We have investigated the photoelectrochemical properties of hybrid films of polythiophenes poly(4,4 '' dimethoxy-3'-methyl-2,2':5',2 '' terthiophene) (PDM), poly(4,4 '' dipentoxy-3'-methyl-2,2':5',2 '' terthiophene) (PDP), and cadmium sulfide/zinc sulfide (CdS(ZnS)) core-shell nanoparticles. Although CdS(Zns) nanoparticles present enhanced exciton trapping, light harvesting by hybrid films was enhanced when compared to those of pure PDM and PDP films. This enhancement is explained in terms of electron and hole transfer mechanisms at different excitation wavelengths. The more efficient light harvesting of PDM/CdS (ZnS) when compared to that of PDP/CdS(ZnS) was attributed to its broader absorption spectrum and more efficient electron hopping. (C) 2009 Elsevier B.V. All rights reserved.