Bimolecular crystals and intercalated molecular structures of polymer/fullerene in bulk heterojunction solar cells

Michael D. McGehee*, Alex C. Mayer, Michael F. Toney, Shawn R. Scully, Jonathan Rivnay, Nichole C. Cates, Roman Gysel, Martin Heeney, Iain McCulloch

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

Abstract

The performance of polymer:fullerene solar cells is heavily influenced by the packing and ordering at the molecular level in the blends as the local packing determines the stability, carrier recombination dynamics, and charge transport properties of these blends. We use x-ray diffraction, ambipolar charge transport measurements, and optical microscopy to demonstrate the formation of stable well-ordered bimolecular crystals of fullerene intercalated between the side-chains of the semiconducting polymer poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene (pBTTT). We show that fullerene intercalation is general and is likely to occur in blends with both amorphous and semicrystalline polymers when there is enough free volume between the side-chains to accommodate the fullerene molecule. These findings offer explanations for why luminescence is completely quenched in crystals much larger than exciton diffusion lengths, how the hole mobility of poly(2-methoxy-5-(3′,7′-dimethyloxy)-p-phylene vinylene) (MDMO-PPV) increases by over 2 orders of magnitude when blended with fullerene derivatives, and why large-scale phase separation occurs in some polymer:fullerene blend ratios while thermodynamically stable mixing on the molecular scale occurs for others, and finally what determines the optimum polymer:fullerene blending ratios.

Original languageEnglish (US)
Title of host publicationAmerican Chemical Society - 237th National Meeting and Exposition, ACS 2009, Abstracts of Scientific Papers
StatePublished - 2009
Externally publishedYes
Event237th National Meeting and Exposition of the American Chemical Society, ACS 2009 - Salt Lake City, UT, United States
Duration: Mar 22 2009Mar 26 2009

Other

Other237th National Meeting and Exposition of the American Chemical Society, ACS 2009
CountryUnited States
CitySalt Lake City, UT
Period03/22/0903/26/09

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)

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