Browsing by Author "Malwela, Thomas"

Now showing 1 - 3 of 3
  • Thumbnail Image
    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.
  • Thumbnail Image
    Item
    Self-catalytic growth of tin oxide nanowires by chemical vapor deposition process
    (Hindawi, 2013) Thabethe, Bongani; Malgas, Gerald; Motaung, David; Malwela, Thomas; Arendse, Christopher
    We 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.
  • Thumbnail Image
    Item
    Study of magnetic properties of nanostructures on self-assembled patterns
    (University of the Western Cape, 2010) Malwela, Thomas; Hillie, Thembela; Tchokonte, Moise Tchoula; Dept. of Physics; Faculty of Science
    In the current study, we give a report when oxalic acid was used as an electrolyte to synthesize an AAO template with hexagonal pore array. Optimum parameters were observed as 0.4 M of oxalic acid, anodizing voltage of 45 V, temperature of approximately 8 °C and the period of 120 minutes. Atomic force microscope (AFM) and High resolution scanning electron microscope (HRSEM) showed that template has an average pore diameter of 103 nm. Co and MnOx (x = 1,2) nanostructures were selectively deposited in the pores of the template using a novel atomic layer deposition (ALD) technique. The diameter sizes and the array of the nanostructures and the template were corresponding. Energy dispersive xrays (EDX) and X-ray photoelectron spectroscopy (XPS) confirmed the presence of Co and MnOx (x =1,2) on the samples while x-ray diffraction (XRD) provided an indication of their orientations. Magnetic force microscopy as main characterization tool showed the existence of multi-domains on both Co and MnOx (x =1,2) nanostructures.