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

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 ⁴F_9/2-²H_13/2 orbital transitions of Dy³⁺ ions, enables phonon-assistant energy transfer to excite ⁴I_15/2- ⁴S_3/2 of Er³⁺ ions. Meanwhile, self-trapped excitons (STEs) contribute additional energy via a 488 nm broadband emission to excite ⁴I_15/2-⁴F_7/2 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.