Regensburg 2025 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 13: Poster
DS 13.46: Poster
Donnerstag, 20. März 2025, 18:00–20:00, P1
Substrate-driven Molecular Orientation of BQQDI-based Organic Thin Films — •Jeya Vishva Jeyaraj Pandian and Gregor Witte — Philipps-Universität Marburg, FB Physik
Thin films of PhC2-BQQDI, a high-performance n-type organic semiconductor, exhibit preferential molecular orientations depending on the substrate. On weakly-interacting amorphous SiO2 substrates, the molecules adopt an upright orientation. Furthermore, a co-existence of thin-film phase was observed depending on the growth parameters, which is characterised by the increased molecular tilt angle with respect to the surface of the substrate. Notably, a domination of thin-film phase was observed at elevated temperatures. This phenomenon contradicts a commonly observed growth behaviour in organic thin films, whereby bulk phase prevails under such growth conditions. However, post-deposition annealing results in a transition from thin-film phase into bulk phase with significant dewetting. In contrast to SiO2, on surfaces of alkali halides such as KCl, the molecules exhibit a recumbent orientation. Furthermore, an epitaxial growth was observed, driven by the templating effect of the underlying substrate. These findings pave the way for a phase-selective preparation of thin films of PhC2-BQQDI which can be used to deepen the understanding of electronic transport in devices based on PhC2-BQQDI.
Keywords: n-type organic semiconductors; organic thin films; molecular epitaxy; polymorphism