1. Karlsruhe Institute of Technology (KIT), Light Technology Institute, Engesserstrasse 13, 76131 Karlsruhe, Germany
2. Karlsruhe Institute of Technology (KIT), Material Research Center for Energy Systems, Strasse am Forum 7, 76131 Karlsruhe, Germany
3. Centre for Organic Photonics & Electronics (COPE), School of Chemistry & Molecular Biosciences, University of Queensland, St. Lucia, QLD, 4072, Australia