Light emitting device and composition

Abstract

To prolong the life of a light-emitting element by managing the complex state of a co-deposited film composed of a metal or a metal compound and an organic substance constituting the element by a simple measuring means.SOLUTION: An intensity ratio (I1600 / I1550) of a peak intensity (I1550) at (1600 ± 20) cm - 1 to a peak intensity (I1600) at> (1550 ± 20) cm - 1 in a Raman spectrum of the layer satisfies (I1550 / I1600) / W ≥ 0.03 with respect to a doping concentration W (mol%) of the metallic dopant to the phenantroline derivative.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a light-emitting device and a composition. [Background technology]

[0002] Light-emitting elements such as organic electroluminescence (EL) elements are widely used in flat panel displays such as televisions and smartphones, backlights, lighting, interior design, signs, billboards, electrophotographic devices, and optical signal generators. However, the characteristics of light-emitting elements (driving voltage, efficiency, and lifespan) vary from lot to lot, which can affect manufacturing yield. This is because the state of each layer of a light-emitting element cannot be easily measured, making it difficult to quantitatively determine whether each layer has been formed as desired.

[0003] In response to this, there is a technique described in Patent Document 1, for example, which is a means for defining the state of an electron injection layer included in a light-emitting device using physical quantities measurable by simple measurement means. Patent Document 1 discloses that the state of an electron injection layer formed from a co-evaporated film made from raw materials of a thermally evaporated product of a metal and / or metal compound and a thermally evaporated product of an organic substance can be measured by measuring its Raman signal, and that this allows the occurrence of defective products originating from the electron injection layer to be quickly detected, thereby improving the production yield of organic EL devices. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-130646 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the organic EL element described in Patent Document 1 has the problem that it does not necessarily have a low driving voltage, a high external quantum efficiency, or a long lifetime. The present inventors hypothesized that the cause of this problem lies in the following point. That is, in Patent Document 1, measurement is performed by focusing on the intensity ratio of signals I1 and I2, which changes in conjunction with the state and concentration of alkali metals and the like that affect the physical properties of the electron injection layer. However, simply measuring this signal intensity ratio does not reveal the specific state of the alkali metals and the like in the co-deposited film of metal and / or metal compound and organic material, and whether this state is effective in terms of the performance of the light-emitting element, such as external quantum efficiency and lifetime.

[0006] Based on this hypothesis, the present inventors have inferred and investigated that if a stable complex is formed between this metal and / or metal compound and a co-deposited film of an organic material, it will be possible to quickly prevent the occurrence of defective products originating from each layer of the light-emitting device, such as the electron injection layer, and not only will this improve the manufacturing yield of the light-emitting device, but also the performance of the light-emitting device itself. As a result, they have found that the state in which the stable complex is formed can be controlled by a measurement quantity using Raman spectroscopy, which is not disclosed in Patent Document 1, and have arrived at the present invention. [Means for solving the problem]

[0007] That is, the present invention has the following configuration. [1] A light-emitting device having at least a light-emitting layer, an electron transport layer, an N-type charge generation layer, a P-type charge generation layer, and an electron injection layer between an anode and a cathode, wherein at least one of the N-type charge generation layer, the electron transport layer, and the electron injection layer contains a phenanthroline derivative and a metal dopant, and the layer containing the phenanthroline derivative and the metal dopant has a Raman spectrum of (1550±20) cm -1 and (1600±20) cm -1 The Raman spectrum shows a peak at (1600±20) cm -1 The peak intensity at I 1600 , (1550±20)cm -1 The peak intensity at I1550 and the doping concentration of the metal dopant in the layer containing the phenanthroline derivative and the metal dopant is W (mol%), (I 1550 / I 1600 ) / W is 0.03 or more. [2] I 1550 / I 1600 ) / W is 0.10 or more and 0.67 or less. [3] The Raman spectrum is (1400±50) cm -1 The Raman spectrum has a peak at (1400±50) cm -1 The peak intensity at I 1400 When I 1400 / I 1600 The light-emitting element according to [1] or [2], wherein is 0.50 or more and 1.50 or less. [4] The light-emitting device according to any one of [1] to [3], wherein the ratio of the thickness of the electron injection layer to the thickness of the N-type charge generation layer (thickness of the electron injection layer / thickness of the N-type charge generation layer) is 0.06 to 18.5. [5] The light-emitting device according to any one of [1] to [4], wherein the phenanthroline derivative is a compound represented by the following general formula (1):

[0008] [ka]

[0009] (In general formula (1), A is a group represented by the following formula (2) or (3), and X and Y are each independently selected from the group consisting of a hydrogen atom, a halogen atom, a cyano group, an alkyl group, a cycloalkyl group, a phenyl group, an aryl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, and an alkoxy group.)

[0010] [ka]

[0011] [6] The light-emitting device according to [5], wherein the content ratio of the phenanthroline derivative to the metal dopant is phenanthroline derivative:metal dopant=97.5±2.4% by weight:2.5±2.4% by weight. [7] The light-emitting device according to [5] or [6], wherein the content ratio of the phenanthroline derivative to the metal dopant is phenanthroline derivative:metal dopant=98.0±0.4% by weight:2.0±0.4% by weight. [8] The light-emitting element according to any one of [5] to [7], wherein the phenanthroline derivative is any one of 1,3-di(1,10-phenanthrolin-2-yl)benzene, 2-phenyl-9-[3-(9-phenyl-1,10-phenanthrolin-2-yl)phenyl]-1,10-phenanthroline, and 2-(3-([2,2':6',2"-terpyridine]-4'-yl)phenyl-9-phenyl-1,10-phenanthroline. [9] The light-emitting device composition film according to any one of [5] to [7], wherein the phenanthroline derivative is 1,3-di(1,10-phenanthroline-2-yl)benzene, and the metal dopant is lithium or ytterbium.

[10] The light-emitting element according to [6] or [7], wherein the phenanthroline derivative is 2-(3-([2,2':6',2"-terpyridin]-4'-yl)phenyl-9-phenyl-1,10-phenanthroline or 2-phenyl-9-[3-(9-phenyl-1,10-phenanthrolin-2-yl)phenyl]-1,10-phenanthroline, and the metal dopant is lithium.

[11] A composition used to form at least one of the N-type charge generating layer, the electron transport layer, and the electron injection layer of the light-emitting element according to claim 1, the composition comprising a compound represented by the following general formula (1) and a metal dopant:

[0012] [ka]

[0013] (In general formula (1), A is a group represented by the following formula (2) or (3), and X and Y are each independently selected from the group consisting of a hydrogen atom, a halogen atom, a cyano group, an alkyl group, a cycloalkyl group, a phenyl group, an aryl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, and an alkoxy group.)

[0014] [ka] [Effects of the Invention]

[0015] According to the present invention, an organic EL device having a low driving voltage, a high external quantum efficiency, and a long life can be obtained. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a cross-sectional view showing an example of the structure of a light-emitting element of the present invention. [Figure 2] 1 is a Raman spectrum obtained from an example of a layer containing a phenanthroline derivative of the present invention and a metal dopant. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, light-emitting devices according to 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 embodiments and can be modified in various ways depending on the purpose and application. Furthermore, matters cited as preferred examples in specific embodiments and embodiments can also be applied to other embodiments and embodiments.

[0018] FIG. 1 is a cross-sectional view showing an example of the structure of a light-emitting device according to an embodiment of the present invention. In this embodiment, light-emitting device 100 is formed on substrate 50 and has organic layer 10 between anode 20 and cathode 30. Organic layer 10 is configured by stacking, in order from the anode 20 side, a first light-emitting layer 4A, a first electron transport layer 2A, an N-type charge generation layer 1, a P-type charge generation layer 5, a second light-emitting layer 4B, a second electron transport layer 2B, and an electron injection layer 3. Light-emitting device 100 is a so-called tandem organic EL device. In the present invention, the configuration of the light-emitting device is not limited to that shown in FIG. 1. That is, the organic layer only needs to have at least a light-emitting layer, an electron transport layer, an N-type charge generation layer, a P-type charge generation layer, and an electron injection layer, and there is no limit to the number of these layers, and other layers may also be included.

[0019] The light-emitting device 100 contains a phenanthroline derivative and a metal dopant in at least one of the N-type charge generating layer 1, the first electron transport layer 2A, the second electron transport layer 2B, and the electron injection layer 3. The layer containing the phenanthroline derivative and the metal dopant exhibits a peak intensity of (1550±20) cm in a Raman spectrum. -1 and (1600±20) cm -1 The Raman spectrum shows a peak at (1600±20) cm -1 The peak intensity at I 1600 , (1550±20)cm -1 The peak intensity at I 1550 and the doping concentration of the metal dopant in the layer containing the phenanthroline derivative and the metal dopant is W (mol%), (I 1550 / I 1600 ) / W is 0.03 or more.

[0020] A Raman spectrum is a spectral distribution diagram obtained by Raman spectroscopy, which is a graph showing the intensity of light at each wavenumber (the reciprocal of the wavelength) obtained by decomposing the light into wavenumbers. Raman spectroscopy is a method for measuring the microscopic environment of molecular chains using Raman scattered light, and in addition to chemical analysis such as the qualitative and quantitative determination of functional groups, it can also obtain microscopic structural information about polymer chains, such as molecular orientation, crystallinity, conformational changes, and microscopic stress load states.

[0021] Raman scattered light is light with a different wavelength from the incident light that is generated when a substance is irradiated with light and the light interacts with the substance. This wavelength difference corresponds to the energy of the molecular vibrations of the substance, so Raman scattered light with different wavelengths can be obtained between substances with different molecular structures, allowing for the investigation of various physical properties such as orientation and crystallinity.

[0022] Raman spectroscopy equipment consists of an excitation light source, a filter to remove Rayleigh scattered light, a spectrometer to resolve the Raman scattered light into a spectrum, and a detector. Excitation light sources include gas lasers and solid-state lasers that emit blue, green, red, near-infrared, and ultraviolet light. Detectors include cooled CCDs (charge-coupled devices), EMCCDs (electron-multiplying CCDs), and InGaAs detectors.

[0023] Raman spectroscopy provides information on chemical bonds from its peak wavenumber, information on molecular structure and differences in crystalline structure from the waveform of the entire spectrum, and information on stress and strain from shifts in peak wavenumber.Raman spectroscopy provides a signal with wavenumber on the horizontal axis and fluorescence intensity on the vertical axis, with fluorescence peaks arising from molecular vibrations occurring in specific wavenumber ranges.

[0024] For example, the wavenumber in the Raman spectrum is (1550±20) cm -1 is the wavenumber region originating from the complex, and the presence of a fluorescence peak at this wavenumber indicates that a complex is formed between the compound and the metal dopant. Wavenumber (1600±20) cm -1is the wavenumber region due to the stretching vibration of the C—C double bond of the aromatic ring, and the presence of a fluorescence peak at this wavenumber indicates that the compound that formed the complex is a compound with a C—C double bond of the aromatic ring, such as a phenanthroline derivative.

[0025] Therefore, in the present invention, 1550 / I 1600 is an index showing the degree of formation of metal complexes of phenanthroline derivatives. 1550 / I 1600 corresponds to the anion intensity ratio of the phenanthroline derivative. 1550 / I 1600 ) / W corresponds to the anion intensity ratio of the phenanthroline derivative corresponding to the doping concentration of the metal dopant.

[0026] Above (I 1550 / I 1600 In the light-emitting device 100 in which the value of ) / W is 0.03 or more, the layer containing the phenanthroline derivative and the metal dopant stably forms a complex even with a small doping amount, and the layer is capable of generating a certain amount or more of anions of the phenanthroline derivative. It is believed that the generation of a certain amount or more of anions of the phenanthroline derivative and the formation of a complex with the metal dopant leads to an organic EL device having a low driving voltage, a high external quantum efficiency, and a long life.

[0027] (I 1550 / I 1600 The higher the value of (I ) / W, the more stable the complex with the metal dopant is formed, and the more anions of the phenanthroline derivative are generated. 1550 / I 1600 On the other hand, from the viewpoint of ease of fabrication of the light-emitting device, the value of (I 1550 / I 1600 ) / W is preferably 0.67 or less.

[0028] In addition, the Raman spectrum is (1400±50)cm -1The Raman spectrum has a peak at (1400±50) cm -1 The peak intensity at I 1400 When I 1400 / I 1600 The wave number in the Raman spectrum is preferably (1400±50) cm -1 is the wavenumber region due to the stretching vibration of the C-N bond, and the presence of a fluorescence peak at this wavenumber indicates that the compound that formed the complex is a compound with a C-N bond structure, such as a phenanthroline derivative.

[0029] Therefore, I 1400 / I 1600 is an index showing the ratio of the C—N bond stretching vibration to the C—C double bond stretching vibration of the aromatic ring. The fact that this ratio is within a certain range indicates that the crystal structure of the phenanthroline derivative does not change significantly even when a complex with a metal dopant is formed, and that the phenanthroline derivative maintains its charge-transfer properties.

[0030] Specifically, I 1400 / I 1600 It is preferable that the value of is 0.50 or more and 1.50 or less, and by being in this range, the manufacturing yield when manufacturing the light emitting device 100 is significantly improved. More preferably, I 1400 / I 1600 is between 0.50 and 1.10. 1400 / I 1600 When the value is 0.60 or more and 0.90 or less, it is considered that the layer consisting of the phenanthroline derivative and the metal dopant is formed with a desired crystal structure, and it is assumed that the layer has very high charge mobility.

[0031] Next, each layer constituting the light-emitting device 100 will be described. The anode 20 is an electrode formed on a substrate, and is not particularly limited as long as it is made of a material that can efficiently inject holes into the organic layer 10. Examples include metals such as gold, silver, aluminum, and chromium; and conductive polymers such as polythiophene, polypyrrole, and polyaniline. When using a metal, it is preferable to make the film thin so that light can be semi-transmitted. In addition, transparent or semi-transparent electrode materials are preferred, and conductive metal oxides such as zinc oxide, tin oxide, indium oxide, indium tin oxide (ITO), and indium zinc oxide (IZO) may be used.

[0032] The anode 20 can be formed by an optimal method depending on the material used, and examples of such methods include sputtering, vapor deposition, and inkjet printing. For example, sputtering is used when the anode 20 is made of a metal oxide, and vapor deposition is used when the anode 20 is made of a metal. The thickness of the anode 20 is not particularly limited, but is preferably several nanometers to several hundred nanometers. These electrode materials may be used alone, or multiple materials may be stacked or mixed. Various wirings, circuits, and switching elements may be interposed between the substrate 50 and the anode 20.

[0033] Cathode 30 is an electrode formed on the surface opposite anode 20, sandwiching organic layer 10. There are no particular limitations on the material used for cathode 30, as long as it is a material that can efficiently inject electrons into light-emitting layer 1. Generally, metals such as platinum, gold, silver, copper, iron, tin, aluminum, and indium, alloys or multilayer laminate films of these metals with low-work-function metals such as lithium, sodium, potassium, calcium, and magnesium, and conductive metal oxides such as zinc oxide, indium tin oxide (ITO), and indium zinc oxide (IZO) are preferred. Among these, metals selected from aluminum, silver, and magnesium as the main component are preferred in terms of electrical resistance, ease of film formation, film stability, and luminous efficiency.

[0034] Cathode 30 is preferably made of, for example, magnesium and silver, because this facilitates electron injection into second electron transport layer 2B and electron injection layer 3 and enables low-voltage drive. A protective layer (cap layer) may be laminated on cathode 30 to protect cathode 30. Materials constituting the protective layer are not particularly limited, and examples thereof include metals such as platinum, gold, silver, copper, iron, tin, aluminum, and indium, alloys using these metals, inorganic substances such as silica, titania, and silicon nitride, and organic polymer compounds such as polyvinyl alcohol, polyvinyl chloride, and hydrocarbon-based polymer compounds.

[0035] The light-emitting layers 4A and 4B are layers that emit light by excitation energy generated by the recombination of holes and electrons. The material of the light-emitting layers 4A and 4B is preferably a phosphor that has fluorescent properties in the visible region and is easy to form into a film, such as Be-benzoquinolinol (BeBq2), 2,5-bis(5,7-di-t-pentyl-2-benzoxazolyl)-1,3,4-thiadiazole, 4,4'-bis(5,7-benzyl-2-benzoxazolyl)stilbene, 2,5-bis([5-α,α-dimethylbenzyl]-2-benzoxazolyl)thiophene, 4,4'-bis(5,7-benzyl-2-benzoxazolyl)stilbene ... benzoxazoles such as bis(2-benzoxazolyl)biphenyl, 5-methyl-2-[2-[4-(5-methyl-2-benzoxazolyl)phenyl]vinyl]benzoxazolyl, 2-[2-(4-chlorophenyl)vinyl]naphtho[1,2-d]oxazole, benzothiazoles such as 2,2'-(p-phenylenedivinylene)-bisbenzothiazole, 2-[2-[4-(2-benzimidazolyl)phenyl]vinyl]benzimidazolyl, benzimidazoles such as tris(8-quinolinol)aluminum, bis(8-quinolinol)magnesium, bis(benzo[f]-8-quinolinol)zinc, bis(2-methyl-8-quinolinolato)aluminum oxide, tris(8-quinolinol)indium and other 8-hydroxyquinoline-based metal complexes; metal chelated oxinoid compounds such as dilithium epindolidine; 1,4-bis(2-methylstyryl)benzene, 1,4-(3 Examples of suitable styrene-based compounds include styrylbenzene compounds such as 1,4-bis(4-methylstyryl)benzene and 1,4-bis(4-methylstyryl)benzene, distyrpyrazine derivatives such as 2,5-bis(4-methylstyryl)pyrazine, naphthalimide derivatives, perylene derivatives, oxadiazole derivatives, aldazine derivatives, cyclopentadiene derivatives, styrylamine derivatives, coumarin derivatives, aromatic dimethylidine derivatives, anthracene, salicylate, pyrene, and coronene.

[0036] The charge generation layer generates or separates charges upon application of a voltage and injects the charges into adjacent layers, with the N-type charge generation layer 1 being a charge generation layer that tends to generate electrons as charges, and the P-type charge generation layer 5 being a charge generation layer that tends to generate holes as charges. In the light-emitting element, the charge generation layer generates charges or separates charges into holes and electrons upon application of a voltage, and these holes and electrons are injected into the light-emitting layers 4A and 4B.

[0037] In a light-emitting element including a plurality of light-emitting layers 4A, 4B, when a charge generation layer is used as an intermediate layer, the N-type charge generation layer 1 supplies electrons to the light-emitting layer 4A located on the anode side 20, and the P-type charge generation layer 5 supplies holes to the light-emitting layer 4B located on the cathode side 30. Therefore, by forming the N-type charge generation layer 1 and the P-type charge generation layer 5 between the plurality of light-emitting layers 4A, 4B in the light-emitting element 100, it is possible to further improve the element efficiency, reduce the driving voltage, and further improve the durability of the element.

[0038] Materials for the N-type charge generation layer 1 may include, in addition to the above-mentioned metal complexes of phenanthroline derivatives, triazine derivatives, oligopyridine derivatives, terpyridine derivatives, etc. Materials for the P-type charge generation layer 5 include HAT-CN6, F4-TCNQ, tetracyanoquinodimethane derivatives, radialene derivatives, iodine, FeCl3, FeF3, SbCl5, etc. Among these, examples include HAT-CN6 and radialene derivatives such as (2E,2'E,2''E)-2,2',2''-(cyclopropane-1,2,3-triylidene)tris(2-(perfluorophenyl)-acetonitrile) and (2E,2'E,2''E)-2,2',2''-(cyclopropane-1,2,3-triylidene)tris(2-(4-cyanoperfluorophenyl)-acetonitrile).

[0039] The electron transport layers 2A and 2B inject electrons generated in the N-type charge generation layer 1 into the light-emitting layers 4A and 4B, and also block the inflow of electrons toward the cathode 30. Examples of materials for the electron transport layers 2A and 4B include metal complexes of the phenanthroline derivatives of the present invention, as well as styryl aromatic ring derivatives such as 4,4'-bis(diphenylethenyl)biphenyl, quinone derivatives such as anthraquinone and diphenoquinone, quinolinol complexes such as tris(8-quinolinolato)aluminum(III), joxadiazole derivatives such as 1,3-bis(4-tert-butylphenyl-1,3,4-oxadiazolyl)phenylene (OXD-7), anthraquinodimethane derivatives, diphenylquinone derivatives, and aluminum quinolinol (Alq) complexes.

[0040] The electron injection layer 3 is formed to assist the injection of electrons from the cathode 30 to the electron transport layer 2, and is a layer that prevents short-circuiting of the light-emitting device and improves the electron injection property. Materials for the electron injection layer 3 include metal complexes of the phenanthroline derivative of the present invention, as well as metal complexes of quinolinol such as tris(8-quinolinolato)aluminum(III), benzoquinolinol, pyridylphenol, flavonol, hydroxyimidazopyridine, hydroxybenzazole, and hydroxytriazole, and compounds having a heteroaryl ring structure containing electron-accepting nitrogen.

[0041] The method for forming the organic layer 10 may be either a dry process or a wet process, and is not particularly limited to resistance heating evaporation, electron beam evaporation, sputtering, molecular lamination, coating, inkjet printing, or the like, but resistance heating evaporation is usually preferred in terms of device characteristics.

[0042] The thickness of the organic layer 10 is not particularly limited because it depends on the resistance value of the light-emitting substance, but is preferably 5 to 1000 nm. The thickness of each of the light-emitting layers 4A, 4B, electron transport layers 2A, 4B, N-type charge generation layer 1, P-type charge generation layer 5, and electron injection layer 3 is preferably 1 nm or more and 200 nm or less, more preferably 5 nm or more and 100 nm or less.

[0043] The ratio of the thickness of the electron injection layer 3 to the thickness of the N-type charge generation layer 1, i.e., (thickness of electron injection layer 3 / thickness of N-type charge generation layer 1), is preferably 0.06 to 18.5. When the ratio (thickness of electron injection layer 3 / thickness of N-type charge generation layer 1) is 0.06 to 18.5, the light-emitting device can be driven at a lower voltage. More preferably, the ratio (thickness of electron injection layer 3 / thickness of N-type charge generation layer 1) is 0.5 to 5. When the ratio (thickness of electron injection layer 3 / thickness of N-type charge generation layer 1) is 0.5 to 5, the region in the N-type charge generation layer 1 where electrons can be generated can be widened, and a light-emitting device with excellent durability can be easily obtained.

[0044] The phenanthroline derivative used in the present invention is preferably a compound represented by the following general formula (1).

[0045] [ka]

[0046] In general formula (1), A is a group represented by the following formula (2) or (3), and X and Y are each independently selected from the group consisting of a hydrogen atom, a halogen atom, a cyano group, an alkyl group, a cycloalkyl group, an aryl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, and an alkoxy group.

[0047] [ka]

[0048] Examples of halogen atoms include chlorine, bromine, iodine, and fluorine atoms. The cyano group is a functional group with strong electron-withdrawing properties, represented by the structure -C≡N, and is bonded to other functional groups via a carbon atom. The cyano group may be substituted by a carboxylic acid or amide through hydrolysis.

[0049] The alkyl group is a saturated aliphatic hydrocarbon group, and examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, a pentyl group, etc. The cycloalkyl group is a saturated alicyclic hydrocarbon group, and examples thereof include a cyclopropyl group, a cyclohexyl group, a norbornyl group, an adamantyl group, etc.

[0050] The aryl group is an aromatic hydrocarbon group, and examples thereof include a phenyl group, a naphthyl group, a fluorenyl group, a benzofluorenyl group, a dibenzofluorenyl group, a phenanthryl group, an anthracenyl group, a benzophenanthryl group, a benzanthracenyl group, a chrysenyl group, a pyrenyl group, a fluoranthenyl group, a triphenylenyl group, a benzofluoranthenyl group, a dibenzanthracenyl group, a perylenyl group, and a helicenyl group.

[0051] The number of ring carbon atoms in the aryl group is not particularly limited, but is preferably in the range of 6 to 40, more preferably 6 to 11. In addition, in a phenyl group, when two adjacent carbon atoms in the phenyl group each have a substituent, these substituents may form a ring structure. Depending on the structure, the resulting group may fall into one or more of the following categories: a "substituted phenyl group," an "aryl group having a structure in which two or more rings are fused," and a "heteroaryl group having a structure in which two or more rings are fused."

[0052] Among the above aryl groups, phenyl, naphthyl, fluorenyl, phenanthryl, anthracenyl, pyrenyl, fluoranthenyl, and triphenylenyl are preferred. Furthermore, among these, compounds in which both X and Y are phenyl are preferred in terms of low-voltage operation, durability, and the like.

[0053] Heterocyclic groups are functional groups with a ring structure containing heteroatoms such as nitrogen, oxygen, and sulfur, and include pyridine, thiophene, pyrrole, quinoline, benzothiophene, indole, benzofuran, acridine, dibenzothiophene, carbazole, dibenzofuran, borirane, borylene, aziridine, azirine, oxirane, oxirene, phosphirane, phosphirene, thiirane, thiylene, diaziridine, diazirine, oxaziridine, dioxirane, diazetidine, diazeto, dioxetane, dioxetane, dithieto, dithieto, stiborane, stibole, arsolane, arsole, bismolane, bismol, borolane, borole, pyrrolidine, pyrrole, tetrahydrofuran, furan, phosphorane, phosphole, selenolane, selenophene, silacyclopentane, silole, tetrahydrothiophene, tellurophene, stanolane, stanol, imidazolidine, and pyrazolidine. , imidazole, pyrazole, oxazolidine, isoxazolidine, oxazole, isoxazole, thiazolidine, isothiazolidine, thiazole, isothiazole, dioxolane, dithiolane, triazole, furazan, oxadiazole, thiadiazole, dioxazole, dithiazole, tetrazole, oxatetrazole, thiatetrazolepentazole, stibinine, bismabenzene, borinane, borabenzene, germinane, germine, piperidine, tetrahydropyran, pyran, phosphinane, phospholine, silinane, siline, thiane, thiopyran, stanninane, stannin, piperazine, diazine, morpholine, oxazine, thiomorpholine, thiazine, dioxane, dioxine, dithiane, dithiin, hexahydro-1,3,5-triazine, triazine, trioxane, trithiane, tetrazine, pentazine, hexazine, and the like.

[0054] Alkenyl groups are unsaturated alicyclic hydrocarbon groups containing double bonds, such as pentenyl, pentadienyl, and hexenyl groups. Cycloalkenyl groups are unsaturated alicyclic hydrocarbon groups containing double bonds, such as cyclopentenyl, cyclopentadienyl, and cyclohexenyl groups. Alkynyl groups are unsaturated aliphatic hydrocarbon groups containing triple bonds, such as ethynyl groups. Alkoxy groups are groups in which an aliphatic hydrocarbon group is bonded via an ether bond, such as methoxy, ethoxy, and propoxy groups.

[0055] Among these phenanthroline derivatives, 1,3-di(1,10-phenanthroline-2-yl)benzene, 2-phenyl-9-[3-(9-phenyl-1,10-phenanthroline-2-yl)phenyl]-1,10-phenanthroline, 2-(3-([2,2':6',2"-terpyridine]-4'-yl)phenyl-9-phenyl-1,10-phenanthroline, 2-methyl-1,10-phenanthroline, 2-ethyl-1,10-phenanthroline, 2-isopropyl-1,10-phenanthroline, 2-butyl-1,10-phenanthroline, 2-tert-butyl-1,10-phenanthroline, 2-cyclohexyl-1,10-phenanthroline, 2-(4-methoxyphenyl)-1,10-phenanthroline, 2-(4-tert-butyl) -phenyl-1,10-phenanthroline, 2-phenyl-1,10-phenanthroline, 2-(4-hydroxyphenyl)-1,10-phenanthroline, 2-(3,5-di-tert-butyl-4-methoxyphenyl)-1,10-phenanthroline, and the like are preferred.

[0056] Furthermore, among these phenanthroline derivatives, any one of 1,3-di(1,10-phenanthroline-2-yl)benzene, 2-phenyl-9-[3-(9-phenyl-1,10-phenanthroline-2-yl)phenyl]-1,10-phenanthroline, and 2-(3-([2,2':6',2"-terpyridine]-4'-yl)phenyl-9-phenyl-1,10-phenanthroline is particularly preferred.

[0057] The metal dopant used in the present invention is preferably a metal element or a metal compound. Examples of metal elements include alkali metals such as Li, Na, K, Rb, and Cs, alkaline earth metals such as Mg, Ca, Sr, and Ba, and rare earth metals such as europium and ytterbium. Examples of metal compounds include inorganic salts containing alkali metals, alkaline earth metals, and rare earth metals, such as metal oxides, carbonates, chlorides, fluorides, and sulfides, as well as complexes of alkali metals, alkaline earth metals, and rare earth metals with organic substances. Among these, metallic lithium, metallic ytterbium, lithium fluoride (LiF), and lithium quinolinol (Liq) are preferred.

[0058] From the viewpoint of facilitating driving at a low voltage and improving durability, the content ratio of the phenanthroline derivative to the metal dopant is preferably in the range of 97.5±2.4 wt %:2.5±2.4 wt %, more preferably 98.0±0.4 wt %:2.0±0.4 wt %, and even more preferably 98.0±0.4 wt %:2.0±0.4 wt %.

[0059] Particularly preferred embodiments include a light-emitting element in which the phenanthroline derivative is 1,3-di(1,10-phenanthroline-2-yl)benzene and the metal dopant is lithium or ytterbium, and a light-emitting element in which the phenanthroline derivative is 2-(3-([2,2':6',2"-terpyridine]-4'-yl)phenyl-9-phenyl-1,10-phenanthroline or 2-phenyl-9-[3-(9-phenyl-1,10-phenanthroline-2-yl)phenyl]-1,10-phenanthroline and the metal dopant is lithium.

[0060] Other particularly preferred embodiments include a light-emitting device in which the phenanthroline derivative is 1,3-di(1,10-phenanthroline-2-yl)benzene and the phenanthroline derivative:metal dopant range is 97.5±2.4% by weight:2.5±2.4% by weight, and a light-emitting device in which the phenanthroline derivative is 2-(3-([2,2':6',2"-terpyridine]-4'-yl)phenyl-9-phenyl-1,10-phenanthroline or 2-phenyl-9-[3-(9-phenyl-1,10-phenanthroline-2-yl)phenyl]-1,10-phenanthroline and the phenanthroline derivative:metal dopant range is 98.0±0.4% by weight:2.0±0.4% by weight. [Example]

[0061] The present invention will be described below with reference to the following examples. In Tables 1 to 4, the abbreviations of the phenanthroline derivatives correspond to the following compounds, respectively. ETM-1: 1,3-di(1,10-phenanthrolin-2-yl)benzene ETM-2: 2-phenyl-9-[3-(9-phenyl-1,10-phenanthrolin-2-yl)phenyl]-1,10-phenanthroline ETM-3: 2-(3-([2,2':6',2"-terpyridin]-4'-yl)phenyl-9-phenyl-1,10-phenanthroline ETM-4: 2-(4-(phenanthrene-9-yl)naphthalen-1-yl)-1,10-phenanthroline Example 1 An anode made of ITO (indium tin oxide) was formed (thickness 100 nm) by sputtering on a substrate made of alkali-free glass with a thickness of 0.7 mm and a size of 75 mm x 75 mm. After performing UV / ozone cleaning, the cleaned substrate and the material for deposition were placed in the chamber of a vacuum deposition device, and the chamber was heated to 3.3 x 10 -4 The chamber was evacuated to a pressure of 100 Pa. After a predetermined degree of vacuum was reached, a hole transport layer made of N,N'-α-dinaphthylbenzidine (α-NPD) was formed on the anode (thickness: 60 nm).

[0062] Next, a 30 nm thick light-emitting layer was formed on the hole-transporting layer. The light-emitting layer was a co-evaporated film of coumarin 6 (1.0 wt%) and tris[8-hydroxyquinolinato]aluminum (Alq3). Next, a 10 nm thick electron-transporting layer made of a benzoquinolinol complex was formed on the light-emitting layer.

[0063] Next, a 25-nm-thick triazine derivative was laminated on the electron transport layer as an N-type charge generation layer, and a 10-nm-thick HAT-CN6 was laminated on top as a P-type charge generation layer.A hole transport layer with a thickness of 25 nm, a 20-nm-thick light-emitting layer, and a 16-nm-thick electron transport layer were laminated on top of that by vapor deposition, each with the same composition as above.

[0064] Next, the chamber was filled with 8.5 x 10 -5 After evacuating the chamber to 100 Pa, an electron injection layer (40 nm thick) was formed on the electron transport layer. The electron injection layer in this example was a co-evaporated film made from a thermally evaporated product of a phenanthroline derivative made of 1,3-di(1,10-phenanthroline-2-yl)benzene and a thermally evaporated product of metallic lithium. The metallic lithium concentration in the electron injection layer was adjusted to 1 wt %. Therefore, the doping concentration W was 0.635 (mol %).

[0065] When forming the electron injection layer, a co-deposited film corresponding to the electron injection layer was also formed in an area other than the area where the light-emitting element was to be formed. The co-deposited film in this area was formed in the same state as the electron injection layer of the light-emitting element. The co-deposited film in this area was used as the area for spectroscopic measurement, which will be described later.

[0066] A cathode (150 nm thick) capable of extracting light from the light-emitting layer was formed on the electron injection layer by sputtering. The cathode was made of ITO (indium tin oxide). Note that no ITO was formed on the area used for spectroscopic measurement. The substrate was then transferred to a glove box and sealed with a glass cap containing a desiccant in a nitrogen atmosphere to obtain a light-emitting device.

[0067] Next, the region for spectroscopic measurement was measured by Raman spectroscopy. The Raman spectrum obtained as a result of the Raman spectroscopy measurement is shown in Figure 2. The measurement conditions for Raman spectroscopy were as follows: Measurement equipment: Renishaw 'inVia Raman' microscopy Excitation light source: 785 nm semiconductor laser (measurement intensity 2 mW) Resolution; 3.0cm -1 Data analysis: Spectral data processing and management software GRAMS / AI (Thermo Scientific).

[0068] In Figure 2, the signal shown in A is (1600±20) cm -1 The signal with the highest intensity in the range of 1600 ) and the signal shown in B is (1550±20) cm -1 The signal with the highest intensity in the range of 1550 ) and the signal shown in C is (1400±50) cm -1 The signal with the highest intensity in the range of 1400 )

[0069] The intensity ratio of this B / A signal (I 1550 / I 1600 ) is 0.10, (I 1550 / I 1600 The value of C / A signal intensity ratio (I 1400 / I 1600 ) was 0.56, which was within the range of 0.5 to 1.0.

[0070] The light-emitting device fabricated using the above procedure was subjected to 10 mA / cm 2The driving voltage was measured when a direct current of 10 mA / cm was applied, and the external quantum efficiency (EQE) was calculated. The driving voltage is an important indicator of initial characteristics related to product life in terms of the power consumption of the element, while the external quantum efficiency is the most important indicator of luminous efficiency, where electrical energy is converted into light energy and extracted into the air. In addition, the environmental temperature was set to 30°C, the total luminous flux correction value was set to 1, and the initial current was set to 10 mA / cm. 2 The device was continuously energized at 100 V, and the time it took for the brightness to reach 95% of the initial brightness (LT95) was measured. The results were a driving voltage of 8.7 V, an external quantum efficiency of 13.7%, and a LT95 of 127 hours.

[0071] Examples 2 to 7 A light-emitting device was fabricated in the same manner as in Example 1, except that the phenanthroline derivative, metal dopant, and metal dopant concentration W (mol%) in the electron injection layer were changed as shown in Table 1, and measurement by Raman spectroscopy was carried out. 2 The driving voltage was measured when a direct current of 1000 kJ / s was passed through the device, the external quantum efficiency (EQE) was calculated, and the time required for the device to reach 95% of its initial brightness (LT95) was measured. The results are shown in Table 1.

[0072] (Examples 8 to 14) A light-emitting device was fabricated in the same manner as in Example 1, except that the N-type charge generation layer was made of a phenanthroline derivative, a metal dopant, and a metal doping concentration W (mol%) as shown in Table 2, and the material of the electron injection layer was changed to an aluminum quinolinol complex. 2 The driving voltage was measured when a direct current of 1000 kJ / s was passed through the device, the external quantum efficiency (EQE) was calculated, and the time required for the device to reach 95% of its initial brightness (LT95) was measured. The results are shown in Table 2.

[0073] (Examples 15 to 21) A light-emitting device was fabricated in the same manner as in Example 1, except that both electron transport layers were made of the phenanthroline derivative, metal dopant, and metal doping concentration W (mol%) shown in Table 3, and the material of the electron injection layer was changed to an aluminum quinolinol complex.2 The driving voltage was measured when a direct current of 1000 kJ / s was passed through the device, the external quantum efficiency (EQE) was calculated, and the time required for the device to reach 95% of its initial brightness (LT95) was measured. The results are shown in Table 3.

[0074] (Comparative Examples 1 to 6) A light-emitting device was fabricated in the same manner as in Example 1, except that the phenanthroline derivative, metal dopant, and metal doping concentration W (mol%) of the electron injection layer were changed as shown in Table 4, and measurement by Raman spectroscopy was carried out. 2 The driving voltage was measured when a direct current of 1000 kJ / s was passed through the device, the external quantum efficiency (EQE) was calculated, and the time required for the device to reach 95% of the initial brightness (LT95) was measured. The results are shown in Table 4.

[0075] As shown in Tables 1 to 4, (I 1550 / I 1600 It is clear that light-emitting devices having a λ / W ratio of 0.03 or more have a lower driving voltage and improved external quantum efficiency (EQE) and time to reach 95% of the initial luminance (LT95), compared to light-emitting devices that do not satisfy this requirement.

[0076] [Table 1]

[0077] [Table 2]

[0078] [Table 3]

[0079] [Table 4] [Explanation of symbols]

[0080] 1 N-type charge generation layer 2A, 2B Electron transport layer 3 Electron injection layer 4A, 4B Light-emitting layer 5 P-type charge generation layer 10 Organic layer 20 Anode 30 cathode 50 boards 100 light-emitting elements

Claims

1. A light-emitting device having at least a light-emitting layer, an electron transport layer, an N-type charge generation layer, a P-type charge generation layer, and an electron injection layer between an anode and a cathode, at least one of the N-type charge generation layer, the electron transport layer, and the electron injection layer contains a phenanthroline derivative and a metal dopant; The layer containing the phenanthroline derivative and the metal dopant has a Raman spectrum of (1550±20) cm －１ and (1600±20) cm －１ shows a peak at The Raman spectrum of (1600±20) cm －１ The peak intensity at I １６００ , (1550±20)cm －１ The peak intensity at I １５５０ and the doping concentration of the metal dopant in the layer containing the phenanthroline derivative and the metal dopant is W (mol %), (I １５５０ / I １６００ ) / W is 0.03 or more.

2. The above (I １５５０ / I １６００ 2. The light-emitting device according to claim 1, wherein λ / W is 0.10 or more and 0.67 or less.

3. The Raman spectrum is (1400±50) cm －１ The Raman spectrum has a peak at (1400±50) cm －１ The peak intensity at I １４００ When I １４００ / I １６００ The light-emitting device according to claim 1 , wherein the value of the σ is 0.50 or more and 1.50 or less.

4. 2. The light-emitting device according to claim 1, wherein the ratio of the thickness of the electron injection layer to the thickness of the N-type charge generation layer (thickness of the electron injection layer / thickness of the N-type charge generation layer) is 0.06 to 18.

5.

5. 2. The light-emitting device according to claim 1, wherein the phenanthroline derivative is a compound represented by the following general formula (1): 【Chemistry 1】 (In general formula (1), A is a group represented by the following formula (2) or (3), and X and Y are each independently selected from the group consisting of a hydrogen atom, a halogen atom, a cyano group, an alkyl group, a cycloalkyl group, a phenyl group, an aryl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, and an alkoxy group.) 【Chemistry 2】

6. 6. The light-emitting device according to claim 5, wherein a content ratio of the phenanthroline derivative to the metal dopant is phenanthroline derivative:metal dopant=97.5±2.4% by weight:2.5±2.4% by weight.

7. 7. The light-emitting device according to claim 6, wherein a content ratio of the phenanthroline derivative to the metal dopant is 98.0±0.4% by weight:2.0±0.4% by weight.

8. The light-emitting element according to any one of claims 5 to 7, wherein the phenanthroline derivative is any one of 1,3-di(1,10-phenanthrolin-2-yl)benzene, 2-phenyl-9-[3-(9-phenyl-1,10-phenanthrolin-2-yl)phenyl]-1,10-phenanthroline, and 2-(3-([2,2':6',2"-terpyridine]-4'-yl)phenyl-9-phenyl-1,10-phenanthroline.

9. 8. The light-emitting device according to claim 5, wherein the phenanthroline derivative is 1,3-di(1,10-phenanthrolin-2-yl)benzene, and the metal dopant is lithium or ytterbium.

10. 8. The light-emitting device according to claim 6, wherein the phenanthroline derivative is 2-(3-([2,2':6',2"-terpyridin]-4'-yl)phenyl-9-phenyl-1,10-phenanthroline or 2-phenyl-9-[3-(9-phenyl-1,10-phenanthrolin-2-yl)phenyl]-1,10-phenanthroline, and the metal dopant is lithium.

11. 2. A composition used to form at least one of the N-type charge generation layer, the electron transport layer, and the electron injection layer of the light-emitting element according to claim 1, the composition comprising a compound represented by the following general formula (1) and a metal dopant: 【Transformation 3】 (In general formula (1), A is a group represented by the following formula (2) or (3), and X and Y are each independently selected from the group consisting of a hydrogen atom, a halogen atom, a cyano group, an alkyl group, a cycloalkyl group, a phenyl group, an aryl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, and an alkoxy group.) 【Chemistry 4】

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