Department of Physics

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Browsing Department of Physics by Author "Emma, Panzi Mukhokosi"

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    Influence of device architectures and mobility on response/recovery time of metal halide perovskites: A review
    (Journal of Materials Science, 2022-01) Emma, Panzi Mukhokosi; Maliki, Maaza
    Organic–Inorganic perovskite materials have attracted great interest in the research community for photo-detector and solar energy applications. For various photo-detector applications, the response time is a very important parameter. In telecommunication, a high response speed is required and for this special class of materials, a fast response time in the order of ns has been realized by some authors. The main challenge is their stability. It is established that the response time is primarily controlled by the electron/hole mobility, electrode spacing and the depletion width. In this review, we discuss the recent developments of photo-detector devices composed of mixed halide perovskites and their performance with the main emphasis on the role played by mobility and internally generated electric field to the response/recovery speed. We discuss how the response speed clear relates to charge carrier mobility and depletion width. We further suggest ways on how to improve the response speed to match those of the conventional commercial photo-detectors like Si and InGaAs. We hope this article will find a suitable audience who will utilize this knowledge in the design and construction of ultra-fast photo-detectors.
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    Optical absorption and photoluminescence properties of Cucurbita maxima dye adsorption on TiO2 nanoparticles
    (IOP Publishing Materials Research Express, 2023-04) Emma, Panzi Mukhokosi; Maliki, Maaza; Muhammed, Tibenkana; Nandipha, L Botha; Loyce, Namanya; Madiba, I G; Michael, Okullo
    Dye-sensitised solar cells (DSSCs) are 3rd generation photovoltaic device that imitate photosynthesis in plants. The fundamental concept of a DSSCs is that the photoanode is covered by the dye as a sensitiser. Natural dyes from plant-based extracts have gained attention as alternatives to toxic and expensive commercial dye sensitisers. Various studies have been conducted on the use of natural plant dye extracts for DSSCs . However, more fundamental studies on their adsorption on TiO2 photoanode nanoparticles are still not well understood. In this study, we investigated the crystal structure, optical absorption, and photoluminescence properties of TiO2, Cucurbita maxima, and Cucurbita maxima dyes adsorbed on TiO2 nanoparticles as potential materials for DSSCs. Raman spectra confirmed the anatase phase of the TiO2 nanoparticles. The particle size of 12 ± 2 nm was confirmed through the transmission electron microscope. The optical absorption properties of Cucurbita maxima show two distinct absorption bands: blue visible (450–500 nm) and red visible (635–674 nm). The photoluminescence spectra of the dye extract and its adsorption onto the TiO2 nanoparticles showed two prominent peaks in the blue and red regions of the electromagnetic spectrum. No significant peak is observed in the green region of the electromagnetic spectrum. These studies shed more light on the fundamental properties of chlorophyll adsorption on TiO2 nanoparticles and their optical and photoluminescence properties for applications as sensitisers in DSSCs.
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    Structural and mechanical properties of non-glazed ceramic tiles developed from selected mineral deposits in Uganda
    (Nano-Horizons: Journal of Nanosciences and Nanotechnologies, 2023-07) George, William Mukwaya; Ben, Enjiku; Emma, Panzi Mukhokosi
    Uganda is well endowed with clay resources; however, comprehensive knowledge about the composition, structure and suitability of these clays for ceramic tile production is lacking. In this study, we provide a comprehensive characterisation of locally sourced clays in Uganda and their suitability for ceramic tile production. In the study, we developed ceramic tiles using feldspar, kaolin, ball clay and sand from four different sites in Uganda. We focused on analysing the surface morphology, crystallographic structure and mineralogical composition of the raw materials. In addition, we examined the mechanical properties of the developed tiles with the different mixture ratios of the clay types. The surface morphology of the raw materials was analysed by using a scanning electron microscope. The structural analysis of the raw clay materials was done using X-ray diffraction. The mineralogical composition of the raw materials was investigated using energy dispersive X-ray spectroscopy and X- ray fluorescence spectroscopy. The results indicated that the strength and rapture modulus are influenced by the composition of kaolin and feldspar. We concluded that the selected mineral deposits can be used in the production of ceramic tiles in Uganda.