Characterization of pigments from spinacea oleracea, beta vulgaris, and rubus fruticosus for application in dye-sensitized solar cells

Abstract

In response to growing energy consumption motivated by demographic growth, renewable energy technologies must rapidly advance and reinvent. Among sustainable energy innovations, solar energy is notably a universally accessible resource. Dye-sensitized Solar Cells (DSSCs) exploit solar energy and are preferred due to lower fabrication cost and eco- friendliness. Reduced optical absorption is a major drawback in utilizing DSSCS. To mitigate these challenges, co-sensitization (utilization of multiple dyes sensitizers in fabricating DSSCs) is employed to broaden the absorption spectrum. In this research, dyes from Spinacea oleracea leaves, Rubus fluzicosus fruits, and Beta vulgaris roots are co-sensitized. The impact of annealing temperature and dye-loading time of TiOz films on the photovoltaic parameters of DSSC were evaluated. Dye's optical absorption spectra were characterized using an ultraviolet- visible spectrophotometer (400-800 nm). Absorption spectra for Spinacea oleracea extract were detected at 400-480 nm (blue region) and 640-700 nm (red region), respectively, and hence reflecting green (chlorophyll). The maximum absorption for Beta vulgaris dye was within the 500-560 nm region, attributed to betanin pigments. Dyes extracted from Rubus fruticosus fruits revealed a wide absoiption in the region of 450-650 nm that was linked to the presence of anthocyanin. The mixture dye showed a broad optical absorption band as compared to individual dyes. Fourier Transform Infrared (FTIR) spectroscopy was applied in confirming the presence of functional groups in dye extracts. DSSCs photovoltaic characteristics were assessed from a solar simulator under a standard AM 1.5 G illumination. According to the experiment results, the optimal annealing temperature and dye-loading time on TiOz film were 450 °C and 40 h, respectively, obtained from the performance of fabricated DSSCs. Open- circuit voltage, short-circuit current density, fill factor, and power conversion efficiency of 0.59 V, 3.6 mA/cmz, 74.78 %, and 1.58 %, respectively, were obtained. These results were also a result of co-sensitizing all three dyes (chlorophyll, anthocyanin, and betanin) in a l:l:l volume ratio. The research concludes that natural dyes are feasible, inexpensive, and ecofriendly sensitizers for DSSC, though their PCE remain restricted by poor photon absorption properties. Mixing chlorophyll, betanin, and anthocyanin improves solar spectra coverage, exhibiting the promise of blending natural dyes to augment DSSC performance. Purification of dye extracts, co-sensitization of natural dyes with ruthenium dyes, and annealing TiOz film after dye loading can be explored in future to improve the quality of dye extracts and TiO2 film for efficient DSSC development