Composition- and Band-Gap-Tunable Synthesis of Wurtzite-Derived Cu₂ZnSn(S_1–xSe_x)₄ Nanocrystals: Theoretical and Experimental Insights

The wurtzite-derived Cu₂ZnSn(S_1–xSe_x)₄ alloys are studied for the first time through combining theoretical calculations and experimental characterizations. Ab initio calculations predict that wurtzite-derived Cu₂ZnSnS₄ and Cu₂ZnSnSe₄ are highly miscible, and the band gaps of the mixed-anion alloys can be linearly tuned from 1.0 to 1.5 eV through changing the composition parameter x from 0 to 1. A synthetic procedure for the wurtzite-derived Cu₂ZnSn(S_1–xSe_x)₄ alloy nanocrystals with tunable compositions has been developed. A linear tunable band-gap range of 0.5 eV is observed in the synthesized alloy nanocrystals, which shows good agreement with the ab initio calculations.