Thermal and electrochemical characterization of a new poly (ethylene oxide) copolymer-gel electrolyte containing polyvalent ion pair of cobalt (CoII/III) or iron (FeII/III)

In this work, gel polymer electrolytes based on the PEO copolymer-poly(ethylene oxide-co-2-(2-methoxyethoxy)ethyl glycidyl ether)), (P(EO-EM))-with a fixed P(EO-EM):GBL (gamma-butyrolactone) weight ratio of 30-70% and different concentrations of redox mediators Co-II:Co-III or Fe-II:Fe-III were prepared as a possible substitute to the redox couple I-/I-3 in dye-sensitized solar cell. The gel polymer electrolytes showed an increase in thermal stability with the addition of iron or cobalt salts. Maximum conductivity of 10(-6) and 10(-5) S cm(-1), at room temperature, was observed for the system containing Co and Fe, respectively. Conductivity variation as a function of temperature showed Arrhenius type thermal activated process. Photoinduced absorption spectroscopy (PAS) tests showed the successful regeneration of the L0 dye by Gel+2 wt% Fe-II/III and Gel+5 wt% Co-II/III. The Gel+2 wt% Fe-II/III electrolyte was also able to reduce the N719, D35, and Z907 dyes.