Effects of selenization on phase transition and S/(S+Se) ratios of as-deposited Cu2ZnSnS4 absorbers sputtered by a quaternary target

• CZTSSe film was prepared by sputtering of a quaternary CZTS target and selenization.
• With the increase of selenization time, S atoms in CZTS were substituted by Se atoms.
• The S/(S+Se) ratios varied exponentially as a function of selenization time.

Cu2ZnSn(S1−x,Sex)4 (CZTSSe) absorbers with different S/(S+Se) ratios were prepared by the sputtering of a Cu2ZnSnS4 (CZTS) quaternary target on Mo-coated SLG followed by a selenization process. Influences of selenization time on properties of CZTSSe absorbers were studied in detail. Both of the crystallinity and grain size of CZTSSe absorbers were enhanced by the selenization process. According to the XRD patterns and Raman spectra, with the increase of selenization time, S atoms in CZTS were substituted by Se atoms, leading to the decrease of S/(S+Se) ratio of CZTSSe from 1 to 0. Judging from ICP-MS results, the S/(S+Se) ratios of CZTSSe absorbers varied exponentially as a function of selenization time. This work demonstrates an alternative, simplified and controllable fabrication method for the preparation of CZTSSe absorbers.