1. Center for Functional Nanostructures, Karlsruhe Institute of Technology; Wolfgang-Gaede-Str. 1a Karlsruhe 76131 Germany
2. Institute of Nanotechnology, Karlsruhe Institute of Technology; Hermann-von-Helmholtz-Platz 1 Eggenstein-Leopoldshafen 76344 Germany
3. BASF SE, Modelling Organic Electronics; GVE/M-B9 Ludwigshafen 67105 Germany