On the Molecular Origin of Charge Separation at the Donor-Acceptor Interface
Lee, Olivia P.
Richter, Thomas V.
MetadataShow full item record
AbstractFullerene-based acceptors have dominated organic solar cells for almost two decades. It is only within the last few years that alternative acceptors rival their dominance, introducing much more flexibility in the optoelectronic properties of these material blends. However, a fundamental physical understanding of the processes that drive charge separation at organic heterojunctions is still missing, but urgently needed to direct further material improvements. Here a combined experimental and theoretical approach is used to understand the intimate mechanisms by which molecular structure contributes to exciton dissociation, charge separation, and charge recombination at the donor–acceptor (D–A) interface. Model systems comprised of polythiophene-based donor and rylene diimide-based acceptor polymers are used and a detailed density functional theory (DFT) investigation is performed. The results point to the roles that geometric deformations and direct-contact intermolecular polarization play in establishing a driving force (energy gradient) for the optoelectronic processes taking place at the interface. A substantial impact for this driving force is found to stem from polymer deformations at the interface, a finding that can clearly lead to new design approaches in the development of the next generation of conjugated polymers and small molecules.
CitationSini G, Schubert M, Risko C, Roland S, Lee OP, et al. (2018) On the Molecular Origin of Charge Separation at the Donor-Acceptor Interface. Advanced Energy Materials: 1702232. Available: http://dx.doi.org/10.1002/aenm.201702232.
SponsorsG.S. and M.S. contributed equally to this work. The authors gratefully thank Jean-Luc Bredas (Georgia Tech, Atlanta, GA, USA) for stimulating discussions throughout this work. G.S. gratefully thanks the calculation center of Cergy-Pontoise University for the computing time and support. C.R. thanks the University of Kentucky Vice President for Research and the Department of the Navy, Office of Naval Research (Award No. N00014-16-1-2985) for support. V.C. thanks the Department of the Navy, Office of Naval Research (Awards Nos. N00014-14-1-0580 and N00014-16-1-2520) for support. M.S. and D.D. acknowledge funding by the German Science Foundation through the SPP 1355 “Elementary Processes in Organic Photovoltaics.” The research data supporting this paper can be accessed at https://doi.org/10.17630/a6935caf-f7ed-48b2-b131-68ae72a26629.
JournalAdvanced Energy Materials