Passivator Assisted Close Space Annealing for High Performance Wide‐bandgap Perovskite Solar Cells

Wide‐bandgap perovskite solar cells (PSCs) play crucial roles in determining the overall efficiencies of all‐perovskite tandem solar cells (TSCs). Tailoring the grain growth process is a key route to improve the film quality and device performance. Here we demonstrate a facile passivator assisted close space annealing (PA‐CSA) strategy to simultaneously enlarge the crystal size and passivate the defects. Filter paper was used as the solvent permeable membrane to slow down the fast crystallization and enlarge the grain size. At the same time, a precisely selected volatile material (fluorizated‐phenethylammonium chloride, F‐PEACl) embedded in the filter paper was employed as the passivator to eliminate defects in wide‐ E g perovskite film during annealing. The PA‐CSA processed wide‐ E g PSCs obtained the champion efficiencies of 21.28% (1.68 eV) and 20.24% (1.73 eV), enabling high‐performance all‐perovskite TSCs with efficiencies reaching 27% in both four‐terminal and monolithic two‐terminal tandem configurations, respectively. This PA‐CSA strategy provides an in‐situ passivating process for high‐performance PSCs and TSCs upon further industrial applications. This article is protected by copyright. All rights reserved.