Regensburg 2013 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 50: Organic semiconductors

HL 50.5: Talk

Wednesday, March 13, 2013, 10:30–10:45, H13

Polarization resolved carrier dynamics in crystalline perfluoropentacene films — •Kolja Kolata, Tobias Breuer, Gregor Witte, and Sangam Chatterjee — Philipps-Universität Marburg

Perfluoropentacene (PFP) is a promising n-type counterpart to the p-type pentacene (PEN) for possible future organic pn-junction applications. Since the synthesis of PFP only dates back to 2004 little is known about the electronic excitations and dynamics in this material system. We performed polarization resolved optical pump-probe spectroscopy on highly ordered, crystalline PFP-films epitaxially grown on NaF(100) in order to investigate its carrier dynamics. Due to the distinct crystal growth of PFP on NaF yielding single crystalline domains of 100 µm² the optical response along the c- and b-axis can be probed independently. Two distinct time-regimes are observed in both crystal directions: an ultrafast decay (≈1ps) of the majority of the carriers followed by slower relaxation and recombination processes. Furthermore, a flat, broadband, induced absorption arises a few tens of femtoseconds after the excitation along the b-axis, where a pronounced π-stacking in the herringbone-structure exists. This induced absorption shifts towards higher energies during the following few tens of picoseconds indicating a relaxing carrier system. This confirms the different carrier dynamics and electronic properties along different directions within the PFP crystal.