Dresden 2014 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 117: Organic semiconductors: Material properties (with CPP/DS)

HL 117.6: Vortrag

Freitag, 4. April 2014, 11:30–11:45, POT 051

Temperature dependent PL measurements of rubrene single crystals with µm-resolution — •T. Schmeiler1, J. Gabel1, R. Claessen1, and J. Pflaum1,21Inst. Exp. Phys. VI/IV, University of Würzburg, 97074 Würzburg — 2ZAE Bayern e.V., 97074 Würzburg

Our previous demonstration of spatial confinement effects on exciton dynamics in rubrene (rub) single crystals, microcrystals and amorphous films [1] has raised fundamental questions on excitonic processes occurring at surfaces and interfaces of molecular stacks. We address this topic by analyzing the temperature dependent PL characteristics of rub single crystals on µm-length scales and under various boundary condition by e.g. capping them with thin films of different polarizability such as Au or LaVO. At first, a pronounced enhancement of the total PL intensity of up to two orders of magnitudes was observed in case of the Au top layer which can be attributed to a resonant coupling of the excited rub states to the surface plasmon modes of the metal. This coupling phenomenon is further corroborated by relative intensity changes within the PL spectra of the Au covered rub upon cooling below 100K. In case of a LaVO capping layer, providing high polarizability without significant contributions by exciton quenching, a strong temperature dependent influence in the rub PL peaks at short wavelengths is observed. This behavior will be discussed in the context of temperature dependent changes of the LaVO layer itself as well as different coupling mechanism for the interfacial excitonic species. Financial support by the DFG research unit FOR 1809 (project PF385/6) is gratefully acknowledged. [1] B. Gieseking et al., arXiv:1309.1107

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