Defect-free phenylene-ethynylene/phenylene-vinylene hybrid polymers (PPE-PPV) have been characterized optically and electrochemically. The presence of -C drop C- within the polymers backbone leads to higher oxidation potentials and higher optical band gaps compared with poly[2-methoxy-5-(3' 7' -dimethyloctyloxy)-1,4-phenylene vinylene] (MDMO-PPV). The new polymers were used as electron donor in polymer solar cells (PSCs). An effective charge transfer from polymer to [6,6]-phenyl C61-butyric acid methyl ester (PCBM) was found via the photoluminescence technique and light-induced electron spin resonance techniques. Photovoltaic devices were prepared on ambient conditions on flexible polyester foils coated with indium tin oxide (ITO) and showed power conversion efficiency (eta(AM1.5)) of 3% (MDMO-PPV:PCBM) and 1.75% as well as 0.5% (PPE-PPV:PCBM). (C) 2004 Elsevier B.V. All rights reserved.