Light-emitting device, light-emitting apparatus, electronic device and lighting apparatus

Abstract

Provided is a light-emitting device having a favorable lifespan. Alternatively, a light-emitting device having a low drive voltage is provided. Provided is a light-emitting device in which an electron transport layer has an organometallic complex of an alkali metal, and an organic compound having electron transport properties, wherein the organometallic complex and the organic compound are combined to form an excitation complex, and the energy conversion value (eV) of the peak wavelength in the emission spectrum of the excitation complex formed when the mass ratio of the organometallic complex and the organic compound is 1:1 is smaller, by at least 0.1 eV, than the difference (eV) between the HOMO level of the organometallic complex and the LUMO level of the organic compound.

Description

[Technical field]

[0001] An 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 an aspect of the present invention is not limited to the above technical field. The technical field of an aspect of the invention disclosed in the present specification and the like relates to an object, a method, or a manufacturing method. Alternatively, an aspect of the present invention relates to a process, a machine, a manufacture, or a composition of matter. Therefore, more specifically, examples of the technical field of an aspect of the present invention disclosed in the present specification include a semiconductor device, a display device, a liquid crystal display device, a light-emitting device, a lighting device, a power storage device, a storage device, an imaging device, a driving method thereof, or a manufacturing method thereof. [Background technology]

[0002] Light-emitting devices (organic EL elements) that utilize electroluminescence (EL) using organic compounds are becoming more and more practical. The basic structure of these light-emitting devices is a pair of electrodes sandwiching an organic compound layer (EL layer) containing a light-emitting material between them. By applying a voltage to this element, carriers are injected, and the recombination energy of the carriers is utilized to emit light from the light-emitting material.

[0003] Since such light-emitting devices are self-emitting, when used as display pixels, they have advantages such as higher visibility than liquid crystals and no need for backlights, making them suitable for use as devices for flat panel displays. Another major advantage of displays using such light-emitting devices is that they can be made thin and lightweight. Another characteristic is that they have an extremely fast response speed.

[0004] In addition, these light-emitting devices can have light-emitting layers formed continuously in two dimensions, making it possible to obtain surface-like light emission. This is a feature that is difficult to obtain with point light sources such as incandescent light bulbs and LEDs, or linear light sources such as fluorescent lamps, making them highly valuable as surface light sources for lighting and other applications.

[0005] Displays and lighting devices using such light-emitting devices are suitable for a variety of electronic devices, but research and development is ongoing to find light-emitting devices with better efficiency and life span.

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

[0007] Although the characteristics of light-emitting devices have improved remarkably, they are still insufficient to meet high demands for efficiency, durability, and all other characteristics. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2016-174161 A Summary of the Invention [Problem to be solved by the invention]

[0009] In view of the above, an object of one embodiment of the present invention is to provide a novel light-emitting device, to provide a light-emitting device with a long lifetime, or to provide a light-emitting device with a low driving voltage.

[0010] Another object of another embodiment of the present invention is to provide a highly reliable light-emitting device, electronic device, and display device.

[0011] One aspect of the present invention is to solve any one of the above problems.

Means for Solving the Problems

[0012] One aspect of the present invention has a first electrode, a second electrode, and an EL layer. The EL layer is located between the first electrode and the second electrode. The EL layer has a light-emitting layer and an electron transport layer. The electron transport layer is located between the light-emitting layer and the second electrode. The electron transport layer has an organometallic complex of an alkali metal and an organic compound having electron transporting properties. The organometallic complex and the organic compound form a combination that forms an exciplex. The value (eV) obtained by converting the peak wavelength of the emission spectrum of the exciplex formed when the organometallic complex and the organic compound have a mass ratio of 1:1 into energy is less than the difference (eV) between the HOMO level of the organometallic complex and the LUMO level of the organic compound by 0.1 eV or more. It is a light-emitting device.

[0013] Alternatively, another aspect of the present invention has a first electrode, a second electrode, and an EL layer. The EL layer is located between the first electrode and the second electrode. The EL layer has a light-emitting layer and an electron transport layer. The electron transport layer is located between the light-emitting layer and the second electrode. The electron transport layer has an organometallic complex of an alkali metal and an organic compound having electron transporting properties. The organometallic complex and the organic compound form a combination that forms an exciplex. The peak wavelength of the emission spectrum of the exciplex formed when the organometallic complex and the organic compound have a mass ratio of 1:1 is 570 nm or more. It is a light-emitting device.

[0014] Alternatively, another aspect of the present invention has a first electrode, a second electrode, and an EL layer. The EL layer is located between the first electrode and the second electrode. The EL layer has a light-emitting layer and an electron transport layer. The electron transport layer is located between the light-emitting layer and the second electrode. The electron transport layer has an organometallic complex of an alkali metal and an organic compound having electron transporting properties. The organometallic complex and the organic compound form a combination that forms an exciplex. The peak wavelength of the emission spectrum of the exciplex formed when the organometallic complex and the organic compound have a mass ratio of 1:1 is 570 nm or more and less than 610 nm. It is a light-emitting device.

[0015] Another embodiment of the present invention is a light-emitting device including a first electrode, a second electrode, and an EL layer, the EL layer being located between the first electrode and the second electrode, the EL layer including a light-emitting layer and an electron-transport layer, the electron-transport layer being located between the light-emitting layer and the second electrode, the electron-transport layer including an organometallic complex of an alkali metal and an organic compound having an electron-transporting property, the organometallic complex and the organic compound being a combination that forms an exciplex, and the peak wavelength of an emission spectrum of the exciplex formed when the organometallic complex and the organic compound are in a mass ratio of 1:1 is 610 nm or longer.

[0016] Another embodiment of the present invention is a light-emitting device having the above structure, in which the organometallic complex of an alkali metal is an organometallic complex of lithium.

[0017] Another embodiment of the present invention is a light-emitting device having the above structure, in which the organometallic complex of an alkali metal has a ligand having a quinolinol skeleton.

[0018] Another embodiment of the present invention is a light-emitting device having the above structure, in which the organometallic complex of an alkali metal is 8-hydroxyquinolinatolithium or a derivative thereof.

[0019] Another embodiment of the present invention is a light-emitting device including a first electrode, a second electrode, and an EL layer, the EL layer being located between the first electrode and the second electrode, the EL layer including a light-emitting layer and an electron-transport layer, the electron-transport layer being located between the light-emitting layer and the second electrode, the electron-transport layer including an organometallic complex of an alkali metal and an organic compound having an electron-transporting property, a difference between a HOMO level of the organometallic complex and a LUMO level of the organic compound being 2.9 eV or less, and an m / z value observed when a mixed film of the organometallic complex and the organic compound is analyzed by mass spectrometry is a value obtained by subtracting 2 from a sum of a molecular weight of the organometallic complex, a molecular weight of the organic compound, and an atomic weight of an alkaline earth metal included in the organometallic complex.

[0020] Another embodiment of the present invention is a light-emitting device having the above structure, in which the organometallic complex of an alkali metal is an organometallic complex of lithium.

[0021] Another embodiment of the present invention is a light-emitting device having the above structure, in which the organometallic complex of an alkali metal is 8-hydroxyquinolinatolithium.

[0022] Another embodiment of the present invention is a light-emitting device having the above structure in which an organometallic complex and an organic compound form an exciplex.

[0023] Another embodiment of the present invention is a light-emitting device having the above structure, in which the energy value (eV) of the peak wavelength of an emission spectrum of an exciplex formed when the mass ratio of an organometallic complex to an organic compound is 1:1 is smaller than the difference (eV) between the HOMO level of the organometallic complex and the LUMO level of the organic compound by 0.1 eV or more.

[0024] Another embodiment of the present invention is a light-emitting device having the above structure, in which an exciplex formed when the organometallic complex and the organic compound are mixed in a mass ratio of 1:1 has an emission spectrum with a peak wavelength of 570 nm or longer.

[0025] Another embodiment of the present invention is a light-emitting device having the above structure, in which an exciplex formed when the organometallic complex and the organic compound are mixed in a mass ratio of 1:1 has an emission spectrum with a peak wavelength of 570 nm or more and less than 610 nm.

[0026] Another embodiment of the present invention is a light-emitting device having the above structure, in which an exciplex formed when the organometallic complex and the organic compound are mixed in a mass ratio of 1:1 has an emission spectrum with a peak wavelength of 610 nm or longer.

[0027] Another embodiment of the present invention is a light-emitting device having the above structure, in which the organic compound has a heteroaromatic ring.

[0028] Another embodiment of the present invention is a light-emitting device having the above structure, in which the electron-transport layer is in contact with the light-emitting layer.

[0029] Alternatively, another embodiment of the present invention is a light-emitting device in which the light-emitting layer includes a host material and a light-emitting material, and the light-emitting material emits blue fluorescence.

[0030] Another embodiment of the present invention is an electronic device including the above light-emitting device and a sensor, an operation button, a speaker, or a microphone.

[0031] Another embodiment of the present invention is a light-emitting device including the above light-emitting device and a transistor or a substrate.

[0032] Another embodiment of the present invention is a lighting device including the above-described light-emitting device and a housing.

[0033] In this specification, the term "light-emitting device" includes an image display device using a light-emitting device. The term "light-emitting device" may also include a module in which a connector, such as an anisotropic conductive film or TCP (Tape Carrier Package), is attached to a light-emitting device, a module in which a printed wiring board is provided at the end of a TCP, or a module in which an IC (integrated circuit) is directly mounted on a light-emitting device by a COG (Chip On Glass) method. Furthermore, lighting fixtures and the like may have a light-emitting device. Effect of the Invention

[0034] According to one embodiment of the present invention, a novel light-emitting device can be provided. Alternatively, a light-emitting device with a long lifetime can be provided. Alternatively, a light-emitting device with high emission efficiency can be provided.

[0035] According to another embodiment of the present invention, a light-emitting device, an electronic device, and a display device each having high reliability can be provided. According to another embodiment of the present invention, a light-emitting device, an electronic device, and a display device each having low power consumption can be provided.

[0036] Note that the description of these effects does not preclude the existence of other effects. Note that one embodiment of the present invention does not necessarily have all of these effects. Note that effects other than these will become apparent from the description in the specification, drawings, claims, etc., and it is possible to extract effects other than these from the description in the specification, drawings, claims, etc. [Brief description of the drawings]

[0037] 1A, 1B, and 1C are diagrams of a light emitting device. 2A and 2B are diagrams of an active matrix type light emitting device. 3A and 3B are diagrams of an active matrix type light emitting device. FIG. 4 is a diagram of an active matrix type light emitting device. 5A and 5B are diagrams illustrating a lighting device. 6A, 6B1, 6B2, and 6C are diagrams showing electronic devices. 7A, 7B and 7C are diagrams showing electronic devices. FIG. 8 is a diagram showing a lighting device. FIG. 9 is a diagram showing a lighting device. FIG. 10 is a diagram showing an in-vehicle display device and a lighting device. 11A, 11B, and 11C are diagrams illustrating electronic devices. 12A and 12B are diagrams illustrating an electronic device. FIG. 13 is a graph showing the luminance-current density characteristics of the light-emitting device 1, the light-emitting device 2, and the comparative light-emitting device 1. In FIG. FIG. 14 is a graph showing the current efficiency-luminance characteristics of the light-emitting device 1, the light-emitting device 2, and the comparative light-emitting device 1. In FIG. FIG. 15 is a graph showing the luminance-voltage characteristics of the light-emitting device 1, the light-emitting device 2, and the comparative light-emitting device 1. In FIG. FIG. 16 is a graph showing the current-voltage characteristics of the light-emitting device 1, the light-emitting device 2, and the comparative light-emitting device 1. In FIG. FIG. 17 is a graph showing the external quantum efficiency-luminance characteristics of the light-emitting device 1, the light-emitting device 2, and the comparative light-emitting device 1. In FIG. FIG. 18 shows the emission spectra of the light-emitting device 1, the light-emitting device 2 and the comparative light-emitting device 1. As shown in FIG. FIG. 19 is a graph showing the normalized luminance-time change characteristics of the light-emitting device 1, the light-emitting device 2, and the comparative light-emitting device 1. In FIG. FIG. 20 shows the emission spectra of an OCET010 film, a Liq film, and a mixed film in which OCET010 and Liq are mixed in a 1:1 (mass ratio). FIG. 21 shows the emission spectra of an NBPhen film, a Liq film, and a mixed film in which NBPhen and Liq are mixed in a 1:1 (mass ratio). FIG. 22 shows the emission spectra of an αN-βNPAnth film, a Liq film, and a mixed film in which αN-βNPAnth and Liq are mixed in a 1:1 (mass ratio). FIG. 23 shows the results of ToF-SIMS analysis of a mixed film of NBPhen and Liq. FIG. 24 is a graph showing the luminance-current density characteristics of the light-emitting device 3. As shown in FIG. FIG. 25 is a graph showing the current efficiency-luminance characteristics of the light-emitting device 3. As shown in FIG. FIG. 26 is a diagram showing the luminance-voltage characteristics of the light-emitting device 3. As shown in FIG. FIG. 27 is a diagram showing the current-voltage characteristics of the light-emitting device 3. As shown in FIG. FIG. 28 is a graph showing the external quantum efficiency-luminance characteristics of the light-emitting device 3. As shown in FIG. FIG. 29 is a graph showing the emission spectrum of the light-emitting device 3. As shown in FIG. FIG. 30 is a graph showing the normalized luminance vs. time change characteristics of the light-emitting device 3. As shown in FIG. FIG. 31 shows the emission spectra of a PyA1PQ film, a Liq film, and a mixed film in which PyA1PQ and Liq are mixed in a 1:1 (mass ratio). FIG. 32 shows the results of ToF-SIMS analysis of a mixed film of PyA1PQ and Liq. FIG. 33 is a graph showing the oxidation-reduction wave of OCET010. FIG. 34 is a graph showing the reduction-oxidation wave of OCET010. FIG. 35 is a graph showing the oxidation-reduction wave of NBPhen. FIG. 36 is a graph showing the reduction-oxidation wave of NBPhen. FIG. 37 is a graph showing the oxidation-reduction wave of Liq. 38A and 38B are graphs showing the reduction-oxidation wave of Liq. FIG. 39 is a graph showing the oxidation-reduction wave of PyA1PQ. FIG. 40 is a graph showing the reduction-oxidation wave of PyA1PQ. FIG. 41 is a graph showing the luminance-current density characteristics of the light-emitting device 4. As shown in FIG. FIG. 42 is a diagram showing the luminance-voltage characteristics of the light-emitting device 4. As shown in FIG. FIG. 43 is a graph showing the current efficiency-luminance characteristics of the light-emitting device 4. As shown in FIG. FIG. 44 is a diagram showing the current-voltage characteristics of the light-emitting device 4. As shown in FIG. FIG. 45 is a graph showing the external quantum efficiency-luminance characteristics of the light-emitting device 4. As shown in FIG. FIG. 46 is a graph showing the emission spectrum of the light-emitting device 4. As shown in FIG. FIG. 47 is a graph showing the normalized luminance vs. time change characteristics of the light-emitting device 4. As shown in FIG. FIG. 48 shows the emission spectra of an mPn-mDMePyPTzn film, a Liq film, and a mixed film in which mPn-mDMePyPTzn and Liq are mixed in a 1:1 (mass ratio). FIG. 49 is a graph showing the reduction-oxidation wave of mPn-mDMePyPTzn. FIG. 50 is a graph showing the luminance-current density characteristics of the light-emitting devices 5, 6, and 7. In FIG. FIG. 51 is a diagram showing the luminance-voltage characteristics of the light-emitting device 5, the light-emitting device 6, and the light-emitting device 7. In FIG. FIG. 52 is a graph showing the current efficiency-luminance characteristics of the light-emitting devices 5, 6, and 7. In FIG. FIG. 53 is a diagram showing the current-voltage characteristics of the light-emitting device 5, the light-emitting device 6, and the light-emitting device 7. In FIG. FIG. 54 is a graph showing the external quantum efficiency-luminance characteristics of the light-emitting devices 5, 6, and 7. In FIG. FIG. 55 is a diagram showing the emission spectra of light-emitting device 5, light-emitting device 6, and light-emitting device 7. As shown in FIG. FIG. 56 is a graph showing the normalized luminance-time change characteristics of the light-emitting device 5, the light-emitting device 6, and the light-emitting device 7. In FIG. Figure 57 shows the emission spectra of an αN-βNPAnth film, a Li-4mq film, and a mixed film in which αN-βNPAnth and Liq are mixed in a 1:1 (mass ratio). FIG. 58 shows the emission spectra of an mPn-mDMePyPTzn film, a Li-4mq film, and a mixed film in which mPn-mDMePyPTzn and Liq are mixed in a 1:1 (mass ratio). FIG. 59 shows the emission spectra of a PyA1PQ film, a Li-4mq film, and a mixed film in which PyA1PQ and Li-4mq are mixed in a 1:1 (mass ratio). FIG. 60 is a graph showing the oxidation-reduction wave of αN-βNPAnth. FIG. 61 is a graph showing the reduction-oxidation wave of αN-βNPAnth. Figure 62 is a graph showing the oxidation-reduction wave of Li-4mq. Figure 63 is a graph showing the reduction-oxidation wave of Li-4mq. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0038] Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and it will be easily understood by those skilled in the art that the form and details of the present invention can be modified in various ways without departing from the spirit and scope of the present invention. Therefore, the present invention should not be interpreted as being limited to the description of the embodiments shown below.

[0039] (Embodiment 1) 1A shows a diagram of a light-emitting device according to one embodiment of the present invention. The light-emitting device according to one embodiment of the present invention includes an anode 101, a cathode 102, and an EL layer 103, and the EL layer includes at least an emitting layer 113 and an electron transport layer 114.

[0040] 1A shows hole injection layer 111, hole transport layer 112, and electron injection layer 115 in addition to light emitting layer 113 and electron transport layer 114, but the configuration of EL layer 103 is not limited thereto. As shown in FIG 1B, hole transport layer 112 may have first hole transport layer 112-1 and second hole transport layer 112-2, and electron transport layer 114 may have first electron transport layer 114-1 and second electron transport layer 114-2.

[0041] In the light-emitting device of one embodiment of the present invention, the electron-transport layer 114 contains an organic compound having an electron-transport property and an organometallic complex of an alkali metal. Note that the mixing ratio thereof is preferably 3:7 to 7:3 (mass ratio).

[0042] The organic compound having electron transport properties and the organometallic complex of an alkali metal are preferably combined to form an exciplex. In this case, the peak wavelength (λp Ex ) converted to energy (E Ex ) is the difference (ΔE LUMO-HOMO ) is preferably 0.1 eV or more smaller. More preferably, it is 0.3 eV or more smaller, and further preferably, it is 0.5 eV or more smaller.

[0043] To convert the peak wavelength into energy, use the energy formula (E = hν = hc / λ, where E is energy [J] and h is Planck's constant (6.626 × 10 -34 [J s]), ν: frequency, c: speed of light (2.998×10 8 [m / s]), λ: wavelength [m], and elementary charge (1.602×10 -19 From the energy (eV) we can calculate E[eV]=1240 / λ[nm], and this formula can be used for conversion.

[0044] In the light-emitting device according to one embodiment of the present invention having such a structure, it is suggested that an organic compound having an electron-transporting property and an organometallic complex of an alkali metal form an exciplex, and that an interaction other than the formation of the exciplex occurs. It is considered that this interaction affects the element characteristics of the light-emitting device according to one embodiment of the present invention, and as a result, the light-emitting device can have a long lifetime.

[0045] In addition, in the light-emitting device according to one embodiment of the present invention, characteristic results were observed when the electron transport layer or a film formed by depositing an organic compound having an electron transport property and an organometallic complex of an alkali metal in the electron transport layer at the same mixing ratio as that of the electron transport layer was measured by mass spectrometry using time-of-flight secondary ion mass spectrometry (TOF-SIMS) or laser desorption / ionization-time of flight (LDI-TOF). That is, the molecular weight of the organic compound having an electron transport property was M E , the molecular weight of the alkali metal organometallic complex M ACom , the molecular weight of the alkali metal is M A When the mass spectrometry result is expressed as m / z=M E +M ACom +M A Positive ions are detected at -2.

[0046] Usually, when measuring positive ions by the above-mentioned mass spectrometry, ions derived from the molecules contained in the film, the substituents removed from those molecules, the molecules from which the substituents have been removed, and their associations are detected. Therefore, the sum M of the molecular weights of the molecules, the substituents possessed by those molecules, the molecules from which the substituents have been removed, etc. (M = M in the light-emitting device of one embodiment of the present invention) E +M ACom +M A (corresponding to M+1) or M+1 is detected as the m / z, and ions corresponding to M-2 are usually rarely detected.

[0047] That is, the detection of the ion M-2 in the positive ion measurement is a characteristic result as an analysis result of a light-emitting device according to one embodiment of the present invention. Note that, even in such a light-emitting device, it is preferable that the organic compound having electron transport properties contained in the electron transport layer and the organometallic complex of an alkali metal form an exciplex. Note that, when the organometallic complex of an alkali metal is measured by ToF-SIMS, the mass-to-charge ratio m / z=M ACom +M A In some cases, the aforementioned aggregate is M produced when an organometallic complex of an alkali metal is ionized. ACom +M A It is believed to be an association between ions and organic compounds.

[0048] In addition, the above ΔE LUMO-HOMO A light-emitting device in which the difference between the LUMO level of an organic compound having electron transport properties and the HOMO level of an organometallic complex of an alkali metal is 2.90 eV or less is a preferred embodiment, because the organic compound having electron transport properties and the organometallic complex of an alkali metal contained in the electron transport layer are likely to form an exciplex.

[0049] In addition, the peak wavelength (λp Ex A light emitting device having a wavelength of 570 nm or more exhibits a small gradient of long-term deterioration and thus exhibits less deterioration during long-term operation.

[0050] In addition, the peak wavelength (λp Ex A light-emitting device having a wavelength of 570 nm or more and less than 610 nm has a small slope of long-term deterioration and also has an increase in luminance at the initial stage of operation, which offsets the initial deterioration and allows the device to have a long life.

[0051] In addition, the peak wavelength (λp ExA light emitting device having a wavelength of 610 nm or more can be a light emitting device having a small long-term degradation rate and high luminous efficiency.

[0052] As an organic compound having an electron transport property, an organic compound having an electron transport property that is more dominant than a hole transport property can be used. In addition, the electron mobility of an organic compound having an electron transport property is 1×10 when the square root of the electric field strength [V / cm] is 600. -7 cm 2 / Vs or more 5×10 -5 cm 2 By lowering the electron transportability in the electron transport layer, the amount of electrons injected into the light-emitting layer can be controlled, and the light-emitting layer can be prevented from becoming an electron-excessive state.

[0053] The organic compound having an electron transporting property preferably has an electron transporting property and a HOMO level of −6.0 eV or more.

[0054] Specific examples of organic compounds that can be used as the organic compound having the electron transporting property include 2,9-di(2-naphthyl)-4,7-diphenyl-1,10-phenanthroline (abbreviation: NBPhen), 2-phenyl-3-[10-(3-pyridyl)-9-anthryl]phenylquinoxaline (abbreviation: PyA1PQ), and the like, and PyA1PQ is particularly preferred. In addition, bis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviation: BeBq 2), bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III) (abbreviation: BAlq), bis(8-quinolinolato)zinc(II) (abbreviation: Znq), bis[2-(2-benzoxazolyl)phenolato]zinc(II) (abbreviation: ZnPBO), bis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ), or other metal complexes, or organic compounds having a π-electron-deficient heteroaromatic ring skeleton are preferred. Examples of organic compounds having a π-electron-deficient heteroaromatic ring skeleton include 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: TAZ), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene, and the like. Poly(dibenzothiophene-4-yl)phenyl]-1-phenyl-1H-benzimidazole (abbreviation: mDBTBIm-II), 9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole (abbreviation: CO11), 2,2',2''-(1,3,5-benzenetriyl)tris(1-phenyl-1H-benzimidazole) (abbreviation: TPBI), 2-[3-(dibenzothiophene-4-yl)phenyl]-1-phenyl-1H-benzimidazole (abbreviation: mDBTBIm-II), etc. Heterocyclic compounds with a riazole skeleton, 2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTPDBq-II), 2-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTBPDBq-II), 2-[3'-(9H-carbazol-9-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: Heterocyclic compounds with diazine skeletons such as 4,6-bis[3-(phenanthren-9-yl)phenyl]pyrimidine (abbreviation: 4,6mPnP2Pm), and 4,6-bis[3-(4-dibenzothienyl)phenyl]pyrimidine (abbreviation: 4,6mDBTP2Pm-II) and 2-[3'-(9,9-dimethyl-9H-fluoren-2-yl)-1,1'-biphenyl-3-yl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mFBPTzn), 2-[(1,1'-biphenyl)-4-yl]-4-phenyl-6-[9,9'-spirobi(9H-fluoren)-2-yl]-1,3,5-triazine (abbreviation: BP-SFTzn), 2-{3-[3-(benzo "b" naphtho[1,2-d]furan-8-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mBnfBPTzn), 2-{3-[3-(benzo "b" naphtho[1,2-d]furan-8-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine and heterocyclic compounds having a triazine skeleton such as 3,5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine (abbreviation: 35DCzPPy) and 1,3,5-tri[3-(3-pyridyl)phenyl]benzene (abbreviation: TmPyPB). In addition, 9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: PCzPA), 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation: CzPA), 7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole (abbreviation: cgDBCzPA), 6-[3-(9,10-diphenyl-2-anthryl)phenyl]-benzo[b]naphtho[1,Examples of anthracene derivatives include 2-d]furan (abbreviation: 2mBnfPPA), 9-phenyl-10-{4-(9-phenyl-9H-fluoren-9-yl)biphenyl-4'-yl}anthracene (abbreviation: FLPPA), etc. Among these, materials that form exciplexes with organometallic complexes of alkali metals to be used together, or whose LUMO level and the HOMO level of the organometallic complex of alkali metals have a difference of 2.90 eV or less, may be selected and used. Among the above, heterocyclic compounds having a diazine skeleton, heterocyclic compounds having a triazine skeleton, and heterocyclic compounds having a pyridine skeleton are preferred from the viewpoint of operating life because the energy is easily stabilized when the exciplex is formed with an organometallic complex of an alkali metal (the emission wavelength of the exciplex is easily lengthened). In particular, heterocyclic compounds having a diazine skeleton and heterocyclic compounds having a triazine skeleton are suitable for stabilizing the energy of exciplexes because of their deep LUMO level.

[0055] The organometallic complex of the alkali metal is preferably an organometallic complex of lithium. Alternatively, the organometallic complex of the alkali metal preferably has a ligand having a quinolinol skeleton. More preferably, the organometallic complex of the alkali metal is 8-hydroxyquinolinatolithium or a derivative thereof.

[0056] In the light-emitting device of one embodiment of the present invention, the light-emitting layer 113 is a layer containing a light-emitting material. Note that the light-emitting layer 113 may further contain a host material for dispersing the light-emitting material.

[0057] The light-emitting material may be a fluorescent material, a phosphorescent material, a material exhibiting thermally activated delayed fluorescence (TADF), or other light-emitting material. The light-emitting material may be a single layer or may be composed of multiple layers. Note that one embodiment of the present invention is more suitable when the light-emitting layer 113 is a layer exhibiting fluorescent emission, particularly a layer exhibiting blue fluorescent emission. On the other hand, one embodiment of the present invention can be used regardless of the emission color of the light-emitting device, and can be used across light-emitting devices (light-emitting elements) of different colors.

[0058] Examples of materials that can be used as the fluorescent substance in the light-emitting layer 113 include 5,6-bis[4-(10-phenyl-9-anthryl)phenyl]-2,2'-bipyridine (abbreviation: PAP2BPy), 5,6-bis[4'-(10-phenyl-9-anthryl)biphenyl-4-yl]-2,2'-bipyridine (abbreviation: PAPP2BPy), N,N'-diphenyl-N,N'-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine (abbreviation: 1,6FLPAPrn), N,N'-bis(3-methylphenyl)pyridine-1,6-diamine (abbreviation: 1,6FLPAPrn), and N,N'-bis(3-methylphenyl)pyridine-1,6-diamine (abbreviation: 1,6FLPAPrn). N,N'-bis[3-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine (abbreviation: 1,6mMemFLPAPrn), N,N'-bis[4-(9H-carbazol-9-yl)phenyl]-N,N'-diphenylstilbene-4,4'-diamine (abbreviation: YGA2S), 4-(9H-carbazol-9-yl)-4'-(10-phenyl-9-anthryl)triphenylamine (abbreviation: YGAPA), 4-(9H-carbazol-9-yl)-4'-(9,10-diphenyl-2-anthryl)triphenylamine 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-carbazol-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-carbazol-3-amine (abbreviation: 2PCAPA), N-[9,10-bis(1,1'-biphenyl-2-yl)-2-anthryl]-N,9-diphenyl-9H-carbazol-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: 2DPABPhA), 9,10-bis(1,1'-biphenyl-2-yl)-N-[4-(9H-carbazol-9-yl)phenyl]-N-phenylanthracen-2-amine (abbreviation: 2YGABPhA), N,N,9-triphenylanthracen-9-amine (abbreviation: DPhAPhA), Coumarin 545T, N,N'-diphenylquinacridone, (abbreviation: DPQd), rubrene, 5,12-bis(1,1'-biphenyl-4-yl)-6,11-diphenyltetrahydrofuran N,N,N',N'-tetrakis(4-methylphenyl)tetracene-5,11-diamine (abbreviation: p-mPhTD), 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]quinolizin-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',N'-tetrakis(4-methylphenyl)acenaphtho[1,2-a]fluoranthene-3,10-diamine (abbreviation: p-mPhAFD), 2-{2-isopropyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-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]quinolizin-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]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: BisDCJTM), N,N'-diphenyl- N,N'-(1,6-pyrene-diyl)bis[(6-phenylbenzo[b]naphtho[1,2-d]furan)-8-amine] (abbreviation: 1,6BnfAPrn-03), 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), 3,10-bis[N-(dibenzofuran-3-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviation: 3,10FrA2Nbf(IV)-02), etc. In particular, condensed aromatic diamine compounds, such as pyrene diamine compounds, such as 1,6FLPAPrn, 1,6mMemFLPAPrn, and 1,6BnfAPrn-03, are preferred because they have high hole trapping properties, excellent luminous efficiency, and excellent reliability.

[0059] In the case where a phosphorescent material is used as the luminescent center material in the light-emitting layer 113, examples of materials that can be used include 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) (abbreviation: [Ir(Mptz1-mp) 3 ]), tris(1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazolato)iridium(III) (abbreviation: [Ir(Prptz1-Me) 3 ]), and fac-tris[(1-2,6-diisopropylphenyl)-2-phenyl-1H-imidazole]iridium(III) (abbreviation: [Ir(iPrpmi) 3 ]), tris[3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-f]phenanthridinato]iridium(III) (abbreviation: [Ir(dmpimpt-Me 3 ]) and bis[2-(4',6'-difluorophenyl)pyridinato-N,C 2’ ]iridium(III) tetrakis(1-pyrazolyl)borate (abbreviation: FIr6), bis[2-(4',6'-difluorophenyl)pyridinato-N,C 2’ ]iridium(III) picolinate (abbreviation: FIrpic), bis{2-[3',5'-bis(trifluoromethyl)phenyl]pyridinato-N,C 2’}Iridium(III) picolinate (abbreviation: [Ir(CF 3 ppy) 2 (pic)]), bis[2-(4',6'-difluorophenyl)pyridinato-N,C 2’ ] Organometallic iridium complexes with phenylpyridine derivatives having electron-withdrawing groups as ligands, such as iridium(III) acetylacetonate (abbreviated as FIracac), are examples of such compounds that exhibit blue phosphorescence and have emission peaks at 440 nm to 520 nm.

[0060] In addition, as a material that can be used for the light-emitting layer 113, 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-(2-methylphenyl)-4-phenylpyrimidinato]iridium(III) (abbreviation: [Ir(mpmppm) 2 (acac)]), (acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III) (abbreviation: [Ir(dppm) 2 and organometallic iridium complexes with pyrimidine skeletons such as (acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazinate)iridium(III) (abbreviation: [Ir(mppr-Me 2 (acac)]), (acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinate)iridium(III) (abbreviation: [Ir(mppr-iPr) 2 Organometallic iridium complexes with pyrazine skeletons such as tris(2-phenylpyridinato-N,C 2’ ) Iridium(III) (abbreviation: [Ir(ppy) 3 ]), bis(2-phenylpyridinato-N,C 2’ ) Iridium(III) acetylacetonate (abbreviation: [Ir(ppy) 2 (acac)]), bis(benzo[h]quinolinato)iridium(III) acetylacetonate (abbreviation: [Ir(bzq)2 (acac)]), tris(benzo[h]quinolinato)iridium(III) (abbreviation: [Ir(bzq) 3 ]), tris(2-phenylquinolinato-N,C 2’ ) Iridium(III) (abbreviation: [Ir(pq) 3 ]), bis(2-phenylquinolinato-N,C 2’ ) Iridium(III) acetylacetonate (abbreviation: [Ir(pq) 2 In addition to organometallic iridium complexes with pyridine skeletons such as tris(acetylacetonato)(monophenanthroline)terbium(III) (abbreviation: [Tb(acac)]), 3 These are compounds that mainly exhibit green phosphorescence, with an emission peak at 500 nm to 600 nm. In addition, organometallic iridium complexes having a pyrimidine skeleton are particularly preferred because they are remarkably excellent in reliability and luminous efficiency.

[0061] In addition, as a material that can be used for the light-emitting layer 113, (diisobutyrylmethanato)bis[4,6-bis(3-methylphenyl)pyrimidinato]iridium(III) (abbreviation: [Ir(5mdppm) 2 (dibm)]), bis[4,6-bis(3-methylphenyl)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: [Ir(5mdppm) 2 (dpm)]), bis[4,6-di(naphthalen-1-yl)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: [Ir(d1npm) 2 and organometallic iridium complexes with pyrimidine skeletons such as (acetylacetonato)bis(2,3,5-triphenylpyrazinate)iridium(III) (abbreviation: [Ir(tppr) 2 (acac)]), bis(2,3,5-triphenylpyrazinate)(dipivaloylmethanato)iridium(III) (abbreviation: [Ir(tppr) 2(dpm)]), (acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III) (abbreviation: [Ir(Fdpq) 2 Organometallic iridium complexes with pyrazine skeletons such as tris(1-phenylisoquinolinato-N,C 2 ') Iridium(III) (abbreviation: [Ir(piq) 3 ]), bis(1-phenylisoquinolinato-N,C 2 ') Iridium(III) acetylacetonate (abbreviation: [Ir(piq) 2 In addition to organometallic iridium complexes with pyridine skeletons such as iridium complexes with pyridine skeletons such as 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin platinum(II) (abbreviation: PtOEP), platinum complexes such as tris(1,3-diphenyl-1,3-propanedionato)(monophenanthroline)europium(III) (abbreviation: [Eu(DBM) 3 (Phen)]), tris[1-(2-thenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(III) (abbreviation: [Eu(TTA) 3 These are compounds that exhibit red phosphorescence, with emission peaks at 600 to 700 nm. In addition, organometallic iridium complexes with a pyrazine skeleton can emit red light with good chromaticity.

[0062] In addition to the phosphorescent compounds described above, known phosphorescent light-emitting materials may be selected and used.

[0063] Examples of TADF materials that can be used include fullerene and its derivatives, acridine and its derivatives, and eosin derivatives. Examples of TADF materials include metal-containing porphyrins that contain magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), or palladium (Pd). Examples of metal-containing porphyrins include protoporphyrin-tin fluoride complexes (SnF), which are represented by the following structural formula: 2(Proto IX)), mesoporphyrin-tin fluoride complex (SnF 2 (Meso IX)), hematoporphyrin-tin fluoride complex (SnF 2 (Hemato IX)), coproporphyrin tetramethyl ester-tin fluoride complex (SnF 2 (Copro III-4Me)), octaethylporphyrin-tin fluoride complex (SnF 2 (OEP)), etioporphyrin-tin fluoride complex (SnF 2 (Etio I)), octaethylporphyrin-platinum chloride complex (PtCl 2 OEP) etc.

[0064] [ka]

[0065] In addition, 2-(biphenyl-4-yl)-4,6-bis(12-phenylindolo[2,3-a]carbazol-11-yl)-1,3,5-triazine (abbreviation: PIC-TRZ) represented by the following structural formula, 9-(4,6-diphenyl-1,3,5-triazin-2-yl)-9'-phenyl-9H,9'H-3,3'-bicarbazole (abbreviation: PCCzTzn), 9-[4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]-9'-phenyl-9H,9'H-3,3'-bicarbazole (abbreviation: PCCzPTzn), 2-[4-(10H-phenoxazin-10-yl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: PXZ-TRZ), 3-[4-(5-phenyl-5,10-dihydrophenazin-10-yl)phenyl]-4,5-diphenyl-1,2,4-triazole (abbreviation: PPZ-3TPT), 3-(9,9-dimethyl-9H-acridin-10-yl)-9H-xanthen-9-one (abbreviation: ACRXTN), bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone (abbreviation: DMAC-DPS), 10-phenyl-10H,10'H-spiro[acridine-9,9'-anthracene]-10'-one (abbreviation: ACRSA), etc., heterocyclic compounds having one or both of a π-electron-excessive heteroaromatic ring and a π-electron-deficient heteroaromatic ring can also be used. Since the heterocyclic compound has a π-electron-excessive heteroaromatic ring and a π-electron-deficient heteroaromatic ring, it has both high electron transportability and hole transportability, which is preferable. Among them, among the skeletons having a π-electron-deficient heteroaromatic ring, a pyridine skeleton, a diazine skeleton (pyrimidine skeleton, pyrazine skeleton, pyridazine skeleton), and a triazine skeleton are preferable because they are stable and have good reliability. In particular, a benzofuropyrimidine skeleton, a benzothienopyrimidine skeleton, a benzofuropyrazine skeleton, and a benzothienopyrazine skeleton are preferable because they have high acceptability and good reliability. Also, among the skeletons having a π-electron-excessive heteroaromatic ring, an acridine skeleton, a phenoxazine skeleton, a phenothiazine skeleton, a furan skeleton, a thiophene skeleton, and a pyrrole skeleton are stable and have good reliability, so it is preferable to have at least one of these skeletons.In addition, the furan skeleton is preferably a dibenzofuran skeleton, and the thiophene skeleton is preferably a dibenzothiophene skeleton. In addition, the pyrrole skeleton is particularly preferably an indole skeleton, a carbazole skeleton, an indolocarbazole skeleton, a bicarbazole skeleton, or a 3-(9-phenyl-9H-carbazol-3-yl)-9H-carbazole skeleton. In addition, a substance in which a π-electron-rich heteroaromatic ring and a π-electron-deficient heteroaromatic ring are directly bonded is particularly preferable because the electron donating property of the π-electron-rich heteroaromatic ring and the electron accepting property of the π-electron-deficient heteroaromatic ring are both strong, and the energy difference between the S1 level and the T1 level is small, so that thermally activated delayed fluorescence can be efficiently obtained. 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. In addition, an aromatic amine skeleton, a phenazine skeleton, or the like can be used as the π-electron-rich skeleton. In addition, examples of the π-electron-deficient skeleton that can be used include a xanthene skeleton, a thioxanthene dioxide skeleton, an oxadiazole skeleton, a triazole skeleton, an imidazole skeleton, an anthraquinone skeleton, a boron-containing skeleton such as phenylborane or boranthrene, an aromatic ring or a heteroaromatic ring having a nitrile group or a cyano group such as benzonitrile or cyanobenzene, a carbonyl skeleton such as benzophenone, a phosphine oxide skeleton, a sulfone skeleton, etc. In this way, a π-electron-deficient skeleton and a π-electron-rich skeleton can be used in place of at least one of a π-electron-deficient heteroaromatic ring and a π-electron-rich heteroaromatic ring.

[0066] [ka]

[0067] TADF materials are materials that have a small difference between the S1 and T1 levels and have the function of converting triplet excitation energy to singlet excitation energy by reverse intersystem crossing. Therefore, triplet excitation energy can be upconverted to singlet excitation energy by a small amount of thermal energy (reverse intersystem crossing), and singlet excitation states can be generated efficiently. In addition, triplet excitation energy can be converted into light emission.

[0068] In addition, exciplexes (also called exciplexes), which form an excited state with two types of substances, have an extremely small difference between the S1 level and the T1 level and function as TADF materials that can convert triplet excitation energy into singlet excitation energy.

[0069] As an index of the T1 level, a phosphorescence spectrum observed at low temperatures (for example, 77 K to 10 K) may be used. For a TADF material, when a tangent line is drawn at the base of the short wavelength side of the fluorescence spectrum, and the energy of the wavelength of the extrapolated line is taken as the S1 level, and a tangent line is drawn at the base of the short wavelength side of the phosphorescence spectrum, and the energy of the wavelength of the extrapolated line is taken as the T1 level, the difference between S1 and T1 is preferably 0.3 eV or less, and more preferably 0.2 eV or less.

[0070] In addition, when a TADF material is used as the emission center material, the S1 level of the host material is preferably higher than the S1 level of the TADF material, and the T1 level of the host material is preferably higher than the T1 level of the TADF material.

[0071] As the host material of the light-emitting layer 113, various carrier transporting materials such as a material having an electron transporting property, a material having a hole transporting property, or the above-mentioned TADF material can be used.

[0072] As a material having hole transport properties that can be used as a host material, an organic compound having an amine skeleton or a π-electron-rich heteroaromatic ring skeleton is preferable. For example, 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB), N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (abbreviation: TPD), 4,4'-bis[N-(spiro-9,9'-bifluoren-2-yl)-N-phenylamino]biphenyl (abbreviation: BSPB), 4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP), 4-phenyl-3'-(9-phenylfluoren-3' ... mBPAFLP, 4-phenyl-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4'-diphenyl-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBBi1BP), 4-(1-naphthyl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBANB), 4,4'-di(1-naphthyl)-4'' -(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBNBB), 9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]fluoren-2-amine (abbreviation: PCBAF), N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]spiro-9,9'-bifluoren-2-amine (abbreviation: PCBASF), N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-bis(9,9 Compounds with aromatic amine skeletons such as 1,3-bis(N-carbazolyl)benzene (abbreviation: mCP), 4,4'-di(N-carbazolyl)biphenyl (abbreviation: CBP), 3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviation: CzTP), 3,3'-bis(9-phenyl-9H-carbazole) (abbreviation: PCCP), and compounds with carbazole skeletons such as 4,4',4''-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation: DBT3P-II), 2,8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene (abbreviation: DBTFLP-III), 4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviation: DBTFLP-IV), and compounds having a furan skeleton such as 4,4',4''-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation: DBF3P-II), 4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran (abbreviation: mmDBFFLBi-II). Among the above, compounds having an aromatic amine skeleton and compounds having a carbazole skeleton are preferable because they have good reliability, high hole transportability, and contribute to reducing the driving voltage. In addition, organic compounds having hole transport properties, which are given as examples of the second substance, can also be used. Among compounds having a carbazole skeleton, compounds having a 3,3'-bi(9H-carbazole) skeleton are particularly preferred because they contribute greatly to reliability, transport properties, and reduced driving voltage.

[0073] An example of a material having an electron transporting property that can be used as a host material is bis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviation: BeBq 2), bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III) (abbreviation: BAlq), bis(8-quinolinolato)zinc(II) (abbreviation: Znq), bis[2-(2-benzoxazolyl)phenolato]zinc(II) (abbreviation: ZnPBO), bis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ), or other metal complexes, or organic compounds having a π-electron-deficient heteroaromatic ring skeleton are preferred. Examples of organic compounds having a π-electron-deficient heteroaromatic ring skeleton include 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: TAZ), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazole-2-yl], nyl]benzene (abbreviation: OXD-7), 9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole (abbreviation: CO11), 2,2',2''-(1,3,5-benzenetriyl)tris(1-phenyl-1H-benzimidazole) (abbreviation: TPBI), 2-[3-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole (abbreviation: mDBTBIm Heterocyclic compounds with polyazole skeletons such as 2-[3-(dibenzothiophene-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-carbazol-9-yl)biphenyl-3-yl]dibenzo [f,h]quinoxaline (abbreviation: 2mCzBPDBq), 4,6-bis[3-(phenanthren-9-yl)phenyl]pyrimidine (abbreviation: 4,6mPnP2Pm), 4,6-bis[3-(4-dibenzothienyl)phenyl]pyrimidine (abbreviation: 4,6mDBTP2Pm-II), 8-(1,1'-biphenyl-4-yl)-4-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 8BP-4mDBtBPBfpm), 11-[(3'-dibenzothiophen-4-yl)biphenyl-3-yl]phenanthro[9',10':4,5]furo[2,3-b]pyrazine (abbreviation: 11mDBtBPPnfpr), 9-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]naphtho[1',2':4,5]furo[2,3-b]pyrazine (abbreviation: 9mDBtBPNfpr), 9-phenyl-9'-(4-phenyl-2-quinazolinyl)-3,3'-bi-9H-carbazole (abbreviation: PCCzQz), and other heterocyclic compounds with diazine skeletons, as well as 3,5-bis[3-(9H Examples of the heterocyclic compounds include heterocyclic compounds having a pyridine skeleton such as 1,3,5-tri[3-(3-pyridyl)phenyl]pyridine (abbreviation: 35DCzPPy) and 1,3,5-tri[3-(3-pyridyl)phenyl]benzene (abbreviation: TmPyPB), 2-[3'-(triphenylene-2-yl)-1,1'-biphenyl-3-yl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mTpBPTzn), and 11-(4-[1,1'-diphenyl]-4-yl-6-phenyl-1,3,5-triazin-2-yl)-11,12-dihydro-12-phenyl-indolo[2,3-a]carbazole (abbreviation: BP-Icz(II)Tzn). Among the above, heterocyclic compounds having a triazine skeleton, heterocyclic compounds having a diazine skeleton, and heterocyclic compounds having a pyridine skeleton are preferable because of their good reliability. In particular, heterocyclic compounds having a triazine skeleton or a diazine (pyrimidine or pyrazine) skeleton have high electron transport properties and contribute to reducing the driving voltage.

[0074] As a TADF material that can be used as a host material, the same TADF materials listed above can be used. When a TADF material is used as a host material, the triplet excitation energy generated in the TADF material is converted to singlet excitation energy by reverse intersystem crossing, and the energy is further transferred to the luminescent center substance, thereby increasing the luminous efficiency of the light-emitting device. In this case, the TADF material functions as an energy donor, and the luminescent center substance functions as an energy acceptor.

[0075] This is very effective when the above luminescent center material is a fluorescent material. Also, at this time, in order to obtain high luminous efficiency, it is preferable that the S1 level of the TADF material is higher than the S1 level of the fluorescent material. Further, it is preferable that the T1 level of the TADF material is higher than the S1 level of the fluorescent material. Therefore, it is preferable that the T1 level of the TADF material is higher than the T1 level of the fluorescent material.

[0076] Also, it is preferable to use a TADF material that exhibits emission overlapping with the wavelength of the absorption band on the lowest energy side of the fluorescent material. Thereby, the transfer of excitation energy from the TADF material to the fluorescent material becomes smooth, and efficient emission can be obtained.

[0077] In addition, in order to efficiently generate singlet excitation energy from triplet excitation energy by reverse intersystem crossing, it is preferable that carrier recombination occurs in the TADF material. In addition, it is preferable that the triplet excitation energy generated in the TADF material does not transfer to the triplet excitation energy of the fluorescent material. For this purpose, it is preferable that the fluorescent material has a protective group around the luminophore (skeleton causing light emission) of the fluorescent material. As the protective group, a substituent having no π bond is preferable, and a saturated hydrocarbon is preferable. Specifically, an alkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, and a trialkylsilyl group having 3 to 10 carbon atoms are mentioned, and it is more preferable that the fluorescent material is substituted with a plurality of protective groups. Since a substituent having no π bond has poor function of transporting carriers, the distance between the TADF material and the luminophore of the fluorescent material can be increased without affecting carrier transport or carrier recombination. Here, the luminophore refers to an atomic group (skeleton) from which light emission originates in the fluorescent material. The luminophore preferably has a skeleton having a π bond, preferably contains an aromatic ring, and preferably has a condensed aromatic ring or a condensed heteroaromatic ring. Examples of the condensed aromatic ring or the condensed heteroaromatic ring include a phenanthrene skeleton, a stilbene skeleton, an acridone skeleton, a phenoxazine skeleton, and a phenothiazine skeleton. In particular, fluorescent substances having a naphthalene skeleton, an anthracene skeleton, a fluorene skeleton, a chrysene skeleton, a triphenylene skeleton, a tetracene skeleton, a pyrene skeleton, a perylene skeleton, a coumarin skeleton, a quinacridone skeleton, or a naphthobisbenzofuran skeleton are preferred because they have a high fluorescence quantum yield.

[0078] When a fluorescent material is used as the luminescence center material, a material having an anthracene skeleton is suitable as the host material. When a material having an anthracene skeleton is used as the host material for a fluorescent material, it is possible to realize an emission layer having both good luminescence efficiency and durability. As a material having an anthracene skeleton that can be used as a host material, a material having a diphenylanthracene skeleton, particularly a 9,10-diphenylanthracene skeleton, is preferable because it is chemically stable. In addition, when the host material has a carbazole skeleton, it is preferable because the injection and transport properties of holes are improved, but when the host material contains a benzocarbazole skeleton in which a benzene ring is further condensed to carbazole, the HOMO is shallower by about 0.1 eV than that of carbazole, making it easier for holes to enter, which is more preferable. In particular, when the host material contains a dibenzocarbazole skeleton, it is preferable because the HOMO is shallower by about 0.1 eV than that of carbazole, making it easier for holes to enter, and it also has excellent hole transport properties and high heat resistance. Therefore, a more preferable host material is a material having both a 9,10-diphenylanthracene skeleton and a carbazole skeleton (or a benzocarbazole skeleton or a dibenzocarbazole skeleton). From the viewpoint of the hole injection / transport property, a benzofluorene skeleton or a dibenzofluorene skeleton may be used instead of the carbazole skeleton. Examples of such a material include 9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: PCzPA), 3-[4-(1-naphthyl)-phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPN), 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation: CzPA), 7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole (abbreviation: CzPA), and 7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole (abbreviation: CzPA). Examples of such compounds include carbazole (abbreviation: cgDBCzPA), 6-[3-(9,10-diphenyl-2-anthryl)phenyl]-benzo[b]naphtho[1,2-d]furan (abbreviation: 2mBnfPPA), 9-phenyl-10-{4-(9-phenyl-9H-fluoren-9-yl)biphenyl-4'-yl}anthracene (abbreviation: FLPPA), and 9-(1-naphthyl)-10-[4-(2-naphthyl)phenyl]anthracene (abbreviation: αN-βNPAnth).In particular, CzPA, cgDBCzPA, 2mBnfPPA, and PCzPA are preferred choices since they exhibit very good properties.

[0079] The host material may be a mixture of a plurality of substances, and when a mixture of host materials is used, it is preferable to mix a material having an electron transporting property with a material having a hole transporting property. By mixing a material having an electron transporting property with a material having a hole transporting property, the transporting property of the light-emitting layer 113 can be easily adjusted, and the recombination region can be easily controlled. The mass ratio of the content of the material having a hole transporting property to the material having an electron transporting property may be 1:19 to 19:1 (material having a hole transporting property:material having an electron transporting property).

[0080] A phosphorescent material can be used as a part of the mixed material. The phosphorescent material can be used as an energy donor that provides excitation energy to a fluorescent material when the fluorescent material is used as the luminescence center material.

[0081] In addition, these mixed materials may form an exciplex. It is preferable to select a combination that forms an exciplex that emits light that overlaps with the wavelength of the lowest energy absorption band of the light-emitting material, because this makes energy transfer smooth and allows efficient light emission. In addition, the use of this structure is preferable because the driving voltage is reduced.

[0082] At least one of the materials forming the exciplex in the light-emitting layer may be a phosphorescent material, which allows the triplet excitation energy to be efficiently converted into singlet excitation energy by reverse intersystem crossing.

[0083] As a combination of materials that efficiently form an exciplex, it is preferable that the HOMO level of the material having hole transport properties is equal to or higher than the HOMO level of the material having electron transport properties. It is also preferable that the LUMO level of the material having hole transport properties is equal to or higher than the LUMO level of the material having electron transport properties. The LUMO level and HOMO level of the material can be derived from the electrochemical properties (reduction potential and oxidation potential) of the material measured by cyclic voltammetry (CV) measurement. The HOMO level can also be obtained from ionization potential measurement (IP measurement) of a thin film. The LUMO level can also be calculated using the HOMO level obtained from the IP measurement and the optical band gap (energy (eV) calculated from the absorption edge on the long wavelength side of the absorption spectrum of the thin film). Specifically, the LUMO level is calculated by adding the energy (eV) calculated from the band gap to the HOMO level.

[0084] The formation of an exciplex can be confirmed by comparing the spectrum of each mixed material (e.g., the emission spectrum of a material having hole transport properties, the emission spectrum of a material having electron transport properties, the spectrum of an organometallic complex, etc.) with the emission spectrum of a mixed film obtained by mixing these materials, and observing the phenomenon that the emission spectrum of the mixed film shifts to a longer wavelength than the emission spectrum of each material (or has a new peak on the longer wavelength side). Alternatively, it can be confirmed by comparing the transient photoluminescence (PL) of each mixed material with the transient PL of a mixed film obtained by mixing these materials, and observing the difference in transient response, such as the transient PL lifetime of the mixed film having a longer lifetime component than the transient PL lifetime of each material, or the proportion of delayed components becoming larger. In addition, the above-mentioned transient PL may be read as transient electroluminescence (EL). In other words, the formation of an exciplex can also be confirmed by comparing the transient EL of each mixed material with the transient EL of a mixed film of these materials, and observing the difference in transient response.

[0085] Next, other layers that can be used for the EL layer 103 will be described.

[0086] The hole-injection layer 111 is a layer for facilitating the injection of holes into the EL layer 103, and is made of a material with high hole-injection properties. The hole-injection layer 111 may be made of a single acceptor substance, but is preferably made of a composite material containing an acceptor substance and an organic compound having a hole-transporting property.

[0087] The acceptor substance is a substance that exhibits electron accepting properties with respect to an organic compound having a hole transporting property contained in the hole transport layer or the hole injection layer.

[0088] As the acceptor substance, both inorganic and organic compounds can be used, but it is preferable to use an organic compound having an electron-withdrawing group (particularly a halogen group such as a fluoro group or a cyano group). As the acceptor substance, a substance that exhibits electron accepting properties toward the organic compound having hole transport properties contained in the hole transport layer or hole injection layer may be appropriately selected from such substances.

[0089] An example of such an acceptor substance is 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation: F 4-TCNQ), chloranil, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviation: HAT-CN), 1,3,4,5,7,8-hexafluorotetracyano-naphthoquinodimethane (abbreviation: F6-TCNNQ), 2-(7-dicyanomethylene-1,3,4,5,6,8,9,10-octafluoro-7H-pyren-2-ylidene)malononitrile, etc. In particular, compounds in which an electron-withdrawing group is bonded to a condensed aromatic ring having a plurality of heteroatoms, such as HAT-CN, are thermally stable and preferable. Radialene derivatives having electron-withdrawing groups (especially halogen groups such as fluoro groups and cyano groups) [3] are preferred because they have very high electron-accepting properties. Specific examples include organic compounds such as α,α',α''-1,2,3-cyclopropanetriylidenetris[4-cyano-2,3,5,6-tetrafluorobenzeneacetonitrile], α,α',α''-1,2,3-cyclopropanetriylidenetris[2,6-dichloro-3,5-difluoro-4-(trifluoromethyl)benzeneacetonitrile], and α,α',α''-1,2,3-cyclopropanetriylidenetris[2,3,4,5,6-pentafluorobenzeneacetonitrile]. When the acceptor substance is an inorganic compound, a transition metal oxide can also be used. In particular, oxides of metals belonging to Groups 4 to 8 of the periodic table are suitable, and as oxides of metals belonging to Groups 4 to 8 of the periodic table, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, rhenium oxide, etc. are preferred due to their high electron-accepting properties. Among them, molybdenum oxide is preferred because it is stable in the air, has low hygroscopicity, and is easy to handle.

[0090] The organic compound having a hole transport property used in the composite material preferably has a relatively deep HOMO level of -5.7 eV or more and -5.4 eV or less. When the organic compound having a hole transport property used in the composite material has a relatively deep HOMO level, the induction of holes is appropriately suppressed, while the induced holes are easily injected into the hole transport layer 112.

[0091] The organic compound having hole transport properties used in the composite material preferably has any one of a carbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton, and an anthracene skeleton. In particular, aromatic amines having a substituent containing a dibenzofuran ring or a dibenzothiophene ring, aromatic monoamines having a naphthalene ring are preferred, or aromatic monoamines in which a 9-fluorenyl group is bonded to the nitrogen of the amine via an arylene group may be used. Note that if these substances have an N,N-bis(4-biphenyl)amino group, it is preferred because a light-emitting device with a long life can be fabricated. Specific examples of such substances 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), 4,4'-bis(6-phenylbenzo[b]naphtho[1,2-d]furan-8-yl- 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 -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)triphenylamine 4,4'-Bis(1-naphthyl)triphenylamine (abbreviation: αNBB1BP), 4,4'-diphenyl-4''-[4'-(carbazol-9-yl)biphenyl-4-yl]triphenylamine (abbreviation: YGTBi1BP), 4'-[4-(3-phenyl-9H-carbazol-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-[4-(9-phenyl-9H-carbazol-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-fluorene)-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-carbazol-3-yl)triphenylamine (abbreviation: PCBBi1BP), 4-(1-naphthyl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBANB), 4,4'-di(1-naphthyl)-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBANB), Examples of such fluorenylamine include PCBNBB, N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]spiro-9,9'-bifluoren-2-amine (PCBASF), and N-(1,1'-biphenyl-4-yl)-9,9-dimethyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9H-fluoren-2-amine (PCBBiF).

[0092] In addition, an organic compound having a hole transport property has a hole mobility of 1×10 when the square root of the electric field strength [V / cm] is 600. -3 cm 2 It is preferable that the value is equal to or less than / Vs.

[0093] The composition ratio of the organic compound having a hole-transporting property to the acceptor material in the composite material is preferably 1:0.01 to 1:0.15 (mass ratio), more preferably 1:0.01 to 1:0.1 (mass ratio).

[0094] In addition, at this time, the electron mobility of the electron transport layer 114 is 1×10 -7 cm 2 / Vs or more 5×10 -5 cm 2 It is preferable that the value is equal to or less than / Vs.

[0095] Furthermore, in this case, the electron transport layer 114 preferably contains an organometallic complex of an alkali metal, and more preferably, the organometallic complex of the alkali metal contains an 8-hydroxyquinolinato structure. Among them, a complex of a monovalent metal ion is preferable, and specifically, for example, 8-hydroxyquinolinato-lithium (abbreviation: Liq) or 8-hydroxyquinolinato-sodium (abbreviation: Naq) is preferable. In particular, a lithium complex is preferable, and Liq is more preferable. In addition, when the 8-hydroxyquinolinato structure is contained, a methyl-substituted product (for example, a 2-methyl-substituted product or a 5-methyl-substituted product) can also be used.

[0096] In addition, it is preferable that the organometallic complex of the alkali metal in the electron transport layer 114 has a concentration difference (including the case where the concentration is 0) in the thickness direction. This makes it possible to obtain a light-emitting device with even better life and reliability.

[0097] The organic compound having an electron transporting property used in the electron transport layer 114 preferably has a HOMO level of −6.0 eV or higher.

[0098] In a light-emitting device having such a configuration, the luminance degradation curve obtained by a drive test under a constant current density condition may show a shape having a maximum value, that is, a shape having a portion where the luminance increases with time. A light-emitting device showing such degradation behavior can offset the rapid degradation at the beginning of drive, so-called initial degradation, with the increase in luminance, and can be made into a light-emitting device with small initial degradation and very good drive life. Such a light-emitting device is called a Recombination-Site Tailoring Injection element (ReSTI element).

[0099] The hole injection layer having the above-mentioned structure contains an organic compound having a deep HOMO level and a hole transporting property, so the induced holes are easily injected into the hole transport layer and the light emitting layer. Therefore, in the initial stage of operation, it is easy to create a state in which a small part of the holes passes through the light emitting layer and reaches the electron transport layer.

[0100] Here, in a light-emitting device having an electron transport layer containing an organic compound having electron transport properties and an organometallic complex of an alkali metal, a phenomenon is observed in which the electron injection and transport properties of the electron transport layer improve when the light-emitting device is continuously lit. On the other hand, as described above, the hole injection layer adequately suppresses the induction of holes, so it is not possible to 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 that holes will recombine with electrons in the light-emitting layer increases. In other words, during continuous lighting, a shift in the carrier balance occurs such that recombination is more likely to occur in the light-emitting layer. This shift allows for the production of a light-emitting device in which the initial deterioration is suppressed and the deterioration curve has a portion where the luminance increases over time.

[0101] The light-emitting device according to one embodiment of the present invention having the above-described structure can be a light-emitting device with an extremely long life. In particular, the life can be significantly extended in a region in which degradation up to about LT95 is extremely small. Furthermore, a light-emitting device using a compound having a first skeleton having a function of transporting electrons, a second skeleton having a function of accepting holes, and a third skeleton that is a monocyclic and π-electron-deficient heteroaromatic ring as an organic compound having electron transport properties is a light-emitting device with extremely small long-term degradation and further with a long life.

[0102] Furthermore, by being able to suppress initial deterioration, it is possible to significantly reduce the problem of burn-in, which is still discussed as one of the major weaknesses of OLED devices, and the effort required for aging before shipment to reduce this problem.

[0103] The hole transport layer 112 may be a single layer (FIG. 1A), but preferably has a first hole transport layer 112-1 and a second hole transport layer 112-2 (FIG. 1B). Alternatively, the hole transport layer 112 may further have a plurality of hole transport layers.

[0104] The hole-transport layer 112 can be formed using an organic compound having a hole-transport property. The organic compound having a hole-transport property used for the hole-transport layer 112 can be the above-mentioned organic compound having a hole-transport property that can be used as a host material or an organic compound having a hole-transport property that can be used as a composite material.

[0105] When the hole transport layer 112 is formed as a plurality of layers, it is preferable that the HOMO levels of the organic compounds having hole transport properties constituting adjacent hole transport layers are deeper in the organic compound used in the hole transport layer closer to the light emitting layer 113, and the difference therebetween is within 0.2 V.

[0106] In addition, when the hole injection layer 111 is formed of a composite material, the HOMO level of the organic compound having hole transport properties used in the hole transport layer 112 in contact with the hole injection layer 111 is deeper than that of the organic compound having hole transport properties used in the composite material, and the difference therebetween is preferably within 0.2 eV.

[0107] The above-mentioned relationship of the HOMO levels allows holes to be smoothly injected into each layer, preventing an increase in driving voltage and a deficiency of holes in the light-emitting layer.

[0108] It is preferable that the organic compound having hole transport properties used in the hole transport layer 112 has a skeleton having a function of transporting holes. As the skeleton having the function of transporting holes, a carbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton, and an anthracene skeleton, which do not make the HOMO level of the organic compound too shallow, are preferable, and a dibenzofuran skeleton is particularly preferable. In addition, it is preferable that these skeletons are common between adjacent layers in the hole injection layer 111 and the multiple hole transport layers 112, because the injection of holes becomes smooth. It is preferable to use an organic compound having the same hole transport properties between adjacent layers in the hole injection layer 111 and the multiple hole transport layers 112 for the same reason.

[0109] When a plurality of hole transport layers are laminated, 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 function as an electron blocking layer.

[0110] A light-emitting device according to one embodiment of the present invention having the above structure can have an extremely long lifetime.

[0111] Next, examples of other structures and materials of the above-mentioned light-emitting device will be described. As described above, the light-emitting device in this embodiment has an EL layer 103 consisting of a plurality of layers between a pair of electrodes, an anode 101 and a cathode 102, and the EL layer 103 includes at least an emitting layer 113 and an electron transport layer 114 from the anode 101 side. The layers included in the EL layer 103 can have various layer structures such as a hole injection layer, a hole transport layer, an electron injection layer, a carrier block layer, an exciton block layer, and a charge generation layer.

[0112] The anode 101 is preferably formed using a metal, alloy, conductive compound, or mixture thereof having a large work function (specifically, 4.0 eV or more). Specific examples include indium oxide-tin oxide (ITO), indium oxide-tin oxide containing silicon or silicon oxide, indium oxide-zinc oxide, and indium oxide containing tungsten oxide and zinc oxide (IWZO). These conductive metal oxide films are usually formed by a sputtering method, but may be formed by applying a sol-gel method or the like. As an example of a method for forming the indium oxide-zinc oxide, there is a method for forming the indium oxide-zinc oxide by a sputtering method using a target containing 1 to 20 wt % zinc oxide added to indium oxide. In addition, indium oxide containing tungsten oxide and zinc oxide (IWZO) can also be formed by a sputtering method 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), and nitrides of metal materials (for example, titanium nitride). Graphene can also be used. Note that here, typical substances having a large work function and used to form an anode are listed. However, in one embodiment of the present invention, a composite material containing an organic compound having a hole-transporting property and a substance showing an electron-accepting property with respect to the organic compound is used for the hole-injection layer 111, and therefore an electrode material can be selected regardless of the work function.

[0113] Hole injection layer 111, hole transport layer 112 (first hole transport layer 112-1, second hole transport layer 112-2), light emitting layer 113 and electron transport layer 114 have already been described in detail, so repeated description will be omitted.

[0114] Between the electron transport layer 114 and the cathode 102, an electron injection layer 115 is formed using lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF 2 The electron injection layer 115 may be a layer containing an alkali metal or alkaline earth metal, such as ZnO, ZnSe, or a compound thereof. The electron injection layer 115 may be a layer made of a substance having an electron transporting property and containing an alkali metal or alkaline earth metal, or a compound thereof, or an electride. Examples of the electride include a substance in which electrons are added at a high concentration to a mixed oxide of calcium and aluminum.

[0115] Alternatively, a charge generation layer may be provided between the electron transport layer 114 and the cathode 102 instead of the electron injection layer 115. The charge generation layer is a layer capable of injecting holes into a layer in contact with the cathode side of the layer and electrons into a layer in contact with the anode side of the layer by applying a potential. The charge generation layer includes at least a P-type layer. The P-type layer is preferably formed using the composite material listed above as a material capable of forming the hole injection layer 111. The P-type layer may be formed by laminating a film containing the acceptor material described above as a material constituting the composite material and a film containing an organic compound having hole transport properties. By applying a potential to the P-type layer, electrons are injected into the electron transport layer and holes are injected into the cathode 102, which is the cathode, and the light-emitting device operates.

[0116] In addition, the charge generating layer preferably includes, in addition to the P-type layer, either one or both of an electron relay layer and an electron injection buffer layer.

[0117] The electron relay layer contains at least a substance having electron transport properties, and has a function of preventing interaction between the electron injection buffer layer and the P-type layer and smoothly transferring electrons. The LUMO level of the substance having electron transport properties contained in the electron relay layer is preferably between the LUMO level of the electron accepting substance in the P-type layer and the LUMO level of the substance contained in the layer in contact with the charge generating layer in the electron transport layer 114. The specific energy level of the LUMO level of the substance having electron transport properties used in the electron relay layer is -5.0 eV or more, preferably -5.0 eV or more and -3.0 eV or less. Note that, as the substance having electron transport properties used in the electron relay layer, it is preferable to use a phthalocyanine-based material or a metal complex having a metal-oxygen bond and an aromatic ligand.

[0118] The electron injection buffer layer can be made of a material with high electron injection properties, 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)).

[0119] In addition, when the electron injection buffer layer is formed containing a substance having an electron transporting property and an electron donating substance, as the electron donating substance, 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)) can be used, as well as organic compounds such as tetrathianaphthacene (abbreviation: TTN), nickelocene, and decamethylnickelocene. Note that the substance having an electron transporting property can be formed using a material similar to the material constituting the electron transporting layer 114 described above.

[0120] As a material for forming the cathode 102, metals, alloys, electrically conductive compounds, and mixtures thereof having a small work function (specifically, 3.8 eV or less) can be used. Specific examples of such cathode materials include alkali metals such as lithium (Li) and cesium (Cs), elements belonging to Group 1 or Group 2 of the periodic table such as magnesium (Mg), calcium (Ca), and strontium (Sr), and alloys containing these (MgAg, AlLi), rare earth metals such as europium (Eu), ytterbium (Yb), and alloys containing these. However, by providing an electron injection layer between the cathode 102 and the electron transport layer, various conductive materials such as Al, Ag, ITO, indium oxide-tin oxide containing silicon or silicon oxide can be used as the cathode 102 regardless of the magnitude of the work function. These conductive materials can be formed into a film by a dry method such as a vacuum deposition method or a sputtering method, an inkjet method, a spin coating method, etc. Also, they may be formed by a wet method using a sol-gel method, or may be formed by a wet method using a paste of a metal material.

[0121] Note that various methods, whether dry or wet, can be used to form the EL layer 103. For example, vacuum deposition, gravure printing, offset printing, screen printing, inkjet printing, spin coating, or the like may be used.

[0122] Moreover, the above-mentioned electrodes or layers may be formed using different film formation methods.

[0123] The configuration of the layer provided between the anode 101 and the cathode 102 is not limited to the above. However, a configuration in which a light-emitting region where holes and electrons recombine is provided at a position away from the anode 101 and the cathode 102 is preferable so as to suppress quenching caused by the proximity of the light-emitting region to metals used in the electrodes and the carrier injection layer.

[0124] In addition, the hole transport layer and electron transport layer in contact with the light-emitting layer 113, particularly the carrier transport layer close to the recombination region in the light-emitting layer 113, are preferably composed of a substance having a band gap larger than the band gap 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.

[0125] Next, an embodiment of a light-emitting device having a configuration in which a plurality of light-emitting units are stacked (also called a stacked element or a tandem element) will be described with reference to FIG. 1C. This light-emitting device has a plurality of light-emitting units between an anode and a cathode. One light-emitting unit has a configuration almost similar to that of the EL layer 103 shown in FIG. 1A or FIG. 1B. In other words, the light-emitting device shown in FIG. 1C is a light-emitting device having a plurality of light-emitting units, and the light-emitting devices shown in FIG. 1A and FIG. 1B can be said to be light-emitting devices having one light-emitting unit.

[0126] 1C, a first light-emitting unit 511 and a second light-emitting unit 512 are laminated between an anode 501 and a 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 the cathode 502 correspond to the anode 101 and the cathode 102 in FIG. 1A, respectively, and the same as those described in the description of FIG. 1A can be applied. In addition, the first light-emitting unit 511 and the second light-emitting unit 512 may have the same configuration or different configurations.

[0127] Charge generation layer 513 has a function of injecting electrons into one light-emitting unit and injecting holes into the other light-emitting unit when a voltage is applied between anode 501 and cathode 502. That is, when a voltage is applied so that the potential of the anode is higher than the potential of the cathode in FIG. 1C, charge generation layer 513 only needs to inject electrons into first light-emitting unit 511 and inject holes into second light-emitting unit 512.

[0128] The charge generation layer 513 is preferably formed in the same structure as the charge generation layer described in FIG. 1B. A composite material of an organic compound and a metal oxide has excellent carrier injection and carrier transport properties, and therefore can realize low voltage driving and low current driving. When the anode side surface of the light emitting unit is in contact with the charge generation layer 513, the charge generation layer 513 can also play the role of the hole injection layer of the light emitting unit, so that the light emitting unit does not need to be provided with a hole injection layer.

[0129] Furthermore, when an electron injection buffer layer is provided in the charge generating layer 513, the electron injection buffer layer plays the role of an electron injection layer in the light emitting unit on the anode side, so that it is not necessarily necessary to form an electron injection layer in the light emitting unit on the anode side.

[0130] Although the light-emitting device having two light-emitting units has been described in Fig. 1C, the present invention can be applied to a light-emitting device having three or more light-emitting units stacked in the same manner. By disposing a plurality of light-emitting units between a pair of electrodes and separating them with a charge generating layer 513 as in the light-emitting device according to the present embodiment, it is possible to realize an element that can emit light with high brightness while keeping the current density low and has a long life. In addition, it is possible to realize a light-emitting device that can be driven at a low voltage and consumes low power.

[0131] Moreover, by making the emission colors of the respective light-emitting units different, it is possible to obtain light emission of a desired color as the whole light-emitting device. For example, in a light-emitting device having two light-emitting units, it is possible to obtain a light-emitting device that emits white light as the whole light-emitting device by obtaining red and green emission colors in the first light-emitting unit and blue emission color in 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 used 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. The tandem type device can obtain white light emission like the above-mentioned light-emitting device.

[0132] In addition, each layer and electrode such as the above-mentioned EL layer 103, the first light-emitting unit 511, the second light-emitting unit 512, and the charge generation layer can be formed by using, for example, a deposition method (including a vacuum deposition method), a droplet discharge method (also called an ink-jet method), a coating method, a gravure printing method, etc. In addition, they may contain a low molecular weight material, a medium molecular weight material (including an oligomer and a dendrimer), or a polymer material.

[0133] (Embodiment 2) In this embodiment, a light emitting apparatus using the light emitting device described in Embodiment 1 will be described.

[0134] In this embodiment, a light-emitting device manufactured using the light-emitting device described in Embodiment 1 will be described with reference to FIG. 2. FIG. 2A is a top view showing the light-emitting device, and FIG. 2B is a cross-sectional view taken along the lines AB and CD in FIG. 2A. This light-emitting device includes a driver circuit section (source line driver circuit) 601, a pixel section 602, and a driver circuit section (gate line driver circuit) 603, all of which are shown by dotted lines, for controlling the light emission of the light-emitting device. Reference numeral 604 denotes a sealing substrate, 605 denotes a sealant, and the inside surrounded by the sealant 605 defines a space 607.

[0135] The lead wiring 608 is a wiring for transmitting signals input to the source line driving circuit 601 and the gate line driving circuit 603, and receives a video signal, a clock signal, a start signal, a reset signal, and the like from an FPC (flexible printed circuit) 609 serving as an external input terminal. Although only an FPC is shown here, a printed wiring 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 a state in which an FPC or a PWB is attached to it.

[0136] Next, the cross-sectional structure will be described with reference to Fig. 2B. A driver circuit section and a pixel section are formed on an element substrate 610, and here, a source line driver circuit 601, which is the driver circuit section, and one pixel in a pixel section 602 are shown.

[0137] The element substrate 610 may be made of a substrate made of glass, quartz, organic resin, metal, alloy, semiconductor, or a plastic substrate made of FRP (Fiber Reinforced Plastics), PVF (Polyvinyl fluoride), polyester, acrylic, or the like.

[0138] The structure of the transistor used in the pixel or the driver circuit is not particularly limited. For example, the transistor may be an inverted staggered type transistor or a staggered type transistor. In addition, the transistor may be a top-gate type transistor or a bottom-gate type transistor. The semiconductor material used for the transistor is not particularly limited, and for example, silicon, germanium, silicon carbide, gallium nitride, or the like may be used. Alternatively, an oxide semiconductor containing at least one of indium, gallium, and zinc, such as an In-Ga-Zn-based metal oxide, may be used.

[0139] The crystallinity of a semiconductor material used for a transistor is not particularly limited, and any of an amorphous semiconductor and a crystalline semiconductor (a microcrystalline semiconductor, a polycrystalline semiconductor, a single crystal semiconductor, or a semiconductor having a crystalline region in a part) may be used. The use of a crystalline semiconductor is preferable because it can suppress deterioration of transistor characteristics.

[0140] Here, in addition to the transistors provided in the pixels and driver circuits, an oxide semiconductor is preferably used for semiconductor devices such as transistors used in touch sensors, which will be described later. In particular, an oxide semiconductor having a wider band gap than silicon is preferably used. By using an oxide semiconductor having a wider band gap than silicon, the current in the off state of the transistor can be reduced.

[0141] The oxide semiconductor preferably contains at least indium (In) or zinc (Zn), and more preferably contains an oxide represented by In-M-Zn oxide (M is a metal such as Al, Ti, Ga, Ge, Y, Zr, Sn, La, Ce, or Hf).

[0142] Here, an oxide semiconductor that can be used in one embodiment of the present invention is described below.

[0143] Oxide semiconductors are classified into single-crystal oxide semiconductors and non-single-crystal oxide semiconductors other than those mentioned above. Examples of non-single-crystal oxide semiconductors include c-axis aligned crystalline oxide semiconductors (CAAC-OS), polycrystalline oxide semiconductors, nano crystalline oxide semiconductors (nc-OS), amorphous-like oxide semiconductors (a-like OS), and amorphous oxide semiconductors.

[0144] CAAC-OS has a c-axis orientation and a distorted crystal structure in which multiple nanocrystals are connected in the ab-plane direction. The distortion refers to a portion where the lattice orientation changes between a region with a uniform lattice arrangement and a region with a different uniform lattice arrangement in the region where multiple nanocrystals are connected.

[0145] Nanocrystals are basically hexagonal, but may be non-regular hexagonal. In addition, the lattice arrangement may be pentagonal or heptagonal due to the distortion. It is difficult to confirm clear grain boundaries in CAAC-OS even near the distortion. In other words, it is found that the formation of grain boundaries is suppressed by the distortion of the lattice arrangement. This is because CAAC-OS can tolerate distortion due to the lack of dense arrangement of oxygen atoms in the ab-plane direction and the change in the bond distance between atoms due to the substitution of metal elements.

[0146] CAAC-OS also tends to have a layered crystal structure (also referred to as a layered structure) in which a layer containing indium and oxygen (hereinafter, In layer) and a layer containing element M, zinc, and oxygen (hereinafter, (M, Zn) layer) are stacked. Note that indium and element M can be substituted for each other, and when element M in an (M, Zn) layer is substituted for indium, it can also be expressed as an (In, M, Zn) layer. When indium in an In layer is substituted for element M, it can also be expressed as an (In, M) layer.

[0147] CAAC-OS is an oxide semiconductor with high crystallinity. On the other hand, it is difficult to identify clear crystal boundaries in CAAC-OS, so it can be said that the decrease in electron mobility caused by crystal boundaries is unlikely to occur. In addition, the crystallinity of oxide semiconductors can be decreased by the introduction of impurities or the generation of defects. Therefore, CAAC-OS is not prone to impurities or defects (oxygen vacancies (V O The oxide semiconductor having the CAAC-OS has stable physical properties. Therefore, the oxide semiconductor having the CAAC-OS has high heat resistance and reliability.

[0148] The nc-OS has periodic atomic arrangement in a microscopic region (for example, a region of 1 nm to 10 nm, particularly a region of 1 nm to 3 nm). In addition, the nc-OS does not show regularity in the crystal orientation between different nanocrystals. Therefore, no orientation is seen throughout the film. Therefore, depending on the analysis method, the nc-OS may be indistinguishable from an a-like OS or an amorphous oxide semiconductor.

[0149] Indium-gallium-zinc oxide (hereinafter, IGZO), a type of oxide semiconductor containing indium, gallium, and zinc, may have a stable structure when made into the above-mentioned nanocrystals. In particular, since IGZO tends to have difficulty in crystal growth in the air, it may be structurally more stable when made into small crystals (for example, the above-mentioned nanocrystals) rather than large crystals (here, crystals of several mm or several cm).

[0150] The a-like OS is an oxide semiconductor having a structure between the nc-OS and an amorphous oxide semiconductor. The a-like OS has a pore or low-density region. That is, the a-like OS has lower crystallinity than the nc-OS and CAAC-OS.

[0151] Oxide semiconductors have a variety of structures and have different characteristics. The oxide semiconductor of one embodiment of the present invention may include two or more of an amorphous oxide semiconductor, a polycrystalline oxide semiconductor, an a-like OS, an nc-OS, and a CAAC-OS.

[0152] As an alternative to the oxide semiconductor, a cloud-aligned composite (CAC)-OS may be used.

[0153] CAC-OS is a material in which some of the material has a conductive function and some of the material has an insulating function, and the material as a whole functions as a semiconductor. When CAC-OS is used in the active layer of a transistor, the conductive function is a function of allowing electrons (or holes) to flow as carriers, and the insulating function is a function of not allowing electrons to flow as carriers. By making the conductive function and the insulating function act in a complementary manner, it is possible to give the CAC-OS a switching function (on / off function). By separating the respective functions in CAC-OS, it is possible to maximize both functions.

[0154] The CAC-OS has a conductive region and an insulating region. The conductive region has the above-mentioned conductive function, and the insulating region has the above-mentioned insulating function. In the material, the conductive region and the insulating region may be separated at the nanoparticle level. In addition, the conductive region and the insulating region may be unevenly distributed in the material. In addition, the conductive region may be observed to be connected in a cloud shape with a blurred periphery.

[0155] In addition, in the CAC-OS, the conductive regions and the insulating regions may each be dispersed in the material with a size of 0.5 nm or more and 10 nm or less, preferably 0.5 nm or more and 3 nm or less.

[0156] In addition, the CAC-OS is composed of components having different band gaps. For example, the CAC-OS is composed of a component having a wide gap due to an insulating region and a component having a narrow gap due to a conductive region. In this configuration, when carriers are caused to flow, the carriers mainly flow in the component having the narrow gap. In addition, the component having the narrow gap acts complementarily to the component having the wide gap, and carriers also flow in the component having the wide gap in conjunction with the component having the narrow gap. Therefore, when the above-mentioned CAC-OS is used in the channel formation region of a transistor, a high current driving force, that is, a large on-current and a high field effect mobility can be obtained in the on-state of the transistor.

[0157] That is, CAC-OS can also be called a matrix composite or a metal matrix composite.

[0158] By using the above-described oxide semiconductor material for the semiconductor layer, a change in electrical characteristics can be suppressed, and a highly reliable transistor can be realized.

[0159] In addition, the transistor having the above-mentioned semiconductor layer can hold charge accumulated in a capacitance through the transistor for a long period of time due to its low off-state current. By applying such a transistor to a pixel, it is possible to stop a driver circuit while maintaining the gray level of an image displayed in each display region. As a result, an electronic device with extremely low power consumption can be realized.

[0160] It is preferable to provide an undercoat film in order to stabilize the characteristics of the transistor. The undercoat film can be prepared as a single layer or a multilayer structure using an inorganic insulating film such as a silicon oxide film, a silicon nitride film, a silicon oxynitride film, or a silicon nitride oxide film. The undercoat film can be formed by a sputtering method, a CVD (Chemical Vapor Deposition) method (such as a plasma CVD method, a thermal CVD method, or a MOCVD (Metal Organic CVD) method), an ALD (Atomic Layer Deposition) method, a coating method, a printing method, or the like. Note that the undercoat film need not be provided if it is not necessary.

[0161] The FET 623 indicates one of the transistors formed in the driving circuit section 601. The driving circuit may be formed of various CMOS circuits, PMOS circuits, or NMOS circuits. Although the present embodiment shows a driver-integrated type in which the driving circuit is formed on a substrate, this is not necessarily required, and the driving circuit may be formed externally instead of on the substrate.

[0162] In addition, the pixel section 602 is formed of a plurality of pixels including a switching FET 611, a current control FET 612, and an anode 613 electrically connected to the drain of the FET 612. However, the present invention is not limited to this, and the pixel section may be formed by combining three or more FETs and a capacitive element.

[0163] An insulator 614 is formed to cover the end of the anode 613. Here, the insulator 614 can be formed by using a positive type photosensitive acrylic.

[0164] In order to improve the covering ability of an EL layer or the like to be formed later, a curved surface having a curvature is formed at the upper end or lower end of the insulator 614. For example, when a positive type photosensitive acrylic is used as the material of the insulator 614, it is preferable that only the upper end of the insulator 614 has a curved surface having a radius of curvature (0.2 μm to 3 μm). In addition, either a negative type photosensitive resin or a positive type photosensitive resin can be used as the insulator 614.

[0165] An EL layer 616 and a cathode 617 are formed on the anode 613. Here, it is desirable to use a material with a large work function as the material used for the anode 613. For example, in addition to a single layer film such as an ITO film, an indium tin oxide film containing silicon, an indium oxide film containing 2 to 20 wt % zinc oxide, a titanium nitride film, a chromium film, a tungsten film, a Zn film, or a Pt film, a laminated structure of a titanium nitride film and a film mainly composed of aluminum, or a three-layer structure of a titanium nitride film, a film mainly composed of aluminum, and a titanium nitride film, can be used. Note that the laminated structure has low resistance as wiring, provides good ohmic contact, and can further function as an anode.

[0166] The EL layer 616 is formed by various methods such as a deposition method using a deposition mask, an inkjet method, a spin coating method, etc. The EL layer 616 includes the configuration described in the embodiment 1. Other materials constituting the EL layer 616 may be low molecular weight compounds or high molecular weight compounds (including oligomers and dendrimers).

[0167] Furthermore, it is preferable to use a material having a small work function (such as Al, Mg, Li, Ca, or alloys or compounds thereof (MgAg, MgIn, AlLi, etc.)) as a material used for the cathode 617 formed on the EL layer 616. When the light generated in the EL layer 616 is transmitted through the cathode 617, it is preferable to use a laminate of a thin metal thin film and a transparent conductive film (ITO, indium oxide containing 2 to 20 wt % zinc oxide, indium tin oxide containing silicon, zinc oxide (ZnO), etc.) as the cathode 617.

[0168] Note that a light-emitting device 618 is formed by the anode 613, the EL layer 616, and the cathode 617. This light-emitting device is the light-emitting device described in Embodiment 1. Note that a pixel portion is formed with a plurality of light-emitting devices, but the light-emitting device in this embodiment may include both the light-emitting device described in Embodiment 1 and a light-emitting device having a different structure.

[0169] Furthermore, by bonding the sealing substrate 604 to the element substrate 610 with a sealant 605, a structure is formed in which a light emitting device 618 is provided in a space 607 surrounded by the element substrate 610, the sealing substrate 604, and the sealant 605. The space 607 is filled with a filler, and may be filled with an inert gas (nitrogen, argon, etc.) or a sealant. A recess is formed in the sealing substrate, and a desiccant is provided therein to suppress deterioration due to the influence of moisture, which is a preferable configuration.

[0170] It is preferable to use epoxy resin or glass frit for the sealing material 605. It is also preferable that these materials are as moisture and oxygen impermeable as possible. In addition to glass and quartz substrates, materials that can be used for the sealing substrate 604 include plastic substrates made of FRP (Fiber Reinforced Plastics), PVF (Polyvinyl Fluoride), polyester, acrylic, etc.

[0171] Although not shown in FIG. 2B, a protective film may be provided on the cathode. The protective film may be formed of an organic resin film or an inorganic insulating film. The protective film may be formed so as to cover the exposed portion of the sealant 605. The protective film may be provided so as to cover the surfaces and side surfaces of the pair of substrates, the exposed side surfaces of the sealing layer, the insulating layer, etc.

[0172] The protective film can be made of a material that is difficult for impurities such as water to permeate, and therefore can effectively prevent impurities such as water from diffusing from the outside to the inside.

[0173] The protective film may be made of an oxide, a nitride, a fluoride, a sulfide, a ternary compound, a metal, a polymer, or the like. For example, a material 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, indium oxide, or the like; a material containing aluminum nitride, hafnium nitride, silicon nitride, tantalum nitride, titanium nitride, niobium nitride, molybdenum nitride, zirconium nitride, gallium nitride, or the like; a nitride containing titanium and aluminum; an oxide containing titanium and aluminum; an oxide containing aluminum and zinc; a sulfide containing manganese and zinc; a sulfide containing cerium and strontium; an oxide containing erbium and aluminum; an oxide containing yttrium and zirconium, or the like.

[0174] The protective film is preferably formed using a film formation method with good step coverage. One such method is the atomic layer deposition (ALD) method. 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 with a uniform thickness. In addition, it is possible to reduce damage to the processed member when forming the protective film.

[0175] For example, by forming a protective film using the ALD method, it is possible to form a uniform protective film with few defects on surfaces with complex uneven shapes, as well as on the top, side, and back surfaces of a touch panel.

[0176] In the above manner, a light-emitting device manufactured using the light-emitting device described in Embodiment 1 can be obtained.

[0177] The light-emitting device in this embodiment uses the light-emitting device described in Embodiment 1, and therefore a light-emitting device with good characteristics can be obtained. Specifically, since the light-emitting device described in Embodiment 1 has a long life, the light-emitting device can be a light-emitting device with good reliability. In addition, since the light-emitting device using the light-emitting device described in Embodiment 1 has good emission efficiency, the light-emitting device can be a light-emitting device with low power consumption.

[0178] 3A and 3B show an example of a full-color light-emitting device in which a light-emitting device that emits white light is formed and a colored layer (color filter) is provided, etc. In Fig. 3A, a substrate 1001, a base insulating film 1002, a gate insulating film 1003, gate electrodes 1006, 1007, 1008, a first interlayer insulating film 1020, a second interlayer insulating film 1021, a peripheral section 1042, a pixel section 1040, a driving circuit section 1041, anodes 1024W, 1024R, 1024G, 1024B of the light-emitting device, a partition wall 1025, an EL layer 1028, a cathode 1029 of the light-emitting device, a sealing substrate 1031, a sealant 1032, etc. are shown.

[0179] In FIG. 3A, the colored layers (red colored layer 1034R, green colored layer 1034G, blue colored layer 1034B) are provided on a transparent base material 1033. A black matrix 1035 may be further provided. The transparent base material 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 FIG. 3A, there are light-emitting layers from which light does not pass through the colored layers and goes out, and light-emitting layers from which light passes through the colored layers of each color and goes out. The light that does not pass through the colored layers is white, and the light that passes through the colored layers is red, green, and blue, so that an image can be expressed by four color pixels.

[0180] 3B shows an example in which the 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. In this manner, the colored layers may be provided between the substrate 1001 and the sealing substrate 1031.

[0181] In the light-emitting device described above, the light-emitting device has a structure (bottom emission type) in which light is extracted on the substrate 1001 side on which the FET is formed, but the light-emitting device may have a structure (top emission type) in which light is extracted on the sealing substrate 1031 side. A cross-sectional view of a top emission type light-emitting device is shown in FIG. 4. In this case, a substrate that does not transmit light can be used as the substrate 1001. The process is performed in the same manner as the bottom emission type light-emitting device until a connection electrode that connects the FET and the anode of the light-emitting device is formed. Thereafter, a third interlayer insulating film 1037 is formed to cover the electrode 1022. This insulating film may play a role of 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.

[0182] Although the anodes 1024W, 1024R, 1024G, and 1024B of the light-emitting device are anodes here, they may be formed as cathodes. In addition, in the case of a top-emission type light-emitting device as shown in FIG. 4, it is preferable that the anodes are reflective electrodes. The EL layer 1028 has the same configuration as that described for the EL layer 103 in the first embodiment, and has an element structure that can emit white light.

[0183] In the top emission structure as shown in FIG. 4, sealing can be performed with a sealing substrate 1031 provided with colored layers (a red colored layer 1034R, a green colored layer 1034G, and a blue colored layer 1034B). The sealing substrate 1031 may be provided with a black matrix 1035 so as to be located between pixels. The colored layers (the red colored layer 1034R, the green colored layer 1034G, and the blue colored layer 1034B) and the black matrix may be covered with an overcoat layer 1036. Note that a substrate having light transmissivity is used as the sealing substrate 1031. In addition, although an example of full color display using four colors, red, green, blue, and white, is shown here, the present invention is not particularly limited, and full color display using four colors, red, yellow, green, and blue, or three colors, red, green, and blue, may be used.

[0184] In top-emission type light-emitting devices, the application of a microcavity structure is suitable. A light-emitting device having a microcavity structure can be obtained by using a reflective electrode as the anode and a semi-transmissive / semi-reflective electrode as the cathode. At least an EL layer is present between the reflective electrode and the semi-transmissive / semi-reflective electrode, and at least a light-emitting layer that becomes the light-emitting region is present.

[0185] The reflectance of the reflective electrode to visible light is 40% to 100%, preferably 70% to 100%, and the resistivity is 1×10 -2 The semi-transmitting and semi-reflective electrode has a visible light reflectance of 20% to 80%, preferably 40% to 70%, and a resistivity of 1×10 -2 It is assumed that the film has a resistance of less than Ωcm.

[0186] Light emitted from a light-emitting layer included in the EL layer is reflected by the reflective electrode and the semi-transmissive and semi-reflective electrode, causing resonance.

[0187] In this light-emitting device, the optical distance between the reflective electrode and the semi-transmissive / semi-reflective electrode can be changed by changing the thickness of the transparent conductive film, the above-mentioned composite material, the carrier transport material, etc. This makes it possible to intensify the light of resonating wavelengths and attenuate the light of non-resonating wavelengths between the reflective electrode and the semi-transmissive / semi-reflective electrode.

[0188] In addition, since the light reflected by the reflective electrode and returned (first reflected light) causes significant interference with the light (first incident light) that is directly incident on the semi-transmissive and semi-reflective electrode from the light-emitting layer, 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 equal to or greater than 1, and λ is the wavelength of the emitted light to be amplified). By adjusting the optical distance, the phase of the first reflected light and the first incident light can be aligned, thereby further amplifying the light emitted from the light-emitting layer.

[0189] In the above configuration, the EL layer may have a structure with a plurality of light-emitting layers or a structure with a single light-emitting layer. For example, in combination with the configuration of the tandem light-emitting device described above, it may be applied to a configuration in which a plurality of EL layers are provided with a charge generation layer interposed therebetween in one light-emitting device, and a single or a plurality of light-emitting layers are formed in each EL layer.

[0190] By having a microcavity structure, it is possible to enhance the light emission intensity in the front direction of a specific wavelength, so that power consumption can be reduced. In the case of a light-emitting device that displays an image with four sub-pixels of red, yellow, green, and blue, in addition to the luminance improvement effect due to yellow light emission, a microcavity structure adapted to the wavelength of each color can be applied to all sub-pixels, resulting in a light-emitting device with good characteristics.

[0191] Since the light-emitting device in the present embodiment uses the light-emitting device described in Embodiment 1, a light-emitting device having good characteristics can be obtained. Specifically, since the light-emitting device described in Embodiment 1 has a long lifespan, a light-emitting device with good reliability can be obtained. In addition, since the light-emitting device using the light-emitting device described in Embodiment 1 has good luminous efficiency, it is possible to obtain a light-emitting device with low power consumption.

[0192] (Embodiment 3) In the present embodiment, an example in which the light-emitting device described in Embodiment 1 is used as an illumination device will be described with reference to FIGS. 5A and 5B. FIG. 5B is a top view of the illumination device, and FIG. 5A is a cross-sectional view taken along the line e-f in FIG. 5B.

[0193] In the illumination device in the present embodiment, an anode 401 is formed on a substrate 400 having translucency, which is a support. The anode 401 corresponds to the anode 101 in Embodiment 1. When extracting light emission from the anode 401 side, the anode 401 is formed of a translucent material.

[0194] A pad 412 for supplying a voltage to the cathode 404 is formed on the substrate 400.

[0195] An EL layer 403 is formed on the anode 401. The EL layer 403 corresponds to the configuration of the EL layer 103 in the embodiment 1, or a combination of the light-emitting units 511 and 512 and the charge generation layer 513. For these configurations, see the description thereof.

[0196] A cathode 404 is formed to cover the EL layer 403. The cathode 404 corresponds to the cathode 102 in the first embodiment. When light is extracted from the anode 401 side, the cathode 404 is formed of a material with high reflectivity. The cathode 404 is connected to a pad 412 to supply a voltage.

[0197] As described above, the lighting device described in this embodiment has a light-emitting device including the anode 401, the EL layer 403, and the cathode 404. Since the light-emitting device has high emission efficiency, the lighting device in this embodiment can consume little power.

[0198] The lighting device is completed by adhering and sealing the substrate 400 on which the light emitting device having the above-mentioned configuration is formed and the sealing substrate 407 using the sealants 405 and 406. Either the sealant 405 or 406 may be used. Also, a desiccant may be mixed into the inner sealant 406 (not shown in FIG. 5B), which can adsorb moisture and improve reliability.

[0199] Moreover, the pad 412 and a part of the anode 401 can be extended outside the sealing materials 405 and 406 to serve as an external input terminal. Also, an IC chip 420 equipped with a converter or the like may be provided thereon.

[0200] As described above, the lighting device described in this embodiment uses the light-emitting device described in Embodiment 1 as its EL element, and can be a highly reliable light-emitting device. In addition, the lighting device can be a light-emitting device with low power consumption.

[0201] (Embodiment 4) In this embodiment, an example of an electronic device including the light-emitting device described in embodiment 1 will be described. The light-emitting device described in embodiment 1 has a long life and is a highly reliable light-emitting device. As a result, the electronic device described in this embodiment can be an electronic device having a highly reliable light-emitting portion.

[0202] Examples of electronic devices to which the light-emitting devices are applied include television sets (also called televisions or television receivers), computer monitors, digital cameras, digital video cameras, digital photo frames, mobile phones (also called mobile phones or mobile phone devices), portable game machines, personal digital assistants, audio playback devices, large game machines such as pachinko machines, etc. Specific examples of these electronic devices are shown below.

[0203] 6A illustrates an example of a television set. In the television set, a display portion 7103 is incorporated in a housing 7101. Here, the housing 7101 is supported by a stand 7105. Images can be displayed by the display portion 7103, and the display portion 7103 has the light-emitting devices described in Embodiment 1 arranged in a matrix.

[0204] The television device can be operated using an operation switch provided on the housing 7101 or a separate remote control 7110. Using operation keys 7109 provided on the remote control 7110, the channel and volume can be controlled, and an image displayed on the display portion 7103 can be operated. The remote control 7110 may be provided with a display portion 7107 that displays information output from the remote control 7110.

[0205] The television device is configured to include a receiver, a modem, etc. The receiver can receive general television broadcasts, and by connecting to a wired or wireless communication network via the modem, it is also possible to perform one-way (from sender to receiver) or two-way (between sender and receiver, or between receivers, etc.) information communication.

[0206] FIG. 6B1 shows a computer, which includes a main body 7201, a housing 7202, a display portion 7203, a keyboard 7204, an external connection port 7205, a pointing device 7206, and the like. Note that this computer is manufactured by arranging the light-emitting devices described in Embodiment 1 in a matrix and using them for the display portion 7203. The computer in FIG. 6B1 may have a form as shown in FIG. 6B2. The computer in FIG. 6B2 is provided with a second display portion 7210 instead of the keyboard 7204 and the pointing device 7206. The second display portion 7210 is a touch panel type, and input can be performed by operating the display for input displayed on the second display portion 7210 with a finger or a dedicated pen. The second display portion 7210 can display not only the display for input but also other images. The display portion 7203 may also be a touch panel. The two screens are connected by a hinge, which can prevent the screens from being scratched or broken during storage or transportation.

[0207] 6C shows an example of a mobile terminal. The mobile phone includes a display portion 7402 incorporated in a housing 7401, operation buttons 7403, an external connection port 7404, a speaker 7405, a microphone 7406, and the like. Note that the mobile phone 7400 includes the display portion 7402 in which the light-emitting devices described in Embodiment 1 are arranged in a matrix.

[0208] 6C can be configured so that information can be input by touching the display portion 7402 with a finger or the like. In this case, operations such as making a call or composing an e-mail can be performed by touching the display portion 7402 with a finger or the like.

[0209] The screen of the display unit 7402 has three main modes. The first is a display mode that is mainly for displaying images, the second is an input mode that is mainly for inputting information such as characters, and the third is a display + input mode that combines the display mode and the input mode.

[0210] For example, when making a call or composing an e-mail, the display portion 7402 may be set to a character input mode mainly for inputting characters, and the character input operation may be performed by inputting characters 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 portion 7402.

[0211] In addition, by providing a detection device having a sensor for detecting tilt, such as a gyro or an acceleration sensor, inside the mobile terminal, the orientation of the mobile terminal (portrait or landscape) can be determined and the screen display of the display portion 7402 can be automatically switched.

[0212] The screen mode can be switched by touching the display portion 7402 or by operating operation buttons 7403 on the housing 7401. The mode can also be switched depending on the type of image displayed on the display portion 7402. For example, if the image signal to be displayed on the display portion is moving image data, the mode is switched to the display mode, and if it is text data, the mode is switched to the input mode.

[0213] In addition, in the input mode, a signal detected by an optical sensor of the display portion 7402 may be detected, and if there is no input by a touch operation on the display portion 7402 for a certain period of time, the screen mode may be controlled to be switched from the input mode to the display mode.

[0214] The display portion 7402 can also function as an image sensor. For example, personal authentication can be performed by touching the display portion 7402 with a palm or a finger to capture an image of a palm print, a fingerprint, or the like. In addition, finger veins, palm veins, or the like can be captured by using a backlight that emits near-infrared light or a sensing light source that emits near-infrared light for the display portion.

[0215] Note that the structure described in this embodiment mode can be used by appropriately combining the structures described in any of Embodiment Modes 1 to 3.

[0216] As described above, the light-emitting device having the light-emitting device described in embodiment 1 can be applied to a wide range of electronic devices in various fields. By using the light-emitting device described in embodiment 1, a highly reliable electronic device can be obtained.

[0217] FIG. 7A is a schematic diagram showing an example of a cleaning robot.

[0218] The cleaning robot 5100 has a display 5101 arranged on the top surface, a plurality of cameras 5102 arranged on the side surface, a brush 5103, and an operation button 5104. Although not shown, the bottom surface of the cleaning robot 5100 is provided with tires, a suction port, etc. The cleaning robot 5100 also has various sensors such as an infrared sensor, an ultrasonic sensor, an acceleration sensor, a piezoelectric sensor, an optical sensor, and a gyro sensor. The cleaning robot 5100 also has wireless communication means.

[0219] The cleaning robot 5100 can move by itself, detect dirt 5120, and suck up the dirt from a suction port provided on the bottom surface.

[0220] In addition, the cleaning robot 5100 can analyze the image captured by the camera 5102 and determine the presence or absence of obstacles such as walls, furniture, steps, etc. Furthermore, when an object that may become entangled in the brush 5103, such as a wire, is detected by image analysis, the rotation of the brush 5103 can be stopped.

[0221] The remaining battery level, the amount of sucked up dirt, etc. can be displayed on the display 5101. The route traveled by the cleaning robot 5100 may be displayed on the display 5101. The display 5101 may be a touch panel, and an operation button 5104 may be provided on the display 5101.

[0222] 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 know the state of the room even when he or she is away from home. Also, the display on the display 5101 can be confirmed on a portable electronic device such as a smartphone.

[0223] The light-emitting device according to one embodiment of the present invention can be used for the display 5101 .

[0224] The robot 2100 shown in FIG. 7B includes a computing device 2110, an illuminance sensor 2101, a microphone 2102, an upper camera 2103, a speaker 2104, a display 2105, a lower camera 2106, an obstacle sensor 2107, and a movement mechanism 2108.

[0225] The microphone 2102 has a function of detecting the user's voice, environmental sounds, etc. The speaker 2104 has a function of emitting sound. The robot 2100 can communicate with the user using the microphone 2102 and the speaker 2104.

[0226] The display 2105 has a function of displaying various kinds of information. The robot 2100 can display 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 removable information terminal, and by installing it in a fixed position on the robot 2100, charging and data transfer are possible.

[0227] The upper camera 2103 and the lower camera 2106 have a function of capturing images of the surroundings of the robot 2100. In addition, the obstacle sensor 2107 can detect the presence or absence of an obstacle in the moving direction when the robot 2100 moves forward using the moving mechanism 2108. The robot 2100 can recognize the surrounding environment and move safely using the upper camera 2103, the lower camera 2106, and the obstacle sensor 2107. The light-emitting device of one embodiment of the present invention can be used for the display 2105.

[0228] 7C is a diagram showing an example of a goggle-type display. The goggle-type display includes, for example, a housing 5000, a display unit 5001, a speaker 5003, an LED lamp 5004, a connection terminal 5006, a sensor 5007 (including a function for measuring force, displacement, position, speed, acceleration, angular velocity, rotation speed, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient, vibration, odor, or infrared), a microphone 5008, a display unit 5002, a support unit 5012, and an earphone 5013.

[0229] The light-emitting device of one embodiment of the present invention can be used for the display portion 5001 and the second display portion 5002 .

[0230] 8 shows an example in which the light-emitting device described in Embodiment 1 is used in a desk lamp, which is a lighting device. The desk lamp shown in FIG. 8 has a housing 2001 and a light source 2002, and the lighting device described in Embodiment 2 may be used as the light source 2002.

[0231] FIG. 9 shows an example in which the light-emitting device described in Embodiment 1 is used as an indoor lighting device 3001. Since the light-emitting device described in Embodiment 1 is a highly reliable light-emitting device, it can be used as a highly reliable lighting device. In addition, since the light-emitting device described in Embodiment 1 can be made large in area, it can be used as a large-area lighting device. In addition, since the light-emitting device described in Embodiment 1 is thin, it can be used as a thin lighting device.

[0232] The light-emitting device described in Embodiment 1 can also be mounted on a windshield or dashboard of an automobile. Fig. 10 shows an example in which the light-emitting device described in Embodiment 1 is used on a windshield or dashboard of an automobile. Display regions 5200 to 5203 are displays provided using the light-emitting device described in Embodiment 1.

[0233] A display region 5200 and a display region 5201 are display devices equipped with the light-emitting device described in embodiment 1, which is provided on the windshield of an automobile. The light-emitting device described in embodiment 1 can be a so-called see-through display device in which the opposite side can be seen through by fabricating the anode and cathode with light-transmitting electrodes. If the display is in a see-through state, the display device can be installed on the windshield of an automobile without interfering with the view. When a transistor for driving is provided, a light-transmitting transistor such as an organic transistor made of an organic semiconductor material or a transistor using an oxide semiconductor is preferably used.

[0234] A display area 5202 is a display device provided on a pillar and equipped with the light-emitting device described in Embodiment 1. By projecting an image from an imaging means provided on the vehicle body onto the display area 5202, the view blocked by the pillar can be complemented. Similarly, a display area 5203 provided on the dashboard can complement the view blocked by the vehicle body by projecting an image from an imaging means provided on the outside of the vehicle, thereby compensating for blind spots and improving safety. By projecting an image to complement the invisible parts, safety can be confirmed more naturally and without discomfort.

[0235] The display area 5203 can also provide various information by displaying navigation information, a speedometer, a tachometer, a mileage, a fuel gauge, a gear status, air conditioning settings, and the like. The display items and layout can be changed as appropriate to suit the user's preferences. Note that this information can also be provided in the display areas 5200 to 5202. The display areas 5200 to 5203 can also be used as lighting devices.

[0236] 11A to 11C show a foldable mobile information terminal 9310. Fig. 11A shows the mobile information terminal 9310 in an unfolded state. Fig. 11B shows the mobile information terminal 9310 in a state in the process of changing from one of the unfolded state and the folded state to the other. Fig. 11C shows the mobile information terminal 9310 in a folded state. The mobile information terminal 9310 has excellent portability in the folded state, and has excellent viewability of the display due to a seamless wide display area in the unfolded state.

[0237] The display panel 9311 is supported by three housings 9315 connected by hinges 9313. Note that the display panel 9311 may be a touch panel (input / output device) equipped with a touch sensor (input device). The display panel 9311 can be reversibly transformed from an unfolded state of the mobile information terminal 9310 to a folded state by bending the two housings 9315 via the hinges 9313. The light-emitting device of one embodiment of the present invention can be used for the display panel 9311.

[0238] 12A and 12B show a foldable mobile information terminal 5150. The foldable mobile information terminal 5150 has a housing 5151, a display area 5152, and a bending portion 5153. Fig. 12A shows the mobile information terminal 5150 in an unfolded state. Fig. 12B shows the mobile information terminal in a folded state. Although the mobile information terminal 5150 has a large display area 5152, it is compact and highly portable when folded.

[0239] 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, and when folding, the expandable member stretches. The bending portion 5153 is folded with a curvature radius of 2 mm or more, preferably 3 mm or more.

[0240] Note that the display region 5152 may be a touch panel (input / output device) equipped with a touch sensor (input device). The light-emitting device of one embodiment of the present invention can be used for the display region 5152. EXAMPLES

[0241] Example 1 This example describes methods for fabricating a light-emitting device 1 and a comparative light-emitting device 2 which are light-emitting devices according to one embodiment of the present invention, and a comparative light-emitting device 1. The structural formulae of materials used in this example are shown below.

[0242] [ka]

[0243] <How to make light-emitting device 1> First, indium tin oxide containing silicon oxide (ITSO) was formed on a glass substrate by sputtering to form an anode 101. The thickness of the anode was 70 nm, and the electrode area was 4 mm2. 2 (2mm x 2mm).

[0244] Next, as a pretreatment for forming a light-emitting device on the 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.

[0245] Then, 10 -4 The substrate was introduced into a vacuum deposition apparatus whose inside had been reduced in pressure to about Pa, and vacuum baking was carried out at 170° C. for 30 minutes in a heating chamber in the vacuum deposition apparatus, and then the substrate was allowed to cool for about 30 minutes.

[0246] Next, the substrate on which the anode 101 was formed was fixed to a substrate holder provided in a vacuum deposition apparatus so that the surface on which the anode 101 was formed faced downward. 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 an electron acceptor material (OCHD-001) were co-deposited on the anode 101 by a deposition method using resistance heating to a thickness of 10 nm in a mass ratio of 1:0.1 (=BBABnf:OCHD-001), to form a hole injection layer 111.

[0247] Next, BBABnf was deposited on the hole injection layer 111 to a thickness of 20 nm as a first hole transport layer 112-1, and then 3,3'-(naphthalene-1,4-diyl)bis(9-phenyl-9H-carbazole (abbreviation: PCzN2) represented by the above structural formula (ii) was deposited on the hole injection layer 111 to a thickness of 10 nm as a second hole transport layer 112-2 to form the hole transport layer 112. Note that the second hole transport layer 112-2 also functions as an electron blocking layer.

[0248] Next, 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-deposited to a thickness of 25 nm in a mass ratio of 1:0.015 (=αN-βNPAnth:3,10PCA2Nbf(IV)-02) to form the light-emitting layer 113.

[0249] Thereafter, OCET010 and 8-hydroxyquinolinato-lithium (abbreviation: Liq) represented by the above structural formula (v) were co-deposited on the light-emitting layer 113 to a thickness of 12.5 nm so as to have a mass ratio of 1:2 (=OCET010:Liq), and then co-deposited on the light-emitting layer 113 to a thickness of 12.5 nm so as to have a mass ratio of 2:1 (=OCET010:Liq) to form the electron-transporting layer 114. Note that OCET010 is an organic compound having electron-transporting properties.

[0250] After forming the electron transport layer 114, Liq was evaporated to a thickness of 1 nm to form the electron injection layer 115, and then aluminum was evaporated to a thickness of 200 nm as the cathode 102 to produce the light-emitting device 1 of this embodiment.

[0251] <How to make light-emitting device 2> Light-emitting device 2 was prepared in the same manner as light-emitting device 1, except that OCET010 in light-emitting device 1 was replaced with 2,9-di(2-naphthyl)-4,7-diphenyl-1,10-phenanthroline (abbreviation: NBPhen) represented by the above structural formula (vi).

[0252] <How to make comparative light-emitting device 1> Comparative light-emitting device 1 was prepared in the same manner as light-emitting device 1, except that OCET010 in light-emitting device 1 was changed to αN-βNPAnth represented by the above structural formula (iii).

[0253] The device structures of light-emitting device 1, light-emitting device 2 and comparative light-emitting device 1 are summarized in the table below.

[0254] [Table 1]

[0255] These light-emitting devices were sealed with a glass substrate in a nitrogen-atmosphere glove box so that the light-emitting devices would not be exposed to the atmosphere (a sealant was applied around the elements, and UV treatment was performed during sealing, followed by heat treatment at 80°C for 1 hour), after which the initial characteristics and reliability of Light-emitting Device 1, Light-emitting Device 2, and Comparative Light-emitting Device 1 were measured. The measurements were performed at room temperature.

[0256] The luminance-current density characteristics of light-emitting device 1, light-emitting device 2, and comparative light-emitting device 1 are shown in Fig. 13, the current efficiency-luminance characteristics in Fig. 14, the luminance-voltage characteristics in Fig. 15, the current-voltage characteristics in Fig. 16, the external quantum efficiency-luminance characteristics in Fig. 17, and the emission spectra in Fig. 18. The 1000 cd / m 2 The main characteristics of the area are shown in Table 2.

[0257] [Table 2]

[0258] 13 to 18 and Table 2 show that all three devices were blue light-emitting devices with good initial characteristics.

[0259] In addition, the current density is 50mA / cm 2 19 is a graph showing the change in luminance with respect to the driving time in the light-emitting device 1. As shown in FIG. 19, it was found that the light-emitting device 1 and the light-emitting device 2, which are light-emitting devices according to one embodiment of the present invention, have a longer lifetime than the comparative light-emitting device 1. In particular, the light-emitting device 1 has a longer lifetime because the luminance increases at the beginning of driving. Furthermore, the light-emitting device 2 has a small slope of long-term deterioration and is durable for long-term driving.

[0260] Here, the results of investigating the photoluminescence properties of the materials used in the electron transport layer in each device are shown. A fluorometer (FS920, manufactured by Hamamatsu Photonics) or a fluorometer (FP-8600, manufactured by JASCO Corporation) was used for the measurements. Figure 20 shows the emission spectra of the OCET010Q film, Liq film, and mixed film in which OCET010 and Liq were mixed at a 1:1 (mass ratio) used in the light-emitting device 1, Figure 21 shows the emission spectra of the NBPhen film, Liq film, and mixed film in which NBPhen and Liq were mixed at a 1:1 (mass ratio) used in the light-emitting device 2, and Figure 22 shows the emission spectra of the αN-βNPAnth film, Liq film, and mixed film in which αN-βNPAnth and Liq were mixed at a 1:1 (mass ratio) used in the comparative light-emitting device 1.

[0261] As shown in Fig. 20, the emission spectrum of the mixed film in which OCET010 and Liq were mixed at a ratio of 1:1 (mass ratio) is significantly shifted to the long wavelength side compared to the emission spectra of the OCET010 film and the Liq film, suggesting that OCET010 and Liq form an exciplex. Similarly, Fig. 21 suggests that NBPhen and Liq form an exciplex. On the other hand, in Fig. 22, the spectrum of the mixed film of αN-βNPAnth and Liq is somewhat broadened to the long wavelength side, but is almost the same as the spectrum of Liq, so it is considered that an exciplex is not formed.

[0262] In addition, an exciplex is formed by the interaction of the molecular orbitals of two substances, and the exciplex is said to emit light having a peak at a wavelength corresponding to the difference between the shallower HOMO level and the deeper LUMO level of the two substances.

[0263] The HOMO level and the LUMO level can be calculated based on cyclic voltammetry (CV) measurements.

[0264] The measurement device used was an electrochemical analyzer (manufactured by BAS Co., Ltd., model number: ALS model 600A or 600C). The solution used for CV measurement was prepared by dissolving the supporting electrolyte tetra-n-butylammonium perchlorate (n-Bu4NClO4) (manufactured by Tokyo Chemical Industry Co., Ltd., catalog number: T0836) in dehydrated dimethylformamide (DMF) (manufactured by Aldrich Co., Ltd., 99.8%, catalog number: 22705-6) to a concentration of 100 mmol / L, and further dissolving the measurement target to a concentration of 2 mmol / L. A platinum electrode (PTE platinum electrode, BAS Co., Ltd.) was used as the working electrode, a platinum electrode (Pt counter electrode (5 cm) for VC-3, BAS Co., Ltd.) was used as the auxiliary electrode, and an Ag / Ag+ electrode (RE7 non-aqueous solvent reference electrode, BAS Co., Ltd.) was used as the reference electrode. The measurements were performed at room temperature (20-25°C). The scan rate during CV measurements 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 the midpoint potential of the oxidation-reduction wave, and Ec was the midpoint potential of the reduction-oxidation wave. Here, since the potential energy of the reference electrode used in this example with respect to the vacuum level is known to be -4.94 [eV], the HOMO level and LUMO level can be calculated from the formulas HOMO level [eV] = -4.94 - Ea and LUMO level [eV] = -4.94 - Ec, respectively (Ea and Ec are the potentials for one-electron oxidation and one-electron reduction, respectively, so the potential values ​​can be directly converted into electron volts for calculation).

[0265] The oxidation-reduction wave of OCET010 is shown in Figure 33. The oxidation peak potential (Epa) in the oxidation-reduction wave of OCET010 was observed at 0.936 V, and the reduction peak potential (Epc) was observed at 0.822 V. From this, Ea was calculated to be 0.88 V, and the HOMO level of OCET010 was calculated to be -5.82 eV.

[0266] Similarly, Figure 34 shows the reduction-oxidation wave of OCET010. The reduction peak potential (Epc) in the reduction-oxidation wave of OCET010 was observed at -2.113 V, and the oxidation peak potential (Epa) was observed at -2.029 V. From this, Ec was calculated to be -2.07 V, and the LUMO level of OCET010 was calculated to be -2.87 eV.

[0267] Figure 35 shows the oxidation-reduction wave of NBPhen. The oxidation peak potential (Epa) in the oxidation-reduction wave of NBPhen was observed as a broad shoulder peak at about 1.3 V. On the other hand, the reduction peak potential (Epc) was not observed, so the difference between Epa and Epc was assumed to be about 0.1 V (because it is known that in an ideal diffusion system in which electron transfer is sufficiently fast, the difference between Epa and Epc is slightly less than 60 mV). In other words, here, Epc in the oxidation-reduction wave of NBPhen was set to 1.2 V. From this, the Ea of NPBhen can be obtained as 1.25 V, but because the Epa peak is broad and based on the above assumption, the calculation should be made with the first decimal place as a significant figure, so the HOMO level of NBPhen is calculated to be about -6.2 eV.

[0268] Similarly, the reduction-oxidation wave of NBPhen is shown in Figure 36. The reduction peak potential (Epc) in the reduction-oxidation wave of NBPhen was observed at -2.166 V, and the oxidation peak potential (Epa) was observed at -2.062 V. From this, Ec was calculated to be -2.12 V, and the LUMO level of NBPhen was calculated to be -2.83 eV.

[0269] Figure 37 shows the oxidation-reduction wave of Liq. The oxidation peak potential (Epa) in the oxidation-reduction wave of Liq was observed as a shoulder peak at around 0.77 eV. On the other hand, the reduction peak potential (Epc) was not observed, so the difference between Epa and Epc was assumed to be about 0.1 V (because it is known that in an ideal diffusion system in which electron transfer is sufficiently fast, the difference between Epa and Epc is slightly less than 60 mV). In other words, here, Epc in the oxidation-reduction wave of Liq was set to 0.67 V. From this, the Ea of Liq can be calculated to be 0.72 eV, but because the above assumption requires that the calculation should be made with the first decimal place as a significant digit, the HOMO level of Liq is calculated to be about -5.7 eV.

[0270] Similarly, the reduction-oxidation wave of Liq is shown in FIG. 38. Note that FIG. 38B is a graph showing an enlarged range of −1.7V to −2.8V in FIG. 38A. From this, the reduction peak potential (Epc) in the reduction-oxidation wave of Liq was observed as a shoulder peak near −2.29V. On the other hand, the oxidation peak potential (Epa) was not observed, so it was assumed that the difference between Epa and Epc was about 0.1V (because it is known that in an ideal diffusion system in which electron transfer is sufficiently fast, the difference between Epa and Epc is slightly less than 60mV). In other words, here, the Epc in the reduction-oxidation wave of Liq was assumed to be −2.19V. From this, the Ec of Liq can be obtained as −2.24eV, but since the above assumption requires that the calculation should be performed with the first decimal place as the significant digit, the LUMO level of Liq is calculated as −2.7eV.

[0271] Table 3 shows the HOMO and LUMO levels of OCET010 and NBPhen, which are organic compounds having electron transport properties used in the electron transport layers of light-emitting device 1 and light-emitting device 2, as determined above, and the difference (ΔE LUMO-HOMO ), the peak wavelength of the emission spectrum of the exciplex with Liq (λp Ex ), the value converted from the peak wavelength to energy (E Ex ), and ΔE LUMO-HOMO From EEx The value subtracted from (ΔE HL -E Ex ) As mentioned above, since the significant figures of the HOMO level of Liq are up to the first decimal place, ΔE LUMO-HOMO , ΔE HL -E Ex In all cases, the significant figures are up to the first decimal place.

[0272] [Table 3]

[0273] As can be seen from Figures 20 and 21, in the electron transport layers of light-emitting device 1 and light-emitting device 2, OCET010 and NBPhen are considered to form exciplexes with Liq, an organometallic complex of an alkali metal (note that, since no new absorption peaks arising from the mixing were observed in the absorption spectrum of the mixed film, it can be identified as an exciplex). As mentioned above, the value obtained by converting the peak wavelength of the emission spectrum of the exciplex into energy should normally be close to the difference between the HOMO level of Liq and the LUMO level of OCET010, or the difference between the HOMO level of Liq and the LUMO level of NBPhen. However, as shown in Table 3, in the light-emitting devices of the present application, the ΔE HL -E Ex The light-emitting device according to one embodiment of the present invention thus exhibits large values ​​of ΔE HL -E Ex It was found that the light-emitting device has a peak wavelength of 0.5 eV or more in the emission spectrum of the exciplex formed in the electron transport layer of the light-emitting device, converted into energy, is smaller than the difference between the HOMO level of Liq and the LUMO level of OCET010 or NBPhen by 0.5 eV or more.

[0274] Furthermore, light-emitting device 2, in which the peak wavelength of the emission spectrum of the exciplex is 570 nm or more, exhibited a smaller slope of long-term deterioration than light-emitting device 1, in which the peak wavelength is 570 nm or less. Furthermore, light-emitting device 2, in which the peak wavelength of the emission spectrum of the exciplex is 610 nm or more, was found to be a light-emitting device with better luminous efficiency.

[0275] Next, FIG. 23 shows some of the results of a ToF-SIMS (Time-of-Flight Secondary Ion Mass Spectrometry) analysis of a mixed film of NBPhen and Liq used in the electron transport layer 114 of the light-emitting device 2. FIG. 23 shows the results of a ToF-SIMS analysis in which the m / z of positive ions is in the range of 730 to 760. In the figure, an ion is detected at m / z=740, which corresponds to an ion with the molecular weight of NBPhen + the molecular weight of Liq + the atomic weight of Li -2. This is a characteristic result obtained when a material having the configuration of the electron transport layer in the light-emitting device of the present invention is measured.

[0276] In a light-emitting device having an electron transport layer containing an organic compound having electron transport properties and an organic compound of an alkali metal, E , the molecular weight of the organometallic complex of the alkali metal is M ACom , the molecular weight of the alkali metal is M A If this is the case, when the electron transport layer or a film equivalent to the electron transport layer is measured by mass spectrometry, the mass-to-charge ratio m / z=M E +M ACom +M A Positive ions are detected at −2, and the above ΔE LUMO-HOMOA light-emitting device in which the difference between the LUMO level of an organic compound having electron transport properties and the HOMO level of an organometallic complex of an alkali metal is 2.9 eV or less can be a light-emitting device with a good life span, such as the light-emitting device 1 and the light-emitting device 2 described above. Note that, although a mixed film of αN-βNPAnth and Liq is used for the electron transport layer of the comparative light-emitting device 1, a mixed film in which αN-βNPAnth and Liq are mixed in a 1:1 (mass ratio) ratio not only does not form an exciplex, but also its ΔE LUMO-HOMO is also 3.0 eV. EXAMPLES

[0277] Example 1 In this example, a method for manufacturing a light-emitting device 3 which is a light-emitting device according to one embodiment of the present invention will be described. The structural formulas of materials used in this example are shown below.

[0278] [ka]

[0279] <How to make light-emitting device 3> First, indium tin oxide containing silicon oxide (ITSO) was formed on a glass substrate by sputtering to form an anode 101. The thickness of the anode was 70 nm, and the electrode area was 4 mm2. 2 (2mm x 2mm).

[0280] Next, as a pretreatment for forming a light-emitting device on the 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.

[0281] Then, 10 -4 The substrate was introduced into a vacuum deposition apparatus whose inside had been reduced in pressure to about Pa, and vacuum baking was carried out at 170° C. for 30 minutes in a heating chamber in the vacuum deposition apparatus, and then the substrate was allowed to cool for about 30 minutes.

[0282] Next, the substrate on which the anode 101 was formed was fixed to a substrate holder provided in a vacuum deposition apparatus so that the surface on which the anode 101 was formed faced downward. 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 an electron acceptor material (OCHD-001) were co-deposited on the anode 101 by a deposition method using resistance heating to a thickness of 10 nm in a mass ratio of 1:0.1 (=BBABnf:OCHD-001), to form a hole injection layer 111.

[0283] Next, BBABnf was deposited on the hole injection layer 111 to a thickness of 20 nm as a first hole transport layer 112-1, and then 3,3'-(naphthalene-1,4-diyl)bis(9-phenyl-9H-carbazole (abbreviation: PCzN2) represented by the above structural formula (ii) was deposited on the hole injection layer 111 to a thickness of 10 nm as a second hole transport layer 112-2 to form the hole transport layer 112. Note that the second hole transport layer 112-2 also functions as an electron blocking layer.

[0284] Next, 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-deposited to a thickness of 25 nm in a mass ratio of 1:0.015 (=αN-βNPAnth:3,10PCA2Nbf(IV)-02) to form the light-emitting layer 113.

[0285] Thereafter, 2-phenyl-3-[10-(3-pyridyl)-9-anthryl]phenylquinoxaline (abbreviation: PyA1PQ) represented by the above structural formula (viii) and 8-hydroxyquinolinatolithium (abbreviation: Liq) represented by the above structural formula (vi) were co-deposited on the light-emitting layer 113 to a thickness of 12.5 nm so as to give a mass ratio of 1:2 (=PyA1PQ:Liq), and then co-deposited on the light-emitting layer 113 to a thickness of 12.5 nm so as to give a mass ratio of 2:1 (=PyA1PQ:Liq) to form an electron transport layer 114.

[0286] After forming the electron transport layer 114, Liq was evaporated to a thickness of 1 nm to form the electron injection layer 115, and then aluminum was evaporated to a thickness of 200 nm as the cathode 102 to produce the light-emitting device 3 of this embodiment.

[0287] The element structure of the light-emitting device 3 is summarized in the table below.

[0288] [Table 4]

[0289] This light-emitting device was sealed with a glass substrate in a nitrogen atmosphere glove box so as not to be exposed to the atmosphere (a sealant was applied around the element, and UV treatment was performed during sealing, followed by heat treatment at 80°C for 1 hour), and then the initial characteristics and reliability of the light-emitting device 3 were measured. The measurements were performed at room temperature.

[0290] The luminance-current density characteristics of the light-emitting device 3 are shown in Fig. 24, the current efficiency-luminance characteristics in Fig. 25, the luminance-voltage characteristics in Fig. 26, the current-voltage characteristics in Fig. 27, the external quantum efficiency-luminance characteristics in Fig. 28, and the emission spectrum in Fig. 29. 2 The main characteristics of the area are shown in Table 5.

[0291] [Table 5]

[0292] 24 to 29 and Table 5 show that the light emitting device 3 is a blue light emitting device having good initial characteristics.

[0293] In addition, the current density is 50mA / cm 2 A graph showing the change in luminance with respect to drive time in the light-emitting device 3 according to one embodiment of the present invention is shown in Fig. 30. As shown in Fig. 30, the light-emitting device 3 has an extremely long life because the initial deterioration is suppressed due to an increase in luminance at the beginning of drive and the slope of long-term deterioration is small.

[0294] Here, we show the results of investigating the photoluminescence properties of the materials used in the electron transport layer of light-emitting device 3. A fluorometer (FS920 manufactured by Hamamatsu Photonics K.K.) was used for the measurements. Figure 31 shows the emission spectra of the PyA1PQ film, Liq film, and a mixed film in which PyA1PQ and Liq were mixed at a 1:1 (mass ratio) used in light-emitting device 3.

[0295] As shown in Figure 31, the emission spectrum of the mixed film in which PyA1PQ and Liq were mixed in a 1:1 (mass ratio) ratio is significantly shifted to the long wavelength side compared to the emission spectra of the PyA1PQ film and the Liq film, suggesting that PyA1PQ and Liq form an exciplex.

[0296] In addition, an exciplex is formed by the interaction of the molecular orbitals of two substances, and the exciplex is said to emit light having a peak at a wavelength corresponding to the difference between the shallower HOMO level and the deeper LUMO level of the two substances.

[0297] Table 6 shows the HOMO level and LUMO level of PyA1PQ, an organic compound having electron transport properties used in the electron transport layer of each light-emitting device 3, and the difference (ΔE LUMO-HOMO ), the peak wavelength of the emission spectrum of the exciplex with Liq (λp Ex ), the value converted from the peak wavelength to energy (E Ex), and ΔE HOMO-LUMO From E Ex The value subtracted from (ΔE HL -E Ex ) is shown. The measurement and calculation methods of the HOMO and LUMO levels are omitted since they are described in Example 1. Please refer to the description in Example 1. Since the significant figures of the HOMO level of Liq are up to the first decimal place, ΔE LUMO-HOMO , ΔE HL -E Ex As in the first embodiment, the significant figures in all of the above are up to the first decimal place.

[0298] The oxidation-reduction wave of PyA1PQ is shown in Figure 39. The oxidation peak potential (Epa) in the oxidation-reduction wave of PyA1PQ was observed at 1.045 V, and the reduction peak potential (Epc) was observed at 0.885 V. From this, Ea was calculated to be 0.97 V, and the HOMO level of PyA1PQ was calculated to be -5.91 eV.

[0299] Similarly, Figure 40 shows the reduction-oxidation wave of PyA1PQ. The reduction peak potential (Epc) in the reduction-oxidation wave of PyA1PQ was observed at -1.984 V, and the oxidation peak potential (Epa) was observed at -1.904 V. From this, Ec was calculated to be -1.94 V, and the LUMO level of PyA1PQ was calculated to be -3.00 eV.

[0300] [Table 6]

[0301] As can be seen from Figure 31, it is believed that PyA1PQ forms an exciplex with Liq in the electron transport layer of light-emitting device 3 (note that since no new absorption peaks arising from mixing were observed in the absorption spectrum of the mixed film, it can be identified as an exciplex). As mentioned above, normally, the value obtained by converting the peak wavelength of the emission spectrum of the exciplex into energy should be close to the difference between the HOMO level of Liq and the LUMO level of PyA1PQ. However, as shown in Table 6, in light-emitting device 3, ΔEHL -E Ex The light-emitting device according to one embodiment of the present invention thus exhibits a large ΔE HL -E Ex It was found that the light-emitting device has a peak wavelength of 0.5 eV or more in the emission spectrum of the exciplex formed in the electron transport layer of the light-emitting device, converted into energy, is smaller than the difference between the HOMO level of Liq and the LUMO level of PyA1PQ by 0.5 eV or more.

[0302] Furthermore, light-emitting device 3, in which the peak wavelength of the emission spectrum of the exciplex is 570 nm or more, is a light-emitting device with a small slope of long-term deterioration. Furthermore, light-emitting device 3, in which the peak wavelength of the emission spectrum of the exciplex is 570 nm or more and less than 610 nm, is a light-emitting device with an extremely good lifespan that combines an increase in luminance at the beginning of operation with a small slope of long-term deterioration.

[0303] Next, FIG. 32 shows a part of the results of ToF-SIMS analysis of a mixed film of PyA1PQ and Liq used in the electron transport layer 114 in the light-emitting device 3. FIG. 32 shows the results of ToF-SIMS analysis of positive ions in the range of m / z 685 to 710. In the figure, an ion is detected at m / z 691, which corresponds to the ion PyA1PQ (molecular weight) + Liq (molecular weight) + Li (atomic weight)-2. This is a characteristic result obtained when measuring a material having the configuration of the electron transport layer in the light-emitting device of the present invention.

[0304] The molecular weight of the organic compound having electron transport properties is M E , the molecular weight of the organometallic complex of the alkali metal is M ACom , the molecular weight of the alkali metal is M A In this case, when the electron transport layer or a film equivalent to the electron transport layer is measured by mass spectrometry, the mass-to-charge ratio m / z=M E +M ACom +M A Positive ions are detected at −2, and the above ΔE LUMO-HOMOA light-emitting device in which the difference between the LUMO level of an organic compound having electron transport properties and the HOMO level of an organometallic complex of an alkali metal is 2.9 eV or less can be a light-emitting device with a long life, like the light-emitting device 3 described above. EXAMPLES

[0305] Example 1 In this example, a method for manufacturing a light-emitting device 4 which is a light-emitting device according to one embodiment of the present invention will be described. The structural formulas of materials used in this example are shown below.

[0306] [ka]

[0307] <How to make light-emitting device 4> First, indium tin oxide containing silicon oxide (ITSO) was formed on a glass substrate by sputtering to form an anode 101. The thickness of the anode was 70 nm, and the electrode area was 4 mm2. 2 (2mm x 2mm).

[0308] Next, as a pretreatment for forming a light-emitting device on the 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.

[0309] Then, 10 -4 The substrate was introduced into a vacuum deposition apparatus whose inside had been reduced in pressure to about Pa, and vacuum baking was carried out at 170° C. for 30 minutes in a heating chamber in the vacuum deposition apparatus, and the substrate was then allowed to cool for about 30 minutes.

[0310] Next, the substrate on which the anode 101 was formed was fixed to a substrate holder provided in a vacuum deposition apparatus so that the surface on which the anode 101 was formed faced downward. 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 an electron acceptor material (OCHD-001) were co-deposited on the anode 101 by a deposition method using resistance heating to a thickness of 10 nm in a mass ratio of 1:0.1 (=BBABnf:OCHD-001), to form a hole injection layer 111.

[0311] Next, BBABnf was deposited on the hole injection layer 111 to a thickness of 20 nm as a first hole transport layer 112-1, and then 3,3'-(naphthalene-1,4-diyl)bis(9-phenyl-9H-carbazole (abbreviation: PCzN2) represented by the above structural formula (ii) was deposited on the hole injection layer 111 to a thickness of 10 nm as a second hole transport layer 112-2 to form the hole transport layer 112. Note that the second hole transport layer 112-2 also functions as an electron blocking layer.

[0312] Next, 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-deposited to a thickness of 25 nm in a mass ratio of 1:0.015 (=αN-βNPAnth:3,10PCA2Nbf(IV)-02) to form the light-emitting layer 113.

[0313] Thereafter, 2-[3-(2,6-dimethyl-3-pyridinyl)-5-(9-phenanthrenyl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mPn-mDMePyPTzn) represented by the above structural formula (viii) and 8-hydroxyquinolinato-lithium (abbreviation: Liq) represented by the above structural formula (vi) were co-deposited on the light-emitting layer 113 to a thickness of 12.5 nm so as to give a mass ratio of 1:2 (=mPn-mDMePyPTzn:Liq), and then co-deposited on the light-emitting layer 113 to a thickness of 12.5 nm so as to give a mass ratio of 2:1 (=mPn-mDMePyPTzn:Liq) to form an electron transport layer 114.

[0314] After forming the electron transport layer 114, Liq was evaporated to a thickness of 1 nm to form the electron injection layer 115, and then aluminum was evaporated to a thickness of 200 nm as the cathode 102 to produce the light-emitting device 4 of this embodiment.

[0315] The element structure of the light-emitting device 4 is summarized in the table below.

[0316] [Table 7]

[0317] This light-emitting device was sealed with a glass substrate in a nitrogen-atmosphere glove box to prevent it from being exposed to the atmosphere (a sealant was applied around the element, and UV treatment was performed during sealing, followed by heat treatment at 80°C for 1 hour), after which the initial characteristics and reliability were measured. The measurements were performed at room temperature.

[0318] The luminance-current density characteristics of the light-emitting device 4 are shown in FIG. 41, the luminance-voltage characteristics in FIG. 42, the current efficiency-luminance characteristics in FIG. 43, the current-voltage characteristics in FIG. 44, the external quantum efficiency-luminance characteristics in FIG. 45, and the emission spectrum in FIG. 46. The 1000 cd / m 2 The main characteristics of the area are shown in Table 8.

[0319] [Table 8]

[0320] 41 to 46 and Table 8 show that the light emitting device 4 is a blue light emitting device having good initial characteristics.

[0321] In addition, the current density is 50mA / cm 2 A graph showing the change in luminance with respect to the driving time in the above case is shown in Fig. 47. As shown in Fig. 47, the light-emitting device 4 which is a light-emitting device according to one embodiment of the present invention has a long lifetime.

[0322] Here, the results of investigating the photoluminescence properties of the material used in the electron transport layer of light-emitting device 4 are shown. Figure 48 shows the emission spectra of the mPn-mDMePyPTzn film, Liq film, and a mixed film in which mPn-mDMePyPTzn and Liq were mixed at a 1:1 (mass ratio) used in light-emitting device 4. A fluorometer (FP-8600, manufactured by JASCO Corporation) was used to measure the mPn-mDMePyPTzn film, and a fluorometer (FS920, manufactured by Hamamatsu Photonics K.K.) was used to measure the other films.

[0323] As shown in Figure 48, the emission spectrum of the mixed film in which mPn-mDMePyPTzn and Liq were mixed in a 1:1 (mass ratio) ratio is shifted to the longer wavelength side compared to the emission spectra of the mPn-mDMePyPTzn film and the Liq film, suggesting that mPn-mDMePyPTzn and Liq form an exciplex.

[0324] In addition, an exciplex is formed by the interaction of the molecular orbitals of two substances, and the exciplex is said to emit light having a peak at a wavelength corresponding to the difference between the shallower HOMO level and the deeper LUMO level of the two substances.

[0325] Table 9 shows the HOMO level and LUMO level of mPn-mDMePyPTzn, which is an organic compound having electron transport properties used in the electron transport layer of the light-emitting device 4, and the difference (ΔELUMO-HOM O ), the peak wavelength of the emission spectrum of the exciplex with Liq (λp Ex ), the value converted from the peak wavelength to energy (E Ex ), and ΔE HOMO-LUMO From E Ex The value subtracted from (ΔE HL -E Ex ) is shown. The measurement and calculation methods of the HOMO and LUMO levels are omitted since they are described in Example 1. Please refer to the description in Example 1. Since the significant figures of the HOMO level of Liq are up to the first decimal place, ΔE LUMO-HOMO , ΔE HL -E Ex As in the first embodiment, the significant figures in all of the above are up to the first decimal place.

[0326] The reduction-oxidation wave of mPn-mDMePyPTzn is shown in Figure 49. The reduction peak potential (Epc) in the reduction-oxidation wave of mPn-mDMePyPTzn was observed at -2.001 V, and the oxidation peak potential (Epa) was observed at -1.917 V. From this, Ec was calculated to be -1.96 V, and the LUMO level of mPn-mDMePyPTzn was calculated to be -2.98 eV.

[0327] [Table 9]

[0328] As can be seen from Figure 49, mPn-mDMePyPTzn and Liq are considered to form an exciplex in the electron transport layer of light-emitting device 4 (note that since no new absorption peaks arising from mixing were observed in the absorption spectrum of the mixed film, it can be identified as an exciplex). As mentioned above, normally, the value obtained by converting the peak wavelength of the emission spectrum of the exciplex into energy should be close to the difference between the HOMO level of Liq and the LUMO level of mPn-mDMePyPTzn. However, as shown in Table 9, in light-emitting device 4, ΔE HL -E ExThe light-emitting device of this embodiment has a large ΔE HL -E Ex It was found that the peak wavelength of the emission spectrum of the exciplex formed in the electron transport layer of the light-emitting device, converted into energy, is smaller than the difference between the HOMO level of Liq and the LUMO level of mPn-mDMePyPTzn by 0.3 eV or more. EXAMPLES

[0329] Example 1 This example describes a method for manufacturing light-emitting devices 5 to 7, which are light-emitting devices according to embodiments of the present invention. The structural formulas of organic compounds used in this example are shown below.

[0330] [ka]

[0331] <How to make light-emitting device 5> First, indium tin oxide containing silicon oxide (ITSO) was formed on a glass substrate by sputtering to form an anode 101. The thickness of the anode was 70 nm, and the electrode area was 4 mm2. 2 (2mm x 2mm).

[0332] Next, as a pretreatment for forming a light-emitting device on the 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.

[0333] Then, 10 -4 The substrate was introduced into a vacuum deposition apparatus whose inside had been reduced in pressure to about Pa, and vacuum baking was carried out at 170° C. for 30 minutes in a heating chamber in the vacuum deposition apparatus, and the substrate was then allowed to cool for about 30 minutes.

[0334] Next, the substrate on which the anode 101 was formed was fixed to a substrate holder provided in a vacuum deposition apparatus so that the surface on which the anode 101 was formed faced downward. 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 an electron acceptor material (OCHD-001) were co-deposited on the anode 101 by a deposition method using resistance heating to a thickness of 10 nm in a mass ratio of 1:0.1 (=BBABnf:OCHD-001), to form a hole injection layer 111.

[0335] Next, BBABnf was deposited on the hole injection layer 111 to a thickness of 20 nm as a first hole transport layer 112-1, and then 3,3'-(naphthalene-1,4-diyl)bis(9-phenyl-9H-carbazole (abbreviation: PCzN2) represented by the above structural formula (ii) was deposited on the hole injection layer 111 to a thickness of 10 nm as a second hole transport layer 112-2 to form the hole transport layer 112. Note that the second hole transport layer 112-2 also functions as an electron blocking layer.

[0336] Next, 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-deposited to a thickness of 25 nm in a mass ratio of 1:0.015 (=αN-βNPAnth:3,10PCA2Nbf(IV)-02) to form the light-emitting layer 113.

[0337] Then, on the light-emitting layer 113, αN-βNPAnth and 4-methyl-8-quinolinolato-lithium (abbreviation: Li-4mq) represented by the above structural formula (ix) were co-deposited to a thickness of 25 nm in a mass ratio of 1:1 (=αN-βNPAnth:Li-4mq) to form an electron transport layer 114.

[0338] After forming the electron transport layer 114, 8-hydroxyquinolinato-lithium (abbreviation: Liq) represented by the above structural formula (vi) was evaporated to a thickness of 1 nm to form the electron injection layer 115, and then aluminum was evaporated to a thickness of 200 nm as the cathode 102 to produce the light-emitting device 5 of this example.

[0339] <How to make light-emitting device 6> Light-emitting device 6 was prepared in the same manner as light-emitting device 5, except that αN-βNPAnth in light-emitting device 5 was changed to 2-[3-(2,6-dimethyl-3-pyridinyl)-5-(9-phenanthrenyl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mPn-mDMePyPTzn) represented by the above structural formula (viii).

[0340] <How to make light-emitting device 7> Light-emitting device 7 was fabricated in the same manner as light-emitting device 5, except that αN-βNPAnth in light-emitting device 5 was changed to 2-phenyl-3-[10-(3-pyridyl)-9-anthryl]phenylquinoxaline (abbreviation: PyA1PQ) represented by the above structural formula (viii).

[0341] The element structures of light-emitting devices 5 to 7 are summarized in the table below.

[0342] [Table 10]

[0343] These light-emitting devices were sealed with a glass substrate in a nitrogen atmosphere glove box so that the light-emitting devices would not be exposed to the atmosphere (a sealant was applied around the elements, and UV treatment was performed during sealing, followed by heat treatment at 80°C for 1 hour), and then the initial characteristics and reliability of light-emitting devices 5 to 7 were measured. The measurements were performed at room temperature.

[0344] The luminance-current density characteristics of the light-emitting devices 5 to 7 are shown in FIG. 50, the luminance-voltage characteristics in FIG. 51, the current efficiency-luminance characteristics in FIG. 52, the current-voltage characteristics in FIG. 53, the external quantum efficiency-luminance characteristics in FIG. 54, and the emission spectra in FIG. 55. The 1000 cd / m 2 The main characteristics of the area are shown in Table 11.

[0345] [Table 11]

[0346] 50 to 55 and Table 11 show that all three devices were blue light-emitting devices with good initial characteristics.

[0347] In addition, the current density is 50mA / cm 2 A graph showing changes in luminance with respect to driving time in the case of the light-emitting device 5 is shown in Fig. 56. As shown in Fig. 56, it was found that the light-emitting devices 5 to 7, which are light-emitting devices according to one embodiment of the present invention, have long lifetimes.

[0348] Here, the results of investigating the photoluminescence properties of the materials used in the electron transport layer in each device are shown. The measurements were performed in the same manner as in Example 1. Figure 57 shows the emission spectra of the αN-βNPAnth film, Li-4mq film, and the mixed film in which αN-βNPAnth and Li-4mq were mixed at 1:1 (mass ratio) used in the light-emitting device 5, Figure 58 shows the emission spectra of the mPn-mDMePyPTzn film, Li-4mq film, and the mixed film in which mPn-mDMePyPTzn and Li-4mq were mixed at 1:1 (mass ratio) used in the light-emitting device 6, and Figure 59 shows the emission spectra of the PyA1PQ film, Li-4mq film, and the mixed film in which PyA1PQ and Li-4mq were mixed at 1:1 (mass ratio) used in the light-emitting device 7.

[0349] As shown in Fig. 57, the emission spectrum of the mixed film in which αN-βNPAnth and Li-4mq were mixed at a ratio of 1:1 (mass ratio) is significantly shifted to the long wavelength side compared to the emission spectra of the αN-βNPAnth film and the Li-4mq film, suggesting that αN-βNPAnth and Li-4mq form an exciplex. Similarly, Fig. 58 suggests that mPn-mDMePyPTzn and Li-4mq form an exciplex, and Fig. 59 suggests that PyA1PQ and Li-4mq form an exciplex.

[0350] In addition, an exciplex is formed by the interaction of the molecular orbitals of two substances, and the exciplex is said to emit light having a peak at a wavelength corresponding to the difference between the shallower HOMO level and the deeper LUMO level of the two substances. The measurement and calculation methods for the HOMO level and LUMO level are omitted because they are described in Example 1. Please refer to the description in Example 1. Since the significant figures of the HOMO level of Liq are up to the first decimal place, ΔE LUMO-HOMO , ΔE HL -E Ex As in the first embodiment, the significant figures in all of the above are up to the first decimal place.

[0351] The oxidation-reduction wave of αN-βNPAnth is shown in Figure 60. The oxidation peak potential (Epa) in the oxidation-reduction wave of αN-βNPAnth was observed at 0.978 V, and the reduction peak potential (Epc) was observed at 0.840 V. From this, Ea was calculated to be 0.91 V, and the HOMO level of αN-βNPAnth was calculated to be -5.85 eV.

[0352] Similarly, the reduction-oxidation wave of αN-βNPAnth is shown in Figure 61. The reduction peak potential (Epc) in the reduction-oxidation wave of αN-βNPAnth was observed at -2.248 V, and the oxidation peak potential (Epa) was observed at -2.161 V. From this, Ec was calculated to be -2.20 V, and the LUMO level of αN-βNPAnth was calculated to be -2.74 eV.

[0353] The reduction-oxidation wave of mPn-mDMePyPTzn is shown in Figure 49. The reduction peak potential (Epc) in the reduction-oxidation wave of mPn-mDMePyPTzn was observed at -2.001 V, and the oxidation peak potential (Epa) was observed at -1.917 V. From this, Ec was calculated to be -1.96 V, and the LUMO level of mPn-mDMePyPTzn was calculated to be -2.98 eV.

[0354] The oxidation-reduction wave of PyA1PQ is shown in Figure 39. The oxidation peak potential (Epa) in the oxidation-reduction wave of PyA1PQ was observed at 1.045 V, and the reduction peak potential (Epc) was observed at 0.885 V. From this, Ea was calculated to be 0.97 V, and the HOMO level of PyA1PQ was calculated to be -5.91 eV.

[0355] Similarly, Figure 40 shows the reduction-oxidation wave of PyA1PQ. The reduction peak potential (Epc) in the reduction-oxidation wave of PyA1PQ was observed at -1.984 V, and the oxidation peak potential (Epa) was observed at -1.904 V. From this, Ec was calculated to be -1.94 V, and the LUMO level of PyA1PQ was calculated to be -3.00 eV.

[0356] In addition, the oxidation-reduction wave of Li-4mq is shown in Figure 62. The oxidation peak potential (Epa) in the oxidation-reduction wave of Li-4mq was observed as a shoulder peak at around 0.70 eV. On the other hand, the reduction peak potential (Epc) was not observed, so the difference between Epa and Epc was assumed to be about 0.1 V (because it is known that in an ideal diffusion system in which electron transfer is sufficiently fast, the difference between Epa and Epc is slightly less than 60 mV). In other words, here, Epc in the oxidation-reduction wave of Li-4mq was set to 0.60 V. From this, the Ea of Li-4mq can be calculated to be 0.65 eV, but because the above assumption requires that the calculation should be made with the first decimal place as the significant digit, the HOMO level of Li-4mq is calculated to be about -5.6 eV.

[0357] Similarly, Figure 63 shows the reduction-oxidation wave of Li-4mq. The reduction peak potential (Epc) in the reduction-oxidation wave of Li-4mq was observed at -2.437 V, and the oxidation peak potential (Epa) was observed at -2.325 V. From this, Ec was calculated to be -2.38 V, and the LUMO level of Li-4mq was calculated to be -2.56 eV.

[0358] Table 12 shows the HOMO and LUMO levels of the organic compounds having electron transport properties, αN-βNPAnth, mPn-mDMePyPTzn, and PyAlPQ, used in the electron transport layers of the light-emitting devices 5 to 7, as determined above, and the differences (ΔE LUMO-HOMO ), the peak wavelength of the emission spectrum of the exciplex with Liq (λp Ex ), the value converted from the peak wavelength to energy (E Ex ), and ΔE LUMO-HOMO From E Ex The value subtracted from (ΔE HL -E Ex ) As mentioned above, since the significant figures of the HOMO level of Liq are up to the first decimal place, ΔE LUMO-HOMO , ΔE HL -E Ex In all cases, the significant figures are up to the first decimal place.

[0359] [Table 12]

[0360] 57 to 59, in the electron transport layers of light-emitting devices 5 to 7, αN-βNPAnth, mPn-mDMePyPTzn, and PyA1PQ are considered to form exciplexes with Li-4mq, an organometallic complex of an alkali metal (note that, since no new absorption peaks resulting from the mixing were observed in the absorption spectrum of the mixed film, it can be identified as an exciplex). As described above, the value obtained by converting the peak wavelength of the emission spectrum of the exciplex into energy should normally be close to the difference between the HOMO level of Li-4mq and the LUMO levels of αN-βNPAnth, mPn-mDMePyPTzn, and PyA1PQ, but in the light-emitting devices of the present application, as shown in Table 12, the ΔE HL -E Ex The light-emitting device according to one embodiment of the present invention thus exhibits a large ΔE HL -E Ex It was found that the light-emitting device has a peak wavelength of 0.3 eV or 0.5 eV or more, and that the value converted into energy from the peak wavelength of the emission spectrum of the exciplex formed in the electron transport layer of the light-emitting device is 0.3 eV or 0.5 eV or more smaller than the difference between the HOMO level of Li-4mq and the LUMO levels of αN-βNPAnth, mPn-mDMePyPTzn, and PyA1PQ.

[0361] (Reference example 1) <Synthesis Example 1> This Reference Example describes a method for synthesizing 2-phenyl-3-[10-(3-pyridyl)-9-anthryl]phenylquinoxaline (abbreviation: PyA1PQ) used in Example 2. The structure of PyA1PQ is shown below.

[0362] [ka]

[0363] In a 50 mL three-neck flask, 0.74 g (2.2 mmol) of 3-(10-bromo-9-anthryl)pyridine, 0.26 g (0.85 mmol) of tri(ortho-tolyl)phosphine, 0.73 g (2.3 mmol) of 4-(3-phenylquinoxalin-2-yl)phenylboronic acid, 1.3 g (9.0 mmol) of potassium carbonate aqueous solution, 40 mL of ethylene glycol dimethyl ether (DME), and 4.4 mL of water were added. The mixture was degassed by stirring under reduced pressure, and the atmosphere in the flask was replaced with nitrogen.

[0364] Palladium (II) acetate (65 mg, 0.29 mmol) was added to the mixture in the flask, and the mixture was stirred at 80°C for 11 hours under a nitrogen stream. After stirring, water was added to the mixture in the flask, and the mixture was extracted with toluene. The resulting extract solution was washed with saturated saline and dried over magnesium sulfate. This was gravity filtered, and the filtrate was concentrated to obtain an oily substance. The resulting oily substance was purified twice by silica gel column chromatography (chloroform and toluene:ethyl acetate = 5:1), and recrystallized from toluene / hexane to obtain the target yellow solid in an amount of 0.43 g and a yield of 36%. The synthesis scheme is shown in the following formula.

[0365] [ka]

[0366] The yellow solid (0.44 g) was purified by train sublimation. The purification was carried out at a pressure of 10 Pa, an argon flow rate of 5.0 mL / min, and a heating temperature of 260°C for 18 hours. After purification, the target yellow solid (0.35 g) was obtained with a recovery rate of 79%.

[0367] The yellow solid obtained in the above reaction was analyzed by nuclear magnetic resonance spectroscopy ( 1 The results of the analysis by H-NMR are shown below. From these results, it was found that PyA1PQ represented by the above structural formula was obtained in this example.

[0368] 1H NMR (CDCl3, 300MHz): δ=7.37-7.50(m,9H), 7.56-7.78(m,9H), 7.82-7.86(m,3H), 8.24-8.30(m,2H), 8.75(dd,J=1.8Hz,0.9Hz,1H), 8.84(dd,J=4.8Hz,1.8Hz,1H). [Explanation of symbols]

[0369] 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, 114: electron transport layer, 114-1: first electron transport layer, 114-2: second electron transport layer, 115: electron injection layer, 400: substrate, 401: anode, 403: EL layer, 404: cathode, 405: sealing material, 406: sealing material, 407: sealing substrate, 412: pad, 420: IC chip, 501: anode, 502: cathode, 511: first light emitting unit, 512: second light emitting unit, 513: Charge generating layer, 601: driving circuit section (source line driving circuit), 602: pixel section, 603: driving circuit section (gate line driving circuit), 604: sealing 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: base 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 wall, 1028: EL layer, 1029: cathode, 1031: sealing substrate, 1032: sealing material, 1033: transparent base material, 1034R: red colored layer, 1034G: green colored layer, 1034B: blue colored layer, 1035: black matrix, 1036: overcoat layer, 1037: third interlayer insulating film, 1040: pixel section, 1041: driving circuit section, 1042: peripheral section, 2001: housing, 2002: light source, 2100: robot, 2110: computing device, 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 unit, 5002: display unit, 5003: speaker, 5004: LED lamp, 5006: connection terminal, 5007: sensor, 5008: microphone, 5012: support unit, 5013: earphone, 5100: cleaning robot, 5101: display,5102: camera, 5103: brush, 5104: operation button, 5150: mobile information terminal, 5151: housing, 5152: display area, 5153: bending portion, 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 key, 7110: remote control unit, 7201: main body , 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 button, 7404: external connection port, 7405: speaker, 7406: microphone, 7400: mobile phone, 9310: mobile information terminal, 9311: display panel, 9313: hinge, 9315: housing,

Claims

1. a first electrode, a second electrode, and a light-emitting layer and an electron transport layer located between the first electrode and the second electrode; the electron transport layer is located between the light emitting layer and the second electrode; the electron transport layer comprises an organometallic complex of an alkali metal and an organic compound having an electron transport property, the organometallic complex and the organic compound are a combination that forms an exciplex, a difference (eV) between the HOMO level of the organometallic complex and the LUMO level of the organic compound minus a value (eV) obtained by converting the peak wavelength of an emission spectrum of a mixed film obtained by mixing the organometallic complex and the organic compound in a mass ratio of 1:1 into energy is 0.3 eV or more and 0.9 eV or less. (However, this does not include the combination in which the organometallic complex is Liq shown below and the organic compound is mPn-mDmePyPTzn shown below), a light-emitting device. 【Chemistry 1】

2. a first electrode, a second electrode, and a light-emitting layer and an electron transport layer located between the first electrode and the second electrode; the electron transport layer is located between the light emitting layer and the second electrode; the electron transport layer comprises an organometallic complex of an alkali metal and an organic compound having an electron transport property, the organometallic complex and the organic compound are a combination that forms an exciplex, a difference (eV) between the HOMO level of the organometallic complex and the LUMO level of the organic compound minus a value (eV) obtained by converting a peak wavelength of an emission spectrum of a mixed film in which the organometallic complex and the organic compound are mixed in a mass ratio of 1:1 into energy is 0.4 eV or more and 0.9 eV or less.

3. a first electrode, a second electrode, and a light-emitting layer and an electron transport layer located between the first electrode and the second electrode; the electron transport layer is located between the light emitting layer and the second electrode; the electron transport layer comprises an organometallic complex of an alkali metal and an organic compound having an electron transport property, the organometallic complex and the organic compound are a combination that forms an exciplex, a difference (eV) between the HOMO level of the organometallic complex and the LUMO level of the organic compound minus a value (eV) obtained by converting a peak wavelength of an emission spectrum of a mixed film in which the organometallic complex and the organic compound are mixed in a mass ratio of 1:1 into energy is 0.5 eV or more and 0.9 eV or less.

4. In any one of claims 1 to 3, A light emitting device wherein the organometallic complex of an alkali metal is an organometallic complex of lithium.

5. In any one of claims 1 to 3, A light-emitting device, wherein the organometallic complex of an alkali metal has a ligand having a quinolinol skeleton.

6. In any one of claims 1 to 3, A light emitting device, wherein the organometallic complex of an alkali metal is 8-hydroxyquinolinato-lithium or a derivative thereof.

7. In any one of claims 1 to 6, A light-emitting device, wherein the organic compound is an organic compound having a heteroaromatic ring.

8. In any one of claims 1 to 7, the electron transport layer contacting the light emitting layer.

9. In any one of claims 1 to 8, The light-emitting layer includes a host material and a light-emitting material, A light emitting device, wherein the luminescent material fluoresces blue.

10. A light emitting device according to any one of claims 1 to 9; At least one of a sensor, an operation button, a speaker, and a microphone; An electronic device having the

11. A light emitting device according to any one of claims 1 to 9; A light emitting device comprising at least one of a transistor and a substrate.

12. A lighting device comprising: the light-emitting device according to claim 1 ; and a housing.

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