Sb3+-Doping in Cesium Zinc Halides Single Crystals Enabling High-Efficiency Near-Infrared Emission

Luminescent metal halide materials with flexible crystallography/electronic structures and tunable emission have demonstrated broad application prospects in the visible light region. However, designing near-infrared (NIR) light-emitting metal halides remains a challenge. Here, an enlightening prototype is proposed to explore the high-efficiency broadband NIR emission in metal halide systems by incorporating Sb3+ into the Cs2ZnCl4 matrix. Combined experimental analysis and density functional theory calculations reveal a modified self-trapped excitons model to elaborate the NIR emission. The high photoluminescence quantum yield of 69.9% peaking at 745 nm and large full width at half maximum of 175 nm, along with excellent air/thermal stability, show the unique advantages of lead-free metal halide Cs2ZnCl4:Sb3+ as the NIR light source. The substitution of Cl- by Br- further enables the red-shift of emission peak from 745 to 823 nm. The NIR light-emitting diode device based on Cs2ZnCl4:Sb3+ demonstrates potential as a non-visible light source in night vision. This study puts forward an effective strategy to design the novel eco-friendly and high-efficiency NIR emissive materials and provides guidance for expanding the application scope of luminescent metal halides.