1. Department of Chemical Engineering, Colorado School of Mines, Golden, Colorado 80401, United States
2. Department of Applied Physics, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands
3. National Center for Photovoltaics, National Renewable Energy Laboratory, Golden, Colorado 80401, United States
4. Department of Mechanical Engineering, Colorado School of Mines, Golden, Colorado 80401, United States