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Engineered doping of organic semiconductors for enhanced thermoelectric efficiency

Nature Materials volume 12, pages 719–723 (2013)Cite this article

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Abstract

Significant improvements to the thermoelectric figure of merit ZT have emerged in recent years, primarily due to the engineering of material composition and nanostructure in inorganic semiconductors1 (ISCs). However, many present high-ZT materials are based on low-abundance elements that pose challenges for scale-up, as they entail high material costs in addition to brittleness and difficulty in large-area deposition. Here we demonstrate a strategy to improve ZT in conductive polymers and other organic semiconductors (OSCs) for which the base elements are earth-abundant. By minimizing total dopant volume, we show that all three parameters constituting ZT vary in a manner so that ZT increases; this stands in sharp contrast to ISCs, for which these parameters have trade-offs. Reducing dopant volume is found to be as important as optimizing carrier concentration when maximizing ZT in OSCs. Implementing this strategy with the dopant poly(styrenesulphonate) in poly(3,4-ethylenedioxythiophene), we achieve Z T = 0.42 at room temperature.

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Figure 1: The doping (or dedoping) trajectory required for efficient maximization of thermoelectric power factor in an OSC.
Figure 2: Selective removal of PSS by EG treatment.
Figure 3: Thermoelectric properties of PEDOT:PSS at various dedoping times.

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Acknowledgements

The authors thank J. Kim and K. Chung for assistance and discussions regarding sample preparation. This work was supported as part of the Center for Solar and Thermal Energy Conversion, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Basic Energy Sciences under Award No. DE-SC0000957.

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Authors and Affiliations

  1. Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan 48109-2125, USA

    G-H. Kim, L. Shao, K. Zhang & K. P. Pipe

  2. Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109-2122, USA

    K. P. Pipe

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  1. G-H. Kim
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  2. L. Shao
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  3. K. Zhang
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  4. K. P. Pipe
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Contributions

G-H.K. developed the ideas for this work, prepared the polymer films, and performed measurements of Seebeck coefficient and electrical conductivity. L.S. performed Al2O3 and gold depositions and and gold depositions as well as sample thickness and XPS measurements. K.Z. performed thermal conductivity measurements. K.P.P. supervised the project. G-H.K. and K.P.P. prepared the manuscript, and all authors participated in editing.

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Correspondence to K. P. Pipe.

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The authors declare no competing financial interests.

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Kim, GH., Shao, L., Zhang, K. et al. Engineered doping of organic semiconductors for enhanced thermoelectric efficiency. Nature Mater 12, 719–723 (2013). https://doi.org/10.1038/nmat3635

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