1. Department of Chemistry, Pohang Accelerator Laboratory, Division of Advanced Materials Science, Center for Electro-Photo Behaviors in Advanced Molecular Systems, BK School of Molecular Science, and Polymer Research Institute, Pohang University of Science and Technology, Pohang 790-784, Republic of Korea
2. Department of Organic and Polymeric Materials, Tokyo Institute of Technology, 2-12-1-S8-36 O-okayama, Meguro-ku Tokyo 152-8552, Japan
3. Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 5376, United States