Formation of Cu₂ZnSnSe₄ through direct selenization of metal oxides

This article describes a fabrication approach to Cu₂ZnSnSe₄ thin films through the direct selenization of precursor films of the metal oxide mixture with elemental selenium at 550 °C for 40 min. The resulting films exhibit a well compacted morphology composed of crystallites of a few micrometers and having reliable photoelectric response in photoelectrochemical determination, suggesting the potential of photovoltaic applications of the films fabricated by this method. To investigate the formation pathway of the Cu₂ZnSnSe₄ film in this direct selenization method, selenization reactions were carried out with individual Cu, Zn, and Sn oxides under the same conditions, and the results showed that the formation rate of Cu₂ZnSnSe₄ from a mixture of metal oxides is comparable with that of Cu₂Se formation, but faster than those of ZnSe and SnSe₂ formation. The facilitated selenization kinetics to form Cu₂ZnSnSe₄ may be attributed to the oxidation state change of Cu(II) to Cu(I) and Sn(II) to Sn(IV) and the formation of cubic ZnO phase during the preparation of the mixture of metal oxides.