1. Department of Physics and Astronomy Vrije Universiteit Amsterdam De Bolelaan 1081, HV Amsterdam 1081 The Netherlands
2. Max Planck Institute for Polymer Research Ackermannweg 10 55128 Mainz Germany
3. Department of Engineering Durham University Lower Mount Joy South Road Durham DH1 3LE UK
4. Fraunhofer Institute for Organic Electronics Electron Beam and Plasma Technology (FEP) 01277 Dresden Germany
5. Faculty of Electrical and Computer Engineering Technical University of Dresden 01069 Dresden Germany