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HL: Halbleiterphysik

HL 61: Organische Halbleiter

HL 61.8: Vortrag

Mittwoch, 9. März 2005, 12:30–12:45, TU P270

Ultrafast transient absorption spectroscopy of perylene derivatives — •E. Engel¹, K. Schmidt², D. Beljonne², J.-L. Brédas², K. Leo¹, and M. Hoffmann¹ — ¹Institut für Angewandte Photophysik, TU Dresden, 01062 Dresden, Germany, www.iapp.de — ²School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, USA

The perylene derivatives N,N’-dimethylperylene-3,4,9,10-dicarboximide (MePTCDI) and 3,4,9,10-perylene-tetracarboxylic dianhydride (PTCDA) are paradigmatic and widely investigated organic semiconductors. Quantitative statements about excitonic relaxation processes require a thorough understanding of the optical transitions involved in time-resolved experiments.

We investigated matrix (SiO₂) isolated molecules and thin films of MePTCDI and PTCDA by means of ultrafast pump-probe spectroscopy. A broad femtosecond white-light continuum was used to record high resolution transient absorption spectra between 1.2 eV and 2.7 eV above the lowest excited state energy. Excited state contributions below the onset of linear absorption exhibit two pronounced peaks. The observed peaks in the monomer (around 1.85 eV and 1.3 eV, respectively) can be clearly correlated to numerical spectra obtained by a highly correlated quantum chemical MRD-CI calculation technique.