Synthesis of CZTS/Se and Their Solid Solution from Electrodeposited Cu–Sn–Zn Metal Precursor: A Study of S and Se Replacement Reaction

Abstract

Selenization, sulfurization, and sulfo-selenization of electrodeposited metal precursor (Cu–Sn–Zn) at high temperature (500–600 °C) in S, Se, or S + Se (mixed) atmospheres are used to understand the thermodynamics of chalcogenide incorporation reaction. Phase-pure CZTSe and CZTS were obtained after annealing at 500 °C for 1 min in Se (selenization) and 600 °C for 10 min in S (sulfurization) atmospheres, respectively. CZTSSe solid solutions are synthesized by the sequential annealing of metal precursors in S and Se atmosphere separately or in the mixed (S + Se) atmosphere. In the S-rich mixed atmosphere, S-rich CZTSSe solid solution is formed at all annealing conditions. Surprisingly, in a Se-rich mixed atmosphere, longer annealing at 600 °C yields S-rich CZTSSe. The CZTSSe film formed by annealing in near equimolar S/Se atmosphere exhibits a compositional gradient across the thickness. These results suggest that the crystallinity, composition, and hence the bandgap of CZTSSe can be precisely controlled by...