Enhancing TiO₂-based dye-sensitized solar cell performance using Br₃⁻/I⁻ electrolyte and natural dyes from pomegranate and teak leaves

This study investigates the novel application of a tribromide/iodide (Br₃⁻/I⁻) redox couple as an alternative electrolyte to enhance the performance of TiO₂-based dye-sensitized solar cells (DSSCs) sensitized with natural dyes extracted from Pomegranate (Punica granatum) and Teak leaf (Tectona grandis). DSSCs were fabricated using an FTO/TiO₂/dye/electrolyte/carbon architecture and evaluated under standard AM 1.5 illumination. Structural and optical characterizations via SEM, XRD, FT-IR, and UV-Vis spectroscopy confirmed successful dye adsorption onto the TiO₂ surface, with the Pomegranate dye showing stronger interaction. The pomegranate-sensitized DSSC using the Br₃⁻/I⁻ electrolyte achieved a Voc of 357 mV, Jsc of 0.54 mA cm⁻², fill factor of 0.409, and a power conversion efficiency (PCE) of 0.0788%. The teak leaf-based cell reached a PCE of 0.0373% under the same conditions. In contrast, cells with the conventional I₃⁻/I⁻ electrolyte yielded lower efficiencies of 0.0255% and 0.0108% for pomegranate and teak leaf dyes, respectively. These results represent significant relative efficiency improvements of 209% and 245%, highlighting the Br₃⁻/I⁻ system as a highly promising, low-cost alternative electrolyte for enhancing the performance of bio-sensitized solar cells.