Browsing by Author "Malgas, Gerald"
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Item Annealing effect of hybrid solar cells based on poly (3-hexylthiophene) and zinc-oxide nanostructures(Elsevier, 2013) Motaung, David; Malgas, Gerald; Ray, Suprakas S.; Arendse, ChristopherThe structural growth and optical and photovoltaic properties of the organic–inorganic hybrid structures of zinc oxide (ZnO)-nanorods/poly-3-hexylthiophene (P3HT) and two variations of organic polymer blends of ZnO/ P3HT:C60 fullerene and ZnO/P3HT:6,6]-phenyl C61 butyric acid methyl ester were studied in detail during thermal annealing. The ordering of the P3HT nanocrystals increased during annealing, which also improved hole transport in the hybrid structures. The optical constants of the ZnO/P3HT:[6,6]-phenyl C61 butyric acid methyl ester (PCBM) films elevated with annealing temperature due to the improved crystallisation induced by the formation of P3HT crystalline domains. As a result, a maximum power conversion efficiency of approximately 1.03% was achieved for the annealed ZnO/P3HT:PCBM device at 140 °C. These findings indicate that ZnO-nanorods/P3HT:PCBM films are stable at temperatures up to 160 °C.Item Comparative study: the effect of annealing conditions on the properties of P3HT:PCBM blends(Springer Verlag, 2013) Motaung, David E.; Malgas, Gerald; Nkosi, Steven S.; Mhlongo, Gugu H.; Mwakikunga, Bonex W.; Malwela, Thomas; Arendse, Christopher; Muller, Theophillus F. G.; Cummings, Franscious R.This paper presents a detailed study on the role of various annealing treatments on organic poly(3-hexylthiophene) and [6]-phenyl-C61-butyric acid methyl ester blends under different experimental conditions. A combination of analytical tools is used to study the alteration of the phase separation, structure and photovoltaic properties of the P3HT:PCBM blend during the annealing process. Results showed that the thermal annealing yields PCBM ‘‘needle-like’’ crystals and that prolonged heat treatment leads to extensive phase separation, as demonstrated by the growth in the size and quantity of PCBM crystals. The substrate annealing method demonstrated an optimal morphology by eradicating and suppressing the formation of fullerene clusters across the film, resulting in longer P3HT fibrils with smaller diameter. Improved optical constants, PL quenching and a decrease in the P3HT optical bad-gap were demonstrated for the substrate annealed films due to the limited diffusion of the PCBM molecules. An effective strategy for determining an optimized morphology through substrate annealing treatment is therefore revealed for improved device efficiency.Item Self-catalytic growth of tin oxide nanowires by chemical vapor deposition process(Hindawi, 2013) Thabethe, Bongani; Malgas, Gerald; Motaung, David; Malwela, Thomas; Arendse, ChristopherWe report on the synthesis of tin oxide (SnO2) nanowires by a chemical vapor deposition (CVD) process. Commercially bought SnO nanopowders were vaporized at 1050∘C for 30 minutes with argon gas continuously passing through the system. The assynthesized products were characterized using UV-visible absorption spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM). The band gap of the nanowires determined from UV-visible absorption was around 3.7 eV.The SEM micrographs revealed “wool-like” structure which contains nanoribbons and nanowires with liquid droplets at the tips. Nanowires typically have diameter in the range of 50–200nm and length 10–100 𝜇m. These nanowires followed the vapor-liquid-solid (VLS) growth mechanism.