High‐Performance Tunable Near‐Infrared Emitters of Cr 3+ ‐Activated Garnet Phosphor Enabled by Chemical Unit Co‐Substitution

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)O₁₂:6%Cr³⁺ (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 Ca²⁺ and Ge⁴⁺ ions into the garnet structure. In particular, Lu₃Ga₅O₁₂:6%Cr³⁺ demonstrates an anti-thermal quenching phenomenon (I_423K = 113.1%). Compared to Lu₃Ga₅O₁₂:6%Cr³⁺, Lu₂CaGa₄GeO₁₂:6%Cr³⁺ exhibits significantly improved FWHM and IQE by 108 nm and 25.5%, respectively, while maintaining good thermal stability (I_423K = 80.4%). Finally, Lu₂CaGa₄GeO₁₂:6%Cr³⁺ 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.