1. Department of Materials Science and EngineeringSouthern University of Science and Technology (SUSTech) Shenzhen 518055 P. R. China
2. Shenzhen Engineering Research and Development Center for Flexible Solar CellsSouthern University of Science and Technology (SUSTech) Shenzhen 518055 P. R. China
3. Guangdong Provincial Key Laboratory of Energy Materials for Electric PowerSouthern University of Science and Technology (SUSTech) Shenzhen 518055 China
4. Center for Infrastructure EngineeringWestern Sydney University Kingswood NSW 275 Australia