Regulating Compressive Strain Enables High-Performance Tin-Based Perovskite Solar Cells

Tin (Sn)-based perovskites have emerged as promising alternatives to lead (Pb)-based perovskites in thin-film photovoltaics due to their comparable properties and reduced toxicity. Strains in perovskites can be tailored to modulate their optoelectronic properties, but mechanisms for the effects of strains on Sn-based perovskite films and devices are unrevealed and corresponding strain engineering is unexplored. Herein, a strain engineering strategy is developed through incorporating 4-fluorobenzylammonium halide salts (FBZAX, X = I, Br, Cl) into the perovskite precursor to regulate the strain effects in resultant Sn-based perovskite films. It is found that a moderate level of compressive strain achieved by FBZABr alleviates the dislocations within perovskites to enhance carrier transport and reduces the defect density to prolong carrier lifetime. These improvements enable a champion efficiency exceeding 14% of Sn-based perovskite solar cells with excellent operational stability.