Grätzel et al. first developed a dye-sensitized solar cell (DSSC) in 1991.1) The DSSC is a liquid-type device that involves nanoporous titanium oxide (TiO2) as a semiconducting electrode, organic dye-sensitizer and electrolyte solution containing a redox component. This is expected to be a low cost solar cell, because there is a simpler device structure compared with the other solar cells.2) The DSSC is usable under conditions with weak light. Thus, it is expected that the DSSC may be installed in a room. A ruthenium complex with a bipyridine ligand is one of popular organic dyes for the solar cell.3) In the polypyridine ligand of the ruthenium complex, we can introduce some carboxyl or phosphonic acid groups forming a linkage with TiO2. In addition, metal-free organic dyes (eg. D-102, D-131 and D-358) were also developed, because they do not contain any expensive ruthenium atoms.4,5) Several examples of DSSC with all solid systems are reported as well.6)

Topics and Information on Solar Cell Materials
References
- 1) B. O'Regan, M. Grätzel, Nature 1991, 353, 737.

- 2) M. K. Nazeeruddin, P. Pechy, M.Grätzel, Chem. Commum. 1997, 1705.

- 3) Review: M. Grätzel, Inorg. Chem. 2005, 44, 6841.
- 4) W. H. Howie, F. Claeyssens, H. Miura, L. M. Peter, J. Am. Chem. Soc. 2008, 130, 1367.

- 5) R. Yoneya Ogura, S. Nakane, M. Morooka, M. Orihashi, Y. Suzuki, K. Noda, Appl. Phys. Lett. 2009, 94, 073308/1.

- 6) L. Schmidt-Mende, U. Bach, R. Humphry-Baker, T. Horiuchi, H. Miura, S. Ito, S. Uchida, M. Grätzel, Adv. Mater. 2005, 17, 813.
