Masters Dissertations

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Browsing Masters Dissertations by Author "Abbas, Hija"

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    Investigation on the performance of Titania and Titania based dye sensitized solar cells: effects of Sodium-boron co-doping and natural dyes
    (University of Dar es Salaam, 2018) Abbas, Hija
    One among the promising Photovoltaic devices for generation of electricity using light from the sun is the Dye Sensitized Solar Cell (DSSC). Among the issues that face DSSCs are high cost and toxicity of the ruthenium based industrial dye used to sensitize the TiO2 semiconducting photoanode layer and low efficiency of the cells. In this work, natural dye solutions were extracted from different locally available plants raw materials. The extracted dye solutions were employed to sensitize TiO2 films with the aim of broadening the absorption range well into visible part of the solar spectrum. Furthermore, sodium and boron dopants were employed into TiO2 films with an eye to possible narrowing band gap and hence absorption of the TiO2 semiconducting metal oxide. The structural, elemental composition and morphology change of the obtained powder samples of unlopped and doped TiO2 were investigated by using XRD, SEM, EDXS and TEM. Optical properties of the extracted natural dyes, undoped and doped TiO2 powders were investigated using UV-Vis and FT-IR spectrometry. The XRD results showed that the prepared samples were anisate phase of TiO2. The crystallite sizes of the doped samples were found to be larger than those of unlopped samples. Crystallite size increases with increase of boron dopant precursor concentration at fixed concentration of sodium dopant precursor. However, no clear trend of the crystallite size change with increase in the sodium dopant precursor concentration was observed. SEM and TEM images also confirmed that the particles size increased after being doped. The FT-IR, HRTEM and SAED confirmed the anatase phase of TiO2 undoped samples. The band gap energies of all doped samples are larger than the undoped ones and are in the range of 3.0 eV – 3.5 eV. The absorption spectra for all extracted dyes showed broad and significant absorption band in the visible region of the solar spectrum. Conversion efficiency of the fabricated solar cells sensitized with natural dyes are in the range of 0.018% for dyes extracted from black raspberry to 0.184% for dyes extracted from pearl of plum fruits while the efficiency of the solar cell fabricated with Euthanizer 535-bis TBA ( N 719) industrial dye as sensitizer was 1.06%.