1. Wuhan National Laboratory
for Optoelectronics, School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan, Hubei 430074, P. R. China
2. State Key Laboratory of Silicate Materials for Architectures, School
of Materials Science and Engineering, Wuhan University of Technology, Wuhan, Hubei 430070, P. R. China
3. Center for Organic Photonics and Electronics (COPE), School of Electrical and Computer Engineering Georgia Institute of Technology, Atlanta, Georgia 30332, United States