Organic electric field light-emitting element

Abstract

A blue-emitting organic EL element with high luminous efficiency and long lifetime is provided. The organic EL element is characterized by comprising a light-emitting layer between opposing anodes and cathodes, and at least one light-emitting layer containing a luminescent dopant whose difference between the excitation singlet energy (S1) and the excitation triplet energy (T1) is less than 0.20 eV and is represented by the following formula (5), a first host selected from biscarbazole compounds, and a second host selected from N-containing 6-membered ring compounds. Here, X... 3 For N-Ar 4 O or S, at least one X 3 For N-Ar 4 .

Description

TECHNICAL FIELD

[0001] The present application relates to an organic electroluminescence element (referred to as an organic EL element). BACKGROUND

[0002] By applying a voltage to an organic EL (electroluminescence) element, holes are injected from an anode to a light-emitting layer, and electrons are injected from a cathode to the light-emitting layer, respectively. Furthermore, in the light-emitting layer, the injected holes and electrons recombine to generate an exciton. At this time, according to the statistical law of electron spin, a singlet exciton and a triplet exciton are generated at a ratio of 1:3. With respect to a fluorescent light-emitting type organic EL element that uses light emission generated from a singlet exciton, it is considered that the limit of internal quantum efficiency is 25%. On the other hand, it is known that a phosphorescent light-emitting type organic EL element that uses light emission generated from a triplet exciton improves the internal quantum efficiency to 100% in a case where intersystem crossing is efficiently performed from a singlet exciton.

[0003] However, with respect to a phosphorescent light-emitting type organic EL element of blue color, long-life becomes a technical problem.

[0004] Furthermore, recently, a high-efficiency organic EL element that utilizes delayed fluorescence is being developed. For example, in Patent Document 1, an organic EL element that utilizes a triplet-triplet fusion (TTF) mechanism, which is one of mechanisms of delayed fluorescence, is disclosed. The TTF mechanism utilizes a phenomenon in which a singlet exciton is generated by collision of two triplet excitons, and it is considered that the internal quantum efficiency is improved to 40% in theory. However, compared with a phosphorescent light-emitting type organic EL element, the efficiency is low, and thus further improvement of efficiency is required.

[0005] On the other hand, in Patent Document 2, an organic EL element that utilizes a thermally activated delayed fluorescence (TADF) mechanism is disclosed. The TADF mechanism is a mechanism that utilizes a phenomenon in which, in a material in which the energy difference between a singlet energy level and a triplet energy level is small, reverse intersystem crossing from a triplet exciton to a singlet exciton occurs, and it is considered that the internal quantum efficiency is improved to 100% in theory. However, similarly to a phosphorescent light-emitting type element, further improvement of the lifetime characteristics is required.

[0006] PRIOR ART DOCUMENTS

[0007] PATENT DOCUMENTS

[0008] Patent Document 1: WO2010 / 134350A

[0009] Patent Literature 2: WO2011 / 070963A

[0010] Patent Literature 3: WO2015 / 102118A

[0011] Patent Literature 4: WO2017 / 115833A

[0012] Patent Literature 5: WO2018 / 212169A

[0013] Patent Literature 6: WO2018 / 181188A

[0014] Patent Literature 7: WO2020 / 040298A

[0015] Patent Literature 8: JP2020-120096A

[0016] In Patent Literature 4, there is disclosed an organic EL element which contains two kinds of host materials represented by the following compounds in the light-emitting layer and contains a TADF material as a light-emitting dopant.

[0017] [Chemical Formula 1]

[0018]

[0019] In Patent Literature 3 and Patent Literature 5, there is disclosed an organic EL element which uses, as a light-emitting dopant, a TADF material containing a polycyclic aromatic compound represented by the following compound.

[0020] [Chemical Formula 2]

[0021]

[0022] In Patent Literature 6, there is disclosed an organic EL element which uses, in the light-emitting layer, a boron-based compound, a TADF material, and a carbazole compound (a3) in admixture.

[0023] In Patent Literature 7, there is disclosed an organic EL element which uses, in the light-emitting layer, a boron-based compound, a TADF material, and a carbazole compound in admixture.

[0024] In Patent Literature 8, there is disclosed an organic EL element which uses, in the light-emitting layer, a boron-based compound (a7), a nitrogen-containing 6-membered ring compound (a8), and a carbazole compound (a9) in admixture.

[0025] [Chemical Formula 3]

[0026]

[0027] However, none of the documents discloses an organic EL element which exhibits sufficient lifetime characteristics. SUMMARY

[0028] In order to apply the organic EL element to a display element or a light source for a flat panel display or the like, it is necessary to improve the light emission efficiency of the element while sufficiently ensuring stability at the time of driving. An object of the present application is to provide an organic EL element which is practically useful and has characteristics of high efficiency and long life.

[0029] The present application is an organic EL element which is an organic EL element comprising one or more light-emitting layers between facing anode and cathode, wherein at least one light-emitting layer contains a first host selected from a compound represented by the following general formula (1) and a second host selected from a compound represented by the following general formula (2), and contains a polycyclic aromatic compound represented by the following general formula (4) as a light-emitting dopant.

[0030] [Chemical Formula 4]

[0031]

[0032] Here, Ar 1 represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbons, a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbons, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 8 of the aromatic rings of these.

[0033] R 1 each independently represents deuterium, an aliphatic hydrocarbon group having 1 to 10 carbons, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbons, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbons.

[0034] a, c, and d independently represent an integer of 0 to 4, b independently represents an integer of 0 to 3, e independently represents an integer of 1 to 4, and f represents an integer of 1 or 2.

[0035] [Chemical Formula 5]

[0036]

[0037] Here, X 1 each independently represents N or C-R 2 , at least one X 1 represents N.

[0038] Ar 2 each independently represents hydrogen, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbons, a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbons, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 8 of the aromatic rings of these.2 all of which are hydrogen.

[0039] R 2 independently represent hydrogen, deuterium, an aliphatic hydrocarbon group having a carbon number of 1 to 10, a substituted or unsubstituted aromatic hydrocarbon group having a carbon number of 6 to 18, or a substituted or unsubstituted aromatic heterocyclic group having a carbon number of 3 to 17.

[0040] [Chemical Formula 6]

[0041]

[0042] Here, ring D, ring E, ring F, ring G, and ring H are each independently a substituted or unsubstituted aromatic hydrocarbon ring having a carbon number of 6 to 24, or a substituted or unsubstituted aromatic heterocyclic ring having a carbon number of 3 to 17,

[0043] Y 1 B, P, P=O, P=S, Al, Ga, As, Si-R 3 , or Ge-R 3 ,

[0044] R 3 are each independently an aliphatic hydrocarbon group having a carbon number of 1 to 10, a substituted or unsubstituted aromatic hydrocarbon group having a carbon number of 6 to 18, or a substituted or unsubstituted aromatic heterocyclic group having a carbon number of 3 to 17,

[0045] X 2 are each independently O, N-Ar 3 , S, or Se,

[0046] Ar 3 are each independently a substituted or unsubstituted aromatic hydrocarbon group having a carbon number of 6 to 18, a substituted or unsubstituted aromatic heterocyclic group having a carbon number of 3 to 17, or a substituted or unsubstituted condensed aromatic group in which 2 to 8 of these are linked, N-Ar 3 may be bonded to any one of ring D, ring E, ring F, ring G, or ring H to form a heterocyclic ring containing N,

[0047] At least one hydrogen in ring D, ring E, ring F, ring G, and ring H can be substituted with deuterium.

[0048] As a preferable form of the general formula (1), Ar 1 in the formula (1) is a substituted or unsubstituted aromatic hydrocarbon group having a carbon number of 6 to 18, or a substituted or unsubstituted condensed aromatic heterocyclic group having a carbon number of 6 to 17.

[0049] As a preferable form of the polycyclic aromatic compound represented by the general formula (4), a polycyclic aromatic compound containing boron represented by the following formula (5) can be given.

[0050] [Chemical Formula 7]

[0051]

[0052] Here, X 3 each independently represents N-Ar 4 , O, or S, at least one X 3 represents N-Ar 4 . Ar 4 each independently represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbons, a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbons, or a substituted or unsubstituted condensed aromatic group formed by linking 2 to 8 of the aromatic rings of these. N-Ar 4 may form a heterocycle containing N by bonding with the benzene ring to which it is bonded.

[0053] R 4 each independently represents a cyano group, a deuterium atom, a diaryl amino group having 12 to 44 carbons, an aliphatic hydrocarbon group having 1 to 10 carbons, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbons, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbons.

[0054] g and h each independently represent an integer of 0 to 4, i and j each independently represent an integer of 0 to 3, and k represents an integer of 0 to 2.

[0055] As a preferable form of the general formula (2), the following formula (6), the following formula (7), or formula (8) can be given.

[0056] [Chemical Formula 8]

[0057]

[0058] Here, Ar 2 and X 1 have the same meanings as those of the general formula (2).

[0059] R 5 and R 6 each independently represents a deuterium atom, an aliphatic hydrocarbon group having 1 to 10 carbons, a triaryl silyl group having 18 to 36 carbons, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbons, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbons.

[0060] l, m, n, o, p, and q each independently represent an integer of 0 to 4.

[0061] The light-emitting dopant preferably has a difference (ΔEST) between the excited singlet state energy (S1) and the excited triplet state energy (T1) of 0.20 eV or less, more preferably 0.10 eV or less.

[0062] The organic EL element of the present application has high luminous efficiency and long lifetime.

[0063] It is considered that the main reason why the organic EL element of the present application has high luminous efficiency is that the energy loss is small because the excitons generated on the host move rapidly to the light-emitting dopant, and that the energy loss is small because the excitons generated on the light-emitting dopant hardly move to the host. In addition, since the carbazole compound has a property of easily injecting holes and the nitrogen-containing 6-membered ring compound has a property of easily injecting electrons, the balance between holes and electrons in the light-emitting layer is maintained, and it is inferred that this is also a main reason for high luminous efficiency. It is presumed that the main reason why the organic EL element of the present application has long lifetime is that, when a voltage is applied to the organic EL element, holes are preferentially injected to the first host containing the biscarbazole compound and electrons are preferentially injected to the second host containing the nitrogen-containing 6-membered ring compound, thereby reducing the electrochemical load on the light-emitting dopant.

[0064] The polycyclic aromatic compound can efficiently perform blue light emission by utilizing the TADF mechanism, but has a tendency that the element lifetime becomes short because of low resistance to holes and electrons. It is considered that the first host used in the present application easily injects holes and further injects electrons through the second host, the electrochemical load on the light-emitting dopant is reduced, and the element characteristics of long lifetime can be exhibited. Further, it is presumed that since the first host and the second host have higher resistance to holes and electrons than known host materials, an organic EL element having longer lifetime can be obtained. BRIEF DESCRIPTION OF DRAWINGS

[0065] Figure 1 is a schematic cross-sectional view showing an example of an organic EL element.

[0066] Explanation of Symbols

[0067] 1: substrate

[0068] 2: anode

[0069] 3: hole injection layer

[0070] 4: hole transport layer

[0071] 5: light-emitting layer

[0072] 6: electron transport layer

[0073] 7: cathode DETAILED DESCRIPTION

[0074] The organic EL element of the present application has one or more light-emitting layers between facing anode and cathode, at least one light-emitting layer contains a first host selected from the compound represented by the general formula (1) and a second host selected from the compound represented by the general formula (2), and contains a polycyclic aromatic compound represented by the general formula (4) as a light-emitting dopant.

[0075] The compound represented by the general formula (1) used as the first host in the present application is described.

[0076] In the general formula (1), Ar 1 represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbons, a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbons, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 8 of the aromatic rings of these. Preferably, it represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbons, a substituted or unsubstituted condensed aromatic heterocyclic group having 6 to 17 carbons, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 4 of the aromatic rings of these. More preferably, it represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 10 carbons, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 of the aromatic rings of these.

[0077] As Ar 1 When it is an unsubstituted aromatic hydrocarbon group, an aromatic heterocyclic group, or a linked aromatic group, specific examples can include a group obtained by removing f hydrogens from a compound of benzene, naphthalene, acenaphthene, acenaphthylene, azulene, anthracene, 1,2- benzophenanthrene, pyrene, phenanthrene, triphenylene, fluorene, benzo[a]anthracene, thiophene, isothiazole, thiazole, pyridazine, pyrrole, pyrazole, imidazole, pyrazine, furan, isoxazole, quinoline, isoquinoline, quinoxaline, quinazoline, phthalazine, indole, pyridine, pyrimidine, triazine, benzofuran, benzothiophene, benzoxazole, benzothiazole, indazole, benzoimidazole, benzotriazole, benzoisothiazole, benzothiadiazole, purine, pyranone, coumarin, isocoumarin, chromone, dibenzofuran, dibenzothiophene, dibenzoselenophene, carbazole, or 2 to 8 of these linked together. Preferably, it can include a group obtained by removing f hydrogens from a compound of benzene, naphthalene, acenaphthene, acenaphthylene, azulene, dibenzofuran, dibenzothiophene, carbazole, or 2 to 4 of these linked together. More preferably, it can include a group obtained by removing f hydrogens from a compound of benzene, naphthalene, or 2 to 3 of the benzene rings linked together.

[0078] In the present specification, a linking aromatic group refers to a group in which aromatic rings of an aromatic hydrocarbon group or an aromatic heterocyclic group are linked by a single bond, and these can be linked linearly or branched, and the aromatic rings can be the same or different.

[0079] R 1 independently represents deuterium, an aliphatic hydrocarbon group having a carbon number of 1 to 10, a substituted or unsubstituted aromatic hydrocarbon group having a carbon number of 6 to 18, or a substituted or unsubstituted aromatic heterocyclic group having a carbon number of 3 to 17. Preferably, it represents an aliphatic hydrocarbon group having a carbon number of 1 to 8, a substituted or unsubstituted aromatic hydrocarbon group having a carbon number of 6 to 12, or a substituted or unsubstituted aromatic heterocyclic group having a carbon number of 3 to 15. More preferably, it represents a substituted or unsubstituted aromatic hydrocarbon group having a carbon number of 6 to 10, or a substituted or unsubstituted aromatic heterocyclic group having a carbon number of 3 to 12.

[0080] Further, preferably, Ar 1 and R 1 is not a group derived from pyridine, pyrimidine, or triazine.

[0081] a, c, and d independently represent an integer of 0 to 4, b independently represents an integer of 0 to 3, e independently represents an integer of 1 to 4, and f represents an integer of 1 or 2. Preferably, a, b, c, and d are independently an integer of 0 to 1, and e is an integer of 1 to 2. These are the number of substitutions.

[0082] In the case where f is 2, the general formula (1) can be symmetrical or asymmetrical.

[0083] As R 1 is an aliphatic hydrocarbon group having a carbon number of 1 to 10, specific examples can include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, or a nonyl group. Preferably, specific examples can include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, or an octyl group.

[0084] As R 1 is a substituted or unsubstituted aromatic hydrocarbon group having a carbon number of 6 to 18, or a substituted or unsubstituted aromatic heterocyclic group having a carbon number of 3 to 17, specific examples are the same as those described in the description of Ar 1 .

[0085] Preferably, specific examples can include a group derived from benzene, naphthalene, dihydronaphthacene, acenaphthene, azulene, dibenzofuran, dibenzothiophene, or carbazole by removing one hydrogen. More preferably, specific examples can include a group derived from benzene, naphthalene, or carbazole by removing one hydrogen.

[0086] In the general formula (1), in the case where multiple carbazoles are linked, preferably, it has a bond structure in which 3,9-positions are linked, as represented by the following formula (1a), or a bond structure in which 4,9-positions are linked, as represented by the formula (1b), but is not limited to these bond structures.

[0087] [Chemistry 9]

[0088]

[0089] In the general formulas (1), (2), (6), (7), and (8), in Ar 1 ~Ar 3 R 1 ~R 5 When the aromatic hydrocarbon group, aromatic heterocyclic group, or linked aromatic group is present, these may have substituents. Preferred substituents include deuterium, cyano, triarylsilylalkyl groups with 18 to 36 carbon atoms, aliphatic hydrocarbon groups with 1 to 10 carbon atoms, and diarylamino groups with 12 to 44 carbon atoms. Here, when the substituent is an aliphatic hydrocarbon group with 1 to 10 carbon atoms, it may be linear, branched, or cyclic. Furthermore, the number of substituents may be 0 to 5, preferably 0 to 2. The carbon number calculation for aromatic hydrocarbon groups and aromatic heterocyclic groups with substituents does not include the carbon number of the substituent. However, it is preferable that the total carbon number, including the carbon number of the substituent, satisfies the aforementioned range.

[0090] Specific examples of the substituents include: cyano, methyl, ethyl, propyl, isopropyl, butyl, tributyl, pentyl, cyclopentyl, hexyl, cyclohexyl, heptyl, octyl, nonyl, decyl, diphenylamino, naphthylphenylamino, dinaphthylamino, dianthrylamino, diphenoxyamino, dipyreneamino, and triphenylsilyl. Preferably, the substituents include: cyano, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, diphenylamino, naphthylphenylamino, or dinaphthylamino.

[0091] In this specification, hydrogen can be understood to be deuterium. That is, in the general formulas (1) to (8), the carbazole skeleton, R 1 Or Ar 1 The H in such a substituent may be some or all of deuterium.

[0092] The following are specific examples of compounds represented by the general formula (1), but are not limited to these exemplified compounds.

[0093] [Chemistry 10]

[0094]

[0095] [Chemistry 11]

[0096]

[0097] [Chemistry 12]

[0098]

[0099] [Chemistry 13]

[0100]

[0101] [Chemistry 14]

[0102]

[0103] [Chemistry 15]

[0104]

[0105] [Chemistry 16]

[0106]

[0107] [Chemistry 17]

[0108]

[0109] [Chemistry 18]

[0110]

[0111] [Chemistry 19]

[0112]

[0113] [Chemistry 20]

[0114]

[0115] [Chemistry 21]

[0116]

[0117] [Chemistry 22]

[0118]

[0119] [Chemistry 23]

[0120]

[0121] [Chemistry 24]

[0122]

[0123] [Chemistry 25]

[0124]

[0125] [Chemistry 26]

[0126]

[0127] [Chemistry 27]

[0128]

[0129] The compounds represented by general formula (2) used as the second subject will be described.

[0130] In the general formula (2), X 1 Represent N or CR independently, respectively. 2 At least one X 1 N represents the number of X's. Preferably, there are two X's. 1 N represents N. More preferably, three X's are used. 1 Triazine compounds with N atoms.

[0131] As preferred forms of the general formula (2), there are formulas (6), (7) and (8), with formula (7) being more preferred. In the general formulas (2), (6), (7) and (8), the common symbols have the same meaning.

[0132] l, m, n, o, p, and q each independently represent integers from 0 to 4, preferably integers from 0 to 2.

[0133] Ar 2 Each of these groups independently represents hydrogen, an aromatic hydrocarbon group having 6 to 18 carbon atoms (substituted or unsubstituted), an aromatic heterocyclic group having 3 to 17 carbon atoms (substituted or unsubstituted), or a linked aromatic group consisting of 2 to 8 of these aromatic rings. Preferably, it represents an aromatic hydrocarbon group having 6 to 12 carbon atoms (substituted or unsubstituted), an aromatic heterocyclic group having 3 to 12 carbon atoms (substituted or unsubstituted), or a linked aromatic group consisting of 2 to 6 of these aromatic rings. More preferably, it represents an aromatic hydrocarbon group having 6 to 10 carbon atoms (substituted or unsubstituted), an aromatic heterocyclic group having 6 to 12 carbon atoms (substituted or unsubstituted), or a linked aromatic group consisting of 2 to 4 of these aromatic rings. Wherein, Ar 2 At least one of them is an aromatic hydrocarbon group, an aromatic heterocyclic group, or a linked aromatic group.

[0134] As Ar 2 Specific examples of unsubstituted aromatic hydrocarbon groups or unsubstituted aromatic heterocyclic groups, and the Ar 1 Or R 1 The same applies to these cases. As an unsubstituted linked aromatic group, it is related to the Ar... 1 The same applies to these cases.

[0135] Preferably, the group is formed by removing one hydrogen atom from compounds consisting of benzene, naphthalene, dihydroacenaphthene, acenaphthene, azulene, pyridine, triazine, dibenzofuran, dibenzothiophene, carbazole, or compounds consisting of two to six links of the above. More preferably, the group is formed by removing one hydrogen atom from compounds consisting of benzene, carbazole, dibenzofuran, dibenzothiophene, or compounds consisting of two to four links of the benzene ring.

[0136] R 2 Each of these groups independently represents hydrogen, deuterium, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms (substituted or unsubstituted), or an aromatic heterocyclic group having 3 to 17 carbon atoms (substituted or unsubstituted). Preferably, it is hydrogen, an aromatic hydrocarbon group having 6 to 12 carbon atoms (substituted or unsubstituted), or an aromatic heterocyclic group having 3 to 15 carbon atoms (substituted or unsubstituted). More preferably, it is an aromatic hydrocarbon group having 6 to 10 carbon atoms.

[0137] In equations (6) and (7), R 5 and R 6 Each of these groups independently represents a deuterium group, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a triarylsilyl group having 18 to 36 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms (substituted or unsubstituted), or an aromatic heterocyclic group having 3 to 17 carbon atoms (substituted or unsubstituted). Preferably, it is an aromatic hydrocarbon group having 6 to 10 carbon atoms (substituted or unsubstituted), or an aromatic heterocyclic group having 3 to 15 carbon atoms (substituted or unsubstituted). More preferably, it is an aromatic hydrocarbon group having 6 to 10 carbon atoms, or an aromatic heterocyclic group having 3 to 15 carbon atoms (substituted or unsubstituted).

[0138] As R 2 R 5 and R 6 Specific examples when referring to aliphatic hydrocarbon groups with 1 to 10 carbon atoms, substituted or unsubstituted aromatic hydrocarbon groups with 6 to 18 carbon atoms, or substituted or unsubstituted aromatic heterocyclic groups with 3 to 17 carbon atoms, are related to R. 1 The description is the same as that described herein. Preferably, it is a group formed by removing one hydrogen atom from benzene, naphthalene, dihydroacenaphthene, acenaphthene, azulene, dibenzofuran, dibenzothiophene, or carbazole. More preferably, it is a group formed by removing one hydrogen atom from benzene, naphthalene, or carbazole.

[0139] The following are specific examples of compounds represented by the general formulas (2), (6), (7) and (8), but are not limited to these exemplified compounds.

[0140] [Chemistry 28]

[0141]

[0142] [Chemistry 29]

[0143]

[0144] [Chemistry 30]

[0145]

[0146] [Chemistry 31]

[0147]

[0148] [Chemistry 32]

[0149]

[0150] [Chemistry 33]

[0151]

[0152] [Chemistry 34]

[0153]

[0154] [Chemistry 35]

[0155]

[0156] [Chemistry 36]

[0157]

[0158] [Chemistry 37]

[0159]

[0160] [Chemistry 38]

[0161]

[0162] [Chemistry 39]

[0163]

[0164] [Chemistry 40]

[0165]

[0166] The luminescent dopant used in the organic EL element of the present invention is a polycyclic aromatic compound represented by the general formula (4). Preferably, it is a boron-containing polycyclic aromatic compound represented by the formula (5).

[0167] In the general formula (4), rings D, E, F, G, and H are each independently a substituted or unsubstituted aromatic hydrocarbon ring having 6 to 24 carbon atoms, or a substituted or unsubstituted aromatic heterocycle having 3 to 17 carbon atoms, preferably a substituted or unsubstituted aromatic hydrocarbon ring having 6 to 20 carbon atoms, or a substituted or unsubstituted aromatic heterocycle having 3 to 15 carbon atoms. As described above, rings D to H are also referred to as aromatic rings because they are aromatic hydrocarbon rings or aromatic heterocycles.

[0168] Specific examples of unsubstituted aromatic rings include those containing benzene, naphthalene, dihydroacenaphthene, acenaphthene, azulene, anthracene, 1,2-benzophenanthrene, pyrene, phenanthrene, triphenylene, fluorene, benzo[a]anthracene, pyridine, pyrimidine, triazine, thiophene, isothiazole, thiazole, pyridazine, pyrrole, pyrazole, imidazole, pyrazine, furan, isoxazole, quinoline, isoquinoline, quinoxoline, quinazoline, phthalazine, indole, benzofuran, benzothiophene, benzoxazole, benzothiazole, indazole, benzimazole, benzotriazole, benzoisothiazole, benzothiadiazole, purine, pyranone, coumarin, isocoumarin, crromone, dibenzofuran, dibenzothiophene, dibenzoselenophene, or carbazole. Preferably, the rings can be benzene ring, naphthalene ring, anthracene ring, triphenylene ring, phenanthrene ring, pyrene ring, pyridine ring, dibenzofuran ring, dibenzothiophene ring, or carbazole ring.

[0169] In rings D, E, F, G, and H, the aromatic hydrocarbon ring or aromatic heterocycle may also have substituents, which can be independently represented by cyano, deuterium, diarylamino with 12-44 carbons, arylheteroarylamino with 12-44 carbons, diheteroarylamino with 12-44 carbons, aliphatic hydrocarbon group with 1-10 carbons, substituted or unsubstituted aromatic hydrocarbon group with 6-18 carbons, or substituted or unsubstituted aromatic heterocyclic group with 3-17 carbons. Preferably, the substituents are diarylamino with 12-36 carbons, arylheteroarylamino with 12-36 carbons, diheteroarylamino with 12-36 carbons, aromatic hydrocarbon group with 6-12 carbons, or aromatic heterocyclic group with 3-15 carbons. More preferably, it is a diarylamino group with 12 to 24 carbon atoms, an arylheteroarylamino group with 12 to 24 carbon atoms, a diheteroarylamino group with 12 to 24 carbon atoms, an aromatic hydrocarbon group with 6 to 10 carbon atoms, or an aromatic heterocyclic group with 3 to 12 carbon atoms. Here, when the substituent is an aliphatic hydrocarbon group with 1 to 10 carbon atoms, it can be linear, branched, or cyclic.

[0170] Specific examples of diarylamino, arylheteroarylamino, diheteroarylamino, or aliphatic hydrocarbon groups having 12 to 44 carbon atoms include: diphenylamino, diphenylamino, phenylbiphenylamino, naphthylphenylamino, dinaphthylamino, dianthrylamino, diphenanthylamino, dipyreneamino, dibenzofuranylphenylamino, dibenzofuranylbiphenylamino, dibenzofuranylnaphthylamino, dibenzofuranylanthrylamino, dibenzofuranylphenanthylamino, dibenzofuranylpyreneamino, bisdibenzofuranylamino, carbazoylphenylamino, carbazoylnaphthylamino, carbazoylanthrylamino, carbazoylphenanthylamino, carbazoylpyreneamino, dicarbazoylamino, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, or nonyl. Preferably, the following are examples: diphenylamino, diphenylamino, phenylbiphenylamino, naphthylphenylamino, dinaphthylamino, dianthrylamino, diphenoxyamino, or dipyreneamino. More preferably, the following are examples: diphenylamino, diphenylamino, phenylbiphenylamino, naphthylphenylamino, dinaphthylamino, dibenzofuranylphenylamino, or carbazoleylphenylamino.

[0171] In general formula (4), Y 1 For B, P, P=O, P=S, Al, Ga, As, Si-R 3 or Ge-R 3 Preferably, it is B, P, P=O or P=S, and more preferably B.

[0172] R 3 Each group is independently an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms. Preferably, it is an aliphatic hydrocarbon group having 1 to 8 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 15 carbon atoms. More preferably, it is 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.

[0173] As R 3 Specific examples of R in general formula (1) are aliphatic hydrocarbon groups with 1 to 10 carbon atoms, substituted or unsubstituted aromatic hydrocarbon groups with 6 to 18 carbon atoms, or substituted or unsubstituted aromatic heterocyclic groups with 3 to 17 carbon atoms. 1 The same applies to these bases.

[0174] X 2 Independently, O and N-Ar respectively 3 S or Se, preferably O or N-Ar 3 Or S, more preferably O or N-Ar3 .

[0175] Ar 3 Each of the following groups is independently a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms, or a linked aromatic group consisting of 2 to 8 of these. Phenyl, biphenyl, or terphenyl are preferred.

[0176] As Ar 3 Specific examples of the use of an unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, an unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms, or a linked aromatic group consisting of 2 to 8 of these, are related to Ar in general formula (1). 1 The same applies to these bases.

[0177] As Ar 3 When the substituent is a substituted aromatic hydrocarbon group having 6 to 18 carbon atoms or a substituted aromatic heterocyclic group having 3 to 17 carbon atoms, the preferred substituents are deuterium, hydroxyl, mercapto, cyano, triarylsilylalkyl with 18 to 36 carbon atoms, aliphatic hydrocarbon group with 1 to 10 carbon atoms, or diarylamino with 12 to 44 carbon atoms. Here, when the substituent is an aliphatic hydrocarbon group with 1 to 10 carbon atoms, it can be linear, branched, or cyclic.

[0178] Specific examples of the substituents include: cyano, methyl, ethyl, propyl, isopropyl, butyl, tert-butyl, pentyl, cyclopentyl, hexyl, cyclohexyl, heptyl, octyl, nonyl, decyl, diphenylamino, naphthylphenylamino, dinaphthylamino, dianthrylamino, diphenoxyamino, dipyreneamino, and triphenylsilyl. Preferably, the substituents include: cyano, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, diphenylamino, naphthylphenylamino, or dinaphthylamino.

[0179] N-Ar 3 It can bond with aromatic rings selected from rings D, E, F, G, or H to form heterocycles containing N. Additionally, in Ar... 3 With substituents, a heterocycle containing N can be formed by bonding the substituent with an aromatic ring selected from ring D, ring E, ring F, ring G, or ring H. 3 At least one hydrogen atom in the atom can be replaced by deuterium.

[0180] The polycyclic aromatic compounds include those represented by the general formula (4) or formula (5).

[0181] In the general formulas (4) and (5), the common symbols have the same meaning.

[0182] In equation (5), g and h independently represent integers from 0 to 4, i and j independently represent integers from 0 to 3, and k represents integers from 0 to 2. Preferably, g, h, i, j, and k are independently 0 or 1.

[0183] In equation (5), X 3 N-Ar are represented independently. 4 O, or S, at least one X 3 Indicates N-Ar 4 Preferably N-Ar 4 , or O. Ar 4 Ar of general formula (4) 3 They have the same meaning. N-Ar 4 It can bond with the aromatic ring (the benzene ring corresponding to ring D to ring H) to form a heterocycle containing N.

[0184] R 4 Each of these groups independently represents a cyano group, a deuterium group, a diarylamino group with 12 to 44 carbon atoms, an aliphatic hydrocarbon group with 1 to 10 carbon atoms, an aromatic hydrocarbon group with 6 to 18 carbon atoms (substituted or unsubstituted), or an aromatic heterocyclic group with 3 to 17 carbon atoms (substituted or unsubstituted). Preferably, it is a diarylamino group with 12 to 36 carbon atoms, an aromatic hydrocarbon group with 6 to 12 carbon atoms (substituted or unsubstituted), or an aromatic heterocyclic group with 3 to 15 carbon atoms (substituted or unsubstituted). More preferably, it is a diarylamino group with 12 to 24 carbon atoms, an aromatic hydrocarbon group with 6 to 10 carbon atoms (substituted or unsubstituted), or an aromatic heterocyclic group with 3 to 12 carbon atoms (substituted or unsubstituted).

[0185] As R 4 Specific examples of diarylamino groups having 12 to 44 carbon atoms, or aliphatic hydrocarbon groups having 1 to 10 carbon atoms, include: diphenylamino, diphenylamino, phenylbiphenylamino, naphthylphenylamino, dinaphthylamino, dianthrylamino, diphenylamino, dipyreneamino, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, or nonyl. Preferably, examples include: diphenylamino, diphenylamino, phenylbiphenylamino, naphthylphenylamino, dinaphthylamino, dianthrylamino, diphenylamino, or dipyreneamino. More preferably, examples include: diphenylamino, diphenylamino, phenylbiphenylamino, naphthylphenylamino, or dinaphthylamino.

[0186] Preferred forms of the polycyclic aromatic compounds of the general formula (4) or formula (5) are those of formulas (4-d), (4-e), (4-f), and (4-h). Formula (4-f) is more preferred.

[0187] [Chemistry 41]

[0188]

[0189] The polycyclic aromatic compounds represented by formulas (4-d), (4-e), and (4-f) correspond, for example, to compounds represented by formulas (4-67), (4-68), and (4-69) as described later.

[0190] The polycyclic aromatic compounds represented by formula (4-h) correspond to compounds represented by formulas (4-71), (4-72), (4-73), (4-74), and (4-75) as described later.

[0191] In equations (4-d) to (4-h), X 2 and Y 1 R has the same meaning as general formula (4). 7 R in equation (5) 4 For the same meaning, r independently represents integers from 0 to 4, s independently represents integers from 0 to 2, and t independently represents integers from 0 to 3.

[0192] The following are specific examples of polycyclic aromatic compounds represented by the general formula (4) or formula (5), but are not limited to these exemplified compounds.

[0193] [Chemistry 42]

[0194]

[0195] [Chemistry 43]

[0196]

[0197] [Chemistry 44]

[0198]

[0199] [Chemistry 45]

[0200]

[0201] [Chemistry 46]

[0202]

[0203] [Chemistry 47]

[0204]

[0205] [Chemistry 48]

[0206]

[0207] [Chemistry 49]

[0208]

[0209] In the organic EL element of the present invention, the organic light-emitting material used as a light-emitting dopant preferably has a ΔEST of 0.20 eV or less. More preferably, it has a ΔEST of 0.15 eV or less, and even more preferably, it has a ΔEST of 0.10 eV or less.

[0210] ΔEST represents the difference between the excited singlet energy (S1) and the excited triplet energy (T1). Here, the conditions for measuring S1 and T1 are based on the methods described in the examples.

[0211] By using a material selected from the polycyclic aromatic compounds represented by the general formula (4) (hereinafter also referred to as polycyclic aromatic compound material) as a luminescent dopant, using a material selected from the compound represented by the general formula (1) as a first host, and using a material selected from the compound represented by the general formula (2) as a second host, an excellent organic EL element can be provided.

[0212] Next, the structure of the organic EL element of the present invention will be described with reference to the accompanying drawings, but the structure of the organic EL element of the present invention is not limited thereto.

[0213] Figure 1 This is a cross-sectional view showing a typical organic EL element structure used in this invention. 1 represents a substrate, 2 represents an anode, 3 represents a hole injection layer, 4 represents a hole transport layer, 5 represents a light-emitting layer, 6 represents an electron transport layer, and 7 represents a cathode. The organic EL element of this invention may have an exciton blocking layer adjacent to the light-emitting layer, and may also have an electron blocking layer between the light-emitting layer and the hole injection layer. The exciton blocking layer may be inserted to either the anode side or the cathode side of the light-emitting layer, or simultaneously to both sides. In the organic EL element of this invention, an anode, a light-emitting layer, and a cathode are required layers, but in addition to these required layers, a hole injection transport layer and an electron injection transport layer may also be included, and a hole blocking layer may be present between the light-emitting layer and the electron injection transport layer. Furthermore, a hole injection transport layer refers to either or both of the hole injection layer and the hole transport layer, and an electron injection transport layer refers to either or both of the electron injection layer and the electron transport layer.

[0214] It can also be with Figure 1 In the opposite structure, the cathode 7, electron transport layer 6, light-emitting layer 5, hole transport layer 4, and anode 2 are sequentially stacked on the substrate 1. In this case, layers may be added or omitted as needed.

[0215] -Substrate-

[0216] The organic EL element of the present invention is preferably supported on a substrate. The substrate is not particularly limited, as long as it is a substrate that has been used for organic EL elements before, such as a substrate containing glass, transparent plastic, quartz, etc.

[0217] -anode-

[0218] As the anode material in an organic electroluminescent (EL) element, materials containing metals, alloys, electrically conductive compounds, or mixtures thereof with a high work function (4 eV or higher) are preferably used. Specific examples of such electrode materials include metals such as Au; conductive transparent materials such as CuI, indium tin oxide (ITO), SnO2, and ZnO. Alternatively, amorphous materials such as IDIXO (In2O3-ZnO) that can be formed into transparent conductive films can also be used. The anode can be formed into a thin film using methods such as vapor deposition or sputtering, and a pattern of the desired shape can be formed using photolithography. Alternatively, when pattern precision is not critical (around 100 μm or higher), a pattern can be formed by separating the desired shape from the electrode material during vapor deposition or sputtering. Alternatively, when using a coatable substance such as an organic conductive compound, wet film formation methods such as printing or coating can be used. When light is emitted from the anode, it is ideal to have a transmittance greater than 10%, and the sheet resistance of the anode is preferably less than several hundred Ω / Y. The film thickness also depends on the material, and is usually selected in the range of 10 nm to 1000 nm, preferably 10 nm to 200 nm.

[0219] -cathode-

[0220] On the other hand, as cathode materials, materials containing metals (called electron-injecting metals), alloys, electrically conductive compounds, or mixtures thereof with low work functions (below 4 eV) can be used. Specific examples of such electrode materials include: sodium, sodium-potassium alloys, magnesium, lithium, magnesium / copper mixtures, magnesium / silver mixtures, magnesium / aluminum mixtures, magnesium / indium mixtures, aluminum / alumina (Al₂O₃) mixtures, indium, lithium / aluminum mixtures, rare earth metals, etc. Among these, in terms of electron injection performance and durability against oxidation, mixtures of electron-injecting metals and second metals that are more stable and have a larger work function than the first metal are suitable, such as magnesium / silver mixtures, magnesium / aluminum mixtures, magnesium / indium mixtures, aluminum / alumina (Al₂O₃) mixtures, lithium / aluminum mixtures, aluminum, etc. Cathodes can be fabricated by forming thin films from these cathode materials using methods such as vapor deposition or sputtering. Furthermore, as a cathode, the sheet resistance is preferably several hundred Ω / Y or less, and the film thickness is typically selected in the range of 10 nm to 5 μm, preferably 50 nm to 200 nm. Furthermore, in order for the emitted light to pass through, if either the anode or cathode of the organic EL element is transparent or translucent, the luminous brightness will be increased, which is appropriate.

[0221] Furthermore, after forming the metal on the cathode with a film thickness of 1 nm to 20 nm, a conductive transparent material listed in the description of the anode is formed on it, thereby making a transparent or semi-transparent cathode. By applying the method described above, an element in which both the anode and cathode are permeable can be made.

[0222] -Emitting Layer-

[0223] The light-emitting layer is a layer that emits light after excitons are generated by the recombination of holes and electrons injected from the anode and cathode, respectively, and contains a light-emitting dopant and a host.

[0224] Regarding the luminescent dopant and the substrate, for example, the luminescent dopant can be used at 0.10% to 10%, and the substrate at 99.9% to 90%. Preferably, the luminescent dopant is 1.0% to 5.0%, and the substrate is 99% to 95%, more preferably, the luminescent dopant is 1.0% to 3.0%, and the substrate is 99% to 97%.

[0225] In this specification, unless otherwise specified, % refers to mass.

[0226] The first and second subjects are used as the main components in the light-emitting layer. Regarding the first and second subjects, for example, the first subject can be used in a proportion of 10% to 90%, and the second subject in a proportion of 90% to 10%. Preferably, the first subject is 30% to 70% and the second subject is 70% to 30%, more preferably, the first subject is 50% to 70% and the second subject is 50% to 30%.

[0227] Furthermore, as other than the aforementioned main body, one or more known main bodies may be used in combination, but their usage may be set to 50% or less, preferably 25% or less, in the total amount of the main body material.

[0228] Other known host materials that can be used are preferably compounds with hole transport capability, electron transport capability, and a high glass transition temperature, and have a T1 greater than that of the luminescent dopant. Specifically, it is preferable that the T1 of the host is 0.010 eV or more higher than that of the luminescent dopant, more preferably 0.030 eV or more higher, and even more preferably 0.10 eV or more higher. Additionally, TADF-active compounds can also be used as host materials, preferably compounds with a ΔEST of 0.20 eV or less.

[0229] Other known entities are known from numerous patent documents and other sources, and can therefore be selected from these. Specific examples of entities are not particularly limited, but can include: metal complexes represented by indole derivatives, carbazole derivatives, indole-carbazole derivatives, triazole derivatives, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, phenylenediamine derivatives, arylamine derivatives, styrene-anthracene derivatives, fluorene derivatives, stilbene derivatives, triphenylene derivatives, carborane derivatives, porphyrin derivatives, phthalocyanine derivatives, metal complexes of 8-hydroxyquinoline derivatives or metal phthalocyanines, metal complexes of benzoxazole or benzothiazole derivatives; poly(N-vinylcarbazole) derivatives, aniline copolymers, thiophene oligomers, polythiophene derivatives, polyphenylene derivatives, polyphenylenevinyl derivatives, polyfluorene derivatives, and other polymers.

[0230] When using multiple substrates, each substrate can be vapor-deposited from different vapor deposition sources, or a premix can be prepared by pre-mixing before vapor deposition, thereby allowing multiple substrates to be vapor-deposited simultaneously from a single vapor deposition source.

[0231] Ideally, premixing methods should aim to achieve the most uniform mixing possible. Examples include pulverization and mixing, heating and melting under reduced pressure or inert gas conditions such as nitrogen, or sublimation, but these methods are not the only options.

[0232] The premix can be in the form of powder, rod, or granules.

[0233] The polycyclic aromatic compound material can be used as a luminescent dopant in the luminescent layer.

[0234] The luminescent layer may contain two or more luminescent dopants. For example, it may be the aforementioned polycyclic aromatic compound material, and luminescent dopants containing other compounds. In this case, the luminescent dopants containing the other compounds are preferably ΔEST below 0.20 eV, but are not limited thereto.

[0235] In cases where the luminescent layer contains two or more luminescent dopants, the first dopant is a compound represented by general formula (4) or formula (5), and a known compound may be used as the luminescent dopant in the second dopant. Preferably, the content of the first dopant is 0.050% to 50% relative to the host material, and the content of the second dopant is 0.050% to 50% relative to the host material, and the total content of the first and second dopants relative to the host material does not exceed 50%.

[0236] Other luminescent dopants are known from numerous patent documents and other sources, and can therefore be selected from these. Specific examples of dopants are not particularly limited, but can include: phenanthrene, anthracene, pyrene, tetraphenylene, pentaphenylene, perylene, naphthylpyrene, dibenzopyrene, fluorene, and condensation ring derivatives such as 1,2-benzophenanthrene; benzoxazole derivatives; benzothiazole derivatives; benzimidazole derivatives; benzotriazole derivatives; oxazole derivatives; oxadiazole derivatives; thiazole derivatives; imidazole derivatives; thiadiazole derivatives; triazole derivatives; pyrazoline derivatives; stilbene derivatives; thiophene derivatives; tetraphenylbutadiene derivatives; cyclopentadiene derivatives; bis(styrene)-anthracene derivatives; or stilbene-phenylene derivatives. Such as bis(styrene) derivatives, bis(styrene) arylene derivatives, diazaindacene derivatives, furan derivatives, benzofuran derivatives, isobenzofuran derivatives, dibenzofuran derivatives, coumarin derivatives, dicyanomethylenepyran derivatives, dicyanomethylenethiaran derivatives, polymethine derivatives, anthocyanin derivatives, oxobenzanthracene derivatives, xanthan derivatives, rhodamine derivatives, fluorescein derivatives, pyranonium derivatives, carbonylstyrene derivatives, acridine derivatives, oxazine derivatives, phenylene oxide derivatives, quinacridone derivatives, quinazoline derivatives, pyrrolopyridine derivatives, furanopyridine derivatives, 1,2,5-thiadiazolium-pyrene derivatives, pyrrolemethylene derivatives, violet ketone derivatives, pyrrolopyrrole derivatives, squaric acid lactone derivatives, isoanthrone violet derivatives, phenazine derivatives, acridine ketone derivatives, denitroflavin derivatives, fluorene derivatives, and benzo[a]fluorene derivatives, etc.

[0237] The luminescent dopant and the first or second host can be deposited from separate evaporation sources, or a premixed mixture can be prepared by premixing before evaporation, thereby depositing the luminescent dopant and the first or second host simultaneously from a single evaporation source.

[0238] -Injection Layer-

[0239] An injection layer is a layer placed between the electrode and the organic layer to reduce the driving voltage or increase the luminous brightness. There are hole injection layers and electron injection layers, which can exist between the anode and the luminescent layer or hole transport layer, and between the cathode and the luminescent layer or electron transport layer. The injection layer can be set as needed.

[0240] -hole blocking layer-

[0241] A hole blocking layer, broadly speaking, functions as an electron transport layer. It comprises hole-blocking materials that can transport electrons but have a significantly lower hole-transporting capacity. By transporting electrons and blocking holes, it increases the recombination probability of electrons and holes in the luminescent layer. Known hole-blocking materials can be used in the hole blocking layer. To leverage the properties of the luminescent dopant, a material used as a second host can also be used as the hole blocking layer material. Furthermore, multiple hole-blocking materials can be used in combination.

[0242] -Electron blocking layer-

[0243] In a broad sense, an electron blocking layer functions as a hole transport layer, increasing the probability of electron-hole recombination in the luminescent layer by transporting holes and blocking electrons. Known electron blocking layer materials can be used as the electron blocking layer material. To leverage the properties of the luminescent dopant, a material used as the primary substrate can also be used as the electron blocking layer material. The preferred thickness of the electron blocking layer is 3 nm to 100 nm, more preferably 5 nm to 30 nm.

[0244] -Exciton blocking layer-

[0245] An exciton blocking layer is a layer used to prevent excitons generated by the recombination of holes and electrons in the light-emitting layer from diffusing into the charge transport layer. By inserting this layer, excitons can be efficiently sealed into the light-emitting layer, thereby improving the luminous efficiency of the device. In devices with two or more adjacent light-emitting layers, the exciton blocking layer can be inserted between two adjacent light-emitting layers.

[0246] Known exciton blocking layer materials can be used as the material for the exciton blocking layer.

[0247] As layers adjacent to the light-emitting layer, there are hole blocking layers, electron blocking layers, exciton blocking layers, etc. In the absence of these layers, hole transport layers, electron transport layers, etc. become adjacent layers.

[0248] -Hole transport layer-

[0249] A hole transport layer is a hole transport material that has the function of transporting holes. A hole transport layer can be a single layer or multiple layers.

[0250] The hole transport material is any material that possesses either hole injection or transport or electron barrier properties, and can be either organic or inorganic. In the hole transport layer, any compound selected from previously known compounds can be used. Examples of such hole transport materials include: porphyrin derivatives, arylamine derivatives, triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, phenylenediamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styrene-anthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aniline copolymers, and conductive polymeric oligomers, particularly thiophene oligomers. Porphyrin derivatives, arylamine derivatives, and styrene-anthracene derivatives are preferred, and arylamine derivatives are more preferred.

[0251] -Electron transport layer-

[0252] An electron transport layer consists of materials that can transport electrons, and can be a single layer or multiple layers.

[0253] As an electron transport material (and sometimes also a hole blocking material), it only needs to have the function of transporting electrons injected from the cathode to the emitting layer. The electron transport layer can be any of the previously known compounds, such as: polycyclic aromatic derivatives of naphthalene, anthracene, phenanthroline, etc.; tris(8-hydroxyquinoline)aluminum(III) derivatives; phosphine oxide derivatives; nitro-substituted fluorene derivatives; diphenylquinone derivatives; thiamethane dioxide derivatives; carbodiimide; fluorenemethane derivatives; anthraquinone dimethane and anthrone derivatives; bipyridine derivatives; quinoline derivatives; oxadiazole derivatives; benzimidazole derivatives; benzothiazole derivatives; indolecarbazole derivatives, etc. Furthermore, polymers incorporating these materials into polymer chains or using these materials as the backbone of polymers can also be used.

[0254] There are no particular limitations on the film-forming methods for each layer when manufacturing the organic EL element of the present invention; either dry or wet processes can be used.

[0255] Example

[0256] The present invention will be described in more detail below through embodiments, but the present invention is not limited to these embodiments.

[0257] The following examples and comparative examples show the compounds used in them.

[0258] [Transformation 50]

[0259]

[0260] The S1 and T1 of compounds BD1, (4-110) and (4-121) were determined.

[0261] S1 and T1 are determined in the following manner.

[0262] On a quartz substrate, vacuum evaporation is used at a vacuum degree of 10. -4 Under conditions below Pa, compounds (1-58) as the main component and compounds BD1, (4-110), or (4-121) as luminescent dopants are co-deposited from different evaporation sources to form a vapor deposition film with a thickness of 100 nm. In this case, co-deposition is performed under evaporation conditions where the concentration of the luminescent dopant is 3%.

[0263] Regarding S1, the emission spectrum of the vapor-deposited film is measured, and a tangent is drawn from the rising short wavelength side of the emission spectrum. The wavelength value λedge [nm] at the intersection of the tangent and the horizontal axis is substituted into the following equation (i) to calculate S1.

[0264] S1[eV]=1239.85 / λedge (i)

[0265] Regarding T1, the phosphorescence spectrum of the vapor-deposited film is measured, and a tangent is drawn from the rising short wavelength side of the phosphorescence spectrum. The wavelength value λedge[nm] at the intersection of the tangent and the horizontal axis is substituted into equation (ii) to calculate T1.

[0266] T1[eV]=1239.85 / λedge (ii)

[0267] The measurement results are shown in Table 1.

[0268] [Table 1]

[0269] Compound S1 (eV) T1 (eV) S1-T1 (eV) BD1 2.79 2.61 0.18 4-110 2.71 2.67 0.04 4-121 2.76 2.71 0.05

[0270] Example 1

[0271] On a glass substrate with an ITO anode having a film thickness of 70 nm, vacuum evaporation was performed at a vacuum degree of 4.0 × 10⁻⁶. -5Pa is used to stack the thin films. First, HAT-CN is formed to a thickness of 10 nm as a hole injection layer on ITO. Next, HT-1 is formed to a thickness of 25 nm as a hole transport layer. Next, compound (1-58) is formed to a thickness of 5 nm as an electron blocking layer. Next, compound (1-58) as the first host, compound (2-6) as the second host, and compound (4-121) as the luminescent dopant are co-deposited from different evaporation sources to form a luminescent layer to a thickness of 30 nm. At this time, co-deposition is performed under evaporation conditions where the concentration of compound (4-121) is 2% and the mixing ratio of the first host to the second host is 70:30. Next, compound (2-6) is formed to a thickness of 5 nm as a hole blocking layer. Next, ET-1 is formed to a thickness of 40 nm as an electron transport layer. On the electron transport layer, lithium fluoride (LiF) is formed to a thickness of 1 nm as an electron injection layer. Finally, aluminum (Al) is formed on the electron injection layer to a thickness of 70 nm as a cathode to fabricate an organic EL device.

[0272] Examples 2 to 9

[0273] Organic EL elements were fabricated in the same manner as in Example 1, except that the luminescent dopant, the first host, the second host, and the mixing ratio of the first host to the second host were set to the compounds shown in Table 2.

[0274] Comparative Example 1

[0275] On a glass substrate with an ITO anode having a film thickness of 70 nm, vacuum evaporation was performed at a vacuum degree of 4.0 × 10⁻⁶. -5 Pa is used to stack various thin films. First, HAT-CN is formed to a thickness of 10 nm as a hole injection layer on ITO. Next, HT-1 is formed to a thickness of 25 nm as a hole transport layer. Next, compound (1-58) is formed to a thickness of 5 nm as an electron blocking layer. Next, compound (1-58) as the first host and compound (4-121) as a luminescent dopant are co-deposited from different evaporation sources to form a luminescent layer to a thickness of 30 nm. At this time, co-deposition is performed under evaporation conditions where the concentration of compound (4-121) is 2%. Next, compound (2-6) is formed to a thickness of 5 nm as a hole blocking layer. Next, ET-1 is formed to a thickness of 40 nm as an electron transport layer. Furthermore, lithium fluoride (LiF) is formed to a thickness of 1 nm on the electron transport layer as an electron injection layer. Finally, aluminum (Al) is formed to a thickness of 70 nm on the electron injection layer as a cathode, thereby fabricating an organic EL device.

[0276] Comparative Example 3, Comparative Example 5, Comparative Example 7

[0277] Organic EL elements were fabricated in the same manner as in Comparative Example 1, except that the luminescent dopant and the first host (without a second host) were set to the compounds shown in Table 2.

[0278] Comparative Example 2, Comparative Example 6

[0279] Organic EL elements were fabricated in the same manner as in Comparative Example 1, except that the luminescent dopant and the second host (without the first host) were set to the compounds shown in Table 2.

[0280] Comparative Example 4, Comparative Example 8, Comparative Example 9, Comparative Example 10

[0281] Organic EL elements were fabricated in the same manner as in Example 1, except that the luminescent dopant, the first host, and the second host were set to the compounds and proportions shown in Table 2.

[0282] [Table 2]

[0283] Dopant First host Second host Example 1 4-121 1-58(70％) 2-6(30％) Example 2 4-121 1-58(50％) 2-6(50％) Example 3 4-121 1-58(30％) 2-6(70％) Example 4 4-121 1-58(70％) 2-84(30％) Example 5 4-121 1-81(50％) 2-84(50％) Example 6 4-110 1-58(50％) 2-6(50％) Example 7 4-110 1-58(50％) 2-1(50％) Example 8 4-110 1-31(50％) 2-84(50％) Example 9 4-110 1-81(50％) 2-11(50％) Comparative Example 1 4-121 1-58 - Comparative Example 2 4-121 - 2-6 Comparative Example 3 4-121 mCBP - Comparative Example 4 4-121 mCBP (50%) 2-6(50％) Comparative Example 5 4-110 1-58 - Comparative Example 6 4-110 - 2-1 Comparative Example 7 4-110 mCBP - Comparative Example 8 BD1 1-58(50％) 2-6(50％) Comparative Example 9 BD1 1-58(50％) 2-84(50％) Comparative Example 10 4-110 mCBP (50%) T2T (50%)

[0284] The emission spectra of the organic EL elements fabricated in the examples and comparative examples, including the maximum emission wavelength, external quantum efficiency, and lifetime, are shown in Table 3. The maximum emission wavelength and external quantum efficiency are for an illuminance of 500 cd / m². 2 The value at that time represents the initial characteristics. Regarding lifetime, the initial luminance was measured to be 500 cd / m². 2 The time it takes for the brightness to decrease to 50% of its initial brightness.

[0285] [Table 3]

[0286]

[0287] As shown in Table 3, the organic EL element of the embodiment has the characteristics of high efficiency and long life, and emits blue light according to the maximum emission wavelength.

[0288] Industrial availability

[0289] The organic EL element of this invention has high luminous efficiency and long lifespan.

Claims

1. An organic electroluminescent element, which is an organic electroluminescent element containing one or more light-emitting layers between facing anode and cathode, characterized by: at least one light-emitting layer contains a first host having a hole-transport property selected from among compounds represented by the following general formula (1), a second host having an electron-transport property selected from among compounds represented by the following general formula (8), and a light-emitting dopant selected from among boron-containing polycyclic aromatic compounds represented by the following general formula (5), Here, Ar 1 represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbons, a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbons, or a substituted or unsubstituted linked aromatic group in which 2 to 8 aromatic rings of these are linked; e independently represents an integer of 1 to 4, and f represents an integer of 1 or 2; in the case where f is 2, the general formula (1) can be symmetrical or asymmetrical; Here, Ar 2 respectively independently represent hydrogen, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbons, a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbons, or a substituted or unsubstituted linked aromatic group in which 2 to 8 of the aromatic rings of these are linked; wherein at least one of Ar 2 is a group other than hydrogen; R 2 independently represent hydrogen, deuterium, an aliphatic hydrocarbon group having a carbon number of 1 to 10, a substituted or unsubstituted aromatic hydrocarbon group having a carbon number of 6 to 18, or a substituted or unsubstituted aromatic heterocyclic group having a carbon number of 3 to 17; Here, X 3 each independently represents N-Ar 4 , O, or S, at least one X 3 represents N-Ar 4 ; Ar 4 each independently represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms, or a substituted or unsubstituted condensed aromatic group formed by linking 2 to 8 of the aromatic rings of these; N-Ar 4 may be linked to the phenyl ring to which it is bonded to form a heterocycle containing N; R 4 each independently represents cyano, deuterium, diarylamino having a carbon number of 12 to 44, an aliphatic hydrocarbon group having a carbon number of 1 to 10, a substituted or unsubstituted aromatic hydrocarbon group having a carbon number of 6 to 18, or a substituted or unsubstituted aromatic heterocyclic group having a carbon number of 3 to 17; g and h each independently represent an integer of 0 to 4, i and j each independently represent an integer of 0 to 3, and k represents an integer of 0 to 2.

2. The organic electroluminescent element according to claim 1, wherein: Ar in the general formula (1) 1 is a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbons, or a substituted or unsubstituted condensed aromatic heterocyclic group having 6 to 17 carbons.

3. The organic electroluminescent element according to claim 1 or 2, wherein: the general formula (8) is the following formula (6), Here, Ar 2 and the same as general formula (8); R 5 respectively and independently represent deuterium, an aliphatic hydrocarbon group having a carbon number of 1 to 10, a triaryl silyl group having a carbon number of 18 to 36, a substituted or unsubstituted aromatic hydrocarbon group having a carbon number of 6 to 18, or a substituted or unsubstituted aromatic heterocyclic group having a carbon number of 3 to 17; l and m each independently represent an integer of 0 to 4.

4. The organic electroluminescent element according to claim 1 or 2, wherein: the general formula (8) is the following formula (7), Here, Ar 2 and the same as general formula (8); R 6 respectively independently represent deuterium, an aliphatic hydrocarbon group having a carbon number of 1 to 10, a triaryl silyl group having a carbon number of 18 to 36, a substituted or unsubstituted aromatic hydrocarbon group having a carbon number of 6 to 18, or a substituted or unsubstituted aromatic heterocyclic group having a carbon number of 3 to 17; n, o, p, and q each independently represent an integer of 0 to 4.

5. The organic electroluminescent element according to claim 1 or 2, wherein: a difference ΔEST between an excitation singlet energy S1 and an excitation triplet energy T1 of the light-emitting dopant is 0.20 eV or less.

6. The organic electroluminescent device according to claim 5, wherein: the ΔEST is 0.10 eV or less.

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