Cl‐Anion Engineering for Halide Perovskite Solar Cells and Modules with Enhanced Photostability

This article shows the new insights for stabilizing the p‐i‐n perovskite solar cells (PSCs) and modules based on double cation CsFAPbI 3 absorber using CsCl additives. The presence of chlorine in the perovskite crystal structure results in the decrease of the lattice parameters by 0.6 ± 0.06%, in the increase of the bandgap value (+0.018 eV), and charge carrier lifetimes with respect to the undoped one. The champion PSCs based on the CsFAPbI 3− x Cl x absorber show an increase in power conversation efficiency from 18.06% up to 20.13% after Cl doping. The light‐soaking stability of PSCs measured at maximum power point demonstrates impressive increase of the T80 from 1128 h for CsFAPbI 3 ‐based devices to more than 3479 h for CsFAPbI 3− x Cl x ones. It is found that the Cl doping suppresses the formation of lead iodide and pure CsPbI 3 induced by decomposition and phase segregation processes only when the perovskite is covered with the C 60 /BCP electron‐transporting layer (ETL), while in the structure without ETL Cl additive is not effective. Finally, the high potential of Cl‐anion engineering for the perovskite modules (5 × 5 cm 2 ) is demonstrated, which shows promising 17.08% of power conversation efficiency and light‐soaking stability for 1396 h.