Photo-Electric Properties of Polypyrrole Based Gel Electrolyte for Hybrid Photoactive Supercapacitors

Abstract

The nature of solar radiation is not steady, therefore having a solar-capacitor device that can simultaneously capture, convert and store solar energy is a considerable device. A self-charging capacitor is designed and fabricated as a functional solar energy storage device, which is accomplished in situ self-assembled storage technique. The solar-capacitor device is assembled on a multilayered photoelectrode combining of cationic dye (i.e. methylene blue, MB) and conducting polymer (i.e. Polypyrrole, Ppy) in contact with a single layer of HCl-Polyvinyl alcohol (PVA) gel electrolyte. Due to the high porosity of the multi-walled carbon nanotube (MWCNT) based counter electrode and the photo-electric properties of Ppy at the working electrode the device is working as photocapacitor. Therefore, the supercapacitor can be charged when the working electrode is illuminated. In this study, a photo-electrochemical device based on two-terminals that combines MWCNT/paper, Ppy/fluorine doped tin oxide conductive substrate (FTO), and a single layer of gel electrolyte is successfully designed and fabricated. This device can work independently as solar cell, supercapacitor, or a solar-capacitor device. Conducting Ppy has been used as a thin film deposited electrochemically on the surface of the FTO. The experiments are carried out in the dark at the beginning and then repeated when the working electrode is under the effect of solar irradiation. The open circuit voltage across the cell in the dark is 52 mV as initial value. Then, the cell voltage is increased gradually from 52 mV to 74 mV in 100 s of illumination. After turning off the light, the voltage is not dropping to the initial dark value immediately, and the slight change is due to the leakage current of the capacitive effect. The results of electrochemical and electrical characterization techniques such as Cyclic Voltammetery (CV), Electrochemical Impedance Spectroscopy (EIS), Open Circuit Voltage (OSV), and Short Circuit Current (SCC) on the hybrid device have been addressed in this study. The results are encouraging for application of Ppy film for solar-capacitor devices to harvest solar energy and store charges in a single device with two-terminals.