Achieving tunable ultra-broadband NIR emission originating from the two-site occupation of Cr3+ ions in Mg3Ga2SnO8:Cr3+Electronic supplementary information (ESI) available. See DOI: https://doi.org/10.1039/d5qi00395d

Near-infrared phosphor-converted light-emitting diodes (NIR pc-LEDs) are considered promising light sources for a variety of applications due to their cost-effectiveness, broadband emission, compact size, and high output power. The key to developing high-performance NIR pc-LEDs lies in the design of phosphors. In this study, we report a NIR Mg₃Ga₂SnO₈:Cr³⁺ (MGS:Cr³⁺) phosphor synthesized via a traditional high-temperature solid-state method. Under 450 nm excitation, MGS:Cr³⁺ exhibited an intense tunable ultra-broadband NIR emission. By adjusting the concentration of Cr³⁺ ions, the full width at half maximum (FWHM) of the spectrum was observed to be broadened from 151 to 223 nm, while the peak wavelength shifted from 715 to 833 nm. Crystal structure analysis, low-temperature spectra, and fluorescence decay curves revealed that these fascinating tunable characteristics originated from the two-site occupation of Cr³⁺ ions. Additionally, the presented phosphor exhibited an impressive internal quantum efficiency (IQE = 57.8%) and superior photoluminescent thermal stability (I_{423 K}/I_{303 K} = 50%). Moreover, the fabricated NIR pc-LED devices based on the MGS:0.08Cr³⁺ and MGS:0.02Cr³⁺ samples proved their potential in night vision imaging, non-invasive detection, and plant growth illumination applications.