Close-loop recyclable and flexible halide perovskite@wool keratin sensor with piezoelectric property

Halide perovskites with excellent piezoelectric properties, but their poor stability hinders their large-scale application. Herein, a sandwich-structured halide perovskite flexible sensor with good stability was developed according to a three-step procedure as follows: (i) in-situ growth of wool keratin-CsPbBr3 (WK-CsPbBr3) using wool keratin in interfacial passivation and coating, (ii) electrospinning of a wool keratin-CsPbBr3/polyacrylonitrile (WCP) nanofiber film, and (iii) coating of the WCP nanofiber with polydimethylsiloxane (PDMS) to obtain a sensor (WCPP). The sensor could generate a piezoelectric voltage of 7.8 V at a pressure of 6 kPa in the stages of pressing and releasing, and the output characteristics did not decline even after 10,000 cycles. Compared to the 4-month stability of the perovskite sensor, WCPP sensor exhibited the output performance even after 16 months, which indicated that wool keratin as a multidentate improved the stability of the halide perovskite. Additionally, the sensor displayed a self-cleaning property and could also light up 14 commercial LEDs. The close-loop recycling of the lead halide perovskite was achieved by dissolving the WCP nanofiber film in DMF and then re-electrospinning. Therefore, the method proposed is a step forward for achieving the commercialization of WK-CsPbBr3 and providing new avenues for further utilization of wool waste.