Impact of Co-sensitization of Natural Dyes Anthocyanin and Chlorophyll with N719 on Dye-sensitized Solar Cells

Abstract

In order to broaden the range of spectrum response for dye-sensitized solar cells (DSSCs) and improve the photoelectric conversion efficiency, natural dyes, like anthocyanin and chlorophyll, were extracted from the flowers and leaves of canna and Chinese loropetal. The results indicate that the extracted natural dyes, whose energy levels matched with that of TiO2 and I-/I3- can be used as sensitizers in DSSCs, but they are of low conversion efficiency. Co-sensitization of the natural anthocyanin and N719 improved the cell efficiency compared with using N719 as sensitizer alone. Co-sensitization of chlorophyll and N719, however, lowered the cell efficiency. The anthocyanins containing many carboxyl or hydroxyl groups can increase the cell efficiency, because they form coordination bond with Ti. Canna chlorophyll is unable to have synergistic effect with N719 for lack of carboxyl or hydroxyl groups.