Charge Delocalization in Oligomers of Poly(2,5-bis(3-alkylthiophene-2-yl)thieno[3,2-b]thiophene), PBTTT

Yuexing Zhang, Robert Steyrleuthner, Jean-Luc Bredas

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24 Scopus citations

Abstract

We investigate theoretically charge delocalization in radical-cations, i.e., positive polarons, formed on oligomer chains of poly(2,5-bis(3-alkylthiophene-2-yl)thieno[3,2-b]thiophene), PBTTT. We use non-empirically tuned range-separated density functionals (TRS-DFT), including LC-ωPBE, LC-BLYP, and ωB97XD. We consider the evolution with oligomer length of the molecular geometric and electronic structures, optical absorption features, and spin densities. The TRS-DFT results indicate that a positive polaron can delocalize ideally over some 10 thiophene rings when the backbone is non-planar and up to 14 rings for a backbone forced to be completely planar. Interestingly, up to six polarons can co-exist side-by-side in a hexamer (which contains 24 thiophene rings), which is consistent with the highest degrees of doping (oxidation) experimentally achievable in polythiophene derivatives.
Original languageEnglish (US)
Pages (from-to)9671-9677
Number of pages7
JournalThe Journal of Physical Chemistry C
Volume120
Issue number18
DOIs
StatePublished - May 4 2016

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