A photoconductivity study of electron transfer between CdS and TiO2 powders in vacuum and in an O2 atmosphere

Abstract

Photoconductance measurements have been carried out in the visible and/or ultraviolet spectral region, under vacuum or under various O2 pressures, at room temperature for the powders CdS, TiO2, mixtures of CdS with a small amount of TiO2(or SiO2 for comparison) and a CdS–TiO2 double pellet. Under vacuum, regardless of the spectral range, the effects of TiO2 on the CdS photoconductance or conductivity after illumination are interpreted by electron transfer from TiO2 to CdS. In the presence of O2, this transfer is limited by oxygen species adsorbed on TiO2, which deplete this material of its free electrons (pressure dependence) and which can also capture free electrons of CdS to an extent which depends on the number and areas of the interfaces between particles of the two semiconductors.