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 mu A current by finger tapping. The ZnWO4/In2O3 heterostructures were synthesized via hydro-thermal 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.