1. Department of Chemistry and Centre for Plastic Electronics Imperial College London London W12 0BZ UK
2. Department of Physics and Centre for Plastic Electronics Imperial College London London SW7 2AZ UK
3. Physical Sciences and Engineering Division KAUST Solar Center (KSC) King Abdullah University of Science and Technology (KAUST) Thuwal 23955‐6900 Saudi Arabia
4. Material Measurement Laboratory National Institute of Standards and Technology Gaithersburg MD 20899 USA
5. SPECIFIC College of Engineering Swansea University Bay Campus SA1 8EN Swansea UK