The cause for the low efficiency of dye sensitized solar cells with a combination of ruthenium dyes and cobalt redox.

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.