1. School of Chemistry and Biochemistry, Center for Organic Photonics and Electronics; Georgia Institute of Technology; Atlanta GA 30332 USA
2. School of Electrical and Computer Engineering; Center for Organic Photonics and Electronics Georgia Institute of Technology; Atlanta GA 30332 USA
3. Wuhan National Laboratory for Optoelectronics; Huazhong University of Science and Technology; Wuhan 430074 China
4. School of Materials Science and Engineering; Center for Organic Photonics and Electronics, Georgia Institute of Technology; Atlanta GA 30332 USA
5. Biomolecular and Organic Electronics, Department of Physics; Chemistry and Biology Linköping University; 58183 Linköping Sweden