1. School
of Engineering, Brown University, Providence, Rhode Island 02912, United States
2. Department
of Physics, Brown University, Providence, Rhode Island 02912, United States
3. School of Physics & Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
4. Energy Research
Institute @ NTU (ERI@N), Interdisciplinary Graduate School, Nanyang Technological University, Singapore 637553, Singapore
5. Department
of Chemistry, Brown University, Providence, Rhode Island 02912, United States
6. School
of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore
7. Energy
Research Institute @ NTU (ERI@N), Nanyang Technological University, Singapore 637553, Singapore