Electrochemical, Corrosion, and Dye Absorption Properties of Hydrothermally Grown 1D Nanostructured ZnO:Al Photoanodes

Abstract

Instability (corrosion), Zn²⁺-dye complex formations, low injection efficiency, fast charge recombination, and low light-harvesting capacity are the factors that limit the potential usage of ZnO nanostructured photoanodes in dye-sensitized solar cells. In this study, innovative strategies such as adding Al element and using hexamethylenediamine capping agent are developed to contribute to the solution of them. 1D ZnO:Al nanomaterials are hydrothermally grown on ZnO-cores produced by sol–gel spin coating. Highly crystalline ZnO:Al nanorods grow preferentially along the c-axis and increase the light-harvesting capacity by absorbing visible light. Hexamethylenediamine increased the average nanorod lengths from 480 to 810 nm while decreasing their diameters from 63 to 41 nm. Hexamethylenediamine caused smaller charge transfer resistance (130.5 kΩ), 2.2 times decrease in corrosion current density because of ZnO passive corrosion shield, and good adsorption of N719 dye. In conclusion, ZnO:Al nanorods synthesized using hexamethylenetetramine–hexamethylenediamine ligand mixture are more suitable photoanode materials due to their improved electrochemical properties, corrosion behavior, and dye-loading capacity.