1. Department of Physics Imperial College London South Kensington London SW7 2AZ UK
2. Centre for Electronics Frontiers Electronics and Computer Science University of Southampton Southampton SO17 1BJ UK
3. Division of Physical Sciences and Engineering and KAUST Solar Centre King Abdullah University of Science and Technology (KAUST) Thuwal 23955–6900 Saudi Arabia
4. Research Center for Electronics and Telecommunication Indonesian Institute of Science Jalan Sangkuriang Komplek LIPI Building 20 level 4 Bandung 40135 Indonesia
5. Institute of Polymer Optoelectronic Materials and Devices State Key Laboratory of Luminescent Materials and Devices South China University of Technology Guangzhou 510640 P. R. China
6. Department of Physics University of Oxford Parks Road Oxford OX1 3PU UK
7. Department of Materials Science and Engineering City University of Hong Kong Tat Chee Avenue Kowloon Hong Kong