Investigation of the photoinduced electron injection processes for natural dye-sensitized solar cells: the impact of anchoring groups

In this study, nine different natural dyes having various anchoring groups were extracted from various plants and used as photo-sensitizers in DSSC applications. The photovoltaic parameters controlling the cell performance were investigated and the results were discussed as a function of anchoring groups. The obtained power conversion efficiencies (PCEs) vary from 0.18 to 1.87%, while the quantum yields are heavily dependent on both the anchoring group and type of pigments. Moreover, the effects of anchoring groups on the photoinduced electron injection dynamics from natural dye molecules to TiO2 nanoparticles were studied using time resolved fluorescence spectroscopy measurements. In these dyes, the long-hydroxyl & carbonyl-chain bearing anthocyanin, with the maximum electron transfer rate (kET), has shown the best photosensitization effect with regard to cell output. Despite the fact that their performance in DSSCs is somewhat lower or close to the metal complexes, these metal-free natural dyes can be treated as a new generation of sensitizers.