Bismuth Chalcohalide Bi13S18Br2 for Fast and Sensitive Near-Infrared Photodetection

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.