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In order to limit global warming to 1.5-2 °C deployed solar photovoltaic (PV) power must increase from today's 0.228 terawatts to 2-10 terawatts installed by 2030, depending on demand. These goals require increasing manufacturing capacity, which, in turn, requires lowering the cost of electricity produced by PV. However, high demand scenarios will require greater cost reductions in order to make PV generated electricity <i> as competitive </i> as it needs to be to enable this growth. It is unclear whether established PV technologies — silicon, CdTe, GaAs, or CuInxGa1-xSe2 — can achieve the necessary breakthroughs in efficiency and price. A newer technology known as the &apos;perovskite solar cell&apos; (PSC) has recently emerged as promising contender. <br>     In the last seven years the efficiency of PSCs increased by the same amount covered by established technologies in the last thirty. However, PSCs suffer from chemical instability under operating conditions and hysteresis in current-voltage measurements used to characterize power output. Characterizing the defect structures formed by this material and how they interact with device performance and degradation may allow stabilization of PSCs. To that end, this work investigates defects in perovskite solar cells, the impact of these defects on performance, and the effect of alloying and degradation on the electronically active defect structure. Chapter I gives a brief introduction, motivating research in solar cells generally and perovskites in particular as well as introducing some challenges the technology faces. Chapter II gives some background in semiconductors and the device physics of solar cells. Chapter III introduces the performance and defect characterization methods employed. Chapter IV discusses results of these measurements on methylammonium lead triiodide cells correlating defects with device performance. Chapter V applies the some of the same techniques to a series of CH3NH3Pb(I1-xBrx)3 based perovskites aged for up to 2400 hours to explore the impact of alloying and aging on the defect structure. Chapter VI discusses implications for perovskite development and directions for future research. <br>     This dissertation includes previously published co-authored material.

Software maintenance accounts for the most part of the software development cost and efforts, with its major activities focused on the detection, location, analysis and removal of defects present in the software. Although software defects can be originated, and be present, at any phase of the software development life-cycle, implementation (i.e., source code) contains more than three-fourths of the total defects. Due to the diverse nature of the defects, their detection and analysis activities have to be carried out by equally diverse tools, often necessitating the application of multiple tools for reasonable defect coverage that directly increases maintenance overhead. Unified detection tools are known to combine different specialized techniques into a single and massive core, resulting in operational difficulty and maintenance cost increment. The objective of this research was to search for a technique that can detect dissimilar defects using a simplified model and a single methodology, both of which should contribute in creating an easy-to-acquire solution. Following this goal, a ‘Supervised Automation Framework’ named FlexTax was developed for semi-automatic defect mapping and taxonomy generation, which was then applied on a large-scale real-world defect dataset to generate a comprehensive Defect Taxonomy that was verified using machine learning classifiers and manual verification. This Taxonomy, along with an extensive literature survey, was used for comprehension of the properties of different classes of defects, and for developing Defect Similarity Metrics. The Taxonomy, and the Similarity Metrics were then used to develop a defect detection model and associated techniques, collectively named Symbolic Range Tuple Analysis, or SRTA. SRTA relies on Symbolic Analysis, Path Summarization and Range Propagation to detect dissimilar classes of defects using a simplified set of operations. To verify the effectiveness of the technique, SRTA was evaluated by processing multiple real-world open-source systems, by direct comparison with three state-of-the-art tools, by a controlled experiment, by using an established Benchmark, by comparison with other tools through secondary data, and by a large-scale fault-injection experiment conducted using a Mutation-Injection Framework, which relied on the taxonomy developed earlier for the definition of mutation rules. Experimental results confirmed SRTA’s practicality, generality, scalability and accuracy, and proved SRTA’s applicability as a new Defect Detection Technique.

Nowadays liquid crystals have widely used for optical devices, even are attractive in display. But a major problem for nematic phase is its long response time, which hinders the phase to be used in high quality displays. Surface Stabilized Ferroelectric Liquid Crystal¡]SSFLC¡^is a thin device which has fast response time and exhibits excellent bistability. It can be applied in display. But it is difficult for SSFLC to achieve alignment without zigzag defects. This defect will reduce contrast ratio of display and cause image irregularities and flickering. This article discusses zigzag defects in SSFLC device. In experiment, we use convenient rubbing method to alignment FLC with high pre-tilt PI film. And we investigate the surface properties of polyimide (PI) films rubbed with different rubbing strength. We fabricate the SSFLCs without zigzag defects, and confirm that the great rubbing strength produce more zigzag defects for FLC alignment. In addition, we discuss the topography of smooth surface results in fewer defects. Finally, with the relationship between surface energy and different rubbing strength in PI film, we show the polarity of surface energy is a important role for FLC alignment.

The study of ferroelectric LiNbO<SUB>3</SUB> and LiTaO<SUB>3</SUB> doped with transition metals involves the characterisation of LiNbO<SUB>3</SUB>/LiTaO<SUB>3</SUB> solid solutions in the systems Li<SUB>2</SUB>O-Nb<SUB>2</SUB>O<SUB>5</SUB>-M<SUB>x</SUB>O<SUB>y</SUB> and Li<SUB>2</SUB>O-Ta<SUB>2</SUB>O<SUB>5</SUB>-M<SUB>x</SUB>O<SUB>y</SUB> (M = Cr, Mn, Fe, Co, Ni, Cu). Compounds were made by solid state reaction at temperatures between 1000 and 1500°C, depending on the system studied. The emphasis of this work is on the characterisation of the defect structure of LiNbO<SUB>3</SUB>/LiTaO<SUB>3</SUB> solid solutions using phase diagram determination, X-ray and neutron powder diffraction, EXAFS, ESR and optical spectroscopy. The valence of the incorporated cations was studied by magnetic measurements. The electrical properties of these materials have been investigated using AC impedance spectroscopy. It can be shown that the physical properties of LiNbO<SUB>3</SUB> and LiTaO<SUB>3</SUB> depend strongly on the defects in the structure which can be controlled by purposeful doping with other cations. Structural refinements of the X-ray and neutron powder diffraction data have shown that the defects arising from nonstoichiometry are accommodated by vacancies created on the Li site. This affects the structure when doped with third cations, giving rise to complex substitution mechanisms Spectroscopic studies have shown that the dopants (Cr<SUP>3+</SUP>, Mn<SUP>2+</SUP>/Mn<SUP>3+</SUP>, Co<SUP>2+</SUP>, Ni<SUP>2+</SUP>, Cu<SUP>+</SUP>, Cu<SUP>2+</SUP>) are shifted from the central octahedral position towards the adjacent empty octahedron. The electrical properties of LiNbO<SUB>3</SUB> and LiTaO<SUB>3</SUB>, measured by AC impedance spectroscopy, depend strongly on the dopant content: the conductivity generally rises, whereas the activation energy for the electrical conductivity drops with increasing dopant concentration. The microstructure of electroceramics can also be probed by AC impedance spectroscopy and it was shown that the texture of all samples was bad due to poor sintering of the pellets. Longer sintering times did not improve the quality of the ceramics which exhibit a large pore size distribution. An important aspect for future work would be the quality improvement of LiNbO<SUB>3</SUB>/LiTaO<SUB>3</SUB> based ceramics.

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No description available.

A number of different aspects of Frenkel defect production are discussed in this thesis. Experiments have been performed to characterise the response of sapphire to radiation and to determine the stability, with respect to temperature and subsequent ionising radiation, of the oxygen vacancies produced. The displacement threshold of the aluminium ion has been determined by irradiating with electrons and comparing measured concentrations of the V centre with theoretical values, and evidence is presented for the stability of the F²⁺ centre at liquid helium temperatures. The efficiency of point defect production in sapphire by a variety of ion beams has been estimated by monitoring the oxygen vacancy colour centre concentration. Results are presented for H, D, He, B, N, Ne, Ar and Kr bombardment at both room temperature and 77K. Experimentally determined values of the mean number of oxygen vacancies produced per incident ion are compared with theoretical values. The latter have been computed by solving the Lindhard integral equations to determine the partitioning of energy between the oxygen and aluminium sublattices. The stopping powers and cross sections of Ziegler, Biersack and Littmark have been used in these calculations and give significantly improved estimates of the damage energy. Two main points emerge from this study. Firstly, a significant Z₁ variation of the damage efficiency is noted for low mass ions. Secondly, in contrast to metals (in particular aluminium) no reduction in efficiency has been found in sapphire with increasing ion mass. This is attributed to differences in the 'thermal spike' behaviour, as a consequence of differing thermodynamic properties, between aluminium and its oxide. The implications of both these results for irradiation characterisation are discussed. In the final chapter we discuss the interaction between conduction electrons and ions in the cooling phase of cascades in metals. Differential equations governing the transfer of heat between the two systems are derived and solved numerically, using physically reasonable parameters for cascades in copper and nickel. Large differences are found in the cooling rates of cascades in these two metals. The degree of cooling due to electronic heat transport is shown to depend on the ratio of a parameter T₀, the temperature at which the electron-phonon mean free path reduces to the radius of the Wigner-Seitz sphere, and γ_e, the coefficient of the electronic heat capacity. The participation of the electronic system in cascade evolution is shown to preclude a universal description of damage efficiency on the basis of simple atomic scaling laws.

Abstract The defect structure of CuMX2 (M&#x00BA;In, Ga and X&#x00BA;S, Se, Te) was investigated. The defect concentrations were derived as a function of nonmolecularity( X) and nonstoichiometry( Y), and the carrier concentrations were calculated quantitatively using a theoretical defect model, which could be used to select the proper region of stoichiometry for device designs with specified carrier concentrations. The compensation reaction between dopants and intrinsic defects in CuMX2, compound semiconductors is quantitatively illustrated. If for a small increment of temperature the Fermi level EF is shifted by £GEF and the concentration of free majority carriers is increased by £Gn, then the ratio£Gn /£GEFis a measure of the defect-level concentration within£GEF. The electrical and optical properties of CuMX2 have been investigated using various types of electrically active intrinsic defects caused by deviations from the ideal stoichiometry of the compound. The defect complexes are formed by reactions among the impurity and native defects and/or among the native defects during crystal growth or during processing, and play a significant role in determining the characteristics and performance of devices by affecting lifetimes, degradation and breakdown etc.

BACKGROUND: The ventricular septal defect (VSD), a hole between the ventricles of the heart, is the most common birth defect. Despite its commonality, little is known about related in utero functional deficits. Furthermore, although about 80% of clinical VSD resolve within a year, the long-term effects after their resolution are unknown due to lack of clinical follow-up. Chemical treatment was used to induce VSD in the rat and to investigate their functional consequences both in utero and postnatally. METHODS: Pregnant Sprague-Dawley rats were administered six 300mg/kg doses of dimethadione (DMO) by oral gavage every 12 hours beginning at 19h00 on gestational day (GD) 8 (Weston et al., 2011). DMO is the N-demethylated metabolite of the anticonvulsant trimethadione, a potent inducer of VSDs clinically and in laboratory animals. Fetal heart structure and function were examined with high-resolution ultrasound on GD 14, 15, 16, 17, and 21. A separate cohort of rats was dosed using the described paradigm, but offspring were allowed to reach parturition and mature naturally. Postnatal heart structure and function were assessed using telemetry (70 days postnatally), high-resolution ultrasound, and electrocardiography (ECG) (one year postnatally). RESULTS: Relative to controls, DMO-treated fetal rats had structural defects including VSD, an increased incidence of bradycardia (23 vs. 45%) and dysrhythmia (1.2 vs. 11%), and a reduction in cardiac output, stroke volume, and mean heart rate. Adult rats exposed to DMO in utero were more physically active, had elevated blood pressure, and had a higher incidence of dysrhythmia associated with ECG disturbances compared to controls. Both in utero and postnatal functional deficits occurred independent of septum patency. CONCLUSIONS: Gestational exposure to DMO disrupted cardiac function both in utero and postnatally, even in the absence of gross structural defects, indicating chemical exposures in utero may have permanent pathophysiological consequences on the heart. / Thesis (Master, Pharmacology & Toxicology) -- Queen's University, 2012-05-30 17:19:35.529