1. IEK-5 Photovoltaik Forschungszentrum Jülich Leo-Brandt-Straße 52425 Jülich Germany
2. Institute for Solar Energy Systems, Guangdong Provincial Key Laboratory of Photovoltaic Technology, School of Physics Sun Yat-sen University 510006 Guangzhou P. R. China
3. Jiangsu Collaborative Innovation Center of Photovoltaic Science and Engineering Changzhou University No. 1 Gehu Road 213164 Changzhou P. R. China