1. Center for Polymers and Organic Solids, Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
2. Department of Physics and Astronomy, California State University, Northridge, CA 91330, USA
3. Department of Organic Material Science and Engineering, School of Chemical Engineering, Pusan National University, Busan, 46241, Republic of Korea
4. Department of Chemistry, National University of Singapore, Singapore 117543, Singapore