Efficient Dye-sensitized Solar Cells with Voltages Exceeding 1 V Through Exploring Tris(4-alkoxyphenyl)amines Mediators in Combination with the Tris(bipyridine) Cobalt Redox System

Tandem redox electrolytes, prepared by the addition of a tris(p-anisyl)amine mediator into classic tris(bipyridine)cobalt based electrolytes, demonstrate a favorable electron transfer and reduced energy loss in dye-sensitized solar cells. Here, we have successfully explored three tris(4-alkoxyphenyl)amines mediators with bulky molecular structures and generated more effective tandem redox systems. This series of tandem redox electrolytes rendered solar cells with very high photovoltages exceeding 1 V, which approaches the theoretical voltage limit of tris(bipyridine)cobalt based electrolytes. Solar cells with power conversion efficiencies of 9.7% to 11.0% under one sun illumination were manufactured. This corresponds to an efficiency improvement of up to 50% as compared to solar cells based on pure tris(bipyridine)cobalt based electrolytes. The photovoltage increases with increasing steric effects of the tris(4-alkoxyphenyl)amine mediators, which is attributed to a retarded recombination kinetics. These r...