Achieving ultra-broadband tunable near-infrared luminescence in Cr3+-doped Li2Mg3SnO6 phosphor for bioimaging and night vision

The expanding application of near-infrared (NIR) spectroscopy in fields such as bioimaging, night vision, and non-invasive analysis has generated an urgent demand for novel phosphors with ultrabroad emission bands and tunable optical properties. In this work, a series of Cr 3+ -doped Li 2 Mg 3 SnO 6 phosphors were synthesized via a conventional high-temperature solid-state reaction. Under blue light excitation, the phosphors exhibit ultrabroad NIR emission, which is attributed to the 4 T 2 → 4 A 2 transition of Cr 3+ ions. The emission spectra can be effectively modulated by adjusting the Cr 3+ doping concentration. As the concentration increases from 0.1 to 1.5 mol%, the emission peak red-shifts from 725 to 798 nm, accompanied by a significant broadening of the full width at half maximum (FWHM) from 2267.4944 cm −1 to 3373.4350 cm −1 . This behavior indicates strong modulation of energy level splitting and crystal field strength. The optimal photoluminescence (PL) intensity is achieved at a Cr 3+ doping concentration of 0.5 mol%. Furthermore, the excitation spectra monitored at different emission wavelengths (702 and 766 nm) exhibit broad spectral region spanning from the ultraviolet to visible light, with a dominant excitation peak centered at approximately 450 nm, well matching the emission of commercial blue light-emitting diode (LED) chips. A NIR phosphor-converted LED (pc-LED) fabricated using the optimized phosphor demonstrates considerable potential for applications in bioimaging and night vision.