Effective Mechanical Energy Harvesting from PVDF Multilayers by Head-to-Head Parallel Assembly

Piezoelectric multilayers can achieve both piezoelectric and triboelectric generation simultaneously by the deformation and contacting–separating process between upper and lower surfaces of adjacent layers. The electrospun poly(vinylidene fluoride) (PVDF) fiber film as a type of piezoelectric multilayer with abundant inner surfaces can generate both large piezoelectric and triboelectric signals. However, in most studies on the piezoelectric fiber films, the high-generation performances are attributed to the piezoelectric properties and their triboelectric contribution is usually ignored. Thus, the contributions of triboelectricity in piezoelectric multilayers should be considered, and a highly effective hybrid nanogenerator needs to be designed by achieving the synergy of triboelectricity and piezoelectricity. Herein, a head-to-head parallel assembly was used in a PVDF multilayer generator to improve the electricity output, and the respective contributions and synergistic effect of triboelectricity and piezoelectricity in multilayer generators were studied. The maximum open-circuit voltage, short-circuit current, and charge values of the designed hybrid nanogenerator device were 150 V, 7 μA, and 100 nC, respectively. Then, the head-to-head parallel assembly method was used for electrospun poly(vinylidene fluoride-co-trifluoroethylene) fiber films, and the output performance was shown to be about 4 times that obtained by the normal series connection. This head-to-head parallel assembly can be used as a common harvesting method to collect piezoelectric and triboelectric energy effectively from piezoelectric multilayers.