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Flexible n-type thermoelectric materials by organic intercalation of layered transition metal dichalcogenide TiS2

Nature Materials volume 14, pages 622–627 (2015)Cite this article

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Abstract

Organic semiconductors are attracting increasing interest as flexible thermoelectric materials owing to material abundance, easy processing and low thermal conductivity. Although progress in p-type polymers and composites has been reported, their n-type counterpart has fallen behind owing to difficulties in n-type doping of organic semiconductors. Here, we present an approach to synthesize n-type flexible thermoelectric materials through a facile electrochemical intercalation method, fabricating a hybrid superlattice of alternating inorganic TiS2 monolayers and organic cations. Electrons were externally injected into the inorganic layers and then stabilized by organic cations, providing n-type carriers for current and energy transport. An electrical conductivity of 790 S cm−1 and a power factor of 0.45 mW m−1 K−2 were obtained for a hybrid superlattice of TiS2/[(hexylammonium)x(H2O)y(DMSO)z], with an in-plane lattice thermal conductivity of 0.12 ± 0.03 W m−1 K−1, which is two orders of magnitude smaller than the thermal conductivities of the single-layer and bulk TiS2. High power factor and low thermal conductivity contributed to a thermoelectric figure of merit, ZT, of 0.28 at 373 K, which might find application in wearable electronics.

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Figure 1: Synthesis of TiS2-based inorganic/organic superlattices.
Figure 2: Significantly enhanced in-plane thermoelectric figure of merit ZT.
Figure 3: Molecular dynamics simulations of the thermal conductivities.
Figure 4: Flexibility tests.

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Acknowledgements

The authors thank R. Sasai for polarized FTIR measurements. C.W. acknowledges financial support from a Murata Science Foundation Research Grant, a Thermal and Electrical Energy Technology Foundation Research Grant, Takahashi Industrial and Economic Research Foundation and JSPS KAKENHI Grant Number 26820295. K.Koumoto acknowledges financial support from JSPS KAKENHI Grant Number 25289226 and TherMAT. G.J.S. acknowledges support from AFOSR-MURI and DOE-EFRC (S3TEC) award number DE-SC0001299. X.G. and R.Y. acknowledge the partial support for this work from the NSF CAREER award (0846561) and AFOSR (FA9550-11-1-0109). The simulation work used the Janus supercomputer, supported by NSF (0821794).

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Authors and Affiliations

  1. Graduate School of Engineering, Nagoya University, Nagoya 464-8603, Japan

    Chunlei Wan, Feng Dang, Tomohiro Itoh, Hitoshi Sasaki, Mami Kondo & Kunihito Koumoto

  2. State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China

    Chunlei Wan

  3. Department of Mechanical Engineering, University of Colorado, Boulder, Colorado 80309, USA

    Xiaokun Gu & Ronggui Yang

  4. College of Material Science and Engineering, Nanjing University of Technology, Nanjing 210009, China

    Yifeng Wang

  5. KOBELCO Research Institute, Kobe, Hyogo 651-2271, Japan

    Kenji Koga & Kazuhisa Yabuki

  6. Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA

    G. Jeffrey Snyder

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  1. Chunlei Wan
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Contributions

C.W. and K.Koumoto initiated the concepts. C.W. designed the experiments. C.W., F.D., T.I., Y.W., H.S., M.K., K.Koga and K.Y. conducted the experiments. X.G. and R.Y. performed the molecular dynamics simulations. C.W., X.G., G.J.S., R.Y. and K.Koumoto analysed the data and wrote the manuscript. All of the authors contributed to manuscript preparation.

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Correspondence to Chunlei Wan or Kunihito Koumoto.

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Wan, C., Gu, X., Dang, F. et al. Flexible n-type thermoelectric materials by organic intercalation of layered transition metal dichalcogenide TiS2. Nature Mater 14, 622–627 (2015). https://doi.org/10.1038/nmat4251

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