Lead-free hybrid halide perovskite-based piezo/triboelectric self-powered wearable dual-functional sensors

Humidity monitoring is crucial for maintaining an ambient atmosphere in various settings such as hospitals, climate sciences, agriculture, automated devices, and intelligent systems. Herein, we report a self-powered dual-functional humidity and pressure sensor based on piezo/triboelectric nanogeneration using tin-based halide perovskites embedded with copper halides. The device can also be used as a colorimetric humidity sensor along with the piezo/triboelectric nanogeneration. The device is capable of sensing humidity colorimetrically as well as in piezo/triboelectric nanogeneration mode in two linear regimes, viz., 10-60% relative humidity (% RH) and 70-90% RH, at sensitivities (% RH-1) of 0.77 V and 0.31 V, respectively. The film possesses excellent colorimetric response/recovery times, suggesting that the rates of adsorption and desorption of moisture are almost equivalent. Additionally, the device is highly reproducible and selective to moisture. Moreover, the room-temperature processability of the material led to the fabrication of the piezo/triboelectric nanogenerator device over a flexible PET-based ITO, thereby demonstrating its application to wearable humidity sensors. The device exhibits high shelf-life stability as it showed a negligible drop in power generation as well as transmittance over a period of nine months. The same device could also sense pressure due to the presence of the piezoelectric perovskites. The fabricated lead-free self-powered wearable multifunctional sensor with high performance stability, fast response/recovery times, high reproducibility and excellent shelf-life has tremendous potential for biomedical applications for the detection of early-stage lung cancer or sleep apnea.