**Acknowledgements**

The authors acknowledge the support from the Australian government through the Australian Renewable Energy Agency (ARENA) and the Australian Centre of Advanced Photovoltaics (ACAP, Grant No. R5-NS01) and UNSW Career Advanced fund. The authors also acknowledge Dr. Kaiwen Sun, Dr. Udo Römer, Mr. Xinyuan Wu, Dr. Chang Yan, Dr. Lei Shi and Dr. Jianghui Zheng and Dr. Jizhong Yao for valuable discussion and advice.
