Journal Articles

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12504/113

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Browsing Journal Articles by Subject "DSSCs"

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    Co-sensitization effect of chlorophyll and anthocyanin on optical absorption properties and power conversion efficiency of dye-sensitized solar cells
    (Springer, 2024-04) Mukhokosi, Emma Panzi; Mohammed, Tibenkana; Loyce, Namanya; Botha, Nandipha L.; Maaza, Maliki; Velauthapillai, Dhayalan
    In this article, the chemical structure, optical absorption and photoluminescence properties of un/adsorbed dyes of hibiscus flower (H), pumpkin leaf (P), sweet potato leaf (S) and their composites (H: P & H: S) have been studied. The chemical structural properties revealed the O–H, C–C and C = O as the main anchoring functional groups. The optical absorption properties revealed two definite bands in between 450–500 nm and 600–680 nm wavelength for chlorophyll-based dyes and a peak at 526 nm for anthocyanin based dye extract. The composite dye extracts revealed optical absorption bands corresponding to chlorophyll and anthocyanin pigments with enhanced absorption of light. Five different solar cells based on H, P, S, H:P-3:1 and H:S-3:1 were developed and revealed an efficiency of ~ 0.08, 0.3, 0.5, 0.7 and ~ 1% respectively. The efficiency was reduced by half after 30 days. The composites had the highest power conversion efficiency due to more O–H, C–C and C = O binding sites on TiO2 nanoparticles, reduced rate of electron–hole pair recombination and a wide range of optical absorption. These studies suggest that co-pigmentation can be an alternative strategy to increasing the power conversion efficiency in DSSCs.
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    Green synthesis of ZnO nanoparticles for DSSC photoanode : a joint experimental and density functional theory study
    (Materials Research Express, 2025-09-29) Balabye, Stephen Emma; Mushebo, Emmanuel; Nasejje, Stella; Egor, Moses; Mukhokosi, Emma Panzi
    Green synthesis, a biological method for nanoparticle preparation, has been suggested as a possible eco-friendly alternative to chemical and physical methods. In this study, we report on first principles calculations and the green synthesis of zinc oxide (ZnO) nanoparticles (NPs) from Erythrina abyssinica stem bark extract calcined under different temperatures (300-700 ℃) for application as a photoanode in dye sensitized solar cells (DSSCs). Synthesized ZnO NPs were subjected to characterization using X-Ray diffraction, Scanning Electron Microscopy, Energy Dispersive X-Ray spectroscopy, Ultraviolet–Visible spectroscopy and photoluminescence analysis. The analysis revealed that highly crystalline hexagonal ZnO NPs were formed at 700 ℃, with the nanospheres agglomeration into non-uniform distinct NPs with a band gap energy of 3.12 eV. The DSSC exhibited a short circuit current density (Jsc) of 56 µA cm-2, open circuit voltage (Voc) of 161 mV, a fill factor of 0.265, and a power conversion efficiency of 0.0024% using 100 mWcm-2 illumination. Density Functional Theory (DFT) calculations were performed on the structural, electronic, and dielectric properties of ZnO at the atomic level. The Projected Density of States (PDOS) analysis revealed that Zn-4s and O-2p orbitals contributed significantly to the conduction band minimum (CBM) and valence band maximum (VBM), respectively, and a direct band gap at Gamma in the electronic band structure. Dielectric function analysis revealed anisotropy in the refractive index and dielectric function, with noticeable transparency in the visible spectrum and strong absorption in the ultraviolet, making them potential candidates in a set of photoelectrochemical applications.