Fluorinated Lead‐Chelating Molecules Boost Performance, Stability, and Safety of Hole Transport Layer‐Free Carbon‐Based Perovskite Solar Cells

Abstract

Abstract Hole transport layer‐free carbon‐based perovskite solar cells (HTL‐free C‐PSCs) hold promise for low‐cost, stable photovoltaics but suffer from poor interfacial charge extraction, inferior defect passivation, and unresolved environmental risk. Here, we reported a multifunctional interfacial engineering strategy using fluorinated lead‐chelating (FLC) molecules containing sulfonate groups, fluoride atoms, and metal ions. Sulfonate groups coordinated with undercoordinated Pb 2+ ions, fluoride atoms formed hydrogen bonds with organic cations, and K + ions stabilized halide anions, synergistically passivating deep‐level defects and enhancing thermal stability. FLC modification also reduced the perovskite work function (from −4.14 to −4.39 eV), improving energy level alignment and facilitating hole extraction at the perovskite/carbon interface. As a result, the optimized devices achieved a champion power conversion efficiency of 20.7%, among the highest for fully solution‐processed planar HTL‐free C‐PSCs. Unencapsulated devices retained over 93% of initial efficiency after 2000 h in ambient air or after 500 h at 60 °C. Importantly, strong FLC‐Pb 2+ chelation significantly reduced lead leakage from severely damaged devices under acidic aqueous environment (334.7 to 53.7 mg m −2  h −1 ), achieving ∼84% sequestration efficiency. This work presents a unified strategy to enhance efficiency, stability, and environmental safety of simplified perovskite photovoltaics.