Structural Rigidity Control toward Cr³⁺-Based Broadband Near-Infrared Luminescence with Enhanced Thermal Stability

Broadband near-infrared (NIR) light sources based on phosphor-converted light-emitting diodes (pc-LEDs) are desirable for biochemical analysis and medical diagnosis applications; however, the development of target NIR phosphor is still a challenge. Herein, broadband NIR phosphors, Cr3+-activated CaSc1–xAl1+xSiO6 (λem = 950 nm), are designed and optimized by chemical substitution toward enhanced quantum efficiency and thermal stability. Structural and spectral analyses along with density functional theory calculations reveal that Sc3+/Al3+ substitution contributes to enhancing the structural rigidity and the local symmetry of the [Sc/AlO6] octahedron so that the nonradiative relaxation of Cr3+ emission centers is suppressed significantly. The as-fabricated phosphor-in-glass-based NIR LED light source demonstrates great potential in the detection of alcohol concentration. This study provides a local structure design principle for exploring NIR phosphors with enhanced thermal stability and will also stimulate further studies on material discovery and quantitative analysis of NIR spectroscopy.