Fluorinated Pseudo‐Halide Anion Enables >19% Efficiency and Durable Perovskite Quantum Dot Solar Cells

Metal halide perovskite quantum dots (PQDs), like formamidinium lead triiodide (FAPbI3), hold significant promise for next-generation photovoltaics. Surface manipulation of PQDs has been extensively reported to be crucial to their photovoltaic performance due to the dynamic binding of capping long-chain ligands. In this work, an efficient surface engineering strategy employing a multifunctional fluorinated pseudo-halide anion ligand, hexafluorophosphate (PF6 -) is reported for achieving efficient FAPbI3 PQD solar cells. Leveraging its coordination capability, large ionic radius (2.38 Å), and intrinsic hydrophobicity, PF6 - simultaneously passivates iodide vacancies, minimizes inter-dot spacing for enhanced electronic coupling, suppresses ion migration, and provides a hydrophobic barrier. By replacing oleate ligands with PF6 - in FAPbI3 PQDs, an unprecedented high efficiency of 19.01% (17.19% for a 1 cm2-sized device) is achieved, and enhanced storage and operational stability. These findings will provide insight into the design of robust surface structures and low-trap-states PQD films toward high-efficiency and stable solar cells.