Study of Beta vulgaris (Beetroot) Extraction in Polar Solvents as Photoabsorber in Dye-Sensitized Solar Cells Application

Abstract

Over the last two centuries, energy needs have increased substantially until non-renewable resources nearly come to depletion. Therefore, the application of renewable energy resources like solar energy is absolutely appointed favorable due to its economical impact and improved technology. Dye-sensitized solar cell (DSSC) being the type of solar cell that utilize dye as light sensitizer for the operation and become the best alternative rather than toxic chemical dyes. Betalains is one of the pigment of natural dyes that can be extracted from fruit and vegetables which majorly available in beetroot (Beta vulgaris). To get the pigment for solar cell application, the optimum extraction is crucial. Hence, in this study, several polar solvents such as distilled water, methanol, ethanol, isopropanol, n-butanol, formic acid and acetic acid were used to extract betalain pigment from Beta vulgaris (BV). Then, several characterizations were carried out to analyze the photoabsorber properties using Ultraviolet-visible Spectroscopy (UV-Vis), Fourier-Transform Infrared Spectroscopy (FTIR), High Performance Liquid Chromatography (HPLC) and Scanning Electron Microscopy (SEM). The energy bandgap of BV in different solvents (ITO/TiO2/BV) are 2.19, 2.35, 2.65, 2.73, 2.78, 2.98 and 3.00 eV for methanol, n-butanol, formic acid, ethanol, acetic acid, water and isopropanol respectively. Whilst, FTIR spectrum shows the presence of functional group of O-H, C=O and C-O-C and HPLC analysis depicted the existence of betacyanin pigment all in samples. SEM images show the presence of porous structure of TiO2 and irregular pits formed due to the formation of BV layer on TiO2. In conclusion, overall findings suggested that methanol is the best solvent for extraction of betalain pigment, answering it has best photoabsorber properties among the sample series. Further detailed study is recommended to maximise the potential of Beta vulgaris pigment as photoabsorber in DSSC application.