PHOTOELECTROCHEMICAL STUDY OF PARA-TYPE COPPER INDIUM DISELENIDE THIN-FILMS FOR PHOTOVOLTAIC APPLICATIONS

A photoelectrochemical study of the behaviour of p-type thin films of CuInSe2 (CIS) in acqueous acidic solutions is presented showing that the liquid junction can be efficiently used for the characterization of as-grown layers. Standard films have doping levels in the range of 1016 cm-3 and their spectral responses present high quantum efficiencies (∼ 0.9). The films have a poor photoresponse in electrolyte without added redox species, which has been attributed to slow interfacial kinetics for the reduction of protons. The deposition on the surface of metal islands that catalyze the hydrogen evolution (Pd, Pt) greatly enhances the photoresponse allowing the transfer towards the solution of the internal photocurrent via the hydrogen evolution. With the addition of Eu3+ ions in solution, the transfer of photocurrent is achieved on bare surfaces allowing the complete characterization of the layer without surface treatment. Changes of the band edge position (i.e. barrier height changes) with the illumination were observed. They are associated with losses of about 0.5 V on the predicted open circuit voltage. The similitude with the behaviour of solid state cells is underlined. © 1990.