1. Guangdong
Provincial Key Laboratory of Optical Fiber Sensing and Communications,
Guangzhou Key Laboratory of Vacuum Coating Technologies and New Energy
Materials, Siyuan Laboratory, Department of Physics, Jinan University, Guangzhou 510632, P. R. China
2. Biomolecular
and Organic Electronics, Department of Physics, Chemistry and Biology
(IFM), Linköping University, Linköping SE-581
83, Sweden