The invention relates to a copolymer for a charge transport layer in an optoelectronic device and in particular in a light-emitting diode (LED), having a charge mobility of at least 1.0×1010 m2/V.s, and comprising at least a first and a second monomer, characterized in that the ratio of the solubilities of homopolymers made from the first and the second monomer in a first solvent is more than 10. This copolymer allows a (semi) conductive polymer to be cast to form a first layer and prevents it from being dissolved in the solvent of a subsequently deposited second, e.g. light-emitting layer. The invention further relates to a LED comprising a copolymer according to the invention.