PHOTOELECTROCHEMISTRY OF COMPOSITE SEMICONDUCTOR THIN-FILMS - PHOTOSENSITIZATION OF SNO2 CDS COUPLED NANOCRYSTALLITES WITH A RUTHENIUM POLYPYRIDYL COMPLEX/

The charge injection from an excited Ru(II) complex (viz., (Ru(bpy)(2) (L))(2+), where L = 4-(2,2'-bipyrid-4-yl)phenyl diphosphonate) into Sn O2 and SnO2/CdS films is investigated to elucidate the beneficial effe ct of composite semiconductor systems. The electrons injected from exc ited Ru(II) into CdS are transferred quickly into SnO2 nanoclusters, t hus promoting the charge separation. Photoelectrochemical measurements suggest improved photon to photocurrent charge carrier generation eff iciency in the SnO2/CdS composite system, The formation of the oxidati on produce, Ru(III), and the recovery of the sensitizer are investigat ed using transient absorption spectroscopy, The rate constant for the back electron transfer in the SnO2/CdS/Ru(II) composite system is slow er by a factor of 2-3 than the one observed in the SnO2/Ru(II) system. The beneficial aspects of composite semiconductor systems in photoche mical solar cells are presented.