Electrochemical and corrosion properties of ZnO and AZO nanostructured films produced by hydrothermal method for dye-sensitized solar cells

Dye-sensitized solar cells are thin-film-based devices belonging to the low-cost third-generation solar cells group. In these devices, the photoanode material has special importance in the processes of dye support, photon absorption and electron transport. ZnO nanorod arrays, which have the potential for widespread use in many technological applications, are remarkable materials as photoanodes. However, to increase the performance of ZnO-based dye-sensitized solar cells, controlled growth of ZnO nanorod arrays and improvement of their properties are required. Our aim in this thesis is to grow unique undoped and constant Al-doped ZnO nanorod arrays with a hydrothermal method, which allows controlled nanostructure production, by using hexamethylenetetramine and hexamethylenetetramine-hexamethylenediamine ligand mixture in the preparation of hydrothermal precursor solutions, and to investigate their potential usage as photoanodes. Within the scope of the thesis, the production of undoped and Al-doped ZnO nanorod arrays was carried out in a two-stage process. First of all, ZnO seed layers were produced on FTO substrates with the sol-gel spin coating technique under the same production parameters, and then nanostructured films were grown on them with the hydrothermal method. Additionally, the properties of undoped and Al-doped ZnO nanorod arrays were modified using hekzametilentetramin-hekzametilendiamin ligand mixture, unlike the literature. To investigate the potential usage of all nanostructured films as photoanode, standard analyzes (XRD, UV/Vis Spectrophotometry, AFM, FESEM-EDS) were performed and N719 dye loading capacities, corrosion resistance, charge transfer kinetics and diffusion mechanisms were analyzed by using advanced analysis techniques (Electrochemical impedance spectroscopy, corrosion and dye loading tests). By evaluating all analyses, it was determined that the ligands and Al incorporation element used in the preparation of hydrothermal precursor solutions had a strong effect on the structural, optical, surface and electrochemical properties, as well as corrosion resistance and dye loading capacities of ZnO nanorod arrays grown on ZnO seed layers with the same properties. Besides, it was concluded that the factors that limit the potential of undoped ZnO nanostructured films as photoanode can be minimized by doping Al element at a constant rate and/or using hexamethylenetetramine-hexamethylenediamine ligand mixture.caktır