Luminescence Properties of Broadband Near-infrared Luminescent Material Ca5Ga6O14:Cr4+

Broadband near-infrared-II (NIR-II) covered phosphors are crucial for LED applications such as biological imaging and optical sensing.In this study, Ca 5 Ga 6-x O 14 : xCr phosphors, where x represents the molar concentration of Cr 4+ substituting Ga sites, were synthesized with x values of 0.0001, 0.0005, 0.005, 0.01, 0.02, 0.03, and 0.04 using a conventional solid-state reaction.X-ray diffraction showed that the main targeted phase was predominantly observed for Cr doping levels below x = 0.001.Optical characterizations revealed that the optimized phosphor (x = 0.0005) exhibited the most intense and broad NIR emission (1150-1600 nm, peak at 1330 nm) by 650 nm excitation, originating from the spin-allowed 3 T 2 3 A 2 transition of tetrahedrally coordinated Cr 4+ ions.Low-temperature photoluminescence further elucidated the energetic and crystal field environment of Cr 4+ .These findings demonstrate that Ca 5 Ga 6 O 14 is an efficient host for Cr 4+ -doped NIR-II phosphors, offering insights for the design of next-generation luminescent materials.