Organic-inorganic hybrid heterojunctions were fabricated from porous silicon (PS) and N,N'-diphenyl-3,4,9,10-perylenctetracarboxylic diimide (DPP). PS was prepared by electrochemical anodization of p-type Si wafers and DPP was embedded into PS by electrodeposition to form DPP/PS composites. Photoluminescence and surface photovoltaic spectra demonstrated a charge transfer process taking place in the composites, resulting in a higher exciton dissociation efficiency for the composites than pristine PS. The exciton dissociation efficiency could also be adjusted by the PS etching time, because the interface area in the composites varied with the PS etching time. (c) 2008 Elsevier B.V. All rights reserved.