Fabrication of Cu 2 ZnSn(S,Se) 4 Thin Films by Sulfurization of Precursor Evaporated from Cu 2 ZnSnSe 4 Compound

Cu 2 ZnSn(S,Se) 4 thin films and solar cells are prepared by sulfurization of the precursors evaporated from Cu 2 ZnSnSe 4 compound and their properties are investigated. Each materials of Cu 2 ZnSnSe 4 , Zn + Sn + Se, and NaF + Se are sequentially evaporated on Mo/soda lime glass substrate. The substrate temperature of Zn + Sn + Se evaporation is changed from 300 to 550 °C. These precursors are crystallized by sulfurization in sulfur/tin mixing atmosphere for 30 min at 550 °C. From the Raman spectra, two kind of precursor formations such as Cu 2 ZnSnSe 4 and Cu 2 SnSe 3 by changing the substrate temperature are confirmed. The high V oc of 574 mV is obtained in the sample which sulfurized from Cu 2 SnSe 3 precursor, and it is higher than the sample which sulfurized from Cu 2 ZnSnSe 4 precursor ( V oc  = 449 mV). The finding of this study is to have revealed a new crystallization process of fabrication of the Cu 2 ZnSn(S,Se) 4 thin film.