Highly Efficient and Thermally Stable NIR‐Emitting Phosphor with Largely Tunable Peak Wavelength and Bandwidth Toward NIR Spectroscopy Applications

Abstract Developing tunable broadband near‐infrared (NIR) fluorescent materials with outstanding luminescence properties and superior thermal robustness remains a significant challenge for next‐generation intelligent NIR light sources. Herein, a high‐performance large‐scale tunable NIR‐emitting garnet‐type phosphor, SrLu 2 Al 3 ScSiO 12 :Cr 3+ (SLASSO:Cr 3+ ), is presented. Upon 450 nm blue light excitation, SLASSO:1%Cr 3+ phosphor yields a broadband emission with full width at half maximum of 108 nm and a prominent sharp peak at 694 nm superimposed on a broadband radiation, which is attributed to the co‐occupation of Cr 3+ ions at the dominant [AlO 6 ] octahedral site (Cr1 site) and subordinate [ScO 6 ] octahedral site (Cr2 site). Remarkably, as the Cr 3 ⁺ content increases, a significant red‐shift in emission peak wavelength spanning from 694 to 785 nm and emission bandwidth broadening from 89 to 152 nm are observed, which stems from the weakening of the crystal field strength and the energy redistribution within Cr1 and Cr2 luminescence centers regulated by the formation of the local Cr 3+ ‐Cr 3+ ion pairs. Notably, the optimal SLASSO:1%Cr 3+ sample boasts an excellent internal quantum efficiency of 89.4% and an exceptional thermal stability (97.6%@423 K). Additionally, the fabricated NIR phosphor‐converted light‐emitting diode devices demonstrate promising multi‐functional applications, including plant cultivation, night vision, bioimaging and non‐destructive detection.