Surface charge density of triboelectric nanogenerators: Theoretical boundary and optimization methodology

Although high charge densities of triboelectric nanogenerators (TENG) were achieved by working in high vacuum or charge pumping techniques in atmosphere, owing to their complex structure and/or stability issues, it still remains a great challenge and necessity to directly obtain the high charge density directly through triboelectrification effect in atmosphere. Here, a basic theory about the limitation factors of surface charge density is comprehensively rebuilt through analytical mathematical derivation of the limitation equation. As a result, high surface charge density can be obtained directly by a new optimization methodology, i.e. using thin dielectric layer, which is demonstrated by the designed contact-separation model TENG and sliding model TENG. In addition, the theoretical models of charge decay and charge accumulation during triboelectrification process were built. This work provides not only a new facile and universal optimization methodology for TENG, but also a new insight in the triboelectrification process, both of which will prompt the applications of TENG ranging from powering electronic devices to harvesting large-scale blue energy.