Browsing by Author "Mkehlane, Moleko Samuel"

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    Electroanalysis of Organo-Chalcogenic Perovskite Nanomaterials
    (University of the Western Cape, 2017) Mkehlane, Moleko Samuel; Iwuoha, Emmanuel
    Organometallic halide perovskite solar cells have developed as one of the most promising contenders for the production of solar cells. The generic perovskite (PS) structure ABX3 allows manufacturing a broad range of PS materials by simple modification of building blocks A, B, and X (A = organic group, B = metal, and X = halide). The preparation of a series of solution-processed solar cells based on methylammonium (MA) lead halide derivatives, CH3NH3PbX3 (X=Cl, Br, and I) has been reported. These solar cells showed tunable optical properties depending on the nature and ratio of the halides employed. The photovoltaic performance of perovskite solar cells is dependent on the absorption of the light spectrum. The photovoltaic performance can be improved by widening the light absorption towards the near infrared spectrum. A panchromatric material that absorbs all the light from the ultra-visible to near infrared of the solar spectrum is an ideal photoactive layer. The optimal bandgap for single junction solar cells is known to be 1.1 and 1.4 eV. However, the bandgaps of methylammonium lead trihalide perovskites are beyond this range, and this inspired the realization of the lower bandgap perovskites.
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    Photovoltaics and spectro-electrochemistry of nicuzn organic-inorganic hybrid perovskite nanomaterials
    (University of Western Cape, 2021) Mkehlane, Moleko Samuel; Iwuoha, Emmanuel I.
    Despite the remarkable progress made by hybrid perovskite thin film materials CH3NH3PbI3 in the arena of thin film photovoltaics, their shift to penetrating the commercial market is still an on-going research due to poor intrinsic stability and the issue of eco-toxicity posed by metal Pb. The chief aim of this study was to prepare air-stable hybrid perovskite thin film materials incorporating earth abundant and non-toxic transition metals which include Ni, Cu & Zn (doped at 1, 5 and 10%); CH3NH3PbI3•Ni, CH3NH3PbI3•Cu & CH3NH3PbI3•Zn, employing a two-step solution deposition technique. The terephthalic acid (TPA) additive was utilized to stabilize thin film materials from deterioration upon exposure to air.
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    Setting the baseline for the modelling of Kesterite solar cells: The case study of tandem application
    (Elsevier, 2023) Jimenez-Arguijo, Alex; Medaille, Axel Gon; Mkehlane, Moleko Samuel
    The Kesterite solar cells research landscape is at a crossroad and despite a much improved understanding of the limitations of this class of materials, the current performance deficit contrasts with the several other thin film technologies reaching conversion efficiency values well above 20%. It is more important than ever for the Kesterite community to collaborate directly or indirectly and data sharing is an essential building block in that regard. This work proposes a detailed set of modelling baselines and parameters, based on a consistent set of properties obtained with experimental devices made by our group. These parameters permit to accurately reproduce all photovoltaic figures of merits of reference experimental Kesterite cells with a relative accuracy of 1% or less. As a case study, and using optical modelling based on the transfer matrix method in complement, the potential of Kesterite materials in tandem devices with either a Perovskite or a Crystalline Silicon partner is evaluated. It is found that a moderate improvement of pure selenium CZTSe, feasible in the short to middle term, would realistically permit to use this material as bottom subcell in tandem with a Perovskite top cell and obtain efficiencies reaching the 30% threshold. On the other hand, using a Kesterite absorber in a top subcell with a silicon bottom subcell appears as particularly ambitious even when considering several important optimizations to the material, and it is believed that only an important breakthrough would render this material viable for such application. The complete set of material parameters, optical indices and modelling files are shared for the Kesterite community to use and build improve upon.