1. National Technical University of Belarus, Nezavisimosti Avenue 65, 220013 Minsk, Belarus
2. B.I. Stepanov Institute of Physics, National Academy of Science of Belarus, Nezavisimosti Avenue 70, 220072 Minsk, Belarus
3. Department of Science and Technology, Organic Electronics, Linköping University, Bredgatan 34, 60174 Norrköping, Sweden
4. Center for Nanostructured Materials and Analytics, Institute of Physics, University of Technology Chemnitz, Reichenhainer Strasse 70, 09107 Chemnitz, Germany