Efficient Blue-Violet-Light-Excitable Near-Infrared Luminescence in Fe3+ Activated Phosphors With High Internal Quantum Efficiency and Superior Thermal Stability

Trivalent iron (Fe 3+ ) has attracted extensive attention as an environmentally friendly and cost-effective near-infrared (NIR) emitting activator ion. However, its weak absorption in the blue-violet light region and relatively low internal quantum efficiency (IQE) have long constrained its practical applications. In this study, a series of Ca 3 Ga 2-x Sn 2 GeO 12 : xFe 3+ NIR phosphors with a cubic garnet structure was successfully synthesized via a high-temperature solid-state reaction method. Efficient NIR luminescence under long-wave ultraviolet (LWUV) chip excitation was observed, exhibiting broadband NIR emission centered at 740 nm. Remarkably, the phosphor achieves an internal quantum efficiency (IQE) as high as 82.3%, representing the highest efficiency reported to date for Fe 3+ -doped NIR phosphors under blue-violet light excitation. Temperature-dependent luminescence analysis reveals excellent thermal stability: the integrated emission intensity at 423 K retains 67.06% of its initial value at room temperature. A prototype NIR phosphor-converted LED (pc-LED) device fabricated with the studied phosphor and a commercial chip (400–410 nm) exhibits stable electroluminescence performance and good output power conversion. In summary, the Ca 3 Ga 2-x Sn 2 GeO 12 : xFe 3+ phosphor, with its efficient luminescence under blue-violet light excitation, outstanding thermal stability, and temperature-independent emission peak position, demonstrates significant application potential in the field of high-efficiency and high-stability NIR light sources.