Characterizing the Polymer:Fullerene Intermolecular Interactions

Abstract
Polymer:fullerene solar cells depend heavily on the electronic coupling of the polymer and fullerene molecular species from which they are composed. The intermolecular interaction between the polymer and fullerene tends to be strong in efficient photovoltaic systems, as evidenced by efficient charge transfer processes and by large changes in the energetics of the polymer and fullerene when they are molecularly mixed. Despite the clear presence of these strong intermolecular interactions between the polymer and fullerene, there is not a consensus on the nature of these interactions. In this work, we use a combination of Raman spectroscopy, charge transfer state absorption, and density functional theory calculations to show that the intermolecular interactions do not appear to be caused by ground state charge transfer between the polymer and fullerene. We conclude that these intermolecular interactions are primarily van der Waals in nature. © 2016 American Chemical Society.

Citation
Sweetnam S, Vandewal K, Cho E, Risko C, Coropceanu V, et al. (2016) Characterizing the Polymer:Fullerene Intermolecular Interactions. Chem Mater 28: 1446–1452. Available: http://dx.doi.org/10.1021/acs.chemmater.5b03378.

Acknowledgements
This work was supported by the Department of the Navy, Office of Naval Research Award N00014-14-1-0580, and by ONR Global, Grant N62909-15-1-2003. S.S. acknowledges support from the National Science Foundation through the National Science Foundation Graduate Research Fellowship under Grant DGE-114747, and support from Stanford University through a Benchmark Stanford Graduate Fellowship.

Publisher
American Chemical Society (ACS)

Journal
Chemistry of Materials

DOI
10.1021/acs.chemmater.5b03378

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