1. Center for Polymers and Organic Solids; University of California Santa Barbara; Santa Barbara CA 93106-9530 USA
2. National Synchrotron Radiation Research Center; Hsinchu 30076 Taiwan
3. Materials Department and Materials Research Laboratory; University of California Santa Barbara; Santa Barbara CA 93106-5050 USA
4. Solar & Photovoltaics Engineering Research Center; Division of Physical Sciences and Engineering; King Abdullah University of Science and Technology; Thuwal 23955-6900 Saudi Arabia