Dye-Sensitized Solar Cells Based on ZnO Films and Natural Dyes

This work employs extracts from Walnuts, Rhubarb, and Pomegranate as natural dyes for fabrication of dye-sensitized solar cells (DSSCs). ZnO nanoparticles with crystallite mean value 12 nm as confirmed from XRD data have been synthesized at pH 12. SEM picture of the ZnO powder reveals homogeneous and well defined nanoparticles with size of about 15 nm. TEM micrograph shows that the powder has a porous agglomerate structure consisting mainly of spherical crystalline particles with about 15–20 nm diameter. ZnO films were deposited on Fluorinated Tin Oxide (FTO) coated glass sheets followed by sintering at 450℃. The samples were sensitized by soaking in the dye solution. A Graphite slab was used as a back electrode, and redox was employed as an electrolyte. Each cell was illuminated with light intensities in the range 40,000–100,000 Lux to measure the photovoltaic parameters. The experimental results shows that the highest Isc value is obtained from the DSSC sensitized with Rhubarb extract while the highest Voc value is obtained from the DSSC sensitized with the Walnuts extract. The Pmax of the DSSC sensitized by the Walnuts extract is greater than those sensitized by Rhubarb and Pomegranate extracts. Moreover, the open circuit voltage Voc decay was found to closely follow a pseudo single exponential form.