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

Abstract

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.