Improvement of Performance of Cu2ZnSn(S,Se)4 Solar Cells by Adding SiNx Buffer Layer and Optimizing its Position and Thickness

Many results have demonstrated that high interfacial recombination is one of the main leading to low power conversion efficiency (PCE) of Cu₂ZnSn(S,Se)₄ (CZTSSe). Herein, interfacial recombination of CZTSSe solar cell by addition of silicon nitride (SiN_x) buffer layer in front interface of CdS/CZTSSe and back interface of CZTSSe/Mo is reduced. It is found that the PCE decreases sharply when the SiN_x layer is deposited at the front interface. Quantitative analysis indicates that the decreased PCE is mainly attributed to the decrease in photogeneration density (J_L), followed by increase in reverse saturation current density (J₀). However, when the SiN_x layer is deposited at the back interface, the PCE increases from 9.11 to 9.78% as the thickness of the SiN_x increases from 0 to 5 nm. Quantitative analysis indicates that the increased PCE is mainly attributed to the increase in J_L, followed by the decrease in J₀ and series resistance (R_s). This work provides a reference for the study of using SiN_x passivation to improve the efficiency of CZTSSe or other solar cells.