In this study, we used simulations and modelling techniques to evaluate the performance of a tandem solar cell. The tandem cell comprises an Top sub-cell based on \(\:{\text{S}\text{b}}_{2}{\text{S}}_{3}\) , exhibiting an energy gap of 1.62 eV as an absorber, and a Bottom sub-cell composed of CZTSe, exhibiting a lower energy gap of 1.1 eV. The defects present in each layer, as well as the interface defects between the two layers, were carefully taken into account to make our study more representative of reality. Our methodology involved manipulating the thickness and carrier density in the lower sub-cell to identify the optimum conditions for its performance. Emphasis was placed on adjusting the thickness of the absorber layers in each sub-cell to determine the critical current matching point, ensuring uniform current levels in both parts of the tandem solar cell. In addition, we assessed the impact of varying the thickness of the absorber layer in the lower sub-cell on the overall performance of our tandem cell. The results obtained highlight the crucial importance of the thickness of the lower sub-cell in achieving maximum device efficiency. In particular, our work achieved an impressive efficiency of close to 23%, effectively demonstrating the relevance of our approach to optimizing the performance of the tandem solar cell.
