Volume distribution of electric charges in multilayer triboelectric generators

Interlayers inserted between the charge-generating layers and electrodes in triboelectric nanogenerators (TENGs) has been shown to significantly enhance power output, suggesting their critical role in charge retention. However, direct experimental evidence of charge distribution in the interlayers has been lacking. In this study, we introduce a novel self-bonding and de-stacking method to quantitatively characterize volume charge distributions within the interlayers as well as the charge-generating layers, where the total charge within each layer is determined by measuring their surface potential. Applying this method to TENGs made of multiple layers of different materials reveals that the charge-generating layer retains approximately the same amount of charge regardless of the interlayer properties, while the charge stored in the interlayer depends on its conductivity and dielectric constant. An optimal balance between these properties leads to a maximum charge density in the storage layer, resulting in a 220 % increase in electrical output over TENGs without interlayers and a 50 % increase over those with a single interlayer. To demonstrate practical application potential, the optimal tri-layer design is tested for biomechanical energy harvesting. Under the same condition, the optimum tri-layer TENG can charge a capacitor 260 % faster than a single-layer device, showcasing its significant promise for efficient, self-powered wearable and implantable medical systems.