Open AccessCharge Delocalization in Oligomers of Poly(2,5-bis(3-alkylthiophene-2-yl)thieno[3,2-b]thiophene) (PBTTT)
Author(s) -
Yuexing Zhang,
Robert Steyrleuthner,
JeanLuc Brédas
Publication year - 2016
Publication title -
the journal of physical chemistry c
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.401
H-Index - 289
eISSN - 1932-7455
pISSN - 1932-7447
DOI - 10.1021/acs.jpcc.6b02378
Subject(s) - thiophene , oligomer , delocalized electron , polaron , polythiophene , density functional theory , materials science , charge density , side chain , polymer chemistry , computational chemistry , photochemistry , chemistry , conductive polymer , polymer , organic chemistry , physics , electron , quantum mechanics , composite material
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
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