Bulk Restructure of Perovskite Films via Surface Passivation for High‐Performance Solar Cells

Abstract Defects in perovskite films and the suboptimal interface contact largely limit the performance and stability of inverted perovskite solar cells (PSCs). A simple surface post‐treatment with N‐benzyloxycarbonyl‐d‐valine (NBDV) is developed to overcome these problems. The device performance following NBDV treatment is systemically investigated. It is showed that NBDV surface post‐treatment results in the bulk restructure of the entire perovskite film and improves the film‐forming property of [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester. The grain sizes, crystallinity, trap states, cathode interfaces, as well as the built‐in field are also improved, which result in PSC performance and stability enhancement. A relatively higher power conversion efficiency (PCE) of 21.80% is reached, which is comparable to the PCE record based on single‐crystal MAPbI₃. Meanwhile, the PCE of the NBDV devices can retain ≈77% and 84% of the initial value after storage for 768 h (32 days) in air and 8376 h (349 days) in N₂, respectively, while the control devices only maintain ≈53% and 38% of their initial PCE values under the same exposure conditions. This work provides means to promote bulk, surface, and interface regulation toward high performance and stable inverted PSCs.