1. Division of Physical Sciences and Engineering; Solar and Photovoltaics Engineering Research Center (SPERC); King Abdullah University of Science and Technology (KAUST); Thuwal 23955-6900 Saudi Arabia
2. Department of Materials & Centre for Plastic Electronics; Imperial College London; SW7 2AZ UK
3. Advanced Nanofabrication, Imaging and Characterization Laboratory; King Abdullah University of Science and Technology; Thuwal 23955-6900 Saudi Arabia