Selenization of Cu2ZnSn(S,Se)4 thin-films with varied pressures

Abstract

• Adjusting nitrogen pressure during annealing improves delamination of CZTSSe absorption layer. • Selenization under varying pressure reduces the thickness of fine crystal layers in CZTSSe films. • Different pressures during selenization can help CZTSSe formation in the low temperature region (∼350 °C) • The CZTSSe cell with 10.4% efficiency was prepared by different pressure selenization with 35% improvement. In this paper, a selenization process using varied nitrogen pressures was proposed to improve the properties of Cu 2 ZnSn(S,Se) 4 (CZTSSe) thin-films. The effect of the different pressures on the formation of CZTSSe was investigated. It was found that the selenization process with different nitrogen pressures can decrease the thickness of the detrimental fine grain layer in the CZTSSe film, which will benefit the performances of CZTSSe solar cells. The varied pressures can assist the formation of CZTSSe at the low temperature region of the selenization process. Although no obvious CZTSSe was detected at 350 °C for the selenization process with constant pressure (50 Torr or 200 Torr), CZTSSe was detected at 350 °C for the selenization process with various pressures. By using the novel selenization process, CZTSSe solar cells were prepared with the best efficiency of 10.4%.