PHD-Department of Physics

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Browsing PHD-Department of Physics by Author "Njoroge, David Kimemia"

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    Synthesis, Fabrication and Characterization of Solid Titanium Dioxide - Based Solar Cell Doped with Different Organic and Inorganic Luminescent Materials
    (Kenyatta University, 2024-01) Njoroge, David Kimemia
    Energy is globally recognized as an important resource for social and economic development. Majority of the world population relies on fossil fuels, hydro and solar radiation as a source of energy. Fossil fuels immensely contribute to air pollution and global warming. Solar cells have been exploited and controlled to generate electrical energy from solar radiation. The available solar radiation is not constant at all times of the day and differs depending on the season of the year. Consequently, the solar cell output varies with the incident radiation. The study investigated use of photo luminescent materials as dopants in the photoactive layer of TiO2 –based solar cells with an aim to prolong the cell output in diminished radiation. Inorganic (Sb/Ca/Mn/Ag:) and organic (rhiodamine, allicin, gingerol, quinolone and neohesperidosyl: extracted from their fresh organic complexes) photo luminescent materials were used as dopants in TiO2 photoactive layer of the solar cell while a mixture of graphite, iodine and potassium iodate was used as the receptive layer. The effect of varying mass ratios and the thicknesses of both photo active and the receptive layers was investigated based on the solar cell output parameters. The synthesized inorganic (Sb/Ca/Mn/Ag) and the extracted organic luminescent materials were chemically characterized using the FTIR. Different masses of the photoactive TiO2 material, inorganic and organic luminescent materials were weighed separately and compressed to form the photoactive layer. Known masses of graphite powder mixed with a matrix of potassium iodate (KI3) were introduced into the molding dice over the photoactive layer and compressed to bind them sufficiently. Potential and short circuit generated by the cells were monitored and the data obtained used to determine their fill factor, and efficiency. The study concluded that the inorganic (Sb/Ca/Mn/Ag) and organic rhiodamine, flourene, allicin, gingerol, quinoline and neohesperidosyl particles absorbed radiation at different wavelengths. The absorption bands were evident at {(360 – 3750), (434.96-3950), (697.28-3750), (290.29-3850), (463.89-3850), (260.39-3750) and (273.90-3700)} cm-1 respectively. All the investigated photo luminescent materials showed promising properties for improving solar cell output in diminished solar radiation. The results obtained also showed different potential delay by the varied thicknesses with improved responsivity and efficiency. The fabricated solar cell employing rhiodamine doped -TiO2 photoactive layer (0.136) mm and 0.164 mm receptive thickness layer had the highest open circuit voltage (VOC =1.023V), and a residual potential of 0.586 V in diminished radiation after one hour. The corresponding fill factor and efficiency were determined as 0.416 and 2.32%, respectively. The study also concluded that optimized FSCs layers generated enhanced open circuit and residual potentials (VOC) observed after 60 minutes. The study recommends that dopant synthesis should be expanded to enhance further d-orbitals splitting for improved charged species d→d transitions and transpose IR spectrum into fluorescence, dopants molecular size with less energy instability should be extended to achieve uniform potential difference with less attenuation, wider dopants complexes ratios should be done to minimize recombination at the convergence within the solute and enhance quantum yield for higher charge carriers’ densities excitation, modified ratios relative dimensions should be investigated together with ambient conditions moderating pigments to balance FSCs interacting systems for uniform output parameters.