1. Photovoltaic Materials and Devices Group, Faculty of Electrical Engineering, Mathematics and Computer Science, Delft University of Technology, Delft NL-2628 CD, The Netherlands
2. Faculty of Sciences of University of Lisbon, Lisbon 1749-016, Portugal
3. Instituto Dom Luis, University of Lisbon, Lisbon 1749-016, Portugal
4. Department of Radiation Science and Technology, Faculty of Applied Sciences, Delft University of Technology, Delft NL-2629 JB, The Netherlands
5. Institute of Applied Physics, University of Tsukuba, Ibaraki 305-8573, Japan
6. Graduate School of Engineering, Nagoya University, Nagoya 464-8603, Japan