EP2358841A1

EP2358841A1 - Organic electroluminescence device

Info

Publication number: EP2358841A1
Application number: EP09756676A
Authority: EP
Inventors: Joachim Kaiser; Arne Buesing; Anja Gerhard; Philipp Stoessel; Susanne Heun
Original assignee: Merck Patent GmbH
Current assignee: Merck Patent GmbH
Priority date: 2008-12-17
Filing date: 2009-11-18
Publication date: 2011-08-24
Also published as: TW201038711A; US20110108818A1; DE102008063470A1; KR20110108240A; CN102076811A; WO2010069442A1; JP2012512535A

Abstract

The present invention relates to organic electroluminescence devices which contain ketone or phosphine oxide derivatives as matrix material and at least two phosphorescent compounds.

Description

Organic electroluminescent device

The present invention relates to phosphorescent organic electroluminescent devices which contain two phosphorescent dopants.

The construction of organic electroluminescent devices (OLEDs) in which organic semiconductors are used as functional materials is described, for example, in US Pat. No. 4,539,507, US Pat. No. 5,151,629, EP 0676461 and WO 98/27136. However, further improvements are needed. There is still room for improvement in the life, efficiency and operating voltage of organic electroluminescent devices. In particular, the so-called roll-off behavior of the OLEDs, ie the efficiency as a function of the brightness of the OLED, there is still room for improvement, since it is often observed that the efficiency drops sharply at high brightness. This applies in particular to electroluminescent devices which are doped with a phosphorescent emitter.

In the prior art, carbazole derivatives, e.g. B. bis (carbazolyl) biphenyl, used as a matrix material for the phosphorescent emitter. There is still room for improvement here, especially with regard to the efficiency and service life of the OLEDs produced with these materials. In addition, these matrix materials often lead to comparatively high operating voltages.

According to the prior art, furthermore, electron-conducting materials, including ketones (for example according to WO 04/093207 or according to the unpublished application DE 102008033943.1), phosphine oxides and sulfones (WO 05/003253) are used as matrix materials for phosphorescent emitters. Especially with ketones, possibly due to the good electron transport properties, very low operating voltages and long lifetimes are achieved, which makes this class of compounds a very interesting matrix material. However, there is still room for improvement when using these matrix materials, especially with respect to the Efficiency. Furthermore, these matrix materials often lead to a stronger roll-off behavior of the OLED, ie a greater decrease in efficiency at high brightness than with other matrix materials. There is therefore still room for improvement here. Furthermore, these matrix materials sometimes show incompatibility with metal complexes containing ketoketonate ligands, for example, acetylacetonate. This is reflected in lower efficiency and lifetime. However, especially these metal complexes have proven to be emitters with very good emission properties, so that many of the currently used phosphorescent emitters are of this type of structure. There is therefore still room for improvement here.

The technical problem underlying this invention is therefore to provide an organic electroluminescent device which exhibits less high-brightness roll-off behavior. The object is furthermore to provide an organic electroluminescent device which contains a metal complex with ketoketonate ligands and which leads to good emission properties with this dopant, in particular to good efficiency, a long service life and a low operating voltage.

Surprisingly, it has been found that an organic electroluminescent device which contains in the emitting layer an aromatic ketone or another of the matrix materials defined below which is substituted by two different phosphorescent emitters simultaneously has high efficiencies, long lifetimes and low Operating voltages, even with phosphorescent emitters containing Ketoketonatliganden show. Furthermore, these electroluminescent devices have a surprisingly low roll-off behavior, so that they can also be operated with good efficiency at high brightness.

From the state of the art, organic electroluminescent devices are known which contain two phosphorescent emitters in a matrix. In US 2007/0247061 organic electroluminescent devices are disclosed which contain a host material and two phosphorescent dopants. In the examples, only CBP (bis (carbazolyl) biphenyl) is given as the matrix material. However, these electroluminescent devices have very high operating voltages. The voltages are comparable or even higher than in

Electroluminescent devices containing only one phosphorescent dopant. An influence on the roll-off behavior of the electroluminescent device is not disclosed.

in US 2002/0125818 organic electroluminescent devices are disclosed which contain a host material, a phosphorescent dopant and a fluorescent or phosphorescent dopant, which emits longer wavelength. Triarylamine derivatives and carbazole derivatives are disclosed in particular as the host material. This results in better efficiencies and a better lifetime especially for combination with a fluorescent dopant. An influence on the lifetime is not disclosed for electroluminescent devices which contain two phosphorescent dopants. Furthermore, an influence on the roll-off behavior of the electroluminescent device is not disclosed.

The invention thus relates to an organic electroluminescent devices comprising in at least one emitting layer

(A) a phosphorescent compound A,

(B) a phosphorescent compound B other than the phosphorescent compound A, and

(C) a matrix material selected from the group consisting of aromatic ketones, aromatic phosphine oxides, aromatic sulfoxides and aromatic sulfones.

In the context of this application, an aromatic ketone is understood to mean a carbonyl group to which two aromatic or heteroaryl aromatic groups or aromatic or heteroaromatic ring systems are directly bonded. An aromatic phosphine oxide in the context of this application means a group P = O to which three aromatic or heteroaromatic groups or aromatic or heteroaromatic ring systems are directly bonded. An aromatic sulfoxide in the context of this application means a group S = O to which two aromatic or heteroaromatic groups or aromatic or heteroaromatic ring systems are directly bonded. For the purposes of this application, an aromatic sulfone is understood to mean a group S (OO) 2, to which two aromatic or heteroaromatic groups or aromatic or heteroaromatic ring systems are directly bonded.

Preferred is an organic electroluminescent device containing in at least one emitting layer

(A) at least one phosphorescent compound A,

(B) a phosphorescent compound B other than the phosphorescent compound A, and

(C) at least one compound selected from the compounds of the formula (1),

Formula 1)

where the symbols and indices used are:

X is C, P or S; Ar is the same or different at each occurrence, an aromatic or heteroaromatic ring system having 5 to 80 aromatic ring atoms, which may be substituted in each case with one or more groups R ¹ ;

R ¹ is the same or different H, D, F, Cl, Br, I at each occurrence

CHO, C (= O) Ar ^1, P (O) (Ar ¹⁾ _2l S (= O) Ar ^1, S (= O) ₂ Ar ^1, CR ² = CR ² Ar ^1, _CN1 _NO2, Si (R ² ) ₃₎ B (OR ² ) ₂ , B (R ² ) ₂ , B (N (R ² ) ₂ ) ₂ , OSO ₂ R ² , a straight-chain alkyl, alkenyl, alkynyl, alkoxy or Thioalkoxygruppe having 1 to 40 carbon atoms or a branched or cyclic alkyl, alkenyl, alkoxy or thioalkoxy group having 3 to 40 carbon atoms, each of which may be substituted by one or more radicals R ² , wherein one or more non-adjacent CH ₂ groups by R ² C = CR ² , C = C, Si (R ² ) ₂ , Ge (R ² ) ₂ , Sn (R ² ) ₂ , C = O, C = S, C = Se, C = NR ² , P (= O) (R ² ), SO, SO ₂ , NR ² , O, S or CONR ² may be replaced and wherein one or more H atoms by F, Cl, Br, I, CN or NO ₂ may be replaced, or an aromatic or heteroaromatic ring system having 5 to 60 aromatic ring atoms, each of which may be substituted by one or more radicals R ² , or an aryloxy or heteroaryloxy group having 5 to 60 aromatic ring atoms which are replaced by an o the plurality of radicals R ² may be substituted, or one

Aralkyl or heteroaralkyl group having 5 to 60 aromatic ring atoms, which may be substituted by one or more radicals R ² , or a combination of these systems; in this case, two or more adjacent substituents R ^{1 can} also be a mono- or polycyclic, aliphatic or aromatic

Form ring system;

Ar ¹ is the same or different at 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 ² ;

R ² is identical or different at each occurrence H, D or an aliphatic, aromatic and / or heteroaromatic organic radical, in particular a hydrocarbon radical having 1 to 20 C atoms, in which also H atoms can be replaced by F; two or more adjacent substituents R ^{2 may} also together form a mono- or polycyclic, aliphatic or aromatic ring system;

n is 0 for X = C or S and is 1 for X = P;

m is 0 for X = C or P and is 0 or 1 for X = S.

In a preferred embodiment of the invention, neither Ar nor Ar ^{1 contains} a triarylamine group or a carbazole group.

An organic electroluminescent device is understood to mean a device which contains the anode, cathode and at least one emitting layer, which is arranged between the anode and the cathode, wherein at least one layer between the anode and the cathode contains at least one organic or organometallic compound. In this case, at least one emitting layer contains at least one phosphorescent emitter A, at least one phosphorescent emitter B and at least one compound of the above-mentioned formula (1). An organic electroluminescent device need not necessarily contain only layers composed of organic or organometallic materials. So it is also possible that one or more layers contain inorganic materials or are constructed entirely of inorganic materials.

A phosphorescent compound in the context of this invention is a compound which exhibits luminescence at room temperature from an excited state with a higher spin multiplicity, ie a spin state> 1, in particular from an excited triplet state. For the purposes of this invention, all luminescent transition metal complexes, in particular all luminescent iridium and platinum compounds, are to be regarded as phosphorescent compounds. An aryl group in the sense of this invention contains at least 6 C atoms; For the purposes of this invention, a heteroaryl group contains at least 2 C atoms and at least 1 heteroatom, with the proviso that the sum of C atoms and heteroatoms gives at least 5. The heteroatoms are preferably selected from N, O and / or S. Here, under an aryl group or heteroaryl either a simple aromatic cycle, ie benzene, or a simple heteroaromatic cycle, for example pyridine, pyrimidine, thiophene, etc., or a fused aryl or heteroaryl group, for example naphthalene, anthracene, pyrene, quinoline, isoquinoline, etc., understood.

An aromatic ring system in the context of this invention contains at least 6 C atoms in the ring system. A heteroaromatic ring system in the sense of this invention contains at least 2 C atoms and at least one heteroatom in the ring system, with the proviso that the sum of C atoms and heteroatoms gives at least 5. The heteroatoms are preferably selected from N, O and / or S. An aromatic or heteroaromatic ring system in the sense of this invention is to be understood as meaning a system which does not necessarily contain only aryl or heteroaryl groups but in which also several aryl or heteroaryl groups a short, non-aromatic moiety (preferably less than 10% of the atoms other than H), e.g. As an sp ³ -hybridized C, N or O atom, may be connected. For example, systems such as 9,9'-spirobifluorene, 9,9-diaryl fluorene, triarylamine, diaryl ether, stilbene, benzophenone, etc. are also to be understood as aromatic ring systems in the context of this invention. Likewise, an aromatic or heteroaromatic ring system is understood as meaning systems in which a plurality of aryl or heteroaryl groups are linked together by single bonds, for example biphenyl, terphenyl or bipyridine.

In the context of the present invention, under a C 1 - to C ₄ -alkyl group in which also individual H atoms or CH ₂ groups can be substituted by the abovementioned groups, particularly preferably the radicals methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, s-butyl, t-butyl, 2-methylbutyl, n-pentyl, s-pentyl, tert-pentyl, 2-pentyl, cyclopentyl, n-hexyl, s -hexyl, tert -hexyl, 2-hexyl, 3-hexyl, cyclohexyl, 2-methylpentyl, n-heptyl, 2-heptyl, 3-heptyl, 4-heptyl, cycloheptyl, 1-methylcyclohexyl, n- Octyl, 2-ethylhexyl, cyclooctyl, 1-bicyclo [2,2,2] octyl, 2-bicyclo [2,2,2] octyl, 2- (2,6-dimethyl) octyl, 3- (3,7 Dimethyl) octyl, trifluoromethyl, pentafluoroethyl and 2,2,2-trifluoroethyl. Among an alkenyl group, the radicals ethenyl, propenyl, butenyl,

Pentenyl, cyclopentenyl, hexenyl, cyclohexenyl, heptenyl, cycloheptenyl, octenyl and cyclooctenyl. An alkynyl group is particularly preferably understood to mean the radicals ethynyl, propynyl, butynyl, pentynyl, hexynyl, heptynyl and octynyl. Among a C 1 to C ₄₀ -alkoxy group, particular preference is given to methoxy, trifluoromethoxy, ethoxy, n-

Propoxy, i-propoxy, n-butoxy, i-butoxy, s-butoxy, t-butoxy or 2-methyl-butoxy understood. By an aromatic or heteroaromatic ring system having 5-60 aromatic ring atoms, which may be substituted in each case with the abovementioned radicals R and which may be linked via any positions on the aromatic or heteroaromatic, are understood in particular groups which are derived from benzene, Naphthalene, anthracene, phenanthrene, benzanthracene, benzphenanthrene, pyrene, chrysene, perylene, fluoranthene, benzfluoranthene, naphthacene, pentacene, benzpyrene, biphenyl, biphenylene, terphenyl, terphenylene, fluorene, benzofluorene, dibenzofluorene, spirobifluorene, dihydrophenanthrene, dihydropyrene, tetrahydropyrene, cis or trans indenofluorene, cis or trans monobenzoindenofluorene, cis or trans dibenzoindenofluorene, 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, phenoxazine, pyrazole, indazole, imidazole, benzimidazole, naphthimidazole, Phenanthrimidazole, pyridimidazole, pyrazine imidazole, quinoxaline imidazole, oxazole, benzoxazole, naphthoxazole, anthroxazole, phenanthroxazole, isoxazole, 1, 2-thiazole, 1, 3-thiazole, benzothiazole, pyridazine, benzopyridazine, pyrimidine, benzpyrimidine, quinoxaline, 1, 5 Diazaanthracene, 2,7-diazapyrene, 2,3-diazapyrene, 1, 6-diazapyrene, 1, 8-diazapyrene, 4,5-diazapyrene, 4,5,9,10-tetraazaperylene, pyrazine, phenazine, phenoxazine, Phenothiazine, fluorubin, naphthyridine, azacarbazole, benzocarboline, Phenanthroline, 1, 2,3-triazole, 1, 2,4-triazole, benzotriazole, 1, 2,3-oxadiazole, 1, 2,4-oxadiazole, 1, 2,5-oxadiazole, 1, 3,4- Oxadiazole, 1, 2,3-thiadiazole, 1, 2,4-thiadiazole, 1, 2,5-thiadiazole, 1, 3,4-thiadiazole, 1, 3,5-triazine, 1, 2,4-triazine, 1, 2,3-triazine, tetrazole, 1, 2,4,5-tetrazine, 1, 2,3,4-tetrazine, 1, 2,3,5-tetrazine, purine, pteridine, indolizine and benzothiadiazole.

The compounds of the formula (1) preferably have a glass transition temperature TQ of greater than 70 ^° C., more preferably greater than 90 ^° C., very particularly preferably greater than 110 ^° C.

In a preferred embodiment of the invention, the photoluminescence maximum of the phosphorescent compound A is at least 20 nm shorter wavelength than that of the phosphorescent compound B, particularly preferably at least 30 nm short-wave. This is especially true when compound A is a green phosphorescent compound and compound B is a red phosphorescent compound or when compound A is a blue phosphorescent compound and compound B is a green phosphorescent compound. When the compound A is a deep blue phosphorescent compound and the compound B is a light blue phosphorescent compound, it is preferred that the compound A emit at least 10 nm short wavelength than the compound B. The photoluminescence maximum is determined by measuring the photoluminescence spectrum of a 50 nm thick layer in which the compound A is doped in a proportion of 5% by volume or the compound B in a proportion of 5% by volume in the ensprechende matrix material according to formula (1).

The emission spectrum of the electroluminescent device as a whole predominantly corresponds to the emission spectrum of the longer-wavelength emitting compound, that is, the compound B.

In one embodiment of the invention, the phosphorescent compound A is a green-luminescent compound and the phosphorescent compound B is a red-luminescent compound. In a further embodiment of the invention, the phosphorescent compound A is a blue-luminescent compound and the phosphorescent compound B is a green-luminescent compound or a red-luminescent compound.

In yet another embodiment of the invention, the phosphorescent compound A is a deep blue luminescent or UV-emitting compound and the compound B is a light blue luminescent compound.

Here, under red luminescence, a luminescence with a

Maximum of the photoluminescence spectrum in the range of 560 to 750 nm understood. Green luminescence is understood as meaning a luminescence with a maximum of the photoluminescence spectrum in the range from 490 to 560 nm. By blue luminescence is meant a luminescence with a maximum of the photoluminescence spectrum in the range of 440 to 490 nm. Deep blue luminescence is understood as meaning a luminescence with a maximum of the photoluminescence spectrum in the range from 350 to 460 nm. By light blue luminescence is meant a luminescence with a maximum of the photoluminescence spectrum in the range of 460 to 490 nm. The photoluminescence spectrum is measured as described above.

The proportion of the phosphorescent compound A in the layer is preferably 5 to 50% by volume, particularly preferably 10 to 25% by volume, very particularly preferably 12 to 20% by volume.

The proportion of phosphorescent compound B in the layer is preferably 1 to 20% by volume, more preferably 3 to 10% by volume, most preferably 4 to 7% by volume.

In the organic electroluminescent device of the present invention, the phosphorescent compound A is preferably a material capable of transporting holes. Since the location of the HOMO (highest occupied molecular orbital) is responsible for the hole transport properties of the material, compound A preferably has a HOMO of> -5.9 eV, more preferably> -5.7 eV and most preferably of> -5.5 eV. The HOMO can be determined by photoelectron spectroscopy using Model AC-2 photon electron spectrometer from Riken Keiki Co. Ltd. (Http://www.rikenkeiki.com/pages/AC2.htm).

In the following, preferred embodiments are carried out for the phosphorescent compounds A and B and for the compound according to formula (1).

Particularly suitable phosphorescent compounds A and B are compounds which, when suitably excited, emit light, preferably in the visible range, and also contain at least one atom of atomic number greater than 20, preferably greater than 38 and less than 84, particularly preferably greater than 56 and less than 80. Preferred phosphorescence emitters A and B are compounds containing copper, molybdenum, tungsten, rhenium, ruthenium, osmium, rhodium, iridium, palladium, platinum, silver, gold or europium, especially compounds containing iridium or platinum.

Particularly preferred organic electroluminescent devices contain as phosphorescent compound A and / or as phosphorescent compound B at least one compound of the formulas (2) to (5),

Formula (2) Formula (3)

Formula (4) Formula (5 ^' wherein R ^{1 has the} same meaning as described above for formula (1), and for the other symbols used:

DCy is, identically or differently on each occurrence, a cyclic group which contains at least one donor atom, preferably nitrogen, carbon in the form of a carbene or phosphorus, via which the cyclic group is bonded to the metal, and which in turn has one or more substituents R ¹ can carry; the groups DCy and CCy are linked by a covalent bond;

CCy is the same or different at each occurrence a cyclic

A group containing a carbon atom through which the cyclic group is bonded to the metal and which in turn may carry one or more substituents R ¹ ;

A is the same or different at each occurrence as a mononionic, bidentate chelating ligand, preferably a diketonate ligand or a picolinate ligand.

In this case, by forming ring systems between a plurality of radicals R ^{1, there may} also be a bridge between the groups DCy and CCy. Furthermore, by forming ring systems between a plurality of radicals R ^{1, there may} also be a bridge between two or three ligands CCy-DCy or between one or two ligands CCy-DCy and the ligand A, so that it is a polydentate or polypodal ligand system ,

Examples of the emitters described above can be found in the applications WO 00/70655, WO 01/41512, WO 02/02714, WO 02/15645, EP 1191613, EP 1191612, EP 1191614, WO 04/081017, WO 05/033244,

WO 05/042550, WO 05/113563, WO 06/008069, WO 06/061182, WO 06/081973 and the unpublished application DE 102008027005.9 are taken. In general, all phosphorescent complexes which are used according to the prior art for phosphorescent OLEDs and as they are suitable for in the field of organic electroluminescence, and those skilled in the art can use other phosphorescent compounds without inventive step. In particular, the expert is aware of phosphorescent complexes with all emission colors.

In this case, the compound A is preferably a compound of the abovementioned formula (3), in particular tris (phenylpyridyl) iridium, which may be substituted by one or more radicals R ¹ . Most preferably, the compound A is tris (phenylpyridyl) iridium.

The compound B is preferably a compound of the above-mentioned formulas (2), (3) or (5), particularly preferably of the formulas (2) or (5), very particularly preferably of the formula (2). Here, A in formula (2) is preferably acetylacetonate or an acetylacetonate derivative.

Examples of preferred phosphorescent compounds A and B are listed in the following table.

(1) (2) (3)

(4) (5) (6)

(52) (53) (54)

(55) (56) (57)

(58) (59) (69)

(61) (62) (63)

(94) (95) (96)

(97) (98) (99)

(100) (101) (102)

(103) (104) (105)

(106) (107) (108)

(109) (110) (111)

(112) (113) (114)

(115) (116) (117)

(118) (119) (120)

(121) (122) (123)

(124) (125) (126)

(127) (128) (129)

(130) (131) (132)

(133) (134) (135)

As the matrix material, as described above, compounds of the formula (1) are used.

Suitable compounds according to formula (1) are the ketones disclosed in WO 04/093207 and the unpublished DE 102008033943.1 and the phosphine oxides, sulfoxides and sulfones disclosed in WO 05/003253. These are via quote part of the present invention. In a preferred embodiment of the compounds of the formula (1), the symbol X is C or P, particularly preferably C. They are therefore preferably ketones or phosphine oxides, more preferably ketones.

The definition of the compound according to formula (1) shows that it not only has to contain a carbonyl or phosphine oxide group, but can also contain several of these groups.

The group Ar in compounds according to formula (1) is preferably an aromatic ring system having 6 to 40 aromatic ring atoms. As defined above, the aromatic ring system need not necessarily have only aromatic groups, but also two aryl groups may be interrupted by a non-aromatic group, for example by another carbonyl group.

In a further preferred embodiment of the invention, the group Ar has no more than two condensed rings. It is therefore preferably composed only of phenyl and / or naphthyl groups, particularly preferably only of phenyl groups, but does not contain any larger condensed aromatics, such as, for example, anthracene.

Preferred groups Ar which are bonded to the carbonyl group are phenyl, 2-, 3- or 4-tolyl, 3- or 4-o-xylyl, 2- or 4-m-xylyl, 2-p-xylyl, , m- or p-tert-butylphenyl, o-, m- or p-fluorophenyl, benzophenone, 1-, 2- or 3-phenylmethanone, 2-, 3- or 4-biphenyl, 2-, 3- or 4- o-terphenyl, 2-, 3- or 4-m-terphenyl, 2-, 3- or 4-p-terphenyl, 2 ^{'-p-terphenyl,} 2', 4 'or ^5' - m-terphenyl, 3 ^'- or ^4' -o-terphenyl, p, m, o, p, m, m, o, m- or o, o-quaterphenyl, quinquephenyl, sexiphenyl, 1-, 2- , 3- or 4-fluorenyl, 2-, 3- or 4-spiro-9,9 ^{'-bifluorenyl,} 1-, 2-, 3- or 4- (9,10-dihydro) phenanthrenyl, 1- or 2- Naphthyl, 2-, 3-, 4-, 5-, 6-, 7- or 8-quinolinyl, 1-, 3-, 4-, 5-, 6-, 7- or 8-iso-quinolinyl, 1- or 2- (4-methylnaphthyl), 1- or 2- (4-phenylnaphthyl), 1- or 2- (4-naphthylnaphthyl), 1-, 2- or 3- (4-naphthyl-phenyl) , 2-, 3- or 4-pyridyl, 2-, 4- or 5-pyrimidinyl, 2- or 3-pyrazinyl, 3- or 4-pyridanzinyl, 2- (1, 3,5-triazine) yl, 2- , 3- or 4- (Ph enylpyridyl), 3-, 4-, 5- or 6- (2,2 ^'bipyridyl), 2-, 4-, 5- or 6- (3,3 ^'bipyridyl), 2- or 3- (4,4'-bipyridyl), and combinations of one or more of these radicals.

The groups Ar may be substituted by one or more radicals R ¹ . These radicals R ¹ are preferably identical or different in each occurrence selected from the group consisting of H, D, F, C (= O) Ar ¹ ,

P (= O) (Ar ¹ ) ₂ , S (= O) Ar ¹ , S (= O) ₂ Ar ¹ , a straight-chain alkyl group with 1 to 4 C atoms or a branched or cyclic alkyl group with 3 to 5 C Atoms, each of which may be substituted by one or more R ² radicals, wherein one or more H atoms may be replaced by F, or an aromatic ring system having 6 to 24 aromatic ring atoms, which may be substituted by one or more radicals R ² , or a combination of these systems; Two or more adjacent substituents R ^{1 may} also together form a mono- or polycyclic, aliphatic or aromatic ring system. When the organic electroluminescent device is applied from solution, straight-chain, branched or cyclic alkyl groups having up to 10 C atoms are also preferred as substituents R ¹ . The radicals R ¹ are more preferably identical or different at each occurrence selected from the group consisting of H, D, C (= O) Ar ¹ or an aromatic ring system having 6 to 24 aromatic ring atoms substituted by one or more radicals R ² may be, but is preferably unsubstituted.

In yet a further preferred embodiment of the invention, the group Ar ^1, identical or different at each occurrence, is an aromatic ring system having 6 to 24 aromatic ring atoms which may be substituted by one or more radicals R ² . Ar ¹ is more preferably identical or different at each occurrence, an aromatic ring system having 6 to 12 aromatic ring atoms.

Preferred aromatic ketones, phosphine oxides, sulfoxides and sulfones are therefore the compounds of the following formulas (6) to (30),

Formula (8)

Formula (12)

Formula (15) Formula (16) Formula (17)

Formula (19) Formula (20)

Formula (21) Formula (22)

Formula (23)

Formula (24)

Formula (25)

Formula (26)

Formula (27)

Formula (28)

Formula (29) Formula (30)

where Ar has the same meaning as described above, and furthermore:

Z is the same or different every occurrence CR ¹ or N, with a maximum of 3 symbols Z per ring for N; preferably Z is CR ¹ ;

m is 1, 2, 3, 4 or 5;

n is the same or different at each occurrence 0, 1, 2, 3 or 4;

p is the same or different 0 or 1 at each occurrence.

Ar in the abovementioned formulas (6) to (30) is preferably an aromatic or heteroaromatic ring system having 5 to 30 aromatic ring atoms which may be substituted by one or more radicals R ¹ . Particularly preferred are the abovementioned groups Ar.

Particularly preferred aromatic ketones are benzophenone derivatives which are each substituted at the 3,3 ', 5,5'-positions by an aromatic or heteroaromatic ring system having 5 to 30 aromatic ring atoms, which in turn is replaced by one or more radicals R ¹ according to the above definition can be substituted. Furthermore, particularly preferred is spirobifluorene, which is substituted by at least one group C = O-Ar, in particular in the 2-position. Furthermore, particularly preferred is spirobifluorene, which is substituted by at least one group P = O (Ar) ₂ , in particular in the 2-position. Examples of suitable compounds according to formula (1) are the compounds (1) to (72) depicted below.

35

In addition to the cathode, anode and one or more emitting layers, the organic electroluminescent device may contain further layers. These are selected, for example, from one or more hole injection layers, hole transport layers, hole blocking layers, electron transport layers, electron injection layers, electron blocking layers, exciton blocking layers, charge generation layers (Charge Generation Layers, IDMC 2003, Taiwan, Session 21 OLED (5), T. Matsumoto, T. Nakada). J. Endo, K. Mori, N. Kawamura, A. Yokoi, J. Kido, Multiphoton Organic EL Device Having Charge Generation Layer) and / or Organic or Inorganic P / N Transitions. In addition, interlayers may be present, which control, for example, the charge balance in the device. Furthermore, the layers, in particular the charge transport layers, may also be doped. The doping of the layers may be advantageous for improved charge transport. It should be noted, however, that not necessarily each of these layers must be present and the choice of layers always depends on the compounds used.

In one embodiment of the invention, the organic electroluminescent device contains a plurality of emitting layers, wherein at least one emitting layer contains at least one phosphorescent compound A, one phosphorescent compound B and one compound according to formula (1). Particularly preferably, these emission layers have a total of a plurality of emission maxima between 380 nm and 750 nm, so that overall white emission results, ie in the emitting layers different emitting compounds are used, which can fluoresce or phosphoresce and emit the blue and yellow, orange or red light. Particularly preferred are three-layer systems, ie systems with three emitting layers, wherein at least one of these layers contains at least one phosphorescent compound A, a phosphorescent compound B and a compound according to formula (1) and wherein the three layers show blue, green and orange or red emission (For the basic structure see eg WO 05/011013). The use of more than three emitting layers may also be preferred.

Also preferred is the use of a plurality of matrix materials as a mixture, wherein a matrix material is selected from compounds of the formula (1). The compounds of formula (1) have predominantly electron transporting properties due to the presence of the group X = O. Therefore, when a mixture of two or more matrix materials is used, another component of the mixture is preferably a hole transporting compound. Preferred hole-conducting matrix materials are triarylamines, carbazole derivatives, e.g. B. CBP (N, N-bis-carbazolylbiphenyl) or in WO 05/039246, US 2005/0069729, JP 2004/288381, EP 1205527 or WO 08/086851 disclosed carbazole derivatives, Azacarbazole, z. B. according to EP 1617710, EP 1617711,

EP 1731584, JP 2005/347160, bipolar matrix materials, e.g. B. according to WO 07/137725, and benzothiophene or Dibenzothiophenderivate, z. B. according to WO 09/021126. The mixture of matrix materials may also contain more than two matrix materials. Furthermore, it is also possible to use the matrix material according to formula (1) as a mixture with a further electron-transporting matrix material, for example with a second matrix material according to formula (1), with bipolar matrix materials, eg. B. according to WO 07/137725, silanes, z. B. according to WO 05/111172, azaboroles or boronic esters, for. B. according to VVO 06/117052. Likewise, two or more materials according to formula (1) can be used.

Further preferred is an organic electroluminescent device, characterized in that one or more layers are coated with a sublimation process. In the process, the materials become in vacuum sublimation at a pressure less than 10 ^"5 mbar, preferably less than 10 ^{" 6} mbar evaporated. It should be noted, however, that the pressure can be even lower, for example less than 10 ^"7 mbar.

Also preferred is an organic electroluminescent device, characterized in that one or more layers with the

OVPD (Organic Vapor Phase Deposition) process or coated by means of a carrier gas sublimation. The materials are applied at a pressure between 10 ^{"applied 5} mbar and 1 bar. A special case of this method is the OVJP (organic vapor jet printing) method in which the materials are applied directly through a nozzle and patterned (eg. BMS Arnold et al., Appl. Phys. Lett., 2008, 92, 053301).

Further preferred is an organic electroluminescent device, characterized in that one or more layers of solution, such. B. by spin coating, or with any printing process, such. As screen printing, flexographic printing or offset printing, but more preferably LITI (Light Induced Thermal Imaging, thermal transfer printing) or inkjet printing (ink jet printing), are produced. For this purpose, soluble compounds are needed. High solubility can be achieved by suitable substitution of the compounds. Not only solutions of individual materials can be applied, but also solutions containing several compounds, for example matrix materials and dopants.

The organic electroluminescent device may also be fabricated as a hybrid system by applying one or more layers of solution and depositing one or more other layers. For example, it is possible to apply an emissive layer containing a compound of the formula (1) and the phosphorescent compounds A and B from solution and then vapor-deposit a hole-blocking layer and / or an electron-transport layer thereon. Likewise, the emitting layer comprising a compound of the formula (1) and the phosphorescent compounds A and B are evaporated in vacuo and one or more other layers can be applied from solution.

These methods are generally known to the person skilled in the art and can be applied by him without inventive step to the organic electroluminescent devices according to the invention.

Another object of the present invention are mixtures comprising at least one phosphorescent compound A, at least one phosphorescent compound B and at least one aromatic ketone, aromatic phosphine oxide, aromatic sulfoxide or aromatic sulfone, preferably a compound according to formula (1).

Yet another object of the present invention are solutions or formulations containing at least one mixture according to the invention and at least one solvent.

The organic electroluminescent devices according to the invention have the following surprising advantages over the prior art:

1. The organic electroluminescent devices according to the invention have a very high efficiency. This is especially true when phosphorescent metal complexes with Ketoketonatliganden, z. Acetylacetonate ligands.

2. The organic electroluminescent devices according to the invention simultaneously have a very good service life. This is especially true when phosphorescent metal complexes are used with Ketoketonatliganden.

3. The organic electroluminescent devices according to the invention simultaneously have a very low operating voltage. In particular, the operating voltage is significantly lower than with matrix materials based on carbazole derivatives. 4. The organic electroluminescent devices according to the invention have a very low roll-off behavior. Thus, the roll-off is significantly lower than with electroluminescent devices, which also contain a compound according to formula (1), but only a phosphorescent compound.

The invention will be described in more detail by the following examples without wishing to limit them thereby. The person skilled in the art, without being inventive, can produce further organic electroluminescent devices according to the invention. 0

Examples:

Example 1-13: Preparation and characterization of organic electroluminescent devices according to the invention

Electroluminescent devices according to the invention can be prepared as described, for example, in WO 05/003253. In the following, the results of different OLEDs are compared. Q Examples 1-13 describe red-emitting OLEDs that are realized by the following layer structure:

Hole Injection Layer (HIL) 20 nm 2,2 ', 7,7'-tetrakis (di-para-tolylamino) spiro-9,9'-bifluorene

Hole transporting layer (HTL) 20 nm NPB (N-naphthyl-N-phenyl-4,4 ¹ - diaminobiphenyl).

Emission Layer (EML) 30 nm Matrix Material: Spiro-Ketone (SK)

(Bis (9,9 ^{'spirobifluorene-2-yl)} ketone) or CBP (4,4'-bis (carbazol-9-yl) biphenyl) dopant: (TER-1, TER-2 or TER-3 see below ); Degree of doping see Table 1. In the examples according to the invention further dopant: Ir (ppy) ₃ (fac-tris [2-phenylpyridylopidium).

Hole blocking layer (HBL) 10 nm SK 5 Electron conductor (ETL) 20 nm AlQ ₃

(Tris (quinolinato) aluminum (III))

Cathode 1 nm LiF ₁ then 100 nm Al.

The structures of TER-1, TER-2, TER-3, lr (ppy) ₃ and SK are shown in the following for clarity:

Spiro-ketone (SK) CBP

These not yet optimized OLEDs are characterized by default; For this purpose, the electroluminescence spectra, the efficiency (measured in cd / A) as a function of the brightness, the operating voltage, calculated from current-voltage-luminance characteristic curves (LUL characteristic curves), and the service life are determined.

Example 1 serves as a comparative example and contains TER-1 as dopant. Example 2 describes an inventive OLED, in addition to TER-1 lr (ppy) ₃ as further dopant. From Table 1 it can be seen that the OLED of the invention compared to the comparative example has a significantly improved efficiency and life, without affecting the color or the operating voltage.

Analogously to this describe Comparative Examples 3-5 and inventive

Examples 6-9 OLEDs with TER-2 as Emitter and Comparative Example 10 and Inventive Example 11 OLEDs with TER-3 as emitter. Here, too, a marked increase in the efficiency and in particular the service life is to be observed. In the case of TER-2, inventive example 7 is found to have 15% Ir (ppy) ₃ concentration and 5% TER-2

Concentration as the one with the highest lifespan. On the other hand, in Comparative Examples, an acceptable lifetime can be obtained only at a higher TER-2 concentration (15%, Comparative Example 3), but this leads to a significantly lower efficiency.

A further significant improvement of the OLEDs according to the invention is shown in the comparison of the efficiency luminance based on Examples 10 and 11 (FIG. 1). The decrease in efficiency (here in the form of the external quantum efficiency EQE) with increasing luminance is significantly lower in the case of the inventive OLED (Example 11) than in Comparative Example 10. While z. B. the EQE of 400 cd / m ² to 4000 cd / m ² in the inventive OLED (Example 11) from 12.2% to 8.3% (and thus by 27%), the waste in the comparative example (Example 10) is 45% from 10.4% to 5.7%.

Comparative Examples 12 and 13 show the effect of a second dopant using the prior art host material CBP. Here, too, there is a slight improvement in efficiency and service life which, in contrast to the already significantly poorer level of the values, is very much lower in percentage terms than when the matrix materials of Examples 1-11 are used. However, this also slightly increases the operating voltage.

Example 14-16: Preparation and characterization of organic electroluminescent devices according to the invention

Examples 14-16 describe blue and green emitting OLEDs that are realized by the following layer construction and can be generated by the general method mentioned above:

Hole Injection Layer (HIL) 20 nm 2,2 ' ₎ 7,7'-tetrakis (di-para-tolylamino) spiro-9,9'-bifluorene

Hole transport layer (HTL) 5 nm NPB (N-naphthyl-N-phenyl-4,4'-diaminobiphenyl).

Electron blocking layer (EBL) 15 nm EBM

Emission layer (EML) 40 nm ketone (K)

To [1, 3 ', 1', 1 ", 3", 1 "', 3' ^J M ^l> "] -quinqephenyl-

5 "-yl-methanone according to

DE 102008033943.1, Example 3,

(Evaporated)

Dotand lr (ppy) ₃ (fac-tris [2-phenylpyridyl] iridium) as a comparative example; in examples according to the invention dopant 1 doped with dopant 2 (degree of doping see table 2). Dotand 1 and Dotand 2 are TEB ₁ Flrpic or Ir (ppy) ₃ ;

Hole Blocking Layer (HBL) 10 nm Ketone (K) Electron Conductor (ETL) 20 nm AlQ ₃

(Tris (quinolinato) aluminum (III))

Cathode 1 nm LiF, then 100 nm Al.

The structures of EBM, TEB, Flrpic, and K are shown below for the sake of clarity.

EBM TEB

Table 2: Device results

As can be seen from the table, the efficiency is increased by the introduction of the dopant Flrpic in a green Ir (ppy) ₃ device. At the same time the color improves. This concept can also be implemented in a blue-green emitting device with high efficiency, as the example 16 shows.

Claims

claims

1. Organic electroluminescent devices comprising in at least one emitting layer

(A) a phosphorescent compound A,

(B) a phosphorescent compound B other than the phosphorescent compound A, and

2. Organic electroluminescent device according to claim 1, characterized in that the aromatic ketone, the aromatic

Phosphine oxide, the aromatic sulfone or the aromatic sulfoxide is selected from compounds according to formula (1),

Formula 1)

where the symbols and indices used are:

X is C, P or S;

Ar is the same or different at each occurrence, an aromatic or heteroaromatic ring system having 5 to 80 aromatic ring atoms, which may be substituted in each case with one or more groups R ¹ ; R ¹ is the same or different at each occurrence H, D, F, Cl, Br, I, CHO, C (= O) Ar ¹ , P (= O) (Ar ¹ ) ₂ , S (= O) Ar ¹ , S (= O) ₂ Ar \ CR ² = CR ² Ar ¹ , CN, NO ₂ , Si (R ² ) _3> B (OR ² ) ₂ , B (R ² ) _2> B (N (R ² ) ₂ ) ₂ , OSO ₂ R ² , a straight-chain alkyl, alkenyl, alkynyl, alkoxy or thioalkoxy group having 1 to 40 carbon atoms or a branched or cyclic alkyl, alkenyl, alkoxy or thioalkoxy group having 3 to 40

C atoms, which may each be substituted by one or more radicals R ² , wherein one or more non-adjacent CH ₂ groups by R ² C = CR ² , C≡C, Si (R ² ) ₂ , Ge (R ² ) ₂ , Sn (R ² ) ₂ , C = O, C = S, C = Se, C = NR ² , P (= O) (R ² ), SO, SO ₂ , NR ² , O, S or CONR ² and wherein one or more H atoms may be replaced by F, Cl, Br, I, CN or NO ₂ , or an aromatic or heteroaromatic ring system having 5 to 60 aromatic ring atoms, each represented by one or more radicals R ² , or an aryloxy or heteroaryloxy group having 5 to 60 aromatic ring atoms, which may be substituted by one or more radicals R ² , or an aralkyl or heteroaralkyl group having 5 to 60 aromatic ring atoms, which by one or more Radicals R ² may be substituted, or a combination of these systems; two or more adjacent substituents R ^{1 may} also together form a mono- or polycyclic, aliphatic or aromatic ring system;

Ar ¹ is the same or different at each instance and is an aromatic or heteroaromatic ring system having from 5 to 40 aromatic

Ring atoms which may be substituted by one or more R ² radicals;

R ² is identical or different at each occurrence H, D or an aliphatic, aromatic and / or heteroaromatic hydrocarbon radical having 1 to 20 C atoms, in which also H atoms may be replaced by F; two or more adjacent substituents R ^{2 may} also together form a mono- or polycyclic, aliphatic or aromatic ring system; n is 0 for X = C or S and is 1 for X = P;

m is O for X = C or P and is 0 or 1 for X = S.

3. Organic electroluminescent device according to claim 1 or 2, characterized in that the photoluminescence maximum of the phosphorescent compound A is at least 20 nm shorter wavelength than that of the phosphorescent compound B, preferably at least 30 nm short-wave.

4. Organic electroluminescent device according to one or more of claims 1 to 3, characterized in that the phosphorescent compound A is a green luminescent compound and the phosphorescent compound B is a red luminescent compound or that the phosphorescent compound A is a blue luminescent compound and the phosphorescent compound B is a green luminescent compound or a red luminescent compound or that the phosphorescent compound A is a deep blue luminescent or emitting in the UV region compound and the compound B is a light blue luminescent compound.

5. Organic electroluminescent device according to one or more of claims 1 to 4, characterized in that the proportion of the phosphorescent compound A in the layer 5 to 50 vol .-%, preferably 10 to 25 vol .-%, particularly preferably 12 to 20 vol .-% is.

6. Organic electroluminescent device according to one or more of claims 1 to 5, characterized in that the proportion of the phosphorescent compound B in the layer 1 to 20 vol .-%, preferably 3 to 10 vol .-%, particularly preferably 4 to 7 vol .-% is.

7. Organic electroluminescent device according to one or more of claims 1 to 6, characterized in that the phosphores- Compound A is a material capable of transporting holes and preferably has a HOMO of> -5.9 eV, more preferably> -5.7 eV, most preferably> -5.5 eV.

8. Organic electroluminescent device according to one or more of claims 1 to 7, characterized in that the phosphorescent compounds A and B at least one atom of atomic number greater than 38 and less than 84, preferably greater 56 and less than 80, more preferably copper, molybdenum, tungsten , Rhenium, ruthenium, osmium, rhodium, iridium, palladium, platinum, silver, gold or europium, especially compounds containing iridium or platinum.

9. Organic electroluminescent device according to one or more of claims 1 to 8, characterized in that the phosphorescent emitters A and / or B are selected from compounds of the formulas (2) to (5),

Formula (2) Formula (3) Formula (4) Formula (5)

wherein R ^{1 has the} same meaning as described in claim 2, and for the other symbols used:

CCy is the same or different at each occurrence a cyclic

10. Organic electroluminescent device according to one or more of claims 1 to 9, characterized in that the group Ar represents an aromatic ring system having 6 to 40 aromatic ring atoms, which is composed only of phenyl and / or naphthyl groups, preferably only as phenyl groups, but none contains larger aromatic ring systems.

11. Organic electroluminescent device according to one or more of claims 1 to 10, characterized in that the radicals R ^{1 are} identical or different in each occurrence selected from the group consisting of H, D, F, C (= O) Ar ¹ , P ( = O) (Ar ¹ ) ₂ , S (= O) Ar ¹ , S (= O) ₂ Ar ¹ , a straight-chain alkyl group having 1 to 4 C atoms or a branched or cyclic alkyl group having 3 to 5 C atoms, each of which may be substituted with one or more R ² radicals, where one or more H atoms may be replaced by F, or an aromatic ring system having from 6 to 24 aromatic ring atoms, which may be substituted by one or more R ² radicals, or a combination of these systems; two or more adjacent substituents R ^{1 may} also together form a mono- or polycyclic, aliphatic or aromatic ring system.

12. Organic electroluminescent device according to one or more of claims 1 to 11, characterized in that the aromatic ketone, the aromatic phosphine oxide, the aromatic sulfone or the aromatic sulfoxide is selected from compounds of the formulas (6) to (30),

Formula (6)

Formula (8)

Formula (9)

Formula (11) Formula (12)

Formula (15)

Formula (16)

Formula (19)

Formula (20)

Formula (21) Formula (22)

Formula (23)

Formula (26)

^[

Formula (27) Formula (28)

Formula (30)

Formula (29)

wherein Ar has the same meaning as described in claim 2, and furthermore:

m is 1, 2, 3, 4 or 5;

n is the same or different at each occurrence 0, 1, 2, 3 or 4;

p is the same or different 0 or 1 at each occurrence.

13. A method for producing an organic electroluminescent device according to one or more of claims 1 to 12, characterized in that one or more layers are coated with a sublimation process and / or that one or more layers with the OVPD (Organic Vapor Phase Deposition) Process or by means of a carrier gas sublimation are coated and / or that one or more layers of solution, such as. B. by spin coating or by any printing method.

14. Mixture containing

(A) at least one phosphorescent compound A,

(B) at least one phosphorescent compound B other than the compound A, and (C) at least one aromatic ketone, aromatic phosphine oxide, aromatic sulfoxide or aromatic sulfone, preferably a compound according to formula (1),

Formula 1 )

wherein the symbols and indices used have the meanings given in claim 2.

15. A solution or formulation containing at least one mixture according to claim 14.