Enhanced β-phase in PVDF polymer nanocomposite and its application for nanogenerator

Abstract

Harvesting energy from the ambient mechanical energy by using flexible piezoelectric nanogenerator is a revolutionary step toward achieving reliable and green energy source. Polyvinylidene fluoride (PVDF), a flexible polymer, can be a potential candidate for the nanogenerator if its piezoelectric property can be enhanced. In the present work, we have shown that the polar crystalline β-phase of PVDF, which is responsible for the piezoelectric property, can be enhanced from 48.2% to 76.1% just by adding ZnO nanorods into the PVDF matrix without any mechanical or electrical treatment. A systematic investigation of PVDF-ZnO nanocomposite films by using X-ray diffractometer, Fourier transform infrared spectroscopy, and polarization-electric field loop measurements supports the enhancement of β-phase in the flexible nanocomposite polymer films. The piezoelectric constant (d33) of the PVDF-ZnO (15 wt%) film is found to be maximum of approximately −1.17 pC/N. Nanogenerators have been fabricated by using these nanocomposite films, and the piezoresponse of PVDF is found to enhance after ZnO loading. A maximum open-circuit voltage ~1.81 V and short-circuit current of 0.57 μA are obtained for 15 wt% ZnO-loaded PVDF nanocomposite film. The maximum instantaneous output power density is obtained as 0.21 μW/cm2 with the load resistance of 7 MΩ, which makes it feasible for the use of energy harvesting that can be integrated to use for driving small-scale electronic devices. This enhanced piezoresponse of the PVDF-ZnO nanocomposite film-based nanogenerators attributed to the enhancement of electroactive β-phase and enhanced d33 value in PVDF with the addition of ZnO nanorods.