Highly Efficient Broadband Near‐Infrared Emission from Sn2+ Alloyed Lead‐Free Cesium Zinc Halides

Abstract Luminescent metal halides have attracted increasing attention because of their tunable emission and superior photoelectric properties. However, it is still challenging to achieve near‐infrared (NIR) emission from metal halides, which is important in applications such as food quality analysis and night vision. In this work, the broadband NIR emission is achieved by alloying Sn 2+ into zero‐dimensional (0D) Cs 2 ZnBr 4 . The incorporating of Sn 2+ cations enables the originally weakly luminescent Cs 2 ZnBr 4 to exhibit an efficient broadband NIR emission. Upon photoexication, the optimized Sn 2+ alloyed Cs 2 ZnBr 4 (Cs 2 Zn 0.875 Sn 0.125 Br 4 ) exhibits a highly efficient broadband NIR emission peaked around 700 nm, with a large Stokes shift of 323 nm, a full width at maximum of 177 nm, and a high quantum efficiency of around 41%. Spectroscopic and theoretical calculations unveil that the efficient NIR emission originates from the self‐trapping emission introduced by the Sn alloying. In addition to the high efficient broadband emission, the Sn 2+ alloyed Cs 2 ZnBr 4 also exhibits high thermal stability, retaining 78% of its initial intensity at 150 °C. The night vision application is demonstrated by using a light source fabricated by combining Sn 2+ alloyed Cs 2 ZnBr 4 phosphor with a 365 nm LED chip in the dark.