Upper limits for output performance of contact-mode triboelectric nanogenerator systems

Intensive research efforts have been devoted to increasing output performance of triboelectric nanogenerators (TENGs) by selecting or modifying materials, increasing effective area, optimizing device structures and harvesting circuits. Considering field emission and gas-ionization for electric breakdown, this paper proposes new theoretical models to predict the upper limits for output performance of contact-mode TENG harvesting system. It reveals that a constant surface charge density exists on the dielectric layer with an effective thickness below a critical value. The resultant TENG exhibits a high output power. The working efficiency of the TENG harvesting system quantitatively highlights the scope and focus of improvement for high output power. The findings would provide a powerful tool to guide the experimental design in selection of materials, structure of TENG, harvesting circuits and storage device for intended applications.