Assessing mechanical energy harvesting performance of ferroelectric polymer nanowires grown by template wetting

Nanowires of the ferroelectric co-polymer poly(vinylidenefluoride-co-triufloroethylene) [P(VDF-TrFE)] are fabricated from solution within nanoporous templates of both “hard” anodic aluminium oxide (AAO) as well as “soft” polyimide (PI) through a facile and scalable template wetting process. The confined geometry afforded by the pores of the templates leads directly to highly crystalline P(VDF-TrFE) nanowires in a macroscopic “poled” state that precludes the need for external electrical poling procedure typically required for piezoelectric performance. The energy harvesting performance of nanogenerators based on these template-grown nanowires are extensively studied and analysed in combination with finite element modelling. We present both experimental results and computational models probing the role of the templates in determining overall nanogenerator performance, including both material and device efficiency. We find that although P(VDF-TrFE) nanowires grown in PI templates exhibit a lower material efficiency due to lower crystallinity as compared to nanowires grown in AAO templates, the overall device efficiency was higher for the PI template-based nanogenerator due to the lower stiffness of the PI template as compared to the AAO template. Our work provides a clear framework to assess the energy conversion efficiency of template grown piezoelectric nanowires and paves the way towards optimisation of template-based nanogenerator devices