Flexible and Robust Piezoelectric Polymer Nanocomposites Based Energy Harvesters

Abstract

Environment friendly, flexible, and robust sensors have attracted considerable research attention due to their potential for a wide range of devices in energy generation and harvesting, sensing, and biomedical applications. In this manuscript, we demonstrate a lead-free, solution processed flexible piezoelectric energy generator based on a nanocomposite film, consisting of MgO nanoparticles of sizes around <50 nm, embedded in poly(vinylidene difluoride) [PVDF] and its copolymer with trifluoroethylene, that is, P(VDF-TrFE) matrix. Piezoelectric, ferroelectric, and leakage current measurements made on samples with various concentrations of MgO nanoparticles revealed a dramatic improvement in these characteristics at 2 wt % MgO with nearly 50% increase in the piezoelectric coefficient as compared to pure P(VDF-TrFE), attributed to the preferred conformation of P(VDF-TrFE) chain, improved crystallinity of the P(VDF-TrFE) matrix, and uniform distribution of nanoparticles. Assessment of the interactions between -OH groups attached to MgO surface and P(VDF-TrFE), carried out using Fourier-transform infrared spectroscopy (FTIR), suggested weak van der Waals forces between -OH groups and P(VDF-TrFE) being responsible for the observed improvement. This flexible nanocomposite device exhibits superior energy harvesting performance with over two-times improvement in the voltage output (2 V) compared to device using P(VDF-TrFE) films alone. Along with superior electrical properties, nanocomposites also exhibit excellent endurance against electrical as well as mechanical fatigue, with piezoelectric coefficient remaining unchanged even after 10 000 bending cycles, supporting their suitability in flexible energy harvesting applications.