Hamburg 2001 – wissenschaftliches Programm
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SYOF: Organische Festkörper
SYOF 4: Optical Properties
SYOF 4.2: Vortrag
Dienstag, 27. März 2001, 15:25–15:40, S6
Femtosecond spectroscopy of charge carrier dissociation in conjugated polymers — •J. G. Müller1, U. Lemmer1, J. Feldmann1, and U. Scherf2 — 1Lehrstuhl für Photonik und Optoelektronik, Sektion Physik & CeNS, Ludwig-Maximilians-Universität München, Amalienstraße 54, 80799 München — 2Institut für Physikalische und Theoretische Chemie, Universität Potsdam, Karl-Liebknecht-Str. 24-25, Haus 25, 14476 Golm
The transition between a neutral excitation and a pair of free charges is the underlying mechanism in both organic photodiodes and light-emitting devices. We investigate the dissociation dynamics of a neutral excitation by combining direct photocurrent measurements with the high time resolution of optical femtosecond experiments. With a first laser pulse neutral excitations in the polymer-photodiode are created, which dissociate to some extent resulting in a photocurrent. A second, temporally delayed, laserpulse is tuned to the stimulated emission band and depletes the excited state, thus decreasing the photocurrent. The dependence of the photocurrent on the delay time and spectral position of the second laserpulse gives insight into the interplay of energy relaxation and dissociation. Excitons and polaron pairs are identified as precursors of photocurrent. Dissociation rates for different excited states are calculated.