Browsing by Author "Nasejje, Stella"

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A dye-sensitized solar cell based on an in-situ hydrothermally grown hematite photo-anode
(Springer Nature Link, 2025-07-22) Nasejje, Stella; Mukhokosi, Emma Panzi; Mmantsae, Diale
Transition metal-oxides have gained research attention for applications in optoelectronics devices like dye-sensitized solar cells (DSSCs). This contribution presents an α-Fe2O3-Pt DSSC configuration. An in-situ hydrothermal technique was used to grow spherically shaped α-Fe2O3 thin films on an FTO substrate, forming the photo-anode. The surface morphology, structural, and optical properties were characterized by standard techniques, confirming the samples’ purity. Pt was drop-cast on the FTO substrate, forming the counter electrode. The photo-anode was soaked in N719 ruthenium dye for 24 h. The electrodes were assembled using crocodile clips, and the iodide electrolyte was injected into the space between them. At an intensity of 100 mW/cm2, the α-Fe2O3-Pt DSSC yielded a short-circuit photocurrent density, open-circuit voltage, fill factor, and efficiency of 0.098 mAcm−2, 0.410 V, 0.247, and 0.01%, respectively. These results provide a simple, cost-effective strategy for synthesizing spherical nanoporous α-Fe2O3 thin films for potential application as photo-anodes in n-DSSCs.
A study of electrical insulation materials developed using selected clay minerals in Uganda
(Kyambogo University [unpublished work], 2012-06) Nasejje, Stella
This study was to investigate appropriate mixtures of different ceramic mineral ingredients needed to make electrical porcelain insulators and to determine the best method of developing the electrical insulator of slip casting, dry pressing, and wet pressing. The mixing of the clay minerals was done using percentage ratios of ball clay. kaolin, feldspar and flint of which the quantity of flint was kept constant at 20% in all compositions and that of ball clay to kaolin changed through a range of 1:1.75 , 1:2 and 1: 2.5, well as that of feldspar took up any remaining percentage. These samples were formed by slip casting. Wet, and dry pressing and then tired at a constant heating rate to a temperature of l 250°C. Then the dielectric strength was tested using the oil test set, Avo Megger foster OTS100A F/2. The mixtures of the clay minerals with a ratio of ball clay to kaolin of 1:2 showed good formability in all forming methods, but those with a ratio of 1:1.75 and 1:2.5 could not easily form good casted and wet pressed samples. The best formulation was that with 55% clay, where the ratio of ball clay to kaolin was 1:2. The sample compositions of the various, minerals were found to affect both voltage breakdown and dielectric strength. The voltage break clown. V was found to be proportional to the thickness. t of the samples according to the expression V= at + b: where a and b are constants of testing conditions like room temperature and frequency. Conversely, the values of dielectric strength; U was found to be inversely proportional to the thickness, d of the samples according to the expression; D = VB over d where VB is the breakdown voltage and d is the thickness of the sample. Values of both the voltage breakdown and dielectric strength of samples tested in air were much lower than those of samples tested in transformer oil due to generated carbon around them when in air as a result of corona discharge. The samples tested in transformer oil had values above 10kV/mm. Thus, the electrical insulation properties of the formulation of the samples developed in this study were found to match that required for international standards.