Fabrication of Millimeter Thick Polymer‐Based Thermoelectric Devices by Solvent‐Free Printing

Abstract Solution‐processable polymer‐based materials allow the fabrication of flexible, light‐weight, and large‐area thermoelectric devices (TEDs). However, solution fabrication processes of polymer‐based materials involve the drying of an organic solvent, which induces an unfavorable material orientation and hinders the formation of a thick thermoelectric layer. These limitations significantly deteriorate the performance of polymer‐based TEDs. In this paper, a polymer‐based TED, fabricated by solvent‐free printing (SFP)—a technique that eliminates the solvent drying process—is reported. A carbon nanotube (CNT)–polymer composite, which is a typical polymer‐based thermoelectric material, has been fabricated by a two‐step process. The deposition of a suspension, composed of CNTs and a liquid polymer precursor, on a substrate is followed by the solidification of the liquid polymer precursor via a cross‐linking reaction. This technique does not involve the drying of organic solvents. Therefore, thermoelectric materials with random material orientation and thicknesses of greater than 1 mm are obtained. The SFP‐fabricated polymer‐based TED exhibits an electric power that is more than four orders of magnitude higher than that of a thin‐layered TED fabricated via a conventional solution process. This work facilitates the realization of various applications of polymer‐based TEDs, such as wearable power sources that can convert body heat to electricity.