1. Helmholtz-Zentrum Berlin; Institute of Silicon Photovoltaics; Kekuléstr. 5 12489 Berlin Germany
2. Currently at École Polytechnique Fédérale de Lausanne (EPFL), Institute of microengineering (IMT); Photovoltaics and Thin Film Electronics Laboratory; Rue de la Maladière 71b CH-2000 Neuchâtel Switzerland
3. Institute for Solar Energy Research Hameln; 31860 Emmerthal Germany