1. Department of Physics and Centre for Plastic Electronics; Imperial College London; South Kensington London SW7 2AZ UK
2. Department of Materials; Imperial College London; South Kensington London SW7 2AZ UK
3. College of Chemistry and Chemical Engineering Guangxi; University for Nationalities; Nanning 530006 P. R. China
4. Department of Chemistry and Centre for Plastic Electronics; Imperial College London; South Kensington London SW7 2AZ UK
5. Department of Physics; Laboratory of Applied Physics; Aristotle University of Thessaloniki; GR-54124 Thessaloniki Greece
6. Sara and Moshe Zisapel Nano-Electronic Center; Department of Electrical Engineering; Technion - Israel Institute of Technology; Haifa 3200 Israel