, compared to when the side surfaces of the insulating layer 156 are vertical (parallel to the Z direction). Even when the insulating layer 156 has a tapered shape on the side surface, specifically a tapered shape with a taper angle of less than 90°, the occurrence of discontinuities in the conductive layer 152 covering the insulating layer 156 can be prevented, compared to when the side surfaces of the insulating layer 156 are vertical. As described above, the display device 100 can be manufactured by a method with a high yield. Furthermore, the occurrence of defects can be prevented, and the display device 100 can be a highly reliable display device.

[0401] 6A , an example of a manufacturing method for the display device 100 will be described with reference to FIGS. 7 to 12. The light-emitting device included in the display device 100 has an organic layer formed by a manufacturing process including a treatment using water. By using the organic compound of one embodiment of the present invention for the organic layer of the light-emitting device included in the display device of one embodiment of the present invention, problems such as dissolution of the layer including the organic compound and penetration of a chemical solution into the layer including the organic compound can be prevented even when the display device is manufactured by a manufacturing method including a treatment using water, and a light-emitting device with excellent characteristics can be provided.

[0402] [Example of manufacturing method] Thin films (insulating films, semiconductor films, conductive films, etc.) that make up display devices can be formed using methods such as sputtering, chemical vapor deposition (CVD), vacuum evaporation, pulsed laser deposition (PLD), or ALD. CVD methods include plasma enhanced chemical vapor deposition (PECVD) and thermal CVD. One type of thermal CVD method is metal organic chemical vapor deposition (MOCVD).

[0403] Furthermore, thin films (insulating films, semiconductor films, conductive films, etc.) that constitute the display device can be formed by wet film formation methods such as spin coating, dipping, spray coating, inkjet, dispensing, screen printing, offset printing, doctor knife method, slit coating, roll coating, curtain coating, or knife coating.

[0404] In particular, vacuum processes such as vapor deposition and solution processes such as spin coating and inkjet printing can be used to fabricate light-emitting devices. Vapor deposition methods include physical vapor deposition (PVD) methods such as sputtering, ion plating, ion beam deposition, molecular beam deposition, and vacuum deposition, and chemical vapor deposition (CVD). In particular, functional layers included in the organic compound layer (e.g., hole injection layer, hole transport layer, hole blocking layer, light-emitting layer, electron blocking layer, electron transport layer, and electron injection layer) can be formed by vapor deposition (e.g., vacuum deposition), coating methods (e.g., dip coating, die coating, bar coating, spin coating, and spray coating), printing methods (e.g., inkjet printing, screen printing, offset printing, flexography, gravure printing, and microcontact printing).

[0405] Furthermore, when processing the thin film that constitutes the display device, it can be processed using, for example, a lithography method. Alternatively, the thin film may be processed using a nanoimprint method, a sandblasting method, a lift-off method, etc. Furthermore, the island-shaped thin film may be directly formed by a film formation method using a shielding mask such as a metal mask.

[0406] As a lithography method, for example, photolithography can be used. There are two typical photolithography methods: one is a method in which a resist mask is formed on a thin film to be processed, the thin film is processed by, for example, etching, and then the resist mask is removed; the other is a method in which a photosensitive thin film is formed, and then the thin film is exposed to light and developed to be processed into a desired shape.

[0407] In photolithography, the light used for exposure can be, for example, i-line (wavelength 365 nm), g-line (wavelength 436 nm), h-line (wavelength 405 nm), or a mixture of these. Other light sources that can be used include ultraviolet light, KrF laser light, and ArF laser light. Exposure can also be performed by immersion exposure technology. Extreme ultraviolet (EUV) light or X-rays can also be used as the light used for exposure. An electron beam can also be used instead of the light used for exposure. Extreme ultraviolet light, X-rays, or an electron beam are preferred because they enable extremely fine processing. When exposure is performed by scanning a beam such as an electron beam, a photomask is not required.

[0408] The thin film can be etched by dry etching, wet etching, sandblasting, or the like.

[0409] Furthermore, in the manufacturing process of light-emitting devices, organic compounds that absorb light and become excited are handled. Excited organic compounds may be highly likely to react with oxygen in the atmosphere or water. In other words, when light with a wavelength that the organic compound absorbs is irradiated in the presence of oxygen, degradation products may be generated in the organic compound.

[0410] Therefore, when processing a substrate on which an organic compound is formed by photolithography, if the processing involves exposure to the atmosphere, it is recommended to carry out the processing in an environment with appropriately controlled lighting. Ideally, the processing should be carried out under lighting with a wavelength that does not excite the organic compound that absorbs and excites light. However, to ensure illuminance or color rendering properties that do not reduce work efficiency, it is recommended to use lighting with the shortest wavelength of the emission edge in the PL spectrum of the light source at 600 nm or less, preferably 580 nm or less.

[0411] For example, it is preferable to use yellow light (fluorescent lamp or light-emitting diode (LED)) that does not contain light with wavelengths shorter than 500 nm for illumination. It is also preferable to use orange light that does not contain light with wavelengths shorter than 530 nm. A low-pressure sodium lamp can be used as the light source for illumination. Furthermore, by using an optical filter that can block short-wavelength light, illumination can be used as the light source, and for example, incandescent lamps, fluorescent lamps, light-emitting diodes (LED), halogen lamps, sunlight, etc. can be used. As optical filters that can block light in the short wavelength range, for example, band-pass filters and long-pass filters (short-wavelength cut filters) can be used. Furthermore, by using such illumination, the illuminance of the illumination light can be reduced.

[0412] 7A, an insulating layer 171 is formed on a substrate (not shown). Subsequently, conductive layers 172 and 179 are formed on the insulating layer 171, and an insulating layer 173 is formed on the insulating layer 171 so as to cover the conductive layers 172 and 179. Subsequently, an insulating layer 174 is formed on the insulating layer 173, and an insulating layer 175 is formed on the insulating layer 174.

[0413] The substrate may be a substrate having heat resistance sufficient to withstand at least subsequent heat treatment. When an insulating substrate is used, a glass substrate, a quartz substrate, a sapphire substrate, a ceramic substrate, an organic resin substrate, or the like may be used. Also, a semiconductor substrate such as a single-crystal semiconductor substrate made ...

Claims

1. 1. A light-emitting device having a first electrode, a second electrode, an intermediate layer, a first light-emitting layer, and a second light-emitting layer, the intermediate layer is located between the first electrode and the second electrode; the first light-emitting layer is located between the first electrode and the intermediate layer, the second light-emitting layer is located between the intermediate layer and the second electrode, the first light-emitting layer has a first luminescent center substance and a first organic compound; the first organic compound has deuterium; the second light-emitting layer has a second luminescent center substance, the first luminescence center substance is a phosphorescent substance having an emission peak in a wavelength range of 440 nm or more and 500 nm or less, a difference between a maximum peak wavelength in the PL spectrum of the first luminescence center substance and a maximum peak wavelength in the PL spectrum of the second luminescence center substance is 30 nm or less; The first light-emitting layer and the second light-emitting layer have light-emitting layers that emit light in a color gamut different from that of the light-emitting layer of at least one light-emitting device among a plurality of other light-emitting devices adjacent to the light-emitting device.

2. 1. A light-emitting device having a first electrode, a second electrode, an intermediate layer, a first light-emitting layer, and a second light-emitting layer, the intermediate layer is located between the first electrode and the second electrode; the first light-emitting layer is located between the first electrode and the intermediate layer, the second light-emitting layer is located between the intermediate layer and the second electrode, the first light-emitting layer has a first luminescent center substance, a first organic compound, and a second organic compound; at least one of the first organic compound and the second organic compound contains deuterium; the second light-emitting layer has a second luminescent center substance, the first luminescence center substance is a phosphorescent substance having an emission peak in a wavelength range of 440 nm or more and 500 nm or less, a difference between a maximum peak wavelength in the PL spectrum of the first luminescence center substance and a maximum peak wavelength in the PL spectrum of the second luminescence center substance is 30 nm or less; The first light-emitting layer and the second light-emitting layer have light-emitting layers that emit light in a color gamut different from that of the light-emitting layer of at least one light-emitting device among a plurality of other light-emitting devices adjacent to the light-emitting device.

3. In claim 2, the first organic compound has a π-electron-deficient heteroaromatic ring, The second organic compound has at least one of a π-electron rich heteroaromatic ring and an aromatic amine skeleton.

4. In claim 3, the second light-emitting layer includes the second light-emitting center substance, a third organic compound, and a fourth organic compound; the third organic compound has a π-electron-deficient heteroaromatic ring, the fourth organic compound has at least one of a π-electron-rich heteroaromatic ring and an aromatic amine skeleton, at least one of the third organic compound and the fourth organic compound contains deuterium; the first organic compound and the second organic compound are a combination that forms a first exciplex, the third organic compound and the fourth organic compound are a combination that forms a second exciplex, an emission edge on a shorter wavelength side in a PL spectrum of the first exciplex is positioned at a wavelength shorter than an absorption edge on a longer wavelength side in an absorption spectrum of the first luminescence center substance; a light-emitting device, wherein the emission edge on the short wavelength side in the PL spectrum of the second exciplex is positioned at a wavelength shorter than the absorption edge on the long wavelength side in the absorption spectrum of the second luminescence center substance.

5. In claim 4, a difference between the lowest triplet excitation energy level of the first organic compound and the lowest triplet excitation energy level of the second organic compound is 0.20 eV or less; a difference between the lowest triplet excitation energy level of the third organic compound and the lowest triplet excitation energy level of the fourth organic compound being 0.20 eV or less;

6. In claim 4, a phosphorescence lifetime or a delayed fluorescence lifetime at 77K of the first organic compound is 1.20 times or more a phosphorescence lifetime or a delayed fluorescence lifetime at 77K of a fifth organic compound in which deuterium in the first organic compound is hydrogen; A light-emitting device, wherein the phosphorescence lifetime or delayed fluorescence lifetime of the second organic compound at 77K is 1.05 times or more the phosphorescence lifetime or delayed fluorescence lifetime of a sixth organic compound at 77K in which the deuterium in the second organic compound is hydrogen.

7. In claim 4, a light-emitting device, wherein, when the phosphorescence lifetime or delayed fluorescence lifetime of the first organic compound at 77K is X times the phosphorescence lifetime or delayed fluorescence lifetime of a fifth organic compound at 77K in which a deuterium in the first organic compound is hydrogen, and the phosphorescence lifetime or delayed fluorescence lifetime of the second organic compound at 77K is Y times the phosphorescence lifetime or delayed fluorescence lifetime of a sixth organic compound at 77K in which a deuterium in the second organic compound is hydrogen, the value obtained by multiplying X and Y is 1.26 or more.

8. In any one of claims 1 to 7, A light-emitting device, wherein the first luminescent center substance and the second luminescent center substance are the same substance.

9. In any one of claims 1 to 7, A light-emitting device, wherein the first luminescent center substance is a platinum complex.

10. In any one of claims 1 to 7, a first hole transport layer between the first electrode and the first light-emitting layer; a second hole transport layer between the intermediate layer and the second light-emitting layer; the first hole transport layer or the second hole transport layer has a laminated structure including at least a first layer having a seventh organic compound and a second layer having an eighth organic compound; the second layer is in contact with the first light-emitting layer or the second light-emitting layer, the seventh organic compound includes an amine skeleton and a polycyclic hydrocarbon; a light-emitting device, wherein the eighth organic compound comprises a π-electron-rich polycyclic heteroaromatic ring;

11. In any one of claims 1 to 7, a first electron transport layer between the second light-emitting layer and the second electrode; the first electron transport layer includes a layer having a ninth organic compound including a triazine skeleton, The intermediate layer is a light-emitting device having a first mixed layer of a tenth organic compound having a phenanthroline skeleton and lithium or a lithium compound.

12. In claim 11, the first electron transport layer includes a second mixed layer of an eleventh organic compound having a triazine skeleton and lithium or a lithium compound; The second mixed layer is located between the layer having the ninth organic compound and the second electrode.

13. A display device having a light-emitting device A and a light-emitting device B having a different emission color from that of the light-emitting device A, The light-emitting device A is A light-emitting device having a first electrode A, a second electrode A, an intermediate layer A, a first light-emitting layer A, and a second light-emitting layer A, the intermediate layer A is located between the first electrode A and the second electrode A, the first light-emitting layer A is located between the first electrode A and the intermediate layer A, the second light-emitting layer A is located between the intermediate layer A and the second electrode A, the first light-emitting layer A includes a first light-emitting center substance A, a first organic compound A, and a second organic compound A; at least one of the first organic compound A and the second organic compound A contains deuterium; the second light-emitting layer A has a second light-emitting center substance A, the first luminescence center substance A and the second luminescence center substance A are phosphorescent luminescent substances having an emission peak in a wavelength range of 440 nm or more and 500 nm or less, a difference between a maximum peak wavelength in the PL spectrum of the first luminescence center substance A and a maximum peak wavelength in the PL spectrum of the second luminescence center substance A is 30 nm or less; The light-emitting device B is A light-emitting device having a first electrode B, a second electrode B, an intermediate layer B, a first light-emitting layer B, and a second light-emitting layer B, the intermediate layer B is located between the first electrode B and the second electrode B, the first light-emitting layer B is located between the first electrode B and the intermediate layer B, the second light-emitting layer B is located between the intermediate layer B and the second electrode B, the first light-emitting layer B has a first light-emitting center substance B, the second light-emitting layer B has a second light-emitting center substance B, a difference between a maximum peak wavelength in the PL spectrum of the first luminescence center substance B and a maximum peak wavelength in the PL spectrum of the second luminescence center substance B is 30 nm or less; A display device in which the first light-emitting layer A and the second light-emitting layer A emit light in a color gamut different from that of the first light-emitting layer B and the second light-emitting layer B.

14. In claim 13, the first light-emitting layer B contains a first organic compound B, A display device, wherein the first organic compound B contains deuterium.

15. A display device having a light-emitting device A, a light-emitting device B having an emission color different from that of the light-emitting device A, and a light-emitting device C having an emission color different from that of the light-emitting device A and the light-emitting device B, The light-emitting device A is A light-emitting device having a first electrode A, a second electrode A, an intermediate layer A, a first light-emitting layer A, and a second light-emitting layer A, the intermediate layer A is located between the first electrode A and the second electrode A, the first light-emitting layer A is located between the first electrode A and the intermediate layer A, the second light-emitting layer A is located between the intermediate layer A and the second electrode A, the first light-emitting layer A includes a first light-emitting center substance A, a first organic compound A, and a second organic compound A; at least one of the first organic compound A and the second organic compound A contains deuterium; the second light-emitting layer A has a second light-emitting center substance A, the first luminescent center substance A and the second luminescent center substance A are phosphorescent luminescent materials, a difference between a maximum peak wavelength in the PL spectrum of the first luminescence center substance A and a maximum peak wavelength in the PL spectrum of the second luminescence center substance A is 30 nm or less; The light-emitting device B is A light-emitting device having a first electrode B, a second electrode B, an intermediate layer B, a first light-emitting layer B, and a second light-emitting layer B, the intermediate layer B is located between the first electrode B and the second electrode B, the first light-emitting layer B is located between the first electrode B and the intermediate layer B, the second light-emitting layer B is located between the intermediate layer B and the second electrode B, the first light-emitting layer B has a first light-emitting center substance B, the second light-emitting layer B has a second light-emitting center substance B, the first luminescent center substance B and the second luminescent center substance B are phosphorescent luminescent substances, a difference between a maximum peak wavelength in the PL spectrum of the first luminescence center substance B and a maximum peak wavelength in the PL spectrum of the second luminescence center substance B is 30 nm or less; The light-emitting device C is A light-emitting device having a first electrode C, a second electrode C, an intermediate layer C, a first light-emitting layer C, and a second light-emitting layer C, the intermediate layer C is located between the first electrode C and the second electrode C, the first light-emitting layer C is located between the first electrode C and the intermediate layer C, the second light-emitting layer C is located between the intermediate layer C and the second electrode C, the first light-emitting layer C has a first light-emitting center substance C, the second light-emitting layer C has a second light-emitting center substance C, the first luminescent center substance C and the second luminescent center substance C are phosphorescent luminescent materials, a difference between a maximum peak wavelength in the PL spectrum of the first luminescence center substance C and a maximum peak wavelength in the PL spectrum of the second luminescence center substance C is 30 nm or less; A display device in which the first light-emitting layer A and the second light-emitting layer A emit light in a color gamut different from that of the first light-emitting layer B and the second light-emitting layer B, and the first light-emitting layer C and the second light-emitting layer C.

16. In claim 15, the first light-emitting layer B contains a first organic compound B, the first organic compound B has deuterium; the first light-emitting layer C includes a first organic compound C, The display device, wherein the first organic compound C contains deuterium.

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