High‐Performance Tunable Near‐Infrared Emitters of Cr3+‐Activated Garnet Phosphor Enabled by Chemical Unit Co‐Substitution

Abstract The escalating demand for portable near‐infrared (NIR) light sources has posed a formidable challenge to the development of NIR phosphors characterized by high efficiency and exceptional thermal stability. Taking inspiration from the chemical unit co‐substitution strategy, high‐performance tunable (Lu 3‐ x Ca x )(Ga 5‐ x Ge x )O 12 :6%Cr 3+ ( x = 0–3) phosphors are designed with an emission center from 704 to 780 nm and a broadest full width at half maximum (FWHM) of up to 172 nm by introducing Ca 2+ and Ge 4+ ions into the garnet structure. In particular, Lu 3 Ga 5 O 12 :6%Cr 3+ demonstrates an anti‐thermal quenching phenomenon ( I 423K = 113.1%). Compared to Lu 3 Ga 5 O 12 :6%Cr 3+ , Lu 2 CaGa 4 GeO 12 :6%Cr 3+ exhibits significantly improved FWHM and IQE by 108 nm and 25.5%, respectively, while maintaining good thermal stability ( I 423K = 80.4%). Finally, Lu 2 CaGa 4 GeO 12 :6%Cr 3+ phosphor is combined with a 465 nm blue LED chip to fabricate NIR LED devices, exhibiting a NIR electroluminescence efficiency of 13.31%@100 mA and demonstrating successful applications in nocturnal illumination and biomedical imaging technology. This work offers a fresh perspective on the design of highly efficient NIR garnet phosphors.