Two-Dimensional WS₂Nanosheet Embedded PVDF Nanocomposites for Photosensitive Flexible Piezoelectric Nanogenerators with a Colossal Energy Conversion Efficiency ~ 25.6%

Here we have demonstrated record efficiency self-poled photosensitive flexible piezoelectric nanogenerators (PENG) using polyvinylidene fluoride (PVDF) polymer and chemically exfoliated tungsten disulfide (WS₂) nanosheets. The two-dimensional (2D) WS₂ nanosheets in PVDF matrix play dual role to enhance the nucleation of electroactive b-phase as well as induces a strong photosensitivity in the nanocomposite. The PVDF-WS₂ composed flexible device is able to produce an enormously high output voltage~116 V (for impact ~ 105 kPa) and a piezoelectric energy conversion efficiency ~25.6%, which is the highest among the reported values on PVDF-2D materials based piezoelectric nanogenerators and also able to harvest energy from biomechanical and natural resources. This self-poled piezophototronic device exhibits strain-dependent photocurrent with photoresponsivity 6.98 mA/W (0.75% strain) under 410 nm at zero bias with higher piezo power harvesting under visible light. These results open up a new horizon in piezophototronics through the fabrication of photosensitive multifunctional highly stable PENGs, which can be scaled up for fabricating compact, high performance, portable and self-powered wearable electronic devices for smart sensor applications.