High-Gain Low-Noise Phototransistors Based on Solution-Processed Bi2S3

Chalcogenide-based semiconductors have recently emerged as promising optoelectronic materials. In particular, bismuth-based sulfides have demonstrated great potential for device applications, such as in photovoltaics and photodetection. However, most of the devices reported have been based on silverbismuth-sulfide-based solar cells. Work on bismuth sulfide based on precursor methods has been barely reported, and studies of its optoelectronic properties are lagging far behind. In this paper, we first report solution processing of Bi2S3 thin films, describe the systematic optimization of the precursors, and investigate the influence of composition and annealing on the properties of the films, including their morphology, crystallinity, charge-carrier dynamics, charge transport, and photoconductive gain. We also demonstrate excellent field-effect transistors based on Bi2S3 thin films, and introduce the use of these Bi2S3 phototransistors for weak-light detection. The optimized devices exhibit extremely high responsivity and low dark current, paving the way for high-performance photodetection.