In2O3 nanocubes and ZnWO4 nanorod-based triboelectric nanogenerator for self-powered humidity sensors

In this study, a self-powered photo-induced humidity sensor was developed using ZnWO4/In2O3 heterostructure based Triboelectric Nanogenerator (TENG). The ZnWO4/In2O3 heterostructure-based TENG generates 44 V voltage and 1 µA current by finger tapping. The ZnWO4/In2O3 heterostructures were synthesized via hydrothermal method. SEM analysis confirmed the In2O3 nanocubes grown on ZnWO4 nanorods. XRD analysis confirmed the polycrystalline nature of ZnWO4/In2O3 heterostructures and the average crystallite size was found to be 32.66 nm. XPS analysis confirmed the presence of Zn2+, In3+, W4+, and O2- oxidation states. Optical properties were analyzed by UV–visible spectroscopy and maximum absorbance was found in the region (315–400 nm) since it is capable of absorbing UV light. In this work, the effect of very low-intensity UV light (2 mW/cm2) on a battery-less moisture detection was investigated at different moisture levels (10–90%RH). The sensor response was around 27.50 at 90%RH of photo-induced self-powered humidity sensor. Also, the fast response and recovery times were observed as 260 ms and 620 ms respectively in the illumination of UV light. The photo-induced self-powered humidity sensor showed highly sensitive and stable for a long time and it can be commercialized for indoor and outdoor humidity detection.