Influence of nanostructured TiO2 film thickness in dye-sensitized solar cells using naturally extracted dye from Thunbergia erecta flowers as a photosensitizer

Dye-sensitized solar cells (DSSCs) have been considered as an alternative energy resource in recent years, due to low-cost fabrication and non-toxic compared to silicon-based and thin film solar cells. Herein, the natural dye containing anthocyanins were extracted from Thunbergia erecta natural flower petals by simple extraction techniques and used as photosensitizers in the DSSC. The extracts showed the UV–Vis absorptions in the 400–800 nm range with broad maxima in visible region around 537 nm. Fourier transform infrared (FTIR) spectrum was obtained after the dye coating on a semi-conductive layer, to identify the presence of anthocyanin according to the functional groups present in the dye molecules. To precise and progressive optimization of the TiO2 photoanodes film thicknesses were prepared by spin coating technique and characterized by atomic force microscopy, field emission scanning electron microscopy and J-V characteristics. The photovoltaic performance studies were carried out to understand the effect of the TiO2 multilayer photoanodes and the interaction with the dye molecules on the cells efficiency. Photovoltaic parameters like short circuit current (JSC), open circuit voltage (VOC) and fill factor (FF) were evaluated for fabricated cells. The optimized film thickness of the TiO2 photoanode is ∼5.5 μm with an efficiency of 0.37% under AM 1.5G illumination of sunlight. The VOC of DSSCs gradually decreases as the thickness increases of the TiO2 thin film and the highest conversion efficiency while it has the maximum short-circuit current density.