Measuring temperature and heat flux is important for regulating any physical, chemical, and biological processes. Traditional thermopiles can provide accurate and stable temperature reading but they are based on brittle inorganic materials with low Seebeck coefficient, and are difficult to manufacture over large areas. Recently, polymer electrolytes have been proposed for thermoelectric applications because of their giant ionic Seebeck coefficient, high flexibility and ease of manufacturing. However, the materials reported to date have positive Seebeck coefficients, hampering the design of ultra-sensitive ionic thermopiles. Here we report an “ambipolar” ionic polymer gel with giant negative ionic Seebeck coefficient. The latter can be tuned from negative to positive by adjusting the gel composition. We show that the ion-polymer matrix interaction is crucial to control the sign and magnitude of the ionic Seebeck coefficient. The ambipolar gel can be easily screen printed, enabling large-area device manufacturing at low cost.
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We acknowledge the Knut and Alice Wallenberg foundation (project “Tail of the sun”), the Swedish Foundation for Strategic Research (Synergy project), the Swedish research council (project “Next generation organic solar cells” and Grant No. 2016–03979, and Grant No. 2015-05070), Swedish Governmental Agency for Innovation Systems (Grant No. 2015–04859), the Swedish Energy Agency, the Advanced Functional Materials Center at Linköping University (Faculty Grant SFO-Mat-LiU No 2009 00971), the Swedish NMR Centre, the United States National Science Foundation Grant (DMR-1262261), VINNOVA (2015–04859), ÅForsk Foundation (18–351 and 18–313).
Supplementary Information accompanies this paper at https://doi.org/10.1038/s41467- 019-08930-7.
Zhao, Dan; Martinelli, Anna; Willfahrt, Andreas; Fischer, Thomas; Bernin, Diana; Khan, Zia Ullah; Shahi, Maryam; Brill, Joseph W.; Jonsson, Magnus P.; Fabiano, Simone; and Crispin, Xavier, "Polymer Gels with Tunable Ionic Seebeck Coefficient for Ultra-Sensitive Printed Thermopiles" (2019). Physics and Astronomy Faculty Publications. 653.