Impact of normal and inverse spinel structure evolution induced by co-substitution of chemical units on the luminescence properties of Ni2+-Activated Gallium Titanate Phosphor NIR-II

The rapid advancement of near-infrared light source technology has positioned phosphor-converted light-emitting diodes (PC-LEDs) operating within the near-infrared spectrum at the forefront of interdisciplinary research, with extensive applications in biomedicine, food quality assessment, and agricultural monitoring. However, the development of light sources that cover the second near-infrared spectral window (NIR-II, 1000–1700 nm) continues to encounter significant technical challenges. Inspired by chemical unit co-substitution strategy, we successfully developed a broadband NIR-II phosphor designated as (Li 0.7 Mg 0.3 )(Ga 0.7 Mg 0.3 )TiO 4 :0.003Ni 2+ ((L 0.7 M 0.3 )(G 0.7 M 0.3 )T:0.003Ni 2+ ) through [Mg 2+ -Mg 2+ ] dual-site substitution in orthorhombic LiGaTiO 4 (LGT) normal spinel. This co-substitution strategy resulted in an impressive enhancement of the internal quantum efficiency by 29.77 %–64.8 %, while maintaining thermal stability without significant attenuation at elevated temperature. To validate its practical utility, we fabricated prototype for a NIR phosphor-converted LED by integrating (L 0.7 M 0.3 )(G 0.7 M 0.3 )T:0.003Ni 2+ a commercial 340 nm chip. The resulting device demonstrates promising potential for applications in food safety inspection and deep-tissue infrared imaging. This work provides a perspective for designing broadband high-efficiency NIR-II phosphors via modulation of crystal field environment.