ORGANIC ELECTROLUMINESCENT DEVICES

Description

[0001] The present invention relates to organic electroluminescent devices containing indenocarbazole derivatives.

[0002] In organic electroluminescent devices (OLEDs), phosphorescent organometallic complexes are often used as emitting materials. The properties of phosphorescent OLEDs are not only determined by the triplet emitters used. The other materials used, especially the matrix materials, are also of particular importance. Improvements to these materials can therefore also lead to significant improvements in OLED properties.

[0003] The object of the present invention is to provide phosphorescent organic electroluminescent devices that exhibit improved properties, in particular an improved lifetime combined with good efficiency and low operating voltage. A further object of the invention is to provide phosphorescent OLEDs with a long lifetime, good efficiency, and low operating voltage that contain only one matrix material rather than a mixture of two matrix materials. The advantage of such an OLED is the simplified processing during its manufacture.

[0004] Surprisingly, it has been found that this object is achieved by using the indenocarbazole derivatives described in more detail below as matrix material for phosphorescent emitters. Organic electroluminescent devices containing such compounds as matrix material for phosphorescent emitters are therefore the subject of the present invention. Indenocarbazole derivatives are known as matrix materials for phosphorescent emitters from WO 2010 / 136109 (A1), KR20180013713 (A), and US2015 / 214492 (A1).

[0005] Matrix materials according to the present invention are not disclosed. The present invention relates to an organic electroluminescent device comprising an anode, a cathode, and at least one emitting layer containing at least one phosphorescent compound, characterized in that the emitting layer contains at least one compound according to formula (1), where the symbols and indices used are: Xtwo adjacent X stand for a group of the following formula (2), and the other two X stand for CR, where the two dashed bonds represent the linkage of this group;

[0006] HetAr is a group according to one of the formulas (HetAr-1d), (HetAr-2a), (HetAr-3a), (HetAr-4a), (HetAr-5a), (HetAr-6a), (HetAr-7a) and (HetAr-8c),

[0007] Ar is, identically or differently on each occurrence, an aromatic or heteroaromatic ring system having 5 to 40 aromatic ring atoms, which may be substituted by one or more radicals R 1<; R is at each occurrence, identically or differently, H, D, F, Cl, Br, I, N(R 1< ) 2 , N(Ar') 2 , CN, NO 2 , OR 1< , SR 1< , COOR 1< , C(=O)N(R 1< ) 2 , Si(R 1< ) 3 , B(OR 1< ) 2 , C(=O)R 1< , P(=O)(R 1< ) 2 , S(=O)R 1< , S(=O) 2 R 1< , OSO 2 R 1< , a straight-chain alkyl group having 1 to 20 C atoms or an alkenyl or alkynyl group having 2 to 20 C atoms or a branched or cyclic alkyl group having 3 to 20 C atoms, where the Alkyl, alkenyl or alkynyl group may each be substituted by one or more radicals R 1< and wherein one or more non-adjacent CH 2 groups may be replaced by Si(R 1< ) 2 , C=O, NR 1< , O, S or CONR 1<, or an aromatic or heteroaromatic ring system having 5 to 60 aromatic ring atoms, preferably having 5 to 40 aromatic ring atoms, which may each be substituted by one or more radicals R 1<;R' is, on each occurrence, identical or different, a straight-chain alkyl group having 1 to 20 C atoms or a branched or cyclic alkyl group having 3 to 20 C atoms, where the straight-chain, branched or cyclic alkyl group may in each case be substituted by one or more radicals R 1< and where one or more non-adjacent CH 2 groups may be replaced by O, or an aromatic or heteroaromatic ring system having 5 to 40 aromatic ring atoms, which may in each case be substituted by one or more radicals R 1<; two radicals R' can also form an aromatic, heteroaromatic, aliphatic or heteroaliphatic ring system with one another; Ar' is, on each occurrence, identical or different, an aromatic or heteroaromatic ring system having 5 to 40 aromatic ring atoms, which may be substituted by one or more radicals R 1<;R 1< is, identically or differently at each occurrence, H, D, F, Cl, Br, I, N(R 2< ) 2 , CN, NO 2 , OR 2< , SR 2< , Si(R 2< ) 3 , B(OR 2< ) 2 , C(=O)R 2< , P(=O)(R 2< ) 2 , S(=O)R 2< , S(=O) 2 R 2< , OSO 2 R 2< , a straight-chain alkyl group having 1 to 20 C atoms or an alkenyl or alkynyl group having 2 to 20 C atoms or a branched or cyclic alkyl group having 3 to 20 C atoms, where the alkyl, alkenyl or alkynyl group may each be substituted by one or more radicals R 2<, where one or more non-adjacent CH 2 groups may be replaced by Si(R 2< ) 2 , C=O, NR 2< , O, S or CONR 2<, or an aromatic or heteroaromatic ring system having 5 to 40 aromatic ring atoms, each of which may be substituted by one or more radicals R 2<;R 2< is, identically or differently at each occurrence, H, D, F or an aliphatic, aromatic or heteroaromatic organic radical, in particular a hydrocarbon radical, having 1 to 20 C atoms, in which one or more H atoms may be replaced by F; m is 0, 1 or 2; n is, identically or differently at each occurrence, 0 or 1. ;

[0008] An aryl group within the meaning of this invention contains 6 to 40 C atoms; a heteroaryl group within the meaning of this invention contains 2 to 40 C atoms and at least one heteroatom, with the proviso that the sum of C atoms and heteroatoms is at least 5. The heteroatoms are preferably selected from N, O and / or S. An aryl group or heteroaryl group is understood to be either a simple aromatic cycle, i.e. benzene, or a simple heteroaromatic cycle, for example pyridine, pyrimidine, thiophene, etc., or a condensed (fused) aryl or heteroaryl group, for example naphthalene, anthracene, phenanthrene, quinoline, isoquinoline, etc. Aromatics linked to one another by a single bond, such as biphenyl, are not referred to as aryl or heteroaryl groups, but as an aromatic ring system.

[0009] An electron-deficient heteroaryl group within the meaning of the present invention is a heteroaryl group that has at least one heteroaromatic six-membered ring with at least two nitrogen atoms or at least one heteroaromatic five-membered ring with at least two heteroatoms, where at least one heteroatom in the five-membered ring is nitrogen and the other heteroatom in the five-membered ring is a substituted nitrogen, oxygen, or sulfur. Further aromatic or heteroaromatic groups can be fused to this heteroaromatic five-membered ring or six-membered ring. In a preferred embodiment of the invention, the electron-deficient heteroaryl group contains at least one heteroaromatic six-membered ring with at least two nitrogen atoms. Examples of electron-deficient heteroaryl groups are pyrimidine, pyrazine, pyridazine, triazine, quinazoline, quinoxaline, benzoquinazoline, or benzimidazole.Further electron-deficient heteroaryl groups are described in more detail in the following description.

[0010] An aromatic ring system within the meaning of this invention contains 6 to 60 C atoms in the ring system, preferably 6 to 40 C atoms. A heteroaromatic ring system within the meaning of this invention contains 2 to 60 C atoms, preferably 2 to 40 C atoms, and at least one heteroatom in the ring system, with the proviso that the sum of C atoms and heteroatoms is at least 5. The heteroatoms are preferably selected from N, O and / or S. An aromatic or heteroaromatic ring system within the meaning of this invention is to be understood as a system that does not necessarily contain only aryl or heteroaryl groups, but in which several aryl or heteroaryl groups can also be connected by a non-aromatic unit, such as a C, N or O atom. For example, systems such as fluorene, 9,9'-spirobifluorene, 9,9-diarylfluorene, triarylamine, diaryl ether, stilbene, etc.are understood as aromatic ring systems within the meaning of this invention, as are systems in which two or more aryl groups are linked, for example, by a short alkyl group. The aromatic ring system is preferably selected from fluorene, 9,9'-spirobifluorene, 9,9-diarylamine, or groups in which two or more aryl and / or heteroaryl groups are linked by single bonds.

[0011] In the context of the present invention, an aliphatic hydrocarbon radical or an alkyl group or an alkenyl or alkynyl group which may contain 1 to 40 C atoms and in which individual H atoms or CH 2 groups may be substituted by the abovementioned groups, preferably the radicals methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, s-butyl, t-butyl, 2-methylbutyl, n-pentyl, s-pentyl, neo-pentyl, cyclopentyl, n-hexyl, neo-hexyl, cyclohexyl, n-heptyl, cycloheptyl, n-octyl, cyclooctyl, 2-ethylhexyl, trifluoromethyl, pentafluoroethyl, 2,2,2-trifluoroethyl, ethenyl, propenyl, butenyl, pentenyl, Cyclopentenyl, hexenyl, cyclohexenyl, heptenyl, cycloheptenyl, octenyl, cyclooctenyl, ethynyl, propynyl, butynyl, pentinyl, hexynyl, heptynyl or octynyl.Unter einer Alkoxygruppe mit 1 bis 40 C-Atomen werden bevorzugt Methoxy, Trifluormethoxy, Ethoxy, n-Propoxy, i-Propoxy, n-Butoxy, i-Butoxy, s-Butoxy, t-Butoxy, n-Pentoxy, s-Pentoxy, 2-Methylbutoxy, n-Hexoxy, Cyclohexyloxy, n-Heptoxy, Cycloheptyloxy, n-Octyloxy, Cyclooctyloxy, 2-Ethylhexyloxy, Pentafluorethoxy und 2,2,2-Trifluorethoxy verstanden. Unter einer Thioalkylgruppe mit 1 bis 40 C-Atomen werden insbesondere Methylthio, Ethylthio, n-Propylthio, i-Propylthio, n-Butylthio, i-Butylthio, s-Butylthio, t-Butylthio, n-Pentylthio, s-Pentylthio, n-Hexylthio, Cyclohexylthio, n-Heptylthio, Cycloheptylthio, n-Octylthio, Cyclooctylthio, 2-Ethylhexylthio, Trifluormethylthio, Pentafluorethylthio, 2,2,2-Trifluorethylthio, Ethenylthio, Propenylthio, Butenylthio, Pentenylthio, Cyclopentenylthio, Hexenylthio, Cyclohexenylthio, Heptenylthio, Cycloheptenylthio, Octenylthio, Cyclooctenylthio, Ethinylthio, Propinylthio, Butinylthio, Pentinylthio, Hexinylthio, Heptinylthio oder Octinylthio verstanden.In general, alkyl, alkoxy, or thioalkyl groups according to the present invention may be straight-chain, branched, or cyclic, wherein one or more non-adjacent CH 2 groups may be replaced by the above-mentioned groups; furthermore, one or more H atoms may also be replaced by D, F, Cl, Br, I, CN, or NO 2 , preferably F, Cl, or CN, more preferably F or CN, particularly preferably CN.

[0012] An aromatic or heteroaromatic ring system with 5 to 60 aromatic ring atoms, which may also be substituted by the above-mentioned radicals and which may be linked to the aromatic or heteroaromatic ring via any desired positions, is understood to mean in particular groups derived from benzene, naphthalene, anthracene, benzanthracene, phenanthrene, pyrene, chrysene, perylene, fluoranthene, naphthacene, pentacene, benzopyrene, biphenyl, biphenylene, terphenyl, triphenylene, fluorene, spirobifluorene, dihydrophenanthrene, dihydropyrene, tetrahydropyrene, cis- or trans-indenofluorene, cis- or trans-indenocarbazole, cis- or trans-indolocarbazole, truxene, isotruxene, spirotruxene, spiroisotruxene, furan, benzofuran, isobenzofuran, dibenzofuran, thiophene, benzothiophene, Isobenzothiophene, dibenzothiophene, pyrrole, indole, isoindole, carbazole, pyridine, quinoline, isoquinoline, acridine, phenanthridine, benzo-5,6-quinoline, benzo-6,7-quinoline, benzo-7,8-quinoline, phenothiazine,Phenoxazin, Pyrazol, Indazol, Imidazol, Benzimidazol, Naphthimidazol, Phenanthrimidazol, Pyridimidazol, Pyrazinimidazol, Chinoxalinimidazol, Oxazol, Benzoxazol, Naphthoxazol, Anthroxazol, Phenanthroxazol, Isoxazol, 1,2-Thiazol, 1,3-Thiazol, Benzothiazol, Pyridazin, Hexaazatriphenylen, Benzopyridazin, Pyrimidin, Benzpyrimidin, Chinoxalin, 1,5-Diazaanthracen, 2,7-Diazapyren, 2,3-Diazapyren, 1,6-Diazapyren, 1,8-Diazapyren, 4,5-Diazapyren, 4,5,9,10-Tetraazaperylen, Pyrazin, Phenazin, Phenoxazin, Phenothiazin, Fluorubin, Naphthyridin, Azacarbazol, Benzocarbolin, Phenanthrolin, 1,2,3-Triazol, 1,2,4-Triazol, Benzotriazol, 1,2,3-Oxadiazol, 1,2,4-Oxadiazol, 1,2,5-Oxadiazol, 1,3,4-Oxadiazol, 1,2,3-Thiadiazol, 1,2,4-Thiadiazol, 1,2,5-Thiadiazol, 1,3,4-Thiadiazol, 1,3,5-Triazin, 1,2,4-Triazin, 1,2,3-Triazin, Tetrazol, 1,2,4,5-Tetrazin, 1,2,3,4-Tetrazin, 1,2,3,5-Tetrazin, Purin, Pteridin, Indolizin und Benzothiadiazol oder Gruppen, die abgeleitet sind von Kombinationen dieser Systeme.,

[0013] When two R' radicals form a ring system, this can be mono- or polycyclic. The radicals forming a ring system are preferably adjacent, meaning that these radicals are bonded to the same carbon atom or to carbon atoms that are directly bonded to one another. When two R' radicals form a ring system, this results in a spiro system.

[0014] For the purposes of this description, the phrase "two or more residues can form a ring" is understood to mean, among other things, that the two residues are linked by a chemical bond with the formal elimination of two hydrogen atoms. This is illustrated by the following scheme.

[0015] Furthermore, the above formulation should also be understood to mean that if one of the two residues represents hydrogen, the second residue binds to the position to which the hydrogen atom was bonded, forming a ring. This is illustrated by the following scheme:

[0016] Depending on the position in which the group of formula (2) is condensed, the organic electroluminescent device according to the invention comprises at least one compound according to one of the following formulas (3), (4) or (5), where the symbols and indices used have the meanings given above.

[0017] In a preferred embodiment of the invention, the compounds of formulas (3), (4) and (5) are selected from the compounds of the following formulas (3a-1), (3a-2), (4a-1), (4a-2), (5a-1) and (5a-2), where HetAr, R and R' have the meanings given above.

[0018] The radical R in the group of formula (2) is preferably H, so that the compounds of formulas (3), (4) and (5) are compounds of the following formulas (3b), (4b) and (5b), respectively, where HetAr, R and R' have the meanings given above.

[0019] In a preferred embodiment of the invention, R in formulas (3b), (4b) and (5b) represents carbazolyl which is substituted on the nitrogen atom by a radical R 1<, where R 1< represents an aromatic or heteroaromatic ring system. The carbazolyl radical is preferably bonded via the 3-position. In a further preferred embodiment of the invention, the radical R in formulas (3b), (4b) and (5b) represents H, so that the compounds are preferably of the following formulas (3c), (4c) and (5c), respectively: where HetAr and R' have the meanings given above.

[0020] Preferred HetAr groups are described below.

[0021] Particularly preferred are the groups (HetAr-1d) and (HetAr-2a), in particular (HetAr-2a).

[0022] Suitable aromatic orHeteroaromatic ring systems Ar are selected from phenyl, biphenyl, in particular ortho-, meta- or para-biphenyl, terphenyl, in particular ortho-, meta-, para- or branched terphenyl, quaterphenyl, in particular ortho-, meta-, para- or branched quaterphenyl, fluorene, which may be linked via the 1-, 2-, 3- or 4-position, spirobifluorene, which may be linked via the 1-, 2-, 3- or 4-position, naphthalene, in particular 1- or 2-linked naphthalene, indole, benzofuran, benzothiophene, carbazole, which may be linked via the 1-, 2-, 3- or 4-position, dibenzofuran, which may be linked via the 1-, 2-, 3- or 4-position, dibenzothiophene, which may be linked via the 1-, 2-, 3- or 4-position, Indenocarbazole, indolocarbazole, pyridine, pyrimidine, pyrazine, pyridazine, triazine, quinoline, isoquinoline, quinazoline, quinoxaline, phenanthrene or triphenylene, each of which may be substituted by one or more radicals R 1<.

[0023] The groups Ar are preferably selected independently of one another from the groups of the following formulas Ar-1 to Ar-75, where R 1< has the meanings given above, the dashed bond represents the bond to HetAr and furthermore: Ar 1< is, on each occurrence, identical or different, a bivalent aromatic or heteroaromatic ring system having 6 to 18 aromatic ring atoms, each of which may be substituted by one or more radicals R 1<; A is, on each occurrence, identical or different, C(R 1<) 2 , NR 1< , O or S; p is 0 or 1, where p = 0 means that the group Ar 1< is not present and that the corresponding aromatic or heteroaromatic group is directly bonded to HetAr; q is 0 or 1, where q = 0 means that no group A is bonded at this position and radicals R 1< are bonded to the corresponding carbon atoms instead.

[0024] If the above-mentioned groups for Ar have multiple A groups, all combinations from the definition of A are possible. Preferred embodiments are then those in which one group A stands for NR 1< and the other group A stands for C(R 1< ) 2 or in which both groups A stand for NR 1< or in which both groups A stand for O.

[0025] When A stands for NR 1<, the substituent R 1< which is bonded to the nitrogen atom preferably stands for an aromatic or heteroaromatic ring system having 5 to 24 aromatic ring atoms, which may also be substituted by one or more radicals R 2<. In a particularly preferred embodiment, this substituent R 1<, identical or different on each occurrence, stands for an aromatic or heteroaromatic ring system having 6 to 24 aromatic ring atoms, in particular having 6 to 18 aromatic ring atoms, which does not have any fused aryl groups and which does not have any fused heteroaryl groups in which two or more aromatic or heteroaromatic 6-ring groups are directly fused to one another, and which may in each case also be substituted by one or more radicals R 2<.Phenyl, biphenyl, terphenyl, and quaterphenyl with linkage patterns as listed above for Ar-1 to Ar-11 are preferred, where these structures may be substituted by one or more R 2< radicals instead of R 1<, but are preferably unsubstituted. Also preferred are triazine, pyrimidine, and quinazoline, as listed above for Ar-47 to Ar-50, Ar-57, and Ar-58, where these structures may be substituted by one or more R 2< radicals instead of R 1<.

[0026] When A stands for C(R 1< ) 2, the substituents R 1< which are bonded to this carbon atom are preferably identical or different on each occurrence and stand for a linear alkyl group having 1 to 10 C atoms or for a branched or cyclic alkyl group having 3 to 10 C atoms or for an aromatic or heteroaromatic ring system having 5 to 24 aromatic ring atoms, which may also be substituted by one or more radicals R 2<. Very particularly preferably, R 1< stands for a methyl group or a phenyl group. The radicals R 1< can also form a ring system with one another, resulting in a spiro system.

[0027] Preferred substituents R and R' that are attached to the backbone of the benzoindenocarbazole are described below.

[0028] In a preferred embodiment of the invention, R is the same or different on each occurrence and is selected from the group consisting of H, D, an aromatic or heteroaromatic ring system having 6 to 30 aromatic ring atoms, which may be substituted by one or more radicals R 1<, or a group N(Ar') 2 . Particularly preferably, R is the same or different on each occurrence and is selected from the group consisting of H or an aromatic or heteroaromatic ring system having 6 to 24 aromatic ring atoms, preferably having 6 to 18 aromatic ring atoms, particularly preferably having 6 to 13 aromatic ring atoms, which may each be substituted by one or more radicals R 1<.

[0029] Suitable aromatic or heteroaromatic ring systems R or Ar' are selected from phenyl, biphenyl, in particular ortho-, meta- or para-biphenyl, terphenyl, in particular ortho-, meta-, para- or branched terphenyl, quaterphenyl, in particular ortho-, meta-, para- or branched quaterphenyl, fluorene, which can be linked via the 1-, 2-, 3- or 4-position, spirobifluorene, which can be linked via the 1-, 2-, 3- or 4-position, naphthalene, in particular 1- or 2-linked naphthalene, indole, benzofuran, benzothiophene, carbazole, which can be linked via the 1-, 2-, 3- or 4-position or which for R can also be linked via the nitrogen atom, dibenzofuran, which can be linked via the 1-, 2-, 3- or 4-position, dibenzothiophene, which can be linked via the 1-, 2-, 3- or 4-position, indenocarbazole, indolocarbazole, pyridine, pyrimidine, pyrazine, pyridazine, triazine, quinoline, isoquinoline, quinazoline, quinoxaline,Phenanthrene or triphenylene, each of which may be substituted by one or more radicals R 1<. Particularly preferred are the structures Ar-1 to Ar-75 listed above.

[0030] Other suitable R groups are groups of the formula -Ar 4< -N(Ar 2< )(Ar 3< ), where Ar 2< , Ar 3< and Ar 4<, identical or different on each occurrence, represent an aromatic or heteroaromatic ring system having 5 to 24 aromatic ring atoms, each of which may be substituted by one or more radicals R 1<. The total number of aromatic ring atoms of Ar 2< , Ar 3< and Ar 4< is a maximum of 60 and preferably a maximum of 40.

[0031] Ar 4< and Ar 2< can be linked to one another and / or Ar 2< and Ar 3< can also be linked to one another by a group selected from C(R 1< ) 2 , NR 1< , O, or S. Preferably, Ar 4< and Ar 2< are linked to one another, or Ar 2< and Ar 3< are linked to one another, in each case ortho to the position of the linkage to the nitrogen atom. In a further embodiment of the invention, none of the groups Ar 2< , Ar 3<, or Ar 4< are linked to one another.

[0032] Preferably, Ar 4< is an aromatic or heteroaromatic ring system having 6 to 24 aromatic ring atoms, preferably having 6 to 12 aromatic ring atoms, each of which may be substituted by one or more R 1< radicals. Ar 4< is particularly preferably selected from the group consisting of ortho-, meta-, or para-phenylene or ortho-, meta-, or para-biphenyl, each of which may be substituted by one or more R 1< radicals, but is preferably unsubstituted. Most preferably, Ar 4< is an unsubstituted phenylene group.

[0033] Preferably, Ar 2< and Ar 3<, identical or different on each occurrence, are an aromatic or heteroaromatic ring system having 6 to 24 aromatic ring atoms, which may each be substituted by one or more radicals R 1<. Particularly preferred groups Ar 2< and Ar 3< are, identically or differently at each occurrence, selected from the group consisting of benzene, ortho-, meta- or para-biphenyl, ortho-, meta-, para- or branched terphenyl, ortho-, meta-, para- or branched quaterphenyl, 1-, 2-, 3- or 4-fluorenyl, 1-, 2-, 3- or 4-spirobifluorenyl, 1- or 2-naphthyl, indole, benzofuran, benzothiophene, 1-, 2-, 3- or 4-carbazole, 1-, 2-, 3- or 4-dibenzofuran, 1-, 2-, 3- or 4-dibenzothiophene, indenocarbazole, indolocarbazole, 2-, 3- or 4-pyridine, 2-, 4- or 5-pyrimidine, Pyrazine, pyridazine, triazine, phenanthrene or triphenylene, each of which may be substituted by one or more radicals R 1<.Very particularly preferably, Ar 2< and Ar 3< are selected, identically or differently on each occurrence, from the group consisting of benzene, biphenyl, in particular ortho-, meta- or para-biphenyl, terphenyl, in particular ortho-, meta-, para- or branched terphenyl, quaterphenyl, in particular ortho-, meta-, para- or branched quaterphenyl, fluorene, in particular 1-, 2-, 3- or 4-fluorene, or spirobifluorene, in particular 1-, 2-, 3- or 4-spirobifluorene.

[0034] In a preferred embodiment of the invention, R' is selected at each occurrence, identically or differently, from the group consisting of a straight-chain alkyl group having 1 to 6 C atoms or a cyclic alkyl group having 3 to 6 C atoms, where the alkyl group may in each case be substituted by one or more radicals R 1<, or an aromatic or heteroaromatic ring system having 6 to 24 aromatic ring atoms, which may in each case be substituted by one or more radicals R 1<; two radicals R' may also form a ring system with one another, thereby forming a spiro system.Particularly preferably, R' is selected, identically or differently at each occurrence, from the group consisting of a straight-chain alkyl group having 1, 2, 3 or 4 C atoms or a branched or cyclic alkyl group having 3 to 6 C atoms, where the alkyl group may in each case be substituted by one or more radicals R 1<, but is preferably unsubstituted, or an aromatic ring system having 6 to 12 aromatic ring atoms, in particular having 6 aromatic ring atoms, which may in each case be substituted by one or more, preferably non-aromatic radicals R 1<, but is preferably unsubstituted; two radicals R' can here form a ring system with one another. If two radicals R' form a ring system with one another, this preferably involves the formation of a fluorene structure.Most preferably, R' is selected at each occurrence, identically or differently, from the group consisting of a straight-chain alkyl group having 1, 2, 3 or 4 C atoms, or a branched alkyl group having 3 to 6 C atoms.

[0035] In a further preferred embodiment of the invention, R 1< is selected, identically or differently on each occurrence, from the group consisting of H, D, F, CN, a straight-chain alkyl group having 1 to 10 C atoms or a branched or cyclic alkyl group having 3 to 10 C atoms, where the alkyl group may in each case be substituted by one or more radicals R 2<, or an aromatic or heteroaromatic ring system having 6 to 24 aromatic ring atoms, which may in each case be substituted by one or more radicals R 2<.In a particularly preferred embodiment of the invention, R 1< is selected, identically or differently on each occurrence, from the group consisting of H, a straight-chain alkyl group having 1 to 6 C atoms, in particular having 1, 2, 3 or 4 C atoms, or a branched or cyclic alkyl group having 3 to 6 C atoms, where the alkyl group may in each case be substituted by one or more radicals R 2<, but is preferably unsubstituted, or an aromatic or heteroaromatic ring system having 6 to 13 aromatic ring atoms, which may in each case be substituted by one or more radicals R 2<, but is preferably unsubstituted.

[0036] In a further preferred embodiment of the invention, R 2< is identical or different on each occurrence and is H, an alkyl group having 1 to 4 C atoms or an aryl group having 6 to 10 C atoms, which may be substituted by an alkyl group having 1 to 4 C atoms, but is preferably unsubstituted.

[0037] In compounds according to the invention that are processed by vacuum evaporation, the alkyl groups preferably have no more than five carbon atoms, more preferably no more than four carbon atoms, and most preferably no more than one carbon atom. For compounds that are processed from solution, compounds substituted by alkyl groups, especially branched alkyl groups, with up to 10 carbon atoms, or substituted by oligoarylene groups, for example ortho-, meta-, para-, or branched terphenyl or quaterphenyl groups, are also suitable.

[0038] Furthermore, it is preferred if the compound does not contain any fused aryl or heteroaryl groups in which more than two six-membered rings are directly fused to one another. Exceptions to this are phenanthrene, triphenylene, and the group (HetAr-3) listed above, which may be preferred due to their high triplet energy despite the presence of fused aromatic six-membered rings.

[0039] The above-mentioned preferred embodiments can be combined with each other as desired within the limitations defined in claim 1. In a particularly preferred embodiment of the invention, the above-mentioned advantages occur simultaneously.

[0040] Examples of preferred compounds according to the embodiments listed above are the compounds listed in the following table.

[0041] The basic structure of the compounds of formula (1) can be prepared according to the methods outlined in the following schemes. The individual synthesis steps, such as Suzuki CC coupling reactions, Hartwig-Buchwald CN coupling reactions, or cyclization reactions, are known in principle to those skilled in the art. Further information on the synthesis of the compounds can be found in the synthesis examples. The synthesis of the basic structure is shown in Scheme 1. This can be achieved by coupling a benzfluorene substituted with a reactive leaving group, for example bromine, with an optionally substituted 2-nitrobenzeneboronic acid, followed by a ring closure reaction. Alternatively, the coupling can be carried out with the amino group of an optionally substituted 2-aminochlorobenzene, followed by a ring closure reaction. Scheme 2 shows the introduction of the HetAr group at the nitrogen atom of the basic structure.A HetAr group substituted with a suitable leaving group, for example chlorine, can be introduced in a nucleophilic aromatic substitution or in a palladium-catalyzed coupling reaction.

[0042] To produce the organic electroluminescent device, the compounds of formula (1) can also be processed together with the phosphorescent compound from the liquid phase, for example, by spin coating or printing. This requires formulations of the compounds, for example, solutions, dispersions, or emulsions. It may be preferable to use mixtures of two or more solvents for this purpose. Suitable and preferred solvents are, for example, toluene, anisole, o-, m- or p-xylene, methyl benzoate, mesitylene, tetralin, veratrole, THF, methyl-THF, THP, chlorobenzene, dioxane, phenoxytoluene, in particular 3-phenoxytoluene, (-)-fenchone, 1,2,3,5-tetramethylbenzene, 1,2,4,5-tetramethylbenzene, 1-methylnaphthalene, 2-methylbenzothiazole, 2-phenoxyethanol, 2-pyrrolidinone, 3-methylanisole, 4-methylanisole, 3,4-dimethylanisole, 3,5-dimethylanisole, acetophenone, α-terpineol, benzothiazole, butylbenzoate, cumene, cyclohexanol, cyclohexanone,Cyclohexylbenzol, Decalin, Dodecylbenzol, Ethylbenzoat, Indan, NMP, p-Cymol, Phenetol, 1,4-Diisopropylbenzol, Dibenzylether, Diethylenglycolbutylmethylether, Triethylenglycolbutylmethylether, Diethylenglycoldibutylether, Triethylenglycoldimethylether, Diethylenglycolmonobutylether, Tripropyleneglycoldimethylether, Tetraethylenglycoldimethylether, 2-Isopropylnaphthalin, Pentylbenzol, Hexylbenzol, Heptylbenzol, Octylbenzol, 1,1-Bis(3,4-dimethylphenyl)ethan, 2-Methylbiphenyl, 3-Methylbiphenyl, 1-Methylnaphthalin, 1-Ethylnaphthalin, Ethyloctanoat, Sebacinsäure-diethylester, Octyloctanoat, Heptylbenzol, Menthyl-isovalerat, Cyclohexylhexanoat oder Mischungen dieser Lösemittel.,

[0043] The present invention therefore further provides a formulation or composition comprising at least one compound according to formula (1), at least one phosphorescent compound, and at least one solvent, in particular one of the above-mentioned solvents or a mixture of these solvents. The formulation may also contain further organic or inorganic compounds, for example one or more further matrix materials. Suitable phosphorescent compounds and further matrix materials are described in more detail below.

[0044] A further object of the present invention is the use of a formulation according to the invention for producing an organic electroluminescent device.

[0045] The organic electroluminescent device according to the invention contains, as defined above, a cathode, an anode, and at least one emitting layer containing at least one phosphorescent compound and at least one compound according to formula (1). In addition to these layers, it may contain further layers, for example one or more hole-injection layers, hole-transport layers, hole-blocking layers, electron-transport layers, electron-injection layers, exciton-blocking layers, electron-blocking layers, and / or charge-generation layers. Interlayers, which, for example, have an exciton-blocking function, may also be introduced between two emitting layers. It should be noted, however, that not every one of these layers necessarily needs to be present.The organic electroluminescent device can contain one emitting layer or it can contain multiple emitting layers. If multiple emitting layers are present, these preferably have a total of multiple emission maxima between 380 nm and 750 nm, resulting in overall white emission. This means that different emitting compounds that can fluoresce or phosphoresce are used in the emitting layers. Systems with three emitting layers are particularly preferred, with the three layers exhibiting blue, green, and orange or red emission. The organic electroluminescent device according to the invention can also be a tandem OLED, in particular for white-emitting OLEDs.

[0046] The electroluminescent device according to the invention preferably contains, as phosphorescent compound, a red, orange or yellow phosphorescent compound, in particular a red phosphorescent compound.

[0047] For the purposes of this invention, phosphorescence refers to luminescence from an excited state with higher spin multiplicity, i.e., a spin state > 1, in particular from an excited triplet state. For the purposes of this application, all luminescent complexes with transition metals or lanthanides, in particular all iridium, platinum, and copper complexes, are considered phosphorescent compounds.

[0048] The mixture of the compound of formula (1) and the phosphorescent compound in the emitting layer of the electroluminescent device contains between 99 and 1 vol.%, preferably between 98 and 10 vol.%, particularly preferably between 97 and 60 vol.%, in particular between 95 and 80 vol.% of the compound of formula (1), based on the total mixture of phosphorescent compound and compound of formula (1). Accordingly, the mixture contains between 1 and 99 vol.%, preferably between 2 and 90 vol.%, particularly preferably between 3 and 40 vol.%, in particular between 5 and 20 vol.% of the phosphorescent compound, based on the total mixture of phosphorescent compound and compound of formula (1). If the electroluminescent device is produced from solution, the same preferred proportions apply, with the corresponding wt.% being used as preferred proportions instead of vol.%.

[0049] In one embodiment of the invention, the compound of formula (1) is used as the sole matrix material ("single host") for the phosphorescent compound, i.e., the emitting layer of the OLED contains only the compound of formula (1) and the phosphorescent compound, but no other compounds. This represents a significant advantage over electroluminescent devices that contain two or more matrix materials in the emitting layer, since such electroluminescent devices can be manufactured significantly more easily than those that contain mixtures of several matrix materials. Surprisingly, it has been found that compounds of formula (1) in particular lead to very good results when these materials are used as the sole matrix material for phosphorescent compounds.It is therefore a preferred embodiment of the invention that the emitting layer consists of exactly one compound of formula (1) and one or more phosphorescent compounds, preferably exactly one phosphorescent compound.

[0050] In a further embodiment of the invention, the emitting layer contains, in addition to the compound of formula (1) and the phosphorescent compound, at least one further matrix material. Suitable matrix materials that can be used in combination with a compound of formula (1) are aromatic ketones, aromatic phosphine oxides or aromatic sulfoxides or sulfones, e.g., according to WO 2004 / 013080, WO 2004 / 093207, WO 2006 / 005627, or WO 2010 / 006680, triarylamines, carbazole derivatives, e.g., B. CBP (N,N-bis-carbazolylbiphenyl) or those in WO 2005 / 039246, US 2005 / 0069729, JP 2004 / 288381, EP 1205527, WO 2008 / 086851 or WO 2013 / 041176, indolocarbazole derivatives, e.g. according to WO 2007 / 063754 or WO 2008 / 056746, indenocarbazole derivatives, e.g. according to WO 2010 / 136109, WO 2011 / 000455, WO 2013 / 041176 or WO 2013 / 056776, azacarbazole derivatives, e.g. according to EP 1617710, EP 1617711, EP 1731584, JP 2005 / 347160, bipolar matrix materials, e.g. according to WO 2007 / 137725, silanes, e.g.according to WO 2005 / 111172, azaboroles or boronate esters, e.g. according to WO 2006 / 117052, triazine derivatives, e.g. according to WO 2007 / 063754, WO 2008 / 056746, WO 2010 / 015306, WO 2011 / 057706, WO 2011 / 060859 or WO 2011 / 060877, zinc complexes, e.g. according to EP 652273 or WO 2009 / 062578, diazasilole or tetraazasilole derivatives, e.g. according to WO 2010 / 054729, diazaphosphole derivatives, e.g. according to WO 2010 / 054730, bridged carbazole derivatives, e.g. B. according to WO 2011 / 042107, WO 2011 / 060867, WO 2011 / 088877 and WO 2012 / 143080, triphenylene derivatives, e.g. B. according to WO 2012 / 048781, dibenzofuran derivatives, e.g. B. according to WO 2015 / 169412, WO 2016 / 015810, WO 2016 / 023608, WO 2017 / 148564 or WO 2017 / 148565 or biscarbazoles, e.g. B. according to JP 3139321 B2.

[0051] Likewise, another phosphorescent compound that emits at a shorter wavelength than the actual emitter can be present as a co-host in the emitting layer. Particularly good results are achieved when a red-phosphorescent compound is used as the emitter and a yellow-phosphorescent compound is used as the co-host in combination with the compound according to formula (1).

[0052] Furthermore, a compound that does not participate, or does not participate significantly, in charge transport can be used as a co-host, as described, for example, in WO 2010 / 108579. In particular, compounds that have a large band gap and that themselves do not participate, or at least do not participate significantly, in the charge transport of the emitting layer are suitable as co-matrix materials in combination with the compound according to formula (1). Such materials are preferably pure hydrocarbons. Examples of such materials can be found, for example, in WO 2009 / 124627 or WO 2010 / 006680.

[0053] Particularly preferred co-host materials which can be used in combination with the compounds according to formula (1) are biscarbazole or indenocarbazole derivatives according to one of the formulas (6), (7) or (8), where Ar and A have the meanings given above and R has the meanings given above, but R radicals here can also form an aromatic or heteroaromatic ring system with one another. In a preferred embodiment of the invention, A is C(R') 2 .

[0054] Preferred embodiments of the compounds of formulas (6), (7) and (8) are the compounds of the following formulas (6a), (7a) and (8a), where the symbols used have the meanings given above.

[0055] Examples of suitable compounds according to formula (6) are the compounds shown below. Struktur CAS Number Struktur CAS Number CAS-1454567-05-5 CAS-1352040-89-1 CAS-1336889-25-8 CAS-1800544-05-1 CAS-1800544-08-4 CAS-1800544-08-4 CAS-1800544-09-5 CAS-1800544-10-8 CAS-1800544-11-9 CAS-1800544-04-0 CAS-1842320-52-8 CAS-1842320-53-9 CAS-1842320-54-0 CAS-1842320-55-1 CAS-1842320-56-2 CAS-1842320-57-3 CAS-1410876-33-3 CAS-1842320-58-4 CAS-1410876-47-9 CAS-1842320-59-5 CAS-1848256-38-1 CAS-1865661-14-8 CAS-1870867-25-6 CAS-1884707-32-7 CAS-1889262-88-7 CAS-2018307-89-4 CAS-1454655-29-8 CAS-1454655-33-4 CAS-1454660-22-0 CAS-1907663-27-7 CAS-1548581-24-3 CAS-1548581-27-6 CAS-1548581-29-8 CAS-1548581-37-8 CAS-1548581-40-3 CAS-1943719-62-7 CAS-1548581-42-5 CAS-1942079-50-6 CAS-1548581-44-7 CAS-1942079-51-7 CAS-1943719-63-8 CAS-1955476-12-6 CAS-1619966-75-4 CAS-1955476-13-7 CAS-1955476-15-9 CAS-1955476-28-4 CAS-1955476-30-8 CAS-1955476-32-0 CAS-1643479-47-3 CAS-1973498-04-2 CAS-1643479-49-5 CAS-1973498-03-1 CAS-1973498-05-3 CAS-2018307-36-1 CAS-1643479-56-4 CAS-2018307-35-0 CAS-2018307-37-2 CAS-2018307-38-3 CAS-2018307-39-4 CAS-2018307-77-0 CAS-2018307-78-1 CAS-2018307-90-7 CAS-2018307-91-8 CAS-1799958-74-9 CAS-2052160-86-6 CAS-1799958-79-4 CAS-1799958-76-1 CAS-2052160-91-3 CAS-1799958-77-2 CAS-2055848-40-1 CAS-1799958-78-3 CAS-2057418-19-4 CAS-1799958-99-8 CAS-1799959-01-5 CAS-1799959-03-7 CAS-1799959-05-9 CAS-1799959-07-1 CAS-1799959-09-3 CAS-1799959-11-7 CAS-1799959-13-9 CAS-2085318-61-0 CAS-2085318-62-1 CAS-2085318-64-3 CAS-2085318-63-2 CAS-2085318-66-5 CAS-2085318-65-4 CAS-2085318-77-8 CAS-2085318-78-9 CAS-2085318-79-0 CAS-57102-51-9 CAS-2085318-81-4 CAS-2085318-80-3 CAS-2085318-83-6 CAS-2085318-82-5 CAS-2085318-88-1 CAS-2085318-87-0 CAS-2085318-92-7 CAS-2085318-89-2 CAS-2085318-94-9 CAS-2085318-93-8 CAS-2085318-98-3 CAS-2085318-97-2 CAS-2085319-00-0 CAS-2085318-99-4 CAS-251316-80-0 CAS- 2085319-17-9 CAS-1427160-09-5 CAS-1643479-72-4 CAS-1799959-65-1 CAS-1799959-74-2 CAS-1799959-75-3 CAS-1799960-24-9 CAS-1799960-25-0 CAS-1340668-17-8 CAS-1340668-19-0 CAS-1289556-24-6 CAS-1799960-56-7 CAS-1336889-27-0 CAS-1799960-58-9 CAS-1340668-17-8 CAS-1340668-19-0 CAS-1812208-18-6 CAS-1340668-35-0 CAS-1340668-37-2 CAS-1830334-82-1 CAS-1340669-19-3 CAS-1830334-85-4 CAS-1830334-94-5 CAS-1830334-88-7 CAS-1340669-32-0 CAS-1830334-90-1 CAS-1340669-33-1 CAS-1830334-91-2 CAS-1830335-02-8 CAS-1830334-97-8 CAS-1830335-71-1 CAS-1830335-07-3 CAS-1830335-76-6 CAS-1830335-72-2 CAS-1354054-11-7 CAS-1830335-85-7 CAS-1830335-82-4 CAS-1830335-79-9 CAS-1830339-40-6 CAS-1830335-95-9 CAS-1377150-35-0 CAS-1830339-41-7 CAS-1830335-90-4 CAS-1830335-87-9 CAS-1399855-37-8 CAS-1830339-42-8 CAS-1399855-38-9 CAS-1399855-39-0 CAS-1399855-46-9 CAS-1399855-47-0 CAS-1413936-92-1 CAS-1413936-95-4 CAS-1413936-96-5 CAS-1413936-97-6 CAS-1413937-08-2 CAS-1890157-92-2 CAS-1415348-93-4 CAS-1889262-89-8 CAS-1415348-99-0 CAS-1890156-90-7 CAS-1415349-00-6 CAS-1890156-91-8 CAS-1415349-01-7 CAS-1890157-12-6 CAS-1415349-02-8 CAS-1890157-13-7 CAS-1415349-03-9 CAS-1890157-14-8 CAS-1415349-04-0 CAS-1890157-37-5 CAS-1415349-05-1 CAS-1415349-06-2 CAS-1415349-07-3 CAS-1890157-41-1 CAS-1415422-76-2 CAS-1890157-42-2 CAS-1422451-46-4 CAS-1890157-43-3 CAS-1422451-48-6 CAS-1890157-64-8 CAS-1445952-53-3 CAS-1445952-58-8 CAS-1450933-86-4 CAS-1894194-07-0 CAS-1894194-09-2 CAS-1894194-08-1 CAS-1919031-93-8 CAS-1919031-92-7 CAS-1919031-95-0 CAS-1919031-94-9 CAS-1919031-97-2 CAS-1919031-96-1 CAS-1919031-99-4 CAS-1919031-98-3 CAS-1598389-98-0 CAS-1919032-02-2 CAS-1604034-14-1 CAS-1943719-67-2 CAS-1604034-02-7 CAS-1943719-70-7 CAS-1604034-07-2 CAS-1943719-71-8 CAS-1604034-12-9 CAS-1943719-72-9 CAS-1622931-00-3 CAS-1604034-15-2 CAS-1622931-01-4 CAS-1622931-04-7 CAS-1630029-28-5 CAS-1630029-29-6 CAS-1643479-51-9 CAS-1643479-52-0 CAS-1643479-54-2 CAS-1643479-59-7 CAS-1643479-62-2 CAS-1643479-68-8 CAS-1643479-69-9 CAS-1643479-74-6 CAS-1643479-72-4 CAS-2018307-43-0 CAS-1643479-75-7 CAS-2018307-47-4 CAS-2018307-50-9 CAS- 2018307-49-6 CAS-1656982-30-7 CAS-1680184-58-0 CAS-1704071-12-4 CAS-1799483-56-9 CAS-1799519-35-9 CAS-1799678-37-7 CAS-2073116-97-7 CAS-2048236-10-6 CAS-1799959-20-8 CAS-1704071-30-6 CAS-1799959-21-9 CAS-1799959-22-0 CAS-1799959-23-1 CAS-1799959-24-2 CAS-1799959-25-3 CAS-1799959-26-4 CAS-1799959-27-5 CAS-1799959-28-6 CAS-1799959-29-7 CAS-1799959-30-0 CAS-1799959-31-1 CAS-1799959-32-2 CAS-1799959-33-3 CAS-1799959-34-4 CAS-1799959-35-5 CAS-1799959-60-6 CAS-1799959-61-7 CAS-1799959-62-8 CAS-1799959-63-9 CAS-1799959-64-0 CAS-1799959-66-2 CAS-1799959-67-3 CAS-1799959-68-4 CAS-1799959-69-5 CAS-1799959-70-8 CAS-1799959-71-9 CAS-1799959-72-0 CAS-1799959-73-1 CAS-1428635-33-9 CAS-1890157-93-3 CAS-1428635-40-8 CAS-1890157-94-4 CAS-1431151-34-6 CAS-1890157-95-5 CAS-1894193-99-7 CAS-1894193-97-5 CAS-1446411-07-9 CAS-1894194-03-6 CAS-1894194-10-5 CAS-1894194-11-6 CAS-1894194-16-1 CAS-1894194-12-7 CAS-1497337-43-5 CAS-1499917-70-2 CAS-1588866-10-7 CAS-1934252-94-4 CAS-1598389-99-1 CAS-1943719-77-4 CAS-1613752-14-9 CAS- 1943719-78-5 CAS-2018307-45-2 CAS-2018307-44-1 CAS-1643479-80-4 CAS-1643479-84-8 CAS-1643479-88-2 CAS-2018307-52-1 CAS-1643480-02-7 CAS-2018307-51-0 CAS-2018307-53-2 CAS-2018307-54-3 CAS-1656982-32-9 CAS-2018307-80-5 CAS-2018307-79-2 CAS- 1799483-31-0 CAS-1704071-33-9 CAS-1792238-01-7 CAS-1799483-43-4 CAS-2020391-63-1 CAS-1799483-44-5 CAS-2020391-71-1 CAS-2020391-73-3 CAS-2020391-72-2 CAS-2020391-75-5 CAS-2020391-74-4 CAS-2079874-13-6 CAS-2075738-96-2 CAS-2075738-98-4 CAS-2075738-97-3 CAS-2075738-99-5 CAS-2075739-04-5 CAS-2075739-05-6 CAS-2075739-06-7 CAS-2075739-07-8

[0056] Other suitable compounds that can be used as co-host together with the compounds of formula (1) are the compounds of the following formula (9), where Ar, identically or differently on each occurrence, has the meanings given above. It is preferred if at least one Ar group represents a 4-fluorenyl group, 4-spirobifluorenyl group, 1-dibenzofuranyl group, or 1-dibenzothienyl group, each of which may optionally be substituted by one or more radicals R. Examples of suitable Ar groups in the compound of formula (9) are the groups of the formulas Ar-1 to Ar-75 shown above.

[0057] Particularly suitable phosphorescent compounds (= triplet emitters) are compounds that emit light upon suitable excitation, preferably in the visible range, and also contain at least one atom with an atomic number greater than 20, preferably greater than 38 and less than 84, particularly preferably greater than 56 and less than 80, in particular a metal with this atomic number. Compounds containing copper, molybdenum, tungsten, rhenium, ruthenium, osmium, rhodium, iridium, palladium, platinum, silver, gold, or europium are preferably used as phosphorescent emitters, in particular compounds containing iridium or platinum.

[0058] Examples of phosphorescent compounds can be found in the applications WO 00 / 70655, WO 2001 / 41512, WO 2002 / 02714, WO 2002 / 15645, EP 1191613, EP 1191612, EP 1191614, WO 05 / 033244, WO 05 / 019373, US 2005 / 0258742, WO 2009 / 146770, WO 2010 / 015307, WO 2010 / 031485, WO 2010 / 054731, WO 2010 / 054728, WO 2010 / 086089, WO 2010 / 099852, WO 2010 / 102709, WO 2011 / 032626, WO 2011 / 066898, WO 2011 / 157339, WO 2012 / 007086, WO 2014 / 008982, WO 2014 / 023377, WO 2014 / 094961, WO 2014 / 094960, WO 2015 / 036074, WO 2015 / 104045, WO 2015 / 117718, WO 2016 / 015815, WO 2016 / 124304, WO 2017 / 032439, WO 2018 / 011186 and WO 2018 / 041769. In general, all phosphorescent complexes as used according to the prior art for phosphorescent OLEDs and as known to the person skilled in the art in the field of organic electroluminescence are suitable, and the person skilled in the art can use further phosphorescent complexes without inventive step.

[0059] Examples of phosphorescent dopants are listed below.

[0060] In a further embodiment of the invention, the organic electroluminescent device is a device as described, for example, in WO 98 / 24271, US 2011 / 0248247, and US 2012 / 0223633. In these multicolor display components, an additional blue emission layer is vapor-deposited over the entire surface of all pixels, even those with a color other than blue.

[0061] In a further embodiment of the invention, the organic electroluminescent device according to the invention does not contain a separate hole-injection layer and / or hole-transport layer and / or hole-blocking layer and / or electron-transport layer, i.e., the emitting layer directly adjoins the hole-injection layer or the anode, and / or the emitting layer directly adjoins the electron-transport layer or the electron-injection layer or the cathode, as described, for example, in WO 2005 / 053051. Furthermore, it is possible to use a metal complex that is the same as or similar to the metal complex in the emitting layer as a hole-transport or hole-injection material directly adjacent to the emitting layer, as described, for example, in WO 2009 / 030981.

[0062] In the further layers of the organic electroluminescent device according to the invention, all materials commonly used in the prior art can be used. Therefore, the person skilled in the art can, without inventive effort, use all materials known for organic electroluminescent devices in combination with the compounds according to formula (1) or the preferred embodiments described above.

[0063] Also preferred is an organic electroluminescent device characterized in that one or more layers are coated using a sublimation process. The materials are vapor-deposited in vacuum sublimation systems at an initial pressure of less than 10 -5 mbar, preferably less than 10 -6 mbar. However, it is also possible for the initial pressure to be even lower, for example, less than 10 -7 mbar.

[0064] Also preferred is an organic electroluminescent device, characterized in that one or more layers are coated using the OVPD (Organic Vapor Phase Deposition) process or by means of carrier gas sublimation. The materials are applied at a pressure between 10 -5 mbar and 1 bar. A special case of this process is the OVJP (Organic Vapor Jet Printing) process, in which the materials are applied directly through a nozzle and thus patterned.

[0065] Also preferred is an organic electroluminescent device characterized in that one or more layers are produced from solution, such as by spin coating, or by any printing process, such as screen printing, flexographic printing, offset printing, LITI (Light Induced Thermal Imaging, thermal transfer printing), inkjet printing, or nozzle printing. Soluble compounds are required for this, which are obtained, for example, by suitable substitution.

[0066] Furthermore, hybrid processes are possible, in which, for example, one or more layers are applied from solution and one or more further layers are vapor-deposited.

[0067] These processes are generally known to the person skilled in the art and can be applied by him without inventive step to organic electroluminescent devices containing the compounds according to the invention.

[0068] The OLEDs according to the invention exhibit a very good lifetime, particularly an improved lifetime compared to similar compounds that, however, have an indenocarbazole framework instead of the benzidenocarbazole framework. The other electronic properties of the OLED, such as efficiency or operating voltage, remain at least equally good. This is especially true when the compounds of formula (1) are used as the sole host material ("single host") and not in a mixture with one or more other host materials. This is a surprising result, since similar compounds lead to poorer results when used as the sole host material than when used as a mixed host. The possibility of using the compound of formula (1) as the sole host material without deteriorating the device results represents a significant advantage in OLED production.

[0069] The invention is further illustrated by the following examples, without intending to limit it. From these descriptions, one skilled in the art can implement the invention within the entire scope of the disclosure and produce further devices according to the invention without inventive step. Examples:

[0070] Unless otherwise stated, the following syntheses are carried out under a protective gas atmosphere in dried solvents. Solvents and reagents are available from ALDRICH or ABCR. The numbers given for non-commercially available starting materials are the corresponding CAS numbers. a) (2-Chlorophenyl)-(11,11-dimethyl-11H-benzo[a]fluoren-9-yl)amine

[0071]

[0072] 47 g (145 mmol) of 9-bromo-11,11-dimethyl-11H-benzo[a]fluorene, 16.8 g (159 mmol) of 2-chloroaniline, 41.9 g (436.2 mmol) of sodium tert-butoxide, and 1.06 g (1.45 mmol) of Pd(dppf)Cl2 were dissolved in 500 mL of toluene and stirred under reflux for 5 h. The reaction mixture was cooled to room temperature, diluted with toluene, and filtered through Celite. The filtrate was concentrated in vacuo, and the residue was crystallized from toluene / heptane. The product was isolated as a colorless solid. Yield: 33 g (89 mmol), 70% of theory.

[0073] The following connections can be made analogously: Educt 1 Educt 2 product yield 1a [1804905-31-4 ] 79% 2a [1800333-59-8 ] 77% 3a [1263204-40-5 ] 78% 1d [1198396-39-2 ] 79% 4a 74% 1f [1198396-29-0 ] 81% 5a [1198396-35-8 ] 78% 6a [1674335-13-7 ] 77% b) Cyclization

[0074]

[0075] 48 g (129 mmol) of (2-chlorophenyl)-(11,11-dimethyl-11H-benzo[a]fluoren-9-yl)-amine, 53 g (389 mmol) of potassium carbonate, 4.5 g (12 mmol) of tricyclohexylphosphine tetrafluoroborate, 1.38 g (6 mmol) of palladium(II) acetate, and 3.3 g (32 mmol) of pivalic acid were suspended in 500 mL of dimethylacetamide and stirred under reflux for 6 h. After cooling, the reaction mixture was added with 300 mL of water and 400 mL of dichloromethane. The mixture was stirred for 30 min., the organic phase was separated, filtered through a short bed of Celite, and the solvent was removed in vacuo. The crude product was extracted hot with toluene and recrystallized from toluene. The product was isolated as a beige solid. Yield: 34 g (102 mmol), 78% of theory.

[0076] The following connections can be made analogously: reactant product yield 1b 79% 2b 77% 3b 78% 4b 75% 5b 78% 6b 73% 7b 71% 8b 76% c) 11,11-Dimethyl-3-(2-nitrophenyl)-11H-benzo[b]fluorene

[0077]

[0078] A well-stirred, degassed suspension of 59 g (183.8 mmol) of 2-nitrobenzeneboronic acid, 54 g (184 mmol) of 3-bromo-11,11-dimethyl-11H-benzo-[b]fluorene, and 66.5 g (212.7 mmol) of potassium carbonate in a mixture of 250 mL of water and 250 mL of THF is treated with 1.7 g (1.49 mmol) of Pd(PPh 3 ) 4 and heated under reflux for 17 h. After cooling, the organic phase is separated, washed three times with 200 mL of water and once with 200 mL of saturated aqueous sodium chloride solution, dried over magnesium sulfate, and evaporated to dryness using a rotary evaporator. The gray residue is recrystallized from hexane. The precipitated crystals are filtered off with suction, washed with a little MeOH, and dried in vacuo. Yield: 53 g (146 mmol), 80% of theory.

[0079] The following connections can be made analogously: Educt 1 Educt 2 product yield 1c [1927921-26-3 ] 74% 2c [1674335-13-7 ] 77% d) Carbazole synthesis

[0080]

[0081] A mixture of 87 g (240 mmol) of 11,11-dimethyl-3-(2-nitrophenyl)-11H-benzo[b]fluorene and 290.3 mL (1669 mmol) of triethyl phosphite was heated under reflux for 12 h. The remaining triethyl phosphite was then distilled off (72-76 °C / 9 mm Hg). The residue was treated with water / MeOH (1:1), and the solid was filtered off and recrystallized. Yield: 58 g (176 mmol), 74% of theory.

[0082] The following connections can be made analogously: reactant product yield 1d 79% 2d 76% e) Nucleophilic substitution

[0083]

[0084] 4.2 g (106 mmol) of NaH (60% in mineral oil) were dissolved in 300 mL of dimethylformamide under a protective atmosphere. 35 g (106 mmol) of 7,9-dihydro-7,7-dimethylbenz[6,7]indeno[2,1-b]carbazole were dissolved in 250 mL of DMF and added dropwise to the reaction mixture. After 1 h at room temperature, a solution of 2-chloro-4,6-diphenyl[1,3,5]triazine (34.5 g, 0.122 mol) in 200 mL of THF was added dropwise. The reaction mixture was stirred for 12 h at room temperature and then poured onto ice. The precipitated solid was warmed to room temperature, filtered, and washed with ethanol and heptane. The residue is extracted with hot toluene, recrystallized from toluene / n-heptane, and finally sublimed under high vacuum. The purity is 99.9%. Yield: 39 g (69 mmol), 66% of theory.

[0085] The following connections can be made analogously: Educt 1 Educt 2 product yield 1e [213765-59-7] [3842-55-5] 60% 2e [2102515-67-1] 1384480-21-0 61% 3e [2102515-67-1] 92853-85-5 57% 4e [213765-59-7] 1260393-65-4 60% 6e [2102515-67-1] [1616499-38-7] 72% 7e [213765-59-7] [1403252-58-3] 74% 8e [213765-59-7] [1373265-66-7] 62% 9e [2102515-67-1] [1373317-91-9] 67% 10e [213765-59-7] [14003252-55-0] 61% 12e [2102515-67-1] [29874-83-7] 67% 13e [2102515-67-1] [6484-25-9] 62% 15e [213765-59-7] [29874-83-7] 63% 16e [1292317-90-8] 60% 17e [213765-59-7] [900463-54-9 ] 61% 18e [3842-55-5] 71% f) Bromination

[0086]

[0087] 129 g (230 mmol) of compound 1e is initially charged in 1000 mL of THF. A solution of 41.7 g (234.6 mmol) of NBS in 500 mL of THF is then added dropwise at -15 °C under exclusion of light, allowed to warm to RT, and stirred for a further 4 h at this temperature. The mixture is then treated with 150 mL of water and extracted with CH 2 Cl 2 . The organic phase is dried over MgSO 4 , and the solvents are removed in vacuo. The product is extracted by stirring with hot hexane and filtered off with suction. Yield: 78.3 g (121 mmol), 53% of theory; purity according to 1< H NMR: approximately 97%.

[0088] The following connections can be made analogously: reactant product yield 1f 56% 2f 61% g) Suzuki reaction

[0089]

[0090] 25.8 g (42.12 mmol) of compound 1f, 13.4 g (47 mmol) of 9-phenylcarbazole-3-boronic acid, and 29.2 g of Rb 2 CO 3 were suspended in 250 mL of p-xylene. 0.95 g (4.2 mmol) of Pd(OAc) 2 and 12.6 mL of a 1M tri-tert-butylphosphine solution in toluene were added to this suspension. The reaction mixture was heated under reflux for 16 h. After cooling, the organic phase was separated, washed three times with 200 mL of water, and then evaporated to dryness. The residue was extracted hot with toluene, recrystallized from toluene, and finally sublimed under high vacuum. The purity was 99.9%. Yield: 24 g (31 mmol), 70% of theory.

[0091] The following connections can be made analogously: Educt 1 Educt 2 product yield 1g [1493715-37-9 ] 60% 2g [1133057-97-2 ] 61% Production of OLEDs

[0092] The following examples E1 to E9 (see Table 1) present the use of the material according to the invention in OLEDs.

[0093] Pretreatment for examples E1-E9: Glass plates coated with 50 nm of structured ITO (indium tin oxide) are treated with an oxygen plasma followed by an argon plasma before coating. These plasma-treated glass plates form the substrates onto which the OLEDs are applied.

[0094] OLEDs generally have the following layer structure: substrate / hole injection layer (HIL) / hole transport layer (HTL) / electron blocking layer (EBL) / emission layer (EML) / optional hole blocking layer (HBL) / electron transport layer (ETL) / optional electron injection layer (EIL), and finally a cathode. The cathode is formed by a 100 nm thick aluminum layer. The exact structure of the OLEDs can be found in Table 1. The materials required for OLED production are shown in Table 2. The OLED data is listed in Table 3.

[0095] All materials are thermally evaporated in a vacuum chamber. The emission layer always consists of at least one matrix material (host material) and one emitting dopant (emitter), which is co-evaporated into the matrix material(s) in a specific volume fraction. A specification such as EG1:IC2:TER5 (55%:35%:10%) means that the EG1 material is present in the layer at a volume fraction of 55%, IC2 at a volume fraction of 35%, and TER5 at a volume fraction of 10%. Similarly, the electron-transport layer can also consist of a mixture of two materials.

[0096] OLEDs are characterized as standard. For this purpose, the electroluminescence spectra, the current efficiency (SE, measured in cd / A), and the external quantum efficiency (EQE, measured in %) are determined as a function of luminance, calculated from current-voltage-luminance curves assuming a Lambertian radiation pattern, as well as the lifetime. The electroluminescence spectra are determined at a luminance of 1000 cd / m², and the CIE 1931 x and y color coordinates are calculated from them. The value U1000 in Table 3 refers to the voltage required for a luminance of 1000 cd / m². SE1000 and EQE1000 refer to the current efficiency and the external quantum efficiency, respectively, achieved at 1000 cd / m². The lifetime LD is defined as the time after which the luminance drops from the starting luminance to a certain fraction L1 when operating at a constant current density j 0.A value of L1=95% in Table 3 means that the lifetime specified in column LD corresponds to the time after which the luminance drops to 95% of its initial value. Use of the compounds of formula (1) as matrix material in OLEDs

[0097] Typically, a mixture of two host materials (matrix materials) is used in the emission layer of OLEDs to achieve optimal charge balance and thus excellent OLED performance. To simplify OLED manufacturing, reducing the number of different materials used is desirable. Therefore, using only one host material in the emission layer instead of a mixture of two host materials is advantageous.

[0098] By using the compounds EG1-EG4, EG6, and EG7 according to the invention in Examples E1-E4, E6-E9 as matrix material in the emission layer of phosphorescent red OLEDs, it can be demonstrated that their use as a single material delivers at least as good or even improved OLED performance compared to a mixture with a second host material IC2 (E2 and E4). This represents a clear advantage from a production-technical perspective. Example E5 is a reference example that is not part of the present invention. Table 1: Structure of the OLEDs e.g. HIL thickness HTL thickness EBL thickness EML thickness HBL thickness ETL thickness EIL thickness E1 HATCN SpMA1 SpMA3 EG1:TER ST2 ST2:LiQ (50%:50%) LiQ 5nm 125nm 10nm (97%:3%) 35nm 10nm 30nm 1nm E2 HATCN SpMA1 SpMA3 EG1:IC2:TER ST2 ST2:LiQ (50%:50%) LiQ 5nm 125nm 10nm (72%:25%:3%) 35nm 10nm 30nm 1nm E3 HATCN SpMA1 <h2 style=";text-align:left;direction:ltr">SpMA3 <h2 style=";text-align:left;direction:ltr"> EG2:TER <h2 style=";text-align:left;direction:ltr"> ST2 <h2 style=";text-align:left;direction:ltr"> ST2:LiQ (50%:50%) <h2 style=";text-align:left;direction:ltr"> LiQ <h2 style=";text-align:left;direction:ltr"> 5nm <h2 style=";text-align:left;direction:ltr"> 125nm <h2 style=";text-align:left;direction:ltr"> 10nm <h2 style=";text-align:left;direction:ltr"> (97%:3%) 35nm <h2 style=";text-align:left;direction:ltr"> 10nm <h2 style=";text-align:left;direction:ltr"> 30nm <h2 style=";text-align:left;direction:ltr"> 1nm E4 <h2 style=";text-align:left;direction:ltr"> HATCN <h2 style=";text-align:left;direction:ltr"> SpMA1 <h2 style=";text-align:left;direction:ltr"> SpMA3 <h2 style=";text-align:left;direction:ltr"> EG2:IC2:TER <h2 style=";text-align:left;direction:ltr"> ST2 <h2 style=";text-align:left;direction:ltr"> ST2:LiQ (50%:50%) <h2 style=";text-align:left;direction:ltr"> LiQ <h2 style=";text-align:left;direction:ltr"> 5nm <h2 style=";text-align:left;direction:ltr"> 125nm <h2 style=";text-align:left;direction:ltr"> 10nm <h2 style=";text-align:left;direction:ltr"> (32%:65%:3%) 35nm <h2 style=";text-align:left;direction:ltr"> 10nm <h2 style=";text-align:left;direction:ltr"> 30nm <h2 style=";text-align:left;direction:ltr"> 1nm E5 <h2 style=";text-align:left;direction:ltr"> HATCN <h2 style=";text-align:left;direction:ltr"> SpMA1 <h2 style=";text-align:left;direction:ltr"> SpMA3 <h2 style=";text-align:left;direction:ltr"> EG3:TER <h2 style=";text-align:left;direction:ltr"> ST2 <h2 style=";text-align:left;direction:ltr"> ST2:LiQ (50%:50%) <h2 style=";text-align:left;direction:ltr"> LiQ <h2 style=";text-align:left;direction:ltr"> 5nm <h2 style=";text-align:left;direction:ltr"> 125nm <h2 style=";text-align:left;direction:ltr"> 10nm <h2 style=";text-align:left;direction:ltr"> (97%:3%) 35nm <h2 style=";text-align:left;direction:ltr"> 10nm <h2 style=";text-align:left;direction:ltr"> 30nm <h2 style=";text-align:left;direction:ltr"> 1nm E6 <h2 style=";text-align:left;direction:ltr"> HATCN <h2 style=";text-align:left;direction:ltr"> SpMA1 <h2 style=";text-align:left;direction:ltr"> SpMA3 <h2 style=";text-align:left;direction:ltr"> EG4:TER <h2 style=";text-align:left;direction:ltr"> ST2 <h2 style=";text-align:left;direction:ltr"> ST2:LiQ (50%:50%) <h2 style=";text-align:left;direction:ltr"> LiQ <h2 style=";text-align:left;direction:ltr"> 5nm <h2 style=";text-align:left;direction:ltr"> 125nm <h2 style=";text-align:left;direction:ltr"> 10nm <h2 style=";text-align:left;direction:ltr"> (97%:3%) 35nm <h2 style=";text-align:left;direction:ltr"> 10nm <h2 style=";text-align:left;direction:ltr"> 30nm <h2 style=";text-align:left;direction:ltr"> 1nm E7 <h2 style=";text-align:left;direction:ltr"> HATCN <h2 style=";text-align:left;direction:ltr"> SpMA1 <h2 style=";text-align:left;direction:ltr"> SpMA3 <h2 style=";text-align:left;direction:ltr"> EG5:TER <h2 style=";text-align:left;direction:ltr"> ST2 <h2 style=";text-align:left;direction:ltr"> ST2:LiQ (50%:50%) <h2 style=";text-align:left;direction:ltr"> LiQ <h2 style=";text-align:left;direction:ltr"> 5nm <h2 style=";text-align:left;direction:ltr"> 125nm <h2 style=";text-align:left;direction:ltr"> 10nm <h2 style=";text-align:left;direction:ltr"> (97%:3%) 35nm <h2 style=";text-align:left;direction:ltr"> 10nm <h2 style=";text-align:left;direction:ltr"> 30nm <h2 style=";text-align:left;direction:ltr"> 1nm E8 <h2 style=";text-align:left;direction:ltr"> HATCN <h2 style=";text-align:left;direction:ltr"> SpMA1 <h2 style=";text-align:left;direction:ltr"> SpMA3 <h2 style=";text-align:left;direction:ltr"> EG6:TER <h2 style=";text-align:left;direction:ltr"> ST2 <h2 style=";text-align:left;direction:ltr"> ST2:LiQ (50%:50%) <h2 style=";text-align:left;direction:ltr"> LiQ <h2 style=";text-align:left;direction:ltr"> 5nm <h2 style=";text-align:left;direction:ltr"> 125nm <h2 style=";text-align:left;direction:ltr"> 10nm <h2 style=";text-align:left;direction:ltr"> (97%:3%) 35nm <h2 style=";text-align:left;direction:ltr"> 10nm <h2 style=";text-align:left;direction:ltr"> 30nm <h2 style=";text-align:left;direction:ltr"> 1nm E9 <h2 style=";text-align:left;direction:ltr"> HATCN <h2 style=";text-align:left;direction:ltr"> SpMA1 <h2 style=";text-align:left;direction:ltr"> SpMA3 <h2 style=";text-align:left;direction:ltr"> EG7:TER <h2 style=";text-align:left;direction:ltr"> ST2 <h2 style=";text-align:left;direction:ltr"> ST2:LiQ (50%:50%) <h2 style=";text-align:left;direction:ltr"> LiQ <h2 style=";text-align:left;direction:ltr"> 5nm <h2 style=";text-align:left;direction:ltr"> 125nm <h2 style=";text-align:left;direction:ltr"> 10nm <h2 style=";text-align:left;direction:ltr"> (97%:3%) 35nm <h2 style=";text-align:left;direction:ltr"> 10nm <h2 style=";text-align:left;direction:ltr"> 30nm <h2 style=";text-align:left;direction:ltr"> 1nm Table 2: Structural formulas of the materials for the OLEDs <h2 style=";text-align:left;direction:ltr"> HATCN <h2 style=";text-align:left;direction:ltr"> SpMA1 <h2 style=";text-align:left;direction:ltr"> SpMA3 <h2 style=";text-align:left;direction:ltr"> TER <h2 style=";text-align:left;direction:ltr"> IC2 <h2 style=";text-align:left;direction:ltr"> LiQ <h2 style=";text-align:left;direction:ltr"> ST2 <h2 style=";text-align:left;direction:ltr"> EG1 <h2 style=";text-align:left;direction:ltr"> EG2 <h2 style=";text-align:left;direction:ltr"> EG3 <h2 style=";text-align:left;direction:ltr"> EG4 <h2 style=";text-align:left;direction:ltr"> EG5 <h2 style=";text-align:left;direction:ltr"> EG6 <h2 style=";text-align:left;direction:ltr"> EG7 Table 3: OLED data <h2 style=";text-align:left;direction:ltr"> Bsp. <h2 style=";text-align:left;direction:ltr"> U1000 (V) <h2 style=";text-align:left;direction:ltr"> SE1000 (cd / A) <h2 style=";text-align:left;direction:ltr"> EQE 1000 (%) <h2 style=";text-align:left;direction:ltr"> CIE x / y <1000 cd / m2 <h2 style=";text-align:left;direction:ltr"> j 0 (mA / cm 2< ) L1 (%) <h2 style=";text-align:left;direction:ltr"> LD (h) E1 3.9 23 21 0.67 / 0.33 20 95 1310 E2 3.8 23 20 0.66 / 0.34 20 95 1160 E3 3.4 23 21 0.67 / 0.33 20 95 110 E4 3.8 24 21 0.67 / 0.33 20 95 70 E5 3.8 22 20 0.66 / 0.34 E6 3.5 23 22 0.66 / 0.34 E7 3.7 22 20 0.67 / 0.33 E8 3.9 23 21 0.66 / 0.34 E9 3.9 22 20 0.67 / 0.34

Claims

1. Organic electroluminescent device comprising anode, cathode and at least one emitting layer containing at least one phosphorescent compound, characterized in that the emitting layer contains at least one compound of formula (1) where the symbols and indices used are as follows: X two adjacent X are a group of the following formula (2), and the two other X are CR, where the two dotted bonds represent the linkage of this group; HetAr is a group of one of the formulae (HetAr-1d), (HetAr-2a), (HetAr-3a), (HetAr-4a), (HetAr-5a), (HetAr-6a), (HetAr-7a) and (HetAr-8c): Ar is the same or different at each instance and is an aromatic or heteroaromatic ring system which has 5 to 40 aromatic ring atoms and may be substituted by one or more R1 radicals; R is the same or different at each instance and is H, D, F, Cl, Br, I, N(R1)2, N(Ar')2, CN, NO2, OR1, SR1, COOR1, C(=O)N(R1)2, Si(R1)3, B(OR1)2, C(=O)R1, P(=O)(R1)2, S(=O)R1, S(=O)2R1, OSO2R1, a straight-chain alkyl group having 1 to 20 carbon atoms or an alkenyl or alkynyl group having 2 to 20 carbon atoms or a branched or cyclic alkyl group having 3 to 20 carbon atoms, where the alkyl, alkenyl or alkynyl group may in each case be substituted by one or more R1 radicals and where one or more nonadjacent CH2 groups may be replaced by Si(R1)2, C=O, NR1, O, S or CONR1, or an aromatic or heteroaromatic ring system which has 5 to 60 aromatic ring atoms and may be substituted in each case by one or more R1 radicals; R' is the same or different at each instance and is a straight-chain alkyl group having 1 to 20 carbon atoms or a branched or cyclic alkyl group having 3 to 20 carbon atoms, where the straight-chain, branched or cyclic alkyl group may in each case be substituted by one or more R1 radicals and where one or more nonadjacent CH2 groups may be replaced by O, or an aromatic or heteroaromatic ring system which has 5 to 40 aromatic ring atoms and may be substituted in each case by one or more R1 radicals; it is also possible here for two R' radicals together to form an aromatic, heteroaromatic, aliphatic or heteroaliphatic ring system; Ar' is the same or different at each instance and is an aromatic or heteroaromatic ring system which has 5 to 40 aromatic ring atoms and may be substituted by one or more R1 radicals; R1 is the same or different at each instance and is H, D, F, Cl, Br, I, N (R2)2, CN, NO2, OR2, SR2, Si (R2)3, B (OR2)2, C(=O)R2, P(=O)(R2)2, S(=O)R2, S(=O)2R2, OSO2R2, a straight-chain alkyl group having 1 to 20 carbon atoms or an alkenyl or alkynyl group having 2 to 20 carbon atoms or a branched or cyclic alkyl group having 3 to 20 carbon atoms, where the alkyl, alkenyl or alkynyl group may in each case be substituted by one or more R2 radicals, where one or more nonadjacent CH2 groups may be replaced by Si(R2)2, C=O, NR2, O, S or CONR2, or an aromatic or heteroaromatic ring system which has 5 to 40 aromatic ring atoms and may be substituted in each case by one or more R2 radicals; R2 is the same or different at each instance and is H, D, F or an aliphatic, aromatic or heteroaromatic organic radical, especially a hydrocarbyl radical, having 1 to 20 carbon atoms, in which it is also possible for one or more hydrogen atoms to be replaced by F; m is 0, 1 or 2; n is the same or different at each instance and is 0 or 1.

2. Organic electroluminescent device according to Claim 1, characterized in that the compound of the formula (1) is selected from the compounds of the formulae (3), (4) and (5): where the symbols and indices have the definitions given in Claim 1.

3. Organic electroluminescent device according to Claim 1 or 2, characterized in that the compound of the formula (1) is selected from the compounds of the formulae (3a-1), (3a-2), (4a-1), (4a-2), (5a-1) and (5a-2): where HetAr, R and R' have the meanings given in Claim 1.

4. Organic electroluminescent device according to one or more of Claims 1 to 3, characterized in that the compound of the formula (1) is selected from the compounds of the formulae (3b), (4b) and (5b): where HetAr, R and R' have the meanings given in Claim 1.

5. Organic electroluminescent device according to one or more of Claims 1 to 4, characterized in that Ar is selected from phenyl, biphenyl, especially ortho-, meta- or para-biphenyl, terphenyl, quaterphenyl, fluorene joined via the 1, 2, 3 or 4 position, spirobifluorene joined via the 1, 2, 3 or 4 position, naphthalene, indole, benzofuran, benzothiophene, carbazole joined via the 1, 2, 3 or 4 position, dibenzofuran joined via the 1, 2, 3 or 4 position, dibenzothiophene joined via the 1, 2, 3 or 4 position, indenocarbazole, indolocarbazole, pyridine, pyrimidine, pyrazine, pyridazine, triazine, quinoline, isoquinoline, quinazoline, quinoxaline, phenanthrene or triphenylene, each of which may be substituted by one or more R1 radicals, or a combination of two or three of these groups.

6. Organic electroluminescent device according to one or more of Claims 1 to 5, characterized in that: R is the same or different at each instance and is selected from the group consisting of H, D, an aromatic or heteroaromatic ring system which has 6 to 30 aromatic ring atoms and may be substituted by one or more R1 radicals, or an N(Ar')2 group; R' is the same or different at each instance and is selected from the group consisting of a straight-chain alkyl group having 1 to 6 carbon atoms or a cyclic alkyl group having 3 to 6 carbon atoms, where the alkyl group may be substituted in each case by one or more R1 radicals, or an aromatic or heteroaromatic ring system which has 6 to 24 aromatic ring atoms and may be substituted in each case by one or more R1 radicals; it is also possible here for two R' radicals together to form a ring system, giving rise to a spiro system; R1 is the same or different at each instance and is selected from the group consisting of H, D, F, CN, a straight-chain alkyl group having 1 to 10 carbon atoms or a branched or cyclic alkyl group having 3 to 10 carbon atoms, where the alkyl group may be substituted in each case by one or more R2 radicals, or an aromatic or heteroaromatic ring system which has 6 to 24 aromatic ring atoms and may be substituted in each case by one or more R2 radicals; R2 is the same or different at each instance and is H, an alkyl group having 1 to 4 carbon atoms or an aryl group which has 6 to 10 carbon atoms and may be substituted by an alkyl group having 1 to 4 carbon atoms, but is preferably unsubstituted.

7. Organic electroluminescent device according to one or more of Claims 1 to 6, characterized in that the phosphorescent compound used is a red-, orange- or yellow-phosphorescing compound.

8. Organic electroluminescent device according to one or more of Claims 1 to 7, characterized in that the emitting layer consists of exactly one compound of the formula (1) and one or more phosphorescent compounds.

9. Organic electroluminescent device according to one or more of Claims 1 to 7, characterized in that the emitting layer, apart from the compound of the formula (1) and the phosphorescent compound, contains at least one further matrix material selected from the group consisting of carbazole derivatives, biscarbazole derivatives, indolocarbazole derivatives, indenocarbazole derivatives, bridged carbazole derivatives or triarylamines.

10. Formulation comprising at least one compound of formula (1) according to one or more of Claims 1 to 6, at least one phosphorescent compound and at least one solvent.

11. Use of a formulation according to Claim 10 for production of an organic electroluminescent device.