1. Key Laboratory for Micro-Nano Optoelectronic Devices of Ministry of Education, College of Physics and Microelectronics, Hunan University, Changsha 410082, China
2. Materials Science and Engineering, The University of Texas at Austin, Austin, TX 78712, USA
3. Functional Nanomaterials Laboratory, Solar and Photovoltaics Engineering Research Center, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
4. School of Materials Science and Engineering, University of Jinan, Jinan 250022, China