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)

Abstract

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 (γ-butyrolactone) weight ratio of 30–70% and different concentrations of redox mediators CoII:CoIII or FeII:FeIII were prepared as a possible substitute to the redox couple I−/I3 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% FeII/III and Gel+5 wt% CoII/III. The Gel+2 wt% FeII/III electrolyte was also able to reduce the N719, D35, and Z907 dyes.