Formulation of an organic functional material

A formulation containing at least one organic functional material and at least two different organic solvents, a first organic solvent A and a second organic solvent B, wherein

• the first organic solvent A has a boiling point in the range from 250 to 350° C. and a viscosity of >15 mPas,
• the second organic solvent B has a boiling point in the range from 200 to 350° C. and a viscosity of ≤10 mPas,
• the solubility of the at least one organic functional material in the second organic solvent B is ≥5 g/l, and
• the boiling point of the first organic solvent A is at least 10° C. higher than the boiling point of the second organic solvent B,
• wherein the first organic solvent A is selected from naphthalene derivatives, partially hydrogenated naphthalene derivatives, fully hydrogenated naphthalene derivatives, indane derivatives and fully hydrogenated anthracene derivatives and is selected from the formula (I), (II), (III) or (IV),
• wherein
• R is a cyclic alkyl group having from 6 to 10 carbon atoms, in which one or more non-adjacent CH2 groups may be replaced by —O—, —S—, —NR1—, —CO—O—, —C═O—, —CH═CH— or —C≡C—, or an aryl or heteroaryl group which has from 6 to 10 carbon atoms and may be substituted by one or more substituents R1, and a plurality of substituents R1, 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 R1,
• R1 is identical or different at each instance, and is a straight-chain alkyl or alkoxy group having from 1 to 12 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 CH2 groups may be replaced by —O—, —S—, —CO—O—, —C═O—, —CH═CH— or —C≡C—;
• and
• the at least one organic functional material is selected from the group consisting of fluorescent emitters, phosphorescent emitters, host materials, matrix materials, exciton-blocking materials, electron-transport materials, electron-injection materials, hole-conductor materials, hole-injection materials, n-dopants, p-dopants, wide-band-gap materials, electron-blocking materials and hole-blocking materials.