**5. Summary**

In conclusion, natural dye is a promising alternative to replace the metal complexes or organic dyes in the DSSC application. They are low-cost, abundant, ecofriendly, simple extraction procedures, and non-toxic. The combination of natural dyes with an optimized choice of the mixture of the volume ratio of the extracting dye extracting solvent accounts for many possible interactions that promise to provide more charge injection upon sensitization and allowed utilization of the photon energy more efficiently. DSSC co-sensitized with the dye mixture shows higher absorbance, and cumulative absorption properties over the entire visible region than the DSSC fabricated with individual dyes.

A blocking layer in DSSC provides good adhesion between the transparent conducting oxide (e.g., ITO, FTO, etc.) and an active semiconductor layer, TCO (e.g., TiO2, ZnO, etc.). It also represses the electron back transport between electrolyte and TCO by blocking direct contact. Also, it offers a more uniform layer than bare TCO glass substrate. The conventional blocking suppresses electron leakage, recombination, and trapping; thus, the photovoltaic performance of the DSSC improves. Introducing a blocking layer in the DSSCs show lower dark current and operates efficiently under high-intensity sunlight and ambient light conditions.

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