Developing Biopolymer-Based Electrolytes for Supercapacitor and Dye-Sensitized Solar Cell Applications

This paper deals with the synthesis, characterization, and application of low-viscosity ionic liquids as dopants and biopolymers as the host. The biopolymer used in the present study is cornstarch, while the ionic liquid 1-ethyl 3-methylimidazolium thiocyanate (EMIm+SCN–) is used to develop an electrochemical double-layer capacitor (EDLC) and a dye-sensitized solar cell (DSSC). Different weight ratios of the ionic liquid are incorporated in the polymer host to develop a highly conducting ionic-liquid-doped biopolymer electrolyte (ILBPE). Electrical, structural, and photoelectrochemical characterizations are carried out in detail. Electrochemical impedance spectroscopy (EIS) shows that doping different weight ratios of the ionic liquid enhances the ionic conductivity and conductivity maxima observed at a weight ratio of 80 of the ionic liquid, with an ionic conductivity value of 2.6 × 10–4 S cm–1. X-ray diffraction (XRD) and polarized optical microscopy (POM) affirm a reduction in the crystallinity, while thermogravimetric analysis (TGA) shows thermal stability of the ILBPE beyond 200 °C. In addition, the 80% ILBPE-based EDLC exhibits a specific capacitance of 140 F g–1–, an energy density of 23.13 Wh kg–1, and a power density of 3600 W kg–1 calculated based on galvanostatic charge–discharge (GDC), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) studies. Moreover, the photovoltaic performance of the DSSC is investigated by using J–V analysis and EIS measurements, while the overall power conversion efficiency is determined as 4% under standard conditions (AM 1.5).