Fluorination‐Induced Dual‐Functionalized Interface with Multiple Passivation Sites for High‐Performance Inverted Perovskite Solar Cells

Abstract Tailoring the self‐assembled monolayer (SAM)/perovskite interface is an effective approach to enhance hole‐extraction in p‐i‐n structured perovskite solar cells (PSCs). However, the co‐SAM strategy faces the challenge of competing anchor sites, which can interfere with the intended function of the original SAM. In this study, a fluorination strategy is used to design and synthesize a dual‐functionalized interfacial material, [2,3,5,6‐tetrafluoro‐4‐(trifluoromethyl) phenyl] phosphonic acid (FPA). Multiple active sites in FPA not only compensate for the anchoring deficiencies of the SAM but also effectively passivate the buried defects of the perovskite through coordination and hydrogen bonding, thereby effectively mitigating both deep and shallow defects at the SAM/perovskite interface. Ultimately, the efficiency of the best‐performing solar cells increases from 23.38% of the control device to 25.08% of the modified devices. In parallel, the unencapsulated devices retain over 90% of its initial efficiency after aging 1000 h at RH (65 ± 5)% in air at (25 ± 5) °C. The study provides an important approach in regulating the SAM/perovskite interface for enhanced charge extraction and environmental stability of the PSCs.