Organic Photovoltaics: Elucidating the Ultra-Fast Exciton Dissociation Mechanism in Disordered Materials

Authors

  • Henry M. Heitzer,

    1. Department of Chemistry, the Materials Research Center, and the the Argonne-Northwestern Solar Energy Research Center, Northwestern University, Evanston, IL, 60208 (USA)
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  • Brett M. Savoie,

    1. Department of Chemistry, the Materials Research Center, and the the Argonne-Northwestern Solar Energy Research Center, Northwestern University, Evanston, IL, 60208 (USA)
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  • Prof. Tobin J. Marks,

    Corresponding author
    1. Department of Chemistry, the Materials Research Center, and the the Argonne-Northwestern Solar Energy Research Center, Northwestern University, Evanston, IL, 60208 (USA)
    • Department of Chemistry, the Materials Research Center, and the the Argonne-Northwestern Solar Energy Research Center, Northwestern University, Evanston, IL, 60208 (USA)===

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  • Prof. Mark A. Ratner

    Corresponding author
    1. Department of Chemistry, the Materials Research Center, and the the Argonne-Northwestern Solar Energy Research Center, Northwestern University, Evanston, IL, 60208 (USA)
    • Department of Chemistry, the Materials Research Center, and the the Argonne-Northwestern Solar Energy Research Center, Northwestern University, Evanston, IL, 60208 (USA)===

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  • This work is supported as part of the ANSER Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, and Office of Basic Energy Sciences under Award Number DE-SC0001059. H.M.H. is supported by the Dept. of Defense (DoD) through the National Defense Science & Engineering Graduate Fellowship (NDSEG) Program, and B.M.S. by the Northwestern MRSEC (NSF DMR-1121262) through a graduate fellowship.

Abstract

Organic photovoltaics (OPVs) offer the opportunity for cheap, lightweight and mass-producible devices. However, an incomplete understanding of the charge generation process, in particular the timescale of dynamics and role of exciton diffusion, has slowed further progress in the field. We report a new Kinetic Monte Carlo model for the exciton dissociation mechanism in OPVs that addresses the origin of ultra-fast (<1 ps) dissociation by incorporating exciton delocalization. The model reproduces experimental results, such as the diminished rapid dissociation with increasing domain size, and also lends insight into the interplay between mixed domains, domain geometry, and exciton delocalization. Additionally, the model addresses the recent dispute on the origin of ultra-fast exciton dissociation by comparing the effects of exciton delocalization and impure domains on the photo-dynamics.This model provides insight into exciton dynamics that can advance our understanding of OPV structure–function relationships.

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