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Tuning the electronic coupling in a low-bandgap donor-acceptor copolymer via the placement of side-chains.

Authors
  • Oberhumer, Philipp M1
  • Huang, Ya-Shih
  • Sylvain Massip
  • James, David T
  • Tu, Guoli
  • Albert-Seifried, Sebastian
  • Beljonne, David
  • Cornil, Jérôme
  • Kim, Ji-Seon
  • Huck, Wilhelm T S
  • Greenham, Neil C
  • Hodgkiss, Justin M
  • Friend, Richard H
Type
Published Article
Journal
The Journal of Chemical Physics
Publisher
American Institute of Physics
Publication Date
Mar 21, 2011
Volume
134
Issue
11
Pages
114901–114901
Identifiers
DOI: 10.1063/1.3562936
PMID: 21428661
Source
Medline
License
Unknown

Abstract

We present a spectroscopic and theoretical investigation of the effect of the presence and position of hexyl side-chains in the novel low-bandgap alternating donor-acceptor copolymer poly[bis-N,N-(4-octylphenyl)-bis-N,N-phenyl-1,4-phenylenediamine-alt-5,5'-4',7',-di-2-thienyl-2',1',3'-benzothiadiazole] (T8TBT). We use electronic absorption and Raman spectroscopic measurements supported by calculations of chain conformation, electronic transitions, and Raman modes. Using these tools, we find that sterically demanding side-chain configurations induce twisting in the electronic acceptor unit and reduce the electronic interaction with the donor. This leads to a blue-shifted and weakened (partial) charge-transfer absorption band together with a higher photoluminescence efficiency. On the other hand, sterically relaxed side-chain configurations promote coupling between donor and acceptor units and exhibit enhanced absorption at the expense of luminescence efficiency. The possibility of tuning the donor-acceptor character of conjugated polymers by varying the placement of side-chains has very important ramifications for light emitting diode, Laser, display, and photovoltaic device optimization.

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