Influence of Solvents and Surface Treatment on Photovoltaic Response of DSSC Based on Natural Curcumin Dye

Dye-sensitized solar cells have recently drawn much attention because of their cost effectiveness and easy manufacturing process. However, the challenge lies in minimizing the cost of sensitizer dyes and the platinum-based counter electrode. Natural dyes such as red cabbage, red perilla, rosella, blue pea, and curcumin represent a low-cost, environmentally friendly alternative to costly ruthenium-based complexes for sensitization of nc-TiO $_2$ . Attempts are being made to improve the efficiency of a cell based on natural dyes by way of selecting a proper sensitizer, modifying the surface of a working electrode by chemical treatment, and replacing a platinum-based counter electrode. We have adopted two approaches to improve the photovoltaic response of a cell, i.e., 1) modifying the surface of a working electrode by treating it with HCl and TiCl $_4$ and 2) using different organic solvents to enhance the extent of sensitization. PEDOT:PSS grown over graphite-coated fluorine-doped tin oxide is used as a counter electrode to catalyze the reduction of triiodide ( ${\rm I}_3^ -$ ) to iodide (I $^-$ ). A TiCl $_4$ -treated photoelectrode, on sensitization with curcumin, gives maximum power conversion efficiency. The impact of the solvent\´s polarity in dye diffusion was determined with cyclic voltametry. Kelvin probe, SEM, and Raman spectroscopy are employed to justify the surface modification of nc-TiO $_2$ induced by TiCl $_4$ treatment.