Thermoelectric Properties of Conjugated Polyelectrolytes

ORAL

Abstract

Conjugated polymers are emerging as promising thermoelectric materials due to their solution processability, low thermal conductivity, and tunability of electrical properties via chemical modification. For the first time, conjugated polyelectrolytes, which are conjugated polymers with charged side chains, are being explored for thermoelectric applications. Charged side chains may be able to dope directly conjugated polymers by stabilizing the radical cations on the $\pi $-conjugated backbone. In this work, we investigate the thermoelectric properties of a novel narrow band gap conjugated polyelectrolyte with anionic side chains, poly[2,6-(4,4-bis-potassiumbutanylsulfonate-4H-cyclopenta-[2,1-b;3,4-b']-dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (CPE-K). We show that doping CPE-K with hydrochloric acid can raise electrical conductivity without significantly changing Seebeck coefficient, resulting in an overall increase in power factor and an indication of how molecular design can be used to increase thermoelectric efficiency. Our results also shed some light on the role of charged side chains and the mechanism of doping in conjugated polyelectrolytes, which is different from that of doping in inorganic materials.

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Authors

  • Cynthia Chen

    University of California, Berkeley

  • Cheng-Kang Mai

    University of California, Santa Barbara, Center for Polymers and Organic Solids, Departments of Chemistry \& Biochemistry and Materials, UCSB

  • Michael Chabinyc

    University of California, Santa Barbara, Dept. of Materials Science, UC Santa Barbara, University of California Santa Barbara, Univ of California - Santa Barbara

  • Jeffrey J. Urban

    Lawrence Berkeley National Laboratory

  • Guillermo Bazan

    University of California, Santa Barbara, Center for Polymers and Organic Solids, Departments of Chemistry \& Biochemistry and Materials, UCSB

  • Rachel Segalman

    Department of Chemical and Biomolecular Engineering, University of California, Berkeley, Berkeley, California, University of California, Berkeley, Dept of Chemical Engineering, UC Berkeley, Univ of California - Berkeley, Department of Chemical and Biomolecular Engineering, UC Berkeley, University of California-Berkeley, Lawrence Berkeley Lab