Toward α-CsPbI₃ Quantum Dots via Dual-Functional Fluorinated Acidic Ligand

Weakly bonded native ligands severely degrade the performance of perovskite quantum dot (PeQD) light-emitting diodes (LEDs). While conventional approaches can be used to strengthen ligand binding, they fail to achieve complete ligand exchange, leaving residual ligands that promote degradation. Herein, we present a dual-functional fluorinated benzyl phosphonic acid (F-BPA) ligand that modulates the acidity and enhances the binding affinity between the phosphonate groups of F-BPA and the perovskite surface compared to BPA due to a significant redistribution of the electrostatic potential of the molecule induced by fluorination. The F-BPA treatment facilitates effective ligand exchange and obtains well-passivated CsPbI 3 PeQDs with improved stability under thermal, light, and polar solvent stress. Red-emissive LEDs achieved a maximum external quantum efficiency of 24.0% with improved device stability (half-lifetime of 1,020 min at 100 cd m –2 ). This study demonstrates a dual-functional ligand strategy and opens a new pathway toward PeQDs for next-generation display technologies.