Surface Reconstruction of Perovskites with Organosilanes for High Performance and Highly Stable Solar Cells

Abstract Surface or interface engineering is one of the most effective strategies to improve the device performance and stability of perovskite solar cells (PSCs), owing to the fact that the defects are mainly located at the surface. Organosilanes are among the most promising surface modifiers due to their unique cross‐linking ability, which makes a robust layer to further protect the underneath perovskites. However, the influence of tail functional groups of organosilanes on the device performance and stability has never been systematically investigated. Herein, a series of organosilanes with different chain lengths, fluorination, and different interactions toward perovskite are applied to modify the perovskite. Tail functional groups that show passivation ability toward perovskite are demonstrated to effectively reduce trap densities and thus improve the power conversion efficiencies (PCEs), while the fluorinated functional groups are beneficial for high stability. Finally, PSCs based on 3,3,3‐trifluoropropyltrimethoxysilane (FPTMS) modification showed a high PCE of 23.0% with the best operational stability. The encapsulated device maintained 85% of the initial PCE after 1725 h under continuous 1 sun equivalent illumination in air. The work may provide important insights into designing modifiers for high‐performance PSCs with high stability.