Efficient deep-blue electroluminescence from Ce-based metal halide
Longbo Yang, Hainan Du, Jinghui Li, Yiqi Luo, Xia Lin, Jincong Pang, Yuxuan Liu, Liang Gao, Siwei He, Jae‐Wook Kang, Wenxi Liang, Haisheng Song, Jiajun Luo, Jiang Tang
Abstract
Abstract Rare earth ions with d-f transitions (Ce 3+ , Eu 2+ ) have emerged as promising candidates for electroluminescence applications due to their abundant emission spectra, high light conversion efficiency, and excellent stability. However, directly injecting charge into 4 f orbitals remains a significant challenge, resulting in unsatisfied external quantum efficiency and high operating voltage in rare earth light-emitting diodes. Herein, we propose a scheme to solve the difficulty by utilizing the energy transfer process. X-ray photoelectron spectroscopy and transient absorption spectra suggest that the Cs 3 CeI 6 luminescence process is primarily driven by the energy transfer from the I 2 -based self-trapped exciton to the Ce-based Frenkel exciton. Furthermore, energy transfer efficiency is largely improved by enhancing the spectra overlap between the self-trapped exciton emission and the Ce-based Frenkel exciton excitation. When implemented as an active layer in light-emitting diodes, they show the maximum brightness and external quantum efficiency of 1073 cd m −2 and 7.9%, respectively.