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Charge and Thermoelectric Transport in Polymer-Sorted Semiconducting Single-Walled Carbon Nanotube Networks.

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Peer-reviewed

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Article

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Authors

Statz, Martin 
Schneider, Severin 
Berger, Felix J 
Lai, Lianglun 
Wood, William A 

Abstract

Understanding the charge transport mechanisms in chirality-selected single-walled carbon nanotube (SWCNT) networks and the influence of network parameters is essential for further advances of their optoelectronic and thermoelectric applications. Here, we report on charge density and temperature-dependent field-effect mobility and on-chip field-effect-modulated Seebeck coefficient measurements of polymer-sorted monochiral small-diameter (6,5) (0.76 nm) and mixed large-diameter SWCNT (1.17-1.55 nm) networks (plasma torch nanotubes, RN) with different network densities and length distributions. All untreated networks display balanced ambipolar transport and electron-hole symmetric Seebeck coefficients. We show that charge and thermoelectric transport in SWCNT networks can be modeled by the Boltzmann transport formalism, incorporating transport in heterogeneous media and fluctuation-induced tunneling. Considering the diameter-dependent one-dimensional density of states (DoS) of the SWCNTs composing the network, we can simulate the charge density and temperature-dependent Seebeck coefficients. Our simulations suggest that scattering in these networks cannot be described as simple one-dimensional acoustic and optical phonon scattering as for single SWCNTs. Instead the relaxation time is inversely proportional to energy (τ ∝ (E - EC)s, s = -1, EC being the energy of the first van Hove singularity), presumably pointing toward the more two-dimensional character of scattering events and the necessity to include scattering at the SWCNT junctions. Finally, our observation of higher power factors in trap-free, 1,2,4,5-tetrakis(tetramethylguanidino)benzene-treated (6,5) networks than in the RN networks emphasizes the importance of chirality selection to tune the width of the DoS. To benefit from both higher intrinsic mobilities and a large thermally accessible DoS, we propose trap-free, narrow DoS distribution, large-diameter SWCNT networks for both electronic and thermoelectric applications.

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Keywords

Boltzmann transport formalism, Seebeck coefficient, charge transport, single-walled carbon nanotubes networks, thermoelectric transport

Journal Title

ACS Nano

Conference Name

Journal ISSN

1936-0851
1936-086X

Volume Title

14

Publisher

American Chemical Society (ACS)

Rights

All rights reserved
Sponsorship
European Research Council (610115)
Engineering and Physical Sciences Research Council (EP/P007767/1)
Engineering and Physical Sciences Research Council (EP/P024947/1)
Engineering and Physical Sciences Research Council (EP/S019367/1)
Engineering and Physical Sciences Research Council (EP/R00661X/1)
We gratefully acknowledge financial support from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (Grant agreement No. 817494 "TRIFECTs") and through an ERC Synergy Grant SC2 (No. 610115). M. Statz acknowledges the support from the Engineering and Physical Sciences Research Council (EPSRC) through an EPSRC studentship. S. Schneider, S. Leingang and H.-J. Himmel acknowledge funding by the Deutsche Forschungsgemeinschaft via the Collaborative Research Center "N-Heteropolycycles as Functional Materials" (SFB 1249, B03, C06). M. Abdi-Jalebi thanks the EPSRC for support as well as Cambridge Materials Limited and Wolfson College, University of Cambridge for their funding and technical support.
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