Formulation of an organic functional material

A formulation containing at least one organic functional material and at least four different organic solvents, a first organic solvent A, a second organic solvent B, a third organic solvent C and a fourth organic solvent D, wherein

• the first organic solvent A comprises a group, which is capable of receiving or giving a hydrogen bonding is an OH group, NH group or NHR4 group wherein R4 is H, a straight-chain alkyl group having from 1 to 12 carbon atoms, a branched or cyclic alkyl group having from 3 to 12 carbon atoms or an aryl or heteroaryl group which has from 4 to 14 carbon atoms, which may be substituted by one or more nonaromatic R5 radicals,
• the second organic solvent B has a boiling point in the range from 150 to 350° C.,
• the third organic solvent C has a boiling point in the range from 100 to 300° C., and
• the fourth organic solvent D has a boiling point in the range from 200 to 400° C., is present in an amount from 0.01 to 15 vol.-% and has a viscosity of ≥15 mPas and wherein the measurement of the viscosity is carried out at a temperature of 25.0° C. (+/−0.2° C.),
• the solubility of the at least one organic functional material in the second organic solvent B and in the fourth organic solvent D is ≥5 g/l,
• the boiling point of the third organic solvent C is at least 10° C. lower than the boiling point of the second organic solvent B, and
• the boiling point of the fourth organic solvent D is at least 10° C. higher than the boiling point of the second organic solvent B
• wherein the at least one organic functional material is selected from the group consisting of organic conductors, organic semiconductors, organic fluorescent compounds, organic phosphorescent compounds, organic light-absorbent compounds, organic light-sensitive compounds, organic photosensitization agents and other organic photoactive compounds.