1. Organic Semiconductor Center SUPA, School of Physics and Astronomy University of St Andrews St Andrews KY16 9SS UK
2. Key Laboratory for Organic Electronics and Information Displays, Institute of Advanced Materials (IAM) Nanjing University of Posts & Telecommunications 9 Wenyuan Road Nanjing 210023 China
3. Shaanxi Institute of Flexible Electronics (SIFE) Northwestern Polytechnical University (NPU) 127 West Youyi Road Xi'an 710072 Shaanxi China