1. Institut für Angewandte Photophysik; Technische Universität Dresden; George-Bähr-Straße 1 01062 Dresden Germany
2. Fraunhofer Research Institution for Organics; Materials and Electronic Devices COMEDD; Maria-Reiche-Str. 2 01109 Dresden Germany
3. Organic Semiconductor Centre; SUPA, School of Physics and Astronomy, University of St. Andrews; KY16 9SS UK