Regensburg 2007 – scientific programme

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SYOE: Symposium Organic Thin Film Electronics: From Molecular Contacts to Devices

SYOE 8: Poster Session SYOE

SYOE 8.44: Poster

Tuesday, March 27, 2007, 18:00–20:00, Poster B

Correlation between the topography and the optical properties of rubrene single crystals — •Rainer Stöhr¹, Gareth Beirne², Peter Michler², Jörg Wrachtrup², and Jens Pflaum¹ — ¹3. Physikalisches Institut, Univ. Stuttgart, 70550 Stuttgart, Germany — ²Institut für Strahlenphysik, Univ. Stuttgart, 70550 Stuttgart, Germany

On the surface of rubrene single crystals high hole mobilities on the order of 15 cm²/Vs have been observed, making this molecule interesting for organic device applications. However, the influence of surface defects on the transport behavior as well as on the optical characteristics is not yet understood in detail.

We present our first studies of the time- and locally-resolved micro-photoluminescense (µ-PL) investigations performed on the (001) surface of rubrene single crystals grown by sublimation. After the growth, the (001) crystal surfaces were investigated by optical microscopy and AFM. Various topologies were found which can be related to different conditions at the respective position in the oven during growth.

Measuring the optical response of numerous rubrene crystals by µ-PL at various positions on the respective (001) surface, four peaks could be identified. These peaks show different intensity and decay-time behaviors upon changes in both temperature (varied from 4 K to 100 K) and applied laser power (varied from 200 nW to 2 mW).

We will carefully discuss the assignment of these peaks to various excitons with respect to studies currently reported in literature [1].

[1] H. Najafov et al., PRL 96, 056604 (2006).