Bismuth Chalcohalide Bi₁₃S₁₈Br₂ for Fast and Sensitive Near‐Infrared Photodetection

Abstract Bismuth chalcohalides demonstrate tunable optical and electronic properties, offering new orientations for the material design and properties exploration. Recently, bismuth sulfide halides (Bi 13 S 18 X 2 , X═Cl, Br, I) have been regarded as a kind of potential infrared (IR) photoelectrical materials, owing to the narrow bandgap, small effective mass, and low toxicity. In this work, (310)‐orientated Bi 13 S 18 Br 2 thin films are synthesized on the α‐Al 2 O 3 (0001) single crystal via mist chemical vapor deposition at atmospheric pressure. Bi 13 S 18 Br 2 thin films possessed a narrow bandgap of ≈0.85 eV, suitable for harvesting the light from ultraviolet to the near‐IR range. The conduction mechanism of Bi 13 S 18 Br 2 is discussed from 2 to 300 K. The Bi 13 S 18 Br 2 ‐based photodetector exhibited interesting near‐IR photodetection performance, which is comparable and even superior to the well‐investigated IR photodetectors. The responsivity reached up to 10.0 and 7.3 A W −1 under the illumination of 808 and 1064 nm light, respectively. This study is expected to contribute to the development of “mixed‐anion electronics” and advance photodetection techniques.