By virtue of simple fabrication, low cost, and high conversion efficiency, nanogenerators play a key role in promoting the development of self-powered systems and large-scale mechanical energy harvesting. Efforts have been ongoing for improving the output power of nanogenerators by maximizing their surface charge density via surface modification or structure optimization. Nevertheless, because of inevitable air breakdown during the operation process, enhancing charge density is not retainable, which is the most crucial limitation for the output performance of nanogenerators. Here, a suppressing breakdown strategy is developed to remarkably enhance the output charge density of the nanogenerator by embedding a dielectric film (polyvinylidene fluoride) with high permittivity into air gaps. Because of the air breakdown suppression and strongly field-induced dielectric polarization effect, the output charge density of ∼470 μC m-2 is obtained at ambient condition, which is ∼4 times larger than the value of the conventional nanogenerator with air breakdown. In addition, the effects of different dielectric materials and their different thicknesses are also studied for enhancing the output charge density of the nanogenerator. These results provide a guide to design the state-of-the-art nanogenerator for efficient mechanical energy harvesting.
Keywords: air breakdown; charge density; dielectrics; electret nanogenerator; energy harvesting.