Molecular Insight Into the Energy Levels at the Organic Donor/Acceptor Interface: A QM/MM Study
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Interface.pdf
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8.24 MB
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Author(s)
Yost, Shane Robert
Wang, Lee-Ping
Van Voorhis, Troy
Date Issued
June 2011
Journal
Journal of Physical Chemistry C
Publisher
American Chemical Society
Citation
Yost, Shane R., Lee-Ping Wang, and Troy Van Voorhis. “Molecular Insight Into the Energy Levels at the Organic Donor/Acceptor Interface: A Quantum Mechanics/Molecular Mechanics Study.” The Journal of Physical Chemistry C 115.29 (2011): 14431–14436. Web.
Version
Author's final manuscript
Abstract
We present an investigation of the band levels and charge transfer (CT) states at the interface between two organic semiconductors, metal-free phthalocyanine (H2Pc) and 3,4,9,10-perylenetetracarboxylic bisbenzimidazole (PTCBI), using a combined quantum mechanics/molecular mechanics (QM/MM) technique. Near the organic–organic interface, significant changes from the bulk, as large as 0.2 eV, are found in the excited state energies, ionization potentials, and electron affinities, due to differences in molecular packing and polarizabilities of the two molecules. The changes in the ionization potential and electron affinity cause the CT states at the interface to be on average higher in energy than fully separated charges in the bulk materials despite having a typical local binding energy of 0.15 eV. Furthermore, we find that thermal fluctuations can induce variations of up to 0.1 eV in the CT binding energy. These results suggest that it is possible for bound interfacial CT states to dissociate in a barrierless fashion without involving “hot” CT states. This observation has direct relevance to the design of more efficient organic photovoltaics.
MIT Department
Massachusetts Institute of Technology. Department of Chemistry
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DOI of Published Version
https://doi.org/10.1021/jp203387m
