Ho3+-sensitized blue-excitable Cs2NaHoCl6:Yb3+, Er3+ double perovskites for effective dual-band NIR emission and multifunctional pc-LED applications

Dual-band near-infrared (NIR) phosphors simultaneously covering the NIR-I (700-1000 nm) and NIR-II (1000-1700 nm) windows are highly desirable for practical optoelectronic devices, yet conventional rare-earth doped systems typically rely on ultraviolet sensitization. Herein, we report Yb 3+ /Er 3+ co-doped Cs 2 NaHoCl 6 double perovskite microcrystals (MCs) synthesized via a green aqueous-phase evaporation method, in which the intrinsic ∼450 nm absorption of Ho 3+ serves as a self-sensitizer, enabling competitive energy transfer from Ho 3+ to Yb 3+ and Er 3+ , predominantly via dipole-dipole interactions. This generates efficient dual-band emissions at 985 nm (NIR-I) and 1540 nm (NIR-II), with a high photoluminescence quantum yield (PLQY) of 85.6% under blue-light excitation, alongside excellent thermal stability and photostability. An NIR phosphor-converted light-emitting diode (pc-LED) fabricated with the optimized phosphor demonstrates practical utility in night vision, non-destructive detection, and high-contrast biological imaging. This work establishes an eco-friendly route for mass-producing efficient dual-band NIR emitters directly compatible with commercial blue LED chips.