Regensburg 2019 – scientific programme

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DS: Fachverband Dünne Schichten

DS 16: Organic Thin Films, Organic-Inorganic Interfaces

DS 16.9: Talk

Wednesday, April 3, 2019, 11:45–12:00, H39

Pentacene and Perfluoropentacene Bilayers – Well-Defined Interfaces vs. Molecular Intermixture — •Pierre Dombrowski, Tobias Breuer, Stefan Renato Kachel, J. Michael Gottfried, and Gregor Witte — Philipps-Universität Marburg, Germany

Precisely studying organic donor/acceptor systems is crucial for the improved understanding and design of organic optoelectronic devices. Heterostructures of p-type organic semiconductors (OSCs) and fluorinated n-type OSCs are particularly attractive donor/acceptor systems as they tend to form H-F bonds that favor the formation of intermixed supramolecular assemblies. Within these, pentacene (PEN) and perfluoropentacene (PFP) are an interisting model system due to their structural compatibility. The present study combines near-edge X-ray absorption fine structure (NEXAFS), temperature programmed desorption (TPD) and scanning tunneling microscopy (STM) measurements to characterize the intermixture of PEN and PFP on molybdenum disulfide as well as the Ag(111) and Au(111) surfaces. NEXAFS spectra of PEN and PFP bilayers show that it is possible to prepare nicely ordered bilayers without mutual intermixing. Only upon annealing, molecular intermixture is activated. TPD measurements reveal an attractive intermolecular interaction in the heterostructure, in contrast to repulsive interaction in the unitary phases, and suggest the formation of a thermally stabilized 1:1 intermixture, in line with previous TPD results [1]. STM images directly show intermixed phases that support the model of a stabilization by H-F bonds.

[1] T. Breuer and G. Witte, J. Chem. Phys. (2013), 138, 114901