1. National Renewable Energy Laboratory, Golden, CO 80401, USA.
2. Lawrence Berkeley National Laboratory, 1 Cyclotron Rd, Berkeley, CA 94720, USA.
3. CNRS, Institut Photovoltaïque d’Île de France, UMR 9006, 30 route départementale 128, Palaiseau 91120, France.
4. Colorado School of Mines, Golden, CO 80401, USA.
5. Colorado State University, Fort Collins, CO 80523, USA.
6. The Pennsylvania State University, University Park, PA 16802, USA.
7. University of California, Berkeley, Berkeley, CA 94704, USA.