1. The Organic Photonics and Electronics Group, Department of Physics, Umeå University, SE-90187 Umeå, Sweden
2. Department of Materials Science and Engineering, Rutgers University, 607 Taylor Road, Piscataway, New Jersey 08854
3. The Transport and Separations Group, Department of Physics, Chemistry and Biology, Linköping University, SE-58183 Linköping, Sweden