Compositional engineering of VOPcPhO-TiO₂ nano-composite to reduce the absolute threshold value of humidity sensors

This research work demonstrates compositional engineering of an organic-inorganic hybrid nano-composites for modifying absolute threshold of humidity sensors. Vanadyl-2,9,16,23-tetraphenoxy-29H,31H-phthalocyanine (VOPcPhO), an organic semiconductor, doped with Titanium-dioxide nanoparticles (TiO₂ NPs) has been employed to fabricate humidity sensors. The morphology of the VOPcPhO:TiO₂ nano-composite films has been analyzed by atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM). The sensors have been examined over a wide range of relative humidity i.e. 20-99% RH. The sensor with TiO₂ (90nm) shows reduced sensitivity-threshold and improved linearity. The VOPcPhO:TiO₂ (90nm) nano-composite film is comprised of uniformly distributed voids which makes the surface more favorable for adsorption of moisture content from environment. The VOPcPhO:TiO₂ nano-composite based sensor demonstrates remarkable improvement in the sensing parameter when equated with VOPcPhO sensors.