3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item Iinvestigation of ZnO, and AZnO and rare earth doped ZnO thin films for spectral conversion and application to solar cells(2018) Otieno, Francis OtienoRecently Zinc oxide has drawn a resurgent attention in semiconductor industry due to its interesting properties with diverse application potential. These properties include high exciton binding energy, high resistance against radiation, high breakdown voltage, insensitivity to visible light, and easy wet chemical etching. The high quantum efficiency for emission by ZnO has seen it being considered a strong candidate for solid-state white lighting applications as well as transparent conductor electrode in solar cells. In order to realize efficient utilization of the multi-functional properties of ZnO for electronic and opto-electric applications, ZnO is usually doped with different elements. Such doping is aimed at enhancing and controlling its electrical, optical and multi-functional properties. Typical dopants widely used are trivalent atoms categorized as group III in the periodic table (Al, In, Ga) through substitution of cations. The as-grown ZnO thin film is usually n-type semiconductor with structural, electrical and optical properties that can be varied depending on the growth conditions as well as post deposition treatment such as thermal annealing. The use of RF sputtering for ZnO deposition has been explored in this work through varying deposition time, RF power and the partial pressure of oxygen. The films were then subjected to ex-situ thermal annealing in Argon filled furnace leading to a significant increase in grain size. Rare earth (RE) doping of materials has been widely investigated owing to the prominent and desirable optical and magnetic properties. Typically trivalent rare earths elements such as Sm+, Tb3+ and Eu3+ are investigated in this research project. ZnO doped with RE has exhibited electroluminescence, thus highlighting its potential for photovoltaic applications as a bi-functional layer. A doped ZnO layer is thus simultaneously utilized as transparent conducting electrode and as a spectral conversion layer. The RE doped luminescent materials provide an opportunity to effectively use the high energy and sub-band gap energy photons from the solar spectrum that would have otherwise been lost in direct band gap absorbers. In solar cells, they have been applied with an intention to reduce the fundamental thermalization losses arising as a result of the intrinsic properties of the semiconductor material namely: (a) sub-bandgap photon loss (b) thermalization of charge carriers resulting from absorption of high energy photons. From the X-ray diffraction (XRD) patterns both pristine and doped ZnO thin films showed growth along the c-axis of the wurtzite structure. The peaks were found to match the reflection planes of (100), (002) and (102) with all the diffraction peaks being well indexed to the wurtzite structure of ZnO of the space group P63mc, which is consistent with the standard values reported in JCPDS, card no. 03-0888. The structural properties of the material were investigated using a -scanning electron microscope (SEM) and Atomic force microscopy (AFM) where the particle size, roughness, skewness and kurtosis were found to change with growth condition and annealing temperature. Most importantly, the results indicated that the photoluminescence (PL) properties reflect the quality of the pristine and doped ZnO. The films were then used in the fabrication of the solar cells as a bi-functional layer and thus as a proof of concept of good transparent conducting oxides (TCOs) and for spectral conversion. RBS measurements indicated the depth profile distribution of Zn, O and various rare earths which showed homogeneity in depth distribution without any external impurity.Item Knowledge management determinants of breakthrough research productivity(2018) Rubin, AsafRecent technological advancements have brought about a wave of drastic change in the global supply and demand of knowledge and subsequently, in the generation of innovation. However, it has been argued that some industries and academic fields do not sufficiently take advantage of new opportunities afforded by the widespread, free and open availability of knowledge. Terms such as the Death of Innovation, Innovation Failure and Academic Failure have been used to describe the market failure of industrial Research and Development (R&D) and certain forms of academic research to sufficiently leverage these new opportunities, particularly with regard to societal problem-solving. An extensive and rapidly growing body of literature pertaining to new modes of knowledge productivity, such as open innovation, crowdsourcing and crowdfunding, through the use of the Internet, has demonstrated evidence that certain new technologies and methodologies may indeed offer significant economies of scope and scale in innovative problem solving. However, misaligned incentives may in some cases prevent the efficient leveraging of these new modes of productivity. These effects may be particularly pronounced in the academic context, which has long been criticised for its strict adherence to tradition and paradigmatic convergence. Despite this body of literature, there is a lack of knowledge as to the extent that academic researchers do indeed take advantage of these new modes of productivity, and furthermore, the extent to which their adoption influences research productivity. Thus, this research seeks to investigate the relationship between a behavioral orientation called ‘technological propensity’, or the extent to which individuals seize opportunities that offer significant economies of scale (such as crowdsourcing) and productivity. This research is undertaken at the individual level of analysis, which necessitates corresponding measurements of proximal, human-resources management determinants which may impact this relationship. These include personality, motivational values, work climate perceptions and human capital investments. Three studies are conducted to ascertain the extent of the relationships between these variables, and to provide a holistic perspective of the relationships between variables. First, a qualitative study, which samples award-winning scientists, academics researchers and innovators from across the world was conducted to develop theory. Amongst these are 3 Nobel Prize winners, 3 Lasker Award winners and 1 Fields Medal winner, among others. Second, a quantitative study, which sampled South African academic researchers, was conducted to test theory. Third and finally, a second quantitative study, which sampled ‘crowd-workers’, or users of an Internet-based crowdsourcing platform known as Amazon’s Mechanical Turk, was conducted to provide ii further insights into the relationships under study, in the open knowledge space (i.e. over the Internet). Qualitative data is analysed inductively, using thematic content analysis. Quantitative data is analysed through a series of statistical analyses, including multiple regression, mediation and moderation analyses. The findings of these studies suggest that the relationship between technological propensity and productivity is context-dependent and may only be suitable as a complementary methodology to certain forms of academic research, which is especially constrained by outside influences. Certain new modes of productivity may indeed enhance the rate at which ‘breakthrough’, or radically innovative research outputs are generated. The findings also suggest that differences in certain values-configurations and human capital investments may significantly impact this relationship. Based on the research findings, recommendations are made to improve research productivity in these contexts and recommendations for practice and for further research are made.