New derivatives of poly(thienylene vinylene) (PTV), more specifically the 3,4-dichloro and 3,4-dibromo derivatives, have been synthesised. Their structural characterisation reveals a high molecular weight ( > 50 000 Da) and an optical band gap of 1.55 ev. For comparison also the properties and behaviour in photovoltaic devices of a soluble poly(bisthienylene isothianaphthene) derivative is discussed. The former materials have been synthesised via the 'sulfinyl' route developed in our group. It could be proven that the polymerisation reaction is proceeding via a p-quinodimethane system using stop flow UV/vis measurements. Photovoltaic devices were produced using a blend of PCBM and the sulfinyl precursor of the PTV derivative (4:1). The conversion of the precursor towards the conjugated polymer was performed on the blend. The photovoltaic devices show satisfying initial device characteristics, which substantially improve on thermal annealing of the device at 70 degreesC for several hours. (C) 2003 Elsevier B.V. All rights reserved.