Band-like Charge Photogeneration at a Crystalline Organic Donor/Acceptor Interface

Michael A. Fusella, Alyssa N. Brigeman, Matthew Welborn, Geoffrey E. Purdum, Yixin Yan, Richard D. Schaller, Yun Hui L. Lin, Yueh Lin Loo, Troy Van Voorhis, Noel C. Giebink, Barry P. Rand

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Abstract

Organic photovoltaic cells possess desirable practical characteristics, such as the potential for low-cost fabrication on flexible substrates, but they lag behind their inorganic counterparts in performance due in part to fundamental energy loss mechanisms, such as overcoming the charge transfer (CT) state binding energy when photogenerated charge is transferred across the donor/acceptor interface. However, recent work has suggested that crystalline interfaces can reduce this binding energy due to enhanced CT state delocalization. Solar cells based on rubrene and C60 are investigated as an archetypal system because it allows the degree of crystallinity to be moldulated from a highly disordered to highly ordered system. Using a postdeposition annealing method to transform as-deposited amorphous rubrene thin films into ones that are highly crystalline, it is shown that the CT state of a highly crystalline rubrene/C60 heterojunction undergoes extreme delocalization parallel to the interface leading to a band-like state that exhibits a linear Stark effect. This state parallels the direct charge formation of inorganic solar cells and reduces energetic losses by 220 meV compared with 12 other archetypal heterojunctions reported in the literature.

Original languageEnglish
Article number1701494
JournalAdvanced Energy Materials
Volume8
Issue number9
DOIs
Publication statusPublished - Mar 26 2018

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Keywords

  • charge transfer state
  • crystal
  • delocalized
  • rubrene
  • solar cells

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • Materials Science(all)

Cite this

Fusella, M. A., Brigeman, A. N., Welborn, M., Purdum, G. E., Yan, Y., Schaller, R. D., Lin, Y. H. L., Loo, Y. L., Voorhis, T. V., Giebink, N. C., & Rand, B. P. (2018). Band-like Charge Photogeneration at a Crystalline Organic Donor/Acceptor Interface. Advanced Energy Materials, 8(9), [1701494]. https://doi.org/10.1002/aenm.201701494