Enhancing the photovoltaic efficiency of CZTSSe thin-film solar cells via Ag-doping induced defect modulation

Defect modulation is one of the key factors in determining the performance of solar cells, and the presence of defects tends to adversely affect carrier recombination and transport, thus having a direct impact on both cell stability and efficiency. Ag doping can modulate the defects, but in-depth studies on the mechanism of the effect are needed. Therefore, an in-depth study of the effect of Ag incorporation on the defect modulation mechanism of Kesterite Cu 2 ZnSn(S,Se) 4 (CZTSSe) solar cells is of great practical significance for understanding the mechanism of action of Ag doping and further optimising the cell performance. In this study, (Ag x Cu 1-x ) 2 ZnSn(S,Se) 4 (0 ≤ x ≤ 1) (ACZTSSe) solar cells were successfully prepared by N, N-dimethylformamide (DMF) solution, which have the characteristics of reducing defects and enhancing photovoltaic performance. After the introduction of Ag, the absorber formed a crystal structure with few holes and penetrating top and bottom. And the electrical performance of the solar cell is significantly improved, J 0 is reduced from 4.6 × 10 −5 A/cm 2 to 2.7 × 10 −6 A/cm 2 , and its contribution to the photovoltaic conversion efficiency (PCE) improvement reaches 142%. This indicates that the introduction of Ag helps to optimize the quality of the absorber, thereby reducing the concentration of interfacial and bulk defects. It also reduces carrier recombination and improves carrier lifetime from 0.86 ms to 1.75 ms. Ultimately increasing our cell efficiency from 7.55% to 10.64% when the Ag content reached 5%. These results clearly show that we have successfully achieved the modulation of defects in CZTSSe solar cells by Ag doping.