Formulation of an organic functional material
The present invention relates to formulations containing at least one organic functional material and at least a first organic solvent, wherein said first organic solvent is an alkyl benzoate solvent, as well as to electronic devices prepared by using these formulations.
1. A formulation containing at least one organic functional material which has a molecular weight of <3,000 g/mol and at least a first organic solvent, wherein said first organic solvent is an alkyl benzoate and the content of the alkyl benzoate is in the range from 50 to 100 vol. %, based on the total amount of solvents in the formulation and said at least one organic functional material is at least one phosphorescent emitting material as dopant and at least one matrix material and wherein the proportion of the phosphorescent emitting material is between 0.5 and 20% by volume and the proportion of the matrix material is between 80 and 99.5% by volume, both based on the total amount of emitting and matrix materials.
2. The formulation according to claim 1 , wherein the first organic solvent is an alkyl benzoate according to general formula (I)
wherein
R 1 is identical or different at each occurrence, and are D, F, Cl, Br, I, NO 2 , CN, a straight-chain alkyl having from 1 to 20 carbon atoms or a branched or cyclic alkyl group having from 3 to 20 carbon atoms, in which one or more non-adjacent CH 2 groups may be replaced by —O—, —S—, —NR 3 —, —CONR 3 —, —CO—O—, —C═O—, —CH═CH— or —C≡C—, and in which one or more hydrogen atoms may be replaced by F, or an aryl or heteroaryl group which has from 4 to 14 carbon atoms and may be substituted by one or more nonaromatic R 3 radicals, and a plurality of substituents R 3 , either on the same ring or on the two different rings, may together in turn form a mono- or polycyclic, aliphatic, aromatic or heteroaromatic ring system, which may be substituted by a plurality of substituents R 3 ;
R 2 is a straight-chain alkyl group having from 1 to 20 carbon atoms or a branched or cyclic alkyl group having from 3 to 20 carbon atoms, in which one or more non-adjacent CH 2 groups non-adjacent to the —CO—O— group in general formula (I) may be replaced by —O—, —S—, —NR 3 —, —CONR 3 —, —CO—O—, —C═O—, —CH═CH— or —C≡C—, and in which one or more hydrogen atoms may be replaced by F, or an aryl or heteroaryl group which has from 4 to 14 carbon atoms and may be substituted by one or more nonaromatic R 3 radicals, and a plurality of substituents R 3 , either on the same ring or on the two different rings, may together in turn form a mono- or polycyclic, aliphatic, aromatic or heteroaromatic ring system, which may be substituted by a plurality of substituents R 3 ;
R 3 are identical or different at each instance, and are a straight-chain alkyl or alkoxy group having from 1 to 20 carbon atoms or a branched or cyclic alkyl or alkoxy group having from 3 to 20 carbon atoms, in which one or more non-adjacent CH 2 groups may be replaced by —O—, —S—, —CO—O—, —C═O—, —CH═CH— or —C≡C—, and in which one or more hydrogen atoms may be replaced by F, or an aryl or heteroaryl group which has from 4 to 14 carbon atoms and may be substituted by one or more nonaromatic R 3 radicals and n is 0 to 3.
3. The formulation according to claim 2 , wherein the first organic solvent is an alkyl benzoate according to general formula (I)
wherein
R 1 is a straight-chain alkyl group having from 1 to 20 carbon atoms or a branched or cyclic alkyl group having from 3 to 20 carbon atoms, in which one or more non-adjacent CH 2 groups may be replaced by —O—, —S—, —CO—O—, —C═O—, —CH═CH— or —C≡C—, and in which one or more hydrogen atoms may be replaced by F, or an aryl or heteroaryl group which has from 4 to 14 carbon atoms and may be substituted by one or more nonaromatic R 5 radicals,
R 2 is a straight-chain alkyl group having from 1 to 20 carbon atoms or a branched or cyclic alkyl group having from 3 to 20 carbon atoms, and
n is 0 or 1.
4. The formulation according to claim 2 , wherein the first organic solvent is an alkyl benzoate according to formula (I)
wherein
R 2 is a straight-chain alkyl group having from 1 to 4 carbon atoms and
n is 0.
5. The formulation according to claim 4 , wherein R 2 is a straight-chain alkyl group having 4 carbon atoms.
6. The formulation according to claim 1 , wherein the first solvent has a surface tension of >20 mN/m.
7. The formulation according to claim 1 , wherein the content of the first solvent is in the range from 75 to 100 vol.-%, based on the total amount of solvents in the formulation.
8. The formulation according to claim 1 , wherein the first solvent has a boiling point in the range from 150 to 350° C.
9. The formulation according to claim 1 , wherein the formulation comprises at least one second solvent which is different from the first solvent.
10. The formulation according to claim 9 , wherein the second solvent has a boiling point in the range from 150 to 350° C.
11. The formulation according to claim 1 , wherein the at least one organic functional material has a solubility in the first as well as in the second solvent in the range from 1 to 250 g/l.
12. The formulation according to claim 1 , wherein the formulation has a surface tension in the range from 15 to 80 mN/m.
13. The formulation according to claim 1 , wherein the formulation has a viscosity in the range from 1 to 50 mPa·s.
14. The formulation according to claim 1 , wherein the content of the at least one organic functional material in the formulation is in the range from 0.001 to 20 weight-%, based on the total weight of the formulation.
15. A process for the preparation of the formulation according to claim 1 , which comprises mixing the at least one organic functional material and the at least first solvent.
16. A process for the preparation of an electroluminescent device which comprises preparing at least one layer of the electroluminescent device in that the formulation according to claim 1 is deposited on a surface and subsequently dried.
17. The formulation according to claim 1 , wherein at least one organic functional material which has a molecular weight of <2,000 g/mol.
18. The formulation according to claim 1 , wherein at least one organic functional material which has a molecular weight of <1,000 g/mol.
19. The formulation according to claim 18 , wherein the proportion of the dopant in the emitting material is between 0.5 and 8% by volume and the proportion of the matrix material in the emitting material is between 92 and 99.5% by volume, both based on the total amount of emitting and matrix materials.
20. The formulation according to claim 1 , wherein the proportion of the dopant in the emitting material is between 0.5 and 8% by volume and the proportion of the matrix material in the emitting material is between 92 and 99.5% by volume, both based on the total amount of emitting and matrix materials.