The nature of p‐type photocathodes as employed in photoelectrochemical cells has been explored in some detail. These cathodes are found to be unstable in both acid and base. The flatband potential has been measured, using capacitance techniques, as well as the p H for zero surface charge, the point of zero zeta potential (PZZP). These data provide a measure of the electron affinity which is in excellent agreement with that calculated using our electronegativity model. The onset of photocurrent occurs at ∼0.7V negative of the flatband potential. It is demonstrated that this is due to a localized state acting as a recombination center. Experimental evidence for this state comes from the infrared photoresponse of these photoelectrodes. It is suggested that this is the same bulk state which controls the efficiency of electroluminescence diodes.
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Butler et al. (1980) studied this question.