Charge photogeneration in donor/acceptor organic solar cells

Safa Shoaee, Tracey M. Clarke, Mattias P. Eng, Chun Huang, Stephen Barlow, Eva Espíldora, Juan Luis Delgado, Bert Campo, Seth R. Marder, Martin Heeney, Iain Mcculloch, Nazario Martín, Dirk Vanderzande, James R. Durrant

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

Abstract

We focus upon the role of interfacial energetics and morphology in influencing the separation of CT states into dissociated charge carriers. In particular, we undertake transient optical studies of films comprising regioregular poly(3-hexylthiophene) (P3HT) blended with a series of perylene-3,4:9,10-tetracarboxydiimide (PDI) fullerene electron acceptors. For the PDI film series, we observe a close correlation between the PDI electron affinity and the efficiency of charge separation. This correlation is discussed in the context of studies of charge photogeneration for other organic donor/acceptor blend films, including other polymers, blend compositions, and the widely used electron phenyl-C61-butyric acid methyl ester(PCBM). Furthermore, we compare the charge recombination dynamics observed in films comprising P3HT blended with three fullerene derivatives: PCBM and two alternative pyrazolinofullerenes. Transient absorption data indicate that replacement of PCBM with either of the pyrazolinofullerene derivatives results in a transition from nongeminate to monomolecular (geminate) recombination dynamics. We show that this transition cannot be explained by a difference in interfacial energetics. However, this transition does correlate with nanomorphology data that indicate that both pyrazolinofullerenes yield a much finer phase segregation with correspondingly smaller domain sizes than observed with PCBM. Our results therefore provide clear evidence of the role of nanomorphology in determining the nature of recombination dynamics in such donor/acceptor blends.

Original languageEnglish (US)
Article number021001
JournalJournal of Photonics for Energy
Volume2
Issue number1
DOIs
StatePublished - Jan 1 2012

Keywords

  • Charge photogeneration
  • Energy for charge separation
  • Nanomorphology

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Renewable Energy, Sustainability and the Environment

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