In dye-sensitized solar cells (DSSCs), a significant dye regeneration force (ΔGreg0 ≥ 0.5 eV) is usually required for effective dye regeneration. This results in a major energy loss and limits the energy conversion efficiency of the state-of-art DSSC. Selection of energy-matching redox couples to significantly minimize the dye regeneration force has not been successful due to the slow dye regeneration kinetics and fast charge recombination kinetics. We have taken two approaches, increasing the dye regeneration kinetics with small dye regeneration force and slowing down the charge recombination process. We will describe that, when dye molecules and redox couples possessing similar conjugated ligands are used, efficient dye regeneration occurs with zero or close-to-zero driving force. Using Ru(dcbpy)(bpy)22+ as the dye and Ru(bpy)2(MeIm)23+//2+ as the redox couple, a short circuit current (Jsc) of 4 mA/cm2 and an open circuit voltage (Voc) of 0.9 V were obtained with ΔGreg0 of 0.07 eV. The same was observed for the N3 dye and Ru(bpy)2(SCN)21+/0 (ΔGreg0 = 0.0 eV), which produced Jsc of 2.5 mA/cm2 and Voc of 0.6 V. Charge recombination occurs at pinholes, limiting the performance of the cells. We will show that high Voc values can be attained by significantly curtailing the dye regeneration force. Our studies suggest that the open nanostructure of nanowire array substrates allow uniform access of surface modification salinization agent and thus the formation of uniform siloxane layer on surface. Consequently the charge recombination process can be more effectively blocked.

Tuning the energetics of components and kinetics of key steps in dye-sensitized solar cells

251st National Meeting (2016)

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