Impurity Ions Codoped Cesium Lead Halide Perovskite Nanocrystals with Bright White Light Emission toward Ultraviolet–White Light-Emitting Diode

White light-emitting diodes (WLEDs) based on all-inorganic perovskite CsPbX3 (X = Cl, Br, I) nanocrystals (NCs) have attracted extensive interests. However, the native ion exchange among halides makes them extremely difficult to realize the white emission. Herein, we demonstrate a novel strategy to obtain WLED phosphors based on the codoping of different metal ion pairs, such as Ce3+/Mn2+, Ce3+/Eu3+, Ce3+/Sm3+, Bi3+/Eu3+, and Bi3+/Sm3+ into stable CsPbCl3 and CsPbClxBr3–x NCs. Notably, by the typical anion exchange reaction, the highly efficient white emission of Ce3+/Mn2+-codoped all-inorganic CsPbCl1.8Br1.2 perovskite NCs was achieved, with an optimal photoluminescence quantum yield of 75%, which is much higher than the present record of 49% for single perovskite phosphors. Moreover, the WLED with a luminous efficiency of 51 lm/W based on the 365 nm ultraviolet chip and CsPbCl1.8Br1.2:Ce3+/Mn2+ nanophosphor was achieved. This work represents a novel device for perovskite-based phosphor-converted WLEDs.