Co‐Substitution Crystal Lattice Engineering and Flux‐Assisted Synthesis of Cr 3+ ‐Activated High‐Performance Phosphors for Efficient Near‐Infrared Pc‐LEDs and Multi‐Application

ABSTRACT The advancement of next‐generation near‐infrared phosphor‐converted LEDs (NIR pc‐LEDs) relies critically on the development of high‐performance NIR phosphors. However, the NIR phosphors is often limited by low external quantum efficiency (EQE) and significant thermal quenching. Herein, we report a series of high‐power tunable NIR phosphors achieved through a combined strategy of [M 2+ ‐Si 4+ ] (M = Mg 2+ , Ca 2+ , Sr 2+ ) co‐substitution and flux‐assisted synthesis. The resulting Cr 3+ ‐doped garnet‐type M x Lu 3‐x Ga 5‐x Si x O 12 phosphors demonstrate both high quantum efficiency and outstanding thermal stability. Notably, the phosphor achieves an EQE of 53.9% and retains over 104.5% of its room‐temperature luminescence intensity at 423 K, enabling an LED output power of 74.5 mW at 200 mA and a high photoelectric conversion efficiency of 16.6%@10 mA. These advances stem from crystal field regulation, Cr 3+ ‐Cr 3+ pairs formation, and co‐substitution induced lattice distortion, which collectively broaden the emission spectrum and boost luminescence intensity. Moreover, the flux‐assisted synthesis improves crystallinity and homogenizes ion diffusion by lowering the viscosity of the molten phase, thereby boosting thermal quenching resistance and overall device efficiency. This work utilizes a dual‐optimization strategy for both microscopic and macroscopic properties and develops a high‐performance NIR phosphor system, providing key insights for future NIR pc‐LEDs.