1. Optoelectronics Group; Cavendish Laboratory; JJ Thomson Avenue Cambridge CB3 0HE UK
2. Department of Chemistry and Centre for Plastic Electronics Imperial College London; Exhibition Road London SW7 2AZ UK
3. Dr. C. B. Nielsen; Materials Research Institute and School of Biological and Chemical Sciences; Queen Mary University of London; Mile End Road London E1 4NS UK
4. Department of Chemistry and Centre for Plastic Electronics; Imperial College London; Exhibition Road London SW7 2AZ UK
5. King Abdullah University of Science and Technology (KAUST); Kaust Solar Center (KSC); Thuwal 23955-6900 Saudi Arabia