Review on mixed cation effect in gel polymer electrolytes for quasi solid-state dye-sensitized solar cells

This paper reviews the efforts made to enhance the power conversion efficiencies of dye-sensitized solar cells (DSCs) by employing binary and ternary iodides in gel polymer electrolytes. Reported studies about mixed cation effects in quasi-solid-state electrolytes have been investigated using polyacrylonitrile (PAN), polyvinylidene fluoride, polyvinyl alcohol, polyethylene oxide, polymethylmethacrylate, and phthaloylchitosan as host polymers, with PAN being the most commonly employed. Ionic conductivities, their dependence on the composition of iodide salts, and the nature of counterion have been studied by preparing many different sets of gel polymer electrolytes. DSCs that were fabricated and characterized using different gel polymer electrolytes containing binary salt combinations showed efficiency enhancements. The general trend of open-circuit voltage (V-oc) is to increase with an increasing radius of counterion, while short-circuit current density (J(sc)) tends to be enhanced with reducing the size of the counterion in the cell. This behavior has been confirmed by studying single salt systems based on alkali metal iodides as well as quaternary ammonium iodides. The studies emphasized a significant enhancement of cell performance for binary cationic systems with respect to their single cation counterparts. In conclusion, the efficiency of the DSCs can be improved by employing a mixed cationic system with high and low charge densities.