Enhancing Light Absorption of LiScSi2O6:Cr3+ NIR-emitting Phosphors via Multisite Cation Substitution
Na+/In3+/Ge4+ singly-doped or co-doped LiScSi2O6∶Cr3+ phosphors were prepared by high-temperature sol-id-state reaction.Light absorption and photoluminescence(PL)properties were studied by diffuse reflection spec-trum,PL excitation/emission spectrum and quantum efficiency measurements.The results show that the absorption to the blue light at 460 nm can be enhanced for the LiScSi2O6∶Cr3+ phosphor by single ion substitution,such as Na+ for Li+,In3+ for Sc3+,and Ge4+ for Si4+.The absorption efficiency(AE)can be further increased by multisite cation substitution with Na+,In3+ and Ge4+,from an AE value of 50.5%for the LiScSi2O6∶Cr3+ phosphor to 60.9%for the Li0.8Na0.2Sc0.4In0.6Si1.6Ge0.4O6∶Cr3+ phosphor.The light absorption enhancement can be attributed to the increased distortion degree of Cr3+ coordination octahedron caused by single ion substitution or multisite cation substitution.The optimized LiSc0.4In0.6Si1.6Ge0.4O6∶Cr3+ phosphor exhibits a broadband near-infrared(NIR)emission peaking at～860 nm,with a full width at half maximum(FWHM)of～160 nm and an internal(external)quantum efficiency of 72.5%(41.8%).The fabricated phosphor-converted LED(pc-LED)device shows a NIR output power of 63.1 mW and an energy conversion efficiency of 22.3%at 100 mA drive current.The study provides an effective approach to enhance the light absorption capacity of Cr3+-activated NIR phosphors.
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