Tetramethyl Succinonitrile as a Solid Plasticizer in a Poly(ethylene oxide)₈ -LiI-I₂ Solid Polymer Electrolyte

Dye-sensitized solar cell (DSSC) is a promising alternative to the commercially available amorphous silicon-based solar cell because of several advantageous properties. A DSSC with a fast ion conducting solid polymer electrolyte is required for the arid atmosphere of Gulf countries. In this work, a new matrix, poly(ethylene oxide)-tetramethyl succinonitrile blend to synthesize a blend-LiI-I₂ solid polymer electrolyte for the DSSC application has been proposed. The tetramethyl succinonitrile is a member of plastic crystal with a solid-solid phase transition temperature (T_pc ) of ≈71 °C and melting temperature (T_m ) of ≈170.5 °C. Its molar fraction, 0.1-0.15 is sufficient enough for synthesizing a polymer electrolyte with electrical conductivity of >10^-4 S cm^-1 at room temperature. This electrolyte shows Vogel-Tamman-Fulcher type behavior with a low value (≈0.083 eV) of pseudo-activation energy for easy ion transport. The results of Fourier-transform infrared spectroscopy, X-ray diffractometry, and differential scanning calorimetry studies reveal the plasticizing effect of tetramethyl succinonitrile to form an amorphous phase. This electrolyte results in a ≈661% gain in short-circuit current density and thereby a ≈552% gain in the cell efficiency (≈3.5%) with respect to the DSSC prepared with the tetramethyl succinonitrile-free electrolyte.