PHOTOELECTROCHEMICAL STUDIES OF COPPER GALLIUM DISELENIDE FILMS

Thin films of copper gallium diselenide of various composition were prepared by vacuum deposition. Spectral responses at several applied potentials were obtained in a photoelectrochemical cell with an acidic electrolyte (1 M HC1) and in a 0.05 M V2+/V3+ solution. They allowed us to test the intrinsic quality of the layers to establish photovoltaic applications. Effective diffusion lengths and acceptor concentrations are determined. It is shown that the samples may be classified into four groups, depending on their photoelectrochemical properties. An attempt is made to correlate behaviour to the chemical composition of the films, by defining convenient deviations from stoichiometry and from molecularity. The results suggests that in the monophasic Cu2SeCuGaSe2 range, the deviation from stoichiometry is due to an excess of copper and to an excess of selenium, or to a defect of gallium. © 1990.