Effect of Deposition Potential and Bath Temperature on One-Step Electrochemical Synthesis of One and Two Dimensional Nanostructured ZnO Thin Films on Fluorine Doped Tin Oxide Substrates

Different zinc oxide (ZnO) morphologies such as platelets, nanowalls and nanorods were electrochemically synthesized on fluorine doped tin oxide (FTO) substrates by varying the deposition potentials and bath temperatures, respectively. Cyclic voltammetry (CV) curves reveal that ZnO deposition potentials are decreased as the bath temperatures are increased. X-ray diffraction (XRD) patterns and transmission electron microscope (TEM) images confirm that the synthesized ZnO nanostructures are hexagonal wurtzite structure. The XRD results reveal that the crystallinity of the films is increased when ZnO deposition potentials and temperatures are increased. Field emission scanning electron microscope (FE-SEM) images display platelets, nanowalls and nanorods structures for films synthesized -1.1 V, -1.2 V and -1.3 V respectively. The increase in deposition potential not only increases the growth rate of ZnO with metallic zinc deposition, but also decreases zinc hydroxide chloride hydrate. Fourier transform infrared microscope (FTIR) spectra confirm that the formation of zinc hydroxide (Zn(OH)₂) is decreased as the bath temperatures are increased from 30 to 70 °C. Photoluminescence (PL) spectra depict that the crystal quality of the ZnO films are notably improved as the bath temperatures are increased. The film thickness is increased as the deposition potentials and bath temperatures are increased. The dye absorbance is increased with respect to the film thickness. The efficiencies of dye sensitized solar cells (DSSCs) fabricated with diverse morphologies such as platelets, nanowalls and nanorods are found to be 0.10, 0.49 and 0.47%, respectively. Electrochemical impedance spectroscopy (EIS) spectra reveal that the charge transfer recombination resistance (R_rec) is continuously decreased as metal zinc deposition is increased in ZnO films with increase in deposition potentials.