1. Laboratoire de Physique des Solides, Batiment 510, Université Paris Sud, 91405 Orsay, France; School of Chemical and Bioprocess Engineering, Centre for Synthesis and Chemical Biology (CSCB), SFI-Strategic Research Cluster in Solar Energy Conversion, University College Dublin, Belfield, Dublin 4, Ireland; and Stranski-Laboratorium, Institut für Chemie, Technische Universität Berlin, Strasse des 17 Juni 124, 10623 Berlin, Germany