Abstract
Discotic liquid crystals are a promising class of materials for molecular electronics thanks to their self-organization and charge transporting properties. The best discotics so far are built around the coronene unit and possess six-fold symmetry. In the discotic phase six-fold-symmetric molecules stack with an average twist of 30∘, whereas the angle that would lead to the greatest electronic coupling is 60∘. Here, a molecule with three-fold symmetry and alternating hydrophilic/hydrophobic side chains is synthesized and X-ray scattering is used to prove the formation of the desired helical microstructure. Time-resolved microwave-conductivity measurements show that the material has indeed a very high mobility, 0.2 cm2 V−1 s−1. The assemblies of molecules are simulated using molecular dynamics, confirming the model deduced from X-ray scattering. The simulated structures, together with quantum-chemical techniques, prove that mobility is still limited by structural defects and that a defect-free assembly could lead to mobilities in excess of 10 cm2 V−1 s−1.
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Acknowledgements
This work was financially supported by the EU project NAIMO (NMP-CT-2004-500355), the Max Planck Society through the program ENERCHEM, the German Science Foundation (Korean–German IRTG) and DFG Priority Program SPP 1355. D.A. acknowledges DFG grant AN 680/1-1. V.M. acknowledges the Alexander von Humboldt Foundation. J.K. acknowledges the EPSRC. V.M., J.K., K.K. and D.A. acknowledge the Multiscale Materials Modeling Initiative of the Max Planck Society. We thank R. Graf and H. W. Spiess for discussions. M.R.H. thanks the Carlsberg Foundation for financial support in the form of a research fellowship. Naurod von Hessen is gratefully acknowledged for catalysing this collaboration.
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Feng, X., Marcon, V., Pisula, W. et al. Towards high charge-carrier mobilities by rational design of the shape and periphery of discotics. Nature Mater 8, 421–426 (2009). https://doi.org/10.1038/nmat2427
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DOI: https://doi.org/10.1038/nmat2427
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