1. Electrical Engineering Program King Abdullah University of Science and Technology (KAUST) Thuwal 23955‐6900 Saudi Arabia
2. State Key Laboratory of Biochemical Engineering Institute of Process Engineering Chinese Academy of Sciences P.O. Box 353 Beijing 100190 China
3. Centre for Clean Environment and Energy Griffith University Gold Coast Queensland 4222 Australia
4. Department of Materials Science and Engineering Stanford University Stanford CA 94305 USA
5. Stanford Institute for Materials and Energy Sciences SLAC National Accelerator Laboratory 2575 Sand Hill Road Menlo Park CA 94025 USA