1. Division of Physical Sciences and Engineering; Solar and Photovoltaic Engineering Research Center (SPERC); King Abdullah University of Science and Technology (KAUST); Thuwal 23955-6900 Kingdom of Saudi Arabia
2. Department of Materials and Centre for Plastic Electronics; Imperial College London; London SW7 2AZ UK
3. Center for Energy Efficient Materials; Department of Chemistry and Biochemistry; Department of Materials; Center for Polymers and Organic Solids; University of California; Santa Barbara CA 93106 USA
4. Cornell High Energy Synchrotron Source; Cornell University; Ithaca NY 14850 USA