Optimizing pigment extraction through controlled heating from Sorghum bicolor and Spirodella polyrhiza for dye-sensitized solar cell applications

Abstract

This study explores the effects of heating on the extraction and characteristics of natural pigments derived from Sorghum bicolor (Guinea Corn) leaves and Spirodella polyrhiza (Duckweed) for their application in dye-sensitized solar cells (DSSCs). Controlled heating facilitated the extraction process for pigment solubility and functional group stability with the use of ethanol and ethyl acetate as solvents for pigment extractions. Fourier-transform infrared (FTIR) and ultraviolet-visible (UV-Vis) spectroscopic results indicated that moderate heating promotes pigment separation and retention of functional groups, particularly with respect to hydroxyl (O-H) and carbonyl (C=O) groups, which are essential for light absorption and electron transfer. Ethanol-extracted samples showed higher stability and absorption efficiencies than the ethyl acetate extracts. Pigment extraction was enhanced with heat treatment; however, sustaining high-temperature conditions caused thermal degradation and lowered light absorption capabilities. Spirodella polyrhiza possessed superior thermal resistance and a wider light absorption spectrum, making it a more robust plant candidate for DSSC applications, while Sorghum bicolor was slightly less productive for use in DSSCs under no heating or very gentle heating conditions. All these findings have attributed optimal heating conditions very important for the extraction efficiency of pigments and their functional stability in paving the way for much more efficient and sustainable DSSCs.