1. Department of Energy Conversion and Storage; Technical University of Denmark; Frederiksborgvej 399, DK-4000 Roskilde Denmark
2. ECN Solar Energy; P.O. Box 1 1755 ZG Petten
3. Chemistry and Physics of Materials Unit and Thematic Unit on Nanochemistry; Jawaharlal Nehru Centre for Advanced Scientific Research; Jakkur P.O. Bangalore 560064 India