The use of bipolar materials as an active layer in polymeric solar cells can be an alternative to 'bulk-heterojunctions' composed of donor-acceptor blends. We have prepared two series of polyalkylthiophene copolymers having acceptor molecules covalently grafted to the backbone. The random copolymerization of thiophene monomers containing an acceptor moiety (anthraquinone or tetracyanoanthraquinodimethane) and 3-alkylthiophene monomers is a powerful strategy to tune both the donor-acceptor content and the electronic properties of the material. Emission measurements show for both copolymer series a photoinduced electron transfer from the donor pi-conjugated backbone to the acceptor substituents, and this process can be modulated as a function of the chemical composition. (C) 2003 Elsevier B.V. All rights reserved.