Study of the multi-equilibria of red wine colorants pyranoanthocyanins and evaluation of their potential in dye-sensitized solar cells

Herein, a series of 3-O-glucosilated pyranoanthocyanin derivatives were synthesized following a bio-mimetic approach. The compounds were studied by means of UV–Vis spectroscopy in order to establish their chemical equilibria and determine the stability of the colored species over the pH range. The resistance of pyranoanthocyanins to hydration grants this family of compounds, closely related to anthocyanins, increased color stability. Finally, the synthetized compounds were successfully applied as light harvesters in DSSCs and relations between dye structure and cell efficiency were found. The influence of different linker units (carboxylate, catechol) and electron-donor groups (methoxy, hydroxyl, methyl), as well as the presence of sugar moieties have impact in the various parameters related to DSSC efficiency. An overall efficiency of 1.57% was obtained for the best performing compound, methylpyranocyanidin-3-O-glucoside. The impact of using different additives was also studied and the results compared with other families.