Breaking Efficiency Barrier: Dual‐Channel Energy Transfer Enables Record 1540  nm NIR LEDs from Er ³⁺ ‐Doped Cs ₃ DyI ₆ Nanocrystals

Abstract

Abstract Er 3+ ‐doped 1.54 µm light‐emitting diodes (LEDs) operating in the optical communication C‐band are central to the development of integrated photonic systems. Given the pressing need for efficient, stable, cost‐effective, and low‐voltage‐driven 1.54 µm light sources, a lanthanide‐based metal halide Cs 3 DyI 6 :Er 3+ nanocrystal is engineered with a tetragonal phase structure. The study reveals a unique dual‐channel energy transfer mechanism. The 574 nm emission, stemming from 4 F 9/2 ‐ 2 H 13/2 orbital transitions of Dy 3+ ions, enables phonon‐assistant energy transfer to excite 4 I 15/2 ‐ 4 S 3/2 of Er 3+ ions. Meanwhile, self‐trapped excitons (STEs) contribute additional energy via a 488 nm broadband emission to excite 4 I 15/2 ‐ 4 F 7/2 of Er 3+ . The two pathways synergize to facilitate efficient 1.54 µm emission from Er 3+ ions, overcoming limitations of traditional single‐path energy transfer systems. To optimize device performance, 2,4,6‐triphenyl‐1,3,5‐trioxane (TPPO) is employed for passivating surface defects to enhance the overall photoluminescence quantum yield up to 87.4%. Precise control of the LiF interlayer thickness (1–2 nm) achieves balanced electron–hole injection, significantly improving both external quantum efficiency (EQE) and operational stability. The fabricated infrared LED device demonstrates outstanding performance, with a record EQE of 2.76% at 1.54 µm and a half‐life of 345 min, marking a significant milestone in optical communication technology.