Efficient mixed-solvent exfoliation of few-quintuple layer Bi₂S₃ and its photoelectric response

A scalable liquid exfoliation of layered Bi₂S₃ employing a mixed-solvent strategy was used for the fabrication of Bi₂S₃ nanosheets. We found that 10% deionized water in 90% isopropyl alcohol is the best mixed solvent for the efficient and effective exfoliation of layered Bi₂S₃. These results are consistent with the absorbance spectra and enthalpy of mixing theory. The obtained Bi₂S₃ nanosheets had few-quintuple layers and were investigated by transmission electron microscopy, atomic force microscopy, and Raman spectroscopy. These Bi₂S₃ nanosheets can be used to fabricate large-scale thin films by filtration method; the films demonstrated sensitive photoelectric response with the rise and decay response of photocurrent on the sub-second scale under visible light excitation. The electronic structures of bulk and one-quintuple layer Bi₂S₃ are calculated by first-principle calculation for better understanding of the photoelectric response. A green mixed-solvent processing of Bi₂S₃ opens up the potential application of Bi₂S₃ optoelectric films to photoelectric detection and solar energy conversion devices.