1. MATIS IMM-CNR and Dipartimento di Fisica e Astronomia, Università di Catania, via S. Sofia 64, 95123 Catania, Italy
2. CNR-IMM, Zona Industriale, VIII strada 5, 95121 Catania, Italy
3. Silicon Photovoltaics, IMEC, Kapeldreef 75, B-3001 Leuven, Belgium
4. KUL, Departement Elektrotechniek - ESAT, Kasteelpark Arenberg 10, B-3001 Leuven, Belgium