1. Photovoltaics Group, Martin Luther University Halle-Wittenberg, 06120 Halle (Saale), Germany
2. Department of Physics, Benue State University, Makurdi PMB 102119, Nigeria
3. Swiss Federal Laboratories for Materials Science and Technology Empa, Ueberlandstrasse 129, 8600 Dübendorf, Switzerland
4. Catalonia Institute for Energy Research (IREC), 08930 Sant Adria de Besos, Barcelona, Spain
5. Research Center for Photovoltaics (RCPV), National Institute of Advanced Industrial Science and Technology (AIST), Central 2, 1-1-1 Umezono, Tsukuba, Ibakari 305-8568, Japan