Approaching 26% Efficiency in Inverted FAPbI ₃ Perovskite Solar Cells Enabled by Tailored Fluoropyridine Derivative Additives

ABSTRACT Formamidinium lead triiodide (FAPbI 3 ) is a leading candidate for high‐performance perovskite solar cells (PSCs) because of its near‐ideal bandgap and excellent thermal stability. However, its practical development is still limited by challenges in crystallization control and phase stability. While compositional engineering strategies often broaden optical bandgap and introduce heterogeneity, additive strategies offer a promising alternative for optimizing perovskite properties. In this study, a series of novel fluoropyridine derivatives are introduced as additives into the precursor solution for fabricating FAPbI 3 ‐based PSCs. Among them, 3,5‐difluoropyridine (DFPy) additive effectively modulates the crystallization process, yielding perovskite films with reduced defect density, suppressed non‐radiative recombination, and enhanced phase stability. The corresponding devices achieved the highest performance, with the optimized inverted PSCs delivering a champion power conversion efficiency (PCE) of nearly 26% along with a J SC of 25.77 mA cm −2 , a V OC of 1.18 V, and an FF of 85.62%. Furthermore, the DFPy modified devices exhibit significantly enhanced humidity and thermal stability, attributed to the superior film quality. This study establishes a new additive paradigm for fabricating efficient and stable FAPbI 3 ‐based PSCs, paving the way for further exploration of pyridine‐derived additives in high‐performance perovskite photovoltaics.