1. Department of Materials Science and Engineering University of Pennsylvania Philadelphia PA 19104 USA
2. Advanced Photovoltaics Research Center Korea Institute of Science and Technology (KIST) Seoul 02792 Republic of Korea
3. College of Architecture and Urban Planning Tongji University Shanghai 200092 China
4. Weitzman School of Design University of Pennsylvania Philadelphia PA 19104 USA
5. School of Electrical and Computer Engineering Center for Smart Sensor System of Seoul (CS4) University of Seoul Seoul 02504 Republic of Korea