Solution-processed bismuth sulfide incorporated with zinc for high-gain and low-noise photodetection

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Bismuth sulfide possesses an extremely high absorption coefficient, a relatively small bandgap, and high charge carrier mobility, which are favorable for photovoltaics and photodetection. However, the device performance of binary Bi2S3 is still limited by the poor charge transport and complicated trap features caused by the stoichiometric imbalance, as both sulfur vacancy and bismuth vacancy could result in tremendous trap states. In this work, we incorporate a small amount of extrinsic elements in the solution-processed Bi2S3 thin films and systematically investigate the influence of extrinsic doping on the charge transport properties of Bi2S3 thin films via time-resolved microwave conductivity and field-effect transistors. We also fabricate photodetectors based on these Zn2+ incorporated Bi2S3 thin films and achieve state-of-the-art device performance, including relatively high on/off ratio, high responsivity, and extremely low dark current and noise, which is promising for next-generation solution-processed photodetection.