17 research outputs found
Influence of cobalt redox couple concentration on the characteristics of liquid and quasi-solid electrolytes and on the photovoltaic parameters of dye-sensitised solar cells
No full textDye-sensitised solar cell (DSSC) is a next-generation solar energy conversion device. The electrolyte, which is one of the key components of a DSSC, greatly affects its short-circuit current density (Jsc) and open-circuit voltage (Voc) and hence, its overall performance. In this work, bis(trifluoromethane)sulfonimide (TFSI) cobalt complex was used for the first time as redox couple in DSSC, and an effort was carried out to study the effects of the varying concentration of cobalt complex redox ions on the characteristics of the prepared liquid electrolytes (LEs) and quasi-solid electrolytes (QEs), and on the photovoltaic parameters of DSSCs. Specifically, the electrolyte characteristics include the viscosity and electrical conductivity, while the photovoltaic parameters of DSSCs include Jsc, Voc, fill factor (FF) and power conversion efficiency (PCE). The viscosity of electrolytes was found to increase with increasing molar concentrations and then further increased with the addition of polyethylene oxide (PEO); the highest viscosity of 2.49 cP was obtained at 44 rpm for QE-50. The highest conductivity measured by electrochemical impedance spectroscopy was 83 mS cm− 1 for LE-50. Finally, zinc oxide-based DSSCs with platinum counter electrodes were fabricated for current-voltage measurements. Among the synthesised electrolytes, QE-35-based DSSC showed a better combination of Jsc and Voc, resulting in a PCE of 0.48%
Perovskite and perovskite inspired materials: synthesis and optoelectronic applications
No full textPerovskite materials have captivated the scientific community with their exceptional optoelectronic properties, but instability and toxicity have hindered their widespread adoption. This thesis presents innovative strategies to address these limitations, unlocking the true potential of perovskite technologies. The first project explores the utilization of FAPbBr3, a relatively stable perovskite composition, for memory device applications. In contrast to the widely studied MAPbI3, FAPbBr3 demonstrates enhanced stability, offering a viable alternative for reliable and long-lasting memory solutions. The second project delves into the microstructural engineering of AgBiI4 perovskites for solar cells. Through strategic antisolvent engineering, the researchers precisely controlled the film morphology, leading to marked improvements in device performance and paving the way for the deployment of AgBiI4 in efficient and environmentally-friendly inverted solar cell architectures. The final project tackles toxicity by investigating in-situ metal passivation for AgBiS2 solar cells. The novel passivation technique mitigated the detrimental effects of defects and grain boundaries, resulting in a significant enhancement in the photovoltaic performance of these lead-free perovskite-inspired materials. Collectively, the insights and advancements presented in this thesis lay the groundwork for a sustainable and prosperous future in perovskite-based technologies, transforming how we harness and utilize clean energy sources.</p
Two dimensional perovskites
No full textPerovskite materials have attracted tremendous attention in the field of material science and technology owing to their unique properties like tunable band gap, high carrier mobility, long diffusion length and high molar absorptivity coefficient. Among 2D perovskites the layered materials have been extensively studied in comparison to non-layered 2D perovskites. But non layered perovskites have emerged as a class of potential materials possessing unique structure and optoelectronic properties which make them suitable for many applications. This chapter will focus on the comprehensive review of synthesis, structure, properties and applications of non-layered 2D perovskites. We will discuss the crystal structure of these materials in comparison to their layered counterparts, followed by an insight of their physical properties and finally their applications. Overall, this chapter will provide insights into the potential of non-layered 2D perovskites as an emerging class of materials.</p
Organic-inorganic halide perovskites for memristors
No full textOrganic-inorganic halides perovskites (OHPs) have drawn the attention of many researchers owing to their astonishing and unique optoelectronic properties. They have been extensively used for photovoltaic applications, achieving higher than 26% power conversion efficiency to date. These materials have potential to be deployed for many other applications beyond photovoltaics like photodetectors, sensors, light-emitting diodes (LEDs), and resistors. To address the looming challenge of Moore's law and the Von Neumann bottleneck, many new technologies regarding the computation of architectures and storage of information are being extensively researched. Since the discovery of the memristor as a fourth component of the circuit, many materials are explored for memristive applications. Lately, researchers have advanced the exploration of OHPs for memristive applications. These materials possess promising memristive properties and various kinds of halide perovskites have been used for different applications that are not only limited to data storage but expand towards artificial synapses, and neuromorphic computing. Herein we summarize the recent advancements of OHPs for memristive applications, their unique electronic properties, fabrication of materials, and current progress in this field with some future perspectives and outlooks.</p
Antenatal HIV Screening and Treatment in South Africa: Social Norms and Policy Options
No full textSouth Africa has one of the highest prevalence of HIV and AIDS in the world, with mother-to-child transmission being an important route for spread of the infection. For years, AIDS scientists and activists locally and internationally have been working desperately for the people of South Africa to have access to treatment for HIV and AIDS. Policymakers in South Africa have consistently maintained that HIV infection is not responsible for AIDS, thus creating the biggest obstacle to implementation of appropriate prevention and therapeutic programmes, including antiretroviral therapy for HIV positive persons. Only recently, people within the government and ruling party, defying previous policy, have agreed that antiretroviral drugs should be given to pregnant women with HIV. The social fabric of South African society is markedly different from that of Western countries. In this paper, the author analyses the likely implications of antenatal testing and treatment of pregnant women in South Africa, in light of the socio-economic and cultural status of women in that society. (Afr J Reprod Health 2004; 8[2]: 77-85
A Sequenced Study of Improved Dielectric Properties of Carbon Nanotubes and Metal Oxide-Reinforced Polymer Composites
No full textPolymers have gained attraction at the industrial level owing to their elastic and lightweight nature, as well as their astonishing mechanical and electrical applications. Their scope is limited due to their organic nature, which eventually leads to the degradation of their properties. The aim of this work was to produce polymer composites with finely dispersed metal oxide nanofillers and carbon nanotubes (CNTs) for the investigation of their charge-storage applications. This work reports the preparation of different polymeric composites with varying concentrations of metal oxide (MO) nanofillers and single-walled carbon nanotubes (SWCNTs). The successful synthesis of nanofillers (i.e., NiO and CuO) was carried out via the sonication and precipitation methods, respectively. After, the smooth and uniform polymeric composite thin films were prepared via the solution-casting methodology. Spectroscopy and diffraction techniques were used for the preliminary characterization. Scanning electron microscopy was used to check the dispersion of carbon nanotubes (CNTs) and MOs in the polymer matrix. The addition of nanofillers and carbon nanotubes (CNTs) tuned the bandgap, reduced the strain, and enhanced the elastic limit of the polymer. The addition of CNT enhanced the mechanical strength of the composite; however, it increased the conductivity, which was tuned by using metal oxides. By increasing the concentration of NiO and CuO from 2% to 6% bandgap of PVA, which is 5–6 eV reduced to 4.41 and 4.34 eV, Young’s moduli of up to 59 and 57.7 MPa, respectively, were achieved. Moreover, improved dielectric properties were achieved, which shows that the addition of metal oxide enhances the dielectric behavior of the material
Antenatal HIV Screening and Treatment in South Africa: Social Norms and Policy Options
No full textSouth Africa has one of the highest prevalence of HIV and AIDS in the world, with mother-to-child transmission being an important route for spread of the infection. For years, AIDS scientists and activists locally and internationally have been working desperately for the people of South Africa to have access to treatment for HIV and AIDS. Policymakers in South Africa have consistently maintained that HIV infection is not responsible for AIDS, thus creating the biggest obstacle to implementation of appropriate prevention and therapeutic programmes, including antiretroviral therapy for HIV positive persons. Only recently, people within the government and ruling party, defying previous policy, have agreed that antiretroviral drugs should be given to pregnant women with HIV. The social fabric of South African society is markedly different from that of Western countries. In this paper, the author analyses the likely implications of antenatal testing and treatment of pregnant women in South Africa, in light of the socio-economic and cultural status of women in that society. (Afr J Reprod Health 2004; 8[2]: 77-85 )
KEY WORDS: HIV screening, South Africa, pregnant women
Dépistage et traitement prénatals du VIH en Afrique du Sud: normes sociales et options des politiques.
L\'Afrique du Sud a une des plus hautes prévalences du VIH et SIDA du monde, dont la transmission de la mère à l\'enfant est une voie importante pour la propagation de l\'infection. Depuis des années, les scientifiques et des activistes du SIDA sur le plan local et international, travaillent désespéremment pour que les gens d\'Afrique du Sud aient un accès au traitement pour le VIH et le SIDA. Les décisionnaires en Afrique du Sud ont systématiquement insisté sur le fait que l\'infection du VIH n\'est pas responsable du SIDA, créant ainsi le plus grand obstacle à la réalisation de la prévention appropriée et des programmes thérapeutiques, y compris la thérapie antirétrovirale pour les personnes séropositives. Très récemment, les fonctionnaires et les membres du parti politique au pouvoir, au mépris de l\'ancienne politique, ont accepté que les médicaments antirétroviraux soient donnés aux femmes enceintes séropositives. Le tissu social de la société sud africaine est remarquablement différent de celui des pays occidentaux. Dans cet article, l\'auteur fait une analyse des implications probables du dépistage et traitement prénatals des femmes enceintes en Afrique du Sud, à la lumière de la situation socio-économique et culturelle des femmes dans cette société-là. (Rev Afr Santé Reprod 2004; 8[2]: 77-85
Advancement in QDs for optoelectronic applications and beyond
No full textThis review focuses on the history and current state of the art optoelectronic applications of quantum dots involving light emission. We focus mainly on three areas of commercial, or potential commercial interest, including quantum dot light emitting devices (QLEDs, sometimes called QD-LEDs), lasing applications, and quantum computing applications. The main connection between these areas is the development of the science and engineering needed to achieve electrical excitation of the quantum dot in an optoelectronic device in order to achieve emission with characteristics particularly suited to the application in question. Due to the special physics of quantum dots, these materials are particularly well suited for both existing commercial applications, and potentially for future applications, such as single photon sources, spin cubits, or polarized emission. We conclude with an analysis of the future prospects for these exciting materials. Given 30 years of progress since the Nobel Prize winning work on monodisperse samples of QDs, our goal is to highlight the current start of the art, discuss the current issues for each technology, and suggest future goals for the next 30 years for quantum dot research. (Figure presented.)</p
Nanomaterials for spin-based quantum information
No full textQuantum information science has garnered significant attention due to its potential in solving problems that are beyond the capabilities of classical computations based on integrated circuits. At the heart of quantum information science is the quantum bit or qubit, which is used to carry information. Achieving large-scale and high-fidelity quantum bits requires the optimization of materials with trap-free characteristics and long coherence times. Nanomaterials have emerged as promising candidates for building qubits due to their inherent quantum confinement effect, enabling the manipulation and addressing of individual spins within nanostructures. In this comprehensive review, we focus on quantum bits based on nanomaterials, including 0D quantum dots, 1D nanotubes and nanowires, and 2D nanoplatelets and nanolayers. Our review aims to bridge the gap between nanotechnology and quantum information science, with a particular emphasis on material science aspects such as material selection, properties, and synthesis. By providing insights into these areas, we contribute to the understanding and advancement of nanomaterial-based quantum information science.</p
A Sequenced Study of Improved Dielectric Properties of Carbon Nanotubes and Metal Oxide-Reinforced Polymer Composites
No full textPolymers have gained attraction at the industrial level owing to their elastic and lightweight nature, as well as their astonishing mechanical and electrical applications. Their scope is limited due to their organic nature, which eventually leads to the degradation of their properties. The aim of this work was to produce polymer composites with finely dispersed metal oxide nanofillers and carbon nanotubes (CNTs) for the investigation of their charge-storage applications. This work reports the preparation of different polymeric composites with varying concentrations of metal oxide (MO) nanofillers and single-walled carbon nanotubes (SWCNTs). The successful synthesis of nanofillers (i.e., NiO and CuO) was carried out via the sonication and precipitation methods, respectively. After, the smooth and uniform polymeric composite thin films were prepared via the solution-casting methodology. Spectroscopy and diffraction techniques were used for the preliminary characterization. Scanning electron microscopy was used to check the dispersion of carbon nanotubes (CNTs) and MOs in the polymer matrix. The addition of nanofillers and carbon nanotubes (CNTs) tuned the bandgap, reduced the strain, and enhanced the elastic limit of the polymer. The addition of CNT enhanced the mechanical strength of the composite; however, it increased the conductivity, which was tuned by using metal oxides. By increasing the concentration of NiO and CuO from 2% to 6% bandgap of PVA, which is 5–6 eV reduced to 4.41 and 4.34 eV, Young’s moduli of up to 59 and 57.7 MPa, respectively, were achieved. Moreover, improved dielectric properties were achieved, which shows that the addition of metal oxide enhances the dielectric behavior of the material
