1. IEK5-Photovoltaik, Forschungszentrum Jülich GmbH; 52425 Jülich Germany
2. Institute of Photo-electronic Thin Film Device and Technique, Nankai University; Tianjin 300071 People's Republic of China
3. Present address: Jiangyin Everise Technology Co., Ltd.; Jiangyin 214434 People's Republic of China