Fabrication and characterization of a graphite dispersed titanium dioxide solid solar cell
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Date
2017-11
Authors
Njoroge, David Kimemia
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Abstract
Energy is globally recognized as one of the most fundamental inputs to social and economic development. Most energy sources are serious pollutants resulting to serious negative effects on the environment. To overcome this challenge, the presence of abundant sunshine has been exploited through the use of solar cells to generate this vital resource through photovoltaic cells. However most photovoltaic cells are silicon based photovoltaic cells which are expensive. This study reports on the fabrication of a cost effective and environmental friendly solar cell by the use of TiO2 and I2/ KI (dispersed in graphite-Cx) layers in their solid form to provide an alternative source of clean energy. TiO2 was preferred due to its photo generation property when excited with a radiation and chemical stability over a wide pH range. The photo excited electrons were replenished by use of iodine/iodide complex and their migration was facilitated by graphite. The mixtures at varying ratios were made into pellets and their electrical properties investigated. The experimental design involved preparation of various ratios of titanium dioxide: graphite /iodine/KI mixtures in each respective layer. Optimization was carried out by varying the mass of the constituents of each layer while maintaining the others constant to obtain the highest current - voltage outputs. The study investigated the effect of the thickness of TiO2, (the photo active layer) and the electronegative material layers on current-voltage output of the fabricated solar cell. The optimum electricity generation was observed at the ratio of TiO2/ Cx: I2: KI as 0.4: 0.3: 0.17: 0.01 g respectively. The presence of KI enabled solubility of iodine enhancing it disperse evenly in graphite whose mass was constant at 0.01g in all the cells fabricated. The effect of the optimized thicknesses of the photo active layer and that of the electronegative layer were investigated and the optimal thicknesses were found to be 2.00 and 1.00 mm respectively. The highest open circuit voltage (Voc) of 0.979V and a short circuit current density (Jsc/cm2) of 12.037μA was observed, giving efficiency (η) of 0.006% and a Fill factor (FF) of 0.64. During the entire three years of study, no corrosion effects were observed because the medium for the charge carrier migration was in dry solid state and thus it was suitable for photovoltaic application. A solar cell was successfully fabricated and characterized. The ratio of constituent materials (TiO2/ Cx: I2: KI) and the optimal thickness of both the photo active and the electronegative layers which generated the optimum Current-Voltage output were determined. The efficiency and Fill factor were calculated from the fabricated overall corrosion-free solar cell. It is therefore recommended that further research work be done using TCO (transparent conducting oxide) as the cathode in addition to employing technologies that can reduce air packets in the solar cell
Description
A thesis submitted in partial fulfillment of the requirements for the award of the degree of Master of Science (electronics and instrumentation) in the school of pure and applied sciences of Kenyatta University, November, 2017