Micro-nano structural design of electrode materials for high performance self-polarized poly (vinylidene fluoride) (PVDF) piezoelectric nanogenerators

Despite the possibility of strengthening the beta (β) phase of self-poled poly (vinylidene fluoride) (PVDF) piezoelectric nanogenerators (NGs) through filler addition, phase separation and heat treatment, they face a major challenge as their performance is limited under mechanical force due to the misaligned electric dipoles of polymer chains. This study aims to confine polymer chains in alumina nanopores and to create hydrogen bonding between the engineered surfaces of electrodes and polymer chains with β phase in order to polarize them perpendicular to the electrodes’ surface. To this end, alumina nanopores were initially fabricated over a wide area by selective etching and anodization process of commercial aluminum, followed by filling the micro-nanostructured electrodes with PVDF using a spin coating method. The resulting NGs fabricated based on the micro-nanostructured films showed a remarkable output voltage of 50 V and current of 90 μA, outperforming the films fabricated on a flat electrode with an output voltage of 8 V and current of 20 μA. Meanwhile, increasing the nanopore diameter from 30 to 110 nm enhanced the NG’s output voltage. The NG performance was further enhanced up to an output voltage of 70 V and current of 110 μA through a phase inversion process of PVDF-filled nanopores with the larger diameter.