Ionic thermoelectric materials, for example, polyelectrolytes such as polystyrene sulfonate sodium (PSSNa), constitute a new class of materials which are attracting interest because of their large Seebeck coefficient and the possibility that they could be used in ionic thermoelectric SCs (ITESCs) and field effect transistors. However, pure polyelectrolyte membranes are not robust or flexible. In this paper, the preparation of ionic thermoelectric paper using a simple, scalable and cost-effective method is described. After a composite was fabricated with nanofibrillated cellulose (NFC), the resulting NFC–PSSNa paper is flexible and mechanically robust, which is desirable if it is to be used in roll-to-roll processes. The robust NFC–PSSNa thermoelectric paper combines high ionic conductivity (9 mS cm−1), high ionic Seebeck coefficient (8.4 mV K−1) and low thermal conductivity (0.75 W m−1 K−1) at 100% relative humidity, resulting in overall figure-of-merit of 0.025 at room temperature which is slightly better than that for the PSSNa alone. Fabricating a composite with cellulose enables flexibility and robustness and this is an advance which will enable future scaling up the manufacturing of ITESCs, but also enables its use for new applications for conformable thermoelectric devices and flexible electronics.
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The authors acknowledge the European Research Council (ERC Starting Grant 307596), the Swedish Foundation for Strategic Research (SSF), the Knut and Alice Wallenberg foundation (KAW), the Swedish Energy Agency, the Advanced Functional Materials Centre at Linköping University and the United States National Science Foundation (Grant No. DMR-1262261).
Electronic supplementary information (ESI) available: Transparency, mechanical properties and details of ionic conductivity, Seebeck coefficient and thermal conductivity characterization. See DOI: 10.1039/c7ta03196c
Jiao, Fei; Naderi, Ali; Zhao, Dan; Schlueter, Joshua; Shahi, Maryam; Sundström, Jonas; Granberg, Hjalmar; Edberg, Jesper; Ail, Ujwala; Brill, Joseph W.; Lindström, Tom; Berggren, Magnus; and Crispin, Xavier, "Ionic Thermoelectric Paper" (2017). Physics and Astronomy Faculty Publications. 498.
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