Regensburg 2013 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 69: Poster Session: II-VI semiconductors; Organic semiconductors; Heterostructures

HL 69.13: Poster

Wednesday, March 13, 2013, 16:00–20:00, Poster A

Polarization-resolved absorption of perfluoropentacene — •Jan Kuhnert, Kolja Kolata, Tobias Breuer, Gregor Witte, and Sangam Chatterjee — Philipps-Universität Marburg

Organic semiconductors are promising materials for future electronic applications. A well investigated and prototypical organic semiconductor is the p-type pentacene (PEN). Crystalline PEN films exhibit a pronounced Davydov-splitting of the excitonic excitations owing to the herringbone arrangement of both molecules within the unit cell (adopting an angle of about 52°). Perfluorination yields an n-type semiconductor (perfluoropentacene, PFP) which also exhibits a herringbone packing in the crystalline phase but with almost orthogonal arrangement (91,2°) between both molecules. Using polarization-resolved absorption measurements we demonstrate the presence of a Davydov-splitting in crystalline PFP films that were epitaxially grown on NaF(100) substrates. Moreover, by employing micro-spot illumination single crystalline domains and their azimuthal dependent excitation were analyzed. Measurements were performed at room temperature and at 10K, and yield an energetic splitting of both Davydov components of 27meV. Azimuthal resolved measurements reveal that the transition dipole moment of the high energy component is maximal for polarization parallel to the b-axis; accordingly, the transition dipole of the low energy component is oriented along the c-axis. The experiments demonstrate a Davydov-splitting like behavior despite an almost orthogonal molecular packing in the unit cell where a degeneration of excitonic components is anticipated.