Achieving broadband near-infrared emission with superior anti-thermal quenching by optimizing the excited-state population of Cr3+ in Gd3ScGa4O12 garnet phosphors†

Abstract

Cr³⁺-activated garnet phosphors with broadband near-infrared (NIR) emission have attracted considerable interest due to their high quantum efficiency (QE) and thermal stability for widespread advanced applications. Nevertheless, how to achieve energy-saving broadband NIR phosphors that possess anti-thermal quenching (anti-TQ) without compromising the high QE has yet to be fully addressed. Herein, we report on site reconstruction within the garnet lattice by strategically positioning Sc and Ga atoms into octahedral B sites with a mole ratio of 1 : 1 to produce Gd₃ScGa₄O₁₂. A reduction in crystal field strength (CFS) is thus induced, leading to a redshift of Cr³⁺ broadband NIR emission. The inherent rigidity of the structure and the weak electron–phonon coupling (EPC) effect lay the groundwork for a thermally robust broadband NIR phosphor. The combination of bandgap engineering, finely optimizing the ⁴T₂ excited state population, and precise control over the doping concentration contributes a high-performance broadband NIR emission (IQE = 82.75%) with unprecedented anti-TQ such that the NIR emission of Cr³⁺ even increases to 198% of its room-temperature intensity at 543 K. A prototype broadband NIR pc-LED is encapsulated to deliver an NIR output power of 125.20 mW@900 mA and a wall-plug efficiency (WPE) of 6.88%@30 mA, enabling night vision, noninvasive imaging, and non-destructive detection applications.