Regensburg 2016 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 18: Molecular Electronics and Photonics
CPP 18.5: Vortrag
Dienstag, 8. März 2016, 10:30–10:45, H42
Ultrahigh time-resolutuion two-dimensional spectroscopy of polymer thin films — Antonietta De Sio1,2, •Ephraim Sommer1,2, Filippo Troiani3, Julien Réhault4, Margherita Maiuri4, Giulio Cerullo4, Elisa Molinari3, and Christoph Lienau1,2 — 1Institut für Physik, Carl von Ossietzky Universität, 26197 Oldenburg, Germany — 2Cernter of Interface Science, Carl von Ossietzky Universität, 26129 Oldenburg, Germany — 3Instituto Nanoscienze - CNR, Centro S3, via Campi 213a, 41125 Modena, Italy — 4IFN-CNR, Dipartimento di Fisica, Politecnico di Milano, 20133 Milano, Italy
Organic semiconductors have the remarkable property that their optical excitation not only generates charge-neutral electron-hole pairs (excitons) but also charge-separated polaron pairs with high yield. Although it is known that polaron pairs are formed on an ultrafast time scale, the microscopic mechanisms governing this formation are debated. We use two-dimensional optical spectroscopy to study this formation in a protoyptical polythiophene thin film with 10-fs time resolution. These spectra revealed multi-period oscillations with ~20 fs period, persisting for hundreds of femtoseconds, and peak splittings as signatures of persistent vibronic coherence at room temperature. Our data suggest that strong vibronic coupling causes polaron pair formation on a sub-20-fs time scale, accelerates charge separation dynamics and makes it insensitive against disorder-induced fluctuations of the vibronic levels.