Dithienopyrrole-based donor-acceptor copolymers: Low band-gap materials for charge transport, photovoltaics and electrochromism

Xuan Zhang, Timothy T. Steckler, Raghunath R. Dasari, Shino Ohira, William J. Potscavage, Shree Prakash Tiwari, Séverine Coppée, Stefan Ellinger, Stephen Barlow, Jean-Luc Bredas, Bernard Kippelen*, John R. Reynolds, Seth R. Marder

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

133 Scopus citations

Abstract

A series of highly soluble donor-acceptor (D-A) copolymers containing N-(3,4,5-tri-n-decyloxyphenyl)-dithieno[3,2-b:2′,3′-d]pyrrole (DTP) or N-(2-decyltetradecyl)-dithieno[3,2-b:2′,3′-d]pyrrole (DTP′) as donor and three different acceptors, 4,7-dithien-2-yl-[2,1,3]- benzothiadiazole, 4,9-dithien-2-yl-6,7-di-n-hexyl-[1,2,5]thiadiazolo[3,4-g] quinoxaline and 4,8-dithien-2-yl-2λ4δ2- benzo[1,2-c;4,5-c′]bis[1,2,5]thiadiazole (BThX, X = BTD, TQHx2, BBT, respectively) were synthesized by Stille coupling polymerizations. The optical and electrochemical properties of these copolymers were investigated, along with their use in field-effect transistors and photovoltaic devices. The band gaps (eV) estimated from UV-vis-NIR spectra and electrochemical measurements of the copolymers varied from ca. 1.5-0.5 eV, and were consistent with quantum-chemical estimates extrapolated using density functional theory. Oxidative and reductive spectroelectrochemistry of the copolymers indicated they can be both p-doped and n-doped, and three to four differently colored redox states of the polymers can be accessed through electrochemical oxidation or reduction. The DTP-BThBTD and DTP-BThTQHx2 copolymers exhibited average field-effect hole mobilities of 1.2 × 10-4 and 2.2 × 10-3 cm2/(Vs), respectively. DTP-BThBBT exhibited ambipolar field-effect characteristics and showed hole and electron mobilities of 1.2 × 10-3 and 5.8 × 10-4 cm 2/(Vs), respectively. Bulk heterojunction photovoltaic devices made from blends of the copolymers with 3′-phenyl-3′H-cyclopropa[1,9] (C60-Ih)[5,6]fullerene-3′-butanoic acid methyl ester (PCBM) (1:3 weight ratio) exhibited average power conversion efficiencies as high as 1.3% under simulated irradiance of 75 mW/cm2.

Original languageEnglish (US)
Pages (from-to)123-134
Number of pages12
JournalJournal of Materials Chemistry
Volume20
Issue number1
DOIs
StatePublished - Mar 24 2010

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Chemistry

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