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

摘要

The favorable energetics of dye-sensitized solar cell (DSC)nconstituents have advanced photoelectrochemical power conversionnefficiencies to an impressive ∼11%.1 However, the performancenof DSCs based on the I-/I3n- redox couple has essentially plateaued,nand additional component modifications have not advanced efficiency.n2 Indeed, the limitations placed on DSC dyes, semiconductors,nand counter electrodes by I-/I3n- compatibility have presentedna major challenge. DSC efficiency rests on a delicate balance ofncharge transport and recombination processes, with attempts to findnredox shuttle alternatives to the I-/I3n- meeting limited success. Tondate, only a handful of cationic redox couples (e.g., Co(II/III)3 andnCu(I/II)4 complexes) and p-type semiconductors5 have functionednas effective redox mediators. While rapidly exchanging, outerspherenredox couples such as ferrocene/ferrocenium (Fc/Fc+) appear,na priori, promising for dyes with low overpotentials, rapid interceptionnof injected electrons by Fc+ leads to inadequate electronndiffusion lengths and charge lifetimes.6