Dresden 2011 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 40: Organic Electronics and Photovoltaics HL-II (jointly with CPP, HL, and O)
DS 40.4: Vortrag
Mittwoch, 16. März 2011, 11:00–11:15, FOE Anorg
Morphological aspects of the exciton transport in molecular thin films — •A.K. Topczak1, T. Roller2, and J. Pflaum1,3 — 1Inst. Exp. Phys. VI, Würzburg University, 97074 Würzburg — 23rd Phys. Inst., Stuttgart University, 70550 Stuttgart — 3ZAE Bayern, 97074 Würzburg
The exciton diffusion length is a key criteria to optimized design of organic thin film photonic devices. This optimisation requires fundamental understanding and control of the excitonic transport. It has been proposed that exciton transport should depend on the extension of crystalline domains [1]. Therefore we performed photoluminescence-quenching measurements to compare the exciton diffusion length (EDL) of the three archetypical semiconductors Diindenoperylene (DIP), Sexithiophene (α-6T) and tris-8-hydroxyquinolate-aluminum (Alq$_3$) and to link this quantity to the polycrystalline structure. A correlation between the exciton transport and the crystalline morphology is demonstrated. Long-range ordered thin films of DIP and α-6T show a high EDL. For these films the necessity of taking interference effects into account for a precise modeling became evident. In comparison, amorphous films of Alq$_3$ showed an EDL which is significantly smaller. We will elucidate the microscopic transport mechanisms and their respective energies by means of temperature dependent measurements. From our results, conclusions on the cell design of planar heterojunction thin film cells can be drawn. Financial support by the DFG (project PF385/4) is gratefully acknowledged. [1] D. Kurrle, J. Pflaum, Appl. Phys. Lett.92 (2008) 133306