1. Bioelectronics Materials and Devices Lab, Central European Institute of Technology, Brno University of Technology, Purkyňova 123, 61200 Brno, Czech Republic
2. Institute of Scientific Instruments of the CAS, Královopolská 147, 61264 Brno, Czech Republic
3. Department of Electrical and Electronic Technology, Faculty of Electrical Engineering and Communication, Brno University of Technology, 616 00 Brno, Czech Republic
4. Czech Metrology Institute, 638 00 Brno, Czech Republic
5. Laboratory of Organic Electronics, ITN Campus Norrköping, Linköping University, SE-60174 Norrköping, Sweden