1. Department of Materials Science and Engineering and The Shenzhen Key Laboratory for Printed Organic Electronics; South University of Science and Technology of China; No. 1088, Xueyuan Road Shenzhen Guangdong 518055 China
2. Department of Chemistry; Wuhan University; Wuhan Hubei 430072 China
3. Research Institute for Natural Sciences, Department of Chemistry; Korea University; Seoul 136-713 South Korea
4. Department of Physics; South University of Science and Technology of China; No. 1088, Xueyuan Road Shenzhen Guangdong 518055 China