Synthesis and optical properties of Cu 2 SnZnS 4 films under different sulfur atmospheres

The electrodeposited precursor is a mixture of Cu, Sn, and Zn alloys, these elements form Cu 6 Sn 5 and CuZn binary phases, and subsequently these phases transform into many binary and ternary intermediates, such as CuS, ZnS, Cu 2 SnS 3 , and Cu 2 ZnSnS 4 (CZTS) at low annealing temperature in pure sulfur and H 2 S atmospheres. Finally, CZTS films can be completely formed by sulfidizing at 550 °C for 1 h in pure sulfur and H 2 S atmospheres. However, the initial temperature of synthesizing CZTS in H 2 S atmosphere is higher than that in pure sulfur atmosphere, but the highest temperature of synthesizing CZTS in H 2 S atmosphere is lower than that in pure sulfur atmosphere. The direct band gaps of the CZTS films synthesized at 550 °C for 1 h in pure sulfur and H 2 S atmospheres are about 1.54 and 1.52 eV, respectively.