Role of pH and pigment concentration for natural dye-sensitized solar cells treated with anthocyanin extracts of common fruits

Natural dyes, extracted from cherry, blackberry, blueberry, raspberry and strawberry fruits, were used as sensitizers to fabricate dye-sensitized solar cells (DSSCs). The conversion efficiency (h%) ranged from 0.14 to 0.69. Specifically, the highest h% was obtained from the dye extracted with ethanol 70% from blueberry fruit and epicarp (1.13 and 0.75, respectively), without other chemicals, pH adjustments and thermal or purification processes. The absorbance spectra of the dyes and their photoelectrochemical performances demonstrated that anthocyanins (ANCs) were the most effectual component of the sensitizer for DSSC. To check the affinity of the dyes for the TiO2 a new adsorption/desorption procedure was established. The comparison of the percentage distribution of each anthocyanin class in blueberry epicarp dye, before its adsorption and after its recovery from TiO2 powder, showed a better sensitizing performance of delphinidine derivatives compared to the other ANCs.