Regensburg 2010 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 7: Electronic and Optical Properties of Organic Systems II
CPP 7.10: Vortrag
Montag, 22. März 2010, 16:15–16:30, H39
The Spectral diffusion in poly(para-phenylene)-type polymers with different energetic disorder — •Sebastian T. Hoffmann1, Heinz Bässler2, Jan-Moritz Koenen3, Michael Forster3, Ullrich Scherf3, Ester Scheler4, Peter Strohriegl4, and Anna Köhler1 — 1Dept. of Physics, Univ. of Bayreuth — 2Physical Chemistry, Philipps-Univ. Marburg — 3Macromol. Chemistry, Bergische Univ. Wuppertal — 4Dept. of Chemistry, Univ. of Bayreuth
We have employed quasi continuous fluorescence and phosphorescence spectroscopy within a temperature range between 10K and 500K to monitor the spectral diffusion of singlet and triplet excitons in a series of pi-conjugated polymers. We investigated (i) how spectral diffusion is controlled by the degree of energetic disorder present in the amorphous film, and (ii) how this process depends on the range of the electronic coupling. For singlets, and for triplets in low-disorder compounds, spectral diffusion results in a bathochromic shift of the fluorescence spectra upon cooling, until saturation sets in. In contrast, for triplets in systems with at least moderate disorder, spectral diffusion is kinetically frustrated, i.e. frozen-out.[1] This is evident through a hypsochromic shift of the phosphorescence spectra upon cooling below a characteristic temperature. The frustration effect is controlled by the jump distance, and thus it is specific for triplet excitations that migrate via short range coupling among strongly localized states as compared to singlet excitons.
[1] S.T. Hoffmann et al, Phys. Rev. B, submitted.