Preparation of device quality CuInSe2 by selenization of Se-containing precursors in H2Se atmosphere

Efficient thin-film photovoltaic cells were fabricated, using CuInSe2 absorber films obtained from the selenization (in H2Se/Ar) of InSe/Cu and InSe/Cu/InSe metallic precursors. The material properties of the CuInSe2 layers were critically influenced by the kinetics of the selenization process and the nature of the precursor films before the reaction step. Selenization of InSe/Cu precursors resulted in layers with poor morphological features (droplet formation) and in cells with relatively low conversion efficiencies (eta = 3-5%). Optimal material properties were obtained when InSe/Cu/InSe precursors were selenized in H2Se/Ar (atmospheric pressure) while ramping the temperature slowly between 200 degrees C and 400 degrees C. This process produced relatively uniform and dense films which exhibited large crystallites of high crystalline quality. Preliminary CuInSe2/CdS/ZnO heterojunction solar cell devices were fabricated using these films, and conversion efficiencies exceeding 10% (total area) were obtained without the use of an antireflective coating.