Light emitting device

Abstract

Provided is a light-emitting device with high reliability. The light-emitting device includes a first electrode formed on an insulating surface, a second electrode facing the first electrode, and an EL layer between the first electrode and the second electrode, one of the first electrode and the second electrode is an anode, and the other is a cathode, the EL layer includes a light-emitting layer, a first layer, and a second layer, the first layer and the second layer are between the light-emitting layer and the cathode, the first layer is between the first electrode and the second layer, the second layer is between the first layer and the second electrode, the light-emitting layer contains a first light-emitting substance and a second light-emitting substance, the first light-emitting substance is a substance capable of converting triplet excitation energy into light emission, the second light-emitting substance is a fluorescent light-emitting substance, the light emission peak wavelength of the first light-emitting substance is shorter than the light emission peak wavelength of the second light-emitting substance, and the GSP_Slope of the second layer is greater than the GSP_Slope of the first layer.

Description

Technical Field

[0001] One aspect of this invention relates to an organic compound, an organic semiconductor element, a light-emitting element, an organic EL element, a photodiode, a display module, a lighting module, a display device, a light-emitting device, an electronic device, a lighting device, and an electronic device. Note that this aspect of the invention is not limited to the aforementioned technical fields. The technical field of one aspect of the invention disclosed in this specification relates to an object, method, or manufacturing method. Furthermore, one aspect of the invention relates to a process, machine, manufacture, or composition of matter. Therefore, more specifically, examples of the technical field of one aspect of the invention disclosed in this specification include semiconductor devices, display devices, liquid crystal display devices, light-emitting devices, lighting devices, energy storage devices, memory devices, imaging devices, and methods for driving or manufacturing these devices. Background Technology

[0002] The practical application of light-emitting devices (organic EL elements) utilizing electroluminescence (EL) with organic compounds is very active. In the basic structure of these organic EL elements, an organic compound layer (EL layer) containing a luminescent material is sandwiched between a pair of electrodes. By applying a voltage to the device and injecting charge carriers, light emission from the luminescent material can be obtained using the recombination energy of these charge carriers.

[0003] Because this type of organic EL element is a self-emissive EL element, it offers advantages over liquid crystal displays (LCDs) in terms of higher visibility and the elimination of the need for a backlight when used in display pixels. Furthermore, displays using this type of EL element can be manufactured to be thin and lightweight, which is a significant advantage. Moreover, its extremely fast response time is also a characteristic of this organic EL element.

[0004] Furthermore, because the light-emitting layer of this organic EL element can be formed continuously in a planar shape, surface emission can be achieved. Since this characteristic is difficult to obtain in point light sources such as incandescent lamps and LEDs, or line light sources such as fluorescent lamps, the aforementioned light-emitting device is highly valuable as a surface light source for illumination and other applications.

[0005] As mentioned above, displays or lighting devices using organic EL elements can be adapted for a wide variety of electronic devices, and research and development of organic EL elements with better characteristics are becoming increasingly active.

[0006] [Non-Patent Literature 1] Hiroshi Noguchi and 2 others, "Orientational Polarization Phenomenon of Polar Molecules and Interfacial Characteristics of Organic Thin Film Devices," Journal of the Vacuum Society of Japan, 2015, Vol. 58, No. 3 Summary of the Invention

[0007] One objective of this invention is to provide a light-emitting device with high reliability. Another objective of this invention is to provide a light-emitting device with high luminous efficiency. Furthermore, one objective of this invention is to provide any one of a light-emitting device, an electronic device, and a display device with high reliability.

[0008] Furthermore, one objective of this invention is to provide a blue light-emitting device with high reliability. Another objective of this invention is to provide a blue light-emitting device with high luminous efficiency.

[0009] Note that the description of these objectives does not preclude the existence of other objectives. Note that one embodiment of the invention does not necessarily require achieving all of the above objectives. Note that objectives other than those described above can be understood and extracted from the description, drawings, claims, etc.

[0010] One aspect of the present invention is a light-emitting device, comprising: a first electrode formed on an insulating surface; a second electrode opposite to the first electrode; and an EL layer located between the first electrode and the second electrode. The EL layer includes 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 and second electron transport layers. The light-emitting layer includes a first light-emitting material and a second light-emitting material. The first light-emitting material is a material capable of converting triple excitation energy into light emission. The second light-emitting material is a fluorescent light-emitting material. The peak wavelength of the emission spectrum of the first light-emitting material is shorter than the peak wavelength of the emission spectrum of the second light-emitting material. 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.

[0011] In addition, another aspect of the present invention is a light-emitting device having the above-described structure, wherein the second electron transport layer is located between the first electron transport layer and the second electrode, and the GSP_Slope (mV / nm) of the light-emitting layer is greater than the GSP_Slope (mV / nm) of the first electron transport layer.

[0012] In addition, another aspect of the present invention is a light-emitting device having the above-described structure, wherein the GSP_Slope (mV / nm) of the light-emitting layer is greater than the GSP_Slope (mV / nm) of the hole transport layer.

[0013] Another aspect of the present invention is a light-emitting device, comprising: a first electrode formed on an insulating surface; a second electrode opposite to the first electrode; and an EL layer located between the first electrode and the second electrode. The EL layer includes 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 and second electron transport layers. The light-emitting layer includes a first light-emitting material and a second light-emitting material. The first light-emitting material is a material capable of converting triple excitation energy into light emission. The second light-emitting material is a fluorescent light-emitting material. The peak wavelength of the emission spectrum of the first light-emitting material is shorter than the peak wavelength of the emission spectrum of the second light-emitting material. The first electron transport layer includes a first organic compound, and the second electron transport layer includes a second organic compound. The first organic compound and the second organic compound have π-electron-deficient heteroaromatic rings. 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 first organic compound.

[0014] Another aspect of the present invention is a light-emitting device, comprising: a first electrode formed on an insulating surface; a second electrode opposite to the first electrode; and an EL layer located between the first electrode and the second electrode. The EL layer includes 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, and 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 light-emitting layer includes a first light-emitting material and a second light-emitting material. The first light-emitting material is a material capable of converting triple excitation energy into light emission, and the second light-emitting material is a fluorescent light-emitting material. The peak wavelength of the emission spectrum of the first light-emitting material is shorter than the peak wavelength of the emission spectrum of the second light-emitting material. The first electron transport layer includes a first organic compound, and the second electron transport layer includes a second organic compound and the first material. The first organic compound and the second organic compound have π-electron-deficient heteroaromatic rings. 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 first organic compound.

[0015] Another aspect of the present invention is a light-emitting device, comprising: a first electrode formed on an insulating surface; a second electrode opposite to the first electrode; and an EL layer located between the first electrode and the second electrode. The EL layer includes 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, and the light-emitting layer is located between the hole transport layer and the first electron transport layer. The light-emitting layer comprises a first light-emitting material and a second light-emitting material, wherein the first light-emitting material is a material capable of converting triple excitation energy into light emission. The second luminescent material is a fluorescent luminescent material. The peak wavelength of the emission spectrum of the first luminescent material is shorter than that of the second luminescent material. The first electron transport layer includes a first organic compound, and the second electron transport layer includes a second organic compound and the first substance. The first organic compound and the second organic compound have π-electron-deficient heteroaromatic rings. When the mixing ratio of the second organic compound and the first substance in the second electron transport layer is x:y, the GSP_Slope (mV / nm) of the vapor-deposited film of the second organic compound is greater than (x+y) / x times the GSP_Slope (mV / nm) of the vapor-deposited film of the first organic compound.

[0016] In addition, another aspect of the present invention is a light-emitting device having the above-described structure, wherein y is greater than or equal to x.

[0017] In addition, another aspect of the present invention is a light-emitting device having the above-described structure, wherein 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 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.

[0018] In addition, another aspect of the present invention is a light-emitting device having the above-described structure, wherein 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.

[0019] In addition, another aspect of the present invention is a light-emitting device having the above-described structure, wherein the hole transport layer comprises a third organic compound, and the GSP_Slope (mV / nm) of the light-emitting layer is greater than or equal to the GSP_Slope (mV / nm) of the vapor-deposited film of the third organic compound.

[0020] In addition, another aspect of the present invention is a light-emitting device having the above-described structure, wherein the HOMO energy level of the host material is lower than the HOMO energy level of the first light-emitting material.

[0021] In addition, another aspect of the present invention is a light-emitting device having the above-described structure, wherein the HOMO energy level of the first light-emitting material is lower than the HOMO energy level of the second light-emitting material.

[0022] In addition, another aspect of the present invention is a light-emitting device having the above-described structure, wherein the hole transport layer comprises a third organic compound, and the GSP_Slope (mV / nm) of the vapor-deposited film of the host material is greater than or equal to the GSP_Slope (mV / nm) of the vapor-deposited film of the third organic compound.

[0023] In addition, another aspect of the present invention is a light-emitting device having the above-described structure, wherein the host material comprises a first material and a second material, and the first material and the second material are organic compounds that form a combination of excitocomplexes.

[0024] In addition, another aspect of the present invention is a light-emitting device having the above-described structure, wherein the HOMO energy levels of the first material and the second material are lower than the HOMO energy level of the first light-emitting material.

[0025] In addition, another aspect of the present invention is a light-emitting device having the above-described structure, wherein the HOMO energy levels of the first material and the second material are lower than the HOMO energy level of the second light-emitting material.

[0026] In addition, another aspect of the present invention is a light-emitting device having the above-described structure, wherein 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-rich heteroaromatic ring or an aromatic amine.

[0027] In addition, another aspect of the present invention is a light-emitting device having the above-described structure, wherein the first substance is a metal complex.

[0028] In addition, another aspect of the present invention is a light-emitting device having the above-described structure, wherein the metal complex is an organic complex containing an alkali metal.

[0029] In addition, another aspect of the present invention is a light-emitting device having the above-described structure, wherein the first light-emitting material is a phosphorescent light-emitting material.

[0030] Another aspect of the present invention is a light-emitting device having the above-described structure, wherein the second light-emitting material emits light when a voltage is applied between the first electrode and the second electrode.

[0031] In addition, another aspect of the present invention is a light-emitting device having the above-described structure, wherein the peak wavelength of the emission spectrum of the second light-emitting material is above 450 nm and below 520 nm.

[0032] In addition, another aspect of the present invention is a light-emitting device having the above-described structure, wherein the energy difference between the lowest triplet excitation level of the first material and the lowest triplet excitation level of the second material is less than 0.20 eV.

[0033] Furthermore, another aspect of the present invention is a light-emitting device having the above-described structure, wherein the absorption end of the second light-emitting material on the long wavelength side of its absorption spectrum is at a longer wavelength than the light-emitting end of the first light-emitting material on the short wavelength side of its emission spectrum. Additionally, the absorption end of the second light-emitting material on the long wavelength side of its absorption spectrum is at a longer wavelength than the absorption end of the first light-emitting material on the long wavelength side of its absorption spectrum. Furthermore, the light-emitting ends of the first material and the second material on the short wavelength side of their phosphorescence spectra are at shorter wavelengths than the light-emitting ends of the first light-emitting material on the short wavelength side of its emission spectrum.

[0034] Furthermore, another aspect of the present invention is a light-emitting device having the above-described structure, wherein the proportion of the first light-emitting material in the light-emitting layer is greater than the proportion of the second light-emitting material.

[0035] Furthermore, another aspect of the present invention is a light-emitting device having the above-described structure, wherein the second light-emitting material comprises a light-emitting element and a protecting group. The light-emitting element is a fused aromatic ring or a fused heteroaromatic ring, and the protecting group comprises any one of an alkyl group having 1 or more but less than 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 or more but less than 10 carbon atoms, and a trialkylsilyl group having 3 or more but less than 10 carbon atoms. Alternatively, the second light-emitting material comprises a light-emitting element and five or more protecting groups. The light-emitting element is a fused aromatic ring or a fused heteroaromatic ring, and the protecting groups each independently comprise any one of an alkyl group having 1 or more but less than 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 or more but less than 10 carbon atoms, and a trialkylsilyl group having 3 or more but less than 10 carbon atoms.

[0036] In addition, another aspect of the present invention is a light-emitting device having the above-described structure, wherein the first light-emitting material includes any one of an alkyl group having 3 or more and 10 or less carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 or more and 10 or less carbon atoms, and a trialkylsilyl group having 3 or more and 10 or less carbon atoms.

[0037] Note that in one embodiment of the invention, GSP_Slope (mV / nm) is expressed as ΔV / Δd, where ΔV (mV) is the change in surface potential and Δd (nm) is the change in thickness.

[0038] One aspect of the present invention can provide a highly reliable light-emitting device. Furthermore, another aspect of the present invention can provide a light-emitting device with high luminous efficiency. Additionally, one aspect of the present invention can provide any one of a reliable light-emitting device, electronic device, and display device.

[0039] Furthermore, one aspect of the present invention can provide a blue light-emitting device with high reliability. Additionally, another aspect of the present invention can provide a blue light-emitting device with high luminous efficiency.

[0040] Note that the description of these effects does not preclude the existence of other effects. Note that one embodiment of the invention does not necessarily require all of the above-described effects. Note that effects other than those described above can be understood and extracted from the description, drawings, claims, etc. Attached Figure Description

[0041] Figure 1A and Figure 1B This is a diagram illustrating the structure of the light-emitting device according to the embodiment;

[0042] Figure 2A and Figure 2B This is a diagram illustrating the structure of the light-emitting device according to the embodiment;

[0043] Figure 3A and Figure 3B This is a diagram illustrating the structure of the light-emitting layer in a light-emitting device according to one embodiment of the present invention;

[0044] Figures 4A to 4D This is a schematic diagram illustrating energy transfer between compounds in the light-emitting layer of a light-emitting device included in one aspect of the present invention;

[0045] Figure 5 This is a graph showing the capacitance-voltage characteristics of measuring device 1;

[0046] Figure 6 This is a graph showing the current density-voltage characteristics of measuring device 1;

[0047] Figure 7A and Figure 7B This is a diagram illustrating the structure of the light-emitting device according to the embodiment;

[0048] Figure 8A and Figure 8B These are the top view and cross-sectional view of the light-emitting device;

[0049] Figure 9A and Figure 9B This is a perspective view showing an example of the structure of a display module;

[0050] Figure 10A and Figure 10BThis is a cross-sectional view showing an example of the structure of a display device;

[0051] Figure 11 This is a perspective view showing an example of the structure of a display device;

[0052] Figure 12 This is a cross-sectional view showing an example of the structure of a light-emitting device;

[0053] Figure 13 This is a cross-sectional view showing an example of the structure of a light-emitting device;

[0054] Figure 14 This is a cross-sectional view showing an example of the structure of a light-emitting device;

[0055] Figures 15A to 15D This is a diagram illustrating an example of an electronic device;

[0056] Figures 16A to 16F This is a diagram illustrating an example of an electronic device;

[0057] Figures 17A to 17G This is a diagram illustrating an example of an electronic device;

[0058] Figure 18 The graph shows the absorption and PL spectra of PtON-TBBI and 1,6mmtBuDPhAPrn.

[0059] Figure 19 It is a graph showing the luminance-current density characteristics of light-emitting device 1-1, light-emitting device 1-2, comparison light-emitting device 1-1, comparison light-emitting device 1-2 and comparison light-emitting device 1-3.

[0060] Figure 20 It is a diagram showing the brightness-voltage characteristics of light-emitting device 1-1, light-emitting device 1-2, comparison light-emitting device 1-1, comparison light-emitting device 1-2 and comparison light-emitting device 1-3.

[0061] Figure 21 It is a graph showing the current efficiency-current density characteristics of light-emitting device 1-1, light-emitting device 1-2, comparison light-emitting device 1-1, comparison light-emitting device 1-2 and comparison light-emitting device 1-3.

[0062] Figure 22 It is a graph showing the current density-voltage characteristics of light-emitting device 1-1, light-emitting device 1-2, comparison light-emitting device 1-1, comparison light-emitting device 1-2 and comparison light-emitting device 1-3.

[0063] Figure 23 This is a diagram showing the external quantum efficiency-current density characteristics of light-emitting device 1-1, light-emitting device 1-2, comparison light-emitting device 1-1, comparison light-emitting device 1-2, and comparison light-emitting device 1-3.

[0064] Figure 24 It is a graph showing the electroluminescence spectra of light-emitting device 1-1, light-emitting device 1-2, comparison light-emitting device 1-1, comparison light-emitting device 1-2 and comparison light-emitting device 1-3.

[0065] Figure 25 It is a graph showing the normalized brightness time variation characteristics of light-emitting device 1-1, light-emitting device 1-2, comparison light-emitting device 1-1, comparison light-emitting device 1-2 and comparison light-emitting device 1-3.

[0066] Figure 26 This is a diagram showing the LT90 time of light-emitting device 1-1, light-emitting device 1-2, comparison light-emitting device 1-1, comparison light-emitting device 1-2, and comparison light-emitting device 1-3.

[0067] Figure 27 This is a graph showing the light-emitting device 2 and comparing the brightness-current density characteristics of the light-emitting device 2.

[0068] Figure 28 This is a diagram showing the light-emitting device 2 and comparing the brightness-voltage characteristics of the light-emitting device 2.

[0069] Figure 29 This is a graph showing the light-emitting device 2 and comparing the current efficiency-current density characteristics of the light-emitting device 2.

[0070] Figure 30 This is a graph showing the light-emitting device 2 and comparing the current density-voltage characteristics of the light-emitting device 2.

[0071] Figure 31 This is a graph showing the light-emitting device 2 and the blue indicator-current density characteristics of the comparative light-emitting device 2.

[0072] Figure 32 This is a diagram showing the light-emitting device 2 and comparing the external quantum efficiency-current density characteristics of the light-emitting device 2.

[0073] Figure 33 This is a graph showing the electroluminescence spectrum of light-emitting device 2 and a comparison light-emitting device 2.

[0074] Figure 34 This is a diagram showing the light-emitting device 2 and a comparison diagram of the chromaticity of the light-emitting device 2.

[0075] Figure 35 This is a graph showing the light-emitting device 2 and comparing the normalized brightness time variation characteristics of the light-emitting device 2.

[0076] Figure 36 The graph shows the absorption and PL spectra of Pt(mmtBubOcz35dm4ppy-d6) and 1,6mmtBuDPhAPrn in solution.

[0077] Figure 37A and Figure 37B This is a graph showing the low-temperature PL measurement results of SiTrzCz2 and PSiCzCz.

[0078] Figure 38 This is a graph showing the PL spectra of thin films including SiTrzCz2 films, PSiCzCz films, and a 1:1 mixture of SiTrzCz2 and PSiCzCz films.

[0079] Figure 39 This is a graph showing the light-emitting device 3 and comparing the brightness-current density characteristics of the light-emitting device 3.

[0080] Figure 40 This is a diagram showing the light-emitting device 3 and comparing the brightness-voltage characteristics of the light-emitting device 3.

[0081] Figure 41 This is a graph showing the light-emitting device 3 and comparing the current efficiency-current density characteristics of the light-emitting device 3.

[0082] Figure 42 This is a graph showing the light-emitting device 3 and comparing the current density-voltage characteristics of the light-emitting device 3.

[0083] Figure 43 This is a graph showing the light-emitting device 3 and the blue indicator-current density characteristics of the comparative light-emitting device 3.

[0084] Figure 44 This is a diagram showing the light-emitting device 3 and comparing the external quantum efficiency-current density characteristics of the light-emitting device 3.

[0085] Figure 45 This is a graph showing the electroluminescence spectrum of light-emitting device 3 and a comparison of light-emitting device 3.

[0086] Figure 46 This is a graph showing the light-emitting device 3 and comparing the normalized brightness time variation characteristics of the light-emitting device 3.

[0087] Figure 47A and Figure 47B This is a graph showing the low-temperature PL measurement results of SiTrzCz2-d16 and PSiCzCz-d15.

[0088] Figure 48 This is a graph showing the PL spectra of the films of SiTrzCz2-d16, PSiCzCz-d15, and a 1:1 mixture of SiTrzCz2-d16 and PSiCzCz-d15.

[0089] Figure 49This is a graph showing the results of measuring the transient EL characteristics of light-emitting device 1-1 and comparing light-emitting device 1-3. Detailed Implementation

[0090] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the contents described below, and its methods and details can be varied in various forms without departing from the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited only to the contents described in the embodiments shown below.

[0091] Furthermore, for ease of understanding, the positions, sizes, and extents of various structures shown in the accompanying drawings, etc., do not necessarily represent their actual positions, sizes, and extents. Therefore, the disclosed invention is not necessarily limited to the positions, sizes, and extents disclosed in the accompanying drawings, etc.

[0092] In this specification, ordinal numbers such as "first" and "second" are used for convenience, but they do not limit the number of constituent elements or their order. The order of constituent elements may include, for example, a process sequence or a stacking sequence. That is, the ordinal numbers used in the embodiments of this specification may differ from those used in the claims. Furthermore, the ordinal numbers used in the embodiments of this specification may differ from those used in the claims.

[0093] Furthermore, in this specification and the like, when the structure of the invention is described using the accompanying drawings, the same symbol is sometimes used in different drawings to show the same parts.

[0094] Furthermore, in this specification and other materials, the terms "film" and "layer" may be interchanged. For example, "conductive layer" may sometimes be replaced with "conductive film." Or, for example, "insulating film" may sometimes be replaced with "insulating layer."

[0095] Note that in this specification, photoluminescence (PL) spectroscopy refers to the spectrum obtained by fixing the excitation wavelength of the excitation light in fluorescence spectrophotometry and separating the light emitted by the sample irradiated by the excitation light according to each wavelength to measure the distribution of the luminescence intensity at each wavelength. It is sometimes also called emission spectrum. Note that emission spectrum sometimes includes fluorescent and phosphorescent components. In this specification, emission spectra consisting of fluorescent components are sometimes specifically referred to as fluorescence spectra, and emission spectra consisting of phosphorescent components are particularly referred to as phosphorescent spectra.

[0096] Implementation Method 1

[0097] In this embodiment, refer to Figure 1A and Figure 1BThe present invention describes a light-emitting device 10A of one embodiment of the present invention and a light-emitting device 10B of another embodiment of the present invention.

[0098] like Figure 1A and Figure 1B As shown, both light-emitting devices 10A and 10B are located on substrate 1000. Both light-emitting devices 10A and 10B include a first electrode 101 located on an insulating surface, a second electrode 102 opposite to the first electrode 101, and an EL layer 103 located between the first electrode 101 and the second electrode 102. Furthermore, as... Figure 1A and Figure 1B As shown, the EL layer 103 includes 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 one of the first electrode 101 and the second electrode 102 to the light-emitting layer 113. Note that the first electron transport layer 114_1 is located between the first electrode 101 and the second electron transport layer 114_2.

[0099] In addition, such as Figure 1A and Figure 1B As shown, in light-emitting devices 10A and 10B, a first electrode 101 is formed on a substrate 1000. The first electrode 101 can be disposed between the second electrode 102 and the substrate 1000. That is, the first electrode 101 is the electrode disposed before the second electrode 102. When a transistor is disposed on the substrate 1000, the first electrode 101 is electrically connected to the transistor via wiring. Alternatively, the first electrode 101 is disposed on an insulating layer on which an external connection electrode is disposed, which is used as a terminal for disposing of an FPC, etc. Alternatively, the end of the first electrode 101 is covered by an insulating film.

[0100] Figure 1A The light-emitting device 10A shown is Figure 1B The difference in the light-emitting device 10B shown lies in the different functions of the first electrode 101 and the second electrode 102. In the light-emitting device 10A, the first electrode 101 is used as the anode, and the second electrode 102 is used as the cathode. In this specification, etc., a light-emitting device, like the light-emitting device 10A, in which the first electrode disposed on one side of the substrate is used as the anode, is sometimes referred to as a positively oriented light-emitting device. On the other hand, in the light-emitting device 10B, the first electrode 101 is used as the cathode, and the second electrode 102 is used as the anode. In this specification, etc., a light-emitting device, like the light-emitting device 10B, in which the first electrode disposed on one side of the substrate is used as the cathode, is sometimes referred to as an inverted light-emitting device.

[0101] Holes injected from the first electrode 101 of the anode into the EL layer 103 and transported by the hole transport layer 112, and electrons injected from the second electrode 102 of the cathode into the EL layer 103 and transported by the electron transport layer 114, recombine in the light-emitting layer 113, thereby causing the upright light-emitting device 10A to emit light. 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.

[0102] Electrons injected into the EL layer 103 from the first electrode 101 (serving as the cathode) and transported by the electron transport layer 114, and holes injected into the EL layer 103 from the second electrode 102 (serving as the anode) and transported by the hole transport layer 112, recombine in the light-emitting layer 113, thereby causing the inverted light-emitting device 10B to emit 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.

[0103] In light-emitting devices 10A and 10B, the electron transport layer has a stacked structure (a stack of the first electron transport layer 114_1 and the second electron transport layer 114_2). Furthermore, the hole transport layer 112 can be a single-layer structure or a stacked structure. Note that sometimes the first electron transport layer 114_1 and the second electron transport layer 114_2 are collectively referred to as electron transport layer 114.

[0104] Furthermore, light-emitting devices 10A and 10B preferably include a hole transport layer 112 between the anode and the light-emitting layer 113, and more preferably include a hole injection layer 111 between the anode and the hole transport layer 112. Furthermore, light-emitting devices 10A and 10B more preferably include an electron injection layer 115 between the cathode and the electron transport layer 114.

[0105] Figure 1A The upright light-emitting device 10A shown 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 serving as a cathode are sequentially stacked on a first electrode 101 serving as an anode. Furthermore, Figure 1B The inverted light-emitting device 10B shown 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 serving as an anode are sequentially stacked on a first electrode 101 serving as a cathode.

[0106] Note that the structures of light-emitting devices 10A and 10B are not limited to... Figure 1A and Figure 1BThe structure shown is an example. For instance, a structure with two hole transport layers, or a structure with one or both of the hole transport layers and electron transport layers having three or more layers, can also be used.

[0107] In light-emitting devices 10A and 10B, which contain a material capable of converting triple excitation energy into light emission and a fluorescent light-emitting material in the light-emitting layer and have a stacked structure in the electron transport layer, the inventors have discovered that by selecting the materials for each layer considering the tilt of the giant surface potential (GSP) of the electron transport layer, the reliability of light-emitting devices 10A and 10B can be improved.

[0108] In other words, in a light-emitting device containing a substance capable of converting triple excitation energy into light emission and a fluorescent light-emitting substance in the light-emitting layer, when the electron transport layer has a stacked structure of a first electron transport layer 114_1 formed first and a second electron transport layer 114_2 formed later, the light-emitting device with a GSP slope (GSP_Slope (mV / nm)) of the second electron transport layer 114_2 being greater than that of the first electron transport layer 114_1 can be a light-emitting device with good reliability.

[0109] Alternatively, in a light-emitting device that includes a substance capable of converting triple excitation energy into light emission and a fluorescent light-emitting substance in the light-emitting layer, when the electron transport layer has a stacked structure of a first electron transport layer 114_1 formed first and a second electron transport layer 114_2 formed subsequently, the light-emitting device with a higher GSP slope (GSP_Slope (mV / nm)) of the film composed of an organic compound with a π-electron-deficient heteroaromatic ring included in the second electron transport layer 114_2 than the GSP_Slope of the film composed of an organic compound with a π-electron-deficient heteroaromatic ring included in the first electron transport layer 114_1 can be a light-emitting device with good reliability.

[0110] Here, GSP is a phenomenon caused by spontaneous polarization (SOP) resulting from the orientation of the permanent electric dipole moment of the vapor-deposited film concentrated in the thickness direction.

[0111] The surface potential of vapor-deposited films exhibiting GSP changes proportionally and in an unsaturated manner with increasing thickness. For example, the surface potential of a vapor-deposited film of tris(8-hydroxyquinoline) aluminum (Alq3) reaches approximately 28V at a thickness of 560nm. Its electric field strength reaches 5×10⁻⁶. 5 V / cm, which is roughly equivalent to the electric field strength when driving a typical light-emitting device.

[0112] The slope of a gas-phase (GSP) is expressed as ΔV / Δd, where ΔV (mV) is the change in surface potential in a film where the GSP varies proportionally to the thickness, with respect to a change in thickness Δd (nm). Furthermore, a positive GSP slope occurs when the surface potential increases with increasing thickness, and a negative GSP slope occurs when the surface potential decreases with increasing thickness. Alq3 described above can be considered a material with a positive GSP slope. Additionally, in layers with a positive GSP slope, the potential on the substrate side is low, and in layers with a negative GSP slope, the potential on the substrate side is high.

[0113] As described above, the GSP (Gravity Spread) is a phenomenon caused by the SOP (Slope of Orientation) resulting from the concentration of the permanent electric dipole moment along the thickness direction. That is, in a layer with a positive GSP_Slope, it can be considered that a negative polarization charge is generated on the substrate side of the layer, and a positive polarization charge is generated on the second electrode side. Similarly, in a layer with a negative GSP_Slope, it can be considered that a positive polarization charge is generated on the substrate side of the layer, and a negative polarization charge is generated on the second electrode side. This polarization charge induction is the source of the GSP. Note that in... Figure 1A and Figure 1B In this context, σ+ and σ- represent the spontaneous polarization (SOP) resulting from the orientation of the permanent electric dipole moments of each layer deposited by vapor deposition concentrated along the thickness direction. σ+ represents positive polarization, and σ- represents negative polarization. Furthermore, the greater the number of σ values ​​near the interfaces of each layer, the greater the spontaneous polarization.

[0114] Most vapor-deposited films of organic compounds have a positive GSP_Slope. In this case, when a second layer is deposited in contact with the first layer, the GSP_Slope of both the first and second layers becomes positive. This can be considered as the generation of negative polarization charge on the substrate side of each layer and positive polarization charge on the second electrode side. At this time, the negative polarization charge on the first layer side of the second layer cancels out the positive polarization charge on the second layer side of the first layer. Therefore, only the remaining charge can be regarded as the interface charge (fixed charge) at the interface between the first and second layers. Note that in this specification, the virtual charge that can be regarded as the interface charge is sometimes referred to as the interface charge.

[0115] Figure 1A This shows a positively positioned light-emitting device 10A. Figure 1BAn inverted light-emitting device 10B is shown. The electron transport layer 114 of this light-emitting device has a stacked structure of a first electron transport layer 114_1 and a second electron transport layer 114_2. Furthermore, the light-emitting layer of this light-emitting device contains a material capable of converting a triple excitation energy into light emission and a fluorescent light-emitting material. Note that the second electron transport layer 114_2 is closer to the second electrode 102 than the first electron transport layer 114_1. In one embodiment of the light-emitting device of the present invention, the GSP_Slope of the second electron transport layer 114_2 is preferably larger than the GSP_Slope of the first electron transport layer 114_1. Alternatively, in one embodiment of the light-emitting device of the present invention, 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 preferably 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.

[0116] In one embodiment of the light-emitting device of the present invention having this structure, a negative interface charge is generated at the interface between the second electron transport layer 114_2 and the first electron transport layer 114_1, thus the injection of electrons from the second electrode 102 or the electron injection layer 115 into the second electron transport layer 114_2 ( Figure 1A When upright) or the injection of electrons from the first electrode 101 or the electron injection layer 115 to the first electron transport layer 114_1 (when upright) Figure 1B When inverted, this is suppressed. Therefore, it prevents the light-emitting layer 113 from becoming over-electron, reduces the bias of the light-emitting layer 113 in the recombination region towards the hole transport layer 112, and thus reduces the degradation of the light-emitting layer 113 and the hole transport layer 112 (or electron blocking layer). Therefore, one embodiment of the light-emitting device of the present invention can be a highly reliable light-emitting device.

[0117] Note that in Figure 1A In the positive-position light-emitting device 10A, the second electron transport layer 114_2 may contain a first substance in addition to the second organic compound. The first substance is preferably an organic complex containing a metal complex, particularly an organic complex containing an alkali metal. Specifically, 8-hydroxyquinoline-lithium (Liq), 8-hydroxyquinoline-sodium (Naq), 8-hydroxyquinoline-potassium (Kq), and their derivatives can be used as organic complexes containing alkali metals. When the second electron transport layer 114_2 contains such a substance, the electron transport properties in the second electron transport layer 114_2 can be controlled. Furthermore, by suppressing the light-emitting layer 113 in the recombination region from being biased towards the hole transport layer 112, the reliability of the light-emitting device can be improved.

[0118] Note that, at this point, when 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, the GSP_Slope (mV / nm) of the second organic compound film is preferably greater than (x+y) / x times the GSP_Slope (mV / nm) of the first organic compound film. By employing this structure, even when the GSP_Slope of the first substance film is smaller than the GSP_Slope of the second organic compound film, the GSP_Slope (mV / nm) of the second electron transport layer 114_2 is greater than that of the first electron transport layer 114_1, thereby generating a negative interface charge and suppressing electron injection, which is therefore preferred. Furthermore, when y is greater than x, the ratio of the second organic compound performing electron transport decreases, and electron transport performance declines, which is also preferred.

[0119] In addition, Figure 1B In the inverted light-emitting device 10B, 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, the electron transport properties in the first electron transport layer 114_1 can be controlled. Furthermore, by suppressing the light-emitting layer 113 in the recombination region from being biased towards the hole transport layer 112, the reliability of the light-emitting device can be improved.

[0120] Here, as described above, the light-emitting layer 113 preferably has the following structure: it includes at least a substance capable of converting triple excitation energy into light emission and a fluorescent light-emitting substance, wherein the fluorescent light-emitting substance emits light. Furthermore, the fluorescent light-emitting substance preferably has the following structure: the substance capable of converting triple excitation energy into light emission is used as an energy donor, and the fluorescent light-emitting substance emits light. Note that the light-emitting layer 113 preferably also includes a host material.

[0121] When the light-emitting layer has the above structure, the light-emitting device of one aspect of the present invention can be a light-emitting device with further improved reliability.

[0122] The structure of the light-emitting layer 113 included in a light-emitting device according to one aspect of the present invention will be described in detail below. Figure 3A and Figure 3B yes Figures 1A to 2B The example shown is a cross-sectional schematic diagram of the light-emitting layer 113. Figure 3A The luminescent layer 113 shown includes compounds 131, 132, 133 and 134. Figure 3BThe luminescent layer 113 shown comprises compounds 131, 133, and 134. Note that compounds 131 and 132 are both substances used as host materials. Furthermore, compound 133 is a substance capable of converting triple excitation energy into luminescence. Furthermore, compound 134 is a fluorescent luminescent substance. Moreover, the luminescent layer 113 can receive luminescence derived from the fluorescent luminescent substance compound 134.

[0123] <Example 1 of the structure of the light-emitting layer>

[0124] First, let's illustrate a specific structural example 1 of the light-emitting layer 113. In this structural example, as shown... Figure 3A As shown, the luminescent layer 113 comprises compounds 131, 132, 133, and 134. Furthermore, in this structural example, the case where compound 133, which is capable of converting the triple excitation energy into luminescence, is a phosphorescent material will be described. The phosphorescent material preferably contains heavy atoms such as Ir, Pt, Os, Ru, and Pd, and is more preferably an organometallic complex containing any number of these heavy atoms.

[0125] Figure 4A An example of energy level correlation in the emitting layer 113 of this structure is shown. The following are examples. Figure 4A Markers and symbols in the text.

[0126] •Comp (131): Compound 131

[0127] •Comp (132): Compound 132

[0128] •Comp (133): Compound 133

[0129] •Guest (134): Compound 134

[0130] •S C1 S1 energy level of compound 131

[0131] •T C1 T1 energy level of compound 131

[0132] •S C2 S1 energy level of compound 132

[0133] •T C2 T1 energy level of compound 132

[0134] •S E S1 energy level of excitocomplex

[0135] •T E T1 energy level of excitocomplex

[0136] •T C3T1 energy level of compound 133

[0137] •S G S1 energy level of compound 134

[0138] •T G T1 energy level of compound 134

[0139] The combination of compounds 131 and 132, used as host materials respectively, is preferably a combination capable of forming an exciplex. More preferably, one of them is a hole-transporting compound and the other is an electron-transporting compound. In this case, donor-acceptor type exciplexes are easily formed, and exciplexes can be formed efficiently. Furthermore, when the combination of compounds 131 and 132 is a combination of a hole-transporting compound and an electron-transporting compound, carrier balance can be easily controlled according to its mixing ratio. Specifically, this mixing ratio is preferably in the range of 1:9 to 9:1 (weight ratio) of the hole-transporting compound to the electron-transporting compound. Moreover, by having this structure, carrier balance can be easily controlled, thereby also allowing for easy control of the carrier recombination region.

[0140] As compounds with hole transport capabilities, more specifically, compounds having one or both of a π-electron-rich heteroaromatic ring and an aromatic amine skeleton can be cited; as compounds with electron transport capabilities, more specifically, compounds having a π-electron-deficient heteroaromatic ring can be cited.

[0141] Furthermore, as a combination of host materials for efficiently forming excitocomplexes, it is preferable that, in compounds 131 and 132, the HOMO energy level of one is higher than that of the other, and the LUMO energy level of one is higher than that of the other. Alternatively, the HOMO energy level of compound 131 may be equal to that of compound 132, or the LUMO energy level of compound 131 may be equal to that of compound 132.

[0142] Note that the LUMO and HOMO energy levels of a compound can be determined from the compound's electrochemical properties (reduction potential and oxidation potential) measured by methods such as cyclic voltammetry (CV).

[0143] like Figure 4A As shown, the S1 energy level (S1) of the excitocomplex formed by compounds 131 and 132 E The T1 energy level (T) of the excitocomplex E ) becomes an adjacent energy level (refer to Figure 4A (path A1 in the path).

[0144] The excitation energy level (S) of the excitocomplex formed by compounds 131 and 132 E and T E The S1 energy level (S1) of the substances (compounds 131 and 132) that form the excitocomplex is compared to that of the other substances. C1 and S C2 The energy level is low, so the excited state can be formed with a lower excitation energy. Therefore, the driving voltage of the light-emitting device can be reduced.

[0145] Note that the energy level correlation between compounds 131 and 132 is not limited to... Figure 4A In other words, the singlet excitation level (S) of compound 131 C1 It can also be higher or lower than the singlet excitation energy level (S) of compound 132. C2 Additionally, the triplet excitation level (T) of compound 131 C1 It can also be higher or lower than the triple excitation energy level (T) of compound 132. C2 ).

[0146] Because compound 133 is a phosphorescent material, both the singlet and triplet excitation energies originate from the S1 energy level (S1) of the excitocomplex formed by compounds 131 and 132. E ) and the T1 energy level (T) of the excitocomplex E It rapidly transitions to the T1 energy level (T1) of compound 133. C3 (Path A2). At this point, it is preferable to satisfy T. E ≥T C3 In pathway A2, the excitokinetic complex is used as an energy donor, and compound 133 is used as an energy acceptor. Furthermore, at this point, the triplet excitation level (T0) of compound 131... C1 ) and the triplet excitation level (T) of compound 132 C2 Preferably, the T1 energy level is higher than that of compound 133 (T C3 More specifically, the energy of the extrapolated wavelength obtained by drawing a tangent at the tail of the short-wavelength side of the phosphorescence spectrum of compound 131 is set to T. C1 The energy of the extrapolated wavelength obtained by drawing a tangent at the tail of the short wavelength side of the phosphorescence spectrum of compound 132 is set as T. C2 Furthermore, the energy of the extrapolated wavelength obtained by drawing a tangent at the tail of the short wavelength side of the emission spectrum (phosphorescence spectrum) of compound 133 is set to T. C3 In this case, it is preferable to satisfy T. C1 ≥T C3 And preferably satisfying T C2 ≥T C3In other words, preferably, the emitting ends of the phosphorescence spectrum of compound 131 and compound 132 are at shorter wavelengths than the emitting ends of the emission spectrum (phosphorescence spectrum) of compound 133.

[0147] The triple excitation energy of compound 133 is converted into the single excitation energy of compound 134, which is a fluorescent luminescent substance (paths A3 and A4). At this time, as... Figure 4A As shown, in T E ≥T C3 ≥S G In this case, energy is efficiently transferred from compound 133 to compound 134, which is therefore preferred. More specifically, it is preferred to draw a tangent at the tail of the short-wavelength side of the phosphorescence spectrum of compound 133, and set the energy of the wavelength of this extrapolated line to T. C3 The energy of the wavelength at the absorption end of the absorption spectrum of compound 134 is set to S. G At this time, T is satisfied. C3 ≥S G That is, preferably, the absorption end on the longer wavelength side of the absorption spectrum of compound 134 is at a longer wavelength compared to the emission end on the shorter wavelength side of the emission spectrum (phosphorescence spectrum) of compound 133. Note that in paths A3 and A4, compound 133 is used as an energy donor and compound 134 is used as an energy acceptor. Alternatively, preferably, the energy at the wavelength of the absorption end of the absorption spectrum of compound 133 is set to T. C3 The energy of the wavelength at the absorption end of the absorption spectrum of compound 134 is set to S. G At this time, T is satisfied. C3 ≥S G In other words, preferably, the absorption end on the longer wavelength side of the absorption spectrum of compound 134 is at a longer wavelength compared to the absorption end on the longer wavelength side of the absorption spectrum of compound 133.

[0148] Here, because compound 134 is a fluorescent material, the energy transfer from the triplet excitation energy of compound 133 to T... G The excitation energy (the energy transferred along path A4) does not contribute to luminescence. Therefore, when energy transfer occurs along path A4, the luminous efficiency of the light-emitting device decreases.

[0149] Generally, the Foster mechanism (dipole-dipole interaction) and the Dexter mechanism (electron exchange interaction) are known as intermolecular energy transfer mechanisms. Because the energy acceptor compound 134 is a fluorescent material, pathway A3 is generated in the Foster-based energy transfer, while both pathways A3 and A4 are generated in the Dexter-based energy transfer. To suppress the non-radiative inactivation pathway A4, it is effective to suppress the Dexter-based energy transfer.

[0150] When the distance between the compound acting as the energy donor and the compound acting as the energy acceptor is less than 1 nm, energy transfer based on the Dexter mechanism is dominant. Therefore, in order to suppress energy transfer via path A4, the distance between the energy donor (compound 133) and the energy acceptor (compound 134) is increased to a level that does not easily induce energy transfer based on the Dexter mechanism.

[0151] As a general method to increase the distance between the energy donor and the energy acceptor, reducing the concentration of the energy acceptor in the mixing membrane is known. However, when the concentration of the energy acceptor is reduced, energy transfer based on the Foster mechanism is also suppressed, in addition to the energy transfer from the energy donor to the energy acceptor based on the Dexter mechanism. In this case, problems such as reduced luminous efficiency or reduced reliability of the light-emitting device occur.

[0152] Here, the T1 energy level (T1) of compound 134, which acts as an energy acceptor, is... G Most of the energy transfer originates from the energy levels of the luminescent material contained in compound 134. That is to say, energy transfer via path A4 can also be suppressed by increasing the distance between the luminescent material contained in compound 134 and compound 133.

[0153] Therefore, compound 134, as the energy acceptor, is preferably a compound that includes a luminescent body and a protecting group that functions to increase the distance between the luminescent body and other energy donors as part of the structure. Therefore, when this compound is used as compound 134 in this structure, even with an increased concentration of compound 134, the distance between compound 133 and compound 134 can be increased, thereby suppressing energy transfer based on the Dexter mechanism while increasing the energy transfer rate based on the Foster mechanism. Therefore, by using this compound as compound 134, the S1 energy level (S1) from compound 133 to compound 134 is... G The transfer of triple excitation energy (path A3) is easy to occur; on the other hand, the T1 energy level (T1) from compound 133 to compound 134 is more likely to occur. G The transfer of triple excitation energy (path A4: energy transfer based on the Dexter mechanism) is suppressed, thereby improving the luminous efficiency of the light-emitting device while suppressing the decrease in luminous efficiency associated with energy transfer along path A4. Furthermore, the reliability of the light-emitting device can be improved.

[0154] Furthermore, as mentioned above, the Dexter mechanism is dominant when the distance between the energy donor and the energy acceptor is less than 1 nm, and the Foster mechanism is dominant when the distance between the energy donor and the energy acceptor is more than 1 nm but less than 10 nm. Therefore, the protecting group is preferably a large substituent that extends within a range of more than 1 nm but less than 10 nm from the emitting element of compound 134.

[0155] Furthermore, in this structural example, by increasing the concentration of compound 134, which acts as the energy acceptor, the energy transfer rate based on the Foster mechanism can be increased while suppressing energy transfer based on the Dexter mechanism. By increasing the energy transfer rate based on the Foster mechanism, the excitation lifetime of the energy acceptor in the light-emitting layer is shortened, thus improving the reliability of the light-emitting device. Specifically, the weight concentration of compound 134 in the light-emitting layer 113 relative to compound 133, which acts as the energy donor, is preferably 2 wt% or more and 50 wt% or less, more preferably 5 wt% or more and 30 wt% or less, and even more preferably 5 wt% or more and 20 wt% or less. Alternatively, the volume concentration of compound 134 in the light-emitting layer 113 relative to compound 133, which acts as the energy donor, is preferably 2 vol% or more and 50 vol% or less, more preferably 5 vol% or more and 30 vol% or less, and even more preferably 5 vol% or more and 20 vol% or less.

[0156] <Example 2 of the structure of the light-emitting layer>

[0157] Next, a specific structural example 2 of the light-emitting layer 113 will be described. In this structural example, as shown... Figure 3A As shown, the luminescent layer 113 comprises compounds 131, 132, 133, and 134. Furthermore, in this structural example, compound 133, which is capable of converting triple excitation energy into luminescence, is a phosphorescent material, and compound 134, which is a fluorescent material, is a thermally activated delayed fluorescence (TADF) material. TADF materials are materials capable of converting both single and triple excitation energies into luminescence. Figure 4B An example of energy level correlation in the emitting layer 113 of this structural example is shown. Note that... Figure 4B The tags, symbols, path A1 and path A2 in the text Figure 4A Since they are the same, their description is omitted.

[0158] go through Figure 4BThe triple excitation energy transferred from the excitocomplex formed by compounds 131 and 132 to compound 133 via path A2 is converted into the single excitation energy of compound 134, which is a TADF material (path A5). At this point, as... Figure 4B As shown, in T E ≥T C3 ≥S G In this case, energy is efficiently transferred from compound 133 to compound 134, which is therefore preferred. More specifically, it is preferred to draw a tangent at the tail of the short-wavelength side of the phosphorescence spectrum of compound 133, and set the energy of the wavelength of this extrapolated line to T. C3 The energy of the wavelength at the absorption end of the absorption spectrum of compound 134 is set to S. G At this time, T is satisfied. C3 ≥S G .

[0159] Furthermore, in the light-emitting layer 113 of the light-emitting device shown in this structural example, in addition to the above, the triple excitation energy of compound 133 is transferred to the T1 energy level of compound 134 ( Figure 4B (Path A6 in the diagram). In this structural example, because compound 134 is a TADF material, it has the ability to convert the triplet excitation energy into a singlet excitation energy via upconversion. Therefore, the triplet excitation energy converted via path A6 is converted into a singlet excitation energy via upconversion (…). Figure 4B In pathway A7), compound 134 exhibits thermally activated delayed fluorescence. Therefore, compound 134 can efficiently emit light from the singlet excited state, thereby improving the luminous efficiency of the light-emitting device. In pathways A5 and A6, compound 133 is used as an energy donor, and compound 134 is used as an energy acceptor.

[0160] In structural examples 1 and 2, the light-emitting layer 113 is shown to comprise four compounds (compound 131, compound 132, compound 133, and compound 134), but one aspect of the invention is not limited thereto. In structural examples 3 and 4 below, the light-emitting layer 113 is illustrated to comprise three compounds (compound 131, compound 133, and compound 134).

[0161] <Example 3 of the structure of the light-emitting layer>

[0162] Example 3 illustrates the specific structure of the light-emitting layer 113. In this structural example, as shown... Figure 3B As shown, the luminescent layer 113 comprises compound 131, compound 133, and compound 134. Furthermore, in this structural example, compound 133, which is capable of converting triple excitation energy into luminescence, is a phosphorescent material, and compound 134 is a fluorescent material. Figure 4CAn example of energy level correlation in the emitting layer 113 of this structure is shown. The following are examples. Figure 4C Markers and symbols in the text.

[0163] •Comp (131): Compound 131

[0164] •Comp (133): Compound 133

[0165] •Guest (134): Compound 134

[0166] •S C1 S1 energy level of compound 131

[0167] •T C1 T1 energy level of compound 131

[0168] •T C3 T1 energy level of compound 133

[0169] •T G T1 energy level of compound 134

[0170] •S G S1 energy level of compound 134

[0171] In this structural example, because carrier recombination mainly occurs in compound 131, both singlet and triplet excitons are generated. By selecting compounds 133 with T... C3 ≤T C1 The phosphorescent material in the compound 133 can transfer both the singlet and triplet excitation energies generated in compound 131 to the T0 of compound 133. C3 energy level( Figure 4C Path A in 18 Note that some charge carriers may recombine in compound 133.

[0172] The triple excitation energy of compound 133 is converted into the excitation energy of compound 134, which is a fluorescent luminescent substance (path A). 19 and path A 20 At this time, such as Figure 4C As shown, in T C3 ≥S G In this case, energy is efficiently transferred from compound 133 to compound 134, which is therefore preferred. More specifically, it is preferred to draw a tangent at the tail of the short-wavelength side of the phosphorescence spectrum of compound 133, and set the energy of the wavelength of this extrapolated line to T. C3 The energy of the wavelength at the absorption end of the absorption spectrum of compound 134 is set to S. G At this time, T is satisfied. C3 ≥SG In path A 19 and path A 20 In this study, compound 133 was used as an energy donor and compound 134 was used as an energy acceptor.

[0173] Here, because compound 134 is a fluorescent material, the energy transfer from the triplet excitation energy of compound 133 to T... G Excitation energy (in path A) 20 The transferred energy does not contribute to luminescence. Therefore, when path A occurs... 20 When energy is transferred, the luminous efficiency of the light-emitting device decreases.

[0174] To suppress this energy transfer (path A) 20 As illustrated in structural example 1 above, it is important that the distance between compounds 133 and 134, i.e., the distance between the luminescent bodies contained in compounds 133 and 134, is relatively long. Therefore, compound 134, as the energy acceptor, is preferably a compound that includes, as part of the structure, a luminescent body and a protecting group that functions to increase the distance between the luminescent body and other energy donors. This allows for suppression of pathway A. 20 Energy transfer.

[0175] <Example 4 of the structure of the light-emitting layer>

[0176] like Figure 3B As shown, in this structural example, the light-emitting layer 113 in the light-emitting device comprises compound 131, compound 134, and compound 133. Note that the case shown is that compound 133, which is capable of converting triple excitation energy into light emission, is a TADF material. Figure 4D An example of energy level correlation in the emitting layer 113 of this structural example is shown. Note that... Figure 4D Marks and symbols in Figure 4C Similarly, other markings and symbols are shown below.

[0177] •S C3 S1 energy level of compound 133

[0178] In this structural example, because carrier recombination mainly occurs in compound 131, both singlet and triplet excitons are generated. By selecting compounds 133 with S... C3 ≤S C1 and T C3 ≤T C1 The TADF material, which relates to the relationship, can transfer both the singlet and triplet excitation energies generated in compound 131 to the S of compound 133. C3 and T C3 energy level( Figure 4D Path A in 21Note that some charge carriers may recombine in compound 133.

[0179] Because compound 133 is a TADF material, it has the function of converting triple excitation energy into single excitation energy through upconversion. Figure 4D Path A in 22 Furthermore, the singlet excitation energy of compound 133 can be rapidly transferred to compound 134 ( ). Figure 4D Path A in 23 At this point, it is preferable to satisfy S. C3 ≥S G More specifically, preferably, a tangent line is drawn at the tail of the short-wavelength side of the fluorescence spectrum of compound 133, and the energy of the wavelength of this extrapolated line is set to S. C3 The energy of the wavelength at the absorption end of the absorption spectrum of compound 134 is set to S. G At this time, S is satisfied. C3 ≥S G .

[0180] Therefore, in the light-emitting layer 113 of the light-emitting device shown in this structural example, through... Figure 4D Path A in 21 Path A 22 and path A 23 The pathway allows the triplet excitation energy generated in compound 133 to be converted into fluorescence emission of compound 134. In pathway A... 23 In this example, compound 133 is used as an energy donor, and compound 134 is used as an energy acceptor. However, in the light-emitting layer 113 of the light-emitting device shown in this structural example, in addition to the above, there is also a pathway for the triple excitation energy of compound 133 to transfer to the T1 energy level of compound 134 (…). Figure 4D Path A in 24 There will be competition between the two. During this energy transfer (path A)... 24 In the case of ), the triple excitation energy of compound 134, which is a fluorescent luminescent material, does not contribute to luminescence, thereby reducing the luminescence efficiency of the light-emitting device.

[0181] To suppress this energy transfer (path A) 24 As illustrated in structural example 1 above, it is important that the distance between compound 133 and compound 134, i.e. the distance between the luminescent bodies contained in compound 133 and compound 134, is relatively long.

[0182] A portion of the structure of a compound of one embodiment of the present invention contains a luminescent material and a protecting group. When the compound acts as an energy acceptor in the luminescent layer 113, the protecting group functions to increase the distance between other energy donors and the luminescent material. Therefore, when a compound of one embodiment of the present invention is used as compound 134 of this structure, even if the concentration of compound 134 increases, the distance between compound 133 and compound 134 can be increased, thereby suppressing energy transfer based on the Dexter mechanism while increasing the energy transfer rate based on the Foster mechanism. Therefore, by using a compound of one embodiment of the present invention as compound 134, the S1 energy level (S1) from compound 133 to compound 134 is... G The transfer of triple excitation energy (path A) 23 This is likely to occur, on the other hand, the T1 energy level (T1) from compound 133 to compound 134 is prone to occur. G The transfer of triple excitation energy (path A) 24 Energy transfer based on the Dexter mechanism is suppressed, thereby enabling the suppression of the associated pathway A. 24 While reducing the energy transfer efficiency, this method can improve the luminous efficiency of the light-emitting device. Additionally, it can enhance the reliability of the light-emitting device.

[0183] In path A2 of structural examples 1 and 2 of the light-emitting layer described above, the excitocomplex formed by compounds 131 and 132 is used as an energy donor. In path A3 of structural example 1 and paths A5 and A6 of structural example 2, compound 133 is used as an energy donor, thereby obtaining a highly efficient light-emitting device. Furthermore, in path A of structural example 3 of the light-emitting layer… 18 Compound 131 is used as an energy donor in pathway A. 19 Compound 133 is used as an energy donor, thereby enabling the acquisition of highly efficient light-emitting devices. Furthermore, in path A of the structure of example 4 of the light-emitting layer... 21 Compound 131 is used as an energy donor in pathway A. 23 Compound 133 is used as an energy donor, thereby enabling the production of highly efficient light-emitting devices.

[0184] Preferably, at least one, any two, and most preferably all of the compounds 131, 132, and 133 used as energy donors in the light-emitting layer contain deuterium. This is because the bond dissociation energy of the carbon-deuterium bond is greater than that of the carbon-protium bond, making it more stable and less prone to breakage. Therefore, compounds containing deuterium are more stable and less prone to degradation compared to non-deuterated compounds. When at least one, any two, and most preferably all of the compounds 131, 132, and 133 contain deuterium, the stability of the compound can be improved, thus suppressing the degradation of the energy donor. Consequently, the energy transfer efficiency to compound 134 can be suppressed from decreasing over time, thereby improving the reliability of the light-emitting device.

[0185] Note that when compounds 131, 132 and 133 contain deuterium, each compound may contain both hydrogen and deuterium, or it may contain deuterium but not hydrogen.

[0186] Furthermore, in compounds 131 and 132, the entire molecule can also be deuterated, but it is preferable that the groups or framework with the lowest triplet excitation energy level are locally deuterated. Thus, compounds 131 and 132 can be obtained more inexpensively than deuterating the entire molecule.

[0187] Furthermore, in compound 133, the entire molecule can be deuterated, but it is preferable that the more easily cleaved groups are deuterated. For example, when at least one organometallic complex comprising an alkyl group such as methyl is used as a ligand in compound 133, the alkyl group is preferably deuterated. Thus, compound 133 can be obtained more inexpensively and the reliability of the light-emitting device can be improved compared to deuterating the entire molecule.

[0188] In this specification, "containing deuterium" means that the proportion of deuterium in the hydrogen and deuterium contained in a compound significantly exceeds the naturally occurring proportion of deuterium, specifically by more than 500 times. "Deuterated compound" refers to a compound in which the proportion of deuterium in the hydrogen and deuterium contained in the compound significantly exceeds the naturally occurring proportion of deuterium, specifically by more than 500 times. Furthermore, this proportion is not relative to a single molecule but rather the average value of multiple target compounds existing in a certain region.

[0189] More preferably, in the above structure, compound 134, which serves as the energy acceptor in the light-emitting layer, also contains deuterium. As described above, compounds containing deuterium are more stable and less prone to degradation compared to non-deuterated compounds; therefore, the stability of compound 134 can be improved when it contains deuterium. Thus, when compound 134 contains deuterium, the decrease in luminous efficiency of the light-emitting device over time can be suppressed, thereby improving the reliability of the light-emitting device.

[0190] In compound 134, the entire molecule can be deuterated, but when using a deuterium-containing fluorescent material as compound 134, it is more preferable to use a fluorescent material with a deuterated protecting group. Compared to deuterating the entire molecule, compound 134 can be obtained more cheaply and the reliability of the light-emitting device can be improved. In particular, when the protecting group is an alkyl group with 3 or more but less than 10 carbon atoms, a substituted or unsubstituted cycloalkyl group with 3 or more but less than 10 carbon atoms, or a trialkylsilyl group with 3 or more but less than 10 carbon atoms, degradation starting from hydrogen in these groups can be suppressed.

[0191] Another reason for improving the reliability of the light-emitting device when at least one, preferably any two, and most preferably all of the compounds 131, 132, and 133 used as energy donors in the emitting layer contains deuterium is that the energy transfer efficiency is improved because the phosphorescence lifetime or delayed fluorescence lifetime of the deuterated compound is longer than that of the undeuterated compound. This is because the intramolecular vibrations in the lowest triplet excited state (T1 state) of the deuterated compound are suppressed compared to the intramolecular vibrations of the undeuterated compound, thus suppressing the nonradiative transfer from the T1 state to a more stable state.

[0192] Furthermore, when compounds 131 and 132 constitute an excitocomplex, a small energy difference between the T1 energy levels of compounds 131 and 132 makes it less likely for the excitation energy to deviate from either organic compound, preventing significant degradation of either compound and thus improving the reliability of the light-emitting device. Specifically, the energy difference between the T1 energy levels of compounds 131 and 132 is 0.20 eV or less, preferably 0.15 eV or less, and more preferably 0.10 eV or less.

[0193] In particular, when compounds 131 and 132 constitute an exciton complex and both compounds 131 and 132 contain deuterium, i.e., when the reliability is improved due to the extended lifetime of the suppressed triple exciton caused by vibrational suppression due to deuteration, one of the compounds is significantly degraded due to deviations in the excitation energy. Therefore, when compounds 131 and 132 constitute an exciton complex and both compounds 131 and 132 contain deuterium, the energy difference between the T1 energy level of compound 131 and the T1 energy level of compound 132 is 0.20 eV or less, preferably 0.15 eV or less, and more preferably 0.10 eV or less.

[0194] Here, organic EL devices require high efficiency and high reliability in blue light-emitting devices. This is because, among efficient phosphorescent light-emitting devices, blue phosphorescent light-emitting devices have lower reliability compared to other phosphorescent light-emitting devices. The structure of the light-emitting layer 113 described above in this light-emitting device is expected to enable the efficient and reliable blue light-emitting device.

[0195] In one aspect of the present invention, when the fluorescent luminescent material (compound 134) from which the luminescent material is obtained is set as a blue fluorescent material and the excitation energy available from the energy donor is considered to be used efficiently, the material (compound 133) that can be converted into luminescent material by the triple excitation energy of the energy donor is a material that exhibits blue luminescence, and is particularly preferred to be a material that exhibits blue phosphorescence.

[0196] On the other hand, when a blue phosphorescent material with a high excitation energy level is used in the light-emitting layer 113, the band gap of the host material increases, making it difficult to control the carrier balance. In many cases, the light-emitting layer 113 of a light-emitting device containing a blue phosphorescent material tends to have an excess of electrons. When the fluorescent material in the light-emitting layer 113, which contains the aforementioned material capable of converting triple excitation energy into light emission and a fluorescent material, is a blue phosphorescent material, the material capable of converting triple excitation energy into light emission is preferably a blue phosphorescent material. It can be said that the light-emitting device is difficult to control the carrier balance of the light-emitting layer 113 and tends to have an excess of electrons.

[0197] When the light-emitting layer 113 is in a state of excess electrons, recombination regions tend to form more easily on the anode side. As a result, the density of excitons generated after recombination also increases on the anode side, thus facilitating interactions between excitons and between excitons and holes in the electron blocking layer, easily generating excitons or holes with extremely high energy. Due to these high-energy excitons or holes, the degradation of the light-emitting layer 113 and the adjacent hole transport layer 112 or electron blocking layer is accelerated.

[0198] However, in one embodiment of the light-emitting device of the present invention, the electron injection can be controlled by making the GSP_Slope of the second electron transport layer greater than that of the first electron transport layer. Therefore, by applying this structure to a light-emitting device having a light-emitting layer 113 with the above structure, the light-emitting layer 113 can be suppressed from becoming an electron-overloaded state, thereby greatly improving the reliability.

[0199] Note that in the light-emitting layer 113, which includes the material capable of converting triple excitation energy into light emission and the fluorescent light-emitting material, the light-emitting layer 113 is more prone to having an excess of electrons when the HOMO energy level of the fluorescent light-emitting material is equal to or higher than the HOMO energy level of the material capable of converting triple excitation energy into light emission. When the light-emitting layer 113 has this structure, the light-emitting device of one aspect of the present invention can achieve a greater improvement in reliability.

[0200] Examples of substances capable of converting triplet excitation energy into luminescence include substances that emit activated delayed fluorescence (TADF) and phosphorescent substances. In this specification, phosphorescent substances refer to compounds that exhibit phosphorescence but not fluorescence at any temperature within a temperature range above low temperature (e.g., 77 K) and below room temperature (i.e., 77 K and above, and 313 K and below). Preferably, such phosphorescent substances contain a metallic element with a high spin-orbit interaction; specifically, transition metal elements are preferred, and platinum group elements (ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), or platinum (Pt)) are particularly preferred. Iridium or platinum is especially preferred, as it increases the probability of a direct transition between the singlet ground state and the triplet excited state.

[0201] As phosphorescent materials, specific examples of organic compounds exhibiting blue phosphorescence with emission peaks in the wavelength region above 450 nm and below 520 nm are shown below. Examples include (2-{3-[3-(3,5-di-tert-butylphenyl)benzimidazol-1-yl-2-ylidene-κC2]phenoxy-κC2}-9-[5-(methyl-d3)-4-phenyl-2-pyridyl-κN]carbazole-2,1-diyl-κC)platinum(II) (abbreviated as: Pt(mmtBubOcz5m4ppy-d3)) shown in structural formula (400) and (2-{3-[3-(3,5-di-tert-butylphenyl)benzimidazol-1-yl-2-ylidene-κC2]phenoxy-κC2}-9-(4-tert-butyl-2-pyridyl-κN)-6-(5-cyano-2-methylphenyl)) shown in structural formula (401). ) carbazole-2,1-diyl-κC) platinum (II) (abbreviation: Pt(mmtBubOm5CPcztBupy)), the structure of (402) {[9-(4-tert-butyl-2-pyridinyl-κN)-[3,9'-bi-9H-carbazole]-2,1-diyl-κC]oxy-9-(4-tert-butyl-2-pyridinyl-κN) carbazole-2,1-diyl-κC} platinum (II) (abbreviation: Pt(cztBucpyOtBucpy)), the structure of (403) {[9-(4-tert-butyl-2-pyridinyl-κN) carbazole-2,1-diyl-κC]oxy-9-(4-tert-butyl-2-pyridin ...N) carbazole-2,1-diyl-κC]oxy-9-(4-tert-butyl-2-pyridinyl-κN) carbazole-2,1-diyl-κC]oxy-9-(4-tert-butyl-2-pyridinyl-κN) carbazole-2,1-diyl-κC]oxy-9-(4-tert-butyl-2-pyridinyl-κN) carbazole-2,1-diyl-κC]oxy-9-(4-tert-butyl-2-pyridinyl-κN) carbazole- -κN)carbazole-2,1-diyl-κC}platinum(II) (abbreviated as: Pt(tBucpy2O)), as shown in structural formula (404) {[9-(2-pyridyl-κN)carbazole-2,1-diyl-κC]oxy-9-(2-pyridyl-κN)carbazole-2,1-diyl-κC}platinum(II) (abbreviated as: PtNON), as shown in structural formula (405) {2-{4-methyl-3-[3-(3,5-di-tert-butylphenyl)benzimidazol-1-yl-2-ylidene-κC2]phenoxy-κC2}-9-[3,5-di(methyl-d3)-4-phenyl-2-pyridyl-κN]carbazole-2,1-diyl-κC)platinum (II) (abbreviation: Pt(Me-mmtBubOcz35dm4ppy-d6)), the structure (406) showing {[3-(3,5-di-tert-butylphenyl)-9-(4-tert-butyl-2-pyridinyl-κN)carbazole-2,1-diyl-κC]oxy-9-(4-tert-butyl-2-pyridinyl-κN)carbazole-2,1-diyl-κC}platinum (II) (abbreviation: Pt(mmtBuptBucpyOtBucpy)), the structure (407) showing (2-{3-[3-(3,5-di-tert-butylphenyl)benzimidazol-1-yl-2-ylidene-κC2]phenoxy-κC2}-9-[3,5-Di(methyl-d3)-4-phenyl-2-pyridyl-κN]carbazole-2,1-diyl-κC)platinum(II) (abbreviated as: Pt(mmtBubOcz35dm4ppy-d6)), structural formula (408) as shown (2-{5-tert-butyl-3-[3-(3,5-di-tert-butylphenyl)benzimidazol-1-yl-2-ylide-κC2]phenoxy-κC2}-9-[3,5-di(methyl-d3)-4-phenyl-2-pyridyl-κN]carbazole-2,1-diyl-κC)platinum(II) (abbreviated as: Pt(tBu-mmtBubOcz35dm4ppy-d6)), structural formula (409) as shown {2-(3-{3-[2,6-di(phenyl-d5) [3,5-di(methyl-d3)-4-phenyl-2-pyridyl-κC2]phenoxy-κC2)-9-[3,5-di(methyl-d3)-4-phenyl-2-pyridyl-κN]carbazole-2,1-diyl-κC1]platinum(II) (abbreviated as: Pt(mTPbOcz35dm4ppy-d16)), and (2-{3-[3-(3,5-di-tert-butylphenyl)benzimidazole-1-yl-2-ylide-κC2]phenoxy-κC2}-9-[4-tert-butylphenyl-3,5-di(methyl-d3)-2-pyridyl-κN]carbazole-2,1-diyl-κC)platinum(II) (abbreviated as: Pt(mmtBubOcz35dm4tBuppy-d6)) shown in structural formula (410). In addition, examples include PtON1 shown in structural formula (411), PtON7 shown in structural formula (412), PtON1-Me shown in structural formula (413), PtON1-tBu shown in structural formula (414), PtON1-NMe2 shown in structural formula (415), PtON6-tBu shown in structural formula (416), PtON7-dtb shown in structural formula (417), PtN1N shown in structural formula (418), and PtN1N shown in structural formula (419). 19) PtN1pyCl, structural formula (420) PtON7-tBu, structural formula (421) Pt(ppzOczpy), structural formula (422) Pt(ppzOczpy-m), structural formula (423) Pt(ppzOczpy-2m), structural formula (424) PdN1N, structural formula (425) PdN1N-dm, structural formula (426) PdN6N, etc. In the above, when the phosphorescent material that serves as the energy donor includes any one of alkyl groups with 3 or more and 10 or less carbon atoms, substituted or unsubstituted cycloalkyl groups with 3 or more and 10 or less carbon atoms, and trialkylsilyl groups with 3 or more and 10 or less carbon atoms, the distance between the phosphorescent material and the fluorescent material that serves as the energy acceptor can be increased, so it is preferred. When using this phosphorescent material,Increasing the concentration of phosphorescent materials can lengthen the distance to fluorescent materials, thereby suppressing energy transfer based on the Dexter mechanism while increasing the rate of energy transfer based on the Foster mechanism.

[0202] [Chemical Formula 1]

[0203]

[0204] [Chemical Formula 2]

[0205]

[0206] [Chemical Formula 3]

[0207]

[0208] Alternatively, organometallic iridium compounds with a 4H-triazole skeleton, such as tris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-κN2]phenyl-κC}iridium(III) (abbreviated as [Ir(mpptz-dmp)3]) and tris(5-methyl-3,4-diphenyl-4H-1,2,4-triazol)iridium(III) (abbreviated as [Ir(Mptz)3]), can be used. Complexes; organometallic iridium complexes with a 1H-triazole skeleton, such as tris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazole]iridium(III) (abbreviated as [Ir(Mptz1-mp)3]) and tris(1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazole)iridium(III) (abbreviated as [Ir(Prptz1-Me)3]); fac-tris[1-(2,6-diisocyanate)[Ir(Ir(Prptz1-Me)3]] [Ir(iPrpim)3][3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-f]phenanthridinato]iridium(III)[Ir(dmpimpt-Me)3], [2-{1-[2,6-bis(1-methylethyl)phenyl]-1H-imidazo-2-yl-] Organometallic iridium complexes with an imidazole skeleton, such as κN3}-4-cyanophenyl-κC)iridium(III) (abbreviated as CNImIr); organometallic complexes with a benzimidazole skeleton, such as tris[(6-tert-butyl-3-phenyl-2H-imidazo[4,5-b]pyrazin-1-yl-κC2)phenyl-κC]iridium(III) (abbreviated as [Ir(cb)3]); and bis[2-(4',6'-difluorophenyl)pyridinium-N,C 2Iridium(III) tetra(1-pyrazolyl)borate (abbreviated as: FIr6), bis[2-(4',6'-difluorophenyl)pyridinium-N,C 2 '] Iridium(III) pyridine carboxylate (abbreviated as: FIRpic), bis{2-[3',5'-bis(trifluoromethyl)phenyl]pyridinium-N,C 2 Iridium(III)pyridinecarboxylate (abbreviated as: [Ir(CF3ppy)2(pic)]), bis[2-(4',6'-difluorophenyl)pyridinium-N,C 2 Organometallic iridium complexes such as iridium(III) acetylacetone (abbreviated as FIracac) with phenylpyridine derivatives having electron-withdrawing groups as ligands; and platinum complexes such as (2-{3-[3-(3,5-di-tert-butylphenyl)benzimidazol-1-yl-2-ylide-κC2]phenoxy-κC2}-9-(4-tert-butyl-2-pyridinyl-κN)carbazole-2,1-diyl-κC1)platinum(II) (abbreviated as PtON-TBBI).

[0209] In addition, the phosphorescent material described in Embodiment 2 can be used as the phosphorescent material.

[0210] Furthermore, TADF materials are an example of materials capable of converting triple excitation energy into luminescence. TADF materials are defined as materials with a small energy difference between the S1 and T1 levels that can convert triple excitation energy into single excitation energy through antisystem crossing. Therefore, they can upconvert triple excitation energy into single excitation energy (antisystem crossing) with minimal thermal energy and efficiently exhibit luminescence (fluorescence) from the single excited state. Exciplexes formed by two substances in an excited state possess the TADF material function due to the extremely small energy difference between the S1 and T1 levels.

[0211] As an indicator of the T1 energy level, the phosphorescence spectrum observed at low temperatures (e.g., 10 K) can be used. For TADF materials, it is preferable that the energy difference between the S1 and T1 energy levels is preferably less than 0.2 eV, where the energy of the extrapolated line obtained by tangenting at the tail of the short wavelength side of the fluorescence spectrum is the S1 energy level, and the energy of the extrapolated line obtained by tangenting at the tail of the short wavelength side of the phosphorescence spectrum is the T1 energy level.

[0212] Specific examples of TADF materials include 2-(biphenyl-4-yl)-4,6-bis(12-phenylindolo[2,3-a]carbazole-11-yl)-1,3,5-triazine (abbreviated as PIC-TRZ), 2-{4-[3-(N-phenyl-9H-carbazole-3-yl)-9H-carbazole-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviated as PCCzPTzn), and 2-[4-(10H-phenoxazine-10-yl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviated as PXZ-). TRZ), 3-[4-(5-phenyl-5,10-dihydrophenazin-10-yl)phenyl]-4,5-diphenyl-1,2,4-triazole (abbreviated as PPZ-3TPT), 3-(9,9-dimethyl-9H-acridin-10-yl)-9H-oxanthracene-9-one (abbreviated as ACRXTN), bis[4-(9,9-dimethyl-9,10-dihydroacridin)phenyl]sulfone (abbreviated as DMAC-DPS), 10-phenyl-10H,10'H-spiro[acridin-9,9'-anthracene]-10'-one (abbreviated as ACRSA), etc. These heterocyclic compounds possess both π-electron-rich and π-electron-deficient heteroaromatic rings, thus exhibiting high electron and hole transport capabilities, making them preferred. In particular, among skeletons including π-electron-deficient heteroaromatic rings, diazine skeletons (pyrimidine skeletons, pyrazine skeletons, pyridazine skeletons) or triazine skeletons are stable and reliable, and are therefore preferred. Furthermore, among skeletons including π-electron-rich heteroaromatic rings, acridine skeletons, phenoxazine skeletons, thiophene skeletons, furan skeletons, and pyrrole skeletons are stable and reliable, and having any one or more of these skeletons is preferred. As pyrrole skeletons, indole skeletons, carbazole skeletons, and 3-(9-phenyl-9H-carbazole-3-yl)-9H-carbazole skeletons are particularly preferred. Moreover, in substances where π-electron-rich and π-electron-deficient heteroaromatic rings are directly bonded, the π-electron-rich heteroaromatic ring exhibits strong donor and acceptor properties, while the energy difference between the singlet and triplet excitation levels decreases, making these skeletons particularly preferred. Furthermore, when the TADF material serving as the energy donor includes any one of alkyl groups with 3 or more but less than 10 carbon atoms, substituted or unsubstituted cycloalkyl groups with 3 or more but less than 10 carbon atoms, or trialkylsilyl groups with 3 or more but less than 10 carbon atoms, the distance between it and the fluorescent luminescent substance acting as the energy acceptor can be increased, making it preferable. When using this TADF material, even increasing the concentration of the TADF material can increase the distance between it and the fluorescent luminescent substance, thereby increasing the energy transfer rate based on the Foster mechanism while suppressing energy transfer based on the Dexter mechanism.

[0213] Furthermore, as TADF materials, fused heteroaromatic compounds containing nitrogen and boron, especially those with a diaza-boron-naphtho-anthracene skeleton, are preferred because their narrow emission spectrum allows for the production of blue luminescence with good color purity. Specific examples include 5,9-diphenyl-5H,9H-[1,4]benzozaborane[2,3,4-kl]phenazaborane (abbreviated: DABNA-1), 9-(diphenyl-3-yl)-N,N,5,11-tetraphenyl-5,9-dihydro-5,9-diaza-13b-boronnaphtho[3,2,1-de]anthracene-3-amine (abbreviated: DABNA-2), and 2,12-di... (tert-butyl)-5,9-bis(4-tert-butylphenyl)-N,N-diphenyl-5H,9H-[1,4]benzozaborane[2,3,4-kl]phenazaborane-7-amine (abbreviated as: DPhA-tBu4DABNA), 2,12-bis(tert-butyl)-N,N,5,9-tetra(4-tert-butylphenyl)-5H,9H-[1,4]benzozaborane[2,3,4-kl]phenazaborane -7-amine (abbreviation: tBuDPhA-tBu4DABNA), 2,12-di(tert-butyl)-5,9-di(4-tert-butylphenyl)-7-methyl-5H,9H-[1,4]benzozaborane[2,3,4-kl]phenazaborane (abbreviation: Me-tBu4DABNA), N7,N7,N13,N13,5,9,11,15-octaphenyl-5H,9H,11H, 15H-[1,4]benzozaborane[2,3,4-kl][1,4]benzozaborane[4',3',2':4,5][1,4]benzozaborane[3,2-b]phenazabor-7,13-diamine (abbreviation: ν-DABNA), 2-(4-tert-butylphenyl)benzo[5,6]indolo[3,2,1-jk]benzo[b]carbazole (abbreviation: tBuPBibc), etc.

[0214] In addition, as a TADF material, 9,10,11-tris[3,6-bis(1,1-dimethylethyl)-9H-carbazole-9-yl]-2,5,15,18-tetra(1,1-dimethylethyl)indolo[3,2,1-de]indolo[3',2',1':8,1][1,4]benzozaborane[2,3,4-kl]phenazaborane (abbreviated as: Compounds with an indole skeleton, such as BBCz-G, 9,11-bis[3,6-bis(1,1-dimethylethyl)-9H-carbazole-9-yl]-2,5,15,18-tetra(1,1-dimethylethyl)indolo[3,2,1-de]indolo[3',2',1':8,1][1,4]benzozaborane[2,3,4-kl]phenazaborane (abbreviated as BBCz-Y), etc.

[0215] TADF materials refer to materials with an energy difference between the triplet and singlet excitation levels, possessing the ability to convert energy from the triplet excited state to the singlet excited state via antisystem crossing. Therefore, they can upconvert the triplet excited state to the singlet excited state with minimal thermal energy (antisystem crossing) and efficiently exhibit luminescence (fluorescence) from the singlet excited state. The conditions for efficiently obtaining thermally activated delayed fluorescence are as follows: the energy difference between the triplet and singlet excitation levels is greater than 0 eV and less than 0.20 eV, preferably greater than 0 eV and less than 0.10 eV.

[0216] Alternatively, the TADF material described in Embodiment 2 can also be used.

[0217] Furthermore, nanostructures of transition metal compounds with perovskite structures can be cited as examples of work substances capable of converting triple excitation energy into luminescence. Metal halide perovskite nanostructures are particularly preferred. Nanoparticles and nanorods are preferred as such nanostructures.

[0218] The preferred fluorescent material is a compound that includes, as part of its structure, a luminescent body and a protecting group that functions to increase the distance between the luminescent body and other energy donors.

[0219] Here, the luminescent body refers to the atomic group (backbone) that causes luminescence in a fluorescent material. The luminescent body generally has π bonds and preferably includes aromatic rings, particularly fused aromatic rings or fused heteroaromatic rings. Alternatively, the luminescent body can be considered as an atomic group (backbone) comprising aromatic rings with transition dipole vectors existing on the ring plane. Furthermore, when a fluorescent material comprises multiple fused aromatic rings or fused heteroaromatic rings, the backbone with the lowest S1 energy level among these multiple fused aromatic rings or fused heteroaromatic rings is sometimes considered the luminescent body of the fluorescent material. Additionally, sometimes the backbone with an absorption end on the longest wavelength side among these multiple fused aromatic rings or fused heteroaromatic rings is considered the luminescent body of the fluorescent material. Furthermore, the luminescent body of the fluorescent material can sometimes be predicted based on the shape of the emission spectrum of each of the multiple fused aromatic rings or fused heteroaromatic rings.

[0220] Examples of luminescent materials include phenanthrene, stilbene, acridinone, phenoxazine, phenothiazine, naphthalene, anthracene, fluorene, β-carbamate, triphenylene, tetraphenylene, pyrene, perylene, coumarin, quinacridone, and naphthobisbenzofuran skeletons. In particular, fluorescent materials having naphthalene, anthracene, fluorene, β-carbamate, triphenylene, tetraphenylene, pyrene, perylene, coumarin, quinacridone, and naphthobisbenzofuran skeletons are preferred because of their high fluorescence quantum yield.

[0221] Substituents used as protecting groups need to have triplet excitation levels higher than the T1 levels of both the luminescent material and the host material. Therefore, saturated hydrocarbon groups are preferred. This is because substituents without π bonds have high triplet excitation levels. Furthermore, substituents without π bonds have low carrier (electron or hole) transport capabilities. Therefore, saturated hydrocarbon groups can increase the distance between the luminescent material and the host material with almost no impact on the excited state or carrier transport properties of the host material. Additionally, in organic compounds that simultaneously include substituents without π bonds and substituents with π conjugation, in many cases, leading orbitals {HOMO (Highest Occupied Molecular Orbital) and LUMO (Lowest Unoccupied Molecular Orbital)} exist on the side with the π conjugated substituent, especially in luminescent materials where leading orbitals are common. As discussed later, the overlap of HOMOs and LUMOs between the energy donor and acceptor is important for energy transfer based on the Dexter mechanism. Therefore, by using saturated hydrocarbon groups as protecting groups, the distance between the leading orbital of the host material as an energy donor and the leading orbital of the guest material as an energy acceptor can be increased, thus suppressing energy transfer based on the Dexter mechanism.

[0222] Specific examples of protecting groups include alkyl groups with 1 to 10 carbon atoms. Since it is necessary to increase the distance between the luminescent material and the host material, a large substituent is preferred. Therefore, alkyl groups with 3 to 10 carbon atoms, substituted or unsubstituted cycloalkyl groups with 3 to 10 carbon atoms, and trialkylsilyl groups with 3 to 10 carbon atoms can be suitably used. In particular, large branched alkyl groups are preferred. Furthermore, this substituent is particularly preferred when it contains a quaternary carbon and is therefore large.

[0223] Furthermore, as described above, the protecting group is more preferably deuterated. In the case where the protecting group contains deuterium, as specific examples, it is suitable to use an alkyl group containing deuterium with 3 or more and 10 or less carbon atoms, a cycloalkyl group containing deuterium (substituted or unsubstituted) with 3 or more and 10 or less carbon atoms, or a trialkylsilyl group containing deuterium with 3 or more and 10 or less carbon atoms.

[0224] Furthermore, it is preferable for a single luminescent body to have five or more protecting groups. By employing this structure, the entire luminescent body can be covered by the protecting groups, thus allowing for appropriate adjustment of the distance between the host material and the luminescent body. Note that it is more preferable that the protecting groups are not directly bonded to the luminescent body. For example, the protecting groups can also be bonded to the luminescent body via divalent or higher substituents such as arylene or amino groups. Bonding the protecting groups to the luminescent body via these substituents effectively increases the distance between the luminescent body and the host material. Therefore, when the luminescent body and the protecting groups are not directly bonded, having four or more protecting groups for a single luminescent body can effectively suppress energy transfer based on the Dexter mechanism.

[0225] Specific examples of fluorescent luminescent materials that include a protective group that functions to increase the distance between the luminescent material and other energy donors include N,N'-(2-phenylanthracene-9,10-diyl)-N,N,N',N'-tetra(3,5-di-tert-butylphenyl)diamine (abbreviated as: 2Ph-mmtBuDPhA2Anth), 2,2',6,6'-tetra(3,5-di-tert-butylphenyl)-N,N,N',N'-tetra(3,5-di-tert-butylphenyl)-[9,9'-bianthra]-10,10'-diamine (abbreviated as: 22'66'mmtBuPh-mmtBuDPhA2BANT), and N,N'-bis[3,5-bis(1-adamantane)phenyl]-N,N'-bis(3,5- (2,6-Di-tert-butylphenyl)-2-phenylanthracene-9,10-diamine (abbreviated as: 2Ph-mmAdtBuDPhA2Anth-03), N,N'-bis(3,5-di-tert-butylphenyl)-N,N'-bis{3,5-bis[4-(1-adamantane)phenyl]phenyl}-2,6-diphenylanthracene-9,10-diamine (abbreviated as: 2,6Ph-mmAdPtBuDPhA2Anth), N,N'-bis(3,5-di-tert-butylphenyl)-N,N'-bis{3,5-bis[4-(1-adamantane)phenyl]phenyl}-2-phenylanthracene-9,10-diamine (abbreviated as: 2Ph-mmAdPtBuDPhA2Anth), N,N'-bis{3,5-bis(tricyclo[5.2.1.0] 2，6[Decan-8-yl)phenyl}-N,N'-bis(3,5-di-tert-butylphenyl)-2-phenylanthracene-9,10-diamine (abbreviation: 2Ph-mmTCDtBuDPhA2Anth), N,N'-bis{3,5-bis(2-bicyclo[2.2.1]heptyl)phenyl}-N,N'-bis(3,5-di-tert-butylphenyl)-2-phenylanthracene-9,10-diamine (abbreviation: 2Ph-mmnbtBuDPhA2Anth), N,N'-bis[3,5-bis(2-adamantane)phenyl]-N,N'-bis[3,5-bis( [3,5-Di-tert-butylphenyl]-2-phenylanthracene-9,10-diamine (abbreviation: 2Ph-mmAdtBuDPhA2Anth-02), N,N'-bis[3,5-bis(2-adamantane)phenyl]-N,N'-bis(3,5-di-tert-butylphenyl)-2-phenylanthracene-9,10-diamine (abbreviation: 2Ph-mmAdtBuDPhA2Anth), N,N'-(2-trimethylsilylanthracene-9,10-diyl)-N,N,N',N'-tetra(3,5-di-tert-butylphenyl)diamine (abbreviation: 2TM) S-mmtBuDPhA2Anth), N,N'-(pyrene-1,6-diyl)bis[N-(2-methylphenyl)-6-cyclohexanebenzo[b]naphtho[1,2-d]furan-8-amine] (abbreviation: 1,6oMechBnfAPrn), N,N'-(pyrene-1,6-diyl)bis(N-phenyl-6-trimethylsilylbenzo[b]naphtho[1,2-d]furan-8-amine) (abbreviation: 1,6TMSBnfAPrn), N,N'-(3,8-dicyclohexanepyrene-1,6-diyl)bis[N-phenyl-(6-cyclohexane)pyrene-1,6-diyl)bis[N-phenyl-6-cyclohexanebenzo[b]naphtho[1,2-d]furan-8-amine] (abbreviation: 1,6TMSBnfAPrn), N,N'-(3,8-dicyclohexanepyrene-1,6-diyl)bis[N-phenyl-6-cyclohexanebenzo[b]naphtho[1,2-d]furan-8-amine] (abbreviation: 1,6oMechB ...) (abbreviation: 1,6oMechBnfAPrn), N,N'-(3,8-dicyclohexanepyrene-1,6- Hexobenzo[b]naphtho[1,2-d]furan-8-amine] (abbreviation: ch-1,6chBnfAPrn), N,N'-bis[9-(3,5-di-tert-butylphenyl)-9H-carbazole-2-yl]-N,N'-diphenyl-naphtho[2,3-b;6,7-b']bisbenzofuran-3,10-diamine (abbreviation: 3,10mmtBuPCA2Nbf(IV)-02), N,N,N',N'-tetra(3,5-di-tert-butylphenyl)pyrene-1,6-diamine (abbreviation: 1,6mmtBuDPhAPrn).

[0226] In addition, the fluorescent luminescent material described in Embodiment 2 can also be used.

[0227] like Figure 2AAs shown, when the positive-type light-emitting device of one embodiment of the present invention includes a hole transport layer 112, the GSP_Slope (mV / nm) of the light-emitting layer 113 is preferably 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 contained in the hole transport layer 112. Alternatively, the GSP_Slope (mV / nm) of the vapor-deposited film of the host material is preferably 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 contained in the hole transport layer 112.

[0228] In addition, such as Figure 2B As shown, when the inverted light-emitting device of one embodiment of the present invention includes a hole transport layer 112, the GSP_Slope (mV / nm) of the light-emitting layer 113 is preferably 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 containing a π-electron-rich heteroaromatic ring or aromatic amine included in the hole transport layer 112. Alternatively, the GSP_Slope (mV / nm) of the vapor-deposited film of the host material is preferably smaller than the GSP_Slope (mV / nm) of the vapor-deposited film of the third organic compound containing a π-electron-rich heteroaromatic ring or aromatic amine included in the hole transport layer 112.

[0229] In one embodiment of the present invention, the light-emitting device with this structure promotes hole injection through the effect of the negative interface charge derived from the difference in GSP_Slope between the two layers in contact with each other. As a result, hole injection into the light-emitting layer is also effectively generated, and the carrier balance is improved. This further expands the recombination region and suppresses the degradation of the light-emitting layer 113 and the hole transport layer 112.

[0230] In addition, such as Figure 1A As shown, in one embodiment of the positive-type light-emitting device of the present invention, the GSP_Slope (mV / nm) of the light-emitting layer 113 is preferably greater than the GSP_Slope (mV / nm) of the first electron transport layer 114_1. Alternatively, the GSP_Slope (mV / nm) of the vapor-deposited film of the host material is preferably greater than the GSP_Slope (mV / nm) of the vapor-deposited film of the first organic compound.

[0231] In addition, such as Figure 1BAs shown, in an inverted light-emitting device according to one embodiment of the present invention, the GSP_Slope (mV / nm) of the light-emitting layer 113 is preferably smaller than the GSP_Slope (mV / nm) of the second electron transport layer 114_2. Alternatively, the GSP_Slope (mV / nm) of the vapor-deposited film of the host material is preferably smaller than the GSP_Slope (mV / nm) of the vapor-deposited film of the second organic compound.

[0232] In one embodiment of the present invention, the light-emitting device with this structure promotes electron injection from the second electron transport layer 114_2 to the first electron transport layer 114_1 due to the positive interface charge arising from the difference in GSP_Slope between the two contacting layers. Therefore, even if electron injection from the first electrode 101 or electron injection layer 115 to the second electron transport layer 114_2 is suppressed in one embodiment of the present invention, a significant increase in the driving voltage will not occur, thus enabling the realization of a light-emitting device with excellent characteristics.

[0233] In addition, such as Figure 1A As shown, in one embodiment of the positive-type light-emitting device of the present invention, the GSP_Slope (mV / nm) of the second electron transport layer 114_2 is preferably greater than the GSP_Slope (mV / nm) of the light-emitting layer 113. Alternatively, the GSP_Slope (mV / nm) of the vapor-deposited film of the second organic compound is preferably greater than the GSP_Slope (mV / nm) of the vapor-deposited film of the host material.

[0234] In addition, such as Figure 1B As shown, in an inverted light-emitting device according to one embodiment of the present invention, the GSP_Slope (mV / nm) of the first electron transport layer 114_1 is preferably smaller than the GSP_Slope (mV / nm) of the light-emitting layer 113. Alternatively, the GSP_Slope (mV / nm) of the vapor-deposited film of the first organic compound is preferably smaller than the GSP_Slope (mV / nm) of the vapor-deposited film of the host material.

[0235] In one embodiment of the present invention, the interface charge between the first electron transport layer 114_1 and the second electron transport layer 114_2 of the light-emitting device having this structure is negative, and this interface charge is less than the interface charge between the light-emitting layer 113 and the first electron transport layer 114_1. Through this effect, although electron injection into the light-emitting layer is suppressed, hole injection into the light-emitting layer is promoted, thus improving carrier balance and further expanding the recombination region while suppressing the degradation of the light-emitting layer 113 and the hole transport layer 112.

[0236] Note that when the light-emitting layer 113 comprises a host material, the host material preferably comprises a first material and a second material. By constituting the host material from multiple materials, it is easier to further control the carrier balance, thus contributing to improved reliability. Alternatively, by using the first material and the second material to form an excimer complex, effects such as improved energy transfer efficiency to the light-emitting material, lower driving voltage, and improved reliability are achieved. Preferably, one of the first material and the second material is an organic compound with a π-electron-deficient heteroaromatic ring, and the other is an organic compound with a π-electron-rich heteroaromatic ring or an aromatic amine, thereby making it easier to adjust the carrier balance.

[0237] When the host material comprises multiple materials, the GSP_Slope (mV / nm) of the film serving as the host material can be the GSP_Slope (mV / nm) of a mixed film of the first and second materials co-deposited in a 1:1 ratio. Alternatively, the GSP_Slope (mV / nm) of the vapor-deposited film of the material with a higher mixing ratio in the first and second materials can be regarded as the GSP_Slope (mV / nm) of the host material film.

[0238] <Methods for determining GSP_Slope>

[0239] Here, we describe a method for determining the GSP_Slope of an organic compound film formed by vacuum evaporation.

[0240] As mentioned above, the phenomenon that the surface potential of a vapor-deposited film increases proportionally with its thickness is called the giant surface potential (GSP). Generally, the magnitude of the GSP is represented by the slope of the surface potential of the vapor-deposited film, measured using a Kelvin probe, plotted along the thickness direction; this slope is denoted as GSP_Slope (mV / nm). However, when two different layers are stacked, the charge density accumulated at their interface (mC / m) can be used as the indicator. 2 The GSP_Slope is estimated by varying in relation to the GSP.

[0241] Non-Patent Document 1 shows that when an organic thin film (thin film 1 and thin film 2) with different spontaneous polarizations is stacked and a voltage is applied, the following formula holds when the charge carriers accumulated at the interface are holes.

[0242] [Equation 1]

[0243]

[0244] [Equation 2]

[0245]

[0246] In formula (1), σacc σ represents the accumulated charge density. int V represents the interface charge density. inj Represents the hole injection voltage, V th d2 represents the threshold voltage, d2 represents the thickness of film 2, and ε2 represents the dielectric constant of film 2. inj V th It can be estimated from the capacitance-voltage characteristics of the device. Furthermore, the dielectric constant can be obtained using the ordinary optical refractive index n. o The square of (the value at a wavelength of 633 nm). Thus, V is estimated from the capacitance-voltage characteristics. inj V th The dielectric constant ε2 of thin film 2, calculated from the refractive index, and the thickness d2 of thin film 2, can be used to calculate the interfacial charge density σ using formula (1). int .

[0247] Next, in equation (2), P n ε represents the spontaneous polarization of the thin film n (n is 1 or 2) along the substrate normal direction. n V represents the dielectric constant of thin film n. n d represents the potential at the membrane surface. n This represents the thickness of the thin film n. Furthermore, the potential (V) at the film surface can be used to determine this. n ) divided by thickness (d) n The value obtained is used to calculate GSP_Slope. Here, the interfacial charge density σ can be obtained from the above formula (1). int Therefore, by using the known material as the GSP_Slope for thin film 2 and employing an appropriate dielectric constant, the GSP_Slope of thin film 1 can be estimated.

[0248] Thus, the following example is shown: As thin film 2, a measuring device 1 is fabricated using tris(8-hydroxyquinoline)aluminum (abbreviated: Alq3) with a known GSP_Slope of 48 (mV / nm) to calculate the GSP_Slope of the 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviated: NPB) membrane.

[0249] Table 1 shows the device structure of the measurement device 1. Note that layer 1_1 of the measurement device 1 is formed from the anode side to the cathode using vacuum evaporation at room temperature and a deposition rate of 0.2 nm / sec to 0.6 nm / sec. Furthermore, deposition continues without stopping while forming a layer. In the measurement device 1, layer 2_1 corresponds to thin film 1 and layer 3_1 corresponds to thin film 2. Additionally, OCHD-003 is an organic compound with electron acceptor properties.

[0250] Note that when manufacturing the measurement device, the deposition rate of each layer is preferably 3 nm / min or more and 600 nm / min or less. Furthermore, the thickness of each layer in the measurement device is preferably 3 nm or more and 500 nm or less, more preferably 50 nm or more and 300 nm or less.

[0251] also, Figure 5 The capacitance-voltage characteristic of measuring device 1 is shown. Note that the capacitance-voltage characteristic was measured using a potentiostat / galvanostat (Biologic SP-300, France) at a frequency of 10 Hz at room temperature.

[0252] [Table 1]

[0253]

[0254] Table 2 shows the utilization Figure 5 The hole injection voltage V of measuring device 1 is obtained by formulas (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 for calculation. o The refractive index was measured using a spectroscopic ellipsometry (JA Woollam Japan M-2000U).

[0255] [Table 2]

[0256]

[0257] Measurement device 2, which has a structure substantially the same as measurement device 1 except that the thickness of Alq3 is 80 nm, was fabricated. It was confirmed that the hole injection voltage drifted to a lower voltage than that of measurement device 1. In other words, it was found that in the above device, holes are injected first, and charge accumulates at the interface with Alq3. Furthermore, it was confirmed that the same results were obtained when estimating the GSP_Slope using measurement device 2 as with measurement device 1.

[0258] Furthermore, it is difficult to estimate the threshold voltage V from the capacitance-voltage characteristics. th Alternatively, the threshold voltage estimated from the current density-voltage characteristic can be used.

[0259] Figure 6 The current density-voltage characteristics of measuring device 1 are shown.

[0260] V estimated from current density-voltage characteristics th The value is 2.0V, which is the same as the value estimated from the capacitor-voltage characteristic.

[0261] Thus, by fabricating a film with a known Alq3 layered GSP_Slope and using a device with a film formed from an organic compound whose GSP_Slope is to be determined, and measuring the capacitance-voltage characteristics, the GSP_Slope of the organic compound can be estimated.

[0262] The above description explains the method for calculating GSP_Slope when the charge carriers accumulated at the interface become holes. However, when calculating the GSP_Slope of an organic membrane when the charge carriers accumulated at the interface become electrons, it can be calculated in the same way using the following formula (3).

[0263] [Equation 3]

[0264]

[0265] The organic compounds used in the light-emitting device are preferably selected based on the GSP_Slope of the vapor-deposited film of the organic compound, which is pre-measured by the above measurement method.

[0266] Furthermore, the structure shown in this embodiment can be implemented by appropriately combining it with the structures shown in other embodiments.

[0267] Implementation Method 2

[0268] In this embodiment, a semiconductor device according to one aspect of the present invention is described in detail.

[0269] Figures 1A to 2B This is a schematic diagram of a light-emitting device according to one aspect of the present invention. In the light-emitting device, a first electrode 101 is disposed on an insulating substrate 1000, and an EL layer 103 is included between the first electrode 101 and the second electrode 102. The EL layer 103 includes a light-emitting layer 113, which contains a light-emitting material. The light-emitting material emits light by applying a voltage between the first electrode 101 and the second electrode 102.

[0270] In addition to the light-emitting layer 113, the EL layer 103 also includes at least a first electron transport layer 114_1 and a second electron transport layer 114_2, having the structure shown in Embodiment 1. A light-emitting device of one embodiment of the present invention having this structure can be a light-emitting device with good characteristics, especially a light-emitting device with good reliability.

[0271] like Figures 1A to 2B As shown, the EL layer 103 preferably includes 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 the aforementioned functional layers such as a hole blocking layer, an electron blocking layer, an exciton blocking layer, and a charge generation layer. Conversely, any of the aforementioned layers may not be provided.

[0272] The first electrode 101 and the second electrode 102 are formed in a single-layer or multilayer structure. When the electrode has a multilayer structure, the layer in contact with the EL layer 103 is used as the anode or cathode. When the electrode has a multilayer structure, there are no restrictions on the work function of the layers other than the layer in contact with the EL layer 103, and the materials can be selected according to the required characteristics such as resistance, ease of processing, reflectivity, light transmittance, and stability.

[0273] The anode is preferably formed using metals, alloys, conductive compounds, and mixtures thereof with a high work function (specifically 4.0 eV or higher). Examples include indium tin oxide (ITO), indium tin oxide (ITSO) containing silicon or silicon oxide, indium zinc oxide, and indium tin oxide (IWZO) containing tungsten oxide and zinc oxide. While these conductive metal oxide films are typically formed by sputtering, sol-gel methods can also be used. Examples of formation methods include sputtering indium tin oxide using a target containing 1 wt% to 20 wt% zinc oxide. Furthermore, indium tin oxide (IWZO) containing tungsten oxide and zinc oxide can be formed by sputtering using a target containing 0.5 wt% to 5 wt% tungsten oxide and 0.1 wt% to 1 wt% zinc oxide. Furthermore, materials used for the anode 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). The anode can also be a layer of the aforementioned materials stacked together. For example, a film sequentially stacked with Al, Ti, and ITSO on Ti is preferred due to its good reflectivity, resulting in high efficiency and achieving high resolution of several thousand ppi. Graphene can also be used as a material for the anode. Furthermore, by using a composite material that can constitute the hole injection layer 111 described later as the layer in contact with the anode (typically a hole injection layer), the work function can be disregarded when selecting the electrode material.

[0274] Hole injection layer 111 is in contact with the anode and facilitates hole injection into EL layer 103. The hole injection layer 111 can be formed using phthalocyanine compounds and phthalocyanine complexes such as phthalocyanine (H2Pc), copper phthalocyanine (CuPc), etc.; aromatic amine compounds such as 4,4'-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (DPAB), 4,4'-bis(N-{4-[N'-(3-methylphenyl)-N'-phenylamino]phenyl}-N-phenylamino)biphenyl (DNTPD), etc.; or polymeric compounds such as poly(3,4-ethylenedioxythiophene) / (polystyrene sulfonic acid) (PEDOT / PSS), etc.

[0275] Furthermore, the hole injection layer 111 can also be composed of a substance with electron-accepting properties. As such, organic compounds with electron-withdrawing groups (halogen groups, cyano groups, etc.) can be used, including 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinone dimethylethane (abbreviated: F4-TCNQ), chloroquinone, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviated: HAT-CN), 1,3,4,5,7,8-hexafluorotetracyano-naphthoquinodimethane (abbreviated: F6-TCNNQ), and 2-(7-dicyanomethylene-1,3,4,5,6,8,9,10-octafluoro-7H-pyrene-2-yl)malononitrile, etc. In particular, compounds such as HAT-CN, which have electron-withdrawing groups bonded to fused aromatic rings with multiple heteroatoms, are thermally stable and therefore preferred. Furthermore, [3] axylene derivatives containing electron-withdrawing groups (especially halogen groups such as fluorine groups, cyano groups, etc.) are preferred due to their very high electron acceptor properties. Specifically, examples include: α,α',α''-1,2,3-cyclopropanetrimethylenetri[4-cyano-2,3,5,6-tetrafluorophenylacetonitrile], α,α',α''-1,2,3-cyclopropanetrimethylenetri[2,6-dichloro-3,5-difluoro-4-(trifluoromethyl)phenylacetonitrile], and α,α',α''-1,2,3-cyclopropanetrimethylenetri[2,3,4,5,6-pentafluorophenylacetonitrile]. In addition to the aforementioned organic compounds, transition metal oxides such as molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, and manganese oxide can be used as acceptor substances.

[0276] Furthermore, the hole injection layer 111 is preferably formed of a composite material comprising the aforementioned acceptor material and an organic compound with hole transport properties.

[0277] Various organic compounds with hole-transporting properties can be used as the organic compound for use in composite materials, such as aromatic amines, heteroaromatics, aromatic hydrocarbons, and polymers (oligomers, dendritic polymers, polymers, etc.). Preferably, the organic compound with a hole mobility of 1×10⁻⁶ is used. -6 cm 2 Organic compounds with a ratio of / Vs or higher. The organic compounds with hole-transporting properties used in composite materials are preferably compounds containing fused aromatic rings or π-electron-rich heteroaromatic rings. As fused aromatic rings, anthracene rings, naphthalene rings, etc., are preferred. Furthermore, as π-electron-rich heteroaromatic rings, fused aromatic rings containing at least one of a pyrrole skeleton, a furan skeleton, and a thiophene skeleton are preferred, specifically carbazole rings, dibenzothiophene rings, or rings that are further fused with aromatic rings or heteroaromatic rings.

[0278] Such hole-transporting organic compounds preferably have at least one of a carbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton, and an anthracene skeleton. In particular, they can be aromatic amines having substituents including a dibenzofuran ring or a dibenzothiophene ring, aromatic monoamines including a naphthyl ring, or aromatic monoamines in which a 9-fluorenyl group is bonded to the nitrogen of the amine via an arylene group. Note that when these hole-transporting organic compounds are substances including N,N-bis(4-biphenyl)amino groups, long-lifetime light-emitting devices can be manufactured, and therefore they are preferred.

[0279] Specifically, examples of the aforementioned hole-transporting organic compounds include N-(4-biphenyl)-6,N-diphenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviated as: BnfABP), N,N-bis(4-biphenyl)-6-phenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviated as: BBABnf), 4,4'-bis(6-phenylbenzo[b]naphtho[1,2-d]furan-8-yl)-4''-phenyltriphenylamine (abbreviated as: BnfBB1BP), and N,N-bis(4-biphenyl)benzo[b]naphtho [1,2-d]furan-6-amine (abbreviation: BBABnf(6)), N,N-bis(4-biphenyl)benzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BBABnf(8)), N,N-bis(4-biphenyl)benzo[b]naphtho[2,3-d]furan-4-amine (abbreviation: BBABnf(II)(4)), N,N-bis[4-(dibenzofuran-4-yl)phenyl]-4-amino-p-terphenyl (abbreviation: DBfBB1TP), N-[4-(dibenzothiophen-4-yl)phenyl]-N-phenyl-4-biphenyl Aniline (abbreviated as: ThBA1BP), 4-(2-naphthyl)-4',4''-diphenyltriphenylamine (abbreviated as: BBAβNB), 4-[4-(2-naphthyl)phenyl]-4',4''-diphenyltriphenylamine (abbreviated as: BBAβNBi), 4,4'-diphenyl-4''-([2,1'-binaphthyl]-6-yl)triphenylamine (abbreviated as: BBAαNβNB), 4,4'-diphenyl-4''-([2,1'-binaphthyl]-7-yl)triphenylamine (abbreviated as: 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-biphenyl)-4'-(2-naphthyl)-4''-phenyltriphenylamine (abbreviation: TPBiAβNB), 4-(3-biphenyl)-4'-[4-(2-naphthyl)phenyl]-4''-phenyltriphenylamine (abbreviation: mTPBiAβNBi), 4-(4-biphenyl)-4'-[4-(2-naphthyl)phenyl]-4''-phenyltriphenylamine (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]tri(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'-spirodi[9H-fluorene]-2-amine (abbreviation: PCBNBSF), N,N-bis(biphenyl-4-yl)-9,9' -spirodi[9H-fluorene]-2-amine (abbreviation: BBASF), N,N-bis(biphenyl-4-yl)-9,9'-spirodi[9H-fluorene]-4-amine (abbreviation: BBASF(4)), N-(biphenyl-2-yl)-N-(9,9-dimethyl-9H-fluorene-2-yl)-9,9'-spirodi[9H-fluorene]-4-amine (abbreviation: oFBiSF), N-(biphenyl-4-yl)-N-(9,9-dimethyl-9H-fluorene-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-Phenylo-3'-(9-phenylfluorene-9-yl)triphenylamine (abbreviation: BPAFLP), 4-Phenylo-3'-(9-phenylfluorene-9-yl)triphenylamine (abbreviation: mBPAFLP), 4-Phenylo-4'-[4-(9-phenylfluorene-9-yl)phenyl]triphenylamine (abbreviation: BPAFLBi), 4-Phenylo-4'-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4'-diphenyl-4''-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBi1BP), 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 (abbreviated as: PCCNBB), N-phenyl-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-9,9'-spirodi[9H-fluorene]-2-amine (abbreviated as: PCBASF), N-(biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-9,9-dimethyl-9H-fluorene-2-amine (abbreviated as: PCBBi) F), N,N-bis(9,9-dimethyl-9H-fluoren-2-yl)-9,9'-spirodi-9H-fluoren-4-amine, N,N-bis(9,9-dimethyl-9H-fluoren-2-yl)-9,9'-spirodi-9H-fluoren-3-amine, N,N-bis(9,9-dimethyl-9H-fluoren-2-yl)-9,9'-spirodi-9H-fluoren-2-amine, N,N-bis(9,9-dimethyl-9H-fluoren-2-yl)-9,9'-spirodi-9H-fluoren-1-amine, etc.

[0280] Furthermore, as materials with hole transport capabilities, other aromatic amine compounds such as N,N'-bis(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) can also be used appropriately. Additionally, organic compounds represented by general formulas (G1) to (G6) in Embodiment 1 can also be appropriately used. When using organic compounds represented by general formulas (G1) to (G6) in Embodiment 1, since these organic compounds are materials with low film refractive index, light-emitting devices with high luminous efficiency can be obtained.

[0281] By forming a hole injection layer 111, hole injection capability can be improved, thereby obtaining a light-emitting device with low driving voltage.

[0282] Furthermore, organic compounds with receptor properties can be easily formed in substances with receptor properties using vapor deposition, making them easy-to-use materials.

[0283] The hole transport layer 112 is formed by comprising an organic compound with hole transport properties. Preferably, the organic compound with hole transport properties has a content of 1 × 10⁻⁶. -6 cm 2 A hole mobility of / Vs or higher. The hole transport layer 112 may also have a single-layer structure or a stacked structure. Furthermore, the hole transport layer in contact with the light-emitting layer preferably functions as an electron blocking layer.

[0284] Examples of materials exhibiting hole transport capabilities include: 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB), N,N'-diphenyl-N,N'-bis(3-methylphenyl)-4,4'-diaminobiphenyl (TPD), N,N'-bis(9,9'-spirobis[9H-fluorene]-2-yl)-N,N'-diphenyl-4,4'-diaminobiphenyl (BSPB), 4-phenyl-4'-(9-phenylfluorene-9-yl)triphenylamine (BPAFLP), 4-phenyl-3'-(9-phenylfluorene-9-yl)triphenylamine (mBPAFLP), and 4-phenyl-4'-(9-phenyl-9H-carbazole-3-yl)triphenylamine (PCBA1BP). Compounds with aromatic amine skeletons include 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: PCCNBB), 9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]fluorene-2-amine (abbreviation: PCBAF), and N-phenyl-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-9,9'-spirodi[9H-fluorene]-2-amine (abbreviation: PCBASF);1,3-Bis(N-carbazolyl)benzene (mCP), 4,4'-bis(N-carbazolyl)biphenyl (CBP), 3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (CzTP), 3,3'-bis(9-phenyl-9H-carbazole) (PCCP), 9,9'-bis(biphenyl-4-yl)-3,3'-bi-9H-carbazole (BisBPCz), 9,9'-bis(biphenyl-3-yl)-3,3'-bi-9H-carbazole (BismBPCz), 9-(biphenyl-3-yl)-9'-(biphenyl-4-yl)-9H,9'H- 3,3'-Bicarbazole (abbreviated as mBPCCBP), 9-(2-naphthyl)-9'-phenyl-3,3'-bi-9H-carbazole (abbreviated as βNCCP), 9-(3-biphenyl)-9'-(2-naphthyl)-3,3'-bi-9H-carbazole (abbreviated as βNCCmBP), 9-(4-biphenyl)-9'-(2-naphthyl)-3,3'-bi-9H-carbazole (abbreviated as βNCCBP), 9,9'-bis-2-naphthyl-3,3'-9H,9'H-bicarbazole (abbreviated as BisβNCz), 9-(2-naphthyl)-9'-[1,1':4',1''-terphenyl]-3- 9-(2-naphthyl)-9'-[1,1':3',1''-terphenyl]-3-yl-3,3'-9H,9'H-bicarbazole, 9-(2-naphthyl)-9'-[1,1':3',1''-terphenyl]-5'-yl-3,3'-9H,9'H-bicarbazole, 9-(2-naphthyl)-9'-[1,1':4',1''-terphenyl]-4-yl-3,3'-9H,9'H-bicarbazole, 9-(2-naphthyl)-9'-[1,1':3',1''-terphenyl]-4-yl-3,3'-9H,9'H-bicarbazole 9-(2-naphthyl)-9'-(triphenyl-2-yl)-3,3'-9H,9'H-bicarbazole, 9-phenyl-9'-(triphenyl-2-yl)-3,3'-9H,9'H-bicarbazole (abbreviated as: PCCzTp), 9,9'-bis(triphenyl-2-yl)-3,3'-9H,9'H-bicarbazole, 9-(4-biphenyl)-9'-(triphenyl-2-yl)-3,3'-9H,9'H-bicarbazole, 9-(triphenyl-2-yl)-9'-[1,1':3',1''-terphenyl]-4-yl-3,3'-9H,9'H-bicarbazole, 9-[3-(triphenylsilyl)] Compounds with a carbazole skeleton, such as [phenyl]-3,9′-bi-9H-carbazole (abbreviated as: PSiCzCz);Compounds with a thiophene skeleton, such as 4,4',4''-(benzyl-1,3,5-triyl)tris(dibenzothiophene) (abbreviated as DBT3P-II), 2,8-diphenyl-4-[4-(9-phenyl-9H-fluorene-9-yl)phenyl]dibenzothiophene (abbreviated as DBTFLP-III), and 4-[4-(9-phenyl-9H-fluorene-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviated as DBTFLP-IV); and compounds with a furan skeleton, such as 4,4',4''-(benzyl-1,3,5-triyl)tris(dibenzofuran) (abbreviated as DBF3P-II) and 4-{3-[3-(9-phenyl-9H-fluorene-9-yl)phenyl]phenyl}dibenzofuran (abbreviated as mmDBFFLBi-II). Compounds with aromatic amine backbones and compounds with carbazole backbones are preferred due to their high reliability and excellent hole transport properties, which help reduce the driving voltage. Note that materials with hole transport properties, such as those used in the hole injection layer 111, can also be appropriately used as materials constituting the hole transport layer 112. Furthermore, organic compounds with amine and fluorene backbones are more preferred. Organic compounds with amine and fluorene backbones have high reliability and high hole transport properties, thus reducing the power consumption of the light-emitting device, and are therefore preferred.

[0285] Note that since the GSP_Slope of the hole transport layer 112 is smaller than that of the light-emitting layer 113, at least one of the interfaces between the hole transport layer and the light-emitting layer can be set with a negative interface charge, so it is easy to perform hole injection near the interface between the anode or hole injection layer and the light-emitting layer, thereby realizing a light-emitting device with low driving voltage.

[0286] One embodiment of the light-emitting device of the present invention includes at least a substance capable of converting triple excitation energy into light emission and a fluorescent light-emitting substance in the light-emitting layer. A phosphorescent light-emitting substance is preferably used as the substance capable of converting triple excitation energy into light emission. Furthermore, a substance exhibiting thermally activated delayed fluorescence (TADF) is also one type of fluorescent light-emitting substance. Note that light-emitting devices using blue light-emitting substances, especially those using blue phosphorescent substances, tend to have an excessive number of electrons in the light-emitting layer 113; therefore, the present invention is suitable for use in the aforementioned light-emitting devices.

[0287] In the luminescent layer, materials that can be used as fluorescent luminescent substances include, for example, the following substances. Additionally, the fluorescent luminescent substance shown in Embodiment 1 can also be used. Furthermore, other fluorescent luminescent substances can also be used.

[0288] Examples include 5,6-bis[4-(10-phenyl-9-anthrayl)phenyl]-2,2'-bipyridine (abbreviated as PAP2BPy), 5,6-bis[4'-(10-phenyl-9-anthrayl)biphenyl-4-yl]-2,2'-bipyridine (abbreviated as PAPP2BPy), N,N'-diphenyl-N,N'-bis[4-(9-phenyl-9H-fluorene-9-yl)phenyl]pyrene-1,6-diamine (abbreviated as 1,6FLPAPrn), N,N'-bis(3-methylphenyl)-N,N'-bis[3-(9-phenyl-9H-fluorene-9-yl)phenyl]pyrene-1,6-diamine (abbreviated as 1,6mMemFLPAPrn), and N,N'-bis[4-(9H-9H-fluorene-9-yl)phenyl]pyrene-1,6-diamine (abbreviated as 1,6mMemFLPAPrn). [-carbazole-9-yl)phenyl]-N,N'-diphenylstilbene-4,4'-diamine (abbreviation: YGA2S), 4-(9H-carbazole-9-yl)-4'-(10-phenyl-9-anthrayl)triphenylamine (abbreviation: YGAPA), 4-(9H-carbazole-9-yl)-4'-(9,10-diphenyl-2-anthrayl)triphenylamine (abbreviation: 2YGAPPA), N,9-diphenyl-N-[4-(10-phenyl-9-anthrayl)phenyl]-9H-carbazole-3-amine (abbreviation: PCAPA), dinaphthalene, 2,5,8,11-tetra-tert-butyl dinaphthalene (abbreviation: TBP), 4-(10-phenyl-9-anthrayl)-4'-(9-phenyl-9H- Carbazole-3-yl)triphenylamine (abbreviated as PCPAPA), N,N''-(2-tert-butylanthracene-9,10-diyldi-4,1-phenylene)bis(,N',N'-triphenyl-1,4-phenylenediamine) (abbreviated as DPABPA), N,9-diphenyl-N-[4-(9,10-diphenyl-2-anthrayl)phenyl]-9H-carbazole-3-amine (abbreviated as 2PCAPPA), N-[4-(9,10-diphenyl-2-anthrayl)phenyl]-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviated as 2DPAPPA), N,N,N',N',N'',N'',N''',N'''-octaphenyldibenzo[g,p](chrys) N-(9,10-diphenyl-2-anthrayl)-N,9-diphenyl-9H-carbazole-3-amine (abbreviated as: DBC1), coumarin 30, N-(9,10-diphenyl-2-anthrayl)-N,9-diphenyl-9H-carbazole-3-amine (abbreviated as: 2PCAPA), N-[9,10-bis(biphenyl-2-yl)-2-anthrayl]-N,9-diphenyl-9H-carbazole-3-amine (abbreviated as: 2PCABPhA), N-(9,10-diphenyl-2-anthrayl)-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviated as: 2DPAPA), N-[9,10-bis(biphenyl-2-yl)-2-anthrayl]-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviated as: 2DPABPhA), 9,10-Bis(biphenyl-2-yl)-N-[4-(9H-carbazol-9-yl)phenyl]-N-phenylanthracene-2-amine (abbreviation: 2YGABPhA), N,N,9-triphenylanthracene-9-amine (abbreviation: DPhAPhA), coumarin 545T, N,N'-diphenylquinacridone (abbreviation: DPQd), rubrene, 5,12-bis(biphenyl-4-yl)-6,11-diphenyltetraphenyl (abbreviation: BPT), 2-(2-{2-[4-(dimethylamino)phenyl]vinyl}-6-methyl-4H-pyran-4-yl)malonitrile (abbreviation: DCM1), 2-{2-methyl-6-[2-(2,3,6,7-tetrahydro-1H, 5H-benzo[ij]quinazine-9-yl)vinyl]-4H-pyran-4-ylidene}malonium (abbreviation: DCM2), N,N,N',N'-tetra(4-methylphenyl)tetraphenyl-5,11-diamine (abbreviation: p-mPhTD), 7,14-diphenyl-N,N,N',N'-tetra(4-methylphenyl)acenaphthene[1,2-a]fluoranthene-3,10-diamine (abbreviation: p-mPhAFD), 2-{2-isopropyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinazine-9-yl)vinyl]-4H-pyran-4-ylidene}malonium (abbreviation: DCJTI) ), 2-{2-tert-butyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinazin-9-yl)vinyl]-4H-pyran-4-ylidene}malonium (abbreviation: DCJTB), 2-(2,6-bis{2-[4-(dimethylamino)phenyl]vinyl}-4H-pyran-4-ylidene)malonium (abbreviation: BisDCM), 2-{2,6-bis[2-(8-methoxy-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinazin-9-yl)vinyl]-4H-pyran-4-ylidene}malonium (abbreviation: BisDCJTM) ), N,N'-diphenyl-N,N'-(1,6-pyrene-diyl)bis[(6-phenylbenzo[b]naphtho[1,2-d]furan)-8-amine] (abbreviation: 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 (abbreviation: 3,10PCA2Nbf(IV)-02), 3,10-bis[N-(dibenzofuran-3-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviation: 3,10FrA2Nbf(IV)-02), etc. In particular, 1,6FLPAPrn, 1,6mMemFLPAPrn, 1,Fused aromatic diamine compounds, such as pyrene diamine compounds like 6BnfAPrn-03, possess high hole-trapping ability, high luminescence efficiency, and high reliability, making them a preferred choice.

[0289] In addition, 5,9-diphenyl-5H,9H-[1,4]benzozaborane[2,3,4-kl]phenazaborane (abbreviated: DABNA-1), 9-(diphenyl-3-yl)-N,N,5,11-tetraphenyl-5,9-dihydro-5,9-diaza-13b-borazanaphtho[3,2,1-de]anthracene-3-amine (abbreviated: DABNA-2), and 2,12-bis(tert-butyl)-5,9-bis(4-tert-butylphenyl)-N,N-diphenyl-5H,9H-[1,4]benzozaborane[2,3,4-kl] can be used appropriately. Fenrazaboron-7-amine (abbreviation: DPhA-tBu4DABNA), 2,12-di(tert-butyl)-N,N,5,9-tetra(4-tert-butylphenyl)-5H,9H-[1,4]benzozaborono[2,3,4-kl]benzozaboron-7-amine (abbreviation: tBuDPhA-tBu4DABNA), 2,12-di(tert-butyl)-5,9-di(4-tert-butylphenyl)-7-methyl-5H,9H-[1,4]benzozaborono[2,3,4-kl]phenrazaboron (abbreviation: Me-tBu4DABNA), N 7 N 7 N 13 N 13 Fused heteroaromatic compounds containing nitrogen and boron, such as 5,9,11,15-octaphenyl-5H,9H,11H,15H-[1,4]benzozaboron[2,3,4-kl][1,4]benzozaboron[4',3',2':4,5][1,4]benzozaboron[3,2-b]phenazaboron-7,13-diamine (abbreviation: ν-DABNA), 2-(4-tert-butylphenyl)benzo[5,6]indole[3,2,1-jk]benzo[b]carbazole (abbreviation: tBuPBibc), especially compounds with a diaza-boron-naphtho-anthracene skeleton, can produce blue luminescence with good color purity due to their narrow emission spectrum.

[0290] In addition to the above, compounds with an indole skeleton, such as 9,10,11-tris[3,6-bis(1,1-dimethylethyl)-9H-carbazole-9-yl]-2,5,15,18-tetra(1,1-dimethylethyl)indole[3,2,1-de]indole[3',2',1':8,1][1,4]benzozaboron[2,3,4-kl]phenazaboron (abbreviated as: BBCz-G) and 9,11-bis[3,6-bis(1,1-dimethylethyl)-9H-carbazole-9-yl]-2,5,15,18-tetra(1,1-dimethylethyl)indole[3,2,1-de]indole[3',2',1':8,1][1,4]benzozaboron[2,3,4-kl]phenazaboron (abbreviated as: BBCz-Y), are also suitable.

[0291] Examples of phosphorescent materials include the following.

[0292] Examples include organometallic iridium complexes with a 4H-triazole skeleton, such as {2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-κN2]phenyl-κC}iridium(III) (abbreviated as [Ir(mpptz-dmp)3]) and tris(5-methyl-3,4-diphenyl-4H-1,2,4-triazole)iridium(III) (abbreviated as [Ir(Mptz)3]). Compounds; organometallic iridium complexes with a 1H-triazole skeleton, such as tris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazole]iridium(III) (abbreviated as [Ir(Mptz1-mp)3]) and tris(1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazole)iridium(III) (abbreviated as [Ir(Prptz1-Me)3]); fac-tris[1-(2,6-diisopropyl] [Ir(iPrpim)3][3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-f]phenanthridinato]iridium(III) (abbreviated as [Ir(dmpimpt-Me)3]), [2-{1-[2,6-bis(1-methylethyl)phenyl]-1H-imidazo-2-yl-κ] Organometallic iridium complexes with an imidazole skeleton, such as N3}-4-cyanophenyl-κC)iridium(III) (abbreviated as CNImIr); organometallic complexes with a benzimidazole skeleton, such as tris[(6-tert-butyl-3-phenyl-2H-imidazo[4,5-b]pyrazin-1-yl-κC2)phenyl-κC]iridium(III) (abbreviated as [Ir(cb)3]); and bis[2-(4',6'-difluorophenyl)pyridinium-N,C 2Iridium(III) tetra(1-pyrazolyl)borate (abbreviated as: FIr6), bis[2-(4',6'-difluorophenyl)pyridinium-N,C 2 '] Iridium(III) pyridine carboxylate (abbreviated as: FIRpic), bis{2-[3',5'-bis(trifluoromethyl)phenyl]pyridinium-N,C 2 Iridium(III)pyridinecarboxylate (abbreviated as: [Ir(CF3ppy)2(pic)]), bis[2-(4',6'-difluorophenyl)pyridinium-N,C 2 Organometallic iridium complexes such as iridium(III) acetylacetone (abbreviated: FIracac) with phenylpyridine derivatives having electron-withdrawing groups as ligands; and platinum complexes such as (2-{3-[3-(3,5-di-tert-butylphenyl)benzimidazol-1-yl-2-ylidene-κC2]phenoxy-κC2}-9-(4-tert-butyl-2-pyridyl-κN)carbazole-2,1-diyl-κC1)platinum(II) (abbreviated: PtON-TBBI). The above substances are compounds that emit blue phosphorescence and have emission peaks in the wavelength region of 450 nm to 520 nm. Note that the phosphorescent material shown in Example 1 can be used as the blue phosphorescent material. Alternatively, compounds in which a portion of the hydrogen is deuterium can also be used.

[0293] In addition, examples include: tris(4-methyl-6-phenylpyrimidine)iridium(III) (abbreviated as [Ir(mppm)3]), tris(4-tert-butyl-6-phenylpyrimidine)iridium(III) (abbreviated as [Ir(tBuppm)3]), (acetylacetonate)bis(6-methyl-4-phenylpyrimidine)iridium(III) (abbreviated as [Ir(mppm)2(acac)]), (acetylacetonate)bis(6-tert-butyl-4-phenylpyrimidine)iridium(III) (abbreviated as [Ir(tBuppm)2(acac)]), (acetylacetonate)bis[6-(2-norborneol)-4-phenylpyrimidine]iridium(III) (abbreviated as [Ir(nbppm)2(acac)]), (acetylacetonate)bis[5-methyl Organometallic iridium complexes with a pyrimidine skeleton, such as 6-(2-methylphenyl)-4-phenylpyrimidinium-iridium(III) (abbreviated as [Ir(mpmppm)2(acac)]) and (acetylacetonium-ionium)bis(4,6-diphenylpyrimidinium-ionium(III)) (abbreviated as [Ir(dppm)2(acac)]); organometallic iridium complexes with a pyrazine skeleton, such as (acetylacetonium-ionium)bis(3,5-dimethyl-2-phenylpyrazine-ionium(III)) (abbreviated as [Ir(mppr-Me)2(acac)]) and (acetylacetonium-ionium)bis(5-isopropyl-3-methyl-2-phenylpyrazine-ionium(III)) (abbreviated as [Ir(mppr-iPr)2(acac)]); tris(2-phenylpyridinium-N,C 2’ Iridium (III) (abbreviated as: [Ir(ppy)3]), bis(2-phenylpyridinium-N,C) 2’ Iridium (III) acetylacetone (abbreviated as: [Ir(ppy)2(acac)]), bis(benzo[h]quinoline)iridium (III) acetylacetone (abbreviated as: [Ir(bzq)2(acac)]), tri(benzo[h]quinoline)iridium (III) (abbreviated as: [Ir(bzq)3]), tri(2-phenylquinoline-N,C 2’ Iridium (III) (abbreviated as: [Ir(pq)3]), bis(2-phenylquinoline-N,C) 2’ Iridium(III)acetylacetone (abbreviated as: [Ir(pq)2(acac)]), [2-d3-methyl-8-(2-pyridyl-κN)benzofurano[2,3-b]pyridyl-κC]bis[2-(5-d3-methyl-2-pyridyl-κN) 2[Ir(5mppy-d3)2(mbfpypy-d3)], {[2-(methyl-d3)-8-[4-(1-methylethyl-1-d)-2-pyridyl-κN]benzofurano[2,3-b]pyridin-7-yl-κC]}bis[5-(methyl-d3)-2-[5-(methyl-d3)-2-pyridinyl-κN]phenyl-κC]iridium(III) (abbreviated as: Ir(5mtpy-d6)2(mbfpypy-iPr-d4)), [2-(methyl-d3)-8-(2-pyridinyl-κN)benzofurano[2,3-b]pyridin-κC]bis[ 2-(2-pyridyl-κN)phenyl-κC]iridium(III) (abbreviation: Ir(ppy)2(mbfpypy-d3)), [2-(4-methyl-5-phenyl-2-pyridyl-κN)phenyl-κC]bis[2-(2-pyridyl-κN)phenyl-κC]iridium(III) (abbreviation: [Ir(ppy)2(mdppy)]), [2-(4-d3-methyl-5-phenyl-2-pyridyl-κN2)phenyl-κC]bis[2-(5-d3-methyl-2-pyridyl-κN2)phenyl-κC]iridium(III) (abbreviation: [Ir(5mppy-d3)2(mdppy-d3)]), [2-methyl -8-(2-pyridyl-κN)benzofurano[2,3-b]pyridyl-κC]bis[2-(2-pyridyl-κN)phenyl-κC]iridium(III) (abbreviated as: Ir(ppy)2(mbfpypy)), tri{2-[5-(methyl-d3)-4-phenyl-2-pyridyl-κN]phenyl-κC}iridium(III) (abbreviated as: Ir(5m4dppy-d3)3) and other organometallic iridium complexes with a pyridyl skeleton; tri(acetylacetonate)(monophenanthroline)terbium(III) (abbreviated as: [Tb(acac)3(Phen)]) and other rare earth metal complexes; and (2-{1-(5-tert-butylbiphenyl-2-yl)-4 Organometallic platinum complexes such as [3-tert-butyl-5-(4-phenyl-2-pyridyl-κN)phenyl-κC6]-2-benzimidazolyl-κN3}-4,6-di-tert-butylphenol-κO]platinum(II) (abbreviated as Pt(tBudppymmtBubiz-tBubp)) and [2-(4-(3,5-di-tert-butylphenyl)-6-{3-[4-(5'-tert-butyl[1,1':3',1''-triphenyl]-2'-yl)-2-pyridyl-κN]phenyl-κC2}-2-pyridyl-κN)phenol-κO]platinum(II) (abbreviated as Pt(4tButpppypyp-mmtBup)) are all present. These substances are primarily compounds exhibiting green phosphorescence and a emission peak in the 500 nm to 600 nm wavelength region.Furthermore, organometallic iridium complexes with a pyrimidine skeleton are particularly preferred due to their exceptionally high reliability or luminescence efficiency. Alternatively, compounds containing a portion of deuterium as hydrogen can also be used.

[0294] In addition, examples of organogolds with pyrimidine skeletons include: (diisobutyrylmethane)bis[4,6-bis(3-methylphenyl)pyrimidinyl]iridium(III) (abbreviated as: [Ir(5mdppm)2(dibm)]), bis[4,6-bis(3-methylphenyl)pyrimidinyl](dineopentaylmethane)iridium(III) (abbreviated as: [Ir(5mdppm)2(dpm)]), and bis[4,6-bis(naphth-1-yl)pyrimidinyl](dineopentaylmethane)iridium(III) (abbreviated as: [Ir(d1npm)2(dpm)]). Organometallic iridium complexes with a pyrazine skeleton, such as (acetylacetonate)bis(2,3,5-triphenylpyrazine)iridium(III) (abbreviated as [Ir(tppr)2(acac)]), bis(2,3,5-triphenylpyrazine)(dinepentanoylmethane)iridium(III) (abbreviated as [Ir(tppr)2(dpm)]), and (acetylacetonate)bis[2,3-bis(4-fluorophenyl)quinoxaloline]iridium(III) (abbreviated as [Ir(Fdpq)2(acac)]); tris(1-phenylisoquinoline-N,C 2’ Iridium (III) (abbreviated as: [Ir(piq)3]), bis(1-phenylisoquinoline-N,C) 2’Organometallic iridium complexes with a pyridine skeleton include iridium(III) acetylacetone (abbreviated as: [Ir(piq)2(acac)]), (3,7-diethyl-4,6-nonanedione-κO4,κO6)bis[2,4-dimethyl-6-[7-(1-methylethyl)-1-isoquinolinyl-κN]phenyl-κC]iridium(III), (3,7-diethyl-4,6-nonanedione-κO4,κO6)bis[2,4-dimethyl-6-[5-(1-methylethyl)-2-quinolinyl-κN]phenyl-κC]iridium(III). The compounds 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) (monopraninol) europium(III) (abbreviated as [Eu(DBM)3(Phen)]) and tris[1-(2-thiophenecarboxyl)-3,3,3-trifluoroacetone] (monopraninol) europium(III) (abbreviated as [Eu(TTA)3(Phen)]). These substances are red phosphorescent compounds with emission peaks in the 600 nm to 700 nm wavelength region. Furthermore, organometallic iridium complexes with a pyrazine skeleton can achieve red emission with good colorimetry. Additionally, compounds containing a portion of deuterium as hydrogen can also be used.

[0295] In addition to the phosphorescent compounds mentioned above, other known phosphorescent compounds may also be used.

[0296] Fullerenes and their derivatives, acridines and their derivatives, and eosin derivatives can be used as TADF materials. In addition, metal porphyrins containing magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), or palladium (Pd) can also be used. Examples of metalloporphyrins include, for instance, protoporphyrin-tin fluoride complexes represented by the following structural formulas: protoporphyrin-tin fluoride complex (SnF2(Proto IX)), mesotoporphyrin-tin fluoride complex (SnF2(Meso IX)), hematoporphyrin-tin fluoride complex (SnF2(Hemato IX)), tetramethyl coprophyrin-tin fluoride complex (SnF2(Copro III-4Me), octaethylporphyrin-tin fluoride complex (SnF2(OEP)), protoporphyrin-tin fluoride complex (SnF2(Etio I)), and octaethylporphyrin-platinum chloride complex (PtCl2OEP).

[0297] [Chemical Formula 4]

[0298]

[0299] In addition, 2-(biphenyl-4-yl)-4,6-bis(12-phenylindol[2,3-a]carbazole-11-yl)-1,3,5-triazine (abbreviated as: PIC-TRZ), 9-(4,6-diphenyl-1,3,5-triazin-2-yl)-9'-phenyl-9H,9'H-3,3'-bicarbazole (abbreviated as: PCCzTzn), 2-{4-[3-(N-phenyl-9H-carbazole-3-yl)-9H-carbazole-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviated as: PCCzPTzn), 2-[4-(10H-phenoxazine-10-yl)phenyl]-4,6-diphenyl-1, Heterocyclic compounds such as 3,5-triazine (PXZ-TRZ), 3-[4-(5-phenyl-5,10-dihydrophenazin-10-yl)phenyl]-4,5-diphenyl-1,2,4-triazole (PPZ-3TPT), 3-(9,9-dimethyl-9H-acridin-10-yl)-9H-oxanthracene-9-one (ACRXTN), bis[4-(9,9-dimethyl-9,10-dihydroacridin)phenyl]sulfone (DMAC-DPS), and 10-phenyl-10H,10'H-spiro[acridin-9,9'-anthracene]-10'-one (ACRSA) possessing one or both π-electron-rich and π-electron-deficient heterocyclic rings are preferred. These heterocyclic compounds exhibit high electron and hole transport properties due to the presence of both π-electron-rich and π-electron-deficient heterocyclic rings. Among the skeletons with π-electron-deficient heteroaromatic rings, pyridine, diazine (pyrimidine, pyrazine, pyridazine), and triazine skeletons are stable and reliable, and are therefore preferred. In particular, benzofuran-pyrimidine, benzothiophene-pyrimidine, benzofuran-pyrazine, and benzothiophene-pyrazine skeletons are highly acceptor and reliable, and are therefore preferred. Furthermore, among the skeletons with π-electron-rich heteroaromatic rings, acridine, phenoxazine, phenothiazine, furan, thiophene, and pyrrole skeletons are stable and reliable, and are therefore preferred to have at least one of these skeletons. Moreover, dibenzofuran skeletons are preferred as furan skeletons, and dibenzothiophene skeletons are preferred as thiophene skeletons. As pyrrole skeletons, indole, carbazole, indolecarbazole, bicarbazole, and 3-(9-phenyl-9H-carbazole-3-yl)-9H-carbazole skeletons are particularly preferred. In substances where π-electron-rich and π-electron-deficient heteroaromatic rings are directly bonded, the π-electron-rich ring exhibits high electron-donating and electron-accepting properties, while the energy difference between the S1 and T1 energy levels decreases, resulting in highly efficient thermally activated delayed fluorescence. Therefore, it is particularly preferred. Note that aromatic rings bonded with electron-withdrawing groups such as cyano groups can also be used instead of π-electron-deficient heteroaromatic rings. Furthermore, aromatic amine skeletons, phenazine skeletons, etc., can be used as π-electron-rich skeletons.Furthermore, as π-electron-deficient skeletons, the following can be used: oxanthracene skeleton, thioxanthene dioxide skeleton, oxadiazole skeleton, triazole skeleton, imidazole skeleton, anthraquinone skeleton, boron-containing skeletons such as phenylborane or boranthrene, aromatic or heteroaromatic rings with nitrile or cyanobenzene, carbonyl skeletons such as benzophenone, phosphine oxide skeleton, sulfone skeleton, etc. Thus, π-electron-deficient and π-electron-rich skeletons can be used to replace at least one of the π-electron-deficient and π-electron-rich heteroaromatic rings.

[0300] [Chemical Formula 5]

[0301]

[0302] TADF materials refer to materials with a small energy difference between the S1 and T1 levels and the ability to convert triple excitation energy into single excitation energy through antisystem crossing. Therefore, they can upconvert triple excitation energy into single excitation energy (antisystem crossing) with minimal thermal energy and efficiently generate singlet excited states. Furthermore, triple excitation energy can be converted into luminescence.

[0303] Exciplexes formed by two substances in an excited state have the function of converting triple excitation energy into single excitation energy due to the extremely small energy difference between the S1 and T1 energy levels.

[0304] Note that the phosphorescence spectrum observed at low temperatures (e.g., 77K to 10K) can be used as an indicator of the T1 energy level. For TADF materials, it is preferable that the energy difference between the S1 and T1 energy levels is 0.3 eV or less, more preferably 0.2 eV or less, when the energy of the extrapolated line obtained by drawing a tangent at the tail of the short-wavelength side of the fluorescence spectrum is taken as the S1 energy level and the energy of the extrapolated line obtained by drawing a tangent at the tail of the short-wavelength side of the phosphorescence spectrum is taken as the T1 energy level.

[0305] Furthermore, when using TADF material as the luminescent material, the S1 energy level of the host material is preferably higher than that of the TADF material. Additionally, the T1 energy level of the host material is preferably higher than that of the TADF material.

[0306] As the main material of the light-emitting layer, various carrier transport materials such as materials with electron transport properties and / or materials with hole transport properties, the aforementioned TADF materials, etc., can be used.

[0307] As a material with hole transport capabilities, organic compounds having an amine skeleton or a π-electron-rich heteroaromatic ring skeleton are preferred. The π-electron-rich heteroaromatic ring is preferably a fused aromatic ring comprising at least one of an acridine skeleton, a phenoxazine skeleton, a phenothiazine skeleton, a furan skeleton, a thiophene skeleton, and a pyrrole skeleton; specifically, a carbazole ring, a dibenzothiophene ring, or a ring fused with an aromatic ring or a heteroaromatic ring.

[0308] Such hole-transporting organic compounds preferably have at least one of a carbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton, and an anthracene skeleton. In particular, they can be aromatic amines having substituents including a dibenzofuran ring or a dibenzothiophene ring, aromatic monoamines including a naphthyl ring, or aromatic monoamines in which a 9-fluorenyl group is bonded to the nitrogen of the amine via an arylene group. Note that when these hole-transporting organic compounds are substances including N,N-bis(4-biphenyl)amino groups, long-lifetime light-emitting devices can be manufactured, and therefore they are preferred.

[0309] Examples of the aforementioned organic compounds include: 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB), N,N'-diphenyl-N,N'-bis(3-methylphenyl)-4,4'-diaminobiphenyl (TPD), N,N'-bis(9,9'-spirobis[9H-fluorene]-2-yl)-N,N'-diphenyl-4,4'-diaminobiphenyl (BSPB), 4-phenyl-4'-(9-phenylfluorene-9-yl)triphenylamine (BPAFLP), 4-phenyl-3'-(9-phenylfluorene-9-yl)triphenylamine (mBPAFLP), 4-phenyl-4'-(9-phenyl-9H-carbazole-3-yl)triphenylamine (PCBA1BP), 4 Compounds with aromatic amine skeletons, such as 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: PCCNBB), 9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]fluorene-2-amine (abbreviation: PCBAF), and N-phenyl-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-9,9'-spirodi[9H-fluorene]-2-amine (abbreviation: PCBASF);1,3-Bis(N-carbazolyl)benzene (abbreviation: mCP), 4,4'-bis(N-carbazolyl)biphenyl (abbreviation: CBP), 3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviation: CzTP), 3,3'-bis(9-phenyl-9H-carbazole) (abbreviation: PCCP), 9,9'-bis(biphenyl-4-yl)-3,3'-bi-9H-carbazole (abbreviation: BisBPCz), 9,9'-bis(biphenyl-3-yl)-3,3'-bi-9H-carbazole (abbreviation: BisBPCz), 9-(biphenyl-3-yl)-9'-(biphenyl-4-yl)-9H,9'H-3,3'-bicarbazole (abbreviation: Named as: mBPCCBP), 9-(2-naphthyl)-9'-phenyl-3,3'-bi-9H-carbazole (abbreviated as: βNCCP), 9-(3-biphenyl)-9'-(2-naphthyl)-3,3'-bi-9H-carbazole (abbreviated as: βNCCmBP), 9-(4-biphenyl)-9'-(2-naphthyl)-3,3'-bi-9H-carbazole (abbreviated as: βNCCBP), 9,9'-di-2-naphthyl-3,3'-9H,9'H-bicarbazole (abbreviated as: BisβNCz), 9-(2-naphthyl)-9'-[1,1':4',1''-terphenyl]-3-yl-3,3'-9H,9'H-bicarbazole, 9-( 2-Naphthyl)-9'-[1,1':3',1''-terphenyl]-3-yl-3,3'-9H,9'H-bicarbazole, 9-(2-naphthyl)-9'-[1,1':3',1''-terphenyl]-5'-yl-3,3'-9H,9'H-bicarbazole, 9-(2-naphthyl)-9'-[1,1':4',1''-terphenyl]-4-yl-3,3'-9H,9'H-bicarbazole, 9-(2-naphthyl)-9'-[1,1':3',1''-terphenyl]-4-yl-3,3'-9H,9'H-bicarbazole, 9-(2-naphthyl)-9'-(triphenyl-2-yl)-3,3'-9H, Compounds with a carbazole skeleton, such as 9'H-bicarbazole, 9-phenyl-9'-(triphenyl-2-yl)-3,3'-9H,9'H-bicarbazole (abbreviated as PCCzTp), 9,9'-bis(triphenyl-2-yl)-3,3'-9H,9'H-bicarbazole, 9-(4-biphenyl)-9'-(triphenyl-2-yl)-3,3'-9H,9'H-bicarbazole, 9-(triphenyl-2-yl)-9'-[1,1':3',1''-terphenyl]-4-yl-3,3'-9H,9'H-bicarbazole, and 9-[3-(triphenylsilyl)phenyl]-3,9′-bi-9H-carbazole (abbreviated as PSiCzCz);Compounds with a thiophene skeleton, such as 4,4',4''-(benzyl-1,3,5-triyl)tris(dibenzothiophene) (abbreviated as DBT3P-II), 2,8-diphenyl-4-[4-(9-phenyl-9H-fluorene-9-yl)phenyl]dibenzothiophene (abbreviated as DBTFLP-III), and 4-[4-(9-phenyl-9H-fluorene-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviated as DBTFLP-IV); and compounds with a furan skeleton, such as 4,4',4''-(benzyl-1,3,5-triyl)tris(dibenzofuran) (abbreviated as DBF3P-II) and 4-{3-[3-(9-phenyl-9H-fluorene-9-yl)phenyl]phenyl}dibenzofuran (abbreviated as mmDBFFLBi-II). Compounds with an aromatic amine backbone or a carbazole backbone are preferred due to their good reliability and high hole transport capacity, which helps reduce the driving voltage. Alternatively, organic compounds with hole transport capacity, such as those used as hole transport layers, can also be used. Furthermore, organic compounds with amine and fluorene backbones are more preferred. Organic compounds with amine and fluorene backbones have high reliability and high hole transport capacity, thus reducing the power consumption of the light-emitting device.

[0310] As a material with electron transport properties, it is preferable to use a material with an electron mobility of 1×10⁻⁶ when the square root of the electric field strength [V / cm] is 600. -7 cm 2 / Vs or more, preferably 1×10 -6 cm 2 Substances with a value of / Vs or higher. Furthermore, any substance other than those mentioned above may be used, provided that its electron transport capacity is higher than its hole transport capacity.

[0311] As materials with electron transport properties, preferred materials include, for example, metal complexes such as tris(8-hydroxyquinoline)aluminum (Alq3), bis(10-hydroxybenzo[h]quinoline)beryllium(II) (BeBq2), bis(2-methyl-8-hydroxyquinoline)(4-phenylphenol)aluminum(III) (BAlq), bis(8-hydroxyquinoline)zinc(II) (Znq), bis[2-(2-benzoxazolyl)phenol]zinc(II) (ZnPBO), and bis[2-(2-benzothiazolyl)phenol]zinc(II) (ZnBTZ), as well as organic compounds including π-electron-deficient heteroaromatic rings. Examples of organic compounds with π-electron-deficient heteroaromatic skeletons include organic compounds containing heteroaromatic rings with polyazole skeletons, organic compounds containing heteroaromatic rings with pyridine skeletons, organic compounds containing heteroaromatic rings with diazine skeletons, and organic compounds containing heteroaromatic rings with triazine skeletons.

[0312] Organic compounds containing heteroaromatic rings with a diazine (pyrimidine, pyrazine, or pyridazine) skeleton, organic compounds containing heteroaromatic rings with a pyridine skeleton, or organic compounds containing heteroaromatic rings with a triazine skeleton are preferred due to their good reliability. In particular, organic compounds containing heteroaromatic rings with a diazine (pyrimidine or pyrazine) skeleton and organic compounds containing heteroaromatic rings with a triazine skeleton exhibit high electron transport properties, which helps to reduce the driving voltage. Furthermore, benzofuran-pyrimidine skeletons, benzothiophene-pyrimidine skeletons, benzofuran-pyrazine skeletons, and benzothiophene-pyrazine skeletons are preferred due to their high acceptor activity and reliability.

[0313] Examples of organic compounds with π-electron-deficient heteroaromatic ring skeletons include: 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviated as PBD), 3-(4-biphenyl)-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), 9-[4-(5-phenyl-1,3,4-oxadiazole-2-yl]benzene... 2,2',2''-(1,3,5-phenyltriyl)tris(1-phenyl-1H-benzimidazole) (abbreviation: TPBI), 2-[3-(dibenzothiophene-4-yl)phenyl]-1-phenyl-1H-benzimidazole (abbreviation: mDBTBIm-II), 4,4'-bis(5-methylbenzoxazol-2-yl)stilbene (abbreviation: BzOs), 2-{4-[9,10-di(2-naphthyl)-2-anthrayl]phenyl}- Organic compounds with an azole skeleton, such as 1-phenyl-1H-benzimidazole (ZADN); 3,5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine (35DCzPPy), 1,3,5-tris[3-(3-pyridyl)phenyl]benzene (TmPyPB), phenanthroline (Bphen), copper hydroxide (BCP), 2,9-bis(naphthyl-2-yl)-4,7-diphenyl-1,10-phenanthroline (NBphen), 2,2 '-(1,3-Phenylidene)bis(9-phenyl-1,10-phenanthroline) (abbreviation: mPPhen2P), 2-[3-(2-triphenylene)phenyl]-1,10-phenanthroline (abbreviation: mTpPPhen), 2-phenyl-9-(2-triphenylene)-1,10-phenanthroline (abbreviation: Ph-TpPhen), 2-[4-(9-phenanthyl)-1-naphthyl]-1,10-phenanthroline (abbreviation: PnNPhen), 2-[4-(2-triphenylene)phenyl]-1,10-Phenanthroline (abbreviated as pTpPPhen) and other organic compounds containing heteroaromatic rings with a pyridine skeleton; 2-[3-(dibenzothiophene-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviated as 2mDBTPDBq-II), 2-[3'-(dibenzothiophene-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviated as 2mDBTBPDBq-II), 2-[3'-(9H-carbazol-9-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviated as 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-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 7mDBTPDBq-II), 6-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 6mDBTPDBq-II), 9-[3'-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 6mDBTPDBq-II), 9-[3'-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 6mDBTPDBq-II), Benzothiophene-4-yl)biphenyl-3-yl]naphtho[1',2':4,5]furano[2,3-b]pyrazine (abbreviation: 9mDBtBPNfpr), 9-[3'-(dibenzothiophene-4-yl)biphenyl-4-yl]naphtho[1',2':4,5]furano[2,3-b]pyrazine (abbreviation: 9pmDBtBPNfpr), 4,6-bis[3-(phenanthrene-9-yl)phenyl]pyrimidine (abbreviation: 4,6mPnP2Pm), 4,6-bis[3-(dibenzothiophene-4-yl)phenyl]pyrimidine ( Abbreviations: 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-(dibenzothiophene-4-yl)phenyl]-[1]benzofurano[3,2-d]pyrimidine (abbreviation: 8BP-4mDBtPBfpm), 3,8 -bis[3-(dibenzothiophene-4-yl)phenyl]benzofurano[2,3-b]pyrazine (abbreviation: 3,8mDBtP2Bfpr), 4,8-bis[3-(dibenzothiophene-4-yl)phenyl]-[1]benzofurano[3,2-d]pyrimidine (abbreviation: 4,8mDBtP2Bfpm), 8-[3'-(dibenzothiophene-4-yl)[biphenyl-3-yl]naphtho[1',2':4,5]furano[3,2-d]pyrimidine (abbreviation: 8mDBtBPNfpm), 8-([(2,2'-Binaphthyl)-6-yl)-4-[3-(dibenzothiophene-4-yl)phenyl]-[1]benzofuran[3,2-d]pyrimidine (abbreviation: 8(βN2)-4mDBtPBfpm), 2,2'-(pyridin-2,6-diyl)bis(4-phenylbenzo[h]quinazolin) (abbreviation: 2,6(P-Bqn)2Py), 2,2'-(pyridin-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-naphthyl) -1-ylphenyl)-4-[4-(3-pyridyl)phenyl]pyrimidine (abbreviation: 2,4NP-6PyPPm), 4-[3,5-bis(9H-carbazol-9-yl)phenyl]-2-phenyl-6-(biphenyl-4-yl)pyrimidine (abbreviation: 6BP-4Cz2PPm), 8-(biphenyl-4-yl)-4-[3'-(dibenzothiophene-4-yl)biphenyl-3-yl]-[1]benzofurano[3,2-d]pyrimidine (abbreviation: 8BP-4mDBtBPBfpm), 8-(p-terphenyl-3-yl)-4-[3-(dibenzothiophene-4-yl)phenyl]-[1]benzofurano[3,2-d]pyrimidine (abbreviation: 8mpTP-4mDBtPBfpm), 7- [4-(9-phenyl-9H-carbazol-2-yl)quinazolin-2-yl]-7H-dibenzo[c,g]carbazole (abbreviation: PC-cgDBCzQz) and other organic compounds with a diazine skeleton; 2-(biphenyl-4-yl)-4-phenyl-6-(9,9'-spirobis[9H-fluorene]-2-yl)-1,3,5-triazine (abbreviation: BP-SFTzn), 2-{3-[3-(benzo[b]naphtho[1,2-d]furan-8-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mBnfBPTzn), 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-triazin-2-yl)phenyl]-9'-phenyl-2,3'-bi-9H-carbazole (abbreviation: mPCCzPTzn-02), 2-[3'-(9,9-dimethyl-9H-fluorene-2-yl)biphenyl-3-yl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mFBPTzn), 5-[3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]-7,7-Dimethyl-5H,7H-indo[2,1-b]carbazole (abbreviation: mINc(II)PTzn), 2-{3-[3-(dibenzothiophene-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-phenanthyl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mPn-mDMePyPTzn), 11- [4-(biphenyl-4-yl)-6-phenyl-1,3,5-triazin-2-yl]-11,12-dihydro-12-phenyl-indolo[2,3-a]carbazole (abbreviation: BP-Icz(II)Tzn), 2-[3'-(triphenyl-2-yl)biphenyl-3-yl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mTpBPTzn), 3-[9-(4,6-diphenyl-1,3,5-triazin-2-yl)-2-dibenzofuranyl]-9-phenyl-9H-carbazole (abbreviation: PCDBfTzn), 2-(biphenyl-3-yl)-4-phenyl-6-[8-([1,1'-] [4',1''-tert-phenyl]-4-yl)-1-dibenzofuranyl]-1,3,5-triazine (abbreviation: mBP-TPDBfTzn), 2-(3'',5',5''-tri-tert-butyl-[1,1':3',1''-tert-phenyl]-4-yl)-4,6-diphenyl-1,3,5-triazine (abbreviation: mmtBumTPTzn-04), 2,4,6-tris[3'-(pyridin-3-yl)-5'-tert-butyl-biphenyl-3-yl]-1,3,5-triazine (abbreviation: tBu-TmPPPyTz), 2,4,6-tris[3'-(pyrimidin-3-yl)-5'-tert-butyl]-1,3,5-triazine Organic compounds containing a heteroaromatic ring with a triazine skeleton, such as butyl-biphenyl-4-yl]-1,3,5-triazine (abbreviated as tBu-TmPPPyTz-02), 2-(3'',5',5''-tri-tert-butyl-[1,1':3',1''-terbiphenyl]-5-yl)-4,6-diphenyl-1,3,5-triazine (abbreviated as mmtBumTPTzn-03), and 2-{3-(2,6-dimethylpyridin-3-yl)-5-[(3,5-di-tert-butyl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviated as mmtBuPh-mDMePyPTzn), are preferred. Furthermore, organic compounds containing a heteroaromatic ring with a diazine skeleton, organic compounds containing a heteroaromatic ring with a pyridine skeleton, or organic compounds containing a heteroaromatic ring with a triazine skeleton are preferred due to their high reliability. In particular,Organic compounds containing heteroaromatic rings with a diazine (pyrimidine or pyrazine) skeleton and organic compounds containing heteroaromatic rings with a triazine skeleton exhibit high electron transport properties, which helps to reduce the driving voltage. Among them, 8BP-4mDBtBPBfpm, 4,6mDBTP2Pm-II, 8mpTP-4mDBtPBfpm, TPBI, ZADN, BP-ICz(II)Tzn, mmtBumTPTzn-04, tBu-TmPPPyTz, tBu-TmPPPyTz-02, mmtBumTPTzn-03, mmtBuPh-mDMePyPTzn, 4,8mDBtP2Bfpm, and Alq3 are organic compounds with large GSP_Slope of vapor-deposited films, and are therefore suitable as materials for the second electron transport layer of the light-emitting device of the present invention.

[0314] As a TADF material that can be used as the host material, the same materials mentioned above as TADF materials can be used. When a TADF material is used as the host material, the triple excitation energy generated by the TADF material is converted into a single excitation energy via antisystem crossing and further transferred to the luminescent material, thereby improving the luminous efficiency of the light-emitting device. In this case, the TADF material acts as an energy donor, and the luminescent material acts as an energy acceptor.

[0315] Furthermore, the host material can also be a mixture of multiple substances. When using a mixed host material, it is preferable to mix materials with electron transport properties and materials with hole transport properties. By mixing materials with electron transport properties and materials with hole transport properties, it is easier to adjust the transport properties of the light-emitting layer 113 and to control the composite region more easily. The weight ratio of the content of the hole transport material and the electron transport material can be from 1:19 to 19:1.

[0316] Note that phosphorescent materials can be used as part of the above-described mixture. When used as a fluorescent material, the phosphorescent material can be used as an energy donor to supply excitation energy to the fluorescent material.

[0317] Furthermore, these mixed materials can also be used to form excimer complexes. By selecting a combination of excimer complexes that emit light with wavelengths overlapping the absorption band on the lowest energy side of the luminescent material, energy transfer can be facilitated, resulting in efficient luminescence, which is therefore preferred. Furthermore, this structure allows for a reduction in the driving voltage, making it also preferred.

[0318] Note that at least one of the materials forming the excitocomplex can be a phosphorescent material. This allows for the efficient conversion of the triple excitation energy into a single excitation energy via an antisystem crosstalk.

[0319] Regarding the combination of materials for efficiently forming excitocomplexes, the HOMO energy level of the material with hole transport is preferably above the HOMO energy level of the material with electron transport. Furthermore, the LUMO energy level of the material with hole transport is preferably above the LUMO energy level of the material with electron transport. Note that the LUMO and HOMO energy levels of the material can be determined from the electrochemical properties (reduction potential and oxidation potential) of the material measured by cyclic voltammetry (CV).

[0320] Note that the formation of excitocomplexes can be confirmed, for example, by comparing the emission spectra of a hole-transporting material, the emission spectra of an electron-transporting material, and the emission spectra of a hybrid film formed by mixing these materials. When the emission spectrum of the hybrid film is observed to shift towards a longer wavelength (or to have a new peak at a longer wavelength) compared to the emission spectra of each material, it indicates the formation of an excitocomplex. Alternatively, 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 hybrid film formed by mixing these materials, when a difference in transient response is observed, such as the mixed film having a longer lifetime component or a higher ratio of delayed components compared to the transient PL lifetimes of each material, it indicates the formation of an excitocomplex. Furthermore, the aforementioned transient PL can be referred to as transient electroluminescence (EL). In other words, by comparing the transient EL of a hole-transporting material, the transient EL of an electron-transporting material, and the transient EL of a hybrid film of these materials, and observing the differences in transient responses, the formation of an excitocomplex can be confirmed.

[0321] Electron transport layer 114 is a layer containing a material with electron transport properties. Preferably, the material with electron transport properties has an electron mobility of 1×10⁻⁶ when the square root of the electric field strength [V / cm] is 600. -7 cm 2 / Vs or more, preferably 1×10 -6 cm 2 Substances with a value of / Vs or higher. Furthermore, any substance other than those described above may be used, as long as its electron transport capability is higher than its hole transport capability. As the aforementioned organic compounds, organic compounds having a π-electron-deficient heteroaromatic ring are preferred. For example, one or more of the following are preferred: organic compounds containing a heteroaromatic ring with a polyazole skeleton, organic compounds containing a heteroaromatic ring with a pyridine skeleton, organic compounds containing a heteroaromatic ring with a diazine skeleton, and organic compounds containing a heteroaromatic ring with a triazine skeleton.

[0322] As an organic compound with electron transport properties that can be used in the electron transport layer 114, the same organic compounds with electron transport properties that can be used in the light-emitting layer 113 can be used. Among them, organic compounds containing heteroaromatic rings with a diazine skeleton, organic compounds containing heteroaromatic rings with a pyridine skeleton, and organic compounds containing heteroaromatic rings with a triazine skeleton are preferred because they have good reliability. In particular, organic compounds containing heteroaromatic rings with a diazine (pyrimidine or pyrazine) skeleton and organic compounds containing heteroaromatic rings with a triazine skeleton have high electron transport properties, which helps to reduce the driving voltage. In particular, organic compounds with a phenanthroline skeleton, such as mTpPPhen, PnNPhen, and mPPhen2P, are preferred, and organic compounds with a phenanthroline dimer structure, such as mPPhen2P, have excellent stability and are therefore more preferred.

[0323] Note that the electron transport layer 114 may also have a stacked structure. The layer in the electron transport layer 114 that is in contact with the light-emitting layer 113 can also be used as a hole blocking layer. When the electron transport layer in contact with the light-emitting layer is used as a hole blocking layer, it is preferable to use a material whose HOMO energy level is more than 0.5 eV lower than the HOMO energy level of the material in the light-emitting layer 113.

[0324] As the electron injection layer 115, a compound or complex containing an alkali metal or alkaline earth metal such as 8-hydroxyquinoline-lithium (Liq) or a layer containing 1,1'-pyridine-2,6-diyl-bis(1,3,4,6,7,8-hexahydro-2H-pyrimidino[1,2-a]pyrimidine) (hpp2Py) may also be provided. As the electron injection layer 115, an alkali metal or alkaline earth metal or its compound may also be included in a layer formed using a substance with electron transport properties.

[0325] In addition, a charge generation layer 116 can be provided instead of an electron injection layer 115. Figure 7A The charge generation layer 116 is a layer that, by applying a potential, can inject holes into the layer in contact with the cathode side of the layer and inject electrons into the layer in contact with the anode side of the layer. The charge generation layer 116 includes at least a p-type layer 117. The p-type layer 117 is preferably formed using the composite material that constitutes the hole injection layer 111 described above. Alternatively, the p-type layer 117 can also be formed by laminating a film containing an acceptor material as described in the composite material description and a film containing a hole transport material. By applying a potential to the p-type layer 117, electrons and holes are injected into the electron transport layer 114 and the cathode, respectively, causing the light-emitting device to operate. In addition, one embodiment of the present invention uses an organic compound with a low refractive index, and by using it in the p-type layer 117, a light-emitting device with good external quantum efficiency can be obtained.

[0326] In addition to the p-type layer 117, the charge generation layer 116 preferably includes one or both of the electron relay layer 118 and the electron injection buffer layer 119.

[0327] The electron relay layer 118 contains at least an electron-transporting material and is capable of preventing the interaction between the electron injection buffer layer 119 and the p-type layer 117, while facilitating electron transfer. Preferably, the LUMO energy level of the electron-transporting material contained in the electron relay layer 118 is set between the LUMO energy level of the acceptor material in the p-type layer 117 and the LUMO energy level of the material contained in the layer in the electron transport layer 114 that contacts the charge-generating layer 116. Specifically, the LUMO energy level of the electron-transporting material in the electron relay layer 118 is -5.0 eV or higher, preferably -5.0 eV or higher and -3.0 eV or lower. Furthermore, phthalocyanine materials or metal complexes having metal-oxygen bonds and aromatic ligands are preferably used as the electron-transporting material in the electron relay layer 118.

[0328] The electron injection buffer layer 119 can use alkali metals, alkaline earth metals, rare earth metals and their compounds (alkali metal compounds (including oxides such as lithium oxide, halides, carbonates such as lithium carbonate or cesium carbonate), alkaline earth metal compounds (including oxides, halides, carbonates) or rare earth metal compounds (including oxides, halides, carbonates)) and other materials with high electron injection properties.

[0329] Furthermore, when the electron injection buffer layer 119 contains both electron transport and donor materials, the donor materials can be alkali metals, alkaline earth metals, rare earth metals, and compounds of these materials (alkali metal compounds (including oxides, halides, and carbonates such as lithium oxide or cesium carbonate), alkaline earth metal compounds (including oxides, halides, and carbonates), or rare earth metal compounds (including oxides, halides, and carbonates)). Organic compounds such as tetrathianaphthacene (TTN), nickel-cadmium, and decamethylnickel-cadmium can also be used. Additionally, the electron transport material can be the same material described above for the electron transport layer 114.

[0330] The second electrode 102 is an electrode that includes a cathode. The second electrode 102 may also have a stacked structure, in which case the layer in contact with the EL layer 103 is used as the cathode. As the material forming the cathode, metals, alloys, conductive compounds, and mixtures thereof with low work functions (specifically below 3.8 eV) 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 Group 2 of the periodic table such as magnesium (Mg), calcium (Ca), or strontium (Sr), alloys containing them (MgAg, AlLi), compounds (lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF2), etc.), rare earth metals such as europium (Eu) and ytterbium (Yb), and alloys containing them. However, by providing an electron injection layer 115 or a thin film of a material with a small work function between the second electrode 102 and the electron transport layer, various conductive materials such as Al, Ag, ITO, indium oxide-tin oxide containing silicon or silicon oxide, etc., can be used as cathodes regardless of the size of the work function.

[0331] When the second electrode 102 is made of a material that is transparent to visible light, a light-emitting device that emits light from one side of the second electrode 102 can be formed.

[0332] These conductive materials can be formed using dry methods such as vacuum evaporation and sputtering, as well as inkjet printing and spin coating. Alternatively, they can be formed using wet methods such as sol-gel or wet methods using pastes of metallic materials.

[0333] Furthermore, various methods, whether dry or wet, can be used to form the EL layer 103. For example, vacuum evaporation, gravure printing, offset printing, screen printing, inkjet printing, or spin coating can also be used.

[0334] In addition, the electrodes or layers described above can also be formed by using different deposition methods.

[0335] Next, refer to Figure 7B This describes a light-emitting device (also called a stacked device or tandem device) with a structure having multiple light-emitting units stacked together. This light-emitting device has multiple light-emitting units between the anode and cathode. Each light-emitting unit has a... Figures 1A to 2B The structure is roughly the same as that of EL layer 103 shown. That is to say, it can be said that... Figure 7B The light-emitting device shown is a light-emitting device with multiple light-emitting units, while Figures 1A to 2B The light-emitting device shown is a light-emitting device with one light-emitting unit.

[0336] exist Figure 7BIn this structure, 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-generating layer 513 is disposed between the first light-emitting unit 511 and the second light-emitting unit 512. The first electrode 501 and the second electrode 502 respectively correspond to... Figures 1A to 2B The first electrode 101 and the second electrode 102 are used in the process, and can be applied to... Figures 1A to 2B The same material as described. Furthermore, the first light-emitting unit 511 and the second light-emitting unit 512 may have the same structure or different structures.

[0337] The charge generation layer 513 has the function of injecting electrons into one light-emitting unit and holes into another light-emitting unit when a voltage is applied to the first electrode 501 and the second electrode 502. In other words, in Figure 7B In this process, when a voltage is applied such that the potential of the anode is higher than that of the cathode, the charge generation layer 513 can inject electrons into the first light-emitting unit 511 and inject holes into the second light-emitting unit 512.

[0338] The charge generation layer 513 preferably has the same as Figure 7A The charge generation layer 116 shown has the same structure. Because the composite material of organic compound and metal oxide has good carrier injection and carrier transport properties, it is possible to achieve low voltage drive and low current drive.

[0339] Note that when the surface of the light-emitting unit on the anode side is in contact with the charge generation layer 513, the charge generation layer 513 can function as the hole injection layer of the light-emitting unit, so the light-emitting unit may not have a hole injection layer.

[0340] In addition, when an electron injection buffer layer 119 is provided in the charge generation layer 513, since the electron injection buffer layer 119 has the function of an electron injection layer in the light-emitting unit on the anode side, it is not necessary to provide an electron injection layer in the light-emitting unit on the anode side.

[0341] Although Figure 7B The description includes a light-emitting device with two light-emitting units, but similarly, light-emitting devices with three or more light-emitting units stacked can be applied. As in the light-emitting device according to this embodiment, by separating and arranging multiple light-emitting units between a pair of electrodes using a charge-generating layer 513, the device can achieve high brightness emission while maintaining low current density, and can also achieve a long lifespan. Furthermore, a light-emitting device capable of low-voltage driving and low power consumption can be realized.

[0342] Furthermore, by making the emission colors of each light-emitting unit different, the desired color of emission can be obtained from the entire light-emitting device. For example, by obtaining red and green emission colors from the first light-emitting unit and blue emission color from the second light-emitting unit in a light-emitting device with two light-emitting units, a light-emitting device that emits white light throughout the entire device can be obtained.

[0343] Furthermore, the aforementioned EL layer 103, first light-emitting unit 511, second light-emitting unit 512, charge-generating layer, and electrodes can be formed using methods such as vapor deposition (including vacuum vapor deposition), droplet jetting (also known as inkjet printing), coating, and gravure printing. Additionally, they may contain low-molecular-weight materials, medium-molecular-weight materials (including oligomers and dendritic polymers), or high-molecular-weight materials.

[0344] Implementation Method 3

[0345] In this embodiment, an example is described of using a light-emitting device according to one aspect of the present invention as a display element of a display device. In this embodiment, the shape of the light-emitting device is shown to be formed using photolithography, but the light-emitting device can also be formed using methods such as high-precision metal masks.

[0346] like Figure 8A and Figure 8B As shown, multiple light-emitting devices 130 are formed on the insulating layer 175 and constitute a display device.

[0347] The display device 100 includes a pixel section 177 in which a plurality of pixels 178 are arranged in a matrix. The pixels 178 include sub-pixels 110R, 110G, and 110B.

[0348] In this specification, for example, when describing the common content among subpixels 110R, 110G, and 110B, they are sometimes referred to as subpixel 110. Similarly, when describing the common content among other constituent elements distinguished by letters, symbols with omitted letters are sometimes used.

[0349] Subpixel 110R emits red light, subpixel 110G emits green light, and subpixel 110B emits blue light. Thus, an image can be displayed on pixel unit 177. In this embodiment, a subpixel of three colors—red (R), green (G), and blue (B)—is used as an example, but combinations of other colors of subpixels can also be used. Furthermore, the number of subpixels is not limited to three; four or more can be used. Examples of four subpixels include: a subpixel of four colors—R, G, B, and white (W); a subpixel of four colors—R, G, B, and yellow (Y); and a subpixel of four colors—R, G, B, and infrared (IR); etc.

[0350] In this specification, the row direction is sometimes referred to as the X direction and the column direction as the Y direction. The X direction and the Y direction intersect, for example, by perpendicular intersection.

[0351] exist Figure 8A In the example shown, subpixels of different colors are arranged in the X direction, and subpixels of the same color are arranged in the Y direction. Note that it is also possible to arrange subpixels of different colors in the Y direction and subpixels of the same color in the X direction.

[0352] A connecting portion 140 may be provided on the outer side of the pixel portion 177, and a region 141 may also be provided thereon. 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. In addition, a conductive layer 151C is provided on the connecting portion 140.

[0353] exist Figure 8A In the example shown, region 141 and connecting portion 140 are located to the right of pixel portion 177, but there are no particular restrictions on the position of region 141 and connecting portion 140. Furthermore, region 141 and connecting portion 140 may be one or more.

[0354] Figure 8B It is along Figure 8A An example of a cross-sectional view of the dashed-dot line A1-A2 in the diagram. For example... Figure 8B As shown, the display device includes an insulating layer 171, a conductive layer 172 on the insulating layer 171, an insulating layer 173 on the insulating layer 171 and 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 disposed on a substrate (not shown). The insulating layers 175, 174, and 173 are provided with openings leading to the conductive layer 172, and a plug 176 is disposed such that it is inserted into the openings.

[0355] In the pixel section 177, a light-emitting device 130 is disposed on the insulating layer 175 and the plug 176. Furthermore, a protective layer 131 is disposed to cover the light-emitting device 130. A substrate 120 is bonded to the protective layer 131 by a resin layer 122. Additionally, an inorganic insulating layer 125 and an insulating layer 127 on the inorganic insulating layer 125 are preferably disposed between adjacent light-emitting devices 130.

[0356] Figure 8B The cross-sections of the plurality of inorganic insulating layers 125 and the plurality of insulating layers 127 are shown, but when viewed from above the display device, the inorganic insulating layers 125 and the insulating layers 127 are preferably formed as a connected layer. That is, the inorganic insulating layers 125 and the insulating layers 127 are preferably insulating layers having openings on the first electrode.

[0357] exist Figure 8BLight-emitting devices 130R, 130G, and 130B are shown as light-emitting devices 130. The light-emitting colors of light-emitting devices 130R, 130G, and 130B are different 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. Alternatively, light-emitting devices 130R, 130G, or 130B can also emit other visible or infrared light. Note that in... Figure 8B In this context, light-emitting devices 130R and 130G, as well as light-emitting devices 130G and 130B, can be referred to as adjacent light-emitting devices.

[0358] One aspect of the display device of the present invention may have a top-emitting structure (top-emitting type) that emits light in a direction opposite to that of the substrate on which the light-emitting device is formed. Furthermore, one aspect of the display device of the present invention may also have a bottom-emitting structure (bottom-emitting type).

[0359] The light-emitting device 130R is a light-emitting device that emits red light (preferably phosphorescence), and preferably has the structure shown in Embodiment 2. The light-emitting device 130R includes a first electrode (pixel electrode) 101R composed of conductive layers 151R and 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.

[0360] The light-emitting device 130G is a green light-emitting device (preferably phosphorescent), and preferably has the structure shown in Embodiment 2. The light-emitting device 130G includes a first electrode (pixel electrode) 101G composed of conductive layers 151G and 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.

[0361] The light-emitting device 130B is a light-emitting device that emits blue light (preferably fluorescence), and preferably has the structure shown in Embodiment 2. The light-emitting device 130B includes a first electrode (pixel electrode) 101B composed of conductive layers 151B and 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.

[0362] In a light-emitting device, one of the pixel electrode (first electrode) and the common electrode (second electrode) is used as the anode, and the other is used as the cathode. In this embodiment, unless otherwise specified, it is sometimes assumed that the pixel electrode is used as the anode and the common electrode is used as the cathode.

[0363] The first layers 135R, 135G, and 135B are arranged independently in an island shape according to each light-emitting device or each light-emitting color. Note that the first layers 135R, 135G, and 135B preferably do not overlap with each other. Sometimes, the first layer including the multiple light-emitting devices 130 formed in the light-emitting device, such as the first layers 135R, 135G, and 135B, is collectively referred to as the first layer group 135A. By arranging the first layer group 135A in an island shape for each light-emitting device 130, leakage current between adjacent light-emitting devices 130 can be suppressed even in high-definition display devices. As a result, crosstalk can be prevented to achieve a display device with extremely high contrast. In particular, a display device with high current efficiency at low brightness can be achieved.

[0364] The island-shaped first layer group 135A is formed by depositing an EL film according to the emission color and processing the EL film using photolithography.

[0365] The first layer 135 is preferably provided in such a way that it covers the top surface and side surface 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 structure where the end of the first layer 135 is located inside the end of the pixel electrode. Furthermore, by covering the side surface 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, thus preventing short circuits in the light-emitting device 130.

[0366] In one aspect of the display device of the present invention, the first electrode 101 (pixel electrode) of the light-emitting device preferably has a stacked structure. For example, in Figure 8B In the example shown, the first electrode 101 of the light-emitting device 130 has a stacked structure of a conductive layer 151 disposed on one side of the insulating layer 171 and a conductive layer 152 disposed on one side of the organic compound layer.

[0367] As the conductive layer 151, a metallic material can be used, for example. 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 thereof can be used.

[0368] As the conductive layer 152, an oxide containing one or more of indium, tin, zinc, gallium, titanium, aluminum, and silicon can be used. For example, conductive oxides including one or more of indium oxide, indium tin oxide, indium zinc oxide, zinc oxide, gallium-containing zinc oxide, titanium oxide, gallium-containing indium zinc oxide, aluminum-containing indium zinc oxide, silicon-containing indium tin oxide, and silicon-containing indium zinc oxide are preferred. In particular, silicon-containing indium tin oxide has a large work function, for example, 4.0 eV or more, so it is suitable for use as the conductive layer 152.

[0369] Conductive layer 151 and conductive layer 152 may each have a stacked structure containing multiple layers of different materials. In this case, conductive layer 151 may also include a layer using a material that can be used in conductive layer 152, such as a conductive oxide, and conductive layer 152 may also include a layer using a material that can be used in conductive layer 151, such as a metallic material. For example, when conductive layer 151 has a stacked structure of two or more layers, the layer in contact with conductive layer 152 may be a layer using a material that can be used in conductive layer 152.

[0370] The ends of the conductive layer 151 preferably have a tapered shape. Specifically, the ends of the conductive layer 151 preferably have a tapered shape with a taper angle of less than 90°. In this case, the conductive layer 152 disposed along the side of the conductive layer 151 also has a tapered shape. By making the ends of the conductive layer 152 tapered, the coverage of the first layer 135 disposed along the side of the conductive layer 152 can be improved.

[0371] Implementation Method 4

[0372] This embodiment describes a display device according to one aspect of the present invention.

[0373] The display device in this embodiment can be a high-definition display device. Therefore, for example, the display device in this embodiment can be used as the display unit of information terminal devices (wearable devices) such as watch-type and bracelet-type devices, as well as the display unit of 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-type devices.

[0374] Furthermore, the display device in this embodiment can be a high-resolution display device or a large-screen display device. Therefore, the display device in this embodiment can be used, for example, as a display unit for devices such as: electronic devices with large screens, such as television sets, desktop or laptop personal computers, monitors for computers, digital signage, and large game machines such as pinball machines; digital cameras; digital video cameras; digital photo frames; mobile phones; portable game consoles; portable information terminals; and sound reproduction devices.

[0375] [Display Module]

[0376] Figure 9A A perspective view of display module 280 is shown. Display module 280 includes display device 100A and FPC 290. Note that the display device included in display module 280 is not limited to display device 100A, but may be any of display devices 100B to 100E, which will be described later.

[0377] The display module 280 includes a substrate 291 and a substrate 292. The display module 280 includes a display section 281. The display section 281 is the image display area in the display module 280, and can display light from each pixel disposed in the pixel section 284.

[0378] Figure 9B This is a three-dimensional schematic diagram of the structure on one side of 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 on the substrate 291. Furthermore, a terminal section 285 for connecting to the FPC 290 is provided on a portion of the substrate 291 that does not overlap with the pixel section 284. The terminal section 285 is electrically connected to the circuit section 282 via a wiring section 286 composed of multiple wirings.

[0379] The pixel unit 284 includes a plurality of pixels 284a arranged periodically. Figure 9B The right side shows a magnified view of pixel 284a. Pixel 284a can adopt various structures described in the above embodiments. Figure 9B In the example shown, pixel 284a has the same structure as pixel 178 shown in FIG8.

[0380] The pixel circuit section 283 includes a plurality of pixel circuits 283a arranged periodically.

[0381] A pixel circuit 283a controls the driving of multiple elements included in a pixel 284a.

[0382] The circuit section 282 includes circuitry for driving each pixel circuit 283a of the pixel circuit section 283. For example, it preferably includes one or both of a gate line driving circuit and a source line driving circuit. Furthermore, it may include at least one of an arithmetic circuit, a storage circuit, and a power supply circuit.

[0383] The FPC290 is used for wiring to supply video signals or power potentials to the circuit section 282 from the outside. Furthermore, integrated circuits (ICs) can be mounted on the FPC290.

[0384] The display module 280 can adopt a structure in which 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, so that the display section 281 can have an extremely high aperture ratio (effective display area ratio).

[0385] This high-definition display module 280 is suitable for use in VR devices such as HMDs or glasses-type AR devices. For example, because the display module 280 has an extremely high-definition display section 281, even when the user views the display section of the display module 280 through a lens and magnifies the display section with the lens, the pixels are not visible, thereby achieving a highly immersive display. Furthermore, the display module 280 is not limited to this and can also be applied to electronic devices with relatively small display sections.

[0386] [Display Device 100A]

[0387] Figure 10A The display device 100A shown includes a substrate 301, light-emitting devices 130R, 130G, 130B, a capacitor 240, and a transistor 310.

[0388] Substrate 301 is equivalent to Figure 9A and Figure 9B The substrate 291 is used in the transistor 310. The transistor 310 is a transistor having a channel formation region in the substrate 301. The substrate 301 can be, for example, a semiconductor substrate such as a single-crystal silicon substrate. The transistor 310 includes a portion of the substrate 301, a conductive layer 311, a low-resistance region 312, an insulating layer 313, and an insulating layer 314. The conductive layer 311 serves as the gate electrode. The insulating layer 313 is located between the substrate 301 and the conductive layer 311 and serves as the gate insulating layer. The low-resistance region 312 is a region in the substrate 301 doped with impurities and serves as the source or drain. The insulating layer 314 covers the sides of the conductive layer 311.

[0389] In addition, a component separation layer 315 is provided between two adjacent transistors 310 in a manner embedded in the substrate 301.

[0390] In addition, an insulating layer 261 is provided to cover the transistor 310, and a capacitor 240 is provided on the insulating layer 261.

[0391] The capacitor 240 includes a conductive layer 241, a conductive layer 245, and an insulating layer 243 located therebetween. The conductive layer 241 serves as one electrode in the capacitor 240, the conductive layer 245 serves as the other electrode in the capacitor 240, and the insulating layer 243 serves as the dielectric of the capacitor 240.

[0392] A conductive layer 241 is disposed on an insulating layer 261 and embedded within an insulating layer 254. The conductive layer 241 is electrically connected to one of the source and drain terminals of the transistor 310 via a connector 271 embedded in the insulating layer 261. An insulating layer 243 is disposed to cover the conductive layer 241. A conductive layer 245 is disposed in the region where it overlaps with the conductive layer 241, separated by the insulating layer 243.

[0393] An insulating layer 255 is provided to cover the capacitor 240, and an insulating layer 174 is provided on the insulating layer 255. Light-emitting devices 130R, 130G, and 130B are provided on the insulating layer 175. Insulators are provided in the areas between adjacent light-emitting devices.

[0394] An insulating layer 156R is provided such that it includes a region overlapping the side surface of conductive layer 151R; an insulating layer 156G is provided such that it includes a region overlapping the side surface of conductive layer 151G; and an insulating layer 156B is provided such that it includes a region overlapping the side surface of conductive layer 151B. Furthermore, a conductive layer 152R is provided such that it covers conductive layer 151R and insulating layer 156R; a conductive layer 152G is provided such that it covers conductive layer 151G and insulating layer 156G; and a conductive layer 152B is provided such that it covers conductive layer 151B and 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.

[0395] Conductive layers 151R, 151G, and 151B are electrically connected to one of the source and drain terminals of transistor 310 via plugs 256 embedded in insulating layers 243, 255, 174, and 175, conductive layer 241 embedded in insulating layer 254, and plug 271 embedded in insulating layer 261. The plugs can be made of various conductive materials.

[0396] Furthermore, a protective layer 131 is provided on the light-emitting devices 130R, 130G, and 130B. A resin layer 122 is attached to the protective layer 131 to bond the substrate 120. Detailed descriptions of the components of the light-emitting devices 130 and the substrate 120 can be found in Embodiment 3. The substrate 120 corresponds to... Figure 9A Substrate 292.

[0397] Figure 10B Show Figure 10A A modified example of the display device 100A shown. Figure 10BThe display device shown includes a color layer 132R, a color layer 132G, and a color layer 132B, and a light-emitting device 130 has a region overlapping one of the color layers 132R, 132G, and 132B. Figure 10B In the display device shown, the light-emitting device 130 can emit white light, for example. In addition, for example, the color layer 132R, color layer 132G and color layer 132B can transmit red light, green light and blue light, respectively.

[0398] [Display device 100B]

[0399] Figure 11 A perspective view of the display device 100B is shown. Figure 12 A cross-sectional view of the display device 100C is shown.

[0400] The display device 100B has a structure that bonds substrate 352 and substrate 351. Figure 11 In the image, substrate 352 is represented by a dashed line.

[0401] The display device 100B includes a pixel unit 177, a connection unit 140, a circuit 356, and wiring 355, etc. Figure 11 An example is shown where display device 100B is equipped with IC354 and FPC353. Therefore, it is also possible to... Figure 11 The structure shown is referred to as a display module including a display device 100B, an IC (integrated circuit), and an FPC. Here, the substrate of the display device on which connectors such as the FPC are mounted, or the substrate on which the IC is mounted, is referred to as the display module.

[0402] The connecting portion 140 is disposed on the outer side of the pixel portion 177. There may be one or more connecting portions 140. In the connecting portion 140, the common electrode of the light-emitting device is electrically connected to the conductive layer, and power can be supplied to the common electrode.

[0403] For example, a scan line drive circuit can be used as circuit 356.

[0404] Wiring 355 has the function of supplying signals and power to pixel unit 177 and circuit 356. The signals and power are input to wiring 355 from the outside via FPC 353 or from IC 354.

[0405] Figure 11 An example is shown where IC 354 is mounted on substrate 351 using methods such as COG (Chip On Glass) or COF (Chip On Film). IC 354 can be, for example, an IC including scan line drive circuitry or signal line drive circuitry. Note that the display device 100B and display module do not necessarily need to have an IC mounted on them. Alternatively, the IC can be mounted on an FPC using a COF method, for example.

[0406] Figure 12 An example of a cross-section of a display device 100C including a portion of an area of ​​FPC 353, a portion of circuitry 356, a portion of pixel portion 177, a portion of connection portion 140, and a portion of an area including an end portion is shown.

[0407] [Display Device 100C]

[0408] Figure 12 The display device 100C shown includes transistors 201 and 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.

[0409] For details on light-emitting devices 130R, 130G, and 130B, please refer to Embodiment 1.

[0410] Light-emitting device 130R includes 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 includes 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 includes a conductive layer 224B, a conductive layer 151B on the conductive layer 224B, and a conductive layer 152B on the conductive layer 151B.

[0411] The conductive layer 224R is connected to the conductive layer 222b included in the transistor 205 through an opening provided in the insulating layer 214. The end of the conductive layer 151R is located outside the end of the conductive layer 224R. The insulating layer 156R is provided in such a way that it includes a region that contacts the side of the conductive layer 151R, and the conductive layer 152R is provided in such a way that it covers the conductive layer 151R and the insulating layer 156R.

[0412] The conductive layers 224G, 151G, 152G, and 156G in the light-emitting device 130G, and the conductive layers 224B, 151B, 152B, and 156B in the light-emitting device 130B, are the same as the conductive layers 224R, 151R, 152R, and 156R in the light-emitting device 130R, so detailed descriptions are omitted.

[0413] The conductive layers 224R, 224G, and 224B have recesses formed in a manner that cover the openings provided in the insulating layer 214. These recesses are filled with layer 128.

[0414] Layer 128 has the function of planarizing the recesses of conductive layers 224R, 224G, and 224B. Conductive layers 151R, 151G, and 151B, which are electrically connected to conductive layers 224R, 224G, and 224B, are disposed on conductive layers 224R, 224G, and 224B. Therefore, the area overlapping the recesses of conductive layers 224R, 224G, and 224B can also be used as a light-emitting area, which can improve the pixel aperture ratio.

[0415] Layer 128 can also be an insulating layer or a conductive layer. Various inorganic insulating materials, organic insulating materials, and conductive materials can be suitably used for layer 128. In particular, layer 128 is preferably formed using an insulating material, and more preferably using an organic insulating material. Layer 128 can, for example, use the organic insulating material described above that can be used in insulating layer 127.

[0416] A protective layer 131 is provided on light-emitting devices 130R, 130G, and 130B. The protective layer 131 and the substrate 352 are bonded together by an adhesive layer 142. A light-shielding layer 157 is provided on the substrate 352. The light-emitting device 130 can be sealed using a solid sealing structure or a hollow sealing structure, etc. Figure 12 In this configuration, the space between substrate 352 and substrate 351 is filled with adhesive layer 142, i.e., it can be filled with an inert gas (nitrogen or argon, etc.), i.e., a hollow sealed structure can be adopted. In this case, adhesive layer 142 can also be set in a frame shape so as not to overlap with the light-emitting device. Alternatively, a resin different from that used for the frame-shaped adhesive layer 142 can be used to fill the space.

[0417] Figure 12 An example is shown below: the connecting portion 140 includes a conductive layer 224C obtained by processing a conductive film identical to conductive layers 224R, 224G, and 224B; a conductive layer 151C obtained by processing a conductive film identical to conductive layers 151R, 151G, and 151B; and a conductive layer 152C obtained by processing a conductive film identical to conductive layers 152R, 152G, and 152B. Furthermore, Figure 12 An example is shown in which the insulating layer 156C is disposed in such a manner that it includes a region that overlaps with the side of the conductive layer 151C.

[0418] Display device 100C is a top-emitting display device. A light-emitting device emits light onto one side of a substrate 352. The substrate 352 is preferably made of a material with high transmittance to visible light. When the light-emitting device emits infrared or near-infrared light, a material with high transmittance to such light is preferably used. The first electrode (pixel electrode) contains a material that reflects visible light, and the second electrode (opposite electrode) contains a material that transmits visible light.

[0419] Insulating layers 211, 213, 215, and 214 are sequentially disposed on substrate 351. A portion of insulating layer 211 serves as the gate insulating layer for each transistor. A portion of insulating layer 213 serves as the gate insulating layer for each transistor. Insulating layer 215 is disposed to cover the transistor. Insulating layer 214 is disposed to cover the transistor and serves as a planarization layer. Furthermore, there is no particular limitation on the number of gate insulating layers and the number of insulating layers covering the transistor; there can be one or more.

[0420] Inorganic insulating films are preferably used as insulating layers 211, 213 and 215.

[0421] The insulating layer 214 used as the planarization layer is preferably an organic insulating layer.

[0422] Transistor 201 and transistor 205 include: a conductive layer 221 serving as a gate; an insulating layer 211 serving as a gate insulating layer; conductive layers 222a and 222b serving as source and drain; a semiconductor layer 231; an insulating layer 213 serving as a gate insulating layer; and a conductive layer 223 serving as a gate.

[0423] A connection portion 204 is provided in the region of substrate 351 that is not overlapped with substrate 352. In the connection portion 204, wiring 355 is electrically connected to FPC 353 via conductive layer 166 and connection layer 242. An example is shown where conductive layer 166 has a stacked structure consisting of a conductive film processed from the same conductive films as conductive layers 224R, 224G, and 224B; a conductive film processed from the same conductive films as conductive layers 151R, 151G, and 151B; and a conductive film processed from the same conductive films as conductive layers 152R, 152G, and 152B. Conductive layer 166 is exposed on the top surface of connection portion 204. Therefore, connection portion 204 can be electrically connected to FPC 353 via connection layer 242.

[0424] Preferably, a light-shielding layer 157 is provided on the surface of the substrate 352 on the substrate 351 side. The light-shielding layer 157 can be provided between adjacent light-emitting devices, in the connection portion 140, and in the circuit 356, etc. In addition, various optical components can be arranged on the outer side of the substrate 352.

[0425] Substrate 351 and substrate 352 may each be made of a material that can be used in substrate 120.

[0426] As the adhesive layer 142, a material suitable for the resin layer 122 can be used.

[0427] As the connecting layer 242, anisotropic conductive film (ACF) or anisotropic conductive paste (ACP) can be used.

[0428] [Display Device 100D]

[0429] Figure 13 The display device 100D shown is Figure 12 The main difference between the display device 100C and the display device 100D is that the display device 100D is a bottom-emitting type display device.

[0430] The light emitted by the light-emitting device is directed onto one side of the substrate 351. The substrate 351 is preferably made of a material with high transmittance to visible light. On the other hand, there are no restrictions on the transmittance of the material used for the substrate 352.

[0431] Preferably, a light-shielding layer 157 is formed between the substrate 351 and the transistor 201 and between the substrate 351 and the transistor 205. Figure 13 An example is shown where a light-shielding layer 157 is disposed on a substrate 351, an insulating layer 153 is disposed on the light-shielding layer 157, and transistors 201, 205, etc. are disposed on the insulating layer 153.

[0432] The light-emitting device 130R includes a conductive layer 112R, a conductive layer 126R on the conductive layer 112R, and a conductive layer 129R on the conductive layer 126R.

[0433] The light-emitting device 130B includes a conductive layer 112B, a conductive layer 126B on the conductive layer 112B, and a conductive layer 129B on the conductive layer 126B.

[0434] The conductive layers 112R, 112B, 126R, 126B, 129R, and 129B all use materials with high transmittance to visible light. A material that reflects visible light is preferably used as the second electrode.

[0435] Note that, although Figure 13 The light-emitting device 130G is not shown in the figure, but it is also provided.

[0436] in addition, Figure 13 Examples are shown where the top surface of layer 128 has a flat portion, but there are no particular restrictions on the shape of layer 128.

[0437] [Display Device 100E]

[0438] Figure 14 The display device 100E shown is Figure 12The main difference between the display device 100E and the display device 100C is that the display device 100E includes color layer 132R, color layer 132G and color layer 132B.

[0439] In the display device 100E, the light-emitting device 130 has a region overlapping one of the coloring layers 132R, 132G, and 132B. The coloring layers 132R, 132G, and 132B can be disposed on a surface of the substrate 352 on one side of the substrate 351. The ends of the coloring layers 132R, 132G, and 132B can overlap the light-shielding layer 157.

[0440] In the display device 100E, the light-emitting device 130 can emit white light, for example. Additionally, for example, the color layers 132R, 132G, and 132B can transmit red light, green light, and blue light, respectively. Alternatively, the display device 100E may also employ a structure in which the color layers 132R, 132G, and 132B are disposed between the protective layer 131 and the adhesive layer 142.

[0441] Figure 12 and Figure 14 Examples are shown where the top surface of layer 128 has a flat portion, but there are no particular restrictions on the shape of layer 128.

[0442] This embodiment can be appropriately combined with other embodiments or examples. Furthermore, where multiple structural examples are shown in one embodiment in this specification, these structural examples can be appropriately combined.

[0443] Implementation Method 5

[0444] In this embodiment, an electronic device according to one aspect of the present invention will be described.

[0445] The electronic device of this embodiment includes 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 units of various electronic devices.

[0446] As electronic devices, in addition to large-screen electronic devices such as television sets, desktop or laptop personal computers, monitors for computers, digital signage, and large game machines such as pinball machines, other examples include digital cameras, digital video cameras, digital photo frames, mobile phones, portable game consoles, portable information terminals, and sound reproduction devices.

[0447] In particular, because the display device of one aspect of the present invention has low power consumption, it can be suitable for use in smaller electronic devices. Examples of such electronic devices include watch-type and bracelet-type information terminal devices (wearable devices), wearable devices that can be worn on the head, VR devices such as head-mounted displays, AR devices such as glasses, and MR devices.

[0448] The electronic device in this embodiment may also include a sensor (which has the function of measuring factors such as force, displacement, position, velocity, acceleration, angular velocity, rotational speed, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, tilt, vibration, odor, or infrared radiation).

[0449] Reference Figures 15A to 15D This illustrates an example of a wearable device that can be worn on the head.

[0450] Figure 15A The electronic device 700A shown and Figure 15B The electronic devices 700B shown 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 components 753, a frame 757, and a pair of nose pads 758.

[0451] The display panel 751 can be used in a display device according to one aspect of the present invention. Thus, an electronic device with low power consumption and the ability to operate for extended periods can be realized.

[0452] Both electronic devices 700A and 700B can project the image displayed by the display panel 751 onto the display area 756 in the optical component 753. Because the optical component 753 is light-transmitting, the user can see the image displayed in the display area by overlapping the image seen through the optical component 753.

[0453] Both electronic devices 700A and 700B can be equipped with cameras capable of capturing images of the front as imaging units. Furthermore, by incorporating accelerometers such as gyroscopes into both electronic devices 700A and 700B, the orientation of the user's head can be detected, and an image corresponding to that orientation can be displayed on the display area 756.

[0454] The communications unit includes a wireless communication device through which video signals can be supplied, for example. Additionally, a connector capable of connecting cables supplying video signals and power potential may be included, either in place of the wireless communication device or in addition to the wireless communication device.

[0455] In addition, electronic devices 700A and 700B are equipped with batteries that can be charged wirelessly or via wired means, or both.

[0456] The housing 721 can also be equipped with a touch sensor module.

[0457] Various touch sensors can be used as touch sensor modules. For example, capacitive, resistive, infrared, electromagnetic induction, surface acoustic wave, and optical sensors can be employed. In particular, capacitive or optical sensors are preferred for use in touch sensor modules.

[0458] Figure 15C The electronic device 800A shown and Figure 15D The electronic devices 800B shown all 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.

[0459] The display unit 820 can be equipped with a display device according to one aspect of the present invention. This allows for the realization of an electronic device with low power consumption and the ability to operate for extended periods.

[0460] The display unit 820 is located inside the housing 821 in a position visible through the lens 832. Furthermore, by displaying different images on each of the pair of display units 820, three-dimensional display utilizing parallax can be achieved.

[0461] Electronic devices 800A and 800B preferably have a mechanism in which the left and right positions of the lens 832 and the display unit 820 can be adjusted so that the lens 832 and the display unit 820 are in the most suitable position according to the position of the user's eyes.

[0462] Users can use the mounting unit 823 to wear electronic device 800A or electronic device 800B on their heads.

[0463] 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. Alternatively, multiple cameras can be provided to accommodate various viewing angles such as telephoto and wide-angle.

[0464] Electronic device 800A may also include a vibration mechanism used as a bone conduction headphone.

[0465] Electronic devices 800A and 800B may also include input terminals. Cables supplying image signals from image output devices and the like, as well as power for charging batteries installed within the electronic devices, can be connected to the input terminals.

[0466] The electronic device of one embodiment of the present invention may also have the function of wireless communication with the earphone 750.

[0467] In addition, electronic devices may also include an earphone unit. Figure 15B The illustrated electronic device 700B includes an earphone unit 727. A portion of the wiring connecting the earphone unit 727 and the control unit may also be configured inside the housing 721 or the mounting unit 723.

[0468] Similarly, Figure 15D The illustrated electronic device 800B includes an earphone unit 827. For example, a structure in which the earphone unit 827 and the control unit 824 are connected in a wired manner can be adopted.

[0469] Thus, as an embodiment of the present invention, both eyeglass type (electronic device 700A and electronic device 700B, etc.) and goggle type (electronic device 800A and electronic device 800B, etc.) are preferred electronic devices.

[0470] Figure 16A The electronic device 6500 shown is a portable information terminal device that can be used as a smartphone.

[0471] 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.

[0472] The display unit 6502 can use a display device according to one aspect of the present invention. This allows for the realization of an electronic device with low power consumption and the ability to operate for extended periods.

[0473] Figure 16B This is a cross-sectional schematic diagram of one end of the microphone 6506, including the housing 6501.

[0474] A light-transmitting protective member 6510 is provided on one side of the display surface of the housing 6501. The space surrounded by the housing 6501 and the protective member 6510 contains a display panel 6511, an optical member 6512, a touch sensor panel 6513, a printed circuit board 6517, a battery 6518, etc.

[0475] The display panel 6511, optical component 6512, and touch sensor panel 6513 are fixed to the protective component 6510 using an adhesive layer (not shown).

[0476] In the area outside the display unit 6502, a portion of the display panel 6511 is folded back, and this folded portion is connected to an FPC 6515. An IC 6516 is mounted on the FPC 6515. The FPC 6515 is connected to terminals disposed on a printed circuit board 6517.

[0477] The display panel 6511 can be used with a display device according to one aspect of the present invention. This allows for the realization of an extremely lightweight electronic device. Furthermore, since the display panel 6511 is extremely thin, a large-capacity battery 6518 can be installed while minimizing the thickness of the electronic device. Additionally, by folding a portion of the display panel 6511 to provide a connection portion with the FPC 6515 on the back of the pixel section, a narrow-bezel electronic device can be achieved.

[0478] Figure 16C An example of a television device is shown. In the television device 7100, a display unit 7000 is assembled in a housing 7171. Here is shown a structure in which the housing 7171 is supported by a bracket 7173.

[0479] The display unit 7000 can use a display device according to one aspect of the present invention. This allows for the realization of an electronic device with low power consumption and the ability to operate for extended periods.

[0480] It can be operated using the operating switch included in the housing 7171 and the separately provided remote control 7151. Figure 16C The operation of the television device 7100 shown.

[0481] Figure 16D An example of a notebook computer is shown. The notebook computer 7200 includes a casing 7211, a keyboard 7212, a pointing device 7213, and an external connection port 7214, etc. A display unit 7000 is assembled in the casing 7211.

[0482] The display unit 7000 can use a display device according to one aspect of the present invention. This allows for the realization of an electronic device with low power consumption and the ability to operate for extended periods.

[0483] Figure 16E and Figure 16F Here is an example of digital signage.

[0484] Figure 16E The digital sign 7300 shown includes a housing 7301, a display unit 7000, and a speaker 7303. It may also include LEDs, operation keys (including a power switch or operation switch), connection terminals, various sensors, a microphone, etc.

[0485] Figure 16FA digital sign 7400 is shown mounted on a cylindrical column 7401. The digital sign 7400 includes a display section 7000 disposed along the curved surface of the column 7401.

[0486] exist Figure 16E and Figure 16F In this embodiment, a display device according to one aspect of the present invention can be used in the display unit 7000. This allows for the realization of a highly reliable electronic device.

[0487] The larger the display unit (7000), the more information it can provide at once. A larger display unit (7000) is also more likely to attract attention, which can improve the effectiveness of advertising.

[0488] like Figure 16E and Figure 16F As shown, the digital signage 7300 or digital signage 7400 preferably can be linked with the user's smartphone or other information terminal device 7311 or information terminal device 7411 via wireless communication.

[0489] Figures 17A to 17G The electronic device shown includes a housing 9000, a display unit 9001, a speaker 9003, operation keys 9005 (including a power switch or operation switch), a connection terminal 9006, a sensor 9007 (which has the function of measuring the following factors: force, displacement, position, velocity, acceleration, angular velocity, rotational speed, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, tilt, vibration, odor, or infrared radiation), a microphone 9008, etc.

[0490] Figures 17A to 17G The electronic device shown has various functions. For example, it may have the following functions: displaying various information (static images, dynamic images, or text images, etc.) on the display unit; touch panel function; displaying calendar, date, or time, etc.; controlled and processed by various software (programs); wireless communication function; reading and processing programs or data stored in the storage medium; etc.

[0491] The following is a detailed explanation. Figures 17A to 17G The electronic device shown.

[0492] Figure 17A This is a perspective view showing a portable information terminal 9171. The portable information terminal 9171 can be used, for example, as a smartphone. Note that a speaker 9003, a connection terminal 9006, a sensor 9007, etc., may also be included in the portable information terminal 9171. Furthermore, as a portable information terminal 9171, text or image information can be displayed on multiple surfaces. Figure 17AThe image shows an example displaying three icons 9050. Alternatively, information 9051, shown as a dashed rectangle, can be displayed on other surfaces of the display unit 9001. Examples of information 9051 include notifications of received emails, SNS messages, or phone calls; the subject of the email or SNS message; the sender's name; the date; the time; remaining battery level; and radio wave strength. Alternatively, icons 9050 can be displayed in the same location where information 9051 is displayed.

[0493] Figure 17B This is a perspective view showing a portable information terminal 9172. The portable information terminal 9172 has the function of displaying information on three or more surfaces of the display unit 9001. Here, examples are shown where information 9052, information 9053, and information 9054 are displayed on different surfaces. For example, when the portable information terminal 9172 is placed in a jacket pocket, the user can view information 9053 displayed in a position seen from above the portable information terminal 9172.

[0494] Figure 17C This is a perspective view of a tablet terminal 9173. The tablet terminal 9173 can, for example, execute various application software such as mobile phone, email, and article reading and editing, music playback, network communication, and computer games. The tablet terminal 9173 includes a display unit 9001, a camera 9002, a microphone 9008, and a speaker 9003 on the front of its casing 9000; operation keys 9005 serving as operating buttons on the left side of the casing 9000; and a connection terminal 9006 on the bottom surface.

[0495] Figure 17D This is a perspective view showing a watch-type portable information terminal 9200. The portable information terminal 9200 can be used, for example, as a smartwatch (registered trademark). Furthermore, the display surface of the display unit 9001 is curved, allowing display along its curved surface. In addition, the portable information terminal 9200 can perform hands-free calls, for example, by communicating with a headset capable of wireless communication. Furthermore, by utilizing the connection terminal 9006, the portable information terminal 9200 can transmit data or charge with other information terminals. Charging can also be performed wirelessly.

[0496] Figures 17E to 17G This is a perspective view showing the foldable portable information terminal 9201. Additionally, Figure 17E This is a 3D view of the portable information terminal 9201 in its unfolded state. Figure 17G It is a 3D image of the folded state. Figure 17F From Figure 17E status and Figure 17GThe portable information terminal 9201 is a three-dimensional representation of the state transitioning between different states. In its folded state, it offers good portability, while in its unfolded state, it provides a large, seamless display area, resulting in excellent browsing capabilities. The display unit 9001 included in the portable information terminal 9201 is supported by three housings 9000 connected by hinges 9055. The display unit 9001 can be bent, for example, within a radius of curvature of 0.1 mm or more and 150 mm or less.

[0497] This embodiment can be appropriately combined with other embodiments or examples. Furthermore, where multiple structural examples are shown in one embodiment in this specification, these structural examples can be appropriately combined.

[0498] Example 1

[0499] In this embodiment, a detailed manufacturing method and characteristics of light-emitting device 1-1, light-emitting device 1-2, and comparative light-emitting devices 1-1 to 1-3 according to one embodiment of the present invention are described. The structural formulas of the main compounds used in this embodiment are shown below.

[0500] [Chemical Formula 6]

[0501]

[0502] (Manufacturing method of light-emitting device 1-1)

[0503] First, indium tin oxide (ITSO) containing silicon oxide is deposited on a glass substrate by sputtering to a thickness of 55 nm, thereby forming a first electrode 101 with a size of 2 mm × 2 mm. Furthermore, ITSO is used as the anode.

[0504] Next, as a pretreatment for forming light-emitting devices on the substrate, the substrate surface is washed with water.

[0505] Then, the substrate is placed inside and depressurized to 1×10⁻⁶. -4 The substrate is placed in a vacuum evaporation apparatus at approximately Pa and then calcined at 170°C for 30 minutes in the heating chamber of the apparatus, followed by cooling for approximately 30 minutes.

[0506] Next, the substrate is fixed on a support provided in a vacuum evaporation apparatus with the surface on which the first electrode 101 is formed facing down. A hole injection layer 111 is formed on the first electrode 101 by evaporation in a weight ratio of N-(biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-9,9-dimethyl-9H-fluorene-2-amine (abbreviated as: PCBBiF) represented by the above structural formula (i) and an electron acceptor material (OCHD-003) containing fluorine with a molecular weight of 672 at 1:0.03 (=PCBBiF:OCHD-003) and a thickness of 10 nm.

[0507] Next, PCBBiF is deposited on the hole injection layer 111 with a thickness of 45 nm, followed by the deposition of 9-[3-(triphenylsilyl)phenyl]-3,9'-bi-9H-carbazole (abbreviated as PSiCzCz) represented by the above structural formula (ii) with a thickness of 5 nm, thereby forming the hole transport layer 112. Note that the PSiCzCz layer is an organic compound with a π-electron-rich heteroaromatic ring and is also used as an electron blocking layer.

[0508] 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), PSiCzCz, and the structure represented by the above structural formula (iii) were co-deposited in a weight ratio of 0.35:0.53:0.12:0.015 (=SiTrzCz2:PSiCzCz:PtON-TBBI:1,6mmtBuDPhAPrn) with a thickness of 40 nm. (iv) represents (2-{3-[3-(3,5-di-tert-butylphenyl)benzimidazol-1-yl-2-ylidene-κC2]phenoxy-κC2}-9-(4-tert-butyl-2-pyridinyl-κN)carbazole-2,1-diyl-κC1)platinum(II) (abbreviation: PtON-TBBI) and N,N,N',N'-tetratetra(3,5-di-tert-butylphenyl)pyrene-1,6-diamine (abbreviation: 1,6mmtBuDPhAPrn) represented by the above structural formula (v), thereby forming the luminescent layer 113.

[0509] Note that PtON-TBBI is an organometallic complex exhibiting blue phosphorescence, while 1,6mmtBuDPhAPrn is an organic compound exhibiting blue fluorescence. Furthermore, PtON-TBBI comprises a tert-butyl alkyl group having four carbon atoms. Additionally, 1,6mmtBuDPhAPrn is an organic compound in which the luminescent component has a pyrene skeleton with fused aromatic rings and comprises eight tert-butyl alkyl groups having four carbon atoms.

[0510] Note that SiTrzCz2 is an organic compound with a π-electron-deficient heteroaromatic ring, while PSiCzCz is an organic compound with a π-electron-rich heteroaromatic ring.

[0511] Then, after depositing 2-phenyl-4,6-bis[3-(triphenylsilyl)phenyl]-1,3,5-triazine (abbreviated as mSiTrz) with a thickness of 5 nm, a second electron transport layer is formed by co-depositing 11-[4-(biphenyl-4-yl)-6-phenyl-1,3,5-triazine-2-yl]-11,12-dihydro-12-phenylindolo[2,3-a]carbazole (abbreviated as BP-Icz(II)Tzn) and 8-hydroxyquinoline-lithium (abbreviated as Liq) with a thickness of 30 nm and a weight ratio of 1:4 (=BP-Icz(II)Tzn):Liq). Note that mSiTrz and BP-Icz(II)Tzn are organic compounds with π-electron-deficient heteroaromatic rings, Liq is an organometallic complex containing an alkali metal, and the first electron transport layer is also used as a hole blocking layer.

[0512] After forming the electron transport layer, lithium fluoride (LiF) is deposited with a thickness of 1 nm to form the electron injection layer 115, and then aluminum (Al) is deposited with a thickness of 200 nm to form the second electrode 102 (cathode).

[0513] Next, in a glove box under a nitrogen atmosphere, a glass substrate is used to seal the light-emitting device in a manner that prevents it from being exposed to the atmosphere (a UV-curable sealing material is applied around the device, and UV is irradiated only to the sealing material without irradiating the light-emitting device, and heat treatment is performed at 80°C for 1 hour under atmospheric pressure), thereby forming the light-emitting device 1-1.

[0514] (Manufacturing method of light-emitting device 1-2)

[0515] The difference between the manufacturing methods of light-emitting device 1-2 and light-emitting device 1-1 lies in the following: SiTrzCz2 in the light-emitting layer of light-emitting device 1-1 is replaced with 9,9'-{6-[3-(triphenylsilyl)phenyl]-1,3,5-triazine-2,4-diyl}bis(9H-carbazole-1,2,3,4,5,6,7,8,1',2',3',4',5',6',7',8'-d16 (abbreviated as: SiTrzCz2-d16) represented by the above structural formula (xii), and PSiCzCz in the light-emitting layer of light-emitting device 1-1 is replaced with 9-[3-(triphenylsilyl)phenyl]-3,9'-(bi-9H-carbazole-d15) (abbreviated as: PSiCzCz-d15) represented by the above structural formula (xii).

[0516] (Compare the manufacturing methods of light-emitting device 1-1)

[0517] The difference between the manufacturing method of the light-emitting device 1-1 and the light-emitting device 1-1 is that the second electron transport layer in the light-emitting device 1-1 is formed by using 2,2'-(1,3-phenylene)bis(9-phenyl-1,10-phenanthroline) (abbreviated as mPPhen2P) represented by the above structural formula (ix).

[0518] (Compare the manufacturing methods of light-emitting devices 1-2)

[0519] The difference between the manufacturing methods of the comparison light-emitting device 1-2 and the comparison light-emitting device 1-1 is that the light-emitting layer of the comparison light-emitting device 1-2 is formed with a weight ratio of SiTrzCz2:PSiCzCz:PtON-TBBI:1,6mmtBuDPhAPrn=0.35:0.53:0.12:0, that is, the light-emitting layer of the comparison light-emitting device 1-1 is not formed using 1,6mmtBuDPhAPrn.

[0520] (Compare the manufacturing methods of light-emitting devices 1-3)

[0521] The difference between the manufacturing methods of light-emitting device 1-3 and light-emitting device 1-1 is that the light-emitting layer of light-emitting device 1-3 is formed with a weight ratio of SiTrzCz2:PSiCzCz:PtON-TBBI:1,6mmtBuDPhAPrn=0.35:0.53:0.12:0, that is, 1,6mmtBuDPhAPrn is not used to form the light-emitting layer of light-emitting device 1-1.

[0522] The following diagram shows the device structures of light-emitting device 1-1, light-emitting device 1-2, comparison light-emitting device 1-1, comparison light-emitting device 1-2, and comparison light-emitting device 1-3.

[0523] [Table 3]

[0524]

[0525] Figure 19 The brightness-current density characteristics of light-emitting device 1-1, light-emitting device 1-2, comparison light-emitting device 1-1, comparison light-emitting device 1-2, and comparison light-emitting device 1-3 are shown. Figure 20 The brightness-voltage characteristics are shown. Figure 21 The current efficiency-current density characteristics are shown. Figure 22 The current density-voltage characteristics are shown. Figure 23 The external quantum efficiency-current density characteristics are shown. Figure 24 The electroluminescence spectrum is shown. Furthermore, Table 4 shows the current density at 10 mA / cm². 2 The main characteristics are as follows. Note that measurements of luminance, CIE chromaticity, and electroluminescence spectrum were performed at room temperature using a spectroradiometer (Topcon, SR-UL1R). Furthermore, the external quantum efficiency was calculated using the measured luminance and emission spectra, assuming a Lambertian distribution.

[0526] Note that the Blue Emission Index (BI) is the value obtained by dividing the current efficiency (cd / A) by the y-value of the CIE(x,y) chromaticity. It is one of the indicators representing the luminous emission characteristics of blue light. Blue light emission tends to have higher color purity with a smaller y-value. By using blue light with a small y-value and high color purity, a wide range of blue hues can be displayed on the monitor. Furthermore, the brightness of the blue light required to display white on the monitor is reduced, thus reducing the monitor's power consumption. Therefore, it is sometimes preferable to use the current efficiency, which takes into account the y-value, as one of the indicators of blue purity, as a method to represent blue luminous efficiency. Thus, it can be said that the higher the BI of a light-emitting device, the better the efficiency of the blue light-emitting device used in a monitor.

[0527] [Table 4]

[0528]

[0529] from Figure 24 It can be seen that the peak wavelength of the electroluminescence spectrum of light-emitting device 1-1, light-emitting device 1-2 and comparison light-emitting device 1-1 is 471 nm and the full width at half maximum (FWHM) is 47 nm. The peak wavelength of the electroluminescence spectrum of comparison light-emitting device 1-2 and comparison light-emitting device 1-3 is 463 nm and the full width at half maximum (FWHM) is 45 nm. The emission spectra of light-emitting device 1-1, light-emitting device 1-2 and comparison light-emitting device 1-1 are different from those of comparison light-emitting device 1-2 and comparison light-emitting device 1-3. 1,6mmtBuDPhAPrn, which is a fluorescent luminescent material in light-emitting device 1-1, light-emitting device 1-2 and comparison light-emitting device 1-1, emits light.

[0530] In addition, from Figure 23 As can be seen, 1,6mmtBuDPhAPrn, as a fluorescent luminescent material in light-emitting devices 1-1, 1-2, and the comparative light-emitting device 1-1, emits light as described above, but the maximum external quantum efficiency is greater than 20%. Thus, by using PtON-TBBI as a phosphorescent luminescent material as an energy donor, light-emitting devices 1-1, 1-2, and the comparative light-emitting device 1-1, although fluorescent luminescent elements, can be light-emitting devices with a high efficiency of greater than 20%.

[0531] then, Figure 25 It shows 10mA / cm 2 The time-varying characteristics of normalized brightness when the current density drives light-emitting device 1-1, light-emitting device 1-2, comparison light-emitting device 1-1, comparison light-emitting device 1-2, and comparison light-emitting device 1-3. Figure 26 This graph shows the elapsed time (LT90) when the brightness of each light-emitting device in this measurement decreases to 90% of its initial brightness. Note that the initial brightness is set to 100% to represent the time-varying characteristics of the normalized brightness.

[0532] from Figure 25 and Figure 26 It is known that the light-emitting device 1-1 of one aspect of the present invention, which has a high GSP_Slope of the second electron transport layer and contains both PtON-TBBI (phosphorescent material) and 1,6mmtBuDPhAPrn (fluorescent material), exhibits very good characteristics at LT90, approximately 1.7 times that of comparative light-emitting devices 1-1 and 1-3, and approximately 2.5 times that of comparative light-emitting device 1-2. Furthermore, the light-emitting device 1-2 exhibits very good characteristics at LT90, approximately 2.1 times that of comparative light-emitting devices 1-1 and 1-3, and approximately 3.2 times that of comparative light-emitting device 1-2.

[0533] Here, Figure 18The emission (PL) and absorption spectra of PtON-TBBI (a material capable of converting triple excitation energy into light emission) and 1,6mmtBuDPhAPrn (a fluorescent luminescent material) in the manufactured light-emitting device 1 and comparative light-emitting device 1-1 are shown. Note that the emission spectrum of PtON-TBBI was measured in dichloromethane solution using a fluorescence spectrophotometer (FP-8600DS, manufactured by Nippon Spectrophotometer Co., Ltd.), and the absorption spectrum was measured using a UV-Vis spectrophotometer (V-770DS, manufactured by Nippon Spectrophotometer Co., Ltd.). Furthermore, the emission spectrum of 1,6mmtBuDPhAPrn was measured in toluene solution using a fluorescence spectrophotometer (FS920, manufactured by Hamamatsu Photonics Co., Ltd.), and the absorption spectrum was measured using a UV-Vis spectrophotometer (V-550DS, manufactured by Nippon Spectrophotometer Co., Ltd.).

[0534] like Figure 18 As shown, the peak wavelength (456 nm) in the emission spectrum of PtON-TBBI is at a shorter wavelength compared to the peak wavelength (467 nm) in the emission spectrum of 1,6mmtBuDPhAPrn. Alternatively, the absorption end on the long wavelength side (465 nm) of the absorption spectrum of 1,6mmtBuDPhAPrn is at a longer wavelength compared to the emission end on the short wavelength side (441 nm) of the emission spectrum of PtON-TBBI. Or, the absorption end on the long wavelength side (465 nm) of the absorption spectrum of 1,6mmtBuDPhAPrn is at a longer wavelength compared to the absorption end on the long wavelength side (457 nm) of the absorption spectrum of PtON-TBBI.

[0535] The light-emitting device 1 with this structure and the comparative light-emitting device 1-1 have efficient energy transfer in the light-emitting layer from PtON-TBBI, a substance capable of converting triple excitation energy into light emission, to 1,6mmtBuDPhAPrn, a fluorescent light-emitting substance, thereby enabling the fluorescent light-emitting substance to emit light and exhibiting a light-emitting device with high luminous efficiency.

[0536] also, Figure 37A and Figure 37B The results of low-temperature PL measurements of SiTrzCz2 and PSiCzCz, the main materials of the fabricated light-emitting device, are shown. Figure 47A and Figure 47BThe results of low-temperature photoluminescence (PL) measurements on SiTrzCz2-d16 and PSiCzCz-d15 are shown. The measurements were performed using a LabRAM HR-PL micro-PL apparatus (manufactured by Horiba Corporation), at a temperature of 10 K. A He-Cd laser (wavelength 325 nm) was used as the excitation light, and a CCD detector was used as the detector. Note that the measured sample was a thin film, deposited on a quartz substrate with a thickness of 50 nm. After depositing the film on this quartz substrate in a nitrogen atmosphere, another quartz substrate was attached to the deposited surface before measurement.

[0537] like Figure 37A and Figure 37B As shown, the wavelengths of the short-wavelength emission ends (the short-wavelength emission ends of the phosphorescence spectrum) in the low-temperature PL measurements of SiTrzCz2 and PSiCzCz are 424 nm and 418 nm, respectively. Therefore, the T1 energy levels of SiTrzCz2 and PSiCzCz are 2.92 eV and 2.97 eV, respectively, with an energy difference of 0.05 eV. Note that when these materials are used as host materials, the energy difference of the T1 energy levels between host materials is less than 0.20 eV. Therefore, the deviation of the triple excitation energy between the host materials of the light-emitting device manufactured in this embodiment is small, thereby realizing a light-emitting device with good reliability.

[0538] In addition, such as Figure 47A and Figure 47B As shown, the wavelengths of the short-wavelength emission ends in the emission spectra of SiTrzCz2-d16 and PSiCzCz-d15 during low-temperature PL measurements are 423 nm and 417 nm, respectively. Therefore, the T1 energy levels of SiTrzCz2-d16 and PSiCzCz-d15 are 2.93 eV and 2.97 eV, respectively, with an energy difference of 0.05 eV. Note that when these materials are used as host materials, the energy difference of the T1 energy levels between host materials is less than 0.20 eV. Therefore, the deviation of the triple excitation energy between the host materials of the light-emitting device manufactured in this embodiment is small, and a reliable light-emitting device can be achieved. Furthermore, the light-emitting device of this embodiment uses a deuterated material as the host material. By using a deuterated material as the host material, the reliability of the light-emitting device is improved. The improved reliability when using a deuterated host material is related to the extended lifetime of the triple excitons of the host material. The extended lifetime of the triple exciton is due to the suppression of the non-radiative deactivation of the triple excitation energy caused by the suppression of deuteration oscillations. At this point, when the energy difference between the T1 level of SiTrzCz2-d16 and the T1 level of PSiCzCz-d15 is small, the excitation energy is less likely to deviate from any organic compound, preventing significant degradation of any organic compound. Therefore, the reliability of the light-emitting device is further improved, making it the preferred option.

[0539] In addition, from Figure 18 It is known that the wavelength of the emitting end of the short-wavelength side of the emission spectrum of PtON-TBBI is 441 nm, and the T1 energy level of PtON-TBBI is estimated to be 2.81 eV. As mentioned above, the T1 energy levels of the host materials SiTrzCz2 and PSiCzCz are 2.92 eV and 2.97 eV, respectively. Therefore, the T1 energy level of PtON-TBBI is lower than that of SiTrzCz2 and PSiCzCz. In the light-emitting device 1-1 and the comparison light-emitting devices 1-1 to 1-3 fabricated in this embodiment with this structure, energy is efficiently transferred from the host material to the material capable of converting the triple excitation energy into light emission, thus realizing a light-emitting device with high luminous efficiency and good reliability.

[0540] Furthermore, the T1 energy levels of the host materials SiTrzCz2-d16 and PSiCzCz-d15 are 2.93 eV and 2.97 eV, respectively, while the T1 energy level of PtON-TBBI is lower than that of SiTrzCz2-d16 and PSiCzCz-d15. In the light-emitting devices 1-2 fabricated in this embodiment with this structure, energy is efficiently transferred from the host material to a substance capable of converting the triple excitation energy into light emission, thus enabling the realization of light-emitting devices with high luminous efficiency and good reliability.

[0541] also, Figure 38 The emission spectra (PL spectra) of the mixed film and individual films of SiTrzCz2 and PSiCzCz mixed in a 1:1 (weight ratio) are shown. Measurements were performed using a fluorescence spectrophotometer (FP-8600DS, manufactured by Nippon Spectrophotometer Co., Ltd.). Figure 38 It can be seen that the mixed film of SiTrzCz2 and PSiCzCz exhibits an emission spectrum that is different from the emission spectrum of the individual films of SiTrzCz2 and PSiCzCz, which is shifted to a longer wavelength. SiTrzCz2 and PSiCzCz are a combination that forms an excitocomplex.

[0542] also, Figure 48 The emission spectra of a hybrid film and individual films of SiTrzCz2-d16 and PSiCzCz-d15 mixed in a 1:1 (weight ratio) are shown. Figure 48 It can be seen that the mixed film of SiTrzCz2-d16 and PSiCzCz-d15 exhibits an emission spectrum that is different from the emission spectrum of the individual films of SiTrzCz2-d16 and PSiCzCz-d15, which is shifted to a longer wavelength. SiTrzCz2-d16 and PSiCzCz-d15 are a combination that forms an excitocomplex.

[0543] Next, Table 5 shows the GSP_Slope of the organic compounds with π-electron-deficient heteroaromatic rings used in the first electron transport layer of light-emitting devices 1-1, 1-2, 1-1, 1-2, and 1-3; the organic compounds with π-electron-deficient heteroaromatic rings used in the second electron transport layer; the organic compounds with π-electron-rich heteroaromatic rings or aromatic amines used in the hole transport layer; and the vapor-deposited films used in the host material of the light-emitting layers. Note that in Table 5, the GSP_Slope was measured using the method shown in Embodiment 1.

[0544] [Table 5]

[0545]

[0546] Thus, in comparison light-emitting devices 1-1 and 1-2, the GSP_Slope of the film containing the organic compound with a π-electron-deficient heteroaromatic ring in the second electron transport layer is smaller than that of the film containing the organic compound with a π-electron-deficient heteroaromatic ring in the first electron transport layer. In this structure, electrons are efficiently injected from the electrode or electron injection layer to the interface of the first electron transport layer. On the other hand, in light-emitting devices 1-1, 1-2, and comparison light-emitting devices 1-3, the GSP_Slope of the film containing the organic compound with a π-electron-deficient heteroaromatic ring in the second electron transport layer is larger than that of the film containing the organic compound with a π-electron-deficient heteroaromatic ring in the first electron transport layer. Consequently, electron injection from the electrode or electron injection layer to the second electron transport layer is suppressed in light-emitting device 1 and comparison light-emitting device 1-3.

[0547] Typically, in an emissive layer containing a blue phosphorescent material, the HOMO and LUMO energy levels of the blue phosphorescent material are higher than those of the host material. Therefore, it traps holes but not electrons, resulting in a recombination region biased towards the anode side of the emissive layer. When the recombination region is biased towards the anode side, the density of excitons generated after recombination also increases on the anode side of the emissive layer. This facilitates interactions between excitons and between excitons and holes in the electron blocking layer, easily generating excitons or holes with extremely high energies. Due to these high-energy excitons or holes, the degradation of the emissive layer and the adjacent electron blocking layer is accelerated.

[0548] As described above, because the second electron transport layer of the light-emitting device of one embodiment of the present invention has a high GSP_Slope and electron injection is suppressed, the recombination region that tends to be biased towards the anode side of the light-emitting layer can be expanded to the cathode side of the light-emitting layer, thereby suppressing the degradation of the hole transport layer used as an electron blocking layer. As a result, the reliability of the comparative light-emitting device 1-3 is improved compared to the comparative light-emitting device 1-2, and the reliability of the light-emitting device 1 is improved compared to the comparative light-emitting device 1-1.

[0549] The light-emitting device 1-1, the comparison light-emitting device 1-1, the comparison light-emitting device 1-2, and the comparison light-emitting device 1-3 manufactured in this embodiment also have the following structure: the HOMO level of PSiCzCz used as the host material in 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 and the LUMO level is -2.98eV, and the HOMO level of PtON-TBBI, which is added to the light-emitting layer as a blue phosphorescent material in a trace amount (12wt%), is -5.50eV and the LUMO level is -2.3eV. Therefore, the HOMO level of PtON-TBBI is higher than that of the host material and it is easier to trap holes.

[0550] The light-emitting device 1-2 also has the following structure: the HOMO level of PSiCzCz-d16, which is used as the host material in the light-emitting layer, is -5.7eV and the LUMO level is -2.05eV. The HOMO level of SiTrzCz2-d16 is lower than that of PSiCzCz-d16 and the LUMO level is -2.98eV. The HOMO level of PtON-TBBI, which is added to the light-emitting layer as a blue phosphorescent material in a trace amount (12wt%), is -5.50eV and the LUMO level is -2.3eV. Therefore, the HOMO level of PtON-TBBI is higher than that of the host material and it is easier to trap holes.

[0551] Note that in light-emitting devices 1-1, 1-2, and the comparative light-emitting device 1-1, a trace amount (1.5 wt%) of 1,6mmtBuDPhAPrn, with a HOMO level of -5.30 eV, is added as a fluorescent material. Therefore, 1,6mmtBuDPhAPrn also easily traps holes. Note that the HOMO level of the fluorescent material is higher than that of the phosphorescent material, and the amount of fluorescent material added is less than that of the phosphorescent material. Therefore, the fluorescent material in this light-emitting layer traps the holes trapped by the phosphorescent material. As a result, holes are strongly trapped in this light-emitting layer, and hole transport is easily reduced. Therefore, by applying the structure of one aspect of the present invention to suppress electron injection, the reduction in reliability can be significantly suppressed, resulting in a light-emitting device with high reliability.

[0552] The values ​​of the HOMO and LUMO energy levels were calculated by cyclic voltammetry (CV).

[0553] In cyclic voltammetry (CV) measurements, the values ​​(E) of the HOMO and LUMO energy levels are calculated from the oxidation peak potential (Epa) and reduction peak potential (Epc) obtained by changing the potential of the working electrode relative to the reference electrode. During the measurement, the HOMO energy level is calculated using a positive potential scan, and the LUMO energy level is calculated using a negative potential scan. Furthermore, the scan rate during the measurement is set to 0.1 V / s.

[0554] Specifically, the standard redox potential (Eo) (=(Epa+Epc) / 2) is calculated from the oxidation peak potential (Epa) and reduction peak potential (Epc) obtained from the cyclic voltammogram of the material. By subtracting Eo from the potential energy (Ex) of the reference electrode relative to the vacuum level, the values ​​(E) of the HOMO level and LUMO level can be calculated respectively (=Ex-Eo).

[0555] Note that the above shows the case where a reversible redox wave can be obtained. However, in the case where an irreversible redox wave can be obtained, the standard redox potential (Eo) to one decimal place is calculated by subtracting a fixed value (0.1 eV) from the oxidation peak potential (Epa) and assuming it to be the reduction peak potential (Epc). The HOMO level is then calculated from this. Furthermore, when calculating the LUMO level, the standard redox potential (Eo) to one decimal place is calculated by adding a fixed value (0.1 eV) to the reduction peak potential (Epc) and assuming it to be the oxidation peak potential (Epa).

[0556] Here, the results of transient EL measurements of light-emitting device 1-1, comparative light-emitting device 1-3, and light-emitting device 1-3 are shown. Light-emitting device 1-3 is a light-emitting device manufactured using N,N,N',N'-tetra(3-methylphenyl)pyrene-1,6-diamine (abbreviated as: 1,6mMeDPhAPrn), represented by the following structural formula (xviii), instead of 1,6mmtBuDPhAPrn of light-emitting device 1-1.

[0557] [Chemical Formula 7]

[0558]

[0559] In the measurements, a picosecond fluorescence lifetime measurement system (manufactured by Hamamatsu Photonics Co., Ltd., Japan) was used. In this measurement, a rectangular pulse voltage of 101.5 μs was applied to the light-emitting device, and a streak camera was used to perform time-resolved measurements of the decaying emission after the voltage drop. Furthermore, the measurements were performed at room temperature (300 K) with a light-emitting device luminance of 2500 cd / m². 2A pulse voltage of approximately 6.8V to 8.2V is applied in a nearby manner, with a pulse duration of 101.5μs and a negative bias of -5V (when the device drive is OFF). The measurement time range is 10μs. Figure 49 The measurement results are shown. Note that in... Figure 49 The vertical axis shows the intensity normalized to the maximum luminous intensity. Additionally, the horizontal axis shows the elapsed time after the pulse voltage drops.

[0560] from Figure 49 The decay curves shown indicate that the decay times of light-emitting devices 1-1 and 1-3 are shorter than those of light-emitting device 1-3. Light-emitting devices 1-1 and 1-3 have structures that emit light from fluorescent materials, thus shortening their decay times.

[0561] In addition to light-emitting device 1-1, light-emitting device 1-2 and comparison light-emitting device 1-1 also have a structure that emits light from a fluorescent light-emitting material. Compared with phosphorescent light-emitting material, fluorescent light-emitting material has a faster luminescence rate constant and a shorter excited-state lifetime, thus exhibiting higher stability against degradation. Furthermore, the energy transfer rate when the excitation energy of the phosphorescent light-emitting material is transferred to the fluorescent light-emitting material is greater than the luminescence rate of the phosphorescent light-emitting material, thereby improving stability against degradation. The reliability of comparison light-emitting device 1-1, which has a structure that emits light from a fluorescent light-emitting material, is improved compared to comparison light-emitting device 1-2, and the reliability of light-emitting device 1-1 is improved compared to comparison light-emitting device 1-3. Moreover, in light-emitting devices 1-1, 1-2, 1-3, and comparison light-emitting device 1-1, fluorescent light-emitting material emits light through energy transfer from the phosphorescent light-emitting material. At this point, especially in light-emitting devices 1-1, 1-2, and the comparative light-emitting device 1-1, the fluorescent luminescent material contains a protecting group. Therefore, energy transfer based on the Dexter mechanism is suppressed, while energy transfer based on the Foster mechanism dominates. The triple excitation energy transfer from the T1 level of the phosphorescent material to the T1 level (non-luminescent) of the fluorescent luminescent material, due to the Dexter mechanism, is suppressed, thereby suppressing the decrease in luminescence efficiency. As a result, this light-emitting device becomes a high-performance light-emitting device that luminesce from the fluorescent luminescent material and has an external quantum efficiency greater than 20%.

[0562] Here, from Figure 26It can be seen that when the LT90 of comparative light-emitting devices 1-1 and 1-3 is approximately 1.5 times that of comparative light-emitting device 1-2, the improvement in LT90 achieved by increasing the GSP_Slope of the second electron transport layer and by including phosphorescent and fluorescent materials in the light-emitting layer can be estimated to be approximately 1.5 times. On the other hand, the LT90 of light-emitting device 1-1 is approximately 1.7 times that of both comparative light-emitting devices 1-1 and 1-3. In other words, the reliability is further improved by having two structures: one with an increased GSP_Slope of the second electron transport layer and the other with a light-emitting layer including phosphorescent and fluorescent materials. Therefore, the combination of these structures has a synergistic effect.

[0563] Furthermore, it is known that light-emitting devices 1-2 using deuterated materials as the main material of the light-emitting layer exhibit better reliability. This is because the bond dissociation energy of the bond between carbon and deuterium is greater than that of the bond between carbon and protium, making it more stable and less prone to breakage. Therefore, compounds containing deuterium are more stable and less prone to degradation compared to non-deuterated compounds.

[0564] Furthermore, in light-emitting devices 1-1, 1-2, and 1-3, the second electron transport layer contains Liq, a metal complex of an alkali metal, in addition to the organic compound with a π-electron-deficient heteroaromatic ring. When the weight ratio of the organic compound with a π-electron-deficient heteroaromatic ring contained in the second electron transport layer to Liq is set as x:y, the GSP_Slope of the film containing the organic compound with a π-electron-deficient heteroaromatic ring contained in the first electron transport layer is (x+y) / x times 51.5 (mV / nm). That is, the GSP_Slope of the film containing the organic compound with a π-electron-deficient heteroaromatic ring contained in the second electron transport layer in light-emitting devices 1-1, 1-2, and 1-3 is greater than the GSP_Slope of the film containing the organic compound with a π-electron-deficient heteroaromatic ring contained in the first electron transport layer.

[0565] Thus, when the weight ratio of the organic compound with a π-electron-deficient heteroaromatic ring in the second electron transport layer to Liq is set to x:y, the GSP_Slope of the film containing the organic compound with a π-electron-deficient heteroaromatic ring in the second electron transport layer is greater than the value of (x+y) / x times the GSP_Slope of the film containing the organic compound with a π-electron-deficient heteroaromatic ring in the first electron transport layer, thereby providing a light-emitting device with good reliability.

[0566] Note that in the above-described light-emitting device, the GSP_Slope of the film of the host material (SiTrzCz2 and PSiCzCz) is greater than the GSP_Slope of the film of the first organic compound. Furthermore, the GSP_Slope of the light-emitting layer is greater than the GSP_Slope of the first electron transport layer.

[0567] With the above structure, a positive interface charge can be set at the interface between the light-emitting layer and the first electron transport layer, thus suppressing the electron injection barrier from the second electron transport layer to the first electron transport layer in the above-mentioned light-emitting device. Therefore, even if the injection of electrons into the second electron transport layer in the above-mentioned light-emitting device is suppressed, it will not cause a significant increase in the driving voltage, so a light-emitting device with excellent characteristics can be realized.

[0568] Furthermore, the GSP_Slope of the BP-Icz(II)Tzn film containing an organic compound with a π-electron-deficient heteroaromatic ring in the second electron transport layer of light-emitting devices 1-1, 1-2, and 1-3 is greater than the GSP_Slope of the film of the host material (SiTrzCz2 and PSiCzCz, etc.). Moreover, the GSP_Slope of the second electron transport layer is greater than the GSP_Slope of the light-emitting layer.

[0569] Therefore, in light-emitting devices 1-1, 1-2, and the comparative light-emitting device 1-3, 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. Through this effect, electron injection from the second electrode or electron injection layer to the second electron transport layer is suppressed. Furthermore, hole injection into the light-emitting layer is promoted. As a result, in light-emitting devices that typically use blue phosphorescent materials, the recombination region biased towards the anode side can be expanded, and the degradation of the hole transport layer, which serves as an electron blocking layer, can be further reduced.

[0570] Furthermore, the aforementioned light-emitting device has a structure in which the GSP_Slope of the light-emitting layer (co-evaporated film of SiTrzCz2, PSiCzCz, PtON-TBBI and 1.6mmtBuDPhAPrn or co-evaporated film of SiTrzCz2-d15, PSiCzCz-d16, PtON-TBBI and 1.6mmtBuDPhAPrn) or the GSP_Slope of the host material film (co-evaporated film of SiTrzCz2 and PSiCzCz or co-evaporated film of SiTrzCz2-d15 and PSiCzCz-d16) is larger than the GSP_Slope of the hole transport layer (evaporated film of PCBiF). Because the GSP_Slopes of the hole transport layer and the light-emitting layer have this relationship, at least one of the interfaces between the hole transport layer and the light-emitting layer can be provided with a negative interface charge. Therefore, hole injection near the interface between the anode or hole injection layer and the light-emitting layer is easily performed, thus enabling the realization of a light-emitting device with a low driving voltage.

[0571] Thus, the light-emitting device of one aspect of the present invention can be a light-emitting device with high reliability and good characteristics.

[0572] Example 2

[0573] In this embodiment, a detailed manufacturing method and characteristics of the light-emitting device 2 and a comparative example of the light-emitting device 2 are described. The structural formulas of the main compounds used in this embodiment are shown below.

[0574] [Chemical Formula 8]

[0575]

[0576] (Manufacturing method of light-emitting device 2)

[0577] First, indium tin oxide (ITSO) containing silicon oxide is deposited on a glass substrate by sputtering to a thickness of 55 nm, thereby forming a first electrode 101 with a size of 2 mm × 2 mm. Furthermore, ITSO is used as the anode.

[0578] Next, as a pretreatment for forming light-emitting devices on the substrate, the substrate surface is washed with water.

[0579] Then, the substrate is placed inside and depressurized to 1×10⁻⁶. -4 The substrate is placed in a vacuum evaporation apparatus at approximately Pa and then calcined at 170°C for 30 minutes in the heating chamber of the apparatus, followed by cooling for approximately 30 minutes.

[0580] Next, the substrate is fixed on a support provided in a vacuum evaporation apparatus with the surface on which the first electrode 101 is formed facing down. A hole injection layer 111 is formed on the first electrode 101 by evaporation in a weight ratio of N-(biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-9,9-dimethyl-9H-fluorene-2-amine (abbreviated as: PCBBiF) represented by the above structural formula (i) and an electron acceptor material (OCHD-003) containing fluorine with a molecular weight of 672 at 1:0.03 (=PCBBiF:OCHD-003) and a thickness of 10 nm.

[0581] Next, PCBBiF is deposited on the hole injection layer 111 with a thickness of 45 nm, followed by the deposition of 9-[3-(triphenylsilyl)phenyl]-3,9'-bi-9H-carbazole (abbreviated as PSiCzCz) represented by the above structural formula (ii) with a thickness of 5 nm, thereby forming the hole transport layer 112. Note that the PSiCzCz layer is an organic compound with a π-electron-rich heteroaromatic ring and is also used as an electron blocking layer.

[0582] 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), PSiCzCz, and the structure represented by the above structural formula (x) were co-deposited in a weight ratio of 0.35:0.53:0.12:0.015 (=SiTrzCz2:PSiCzCz:Pt(mmtBubOcz35dm4ppy-d6):1,6mmtBuDPhAPrn) with a thickness of 40 nm. (2-{3-[3-(3,5-di-tert-butylphenyl)benzimidazol-1-yl-2-ylide-κC2]phenoxy-κC2}-9-[3,5-di(methyl-d3)-4-phenyl-2-pyridyl-κN]carbazole-2,1-diyl-κC)platinum(II) (abbreviated as Pt(mmtBubOcz35dm4ppy-d6)) and N,N,N',N'-tetratetra(3,5-di-tert-butylphenyl)pyrene-1,6-diamine (abbreviated as 1,6mmtBuDPhAPrn) represented by the above structural formula (v) thereby form the luminescent layer 113.

[0583] Note that Pt(mmtBubOcz35dm4ppy-d6) is an organometallic complex exhibiting blue phosphorescence, while 1,6mmtBuDPhAPrn is an organic compound exhibiting blue fluorescence. Furthermore, Pt(mmtBubOcz35dm4ppy-d6) comprises a tert-butyl alkyl group with four carbon atoms. Additionally, 1,6mmtBuDPhAPrn is an organic compound in which the luminescent component has a pyrene skeleton with fused aromatic rings and comprises eight tert-butyl alkyl groups with four carbon atoms.

[0584] Note that SiTrzCz2 is an organic compound with a π-electron-deficient heteroaromatic ring, while PSiCzCz is an organic compound with a π-electron-rich heteroaromatic ring.

[0585] Then, after depositing 2-phenyl-4,6-bis[3-(triphenylsilyl)phenyl]-1,3,5-triazine (abbreviated as mSiTrz) with a thickness of 5 nm, a second electron transport layer is formed by co-depositing 11-[4-(biphenyl-4-yl)-6-phenyl-1,3,5-triazine-2-yl]-11,12-dihydro-12-phenylindolo[2,3-a]carbazole (abbreviated as BP-Icz(II)Tzn) and 8-hydroxyquinoline-lithium (abbreviated as Liq) with a thickness of 30 nm and a weight ratio of 1:4 (=BP-Icz(II)Tzn):Liq). Note that mSiTrz and BP-Icz(II)Tzn are organic compounds with π-electron-deficient heteroaromatic rings, Liq is an organometallic complex containing an alkali metal, and the first electron transport layer is also used as a hole blocking layer.

[0586] After forming the electron transport layer, lithium fluoride (LiF) is deposited with a thickness of 1 nm to form the electron injection layer 115, and then aluminum (Al) is deposited with a thickness of 200 nm to form the second electrode 102 (cathode).

[0587] Next, in a glove box under a nitrogen atmosphere, a glass substrate is used to seal the light-emitting device in a manner that prevents it from being exposed to the atmosphere (UV-curable sealing material is applied around the device, and UV is irradiated only to the sealing material without irradiating the light-emitting device, and heat treatment is performed at 80°C for 1 hour under atmospheric pressure), thereby forming the light-emitting device 2.

[0588] (Compare the manufacturing methods of light-emitting device 2)

[0589] The difference between the light-emitting device 2 and the manufacturing method of the light-emitting device 2 is that the second electron transport layer in the light-emitting device 2 is formed by using 2,2'-(1,3-phenyl)bis(9-phenyl-1,10-phenanthroline) (abbreviated as mPPhen2P) represented by the above structural formula (ix).

[0590] The following shows the device structure of light-emitting device 2 and comparison light-emitting device 2.

[0591] [Table 6]

[0592]

[0593] Figure 27 The light-emitting device 2 is shown, and its brightness-current density characteristics are compared with those of the light-emitting device 2. Figure 28 The brightness-voltage characteristics are shown. Figure 29 The current efficiency-current density characteristics are shown. Figure 30 The current density-voltage characteristics are shown. Figure 31 The blue indicator shows the current density characteristic. Figure 32 The external quantum efficiency-current density characteristics are shown. Figure 33 The electroluminescence spectrum is shown. Furthermore, Figure 34 The current density is shown to be 10 mA / cm². 2 The chromaticity diagram below, and Table 7, shows the main characteristics. Note that measurements of luminance, CIE chromaticity, and electroluminescence spectrum were performed at room temperature using a spectroradiometer (Topcon SR-UL1R). Furthermore, the external quantum efficiency was calculated using the measured luminance and emission spectra, assuming a Lambertian distribution.

[0594] [Table 7]

[0595]

[0596] In addition, from Figure 32 It is known that 1,6mmtBuDPhAPrn, which serves as a fluorescent luminescent material in both light-emitting device 2 and comparative light-emitting device 2, emits light, but its external quantum efficiency is greater than 20%. Thus, by using Pt (mmtBubOcz35dm4ppy-d6) as a phosphorescent luminescent material as an energy donor and 1,6mmtBuDPhAPrn as a fluorescent luminescent material with a protective group as a luminescent material, light-emitting device 2 and comparative light-emitting device 2 can be light-emitting devices that, although fluorescent luminescent elements, have a high efficiency of greater than 20%.

[0597] then, Figure 35 It shows 10mA / cm 2The time-varying characteristics of normalized brightness when driving light-emitting device 2 and comparing light-emitting device 2. Furthermore, in this measurement, the elapsed time (LT90) when the brightness of light-emitting device 2 and comparing light-emitting device 2 decreases to 90% of their initial brightness is 54 hours and 35 hours, respectively. Note that the initial brightness is set to 100% to represent the time-varying characteristics of normalized brightness.

[0598] Here, Figure 36 The emission (PL) and absorption spectra of the manufactured light-emitting device 2 and the comparative light-emitting device 2 are shown, along with the measurement results of the emission spectra of Pt (mmtBubOcz35dm4ppy-d6), a material capable of converting triple excitation energy into light emission, and 1,6mmtBuDPhAPrn, a fluorescent light-emitting material. Note that the emission spectrum of Pt (mmtBubOcz35dm4ppy-d6) was measured using a fluorescence spectrophotometer (FP-8600DS, manufactured by Nippon Spectrophotometer Co., Ltd.) in a dichloromethane solution, and the absorption spectrum was measured using a UV-Vis spectrophotometer (V-770DS, manufactured by Nippon Spectrophotometer Co., Ltd.). Furthermore, the emission spectrum of 1,6mmtBuDPhAPrn was measured using a fluorescence spectrophotometer (FS920, manufactured by Hamamatsu Photonics Co., Ltd.) in a toluene solution, and the absorption spectrum was measured using a UV-Vis spectrophotometer (V-550DS, manufactured by Nippon Spectrophotometer Co., Ltd.).

[0599] like Figure 36 As shown, the peak wavelength (461 nm) in the emission spectrum of Pt(mmtBubOcz35dm4ppy-d6) is at a shorter wavelength compared to the peak wavelength (467 nm) in the emission spectrum of 1,6mmtBuDPhAPrn. Alternatively, the absorption end (465 nm) on the longer wavelength side of the absorption spectrum of 1,6mmtBuDPhAPrn is at a longer wavelength compared to the emission end (445 nm) on the shorter wavelength side of the emission spectrum of Pt(mmtBubOcz35dm4ppy-d6). Or, the absorption end (465 nm) on the longer wavelength side of the absorption spectrum of 1,6mmtBuDPhAPrn is at a longer wavelength compared to the absorption end (463 nm) on the longer wavelength side of the absorption spectrum of Pt(mmtBubOcz35dm4ppy-d6).

[0600] In the light-emitting device 2 and the comparative light-emitting device 2 with this structure, the energy transfer from Pt (mmtBubOcz35dm4ppy-d6), a substance capable of converting triple excitation energy into light emission, to 1,6mmtBuDPhAPrn, a fluorescent light-emitting substance, occurs efficiently in the light-emitting layer, thereby enabling the fluorescent light-emitting substance to emit light and exhibiting a light-emitting device with high luminous efficiency.

[0601] also, Figure 37A and Figure 37B The results of low-temperature photoluminescence (PL) measurements of SiTrzCz2 and PSiCzCz, the main materials of the fabricated light-emitting device, are shown. The measurements were performed using a LabRAM HR-PL microscopic PL apparatus (manufactured by Horiba Corporation), at a temperature of 10 K. A He-Cd laser (wavelength 325 nm) was used as the excitation light, and a CCD detector was used as the detector. Note that the measured sample was a thin film, deposited on a quartz substrate with a thickness of 50 nm. The film was then attached to the vapor-deposited surface of the quartz substrate in a nitrogen atmosphere before measurement.

[0602] like Figure 37A and Figure 37B As shown, the wavelengths of the short-wavelength emission ends (the short-wavelength emission ends of the phosphorescence spectrum) in the low-temperature PL measurements of SiTrzCz2 and PSiCzCz are 424 nm and 418 nm, respectively. Therefore, the T1 energy levels of SiTrzCz2 and PSiCzCz are 2.92 eV and 2.97 eV, respectively, with an energy difference of 0.05 eV. The energy difference of the T1 energy levels between the host materials is less than 0.20 eV. Therefore, the deviation of the triple excitation energy between the host materials of the light-emitting device manufactured in this embodiment is small, thereby realizing a light-emitting device with good reliability.

[0603] In addition, from Figure 36 It is known that the wavelength of the emission spectrum of Pt(mmtBubOcz35dm4ppy-d6) at the short wavelength end is 445nm, and the T1 energy level of Pt(mmtBubOcz35dm4ppy-d6) is estimated to be 2.78eV. As mentioned above, the T1 energy levels of the host materials SiTrzCz2 and PSiCzCz are 2.92eV and 2.97eV, respectively. Therefore, the T1 energy level of Pt(mmtBubOcz35dm4ppy-d6) is lower than that of SiTrzCz2 and PSiCzCz. In the light-emitting device fabricated in this embodiment with this structure, energy is efficiently transferred from the host material to a substance capable of converting the triple excitation energy into light emission, thus enabling the realization of a light-emitting device with high luminous efficiency and good reliability.

[0604] also, Figure 38 The emission spectra (PL spectra) of the mixed film and individual films of SiTrzCz2 and PSiCzCz mixed in a 1:1 (weight ratio) are shown. Measurements were performed using a fluorescence spectrophotometer (FP-8600DS, manufactured by Nippon Spectrophotometer Co., Ltd.). Figure 38It can be seen that the mixed film of SiTrzCz2 and PSiCzCz exhibits an emission spectrum that is different from the emission spectrum of the individual films of SiTrzCz2 and PSiCzCz, which is shifted to a longer wavelength. SiTrzCz2 and PSiCzCz are a combination that forms an excitocomplex.

[0605] Figure 35 The light-emitting device 2 of one embodiment of the present invention, which shows a high GSP_Slope of the second electron transport layer and an emitting layer comprising both Pt(mmtBubOcz35dm4ppy-d6) (phosphorescent material) and 1,6mmtBuDPhAPrn (fluorescent material), has good reliability compared to the comparative light-emitting device 2.

[0606] Table 8 shows the GSP_Slope of the organic compound with a π-electron-deficient heteroaromatic ring used in the first electron transport layer of the light-emitting device 2 and the comparative light-emitting device 2, the organic compound with a π-electron-deficient heteroaromatic ring used in the second electron transport layer, the organic compound with a π-electron-rich 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. Note that in Table 8, the GSP_Slope was measured by the method shown in Embodiment 1.

[0607] [Table 8]

[0608]

[0609] Thus, in the comparison light-emitting device 2, the GSP_Slope of the film containing the organic compound with a π-electron-deficient heteroaromatic ring in the second electron transport layer is smaller than that of the film containing the organic compound with a π-electron-deficient heteroaromatic ring in the first electron transport layer. In this structure, electrons are well injected from the electrode or electron injection layer to the interface of the first electron transport layer. On the other hand, in the light-emitting device 2, the GSP_Slope of the film containing the organic compound with a π-electron-deficient heteroaromatic ring in the second electron transport layer is larger than that of the film containing the organic compound with a π-electron-deficient heteroaromatic ring in the first electron transport layer. As a result, electron injection from the electrode or electron injection layer to the second electron transport layer is suppressed in the light-emitting device 2.

[0610] Typically, in an emissive layer containing a blue phosphorescent material, the HOMO and LUMO energy levels of the blue phosphorescent material are higher than those of the host material. Therefore, it traps holes but not electrons, resulting in a recombination region biased towards the anode side of the emissive layer. When the recombination region is biased towards the anode side, the density of excitons generated after recombination also increases on the anode side of the emissive layer. This facilitates interactions between excitons and between excitons and holes in the electron blocking layer, easily generating excitons or holes with extremely high energies. Due to these high-energy excitons or holes, the degradation of the emissive layer and the adjacent electron blocking layer is accelerated.

[0611] As described above, because the second electron transport layer of the light-emitting device 2 of one embodiment of the present invention has a high GSP_Slope and electron injection is suppressed, the recombination region that tends to be biased towards the anode side of the light-emitting layer can be expanded to the cathode side of the light-emitting layer, thereby suppressing the degradation of the hole transport layer used as an electron blocking layer. As a result, the reliability of the light-emitting device 2 is improved compared to the comparative light-emitting device 2.

[0612] The light-emitting device manufactured in this embodiment also has the following structure: the HOMO level of PSiCzCz, used as the main material for the light-emitting layer, is -5.7 eV and the LUMO level is -2.06 eV; the HOMO level of SiTrzCz2 is lower than that of PSiCzCz and the LUMO level is -2.98 eV; a trace amount (12 wt%) of Pt (mmtBubOcz35dm4ppy-d6) added to the light-emitting layer as a blue phosphorescent material has a HOMO level of -5.50 eV and a LUMO level of -2.47 eV, thus easily trapping holes. Note that in light-emitting device 2, a trace amount (1.5 wt%) of 1,6mmtBuDPhAPrn added as a fluorescent material has a HOMO level of -5.30 eV, therefore 1,6mmtBuDPhAPrn also easily traps holes, just like the phosphorescent material. Note that the HOMO energy level of the fluorescent material is higher than that of the phosphorescent material, and the amount of fluorescent material added is less than that of phosphorescent material. Therefore, the fluorescent material in this luminescent layer traps the holes trapped by the phosphorescent material. As a result, holes are strongly trapped in this luminescent layer, and hole transport is easily reduced.

[0613] The values ​​of the HOMO and LUMO energy levels were calculated in the same manner as in Example 1.

[0614] Furthermore, in the comparative light-emitting device 2, the second electron transport layer contains Liq, a metal complex containing an alkali metal, in addition to the organic compound with a π-electron-deficient heteroaromatic ring. When the weight ratio of the organic compound with a π-electron-deficient heteroaromatic ring contained in the second electron transport layer to Liq is set to x:y, the GSP_Slope of the film containing the organic compound with a π-electron-deficient heteroaromatic ring contained in the first electron transport layer is (x+y) / x times 51.5 (mV / nm). That is, in the light-emitting device 2, the GSP_Slope of the film containing the organic compound with a π-electron-deficient heteroaromatic ring contained in the second electron transport layer is greater than the GSP_Slope of the film containing the organic compound with a π-electron-deficient heteroaromatic ring contained in the first electron transport layer is (x+y) / x times.

[0615] Thus, when the weight ratio of the organic compound with a π-electron-deficient heteroaromatic ring in the second electron transport layer to Liq is set to x:y, the GSP_Slope of the film containing the organic compound with a π-electron-deficient heteroaromatic ring in the second electron transport layer is greater than the value of (x+y) / x times the GSP_Slope of the film containing the organic compound with a π-electron-deficient heteroaromatic ring in the first electron transport layer, thereby providing a light-emitting device with good reliability.

[0616] Note that in the above-described light-emitting device 2 and comparative light-emitting device 2, the GSP_Slope of the film of the host material (SiTrzCz2 and PSiCzCz) is greater than the GSP_Slope of the film of the first organic compound. Furthermore, the GSP_Slope of the light-emitting layer is greater than the GSP_Slope of the first electron transport layer.

[0617] With the above structure, a positive interface charge can be set at the interface between the light-emitting layer and the first electron transport layer, thus suppressing the electron injection barrier from the second electron transport layer to the first electron transport layer in the light-emitting device. Therefore, even if the injection of electrons into the second electron transport layer in the light-emitting device 2 is suppressed, it will not cause a significant increase in the driving voltage, thus enabling the realization of a light-emitting device with excellent characteristics.

[0618] Furthermore, the GSP_Slope of the BP-Icz(II)Tzn film containing an organic compound with a π-electron-deficient heteroaromatic ring in the second electron transport layer of the light-emitting device 2 is greater than the GSP_Slope of the film of the host material (SiTrzCz2 and PSiCzCz, etc.). Moreover, the GSP_Slope of the second electron transport layer is greater than the GSP_Slope of the light-emitting layer.

[0619] Therefore, the interface charge between the first electron transport layer and the second electron transport layer in the light-emitting device 2 is negative and smaller than the interface charge between the light-emitting layer and the first electron transport layer. Through this effect, electron injection from the second electrode or electron injection layer to the second electron transport layer is suppressed. Furthermore, hole injection into the light-emitting layer is promoted. As a result, in light-emitting devices that typically use blue phosphorescent materials, the recombination region biased towards the anode side can be expanded, and the degradation of the hole transport layer, which serves as an electron blocking layer, can be further reduced.

[0620] Furthermore, the aforementioned light-emitting device has the following structure: the GSP_Slope of the light-emitting layer (co-evaporated film of SiTrzCz2, PSiCzCz, Pt (mmtBubOcz35dm4ppy-d6) and 1,6mmtBuDPhAPrn) or the GSP_Slope of the body material film (co-evaporated film of SiTrzCz2 and PSiCzCz) is greater than the GSP_Slope of the hole transport layer (evaporated film of PCBiF). Because the GSP_Slopes of the hole transport layer and the light-emitting layer have this relationship, at least one of the interfaces between the hole transport layer and the light-emitting layer can be fitted with a negative interface charge. Therefore, hole injection near the interface between the anode or hole injection layer and the light-emitting layer is easily performed, thus enabling the realization of a light-emitting device with a low driving voltage.

[0621] Thus, the light-emitting device of one aspect of the present invention can be a light-emitting device with high reliability and good characteristics.

[0622] Example 3

[0623] In this embodiment, the detailed manufacturing method and characteristics of the light-emitting device 3 and the comparative light-emitting device 3 of the comparative example are described. The structural formulas of the main compounds used in this embodiment are shown below.

[0624] [Chemical Formula 9]

[0625]

[0626] [Chemical Formula 10]

[0627]

[0628] (Manufacturing met...

Claims

1. A light-emitting device, comprising: The first electrode on the insulating surface; A second electrode opposite to the first electrode; as well as The EL layer located between the first electrode and the second electrode, The EL layer includes 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 light-emitting layer comprises a first light-emitting material and a second light-emitting material. The first luminescent material is one that can convert triple excitation energy into light emission. The second luminescent material is a fluorescent luminescent material. The peak wavelength of the emission spectrum of the first luminescent material is shorter than the peak wavelength of the emission spectrum of the second luminescent material. The GSP_Slope (mV / nm) of the second electron transport layer is greater than that of the first electron transport layer (mV / nm). Furthermore, the GSP_Slope (mV / nm) is expressed as ΔV / Δd, where ΔV (mV) is the change in surface potential and Δd (nm) is the change in thickness.

2. A light-emitting device, comprising: The first electrode on the insulating surface; A second electrode opposite to the first electrode; as well as The EL layer located between the first electrode and the second electrode, The EL layer includes 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 light-emitting layer comprises a first light-emitting material and a second light-emitting material. The first luminescent material is one that can convert triple excitation energy into light emission. The second luminescent material is a fluorescent luminescent material. The peak wavelength of the emission spectrum of the first luminescent material is shorter than the peak wavelength of the emission spectrum of the second luminescent material. The first electron transport layer contains a first organic compound. The second electron transport layer contains a second organic compound. The first organic compound and the second organic compound each independently possess a π-electron-deficient heteroaromatic ring. The GSP_Slope (mV / nm) of the vapor-deposited film of the second organic compound is greater than that of the vapor-deposited film of the first organic compound. Furthermore, the GSP_Slope (mV / nm) is expressed as ΔV / Δd, where ΔV (mV) is the change in surface potential and Δd (nm) is the change in thickness.

3. A light-emitting device, comprising: The first electrode on the insulating surface; A second electrode opposite to the first electrode; as well as The EL layer located between the first electrode and the second electrode, The EL layer includes 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 light-emitting layer comprises a first light-emitting material and a second light-emitting material. The first luminescent material is one that can convert triple excitation energy into light emission. The second luminescent material is a fluorescent luminescent material. The peak wavelength of the emission spectrum of the first luminescent material is shorter than the peak wavelength of the emission spectrum of the second luminescent material. The first electron transport layer contains 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 each independently possess a π-electron-deficient heteroaromatic ring. The GSP_Slope (mV / nm) of the vapor-deposited film of the second organic compound is greater than that of the vapor-deposited film of the first organic compound. Furthermore, the GSP_Slope (mV / nm) is expressed as ΔV / Δd, where ΔV (mV) is the change in surface potential and Δd (nm) is the change in thickness.

4. The light-emitting device according to claim 3, When the mixing ratio of the second organic compound and the first substance contained in the second electron transport layer is x:y, the GSP_Slope (mV / nm) of the vapor-deposited film of the second organic compound is greater than (x+y) / x times the GSP_Slope (mV / nm) of the vapor-deposited film of the first organic compound.

5. The light-emitting device according to claim 4, Where y is greater than or equal to x.

6. The light-emitting device according to claim 2, 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. Furthermore, 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.

7. The light-emitting device according to claim 6, 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.

8. The light-emitting device according to claim 6, The hole transport layer contains a third organic compound. Furthermore, the GSP_Slope (mV / nm) of the light-emitting layer is greater than or equal to the GSP_Slope (mV / nm) of the vapor-deposited film of the third organic compound.

9. The light-emitting device according to claim 6, The hole transport layer contains a third organic compound. Furthermore, the GSP_Slope (mV / nm) of the vapor-deposited film of the main material is greater than or equal to the GSP_Slope (mV / nm) of the vapor-deposited film of the third organic compound.

10. The light-emitting device according to claim 6, The main material comprises a first material and a second material. Furthermore, the first material and the second material are organic compounds that form a combination of excitocomplexes.

11. The light-emitting device according to claim 10, The first material is an organic compound with a π-electron-deficient heteroaromatic ring. Furthermore, the second material is an organic compound having a π-electron-rich heteroaromatic ring or an aromatic amine.

12. The light-emitting device according to claim 10, The HOMO energy levels of the first material and the second material are lower than the HOMO energy level of the first luminescent material.

13. The light-emitting device according to claim 12, The HOMO energy level of the first material and the HOMO energy level of the second material are lower than the HOMO energy level of the second luminescent material.

14. The light-emitting device according to claim 3, The first substance is a metal complex.

15. The light-emitting device according to claim 14, The metal complex is an organic complex containing an alkali metal.

16. The light-emitting device according to claim 1, The first luminescent material is a phosphorescent material.

17. The light-emitting device according to claim 1, When a voltage is applied between the first electrode and the second electrode, the second luminescent material emits light.

18. The light-emitting device according to claim 2, The first luminescent material is a phosphorescent material.

19. The light-emitting device according to claim 3, The first luminescent material is a phosphorescent material.

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