1. Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
2. Department of Materials Science and Engineering and the Center for Organic Light Emitting Diode, Seoul National University, Seoul, 151‐744, South Korea
3. Institute of Physics, National Academy of Sciences of Ukraine, Prospect Nauky 46, 03028 Kyiv, Ukraine
4. IMEC, Kapeldreef 75, B-3001 Leuven, Belgium
5. Merck KGaA, 64293 Darmstadt, Germany