1. Department of Physics; Imperial College London; South Kensington London SW7 2AZ UK
2. Centre for Plastic Electronics; Imperial College London; South Kensington London SW7 2AZ UK
3. Department of Chemistry; Imperial College London; South Kensington London SW7 2AZ UK
4. Tsukuba Material Development Laboratory; Sumitomo Chemical Co., Ltd.; 6, Kitahara Tsukuba City Ibaraki 300-3294 Japan
5. IEK5-Photovoltaik; Forschungszentrum Jülich; 52425 Jülich Germany
6. Faculty of Engineering and CENIDE; University of Duisburg-Essen; Carl-Benz-Str. 199 47057 Duisburg Germany