Effect of Seed Layer on the Morphology of ‎Zinc Oxide Nanorods as an Electron ‎Transport Layer in Polymer Solar Cells ‎

   Zinc oxide has been considered as a promising semiconductor material for fabrication of transparent conductive oxides (TCOs), electronic devices, optoelectronics, and solar cells. Among the various morphologies of zinc oxide, nanorods are more widely used because of the ease of synthesis and providing a direct path for the transport of charge carriers. The electrochemical deposition method (ECD), due to its simplicity, low cost, and production of nanostructures with fewer defects is a more suitable method for producing zinc oxide nanorods. Heretofore, the effect of different parameters such as the temperature of growth solution, the concentration of precursors and pH on the morphology of the final product were studied. In this paper, the effect of the seed layer number on morphology, absorption, and electrical conductivity of zinc oxide nanorods was investigated using SEM images, UV-Vis spectroscopy, and four-point probe. The results showed that increasing the number of seed layers from 0 to 5 lead to the production of vertical, uniform, regular, and high-density nanorods. Also, the use of high-density zinc oxide nanorods, in the structure of polymer solar cells increased the performance of polymer solar cells by 68%. The polymer solar cell with zinc oxide nanorods as the electron transport layer showed short-circuit current, open-circuit voltage, and the power conversion efficiency of equal to 9.04 mA/cm2, 0.53V, and 2.51%, respectively.