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

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-C 61 -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 MAPbI 3 . 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 N 2 , 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.