On the Effect of Dielectric Relaxation Mechanisms on the Performance of a Multi-layered Triboelectric Nanogenerator

With the rapid development of the Internet of Things (IoT), a growing number of mobile electronics are being connected to the internet and working in an environment without human interventions. Therefore, there is a crucial need for an alternative energy technology that can harvest energy from ambient environment to self-power devices, due to the inadequacy of conventional energy sources. Among the many energy harvesting technologies, the triboelectric nanogenerator (TENG) is attracting attention recently since it is flexible, portable, cost effective and light in weight. TENGs utilize the triboelectric effect to generate electrical energy when two materials come in contact. The ubiquity of triboelectric effect makes TENG a potential energy source for many applications, such as wearable electronics, smart buildings, and implantable medical devices. Currently, TENGs are capable of milliwatt power; for this reason, their output needs to be enhanced to realize widespread adoption. Previous studies have found that the performance of TENGs can be improved by employing a muti-layer material configuration where each layer contributes to a unique part in the charge generation and transport mechanisms. This improvement cannot be explained using theory since the theoretical calculations of the power output assume that the charges are confined at the contact surface. Therefore, a comprehensive study of the mechanism behind the enhancement of triboelectric output for multi-layer materials is needed. In this work, layered materials of Polydimethylsiloxane (PDMS) and P(VDF-TrFE) are investigated and assessed against single layered PDMS as the control material. The number of layers, as well as the polarization and dielectric properties of P(VDF-TrFE) are tuned to maximize the triboelectric output. For example, a two-layer material consisting of PDMS and electrically poled P(VDF-TrFE) shows a 25% increase in the triboelectric output compared to a single-layer PDMS sample. The enhancement of the triboelectric output is then interpreted using dielectric spectroscopy. Specifically, the triboelectric output of the designed muti-layer material configuration along with the control TENG is quantified by measuring the open-circuit voltage and short-circuit current of the samples. In addition, the TENGs are characterized using dielectric spectroscopy to probe the charge transport, interfacial polarization, and other polarization effects in the multilayered materials. This study aims to relate the charge propagation and trapping to the change in the triboelectric output in multilayered dielectric materials. The findings will shed light on the mechanisms and contribute to the widespread adoption of TENG as an environmental-friendly energy technology for our society.