Application of new natural dyes extracted from Nasturtium flowers (Tropaeolum majus) as photosensitizer in dye-sensitized solar cells

This work reported the natural dyes extracted from yellow and orange Nasturtium (Tropaeolum majus) flower petals and then used them as sensitizer in dye-sensitized solar cells (DSSCs) for the first time. The functional groups present in the dyes were identified by FTIR spectroscopy which revealed the characteristic peaks of pigments anthocyanins and carotenoids. The UV–Visible analysis of dye extracts showed absorption in the visible region and the dye loaded TiO2 exhibited broad absorption. The density functional theory (DFT) calculation was performed on Lutein, Cyanidin-3-sophoroside, Delphinidine-3-dihexoside and Pelargonidin-3-sophoroside to find out the HOMO and LUMO levels of each. The DSSCs were constructed using these natural extracts as sensitizer dye and photovoltaic performance such as conversion efficiency (η), short-circuit current density (Jsc), open-circuit voltage (Voc) and fill factor (FF) were investigated. The electrochemical impedance spectroscopy (EIS) studies were performed to analyze the charge transfer characteristics. The light-to-electricity conversion efficiency of 0.28% is achieved with Voc of 0.556 V, Jsc of 0.72 mA/cm2 and FF of 0.70 for natural sensitizer extracted from orange petals of Nasturtium flowers.