Functional titanium oxide nano-particles as electron lifetime, electrical conductance enhancer, and long-term performance booster in quasi-solid-state electrolyte for dye-sensitized solar cells

Abstract

This research investigates the design of a quasi-solid-state electrolyte for improving the photovoltaic efficiency and long-term performance stability of dye-sensitized solar cells (DSSCs). In this study, agarose gel and titanium oxide (TiO2) nano-particles are incorporated into an iodine/iodide electrolyte solution in a 1-methyl-2-pyrrolidinone (NMP)/3-methoxypropionitrile (MPN) solvent mixture to fabricate quasi-solid-state electrolytes for 2.0-cm2 DSSCs. The electrolyte also contains an ionic liquid, 1-methyl-3-propylimidazolium iodide, and a co-additive, 1-methylbenzimidazole. The negatively charged TiO2 nano-particles exhibit an anatase crystal structure. Without agarose and TiO2, the control cell's photovoltaic efficiency drops by more than 50% over 2400 h of aging due to a significant decrease in the short-circuit current. Incorporating 1% agarose into the electrolyte not only enhances the retention of the solvent but also maintains the short-circuit current. Furthermore, adding 0.5% TiO2 to 1% agarose electrolyte provides sufficient ion and electron transfer routes and improves the fill factor of the corresponding DSSC. The photoconversion efficiency of the agarose/TiO2-containing DSSC monotonically increases from an initial value of 5.08% to 6.48% within 2400 h. The improved cell efficiency is correlated to the longer electron lifetime in the DSSC, higher ion diffusivity, and the smaller electrical resistance of the electrolyte.