The pH dependent tannic acid and Fe-tannic acid complex dye for dye sensitized solar cell applications

We report a novel pH-dependent dye-sensitized solar cells by using tannic acid and Fe-tannic acid complex. We have synthesized TiO2 nanoparticles by microwave hydrothermal method, and TiO2 photoanode has been developed via doctor blade technique. The TiO2 nanoparticles and photoanode were characterized by XRD, FE-SEM, Raman and DRS technique. Dye-sensitized solar cells have been assembled by TiO2 photoanode and tannic acid or Fe-tannic acid complex dye as sensitizers at different pH values. The UV-vis absorbance and cyclic voltammetry results for these dyes at different pH values were discussed. The maximum cell efficiency of DSSC based on tannic acid and Fe-tannic acid dyes were 1.56% and 2.95% at pH 7.5, respectively. The cell efficiencies demonstrated decrement above and below pH 7.5, which was explained in detail in this study by suggesting possible reasons. In particular, the Fe-tannic acid structure at the range of pH 6-8 had comparable cell efficiency values compared to synthetic organic dyes. This phenomenon also gave a new way to the use of a novel simple cell with environmental friendly metal complex dye based sensitizers for dye-sensitized solar cells. This study has highlighted the importance of tannic acid and Fe-tannic acid at different pH values for solar cell efficiency. Additionally, the Fe-tannic acid sensitizer is an alternative to synthetic organic dyes and has advantages such as easy synthesis, low cost and abundantly found in nature.