An Organic Thermoelectric Generator by Local Doping of Highly-Aligned Polymer Films

The growing number of distributed microelectronics in the Internet of Things (IoT) requires versatile, scalable and affordable power sources. Heat-harvesting organic thermoelectric generators (TEGs) are regarded as a potential key component of the future energy landscape. Research surrounding the structure-property relationships in organic thermoelectric materials has led to extraordinary advances in the power factors of preferentially aligned polymer films [1-2], yet there has been little effort to actually leverage these advances and transfer aligned polymer films into a functional TEG. In this work, a previously reported shear-force method is used to induce in-plane orientation of regioregular poly(3-hexylthiophene) (P3HT) and poly[bis(thiophen-2-yl)thieno[3,2,b]thiophene (PBTTT) films which are then floated onto ultrathin parylene substrates. A scalable inkjet printing method along with an ink formulation of the p-type dopant tris(4-bromophenyl)ammoniumyl hexachloroantimonate), known as magic blue (MB), enabled high-precision local doping of the oriented polymer films to pattern a conductive TEG architecture. This novel fabrication method was used to scale the oriented TEGs up to 10 thermocouple pairs resulting in a maximum power output of 1.1 nW and an open circuit voltage of 6.6mV at Δ<i>T</i>=50K. This work represents the first example of an oriented organic TEG and demonstrates the value of local doping as a precise and scalable fabrication method for future TEGs.<br/><br/>[1] Viktoriia Untilova, Till Biskup, Laure Biniek, Vishnu Vijayakumar, and Martin Brinkmann<br/>Macromolecules 2020 53 (7), 2441-2453<br/>[2] Vijayakumar, V., Zhong, Y., Untilova, V., Bahri, M., Herrmann, L., Biniek, L., Leclerc, N., Brinkmann, M., Bringing Conducting Polymers to High Order: Toward Conductivities beyond 105 S cm−1 and Thermoelectric Power Factors of 2 mW m−1 K−2. Adv. Energy Mater. 2019, 9, 1900266.