Self-powered piezoelectric ultraviolet photodetectors based on TiO2-NFs:P (VDF-TrFE) nanocomposites via ultraviolet-assisted thermal annealing for the prevention of ultraviolet overexposure

Background: Ultraviolet (UV) radiation overexposure due to severe ozone layer depletion increases the risk of skin cancer. However, the traditional UV index meter needs the power supply which is not convenient for outdoor use. The study aims to develop a UV overexposure warning system with a self-powered piezoelectric UV photodetector to provide a real-time UV index. Method: A self-powered piezoelectric UV photodetector with TiO2-nanofibers (TiO2-NFs)-doped poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) nanocomposite films via ultraviolet-assisted thermal annealing was fabricated. A lumped circuit was designed to realize the stepping illumination of light-emitting diodes (LEDs) under continuous tapping of self-powered piezoelectric UV photodetectors. Significant Findings: At a fixed 40-kPa pressure and 2-Hz frequency with varying UV irradiation power densities, the self-powered piezoelectric UV photodetectors exhibited outstanding UV detection capabilities, with a responsivity and detectivity for 0.14 mA/W and 4 x 108 Jones, respectively. A UV overexposure warning system was established by connecting a self-powered piezoelectric UV photodetector with a lumped circuit to achieve the stepping illumination of LEDs under continuous tapping, giving warnings for those performing outdoor activities to avoid UV overexposure.