1. Michael Grätzel Center
for Mesoscopic Solar Cells, Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, 1037
Luoyu Road, 430074 Wuhan, P. R. China
2. Laboratory for Photonics and
Interfaces, Institute of Chemical Sciences and Engineering, Swiss Federal Institute of Technology, CH 1015 Lausanne,
Switzerland