Light-emitting apparatus, electronic device, and display device

Abstract

A long-lifetime light-emitting device is provided. The light-emitting device includes a first light-emitting device and a first color conversion layer. The first color conversion layer contains a first material. The EL layer of the first light-emitting device, from the anode side, sequentially includes a first layer, a second layer, a third layer, a light-emitting layer, and a fourth layer. The first layer contains a first organic compound and a second organic compound. The second layer contains a third organic compound. The third layer contains a fourth organic compound. The light-emitting layer contains a fifth organic compound and a sixth organic compound. The fourth layer contains a seventh organic compound. The first organic compound is an electron-accepting organic compound of the second organic compound. The fifth organic compound is the light-emitting center material. The HOMO energy level of the second organic compound is above -5.7 eV and below -5.4 eV.

Description

[Technical Field]

[0001] One embodiment of the present invention relates to a light-emitting element, a light-emitting device, a display module, a lighting module, a display device, a light-emitting device, an electronic device, and a lighting equipment. Note that one embodiment of the present invention is not limited to the above-described technical fields. The technical field of one embodiment of the invention disclosed in this specification relates to an object, method, or manufacturing method. Furthermore, one embodiment of the present invention relates to a process, machine, product, or composition of matter. Therefore, more specifically, as examples of the technical field of one embodiment of the present invention disclosed in this specification, examples include semiconductor devices, display devices, liquid crystal display devices, light-emitting devices, lighting equipment, energy storage devices, memory devices, imaging devices, their driving methods, or their manufacturing methods. [Previous Technology]

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

[0003] Because this type of light-emitting device is a self-emissive device, it offers advantages over liquid crystal displays (LCDs) in terms of higher visibility and the elimination of the need for a backlight when used in display pixels. Therefore, this light-emitting device is suitable for flat panel display components. Furthermore, displays using this type of light-emitting device can be manufactured to be thin and lightweight, which is also a significant advantage. Moreover, its extremely high-speed response is another characteristic of this light-emitting device.

[0004] Furthermore, because the light-emitting layer of this light-emitting device can be continuously formed in two dimensions, surface light emission can be achieved. Since this is a feature that is difficult to obtain in point light sources represented by incandescent lamps or LEDs, or in line light sources represented by fluorescent lamps, the above-mentioned light-emitting device is also highly valuable as a surface light source that can be used for lighting and the like.

[0005] When the light-emitting device is used as a pixel in a full-color display, it is necessary to obtain light of at least three colors: red, green, and blue. To achieve this, there are generally two typical methods. One method is to use light-emitting devices that display light of each color. The other method is to use all light-emitting devices that display the same color of light and convert that light into light of the desired wavelength corresponding to each pixel.

[0006] The former is advantageous in terms of luminous efficiency due to less light loss, while the latter is advantageous in terms of cost because it is easy to manufacture and thus easy to increase production volume since it does not require manufacturing light-emitting devices for each pixel separately.

[0007] Furthermore, as a method for converting the aforementioned light emission into light of a desired wavelength for each pixel, there are typically methods that obtain light of the desired wavelength by cutting off a portion of the light emission from the light-emitting device, and methods that obtain light of the desired wavelength by converting the aforementioned light emission. Compared to the former, which only cuts off a portion of the obtained light emission, the latter, although dependent on the conversion efficiency, results in relatively less energy loss. Therefore, it can be said that the latter is a method that more easily achieves a low-power light-emitting device.

[0008] As described above, as a method for obtaining light of a desired wavelength by converting light emitted from a light-emitting device, a photoluminescent color conversion layer can be used. This color conversion layer contains a substance that emits light upon excitation by absorbing light. Color conversion layers using organic compounds have existed for a long time, but in recent years, color conversion layers using quantum dots (QDs) have been put into practical use.

[0009] [Patent Document 1] International Publication No. 2016 / 098570 [Summary of the Invention]

[0010] Therefore, an object of one embodiment of the present invention is to provide a novel light-emitting device. Furthermore, an object of one embodiment of the present invention is to provide a light-emitting device with good luminous efficiency. Furthermore, an object of one embodiment of the present invention is to provide a light-emitting device with good lifespan. Furthermore, an object of one embodiment of the present invention is to provide a light-emitting device with low driving voltage.

[0011] Furthermore, another objective of the present invention is to provide a highly reliable light-emitting device, electronic device, and display device. Additionally, another objective of the present invention is to provide a light-emitting device, electronic device, and display device with low power consumption.

[0012] Any one of the above objectives can be achieved in one embodiment of the present invention.

[0013] One embodiment of the present invention is a light-emitting device, including a first light-emitting device and a first color conversion layer. The first color conversion layer contains a first material that absorbs light and emits light. When light emitted from the first light-emitting device is incident on the first color conversion layer, the degradation curve of the brightness change of the emitted light obtained when a constant current flows through the first light-emitting device has a maximum value.

[0014] In another embodiment of the present invention, the light-emitting device includes a first light-emitting device and a first color conversion layer, wherein the first color conversion layer contains a first substance that absorbs light and emits light, and light emitted from the first light-emitting device is incident on the first color conversion layer. The first light-emitting device includes an anode, a cathode, and an EL layer located between the anode and the cathode. The EL layer includes, from the anode side, a first layer, a second layer, a third layer, a light-emitting layer, and a fourth layer in sequence. The first layer is in contact with the anode, and the first layer contains a first organic compound and a second organic compound. The second layer contains a third organic compound. The third layer contains a fourth organic compound. The light-emitting layer contains a fifth organic compound and a sixth organic compound. The fourth layer contains a seventh organic compound. The first organic compound is an organic compound that exhibits electron-acceptance properties to the second organic compound. The fifth organic compound is a light-emitting center substance. The HOMO energy level of the second organic compound is above -5.7 eV and below -5.4 eV. The seventh organic compound has an electron mobility of more than 1×10⁻⁷ cm² / Vs and less than 5×10⁻⁵ cm² / Vs when the square root of the electric field strength [V / cm] is 600.

[0015] In another embodiment of the present invention, the light-emitting device includes a first light-emitting device and a first color conversion layer, wherein the first color conversion layer contains a first substance that absorbs light and emits light, and light emitted from the first light-emitting device is incident on the first color conversion layer. The first light-emitting device includes an anode, a cathode, and an EL layer located between the anode and the cathode. The EL layer includes, from the anode side, a first layer, a second layer, a third layer, a light-emitting layer, and a fourth layer in sequence. The first layer is in contact with the anode, and the fourth layer is in contact with the light-emitting layer. The first layer contains a first organic compound and a second organic compound, the second layer contains a third organic compound, the third layer contains a fourth organic compound, the light-emitting layer contains a fifth organic compound and a sixth organic compound, and the fourth layer contains a seventh organic compound. The first organic compound is an organic compound that exhibits electron accepting behavior towards the second organic compound, the fifth organic compound is a light-emitting center, the HOMO energy level of the second organic compound is above -5.7 eV and below -5.4 eV, the electron mobility of the seventh organic compound at the square root of the electric field strength [V / cm] of 600 is above 1×10-7 cm² / Vs and below 5×10-5 cm² / Vs, and the HOMO energy level of the seventh organic compound is above -6.0 eV.

[0016] In addition, another embodiment of the light-emitting device of the present invention includes a first light-emitting device and a first color conversion layer, wherein the first color conversion layer contains a first substance that absorbs light and emits light, and light emitted from the first light-emitting device is incident on the first color conversion layer. The first light-emitting device includes an anode, a cathode, and an EL layer located between the anode and the cathode. The EL layer includes, from the anode side, a first layer, a second layer, a third layer, a light-emitting layer, and a fourth layer in sequence. The first layer is in contact with the anode, and the fourth layer is in contact with the light-emitting layer. The first layer contains a first organic compound and a second organic compound, the second layer contains a third organic compound, the third layer contains a fourth organic compound, and the light-emitting layer contains a fifth organic compound and a sixth organic compound. The four-layer structure contains a seventh organic compound, the first organic compound being an electron-accepting organic compound to the second organic compound, the fifth organic compound being a luminescent center, the HOMO energy level of the second organic compound being -5.7 eV or higher and -5.4 eV or lower, the HOMO energy level difference between the third organic compound and the second organic compound being 0.2 eV or lower, the HOMO energy level of the third organic compound being the same as or deeper than the HOMO energy level of the second organic compound, the electron mobility of the seventh organic compound being 1×10⁻⁷ cm² / Vs or higher and 5×10⁻⁵ cm² / Vs or lower when the square root of the electric field strength [V / cm] is 600, and the HOMO energy level of the seventh organic compound being -6.0 eV or higher.

[0017] In addition, another embodiment of the light-emitting device of the present invention includes a first light-emitting device and a first color conversion layer, wherein the first color conversion layer contains a first substance that absorbs light and emits light, and light emitted from the first light-emitting device is incident on the first color conversion layer. The first light-emitting device includes an anode, a cathode, and an EL layer between the anode and the cathode. The EL layer includes, from the anode side, a first layer, a second layer, a third layer, a light-emitting layer, and a fourth layer in sequence. The first layer is in contact with the anode, and the fourth layer is in contact with the light-emitting layer. The first layer contains a first organic compound and a second organic compound, the second layer contains a third organic compound, the third layer contains a fourth organic compound, the light-emitting layer contains a fifth organic compound and a sixth organic compound, and the fourth layer contains a seventh organic compound. The first organic compound is a first organic compound that is reacted with the second organic compound. The compound is an electron-accepting organic compound, wherein the second organic compound contains a first hole-transporting framework, the third organic compound contains a second hole-transporting framework, the fourth organic compound contains a third hole-transporting framework, the fifth organic compound is a luminescent center, the HOMO level of the second organic compound is above -5.7 eV and below -5.4 eV, the first, second, and third hole-transporting frameworks are each independently one of a carbazole framework, a dibenzofuran framework, a dibenzothiophene framework, and an anthracene framework, the seventh organic compound has an electron mobility of above 1 × 10⁻⁷ cm² / Vs and below 5 × 10⁻⁵ cm² / Vs when the square root of the electric field strength [V / cm] is 600, and the HOMO level of the seventh organic compound is above -6.0 eV.

[0018] In addition, another embodiment of the display device of the present invention includes a first light-emitting device and a first color conversion layer, wherein the first color conversion layer contains a first substance that absorbs light and emits light, and light emitted from the first light-emitting device is incident on the first color conversion layer. The first light-emitting device includes an anode, a cathode, and an EL layer located between the anode and the cathode. The EL layer includes, from the anode side, a first layer, a second layer, a third layer, a light-emitting layer, and a fourth layer in sequence. The first layer is in contact with the anode, and the fourth layer is in contact with the light-emitting layer. The first layer contains a first organic compound and a second organic compound. The second layer contains a third organic compound. The third layer contains a fourth organic compound. The light-emitting layer contains a fifth organic compound and a sixth organic compound. The fourth layer contains a seventh organic compound and an eighth organic compound. The first organic compound is an organic compound that exhibits electron acceptance to the second organic compound. The fifth organic compound is a light-emitting center substance. The HOMO energy level of the second organic compound is above -5.7 eV and below -5.4 eV. The seventh organic compound is an organic compound having an anthracene skeleton. The eighth organic compound is an organic complex of an alkali metal or an alkaline earth metal.

[0019] In addition, another embodiment of the display device of the present invention includes a first light-emitting device and a first color conversion layer, wherein the first color conversion layer contains a first substance that absorbs light and emits light, and light emitted from the first light-emitting device is incident on the first color conversion layer. The first light-emitting device includes an anode, a cathode, and an EL layer located between the anode and the cathode. The EL layer includes, from the anode side, a first layer, a second layer, a third layer, a light-emitting layer, and a fourth layer in sequence. The first layer is in contact with the anode, and the fourth layer is in contact with the light-emitting layer. The first layer contains a first organic compound and a second organic compound, the second layer contains a third organic compound, the third layer contains a fourth organic compound, and the light-emitting layer contains... The fourth layer contains a fifth organic compound and a sixth organic compound, and includes a seventh organic compound and an eighth organic compound. The first organic compound is an organic compound that exhibits electron acceptance to the second organic compound. The fifth organic compound is a luminescent center. The HOMO energy level of the second organic compound is above -5.7 eV and below -5.4 eV. The HOMO energy level difference between the third organic compound and the second organic compound is below 0.2 eV. The HOMO energy level of the third organic compound is the same as or deeper than that of the second organic compound. The seventh organic compound is an organic compound with an anthracene skeleton. The eighth organic compound is an organic complex of an alkali metal or alkaline earth metal.

[0020] In addition, another embodiment of the present invention is a light-emitting device in which the concentration of the eighth organic compound in the fourth layer of the above structure decreases from the light-emitting layer side to the cathode side.

[0021] In addition, another embodiment of the display device of the present invention includes a first light-emitting device and a first color conversion layer, wherein the first color conversion layer contains a first substance that absorbs light and emits light, and light emitted from the first light-emitting device is incident on the first color conversion layer. The first light-emitting device includes an anode, a cathode, and an EL layer located between the anode and the cathode. The EL layer includes, from the anode side, a first layer, a second layer, a third layer, a light-emitting layer, and a fourth layer in sequence. The first layer is in contact with the anode, and the fourth layer is in contact with the light-emitting layer. The first layer contains a first organic compound and a second organic compound, the second layer contains a third organic compound, the third layer contains a fourth organic compound, the light-emitting layer contains a fifth organic compound and a sixth organic compound, and the fourth layer contains a seventh organic compound. The first organic compound is an organic compound that exhibits electron-acceptance to the second organic compound, the second organic compound contains a first hole-transporting framework, the third organic compound contains a second hole-transporting framework, the fourth organic compound contains a third hole-transporting framework, the fifth organic compound is a luminescent center, the HOMO energy level of the second organic compound is above -5.7 eV and below -5.4 eV, the first hole-transporting framework, the second hole-transporting framework and the third hole-transporting framework are each independently one of a carbazole framework, a dibenzofuran framework, a dibenzothiophene framework and an anthracene framework, the seventh organic compound is an organic compound having an anthracene framework, and the eighth organic compound is an organic complex of an alkali metal or an alkaline earth metal.

[0022] In addition, another embodiment of the present invention is a light-emitting device in which the electron mobility of the seventh organic compound in the above structure is less than that of the sixth organic compound.

[0023] In addition, another embodiment of the present invention is a light-emitting device in which the difference between the HOMO energy level of the fourth organic compound and the HOMO energy level of the third organic compound in the above structure is less than 0.2 eV.

[0024] In addition, another embodiment of the present invention is a light-emitting device in which the HOMO energy level of the fourth organic compound in the above structure is deeper than the HOMO energy level of the third organic compound.

[0025] In another embodiment of the present invention, the second organic compound in the above structure is a light-emitting device having an organic compound having a dibenzofuran skeleton.

[0026] In addition, another embodiment of the present invention is a light-emitting device in which the second organic compound and the third organic compound are the same substance in the above structure.

[0027] In addition, another embodiment of the present invention is a light-emitting device in which the fifth organic compound in the above structure is a blue fluorescent material.

[0028] In addition, another embodiment of the present invention is a light-emitting device in which the degradation curve of the brightness change of the light emitted when a constant current flows through the first light-emitting device is maximized in the above structure.

[0029] In addition, another embodiment of the present invention is a light-emitting device in which the first material that absorbs light and emits light in the above structure is a quantum dot.

[0030] In addition, another embodiment of the present invention is a light-emitting device in which the first light-emitting device has a microcavity structure in the above structure.

[0031] In addition, another embodiment of the present invention is a light-emitting device as follows: In the above structure, the light-emitting device further includes a second light-emitting device and a second color conversion layer, the second color conversion layer contains a second material that absorbs light and emits light, the light emitted by the second light-emitting device is incident on the second color conversion layer, the second light-emitting device has the same structure as the first light-emitting device, and the wavelength of the light emitted from the first material is different from the wavelength of the light emitted from the second material.

[0032] In addition, another embodiment of the present invention is a light-emitting device in which the second material is a quantum dot in the above structure.

[0033] In addition, another embodiment of the present invention is a light-emitting device in which the second light-emitting device has a microcavity structure in the above structure.

[0034] In addition, another embodiment of the present invention is a light-emitting device as follows: In the above structure, the light-emitting device further includes a third light-emitting device, the third light-emitting device having the same structure as the first light-emitting device, and the light emitted from the third light-emitting device is emitted to the outside of the light-emitting device without passing through the color conversion layer.

[0035] In addition, another embodiment of the present invention is a light-emitting device as follows: In the above structure, the light-emitting device further includes a third light-emitting device and a structure having the function of scattering light. The third light-emitting device has the same structure as the first light-emitting device, and the light emitted from the third light-emitting device is emitted outside the light-emitting device through the structure having the function of scattering light.

[0036] In another embodiment of the present invention, the light-emitting device further includes a third light-emitting device, a first color layer, a second color layer, and a resin layer. Light emitted from the first light-emitting device is emitted through the first color conversion layer and the first color layer. Light emitted from the second light-emitting device is emitted through the second color conversion layer and the second color layer. The third light-emitting device has the same structure as the first light-emitting device, and light emitted from the third light-emitting device is emitted through the resin layer.

[0037] In addition, another embodiment of the present invention is a light-emitting device in which the third light-emitting device in the above structure has a microcavity structure.

[0038] In addition, another embodiment of the present invention includes an electronic device in the above structure that includes a sensor, an operation button, a speaker or a microphone.

[0039] In addition, another embodiment of the present invention is a light-emitting device that includes a transistor or a substrate in the above structure.

[0040] In addition, another embodiment of the present invention is a lighting device that includes a housing in the above structure.

[0041] In this specification, a light-emitting device includes an image display device that uses a light-emitting element. Additionally, a light-emitting device may sometimes include modules such as: modules in which the light-emitting element is mounted with connectors such as anisotropic conductive films or TCP (Tape Carrier Package); modules in which printed circuit boards are provided at the ends of the TCP; or modules in which ICs (integrated circuits) are directly mounted on the light-emitting element using a COG (Chip On Glass) method. Furthermore, lighting equipment and the like sometimes include light-emitting devices.

[0042] One embodiment of the present invention can provide a novel light-emitting device. Furthermore, it can provide a light-emitting device with good lifespan. Furthermore, it can provide a light-emitting device with good luminous efficiency. Furthermore, it can provide a light-emitting device with low driving voltage.

[0043] Furthermore, another embodiment of the present invention can provide a light-emitting device, electronic device, and display device with high reliability. Additionally, another embodiment of the present invention can provide a light-emitting device, electronic device, and display device with low power consumption.

[0044] Note that the description of these effects does not preclude the existence of other effects. Furthermore, one embodiment of the present invention does not necessarily require all of the aforementioned effects. Additionally, effects other than these are obvious from the description in the specification, drawings, claims, etc., and can be derived from said description.

Implementation Method

[0046] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and those skilled in the art will readily understand that its methods and details can be varied in many ways without departing from the spirit and scope of the present invention. Therefore, one embodiment of the present invention should not be construed as being limited to the contents described in the embodiments shown below.

[0047] Implementation Method 1 In recent years, color conversion technology using quantum dots (QDs) has been practically applied in fields such as liquid crystal displays. A QD is a semiconductor nanocrystal with a size of a few nm, comprising approximately 1 × 10³ to 1 × 10⁶ atoms. Electrons, holes, and excitons are enclosed within the QD, thus generating discrete energy states, and energy movement depends on its size. That is, even QDs containing the same material have different emission wavelengths depending on their size; therefore, by changing the size of the QD used, the emission wavelength can be easily adjusted.

[0048] Furthermore, because the dispersion of QD restricts phase relaxation, the emission spectrum of quantum dots has a narrow peak width. This results in high color purity emission. In other words, by using a color conversion layer employing QD, emission with high color purity can be obtained, achieving emission covering the Rec.2020 color gamut, which corresponds to the BT.2020 and BT.2100 standards.

[0049] Similar to color conversion layers using organic compound luminescent materials, QD color conversion layers convert the light from a light-emitting device into light with a longer wavelength through photoluminescence, which absorbs the light emitted from the light-emitting device and re-emits the light. Therefore, when the color conversion layer is used as a display, the following structure is adopted: blue light, the shortest wavelength of the three primary colors required to reproduce full color, is obtained from the light-emitting device, and green and red light are obtained through color conversion.

[0050] In other words, in a display that uses a color conversion method, the characteristics of the blue light-emitting device used dominate most of the characteristics, so a blue light-emitting device with better characteristics is needed.

[0051] As shown in FIG1A, a light-emitting device according to one embodiment of the present invention has a pixel 208 including a light-emitting device 207 and a color conversion layer 205, wherein light emitted from the light-emitting device 207 is incident on the color conversion layer 205. The light-emitting device 207 has an EL layer 202 between a first electrode 201 and a second electrode 203. In addition, the color conversion layer 205 preferably contains a QD and is capable of absorbing incident light and emitting light of a predetermined wavelength. When the color conversion layer 205 contains a QD, light emission with a narrow peak width of the emission spectrum and good color purity can be obtained.

[0052] The aforementioned color conversion layer 205 contains a material capable of absorbing incident light and emitting light of a predetermined wavelength. Various light-emitting materials, such as inorganic and organic materials that exhibit photoluminescence, can be used as this material. In particular, a QD made of inorganic materials can achieve light emission with a narrow peak width and high color purity in the aforementioned emission spectrum. Furthermore, when the QD is inorganic, it possesses high inherent stability and a theoretical internal quantum efficiency of almost 100%, making it very suitable for the reasons stated above.

[0053] The color conversion layer 205 containing QD can be formed by coating a solvent in which QD is dispersed and then drying and calcining it. In addition, a film pre-dispersed with QD has also been developed. The separate coating of each color can be performed by methods such as inkjet or other droplet spraying or printing; or, the solvent in which QD is dispersed can be coated onto the forming surface, dried, calcined, cured, etc., and then etched using photolithography or the like.

[0054] As a QD, examples include Group 14 elements, Group 15 elements, Group 16 elements, compounds containing multiple Group 14 elements, compounds of elements belonging to Groups 4 to 14 and Group 16 elements, compounds of Group 2 elements and Group 16 elements, compounds of Group 13 elements and Group 15 elements, compounds of Group 13 elements and Group 17 elements, compounds of Group 14 elements and Group 15 elements, compounds of Group 11 elements and Group 17 elements, iron oxides, titanium oxides, spinel, various semiconductor clusters, metal halide perovskite materials, and other nano-sized particles.

[0055] Specifically, examples include cadmium selenide (CdSe), cadmium sulfide (CdS), cadmium telluride (CdTe), zinc selenide (ZnSe), zinc oxide (ZnO), zinc sulfide (ZnS), zinc telluride (ZnTe), mercuric sulfide (HgS), mercuric selenide (HgSe), mercuric telluride (HgTe), indium arsenide (InAs), indium phosphide (InP), gallium arsenide (GaAs), gallium phosphide (GaP), indium nitride (InN), gallium nitride (GaN), indium antimonide (InSb), gallium antimonide (GaSb), aluminum phosphide (AlP), aluminum arsenide (AlAs), aluminum antimonide (AlSb), lead selenide (II) (PbSe), and lead telluride (II). (PbTe), Lead(II) sulfide (PbS), Indium selenide (In2Se3), Indium telluride (In2Te3), Indium sulfide (In2S3), Gallium selenide (Ga2Se3), Arsenic(III) sulfide (As2S3), Arsenic(III) selenide (As2Se3), Arsenic(III) telluride (As2Te3), Antimony(III) sulfide (Sb2S3), Antimony(III) selenide (Sb2Se3), Antimony(III) telluride (Sb2Te3), Bismuth(III) sulfide (Bi2S3), Bismuth(III) selenide (Bi2Se3), Bismuth(III) telluride (III) (Bi2Te3), Silicon (Si), Silicon Carbide (SiC), Germanium (Ge), Tin (Sn), Selenium (Se), Tellurium (Te), Boron (B), Carbon (C), Phosphorus (P), Boron Nitride (BN), Boron Phosphide (BP), Boron Arsenide (BAs), Aluminum Nitride (AlN), Aluminum Sulfide (Al2S3), Barium Sulfide (BaS), Barium Selenide (BaSe), Barium Telluride (BaTe), Calcium Sulfide (CaS), Calcium Selenide (CaSe), Calcium Telluride (CaTe), Beryllium Sulfide (BeS), Beryllium Selenide (BeSe), Beryllium Telluride (BeTe), Magnesium Sulfide (MgS), Magnesium Selenide (MgSe), Germanium Sulfide (GeS), Germanium Selenide (GeSe), Germanium Telluride (GeTe), Tin Sulfide (IV) (SnS2), Tin Sulfide (II)(SnS), Tin Selenide (II)(SnSe), Tin Telluride (II) (SnTe), Lead(II) oxide (PbO), Copper(I) fluoride (CuF), Copper(I) chloride(CuCl), Copper bromide (I) (CuBr), Copper iodide (I) (CuI), Copper oxide (I) (Cu2O), Copper selenide (I) (Cu2Se), Nickel oxide (II) (NiO), Cobalt oxide (II) (CoO), Cobalt sulfide (II) (CoS), Iron tetroxide (Fe3O4), Iron sulfide (II) (FeS), Manganese oxide (II) (MnO), Molybdenum sulfide (IV) (MoS2), Vanadium oxide (II) (VO), Vanadium oxide (IV) (VO2), Tungsten oxide (IV) (WO2), Tantalum oxide (V) (Ta2O5), Titanium oxide (TiO2, Ti2O5) The following compounds are used, but not limited to: O5, Ti2O3, Ti5O9, etc.; zirconium oxide (ZrO2); silicon nitride (Si3N4); germanium nitride (Ge3N4); aluminum oxide (Al2O3); barium titanate (BaTiO3); compounds of zinc cadmium selenide (CdZnSe); compounds of indium arsenide phosphate (InAsP); compounds of cadmium selenide sulfide (CdSeS); compounds of cadmium selenide tellurium (CdSeTe); compounds of indium gallium arsenide (InGaAs); compounds of indium gallium selenide (InGaSe); compounds of indium selenide sulfide (InSeS); compounds of copper indium sulfide (e.g., CuInS2); and combinations thereof. Furthermore, so-called alloy-type QDs with compositions expressed in arbitrary ratios can also be used. For example, since alloy-type QDs represented by CdSxSe(1-x) (where x is any number from 0 to 1) can change the emission wavelength by changing x, they are one of the effective means of obtaining blue emission.

[0056] The structures of quantum luminescence (QDs) include core-type, core-shell type, and core-multishell type. Any of these can be used, but by using other inorganic materials that cover the core and have a wider band gap to form the shell, the influence of defects or dangling bonds present on the nanocrystal surface can be reduced, thereby significantly improving the quantum efficiency of luminescence. Therefore, core-shell or core-multishell type QDs are preferred. Examples of shell materials include zinc sulfide (ZnS) or zinc oxide (ZnO).

[0057] Furthermore, in QDs, due to the high proportion of surface atoms, reactivity is high and aggregation is prone to occur. Therefore, the surface of QDs is preferably coated with a protective agent or has protective groups. This can prevent aggregation and improve solubility in solvents. In addition, electrical stability can be improved by reducing reactivity. Examples of protective agents (or protecting groups) include: polyoxyethylene alkyl ethers such as lauryl alcohol polyoxyethylene ether, polyoxyethylene stearyl ether, and polyoxyethylene stearyl ether; trialkylphosphines such as tripropylphosphine, tributylphosphine, trihexylphosphine, and trioctylphosphine; polyoxyethylene alkylphenyl ethers such as polyoxyethylene n-octylphenyl ether and polyoxyethylene n-nonylphenyl ether; tertiary amines such as tri(n-hexyl)amine, tri(n-octyl)amine, and tri(n-decyl)amine; organophosphorus compounds such as tripropylphosphine oxide, tributylphosphine oxide, trihexylphosphine oxide, trioctylphosphine oxide, and tridecylphosphine oxide; and polyethylene glycol dilaurate, ... Polyethylene glycol diesters such as glycol distearate; organic nitrogen compounds such as nitrogen-containing aromatic compounds such as pyridine, dimethylpyridine, succinylphenol, and quinolines; amino alkanes such as hexylamine, octylamine, decylamine, dodecylamine, tetradecylamine, hexadecylamine, and octadecylamine; dialkyl sulfides such as dibutyl sulfide; dialkyl sulfides such as dimethyl sulfide and dibutyl sulfide; organic sulfur compounds such as sulfur-containing aromatic compounds such as thiophene; higher fatty acids such as palmitic acid, stearic acid, and oleic acid; ethanol compounds; sorbitan fatty acid esters; fatty acid-modified polyesters; tertiary amine-modified polyurethanes; and polyethyleneimine compounds.

[0058] When the color conversion layer 205 contains a QD material, the QD has a continuous absorption spectrum from near its own emission wavelength to the shorter wavelength side, where the absorption intensity increases with increasing light intensity. Therefore, when a display with multiple emission colors is required, the emission center material contained in the emission device of each color pixel can be the same material, as shown in FIG1B. It is not necessary to manufacture emission devices separately for each color of the pixel, so the emission device can be manufactured at a relatively low cost.

[0059] In FIG1B, as an example, pixels displaying blue, green, and red light are shown respectively. The first pixel 208B displays blue light. The first pixel 208B includes a first electrode 201B and a second electrode 203, one of which is a reflective electrode and the other is a semi-transmissive and semi-reflective electrode, and one is an anode and the other is a cathode. Similarly, the second pixel 208G displaying green light and the third pixel 208R displaying red light shown in the figure respectively include a first electrode 201G and a second electrode 203, and a first electrode 201R and a second electrode 203. FIG1B shows a structure in which the first electrodes 201B, 201G, and 201R are reflective electrodes and anodes, while the second electrode 203 is a semi-transmissive and semi-reflective electrode. The first electrodes 201B, 201G, and 201R are formed on the insulator 200. In addition, in order to prevent light mixing between adjacent pixels, a black matrix 206 is preferably provided between pixels. Black Matrix 206 can also be used as a bank when forming color conversion layers using inkjet printing or other methods.

[0060] Furthermore, an EL layer 202 is sandwiched between the first electrodes 201B, 201G, 201R and the second electrode 203 in the first pixel 208B, the second pixel 208G, and the third pixel 208R. Although the EL layer 202 is shared in the first pixel 208B, the second pixel 208G, and the third pixel 208R, it can also be set separately. Sharing the EL layer in multiple pixels is easier to manufacture and is advantageous in terms of cost. In addition, the EL layer 202 is usually composed of multiple layers with different functions, but it can also adopt a structure in which part is shared by multiple pixels and part is independent in each pixel.

[0061] The first pixel 208B, the second pixel 208G, and the third pixel 208R include a first light-emitting device 207B, a second light-emitting device 207G, and a third light-emitting device 207R, which are composed of a first electrode, a second electrode, and an EL layer. Figure 1B shows the structure of the first pixel 208B, the second pixel 208G, and the third pixel 208R including a common EL layer 202.

[0062] In the first light-emitting device 207B, the second light-emitting device 207G, and the third light-emitting device 207R, a light-emitting device with a microcavity structure can be formed by making one of the first electrode and the second electrode a reflective electrode and the other a transmissive / transmissive electrode. The wavelength at which resonance can be generated is determined by the optical distance 209 between the surface of the reflective electrode and the surface of the transmissive / transmissive electrode. If the wavelength at which resonance is generated is λ, the light of wavelength λ can be amplified by making the optical distance 209 an integer multiple of λ / 2. In addition, the optical distance 209 can be adjusted by adjusting the hole injection layer, the hole transport layer, and the transparent electrode layer formed on the reflective electrode as part of the electrode of the EL layer. In the light-emitting device of FIG1B, the EL layer is shared by the first light-emitting device 207B, the second light-emitting device 207G, and the third light-emitting device 207R, and the light-emitting center material is also the same. Therefore, the optical distance 209 of the light-emitting device is the same in the first pixel 208B, the second pixel 208G, and the third pixel 208R, which can be easily formed. Note that when an EL layer 202 is formed for each pixel, an optical distance 209 can be formed based on the light from the EL layer.

[0063] A protective layer 204 is disposed on the second electrode 203. The protective layer 204 is provided to protect the first light-emitting device 207B, the second light-emitting device 207G, and the third light-emitting device 207R from substances or environments that are detrimental to them. As the protective layer 204, oxides, nitrides, fluorides, sulfides, ternary compounds, metals, or polymers can be used. For example, the material may contain aluminum oxide, hafnium oxide, hafnium silicate, lanthanum oxide, silicon oxide, strontium titanate, tantalum oxide, titanium oxide, zinc oxide, niobium oxide, zirconium oxide, tin oxide, yttrium oxide, cerium oxide, scandium oxide, erbium oxide, vanadium oxide, indium oxide, aluminum nitride, hafnium nitride, silicon nitride, tantalum nitride, titanium nitride, niobium nitride, molybdenum nitride, zirconium nitride, gallium nitride, nitrides containing titanium and aluminum, oxides containing titanium and aluminum, oxides containing aluminum and zinc, sulfides containing manganese and zinc, sulfides containing cerium and strontium, oxides containing erbium and aluminum, oxides containing yttrium and zirconium, etc.

[0064] The first color conversion layer 205G contains a material that absorbs light from the second light-emitting device 207G and emits light. Light emitted from the second light-emitting device 207G is incident on the first color conversion layer 205G and converted into light of a longer wavelength before being emitted. The second color conversion layer 205R contains a material that absorbs light from the third light-emitting device 207R and emits light. Light emitted from the third light-emitting device 207R is incident on the second color conversion layer 205R and converted into light of a longer wavelength before being emitted.

[0065] Note that since the first pixel 208B does not emit light through a color conversion layer, it is preferable that it be the pixel of blue light, which has the highest energy among the three primary colors of emitted light. Furthermore, for the same reason, when the first pixel 208B, the second pixel 208G, and the third pixel 208R emit light of the same color, it is preferable that they emit blue light. In this case, the light-emitting devices contain the same light-emitting center material, which is advantageous in terms of cost; however, different light-emitting center materials can also be used.

[0066] Furthermore, when the light-emitting device is not manufactured separately for each color of the pixel, it is preferable that the light-emitting center material contained in the light-emitting device emits blue light (the peak wavelength of the emitted light is about 420 nm to 480 nm). The emission of the light-emitting center material is calculated using the PL spectrum in solution. The relative permittivity of the organic compound constituting the EL layer of the light-emitting device is about 3. In order to avoid inconsistency with the emission spectrum of the light-emitting device, it is preferable that the relative permittivity of the solvent used to make the light-emitting center material into solution is 1 or more and 10 or less at room temperature, and more preferably 2 or more and 5 or less. Specific examples of solvents include hexane, benzene, toluene, diethyl ether, ethyl acetate, chloroform, chlorobenzene, and dichloromethane. Furthermore, it is preferable to use a general solvent with high solubility that has a relative permittivity of 2 or more and 5 or less at room temperature. For example, toluene or chloroform is preferred.

[0067] Note that these pixels can also each have a color filter.

[0068] The light-emitting device 207 has the structure shown in Figures 2A to 2C. The light-emitting device of a light-emitting apparatus used in one embodiment of the present invention will be described below.

[0069] FIG2A is a diagram illustrating a light-emitting device of a light-emitting apparatus according to one embodiment of the present invention. The light-emitting device of the light-emitting apparatus according to one embodiment of the present invention includes a first electrode 101, a second electrode 102, and an EL layer 103. The EL layer includes a hole injection layer 111, a hole transport layer 112, a light-emitting layer 113, and an electron transport layer 114. The first electrode 101, the second electrode 102, and the EL layer 103 in FIG2A and FIG2B correspond to the first electrode 201, the second electrode 203, and the EL layer 202 in FIG1A.

[0070] Note that although an electron injection layer 115 is shown in addition to the above in the EL layer 103 in FIG2A, the structure of the light-emitting device is not limited to this. As long as the above structure is present, layers with other functions may also be included.

[0071] The hole injection layer 111 includes a first organic compound and a second organic compound. The first organic compound is a substance that exhibits electron-accepting properties towards the second organic compound. Furthermore, the second organic compound is a substance with a deep HOMO energy level, ranging from -5.7 eV to -5.4 eV. By giving the second organic compound a deep HOMO energy level, holes can be easily injected into the hole transport layer 112.

[0072] The first organic compound can be an organic compound having an electron-withdrawing group (especially a halogen or cyano group such as a fluorine group), and a substance that exhibits electron acceptance to the aforementioned second organic compound can be appropriately selected from such substances. Examples of such organic compounds include 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinone dimethyl ether (abbreviated as F4-TCNQ), chloroquinone, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatribenzene (abbreviated as HAT-CN), 1,3,4,5,7,8-hexafluorotetracyano-naphthoquinone dimethyl ether (abbreviated as F6-TCNNQ), 2-(7-dicyanomethylene-1,3,4,5,6,8,9,10-octafluoro-7H-pyrene-2-ylidene)malonitrile, etc. In particular, compounds with electron-withdrawing groups bonded to fused aromatic rings having multiple heteroatoms, such as HAT-CN, are thermally stable and therefore preferred. In addition, [3] axylene derivatives including electron-withdrawing groups (especially halogen groups such as fluorine groups and cyano groups) are particularly preferred because they have very high electron acceptability. Specifically, examples include: α,α',α”-1,2,3-cyclopropanetrimethylenetri[4-cyano-2,3,5,6-tetrafluorophenylacetonitrile], α,α',α”-1,2,3-cyclopropanetrimethylenetri[2,6-dichloro-3,5-difluoro-4-(trifluoromethyl)phenylacetonitrile], α,α',α”-1,2,3-cyclopropanetrimethylenetri[2,3,4,5,6-pentafluorophenylacetonitrile], etc.

[0073] The second organic compound is preferably an organic compound with hole-transporting properties, and preferably has any one of a carbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton, and an anthracene skeleton. In particular, it can be an aromatic amine having substituents including a dibenzofuran ring or a dibenzothiophene ring, an aromatic monoamine including a naphthyl ring, or an aromatic monoamine with a 9-pyrenyl group bonded to the nitrogen of the amine by an aryl group. Note that when these second organic compounds are substances including N,N-bis(4-biphenyl)amine groups, it is preferable to manufacture light-emitting devices with good lifetimes. Specifically, examples of the aforementioned second organic compounds include N-(4-biphenyl)-6,N-diphenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviated as: BnfABP), N,N-bis(4-biphenyl)-6-phenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviated as: BBABnf), 4,4'-bis(6-phenylbenzo[b]naphtho[1,2-d]furan-8-yl)-4”-phenyltriphenylamine (abbreviated as: BnfBB1BP), and N,N-bis(4-biphenyl)benzo[b]naphtho[1”] [2-d]furan-6-amine (abbreviation: BBABnf(6)), N,N-bis(4-biphenyl)benzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BBABnf(8)), N,N-bis(4-biphenyl)benzo[b]naphtho[2,3-d]furan-4-amine (abbreviation: BBABnf(II)(4)), N,N-bis[4-(dibenzofuran-4-yl)phenyl]-4-amino-p-terphenyl (abbreviation: DBfBB1TP), N-[4-(dibenzothiophen-4-yl)phenyl]-N-phenyl 4-(2-naphthyl)-4',4”-diphenyltriphenylamine (BBAβNB), 4-[4-(2-naphthyl)phenyl]-4',4”-diphenyltriphenylamine (BBAβNBi), 4-(2;1'-binathyl-6-yl)-4',4”-diphenyltriphenylamine (BBAαNβNB), 4,4'-diphenyl-4”-(7;1'-binathyl-2-yl)triphenylamine (BBAαNβNB-03), 4,4'-diphenyl 4-(7-phenyl)naphthyl-2-yltriphenylamine (abbreviation: BBAPβNB-03), 4-(6;2'-binathyl-2-yl)-4',4"-diphenyltriphenylamine (abbreviation: BBA(βN2)B), 4-(2;2'-binathyl-7-yl)-4',4"-diphenyltriphenylamine (abbreviation: BBA(βN2)B-03), 4-(1;2'-binathyl-4-yl)-4',4"-diphenyltriphenylamine (abbreviation: BBAβNαNB), 4-(1;2'-binathyl-5-yl)-4',4”-Diphenyltriphenylamine (abbreviation: BBAβNαNB-02), 4-(4-biphenyl)-4'-(2-naphthyl)-4”-phenyltriphenylamine (abbreviation: TPBiAβNB), 4-(3-biphenyl)-4'-[4-(2-naphthyl)phenyl]-4”-phenyltriphenylamine (abbreviation: mTPBiAβNBi), 4-(4-biphenyl)-4'-[4-(2-naphthyl)phenyl]-4”-phenyltriphenylamine (abbreviation: TPBiAβNBi), 4-(1-naphthyl)-4'-phenyltriphenylamine (abbreviation: αNBA1BP), 4,4'-bis(1-naphthyl)triphenylamine (abbreviation: αNBB1BP), 4,4'-diphenyl-4”-[4' -(carbazole-9-yl)biphenyl-4-yl]triphenylamine (abbreviation: YGTBi1BP), 4'-[4-(3-phenyl-9H-carbazole-9-yl)phenyl]tri(1,1'-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'-spirobis[9H-furan]-2-amine (abbreviation: PCBNBSF), N,N-bis([1,1'-biphenyl]-4-yl)-9,9'-spirobis[9H-furan]-2-amine H-[9H ... 4-Phenylacetyl-4'-(9-phenylenylacetyl-9-yl)triphenylamine (abbreviation: BPAFLP), 4-Phenylacetyl-3'-(9-phenylenylacetyl-9-yl)triphenylamine (abbreviation: mBPAFLP), 4-Phenylacetyl-4'-[4-(9-phenylenylacetyl-9-yl)phenyl]triphenylamine (abbreviation: BPAFLBi), 4-Phenylacetyl-4'-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4'-diphenyl-4”-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCCBI1BP), 4-(1-naphthyl)-4'-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBANB), 4,4'-Di(1-naphthyl)-4”-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviated as: PCCNBB), N-phenyl-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-9,9'-spirobis[9H-furan]-2-amine (abbreviated as: PCBASF), N-(1,1'-biphenyl-4-yl)-9,9-dimethyl-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-9H-furan-2-amine (abbreviated as: PCBiF), etc.

[0074] The hole transport layer 112 includes a first hole transport layer 112-1 and a second hole transport layer 112-2. The first hole transport layer 112-1 is located closer to the first electrode 101 than the second hole transport layer 112-2. Note that sometimes the second hole transport layer 112-2 also functions as an electron barrier layer.

[0075] The first hole transport layer 112-1 includes a third organic compound, and the second hole transport layer 112-2 includes a fourth organic compound.

[0076] The third and fourth organic compounds are preferably organic compounds with hole transport properties. The third and fourth organic compounds can also be organic compounds that can be used as the second organic compound described above.

[0077] Preferably, the materials are selected such that the HOMO energy level of the second organic compound is deeper than that of the third organic compound, and the difference between them is less than 0.2 eV. Furthermore, it is even more preferable that the second and third organic compounds are the same substance.

[0078] Furthermore, regarding the HOMO energy levels of the third and fourth organic compounds, it is preferable that the HOMO energy level of the fourth organic compound is deeper. Moreover, it is preferable to select materials whose difference is less than 0.2 eV. By ensuring the HOMO energy levels of the second to fourth organic compounds have the aforementioned relationship, holes can be smoothly injected into each layer, thereby preventing the driving voltage from rising and the state of insufficient holes in the light-emitting layer.

[0079] Furthermore, the second to fourth organic compounds preferably each have a hole-transporting framework. As this hole-transporting framework, carbazole, dibenzofuran, dibenzothiophene, and anthracene frameworks are preferred, as they do not cause the HOMO level of the aforementioned organic compounds to be too shallow. Additionally, when the aforementioned hole-transporting framework is shared in adjacent layers (e.g., the second and third organic compounds or the third and fourth organic compounds), hole injection can be performed smoothly, which is therefore preferable. The dibenzofuran framework is particularly preferred as the aforementioned hole-transporting framework.

[0080] Furthermore, by making the materials contained in adjacent layers (e.g., the second organic compound and the third organic compound, or the third organic compound and the fourth organic compound) the same material, hole injection can be smoothly performed, which is therefore a preferred structure. It is particularly preferred that the second organic compound and the third organic compound are the same material.

[0081] The luminescent layer 113 includes a fifth organic compound and a sixth organic compound. The fifth organic compound is the luminescent center material, and the sixth organic compound is the main material used to disperse the fifth organic compound.

[0082] The luminescent center material can be a fluorescent luminescent material, a phosphorescent luminescent material, a material exhibiting thermally activated delayed fluorescence (TADF), or other luminescent materials. Alternatively, it can be a single layer or composed of multiple layers containing different luminescent materials. In one embodiment of the invention, it is preferable to use the luminescent layer 113 as a layer exhibiting fluorescent emission, particularly a layer exhibiting blue fluorescent emission.

[0083] In the light-emitting layer 113, materials that can be used as fluorescent light-emitting substances can be, for example, the following substances. Note that, in addition to these, other fluorescent light-emitting substances can also be used.

[0084] For example, examples include 5,6-bis[4-(10-phenyl-9-anthrayl)phenyl]-2,2'-bipyridine (abbreviated as: PAP2BPy), 5,6-bis[4'-(10-phenyl-9-anthrayl)biphenyl-4-yl]-2,2'-bipyridine (abbreviated as: PAPP2BPy), N,N'-diphenyl-N,N'-bis[4-(9-phenyl-9H-enta-9-yl)phenyl]pyrene-1,6-diamine (abbreviated as: 1,6FLPAPrn), N,N'-bis(3-methylphenyl)-N,N'-bis[3-(9-phenyl-9H-enta-9-yl)phenyl]pyrene-1,6-diamine (abbreviated as: 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-anthrayl)triphenylamine (abbreviation: YGAPA), 4-(9H-carbazole-9-yl)-4'-(9,10-diphenyl-2-anthrayl)triphenylamine (abbreviation: 2YGAPPA), N,9-diphenyl-N-[4-(10-phenyl-9-anthrayl)phenyl]-9H-carbazole-3-amine (abbreviation: PCAPA), perylene, 2,5,8,11-tetra(tertiary butyl)perylene (abbreviation: TBP), 4-(10-phenyl-9-anthrayl)-4'-(9-phenyl-9H-carbazole-3-yl) Triphenylamine (abbreviated as PCPAPA), N,N”-(2-tert-butylanthracene-9,10-diyl-4,1-epenylphenyl)bis[N,N',N'-triphenyl-1,4-phenylenediamine] (abbreviated as DPABPA), N,9-diphenyl-N-[4-(9,10-diphenyl-2-anthrayl)phenyl]-9H-carbazole-3-amine (abbreviated as 2PCAPPA), N-[4-(9,10-diphenyl-2-anthrayl)phenyl]-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviated as 2DPAPPA), N,N,N',N',N”,N”,N''',N'''-octaphenyldibenzo[g,p] ⇌ chrysene-2,7,10,1 5-Tetraamine (abbreviated as: DBC1), Coumarin 30, N-(9,10-diphenyl-2-anthrayl)-N,9-diphenyl-9H-carbazole-3-amine (abbreviated as: 2PCAPA), N-[9,10-bis(1,1'-biphenyl-2-yl)-2-anthrayl]-N,9-diphenyl-9H-carbazole-3-amine (abbreviated as: 2PCABPhA), N-(9,10-diphenyl-2-anthrayl)-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviated as: 2DPAPA), N-[9,10-bis(1,1'-biphenyl-2-yl)-2-anthrayl]-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviated as: 2DPABPhA), 9,10-bis(1,1'-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), fluorene, 5,12-bis(1,1'-biphenyl-4-yl)-6,11-diphenyltetraphenyl (abbreviation: BPT), 2-(2-{2-[4-(dimethylamino)phenyl]vinyl}-6-methyl-4H-pyran-4-yl)malonitrile (abbreviation: DCM1), 2-{2-methyl-6-[2-(2,3,6,7-tetrahydro] -1H,5H-Benzo[ij]quinazine-9-yl)vinyl]-4H-pyran-4-ylidene}malonitrile (abbreviation: DCM2), N,N,N',N'-tetra(4-methylphenyl)tetraphenyl-5,11-diamine (abbreviation: p-mPhTD), 7,14-diphenyl-N,N,N',N'-tetra(4-methylphenyl)acenaphthene[1,2-a]propadiene-3,10-diamine (abbreviation: p-mPhAFD), 2-{2-isopropyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinazine-9-yl)vinyl]-4H-pyran-4-ylidene}malonitrile (Abbreviation: DCJTI), 2-{2-tert-butyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinazin-9-yl)vinyl]-4H-pyran-4-ylidene}malonium (Abbreviation: DCJTB), 2-(2,6-bis{2-[4-(dimethylamino)phenyl]vinyl}-4H-pyran-4-ylidene)malonium (Abbreviation: BisDCM), 2-{2,6-bis[2-(8-methoxy-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinazin-9-yl)vinyl]-4H-pyran-4-ylidene}malonium (Abbreviation: BisDCJTM), N,N'-(pyrene-1,6-diyl)bis[(6,N-diphenylbenzo[b]naphtho[1,2-d]furan)-8-amine] (Abbreviation: 1,6BnfAPrn-03), 3,10-bis[N-(9-phenyl-9H-carbazole-2-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (Abbreviation: 3,10PCA2Nbf(IV)-02), 3,10-bis[N-(dibenzofuran-3-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (Abbreviation: 3,10FrA2Nbf(IV)-02), etc. In particular, 1,6FLPAPrn, 1,6mMemFLPAPrn, 1,Fused aromatic diamine compounds, represented by pyrene diamine derivatives such as 6BnfAPrn-03, possess suitable hole-trapping properties and exhibit good luminescent efficiency and reliability, making them a superior choice.

[0085] In the light-emitting layer 113, when a phosphorescent material is used as the light-emitting center material, the following materials can be used as examples.

[0086] For example, materials such as tris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-κN2]phenyl-κC}iridium(III) (abbreviated as: [Ir(mpptz-dmp)3]), tris(5-methyl-3,4-diphenyl-4H-1,2,4-triazole)iridium(III) (abbreviated as: [Ir(Mptz)3]), and tris[4-(3-biphenyl)-5-isopropyl-3-phenyl-4H-1,2,4-triazole]iridium(III) (abbreviated as: [Ir(Mptz)3]) can be used. Organometallic iridium complexes with a 4H-triazole skeleton, such as [Ir(iPrptz-3b)3]; organometallic iridium complexes with a 1H-triazole skeleton, such as tris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazole]iridium(III) (abbreviated as [Ir(Mptz1-mp)3]) and tris(1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazole)iridium(III) (abbreviated as [Ir(Prptz1-Me)3]); fac-tris[1-(2,6-diisopropyl]iridium(III) Organometallic iridium complexes with an imidazole skeleton, such as [Ir(iPrpmi)3]iridium(III) (abbreviated as [Ir(iPrpmi)3] and [tris[3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-f]phenanthridinato]iridium(III) (abbreviated as [Ir(dmpimpt-Me)3]); and bis[2-(4',6'-difluorophenyl)pyridinium-N,C2']iridium(III)tetra(1-pyrazolyl)borate (abbreviated as FIr6), Organometallic iridium complexes with electron-withdrawing phenylpyridine derivatives as ligands, such as bis[2-(4',6'-difluorophenyl)pyridinium-N,C2']iridium(III)pyridinecarboxylate (FIrpic), bis{2-[3',5'-bis(trifluoromethyl)phenyl]pyridinium-N,C2'}iridium(III)pyridinecarboxylate ([Ir(CF3ppy)2(pic)]), and bis[2-(4',6'-difluorophenyl)pyridinium-N,C2']iridium(III)acetoacetone (FIr(acac)), are emitting blue phosphorescence and exhibiting a peak emission at 440 nm to 520 nm.

[0087] In addition, examples include: tris(4-methyl-6-phenylpyrimidine)iridium(III) (abbreviated as: [Ir(mppm)3]), tris(4-tert-butyl-6-phenylpyrimidine)iridium(III) (abbreviated as: [Ir(tBuppm)3]), (acetylacetone)bis(6-methyl-4-phenylpyrimidine)iridium(III) (abbreviated as: [Ir(mppm)2(acac)]), (acetylacetone)bis(6-tert-butyl-4-phenylpyrimidine)iridium(III) (abbreviated as: [Ir(tBuppm)2(acac)]), (acetylacetone)bis[6-(2-norkenyl)-4-phenylpyrimidine] Organometallic iridium complexes with a pyrimidine skeleton, such as iridium(III) (abbreviated as [Ir(nbppm)2(acac)]), (acetylacetone)bis[5-methyl-6-(2-methylphenyl)-4-phenylpyrimidine]iridium(III) (abbreviated as Ir(mpmppm)2(acac)), (acetylacetone)bis(4,6-diphenylpyrimidine)iridium(III) (abbreviated as [Ir(dppm)2(acac)]); (acetylacetone)bis(3,5-dimethyl-2-phenylpyrazine)iridium(III) (abbreviated as [Ir(mppr-Me)2(acac)]), (acetylacetone)bis(5-isopropyl)iridium(III) (abbreviated as [Ir(mppr-Me)2(acac)]), and (acetylacetone)bis(5-isopropyl)iridium(III) (abbreviated as [Ir(mppr-Me)2(acac)]). Organometallic iridium complexes with a pyrazine skeleton, such as tris(2-phenylpyridinium-N,C2')iridium(III)([Ir(mppr-iPr)2(acac)]), bis(2-phenylpyridinium-N,C2')iridium(III)acetone ([Ir(ppy)3]), bis(2-phenylpyridinium-N,C2')iridium(III)acetone ([Ir(ppy)2(acac)]), bis(benzo[h]quinoline)iridium(III)acetone ([Ir(bzq)2(acac)]), tris(benzo[h]quinoline)iridium(III)([Ir(bzq)3]), and tris(2-phenylpyridinium-N,C2')iridium(III)acetone ([Ir(bzq)3]), are also mentioned. Organometallic iridium complexes with a pyridine backbone, such as [Ir(pq)3]iridium(III) (abbreviated as [Ir(pq)3]) and [Ir(pq)2(acac)] bis(2-phenylquinoline-N,C2')iridium(III)acetophenone (abbreviated as [Ir(pq)2(acac)]), and rare earth metal complexes, such as [Tb(acac)3(Phen)] pyridine-based iridium(III) (abbreviated as [Tb(acac)3(Phen)]), are included. These substances are primarily compounds that emit green phosphorescence and exhibit an emission peak in the 500 nm to 600 nm range. Furthermore, organometallic iridium complexes with a pyrimidine backbone are particularly preferred due to their exceptionally high reliability and luminescence efficiency.

[0088] In addition, examples include: (diisobutylmethane)bis[4,6-bis(3-methylphenyl)pyrimidinyl]iridium(III) (abbreviated as: [Ir(5mdppm)2(dibm)]), and bis[4,6-bis(3-methylphenyl)pyrimidinyl)(dineopentylmethane)iridium(III) Organometallic iridium complexes with a pyrimidine skeleton, such as [Ir(5mdppm)2(dpm)], bis[4,6-di(naphthyl-1-yl)pyrimidinium](dineopentylmethane)iridium(III) (abbreviated as [Ir(d1npm)2(dpm)]); organometallic iridium complexes with a pyrazine skeleton, such as (acetyl acetone)bis(2,3,5-triphenylpyrazine)iridium(III) (abbreviated as [Ir(tppr)2(acac)]), bis(2,3,5-triphenylpyrazine)(dineopentylmethane)iridium(III) (abbreviated as [Ir(tppr)2(dpm)]), and (acetyl acetone)bis[2,3-bis(4-fluorophenyl)quinoline]iridium(III) (abbreviated as [Ir(Fdpq)2(acac)]); tri(1-phenylisoquinoline- Organometallic iridium complexes with a pyridine skeleton, such as N,C2')iridium(III) (abbreviated as [Ir(piq)3]) and bis(1-phenylisoquinoline-N,C2')iridium(III)acetophenone (abbreviated as [Ir(piq)2(acac)]); platinum complexes such as 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin platinum(II) (abbreviated as PtOEP); and rare earth metal complexes such as tris(1,3-diphenyl-1,3-propanedionato) (monoporphyrin) europium(III) (abbreviated as [Eu(DBM)3(Phen)]) and tris[1-(2-thiophenecarboxyl)-3,3,3-trifluoroacetophenone] (monoporphyrin) europium(III) (abbreviated as [Eu(TTA)3(Phen)]). The aforementioned substances are compounds that emit red phosphorescence and exhibit an emission peak in the 600 nm to 700 nm range. Additionally, organometallic iridium complexes with a pyrazine framework can produce red emission with good colorimetric properties.

[0089] In addition to the phosphorescent compounds mentioned above, known phosphorescent materials may also be used.

[0090] Fullerenes and their derivatives, acridines and their derivatives, and eosin derivatives can be used as TADF materials. In addition, metal porphyrins containing magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), or palladium (Pd) can also be used. Examples of metalloporphyrins include, for instance, protoporphyrin-tin fluoride complexes represented by the following structural formulas: protoporphyrin-tin fluoride complex (SnF2(Proto IX)), mesotoporphyrin-tin fluoride complex (SnF2(Meso IX)), hematoporphyrin-tin fluoride complex (SnF2(Hemato IX)), tetramethyl coprophyrin-tin fluoride complex (SnF2(Copro III-4Me), octaethylporphyrin-tin fluoride complex (SnF2(OEP)), protoporphyrin-tin fluoride complex (SnF2(Etio I)), and octaethylporphyrin-platinum chloride complex (PtCl2OEP).

[0091]

[0092] In addition, 2-(biphenyl-4-yl)-4,6-bis(12-phenylindol[2,3-a]carbazole-11-yl)-1,3,5-triazine (abbreviated as: PIC-TRZ), 9-(4,6-diphenyl-1,3,5-triazin-2-yl)-9'-phenyl-9H,9'H-3,3'-bicarbazole (abbreviated as: PCCzTzn), 2-{4-[3-(N-phenyl-9H-carbazole-3-yl)-9H-carbazole-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviated as: PCCzPTzn), 2-[4-(10H-phenanthroline-10-yl)phenyl]-4,6-diphenyl- Heterocyclic compounds such as 1,3,5-triazine (abbreviated as PXZ-TRZ), 3-[4-(5-phenyl-5,10-dihydrophenanthrene-10-yl)phenyl]-4,5-diphenyl-1,2,4-triazole (abbreviated as PPZ-3TPT), 3-(9,9-dimethyl-9H-acridin-10-yl)-9H-oxazanth-9-one (abbreviated as ACRXTN), bis[4-(9,9-dimethyl-9,10-dihydroacridin)phenyl]thiosulfate (abbreviated as DMAC-DPS), and 10-phenyl-10H,10'H-spiro[acridin-9,9'-anthracene]-10'-one (abbreviated as ACRSA) are heterocyclic compounds with one or both of π-electron-rich and π-electron-deficient heterocyclic rings. The heterocyclic compound possesses both π-electron-rich and π-electron-deficient heteroaromatic rings, exhibiting high electron transport and hole transport properties, thus it is preferred. In particular, among the skeletons possessing π-electron-deficient heteroaromatic rings, pyridine, diazine (pyrimidine, pyrazine, and triazine) skeletons are stable and reliable, thus they are preferred. Especially, benzofuran-pyrimidine, benzothiophene-pyrimidine, benzofuran-pyrazine, and benzothiophene-pyrazine skeletons exhibit high electron acceptability and good reliability, thus they are preferred. Furthermore, among the skeletons possessing π-electron-rich heteroaromatic rings, acridine, phenanthrene, phenanthrene-thiophene, furan, thiophene, and pyrrole skeletons are stable and reliable, thus having at least one of the aforementioned skeletons is preferred. Additionally, dibenzofuran skeletons are preferred as furan skeletons, and dibenzothiophene skeletons are preferred as thiophene skeletons. As the pyrrole skeleton, indole, carbazole, indole-carbazole, bicarbazole, and 3-(9-phenyl-9H-carbazole-3-yl)-9H-carbazole skeletons are particularly preferred. In substances where π-electron-rich and π-electron-deficient aromatic heterocycles are directly bonded, the electron-donating capacity of the π-electron-rich aromatic heterocycle and the electron-accepting capacity of the π-electron-deficient aromatic heterocycle are both high, and the energy difference between the S1 and T1 energy levels is smaller, resulting in highly efficient thermally activated delayed fluorescence, making it particularly preferred. Note that aromatic rings bonded with electron-withdrawing groups such as cyano groups can also be used instead of π-electron-deficient aromatic heterocycles.Furthermore, as π-electron-rich skeletons, aromatic amine skeletons, phenazine skeletons, etc., can be used. Conversely, as π-electron-deficient skeletons, xanthane skeletons, thioxanthene dioxide skeletons, diazole skeletons, triazole skeletons, imidazole skeletons, anthraquinone skeletons, boron-containing skeletons such as phenylborane or boranthrene, aromatic or heteroaromatic rings with nitrile or cyanobenzene groups, carbonyl skeletons such as benzophenone, phosphine oxide skeletons, uranium skeletons, etc., can be used. Thus, π-electron-deficient and π-electron-rich skeletons can be used to replace at least one of the π-electron-deficient and π-electron-rich heteroaromatic rings.

[0093]

[0094] TADF materials refer to materials with a small difference between the S1 and T1 energy levels and the ability to convert triple excitation energy into single excitation energy through antisystem crossing. Therefore, they can upconvert triple excitation energy into single excitation energy (antisystem crossing) with minimal thermal energy and efficiently generate single excited states. Furthermore, triple excitation energy can be converted into luminescence.

[0095] The exciplex formed by two substances in an excited state has the function of converting triple excitation energy into single excitation energy due to the extremely small difference between the S1 and T1 energy levels.

[0096] Note that the phosphorescence spectrum observed at low temperatures (e.g., 77K to 10K) can be used as an indicator of the T1 energy level. For TADF materials, it is preferable that the difference between S1 and T1 is 0.3 eV or less, more preferably 0.2 eV or less, when the wavelength energy of the extrapolated line obtained by drawing a tangent at the tail of the short-wavelength side of the fluorescence spectrum is taken as the S1 energy level and the wavelength energy of the extrapolated line obtained by drawing a tangent at the tail of the short-wavelength side of the phosphorescence spectrum is taken as the T1 energy level.

[0097] Furthermore, when using TADF material as the luminescent center material, the S1 energy level of the host material is preferably higher than that of the TADF material. Additionally, the T1 energy level of the host material is preferably higher than that of the TADF material.

[0098] As the main material of the light-emitting layer, various carrier transport materials such as materials with electron transport properties, materials with hole transport properties, and the aforementioned TADF material can be used.

[0099] As materials with hole transport properties, examples include: 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviated as: NPB), N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (abbreviated as: TPD), 4,4'-bis[N-(spiro-9,9'-bifuron-2-yl)-N-phenylamino]biphenyl (abbreviated as: BSPB), 4-phenyl-4'-(9-phenylfuron-9-yl)triphenylamine (abbreviated as: BPAFLP), 4-phenyl-3'-(9-phenylfuron-9-yl)triphenylamine (abbreviated as: mBPAFLP), 4-phenyl 4,4'-diphenyl-4”-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4'-diphenyl-4”-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBBi1BP), 4-(1-naphthyl)-4'-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBANB), 4,4'-di(1-naphthyl)-4”-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCCNBB), 9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]furo-2-amine (abbreviation: PCBAF) Compounds with an aromatic amine skeleton, such as N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9'-spirobis[9H-en]-2-amine (abbreviated as PCBASF); compounds with a carbazole skeleton, such as 1,3-bis(N-carbazolyl)benzene (abbreviated as mCP), 4,4'-bis(N-carbazolyl)biphenyl (abbreviated as CBP), 3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviated as CzTP), and 3,3'-bis(9-phenyl-9H-carbazole) (abbreviated as PCCP); and compounds with a carbazole skeleton, such as 4,4',4”-(benzene-1,3,5-triyl)tris(dibenzothiophene) (abbreviated as DBT). Compounds with a thiophene skeleton, such as 3P-II, 2,8-diphenyl-4-[4-(9-phenyl-9H-peroxy-9-yl)phenyl]dibenzothiophene (abbreviated: DBTFLP-III), and 4-[4-(9-phenyl-9H-peroxy-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviated: DBTFLP-IV); and compounds with a furan skeleton, such as 4,4',4”-(phenyl-1,3,5-triyl)tris(dibenzofuran) (abbreviated: DBF3P-II) and 4-{3-[3-(9-phenyl-9H-peroxy-9-yl)phenyl]phenyl}dibenzofuran (abbreviated: mmDBFFLBi-II). Among these, compounds with an aromatic amine skeleton and compounds with a carbazole skeleton are preferred due to their good reliability, high hole transport, and ability to reduce the driving voltage. Additionally, organic compounds exemplified as the second organic compound mentioned above can also be used.

[0100] For example, as materials with electron transport properties, examples include: bis(10-hydroxybenzo[h]quinoline)beryllium(II) (abbreviated as: BeBq2), bis(2-methyl-8-hydroxyquinoline)(4-phenylphenol)aluminum(III) (abbreviated as: BAlq), bis(8-hydroxyquinoline)zinc(II) (abbreviated as: Znq), bis[2-(2-benzothiazolyl)phenol]zinc(II) (abbreviated as: ZnPBO), bis[2-(2-benzothiazolyl)phenol]zinc(II) (abbreviated as: ZnBTZ), etc.; 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-diphenyl Triazole (abbreviated as PBD), 3-(4-biphenyl)-4-phenyl-5-(4-tertiary butylphenyl)-1,2,4-triazole (abbreviated as TAZ), 1,3-bis[5-(p-tertiary butylphenyl)-1,3,4-diazol-2-yl]phenyl (abbreviated as OXD-7), 9-[4-(5-phenyl-1,3,4-diazol-2-yl)phenyl]-9H-carbazole (abbreviated as CO11), 2,2',2”-(1,3,5-phenyltriyl)tris(1-phenyl-1H-benzimidazole) (abbreviated as TPBI), 2-[3-(dibenzothiophene-4-yl)phenyl]-1-phenyl-1H-benzimidazole (abbreviated as PBD) Heterocyclic compounds with a polyazole skeleton, such as mDBTBIm-II; 2-[3-(dibenzothiophene-4-yl)phenyl]dibenzo[f,h]quinoline (abbreviation: 2mDBTPDBq-II), 2-[3'-(dibenzothiophene-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoline (abbreviation: 2mDBTBPDBq-II), 2-[3'-(9H-carbazol-9-yl)biphenyl-3-yl]dibenzo[f,h]quinoline (abbreviation: 2mCzBPDBq), 4,6-bis[3-(phenanthrene-9-yl)phenyl]pyrimidine (abbreviation: 4,6mPnP2Pm), 4,6-bis[3- Heterocyclic compounds with a diazine skeleton, such as (4-dibenzothienyl)phenyl]pyrimidine (abbreviated as 4,6mDBTP2Pm-II); and heterocyclic compounds with a pyridine skeleton, such as 3,5-bis[3-(9H-carbazole-9-yl)phenyl]pyridine (abbreviated as 35DCzPPy) and 1,3,5-tris[3-(3-pyridyl)-phenyl]benzene (abbreviated as TmPyPB). Among these, heterocyclic compounds with a diazine skeleton or heterocyclic compounds with a pyridine skeleton are preferred due to their good reliability. In particular, heterocyclic compounds with a diazine (pyrimidine or pyrazine) skeleton have high electron transport properties, which also helps to reduce the driving voltage.

[0101] The same material as described above can be used as the TADF material that can be used as the host material. When the TADF material is used as the host material, the triple excitation energy generated by the TADF material is converted into a single excitation energy via antisystem crosstalk and further transferred to the luminescent center material, thereby improving the luminous efficiency of the light-emitting device. In this case, the TADF material is used as an energy donor and the luminescent center material is used as an energy acceptor.

[0102] This is very effective when the aforementioned luminescent center material is a fluorescent material. Furthermore, in order to obtain high luminescence efficiency, the S1 energy level of the TADF material is preferably higher than the S1 energy level of the fluorescent material. Additionally, the T1 energy level of the TADF material is preferably higher than the S1 energy level of the fluorescent material. Therefore, the T1 energy level of the TADF material is preferably higher than the T1 energy level of the fluorescent material.

[0103] Furthermore, it is preferable to use a TADF material that emits light at a wavelength that overlaps with the absorption band on the lowest energy side of the fluorescent material. This allows for efficient transfer of excitation energy from the TADF material to the fluorescent material, resulting in highly efficient light emission, which is therefore preferable.

[0104] In order to efficiently generate a single excitation energy from a triple excitation energy via anti-system jumps, it is preferable to generate carrier recombination in the TADF material. Furthermore, it is preferable that the triple excitation energy generated in the TADF material does not transfer to the fluorescent luminescent material. For this purpose, the fluorescent luminescent material preferably has a protecting group around the luminescent body (the skeleton that causes luminescence) of the fluorescent luminescent material. As this protecting group, it is preferable to be a substituent without π bonds, preferably a saturated hydrocarbon; specifically, examples include alkyl groups with 3 or more but less than 10 carbon atoms, substituted or unsubstituted cycloalkyl groups with 3 or more but less than 10 carbon atoms, and trialkylsilyl groups with 3 or more but less than 10 carbon atoms; more preferably, it has multiple protecting groups. Substituents without π bonds have almost no carrier transport function, so they have almost no effect on carrier transport or carrier recombination, and can keep the luminescent body of the TADF material and the fluorescent luminescent material far apart. Here, the luminescent body refers to the atomic group (skeleton) that causes luminescence in the fluorescent luminescent material. The luminescent material preferably has a π-bonded framework, preferably contains an aromatic ring, and preferably has a fused aromatic ring or a fused heteroaromatic ring. Examples of fused aromatic rings or fused heteroaromatic rings include phenanthrene frameworks, stilbene frameworks, acridinone frameworks, phenanthrene-acridinone frameworks, and phenanthrene-thiacridinone frameworks. In particular, fluorescent materials having naphthalene frameworks, anthracene frameworks, benzo[a]ene frameworks, benzo[b]ene frameworks, triphenylene frameworks, fused tetraphenylene frameworks, pyrene frameworks, perylene frameworks, coumarin frameworks, quinacridone frameworks, and naphthobisbenzofuran frameworks are preferred due to their high fluorescence quantum yield.

[0105] When using a fluorescent luminescent material as the luminescent center material, it is preferable to use a material with an anthracene framework as the host material. By using a material with an anthracene framework as the host material of the fluorescent luminescent material, a luminescent layer with good luminescence efficiency and durability can be achieved. Among the anthracene framework materials used as host materials, those with a diphenylanthracene framework (especially 9,10-diphenylanthracene framework) are chemically stable and therefore preferred. In addition, when the host material has a carbazole framework, the hole injection / transportation is improved, which is also preferred. In particular, when the host material contains a benzo[a]carbazole framework containing a benzene ring fused to a carbazole, its HOMO level is about 0.1 eV shallower than that of carbazole, making hole injection easier, which is even better. In particular, when the host material has a dibenzo[a]carbazole framework, its HOMO level is about 0.1 eV shallower than that of carbazole, which not only makes hole injection easier but also improves hole transport and heat resistance, which is also preferred. Therefore, it is further preferred that the material used as the host material be a material having a 9,10-diphenylanthracene skeleton and a carbazole skeleton (or a benzo[a]carbazole skeleton or a dibenzo[a]carbazole skeleton). Note that from the viewpoint of the aforementioned hole injection / transportation, a benzo[a]carbazole skeleton or a dibenzo[a]carbazole skeleton can also be used instead of a carbazole skeleton. Examples of such materials include 9-phenyl-3-[4-(10-phenyl-9-anthrayl)phenyl]-9H-carbazole (abbreviated as PCzPA), 3-[4-(1-naphthyl)-phenyl]-9-phenyl-9H-carbazole (abbreviated as PCPN), 9-[4-(10-phenylanthracene-9-yl)phenyl]-9H-carbazole (abbreviated as CzPA), and 7-[4-(10-phenyl-9-anthrayl)phenyl]-7H-dibenzo[c,g] Carbazole (abbreviated as cgDBCzPA), 6-[3-(9,10-diphenyl-2-anthrayl)phenyl]-benzo[b]naphtho[1,2-d]furan (abbreviated as 2mBnfPPA), 9-phenyl-10-{4-(9-phenyl-9H-en-9-yl)-biphenyl-4'-yl}-anthracene (abbreviated as FLPPA), 9-(1-naphthyl)-10-[4-(2-naphthyl)phenyl]anthracene (abbreviated as αN-βNPAnth), etc. In particular, CzPA, cgDBCzPA, 2mBnfPPA, and PCzPA exhibit very good properties and are therefore preferred.

[0106] Alternatively, the host material can be a mixture of multiple substances. When using a mixed host material, it is preferable to mix a material with electron transport properties and a material with hole transport properties. By mixing a material with electron transport properties and a material with hole transport properties, it is easier to adjust the transport properties of the light-emitting layer 113 and to more easily control the rebinding region. The weight ratio of the material with hole transport properties to the material with electron transport properties can be 1:19 to 19:1.

[0107] Note that phosphorescent materials can be used as part of the above-described mixture. When phosphorescent materials are used as luminescent center materials in conjunction with fluorescent materials, they can be used as energy donors to supply excitation energy to the fluorescent materials.

[0108] Alternatively, these mixed materials can be used to form excited-state complexes. By selecting the mixed materials in a way that forms an excited-state complex with wavelengths overlapping the absorption bands on the lowest energy side of the emitting and luminescent materials, energy transfer can be facilitated, thereby achieving efficient luminescence, which is preferable. In addition, by adopting this structure, the driving voltage can be reduced, which is also preferable.

[0109] Note that at least one of the materials forming the excited-state complex can be a phosphorescent material. Thus, the triple excitation energy can be efficiently converted into a single excitation energy via antisystem crossing.

[0110] Regarding the combination of materials that efficiently form excited-state complexes, the HOMO level of the material with hole transport is preferably higher than that of the material with electron transport. Furthermore, the LUMO level of the material with hole transport is preferably higher than that of the material with electron transport. Note that the LUMO and HOMO levels of the material can be determined from the electrochemical properties (reduction potential and oxidation potential) of the material measured by cyclic voltammetry (CV).

[0111] Note that the formation of excited-state complexes can be confirmed, for example, by comparing the emission spectra of materials with hole transport properties, materials with electron transport properties, and the emission spectra of a mixed film formed by mixing these materials. When the emission spectrum of the mixed film is observed to shift towards a longer wavelength side (or to have a new peak on the longer wavelength side) compared to the emission spectra of each material, it indicates the formation of excited-state complexes. Alternatively, by comparing the transient photoluminescence (PL) of materials with hole transport properties, the transient PL of materials with electron transport properties, and the transient PL of a mixed film formed by mixing these materials, when a difference in transient response is observed, such as the transient PL lifetime of the mixed film having a longer lifetime component or a larger ratio of delayed components compared to the transient PL lifetimes of each material, it indicates the formation of excited-state complexes. Furthermore, the aforementioned transient PL can be referred to as transient electroluminescence (EL). In other words, by comparing the transient EL of materials with hole transport properties, the transient EL of materials with electron transport properties, and the transient EL of a mixed film of these materials, and observing the differences in transient responses, the formation of excited-state complexes can be confirmed.

[0112] The electron transport layer 114 is disposed in contact with the light-emitting layer 113. Furthermore, the electron transport layer 114 has electron transport properties and includes a seventh organic compound with a HOMO energy level of -6.0 eV or higher. The seventh organic compound is an organic compound with electron transport properties, preferably containing an anthracene framework. Additionally, the electron transport layer 114 may also include an eighth organic compound, which is an organic complex of an alkali metal or alkaline earth metal. That is, the electron transport layer 114 may be composed solely of the seventh organic compound, or it may be composed of a mixture of the seventh organic compound and other substances, such as a mixture of the seventh and eighth organic compounds.

[0113] Furthermore, more preferably, the aforementioned seventh organic compound comprises an anthracene skeleton and a heterocyclic skeleton, wherein the heterocyclic skeleton is preferably a nitrogen-containing five-membered ring skeleton. As a nitrogen-containing five-membered ring skeleton, it is particularly preferred to contain a nitrogen-containing five-membered ring skeleton containing two heteroatoms in the ring, such as a pyrazole ring, imidazole ring, thiazole ring, or pyrazolium ring.

[0114] As other organic compounds with electron transport properties that can be used as the seventh organic compound, organic compounds with electron transport properties that can be used in the above-mentioned host material or organic compounds that can be used in the host material of the above-mentioned fluorescent luminescent material can be used.

[0115] In addition, as the above-mentioned organic complex of alkali metal or alkaline earth metal, it is preferred to use an organic complex of lithium, especially lithium 8-hydroxyquinoline (abbreviated as: Liq).

[0116] In addition, it is preferable that the material constituting the electron transport layer 114 has an electron mobility of 1×10-7 cm2 / Vs or more and 5×10-5 cm2 / Vs or less when the square root of the electric field strength [V / cm] is 600.

[0117] Furthermore, it is preferable that the electron mobility of the material constituting the electron transport layer 114 at the square root of the electric field strength [V / cm] of 600 is lower than that of the sixth organic compound or the material constituting the light-emitting layer 113 at the square root of the electric field strength [V / cm] of 600. By reducing the electron transport properties in the electron transport layer, the amount of electrons injected into the light-emitting layer can be controlled, thereby preventing the light-emitting layer from becoming an electron-overloaded state.

[0118] When the light-emitting layer becomes overloaded with electrons, as shown in FIG3A, the light-emitting region 120 is confined to a portion of the region, increasing the burden on that portion and accelerating degradation. Furthermore, the inability of electrons to recombine and pass through the light-emitting layer also leads to a decrease in lifetime and luminous efficiency. In one embodiment of the present invention, by reducing the electron transport properties in the electron transport layer 114, as shown in FIG3B, the light-emitting region 120 can be widened to distribute the burden on the material constituting the light-emitting layer 113, thereby providing a light-emitting device with long lifetime and good luminous efficiency.

[0119] Furthermore, in light-emitting devices having the above-described structure, the brightness degradation curve obtained by driving tests under constant current density conditions sometimes exhibits a shape with a maximum value. That is, the degradation curve of the light-emitting device used in one embodiment of the present invention sometimes has a shape with a brightness increase over time. The light-emitting device exhibiting this degradation behavior can use this brightness increase to offset the rapid degradation in the early stages of driving (i.e., the so-called initial degradation), thereby realizing a light-emitting device with small initial degradation and very good driving life.

[0120] Note that when taking the derivative of such a degradation curve with a maximum value, there exists a part where the value is 0. In other words, the light-emitting device of an embodiment of the present invention, in which the derivative of the degradation curve has a part of 0, can be a light-emitting device with small initial degradation and very long life.

[0121] Furthermore, as shown in FIG4A, this phenomenon can be considered to be caused by the non-luminescent recombination occurring in the non-luminescent recombination region 121. In the light-emitting device of the present invention having the above structure, during the initial driving stage, due to the small hole injection barrier and the low electron transport of the electron transport layer 114, the luminescent region 120 (i.e., the recombination region) is formed close to the electron transport layer 114. In addition, since the HOMO energy level of the seventh organic compound in the electron transport layer 114 is relatively high (-6.0 eV or above), some holes reach the electron transport layer 114 and recombine in the electron transport layer 114, thereby forming the non-luminescent recombination region 121. Note that this phenomenon may also occur when the difference between the HOMO energy levels of the sixth and seventh organic compounds is within 0.2 eV.

[0122] Here, as the driving time progresses, the balance of carriers changes, and as shown in FIG4B, the light-emitting region 120 (recombination region) gradually moves towards the hole transport layer 112. Since the non-light-emitting recombination region 121 decreases, the energy of the recombined carriers can be effectively used for light emission, resulting in an increase in brightness compared to the initial driving stage. This increase in brightness offsets the sharp decrease in brightness that occurs in the initial driving stage of the light-emitting device (i.e., the so-called initial degradation), thereby providing a light-emitting device with low initial degradation and a long driving lifetime. Furthermore, in this specification, the above-described light-emitting device is sometimes referred to as a Recombination-Site Tailoring Injection structure (ReSTI structure).

[0123] In addition, since initial degradation can be suppressed, the burn-in problem, one of the major drawbacks of organic EL devices, can be greatly reduced, as well as the time and labor required for the aging process before shipment to reduce this problem.

[0124] Furthermore, the aforementioned increase in brightness is particularly noticeable when a region is formed within the electron transport layer where the mixing ratio of the electron-transporting organic compound and the electron-donating substance changes. In other words, the electron transport layer 114 is formed such that the concentration of the electron-donating substance increases from the second electrode side to the first electrode. As a structure capable of achieving this configuration, examples include structures with a concentration gradient, or stacked structures of multiple layers with different mixing ratios of the electron-transporting organic compound and the electron-donating substance.

[0125] Figures 22A to 22D illustrate the concentration of the electron-donating substance in the electron transport layer 114. Figures 22A and 22B show a schematic diagram of a continuous change in the concentration of the electron-donating substance, while Figures 22C and 22D show a schematic diagram of a stepwise change in the concentration of the electron-donating substance. Furthermore, Figures 22A and 22B show a structure where the electron transport layer 114 has a concentration gradient within a single layer, Figure 22C shows a structure where the electron transport layer 114 is a two-layer stacked structure with concentration gradients in each of the two layers, and Figure 22D shows a structure where the electron transport layer 114 is a three-layer stacked structure with concentration gradients in each of the three layers.

[0126] As shown in Figures 22A to 22D, a high concentration of electron-supplying material on the anode side (i.e., the light-emitting layer 113 side) of the electron transport layer 114 can suppress initial degradation, which is preferable. However, the light-emitting device of one embodiment of the present invention is not limited to this, and the concentration of electron-supplying material on the anode side, i.e., the light-emitting layer 113 side, can also be lower.

[0127] The light-emitting device of a light-emitting device for one embodiment of the present invention having the structure as described above can be a light-emitting device with a long lifespan.

[0128] Next, examples of other structures and materials in the light-emitting device described above will be described. As described above, the light-emitting device of the light-emitting apparatus used in one embodiment of the present invention includes an EL layer 103 composed of multiple layers between the first electrode 101 and the second electrode 102, and the EL layer 103 includes a hole injection layer 111, a first hole transport layer 112-1, a second hole transport layer 112-2, a light-emitting layer 113, and an electron transport layer 114 from the first electrode 101 side.

[0129] There are no special restrictions on the layers other than those mentioned above in the EL layer 103. Various layer structures such as hole injection layer, hole transport layer, electron transport layer, electron injection layer, carrier barrier layer, exciton barrier layer, and charge generation layer can be adopted.

[0130] The first electrode 101 is preferably formed using a metal, alloy, conductive compound, or mixture thereof with a high work function (specifically 4.0 eV or higher). Specifically, examples include indium tin oxide (ITO), indium tin oxide containing silicon or silicon oxide, indium zinc oxide, and indium oxide (IWZO) containing tungsten oxide and zinc oxide. While these conductive metal oxide films are typically formed by sputtering, they can also be formed using sol-gel methods. Examples of formation methods include sputtering a method using a target containing 1 wt% to 20 wt% zinc oxide to form indium oxide. Alternatively, sputtering can be used to form indium oxide (IWZO) containing tungsten oxide and zinc oxide using a target containing 0.5 wt% to 5 wt% tungsten oxide and 0.1 wt% to 1 wt% zinc oxide to form indium oxide. Additionally, examples include nitrides of gold (Au), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), or metallic materials (e.g., titanium nitride). Graphene can also be used. Note that while materials with high work functions and typically used to form anodes are mentioned here, in one embodiment of the invention, a composite material comprising an organic compound with hole transport properties and a substance exhibiting electron acceptability of that organic compound is used as the hole injection layer 111. Therefore, the work function can be disregarded when selecting the electrode material.

[0131] In this embodiment, as the stacked structure of the EL layer 103, the following two structures will be described: As shown in FIG2A, a structure including a hole injection layer 111, a first hole transport layer 112-1, a second hole transport layer 112-2, a light-emitting layer 113, an electron transport layer 114, and an electron injection layer 115 is adopted; As shown in FIG2B, a structure including a hole injection layer 111, a first hole transport layer 112-1, a second hole transport layer 112-2, a light-emitting layer 113, an electron transport layer 114, and a charge generation layer 116 is adopted. The materials constituting each layer are shown in detail below.

[0132] Since the hole injection layer 111, hole transport layer 112 (first hole transport layer 112-1, second hole transport layer 112-2), luminescent layer 113 and electron transport layer 114 have been described above, repeated descriptions are omitted. Refer to the previous description.

[0133] An electron injection layer 115, formed of an alkali metal, alkaline earth metal, or a compound thereof, such as lithium fluoride (LiF), cesium fluoride (CsF), or calcium fluoride (CaF2), may be provided between the electron transport layer 114 and the second electrode 102. The electron injection layer 115 may be a layer or an electron compound in which an alkali metal, alkaline earth metal, or a compound thereof is contained in a layer composed of a substance with electron transport properties. Examples of electron compounds include, for instance, a mixture of calcium and aluminum oxides to which electrons are added at a high concentration.

[0134] Alternatively, a charge generation layer 116 can be provided between the electron transport layer 114 and the second electrode 102, instead of the electron injection layer 115 (FIG. 2B). The charge generation layer 116 is a layer that, by applying a potential, can inject holes into the layer in contact with the cathode side of the layer and inject electrons into the layer in contact with the anode side of the layer. The charge generation layer 116 includes at least a P-type layer 117. The P-type layer 117 is preferably formed using the composite material that constitutes the hole injection layer 111 described above. Alternatively, the P-type layer 117 can also be formed by laminating a film containing the electron-accepting material and a film containing a hole transport material as the composite material. By applying a potential to the P-type layer 117, electrons and holes are injected into the electron transport layer 114 and the second electrode 102, which serves as the cathode, respectively, causing the light-emitting device to operate.

[0135] In addition, the charge generation layer 116 preferably includes one or two of the electron relay layer 118 and the electron injection buffer layer 119, in addition to the P-type layer 117.

[0136] The electron relay layer 118 contains at least an electron transport material and is capable of preventing the interaction between the electron injection buffer layer 119 and the p-type layer 117, and smoothly transferring electrons. Preferably, the LUMO energy level of the electron transport material contained in the electron relay layer 118 is set between the LUMO energy level of the electron acceptor material in the p-type layer 117 and the LUMO energy level of the material contained in the layer in the electron transport layer 114 that is in contact with the charge generation layer 116. Specifically, the LUMO energy level of the electron transport material 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. In addition, the electron transport material in the electron relay layer 118 is preferably a phthalocyanine material or a metal complex having metal-oxygen bonds and aromatic ligands.

[0137] The electron injection buffer layer 119 can use alkali metals, alkaline earth metals, rare earth metals and compounds of these substances (alkali metal compounds (including oxides such as lithium oxide, halides, carbonates such as lithium carbonate or cesium carbonate), alkaline earth metal compounds (including oxides, halides, carbonates) or rare earth metal compounds (including oxides, halides, carbonates)) and other substances with high electron injection properties.

[0138] Furthermore, when the electron injection buffer layer 119 contains an electron transport material and an electron donor material, the electron donor material can be alkali metals, alkaline earth metals, rare earth metals, and compounds of these materials (alkali metal compounds (including oxides such as lithium oxide, halides, carbonates such as lithium carbonate or cesium carbonate), alkaline earth metal compounds (including oxides, halides, and carbonates), or rare earth metal compounds (including oxides, halides, and carbonates)). Organic compounds such as tetrathianaphthacene (TTN), nickel dicene, and decamethylnickel dicene can also be used. Additionally, the electron transport material can be formed using the same material described above for the electron transport layer 114.

[0139] As the material forming the second electrode 102, metals, alloys, conductive compounds, and mixtures thereof with a low work function (specifically 3.8 eV or less) can be used. Specific examples of such cathode materials include alkali metals such as lithium (Li) or cesium (Cs), elements belonging to Group 1 or Group 2 of the periodic table such as magnesium (Mg), calcium (Ca), or strontium (Sr), alloys containing them (MgAg, AlLi), rare earth metals such as europium (Eu) and ytterbium (Yb), and alloys containing them. However, by providing an electron injection layer between the second electrode 102 and the electron transport layer, various conductive materials such as Al, Ag, ITO, and indium oxide-tin oxide containing silicon or silicon oxide can be used as the second electrode 102 regardless of the work function.

[0140] These conductive materials can be formed by dry processing methods such as vacuum evaporation and sputtering, inkjet printing, and spin coating. In addition, electrodes can be formed by wet processing methods such as sol-gel or by wet processing of metal materials in the form of a paste.

[0141] In addition, various methods can be used as the method for forming the EL layer 103, whether dry or wet processing. For example, vacuum evaporation, gravure printing, photogravure printing, screen printing, inkjet printing, or spin coating can also be used.

[0142] Alternatively, the electrodes or layers described above can be formed by using different film-forming methods.

[0143] Note that the structure of the layer disposed between the first electrode 101 and the second electrode 102 is not limited to the structure described above. However, it is preferable to adopt a structure in which a light-emitting region for the recombination of holes and electrons is disposed in a portion far from the first electrode 101 and the second electrode 102, so as to suppress quenching that occurs due to the proximity of the light-emitting region to the metal used for the electrode or carrier injection layer.

[0144] In addition, in order to suppress energy transfer from excitons generated in the light-emitting layer, the hole transport layer and electron transport layer in contact with the light-emitting layer 113, especially the carrier transport layer near the recombination region in the light-emitting layer 113, are preferably made of a material that has a band gap larger than that of the light-emitting material constituting the light-emitting layer or the light-emitting material contained in the light-emitting layer.

[0145] Next, a light-emitting device (hereinafter also referred to as a stacked element or series element) having a structure with multiple light-emitting units stacked will be described with reference to FIG2C. This light-emitting device has multiple light-emitting units between the anode and the cathode. One light-emitting unit has a structure substantially the same as that of the EL layer 103 shown in FIG2A. That is to say, it can be said that the light-emitting device shown in FIG2C is a light-emitting device with multiple light-emitting units, while the light-emitting device shown in FIG2A or FIG2B is a light-emitting device with one light-emitting unit.

[0146] In FIG. 2C, a first light-emitting unit 161 and a second light-emitting unit 162 are stacked between the first electrode 151 and the second electrode 152, and a charge-generating layer 163 is disposed between the first light-emitting unit 161 and the second light-emitting unit 162. The first electrode 151 and the second electrode 152 are respectively equivalent to the first electrode 101 and the second electrode 102 in FIG. 2A, and the same materials as described in FIG. 2A can be used. In addition, the first light-emitting unit 161 and the second light-emitting unit 162 can have the same structure or different structures.

[0147] The charge generation layer 163 has the function of injecting electrons into one light-emitting unit and injecting holes into the other light-emitting unit when a voltage is applied to the first electrode 151 and the second electrode 152. That is, in FIG2C, when a voltage is applied in such a way that the potential of the anode is higher than that of the cathode, the charge generation layer 163 only needs to be a layer that injects electrons into the first light-emitting unit 161 and injects holes into the second light-emitting unit 162.

[0148] The charge generation layer 163 preferably has the same structure as the charge generation layer 116 shown in FIG. 2B. Because the composite material of organic compound and metal oxide has good carrier injection and carrier transport properties, low voltage drive and low current drive can be achieved. Note that when the surface of the light-emitting unit on the anode side is in contact with the charge generation layer 163, the charge generation layer 163 can function as the hole injection layer of the light-emitting unit, so the hole injection layer may not be provided in the light-emitting unit.

[0149] In addition, when an electron injection buffer layer 119 is provided in the charge generation layer 163, since the electron injection buffer layer 119 has the function of an electron injection layer in the light-emitting unit on the anode side, it is not necessary to provide an electron injection layer in the light-emitting unit on the anode side.

[0150] Although a light-emitting device with two light-emitting units is illustrated in FIG2C, a similar light-emitting device with three or more light-emitting units stacked can be applied. As shown in FIG2C, by separating and arranging multiple light-emitting units between a pair of electrodes using a charge-generating layer 163, this device can achieve high brightness emission while maintaining low current density and can achieve a long lifespan. In addition, a light-emitting device capable of low-voltage driving and low power consumption can be realized.

[0151] Similar to FIG. 2C, FIG. 21 shows a schematic diagram of a light-emitting device according to one embodiment of the present invention when using a light-emitting device having multiple light-emitting units. A first electrode 151 is formed on a substrate 100, and a first light-emitting unit 161 including a first light-emitting layer 113-1 and a second light-emitting unit 162 including a second light-emitting layer 113-2 are stacked across a charge-generating layer 163. The light emitted by the light-emitting device is emitted directly or through a color conversion layer 205. In addition, color purity can be improved by using color filters 225R, 225G, and 225B. Note that although FIG. 21 shows a structure with a color filter 225B, it is not limited thereto. For example, an outer coating layer can be used instead of the structure with a color filter 225B shown in FIG. 21. The outer coating layer is preferably made of an organic resin material, such as an acrylic resin or a polyimide resin. Note that in this specification, the color filter layer is sometimes referred to as a color layer and the outer coating layer is sometimes referred to as a resin layer. Therefore, color filter 225R can also be called the first color layer, and color filter 225G can be called the second color layer.

[0152] Furthermore, the aforementioned EL layer 103, first light-emitting unit 161, second light-emitting unit 162, charge-generating layer, and electrodes can be formed using methods such as vapor deposition (including vacuum vapor deposition), droplet jetting (also known as inkjet printing), coating, and gravure printing. Additionally, they may contain low-molecular-weight materials, medium-molecular-weight materials (including oligomers and dendritic polymers), or high-molecular-weight materials.

[0153] Here, when considering the color reproduction of a full-color display, it is important to obtain light with high color purity in order to display a richer color gamut. Compared with light emission from inorganic compounds, light emission from organic compounds often has a wider spectrum. Therefore, in order to obtain light emission with sufficiently high color purity, it is preferable to use a microcavity structure to narrow the spectrum.

[0154] In fact, by using appropriate dopants and having appropriate microcavity structures, light-emitting devices can achieve blue light emission that conforms to the previously described BT.2020 standard. At this time, by making the microcavity structure of the light-emitting device a structure that enhances blue light, a high-efficiency light-emitting device with high color purity can be formed.

[0155] A light-emitting device with a microcavity structure is obtained by forming a pair of electrodes consisting of a reflective electrode and a semi-transparent and semi-reflective electrode. The reflective electrode and the semi-transparent and semi-reflective electrode are equivalent to the first electrode 101 and the second electrode 102 described above, one being a reflective electrode and the other being a semi-transparent and semi-reflective electrode.

[0156] A light-emitting device with a microcavity structure amplifies light of a certain wavelength or makes the light directional by resonating the light emitted from the light-emitting layer included in the EL layer in all directions by reflecting the light emitted by the reflective electrode and the semi-transmitting and semi-reflective electrode.

[0157] The reflectivity of the reflective electrode to visible light is 40% to 100%, preferably 70% to 100%, and its resistivity is 1×10⁻² Ωcm or less. Examples of materials forming the reflective electrode include aluminum (Al) or alloys containing Al. Examples of alloys containing Al include alloys containing Al and L (L represents one or more of titanium (Ti), neodymium (Nd), nickel (Ni), and lanthanum (La), such as alloys containing Al and Ti or alloys containing Al, Ni, and La. Aluminum has low resistivity and high light reflectivity. Furthermore, since aluminum is abundant in the Earth's crust and inexpensive, using aluminum can reduce the manufacturing cost of light-emitting devices. In addition, alloys containing silver (Ag), or alloys containing one or more of Ag, N (N representing yttrium (Y), Nd, magnesium (Mg), ytterbium (Yb), Al, Ti, gallium (Ga), zinc (Zn), indium (In), tungsten (W), manganese (Mn), tin (Sn), iron (Fe), Ni, copper (Cu), palladium (Pd), iridium (Ir), and gold (Au) can also be used. Examples of silver-containing alloys include: alloys containing silver, palladium, and copper; alloys containing silver and copper; alloys containing silver and magnesium; alloys containing silver and nickel; alloys containing silver and gold; and alloys containing silver and ytterbium. Besides the materials mentioned above, transition metals such as tungsten, chromium (Cr), molybdenum (Mo), copper, and titanium can also be used.

[0158] Alternatively, a transparent electrode layer can be formed between the reflective electrode and the EL layer 103 as an optical path length adjustment layer, using a transparent electrode layer and both layers (reflective electrode and transparent electrode layer) as the first electrode 101. The optical path length (cavity length) of the microcavity structure can also be adjusted by using a transparent electrode layer. For example, indium tin oxide (ITO), indium tin oxide containing silicon or silicon oxide (ITSO), indium zinc oxide, indium tin oxide containing titanium, indium titanium oxide, and indium oxide containing tungsten oxide and zinc oxide can be used.

[0159] The visible light reflectance of the semi-transmissive and semi-reflective electrode is 20% to 80%, preferably 40% to 70%, and its resistivity is 1×10⁻² Ωcm or less. The semi-transmissive and semi-reflective electrode can be formed using one or more conductive metals, conductive alloys, and conductive compounds. Specifically, for example, indium tin oxide (ITO), indium tin oxide containing silicon or silicon oxide (ITSO), indium zinc oxide, indium tin oxide containing titanium, indium titanium oxide, indium oxide containing tungsten oxide and zinc oxide, and other metal oxides can be used. In addition, a metal film with a thickness (preferably 1 nm or more and 30 nm or less) that allows light to pass through can be used. As the metal, alloys of Ag, Ag and Al, Ag and Mg, Ag and Au, and Ag and Yb can be used, for example.

[0160] The reflective electrode and the semi-transmitting / semi-reflective electrode can be either the first electrode 101 or the second electrode 102. Alternatively, they can be either the anode or the cathode.

[0161] Note that when the light-emitting device has a top-emitting structure, the light extraction efficiency can be improved by providing an organic capping layer on the side of the second electrode 102 opposite to the surface in contact with the EL layer 103. By providing an organic capping layer, the refractive index difference between the electrode and the air interface can be reduced, thereby improving the light extraction efficiency. The thickness of the organic capping layer is preferably 5 nm or more and 120 nm or less. More preferably, it is 30 nm or more and 90 nm or less. In addition, the organic capping layer can be an organic compound layer with a molecular weight of 300 or more and 1200 or less. Furthermore, it is preferable to use a conductive organic material. The transmissive and semi-reflective electrode needs to be thin to maintain a certain level of light transmittance, but a thin film can sometimes lead to a decrease in conductivity. Here, by using a conductive material as the organic capping layer, conductivity can be ensured while improving the light extraction efficiency, thereby improving the yield of the light-emitting device manufacturing. In addition, it is preferable to use an organic compound that absorbs less light in the visible light region. The organic capping layer can be an organic compound that can be used in the EL layer 103. In this case, since an organic capping layer can be easily formed in the film-forming apparatus or film-forming chamber that forms the EL layer 103, the organic capping layer can be easily formed.

[0162] This light-emitting device changes the optical path (cavity length) between the reflective electrode and the semi-transparent / semi-reflective electrode by changing the thickness of the carrier transport layers, such as the transparent electrode, hole injection layer, and hole transport layer, which are disposed in contact with the reflective electrode. As a result, light of the resonant wavelength can be enhanced and light of the non-resonant wavelength can be attenuated between the reflective electrode and the semi-transparent / semi-reflective electrode.

[0163] In addition, as a microcavity structure, when the wavelength to be amplified is λnm, it is preferable that the optical distance (optical path length) between the interface on the EL layer side of the reflective electrode and the interface on the EL layer side of the semi-transparent and semi-reflective electrode is an integer multiple of λ / 2.

[0164] Furthermore, the light reflected back by the reflecting electrode during emission (the first reflected light) will cause significant interference to the light directly incident from the emissive layer to the semi-transmissive and semi-reflective electrode (the first incident light). Therefore, it is preferable to adjust the optical path between the reflecting electrode and the emissive layer to (2n-1)λ / 4 (note that n is a natural number greater than 1, and λ is the wavelength of the light to be amplified). By adjusting this optical path, the phase of the first reflected light and the first incident light can be made to match, thereby further amplifying the light emitted from the emissive layer.

[0165] By employing a microcavity structure, the luminescence intensity in the front direction at a specified wavelength can be enhanced, thereby achieving low power consumption. In addition, the probability of light entering the color conversion layer can be increased.

[0166] It is known that light narrowed by a microcavity structure has strong directionality in the vertical direction of the screen. However, light passing through the color conversion layer of the aforementioned QD (Quantity Diode) is emitted in all directions from the QD or the luminescent organic compound, thus exhibiting almost no directionality. Essentially, the light emission of the light-emitting device undergoes some loss after passing through the color conversion layer. Therefore, displays using color conversion layers employ blue light, which is the shortest wavelength light extracted directly from the light-emitting device, while green and red light are obtained through the color conversion layer. Consequently, there are differences in the light distribution characteristics between green and red pixels and blue pixels. This significant difference in light distribution characteristics creates viewing angle dependence, directly leading to a decrease in display quality. This effect is particularly pronounced when many people are watching large screens such as televisions.

[0167] Therefore, in a light-emitting device according to one embodiment of the present invention, a pixel without a color conversion layer can be configured to have a structure that scatters light, or a pixel with a color conversion layer can be configured to have a structure that imparts directionality.

[0168] A structure capable of scattering light can be placed in the light path from which the light emitted by the light-emitting device exits the light source. The light emitted by a light-emitting device with a microcavity structure is highly directional, but this can be weakened by scattering it through a structure capable of scattering the light. Alternatively, the scattered light can be made directional, and the light passing through the color conversion layer and the light not passing through the color conversion layer can be made to have the same light distribution characteristics. This reduces the aforementioned viewing angle dependence.

[0169] Figures 5A to 5C show the structure of the first pixel 208B having a structure 205B that functions to scatter the light emitted by the first light-emitting device 207B. As the structure 205B that functions to scatter the light emitted by the first light-emitting device 207B, a layer containing a material that scatters the light emitted by the first light-emitting device, as shown in Figures 5A and 5B, can be used, or a structure having a structure that scatters the light emitted by the first light-emitting device, as shown in Figure 5C, can be used.

[0170] Figures 6A to 6C show modified examples. In Figure 6A, instead of the light-scattering structure 205B in Figure 5A, a layer 215B that also functions as a blue filter is used. Figures 6B and 6C show the light-scattering structure 205B and the blue filter 225B. The blue filter 225B can be formed in contact with the light-scattering structure 205B as shown in Figures 6B and 6C, but it can also be formed on other structures such as a sealing substrate. Therefore, this light-emitting device can further improve color purity while scattering directional light. Furthermore, since the reflection of external light can be suppressed, better display can be obtained.

[0171] By emitting light from the first pixel 208B and light from the first light-emitting device 207B through the structure 205B, light with low directionality can be obtained. As a result, the differences in light distribution characteristics between colors are mitigated, thereby obtaining a light-emitting device with high display quality.

[0172] Furthermore, in the light-emitting device of one embodiment of the present invention shown in Figures 7A and 7B, means 210G and 210R are provided to impart directionality to the light emitted by the first color conversion layer. Various means can be employed to impart directionality to the light emitted by the first color conversion layer; for example, a transmissive and reflective layer can be formed with the color conversion layer sandwiched between it, thereby forming a microcavity structure. Additionally, Figure 7A shows the case where transmissive and reflective layers are formed above and below the color conversion layer, and Figure 7B shows the case where the transmissive and reflective layer on the light-emitting device side of the color conversion layer also serves as the second electrode (transmissive and reflective electrode) of the light-emitting device.

[0173] As light from the second pixel 208G and the third pixel 208R, by providing means 210G and 210R to give directionality to the light emitted by the color conversion layer, highly directional light can be obtained. As a result, the differences in light distribution characteristics between colors are mitigated, and a light-emitting device with high display quality can be obtained.

[0174] Embodiment 2 In this embodiment, a display device using the light-emitting device shown in Embodiment 1 will be described.

[0175] In this embodiment, a display device manufactured using the light-emitting device shown in Embodiment 1 will be described with reference to FIGS. 8A and 8B. Note that FIG. 8A is a top view showing the display device, and FIG. 8B is a cross-sectional view taken along lines AB and CD in FIG. 8A. The display device includes a drive circuit section (source line drive circuit) 601, a pixel section 602, and a drive circuit section (gate line drive circuit) 603, indicated by dashed lines, as a unit for controlling the light emission of the light-emitting device. In addition, component symbol 604 is a sealing substrate, component symbol 605 is a sealing material, and the inner side surrounded by the sealing material 605 is a space 607.

[0176] Note that the guide wiring 608 is used to transmit signals input to the source line drive circuit 601 and the gate line drive circuit 603, and to receive video signals, clock signals, start signals, reset signals, etc., from the FPC (Flexible Printed Circuit) 609, which serves as an external input terminal. Note that although only the FPC is shown here, the FPC may also be equipped with a printed circuit board (PWB). The light-emitting device in this specification includes not only the main body of the light-emitting device, but also the light-emitting device equipped with an FPC or PWB.

[0177] The cross-sectional structure will now be described with reference to FIG8B. Although a drive circuit section and a pixel section are formed on the component substrate 610, a pixel is shown here as the source line drive circuit 601 of the drive circuit section and one of the pixels 602.

[0178] In addition to substrates made of glass, quartz, organic resin, metal, alloy, semiconductor, etc., plastic substrates made of FRP (Fiber Reinforced Plastics), PVF (Polyvinyl Fluoride), polyester or acrylic resin, etc., can be used to manufacture the component substrate 610.

[0179] There are no particular restrictions on the structure of the transistor used in the pixel or driving circuit. For example, an anti-interlaced transistor or an interlaced transistor can be used. Additionally, top-gate transistors or bottom-gate transistors can be used. There are no particular restrictions on the semiconductor material used for the transistor; for example, silicon, germanium, silicon carbide, gallium nitride, etc., can be used. Alternatively, oxide semiconductors containing at least one of indium, gallium, and zinc, such as In-Ga-Zn metal oxides, can be used.

[0180] There are no particular restrictions on the crystallinity of the semiconductor material used for the transistor; amorphous semiconductors or crystalline semiconductors (microcrystalline semiconductors, polycrystalline semiconductors, single-crystal semiconductors, or semiconductors with a portion thereof having crystalline regions) can be used. When using crystalline semiconductors, the degradation of transistor characteristics can be suppressed, so it is preferable.

[0181] Here, the oxide semiconductor is preferably a semiconductor device such as a transistor used in the aforementioned pixel or driving circuit and a transistor used in the touch sensor, etc., which will be described later. In particular, it is more preferable to use an oxide semiconductor whose band gap is wider than that of silicon. By using an oxide semiconductor with a band gap wider than that of silicon, the off-state current of the transistor can be reduced.

[0182] Preferably, the oxide semiconductor described above contains at least indium (In) or zinc (Zn). Furthermore, the oxide semiconductor described above is more preferably an oxide semiconductor containing oxides represented by In-M-Zn type oxides (M being metals such as Al, Ti, Ga, Ge, Y, Zr, Sn, La, Ce, or Hf).

[0183] Hereinafter, an oxide semiconductor that can be used in one embodiment of the present invention will be described.

[0184] Oxide semiconductors are classified into single-crystal oxide semiconductors and non-single-crystal oxide semiconductors. Examples of non-single-crystal oxide semiconductors include CAAC-OS (c-axis aligned crystalline oxide semiconductor), polycrystalline oxide semiconductors, nc-OS (nano crystalline oxide semiconductor), a-like OS (amorphous-like oxide semiconductor), and amorphous oxide semiconductors.

[0185] CAAC-OS exhibits c-axis alignment, with its multiple nanocrystals connected along the ab plane, resulting in a distorted crystal structure. Distortion refers to the change in the orientation of the lattice arrangement between regions with consistent lattice arrangement and other regions with consistent lattice arrangement within the region where multiple nanocrystals are connected.

[0186] Nano crystals are generally hexagonal, but not limited to regular hexagons; sometimes they are non-regular hexagonal. Furthermore, nano crystals sometimes exhibit pentagonal or heptagonal lattice arrangements during distortion. Additionally, in CAAC-OS, no distinct grain boundaries (also called grain boundaries) are observed even near the distortion. That is, it is known that lattice arrangement distortion can suppress grain boundary formation. This is because CAAC-OS can contain distortion due to the low density of oxygen atoms along the ab plane or changes in the bonding distance between atoms caused by the substitution of metal elements.

[0187] CAAC-OS tends to have a layered crystal structure (also called a layered structure), in which layers containing indium and oxygen (hereinafter referred to as In layers) and layers containing elements M, zinc, and oxygen (hereinafter referred to as (M, Zn) layers) are stacked. Furthermore, indium and element M can substitute for each other; when element M in the (M, Zn) layer is replaced by indium, the layer can also be represented as an (In, M, Zn) layer. Similarly, when indium in the In layer is replaced by element M, the layer can also be represented as an (In, M) layer.

[0188] CAAC-OS is a highly crystalline oxide semiconductor. Furthermore, distinct grain boundaries are not easily observed in CAAC-OS, thus reducing the likelihood of a decrease in electron mobility due to grain boundaries. Additionally, the crystallinity of oxide semiconductors can sometimes decrease due to the introduction of impurities or the formation of defects; therefore, CAAC-OS can be considered an oxide semiconductor with few impurities or defects (such as oxygen vacancies). Consequently, oxide semiconductors containing CAAC-OS exhibit stable physical properties. Therefore, oxide semiconductors containing CAAC-OS possess high heat resistance and high reliability.

[0189] In nc-OS, the atomic arrangement in tiny regions (e.g., regions above 1 nm and below 10 nm, particularly regions above 1 nm and below 3 nm) exhibits periodicity. Furthermore, no regularity in crystal orientation is observed between different nanocrystals in nc-OS. Therefore, no alignment is observed in the overall film. Thus, sometimes nc-OS is indistinguishable from a-like OS or amorphous oxide semiconductors in certain analytical methods.

[0190] Furthermore, indium gallium zinc oxide (hereinafter, IGZO), an oxide semiconductor comprising indium, gallium, and zinc, sometimes exhibits a stable structure when composed of the aforementioned nanocrystals. In particular, IGZO tends to be difficult to grow in the atmosphere, so it is sometimes structurally more stable when formed from small crystals (e.g., the aforementioned nanocrystals) than when formed from large crystals (here, crystals a few millimeters or a few centimeters).

[0191] a-like OS is an oxide semiconductor with a structure intermediate between nc-OS and amorphous oxide semiconductors. a-like OS contains voids or low-density regions. That is, a-like OS has lower crystallinity than nc-OS and CAAC-OS.

[0192] Oxide semiconductors have various structures and properties. In one embodiment of the present invention, the oxide semiconductor may also include two or more of amorphous oxide semiconductors, polycrystalline oxide semiconductors, a-like OS, nc-OS, and CAAC-OS.

[0193] In addition to the oxide semiconductors mentioned above, CAC (Cloud-Aligned Composite)-OS can also be used.

[0194] Furthermore, CAC-OS possesses conductivity in one part of the material and insulation in another part, thus functioning as a semiconductor as a whole. Moreover, when CAC-OS is used as the active layer of a transistor, the conductivity function allows electrons (or holes) used as carriers to flow through, while the insulation function prevents electrons from flowing through. Through the complementary effect of conductivity and insulation, CAC-OS can possess a switching function (on / off function). By separating these functions within CAC-OS, each function can be maximized.

[0195] Furthermore, CAC-OS has conductive regions and insulating regions. The conductive regions have the aforementioned conductive function, and the insulating regions have the aforementioned insulating function. In addition, in the material, the conductive and insulating regions are sometimes separated at the nanoparticle level. Furthermore, the conductive and insulating regions are sometimes unevenly distributed in the material. Furthermore, sometimes conductive regions with blurred edges and cloud-like connections are observed.

[0196] Furthermore, in CAC-OS, conductive regions and insulating regions are sometimes dispersed in the material with a size of 0.5 nm or more and 10 nm or less, preferably 0.5 nm or more and 3 nm or less.

[0197] Furthermore, the CAC-OS is composed of components with different band gaps. For example, the CAC-OS is composed of a component with a wide gap originating from an insulating region and a component with a narrow gap originating from a conductive region. In this structure, when carriers flow through, the carriers mainly flow through the component with the narrow gap. In addition, the component with the narrow gap and the component with the wide gap complement each other, and the carriers flow through the component with the wide gap in conjunction with the component with the narrow gap. Therefore, when the above-mentioned CAC-OS is used in the channel forming region of a transistor, a high current driving force, that is, a large on-state current and a high field-effect mobility, can be obtained in the conduction state of the transistor.

[0198] In other words, CAC-OS can also be called matrix composite or metal matrix composite.

[0199] By using the above-mentioned oxide semiconductor material as a semiconductor layer, a highly reliable transistor with suppressed changes in electrical characteristics can be realized.

[0200] Furthermore, since the transistor having the aforementioned semiconductor layer has a low off-state current, it is possible to retain the charge stored in the capacitor by the transistor for a long period of time. By using such a transistor in pixels, the driving circuit can be stopped while maintaining the grayscale of the image displayed in each display area. As a result, an electronic device with extremely low power consumption can be realized.

[0201] To stabilize the characteristics of the transistor, a base film is preferably provided. As the base film, inorganic insulating films such as silicon oxide films, silicon nitride films, silicon oxynitride films, and silicon oxynitride films can be used and manufactured as a single layer or in layers. The base film can be formed by sputtering, CVD (Chemical Vapor Deposition) methods (plasma CVD, thermal CVD, MOCVD (Metal Organic Chemical Vapor Deposition), etc.), ALD (Atomic Layer Deposition), coating, printing, etc. Note that a base film may be omitted if not required.

[0202] Note that FET623 shows one of the transistors formed in the source line drive circuit 601. Alternatively, the drive circuit can also be formed using various CMOS, PMOS, or NMOS circuits. Furthermore, although this embodiment shows an integrated driver type with the drive circuit formed on the substrate, this structure is not mandatory; the drive circuit can also be formed externally instead of on the substrate.

[0203] In addition, the pixel unit 602 is formed by a plurality of pixels, each of which includes a switching FET 611, a current control FET 612 and an anode 613 electrically connected to the drain of the current control FET 612. However, it is not limited to this, and a pixel unit combining three or more FETs and capacitors may also be used.

[0204] Note that the insulator 614 is formed in such a way that it covers the end of the anode 613. Here, positive photosensitive acrylic can be used to form the insulator 614.

[0205] Furthermore, the upper or lower end of the insulator 614 is formed as a curved surface to obtain good coverage for the subsequently formed EL layer, etc. For example, when using a positive photosensitive acrylic resin as the material of the insulator 614, it is preferable that only the upper end of the insulator 614 includes a curved surface with a radius of curvature (0.2 μm to 3 μm). Alternatively, a negative photosensitive resin or a positive photosensitive resin can be used as the insulator 614.

[0206] An EL layer 616 and a cathode 617 are formed on the anode 613. Preferably, a material with a high work function is used for the anode 613. For example, in addition to single-layer films such as ITO films, indium tin oxide films containing silicon, indium oxide films containing 2 wt% to 20 wt% zinc oxide, titanium nitride films, chromium films, tungsten films, Zn films, and Pt films, multilayer films composed of titanium nitride films and films with aluminum as the main component, as well as three-layer structures composed of titanium nitride films, films with aluminum as the main component, and titanium nitride films, can also be used. Note that if a multilayer structure is used here, good ohmic contact can be obtained due to the lower resistance of the wiring, and it can also be used as an anode.

[0207] In addition, the EL layer 616 is formed by various methods such as vapor deposition using a vapor deposition mask, inkjet printing, spin coating, etc. The EL layer 616 includes the structure shown in Figures 2A to 2C. In addition, low molecular weight compounds or high molecular weight compounds (including oligomers and dendritic polymers) may be used as other materials constituting the EL layer 616.

[0208] Furthermore, as the material used for the cathode 617 formed on the EL layer 616, it is preferable to use a material with a low work function (Al, Mg, Li, Ca, or their alloys or compounds (MgAg, MgIn, AlLi, etc.)). Note that when light generated in the EL layer 616 is transmitted through the cathode 617, it is preferable to use a stack of a metal thin film with reduced film thickness and a transparent conductive film (ITO, indium oxide containing 2wt% to 20wt% zinc oxide, indium tin oxide containing silicon, zinc oxide (ZnO), etc.) as the cathode 617.

[0209] Furthermore, the light-emitting device is formed of an anode 613, an EL layer 616, and a cathode 617. This light-emitting device is the light-emitting device shown in Embodiment 1. In addition, the pixel portion is composed of multiple light-emitting devices, and the light-emitting device of this embodiment may also include both the light-emitting device shown in Embodiment 1 and light-emitting devices having other structures.

[0210] Furthermore, by attaching the sealing substrate 604 to the element substrate 610 using the sealing material 605, the light-emitting device 618 is disposed in the space 607 surrounded by the element substrate 610, the sealing substrate 604, and the sealing material 605. Note that the space 607 is filled with a filler, which can be an inert gas (nitrogen or argon, etc.) or a sealant. It is preferable to form a recess in the sealing substrate and place a desiccant therein to suppress deterioration caused by moisture.

[0211] Furthermore, it is preferable to use epoxy resin or glass powder as the sealing material 605. Additionally, these materials are preferably those that prevent water or oxygen from permeating as much as possible. Furthermore, as the material used for the sealing substrate 604, in addition to glass substrates or quartz substrates, plastic substrates made of FRP (Fiber Reinforced Plastics), PVF (Polyvinyl Fluoride), polyester, acrylic resin, etc., can also be used.

[0212] Although not shown in Figures 8A and 8B, a protective film may also be provided on the cathode. The protective film may be formed of an organic resin film or an inorganic insulating film. Alternatively, the protective film may be formed in a manner that covers the exposed portion of the sealing material 605. Furthermore, the protective film may be provided to cover the surface and side surfaces of a pair of substrates, the exposed sides of the sealing layer, the insulating layer, etc.

[0213] As a protective film, a material that is not easily permeable to water and other impurities can be used. Therefore, it is possible to effectively suppress the diffusion of water and other impurities from the outside to the inside.

[0214] As the material constituting the protective film, oxides, nitrides, fluorides, sulfides, ternary compounds, metals, or polymers can be used. For example, the material may contain aluminum oxide, hafnium oxide, hafnium silicate, lanthanum oxide, silicon oxide, strontium titanate, tantalum oxide, titanium oxide, zinc oxide, niobium oxide, zirconium oxide, tin oxide, yttrium oxide, cerium oxide, scandium oxide, erbium oxide, vanadium oxide, indium oxide, aluminum nitride, hafnium nitride, silicon nitride, tantalum nitride, titanium nitride, niobium nitride, molybdenum nitride, zirconium nitride, gallium nitride, nitrides containing titanium and aluminum, oxides containing titanium and aluminum, oxides containing aluminum and zinc, sulfides containing manganese and zinc, sulfides containing cerium and strontium, oxides containing erbium and aluminum, oxides containing yttrium and zirconium, etc.

[0215] The protective film is preferably formed using a film-forming method with good step coverage. One such method is atomic layer deposition (ALD). It is preferable to use a material that can be formed by ALD for the protective film. ALD can form a dense protective film with reduced or uniform thickness, minimizing defects such as cracks or pinholes. Furthermore, it can reduce damage to the processed parts during the formation of the protective film.

[0216] For example, a uniform protective film with few defects can be formed on the top, side and back surfaces of a touch panel with a complex uneven shape by means of the ALD method.

[0217] As described above, a display device manufactured using the light-emitting device shown in Embodiment 1 can be obtained.

[0218] Because the display device in this embodiment uses the light-emitting device shown in Embodiment 1, a display device with excellent characteristics can be formed. Specifically, the light-emitting device shown in Embodiment 1 is a long-life light-emitting device, thereby enabling a display device with good reliability. In addition, the display device using the light-emitting device shown in Embodiment 1 has good luminous efficiency, thereby enabling a low-power display device.

[0219] Figures 9A and 9B show an example of a light-emitting device that achieves full-color illumination by setting a color conversion layer to form a light-emitting device that emits blue light. Figure 9A shows a substrate 1001, a substrate insulating film 1002, a gate insulating film 1003, gate electrodes 1006, 1007, 1008, a first interlayer insulating film 1020, a second interlayer insulating film 1021, a peripheral portion 1042, a pixel portion 1040, a driving circuit portion 1041, first electrodes of the light-emitting device 1024R, 1024G, 1024B, a partition wall 1025, an EL layer 1028, a second electrode of the light-emitting device 1029, a sealing substrate 1031, a sealing material 1032, etc.

[0220] In addition, in FIG9A, color conversion layers (red color conversion layer 1034R and green color conversion layer 1034G) are provided on the transparent substrate 1033. A black matrix 1035 may also be provided. The transparent substrate 1033, on which the color conversion layers and black matrix are provided, is aligned and fixed to the substrate 1001. Furthermore, the color conversion layers and black matrix 1035 are covered by an outer coating layer 1036.

[0221] FIG9B shows an example in which a color conversion layer (red color conversion layer 1034R, green color conversion layer 1034G) is formed between the gate insulating film 1003 and the first interlayer insulating film 1020. As described above, a color layer may also be disposed between the substrate 1001 and the sealing substrate 1031.

[0222] Furthermore, in the light-emitting device described above, although a light-emitting device with a structure that emits light from the side of the substrate 1001 on which the FET is formed (bottom-emitting type) has been described, a light-emitting device with a structure that emits light from the side of the sealing substrate 1031 (top-emitting type) can also be used. FIG10 shows a cross-sectional view of the top-emitting type light-emitting device. In this case, the substrate 1001 can be a substrate that does not allow light to pass through. The process up to manufacturing the connection electrode for connecting the FET to the anode of the light-emitting device is performed in the same way as the bottom-emitting type light-emitting device. Then, a third interlayer insulating film 1037 is formed in a manner that covers the electrode 1022. This insulating film may also have a planarization function. The third interlayer insulating film 1037 can be formed using the same material as the second interlayer insulating film or other known materials.

[0223] Although the first electrodes 1024R, 1024G, and 1024B of this light-emitting device are all anodes, they can also be cathodes. Furthermore, in the case of a top-emitting type light-emitting device as shown in Figure 10, the first electrode is preferably a reflective electrode. The structure of the EL layer 1028 employs an element structure capable of obtaining blue light emission.

[0224] When using the top-emitting structure shown in FIG10, a sealing substrate 1031 with color conversion layers (red color conversion layer 1034R and green color conversion layer 1034G) can be used for sealing. The sealing substrate 1031 may also have a black matrix 1035 located between pixels. The color conversion layers (red color conversion layer 1034R and green color conversion layer 1034G) and the black matrix may also be covered by an outer cover layer 1036. In addition, a light-transmitting substrate is used as the sealing substrate 1031. Furthermore, the color conversion layers (red color conversion layer 1034R and green color conversion layer 1034G) may be directly disposed on the second electrode 1029 (or disposed on a protective film on the second electrode 1029).

[0225] In addition, in the above structure, the EL layer may contain multiple light-emitting layers or only one light-emitting layer. For example, the following structure may also be adopted: combining the above-described series-type light-emitting device structure, multiple EL layers are disposed in a light-emitting device with a charge generation layer sandwiched in between, and one or more light-emitting layers are formed in each EL layer.

[0226] Microcavity structures are particularly suitable for top-emitting light-emitting devices. By using a reflective electrode as the anode and a semi-transparent / semi-reflective electrode as the cathode, a light-emitting device with a microcavity structure can be obtained. At least an EL layer is present between the reflective electrode and the semi-transparent / semi-reflective electrode, and at least a light-emitting layer that forms the light-emitting region is also present.

[0227] Note that the reflective electrode is a film with a visible light reflectance of 40% to 100%, preferably 70% to 100%, and a resistivity of 1×10⁻² Ωcm or less. Furthermore, the semi-transmissive / semi-reflective electrode is a film with a visible light reflectance of 20% to 80%, preferably 40% to 70%, and a resistivity of 1×10⁻² Ωcm or less.

[0228] Light emitted from the light-emitting layer contained in the EL layer is reflected by the reflective electrode and the semi-transparent and semi-reflective electrode, and resonates.

[0229] In this light-emitting device, the optical path between the reflective electrode and the semi-transparent / semi-reflective electrode can be changed by altering the thickness of the transparent conductive film, the aforementioned composite material, or the carrier transport material. This allows for the enhancement of resonant wavelengths of light between the reflective electrode and the semi-transparent / semi-reflective electrode, while attenuating non-resonant wavelengths of light.

[0230] Note that the light reflected back by the reflective electrode (the first reflected light) will cause significant interference to the light directly incident from the light-emitting layer to the semi-transparent and semi-reflective electrode (the first incident light). Therefore, it is preferable to adjust the optical path between the reflective electrode and the light-emitting layer to (2n-1)λ / 4 (note that n is a natural number greater than 1, and λ is the wavelength of the light to be amplified). By adjusting this optical path, the phase of the first reflected light and the first incident light can be made to match, thereby further amplifying the light emitted from the light-emitting layer.

[0231] In addition, in the above structure, the EL layer may contain multiple light-emitting layers or only one light-emitting layer. For example, the following structure may also be adopted: combining the above-described series-type light-emitting device structure, multiple EL layers are disposed in a light-emitting device with a charge generation layer sandwiched in between, and one or more light-emitting layers are formed in each EL layer.

[0232] Embodiment 3 In this embodiment, an example of an electronic device that includes, in part, the light-emitting devices shown in Embodiments 1 and 2. The light-emitting devices shown in Embodiments 1 and 2 are light-emitting devices with good lifespan and high reliability. As a result, the electronic device described in this embodiment can realize an electronic device including a light-emitting part with high reliability.

[0233] Examples of electronic devices employing the aforementioned light-emitting devices include television sets (also called television sets or television receivers), monitors for computers, digital cameras, digital camcorders, digital photo frames, mobile phones (also called mobile phones or mobile phone devices), portable game consoles, portable information terminals, audio playback devices, pinball machines, and other large-scale game machines. Specific examples of these electronic devices are shown below.

[0234] Figure 11A shows an example of a television set. In the television set, a display unit 7103 is assembled in the housing 7101. Also shown here is a structure in which the housing 7101 is supported by a bracket 7105. Images can be displayed using the display unit 7103, and the light-emitting devices shown in Embodiments 1 and 2 are arranged in a matrix to form the display unit 7103.

[0235] The television can be operated using the operation switch provided in the casing 7101 or the separately provided remote control 7110. The operation keys 7109 provided in the remote control 7110 can be used to control the channel and volume, thereby controlling the image displayed on the display unit 7103. Alternatively, a structure can be adopted in which a display unit 7107 for displaying information output from the remote control 7110 is provided in the remote control 7110.

[0236] In addition, the television set adopts a structure that includes a receiver, a modem, etc. It can receive general television broadcasts through the receiver. Furthermore, by connecting to a wired or wireless communication network through the modem, it can conduct one-way (from sender to receiver) or two-way (between sender and receiver or between receivers, etc.) information communication.

[0237] Figure 11B1 shows a computer, which includes a main body 7201, a casing 7202, a display unit 7203, a keyboard 7204, an external connection port 7205, a pointing device 7206, etc. Furthermore, this computer is manufactured by arranging the light-emitting devices shown in Embodiments 1 and 2 in a matrix and using them in the display unit 7203. The computer in Figure 11B1 can also be as shown in Figure 11B2. The computer shown in Figure 11B2 has a second display unit 7210 instead of the keyboard 7204 and the pointing device 7206. The second display unit 7210 is a touch panel, and input can be performed by operating the input display on the second display unit 7210 with a finger or a special stylus. In addition, the second display unit 7210 can display not only the input display but also other images. Furthermore, the display unit 7203 can also be a touch panel. Because the two screens are connected by a hinge, problems such as screen damage or breakage can be prevented during storage or transportation.

[0238] Figure 11C shows an example of a portable terminal. The portable terminal includes a display unit 7402, operation buttons 7403, an external connection port 7404, a speaker 7405, a microphone 7406, etc., assembled in a housing 7401. In addition, the portable terminal includes a display unit 7402 manufactured by arranging the light-emitting devices shown in Embodiment 1 and Embodiment 2 in a matrix.

[0239] The portable terminal shown in FIG11C may also have a structure in which information is input using a touch display unit 7402 such as a finger. In this case, operations such as making phone calls or composing emails can be performed using the touch display unit 7402 such as a finger.

[0240] The display unit 7402 has three main screen modes. The first is a display mode that is mainly for displaying images, the second is an input mode that is mainly for inputting information such as text, and the third is a display-input mode that combines display mode and input mode.

[0241] For example, when making a phone call or composing an email, the text displayed on the screen can be entered using a text input mode where the display unit 7402 is primarily used for text input. In this case, it is preferable to display a keyboard or number buttons in most of the screen of the display unit 7402.

[0242] In addition, by installing a detection device with a gyroscope and an accelerometer inside the portable terminal to detect tilt, the orientation (vertical or horizontal) of the portable terminal can be determined and the screen display of the display unit 7402 can be switched automatically.

[0243] In addition, the screen mode can be switched by touching the display unit 7402 or by operating the operation button 7403 on the housing 7401. Furthermore, the screen mode can also be switched according to the type of image displayed on the display unit 7402. For example, when the image signal displayed on the display unit is moving image data, the screen mode is switched to display mode, and when the image signal is text data, the screen mode is switched to input mode.

[0244] In addition, when it is known that there is no touch operation input on the display unit 7402 within a certain period of time by detecting the signal detected by the light sensor of the display unit 7402 in the input mode, the screen mode can also be switched from the input mode to the display mode.

[0245] The display unit 7402 can also be used as an image sensor. For example, by touching the display unit 7402 with the palm or fingers, palm prints, fingerprints, etc. can be captured for personal identification. In addition, by using a backlight that emits near-infrared light or a sensing light source that emits near-infrared light in the display unit, finger veins, palm veins, etc. can also be captured.

[0246] In addition, the structure shown in this embodiment can be used in appropriate combination with the structures shown in Embodiment 1 and Embodiment 2.

[0247] As described above, the light-emitting device equipped with the light-emitting device shown in Embodiment 1 and Embodiment 2 has a very wide range of applications, and can be used in electronic devices in various fields. By using the light-emitting device shown in Embodiment 1 and Embodiment 2, a highly reliable electronic device can be obtained.

[0248] Figure 12A is a schematic diagram showing an example of a robotic vacuum cleaner.

[0249] The robotic vacuum cleaner 5100 includes a display 5101 on its top surface, multiple cameras 5102 on its sides, a brush 5103, and operation buttons 5104. Although not shown, the bottom surface of the robotic vacuum cleaner 5100 is provided with tires and a suction port. Furthermore, the robotic vacuum cleaner 5100 also includes various sensors such as an infrared sensor, an ultrasonic sensor, an accelerometer, a piezoelectric sensor, a light sensor, and a gyroscope sensor. Additionally, the robotic vacuum cleaner 5100 includes a wireless communication unit.

[0250] The 5100 robotic vacuum cleaner can walk automatically and detect garbage 5120, which can suck up garbage from the suction port on the bottom.

[0251] In addition, the robot vacuum cleaner 5100 analyzes the images captured by the camera 5102 to determine the presence or absence of obstacles such as walls, furniture, or steps. Furthermore, if the image analysis detects objects such as wiring that may get tangled in the brush 5103, the rotation of the brush 5103 can be stopped.

[0252] The remaining battery power and the amount of debris collected can be displayed on the display 5101. The walking path of the robot vacuum cleaner 5100 can also be displayed on the display 5101. In addition, the display 5101 can be a touch panel, on which the operation buttons 5104 can be displayed.

[0253] The robotic vacuum cleaner 5100 can communicate with portable electronic devices 5140 such as smartphones. Images captured by the camera 5102 can be displayed on the portable electronic device 5140. Therefore, the owner of the robotic vacuum cleaner 5100 can know the status of the room when leaving home. In addition, the content displayed on the monitor 5101 can be checked using a portable electronic device such as a smartphone.

[0254] The light-emitting device of one embodiment of the present invention can be used in a display 5101.

[0255] The robot 2100 shown in FIG12B includes a computing device 2110, an illuminance sensor 2101, a microphone 2102, an upper camera 2103, a speaker 2104, a display 2105, a lower camera 2106, an obstacle sensor 2107, and a movement mechanism 2108.

[0256] The microphone 2102 has the function of detecting the user's voice and surrounding sounds. In addition, the speaker 2104 has the function of emitting sound. The robot 2100 can use the microphone 2102 and the speaker 2104 to communicate with the user.

[0257] The display 2105 has the function of displaying various information. The robot 2100 can display the information desired by the user on the display 2105. The display 2105 may be equipped with a touch panel. The display 2105 may be a detachable information terminal, which can be charged and send and receive data by setting the information terminal at a designated position on the robot 2100.

[0258] The upper camera 2103 and the lower camera 2106 are capable of capturing images of the surrounding environment of the robot 2100. Additionally, the obstacle sensor 2107 can detect the presence or absence of obstacles in front of the robot 2100 when it moves using the mobility mechanism 2108. The robot 2100 can use the upper camera 2103, the lower camera 2106, and the obstacle sensor 2107 to perceive its surrounding environment and move safely. The light-emitting device of one embodiment of the present invention can be used in the display 2105.

[0259] Figure 12C is a diagram showing an example of a goggle-type display. The goggle-type display includes, for example, a housing 5000, a display unit 5001, a speaker 5003, an LED light 5004, a connection terminal 5006, a sensor 5007 (which has the function of measuring factors such as force, displacement, position, velocity, acceleration, angular velocity, rotational speed, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, tilt, vibration, odor, or infrared radiation), a microphone 5008, a display unit 5002, a support unit 5012, and headphones 5013, etc.

[0260] The light-emitting device of one embodiment of the present invention can be used in display unit 5001 and display unit 5002.

[0261] The light-emitting devices shown in Embodiments 1 and 2 can also be installed on the windshield or dashboard of an automobile. Figure 13 shows one embodiment of using the light-emitting devices shown in Embodiments 1 and 2 on the windshield or dashboard of an automobile. Display areas 5200 to 5203 are display areas provided using the light-emitting devices shown in Embodiments 1 and 2.

[0262] Display areas 5200 and 5201 are display devices installed on the windshield of an automobile and equipped with the light-emitting devices shown in Embodiments 1 and 2. By using light-transmitting electrodes to manufacture the anode and cathode of the light-emitting devices shown in Embodiments 1 and 2, a so-called see-through display device that allows the view of the opposite side can be obtained. If a see-through display is used, the view is not obstructed even when installed on the windshield of an automobile. In addition, when providing the transistors or the like used for driving, it is preferable to use light-transmitting transistors, such as organic transistors using organic semiconductor materials or transistors using oxide semiconductors.

[0263] Display area 5202 is a display device installed on the pillar portion and equipped with the light-emitting devices shown in Embodiments 1 and 2. By displaying images from the imaging unit installed on the vehicle compartment on display area 5202, the view obstructed by the pillar can be supplemented. Similarly, display area 5203 installed on the dashboard portion can supplement blind spots in the view obstructed by the vehicle compartment by displaying images from the imaging unit installed on the exterior of the vehicle, thereby improving safety. By displaying images to supplement unseen parts, safety can be confirmed more naturally and simply.

[0264] Display area 5203 can also provide various information such as navigation information, speedometer, tachometer, driving distance, fuel level, gear position, and air conditioning settings. Users can appropriately change the display content and arrangement. In addition, this information can also be displayed on display areas 5200 to 5202. Furthermore, display areas 5200 to 5203 can also be used as lighting equipment.

[0265] Figures 14A and 14B show a foldable portable information terminal 5150. The foldable portable information terminal 5150 includes a housing 5151, a display area 5152, and a bending portion 5153. Figure 14A shows the portable information terminal 5150 in its unfolded state. Figure 14B shows the portable information terminal in its folded state. Although the portable information terminal 5150 has a large display area 5152, it becomes smaller by folding, thus achieving excellent portability.

[0266] The display area 5152 can be folded in half by the bending portion 5153. The bending portion 5153 is composed of a telescopic member and multiple support members. When folding, the telescopic member is stretched and folded in such a way that the bending portion 5153 has a radius of curvature of 2 mm or more, preferably 3 mm or more.

[0267] Alternatively, the display area 5152 may also be a touch panel (input / output device) equipped with a touch sensor (input device). The light-emitting device of one embodiment of the present invention may be used in the display area 5152.

[0268] Furthermore, Figures 15A to 15C show a foldable portable information terminal 9310. Figure 15A shows the portable information terminal 9310 in its unfolded state. Figure 15B shows the portable information terminal 9310 in a state transitioning between the unfolded and folded states. Figure 15C shows the portable information terminal 9310 in its folded state. The portable information terminal 9310 is highly portable in its folded state, and in its unfolded state, it offers a large, seamless display area, resulting in a clear and easy-to-view display.

[0269] The display panel 9311 is supported by three housings 9315 connected by a hinge portion 9313. Note that the display panel 9311 can also be a touch panel (input / output device) equipped with a touch sensor (input device). Furthermore, by bending the display panel 9311 at the hinge portion 9313 between two housings 9315, the portable information terminal 9310 can be reversibly changed from an unfolded state to a folded state. A light-emitting device according to one embodiment of the present invention can be used in the display panel 9311.

[0270] <Reference Example> In this reference example, the methods for calculating the HOMO level, LUMO level and electron mobility of the organic compounds used in each embodiment will be explained.

[0271] The HOMO and LUMO energy levels can be calculated by cyclic voltammetry (CV).

[0272] An electrochemical analyzer (BAS Inc. ALS model 600A or 600C) was used as the measuring apparatus. The solution for CV determination was prepared as follows: as a solvent, tetrabutylammonium perchlorate (n-Bu4NClO4) (manufactured by Aldrich Co., Ltd., 99.8%, catalog number: 22705-6) as a supporting electrolyte was dissolved at a concentration of 100 mmol / L, and the analyte was dissolved at a concentration of 2 mmol / L. In addition, a platinum electrode (manufactured by BAS Corporation, PTE platinum electrode) was used as the working electrode, a platinum electrode (manufactured by BAS Corporation, VC-3 Pt counter electrode (5cm)) was used as the auxiliary electrode, and an Ag / Ag+ electrode (manufactured by BAS Corporation, RE7 non-aqueous solvent type reference electrode) was used as the reference electrode. Note that the measurements were performed at room temperature (20°C to 25°C). The scan rate during CV measurement was uniformly set to 0.1 V / sec, and the oxidation potential Ea [V] and reduction potential Ec [V] relative to the reference electrode were measured. Ea is the intermediate potential between the oxidation-reduction wave and Ec is the intermediate potential between the reduction-oxidation wave. Here, it is known that the potential energy of the reference electrode used in this reference example relative to the vacuum energy level is -4.94 [eV]. Therefore, the HOMO energy level and LUMO energy level were obtained using the formulas HOMO energy level [eV] = -4.94 - Ea and LUMO energy level [eV] = -4.94 - Ec, respectively.

[0273] Electron mobility can be determined by impedance spectroscopy (IS method).

[0274] As methods for measuring carrier mobility in EL materials, known methods include the time-of-flight (TOF) method and the method of determining it from the IV characteristics of the space-charge-limited current (SCLC) (SCLC method). The TOF method requires a sample with a much thicker film compared to actual organic EL elements. The SCLC method has the disadvantage of not being able to obtain the electric field intensity dependence of carrier mobility. In the IS method, since the thickness of the organic film required for measurement is thin, i.e., about a few hundred nm, a smaller amount of EL material can be used to form the film, and the mobility can be measured with a film thickness close to that of actual EL elements, and the electric field intensity dependence of carrier mobility can be obtained.

[0275] In the IS method, a small sinusoidal voltage signal (V=V0[exp(jωt)]) is applied to the EL element, and the impedance of the EL element (Z=V / I) is obtained from the phase difference between the current amplitude of its response current signal (I=I0exp[j(ωt+ϕ)]) and the input signal. By applying a voltage from a high frequency to a low frequency to the element, components with various relaxation times that contribute to impedance can be separated and measured.

[0276] Here, the admittance Y (=1 / Z), the reciprocal of the impedance, can be expressed by the conductance G and the susceptance B as shown in the following formula (1).

[0277]

[0278] Furthermore, using the single injection model, the following formulas (2) and (3) can be calculated. Here, g (formula (4)) is the differential conductance. Note that in the formulas, C represents the electrostatic capacitance (capacitance), θ represents the transit angle (ωt), and ω represents the angular frequency. t is the transit time. The analysis uses the current equation, Poisson equation, and current continuity equation, and ignores the existence of diffusion current and trapped states.

[0279]

[0280] The method for calculating the mobility from the frequency characteristics of electrostatic capacitance is the -ΔB method. Alternatively, the method for calculating the mobility from the frequency characteristics of conductivity is the ωΔG method.

[0281] In fact, firstly, an electronic-only element of the material to which the electron mobility is to be calculated is manufactured. An electronic-only element is a component designed so that only electrons flow through it as carriers. In this specification, a method for calculating the mobility from the frequency characteristics of electrostatic capacitance (-ΔB method) will be explained. Figure 16 shows a schematic diagram of the electronic-only element used.

[0282] This time, for the purpose of measuring the manufactured electronic components, as shown in Figure 16, a first layer 1210, a second layer 1211, and a third layer 1212 are included between the first electrode 1201 and the second electrode 1202. The material for which the electron mobility needs to be determined is used as the material of the second layer 1211. This time, the measurement of the electron mobility of a co-evaporated film of 2-{4-[9,10-bis(naphthyl-2-yl)-2-anthrayl]phenyl}-1-phenyl-1H-benzimidazole (abbreviated as ZADN) and Liq in a 1:1 (weight ratio) will be used as an example. The specific structure is shown in the table below.

[0283]

[0284] Figure 17 shows the current density-voltage characteristics of electronic components formed using a co-evaporation coating of ZADN and Liq as the second layer 1211.

[0285] Impedance measurement was performed while applying a DC voltage in the range of 5.0V to 9.0V, and under conditions of AC voltage of 70mV and frequency of 1Hz to 3MHz. The capacitance was calculated from the admittance of the reciprocal of the impedance obtained here (formula (1) above). Figure 18 shows the frequency characteristic of the capacitance C calculated when the applied voltage is 7.0V.

[0286] Since the space charge generated by the carrier injected by the small voltage signal cannot keep up with the small AC voltage, the frequency characteristics of the capacitor C are obtained from the phase difference generated by the current. Here, the travel time of the carrier in the membrane is defined by the time T when the injected carrier reaches the opposite electrode, and is expressed by the following formula (5).

[0287]

[0288] The change in negative susceptance (-ΔB) corresponds to the change in electrostatic capacitance -ΔC multiplied by the angular frequency ω (-ωΔC). From formula (3), the relationship between the peak frequency f'max (=ωmax / 2π) on the lowest frequency side and the travel time T satisfies the following formula (6).

[0289]

[0290] Figure 19 shows the frequency response of -ΔB calculated from the above measurements (i.e., when the DC voltage is 7.0V). The peak frequency f'max on the lowest frequency side obtained from Figure 19 is indicated by an arrow in the figure.

[0291] Since the travel time T is obtained from f'max obtained by the above measurement and analysis (refer to the above formula (6)), the electron mobility at a voltage of 7.0V can be obtained from the above formula (5). By performing the same measurement in the range of DC voltage from 5.0V to 9.0V, the electron mobility at each voltage (electric field strength) can be calculated, and thus the electric field strength dependence of the mobility can also be determined.

[0292] Figure 20 shows the final electric field strength dependence of the electron mobility of each organic compound obtained by the above calculation method, and Table 10 shows the electron mobility values ​​when the square root of the electric field strength [V / cm] read from Figure 20 is 600 [V / cm]1 / 2.

[0293]

[0294] The electron mobility can be calculated as described above. Note that for detailed measurement methods, refer to "Japanese Journal of Applied Physics" by Takayuki Okachi et al., Vol. 47, No. 12, 2008, pp. 8965-8972.

[0295] Embodiment 4 <Structural Example of a Semiconductor Device> An embodiment of the present invention will be described with reference to the drawings. FIG23 is a perspective view showing the appearance of a semiconductor device 400 that can be used in an HMD (Head Mounted Display).

[0296] The semiconductor device 400 includes a display module 401 (display module 401R and display module 401L), a display control unit 402, a power supply unit 403, an operation unit 404, a speaker 405, an external input / output terminal 406, a fixing tool 407, and a lens 408.

[0297] The display module 401 displays based on signals supplied by the display control unit 402. The display control unit 402 includes a CPU (Central Processing Unit) and GPU (Graphics Processing Unit) and other computing circuits to process externally supplied image signals. The power supply unit 403 generates and supplies power voltage for driving the semiconductor device 400. The operation unit 404 is used when the user operates the semiconductor device 400. The speaker 405 operates based on audio signals supplied externally via the external input / output terminal 406. The external input / output terminal 406 handles the input and output of various signals, such as image signals and audio signals supplied externally. The fixing tool 407 is used to fix the semiconductor device 400 to the user's head. The lens 408 is used to magnify the display module 401 for viewing.

[0298] The user views the display module 401 through the lens. Since the user sees the magnified image of the display module 401, a high degree of immersion can be achieved.

[0299] <Example of Display Module Structure> To view the display module 401 in a magnified manner, the display panel used for the display module 401 is preferably a high-resolution display module. Figures 24A and 24B show perspective views of the display module 401.

[0300] The display module 401 shown in FIG24A includes a display device 411 and an FPC 412 (Flexible Printed Circuit). The display device 411 may use a light-emitting device according to an embodiment of the present invention.

[0301] The display module 401 includes a substrate 421 and a substrate 422. The display module 401 includes a display unit 431.

[0302] FIG24B schematically shows a perspective view of the structure on the substrate 421 side. The display unit 431 has a circuit section 441, a pixel circuit section 442, and a pixel section 443 sequentially stacked on the substrate 421. Furthermore, on the outer side of the display unit 431, a terminal section 444 for connection to the FPC 412 is provided on the substrate 421. The terminal section 444 is electrically connected to the circuit section 441 via a wiring section 445 composed of multiple wirings.

[0303] The pixel unit 443 includes a plurality of pixels 443a arranged in a matrix. A magnified view of a pixel 443a is shown on the right side of FIG24B. Pixel 443a includes sub-pixels of four colors: R (red), G (green), B (blue), and W (white). Note that although a structure with four-color sub-pixels is shown in this embodiment, it is not limited thereto. For example, a structure with three-color sub-pixels (R (red), G (green), and B (blue)) may also be used.

[0304] The pixel circuit section 442 includes a plurality of pixel circuits 442a arranged in a matrix. One pixel circuit 442a controls the light emission of four sub-pixels included in one pixel 443a. One pixel circuit 442a may be composed of four circuits that control the light emission of one sub-pixel. For example, the pixel circuit 442a may adopt a structure that has at least one selection transistor, one current control transistor (driving transistor), and a capacitor for each sub-pixel. In this case, the gate of the selection transistor is input with a gate signal, and either the source or the drain is input with a source signal. Thus, an active matrix display device can be realized.

[0305] The circuit section 441 includes circuitry for driving each pixel circuit 442a of the pixel circuit section 442. For example, it is preferably equipped with one or both of a gate driver and a source driver. In addition, it may also include arithmetic circuitry, memory circuitry, power supply circuitry, etc.

[0306] The FPC412 is used for wiring to supply video signals and power potential to the circuit section 441 from the outside. In addition, ICs can also be mounted on the FPC412.

[0307] The display module 401 can adopt a structure in which pixel circuit section 442, circuit section 441, etc. are stacked on the lower side of pixel section 443, so that display section 431 can have an extremely high aperture ratio (effective display area ratio). For example, the aperture ratio of display section 431 can be 40% or more and less than 100%, preferably 50% or more and less than 95%, and more preferably 60% or more and less than 95%. In addition, the pixels 443a can be arranged in an extremely high density, thereby enabling display section 431 to have extremely high resolution. For example, display section 431 preferably has pixels 443a arranged in a resolution of 2000ppi or more, more preferably 3000ppi or more, further preferably 5000ppi or more, and even more preferably 6000ppi or more and less than 20000ppi or less than 30000ppi.

[0308] The high-definition display module 401 is suitable for use in semiconductor devices 400 such as HMDs (Virtual Reality Devices) or glasses-type AR (Augmented Reality) devices shown in FIG23. Even when the high-definition display module 401 is used in a device that views the display unit through a lens, the pixels of the display unit magnified by the lens are not easily seen by the user, thereby enabling a highly immersive display. In addition, the display module 401 is also suitable for electronic devices with relatively small display units. For example, it is suitable for use in the display units of wearable electronic devices such as smartwatches.

[0309] <Example of Transistor Structure> In the high-definition display module 401, it is preferable to use a micro-manufacturing-capable transistor in the pixel circuit section 442, etc. Figures 25A and 25B show cross-sectional views of a transistor that can be used in the display device 411.

[0310] FIG25A is a cross-sectional view of the transistor 500 in the channel length direction that can be used in the display device 411, and FIG25B is a cross-sectional view of the transistor 500 in the channel width direction.

[0311] As shown in Figures 25A and 25B, the transistor 500 includes: an insulator 512; an insulator 514 and an insulator 516 disposed on the insulator 512; a conductor 503 embedded in the insulator 514 and the insulator 516; an insulator 520 disposed on the insulator 516 and the conductor 503; an insulator 522 disposed on the insulator 520; an insulator 524 disposed on the insulator 522; an oxide 530a disposed on the insulator 524; and an oxide 530a disposed on the oxide 530a. The oxide 530b on the oxide 530a; the conductors 542a and 542b disposed on the oxide 530b and spaced apart from each other; the insulator 580 disposed on the conductors 542a and 542b and having an opening overlapping between the conductors 542a and 542b; the oxide 530c disposed on the bottom and side surfaces of the opening; the insulator 550 disposed on the forming surface of the oxide 530c; and the conductor 560 disposed on the forming surface of the insulator 550.

[0312] Furthermore, as shown in Figures 25A and 25B, it is preferable to provide the insulator 544 between the oxide 530a, oxide 530b, conductor 542a, conductor 542b, and insulator 580. Additionally, as shown in Figures 25A and 25B, the conductor 560 preferably includes a conductor 560a disposed inside the insulator 550 and a conductor 560b embedded inside the conductor 560a. Furthermore, as shown in Figures 25A and 25B, it is preferable to provide the insulator 574 on the insulator 580, conductor 560, and insulator 550.

[0313] Note that oxides 530a, 530b and 530c are sometimes collectively referred to as oxide 530.

[0314] In the transistor 500, three layers of oxide 530a, oxide 530b, and oxide 530c are stacked in and around the region forming the channel, but the present invention is not limited thereto. For example, a single layer of oxide 530b, a two-layer structure of oxide 530b and oxide 530a, a two-layer structure of oxide 530b and oxide 530c, or a stacked structure of four or more layers can be provided. In addition, in the transistor 500, the conductor 560 has a two-layer structure, but the present invention is not limited thereto. For example, the conductor 560 may also have a single-layer structure or a stacked structure of three or more layers. Note that the structure of the transistor 500 shown in FIG. 25A and FIG. 25B is only an example and is not limited to the above structure. Appropriate transistors can be used according to the circuit structure or driving method.

[0315] Here, conductor 560 is used as the gate electrode of transistor 500, and conductors 542a and 542b are used as source electrodes or drain electrodes. As described above, conductor 560 is embedded in the opening of insulator 580 and in the region between conductors 542a and 542b. The arrangement of conductors 560, 542a, and 542b relative to the opening of insulator 580 is self-aligned. In other words, in transistor 500, the gate electrode can be self-aligned between the source electrode and the drain electrode. Therefore, conductor 560 can be formed without providing space for alignment, thus reducing the occupied area of ​​transistor 500. This enables miniaturization and high integration of semiconductor devices.

[0316] Furthermore, the conductor 560 is self-aligned and formed in the region between conductors 542a and 542b, so the conductor 560 does not include the region overlapping with conductors 542a and 542b. This reduces the parasitic capacitance formed between the conductor 560 and conductors 542a and 542b. Therefore, the switching speed of the transistor 500 can be increased, allowing the transistor 500 to have high-frequency characteristics.

[0317] Conductor 560 is sometimes used as the first gate (also called the top gate) electrode. Conductor 503 is sometimes used as the second gate (also called the bottom gate) electrode. In this case, the critical voltage of transistor 500 can be controlled by independently changing the potential supplied to conductor 503 without linking it to the potential supplied to conductor 560. In particular, by supplying a negative potential to conductor 503, the critical voltage of transistor 500 can be made greater than 0V and the off-state current can be reduced. Therefore, compared with not applying a negative potential to conductor 503, applying a negative potential to conductor 503 can reduce the drain current when the potential supplied to conductor 560 is 0V.

[0318] The conductor 503 is arranged such that it overlaps with the oxide 530 and the conductor 560. Therefore, when a potential is supplied to the conductor 560 and the conductor 503, the electric field generated from the conductor 560 and the electric field generated from the conductor 503 are connected, and the channel forming region formed in the oxide 530 can be covered. In this specification, the structure of a transistor in which the electric field of the first gate electrode and the electric field of the second gate electrode surround the channel forming region is referred to as a surrounded channel (S-channel) structure.

[0319] Furthermore, as a conductor 503, a conductor 503a is formed in contact with the inner wall of the opening of the insulator 514 and the insulator 516, and a conductor 503b is formed on its inner side. In addition, the transistor 500 has conductors 503a and conductors 503b stacked together, but the present invention is not limited thereto. For example, the conductor 503 may have a single-layer structure or a stacked structure of three or more layers.

[0320] Here, the conductor 503a is preferably a conductive material that has the function of suppressing the diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, and copper atoms (making it difficult for the aforementioned impurities to permeate). Furthermore, it is preferable to use a conductive material that has the function of suppressing the diffusion of oxygen (e.g., at least one of oxygen atoms and oxygen molecules) (making it difficult for the aforementioned oxygen to permeate). In this specification, "the function of suppressing the diffusion of impurities or oxygen" refers to the function of suppressing the diffusion of any one or all of the aforementioned impurities and oxygen.

[0321] For example, by giving conductor 503a the function of inhibiting oxygen diffusion, the decrease in conductivity caused by oxidation of conductor 503b can be suppressed.

[0322] Furthermore, when the conductor 503 also functions as a wiring element, it is preferable to use a highly conductive material with tungsten, copper, or aluminum as the main components of the conductor 503b. In this case, it is not necessary to provide the conductor 503a. In the drawings, the conductor 503b has a single-layer structure, but it may also have a multilayer structure, for example, a multilayer structure of titanium or titanium nitride and the aforementioned conductive material may be used.

[0323] Insulators 520, 522 and 524 are used as the second gate insulating film.

[0324] Here, the insulator 524 in contact with the oxide 530 is preferably an insulator containing oxygen in excess of its stoichiometric composition. In other words, it is preferable to form an excess oxygen region in the insulator 524. By providing the aforementioned insulator containing excess oxygen in a manner that allows it to contact the oxide 530, oxygen vacancies in the oxide 530 can be reduced, thereby improving the reliability of the transistor 500.

[0325] Specifically, as an insulator with an excess oxygen region, it is preferable to use an oxide material that allows a portion of the oxygen to be removed by heating. An oxide that allows oxygen to be removed by heating refers to an oxide film in which the amount of oxygen removed, converted to oxygen atoms in TDS (Thermal Desorption Spectroscopy) analysis, is 1.0 × 10¹⁸ atoms / cm³ or more, preferably 1.0 × 10¹⁹ atoms / cm³ or more, further preferably 2.0 × 10¹⁹ atoms / cm³ or more, or 3.0 × 10²⁰ atoms / cm³ or more. Furthermore, the surface temperature of the film during the above TDS analysis is preferably in the range of 100°C or higher and 700°C or lower, or 100°C or higher and 400°C or lower.

[0326] Alternatively, the insulator having the aforementioned excess oxygen region may be contacted with the oxide 530 and subjected to one or more of the following treatments: heat treatment, microwave treatment, and RF treatment. By performing this treatment, water or hydrogen can be removed from the oxide 530. For example, in the oxide 530, a bond-breaking reaction of VoH occurs; in other words, a reaction of "VoH→Vo+H" occurs, thereby achieving dehydrogenation. A portion of the hydrogen produced here sometimes bonds with oxygen and is removed as H2O from the oxide 530 or the insulator near the oxide 530. Additionally, a portion of the hydrogen sometimes diffuses into the conductor 542 or is captured by the conductor 542 (also known as gettering).

[0327] Furthermore, the microwave processing described above is preferably performed using a device that generates high-density plasma or a device that applies RF power to one side of the substrate. For example, by using a gas containing oxygen and using high-density plasma, a high density of oxygen free radicals can be generated, and by applying RF to one side of the substrate, the oxygen free radicals generated by the high-density plasma can be effectively introduced into the oxide 530 or the insulator near the oxide 530. In addition, in the microwave processing described above, the pressure is 133 Pa or more, preferably 200 Pa or more, and more preferably 400 Pa or more. Furthermore, oxygen and argon are used as the gases introduced into the device for performing microwave processing, and the microwave processing is performed under conditions where the oxygen flow ratio (O2 / (O2+Ar)) is 50% or less, preferably 10% or more and 30% or less.

[0328] Furthermore, in the manufacturing process of the transistor 500, it is preferable to perform heat treatment with the surface of the oxide 530 exposed. This heat treatment is preferably performed at a temperature of 100°C or higher and 450°C or lower, more preferably at 350°C or higher and 400°C or lower. The heat treatment is performed in a nitrogen or inert gas atmosphere, or in an atmosphere containing 10 ppm or higher, 1% or higher, or 10% or higher of an oxidizing gas. Therefore, oxygen can be supplied to the oxide 530, thereby reducing oxygen vacancies (Vo). Alternatively, the heat treatment can also be performed under reduced pressure. For example, the heat treatment is preferably performed in an oxygen atmosphere. Alternatively, the heat treatment can be performed in a nitrogen or inert gas atmosphere, and then, to replenish the released oxygen, heat treatment can be performed in an atmosphere containing 10 ppm or higher, 1% or higher, or 10% or higher of an oxidizing gas. Alternatively, heat treatment can be performed in an atmosphere containing 10 ppm or higher, 1% or higher, or 10% or higher of an oxidizing gas, followed by continuous heat treatment in a nitrogen or inert gas atmosphere.

[0329] Furthermore, by subjecting oxide 530 to oxidation treatment, oxygen vacancies in oxide 530 can be filled by the supplied oxygen; in other words, the reaction “Vo + O → null” can be promoted. Moreover, the hydrogen remaining in oxide 530 reacts with the oxygen supplied to oxide 530, removing the hydrogen as H2O (dehydration). Thus, the recombination of hydrogen remaining in oxide 530 with oxygen vacancies to form VoH can be inhibited.

[0330] When the insulator 524 has an excess oxygen region, the insulator 522 preferably has the function of inhibiting the diffusion of oxygen (e.g., oxygen atoms, oxygen molecules, etc.) (making it difficult for the aforementioned oxygen to pass through).

[0331] When the insulator 522 has the function of suppressing the diffusion of oxygen or impurities, it is preferable that the oxygen contained in the oxide 530 does not diffuse to the side of the insulator 520. In addition, it is possible to suppress the reaction between the conductor 503 and the oxygen contained in the insulator 524 or the oxide 530.

[0332] As the insulator 522, it is preferably a single layer or a stack of so-called high-k materials such as alumina, hafnium oxide, oxides containing aluminum and hafnium (hafnium aluminate), tantalum oxide, zirconium oxide, lead zirconate titanate (PZT), strontium titanate (SrTiO3), or (Ba,Sr)TiO3 (BST). When miniaturizing and hyper-integrating transistors, problems such as leakage current sometimes occur due to the thinning of the gate insulating film. By using a high-k material as the insulator used as the gate insulating film, the gate potential during transistor operation can be reduced while maintaining the physical thickness.

[0333] In particular, it is preferable to use an insulator containing an oxide of one or both of aluminum and hafnium, which serves as an insulating material that inhibits the diffusion of impurities and oxygen (making it difficult for the aforementioned oxygen to permeate). As an insulator containing an oxide of one or both of aluminum and hafnium, aluminum oxide, hafnium oxide, or an oxide containing aluminum and hafnium (hafnium aluminate) are preferred. When such a material is used to form the insulator 522, the insulator 522 serves as a layer that inhibits the release of oxygen from the oxide 530 or the entry of impurities such as hydrogen from the periphery of the transistor 500 into the oxide 530.

[0334] Alternatively, for example, aluminum oxide, bismuth oxide, germanium oxide, niobium oxide, silicon oxide, titanium oxide, tungsten oxide, yttrium oxide, or zirconium oxide may be added to the above-mentioned insulator. Furthermore, the above-mentioned insulator may be subjected to nitriding treatment. Silicon oxide, silicon oxynitride, or silicon nitride may also be laminated onto the above-mentioned insulator.

[0335] The insulator 520 preferably has thermal stability. For example, silicon oxide and silicon oxynitride are preferred because they have thermal stability. In addition, by combining a high-k material insulator with silicon oxide or silicon oxynitride, an insulator 520 with a multilayer structure that has thermal stability and a high relative permittivity can be formed.

[0336] In the transistor 500 of Figures 25A and 25B, insulators 520, 522, and 524 are used as the second gate insulating film, which is composed of a three-layer stacked structure. However, the second gate insulating film may also have a single-layer, two-layer, or four-layer or more stacked structure. In this case, it is not limited to using a stacked structure made of the same material, but may also be a stacked structure formed of different materials.

[0337] In the transistor 500, it is preferable to use a metal oxide, which is used as an oxide semiconductor, in the oxide 530 containing the channel forming region. For example, as the oxide 530, it is preferable to use an In-M-Zn oxide (element M is selected from one or more of aluminum, gallium, yttrium, copper, vanadium, beryllium, boron, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, and magnesium). In particular, the In-M-Zn oxide that can be used for the oxide 530 is preferably CAAC-OS (C-Aligned Crystal Oxide Semiconductor) or CAC-OS (Cloud-Aligned Composite Oxide Semiconductor). CAAC-OS and CAC-OS will be described later. In addition, In-Ga oxide and In-Zn oxide can also be used as the oxide 530. When it is desired to increase the on-state current of the transistor 500, it is preferable to use an In-Zn oxide as the oxide 530. When In-Zn oxide is used as oxide 530, for example, the following structures can be described: a stacked structure in which oxide 530a uses In-Zn oxide and oxides 530b and oxide 530c use In-M-Zn oxide; or a stacked structure in which oxide 530a uses In-M-Zn oxide and either oxide 530b or oxide 530c uses In-Zn oxide, etc.

[0338] Furthermore, a metal oxide with a low carrier density is preferably used as the transistor 500. By reducing the carrier density of the metal oxide, the impurity concentration in the metal oxide can be reduced, thereby reducing the defect state density. In this specification, the state of low impurity concentration and low defect state density is referred to as "high purity nature" or "substantially high purity nature." Examples of impurities in the metal oxide include hydrogen, nitrogen, alkali metals, alkaline earth metals, iron, nickel, and silicon.

[0339] In particular, hydrogen contained in metal oxides reacts with oxygen bonded to metal atoms to form water, thus sometimes forming oxygen vacancies in metal oxides. Furthermore, when hydrogen enters an oxygen vacancy in oxide 530, the oxygen vacancy sometimes bonds with hydrogen to form VoH. VoH sometimes acts as a donor and generates electrons as carriers. Additionally, sometimes a portion of the hydrogen bonds with oxygen bonded to metal atoms, generating electrons as carriers. Therefore, transistors using metal oxides containing a large amount of hydrogen tend to have always-on characteristics. Furthermore, hydrogen in metal oxides is easily moved by heat, electric fields, etc., so the reliability of the transistor may decrease when the metal oxide contains a large amount of hydrogen. In one embodiment of the present invention, it is preferable to minimize the VoH in oxide 530 to achieve a high-purity or substantially high-purity nature. To obtain metal oxides with significantly reduced VoH, it is important to: remove impurities such as water and hydrogen from the metal oxide (sometimes referred to as dehydration or dehydrogenation treatment); and supply oxygen to the metal oxide to fill oxygen vacancies (sometimes referred to as oxidation treatment). By using metal oxides with significantly reduced impurities such as VoH in the channel formation region of transistors, stable electrical properties can be imparted.

[0340] Defects resulting from hydrogen entering oxygen vacancies can serve as donors in metal oxides. However, it is difficult to quantitatively evaluate these defects. Therefore, in metal oxides, the carrier concentration is sometimes used instead of the donor concentration for evaluation. Consequently, in this specification and the like, the carrier concentration under conditions assuming no applied electric field is sometimes used instead of the donor concentration as a parameter for metal oxides. In other words, the "carrier concentration" described in this specification and the like can sometimes also be referred to as the "donor concentration".

[0341] Therefore, when using metal oxides for oxide 530, it is preferable to minimize the amount of hydrogen in the metal oxide. Specifically, the hydrogen concentration in the metal oxide, as measured by secondary ion mass spectrometry (SIMS), is less than 1 × 10²⁰ atoms / cm³, preferably less than 1 × 10¹⁹ atoms / cm³, more preferably less than 5 × 10¹⁸ atoms / cm³, and even more preferably less than 1 × 10¹⁸ atoms / cm³. By using metal oxides with sufficiently reduced impurities such as hydrogen in the channel-forming region of the transistor, the transistor can have stable electrical properties.

[0342] Furthermore, when using a metal oxide as oxide 530, the carrier concentration of the metal oxide in the channel forming region is preferably less than 1×10¹⁸ cm⁻³, more preferably less than 1×10¹⁷ cm⁻³, further preferably less than 1×10¹⁶ cm⁻³, even more preferably less than 1×10¹³ cm⁻³, and still more preferably less than 1×10¹² cm⁻³. Note that there is no particular limitation on the lower limit of the carrier concentration of the metal oxide in the channel forming region; for example, it can be set to 1×10⁻⁹ cm⁻³.

[0343] Furthermore, when a metal oxide is used as oxide 530, when the conductor 542 (conductor 542a and conductor 542b) comes into contact with the oxide 530, oxygen in the oxide 530 may diffuse into the conductor 542, causing the conductor 542 to be oxidized. When the conductor 542 is oxidized, the conductivity of the conductor 542 is likely to decrease. Alternatively, the phenomenon of "oxygen in oxide 530 diffusing into conductor 542" can also be referred to as "oxygen in oxide 530 being absorbed by conductor 542".

[0344] Furthermore, when oxygen diffuses from oxide 530 to conductor 542 (conductor 542a and conductor 542b), a layer may sometimes form between conductor 542a and oxide 530b, and between conductor 542b and oxide 530b. This layer contains more oxygen than conductor 542, and it can be inferred that this layer has insulating properties. In this case, the three-layer structure of conductor 542, this layer, and oxide 530b can be regarded as a three-layer structure composed of metal, insulator, and semiconductor, sometimes called a MIS (Metal-Insulator-Semiconductor) structure or a diode junction structure with MIS structure as the main structure.

[0345] Note that the above-mentioned layer is not limited to being formed between the conductor 542 and the oxide 530b. For example, sometimes the layer is formed between the conductor 542 and the oxide 530c. Or, sometimes it is formed between the conductor 542 and the oxide 530b and between the conductor 542 and the oxide 530c.

[0346] Furthermore, the metal oxide used as the channel forming region in oxide 530 is preferably a metal oxide with a band gap of 2 eV or more, and more preferably 2.5 eV or more. In this way, by using a metal oxide with a wider band gap, the off-state current of the transistor can be reduced.

[0347] In oxide 530, when oxide 530a is disposed below oxide 530b, impurities can be prevented from diffusing from the structure formed below oxide 530a to oxide 530b. When oxide 530c is disposed above oxide 530b, impurities can be prevented from diffusing from the structure formed above oxide 530c to oxide 530b.

[0348] Furthermore, oxide 530 is preferably a stacked structure of multiple oxide layers having different ratios of the number of each metal atom. Specifically, the ratio of the number of atoms of element M in the constituent elements of the metal oxide used for oxide 530a is preferably greater than the ratio of the number of atoms of element M in the constituent elements of the metal oxide used for oxide 530b. Furthermore, the ratio of the number of atoms of element M relative to In in the metal oxide used for oxide 530a is preferably greater than the ratio of the number of atoms of element M relative to In in the metal oxide used for oxide 530b. Furthermore, the ratio of the number of atoms of In relative to element M in the metal oxide used for oxide 530b is preferably greater than the ratio of the number of atoms of In relative to element M in the metal oxide used for oxide 530a. Additionally, oxide 530c can use a metal oxide that can be used for oxide 530a or oxide 530b.

[0349] Specifically, oxide 530a can use metal oxides with an In:Ga:Zn ratio of 1:3:4 or 1:1:0.5. Furthermore, oxide 530b can use metal oxides with an In:Ga:Zn ratio of 4:2:3 or 1:1:1. Additionally, oxide 530c can use metal oxides with an In:Ga:Zn ratio of 1:3:4, Ga:Zn ratio of 2:1, or Ga:Zn ratio of 2:5. Specific examples of oxide 530c with a multilayer structure include multilayer structures with In:Ga:Zn = 4:2:3 (atomic ratio) and In:Ga:Zn = 1:3:4 (atomic ratio), multilayer structures with Ga:Zn = 2:1 (atomic ratio) and In:Ga:Zn = 4:2:3 (atomic ratio), multilayer structures with Ga:Zn = 2:5 (atomic ratio) and In:Ga:Zn = 4:2:3 (atomic ratio), and multilayer structures with gallium oxide and In:Ga:Zn = 4:2:3 (atomic ratio).

[0350] Preferably, the conduction band bottom energies of oxides 530a and 530c are higher than those of oxide 530b. In other words, the electron affinity of oxides 530a and 530c is preferably lower than that of oxide 530b.

[0351] Here, in the junction of oxides 530a, 530b, and 530c, the energy level of the conduction band bottom changes gradually. In other words, the above situation can also be expressed as the energy level of the conduction band bottom at the junction of oxides 530a, 530b, and 530c changing continuously or continuously joining. For this purpose, it is preferable to reduce the defect state density of the mixed layer formed at the interface between oxides 530a and 530b and the interface between oxides 530b and 530c.

[0352] Specifically, by making oxides 530a and 530b, and oxides 530b and 530c contain common elements (as the main components) other than oxygen, a mixed layer with low defect state density can be formed. For example, when oxide 530b is an In-Ga-Zn oxide, it is preferable to use In-Ga-Zn oxide, Ga-Zn oxide, and gallium oxide as oxides 530a and 530c.

[0353] At this time, the main pathway for the carrier is oxide 530b. By giving oxides 530a and 530c the above-described structure, the defect state density at the interface between oxides 530a and 530b, and at the interface between oxides 530b and 530c, can be reduced. Therefore, the influence of interface scattering on carrier conduction is reduced, and the on-state current of transistor 500 can be increased.

[0354] Note that the semiconductor materials that can be used in oxide 530 are not limited to the metal oxides described above. Oxide 530 can also be a semiconductor material with a band gap (a semiconductor material that is not a zero-bandgap semiconductor). For example, it is preferable to use a single-element semiconductor such as silicon, a compound semiconductor such as gallium arsenide, or a layered material used as a semiconductor (also called an atomic layer material, a two-dimensional material, etc.). In particular, it is preferable to use a layered material used as a semiconductor as the semiconductor material.

[0355] Herein, in this specification and the like, layered materials are a general term for a group of materials having a layered crystalline structure. A layered crystalline structure is a structure in which layers formed by covalent or ionic bonds are stacked by bonds weaker than covalent or ionic bonds, such as van der Waals forces. Layered materials have high conductivity per unit layer, that is, high two-dimensional conductivity. By using a material that is used as a semiconductor and has high two-dimensional conductivity in the channel forming region, transistors with large on-state currents can be provided.

[0356] As layered materials, there are graphene, silicon, chalcogenides, etc. Chalcogenides are compounds containing chalcogen elements. Furthermore, chalcogen elements are a collective term for elements belonging to Group 16, including oxygen, sulfur, selenium, tellurium, polonium, and protium. Other examples of chalcogenides include transition metal chalcogenides and Group 13 chalcogenides.

[0357] As oxide 530, it is preferred to use a transition metal chalcogenide that is used as a semiconductor. Examples of transition metal chalcogenides that can be used as oxide 530 include molybdenum sulfide (typically MoS2), molybdenum selenide (typically MoSe2), molybdenum telluride (typically MoTe2), tungsten sulfide (typically WS2), tungsten selenide (typically WSe2), tungsten telluride (typically WTe2), hafnium sulfide (typically HfS2), hafnium selenide (typically HfSe2), zirconium sulfide (typically ZrS2), and zirconium selenide (typically ZrSe2).

[0358] Conductors 542a and 542b, serving as source and drain electrodes, are provided on oxide 530b. Preferably, conductors 542a and 542b are metal elements selected from aluminum, chromium, copper, silver, gold, platinum, tantalum, nickel, titanium, molybdenum, tungsten, hafnium, vanadium, niobium, manganese, magnesium, zirconium, beryllium, indium, ruthenium, iridium, strontium, and lanthanum, alloys containing the aforementioned metal elements, or alloys combining the aforementioned metal elements. For example, tantalum nitride, titanium nitride, tungsten, nitrides containing titanium and aluminum, nitrides containing tantalum and aluminum, ruthenium oxide, ruthenium nitride, oxides containing strontium and ruthenium, and oxides containing lanthanum and nickel are preferred. In addition, tantalum nitride, titanium nitride, nitrides containing titanium and aluminum, nitrides containing tantalum and aluminum, ruthenium oxide, ruthenium nitride, oxides containing strontium and ruthenium, and oxides containing lanthanum and nickel are conductive materials that are not easily oxidized or maintain conductivity even after absorbing oxygen, so they are preferred. Furthermore, metal nitride films such as tantalum nitride have a barrier effect against hydrogen or oxygen, so they are also preferred.

[0359] Furthermore, although single-layer conductors 542a and 542b are shown in Figures 25A and 25B, stacked structures of two or more layers may also be used. For example, a stacked tantalum nitride film and a tungsten film are preferred. Alternatively, a titanium film and an aluminum film may be stacked. Additionally, a two-layer structure with an aluminum film stacked on a tungsten film, a two-layer structure with a copper film stacked on a copper-magnesium-aluminum alloy film, a two-layer structure with a copper film stacked on a titanium film, and a two-layer structure with a copper film stacked on a tungsten film may also be used.

[0360] Alternatively, a three-layer structure can be used, in which an aluminum film or a copper film is laminated on a titanium film or a titanium nitride film and a titanium film or titanium nitride film is formed thereon; or a three-layer structure can be used, in which an aluminum film or a copper film is laminated on a molybdenum film or a molybdenum nitride film and a molybdenum film or molybdenum nitride film is formed thereon. Additionally, transparent conductive materials containing indium oxide, tin oxide, or zinc oxide can also be used.

[0361] Additionally, as shown in FIG25A, regions 543a and 543b are sometimes formed as low-resistance regions at and near the interface between oxide 530 and conductor 542a (conductor 542b). In this case, region 543a is used as one of the source region and drain region, and region 543b is used as the other of the source region and drain region. Furthermore, a channel forming region is formed in the region sandwiched between region 543a and region 543b.

[0362] By forming the aforementioned conductor 542a (conductor 542b) in contact with oxide 530, the oxygen concentration in region 543a (region 543b) sometimes decreases. Furthermore, a metal compound layer comprising the metal contained in conductor 542a (conductor 542b) and the oxide 530 sometimes forms in region 543a (region 543b). In this case, the carrier concentration in region 543a (region 543b) increases, and region 543a (region 543b) becomes a low-resistance region.

[0363] The insulator 544 is provided in such a way that it covers the conductors 542a and 542b to suppress the oxidation of the conductors 542a and 542b. At this time, the insulator 544 may also be provided in such a way that it covers the side of the oxide 530 and is in contact with the insulator 524.

[0364] As the insulator 544, one or more metal oxides selected from hafnium, aluminum, gallium, yttrium, zirconium, tungsten, titanium, tantalum, nickel, germanium, neodymium, lanthanum, and magnesium may be used. Alternatively, silicon oxynitride or silicon nitride may also be used as the insulator 544.

[0365] In particular, as the insulator 544, it is preferable to use alumina, hafnium oxide, or an oxide containing aluminum and hafnium (hafnium aluminate) as an insulator that is an oxide containing one or both of aluminum and hafnium. In particular, hafnium aluminate has higher heat resistance than hafnium oxide film. Therefore, it is less prone to crystallization during subsequent heat treatment processes, which is preferable. In addition, if the conductors 542a and 542b are oxidation-resistant materials or their conductivity does not decrease significantly upon oxygen absorption, it is not necessary to provide the insulator 544. It can be appropriately designed according to the required transistor characteristics.

[0366] By including insulator 544, it is possible to suppress the diffusion of impurities such as water and hydrogen contained in insulator 580 through oxide 530c and insulator 550 to oxide 530b. In addition, it is possible to suppress the oxidation of conductor 560 by excess oxygen contained in insulator 580.

[0367] In addition, insulator 550 is used as a first gate insulating film. Insulator 550 is preferably disposed in contact with the inner side (top and side) of oxide 530c. Similar to insulator 524 described above, insulator 550 is preferably formed using an insulator containing excess oxygen and releasing oxygen by heating.

[0368] Specifically, silicon oxide containing excess oxygen, silicon oxynitride, silicon oxynitride, silicon nitride, silicon oxide with added fluorine, silicon oxide with added carbon, silicon oxide with added carbon and nitrogen, and porous silicon oxide can be used. In particular, silicon oxide and silicon oxynitride have thermal stability, so they are preferred.

[0369] By providing an insulator 550 in contact with the top surface of oxide 530c, which releases oxygen upon heating, oxygen can be effectively supplied from the channel formation region of oxide 530b through oxide 530c in the insulator 550. Furthermore, similar to insulator 524, it is preferable to reduce the concentration of impurities such as water or hydrogen in the insulator 550. The thickness of the insulator 550 is preferably 1 nm or more and 20 nm or less.

[0370] Furthermore, in order to efficiently supply excess oxygen contained in the insulator 550 to the oxide 530, a metal oxide may be disposed between the insulator 550 and the conductor 560. Preferably, this metal oxide is capable of suppressing oxygen diffusion from the insulator 550 to the conductor 560. By disposing of a metal oxide capable of suppressing oxygen diffusion, the diffusion of excess oxygen from the insulator 550 to the conductor 560 is suppressed. In other words, the reduction of excess oxygen supplied to the oxide 530 can be suppressed. Additionally, oxidation of the conductor 560 due to excess oxygen can be suppressed. As this metal oxide, a material suitable for the insulator 544 can be used.

[0371] Furthermore, similar to the second gate insulating film, the insulator 550 can also have a laminated structure. When miniaturizing and hyper-integrating transistors, leakage current and other problems sometimes occur due to the thinning of the gate insulating film. Therefore, by having the insulator used as the gate insulating film have a laminated structure of a high-k material and a thermally stable material, the gate potential during transistor operation can be reduced while maintaining the physical thickness. In addition, a laminated structure with thermal stability and a high relative permittivity can be achieved.

[0372] In Figures 25A and 25B, the conductor 560 used as the first gate electrode has a two-layer structure, but it may also have a single-layer structure or a stacked structure of three or more layers.

[0373] As the conductor 560a, it is preferable to use a conductive material that has the function of suppressing the diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, nitrogen atoms, nitrogen molecules, nitrogen oxide molecules (N2O, NO, NO2, etc.), and copper atoms. Furthermore, it is preferable to use a conductive material that has the function of suppressing the diffusion of oxygen (e.g., at least one of oxygen atoms, oxygen molecules, etc.). By giving the conductor 560a the function of suppressing oxygen diffusion, the decrease in conductivity caused by the oxidation of the conductor 560b due to oxygen contained in the insulator 550 can be suppressed. For example, tantalum, tantalum nitride, ruthenium, or ruthenium oxide are preferred conductive materials for suppressing oxygen diffusion. Additionally, an oxide semiconductor suitable for use in the oxide 530 can be used as the conductor 560a. In this case, by forming the conductor 560a using a sputtering method, the resistance value of the conductor 560b can be reduced, making it a conductor. This conductor can be referred to as an OC (Oxide Conductor) electrode.

[0374] As the conductor 560b, it is preferable to use a conductive material with tungsten, copper, or aluminum as the main components. Since the conductor 560b is also used for wiring, it is preferable to use a conductor with high conductivity. The conductor 560b may also have a multilayer structure, for example, a multilayer structure of titanium or titanium nitride and the above-mentioned conductive material may be used.

[0375] The insulator 580 is preferably disposed on the conductors 542a and 542b, separated by an insulator 544. The insulator 580 preferably has an excess oxygen region. For example, the insulator 580 is preferably composed of silicon oxide, silicon oxynitride, silicon oxynitride, silicon nitride, fluorine-added silicon oxide, carbon-added silicon oxide, silicon oxide with both carbon and nitrogen added, porous silicon oxide, or resin, etc. In particular, silicon oxide and silicon oxynitride are preferred due to their thermal stability. In particular, silicon oxide and porous silicon oxide are preferred because they readily form excess oxygen regions in subsequent processes.

[0376] The insulator 580 preferably has a region with excess oxygen. By providing the insulator 580, which releases oxygen upon heating, in such a way that it has a region in contact with the oxide 530c, the oxygen in the insulator 580 can be efficiently supplied to the oxides 530a and 530b via the oxide 530c. Furthermore, it is preferable to reduce the concentration of impurities such as water or hydrogen in the insulator 580.

[0377] The opening of the insulator 580 is formed in such a way that it overlaps with the area between the conductors 542a and 542b. Thus, the conductor 560 is embedded in the opening of the insulator 580 and in the area between the conductors 542a and 542b.

[0378] When miniaturizing semiconductor devices, it is necessary to shorten the gate length, but it is also necessary to prevent a decrease in the conductivity of the conductor 560. Therefore, by increasing the thickness of the conductor 560, the conductor 560 may have a shape with a high aspect ratio. In this embodiment, since the conductor 560 is embedded in the opening of the insulator 580, even if the conductor 560 has a high aspect ratio, it can be formed without the conductor 560 collapsing during the manufacturing process.

[0379] Preferably, the insulator 574 is disposed on the top surface of the insulator 580, the top surface of the conductor 560, and the top surface of the insulator 550. By forming the insulator 574 using a sputtering method, an excess oxygen region can be formed in the insulator 550 and the insulator 580. Oxygen can then be supplied from this excess oxygen region to the oxide 530.

[0380] For example, as insulator 574, one or more metal oxides selected from hafnium, aluminum, gallium, yttrium, zirconium, tungsten, titanium, tantalum, nickel, germanium and magnesium may be used.

[0381] In particular, alumina has high barrier properties, and even thin films of 0.5 nm or larger and 3.0 nm or smaller can suppress the diffusion of hydrogen and nitrogen. Therefore, alumina formed by sputtering can function as a barrier film against impurities such as hydrogen while being used as an oxygen supply source.

[0382] Furthermore, it is preferable to provide an insulator 581, which serves as an interlayer film, on the insulator 574. Similar to the insulator 524, it is preferable to reduce the concentration of impurities such as water or hydrogen in the insulator 581.

[0383] In addition, conductors 540a and 540b are disposed in the openings formed in insulators 581, 574, 580 and 544. Conductors 540a and 540b are disposed opposite to each other with a distance between them and conductors 560.

[0384] By adopting this structure, miniaturization or high integration of semiconductor devices using transistors containing oxide semiconductors can be achieved.

[0385] <Structural Example of an Electronic Device That Can Use a Display Module> Next, an example of an electronic device that can use the above-described display module 401 will be described with reference to FIG26.

[0386] The display module 401 can be installed in the display section of TV devices (television receivers) 7000, smartwatches 7010, smartphones 7020, digital cameras 7030, glasses-type information terminals 7040, notebook PCs (personal computers) 7050, PCs 7060, game consoles 7070, etc.

[0387] By using display module 401 on the display units of TV devices 7000, smartwatches 7010, smartphones 7020, digital cameras 7030, glasses-type information terminals 7040, laptop PCs 7050 and 7060, game consoles 7070, etc., high-definition images can be displayed. Users can see realistic images.

[0388] This embodiment can be implemented by appropriately combining it with structures described in other embodiments, etc. Example

[0389] In this embodiment, a light-emitting device according to one embodiment of the present invention is manufactured and its reliability test results are described. Note that the light-emitting device in this embodiment corresponds to the structure shown in FIG2A.

[0390] In this embodiment, four devices, namely device 1, device 2, device 3, and device 4, are manufactured as light-emitting devices using one embodiment of the present invention. All four devices are blue light-emitting devices.

[0391] In addition, in this embodiment, eight devices are used as comparison light-emitting devices: device 11, device 12, device 13, device 14, device 15, device 16, device 17, and device 18. All eight devices are light-emitting devices that emit blue light.

[0392] Figure 27 shows the reliability test results of devices 11 and 12 for comparison. In Figure 27, the vertical axis represents the normalized brightness when the initial brightness is 100%, and the horizontal axis represents the driving time of the device.

[0393] Devices 11 and 12 are driven under the same stress conditions. The equivalent stress brightness is calculated using the formula: Equivalent stress brightness = Initial brightness ÷ Transmittance of the circular polarizer ÷ Aperture ratio. It is assumed that the transmittance of the circular polarizer is approximately 40%. The aperture ratios of devices 11 and 12 are approximately 4.87%. The equivalent stress brightness of devices 11 and 12 is approximately 2300 cd / m².

[0394] The chromaticity (x, y) of devices 11 and 12 is (0.145 to 0.146, 0.045 to 0.047).

[0395] As shown in Figure 27, the LT95 (time taken for the brightness to drop to 95% of the initial brightness) of device 11 is 242hr, while the LT95 of device 12 is 106hr.

[0396] Figure 28 shows the reliability test results of devices 1 and 2 using a light-emitting device according to one embodiment of the present invention, and devices 13, 14, 15 and 16 for comparison. In Figure 28, the vertical axis represents the normalized brightness when the initial brightness is 100%, and the horizontal axis represents the driving time of the device.

[0397] Devices 1, 2, 13, 14, 15, and 16 are driven under the same stress conditions. The equivalent stress luminance of the six devices is approximately 1300 cd / m². Furthermore, it is assumed that the transmittance of the circular polarizer is approximately 40%. The aperture ratio of devices 13, 14, 15, and 16 is approximately 7.29%.

[0398] The chromaticity (x, y) of devices 13, 14, 15 and 16 is (0.142 to 0.144, 0.047 to 0.051).

[0399] As shown in FIG28, the LT95 of devices 1 and 2 using one embodiment of the present invention is 400 hours or more. In addition, as shown in FIG28, the LT95 of device 13 is 17 hours, the LT95 of device 14 is 55 hours, the LT95 of device 15 is 103 hours, and the LT95 of device 16 is 62 hours.

[0400] Figure 29 shows the reliability test results of devices 3 and 4 using a light-emitting device according to one embodiment of the present invention, and devices 17 and 18 for comparison. In Figure 29, the vertical axis represents the normalized brightness when the initial brightness is 100%, and the horizontal axis represents the driving time of the device.

[0401] Devices 3, 4, 17, and 18 are driven under the same stress conditions. The equivalent stress luminance of the four devices is approximately 1450 cd / m². Additionally, it is assumed that the transmittance of the circular polarizer is approximately 40%. The aperture ratio of devices 17 and 18 is approximately 6.78%.

[0402] The chromaticity (x, y) of devices 17 and 18 is (0.140 to 0.141, 0.055 to 0.057).

[0403] As shown in Figure 29, the LT95 of devices 3 and 4 using one embodiment of the present invention is 400hr or more. In addition, as shown in Figure 29, the LT95 of device 17 is 67hr and the LT95 of device 18 is 92hr.

[0404] As can be seen from the above, the LT95 of the light-emitting device using one embodiment of the present invention is 400 hours or more. The results of this embodiment show that the light-emitting device using one embodiment of the present invention has an extremely long lifespan compared to the comparative light-emitting device. [Simplified Explanation of the Diagram]

[0045] In the figures: [Figure 1A] and [Figure 1B] are schematic diagrams of the light-emitting device; [Figure 2A] to [Figure 2C] are schematic diagrams of the light-emitting device; [Figure 3A] and [Figure 3B] are diagrams illustrating the light-emitting area of ​​the light-emitting device; [Figure 4A] and [Figure 4B] are diagrams illustrating the light-emitting area of ​​the light-emitting device; [Figure 5A] to [Figure 5C] are schematic diagrams of the light-emitting device; [Figure 6A] to [Figure 6C] are schematic diagrams of the light-emitting device; [Figure 7A] and [Figure 7B] are schematic diagrams of the light-emitting device; [Figure 8A] is a top view of the display device, and [Figure 8B] is a cross-sectional view of the display device; [Figure 9A] and [Figure 9B] are cross-sectional views of the light-emitting device; [Figure 10] is a cross-sectional view of the light-emitting device; [Figure 11A], [Figure 11B1], [Figure 11B2] and [Figure 11C] are diagrams showing the electronic device; [Figure 12A] to [Figure 12C] are diagrams showing the electronic device; [Figure 13] is a diagram showing an in-vehicle display device and lighting equipment; [Figure 14A] and [Figure 14B] are diagrams showing electronic devices; [Figure 15A] to [Figure 15C] are diagrams showing electronic devices; [Figure 16] is a diagram showing the structure of an electron-only element; [Figure 17] is a diagram showing the current density-voltage characteristics of an electron-only element; [Figure 18] is a diagram showing the frequency characteristics of the capacitance C calculated by ZADN:Liq(1:1) at a DC voltage of 7.0V; [Figure 19] is a diagram showing the frequency characteristics of -ΔB of ZADN:Liq(1:1) at a DC voltage of 7.0V; [Figure 20] is a diagram showing the electric field intensity dependence of the electron mobility of various organic compounds; [Figure 21] is a schematic diagram of a light-emitting device; [Figure 22A] to [Figure 22D] are diagrams illustrating the concentration of the electron transport layer; [Figure 23] is a perspective view showing an example of the structure of a semiconductor device; [Fig. 24A] and [Fig. 24B] are perspective views showing structural examples of semiconductor devices; [Fig. 25A] and [Fig. 25B] are cross-sectional views showing structural examples of transistors; [Fig. 26] is a diagram illustrating an electronic device; [Fig. 27] is a graph showing the time-varying normalized brightness of the device of the embodiment; [Fig. 28] is a graph showing the time-varying normalized brightness of the device of the embodiment; [Fig. 29] is a graph showing the time-varying normalized brightness of the device of the embodiment.

Claims

1. A light-emitting device, comprising: a first light-emitting element; and a first color conversion layer, wherein: The first color conversion layer contains a first material capable of absorbing and emitting light. Light from the first light-emitting device is configured to be incident on the first color conversion layer. The first light-emitting device includes an anode, a cathode, and an EL layer located between the anode and the cathode. The EL layer, from the anode side, sequentially includes a first layer, a second layer, a third layer, an emitting layer, and a fourth layer. The first layer is in contact with the anode. The first layer contains a first organic compound and a second organic compound. The second layer contains a third organic compound. The third layer contains a fourth organic compound. The emitting layer contains a fifth organic compound and a sixth organic compound. The fourth layer contains a seventh organic compound. The fourth layer is in contact with the emitting layer. The first organic compound is an organic compound having one of a cyano group and a fluorine group. The fifth organic compound is the emitting center material. The HOMO energy difference between the fourth organic compound and the third organic compound is less than 0.2 eV. The HOMO energy level of the fourth organic compound is deeper than that of the third organic compound, and the electron mobility of the seventh organic compound is greater than 1×10-7 cm2 / Vs and less than 5×10-5 cm2 / Vs when the square root of the electric field strength [V / cm] is 600.

2. The light-emitting device according to claim 1, wherein, The third layer is in contact with the light-emitting layer.

3. The light-emitting device according to claim 1, wherein, The HOMO level of this seventh organic compound is above -6.0 eV.

4. The light-emitting device according to claim 1, wherein: The HOMO energy level difference between the third organic compound and the second organic compound is less than 0.2 eV, the HOMO energy level of the third organic compound is the same as or deeper than the HOMO energy level of the second organic compound, and the HOMO energy level of the seventh organic compound is greater than -6.0 eV.

5. The light-emitting device according to claim 1, wherein: The second organic compound includes a first hole-transporting framework, the third organic compound includes a second hole-transporting framework, the fourth organic compound includes a third hole-transporting framework, the first hole-transporting framework, the second hole-transporting framework and the third hole-transporting framework independently represent any one of the carbazole framework, the dibenzofuran framework, the dibenzothiophene framework and the anthracene framework, and the seventh organic compound has a HOMO level of -6.0 eV or higher.

6. The light-emitting device according to claim 1, wherein the electron mobility of the seventh organic compound is less than that of the sixth organic compound.

7. The light-emitting device according to claim 1, wherein the second organic compound is an organic compound comprising a dibenzofuran skeleton.

8. The light-emitting device according to claim 1, wherein the second organic compound and the third organic compound are the same substance.

9. The light-emitting device according to claim 1, wherein the fifth organic compound is a blue fluorescent material.

10. The light-emitting device according to claim 1, wherein the degradation curve representing the brightness change of the light emitted when a constant current is supplied to the first light-emitting device has a maximum value.

11. The light-emitting device according to claim 1, wherein the first substance capable of absorbing light and emitting light is a quantum dot.

12. The light-emitting device according to claim 1, wherein the first light-emitting device has a microcavity structure.

13. The light-emitting device according to claim 1 further comprises: a second light-emitting device; and a second color conversion layer, wherein: The second color conversion layer contains a second material capable of absorbing and emitting light. Light from the second light-emitting device is configured to be incident on the second color conversion layer. The second light-emitting device has the same structure as the first light-emitting device, and the wavelength of the light from the first material is different from the wavelength of the light from the second material.

14. The light-emitting device according to claim 13, wherein the second substance is a quantum dot.

15. The light-emitting device according to claim 13, wherein the second light-emitting device has a microcavity structure.

16. The light-emitting device according to claim 13 further includes a third light-emitting device, wherein: The third light-emitting device has the same structure as the first light-emitting device, and the light from the third light-emitting device is configured to be emitted outside the light-emitting device without passing through the color conversion layer.

17. The light-emitting device according to claim 13 further comprises: a third light-emitting device; a first color layer; a second color layer; and a resin layer, wherein: Light from the first light-emitting device is configured to be emitted through the first color conversion layer and the first color layer; light from the second light-emitting device is configured to be emitted through the second color conversion layer and the second color layer; the third light-emitting device has the same structure as the first light-emitting device; and light from the third light-emitting device is configured to be emitted through the resin layer.

18. An electronic device comprising: a light-emitting device according to claim 1; and any one of a sensor, an operation button, a speaker, and a microphone.

19. A display device comprising a light-emitting device according to claim 1.

20. An electronic device comprising: a light-emitting device according to claim 1; and a transistor, wherein, The transistor includes an oxide semiconductor.

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