It has been a concern that the cobalt redox cannot give a good performance for the dye-sensitized solar cells when it is used with ruthenium dyes. The electron dynamics measurements clarified the electron loss processes, and clarified the cause. The result indicated the direct interaction between the ruthenium dyes with the cobalt redox, and it reduced the charge injection from the triplet state of the dyes to the titanium oxide, and also it increased the electron recombination process with the cobalt redox species. Both the problems of injection and recombination were solved by using the ruthenium dye with alkyl chains keeping a distance between the dye and the cobalt redox.

A blocking effect on the approach of electron acceptors into a dye/TiO2 electrode in a dye-sensitized solar cell was confirmed by the observation of charge dynamics at the interface when an alkyl-functionalized dye was used. It was found that the density of the adsorbed MK-2 on the TiO2 surface affected the ionic motion in an electrolyte at the interface, and that electron–electrolyte recombination was suppressed with a high density of adsorbed MK-2 molecules, causing prevention of the approach of the redox ions.