1. Department of Materials Science & Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, U.K.
2. Photovoltaics Department, imec, Thin Film PV Group, Kapeldreef 75, 3001 Leuven, Belgium
3. Departement Electrotechniek − ESAT, KU Leuven, 3001 Leuven, Belgium