Purity-performance relationship of anthocyanidins as sensitizer in dye-sensitized solar cells

Abstract

A comparative analysis between crude and purified extracts obtained from withered leaves of Terminalia catappa (T. catappa) and pure compounds of anthocyanidins as organic sensitizers in solar cells. The chemical and electronic properties of the extracts and the pure anthocyanidins were examined using spectroscopic studies: ultraviolet (UV), Fourier transform infrared (FT-IR) and gas chromatography coupled with flame ionization detector (GC-FID). Solar cells were fabricated using TiO2 mesoporous film and the extracts and pure compounds as sensitizers. The prominent transitions in U-V spectra were  in nature. There were observed shifts in the wavelengths of the absorptions (around 350 to 380 nm) and a characteristic decrease in the absorption between the crude (TCE) and purified (TCP) extracts. The FT-IR spectra of the crude and purified sample have similar absorbances with bathochromic (red) shifts on the hydroxyl group and hypsochromic (blue) shifts on the benzene ring. The GC-FID chromatograms and spectra revealed the presence of six anthocyanidins and their amounts in mg per 100 g of the sample. The results showed that delphinidin was most abundant, and its quantity increases with purification of the extracts, while other anthocyanidins decreased with purification in both extracts. The photovoltaic performances also increase with purity. The best results were obtained with cyanidin-TiO2 ­solar cells with efficiencies up to 2.27%.\r\r\t \r\r\tKey words: Terminalia catappa, anthocyanins, solar cell, efficiency, purification, extracts.