Efficiency enhancement is achieved in dye sensitized solar cells (DSSCs) fabricated with polyethylene oxide (PEO) based gel electrolyte by optimizing the iodide ion conductivity using a binary iodide salt and TiO2 nanofiller. The binary iodide salt system consists of K+ as the small cation and Pr4N+ as the large cation. The correlation between the efficiency variation and the short circuit current density variation with salt composition suggests that the improved iodide ion conductivity of the electrolyte plays a dominant role in enhancing the solar cell performance. The highest DSSC efficiency of 4.12% is obtained for the electrolyte with salt composition 25 wt% Pr4N+I-: 75 wt.% KI. The incorporation of 2.5 wt% TiO2 nano fillers into the polymer electrolyte further enhances the solar cell efficiency to 5.31%, very likely due to the increased ionic mobility caused by the increased amorphous phase content of the PEO based polymer electrolyte. (C) 2014 Elsevier Ltd. All rights reserved.