1. Hybrid Solar Cells, Faculty of Engineering and Natural Sciences, Tampere University, P.O. Box 541, FI-33014 Tampere, Finland
2. Department of Physics “Ettore Pancini”, University of Naples Federico II, Comp. Univ. Monte Sant’Angelo, 80126 Naples, Italy
3. Department of Chemical Sciences, University of Naples Federico II, Comp. Univ. Monte Sant’Angelo, 80126 Naples, Italy