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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 24: Organic Semiconductors
CPP 24.5: Talk
Wednesday, March 13, 2013, 10:45–11:00, H40
Characteristics of the temperature dependent excitonic transport of organic semiconductors — •A. K. Topczak1 and J. Pflaum1,2 — 1Exp. Phys. VI, University of Würzburg, D-97074 Würzburg — 2ZAE Bayern, D-97074 Würzburg
The excitonic transport in organic materials is described either by a temperature activated incoherent hopping model (polymers) or by a band-like coherent transport (single crystals) [1]. To gain insights into the respective behavior we performed temperature dependent Photoluminescence (PL) quenching measurements on the excitonic transport of the archetypical material C60 and Diindenoperylene (DIP). The morphological thin film structure of these two materials differs substantially. Whereas C60 is X-ray amorphous, DIP shows high crystalline order along the direction of exciton transport. By the PL quenching technique we obtained information of the temperature dependence of exciton diffusion and thereby on the related activation energies in correlation to the underlying film morphology. In the case of DIP we observed indication for a temperature independent exciton motion below 80 K and below a critical thickness of 80 nm. Together, this hints at a coherent exciton transport within the single crystalline domains of DIP and which becomes thermally activated if the exciton has to cross grain boundaries within the layer. This result emphasizes the importance of long range crystalline order to achieve maximum exciton harvesting in planar heterojunction photovoltaic cells and thereby to enhance their performance. Financial support by the DFG (project SPP1355). [1] P. Stallinga, Adv. Mater. 23 (2011) 3356-3362