1. Department of Physics, Imperial College, London, South Kensington, London SW7 2AZ, United Kingdom
2. Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305
3. King Abdullah University of Science and Technology Solar Center, Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal 23955, Saudi Arabia
4. Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Göteborg 412 96, Sweden
5. Department of Chemistry, Imperial College, London, South Kensington, London SW7 2AZ, United Kingdom