Highly efficient and stable ionic liquid-based gel electrolytes†

Gel electrolytes are promising candidates for dye-sensitized solar cells (DSSCs) and other devices, but the ways to obtain stable gels always result in sacrifice of their ionic conductivity. This contradiction seriously limits the practical application of gel electrolytes. Herein, a new design strategy using rich carboxylic group-modified silica nanoparticles (COOH-SiO2) with a branched, well-organized framework to develop ionic liquid-based gel electrolytes possessing high conductivity is demonstrated. The branched network of COOH-SiO2 and the strong interaction in electrolytes result in the effective solidification of ionic liquids. Moreover, adding COOH-SiO2 to ionic liquid electrolytes contributes to salt dissociation, decreases the activation energy, and improves the charge transport and recombination characteristics at the electrolyte/electrode interface. DSSCs fabricated with COOH-SiO2 nanoparticles deliver a higher short-circuit photocurrent density (J(sc)) than the reference cell. A maximum efficiency of 8.02% with the highest J(sc) value of 16.60 mA cm(-2) is obtained for solar cells containing 6 wt% COOH-SiO2.