Breaking Efficiency Barrier: Dual‐Channel Energy Transfer Enables Record 1540 nm NIR LEDs from Er3+‐Doped Cs3DyI6 Nanocrystals

Er3+-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 Cs3DyI6:Er3+ nanocrystal is engineered with a tetragonal phase structure. The study reveals a unique dual-channel energy transfer mechanism. The 574 nm emission, stemming from 4F9/2-2H13/2 orbital transitions of Dy3+ ions, enables phonon-assistant energy transfer to excite 4I15/2- 4S3/2 of Er3+ ions. Meanwhile, self-trapped excitons (STEs) contribute additional energy via a 488 nm broadband emission to excite 4I15/2-4F7/2 of Er3+. The two pathways synergize to facilitate efficient 1.54 µm emission from Er3+ 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.