Efficient Deep-Blue Light-Emitting Diodes from Highly Luminescent Eu<sup>2+</sup>-Doped Alkali Metal Halide Nanocrystals via Lattice Field Modulation
Li Xu, Xu Chen, Huifang Jiang, Meng Wang, Shuailing Lin, Zhuangzhuang Ma, Hui Wang, Huifang Ji, Mochen Jia, Yanbing Han, Jinyang Zhu, Gencai Pan, Di Wu, Xinjian Li, Wen Xu, Ying Liu, Chongxin Shan, Zhifeng Shi
Abstract
Lead-halide perovskite nanocrystals (NCs) are promising for fabricating deep-blue (<460 nm) light-emitting diodes (LEDs), but their development is plagued by low electroluminescent performance and lead toxicity. Herein, the synthesis of 12 kinds of highly luminescent and eco-friendly deep-blue europium (Eu 2+ )-doped alkali-metal halides (AX:Eu 2+; A = Na +, K +, Rb +, Cs +; X = Cl –, Br –, I – ) NCs is reported. Through adjustment of the coordination environment, efficient deep-blue emission from Eu-5 d → Eu-4 f transitions is realized. The representative CsBr:Eu 2+ NCs exhibit a high photoluminescence quantum yield of 91.1% at 441 nm with a color coordinate at (0.158, 0.023) matching with the Rec. 2020 blue specification. Electrically driven deep-blue LEDs from CsBr:Eu 2+ NCs are demonstrated, achieving a record external quantum efficiency of 3.15% and half-lifetime of ∼1 h, surpassing the reported metal-halide deep-blue NCs-based LEDs. Importantly, large-area LEDs with an emitting area of 12.25 cm 2 are realized with uniform emission, representing a milestone toward commercial display applications.