X-Ray Absorption Spectroscopy Study of Structure and Stability of Disordered (Cu $_{\bf 2}$SnS$_{\bf 3}$) $_{\bf 1-x}$(ZnS)$_{\bf x}$ Alloys

Secondary phase segregation is hypothesized to have detrimental impacts on Cu
₂
ZnSnS
₄
(CZTS) thin-film solar cells. In this study, we demonstrate the potential of using kinetic stabilization to inhibit phase decomposition in CZTS. By growing CZTS films at low temperature, we achieve a kinetically stabilized alloy with an expanded solid solution window in the pseudoternary CuS-ZnS-SnS phase diagram. Using X-ray absorption spectroscopy, we study the structural evolution and stability of this metastable alloy upon annealing. For near-stoichiometric samples, we observe a continuous emergence of short-range order toward crystalline CZTS that is nearly complete after a 1-min anneal at 450 °C. For Zn-rich samples, we detect precipitation of ZnS upon annealing, which suggests that the excess Zn exists as cation antisite defects in metastable CZTS.