Liquid crystal semiconductors
Since the discovery of Haarer et al. in 1993 [Phys. Rev. Lett. 70, 457 (1993)] that the columnar phases of discotic liquid crystals are 1D-photo-conductors, the electric charge transport in columnar liquid crystals has turned into one of the most active fields in organic materials leading to potential applications such as organic field effect transistors (OFETs), organic light emitting diodes (OLEDs) or organic photovoltaic cells (OPVs). Even after 20 years of intense research the molecular design of discotic mesogens tailored for these applications is still a challenging task: apparently minor changes in the molecular structure of the mesogen can highly affect the packing and the transport properties of the columnar phases.
In close collaboration with the groups of Sabine Laschat (Organic Chemistry, Stuttgart) and Sabine Ludwigs (Functional Polymers, Stuttgart) we investigate the connections between the structures and the charge transport properties of new liquid crystal materials. Recent work focused on crown-ether based discotic mesogens, where molecular flexibility and geometry can be varied without changing the π-electronic system of the mesogens.
Design of conductive crown ether based columnar liquid crystals: impact of molecular flexibility and geometry
P. Staffeld, M. Kaller, S. J. Beardsworth, K. Tremel, S. Ludwigs, S. Laschat, F. Giesselmann, Journal of Materials Chemistry C 1, 892-901 (2013). DOI: 10.1039/C2TC00284A
Discotic Liquid Crystals: From Tailor-Made Synthesis to Plastic Electronics
S. Laschat, A. Baro, N. Steinke, F. Giesselmann, C. Hägele, G. Scalia, R. Judele, E. Kapatsina, S. Sauer, A. Schreivogel, and M. Tosoni, Angewandte Chemie International Edition 46, 4832-4887 (2007). DOI: 10.1002/anie.200604203