Influence of acceptor structure on barriers to charge separation in organic photovoltaic materials

Ryan D. Pensack, Changhe Guo, Kiarash Vakhshouri, Enrique D. Gomez, John B. Asbury

Research output: Contribution to journalArticlepeer-review

84 Scopus citations


Energetic barriers to charge separation are examined in photovoltaic polymer blends based on regioregular-poly(3-hexylthiophene) (P3HT) and two classes of electron acceptors: a perylene diimide (PDI) derivative and a fullerene (PCBM). Temperature-dependent measurements using ultrafast vibrational spectroscopy are used to directly measure the free energy barriers to charge separation. Charge separation in P3HT:PDI polymer blends occurs through activated pathways, whereas P3HT:PCBM blends exhibit activationless charge separation. X-ray scattering measurements reveal that neither the PDI derivative nor PCBM form highly crystalline domains in their polymer blends with P3HT. The present findings suggest that fullerenes are able to undergo barrierless charge separation even in the presence of structural disorder. In contrast, perylene diimides may require greater molecular order to achieve barrierless charge separation.

Original languageEnglish (US)
Pages (from-to)4824-4831
Number of pages8
JournalJournal of Physical Chemistry C
Issue number7
StatePublished - Feb 23 2012

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • General Energy
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films


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