Regensburg 2016 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 20: Frontiers of Electronic Structure Theory: Focus on Topology and Transport
HL 20.7: Talk
Monday, March 7, 2016, 17:30–17:45, H51
Ab Initio Molecular Dynamics Study of Conjugated Polymer Systems: The Elusive Localization of the Polaron — •Håkan W. Hugosson1, Amina Mirsakiyeva1, and Anna Delin1,2 — 1Department of Materials och Nano Physics, KTH Royal Institute of Technology, Stockholm, Sweden. — 2Ångstrom Laboratory, Uppsala University, Uppsala, Sweden.
The thermoelectric conjugated polymer poly(3,4-ethylenedioxythiophene), or PEDOT, contains a carbon backbone consisting of alternating short and long carbon bonds. Therefore there are two isomeric states: aromatic and quinoid. Charge injection or the presence of charged doping agents leads to the formation of localized charge in the conjugated polymer - a so-called polaron. This polaron induces a localized structural distortion (a shift from the aromatic form towards the quinoid) in the conjugated carbon backbone.
Self-localized polarons in conjugated carbon systems have been found using semi-empirical or HF-theory, but formerly never using DFT with local or gradient corrected functionals (e.g. LDA/BLYP). Self-localization has been seen using DFT and long range hybrid functionals with partial exact exchange included.
Using modern ab initio molecular dynamics methods based on DFT we have studied PEDOT and its charge carrying polarons. A localized polaron is now found when studying the time-averaged changes in bond-distances and also in snap-shots for the frontier orbitals for long oligomers (12 monomers).