Highly Conductive Redox-Couple Solid Polymer Electrolyte System : Blend-KI-I2 for Dye-Sensitized Solar Cells

Ionic conductivity of a redox-couple solid polymer electrolyte system, (1−x) blend: x[0.9KI : 0.1I2] with x=0-0.15 in weight fraction, is reported. A blend of poly(ethylene oxide) (abbreviated as PEO) and succinonitrile in equal weight fraction was used as a polymeric matrix instead of the PEO and succinonitrile because of its low-cost, electrical conductivity superior to the PEO, and thermal stability better than the succinonitrile. The electrolyte with x=0.15 showed ionic conductivity of 7×10−4 S cm−1 and iodine ion diffusivity of nearly 4×10−7 cm2 s−1 at 25°C. The conductivity and diffusivity values were nearly two orders of magnitude higher than those of the PEO-KI-I2 due to the improved PEO crystallinity. It also exhibited dye-sensitized solar cell efficiency of 2.2% at 100 mW cm−2, which is twice of the cell prepared using the PEO-KI-I2 only.