Photosensitization of composite metal oxide semiconductor films

New approach of surface modification consisting on mixing SnO2 and TiO2 colloids and packing them as a composite film (SnO2-TiO2) on a conducting glass surface has led to the increased sensitized photocurrent quantum yields. The photoinjected electrons from the sensitizer into TiO2 are quickly transferred into lower lying conduction band of SnO2 carriers thus promoting the charge separation. High internal photocurrent quantum yield for CdS film as sensitizer, approaching unity (Phi = 95%), has been obtained. In addition, composite SnO2-TiO2 nanocrystalline films improve the charge separation in adsorbed bis(2,2'-bipyridine)(2,2'-bipyridine-4,4'-dicarboxylic acid) ruthenium complex (Ru(II)) too. Higher internal photocurrent quantum yield (Phi = 92%) has been obtained for Ru(II) by replacing SnO2 carriers against composite SnO2-TiO2 particles in the film. On the other hand, the later composition does not show any increase in the photovoltage.