Dresden 2020 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 49: Poster Session II
CPP 49.27: Poster
Tuesday, March 17, 2020, 14:00–16:00, P1A
What is the role of planarity and flexibility for aggregation in organic semiconductor materials? — •Stefan Wedler1, Axel Bourdick2, Stavros Athanasopoulos3, Stephan Gekle2, Fabian Panzer1, Caitlin McDowell4, Guillermo C. Bazan4, and Anna Köhler1,5 — 1Soft Matter Optoelectronics, U Bayreuth — 2Biofluid Simulation and Modeling, U Bayreuth — 3Universidad Carlos III de Madrid — 4Center for Polymers and Organic Solids, UC Santa Barbara — 5BIMF, U Bayreuth
Planarity and flexibility play an important role for the aggregation process in organic semiconductors. Stiff and planar molecules seem to aggregate more easily. However, it is not clear whether these factors are a prerequisite or just a side effect of aggregation. We have investigated their influence on the aggregation properties using two similar conjugated molecules, with benzothiadioazole donor moieties and thiophene acceptor units. They differ only by their central unit, where a bithiophene unit either allows for flexible twists (TT), or where it is bridged to provide a rigid planar connection (CT). Temperature dependent absorption and luminescence spectroscopy in solution shows that both molecules can readily form aggregates. However, CT exhibits only weak aggregation signatures. MD simulations and DFT calculations reveal that although TT planarizes upon aggregation, its flexibility prevents the formation of excimer-like states, which seems to be the case for CT.