Dresden 2003 – wissenschaftliches Programm
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CPP: Chemische Physik und Polymerphysik
CPP 5: Elektronische Eigenschaften von Polymeren
CPP 5.4: Vortrag
Montag, 24. März 2003, 17:45–18:00, ZEU/160
Energy transfer in single conjugated polymer chains — •J.G. Müller1, U. Lemmer2, J.M. Lupton1, F. Schindler1, F. Saas1, M. Anni3, U. Scherf4, and J. Feldmann1 — 1Lehrstuhl für Photonik und Optoelektronik, Ludwig-Maximilians-Universität München — 2Lichttechnisches Institut, Universität Karlsruhe — 3Universität Lecce, Italien — 4Universität Wuppertal, Department 9-Polymerchemistry
Energy transfer determines the photoexcitation dynamics in conjugated semiconducting polymers. In particular exciton diffusion is driven by energy transfer between different polymer chains or chain segments (chromophores). In our investigation we study the energy transfer in single chains of a ladder-type methyl-substituted poly(p-phenylene) (MeLPPP) by time- and polarization resolved measurements of the photoluminescence at temperatures between 5 K and 300 K. We find that at low temperatures the homogeneous linewidth is < 5 meV, which is much smaller than the energetic difference between the individual chromophores on the chain. This leads to a limited on-chain energy transfer between the different chromophores. The polymer chain emission is therefore given by the emission of several decoupled chromophores. At room temperature, however, the energetic levels of the chromophores are strongly homogeneously broadened. The resulting spectral overlap enables an efficient energy transfer over the entire chain. Using a gated image intensifier with 200 ps time resolution, the energy transfer is observed directly by a redshift of the chain emission. This also leads to fast and pronounced blinking of the chain.