Rare earth ions with d-f transitions (Ce³⁺, Eu²⁺) 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 4f 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 Cs₃CeI₆ luminescence process is primarily driven by the energy transfer from the I₂-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.

具有df跃迁的稀土离子（Ce ³⁺ 、Eu ²⁺ ）由于其丰富的发射光谱、高光转换效率和优异的稳定性而成为电致发光应用的有前景的候选者。然而，直接将电荷注入4f轨道仍然是一个重大挑战，导致稀土发光二极管的外部量子效率不理想且工作电压较高。在此，我们提出了一种利用能量转移过程来解决这一困难的方案。 X射线光电子能谱和瞬态吸收光谱表明，Cs ₃ CeI ₆发光过程主要是由I ₂基自陷激子到Ce基弗伦克尔激子的能量转移驱动的。此外，通过增强自捕获激子发射和基于Ce的弗伦克尔激子激发之间的光谱重叠，大大提高了能量转移效率。当用作发光二极管中的有源层时，它们表现出最大亮度和外量子效率分别为1073 cd m ^-2和7.9%。