Cu₂ZnSnSe₄ thin film solar cells prepared by rapid thermal annealing of co-electroplated Cu-Zn-Sn precursors

Cu₂ZnSnSe₄ (CZTSe) thin films were prepared by selenization of co-electrodeposited Cu-Zn-Sn precursors, which were electrodeposited on Mo-coated glass substrates in one-step process. Two annealing processes, rapid thermal annealing (RTA) and conventional furnace annealing (CFA), were carried out for selenizing the precursors at 500°C. The structure and morphology of the CZTSe thin films were characterized using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). It is found that the RTA process benefits the formation of single phase CZTSe absorbers with large grains and the energy band gap of CZTSe film is 0.98eV. Photovoltaic cells with the structure of glass/Mo/CZTSe/CdS/i-ZnO/ZnO:Al were fabricated using the RTA-CZTSe films as absorbers. The highest efficiency of 4.5% so far for a co-electrodeposited CZTSe solar cell was achieved.