1. Physical Science and Engineering Division; Solar & Photovoltaic Engineering Research Center (SPERC); King Abdullah University of Science and Technology (KAUST); Thuwal 23955-6900 Saudi Arabia
2. School of Chemistry and Biochemistry & Center for Organic Photonics and Electronics (COPE); Georgia Institute of Technology; Atlanta GA 30332-0400 USA
3. Institute of Physical Chemistry; Westfälische Wilhelms-Universität Münster; Corrensstr. 28/30 D-48149 Münster Germany