Study of Cd‐Chalcogenide/Ferri‐Ferrocyanide Photoelectrochemical Cells: Effect of Surface Morphology and Added Salt

Abstract

Successive etching with 3% Br in MeOH, aqua regia, and finally photoetching increases the surface roughness of CdSe (CdS, CdTe) which has a marked effect on the cell characteristics in the ferri-ferrocyanide electrolyte (and polysulfide electrolyte as well). In contrast with polysulfide electrolyte, added salts decrease the output stability of the cell and the onset potential for the photocurrent, which can be explained by the removal of the phys. sorbed ferrocyanide ions from the electrode surface by the ions of the salt. On increasing the surface roughness of the electrode, while keeping the salt concn. unchanged, the output stability and the onset potential were increased. A kinetic model is used to explain these phenomena. Thus, added salts can be used to probe the strength of the adsorption of the active electrolyte on the surface, of the photoelectrode. Finally, the surface morphol. of CdSe and CdTe after irradn. in ferri-ferrocyanide soln. is reported and compared to surface morphologies obsd. previously with the help of photoelectrochem. etching. Small rectangular crystallites, probably of Cd2[Fe(CN)6], deposit on the crystal surface during the photocorrosion process in addn. to Se(Te). [on SciFinder (R)]