Tailored semiconducting carbon nanotube networks with enhanced thermoelectric properties


Thermoelectric power generation, allowing recovery of part of the energy wasted as heat, is emerging as an important component of renewable energy and energy efficiency portfolios. Although inorganic semiconductors have traditionally been employed in thermoelectric applications, organic semiconductors garner increasing attention as versatile thermoelectric materials. Here we present a combined theoretical and experimental study suggesting that semiconducting single-walled carbon nanotubes with carefully controlled chirality distribution and carrier density are capable of large thermoelectric power factors, higher than 340 μW m−1 K−2, comparable to the best-performing conducting polymers and larger than previously observed for carbon nanotube films. Furthermore, we demonstrate that phonons are the dominant source of thermal conductivity in the networks, and that our carrier doping process significantly reduces the thermal conductivity relative to undoped networks. These findings provide the scientific underpinning for improved functional organic thermoelectric composites with carbon nanotube inclusions.

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Figure 1: Density functional theory calculations of thermopower for metallic and semiconducting SWCNTs.
Figure 2: Dispersions of highly enriched s-SWCNTs and deposition of well-coupled s-SWCNT thin films.
Figure 3: p-type doping of semiconducting single-walled carbon nanotube thin-film networks with triethyloxonium hexachloroantimonate (OA).
Figure 4: Thermoelectric properties of various polyfluorene/s-SWCNT thin films.
Figure 5: Temperature dependence of the TE properties of a moderately doped PFO-BPy:LV s-SWCNT network.


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The investigation of the thermoelectric properties of the SWCNT networks carried out by the NREL authors was performed under a grant from the Laboratory Directed Research and Development Program at the National Renewable Energy Laboratory (NREL). The development of the s-SWCNT separations at NREL was funded by the Solar Photochemistry Program, Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences, US Department of Energy (DOE). NREL is supported by the US Department of Energy under Contract No. DE-AC36-08GO28308. E.M.M. would like to thank the National Renewable Energy Laboratory Director’s Fellowship for funding. B.H.Z. and S.L.G. would like to thank the Department of Energy, Office of Science, Science Undergraduate Laboratory Internship (SULI) Program for funding. Work at KAIST was supported by the National Research Foundation of Korea (2015R1A2A2A05027766) and Global Frontier R&D (2011-0031566: Center for Multiscale Energy Systems) programmes. Work at D.U. is supported by NSF-DMR (DMR-0847796 and DMR-1410247). This work was performed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the US Department of Energy (DOE) Office of Science by Los Alamos National Laboratory (Contract DE-AC52-06NA25396) and Sandia National Laboratories (Contract DE-AC04-94AL85000).

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A.D.A., B.H.Z., R.I., K.S.M. and S.L.G. fabricated various polymer:s-SWCNT thin films. A.D.A., B.H.Z., J.L.B. and A.J.F. characterized the thermoelectric and optical properties of polymer:s-SWCNT thin films. J.L., E.-S.L. and Y.-H.K. conducted the theoretical calculations. E.M.M. conducted the photoelectron spectroscopy characterization. D.W. and B.L.Z. conducted the thermal conductivity measurements and some electrical conductivity measurements. A.D.A. and R.I. measured film thickness using atomic force microscopy. A.D.A., B.L.Z., Y.-H.K., J.L.B. and A.J.F. provided theoretical insight, data interpretation and project direction. A.D.A., J.L., E.-S.L., E.M.M., B.L.Z., Y.-H.K., J.L.B. and A.J.F. were involved in the redaction of the manuscript.

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Correspondence to Jeffrey L. Blackburn or Andrew J. Ferguson.

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Supplementary Methods, Supplementary Notes 19, Supplementary Figures 1–10, Supplementary Table 1, Supplementary References. (PDF 1171 kb)

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Avery, A., Zhou, B., Lee, J. et al. Tailored semiconducting carbon nanotube networks with enhanced thermoelectric properties. Nat Energy 1, 16033 (2016). https://doi.org/10.1038/nenergy.2016.33

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