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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 18: Organic Electronics and Photovoltaics I
CPP 18.11: Vortrag
Dienstag, 19. März 2024, 12:30–12:45, H 0110
On the decisive influence of surface energy on crystal orientation in films of polythiophenes — •Oleksandr Dolynchuk1, Robert Kahl1, Florian Meichsner2, Alexander Much1, Mukundan Thelakkat2, and Thomas Thurn-Albrecht1 — 1Experimental Polymer Physics, Martin Luther University Halle-Wittenberg, Germany — 2Applied Functional Polymers, University of Bayreuth, Germany
Semiconducting polymers are an appealing class of functional materials with diverse applications in electronics. Understanding and controlling the crystal orientation in semiconducting polymers is critical to optimizing their efficiency and has long been a major challenge. Using substituted polythiophenes as model semiconducting polymers, it is shown that interfacial interactions at the substrate and vacuum interfaces determine the crystal orientation formed in films of polythiophenes during crystallization from the melt. Namely, we gradually increase the surface energies of the edge-on crystals formed at the vacuum interface by attaching various polar groups at the end of the polymer side chains. As a result, a uniform face-on crystal orientation induced by graphene is achieved in films of the polythiophene with the most polar end group as thick as 200 nm. The face-on crystal orientation is formed in the modified polythiophenes crystallized even on the amorphous surfaces, but by a different growth mechanism. Furthermore, we show that the crystal orientation can be switched in the same sample depending on the crystallization conditions if the competition of interfacial interactions at both interfaces is present.
Keywords: Semiconducting polymers; Crystal orientation; Polythiophenes; Surface energy; Thin films