Influence of natural dye adsorption on the structural, morphological and optical properties of TiO₂ based photoanode of dye-sensitized solar cell

Porous photoanodes of dye-sensitized solar cells (DSSCs) can adsorb specific type of natural or organic dyes. Adsorption of the dye results in a change of the structural, morphological and optical characteristics of the photoanode. In this work, we present a comparative study on the adsorption effect of natural dye (Curcuma Longa sp.) on the structural, morphological and optical properties of mesoporous titanium dioxide (TiO₂) photoanode on indium tin oxide (ITO) coated glass. A number of investigations including XRD, UV-Vis spectroscopy, EDS, and SEM were carried out to observe the variations due to adsorbed dye on TiO₂ surface. XRD characterization revealed the effect of dye adsorption on specific surface area (SSA), crystallite size, and morphological index (MI). In this case, increasing SSA with decreasing particle size was found for both dye adsorbed and dye free DSSC photoanode samples. Also, the MI and SSA were found to be directly and inversely proportional to the crystallite size respectively. UV-Vis-NIR spectroscopy showed that dye adsorption changes the light absorption, transmittance, and optical bandgap of the photoanode. Average atomic mass percentage of titanium (Ti) and oxygen (O) obtained from EDS analysis proved the presence of TiO₂ in the mesoporous photoanode. In SEM images, significant morphological changes of mesoporous TiO2 surface appeared because of dye adsorption.