Molecular Ferroelectric with Directional Polarization Field for Efficient Tin‐Based Perovskite Solar Cells

Abstract Due to the relatively inferior dielectric constant, Sn‐based perovskites exhibit lower defect tolerance and insufficient shielding effect compared with Pb‐perovskites. Upgrading built‐in electric field (BEF) in perovskite solar cells (PSCs) can be effective reduce large voltage deficit improve poor performance caused by low resulting from intrinsic of perovskites. Herein, 2‐methylbenzimidazole (MBI) molecular ferroelectric coercive high Curie‐temperature is introduced construct an additional FASnI 3 ‐based PSCs. The MBI promote exciton dissociation, enhance carrier population, suppress adverse residual defects on carriers, directional polarization film driven BEF PSCs broaden width depletion region. Additionally, molecules amine functional groups effectively regulate crystallization, passivate Sn‐related defects, oxidation barrier. Profiting above advantages, MBI‐modified device achieves a champion power conversion efficiency (PCE) 12.91%, keeping over 94% average PCE after 1056 h N 2 glovebox for unencapsulated device. This study highlights significant role ferroelectrics photovoltaics.