Study on High-Efficiency Double Perovskite/Silicon Heterojunction Tandem Cells with Sb-Doped Cs2AgBiBr6

In this work, we use Silvaco ATLAS simulation software to design and study the optimal scale of the Cs2AgBiBr6 double perovskite/silicon heterojunction tandem structure under ideal conditions, with theoretical efficiency of 27.25% in numerical simulation, and when Cs2AgBi0.75Sb0.25Br6 is used as the top cell, the theoretical efficiency increases to 37.14%, which is higher than the efficiency of each sub-cell. The lead-free double perovskite has advantages including stable structure, adjustable bandgap, and non-polluting nature, and thus has great photovoltaic application potential. Density functional theory calculations were performed using CASTEP to study the crystal structure and electronic properties of the mixed halide Cs2AgBi1−xSbxBr6 (x = 0, 0.25). The study shows that Sb-doped Cs2AgBi0.75Sb0.25Br6 with a bandgap of 1.8 eV is more suitable for the top cell than Cs2AgBiBr6 with a bandgap of 2.05 eV, which realizes a more suitable absorption spectral distribution, current matching, and correspondingly higher efficiency, with a theoretical efficiency significantly higher than that of current mainstream perovskite tandem cells.