Efficient charge generation by relaxed charge-transfer states at organic interfaces

Koen Vandewal, Steve N. Albrecht, Eric T. Hoke, Kenneth Graham, Johannes Widmer, Jessica D. Douglas, Marcel Schubert, William R. Mateker, Jason T. Bloking, George F. Burkhard, Alan Sellinger, Jean Frechet, Aram Amassian, Moritz Kilian Riede, Michael D. McGehee, Dieter Neher, Alberto Salleo

Research output: Contribution to journalArticlepeer-review

547 Scopus citations

Abstract

Interfaces between organic electron-donating (D) and electron-accepting (A) materials have the ability to generate charge carriers on illumination. Efficient organic solar cells require a high yield for this process, combined with a minimum of energy losses. Here, we investigate the role of the lowest energy emissive interfacial charge-transfer state (CT1) in the charge generation process. We measure the quantum yield and the electric field dependence of charge generation on excitation of the charge-transfer (CT) state manifold via weakly allowed, low-energy optical transitions. For a wide range of photovoltaic devices based on polymer:fullerene, small-molecule:C60 and polymer:polymer blends, our study reveals that the internal quantum efficiency (IQE) is essentially independent of whether or not D, A or CT states with an energy higher than that of CT1 are excited. The best materials systems show an IQE higher than 90% without the need for excess electronic or vibrational energy. © 2014 Macmillan Publishers Limited.
Original languageEnglish (US)
Pages (from-to)63-68
Number of pages6
JournalNature Materials
Volume13
Issue number1
DOIs
StatePublished - Nov 17 2013

ASJC Scopus subject areas

  • Mechanics of Materials
  • Materials Science(all)
  • Chemistry(all)
  • Mechanical Engineering
  • Condensed Matter Physics

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