1. Fraunhofer Institute for Solar Energy Systems; Heidenhofstr. 2 79110 Freiburg Germany
2. Department of Materials; University of Oxford; Parks Rd Oxford OX1 3PH UK
3. CNR-IMM Sez. di Bologna; via Gobetti 101 40129 Bologna Italy
4. École Polytechnique Fédérale de Lausanne, Institute of Microengineering; Photovoltaics and Thin Film Electronics Laboratory; Rue de la Maladière 71b 2002 Neuchâtel 2 Switzerland