Synthesis and characterization of low bandgap conjugated donor-acceptor polymers for polymer:PCBM solar cells

Guoli Tu, Sylvain Massip, Philipp M. Oberhumer, Ximin He, Richard H. Friend, Neil C. Greenham, Wilhelm T.S. Huck

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


We report on the synthesis, characterization and photovoltaic performance of three novel semiconducting polymers based on 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]. They differ only in the presence and position of hexyl side-chains on the thienyl groups. T8TBT-0 has no such side-chains, they face towards the benzothiadiazole in T8TBT-in and away in T8TBT-out. Based on electron-donating triarylamine and electron-accepting dithienyl-benzothiadiazole groups, the new polymers exhibit low bandgaps and enhanced absorption in the red part of the visible spectrum. Despite their identical backbone they differ in their synthesis and photophysics: T8TBT-0 and T8TBT-in can be synthesized by direct Suzuki coupling but a new synthesis procedure is necessary for T8TBT-out. In absorption and luminescence a blue shift is induced by the inward facing, and to a lesser extent by the outward-facing side-chains. From comparison of the photophysics in solutions and films, we conclude that the addition of side-chains reduces formation of aggregates in films and that this effect is stronger for inward-facing side-chains. By blending the three polymers with PCBM in a standard photovoltaic device architecture, T8TBT-0 performs best with a power conversion efficiency (PCE) of 1.0% (under AM1.5G illumination at 100 mW cm -2) compared to 0.17% and 0.27% for T8TBT-out and T8TBT-in, respectively.

Original languageEnglish (US)
Pages (from-to)9231-9238
Number of pages8
JournalJournal of Materials Chemistry
Issue number41
StatePublished - Nov 7 2010
Externally publishedYes

ASJC Scopus subject areas

  • General Chemistry
  • Materials Chemistry


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