Dye-sensitized solar cells (DSCs), invented by Gratzel and O’Regan in 1991, offer the prospect of replacing conventional solid-state photovoltaic devices made with a signifi cant amount of the semiconductor material silicon. [ 1 , 2 ] DSCs have generated excitement because they consist mainly of nontoxic materials and offer a low-cost processing route (such as coating or printing) to thin-fi lm device fabrication. Furthermore, they can be adapted for a variety of indoor and outdoor applications, and achieve high performance with minimal environmental impact. A DSC operates based on the interactions between the cell’s anode and cathode, and a fi lm of titanium oxide nanoparticles covered with light-sensitive dye molecules. An electrolyte, usually in form of iodide, fi lls the space between the TiO 2 nanoparticles, and helps transfer electrons from the cathode to the dye molecules. The fabrication of DSCs typically requires an electrolyte that enables high charge-collection effi ciencies and high open-circuit voltages. The iodide electrolyte is particularly attractive in this regard as its oxidized form, I 3 − , does not readily accept electrons from the titania surface. This minimizes charge recombination in functioning cell devices. Despite all the benefi t and relatively high conversion effi ciencies for solar energy, DSCs typically have durability issues associated with the liquid electrolyte, such as electrode corrosion or electrolyte leakage. These issues have lead to a signifi cant decrease in conversion effi ciency, making these solar cells unsuitable for long-term use. Although numerous attempts have been made to replace the liquid electrolytes with a wide range of materials, including p -type semiconductors, organic hole-conducting polymers, organic ionic crystals, and ionic gel electrolytes, the effi ciency is compromised as a result of either poor