Browsing by Author "Aduda, Bernard"

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    Electrophoretic Deposition and Characterization of TiO2/Nb2O5 Composite Thin Films for Dye Sensitized Solar Cells
    (Journal of Materials Physics and Chemistry, 2018) Nguu, John; Nyongesa, Francis; Musembi, Robinson; Aduda, Bernard
    In this study, Electrophoretic Deposition (EPD) technique was used to fabricate TiO2/Nb2O5 composite thin films on FTO coated glass for application as photoelectrodes in Dye Sensitized Solar Cells (DSSC). A TiO2/Nb2O5 ratio of 1:1 was used in a 2-propanol suspension solution with a solid loading of 0.25g/L. Optical investigations showed that the film with thickness of 5.5 μm deposited at 35.0 V for 90.0 s had the highest transmittance of 55.0 % at a wavelength (λ) of 1,300 nm. The optical band gap energy (Eg) was 3.884 eV and was found to be dependent on the annealing time. The solar cell fabricated from this film had an open circuit voltage (VOC) of 0.66 V, fill factor (FF) of 57.0%, short current density (JSC) of 5.25 mA/cm2 and photo conversion efficiency (PCE) of 2.0%. Electrochemical Impedance Spectroscopy (EIS) analysis indicate that the DSSC device with thinner photoelectrodes have more efficient electron transport in the photoanode compared to thicker photoelectrodes to achieve higher conversion efficiencies.
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    Electrophoretic Deposition of TiO2/Nb2O5 Composite Electrode Thin Films for Photovoltaic Application
    (Electrophoretic Deposition of TiO2/Nb2O5 Composite Electrode Thin Films for Photovoltaic Application. Journal of Energy and Power Engineering 8 (2014) 757-764, 2014-04) Nguu, John; Aduda, Bernard; Nyongesa, Francis Wanjala; Musembi, Robinson Juma
    Nano sized powders of TiO2 (titanium dioxide) and Nb2O5 (Niobium (V) oxide) were used to fabricate TiO2/Nb2O5 composites thin films by EPD (electrophoretic deposition) technique. The metal oxide powders, together with magnesium nitrate hexahydrate pellets, were suspended in propan-2-ol inside an EPD cell. The electrodes, placed 1.2 cm apart, were partially immersed in the suspension and a DC potential applied across them. Key EPD process parameters, which include applied DC electric field, deposition time and solid concentration in suspension, were optimized through visual inspection and from UV-Vis-NIR spectrophotometer spectra. The highest (55%) transmittance was obtained for films with deposition time of 90 s, powder concentration of 0.01 g/40 mL, and 35 V DC (direct current) voltage. XRD micrographs confirmed that TiO2 and Nb2O5 particles were presented in the composite film. SEM (scanning electron microscope) micrographs of the composite electrode thin films showed that porous films of high quality with well controlled morphology were deposited by using the EPD technique.