Light-emitting devices, light-emitting apparatus, electronic equipment and lighting apparatus

Abstract

To provide a novel light-emitting device, to provide a light-emitting device with high emission efficiency, to provide a light-emitting device with a favorable lifetime, or to provide a light-emitting device with low driving voltage.SOLUTION: There is provided a light-emitting device which includes an anode, a cathode, and an EL layer positioned between the anode and the cathode. The EL layer includes a hole-injection layer, a light-emitting layer, and an electron-transport layer. The hole-injection layer contains a hole-transport material and an electron-accepting material. The electron-transport layer contains: an electron-transport material; and an alkali metal itself, an alkaline earth metal itself, a compound of an alkali metal or an alkaline earth metal, or a complex thereof. The spin density of the hole-injection layer measured by an ESR method is lower than or equal to 1×1019 spins / cm3.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] One aspect of the present invention relates to a light-emitting device, a light-emitting element, a display module, a lighting module, a display device, a light-emitting device, an electronic device, and a lighting device. Note that one aspect of the present invention is not limited to the above technical field. The technical field of one aspect of the invention disclosed in this specification and the like relates to an object, a method, or a manufacturing method. Or, one aspect of the present invention relates to a process, a machine, a manufacture, or a composition (composition of matter). Therefore, more specifically, as the technical field of one aspect of the present invention disclosed in this specification, semiconductor devices, display devices, liquid crystal display devices, light-emitting devices, lighting devices, power storage devices, storage devices, imaging devices, driving methods thereof, or manufacturing methods thereof can be cited as an example.

Background Art

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

[0003] Since such a light-emitting device is self-emissive, when used as a pixel of a display, it has advantages such as higher visibility than liquid crystal and the absence of a need for a backlight, and is suitable as a flat panel display element. In addition, a display using such a light-emitting device can be manufactured to be thin and lightweight, which is also a great advantage. Furthermore, it is also characterized by a very fast response speed.

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

[0005] Displays and lighting devices using such light-emitting devices are suitable for use in various electronic devices, and research and development are underway to obtain light-emitting devices with better efficiency and longer lifespan.

[0006] In Patent Document 1, a configuration is disclosed in which a hole-transporting material having a HOMO level between the HOMO level of a first hole-injecting layer and the HOMO level of a host material is provided between a first hole-transporting layer in contact with the hole-injecting layer and a light-emitting layer.

[0007] Although the characteristics of light-emitting devices have improved remarkably, it still has to be said that they are insufficient to meet the high demands for all characteristics, including efficiency and durability.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] Therefore, an aspect of the present invention aims to provide a novel light-emitting device. Or, it aims to provide a light-emitting device with good luminous efficiency. Or, it aims to provide a light-emitting device with good lifespan. Or, it aims to provide a light-emitting device with low driving voltage.

[0010] Alternatively, another aspect of the present invention aims to provide highly reliable light-emitting devices, electronic devices, and display devices, respectively. Alternatively, another aspect of the present invention aims to provide light-emitting devices, electronic devices, and display devices, respectively, that consume little power.

[0011] The present invention only needs to solve one of the above-mentioned problems. [Means for solving the problem]

[0012] One aspect of the present invention comprises an anode, a cathode, and an EL layer located between the anode and the cathode, wherein the EL layer comprises a hole injection layer, an emissive layer, and an electron transport layer, the hole injection layer comprising a hole transport material and an electron-accepting material, the electron transport layer comprising an electron transport material and an alkali metal or alkaline earth metal element, compound, or complex, and the spin density of the hole injection layer measured by ESR is 1 × 10⁻¹⁶ 19 spins / cm 3 The following is the light-emitting device.

[0013] Alternatively, another aspect of the present invention comprises an anode, a cathode, and an EL layer located between the anode and the cathode, wherein the EL layer comprises a hole injection layer, an emissive layer, and an electron transport layer, the hole injection layer comprising a hole transport material and an electron-accepting material, the electron transport layer comprising an electron transport material and a metal complex having a ligand comprising an 8-hydroxyquinolinate structure and a monovalent metal ion, and the spin density of the hole injection layer measured by ESR is 1 × 10⁻¹⁶ 19 spins / cm 3 The following is the light-emitting device.

[0014] Alternatively, another aspect of the present invention comprises an anode, a cathode, and an EL layer located between the anode and the cathode, wherein the EL layer comprises a hole injection layer, an emissive layer, and an electron transport layer, the hole injection layer comprising a hole transport material and an electron-accepting material, the electron transport layer comprising an electron transport material and a lithium complex having a ligand comprising an 8-hydroxyquinolinate structure, and the spin density of the hole injection layer measured by ESR is 1 × 10⁻⁶ 19spins / cm 3 The light-emitting device is as follows.

[0015] Alternatively, another aspect of the present invention has an anode, a cathode, and an EL layer located between the anode and the cathode. The EL layer has a hole injection layer, a light-emitting layer, and an electron transport layer. The hole injection layer contains a hole transport material and an electron-accepting material. The electron transport layer has an electron transport material, and the HOMO level of the electron transport material is -6.0 eV or higher. The spin density measured by the ESR method of the hole injection layer is 1×10 19 spins / cm 3 The light-emitting device is as follows.

[0016] Alternatively, another aspect of the present invention has an anode, a cathode, and an EL layer located between the anode and the cathode. The EL layer has a hole injection layer, a light-emitting layer, and an electron transport layer. The hole injection layer contains a hole transport material and an electron-accepting material. The electron transport layer has an electron transport material, and the electron transport material is an organic compound having an anthracene skeleton. The spin density measured by the ESR method of the hole injection layer is 1×10 19 spins / cm 3 The light-emitting device is as follows.

[0017] Alternatively, another aspect of the present invention has an anode, a cathode, and an EL layer located between the anode and the cathode. The EL layer has a hole injection layer, a light-emitting layer, and an electron transport layer. The hole injection layer contains a hole transport material and an electron-accepting material. When the square root of the electric field strength [V / cm] of the electron transport layer is 600, the electron mobility is 1×10 -7 cm 2 / Vs or more and 5×10 -5 cm 2 / Vs or less, and the spin density measured by the ESR method of the hole injection layer is 1×10 19 spins / cm 3 The light-emitting device is as follows.

[0018] Alternatively, another aspect of the present invention comprises an anode, a cathode, and an EL layer located between the anode and the cathode, wherein the EL layer comprises a hole injection layer, an emissive layer, and an electron transport layer, the hole injection layer comprises a hole transport material and an electron-accepting material, the electron transport layer comprises an electron transport material and elements, compounds, or complexes of alkali metals or alkaline earth metals, the concentration of the elements, compounds, or complexes of alkali metals or alkaline earth metals is higher in the region on the emissive layer side than in the region on the cathode side, the electron transport layer comprises a first region and a second region, the first region is located between the emissive layer and the second region, the concentrations of the elements, compounds, or complexes of alkali metals or alkaline earth metals in the first region and the second region are different, and the spin density of the hole injection layer, as measured by ESR, is 1 × 10⁻⁶ 19 spins / cm 3 The following is the light-emitting device.

[0019] Alternatively, another aspect of the present invention is a light-emitting device in which the concentration of the alkali metal or alkaline earth metal element, compound, or complex in the first region is high.

[0020] Alternatively, another aspect of the present invention is a light-emitting device in which, in the above configuration, the electron transport layer is composed of a plurality of layers, and the concentration of the alkali metal or alkaline earth metal element, compound, or complex in the second region is high.

[0021] Alternatively, another aspect of the present invention is a light-emitting device in which the concentration of the alkali metal or alkaline earth metal element, compound, or complex in the first region or the second region is 0.

[0022] Alternatively, in another aspect of the present invention, the electron-accepting material in the above configuration is a material that exhibits electron-acceptance to the hole-transporting material, and the hole-transporting material is an organic compound with a HOMO level of -5.7 eV or higher and -5.4 eV or lower, which is a light-emitting device.

[0023] Alternatively, in another aspect of the present invention, in the above configuration, the hole mobility when the square root of the electric field strength [V / cm] of the hole transport material is 600 is 1 × 10⁻⁶. -3 cm 2 This is a light-emitting device with a Vs value of less than or equal to / Vs.

[0024] Alternatively, in another aspect of the present invention, in the above configuration, the spin density measured by the ESR method of the hole injection layer is 1 × 10⁻⁶ 16 spins / cm 3 The above describes the light-emitting device.

[0025] Alternatively, in another aspect of the present invention, in the above configuration, the spin density measured by the ESR method of the hole injection layer is 1 × 10 17 spins / cm 3 The above describes the light-emitting device.

[0026] Alternatively, in another aspect of the present invention, in the above configuration, the spin density measured by the ESR method of the hole injection layer is 3 × 10 17 spins / cm 3 The above describes the light-emitting device.

[0027] Alternatively, in another aspect of the present invention, the EL layer is a light-emitting device having a hole transport layer between the hole injection layer and the light-emitting layer, in the above configuration.

[0028] Alternatively, another aspect of the present invention is a light-emitting device in which, in the above configuration, the hole transport layer has a two-layer structure consisting of a first hole transport layer located on the hole injection layer side and a second hole transport layer located on the light-emitting layer side.

[0029] Alternatively, in another aspect of the present invention, the light-emitting device is configured such that the second hole transport layer also functions as an electron blocking layer.

[0030] Alternatively, another aspect of the present invention is a light-emitting device in which the light-emitting layer comprises a host material and a light-emitting center material, and the electron mobility of the electron transport material is smaller than the electron mobility of the host material.

[0031] Alternatively, another aspect of the present invention is a light-emitting device in which the light-emitting central material exhibits fluorescence emission in the above configuration.

[0032] Alternatively, another aspect of the present invention is a light-emitting device in which the light-emitting central material exhibits blue fluorescence emission.

[0033] Alternatively, another aspect of the present invention is an electronic device having at least one of a sensor, an operating button, a speaker, or a microphone in the above configuration.

[0034] Alternatively, another aspect of the present invention is a light-emitting device having a transistor and a substrate in the above configuration.

[0035] Alternatively, another aspect of the present invention is a lighting device having a housing and, in the above configuration.

[0036] In this specification, the term "light-emitting device" includes image display devices that use light-emitting devices. Furthermore, modules to which connectors, such as anisotropic conductive films or TCPs (Tape Carrier Packages), are attached to light-emitting devices, modules to which printed circuit boards are provided at the end of TCPs, or modules to which ICs (integrated circuits) are directly mounted using the COG (Chip On Glass) method may also be included as light-emitting devices. Additionally, lighting fixtures and the like may have light-emitting devices. [Effects of the Invention]

[0037] In one aspect of the present invention, a novel light-emitting device can be provided. Alternatively, a light-emitting device with a good lifespan can be provided. Alternatively, a light-emitting device with good luminous efficiency can be provided. Alternatively, a light-emitting device with a low driving voltage can be provided.

[0038] Alternatively, in another aspect of the present invention, highly reliable light-emitting devices, electronic devices, and display devices can be provided, respectively. Alternatively, in another aspect of the present invention, light-emitting devices, electronic devices, and display devices with low power consumption can be provided, respectively.

[0039] Furthermore, the description of these effects does not preclude the existence of other effects. Moreover, one aspect of the present invention does not necessarily have to possess all of these effects. Other effects will naturally become apparent from the description in the specification, drawings, and claims, and it is possible to extract other effects from the description in the specification, drawings, and claims. [Brief explanation of the drawing]

[0040] [Figure 1] Figures 1A1, 1A2, 1B, and 1C are schematic diagrams of the light-emitting device. [Figure 2] Figures 2A1, 2A2, 2B1, and 2B2 show the concentration distribution of the eighth substance in the electron transport layer. [Figure 3] Figures 3A and 3B illustrate the recombination region of the light-emitting device. [Figure 4] Figures 4A and 4B are conceptual diagrams of an active matrix type light-emitting device. [Figure 5] Figures 5A and 5B are conceptual diagrams of an active matrix type light-emitting device. [Figure 6] Figure 6 is a conceptual diagram of an active matrix type light-emitting device. [Figure 7] Figures 7A and 7B represent lighting devices. [Figure 8] Figures 8A, 8B1, 8B2, and 8C are diagrams representing electronic devices. [Figure 9] Figures 9A, 9B, and 9C are diagrams representing electronic devices. [Figure 10] Figure 10 is a diagram representing a lighting device. [Figure 11]Figure 11 is a diagram representing a lighting device. [Figure 12] Figure 12 is a diagram representing an in-vehicle display device. [Figure 13] Figures 13A and 13B are diagrams representing electronic devices. [Figure 14] Figures 14A, 14B, and 14C are diagrams representing electronic devices. [Figure 15] Figure 15 shows the brightness-current density characteristics of light-emitting devices 1-1, 1-2, 2-1, 2-2, and a comparison light-emitting device. [Figure 16] Figure 16 shows the current efficiency-luminance characteristics of light-emitting devices 1-1, 1-2, 2-1, 2-2, and the comparative light-emitting device. [Figure 17] Figure 17 shows the luminance-voltage characteristics of light-emitting devices 1-1, 1-2, 2-1, 2-2, and the comparison light-emitting device. [Figure 18] Figure 18 shows the current-voltage characteristics of light-emitting devices 1-1, 1-2, 2-1, 2-2, and the comparison light-emitting device. [Figure 19] Figure 19 shows the external quantum efficiency-luminance characteristics of light-emitting devices 1-1, 1-2, 2-1, 2-2, and the comparative light-emitting device. [Figure 20] Figure 20 shows the emission spectra of light-emitting devices 1-1, 1-2, 2-1, 2-2, and the reference light-emitting device. [Figure 21] Figure 21 shows the normalized brightness-time variation characteristics of light-emitting devices 1-1, 1-2, 2-1, 2-2, and the comparative light-emitting device. [Figure 22] Figure 22 shows the spin densities calculated from the electron spin resonance spectra of samples 1-1, 1-2, 1-3, 2-1, 2-2, 3-1, and 3-2. [Figure 23] Figure 23 shows the structure of the measuring element. [Figure 24] Figure 24 shows the current density-voltage characteristics of the measuring element. [Figure 25] Figure 25 shows the frequency characteristics of the calculated capacitance C in ZADN:Liq(1:1) at a DC power supply of 7.0V. [Figure 26] Figure 26 shows the frequency response of -ΔB for ZADN:Liq(1:1) at a DC voltage of 7.0V. [Figure 27] Figure 27 shows the electric field strength dependence characteristics of electron mobility in each organic compound. [Modes for carrying out the invention]

[0041] The embodiments of the present invention will be described in detail below with reference to the drawings. However, it will be readily apparent to those skilled in the art that the present invention is not limited to the following description, and that its form and details can be modified in various ways without departing from the spirit and scope of the present invention. Accordingly, the present invention shall not be interpreted as being limited to the contents of the embodiments shown below.

[0042] (Embodiment 1) Figures 1A1 and 1A2 show diagrams representing a light-emitting device according to one aspect of the present invention. The light-emitting device according to one aspect of the present invention has an anode 101, a cathode 102, and an EL layer 103, the EL layer having a hole injection layer 111, a hole transport layer 112, a light-emitting layer 113, and an electron transport layer 114. Preferably, the hole transport layer 112 has a first hole transport layer 112-1 and a second hole transport layer 112-2, and the electron transport layer 114 has a first electron transport layer 114-1 and a second electron transport layer 114-2, as shown in Figure 1A2.

[0043] In addition to the EL layer 103 shown in Figures 1A1 and 1A2, an electron injection layer 115 is also depicted, but the configuration of the light-emitting device is not limited to this. As long as it has the above configuration, it may include layers with other functions.

[0044] The hole injection layer 111 is a layer designed to facilitate hole injection into the EL layer 103, and is constructed using a material with high hole injection capabilities. The hole injection layer 111 may be composed of a single material, but it is preferable that it be composed of a material containing a first substance and a second substance. The first substance is an acceptor substance that exhibits electron-accepting properties towards the second substance. The second substance is a hole transport material, and it is preferable that its HOMO level is relatively deep, between -5.7 eV and -5.4 eV. The relatively deep HOMO level of the second substance moderately suppresses hole induction, while facilitating the injection of induced holes into the hole transport layer 112.

[0045] In one embodiment of the present invention, the material constituting the hole injection layer 111 has a spin density of 1 × 10⁻¹⁶ as measured by electron spin resonance (ESR). 19 spins / cm 3 The following conditions must be met: The light-emitting device has a good lifespan, and the light-emitting apparatus using this device can be made into a light-emitting apparatus with good display quality and suppressed crosstalk. However, if the spin density is too low, it becomes difficult to inject holes from the anode, so the spin density should be 1 × 10⁻⁶. 16 spins / cm 3 The above 1 x 10 19 spins / cm 3 The following is preferred, and more preferably, 1 × 10 17 spins / cm 3 The above 1 x 10 19 spins / cm 3 More preferably, 3 × 10 16 spins / cm 3 The above 1 x 10 19 spins / cm 3 The following applies:

[0046] The first substance can be either an inorganic or organic compound, but it is preferable to use an organic compound having an electron-withdrawing group (especially a halogen group such as a fluoro group or a cyano group). The first substance can be appropriately selected from such substances that exhibit electron-accepting properties toward the second substance. Examples of such organic compounds include 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviated as F4-TCNQ), chloranil, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviated as HAT-CN), 1,3,4,5,7,8-hexafluorotetracyano-naphthoquinodimethane (abbreviated as F6-TCNNQ), and 2-(7-dicyanomethylene-1,3,4,5,6,8,9,10-octafluoro-7H-pyrene-2-ylidene)malononitrile. Compounds in which an electron-withdrawing group is bonded to a condensed aromatic ring having multiple heteroatoms, such as HAT-CN, are thermally stable and therefore preferred. Furthermore, radialene derivatives having electron-withdrawing groups (especially halogen groups such as fluoro groups or cyano groups) [3] are preferred because they have very high electron-accepting properties. Specifically, examples include α,α',α''-1,2,3-cyclopropanetriylidenates[4-cyano-2,3,5,6-tetrafluorobenzeneacetonitrile], α,α',α''-1,2,3-cyclopropanetriylidenates[2,6-dichloro-3,5-difluoro-4-(trifluoromethyl)benzeneacetonitrile], and α,α',α''-1,2,3-cyclopropanetriylidenates[2,3,4,5,6-pentafluorobenzeneacetonitrile]. When the first substance is an inorganic compound, transition metal oxides can also be used. In particular, oxides of metals belonging to groups 4 through 8 of the periodic table are preferred. Among the oxides of metals belonging to groups 4 through 8 of the periodic table, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, and rhenium oxide are preferred due to their high electron-accepting properties. Of these, molybdenum oxide is preferred because it is stable in air, has low hygroscopicity, and is easy to handle.

[0047] The second substance is a hole transport material, and is preferably an organic compound having hole transport properties, and more preferably has one of the following skeletons: carbazole skeleton, dibenzofuran skeleton, dibenzothiophene skeleton, or anthracene skeleton. Particularly preferred are aromatic amines having substituents including a dibenzofuran ring or a dibenzothiophene ring, aromatic monoamines having a naphthalene ring, or aromatic monoamines in which a 9-fluorenyl group is bonded to the nitrogen of the amine via an arylene group. Furthermore, if the second substance is a substance having an N,N-bis(4-biphenyl)amino group, it is preferable because it is possible to create a light-emitting device with a good lifetime. Specifically, the second substances mentioned above include N-(4-biphenyl)-6,N-diphenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BnfABP), N,N-bis(4-biphenyl)-6-phenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BBABnf), and 4,4'-bis(6-phenylbenzo[b]naphtho[1,2-d]furan-8-amine). ru-4''-phenyltriphenylamine (abbreviation: BnfBB1BP), 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-8-amine (abbreviation: BBABnf(8)), N,N-bis(4-biphenyl)benzo[b]naphtho[2,3-d]furan-6-amine (abbreviation: BBABnf(6)), N,N-bis(4-biphenyl)benzo[b]naphtho[2,3-d]furan-8-amine (abbreviation: BBABnf(8)), N,N-bis(4-biphenyl)benzo[b]naphtho[2,3-d]furan-6-amine (abbreviation: BnfBB1BP), 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-8-amine (abbreviation: BBABnf(6 N-4-amine (abbreviation: BBABnf(II)(4)), N,N-bis[4-(dibenzofuran-4-yl)phenyl]-4-amino-p-terphenyl (abbreviation: DBfBB1TP), N-[4-(dibenzothiophen-4-yl)phenyl]-N-phenyl-4-biphenylamine (abbreviation: ThBA1BP), 4-(2-naphthyl)-4',4''-diphenyltriphenylamine (abbreviation: BBAβNB), 4-[4-(2-naphthyl)phenyl]-4',4''-diphenyltriphenylamine (abbreviation: BBAβNBi), 4,4'-diphenyl-4''-(6;1'-binaphthyl-2-yl)triphenylamine (abbreviation: BBAαNβNB), 4,4'-diphenyl-4''-(7;1'-binaphthyl-2-yl)triphenylamine (abbreviation: BBAαNβNB-03), 4,4'-Diphenyl-4''-(7-phenyl)naphthyl-2-yltriphenylamine (abbreviation: BBAPβNB-03), 4,4'-Diphenyl-4''-(6;2'-binaphthyl-2-yl)triphenylamine (abbreviation: BBA(βN2)B), 4,4'-Diphenyl-4''-(7;2'-binaphthyl-2-yl)triphenylamine (abbreviation: BBA(βN2)B-03), 4,4'-Diphenyl-4''-(4;2'-binaphthyl-1-yl)triphenylamine (abbreviation: BBAβNαNB), 4,4'-Diphenyl-4''-(5;2'- Binaphthyl-1-yl)triphenylamine (abbreviation: BBAβNαNB-02), 4-(4-biphenylyl)-4'-(2-naphthyl)-4''-phenyltriphenylamine (abbreviation: TPBiAβNB), 4-(3-biphenylyl)-4'-[4-(2-naphthyl)phenyl]-4''-phenyltriphenylamine (abbreviation: mTPBiAβNBi), 4-(4-biphenylyl)-4'-[4-(2-naphthyl)phenyl]-4''-phenyltriphenylamine (abbreviation: TPBiAβNBi), 4-phenyl-4'-(1-naphthyl)triphenyl Luamine (abbreviation: αNBA1BP), 4,4'-bis(1-naphthyl)triphenylamine (abbreviation: αNBB1BP), 4,4'-diphenyl-4''-[4'-(carbazole-9-yl)biphenyl-4-yl]triphenylamine (abbreviation: YGTBi1BP), 4'-[4-(3-phenyl-9H-carbazole-9-yl)phenyl]tris(1,1'-biphenyl-4-yl)amine (abbreviation: YGTBi1BP-02), 4-diphenyl-4'-(2-naphthyl)-4''-{9-(4-biphenylyl)carbazole)}triphenylamine N (abbreviation: YGTBiβNB), N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-N-[4-(1-naphthyl)phenyl]-9,9'-spirobi(9H-fluorene)-2-amine (abbreviation: PCBNBSF), N,N-bis(4-biphenylyl)-9,9'-spirobi[9H-fluorene]-2-amine (abbreviation: BBASF), N,N-bis(1,1'-biphenyl-4-yl)-9,9'-spirobi[9H-fluorene]-4-amine (abbreviation: BBASF(4)), N-(1,1'-biphenyl-2-yl)-N-(9,9-dimethyl-9H-fluoren-2-yl)-9,9'-spirobi(9H-fluoren)-4-amine (abbreviation: oFBiSF), N-(4-biphenyl)-N-(dibenzofuran-4-yl)-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: FrBiF), N-[4-(1-naphthyl)phenyl]-N-[3-(6-phenyldibenzofuran-4-yl)phenyl]-1-naphthylamine (abbreviation: mPDBf) BNBN), 4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP), 4-phenyl-3'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: mBPAFLP), 4-phenyl-4'-[4-(9-phenylfluoren-9-yl)phenyl]triphenylamine (abbreviation: BPAFLBi), 4-phenyl-4'-(9-phenyl-9H-carbazole- 3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4'-diphenyl-4''-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBBi1BP), 4-(1-naphthyl)-4'-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBANB), 4,4'-di(1-naphthyl)-4''-(9-phenyl-9H-carbazole-3-yl)trif Examples include phenylamine (abbreviation: PCBNBB), N-phenyl-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]spiro-9,9'-bifluoren-2-amine (abbreviation: PCBASF), N-(1,1'-biphenyl-4-yl)-9,9-dimethyl-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-9H-fluoren-2-amine (abbreviation: PCBBiF), etc.

[0048] Furthermore, for the second substance, if the square root of its electric field strength [V / cm] is 600, the hole mobility is 1 × 10⁻⁶. -3 cm 2 It is preferable that it is less than or equal to / Vs.

[0049] The composition of the first substance and the second substance in the hole injection layer 111 is preferably 1:0.01 to 1:0.15 (by weight). More preferably, it is 1:0.01 to 1:0.1 (by weight).

[0050] Preferably, the hole transport layer 112 has 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 anode 101 than the second hole transport layer 112-2. The second hole transport layer 112-2 may also simultaneously function as an electron blocking layer.

[0051] The first hole transport layer 112-1 contains a third substance, and the second hole transport layer 112-2 contains a fourth substance.

[0052] The third and fourth substances are preferably organic compounds that have hole-transporting properties. The third and fourth substances can be the same as the organic compounds listed above that can be used as the second substance.

[0053] It is preferable to select materials such that the HOMO level of the third material is deeper than the HOMO level of the second material, and the difference between them is 0.2 eV or less.

[0054] Furthermore, it is preferable that the HOMO level of the fourth material is deeper than that of the third material. Additionally, it is preferable to select materials such that the difference between the HOMO levels is 0.2 eV or less. This relationship between the HOMO levels of the second through fourth materials allows for smooth hole injection into each layer, preventing increases in the driving voltage and insufficient holes in the light-emitting layer.

[0055] Furthermore, it is preferable that the second to fourth substances each have a hole-transporting skeleton. Preferred hole-transporting skeletons are carbazole skeletons, dibenzofuran skeletons, dibenzothiophene skeletons, and anthracene skeletons, which do not cause the HOMO level of these organic compounds to become too shallow. It is also preferable that these hole-transporting skeletons are common to materials in adjacent layers (for example, the second substance and the third substance or the third substance and the fourth substance) because this facilitates hole injection. In particular, the dibenzofuran skeleton is preferred as one of these hole-transporting skeletons.

[0056] Furthermore, it is preferable that the materials contained in adjacent layers (for example, the second and third materials or the third and fourth materials) are the same material, as this allows for smoother hole injection. In particular, a configuration in which the second and third materials are the same material is preferred.

[0057] The light-emitting layer 113 contains a fifth substance and a sixth substance. The fifth substance is a light-emitting central substance, and the sixth substance is a host material for dispersing the fifth substance. The light-emitting layer 113 may also contain other materials different from the fifth and sixth substances. Furthermore, it may be a laminate of two layers with different compositions.

[0058] The luminescent central material may be a fluorescent material, a phosphorescent material, a material exhibiting thermally activated delayed fluorescence (TADF), or any other luminescent material. It may also be a single layer or consist of multiple layers. One aspect of the present invention is more preferably applicable when the luminescent layer 113 is a layer that exhibits fluorescent emission, particularly a layer that exhibits blue fluorescent emission.

[0059] Examples of materials that can be used as fluorescent materials in the light-emitting layer 113 include the following. Other fluorescent materials can also be used.

[0060] 5,6-Bis[4-(10-phenyl-9-antryl)phenyl]-2,2'-bipyridine (abbreviation: PAP2BPy), 5,6-Bis[4'-(10-phenyl-9-antryl)biphenyl-4-yl]-2,2'-bipyridine (abbreviation: PAPP2BPy), N,N'-Diphenyl-N,N'-Bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]pyren-1,6-diamine (abbreviation: 1,6FLPAPrn), N,N'-Bis(3-methylphenyl)-N,N'-Bis[3-(9-phenyl-9H-fluoren-9-yl )phenyl]pyrene-1,6-diamine (abbreviation: 1,6mMemFLPAPrn), N,N'-bis[4-(9H-carbazole-9-yl)phenyl]-N,N'-diphenylstilbene-4,4'-diamine (abbreviation: YGA2S), 4-(9H-carbazole-9-yl)-4'-(10-phenyl-9-anthryl)triphenylamine (abbreviation: YGAPA), 4-(9H-carbazole-9-yl)-4'-(9,10-diphenyl-2-anthryl)triphenylamine (abbreviation: 2YGAPPA), N,9-diphenyl-N-[4-( 10-phenyl-9-anthryl)phenyl]-9H-carbazole-3-amine (abbreviation: PCAPA), perylene, 2,5,8,11-tetra-tert-butylperylene (abbreviation: TBP), 4-(10-phenyl-9-anthryl)-4'-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBAPA), N,N''-(2-tert-butylanthracene-9,10-diyldi-4,1-phenylene)bis[N,N',N'-triphenyl-1,4-phenylenediamine] (abbreviation: DPABPA), N,9 -Diphenyl-N-[4-(9,10-diphenyl-2-anthryl)phenyl]-9H-carbazole-3-amine (abbreviation: 2PCAPPA), N-[4-(9,10-diphenyl-2-anthryl)phenyl]-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPPA), N,N,N',N',N'',N'',N''',N'''-octaphenyldibenzo[g,p]chrysene-2,7,10,15-tetraamine (abbreviation: DBC1), coumarin 30, N-(9,10-diphenyl-2-anthryl)-N,9-Diphenyl-9H-carbazole-3-amine (abbreviation: 2PCAPA), N-[9,10-bis(1,1'-biphenyl-2-yl)-2-anthryl]-N,9-diphenyl-9H-carbazole-3-amine (abbreviation: 2PCABPhA), N-(9,10-diphenyl-2-anthryl)-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPA), N-[9,10-bis(1,1'-biphenyl-2-yl)-2-anthryl]-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviation: 2DPAB) PhA), 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), rubren, 5,12-bis(1,1'-biphenyl-4-yl)-6,11-diphenyltetracene (abbreviation: BPT), 2-(2-{2-[4-(dimethylamino)phenyl]ethenyl}-6 -methyl-4H-pyran-4-ylidene)propanedinitrile (abbreviation: DCM1), 2-{2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinoridine-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCM2), N,N,N',N'-tetrakis(4-methylphenyl)tetracene-5,11-diamine (abbreviation: p-mPhTD), 7,14-diphenyl-N,N,N',N'-tetrakis(4-methylphenyl)acenaphtho[1,2-a]fluorantene-3,10-di Amine (abbreviation: p-mPhAFD), 2-{2-isopropyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinoridine-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCJTI), 2-{2-tert-butyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinoridine-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCJTB), 2-(2,6-Bis{2-[4-(dimethylamino)phenyl]ethenyl}-4H-pyran-4-ylidene)propanedinitrile (abbreviation: BisDCM), 2-{2,6-Bis[2-(8-methoxy-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinoridine-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: BisDCJTM), N,N'-diphenyl-N,N'-(1,6-pyrene-diyl)bis[(6-phenylbenzo[b Examples include ]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), and 3,10-bis[N-(dibenzofuran-3-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviation: 3,10FrA2Nbf(IV)-02). In particular, condensed aromatic diamine compounds, such as pyrenediamine compounds like 1,6FLPAPrn, 1,6mMemFLPAPrn, and 1,6BnfAPrn-03, are preferred because they have high hole-trapping properties and excellent luminescence efficiency and reliability.

[0061] When a phosphorescent material is used as the light-emitting center material in the light-emitting layer 113, the following are some examples of materials that can be used.

[0062] Organometallic iridium complexes having a 4H-triazole skeleton, such as Tris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-κN2]phenyl-κC}iridium(III) (abbreviation: [Ir(mpptz-dmp)3]), Tris(5-methyl-3,4-diphenyl-4H-1,2,4-triazolato)iridium(III) (abbreviation: [Ir(Mptz)3]), Tris[4-(3-biphenyl)-5-isopropyl-3-phenyl-4H-1,2,4-triazolato]iridium(III) (abbreviation: [Ir(iPrptz-3b)3]), and Tris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazolato]iridium(III) ( Organometallic iridium complexes having a 1H-triazole skeleton, such as tris(1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazolato)iridium(III) (abbreviated as [Ir(Prptz1-Me)3]), or organometallic iridium complexes having an imidazole skeleton, such as fac-tris[(1-2,6-diisopropylphenyl)-2-phenyl-1H-imidazole]iridium(III) (abbreviated as [Ir(iPrpmi)3]), tris[3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-f]phenanthridine]iridium(III) (abbreviated as [Ir(dmpimpt-Me)3]), or bis[2-(4',6'-difluorophenyl)pyridinate-N,C 2’ Iridium(III) tetrakis(1-pyrazolyl) borate (abbreviation: FIr6), bis[2-(4',6'-difluorophenyl)pyridinate-N,C 2’ Iridium(III) picolinate (abbreviation: Firpic), bis{2-[3',5'-bis(trifluoromethyl)phenyl]pyridinate-N,C 2’ Iridium(III) picolinate (abbreviation: [Ir(CF3ppy)2(pic)]), bis[2-(4',6'-difluorophenyl)pyridinate-N,C 2’Examples include organometallic iridium complexes that use phenylpyridine derivatives having electron-withdrawing groups, such as iridium(III) acetylacetonate (abbreviated as FIracac), as ligands. These compounds exhibit blue phosphorescence and have emission peaks between 440 nm and 520 nm.

[0063] Also, tris(4-methyl-6-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(mppm)3]), tris(4-t-butyl-6-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(tBuppm)3]), (acetylacetonato)bis(6-methyl-4-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(mppm)2(acac)]), (acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(tBuppm)2(acac)]), (acetylacetonato)bis[6-(2-norbornyl)-4-phenylpyrimidinato]iridium(III) (abbreviation: [Ir(nbppm)2(acac)]), (acetylacetonato)bis[5-methyl-6-( Organometallic iridium complexes having a pyrimidine skeleton, such as [2-methylphenyl)-4-phenylpyrimidinato]iridium(III) (abbreviation: [Ir(mpmppm)2(acac)]), (acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III) (abbreviation: [Ir(dppm)2(acac)]), organometallic iridium complexes having a pyrazine skeleton, such as [acetylacetonato]bis(3,5-dimethyl-2-phenylpyradinato)iridium(III) (abbreviation: [Ir(mppr-Me)2(acac)]), (acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyradinato)iridium(III) (abbreviation: [Ir(mppr-iPr)2(acac)]), and tris(2-phenylpyridinato-N,C 2’ Iridium(III) (abbreviation: [Ir(ppy)3]), bis(2-phenylpyridinate-N,C) 2’Iridium(III) acetylacetonate (abbreviation: [Ir(ppy)2(acac)]), bis(benzo[h]quinolinate)iridium(III) acetylacetonate (abbreviation: [Ir(bzq)2(acac)]), tris(benzo[h]quinolinate)iridium(III) (abbreviation: [Ir(bzq)3]), tris(2-phenylquinolinate-N,C) 2’ Iridium(III) (abbreviation: [Ir(pq)3]), bis(2-phenylquinolinato-N,C) 2’ Examples include organometallic iridium complexes with a pyridine skeleton, such as iridium(III) acetylacetonate (abbreviated as [Ir(pq)2(acac)]), and rare earth metal complexes, such as tris(acetylacetonate)(monophenanthroline)terbium(III) (abbreviated as [Tb(acac)3(Phen)]). These compounds mainly exhibit green phosphorescence and have an emission peak in the 500nm-600nm range. Organometallic iridium complexes with a pyrimidine skeleton are particularly preferred due to their outstanding reliability and luminescence efficiency.

[0064] Furthermore, organometallic iridium complexes having a pyrimidine skeleton, such as (diisobutyrylmethanato)bis[4,6-bis(3-methylphenyl)pyrimidinato]iridium(III) (abbreviation: [Ir(5mdppm)2(dibm)]), bis[4,6-bis(3-methylphenyl)pyrimidinato](dipvaloylmethanato)iridium(III) (abbreviation: [Ir(5mdppm)2(dpm)]), and bis[4,6-di(naphthalene-1-yl)pyrimidinato](dipvaloylmethanato)iridium(III) (abbreviation: [Ir(d1npm)2(dpm)]), Organometallic iridium complexes with a pyrazine skeleton, such as (acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III) (abbreviation: [Ir(tppr)2(acac)]), bis(2,3,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III) (abbreviation: [Ir(tppr)2(dpm)]), and (acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III) (abbreviation: [Ir(Fdpq)2(acac)]), as well as tris(1-phenylisoquinolinato-N,C) 2’ Iridium(III) (abbreviation: [Ir(piq)3]), bis(1-phenylisoquinolinato-N,C) 2’ Examples include organometallic iridium complexes with a pyridine skeleton, such as iridium(III) acetylacetonate (abbreviated as [Ir(piq)2(acac)]), as well as platinum complexes such as 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin platinum(II) (abbreviated as PtOEP), and rare earth metal complexes such as tris(1,3-diphenyl-1,3-propanedionato)(monophenanthroline)europium(III) (abbreviated as [Eu(DBM)3(Phen)]) and tris[1-(2-tenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(III) (abbreviated as [Eu(TTA)3(Phen)]). These compounds exhibit red phosphorescence and have an emission peak between 600 nm and 700 nm. Furthermore, organometallic iridium complexes with a pyrazine skeleton produce a red emission with good chromaticity.

[0065] In addition to the phosphorescent compounds described above, other known phosphorescent light-emitting materials may be selected and used.

[0066] As TADF materials, fullerenes and their derivatives, acridines and their derivatives, eosin derivatives, etc., can be used. Also, metal-containing porphyrins containing magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), or palladium (Pd) can be used. Examples of metal-containing porphyrins include protoporphyrin-tin fluoride complexes (SnF2(Proto IX)), mesoporphyrin-tin fluoride complexes (SnF2(Meso IX)), hematoporphyrin-tin fluoride complexes (SnF2(Hemato IX)), coproporphyrin tetramethyl ester-tin fluoride complexes (SnF2(Copro III-4Me)), octaethylporphyrin-tin fluoride complexes (SnF2(OEP)), etioporphyrin-tin fluoride complexes (SnF2(Etio I)), and octaethylporphyrin-platinum chloride complexes (PtCl2OEP), as shown in the following structural formulas.

[0067] [ka]

[0068] Furthermore, there are 2-(biphenyl-4-yl)-4,6-bis(12-phenylindoro[2,3-a]carbazol-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), 9-[4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]-9'-phenyl-9H,9'H-3,3'-bicarbazole (abbreviated as PCCzPTzn), and 2-[4-(10H-phenoxazine-10-yl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviated as P Heterocyclic compounds having one or both of a π-electron-rich heteroaromatic ring and a π-electron-deficient heteroaromatic ring can also be used, such as XZ-TRZ, 3-[4-(5-phenyl-5,10-dihydrophenazine-10-yl)phenyl]-4,5-diphenyl-1,2,4-triazole (abbreviated as PPZ-3TPT), 3-(9,9-dimethyl-9H-acridine-10-yl)-9H-xanthene-9-one (abbreviated as ACRXTN), bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone (abbreviated as DMAC-DPS), and 10-phenyl-10H,10'H-spiro[acridine-9,9'-anthracene]-10'-one (abbreviated as ACRSA). The heterocyclic compound is preferred because it has both a π-electron-excess heteroaromatic ring and a π-electron-deficient heteroaromatic ring, resulting in high electron transport and hole transport properties. Among the skeletons having a π-electron-deficient heteroaromatic ring, the pyridine skeleton, diazine skeleton (pyrimidine skeleton, pyrazine skeleton, pyridazine skeleton), and triazine skeleton are preferred because they are stable and reliable. In particular, the benzoflopyrimidine skeleton, benzothienopyrimidine skeleton, benzoflopyrazine skeleton, and benzothienopyrazine skeleton are preferred because they have high acceptor properties and are reliable. Furthermore, among the skeletons having a π-electron-excess heteroaromatic ring, the acridine skeleton, phenoxazine skeleton, phenothiazine skeleton, furan skeleton, thiophene skeleton, and pyrrole skeleton are preferred because they are stable and reliable, and therefore it is preferable to have at least one of these skeletons.Furthermore, a dibenzofuran skeleton is preferred as the furan skeleton, and a dibenzothiophene skeleton is preferred as the thiophene skeleton. In addition, as the pyrrole skeleton, indole skeleton, carbazole skeleton, indrocarbazole skeleton, bicarbazole skeleton, and 3-(9-phenyl-9H-carbazole-3-yl)-9H-carbazole skeleton are particularly preferred. Substances in which a π-electron-rich heteroaromatic ring and a π-electron-deficient heteroaromatic ring are directly bonded are particularly preferred because both the electron-donating and electron-accepting properties of the π-electron-rich heteroaromatic ring are strengthened, and the energy difference between the S1 and T1 levels is reduced, thus efficiently obtaining thermally activated delayed fluorescence. In addition, an aromatic ring to which an electron-withdrawing group such as a cyano group is bonded may be used instead of the π-electron-deficient heteroaromatic ring. Furthermore, aromatic amine skeletons, phenazine skeletons, etc., can be used as the π-electron-rich skeleton. Furthermore, as π-electron-deficient skeletons, xanthene skeletons, thioxanthene dioxide skeletons, oxadiazole skeletons, triazole skeletons, imidazole skeletons, anthraquinone skeletons, boron-containing skeletons such as phenylborane and volanthrene, aromatic rings or heteroaromatic rings having a nitrile group or a cyano group such as benzonitrile or cyanobenzene, carbonyl skeletons such as benzophenone, phosphine oxide skeletons, sulfone skeletons, etc., can be used. In this way, π-electron-deficient skeletons and π-electron-excess skeletons can be used instead of at least one of π-electron-deficient heteroaromatic rings and π-electron-excess heteroaromatic rings.

[0069] [ka]

[0070] TADF materials are materials that have a small difference between the S1 and T1 energy levels and possess the ability to convert energy from triplet excitation energy to singlet excitation energy through reverse intersystem crossing. Therefore, triplet excitation energy can be upconverted to singlet excitation energy with only a small amount of thermal energy (reverse intersystem crossing), and singlet excited states can be efficiently generated. Furthermore, triplet excitation energy can be converted into luminescence.

[0071] Furthermore, an excited complex (also called an exciplex) that forms an excited state with two types of substances has an extremely small difference between the S1 and T1 levels and functions as a TADF material that can convert triplet excitation energy into singlet excitation energy.

[0072] Furthermore, the phosphorescence spectrum observed at low temperatures (e.g., 77K to 10K) can be used as an indicator of the T1 level. For TADF materials, when a tangent is drawn at the short-wavelength tail of the fluorescence spectrum and the energy at the wavelength of the extrapolation is taken as the S1 level, and when a tangent is drawn at the short-wavelength tail of the phosphorescence spectrum and the energy at the wavelength of the extrapolation is taken as the T1 level, it is preferable that the difference between S1 and T1 is 0.3 eV or less, and more preferably 0.2 eV or less.

[0073] Furthermore, when using TADF material as the luminescence center material, it is preferable that the S1 level of the host material is higher than the S1 level of the TADF material. Also, it is preferable that the T1 level of the host material is higher than the T1 level of the TADF material.

[0074] Various carrier transport materials can be used as the host material for the light-emitting layer, such as materials with electron transport properties, materials with hole transport properties, and the TADF material mentioned above.

[0075] As materials possessing hole transport properties, organic compounds having an amine skeleton or a π-electron-rich heteroaromatic ring skeleton are preferred. For example, 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'-bifluoren-2-yl)-N-phenylamino]biphenyl (abbreviated as BSPB), 4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviated as BPAFLP), 4-phenyl Nyl-3'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: mBPAFLP), 4-phenyl-4'-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4'-diphenyl-4''-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBBi1BP), 4-(1-naphthyl)-4'-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBANB) Aromatic amine skeletons such as 4,4'-di(1-naphthyl)-4''-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBNBB), 9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]fluoren-2-amine (abbreviation: PCBAF), and N-phenyl-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]spiro-9,9'-bifluoren-2-amine (abbreviation: PCBASF) Compounds containing this, as well as compounds with a carbazole skeleton such as 1,3-bis(N-carbazolyl)benzene (abbreviated as mCP), 4,4'-di(N-carbazolyl)biphenyl (abbreviated as CBP), 3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviated as CzTP), 3,3'-bis(9-phenyl-9H-carbazole) (abbreviated as PCCP), and 4,4',4''-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviated as DBT3P-II), 2,Examples include compounds having a thiophene skeleton such as 8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene (abbreviated as DBTFLP-III) and 4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviated as DBTFLP-IV), and compounds having a furan skeleton such as 4,4',4''-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviated as DBF3P-II) and 4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran (abbreviated as mmDBFFLBi-II). Among the above, compounds having an aromatic amine skeleton and compounds having a carbazole skeleton are preferred because they have good reliability, high hole transportability, and contribute to reducing the driving voltage. In addition, the hole transport materials listed as examples of the second substance above can also be used.

[0076] Preferred electron-transporting materials include metal complexes such as bis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviated as BeBq2), bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III) (abbreviated as BAlq), bis(8-quinolinolato)zinc(II) (abbreviated as Znq), bis[2-(2-benzoxazollyl)phenolato]zinc(II) (abbreviated as ZnPBO), and bis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviated as ZnBTZ), as well as organic compounds having a π-electron-deficient heteroaromatic ring skeleton.Examples of organic compounds having a π-electron-deficient heteroaromatic ring skeleton include 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviated as PBD), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviated as TAZ), and 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazole-2-yl]benzene (abbreviated as OXD-7). Heterocyclic compounds having a polyazole skeleton, such as 9-[4-(5-phenyl-1,3,4-oxadiazole-2-yl)phenyl]-9H-carbazole (abbreviated as CO11), 2,2',2''-(1,3,5-benzenetriyl)tris(1-phenyl-1H-benzoimidazole) (abbreviated as TPBI), and 2-[3-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzoimidazole (abbreviated as mDBTBIm-II), as well as 2-[3-(di Benzothiophene-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTPDBq-II), 2-[3'-(dibenzothiophene-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTBPDBq-II), 2-[3'-(9H-carbazole-9-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mCzBPDBq), 4,6-bis[3-(phenanthrene-9-yl)phenyl Examples include heterocyclic compounds having a diazine skeleton, such as [nyl]pyrimidine (abbreviated as 4,6mPnP2Pm) and 4,6-bis[3-(4-dibenzothienyl)phenyl]pyrimidine (abbreviated as 4,6mDBTP2Pm-II), and heterocyclic compounds having a pyridine skeleton, such as 3,5-bis[3-(9H-carbazole-9-yl)phenyl]pyridine (abbreviated as 35DCzPPy) and 1,3,5-tri[3-(3-pyridyl)phenyl]benzene (abbreviated as TmPyPB). Among the above, heterocyclic compounds having a diazine skeleton and heterocyclic compounds having a pyridine skeleton are preferred due to their good reliability. In particular, heterocyclic compounds having a diazine (pyrimidine or pyrazine) skeleton have high electron transport properties and contribute to reducing the driving voltage.

[0077] The TADF materials listed above can be used as host materials. When a TADF material is used as a host material, the triplet excitation energy generated by the TADF material is converted into singlet excitation energy through reverse intersystem crossing, and this energy is then transferred to the luminescent center material, thereby increasing the luminescence efficiency of the light-emitting device. In this case, the TADF material functions as an energy donor, and the luminescent center material functions as an energy acceptor.

[0078] This is particularly effective when the luminescence center material is a fluorescent material. Furthermore, in order to obtain high luminescence efficiency, it is preferable that the S1 level of the TADF material is higher than that of the fluorescent material. Also, it is preferable that the T1 level of the TADF material is higher than that of the fluorescent material. Therefore, it is preferable that the T1 level of the TADF material is higher than that of the fluorescent material.

[0079] Furthermore, it is preferable to use a TADF material that exhibits emission that overlaps with the wavelength of the lowest-energy absorption band of the fluorescent material. This is preferable because it allows for smooth transfer of excitation energy from the TADF material to the fluorescent material, resulting in efficient emission.

[0080] Furthermore, for singlet excitation energy to be efficiently generated from triplet excitation energy by reverse intersystem crossing, it is preferable that carrier recombination occurs in the TADF material. It is also preferable that the triplet excitation energy generated in the TADF material does not transfer to the triplet excitation energy of the fluorescent material. To achieve this, it is preferable that the fluorescent material has protecting groups around the luminescent phosphodiocyte (the skeleton that causes luminescence). Preferred protecting groups are substituents without π bonds, and saturated hydrocarbons are preferred. Specifically, examples include alkyl groups having 3 to 10 carbon atoms, substituted or unsubstituted cycloalkyl groups having 3 to 10 carbon atoms, and trialkylsilyl groups having 3 to 10 carbon atoms. It is even preferable to have multiple protecting groups. Substituents without π bonds have poor carrier transport function, and therefore can increase the distance between the TADF material and the luminescent phosphodiocyte of the fluorescent material with little effect on carrier transport or carrier recombination. Here, the luminescent phosphodiocyte refers to the atomic group (skeleton) that causes luminescence in the fluorescent material. The luminescent phosphodiosity preferably has a skeleton containing π bonds, preferably contains an aromatic ring, and preferably has a condensed aromatic ring or a condensed heteroaromatic ring. Examples of condensed aromatic rings or condensed heteroaromatic rings include phenanthrene skeletons, stilbene skeletons, acridone skeletons, phenoxazine skeletons, and phenothiazine skeletons. Fluorescent materials having naphthalene, anthracene, fluorene, chrysene, triphenylene, tetracene, pyrene, perylene, coumarin, quinacridone, or naphthobisbenzofuran skeletons are particularly preferred due to their high fluorescence quantum yield.

[0081] When using a fluorescent material as the luminescence center material, a material having an anthracene skeleton is preferred as the host material. Using a material having an anthracene skeleton as the host material for a fluorescent material makes it possible to realize a luminescence layer with good luminescence efficiency and durability. Among the materials having an anthracene skeleton to be used as the host material, materials having a diphenylanthracene skeleton, and especially a 9,10-diphenylanthracene skeleton, are preferred because they are chemically stable. Furthermore, when the host material has a carbazole skeleton, it is preferred because it improves hole injection and transportability, but when it contains a benzocarbazole skeleton in which a benzene ring is further condensed into carbazole, the HOMO becomes about 0.1 eV shallower than carbazole, making it easier for holes to enter, which is even more preferred. In particular, when the host material contains a dibenzocarbazole skeleton, the HOMO becomes about 0.1 eV shallower than carbazole, making it easier for holes to enter, and it is also preferred because it has excellent hole transportability and high heat resistance. Therefore, a more preferable host material is a substance that simultaneously possesses a 9,10-diphenylanthracene skeleton and a carbazole skeleton (or a benzocarbazole skeleton or dibenzocarbazole skeleton). Furthermore, from the viewpoint of hole injection and transport properties, a benzofluorene skeleton or a dibenzofluorene skeleton may be used instead of the carbazole skeleton. Examples of such substances include 9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviated as PCzPA), 3-[4-(1-naphthyl)-phenyl]-9-phenyl-9H-carbazole (abbreviated as PCPN), 9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviated as CzPA), and 7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole. Examples include ruvasol (abbreviated as cgDBCzPA), 6-[3-(9,10-diphenyl-2-anthryl)phenyl]-benzo[b]naphtho[1,2-d]furan (abbreviated as 2mBnfPPA), 9-phenyl-10-{4-(9-phenyl-9H-fluoren-9-yl)biphenyl-4'-yl}anthracene (abbreviated as FLPPA), and 9-(1-naphthyl)-10-[4-(2-naphthyl)phenyl]anthracene (abbreviated as αN-βNPAnth).In particular, CzPA, cgDBCzPA, 2mBnfPPA, and PCzPA exhibit very good characteristics and are therefore preferred choices.

[0082] The host material may be a mixture of multiple substances, and when using a mixed host material, it is preferable to mix an electron-transporting material with a hole-transporting material. By mixing an electron-transporting material with a hole-transporting material, the transport properties of the light-emitting layer 113 can be easily adjusted, and the recombination region can also be easily controlled. The weight ratio of the hole-transporting material to the electron-transporting material should be 1:19 to 19:1.

[0083] Furthermore, phosphorescent materials can be used as part of the above-mentioned mixed materials. When a fluorescent material is used as the light-emitting center material, the phosphorescent material can be used as an energy donor to supply excitation energy to the fluorescent material.

[0084] Furthermore, these mixed materials may form excited complexes. When selecting a combination of materials to mix, it is preferable to choose one that forms an excited complex that exhibits emission overlapping with the wavelength of the lowest-energy absorption band of the luminescent material. This allows for smoother energy transfer and efficient emission. This configuration is also preferable because it reduces the driving voltage.

[0085] Furthermore, at least one of the materials forming the excitation complex may be a phosphorescent material. By doing so, the triplet excitation energy can be efficiently converted to singlet excitation energy through reverse intersystem crossing.

[0086] For efficient excitation complex formation, it is preferable that the HOMO level of the hole-transporting material is above the HOMO level of the electron-transporting material. Furthermore, it is preferable that the LUMO level of the hole-transporting material is above the LUMO level of the electron-transporting material. The LUMO and HOMO levels of the materials can be derived from the electrochemical properties (reduction potential and oxidation potential) of the materials measured by cyclic voltammetry (CV).

[0087] The formation of excited complexes can be confirmed, for example, by comparing the emission spectra of a hole-transporting material, an electron-transporting material, and a mixed film made by mixing these materials, and observing that the emission spectrum of the mixed film shifts to a longer wavelength than the emission spectra of each individual material (or has a new peak on the longer wavelength side). Alternatively, it can be confirmed by comparing the transient photoluminescence (PL) of a hole-transporting material, the transient PL of an electron-transporting material, and the transient PL of a mixed film made by mixing these materials, and observing differences in the transient response, such as the transient PL lifetime of the mixed film having a longer lifetime component or a larger proportion of the delayed component than the transient PL lifetime of each individual material. Furthermore, the transient PL mentioned above can be replaced with transient electroluminescence (EL). That is, the formation of excited complexes can also be confirmed by comparing the transient EL of a hole-transporting material, the transient EL of an electron-transporting material, and the transient EL of a mixed film made by mixing these materials, and observing the differences in the transient response.

[0088] The electron transport layer 114 is preferably provided in contact with the light-emitting layer 113 as shown in Figure 1A1 and has a seventh material and an eighth material. The seventh material is an organic compound in which electron transport properties are dominant over hole transport properties. Furthermore, the electron mobility of the electron transport layer 114 is 1 × 10⁻¹⁴ at an electric field strength [V / cm] square root of 600. -7 cm 2 / Vs or more 5×10 -5 cm 2 It is preferable that it is less than or equal to / Vs.

[0089] The eighth substance is an alkali metal or an alkali metal element, compound, or complex, preferably containing an 8-hydroxyquinolinate structure. Specifically, examples include 8-hydroxyquinolinate-lithium (abbreviated as Liq) and 8-hydroxyquinolinate-sodium (abbreviated as Naq). In particular, a complex of a monovalent metal ion is preferred, among which a lithium complex is preferred, and Liq is more preferred. When an 8-hydroxyquinolinate structure is included, methyl-substituted derivatives thereof (e.g., 2-methyl-substituted derivatives or 5-methyl-substituted derivatives) can also be used.

[0090] Furthermore, it is preferable that the eighth substance in the electron transport layer 114 has a concentration difference in the thickness direction (including the case where the concentration of the eighth substance is 0). This makes it possible to make the light-emitting device of one aspect of the present invention a light-emitting device with good lifespan and reliability.

[0091] There are many possible configurations in which the electron transport layer 114 has a concentration difference in the thickness direction, but for example, there is a configuration in which the concentration of the eighth substance has a concentration gradient in which it decreases (including cases where it is 0) from the light-emitting layer side to the cathode side in the electron transport layer 114, or as shown in Figure 1A2, the electron transport layer 114 has multiple layers such as the first electron transport layer 114-1 and the second electron transport layer 114-2 from the light-emitting layer 113 side, and the concentration of the eighth substance is higher in the layers closer to the light-emitting layer than in the layers closer to the cathode, or the electron transport layer 114 has a first electron transport layer located on the light-emitting layer side and a second electron transport layer located on the cathode side, and the concentration of the eighth substance in the first electron transport layer is higher than the concentration of the eighth substance in the second electron transport layer. In another embodiment, the electron transport layer 114 may have multiple layers, and one of the remaining layers may have a higher concentration of the eighth substance than the layer closest to the cathode. Alternatively, the electron transport layer 114 may have a first region located on the light-emitting layer side and a second region located on the cathode side, and a difference in the concentration of the eighth substance may exist between the first and second regions. The concentration of the eighth substance may be higher in the first region or higher in the second region, but the embodiment where the concentration is higher in the first region is more preferable because it is easier to obtain a light-emitting device with a good lifetime. The electron transport layer 114 may also have regions other than the first and second regions.

[0092] Furthermore, the concentration of the eighth substance may change continuously as shown in Figures 2A1 and 2A2 if there is no clear layered boundary as shown in Figure 1A1, or it may change in a stepwise manner as shown in Figures 2B1 and 2B2 if it can be seen as being separated into layers as shown in Figure 1A2.

[0093] Furthermore, it is preferable that the seventh substance has electron transport properties and its HOMO level is -6.0 eV or higher.

[0094] Other electron-transporting organic compounds that can be used as the seventh substance include those listed as electron-transporting organic compounds that can be used as the host material, or those listed as organic compounds that can be used as the host material for the fluorescent substance.

[0095] Furthermore, the region where the concentration of the eighth substance is low also includes the region where the concentration of the eighth substance is 0.

[0096] Furthermore, regions with high concentrations of the eighth substance and regions with low concentrations of the eighth substance can be formed by changing the mixing ratio of the seventh substance and the eighth substance. However, the seventh substance and the eighth substance may be different in the regions with high concentrations of the eighth substance and the regions with low concentrations of the eighth substance.

[0097] Furthermore, it is preferable that the electron mobility of the seventh material at a square root of the electric field strength [V / cm] of 600 is smaller than that of the sixth material or the light-emitting layer 113.

[0098] When the light-emitting layer becomes electron-rich, as shown in Figure 3A, the light-emitting region 113-1 becomes limited to a portion, increasing the burden on that portion and accelerating its degradation. Furthermore, if electrons pass through the light-emitting layer without being able to recombine, the lifespan and luminous efficiency also decrease. In one aspect of the present invention, by reducing the electron transportability of the electron transport layer 114, the light-emitting region 113-1 is expanded as shown in Figure 3B, and the burden on the material constituting the light-emitting layer 113 is distributed, thereby providing a light-emitting device with a long lifespan and good luminous efficiency.

[0099] Furthermore, in light-emitting devices having such a configuration, the degradation curve of brightness obtained by a driving test under constant current density conditions may exhibit a shape with a maximum value. That is, the degradation curve of a light-emitting device according to one aspect of the present invention may have a shape in which the brightness increases over time. In light-emitting devices exhibiting such degradation behavior, it is possible to offset the rapid degradation in the initial stages of operation, known as initial degradation, with this increase in brightness, making it possible to create a light-emitting device with low initial degradation and a very good driving life. Such a light-emitting device shall be called a Recombination-Site Tailoring Injection element (ReSTI element).

[0100] Furthermore, when the derivative of a degradation curve having such a maximum value is taken, there is a portion where the derivative is zero. Therefore, a light-emitting device according to one embodiment of the present invention, in which a portion of the derivative of the degradation curve is zero, can be said to have low initial degradation and a very good lifespan.

[0101] A light-emitting device according to one aspect of the present invention having the above configuration can be made into a light-emitting device with a very good lifespan. In particular, it is possible to significantly extend the lifespan in the region where degradation is extremely small, up to about LT95.

[0102] Furthermore, by suppressing initial degradation, it becomes possible to significantly reduce the burn-in problem, which is still a major weakness of OLED devices, and the effort required for pre-shipment aging to mitigate it.

[0103] As described above, the hole injection layer in one embodiment of the light-emitting device of the present invention has a hole transport material with a deep HOMO level, so induced holes are easily injected into the hole transport layer and the light-emitting layer. Therefore, in the initial stages of operation, it is easy to create a state in which a small number of holes pass through the light-emitting layer and reach the electron transport layer.

[0104] In one aspect of the present invention, the electron transport layer of the light-emitting device includes an electron transport material and an alkali metal or alkaline earth metal element, compound, or complex (or includes an electron transport material and a metal complex having a ligand containing an 8-hydroxyquinolinate structure and a monovalent metal ion). Therefore, when the light-emitting device is continuously lit, an improvement in the electron injection and transport performance of the electron transport layer is observed. On the other hand, as described above, the hole injection layer has moderately suppressed hole induction, so it cannot supply many holes to the electron transport layer. As a result, the number of holes that can reach the electron transport layer decreases over time, and the probability of holes recombining with electrons in the light-emitting layer increases. In other words, during continuous operation, a shift in the carrier balance occurs that makes recombination more likely to occur in the light-emitting layer. This shift results in a light-emitting device with suppressed initial degradation.

[0105] (Embodiment 2) Next, we will describe the detailed structure and material examples of the light-emitting device described above. In this embodiment, an EL layer 103 consisting of multiple layers is provided between a pair of electrodes, an anode 101 and a cathode 102. The EL layer 103 is described as having a configuration that includes, at least from the anode 101 side, 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. However, various layer structures can be applied to the layers included in the EL layer 103, such as hole injection layers, hole transport layers, electron injection layers, carrier block layers, exciton block layers, and charge generation layers.

[0106] The anode 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. These conductive metal oxide films are usually deposited by sputtering, but they may also be fabricated using methods such as the sol-gel method. As an example of a fabrication method, indium zinc oxide can be formed by sputtering using a target containing 1 to 20 wt% zinc oxide relative to indium oxide. Indium oxide (IWZO) containing tungsten oxide and zinc oxide can also be formed by sputtering using a target containing 0.5 to 5 wt% tungsten oxide and 0.1 to 1 wt% zinc oxide relative to indium oxide. Other examples include gold (Au), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), or nitrides of metallic materials (e.g., titanium nitride). Graphene can also be used. Here, we have listed representative materials for forming the anode with a large work function, but in one aspect of the present invention, a composite material containing an organic compound having hole transport properties and a substance that exhibits electron-accepting properties for the organic compound is used for the hole injection layer 111, so the electrode material can be selected regardless of the work function.

[0107] Regarding the laminated structure of the EL layer 103, this embodiment describes two types of configurations: one having a hole injection layer 111, a hole transport layer 112 (first hole transport layer 112-1, second hole transport layer 112-2), a light-emitting layer 113, an electron transport layer 114 (first electron transport layer 114-1, second electron transport layer 114-2), and an electron injection layer 115, as shown in Figures 1A1 and 1A2; and another having a charge generation layer 116 instead of the electron injection layer 115, as shown in Figure 1B. The materials constituting each layer are specifically described below.

[0108] The hole injection layer 111, hole transport layer 112 (hole transport layer 112-1, hole transport layer 112-2), light-emitting layer 113, and electron transport layer 114 (electron transport layer 114-1, electron transport layer 114-2) have been described in detail in Embodiment 1, so a repetitive description will be omitted. Please refer to the description in Embodiment 1.

[0109] Between the electron transport layer 114 and the cathode 102, an electron injection layer 115 may be provided, which contains an alkali metal or alkaline earth metal, such as lithium fluoride (LiF), cesium fluoride (CsF), or calcium fluoride (CaF2), or a compound thereof. The electron injection layer 115 may be a layer made of an electron-transporting material containing an alkali metal or alkaline earth metal or a compound thereof, or an electride may be used. Examples of electrides include a material obtained by adding a high concentration of electrons to a mixed oxide of calcium and aluminum.

[0110] Alternatively, instead of the electron injection layer 115, a charge generation layer 116 may be provided between the electron transport layer 114 and the cathode 102 (Figure 1B). The charge generation layer 116 is a layer that can inject holes into the layer in contact with the cathode side and electrons into the layer in contact with the anode side by applying a potential. The charge generation layer 116 includes at least a P-type layer 117. The P-type layer 117 is preferably formed using a composite material listed above as a material that can constitute the hole injection layer 111. The P-type layer 117 may also be formed by laminating a film containing the electron-accepting material and a film containing the hole transport material as materials that constitute the composite material. By applying a potential to the P-type layer 117, electrons are injected into the electron transport layer 114 and holes into the cathode 102, and the light-emitting device operates.

[0111] Furthermore, it is preferable that the charge generation layer 116 includes, in addition to the P-type layer 117, one or both of the electron relay layer 118 and the electron injection buffer layer 119.

[0112] The electron relay layer 118 contains at least an electron-transporting material and has the function of preventing interaction between the electron injection buffer layer 119 and the P-type layer 117, thereby smoothly transferring electrons. The LUMO level of the electron-transporting material contained in the electron relay layer 118 is preferably between the LUMO level of the electron-accepting material in the P-type layer 117 and the LUMO level of the material contained in the layer in contact with the charge generation layer 116 in the electron transport layer 114. The specific energy level of the LUMO level of the electron-transporting material used in the electron relay layer 118 is preferably -5.0 eV or higher, more preferably -5.0 eV or higher and -3.0 eV or lower. It is preferable to use a phthalocyanine-based material or a metal complex having a metal-oxygen bond and an aromatic ligand as the electron-transporting material used in the electron relay layer 118.

[0113] The electron injection buffer layer 119 can use materials with high electron injection potential, such as alkali metals, alkaline earth metals, rare earth metals, and compounds thereof (alkali metal compounds (including oxides such as lithium oxide, halides, and carbonates such as lithium carbonate and cesium carbonate), alkaline earth metal compounds (including oxides, halides, and carbonates), or rare earth metal compounds (including oxides, halides, and carbonates)).

[0114] Furthermore, if the electron injection buffer layer 119 is formed by including an electron-transporting substance and an electron-donating substance, the electron-donating substance can include alkali metals, alkaline earth metals, rare earth metals, and compounds thereof (alkali metal compounds (including oxides such as lithium oxide, halides, and carbonates such as lithium carbonate and cesium carbonate), alkaline earth metal compounds (including oxides, halides, and carbonates), or rare earth metal compounds (including oxides, halides, and carbonates)), as well as organic compounds such as tetratianaphthalene (abbreviated as TTN), nickerosene, and decamethylnickerosene. The electron-transporting substance can be formed using the same materials as those used to constitute the electron transport layer 114 described earlier.

[0115] As the material forming the cathode 102, metals, alloys, electrically 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) and cesium (Cs), elements belonging to Group 1 or 2 of the periodic table such as magnesium (Mg), calcium (Ca), and strontium (Sr), and alloys containing these elements (MgAg, AlLi), rare earth metals such as europium (Eu) and ytterbium (Yb), and alloys containing these elements. However, by providing an electron injection layer between the cathode 102 and the electron transport layer, various conductive materials such as Al, Ag, ITO, silicon, or indium oxide-tin oxide containing silicon oxide can be used as the cathode 102, regardless of the magnitude of their work functions. These conductive materials can be deposited using dry methods such as vacuum deposition and sputtering, as well as inkjet and spin coating methods. Alternatively, the material may be formed using a wet process with a sol-gel method, or it may be formed using a wet process with a paste of a metallic material.

[0116] Furthermore, various methods can be used to form the EL layer 103, regardless of whether they are dry or wet methods. For example, vacuum deposition, gravure printing, offset printing, screen printing, inkjet printing, or spin coating may be used.

[0117] Furthermore, each electrode or layer described above may be formed using different film deposition methods.

[0118] The configuration of the layer provided between the anode 101 and the cathode 102 is not limited to those described above. However, a configuration is preferred in which a light-emitting region is provided at a location away from the anode 101 and cathode 102 where holes and electrons recombine, in order to suppress quenching caused by the proximity of the light-emitting region to the metal used in the electrodes and carrier injection layer.

[0119] Furthermore, the hole transport layer and electron transport layer in contact with the light-emitting layer 113, and especially the carrier transport layer near the recombination region in the light-emitting layer 113, are preferably made of a material whose band gap is larger than that of the light-emitting material constituting the light-emitting layer or the light-emitting material contained in the light-emitting layer, in order to suppress energy transfer from excitons generated in the light-emitting layer.

[0120] Next, an embodiment of a light-emitting device (also called a stacked element or tandem element) with a configuration in which multiple light-emitting units are stacked will be described with reference to Figure 1C. This light-emitting device has multiple light-emitting units between the anode and the cathode. Each light-emitting unit has a configuration almost identical to the EL layer 103 shown in Figure 1A1 or Figure 1A2. In other words, the light-emitting device shown in Figure 1C is a light-emitting device having multiple light-emitting units, while the light-emitting devices shown in Figures 1A1, 1A2, and 1B are light-emitting devices having one light-emitting unit.

[0121] In Figure 1C, a first light-emitting unit 511 and a second light-emitting unit 512 are stacked between the anode 501 and the cathode 502, and a charge generation layer 513 is provided between the first light-emitting unit 511 and the second light-emitting unit 512. The anode 501 and cathode 502 correspond to the anode 101 and cathode 102 in Figure 1A1, respectively, and the same components described in the explanation of Figure 1A1 can be applied. Furthermore, the first light-emitting unit 511 and the second light-emitting unit 512 may have the same configuration or different configurations.

[0122] The charge generation layer 513 has the function of injecting electrons into one light-emitting unit and holes into the other light-emitting unit when a voltage is applied to the anode 501 and cathode 502. That is, in Figure 1C, when a voltage is applied such that the potential of the anode is higher than the potential of the cathode, the charge generation layer 513 only needs to inject electrons into the first light-emitting unit 511 and holes into the second light-emitting unit 512.

[0123] The charge generation layer 513 is preferably formed with the same configuration as the charge generation layer 116 described in Figure 1B. The composite material of organic compound and metal oxide has excellent carrier implantation and carrier transport properties, enabling low-voltage and low-current operation. If the anode side of the light-emitting unit is in contact with the charge generation layer 513, the charge generation layer 513 can also act as a hole injection layer for the light-emitting unit, so the light-emitting unit does not need to have a hole injection layer.

[0124] Furthermore, when an electron injection buffer layer 119 is provided in the charge generation layer 513, the electron injection buffer layer 119 plays the role of an electron injection layer in the anode-side light-emitting unit, so it is not necessarily required to form an electron injection layer in the anode-side light-emitting unit.

[0125] Figure 1C illustrates a light-emitting device having two light-emitting units, but the same principles can be applied to light-emitting devices with three or more stacked light-emitting units. As in the light-emitting device according to this embodiment, by arranging multiple light-emitting units separated between a pair of electrodes by a charge generation layer 513, high-brightness light emission can be achieved while maintaining a low current density, and a longer-life element can be realized. Furthermore, a light-emitting device that can be driven at a low voltage and consumes little power can be realized.

[0126] Furthermore, by making the light-emitting colors of each light-emitting unit different, the light-emitting device as a whole can emit light of a desired color. For example, in a light-emitting device having two light-emitting units, it is possible to obtain a light-emitting device that emits white light as a whole by obtaining red and green light-emitting colors from the first light-emitting unit and blue light-emitting color from the second light-emitting unit. In addition, as a configuration of a light-emitting device in which three or more light-emitting units are stacked, for example, a tandem type device can be formed in which the first light-emitting unit has a first blue light-emitting layer, the second light-emitting unit has a yellow or yellow-green light-emitting layer and a red light-emitting layer, and the third light-emitting unit has a second blue light-emitting layer. This tandem type device can emit white light in the same way as the light-emitting device described above.

[0127] Furthermore, each layer and electrode, such as the EL layer 103, the first light-emitting unit 511, the second light-emitting unit 512, and the charge generation layer, can be formed using methods such as vapor deposition (including vacuum deposition), droplet ejection (also known as inkjet printing), coating, and gravure printing. They may also contain low-molecular-weight materials, medium-molecular-weight materials (including oligomers and dendrimers), or polymer materials.

[0128] (Embodiment 3) This embodiment describes a light-emitting device using the light-emitting devices described in Embodiment 1 and Embodiment 2.

[0129] In this embodiment, a light-emitting device manufactured using the light-emitting devices described in Embodiment 1 and Embodiment 2 will be described with reference to Figure 4. Figure 4A is a top view showing the light-emitting device, and Figure 4B is a cross-sectional view obtained by cutting Figure 4A along lines AB and CD. This light-emitting 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, all indicated by dotted lines, to control the light emission of the light-emitting device. Furthermore, 604 is a sealing substrate, and 605 is a sealing material, with the area enclosed by the sealing material 605 being a space 607.

[0130] The routing wiring 608 is for transmitting signals input to the source line drive circuit 601 and the gate line drive circuit 603, and receives video signals, clock signals, start signals, reset signals, etc. from the FPC (flexible printed circuit) 609, which serves as an external input terminal. Although only the FPC is shown in this illustration, a printed circuit board (PWB) may be attached to this FPC. In this specification, the light-emitting device includes not only the light-emitting device itself, but also the state in which the FPC or PWB is attached to it.

[0131] Next, the cross-sectional structure will be explained using Figure 4B. A drive circuit section and a pixel section are formed on the element substrate 610, and here, the source line drive circuit 601, which is the drive circuit section, and one pixel in the pixel section 602 are shown.

[0132] The element substrate 610 may be manufactured using a substrate made of glass, quartz, organic resin, metal, alloy, semiconductor, or other materials, as well as a plastic substrate made of FRP (Fiber Reinforced Plastics), PVF (Polyvinyl Fluoride), polyester, or acrylic.

[0133] The structure of the transistors used in pixels and driving circuits is not particularly limited. For example, they may be inverse staggered transistors or staggered transistors. They may also be top-gate or bottom-gate transistors. The semiconductor material used for the transistors is not particularly limited; for example, silicon, germanium, silicon carbide, gallium nitride, etc., can be used. Alternatively, an oxide semiconductor containing at least one of indium, gallium, and zinc, such as an In-Ga-Zn metal oxide, may be used.

[0134] The crystallinity of the semiconductor material used in the transistor is not particularly limited; amorphous semiconductors, crystalline semiconductors (microcrystalline semiconductors, polycrystalline semiconductors, single-crystal semiconductors, or semiconductors having a crystalline region in part) may be used. Using a crystalline semiconductor is preferable because it can suppress the degradation of transistor characteristics.

[0135] Here, it is preferable to use oxide semiconductors for semiconductor devices such as transistors used in the pixels and driving circuits described above, as well as transistors used in touch sensors and the like, which will be described later. In particular, it is preferable to use oxide semiconductors with a wider bandgap than silicon. By using oxide semiconductors with a wider bandgap than silicon, the current in the off state of the transistor can be reduced.

[0136] The above oxide semiconductor preferably contains at least indium (In) or zinc (Zn). More preferably, it is an oxide semiconductor containing an oxide represented as an In-M-Zn oxide (where M is a metal such as Al, Ti, Ga, Ge, Y, Zr, Sn, La, Ce, or Hf).

[0137] Herein, an oxide semiconductor that can be used in one aspect of the present invention will be described below.

[0138] Oxide semiconductors are divided into single-crystal oxide semiconductors and other 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), pseudo-amorphous oxide semiconductors (a-like OS: amorphous-like oxide semiconductor), and amorphous oxide semiconductors.

[0139] CAAC-OS has a c-axis orientation and a crystal structure in which multiple nanocrystals are linked in the ab-plane direction, resulting in a strained structure. The strain refers to the region where the orientation of the lattice arrangement changes between a region with a aligned lattice arrangement and another region with a aligned lattice arrangement, within the region where multiple nanocrystals are linked.

[0140] Nanocrystals are based on a hexagonal structure, but they are not necessarily regular hexagonal and may have non-regular hexagonal shapes. Furthermore, under strain, they may have lattice arrangements such as pentagons and heptagons. In CAAC-OS, however, it is difficult to observe clear grain boundaries (also called grain boundaries) even near strain. This indicates that the formation of grain boundaries is suppressed by the strain in the lattice arrangement. This is because CAAC-OS can tolerate strain due to the sparse arrangement of oxygen atoms in the ab-plane direction and the changes in interatomic bond distances caused by the substitution of metal elements.

[0141] Furthermore, CAAC-OS tends to have a layered crystalline structure (also called a layered structure) in which layers containing indium and oxygen (hereinafter referred to as the In layer) and layers containing element M, zinc, and oxygen (hereinafter referred to as the (M,Zn) layer) are stacked. Note that indium and element M are mutually substitutable, and when element M in the (M,Zn) layer is substituted with indium, it can also be represented as the (In,M,Zn) layer. Similarly, when indium in the In layer is substituted with element M, it can also be represented as the (In,M) layer.

[0142] CAAC-OS is a highly crystalline oxide semiconductor. On the other hand, because it is difficult to clearly identify grain boundaries in CAAC-OS, it can be said that a decrease in electron mobility due to grain boundaries is less likely to occur. Also, the crystallinity of oxide semiconductors can decrease due to the inclusion of impurities or the formation of defects, so CAAC-OS is less susceptible to impurities and defects (oxygen vacancies (V O It can be described as an oxide semiconductor with low oxygen vacancy (also known as CAAC-OS). Therefore, oxide semiconductors with CAAC-OS have stable physical properties. Consequently, oxide semiconductors with CAAC-OS are heat resistant and highly reliable.

[0143] nc-OS exhibits periodicity in atomic arrangement within minute regions (e.g., regions between 1 nm and 10 nm, particularly between 1 nm and 3 nm). Furthermore, nc-OS lacks regularity in crystal orientation between different nanocrystals. Therefore, no orientation is observed across the entire film. Consequently, depending on the analytical method, nc-OS may be indistinguishable from a-like OS or amorphous oxide semiconductors.

[0144] Furthermore, indium-gallium-zinc oxide (IGZO), a type of oxide semiconductor containing indium, gallium, and zinc, can sometimes adopt a stable structure when formed into the nanocrystals described above. In particular, since IGZO tends to have difficulty growing crystals in the atmosphere, smaller crystals (for example, the nanocrystals described above) may be structurally more stable than larger crystals (here, crystals of several millimeters or several centimeters).

[0145] a-like OS is an oxide semiconductor having a structure between nc-OS and amorphous oxide semiconductors. a-like OS has porous or low-density regions. In other words, a-like OS has lower crystallinity compared to nc-OS and CAAC-OS.

[0146] Oxide semiconductors can take on diverse structures, each possessing different properties. One embodiment of the present invention may include two or more of the following: amorphous oxide semiconductors, polycrystalline oxide semiconductors, a-like OS, nc-OS, and CAAC-OS.

[0147] In addition to the oxide semiconductors mentioned above, CAC (Cloud-Aligned Composite)-OS may also be used.

[0148] CAC-OS is a material that possesses conductive properties in some parts, insulating properties in others, and semiconductor properties as a whole. When CAC-OS is used as the active layer of a transistor, the conductive function is the function of allowing electrons (or holes) to flow, and the insulating function is the function of preventing electrons from flowing. By making the conductive and insulating functions work complementaryly, a switching function (on / off function) can be given to CAC-OS. By separating each function in CAC-OS, both functions can be maximized.

[0149] Furthermore, CAC-OS has conductive regions and insulating regions. The conductive regions have the conductive function described above, and the insulating regions have the insulating function described above. In addition, the conductive regions and insulating regions may be separated at the nanoparticle level within the material. Also, the conductive regions and insulating regions may be unevenly distributed within the material. Furthermore, the conductive regions may be observed as blurred around the edges and connected in a cloud-like manner.

[0150] Furthermore, in CAC-OS, conductive regions and insulating regions may be dispersed in the material with a size of 0.5 nm to 10 nm, preferably 0.5 nm to 3 nm.

[0151] Furthermore, CAC-OS is composed of components with different band gaps. For example, CAC-OS is composed of a component with a wide band gap due to the insulating region and a component with a narrow band gap due to the conductive region. In this configuration, when carriers flow, the carriers mainly flow in the component with the narrow band gap. In addition, the component with the narrow band gap acts complementaryly to the component with the wide band gap, and carriers also flow in the component with the wide band gap in conjunction with the component with the narrow band gap. For this reason, when the above CAC-OS is used in the channel formation region of a transistor, a high current driving force, i.e., a large on-current, and a high field-effect mobility can be obtained in the on-state of the transistor.

[0152] In other words, CAC-OS can also be referred to as a matrix composite or a metal matrix composite.

[0153] By using the aforementioned oxide semiconductor material as the semiconductor layer, fluctuations in electrical properties are suppressed, enabling the realization of highly reliable transistors.

[0154] Furthermore, due to its low off-current, the transistor having the aforementioned semiconductor layer can retain the charge stored in the capacitor via the transistor for a long period of time. By applying such transistors to pixels, it becomes possible to maintain the gradation of the image displayed in each display area while simultaneously stopping the drive circuit. As a result, electronic devices with extremely reduced power consumption can be realized.

[0155] It is preferable to provide an undercoat to stabilize the characteristics of the transistor. As the undercoat, an inorganic insulating film such as a silicon oxide film, silicon nitride film, silicon oxynitride film, or silicon nitride film can be used and fabricated as a single layer or in layers. The undercoat can be formed using sputtering, CVD (Chemical Vapor Deposition) (plasma CVD, thermal CVD, MOCVD (Metal Organic CVD), etc.), ALD (Atomic Layer Deposition), coating, printing, etc. Note that the undercoat may be omitted if not necessary.

[0156] Note that FET623 is one of the transistors formed in the drive circuit section 601. The drive circuit can be formed using various CMOS, PMOS, or NMOS circuits. In this embodiment, a driver-integrated type with the drive circuit formed on the substrate is shown, but this is not necessarily required, and the drive circuit can be formed externally instead of on the substrate.

[0157] Furthermore, although the pixel section 602 is formed by a plurality of pixels including a switching FET 611 and a current control FET 612 and an anode 613 electrically connected to its drain, it is not limited to this, and the pixel section may be a combination of three or more FETs and a capacitive element.

[0158] Furthermore, an insulator 614 is formed to cover the end of the anode 613. This can be formed by using positive-type photosensitive acrylic.

[0159] Furthermore, in order to ensure good coverage of the EL layer and the like that will be formed later, a curved surface with curvature is formed at the upper or lower end of the insulator 614. For example, when a positive-type photosensitive acrylic is used as the material for the insulator 614, it is preferable to have a curved surface with a radius of curvature (0.2 μm to 3 μm) only at the upper end of the insulator 614. In addition, either a negative-type photosensitive resin or a positive-type photosensitive resin can be used as the insulator 614.

[0160] An EL layer 616 and a cathode 617 are formed on the anode 613. It is desirable to use a material with a high work function for the anode 613. For example, single-layer films such as ITO films, silicon-containing indium tin oxide films, indium oxide films containing 2-20 wt% zinc oxide, titanium nitride films, chromium films, tungsten films, Zn films, and Pt films can be used. Laminated structures of titanium nitride and aluminum-based films, and three-layer structures of titanium nitride, aluminum-based films, and titanium nitride films can also be used. Furthermore, a laminated structure offers low resistance as wiring, good ohmic contact, and the ability to function as an anode.

[0161] Furthermore, the EL layer 616 is formed by various methods such as vapor deposition using a vapor deposition mask, inkjet printing, and spin coating. The EL layer 616 includes the configuration described in Embodiment 1 and Embodiment 2. Other materials constituting the EL layer 616 may be low molecular weight compounds or high molecular weight compounds (including oligomers and dendrimers).

[0162] Furthermore, it is preferable to use a material with a low work function (such as Al, Mg, Li, Ca, or alloys or compounds thereof (MgAg, MgIn, AlLi, etc.)) for the cathode 617 formed on the EL layer 616. When light generated in the EL layer 616 is transmitted through the cathode 617, it is preferable to use a laminate of a thin metal film and a transparent conductive film (such as ITO, indium oxide containing 2-20 wt% zinc oxide, indium tin oxide containing silicon, or zinc oxide (ZnO)) as the cathode 617.

[0163] The anode 613, EL layer 616, and cathode 617 form a light-emitting device. This light-emitting device is the light-emitting device described in Embodiment 1 and Embodiment 2. Although the pixel portion is made up of multiple light-emitting devices, the light-emitting device in this embodiment may include both the light-emitting devices described in Embodiment 1 and Embodiment 2 and light-emitting devices having other configurations.

[0164] Furthermore, by bonding the sealing substrate 604 to the element substrate 610 with the sealing material 605, the light-emitting device 618 is provided in the space 607 surrounded by the element substrate 610, the sealing substrate 604, and the sealing material 605. The space 607 is filled with a filler material, which may be an inert gas (such as nitrogen or argon) or a sealing material. A recess is formed in the sealing substrate, and a desiccant is placed therein to suppress deterioration due to the effects of moisture, which is a preferred configuration.

[0165] Furthermore, it is preferable to use epoxy resin or glass frit for the sealing material 605. It is also desirable that these materials are as impermeable to moisture and oxygen as possible. In addition to glass substrates and quartz substrates, plastic substrates made of FRP (Fiber Reinforced Plastics), PVF (Polyvinyl Fluoride), polyester, or acrylic can be used as the material for the sealing substrate 604.

[0166] Although not shown in Figure 4, a protective film may be provided on the cathode. The protective film may be formed from an organic resin film or an inorganic insulating film. Alternatively, the protective film may be formed to cover the exposed portion of the sealing material 605. Furthermore, the protective film can be provided to cover the surface and sides of the pair of substrates, the sealing layer, the insulating layer, and other exposed sides.

[0167] The protective film can be made of a material that is impermeable to impurities such as water. Therefore, it is possible to effectively suppress the diffusion of impurities such as water from the outside to the inside.

[0168] Materials that constitute the protective film can include oxides, nitrides, fluorides, sulfides, ternary compounds, metals, or polymers. For example, materials containing aluminum oxide, hafnium oxide, hafnium silicate, lanthanum oxide, silicon oxide, strontium titanate, tantalum oxide, titanium oxide, zinc oxide, niobium oxide, zirconium oxide, tin oxide, yttrium oxide, cerium oxide, scandium oxide, erbium oxide, vanadium oxide, or indium oxide can be used. Other materials containing aluminum nitride, hafnium nitride, silicon nitride, tantalum nitride, titanium nitride, niobium nitride, molybdenum nitride, zirconium nitride, or gallium nitride can be used. 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 can be used.

[0169] It is preferable to form the protective film using a film deposition method that provides good step coverage. One such method is atomic layer deposition (ALD). It is preferable to use a material that can be formed using the ALD method for the protective film. By using the ALD method, it is possible to form a dense protective film with reduced defects such as cracks and pinholes, or a protective film with a uniform thickness. Furthermore, it is possible to reduce the damage inflicted on the processed workpiece when forming the protective film.

[0170] For example, by using the ALD method to form a protective film, it is possible to create a uniform, low-defect protective film on surfaces with complex uneven shapes, as well as on the top, sides, and back surfaces of touch panels.

[0171] As described above, a light-emitting device can be obtained using the light-emitting devices described in Embodiment 1 and Embodiment 2.

[0172] Since the light-emitting device in this embodiment uses the light-emitting devices described in Embodiments 1 and 2, a light-emitting device with good characteristics can be obtained. Specifically, since the light-emitting devices described in Embodiments 1 and 2 are long-life light-emitting devices, a highly reliable light-emitting device can be obtained. In addition, since the light-emitting device using the light-emitting devices described in Embodiments 1 and 2 has good luminous efficiency, it is possible to create a light-emitting device with low power consumption.

[0173] Figure 5 shows an example of a light-emitting device that is made full-color by forming a light-emitting device that emits white light and providing a colored layer (color filter), etc. Figure 5A shows the substrate 1001, the underlayer insulating film 1002, the gate insulating film 1003, the gate electrodes 1006, 1007, 1008, the first interlayer insulating film 1020, the second interlayer insulating film 1021, the peripheral part 1042, the pixel part 1040, the drive circuit part 1041, the anodes 1024W, 1024R, 1024G, 1024B of the light-emitting device, the partition wall 1025, the EL layer 1028, the cathode 1029 of the light-emitting device, the sealing substrate 1031, the sealing material 1032, etc.

[0174] In Figure 5A, the colored layers (red colored layer 1034R, green colored layer 1034G, and blue colored layer 1034B) are provided on a transparent substrate 1033. A black matrix 1035 may also be provided. The transparent substrate 1033 on which the colored layers and black matrix are provided is aligned and fixed to the substrate 1001. The colored layers and black matrix 1035 are covered with an overcoat layer 1036. In Figure 5A, there is an emissive layer that emits light to the outside without passing through the colored layers, and an emissive layer that emits light to the outside by passing through each colored layer. Light that does not pass through the colored layers is white, and light that passes through the colored layers is red, green, and blue, so an image can be represented with four colored pixels.

[0175] Figure 5B shows an example in which colored layers (red colored layer 1034R, green colored layer 1034G, and blue colored layer 1034B) are formed between the gate insulating film 1003 and the first interlayer insulating film 1020. Thus, the colored layers may also be provided between the substrate 1001 and the encapsulating substrate 1031.

[0176] Furthermore, although the light-emitting device described above is a bottom-emission type device that extracts light from the substrate 1001 on which the FET is formed, it may also be a top-emission type device that extracts light from the sealing substrate 1031 on which the light-emitting device is formed. A cross-sectional view of the top-emission type light-emitting device is shown in Figure 6. In this case, the substrate 1001 can be a substrate that does not transmit light. The process is the same as for the bottom-emission type light-emitting device until the connecting electrode that connects the FET and the anode of the light-emitting device is fabricated. After that, a third interlayer insulating film 1037 is formed covering the electrode 1022. This insulating film may also play a role in planarization. The third interlayer insulating film 1037 can be formed using the same material as the second interlayer insulating film, as well as other known materials.

[0177] The anodes 1024W, 1024R, 1024G, and 1024B of the light-emitting device are described here as anodes, but they may also be formed as cathodes. Furthermore, in the case of a top-emission type light-emitting device as shown in Figure 6, it is preferable to use a reflective electrode as the anode. The configuration of the EL layer 1028 is the same as that described as the EL layer 103 in Embodiments 1 and 2, and the element structure is such that white light emission can be obtained.

[0178] In the top emission structure shown in Figure 6, sealing can be performed with a sealing substrate 1031 having colored layers (red colored layer 1034R, green colored layer 1034G, and blue colored layer 1034B). A black matrix 1035 may be provided on the sealing substrate 1031 so as to be located between pixels. The colored layers (red colored layer 1034R, green colored layer 1034G, and blue colored layer 1034B) and the black matrix may be covered with an overcoat layer 1036. The sealing substrate 1031 should be a translucent substrate. In addition, although an example of full-color display using four colors, red, green, blue, and white, is shown here, it is not particularly limited, and full-color display may also be performed using four colors, red, yellow, green, and blue, or three colors, red, green, and blue.

[0179] In top-emission type light-emitting devices, a microcavity structure can be suitably applied. A light-emitting device having a microcavity structure is obtained by using a reflective electrode as the anode and a semi-transparent / semi-reflective electrode as the cathode. There is at least an EL layer between the reflective electrode and the semi-transparent / semi-reflective electrode, and there is at least a light-emitting layer that forms a light-emitting region.

[0180] The reflective electrode has a visible light reflectance of 40% to 100%, preferably 70% to 100%, and its resistivity is 1 × 10⁻⁶. -2 The film thickness is assumed to be Ωcm or less. Furthermore, the semi-transparent / semi-reflective electrode has a visible light reflectance of 20% to 80%, preferably 40% to 70%, and its resistivity is 1 × 10⁻⁶. -2 Assume the membrane is less than Ωcm in diameter.

[0181] The light emitted from the light-emitting layer contained in the EL layer is reflected by the reflective electrode and the semi-transparent / semi-reflective electrode, causing resonance.

[0182] This light-emitting device allows for changing the optical distance between the reflective electrode and the semi-transparent / semi-reflective electrode by varying the thickness of the transparent conductive film, the aforementioned composite material, or the carrier transport material. This makes it possible to enhance light of resonant wavelengths and attenuate light of non-resonant wavelengths between the reflective electrode and the semi-transparent / semi-reflective electrode.

[0183] Furthermore, since the light reflected back by the reflective electrode (first reflected light) interferes significantly with the light that directly enters the semi-transparent / semi-reflective electrode from the light-emitting layer (first incident light), it is preferable to adjust the optical distance between the reflective electrode and the light-emitting layer to (2n-1)λ / 4 (where n is a natural number greater than or equal to 1, and λ is the wavelength of the light emission to be amplified). By adjusting this optical distance, the phases of the first reflected light and the first incident light can be aligned, and the light emission from the light-emitting layer can be further amplified.

[0184] In the above configuration, the EL layer may have multiple light-emitting layers or a single light-emitting layer. For example, it may be applied to a configuration in which multiple EL layers are provided in a single light-emitting device with a charge generation layer in between, and one or more light-emitting layers are formed in each EL layer, in combination with the tandem light-emitting device configuration described above.

[0185] By incorporating a microcavity structure, it becomes possible to enhance the emission intensity in the front direction at specific wavelengths, thereby reducing power consumption. Furthermore, in the case of a light-emitting device that displays images using four sub-pixels of red, yellow, green, and blue, in addition to the brightness enhancement effect of yellow emission, a microcavity structure tailored to the wavelength of each color can be applied to all sub-pixels, resulting in a light-emitting device with excellent characteristics.

[0186] Since the light-emitting device in this embodiment uses the light-emitting devices described in Embodiments 1 and 2, a light-emitting device with good characteristics can be obtained. Specifically, since the light-emitting devices described in Embodiments 1 and 2 are long-life light-emitting devices, a highly reliable light-emitting device can be obtained. In addition, since the light-emitting device using the light-emitting devices described in Embodiments 1 and 2 has good luminous efficiency, it is possible to create a light-emitting device with low power consumption.

[0187] (Embodiment 4) In this embodiment, examples of using the light-emitting devices described in Embodiment 1 and Embodiment 2 as illumination devices will be explained with reference to Figure 7. Figure 7B is a top view of the illumination device, and Figure 7A is a cross-sectional view of ef in Figure 7B.

[0188] In this embodiment, the lighting device has an anode 401 formed on a translucent substrate 400 which serves as a support. The anode 401 corresponds to the anode 101 in Embodiment 2. When light is extracted from the anode 401 side, the anode 401 is formed from a translucent material.

[0189] A pad 412 for supplying voltage to the cathode 404 is formed on the substrate 400.

[0190] An EL layer 403 is formed on the anode 401. The EL layer 403 corresponds to the configuration of the EL layer 103 in Embodiment 1 and Embodiment 2, or to a configuration combining the light-emitting units 511, 512 and the charge generation layer 513. Please refer to the relevant descriptions for details on these configurations.

[0191] A cathode 404 is formed by covering the EL layer 403. The cathode 404 corresponds to the cathode 102 in Embodiment 2. When light emission is taken from the anode 401 side, the cathode 404 is formed of a material with high reflectivity. Voltage is supplied to the cathode 404 by connecting it to the pad 412.

[0192] As described above, the lighting device shown in this embodiment has a light-emitting device having an anode 401, an EL layer 403, and a cathode 404. Since this light-emitting device is a light-emitting device with high luminous efficiency, the lighting device in this embodiment can be a lighting device with low power consumption.

[0193] The lighting device is completed by fixing and sealing the substrate 400, on which the light-emitting device having the above configuration is formed, and the sealing substrate 407 using sealing materials 405 and 406. Either sealing material 405 or 406 may be used. In addition, a desiccant can be mixed into the inner sealing material 406 (not shown in Figure 7B), which allows for the adsorption of moisture and leads to improved reliability.

[0194] Furthermore, by extending a portion of the pad 412 and anode 401 outside the sealing materials 405 and 406, they can be used as external input terminals. Alternatively, an IC chip 420 with a converter or the like may be placed on top of them.

[0195] As described above, the lighting device described in this embodiment uses the light-emitting devices described in Embodiments 1 and 2 as EL elements, and can be made into a highly reliable light-emitting device. Furthermore, it can be made into a light-emitting device with low power consumption.

[0196] (Embodiment 5) This embodiment describes examples of electronic devices that include the light-emitting devices described in Embodiments 1 and 2 as part of their components. The light-emitting devices described in Embodiments 1 and 2 have a good lifespan and are highly reliable. As a result, the electronic device described in this embodiment can be an electronic device having a highly reliable light-emitting section.

[0197] Examples of electronic devices to which the above-mentioned light-emitting devices are applied include television equipment (also called televisions or television receivers), monitors for computers, digital cameras, digital video cameras, digital photo frames, mobile phones (also called mobile phones or mobile phone devices), portable game consoles, personal digital assistants, sound playback devices, and large game machines such as pachinko machines. Specific examples of these electronic devices are shown below.

[0198] Figure 8A shows an example of a television system. The television system has a display unit 7103 incorporated into a housing 7101. This figure also shows a configuration in which the housing 7101 is supported by a stand 7105. The display unit 7103 is capable of displaying images, and the display unit 7103 is constructed by arranging the light-emitting devices described in Embodiment 1 and Embodiment 2 in a matrix.

[0199] The television system can be operated using the operation switches on the housing 7101 or a separate remote control unit 7110. The operation keys 7109 on the remote control unit 7110 allow for channel and volume control, and the image displayed on the display unit 7103 can be controlled. Alternatively, the remote control unit 7110 may be configured to include a display unit 7107 that displays information output from the remote control unit 7110.

[0200] The television system will consist of a receiver, modem, and other components. The receiver will be able to receive general television broadcasts, and by connecting to a wired or wireless communication network via the modem, it will also be possible to perform one-way (from sender to receiver) or two-way (between sender and receiver, or between receivers, etc.) information communication.

[0201] Figure 8B1 shows a computer, which includes a main unit 7201, a housing 7202, a display unit 7203, a keyboard 7204, an external connection port 7205, a pointing device 7206, etc. This computer is manufactured by arranging the light-emitting devices described in Embodiments 1 and 2 in a matrix and using them in the display unit 7203. The computer in Figure 8B1 may also take the form shown in Figure 8B2. The computer in Figure 8B2 has a second display unit 7210 instead of the keyboard 7204 and pointing device 7206. The second display unit 7210 is a touch panel, and input can be performed by operating the input display shown on the second display unit 7210 with a finger or a dedicated pen. In addition to the input display, the second display unit 7210 can also display other images. The display unit 7203 may also be a touch panel. The two screens are connected by a hinge, which prevents problems such as scratching or damaging the screens when storing or transporting the device.

[0202] Figure 8C shows an example of a mobile terminal. The mobile phone has a display unit 7402 made by arranging the light-emitting devices described in Embodiment 1 and Embodiment 2 in a matrix. In addition to the display unit 7402 incorporated into the housing 7401, the mobile phone also includes operation buttons 7403, an external connection port 7404, a speaker 7405, a microphone 7406, and the like.

[0203] The mobile terminal shown in Figure 8C can also be configured to allow information input by touching the display unit 7402 with a finger or other object. In this case, operations such as making a phone call or composing an email can be performed by touching the display unit 7402 with a finger or other object.

[0204] The display unit 7402 has three main modes. The first is a display mode that primarily displays images, the second is an input mode that primarily inputs information such as text, and the third is a display + input mode that combines the display mode and the input mode.

[0205] For example, when making a phone call or composing an email, the display unit 7402 should be set to a text input mode, which primarily focuses on text input, and the user should perform the text input operation displayed on the screen. In this case, it is preferable to display a keyboard or number buttons on most of the screen of the display unit 7402.

[0206] Furthermore, by providing a detection device with a tilt sensor such as a gyroscope or accelerometer inside the mobile terminal, the orientation of the mobile terminal (portrait or landscape) can be determined, and the screen display of the display unit 7402 can be automatically switched accordingly.

[0207] Furthermore, the screen mode can be switched by touching the display unit 7402 or by operating the operation button 7403 on the housing 7401. It is also possible to switch modes depending on the type of image displayed on the display unit 7402. For example, if the image signal displayed on the display unit is video data, it can be switched to display mode; if it is text data, it can be switched to input mode.

[0208] Furthermore, in input mode, the system may detect a signal detected by the optical sensor of the display unit 7402 and, if there is no input via touch operation on the display unit 7402 for a certain period of time, control may be made to switch the screen mode from input mode to display mode.

[0209] The display unit 7402 can also function as an image sensor. For example, by touching the display unit 7402 with the palm or fingers, palm prints, fingerprints, etc., can be captured to perform user authentication. Furthermore, by using a backlight that emits near-infrared light or a sensing light source that emits near-infrared light in the display unit, it is also possible to capture images of finger veins, palm veins, etc.

[0210] Furthermore, the configuration shown in this embodiment can be used by appropriately combining the configurations shown in Embodiments 1 to 4.

[0211] As described above, the application range of the light-emitting device equipped with the light-emitting device described in Embodiment 1 and Embodiment 2 is extremely broad, and this light-emitting device can be applied to electronic devices in all fields. By using the light-emitting device described in Embodiment 1 and Embodiment 2, highly reliable electronic devices can be obtained.

[0212] Figure 9A is a schematic diagram showing an example of a cleaning robot.

[0213] The cleaning robot 5100 has a display 5101 on its top surface, multiple cameras 5102 on its sides, a brush 5103, and control buttons 5104. Although not shown in the illustration, the cleaning robot 5100 also has wheels, a suction port, etc. on its underside. The cleaning robot 5100 is also equipped with various sensors, including an infrared sensor, an ultrasonic sensor, an accelerometer, a piezoelectric sensor, a light sensor, and a gyroscope. Furthermore, the cleaning robot 5100 is equipped with a means of wireless communication.

[0214] The cleaning robot 5100 is self-propelled, can detect dirt 5120, and can suck up the dirt through a suction port located on its underside.

[0215] Furthermore, the cleaning robot 5100 can analyze images captured by the camera 5102 to determine the presence or absence of obstacles such as walls, furniture, or steps. If the image analysis detects objects that could become entangled in the brush 5103, such as wiring, it can stop the brush 5103 from rotating.

[0216] The display 5101 can display information such as the remaining battery level and the amount of dirt collected. The path taken by the cleaning robot 5100 may also be displayed on the display 5101. Alternatively, the display 5101 may be a touch panel, and operation buttons 5104 may be provided on the display 5101.

[0217] The cleaning robot 5100 can communicate with a portable electronic device 5140, such as a smartphone. Images captured by the camera 5102 can be displayed on the portable electronic device 5140. Therefore, the owner of the cleaning robot 5100 can check the status of the room even when they are away from home. In addition, the display on the display 5101 can be checked on a portable electronic device such as a smartphone.

[0218] A light-emitting device according to one aspect of the present invention can be used in a display 5101.

[0219] The robot 2100 shown in Figure 9B includes a computing unit 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.

[0220] The microphone 2102 has the function of detecting the user's voice and ambient sounds. The speaker 2104 has the function of emitting sound. The robot 2100 can communicate with the user using the microphone 2102 and speaker 2104.

[0221] The display 2105 has the function of displaying various types of 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 also be a detachable information terminal, and by installing it in a fixed position on the robot 2100, charging and data transfer can be made possible.

[0222] The upper camera 2103 and the lower camera 2106 have the function of imaging the area around the robot 2100. In addition, the obstacle sensor 2107 can detect the presence or absence of obstacles in the direction of travel when the robot 2100 moves forward using the movement mechanism 2108. The robot 2100 can recognize its surrounding environment and move safely using the upper camera 2103, the lower camera 2106 and the obstacle sensor 2107. The light-emitting device according to one aspect of the present invention can be used in the display 2105.

[0223] Figure 9C shows 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 lamp 5004, a connection terminal 5006, a sensor 5007 (including functions for measuring force, displacement, position, velocity, acceleration, angular velocity, rotational speed, distance, light, liquid, magnetism, temperature, chemical substances, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient, vibration, odor, or infrared radiation), a microphone 5008, a display unit 5002, a support unit 5012, an earphone 5013, etc.

[0224] A light-emitting device according to one aspect of the present invention can be used in the display unit 5001 and the display unit 5002.

[0225] Figure 10 shows an example of using the light-emitting devices described in Embodiments 1 and 2 in a desk lamp, which is a lighting device. The desk lamp shown in Figure 10 has a housing 2001 and a light source 2002, and the lighting device described in Embodiment 3 may be used as the light source 2002.

[0226] Figure 11 shows an example of using the light-emitting devices described in Embodiments 1 and 2 as indoor lighting devices 3001. Since the light-emitting devices described in Embodiments 1 and 2 are highly reliable, they can be used as reliable lighting devices. Furthermore, since the light-emitting devices described in Embodiments 1 and 2 can be made to cover a large area, they can be used as large-area lighting devices. In addition, since the light-emitting devices described in Embodiments 1 and 2 are thin, they can be used as thin lighting devices.

[0227] The light-emitting devices described in Embodiments 1 and 2 can also be mounted on the windshield and dashboard of an automobile. Figure 12 shows one embodiment in which the light-emitting devices described in Embodiments 1 and 2 are used on the windshield and dashboard of an automobile. Display areas 5200 to 5203 are display areas provided using the light-emitting devices described in Embodiments 1 and 2.

[0228] Display area 5200 and display area 5201 are display devices equipped with the light-emitting devices described in Embodiment 1 and Embodiment 2, which are installed on the windshield of an automobile. The light-emitting devices described in Embodiment 1 and Embodiment 2 can be made into so-called see-through display devices, where the opposite side is visible, by making the anode and cathode from translucent electrodes. If the display is in a see-through state, it can be installed on the windshield of an automobile without obstructing the view. When providing transistors for driving, it is preferable to use translucent transistors such as organic transistors made of organic semiconductor materials or transistors made of oxide semiconductors.

[0229] The display area 5202 is a display device equipped with the light-emitting devices described in Embodiments 1 and 2, which are provided on the pillar portion. By displaying images from an imaging means provided on the vehicle body on the display area 5202, the field of view obstructed by the pillar can be compensated for. Similarly, the display area 5203 provided on the dashboard portion can compensate for the field of view obstructed by the vehicle body by displaying images from an imaging means provided on the outside of the vehicle, thereby compensating for blind spots and enhancing safety. By displaying images in a way that compensates for the parts that are not visible, safety checks can be performed more naturally and without discomfort.

[0230] Display area 5203 can also provide various other information, such as navigation information, speedometer and tachometer, and air conditioning settings. The display items and layout can be changed as needed to suit the user's preferences. This information can also be provided in display areas 5200 to 5202. Furthermore, display areas 5200 to 5203 can also be used as illumination devices.

[0231] Figures 13A and 13B also show a foldable portable information terminal 5150. The foldable portable information terminal 5150 has a housing 5151, a display area 5152, and a bending section 5153. Figure 13A shows the portable information terminal 5150 in its unfolded state. Figure 13B shows the portable information terminal in its folded state. Despite having a large display area 5152, the portable information terminal 5150 is compact and highly portable when folded.

[0232] The display area 5152 can be folded in half by the bending portion 5153. The bending portion 5153 is composed of an expandable member and a plurality of support members. When folded, the expandable member extends, and the bending portion 5153 folds to have a radius of curvature of 2 mm or more, preferably 3 mm or more.

[0233] The display area 5152 may also be a touch panel (input / output device) equipped with a touch sensor (input device). A light-emitting device according to one aspect of the present invention can be used in the display area 5152.

[0234] Figures 14A to 14C also show the foldable portable information terminal 9310. Figure 14A shows the portable information terminal 9310 in its unfolded state. Figure 14B shows the portable information terminal 9310 in an intermediate state, either unfolded or folded. Figure 14C shows the portable information terminal 9310 in its folded state. The portable information terminal 9310 offers excellent portability in its folded state and excellent readability of the display due to its seamless, wide display area in its unfolded state.

[0235] The display panel 9311 is supported by three housings 9315 connected by a hinge 9313. The display panel 9311 may also be a touch panel (input / output device) equipped with a touch sensor (input device). Furthermore, the display panel 9311 can be reversibly transformed from an unfolded state to a folded state by bending the two housings 9315 via the hinge 9313. A light-emitting device according to one aspect of the present invention can be used in the display panel 9311. [Examples]

[0236] This embodiment describes a light-emitting device 1 according to one aspect of the present invention. The structural formula of the organic compound used in the light-emitting device 1 is shown below.

[0237] [ka]

[0238] (Method for fabricating light-emitting device 1-1) First, an anode 101 was formed on a glass substrate by sputtering an indium tin oxide (ITSO) film containing silicon oxide. The film thickness was 70 nm, and the electrode area was 2 mm × 2 mm.

[0239] Next, as a pretreatment for forming a light-emitting device on a substrate, the substrate surface was washed with water, baked at 200 °C for 1 hour, and then subjected to UV ozone treatment for 370 seconds.

[0240] After that, 10 -4 The substrate was introduced into a vacuum evaporation apparatus whose interior was evacuated to about 10 Pa, and in a heating chamber in the vacuum evaporation apparatus, vacuum baking was performed at 170 °C for 30 minutes, and then the substrate was allowed to cool for about 30 minutes.

[0241] Next, with the surface on which the anode 101 was formed facing downward, the substrate with the anode 101 formed thereon was fixed to a substrate holder provided in the vacuum evaporation apparatus, and on the anode 101, N,N-bis(4-biphenyl)-6-phenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BBABnf) represented by the above structural formula (i) and ALD-MP001Q (Analytical Works Co., Ltd., material serial number: 1S20180314) were co-evaporated at a weight ratio of 1:0.05 (=BBABnf:ALD-MP001Q) to form a hole injection layer 111 by 10 nm co-evaporation.

[0242] Next, on the hole injection layer 111, as the first hole transport layer 112-1, BBABnf was evaporated to a thickness of 20 nm, and then as the second hole transport layer 112-2, 3,3'-(naphthalene-1,4-diyl)bis(9-phenyl-9H-carbazole) (abbreviation: PCzN2) represented by the above structural formula (ii) was evaporated to a thickness of 10 nm to form a hole transport layer 112. Note that the second hole transport layer 112-2 also functions as an electron blocking layer.

[0243] Subsequently, 9-(1-naphthyl)-10-[4-(2-naphthyl)phenyl]anthracene (abbreviation: αN-βNPAnth) represented by the above structural formula (iii) and 3,10-bis[N-(9-phenyl-9H-carbazol-2-yl)-N-phenylamino]naphtho[2,3-b;6,7-b’]bisbenzofuran (abbreviation: 3,10PCA2Nbf(IV)-02) represented by (iv) were co-evaporated at a weight ratio of 1:0.015 (=αN-βNPAnth:3,10PCA2Nbf(IV)-02) to form a light-emitting layer 113 with a thickness of 25 nm.

[0244] Thereafter, on the light-emitting layer 113, 2-{4-[9,10-di(naphthalen-2-yl)-2-anthryl]phenyl}-1-phenyl-1H-benzimidazole (abbreviation: ZADN) represented by the above structural formula (v) and lithium 8-hydroxyquinolinate (abbreviation: Liq) represented by the above structural formula (vi) were co-evaporated at a weight ratio of 1:1 (=ZADN:Liq) to form an electron transport layer 114 with a thickness of 25 nm.

[0245] After forming the electron transport layer 114, Liq was evaporated to a film thickness of 1 nm to form an electron injection layer 115, and then aluminum was evaporated to a film thickness of 200 nm to form a cathode 102, thereby fabricating the light-emitting device 1 of this example.

[0246] (Fabrication method of light-emitting device 1-2) The light-emitting device 1-2 was fabricated in the same manner as the light-emitting device 1-1, except that the hole injection layer 111 was co-evaporated with BBABnf:ALD-MP001Q = 1:0.1 (weight ratio) to a thickness of 10 nm.

[0247] (Fabrication method of light-emitting device 2-1) The light-emitting device 2-1 was fabricated in the same manner as the light-emitting device 1-1, except that BBABnf in the light-emitting device 1-1 was replaced with 4-(10-phenyl-9-anthryl)-4’-(9-phenyl-9H-fluoren-9-yl)triphenylamine (abbreviation: FLPAPA) represented by the above structural formula (vii).

[0248] (Method for fabricating light-emitting device 2-2) Light-emitting device 2-2 was fabricated in the same manner as light-emitting device 1-2, except that BBABnf was replaced with FLPAPA.

[0249] (Method for fabricating comparative light-emitting devices) The comparative light-emitting device was fabricated in the same manner as light-emitting devices 1-2, except that BBABnf in light-emitting devices 1-2 was replaced with N-(1,1'-biphenyl-4-yl)-9,9-dimethyl-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-9H-fluoren-2-amine (abbreviated as PCBBiF), represented by the above structural formula (viii), and PCzN2 was replaced with N,N-bis[4-(dibenzofuran-4-yl)phenyl]-4-amino-p-terphenyl (abbreviated as DBfBB1TP), represented by the above structural formula (ix).

[0250] The element structures of light-emitting devices 1-1, 1-2, 2-1, 2-2, and the comparative light-emitting device are summarized in the table below.

[0251] [Table 1]

[0252] The following table summarizes the HOMO level, LUMO level, and electron mobility at a square root of the electric field strength [V / cm] of 600 for the organic compounds used in this example.

[0253] [Table 2]

[0254] These light-emitting devices were sealed with a glass substrate in a glove box under a nitrogen atmosphere to prevent exposure to the atmosphere (sealant was applied around the device, UV treatment was performed during sealing, and heat treatment was performed at 80°C for 1 hour). After this, the initial characteristics and reliability of light-emitting devices 1-1, 1-2, 2-1, 2-2, and the comparative light-emitting device were measured. The measurements were performed at room temperature.

[0255] Figure 15 shows the luminance-current density characteristics of light-emitting device 1, Figure 16 shows the current efficiency-luminance characteristics, Figure 17 shows the luminance-voltage characteristics, Figure 18 shows the current-voltage characteristics, Figure 19 shows the external quantum efficiency-luminance characteristics, and Figure 20 shows the emission spectrum. Furthermore, the emission spectrum of light-emitting device 1 at 1000 cd / m² is also shown. 2 Table 3 shows the main characteristics of the vicinity.

[0256] [Table 3]

[0257] From Figures 15 to 20 and Table 3, it can be seen that the light-emitting device 1, which is one embodiment of the present invention, is a blue light-emitting device with good initial characteristics.

[0258] Furthermore, the current density is 50 mA / cm². 2 Figure 21 shows a graph illustrating the change in brightness with respect to operating time. As shown in Figure 21, it can be seen that the brightness of light-emitting devices 1-1, 1-2, 2-1, and 2-2 increases after operation, reaching a brightness higher than the initial brightness, and then gradually decreases. This shows that the operating life, particularly when using a low degradation state of about 2-5% as a baseline, has been significantly improved.

[0259] Next, electron spin resonance spectra were obtained for the materials constituting the hole injection layer in each light-emitting device using the ESR method.

[0260] The samples used in the measurement will be described below. All samples were formed by co-evaporating an acceptor material (ALD-MP001Q in this example), which is the first substance, and a hole transport material (BBABnf in light-emitting devices 1-1 and 1-2, FLPAPA in light-emitting devices 2-1 and 2-2, and PCBBiF in the comparative light-emitting device), which is the second substance, on a quartz substrate with a size of 3.0 mm × 19 - 22 mm.

[0261] The quartz substrate was fixed to a holder provided in a vacuum evaporation apparatus so that the surface to be evaporated faced downward, and the inside of the vacuum apparatus was depressurized to 10 -4 Pa, and then the first substance and the second substance were co-evaporated to produce the sample. The film thickness of the sample was adjusted within the range of 100 nm to 1000 nm.

[0262] Also, the molar ratio of the first substance and the second substance in each sample was adjusted by the evaporation rate. The weight ratio and molar ratio of the first substance and the second substance in each sample are shown in Table 4 below. In the ESR measurement, samples with the same type of organic compound and the same molar ratio were measured by stacking two or four samples. In this example, samples with a mixing ratio different from the mixing ratio used in the above light-emitting device were also prepared and measured.

[0263]

Table 4

[0264] The measurement of the electron spin resonance spectrum by the ESR method was performed using an electron spin resonance measuring device JES FA300 type (manufactured by JEOL Ltd.). The above measurement was performed at room temperature with a resonance frequency (about 9.2 GHz), output (1 mW), modulation magnetic field (50 mT), modulation width (0.5 mT), time constant (0.03 sec), sweep time (1 min.). Then, the magnetic field correction was performed based on the positions of the third and fourth signals, and the spin density was calculated from the peak area of the electron spin resonance spectrum obtained by the measurement. The g value calculated from the peak of the above electron spin resonance spectrum was about 2.00, which was consistent with the g value of free electrons. 2+ The magnetic field correction was performed based on the positions of the third and fourth signals, and the spin density was calculated from the peak area of the electron spin resonance spectrum obtained by the measurement. The g value calculated from the peak of the above electron spin resonance spectrum was about 2.00, which was consistent with the g value of free electrons.

[0265] Figure 22 is a graph showing the relationship between the molar ratio of the first material to the second material in each sample and the spin density calculated by measuring the electron spin resonance spectrum. From Figure 22, the spin densities of samples 1-1, 1-2, 2-1, 2-2, and sample 1-3, which use the same hole transport material and have the same molar ratio as the materials constituting the hole injection layers of light-emitting devices 1-1, 1-2, 2-1, and 2-2, are 1 × 10⁻⁶. 19 spins / cm 3 It was found that the following was true.

[0266] Furthermore, if the spin density is too low, the hole injection capability will be impaired, so 1 × 10 16 spins / cm 3 The above, and more preferably 1 × 10 17 spins / cm 3 More preferably 3 × 10 17 spins / cm 3 It was found that the above is sufficient.

[0267] <Reference example 1> This reference example describes the methods for calculating the HOMO level, LUMO level, and electron mobility of the organic compounds used in each example.

[0268] The HOMO and LUMO levels can be calculated based on cyclic voltammetry (CV) measurements.

[0269] An electrochemical analyzer (manufactured by BAS Corporation, model number: ALS Model 600A or 600C) was used as the measuring device. For the CV measurement, the solution was prepared by dissolving anhydrous dimethylformamide (DMF) (manufactured by Aldrich Corporation, 99.8%, catalog number: 22705-6) as the solvent, dissolving tetra-n-butylammonium perchlorate (n-Bu4NClO4) (manufactured by Tokyo Chemical Industry Co., Ltd., catalog number: T0836) as the supporting electrolyte to a concentration of 100 mmol / L, and then dissolving the target substance to a concentration of 2 mmol / L. Furthermore, a platinum electrode (PTE platinum electrode, manufactured by BAS Corporation) was used as the working electrode, a platinum electrode (Pt counter electrode for VC-3 (5cm), manufactured by BAS Corporation) was used as the auxiliary electrode, and an Ag / Ag+ electrode (RE7 non-aqueous solvent reference electrode, manufactured by BAS Corporation) was used as the reference electrode. The measurements were performed at room temperature (20-25°C). The scan speed during CV measurement was standardized to 0.1 V / sec, and the oxidation potential Ea [V] and reduction potential Ec [V] relative to the reference electrode were measured. Ea was defined as the midpoint potential of the oxidation-reduction wave, and Ec was defined as the midpoint potential of the reduction-oxidation wave. Here, since the potential energy of the reference electrode used in this embodiment with respect to the vacuum level is known to be -4.94 [eV], the HOMO level [eV] = -4.94 - Ea and the LUMO level [eV] = -4.94 - Ec can be used to determine the HOMO level and the LUMO level, respectively.

[0270] Electron mobility can be measured using impedance spectroscopy (IS method).

[0271] For measuring the carrier mobility of EL materials, methods such as the transient photocurrent method (Time-of-flight: TOF method) and the method of determining it from the IV characteristics of space-charge-limited current (SCLC method) have been known for a long time. The TOF method requires a sample with a considerably thicker film thickness compared to actual organic EL devices. The SCLC method has drawbacks such as not being able to obtain the electric field strength dependence of the carrier mobility. The IS method requires an organic film thickness of only a few hundred nanometers for measurement, so it is possible to deposit a film even with a relatively small amount of EL material, and it is characterized by being able to measure mobility with a film thickness close to that of actual EL devices, and it is also possible to obtain the electric field strength dependence of the carrier mobility.

[0272] In the IS method, a small sinusoidal voltage signal (V=V0[exp(jωt)]) is applied to an EL element, and the impedance of the EL element (Z=V / I) is determined from the phase difference between the current amplitude of the response current signal (I=I0exp[j(ωt+φ)]) and the input signal. By varying the voltage from high frequency to low frequency and applying it to the element, various components with different relaxation times that contribute to the impedance can be separated and measured.

[0273] Here, the admittance Y (=1 / Z), which is the reciprocal of impedance, can be expressed in terms of conductance G and susceptance B as shown in equation (1) below.

[0274]

number

[0275] Furthermore, equations (2) and (3) below can be calculated using the single-charge injection model. Here, g (equation (4)) is the differential conductance. In the equations, C is capacitance, θ is ωt (the travel angle), and ω is the angular frequency. t is the travel time. The current equation, Poisson's equation, and the current continuity equation are used in the analysis, and the existence of diffusion current and trap levels is ignored.

[0276]

number

[0277] The -ΔB method is a method for calculating mobility from the frequency characteristics of capacitance. The ωΔG method is another method for calculating mobility from the frequency characteristics of conductance.

[0278] In practice, the first step is to fabricate a measurement element for the material whose electron mobility is to be determined. This measurement element is designed so that only electrons flow as carriers. This specification describes a method for calculating mobility from the frequency characteristics of capacitance (-ΔB method). A schematic diagram of the measurement element used is shown in Figure 23.

[0279] The structure of the measurement element fabricated for this measurement, as shown in Figure 23, has a first layer 210, a second layer 211, and a third layer 212 between the anode 201 and the cathode 202. The material whose electron mobility is to be determined can be used as the material for the second layer 211. This time, we will explain using an example of measuring the electron mobility of a 1:1 (weight ratio) co-evaporated film of ZADN and Liq. A specific example configuration is summarized in the table below.

[0280] [Table 5]

[0281] Figure 24 shows the current density-voltage characteristics of an electron-only device fabricated with a co-evaporated film of ZADN and Liq as the second layer 211.

[0282] Impedance measurements were performed under the conditions of applying a DC voltage in the range of 5.0V to 9.0V while maintaining an AC voltage of 70mV and a frequency of 1Hz to 3MHz. Capacitance was calculated from the admittance (equation (1) above), which is the reciprocal of the impedance obtained. Figure 25 shows the frequency characteristics of the calculated capacitance C at an applied voltage of 7.0V.

[0283] The frequency characteristics of capacitance C are obtained because the space charge due to carriers injected by a small voltage signal cannot completely follow the small AC voltage, resulting in a phase difference in the current. Here, the travel time of carriers in the film is defined as the time T it takes for the injected carriers to reach the counter electrode, and is expressed by the following equation (5).

[0284]

number

[0285] The negative susceptance change (-ΔB) corresponds to the value obtained by multiplying the capacitance change (-ΔC) by the angular frequency ω (-ωΔC). Its lowest frequency peak frequency is f'. max (=ω max From equation (3), it can be derived that the following relationship (6) exists between (2π) and the travel time T.

[0286]

number

[0287] Figure 26 shows the frequency characteristics of -ΔB calculated from the above measurements (i.e., when the DC voltage is 7.0V). The lowest frequency peak frequency f' can be found from Figure 26. max This is indicated by the arrows in the diagram.

[0288] f' obtained from the above measurements and analysis max From this, the travel time T can be determined (see equation (6) above), and from equation (5) above, in this case, the electron mobility at a voltage of 7.0V can be determined. By performing similar measurements 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 the electric field strength dependence of the mobility can also be measured.

[0289] Using the calculation method described above, the electric field strength dependence of the final electron mobility obtained for each organic compound is shown in Figure 27. The square root of the electric field strength [V / cm] read from the figure is 600 [V / cm]. 1 / 2 Table 9 shows the electron mobility values ​​for each of these conditions.

[0290] [Table 6]

[0291] As described above, it is possible to calculate electron mobility. For detailed measurement methods, please refer to Takayuki Okachi et al., "Japanese Journal of Applied Physics" Vol. 47, No. 12, 2008, pp. 8965-8972. [Explanation of symbols]

[0292] 101: Anode, 102: Cathode, 103: EL layer, 111: Hole injection layer, 112: Hole transport layer, 112-1: First hole transport layer, 112-2: Second hole transport layer, 113: Light-emitting layer, 113-1: Light-emitting region, 114: Electron transport layer, 114-1: First electron transport layer, 114-2: Second electron transport layer, 115: Electron injection layer, 116: Charge generation layer, 117: P-type layer, 118: Electron relay layer, 119: Electron injection buffer layer, 201: Anode, 202: Cathode, 210: First layer, 211: Second layer, 212: Third layer, 400: Substrate, 401: Anode, 403: EL layer, 40 4: Cathode, 405: Sealing material, 406: Sealing material, 407: Encapsulation substrate, 412: Pad, 420: IC chip, 501: Anode, 502: Cathode, 511: First light-emitting unit, 512: Second light-emitting unit, 513: Charge generation layer, 601: Drive circuit section (source line drive circuit), 602: Pixel section, 603: Drive circuit section (gate line drive circuit), 604: Encapsulation substrate, 605: Sealing material, 607: Space, 608: Wiring, 609: FPC (Flexible Printed Circuit), 610: Element substrate, 611: Switching FET, 612: Current control FET, 613: Anode 614: Insulator, 616: EL layer, 617: Cathode, 618: Light-emitting device, 1001: Substrate, 1002: Underlying insulating film, 1003: Gate insulating film, 1006: Gate electrode, 1007: Gate electrode, 1008: Gate electrode, 1020: First interlayer insulating film, 1021: Second interlayer insulating film, 1022: Electrode, 1024W: Anode, 1024R: Anode, 1024G: Anode, 1024B: Anode, 1025: Partition, 1028: EL layer, 1029: Cathode, 1031: Encapsulating substrate, 1032: Seal material, 1033: Transparent substrate, 1034R: Red colored layer, 1034G: Green colored layer Color layer, 1034B: Blue colored layer, 1035: Black matrix, 1036: Overcoat layer, 1037: Third interlayer insulating film, 1040: Pixel section, 1041: Drive circuit section, 1042: Peripheral section, 2001: Housing, 2002: Light source, 2100: Robot, 2110: Processing unit, 2101: Illuminance sensor, 2102: Microphone, 2103: Upper camera, 2104: Speaker, 2105: Display, 2106: Lower camera, 2107: Obstacle sensor, 2108: Moving mechanism, 3001: Lighting device, 5000: Housing, 5001: Display section, 5002: Display section,5003: Speaker, 5004: LED lamp, 5006: Connection terminal, 5007: Sensor, 5008: Microphone, 5012: Support part, 5013: Earphone, 5100: Cleaning robot, 5101: Display, 5102: Camera, 5103: Brush, 5104: Operation button, 5150: Portable information terminal, 5151: Housing, 5152: Display area, 5153: Bending part, 5120: Dust, 5200: Display area, 5201: Display area, 5202: Display area, 5203: Display area, 7101: Housing, 7103 : Display unit, 7105: Stand, 7107: Display unit, 7109: Operation keys, 7110: Remote control unit, 7201: Main unit, 7202: Housing, 7203: Display unit, 7204: Keyboard, 7205: External connection port, 7206: Pointing device, 7210: Second display unit, 7401: Housing, 7402: Display unit, 7403: Operation buttons, 7404: External connection port, 7405: Speaker, 7406: Microphone, 9310: Portable information terminal, 9311: Display panel, 9313: Hinge, 9315: Housing,

Claims

1. Anode and, Cathode and, Between the anode and the cathode, there is a hole injection layer, a light-emitting layer, and an electron transport layer. The hole injection layer comprises a hole transport material and an electron-accepting material. The electron transport layer has a region in contact with the light-emitting layer, The electron transport layer comprises an electron transport material and any of the following: an alkali metal element, an alkali metal compound, an alkali metal complex, an alkaline earth metal element, an alkaline earth metal compound, or an alkaline earth metal complex. The electron-accepting material is a material that exhibits electron-acceptance properties to the hole transport material, The hole transport material is an organic compound with a HOMO level of -5.7 eV or higher and -5.4 eV or lower. The spin density of the material constituting the hole injection layer, as measured by ESR, is 1 × 10⁻⁶. １９ spins / cm ３ The following: A light-emitting device in which the mixing ratio of the hole transport material and the electron acceptor material in the film in which the spin density is measured is the same as the mixing ratio of the hole transport material and the electron acceptor material in the hole injection layer.

2. Anode and, Cathode and, Between the anode and the cathode, there is a hole injection layer, a light-emitting layer, and an electron transport layer. The hole injection layer comprises a hole transport material and an electron-accepting material. The electron transport layer has a region in contact with the light-emitting layer, The electron transport layer comprises an electron transport material and a metal complex having a ligand containing an 8-hydroxyquinolinate structure and a monovalent metal ion. The electron-accepting material is a material that exhibits electron-acceptance properties to the hole transport material, The hole transport material is an organic compound with a HOMO level of -5.7 eV or higher and -5.4 eV or lower. The spin density of the material constituting the hole injection layer, as measured by ESR, is 1 × 10⁻⁶. １９ spins / cm ３ The following: A light-emitting device in which the mixing ratio of the hole transport material and the electron acceptor material in the film in which the spin density is measured is the same as the mixing ratio of the hole transport material and the electron acceptor material in the hole injection layer.

3. Anode and, Cathode and, Between the anode and the cathode, there is a hole injection layer, a light-emitting layer, and an electron transport layer. The hole injection layer comprises a hole transport material and an electron-accepting material. The electron transport layer has a region in contact with the light-emitting layer, The electron transport layer comprises an electron transport material and a lithium complex having a ligand containing an 8-hydroxyquinolinate structure. The electron-accepting material is a material that exhibits electron-acceptance properties to the hole transport material, The hole transport material is an organic compound with a HOMO level of -5.7 eV or higher and -5.4 eV or lower. The spin density of the material constituting the hole injection layer, as measured by ESR, is 1 × 10⁻⁶. １９ spins / cm ３ The following: A light-emitting device in which the mixing ratio of the hole transport material and the electron acceptor material in the film in which the spin density is measured is the same as the mixing ratio of the hole transport material and the electron acceptor material in the hole injection layer.

4. Anode and, Cathode and, Between the anode and the cathode, there is a hole injection layer, a light-emitting layer, and an electron transport layer. The hole injection layer comprises a hole transport material and an electron-accepting material. The electron transport layer has a region in contact with the light-emitting layer, The electron transport layer comprises an electron transport material, The HOMO level of the electron transport material is -6.0 eV or higher. The electron-accepting material is a material that exhibits electron-acceptance properties to the hole transport material, The hole transport material is an organic compound with a HOMO level of -5.7 eV or higher and -5.4 eV or lower. The spin density of the material constituting the hole injection layer, as measured by ESR, is 1 × 10⁻⁶. １９ spins / cm ３ The following: A light-emitting device in which the mixing ratio of the hole transport material and the electron acceptor material in the film in which the spin density is measured is the same as the mixing ratio of the hole transport material and the electron acceptor material in the hole injection layer.

5. Anode and, Cathode and, Between the anode and the cathode, there is a hole injection layer, a light-emitting layer, and an electron transport layer. The hole injection layer comprises a hole transport material and an electron-accepting material. The electron transport layer has a region in contact with the light-emitting layer, The electron transport layer comprises an electron transport material, The electron transport material is an organic compound having an anthracene skeleton. The electron-accepting material is a material that exhibits electron-acceptance properties to the hole transport material, The hole transport material is an organic compound with a HOMO level of -5.7 eV or higher and -5.4 eV or lower. The spin density measured by the ESR method of the material constituting the hole injection layer is 1×10 １９ spins / cm ３ or less, A light-emitting device in which the mixing ratio of the hole transport material and the electron acceptor material in the film in which the spin density is measured is the same as the mixing ratio of the hole transport material and the electron acceptor material in the hole injection layer.

6. Anode and, Cathode and, Between the anode and the cathode, there is a hole injection layer, a light-emitting layer, and an electron transport layer. The hole injection layer comprises a hole transport material and an electron-accepting material. The electron transport layer has a region in contact with the light-emitting layer, When the square root of the electric field strength [V / cm] of the material constituting the electron transport layer is 600, the electron mobility is 1 × 10⁻⁶. －７ cm ２ / Vs or more 5×10 －５ cm ２ / Vs is less than or equal to, The electron-accepting material is a material that exhibits electron-acceptance properties to the hole transport material, The hole transport material is an organic compound with a HOMO level of -5.7 eV or higher and -5.4 eV or lower. The spin density of the material constituting the hole injection layer, as measured by ESR, is 1 × 10⁻⁶. １９ spins / cm ３ The following: A light-emitting device in which the mixing ratio of the hole transport material and the electron acceptor material in the film in which the spin density is measured is the same as the mixing ratio of the hole transport material and the electron acceptor material in the hole injection layer.

7. Anode and, Cathode and, Between the anode and the cathode, there is a hole injection layer, a light-emitting layer, and an electron transport layer. The hole injection layer comprises a hole transport material and an electron-accepting material. The electron transport layer has a region in contact with the light-emitting layer, The electron transport layer comprises an electron transport material and one of the following: an alkali metal element, an alkali metal compound, an alkali metal complex, an alkaline earth metal element, an alkaline earth metal compound, or an alkaline earth metal complex. The electron transport layer has a first region and a second region, The first region is located between the light-emitting layer and the second region. The concentrations of the alkali metal element, alkali metal compound, alkali metal complex, alkaline earth metal element, alkaline earth metal compound, or alkaline earth metal complex in the first and second regions are different. The electron-accepting material is a material that exhibits electron-acceptance properties to the hole transport material, The hole transport material is an organic compound with a HOMO level of -5.7 eV or higher and -5.4 eV or lower. The spin density of the material constituting the hole injection layer, as measured by ESR, is 1 × 10⁻⁶. １９ spins / cm ３ The following: A light-emitting device in which the mixing ratio of the hole transport material and the electron acceptor material in the film in which the spin density is measured is the same as the mixing ratio of the hole transport material and the electron acceptor material in the hole injection layer.

8. In claim 7, A light-emitting device in which the concentration of the alkali metal element, alkali metal compound, alkali metal complex, alkaline earth metal element, alkaline earth metal compound, or alkaline earth metal complex in the first region is higher than the concentration of the alkali metal element, alkali metal compound, alkali metal complex, alkaline earth metal element, alkaline earth metal compound, or alkaline earth metal complex in the second region.

9. In claim 7, A light-emitting device in which the concentration of the alkali metal element, alkali metal compound, alkali metal complex, alkaline earth metal element, alkaline earth metal compound, or alkaline earth metal complex in the first region or the second region is 0.

10. In any one of claims 1 to 5 and claims 7 to 9, The light-emitting layer comprises a host material and a light-emitting center material. A light-emitting device in which the electron mobility of the electron transport material is smaller than that of the host material.

11. In claim 10, A light-emitting device in which the aforementioned light-emitting central material exhibits fluorescence emission.

12. In claim 10, A light-emitting device in which the light-emitting central material exhibits blue fluorescence.

13. In any one of claims 1 to 12, When the square root of the electric field strength [V / cm] of the hole transport material is 600, the hole mobility is 1 × 10⁻⁶. －３ cm ２ Light-emitting devices with a Vs value of less than or equal to / Vs.

14. In any one of claims 1 to 13, A light-emitting device having a hole transport layer between the hole injection layer and the light-emitting layer.

15. In claim 14, A light-emitting device in which the hole transport layer has a two-layer structure consisting of a first hole transport layer located on the hole injection layer side and a second hole transport layer located on the light-emitting layer side.

16. In claim 15, A light-emitting device in which the second hole transport layer also functions as an electron blocking layer.

17. In claim 15 or claim 16, The first hole transport layer has a first organic compound, The second hole transport layer has a second organic compound, The HOMO level of the second organic compound is deeper than the HOMO level of the first organic compound. A light-emitting device in which the difference between the HOMO level of the first organic compound and the HOMO level of the second organic compound is 0.2 eV or less.

18. A light-emitting device according to any one of claims 1 to 17, An electronic device having a sensor, an operating button, a speaker, or a microphone.

19. A light-emitting device according to any one of claims 1 to 17, A light-emitting device having a transistor or a substrate.

20. A lighting device comprising a light-emitting device according to any one of claims 1 to 17 and a housing.

Images