Formulation comprising at least one organic semiconductor, at least one metal complex and at least two organic solvents, where the solubility at 20°C of the metal complex is ≥ 5 g/l in at least one organic solvent and the solubility at 20°C of the organic semiconductor is ≥ 10 g/l in at least one organic solvent, wherein the at least one organic semiconductor is selected from the group consisting of hole-transport materials and hole-injection materials; and wherein a first solvent has a boiling point of from 100°C to 300°C and a second solvent has a boiling point of from 40°C to 100°C, characterised in that the at least one metal complex comprises a metal atom of group 13 to 15 and a ligand of the following structure where R 11 and R 12 are selected, identically or differently, from the group consisting of O, S, Se, NH or NR 14, where R 14 is an alkyl or aryl group; where R 14 and R 13 may form a ring with one other; and R 13 is selected from the group consisting of a straight-chain alkyl, alkoxy or thioalkyl group having 1 to 40 C atoms or an alkenyl or alkinyl group having 2 to 40 C atoms or a branched or cyclic alkyl, alkoxy or thioalkyl group having 3 to 40 C atoms, each of which may be substituted by one or more radicals R 1, where in each case one or more non-adjacent CH 2 groups may be replaced by R 1 C=CR 1, C≡C, Si(R 1) 2, C=O, C=S, C=NR 1, P(=O)(R 1), SO, SO 2, NR 1, O, S or CONR 1 and where one or more H atoms may be replaced by D, F, Cl, Br, I or CN, an aromatic or heteroaromatic ring system having 5 to 60 aromatic ring atoms, which may in each case be substituted by one or more radicals R 1, an aryloxy or heteroaryloxy group having 5 to 60 aromatic ring atoms, which may substituted by one or more radicals R 1, or an aralkyl or heteroaralkyl group having 5 to 60 aromatic ring atoms, which may in each case be substituted by one or more radicals R 1, or a diarylamino group, diheteroarylamino group or arylheteroarylamino group having 10 to 40 aromatic ring atoms, which may be substituted by one or more radicals R 1; where R 13 may form a ring with at least one of the radical R 12; and R 1 is on each occurrence, identically or differently, H, D, F or an aliphatic hydrocarbon radical having 1 to 20 C atoms, an aromatic and/or a heteroaromatic hydrocarbon radical having 5 to 20 C atoms, in which, in addition, one or more H atoms may be replaced by F; where two or more substituents R 1 may also form a mono- or polycyclic, aliphatic or aromatic ring system with one another. R 11 and R 12 are selected, identically or differently, from the group consisting of O, S, Se, NH or NR 14, where R 14 is an alkyl or aryl group; where R 14 and R 13 may form a ring with one other; and R 13 is selected from the group consisting of a straight-chain alkyl, alkoxy or thioalkyl group having 1 to 40 C atoms or an alkenyl or alkinyl group having 2 to 40 C atoms or a branched or cyclic alkyl, alkoxy or thioalkyl group having 3 to 40 C atoms, each of which may be substituted by one or more radicals R 1, where in each case one or more non-adjacent CH 2 groups may be replaced by R 1 C=CR 1, C≡C, Si(R 1) 2, C=O, C=S, C=NR 1, P(=O)(R 1), SO, SO 2, NR 1, O, S or CONR 1 and where one or more H atoms may be replaced by D, F, Cl, Br, I or CN, an aromatic or heteroaromatic ring system having 5 to 60 aromatic ring atoms, which may in each case be substituted by one or more radicals R 1, an aryloxy or heteroaryloxy group having 5 to 60 aromatic ring atoms, which may substituted by one or more radicals R 1, or an aralkyl or heteroaralkyl group having 5 to 60 aromatic ring atoms, which may in each case be substituted by one or more radicals R 1, or a diarylamino group, diheteroarylamino group or arylheteroarylamino group having 10 to 40 aromatic ring atoms, which may be substituted by one or more radicals R 1; where R 13 may form a ring with at least one of the radical R 12; and R 1 is on each occurrence, identically or differently, H, D, F or an aliphatic hydrocarbon radical having 1 to 20 C atoms, an aromatic and/or a heteroaromatic hydrocarbon radical having 5 to 20 C atoms, in which, in addition, one or more H atoms may be replaced by F; where two or more substituents R 1 may also form a mono- or polycyclic, aliphatic or aromatic ring system with one another.