1. Max Planck Research Group for Organic Optoelectronics, Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz D-55128, Germany
2. Department of Advanced Materials, Hannam University, Daejeon 305-811, Republic of Korea
3. IT Convergence Technology Research Laboratory, Electronics and Telecommunications Research Institute, Daejeon 305-700, Republic of Korea