Ni(III)/(IV) Bis(dicarbollide) as a Fast, Noncorrosive Redox Shuttle for Dye-Sensitized Solar Cells

Nickel bis(dicarbollide) is used as a fast, one-electron outer sphere redox couple in dye-sensitized solar cells. Device performances with this anionic shuttle are investigated with different electrolyte concentrations and additives, using only 0.030 M of the Ni(III) bis(dicarbollide) to efficiently regenerate the ruthenium dye. Atomic layer deposition of Al2O3 on the nanoparticulate TiO2 photoanodes is further used to improve device performances, increasing current densities almost 2-fold and attaining power conversion efficiencies ∼10× greater than its metallocene analogue, ferrocene/ferrocenium. Open-circuit voltage decay is used to probe the kinetics of the Ni(III)/(IV) bis(dicarbollide) redox couple, and electron interception is found to be ∼103× slower than ferrocene/ferrocenium, explaining the large discrepancy in open-circuit voltage potentials between these two redox shuttles.