1. M. Grätzel, Nature 338, 414 (2001)
2. Y.S. Ko, M.H. Kim, Y.U. Kwon, Bull Korean Chem Soc 463, 29 (2008)
3. K.J. Hwang, S.J. Yoo, S.H. Jung, D.W. Park et al., Bull Korean Chem Soc 172, 30 (2009)
4. Z.J. Ning, Y. Fu, H. Tian, Energy Environ Sci 1170, 3 (2010)
5. N.S. Baek, J.H. Yum, X. Zhang, H.K. Kim et al., Energy Environ Sci 1082, 2 (2009)