Dresden 2009 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 33: Organic Photovoltaics II
CPP 33.5: Vortrag
Donnerstag, 26. März 2009, 15:00–15:15, ZEU 222
A synthetic way towards rational design of discotic liquid crystals with high charge carrier mobilities — •Denis Andrienko1, Xinliang Feng1, Valentina Marcon1, Wojciech Pisula1, James Kirpkpatrick2, Ferdinand Grozema3, Kurt Kremer1, and Klaus Muellen1 — 1Max Planck Institute for Polymer Research, Mainz, Germany — 2Imperial College London, UK — 3Delft University of Technology, The Netherlands
Conjugated materials offer the revolutionary prospect of producing semiconductor devices at low cost. The best to date discotics are built around the coronene unit and possess six fold symmetry. In the discotic phase six fold symmetric molecules stack with an average azimuthal twist of 30 deg, whereas the angle which would lead to the greatest electronic coupling and hence highest charge mobility is 60 deg. 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. Pulse radiolysis time resolved microwave conductivity measurements show that the material has indeed a very high mobility in the plastic crystalline phase, in the range of 0.1−0.2 cm2/Vs. The physical structure of the assemblies of molecules are simulated using molecular dynamics. This, together with quantum chemical techniques, allows the computation of charge mobilities without fitting parameters. The calculations prove that mobility is still limited by structural defects and that a defect free assembly would lead to mobilities in excess of 10 cm2/Vs.