1. Chemistry & Nanoscience Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, USA
2. MiaSolé Hi-Tech Corp., Santa Clara, California 95051, USA
3. The Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210 USA
4. Department of Applied Physics, Aalto University, P.O. Box 15100, FI-00076 Aalto, Finland
5. Department of Physics and Helsinki Institute of Physics, University of Helsinki, P.O. Box 43, FI-00014 Helsinki, Finland