Effect of shape and alignment of carbon-based nanofillers on quantum tunneling effect of triboelectric nanogenerators

Triboelectric nanogenerators (TENGs) have received recent interest in converting unconventional mechanical energy to electricity, particularly as a sustainable form of energy generation from sources such as wind and friction. Energy conversion in TENGs is based on triboelectrification and electrostatic induction effects. However, its output electrical characteristics still need more fundamental investigation and development. Based on equations, increasing the triboelectric polymer dielectric constant should enhance the charge density and lead to higher current density and voltage by facilitating charge transfer from the contact surface toward electrodes. Nanoparticles can enhance charge transfer in TENGs by increasing the polymer matrix's dielectric constant, especially when their concentration approaches the percolation threshold. However, the maximum dielectric constant around the percolation threshold does not track the maximum electrical performance of the TENG device. The shape, and orientation of anisotropic nanoparticles, also play a role in the outcome of the polymer's dielectric constant. This research investigates the effect of carbon-based nanoparticles on PDMS nanocomposite/aluminum TENG output, considering the aforementioned factors. The particles are chosen from various molecular shapes and dielectric constants, including carbon black (CB), multiwall carbon nanotube (CNT), graphene oxide (GO), and reduced graphene oxide (r-GO). Here we show the optimum filler weight fraction for maximum voltage and current usually differs from the concentration for the highest dielectric constant near the percolation threshold, due to the quantum tunnel effect. Here we show that the gap between the concentration with the highest triboelectric performance and the concentration with the highest dielectric nanofillers depends on the shape and angle of the nanofillers in the device.