Berlin 2008 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 34: POSTERS Polymerphysics
CPP 34.16: Poster
Thursday, February 28, 2008, 17:00–19:30, Poster A
Temperature dependent optical spectroscopy of rubrene single crystals — •Olga Krylova1, Jens Pflaum2, Rainer Stöhr2, Linus Gisslen3, Reinhard Scholz3, and Moritz Sokolowski1 — 1Institut für Physikalische und Theoretische Chemie, Universität Bonn — 23. Physikalisches Institut, Universität Stuttgart — 3Walter Schottky Institut, Technische Universität München
High quality rubrene crystals were grown by sublimation under streaming hydrogen. Polarized and angle-resolved fluorescence and absorption spectra were measured as a function of temperature. The fluorescence spectrum shows a strong reversible variation with temperature. The spectral changes are accompanied by a very strong (1000 fold) increase of the luminescence intensity at low T. At room temperature, the luminescence can be understood by the formation of H-aggregates of the transition dipoles due to efficient coupling in the (b,c)-crystal plane. This leads to emission from the zone boundary and hence causes a low luminescence yield and a large Stokes shift. At low temperatures, the luminescence spectrum is more reminiscent to that of a J-aggregate. This would imply that at low T, there exists a minimum of the exciton dispersion at the center of the Brillouin zone, which allows luminescent decay with high efficiency. We plan time-dependent PL measurements, which allow us assign temperature-dependent decay rates of the various PL bands, allowing estimates of the respective radiative lifetimes and the activation energies of non-radiative quenching mechanisms. Supported by DFG through the research unit 557.