Design of a Broadband NIR Phosphor for Security-Monitoring LEDs: Tunable Photoluminescence Properties and Enhanced Thermal Stability

Near-infrared (NIR) phosphors with capability for blue light to 850 nm broadband NIR emission conversion are highly desirable for security-monitoring LEDs. Targeted phosphor LaSc2.93-yGayB4O12(LSGB): 0.07Cr3+ (y = 0.6) is designed from the initial model of LaSc2.93B4O12(LSB): 0.07Cr3+ by chemical composition modification. The correlations among crystal-field environment, structural evolution, and luminescence properties of LSGB: 0.07Cr3+ (0 ≤ y ≤ 1.5) are elucidated by the Dq/B values, decay curves, and polyhedron distortion. The substitution of Sc3+ by Ga3+ in LSGB: Cr3+ (0 ≤ y ≤ 1.5) leads to decreasing structural polyhedron distortion and strengthened crystal field, consequently resulting in the blue-shift of broadband emission and enhanced thermal stability of LSGB: 0.07Cr3+ (y = 0.6) compared to that of LSB: 0.07Cr3+. The above results demonstrate that the superiority of blue-shift and enhanced thermal stability of LSGB: 0.07Cr3+ (y = 0.6) make it more suitable for the blue-pumped security-monitoring LEDs.