Research progress on optimizing performance of Cu₂ZnSnS₄(Cu₂ZnSn(S,Se)₄) thin-film solar cells by bivalent cations doping

Cation doping measures are considered as one of the effective measures to optimize the performance of Cu₂ZnSn(S,Se)₄ (CZTS(Se)) thin film solar cells, and divalent cation doping measures are the most studied and widely applied in all cation doping measures. Here, the research progress of divalent cation measures in optimizing the performance of CZTS(Se) thin film solar cells is introduced from two aspects: Cations substitution and extra cations addition. Divalent cations substitution measures, such as, substitution of Zn²⁺ with Cd²⁺, mainly reduce the defect density of the absorber layer of CZTS(Se) thin film solar cells, improve the crystalline quality, and solve the problem of large interface energy band offset between the absorber layer and buffer layer, thus reducing the open voltage circuit loss of the device and improving its efficiency. The extra addition of divalent cations, such as, the extra addition of Co²⁺/Mn²⁺, can optimize the crystallinity of the film, help the carrier transport, and improve the electrical properties of the absorber layer. Finally, their advantages, disadvantages, and the application prospects are also summarized.