In this chapter, a series of asymmetric and symmetric ionic liquids (ILs) and IL-modified materials were considered for their versatile application as electrolytes and redox mediators in Photoelectrochemical (PEC) cells. Dye-sensitized solar cells (DSSCs) are PEC cells and third-generation photovoltaic (PV) cells that convert solar PV energy into electrical energy. They have piqued the interest of researchers worldwide due to their simple cell fabrication methods under ambient conditions, as well as their enormous commercialization potential due to their low cost; additionally, the benefits of colorfulness, probable plasticity and high power conversion efficiency (PCE) under indoor irradiation make PEC cells appealing. To attain a high PCE of cells, an organic solvent has to be included with the formulation of the redox mediator in the electrolyte. However, organic solvents are prone to evaporation and leakage. Consequently, PEC cells’ durability is reduced because of the chemical and thermal instability of the redox mediator in the electrolyte. The purpose of including ionic liquids into the redox mediator in the electrolyte was to solve the above-mentioned issue and to allow the PEC cells to act as sustainable energy cells. The chapter describes the integration of ionic liquids into the redox mediator in the electrolyte formulation and evaluates the impact of ionic liquids on the PCE of the cell in various electrolyte conditions.
Keywords: Dye-sensitized solar cells, Electrolyte, Ionic liquid, Open circuit photovoltage, Organic solvent, Photoelectrochemical cells, Power conversion efficiency (PCE), Redox mediator, Solar cell, Short-circuit photocurrent density.