THE EFFECT OF ILLUMINATION INTENSITY ON THE KINETICS OF HYDROGEN EVOLUTION AT P-TYPE SILICON

The effect of illumination intensity on the kinetics of hydrogen photo generation is studied experimentally at the silicon electrode in acid solutions. The charge-transfer and surface-recombination rate constant s are found to increase with the light intensity. This effect is expla ined by a decrease in the band bending near the semiconductor surface and a corresponding change in the potential drop across the Helmholtz layer, both effects being due to accumulation of a photoelectron charg e at the semiconductor surface. For a light intensity of 1.5 mW cm(-2) , the change in the band bending amounts to ca. 0.2 eV, which results in a nearly tenfold increase of the pertinent rate constants.