1. Solar and Photovoltaic Engineering Research Center (SPERC), King Abdullah University of Science and Technology (KAUST), 23955-6900 Thuwal, Saudi Arabia.
2. Department of Electrical and Computer Engineering, University of Toronto, Toronto, Ontario M5S 3G4, Canada.
3. Department of Chemistry, Indiana University, Bloomington, IN 47405, USA.
4. Department of Physics and Astronomy, University of Nebraska, Lincoln, NE 68588, USA.