1. Department of Electrical and Computer Engineering; University of Toronto; 10 King's College Road Toronto Ontario M5S 3G4 Canada
2. Department of Electrical and Computer Engineering; Johns Hopkins University; Baltimore Maryland 21218 USA
3. Fuel Cell Research Center; Korea Institute of Science and Technology (KIST); Seoul 136-791 South Korea
4. Physical Sciences and Engineering Division, Solar and Photovoltaic Engineering Research Center; King Abdullah University of Science and Technology (KAUST); Thuwal 23955-6900 Saudi Arabia