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Polaron formation mechanisms in conjugated polymers

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Abstract

In semiconducting polymers, interactions with conformational degrees of freedom can localize charge carriers, and strongly affect charge transport. Polarons can form when charges induce deformations of the surrounding medium, including local vibrational modes or dielectric polarization. These deformations then interact attractively with the charge, tending to localize it. First we investigate vibrational polaron formation in poly(3-hexylthiophene) [P3HT], with a tight-binding model for charges hopping between adjacent rings, coupled to ring distortions. We use density functional theory (DFT) calculations to determine coupling constants, including the “spring constant” for ring distortions and the coupling to the charge carrier. On single chains, we find only broad, weakly bound polarons by this mechanism. In 2d crystalline layers of P3HT, even weak transverse hopping between chains destabilizes this polaron. Then, we consider polarons stabilized by dielectric polarization, described semiclassically with a polarizable continuum interacting with the carrier wavefunction. In contrast to vibrational polarons, we find dielectrically stabilized polarons in P3HT are narrower, more strongly bound, and stable in 2d crystalline layers.

Graphical abstract: Polaron formation mechanisms in conjugated polymers

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Publication details

The article was received on 28 Jun 2017, accepted on 18 Nov 2017 and first published on 05 Dec 2017


Article type: Paper
DOI: 10.1039/C7CP04355D
Citation: Phys. Chem. Chem. Phys., 2018, Advance Article
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    Polaron formation mechanisms in conjugated polymers

    J. H. Bombile, M. J. Janik and S. T. Milner, Phys. Chem. Chem. Phys., 2018, Advance Article , DOI: 10.1039/C7CP04355D

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