Nanowire-percolated piezoelectric copolymer-based highly transparent and flexible self-powered sensors

With the expansion of Internet of Things (IoT) and sensor network systems, transparent and flexible energy supply devices are becoming more vital for ultra-connected and highly convenient human interfaces. In particular, the mechanical energy harvesting technology using piezoelectric materials is very attractive due to the ability of direct energy conversion from wasted mechanical energy to useful electrical energy. In this work, we demonstrate a highly transparent and flexible piezoelectric energy harvester (f-PEH) using a metallic nanowire-percolated piezoelectric copolymer on a flexible plastic substrate. The silver nanowire (Ag NWs)-based conductor has been considered as a powerful future electrode material with high transparency and flexibility, while poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) is a representative high-performance piezoelectric polymer material. Based on these two attractive materials, the proposed transparent f-PEH generated an output voltage, current, and power of ∼17 V, ∼2.5 μA, and ∼12 μW, respectively, which are a record-high performance compared to previously reported transparent f-PEHs. Besides material and device characterizations, a multiphysics simulation was firmly investigated to clarify the properties of the transparent f-PEH devices. Finally, the transparent f-PEH devices were directly modified and used as a self-powered pressure sensor array (5 × 5), which well detected the pattern images of the external pressure input without serious cross-talk. This work can guide the field of transparent and flexible piezoelectric devices to the way to accomplish transparent self-powered electronics for high-performance applications.