1. Nano Science and
Technology Program, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon,
Hong Kong
2. Department
of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong
Kong
3. Michael Grätzel
Centre
for Mesoscopic Solar Cells, Wuhan National Laboratory for Optoelectronics
and College of Optoelectronic Science and Engineering, Huazhong University of Science and Technology, Wuhan
430074, P. R. China