Browsing by Author "Nwambaekwe, Kelechi C."

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    Enhanced photovoltaic effects of microwave-assisted polyolsynthesized Cu2(Pd/Zn)SnS4 kesterite nanoparticles
    (Elsevier, 2023) Nwambaekwe, Kelechi C.; Ramoroka, Morongwa E.; Iwuoha, Emmanuel I.
    Kesterite materials show excellent optical and semiconductive properties for use as petype absorber layer in photovoltaic (PV) applications, but they have a high open circuit voltage deficit (Voc,def) due to high antisite defect and secondary phase formation, resulting in poor device performance. This work reports a PV cell composed of Cu2PdSnS4 (CPTS) nanoparticles as an absorber layer yielding highly improved Voc of 900 mV, which is two times that of fabricated pristine Cu2ZnSnS4 (CZTS) PV cell. Improved PV cell parameters such as fillefactor (FF) of 83.4% and power conversion efficiency (PCE) of 1.01% were obtained for CPTS devices which are 3efold that of pristine CZTS devices. Optical studies revealed enhanced redshift absorption for CPTS nanoparticles. Electrochemical studies show improved current production, high electron mobility and low charge resistance for CPTS nanoparticles. This study shows that the improved photovoltaic properties can be attributed to enhancement in the bulk properties when Zn atoms are replaced by Pd atoms in kesterite nanomaterials as absorber layer material for PV applications.
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    Spray‐pyrolyzed Cd‐substituted kesterite thin‐films for photovoltaic applications: Post annealing conditions and property studies
    (Elsevier, 2023) Nwambaekwe, Kelechi C.; Batir, Valentin P.; Dermenji, Lazari
    Kesterite materials were investigated for their suitability as absorber layers for thin-film photovoltaic cells. Thin- films of copper cadmium zinc tin sulfide (Cu2CdxZn1-xSnS4) were prepared by spray pyrolysis on soda-lime glass. The obtained thin-films were subjected to post annealing treatment at 525 ◦C in a sulfur atmosphere to study the effects on morphology, stoichiometry, phase formation and optical properties by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and ultraviolet visible spectroscopy (UV–Vis). The XRD patterns revealed the presence of prominent kesterite peaks in the unannealed and annealed thin-films, with enhanced crystallinity in the annealed thin-films. The crystal sizes of the unannealed and annealed thin-films were estimated from the XRD data and ranged from 5 nm to 27 nm for unannealed thin-films and 13 nm–25 nm for annealed thin-films. The unannealed thin-films exhibited a non-uniformly shaped morphology, which was a mixture of cube-shaped and rod-shaped nanoparticles, while the annealed thin-films exhibited a uniformly shaped morphology of flake-shaped nanoparticles, indicating enhanced crystallinity.