Light-emitting device

Abstract

The present invention provides a light-emitting device with good reliability. Provided is a light-emitting device having a first electrode formed on an insulating surface, a second electrode facing the first electrode, and an EL layer located between the first electrode and the second electrode. Out of the first electrode and the second electrode, one is an anode and the other is a cathode. The EL layer has an emissive layer, a first layer, and a second layer. The first layer and the second layer are located between the emissive layer and the cathode. The first layer is located between the first electrode and the second layer. The second layer is located between the first layer and the second electrode. The normal refractive index of a second electron transport layer at any wavelength between 455 nm and 520 nm is 1.70 or less, and the GSP_Slope (mV / nm) of the second layer is greater than the GSP_Slope (mV / nm) of the first layer.

Description

Light-emitting devices

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

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

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

[0004] Furthermore, because these organic EL elements can have their light-emitting layers formed continuously in a planar manner, they can produce light in a planar manner. This is a feature that is difficult to obtain with point light sources such as incandescent bulbs and LEDs, or line light sources such as fluorescent lamps, and therefore has high value as a surface light source that can be applied to lighting and other applications.

[0005] As described above, displays and lighting devices using organic EL elements are suitable for a variety of electronic devices, but research and development are underway to find organic EL elements with even better characteristics.

[0006] Hiroshi Noguchi, et al., "Orientational Polarization Phenomena of Polar Molecules and Interface Properties of Organic Thin Film Devices," Journal of the Vacuum Society of Japan, 2015, Vol. 58, No. 3.

[0007] One aspect of the present invention aims to provide a reliable light-emitting device. Another aspect of the present invention aims to provide a light-emitting device with high luminous efficiency. Furthermore, one aspect of the present invention aims to provide a reliable light-emitting device, electronic device, or display device.

[0008] Alternatively, one aspect of the present invention aims to provide a highly reliable blue light-emitting device. Alternatively, another aspect of the present invention aims to provide a blue light-emitting device with high luminous efficiency. Another aspect of the present invention aims to provide a blue light-emitting device with a low driving voltage.

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

[0010] One aspect of the present invention is a light-emitting device comprising a first electrode formed on an insulating surface, a second electrode facing the first electrode, and an EL layer located between the first electrode and the second electrode, wherein the EL layer comprises a light-emitting layer, a hole transport layer, a first electron transport layer, and a second electron transport layer, the first electron transport layer located between the first electrode and the second electron transport layer, the light-emitting layer located between the hole transport layer, the first electron transport layer and the second electron transport layer, the paraphotometric refractive index of the second electron transport layer at any wavelength from 455 nm to 520 nm being 1.70 or less, and the GSP_Slope (mV / nm) of the second electron transport layer being greater than the GSP_Slope (mV / nm) of the first electron transport layer.

[0011] Alternatively, in another aspect of the present invention, in the above configuration, the second electron transport layer is located between the first electron transport layer and the second electrode, and the light-emitting device is such that the GSP_Slope (mV / nm) of the light-emitting layer is greater than the GSP_Slope (mV / nm) of the first electron transport layer.

[0012] Alternatively, another aspect of the present invention is a light-emitting device in which the GSP_Slope (mV / nm) of the light-emitting layer is greater than the GSP_Slope (mV / nm) of the hole transport layer.

[0013] Alternatively, another aspect of the present invention, in the above configuration, comprises a first electrode formed on an insulating surface, a second electrode facing the first electrode, and an EL layer located between the first electrode and the second electrode, wherein the EL layer comprises a light-emitting layer, a hole transport layer, a first electron transport layer, and a second electron transport layer, the first electron transport layer located between the first electrode and the second electron transport layer, the light-emitting layer located between the hole transport layer, the first electron transport layer and the second electron transport layer, the first electron transport layer having a first organic compound, and the second electron transport layer having a second organic compound. The second organic compound has an ordinary refractive index of 1.70 or less at any wavelength between 455 nm and 520 nm, the first and second organic compounds have π-electron-deficient heteroaromatic rings, and the light-emitting device has a GSP_Slope (mV / nm) in the vapor-deposited film of the second organic compound that is greater than the GSP_Slope (mV / nm) in the vapor-deposited film of the first organic compound (where GSP_Slope (mV / nm) is a parameter expressed as ΔV / Δd when the change in surface potential ΔV (mV) is equal to the change in film thickness Δd (nm)).

[0014] Alternatively, another aspect of the present invention comprises a first electrode formed on an insulating surface, a second electrode facing the first electrode, and an EL layer located between the first electrode and the second electrode, wherein the EL layer comprises a light-emitting layer, a hole transport layer, a first electron transport layer, and a second electron transport layer, the first electron transport layer located between the light-emitting layer and the second electron transport layer, the second electron transport layer located between the first electron transport layer and the second electrode, and the light-emitting layer located between the hole transport layer and the first electron transport layer, and the first The electron transport layer of the device has a first organic compound, and the second electron transport layer has a second organic compound and a first substance, the paraphotometric refractive index of the second organic compound at any wavelength from 455 nm to 520 nm is 1.70 or less, the first and second organic compounds have π-electron-deficient heteroaromatic rings, and the GSP_Slope (mV / nm) in the vapor-deposited film of the second organic compound is greater than the GSP_Slope (mV / nm) in the vapor-deposited film of the first organic compound, making it a light-emitting device.

[0015] Alternatively, another aspect of the present invention comprises a first electrode formed on an insulating surface, a second electrode facing the first electrode, and an EL layer located between the first electrode and the second electrode, wherein the EL layer comprises a light-emitting layer, a hole transport layer, a first electron transport layer, and a second electron transport layer, the first electron transport layer located between the light-emitting layer and the second electron transport layer, the second electron transport layer located between the first electron transport layer and the second electrode, the light-emitting layer located between the hole transport layer and the first electron transport layer, the first electron transport layer having a first organic compound, and the second electron A light-emitting device in which the electron transport layer comprises a second organic compound and a first substance, the paraphotometric refractive index of the second organic compound at any wavelength from 455 nm to 520 nm is 1.70 or less, the first organic compound and the second organic compound have π-electron-deficient heteroaromatic rings, and when the mixing ratio of the second organic compound and the first substance in the second electron transport layer is x:y, the GSP_Slope (mV / nm) in the vapor-deposited film of the second organic compound is greater than (x+y) / x times the GSP_Slope (mV / nm) in the vapor-deposited film of the first organic compound.

[0016] Alternatively, another aspect of the present invention is a light-emitting device in the above configuration in which y is greater than or equal to x.

[0017] Alternatively, another aspect of the present invention is a light-emitting device in which the second organic compound has a saturated hydrocarbon group.

[0018] Alternatively, another aspect of the present invention is a light-emitting device in which the second organic compound has a plurality of saturated hydrocarbon groups in the above configuration.

[0019] Alternatively, another aspect of the present invention is a light-emitting device in which the light-emitting layer comprises a material that exhibits phosphorescence.

[0020] Alternatively, another aspect of the present invention is a light-emitting device in which, in the above configuration, a phosphorescent material emits light when a voltage is applied between the first electrode and the second electrode.

[0021] Alternatively, in another aspect of the present invention, in the above configuration, the second electron transport layer is located between the first electron transport layer and the second electrode, and the light-emitting layer comprises a host material and a light-emitting substance, wherein the GSP_Slope (mV / nm) in the vapor-deposited film of the host material is greater than the GSP_Slope (mV / nm) in the vapor-deposited film of the first organic compound.

[0022] Alternatively, another aspect of the present invention is a light-emitting device in which, in the above configuration, the GSP_Slope (mV / nm) in the vapor-deposited film of the second organic compound is greater than the GSP_Slope (mV / nm) in the vapor-deposited film of the host material.

[0023] Alternatively, another aspect of the present invention is a light-emitting device in which, in the above configuration, the hole transport layer has a third organic compound, and the GSP_Slope (mV / nm) of the light-emitting layer is equal to or greater than the GSP_Slope (mV / nm) of the vapor-deposited film of the third organic compound.

[0024] Alternatively, another aspect of the present invention is a light-emitting device in which the hole transport layer has a third organic compound, and the GSP_Slope (mV / nm) in the vapor-deposited film of the host material is greater than or equal to the GSP_Slope (mV / nm) in the vapor-deposited film of the third organic compound.

[0025] Alternatively, another aspect of the present invention is a light-emitting device in which, in the above configuration, the host material is an organic compound comprising a first material and a second material, wherein the first material and the second material form an excited complex in a combination.

[0026] Alternatively, another aspect of the present invention is a light-emitting device in which, in the above configuration, the first material is an organic compound having a π-electron-deficient heteroaromatic ring, and the second material is an organic compound having a π-electron-excess heteroaromatic ring or an aromatic amine.

[0027] Alternatively, another aspect of the present invention is a light-emitting device in which the first substance is a metal complex.

[0028] Alternatively, another aspect of the present invention is a light-emitting device in which the metal complex is an organic complex having an alkali metal, in the above configuration.

[0029] Alternatively, another aspect of the present invention is a light-emitting device in which, in the above configuration, the peak wavelength of the emission spectrum of the phosphorescent material is 455 nm or more and 520 nm or less.

[0030] Alternatively, another aspect of the present invention is a light-emitting device in which, in the above configuration, the peak wavelength of the emission spectrum of the light-emitting material is 455 nm or more and 520 nm or less.

[0031] Alternatively, another aspect of the present invention is a light-emitting device in which, in the above configuration, the paraphotometric refractive index of the second electron transport layer is 1.70 or less at the peak wavelength of the electroluminescence spectrum of the light-emitting device.

[0032] Alternatively, another aspect of the present invention is a light-emitting device in which, in the above configuration, the paraphotometric refractive index of the film of the second organic compound is 1.70 or less at the peak wavelength of the emission spectrum of the light-emitting material.

[0033] However, in one embodiment of the present invention, GSP_Slope(mV / nm) is a parameter expressed as ΔV / Δd when the change in surface potential ΔV(mV) is equal to the change in film thickness Δd(nm).

[0034] In one aspect of the present invention, a highly reliable light-emitting device can be provided. Alternatively, in another aspect of the present invention, a light-emitting device with high luminous efficiency can be provided. Furthermore, in one aspect of the present invention, a highly reliable light-emitting device, electronic device, or display device can be provided.

[0035] Alternatively, one aspect of the present invention can provide a highly reliable blue light-emitting device. Alternatively, another aspect of the present invention can provide a blue light-emitting device with high luminous efficiency.

[0036] Furthermore, the description of these effects does not preclude the existence of other effects. Moreover, one aspect of the present invention does not necessarily have to possess all of these effects. Other effects will naturally become apparent from the description in the specification, drawings, and claims, and it is possible to extract other effects from the description in the specification, drawings, and claims.

[0037] Figures 1A and 1B illustrate the configuration of a light-emitting device according to an embodiment. Figures 2A and 2B illustrate the configuration of a light-emitting device according to an embodiment. Figure 3 shows the capacitance-voltage characteristics of the measuring device 1. Figure 4 shows the current density-voltage characteristics of the measuring device 1. Figures 5A and 5B illustrate the configuration of a light-emitting device according to an embodiment. Figures 6A and 6B are a top view and a cross-sectional view of the light-emitting device. Figures 7A and 7B are perspective views showing an example configuration of a display module. Figures 8A and 8B are cross-sectional views showing an example configuration of a display device. Figure 9 is a perspective view showing an example configuration of a display device. Figure 10 is a cross-sectional view showing an example configuration of a display device. Figure 11 is a cross-sectional view showing an example configuration of a display device. Figure 12 is a cross-sectional view showing an example configuration of a display device. Figures 13A, 13B, 13C, and 13D are diagrams showing an example of electronic equipment. Figures 14A, 14B, 14C, 14D, 14E, and 14F are diagrams showing an example of electronic equipment. Figures 15A, 15B, 15C, 15D, 15E, 15F, and 15G show examples of electronic devices. Figure 16 shows the refractive indices of mmtBuPh-mDMePyPTZn film, BP-Icz(II)TZn film, and mPPhen2P film. Figure 17 shows the luminance-current density characteristics of light-emitting device 1, comparative light-emitting device 1-1, and comparative light-emitting device 1-2. Figure 18 shows the luminance-voltage characteristics of light-emitting device 1, comparative light-emitting device 1-1, and comparative light-emitting device 1-2. Figure 19 shows the current efficiency-current density characteristics of light-emitting device 1, comparative light-emitting device 1-1, and comparative light-emitting device 1-2. Figure 20 shows the current density-voltage characteristics of light-emitting device 1, comparative light-emitting device 1-1, and comparative light-emitting device 1-2. Figure 21 shows the blue index-current density characteristics of light-emitting device 1, comparative light-emitting device 1-1, and comparative light-emitting device 1-2. Figure 22 shows the external quantum efficiency-current density characteristics of light-emitting device 1, comparative light-emitting device 1-1, and comparative light-emitting device 1-2. Figure 23 shows the electroluminescence spectra of light-emitting device 1, comparative light-emitting device 1-1, and comparative light-emitting device 1-2.Figure 24 shows the normalized brightness time-vary characteristics of light-emitting device 1, comparative light-emitting device 1-1, and comparative light-emitting device 1-2. Figure 25 shows the LT90 time of light-emitting device 1, comparative light-emitting device 1-1, and comparative light-emitting device 1-2. Figure 26 shows the refractive index of the films mmtBumTPTZn-03, mmtBumTPTZn-04, and mPPhen2P. Figure 27 shows the brightness-current density characteristics of light-emitting device 2-1, light-emitting device 2-2, and comparative light-emitting device 2-1. Figure 28 shows the brightness-voltage characteristics of light-emitting device 2-1, light-emitting device 2-2, and comparative light-emitting device 2-1. Figure 29 shows the current efficiency-current density characteristics of light-emitting device 2-1, light-emitting device 2-2, and comparative light-emitting device 2-1. Figure 30 shows the current density-voltage characteristics of light-emitting device 2-1, light-emitting device 2-2, and comparative light-emitting device 2-1. Figure 31 shows the blue index-current density characteristics of light-emitting device 2-1, light-emitting device 2-2, and comparative light-emitting device 2-1. Figure 32 shows the external quantum efficiency-current density characteristics of light-emitting device 2-1, light-emitting device 2-2, and comparative light-emitting device 2-1. Figure 33 shows the electroluminescence spectra of light-emitting device 2-1, light-emitting device 2-2, and comparative light-emitting device 2-1. Figure 34 shows the normalized brightness time-vary characteristics of light-emitting device 2-1, light-emitting device 2-2, and comparative light-emitting device 2-1. Figure 35 shows the absorption and PL spectra of a mixed film of SiTrzCz2 and PSiCzCz in a 1:1 (weight ratio) ratio, and of the individual films.

[0038] The embodiments of the present invention will be described in detail below with reference to the drawings. However, the present invention is not limited to the following description, and its form and details can be modified in various ways without departing from the spirit and scope of the present invention. Accordingly, the present invention shall not be interpreted as being limited to the contents of the embodiments shown below.

[0039] Please note that the positions, sizes, and ranges of each component shown in the drawings may not represent their actual positions, sizes, and ranges for the sake of ease of understanding. Therefore, the disclosed invention is not necessarily limited to the positions, sizes, and ranges disclosed in the drawings.

[0040] In this specification, the ordinal numbers "first," "second," etc., are used for convenience only and do not limit the number of components or the order of components. The order of components includes, for example, the order of processes or the order of stacking. That is, the ordinal numbers used in the embodiments of this specification may not match the ordinal numbers used in the claims. Also, the ordinal numbers used in the examples of this specification may not match the ordinal numbers used in the claims. Also, the ordinal numbers used in the embodiments of this specification may not match the ordinal numbers used in the examples of this specification.

[0041] Furthermore, in this specification and other documents, when describing the structure of the invention using drawings, reference numerals that refer to the same thing may be used in common across different drawings.

[0042] Furthermore, in this specification, the terms "film" and "layer" are interchangeable. For example, the term "conductive layer" may be changed to "conductive film." Or, for example, the term "insulating film" may be changed to "insulating layer."

[0043] In this specification, a photoluminescence (PL) spectrum refers to a spectrum obtained by fixing the excitation wavelength of the excitation light in fluorescence photometry and spectrally analyzing the emission from a sample irradiated with excitation light at each wavelength, thereby measuring the emission intensity distribution at each wavelength. It may also be called an emission spectrum. An emission spectrum may contain both a fluorescent component and a phosphorescent component. In this specification, an emission spectrum consisting of a fluorescent component may be specifically called a fluorescence spectrum, and an emission spectrum consisting of a phosphorescent component may be specifically called a phosphorescent spectrum.

[0044] Furthermore, when light is incident on a material with optical anisotropy, light from a vibration plane parallel to the optical axis is called extraordinary light (ray), and light from a vibration plane perpendicular to the optical axis is called ordinary light (ray). However, the refractive index of the material for ordinary light and the refractive index for extraordinary light may differ. In such cases, by performing anisotropy analysis, the refractive index of ordinary light and the refractive index of extraordinary light can be separated and their respective refractive indices can be calculated. In this specification, if both ordinary and extraordinary refractive indices exist in the measured material, the refractive index of ordinary light will be used as the index.

[0045] (Embodiment 1) In this embodiment, a light-emitting device 10A, which is a light-emitting device according to one aspect of the present invention, and a light-emitting device 10B, which is a light-emitting device according to another aspect of the present invention, will be described with reference to Figures 1A and 1B.

[0046] As shown in Figures 1A and 1B, the light-emitting devices 10A and 10B are each located on the substrate 1000. The light-emitting devices 10A and 10B each have a first electrode 101, a second electrode 102, and an EL layer 103 located between the first electrode 101 and the second electrode 102. Also, as shown in Figures 1A and 1B, the EL layer 103 has at least a light-emitting layer 113, a first electron transport layer 114_1, and a second electron transport layer 114_2. The first electron transport layer 114_1 and the electron transport layer 114_2 have the function of transporting electrons injected into the EL layer 103 from either the first electrode 101 or the second electrode 102 to the light-emitting layer 113. The first electron transport layer 114_1 is located between the first electrode 101 and the second electron transport layer 114_2.

[0047] Furthermore, as shown in Figures 1A and 1B, in the light-emitting devices 10A and 10B, the first electrode 101 is formed on the substrate 1000. It can also be said that the first electrode 101 is provided between the second electrode 102 and the substrate 1000. That is, the first electrode 101 is an electrode provided before the second electrode 102. When a transistor is provided on the substrate 1000, the first electrode 101 is electrically connected to the transistor via wiring. Alternatively, the first electrode 101 is provided on an insulating layer on which external connection electrodes are provided, such as terminals for attaching FPCs. Alternatively, the ends of the first electrode 101 are covered with an insulating film.

[0048] The light-emitting device 10A shown in Figure 1A and the light-emitting device 10B shown in Figure 1B differ in the functions of the first electrode 101 and the second electrode 102. In light-emitting device 10A, the first electrode 101 functions as an anode, and the second electrode 102 functions as a cathode. In this specification, a light-emitting device like light-emitting device 10A, in which the first electrode provided on the substrate side functions as an anode, is sometimes referred to as a forward-stacked light-emitting device. On the other hand, in light-emitting device 10B, the first electrode 101 functions as a cathode, and the second electrode 102 functions as an anode. In this specification, a light-emitting device like light-emitting device 10B, in which the first electrode provided on the substrate side functions as a cathode, is sometimes referred to as a reverse-stacked light-emitting device.

[0049] In the sequentially stacked light-emitting device 10A, holes are injected from the first electrode 101, which is the anode, into the EL layer 103 and transported by the hole transport layer 112, and electrons are injected from the second electrode 102, which is the cathode, into the EL layer 103 and transported by the electron transport layer 114. These recombine in the light-emitting layer 113 to produce 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.

[0050] In the inverted stacked light-emitting device 10B, electrons are injected into the EL layer 103 from the first electrode 101, which functions as a cathode, and transported by the electron transport layer 114. These electrons are then injected into the EL layer 103 from the second electrode 102, which functions as an anode, and transported by the hole transport layer 112. These electrons then recombine in the light-emitting layer 113, thereby emitting light. Therefore, in the light-emitting device 10B, the hole transport layer 112 is located between the second electrode 102 and the light-emitting layer 113, and the electron transport layer 114 is located between the first electrode 101 and the light-emitting layer 113.

[0051] In the light-emitting devices 10A and 10B, the electron transport layer has a laminated structure (a laminate of the first electron transport layer 114_1 and the second electron transport layer 114_2). The hole transport layer 112 may be a single layer or have a laminated structure. The first electron transport layer 114_1 and the second electron transport layer 114_2 are sometimes collectively referred to as the electron transport layer 114.

[0052] Furthermore, it is preferable that the light-emitting devices 10A and 10B have a hole transport layer 112 between the anode and the light-emitting layer 113, and it is more preferable that they have a hole injection layer 111 between the anode and the hole transport layer 112. Furthermore, it is more preferable that the light-emitting devices 10A and 10B have an electron injection layer 115 between the cathode and the electron transport layer 114.

[0053] Figure 1A shows an example of a forward-stacked light-emitting device 10A having 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 that functions as a cathode are sequentially stacked on a first electrode 101 that functions as an anode. Figure 1B shows an example of a reverse-stacked light-emitting device 10B having 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 that functions as an anode are sequentially stacked on a first electrode 101 that functions as a cathode.

[0054] Note that the configurations of the light-emitting devices 10A and 10B are not limited to those shown in Figures 1A and 1B. For example, a configuration with two hole transport layers, or a configuration with three or more layers of either the hole transport layer or the electron transport layer, or both, may be used.

[0055] The present inventors have found that in light-emitting devices 10A and 10B having a laminated structure of electron transport layers, by selecting the materials used for each layer while considering the refractive index and the slope of the giant surface potential (GSP) of the electron transport layer, it is possible to make light-emitting devices 10A and 10B light-emitting devices that have good luminous efficiency and reliability.

[0056] In other words, when the electron transport layer has a laminated structure of a first electron transport layer 114_1 formed earlier and a second electron transport layer 114_2 formed later, the slope of the GSP of the second electron transport layer 114_2 (GSP_Slope (mV / nm)) is greater than that of the GSP_Slope of the first electron transport layer 114_1, and the refractive index of the second electron transport layer 114_2 is lower, making it possible to create a light-emitting device with good reliability.

[0057] Alternatively, when the electron transport layer has a laminated structure of a first electron transport layer 114_1 formed earlier and a second electron transport layer 114_2 formed later, the slope of the GSP (GSP_Slope (mV / nm)) in the vapor-deposited film of the organic compound having a π-electron-deficient heteroaromatic ring contained in the second electron transport layer 114_2 is greater than the GSP_Slope in the vapor-deposited film of the organic compound having a π-electron-deficient heteroaromatic ring contained in the first electron transport layer 114_1. This makes it possible to create a light-emitting device with a low refractive index in the vapor-deposited film of the organic compound having a π-electron-deficient heteroaromatic ring contained in the second electron transport layer 114_2 that has good luminous efficiency and reliability.

[0058] Here, GSP refers to a phenomenon caused by spontaneous polarization (SOP) resulting from the orientation of the permanent electric dipole moment of a deposited film being biased in the direction of film thickness.

[0059] The surface potential of a vapor-deposited film exhibiting GSP changes at a constant rate without saturating as the film thickness increases. For example, tris(8-quinolinolato)aluminum (abbreviated as Alq ３ The deposited film of ) has a surface potential of approximately 28V at a film thickness of 560nm. This electric field strength is 5 × 10⁻¹⁰ ５ It reaches V / cm, which is about the same magnitude as the electric field strength during operation of a typical light-emitting device.

[0060] The GSP slope (GSP_Slope) is a parameter expressed as ΔV / Δd when the change in surface potential is ΔV (mV) for a film in which the GSP changes proportionally to the film thickness, and the change in surface potential is ΔV (mV) for a change in film thickness Δd (nm). Note that if the surface potential increases with increasing film thickness, the GSP_Slope is positive; if the surface potential decreases with increasing film thickness, the GSP_Slope is negative. (See Alq above) ３ This can be described as a material having a positive GSP_Slope. In layers where the GSP_Slope is positive, the substrate side has a low potential, and in layers where the GSP_Slope is negative, the substrate side has a high potential.

[0061] As mentioned above, this GSP is a phenomenon caused by SOP resulting from the bias in the orientation of the permanent electric dipole moment in the film thickness direction. That is, in layers where GSP_Slope is positive, it can be considered that a negative polarization charge is induced on the substrate side of that layer and a positive polarization charge is induced on the second electrode side. Similarly, in layers where GSP_Slope is negative, it can be considered that a positive polarization charge is induced on the substrate side of that layer and a negative polarization charge is induced on the second electrode side. The induction of such polarization charges is the origin of GSP. In Figures 1A and 1B, the SOP resulting from the bias in the orientation of the permanent electric dipole moment in the film thickness direction of each layer deposited by vapor deposition is shown using σ+ and σ−. σ+ indicates positive polarization, and σ− indicates negative polarization. Furthermore, a larger number of σ near the interface in each layer means that the spontaneous polarization is greater.

[0062] Deposition films of organic compounds often have a positive GSP_Slope. In this case, when a second layer is deposited in contact with a first layer, the signs of the GSP_Slopes of the first and second layers become the same positive, and it can be considered that negative polarization charges are induced on the substrate side of each layer, and positive polarization charges are induced on the second electrode side. At this time, the negative polarization charge on the first layer side of the second layer cancels out with the positive polarization charge on the second layer side of the first layer, and only the remaining charge becomes the interfacial charge (fixed charge) at the interface between the first and second layers.

[0063] Figure 1A shows a forward-stacked light-emitting device 10A, and Figure 1B shows a reverse-stacked light-emitting device. The electron transport layer 114 has a laminated structure of a first electron transport layer 114_1 and a second electron transport layer 114_2. The second electron transport layer 114_2 is provided on the second electrode 102 side of the first electron transport layer 114_1. In one embodiment of the present invention, it is preferable that the GSP_Slop of the second electron transport layer 114_2 is larger than the GSP_Slop of the first electron transport layer 114_1. Alternatively, in one embodiment of the present invention, it is preferable that the GSP_Slop of the vapor-deposited film of the second organic compound having a π-electron-deficient heteroaromatic ring contained in the second electron transport layer 114_2 is larger than the GSP_Slop 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.

[0064] In a light-emitting device according to one aspect of the present invention having such a configuration, a negative interfacial charge is generated at the interface between the second electron transport layer 114_2 and the first electron transport layer 114_1. This suppresses the injection of electrons from the second electrode 102 or electron injection layer 115 into the second electron transport layer 114_2 (in the case of forward stacking, Figure 1A), or the injection of electrons from the first electrode 101 or electron injection layer 115 into the first electron transport layer 114_1 (in the case of reverse stacking, Figure 1B). This prevents the light-emitting layer 113 from becoming electron-excessive, reduces the bias towards the hole transport layer 112 in the recombination region of the light-emitting layer 113, and reduces the degradation of the light-emitting layer 113 and the hole transport layer 112 (or electron blocking layer). As a result, a light-emitting device according to one aspect of the present invention can be made into a highly reliable light-emitting device.

[0065] Furthermore, it is preferable that the light-emitting layer 113 contains at least a light-emitting substance and also has a host material. Blue light-emitting substances with high excitation energy levels as the light-emitting substance result in a large band gap in the host material, making it difficult to control the carrier balance. In particular, blue phosphorescent light-emitting devices containing blue phosphorescent substances often have a configuration in which the light-emitting layer 113 tends to have an excess of electrons. Therefore, the present invention can be suitably applied to phosphorescent light-emitting devices, especially blue phosphorescent light-emitting devices, and provides a significant improvement in reliability.

[0066] Furthermore, in one embodiment of the present invention, the low refractive index of the second electron transport layer 114_2 makes it possible to provide a light-emitting device with good luminescence efficiency and reliability.

[0067] Specifically, the paraphotometric refractive index of the second electron transport layer 114_2 at any wavelength from 455 nm to 520 nm is preferably 1.75 or less, preferably 1.70 or less, and more preferably 1.67 or less. It is preferable that the paraphotometric refractive index of the second electron transport layer 114_2 at any wavelength from 455 nm to 520 nm is 1.00 or higher. Alternatively, the refractive index of the second electron transport layer 114_2 at the peak wavelength of the emission spectrum of the light-emitting device is preferably 1.75 or less, preferably 1.70 or less, and more preferably 1.67 or less. Furthermore, it is preferable that the refractive index of the second electron transport layer 114_2 at the peak wavelength of the emission spectrum of the light-emitting device is 1.00 or higher.

[0068] Alternatively, the refractive index 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 1.75 or less, more preferably 1.70 or less, and more preferably 1.67 or less. The ordinary refractive index of the vapor-deposited film of the second organic compound at any wavelength from 455 nm to 520 nm is preferably 1.00 or higher. Alternatively, the refractive index of the second electron transport layer 114_2 is preferably 1.75 or less, more preferably 1.70 or less, and more preferably 1.67 or less at the peak wavelength of the emission spectrum of the luminescent material contained in the light-emitting layer of the light-emitting device. The refractive index of the second electron transport layer 114_2 is preferably 1.00 or higher at the peak wavelength of the emission spectrum of the luminescent material contained in the light-emitting layer of the light-emitting device.

[0069] In other words, it is preferable that the second organic compound having a π-electron-deficient heteroaromatic ring contained in the second electron transport layer 114_2 is an organic compound whose deposited film has a large GSP_slope and a small refractive index. Specifically, it is preferable that the second organic compound having a π-electron-deficient heteroaromatic ring contained in the second electron transport layer 114_2 has a GSP_slope of its deposited film that is larger than that of the first organic compound having a π-electron-deficient heteroaromatic ring contained in the first electron transport layer 114_1, and that its refractive index is 1.75 or less, preferably 1.70 or less, and more preferably 1.67 or less, with a paraphotonic refractive index at any wavelength from 455 nm to 520 nm.

[0070] As a second organic compound having a π-electron-deficient heteroaromatic ring with a large GSP_slope and low refractive index in the vapor-deposited film, an organic compound having a π-electron-deficient heteroaromatic ring and a saturated hydrocarbon group is preferred. The saturated hydrocarbon group also includes cyclic saturated hydrocarbon groups that form a ring. Furthermore, as the saturated hydrocarbon group, a saturated hydrocarbon group having 1 to 12 carbon atoms is preferred, an alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 6 to 12 carbon atoms is preferred, and an alkyl group having 3 to 6 carbon atoms or a cycloalkyl group having 6 to 10 carbon atoms is more preferred.

[0071] Since saturated hydrocarbon groups are substituents with low polarization, organic compounds containing saturated hydrocarbon groups can produce films with lower refractive indices than organic compounds composed solely of unsaturated hydrocarbons. Furthermore, since a larger number of saturated hydrocarbon groups results in a film with a lower refractive index, it is preferable that the second organic compound has multiple saturated hydrocarbon groups, preferably two or more. However, from the viewpoint of carrier transport, it is preferable that the second organic compound has five or fewer saturated hydrocarbon groups.

[0072] Furthermore, because saturated hydrocarbon groups are not conjugated, the dispersion forces between molecules are smaller compared to unsaturated hydrocarbon groups, resulting in smaller van der Waals forces. Due to this effect, when forming a vacuum-deposited film using a compound containing both saturated and unsaturated hydrocarbon groups, the molecules tend to orient themselves such that the saturated hydrocarbon group portion, where large van der Waals forces act, faces the substrate or the already deposited film side, while the saturated hydrocarbon group portion, where small van der Waals forces act, faces the film surface side. In addition, since saturated hydrocarbon groups are electron-donating groups, the molecular dipole moment tends to be positive on the saturated hydrocarbon group side. From this relationship between the orientation obtained by vacuum deposition and the molecular dipole moment, films formed with compounds containing saturated hydrocarbon groups tend to exhibit a large positive GSP_slope. Therefore, since it is easy to obtain a second electron transport layer 114_2 with a large GSP_slope by using an organic compound containing saturated hydrocarbon groups, an organic compound containing a π-electron-deficient heteroaromatic ring and a saturated hydrocarbon group is preferred as the second organic compound.

[0073] Further, as an example of the second organic compound contained in the second electron transport layer 114_2, for example, an organic compound represented by the following general formula (G1) is preferable. From these, by selecting an organic compound having a larger GSP_slope and a lower refractive index than the first organic compound contained in the first electron transport layer 114_1, a light-emitting device with better characteristics can be provided. However, the second organic compound may be an organic compound other than these.

[0074]

[0075] In the above general formula (G1), A represents a substituted or unsubstituted heteroaromatic ring, and the heteroaromatic ring may be a monocyclic ring or a condensed ring, and R ０ to R １５ each independently represents hydrogen (including deuterium), a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted alicyclic group having 3 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, a substituted or unsubstituted heteroaromatic hydrocarbon group having 1 to 30 carbon atoms, or a group represented by the general formula (G1-1).

[0076] In the above general formula (G1) or general formula (G1-1), R ０ to R １５ at least one of or R ０ to R １５ at least one of the substituents possessed by is preferably either a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms or a substituted or unsubstituted alicyclic group having 3 to 10 carbon atoms.

[0077] A in the general formula (G1) is preferably any one of a pyridine ring, a pyrimidine ring, a pyrazine ring, a pyridazine ring, a triazine ring, a quinoline ring, a quinazoline ring, a quinoxaline ring, a benzoquinoxaline ring, a dibenzoquinoxaline ring, a benzoquinazoline ring, a dibenzoquinazoline ring, and particularly preferably a triazine ring among the pyridine ring, pyrimidine ring, pyrazine ring, pyridazine ring, and triazine ring.

[0078] Further, in the above general formula (G1), R ０ to R １５If R is hydrogen (including deuterium), a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, or a substituted or unsubstituted alicyclic group having 3 to 10 carbon atoms, ２ and R ４ It is preferable that R is an alkyl group or an alicyclic group, １ , R ３ and R ５ It is preferable that R is hydrogen (including deuterium). In this case, ２ and R ４ Because the substituents are located in meta positions relative to each other or in a meta position relative to A, steric hindrance can be reduced compared to cases where substituents are bonded to adjacent carbons or in an ortho position relative to A, resulting in a stable molecular structure, which is preferable from a reliability standpoint. Furthermore, such a molecular structure makes synthesis easy or possible, thus increasing the synthesis yield, which is preferable from the viewpoint of reducing synthesis costs or increasing the purity of the target product, and improving reliability. Similarly, R ６ , R ８ and R １０ It is preferable that is hydrogen (including deuterium). Similarly, for general formula (G1-1), R １１ , R １３ and R １５ It is preferable that it is hydrogen (including deuterium).

[0079] In the above general formula (G1), R ０ ~R １５ However, if the group is hydrogen (including deuterium), a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, a substituted or unsubstituted heteroaromatic hydrocarbon group having 1 to 30 carbon atoms, or a group represented by general formula (G1-1), the substituents other than hydrogen (including deuterium) may be bonded to adjacent carbon atoms.

[0080] Furthermore, in the above general formula (G1), R ０ ~R １５ At least one of these can be a group represented by the following formula (G1-2).

[0081]

[0082] In the above general formula (G1-2), α represents a substituted or unsubstituted benzene ring, or a substituted or unsubstituted biphenyl skeleton. Also, R ２０ α represents a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted alicyclic group having 3 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, or a substituted or unsubstituted heteroaromatic group having 1 to 30 carbon atoms. Also, m represents 0 to 2. Also, n represents 1 or 4. Note that when m is 2, the multiple αs may be the same or different. Also, when n is 2 or more, multiple R ２０ These may be the same or different. If α is a benzene ring with a substituent, it is preferable that the substituent is located in the meta position relative to other groups bonded to the benzene ring. Also, if n is 2, there are two R ２０ It is preferable that they are located in meta positions relative to each other.

[0083] Furthermore, if the benzene ring or biphenyl skeleton has substituents, examples of substituents include substituted or unsubstituted alkyl groups having 1 to 4 carbon atoms, substituted or unsubstituted alicyclic groups having 3 to 6 carbon atoms, or substituted or unsubstituted aromatic hydrocarbon groups having 6 to 13 carbon atoms.

[0084] In the above general formula (G1), R ２ and R ４ Preferably, one or both of these are groups represented by the general formula (G1-2). However, R ２ and R ４ If both of the groups are represented by (G1-2) above, then R ２ and R ４ These may be the same or different in each case.

[0085] In the above general formula (G1-2), specific examples of α are given by the following formulas (α-1) to (α-14). In the following formulas (α-1) to (α-14), * represents a coupling.

[0086]

[0087] Furthermore, in general formula (G1), general formula (G1-1), or general formula (G1-2), R ０ ~R１５ , R ２０ , R ０ ~R １５ The substituents that R has, ２０ Preferably, at least one of the substituents is independently one of a substituted or unsubstituted phenyl group, a substituted or unsubstituted naphthyl group, a substituted or unsubstituted phenanthryl group, or a substituted or unsubstituted fluorenyl group. When these substituents are combined, the effective conjugation length becomes short wavelength, making it possible to design molecules that do not absorb in the visible light region, which is effective in improving extraction efficiency. When the phenyl group, naphthyl group, phenanthryl group, or fluorenyl group has substituents, examples of substituents include 1 to 4 alkyl groups, 3 to 6 alicyclic groups, or 6 to 13 aromatic hydrocarbon groups.

[0088] Also, R ０ ~R １５ , R ２０ , R ０ ~R １５ The substituents that R has, ２０At least one of the substituents on the compound is preferably a heteroaromatic ring or heteroaromatic ring group containing nitrogen in the element forming the substituted or unsubstituted ring, in order to reduce the refractive index. More preferably, the heteroaromatic ring or heteroaromatic ring group has two or more nitrogen atoms, and even more preferably, it has three or more nitrogen atoms. Specific examples of heteroaromatic ring or heteroaromatic ring group skeletons include pyridine, pyrazine, pyrimidine, pyridazine, 1,2,3-triazine, 1,2,4-triazine, 1,3,5-triazine, quinoline, quinazoline, quinoxaline, benzoquinoxaline, dibenzoquinoxaline, benzoquinazoline, or dibenzoquinazoline. However, when used in common with the electron transport layer or injection layer, the pyridine skeleton is preferred. Furthermore, the heteroaromatic ring or heteroaromatic ring group preferably has one or more saturated hydrocarbon groups, and when used in common with the electron transport layer or electron injection layer, it is preferable to have a methyl group in order to improve electron injection and transport properties. A particularly preferred configuration is a pyridine skeleton having one or more methyl groups. When the pyridine skeleton has substituents, examples of substituents include alkyl groups with 1 to 4 carbon atoms, alicyclic groups with 3 to 6 carbon atoms, or aromatic hydrocarbon groups with 6 to 13 carbon atoms.

[0089] Also, R ０ ~R １５ , R ２０ , R ０ ~R １５ The substituents that R has, ２０ Specific examples of substituents that can be found are shown in the following formulas (r-1) to (r-20). In the following formulas (r-1) to (r-20), * represents a bond.

[0090]

[0091] As shown in formulas (r-1), (r-2), (r-5), and (r-6), it is preferable that the alkyl group or alicyclic group is bonded to the meta position of the phenyl group, compared to cases where it is bonded to the para and ortho positions, as this results in a lower film density and a lower refractive index. Furthermore, as shown in formulas (r-5) and (r-6), having a total of two alkyl groups and / or alicyclic groups relative to the phenyl group is preferable because it allows for an easy increase in the total number of carbon atoms forming sp3 hybrid orbitals, thereby reducing synthesis costs. In addition, as shown in formulas (r-19) or (r-20), having a pyridyl group is preferable because the element forming the ring contains nitrogen, resulting in a lower refractive index compared to an all-carbon aromatic ring. Furthermore, when used in common with an electron transport layer or electron injection layer, it is preferable to have a methyl group because it enhances electron injection and transport properties. A particularly preferred configuration is a pyridine skeleton having one or more methyl groups.

[0092] Furthermore, all hydrogen atoms may be deuterium, and aromatic hydrocarbon groups and heteroaromatic hydrocarbon groups may have structures in which multiple rings are bonded to each other. If they consist of multiple rings, there may be multiple aromatic hydrocarbon groups, and there may also be multiple heteroaromatic hydrocarbon groups, and both aromatic hydrocarbon groups and heteroaromatic hydrocarbon groups may be present.

[0093] Furthermore, all hydrogen atoms in the organic compound represented by general formula (G1) may independently be deuterium.

[0094] In the above general formula (G1), examples of skeletons constituting an aromatic hydrocarbon group having 6 to 30 carbon atoms include benzene, biphenyl, naphthalene, phenylnaphthalene, terphenyl, fluorene, 9,9-dimethylfluorene, quaterphenyl, spirobifluorene, phenanthrene, anthracene, phenylbinaphthalene, fluorantene, and triphenylene. A monovalent group obtained by removing one hydrogen atom from these skeletons becomes an aromatic hydrocarbon group having 6 to 30 carbon atoms. In addition, in the above skeletons, skeletons consisting of multiple rings may form bonds at any position on the rings, and carbon atoms at any position on these skeletons may form substituent bonds. Furthermore, when an aromatic hydrocarbon group having 6 to 30 carbon atoms has substituents, such substituents can be alkyl groups having 1 to 4 carbon atoms, alicyclic groups having 3 to 6 carbon atoms, or aromatic hydrocarbon groups having 6 to 13 carbon atoms. Preferred substituent skeletons include methylbenzene, dimethylbenzene, trimethylbenzene, dimethylfluorene, diphenylfluorene, and diphenylanthracene.

[0095] Furthermore, specific examples of heteroaromatic groups having 1 to 30 carbon atoms in the above general formula (G1) include 1,3,5-triazine-yl group, 1,2,4-triazine-yl group, pyrimidine-yl group, pyrazine-yl group, pyridyl group, carbazolyl group, dibenzofuranyl group, dibenzothiophenyl group, benzonaphthofuranyl group, benzonaphthothiophenyl group, dinaphthofuranyl group, dinaphthothiophenyl group, indrocarbazolyl group, benzoflocarbazolyl group, benzothienocarbazolyl group, indenocarbazolyl group, dibenzocarbazolyl group, indolyl group, pyrrolyl group, 1,2,3-triazol-yl group, and 1,2,4-triazole-yl group. Furthermore, if a heteroaromatic hydrocarbon group having 1 to 30 carbon atoms has substituents, these substituents may include alkyl groups having 1 to 4 carbon atoms, alicyclic groups having 3 to 6 carbon atoms, or aromatic hydrocarbon groups having 6 to 13 carbon atoms.

[0096] Examples of C1 to C6 alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, isobutyl, tert-butyl, pentyl, isopentyl, sec-pentyl, tert-pentyl, neopentyl, hexyl, isohexyl, 3-methylpentyl, 2-methylpentyl, 2-ethylbutyl, 1,2-dimethylbutyl, 2,3-dimethylbutyl, and 1-ethylpropyl. When a C1 to C6 alkyl group has substituents, these substituents may include alicyclic groups with C3 to C6 or aromatic hydrocarbon groups with C6 to C13.

[0097] Furthermore, as the alicyclic group having 3 to 10 carbon atoms, cycloalkyl groups are preferred, specifically including cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group, cyclononanyl group and cyclodecanyl group, adamantyl group, bicyclo[2.2.1]heptyl group, tricyclo[5.2.1.0(2,6)]decanyl group, noadamantyl group, 1-methylcyclohexyl group, bicyclo[2,2,2]octyl group, norbornanyl group, and the like. When the alicyclic group having 3 to 10 carbon atoms has substituents, the substituents can be alkyl groups having 1 to 4 carbon atoms, alicyclic groups having 3 to 6 carbon atoms, or aromatic hydrocarbon groups having 6 to 13 carbon atoms.

[0098] Specific examples of organic compounds having an electron-transporting skeleton and saturated hydrocarbon groups having the above-described structure include the organic compounds represented by the following structural formulas (100) to (131), (200) to (223), (300) to (316), (400) to (435), and (450) to (456).

[0099]

[0100]

[0101]

[0102]

[0103]

[0104]

[0105]

[0106]

[0107]

[0108]

[0109]

[0110]

[0111]

[0112]

[0113]

[0114]

[0115]

[0116]

[0117]

[0118] A light-emitting device according to one aspect of the present invention having such a configuration can be a light-emitting device with good luminous efficiency and good reliability.

[0119] In the sequentially stacked light-emitting device 10A shown in Figure 1A, the second electron transport layer 114_2 may contain a first substance in addition to the second organic compound. The first substance is preferably a metal complex, particularly an organic complex containing an alkali metal. Specifically, examples of organic complexes containing alkali metals include 8-quinolinolato-lithium (abbreviated as Liq), 8-quinolinolato-sodium (abbreviated as Naq), 8-quinolinolato-potassium (abbreviated as Kq), and their derivatives. When the second electron transport layer 114_2 contains such a substance, it becomes possible to control the electron transport properties in the second electron transport layer 114_2, and furthermore, by suppressing the bias of the recombination region in the light-emitting layer 113 toward the hole transport layer 112, the reliability of the light-emitting device can be improved.

[0120] In this case, if the mixing ratio (weight ratio) of the second organic compound and the first substance in the second electron transport layer 114_2 is x:y, it is preferable that the GSP_Slope (mV / nm) of the film of the second organic compound is greater than (x+y) / x times the GSP_Slope (mV / nm) of the film of the first organic compound. With this configuration, even if the GSP_Slope of the film of the first substance is smaller than the GSP_Slope of the film of the second organic compound, the GSP_Slope (mV / nm) of the second electron transport layer 114_2 will be larger than that of the first electron transport layer 114_1, so a negative interfacial charge is generated and electron injection is suppressed, which is preferable. Also, it is preferable that y is greater than x, as this reduces the proportion of the second organic compound responsible for electron transport and thus reduces electron transport performance.

[0121] Furthermore, in the inverted stacking type light-emitting device 10B shown in Figure 1B, the first electron transport layer 114_1 may contain a first substance in addition to the first organic compound. The first substance is preferably a metal complex, particularly an organic complex containing an alkali metal. When the first electron transport layer 114_1 contains such a substance, it becomes possible to control the electron transport properties in the first electron transport layer 114_1, and furthermore, the bias of the recombination region in the light-emitting layer 113 toward the hole transport layer 112 can be suppressed, thereby improving the reliability of the light-emitting device.

[0122] Furthermore, as shown in Figure 2A, if a sequentially stacked light-emitting device according to one embodiment of the present invention has a hole transport layer 112 in contact with the light-emitting layer 113, it is preferable that the GSP_Slope (mV / nm) of the light-emitting layer 113 is greater than the GSP_Slope (mV / nm) of the hole transport layer or the GSP_Slope (mV / nm) of the vapor-deposited film of the third organic compound having a π-electron-rich heteroaromatic ring or aromatic amine present in the hole transport layer 112. Alternatively, it is preferable that the GSP_Slope (mV / nm) of the vapor-deposited film of the host material is greater than the GSP_Slope (mV / nm) of the vapor-deposited film of the third organic compound having a π-electron-rich heteroaromatic ring or aromatic amine present in the hole transport layer 112.

[0123] Furthermore, as shown in Figure 2B, if an inverted stacking type light-emitting device according to one embodiment of the present invention has a hole transport layer 112 in contact with the light-emitting layer 113, it is preferable that the GSP_Slope (mV / nm) of the light-emitting layer 113 is smaller than the GSP_Slope (mV / nm) of the hole transport layer or the GSP_Slope (mV / nm) of the vapor-deposited film of the third organic compound having a π-electron-rich heteroaromatic ring or aromatic amine present in the hole transport layer 112. Alternatively, it is preferable that the GSP_Slope (mV / nm) of the vapor-deposited film of the host material is smaller than the GSP_Slope (mV / nm) of the vapor-deposited film of the third organic compound having a π-electron-rich heteroaromatic ring or aromatic amine present in the hole transport layer 112.

[0124] In one embodiment of the present invention having this configuration, the effect of the negative interfacial charge originating from the difference in GSP slopes of the two contacting layers promotes the injection of holes from the hole injection layer 111 to the hole transport layer 112. As a result, hole injection into the light-emitting layer also occurs effectively, improving the carrier balance and expanding the recombination region, thereby suppressing the degradation of the light-emitting layer 113 and the hole transport layer 112.

[0125] Furthermore, as shown in Figure 1A, in a sequential stacking type light-emitting device according to one embodiment of the present invention, it is preferable that the GSP_Slope (mV / nm) of the light-emitting layer 113 is greater than the GSP_Slope (mV / nm) of the first electron transport layer 114_1. Alternatively, it is preferable that the GSP_Slope (mV / nm) of the vapor-deposited film of the host material is greater than the GSP_Slope (mV / nm) of the vapor-deposited film of the first organic compound.

[0126] Furthermore, as shown in Figure 1B, in an inverted stacking type light-emitting device according to one embodiment of the present invention, it is preferable that the GSP_Slope (mV / nm) of the light-emitting layer 113 is smaller than the GSP_Slope (mV / nm) of the second electron transport layer 114_2. Alternatively, it is preferable that the GSP_Slope (mV / nm) of the vapor-deposited film of the host material is smaller than the GSP_Slope (mV / nm) of the vapor-deposited film of the second organic compound.

[0127] In one embodiment of the present invention having this configuration, the injection of electrons from the second electron transport layer 114_2 to the first electron transport layer 114_1 is promoted due to the influence of the positive interfacial charge originating from the difference in GSP_slope. Therefore, even if the injection of electrons from the first electrode 101 or the electron injection layer 115 to the second electron transport layer 114_2 is suppressed, the light-emitting device of one embodiment of the present invention does not cause a significant increase in the driving voltage, making it possible to obtain a light-emitting device with good characteristics.

[0128] Furthermore, as shown in Figure 1A, in a sequentially stacked light-emitting device according to one embodiment of the present invention, it is preferable that the GSP_Slope (mV / nm) of the second electron transport layer 114_2 is greater than the GSP_Slope (mV / nm) of the light-emitting layer 113. Alternatively, it is preferable that the GSP_Slope (mV / nm) of the vapor-deposited film of the second organic compound is greater than the GSP_Slope (mV / nm) of the vapor-deposited film of the host material.

[0129] Furthermore, as shown in Figure 1B, in an inverted stacking type light-emitting device according to one embodiment of the present invention, it is preferable that the GSP_Slope (mV / nm) of the first electron transport layer 114_1 is smaller than the GSP_Slope (mV / nm) of the light-emitting layer 113. Alternatively, it is preferable that the GSP_Slope (mV / nm) of the vapor-deposited film of the first organic compound is smaller than the GSP_Slope (mV / nm) of the vapor-deposited film of the host material.

[0130] In one embodiment of the present invention having this configuration, the interfacial charge between the first electron transport layer 114_1 and the second electron transport layer 114_2 is negative and smaller than the interfacial charge between the light-emitting layer 113 and the first electron transport layer 114_1. This effect suppresses electron injection into the light-emitting layer while promoting hole injection within the light-emitting layer, thereby improving the carrier balance, expanding the recombination region, and suppressing the degradation of the light-emitting layer 113 and the hole transport layer 112.

[0131] Furthermore, if the light-emitting layer 113 includes a host material, it is preferable that the host material includes a first material and a second material. By composing the host material with multiple materials, it becomes easier to control the carrier balance, contributing to improved reliability. Alternatively, by forming an excitation complex with the first material and the second material, effects such as improved energy transfer efficiency to the light-emitting substance, lower driving voltage, and improved reliability can be achieved. It is preferable that one of the first and second materials is an organic compound having a π-electron-deficient heteroaromatic ring, and the other is an organic compound having a π-electron-rich heteroaromatic ring or aromatic amine, as this makes it easier to adjust the carrier balance.

[0132] When the host material contains multiple materials, the GSP_Slope (mV / nm) of the host material can be the GSP_Slope (mV / nm) of a mixed film obtained by co-depositing the first material and the second material in a 1:1 ratio. Alternatively, the GSP_Slope (mV / nm) of the deposited film of the material with the higher mixing ratio among the first and second materials can be considered as the GSP_Slope (mV / nm) of the host material.

[0133] <Method for determining GSP_Slope> Here, we will explain the method for determining the GSP_Slope of a film formed by vacuum deposition of an organic compound.

[0134] The phenomenon in which the surface potential of a deposited film increases in proportion to its thickness is called a giant surface potential, as mentioned above. Generally, the slope when the surface potential of a deposited film measured by a Kelvin probe is plotted in the direction of film thickness is discussed as the magnitude of the giant surface potential, i.e., GSP_Slope (mV / nm). However, when two different layers are stacked, the charge density accumulated at their interface (mC / m) is also discussed. ２ By utilizing the fact that ) changes in relation to GSP, GSP_Slope can be estimated.

[0135] Non-patent document 1 shows that when organic thin films with different spontaneous polarizations (thin film 1 and thin film 2, where thin film 1 is on the anode side and thin film 2 is on the cathode side, and the anode is located on the substrate side) are stacked and a voltage is applied, the following equation holds true if the carriers accumulated at the interface are holes.

[0136]

[0137]

[0138] In equation (1), σ ａｃｃ σ is the accumulated charge density. ｉｎｔ V is the interfacial charge density. ｉｎｊ V is the hole injection voltage. ｔｈ d is the threshold voltage, ２ ε is the film thickness of thin film 2. ２ V is the dielectric constant of thin film 2. ｉｎｊ , V ｔｈ This can be estimated from the capacitance-voltage characteristics of the device. Furthermore, the dielectric constant is the refractive index n. ｏ The square of (633 nm) can be used. In this way, V estimated from the capacitance-voltage characteristics ｉｎｊ , V ｔｈ And the dielectric constant ε of thin film 2 calculated from the refractive index. ２ , and the film thickness d of thin film 2 ２ Therefore, using equation (1), the interfacial charge density σ ｉｎｔ It is possible to find this.

[0139] Next, in equation (2), P ｎ ε is the spontaneous polarization of the thin film n in the direction normal to the substrate. ｎ V is the dielectric constant of the thin film n. ｎ d is the potential of the film surface, ｎ n is the thickness of the thin film. And the potential (V) of the film surface. ｎ ) film thickness (d ｎ The GSP_Slope can be calculated from the value obtained by dividing by (1) above. Here, the interface charge density σ ｉｎｔ Since this can be determined, the GSP_Slope of thin film 1 can be estimated by using a material with a known GSP_Slope as thin film 2 and adopting an appropriate dielectric constant.

[0140] Therefore, as thin film 2, tris(8-quinolinolato)aluminum (abbreviated as Alq) has a known GSP_Slope of (48 (mV / nm)). ３ An example of using the above to fabricate a measurement device 1 and determining the GSP_Slope of a 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviated as NPB) film is shown below.

[0141] The device structure of measurement device 1 is shown in Table 1. The cathode from layer 1_1 of measurement device 1 was formed by vacuum deposition from the anode side, with the substrate temperature at room temperature and the deposition rate from 0.2 nm / s to 0.6 nm / s. Deposition was carried out without stopping the deposition process while forming one layer at a time. In measurement device 1, layer 2_1 corresponds to thin film 1, and layer 3_1 corresponds to thin film 2. OCHD-003 is an organic compound that has electron acceptor properties.

[0142] When fabricating the measurement device, the deposition rate of each layer is preferably 3 nm / min to 600 nm / min. Furthermore, the film thickness of each layer in the measurement device is preferably 3 nm to 500 nm, and more preferably 50 nm to 300 nm.

[0143] Furthermore, the capacitance-voltage characteristics of the measurement device 1 are shown in Figure 3. The capacitance-voltage characteristics were measured using a potentiometer / galvanostat (SP-300, manufactured by Biologic, France) at a frequency of 10 Hz at room temperature.

[0144]

[0145] Table 2 shows the Hole injection voltage V of the measuring device 1, which was determined using Figure 3 and equations (1) and (2). ｉｎｊ , threshold voltage V ｔｈ , interfacial charge density σ ｉｎｔ , GSP_Slope and the refractive index n of each material used in the calculation ｏ This shows the results. The refractive index was measured using a spectroscopic ellipsometer (M-2000U, manufactured by J.A. Woolam Japan Co., Ltd.).

[0146]

[0147] Furthermore, it has almost the same configuration as the measurement device 1, Alq ３ A measurement device 2 with a film thickness of only 80 nm was fabricated, and it was confirmed that the hole injection voltage of each device was shifted to a lower voltage than that of measurement device 1. In other words, in such a device, the holes are injected first, and Alq ３ This suggests that charge is accumulating at the interface. Furthermore, using measurement device 2, we performed an estimation of GSP_Slope in the same way as with measurement device 1 and confirmed that the same result was obtained.

[0148] Furthermore, the threshold voltage V can be obtained from the capacitance-voltage characteristics. ｔｈ If it is difficult to determine, the threshold voltage of the current density-voltage characteristic may be used.

[0149] Figure 4 shows the current density-voltage characteristics of the measuring device 1.

[0150] V calculated from current density-voltage characteristics ｔｈ The voltage was 2.0V, which was the same value as the one calculated from the capacitance-voltage characteristics.

[0151] Thus, Alq, whose membrane GSP_Slope is known ３ The GSP_Slope can be estimated by fabricating a device by stacking a film formed with the organic compound for which the GSP_Slope is to be determined, and then measuring its capacitance-voltage characteristics.

[0152] In the above explanation, we described a method for calculating GSP_Slope in a configuration where the carriers accumulated at the interface are holes. However, when calculating the GSP_Slope of an organic film in a configuration where the carriers accumulated at the interface are electrons, the same calculation can be performed using the following equation (3).

[0153]

[0154]

[0155] It is preferable to select the organic compounds to be used in each layer of the light-emitting device, taking into consideration the GSP_Slope of the vapor-deposited film of the organic compound measured in advance by the measurement method described above.

[0156] The configuration shown in this embodiment can be used in appropriate combination with the configurations shown in other embodiments.

[0157] (Embodiment 2) In this embodiment, a light-emitting device according to one aspect of the present invention will be described in detail.

[0158] Figures 1A to 2B are schematic diagrams of a light-emitting device according to one embodiment of the present invention. The light-emitting device has a first electrode 101 provided on an insulator 1000, and an EL layer 103 between the first electrode 101 and a second electrode 102. The EL layer 103 contains a light-emitting material, and the light-emitting material emits light when a voltage is applied between the first electrode 101 and the second electrode 102.

[0159] The EL layer 103 has, in addition to the light-emitting layer 113, at least a first electron transport layer 114_1 and a second electron transport layer 114_2, and has the configuration shown in Embodiment 1. A light-emitting device according to one aspect of the present invention having such a configuration can be made into a light-emitting device with good characteristics, in particular good luminous efficiency and reliability.

[0160] Furthermore, as shown in Figures 1A to 2B, it is preferable that a light-emitting device according to one embodiment of the present invention has other functional layers such as a hole injection layer 111, a hole transport layer 112, and an electron injection layer 115. The EL layer 103 may also include functional layers other than those described above, such as a hole blocking layer, an electron blocking layer, an exciton blocking layer, and a charge generation layer. Conversely, none of the layers described above may be provided.

[0161] The first electrode 101 and the second electrode 102 are formed as a single-layer structure or a multilayer structure. If they have a multilayer structure, the layer in contact with the EL layer 103 functions as the anode or cathode. When the electrodes have a multilayer structure, there are no constraints on the work function of the layers other than the layer in contact with the EL layer 103, and materials can be selected according to the required properties such as resistance, ease of processing, reflectivity, light transmittance, and stability.

[0162] The anode is preferably formed using a metal, alloy, conductive compound, or mixture thereof with a large work function (specifically, 4.0 eV or more). Specifically, examples include indium tin oxide (ITO), indium tin silicon oxide (ITSO) containing silicon or silicon oxide, indium zinc oxide, and indium oxide (IWZO) containing tungsten oxide and zinc oxide. These conductive metal oxide films are usually deposited by sputtering, but they may also be fabricated using methods such as the sol-gel method. An example of a fabrication method is to form indium zinc oxide by sputtering using a target to which 1 to 20 wt% zinc oxide is added to indium oxide. Furthermore, indium oxide containing tungsten oxide and zinc oxide (IWZO) can also be formed by sputtering using a target containing 0.5 to 5 wt% tungsten oxide and 0.1 to 1 wt% zinc oxide relative to indium oxide. Other materials that can be used as anodes include, for example, gold (Au), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), titanium (Ti), aluminum (Al), or nitrides of metallic materials (e.g., titanium nitride). Alternatively, a layer of these materials can be used as the anode. For example, a film in which Al, Ti, and ITSO are laminated on Ti is preferred because it has good reflectivity, is highly efficient, and enables high resolution of several thousand ppi. Alternatively, graphene can also be used as a material for the anode. Furthermore, by using a composite material capable of forming the hole injection layer 111 (described later) as the layer in contact with the anode (typically the hole injection layer), it becomes possible to select the electrode material regardless of the work function.

[0163] The hole injection layer 111 is provided in contact with the anode and has the function of facilitating the injection of holes into the EL layer 103. The hole injection layer 111 is made of phthalocyanine (abbreviated as H ２It can be formed from phthalocyanine compounds such as Pc, copper phthalocyanine (abbreviated as CuPc), phthalocyanine-based complex compounds, aromatic amine compounds such as 4,4'-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviated as DPAB), 4,4'-bis(N-{4-[N'-(3-methylphenyl)-N'-phenylamino]phenyl}-N-phenylamino)biphenyl (abbreviated as DNTPD), or polymer compounds such as poly(3,4-ethylenedioxythiophene) / (polystyrene sulfonic acid) (abbreviated as PEDOT / PSS).

[0164] Furthermore, the hole injection layer 111 may be formed from a substance having electron-accepting properties. Examples of substances having electron-accepting properties include organic compounds having electron-withdrawing groups (halogen groups, cyano groups, etc.), such as 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviated as F4-TCNQ), chloranil, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviated as HAT-CN), 1,3,4,5,7,8-hexafluorotetracyano-naphthoquinodimethane (abbreviated as F6-TCNNQ), and 2-(7-dicyanomethylene-1,3,4,5,6,8,9,10-octafluoro-7H-pyrene-2-ylidene)malononitrile. In particular, compounds in which an electron-withdrawing group is bonded to a condensed aromatic ring having multiple complex atoms, such as HAT-CN, are thermally stable and preferred. Furthermore, [3]radialene derivatives having an electron-withdrawing group (especially halogen groups such as fluoro groups, cyano groups, etc.) are preferred because they have very high electron-accepting properties. Specific examples include α,α',α''-1,2,3-cyclopropanetriylidenates(4-cyano-2,3,5,6-tetrafluorobenzeneacetonitrile) (abbreviated as Rad), α,α',α''-1,2,3-cyclopropanetriylidenates[2,6-dichloro-3,5-difluoro-4-(trifluoromethyl)benzeneacetonitrile], and α,α',α''-1,2,3-cyclopropanetriylidenates[2,3,4,5,6-pentafluorobenzeneacetonitrile]. In addition to the organic compounds mentioned above, other acceptor materials that can be used include transition metal oxides such as molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, and manganese oxide.

[0165] Furthermore, it is preferable that the hole injection layer 111 be formed from a composite material containing the acceptor material and an organic compound having hole transport properties.

[0166] As the organic compound having hole transporting property used in the composite material, various organic compounds such as aromatic amine compounds, heteroaromatic compounds, aromatic hydrocarbons, polymer compounds (oligomers, dendrimers, polymers, etc.) can be used. Incidentally, as the organic compound having hole transporting property used in the composite material, it is preferably an organic compound having a hole mobility of 1×10 −６ cm ２ / Vs or more. The organic compound having hole transporting property used in the composite material is preferably a compound having a condensed aromatic hydrocarbon ring or a π-electron excessive type heteroaromatic ring. As the condensed aromatic hydrocarbon ring, an anthracene ring, a naphthalene ring, etc. are preferable. Further, as the π-electron excessive type heteroaromatic ring, a condensed aromatic ring containing at least any one of a pyrrole skeleton, a furan skeleton, and a thiophene skeleton in the ring is preferable. Specifically, a carbazole ring, a dibenzothiophene ring, or a ring in which an aromatic ring or a heteroaromatic ring is further condensed thereto is preferable.

[0167] As such an organic compound having hole transporting property, it is more preferable to have at least any one of a carbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton, and an anthracene skeleton. In particular, an aromatic amine having a substituent containing a dibenzofuran ring or a dibenzothiophene ring, an aromatic monoamine having a naphthalene ring, or an aromatic monoamine in which a 9-fluorenyl group is bonded to the nitrogen of the amine via an arylene group may be used. Incidentally, it is preferable that these organic compounds having hole transporting property are substances having an N,N-bis(4-biphenyl)amino group because a light emitting device having good durability can be manufactured.

[0168] Specifically, organic compounds having hole transport properties as described above 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]naph To[1,2-d]furan-6-amine (abbreviation: BBABnf(6)), N,N-bis(4-biphenyl)benzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BBABnf(8)), N,N-bis(4-biphenyl)benzo[b]naphtho[2,3-d]furan-4-amine (abbreviation: BBABnf(II)(4)), N,N-bis[4-(dibenzofuran-4-yl)phenyl]-4-amino-p-terphenyl (abbreviation: DBfBB1TP), N-[4-(dibenzothiophen-4-yl)phenyl]-N-phenyl-4-bife Nylamine (abbreviation: ThBA1BP), 4-(2-naphthyl)-4',4''-diphenyltriphenylamine (abbreviation: BBAβNB), 4-[4-(2-naphthyl)phenyl]-4',4''-diphenyltriphenylamine (abbreviation: BBAβNBi), 4,4'-diphenyl-4''-([2,1'-binaphthyl]-6-yl)triphenylamine (abbreviation: BBAαNβNB), 4,4'-diphenyl-4''-([2,1'-binaphthyl]-7-yl)triphenylamine (abbreviation: BBAαNβNB-03), 4,4'-diphenyl -4''-(7-phenyl)naphthyl-2-yltriphenylamine (abbreviation: BBAPβNB-03), 4,4'-diphenyl-4''-([2,2'-binaphthyl]-6-yl)triphenylamine (abbreviation: BBA(βN2)B), 4,4'-diphenyl-4''-([2,2'-binaphthyl]-7-yl)triphenylamine (abbreviation: BBA(βN2)B-03), 4,4'-diphenyl-4''-([1,2'-binaphthyl]-4-yl)triphenylamine (abbreviation: BBAβNαNB), 4,4'-diphenyl-4''-([1,2'-binaphthyl]-5-yl)triphenylamine (abbreviation: BBAβNαNB-02), 4-(4-biphenylyl)-4'-(2-naphthyl)-4''-phenyltriphenylamine (abbreviation: TPBiAβNB), 4-(3-biphenylyl)-4'-[4-(2-naphthyl)phenyl]-4''-phenyltriphenylamine (abbreviation: mTPBiAβNBi), 4-(4-biphenylyl)-4'-[4-(2-naphthyl)phenyl]-4''-phenyl Triphenylamine (abbreviation: TPBiAβNBi), 4-phenyl-4'-(1-naphthyl)triphenylamine (abbreviation: αNBA1BP), 4,4'-bis(1-naphthyl)triphenylamine (abbreviation: αNBB1BP), 4,4'-diphenyl-4''-[4'-(carbazole-9-yl)biphenyl-4-yl]triphenylamine (abbreviation: YGTBi1BP), 4'-[4-(3-phenyl-9H-carbazole-9-yl)phenyl]tris (Biphenyl-4-yl)amine (abbreviation: YGTBi1BP-02), 4-[4'-(carbazole-9-yl)biphenyl-4-yl]-4'-(2-naphthyl)-4''-phenyltriphenylamine (abbreviation: YGTBiβNB), N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-N-[4-(1-naphthyl)phenyl]-9,9'-spirobio[9H-fluorene]-2-amine (abbreviation: PCBNBSF), N,N-bis( Biphenyl-4-yl)-9,9'-spirobi[9H-fluorene]-2-amine (abbreviation: BBASF), N,N-bis(biphenyl-4-yl)-9,9'-spirobi[9H-fluorene]-4-amine (abbreviation: BBASF(4)), N-(biphenyl-2-yl)-N-(9,9-dimethyl-9H-fluorene-2-yl)-9,9'-spirobi[9H-fluorene]-4-amine (abbreviation: oFBiSF), N-(biphenyl-4-yl)-N-(9,9-dimethyl-9H-fluoren-2-yl)dibenzofuran-4-amine (abbreviation: FrBiF), N-[4-(1-naphthyl)phenyl]-N-[3-(6-phenyldibenzofuran-4-yl)phenyl]-1-naphthylamine (abbreviation: mPDBfBNBN), 4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP), 4-phenyl-3'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: mBPAFLP), 4-phenyl-4' −[4-(9-phenylfluoren-9-yl)phenyl]triphenylamine (abbreviation: BPAFLBi), 4-phenyl-4'-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4'-diphenyl-4''-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: 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 (abbreviation: PCBNBB), N-phenyl-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-9,9'-spirobi[9H-fluorene]-2-amine (abbreviation: PCBASF), N-(biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-9,9-dimethyl-9H-fluorene-2-amine (abbreviation: PCBBiF), N,N-bis( Examples include 9,9-dimethyl-9H-fluoren-2-yl)-9,9'-spirobi-9H-fluoren-4-amine, N,N-bis(9,9-dimethyl-9H-fluoren-2-yl)-9,9'-spirobi-9H-fluoren-3-amine, N,N-bis(9,9-dimethyl-9H-fluoren-2-yl)-9,9'-spirobi-9H-fluoren-2-amine, and N,N-bis(9,9-dimethyl-9H-fluoren-2-yl)-9,9'-spirobi-9H-fluoren-1-amine.

[0169] Furthermore, other aromatic amine compounds that possess hole-transporting properties can also be used, such as N,N'-di(p-tolyl)-N,N'-diphenyl-p-phenylenediamine (abbreviated as DTDPPA), 4,4'-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviated as DPAB), 4,4'-bis(N-{4-[N'-(3-methylphenyl)-N'-phenylamino]phenyl}-N-phenylamino)biphenyl (abbreviated as DNTPD), and 1,3,5-tris[N-(4-diphenylaminophenyl)-N-phenylamino]benzene (abbreviated as DPA3B).

[0170] By forming the hole injection layer 111, the hole injection performance is improved, and a light-emitting device with a low driving voltage can be obtained.

[0171] Furthermore, among substances with acceptor properties, organic compounds with acceptor properties are easy to use because they are readily deposited and easy to form films.

[0172] The hole transport layer 112 is formed by including an organic compound having hole transport properties. The organic compound having hole transport properties is 1 × 10 −６ cm ２ It is preferable that the hole mobility is greater than or equal to / Vs.

[0173] Materials having the above-mentioned hole transport properties include 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviated as NPB), N,N'-diphenyl-N,N'-bis(3-methylphenyl)-4,4'-diaminobiphenyl (abbreviated as TPD), N,N'-bis(9,9'-spirobi[9H-fluoren]-2-yl)-N,N'-diphenyl-4,4'-diaminobiphenyl (abbreviated as BSPB), 4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviated as BPAFLP), and 4-phenyl-3' −(9-phenylfluoren-9-yl)triphenylamine (abbreviation: mBPAFLP), 4-phenyl-4'-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4'-diphenyl-4''-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBi1BP), 4-(1-naphthyl)-4'-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBANB), 4,4'-di(1-naphthyl)-4''-(9-phenyl- Compounds containing aromatic amines such as 9H-carbazole-3-yl)triphenylamine (abbreviation: PCBNBB), 9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]fluoren-2-amine (abbreviation: PCBAF), N-phenyl-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-9,9'-spirobi[9H-fluoren]-2-amine (abbreviation: PCBASF), 1,3-bis(N-carbazolyl)benzene (abbreviation: mCP), 4,4'-di(N-carbazolyl) Basolyl)biphenyl (abbreviated as CBP), 3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviated as CzTP), 9,9'-diphenyl-9H,9'H-3,3'-bicarbazole (abbreviated as PCCP), 9,9'-bis(biphenyl-4-yl)-3,3'-bi-9H-carbazole (abbreviated as BisBPCz), 9,9'-bis(biphenyl-3-yl)-3,3'-bi-9H-carbazole (abbreviated as BismBPCz), 9-(biphenyl-3-yl)-9'-(biphenyl-4-yl)-9H,9'H-3,3'-bicarbazole (abbreviation: mBPCCBP), 9-(2-naphthyl)-9'-phenyl-3,3'-bi-9H-carbazole (abbreviation: βNCCP), 9-(3-biphenyl)-9'-(2-naphthyl)-3,3'-bi-9H-carbazole (abbreviation: βNCCmBP), 9-(4-biphenyl)-9'-(2-naphthyl)-3,3'-bi-9H-carbazole (abbreviation: βNCBP), 9,9'-di-2-naphthyl-3,3'-9H,9'H-bicarbazole (abbreviation: BisβNCz), 9-(2-naphthyl)-9'-[1,1':4',1”-turf [phenyl]-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'-(triphenylene-2-yl)-3,3'-9H,9'H-bicarbazole, 9-phenyl-9'-(triphenylene-2-yl)-3,3'-9H,9'H-bicarbazole (abbreviation: PCCzTp), 9,9'-bis(triphenylene-2-yl)-3,3'-9H,9'H-bicarbazole, 9-(4-biphenyl)-9'-(triphenylene-2-yl)-3,3'-9H,9'H-bicarbazole, 9-(triphenylene-2-yl)-9'-[1,1':3',1"-tafe Compounds having a carbazole skeleton such as nyl]-4-yl-3,3'-9H,9'H-bicarbazole, compounds having a thiophene skeleton such as 4,4',4''-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation: DBT3P-II), 2,8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene (abbreviation: DBTFLP-III), 4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviation: DBTFLP-IV), 4,Examples of compounds having a furan skeleton include 4',4''-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation: DBF3P-II) and 4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran (abbreviation: mmDBFFLBi-II). Among the above, compounds having aromatic amines and compounds having a carbazole skeleton are preferred because they have good reliability, high hole transportability, and contribute to reducing the driving voltage. Furthermore, the materials listed as having hole transportability used in the composite material of the hole injection layer 111 can also be suitably used as materials constituting the hole transport layer 112.

[0174] The light-emitting material may be a fluorescent material, a phosphorescent material, a material exhibiting thermally activated delayed fluorescence (TADF), or any other light-emitting material. Furthermore, in light-emitting devices using blue light-emitting materials, particularly blue phosphorescent materials, the light-emitting layer 113 tends to become electron-rich; therefore, applying the present invention can be expected to produce a more pronounced effect.

[0175] Examples of materials that can be used as fluorescent materials in the light-emitting layer include the following. Other fluorescent materials can also be used.

[0176] 5,6-bis[4-(10-phenyl-9-antryl)phenyl]-2,2'-bipyridine (abbreviation: PAPP2BPy), 5,6-bis[4'-(10-phenyl-9-antryl)biphenyl-4-yl]-2,2'-bipyridine (abbreviation: PAPP2BPy), N,N'-diphenyl-N,N'-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]pyren-1,6-diamine (abbreviation: 1,6FLPAPrn), N,N'-bis(3-methylphenyl)-N,N'-bis[3-(9-phenyl-9H-fluoren-9-yl] )phenyl]pyrene-1,6-diamine (abbreviation: 1,6mMemFLPAPrn), N,N'-bis[4-(9H-carbazole-9-yl)phenyl]-N,N'-diphenylstilbene-4,4'-diamine (abbreviation: YGA2S), 4-(9H-carbazole-9-yl)-4'-(10-phenyl-9-anthryl)triphenylamine (abbreviation: YGAPA), 4-(9H-carbazole-9-yl)-4'-(9,10-diphenyl-2-anthryl)triphenylamine (abbreviation: 2YGAAPPA), N,9-diphenyl-N-[4-( 10-phenyl-9-anthryl)phenyl]-9H-carbazole-3-amine (abbreviation: PCAPA), perylene, 2,5,8,11-tetra-tert-butylperylene (abbreviation: TBP), 4-(10-phenyl-9-anthryl)-4'-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBAPA), N,N''-(2-tert-butylanthracene-9,10-diyldi-4,1-phenylene)bis(N,N',N'-triphenyl-1,4-phenylenediamine) (abbreviation: DPABPA), N,9 -Diphenyl-N-[4-(9,10-diphenyl-2-anthryl)phenyl]-9H-carbazole-3-amine (abbreviation: 2PCAPPA), N-[4-(9,10-diphenyl-2-anthryl)phenyl]-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPPA), N,N,N',N',N'',N'',N''',N'''-octaphenyldibenzo[g,p]chrysene-2,7,10,15-tetraamine (abbreviation: DBC1), coumarin 30, N-(9,10-diphenyl-2-anthryl)-N,9-diphenyl-9H-carbazole-3-amine (abbreviation: 2PCAPA), N-[9,10-bis(biphenyl-2-yl)-2-anthryl]-N,9-diphenyl-9H-carbazole-3-amine (abbreviation: 2PCABPhA), N-(9,10-diphenyl-2-anthryl)-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPA), N-[9,10-bis(biphenyl-2-yl)-2-anthryl]-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviation: 2DPABPhA) 9,10-bis(biphenyl-2-yl)-N-[4-(9H-carbazole-9-yl)phenyl]-N-phenylanthracene-2-amine (abbreviation: 2YGABPhA), N,N,9-triphenylanthracene-9-amine (abbreviation: DPhAPhA), coumarin 545T, N,N'-diphenylquinacridone (abbreviation: DPQd), rubren, 5,12-bis(biphenyl-4-yl)-6,11-diphenyltetracene (abbreviation: BPT), 2-(2-{2-[4-(dimethylamino)phenyl]ethenyl}-6-methyl-4H-pyra N-4-ylidene)propanedinitrile (abbreviation: DCM1), 2-{2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinoridine-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCM2), N,N,N',N'-tetrakis(4-methylphenyl)tetracene-5,11-diamine (abbreviation: p-mPhTD), 7,14-diphenyl-N,N,N',N'-tetrakis(4-methylphenyl)acenaphtho[1,2-a]fluorantene-3,10-diamine (abbreviation) Name: p-mPhAFD), 2-{2-isopropyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinoridine-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCJTI), 2-{2-tert-butyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinoridine-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCJTB), 2-(2,6-bis{2-[4-(dimethylamino)phenyl]ethenyl}-4H-pyran-4-ylidene)propanedinitrile (abbreviation: BisDCM), 2-{2,6-bis[2-(8-methoxy-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinoridine-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: BisDCJTM), N,N'-diphenyl-N,N'-(1,6-pyrene-diyl)bis[(6-phenylbenzo[b]naph Examples include to[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), and 3,10-bis[N-(dibenzofuran-3-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviation: 3,10FrA2Nbf(IV)-02). In particular, condensed aromatic diamine compounds, such as pyrenediamine compounds like 1,6FLPAPrn, 1,6mMemFLPAPrn, and 1,6BnfAPPrn-03, are preferred because they exhibit high hole-trapping properties and excellent luminescence efficiency or reliability.

[0177] Also, 5,9-diphenyl-5H,9H-[1,4]benzazaborino[2,3,4-kl]phenazavolin (abbreviated as DABNA-1), 9-(diphenyl-3-yl)-N,N,5,11-tetraphenyl-5,9-dihydro-5,9-diaza-13b-boranaphtho[3,2,1-de]anthracene-3-amine (abbreviated as DABNA-2), 2,12-di(tert-butyl)-5,9-di(4-tert-butylphenyl)-N,N-diphenyl-5H,9H-[1,4]benzazaborino[2,3,4-kl]phenazavolin Phosphorus-7-amine (abbreviation: DPhA-tBu4DABNA), 2,12-di(tert-butyl)-N,N,5,9-tetra(4-tert-butylphenyl)-5H,9H-[1,4]benzazabolino[2,3,4-kl]phenazavolin-7-amine (abbreviation: tBuDPhA-tBu4DABNA), 2,12-di(tert-butyl)-5,9-di(4-tert-butylphenyl)-7-methyl-5H,9H-[1,4]benzazabolino[2,3,4-kl]phenazavolin (abbreviation: Me-tBu4DABNA), N ７ , N ７ , N １３ , N １３ Condensed heteroaromatic compounds containing nitrogen and boron, such as 5,9,11,15-octaphenyl-5H,9H,11H,15H-[1,4]benzazabolino[2,3,4-kl][1,4]benzazabolino[4',3',2':4,5][1,4]benzazabolino[3,2-b]phenazabolin-7,13-diamine (abbreviation: ν-DABNA) and 2-(4-tert-butylphenyl)benz[5,6]indro[3,2,1-jk]benzo[b]carbazole (abbreviation: tBuPBibc), particularly compounds having a diazaboranaphtho-anthracene skeleton, can be suitably used because they produce blue emission with a narrow emission spectrum and good color purity.

[0178] In addition to these, 9,10,11-tris[3,6-bis(1,1-dimethylethyl)-9H-carbazol-9-yl]-2,5,15,18-tetrakis(1,1-dimethylethyl)indolo[3,2,1-de]indolo[3',2',1':8,1][1,4]benzazaborino[2,3,4-kl]phenazaborine (abbreviation: BBCz-G), 9,11-bis[3,6-bis(1,1-dimethylethyl)-9H-carbazol-9-yl]-2,5,15,18-tetrakis(1,1-dimethylethyl)indolo[3,2,1-de]indolo[3',2',1':8,1][1,4]benzazaborino[2,3,4-kl]phenazaborine (abbreviation: BBCz-Y), etc. can preferably use an indole skeleton.

[0179] When a phosphorescent material is used as the luminescent material in the light-emitting layer, examples of the phosphorescent material include the following materials.

[0180] Tris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-κN2]phenyl-κC}iridium(III) (abbreviation: [Ir(mpptz-dmp) ３ ]), tris(5-methyl-3,4-diphenyl-4H-1,2,4-triazolato)iridium(III) (abbreviation: [Ir(Mptz) ３ ]), an organometallic iridium complex having a 4H-triazole skeleton such as tris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazolato]iridium(III) (abbreviation: [Ir(Mptz1-mp) ３ ]), tris(1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazolato)iridium(III) (abbreviation: [Ir(Prptz1-Me) ３ ]), an organometallic iridium complex having a 1H-triazole skeleton such as fac-tris[1-(2,6-diisopropylphenyl)-2-phenyl-1H-imidazole]iridium(III) (abbreviation: [Ir(iPrpim) ３]), Tris[3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-f]phenanthridine]iridium(III) (abbreviation: [Ir(dmpimpt-Me) ３ ]), organometallic iridium complexes having an imidazole skeleton such as tris(2-{1-[2,6-bis(1-methylethyl)phenyl]-1H-imidazole-2-yl-κN3}-4-cyanophenyl-κC) iridium(III) (abbreviation: CNImIr), tris[(6-tert-butyl-3-phenyl-2H-imidazol[4,5-b]pyrazine-1-yl-κC2)phenyl-κC] iridium(III) (abbreviation: [Ir(cb) ３ Organometallic complexes having a benzimidazolidene skeleton such as ]), bis[2-(4',6'-difluorophenyl)pyridinato-N,C ２’ Iridium(III) tetrakis(1-pyrazolyl) borate (abbreviation: FIr6), bis[2-(4',6'-difluorophenyl)pyridinate-N,C ２’ Iridium(III) picolinate (abbreviation: FIrpic), bis{2-[3',5'-bis(trifluoromethyl)phenyl]pyridinate-N,C ２’ Iridium (III) picolinate (abbreviation: [Ir(CF ３ ppy) ２ (pic)]), bis[2-(4',6'-difluorophenyl)pyridinate-N,C ２’ Examples include organometallic iridium complexes that use phenylpyridine derivatives having electron-withdrawing groups, such as iridium(III) acetylacetonate (abbreviated as Firaca), as ligands. These compounds exhibit blue phosphorescence and have emission peaks in the wavelength range from 455 nm to 520 nm.

[0181] Also, tris(4-methyl-6-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(mppm) ３ ]), Tris(4-t-butyl-6-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(tBuppm) ３]), (acetylacetonato)bis(6-methyl-4-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(mppm) ２ (acac)), (acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(tBuppm) ２ (acac)), (acetylacetonate)bis[6-(2-norbornyl)-4-phenylpyrimidinato]iridium(III) (abbreviation: [Ir(nbppm) ２ (acac)), (acetylacetonato)bis[5-methyl-6-(2-methylphenyl)-4-phenylpyrimidinato]iridium(III) (abbreviation: [Ir(mpmpppm) ２ (acac)), (acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III) (abbreviation: [Ir(dppm) ２ Organometallic iridium complexes having a pyrimidine skeleton such as (acac) (acetylacetonato)bis(3,5-dimethyl-2-phenylpyradinato)iridium(III) (abbreviation: [Ir(mppr-Me) ２ (acac)), (acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyradinato)iridium(III) (abbreviation: [Ir(mppr-iPr) ２ Organometallic iridium complexes having a pyrazine skeleton such as (acac), Tris(2-phenylpyridinato-N,C) ２’ Iridium (III) (abbreviation: [Ir(ppy) ３ ]), bis(2-phenylpyridinate-N,C ２’ ) Iridium(III) acetylacetonate (abbreviation: [Ir(ppy) ２ (acac)), bis(benzo[h]quinolinate)iridium(III)acetylacetonate (abbreviation: [Ir(bzq) ２ (acac)), Tris(benzo[h]quinolinate) Iridium(III) (abbreviation: [Ir(bzq) ３ ]), Tris(2-phenylquinolinato-N,C) ２’ Iridium (III) (abbreviation: [Ir(pq) ３]), bis(2-phenylquinolinato-N,C ２’ Iridium(III) acetylacetonate (abbreviation: [Ir(pq) ２ (acac)]), [2-d3-methyl-8-(2-pyridinyl-κN)benzofl[2,3-b]pyridine-κC]bis[2-(5-d3-methyl-2-pyridinyl-κN2)phenyl-κC]iridium(III) (abbreviation: [Ir(5mppy-d ３ ) ２ (mbfpypy-d ３ )]), {2-(methyl-d ３ )-8-[4-(1-methylethyl-1-d)-2-pyridinyl-κN]benzofl[2,3-b]pyridin-7-yl-κC]bis{5-(methyl-d ３ )-2-[5-(methyl-d ３ )-2-pyridinyl-κN]phenyl-κC}iridium(III) (abbreviation: Ir(5mtpy-d) ６ ) ２ (mbfpypy-iPr-d ４ )), [2-(methyl-d ３ )-8-(2-pyridinyl-κN)benzofloxacin[2,3-b]pyridinyl-κC]bis[2-(2-pyridinyl-κN)phenyl-κC]iridium(III) (abbreviation: [Ir(ppy) ２ (mbfpypy-d ３ )]), [2-(4-methyl-5-phenyl-2-pyridinyl-κN)phenyl-κC]bis[2-(2-pyridinyl-κN)phenyl-κC]iridium(III) (abbreviation: [Ir(ppy) ２ (mdppy)]), [2-(4-d ３ [methyl-5-phenyl-2-pyridinyl-κN2)phenyl-κC]bis[2-(5-d ３ [Methyl-2-pyridinyl-κN2)phenyl-κC]iridium(III) (abbreviation: [Ir(5mppy-d3) ２ (mdppy-d ３ ) )]), [2-methyl-8-(2-pyridinyl-κN)benzofl[2,3-b]pyridine-κC]bis[2-(2-pyridinyl-κN)phenyl-κC]iridium(III) (abbreviation: [Ir(ppy) ２In addition to organometallic iridium complexes with a pyridine skeleton such as (mbfpypy), there is also tris(acetylacetonato)(monophenanthroline)terbium(III) (abbreviation: [Tb(acac) ３ Examples include rare earth metal complexes such as (Phen)). These are compounds that mainly exhibit green phosphorescence and have emission peaks in the wavelength range of 500 nm to 600 nm. Organometallic iridium complexes with a pyrimidine skeleton are particularly preferred because they exhibit outstanding reliability and luminescence efficiency.

[0182] Also, (diisobutyrylmethanato)bis[4,6-bis(3-methylphenyl)pyrimidinato]iridium(III) (abbreviation: [Ir(5mdppm) ２ (dibm)]), bis[4,6-bis(3-methylphenyl)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: [Ir(5mdppm) ２ (dpm)]), bis[4,6-di(naphthalene-1-yl)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: [Ir(d1npm) ２ Organometallic iridium complexes having a pyrimidine skeleton such as (dpm)]), (acetylacetonato)bis(2,3,5-triphenylpyradinato)iridium(III) (abbreviation: [Ir(tppr) ２ (acac)), bis(2,3,5-triphenylpyrazinate)(dipivaloylmethanato) iridium(III) (abbreviation: [Ir(tppr) ２ (dpm)]), (acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III) (abbreviation: [Ir(Fdpq) ２ Organometallic iridium complexes having a pyrazine skeleton such as (acac), tris(1-phenylisoquinolinato-N,C) ２’ Iridium (III) (abbreviation: [Ir(piq) ３ ]), bis(1-phenylisoquinolinato-N,C ２’ Iridium (III) acetylacetonate (abbreviation: [Ir(piq) ２(acac)), (3,7-diethyl-4,6-nonanedionato-κO4,κO6)bis[2,4-dimethyl-6-[7-(1-methylethyl)-1-isoquinolinyl-κN]phenyl-κC]iridium(III), (3,7-diethyl-4,6-nonanedionato-κO4,κO6)bis[2,4-dimethyl-6-[5-(1-methylethyl)-2-quinolinyl-κN]phenyl In addition to organometallic iridium complexes with a pyridine skeleton such as [-κC]iridium(III), there are platinum complexes such as 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin platinum(II) (abbreviation: PtOEP), and tris(1,3-diphenyl-1,3-propanedionato)(monophenanthroline)europium(III) (abbreviation: [Eu(DBM)] ３ (Phen)]), Tris[1-(2-tenoyl)-3,3,3-trifluoroacetonate](monophenanthroline) europium(III) (abbreviation: [Eu(TTA) ３ Examples include rare earth metal complexes such as (Phen)). These are compounds that exhibit red phosphorescence and have emission peaks in the wavelength range of 600 nm to 700 nm. In addition, organometallic iridium complexes with a pyrazine skeleton yield red emission with good chromaticity.

[0183] In addition to the phosphorescent compounds described above, other known phosphorescent compounds may be selected and used.

[0184] As TADF materials, fullerenes and their derivatives, acridines and their derivatives, eosin derivatives, etc. can be used. Also, metal-containing porphyrins containing magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), or palladium (Pd) can be used. As a metal-containing porphyrin, for example, the protoporphyrin-tin fluoride complex (SnF) shown in the following structural formula is used. ２ (Proto IX)), Mesoporphyrin-Tin Fluoride Complex (SnF ２ (Meso IX), hematoporphyrin-tin fluoride complex (SnF ２(Hemato IX), coproporphyrin tetramethyl ester-tin fluoride complex (SnF ２ (Copro III-4Me)), Octaethylporphyrin-Tin Fluoride Complex (SnF ２ (OEP)), Ethioporphyrin-Tin Fluoride Complex (SnF ２ (Etio I)), Octaethylporphyrin-Platinum Chloride Complex (PtCl ２ OEP (Open Economic Programme) and others can also be mentioned.

[0185]

[0186] Furthermore, the following structural formulas represent 2-(biphenyl-4-yl)-4,6-bis(12-phenylindoro[2,3-a]carbazole-11-yl)-1,3,5-triazine (abbreviation: PIC-TRZ), 9-(4,6-diphenyl-1,3,5-triazine-2-yl)-9'-phenyl-9H,9'H-3,3'-bicarbazole (abbreviation: PCCzTZn), 2-{4-[3-(N-phenyl-9H-carbazole-3-yl)-9H-carbazole-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: PCCzPTZn), 2-[4-(10H-phenoxazine-10-yl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: PCCzPTZn), Heterocyclic compounds having one or both of a π-electron-rich heteroaromatic ring and a π-electron-deficient heteroaromatic ring can also be used, such as PXZ-TRZ), 3-[4-(5-phenyl-5,10-dihydrophenadin-10-yl)phenyl]-4,5-diphenyl-1,2,4-triazole (abbreviated as PPZ-3TPT), 3-(9,9-dimethyl-9H-acridine-10-yl)-9H-xanthene-9-one (abbreviated as ACRXTN), bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone (abbreviated as DMAC-DPS), and 10-phenyl-10H,10'H-spiro[acridine-9,9'-anthracene]-10'-one (abbreviated as ACRSA). The heterocyclic compound is preferred because it has both a π-electron-excess heteroaromatic ring and a π-electron-deficient heteroaromatic ring, resulting in high electron transport and hole transport properties. Among the skeletons having a π-electron-deficient heteroaromatic ring, the pyridine skeleton, diazine skeleton (pyrimidine skeleton, pyrazine skeleton, pyridazine skeleton), and triazine skeleton are preferred because they are stable and reliable. In particular, the benzoflopyrimidine skeleton, benzothienopyrimidine skeleton, benzoflopyrazine skeleton, and benzothienopyrazine skeleton are preferred because they have high acceptability and are reliable. Furthermore, among the skeletons having a π-electron-excess heteroaromatic ring, the acridine skeleton, phenoxazine skeleton, phenothiazine skeleton, furan skeleton, thiophene skeleton, and pyrrole skeleton are preferred because they are stable and reliable, and therefore it is preferable to have at least one of these skeletons.Furthermore, a dibenzofuran skeleton is preferred as the furan skeleton, and a dibenzothiophene skeleton is preferred as the thiophene skeleton. In addition, an indole skeleton, carbazole skeleton, indrocarbazole skeleton, bicarbazole skeleton, and 3-(9-phenyl-9H-carbazole-3-yl)-9H-carbazole skeleton are particularly preferred as the pyrrole skeleton. Furthermore, in a substance in which a π-electron-rich heteroaromatic ring and a π-electron-deficient heteroaromatic ring are directly bonded, both the electron-donating ability of the π-electron-rich heteroaromatic ring and the electron-accepting ability of the π-electron-deficient heteroaromatic ring are strengthened. １ Level and T １ This is particularly preferable because the energy difference between the energy levels becomes small, allowing for efficient acquisition of thermally activated delayed fluorescence. Alternatively, an aromatic ring to which an electron-withdrawing group such as a cyano group is attached may be used instead of the π-electron-deficient heteroaromatic ring. Furthermore, aromatic amine skeletons, phenazine skeletons, etc., can be used as the π-electron-rich skeleton. Additionally, boron-containing skeletons such as xanthene skeletons, thioxanthene dioxide skeletons, oxadiazole skeletons, triazole skeletons, imidazole skeletons, anthraquinone skeletons, phenylborane, volanthrene, aromatic rings having a nitrile group or cyano group such as benzonitrile or cyanobenzene, heteroaromatic rings, carbonyl skeletons such as benzophenone, phosphine oxide skeletons, sulfone skeletons, etc., can be used as the π-electron-deficient skeleton and the π-electron-rich heteroaromatic ring. Thus, a π-electron-deficient skeleton and a π-electron-rich skeleton can be used instead of at least one of the π-electron-deficient heteroaromatic ring and the π-electron-rich heteroaromatic ring.

[0187]

[0188] Note that TADF material is S １ Level and T １ This material has a small energy difference with its energy levels and possesses the ability to convert energy from triplet excitation energy to singlet excitation energy through reverse intersystem crossing. Therefore, triplet excitation energy can be upconverted to singlet excitation energy with only a small amount of thermal energy (reverse intersystem crossing), and singlet excited states can be efficiently generated. Furthermore, triplet excitation energy can be converted into luminescence.

[0189] Furthermore, an excited complex (also called an exciplex) that forms an excited state with two types of substances is S １ Level and T １ It has an extremely small energy difference with the energy level and functions as a TADF material capable of converting triplet excitation energy into singlet excitation energy.

[0190] Note, - １ As an indicator of the energy level, the phosphorescence spectrum observed at low temperatures (e.g., from 77K to 10K) can be used. For TADF materials, a tangent line is drawn at the short-wavelength tail of its fluorescence spectrum, and the energy at the wavelength of the extrapolation line is S. １ Set the energy level as T, draw a tangent line at the short-wavelength tail of the phosphorescence spectrum, and define the energy of the extrapolation line at the wavelength as T. １ When it is set as a level, that S １ Level and T １ The energy difference with respect to the level is preferably 0.3 eV or less, and more preferably 0.2 eV or less.

[0191] Furthermore, when using TADF material as a light-emitting material, the S of the host material １ The level is S of the TADF material. １ A higher level is preferable. Also, the T of the host material １ The level is T of the TADF material. １ A level higher than the current level is preferable.

[0192] Various carrier transport materials can be used as the host material for the light-emitting layer, such as materials with electron transport properties and / or hole transport properties, and the TADF material mentioned above.

[0193] Preferred materials with hole transport properties include organic compounds having an amine skeleton or a π-electron-rich heteroaromatic ring skeleton. Preferred π-electron-rich heteroaromatic rings are condensed aromatic rings containing at least one of the following: acridine skeleton, phenoxazine skeleton, phenothiazine skeleton, furan skeleton, thiophene skeleton, and pyrrole skeleton. Specifically, carbazole rings, dibenzothiophene rings, or rings obtained by further condensing an aromatic ring or heteroaromatic ring with these are preferred.

[0194] Organic compounds having such hole-transporting properties more preferably have at least one of the following skeletons: a carbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton, and an anthracene skeleton. In particular, they may be aromatic amines having substituents including a dibenzofuran ring or a dibenzothiophene ring, aromatic monoamines having a naphthalene ring, or aromatic monoamines in which a 9-fluorenyl group is bonded to the nitrogen of the amine via an arylene group. Furthermore, it is preferable that these hole-transporting organic compounds are substances having an N,N-bis(4-biphenyl)amino group, as this allows for the creation of light-emitting devices with a good lifetime.

[0195] Examples of such organic compounds include 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviated as NPB), N,N'-diphenyl-N,N'-bis(3-methylphenyl)-4,4'-diaminobiphenyl (abbreviated as TPD), N,N'-bis(9,9'-spirobi[9H-fluoren]-2-yl)-N,N'-diphenyl-4,4'-diaminobiphenyl (abbreviated as BSPB), 4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviated as BPAFLP), and 4-phenyl Lu-3'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: mBPAFLP), 4-phenyl-4'-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4'-diphenyl-4''-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBi1BP), 4-(1-naphthyl)-4'-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBANB), 4,4'-di(1-naphthyl)-4''- Compounds containing aromatic amines such as (9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBNBB), 9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]fluoren-2-amine (abbreviation: PCBAF), N-phenyl-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-9,9'-spirobi[9H-fluoren]-2-amine (abbreviation: PCBASF), 1,3-bis(N-carbazolyl)benzene (abbreviation: mCP), Compounds having a carbazole skeleton such as 4,4'-di(N-carbazolyl)biphenyl (abbreviated as CBP), 3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviated as CzTP), 9,9'-diphenyl-9H,9'H-3,3'-bicarbazole (abbreviated as PCCP), 9-[3-(triphenylsilyl)phenyl]-3,9'-bi-9H-carbazole (abbreviated as PSiCzCz), 4,4',4''-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviated as DBT3P-II), 2,Examples include compounds having a thiophene skeleton such as 8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene (abbreviated as DBTFLP-III) and 4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviated as DBTFLP-IV), and compounds having a furan skeleton such as 4,4',4''-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviated as DBF3P-II) and 4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran (abbreviated as mmDBFFLBi-II). Among the above, compounds having an aromatic amine or a carbazole skeleton are preferred because they have good reliability, high hole transportability, and contribute to reducing the driving voltage. Furthermore, organic compounds listed as examples of hole-transporting materials can also be used in the hole transport layer.

[0196] For materials exhibiting electron transport properties, the electron mobility at which the square root of the electric field strength [V / cm] is 600 is 1 × 10⁻⁶. −７ cm ２ / Vs or more, preferably 1 x 10 −６ cm ２ A material having an electron mobility of / Vs or higher is preferred. However, any material with higher electron transport capabilities than holes can be used.

[0197] Examples of electron-transporting materials include bis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviated as BeBq). ２Preferably, metal complexes such as bis(2-methyl-8-quinolinolato)(4-phenylphenololato)aluminum(III) (abbreviated as BAlq), bis(8-quinolinolato)zinc(II) (abbreviated as Znq), bis[2-(2-benzoxazollyl)phenololato]zinc(II) (abbreviated as ZnPBO), and bis[2-(2-benzothiazolyl)phenololato]zinc(II) (abbreviated as ZnBTZ), and organic compounds having a π-electron-deficient heteroaromatic ring are preferred. Examples of organic compounds having a π-electron-deficient heteroaromatic ring skeleton include organic compounds containing a heteroaromatic ring having an azole skeleton, organic compounds containing a heteroaromatic ring having a pyridine skeleton, organic compounds containing a heteroaromatic ring having a diazine skeleton, and organic compounds containing a heteroaromatic ring having a triazine skeleton.

[0198] Among these, organic compounds containing heteroaromatic rings having a diazine skeleton (pyrimidine skeleton, pyrazine skeleton, pyridazine skeleton), organic compounds containing heteroaromatic rings having a pyridine skeleton, and organic compounds containing heteroaromatic rings having a triazine skeleton are preferred due to their good reliability. In particular, organic compounds containing heteroaromatic rings having a diazine (pyrimidine or pyrazine) skeleton and organic compounds containing heteroaromatic rings having a triazine skeleton have high electron transport properties and contribute to reducing the driving voltage. Furthermore, benzoflopyrimidine skeletons, benzothienopyrimidine skeletons, benzoflopyrazine skeletons, and benzothienopyrazine skeletons are preferred because they have high acceptability and good reliability.

[0199] Examples of organic compounds having a π-electron-deficient heteroaromatic ring skeleton include 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviated as PBD), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviated as TAZ), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazole-2-yl]benzene (abbreviated as OXD-7), and 9-[4-(5-phenyl-1,3,4-oxadiazole- Organic compounds having an azole skeleton, such as 2-yl)phenyl]-9H-carbazole (abbreviation: CO11), 2,2',2''-(1,3,5-benzenetriyl)tris(1-phenyl-1H-benzimidazole) (abbreviation: TPBI), 2-[3-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole (abbreviation: mDBTBIm-II), 4,4'-bis(5-methylbenzoxazole-2-yl)stilbene (abbreviation: BzOs), and 3,5-bis[3-(9H-carbazole-9-yl] [3-(3-pyridyl)phenyl]pyridine (abbreviation: 35DCzPPy), 1,3,5-tri[3-(3-pyridyl)phenyl]benzene (abbreviation: TmPyPB), vasophenanthroline (abbreviation: Bphen), vasocuproin (abbreviation: BCP), 2,9-di(naphthalene-2-yl)-4,7-diphenyl-1,10-phenanthroline (abbreviation: NBphen), 2,2'-(1,3-phenylene)bis(9-phenyl-1,10-phenanthroline) (abbreviation: mPPhen2P), 2-[3-(2-triphenylenyl)phenyl]-1, Organic compounds containing heteroaromatic rings with a pyridine skeleton, such as 10-phenanthroline (abbreviation: mTpPPhen), 2-phenyl-9-(2-triphenylenyl)-1,10-phenanthroline (abbreviation: Ph-TpPhen), 2-[4-(9-phenanthryl)-1-naphthyl]-1,10-phenanthroline (abbreviation: PnNPhen), and 2-[4-(2-triphenylenyl)phenyl]-1,10-phenanthroline (abbreviation: pTpPPhen), 2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,[h]Quinoxaline (abbreviation: 2mDBTPDBq-II), 2-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]Quinoxaline (abbreviation: 2mDBTPDBq-II), 2-[3'-(9H-carbazole-9-yl)biphenyl-3-yl]dibenzo[f,h]Quinoxaline (abbreviation: 2mCzBPDBq), 2-[4'-(9-phenyl-9H-carbazole-3-yl)-3,1'-biphenyl-1-yl]dibenzo[f,h]Quinoxaline (abbreviation: 2mpPCBPDBq), 2-[4-(3,6-diphenyl [Lu-9H-carbazole-9-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2CzPDBq-III), 7-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 7mDBTPDBq-II), and 6-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 6mDBTPDBq-II), 9-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]naphtho[1',2':4,5]flo[2,3-b]pyrazine (abbreviation: 9mDBtBPNF pr), 9-[3'-(dibenzothiophen-4-yl)biphenyl-4-yl]naphtho[1',2':4,5]flo[2,3-b]pyrazine (abbreviation: 9pmDBtBPNfpr), 4,6-bis[3-(phenanthren-9-yl)phenyl]pyrimidine (abbreviation: 4,6mPnP2Pm), 4,6-bis[3-(dibenzothiophen-4-yl)phenyl]pyrimidine (abbreviation: 4,6mDBTP2Pm-II), 4,6-bis[3-(9H-carbazole-9-yl)phenyl]pyrimidine (abbreviation: 4,6mCzP2Pm), 9,9'-[pyrimidine n-4,6-diylbis(biphenyl-3,3'-diyl)]bis(9H-carbazole) (abbreviation: 4,6mCzBP2Pm), 8-(biphenyl-4-yl)-4-[3-(dibenzothiophen-4-yl)phenyl]-[1]benzoflo[3,2-d]pyrimidine (abbreviation: 8BP-4mDBtPBfpm), 3,8-bis[3-(dibenzothiophen-4-yl)phenyl]benzoflo[2,3-b]pyrazine (abbreviation: 3,8mDBtP2Bfpr), 4,8-bis[3-(dibenzothiophen-4-yl)phenyl]-[1]benzoflo[3,2-d]pyrimidine (abbreviation: 4,8mDBtP2Bfpm), 8-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]naphtho[1',2':4,5]flo[3,2-d]pyrimidine (abbreviation: 8mDBtBPNfpm), 8-([2,2'-binaphthalene]-6-yl)-4-[3-(dibenzothiophen-4-yl)phenyl]-[1]benzoflo[3,2-d]pyrimidine (abbreviation: 8(βN2)-4mDBtPBfpm), 2,2'-(pyridine-2,6-diyl)bis(4-phenylbenzo[h]quinazoline) (abbreviation: 2,6( P-Bqn)2Py), 2,2'-(pyridine-2,6-diyl)bis{4-[4-(2-naphthyl)phenyl]-6-phenylpyrimidine} (abbreviation: 2,6(NP-PPm)2Py), 6-(biphenyl-3-yl)-4-[3,5-bis(9H-carbazole-9-yl)phenyl]-2-phenylpyrimidine (abbreviation: 6mBP-4Cz2PPm), 2,6-bis(4-naphthalene-1-ylphenyl)-4-[4-(3-pyridyl)phenyl]pyrimidine (abbreviation: 2,4NP-6PyPPm), 4-[3,5-bis(9H-carbazole-9-yl] [Phenyl]-2-phenyl-6-(biphenyl-4-yl)pyrimidine (abbreviation: 6BP-4Cz2PPm), 7-[4-(9-phenyl-9H-carbazole-2-yl)quinazoline-2-yl]-7H-dibenzo[c,g]carbazole (abbreviation: PC-cgDBCzQz), 8-(p-terphenyl-3-yl)-4-[3-(dibenzothiophen-4-yl)phenyl]-[1]benzofl[3,2-d]pyrimidine (abbreviation: 8mpTP-4mDBtPBfpm), 2,2'-([2,2'-bipyridine]-6,6'-diyl)bis(4-f Organic compounds having a diazine skeleton such as phenylbenzo[h]quinazoline) (abbreviation: 6,6'(P-Bqn)2BPy), 2-{3-[3-(N-phenyl-9H-carbazole-3-yl)-9H-carbazole-9-yl]phenyl}dibenzo[f,h]quinoxaline (abbreviation: 2mPCCzPDBq), 11-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]phenantro[9',10':4,5]flo[2,3-b]pyrazine (abbreviation: 11mDBtBPPnfpr), 2-(biphenyl-4-yl)-4-phenyl-6-(9,9'-Spirobi[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-carbazol [3-(4,6-diphenyl-1,3,5-triazine)]phenyl-4,6-diphenyl-1,3,5-triazine (abbreviation: PCCzPTZn), 9-[3-(4,6-diphenyl-1,3,5-triazine-2-yl)phenyl]-9'-phenyl-2,3'-bi-9H-carbazole (abbreviation: mPCCzPTZn-02), 2-[3'-(9,9-dimethyl-9H-fluoren-2-yl)biphenyl-3-yl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mFBPTZn), 5-[3-(4,6-diphenyl -1,3,5-triazine-2-yl)phenyl]-7,7-dimethyl-5H,7H-indeno[2,1-b]carbazole (abbreviation: mINc(II)PTZn), 2-{3-[3-(dibenzothiophen-4-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mDBtBPTZn), 2,4,6-tris[3'-(pyridin-3-yl)biphenyl-3-yl]-1,3,5-triazine (abbreviation: TmPPPyTz), 2-[3-(2,6-dimethyl-3-pyridinyl)-5-(9-phenyl] Nanthril)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mPn-mDMePyPTZn), 11-[4-(biphenyl-4-yl)-6-phenyl-1,3,5-triazine-2-yl]-11,12-dihydro-12-phenylindoro[2,3-a]carbazole (abbreviation: BP-Icz(II)TZn), 2-[3'-(triphenylene-2-yl)biphenyl-3-yl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mTpBPTZn), 3-[9-(4,6-diphenyl-1,3,5-triazine-2-yl)-2-dibenzofuranyl]-9-phenyl-9H-carbazole (abbreviation: PCDBfTZn), 2-(biphenyl-3-yl)-4-phenyl-6-[8-([1,1':4',1''-terphenyl]-4-yl)-1-dibenzofuranyl]-1,3,5-triazine (abbreviation: mBP-TPDBfTZn), 2-[4-(2-naphthyl)phenyl]-4-phenyl-6-spiro[9H-fluoren-9,9'-[9H]xanthene]-4-yl-1,3,5-triazine Examples of organic compounds containing heteroaromatic rings having a triazine skeleton include (abbreviated as βNP-SFx(4)TZn), 2-phenyl-4,6-bis[3-(triphenylsilyl)phenyl]-1,3,5-triazine (abbreviated as mSiTrz), 9,9'-{6-[3-(triphenylsilyl)phenyl]-1,3,5-triazine-2,4-diyl}bis(9H-carbazole) (abbreviated as SiTrzCz2), and 2,4,6-tris(2-pyridyl)-1,3,5-triazine (abbreviated as 2Py3TZn). Furthermore, organic compounds containing heteroaromatic rings having a diazine skeleton, or organic compounds containing heteroaromatic rings having a pyridine skeleton, or organic compounds containing heteroaromatic rings having 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 and contribute to reducing the driving voltage.

[0200] The TADF materials listed above can be used as host materials. When a TADF material is used as a host material, the triplet excitation energy generated by the TADF material is converted into singlet excitation energy through reverse intersystem crossing, and this energy is then transferred to the light-emitting material, thereby increasing the luminescence efficiency of the light-emitting device. In this case, the TADF material functions as an energy donor, and the light-emitting material functions as an energy acceptor.

[0201] This is very effective when the above-mentioned luminescent material is a fluorescent luminescent material. Also, in order to obtain high luminescence efficiency in this case, the S of the TADF material １ The energy level is S of the fluorescent material.１ It is preferable that the level be higher than the level. Also, the T of the TADF material １ The energy level is S of the fluorescent material. １ It is preferable that the level be higher than the level of the TADF material. １ The energy level is the T of the fluorescent material. １ A level higher than the current level is preferable.

[0202] Furthermore, it is preferable to use a TADF material that exhibits emission that overlaps with the wavelength of the lowest-energy absorption band of the fluorescent material. This is preferable because it allows for a smooth transfer of excitation energy from the TADF material to the fluorescent material, resulting in efficient emission.

[0203] Furthermore, for singlet excitation energy to be efficiently generated from triplet excitation energy by reverse intersystem crossing, it is preferable that carrier recombination occurs in the TADF material. It is also preferable that the triplet excitation energy generated in the TADF material does not transfer to the triplet excitation energy of the fluorescent material. To achieve this, it is preferable that the fluorescent material has protecting groups around the luminescent phosphoform (the skeleton that causes luminescence). Preferred protecting groups are substituents without π bonds, saturated hydrocarbons, specifically alkyl groups having 3 to 10 carbon atoms, substituted or unsubstituted cycloalkyl groups having 3 to 10 carbon atoms, and trialkylsilyl groups having 3 to 10 carbon atoms. It is even more preferable to have multiple protecting groups. Substituents without π bonds have poor carrier transport function, and therefore can increase the distance between the TADF material and the luminescent phosphoform of the fluorescent material with little effect on carrier transport or carrier recombination. Here, the luminescent phosphoform refers to the atomic group (skeleton) that causes luminescence in the fluorescent material. The luminescent phosphophore preferably has a skeleton containing π bonds, preferably contains an aromatic ring, and preferably has a condensed aromatic ring or a condensed heteroaromatic ring. Examples of such luminescent phosphophores include phenanthrene skeletons, stilbene skeletons, acridone skeletons, phenoxazine skeletons, phenothiazine skeletons, naphthalene skeletons, anthracene skeletons, fluorene skeletons, chrysene skeletons, triphenylene skeletons, tetracene skeletons, pyrene skeletons, perylene skeletons, coumarin skeletons, quinacridone skeletons, and naphthobisbenzofuran skeletons. Fluorescent materials having naphthalene, anthracene, fluorene, chrysene, triphenylene, tetracene, pyrene, perylene, coumarin, quinacridone, and naphthobisbenzofuran skeletons are particularly preferred due to their high fluorescence quantum yield.

[0204] When using a fluorescent material as a light-emitting material, a material having an acene skeleton, particularly an anthracene skeleton, is preferred as the host material. Using a material having an anthracene skeleton as the host material for a fluorescent material makes it possible to realize a light-emitting layer with good luminescence efficiency and durability. Among the materials having an anthracene skeleton to be used as the host material, a material having a diphenylanthracene skeleton, particularly a 9,10-diphenylanthracene skeleton, is preferred because it is chemically stable. Furthermore, while a host material having a carbazole skeleton is preferred because it improves hole injection and transport, a host material containing a benzocarbazole skeleton, in which a benzene ring is further condensed into the carbazole skeleton, is even more preferred because the HOMO level is about 0.1 eV higher than that of a host material having a carbazole skeleton, making it easier for holes to enter. In particular, a host material containing a dibenzocarbazole skeleton is preferred because the HOMO level is about 0.1 eV higher than that of a host material having a carbazole skeleton, making it easier for holes to enter, as well as providing excellent hole transport and high heat resistance. Therefore, a more preferred host material is a substance having both a 9,10-diphenylanthracene skeleton and a carbazole skeleton (or a benzocarbazole skeleton or dibenzocarbazole skeleton). Furthermore, from the viewpoint of hole injection and transport properties, a benzofluorene skeleton or a dibenzofluorene skeleton may be used instead of the carbazole skeleton.

[0205] Examples of such substances include 9-phenyl-3-[4-(10-phenyl-9-antryl)phenyl]-9H-carbazole (abbreviated as PCzPA), 3-[4-(1-naphthyl)phenyl]-9-phenyl-9H-carbazole (abbreviated as PCPN), 9-[4-(10-phenyl-9-antryl)phenyl]-9H-carbazole (abbreviated as CzPA), 7-[4-(10-phenyl-9-antryl)phenyl]-7H-dibenzo[c,g]carbazole (abbreviated as cgDBCzPA), 6-[3-(9,10-diphenyl-2-antryl)phenyl]benzo[b]naphtho[1,2-d]furan (abbreviated as 2mBnfPPA), and 9-phenyl-10-[4-(9-phenyl-9H-fluoren-9-yl)biphenyl-4' -yl]anthracene (abbreviation: FLPPA), 9-(1-naphthyl)-10-[4-(2-naphthyl)phenyl]anthracene (abbreviation: αN-βNPAnth), 9-(1-naphthyl)-10-(2-naphthyl)anthracene (abbreviation: α,βADN), 2-(10-phenylanthracene-9-yl)dibenzofuran, 2-(10-phenyl-9-antryl)ben Examples include zo[b]naphtho[2,3-d]furan (abbreviated as Bnf(II)PhA), 9-(2-naphthyl)-10-[3-(2-naphthyl)phenyl]anthracene (abbreviated as βN-mβNPAnth), and 1-{4-[10-(biphenyl-4-yl)-9-anthryl]phenyl}-2-ethyl-1H-benzimidazole (abbreviated as EtBImPBPhA). In particular, CzPA, cgDBCzPA, 2mBnfPPA, and PCzPA are preferred choices because they exhibit very good properties.

[0206] The host material may be a mixture of multiple substances, and when using a mixed host material, it is preferable to mix an electron-transporting material with a hole-transporting material. By mixing an electron-transporting material with a hole-transporting material, the transport properties of the light-emitting layer 113 can be easily adjusted, and the recombination region can also be easily controlled. The weight ratio of the hole-transporting material to the electron-transporting material should be 1:19 to 19:1.

[0207] Furthermore, phosphorescent materials can be used as part of the above-mentioned mixed materials. When a fluorescent material is used as the light-emitting material, the phosphorescent material can be used as an energy donor to supply excitation energy to the fluorescent material.

[0208] Furthermore, these mixed materials may form an excited complex. It is preferable to select a combination that forms an excited complex that exhibits emission overlapping with the wavelength of the lowest-energy absorption band of the luminescent material, as this facilitates smooth energy transfer and efficiently obtains light emission. This configuration is also preferable because it reduces the driving voltage.

[0209] Furthermore, at least one of the materials forming the excitation complex may be a phosphorescent material. This allows for the efficient conversion of the triplet excitation energy to the singlet excitation energy through reverse intersystem crossing.

[0210] For efficient excitation complex formation, it is preferable that the HOMO level of the hole-transporting material is above the HOMO level of the electron-transporting material. Furthermore, it is preferable that the LUMO level of the hole-transporting material is above the LUMO level of the electron-transporting material. The LUMO and HOMO levels of the materials can be derived from the electrochemical properties (reduction potential and oxidation potential) of the materials measured by cyclic voltammetry (CV).

[0211] The formation of excited complexes can be confirmed, for example, by comparing the emission spectra of a hole-transporting material, an electron-transporting material, and a mixed film made by mixing these materials, and observing that the emission spectrum of the mixed film shifts to a longer wavelength than the emission spectra of each individual material (or has a new peak on the longer wavelength side). Alternatively, it can be confirmed by comparing the transient photoluminescence (PL) of a hole-transporting material, the transient PL of an electron-transporting material, and the transient PL of a mixed film made by mixing these materials, and observing differences in the transient response, such as the transient PL lifetime of the mixed film having a longer lifetime component or a larger proportion of the delayed component than the transient PL lifetime of each individual material. Furthermore, the transient PL mentioned above may be read as transient electroluminescence (EL). That is, the formation of excited complexes can also be confirmed by comparing the transient EL of a hole-transporting material, the transient EL of an electron-transporting material, and the transient EL of a mixed film made by mixing these materials, and observing the differences in the transient response.

[0212] The electron transport layer 114 is a layer containing an electron-transporting material. The electron-transporting material has an electron mobility of 1 × 10⁻¹⁶ at an electric field strength [V / cm] square root of 600. −７ cm ２ / Vs or more, preferably 1 x 10 −６ cm ２ A substance having an electron mobility of 1 / Vs or higher is preferred. However, any substance that has higher electron transport capacity than holes can be used. As the above organic compound, an organic compound having a π-electron-deficient heteroaromatic ring is preferred. As an organic compound having a π-electron-deficient heteroaromatic ring, it is preferable that it be any or more of the following: an organic compound containing a heteroaromatic ring having an azole skeleton, an organic compound containing a heteroaromatic ring having a pyridine skeleton, an organic compound containing a heteroaromatic ring having a diazine skeleton, and an organic compound containing a heteroaromatic ring having a triazine skeleton.

[0213] As an organic compound having electron-transporting properties that can be used in the electron transport layer 114, the same organic compounds that can be used as an organic compound having electron-transporting properties in the light-emitting layer 113 can be used. In particular, organic compounds containing a heteroaromatic ring having a diazine skeleton, an organic compound containing a heteroaromatic ring having a pyridine skeleton, or an organic compound containing a heteroaromatic ring having a triazine skeleton are preferred due to their good reliability. In particular, organic compounds containing a heteroaromatic ring having a diazine (pyrimidine or pyrazine) skeleton, or an organic compound containing a heteroaromatic ring having a triazine skeleton, have high electron-transporting properties and contribute to reducing the driving voltage.

[0214] Furthermore, it is preferable that the electron transport layer 114 has a laminated structure. In addition, the layer in contact with the light-emitting layer 113 in the electron transport layer 114 having a laminated structure may function as a hole-blocking layer. When the electron transport layer in contact with the light-emitting layer functions as a hole-blocking layer, it is preferable to use a material whose HOMO level is 0.5 eV or more lower than the HOMO level of the material contained in the light-emitting layer 113. When the electron transport layer 114 has a laminated structure, by having the configuration described in Embodiment 1, it is possible to make a light-emitting device with good luminescence efficiency and good reliability. Furthermore, when the electron transport layer 114 has a laminated structure, it is preferable that the electron transport layer on the cathode side contains a metal compound or complex, preferably an alkali metal or alkaline earth metal compound or complex such as 8-quinolinolatolithium (abbreviated as Liq).

[0215] The electron injection layer 115 may include a layer containing an alkali metal or alkaline earth metal compound or complex such as 8-quinolinolatolithium (abbreviated as Liq), or 1,1'-pyridine-2,6-diylbis(1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine) (abbreviated as hpp2Py). The electron injection layer 115 may also be a layer containing an alkali metal or alkaline earth metal or a compound thereof within a layer made of an electron-transporting material.

[0216] Alternatively, a charge generation layer 116 may be provided instead of the electron injection layer 115 (Figure 5A). The charge generation layer 116 is a layer that can inject holes into the layer in contact with the cathode side and electrons into the layer in contact with the anode side by applying a potential. The charge generation layer 116 includes at least a p-type layer 117. The p-type layer 117 is preferably formed using a composite material listed above as a material that can constitute the hole injection layer 111. The p-type layer 117 may also be formed by laminating a film containing the acceptor material and a film containing the hole transport material as materials constituting the composite material. By applying a potential to the p-type layer 117, electrons are injected into the electron transport layer 114 and holes into the cathode, and the light-emitting device operates. Furthermore, since the organic compound in one embodiment of the present invention is an organic compound with a low refractive index of the film, by using it in the p-type layer 117, a light-emitting device with good external quantum efficiency can be obtained.

[0217] Furthermore, it is preferable that the charge generation layer 116 includes, in addition to the p-type layer 117, one or both of the electron relay layer 118 and the electron injection buffer layer 119.

[0218] The electron relay layer 118 contains at least an electron-transporting material and has the function of preventing interaction between the electron injection buffer layer 119 and the p-type layer 117, thereby smoothly transferring electrons. The LUMO level of the electron-transporting material contained in the electron relay layer 118 is preferably between the LUMO level of the acceptor material in the p-type layer 117 and the LUMO level of the material contained in the layer in contact with the charge generation layer 116 in the electron transport layer 114. The specific energy level of the LUMO level of the electron-transporting material used in the electron relay layer 118 is preferably -5.0 eV or higher, more preferably -5.0 eV or higher and -3.0 eV or lower. It is preferable to use a phthalocyanine-based material or a metal complex having a metal-oxygen bond and an aromatic ligand as the electron-transporting material used in the electron relay layer 118.

[0219] The electron injection buffer layer 119 can be made of materials with high electron injection potential, such as alkali metals, alkaline earth metals, rare earth metals, and compounds thereof (alkali metal compounds (including oxides such as lithium oxide, halides, and carbonates such as lithium carbonate and cesium carbonate), alkaline earth metal compounds (including oxides, halides, and carbonates), or rare earth metal compounds (including oxides, halides, and carbonates)).

[0220] Furthermore, if the electron injection buffer layer 119 is formed by including an electron-transporting substance and a donor substance, the donor substance can include alkali metals, alkaline earth metals, rare earth metals, and compounds thereof (alkali metal compounds (including oxides such as lithium oxide, halides, and carbonates such as lithium carbonate and cesium carbonate), alkaline earth metal compounds (including oxides, halides, and carbonates), or rare earth metal compounds (including oxides, halides, and carbonates)), as well as organic compounds such as tetratianaphthalene (abbreviated as TTN), nickerosene, and decamethylnickerosene. The electron-transporting substance can be formed using the same materials as those used to constitute the electron transport layer 114 described above.

[0221] The second electrode 102 is an electrode that includes a cathode. The second electrode 102 may have a layered structure, in which case the layer in contact with the EL layer 103 functions as the cathode. As the material forming the cathode, metals, alloys, electrically conductive compounds, and mixtures thereof with a small work function (specifically 3.8 eV or less) can be used. Specific examples of such cathode materials include alkali metals such as lithium (Li) or cesium (Cs), and elements belonging to Group 1 or Group 2 of the periodic table such as magnesium (Mg), calcium (Ca), and strontium (Sr), and alloys (MgAg, AlLi) and compounds (lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF)) containing these. ２Examples include rare earth metals such as europium (Eu) and ytterbium (Yb), and alloys containing these. However, by providing an electron injection layer 115 or a thin film of the aforementioned material with a small work function between the second electrode 102 and the electron transport layer, various conductive materials such as Al, Ag, ITO, silicon, or indium oxide-tin oxide containing silicon oxide can be used as cathodes, regardless of the magnitude of the work function.

[0222] Furthermore, if the second electrode 102 is formed from a material that is transparent to visible light, it can be made into a light-emitting device that emits light from the second electrode 102 side.

[0223] These conductive materials can be formed using dry methods such as vacuum deposition or sputtering, inkjet printing, or spin coating. Alternatively, they may be formed using a wet method with a sol-gel process, or using a metal paste.

[0224] Furthermore, various methods can be used to form the EL layer 103, regardless of whether they are dry or wet methods. For example, vacuum deposition, gravure printing, offset printing, screen printing, inkjet printing, or spin coating may be used.

[0225] Furthermore, each electrode or layer described above may be formed using different film deposition methods.

[0226] Next, an embodiment of a light-emitting device (also called a stacked element or tandem element) with a configuration in which multiple light-emitting units are stacked will be described with reference to Figure 5B. This light-emitting device has multiple light-emitting units between the anode and the cathode. Each light-emitting unit has a configuration substantially similar to the EL layer 103 shown in Figures 1A to 2B. In other words, the light-emitting device shown in Figure 5B is a light-emitting device having multiple light-emitting units, while the light-emitting devices shown in Figures 1A to 2B are light-emitting devices having one light-emitting unit.

[0227] In Figure 5B, a first light-emitting unit 511 and a second light-emitting unit 512 are stacked between the first electrode 501 and the second electrode 502, and a charge generation layer 513 is provided between the first light-emitting unit 511 and the second light-emitting unit 512. The first electrode 501 and the second electrode 502 correspond to the first electrode 101 and the second electrode 102 in Figures 1A to 2B, respectively, and the same components described in the explanation of Figures 1A to 2B can be applied. Furthermore, the first light-emitting unit 511 and the second light-emitting unit 512 may have the same configuration or different configurations.

[0228] The charge generation layer 513 has the function of injecting electrons into one light-emitting unit and holes into the other light-emitting unit when a voltage is applied to the first electrode 501 and the second electrode 502. That is, in Figure 5B, when a voltage is applied such that the potential of the anode is higher than the potential of the cathode, the charge generation layer 513 only needs to inject electrons into the first light-emitting unit 511 and holes into the second light-emitting unit 512.

[0229] The charge generation layer 513 is preferably formed with the same configuration as the charge generation layer 116 described in Figure 5A. Because the composite material of the organic compound and the metal oxide has excellent carrier implantation and carrier transport properties, it can achieve low voltage drive and low current drive.

[0230] Furthermore, if the anode side of the light-emitting unit is in contact with the charge generation layer 513, the charge generation layer 513 can also serve as the hole injection layer of the light-emitting unit, so the light-emitting unit does not need to have a hole injection layer.

[0231] Furthermore, when an electron injection buffer layer 119 is provided in the charge generation layer 513, the electron injection buffer layer 119 plays the role of an electron injection layer in the anode-side light-emitting unit, so it is not necessarily required to form an electron injection layer in the anode-side light-emitting unit.

[0232] Figure 5B illustrates a light-emitting device having two light-emitting units, but the same principles can be applied to light-emitting devices with three or more stacked light-emitting units. As in the light-emitting device according to this embodiment, by arranging multiple light-emitting units separated between a pair of electrodes by a charge generation layer 513, high-brightness light emission can be achieved while maintaining a low current density, and a long-life element can be realized. Furthermore, a light-emitting device that can be driven at a low voltage and consumes little power can be realized.

[0233] Furthermore, by making the light-emitting colors of each light-emitting unit different, it is possible to obtain a desired color of light emission from the entire light-emitting device. For example, in a light-emitting device having two light-emitting units, it is possible to obtain a light-emitting device that emits white light as a whole by obtaining red and green light-emitting colors from the first light-emitting unit and blue light-emitting color from the second light-emitting unit.

[0234] Furthermore, each layer, such as the EL layer 103, the first light-emitting unit 511, the second light-emitting unit 512, and the charge generation layer, as well as the electrodes, can be formed using methods such as vapor deposition (including vacuum deposition), droplet ejection (also known as inkjet printing), coating, and gravure printing. They may also contain low-molecular-weight materials, medium-molecular-weight materials (including oligomers and dendrimers), or polymer materials.

[0235] (Embodiment 3) This embodiment describes an example in which a light-emitting device according to one aspect of the present invention is used as a display element for a display device. In this embodiment, the light-emitting device is shown in a shape formed by photolithography, but it may also be formed by a method using a fine metal mask or the like.

[0236] As illustrated in Figures 6A and 6B, multiple light-emitting devices 130 are formed on the insulating layer 175 to constitute a display device.

[0237] The display device has a pixel section 177 in which a plurality of pixels 178 are arranged in a matrix. The pixels 178 include sub-pixels 110R, sub-pixels 110G, and sub-pixels 110B.

[0238] In this specification, when describing matters common to, for example, sub-pixels 110R, 110G, and 110B, they may be referred to simply as sub-pixel 110. Similarly, when describing matters common to other components distinguished by letters, the letters may be omitted and the corresponding symbols used.

[0239] Sub-pixel 110R emits red light, sub-pixel 110G emits green light, and sub-pixel 110B emits blue light. This allows an image to be displayed on the pixel section 177. In this embodiment, three sub-pixels of red (R), green (G), and blue (B) are used as an example, but combinations of other colors of sub-pixels may also be used. Furthermore, the number of sub-pixels is not limited to three, but may be four or more. Examples of four sub-pixels include four sub-pixels of R, G, B, and white (W), four sub-pixels of R, G, B, and yellow (Y), and four sub-pixels of R, G, B, and infrared (IR).

[0240] In this specification and other documents, the row direction may be referred to as the X direction and the column direction as the Y direction. The X and Y directions intersect, for example, perpendicularly.

[0241] Figure 6A shows an example where subpixels of different colors are arranged in the X direction, and subpixels of the same color are arranged in the Y direction. Alternatively, subpixels of different colors may be arranged in the Y direction, and subpixels of the same color may be arranged in the X direction.

[0242] A connecting portion 140 and a region 141 may be provided on the outside of the pixel portion 177. The region 141 is provided between the pixel portion 177 and the connecting portion 140. An EL layer 103 is provided in the region 141. A conductive layer 151C is provided in the connecting portion 140.

[0243] Figure 6A shows an example where region 141 and connection portion 140 are located to the right of the pixel portion 177, but the positions of region 141 and connection portion 140 are not particularly limited. Also, region 141 and connection portion 140 may be singular or multiple.

[0244] Figure 6B is an example of a cross-sectional view between the dashed line A1 and A2 in Figure 6A. As shown in Figure 6B, the display device has an insulating layer 171, a conductive layer 172 on the insulating layer 171, an insulating layer 173 on the insulating layer 171 and on the conductive layer 172, an insulating layer 174 on the insulating layer 173, and an insulating layer 175 on the insulating layer 174. The insulating layer 171 is provided on a substrate (not shown). The insulating layer 175, insulating layer 174, and insulating layer 173 are provided with openings that reach the conductive layer 172, and plugs 176 are provided to fill these openings.

[0245] In the pixel section 177, a light-emitting device 130 is provided on an insulating layer 175 and a plug 176. A protective layer 131 is provided so as to cover the light-emitting device 130. A substrate 120 is bonded to the protective layer 131 by a resin layer 122. Preferably, an inorganic insulating layer 125 and an insulating layer 127 on the inorganic insulating layer 125 are provided between adjacent light-emitting devices 130.

[0246] In Figure 6B, multiple cross-sections of the inorganic insulating layer 125 and the insulating layer 127 are shown, but when the display device is viewed from above, it is preferable that the inorganic insulating layer 125 and the insulating layer 127 are connected as one unit. In other words, it is preferable that the inorganic insulating layer 125 and the insulating layer 127 are insulating layers having an opening on the first electrode.

[0247] In Figure 6B, the light-emitting devices 130 are shown as light-emitting devices 130R, 130G, and 130B. Light-emitting devices 130R, 130G, and 130B are assumed to emit different colors of light from each other. For example, light-emitting device 130R can emit red light, light-emitting device 130G can emit green light, and light-emitting device 130B can emit blue light. In addition, light-emitting devices 130R, 130G, or 130B may emit other visible light or infrared light. Note that in Figure 6B, light-emitting devices 130R and 130G, and light-emitting devices 130G and 130B can be said to be adjacent light-emitting devices.

[0248] One embodiment of the present invention can be a top-emission type, for example, which emits light in the opposite direction to the substrate on which the light-emitting device is formed. Alternatively, one embodiment of the present invention may be a bottom-emission type.

[0249] The light-emitting device 130R is a light-emitting device that emits red light (phosphorescence is preferred), and preferably has the configuration shown in Embodiment 2. It has a first electrode (pixel electrode) consisting of a conductive layer 151R and a conductive layer 152R, a first layer 135R on the first electrode, 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.

[0250] The light-emitting device 130G is a light-emitting device that emits green light (phosphorescence is preferred), and preferably has the configuration shown in Embodiment 2. It has a first electrode (pixel electrode) consisting of a conductive layer 151G and a conductive layer 152G, a first layer 135G on the first electrode, 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.

[0251] The light-emitting device 130B is a light-emitting device that emits blue light (fluorescence is preferred), and preferably has the configuration shown in Embodiment 2. It has a first electrode (pixel electrode) consisting of a conductive layer 151B and a conductive layer 152B, a first layer 135B on the first electrode, 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.

[0252] Of the pixel electrodes (first electrodes) and common electrodes (second electrodes) of the light-emitting device, one functions as the anode and the other as the cathode. In this embodiment, unless otherwise specified, the pixel electrodes function as the anode and the common electrodes function as the cathode.

[0253] The first layer 135R, the first layer 135G, and the first layer 135B are independent island-like layers for each light-emitting device or for each light-emitting color. Furthermore, it is preferable that the first layer 135R, the first layer 135G, and the first layer 135B do not overlap with each other. Note that the first layers formed on multiple light-emitting devices 130 in the light-emitting device, such as the first layer 135R, the first layer 135G, and the first layer 135B, may be collectively referred to as the first layer group 135A. By providing the first layer group 135A in an island-like manner for each light-emitting device 130, leakage current between adjacent light-emitting devices 130 can be suppressed even in high-definition display devices. This prevents crosstalk and enables the realization of a display device with extremely high contrast. In particular, it enables the realization of a display device with high current efficiency at low brightness.

[0254] The island-shaped first layer group 135A is formed by depositing an EL film for each emission color and processing the EL film using photolithography.

[0255] Preferably, the first layer 135 is provided so as to cover the top and side surfaces of the first electrode 101 (pixel electrode) of the light-emitting device 130. This makes it easier to increase the aperture ratio of the display device compared to a configuration in which the edge of the first layer 135 is located inside the edge of the pixel electrode. In addition, by covering the side surfaces of the pixel electrode of the light-emitting device 130 with the first layer 135, contact between the first electrode 101 and the second electrode 102 can be suppressed, thereby suppressing short circuits of the light-emitting device 130.

[0256] Furthermore, in a display device according to one aspect of the present invention, it is preferable that the first electrode 101 (pixel electrode) of the light-emitting device be in a stacked configuration. For example, in the example shown in Figure 6B, the first electrode 101 of the light-emitting device 130 is in a stacked configuration of a conductive layer 151 provided on the insulating layer 171 side and a conductive layer 152 provided on the organic compound layer side.

[0257] For example, a metallic material can be used as the conductive layer 151. Specifically, metals such as aluminum (Al), titanium (Ti), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), gallium (Ga), zinc (Zn), indium (In), tin (Sn), molybdenum (Mo), tantalum (Ta), tungsten (W), palladium (Pd), gold (Au), platinum (Pt), silver (Ag), yttrium (Y), neodymium (Nd), and alloys containing these in appropriate combinations can also be used.

[0258] As the conductive layer 152, an oxide having one or more selected from indium, tin, zinc, gallium, titanium, aluminum, and silicon can be used. For example, it is preferable to use a conductive oxide containing one or more of the following: indium oxide, indium tin oxide, indium zinc oxide, zinc oxide, zinc oxide containing gallium, titanium oxide, indium zinc oxide containing gallium, indium zinc oxide containing aluminum, indium tin oxide containing silicon, and indium zinc oxide containing silicon. In particular, indium tin oxide containing silicon has a large work function, for example, a work function of 4.0 eV or more, so it can be suitably used as the conductive layer 152.

[0259] The conductive layer 151 may be a laminated structure of multiple layers having different materials, and the conductive layer 152 may be a laminated structure of multiple layers having different materials. In this case, the conductive layer 151 may have a layer made of a material that can be used for the conductive layer 152, such as a conductive oxide, and the conductive layer 152 may have a layer made of a material that can be used for the conductive layer 151, such as a metallic material. For example, if the conductive layer 151 has a laminated structure of two or more layers, the layer in contact with the conductive layer 152 may be a layer made of a material that can be used for the conductive layer 152.

[0260] Furthermore, it is preferable that the end of the conductive layer 151 has a tapered shape. Specifically, it is preferable that the end of the conductive layer 151 has a tapered shape with a taper angle of less than 90°. In this case, the conductive layer 152 provided along the side surface of the conductive layer 151 also has a tapered shape. By making the side surface of the conductive layer 152 tapered, the coverage of the first layer 135 provided along the side surface of the conductive layer 152 can be improved.

[0261] (Embodiment 4) This embodiment describes a display device according to one aspect of the present invention.

[0262] The display device of this embodiment can be a high-definition display device. Therefore, the display device of this embodiment can be used, for example, as a display unit for information terminals (wearable devices) such as wristwatches and bracelets, as well as as a display unit for wearable devices that can be worn on the head, such as VR devices such as head-mounted displays (HMDs) and AR devices such as glasses.

[0263] Furthermore, the display device of this embodiment can be a high-resolution display device or a large-screen display device. Therefore, the display device of this embodiment can be used in electronic devices with relatively large screens, such as television equipment, desktop or notebook personal computers, computer monitors, digital signage, and large game machines such as pachinko machines, as well as in the display units of digital cameras, digital video cameras, digital photo frames, mobile phones, portable game consoles, personal information terminals, and audio playback devices.

[0264] [Display Module] Figure 7A shows a perspective view of the display module 280. The display module 280 includes a display device 100A and an FPC 290. Note that the display device included in the display module 280 is not limited to the display device 100A, but may be any of the display devices 100B to 100E described later.

[0265] The display module 280 has substrates 291 and 292. The display module 280 has a display unit 281. The display unit 281 is an area in the display module 280 that displays an image, and is an area in which light from each pixel provided in the pixel unit 284, which will be described later, can be seen.

[0266] Figure 7B shows a schematic perspective view illustrating the configuration 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. A terminal section 285 for connecting to the FPC 290 is provided in a portion of the substrate 291 that does not overlap with the pixel section 284. The terminal section 285 and the circuit section 282 are electrically connected by a wiring section 286, which is composed of multiple wires.

[0267] The pixel section 284 has a plurality of pixels 284a arranged periodically. An enlarged view of one pixel 284a is shown on the right side of Figure 7B. Various configurations described in the previous embodiment can be applied to the pixel 284a. Figure 7B shows an example where the pixel 284a has the same configuration as the pixel 178 shown in Figure 6.

[0268] The pixel circuit section 283 has a plurality of pixel circuits 283a arranged periodically.

[0269] One pixel circuit 283a is a circuit that controls the driving of multiple elements that a single pixel 284a has.

[0270] The circuit section 282 has circuits for driving each pixel circuit 283a of the pixel circuit section 283. For example, it is preferable to have one or both of a gate line drive circuit and a source line drive circuit. In addition, it may have at least one of the following: an arithmetic circuit, a memory circuit, and a power supply circuit.

[0271] The FPC 290 functions as wiring for supplying video signals or power potential, etc., to the circuit section 282 from an external source. An IC may also be mounted on the FPC 290.

[0272] The display module 280 can be configured such that one or both of the pixel circuit section 283 and the circuit section 282 are stacked on the lower side of the pixel section 284, thereby making it possible to achieve an extremely high aperture ratio (effective display area ratio) for the display section 281.

[0273] Because such a display module 280 is extremely high-resolution, it can be suitably used in VR devices such as HMDs or AR devices in the form of glasses. For example, even in a configuration where the display part of the display module 280 is viewed through lenses, the display module 280 has an extremely high-resolution display part 281, so even when the display part is magnified with lenses, pixels are not visible, enabling a highly immersive display. Furthermore, the display module 280 is not limited to this and can be suitably used in electronic devices having relatively small display parts.

[0274] [Display device 100A] The display device 100A shown in Figure 8A includes a substrate 301, a light-emitting device 130R, a light-emitting device 130G, a light-emitting device 130B, a capacitor 240, and a transistor 310.

[0275] The substrate 301 corresponds to the substrate 291 in Figures 7A and 7B. The transistor 310 is a transistor having a channel formation region in the substrate 301. For example, a semiconductor substrate such as a single-crystal silicon substrate can be used as the substrate 301. The transistor 310 has a part 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 functions as a gate electrode. The insulating layer 313 is located between the substrate 301 and the conductive layer 311 and functions as a gate insulating layer. The low-resistance region 312 is a region of the substrate 301 doped with impurities and functions as a source or drain. The insulating layer 314 is provided covering the side surface of the conductive layer 311.

[0276] Furthermore, an element isolation layer 315 is provided between two adjacent transistors 310 so as to be embedded in the substrate 301.

[0277] Furthermore, an insulating layer 261 is provided to cover the transistor 310, and a capacitance 240 is provided on the insulating layer 261.

[0278] The capacitor 240 has a conductive layer 241, a conductive layer 245, and an insulating layer 243 located between them. The conductive layer 241 functions as one electrode of the capacitor 240, the conductive layer 245 functions as the other electrode of the capacitor 240, and the insulating layer 243 functions as the dielectric of the capacitor 240.

[0279] The conductive layer 241 is provided on the insulating layer 261 and embedded in the insulating layer 254. The conductive layer 241 is electrically connected to either the source or drain of the transistor 310 by a plug 271 embedded in the insulating layer 261. The insulating layer 243 is provided covering the conductive layer 241. The conductive layer 245 is provided in the region that overlaps with the conductive layer 241 via the insulating layer 243.

[0280] An insulating layer 255 is provided covering the capacitance 240, an insulating layer 174 is provided on the insulating layer 255, and an insulating layer 175 is provided on the insulating layer 174. Light-emitting devices 130R, 130G, and 130B are provided on the insulating layer 175. An insulator is provided in the region between adjacent light-emitting devices.

[0281] An insulating layer 156R is provided so as to have a region that overlaps with the side surface of the conductive layer 151R, an insulating layer 156G is provided so as to have a region that overlaps with the side surface of the conductive layer 151G, and an insulating layer 156B is provided so as to have a region that overlaps with the side surface of the conductive layer 151B. Furthermore, a conductive layer 152R is provided so as to cover the conductive layer 151R and the insulating layer 156R, a conductive layer 152G is provided so as to cover the conductive layer 151G and the insulating layer 156G, and a conductive layer 152B is provided so as to cover the conductive layer 151B and the insulating layer 156B. A sacrificial layer 158R is located on the first layer 135R, a sacrificial layer 158G is located on the first layer 135G, and a sacrificial layer 158B is located on the first layer 135B.

[0282] The conductive layers 151R, 151G, and 151B are electrically connected to either the source or drain of the transistor 310 by the insulating layers 243, 255, 174, and plugs 256 embedded in the insulating layer 175, the conductive layer 241 embedded in the insulating layer 254, and plugs 271 embedded in the insulating layer 261. Various conductive materials can be used for the plugs.

[0283] Furthermore, a protective layer 131 is provided on the light-emitting devices 130R, 130G, and 130B. A substrate 120 is bonded to the protective layer 131 by a resin layer 122. Details of the components from the light-emitting devices 130 to the substrate 120 can be found in Embodiment 3. The substrate 120 corresponds to the substrate 292 in Figure 7A.

[0284] Figure 8B is a modified version of the display device 100A shown in Figure 8A. The display device shown in Figure 8B has a colored layer 132R, a colored layer 132G, and a colored layer 132B, and the light-emitting device 130 has a region that overlaps with one of the colored layers 132R, 132G, and 132B. In the display device shown in Figure 8B, the light-emitting device 130 can emit, for example, white light. Also, for example, the colored layer 132R can transmit red light, the colored layer 132G can transmit green light, and the colored layer 132B can transmit blue light.

[0285] [Display device 100B] Figure 9 shows a perspective view of the display device 100B, and Figure 10 shows a cross-sectional view of the display device 100C.

[0286] The display device 100B has a configuration in which substrate 352 and substrate 351 are bonded together. In Figure 9, substrate 352 is shown by a dashed line.

[0287] The display device 100B includes a pixel section 177, a connection section 140, a circuit 356, and wiring 355, etc. Figure 9 shows an example in which an IC 354 and an FPC 353 are mounted on the display device 100B. Therefore, the configuration shown in Figure 9 can also be called a display module having a display device 100B, an IC (integrated circuit), and an FPC. Here, a display module is a display device on which a connector such as an FPC is attached to the circuit board, or on which an IC is mounted.

[0288] The connection portion 140 is provided on the outside of the pixel portion 177. There may be one or more connection portions 140. The connection portion 140 is electrically connected to the common electrode of the light-emitting device and the conductive layer, and can supply potential to the common electrode.

[0289] For example, a scan line drive circuit can be used as circuit 356.

[0290] The wiring 355 has the function of supplying signals and power to the pixel unit 177 and the circuit 356. These signals and power are input to the wiring 355 from an external source via the FPC 353 or from the IC 354.

[0291] Figure 9 shows an example in which IC 354 is provided on substrate 351 using the COG (Chip On Glass) method or COF (Chip On Film) method, etc. IC 354 can be an IC having, for example, a scan line drive circuit or a signal line drive circuit. Note that the display device 100B and the display module may be configured without an IC. Alternatively, the IC may be mounted on an FPC, for example, using the COF method.

[0292] Figure 10 shows an example of a cross-section obtained by cutting a portion of the display device 100B, including the FPC 353, a portion of the circuit 356, a portion of the pixel portion 177, a portion of the connection portion 140, and a portion of the end portion.

[0293] [Display device 100C] The display device 100C shown in Figure 10 has a transistor 201, a transistor 205, a light-emitting device 130R that emits red light, a light-emitting device 130G that emits green light, and a light-emitting device 130B that emits blue light, etc., between the substrate 351 and the substrate 352.

[0294] Details of the light-emitting devices 130R, 130G, and 130B can be found in Embodiment 1.

[0295] Light-emitting device 130R has a conductive layer 224R, a conductive layer 151R on the conductive layer 224R, and a conductive layer 152R on the conductive layer 151R. Light-emitting device 130G has a conductive layer 224G, a conductive layer 151G on the conductive layer 224G, and a conductive layer 152G on the conductive layer 151G. Light-emitting device 130B has a conductive layer 224B, a conductive layer 151B on the conductive layer 224B, and a conductive layer 152B on the conductive layer 151B.

[0296] The conductive layer 224R is connected to the conductive layer 222b of the transistor 205 through an opening provided in the insulating layer 214. The end of the conductive layer 151R is located outside the end of the conductive layer 224R. The insulating layer 156R is provided so as to have a region in contact with the side surface of the conductive layer 151R, and the conductive layer 152R is provided so as to cover the conductive layer 151R and the insulating layer 156R.

[0297] The conductive layers 224G, 151G, 152G, and insulating layer 156G in the light-emitting device 130G, and the conductive layers 224B, 151B, 152B, and insulating layer 156B in the light-emitting device 130B are the same as the conductive layers 224R, 151R, 152R, and insulating layer 156R in the light-emitting device 130R, so a detailed explanation is omitted.

[0298] The conductive layer 224R, conductive layer 224G, and conductive layer 224B have recesses formed to cover the openings provided in the insulating layer 214. Layer 128 is embedded in these recesses.

[0299] Layer 128 has the function of flattening the recesses of conductive layers 224R, 224G, and 224B. Conductive layers 151R, 151G, and 151B are provided on conductive layers 224R, 224G, and 224B and on layer 128, and are electrically connected to conductive layers 224R, 224G, and 224B. Therefore, regions overlapping with the recesses of conductive layers 224R, 224G, and 224B can also be used as light-emitting regions, thereby increasing the aperture ratio of the pixels.

[0300] Layer 128 may be an insulating layer or a conductive layer. Various inorganic insulating materials, organic insulating materials, and conductive materials can be used for layer 128 as appropriate. In particular, it is preferable that layer 128 be formed using an insulating material, and especially preferable that it be formed using an organic insulating material. For example, an organic insulating material that can be used for the insulating layer 127 described above can be applied to layer 128.

[0301] A protective layer 131 is provided on the light-emitting devices 130R, 130G, and 130B. The protective layer 131 and the substrate 352 are bonded via an adhesive layer 142. A light-shielding layer 157 is provided on the substrate 352. A solid sealing structure or a hollow sealing structure can be applied to seal the light-emitting devices 130. In Figure 10, the space between the substrate 352 and the substrate 351 is filled with the adhesive layer 142, indicating a solid sealing structure. Alternatively, the space may be filled with an inert gas (such as nitrogen or argon), indicating a hollow sealing structure. In this case, the adhesive layer 142 may be provided so as not to overlap with the light-emitting devices. Furthermore, the space may be filled with a resin different from the adhesive layer 142, which is provided in a frame shape.

[0302] Figure 10 shows an example in which the connection portion 140 has a conductive layer 224C obtained by processing the same conductive film as conductive layers 224R, 224G, and 224B; a conductive layer 151C obtained by processing the same conductive film as conductive layers 151R, 151G, and 151B; and a conductive layer 152C obtained by processing the same conductive film as conductive layers 152R, 152G, and 152B. Figure 10 also shows an example in which an insulating layer 156C is provided so as to have a region that overlaps with the side surface of conductive layer 151C.

[0303] The display device 100B is a top-emission type. The light emitted by the light-emitting device is emitted towards the substrate 352. It is preferable to use a material with high transmittance to visible light for the substrate 352. If the light-emitting device emits infrared or near-infrared light, it is preferable to use a material with high transmittance to those. The first electrode (pixel electrode) contains a material that reflects visible light, and the second electrode (counter electrode) contains a material that transmits visible light.

[0304] On the substrate 351, insulating layers 211, 213, 215, and 214 are provided in this order. A portion of insulating layer 211 functions as a gate insulating layer for each transistor. A portion of insulating layer 213 functions as a gate insulating layer for each transistor. Insulating layer 215 is provided covering the transistors. Insulating layer 214 is provided covering the transistors and functions as a planarization layer. The number of gate insulating layers and insulating layers covering the transistors are not limited and may be a single layer or two or more layers, respectively.

[0305] It is preferable to use an inorganic insulating film as the insulating layer 211, insulating layer 213, and insulating layer 215.

[0306] An organic insulating layer is preferred for the insulating layer 214, which functions as a planarizing layer.

[0307] Transistors 201 and 205 have a conductive layer 221 that functions as a gate, an insulating layer 211 that functions as a gate insulating layer, conductive layers 222a and 222b that function as source and drain, a semiconductor layer 231, an insulating layer 213 that functions as a gate insulating layer, and a conductive layer 223 that functions as a gate.

[0308] A connection portion 204 is provided in the region of the substrate 351 that does not overlap with the substrate 352. At the connection portion 204, the wiring 355 is electrically connected to the FPC 353 via the conductive layer 166 and the connecting layer 242. The conductive layer 166 is shown as an example of a laminated structure consisting of a conductive film obtained by processing the same conductive film as conductive layers 224R, 224G, and 224B, a conductive film obtained by processing the same conductive film as conductive layers 151R, 151G, and 151B, and a conductive film obtained by processing the same conductive film as conductive layers 152R, 152G, and 152B. The conductive layer 166 is exposed on the upper surface of the connection portion 204. This allows the connection portion 204 and the FPC 353 to be electrically connected via the connecting layer 242.

[0309] It is preferable to provide a light-shielding layer 157 on the surface of the substrate 352 that faces the substrate 351. The light-shielding layer 157 can be provided between adjacent light-emitting devices, at connection points 140, and in circuits 356, etc. Various optical components can also be arranged on the outside of the substrate 352.

[0310] Materials suitable for use on substrate 120 can be applied to substrate 351 and substrate 352, respectively.

[0311] As the adhesive layer 142, a material that can be used for the resin layer 122 can be applied.

[0312] As the connecting layer 242, an anisotropic conductive film (ACF) or an anisotropic conductive paste (ACP) can be used.

[0313] [Display device 100D] The display device 100D shown in Figure 11 differs from the display device 100C shown in Figure 10 mainly in that it is a bottom-emission type display device.

[0314] The light emitted by the light-emitting device is emitted towards the substrate 351. It is preferable to use a material with high transmittance to visible light for the substrate 351. On the other hand, the light transmittance of the material used for the substrate 352 is not a requirement.

[0315] It is preferable to form a light-shielding layer 1117 between the substrate 351 and the transistor 201, and between the substrate 351 and the transistor 205. Figure 11 shows an example in which a light-shielding layer 1117 is provided on the substrate 351, an insulating layer 153 is provided on the light-shielding layer 1117, and transistors 201, 205, etc. are provided on the insulating layer 153.

[0316] 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.

[0317] 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.

[0318] The conductive layers 112R, 112B, 126R, 126B, 129R, and 129B are made of materials with high transmittance to visible light. It is preferable to use a material that reflects visible light for the second electrode.

[0319] Although the light-emitting device 130G is not shown in Figure 11, it is also provided.

[0320] Furthermore, while Figure 11 and other figures show an example where the upper surface of layer 128 has a flat portion, the shape of layer 128 is not particularly limited.

[0321] [Display device 100E] The display device 100E shown in Figure 12 is a modified version of the display device 100C shown in Figure 10, and differs from the display device 100C mainly in that it has a colored layer 132R, a colored layer 132G, and a colored layer 132B.

[0322] In the display device 100E, the light-emitting device 130 has a region that overlaps with one of the colored layers 132R, 132G, and 132B. The colored layers 132R, 132G, and 132B can be provided on the substrate 351 side of the substrate 352. The edges of the colored layer 132R, the edges of the colored layer 132G, and the edges of the colored layer 132B can overlap with the light-shielding layer 157.

[0323] In the display device 100E, the light-emitting device 130 can emit, for example, white light. Also, for example, the colored layer 132R can transmit red light, the colored layer 132G can transmit green light, and the colored layer 132B can transmit blue light. The display device 100E may also be configured to have the colored layers 132R, 132G, and 132B placed between the protective layer 131 and the adhesive layer 142.

[0324] Figures 10 and 12 show an example where the upper surface of layer 128 has a flat portion, but the shape of layer 128 is not particularly limited.

[0325] This embodiment can be appropriately combined with other embodiments or examples. Furthermore, if multiple configuration examples are shown within a single embodiment in this specification, these configuration examples can be appropriately combined.

[0326] (Embodiment 5) This embodiment describes an electronic device according to one aspect of the present invention.

[0327] The electronic device of this embodiment has a display device according to one aspect of the present invention in its display unit. The display device according to one aspect of the present invention has low power consumption. Therefore, it can be used in the display unit of various electronic devices.

[0328] Examples of electronic devices include television sets, desktop or notebook personal computers, computer monitors, digital signage, large game machines such as pachinko machines, and other electronic devices with relatively large screens, as well as digital cameras, digital video cameras, digital photo frames, mobile phones, portable game consoles, personal digital assistants, and audio playback devices.

[0329] In particular, since the display device according to one aspect of the present invention has low power consumption, it can be suitably used for relatively small electronic devices. Examples of such electronic devices include wristwatch-type and bracelet-type information terminals (wearable devices), as well as VR devices such as head-mounted displays, glasses-type AR devices, and MR devices, and other wearable devices that can be worn on the head, such as those mentioned above.

[0330] The electronic device of the present embodiment may have a sensor (including a function of measuring force, displacement, position, velocity, acceleration, angular velocity, rotation speed, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient, vibration, odor or infrared rays).

[0331] An example of a wearable device that can be worn on the head will be described using FIGS. 13A to 13D.

[0332] The electronic device 700A shown in FIG. 13A and the electronic device 700B shown in FIG. 13B each have a pair of display panels 751, a pair of housings 721, a communication unit (not shown), a pair of mounting parts 723, a control unit (not shown), an imaging unit (not shown), a pair of optical members 753, a frame 757, and a pair of nose pads 758.

[0333] The display device according to one aspect of the present invention can be applied to the display panel 751. Therefore, it can be an electronic device with low power consumption and capable of long-time driving.

[0334] The electronic device 700A and the electronic device 700B can each project the image displayed on the display panel 751 onto the display area 756 of the optical member 753. Since the optical member 753 has translucency, the user can view the image displayed in the display area by overlapping it with the transmitted image visible through the optical member 753.

[0335] The electronic device 700A and the electronic device 700B may be provided with a camera capable of imaging the front as an imaging unit. Further, the electronic device 700A and the electronic device 700B may each include an acceleration sensor such as a gyro sensor to detect the orientation of the user's head and display an image corresponding to the orientation in the display area 756.

[0336] The communication unit has a wireless communication device, and the wireless communication device can supply, for example, a video signal. In addition to or instead of the wireless communication device, a connector to which a cable for supplying a video signal and a power potential can be connected may be provided.

[0337] Further, the electronic device 700A and the electronic device 700B are provided with a battery and can be charged by one or both of wireless and wired methods.

[0338] The housing 721 may be provided with a touch sensor module.

[0339] As the touch sensor module, various touch sensors can be applied. For example, various methods such as a capacitance method, a resistive film method, an infrared method, an electromagnetic induction method, a surface acoustic wave method, or an optical method can be adopted. In particular, it is preferable to apply a capacitance method or an optical method sensor to the touch sensor module.

[0340] The electronic device 800A shown in FIG. 13C and the electronic device 800B shown in FIG. 13D each have 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.

[0341] The display device according to an aspect of the present invention can be applied to the display unit 820. Therefore, it is possible to obtain an electronic device with low power consumption and capable of long-time driving.

[0342] The display unit 820 is provided at a position inside the housing 821 where it can be visually recognized through the lens 832. Also, by displaying different images on the pair of display units 820, three-dimensional display using parallax can be performed.

[0343] Preferably, electronic devices 800A and 800B have a mechanism that allows the left and right positions of the lens 832 and the display unit 820 to be in an optimal position according to the user's eye position.

[0344] The attachment portion 823 allows the user to attach the electronic device 800A or the electronic device 800B to their head.

[0345] The imaging unit 825 has the function of acquiring external information. The data acquired by the imaging unit 825 can be output to the display unit 820. An image sensor can be used in the imaging unit 825. In addition, multiple cameras may be provided to accommodate multiple angles of view, such as telephoto and wide-angle.

[0346] The electronic device 800A may have a vibration mechanism that functions as a bone conduction earphone.

[0347] Electronic devices 800A and 800B may each have input terminals. Cables can be connected to the input terminals to supply video signals from video output devices, etc., and power for charging batteries provided in the electronic devices.

[0348] An electronic device according to one aspect of the present invention may have a function for wireless communication with an earphone 750.

[0349] Furthermore, the electronic device may have an earphone section. The electronic device 700B shown in Figure 13B has an earphone section 727. Some of the wiring connecting the earphone section 727 and the control unit may be located inside the housing 721 or the mounting section 723.

[0350] Similarly, the electronic device 800B shown in Figure 13D has an earphone unit 827. For example, the earphone unit 827 and the control unit 824 can be connected to each other by a wire.

[0351] Thus, as one embodiment of the present invention, both eyeglass-type (electronic devices 700A and 700B, etc.) and goggle-type (electronic devices 800A and 800B, etc.) are preferred as electronic devices.

[0352] The electronic device 6500 shown in Figure 14A is a portable information terminal that can be used as a smartphone.

[0353] The electronic device 6500 includes a housing 6501, a display unit 6502, a power button 6503, a button 6504, a speaker 6505, a microphone 6506, a camera 6507, and a light source 6508, etc. The display unit 6502 has a touch panel function.

[0354] A display device according to one embodiment of the present invention can be applied to the display unit 6502. Therefore, an electronic device with low power consumption and long operating time can be made.

[0355] Figure 14B is a schematic cross-sectional view of the housing 6501 including the end on the microphone 6506 side.

[0356] A light-transmitting protective member 6510 is provided on the display side of the housing 6501, and the display panel 6511, optical member 6512, touch sensor panel 6513, printed circuit board 6517, and battery 6518 are arranged in the space enclosed by the housing 6501 and the protective member 6510.

[0357] The protective member 6510 is fixed to the display panel 6511, the optical member 6512, and the touch sensor panel 6513 by an adhesive layer (not shown).

[0358] In the area outside the display unit 6502, a portion of the display panel 6511 is folded back, and the FPC 6515 is connected to this folded portion. IC 6516 is mounted on the FPC 6515. The FPC 6515 is connected to terminals provided on the printed circuit board 6517.

[0359] A display device according to one embodiment of the present invention can be applied to the display panel 6511. This makes it possible to realize an extremely lightweight electronic device. Furthermore, because the display panel 6511 is extremely thin, it is possible to incorporate a large-capacity battery 6518 while keeping the thickness of the electronic device low. In addition, by folding back a part of the display panel 6511 and placing the connection part with the FPC 6515 on the back of the pixel section, an electronic device with a narrow bezel can be realized.

[0360] FIG. 14C shows an example of a television apparatus. In the television apparatus 7100, a display unit 7000 is incorporated in a housing 7171. Here, a configuration in which the housing 7171 is supported by a stand 7173 is shown.

[0361] The display device according to an aspect of the present invention can be applied to the display unit 7000. Therefore, an electronic device with low power consumption and capable of long-time driving can be obtained.

[0362] The operation of the television apparatus 7100 shown in FIG. 14C can be performed by an operation switch provided in the housing 7171 and a separate remote control operation unit 7151.

[0363] FIG. 14D shows an example of a notebook personal computer. The notebook personal computer 7200 has a housing 7211, a keyboard 7212, a pointing device 7213, an external connection port 7214, etc. A display unit 7000 is incorporated in the housing 7211.

[0364] The display device according to an aspect of the present invention can be applied to the display unit 7000. Therefore, an electronic device with low power consumption and capable of long-time driving can be obtained.

[0365] FIGS. 14E and 14F show an example of digital signage.

[0366] The digital signage 7300 shown in FIG. 14E has a housing 7301, a display unit 7000, a speaker 7303, etc. Further, it can have an LED lamp, operation keys (including a power switch or an operation switch), connection terminals, various sensors, a microphone, etc.

[0367] FIG. 14F shows a digital signage 7400 attached to a columnar pillar 7401. The digital signage 7400 has a display unit 7000 provided along the curved surface of the pillar 7401.

[0368] In FIGS. 14E and 14F, the display device according to an aspect of the present invention can be applied to the display unit 7000. Therefore, a highly reliable electronic device can be obtained.

[0369] The larger the display area 7000, the more information can be provided at once. Furthermore, a larger display area 7000 is more eye-catching, which can, for example, enhance the effectiveness of advertising.

[0370] Furthermore, as shown in Figures 14E and 14F, it is preferable that the digital signage 7300 or digital signage 7400 can be linked wirelessly with an information terminal device 7311 or information terminal device 7411 such as a smartphone owned by the user.

[0371] The electronic device shown in Figures 15A to 15G includes a housing 9000, a display unit 9001, a speaker 9003, operation keys 9005 (including a power switch or operation switch), connection terminals 9006, sensors 9007 (including functions for measuring force, displacement, position, velocity, acceleration, angular velocity, rotational speed, distance, light, liquid, magnetism, temperature, chemical substances, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient, vibration, odor, or infrared radiation), a microphone 9008, and the like.

[0372] The electronic devices shown in Figures 15A to 15G have various functions. For example, they may have functions to display various information (still images, videos, text images, etc.) on a display unit, a touch panel function, a function to display a calendar, date or time, a function to control processing by various software (programs), a wireless communication function, a function to read and process programs or data recorded on a recording medium, and so on.

[0373] Details of the electronic equipment shown in Figures 15A to 15G will be explained below.

[0374] Figure 15A is a perspective view showing a personal digital information terminal (PDI) 9171. The PDI 9171 can be used, for example, as a smartphone. The PDI 9171 may also be equipped with a speaker 9003, a connection terminal 9006, or a sensor 9007. Furthermore, the PDI 9171 can display text and image information on multiple surfaces. Figure 15A shows an example where three icons 9050 are displayed. Information 9051, indicated by a dashed rectangle, can also be displayed on other surfaces of the display unit 9001. Examples of information 9051 include notifications of incoming emails, SNS messages, phone calls, etc., the title of emails or SNS messages, the sender's name, date and time, time, battery level, signal strength, etc. Alternatively, icons 9050, etc., may be displayed in the position where the information 9051 is displayed.

[0375] Figure 15B is a perspective view showing a personal digital assistant (PDA) 9172. The PDA 9172 has the function of displaying information on three or more sides of the display unit 9001. Here, an example is shown in which information 9052, information 9053, and information 9054 are displayed on different sides. For example, a user can check information 9053, which is displayed in a position that can be observed from above the PDA 9172, while the PDA 9172 is stored in the breast pocket of their clothing.

[0376] Figure 15C is a perspective view showing the tablet terminal 9173. The tablet terminal 9173 can run various applications, such as mobile phone calls, email, document viewing and creation, music playback, internet communication, and computer games. The tablet terminal 9173 has a display unit 9001, a camera 9002, a microphone 9008, and a speaker 9003 on the front of the housing 9000. The left side of the housing 9000 has operation keys 9005 as buttons for operation, and the bottom has connection terminals 9006.

[0377] Figure 15D is a perspective view showing a wristwatch-type personal information terminal 9200. The personal information terminal 9200 can be used, for example, as a smartwatch (registered trademark). The display unit 9001 has a curved display surface, allowing it to display information along the curved surface. The personal information terminal 9200 can also make hands-free calls by communicating with, for example, a wireless communication headset. Furthermore, the personal information terminal 9200 can transmit data to other information terminals and be charged via a connection terminal 9006. Charging may be performed by wireless power supply.

[0378] Figures 15E to 15G are perspective views showing a foldable portable information terminal 9201. Figure 15E shows the portable information terminal 9201 in an unfolded state, Figure 15G shows it in a folded state, and Figure 15F shows a perspective view of the state in between, transitioning from one of Figures 15E or 15G to the other. The portable information terminal 9201 offers excellent portability in its folded state and excellent readability of the display due to its seamless, wide display area in its unfolded state. The display unit 9001 of the portable information terminal 9201 is supported by three housings 9000 connected by hinges 9055. For example, the display unit 9001 can be bent with a radius of curvature of 0.1 mm to 150 mm.

[0379] This embodiment can be appropriately combined with other embodiments or examples. Furthermore, if multiple configuration examples are shown within a single embodiment in this specification, these configuration examples can be appropriately combined.

[0380] In this example, the detailed manufacturing methods and characteristics of light-emitting device 1, which is a light-emitting device according to one aspect of the present invention, and comparative light-emitting devices 1-1 and 1-2 will be described. The structural formulas of the main compounds used in this example are shown below.

[0381]

[0382] (Method for fabricating light-emitting device 1) First, a layer of silver (Ag) 100 nm thick was formed on a glass substrate, and then a layer of indium tin oxide (ITSO) containing silicon oxide 10 nm thick was deposited by sputtering to form a first electrode 101 measuring 2 mm x 2 mm. The ITSO functions as an anode.

[0383] Next, as a pretreatment for forming a light-emitting device on the substrate, the substrate surface was washed with water.

[0384] After that, approximately 1 x 10 −４ The substrate was introduced into a vacuum deposition apparatus where the internal pressure was reduced to Pa. After vacuum firing at 170°C for 30 minutes in the heating chamber of the vacuum deposition apparatus, the substrate was allowed to cool for approximately 30 minutes.

[0385] Next, the substrate was fixed to a holder provided in a vacuum deposition apparatus so that the surface on which the first electrode 101 was formed was facing downwards. A hole injection layer 111 was then formed by co-depositing N-(biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviated as PCBBiF), represented by the above structural formula (i), and an electron acceptor material (OCHD-003) containing fluorine with a molecular weight of 672, on the inorganic insulating film and the first electrode 101 in a weight ratio of 1:0.03 (= PCBBiF:OCHD-003) with a film thickness of 10 nm.

[0386] PCBiF was deposited onto the hole injection layer 111 to a thickness of 125 nm, and then 9-[3-(triphenylsilyl)phenyl]-3,9'-bi-9H-carbazole (abbreviated as PSiCzCz), represented by the above structural formula (ii), was deposited to a thickness of 5 nm to form a hole transport layer 112. PCBiF is an organic compound having an aromatic amine, and PSiCzCz is an organic compound having a π-electron-rich heteroaromatic ring. The PSiCzCz layer also functions as an electron blocking layer.

[0387] Next, on the hole transport layer, 9,9'-{6-[3-(triphenylsilyl)phenyl]-1,3,5-triazine-2,4-diyl}bis(9H-carbazole) (abbreviated as SiTrzCz2), represented by the above structural formula (iii), PSiCzCz, and (2-{3-[3-(3,5-di-tert-butylphenyl)benzimidazole-1-i), represented by the above structural formula (iv), are placed. A light-emitting layer 113 was formed by co-depositing 2-ylidene-κC2]phenoxy-κC2}-9-(4-tert-butyl-2-pyridinyl-κN)carbazole-2,1-diyl-κC1)platinum(II) (abbreviated as PtON-TBBI) in a weight ratio of 0.35:0.53:0.12 (=SiTrzCz2:PSiCzCz:PtON-TBBI) with a film thickness of 40 nm. Note that SiTrzCz2 and PSiCzCz are a combination that forms an excited complex, and PtON-TBBI is an organometallic complex that exhibits blue phosphorescence. Furthermore, SiTrzCz2 is an organic compound having a π-electron-deficient heteroaromatic ring, and PSiCzCz is an organic compound having a π-electron-rich heteroaromatic ring.

[0388] Next, 2-phenyl-4,6-bis[3-(triphenylsilyl)phenyl]-1,3,5-triazine (abbreviated as mSiTrz), represented by the above structural formula (v), was deposited to a thickness of 5 nm to form a first electron transport layer. Then, 2-{3-(2,6-dimethylpyridine-3-yl)-5-[(3,5-di-tert-butyl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviated as mmtBuPh-mDMePyPTZn), represented by the above structural formula (vi), and 8-quinolinolato-lithium (abbreviated as Liq), represented by the above structural formula (viii), were co-deposited in a weight ratio of 1:4 (= mmtBuPh-mDMePyPTZn:Liq) to a film thickness of 20 nm to form a second electron transport layer. Furthermore, mSiTrz and mmtBuPh-mDMePyPTZn are organic compounds having a π-electron-deficient heteroaromatic ring, and the first electron transport layer is a layer that also functions as a hole blocking layer. In addition, mmtBuPh-mDMePyPTZn is an organic compound with an ordinary refractive index of 1.70 or less at any wavelength between 455 nm and 520 nm, as shown in Figure 16, and has multiple saturated hydrocarbon groups.

[0389] After the electron transport layer was formed, lithium fluoride (abbreviated as LiF) was deposited to a thickness of 1 nm to form an electron injection layer 115. Subsequently, silver (Ag) and magnesium (Mg) were co-deposited in a volume ratio of 1:0.1 to a film thickness of 15 nm to form a second electrode. Then, a cap layer was formed by depositing 4,4',4''-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviated as DBT3P-II), represented by the above structural formula (viii), to a thickness of 70 nm.

[0390] Next, in a glove box under a nitrogen atmosphere, the light-emitting device was sealed with a glass substrate to prevent exposure to the atmosphere (applying a UV-curable sealant around the element, irradiating only the sealant with UV light without irradiating the light-emitting device, and heat-treating at 80°C for 1 hour under atmospheric pressure) to form the light-emitting device 1.

[0391] (Method for fabricating comparative light-emitting device 1-1) Comparative light-emitting device 1-1 was fabricated in the same manner as light-emitting device 1, except that mmtBuPh-mDMePyPTZn used in the second electron transport layer of light-emitting device 1 was replaced with 11-[4-(biphenyl-4-yl)-6-phenyl-1,3,5-triazine-2-yl]-11,12-dihydro-12-phenylindoro[2,3-a]carbazole (abbreviated as BP-Icz(II)TZn), represented by the above structural formula (ix). As shown in Figure 16, BP-Icz(II)TZn is an organic compound having a π-electron-deficient heteroaromatic ring and a paraphotonic refractive index greater than 1.70 at any wavelength between 455 nm and 520 nm.

[0392] (Method for fabricating comparative light-emitting devices 1-2) Comparative light-emitting devices 1-2 were fabricated in the same manner as light-emitting devices 1, except that the second electron transport layer in light-emitting device 1 was formed of 2,2'-(1,3-phenylene)bis(9-phenyl-1,10-phenanthroline) (abbreviated as mPPhen2P), represented by the above structural formula (x). As shown in Figure 16, mPPhen2P is an organic compound having a paraphotonic refractive index greater than 1.70 at any wavelength between 455 nm and 520 nm and possessing a π-electron-deficient heteroaromatic ring.

[0393] The device structures of light-emitting device 1, comparative light-emitting device 1-1, and comparative light-emitting device 1-2 are shown in the table below.

[0394]

[0395] Figure 17 shows the luminance-current density characteristics of light-emitting device 1, comparative light-emitting device 1-1, and comparative light-emitting device 1-2; Figure 18 shows the luminance-voltage characteristics; Figure 19 shows the current efficiency-current density characteristics; Figure 20 shows the current density-voltage characteristics; Figure 21 shows the blue index-current density characteristics; Figure 22 shows the external quantum efficiency-current density characteristics; and Figure 23 shows the field emission spectrum. Furthermore, the current density is 10 mA / cm². ２Table 4 shows the main characteristics of the device. A spectroradiometer (Topcon SR-UL1R) was used to measure luminance, CIE chromaticity, and field emission spectrum at room temperature. The external quantum efficiency was calculated using the measured luminance and emission spectrum, assuming a Lambertsian light distribution pattern.

[0396]

[0397] Furthermore, Figures 19, 21, and 22 show that light-emitting device 1 has a higher luminous efficiency than comparative light-emitting devices 1-1 and 1-2. Also, Figure 23 shows that light-emitting device 1, comparative light-emitting device 1-1, and comparative light-emitting device 1-2 emit blue light with a peak wavelength of 463 nm in their electroluminescence spectra.

[0398] Next, the 10 mA / cm² values ​​for light-emitting device 1, comparative light-emitting device 1-1, and comparative light-emitting device 1-2 are measured. ２ Figure 24 shows the time-dependent characteristics of the normalized brightness when driven by [the specified method], and Figure 25 shows a graph of the elapsed time (LT90) for each light-emitting device until the brightness decreased to 90% of the initial brightness in this measurement. Note that the time-dependent characteristics of the normalized brightness are shown with the initial brightness set to 100%.

[0399] Figures 24 and 25 show that a light-emitting device 1 according to one embodiment of the present invention, in which the GSP_Slop of the second electron transport layer is high and the second electron transport layer contains an organic compound having a paraphotometric refractive index of 1.70 or less at any wavelength from 455 nm to 520 nm, is a light-emitting device with high luminescence efficiency and good reliability.

[0400] Next, Table 5 shows the GSP_Slope of the organic compound having a π-electron-deficient heteroaromatic ring used in the first electron transport layer of light-emitting device 1, comparative light-emitting device 1-1, and comparative light-emitting device 1-2, the organic compound having a π-electron-deficient heteroaromatic ring used in the second electron transport layer, the organic compound having 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 5, the GSP_Slope was measured by the method shown in Embodiment 1.

[0401]

[0402] Thus, in comparative light-emitting devices 1-2, the GSP_Slope of the organic compound having a π-electron-deficient heteroaromatic ring contained in the second electron transport layer is smaller than the GSP_Slope of the organic compound having a π-electron-deficient heteroaromatic ring contained in the first electron transport layer. In this configuration, 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 light-emitting devices 1 and comparative light-emitting devices 1-2, the GSP_Slope of the organic compound having a π-electron-deficient heteroaromatic ring contained in the second electron transport layer is larger than the GSP_Slope of the organic compound having a π-electron-deficient heteroaromatic ring contained in the first electron transport layer. As a result, in light-emitting devices 1 and comparative light-emitting devices 1-2, the injection of electrons from the electrode or electron injection layer to the second electron transport layer is suppressed.

[0403] Typically, in light-emitting layers containing blue phosphorescent material, the HOMO and LUMO levels of the blue phosphorescent material are both higher than those of the host material. This makes it easier to trap holes rather than electrons, and thus the recombination region tends to be biased towards the anode side of the light-emitting 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 light-emitting layer. This makes it easier for interactions between excitons and between excitons and holes in the electron-blocking layer to occur, leading to the generation of very high-energy excitons or holes. These high-energy excitons or holes accelerate the degradation of the light-emitting layer and the electron-blocking layer adjacent to it.

[0404] In one embodiment of the present invention, as described above, electron injection is suppressed due to the high GSP_slope of the second electron transport layer. This allows the recombination region, which tends to be biased towards the anode side of the light-emitting layer, to be extended to the cathode side as well, thereby suppressing the degradation of the hole transport layer, which functions as an electron blocking layer. As a result, the reliability of light-emitting device 1 and comparative light-emitting device 1-2 is improved compared to comparative light-emitting device 1-3.

[0405] In the light-emitting device fabricated in this embodiment, the HOMO level of PSiCzCz used as the host material in 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, with a LUMO level of -2.98 eV. The HOMO level of PtON-TBBI, which was added in a small amount (12 wt%) to the light-emitting layer as a blue phosphorescent material, is -5.50 eV and the LUMO level is -2.3 eV. This configuration facilitates hole trapping. Therefore, in this light-emitting layer, holes are strongly trapped, and the hole transportability tends to be low.

[0406] The HOMO and LUMO levels were determined by cyclic voltammetry (CV) measurements.

[0407] In cyclic voltammetry (CV) measurements, the HOMO and LUMO levels (E) were calculated based on the oxidation peak potential (Epa) and reduction peak potential (Epc) obtained by changing the potential of the working electrode relative to the reference electrode. In the measurement, the HOMO level was determined from the positive potential scan, and the LUMO level was determined from the negative potential scan. The scan speed in the measurement was set to 0.1 V / s.

[0408] Specifically, the standard redox potential (Eo) (= (Epa + Epc) / 2) was determined from the oxidation peak potential (Epa) and reduction peak potential (Epc) obtained from the cyclic voltammogram of the material. The values ​​(E) (= Ex - Eo) of the HOMO level and LUMO level were then determined by subtracting this from the potential energy (Ex) of the reference electrode relative to the vacuum level.

[0409] The above describes the case where a reversible redox wave is obtained. However, when an irreversible redox wave is obtained, the HOMO level is calculated by assuming that the reduction peak potential (Epc) is obtained by subtracting a certain value (0.1 eV) from the oxidation peak potential (Epa), and the standard redox potential (Eo) is calculated to one decimal place. Similarly, the LUMO level is calculated by assuming that the oxidation peak potential (Epa) is obtained by adding a certain value (0.1 eV) to the reduction peak potential (Epc), and the standard redox potential (Eo) is calculated to one decimal place.

[0410] In the above-described light-emitting device, the GSP_Slope of the host material (SiTrzCz2 and PSiCzCz) is larger than that of the first organic compound. Furthermore, the GSP_Slope of the light-emitting layer is larger than that of the first electron transport layer.

[0411] This configuration allows a positive interfacial charge to be placed at the interface between the light-emitting layer and the first electron transport layer, thereby suppressing the electron injection barrier from the second electron transport layer to the first electron transport layer in the light-emitting device. As a result, even if electron injection from the second electron transport layer is suppressed, the light-emitting device does not cause a significant increase in the driving voltage, making it possible to create a light-emitting device with good characteristics.

[0412] Furthermore, the above-mentioned light-emitting device has a configuration in which the GSP_Slope of the light-emitting layer (SiTrzCz2, PSiCzCz, and PtON-TBBI) or the host material (co-evaporated film of SiTrzCz2 and PSiCzCz) is larger than the GSP_Slope of the hole transport layer (evaporated film of PCBBiF and / or evaporated film of PSiCzCz). Due to this relationship between the GSP_Slopes of the hole transport layer and the light-emitting layer, a negative interfacial charge can be established at at least one of the interfaces present from the hole transport layer to the light-emitting layer. This facilitates the injection of holes from the anode or hole injection layer to the vicinity of the light-emitting layer interface, making it possible to create a light-emitting device with a low driving voltage.

[0413] Figure 35 also shows the emission spectra (PL spectra) of a mixed film of SiTrzCz2 and PSiCzCz in a 1:1 (weight ratio) ratio, and of the individual films. The measurements were performed using a spectrofluorometer (FP-8600DS, JASCO Corporation). As shown in Figure 35, the mixed film of SiTrzCz2 and PSiCzCz exhibited emission spectra that were shifted to longer wavelengths, different from the emission spectra of either individual film. This indicates that SiTrzCz2 and PSiCzCz are a combination that forms an excitation complex. Therefore, the light-emitting device fabricated in this embodiment can be made into a light-emitting device with high luminous efficiency and good reliability.

[0414] Thus, a light-emitting device according to one aspect of the present invention can be a light-emitting device with high reliability and good characteristics.

[0415] In this example, the detailed manufacturing methods and characteristics of light-emitting devices 2-1 and 2-2, which are light-emitting devices according to one aspect of the present invention, and comparative light-emitting device 2-1, which is a comparative light-emitting device, will be described. The structural formulas of the main compounds used in this example are shown below.

[0416]

[0417] (Method for fabricating light-emitting device 2-1) First, indium tin oxide (ITSO) containing silicon oxide was layered onto a glass substrate at a thickness of 55 nm by sputtering to form a first electrode 101 measuring 2 mm x 2 mm. The ITSO functions as an anode.

[0418] Next, as a pretreatment for forming a light-emitting device on the substrate, the substrate surface was washed with water.

[0419] After that, approximately 1 x 10 −４ The substrate was introduced into a vacuum deposition apparatus where the internal pressure was reduced to Pa. After vacuum firing at 170°C for 30 minutes in the heating chamber of the vacuum deposition apparatus, the substrate was allowed to cool for approximately 30 minutes.

[0420] Next, the substrate was fixed to a holder provided in a vacuum deposition apparatus so that the surface on which the first electrode 101 was formed was facing downwards. A hole injection layer 111 was then formed by co-depositing N-(biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviated as PCBBiF), represented by the above structural formula (i), and an electron acceptor material (OCHD-003) containing fluorine with a molecular weight of 672, on the inorganic insulating film and the first electrode 101 in a weight ratio of 1:0.03 (= PCBBiF:OCHD-003) with a film thickness of 10 nm.

[0421] After depositing PCBiF onto the hole injection layer 111 to a thickness of 45 nm, a hole transport layer 112 was formed by depositing 9-[3-(triphenylsilyl)phenyl]-3,9'-bi-9H-carbazole (abbreviated as PSiCzCz), represented by the above structural formula (ii), to a thickness of 5 nm. PCBiF is an organic compound having an aromatic amine, and PSiCzCz is an organic compound having a π-electron-rich heteroaromatic ring. The PSiCzCz layer also functions as an electron blocking layer.

[0422] Next, on the hole transport layer, 9,9'-{6-[3-(triphenylsilyl)phenyl]-1,3,5-triazine-2,4-diyl}bis(9H-carbazole) (abbreviated as SiTrzCz2), represented by the above structural formula (iii), PSiCzCz, and (2-{3-[3-(3,5-di-tert-butylphenyl)benzimidazole-1-i), represented by the above structural formula (iv), are placed. A light-emitting layer 113 was formed by co-depositing 2-ylidene-κC2]phenoxy-κC2}-9-(4-tert-butyl-2-pyridinyl-κN)carbazole-2,1-diyl-κC1)platinum(II) (abbreviated as PtON-TBBI) in a weight ratio of 0.35:0.53:0.12 (=SiTrzCz2:PSiCzCz:PtON-TBBI) with a film thickness of 40 nm. Note that SiTrzCz2 and PSiCzCz are a combination that forms an excited complex, and PtON-TBBI is an organometallic complex that exhibits blue phosphorescence. Furthermore, SiTrzCz2 is an organic compound having a π-electron-deficient heteroaromatic ring, and PSiCzCz is an organic compound having a π-electron-rich heteroaromatic ring.

[0423] Next, 2-phenyl-4,6-bis[3-(triphenylsilyl)phenyl]-1,3,5-triazine (abbreviated as mSiTrz), represented by the above structural formula (v), was deposited to a thickness of 5 nm to form a first electron transport layer. Then, 2-(3'',5',5''-tri-t-butyl-[1,1':3',1''-terphenyl]-5-yl)-4,6-diphenyl-1,3,5-triazine (abbreviated as mmtBumTPTzn-03), represented by the above structural formula (xi), and 8-quinolinolatolithium (abbreviated as Liq), represented by the above structural formula (vii), were co-deposited in a weight ratio of 1:4 (= mmtBumTPTzn-03:Liq) to a film thickness of 30 nm to form a second electron transport layer. Furthermore, mSiTrz and mmtBumTPTZn-03 are organic compounds having a π-electron-deficient heteroaromatic ring, and the first electron transport layer is a layer that also functions as a hole blocking layer. In addition, mmtBumTPTZn-03 is an organic compound with an ordinary refractive index of 1.70 or less at any wavelength between 455 nm and 520 nm, as shown in Figure 26, and has multiple saturated hydrocarbon groups.

[0424] After the electron transport layer was formed, lithium fluoride (abbreviated as LiF) was deposited to a thickness of 1 nm to form an electron injection layer 115, and then aluminum (Al) was deposited to a thickness of 200 nm to form a second electrode.

[0425] Next, in a glove box under a nitrogen atmosphere, the light-emitting device was sealed with a glass substrate to prevent exposure to the atmosphere (applying a UV-curable sealant around the element, irradiating only the sealant with UV light without irradiating the light-emitting device, and heat-treating at 80°C for 1 hour under atmospheric pressure) to form the light-emitting device 1.

[0426] (Method for fabricating light-emitting device 2-2) Light-emitting device 2-2 was fabricated in the same manner as light-emitting device 2-1, except that mmtBumTPTZn-03 used in the second electron transport layer of light-emitting device 2-1 was replaced with 2-(3'',5',5''-tri-t-butyl-[1,1':3',1''-terphenyl]-4-yl)-4,6-diphenyl-1,3,5-triazine (abbreviated as mmtBumTPTZn-04), represented by the above structural formula (xii). As shown in Figure 26, mmtBumTPTZn-04 has an ordinary refractive index of 1.70 or less at any wavelength between 455 nm and 520 nm and is an organic compound having a π-electron-deficient heteroaromatic ring.

[0427] (Method for fabricating comparative light-emitting device 2-1) Comparative light-emitting device 2-1 was fabricated in the same manner as light-emitting device 2-1, except that the second electron transport layer in light-emitting device 2-1 was formed of 2,2'-(1,3-phenylene)bis(9-phenyl-1,10-phenanthroline) (abbreviated as mPPhen2P), represented by the above structural formula (x). As shown in Figure 26, mPPhen2P is an organic compound having a paraphotonic refractive index greater than 1.70 at any wavelength between 455 nm and 520 nm and possessing a π-electron-deficient heteroaromatic ring.

[0428] The device structures of light-emitting device 2-1, light-emitting device 2-2, and comparative light-emitting device 2-1 are shown in the table below.

[0429]

[0430] Figure 27 shows the luminance-current density characteristics of light-emitting device 2-1, light-emitting device 2-2, and comparative light-emitting device 2-1; Figure 28 shows the luminance-voltage characteristics; Figure 29 shows the current efficiency-current density characteristics; Figure 30 shows the current density-voltage characteristics; Figure 31 shows the blue index-current density characteristics; Figure 32 shows the external quantum efficiency-current density characteristics; and Figure 33 shows the field emission spectrum. Furthermore, the current density is 10 mA / cm². ２Table 7 shows the main characteristics of the device. A spectroradiometer (Topcon SR-UL1R) was used to measure luminance, CIE chromaticity, and field emission spectrum at room temperature. The external quantum efficiency was calculated using the measured luminance and emission spectrum, assuming a Lambertsian light distribution pattern.

[0431]

[0432] Figures 29, 31, and 32 show that light-emitting devices 2-1 and 2-2 have higher luminous efficiency than the comparative light-emitting device 2-1. Furthermore, Figure 33 shows that light-emitting devices 2-1, 2-2, and the comparative light-emitting device 2-1 emit blue light with a peak wavelength of 464 nm in their electroluminescence spectra.

[0433] Next, the 10 mA / cm of light-emitting device 2-1, light-emitting device 2-2, and comparative light-emitting device 2-1. ２ Figure 34 shows the time-dependent characteristics of the normalized brightness when driven by [the specified method]. Note that the time-dependent characteristics of the normalized brightness are shown with the initial brightness set to 100%.

[0434] As shown in Figure 34, it was found that light-emitting devices 2-1 and 2-2 according to one embodiment of the present invention, in which the GSP_Slop of the second electron transport layer is high and the second electron transport layer contains an organic compound having a paraphotonic refractive index of 1.70 or less at any wavelength from 455 nm to 520 nm, are light-emitting devices with high luminescence efficiency and good reliability.

[0435] Next, Table 5 shows the GSP_Slope of the organic compound having a π-electron-deficient heteroaromatic ring used in the first electron transport layer of light-emitting device 2-1, light-emitting device 2-2, and comparative light-emitting device 2-1, the organic compound having a π-electron-deficient heteroaromatic ring used in the second electron transport layer, the organic compound having a π-electron-excess heteroaromatic ring or aromatic amine used in the hole transport layer, and the vapor-deposited film of the host material used in the light-emitting layer. Note that in Table 8, the GSP_Slope was measured by the method shown in Embodiment 1.

[0436]

[0437] Thus, in comparative light-emitting device 2-1, the GSP_Slope of the organic compound having a π-electron-deficient heteroaromatic ring contained in the second electron transport layer is smaller than the GSP_Slope of the organic compound having a π-electron-deficient heteroaromatic ring contained in the first electron transport layer. In this configuration, 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 light-emitting devices 2-1 and 2-2, the GSP_Slope of the organic compound having a π-electron-deficient heteroaromatic ring contained in the second electron transport layer is larger than the GSP_Slope of the organic compound having a π-electron-deficient heteroaromatic ring contained in the first electron transport layer. As a result, in light-emitting devices 2-1 and 2-2, the injection of electrons from the electrode or electron injection layer to the second electron transport layer is suppressed.

[0438] Typically, in light-emitting layers containing blue phosphorescent material, the HOMO and LUMO levels of the blue phosphorescent material are both higher than those of the host material. As a result, it traps holes rather than electrons, causing the recombination region to be biased towards the anode side of the light-emitting 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 light-emitting layer. This makes it easier for interactions between excitons and between excitons and holes in the electron-blocking layer to occur, leading to the generation of very high-energy excitons or holes. These high-energy excitons or holes accelerate the degradation of the light-emitting layer and the electron-blocking layer adjacent to it.

[0439] In one embodiment of the present invention, as described above, electron injection is suppressed due to the high GSP_slope of the second electron transport layer. This allows the recombination region, which tends to be biased towards the anode side of the light-emitting layer, to be extended to the cathode side as well, thereby suppressing the degradation of the hole transport layer, which functions as an electron blocking layer. As a result, light-emitting devices 2-1 and 2-2 exhibit improved reliability compared to comparative light-emitting device 2-1.

[0440] In the light-emitting device fabricated in this embodiment, the HOMO level of PSiCzCz used as the host material in 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, with a LUMO level of -2.98 eV. The HOMO level of PtON-TBBI, which was added in a small amount (12 wt%) to the light-emitting layer as a blue phosphorescent material, is -5.50 eV and the LUMO level is -2.3 eV. This configuration facilitates hole trapping. Therefore, in this light-emitting layer, holes are strongly trapped, and the hole transportability tends to be low.

[0441] The HOMO and LUMO levels were determined using the same measurement method as in Example 1.

[0442] In the light-emitting device fabricated in this embodiment, the GSP_Slope of the host material (SiTrzCz2 and PSiCzCz) is larger than that of the first organic compound. Furthermore, the GSP_Slope of the light-emitting layer is larger than that of the first electron transport layer.

[0443] This configuration allows a positive interfacial charge to be placed at the interface between the light-emitting layer and the first electron transport layer, thereby suppressing the electron injection barrier from the second electron transport layer to the first electron transport layer in the light-emitting device. As a result, even if electron injection from the second electron transport layer is suppressed, the light-emitting device does not cause a significant increase in the driving voltage, making it possible to create a light-emitting device with good characteristics.

[0444] Furthermore, the light-emitting device fabricated in this embodiment has a configuration in which the GSP_Slope of the light-emitting layer (SiTrzCz2, PSiCzCz, and PtON-TBBI) or the host material (co-evaporated film of SiTrzCz2 and PSiCzCz) is larger than the GSP_Slope of the hole transport layer (evaporated film of PCBBiF and / or evaporated film of PSiCzCz). This relationship between the GSP_Slopes of the hole transport layer and the light-emitting layer allows for the establishment of a negative interfacial charge at at least one of the interfaces between the hole transport layer and the light-emitting layer. This facilitates the injection of holes from the anode or hole injection layer to the vicinity of the light-emitting layer interface, making it possible to create a light-emitting device with a low driving voltage.

[0445] Figure 35 also shows the emission spectra (PL spectra) of a mixed film of SiTrzCz2 and PSiCzCz in a 1:1 (weight ratio) ratio, and of the individual films. The measurements were performed using a spectrofluorometer (FP-8600DS, JASCO Corporation). As shown in Figure 35, the mixed film of SiTrzCz2 and PSiCzCz exhibited emission spectra that were shifted to longer wavelengths, different from the emission spectra of either individual film. This indicates that SiTrzCz2 and PSiCzCz are a combination that forms an excitation complex. Therefore, the light-emitting device fabricated in this embodiment can be made into a light-emitting device with high luminous efficiency and good reliability.

[0446] Thus, a light-emitting device according to one aspect of the present invention can be a light-emitting device with high reliability and good characteristics.

[0447] 10A: Light-emitting device, 10B: Light-emitting device, 100A: Display device, 100B: Display device, 100C: Display device, 100E: Display device, 100D: Display device, 100: Insulator, 101: First electrode, 102: Second electrode, 103: EL layer, 110B: Sub-pixel, 110G: Sub-pixel, 110R: Sub-pixel, 110: Sub-pixel, 111: Hole injection layer, 112: Hole transport layer, 112B: Conductive layer, 112R: Conductive layer, 113: Light-emitting layer, 114_1: First electron transport layer, 114_2: Second electron transport layer, 115: Electron injection layer, 116: Charge generation layer, 117: p-type layer, 1 18: Electronic relay layer, 119: Electron injection buffer layer, 120: Substrate, 122: Resin layer, 125: Inorganic insulating layer, 126R: Conductive layer, 126B: Conductive layer, 127: Insulating layer, 128: Layer, 129R: Conductive layer, 129B: Conductive layer, 130B: Light-emitting device, 130G: Light-emitting device, 130R: Light-emitting device, 130: Light-emitting device, 131: Protective layer, 132B: Colored layer, 132G: Colored layer, 132R: Colored layer, 135: First layer, 135A: First layer group, 135R: First layer, 135G: First layer, 135B: First layer, 136: Common layer, 140: Connection part, 14 1: Region, 142: Adhesive layer, 151B: Conductive layer, 151C: Conductive layer, 151G: Conductive layer, 151R: Conductive layer, 151: Conductive layer, 152B: Conductive layer, 152C: Conductive layer, 152G: Conductive layer, 152R: Conductive layer, 152: Conductive layer, 153: Insulating layer, 156B: Insulating layer, 156C: Insulating layer, 156G: Insulating layer, 156R: Insulating layer, 157: Light-shielding layer, 158B: Sacrificial layer, 158G: Sacrificial layer, 158R: Sacrificial layer, 166: Conductive layer, 171: Insulating layer, 172: Conductive layer, 173: Insulating layer, 174: Insulating layer, 175: Insulating layer, 176: Plug, 177: Pixel area, 178: Image Element, 201: Transistor, 204: Connector, 205: Transistor, 211: Insulating layer, 213: Insulating layer, 214: Insulating layer, 215: Insulating layer, 221: Conductive layer, 222a: Conductive layer, 222b: Conductive layer, 223: Conductive layer, 224B: Conductive layer, 224C: Conductive layer, 224G: Conductive layer, 224R: Conductive layer, 231: Semiconductor layer, 240: Capacitor, 241: Conductive layer, 242: Connector layer, 243: Insulating layer, 245: Conductive layer, 254: Insulating layer, 255: Insulating layer, 256: Plug, 261: Insulating layer, 271: Plug, 280: Display module, 281: Display unit, 282: Circuit unit,283a: Pixel circuit, 283: Pixel circuit section, 284a: Pixel, 284: Pixel section, 285: Terminal section, 286: Wiring section, 290: FPC, 291: Substrate, 292: Substrate, 301: Substrate, 310: Transistor, 311: Conductive layer, 312: Low-resistance region, 313: Insulating layer, 314: Insulating layer, 315: Element isolation layer, 351: Substrate, 352: Substrate, 353: FPC, 354: IC, 355: Wiring, 356: Circuit, 501: First electrode, 502: Second electrode, 513: Charge generation layer, 700A: Electronic equipment, 700B: Electronic equipment, 721: Housing, 723: Mounting 727: Earphone section, 750: Earphone, 751: Display panel, 753: Optical component, 756: Display area, 757: Frame, 758: Nose pad, 800A: Electronic equipment, 800B: Electronic equipment, 820: Display unit, 821: Housing, 822: Communication unit, 823: Mounting section, 824: Control unit, 825: Imaging unit, 827: Earphone section, 832: Lens, 1117: Light-shielding layer, 6500: Electronic equipment, 6501: Housing, 6502: Display unit, 6503: Power button, 6504: Button, 6505: Speaker, 6506: Microphone, 6507: Camera, 6 508: Light source, 6510: Protective member, 6511: Display panel, 6512: Optical member, 6513: Touch sensor panel, 6515: FPC, 6516: IC, 6517: Printed circuit board, 6518: Battery, 7000: Display unit, 7100: Television equipment, 7151: Remote control operator, 7171: Enclosure, 7173: Stand, 7200: Notebook personal computer, 7211: Enclosure, 7212: Keyboard, 7213: Pointing device, 7214: External connection port, 7300: Digital signage, 7301: Enclosure, 73 03: Speaker, 7311: Information terminal, 7400: Digital signage, 7401: Pillar, 7411: Information terminal, 9000: Enclosure, 9001: Display unit, 9002: Camera, 9003: Speaker, 9005: Operation key, 9006: Connection terminal, 9007: Sensor, 9008: Microphone, 9050: Icon, 9051: Information, 9052: Information, 9053: Information, 9054: Information, 9055: Hinge, 9171: Portable information terminal, 9172: Portable information terminal, 9173: Tablet terminal, 9200: Portable information terminal, 9201: Portable information terminal,

Claims

1. The device comprises a first electrode formed on an insulating surface, a second electrode facing the first electrode, and an EL layer located between the first electrode and the second electrode, wherein the EL layer comprises a light-emitting layer, a hole transport layer, a first electron transport layer, and a second electron transport layer, the first electron transport layer is located between the first electrode and the second electron transport layer, the light-emitting layer is located between the hole transport layer, the first electron transport layer and the second electron transport layer, and the ordinary refractive index of the second electron transport layer at any wavelength from 455 nm to 520 nm is 1.70 or less. A light-emitting device in which the GSP_Slope (mV / nm) of the second electron transport layer is greater than the GSP_Slope (mV / nm) of the first electron transport layer (where GSP_Slope (mV / nm) is a parameter expressed as ΔV / Δd when the change in surface potential is ΔV (mV) with respect to the change in film thickness Δd (nm)).

2. The light-emitting device according to claim 1, 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.

3. The light-emitting device according to claim 2, wherein the GSP_Slope (mV / nm) of the light-emitting layer is greater than the GSP_Slope (mV / nm) of the hole transport layer.

4. The device comprises a first electrode formed on an insulating surface, a second electrode facing the first electrode, and an EL layer located between the first electrode and the second electrode, wherein the EL layer comprises a light-emitting layer, a hole transport layer, a first electron transport layer, and a second electron transport layer, the first electron transport layer is located between the first electrode and the second electron transport layer, the light-emitting layer is located between the hole transport layer, the first electron transport layer and the second electron transport layer, the first electron transport layer comprises a first organic compound, the second electron transport layer comprises a second organic compound, the paraphotometric refractive index of the film of the second organic compound at any wavelength from 455 nm to 520 nm is 1.70 or less, and the first organic compound and the second organic compound have a π-electron-deficient heteroaromatic ring. A light-emitting device in which the GSP_Slope (mV / nm) in the vapor-deposited film of the second organic compound is greater than the GSP_Slope (mV / nm) in the vapor-deposited film of the first organic compound (where GSP_Slope (mV / nm) is a parameter expressed as ΔV / Δd when the change in surface potential is ΔV (mV) relative to the change in film thickness Δd (nm)).

5. The device comprises a first electrode formed on an insulating surface, a second electrode facing the first electrode, and an EL layer located between the first electrode and the second electrode, wherein the EL layer comprises a light-emitting layer, a hole transport layer, a first electron transport layer, and a second electron transport layer, the first electron transport layer is located between the light-emitting layer and the second electron transport layer, the second electron transport layer is located between the first electron transport layer and the second electrode, the light-emitting layer is located between the hole transport layer and the first electron transport layer, the first electron transport layer comprises a first organic compound, the second electron transport layer comprises a second organic compound and a first substance, the paraphotometric refractive index of the film of the second organic compound at any wavelength from 455 nm to 520 nm is 1.70 or less, and the first organic compound and the second organic compound have a π-electron-deficient heteroaromatic ring. A light-emitting device in which the GSP_Slope (mV / nm) in the vapor-deposited film of the second organic compound is greater than the GSP_Slope (mV / nm) in the vapor-deposited film of the first organic compound (where GSP_Slope (mV / nm) is a parameter expressed as ΔV / Δd when the change in surface potential is ΔV (mV) relative to the change in film thickness Δd (nm)).

6. The device comprises a first electrode formed on an insulating surface, a second electrode facing the first electrode, and an EL layer located between the first electrode and the second electrode, wherein the EL layer comprises a light-emitting layer, a hole transport layer, a first electron transport layer, and a second electron transport layer, the first electron transport layer is located between the light-emitting layer and the second electron transport layer, the second electron transport layer is located between the first electron transport layer and the second electrode, the light-emitting layer is located between the hole transport layer and the first electron transport layer, the first electron transport layer comprises a first organic compound, the second electron transport layer comprises a second organic compound and a first substance, the paraphotometric refractive index of the film of the second organic compound at any wavelength from 455 nm to 520 nm is 1.70 or less, and the first organic compound and the second organic compound have a π-electron-deficient heteroaromatic ring. When the mixing ratio of the second organic compound to the first substance in the second electron transport layer is x:y, the light-emitting device is such that the GSP_Slope (mV / nm) in the vapor-deposited film of the second organic compound is greater than (x+y) / x times the GSP_Slope (mV / nm) in the vapor-deposited film of the first organic compound (where GSP_Slope (mV / nm) is a parameter expressed as ΔV / Δd when the change in surface potential is ΔV (mV) relative to the change in film thickness Δd (nm)).

7. The light-emitting device according to claim 6, wherein y is greater than or equal to x.

8. A light-emitting device according to any one of claims 2 to 7, wherein the second organic compound has a saturated hydrocarbon group.

9. The light-emitting device according to claim 8, wherein the second organic compound has a plurality of saturated hydrocarbon groups.

10. A light-emitting device according to any one of claims 1 to 7, wherein the light-emitting layer comprises a material that exhibits phosphorescence.

11. The light-emitting device according to claim 10, wherein the phosphorescent substance emits light when a voltage is applied between the first electrode and the second electrode.

12. A light-emitting device according to any one of claims 4 to 7, 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 a light-emitting substance, and the GSP_Slope (mV / nm) in the vapor-deposited film of the host material is greater than the GSP_Slope (mV / nm) in the vapor-deposited film of the first organic compound.

13. The light-emitting device according to claim 12, wherein the GSP_Slope (mV / nm) in the vapor-deposited film of the second organic compound is greater than the GSP_Slope (mV / nm) in the vapor-deposited film of the host material.

14. The light-emitting device according to claim 12, wherein the hole transport layer has a third organic compound, and the GSP_Slope (mV / nm) of the light-emitting layer is equal to or greater than the GSP_Slope (mV / nm) of the vapor-deposited film of the third organic compound.

15. The light-emitting device according to claim 12, wherein the hole transport layer has a third organic compound, and the GSP_Slope (mV / nm) in the vapor-deposited film of the host material is equal to or greater than the GSP_Slope (mV / nm) in the vapor-deposited film of the third organic compound.

16. The light-emitting device according to claim 12, wherein the host material is an organic compound comprising a first material and a second material, wherein the first material and the second material form an excited complex in a combination.

17. A light-emitting device according to claim 16, 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-excess heteroaromatic ring or an aromatic amine.

18. A light-emitting device according to claim 5 or claim 6, wherein the first substance is a metal complex.

19. The light-emitting device according to claim 18, wherein the metal complex is an organic complex having an alkali metal.

20. The light-emitting device according to claim 11, wherein the peak wavelength of the emission spectrum of the phosphorescent material is 455 nm or more and 520 nm or less.

21. The light-emitting device according to claim 12, wherein the peak wavelength of the emission spectrum of the light-emitting material is 455 nm or more and 520 nm or less.

22. The light-emitting device according to any one of claims 1 to 3, wherein the paraphotometric refractive index of the second electron transport layer at the peak wavelength of the electroluminescence spectrum of the light-emitting device is 1.70 or less.

23. The light-emitting device according to claim 12, wherein the paraphotometric refractive index of the film of the second organic compound is 1.70 or less at the peak wavelength of the emission spectrum of the light-emitting material.

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