Organic electroluminescent device

Abstract

Provided is a blue light-emitting organic EL element which has high luminous efficiency and a long service life. This organic EL element is characterized by: including a light-emitting layer between an positive electrode and a negative electrode that face each other; at least one light-emitting layer having a difference between an excited singlet energy (S1) and an excited triplet energy (T1) of 0.20 eV or less; and containing a light-emitting dopant such as that represented by formula (5), a first host selected from among biscarbazole compounds, and a second host selected from among nitrogen-containing 6-membered ring compounds. Here, X3 is N-Ar4, O or S, but at least one X3 moiety is N-Ar4.

Description

[Technical Field]

[0001] The present invention relates to an organic electroluminescent device (referred to as an organic EL device).

[0002] When a voltage is applied to an organic EL element, holes are injected from the anode and electrons are injected from the cathode into the light-emitting layer. The injected holes and electrons then recombine in the light-emitting layer, generating excitons. Due to the statistical laws of electron spin, singlet and triplet excitons are generated in a ratio of 1:3. It is said that the internal quantum efficiency of fluorescent organic EL elements, which 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 elements, which use emission from triplet excitons, can be increased to 100% if intersystem crossing from singlet excitons is efficiently achieved. However, extending the life of blue phosphorescent organic EL elements remains a technical challenge.

[0003] More recently, highly efficient organic EL devices utilizing delayed fluorescence have been developed. For example, Patent Document 1 discloses an organic EL device utilizing the TTF (Triplet-Triplet Fusion) mechanism, which is one of the mechanisms of delayed fluorescence. The TTF mechanism utilizes the phenomenon in which singlet excitons are generated by the collision of two triplet excitons, and is thought to theoretically increase the internal quantum efficiency to 40%. However, since the efficiency is lower than that of phosphorescent organic EL devices, further improvements in efficiency are required.

[0004] Meanwhile, Patent Document 2 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 lifetime characteristics are required. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] WO2010 / 134350A [Patent Document 2] WO2011 / 070963A [Patent Document 3] WO2015 / 102118A [Patent Document 4] WO2017 / 115833A [Patent Document 5] WO2018 / 212169A [Patent Document 6] WO2018 / 181188A [Patent Document 7] WO2020 / 040298A [Patent Document 8] JP2020-120096A

[0006] Patent Document 4 discloses an organic EL device in which two types of host materials, typified by the compounds below, and a TADF material are contained as light-emitting dopants in the light-emitting layer. [ka]

[0007] Patent Documents 3 and 5 disclose organic EL devices that use, as a light-emitting dopant, a TADF material made of a polycyclic aromatic compound, such as the following compound: [ka]

[0008] Patent Document 6 discloses an organic EL device in which a mixture of a boron-based compound, a TADF material, and a carbazole compound (a3) ​​is used in the light-emitting layer.

[0009] Patent Document 7 discloses an organic EL device in which a mixture of a boron-based compound, a TADF material, and a carbazole compound is used in the light-emitting layer. Patent Document 8 discloses an organic EL device in which a mixture of a boron-based compound (a7), a nitrogen-containing six-membered ring compound (a8), and a carbazole compound (a9) is used in the light-emitting layer. [ka]

[0010] However, none of the documents discloses an organic EL device that exhibits sufficient life characteristics.

[0011] Summary of the Invention

[0012] In order to apply organic EL elements to display elements such as flat panel displays and light sources, it is necessary to improve the luminous efficiency of the elements while ensuring sufficient stability during operation. An object of the present invention is to provide a practically useful organic EL element that has high efficiency and long life.

[0013] The present invention provides an organic EL device comprising one or more emitting layers between an anode and a cathode facing each other, wherein at least one emitting layer contains a first host selected from compounds represented by the following general formula (1), a second host selected from compounds represented by the following general formula (2), and a polycyclic aromatic compound represented by the following general formula (4) as a emitting dopant:

[0014] [ka] where Ar 1 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 linked aromatic group formed by linking 2 to 8 of these aromatic rings. R 1each independently represents deuterium, 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. 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 independently represents an integer of 1 or 2.

[0015] [ka] where X 1 are each independently N or CR 2 represents a 1 represents N. Ar 2 each independently represents hydrogen, 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 linked aromatic group formed by linking 2 to 8 of these aromatic rings. 2 cannot all be hydrogen. R 2 independently represent hydrogen, deuterium, 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.

[0016] [ka] wherein ring D, ring E, ring F, ring G, and ring 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; Y 1 is B, P, P=O, P=S, Al, Ga, As, Si―R 3 or Ge-R 3 and R 3each independently represents 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, X 2 are independently O, N-Ar 3 , S or Se; Ar 3 are each 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 substituted or unsubstituted linked aromatic group formed by linking 2 to 8 of these, and N-Ar 3 may bond with any of ring D, ring E, ring F, ring G, or ring H to form a heterocycle containing N, At least one hydrogen atom in ring D, ring E, ring F, ring G, and ring H may be substituted with deuterium.

[0017] A preferred embodiment of the general formula (1) is Ar 1 is a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, or a substituted or unsubstituted fused aromatic heterocyclic group having 6 to 17 carbon atoms.

[0018] A preferred embodiment of the polycyclic aromatic compound represented by the general formula (4) is a boron-containing polycyclic aromatic compound represented by the following formula (5).

[0019] [ka] where X 3 are each independently N-Ar 4 , O, or S, but at least one X 3 is N-Ar 4 Represents Ar 4 N-Ar each independently represent 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 linked aromatic group formed by linking 2 to 8 of these aromatic rings. 4may combine with the benzene ring to which it is attached to form a heterocyclic ring containing N. R 4 each independently represents a cyano group, deuterium, a diarylamino group having 12 to 44 carbon atoms, 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. g and h each independently represent an integer of 0 to 4; i and j each independently represent an integer of 0 to 3; k represents an integer of 0 to 2;

[0020] Preferred embodiments of the general formula (2) include the following formula (6), (7) or (8). [ka] where Ar 2 and X 1 is the same as general formula (2). R 5 and R 6 each independently represents deuterium, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a triarylsilyl group having 18 to 36 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. l, m, n, o, p and q each independently represent an integer of 0 to 4.

[0021] The light-emitting dopant preferably has a difference (ΔEST) between the excited singlet energy (S1) and the excited triplet energy (T1) of 0.20 eV or less, more preferably 0.10 eV or less.

[0022] The organic EL device of the present invention has the characteristics of high luminous efficiency and long life. The organic EL device of the present invention exhibits high luminous efficiency due to the fact that excitons generated on the host rapidly transfer to the luminescent dopant, resulting in little energy loss, and that excitons generated on the luminescent dopant are less likely to transfer to the host, resulting in little energy loss. Furthermore, since the carbazole compound has the property of easily injecting holes and the nitrogen-containing six-membered ring compound has the property of easily injecting electrons, it is presumed that the high luminous efficiency is also due to the ability to maintain a balance between holes and electrons in the luminescent layer. The organic EL device of the present invention exhibits long life due to the fact that, when a voltage is applied to the organic EL device, holes are preferentially injected into the first host composed of a biscarbazole compound and electrons are preferentially injected into the second host composed of a nitrogen-containing six-membered ring compound, thereby reducing the electrochemical load on the luminescent dopant.

[0023] The above polycyclic aromatic compounds can emit blue light with high efficiency by utilizing the TADF mechanism, but their low tolerance to holes and electrons tends to shorten the device lifetime. The first host used in the present invention facilitates hole injection, and the second host also facilitates electron injection, which is thought to reduce the electrochemical load on the luminescent dopant and enable the development of long-life device characteristics. Furthermore, since the above first host and second host have higher tolerance to holes and electrons than known host materials, it is expected that an organic EL device with a longer lifetime can be obtained. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of an organic EL element. DETAILED DESCRIPTION OF THE INVENTION

[0025] The organic EL device of the present invention has one or more emitting layers between an anode and a cathode facing each other, and at least one emitting layer contains a first host selected from the compounds represented by the general formula (1) above, a second host selected from the compounds represented by the general formula (2) above, and a polycyclic aromatic compound represented by the general formula (4) above as a emitting dopant.

[0026] The compound represented by the general formula (1) used as the first host in the present invention will be explained below.

[0027] In the general formula (1), Ar 1 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 linked aromatic group formed by linking 2 to 8 of these aromatic rings. Preferably, represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, a substituted or unsubstituted fused aromatic heterocyclic group having 6 to 17 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 4 of these aromatic rings. More preferably, represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 10 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 3 of these aromatic rings.

[0028] Ar 1Specific examples of when is an unsubstituted aromatic hydrocarbon group, aromatic heterocyclic group, or linking aromatic group include benzene, naphthalene, acenaphthene, acenaphthylene, azulene, anthracene, chrysene, 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, benzimidazole, benzotriazole, benzisothiazole, benzothiadiazole, purine, pyranone, coumarin, isocoumarin, chromone, dibenzofuran, dibenzothiophene, dibenzoselenophene, carbazole, or a group formed by removing f hydrogen atoms from a compound formed by linking 2 to 8 of these. Preferred examples include groups obtained by removing f hydrogen atoms from benzene, naphthalene, acenaphthene, acenaphthylene, azulene, dibenzofuran, dibenzothiophene, carbazole, or a compound formed by linking 2 to 4 of these rings together. More preferred examples include groups obtained by removing f hydrogen atoms from benzene, naphthalene, or a compound formed by linking 2 to 3 benzene rings together.

[0029] 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.

[0030] R 1independently represent deuterium, 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. In addition, Ar 1 and R 1 is preferably not a group derived from a pyridine, pyrimidine or triazine.

[0031] a, c, and d independently represent an integer of 0 to 4, b independently represent an integer of 0 to 3, e independently represent an integer of 1 to 4, and f represents an integer of 1 or 2. Preferably, a, b, c, and d independently represent an integer of 0 to 1, and e represents an integer of 1 or 2. These are the numbers of substitutions. When f is 2, general formula (1) may be symmetrical or asymmetrical.

[0032] R 1 When is an aliphatic hydrocarbon group having 1 to 10 carbon atoms, specific examples include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, and nonyl. Preferred examples include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, and octyl.

[0033] R 1 Specific examples of when Ar is an unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms or an unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms include the above-mentioned Ar 1 It was just as described. Preferred examples include groups formed by removing one hydrogen atom from benzene, naphthalene, acenaphthene, acenaphthylene, azulene, dibenzofuran, dibenzothiophene, or carbazole, and more preferred examples include groups formed by removing one hydrogen atom from benzene, naphthalene, or carbazole.

[0034] In the general formula (1), when a plurality of carbazoles are linked, it is preferable that they have a 3,9-position linked structure as shown in the following formula (1a) or a 4,9-position linked structure as shown in (1b), but is not limited to these bond structures. [ka]

[0035] In the general formula (1), general formula (2), formula (6), formula (7) and formula (8), Ar 1 ~Ar 3 , R 1 ~R 5 When is an aromatic hydrocarbon group, an aromatic heterocyclic group, or a linking aromatic group, these may have a substituent, and the substituent is preferably deuterium, a cyano group, a triarylsilyl group having 18 to 36 carbon atoms, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, or a diarylamino group having 12 to 44 carbon atoms. When the substituent is an aliphatic hydrocarbon group having 1 to 10 carbon atoms, it may be linear, branched, or cyclic. The number of substituents is 0 to 5, preferably 0 to 2. When the aromatic hydrocarbon group or aromatic heterocyclic group has a substituent, the number of carbon atoms in the substituent is not included in the calculation of the carbon number. However, it is preferable that the total number of carbon atoms, including the carbon atoms in the substituent, satisfies the above range.

[0036] Specific examples of the substituent include cyano, methyl, ethyl, propyl, i-propyl, butyl, t-butyl, pentyl, cyclopentyl, hexyl, cyclohexyl, heptyl, octyl, nonyl, decyl, diphenylamino, naphthylphenylamino, dinaphthylamino, dianthranylamino, diphenanthrenylamino, dipyrenylamino, and triphenylsilyl. Preferred are cyano, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, diphenylamino, naphthylphenylamino, and dinaphthylamino.

[0037] In this specification, it is understood that hydrogen may be deuterium. That is, in the above general formulas (1) to (8), the carbazole skeleton, R 1 and Ar 1 Some or all of the H's in such a substituent may be deuterium.

[0038] Specific examples of the compound represented by the 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] [ka] [ka] [ka]

[0044] [ka] [ka] [ka]

[0045] The compound represented by formula (2) used as the second host will be described below.

[0046] In the general formula (2), X 1 are each independently N or CR 2 represents a 1 represents N. Preferably, two X 1 represents N. More preferably, three X 1 is a triazine compound in which

[0047] Preferred embodiments of the general formula (2) include the above 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. l, m, n, o, p and q each independently represent an integer of 0 to 4, preferably an integer of 0 to 2.

[0048] Ar 2each independently represents hydrogen, 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 linked aromatic group formed by linking 2 to 8 of these aromatic rings. Preferably, they represent a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 12 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 6 of these aromatic rings. More preferably, they represent a substituted or unsubstituted aromatic hydrocarbon group having 6 to 10 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 6 to 12 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 4 of these aromatic rings. However, Ar 2 At least one of the groups is the aromatic hydrocarbon group, aromatic heterocyclic group, or linking aromatic group.

[0049] Ar 2 Specific examples of the unsubstituted aromatic hydrocarbon group or unsubstituted aromatic heterocyclic group include the above Ar 1 or R 1 The unsubstituted linking aromatic group is the same as the above Ar 1 is the same as in these cases. Preferred examples include groups obtained by removing one hydrogen from benzene, naphthalene, acenaphthene, acenaphthylene, azulene, pyridine, triazine, dibenzofuran, dibenzothiophene, carbazole, or a compound formed by linking 2 to 6 of these rings. More preferred examples include groups obtained by removing one hydrogen from benzene, carbazole, dibenzofuran, dibenzothiophene, or a compound formed by linking 2 to 4 benzene rings.

[0050] R 2each independently represents hydrogen, deuterium, 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 hydrogen, 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 an aromatic hydrocarbon group having 6 to 10 carbon atoms.

[0051] In formula (6) and formula (7), R 5 and R 6 each independently represents deuterium, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a triarylsilyl group having 18 to 36 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 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 an aromatic hydrocarbon group having 6 to 10 carbon atoms, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 15 carbon atoms.

[0052] R 2 , R 5 and R 6 Specific examples of when R represents 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 include 1 The same applies as in the description above. Preferably, the group is formed by removing one hydrogen atom from benzene, naphthalene, acenaphthene, acenaphthylene, azulene, dibenzofuran, dibenzothiophene, or carbazole. More preferably, the group is formed by removing one hydrogen atom from benzene, naphthalene, or carbazole.

[0053] Specific examples of the compounds represented by the general formula (2), formula (6), formula (7) and formula (8) are shown below, but the compounds are not limited to these exemplary compounds.

[0054] [ka] [ka] [ka]

[0055] [ka] [ka] [ka]

[0056] [ka] [ka] [ka]

[0057] [ka] [ka] [ka] [ka]

[0058] The light-emitting dopant used in the organic EL device of the present invention is a polycyclic aromatic compound represented by the above general formula (4), preferably a boron-containing polycyclic aromatic compound represented by the above formula (5).

[0059] In the general formula (4), ring D, ring E, ring F, ring G, and ring H are each independently a substituted or unsubstituted aromatic hydrocarbon ring having 6 to 24 carbon atoms or a substituted or unsubstituted aromatic heterocyclic ring having 3 to 17 carbon atoms, and preferably a substituted or unsubstituted aromatic hydrocarbon ring having 6 to 20 carbon atoms or a substituted or unsubstituted aromatic heterocyclic ring having 3 to 15 carbon atoms. Since rings D to H are aromatic hydrocarbon rings or aromatic heterocyclic rings as described above, they are also referred to as aromatic rings.

[0060] Specific examples of the unsubstituted aromatic ring include rings consisting of benzene, naphthalene, acenaphthene, acenaphthylene, azulene, anthracene, chrysene, pyrene, phenanthrene, triphenylene, fluorene, benzo[a]anthracene, pyridine, pyrimidine, triazine, thiophene, isothiazole, thiazole, pyridazine, pyrrole, pyrazole, imidazole, pyrazine, furan, isoxazole, quinoline, isoquinoline, quinoxaline, quinazoline, phthalazine, indole, benzofuran, benzothiophene, benzoxazole, benzothiazole, indazole, benzimidazole, benzotriazole, benzisothiazole, benzothiadiazole, purine, pyranone, coumarin, isocoumarin, chromone, dibenzofuran, dibenzothiophene, dibenzoselenophene, or carbazole. Preferred examples include a benzene ring, a naphthalene ring, an anthracene ring, a triphenylene ring, a phenanthrene ring, a pyrene ring, a pyridine ring, a dibenzofuran ring, a dibenzothiophene ring, and a carbazole ring.

[0061] In ring D, ring E, ring F, ring G, and ring H, the aromatic hydrocarbon ring or aromatic heterocycle may have a substituent, and the substituents each independently represent a cyano group, deuterium, a diarylamino group having 12 to 44 carbon atoms, an arylheteroarylamino group having 12 to 44 carbon atoms, a diheteroarylamino group having 12 to 44 carbon atoms, 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. Preferred are a diarylamino group having 12 to 36 carbon atoms, an arylheteroarylamino group having 12 to 36 carbon atoms, a diheteroarylamino group having 12 to 36 carbon atoms, an aromatic hydrocarbon group having 6 to 12 carbon atoms, or an aromatic heterocycle having 3 to 15 carbon atoms. More preferred are diarylamino groups having 12 to 24 carbon atoms, arylheteroarylamino groups having 12 to 24 carbon atoms, diheteroarylamino groups having 12 to 24 carbon atoms, aromatic hydrocarbon groups having 6 to 10 carbon atoms, and aromatic heterocyclic groups having 3 to 12 carbon atoms. When the substituent is an aliphatic hydrocarbon group having 1 to 10 carbon atoms, it may be linear, branched, or cyclic.

[0062] Specific examples of the diarylamino group having 12 to 44 carbon atoms, the arylheteroarylamino group having 12 to 44 carbon atoms, the diheteroarylamino group having 12 to 44 carbon atoms, or the aliphatic hydrocarbon group having 1 to 10 carbon atoms include diphenylamino, dibiphenylamino, phenylbiphenylamino, naphthylphenylamino, dinaphthylamino, dianthranylamino, diphenanthrenylamino, dipyrenylamino, dibenzofuranylphenylamino, dibenzofuranylbiphenylamino, dibenzofuranylnaphthylamino, dibenzofuranylanthranylamino, dibenzofuranylphenanthrenylamino, dibenzofuranylpyrenylamino, bisdibenzofuranylamino, carbazolylphenylamino, carbazolylnaphthylamino, carbazolylanthranylamino, carbazolylphenanthrenylamino, carbazolylpyrenylamino, dicarbazolylamino, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, and nonyl. Preferred are diphenylamino, dibiphenylamino, phenylbiphenylamino, naphthylphenylamino, dinaphthylamino, dianthranylamino, diphenanthrenylamino, and dipyrenylamino, and more preferred are diphenylamino, dibiphenylamino, phenylbiphenylamino, naphthylphenylamino, dinaphthylamino, dibenzofuranylphenylamino, and carbazolylphenylamino.

[0063] In general formula (4), Y 1 is B, P, P=O, P=S, Al, Ga, As, Si―R 3 or Ge-R 3 and preferably B, P, P=O or P=S, and more preferably B.

[0064] R 3are each 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, they are 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, they are 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.

[0065] R 3 Specific examples of when R is 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 include R 1 is one of these groups.

[0066] X 2 are independently O, N-Ar 3 , S or Se, preferably O, N-Ar 3 or S, more preferably O or N-Ar 3 is.

[0067] Ar 3 are each 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 formed by linking 2 to 8 of these groups. A phenyl group, a biphenyl group, or a terphenyl group is preferred.

[0068] Ar 3 Specific examples of when is 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 formed by linking 2 to 8 of these groups include Ar 1 is one of these groups.

[0069] Ar 3When 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 substituent is preferably deuterium, a hydroxyl group, a hydrosulfide group, a cyano group, a triarylsilyl group having 18 to 36 carbon atoms, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, or a diarylamino group having 12 to 44 carbon atoms. When the substituent is an aliphatic hydrocarbon group having 1 to 10 carbon atoms, it may be linear, branched, or cyclic.

[0070] Specific examples of the substituent include cyano, methyl, ethyl, propyl, i-propyl, butyl, t-butyl, pentyl, cyclopentyl, hexyl, cyclohexyl, heptyl, octyl, nonyl, decyl, diphenylamino, naphthylphenylamino, dinaphthylamino, dianthranylamino, diphenanthrenylamino, dipyrenylamino, and triphenylsilyl. Preferred are cyano, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, diphenylamino, naphthylphenylamino, and dinaphthylamino.

[0071] N-Ar 3 may be bonded to an aromatic ring selected from ring D, ring E, ring F, ring G, or ring H to form a heterocycle containing N. 3 When Ar has a substituent, it may be bonded to an aromatic ring selected from ring D, ring E, ring F, ring G, or ring H via the substituent to form a heterocycle containing N; 3 At least one hydrogen atom in the formula (I) may be substituted with deuterium.

[0072] The polycyclic aromatic compound includes the compounds represented by the general formula (4) or (5). In the general formula (4) and the formula (5), the common symbols have the same meaning. In the formula (5), 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. Preferably, g, h, i, j, and k are independently 0 or 1.

[0073] In the formula (5), X3 are each independently N-Ar 4 , O, or S, but at least one X 3 is N-Ar 4 and preferably represents N-Ar 4 , or O. Ar 4 is Ar in general formula (4) 3 This is the same as N-Ar. 4 may bond with the aromatic ring (the benzene ring corresponding to rings D to H) to form a heterocycle containing nitrogen.

[0074] R 4 each independently represents a cyano group, deuterium, a diarylamino group having 12 to 44 carbon atoms, 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 a diarylamino group having 12 to 36 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 diarylamino group having 12 to 24 carbon atoms, 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.

[0075] R 4 When represents a diarylamino group having 12 to 44 carbon atoms or an aliphatic hydrocarbon group having 1 to 10 carbon atoms, specific examples include diphenylamino, dibiphenylamino, phenylbiphenylamino, naphthylphenylamino, dinaphthylamino, dianthranylamino, diphenanthrenylamino, dipyrenylamino, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, and nonyl. Preferred examples include diphenylamino, dibiphenylamino, phenylbiphenylamino, naphthylphenylamino, dinaphthylamino, dianthranylamino, diphenanthrenylamino, and dipyrenylamino. More preferred examples include diphenylamino, dibiphenylamino, phenylbiphenylamino, naphthylphenylamino, and dinaphthylamino.

[0076] Preferred embodiments of the polycyclic aromatic compound of general formula (4) or formula (5) include the following formulae (4-d), (4-e), (4-f), and (4-h). The following formula (4-f) is more preferred. [ka]

[0077] The polycyclic aromatic compounds represented by formula (4-d), formula (4-e), and formula (4-f) correspond to compounds represented by formula (4-67), formula (4-68), and formula (4-69) described later, for example. The polycyclic aromatic compound represented by formula (4-h) corresponds to, for example, compounds represented by formulas (4-71), (4-72), (4-73), (4-74), and (4-75) described later.

[0078] In the formulas (4-d) to (4-h), X 2 and Y 1 is the same as general formula (4), and R 7 is R in equation (5). 4 wherein each r independently represents an integer of 0 to 4, each s independently represents an integer of 0 to 2, and each t independently represents an integer of 0 to 3.

[0079] Specific examples of polycyclic aromatic compounds represented by the general formula (4) or (5) are shown below, but the compounds are not limited to these examples.

[0080] [ka] [ka] [ka] [ka]

[0081] [ka] [ka] [ka] [ka]

[0082] The organic light-emitting material used as a light-emitting dopant in the organic EL device of the present invention preferably has a ΔEST of 0.20 eV or less, more preferably 0.15 eV or less, and even more preferably 0.10 eV or less.

[0083] ΔEST represents the difference between the excited singlet energy (S1) and the excited triplet energy (T1), where the measurement conditions for S1 and T1 are the same as those described in the Examples.

[0084] An excellent organic EL device can be provided by using a material selected from the polycyclic aromatic compounds represented by the general formula (4) (hereinafter also referred to as a polycyclic aromatic compound material) as a light-emitting dopant, a material selected from the compounds represented by the general formula (1) as a first host, and a material selected from the compounds represented by the general formula (2) as a second host.

[0085] 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 this.

[0086] 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 layers can be inserted simultaneously. The organic EL device of the present invention has 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 in addition to the essential layers, and may further have a hole blocking layer between the emitting layer and the electron injection transport layer. Note that the hole injection transport layer refers to either the hole injection layer or the hole transport layer, or both, and the electron injection transport layer refers to either the electron injection layer or the electron transport layer, or both.

[0087] It is also possible to have the reverse structure to that shown in Figure 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, and in this case too, layers can be added or omitted as necessary.

[0088] -substrate- The organic EL device of the present invention is preferably supported by a substrate. There are no particular limitations on the substrate, and any substrate conventionally used in organic EL devices, such as glass, transparent plastic, or quartz, can be used.

[0089] -anode- Anode materials for organic EL devices are preferably 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, if pattern precision is not required (approximately 100 μm or higher), a mask of the desired shape may be used during vapor deposition or sputtering of the electrode material to form the pattern. Alternatively, when a coatable material such as an organic conductive compound is used, wet film formation methods such as printing or coating can 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 / □. The film thickness varies depending on the material, but is usually selected in the range of 10 to 1000 nm, preferably 10 to 200 nm.

[0090] -cathode- On the other hand, cathode materials are typically made of metals (referred to as electron-injecting metals), alloys, electrically conductive compounds, or mixtures thereof with a low work function (4 eV or less). 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 / aluminum oxide (Al2O3) mixtures, indium, lithium / aluminum mixtures, and rare earth metals. Among these, mixtures of electron-injecting metals and stable second metals with higher work functions, such as magnesium / silver mixtures, magnesium / aluminum mixtures, magnesium / indium mixtures, aluminum / aluminum oxide (Al2O3) mixtures, lithium / aluminum mixtures, and aluminum, are preferred in terms of electron injection properties and durability against oxidation. Cathode materials can be fabricated by forming thin films of these cathode materials using methods such as vapor deposition or sputtering. Furthermore, the cathode preferably has a sheet resistance of several hundred Ω / □ or less, and the film thickness is typically selected from the range of 10 nm to 5 μm, preferably 50 to 200 nm. It is advantageous if either the anode or cathode of the organic EL element is transparent or semi-transparent to allow the emitted light to pass through, as this improves the luminance of the emitted light.

[0091] Furthermore, a transparent or semi-transparent cathode can be fabricated by forming the above metal in a thickness of 1 to 20 nm on the cathode and then forming the conductive transparent material described in the description of the anode thereon. This can be applied to fabricate an element in which both the anode and cathode are transparent.

[0092] -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 a light-emitting dopant and a host. The light-emitting dopant and the host can be used so that the light-emitting dopant accounts for 0.10 to 10% and the host accounts for 99.9 to 90%, for example, preferably 1.0 to 5.0% of the light-emitting dopant and 99 to 95% of the host, and more preferably 1.0 to 3.0% of the light-emitting dopant and 99 to 97% of the host. In this specification, % means % by mass unless otherwise specified.

[0093] The hosts in the light-emitting layer are the first host and the second host described above. The first host and the second host can be used, for example, in a ratio of 10 to 90% of the first host and 90 to 10% of the second host. Preferably, the ratio is 30 to 70% of the first host and 70 to 30% of the second host, and more preferably, 50 to 70% of the first host and 50 to 30% of the second host. Furthermore, as other hosts than those mentioned above, one or more known hosts may be used in combination, but the amount used should be 50% or less, preferably 25% or less of the total amount of the host material. Other known hosts that can be used are compounds that have hole-transporting and electron-transporting capabilities and a high glass transition temperature, and preferably have a T1 greater than that of the luminescent dopant. Specifically, the T1 of the host is preferably at least 0.010 eV higher than that of the luminescent dopant, more preferably at least 0.030 eV higher, and even more preferably at least 0.10 eV higher. A TADF-active compound may also be used as the host material, and this compound preferably has a ΔEST of 0.20 eV or less.

[0094] The other known hosts can be selected from numerous patent documents, etc. Specific examples of the host include, but are not limited to, indole derivatives, carbazole derivatives, indolocarbazole derivatives, triazole derivatives, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, phenylenediamine derivatives, arylamine derivatives, styrylanthracene derivatives, fluorenone derivatives, stilbene derivatives, triphenylene derivatives, carborane derivatives, porphyrin derivatives, phthalocyanine derivatives, various metal complexes typified by metal complexes of 8-quinolinol derivatives, metal phthalocyanines, benzoxazole and benzothiazole derivatives, polymer compounds such as poly(N-vinylcarbazole) derivatives, aniline copolymers, thiophene oligomers, polythiophene derivatives, polyphenylene derivatives, polyphenylenevinylene derivatives, and polyfluorene derivatives.

[0095] When multiple types of hosts are used, each host can be vapor-deposited from a different vapor deposition source, or multiple hosts can be simultaneously vapor-deposited from one vapor deposition source by premixing them before vapor deposition to form a premixture.

[0096] The premixing method is preferably a method that allows mixing as uniformly as possible, and examples thereof include pulverization and mixing, heating and melting under reduced pressure or in an inert gas atmosphere such as nitrogen, and sublimation, but are not limited to these methods.

[0097] The premix may be in the form of a powder, stick, or granules.

[0098] The above-mentioned polycyclic aromatic compound materials can be used as the light-emitting dopant in the light-emitting layer. The light-emitting layer may contain two or more light-emitting dopants. For example, the light-emitting layer may contain the polycyclic aromatic compound material and a light-emitting dopant composed of another compound. In this case, the light-emitting dopant composed of the other compound preferably has a ΔEST of 0.20 eV or less, but is not limited thereto.

[0099] When two or more types of luminescent dopants are contained in the luminescent layer, the first dopant is a compound represented by general formula (4) or (5), and a known compound may be used in combination as the second dopant. The content of the first dopant is preferably 0.050 to 50% relative to the host material, and the content of the second dopant is preferably 0.050 to 50% relative to the host material, and the total content of the first dopant and the second dopant does not exceed 50% relative to the host material.

[0100] Such other luminescent dopants are known in many patent documents, etc., and can be selected from them. Specific examples of the dopant include, but are not limited to, fused ring derivatives such as phenanthrene, anthracene, pyrene, tetracene, pentacene, perylene, naphthopyrene, dibenzopyrene, rubrene, and chrysene, 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, bisstyryl derivatives such as bisstyrylanthracene derivatives and distyrylbenzene derivatives, bisstyrylarylene derivatives, diazaindacene derivatives, furan derivatives, benzofuran derivatives, benzophenone ... Examples of the benzofluorene derivatives include benzophenone derivatives, isobenzofuran derivatives, dibenzofuran derivatives, coumarin derivatives, dicyanomethylenepyran derivatives, dicyanomethylenethiopyran derivatives, polymethine derivatives, cyanine derivatives, oxobenzoanthracene derivatives, xanthene derivatives, rhodamine derivatives, fluorescein derivatives, pyrylium derivatives, carbostyril derivatives, acridine derivatives, oxazine derivatives, phenylene oxide derivatives, quinacridone derivatives, quinazoline derivatives, pyrrolopyridine derivatives, furopyridine derivatives, 1,2,5-thiadiazolopyrene derivatives, pyrromethene derivatives, perinone derivatives, pyrrolopyrrole derivatives, squarylium derivatives, violanthrone derivatives, phenazine derivatives, acridone derivatives, deazaflavin derivatives, fluorene derivatives, and benzofluorene derivatives.

[0101] The luminescent dopant and the first host or the second host can be deposited from different deposition sources, or can be premixed before deposition to form a premixture, so that the luminescent dopant and the first host or the second host can be simultaneously deposited from a single deposition source.

[0102] -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.

[0103] -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 a significantly low ability to transport holes. By transporting electrons while blocking holes, the hole-blocking layer can improve the probability of electron-hole recombination in the light-emitting layer. Known hole-blocking materials can be used for the hole-blocking layer. To bring out the properties of the light-emitting dopant, the material used as the second host can also be used as the material for the hole-blocking layer. Multiple hole-blocking materials may also be used in combination.

[0104] -Electron blocking layer- In a broad sense, the electron blocking layer functions as a hole transport layer, and by transporting holes while blocking electrons, it can improve the probability of electron and hole recombination in the light-emitting layer. Known electron blocking layer materials can be used as the material for the electron blocking layer. To bring out the properties of the light-emitting dopant, the material used as the first host can also be used as the material for the electron blocking layer. The thickness of the electron blocking layer is preferably 3 to 100 nm, more preferably 5 to 30 nm.

[0105] -Exciton blocking layer- The exciton-blocking layer is a layer that prevents excitons generated by the recombination of holes and electrons in the light-emitting layer from diffusing into the charge-transporting layer. Inserting this layer makes it possible to efficiently confine excitons within 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. As the material for the exciton blocking layer, known exciton blocking layer materials can be used.

[0106] Layers adjacent to the light-emitting layer include a hole-blocking layer, an electron-blocking layer, an exciton-blocking layer, etc., but if these layers are not provided, the adjacent layers are a hole-transporting layer, an electron-transporting layer, etc.

[0107] -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.

[0108] The hole transport material has either hole injection or transport properties or electron barrier properties, and may be either organic or inorganic. Any conventionally known compound can be selected and used for the hole transport layer. Examples of such hole transport materials include porphyrin derivatives, arylamine derivatives, triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aniline-based copolymers, and conductive polymer oligomers, particularly thiophene oligomers. Porphyrin derivatives, arylamine derivatives, and styrylamine derivatives are preferred, and arylamine compounds are more preferred.

[0109] -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.

[0110] The electron transport material (which may also serve as a hole blocking material) may be any material capable of transporting electrons injected from the cathode to the light-emitting layer. The electron transport layer may be formed from any of a variety of conventionally known compounds, including polycyclic aromatic derivatives such as naphthalene, anthracene, and phenanthroline, tris(8-quinolinolato)aluminum(III) derivatives, phosphine oxide derivatives, nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, carbodiimides, fluorenylidenemethane derivatives, anthraquinodimethane and anthrone derivatives, bipyridine derivatives, quinoline derivatives, oxadiazole derivatives, benzimidazole derivatives, benzothiazole derivatives, and indolocarbazole derivatives. Furthermore, polymeric materials incorporating these materials into polymer chains or containing these materials as the polymer backbone may also be used.

[0111] When the organic EL device of the present invention is produced, the method for forming each layer is not particularly limited, and the layers may be produced by either a dry process or a wet process. [Example]

[0112] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0113] The compounds used in the examples and comparative examples are listed below. [ka]

[0114] The S1 and T1 of the compounds BD1, (4-110) and (4-121) were measured. S1 and T1 were measured as follows. Vacuum deposition method on a quartz substrate at a vacuum level of 10 -4Compound (1-58) as a host and Compound BD1, Compound (4-110), or Compound (4-121) as an emitting dopant were co-deposited from different evaporation sources to form a deposited film with a thickness of 100 nm under conditions of ≤ Pa. The co-deposition was performed under evaporation conditions such that the concentration of the emitting dopant was 3%. S1 is calculated by measuring the emission spectrum of this vapor-deposited film, drawing a tangent to the rising edge on the short wavelength side of this emission spectrum, and substituting the wavelength value λedge [nm] at the intersection of this tangent and the horizontal axis into the following formula (i). S1[eV] = 1239.85 / λedge (i) T1 is calculated by measuring the phosphorescence spectrum of the above-mentioned vapor-deposited film, drawing a tangent to the rising edge on the short wavelength side of this phosphorescence spectrum, and substituting the wavelength value λedge [nm] at the intersection of this tangent and the horizontal axis into formula (ii). T1[eV] = 1239.85 / λedge (ii)

[0115] The measurement results are shown in Table 1. [Table 1]

[0116] Example 1 Each thin film was deposited by vacuum deposition on a glass substrate with an anode made of ITO with a film thickness of 70 nm at a vacuum of 4.0 × 10 -5The layers were laminated at 1000 Pa. First, HAT-CN was formed on ITO as a hole injection layer to a thickness of 10 nm, and then HT-1 was formed on ITO as a hole transport layer to a thickness of 25 nm. Next, compound (1-58) was formed on ITO as an electron blocking layer to a thickness of 5 nm. Next, compound (1-58) was co-deposited from different evaporation sources as a first host, compound (2-6) as a second host, and compound (4-121) as an emitting dopant to a thickness of 30 nm to form an emitting layer. The co-deposition was performed under evaporation conditions where the concentration of compound (4-121) was 2% and the blending ratio of the first host to the second host was 70:30. Next, compound (2-6) was formed on ITO as a hole blocking layer to a thickness of 5 nm. Next, ET-1 was formed on ITO as an electron transport layer to a thickness of 40 nm. Lithium fluoride (LiF) was formed on the electron transport layer to a thickness of 1 nm to form an electron injection layer. Finally, aluminum (Al) was formed as a cathode to a thickness of 70 nm on the electron injection layer to fabricate an organic EL device.

[0117] Examples 2 to 9 An organic EL device was fabricated in the same manner as in Example 1, except that the light-emitting dopant, the first host, the second host, and the compounding ratio of the first host to the second host were the compounds shown in Table 2.

[0118] Comparative Example 1 Each thin film was deposited by vacuum deposition on a glass substrate with an anode made of ITO with a film thickness of 70 nm at a vacuum of 4.0 × 10 -5The layers were laminated at 1000 W / m². First, HAT-CN was formed on the ITO as a hole-injection layer to a thickness of 10 nm, followed by HT-1 as a hole-transport layer to a thickness of 25 nm. Next, compound (1-58) was formed as an electron-blocking layer to a thickness of 5 nm. Next, compound (1-58) was co-deposited as the first host and compound (4-121) as the luminescent dopant from different evaporation sources to form an emitting layer to a thickness of 30 nm. The co-deposition was carried out under evaporation conditions that resulted in a 2% concentration of compound (4-121). Next, compound (2-6) was 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 40 nm. Furthermore, lithium fluoride (LiF) was formed as an electron-injection layer to a thickness of 1 nm on the electron-transport layer. Finally, aluminum (Al) was formed as a cathode to a thickness of 70 nm on the electron-injection layer to fabricate an organic EL device.

[0119] Comparative Examples 3, 5, and 7 An organic EL device was prepared in the same manner as in Comparative Example 1, except that the light-emitting dopant and the first host (no second host) were the compounds shown in Table 2.

[0120] Comparative Examples 2 and 6 An organic EL device was prepared in the same manner as in Comparative Example 1, except that the light-emitting dopant and the second host (no first host) were the compounds shown in Table 2.

[0121] Comparative Examples 4, 8, 9, and 10 An organic EL device was fabricated in the same manner as in Example 1, except that the light-emitting dopant, first host, and second host were the compounds shown in Table 2 in the compounding ratios.

[0122] [Table 2]

[0123] The maximum emission wavelength, external quantum efficiency, and lifetime of the organic EL devices fabricated in the examples and comparative examples are shown in Table 3. The maximum emission wavelength and external quantum efficiency were 2 The value is the initial value, and is the initial characteristic.2 The time it took for the brightness to decay to 50% of the initial brightness was measured.

[0124] [Table 3]

[0125] From Table 3, it can be seen that the organic EL devices of the examples have high efficiency and long life characteristics, and emit blue light from the maximum emission wavelength.

[0126] The organic EL device of the present invention has high luminous efficiency and a long life. [Explanation of symbols]

[0127] 1 substrate, 2 anode, 3 hole injection layer, 4 hole transport layer, 5 light-emitting layer, 6 electron transport layer, 7 cathode

Claims

1. The organic electroluminescent device includes one or more light-emitting layers between an anode and a cathode facing each other, wherein at least one of the light-emitting layers contains a first host having a hole-transporting property selected from compounds represented by the following general formula (1), a second host having an electron-transporting property selected from compounds represented by the following general formula (8), and a light-emitting dopant selected from boron-containing polycyclic aromatic compounds represented by the following general formula (5): 【Chemical 1】 Here, Ar １ represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, a substituted or unsubstituted fused aromatic heterocyclic group having 6 to 17 carbon atoms, or a substituted or unsubstituted linked aromatic group formed by linking 2 to 8 of these aromatic rings. e independently represents an integer of 1 to 4; f represents an integer of 1 or 2; When f is 2, general formula (1) may be symmetric or asymmetric. 【Chemistry 2】 Here, Ar ２ each independently represents hydrogen, 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 linked aromatic group formed by linking 2 to 8 of these aromatic rings. ２ At least one of is a group other than hydrogen. 【Chemistry 3】 Here, each X 3 independently represents N—Ar 4 , O, or S, provided that 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 linked aromatic group formed by linking 2 to 8 of these aromatic rings. N-Ar 4 may be bonded to the benzene ring to which it is bonded to form a heterocycle containing N. Each R 4 independently represents a cyano group, deuterium, a diarylamino group having 12 to 44 carbon atoms, 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. g and h each independently represent an integer of 0 to 4; i and j each independently represent an integer of 0 to 3; k represents an integer of 0 to 2;

2. Ar in the general formula (1) １ 2. The organic electroluminescent device according to claim 1, wherein is a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, or a substituted or unsubstituted fused aromatic heterocyclic group having 6 to 17 carbon atoms.

3. 3. The organic electroluminescent device according to claim 1, wherein the general formula (8) is the following formula (6): 【Chemistry 4】 Here, Ar ２ is the same as general formula (8). R ５ each independently represents deuterium, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a triarylsilyl group having 18 to 36 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. l and m each independently represent an integer of 0 to 4;

4. 4. The organic electroluminescent device according to claim 1, wherein the general formula (8) is the following formula (7): 【Chemistry 5】 Here, Ar ２ is the same as general formula (8). R ６ each independently represents deuterium, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a triarylsilyl group having 18 to 36 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. n, o, p and q each independently represent an integer of 0 to 4;

5. 5. The organic electroluminescent device according to claim 1, wherein the light-emitting dopant has a difference (ΔEST) between the excited singlet energy (S1) and the excited triplet energy (T1) of 0.20 eV or less.

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

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