Dye-sensitized solar cells based on cobalt-containing room temperature ionic liquid redox shuttles

Abstract

An imidazolium-based co-containing room temperature ionic liquid, bis(3-butyl-1-methylimidazolium) tetraisothiocyanato cobalt [BMI]2[Co(NCS)4], was synthesized and characterized. The prepared [BMI]2[Co(NCS)4]/1-propyl-3-methylimidazolium iodine (PMII) hybrid redox couple showed higher redox potential than that of the iodide/triiodide (I−/I3−) redox couple. The resultant dye-sensitized solar cells (DSSCs) containing the [BMI]2[Co(NCS)4]/PMII hybrid redox couple exhibited an average overall power conversion efficiency of 8.1% under simulated air mass 1.5 solar spectrum illumination at 100 mW cm−2, which is higher than that of traditional PMII/I2 based electrolytes probably due to the enhancement of the Voc values of the hybrid electrolytes. Furthermore, the cell based on the [BMI]2[Co(NCS)4]/PMII hybrid redox couple tested in this study showed excellent long-term stability under ambient conditions over 120 days.