Browsing by Author "January, Jaymi"

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    Ccu2pdsnse4 and cu2pdsn(s,se)4 palladium-substituted kesterite nanomaterials for thin-film solar cells
    (American Chemical Society, 2025) Nwambaekwe, Kelechi; Yussuf, Sodiq; Tshobeni, Ziyanda; Ikpo, Chinwe; January, Jaymi; Cox, Meleskow; Ekwere, Precious; Iwuoha, Emmanuel
    Kesterites are being studied intensively as sustainable absorber materials for solar cell development. However, elements such as Zn and Cu exhibit antisite defects that function as charge traps and recombination centers that affect the light absorption and carrier transport efficiencies of kesterite solar cells. The substitution of Zn or Cu with other metals is one of the strategies used to improve the photovoltaic performance of kesterites. This study focuses on the preparation and photovoltaics of Cu2PdSnSe4 (CPTSe) and Cu2PdSn(S,Se)4 (CPTSSe) kesterite nanoparticles (containing Pd instead of Zn) by a modified solvothermal (polyol) microwave synthesis method. The nanomaterials exhibited a tetragonal kesterite crystal structure with polydispersed morphology and average crystallite sizes of 22 and 17 nm for CPTSe and CPTSSe, respectively. DAMMIF ab initio analysis of the small-angle X-ray scattering data determined the shape of CPTSe and CPTSSe nanomaterials to be ellipsoidal. Ultraviolet-visible (UV-vis) spectroscopy revealed red-shift absorption properties, with bandgap energy values of 1.13 eV (CPTSe) and 1.20 eV (CPTSSe), thereby making them suitable light absorber materials for photovoltaic applications. Photoluminescence spectroscopy characterization confirmed the attenuation of defect concentrations in CPTSe and CPTSSe compared to the Zn analogue, which positively impacts the charge-carrier transport and recombination properties. A preliminary test of the materials in superstrate photovoltaic cell devices yielded power conversion efficiency values of 1.32% (CPTSe) and 3.5% (CPTSSe). The CPTSe- and CPTSSe-based photovoltaic devices maintained ∼70% mean open-circuit voltage (Voc), which is a significant improvement over the ∼20% Voc retained by Zn-based kesterites after 24 days.
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    Green synthesis, XRD/SAXS modelling and electrochemistry of indium iron oxide nanocomposite
    (Springer Science and Business Media B.V., 2025) Ngema, Nokwanda Precious; Tshobeni, Ziyanda; January, Jaymi; Iwuoha, Emmanuel; Ngece-Ajayi, Rachel Fanelwa; Mulaudzi, Takalani
    A green synthesis approach was utilized to prepare indium iron oxide (InFeO 3 ) nanocomposites using coffee extract as a reducing and capping agent. The structural, morphological, optical, and electrochemical properties of the synthesized materials were systematically characterized through X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), high-resolution electron microscopy (HRTEM/HRSEM), Fourier-transform infrared spectroscopy (FTIR), UV–Vis spectroscopy, photoluminescence (PL), vibrating sample magnetometry (VSM), and Mössbauer spectroscopy. XRD analysis confirmed the formation of a rhombohedral InFeO 3 structure with an average crystallite size of 27 nm, while HRTEM revealed spherical nanoparticles with partial agglomeration. SAXS and HRTEM data corroborated the nanoscale dimensions, with particle sizes ranging from 24 to 38 nm. Optical studies demonstrated a reduced bandgap (2.85 eV) for the composite compared to pure In 2 O 3 (3.3 eV) and Fe 2 O 3 (3.15 eV), attributed to charge transfer transitions between Fe 3+ and In 3+ . The nanocomposite exhibited enhanced magnetic properties, with a saturation magnetization (Ms) of 18.48 emu/g, and Mössbauer spectroscopy revealed disrupted super-exchange interactions due to In 3+ incorporation. Electrochemical analysis showed superior performance of the InFeO 3 -modified electrode, characterized by a higher diffusion coefficient (9.72 × 10 –5 cm 2 s −1 ) and surface concentration (4.62 × 10 –7 mol cm −2 ) compared to individual oxides, indicating improved charge transfer kinetics. These results highlight the potential of green-synthesized InFeO 3 as a promising material for electrochemical sensing applications, combining sustainability with enhanced functional properties.