Dual-Strategy Optimization of Ni2+-Activated NIR Emission in CaLu2Mg2Ge3O12 via Zn2+-Drivened Internal Quantum Efficiency Boost and Cr3+-Enhanced Absorption

Abstract

Near-infrared phosphor-converted light-emitting diodes (NIR pc-LEDs) are versatile solid-state light sources, whose performance is largely governed by the properties of the NIR phosphors. Herein, we report a series of Cr3+/Ni2+ co-doped CaLu2(Mg1-xZnx)2Ge3O12 (CL(M1-xZx)2GO) garnet-type solid solution near-infrared phosphors. At the optimal Zn2+ content (x = 0.8), CL(M1-xZx)2GO:Ni2+ phosphor exhibits a threefold enhancement in emission intensity, accompanied by an increase in external quantum efficiency from 56.9% to 86.2%. With Cr3+ co-doping, efficient Cr3+→Ni2+ energy transfer (up to 75%) shifts the main excitation band from 410 to 460 nm and produces continuous 600–1800 nm emission covering the NIR-I and NIR-II windows. A prototype NIR pc-LED fabricated by combining the optimized phosphor with a commercial 450 nm blue LED chip demonstrates strong potential for applications in information encryption, defect inspection, and optical wireless communication. This work offers an effective strategy for designing high-performance, ultra-broadband NIR-emitting phosphors through local structural engineering and Cr3+→Ni2+ sensitization.