Thermoelectricity in polymer composites due to fluctuation-induced tunneling

Abstract

Transport in heavily-doped polymer composites, characterized by localized charge regions, is examined in light of the recent interest in polymers for thermoelectric applications. The developed fundamental transport theory describes carrier tunneling between charged localizations by taking into account thermally induced fluctuations of the applied potential. A range of characteristic behaviors corresponding to experimental data are described. Deviations from the Wiedemann-Franz law are also identified. This novel theory enables the determination of factors dominating the transport in polymers and a comparison to tunneling without thermal fluctuations is also provided. The obtained asymptotic expressions for the conductivity, Seebeck coefficient, and carrier thermal conductivity are particularly useful for elucidating possible routes for thermoelectric transport control and optimization.

A synthetic approach for enhanced thermoelectric properties of PEDOT:PSS bulk composites

“…24 The composites basically consist of many large conducting regions beyond the percolation limit, thus the transport is mainly due to tunneling between the formed junctions ( Figure 1(e)). The tunneling process in such systems is affected by the thermal voltage fluctuations from the excess or deficit charges across the junction 20,23,25 which create a local thermal field, E T , in addition to the external field E. There is, in effect, a parallel plate capacitor with probability…”

“…20 While the theory of polaron hopping has been developed by several authors, 21,22 only recently has a complete transport model for fluctuation-induced tunneling becomes available. 23 An investigation targeting the underlying experimental and theoretical aspects of bulk conducting polymers is therefore of great interest.…”

“…20,23 The transport is further characterized using an effective medium theory 26,27 for an inhomogeneous system, assuming that the composite can be represented by a medium with average junction parameters (Figure 1(f)). The tunneling charge (j) and heat (j q ) currents are determined using a Landauer-type theory for carriers with energy E ¼…”

Compositional Effects and Electron Lone‐pair Distortions in Doped Bournonites

“…Tuning the carrier properties of several representatives of these materials has been viewed as a promising route to enhance ZT of such systems, resulting in higher efficiency thermoelectric conversion devices. [12][13][14][15][16] Certain compositions have been shown to exhibit low thermal conductivities and promising ZT values (ZT / 1 at high temperature regimes for bornites and tetrahedrites, for example). [12][13][14][15][16] Certain compositions have been shown to exhibit low thermal conductivities and promising ZT values (ZT / 1 at high temperature regimes for bornites and tetrahedrites, for example).…”

“…[11] Recently, many naturally occurring minerals with non-toxic and earth-abundant constituents have attracted significant interest in thermoelectricity. [12][13][14][15][16] Certain compositions have been shown to exhibit low thermal conductivities and promising ZT values (ZT / 1 at high temperature regimes for bornites and tetrahedrites, for example). [17,18] Naturally occurring materials are promising as they would result in an overall reduced cost.…”