Blue-Light-Excited Y₂MgTiO₆:Ni²⁺, Cr³⁺ Phosphors with Ultrabroadband NIR Emission for Multifunctional Applications

The creation of high-performance broadband near-infrared (NIR) phosphors, excitable by blue-light-emitting diode (LED) chips, holds significant implications for advancing NIR phosphor-converted LEDs (pc-LEDs). Herein, we report a Ni²⁺-doped Y₂MgTiO₆ (YMTO) phosphor that exhibits a broadband emission in the NIR-II region (1100-1650 nm), featuring a peak at 1350 nm and a full width at half-maximum (fwhm) of 235 nm. Analysis of D_q/B and electron localization function (ELF) indicates that the broadband NIR-II emission originates from Ni²⁺ ions situating in a weak octahedral crystal field. Co-doping with Cr³⁺ results in a redshift of the excitation wavelength to 460 nm, thereby allowing effective excitation by commercially available blue LED chips. Meanwhile, the luminescence intensity in the NIR-II region has boosted by 200%, and the NIR emission stability is enhanced from 42.1%@398 K to 56.0%@398 K. Finally, the multifunctional applications of the YMTO:0.015Ni²⁺, 0.015Cr³⁺ phosphor have been demonstrated in night vision, nondestructive testing, compound identification, and optical temperature sensing.