An optimal driving force for converting excitons into free carriers in excitonic solar cells

David C. Coffey, Bryon W. Larson, Alexander W. Hains, James B. Whitaker, Nikos Kopidakis, Olga V. Boltalina, Steven H. Strauss, Garry Rumbles

Research output: Contribution to journalArticlepeer-review

116 Citations (Scopus)

Abstract

A general but limiting characteristic in excitonic photovoltaics is that a portion of the incident photon energy appears necessary for converting excitons into electrical charges, resulting in a loss of efficiency. Currently, the mechanism underlying this process is unclear. Here, we describe the development of an experimental method for measuring charge creation yields in organic solar cell materials. We use this method to examine a series of conjugated polymer:fullerene blend films and observe two unexpected features: the existence of an optimal driving force and a loss in conversion efficiency if this force is exceeded. These observations have implications for the design of excitonic photovoltaic devices and can be explained by a simple Marcus formulation that introduces the importance of reorganization energy.

Original languageEnglish
Pages (from-to)8916-8923
Number of pages8
JournalJournal of Physical Chemistry C
Volume116
Issue number16
DOIs
Publication statusPublished - Apr 26 2012

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

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