Ms. Hala obtained her MSc degree in Environmental Science; Nano-photochemistry (2012). She holds an Analytical Biochemistry Diploma (2006) from the Faculty of Science, Minoufiya University. Now she is a member of Scientists of Next Generation (SNG) scholarship organized by the Academy of Scientific Research and Technology (ASRT)

Dye-sensitized solar cells (DSSCs) have attracted great attention for the past decade because of high energy conversion efficiency (10%) and low production cost. The most efficient DSSCs reported until now contain liquid electrolytes with iodide/triiodide (I-/I3-) redox couple. However, the disadvantages of liquid electrolytes are corrosion, sealing, short-term stability, which reduces the impact of DSSCs, therefore, many attempts have been made to replace liquid electrolytes with quasi-solid/solid-state electrolytes, such as ionic liquid-based gel electrolytes, Gel Polymer Electrolytes (GPEs) and solid polymer electrolytes. Although significantly high efficiencies have been accomplished from the solid polymer electrolyte, solvent absence in the electrolyte can easily lead to serious problems, such as crystallization of the iodide salt, and consequently, deterioration of the cell. This problem can be overcome by using gel polymer electrolytes, which are on the boundary between liquid and solid electrolytes. The polymer matrix acts as a host for a plasticizer which interpenetrates or swells the polymer. Thus, a gel is formed between the plasticizer and the polymer host structure, presenting a high boiling point and assuring the nonvolatile nature of the electrolyte. Owing to their unique hybrid network structure, gels always possess, simultaneously, both the cohesive properties of solids and the diffusive transport properties of liquids. In this work Polyethylene Glycol (PEG) is introduced as a polymer matrix in small fractions (0%, 1%, 5%, 10%, 15%, 20% w/v) into the liquid iodine/iodide electrolyte matrix in order to maintain the efficiency of the solar cells through holding the organic solvent and suppression of evaporation of solvent molecules from the hole-transport layer, which leads to a decrease in the weight loss making GPEs based cells more thermally stable compared to liquid electrolyte based cells. The roughness and homogeneity of the GPE on the surface of the TiO2 electrodes in the DSSCs measured by Atomic Force Microscope (AFM) indicates a physical cross linking of polymer chains in a gel network. The conductivity (σ), the thermal stability (TGA), photostability, as well as the photovoltaic characteristics [Voc, Isc, Fill Factor (FF) and Efficiency (η)] of the DSSCs based GPEs were studied in details. The results reveal that the polymer gel electrolyte (GPE) contains I-/I3- redox couple using Polyethylene Glycol (PEG) as polymer matrix, can produce several disadvantages of the current liquid electrolytes without severe degradation in the photoelectric conversion performance.