When operated at the current densities in excess of 10 mA/cm2 that are typical of efficient solar‐irradiated photovoltaic cells, semiconductor‐liquid junction cells deteriorate with time. In electrodes that have lost activity, formation of a film has been detected by means of Auger spectroscopy and electron beam‐induced luminescence. Such a layer is a barrier to the flow of holes to the surface. The rate of deterioration increases with light flux, usually decreases with stirring, and depends on the crystal face exposed to the solution. Addition of small amounts of elemental selenium to the solution substantially improves the stability by preventing excessive sulfide enrichment of the surface. For example, with 0.5M Se added, the output of face electrodes run at 35 mA/cm2 is essentially unchanged beyond charge passage.