Suppression of Formamidinium Deprotonation and Regulation of Thin‐Film Stress Toward High Performance and Stability of Perovskite Solar Cells

ABSTRACT The efficiency of halide perovskite solar cells now rivals that of silicon‐based solar cells, but their commercialization is hindered by the deprotonation of formamidine cation (FA ⁺ ) in precursor solutions and subsequent stress accumulation during film crystallization. This work proposes an integrated molecular strategy that uses 4‐amino‐2,3,5,6‐tetrafluorobenzamide (4‐ATB) to achieve holistic stability management from solution chemistry to solid‐state thin films. By forming a multifaceted hydrogen‐bonding network through its amines and fluorine atoms, 4‐ATB suppressed FA ⁺ deprotonation and I ₂ generation, thereby maintaining precursor stability. During film formation, its rigid aromatic backbone showed close lattice matching with perovskite. Through dual‐site anchoring, 4‐ATB converted the film from a tensile‐stress state into a compressive‐stress state and suppressed thermal expansion upon heating, thereby enhancing the structural integrity. The n‐i‐p devices fabricated using this strategy achieved a power conversion efficiency exceeding 26%, along with retaining 97.15% of their initial efficiency over 1200 h of continuous one‐sun illumination at the maximum power point (MPP). This strategy regulated multi‐scale stability via a single molecular additive, helping facilitate the commercialization of perovskite optoelectronic devices.