Natural pigment dyes as eco-friendly sensitizers for dye-sensitized solar cells

Abstract In this study, several dye-sensitized solar cells (DSSCs) were fabricated using biopigments derived from prodigiosin, pomegranate, and hibiscus as sensitizers paired with TiO 2 photoelectrodes. Prodigiosin solutions were prepared at various pH levels of acidic, neutral, and alkaline with a concentration of 0.005 M in methanol to serve as the sensitizing agent, while the pomegranate and hibiscus pigments were used directly without further modification. The TiO 2 films were immersed in these pigment solutions at room temperature for an appropriate duration, allowing complete penetration of the dye into the TiO 2 layers. The absorbance properties of the sensitized photoelectrodes were characterized using UV–Vis spectrophotometry, comparing them with those of the pigment solutions and bare TiO 2 electrodes. The assembled DSSCs, with the two electrodes connected, were tested for their current–voltage characteristics using a Keithley instrument. The study explored the influence of pigment type, counter electrode materials, and the number of TiO 2 layers on DSSC performance. The results demonstrated that prodigiosin can effectively function as a sensitizing dye for DSSCs, with the highest efficiency observed in a configuration using neutral prodigiosin on TiO 2 and a platinum-graphite counter electrode. Plant-based pigments outperformed the bacterial pigment, with the pomegranate dye achieving an efficiency 5.74 times greater than that of prodigiosin, while hibiscus pigment exhibited an efficiency 4.53 times higher. The novelty of this work lies in the use of prodigiosin, a microbial pigment, as a natural photosensitizer in DSSCs, alongside plant-based dyes, and the demonstration of its performance across different pH levels.