Large-scale integration of flexible materials into rolled and corrugated thermoelectric modules Haiyu Fang, 1 Bhooshan C. Popere, 1 Elayne M. Thomas, 2 Cheng-Kang Mai, 3 William B. Chang, 1 Guillermo C. Bazan, 2,3 Michael L. Chabinyc, 2 Rachel A. Segalman 1,2 1 Department of Chemical Engineering, University of California, Santa Barbara, California 2 Materials Department, University of California, Santa Barbara, California 3 Department of Chemistry, University of California, Santa Barbara, California H. Fang and B. C. Popere contributed equally to this article. Correspondence: R. A. Segalman (E-mail: segalman@engineering.ucsb.edu) ABSTRACT: Organic materials are promising candidates for thermoelectric applications owing to their tunable structure and therefore, properties, low cost, earth abundance, and solution processability. Conventional thermoelectric module architecture that relies on rel- atively thick ( mm) “legs” has limited the incorporation of organics into scalable modules. Herein, we report the fabrication of thermoelectric modules based on organic thermoelectric materials consisting of 100 or more p- and n-legs. This approach utilizes an innovative rolled module design that is shown to easily maintain a temperature gradient above 50 K in the axial direction. Rolled modules comprising PEDOT:PSS (p-type) and nickel (n-type) material system with 288 legs were shown to produce an open circuit voltage and a power output of 260 mV and 46 lW, respectively at a temperature difference of 65 K. We note that the thermoelectric power generated by such modules is sufficient to simultaneously light up nine blue LEDs after boosting the output voltage with a voltage step up converter. We also demonstrate the versatility of this approach by fabricating corrugated modules, which enables facile module assembly onto rigid (polylactic acid, PLA) or flexible (polydimethylsiloxane, PDMS) substrates, without significant loss in the power output compared to the rolled modules. V C 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44208. KEYWORDS: Thermoelectric modules; PEDOT:PSS; n-type carbon nanotube composite; nickel; printing DOI: 10.1002/app.44208 INTRODUCTION Organic thermoelectric materials have emerged as promising candidates for the fabrication of flexible, printable, and scalable thermoelectric modules. 1–3 Traditional thermoelectric modules are usually made of rigid and brittle inorganic materials 4 and the fabrication process includes dicing and high temperature manufacturing, limiting its scalability and cost-effectiveness. 5,6 In comparison, most organic thermoelectric materials are solution-processable, making it feasible to use easily scalable printing techniques to fabricate thermoelectric modules on a commercial scale. 7–9 Moreover, flexible organic thermoelectric materials can be used to make conformable modules 8,10 that enable applications such as harvesting body heat to power health monitoring systems, portable electronics, and other low power consumption (10–100 mW) devices. Although the fundamental interplay of electron and phonon transport in organic thermoelectrics is not fully understood, some promising organic thermoelectric materials have been identified in the last decade. For example, the p-type PEDOT:Tos (poly(3,4-ethylene- dioxythiophene):tosylate) system was demonstrated to have a very high power factor, S 2 r, of 450 lW/m K 2 , 11,12 where S is Seebeck coefficient and r is electrical conductivity. Some n-type carbon nanotube nanocomposites also show a relatively high power factor of 20 to 70 lW/m K 2 . 13–15 Needless to say, this materials discovery has led to an increased interest in the fabri- cation of high-performance organic thermoelectric modules. 3 A typical thermoelectric module is comprised of a number of p- and n-type “legs” connected electrically in series but thermally in parallel. A repeating unit of the module is composed of one p-type and one n-type material, as shown in the inset of Figure Additional Supporting Information may be found in the online version of this article. H. Fang and B. C. Popere contributed equally to this article. V C 2016 Wiley Periodicals, Inc. WWW.MATERIALSVIEWS.COM J. APPL. POLYM. SCI. 2016, DOI: 10.1002/APP.44208 44208 (1 of 7)