1. School of Materials Shenzhen Campus of Sun Yat‐sen University Shenzhen 518107 P. R. China
2. State Key Laboratory of Optoelectronic Materials and Technologies Sun Yat‐sen University Guangzhou 510275 P. R. China
3. Physikalisches Institut and Center for Nanotechnology (CeNTech) Universität Münster 48149 Münster Germany