Study of Beta vulgaris (Beetroot) extraction in polar solvents for photoabsorber in dye-sensitized solar cells application

Over the last two centuries, energy needs have increased substantially until non-renewable resources such as fossil fuel, coal and natural gas which nearly come to depletion. Therefore, application of renewable energy resources like solar energy is absolutely appointed to become economical in the subsequent years and expanding as improved technology in terms of cost and applications. Dye-Sensitized Solar Cell (DSSC) being the new type of solar cell can utilize dye as light sensitizer for the operation and natural dye is the best alternative to avoid environmental issues regarding toxicity of chemical dye and its costly purification. Betalains are one of pigments in natural dyes extracted from fruit and vegetables which is majorly available in beetroot (Beta vulgaris) and a good source of natural red colour. Good extraction is crucial for high performance in photoabsorber properties, hence, polar solvents like water, methanol, ethanol, isopropanol, n-butanol, formic acid and acetic acid were used to extract betalain pigment from Beta vulgaris to observe which solvent are able to extract the red-violet colour. Several characterizations were done to analyze the photoabsorber properties of the extracted dyes including ultraviolet-visible spectroscopy (UV-Vis), Fourier Transform Infrared Spectroscopy (FTIR), High Performance Liquid Chromatography (HPLC) and scanning electron microscopy (SEM). The energy bandgap of indium tin oxide (ITO) deposited with titanium dioxide and Beta vulgaris (beetroot) dye extracted by different solvents (ITO/TiO2/beetroot) were 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. FTIR analysis shown the presence of functional group 0-H, C=O and C-O-C for most of the solvents. HPLC analysis prove the availability of betacyanin compound in all extracted beetroot dyes while SEM show the presence of hole structure from the thin films. This study highlighted that methanol is the best solvent for extraction of betalain pigment showing that it has better photoabsorber properties. Further and more detailed study is required to optimize the potential of natural pigment in photoabsorber application.