Regensburg 2004 – wissenschaftliches Programm
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SYOH: Organic and Hybrid Systems for Future Electronics
SYOH 2: Spectroscopy
SYOH 2.2: Vortrag
Donnerstag, 11. März 2004, 15:00–15:15, H37
Femtosecond near-field spectroscopy of semiconducting polymers — •Kerstin Müller1, Christoph Lienau1, Dario Polli2, Giulio Cerullo2, and Guglielmo Lanzani2 — 1Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, 12489 Berlin — 2Politecnico di Milano, Dipartimento di Fisica, 20133 Milano, Italy
During recent years, ultrafast spectroscopy has provided a wealth of new insight into the dynamics of optical excitations of semiconducting polymers and thus into the function of polymer-based optoelectronic devices. So far from these studies little is known about spatial inhomogeneities of optical nonlinearities in such systems. Such information is crucial, however, for a detailed microscopic understanding of the optolectronic properties of polymers, which are strongly influenced by effects of disorder, e.g, fluctuations in size and orientation of polymer chains on nanoscopic and mesoscopic length scales. Here, we introduce a novel technique, femtosecond near-field pump-probe spectroscopy, for spatially mapping the temporal dynamics of polymer optical nonlinearities on a 100 nm length scale with sub-picosecond resolution. We report first experimental studies of the time- and space-resolved photo-induced absorption of thin films of methyl-substituted poly(para-phenylene) ladder-type polymers (m-LPPP) and of mixed phase segregated polyfluorene/dye blends. Even on nominally homogeneous m-LPPP films, we observe pronounced spatial fluctuations in both magnitude and dynamics of the ultrafast picosecond decay of the photoinduced absorption on sub-micron length scales. In this paper, we introduce our novel experimental technique and discuss the implications of our findings.