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Can Mobility Negative Temperature Coefficient Be Reconciled with the Hopping Character of Transport in Conducting Polymers?
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology. Linköping Univ, Lab Organ Elect, ITN, SE-60174 Norrköping, Sweden.
Linköping Univ, Lab Organ Elect, ITN, SE-60174 Norrköping, Sweden..ORCID iD: 0000-0002-5095-5257
Linköping Univ, Lab Organ Elect, ITN, SE-60174 Norrköping, Sweden..
2019 (English)In: ACS APPLIED POLYMER MATERIALS, ISSN 2637-6105, Vol. 1, no 11, p. 2833-2839Article in journal (Refereed) Published
Abstract [en]

Poly(3,4-ethylenedioxythiophene) (PEDOT) is a conducting polymer that is used in a wide range of applications such as electronics, optoelectronics, and bio-electronics, where the fundamental understanding of the charge transport, and in particular of the electrical conductivity sigma, is a prerequisite to develop new high performance devices. There are many reports in the literature where the conductivity of archetypical conducting polymer PEDOT doped with tosylate (PEDOT:TOS) exhibits a dry negative temperature coefficient, d sigma/dT < 0, which is strikingly different from the activated-type behavior with d sigma/dT > 0 commonly observed in most conducting polymers. This unusual temperature dependence was attributed to the transition from the photon-assisted hopping to the metallic behavior, which is however difficult to rationalize taking into account that this transition occurs at high temperatures. In order to understand the origin of this unusual behavior, multiscale mobility calculations in PEDOT:TOS for the model of hopping transport were performed, where changes in the morphology and the density of states (DOS) with the temperature were explicitly taken into account. The morphology was calculated using the Molecular Dynamics simulations, and the hopping rates between the chains were calculated quantum-mechanically following the Miller-Abrahams formalism. Our results reproduce the observed negative temperature coefficient, where however the percolation analysis shows that this behavior mainly arises because of the changes in morphology upon heating when the system becomes less ordered. This results in a less efficient pi-pi stacking and hence lower mobility in the system. We therefore conclude that experimentally observed negative mobility temperature coefficient in conducting polymers at high temperatures is consistent with the hopping transport, and does not necessarily reflect the transition to a metallic band-like transport. Based on our multiscale modeling, we introduce a simple Gaussian Disorder Model for the efficient mobility calculations, where the DOS broadening is a function of the temperature, and where the transfer integral distribution is a bimodal distribution evolving with temperature.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC , 2019. Vol. 1, no 11, p. 2833-2839
Keywords [en]
PEDOT, electrical mobility, negative temperature coefficient, hopping transport, band transport, multiscale calculation
National Category
Chemical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-264875DOI: 10.1021/acsapm.9b00435ISI: 000496040500004OAI: oai:DiVA.org:kth-264875DiVA, id: diva2:1380032
Note

QC 20191218

Available from: 2019-12-18 Created: 2019-12-18 Last updated: 2019-12-20Bibliographically approved

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