1. Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
2. School of Physical Science and Technology, ShanghaiTech University, 393 Middle Huaxia Road, Shanghai 201210, China
3. Department of Chemistry, University of California, Berkeley, California 94720, United States
4. Department of Physics, University of California, Berkeley, California 94720, United States
5. Kavli Energy NanoScience Institute at the University of California Berkeley and the Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
6. Polymer Science and Engineering Department, University of Massachusetts, Conte Center for Polymer Research, Amherst, Massachusetts 01003, United States
7. The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States