1. Innovative Centre for Flexible Devices (iFLEX)School of Materials Science and EngineeringNanyang Technological University 50 Nanyang Avenue Singapore 639798 Singapore
2. Tianjin Key Laboratory of Molecular Optoelectronic SciencesDepartment of ChemistrySchool of ScienceTianjin University Tianjin 300072 China
3. College of Chemistry and Chemical EngineeringShanghai University of Engineering Science NO. 333 Longteng Road Shanghai 201620 China