Dual-function smart electrolyte for dye-sensitized solar cells: 5-mercaptotetrazoles as redox mediator and corrosion repressor?

Metal charge collectors are an essential component of photovoltaic modules, facilitating charge collection over larger areas. Their application in dye-sensitized solar cells has so far been hampered by two major factors: (1) the redox mediators employed in these photoelectrochemical devices are generally corrosive to metals, and (2) they generally show low overpotentials for their redox reactions on these metal surfaces, which leads to significant recombination losses at the photoanode. Here, a thiolate-based redox mediator, sodium 1-phenyl-1H-5-mercaptotetrazole (T< inf>ph< /inf>), is shown to form self-assembled monolayers on silver electrodes and to act as an effective corrosion protection layer while also exhibiting high overpotentials on these metals at the photoanode. The anticorrosive properties are strongly dependent on the structure of the thiolate. Replacement of the phenyl group in T< inf>ph< /inf> with a methyl substituent accelerates the corrosion process by orders of magnitude. Finally, we demonstrate the applicability of T< inf>ph< /inf>-based electrolytes in a 60 cm< sup>2< /sup> dye-sensitized solar cell comprising unprotected silver charge-collecting electrodes. (Chemical Equation Presented).