Understanding the Electrical Transport-Structure Relationship and Photovoltaic Properties of a [Succinonitrile-Ionic Liquid]-LiI-I₂ Redox Electrolyte.

ABSTRACT: The properties of succinonitrile-based electrolytes can be enhanced by the addition of an ionic liquid (IL). Here, we have reported the relationship between the electrical transport properties and the structure of a new [(1 - x)succinonitrile:xIL]-LiI-I₂ electrolyte, where the mole fraction (x) of the IL (1-butyl-3-methyl imidazolium iodide) was varied from 0 to 40%. Compositional variation revealed the optimum conducting electrolyte (OCE) at x = 10 mol %, possessing an electrical conductivity (?_25°C) of ?7.5 mS cm^-1 with an enhancement of ?369%. The partial replacement of succinonitrile by the IL eliminated the abrupt change in the slope of the log?? vs T ^-1 plot at the melting temperature of the succinonitrile-LiI-I₂ system, showing the Vogel-Tamman-Fulcher-type behavior owing to molecular chain disorder. Raman spectroscopy showed the I₃ ^- concentration nearly twice the I₅ ^- concentration for the OCE. Vibrational spectroscopy exhibited red shifts in the ?_C?N, ?_CH2 , ?_a,CC, ?_a,N-CH3 , and ?_s,N-butyl modes, indicating an interaction between succinonitrile and the IL. The area ratio A _CH2 /A _C?N increased slightly for x = 10 mol % (OCE) and largely for x > 10 mol %, indicating an increase in the C-H bond length. These observations indicated that the interaction between succinonitrile and the IL was enhanced at x > 10 mol %, which decreased the electrical conductivity of these electrolytes. Owing to fast ion transport, an OCE-based dye-sensitized solar cell showed a 40-55% decrease in the charge-transfer and Warburg resistances, resulting in ?139 and ?122% increases in J _SC and ?, respectively.

SUBMITTER: Gupta RK 

PROVIDER: S-EPMC7271363 | biostudies-literature | 2020 Jun

REPOSITORIES: biostudies-literature