An efficient and thermally stable near-infrared phosphor derived from the Ln3ScInGa3O12:Cr3+ (Ln = La, Gd, Y, and Lu) garnet family

Abstract

A broadband near-infrared (NIR) light source based on a phosphor-converted light-emitting diode (pc-LED) has attracted increasing interest to be used in non-destructive examination, security-monitoring and medical diagnosis fields, which stimulates the exploration of NIR phosphors with high performance. Herein, a series of Cr³⁺-activated garnet Ln₃ScInGa₃O₁₂:Cr³⁺ (Ln = La, Gd, Y, and Lu) phosphors were reported, allowing an emission peak ranging from 726 to 822 nm. Among them, Y₃ScInGa₃O₁₂:Cr³⁺ with an optimized Cr³⁺-doping concentration of 6 mol% exhibits a high internal quantum efficiency (IQE = 83.1%) and excellent absorption efficiency (AE = 44.2%) under 450 nm blue light excitation, enabling an external quantum efficiency as high as 36.7%. Moreover, this material can maintain 93.0% of the initial intensity when heated up to 423 K, implying outstanding thermal stability. Finally, a prototype NIR pc-LED device was fabricated by coating the optimized phosphor on a 455 nm LED chip, which generates a broadband NIR emission with a peak located at 765 nm and a full width at half maximum of 127 nm. The NIR output power and NIR photoelectric conversion efficiency of this device were found to be 38.01 mW and 11.0%, respectively, under 100 mA driving current, demonstrating the feasibility of this material to be applied in NIR pc-LEDs.