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Charge-transport model for conducting polymers


The growing technological importance of conducting polymers makes the fundamental understanding of their charge transport extremely important for materials and process design. Various hopping and mobility edge transport mechanisms have been proposed, but their experimental verification is limited to poor conductors. Now that advanced organic and polymer semiconductors have shown high conductivity approaching that of metals, the transport mechanism should be discernible by modelling the transport like a semiconductor with a transport edge and a transport parameter s. Here we analyse the electrical conductivity and Seebeck coefficient together and determine that most polymers (except possibly PEDOT:tosylate) have s = 3 and thermally activated conductivity, whereas s = 1 and itinerant conductivity is typically found in crystalline semiconductors and metals. The different transport in polymers may result from the percolation of charge carriers from conducting ordered regions through poorly conducting disordered regions, consistent with what has been expected from structural studies.

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Figure 1: Schematic of the σE transport model and analysis procedure.
Figure 2: Percolation transport in polymers.
Figure 3: The thermopower versus electrical conductivity relation at room temperature, comparing various models.
Figure 4: Contour plot (dashed lines) of thermoelectric figure of merit zT (assuming κl = 0.2 W m−1 K−1 and T = 300 K).


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The authors thank H. Katz, M. L. Chabinyc, A. M. Glaudell and H.-S. Kim for valuable discussions and O.-Y. Choi for assistance in figure illustration. This work was supported by the AFOSR MURI programme under FA9550-12-1-0002.

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S.D.K. developed the ideas and theory for this work. S.D.K. and G.J.S. prepared and edited the manuscript.

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Correspondence to G. Jeffrey Snyder.

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The authors declare no competing financial interests.

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Kang, S., Snyder, G. Charge-transport model for conducting polymers. Nature Mater 16, 252–257 (2017).

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