Synergistic Dual‐Valence Distortion and Energy Transfer Enable Ultra‐Broadband NIR Emission for Advanced Detection Systems

Broadband near‐infrared (NIR) phosphors are essential for advanced applications ranging from night vision to biochemical sensing. However, conventional Cr 3+ ‐activated materials suffer from inherently low efficiency due to parity‐forbidden d‐d transitions. Here, we introduce a “dual‐valence distortion” strategy to overcome this fundamental limitation. By co‐substituting Sn 4+ in Li 2 SnO 3 :Cr 3+ with a size‐mismatched larger Sb 3+ and smaller Sb 5+ ions, we induce intense, controlled lattice distortion around the Cr 3+ sites. The tailored disruption of local symmetry relaxes the selection rules, enabling a remarkable 26‐fold enhancement in NIR emission intensity and a 6.4‐fold increase in quantum yield (QY). To achieve an ultra‐broadband emission, this highly efficient platform is synergistically coupled with a Cr 3+ → Yb 3+ energy transfer (ET) strategy. Yb 3+ co‐doping broadens the spectrum to a 336 nm bandwidth while maintaining high efficiency. Furthermore, the ET mechanism enhances thermal stability, demonstrating a “1+1>2” effect. The fabricated NIR phosphor‐converted LEDs enable advanced applications in non‐destructive testing, grain impurity detection, and a real‐time alcohol concentration monitoring system with threshold alarming. This work establishes a rational, chemistry‐driven framework for designing next‐generation ultra‐broadband NIR phosphors.