Selenization of mixed metal oxides for dense and ZnSe-free Cu2ZnSnSe4 absorber films

•ZnSe-free CZTSe films with large grains was prepared from mixed oxides nanopraticles.•Appearance of Zn2SnO4 in mixed oxides precursors leads to the absence of ZnSe secondary phrase.•To obtain pure CZTSe phase, different treating temperature was used.

Cu2ZnSnSe4 (CZTSe) films were prepared by direct selenization of Cu2O, SnO2 and Zn2SnO4 precursors. Oxides precursors were prepared by baking hydroxides precipitation. In order to obtain ZnSe-free CZTSe films, Zn2SnO4 was used to replace separated ZnO and SnO2 as one of the precursors. Through X-ray diffraction (XRD), scanning electron microscopy (SEM), it was found that CZTSe films, with micron-sized dense grains, were obtained in our work. From Raman spectra, it was also found that the ZnSe secondary phase was absent after the selenization. An energy bandgap about 0.86 eV was obtained in our work, which confirmed the Stannite-CZTSe structure.