Large-Area Freestanding Bi₂S₃ Nanofibrous Membranes for Fast Photoresponse Flexible IR Imaging Photodetector

Films with excellent flexibility and mechanical stability are important for flexible and wearable devices. However, most films reported are prepared on substrates, and the synthesis of freestanding flexible films remains a challenge. Herein, a freestanding Bi₂S₃ nanofibrous membrane (NFM) is successfully prepared via a one-step hydrothermal method, which is self-assembled from ultralong Bi₂S₃ nanowires (NWs) over a length of millimeter-scale crisscrossing each other. Significantly, the Bi₂S₃ NFM can be bent or clipped into an arbitrarily desired form. Based on the freestanding Bi₂S₃ NFM, an IR photodetector is fabricated, depicting a robust responsivity of 2.23 (2.06) µA W⁻¹ under 850 (940) nm illumination. The Bi₂S₃ NFM photodetector exhibits a relatively fast response time (47.1 ms), which is attributed to high-speed carrier transport efficiency in the NWs network. Under the bending states, the device still exhibits excellent detection performance, maintaining more than 86% of the initial photocurrent even after 1000 bending-flattening times. The robust photoresponse of the Bi₂S₃ NFM photodetector after 2 months of storage in air and after 1 week in the bending state illustrates its excellent air stability and flexible detection ability. Besides, the photodetector can clearly identify the target image, indicating widespread potential applications in flexible and wearable fields.