The present invention relates to a blend comprising; a) at least one polymer or copolymer or a mixture of a plurality of polymers and/or copolymers which contain a main chain and a side chain, where at least one side chain contains a structural unit of the following formula (I), the symbols and indices used here are as defined below; b) at least one host molecule which has electron- or hole-transporting functionality, and c) at least one emitter molecule.