1. Department of Chemistry and Centre for Processable Electronics Imperial College London London W12 0BZ UK
2. Heeger Center for Advanced Materials and Research Institute for Solar and Sustainable Energies Gwangju Institute of Science and Technology Gwangju Republic of Korea
3. Department of Physics and Centre for Processable Electronics Imperial College London London SW7 2AZ UK
4. School of Chemistry and Chemical Engineering Chongqing University Chongqing 401331 China
5. Pohang Accelerator Laboratory Pohang University of Science and Technology Pohang Republic of Korea
6. Division of Physical Sciences and Engineering King Abdullah University of Science and Technology (KAUST) KAUST Solar Centre Thuwal 23955-6900 Saudi Arabia