Sustainable Cu₂ZnSnSe₄ photovoltaic cells fabricated with a sputtered CdS buffer layer

In this study, the effect of the Cu concentration on the characteristics of the Cu₂ZnSnSe₄ (CZTSe) absorber layers and solar cells was systematically analyzed by postselenization of the evaporated precursor deposits. The results demonstrated that an increase in the copper concentration of the precursor linearly increased the Cu content in the final CZTSe thin-film formation. This significantly increased the particle size and improved the re-evaporation loss of the SnSe, thus improving the solar cell characteristics. However, a further increase in the Cu concentration reduced the quality of the absorber layer and formed either Cu_xSe or CTSe secondary phases, which was detrimental to the solar cell characteristics. Here, we introduce a sputtered CdS buffer layer for the CZTSe solar cells. These findings offer new research directions for solving the persistent challenges in the chemical bath deposition (CBD) of the CdS in the CZTSe solar cells.