S<sub>8</sub> Additive Enables CsPbI<sub>2</sub>Br Perovskite with Reduced Defects and Improved Hydrophobicity for Inverted Solar Cells
Quan Yuan, Siwei Yi, Dongwei Han, Feng Wang, Qiaoyan Li, Rong Huang, Yi Cui, Ruyue Zheng, Dong‐Ying Zhou, Lai Feng
Abstract
Though prized for excellent thermal stability, inorganic perovskites are still behind organic/inorganic hybrid perovskites due to their high‐density defects and poor hydrophobicity. Herein, trace hydrophobic S 8 is used as additive to optimize the solution‐processed CsPbI 2 Br perovskite film. A series of characterizations reveal that S 8 additive not only leads to retarded crystallization of α‐CsPbI 2 Br perovskite at low temperature (<150 °C) via self‐formed Pb(S 8 ) x 2+ intermediate but also induces efficient grain‐boundary passivation via distinctive PbS coordination interaction and reduced wettability on perovskite surface, which all point to the formation of the perovskite film with reduced defects and improved hydrophobicity. As a result, the inverted perovskite solar cells (PSCs) based on the optimized all‐inorganic perovskite of CsPbI 2 Br:S 8 deliver an increased power conversion efficiency (PCE) from 12.76% to 14.46% as well as remarkably enhanced device stability under thermal or ambient condition. This work thus provides a simple way as well as new insights for boosting the performance of solution‐processed all‐inorganic perovskite.