Halogen vacancies are of great concern in blue‐emitting perovskite quantum‐dot light‐emitting diodes because they affect their efficiency and spectral shift. Here, an enriched‐bromine surface state is realized using a facile strategy that employs a PbBr2 stock solution for anion exchange based on Cd‐doped perovskite quantum dots. It is found that the doped Cd ions are expected to reduce the formation energy of halogen vacancies filled by the external bromine ions, and the excess free bromine ions in solution are enriched in the surface by anchoring with halogen vacancies as sites, accompanied with the shedding of surface long‐chain ligands during the anion exchange process, resulting in a Br‐rich and “neat” surface. Moreover, the surface state exhibits good passivation of the surface defects of the controlled perovskite QDs and simultaneously increases the exciton binding energy, leading to excellent optical properties and stability. Finally, the sky‐blue emitting perovskite quantum‐dot light‐emitting diodes (QLEDs) (490 nm) are conducted with a record external quantum efficiency of 14.6% and current efficiency of 19.9 cd A−1. Meanwhile, the electroluminescence spectra exhibit great stability with negligible shifts under a constant operating voltage from 3 to 7 V. This strategy paves the way for improving the efficiency and stability of perovskite QLEDs.

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Lead‐free halide perovskites are emerging as promising eco‐friendly candidates for next‐generation solid‐state lighting because of their nontoxicity and availability for broad emission. Herein, a modified room‐temperature anti‐solvent precipitation method is developed to synthesize the Sb3+‐doped, In‐based, lead‐free halide perovskites in microplate/microcrystal structure with different emission colors. The layered structure of InCl3 serves as the template for the growth of Cs2InCl5(H2O):Sb3+ microplate phosphors. Moreover, the presence of HCl not only improves the solubility of precursors, but also provides the acid etching effect. The resultant Sb3+‐doped Cs2InCl5(H2O) microplate phosphors show bright yellow emission with photoluminescence quantum yield up to 92.4%. Furthermore, Cs3InCl6:Sb3+ and Cs2NaInCl6:Sb3+ are synthesized through the similar method, which displays the bright green and deep‐blue emission, respectively. Subsequently, the proof‐of‐concept white light‐emitting diodes (WLEDs) are fabricated based on Cs2NaInCl6:Sb3+ + Cs2InCl5(H2O):Sb3+ and Cs2NaInCl6:Sb3+ + Cs3InCl6:Sb3+ + Cs2InCl5(H2O):Sb3+ phosphors, which achieves high‐quality white light with the color rendering index (CRI) of 91.6 and 95.4, respectively. The results greatly advance the development of lead‐free halide perovskite phosphors synthesis, which may offer new possibilities for high CRI WLEDs fabrication.

Ligand exchange has been demonstrated as an efficient strategy to improve the photoluminescence quantum yield (PLQY) and stability of quantum dots (QDs). Long-term illumination can considerably accelerate the ligand desorption after ligand exchange because of the weak bonding between the ligand and QDs. Here, a novel light-driven luminescence evolution strategy in combination with ligand exchange is devised by using N-acetyl-L-cysteine (NAC) as a ligand. NAC is expected to coordinate with the uncoordinated Pb 2+ to improve the bonding between NAC and QDs. Light illumination is employed to accelerate the digestive ripening process and realize the uniform distribution of QDs. On the basis of the synergistic effect of NAC ligand exchange and light illumination, the CsPbBr 3 QDs show reduced surface defects with nearly 100% PLQY and remarkable stability in polar solvents. Furthermore, a white light-emitting diode is demonstrated with a high rendering index of 80.7 and color temperature of 5595 K.

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