1. School of Electrical, Computer and Energy Engineering, Arizona State University, Tempe, Arizona 85287, USA
2. Intel Corporation, 3585 SW 198th Avenue, Aloha, Oregon 97007, USA
3. Photovoltaics and Thin-Film Electronics Laboratory (PV-Lab), Institute of Microengineering (IMT), Ecole Polytechnique Fédérale de Lausanne (EPFL), Neuchâtel 2002, Switzerland