Fluorination-Driven Multi-Site Anchoring for Highly Efficient and Stable Perovskite Solar Cells

Molecular passivation has been demonstrated to be effective in mitigating interfacial defects in perovskite solar cells (PSCs). However, achieving balanced interfacial interactions that can simultaneously suppress defects and promote charge extraction remains challenging. Herein, a fluorination-driven multi-site anchoring strategy is proposed to deliver highly efficient and stable PSCs through the outstanding passivation effect of 3-fluoro-4-(aminomethyl)pyridinium ammonium diiodide (3-F-AMP). The fluorination in 3-F-AMP modulates the molecular dipole and enforces a nearly planar geometry, enabling the fluorine atom, protonated amino, and protonated pyridine nitrogen sites to cooperatively interact with the perovskite surface. This multi-site anchoring strategy can not only inhibit the formation of residual PbI 2 and then stabilize the perovskite lattice but also reduce nonradiative recombination and create a well-matched perovskite/electron-transport layer interface with improved charge extraction. As such, the 3-F-AMP-treated devices exhibit significantly enhanced photovoltaic performance, achieving champion efficiencies of 25.82 and 22.69% for the 1.53 and 1.68 eV perovskites, respectively, and a power conversion efficiency of 25.07% for 1.24 cm 2 large-area devices, together with markedly improved operational stability under ISOS protocols. This work paves a novel path for the rational design of multi-site passivators to facilitate the industrialization of PSCs.