Thermoelectric Fibers

Flexible thermoelectrics enables a direct and green conversion between heat and electricity to power or refrigerate flexible and wearable electronics. Organic polymer-based flexible thermoelectric materials are particularly fascinating because of their intrinsic flexibility, affordability, and low toxicity, but low thermoelectric performance limits their development. The other promising alternatives of inorganic-based flexible thermoelectric materials that have high energy-conversion efficiency, large power output, and stability at relatively high temperature, yet it is impeded by inferior flexibility. Hence, researchers propose a paradigm shift in material research as flexible thermoelectrics requires the material of which the device is made to simultaneously have inorganic semiconductor-like high thermoelectric performance and organic material-like mechanical flexibility. In this chapter, this dilemma is tackled, on both material level and device level, by introducing a new kind of flexible thermoelectric fibers, which overcomes the problems that thin film-based thermoelectrics can only be bent in one direction and lack essential wearable properties such as air permeability. Herein, the state-of-the-art in the development of flexible thermoelectric fibers and devices is summarized, including organic conducting polymer thermoelectric fibers, fully inorganic flexible thermoelectric fibers, and inorganic TE materials hybridized with organic polymer fibers. Finally, the remaining challenges in flexible thermoelectric fibers are discussed in conclusion, and suggestions and a framework to guide future development are provided, which may pave the way for a bright future of fiber-based flexible thermoelectric devices in the energy market.