LAUSR

Abstract Cu 2 ZnSnSe 4 (CZTSe) films with different Zn/Sn ratios were fabricated using Cu 2 SnSe 3 (CTSe) and ZnSe bilayer precursors (ZnSe/CTSe/Mo) and sandwich-structured precursors (ZnSe/CTSe/ZnSe/Mo). Using the bilayer precursor, excessive ZnSe on top of the CZTSe films with a Zn/Sn ratio of 1.3 that acts as a current-blocking barrier was observed, reducing the short-circuit current density of the CZTSe solar cells. Modification of the precursor structure from the bilayer to the sandwiched structure eliminates the segregation of ZnSe phase on top of the film even for a high (1.25) Zn/Sn ratio. This modification improved the cell efficiency from 6% (bilayer precursor) to 9% (sandwich-structured precursor).