Performance of Dye-Sensitized Solar Cells Based on Zinc Oxide Nanostructures

One-dimensional Zinc Oxide nanorods (ZnO NRs) were grown on Indium-Tin-Oxide (ITO) substrates by a hydrothermal technique using zinc nitrate hexahydrate and hexamethylenetetramine (HMTA) at 95 °C for 2 hours. The surface morphology and crystal structure of the as-prepared ZnO NRs were studied using a scanning electron microscope (SEM) and X-ray powder diffraction (XRD), respectively. The results revealed that ZnO NRs are related to the wurtzite structure of pure ZnO. The optical properties of ZnO NRs were then investigated using UV/Vis and FT-IR spectra. A strong exciton absorption peak was observed at 369 nm with an energy gap of 3.36 ev. The FT-IR spectrum displayed the presence of an infrared band belonging to the (Zn-O) stretching mode around 500 cm
^-1
. ZnO-NR-based DSSCs were successfully prepared using black dye N749 as the photosensitizer. The current-voltage measurements of DSSCs were evaluated at different concentrations of electrolyte. Namely, the increasing KI concentration can effectively enhance the short-circuit current density (J
sc
) as well as the power conversion efficiency of ZnO NRs-based DSSCs, in contrast to the open-circuit voltage values (V
oc
), which are almost unaffected by increasing the KI concentration. These observations confirm that DSSCs are based only on ZnO NRs as photoanodes.