| dc.description.abstract | The utilization and overreliance on fossil fuels have dramatically spiked negative global climatic changes. When combusted to produce energy, they emit products including but not limited to oxides of carbon, which contribute to global warming. Therefore, it is prudent to find alternative energy sources that are green and renewable. In this realization, solar to electrical energy converters such as Dye-sensitized solar cells (DSSC) are fronted due to their excellent properties, however, its inefficiency in converting light of wavelength above 400nm to electrical power threatens its reliance on meeting the tremendous energy demand. To improve its efficiency, several semiconductors, including titanium dioxide (TiO2), have been applied due to their stability in terms of electrical, optical, and physical properties, albeit, its most significant drawback lies in the relatively high energy band gap (3.2 eV), and a high recombination rate in the visible spectrum. Doping improves photocatalytic activity by creating fermi-level that reduce electron/hole recombination rate. This research study therefore, outlines the effects of growth temperature (400 to 900 oC; in steps of 100 oC) on TiO2 nanoparticles (NPs), the impact on optical and structural properties of different % mol (1, 2, 3, 5, 7, 9, 10) Zn and Fe doped TiO2 anatase phase, and the effects on structural and optical properties of the different Zn:Fe co-doped ratios (1:1, 1:0.5, 1:1.5, 0.5:1, and 1.5:1) on TiO2 NPs for use as photoanode in the DSSC. The sol-gel method is used to synthesize nanoparticles followed by structural, optical and morphological characterization using X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), UV-Vis spectroscopy, and Scanning Electron Microscope (SEM). The FTIR spectra on effects of growth temperature on TiO2, showed symmetrical stretching vibration at wavenumbers 1033 and 668 cm-1 for Ti-O-Ti vibrations. Zn- doped TiO2 and Fe doped TiO2 NPs, showed symmetrical and asymmetrical vibrations at wave numbers 668 and 1033 cm-1 for Zn-O and Fe-O, and Ti-O-Zn and Ti-O-Fe stretching vibration, respectively. The Zn-O and Fe-O symmetrical stretching vibration confirms substitution doping at 1 % mol for Zn-doped TiO2 and 5 % mol for Fe-doped TiO2 NPs. X-ray diffraction patterns on effects of annealing temperature showed the phase transformation from anatase to rutile occurred at 600 oC. Crystal size calculated using the Debye Scherer equation increased from 10.83 to 23.90 nm for 400 and 900 oC, respectively. Fe-doped TiO2 NPs crystallite size increased with 2.7 nm, and Zn-doped TiO2 NPs decline with 3.9 nm, the anatase phase of Zn:Fe co-doped NPs showed an increased crystallite size by 10.7 nm for the 1:0.5 Zn:Fe co-doped TiO2 NPs. UV-Vis analysis showed that the indirect band gap for TiO2 NPs annealed at different temperature decreased from 3.5 to 3.26 eV. The highest optical band gap registered is 5.18 eV for 1:1.5 Zn:Fe co-doped TiO2 NPs rutile phase. Scanning Electron Microscope (SEM) showed that the nanoparticles are in nm, with an improvement of in the surface morphology as the annealing temperature is raised, and when TiO2 NPs are doped or co doped with Zn and Fe. Energy Dispersive Spectroscopy (EDS) showed the elemental composition in the Zn doped, Fe doped and Zn:Fe co-doped TiO2 NPs, that are Zn, O, Ti, and Fe. TiO2 thin films can be grown on a glass substrate and structural, morphological, and optical analyzed. Sol-gel synthesis method was successful in synthesizing the Zn and Fe doped and Co-doped TiO2 and the deposition of TiO2 thin films. | en_US |
