1. Key Laboratory of Organic Optoelectronics & Molecular Engineering of Ministry of Education Department of Chemistry Tsinghua University Beijing 100084 China
2. School of Materials Science and Engineering Tsinghua University Beijing 100084 China
3. Institute of Polymer Optoelectronic Materials and Devices State Key Laboratory of Luminescent Materials and Devices South China University of Technology Guangzhou 510640 China
4. Center for Flexible Electronics Technology Tsinghua University Beijing 100084 China