Solutions and dispersions of organic semiconductors

A solution or dispersion which comprises an undoped polymeric organic semiconductor in a solvent mixture of at least two different organic solvents, wherein

• A. Each of the solvents on its own has a boiling point of at least 100° C. and below 200° C. and a melting point of 15° C. or less,
• B. at least one of the solvents has a boiling point in the range from greater than 140 to less than 200° C.,
• C. the solvents used have no benzylic CH2 or CH groups,
• D. the solvents used are not benzene derivatives containing tert-butyl substituents or more than two methyl substituents and
• wherein the solution or the dispersion comprises only solvents having a boiling point of at least 100° C. and wherein said polymeric organic semiconductor used is a substituted, soluble copolymer comprising structural units of at least two of the polymer classes selected from the group consisting of a soluble poly-p-arylene-vinylene (PAV), polyfluorenes (PFs), a soluble polyspirobifluorene (PSF), a soluble poly-para-phenylene (PPP), substituted, soluble polythiophene (PT), a substituted, soluble polypyridine (Ppy) and a substituted, soluble polypyrrole.