Five-membered ring products of cyclometalation reactions are utilized as dyesensitizers
for manufacturing very stable dye-sensitized solar cells. Such solar cells have
greater stability than standard chelate-type N719 solar cells because the cyclometalated
ligands in the five-membered ring products are stronger donors than the thiocyanate groups
in the standard type. Solar cells with high overall energy conversion efficiencies are manufactured
primarily by using three types of cyclometalated five-membered-ring ruthenium
1. A solar cell prepared with a phenylpyridine ruthenium compound, e.g., bis(4,4'-dicarboxy-
2,2'-bipyridine) 2-(2,4-difluorophenyl)pyridine ruthenium, shows an overall energy conversion
efficiency of 10.1 %.
2. A solar cell with the ruthenium compound with 2,2’-bipyridine bearing two carboxyl ligands and two alkylthienothophene
ligands and 2,3’-bipyridine bearing two alkyloxy ligands shows a high overall energy conversion
efficiency with 9.4 % with the cobalt electrolyte [Co(phen)3]3+/2+.
3. A solar cell using a clometalated CNN tridentate ruthenium compound bearing an electron-donating substituent
of a terminal substituent placed para to the triphenylamine achieves a high overall solar-to-electric energy conversion
efficiency of 8.02 %. This result is almost the same as that of N3 under the same conditions.