PHOTOELECTROCHEMICAL BEHAVIOR OF THIN CDSE AND COUPLED TIO2 CDSE SEMICONDUCTOR-FILMS

Photoelectrochemical effects at CdSe thin film electrodes (thickness 30-200 angstrom) have been investigated by monitoring open-circuit voltage and short-circuit cur-rent at varying film thicknesses and incident light intensities. Unlike the situation in conventional photoelectrochemical cells that employ single-crystal or polycrystalline semiconductors, the charge separation in thin CdSe films is not controlled by the space charge layer at the semiconductor-electrolyte interface, but it is controlled by the differing rates of electron and hole transfer into the solution. Quick decay of the photocurrent, even in the presence of a redox couple such as [Fe(CN)6]3-/4-, suggests high degree of charge recombination within the thin CdSe film. It is possible to improve the photocurrent stability of a thin CdSe film by coupling it with a TiO2 particulate film. The improved charge separation in the coupled semiconductor system has a beneficial effect in improving the photocurrent stability of thin semiconductor films.