Microstructure and Mechanism of a PDMS/PTFE Charge-Trapping Layer with Functionality for Contact-Separation Triboelectric Nanogenerators

Triboelectric nanogenerators (TENGs) for mechanical energy harvesting are considered to be candidate materials for realizing clean energy and self-powered sensing systems. However, the issue of charge decay in the friction layer caused by the recombination of triboelectric charges is complex and still unclear. This phenomenon reduces the surface charge density through charge decay and energy loss, which limits the overall electrical performance of TENGs. In this study, a composite structure triboelectric nanogenerator (CS-TENG) that is designed to achieve a high triboelectric charge density and low charge dissipation is proposed. The CS-TENG consists of a micropyramid-array surface and a charge storage layer, which enables a higher surface triboelectric charge and reduced charge decay induced by the built-in potential. To increase the device performance, surface functionality was realized to expand the effective surface area through the design of a suitable pyramid structure by using polydimethylsiloxane (PDMS). By inserting polytetrafluoroethylene (PTFE), a charge storage layer with a low recombination rate was obtained. Moreover, the charge storage layer thickness controlled the output voltage and current of the CS-TENG. In this study, a surface pyramid structure combined with a charge-trapping layer with a low recombination rate and an appropriate thickness is proposed to address power generation limitations. As an application, a 70 μm thick CS-TENG was demonstrated to generate a remarkable open-circuit voltage of 21.99 V/cm2 and a short-circuit current of 2.57 μA/cm2 and to successfully light up 50 light-emitting diodes (LEDs). Additionally, the device exhibited great stability in terms of the open-circuit voltage and short-circuit current throughout 2000 cycles. This study demonstrates both the realization of surface functionality and the insertion of a charge storage layer to enhance the output performance of a PDMS-based TENG.