A tandem redox system with a cobalt complex and 2-azaadamantane-N-oxyl for fast dye regeneration and open circuit voltages exceeding 1 V

A new tandem electrolyte composed of two redox pairs, the organic radical 2-azaadamantane-N-oxyl (AZ) and the well-known redox pair Co(bpy)(3) was investigated in dye sensitized solar cells. Importantly, an increase in V-OC was achieved using the new tandem redox system with values up to 1007 mV, compared to only 896 mV for the reference Co(bpy)(3) couple. Consequently, the tandem electrolytes presented higher device performance in conjunction with the organic dye XY1. It was determined that the V-OC improvement is mainly attributed to the combined effect of two factors: the more positive redox potential of the small donor AZ (0.81 V vs. SHE) and improved recombination resistance in the tandem electrolytes.