Material for organic electroluminescent element and organic electroluminescent element

Abstract

To provide an organic EL element having high efficiency and high driving stability, and a material for an organic EL element suitable therefor.SOLUTION: The material for an organic EL element includes a specific indolocarbazole compound. The material for the organic EL element is suitable as a material for a host of a light-emitting layer or for a hole blocking layer of the organic EL element.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a material for an organic electroluminescent device and an organic electroluminescent device using the same. [Background technology]

[0002] When a voltage is applied to an organic electroluminescent device (referred to as an organic EL device), holes are injected from the anode and electrons are injected from the cathode into the light-emitting layer. In the light-emitting layer, the injected holes and electrons recombine to generate excitons. At this time, due to the statistical laws of electron spin, singlet excitons and triplet excitons are generated in a ratio of 1:3. It is said that the internal quantum efficiency of fluorescent organic EL devices that use emission from singlet excitons is limited to 25%. On the other hand, it is known that the internal quantum efficiency of phosphorescent organic EL devices that use emission from triplet excitons can be increased to 100% if intersystem crossing from singlet excitons is efficiently performed. However, for phosphorescent organic EL devices, further improvement in efficiency and low voltage characteristics remain technical challenges.

[0003] Recently, highly efficient organic EL devices that utilize delayed fluorescence have been developed. For example, organic EL devices that utilize the TTF (Triplet-Triplet Fusion) mechanism, which is one of the mechanisms of delayed fluorescence, are known. The TTF mechanism utilizes the phenomenon in which singlet excitons are generated by the collision of two triplet excitons, and it is thought that the internal quantum efficiency can theoretically be increased to 40%. However, since the efficiency is lower than that of phosphorescent organic EL devices, further improvements in efficiency are required. Patent Document 1 discloses an organic EL device that utilizes the TADF (Thermally Activated Delayed Fluorescence) mechanism. The TADF mechanism utilizes the phenomenon of reverse intersystem crossing from triplet excitons to singlet excitons in a material with a small energy difference between the singlet and triplet levels, and is thought to theoretically be able to increase the internal quantum efficiency to 100%. However, as with phosphorescent devices, further improvements in efficiency characteristics and low-voltage characteristics are required. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] WO2011 / 070963 A [Patent Document 2] KR 2014094408 A [Patent Document 3] KR 2017060836 A [Patent Document 4] CN 103193717 A [Patent Document 5] WO2011 / 005060 A

[0005] Patent Documents 2 and 3 disclose compounds having two triazine rings. Patent Documents 4 and 5 disclose compounds having two pyrimidine rings linked together by a phenylene group.

[0006] However, these do not teach the compound of the present invention, nor do they demonstrate the usefulness of an organic EL device using this compound. Summary of the Invention

[0007] In order to apply organic EL elements to display elements such as flat panel displays, it is necessary to improve the luminous efficiency of the elements while ensuring sufficient stability during operation. In view of the above-mentioned current situation, an object of the present invention is to provide a practically useful organic EL element that achieves high efficiency and low voltage characteristics, and a compound suitable for such an organic EL element.

[0008] As a result of extensive research, the present inventors have found that excellent properties can be exhibited by using a fused aromatic heterocyclic compound represented by the following general formula (1) in an organic EL device, and have thus completed the present invention.

[0009] The present invention is a material for organic electroluminescent devices, which comprises a compound represented by general formula (1). [ka]

[0010] Here, ring a is represented by formula (1a), and ring a is fused to an adjacent ring at any position, X is NR 11 , S, O, or CR 12 R 13 and R 11 , R 12 , and R 13 each independently represents an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 16 carbon atoms, or a substituted or unsubstituted linked aromatic group in which 2 to 5 of these aromatic rings are linked together. R independently represents hydrogen, deuterium, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 16 carbon atoms. Ar 1 and Ar 2 are independently an aromatic heterocyclic group represented by formula (1b), Ar 3each independently represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 16 carbon atoms, or a substituted or unsubstituted linked aromatic group in which 2 to 5 of these aromatic rings are linked together. R 14 each independently represents hydrogen, deuterium, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 16 carbon atoms, or a substituted or unsubstituted linked aromatic group in which 2 to 5 of these aromatic rings are linked together. Y is independently N or CR 14 and at least one is N. L 1 represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms.

[0011] L 1 Examples of the phenylene group include a phenylene group represented by the following formula (1c) or (1d). [ka]

[0012] X is NR 11 where R 11 is R in general formula (1). 11 I agree with this.

[0013] The compound represented by general formula (1) includes a compound represented by general formula (2). [ka] (Here, ring a, R, R 14 , L 1 , Ar 2 , Ar 3 are the same as those in general formula (1).

[0014] More specifically, compounds represented by any one of the general formulas (3) to (8) are included. [ka] [ka] (where R, L 1 , Ar 2 , Ar 3 are the same as those in general formula (1), and R 15 is R in general formula (1) 11 I agree with that.) Among these, compounds represented by any one of general formulas (3) to (5) are preferred.

[0015] The compound represented by general formula (1) preferably has an absolute value of electron affinity (EA) of more than 2.6 eV and an absolute value of ionization potential (IP) of less than 6.1 eV.

[0016] The present invention provides an organic electroluminescent device comprising an anode, an organic layer, and a cathode laminated on a substrate, wherein at least one of the organic layers contains the above-described material for organic electroluminescent devices.

[0017] The organic layer containing the material for an organic electroluminescent device can be at least one layer selected from the group consisting of a light-emitting layer, an electron-transporting layer, and a hole-blocking layer.

[0018] The light-emitting layer contains a host and a light-emitting dopant material, and the light-emitting dopant material can be an organometallic complex containing at least one metal selected from the group consisting of ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum, and gold. Preferably, the light-emitting layer contains a material for an organic electroluminescent device as a host.

[0019] The light-emitting dopant material may also be a thermally activated delayed fluorescent dopant material. Alternatively, a hole-blocking layer may be provided adjacent to the light-emitting layer, and the above-mentioned material for organic electroluminescent devices may be contained in the hole-blocking layer.

[0020] The material for an organic EL device of the present invention has a structure represented by general formula (1). In a compound having such a structural feature, the lowest unoccupied molecular orbital (LUMO), which affects the electron injection and transport properties of the material, is distributed mainly on the nitrogen-containing six-membered ring. Furthermore, since the compound of the present invention has two or more nitrogen-containing six-membered rings, the electron injection and transport properties of the material can be highly controlled by, for example, widening the LUMO orbital and increasing the electron injection and transport properties by changing the number and linking mode of linking groups present between the nitrogen-containing six-membered rings. On the other hand, the highest occupied molecular orbital (HOMO), which affects the hole injection and transport properties of a material, is distributed on fused aromatic heterocycles, such as indolocarbazole. The distribution of the HOMO orbital can be adjusted by changing the fused aromatic heterocycle ring type, the type of substituent, and the position where the substituent is introduced, thereby enabling high-level control of the hole injection and transport properties of the material. Due to the above-mentioned characteristics, the material of the present invention is a material having both charge (electron and hole) injection and transport properties suitable for device construction, and by using this in an organic EL device, it is possible to reduce the device's driving voltage and achieve high luminous efficiency. Furthermore, the material for organic EL devices of the present invention exhibits good amorphous properties and high thermal stability, and is also extremely stable in the excited state, so that organic EL devices using this material have a long operating life and durability at a practical level. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a cross-sectional view showing an example of the structure of an organic EL element. DETAILED DESCRIPTION OF THE INVENTION

[0022] The material for organic electroluminescent devices of the present invention is represented by the general formula (1). In general formula (1), ring a is a ring represented by formula (1a), and this ring a is fused to the adjacent ring at any position.

[0023] Ar 1 and Ar 2are independently an aromatic heterocyclic group represented by formula (1b), wherein Y is independently N or CR 14 and at least one is N. Preferably, at least two of Y in formula (1b) are N, and more preferably, all of Y are N.

[0024] R 14 each independently represents hydrogen, deuterium, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 16 carbon atoms, or a substituted or unsubstituted linked aromatic group in which 2 to 5 of these aromatic rings are linked together. A substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms or a substituted or unsubstituted aromatic heterocyclic group having 3 to 16 carbon atoms is preferred. A substituted or unsubstituted aromatic hydrocarbon group having 6 to 10 carbon atoms is more preferred. A phenyl group is even more preferred.

[0025] In this specification, the linking aromatic group refers to a group in which aromatic rings of aromatic hydrocarbon groups or aromatic heterocyclic groups are linked by a single bond, and these may be linked in a linear or branched manner, and the aromatic rings may be the same or different.

[0026] Ar 3 is a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 16 carbon atoms, or a substituted or unsubstituted linked aromatic group in which 2 to 5 of these aromatic rings are linked together, preferably a substituted or unsubstituted aromatic hydrocarbon group having 6 to 10 carbon atoms, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 12 carbon atoms, more preferably a substituted or unsubstituted aromatic hydrocarbon group having 6 to 10 carbon atoms. The aromatic heterocyclic group preferably contains N, O, or S as a heteroatom.

[0027] Ar 3Specific examples of when is an unsubstituted aromatic hydrocarbon group or an unsubstituted aromatic heterocyclic group include groups derived from benzene, naphthalene, anthracene, fluoranthene, phenanthrene, triphenylene, pyridine, pyrimidine, triazine, thiophene, isothiazole, thiazole, pyridazine, pyrrole, pyrazole, imidazole, pyrazine, furan, isoxazole, oxazole, quinoline, isoquinoline, quinoxaline, quinazoline, benzotriazole, phthalazine, indole, benzofuran, benzothiophene, benzoxazole, benzothiazole, indazole, benzimidazole, benzisothiazole, benzothiadiazole, dibenzofuran, dibenzothiophene, dibenzoselenophene, benzocarbazole, benzonaphthothiophene, benzonaphthofuran, phenanthroline, or carbazole. Preferred examples include aromatic groups derived from benzene, naphthalene, pyridine, pyrimidine, triazine, thiophene, isothiazole, thiazole, pyridazine, pyrrole, pyrazole, imidazole, triazole, thiadiazole, pyrazine, furan, isoxazole, oxazole, quinoline, isoquinoline, quinoxaline, quinazoline, phthalazine, indole, benzofuran, benzothiophene, benzoxazole, benzothiazole, indazole, benzimidazole, benzisothiazole, or benzothiadiazole, dibenzofuran, dibenzothiophene, or carbazole. More preferred examples include aromatic groups derived from benzene, such as a phenyl group.

[0028] L 1 is a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, and is preferably a p-phenylene group or m-phenylene group represented by the above formula (1c) or formula (1d). Specific examples of aromatic hydrocarbon groups include Ar 3 is an aromatic hydrocarbon group.

[0029] X is NR 11 , S, O, or CR 12 R 13 and preferably NR 11 is.

[0030] R 11 , R 12 and R 13 are each independently an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 16 carbon atoms, or a linked aromatic group in which 2 to 5 of these aromatic rings are linked together. Preferably, they are substituted or unsubstituted aromatic hydrocarbon groups having 6 to 30 carbon atoms, or substituted or unsubstituted aromatic heterocyclic groups having 3 to 16 carbon atoms, and more preferably, they are substituted or unsubstituted aromatic hydrocarbon groups having 6 to 10 carbon atoms. Also preferred are linked aromatic groups in which 2 to 3 aromatic rings of aromatic hydrocarbon groups having 6 to 10 carbon atoms are linked together.

[0031] R independently represents hydrogen, deuterium, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, an aromatic hydrocarbon group having 6 to 30 carbon atoms, or an aromatic heterocyclic group having 3 to 16 carbon atoms. Preferably, R represents hydrogen, deuterium, a phenyl group, or an aromatic heterocyclic group having 3 to 12 carbon atoms. More preferably, R represents hydrogen, deuterium, a phenyl group, or a carbazolyl group.

[0032] R, R 14 and Ar 3 is a monovalent group, and when these symbols appear multiple times in a formula, they may be the same or different on each occurrence.

[0033] R, R 11 , R 12 , R 13 and R 14 When is an aliphatic hydrocarbon group having 1 to 10 carbon atoms, it may be linear or branched, or cyclic, and specific examples include methyl, ethyl, propyl, butyl, t-butyl, pentyl, hexyl, cyclohexyl, heptyl, octyl, nonyl, decyl, etc. Preferably, it is an alkyl group having 1 to 4 carbon atoms.

[0034] R, R 11 , R 12 , R 13 and R 14Specific examples of when is an aromatic hydrocarbon group or an aromatic heterocyclic group include groups derived from benzene, naphthalene, anthracene, fluoranthene, phenanthrene, triphenylene, pyridine, pyrimidine, triazine, thiophene, isothiazole, thiazole, pyridazine, pyrrole, pyrazole, imidazole, pyrazine, furan, isoxazole, oxazole, quinoline, isoquinoline, quinoxaline, quinazoline, benzotriazole, phthalazine, indole, benzofuran, benzothiophene, benzoxazole, benzothiazole, indazole, benzimidazole, benzisothiazole, benzothiadiazole, dibenzofuran, dibenzothiophene, dibenzoselenophene, benzocarbazole, benzonaphthothiophene, benzonaphthofuran, phenanthroline, or carbazole. Preferred examples include aromatic groups derived from benzene, naphthalene, pyridine, pyrimidine, triazine, thiophene, isothiazole, thiazole, pyridazine, pyrrole, pyrazole, imidazole, triazole, thiadiazole, pyrazine, furan, isoxazole, oxazole, quinoline, isoquinoline, quinoxaline, quinazoline, phthalazine, indole, benzofuran, benzothiophene, benzoxazole, benzothiazole, indazole, benzimidazole, benzisothiazole, benzothiadiazole, dibenzofuran, dibenzothiophene, or carbazole. More preferred are aromatic groups derived from benzene or carbazole.

[0035] In this specification, the aromatic hydrocarbon group, aromatic heterocyclic group, and linked aromatic ring group may have a substituent. In the case of the aromatic hydrocarbon group, aromatic heterocyclic group, and linked aromatic ring group, preferred substituents include an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, deuterium, halogen, an amino group, and a cyano group.

[0036] A preferred embodiment of the compound represented by general formula (1) is a compound represented by any one of the above general formulas (2) or (3) and (8), and more preferably a compound represented by any one of general formulas (3) to (5). In general formulas (2) to (8), symbols common to general formula (1) have the same meanings.

[0037] It is also preferable that the absolute value of the electron affinity (EA) of the compound represented by general formula (1) is greater than 2.6 eV and the absolute value of the ionization potential (IP) is less than 6.1 eV. The IP value can be calculated by measuring the absorption spectrum of a thin film obtained by vapor deposition of the material, using the IP value and the energy gap value determined from the absorption edge.

[0038] Specific examples of the compound represented by general formula (1) are shown below, but the compound is not limited to these exemplary compounds.

[0039] [ka] [ka] [ka]

[0040] [ka] [ka] [ka]

[0041] [ka] [ka] [ka]

[0042] [ka] [ka] [ka]

[0043] The material for organic electroluminescent devices of the present invention (also referred to as the compound of the present invention, the compound represented by general formula (1), or the azine compound) can be incorporated into at least one organic layer of an organic EL device having an anode, multiple organic layers, and a cathode stacked on a substrate to provide an excellent organic electroluminescent device. The organic layer to be incorporated is suitably an emitting layer, an electron transport layer, or a hole blocking layer. When used in the emitting layer, the compound of the present invention can be used as a host material for an emitting layer containing a fluorescent, delayed fluorescent, or phosphorescent dopant, and can also be used as an organic emitting material that emits fluorescence and delayed fluorescence. It is particularly preferred to incorporate the compound of the present invention as a host material for an emitting layer containing a phosphorescent dopant. When the compound of the present invention is used as an organic light-emitting material that emits fluorescence and delayed fluorescence (also referred to as a thermally activated delayed fluorescent dopant material), it is preferable to use, as a host material, another organic compound having at least one of excited singlet energy and excited triplet energy higher than that of the compound of the present invention.

[0044] Next, an organic EL device using the material for organic electroluminescent devices of the present invention will be described.

[0045] The organic EL device of the present invention has organic layers including at least one light-emitting layer between an anode and a cathode stacked on a substrate, and the at least one organic layer contains the material for organic electroluminescent devices of the present invention. Advantageously, the material for organic electroluminescent devices of the present invention is contained in the light-emitting layer together with a phosphorescent dopant.

[0046] Next, the structure of the organic EL element of the present invention will be described with reference to the drawings, but the structure of the organic EL element of the present invention is not limited to the one shown in the drawings.

[0047] FIG. 1 is a cross-sectional view showing an example of the structure of a typical organic EL device used in the present invention, where 1 represents a substrate, 2 represents an anode, 3 represents a hole injection layer, 4 represents a hole transport layer, 5 represents an emitting layer, 6 represents an electron transport layer, and 7 represents a cathode. The organic EL device of the present invention may have an exciton blocking layer adjacent to the emitting layer, or an electron blocking layer between the emitting layer and the hole injection layer. The exciton blocking layer can be inserted on either the anode side or the cathode side of the emitting layer, or both can be inserted simultaneously. The organic EL device of the present invention has a substrate, an anode, an emitting layer, and a cathode as essential layers, but may also have a hole injection transport layer and an electron injection transport layer as layers other than the essential layers, and may further have a hole blocking layer between the emitting layer and the electron injection transport layer. The hole injection transport layer refers to either or both of the hole injection layer and the hole transport layer, and the electron injection transport layer refers to either or both of the electron injection layer and the electron transport layer.

[0048] It is also possible to use the reverse structure to that shown in FIG. 1, i.e., to stack the cathode 7, electron transport layer 6, light-emitting layer 5, hole transport layer 4, and anode 2 on the substrate 1 in this order. In this case, too, layers can be added or omitted as necessary.

[0049] -substrate- The organic EL device of the present invention is preferably supported on a substrate. There are no particular limitations on the substrate, and it may be any substrate that has been conventionally used for organic EL devices, such as glass, transparent plastic, or quartz.

[0050] -anode- Anodes in organic EL devices are preferably made of metals, alloys, electrically conductive compounds, or mixtures thereof with a high work function (4 eV or higher). Specific examples of such electrode materials include metals such as Au, and conductive transparent materials such as CuI, indium tin oxide (ITO), SnO2, and ZnO. Amorphous materials capable of forming transparent conductive films, such as IDIXO (In2O3-ZnO), may also be used. These electrode materials may be formed into thin films by methods such as vapor deposition or sputtering, and then patterned into the desired shape by photolithography. Alternatively, when pattern precision is not required (approximately 100 μm or higher), the electrode material may be patterned using a mask of the desired shape during vapor deposition or sputtering. Alternatively, when a coatable material, such as an organic conductive compound, is used, wet film formation methods such as printing or coating can also be used. When light is emitted from this anode, a transmittance of more than 10% is desirable, and the sheet resistance of the anode is preferably less than several hundred Ω / □. Furthermore, the film thickness depends on the material, but is usually selected in the range of 10 to 1000 nm, preferably 10 to 200 nm.

[0051] -cathode- On the other hand, the cathode is typically made of a metal (referred to as an electron-injecting metal), alloy, electrically conductive compound, or mixture thereof with a low work function (4 eV or less). Specific examples of such electrode materials include sodium, sodium-potassium alloy, magnesium, lithium, a magnesium / copper mixture, a magnesium / silver mixture, a magnesium / aluminum mixture, a magnesium / indium mixture, an aluminum / aluminum oxide (Al2O3) mixture, indium, a lithium / aluminum mixture, and rare earth metals. Among these, mixtures of an electron-injecting metal and a second metal with a larger and more stable work function than the electron-injecting metal are preferred in terms of electron injection properties and durability against oxidation, etc., such as a magnesium / silver mixture, a magnesium / aluminum mixture, a magnesium / indium mixture, an aluminum / aluminum oxide (Al2O3) mixture, a lithium / aluminum mixture, and aluminum. The cathode can be fabricated by forming a thin film of these electrode materials by methods such as vapor deposition or sputtering. The sheet resistance of the cathode is preferably several hundred Ω / □ or less, and the film thickness is usually selected in the range of 10 nm to 5 μm, preferably 50 to 200 nm. In order to transmit emitted light, it is advantageous to make either the anode or cathode of the organic EL element transparent or semi-transparent, as this improves the luminance of emitted light.

[0052] Furthermore, a transparent or semitransparent cathode can be fabricated by forming the above-mentioned metal in a thickness of 1 to 20 nm as the cathode and then forming the conductive transparent material mentioned in the description of the anode on top of it. This can be applied to fabricate an element in which both the anode and cathode are transparent.

[0053] -Emitting layer- The light-emitting layer is a layer that emits light after excitons are generated by recombination of holes and electrons injected from the anode and cathode, respectively, and contains an organic light-emitting material and a host material. When the light-emitting layer is a fluorescent-emitting layer, at least one fluorescent-emitting material may be used alone, but it is preferred that the fluorescent-emitting material is used as a fluorescent-emitting dopant and contains a host material.

[0054] The fluorescent material in the light-emitting layer may be an azine compound represented by general formula (1), or may be selected from a number of known materials disclosed in patent documents, etc. Examples include benzoxazole derivatives, benzothiazole derivatives, benzimidazole derivatives, styrylbenzene derivatives, polyphenyl derivatives, diphenylbutadiene derivatives, tetraphenylbutadiene derivatives, naphthalimide derivatives, coumarin derivatives, condensed aromatic compounds, perinone derivatives, oxadiazole derivatives, oxazine derivatives, aldazine derivatives, cyclopentadiene derivatives, bisstyrylanthracene derivatives, quinacridone derivatives, pyrrolopyridine derivatives, thiadiazolopyridine derivatives, styrylamine derivatives, diketopyrrolopyrrole derivatives, aromatic dimethylidine compounds, various metal complexes such as metal complexes of 8-quinolinol derivatives, metal complexes of pyrromethene derivatives, rare earth complexes, and transition metal complexes, polymer compounds such as polythiophene, polyphenylene, and polyphenylenevinylene, and organosilane derivatives. Preferred examples include condensed aromatic compounds, styryl compounds, diketopyrrolopyrrole compounds, oxazine compounds, pyrromethene metal complexes, transition metal complexes, and lanthanoid complexes, and more preferred examples include naphthacene, pyrene, chrysene, triphenylene, benzo[c]phenanthrene, benzo[a]anthracene, pentacene, perylene, fluoranthene, acenaphthofluoranthene, dibenzo[a,j]anthracene, dibenzo[a,h]anthracene, benzo[a]naphthacene, hexacene, anthanthrene, naphtho[2,1-f]isoquinoline, α-naphthaphenanthridine, phenanthroxazole, quinolino[6,5-f]quinoline, and benzothiophanthrene. These may have an alkyl group, an aryl group, an aromatic heterocyclic group, or a diarylamino group as a substituent.

[0055] The fluorescent host material in the light-emitting layer may be an azine compound represented by general formula (1), or may be selected from a number of known compounds in patent documents, etc. Examples of such compounds include compounds having condensed aryl rings such as naphthalene, anthracene, phenanthrene, pyrene, chrysene, naphthacene, triphenylene, perylene, fluoranthene, fluorene, and indene, and derivatives thereof; aromatic amine derivatives such as N,N'-dinaphthyl-N,N'-diphenyl-4,4'-diphenyl-1,1'-diamine; metal chelated oxinoid compounds such as tris(8-quinolinato)aluminum(III); bisstyryl derivatives such as distyrylbenzene derivatives; and tetraphenylbenzene derivatives. Examples of the usable polymers include, but are not limited to, thiadiazole derivatives, dibenzofuran derivatives, indene derivatives, coumarin derivatives, oxadiazole derivatives, pyrrolopyridine derivatives, perinone derivatives, cyclopentadiene derivatives, pyrrolopyrrole derivatives, thiadiazolopyridine derivatives, dibenzofuran derivatives, carbazole derivatives, indolocarbazole derivatives, and triazine derivatives. In the case of polymers, polyphenylene vinylene derivatives, polyparaphenylene derivatives, polyfluorene derivatives, polyvinyl carbazole derivatives, and polythiophene derivatives can be used.

[0056] When the fluorescent material is used as a fluorescent dopant and a host material is contained, the amount of the fluorescent dopant contained in the light-emitting layer is in the range of 0.01 to 20% by weight, preferably 0.1 to 10% by weight.

[0057] Typically, organic EL devices inject charges into a light-emitting substance from both the anode and cathode electrodes, generating an excited light-emitting substance and causing it to emit light. In charge-injection organic EL devices, it is said that 25% of the generated excitons are excited to a singlet excited state, while the remaining 75% are excited to a triplet excited state. As shown in Advanced Materials 2009, 21, 4802-4806, certain fluorescent materials undergo energy transition to a triplet excited state via intersystem crossing or other means, and then undergo reverse intersystem crossing back to the singlet excited state via triplet-triplet annihilation or thermal energy absorption, resulting in fluorescent emission and thermally activated delayed fluorescence. The organic EL device of the present invention can also exhibit delayed fluorescence. In this case, both fluorescent emission and delayed fluorescent emission may be present. However, some or all of the emission may be due to emission from the host material.

[0058] When the light-emitting layer is a delayed fluorescent light-emitting layer, at least one delayed light-emitting material may be used alone, but it is preferred that the delayed fluorescent material is used as a delayed fluorescent light-emitting dopant and a host material is contained.

[0059] The delayed fluorescent material in the light-emitting layer can be an azine compound represented by general formula (1) if the compound has a small energy difference between the singlet level and the triplet level. However, it can also be selected from known delayed fluorescent materials. Examples include tin complexes, indolocarbazole derivatives, copper complexes, and carbazole derivatives. Specific examples include compounds described in the following non-patent and patent documents, but are not limited to these compounds.

[0060] 1) Adv. Mater. 2009, 21, 4802-4806, 2) Appl. Phys. Lett. 98, 083302 (2011), 3) JP 2011-213643, 4) J. Am. Chem. Soc. 2012, 134, 14706-14709.

[0061] Specific examples of delayed luminescent materials are shown below, but are not limited to the following compounds. [ka]

[0062] When the delayed fluorescent material is used as a delayed fluorescent dopant and a host material is contained, the amount of the delayed fluorescent dopant contained in the light-emitting layer is in the range of 0.01 to 50% by weight, preferably 0.1 to 20% by weight, and more preferably 0.01 to 10%.

[0063] The delayed fluorescent host material in the light-emitting layer can be an azine compound represented by general formula (1), but can also be selected from other compounds. For example, compounds having a fused aryl ring such as naphthalene, anthracene, phenanthrene, pyrene, chrysene, naphthacene, triphenylene, perylene, fluoranthene, fluorene, and indene, and derivatives thereof, aromatic amine derivatives such as N,N'-dinaphthyl-N,N'-diphenyl-4,4'-diphenyl-1,1'-diamine, metal chelated oxinoid compounds such as tris(8-quinolinato)aluminum(III), bisstyryl derivatives such as distyrylbenzene derivatives, and tetraphenylbutadiene derivatives can be used. , indene derivatives, coumarin derivatives, oxadiazole derivatives, pyrrolopyridine derivatives, perinone derivatives, cyclopentadiene derivatives, pyrrolopyrrole derivatives, thiadiazolopyridine derivatives, dibenzofuran derivatives, carbazole derivatives, indolocarbazole derivatives, triazine derivatives, and in the case of polymers, polyphenylene vinylene derivatives, polyparaphenylene derivatives, polyfluorene derivatives, polyvinyl carbazole derivatives, polythiophene derivatives, aryl silane derivatives, etc. can be used, but are not limited to these.

[0064] When the light-emitting layer is a phosphorescent light-emitting layer, the light-emitting layer contains a phosphorescent dopant and a host material. The phosphorescent dopant material preferably contains an organometallic complex containing at least one metal selected from the group consisting of ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum, and gold.

[0065] Preferable phosphorescent dopants include complexes having a noble metal element such as Ir as a central metal, such as Ir(ppy)3, complexes such as Ir(bt)2·acac3, and complexes such as PtOEt3. Specific examples of these complexes are shown below, but are not limited to the following compounds.

[0066] [ka]

[0067] The amount of the phosphorescent dopant contained in the light-emitting layer is in the range of 2 to 40% by weight, preferably 5 to 30% by weight.

[0068] When the light-emitting layer is a phosphorescent light-emitting layer, the azine compound of the present invention is preferably used as a host material in the light-emitting layer. However, when the azine compound is used in any organic layer other than the light-emitting layer, another host material may be used. Furthermore, the compound of the present invention may be used in combination with another host material. Furthermore, a plurality of known host materials may be used in combination. The known host compound is preferably a compound that has hole transporting ability and electron transporting ability, prevents the emission wavelength from shifting to longer wavelength, and has a high glass transition temperature.

[0069] Such other host materials can be selected from among those known in numerous patent documents, etc. Specific examples of the host material include, but are not limited to, indole derivatives, carbazole derivatives, indolocarbazole derivatives, triazole derivatives, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aromatic tertiary amine compounds, styrylamine compounds, aromatic dimethylidene compounds, porphyrin compounds, etc. Examples of the metal complexes include heterocyclic tetracarboxylic acid anhydrides such as naphthalene perylene, phthalocyanine derivatives, metal complexes of 8-quinolinol derivatives, metal phthalocyanines, and metal complexes of benzoxazole and benzothiazole derivatives; and polymer compounds such as polysilane compounds, poly(N-vinylcarbazole) derivatives, aniline copolymers, thiophene oligomers, polythiophene derivatives, polyphenylene derivatives, polyphenylene vinylene derivatives, and polyfluorene derivatives.

[0070] The light-emitting layer may be a fluorescent light-emitting layer, a delayed fluorescent light-emitting layer, or a phosphorescent light-emitting layer, but is preferably a phosphorescent light-emitting layer.

[0071] -Injection layer- The injection layer is a layer provided between an electrode and an organic layer to reduce the driving voltage and improve the luminance of light emitted, and includes a hole injection layer and an electron injection layer, and may be provided between the anode and the light emitting layer or the hole transport layer, and between the cathode and the light emitting layer or the electron transport layer. The injection layer can be provided as needed.

[0072] -Hole blocking layer- In a broad sense, a hole-blocking layer functions as an electron-transporting layer and is made of a hole-blocking material that has the ability to transport electrons but has an extremely low ability to transport holes, and by transporting electrons while blocking holes, the recombination probability of electrons and holes can be improved.

[0073] Although the azine compound of the present invention is preferably used in the hole-blocking layer, when the compound is used in any other organic layer, known hole-blocking layer materials may be used. Furthermore, the materials for the electron-transporting layer described later may be used as the hole-blocking layer material, if necessary.

[0074] -Electron blocking layer- The electron blocking layer is made of a material that has the function of transporting holes but has an extremely low ability to transport electrons, and by transporting holes while blocking electrons, it can improve the probability of electron and hole recombination.

[0075] As the material for the electron blocking layer, the materials for the hole transport layer described below can be used as needed. The thickness of the electron blocking layer is preferably 3 to 100 nm, more preferably 5 to 30 nm.

[0076] -Exciton blocking layer- The exciton-blocking layer is a layer for preventing excitons generated by the recombination of holes and electrons in the light-emitting layer from diffusing into the charge-transporting layer. Insertion of this layer makes it possible to efficiently confine excitons within the light-emitting layer, thereby improving the luminous efficiency of the device. The exciton-blocking layer can be inserted adjacent to the light-emitting layer on either the anode side or the cathode side, or both sides at the same time.

[0077] The exciton blocking layer may be made of the hole transport layer or electron transport layer, as described below, if necessary. The azine compound represented by general formula (1) may also be used, but other materials include 1,3-dicarbazolylbenzene (mCP) and bis(2-methyl-8-quinolinolato)-4-phenylphenolatoaluminum(III) (BAlq).

[0078] -Hole transport layer- The hole transport layer is made of a hole transport material having a function of transporting holes, and the hole transport layer may be provided as a single layer or as a plurality of layers.

[0079] The hole transport material may be either an organic or inorganic material that injects or transports holes or provides a barrier to electrons. Any of these known hole transport materials can be selected and used. Examples of known hole transport materials that can be used include triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives and pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aniline copolymers, and conductive polymer oligomers, particularly thiophene oligomers. Porphyrin compounds, aromatic tertiary amine compounds, and styrylamine compounds are preferred, with aromatic tertiary amine compounds being more preferred. Furthermore, an azine compound represented by general formula (1) can be used as the hole transport material.

[0080] -Electron transport layer- The electron transport layer is made of a material having the function of transporting electrons, and the electron transport layer may be a single layer or a plurality of layers.

[0081] The electron transport material (which may also serve as a hole-blocking material) may have the function of transporting electrons injected from the cathode to the light-emitting layer. The electron transport layer may contain the azine compound of the present invention, but any conventionally known compound may be used. Examples include nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, carbodiimides, fluorenylidenemethane derivatives, anthraquinodimethane and anthrone derivatives, and oxadiazole derivatives. Furthermore, among the above-mentioned oxadiazole derivatives, thiadiazole derivatives in which the oxygen atom of the oxadiazole ring is replaced with a sulfur atom, and quinoxaline derivatives having a quinoxaline ring, which is known as an electron-withdrawing group, may also be used as the electron transport material. Furthermore, polymeric materials in which these materials are incorporated into the polymer chain or which contain these materials as the polymer backbone may also be used. It is preferable that the difference in electron affinity (EA) between the electron transport material (including when it also serves as a hole-blocking material) and the organic light-emitting dopant material or host is 0.3 eV. [Example]

[0082] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples and can be implemented in various forms as long as they do not deviate from the gist of the invention.

[0083] Azine compounds serving as materials for organic electroluminescent devices were synthesized according to the following route: The compound numbers correspond to the numbers assigned to the above chemical formulas.

[0084] Example 1 Compounds 1-6 were synthesized according to the following reaction scheme. [ka] Under a nitrogen atmosphere, 12.0 g (23.0 mmol) of intermediate (B), 10.0 g (23.0 mmol) of intermediate (C), 1.33 g (1.15 mmol) of catalyst A, 15.0 g of cesium carbonate, and 200 ml of DMA were added and stirred at 130 °C for 30 minutes. After cooling to room temperature, the reaction solution was added to a mixture of methanol (400 ml) and distilled water (400 ml) with stirring, and the resulting precipitated solid was collected by filtration. The resulting solid was purified by silica gel column chromatography and crystallization to give compound 1-6 (8.1 g, 10.2 mmol, 44.1% yield) as a yellow solid (APCI-TOFMS, m / z 796 [M+H]). + ). Here, catalyst A is tetrakis(triphenylphosphine)palladium(0) and DMA is N,N'-dimethylacetamide.

[0085] Example 2 Compounds 1-7 were synthesized according to the following reaction scheme. [ka] Under a nitrogen atmosphere, 3.1 g (4.5 mmol) of intermediate (D), 1.15 g (4.95 mmol) of 2-bromo-6-phenylpyridine, 0.26 g (0.22 mmol) of catalyst A, 2.93 g of cesium carbonate, and 50 ml of 1,4-dioxane were added and stirred at 120°C for 2 hours. After cooling to room temperature, the reaction solution was added to a mixed solution of methanol (150 ml) and distilled water (100 ml) with stirring. The resulting precipitated solid was collected by filtration. The resulting solid was purified in the same manner as in Example 1 to obtain 2.3 g (3.2 mmol, 71.1% yield) of compound 1-7 as a pale yellow solid (APCI-TOFMS, m / z 717 [M+H]). + ).

[0086] Example 3 Compound 1-16 was synthesized according to the following reaction scheme. [ka] Under a nitrogen atmosphere, 7.0 g (16.1 mmol) of intermediate (C), 9.6 g (16.1 mmol) of intermediate (E), 0.47 g (0.40 mmol) of catalyst A, 10.5 g of cesium carbonate, and 200 ml of DMA were added and stirred overnight at 120 °C. After cooling to room temperature, the reaction solution was added to a mixed solution of methanol (400 ml) and distilled water (240 ml) with stirring, and the resulting precipitated solid was collected by filtration. The resulting solid was purified in the same manner as in Example 1 to obtain 5.7 g (6.55 mmol, 40.7% yield) of compound 1-16 as a yellow solid (APCI-TOFMS, m / z 871 [M+H]). + ).

[0087] Example 4 Compound 1-137 was synthesized according to the following reaction scheme. [ka] Under a nitrogen atmosphere, 9.0 g (13.0 mmol) of intermediate (D), 4.0 g (14.3 mmol) of intermediate (F), 0.75 g (0.65 mmol) of catalyst A, 8.5 g of cesium carbonate, and 50 ml of DMA were added and stirred at 120°C for 4 hours. After cooling to room temperature, the reaction solution was added to a mixed solution of methanol (400 ml) and distilled water (240 ml) with stirring. The resulting precipitated solid was collected by filtration. The resulting solid was purified in the same manner as in Example 1 to obtain 7.2 g (8.9 mmol, 68.5% yield) of compound 1-137 as a pale yellow solid (APCI-TOFMS, m / z 806 [M+H]). + ).

[0088] In addition to compounds 1-6, 1-7, 1-16, and 1-137, compounds 1-1, 1-5, 1-12, 1-27, 1-28, and 1-198 were synthesized according to the above synthesis examples. Furthermore, compounds H-1, H-2, H-3, and H-4 were synthesized for comparison.

[0089] [ka]

[0090] The measured value of the ionization potential (IP) in this specification is obtained by photoelectron spectroscopy of a thin film of the host material. The measured value of the electron affinity (EA) can be calculated using the value of the ionization potential and the energy gap value obtained from the absorption edge of the measured absorption spectrum.

[0091] Table 1 shows the absolute values ​​of the electron affinity (EA) and ionization potential (IP) of compounds 1-6, 1-7, 1-16, 1-137, and H-1, H-2, H-3, and H-4. [Table 1]

[0092] Example 5 Each thin film was deposited by vacuum deposition on a glass substrate with an anode made of ITO with a film thickness of 110 nm at a vacuum of 4.0 × 10 -5 The layers were laminated using a Pa process. First, CuPc was formed as a hole-injection layer to a thickness of 25 nm on the ITO, followed by NPD as a hole-transport layer to a thickness of 30 nm. Next, HT-1 was formed as an electron-blocking layer to a thickness of 10 nm. Next, Compound 1-1 as a host material and Ir(ppy)3 as an emitting dopant were co-evaporated from different evaporation sources to form a 40 nm-thick emitting layer. The Ir(ppy)3 concentration was 10 wt%. Furthermore, H-3 was formed as a hole-blocking layer to a thickness of 10 nm. Next, ET-1 was formed as an electron-transport layer to a thickness of 10 nm. Furthermore, LiF was formed as an electron-injection layer to a thickness of 1 nm on the electron-transport layer. Finally, Al was formed as a cathode to a thickness of 70 nm on the electron-injection layer to fabricate an organic EL device. When an external power supply was connected to the obtained organic EL device and a DC voltage was applied, an emission spectrum with a maximum wavelength of 517 nm was observed, indicating that light was emitted from Ir(ppy)3.

[0093] Examples 6 to 14 An organic EL device was prepared in the same manner as in Example 5, except that compounds 1-5, 1-6, 1-7, 1-12, 1-16, 1-27, 1-28, 1-137, and 1-198 were used instead of compound 1-1 as the host material for the emitting layer in Example 5. When an external power supply was connected to the obtained organic EL device and a DC voltage was applied, an emission spectrum with a maximum wavelength of 517 nm was observed.

[0094] Comparative Examples 1-2 An organic EL device was prepared in the same manner as in Example 5, except that H-1 and H-3 were used as the host materials for the emitting layer in Example 5. When an external power supply was connected to the obtained organic EL device and a DC voltage was applied, an emission spectrum with a maximum wavelength of 517 nm was observed.

[0095] The evaluation results of the fabricated organic EL devices are shown in Table 2. In the table, the luminance, driving voltage, and luminous efficiency are measured at a driving current of 20 mA / cm. 2 LT70 is the time it takes for the initial brightness to decay to 70% and indicates the lifespan characteristics.

[0096] [Table 2]

[0097] Example 15 Each thin film was deposited by vacuum deposition on a glass substrate with an anode made of ITO with a film thickness of 110 nm at a vacuum of 4.0 × 10 -5The layers were laminated using a 1000-membrane (Pa) deposition process. First, CuPc was formed on the ITO substrate as a hole-injection layer to a thickness of 25 nm, followed by NPD as a hole-transport layer to a thickness of 45 nm. Next, HT-1 was formed as an electron-blocking layer to a thickness of 10 nm. Compound 1-1 as a host material and Ir(piq)2acac as a dopant were co-evaporated from separate evaporation sources to form a 40 nm-thick light-emitting layer. The Ir(piq)2acac concentration was 6.0 wt%. Furthermore, H-3 was formed as a hole-blocking layer to a thickness of 10 nm. Next, ET-1 was formed as an electron-transport layer to a thickness of 27.5 nm. Then, LiF was formed as an electron-injection layer to a thickness of 1 nm on the electron-transport layer. Finally, Al was formed as a cathode to a thickness of 70 nm on the electron-injection layer to fabricate an organic EL device. When an external power supply was connected to the obtained organic EL device and a DC voltage was applied, an emission spectrum with a maximum wavelength of 620 nm was observed, indicating that light emission was obtained from Ir(piq)2acac.

[0098] Examples 16 to 24 An organic EL device was prepared in the same manner as in Example 5, except that compounds 1-5, 1-6, 1-7, 1-12, 1-16, 1-27, 1-28, 1-137, and 1-198 were used instead of compound 1-1 as the host material for the emitting layer in Example 15. When a direct current voltage was applied to the obtained organic EL device, an emission spectrum with a maximum wavelength of 620 nm was observed.

[0099] Comparative Examples 3 to 5 An organic EL device was prepared in the same manner as in Example 5, except that H-1, H-2, and H-3 were used as the host materials for the emitting layer in Example 15. When a direct current voltage was applied to the obtained organic EL device, an emission spectrum with a maximum wavelength of 620 nm was observed.

[0100] The evaluation results of the produced organic EL devices are shown in Table 3. The evaluation conditions were the same as in Examples 5 to 14, but LT90 is the time it takes for the initial luminance to decay to 90%.

[0101] [Table 3]

[0102] It can be seen from Tables 2 and 3 that Examples 5 to 24 have improved power efficiency and life characteristics, and exhibit favorable characteristics.

[0103] Example 25 Each thin film was deposited by vacuum deposition on a glass substrate with an anode made of ITO with a film thickness of 110 nm at a vacuum of 4.0 × 10 -5 The layers were laminated using a Pa process. First, CuPc was formed as a hole-injection layer to a thickness of 25 nm on the ITO, followed by NPD as a hole-transport layer to a thickness of 30 nm. Next, HT-1 was formed as an electron-blocking layer to a thickness of 10 nm. Next, compound H-1 as a host material and Ir(ppy)3 as an emitting dopant were co-evaporated from different evaporation sources to form a 40 nm-thick emitting layer. The Ir(ppy)3 concentration was 10 wt%. Compound 1-1 was then formed as a hole-blocking layer to a thickness of 5 nm. Next, ET-1 was formed as an electron-transport layer to a thickness of 15 nm. Furthermore, LiF was formed as an electron-injection layer to a thickness of 1 nm on the electron-transport layer. Finally, Al was formed as a cathode to a thickness of 70 nm on the electron-injection layer to fabricate an organic EL device.

[0104] Examples 26 to 34 Organic EL devices were prepared in the same manner as in Example 25, except that compounds 1-5, 1-6, 1-7, 1-12, 1-16, 1-27, 1-28, 1-137 and 1-198 were used in place of compound 1-1 in the hole blocking layer.

[0105] Example 35 An organic EL device was prepared in the same manner as in Example 25, except that compound 1-1 was used as the host material for the light-emitting layer in place of H-1.

[0106] Comparative Examples 6-7 An organic EL device was prepared in the same manner as in Example 25, except that H-1 and H-3 were used as the hole blocking layer.

[0107] Table 4 shows the evaluation results of the prepared organic EL devices.

[0108] [Table 4]

[0109] The compounds used in the examples are listed below. [ka]

Claims

1. A material for organic electroluminescent elements, which is contained in at least one organic layer of an organic electroluminescent element having an anode, a plurality of organic layers, and a cathode laminated on a substrate, the material comprising a compound represented by any one of general formulas (3) to (8), and the organic layer containing the material for organic electroluminescent elements is any one selected from the group consisting of a light-emitting layer, an electron-transporting layer, and a hole-blocking layer. 【Chemical 1】 【Chemistry 2】 【Chemistry 3】 (wherein R independently represents hydrogen, deuterium, a phenyl group, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 12 carbon atoms. R １５ represents an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 16 carbon atoms, or a substituted or unsubstituted linked aromatic group in which 2 to 5 of these aromatic rings are linked together. Ar ２ are independently an aromatic heterocyclic group represented by formula (1b), Ar ３ each independently represents hydrogen, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 10 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 12 carbon atoms, or a substituted or unsubstituted linked aromatic group in which 2 to 5 of these aromatic rings are linked together. Y is independently N or CR １４ and at least one is N. R １４ each independently represents hydrogen, deuterium, or a substituted or unsubstituted aromatic hydrocarbon group having 6 carbon atoms. L １ represents a substituted or unsubstituted phenylene group. Here, when the aromatic hydrocarbon group, aromatic heterocyclic group, or linking aromatic ring group has a substituent, the substituent is selected from the group consisting of an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, deuterium, a halogen, an amino group, and a cyano group.

2. L １ The material for organic electroluminescent devices according to claim 1, wherein is a phenylene group represented by the following formula (1c) or (1d): 【Chemistry 4】

3. 3. The material for organic electroluminescent devices according to claim 1, which is a compound represented by any one of general formulas (3) to (5).

4. An organic electroluminescent element comprising an anode, a plurality of organic layers, and a cathode laminated on a substrate, wherein at least one of the organic layers comprises the material for organic electroluminescent elements according to any one of claims 1 to 3, and the organic layer comprising the material for organic electroluminescent elements is any one selected from the group consisting of a light-emitting layer, an electron-transporting layer, and a hole-blocking layer.

5. 5. The organic electroluminescent device according to claim 4, wherein the organic layer containing the material for an organic electroluminescent device is a light-emitting layer.

6. 6. The organic electroluminescent device according to claim 5, wherein the light-emitting layer comprises a host and a light-emitting dopant material, and the light-emitting dopant material is an organometallic complex containing at least one metal selected from the group consisting of ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum, and gold.

7. 6. The organic electroluminescent device according to claim 5, wherein the light-emitting layer comprises a host and a light-emitting dopant material, and the light-emitting dopant material is a thermally activated delayed fluorescent dopant material.

8. 8. The organic electroluminescent device according to claim 4, wherein a hole-blocking layer is provided adjacent to the light-emitting layer, and the hole-blocking layer contains the material for organic electroluminescent devices.

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