Generally, natural dyes which act as photosensitizers in DSSC showed very low efficiencies and low VOC compared to ruthenium dyes, which is because of their molecular structures. Natural dyes
mostly have AOH and AO ligands and lack ACOOH ligands, whereas the ACOOH ligands of the ruthenium dyes combine with the hydroxyl group of the TiO2 nanoparticles to produce an ester and allow easy electron transfer to the TiO2 conduction band to acquire a rapid electron-transport rate [31].