Light-emitting devices

Abstract

To provide highly reliable light-emitting devices. [Solution] A light-emitting device is provided having a first electrode formed on an insulating surface, a second electrode facing the first electrode, and an EL layer located between the first electrode and the second electrode, wherein one of the first electrode and the second electrode is an anode and the other is a cathode, and the EL layer has a light-emitting layer, a first layer and a second layer, the first layer and the second layer are located between the light-emitting layer and the cathode, the first layer is located between the first electrode and the second layer, the second layer is located between the first layer and the second electrode, and the GSP_Slope(mV / nm) of the second layer is greater than the GSP_Slope(mV / nm) of the first layer (where GSP_Slope(mV / nm) is expressed as ΔV / Δd when the change in surface potential ΔV(mV) is equal to the change in film thickness Δd(nm)).

Description

[Technical Field]

[0001] One aspect of the present invention relates to organic compounds, organic semiconductor elements, light-emitting elements, organic EL elements, photodiodes, display modules, lighting modules, display devices, light-emitting devices, electronic devices, lighting devices, and electronic devices. However, one aspect of the present invention is not limited to the above-mentioned technical field. The technical field of one aspect of the invention disclosed herein relates to a product, a method, or a method of manufacture. Alternatively, one aspect of the present invention relates to a process, a machine, a manufacture, or a composition of matter. More specifically, examples of the technical field of one aspect of the present invention disclosed herein include semiconductor devices, display devices, liquid crystal display devices, light-emitting devices, lighting devices, energy storage devices, memory devices, imaging devices, methods for driving them, or methods for manufacturing them. [Background technology]

[0002] The practical application of light-emitting devices (organic EL elements) that utilize electroluminescence (EL) using organic compounds is progressing. The basic structure of these organic EL elements is an organic compound layer (EL layer) containing a light-emitting material sandwiched between a pair of electrodes. By applying a voltage to this device, carriers are injected, and by utilizing the recombination energy of these carriers, light emission can be obtained from the light-emitting material.

[0003] Because these organic EL elements are self-emissive, using them as pixels in a display offers advantages over liquid crystal displays, such as higher visibility and the elimination of the need for a backlight, making them particularly suitable for flat-panel displays. Another major advantage of displays using such organic EL elements is that they can be manufactured to be thin and lightweight. Furthermore, they are characterized by their extremely fast response speed.

[0004] In addition, since these organic EL elements can form a light-emitting layer continuously in a planar shape, planar light emission can be obtained. This is a characteristic that is difficult to achieve with point light sources typified by incandescent bulbs and LEDs, or line light sources typified by fluorescent lamps. Therefore, it has high utility value as a surface light source that can be applied to lighting and the like.

[0005] As described above, displays and lighting devices using organic EL elements are suitable for various electronic devices, and research and development are being advanced to obtain organic EL elements having better characteristics.

Prior Art Documents

Non-Patent Documents

[0006]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] One aspect of the present invention aims to provide a light-emitting device with good reliability. Or, another aspect of the present invention aims to provide a light-emitting device with high luminous efficiency. One aspect of the present invention aims to provide a light-emitting device with a low driving voltage. Also, one aspect of the present invention aims to provide any one of a light-emitting device, an electronic device, or a display device with good reliability.

[0008] Or, one aspect of the present invention aims to provide a blue phosphorescent light-emitting device with good reliability. Or, another aspect of the present invention aims to provide a blue phosphorescent light-emitting device with high luminous efficiency. One aspect of the present invention aims to provide a blue phosphorescent light-emitting device with a low driving voltage.

[0009] Furthermore, the description of these problems does not preclude the existence of other problems. Moreover, one aspect of the present invention does not need to solve all of these problems. Other problems will naturally become apparent from the description in the specification, drawings, and claims, and it is possible to extract other problems from the description in the specification, drawings, and claims. [Means for solving the problem]

[0010] One aspect of the present invention is a light-emitting device comprising a first electrode formed on an insulating surface, a second electrode facing the first electrode, and an EL layer located between the first electrode and the second electrode, wherein the EL layer comprises a light-emitting layer, a hole transport layer, a first electron transport layer, and a second electron transport layer, the first electron transport layer located between the first electrode and the second electron transport layer, and the light-emitting layer located between the hole transport layer, the first electron transport layer and the second electron transport layer, and the GSP_Slope(mV / nm) of the second electron transport layer being greater than the GSP_Slope(mV / nm) of the first electron transport layer.

[0011] Alternatively, another aspect of the present invention is a light-emitting device comprising a first electrode formed on an insulating surface, a second electrode facing the first electrode, and an EL layer located between the first electrode and the second electrode, wherein the EL layer comprises a light-emitting layer, a hole transport layer, a first electron transport layer, and a second electron transport layer, the first electron transport layer located between the first electrode and the second electron transport layer, the light-emitting layer located between the hole transport layer, the first electron transport layer and the second electron transport layer, the first electron transport layer having a first organic compound, the second electron transport layer having a second organic compound, the first and second organic compounds having π-electron-deficient heteroaromatic rings, and the GSP_Slope(mV / nm) in the vapor-deposited film of the second organic compound being greater than the GSP_Slope(mV / nm) in the vapor-deposited film of the first organic compound.

[0012] Alternatively, another aspect of the present invention includes a first electrode formed on an insulating surface, a second electrode facing the first electrode, and an EL layer located between the first electrode and the second electrode, wherein the EL layer comprises a light-emitting layer, a hole transport layer, a first electron transport layer, and a second electron transport layer, the first electron transport layer being located between the light-emitting layer and the second electron transport layer, the second electron transport layer being located between the first electron transport layer and the second electrode, and the light-emitting layer is A light-emitting device comprising a hole transport layer and a first electron transport layer, wherein the first electron transport layer has a first organic compound, and the second electron transport layer has a second organic compound and a first substance, wherein the first and second organic compounds have π-electron-deficient heteroaromatic rings, and the GSP_Slope(mV / nm) in the vapor-deposited film of the second organic compound is greater than the GSP_Slope(mV / nm) in the vapor-deposited film of the first organic compound.

[0013] Alternatively, another aspect of the present invention comprises a first electrode formed on an insulating surface, a second electrode facing the first electrode, and an EL layer located between the first electrode and the second electrode, wherein the EL layer comprises a light-emitting layer, a hole transport layer, a first electron transport layer, and a second electron transport layer, the first electron transport layer located between the light-emitting layer and the second electron transport layer, the second electron transport layer located between the first electron transport layer and the second electrode, and the light-emitting layer located between the hole transport layer and the first electron transport layer, and the first The electron transport layer has a first organic compound, and the second electron transport layer has a second organic compound and a first substance, and both the first and second organic compounds have π-electron-deficient heteroaromatic rings, and when the mixing ratio of the second organic compound and the first substance in the second electron transport layer is x:y, the light-emitting device is such that the GSP_Slope (mV / nm) in the evaporated film of the second organic compound is greater than (x+y) / x times the GSP_Slope (mV / nm) in the evaporated film of the first organic compound.

[0014] Alternatively, another aspect of the present invention is a light-emitting device in the above configuration in which y is greater than or equal to x.

[0015] Alternatively, another aspect of the present invention is a light-emitting device in which the light-emitting layer comprises a material that exhibits phosphorescence.

[0016] Alternatively, another aspect of the present invention is a light-emitting device in which, in the above configuration, a phosphorescent material emits light when a voltage is applied between the first electrode and the second electrode.

[0017] Alternatively, in another aspect of the present invention, in the above configuration, the second electron transport layer is located between the first electron transport layer and the second electrode, and the light-emitting device is such that the GSP_Slope(mV / nm) of the light-emitting layer is greater than the GSP_Slope(mV / nm) of the first electron transport layer.

[0018] Alternatively, another aspect of the present invention is a light-emitting device in which the GSP_Slope(mV / nm) of the light-emitting layer is greater than the GSP_Slope(mV / nm) of the hole transport layer.

[0019] Alternatively, in another aspect of the present invention, in the above configuration, the second electron transport layer is located between the first electron transport layer and the second electrode, and the light-emitting layer comprises a host material and a light-emitting substance, wherein the GSP_Slope(mV / nm) in the vapor-deposited film of the host material is greater than the GSP_Slope(mV / nm) in the vapor-deposited film of the first organic compound.

[0020] Alternatively, another aspect of the present invention is a light-emitting device in which, in the above configuration, the GSP_Slope(mV / nm) in the vapor-deposited film of the second organic compound is greater than the GSP_Slope(mV / nm) in the vapor-deposited film of the host material.

[0021] Alternatively, another aspect of the present invention is a light-emitting device in which, in the above configuration, the hole transport layer has a third organic compound, and the GSP_Slope(mV / nm) of the light-emitting layer is equal to or greater than the GSP_Slope(mV / nm) of the vapor-deposited film of the third organic compound.

[0022] Alternatively, another aspect of the present invention is a light-emitting device in which, in the above configuration, the hole transport layer has a third organic compound, and the GSP_Slope(mV / nm) in the vapor-deposited film of the host material is greater than or equal to the GSP_Slope(mV / nm) in the vapor-deposited film of the third organic compound.

[0023] Alternatively, another aspect of the present invention is a light-emitting device in which, in the above configuration, the host material is an organic compound comprising a first material and a second material, wherein the first material and the second material form an excited complex in a combination.

[0024] Alternatively, another aspect of the present invention is a light-emitting device in which, in the above configuration, the first material is an organic compound having a π-electron-deficient heteroaromatic ring, and the second material is an organic compound having a π-electron-excess heteroaromatic ring or an aromatic amine.

[0025] Alternatively, another aspect of the present invention is a light-emitting device in which the first substance is a metal complex.

[0026] Alternatively, another aspect of the present invention is a light-emitting device in which, in the above configuration, the metal complex is an organic complex having an alkali metal.

[0027] Alternatively, another aspect of the present invention is a light-emitting device in which, in the above configuration, the peak wavelength of the emission spectrum of the phosphorescent material is 450 nm or more and 520 nm or less.

[0028] Alternatively, another aspect of the present invention is a light-emitting device in which, in the above configuration, the peak wavelength of the emission spectrum of the light-emitting material is 450 nm or more and 520 nm or less.

[0029] However, in one embodiment of the present invention, GSP_Slope(mV / nm) is expressed as ΔV / Δd when the change in surface potential ΔV(mV) is equal to the change in film thickness Δd(nm). [Effects of the Invention]

[0030] In one aspect of the present invention, a highly reliable light-emitting device can be provided. Alternatively, in another aspect of the present invention, a light-emitting device with high luminous efficiency can be provided. In one aspect of the present invention, a light-emitting device with a low driving voltage can be provided. Furthermore, in one aspect of the present invention, a highly reliable light-emitting device, electronic device, or display device can be provided.

[0031] Alternatively, one aspect of the present invention can provide a highly reliable blue phosphorescent light-emitting device. Alternatively, another aspect of the present invention can provide a blue phosphorescent light-emitting device with high luminous efficiency. Another aspect of the present invention can provide a blue phosphorescent light-emitting device with a low driving voltage.

[0032] Furthermore, the description of these effects does not preclude the existence of other effects. Moreover, one aspect of the present invention does not necessarily have to possess all of these effects. Other effects will naturally become apparent from the description in the specification, drawings, and claims, and it is possible to extract other effects from the description in the specification, drawings, and claims. [Brief explanation of the drawing]

[0033] [Figure 1] Figures 1(A) and 1(B) illustrate the configuration of a light-emitting device according to an embodiment. [Figure 2] Figures 2(A) and 2(B) illustrate the configuration of a light-emitting device according to an embodiment. [Figure 3] Figure 3 shows the capacitance-voltage characteristics of the measurement device 1. [Figure 4] Figure 4 shows the current density-voltage characteristics of the measuring device 1. [Figure 5] Figures 5(A) and 5(B) illustrate the configuration of a light-emitting device according to an embodiment. [Figure 6] Figures 6(A) and 6(B) are a top view and a cross-sectional view of the light-emitting device. [Figure 7]Figures 7(A) and 7(B) are perspective views showing examples of the display module configuration. [Figure 8] Figures 8(A) and 8(B) are cross-sectional views showing examples of the configuration of a display device. [Figure 9] Figure 9 is a perspective view showing an example of a display device configuration. [Figure 10] Figure 10 is a cross-sectional view showing an example of the configuration of a display device. [Figure 11] Figure 11 is a cross-sectional view showing an example of the configuration of a display device. [Figure 12] Figure 12 is a cross-sectional view showing an example of the configuration of a display device. [Figure 13] Figures 13(A) to 13(D) show examples of electronic devices. [Figure 14] Figures 14(A) to 14(F) show examples of electronic devices. [Figure 15] Figures 15(A) through 15(G) show examples of electronic devices. [Figure 16] Figure 16 shows the luminance-current density characteristics of light-emitting devices 1-1, 1-2, and 1-3. [Figure 17] Figure 17 shows the luminance-voltage characteristics of light-emitting devices 1-1, 1-2, and 1-3. [Figure 18] Figure 18 shows the current efficiency-current density characteristics of light-emitting devices 1-1, 1-2, and 1-3. [Figure 19] Figure 19 shows the current density-voltage characteristics of light-emitting devices 1-1, 1-2, and 1-3. [Figure 20] Figure 20 shows the blue index-current density characteristics of light-emitting devices 1-1, 1-2, and 1-3. [Figure 21] Figure 21 shows the external quantum efficiency-current density characteristics of light-emitting devices 1-1, 1-2, and 1-3. [Figure 22]Figure 22 shows the electroluminescence spectra of light-emitting devices 1-1, 1-2, and 1-3. [Figure 23] Figure 23 shows the chromaticity diagrams for light-emitting devices 1-1, 1-2, and 1-3. [Figure 24] Figure 24 shows the normalized luminance time-varying characteristics of light-emitting devices 1-1, 1-2, and 1-3. [Figure 25] Figure 25 shows the voltage change-time characteristics of light-emitting devices 1-1, 1-2, and 1-3. [Figure 26] Figure 26 shows the luminance-current density characteristics of light-emitting devices 2-1a, 2-1b, 2-2a, and 2-2b, as well as comparative light-emitting devices 2-1, 2-2a, and 2-2b. [Figure 27] Figure 27 shows the luminance-voltage characteristics of light-emitting devices 2-1a, 2-1b, 2-2a, and 2-2b, as well as comparative light-emitting devices 2-1, 2-2a, and 2-2b. [Figure 28] Figure 28 shows the current efficiency-current density characteristics of light-emitting devices 2-1a, 2-1b, 2-2a, and 2-2b, as well as comparative light-emitting devices 2-1, 2-2a, and 2-2b. [Figure 29] Figure 29 shows the current density-voltage characteristics of light-emitting devices 2-1a, 2-1b, 2-2a, and 2-2b, as well as comparative light-emitting devices 2-1, 2-2a, and 2-2b. [Figure 30] Figure 30 shows the blue index-current density characteristics of light-emitting devices 2-1a, 2-1b, 2-2a, and 2-2b, as well as comparative light-emitting devices 2-1, 2-2a, and 2-2b. [Figure 31] Figure 31 shows the external quantum efficiency-current density characteristics of light-emitting devices 2-1a, 2-1b, 2-2a, and 2-2b, as well as comparative light-emitting devices 2-1, 2-2a, and 2-2b. [Figure 32] Figure 32 shows the electroluminescence spectra of light-emitting devices 2-1a, 2-1b, 2-2a, and 2-2b, as well as comparative light-emitting devices 2-1, 2-2a, and 2-2b. [Figure 33] Figure 33 shows the normalized luminance time-varying characteristics of light-emitting devices 2-1a, 2-1b, 2-2a, and 2-2b, as well as comparative light-emitting devices 2-1, 2-2a, and 2-2b. [Figure 34] Figures 34(A) and 34(B) show the capacitance-voltage characteristics of light-emitting device 2 and comparison light-emitting device 2. [Figure 35] Figure 35 shows the luminance-current density characteristics of light-emitting device 3 and comparison light-emitting device 3. [Figure 36] Figure 36 shows the current efficiency-current density characteristics of the light-emitting device 3 and the comparative light-emitting device 3. [Figure 37] Figure 37 shows the luminance-voltage characteristics of light-emitting device 3 and comparison light-emitting device 3. [Figure 38] Figure 38 shows the current density-voltage characteristics of light-emitting device 3 and comparison light-emitting device 3. [Figure 39] Figure 39 shows the blue index-current density characteristics of light-emitting device 3 and comparative light-emitting device 3. [Figure 40] Figure 40 shows the external quantum efficiency-current density characteristics of light-emitting device 3 and comparative light-emitting device 3. [Figure 41] Figure 41 shows the electroluminescence spectra of light-emitting device 3 and comparison light-emitting device 3. [Figure 42]Figure 42 shows the chromaticity diagrams of the light-emitting device 3 and the comparative light-emitting device 3. [Figure 43] Figure 43 shows the normalized brightness time-varying characteristics of light-emitting device 3 and comparative light-emitting device 3. [Figure 44] Figure 44 shows the emission spectra of single films of SiTrzCz2 and PSiCzCz, and the PL spectrum of a mixed film with a weight ratio of 1:1. [Modes for carrying out the invention]

[0034] The embodiments of the present invention will be described in detail below with reference to the drawings. However, the present invention is not limited to the following description, and its form and details can be modified in various ways without departing from the spirit and scope of the present invention. Accordingly, the present invention shall not be interpreted as being limited to the contents of the embodiments shown below.

[0035] Please note that the positions, sizes, and ranges of each component shown in the drawings may not represent their actual positions, sizes, and ranges for the sake of ease of understanding. Therefore, the disclosed invention is not necessarily limited to the positions, sizes, and ranges disclosed in the drawings.

[0036] In this specification, the ordinal numbers "first," "second," etc., are used for convenience only and do not limit the number of components or the order of components. The order of components includes, for example, the order of processes or the order of stacking. That is, the ordinal numbers used in the embodiments of this specification may not match the ordinal numbers used in the claims. Also, the ordinal numbers used in the examples of this specification may not match the ordinal numbers used in the claims. Also, the ordinal numbers used in the embodiments of this specification may not match the ordinal numbers used in the examples of this specification.

[0037] Furthermore, in this specification and other documents, when describing the structure of the invention using drawings, reference numerals that refer to the same thing may be used in common across different drawings.

[0038] Furthermore, in this specification, the terms "film" and "layer" are interchangeable. For example, the term "conductive layer" may be changed to "conductive film." Or, for example, the term "insulating film" may be changed to "insulating layer."

[0039] In this specification, a photoluminescence (PL) spectrum refers to a spectrum obtained by fixing the excitation wavelength of the excitation light in fluorescence photometry and spectrally analyzing the emission from a sample irradiated with excitation light at each wavelength, thereby measuring the emission intensity distribution at each wavelength. It may also be called an emission spectrum. An emission spectrum may contain both a fluorescent component and a phosphorescent component. In this specification, an emission spectrum consisting of a fluorescent component may be specifically called a fluorescence spectrum, and an emission spectrum consisting of a phosphorescent component may be specifically called a phosphorescent spectrum.

[0040] (Embodiment 1) In this embodiment, a light-emitting device 10A, which is a light-emitting device according to one aspect of the present invention, and a light-emitting device 10B, which is a light-emitting device according to another aspect of the present invention, will be described with reference to Figures 1(A) and 1(B).

[0041] As shown in Figures 1(A) and 1(B), the light-emitting devices 10A and 10B are each located on the substrate 1000. The light-emitting devices 10A and 10B each have a first electrode 101, a second electrode 102, and an EL layer 103 located between the first electrode 101 and the second electrode 102. Also, as shown in Figures 1(A) and 1(B), the EL layer 103 has at least a light-emitting layer 113, a first electron transport layer 114_1, and a second electron transport layer 114_2. The first electron transport layer 114_1 and the second electron transport layer 114_2 have the function of transporting electrons injected into the EL layer 103 from either the first electrode 101 or the second electrode 102 to the light-emitting layer 113. The first electron transport layer 114_1 is located between the first electrode 101 and the second electron transport layer 114_2.

[0042] Furthermore, as shown in Figures 1(A) and 1(B), in the light-emitting devices 10A and 10B, the first electrode 101 is formed on the substrate 1000. It can also be said that the first electrode 101 is provided between the second electrode 102 and the substrate 1000. That is, the first electrode 101 is an electrode provided before the second electrode 102. When a transistor is provided on the substrate 1000, the first electrode 101 is electrically connected to the transistor via wiring. Alternatively, the first electrode 101 is provided on an insulating layer on which external connection electrodes are provided, such as terminals for attaching FPCs (Flexible Printed Circuits). Alternatively, the ends of the first electrode 101 are covered with an insulating film.

[0043] The light-emitting device 10A shown in Figure 1(A) and the light-emitting device 10B shown in Figure 1(B) differ in the functions of the first electrode 101 and the second electrode 102. In light-emitting device 10A, the first electrode 101 functions as the anode, and the second electrode 102 functions as the cathode. In this specification, etc., a light-emitting device like light-emitting device 10A, in which the first electrode provided on the substrate side functions as the anode, is sometimes referred to as a forward-stacked light-emitting device. On the other hand, in light-emitting device 10B, the first electrode 101 functions as the cathode, and the second electrode 102 functions as the anode. In this specification, etc., a light-emitting device like light-emitting device 10B, in which the first electrode provided on the substrate side functions as the cathode, is sometimes referred to as a reverse-stacked light-emitting device.

[0044] In the sequentially stacked light-emitting device 10A, light is emitted when holes injected from the first electrode 101, which is the anode, into the EL layer 103 and transported by the hole transport layer 112, and electrons injected from the second electrode 102, which is the cathode, into the EL layer 103 and transported by the electron transport layer 114, recombine in the light-emitting layer 113. Therefore, in the light-emitting device 10A, the hole transport layer 112 is located between the first electrode 101 and the light-emitting layer 113, and the electron transport layer 114 is located between the second electrode 102 and the light-emitting layer 113.

[0045] In the inverted stacked light-emitting device 10B, electrons are injected into the EL layer 103 from the first electrode 101, which functions as the cathode, and transported by the electron transport layer 114. These electrons are then injected into the EL layer 103 from the second electrode 102, which functions as the anode, and transported by the hole transport layer 112. These electrons then recombine in the light-emitting layer 113, thereby emitting light. Therefore, in the light-emitting device 10B, the hole transport layer 112 is located between the second electrode 102 and the light-emitting layer 113, and the electron transport layer 114 is located between the first electrode 101 and the light-emitting layer 113.

[0046] In light-emitting devices 10A and 10B, the electron transport layer has a multilayer structure (a stack of the first electron transport layer 114_1 and the second electron transport layer 114_2). The hole transport layer 112 may be a single layer or have a multilayer structure. The first electron transport layer 114_1 and the second electron transport layer 114_2 are sometimes collectively referred to as the electron transport layer 114.

[0047] Furthermore, it is preferable that the light-emitting devices 10A and 10B have a hole transport layer 112 between the anode and the light-emitting layer 113, and it is more preferable that they have a hole injection layer 111 between the anode and the hole transport layer 112. Furthermore, it is more preferable that the light-emitting devices 10A and 10B have an electron injection layer 115 between the cathode and the electron transport layer 114.

[0048] Figure 1(A) shows a forward-stacked light-emitting device 10A, which has a structure in which a hole injection layer 111, a hole transport layer 112, a light-emitting layer 113, an electron transport layer 114, an electron injection layer 115, and a second electrode 102, which functions as a cathode, are sequentially stacked on a first electrode 101, which functions as an anode. Figure 1(B) shows an inverted-stacked light-emitting device 10B, which has a structure in which an electron injection layer 115, an electron transport layer 114, a light-emitting layer 113, a hole transport layer 112, a hole injection layer 111, and a second electrode 102, which functions as an anode, are sequentially stacked on a first electrode 101, which functions as a cathode.

[0049] Note that the configurations of light-emitting devices 10A and 10B are not limited to those shown in Figures 1(A) and 1(B). For example, a configuration with two hole transport layers, or a configuration with three or more layers of either the hole transport layer or the electron transport layer, or both, may be used.

[0050] The present inventors have found that in light-emitting devices 10A and 10B having a laminated structure of electron transport layers, the reliability of the light-emitting devices 10A and 10B can be improved by selecting the materials used for each layer while considering the slope of the giant surface potential (GSP) of the electron transport layer.

[0051] In other words, when the electron transport layer has a stacked structure consisting of a first electron transport layer 114_1 formed earlier and a second electron transport layer 114_2 formed later, a light-emitting device in which the GSP slope (GSP_Slope(mV / nm)) of the second electron transport layer 114_2 is larger than the GSP_Slope of the first electron transport layer 114_1 can be made into a highly reliable light-emitting device.

[0052] Alternatively, when the electron transport layer has a stacked structure of a first electron transport layer 114_1 formed earlier and a second electron transport layer 114_2 formed later, a light-emitting device in which the GSP slope (GSP_Slope(mV / nm)) of the film of the organic compound having a π-electron-deficient heteroaromatic ring contained in the second electron transport layer 114_2 is greater than the GSP_Slope of the film of the organic compound having a π-electron-deficient heteroaromatic ring contained in the first electron transport layer 114_1 can be made into a highly reliable light-emitting device.

[0053] Here, GSP refers to a phenomenon caused by spontaneous orientation polarization (SOP), which occurs when the orientation of the permanent electric dipole moment of a deposited film is biased in the direction of film thickness.

[0054] The surface potential of a vapor-deposited film exhibiting GSP changes at a constant rate without saturating as the film thickness increases. For example, a vapor-deposited film of tris(8-quinolinolato)aluminum (abbreviated as Alq3) has a surface potential of approximately 28V at a film thickness of 560nm. This electric field strength is 5 × 10⁻¹⁰ 5 It reaches V / cm, which is about the same magnitude as the electric field strength during operation of a typical light-emitting device.

[0055] The GSP slope (GSP_Slope) is expressed as ΔV / Δd when the change in surface potential is ΔV (mV) for a film in which the GSP changes proportionally to the film thickness, and the change in surface potential is ΔV (mV) for a change in film thickness Δd (nm). Note that a positive GSP_Slope occurs when the surface potential increases with increasing film thickness, and a negative GSP_Slope occurs when the surface potential decreases with increasing film thickness. Alq3 can be described as a material with a positive GSP_Slope. Furthermore, layers with a positive GSP_Slope have a low potential on the substrate side, while layers with a negative GSP_Slope have a high potential on the substrate side.

[0056] As mentioned above, this GSP is a phenomenon caused by SOP resulting from the bias in the orientation of the permanent electric dipole moment in the film thickness direction. That is, in layers where GSP_Slope is positive, it can be considered that a negative polarization charge is induced on the substrate side of that layer and a positive polarization charge is induced on the second electrode side. Similarly, in layers where GSP_Slope is negative, it can be considered that a positive polarization charge is induced on the substrate side of that layer and a negative polarization charge is induced on the second electrode side. The induction of such polarization charges is the origin of GSP. In Figures 1(A) and 1(B), the SOP resulting from the bias in the orientation of the permanent electric dipole moment in the film thickness direction of each layer deposited by vapor deposition is shown using σ+ and σ-. σ+ indicates positive polarization, and σ- indicates negative polarization. Furthermore, in each layer, the more σ values ​​there are near the interface, the greater the spontaneous polarization.

[0057] Deposition films of organic compounds often have a positive GSP_Slope. In this case, when a second layer is deposited in contact with a first layer, the signs of the GSP_Slope of the first and second layers become the same positive, and it can be considered that negative polarization charges are induced on the substrate side of each layer, and positive polarization charges are induced on the electrode side of the second layer. In this case, the negative polarization charge on the first layer side of the second layer cancels out with the positive polarization charge on the second layer side of the first layer, and only the remaining charge can be considered as the interfacial charge (fixed charge) at the interface between the first and second layers. Note that in this specification, the virtual charge that can be considered as an interfacial charge is sometimes called an interfacial charge.

[0058] Figure 1(A) shows a forward-stacked light-emitting device 10A, and Figure 1(B) shows an inverted-stacked light-emitting device 10B. The electron transport layer 114 has a laminated structure of a first electron transport layer 114_1 and a second electron transport layer 114_2. The second electron transport layer 114_2 is provided on the second electrode 102 side of the first electron transport layer 114_1. In one embodiment of the present invention, it is preferable that the GSP_Slope of the second electron transport layer 114_2 is larger than the GSP_Slope of the first electron transport layer 114_1. Alternatively, in one embodiment of the present invention, it is preferable that the GSP_Slope of the vapor-deposited film of the second organic compound having a π-electron-deficient heteroaromatic ring contained in the second electron transport layer 114_2 is larger than the GSP_Slope of the vapor-deposited film of the first organic compound having a π-electron-deficient heteroaromatic ring contained in the first electron transport layer 114_1.

[0059] In a light-emitting device according to one aspect of the present invention having such a configuration, a negative interfacial charge is generated at the interface between the second electron transport layer 114_2 and the first electron transport layer 114_1. This suppresses the injection of electrons from the second electrode 102 or electron injection layer 115 into the second electron transport layer 114_2 (in the case of forward stacking, Figure 1(A)), or the injection of electrons from the first electrode 101 or electron injection layer 115 into the first electron transport layer 114_1 (in the case of reverse stacking, Figure 1(B)). This prevents the light-emitting layer 113 from becoming electron-excessive, reduces the bias towards the hole transport layer 112 in the recombination region of the light-emitting layer 113, and reduces the degradation of the light-emitting layer 113 and the hole transport layer 112 (or electron blocking layer). As a result, a light-emitting device according to one aspect of the present invention can be made into a highly reliable light-emitting device.

[0060] Furthermore, it is preferable that the light-emitting layer 113 contains at least a light-emitting substance and also has a host material. Blue light-emitting substances with high excitation energy levels as the light-emitting substance result in a large band gap in the host material, making it difficult to control the carrier balance. In particular, blue phosphorescent light-emitting devices containing blue phosphorescent substances often have a configuration in which the light-emitting layer 113 tends to have an excess of electrons. Therefore, the present invention can be suitably applied to phosphorescent light-emitting devices, especially blue phosphorescent light-emitting devices, and provides a significant improvement in reliability.

[0061] Furthermore, in the sequentially stacked light-emitting device 10A shown in Figure 1(A), the second electron transport layer 114_2 may contain a first substance in addition to the second organic compound. The first substance is preferably a metal complex, particularly an organic complex containing an alkali metal. Specifically, examples of organic complexes containing alkali metals include 8-quinolinolato-lithium (abbreviated as Liq), 8-quinolinolato-sodium (abbreviated as Naq), 8-quinolinolato-potassium (abbreviated as Kq), and their derivatives. When the second electron transport layer 114_2 contains such a substance, it becomes possible to control the electron transport properties in the second electron transport layer 114_2, and furthermore, the reliability of the light-emitting device can be improved by suppressing the bias towards the hole transport layer 112 in the light-emitting layer 113 of the recombination region.

[0062] In this case, if the mixing ratio (weight ratio) of the second organic compound and the first substance in the second electron transport layer 114_2 is x:y, it is preferable that the GSP_Slope (mV / nm) of the film of the second organic compound is greater than (x+y) / x times the GSP_Slope (mV / nm) of the film of the first organic compound. With this configuration, even if the GSP_Slope of the film of the first substance is smaller than the GSP_Slope of the film of the second organic compound, the GSP_Slope (mV / nm) of the second electron transport layer 114_2 will be larger than that of the first electron transport layer 114_1, so a negative interfacial charge is generated and electron injection is suppressed, which is preferable. Also, it is preferable that y is greater than x, as this reduces the proportion of the second organic compound responsible for electron transport and thus reduces electron transport performance.

[0063] Furthermore, in the inverted stacking type light-emitting device 10B shown in Figure 1(B), the first electron transport layer 114_1 may contain a first substance in addition to the first organic compound. The first substance is preferably a metal complex, particularly an organic complex containing an alkali metal. When the first electron transport layer 114_1 contains such a substance, it becomes possible to control the electron transport properties in the first electron transport layer 114_1, and furthermore, the reliability of the light-emitting device can be improved by suppressing the bias towards the hole transport layer 112 in the light-emitting layer 113 of the recombination region.

[0064] Furthermore, as shown in Figure 2(A), if a sequential light-emitting device according to one embodiment of the present invention has a hole transport layer 112 in contact with the light-emitting layer 113, it is preferable that the GSP_Slope (mV / nm) of the light-emitting layer 113 is greater than the GSP_Slope (mV / nm) of the hole transport layer or the GSP_Slope (mV / nm) of the vapor-deposited film of the third organic compound having a π-electron-rich heteroaromatic ring or aromatic amine present in the hole transport layer 112. Alternatively, it is preferable that the GSP_Slope (mV / nm) of the vapor-deposited film of the host material is greater than the GSP_Slope (mV / nm) of the vapor-deposited film of the third organic compound having a π-electron-rich heteroaromatic ring or aromatic amine present in the hole transport layer 112.

[0065] Furthermore, as shown in Figure 2(B), if an inverted stacking type light-emitting device according to one embodiment of the present invention has a hole transport layer 112 in contact with the light-emitting layer 113, it is preferable that the GSP_Slope (mV / nm) of the light-emitting layer 113 is smaller than the GSP_Slope (mV / nm) of the hole transport layer or the GSP_Slope (mV / nm) of the vapor-deposited film of the third organic compound having a π-electron-rich heteroaromatic ring or aromatic amine on the hole transport layer 112. Alternatively, it is preferable that the GSP_Slope (mV / nm) of the vapor-deposited film of the host material is smaller than the GSP_Slope (mV / nm) of the vapor-deposited film of the third organic compound having a π-electron-rich heteroaromatic ring or aromatic amine on the hole transport layer 112.

[0066] In one embodiment of the present invention having this configuration, the effect of the negative interfacial charge originating from the difference in GSP slope of the two contacting layers promotes the injection of holes from the hole injection layer 111 to the hole transport layer 112. As a result, hole injection into the light-emitting layer also occurs effectively, improving the carrier balance and expanding the recombination region, thereby suppressing the degradation of the light-emitting layer 113 and the hole transport layer 112.

[0067] Furthermore, as shown in Figure 1(A), in a sequential stacking type light-emitting device according to one embodiment of the present invention, it is preferable that the GSP_Slope (mV / nm) of the light-emitting layer 113 is greater than the GSP_Slope (mV / nm) of the first electron transport layer 114_1. Alternatively, it is preferable that the GSP_Slope (mV / nm) of the vapor-deposited film of the host material is greater than the GSP_Slope (mV / nm) of the vapor-deposited film of the first organic compound.

[0068] Furthermore, as shown in Figure 1(B), in an inverted stacking type light-emitting device according to one embodiment of the present invention, it is preferable that the GSP_Slope (mV / nm) of the light-emitting layer 113 is smaller than the GSP_Slope (mV / nm) of the second electron transport layer 114_2. Alternatively, it is preferable that the GSP_Slope (mV / nm) of the vapor-deposited film of the host material is smaller than the GSP_Slope (mV / nm) of the vapor-deposited film of the second organic compound.

[0069] In one embodiment of the present invention having this configuration, the injection of electrons from the second electron transport layer 114_2 to the first electron transport layer 114_1 is promoted due to the influence of the positive interfacial charge originating from the difference in the GSP slope of the two contacting layers. Therefore, even if the injection of electrons from the first electrode 101 or the electron injection layer 115 to the second electron transport layer 114_2 is suppressed, the light-emitting device of one embodiment of the present invention does not cause a significant increase in the driving voltage, making it possible to produce a light-emitting device with good characteristics.

[0070] Furthermore, as shown in Figure 1(A), in a sequentially stacked light-emitting device according to one embodiment of the present invention, it is preferable that the GSP_Slope (mV / nm) of the second electron transport layer 114_2 is greater than the GSP_Slope (mV / nm) of the light-emitting layer 113. Alternatively, it is preferable that the GSP_Slope (mV / nm) of the vapor-deposited film of the second organic compound is greater than the GSP_Slope (mV / nm) of the vapor-deposited film of the host material.

[0071] Furthermore, as shown in Figure 1(B), in an inverted stacking type light-emitting device according to one embodiment of the present invention, it is preferable that the GSP_Slope (mV / nm) of the first electron transport layer 114_1 is smaller than the GSP_Slope (mV / nm) of the light-emitting layer 113. Alternatively, it is preferable that the GSP_Slope (mV / nm) of the vapor-deposited film of the first organic compound is smaller than the GSP_Slope (mV / nm) of the vapor-deposited film of the host material.

[0072] In one embodiment of the present invention having this configuration, the interfacial charge between the first electron transport layer 114_1 and the second electron transport layer 114_2 is negative and smaller than the interfacial charge between the light-emitting layer 113 and the first electron transport layer 114_1. This effect suppresses electron injection into the light-emitting layer while promoting hole injection into the light-emitting layer, thereby improving the carrier balance, expanding the recombination region, and suppressing the degradation of the light-emitting layer 113 and the hole transport layer 112.

[0073] Furthermore, if the light-emitting layer 113 includes a host material, it is preferable that the host material includes a first material and a second material. By composing the host material with multiple materials, it becomes easier to control the carrier balance, contributing to improved reliability. Alternatively, by forming an excitation complex with the first material and the second material, effects such as improved energy transfer efficiency to the light-emitting substance, lower driving voltage, and improved reliability can be achieved. It is preferable that one of the first and second materials is an organic compound having a π-electron-deficient heteroaromatic ring, and the other is an organic compound having a π-electron-rich heteroaromatic ring or aromatic amine, as this makes it easier to adjust the carrier balance.

[0074] When the host material contains multiple materials, the GSP_Slope(mV / nm) of the host material film can be the GSP_Slope(mV / nm) of a mixed film obtained by co-depositing the first material and the second material in a 1:1 ratio. Alternatively, the GSP_Slope(mV / nm) of the deposited film of the material with the higher mixing ratio among the first and second materials can be considered as the GSP_Slope(mV / nm) of the host material film.

[0075] <How to calculate GSP_Slope> Here, we will explain how to determine the GSP_Slope of a film formed by vacuum deposition of an organic compound.

[0076] The phenomenon in which the surface potential of a deposited film increases in proportion to its thickness is called giant surface potential, as mentioned above. Generally, the slope when the surface potential of a deposited film measured by a Kelvin probe is plotted in the direction of film thickness is discussed as the magnitude of the giant surface potential, i.e., GSP_Slope (mV / nm). However, when two different layers are stacked, the charge density accumulated at their interface (mC / m) is also considered. 2 By utilizing the fact that ) changes in relation to GSP, we can estimate GSP_Slope.

[0077] Non-patent document 1 shows that when organic thin films with different spontaneous polarizations (thin film 1 and thin film 2, where thin film 1 is on the anode side and thin film 2 is on the cathode side, and the anode is located on the substrate side) are stacked and a voltage is applied, the following equation holds true if the carriers accumulated at the interface are holes.

[0078]

number

[0079]

number

[0080] In equation (1), σ accis the accumulated charge density, σ int is the interface charge density, V inj is the hole injection voltage, V th is the threshold voltage, d2 is the film thickness of the thin film 2, and ε2 is the dielectric constant of the thin film 2. V inj 、V th can be estimated from the capacitance-voltage characteristics of the device. Also, the dielectric constant can use the value obtained by multiplying the square of the ordinary light refractive index n o (wavelength 633 nm) by the dielectric constant of vacuum. Thus, from the capacitance-voltage characteristics, the estimated V inj 、V th and, from the dielectric constant ε2 of the thin film 2 calculated from the refractive index and the film thickness d2 of the thin film 2, the interface charge density σ int can be obtained using Equation (1).

[0081] Subsequently, in Equation (2), P n is the spontaneous polarization in the substrate normal direction of the thin film n (n is 1 or 2), ε n is the dielectric constant of the thin film n, V n is the potential of the film surface, d n is the film thickness of the thin film n. And the GSP_slope can be calculated from the value obtained by dividing the potential of the film surface (V n ) by the film thickness (d n ). Here, since the interface charge density σ int can be obtained from Equation (1) above, by using a substance with a known GSP_slope as the thin film 2 and adopting an appropriate dielectric constant, the GSP_slope of the thin film 1 can be estimated.

[0082] Therefore, an example of fabricating the measurement device 1 using tris(8-hydroxyquinolinato)aluminum (abbreviation: Alq3), which is known to have a GSP_Slope of (48 (mV / nm)) as the thin film 2 and obtaining the GSP_Slope of the film of 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB) is shown below.

[0083] The device structure of measurement device 1 is shown in Table 1. The cathode layer 1_1 of measurement device 1 was formed by vacuum deposition from the anode side, with a substrate temperature of room temperature and a deposition rate of 0.2 nm / s to 0.6 nm / s. Deposition was carried out without stopping the deposition process between layers. In measurement device 1, layer 2_1 corresponds to thin film 1, and layer 3_1 corresponds to thin film 2. OCHD-003 is an organic compound with electron acceptor properties.

[0084] When fabricating the measurement device, the deposition rate of each layer is preferably 3 nm / min to 600 nm / min. Furthermore, the film thickness of each layer in the measurement device is preferably 3 nm to 500 nm, and more preferably 50 nm to 300 nm.

[0085] Furthermore, the capacitance-voltage characteristics of measurement device 1 are shown in Figure 3. The capacitance-voltage characteristics were measured using a potentiometer / galvanostat (SP-300, manufactured by Biologic, France) at a frequency of 10 Hz and at room temperature.

[0086] [Table 1]

[0087] Table 2 shows the Hole injection voltage V of the measuring device 1, which was determined using Figure 3 and equations (1) and (2). inj , threshold voltage V th , interfacial charge density σ int SOP, GSP_Slope, and the refractive index n of each material used in the calculation o The results are shown. The refractive index was measured using a spectroscopic ellipsometer (M-2000U, manufactured by J.A. Woolam Japan Co., Ltd.).

[0088] [Table 2]

[0089] Furthermore, we fabricated a measurement device 2 with almost the same configuration as measurement device 1, except that the Alq3 film thickness was 80 nm, and confirmed that the hole injection voltage shifted to a lower voltage than that of measurement device 1. This suggests that in such a device, holes are injected first, and charge accumulates at the interface with Alq3. We also used measurement device 2 to estimate the GSP_Slope in the same way as measurement device 1 and confirmed that the same results were obtained.

[0090] Furthermore, the threshold voltage V can be obtained from the capacitance-voltage characteristics. th If it is difficult to estimate, the threshold voltage estimated from the current density-voltage characteristics may be used.

[0091] Figure 4 shows the current density-voltage characteristics of measuring device 1.

[0092] V estimated from current density-voltage characteristics th The voltage was 2.0V, which was the same value as the one estimated from the capacitance-voltage characteristics.

[0093] In this way, by fabricating a device in which a film of Alq3 with a known GSP_Slope and a film formed of an organic compound whose GSP_Slope is to be determined are stacked, and measuring the capacitance-voltage characteristics, the GSP_Slope of the organic compound can be estimated.

[0094] In the above explanation, we described a method for calculating GSP_Slope in a configuration where the carriers accumulating at the interface are holes. However, when calculating the GSP_Slope of an organic film in a configuration where the carriers accumulating at the interface are electrons, the same calculation can be performed using the following equation (3).

[0095]

number

[0096] It is preferable to select the organic compounds to be used in each layer of the light-emitting device, taking into account the GSP_Slope of the vapor-deposited film of the organic compound measured in advance using the measurement method described above.

[0097] The configuration shown in this embodiment can be used in appropriate combination with the configurations shown in other embodiments.

[0098] (Embodiment 2) This embodiment will describe in detail a light-emitting device according to one aspect of the present invention.

[0099] Figures 1(A) to 2(B) are schematic diagrams of a light-emitting device according to one embodiment of the present invention. The light-emitting device has a first electrode 101 provided on an insulating substrate 1000, and an EL layer 103 between the first electrode 101 and a second electrode 102. The EL layer 103 has a light-emitting layer 113, and the light-emitting layer 113 contains a light-emitting material. The light-emitting material emits light when a voltage is applied between the first electrode 101 and the second electrode 102.

[0100] The EL layer 103 has, in addition to the light-emitting layer 113, at least a first electron transport layer 114_1 and a second electron transport layer 114_2, and has the configuration shown in Embodiment 1. A light-emitting device according to one embodiment of the present invention having such a configuration can be a light-emitting device with good characteristics, and in particular, good reliability.

[0101] Furthermore, as shown in Figures 1(A) to 2(B), it is preferable to have other functional layers such as a hole injection layer 111, a hole transport layer 112, and an electron injection layer 115. Note that the EL layer 103 may also include functional layers other than those described above, such as a hole blocking layer, an electron blocking layer, an exciton blocking layer, and a charge generation layer. Conversely, none of the above-mentioned layers may be provided.

[0102] The first electrode 101 and the second electrode 102 are formed as a single-layer structure or a multilayer structure. If a multilayer structure is present, the layer in contact with the EL layer 103 functions as the anode or cathode. When the electrodes have a multilayer structure, there are no constraints on the work function of the layers other than the layer in contact with the EL layer 103, and materials can be selected according to the required properties such as resistance, ease of processing, reflectivity, light transmittance, and stability.

[0103] The anode is preferably formed using a metal, alloy, conductive compound, or mixture thereof with a high work function (specifically, 4.0 eV or higher). Specifically, examples include indium tin oxide (ITO), indium tin silicon oxide (ITSO) containing silicon or silicon oxide, indium zinc oxide, and indium oxide (IWZO) containing tungsten oxide and zinc oxide. These conductive metal oxide films are usually deposited by sputtering, but they may also be fabricated using methods such as the sol-gel method. An example of a fabrication method is to form indium zinc oxide by sputtering using a target to which 1 to 20 wt% zinc oxide is added to indium oxide. Furthermore, indium oxide (IWZO) containing tungsten oxide and zinc oxide can also be formed by sputtering using a target containing 0.5-5 wt% tungsten oxide and 0.1-1 wt% zinc oxide relative to indium oxide. Other materials that can be used as anodes include, for example, gold (Au), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), titanium (Ti), aluminum (Al), or nitrides of metallic materials (e.g., titanium nitride). Alternatively, a layer of these materials can be used as the anode. For example, a film in which Al, Ti, and ITSO are layered on Ti is preferable because it has good reflectivity, is highly efficient, and enables high resolution of several thousand ppi. Alternatively, graphene can also be used as a material for the anode. Furthermore, by using a composite material capable of forming the hole injection layer 111 (described later) as the layer in contact with the anode (typically the hole injection layer), it becomes possible to select the electrode material regardless of the work function.

[0104] The hole injection layer 111 is provided in contact with the anode and has the function of facilitating the injection of holes into the EL layer 103. The hole injection layer 111 can be formed from phthalocyanine compounds such as phthalocyanine (abbreviated as H2Pc) and copper phthalocyanine (abbreviated as CuPc), phthalocyanine-based complex compounds, aromatic amine compounds such as 4,4'-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviated as DPAB) and 4,4'-bis(N-{4-[N'-(3-methylphenyl)-N'-phenylamino]phenyl}-N-phenylamino)biphenyl (abbreviated as DNTPD), or polymer compounds such as poly(3,4-ethylenedioxythiophene) / (polystyrene sulfonic acid) (abbreviated as PEDOT / PSS).

[0105] Furthermore, the hole injection layer 111 may be formed from a substance having electron-accepting properties. Examples of substances having electron-accepting properties include organic compounds having electron-withdrawing groups (halogen groups, cyano groups, etc.), such as 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviated as F4-TCNQ), chloranil, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexazatriphenylene (abbreviated as HAT-CN), 1,3,4,5,7,8-hexafluorotetracyano-naphthoquinodimethane (abbreviated as F6-TCNNQ), and 2-(7-dicyanomethylene-1,3,4,5,6,8,9,10-octafluoro-7H-pyrene-2-ylidene)malononitrile. In particular, compounds in which an electron-withdrawing group is bonded to a condensed aromatic ring having multiple heteroatoms, such as HAT-CN, are thermally stable and preferred. Furthermore, radialene derivatives having an electron-withdrawing group (especially halogen groups such as fluoro groups, cyano groups, etc.) are preferred because they have very high electron-accepting properties. Specific examples include α,α',α''-1,2,3-cyclopropanetriylidenates[4-cyano-2,3,5,6-tetrafluorobenzeneacetonitrile], α,α',α''-1,2,3-cyclopropanetriylidenates[2,6-dichloro-3,5-difluoro-4-(trifluoromethyl)benzeneacetonitrile], and α,α',α''-1,2,3-cyclopropanetriylidenates[2,3,4,5,6-pentafluorobenzeneacetonitrile]. In addition to the organic compounds mentioned above, other acceptor materials that can be used include transition metal oxides such as molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, and manganese oxide.

[0106] Furthermore, it is preferable that the hole injection layer 111 be formed from a composite material containing the acceptor material and an organic compound having hole transport properties.

[0107] Various organic compounds with hole-transporting properties can be used in composite materials, including aromatic amine compounds, heteroaromatic compounds, aromatic hydrocarbons, and polymer compounds (oligomers, dendrimers, polymers, etc.). -6 cm 2 It is preferable that the organic compound has a hole mobility of / Vs or greater. The hole-transporting organic compound used in the composite material is preferably a compound having a condensed aromatic hydrocarbon ring or a π-electron-rich heteroaromatic ring. As the condensed aromatic hydrocarbon ring, anthracene rings, naphthalene rings, etc. are preferred. As the π-electron-rich heteroaromatic ring, a condensed aromatic ring containing at least one of a pyrrole skeleton, a furan skeleton, or a thiophene skeleton is preferred, and specifically, a carbazole ring, a dibenzothiophene ring, or a ring in which an aromatic ring or heteroaromatic ring is further condensed thereon is preferred.

[0108] Organic compounds having such hole-transporting properties more preferably have at least one of the following skeletons: a carbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton, and an anthracene skeleton. In particular, they may be aromatic amines having substituents including 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. Furthermore, it is preferable that these hole-transporting organic compounds are substances having an N,N-bis(4-biphenyl)amino group, as this allows for the creation of light-emitting devices with a good lifetime.

[0109] Organic compounds that possess the hole transport properties described above include, specifically, 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), and N,N-bis(4-biphenyl)benzo[b]naph To[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-bife Nylamine (abbreviation: ThBA1BP), 4-(2-naphthyl)-4',4''-diphenyltriphenylamine (abbreviation: BBAβNB), 4-[4-(2-naphthyl)phenyl]-4',4''-diphenyltriphenylamine (abbreviation: BBAβNBi), 4,4'-diphenyl-4''-([2,1'-binaphthyl]-6-yl)triphenylamine (abbreviation: BBAαNβNB), 4,4'-diphenyl-4''-([2,1'-binaphthyl]-7-yl)triphenylamine (abbreviation: BBAαNβNB-03), 4,4'-diphenyl -4''-(7-phenyl)naphthyl-2-yltriphenylamine (abbreviation: BBAPβNB-03), 4,4'-diphenyl-4''-([2,2'-binaphthyl]-6-yl)triphenylamine (abbreviation: BBA(βN2)B), 4,4'-diphenyl-4''-([2,2'-binaphthyl]-7-yl)triphenylamine (abbreviation: BBA(βN2)B-03), 4,4'-diphenyl-4''-([1,2'-binaphthyl]-4-yl)triphenylamine (abbreviation: BBAβNαNB), 4,4'-diphenyl-4''-([1,2'-binaphthyl]-5-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''-phenyl Triphenylamine (abbreviation: TPBiAβNBi), 4-phenyl-4'-(1-naphthyl)triphenylamine (abbreviation: αNBA1BP), 4,4'-bis(1-naphthyl)triphenylamine (abbreviation: αNBB1BP), 4,4'-diphenyl-4''-[4'-(carbazole-9-yl)biphenyl-4-yl]triphenylamine (abbreviation: YGTBi1BP), 4'-[4-(3-phenyl-9H-carbazole-9-yl)phenyl]tris (Biphenyl-4-yl)amine (abbreviation: YGTBi1BP-02), 4-[4'-(carbazole-9-yl)biphenyl-4-yl]-4'-(2-naphthyl)-4''-phenyltriphenylamine (abbreviation: YGTBiβNB), N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-N-[4-(1-naphthyl)phenyl]-9,9'-spirobio[9H-fluorene]-2-amine (abbreviation: PCBNBSF), N,N-bis( Biphenyl-4-yl)-9,9'-spirobio[9H-fluorene]-2-amine (abbreviation: BBASF), N,N-bis(biphenyl-4-yl)-9,9'-spirobio[9H-fluorene]-4-amine (abbreviation: BBASF(4)), N-(biphenyl-2-yl)-N-(9,9-dimethyl-9H-fluorene-2-yl)-9,9'-spirobio[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)phenyl]triphenylamine (abbreviation: BPAFLBi), 4-phenyl-4'-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4'-diphenyl-4''-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBBi1BP), 4-(1-naphthyl)-4'-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBANB), 4,4'- Di(1-naphthyl)-4''-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBNBB), N-phenyl-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-9,9'-spirobi[9H-fluorene]-2-amine (abbreviation: PCBASF), N-(biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-9,9-dimethyl-9H-fluorene-2-amine (abbreviation: PCBBiF), N,N-bis( Examples include 9,9-dimethyl-9H-fluoren-2-yl)-9,9'-spirobio-9H-fluoren-4-amine, N,N-bis(9,9-dimethyl-9H-fluoren-2-yl)-9,9'-spirobio-9H-fluoren-3-amine, N,N-bis(9,9-dimethyl-9H-fluoren-2-yl)-9,9'-spirobio-9H-fluoren-2-amine, and N,N-bis(9,9-dimethyl-9H-fluoren-2-yl)-9,9'-spirobio-9H-fluoren-1-amine.

[0110] Furthermore, other aromatic amine compounds that possess hole-transporting properties can also be used, such as N,N'-di(p-tolyl)-N,N'-diphenyl-p-phenylenediamine (abbreviated as DTDPPA), 4,4'-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviated as DPAB), 4,4'-bis(N-{4-[N'-(3-methylphenyl)-N'-phenylamino]phenyl}-N-phenylamino)biphenyl (abbreviated as DNTPD), and 1,3,5-tris[N-(4-diphenylaminophenyl)-N-phenylamino]benzene (abbreviated as DPA3B).

[0111] By forming the hole injection layer 111, the hole injection performance is improved, and a light-emitting device with a low driving voltage can be obtained.

[0112] Furthermore, among substances with acceptor properties, organic compounds with acceptor properties are easy to use because they are readily deposited and easy to form films.

[0113] The hole transport layer 112 is formed by including an organic compound having hole-transporting properties. The organic compound having hole-transporting properties is 1 × 10⁻⁶ -6 cm 2 It is preferable that the hole mobility is greater than or equal to / Vs.

[0114] Materials exhibiting the above hole transport properties include 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviated as NPB), N,N'-diphenyl-N,N'-bis(3-methylphenyl)-4,4'-diaminobiphenyl (abbreviated as TPD), N,N'-bis(9,9'-spirobi[9H-fluoren]-2-yl)-N,N'-diphenyl-4,4'-diaminobiphenyl (abbreviated as BSPB), 4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviated as BPAFLP), and 4-phenyl-3 '-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: mBPAFLP), 4-phenyl-4'-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4'-diphenyl-4''-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBBi1BP), 4-(1-naphthyl)-4'-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBANB), 4,4'-di(1-naphthyl)-4''-(9-phenyl Compounds having an aromatic amine skeleton such as 9,9-9H-carbazol-3-yl)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'-spirobio[9H-fluoren]-2-amine (abbreviation: PCBASF), 1,3-bis(N-carbazolyl)benzene (abbreviation: mCP), 4,4'-di( N-carbazolyl)biphenyl (abbreviated as CBP), 3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviated as CzTP), 3,3'-bis(9-phenyl-9H-carbazole) (abbreviated as PCCP), 9,9'-bis(biphenyl-4-yl)-3,3'-bi-9H-carbazole (abbreviated as BisBPCz), 9,9'-bis(biphenyl-3-yl)-3,3'-bi-9H-carbazole (abbreviated as 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 Lubazole, 9-(2-naphthyl)-9'-[1,1':3',1”-terphenyl]-4-yl-3,3'-9H,9'H-bicarbazole, 9-(2-naphthyl)-9'-(triphenylene-2-yl)-3,3'-9H,9'H-bicarbazole, 9-phenyl-9'-(triphenylene-2-yl)-3,3'-9H,9'H-bicarbazole (abbreviation: PCCzTp), 9,9'-bis(triphenylene-2-yl)-3,3'-9H,9'H-bicarbazole, 9-(4-biphenyl)-9 Compounds having a carbazole skeleton such as '-(triphenylene-2-yl)-3,3'-9H,9'H-bicarbazole, 9-(triphenylene-2-yl)-9'-[1,1':3',1”-terphenyl]-4-yl-3,3'-9H,9'H-bicarbazole, 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 include compounds having a thiophene skeleton such as 8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene (abbreviated as DBTFLP-III) and 4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviated as DBTFLP-IV), and compounds having a furan skeleton such as 4,4',4''-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviated as DBF3P-II) and 4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran (abbreviated as 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 transportability, and contribute to reducing the driving voltage. Furthermore, the materials listed as having hole-transporting properties for the composite material of the hole injection layer 111 can also be suitably used as materials constituting the hole transport layer 112. Moreover, the use of organic compounds having an amine skeleton and a fluorene skeleton is even more preferable. Organic compounds having an amine skeleton and a fluorene skeleton are preferable because they have good reliability and high hole-transporting properties, thereby reducing the power consumption of the light-emitting device.

[0115] The luminescent material may be a fluorescent material, a phosphorescent material, a material exhibiting thermally activated delayed fluorescence (TADF), or any other luminescent material. Furthermore, light-emitting devices using blue luminescent materials, particularly blue phosphorescent materials, as the luminescent material tend to have an excess of electrons in the luminescent layer 113, making the present invention particularly suitable for application.

[0116] Examples of materials that can be used as fluorescent materials in the light-emitting layer include the following. Other fluorescent materials can also be used.

[0117] 5,6-Bis[4-(10-phenyl-9-antryl)phenyl]-2,2'-bipyridine (abbreviation: PAP2BPy), 5,6-Bis[4'-(10-phenyl-9-antryl)biphenyl-4-yl]-2,2'-bipyridine (abbreviation: PAPP2BPy), N,N'-Diphenyl-N,N'-Bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]pyren-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 (abbreviation: 1,6mMemFLPAPrn), N,N'-bis[4-(9H-carbazole-9-yl)phenyl]-N,N'-diphenylstilbene-4,4'-diamine (abbreviation: YGA2S), 4-(9H-carbazole-9-yl)-4'-(10-phenyl-9-anthryl)triphenylamine (abbreviation: YGAPA), 4-(9H-carbazole-9-yl)-4'-(9,10-diphenyl-2-anthryl)triphenylamine (abbreviation: 2YGAPPA), N,9-diphenyl-N-[4-( 10-phenyl-9-anthryl)phenyl]-9H-carbazole-3-amine (abbreviation: PCAPA), perylene, 2,5,8,11-tetra-tert-butylperylene (abbreviation: TBP), 4-(10-phenyl-9-anthryl)-4'-(9-phenyl-9H-carbazole-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-carbazole-3-amine (abbreviation: 2PCAPPA), N-[4-(9,10-diphenyl-2-anthryl)phenyl]-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPPA), N,N,N',N',N'',N'',N''',N'''-octaphenyldibenzo[g,p]chrysene-2,7,10,15-tetraamine (abbreviation: DBC1), coumarin 30, N-(9,10-diphenyl-2-anthryl)-N,9-Diphenyl-9H-carbazole-3-amine (abbreviation: 2PCAPA), N-[9,10-bis(biphenyl-2-yl)-2-anthryl]-N,9-diphenyl-9H-carbazole-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-carbazole-9-yl)phenyl]-N-phenylanthracene-2-amine (abbreviation: 2YGABPhA), N,N,9-triphenylanthracene-9-amine (abbreviation: DPhAPhA), coumarin 545T, N,N'-diphenylquinacridone (abbreviation: DPQd), rubren, 5,12-bis(biphenyl-4-yl)-6,11-diphenyltetracene (abbreviation: BPT), 2-(2-{2-[4-(dimethylamino)phenyl]ethenyl}-6-methyl-4H-pyra n-4-ylidene)propanedinitrile (abbreviation: DCM1), 2-{2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinoridine-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]fluorantene-3,10-diamine (abbreviation) Name: p-mPhAFD), 2-{2-isopropyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinoridine-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]quinoridine-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCJTB), 2-(2,6-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]quinoridine-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: BisDCJTM), N,N'-diphenyl-N,N'-(1,6-pyrene-diyl)bis[(6-phenylbenzo[b]naph Examples include [1,2-d]furan)-8-amine] (abbreviated as 1,6BnfAPrn-03), N,N'-diphenyl-N,N'-bis(9-phenyl-9H-carbazole-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 like 1,6FLPAPrn, 1,6mMemFLPAPrn, and 1,6BnfAPrn-03, are preferred because they have high hole-trapping properties and excellent luminescence efficiency or reliability.

[0118] Also, 5,9-diphenyl-5H,9H-[1,4]benzazaborino[2,3,4-kl]phenazavorin (abbreviation: DABNA-1), 9-(diphenyl-3-yl)-N,N,5,11-tetraphenyl-5,9-dihydro-5,9-diaza-13b-boranaphtho[3,2,1-de]anthracene-3-amine (abbreviation: DABNA-2), 2,12-di(tert-butyl)-5,9-di(4-tert-butylphenyl)-N,N-diphenyl-5H,9H-[1,4]benzazaborino[2,3,4-kl]phenazavorin Phosphorus-7-amine (abbreviation: DPhA-tBu4DABNA), 2,12-di(tert-butyl)-N,N,5,9-tetra(4-tert-butylphenyl)-5H,9H-[1,4]benzazabolino[2,3,4-kl]phenazavolin-7-amine (abbreviation: tBuDPhA-tBu4DABNA), 2,12-di(tert-butyl)-5,9-di(4-tert-butylphenyl)-7-methyl-5H,9H-[1,4]benzazabolino[2,3,4-kl]phenazavolin (abbreviation: Me-tBu4DABNA), N 7 ,N 7 ,N 13 ,N 13 Condensed heteroaromatic compounds containing nitrogen and boron, such as ,5,9,11,15-octaphenyl-5H,9H,11H,15H-[1,4]benzazabolino[2,3,4-kl][1,4]benzazabolino[4',3',2':4,5][1,4]benzazabolino[3,2-b]phenazabolin-7,13-diamine (abbreviation: ν-DABNA) and 2-(4-tert-butylphenyl)benz[5,6]indro[3,2,1-jk]benzo[b]carbazole (abbreviation: tBuPBibc), particularly compounds having a diaza-boranaphtho-anthracene skeleton, can be suitably used because they produce blue emission with a narrow emission spectrum and good color purity.

[0119] In addition to these, there is 9,10,11-tris[3,6-bis(1,1-dimethylethyl)-9H-carbazolyl-9-yl]-2,5,15,18-tetrakis(1,1-dimethylethyl)indoro[3,2,1-de]indoro[3',2',1':8,1][1,4]benzazavolino[2,3,4-kl]phenazavolin (abbreviation: BBCz-G), 9,11-bis[ Compounds having an indole skeleton, such as 3,6-bis(1,1-dimethylethyl)-9H-carbazolyl-9-yl]-2,5,15,18-tetrakis(1,1-dimethylethyl)indoro[3,2,1-de]indoro[3',2',1':8,1][1,4]benzazavolino[2,3,4-kl]phenazavolin (abbreviation: BBCz-Y), can be suitably used.

[0120] When a phosphorescent material is used as the light-emitting material in the light-emitting layer, the following materials are examples of suitable phosphorescent materials.

[0121] Organometallic iridium complexes having 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]). , organometallic iridium complexes having a 1H-triazole skeleton 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-di Isopropylphenyl)-2-phenyl-1H-imidazole]iridium(III) (abbreviation: [Ir(iPrpim)3]), Tris[3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-f]phenanthridine]iridium(III) (abbreviation: [Ir(dmpimpt-Me)3]), Tris(2-{1-[2,6-bis(1-methylethyl)phenyl]-1H-imidazole-2-yl-κN3}-4-cyanoph Organometallic iridium complexes having an imidazole skeleton, such as phenyl-κC)iridium(III) (abbreviation: CNImIr), organometallic complexes having a benzimidazolidene skeleton, such as tris[(6-tert-butyl-3-phenyl-2H-imidazo[4,5-b]pyrazine-1-yl-κC2)phenyl-κC]iridium(III) (abbreviation: [Ir(cb)3]), and bis[2-(4',6'-difluorophenyl)pyridinato-N,C 2’ Iridium(III) tetrakis(1-pyrazolyl) borate (abbreviation: FIr6), bis[2-(4',6'-difluorophenyl)pyridinate-N,C 2’ Iridium(III) picolinate (abbreviation: Firpic), bis{2-[3',5'-bis(trifluoromethyl)phenyl]pyridinate-N,C 2’Iridium(III) picolinate (abbreviation: [Ir(CF3ppy)2(pic)]), bis[2-(4',6'-difluorophenyl)pyridinate-N,C 2’ Examples include organometallic iridium complexes with phenylpyridine derivatives having electron-withdrawing groups, such as iridium(III) acetylacetonate (FIracac), and platinum complexes such as (2-{3-[3-(3,5-di-tert-butylphenyl)benzimidazole-1-yl-2-ylidene-κC2]phenoxy-κC2}-9-(4-tert-butyl-2-pyridinyl-κN)carbazole-2,1-diyl-κC1)platinum(II) (PtON-TBBI). These compounds exhibit blue phosphorescence and have emission peaks in the wavelength range from 450 nm to 520 nm. Compounds in which some of the hydrogen atoms in these compounds are replaced with deuterium can also be used.

[0122] Also, 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 having a pyrimidine skeleton, such as (2-methylphenyl)-4-phenylpyrimidinato]iridium(III) (abbreviation: [Ir(mpmppm)2(acac)]), (acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III) (abbreviation: [Ir(dppm)2(acac)]), organometallic iridium complexes having a pyrazine skeleton, such as (acetylacetonato)bis(3,5-dimethyl-2-phenylpyradinato)iridium(III) (abbreviation: [Ir(mppr-Me)2(acac)]), (acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyradinato)iridium(III) (abbreviation: [Ir(mppr-iPr)2(acac)]), and tris(2-phenylpyrimidinato-N,C 2’ Iridium(III) (abbreviation: [Ir(ppy)3]), bis(2-phenylpyridinate-N,C) 2’ Iridium(III) acetylacetonate (abbreviation: [Ir(ppy)2(acac)]), bis(benzo[h]quinolinate)iridium(III) acetylacetonate (abbreviation: [Ir(bzq)2(acac)]), tris(benzo[h]quinolinate)iridium(III) (abbreviation: [Ir(bzq)3]), tris(2-phenylquinolinate-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)benzoflof[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]benzofl[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-(methyl-d3)- 8-(2-pyridinyl-κN)benzofloxacin[2,3-b]pyridinyl-κC]bis[2-(2-pyridinyl-κN)phenyl-κC]iridium(III) (abbreviation: [Ir(ppy)2(mbfpypy-d3)]), [2-(4-methyl-5-phenyl-2-pyridinyl-κN)phenyl-κC]bis[2-(2-pyridinyl-κN)phenyl-κC]iridium(III) (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-8-(2-pyridinyl-κN)benzofloxacin[2,In addition to organometallic iridium complexes with a pyridine skeleton, such as 3-b]pyridine-κC]bis[2-(2-pyridinyl-κN)phenyl-κC]iridium(III) (abbreviation: [Ir(ppy)2(mbfpypy)]) and tris{2-[5-(methyl-d3)-4-phenyl-2-pyridinyl-κN]phenyl-κC}iridium(III) (abbreviation: Ir(5m4dppy-d3)3), there are also rare earth metal complexes such as tris(acetylacetonato)(monophenanthroline)terbium(III) (abbreviation: [Tb(acac)3(Phen)]), and (2-{1-(5-tert-butylbiphenyl-2-yl)-4-[3-ter Examples of organometallic platinum complexes include t-butyl-5-(4-phenyl-2-pyridinyl-κN)phenyl-κC6]-2-benzimidazolyl-κN3}-4,6-di-tert-butylphenolato-κO)platinum(II) (abbreviation: Pt(tBudppymmtBubiz-tBubp)) and [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)). These compounds mainly exhibit green phosphorescence and have emission peaks in the wavelength range from 500 nm to 600 nm. Furthermore, organometallic iridium complexes having a pyrimidine skeleton are particularly preferred due to their outstanding reliability and luminescence efficiency. Compounds in which some of the hydrogen atoms are replaced with deuterium can also be used.

[0123] Furthermore, 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(naphthalene-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)]), and tris(1-phenylisoquinolinato-N,C) 2’ Iridium(III) (abbreviation: [Ir(piq)3]), bis(1-phenylisoquinolinato-N,C) 2’) Iridium(III) acetylacetonate (abbreviation: [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), (3,7-diethyl-4,6-nonanedionato-κO4,κO6)bis[2,4-dimethyl-6-[5-(1-methylethyl)-2-quinolinyl-κN]phenyl-κC]iridium(III) are organometallic iridium compounds with a pyridine skeleton. In addition to dinium complexes, other examples include platinum complexes such as 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin platinum(II) (abbreviated as PtOEP), and rare earth metal complexes such as tris(1,3-diphenyl-1,3-propanedionato)(monophenanthroline)europium(III) (abbreviated as [Eu(DBM)3(Phen)]) and tris[1-(2-tenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(III) (abbreviated as [Eu(TTA)3(Phen)]). These compounds exhibit red phosphorescence and have emission peaks in the wavelength range of 600 nm to 700 nm. Furthermore, organometallic iridium complexes with a pyrazine skeleton yield red emission with good chromaticity. Compounds in which some of the hydrogen atoms in these compounds are replaced with deuterium can also be used.

[0124] In addition to the phosphorescent compounds described above, other known phosphorescent compounds may be selected and used.

[0125] As TADF materials, fullerenes and their derivatives, acridines and their derivatives, eosin derivatives, etc., can be used. Also, metal-containing porphyrins containing magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), or palladium (Pd) can be used. Examples of metal-containing porphyrins include protoporphyrin-tin fluoride complexes (SnF2(Proto IX)), mesoporphyrin-tin fluoride complexes (SnF2(Meso IX)), hematoporphyrin-tin fluoride complexes (SnF2(Hemato IX)), coproporphyrin tetramethyl ester-tin fluoride complexes (SnF2(Copro III-4Me)), octaethylporphyrin-tin fluoride complexes (SnF2(OEP)), etioporphyrin-tin fluoride complexes (SnF2(Etio I)), and octaethylporphyrin-platinum chloride complexes (PtCl2OEP), as shown in the following structural formulas.

[0126] [ka]

[0127] Furthermore, the following structural formulas represent 2-(biphenyl-4-yl)-4,6-bis(12-phenylindoro[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'-bicarbazol (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-phenoxazine-10-yl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: PCCzPTzn) Heterocyclic compounds having one or both of a π-electron-rich heteroaromatic ring and a π-electron-deficient heteroaromatic ring can also be used, such as PXZ-TRZ, 3-[4-(5-phenyl-5,10-dihydrophenazine-10-yl)phenyl]-4,5-diphenyl-1,2,4-triazole (abbreviated as PPZ-3TPT), 3-(9,9-dimethyl-9H-acridine-10-yl)-9H-xanthene-9-one (abbreviated as ACRXTN), bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone (abbreviated as DMAC-DPS), and 10-phenyl-10H,10'H-spiro[acridine-9,9'-anthracene]-10'-one (abbreviated as ACRSA). The heterocyclic compound is preferred because it has both a π-electron-excess heteroaromatic ring and a π-electron-deficient heteroaromatic ring, resulting in high electron transport and hole transport properties. Among the skeletons having a π-electron-deficient heteroaromatic ring, the pyridine skeleton, diazine skeleton (pyrimidine skeleton, pyrazine skeleton, pyridazine skeleton), and triazine skeleton are preferred because they are stable and reliable. In particular, the benzoflopyrimidine skeleton, benzothienopyrimidine skeleton, benzoflopyrazine skeleton, and benzothienopyrazine skeleton are preferred because they have high acceptability and are reliable. Furthermore, among the skeletons having a π-electron-excess heteroaromatic ring, the acridine skeleton, phenoxazine skeleton, phenothiazine skeleton, furan skeleton, thiophene skeleton, and pyrrole skeleton are preferred because they are stable and reliable, and therefore it is preferable to have at least one of these skeletons.Furthermore, a dibenzofuran skeleton is preferred as the furan skeleton, and a dibenzothiophene skeleton is preferred as the thiophene skeleton. In addition, as the pyrrole skeleton, indole skeleton, carbazole skeleton, indrocarbazole skeleton, bicarbazole skeleton, and 3-(9-phenyl-9H-carbazole-3-yl)-9H-carbazole skeleton are particularly preferred. Substances in which a π-electron-rich heteroaromatic ring and a π-electron-deficient heteroaromatic ring are directly bonded are particularly preferred because both the electron-donating and electron-accepting properties of the π-electron-rich heteroaromatic ring are strengthened, and the energy difference between the S1 and T1 levels is reduced, thus efficiently obtaining thermally activated delayed fluorescence. In addition, an aromatic ring to which an electron-withdrawing group such as a cyano group is bonded may be used instead of the π-electron-deficient heteroaromatic ring. Furthermore, aromatic amine skeletons, phenazine skeletons, etc., can be used as the π-electron-rich skeleton. Furthermore, as π-electron-deficient skeletons, xanthene skeletons, thioxanthene dioxide skeletons, oxadiazole skeletons, triazole skeletons, imidazole skeletons, anthraquinone skeletons, boron-containing skeletons such as phenylborane and volanthrene, aromatic rings having a nitrile group or a cyano group such as benzonitrile or cyanobenzene, heteroaromatic rings, carbonyl skeletons such as benzophenone, phosphine oxide skeletons, sulfone skeletons, etc., can be used. In this way, π-electron-deficient skeletons and π-electron-excess skeletons can be used instead of at least one of π-electron-deficient heteroaromatic rings and π-electron-excess heteroaromatic rings.

[0128] [ka]

[0129] TADF materials are materials that have a small energy difference between the S1 and T1 levels and possess the ability to convert energy from triplet excitation energy to singlet excitation energy through reverse intersystem crossing. Therefore, triplet excitation energy can be upconverted to singlet excitation energy with only a small amount of thermal energy (reverse intersystem crossing), and singlet excited states can be efficiently generated. Furthermore, triplet excitation energy can be converted into luminescence.

[0130] Furthermore, an excited complex (also called an exciplex) that forms an excited state with two types of substances has an extremely small energy difference between the S1 and T1 levels and functions as a TADF material that can convert triplet excitation energy into singlet excitation energy.

[0131] Furthermore, the phosphorescence spectrum observed at low temperatures (e.g., 77K to 10K) can be used as an indicator of the T1 level. For TADF materials, when a tangent is drawn at the short-wavelength tail of the fluorescence spectrum and the energy at the wavelength of the extrapolation is taken as the S1 level, and when a tangent is drawn at the short-wavelength tail of the phosphorescence spectrum and the energy at the wavelength of the extrapolation is taken as the T1 level, it is preferable that the energy difference between S1 and T1 is 0.3 eV or less, and more preferably 0.2 eV or less.

[0132] Furthermore, when using TADF material as a light-emitting material, it is preferable that the S1 level of the host material is higher than the S1 level of the TADF material. Also, it is preferable that the T1 level of the host material is higher than the T1 level of the TADF material.

[0133] Various carrier transport materials can be used as the host material for the light-emitting layer, such as materials with electron transport properties and / or hole transport properties, and the TADF material mentioned above.

[0134] Preferred materials with hole transport properties include organic compounds having an amine skeleton or a π-electron-rich heteroaromatic ring skeleton. Preferred π-electron-rich heteroaromatic rings are condensed aromatic rings containing at least one of the following: acridine skeleton, phenoxazine skeleton, phenothiazine skeleton, furan skeleton, thiophene skeleton, and pyrrole skeleton. Specifically, carbazole rings, dibenzothiophene rings, or rings obtained by further condensing an aromatic ring or heteroaromatic ring with these are preferred.

[0135] Organic compounds having such hole-transporting properties more preferably have at least one of the following skeletons: carbazole, dibenzofuran, dibenzothiophene, and anthracene. In particular, they may be aromatic amines having substituents including 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. Furthermore, it is preferable that these hole-transporting organic compounds are substances having an N,N-bis(4-biphenyl)amino group, as this allows for the creation of light-emitting devices with a good lifetime.

[0136] Examples of such organic compounds include 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviated as NPB), N,N'-diphenyl-N,N'-bis(3-methylphenyl)-4,4'-diaminobiphenyl (abbreviated as TPD), N,N'-bis(9,9'-spirobi[9H-fluoren]-2-yl)-N,N'-diphenyl-4,4'-diaminobiphenyl (abbreviated as BSPB), 4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviated as BPAFLP), and 4-phenyl-3 '-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: mBPAFLP), 4-phenyl-4'-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4'-diphenyl-4''-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBBi1BP), 4-(1-naphthyl)-4'-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBANB), 4,4'-di(1-naphthyl)-4''-(9-phenyl Compounds having an aromatic amine skeleton such as 9,9-9H-carbazol-3-yl)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'-spirobio[9H-fluoren]-2-amine (abbreviation: PCBASF), 1,3-bis(N-carbazolyl)benzene (abbreviation: mCP), 4,4'-di( N-carbazolyl)biphenyl (abbreviated as CBP), 3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviated as CzTP), 3,3'-bis(9-phenyl-9H-carbazole) (abbreviated as PCCP), 9,9'-bis(biphenyl-4-yl)-3,3'-bi-9H-carbazole (abbreviated as BisBPCz), 9,9'-bis(biphenyl-3-yl)-3,3'-bi-9H-carbazole (abbreviated as 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 Lubazole, 9-(2-naphthyl)-9'-[1,1':3',1”-terphenyl]-4-yl-3,3'-9H,9'H-bicarbazole, 9-(2-naphthyl)-9'-(triphenylene-2-yl)-3,3'-9H,9'H-bicarbazole, 9-phenyl-9'-(triphenylene-2-yl)-3,3'-9H,9'H-bicarbazole (abbreviation: PCCzTp), 9,9'-bis(triphenylene-2-yl)-3,3'-9H,9'H-bicarbazole, 9-(4-biphenyl)-9 Compounds having a carbazole skeleton such as '-(triphenylene-2-yl)-3,3'-9H,9'H-bicarbazole, 9-(triphenylene-2-yl)-9'-[1,1':3',1”-terphenyl]-4-yl-3,3'-9H,9'H-bicarbazole, 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 include compounds having a thiophene skeleton such as 8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene (abbreviated as DBTFLP-III) and 4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviated as DBTFLP-IV), and compounds having a furan skeleton such as 4,4',4''-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviated as DBF3P-II) and 4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran (abbreviated as mmDBFFLBi-II). Among the above, compounds having an aromatic amine skeleton or a carbazole skeleton are preferred because they have good reliability, high hole transportability, and contribute to reducing the driving voltage. In addition, organic compounds listed as examples of hole transportable materials in the hole transport layer can also be used. Furthermore, it is more preferable to use organic compounds having an amine skeleton and a fluorene skeleton. Organic compounds having an amine skeleton and a fluorene skeleton are preferable because they have good reliability and high hole transport properties, thus reducing the power consumption of the light-emitting device.

[0137] For materials exhibiting electron transport properties, the electron mobility at which the square root of the electric field strength [V / cm] is 600 is 1 × 10⁻⁶. -7 cm 2 / Vs or more, preferably 1 × 10 -6 cm 2 A material having an electron mobility of / Vs or higher is preferred. However, any material with higher electron transport capabilities than holes can be used.

[0138] Preferred electron-transporting materials include metal complexes such as tris(8-quinolinolato)aluminum (abbreviated as Alq3), bis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviated as BeBq2), bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III) (abbreviated as BAlq), bis(8-quinolinolato)zinc(II) (abbreviated as Znq), bis[2-(2-benzoxazollyl)phenolato]zinc(II) (abbreviated as ZnPBO), and bis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviated as ZnBTZ), as well as organic compounds having a π-electron-deficient heteroaromatic ring. Examples of organic compounds having a π-electron-deficient heteroaromatic ring skeleton include organic compounds containing a heteroaromatic ring having an azole skeleton, organic compounds containing a heteroaromatic ring having a pyridine skeleton, organic compounds containing a heteroaromatic ring having a diazine skeleton, and organic compounds containing a heteroaromatic ring having a triazine skeleton.

[0139] Among these, organic compounds containing heteroaromatic rings having a diazine skeleton (pyrimidine skeleton, pyrazine skeleton, pyridazine skeleton), organic compounds containing heteroaromatic rings having a pyridine skeleton, and organic compounds containing heteroaromatic rings having a triazine skeleton are preferred due to their good reliability. In particular, organic compounds containing heteroaromatic rings having a diazine (pyrimidine or pyrazine) skeleton and organic compounds containing heteroaromatic rings having a triazine skeleton have high electron transport properties and contribute to reducing the driving voltage. Furthermore, benzoflopyrimidine skeletons, benzothienopyrimidine skeletons, benzoflopyrazine skeletons, and benzothienopyrazine skeletons are preferred because they have high acceptability and good reliability.

[0140] Examples of organic compounds having a π-electron-deficient heteroaromatic ring skeleton include 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviated as PBD), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviated as TAZ), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazole-2-yl]benzene (abbreviated as OXD-7), and 9-[4-(5-phenyl-1,3,4-oxadi Azole-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-methylbenzoxazole-2-yl)stilbene (abbreviation: BzOs), 2-{4-[9,10-di(2-naphthyl)-2-anthryl]phen Organic compounds having an azole skeleton such as 1 / 2-phenyl-1H-benzimidazole (abbreviation: ZADN), 3,5-bis[3-(9H-carbazole-9-yl)phenyl]pyridine (abbreviation: 35DCzPPy), 1,3,5-tri[3-(3-pyridyl)phenyl]benzene (abbreviation: TmPyPB), vasophenanthroline (abbreviation: Bphen), vasocuproin (abbreviation: BCP), 2,9-di(naphthalene-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), 2-phenyl-9-(2-triphenylenyl)-1,10-phenanthroline (abbreviation: Ph-TpPhen), 2-[4-(9-phenanthryl)-1-naphthyl]-1,10-phenanthroline (abbreviation: PnNPhen), 2-[4-(2-triphenylenyl)phenyl]-1,Organic compounds containing heteroaromatic rings with a pyridine skeleton, such as 10-phenanthroline (abbreviation: pTpPPhen), 2-{3-[3-(N-phenyl-9H-carbazole-3-yl)-9H-carbazole-9-yl]phenyl}dibenzo[f,h]quinoxaline (abbreviation: 2mPCCzPDBq), 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 Sarin (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-9H-carbazol-9-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2CzPDBq-III), 7-[3-(dibenzo Zothiophene-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 7mDBTPDBq-II), and 6-[3-(dibenzothiophene-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 6mDBTPDBq-II), 9-[3'-(dibenzothiophene-4-yl)biphenyl-3-yl]naphtho[1',2':4,5]flo[2,3-b]pyrazine (abbreviation: 9mDBtBPNfpr), 9-[3'-(dibenzothiophene-4-yl)biphenyl-4-yl]naphtho[1',2':4,5]flo[2 ,3-b]pyrazine (abbreviation: 9pmDBtBPNfpr), 4,6-bis[3-(phenanthrene-9-yl)phenyl]pyrimidine (abbreviation: 4,6mPnP2Pm), 4,6-bis[3-(dibenzothiophen-4-yl)phenyl]pyrimidine (abbreviation: 4,6mDBTP2Pm-II), 4,6-bis[3-(9H-carbazole-9-yl)phenyl]pyrimidine (abbreviation: 4,6mCzP2Pm), 9,9'-[pyrimidine-4,6-diylbis(biphenyl-3,3'-diyl)]bis(9H-carbazole) (abbreviation: 4,6mCzBP2Pm), 8-(biphenyl-4-yl)-4-[3-(dibenzothiophen-4-yl)phenyl]-[1]benzoflo[3,2-d]pyrimidine (abbreviation: 8BP-4mDBtPBfpm), 3,8-bis[3-(dibenzothiophen-4-yl)phenyl]benzoflo[2,3-b]pyrazine (abbreviation: 3,8mDBtP2Bfpr), 11-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]phenantro[9',10':4,5]flo[2,3-b]pyrazine (abbreviation: 11mDBtBPPnfpr), 4, 8-Bis[3-(dibenzothiophen-4-yl)phenyl]-[1]benzoflo[3,2-d]pyrimidine (abbreviation: 4,8mDBtP2Bfpm), 8-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]naphtho[1',2':4,5]flo[3,2-d]pyrimidine (abbreviation: 8mDBtBPNfpm), 8-([2,2'-binaphthalene]-6-yl)-4-[3-(dibenzothiophen-4-yl)phenyl]-[1]benzoflo[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-carbazole-9-yl)phenyl]-2-phenylpyrimidine (abbreviation: 6mBP-4Cz2PPm), 2,6-bis(4-naphthalene-1-ylphenyl)-4-[4-(3-pyridyl)phenyl ]pyrimidine (abbreviation: 2,4NP-6PyPPm), 4-[3,5-bis(9H-carbazole-9-yl)phenyl]-2-phenyl-6-(biphenyl-4-yl)pyrimidine (abbreviation: 6BP-4Cz2PPm), 8-(biphenyl-4-yl)-4-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]-[1]benzoflo[3,2-d]pyrimidine (abbreviation: 8BP-4mDBtBPBfpm), 8-(p-terphenyl-3-yl)-4-[3-(dibenzothiophen-4-yl)phenyl]-[1]benzoflo[3,Organic compounds having a diazine skeleton such as 2-d]pyrimidine (abbreviation: 8mpTP-4mDBtPBfpm), 7-[4-(9-phenyl-9H-carbazole-2-yl)quinazoline-2-yl]-7H-dibenzo[c,g]carbazole (abbreviation: PC-cgDBCzQz), 2-(biphenyl-4-yl)-4-phenyl-6-(9,9'-spirobio[9H-fluoren]-2-yl)-1,3,5-triazine (abbreviation: BP-SFTzn), and 2-{3-[3-(benzo[b]naphtho[1,2-d]furan-8-yl)phenyl]phenyl}-4 ,6-diphenyl-1,3,5-triazine (abbreviation: mBnfBPTzn), 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-carbazole-3-yl)-9H-carbazole-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: PCCzPTzn), 9-[3-(4,6-diphenyl-1,3,5-triazine-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-triazine-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-triazine-2-yl]-11,12-dihydro-12-phenylindro[2,3-a]carbazole (abbreviation: BP-Icz(II)Tzn), 2-[3'-(triphenylene-2-yl)biphenyl-3-yl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mTpBPTzn), 3-[9-(4,6-diphenyl-1,3,5-triazine-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-(3'',5',5''-tri-t-butyl-[1,1':3',1''-terphenyl]-4-yl)-4,6-diphenyl-1,3,5-triazine (abbreviation: mmtBumTPTzn-04), 2,4,6-tris[3' -(pyridine-3-yl)-5'-tert-butyl-biphenyl-3-yl]-1,3,5-triazine (abbreviation: tBu-TmPPPyTz), 2,4,6-tris[3'-(pyridine-3-yl)-5'-tert-butyl-biphenyl-4-yl]-1,3,5-triazine (abbreviation: tBu-TmPPPyTz-02), 2-(3'',5',5''-tri-t-butyl-[1,1':3',1''-ter Examples of organic compounds containing heteroaromatic rings having a triazine skeleton include phenyl]-5-yl)-4,6-diphenyl-1,3,5-triazine (abbreviation: mmtBumTPTzn-03) and 2-{3-(2,6-dimethylpyridine-3-yl)-5-[(3,5-di-tert-butyl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mmtBuPh-mDMePyPTzn). Furthermore, organic compounds containing heteroaromatic rings having a diazine skeleton, or heteroaromatic rings having a pyridine skeleton, or heteroaromatic rings having a triazine skeleton are preferred due to their good reliability. In particular, organic compounds containing heteroaromatic rings having a diazine (pyrimidine or pyrazine) skeleton, and organic compounds containing heteroaromatic rings having a triazine skeleton have high electron transport properties and contribute to reducing the drive voltage. Among these, 8BP-4mDBtBPBfpm, 4,6mDBTP2Pm-II, 8mpTP-4mDBtPBfpm, TPBI, ZADN, BP-ICz(II)Tzn, mmtBumTPTzn-04, tBu-TmPPPyTz, tBu-TmPPPyTz-02, mmtBumTPTzn-03, mmtBuPh-mDMePyPTzn, and 4,8mDBtP2Bfpm, Alq3 are organic compounds with a large GSP_Slope of the deposited film, and therefore can be suitably used as materials for the second electron transport layer in the light-emitting device of the present invention.

[0141] The TADF materials listed above can be used as host materials. When a TADF material is used as a host material, the triplet excitation energy generated by the TADF material is converted into singlet excitation energy through reverse intersystem crossing, and this energy is then transferred to the light-emitting material, thereby increasing the luminescence efficiency of the light-emitting device. In this case, the TADF material functions as an energy donor, and the light-emitting material functions as an energy acceptor.

[0142] This is particularly effective when the light-emitting material is a fluorescent material. Furthermore, in order to obtain high luminescence efficiency, it is preferable that the S1 level of the TADF material is higher than that of the fluorescent material. Also, it is preferable that the T1 level of the TADF material is higher than that of the fluorescent material. Therefore, it is preferable that the T1 level of the TADF material is higher than that of the fluorescent material.

[0143] Furthermore, it is preferable to use a TADF material that exhibits emission that overlaps with the wavelength of the lowest-energy absorption band of the fluorescent material. This is preferable because it allows for smooth transfer of excitation energy from the TADF material to the fluorescent material, resulting in efficient emission.

[0144] Furthermore, for singlet excitation energy to be efficiently generated from triplet excitation energy by reverse intersystem crossing, it is preferable that carrier recombination occurs in the TADF material. It is also preferable that the triplet excitation energy generated in the TADF material does not transfer to the triplet excitation energy of the fluorescent material. To achieve this, it is preferable that the fluorescent material has protecting groups around the luminescent phosphoform (the skeleton that causes luminescence). Preferred protecting groups are substituents without π bonds, and saturated hydrocarbons are preferred. Specifically, examples include alkyl groups having 3 to 10 carbon atoms, substituted or unsubstituted cycloalkyl groups having 3 to 10 carbon atoms, and trialkylsilyl groups having 3 to 10 carbon atoms. It is even preferable to have multiple protecting groups. Substituents without π bonds have poor carrier transport function, and therefore can increase the distance between the TADF material and the luminescent phosphoform of the fluorescent material with little effect on carrier transport or carrier recombination. Here, the luminescent phosphoform refers to the atomic group (skeleton) that causes luminescence in the fluorescent material. The luminescent phosphophore preferably has a skeleton containing π bonds, preferably contains an aromatic ring, and preferably has a condensed aromatic ring or a condensed heteroaromatic ring. Examples of such luminescent phosphophores include phenanthrene skeletons, stilbene skeletons, acridone skeletons, phenoxazine skeletons, phenothiazine skeletons, naphthalene skeletons, anthracene skeletons, fluorene skeletons, chrysene skeletons, triphenylene skeletons, tetracene skeletons, pyrene skeletons, perylene skeletons, coumarin skeletons, quinacridone skeletons, and naphthobisbenzofuran skeletons. Fluorescent materials having naphthalene, anthracene, fluorene, chrysene, triphenylene, tetracene, pyrene, perylene, coumarin, quinacridone, and naphthobisbenzofuran skeletons are particularly preferred due to their high fluorescence quantum yield.

[0145] When using a fluorescent material as the light-emitting material, a material having an acene skeleton, particularly an anthracene skeleton, is preferred as the host material. Using a material having an anthracene skeleton as the host material for a fluorescent material makes it possible to realize a light-emitting layer with good luminescence efficiency and durability. Among the materials having an anthracene skeleton to be used as the host material, a material having a diphenylanthracene skeleton, particularly a 9,10-diphenylanthracene skeleton, is preferred because it is chemically stable. Furthermore, while a host material having a carbazole skeleton is preferred because it improves hole injection and transportability, a benzocarbazole skeleton, in which a benzene ring is further condensed into the carbazole skeleton, is even more preferred because the HOMO (Highest Occupied Molecular Orbital) level is about 0.1 eV higher than that of a host material having only a carbazole skeleton, making it easier for holes to enter. In particular, when the host material contains a dibenzocarbazole skeleton, the HOMO level is about 0.1 eV higher than that of a host material containing only a carbazole skeleton, making it easier for holes to enter, and it is also preferable because it exhibits excellent hole transport properties and high heat resistance. Therefore, an even more preferable host material is a substance that simultaneously contains a 9,10-diphenylanthracene skeleton and a carbazole skeleton (or a benzocarbazole skeleton or a dibenzocarbazole skeleton). Furthermore, from the viewpoint of the above-mentioned hole injection and transport properties, a benzofluorene skeleton or a dibenzofluorene skeleton may be used instead of the carbazole skeleton.

[0146] Examples of such substances include 9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviated as PCzPA), 3-[4-(1-naphthyl)phenyl]-9-phenyl-9H-carbazole (abbreviated as PCPN), 9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviated as CzPA), 7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole (abbreviated as cgDBCzPA), 6-[3-(9,10-diphenyl-2-anthryl)phenyl]benzo[b]naphtho[1,2-d]furan (abbreviated as 2mBnfPPA), and 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-phenylanthracene-9-yl)dibenzofuran, 2-(10-phenyl-9-anthryl)ben Examples include zo[b]naphtho[2,3-d]furan (abbreviated as Bnf(II)PhA), 9-(2-naphthyl)-10-[3-(2-naphthyl)phenyl]anthracene (abbreviated as βN-mβNPAnth), and 1-{4-[10-(biphenyl-4-yl)-9-anthryl]phenyl}-2-ethyl-1H-benzimidazole (abbreviated as EtBImPBPhA). In particular, CzPA, cgDBCzPA, 2mBnfPPA, and PCzPA exhibit very good properties and are therefore preferred choices.

[0147] The host material may be a mixture of multiple substances, and when using a mixed host material, it is preferable to mix an electron-transporting material with a hole-transporting material. By mixing an electron-transporting material with a hole-transporting material, 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 hole-transporting material to the electron-transporting material should be 1:19 to 19:1.

[0148] Furthermore, phosphorescent materials can be used as part of the above-mentioned mixed materials. When a fluorescent material is used as the light-emitting material, the phosphorescent material can be used as an energy donor to supply excitation energy to the fluorescent material.

[0149] Furthermore, these mixed materials may form an excited complex. It is preferable to select a combination that forms an excited complex that exhibits emission overlapping with the wavelength of the lowest-energy absorption band of the luminescent material, as this facilitates smooth energy transfer and efficiently obtains light emission. This configuration is also preferable because it reduces the driving voltage.

[0150] Furthermore, at least one of the materials forming the excitation complex may be a phosphorescent material. This allows for the efficient conversion of the triplet excitation energy to the singlet excitation energy through reverse intersystem crossing.

[0151] For efficient excitation complex formation, it is preferable that the HOMO level of the hole-transporting material is above the HOMO level of the electron-transporting material. Furthermore, it is preferable that the LUMO (Lowest Unoccupied Molecular Orbital) level of the hole-transporting material is above the LUMO level of the electron-transporting material. The LUMO and HOMO levels of the materials can be derived from the electrochemical properties (reduction potential and oxidation potential) of the materials measured by cyclic voltammetry (CV).

[0152] The formation of excited complexes can be confirmed, for example, by comparing the emission spectra of a hole-transporting material, an electron-transporting material, and a mixed film made by mixing these materials, and observing that the emission spectrum of the mixed film shifts to a longer wavelength than the emission spectra of each individual material (or has a new peak on the longer wavelength side). Alternatively, it can be confirmed by comparing the transient photoluminescence (PL) of a hole-transporting material, the transient PL of an electron-transporting material, and the transient PL of a mixed film made by mixing these materials, and observing differences in the transient response, such as the transient PL lifetime of the mixed film having a longer lifetime component or a larger proportion of the delayed component than the transient PL lifetime of each individual material. Furthermore, the transient PL mentioned above can be replaced with transient electroluminescence (EL). That is, the formation of excited complexes can also be confirmed by comparing the transient EL of a hole-transporting material, the transient EL of an electron-transporting material, and the transient EL of a mixed film made by mixing these materials, and observing the differences in the transient response.

[0153] The electron transport layer 114 is a layer containing an electron-transporting material. The electron-transporting material has an electron mobility of 1 × 10⁻¹⁰ at an electric field strength [V / cm] square root of 600. -7 cm 2 / Vs or more, preferably 1 × 10 -6 cm 2 A substance having an electron mobility of / Vs or higher is preferred. However, any substance that has higher electron transport capacity than holes can be used. As the above organic compound, an organic compound having a π-electron-deficient heteroaromatic ring is preferred. As an organic compound having a π-electron-deficient heteroaromatic ring, it is preferable that it be any or more of the following: an organic compound containing a heteroaromatic ring having an azole skeleton, an organic compound containing a heteroaromatic ring having a pyridine skeleton, an organic compound containing a heteroaromatic ring having a diazine skeleton, and an organic compound containing a heteroaromatic ring having a triazine skeleton.

[0154] As an organic compound having electron-transporting properties that can be used in the electron transport layer 114, the same organic compounds that can be used as an organic compound having electron-transporting properties in the light-emitting layer 113 can be used. Among these, organic compounds containing a heteroaromatic ring having a diazine skeleton, or an organic compound containing a heteroaromatic ring having a pyridine skeleton, or an organic compound containing a heteroaromatic ring having a triazine skeleton are preferred due to their good reliability. In particular, organic compounds containing a heteroaromatic ring having a diazine (pyrimidine or pyrazine) skeleton, or an organic compound containing a heteroaromatic ring having a triazine skeleton, have high electron-transporting properties and contribute to reducing the driving voltage. In particular, organic compounds having a phenanthroline skeleton such as mTpPPhen, PnNPhen, and mPPhen2P are preferred, and organic compounds having a phenanthroline dimer structure such as mPPhen2P are more preferred due to their superior stability.

[0155] The electron transport layer 114 may have a multilayer structure. Furthermore, the layer in contact with the light-emitting layer 113 in the multilayer electron transport layer 114 may function as a hole-blocking layer. When the electron transport layer in contact with the light-emitting layer functions as a hole-blocking layer, it is preferable to use a material whose HOMO level is 0.5 eV or more lower than the HOMO level of the material contained in the light-emitting layer 113.

[0156] The electron injection layer 115 may include a layer containing an alkali metal or alkaline earth metal compound or complex such as 8-quinolinolatolithium (abbreviated as Liq), or 1,1'-pyridine-2,6-diyl-bis(1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine) (abbreviated as hpp2Py). The electron injection layer 115 may also be a layer containing an alkali metal or alkaline earth metal or a compound thereof within a layer made of an electron-transporting material.

[0157] Alternatively, a charge generation layer 116 may be provided instead of the electron injection layer 115 (Figure 5(A)). The charge generation layer 116 is a layer that can inject holes into the layer in contact with the cathode side and electrons into the layer in contact with the anode side by applying a potential. The charge generation layer 116 includes at least a p-type layer 117. The p-type layer 117 is preferably formed using a composite material listed above as a material that can constitute the hole injection layer 111. The p-type layer 117 may also be formed by laminating a film containing the acceptor material and a film containing the hole transport material as materials constituting the composite material. By applying a potential to the p-type layer 117, electrons are injected into the electron transport layer 114 and holes into the cathode, and the light-emitting device operates. Furthermore, since the organic compound in one embodiment of the present invention is an organic compound with a low refractive index of the film, by using it in the p-type layer 117, a light-emitting device with good external quantum efficiency can be obtained.

[0158] Furthermore, it is preferable that the charge generation layer 116 includes, in addition to the p-type layer 117, one or both of the electron relay layer 118 and the electron injection buffer layer 119.

[0159] The electron relay layer 118 contains at least an electron-transporting material and has the function of preventing interaction between the electron injection buffer layer 119 and the p-type layer 117, thereby smoothly transferring electrons. The LUMO level of the electron-transporting material contained in the electron relay layer 118 is preferably between the LUMO level of the acceptor material in the p-type layer 117 and the LUMO level of the material contained in the layer in contact with the charge generation layer 116 in the electron transport layer 114. The specific energy level of the LUMO level of the electron-transporting material used in the electron relay layer 118 is preferably -5.0 eV or higher, more preferably -5.0 eV or higher and -3.0 eV or lower. It is preferable to use a phthalocyanine-based material or a metal complex having a metal-oxygen bond and an aromatic ligand as the electron-transporting material used in the electron relay layer 118.

[0160] The electron injection buffer layer 119 can use materials with high electron injection potential, such as alkali metals, alkaline earth metals, rare earth metals, and compounds thereof (alkali metal compounds (including oxides such as lithium oxide, halides, and carbonates such as lithium carbonate and cesium carbonate), alkaline earth metal compounds (including oxides, halides, and carbonates), or rare earth metal compounds (including oxides, halides, and carbonates)).

[0161] Furthermore, if the electron injection buffer layer 119 is formed by including an electron-transporting substance and a donor substance, the donor substance can include alkali metals, alkaline earth metals, rare earth metals, and compounds thereof (alkali metal compounds (including oxides such as lithium oxide, halides, and carbonates such as lithium carbonate and cesium carbonate), alkaline earth metal compounds (including oxides, halides, and carbonates), or rare earth metal compounds (including oxides, halides, and carbonates)), as well as organic compounds such as tetratianaphthalene (abbreviated as TTN), nickerosene, and decamethylnickerosene. The electron-transporting substance can be formed using the same materials as those used to constitute the electron transport layer 114 described above.

[0162] The second electrode 102 is an electrode that includes a cathode. The second electrode 102 may have a layered structure, in which case the layer in contact with the EL layer 103 functions as the cathode. As the material forming the cathode, metals, alloys, electrically conductive compounds, and mixtures thereof with a small work function (specifically 3.8 eV or less) can be used. Specific examples of such cathode materials include alkali metals such as lithium (Li) or cesium (Cs), elements belonging to group 1 or 2 of the periodic table such as magnesium (Mg), calcium (Ca), and strontium (Sr), and alloys (MgAg, AlLi) and compounds (lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF2), etc.) containing these, rare earth metals such as europium (Eu) and ytterbium (Yb), and alloys containing these. However, by providing an electron injection layer 115 or a thin film of a material with a low work function between the second electrode 102 and the electron transport layer, various conductive materials such as Al, Ag, ITO, silicon, or indium oxide-tin oxide containing silicon oxide can be used as the cathode, regardless of the magnitude of the work function.

[0163] Furthermore, if the second electrode 102 is formed from a material that is transparent to visible light, it can be made into a light-emitting device that emits light from the second electrode 102 side.

[0164] These conductive materials can be formed using dry methods such as vacuum deposition or sputtering, inkjet printing, or spin coating. Alternatively, they may be formed using a wet method with a sol-gel process, or using a metal paste.

[0165] Furthermore, various methods can be used to form the EL layer 103, regardless of whether they are dry or wet methods. For example, vacuum deposition, gravure printing, offset printing, screen printing, inkjet printing, or spin coating may be used.

[0166] Furthermore, each electrode or layer described above may be formed using different film deposition methods.

[0167] Next, an embodiment of a light-emitting device (also called a stacked element or tandem element) with a configuration in which multiple light-emitting units are stacked will be described with reference to Figure 5(B). This light-emitting device has multiple light-emitting units between the anode and the cathode. Each light-emitting unit has a configuration substantially similar to the EL layer 103 shown in Figures 1(A) to 2(B). In other words, the light-emitting device shown in Figure 5(B) is a light-emitting device having multiple light-emitting units, while the light-emitting devices shown in Figures 1(A) to 2(B) are light-emitting devices having one light-emitting unit.

[0168] In Figure 5(B), a first light-emitting unit 511 and a second light-emitting unit 512 are stacked between the first electrode 501 and the second electrode 502, and a charge generation layer 513 is provided between the first light-emitting unit 511 and the second light-emitting unit 512. The first electrode 501 and the second electrode 502 correspond to the first electrode 101 and the second electrode 102 in Figures 1(A) to 2(B), respectively, and the same components described in the explanations of Figures 1(A) to 2(B) can be applied. Furthermore, the first light-emitting unit 511 and the second light-emitting unit 512 may have the same configuration or different configurations.

[0169] The charge generation layer 513 has the function of injecting electrons into one light-emitting unit and holes into the other light-emitting unit when a voltage is applied to the first electrode 501 and the second electrode 502. That is, in Figure 5(B), when a voltage is applied such that the potential of the anode is higher than the potential of the cathode, the charge generation layer 513 only needs to inject electrons into the first light-emitting unit 511 and holes into the second light-emitting unit 512.

[0170] The charge generation layer 513 is preferably formed with the same configuration as the charge generation layer 116 described in Figure 5(A). Because the composite material of the organic compound and the metal oxide has excellent carrier implantation and carrier transport properties, it can achieve low voltage drive and low current drive.

[0171] Furthermore, if the anode side of the light-emitting unit is in contact with the charge generation layer 513, the charge generation layer 513 can also serve as the hole injection layer of the light-emitting unit, so the light-emitting unit does not need to have a hole injection layer.

[0172] Furthermore, when an electron injection buffer layer 119 is provided in the charge generation layer 513, the electron injection buffer layer 119 plays the role of an electron injection layer in the anode-side light-emitting unit, so it is not necessarily required to form an electron injection layer in the anode-side light-emitting unit.

[0173] Figure 5(B) illustrates a light-emitting device having two light-emitting units, but the same principles can be applied to light-emitting devices with three or more stacked light-emitting units. As in the light-emitting device according to this embodiment, by arranging multiple light-emitting units separated between a pair of electrodes by a charge generation layer 513, high-brightness light emission can be achieved while maintaining a low current density, and a longer-life element can be realized. Furthermore, a light-emitting device that can be driven at a low voltage and consumes little power can be realized.

[0174] Furthermore, by making the light-emitting colors of each light-emitting unit different, it is possible to obtain a desired color of light emission from the entire light-emitting device. For example, in a light-emitting device having two light-emitting units, it is possible to obtain a light-emitting device that emits white light as a whole by obtaining red and green light-emitting colors from the first light-emitting unit and blue light-emitting color from the second light-emitting unit.

[0175] Furthermore, each layer, such as the EL layer 103, the first light-emitting unit 511, the second light-emitting unit 512, and the charge generation layer, as well as the electrodes, can be formed using methods such as vapor deposition (including vacuum deposition), droplet ejection (also known as inkjet printing), coating, and gravure printing. They may also contain low-molecular-weight materials, medium-molecular-weight materials (including oligomers and dendrimers), or polymer materials.

[0176] (Embodiment 3) In this embodiment, an example in which a light-emitting device according to one aspect of the present invention is used as a display element for a display device will be described. In this embodiment, the light-emitting device is shown in a shape formed by photolithography, but it may also be formed by a method using a fine metal mask or the like.

[0177] As illustrated in Figures 6(A) and 6(B), multiple light-emitting devices 130 are formed on the insulating layer 175 to constitute a display device.

[0178] The display device 100 has a pixel section 177 in which a plurality of pixels 178 are arranged in a matrix. The pixels 178 include sub-pixels 110R, sub-pixels 110G, and sub-pixels 110B.

[0179] In this specification, for example, when describing matters common to sub-pixels 110R, 110G, and 110B, they may be referred to simply as sub-pixel 110. Similarly, when describing matters common to other components distinguished by letters, the letters may be omitted and the corresponding symbols used.

[0180] Sub-pixel 110R emits red light, sub-pixel 110G emits green light, and sub-pixel 110B emits blue light. This allows an image to be displayed on the pixel section 177. In this embodiment, three sub-pixels of red (R), green (G), and blue (B) are used as an example, but other combinations of sub-pixels of other colors may be used. Furthermore, the number of sub-pixels is not limited to three, but may be four or more. Examples of four sub-pixels include four sub-pixels of R, G, B, and white (W), four sub-pixels of R, G, B, and yellow (Y), and four sub-pixels of R, G, B, and infrared (IR).

[0181] In this specification and other documents, the row direction is sometimes referred to as the X direction, and the column direction as the Y direction. The X and Y directions intersect, for example, perpendicularly.

[0182] Figure 6(A) shows an example where subpixels of different colors are arranged in the X direction, and subpixels of the same color are arranged in the Y direction. Alternatively, subpixels of different colors may be arranged in the Y direction, and subpixels of the same color may be arranged in the X direction.

[0183] A connecting portion 140 and a region 141 may be provided on the outside of the pixel portion 177. The region 141 is provided between the pixel portion 177 and the connecting portion 140. An EL layer 103 is provided in the region 141. A conductive layer 151C is provided in the connecting portion 140.

[0184] Figure 6(A) shows an example where region 141 and connection portion 140 are located to the right of the pixel portion 177, but the positions of region 141 and connection portion 140 are not particularly limited. Also, region 141 and connection portion 140 may be singular or multiple.

[0185] Figure 6(B) is an example of a cross-sectional view between the dashed line A1-A2 in Figure 6(A). As shown in Figure 6(B), the display device has 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, insulating layer 174, and insulating layer 173 are provided with openings that reach the conductive layer 172, and plugs 176 are provided to fill these openings.

[0186] In the pixel section 177, a light-emitting device 130 is provided on an insulating layer 175 and a plug 176. A protective layer 131 is provided so as to cover the light-emitting device 130. A 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.

[0187] In Figure 6(B), multiple cross-sections of the inorganic insulating layer 125 and the insulating layer 127 are shown, but when the display device is viewed from above, it is preferable that the inorganic insulating layer 125 and the insulating layer 127 are connected as one unit. In other words, it is preferable that the inorganic insulating layer 125 and the insulating layer 127 are insulating layers having an opening on the first electrode.

[0188] In Figure 6(B), the light-emitting devices 130 are shown as light-emitting devices 130R, 130G, and 130B. Light-emitting devices 130R, 130G, and 130B are assumed to emit different colors from each other. 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. In addition, light-emitting devices 130R, 130G, or 130B may emit other visible light or infrared light. Note that in Figure 6(B), light-emitting devices 130R and 130G, and light-emitting devices 130G and 130B can be considered adjacent light-emitting devices.

[0189] One embodiment of the present invention can be a top-emission type, for example, which emits light in the opposite direction to the substrate on which the light-emitting device is formed. Alternatively, one embodiment of the present invention may be a bottom-emission type.

[0190] The light-emitting device 130R is a light-emitting device that exhibits red light emission (phosphorescence is preferred), and preferably has the configuration shown in Embodiment 2. It has a first electrode (pixel electrode) 101R consisting of a conductive layer 151R and a conductive layer 152R, a first layer 135R on the first electrode 101R, a common layer 136 on the first layer 135R, and a second electrode (common electrode) 102 on the common layer 136. The common layer 136 is preferably an electron injection layer.

[0191] The light-emitting device 130G is a light-emitting device that emits green light (phosphorescence is preferred), and preferably has the configuration shown in Embodiment 2. It has a first electrode (pixel electrode) 101G consisting of a conductive layer 151G and a conductive layer 152G, a first layer 135G on the first electrode 101G, a common layer 136 on the first layer 135G, and a second electrode (common electrode) 102 on the common layer 136. The common layer 136 is preferably an electron injection layer.

[0192] The light-emitting device 130B is a light-emitting device that emits blue light (fluorescence is preferred), and preferably has the configuration shown in Embodiment 2. It has a first electrode (pixel electrode) 101B consisting of a conductive layer 151B and a conductive layer 152B, a first layer 135B on the first electrode 101B, a common layer 136 on the first layer 135B, and a second electrode (common electrode) 102 on the common layer 136. The common layer 136 is preferably an electron injection layer.

[0193] Of the pixel electrodes (first electrodes) and common electrodes (second electrodes) of the light-emitting device, one functions as the anode and the other as the cathode. In this embodiment, unless otherwise specified, the pixel electrodes function as the anode and the common electrodes function as the cathode.

[0194] The first layer 135R, the first layer 135G, and the first layer 135B are independent island-like layers for each light-emitting device or for each light-emitting color. Furthermore, it is preferable that the first layer 135R, the first layer 135G, and the first layer 135B do not overlap with each other. Note that the first layers formed on multiple light-emitting devices 130 in the light-emitting device, such as the first layer 135R, the first layer 135G, and the first layer 135B, may be collectively referred to as the first layer group 135A. By providing the first layer group 135A in an island-like manner for each light-emitting device 130, leakage current between adjacent light-emitting devices 130 can be suppressed even in high-definition display devices. This prevents crosstalk and enables the realization of a display device with extremely high contrast. In particular, it enables the realization of a display device with high current efficiency at low brightness.

[0195] The island-like first layer group 135A is formed by depositing an EL film for each emission color and processing the EL film using photolithography.

[0196] Preferably, the first layer 135 is provided so as to cover the top and side surfaces of the first electrode 101 (pixel electrode) of the light-emitting device 130. This makes it easier to increase the aperture ratio of the display device compared to a configuration in which the edges of the first layer 135 are located inward from the edges of the pixel electrode. In addition, by covering the side surfaces of the pixel electrode of the light-emitting device 130 with the first layer 135, contact between the first electrode 101 and the second electrode 102 can be suppressed, thereby suppressing short circuits of the light-emitting device 130.

[0197] Furthermore, in a display device according to one aspect of the present invention, it is preferable that the first electrode 101 (pixel electrode) of the light-emitting device be in a stacked configuration. For example, in the example shown in Figure 6(B), the first electrode 101 of the light-emitting device 130 is in a stacked configuration of a conductive layer 151 provided on the insulating layer 171 side and a conductive layer 152 provided on the organic compound layer side.

[0198] For example, a metallic material can be used as 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), and alloys containing these in appropriate combinations can also be used.

[0199] As the conductive layer 152, an oxide having one or more selected from indium, tin, zinc, gallium, titanium, aluminum, and silicon can be used. For example, it is preferable to use a conductive oxide containing one or more of the following: 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, so it can be suitably used as the conductive layer 152.

[0200] The conductive layer 151 may be a laminated structure of multiple layers having different materials, and the conductive layer 152 may be a laminated structure of multiple layers having different materials. In this case, the conductive layer 151 may have a layer made of a material that can be used for the conductive layer 152, such as a conductive oxide, and the conductive layer 152 may have a layer made of a material that can be used for the conductive layer 151, such as a metallic material. For example, if the conductive layer 151 has a laminated structure of two or more layers, the layer in contact with the conductive layer 152 may be a layer made of a material that can be used for the conductive layer 152.

[0201] Furthermore, it is preferable that the end of the conductive layer 151 has a tapered shape. Specifically, it is preferable that the end of the conductive layer 151 has a tapered shape with a taper angle of less than 90°. In this case, the conductive layer 152 provided along the side surface of the conductive layer 151 also has a tapered shape. By making the side surface of the conductive layer 152 tapered, the coverage of the first layer 135 provided along the side surface of the conductive layer 152 can be improved.

[0202] (Embodiment 4) This embodiment describes a display device according to one aspect of the present invention.

[0203] The display device of this embodiment can be a high-definition display device. Therefore, the display device of this embodiment can be used, for example, as a display unit for information terminals (wearable devices) such as wristwatches and bracelets, and as a display unit for wearable devices that can be worn on the head, such as VR (Virtual Reality) devices such as head-mounted displays (HMDs) and AR (Augmented Reality) devices such as glasses.

[0204] Furthermore, the display device of this embodiment can be a high-resolution display device or a large-screen display device. Therefore, the display device of this embodiment can be used in electronic devices with relatively large screens, such as television equipment, desktop or notebook personal computers, computer monitors, digital signage, and large game machines such as pachinko machines, as well as in the display units of digital cameras, digital video cameras, digital photo frames, mobile phones, portable game consoles, personal information terminals, and audio playback devices.

[0205] [Display Module] Figure 7(A) shows a perspective view of the display module 280. The display module 280 includes a display device 100A and an FPC 290. Note that the display device included in the display module 280 is not limited to display device 100A, but may be any of the display devices 100B to 100E described later.

[0206] The display module 280 has substrates 291 and 292. The display module 280 has a display unit 281. The display unit 281 is an area in the display module 280 that displays an image, and is an area in which light from each pixel provided in the pixel unit 284, which will be described later, can be seen.

[0207] Figure 7(B) shows a schematic perspective view illustrating the configuration of the substrate 291. On the substrate 291, a circuit section 282, a pixel circuit section 283 on the circuit section 282, and a pixel section 284 on the pixel circuit section 283 are stacked. In addition, a terminal section 285 for connecting to the FPC 290 is provided in the portion of the substrate 291 that does not overlap with the pixel section 284. The terminal section 285 and the circuit section 282 are electrically connected by a wiring section 286 composed of multiple wires.

[0208] The pixel section 284 has a plurality of pixels 284a arranged periodically. A magnified view of one pixel 284a is shown on the right side of Figure 7(B). Various configurations described in the previous embodiment can be applied to the pixels 284a. Figure 7(B) shows an example where the pixel 284a has the same configuration as the pixel 178 shown in Figure 6.

[0209] The pixel circuit section 283 has a plurality of pixel circuits 283a arranged periodically.

[0210] One pixel circuit 283a is a circuit that controls the driving of multiple elements that a single pixel 284a has.

[0211] The circuit section 282 has circuits for driving each pixel circuit 283a of the pixel circuit section 283. For example, it is preferable to have one or both of a gate line drive circuit and a source line drive circuit. In addition, it may have at least one of the following: an arithmetic circuit, a memory circuit, and a power supply circuit.

[0212] The FPC290 functions as wiring for supplying video signals or power potential, etc., to the circuit section 282 from an external source. An IC (Integrated Circuit) may also be mounted on the FPC290.

[0213] Since the display module 280 can be configured such that one or both of the pixel circuit section 283 and the circuit section 282 are stacked on the lower side of the pixel section 284, the aperture ratio (effective display area ratio) of the display section 281 can be made extremely high.

[0214] Because such a display module 280 is extremely high-resolution, it can be suitably used in VR devices such as HMDs or AR devices such as glasses. For example, even in a configuration where the display part of the display module 280 is viewed through lenses, the display module 280 has an extremely high-resolution display part 281, so even when the display part is magnified with lenses, pixels are not visible, and a highly immersive display can be achieved. Furthermore, the display module 280 is not limited to this and can be suitably used in electronic devices having relatively small display parts.

[0215] [Display device 100A] The display device 100A shown in Figure 8(A) includes a substrate 301, light-emitting devices 130R, 130G, 130B, a capacitor 240, and a transistor 310.

[0216] Substrate 301 corresponds to substrate 291 in Figures 7(A) and 7(B). Transistor 310 is a transistor having a channel formation region in substrate 301. For substrate 301, a semiconductor substrate such as a single-crystal silicon substrate can be used. Transistor 310 has a part of substrate 301, a conductive layer 311, a low-resistance region 312, an insulating layer 313, and an insulating layer 314. The conductive layer 311 functions as a gate electrode. The insulating layer 313 is located between substrate 301 and the conductive layer 311 and functions as a gate insulating layer. The low-resistance region 312 is a region of substrate 301 doped with impurities and functions as a source or drain. The insulating layer 314 is provided covering the side surface of the conductive layer 311.

[0217] Furthermore, an element isolation layer 315 is provided between two adjacent transistors 310 so as to be embedded in the substrate 301.

[0218] Furthermore, an insulating layer 261 is provided covering the transistor 310, and a capacitance 240 is provided on the insulating layer 261.

[0219] The capacitor 240 has a conductive layer 241, a conductive layer 245, and an insulating layer 243 located between them. The conductive layer 241 acts as one electrode of the capacitor 240, the conductive layer 245 acts as the other electrode of the capacitor 240, and the insulating layer 243 acts as the dielectric of the capacitor 240.

[0220] The conductive layer 241 is provided on the insulating layer 261 and embedded in the insulating layer 254. The conductive layer 241 is electrically connected to either the source or drain of the transistor 310 by a plug 271 embedded in the insulating layer 261. The insulating layer 243 is provided covering the conductive layer 241. The conductive layer 245 is provided in the region that overlaps with the conductive layer 241 via the insulating layer 243.

[0221] An insulating layer 255 is provided covering the capacitance 240, an insulating layer 174 is provided on the insulating layer 255, and an insulating layer 175 is provided on the insulating layer 174. Light-emitting devices 130R, 130G, and 130B are provided on the insulating layer 175. An insulator is provided in the region between adjacent light-emitting devices.

[0222] An insulating layer 156R is provided so as to have a region that overlaps with the side surface of the conductive layer 151R, an insulating layer 156G is provided so as to have a region that overlaps with the side surface of the conductive layer 151G, and an insulating layer 156B is provided so as to have a region that overlaps with the side surface of the conductive layer 151B. Furthermore, a conductive layer 152R is provided so as to cover the conductive layer 151R and the insulating layer 156R, a conductive layer 152G is provided so as to cover the conductive layer 151G and the insulating layer 156G, and a conductive layer 152B is provided so as to cover the conductive layer 151B and the insulating layer 156B. A sacrificial layer 158R is located on the first layer 135R, a sacrificial layer 158G is located on the first layer 135G, and a sacrificial layer 158B is located on the first layer 135B.

[0223] The conductive layers 151R, 151G, and 151B are electrically connected to either the source or drain of the transistor 310 by the insulating layers 243, 255, 174, and plugs 256 embedded in the insulating layer 175, the conductive layer 241 embedded in the insulating layer 254, and plugs 271 embedded in the insulating layer 261. Various conductive materials can be used for the plugs.

[0224] Furthermore, a protective layer 131 is provided on the light-emitting devices 130R, 130G, and 130B. A substrate 120 is bonded to the protective layer 131 by a resin layer 122. Details of the components from the light-emitting devices 130 to the substrate 120 can be found in Embodiment 3. The substrate 120 corresponds to the substrate 292 in Figure 7(A).

[0225] Figure 8(B) shows a modified version of the display device 100A shown in Figure 8(A). The display device shown in Figure 8(B) has a colored layer 132R, a colored layer 132G, and a colored layer 132B, and the light-emitting device 130 has a region that overlaps with one of the colored layers 132R, 132G, and 132B. In the display device shown in Figure 8(B), the light-emitting device 130 can emit, for example, white light. Also, for example, the colored layer 132R can transmit red light, the colored layer 132G can transmit green light, and the colored layer 132B can transmit blue light.

[0226] [Display device 100B] Figure 9 shows a perspective view of the display device 100B, and Figure 10 shows a cross-sectional view of the display device 100C.

[0227] The display device 100B has a configuration in which substrate 352 and substrate 351 are bonded together. In Figure 9, substrate 352 is shown with a dashed line.

[0228] The display device 100B includes a pixel portion 177, a connection portion 140, a circuit 356, a wiring 355, etc. FIG. 9 shows an example in which an IC 354 and an FPC 353 are mounted on the display device 100B. Therefore, the configuration shown in FIG. 9 can also be referred to as a display module having the display device 100B, an IC, and an FPC. Here, a display device substrate to which a connector such as an FPC is attached or on which an IC is mounted is called a display module.

[0229] The connection portion 140 is provided outside the pixel portion 177. The connection portion 140 may be singular or plural. The connection portion 140 electrically connects the common electrode of the light-emitting device and the conductive layer and can supply a potential to the common electrode.

[0230] As the circuit 356, for example, a scanning line driving circuit can be used.

[0231] The wiring 355 has a function of supplying signals and power to the pixel portion 177 and the circuit 356. The signals and power are input to the wiring 355 from the outside via the FPC 353 or from the IC 354.

[0232] FIG. 9 shows an example in which an IC 354 is provided on a substrate 351 by a COG (Chip On Glass) method, a COF (Chip On Film) method, or the like. As the IC 354, for example, an IC having a scanning line driving circuit, a signal line driving circuit, or the like can be applied. Note that the display device 100B and the display module may be configured without an IC. Further, the IC may be mounted on the FPC by, for example, a COF method.

[0233] FIG. 10 shows an example of a cross section when a part of the region including the FPC 353, a part of the circuit 356, a part of the pixel portion 177, a part of the connection portion 140, and a part of the region including the end portion of the display device 100C are each cut.

[0234] [Display device 100C] The display device 100C shown in Figure 10 has a transistor 201, a transistor 205, a light-emitting device 130R that emits red light, a light-emitting device 130G that emits green light, and a light-emitting device 130B that emits blue light, etc., between substrates 351 and 352.

[0235] Details of the light-emitting devices 130R, 130G, and 130B can be found in Embodiment 1.

[0236] Light-emitting device 130R has a conductive layer 224R, a conductive layer 151R on the conductive layer 224R, and a conductive layer 152R on the conductive layer 151R. Light-emitting device 130G has a conductive layer 224G, a conductive layer 151G on the conductive layer 224G, and a conductive layer 152G on the conductive layer 151G. Light-emitting device 130B has a conductive layer 224B, a conductive layer 151B on the conductive layer 224B, and a conductive layer 152B on the conductive layer 151B.

[0237] The conductive layer 224R is connected to the conductive layer 222b of the transistor 205 through an opening provided in the insulating layer 214. The edge of the conductive layer 151R is located outside the edge of the conductive layer 224R. The insulating layer 156R is provided so as to have a region in contact with the side surface of the conductive layer 151R, and the conductive layer 152R is provided so as to cover the conductive layer 151R and the insulating layer 156R.

[0238] The conductive layers 224G, 151G, 152G, and insulating layer 156G in the light-emitting device 130G, and the conductive layers 224B, 151B, 152B, and insulating layer 156B in the light-emitting device 130B are the same as the conductive layers 224R, 151R, 152R, and insulating layer 156R in the light-emitting device 130R, so a detailed explanation is omitted.

[0239] The conductive layer 224R, conductive layer 224G, and conductive layer 224B have recesses formed to cover the openings provided in the insulating layer 214. Layer 128 is embedded in these recesses.

[0240] Layer 128 has the function of flattening the recesses of conductive layers 224R, 224G, and 224B. Conductive layers 151R, 151G, and 151B are provided on conductive layers 224R, 224G, and 224B and on layer 128, and are electrically connected to conductive layers 224R, 224G, and 224B. Therefore, regions overlapping with the recesses of conductive layers 224R, 224G, and 224B can also be used as light-emitting regions, thereby increasing the aperture ratio of the pixels.

[0241] Layer 128 may be an insulating layer or a conductive layer. Various inorganic insulating materials, organic insulating materials, and conductive materials can be used for layer 128 as appropriate. In particular, it is preferable that layer 128 be formed using an insulating material, and especially preferable that it be formed using an organic insulating material. For example, an organic insulating material that can be used for the insulating layer 127 described above can be applied to layer 128.

[0242] A protective layer 131 is provided on the light-emitting devices 130R, 130G, and 130B. The protective layer 131 and the substrate 352 are bonded via an adhesive layer 142. A light-shielding layer 157 is provided on the substrate 352. A solid encapsulation structure or a hollow encapsulation structure can be applied to encapsulate the light-emitting devices 130. In Figure 10, the space between the substrate 352 and the substrate 351 is filled with the adhesive layer 142, indicating a solid encapsulation structure. Alternatively, the space may be filled with an inert gas (such as nitrogen or argon), indicating a hollow encapsulation structure. In this case, the adhesive layer 142 may be provided in a frame shape so as not to overlap with the light-emitting devices. Furthermore, the space may be filled with a resin different from the adhesive layer 142 provided in a frame shape.

[0243] Figure 10 shows an example in which the connection portion 140 has a conductive layer 224C obtained by processing the same conductive film as conductive layers 224R, 224G, and 224B; a conductive layer 151C obtained by processing the same conductive film as conductive layers 151R, 151G, and 151B; and a conductive layer 152C obtained by processing the same conductive film as conductive layers 152R, 152G, and 152B. Figure 10 also shows an example in which an insulating layer 156C is provided so as to have a region that overlaps with the side surface of conductive layer 151C.

[0244] The display device 100C is a top-emission type. The light emitted by the light-emitting device is emitted towards the substrate 352. It is preferable to use a material with high transmittance to visible light for the substrate 352. If the light-emitting device emits infrared or near-infrared light, it is preferable to use a material with high transmittance to those. The first electrode (pixel electrode) contains a material that reflects visible light, and the second electrode (counter electrode) contains a material that transmits visible light.

[0245] On the substrate 351, insulating layers 211, 213, 215, and 214 are provided in this order. A portion of insulating layer 211 functions as a gate insulating layer for each transistor. A portion of insulating layer 213 functions as a gate insulating layer for each transistor. Insulating layer 215 is provided covering the transistors. Insulating layer 214 is provided covering the transistors and functions as a planarization layer. The number of gate insulating layers and insulating layers covering the transistors are not limited and may be a single layer or two or more layers, respectively.

[0246] It is preferable to use an inorganic insulating film as the insulating layer 211, insulating layer 213, and insulating layer 215.

[0247] An organic insulating layer is preferred for the insulating layer 214, which functions as a planarizing layer.

[0248] Transistors 201 and 205 each have a conductive layer 221 that functions as a gate, an insulating layer 211 that functions as a gate insulating layer, conductive layers 222a and 222b that function as source and drain, a semiconductor layer 231, an insulating layer 213 that functions as a gate insulating layer, and a conductive layer 223 that functions as a gate.

[0249] A connection portion 204 is provided in the region of substrate 351 where substrate 352 does not overlap. At the connection portion 204, the wiring 355 is electrically connected to the FPC 353 via the conductive layer 166 and the connecting layer 242. The conductive layer 166 is shown as an example of a laminated structure consisting of a conductive film obtained by processing the same conductive film as conductive layers 224R, 224G, and 224B, a conductive film obtained by processing the same conductive film as conductive layers 151R, 151G, and 151B, and a conductive film obtained by processing the same conductive film as conductive layers 152R, 152G, and 152B. On the upper surface of the connection portion 204, the conductive layer 166 is exposed. This allows the connection portion 204 and the FPC 353 to be electrically connected via the connecting layer 242.

[0250] It is preferable to provide a light-shielding layer 157 on the surface of the substrate 352 that faces the substrate 351. The light-shielding layer 157 can be provided between adjacent light-emitting devices, at connection points 140, and in circuits 356, etc. In addition, various optical components can be arranged on the outside of the substrate 352.

[0251] Materials that can be used for substrate 120 can be applied to substrate 351 and substrate 352, respectively.

[0252] As the adhesive layer 142, a material that can be used for the resin layer 122 can be applied.

[0253] As the connecting layer 242, an anisotropic conductive film (ACF) or an anisotropic conductive paste (ACP) can be used.

[0254] [Display device 100D] The display device 100D shown in FIG. 11 is mainly different from the display device 100C shown in FIG. 10 in that it is a bottom emission type display device.

[0255] The light emitted by the light-emitting device is emitted toward the substrate 351 side. It is preferable to use a material with high transmittance for visible light for the substrate 351. On the other hand, the light transmittance of the material used for the substrate 352 is not limited.

[0256] It is preferable to form a light-shielding layer 157 between the substrate 351 and the transistor 201 and between the substrate 351 and the transistor 205. FIG. 11 shows an example in which a light-shielding layer 157 is provided on the substrate 351, an insulating layer 153 is provided on the light-shielding layer 157, and transistors 201, 205, etc. are provided on the insulating layer 153.

[0257] The light-emitting device 130R has a conductive layer 112R, a conductive layer 126R on the conductive layer 112R, and a conductive layer 129R on the conductive layer 126R.

[0258] The light-emitting device 130B has a conductive layer 112B, a conductive layer 126B on the conductive layer 112B, and a conductive layer 129B on the conductive layer 126B.

[0259] For the conductive layers 112R, 112B, 126R, 126B, 129R, and 129B, materials with high transmittance for visible light are used respectively. It is preferable to use a material that reflects visible light for the second electrode.

[0260] In FIG. 11, although the light-emitting device 130G is not shown, the light-emitting device 130G is also provided.

[0261] Also, in FIG. 11 and the like, an example in which the upper surface of the layer 128 has a flat portion is shown, but the shape of the layer 128 is not particularly limited.

[0262] [Display device 100E] The display device 100E shown in Figure 12 is a modified version of the display device 100C shown in Figure 10, and differs from the display device 100C mainly in that it has a colored layer 132R, a colored layer 132G, and a colored layer 132B.

[0263] In the display device 100E, the light-emitting device 130 has a region that overlaps with one of the colored layers 132R, 132G, and 132B. The colored layers 132R, 132G, and 132B can be provided on the substrate 351 side of the substrate 352. The edges of the colored layer 132R, the edges of the colored layer 132G, and the edges of the colored layer 132B can overlap with the light-shielding layer 157.

[0264] In the display device 100E, the light-emitting device 130 can emit, for example, white light. Furthermore, for example, the colored layer 132R can transmit red light, the colored layer 132G can transmit green light, and the colored layer 132B can transmit blue light. The display device 100E may also be configured with the colored layers 132R, 132G, and 132B placed between the protective layer 131 and the adhesive layer 142.

[0265] Figures 10 and 12 show an example where the upper surface of layer 128 has a flat portion, but the shape of layer 128 is not particularly limited.

[0266] This embodiment can be appropriately combined with other embodiments or examples. Furthermore, if multiple configuration examples are shown within a single embodiment in this specification, these configuration examples can be appropriately combined.

[0267] (Embodiment 5) This embodiment describes an electronic device according to one aspect of the present invention.

[0268] The electronic device of this embodiment has a display device according to one aspect of the present invention in its display unit. The display device according to one aspect of the present invention has low power consumption. Therefore, it can be used in the display unit of various electronic devices.

[0269] Examples of electronic devices include television sets, desktop or notebook personal computers, computer monitors, digital signage, large game machines such as pachinko machines, and other electronic devices with relatively large screens, as well as digital cameras, digital video cameras, digital photo frames, mobile phones, portable game consoles, personal digital assistants, and audio playback devices.

[0270] In particular, a display device according to one aspect of the present invention consumes little power and is therefore suitable for use in relatively small electronic devices. Examples of such electronic devices include wristwatch-type and bracelet-type information terminals (wearable devices), as well as wearable devices that can be worn on the head, such as VR devices such as head-mounted displays, AR devices such as glasses, and MR devices.

[0271] The electronic device of this embodiment may have sensors (including those with functions to measure force, displacement, position, velocity, acceleration, angular velocity, rotational speed, distance, light, liquid, magnetism, temperature, chemical substances, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient, vibration, odor, or infrared radiation).

[0272] An example of a wearable device that can be worn on the head is illustrated using Figures 13(A) to 13(D).

[0273] The electronic device 700A shown in Figure 13(A) and the electronic device 700B shown in Figure 13(B) each include a pair of display panels 751, a pair of housings 721, a communication unit (not shown), a pair of mounting units 723, a control unit (not shown), an imaging unit (not shown), a pair of optical members 753, a frame 757, and a pair of nose pads 758.

[0274] A display device according to one aspect of the present invention can be applied to the display panel 751. Therefore, it is possible to create an electronic device that consumes little power and can be operated for a long time.

[0275] Electronic devices 700A and 700B can project an image displayed on the display panel 751 onto the display area 756 of the optical element 753. Because the optical element 753 is translucent, the user can see the image displayed on the display area superimposed on the transmitted image visible through the optical element 753.

[0276] Electronic devices 700A and 700B may be equipped with cameras capable of capturing images of the area in front of them as imaging units. Furthermore, electronic devices 700A and 700B may each be equipped with acceleration sensors such as gyro sensors to detect the orientation of the user's head and display an image corresponding to that orientation in the display area 756.

[0277] The communications unit has a wireless communication device, which can supply, for example, a video signal. Alternatively, instead of the wireless communication device, or in addition to the wireless communication device, it may be equipped with a connector to which a cable for supplying video signals and power potential can be connected.

[0278] Furthermore, electronic devices 700A and 700B are equipped with batteries that can be charged wirelessly, wired, or both.

[0279] The housing 721 may be provided with a touch sensor module.

[0280] Various types of touch sensors can be used in the touch sensor module. For example, various methods such as capacitive, resistive, infrared, electromagnetic induction, surface acoustic wave, or optical sensors can be employed. In particular, it is preferable to apply capacitive or optical sensors to the touch sensor module.

[0281] The electronic device 800A shown in Figure 13(C) and the electronic device 800B shown in Figure 13(D) each include a pair of display units 820, a housing 821, a communication unit 822, a pair of mounting units 823, a control unit 824, a pair of imaging units 825, and a pair of lenses 832.

[0282] A display device according to one aspect of the present invention can be applied to the display unit 820. Therefore, it is possible to create an electronic device that consumes little power and can be operated for a long time.

[0283] The display unit 820 is located inside the housing 821, in a position where it can be seen through the lens 832. Furthermore, by displaying different images on a pair of display units 820, a three-dimensional display using parallax can also be performed.

[0284] Preferably, electronic devices 800A and 800B have a mechanism that allows the left and right positions of the lens 832 and the display unit 820 to be in an optimal position according to the user's eye position.

[0285] The attachment part 823 allows the user to attach the electronic device 800A or the electronic device 800B to their head.

[0286] The imaging unit 825 has the function of acquiring external information. The data acquired by the imaging unit 825 can be output to the display unit 820. An image sensor can be used in the imaging unit 825. In addition, multiple cameras may be provided to accommodate multiple angles of view, such as telephoto and wide-angle.

[0287] The electronic device 800A may have a vibration mechanism that functions as a bone conduction earphone.

[0288] Electronic devices 800A and 800B may each have input terminals. Cables can be connected to the input terminals to supply video signals from video output devices, etc., and power for charging batteries provided within the electronic devices.

[0289] An electronic device according to one aspect of the present invention may have a function for wireless communication with an earphone 750.

[0290] Furthermore, the electronic device may have an earphone section. The electronic device 700B shown in Figure 13(B) has an earphone section 727. Some of the wiring connecting the earphone section 727 and the control unit may be located inside the housing 721 or the mounting section 723.

[0291] Similarly, the electronic device 800B shown in Figure 13(D) has an earphone unit 827. For example, the earphone unit 827 and the control unit 824 can be connected to each other by a wire.

[0292] Thus, as one embodiment of the present invention, both eyeglass-type (electronic devices 700A and 700B, etc.) and goggle-type (electronic devices 800A and 800B, etc.) are preferred as electronic devices.

[0293] The electronic device 6500 shown in Figure 14(A) is a portable information terminal that can be used as a smartphone.

[0294] The electronic device 6500 includes a housing 6501, a display unit 6502, a power button 6503, a button 6504, a speaker 6505, a microphone 6506, a camera 6507, and a light source 6508, etc. The display unit 6502 has a touch panel function.

[0295] A display device according to one embodiment of the present invention can be applied to the display unit 6502. Therefore, an electronic device with low power consumption and long operating time can be made.

[0296] Figure 14(B) is a schematic cross-sectional view of the housing 6501 including the end on the microphone 6506 side.

[0297] A light-transmitting protective member 6510 is provided on the display side of the housing 6501, and the display panel 6511, optical member 6512, touch sensor panel 6513, printed circuit board 6517, and battery 6518 are arranged in the space enclosed by the housing 6501 and the protective member 6510.

[0298] The protective member 6510 is fixed to the display panel 6511, the optical member 6512, and the touch sensor panel 6513 by an adhesive layer (not shown).

[0299] In the area outside the display unit 6502, a portion of the display panel 6511 is folded back, and the FPC 6515 is connected to this folded portion. IC 6516 is mounted on the FPC 6515. The FPC 6515 is connected to terminals provided on the printed circuit board 6517.

[0300] A display device according to one embodiment of the present invention can be applied to the display panel 6511. This makes it possible to realize an extremely lightweight electronic device. Furthermore, because the display panel 6511 is extremely thin, it is possible to incorporate a large-capacity battery 6518 while keeping the thickness of the electronic device low. In addition, by folding back a part of the display panel 6511 and placing the connection part with the FPC 6515 on the back of the pixel section, an electronic device with a narrow bezel can be realized.

[0301] Figure 14(C) shows an example of a television system. The television system 7100 has a display unit 7000 incorporated into a housing 7171. Here, the housing 7171 is shown supported by a stand 7173.

[0302] A display device according to one aspect of the present invention can be applied to the display unit 7000. Therefore, an electronic device with low power consumption and long operating time can be obtained.

[0303] The television device 7100 shown in Figure 14(C) can be operated using the operation switches on the housing 7171 and a separate remote control unit 7151.

[0304] Figure 14(D) shows an example of a notebook personal computer. The notebook personal computer 7200 has a casing 7211, a keyboard 7212, a pointing device 7213, and an external connection port 7214, etc. A display unit 7000 is incorporated into the casing 7211.

[0305] A display device according to one aspect of the present invention can be applied to the display unit 7000. Therefore, an electronic device with low power consumption and long operating time can be obtained.

[0306] Figures 14(E) and 14(F) show examples of digital signage.

[0307] The digital signage 7300 shown in Figure 14(E) comprises a housing 7301, a display unit 7000, and a speaker 7303, etc. Furthermore, it may have LED lamps, operation keys (including a power switch or operation switch), connection terminals, various sensors, a microphone, etc.

[0308] Figure 14(F) shows a digital signage 7400 mounted on a cylindrical column 7401. The digital signage 7400 has a display unit 7000 that is provided along the curved surface of the column 7401.

[0309] In Figures 14(E) and 14(F), a display device according to one embodiment of the present invention can be applied to the display unit 7000. Therefore, a highly reliable electronic device can be made.

[0310] The larger the display area 7000, the more information can be provided at once. Furthermore, a larger display area 7000 is more eye-catching, which can, for example, enhance the effectiveness of advertising.

[0311] Furthermore, as shown in Figures 14(E) and 14(F), it is preferable that the digital signage 7300 or digital signage 7400 can be linked wirelessly with an information terminal device 7311 or information terminal device 7411 such as a smartphone owned by the user.

[0312] The electronic equipment shown in Figures 15(A) to 15(G) includes a housing 9000, a display unit 9001, a speaker 9003, operation keys 9005 (including a power switch or operation switch), connection terminals 9006, sensors 9007 (including functions for measuring force, displacement, position, velocity, acceleration, angular velocity, rotational speed, distance, light, liquid, magnetism, temperature, chemical substances, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient, vibration, odor, or infrared radiation), a microphone 9008, etc.

[0313] The electronic devices shown in Figures 15(A) to 15(G) have various functions. For example, they may have functions to display various information (still images, videos, text images, etc.) on a display unit, touch panel functions, functions to display a calendar, date or time, functions to control processing by various software (programs), wireless communication functions, functions to read and process programs or data recorded on a recording medium, etc.

[0314] Details of the electronic equipment shown in Figures 15(A) to 15(G) will be explained below.

[0315] Figure 15(A) is a perspective view showing a personal digital assistant (PDA) 9171. The PDA 9171 can be used, for example, as a smartphone. The PDA 9171 may also be equipped with a speaker 9003, a connection terminal 9006, or a sensor 9007. The PDA 9171 can also display text and image information on multiple surfaces. Figure 15(A) shows an example where three icons 9050 are displayed. Information 9051, indicated by a dashed rectangle, can also be displayed on other surfaces of the display unit 9001. Examples of information 9051 include notifications of incoming emails, SNS messages, phone calls, etc., the subject of the email or SNS message, the sender's name, date and time, time, battery level, signal strength, etc. Alternatively, icons 9050, etc., may be displayed in the position where the information 9051 is displayed.

[0316] Figure 15(B) is a perspective view showing the personal digital assistant (PDA) 9172. The PDA 9172 has the function of displaying information on three or more sides of the display unit 9001. Here, an example is shown in which information 9052, information 9053, and information 9054 are displayed on different sides. For example, a user can check information 9053, which is displayed in a position that can be observed from above the PDA 9172, while the PDA 9172 is stored in the breast pocket of their clothing.

[0317] Figure 15(C) is a perspective view showing the tablet terminal 9173. The tablet terminal 9173 can run various applications, such as mobile phone calls, email, document viewing and creation, music playback, internet communication, and computer games. The tablet terminal 9173 has a display unit 9001, a camera 9002, a microphone 9008, and a speaker 9003 on the front of the housing 9000. Operation keys 9005 are located on the left side of the housing 9000, and connection terminals 9006 are located on the bottom.

[0318] Figure 15(D) is a perspective view showing a wristwatch-type personal information terminal 9200. The personal information terminal 9200 can be used, for example, as a smartwatch (registered trademark). The display unit 9001 has a curved display surface, allowing it to display information along the curved surface. The personal information terminal 9200 can also make hands-free calls by communicating with, for example, a wireless communication headset. Furthermore, the personal information terminal 9200 can transmit data to other information terminals and be charged via the connection terminal 9006. Charging may be performed by wireless power supply.

[0319] Figures 15(E) to 15(G) are perspective views showing a foldable personal information terminal 9201. Figure 15(E) shows the personal information terminal 9201 in an unfolded state, Figure 15(G) shows it in a folded state, and Figure 15(F) shows a state in between, transitioning from one of Figures 15(E) or 15(G) to the other. The personal information terminal 9201 offers excellent portability in its folded state and excellent readability of the display due to its seamless, wide display area in its unfolded state. The display unit 9001 of the personal information terminal 9201 is supported by three housings 9000 connected by hinges 9055. For example, the display unit 9001 can be bent with a radius of curvature of 0.1 mm to 150 mm.

[0320] This embodiment can be appropriately combined with other embodiments or examples. Furthermore, if multiple configuration examples are shown within a single embodiment in this specification, these configuration examples can be appropriately combined. [Examples]

[0321] In this example, the detailed manufacturing methods and characteristics of light-emitting devices 1-1, 1-2, and 1-3 will be described. The structural formulas of the main compounds used in this example are shown below.

[0322] [ka]

[0323] (Method for fabricating light-emitting device 1-1) First, indium tin oxide (ITSO) containing silicon oxide was layered onto a glass substrate by sputtering to a thickness of 55 nm, forming a first electrode 101 measuring 2 mm x 2 mm. The ITSO functions as an anode.

[0324] Next, as a pretreatment for forming a light-emitting device on the substrate, the substrate surface was washed with water.

[0325] After that, approximately 1 × 10 -4The substrate was introduced into a vacuum deposition apparatus where the internal pressure was reduced to Pa. After vacuum firing at 170°C for 30 minutes in the heating chamber of the vacuum deposition apparatus, the substrate was allowed to cool for approximately 30 minutes.

[0326] Next, the substrate was fixed to a holder provided in a vacuum deposition apparatus so that the surface on which the first electrode 101 was formed was facing downwards. A hole injection layer 111 was then formed by co-depositing N-(biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviated as PCBBiF), represented by the above structural formula (i), and an electron acceptor material (OCHD-003) with a molecular weight of 672 and containing fluorine, on the inorganic insulating film and the first electrode 101 in a weight ratio of 1:0.03 (=PCBBiF:OCHD-003) and with a film thickness of 10 nm.

[0327] After depositing PCBBiF onto the hole injection layer 111 to a thickness of 45 nm, a hole transport layer 112 was formed by depositing 9-[3-(triphenylsilyl)phenyl]-3,9′-bi-9H-carbazole (abbreviated as PSiCzCz), represented by the above structural formula (ii), to a thickness of 5 nm. PSiCzCz is an organic compound having a π-electron-rich heteroaromatic ring, and the PSiCzCz layer also functions as an electron blocking layer.

[0328] Next, on the hole transport layer, 9,9'-{6-[3-(triphenylsilyl)phenyl]-1,3,5-triazine-2,4-diyl}bis(9H-carbazole) (abbreviated as SiTrzCz2), represented by the above structural formula (iii), PSiCzCz, and (2-{3-[3-(3,5-di-tert-butylphenyl)benzimidazole-1-yl-2- A light-emitting layer 113 was formed by co-depositing ilidene-κC2]phenoxy-κC2}-9-(4-tert-butyl-2-pyridinyl-κN)carbazole-2,1-diyl-κC1)platinum(II) (abbreviated as PtON-TBBI) in a weight ratio of 0.35:0.53:0.12 (=SiTrzCz2:PSiCzCz:PtON-TBBI) and a film thickness of 40 nm. PtON-TBBI is an organometallic complex that exhibits blue phosphorescence. SiTrzCz2 is an organic compound having a π-electron-deficient heteroaromatic ring, and PSiCzCz is an organic compound having a π-electron-rich heteroaromatic ring.

[0329] Subsequently, 2-phenyl-4,6-bis[3-(triphenylsilyl)phenyl]-1,3,5-triazine (abbreviated as mSiTrz), represented by the above structural formula (v), was deposited to a thickness of 5 nm to form a first electron transport layer. Then, 2-{4-[9,10-di(2-naphthyl)-2-anthryl]phenyl}-1-phenyl-1H-benzimidazole (abbreviated as ZADN), represented by the above structural formula (vi), and PtON-TBBI were co-deposited in a weight ratio of 0.9:0.1 (=ZADN:PtON-TBBI) to a thickness of 30 nm to form a second electron transport layer. Note that mSiTrz and ZADN are organic compounds having π-electron-deficient heteroaromatic rings, and the first electron transport layer also functions as a hole blocking layer.

[0330] After the electron transport layer was formed, lithium fluoride (abbreviated as LiF) was deposited to a thickness of 1 nm to form an electron injection layer 115, and then aluminum (abbreviated as Al) was deposited to a thickness of 200 nm to form a second electrode 102 (cathode).

[0331] Next, in a glove box under a nitrogen atmosphere, the light-emitting device was sealed with a glass substrate to prevent exposure to the atmosphere (applying a UV-curable sealant around the element, irradiating only the sealant with UV light without irradiating the light-emitting device, and heat-treating at 80°C for 1 hour under atmospheric pressure) to form light-emitting device 1-1.

[0332] (Method for fabricating light-emitting devices 1-2) Light-emitting device 1-2 was fabricated in the same manner as light-emitting device 1-1, except that ZADN used in the second electron transport layer of light-emitting device 1-1 was replaced with 11-[4-(biphenyl-4-yl)-6-phenyl-1,3,5-triazine-2-yl]-11,12-dihydro-12-phenylindoro[2,3-a]carbazole (abbreviated as BP-Icz(II)Tzn), represented by the above structural formula (vii). BP-Icz(II)Tzn is an organic compound having a π-electron-deficient heteroaromatic ring.

[0333] (Method for fabricating light-emitting devices 1-3) Light-emitting device 1-3 was fabricated in the same manner as light-emitting device 1-1, except that ZADN used in the second electron transport layer of light-emitting device 1-1 was replaced with mSiTrz.

[0334] The device structures of light-emitting devices 1-1, 1-2, and 1-3 are shown in the table below.

[0335] [Table 3]

[0336] Figure 16 shows the luminance-current density characteristics, Figure 17 shows the luminance-voltage characteristics, Figure 18 shows the current efficiency-current density characteristics, Figure 19 shows the current density-voltage characteristics, Figure 20 shows the blue index-current density characteristics, Figure 21 shows the external quantum efficiency-current density characteristics, Figure 22 shows the field emission spectrum, and Figure 23 shows the chromaticity diagram for light-emitting devices 1-1, 1-2, and 1-3. 2Table 4 shows the main characteristics of the device. A spectroradiometer (Topcon SR-UL1R) was used to measure luminance, CIE chromaticity, and field emission spectrum at room temperature. The external quantum efficiency was calculated using the measured luminance and emission spectrum, assuming a Lambertsian optical distribution pattern.

[0337] [Table 4]

[0338] Thus, it was found that light-emitting devices 1-1 and 1-2 are light-emitting devices with low driving voltage and high power efficiency.

[0339] Furthermore, light-emitting devices 1-1, 1-2, and 1-3 are set to 10 mA / cm². 2 Figures 24 and 25 show the time-varying characteristics of normalized brightness and voltage when driven at the specified current density. The time-varying characteristics of normalized brightness are shown with the initial brightness set to 100%, while the time-varying characteristics of voltage show the change in voltage from the initial voltage.

[0340] Figures 24 and 25 show that light-emitting devices 1-1 and 1-2 are reliable light-emitting devices with small decreases in brightness and voltage increases over time.

[0341] Figure 44 shows the emission spectra (PL spectra) of single films of SiTrzCz2 and PSiCzCz, and the emission spectra (PL spectra) of a mixed film with a weight ratio of 1:1. The samples were deposited onto a quartz substrate to a thickness of 50 nm, and measurements were taken at room temperature. A fluorometer (JASCO FP-8600) was used. The excitation light wavelengths were 330 nm (SiTrzCz2 single film), 310 nm (PSiCzCz single film), and 355 nm (SiTrzCz2 and PSiCzCz mixed film). As shown in Figure 44, compared to the emission spectra of each single film, the emission spectrum of the mixed film is located at longer wavelengths, indicating that SiTrzCz2 and PSiCzCz form an excited complex in the mixed film. In other words, SiTrzCz2 and PSiCzCz are a combination that forms an excited complex.

[0342] Table 5 also shows the GSP_Slope of the organic compounds having a π-electron-rich heteroaromatic ring or aromatic amine used in the hole transport layers of light-emitting devices 1-1, 1-2, and 1-3, the organic compound having a π-electron-deficient heteroaromatic ring used in the first electron transport layer, the organic compound having a π-electron-deficient heteroaromatic ring used in the second electron transport layer, and the deposited film of the host material used in the light-emitting layer. Table 5 also shows the GSP_Slope of the film formed by co-depositing SiTrzCz2, PSiCzCz, and PtON-TBBI, which constitute the composition of the light-emitting layer, in a weight ratio of 0.45:0.45:0.10 (=SiTrzCz2:PSiCzCz:PtON-TBBI). Note that in Table 5, the GSP_Slope was measured by the method shown in Embodiment 1.

[0343] [Table 5]

[0344] Thus, in light-emitting devices 1-1 and 1-2, the GSP_Slope of the film of the organic compound having a π-electron-deficient heteroaromatic ring contained in the second electron transport layer is larger than the GSP_Slope of the film of the organic compound having a π-electron-deficient heteroaromatic ring contained in the first electron transport layer. In light-emitting device 1-3, the GSP_Slope of the film of the organic compound having a π-electron-deficient heteroaromatic ring contained in the second electron transport layer is the same as the GSP_Slope of the film of the organic compound having a π-electron-deficient heteroaromatic ring contained in the first electron transport layer.

[0345] Therefore, in light-emitting devices 1-1 and 1-2, a negative interfacial charge originating from the difference in GSP_Slope is placed at the interface between the first electron transport layer and the second electron transport layer. This effect suppresses the injection of electrons from the second electrode or electron injection layer into the second electron transport layer. As a result, the recombination region, which tends to be biased towards the anode side in the light-emitting layer of typical blue phosphorescent devices, can be expanded, and the degradation of the hole transport layer, which functions as an electron blocking layer, can be reduced. Consequently, the reliability of light-emitting devices 1-1 and 1-2 was improved.

[0346] In the above-described light-emitting device, the GSP_Slope of the host material (SiTrzCz2 and PSiCzCz) film is greater than the GSP_Slope of the first organic compound (mSiTrz) film. Furthermore, the GSP_Slope of the light-emitting layer is greater than the GSP_Slope of the first electron transport layer.

[0347] This configuration allows for smooth electron injection from the second electron transport layer to the first electron transport layer in the light-emitting device. Therefore, in light-emitting devices 1-1 and 1-2, even if electron injection from the second electrode or electron injection layer to the second electron transport layer is suppressed, a significant increase in the driving voltage is not caused, making it possible to produce light-emitting devices with good characteristics.

[0348] Furthermore, ZADN and BP-Icz(II)Tzn, which are organic compounds having a π-electron-deficient heteroaromatic ring contained in the second electron transport layer of light-emitting devices 1-1 and 1-2, have a larger GSP_Slope than the host materials (SiTrzCz2 and PSiCzCz). Also, the GSP_Slope of the second electron transport layer is larger than the GSP_Slope of the light-emitting layer.

[0349] As a result, in light-emitting devices 1-1 and 1-2, the interface charge between the first electron transport layer and the second electron transport layer is negative and smaller than the interface charge between the light-emitting layer and the first electron transport layer. This effect suppresses the injection of electrons from the second electrode or electron injection layer into the second electron transport layer, and promotes the injection of holes into the light-emitting layer. Consequently, the recombination region, which tends to be biased towards the anode side in the light-emitting layer of typical blue phosphorescent devices, can be expanded, and the degradation of the hole transport layer, which functions as an electron blocking layer, can be further reduced.

[0350] Furthermore, the above-mentioned light-emitting device has a configuration in which the GSP_Slope of the light-emitting layer (co-evaporated film of SiTrzCz2, PSiCzCz, and PtON-TBBI) is larger than the GSP_Slope of the hole transport layer (evaporated film of PSiCzCz). This facilitates the injection of holes from the hole injection layer to the hole transport layer, making it possible to create a light-emitting device with a low driving voltage.

[0351] Thus, a light-emitting device according to one aspect of the present invention can be a light-emitting device with high reliability, low driving voltage, and good characteristics. [Examples]

[0352] In this example, the detailed manufacturing methods and characteristics of light-emitting devices 2-1a, 2-1b, 2-2a, and 2-2b according to one embodiment of the present invention, and comparative light-emitting devices 2-1, 2-2a, and 2-2b of comparative examples will be described. The structural formulas of the main compounds used in this example are shown below.

[0353] [ka]

[0354] (Method for fabricating light-emitting device 2-1a) First, indium tin oxide (ITSO) containing silicon dioxide was layered onto a glass substrate by sputtering to a thickness of 55 nm, forming a first electrode 101 measuring 2 mm x 2 mm. The ITSO functions as an anode.

[0355] Next, as a pretreatment for forming a light-emitting device on the substrate, the substrate surface was washed with water.

[0356] After that, approximately 1 × 10 -4 The substrate was introduced into a vacuum deposition apparatus where the internal pressure was reduced to Pa. After vacuum firing at 170°C for 30 minutes in the heating chamber of the vacuum deposition apparatus, the substrate was allowed to cool for approximately 30 minutes.

[0357] Next, the substrate was fixed to a holder provided in a vacuum deposition apparatus so that the surface on which the first electrode 101 was formed was facing downwards. A hole injection layer 111 was then formed by co-depositing N-(biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviated as PCBBiF), represented by the above structural formula (i), and an electron acceptor material (OCHD-003) with a molecular weight of 672 and containing fluorine, on the inorganic insulating film and the first electrode 101 in a weight ratio of 1:0.03 (=PCBBiF:OCHD-003) and with a film thickness of 10 nm.

[0358] After depositing PCBBiF onto the hole injection layer 111 to a thickness of 45 nm, a hole transport layer 112 was formed by depositing 9-[3-(triphenylsilyl)phenyl]-3,9′-bi-9H-carbazole (abbreviated as PSiCzCz), represented by the above structural formula (ii), to a thickness of 5 nm. PSiCzCz is an organic compound having a π-electron-rich heteroaromatic ring, and the PSiCzCz layer also functions as an electron blocking layer.

[0359] Next, on the hole transport layer 112, 9,9'-{6-[3-(triphenylsilyl)phenyl]-1,3,5-triazine-2,4-diyl}bis(9H-carbazole) (abbreviation: SiTrzCz2) represented by the above structural formula (iii), PSiCzCz, and (2-{3-[3-(3,5-di-tert-butylphenyl)benzimidazole-1-yl-2) represented by the above structural formula (iv) A light-emitting layer 113 was formed by co-depositing -ylidene-κC2]phenoxy-κC2}-9-(4-tert-butyl-2-pyridinyl-κN)carbazole-2,1-diyl-κC1)platinum(II) (abbreviated as PtON-TBBI) in a weight ratio of 0.35:0.53:0.12 (=SiTrzCz2:PSiCzCz:PtON-TBBI) and a film thickness of 40 nm. PtON-TBBI is an organometallic complex that exhibits blue phosphorescence (peak wavelength of emission spectrum is between 450 nm and 520 nm). SiTrzCz2 is an organic compound having a π-electron-deficient heteroaromatic ring, and PSiCzCz is an organic compound having a π-electron-rich heteroaromatic ring.

[0360] Subsequently, 2-phenyl-4,6-bis[3-(triphenylsilyl)phenyl]-1,3,5-triazine (abbreviated as mSiTrz), represented by the above structural formula (v), was deposited to a thickness of 5 nm to form a first electron transport layer. Then, 2-{4-[9,10-di(2-naphthyl)-2-anthryl]phenyl}-1-phenyl-1H-benzimidazole (abbreviated as ZADN), represented by the above structural formula (vi), and 8-quinolinolato-lithium (abbreviated as Liq), represented by the above structural formula (viii), were co-deposited in a weight ratio of 1:1 and to a thickness of 30 nm to form a second electron transport layer. Note that mSiTrz and ZADN are organic compounds having a π-electron-deficient heteroaromatic ring, and Liq is an organometallic complex containing an alkali metal. The first electron transport layer also functions as a hole blocking layer.

[0361] After the electron transport layer was formed, lithium fluoride (abbreviated as LiF) was deposited to a thickness of 1 nm to form an electron injection layer 115, and then aluminum (abbreviated as Al) was deposited to a thickness of 200 nm to form a second electrode 102 (cathode).

[0362] Next, in a glove box under a nitrogen atmosphere, the light-emitting device was sealed with a glass substrate to prevent exposure to the atmosphere (applying a UV-curable sealant around the element, irradiating only the sealant with UV light without irradiating the light-emitting device, and heat-treating at 80°C for 1 hour under atmospheric pressure) to form the light-emitting device 2-1a.

[0363] (Method for fabricating light-emitting device 2-1b) Light-emitting device 2-1b was fabricated in the same manner as light-emitting device 2-1a, except that the second electron transport layer was co-deposited with ZADN and Liq in a ratio of 1:4 (=ZADN:Liq).

[0364] (Method for fabricating light-emitting device 2-2a) Light-emitting device 2-2a was fabricated in the same manner as light-emitting device 2-1a, except that the ZADN in the second electron transport layer was replaced with 11-[4-(biphenyl-4-yl)-6-phenyl-1,3,5-triazine-2-yl]-11,12-dihydro-12-phenylindoro[2,3-a]carbazole (abbreviated as BP-Icz(II)Tzn), represented by the above structural formula (vii). BP-Icz(II)Tzn is an organic compound having a π-electron-deficient heteroaromatic ring.

[0365] (Method for fabricating light-emitting device 2-2b) Light-emitting device 2-2b was fabricated in the same manner as light-emitting device 2-1b, except that the ZADN in the second electron transport layer was replaced with BP-Icz(II)Tzn.

[0366] (Method for fabricating comparative light-emitting device 2-1) Comparative light-emitting device 2-1 was fabricated in the same manner as light-emitting device 2-1a, except that the second electron transport layer was formed of 2,2'-(1,3-phenylene)bis(9-phenyl-1,10-phenanthroline) (abbreviated as mPPhen2P) represented by the above structural formula (ix).

[0367] (Method for fabricating comparative light-emitting device 2-2a) Comparative light-emitting device 2-2a was fabricated in the same manner as light-emitting device 2-1a, except that ZADN used in the second electron transport layer of light-emitting device 2-1a was replaced with mSiTrz.

[0368] (Method for fabricating comparative light-emitting device 2-2b) Comparative light-emitting device 2-2b was fabricated in the same manner as light-emitting device 2-1b, except that the ZADN used in the second electron transport layer of light-emitting device 2-1b was replaced with mSiTrz.

[0369] The device structures of light-emitting devices 2-1a, 2-1b, 2-2a, and 2-2b, and comparative light-emitting devices 2-1, 2-2a, and 2-2b are shown in the table below.

[0370] [Table 6]

[0371] [Table 7]

[0372] Figure 26 shows the luminance-current density characteristics, Figure 27 shows the luminance-voltage characteristics, Figure 28 shows the current efficiency-current density characteristics, Figure 29 shows the current density-voltage characteristics, Figure 30 shows the blue index-current density characteristics, Figure 31 shows the external quantum efficiency-current density characteristics, and Figure 32 shows the field emission spectra for light-emitting devices 2-1a, 2-1b, 2-2a, and 2-2b, as well as comparative light-emitting devices 2-1, 2-2a, and 2-2b. 2 Table 8 shows the main characteristics of the device. Luminance, CIE chromaticity, and field emission spectrum were measured using a spectroradiometer (Topcon SR-UL1R) at room temperature. External quantum efficiency was calculated using the measured luminance and emission spectrum, assuming a Lambertsian optical distribution pattern.

[0373] [Table 8]

[0374] Thus, it was found that light-emitting devices 2-1a, 2-1b, 2-2a, and 2-2b, as well as comparative light-emitting devices 2-1, 2-2a, and 2-2b, all exhibit good characteristics.

[0375] Furthermore, the light-emitting devices 2-1a, 2-1b, 2-2a, and 2-2b, along with the comparative light-emitting devices 2-1, 2-2a, and 2-2b, are set to 10mA / cm². 2 Figure 33 shows the time-dependent characteristics of the normalized brightness when driven at the specified current density. Note that the time-dependent characteristics of the normalized brightness are shown with the initial brightness set to 100%.

[0376] Figure 33 shows that light-emitting devices 2-1a, 2-1b, 2-2a, and 2-2b exhibit less brightness degradation with respect to operating time compared to comparative light-emitting devices 2-1, 2-2a, and 2-2b, indicating they are reliable light-emitting devices.

[0377] Figure 44 shows the emission spectra (PL spectra) of single films of SiTrzCz2 and PSiCzCz, and the emission spectra (PL spectra) of a mixed film with a weight ratio of 1:1. The samples were deposited onto a quartz substrate to a thickness of 50 nm, and measurements were taken at room temperature. A fluorometer (JASCO FP-8600) was used. The excitation light wavelengths were 330 nm (SiTrzCz2 single film), 310 nm (PSiCzCz single film), and 355 nm (SiTrzCz2 and PSiCzCz mixed film). As shown in Figure 44, compared to the emission spectra of each single film, the emission spectrum of the mixed film is located at longer wavelengths, indicating that SiTrzCz2 and PSiCzCz form an excited complex in the mixed film. In other words, SiTrzCz2 and PSiCzCz are a combination that forms an excited complex.

[0378] Table 9 shows the GSP_Slope of the vapor-deposited films of the organic compounds having π-electron-deficient heteroaromatic rings used in the first electron transport layer and the organic compounds having π-electron-deficient heteroaromatic rings used in the second electron transport layer of light-emitting devices 2-1a, 2-1b, 2-2a, and 2-2b, as well as the organic compounds having π-electron-deficient heteroaromatic rings used in the hole transport layer, the organic compounds having π-electron-rich heteroaromatic rings or aromatic amines used in the hole transport layer, and the host material used in the light-emitting layer. Table 9 also shows the GSP_Slope of films formed by co-depositing SiTrzCz2, PSiCzCz, and PtON-TBBI, which constitute the light-emitting layer, in a weight ratio of 0.45:0.45:0.10 (=SiTrzCz2:PSiCzCz:PtON-TBBI). In Table 9, GSP_Slope was measured using the method described in Embodiment 1.

[0379] [Table 9]

[0380] Thus, the light-emitting devices 2-1a, 2-1b, 2-2a, and 2-2b have a configuration in which the GSP_Slope of the film of the organic compound having a π-electron-deficient heteroaromatic ring contained in the second electron transport layer is larger than the GSP_Slope of the film of the organic compound having a π-electron-deficient heteroaromatic ring contained in the first electron transport layer.

[0381] On the other hand, in comparative light-emitting device 2-1, the GSP_Slope of the film of the organic compound having a π-electron-deficient heteroaromatic ring contained in the second electron transport layer is lower than the GSP_Slope of the film of the organic compound having a π-electron-deficient heteroaromatic ring contained in the first electron transport layer. In comparative light-emitting devices 2-2a and 2-2b, the GSP_Slope of the film of the organic compound having a π-electron-deficient heteroaromatic ring contained in the second electron transport layer is the same as the GSP_Slope of the film of the organic compound having a π-electron-deficient heteroaromatic ring contained in the first electron transport layer.

[0382] Here, to investigate the carrier injection behavior of a light-emitting device according to one aspect of the present invention (light-emitting device 2) and a comparative light-emitting device (comparative light-emitting device 2), the results of measuring the capacitance-voltage characteristics are shown. Light-emitting device 2 is a light-emitting device having the same configuration as light-emitting device 2-2b, and comparative light-emitting device 2 is a light-emitting device having the same configuration as comparative light-emitting device 2-1a. A potentiometer / galvanostat (SP-300, manufactured by Biologic, France) was used to measure the capacitance-voltage characteristics at a frequency of 10 Hz at room temperature.

[0383] The measurement results for comparative light-emitting device 2 are shown in Figure 34(B). Figure 34(B) shows that electrons began to be injected from the electron injection layer to the second electron transport layer at around -7.0V, and from the second electron transport layer to the first electron transport layer at around -3.0V.

[0384] Figure 34(A) shows the measurement results for light-emitting device 2. Figure 34(A) shows that electrons began to be injected from the electron injection layer to the second electron transport layer at around -1.0V, and from the second electron transport layer to the first electron transport layer at around 0V.

[0385] These results show that electron injection is suppressed in the light-emitting device according to one embodiment of the present invention.

[0386] Thus, in light-emitting devices 2-1a, 2-1b, 2-2a, and 2-2b, electron injection into the second electron transport layer is further suppressed. In the light-emitting layer of a typical blue phosphorescent device, since both the HOMO and LUMO levels of the blue phosphorescent material are higher than those of the host material, the recombination region tends to be biased towards the anode side because it traps holes instead of electrons. In a light-emitting device according to one aspect of the present invention, the above configuration suppresses electron injection into the second electron transport layer, thereby broadening the recombination region which tends to be biased towards the anode side, and reducing the degradation of the hole transport layer which functions as an electron blocking layer. As a result, the reliability of light-emitting devices 2-1a, 2-1b, 2-2a, and 2-2b is improved. In this embodiment, the HOMO level of PSiCzCz used as the host material for the luminescent layer is -5.7eV and the LUMO level is -2.06eV. The HOMO level of SiTrzCz2 is lower than that of PSiCzCz, with a LUMO level of -2.98eV. The HOMO level of PtON-TBBI, a blue phosphorescent material, is -5.50eV and the LUMO level is -2.3eV. As described above, the configuration traps holes without trapping electrons.

[0387] The HOMO and LUMO levels were determined by cyclic voltammetry (CV) measurements.

[0388] In cyclic voltammetry (CV) measurements, the HOMO and LUMO levels (E) were calculated based on the oxidation peak potential (Epa) and reduction peak potential (Epc) obtained by changing the potential of the working electrode relative to the reference electrode. The HOMO level was determined from the positive potential scan, and the LUMO level from the negative potential scan. The scan speed was set to 0.1 V / s.

[0389] Specifically, the standard redox potential (Eo) (=(Epa+Epc) / 2) was determined from the oxidation peak potential (Epa) and reduction peak potential (Epc) obtained from the cyclic voltammogram of the material. The values ​​of the HOMO and LUMO levels (E) (=Ex-Eo) were then determined by subtracting this from the potential energy (Ex) of the reference electrode relative to the vacuum level.

[0390] The above describes the case where a reversible redox wave is obtained. However, when an irreversible redox wave is obtained, the HOMO level is calculated by assuming that the reduction peak potential (Epc) is obtained by subtracting a certain value (0.1 eV) from the oxidation peak potential (Epa), and the standard redox potential (Eo) is calculated to one decimal place. Similarly, the LUMO level is calculated by assuming that the oxidation peak potential (Epa) is obtained by adding a certain value (0.1 eV) to the reduction peak potential (Epc), and the standard redox potential (Eo) is calculated to one decimal place.

[0391] Furthermore, in light-emitting devices 2-1a, 2-1b, 2-2a, and 2-2b, and comparative light-emitting devices 2-2a and 2-2b, the second electron transport layer contains Liq, a metal complex containing an alkali metal, in addition to the organic compound having a π-electron-deficient heteroaromatic ring. When the weight ratio of the organic compound having a π-electron-deficient heteroaromatic ring to Liq in the second electron transport layer is x:y, the GSP_Slope of the film of the organic compound having a π-electron-deficient heteroaromatic ring contained in the first electron transport layer multiplied by (x+y) / x is 20.6 (mV / nm) for light-emitting devices 2-1a, 2-2a, and comparative light-emitting device 2-2a, and 51.5 (mV / nm) for light-emitting devices 2-1b, 2-2b, and comparative light-emitting device 2-2b. In light-emitting devices 2-1a, 2-1b, 2-2a, and 2-2b, the GSP_Slope of the film of the organic compound having a π-electron-deficient heteroaromatic ring contained in the second electron transport layer is greater than the GSP_Slope of the film of the organic compound having a π-electron-deficient heteroaromatic ring contained in the first electron transport layer multiplied by (x+y) / x. In comparative light-emitting devices 2-2a and 2-2b, the GSP_Slope is equal to or smaller than the GSP_Slope of the film of the organic compound having a π-electron-deficient heteroaromatic ring contained in the first electron transport layer.

[0392] Thus, when the weight ratio of the organic compound having a π-electron-deficient heteroaromatic ring in the second electron transport layer to Liq is x:y, if the GSP_Slope of the film of the organic compound having a π-electron-deficient heteroaromatic ring contained in the second electron transport layer is greater than the GSP_Slope of the film of the organic compound having a π-electron-deficient heteroaromatic ring contained in the first electron transport layer multiplied by (x+y) / x, then electron injection from the second electrode or electron injection layer to the second electron transport layer can be suppressed, making it possible to provide a highly reliable light-emitting device.

[0393] In the above-described light-emitting device, the GSP_Slope of the host material (SiTrzCz2 and PSiCzCz) film is larger than the GSP_Slope of the first organic compound film. Furthermore, the GSP_Slope of the light-emitting layer is larger than the GSP_Slope of the first electron transport layer.

[0394] This configuration allows a positive interfacial charge to be placed at the interface between the light-emitting layer and the first electron transport layer, resulting in smooth electron injection from the second electron transport layer to the first electron transport layer in the light-emitting device. Therefore, in light-emitting devices 2-1a, 2-1b, 2-2a, and 2-2b, even if electron injection into the second electron transport layer is suppressed, a significant increase in the driving voltage is not caused, making it possible to produce light-emitting devices with good characteristics.

[0395] Furthermore, ZADN and BP-Icz(II)Tzn, which are organic compounds having a π-electron-deficient heteroaromatic ring and are included in the second electron transport layer of light-emitting devices 2-1a, 2-1b, 2-2a, and 2-2b, have a larger GSP_Slope than the host materials (SiTrzCz2 and PSiCzCz). Also, the GSP_Slope of the second electron transport layer is larger than the GSP_Slope of the light-emitting layer.

[0396] As a result, in light-emitting devices 2-1a, 2-1b, 2-2a, and 2-2b, the interface charge between the first electron transport layer and the second electron transport layer is negative and smaller than the interface charge between the light-emitting layer and the first electron transport layer. This effect suppresses the injection of electrons from the second electrode or electron injection layer into the second electron transport layer, and promotes the injection of holes within the light-emitting layer. Consequently, the recombination region, which tends to be biased towards the anode side in the light-emitting layer of typical blue phosphorescent devices, can be expanded, and the degradation of the hole transport layer, which functions as an electron blocking layer, can be further reduced.

[0397] Furthermore, the above-mentioned light-emitting device has a configuration in which the GSP_Slope of the light-emitting layer (co-evaporated film of SiTrzCz2, PSiCzCz, and PtON-TBBI) is larger than the GSP_Slope of the hole transport layer (evaporated film of PSiCzCz). This facilitates the injection of holes from the hole transport layer to the light-emitting layer, making it possible to create a light-emitting device with a low driving voltage.

[0398] Thus, a light-emitting device according to one aspect of the present invention can be a light-emitting device with high reliability and good characteristics. [Examples]

[0399] In this example, the detailed manufacturing method and characteristics of a light-emitting device 3 according to one embodiment of the present invention and a comparative light-emitting device 3 in a comparative example will be described. The structural formulas of the main compounds used in this example are shown below.

[0400] [ka]

[0401] (Method for fabricating light-emitting device 3) First, indium tin oxide (ITSO) containing silicon dioxide was layered onto a glass substrate by sputtering to a thickness of 55 nm, forming a first electrode 101 measuring 2 mm x 2 mm. The ITSO functions as an anode.

[0402] Next, as a pretreatment for forming a light-emitting device on the substrate, the substrate surface was washed with water.

[0403] After that, approximately 1 × 10 -4 The substrate was introduced into a vacuum deposition apparatus where the internal pressure was reduced to Pa. After vacuum firing at 170°C for 30 minutes in the heating chamber of the vacuum deposition apparatus, the substrate was allowed to cool for approximately 30 minutes.

[0404] Next, the substrate was fixed to a holder provided in a vacuum deposition apparatus so that the surface on which the first electrode 101 was formed was facing downwards. A hole injection layer 111 was then formed by co-depositing N-(biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviated as PCBBiF), represented by the above structural formula (i), and an electron acceptor material (OCHD-003) with a molecular weight of 672 and containing fluorine, on the inorganic insulating film and the first electrode 101 in a weight ratio of 1:0.03 (=PCBBiF:OCHD-003) and with a film thickness of 10 nm.

[0405] After depositing PCBBiF onto the hole injection layer 111 to a thickness of 45 nm, a hole transport layer 112 was formed by depositing 9-[3-(triphenylsilyl)phenyl]-3,9′-bi-9H-carbazole (abbreviated as PSiCzCz), represented by the above structural formula (ii), to a thickness of 5 nm. PSiCzCz is an organic compound having a π-electron-rich heteroaromatic ring, and the PSiCzCz layer also functions as an electron blocking layer.

[0406] Next, on the hole transport layer 112, 9,9'-{6-[3-(triphenylsilyl)phenyl]-1,3,5-triazine-2,4-diyl}bis(9H-carbazole) (abbreviated as SiTrzCz2), represented by the above structural formula (iii), PSiCzCz, and (2-{3-[3-(3,5-di-tert-butylphenyl)benzimidazole-1-yl-2-ylidene-κC2]phenoxy-κC2] represented by the above structural formula (x) -9-[3,5-di(methyl-d3)-4-phenyl-2-pyridinyl-κN]carbazole-2,1-diyl-κC)platinum(II) (abbreviated as Pt(mmtBubOcz35dm4ppy-d6)) was co-deposited with platinum(II) in a weight ratio of 0.35:0.53:0.12 (=SiTrzCz2:PSiCzCz:Pt(mmtBubOcz35dm4ppy-d6)) and with a film thickness of 40 nm to form the luminescent layer 113. Note that Pt(mmtBubOcz35dm4ppy-d6) is an organometallic complex that exhibits blue phosphorescence (peak wavelength of emission spectrum is between 450 nm and 520 nm). Furthermore, SiTrzCz2 is an organic compound having a π-electron-deficient heteroaromatic ring, while PSiCzCz is an organic compound having a π-electron-rich heteroaromatic ring.

[0407] Next, 2-phenyl-4,6-bis[3-(triphenylsilyl)phenyl]-1,3,5-triazine (abbreviated as mSiTrz), represented by the above structural formula (v), was deposited to a thickness of 5 nm to form a first electron transport layer. Then, 11-[4-(biphenyl-4-yl)-6-phenyl-1,3,5-triazine-2-yl]-11,12-dihydro-12-phenylindoro[2,3-a]carbazole (abbreviated as BP-Icz(II)Tzn), represented by the above structural formula (vii), and 8-quinolinolato-lithium (abbreviated as Liq), represented by the above structural formula (viii), were co-deposited in a weight ratio of 1:4 and to a thickness of 30 nm to form a second electron transport layer. Furthermore, mSiTrz and BP-Icz(II)Tzn are organic compounds having π-electron-deficient heteroaromatic rings, Liq is an organometallic complex containing an alkali metal, and the first electron transport layer is a layer that also functions as a hole blocking layer.

[0408] After the electron transport layer was formed, lithium fluoride (abbreviated as LiF) was deposited to a thickness of 1 nm to form an electron injection layer 115, and then aluminum (abbreviated as Al) was deposited to a thickness of 200 nm to form a second electrode 102 (cathode).

[0409] Next, in a glove box under a nitrogen atmosphere, the light-emitting device was sealed with a glass substrate to prevent exposure to the atmosphere (applying a UV-curable sealant around the element, irradiating only the sealant with UV light without irradiating the light-emitting device, and heat-treating at 80°C for 1 hour under atmospheric pressure) to form the light-emitting device 3.

[0410] (Method for fabricating comparative light-emitting device 3) Comparative light-emitting device 3 was fabricated in the same manner as light-emitting device 3, except that the second electron transport layer was formed of 2,2'-(1,3-phenylene)bis(9-phenyl-1,10-phenanthroline) (abbreviated as mPPhen2P) represented by the above structural formula (ix).

[0411] The device structures of light-emitting device 3 and comparative light-emitting device 3 are shown in the table below.

[0412] [Table 10]

[0413] Figure 35 shows the luminance-current density characteristics of light-emitting device 3 and comparative light-emitting device 3, Figure 36 shows the current efficiency-current density characteristics, Figure 37 shows the luminance-voltage characteristics, Figure 38 shows the current density-voltage characteristics, Figure 39 shows the blue index-current density characteristics, Figure 40 shows the external quantum efficiency-current density characteristics, Figure 41 shows the field emission spectrum, and Figure 42 shows the CIE chromaticity diagram. Furthermore, the current density is 10 mA / cm². 2Table 11 shows the main characteristics of the device. A spectroradiometer (Topcon SR-UL1R) was used to measure luminance, CIE chromaticity, and field emission spectrum at room temperature. The external quantum efficiency was calculated using the measured luminance and emission spectrum, assuming a Lambertsian optical distribution pattern.

[0414] [Table 11]

[0415] Thus, both light-emitting device 3 and comparative light-emitting device 3 were found to be light-emitting devices exhibiting good characteristics. Furthermore, light-emitting device 3 was found to be a light-emitting device with particularly good current efficiency and external quantum efficiency.

[0416] Furthermore, the light-emitting device 3 and the comparison light-emitting device 3 are set to 10 mA / cm². 2 Figure 43 shows the time-dependent characteristics of the normalized brightness when driven at the specified current density. Note that the time-dependent characteristics of the normalized brightness are shown with the initial brightness set to 100%.

[0417] Figure 43 shows that light-emitting device 3 exhibits less brightness degradation with respect to operating time compared to comparative light-emitting device 3, indicating that it is a highly reliable light-emitting device.

[0418] Figure 44 shows the emission spectra (PL spectra) of single films of SiTrzCz2 and PSiCzCz, and the emission spectra (PL spectra) of a mixed film with a weight ratio of 1:1. The samples were deposited onto a quartz substrate to a thickness of 50 nm, and measurements were taken at room temperature. A fluorometer (JASCO FP-8600) was used. The excitation light wavelengths were 330 nm (SiTrzCz2 single film), 310 nm (PSiCzCz single film), and 355 nm (SiTrzCz2 and PSiCzCz mixed film). As shown in Figure 44, compared to the emission spectra of each single film, the emission spectrum of the mixed film is located at longer wavelengths, indicating that SiTrzCz2 and PSiCzCz form an excited complex in the mixed film. In other words, SiTrzCz2 and PSiCzCz are a combination that forms an excited complex.

[0419] Table 12 also shows the GSP_Slope of the organic compound having a π-electron-deficient heteroaromatic ring used in the first electron transport layer of the light-emitting device 3 and the comparative light-emitting device 3, the organic compound having a π-electron-deficient heteroaromatic ring used in the second electron transport layer, the organic compound having a π-electron-excess heteroaromatic ring or aromatic amine used in the hole transport layer, and the vapor-deposited film of the host material used in the light-emitting layer. In Table 12, the GSP_Slope was measured by the method shown in Embodiment 1.

[0420] [Table 12]

[0421] Thus, the light-emitting device 3 has a configuration in which the GSP_Slope of the film of the organic compound having a π-electron-deficient heteroaromatic ring contained in the second electron transport layer is larger than the GSP_Slope of the film of the organic compound having a π-electron-deficient heteroaromatic ring contained in the first electron transport layer.

[0422] On the other hand, in comparative light-emitting device 3, the GSP_Slope of the film of the organic compound having a π-electron-deficient heteroaromatic ring contained in the second electron transport layer is lower than the GSP_Slope of the film of the organic compound having a π-electron-deficient heteroaromatic ring contained in the first electron transport layer.

[0423] As a result, electron injection into the second electron transport layer is further suppressed in the light-emitting device 3. In the light-emitting layer of a typical blue phosphorescent device, since both the HOMO and LUMO levels of the blue phosphorescent material are higher than those of the host material, the recombination region tends to be biased towards the anode side because it traps holes instead of electrons. In one embodiment of the present invention, the above configuration suppresses electron injection into the second electron transport layer, thereby broadening the recombination region which tends to be biased towards the anode side, and reducing the degradation of the hole transport layer which functions as an electron blocking layer. As a result, the reliability of the light-emitting device 3 is improved. In this embodiment, the HOMO level of PSiCzCz used as the host material for the light-emitting layer is -5.7eV and the LUMO level is -2.06eV. The HOMO level of SiTrzCz2 is lower than that of PSiCzCz, with a LUMO level of -2.98eV. The HOMO level of Pt(mmtBubOcz35dm4ppy-d6), a blue phosphorescent material, is -5.50eV and the LUMO level is -2.47eV. As described above, the configuration traps holes without trapping electrons.

[0424] The HOMO and LUMO levels were determined by cyclic voltammetry (CV) measurement. The CV measurement was performed in the same manner as described in Example 2.

[0425] Furthermore, the light-emitting device 3 contains Liq, a metal complex containing an alkali metal, in addition to an organic compound having a π-electron-deficient heteroaromatic ring, in its second electron transport layer. When the weight ratio of the organic compound having a π-electron-deficient heteroaromatic ring to Liq in the second electron transport layer of the light-emitting device 3 is x:y, the GSP_Slope of the film of the organic compound having a π-electron-deficient heteroaromatic ring contained in the first electron transport layer multiplied by (x+y) / x is 51.5 (mV / nm). The light-emitting device 3 is a light-emitting device in which the GSP_Slope of the film of the organic compound having a π-electron-deficient heteroaromatic ring contained in the second electron transport layer is greater than the GSP_Slope of the film of the organic compound having a π-electron-deficient heteroaromatic ring contained in the first electron transport layer multiplied by (x+y) / x.

[0426] Thus, when the weight ratio of the organic compound having a π-electron-deficient heteroaromatic ring to Liq in the second electron transport layer is x:y, a more reliable light-emitting device can be provided if the GSP_Slope of the film of the organic compound having a π-electron-deficient heteroaromatic ring contained in the second electron transport layer is greater than the GSP_Slope of the film of the organic compound having a π-electron-deficient heteroaromatic ring contained in the first electron transport layer multiplied by (x+y) / x.

[0427] In the above-described light-emitting device, the GSP_Slope of the host material (SiTrzCz2 and PSiCzCz) film is larger than the GSP_Slope of the first organic compound film. Furthermore, the GSP_Slope of the light-emitting layer is larger than the GSP_Slope of the first electron transport layer.

[0428] This configuration allows a positive interfacial charge to be placed at the interface between the light-emitting layer and the first electron transport layer, resulting in smooth electron injection from the second electron transport layer to the first electron transport layer in the light-emitting device. Therefore, even if electron injection into the second electron transport layer is suppressed in the light-emitting device 3, it does not cause a significant increase in the driving voltage, making it possible to create a light-emitting device with good characteristics.

[0429] Furthermore, BP-Icz(II)Tzn, an organic compound having a π-electron-deficient heteroaromatic ring contained in the second electron transport layer of the light-emitting device 3, has a larger GSP_Slope than the host materials (SiTrzCz2 and PSiCzCz). Also, the GSP_Slope of the second electron transport layer is larger than the GSP_Slope of the light-emitting layer.

[0430] As a result, in the light-emitting device 3, the interface charge between the first electron transport layer and the second electron transport layer is negative and smaller than the interface charge between the light-emitting layer and the first electron transport layer. This effect suppresses the injection of electrons from the second electrode or electron injection layer into the second electron transport layer, and promotes the injection of holes in the light-emitting layer. Consequently, the recombination region, which tends to be biased towards the anode side in the light-emitting layer of a typical blue phosphorescent device, can be expanded, and the degradation of the hole transport layer, which functions as an electron blocking layer, can be further reduced.

[0431] Thus, a light-emitting device according to one aspect of the present invention can be a light-emitting device with high reliability and good characteristics. [Explanation of Symbols]

[0432] 10A Light-Emitting Device 10B Light-emitting device 100A display device 100B display device 100C display device 100E display device 100D display device 100 Insulator 101 First electrode 102 Second electrode 103 EL layer 110B subpixel 110G sub-pixels 110R sub-pixel 110 subpixels 111 Hole injection layer 112 Hole transport layer 112B Conductive layer 112R conductive layer 113 Emitting layer 114_1 First electron transport layer 114_2 Second electron transport layer 115 Electron injection layer 116 Charge generation layer 117 p-type layer 118 Electron relay layer 119 Electron injection buffer layer 120 circuit boards 122 Resin layer 125 Inorganic insulating layer 126R conductive layer 126B Conductive layer 127 Insulating layer 128 layers 129R conductive layer 129B Conductive layer 130B Light-emitting device 130G Light-emitting Device 130R Light-emitting Device 130 Light-emitting devices 131 Protective layer 132B Colored layer 132G colored layer 132R colored layer 135 The first layer 135A First Strata Group 135R Layer 1 135G Layer 1 135B Layer 1 136 Common layer 140 Connection part 141 areas 142 Adhesive layer 151B Conductive layer 151C conductive layer 151G conductive layer 151R conductive layer 151 Conductive layer 152B Conductive layer 152C conductive layer 152G conductive layer 152R conductive layer 152 Conductive layer 153 Insulating layer 156B Insulating layer 156C insulating layer 156G insulating layer 156R Insulating Layer 157 Light blocking layer 158B Sacrifice Layer 158G Sacrifice Layer 158R Sacrifice Layer 166 Conductive layer 171 Insulating layer 172 Conductive layer 173 Insulating layer 174 Insulating layer 175 Insulating layer 176 plug 177 pixel section 178 pixels 201 Transistors 204 Connection part 205 transistors 211 Insulating layer 213 Insulating layer 214 Insulating layer 215 Insulating layer 221 Conductive layer 222a conductive layer 222b Conductive layer 223 Conductive layer 224B Conductive layer 224C conductive layer 224G conductive layer 224R conductive layer 231 Semiconductor layer 240 capacity 241 Conductive layer 242 Connecting Layers 243 Insulating layer 245 Conductive layer 254 Insulating layer 255 Insulating layer 256 plug 261 Insulating layer 271 Plug 280 Display Modules 281 Display section 282 Circuit section 283a Pixel Circuit 283 Pixel Circuit Section 284a pixels 284 pixel section 285 Terminal section 286 Wiring section 290 FPC 291 circuit boards 292 circuit boards 301 circuit board 310 transistors 311 Conductive layer 312 Low resistance region 313 Insulating layer 314 Insulating layer 315 element isolation layer 351 circuit board 352 circuit boards 353 FPC 354 IC 355 Wiring 356 circuits 501 First electrode 502 Second electrode 513 Charge generation layer 700A electronic equipment 700B Electronic equipment 721 cabinet 723 Mounting part 727 Earphone section 750 Earphones 751 Display Panel 753 Optical components 756 Display area 757 frames 758 Nose pads 800A electronic equipment 800B Electronic equipment 820 Display section 821 cabinet 822 Communications Department 823 Mounting part 824 Control Unit 825 Imaging Unit 827 Earphone section 832 Lens 6500 Electronic equipment 6501 enclosure 6502 Display section 6503 Power button 6504 button 6505 Speaker 6506 Mike 6507 Camera 6508 Light source 6510 Protective component 6511 Display Panel 6512 Optical components 6513 Touch Sensor Panel 6515 FPC 6516 IC 6517 Printed circuit board 6518 Battery 7000 Display 7100 Television equipment 7151 Remote Control Unit 7171 enclosure 7173 Stand 7200 Notebook Personal Computer 7211 enclosure 7212 Keyboard 7213 Pointing device 7214 External connection port 7300 Digital Signage 7301 enclosure 7303 Speaker 7311 Information terminal 7400 Digital Signage 7401 pillars 7411 Information terminal 9000 cabinets 9001 Display section 9002 Camera 9003 Speaker 9005 Operation Keys 9006 Connection terminal 9007 Sensor 9008 Microphone 9050 Icon 9051 Information 9052 Information 9053 Information 9054 Information 9055 Hinge 9171 Mobile Information Terminal 9172 Mobile Information Terminal 9173 Tablet device 9200 Mobile Information Terminal 9201 Mobile Information Terminal

Claims

1. A first electrode formed on an insulating surface, A second electrode facing the first electrode, The present invention has an EL layer located between the first electrode and the second electrode, The EL layer comprises a light-emitting layer, a hole transport layer, a first electron transport layer, and a second electron transport layer. The first electron transport layer is located between the first electrode and the second electron transport layer. The light-emitting layer is located between the hole transport layer and the first electron transport layer and the second electron transport layer. A light-emitting device in which the GSP_Slope (mV / nm) of the second electron transport layer is greater than the GSP_Slope (mV / nm) of the first electron transport layer (where GSP_Slope (mV / nm) is expressed as ΔV / Δd when the change in surface potential ΔV (mV) is equal to the change in film thickness Δd (nm)).

2. A first electrode formed on an insulating surface, A second electrode facing the first electrode, The present invention has an EL layer located between the first electrode and the second electrode, The EL layer comprises a light-emitting layer, a hole transport layer, a first electron transport layer, and a second electron transport layer. The first electron transport layer is located between the first electrode and the second electron transport layer. The light-emitting layer is located between the hole transport layer and the first electron transport layer and the second electron transport layer. The first electron transport layer comprises a first organic compound, The second electron transport layer comprises a second organic compound, The first organic compound and the second organic compound have a π-electron-deficient heteroaromatic ring, A light-emitting device in which the GSP_Slope (mV / nm) in the vapor-deposited film of the second organic compound is greater than the GSP_Slope (mV / nm) in the vapor-deposited film of the first organic compound (where GSP_Slope (mV / nm) is expressed as ΔV / Δd when the change in surface potential ΔV (mV) is equal to the change in film thickness Δd (nm)).

3. A first electrode formed on an insulating surface, A second electrode facing the first electrode, The present invention has an EL layer located between the first electrode and the second electrode, The EL layer comprises a light-emitting layer, a hole transport layer, a first electron transport layer, and a second electron transport layer. The first electron transport layer is located between the light-emitting layer and the second electron transport layer. The second electron transport layer is located between the first electron transport layer and the second electrode. The light-emitting layer is located between the hole transport layer and the first electron transport layer. The first electron transport layer comprises a first organic compound, The second electron transport layer comprises a second organic compound and a first substance. The first organic compound and the second organic compound have a π-electron-deficient heteroaromatic ring, A light-emitting device in which the GSP_Slope (mV / nm) in the vapor-deposited film of the second organic compound is greater than the GSP_Slope (mV / nm) in the vapor-deposited film of the first organic compound (where GSP_Slope (mV / nm) is expressed as ΔV / Δd when the change in surface potential ΔV (mV) is equal to the change in film thickness Δd (nm)).

4. A first electrode formed on an insulating surface, A second electrode facing the first electrode, The present invention has an EL layer located between the first electrode and the second electrode, The EL layer comprises a light-emitting layer, a hole transport layer, a first electron transport layer, and a second electron transport layer. The first electron transport layer is located between the light-emitting layer and the second electron transport layer. The second electron transport layer is located between the first electron transport layer and the second electrode. The light-emitting layer is located between the hole transport layer and the first electron transport layer. The first electron transport layer comprises a first organic compound, The second electron transport layer comprises a second organic compound and a first substance. The first organic compound and the second organic compound have a π-electron-deficient heteroaromatic ring, When the mixing ratio of the second organic compound and the first substance in the second electron transport layer is x:y, A light-emitting device in which the GSP_Slope (mV / nm) in the vapor-deposited film of the second organic compound is greater than (x+y) / x times the GSP_Slope (mV / nm) in the vapor-deposited film of the first organic compound (where GSP_Slope (mV / nm) is expressed as ΔV / Δd when the change in surface potential ΔV (mV) is equal to the change in film thickness Δd (nm)).

5. In claim 4, A light-emitting device in which the aforementioned y is greater than or equal to the aforementioned x.

6. In any one of claims 1 to 4, A light-emitting device comprising a material that exhibits phosphorescence in the light-emitting layer.

7. In claim 6, A light-emitting device in which a phosphorescent substance emits light when a voltage is applied between the first electrode and the second electrode.

8. In claim 1, The second electron transport layer is located between the first electron transport layer and the second electrode. A light-emitting device in which the GSP_Slope (mV / nm) of the light-emitting layer is greater than the GSP_Slope (mV / nm) of the first electron transport layer.

9. In claim 8, A light-emitting device in which the GSP_Slope (mV / nm) of the light-emitting layer is greater than the GSP_Slope (mV / nm) of the hole transport layer.

10. In any one of claims 2 to 4, The second electron transport layer is located between the first electron transport layer and the second electrode. The light-emitting layer comprises a host material and a light-emitting substance. A light-emitting device in which the GSP_Slope (mV / nm) in the vapor-deposited film of the host material is greater than the GSP_Slope (mV / nm) in the vapor-deposited film of the first organic compound.

11. In claim 10, A light-emitting device in which the GSP_Slope (mV / nm) in the vapor-deposited film of the second organic compound is greater than the GSP_Slope (mV / nm) in the vapor-deposited film of the host material.

12. In claim 10, The hole transport layer has a third organic compound, A light-emitting device in which the GSP_Slope (mV / nm) of the light-emitting layer is equal to or greater than the GSP_Slope (mV / nm) of the vapor-deposited film of the third organic compound.

13. In claim 10, The hole transport layer has a third organic compound, A light-emitting device in which the GSP_Slope (mV / nm) in the vapor-deposited film of the host material is equal to or greater than the GSP_Slope (mV / nm) in the vapor-deposited film of the third organic compound.

14. In claim 10, The host material comprises a first material and a second material, A light-emitting device which is an organic compound in which the first material and the second material form an excited complex.

15. In claim 14, The first material is an organic compound having a π-electron-deficient heteroaromatic ring, A light-emitting device in which the second material is an organic compound having a π-electron-rich heteroaromatic ring or an aromatic amine.

16. In claim 3 or claim 4, The first material is a metal complex, which is used in this light-emitting device.

17. In claim 16, The aforementioned metal complex is an organic complex containing an alkali metal, which is used as a light-emitting device.

18. In claim 7, A light-emitting device in which the peak wavelength of the emission spectrum of the phosphorescent material is 450 nm or more and 520 nm or less.

19. In claim 10, A light-emitting device in which the peak wavelength of the emission spectrum of the light-emitting material is 450 nm or more and 520 nm or less.

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