Browsing by Author "Ramoroka, Morongwa E."

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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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    Fabrication, characterization, and photovoltaic performance of titanium dioxide/metal-organic framework composite
    (Elsevier, 2022) Ramaripa, Phuti S.; Modibane, Kwena D.; Ramoroka, Morongwa E.
    The titanium dioxide-metal-organic framework (TiO2−MOF) composite was prepared using the sol-gel method for photovoltaic applications. Raman analyses showed the presence of MOF clusters in the TiO2 sol-gel network. Using the Brunauer-Emmett-Teller method, the resultant composite material exhibited a surface area of 111.10 m2 g−1 as compared to the surface area values of 262.90 and 464.76 m2 g−1 for TiO2 and MOF, respectively. The small optical band gap values of 2.63 for direct electronic transition and 2.70 eV for indirect allowed electronic transition in TiO2/MOF composite were observed using ultraviolet-visible supported by cyclic voltammetry (CV).
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    Synthesis and photovoltaics of novel 2,3,4,5-tetrathienylthiophene-co-poly(3-hexylthiophene-2,5-diyl) donor polymer for organic solar cell
    (MPDI, 2021) Ramoroka, Morongwa E.; Mdluli, Siyabonga Beizel; John-Denk, Vivian S.
    This report focuses on the synthesis of novel 2,3,4,5-tetrathienylthiophene-co-poly(3-hexylthiophene-2,5-diyl) (TTT-co-P3HT) as a donor material for organic solar cells (OSCs). The properties of the synthesized TTT-co-P3HT were compared with those of poly(3-hexylthiophene-2,5-diyl (P3HT). The structure of TTT-co-P3HT was studied using nuclear magnetic resonance spectroscopy (NMR) and Fourier-transform infrared spectroscopy (FTIR). It was seen that TTT-co-P3HT possessed a broader electrochemical and optical band-gap as compared to P3HT. Cyclic voltammetry (CV) was used to determine lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) energy gaps of TTT-co-P3HT and P3HT were found to be 2.19 and 1.97 eV, respectively. Photoluminescence revealed that TTT-co-P3HT:PC71 BM have insuffi-cient electron/hole separation and charge transfer when compared to P3HT:PC71 BM. All devices were fabricated outside a glovebox. Power conversion efficiency (PCE) of 1.15% was obtained for P3HT:PC71 BM device and 0.14% was obtained for TTT-co-P3HT:PC71 BM device. Further studies were done on fabricated OSCs during this work using electrochemical methods.
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    Synthesis and reactivities of conducting hexathienylbenzene-co-poly(3-hexylthiophene) star-branched copolymer as donor material for organic photovoltaic cell
    (Frontiers Media, 2022) Ramoroka, Morongwa E.; Mdluli, Siyabonga B.; John-Denk, Vivian S.
    The hexathienylbenzene-co-poly(3-hexylthiophene-2,5diyl) (HTB-co-P3HT) conducting polymer was synthesized by oxidative co-polymerization of hexathienylbenzene (HTB) and 3-hexylthiophene using iron chloride (FeCl3) as an oxidant. The effect of chlorobenzene, toluene and chloroform on the optoelectronic characteristics of the polymer was investigated. The study revealed that spectroscopic and electrochemical responses of HTB-co-P3HT are affected by the nature of the solvent. The lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) energy levels of HTB-co-P3HT were determined from cyclic voltammetry (CV) and were compared to those of (6,6)-Phenyl C71 butyric acid methyl ester (PC71BM) and it was found that the LUMO energy levels of HTB-co-P3HT in toluene were lower than those for chlorobenzene and chloroform.