Geometry of Molecular Motions in Dye Monolayers at Various Coverages
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Vaissier17JPCC.pdf
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Author(s)
Vaissier, Valerie
Van Voorhis, Troy
Date Issued
May 2017
Journal
Journal of Physical Chemistry C
Publisher
American Chemical Society (ACS)
Citation
Vaissier, Valérie, and Troy Van Voorhis. “Geometry of Molecular Motions in Dye Monolayers at Various Coverages.” The Journal of Physical Chemistry C 121, 23 (June 2017): 12562–12568 © 2017 American Chemical Society
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Author's final manuscript
Abstract
Molecular motion in monolayers is thought to influence the kinetics of charge transport and recombination in systems such as dye-sensitized solar cells (DSSCs). In this work, we use ab initio molecular dynamics to evaluate the geometry and time scale of such molecular motion in a D102 monolayer. D102, a dye that is routinely used in DSSCs, contains two chemical groups, namely, indoline and triphenylethylene, that are also present in many other dyes. We find that, at low surface coverage, the dye molecule exhibits two main tilting axes around which it heavily distorts within 10 ps. Further, the two benzene rings in the triphenylethylene group rotate with a 3–4-ps period. We observe that these large-amplitude movements are suppressed at full coverage, meaning that dye molecules in a monolayer are locked into place and undergo only minor conformational changes. Our observations indicate that, counterintuitively, charge diffusion across dye monolayers might be faster in the parts of the system that are characterized by a lower surface coverage. Because charge transport in dye monolayers has been shown to accelerate recombination kinetics in DSSCs, these results provide the basis for a new understanding of the electronic properties of sensitized systems and device efficiency.
MIT Department
Massachusetts Institute of Technology. Department of Chemistry
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DOI of Published Version
https://doi.org/10.1021/acs.jpcc.7b02416
