| Summary: | The solar cell has been considered one of the safest modes for electricity generation. In a dye-sensitized solar cell, a commonly used iodide/triiodide redox mediator inhibits back-electron transfer reactions, regenerates dyes, and reduces triiodide into iodide. The use of iodide/triiodide redox, however, imposes several problems and hence needs to be replaced by alternative redox. This paper reports the first Co<sup>2+</sup>/Co<sup>3+</sup> solid redox mediators, prepared using [(1−<i>x</i>)succinonitrile: <i>x</i>PEO] as a matrix and LiTFSI, Co(bpy)<sub>3</sub>(TFSI)<sub>2</sub>, and Co(bpy)<sub>3</sub>(TFSI)<sub>3</sub> as sources of ions. The electrolytes are referred to as SN_E (<i>x</i> = 0), Blend 1_E (<i>x</i> = 0.5 with the ethereal oxygen of the PEO-to-lithium ion molar ratio (EO/Li<sup>+</sup>) of 113), Blend 2_E (<i>x</i> = 0.5; EO/Li<sup>+</sup> = 226), and PEO_E (<i>x</i> = 1; EO/Li<sup>+</sup> = 226), which achieved electrical conductivity of 2.1 × 10<sup>−3</sup>, 4.3 × 10<sup>−4</sup>, 7.2 × 10<sup>−4</sup>, and 9.7 × 10<sup>−7</sup> S cm<sup>−1</sup>, respectively at 25 °C. Only the blend-based polymer electrolytes exhibited the Vogel-Tamman-Fulcher-type behavior (vitreous nature) with a required low pseudo-activation energy (0.05 eV), thermal stability up to 125 °C, and transparency in UV-A, visible, and near-infrared regions. FT-IR spectroscopy demonstrated the interaction between salt and matrix in the following order: SN_E < Blend 2_E < Blend 1_E << PEO_E. The results were compared with those of acetonitrile-based liquid electrolyte, ACN_E.
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