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

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.