Improved efficiency and stability of dye-sensitized solar cells by using iodide-based electrolyte with high viscosity solvent

Abstract

Dye-sensitized solar cell (DSSC) performance with a liquid electrolyte depends strongly on the choice of electrolyte solvent. Acetonitrile (AN) is the most widely used organic solvent due to its low viscosity and good solubility to dissolve iodide salts. However, the stability has become critical due to the high vapor pressure of AN. In this study, the efficiency and stability of DSSC using iodide-based electrolyte were observed by using high viscosity solvents namely dimethylformamide (DMF) and γ-butyrolactone (GBL). The cell using DMF shows the best performance with an efficiency of 7.69 %, higher than that of the cell with commercial AN-based electrolyte with an efficiency of 7.14 %. Impedance spectroscopy measurement to the cell using DMF reveals a relatively low charge transfer resistance, both at TiO2-dye/electrolyte and counter electrode/electrolyte interfaces, compared to other solvents. Furthermore, the efficiency is retained at 76 % after 4 weeks of storage under ambient air, the best among various solvents tested in the present study.