Crystallization Behavior of CZTSSe by Selenization of Sputtered CZTS Precursors

Abstract

In this work, we study the effect of annealing on crystallization behavior of Cu₂ZnSn(S_xSe_1-x)₄ (CZTSSe) absorbers. Cu-Zn-Sn-S precursors are deposited on glass/Mo substrate by cosputtering of Cu, ZnS, and SnS. In order to have a better understanding of the mechanisms of formation of CZTSSe and secondary phases during annealing, the effect of annealing temperatures between 300 and 600°C, and annealing time from 1 to 60 min on structural and compositional properties of the cells have been studied. For the best annealing conditions, efficiencies between 2.3% and 7% were obtained. A comparison of material and solar cells properties extracted from chemical, structural and opto-electronic characterizations shows that whatever the annealing conditions, there is a simultaneous formation of CZTSSe and SnSe₂ phases. We showed that these binaries are detrimental for the performance of solar cells, leading to a decrease of the V_oc and FF.