Strain-Negligible Eu Doping Enabled Color-Tunable Harsh Condition-Resistant Perovskite Nanocrystals for Superior Light-Emitting Diodes.

Cesium lead halide (CsPbX, X = Br, Cl, I) perovskite nanocrystals (NCs) possess tunable band gaps across the entire visible spectral range and are promising for various optoelectronic device applications. However, poor performance in adverse conditions limits their further development in practical optoelectronics. Herein, highly stable perovskite NCs are developed by doping europium(II) (Eu) into the B-site of CsPbBr with negligible lattice distortion/strain. Eu-doped CsPbBr NCs exhibit tunable green-to-cyan emissions, high photoluminescence quantum yield, and good resistance to harsh conditions, including ultraviolet irradiation, erosion of moisture, and corrosion of polar solvent molecules. In particular, the thermal stability of CsPbBr NCs after Eu doping is greatly enhanced under continuous heating in air, while exhibiting the emissions of Eu. Furthermore, a Eu-doped CsPbBr NC-based cyan light-emitting diode is fabricated, which exhibits narrow exciton emission driven under different current densities. This work would open the avenue to develop the rational lanthanide ion doping strategy for further advancing perovskite nanomaterials toward practical applications.