Ultra-broadband near-infrared emission and enhanced thermal stability in Lu3Ga3MgSiO12:Cr3+, Yb3+ garnet phosphor via chemical unit co-substitution and energy transfer

The development of highly efficient and thermally stable phosphors with ultra-broadband emission is critical to advancing the practical applications of portable near-infrared phosphor-converted light-emitting diodes (NIR pc-LEDs). Herein, we employ the chemical unit co-substitution strategy to quantitatively introduce Mg²⁺ and Si⁴⁺ ions into the garnet lattice, yielding the high-performance Lu₃Ga₃MgSiO₁₂:Cr³⁺ (LGMSO:Cr³⁺) phosphor, which exhibits an ultra-broadband emission with a full width at half maximum (FWHM) of 181 nm and a photoluminescence quantum yield (PLQY) of 63.7 %. Structural analysis reveals that Mg²⁺-Si⁴⁺ co-substitution induces multiple Cr³⁺ occupancy within distorted (Ga/Mg)O₆ octahedra, broadening emission band via a multisite-induced effect, as confirmed by low-temperature spectral analysis (80 K) and crystal field calculations. Furthermore, co-doping with Yb³⁺ enhances the emission bandwidth and thermal stability (from 48.4 % to 71.0 % at 423 K), attributed to the combined contributions of Cr³⁺ emission (${{}^{4}T}_2\left({}^{4}F\right){\to }^4{A}_2$) and Yb³⁺ emission (${}^2{F}_{5/2}{\to }^2{F}_{7/2}$) excited via Cr³⁺ energy transfer. Packaged LED devices show superior night vision and non-destructive biological penetration capabilities, highlighting the phosphor’s potential for NIR pc-LED applications.