Hole-diffusion length and transport parameters of thin CdS films from a Schottky barrier

The optoelectronic and transport properties of thin sprayed CdS films, having a thickness of less than 2 μm are reported. The use of two independent technics, surface photovoltage and photoelectrochemical measurements, led to a good agreement in the hole-diffusion length values. These range from 0.017 to 0.15 μm and behaved differently in two zones. A rapid increase of this parameter is observed below a film thickness of 0.4 μm. Above this thickness, the value obtained is constant. Specific space-charge widths are expected because of the respective measurement conditions. The hole-diffusion length decreases as carrier density increases. The hole lifetime shows a regular decrease as the thickness factor increases, while the hole-diffusion coefficient and mobility patterns are similar to that of the photocurrent.