Surface Ligand Reorganization of Perovskite Quantum Dots for High‐Performance Pure‐Blue Light‐Emitting Diodes

ABSTRACT Perovskite quantum dots (PeQDs) hold great promise for pure‐blue perovskite light‐emitting diodes (PeLEDs), yet their development remains constrained by the disordered long‐chain organic ligand arrangement inherent to synthesis and severe surface defects. These issues lead to inefficient radiative recombination under electrical bias, hindering both efficiency and color purity. Herein, we demonstrate a controlled thermally induced surface engineering strategy that triggers the dynamic reorganization and densification of long‐chain organic ligands on CsPbBr x Cl 3‐x PeQD surfaces. This thermally driven surface healing process strengthens ligand‐PeQD coordination and substantially increases surface coverage, enabling effective defect passivation while preserving the structural integrity of the PeQD cores. The optimized annealing yields pure‐blue PeLEDs with an external quantum efficiency (EQE) of 8.55%, an electroluminescence peak at 465.2 nm, a narrow full‐width at half‐maximum of 18.5 nm, and Commission Internationale de l'Éclairage coordinates (0.131, 0.056) that closely approach the Rec. 2020 blue standard. Moreover, the annealed PeQDs exhibit outstanding colloidal and structural stability, and devices fabricated from PeQDs stored for 30 days retain 90% of their initial EQE. By elucidating the temperature‐dependent competition between kinetically favored ligand reorganization and thermodynamically driven ligand desorption, this work establishes a mechanistic framework and a practical route toward high‐performance, spectrally stable pure‐blue PeLEDs.