Hamburg 2001 – wissenschaftliches Programm

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SYOF: Organische Festkörper

SYOF 5: Poster Session

SYOF 5.3: Poster

Dienstag, 27. März 2001, 17:00–19:00, Aula S3

Surface states and quantum confinement in linear molecular chains — •Karin Schmidt¹, Vladimir M. Agranovich², Michael Hoffmann¹, and Karl Leo¹ — ¹Institut für Angewandte Photophysik, Technische Universität Dresden, 01062 Dresden — ²Institute of Spectroscopy, Russian Academy of Sciences, Troitsk, Moscow obl. 142190 Russia

Organic materials have recently become attractive for the application in optoelectronic devices such as light emitting diodes and solar cells. Particularly attractive are materials like MePTCDI (N,N^′- dimethylperylene-3,4:9,10-dicarboximide) and PTCDA (perylen-3,4:9,10-tetracarboxylic dianhydride), which form quasi- one-dimensional molecular crystals with potentially high mobility in the stacking direction. Recently, it was shown that the lowest electronic excited states of these materials are determined by the strong interaction between Frenkel- and Charge-Transfer excitons within the one-dimensional tight-packed molecular stacks [1]. Here, we study the consequences of such a strong exciton mixing for stacks of arbitrary size. We have found two types of excited states: the first type can be well understood with the behavior known from infinite stacks; additionally, surface states can appear [2]. The properties of these allow to predict quantum confinement effects in quasi-one-dimensional crystals. The manifestation of the various states in the optical absorption spectra is discussed for the case of MePTCDI and PTCDA.

[1] M. Hoffmann et al., Chem. Phys. 258, 73 (2000)

[2] V.M. Agranovich et al., Chem. Phys. Lett. 325, 308 (2000)