“Whole‐Body” Fluorination for Highly Efficient and Ultra‐Stable All‐Inorganic Halide Perovskite Quantum Dots

Abstract Inherent “soft” ionic lattice nature of halide perovskite quantum dots (QDs), triggered by the weak Pb−X (X=Cl, Br, I) bond, is recognized as the primary culprit for their serious instability. A promising way is to construct exceedingly strong ionic interaction inside the QDs and increase their crystal cohesive energy by substituting the interior X − with highly electronegative F − , however, which is challenging and hitherto remains unreported. Here, a “whole‐body” fluorination strategy is proposed for strengthening the interior bonding architecture of QDs, wherein the F − are uniformly distributed throughout the whole nanocrystal encompassing both the interior lattice and surface, successfully stabilizing their “soft” crystal lattice and passivating surface defects. This approach effectively mitigates their intrinsic instability issues including light‐induced phase segregation. As a result, light‐emitting devices based on these QDs exhibit exceptional efficiency and remarkable stability.