1. Catalonia Institute for Energy Research (IREC), Jardins de les Dones de
Negre 1, 08930 Sant Adrià de Besòs, Barcelona, Spain
2. Department of Electronics, University of Barcelona, Marti i Franquès 1,
08028 Barcelona, Spain
3. Institute
of Chemical Research
of Catalonia (ICIQ), Av. Països
Catalans 16, 43007 Tarragona,
Spain