An Organic Electronic Device Comprising a Hole Injection Layer That Comprises a Hole Transport Compound

Abstract

The present invention relates to an organic electronic device comprising an anode layer, a cathode layer and a hole injection layer, wherein the hole injection layer is arranged between the anode layer and the cathode layer and wherein the hole injection layer comprises a hole transport compound and a metal complex.

Claims

1. An organic electronic device comprising an anode layer, a cathode layer and a hole injection layer, wherein the hole injection layer is arranged between the anode layer and the cathode layer and wherein the hole injection layer comprises a hole transport compound and a metal complex, wherein the hole transport compound comprises covalently bound atoms selected from: covalently bound C, H, O, N, Si and/or S; or covalently bound C, H, O, N, B and P, and wherein the hole transport compound has a molecular weight Mw of ≥400 and ≤2000 g/mol, the HOMO level of the hole transport compound is further away from vacuum level than the HOMO level of N4,N4″′-di(naphthalen-1-yl)-N4,N4″′-diphenyl-[1,1′:4′,1″:4″,1″′-quaterphenyl]-4,4″′-diamine when determined under the same conditions; and the metal complex has the formula (II): ##STR00071## wherein M is a metal ion, n is the valency of M, wherein n is an integer from 1 to 4, L is a ligand comprising at least two carbon atoms; and wherein the hole injection layer is arranged adjacent to the anode layer.

2. An organic electronic device comprising an anode layer, a cathode layer and a hole injection layer, wherein the hole injection layer is arranged between the anode layer and the cathode layer and wherein the hole injection layer comprises a hole transport compound and a metal complex, wherein the hole transport compound has the formula (I):
(Ar.sup.1).sub.k—(Ar.sup.2).sub.m-Ar.sup.3—(Ar.sup.4).sub.p—(Ar.sup.5).sub.q—(Ar.sup.6).sub.r  (I), wherein k, m, q, r are independently from each other 0, 1 or 2, p is 1, 2 or 3, wherein 2≤k+m+q+r+p≤11, Ar.sup.1 to Ar.sup.6 are independently selected from a substituted or unsubstituted unsaturated 5- to 7-member ring of a heterocycle, a substituted or unsubstituted C.sub.6 to C.sub.30 aryl, a substituted or unsubstituted C.sub.3 to C.sub.30 heteroaryl, a substituted or unsubstituted fluorene, or a fused ring system comprising 2 to 6 substituted or unsubstituted 5- to 7-member rings and the rings are selected from the group comprising (i) unsaturated 5- to 7-member ring of a heterocycle, (ii) 5- to 6-member of an aromatic heterocycle, (iii) unsaturated 5- to 7-member ring of a non-heterocycle, (iv) 6-member ring of an aromatic non-heterocycle; wherein the substituents are selected from the group H, D, C.sub.1 to C.sub.12 alkyl, unsubstituted C.sub.6 to C.sub.18 aryl, unsubstituted C.sub.3 to C.sub.18 heteroaryl, a fused ring system comprising 2 to 6 unsubstituted 5- to 7-member rings and the rings are selected from the group comprising unsaturated 5- to 7-member ring of a heterocycle, 5- to 6-member of an aromatic heterocycle, unsaturated 5- to 7-member ring of a non-heterocycle, and 6-member ring of an aromatic non-heterocycle; and the metal complex has the formula (II): ##STR00072## wherein M is a metal ion, n is the valency of M, wherein n is an integer from 1 to 4, L is a ligand comprising at least two carbon atoms; and wherein the hole injection layer is arranged adjacent to the anode layer.

3. The organic electronic device according to claim 2, wherein the HOMO level of the hole transport compound is further away from vacuum level than the HOMO level of N4,N4″′-di(naphthalen-1-yl)-N4,N4″′-diphenyl-[1,1′:4″, 1″:4″,1″′-quaterphenyl]-4,4″′-diamine when determined under the same conditions.

4. The organic electronic device according to claim 1 or 2, wherein the hole injection layer is non-emissive.

5. The organic electronic device according to claim 1, wherein the hole transport compound of claim 1 has the formula (I):
(Ar.sup.1).sub.k—(Ar.sup.2).sub.m-Ar.sup.3—(Ar.sup.4).sub.p—(Ar.sup.5).sub.q—(Ar.sup.6).sub.r  (I), wherein k, m, q, r are independently from each other 0, 1 or 2, p is 1, 2 or 3, wherein 2≤k+m+q+r+p≤11, Ar.sup.1 to Ar.sup.6 are independently selected from a substituted or unsubstituted unsaturated 5- to 7-member ring of a heterocycle, a substituted or unsubstituted C.sub.6 to C.sub.30 aryl, a substituted or unsubstituted C.sub.3 to C.sub.30 heteroaryl, a substituted or unsubstituted fluorene, or a fused ring system comprising 2 to 6 substituted or unsubstituted 5- to 7-member rings and the rings are selected from the group comprising unsaturated 5- to 7-member ring of a heterocycle, 5- to 6-member of an aromatic heterocycle, unsaturated 5- to 7-member ring of a non-heterocycle, 6-member ring of an aromatic non-heterocycle, substituted or unsubstituted biphenylene, substituted or unsubstituted fluorene, substituted or unsubstituted naphthalene, substituted or unsubstituted anthracene, substituted or unsubstituted phenanthrene, substituted or unsubstituted pyrene, substituted or unsubstituted perylene, substituted or unsubstituted triphenylene, substituted or unsubstituted tetracene, substituted or unsubstituted tetraphene, substituted or unsubstituted dibenzofurane, substituted or unsubstituted dibenzothiophene, substituted or unsubstituted xanthene, substituted or unsubstituted carbazole, substituted or unsubstituted azepine, substituted or unsubstituted dibenzo[b,f]azepine, 9,9′-spirobi[fluorene], substituted or unsubstituted spiro[fluorene-9,9′-xanthene], substituted or unsubstituted 9,14-dihydrodibenzo[2,3:6,7]azepino[4,5-b]indole, or a substituted or unsubstituted aromatic fused ring system comprising at least three substituted or unsubstituted aromatic rings selected from the group comprising substituted or unsubstituted non-hetero, substituted or unsubstituted hetero 5-member rings, substituted or unsubstituted 6-member rings and/or substituted or unsubstituted 7-member rings, wherein the substituents are selected from the group H, D, C.sub.1 to C.sub.12 alkyl, unsubstituted C.sub.6 to C.sub.18 aryl, or unsubstituted C.sub.3 to C.sub.18 heteroaryl, fused ring system comprising 2 to 6 unsubstituted 5- to 7-member rings and the rings are selected from the group comprising unsaturated 5- to 7-member ring of a heterocycle, 5- to 6-member of an aromatic heterocycle, unsaturated 5- to 7-member ring of a non-heterocycle, and 6-member ring of an aromatic non-heterocycle.

6. The organic electronic device according to claim 1 or 2, wherein the hole transport compound according to claim 1 and the hole transport compound according of formula (I) has a molecular weight Mw of ≥400 and ≤2000 g/mol.

7. The organic electronic device according to claim 1 or 2, wherein M is selected from the group comprising of a metal ion wherein the corresponding metal has an electronegativity value according to Allen of less than 2.4, an alkali, alkaline earth, rare earth or transition metal, a metal with an atomic mass≥24 Da, a metal with an atomic mass≥24 Da and M has an oxidation number≥2.

8. The organic electronic device according to claim 1 or 2, wherein the metal complex has a molecular weight Mw of ≥287 and ≤2000 g/mol.

9. The organic electronic device according to claim 1 or 2, wherein L is selected from a group comprising at least three carbon atoms, alternatively at least four carbon atoms, and/or at least two oxygen atoms or one oxygen and one nitrogen atom, two to four oxygen atoms, two to four oxygen atoms and zero to two nitrogen atoms, and/or at least one or more groups selected from halogen, F, CN, substituted or unsubstituted C.sub.1 to C.sub.6 alkyl, substituted or unsubstituted C.sub.1 to C.sub.6 alkoxy, alternatively two or more groups selected from halogen, F, CN, substituted or unsubstituted C.sub.1 to C.sub.6 alkyl, substituted or unsubstituted C.sub.1 to C.sub.6 alkoxy, at least one or more groups selected from halogen, F, CN, substituted C.sub.1 to C.sub.6 alkyl, substituted C.sub.1 to C.sub.6 alkoxy, alternatively two or more groups selected from halogen, F, CN, perfluorinated C.sub.1 to C.sub.6 alkyl, perfluorinated C.sub.1 to C.sub.6 alkoxy, one or more groups selected from substituted or unsubstituted C.sub.1 to C.sub.6 alkyl, substituted or unsubstituted C.sub.6 to C.sub.12 aryl, and/or substituted or unsubstituted C.sub.3 to C.sub.12 heteroaryl, wherein the substituents are selected from D, C.sub.6 aryl, C.sub.3 to C.sub.9 heteroaryl, C.sub.1 to C.sub.6 alkyl, C.sub.1 to C.sub.6 alkoxy, C.sub.3 to C.sub.6 branched alkyl, C.sub.3 to C.sub.6 cyclic alkyl, C.sub.3 to C.sub.6 branched alkoxy, C.sub.3 to C.sub.6 cyclic alkoxy, partially or perfluorinated C.sub.1 to C.sub.16 alkyl, partially or perfluorinated C.sub.1 to C.sub.16 alkoxy, partially or perdeuterated C.sub.1 to C.sub.6 alkyl, partially or perdeuterated C.sub.1 to C.sub.6 alkoxy, COR.sup.E, COOR.sup.6, halogen, F or CN; wherein R.sup.6 is selected from C.sub.6 aryl, C.sub.3 to C.sub.9 heteroaryl, C.sub.1 to C.sub.6 alkyl, C.sub.1 to C.sub.6 alkoxy, C.sub.3 to C.sub.6 branched alkyl, C.sub.3 to C.sub.6 cyclic alkyl, C.sub.3 to C.sub.6 branched alkoxy, C.sub.3 to C.sub.6 cyclic alkoxy, partially or perfluorinated C.sub.1 to C.sub.16 alkyl, partially or perfluorinated C.sub.1 to C.sub.16 alkoxy, partially or perdeuterated C.sub.1 to C.sub.6 alkyl, partially or perdeuterated C.sub.1 to C.sub.6 alkoxy.

10. The organic electronic device according to claim 1 or 2, wherein the metal complex according to formula (II) is non-emissive.

11. The organic electronic device according to claim 1 or 2, wherein the hole injection layer comprises a hole transport compound and a metal complex: wherein the hole transport compound has the formula (I):
(Ar.sup.1).sub.k—(Ar.sup.2).sub.m-Ar.sup.3—(Ar.sup.4).sub.p—(Ar.sup.5).sub.q—(Ar.sup.6).sub.r  (I), wherein k, m, q, r are independently from each other 0, 1 or 2, p is 1, 2 or 3, wherein 2≤k+m+q+r+p≤11, Ar.sup.1 to Ar.sup.6 are independently selected from substituted or unsubstituted unsaturated 5- to 7-member ring of a heterocycle, substituted or unsubstituted C.sub.6 to C.sub.30 aryl, substituted or unsubstituted C.sub.3 to C.sub.30 heteroaryl, a substituted or unsubstituted fluorene, or a fused ring system comprising 2 to 6 substituted or unsubstituted 5- to 7-member rings and the rings are selected from the group comprising (i) unsaturated 5- to 7-member ring of a heterocycle, (ii) 5- to 6-member of an aromatic heterocycle, (iii) unsaturated 5- to 7-member ring of a non-heterocycle, (iv) 6-member ring of an aromatic non-heterocycle; Ar.sup.2 if k=1, Ar.sup.3, Ar.sup.4 if q=1, Ar.sup.y if r=1: are independently selected from substituted or unsubstituted unsaturated 5- to 7-member ring of a heterocycle, substituted or unsubstituted C.sub.6 to C.sub.30 arylene, substituted or unsubstituted C.sub.3 to C.sub.30 heteroarylene, substituted or unsubstituted biphenylene, substituted or unsubstituted fluorene, substituted or unsubstituted naphthalene, substituted or unsubstituted anthracene, substituted or unsubstituted phenanthrene, substituted or unsubstituted pyrene, substituted or unsubstituted perylene, substituted or unsubstituted triphenylene, substituted or unsubstituted tetracene, substituted or unsubstituted tetraphene, substituted or unsubstituted dibenzofurane, substituted or unsubstituted dibenzothiophene, substituted or unsubstituted xanthene, substituted or unsubstituted carbazole, substituted or unsubstituted azepine, substituted or unsubstituted dibenzo[b,f]azepine, 9,9′-spirobi[fluorene], substituted or unsubstituted spiro[fluorene-9,9′-xanthene], substituted or unsubstituted 9,14-dihydrodibenzo[2,3:6,7]azepino[4,5-b]indole, or a substituted or unsubstituted aromatic fused ring system comprising at least three substituted or unsubstituted aromatic rings selected from the group comprising substituted or unsubstituted non-hetero, substituted or unsubstituted hetero 5-member rings, substituted or unsubstituted 6-member rings and/or substituted or unsubstituted 7-member rings; Ar.sup.2 if k=0, Ar.sup.3 if m=0 and k=0, Ar.sup.4 if q and r=0, Ar.sup.y if r=0: are independently selected from substituted or unsubstituted unsaturated 5- to 7-member ring of a heterocycle, substituted or unsubstituted C.sub.6 to C.sub.30 aryl, substituted or unsubstituted C.sub.3 to C.sub.30 heteroaryl, substituted or unsubstituted biphenyl, substituted or unsubstituted fluorenyl, substituted or unsubstituted naphthalenyl, substituted or unsubstituted anthracenyl, substituted or unsubstituted phenanthrenyl, substituted or unsubstituted pyrenyl, substituted or unsubstituted perylenyl, substituted or unsubstituted triphenylenyl, substituted or unsubstituted tetracenyl, substituted or unsubstituted tetraphenyl, substituted or unsubstituted dibenzofuranyl, substituted or unsubstituted dibenzothiophenyl, substituted or unsubstituted xanthenyl, substituted or unsubstituted carbazole, substituted or unsubstituted azepine, substituted or unsubstituted dibenzo[b,f]azepine, 9,9′-spirobi[fluorenyl], substituted or unsubstituted spiro[fluorenyl-9,9′-xanthene], substituted or unsubstituted 9,14-dihydrodibenzo[2,3:6,7]azepino[4,5-b]indole, or a substituted or unsubstituted aromatic fused ring system comprising at least three substituted or unsubstituted aromatic rings selected from the group comprising substituted or unsubstituted non-hetero, substituted or unsubstituted hetero 5-member rings, substituted or unsubstituted 6-member rings and/or substituted or unsubstituted 7-member rings; wherein the substituents are selected from the group H, D, C.sub.1 to C.sub.12 alkyl, unsubstituted C.sub.6 to C.sub.18 aryl, or unsubstituted C.sub.3 to C.sub.18 heteroaryl; and wherein the metal complex has the formula (II).

12. The organic electronic device according to claim 1 or 2, wherein the hole transport compound is selected from a group of compounds comprising at least ≥1 to ≤6 substituted or unsubstituted aromatic fused ring systems comprising heteroaromatic rings, at least ≥1 to ≤3 substituted or unsubstituted unsaturated 5- to 7-member ring of a heterocycle, ≥2 to ≤5 substituted or unsubstituted aromatic fused ring systems comprising heteroaromatic rings, at least ≥1 to ≤3 substituted or unsubstituted unsaturated 5- to 7-member ring of a heterocycle, 3 or 4 substituted or unsubstituted aromatic fused ring systems comprising heteroaromatic rings, at least ≥1 to ≤3 substituted or unsubstituted unsaturated 5- to 7-member ring of a heterocycle, an aromatic fused ring systems comprising heteroaromatic rings are unsubstituted, or at least ≥1 to ≤3 unsubstituted unsaturated 5- to 7-member ring of a heterocycle.

13. The organic electronic device according to claim 1 or 2, wherein the hole transport compound according to claim 1 or 2 is selected from a group of compounds comprising a substituted or unsubstituted aromatic fused ring systems with at least ≥2 to ≤6 fused aromatic rings selected from the group comprising substituted or unsubstituted non-hetero aromatic rings, substituted or unsubstituted hetero 5-member rings, substituted or unsubstituted 6-member rings and/or substituted or unsubstituted unsaturated 5- to 7-member ring of a heterocycle an unsubstituted aromatic fused ring systems with at least ≥2 to ≤6 fused aromatic rings selected from the group comprising unsubstituted non-hetero aromatic rings, unsubstituted hetero 5-member rings, unsubstituted 6-member rings and unsubstituted unsaturated 5- to 7-member ring of a heterocycle.

14. The organic electronic device according to claim 1 or 2, wherein the hole transport compound according to claim 1 or 2 is selected from a group of compounds comprising at least at least ≥1 to ≤6 of the substituted or unsubstituted aromatic fused ring systems with at least one unsaturated 5-member ring, at least one unsaturated 6-member ring, at least one unsaturated 7-member ring, at least one unsaturated 5- or at least one unsaturated 7-member ring comprising at least 1 to 3 hetero-atoms.

15. The organic electronic device according to claim 1 or 2, wherein for the hole transport compound according to claim 1 or the hole transport compound of formula (I) the hetero-atom is selected from the group comprising O, S, N, B or P.

16. The organic electronic device according to claim 1 or 2, wherein the hole transport compound according to claim 1 or 2 is selected from a group of compounds that is free of hetero-atoms which are not part of an aromatic ring and/or part of an unsaturated 7-member-ring, or is free on N-atoms except N-atoms which are part of an aromatic ring or are part of an unsaturated 7-member-ring.

17. The organic electronic device according to claim 1 or 2, wherein the hole transport compound according to claim 1 or 2 is selected from a group of compounds comprising: at least ≥6 to ≤12 aromatic rings; at least ≥4 to ≤11 non-hetero aromatic rings; at least ≥1 to ≤4 aromatic 5-member-rings; at least 1 or 2 unsaturated 5- to 7-member-ring of a heterocycle; at least ≥6 to ≤12 aromatic rings, wherein therefrom at least ≥4 to ≤11 are non-hetero aromatic rings, and at least ≥1 to ≤4 aromatic rings are hetero aromatic rings, wherein the total number of non-hetero aromatic rings and hetero aromatic rings in total does not exceed 12 aromatic rings; at least ≥6 to ≤12 aromatic rings, wherein therefrom at least ≥4 to ≤11, are non-hetero aromatic rings, and at least ≥1 to ≤4 aromatic rings are hetero aromatic rings, wherein the total number of non-hetero aromatic rings and hetero aromatic rings in total does not exceed 12 aromatic rings; and the hole transport compound comprises at least ≥1 to ≤4 aromatic 5-member-rings.

18. The organic electronic device according to claim 1 or 2, wherein for formula (I): Ar.sup.3 is selected from D1 to D17: ##STR00073## ##STR00074## Ar.sup.1 is selected from D7 to D15 and D17, if m>0 and k>0, or is selected from D7 to D15 and D17, if k>0 and m=0, or is selected from D1 to D6, if k>1; Ar.sup.2 is selected from D1 to D6, if m>0 and k>0; or is selected from D7 to D15 and D17, if m>0 and k=0; Ar.sup.4 is selected from D1 to D6, if q>0, or is selected from D1 to D6, if q=0 and r>0; or is selected from D7 to D15 and D17, if q and r=0; Ar.sup.5 is selected from D1 to D6, if q≥0 and r≥0, or is selected from D7 to D15 and D17, if q≥0 and r=0; Ar.sup.6 is selected from D7 to D15 and D17, if r>0, q>0, or is selected from D7 to D15 and D17, if r>0, q=0, or is selected from D1 to D6, if r>1.

19. The organic electronic device according to claim 1 or 2, wherein the hole transport compound according claim 1 or the hole transport compound according to formula (I) is selected from F1 to F13: ##STR00075## ##STR00076## ##STR00077##

20. The organic electronic device according to claim 1 or 2, wherein n is an integer from 1 to 4.

21. The organic electronic device according to claim 1 or 2, wherein the metal complex may be selected from the following formulas (IIa) to (IIe): ##STR00078## wherein M is a metal ion; n is the valency of M, wherein n is an integer from 1 to 4; A.sup.1 and A.sup.2 are independently selected from substituted or unsubstituted C.sub.1 to C,2 alkyl, substituted or unsubstituted C.sub.6 to C.sub.12 aryl, substituted or unsubstituted C.sub.3 to C.sub.12 heteroaryl; A.sup.3 is selected from H, D, substituted or unsubstituted C.sub.1 to C.sub.12 alkyl, substituted or unsubstituted C.sub.6 to C.sub.12 aryl, substituted or unsubstituted C.sub.3 to C.sub.12 heteroaryl; wherein the substituents of A.sup.1 and A.sup.2 and/or A.sup.3 are independently selected from D, C.sub.6 aryl, C.sub.3 to C.sub.9 heteroaryl, C.sub.1 to C.sub.6 alkyl, C.sub.1 to C.sub.6 alkoxy, C.sub.3 to C.sub.6 branched alkyl, C.sub.3 to C.sub.6 cyclic alkyl, C.sub.3 to C.sub.6 branched alkoxy, C.sub.3 to C.sub.6 cyclic alkoxy, partially or perfluorinated C.sub.1 to C.sub.16 alkyl, partially or perfluorinated C.sub.1 to C.sub.16 alkoxy, partially or perdeuterated C.sub.1 to C.sub.6 alkyl, partially or perdeuterated C.sub.1 to C.sub.6 alkoxy, COR.sup.1 COOR.sup.1 halogen, F or CN, wherein is selected from C.sub.6 aryl, C.sub.3 to C.sub.9 heteroaryl, C.sub.1 to C.sub.6 alkyl, C.sub.1 to C.sub.6 alkoxy, C.sub.3 to C.sub.6 branched alkyl, C.sub.3 to C.sub.6 cyclic alkyl, C.sub.3 to C.sub.6 branched alkoxy, C.sub.3 to C.sub.6 cyclic alkoxy, partially or perfluorinated C.sub.1 to C.sub.16 alkyl, partially or perfluorinated C.sub.1 to C.sub.16 alkoxy, partially or perdeuterated C.sub.1 to C.sub.6 alkyl, partially or perdeuterated C.sub.1 to C.sub.6 alkoxy.

22. The organic electronic device according to claim 21, wherein A.sup.1 and A.sup.2 and/or A.sup.3 are selected from a group wherein at least one of A.sup.1 and A.sup.2 and/or A.sup.3 comprises a substituent, wherein at least one of the substituents of A.sup.1 and A.sup.2 and/or A.sup.3 is independently selected from C.sub.3 to C.sub.9 heteroaryl, C.sub.1 to C.sub.6 alkoxy, C.sub.3 to C.sub.6 branched alkoxy, C.sub.3 to C.sub.6 cyclic alkoxy, partially or perfluorinated C.sub.1 to C.sub.16 alkyl, partially or perfluorinated C.sub.1 to C.sub.16 alkoxy, partially or perdeuterated C.sub.1 to C.sub.6 alkoxy, COR.sup.1, COOR.sup.1, halogen, F or CN, at least one of A.sup.1 and A.sup.2 and/or A.sup.3 comprises at least two substituents, wherein the substituents on A.sup.1 and A.sup.2 and/or A.sup.3 are independently selected from C.sub.3 to C.sub.9 heteroaryl, C.sub.1 to C.sub.6 alkoxy, C.sub.3 to C.sub.6 branched alkoxy, C.sub.3 to C.sub.6 cyclic alkoxy, partially or perfluorinated C.sub.1 to C.sub.16 alkyl, partially or perfluorinated C.sub.1 to C.sub.16 alkoxy, partially or perdeuterated C.sub.1 to C.sub.6 alkoxy, COR.sup.1, COOR.sup.1, halogen, F or CN.

23. The organic electronic device according to claim 1, 2, or 22, wherein L is independently selected from G1 to G64: ##STR00079## ##STR00080## ##STR00081## ##STR00082## ##STR00083## ##STR00084## ##STR00085##

24. The organic electronic device according to claim 1 or 2, wherein the organic electronic device further comprises at least one photoactive layer, wherein the photoactive layer is arranged between the hole injection layer and the cathode layer.

25. The organic electronic device according to claim 1 or 2, wherein the at least one photoactive layer is an emission layer.

26. The organic electronic device according to claim 1 or 2, wherein the hole injection layer comprises a first sub-layer comprising the metal complex of formula (II) and a second sub-layer comprising the hole transport compound according to claim 1 or a hole transport compound of formula (I), wherein the first sub-layer is arranged closer to the anode layer and the second sub-layer is arranged closer to the cathode layer.

27. The organic electronic device according to claim 1 or 2, wherein the hole injection layer comprises a first sub-layer consisting of the metal complex of formula (II) and a second sub-layer comprising the hole transport compound according to claim 1 or a hole transport compound of formula (I), wherein the first sub-layer is arranged closer to the anode layer and the second sub-layer is arranged closer to the cathode layer.

28. The organic electronic device according to claim 1 or 2, wherein the hole injection layer comprises a first sub-layer comprising the metal complex of formula (II) and a second sub-layer comprising the hole transport compound according to claim 1 or the hole transport compound of formula (I) and the metal complex, wherein the first sub-layer is arranged closer to the anode layer and the second sub-layer is arranged closer to the cathode layer.

29. The organic electronic device according to claim 1 or 2, wherein the organic electronic device further comprises a hole transport layer, wherein the hole transport layer is arranged between the hole injection layer and the cathode layer, alternatively the hole transport layer is arranged between the hole injection layer and the at least one photoactive layer or at least one emission layer.

30. The organic electronic device according to claim 1 or 2, wherein the hole transport layer comprises the hole transport compound according to claim 1 or 2.

31. The organic electronic device according to claim 1 or 2, wherein the electronic device is a light emitting device, thin film transistor, a display device or a photovoltaic cell.

32. The organic electronic device according to claim 30, wherein the hole transport compound of formula (I) in the hole injection layer and in the hole transport layer are selected the same.

Description

DESCRIPTION OF THE DRAWINGS

[0427] The aforementioned components, as well as the claimed components and the components to be used in accordance with the invention in the described embodiments, are not subject to any special exceptions with respect to their size, shape, material selection and technical concept such that the selection criteria known in the pertinent field can be applied without limitations.

[0428] Additional details, characteristics and advantages of the object are disclosed in the dependent claims and the following description of the respective figures which in an exemplary fashion show preferred embodiments according to the invention. Any embodiment does not necessarily represent the full scope, however, and reference is made therefore to the claims and herein for interpreting the scope. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide further explanation of the present invention as claimed.

[0429] FIG. 1 is a schematic sectional view of an organic electronic device, according to an exemplary embodiment of the present invention;

[0430] FIG. 2 is a schematic sectional view of an organic light-emitting diode (OLED), according to an exemplary embodiment of the present invention;

[0431] FIG. 3 is a schematic sectional view of an OLED, according to an exemplary embodiment of the present invention.

[0432] Hereinafter, the figures are illustrated in more detail with reference to examples. However, the present disclosure is not limited to the following figures.

[0433] Herein, when a first element is referred to as being formed or disposed “on” or “onto” a second element, the first element can be disposed directly on the second element, or one or more other elements may be disposed there between. When a first element is referred to as being formed or disposed “directly on” or “directly onto” a second element, no other elements are disposed there between.

[0434] FIG. 1 is a schematic sectional view of an organic electronic device 100, according to an exemplary embodiment of the present invention. The organic electronic device 100 includes a substrate 110, an anode layer 120 and a hole injection layer (HIL) (130). The HIL 130 is disposed on the anode layer 120. Onto the HIL 130, a photoactive layer (PAL) 170 and a cathode layer 190 are disposed.

[0435] The hole injection layer (HIL) 130 may comprise a first and a second sub-layer wherein the first sub-layer is disposed on the anode and the second sub-layer is disposed on the first sub-layer. The photoactive layer (PAL) 170 is disposed on the second-sub-layer.

[0436] FIG. 2 is a schematic sectional view of an organic light-emitting diode (OLED) 100, according to an exemplary embodiment of the present invention. The OLED 100 includes a substrate 110, an anode layer 120 and a hole injection layer (HIL) 130, The HIL 130 is disposed on the anode layer 120. Onto the HIL 130, a hole transport layer (HTL) 140, an emission layer (EML) 150, an electron transport layer (ETL) 160, an electron injection layer (EIL) 180 and a cathode layer 190 are disposed. Instead of a single electron transport layer 160, optionally an electron transport layer stack (ETL) can be used.

[0437] The hole injection layer (HIL) 130 may comprise a first and a second sub-layer wherein the first sub-layer is disposed on the anode and the second sub-layer is disposed on the first sub-layer. The hole transport layer (HTL) 140 is disposed on the second-sub-layer.

[0438] FIG. 3 is a schematic sectional view of an OLED 100, according to another exemplary embodiment of the present invention. FIG. 2 differs from FIG. 1 in that the OLED 100 of FIG. 2 comprises an electron blocking layer (EBL) 145 and a hole blocking layer (HBL) 155.

[0439] Referring to FIG. 3, the OLED 100 includes a substrate 110, an anode layer 120, a hole injection layer (HIL) 130, a hole transport layer (HTL) 140, an electron blocking layer (EBL) 145, an emission layer (EML) 150, a hole blocking layer (HBL) 155, an electron transport layer (ETL) 160, an electron injection layer (EIL) 180 and a cathode layer 190.

[0440] While not shown in FIG. 1, FIG. 2 and FIG. 3, a sealing layer may further be formed on the cathode layer 190, in order to seal the organic electronic device 100. In addition, various other modifications may be applied thereto.

[0441] Hereinafter, the embodiments are illustrated in more detail with reference to examples. However, the present disclosure is not limited to the following examples.

DETAILED DESCRIPTION

[0442] The invention is furthermore illustrated by the following examples which are illustrative only and non-binding.

[0443] Hole transport compounds and hole transport compound of formula (I) and metal complexes of formula (II) may be prepared as described in the literature.

Rate Onset Temperature

[0444] The rate onset temperature (TRO) is determined by loading 100 mg hole transport compound into a VTE source. As VTE source a point source for organic materials may be used as supplied by Kurt J. Lesker Company (www.lesker.com) or CreaPhys GmbH (http://www.creaphys.com). The VTE source is heated at a constant rate of 15 K/min at a pressure of less than 10.sup.−5 mbar and the temperature inside the source measured with a thermocouple. Evaporation of the hole transport compound is detected with a QCM detector which detects deposition of the hole transport compound on the quartz crystal of the detector. The deposition rate on the quartz crystal is measured in Ångstrom per second. To determine the rate onset temperature, the deposition rate is plotted against the VTE source temperature. The rate onset is the temperature at which noticeable deposition on the QCM detector occurs. For accurate results, the VTE source is heated and cooled three time and only results from the second and third run are used to determine the rate onset temperature.

[0445] To achieve good control over the evaporation rate of a metal complex of formula (II), the rate onset temperature may be in the range of ≥110° C. to ≤300° C., preferably ≥115° C. to ≤290° C. If the rate onset temperature is too low the evaporation may be too rapid and therefore difficult to control. If the rate onset temperature is too high the evaporation rate may be too low which may result in low tact time and/or decomposition of the metal complex of formula (II) in VTE source may occur due to prolonged exposure to elevated temperatures.

[0446] To achieve good control over the evaporation rate of the hole transport compound of the present invention, the rate onset temperature may be in the range of 120° C. to 300° C. If the rate onset temperature is too low the evaporation may be too rapid and therefore difficult to control. If the rate onset temperature is too high the evaporation rate may be too low which may result in low tact time.

[0447] The rate onset temperature is an indirect measure of the volatility of a compound. The higher the rate onset temperature the lower is the volatility of a compound.

HOMO and LUMO

[0448] The HOMO level and LUMO level are calculated with the program package TURBOMOLE V6.5 (TURBOMOLE GmbH, Litzenhardtstrasse 19, 76135 Karlsruhe, Germany). The optimized geometries and the HOMO level and LUMO levels of the molecular structures are determined by applying the hybrid functional B3LYP with a 6-31G* basis set in the gas phase. If more than one conformation is viable, the conformation with the lowest total energy may be selected. The HOMO and LUMO levels are recorded in electron volt (eV).

General Procedure for Fabrication of OLEDs Comprising a Hole Injection Layer and an Emission Layer Comprising a Fluorescent Blue Emitter

[0449] For OLEDs, see Examples 1 to 11 and comparative examples 1 to 3 in Table 3 and 4, a 15Ω/cm.sup.2 glass substrate with 90 nm ITO (available from Corning Co.) was cut to a size of 50 mm×50 mm×0.7 mm, ultrasonically washed with isopropyl alcohol for 5 minutes and then with pure water for 5 minutes, and washed again with UV ozone for 30 minutes, to prepare the anode layer.

[0450] Then, 70 vol.-% hole transport compound and 30 vol.-% metal complex were co-deposited in vacuum on the anode layer, to form a hole injection layer (HIL) having a thickness of 10 nm. The composition of the hole injection layer can be seen in Table 3 and 4. In comparative examples 1 to 3.70 vol.-% hole transport compound and 30 vol.-% HAT-CN were co-deposited in vacuum on the anode layer to form a HIL having a thickness of 10 nm.

[0451] Then, the hole transport compound was vacuum deposited on the HIL, to form a HTL having a thickness of 128 nm. The hole transport compound in the HTL is selected the same as the hole transport compound in the HIL. The hole transport compound can be seen in Table 3 and 4.

[0452] Then N,N-bis(4-(dibenzo[b,d]furan-4-yl)phenyl)-[1,1′:4′,1″-terphenyl]-4-amine (CAS 1198399-61-9) was vacuum deposited on the HTL, to form an electron blocking layer (EBL) having a thickness of 5 nm.

[0453] Then 97 vol.-% HTC-6 as EML host and 3 vol.-% BD200 (Sun Fine Chemicals, Korea) as fluorescent blue emitter dopant were deposited on the EBL, to form a blue-emitting EML with a thickness of 20 nm.

[0454] Then a hole blocking layer was formed with a thickness of 5 nm by depositing 2-(3′-(9,9-dimethyl-9H-fluoren-2-yl)-[1,1′-biphenyl]-3-yl)-4,6-diphenyl-1,3,5-triazine on the emission layer EML.

[0455] Then the electron transporting layer having a thickness of 31 nm was formed on the hole blocking layer by depositing 50 wt.-% 4′-(4-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)naphthalen-1-yl)[1,1′-biphenyl]-4-carbonitrile and 50 wt.-% of LiQ

[0456] Then Al was evaporated at a rate of 0.01 to 1 Å/s at 10.sup.−7 mbar to form a cathode layer with a thickness of 100 nm on the electron transporting layer.

[0457] The OLED stack was protected from ambient conditions by encapsulation of the device with a glass slide. Thereby, a cavity is formed, which includes a getter material for further protection.

General Procedure for Fabrication of OLEDs Comprising a Hole Injection Layer and an Emission Layer Comprising a Phosphorescent Green Emitter

[0458] For OLEDs, see Examples 12 and 13 and comparative examples 4 and 5 in Table 5, a 15Ω/cm.sup.2 glass substrate with 90 nm ITO (available from Corning Co.) was cut to a size of 50 mm×50 mm×0.7 mm, ultrasonically washed with isopropyl alcohol for 5 minutes and then with pure water for 5 minutes, and washed again with UV ozone for 30 minutes, to prepare the anode layer.

[0459] Then, 70 vol.-% hole transport compound and 30 vol.-% metal complex were co-deposited in vacuum on the anode layer, to form a hole injection layer (HIL) having a thickness of 10 nm. The composition of the hole injection layer can be seen in Table 5. In comparative examples 4 and 5.70 vol.-% hole transport compound and 30 vol.-% HAT-CN were deposited on the anode layer to form a HIL having a thickness of 10 nm.

[0460] Then, the hole transport compound was vacuum deposited on the HIL, to form a HTL having a thickness of 165 nm. The hole transport compound in the HTL is selected the same as the hole transport compound in the HIL. The hole transport compound can be seen in Table 5.

[0461] Then, 90 vol.-% GH-1 as EML host and 10 vol.-% GD-1 as phosphorescent green emitter dopant were co-deposited in vacuum on the HTL, to form a green-emitting EML with a thickness of 40 nm. The formulas of GH-1 and GD-1 are shown below:

##STR00041##

[0462] Then a hole blocking layer was formed with a thickness of 25 nm by depositing 2,4-diphenyl-6-(3′-(triphenylen-2-yl)-[1,1′-biphenyl]-3-yl)-1,3,5-triazine on the emission layer EML.

[0463] Then the electron transporting layer having a thickness of 10 nm was formed on the hole blocking layer by depositing 99 vol.-% 3-Phenyl-3H-benzo[b]dinaphtho[2,1-d:1′,2′-f]phosphepine-3-oxide and 1 vol.-% Yb.

[0464] Then Al was evaporated at a rate of 0.01 to 1 Å/s at 10.sup.−7 mbar to form a cathode layer with a thickness of 100 nm on the electron transporting layer.

[0465] The OLED stack is protected from ambient conditions by encapsulation of the device with a glass slide. Thereby, a cavity is formed, which includes a getter material for further protection.

General Procedure for Fabrication of OLEDs Comprising a Hole Injection Layer Comprising a First and Second Sub-Layer

[0466] For OLEDs, see Examples 14 to 28 and comparative examples 6 to 11 in Table 6, a 15Ω/cm.sup.2 glass substrate with 90 nm ITO (available from Corning Co.) was cut to a size of 50 mm×50 mm×0.7 mm, ultrasonically washed with isopropyl alcohol for 5 minutes and then with pure water for 5 minutes, and washed again with UV ozone for 30 minutes, to prepare the anode layer.

[0467] Then, the hole injection layer comprising a first and a second sub-layer was vacuum deposited on the anode layer. First, a metal complex was vacuum deposited on the anode layer to form a first sub-layer with a thickness of 3 or 5 nm, see Table 6. In comparative examples 6 to 11, HAT-CN is deposited on the anode layer to form a first sub-layer with a thickness of 3 or 5 nm, see Table 6.

[0468] Then, the hole transport compound was vacuum deposited on the first sub-layer to form a second sub-layer with a thickness of 7 or 5 nm, see Table 6.

[0469] Then, the hole transport compound was vacuum deposited on the hole injection layer to form a HTL. The hole transport compound in the HTL is selected the same as the hole transport compound in the HIL, see Table 6. The thickness is selected in such a way, that the thickness of the second sub-layer and the thickness of the HTL add up to 128 nm in total.

[0470] Then N,N-bis(4-(dibenzo[b,d]furan-4-yl)phenyl)-[1,1′:4′,1″-terphenyl]-4-amine (CAS 1198399-61-9) was vacuum deposited on the HTL, to form an electron blocking layer (EBL) having a thickness of 5 nm.

[0471] Then 97 vol.-% HTC-6 as EML host and 3 vol.-% BD200 (Sun Fine Chemicals, Korea) as fluorescent blue emitter dopant were deposited on the EBL, to form a blue-emitting EML with a thickness of 20 nm.

[0472] Then a hole blocking layer was formed with a thickness of 5 nm by depositing 2-(3′-(9,9-dimethyl-9H-fluoren-2-yl)-[1,1′-biphenyl]-3-yl)-4,6-diphenyl-1,3,5-triazine on the emission layer EML.

[0473] Then the electron transporting layer having a thickness of 31 nm was formed on the hole blocking layer by depositing 50 wt.-% 4′-(4-(4-(4,6-diphenyl-1,3,5-triazin yl)phenyl)naphthalen-1-yl)-[1,1′-biphenyl]-4-carbonitrile and 50 wt.-% of LiQ

[0474] Then Al was evaporated at a rate of 0.01 to 1 Å/s at 10.sup.−7 mbar to form a cathode layer with a thickness of 100 nm on the electron transporting layer.

[0475] The OLED stack is protected from ambient conditions by encapsulation of the device with a glass slide. Thereby, a cavity is formed, which may include a getter material for further protection.

[0476] To assess the performance of the inventive examples compared to the prior art, the current efficiency is measured at 20° C. The current-voltage characteristic is determined using a Keithley 2635 source measure unit, by sourcing an operating voltage U in V and measuring the current in mA flowing through the device under test. The voltage applied to the device is varied in steps of 0.1V in the range between 0V and 10V. To protect the instruments from damage, the measurement was stopped at 10 V.

Technical Effect

[0477] In order to investigate the usefulness of the inventive hole injection layer preferred materials were tested in view of their physical properties, see Tables 1 and 2.

[0478] In Table 1 are shown the HOMO levels calculated with program TURBOMOLE V6.5 (TURBOMOLE GmbH, Litzenhardtstrasse 19, 76135 Karlsruhe, Germany) and the rate onset temperatures TRO of hole transport compounds of the present invention.

TABLE-US-00002 TABLE 1 Chemical formulas and physical properties of hole transport compounds of the present invention HOMO level T.sub.RO Name Chemical formula (eV) (° C.) 9-phenyl-10-(3′,4,5′- triphenyl-[1,1′:2′,1″ terphenyl]-3-yl)anthracene HTC-1 [00042] −5.04 210 1,3-bis(10-phenylanthracen- 9-yl)benzene HTC-2 [00043] −5.08 230 9-phenyl-10-(3′-(9-phenyl- 9H-fluoren-9-yl)-[1,1′- biphenyl]-3-yl)anthracene HTC-3 [00044] −5.08 226 9-([1,1′-biphenyl]-3-yl)-9′- ([1,1′-biphenyl]-4-yl)- 9H,9′H-3,3′-bicarbazole HTC-4 [00045] −5.09 265 9-(4-(naphthalen-1- yl)phenyl)-10- phenylanthracene HTC-5 [00046] −5.1 approx. 130 2-(10-phenylanthracen-9- yl)dibenzo[b,d]furan HTC-6 [00047] −5.11 — 2-phenyl-8-(10- phenylanthracen-9- yl)dibenzo[b,d]furan HTC-7 [00048] −5.13 216 7-(3-(10-phenylanthracen-9- yl)phenyl)dibenzo[c,h]acridine HTC-8 [00049] −5.17 282 7-(4-(3,6-diphenyl-9H- carbazol-9- yl)phenyl)dibenzo[c,h]acridine HTC-9 [00050] −5.28 291 4,4′-Bis(carbazol-9-yl)- biphenyl HTC-10 [00051] −5.3 approx. 240 2,7-di([1,1′-biphenyl]-4- yl)spiro[fluorene-9,9′- xanthene] HTC-11 [00052] −5.38 242 7-(3-(9H-carbazol-9- yl)phenyl)dibenzo[c,h]acridine HTC-12 [00053] −5.42 214 4,4′,4″-(1,3,5- Benzenetriyl)tris[dibenzo- thiophene] HTC-13 [00054] −5.67 272

[0479] As can be seen in Table 1, the hole transport compounds have rate onset temperatures suitable for mass production of organic electronic devices.

[0480] In Table 2 are shown rate onset temperatures TRO for metal complexes of formula (II).

TABLE-US-00003 TABLE 2 Metal complexes of formula (II) T.sub.RO Name Chemical formula (° C.) MC-1  Li TFSI 222 MC-2  K TFSI 236 MC-3  Cs TFSI 224 MC-4  Ag TFSI 258 MC-5  Mg (TFSI).sub.2 243 MC-6  Mn (TFSI).sub.2 229 MC-7  Sc (TFSI).sub.3 258 MC-8  Mg [N(SO.sub.2.sup.iC.sub.3F.sub.7).sub.2].sub.2 166 MC-9  Zn [N(SO.sub.2.sup.iC.sub.3F.sub.7).sub.2].sub.2 118 MC-10 Ag [N(SO.sub.2.sup.iC.sub.3F.sub.7).sub.2].sub.2 232 MC-11 Ag [N(SO.sub.2C3F.sub.7).sub.2] 254 MC-12 Ag [N(SO.sub.2C.sub.4F.sub.9).sub.2] 262 MC-13 Ag [N(SO.sub.2CF.sub.3)(SO.sub.2C.sub.4F.sub.9)] 230 MC-14 Cu [N(SO.sub.2.sup.iC.sub.3F.sub.7).sub.2].sub.2 101 MC-15 Cu [N(SO.sub.2C.sub.3F.sub.7).sub.2].sub.2 118 MC-16 Cu [N(SO.sub.2CF.sub.3) (SO.sub.2C.sub.4F.sub.9)].sub.2 113 MC-17 Mg [N(SO.sub.2CF.sub.3) (SO.sub.2C.sub.4F.sub.9)].sub.2 124 MC-18 Mn [N(SO.sub.2CF.sub.3) (SO.sub.2C.sub.4F.sub.9)].sub.2 202 MC-19 Cu [N(SO.sub.2CH.sub.3) (SO.sub.2C.sub.4F.sub.9)].sub.2 179 MC-20 Ag [N(SO.sub.2CH.sub.3) (SO.sub.2C.sub.4F.sub.9)] — MC-21 [00055] 254 MC-22 [00056] 238 MC-23 [00057] 262 MC-24 [00058] 180 MC-25 [00059] — MC-26 [00060] 167 MC-27 [00061] 282 MC-28 [00062] 263 MC-29 [00063] 194 MC-30 [00064] 190 MC-31 [00065] 128 MC-32 [00066] 196 MC-33 [00067] 105 MC-34 [00068] 187 MC-35 [00069] 194

[0481] As can be seen in Table 2, the metal complexes of formula (II) have rate onset temperatures suitable for mass production of organic electronic devices.

[0482] In Table 3 are shown operating voltages at 10 mA/cm.sup.2 in OLEDs comprising a fluorescent blue emitter and a hole injection layer comprising 70 vol.-% HTC-10 and 30 vol.-% metal complex of formula (II). HTC-10 has a HOMO level of −5.30 eV.

TABLE-US-00004 TABLE 3 Performance of OLEDs comprising a fluorescent blue emitter Hole transport Metal U at 10 compound complex mA/cm.sup.2 [V] Comparative example 1 HTC-10 HAT-CN >10 Example 1 HTC-10 Cu (TFSI).sub.2 6.9 Example 2 HTC-10 MC-24 6.3 Example 3 HTC-10 MC-6 5.3 Example 4 HTC-10 MC-27 5.4 Example 5 HTC-10 MC-29 5.2

[0483] In comparative example 1, HAT-CN, a state of the art material, is used at a concentration of 30 vol.-%. HAT-CN has the formula shown below:

##STR00070##

[0484] HAT-CN has a HOMO of −8.83 eV. The operating voltage is over 10 V.

[0485] In example 1, the hole injection layer comprises Cu(TFSI).sub.2 as metal complex. The operating voltage is substantially improved to 6.9 V.

[0486] In example 2, the hole injection layer comprises a different Cu(II) complex, namely MC-24. Compared to example 1, the TFSI ligand has been replaced by an amide ligand comprising one trifluoro methyl and one substituted aryl group. The operating voltage is further improved to 6.3 V.

[0487] In example 3, the hole injection layer comprises MC-6. Compared to example 1, the Cu(II) cation has been replaced by a Mn(II) cation. The operating voltage compared to example 1 is improved from 6.9 to 5.3 V.

[0488] In example 4, the hole injection layer comprises a Mg complex. Compared to example 2, Cu(II) cation has been replaced by Mg(II) cation. The operating voltage is improved from 6.3 to 5.4 V.

[0489] In example 5, the hole injection layer comprises a Zn(II) complex. Compared to example 4, the Mg(II) cation has been replaced by a Zn(II) cation and the amide ligand has been replaced by a ligand comprising an N-aryl group. The operating voltage is still within the range acceptable for mass production.

[0490] In Table 4 are shown operating voltages at 10 mA/cm.sup.2 in OLEDs comprising a fluorescent blue emitter and a hole injection layer comprising 70 vol.-% hole transport compound and 30 vol.-% metal complex of formula (II).

TABLE-US-00005 TABLE 4 Performance of OLEDs comprising a fluorescent blue emitter Hole transport HOMO level Metal U at 10 compound [eV] complex mA/cm.sup.2 [V] Comparative HTC-5 −5.10 HAT-CN >10 example 2 Comparative HTC-13 −5.67 HAT-CN >10 example 3 Example 6 HTC-5 −5.10 MC-29 4.1 Example 7 HTC-6 −5.13 MC-29 4.1 Example 8 HTC-7 −5.13 MC-29 5.1 Example 9 HTC-9 −5.28 MC-29 5.7 Example 10 HTC-10 −5.30 MC-29 5.9 Example 11 HTC-13 −5.67 MC-29 7.0

[0491] In comparative example 2, the hole injection layer comprises hole transport compound HTC-5 and 30 vol.-% HAT-CN. HAT-CN is free of metal complex. HTC-5 comprises an anthracene group. The HOMO level of HTC-5 is −5.10 eV. The operating voltage is over 10 V.

[0492] In comparative example 3, the hole injection layer comprises hole transport compound HTC-13 and 30 vol.-% HAT-CN. HTC-13 comprises three dibenzofuranyl groups. The HOMO level is −5.67 eV and is therefore further away from vacuum level compared to comparative example 2. The operating voltage is over 10 V.

[0493] In example 6, the hole injection layer comprises HTC-5 and metal complex MC-29. The operating voltage is reduced substantially to 4.1 V.

[0494] In example 7, the hole injection layer comprises HTC-6 and metal complex MC-29. HTC-6 comprises an anthracene and a dibenzofuranyl group. The HOMO level is −5.13 eV and is therefore further away from vacuum level compared to comparative example 2. The operating voltage is unchanged at 4.1 V.

[0495] In example 8, the hole injection layer comprises HTC-7 and metal complex MC-29. HTC-7 comprises an anthracene and a dibenzofuranyl group. The HOMO level is −5.13 eV and is therefore further away from vacuum level compared to example 6. The operating voltage is a little bit higher than in example 7. However, the operating voltage is substantially reduced compared to comparative example 2.

[0496] In example 9, the hole injection layer comprises HTC-9 and metal complex MC-29. HTC-9 comprises a dibenzoacridine and a carbazole group. The HOMO level is −5.28 eV and is therefore further away from vacuum level compared to example 6. The operating voltage is a little bit higher than in example 8. However, the operating voltage is substantially reduced compared to comparative example 2.

[0497] In example 10, the hole injection layer comprises HTC-10 and metal complex MC-29. HTC-10 comprises a two carbazole groups. The HOMO level is −5.30 eV and is therefore further away from vacuum level compared to example 9. However, the operating voltage is substantially reduced compared to comparative example 2.

[0498] In example 11, the hole injection layer comprises HTC-13 and metal complex MC-29. HTC-13 comprises three dibenzofuranyl groups. The HOMO level is −5.67 eV and is therefore further away from vacuum level compared to example 6. The operating voltage is a little bit higher than in example 10. However, the operating voltage is substantially reduced compared to comparative example 2.

[0499] In Table 5 are shown operating voltages at 10 mA/cm.sup.2 in OLEDs comprising a phosphorescent green emitter and a hole injection layer comprising a hole transport compound and 30 vol.-% metal complex of formula (II).

TABLE-US-00006 TABLE 5 Performance of OLEDs comprising a phosphorescent green emitter Hole transport HOMO level Metal U at 10 compound [eV] complex mA/cm.sup.2 [V] Comparative HTC-5 −5.10 HAT-CN >10 example 4 Example 12 HTC-5 −5.10 MC-29 4.5 Comparative HTC-10 −5.30 HAT-CN >10 example 5 Example 13 HTC-10 −5.30 MC-29 6.3

[0500] In comparative example 4, the hole injection layer comprises hole transport compound HTC-5 and 30 vol.-% HAT-CN. HTC-5 comprises an anthracene group. The HOMO level of HTC-5 is −5.10 eV. The operating voltage is over 10 V.

[0501] In example 12, the hole injection layer comprises HTC-5 and metal complex MC-29. The operating voltage is reduced substantially to 4.1 V.

[0502] In comparative example 5, the hole injection layer comprises hole transport compound HTC-10 and 30 vol.-% HAT-CN. HTC-10 comprises two carbazole groups. The HOMO level of HTC-10 is −5.30 eV. The operating voltage is over 10 V.

[0503] In example 13, the hole injection layer comprises HTC-10 and metal complex MC-29. The operating voltage is reduced substantially to 6.3 V.

[0504] In Table 6 are shown operating voltages at 10 mA/cm.sup.2 in OLEDs comprising a fluorescent blue emitter and a hole injection layer, wherein the hole injection layer comprises a first sub-layer consisting of metal complex of formula (II) and a second sub-layer consisting of hole transport compound.

[0505] In comparative example 6, the first sub-layer comprises HAT-CN as a state-of-the-art hole injection material with a thickness of 3 nm. The second sub-layer comprises hole transport compound HTC-6. The operating voltage is over 10 V.

[0506] In comparative example 7, the first sub-layer comprises HAT-CN and the second sub-layer comprises hole transport compound HTC-7. The operating voltage is over 10 V.

[0507] In comparative example 8, the first sub-layer comprises HAT-CN and the second sub-layer comprises hole transport compound HTC-10. The operating voltage is over 10 V.

[0508] In Example 14, the first sub-layer comprises metal complex MC-29 with a thickness of 3 nm. The second sub-layer comprises hole transport compound HTC-6. The operating voltage is 4.0 V and thereby substantially improved over comparative example 6.

[0509] In Examples 15 to 17, the first sub-layer is the same as in Example 14. The second sub-layer comprises a range of hole transport compounds with a HOMO level further away from vacuum level than HTC-6. In all examples, the operating voltage is substantially improved over comparative examples 6, 7 and 8.

[0510] In Examples 18 to 20, the first sub-layer comprises metal complex MC-27. MC-27 differs from MC-29 in the metal cation and ligand, see Table 2. The second sub-layer comprises a range of hole transport compounds. In all examples, the operating voltage is substantially improved over comparative examples 6, 7 and 8.

[0511] In Example 21, the first sub-layer comprises metal complex MC-30. MC-30 differs from MC-29 in the metal cation and ligand, see Table 2. The second sub-layer comprises HTC-7. The operating voltage is 6.6 V and thereby improved over comparative example 7.

[0512] In comparative examples 9 to 11, the first sub-layer comprises HAT-CN as a state-of-the-art hole injection material with a thickness of 5 nm. The second sub-layer comprises a range of hole transport compounds. The operating voltage is over 10 V.

[0513] In Example 22, the first sub-layer comprises metal complex MC-29 with a thickness of 5 nm. The second sub-layer comprises hole transport compound HTC-6. The operating voltage is 4.0 V and thereby substantially improved over comparative example 9. The performance is comparable to Example 14.

[0514] In Examples 23 to 25, the first sub-layer is the same as in Example 22. The second sub-layer comprises various hole transport compounds with a HOMO level further away from vacuum level than HTC-6. In all examples, the operating voltage is substantially improved over comparative examples 9, 10 and 11.

[0515] In Examples 26 and 27, the first sub-layer comprises metal complex MC-27. MC-27 differs from MC-29 in the metal cation and ligand, see Table 2. The second sub-layer comprises various hole transport compounds. In all examples, the operating voltage is substantially improved over comparative examples 9, 10 and 11.

[0516] In Example 28, the first sub-layer comprises metal complex MC-30. MC-30 differs from MC-29 in the metal cation and ligand, see Table 2. The second sub-layer comprises HTC-7. The operating voltage is 5.4 V and thereby improved over comparative example 10.

[0517] In summary, a substantial improvement in operating voltage has been obtained for OLEDs comprising a hole injection layer according to invention.

[0518] A reduction in operating voltage may be beneficial for reduced power consumption and improved battery life, in particular in mobile devices.

TABLE-US-00007 TABLE 6 Performance of OLEDs comprising a hole injection layer (HIL), wherein the hole injection layer comprises a first and a second sub-layer Composition Thickness of Composition of HOMO level of hole Thickness of U at 10 of first sub- first sub-layer second sub- transport compound in second sub- Composition mA/cm.sup.2 layer [nm] layer second sub-layer [eV] layer [nm] of HTL [V] Comparative HAT-CN 3 HTC-6 −5.10 7 HTC-6 >10 example 6 Comparative HAT-CN 3 HTC-7 −5.28 7 HTC-7 >10 example 7 Comparative HAT-CN 3 HTC-10 −5.30 7 HTC-10 >10 example 8 Example 14 MC-29 3 HTC-6 −5.10 7 HTC-6 4.0 Example 15 MC-29 3 HTC-5 −5.13 7 HTC-5 4.4 Example 16 MC-29 3 HTC-7 −5.28 7 HTC-7 4.5 Example 17 MC-29 3 HTC-10 −5.30 7 HTC-10 4.6 Example 18 MC-27 3 HTC-6 −5.10 7 HTC-6 4.1 Example 19 MC-27 3 HTC-5 −5.13 7 HTC-5 4.7 Example 20 MC-27 3 HTC-7 −5.28 7 HTC-7 4.4 Example 21 MC-30 3 HTC-7 −5.28 7 HTC-7 6.6 Comparative HAT-CN 5 HTC-6 −5.10 5 HTC-6 >10 example 9 Comparative HAT-CN 5 HTC-7 −5.28 5 HTC-7 >10 example 10 Comparative HAT-CN 5 HTC-10 −5.30 5 HTC-10 >10 example 11 Example 22 MC-29 5 HTC-6 −5.10 5 HTC-6 4.0 Example 23 MC-29 5 HTC-5 −5.13 5 HTC-5 4.2 Example 24 MC-29 5 HTC-7 −5.28 5 HTC-7 4.4 Example 25 MC-29 5 HTC-10 −5.30 5 HTC-10 4.4 Example 26 MC-27 5 HTC-5 −5.13 5 HTC-5 4.9 Example 27 MC-27 5 HTC-7 −5.28 5 HTC-7 4.6 Example 28 MC-30 5 HTC-7 −5.28 5 HTC-7 5.4

[0519] The particular combinations of elements and features in the above detailed embodiments are exemplary only; the interchanging and substitution of these teachings with other teachings in this and the patents/applications incorporated by reference are also expressly contemplated. As those skilled in the art will recognize, variations, modifications, and other implementations of what is described herein can occur to those of ordinary skill in the art without departing from the spirit and the scope of the invention as claimed. Accordingly, the foregoing description is by way of example only and is not intended as limiting. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. The invention's scope is defined in the following claims and the equivalents thereto. Furthermore, reference signs used in the description and claims do not limit the scope of the invention as claimed.