Insight into band alignment of Zn(O,S)/CZTSe solar cell by simulation.

Cd-free kesterite structured solar cells are currently attracting attention because they are environmentally friendly. It is reported that Zn(O,S) can be used as a buffer layer in these solar cells. However, the band alignment is not clear and the carrier concentration of Zn(O,S) layer is low. In this study, the band alignment of the Zn(O,S)/Cu2ZnSnSe4 p–n junction solar cell and the effect of In2S3/Zn(O,S) double buffer layer are studied by numerically simulation with wxAMPS software. By optimizing the band gap structure between Zn(O,S) buffer layer and Cu2ZnSnSe4 absorber layer and enhancing the carrier concentration of Zn(O,S) layer, the device efficiency can be improved greatly. The value of CBO is in a range of 0 eV–0.4 eV for S/(S + O)–0.8 in Zn(O,S). The In2S3 is mainly used to increase the carrier concentration when it is used as a buffer layer together with Zn(O,S). [ABSTRACT FROM AUTHOR]