1. School of Engineering University of Warwick Coventry CV4 7AL UK
2. Trina Solar Limited State Key Laboratory for PV Science and Technology (SKL) Changzhou 213031 China
3. Fraunhofer Institute for Solar Energy Systems ISE Heidenhofstraße 2 79110 Freiburg Germany
4. Laboratory for Photovoltaic Energy Conversion Department of Sustainable Systems Engineering (INATECH) University of Freiburg Emmy-Noether-Str. 2 79110 Freiburg Germany