This study presents the influence of pH control agents and pH value on the physical properties of ZnO thin films obtained by chemical bath deposition. ZnO thin films were synthesized on glass substrates using precursor solutions of different pHs prepared from two bases: sodium hydroxide (NaOH) and ammonia (NH₃). The effect of pH values on the morphological, structural, and optical properties of ZnO thin films was investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and UV–Visible spectroscopy. XRD results showed that all the synthesized ZnO thin films are polycrystalline and crystallize in a hexagonal wurtzite structure. The crystallite size, calculated using the Debye–Scherrer formula, varied from 10.50 nm to 11.69 nm for ZnO thin films obtained with NH₃ and from 20.79 nm to 27.76 nm for those obtained with NaOH. FTIR analysis confirmed the presence of functional groups. SEM images indicated that not only the base but also the pH affects the morphology of the films, giving rise to different granular shapes. Overall, the ZnO thin films obtained with NaOH looked more mesoporous compared to those obtained with NH₃. Optical characterization results showed that whatever the base used, the pH of the precursor solution affected the ZnO thin film transmittance. Films synthesized with NH₃ exhibited the best transmittance (80%) at pH 8.5, while the best transmittance (81%) of films synthesized with NaOH was obtained at pH 8 in the visible region. Based on optical and morphological properties, ZnO films obtained from NH₃ at pH 8.5 are found to be more suitable as photoanodes in dye-sensitized solar cells.

This study investigates the effect of deposition time on the structural, morphological, and optical properties of ZnO thin films synthesized by single-step chemical bath deposition (CBD) without the use of a seed layer. The films were systematically characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and UV-Visible spectroscopy in order to establish correlations between growth conditions and film properties. XRD analysis confirmed that all synthesized films are polycrystalline and crystallize in the hexagonal wurtzite structure, with average lattice parameters of a = 3.247 Å and c = 5.209 Å. The crystallite size increased slightly from 13.27 nm to 14.05 nm with increasing deposition time, indicating improved structural ordering and crystallinity. FTIR spectra verified the presence of characteristic Zn–O vibrational modes together with surface hydroxyl groups and other functional bonds related to the growth process. SEM images revealed a strong dependence of surface morphology on deposition time: ZnO microrods evolved from loosely distributed to more compact and densely packed assemblies as the deposition progressed, confirming enhanced film coverage. Optical measurements highlighted significant modifications in the transparency and band structure of the films. The average optical transmittance in the visible range decreased progressively from 68% to 52% when deposition time was extended from 30 to 120 minutes, reflecting increased film density. Concurrently, the optical band gap narrowed from 3.27 eV to 3.22 eV. These findings demonstrate that single-step CBD provides a reliable and controllable route for synthesizing ZnO thin films with tunable physical properties.

The collection and transport of charges at the electrodes are the main factors limiting the efficiency of organic solar cells. Zinc oxide (ZnO) in nanostructured form helps to overcome this problem by introducing a ZnO buffer layer between the photoanode and the donor material. To achieve this, the ZnO thin film must exhibit good crystallinity, along with good electrical conductivity and high optical transparency in the visible range. The aim of this work is to investigate the effect of precursor sources and precursor concentrations on the structural, morphological, and optical properties of ZnO thin films. Three different precursor sources have been used: zinc acetate, zinc chloride and zinc nitrate. In each deposition solution, the precursor concentration varied from 0.1 M to 0.3 M. The ZnO films were deposited on glass substrates and all the films were annealed at 400°C for 3 hours. The structural, morphological and optical properties of deposited films were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV-visible spectroscopy respectively. XRD results showed that, regardless of the precursor source, all the ZnO films are polycrystalline with a hexagonal wurtzite structure. ZnO films obtained from acetate and nitrate sources crystallize preferentially along (002) and the peak intensity increases as the precursor concentration increases. SEM images showed that all the ZnO films are homogeneous, but films deposited from zinc acetate and zinc nitrate looked more compact and smoother than those obtained with zinc chloride which looked porous. UV-visible spectroscopy results revealed that the films transmittance depends both on precursor source and concentration. ZnO thin films deposited from zinc acetate at 0.3M concentration exhibit the best transmittance of 95% due to their smooth and uniform surfaces. The band gap of ZnO obtained from the zinc acetate precursor decreases with increasing solution concentration. It is found to be 3.29 eV, 3.26 eV, and 3.22 eV for concentrations of 0.1 M, 0.2 M, and 0.3 M, respectively. It therefore appears that ZnO films obtained from zinc acetate can be used as an electron transport layer for solar cells as they exhibit the best crystallinity and the highest transmittance.

This work investigates the influence of deposition temperature on the structural, morphological, and optical properties of zinc oxide (ZnO) thin films synthesized by spray pyrolysis. Films were deposited at 300 °C, 350 °C, and 400 °C using a 0.3 M zinc acetate precursor solution, followed by annealing at 400 °C for 3 hours. X-ray diffraction revealed that all films are polycrystalline with a hexagonal wurtzite structure, exhibiting a preferred (002) orientation that becomes more pronounced at higher deposition temperatures. Fourier-transform infrared spectroscopy confirmed the presence of characteristic Zn–O vibrations and surface functional groups. Scanning electron microscopy showed uniform and dense film coverage, with a distinct change in morphology from aggregated nanocrystals at 300 °C to microplates and nanograins at 350 °C and 400 °C. UV-visible spectroscopy indicated an increase in optical transmittance with temperature, reaching up to 85% at 400 °C in the visible range. The optical band gap slightly increased with deposition temperature, ranging from 3.26 eV to 3.28 eV. Based on the structural, morphological, and optical properties, 400 °C is identified as the optimal deposition temperature for ZnO thin films, offering enhanced crystallinity, surface quality, and optical transparency essential for improving the performance of photovoltaic devices.

The present work investigates the combined effect of precursor source and solvent on the structural, morphological, and optical properties of ZnO thin films prepared by the spin-coating technique. Three precursor sources (zinc acetate dihydrate, zinc chloride, and zinc nitrate hexahydrate) and four solvents (ethanol, 2-methoxyethanol, 2-propanol, and 1-methoxy-2-propanol) were systematically explored. X-ray diffraction analysis confirms that all films crystallize in the hexagonal wurtzite structure, with a pronounced (002) preferential orientation for zinc acetate-derived and most of the zinc chloride-derived films. Scanning electron microscopy reveals that both precursor and solvent strongly influence surface morphology. Zinc acetate yields smoother and more compact films, zinc chloride promotes larger hexagonal grains, and zinc nitrate leads to relatively porous structures. Among the solvents, 2-methoxyethanol produces the most uniform and dense films regardless of the precursor. Optical measurements show that transmittance is highly dependent on synthesis conditions, reaching up to 90% in the visible range for zinc acetate-based films, particularly with 2-methoxyethanol. The optical band gap varies between 3.20 and 3.37 eV, reflecting differences in crystallinity and defect density. Overall, these results highlight the key role of precursor–solvent interactions in tailoring ZnO thin film properties for optoelectronic applications.