Recent developments in flexible thermoelectrics: From materials to devices

Abstract

Thermoelectric (TE) materials/devices that can directly convert thermal energy into electricity provide a promising solution for sustainable energy development. As the flexible power supplies are urgently required for miniaturized and portable electronics, the development of flexible TE (FTE) devices, which have widespread application in the fields of power generation, flexible electronics, and wearable devices, has gained widespread attention. Over the past decades, research has largely focused on enhancing the ZT values of FTE materials and developing high-efficiency FTE generators (FTEGs). However, it is noted that in the past five years, research into FTE technologies is no longer confined to the electronic FTE materials and FTEGs. Many novel FTE applications, including self-powered multifunctional FTE sensors, ionic TE devices based on the Soret effect, multi-technology integrated TE devices, and even evaporation-driven quasi-TE nanogenerators, are emerging and demonstrate great practical significance. In this paper, recent advances achieved in wide FTE-related technologies are reviewed from the view of materials to devices. The specific structural designs and working principles of the FTE devices, the properties of the materials involved, the manufacturing strategies for device assembly, and their real functioning performances are comprehensively addressed with a few representative examples. Finally, several conclusions and future prospects for the development of FTE materials and devices are also provided. This review features a comprehensive understanding of the development roadmap for FTEs, which will help to guide future studies on flexible thermal energy harvesting/sensing applications and self-powered wearable electronics.