1. Center
for Organic Photonics and Electronics and School of Chemistry and
Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
2. Department
of Materials Science and Engineering, University of California, Berkeley, California 94720, United States
3. Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, United States
4. Materials
Department, Department of Chemistry and Biochemistry, and Materials
Research Laboratory, University of California, Santa Barbara, California 93106, United States