Efficiency potential of MA_xFA_1-xPbBrI₂/MASnI₃ tandem solar cells unveiled by full opto-electronic simulation

Abstract All-perovskite tandem solar cell is a novel device structure that employs multilayers to enhance photovoltaic conversion efficiency, this technology has the potential to exceed the Shockley–Queisser (S-Q) theoretical efficiency limit for single-junction solar cells. Although the research and development of all-perovskite tandem solar cells are still in the early stages, they have attracted widespread attention and interest. This study focuses on the numerical analysis of MA x FA 1-x PbBrI 2 /MASnI 3 all-perovskite tandem solar cells, combining electrical and optical simulations to investigate two-terminal (2-T) and four-terminal (4-T) tandem solar cells. These cells are composed of an MA x FA 1-x PbBrI 2 -based top cell and an MASnI 3 -based bottom cell. This study aims to analyze the influences of charge transport layers and the material composition, thickness, and defect density of the perovskite absorber layers on the performance of the tandem cells. High-efficiency 4-T all-perovskite tandem solar cells have been realized through optimizing the thickness of the absorber layers of the sub-cells, and high-efficiency 2-T all-perovskite tandem solar cells have been achieved through current matching, inserting a SiO 2 layer between the Ag back electrode and the HTL of the bottom cell of the 2-T tandem cell can further improve the J sc of the top and bottom cells. The optimized 2-T all-perovskite tandem solar cells demonstrate a maximum efficiency of 35.16% when MA 0.75 FA 0.25 PbBrI 2 is used to make the top cell absorber layer, while the optimized 4-T all-perovskite tandem solar cells achieve a maximum efficiency of 35.60% when MA 0.25 FA 0.75 PbBrI 2 is used. These results provide valuable insights and direction for the design of high-efficiency all-perovskite tandem solar cells.