Dual-strategy optimization of Ni2+-activated NIR emission in CaLu2Mg2Ge3O12via Zn2+-driven 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(Mg_1−xZn_x)₂Ge₃O₁₂ (CL(M_1−xZ_x)₂GO) garnet-type solid solution near-infrared phosphors. At the optimal Zn²⁺ content (x = 0.8), the CL(M_1−xZ_x)₂GO:Ni²⁺ phosphor exhibits a threefold enhancement in emission intensity, accompanied by an increase in internal 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 demonstrated 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.