Unequal partnership: Asymmetric roles of polymeric donor and fullerene acceptor in generating free charge

Brett M. Savoie, Akshay Rao, Artem A. Bakulin, Simon Gelinas, Bijan Movaghar, Richard H. Friend, Tobin J. Marks, Mark A. Ratner

Research output: Contribution to journalArticle

195 Citations (Scopus)

Abstract

Natural photosynthetic complexes accomplish the rapid conversion of photoexcitations into spatially separated electrons and holes through precise hierarchical ordering of chromophores and redox centers. In contrast, organic photovoltaic (OPV) cells are poorly ordered, utilize only two different chemical potentials, and the same materials that absorb light must also transport charge; yet, some OPV blends achieve near-perfect quantum efficiency. Here we perform electronic structure calculations on large clusters of functionalized fullerenes of different size and ordering, predicting several features of the charge generation process, outside the framework of conventional theories but clearly observed in ultrafast electro-optical experiments described herein. We show that it is the resonant coupling of photogenerated singlet excitons to a high-energy manifold of fullerene electronic states that enables efficient charge generation, bypassing localized charge-transfer states. In contrast to conventional views, our findings suggest that fullerene cluster size, concentration, and dimensionality control charge generation efficiency, independent of exciton delocalization.

Original languageEnglish
Pages (from-to)2876-2884
Number of pages9
JournalJournal of the American Chemical Society
Volume136
Issue number7
DOIs
Publication statusPublished - Feb 19 2014

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ASJC Scopus subject areas

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

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