Materials for organic electroluminescent devices

Abstract

The present invention relates to the fluorene derivatives and to organic electronic devices in which these Compounds are used as matrix material in the emitting layer and/or as hole transport material and/or as electron blocker or exciton blocker material and/or as electron transport material.

Claims

1. A compound comprising at least one structure of the formula (I) ##STR00327## where the symbols used are as follows: A.sup.1, A.sup.2, A.sup.3, A.sup.4 is the same or different at each instance and is N or CR.sup.1, with the proviso that not more than two of the A.sup.1, A.sup.2, A.sup.3, A.sup.4 groups in one cycle are N; V.sup.1, V.sup.2, V.sup.3 is the same or different at each instance and is N or CR.sup.2, with the proviso that not more than two of the V.sup.1, V.sup.2, V.sup.3 groups in one cycle are N; W.sup.1, W.sup.2, W.sup.3 is the same or different at each instance and is N or CR.sup.3, with the proviso that not more than two of the W.sup.1, W.sup.2, W.sup.3 groups in one cycle are N; X.sup.1, X.sup.2, X.sup.3 is the same or different at each instance and is N or CR.sup.4, with the proviso that not more than two of the X.sup.1, X.sup.2, X.sup.3 groups in one cycle are N; R.sup.1, R.sup.2, R.sup.3, R.sup.4 is the same or different at each instance and is H, D, F, Cl, Br, I, B(OR.sup.5).sub.2, CHO, C(O)R.sup.5, CR.sup.5C(R.sup.5).sub.2, CN, C(O)OR.sup.5, C(O)N(R.sup.5).sub.2, Si(R.sup.5).sub.3, N(R.sup.5).sub.2, NO.sub.2, P(O)(R.sup.5).sub.2, OSO.sub.2R.sup.5, OR.sup.5, S(O).sub.5R.sup.5, a straight-chain alkyl, alkoxy or thioalkoxy group having 1 to 40 carbon atoms or a branched or cyclic alkyl, alkoxy or thioalkoxy group having 3 to 40 carbon atoms, each of which may be substituted by one or more R.sup.5 radicals, where one or more nonadjacent CH.sub.2 groups may be replaced by R.sup.5CCR.sup.5, CC, Si(R.sup.5).sub.2, Ge(R.sup.5).sub.2, Sn(R.sup.5).sub.2, CO, CS, CSe, CNR.sup.5, C(O)O, C(O)NR.sup.5, NR.sup.5, P(O)(R.sup.5), O, S, SO or SO.sub.2 and where one or more hydrogen atoms may be replaced by D, F, Cl, Br, I, CN or NO.sub.2, or an aromatic ring system which has 6 to 40 aromatic ring atoms and may be substituted in each case by one or more R.sup.5 radicals, or an aryloxy or heteroaryloxy group which has 5 to 40 aromatic ring atoms and may be substituted in each case by one or more R.sup.5 radicals, or a combination of these systems; at the same time, it is also possible for two or more adjacent R.sup.1 substituents together to form a mono- or polycyclic, aliphatic or aromatic ring system; at the same time, it is also possible for two or more adjacent R.sup.2 substituents together to form a mono- or polycyclic, aliphatic or aromatic ring system; at the same time, it is also possible for two or more adjacent R.sup.3 substituents together to form a mono- or polycyclic, aliphatic or aromatic ring system; at the same time, it is also possible for two or more adjacent R.sup.4 substituents together to form a mono- or polycyclic, aliphatic or aromatic ring system; R.sup.5 is the same or different at each instance and is H, D, F, Cl, Br, I, B(OR.sup.6).sub.2, CHO, C(O)R.sup.6, CR.sup.6C(R.sup.6).sub.2, CN, C(O)OR.sup.6, C(O)N(R.sup.6).sub.2, Si(R.sup.6).sub.3, N(R.sup.6).sub.2, NO.sub.2, P(O)(R.sup.6).sub.2, OSO.sub.2R.sup.6, OR.sup.6, S(O)R.sup.6, S(O).sub.2R.sup.6, a straight-chain alkyl, alkoxy or thioalkoxy group having 1 to 40 carbon atoms or a branched or cyclic alkyl, alkoxy or thioalkoxy group having 3 to 40 carbon atoms, each of which may be substituted by one or more R.sup.6 radicals, where one or more nonadjacent CH.sub.2 groups may be replaced by R.sup.6CCR.sup.6, CC, Si(R.sup.6).sub.2, Ge(R.sup.6).sub.2, Sn(R.sup.6).sub.2, CO, CS, CSe, CNR.sup.6, C(O)O, C(O)NR.sup.6, NR.sup.6, P(O)(R.sup.6), O, S, SO or SO.sub.2 and where one or more hydrogen atoms may be replaced by D, F, Cl, Br, I, CN or NO.sub.2, or an aromatic ring system which has 6 to 40 aromatic ring atoms and may be substituted in each case by one or more R.sup.6 radicals, or an aryloxy or heteroaryloxy group which has 5 to 40 aromatic ring atoms and may be substituted by one or more R.sup.6 radicals, or a combination of these systems; at the same time, it is also possible for two or more adjacent R.sup.5 substituents together to form a mono- or polycyclic, aliphatic or aromatic ring system; R.sup.6 is the same or different at each instance and is H, D, F or an aliphatic, and/or aromatic hydrocarbyl radical having 1 to 20 carbon atoms, in which hydrogen atoms may also be replaced by F; at the same time, it is also possible for two or more adjacent R.sup.6 substituents together to form a mono- or polycyclic, aliphatic or aromatic ring system; with the proviso that the W.sup.1 and V.sup.1 radicals are not bridged to one another; the R.sup.2 radicals in the V.sup.1, V.sup.2, V.sup.3 groups and the R.sup.4 radicals in the X.sup.1, X.sup.2, X.sup.3 groups comprise a total of at least 12 aromatic carbon ring atoms; the R.sup.1, R.sup.2, R.sup.3 and R.sup.4 radicals do not include a triazine structure and the V.sup.1, V.sup.2, V.sup.3 and W.sup.1, W.sup.2, W.sup.3 groups comprise a total of not more than two CR.sup.2 and CR.sup.3 groups comprising an aromatic or heteroaromatic ring system.

2. The compound according to claim 1, wherein A.sup.1, A.sup.2, A.sup.3, A.sup.4 is the same or different at each instance and is CR.sup.1, with the proviso that not more than two of the A.sup.1, A.sup.2, A.sup.3, A.sup.4 groups in one cycle are N; V.sup.1, V.sup.2, V.sup.3 is the same or different at each instance and is CR.sup.2, with the proviso that not more than two of the V.sup.1, V.sup.2, V.sup.3 groups in one cycle are N; W.sup.1, W.sup.2, W.sup.3 is the same or different at each instance and CR.sup.3, with the proviso that not more than two of the W.sup.1, W.sup.2, W.sup.3 groups in one cycle are N; X.sup.1, X.sup.2, X.sup.3 is the same or different at each instance and is CR.sup.4, with the proviso that not more than two of the X.sup.1, X.sup.2, X.sup.3 groups in one cycle are N.

3. The compound according to claim 1, comprising at least one structure of the formula (II) ##STR00328## where the symbols used are as defined in claim 1, where the V.sup.1, V.sup.2, V.sup.3 and W.sup.1, W.sup.2, W.sup.3 groups comprise not more than one R.sup.2 or R.sup.3 radical comprising an aromatic ring system.

4. The compound according to claim 1, wherein the compound has a molecular weight of not more than 5000 g/mol.

5. The compound according to claim 1, wherein the compound has a molecular weight of not more than 1000 g/mol.

6. The compound according to claim 1, wherein the compound has a total of not more than 5 nitrogen atoms.

7. The compound according to claim 1, wherein the compound has a total of not more than 3 nitrogen atoms.

8. The compound according to claim 1, wherein the compound has a total of not more than 5 heteroatoms apart from fluorine.

9. The compound according to claim 1, wherein the compound is a hydrocarbon or a fluorinated hydrocarbon.

10. The compound according to claim 1, wherein the compound is a hydrocarbon.

11. The compound according to claim 1, wherein the compound is a wide band gap material.

12. The compound according to claim 1, wherein the R.sup.1 radicals in the A.sup.1, A.sup.2, A.sup.3, A.sup.4 groups do not form a fused ring system with the ring atoms of the fluorene structure.

13. The compound according to claim 1, wherein the R.sup.2 radicals in the V.sup.1, V.sup.2, V.sup.3 groups do not form a fused ring system with the ring atoms of the phenyl group to which the R.sup.2 radicals are bonded.

14. The compound according to claim 1, wherein the R.sup.3 radicals in the W.sup.1, W.sup.2, W.sup.3 groups do not form a fused ring system with the ring atoms of the phenyl group to which the R.sup.3 radicals are bonded.

15. The compound according to claim 1 which can be represented by a structure of the formula (III) ##STR00329## where the R.sup.1, R.sup.2, R.sup.3, R.sup.4 symbols used are as defined in claim 1 and each m is independently 0 or 1, where the sum total of the indices m is not more than 1, each n is independently 0, 1, 2, 3 or 4, and each o is independently 0, 1, 2, 3, 4 or 5.

16. The compound according to claim 1 which can be represented by a structure of the formula (IV) ##STR00330## where the R.sup.4 symbol used is as defined in claim 1.

17. A composition comprising at least one compound according to claim 1 and at least one further compound selected from the group consisting of fluorescent emitters, phosphorescent emitters, host materials, matrix materials, electron transport materials, electron injection materials, hole conductor materials, hole injection materials, electron blocker materials and hole blocker materials.

18. A formulation comprising at least one compound according to claim 1 and at least one solvent.

19. An electronic device comprising at least one compound according to claim 1.

20. The electronic device according to claim 19, wherein the electronic device is selected from the group consisting of organic electroluminescent devices (OLEDs, PLEDs), organic field-effect transistors (O-FETs), organic thin-film transistors (O-TFTs), organic light-emitting transistors (O-LETs), organic integrated circuits (O-ICs), organic solar cells (O-SCs), organic field-quench devices (O-FQDs), light-emitting electrochemical cells (LECs), organic laser diodes (O-lasers) and organic photoreceptors.

21. The compound according to claim 1, wherein the compound has a band gap of 3.0 eV or more.

Description

EXAMPLES

(1) All syntheses are conducted in an argon atmosphere and in dry solvents, unless stated otherwise. The figures in brackets for the substances known from the literature are the corresponding CAS numbers.

Part A: Preparation of Compounds of the Invention

A.1 Preparation of 3,3-dibromobenzophenone K1

(2) ##STR00290##

(3) 3,3-Dibromobenzophenone K1 can be prepared according to J. Mater. Chem. C 2014, 2, 2028-2036.

A.2 Preparation of 9,9-bis(3-bromophenyl)fluorene F(Br)2

(4) ##STR00291##

(5) About 10 ml of a solution of 2-bromobiphenyl (80.0 g, 343 mmol) and 1,2-dibromoethane (3.6 ml, 43 mmol) in a mixture of 640 ml of toluene, 520 ml of tetrahydrofuran and 60 ml of ethylene glycol dimethyl ether are added to 8.8 g of magnesium (334 mmol) and heated. After onset of the reaction, the heating is removed and the remaining solution is added dropwise in such a way that reflux is maintained. On completion of addition, the mixture is heated to reflux for 1 h. Subsequently, under gentle reflux, a solution of the ketone K1 (80.0 g, 235 mmol) in 800 ml of tetrahydrofuran is added dropwise and the mixture is stirred under reflux for 5 h. The heating is removed and the mixture is stirred for 14 h. The solvents are removed completely on a rotary evapourator. The remaining residue is taken up in a mixture of 920 ml of glacial acetic acid and 13.2 ml of a 33% solution of hydrogen bromide in acetic acid, and heated to reflux for 6 h. After removing the heating, the mixture is stirred for 16 h. The solid material formed is filtered off with suction, washed with about 150 ml of glacial acetic acid and three times with 250 ml each time of ethanol and then dried in a vacuum drying cabinet. This leaves 101.6 g (213 mmol, 91% of theory) of the product as a light grey solid having a purity of about 99% by 1H NMR.

(6) In an analogous manner, it is possible to prepare the following compound BuF(Br).sub.2 from the ketone K1 and the appropriate bromide:

(7) TABLE-US-00003 Ex. Bromide Product Yield BuF(Br).sub.2 82%

A.3 Preparation of Substituted 9,9-Diphenylfluorene Derivatives

(8) The boronic acids and boronic esters used in the syntheses described hereinafter are summarized in the following table:

(9) TABLE-US-00004 BS1 BS2 BS3 BS4

A.3.1 Preparation of F(BS1)2

(10) ##STR00298##

(11) 9,9-Bis-(3-bromophenyl)fluorene F(Br).sub.2 (15.4 g, 32.4 mmol), 2-[3-(3,5-diphenylphenyl)phenyl]-4,4,5,5-tetramethyl-1,3,2-dioxoborolane (28.7 g, 66.4 mmol), 1.87 g of tetrakis(triphenylphosphine)palladium(0) and 100 ml of a 20% solution of tetraethylammonium hydroxide in water are heated under reflux in 350 ml of tetrahydrofuran for 14 h. After cooling, the solvents are removed on a rotary evapourator. The remaining residue is hot-extracted with about 300 ml of ethyl acetate over a bed of alumina (basic, activity level 1). After removing the heating, the mixture is stirred at room temperature for a further 48 h. The solid material formed is filtered off with suction, recrystallized five times from toluene and finally fractionally sublimed twice (390 C., p about 10.sup.5 mbar). This leaves 10.2 g (11.0 mmol, 34% of theory) as a colourless solid having a purity of 99.9% by HPLC.

(12) In an analogous manner, it is possible to prepare the following compounds:

(13) TABLE-US-00005 Ex. Fluorene Boronic acid/ester Product Yield F(BS3).sub.2 F(Br).sub.2 00 41% F(BS4).sub.2 F(Br).sub.2 01 02 28% BuF(BS4).sub.2 BuF(Br).sub.2 03 04 32%

A.3.2 Preparation of Asymmetrically Substituted 9,9-diphenylfluorenes

(14) Method A)

(15) Compounds asymmetrically substituted with respect to the mirror plane of the 9,9-diphenylfluorene can be obtained in analogy to the preparation of F(BS1).sub.2 by simultaneous reaction of F(Br).sub.2 with 0.55 equivalent each of two different boronic acids and/or boronic esters (Boron A and Boron B in Table 1) as mixtures of three products, as shown by way of example by the following scheme:

(16) ##STR00305##

(17) The crude products of this mixed substitution can be separated by chromatography (e.g. CombiFlash Torrent from A. Semrau).

(18) Chromatographic media and eluent mixtures suitable for this purpose are known to those skilled in the art. The products thus isolated can optionally finally be purified further by recrystallization and/or sublimation analogously to the preparation of F(BS1).sub.2 as per A.3.1.

(19) TABLE-US-00006 TABLE 1 Products from the simultaneous reaction of F(Br).sub.2 with two boronic acids/boronic esters (Boron A and Boron B) by Method A Boron Boron Ex. A B Product isolated Yield F(BS1).sub.2 0.55 eq BS1 0.55 eq BS2 06 23% B(BS1)(BS2) 07 30% (22%) F(BS2).sub.2 08 32%

(20) The yield reported is based in each case on the products isolated after chromatographic separation and, in brackets, after sublimation thereof.

(21) Method B)

(22) Further compounds asymmetrically substituted with respect to the mirror plane of the 9,9-diphenylfluorene can be obtained in analogy to Method A by reaction of F(Br).sub.2 with just 0.5 equivalent of a boronic acid or boronic ester as a mixture of three products, as shown by way of example by the following scheme:

(23) ##STR00309##

(24) The crude products of this substoichiometric substitution can be separated by chromatography (e.g. CombiFlash Torrent from A. Semrau).

(25) Chromatographic media and eluent mixtures suitable for this purpose are known to those skilled in the art.

(26) TABLE-US-00007 Boron Ex. A Product isolated Yield F(BS1).sub.2 0.5% BS1 0 21% F(BS1)(Br) 33% F(Br).sub.2 29%

(27) The F(BS1)(Br) thus obtained can be used, without further purification, to prepare F(BS1)(H) by reaction with n-butyllithium and subsequent quenching with water:

(28) ##STR00313##

(29) F(BS1)(Br) (4.9 g, 7.0 mmol) is initially charged in 50 ml of tetrahydrofuran and cooled down to 78 C. 2.85 ml of an n-butyllithium solution (2.5 M in n-hexane, 7.1 mmol) are slowly added dropwise and the mixture is stirred for 1 h, then the cooling is removed. At an internal temperature of about 0 C., 1 ml of water is added dropwise. The mixture is stirred for 1 h and then dried over sodium sulphate. The organic solvents are removed on a rotary evapourator. The residue is recrystallized once from a mixture of toluene and heptane (2:1 v/v). Final fractional sublimation (340 C., p about 10.sup.5 mbar) leaves 2.5 g of F(BS1)(H) (4.0 mmol, 57% of theory) as a colourless solid having a purity of 99.9% by HPLC.

Part B: Device Examples

(30) There are already many descriptions of the production of completely solution-based OLEDs in the literature, for example in WO 2004/037887. There have likewise been many previous descriptions of the production of vacuum-based OLEDs, including in WO 2004/058911. In the examples discussed hereinafter, layers applied in a solution-based and vacuum-based manner are combined within an OLED, and so the processing up to and including the emission layer was effected from solution and in the subsequent layers (hole blocker layer and electron transport layer) from vacuum. For this purpose, the previously described general methods are matched to the circumstances described here and combined as follows:

(31) The structure of the components is as follows: substrate ITO (50 nm) hole injection layer (HIL) (20 nm) hole transport layer (HTL) (20 nm) emission layer (EML) (60 nm) hole blocker layer (HBL) (10 nm) electron transport layer (ETL) (40 nm) cathode

(32) Substrates used are glass plates coated with structured ITO (indium tin oxide) of thickness 50 nm. For better processing, they are coated with PEDOT: PSS (poly(3,4-ethylenedioxy-2,5-thiophene) polystyrenesulphonate, purchased from Heraeus Precious Metals GmbH & Co. KG, Germany). PEDOT:PSS is spun on from water under air and subsequently baked under air at 180 C. for 10 minutes in order to remove residual water. The hole transport layer and the emission layer are applied to these coated glass plates. The hole transport layer used is crosslinkable. A polymer of the structure shown below is used, which can be synthesized according to WO 2010/097155.

(33) ##STR00314##

(34) The hole transport polymer is dissolved in toluene. The typical solids content of such solutions is about 5 g/l when, as here, the layer thickness of 20 nm which is typical of a device is to be achieved by means of spin-coating. The layers are spun on in an inert gas atmosphere, argon in the present case, and baked at 180 C. for 60 minutes.

(35) The emission layer is always composed of at least one matrix material (host material) and an emitting dopant (emitter). In addition, mixtures of a plurality of matrix materials and co-dopants may occur. Details given in such a form as H1 (40%):H2 (40%):D (20%) mean here that the material H1 is present in the emission layer in a proportion by weight of 40%, the material H2 in a proportion by weight of likewise 40%, and the dopant D in a proportion by weight of 20%. The mixture for the emission layer is dissolved in toluene or optionally chlorobenzene. The typical solids content of such solutions is about 18 g/l when, as here, the layer thickness of 60 nm which is typical of a device is to be achieved by means of spin-coating. The layers are spun on in an inert gas atmosphere, argon in the present case, and baked at 160 C. for 10 minutes. Materials used are listed in Tables 2 and 3these are both compounds of the invention and comparative examples.

(36) The materials for the electron transport layer are applied by thermal vapour deposition in a vacuum chamber. The electron transport layer, for example, may consist of more than one material, the materials being added to one another by co-evapouration in a particular proportion by volume. Details given in such a form as ETM1:ETM2 (50%:50%) mean here that the ETM1 and ETM2 materials are present in the layer in a proportion by volume of 50% each. The materials used in the present case are shown in Table 2.

(37) The cathode is formed by the thermal evapouration of an aluminium layer of thickness 100 nm.

(38) The OLEDs are characterized in a standard manner. For this purpose, the electroluminescence spectra, current-voltage-luminance characteristics (IUL characteristics) assuming Lambertian radiation characteristics and the (operating) lifetime are determined. The IUL characteristics are used to determine parameters such as the operating voltage U (in V) and the external quantum efficiency (in %) at a particular brightness. LD80 @10 000 cd/m.sup.2 is the lifetime until the OLED, given a starting brightness of 10 000 cd/m.sup.2, has dropped to 80% of the starting intensity, i.e. to 8000 cd/m.sup.2. The optoelectronic characteristics of the various OLEDs are collated in Table 5. The example Comp. is a comparative example according to the prior art; examples 11-19 show data of OLEDs comprising materials of the invention. The exact description of the materials used in the EML can be found in Table 4.

(39) Some of the examples are elucidated in detail hereinafter, in order to illustrate the advantages of the inventive compounds.

(40) TABLE-US-00008 TABLE 2 Structural formulae of the materials used in the OLEDs (without materials of the invention) 0

(41) TABLE-US-00009 TABLE 3 Structural formulae of the materials of the invention used in the OLEDs

(42) TABLE-US-00010 TABLE 4 EML mixtures in the different device examples (in examples Comp1 and I1 to I6, RefH1, H2 and DG are mixed in a ratio of 40:40:20; in the examples Comp2 and I7 to I9, a mixture of RefH1, H2, DG and DR in a ratio of 20:54:20:6 is used). EML composition Comp1 RefH1; RefH2; DG I1 RefH1; F(BS1).sub.2; DG I2 RefH1; F(BS3).sub.2; DG I3 RefH1; F(BS4).sub.2; DG I4 RefH1; F(BS1)(BS2); DG I5 RefH1; F(BS1)(H); DG I6 RefH1; BuF(BS4).sub.2; DG Comp2 RefH1; RefH2; DG; DR I7 RefH1; F(BS1).sub.2; DG; DR I8 RefH1; F(BS1)(BS2); DG; DR I9 RefH1; F(BS1)(H); DG; DR

(43) TABLE-US-00011 TABLE 5 Working examples comprising the materials of the invention Voltage at Efficiency at LT80 at 10 1000 10 000 Exp. mA/cm.sup.2 cd/m.sup.2 cd/m.sup.2 [h] Comp1 7.4 15.0% 220 I1 7.5 16.1% 300 I2 7.3 15.4% 210 I3 7.0 15.5% 200 I4 7.5 16.0% 250 I5 7.0 15.1% 190 I6 6.9 16.3% 230 Comp2 7.9 13.6% 245 I7 8.0 13.6% 305 I8 7.8 13.9% 290 I9 7.5 13.5% 270

(44) As Table 5 shows, the materials of the invention, when used as wide bandgap material in the EML of the OLEDs, result in improvements over the prior art, particularly with regard to lifetime, but also efficiency and operating voltage.