Gel polymer electrolyte system based on starch grafted with ionic liquid: Synthesis, characterization and its application in dye-sensitized solar cell

Abstract

The electrolyte system is a critical component in a dye-sensitized solar cell (DSSC). A starch-based gel polymer electrolyte (GPE) is described herein as a potential quasi-solid-state electrolyte system for DSSC. Potato starch was modified by grafting 1-glycidyl-3-methylimidazolium chloride (GMIC) ionic liquid onto the polysaccharide chain to afford a cationic starch (CS) as confirmed by elemental analysis (nitrogen content = 1.33%), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). Despite its low degree of substitution (0.084), the resulting properties of the new cationic starch such as its coarse yellowish brown coloration, high-water solubility, flaky morphology, higher thermal stability, and higher gelatinization temperature differentiate it distinctly from the raw starch. In DMSO solvent, the cationic starch (CS) forms a gel and addition of GMIC ionic liquid (CS:GMIC ratio 1:3) as plasticizer afforded a gel polymer electrolyte (GPE) system after doping with the KI/I2 (70 wt%) redox couple. Electrochemical impedance spectroscopy revealed high conductivity and efficient ion migration. The optimized CS-GPE was incorporated in DSSC as quasi-solid-state electrolyte system affording 0.514% efficiency. Despite its low performance against the liquid electrolyte control, it exhibited relative stability due to its good filling contact between the electrodes.