Berlin 2018 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 39: Organic Photovoltaics II
CPP 39.3: Vortrag
Mittwoch, 14. März 2018, 10:15–10:30, C 243
Does electron delocalization influence charge separation at donor- — •Anna Köhler1, Frank-Julian Kahle1, Christina Saller1, Selina Olthof2, Cheng Li1, Eva Herzig1,3, and Peter Strohriegl1 — 1Universität Bayreuth, Bayreuth, Germany — 2Universität Köln, Köln, Germany — 3TUM, München, Germany
Recent reports on organic solar cells have shown that efficiencies of up to 13% are possible using a polymeric donor and a small molecular acceptor. Yet, fundamental processes governing efficient dissociation, especially at the donor-acceptor interface are still not fully understood. In this work, we use bilayer devices with a series of three fullerene acceptors differing in order, intermolecular coupling and LUMO localization to systematically explore the influence of electron delocalization in the acceptor phase on the dissociation efficiency of charge transfer states. Structural information from GIWAXS measurements are combined with the results of optical and electrical characterization via photocurrent and photoemission spectroscopy, electroabsorption and electroluminescence as well as theoretical modelling. We find that stronger intermolecular coupling and higher order within the acceptor phase is correlated with lower CT binding energies implying a higher degree of electron delocalization. Theoretical modelling of experimental field dependent photocurrent measurements reveals that an enhancement in electron delocalization is directly coupled to an increase in CT dissociation efficiency. Therefore, our results substantiate the concept of delocalization of electrons taking an important and positive role in the charge separation process.