1. SDU Centre for Photonics Engineering, University of Southern Denmark, Sønderborg DK-6400, Denmark
2. Department of Physics, Philipps University of Marburg, Marburg D-35032, Germany
3. Institute of Physics, University of Oldenburg, Oldenburg D-26111, Germany
4. Center for Surface- and Nanoanalytics (ZONA), Institute for Physical Chemistry (IPC) & Linz Institute for Organic Solar Cells (LIOS), Johannes Kepler University, Linz A-4040, Austria