Ultrawide-Bandgap FAPbBr₃-Based Four-Terminal Perovskite/Silicon Tandem Solar Cell

Although perovskite/c-Si four-terminal (4T) tandem solar cells (TSCs) hold significant promise for commercialization, the frequently used midbandgap (1.50-1.80 eV) perovskite subcells are unstable and disproportionately contribute (∼60%) to the total power output, inducing the instability issue a formidable challenge. Herein, an ultrawide-bandgap (UWBG, >2.0 eV) FAPbBr₃ subcell is designed to shift major power generation to silicon subcell, while maintaining high efficiency. S-Q limit calculation predicts maximum efficiency ∼43% with over 60% of the output from the c-Si subcell. Furthermore, a Lewis base/acid dual-passivation strategy is developed to effectively suppress defects in FAPbBr₃, enabling a remarkable efficiency of 10.76% with a record V_OC of 1.63 V and a fill factor of 86.67%. The 4T perovskite/c-Si tandem reaches 29.62% efficiency, with the silicon subcell contributing 66.61%. Besides, the FAPbBr₃ device retains 95% efficiency after 4800 h of storage. Therefore, our work offers a viable route to stable, commercial perovskite/c-Si-4T TSCs.