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

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 I₂ 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.