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.