Linear side chains in benzo[1,2-b:4,5-b′]dithiophene-thieno[3,4-c] pyrrole-4,6-dione polymers direct self-assembly and solar cell performance

Clement Cabanetos, Abdulrahman El Labban, Jonathan A. Bartelt, Jessica D. Douglas, William R. Mateker, Jean Frechet, Michael D. McGehee, Pierre Beaujuge

Research output: Contribution to journalArticlepeer-review

618 Scopus citations

Abstract

While varying the size and branching of solubilizing side chains in π-conjugated polymers impacts their self-assembling properties in thin-film devices, these structural changes remain difficult to anticipate. This report emphasizes the determining role that linear side-chain substituents play in poly(benzo[1,2-b:4,5-b′]dithiophene-thieno[3,4-c]pyrrole-4,6-dione) (PBDTTPD) polymers for bulk heterojunction (BHJ) solar cell applications. We show that replacing branched side chains by linear ones in the BDT motifs induces a critical change in polymer self-assembly and backbone orientation in thin films that correlates with a dramatic drop in solar cell efficiency. In contrast, we show that for polymers with branched alkyl-substituted BDT motifs, controlling the number of aliphatic carbons in the linear N-alkyl-substituted TPD motifs is a major contributor to improved material performance. With this approach, PBDTTPD polymers were found to reach power conversion efficiencies of 8.5% and open-circuit voltages of 0.97 V in BHJ devices with PC71BM, making PBDTTPD one of the best polymer donors for use in the high-band-gap cell of tandem solar cells. © 2013 American Chemical Society.
Original languageEnglish (US)
Pages (from-to)4656-4659
Number of pages4
JournalJournal of the American Chemical Society
Volume135
Issue number12
DOIs
StatePublished - Mar 19 2013

ASJC Scopus subject areas

  • Biochemistry
  • Colloid and Surface Chemistry
  • Chemistry(all)
  • Catalysis

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