1. National Laboratory of Solid State Microstructures
2. School of Electronics Science and Engineering
3. Collaborative Innovation Centre of Advanced Microstructures
4. Nanjing University
5. Nanjing 210093
6. School of Materials Science and Engineering
7. Hefei University of Technology
8. Hefei 230009
9. P. R. China
10. State Key Lab of Photovoltaic Science and Technology
11. Trina Solar
12. Changzhou 213031