Engineering the Ligand Reactivity through Tailored Electron‐Withdrawing Effects for Outdoor‐Stable Perovskite Solar Cells and Modules

ABSTRACT 2D/3D perovskite heterostructures have advanced the performance of perovskite solar cells. However, ion diffusion at the 2D/3D interface under illumination and prolonged heat affects device stability and scalability. Here, we studied the electron‐withdrawing strength of aromatic ammonium ligand on perovskite interface stability. We tuned the electron‐withdrawing strength of the ligand through the incorporation of oxygen atoms on heterocyclic rings, and found that the ligand possessing the strongest electron‐withdrawing capability effectively suppresses 2D formation while preventing cation interdiffusion and maximizing defect passivation, outperforming conventional 2D/3D strategies. Consequently, we achieved power conversion efficiencies of 26.1% in 0.16 cm 2 lab‐scale cells and 19.1% in 809 cm 2 industrial‐scale solar modules. These encapsulated modules exhibited excellent damp‐heat (85°C/85% relative humidity) stability and operational durability, with <10% efficiency loss after 2500 and 3000 h, respectively. Moreover, the modules maintained steady power output over 30 days of outdoor operation, underscoring their potential for practical real‐world applications.