**Abstract**

The sensitizer-mediator redox reaction is a vital component of the dye-sensitized solar cells (DSSCs). The efficiency and stability of dye-sensitized solar cells are aided by the kinetics of this redox process. Several reaction parameters influence the kinetics of a reaction, and if those parameters are controlled, the rate of the process and its results can be controlled. One of the most important aspects of the sensitizer-mediator interaction is the reaction medium. Aqueous DSSCs are unquestionably a good replacement when it comes to taking a green approach to avoiding toxic, flammable, and volatile organic solvents and their mixtures, which are commonly used in DSSCs and are known to harm the environment while also reducing the lifetime and stability of the DSSCs. The catalytic role of a small volume fraction of organic solvent in the aqueous electron transfer kinetics of a few putative sensitizer-mediator reactions is discussed in this chapter. In binary solvent media including dilute tertiary butyl alcohol (TBA)-water and dilute 1,4-dioxane-water, the reduction of dicyanobis(2,2′ dipyridyl)iron(III) and dicyanobis(1,10-phenanthroline)iron(III) was investigated. The reactions were carried out in a 10% TBA or dioxane to water media with a volume-volume fraction of both solvents using iodide as a reducing agent. The effect of several parameters on the rate constant was also calculated and analyzed.

**Keywords:** dye-sensitized solar cells, solvents, kinetics, redox reaction, catalysis
