Novel Quasi-Solid-State Electrolyte Based on γ-Butyrolactone and Tetrapropylammonium Iodide for Dye-Sensitized Solar Cells Using Fumed Silica as the Gelling Agent

Dye-sensitized solar cells (DSCs) have emerged recently as low-cost photovoltaic devices, giving impressive photovoltaic conversion efficiencies. However, the use of organic solvent-based liquid electrolytes in DSCs arises many problems in long-term applications. To overcome the drawbacks associated with the liquid electrolytes, quasi-solid-state electrolytes have been introduced. Hence, this study is focused on preparation of a novel gel electrolyte system using fumed silica as the gelling agent, γ-butyrolactone (γ-BL) as the plasticizer, tetrapropylammonium iodide (Pr4N+I−) as the salt and iodine. DSCs were assembled according to the configuration of glass/FTO/TiO2/dye (N719)/gel electrolyte/Pt/FTO/glass. The cell performances have been studied, by varying the amounts of Pr4N+I− salt and plasticizer in the gel electrolyte, in order to obtain the optimum conditions. The gel electrolyte containing weight percentages of 77% of γ-BL and 23% of Pr4N+I− salt gave the best light-to-electricity conversion efficiency of 6.33%, saturated current density of 15.7 mA cm-2 and open circuit voltage of 0.636 V under simulated AM 1.5 irradiation. Here, I-:I2 molar ratio was kept at 10:1 in the optimized gel system and fumed silica was added 10% of the total mass. The optimized gel composition is exhibited an ionic conductivity of 8.69×10-3 S cm-1 at 25 oC.