Regensburg 2016 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 39: Focus: Triplet States in Organic Optoelectronics II

CPP 39.5: Vortrag

Mittwoch, 9. März 2016, 16:15–16:30, H37

Triplet and Charge Transfer Excitons in Organic Solar Cells: Influene of Energetics and Morphology — •Andreas Sperlich¹, Stefan Väth¹, Hannes Kraus¹, and Vladimir Dyakonov^1,2 — ¹Experimental Physics VI, Julius Maximilian University of Würzburg, 97074 Würzburg — ²Bayerisches Zentrum für Angewandte Energieforschung (ZAE Bayern), 97074 Würzburg

To improve organic solar cells it is necessary to develop a deeper understanding of fundamental processes, such as harvesting of singlet and charge transfer (CT) excitons, but also loss mechanisms like electron back transfer (EBT) reactions to the triplet state. These processes depend on the energy levels of constituting donor and acceptor molecules, on microscopic structure of blends but also on the relative spin orientation of charges carriers within the e-h pair. Here, we use electron paramagnetic resonance (EPR) methods to study several polymer-fullerene blend systems and found remarkable correlations between electrical performance of solar cells and formation of CT and triplet excitons. Combining results of complementary experiments, we offer a physical picture on how pushing up the LUMO level of acceptors or tailoring the blends’ morphology may end up in unwanted loss mechanisms in bulk-heterojunction solar cells.