The successful electropolymerization of pyrrole and its codeposition with Bi2S3 nanoparticles on chemically deposited bismuth sulfide substrates is described. The materials were designed to explore new approaches to improve light-collection efficiency in polymer photovoltaics. We report the effect of bismuth sulfide nanoparticles on the electropolymerization of pyrrole and on the morphology and optoelectronic properties of the composite film. The differences observed on the optical band gaps, photoaction spectra and open-circuit photovoltages, led to the conclusion that polymerization under the presence of nanoparticles produces tighter and thinner polymeric coatings than the ones obtained without nanoparticles. Under illumination, the composite polymeric coating has low absorption and high electronic conductivity, typical of the oxidized form of polypyrrole. This suggests a photoinduced charge transfer reaction compatible with the electron-accepting nature of bismuth sulfide nanoparticles. When subjected to long time illumination, atomic force microscopy, optical characterization and photoelectrochemical studies showed that the presence of Bi2S3 nanoparticles in the polymeric film improves the efficiency of the coating against photocorrosion. (C) 2002 Elsevier Science B.V. All rights reserved.