STRUCTURAL, OPTICAL AND ELECTRICAL PROPERTIES OF ANNEALED Sb-DOPED CuInS 2 THIN FILMS GROWN BY THERMAL EVAPORATION METHOD

Structural optical and electrical properties of undoped and Sb-doped CuInS 2 thin films grown by single source thermal evaporation method on corning 7059 glass substrates heated at 100°C were studied. Sb species was mixed in the starting powders. The amount of the Sb source was determined to be in the range 0-4 Wt % molecular weight compared with the CuInS 2 alloy source. The films were annealed in vacuum at temperature of 200°C and in air atmosphere at temperature of 400°C for 2h. The effect of these annealing atmospheres on the properties of the films was studied by means of X-ray diffraction (XRD), optical reflection and transmission and resistance measurement. All the CuInS 2 /Sb films have relatively high absorption coefficient between 2.10 4 cm -1 and 10 5 cm -1 in the visible and the near-IR spectral range. We found that Sb-doped CuInS 2 thin films exhibit p-type conductivity and air annealing exhibit n-type conductivity

Progress in development of graded bandgap thin film solar cells with electroplated materials

Photovoltaic devices are developed mainly based on p-n or p-i-n type device structures, and these devices can utilise only a fraction of the solar spectrum. In order to further improve device parameters and move towards low-cost and high-efficiency next generation solar cells, device architectures capable of harvesting all photons available should be designed and developed. One such architecture is the fully graded bandgap device structure as proposed recently based on both n-type and p-type window layers. These designs have been experimentally tested using well researched GaAs/AlGaAs system producing impressive device parameters of open circuit voltage (Voc) ~1175 mV and fill factor (FF) ~0.85. The devices have also been experimentally tested for the evidence of impurity photovoltaic (PV) effect and impact ionisation taking place within the same device. Since these structures have been experimentally proved with a well-established semiconductor, the effort has been focussed on developing these devices using low-cost and scalable electroplated semiconductors, in order to minimise manufacturing cost. This paper reviews and summarises the work carried out during the past decade on this subject. Graded bandgap devices produced using only two or three electroplated semiconductor layers have been explored and their conversion efficiencies have gradually increased from 10.0%, through 12.8% to 15.3% for different structures. While the work is progressing along this line, the paper summarises the achievements to date

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance.

Investment in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing in Africa over the past year has led to a major increase in the number of sequences that have been generated and used to track the pandemic on the continent, a number that now exceeds 100,000 genomes. Our results show an increase in the number of African countries that are able to sequence domestically and highlight that local sequencing enables faster turnaround times and more-regular routine surveillance. Despite limitations of low testing proportions, findings from this genomic surveillance study underscore the heterogeneous nature of the pandemic and illuminate the distinct dispersal dynamics of variants of concern-particularly Alpha, Beta, Delta, and Omicron-on the continent. Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve while the continent faces many emerging and reemerging infectious disease threats. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Effect of Zinc Incorporation in CuInS2CuInS_{2} Thin Films Grown by Vacuum Evaporation Method

Structural, optical and electrical properties of Zn-doped $CuInS_2$ thin films grown by double source thermal evaporation method were studied. Evaporated thin films were grown from $CuInS_2$ powder by vacuum evaporation using resistively heated tungsten boats. The element Zn was evaporated from a thermal evaporation source. The amount of the Zn source was determined to be 0-4% molecular weight compared with $CuInS_2$ source. The effects of Zn on films properties were investigated using X-ray diffraction, optical transmission and reflection spectra. The films were annealed in vacuum at 260°C for 2 h. The Zn-doped samples have band-gap energy of 1.474-1.589 eV. We found that the Zn-doped $CuInS_2$ thin films exhibit p-type conductivity and we predict that Zn species can be considered as suitable candidates for use as doped acceptors to fabricate $CuInS_2$-based solar cells

Effect of Zinc Incorporation in CuInS 2

Structural, optical and electrical properties of Zn-doped $CuInS_2$ thin films grown by double source thermal evaporation method were studied. Evaporated thin films were grown from $CuInS_2$ powder by vacuum evaporation using resistively heated tungsten boats. The element Zn was evaporated from a thermal evaporation source. The amount of the Zn source was determined to be 0-4% molecular weight compared with $CuInS_2$ source. The effects of Zn on films properties were investigated using X-ray diffraction, optical transmission and reflection spectra. The films were annealed in vacuum at 260°C for 2 h. The Zn-doped samples have band-gap energy of 1.474-1.589 eV. We found that the Zn-doped $CuInS_2$ thin films exhibit p-type conductivity and we predict that Zn species can be considered as suitable candidates for use as doped acceptors to fabricate $CuInS_2$-based solar cells

Structural, morphological and optical properties of Cu2ZnxFe1-xSnS4 thin films grown by thermal evaporation

International audienceIn this study, Cu2ZnxFe1-xSnS4 (CZFTS) (0 ≤ x ≤ 1) thin films were grown under vacuum evaporation on unheated glass substrates followed by sulfurization at 400 °C. The effects of sulfurization on the structural, morphological and optical properties were investigated for CZFTS material by varying Fe content. Crystal structure and phase of CZFTS thin films were analyzed by X-ray diffraction technique and Raman spectroscopy. In addition, the elemental composition and the stoichiometry of films were studied using energy dispersive spectroscopy. Surface morphology of samples was examined by scanning electron microscopy. Optical properties such as absorption coefficient, and gap energies were determined by the measurement of transmittance and reflectance in the spectral range 300–1800 nm. X-ray analysis indicates that all sulfurized CZFTS films present a polycrystalline nature and exhibit a preferential orientation along (112) plane. Cu2FeSnS4 (x = 0) and Cu2ZnSnS4 (x = 1) crystallize in stannite structure with I-42 m and kesterite structure with I-4 space group, respectively. Raman analysis and elemental composition confirm that only the Cu2ZnSnS4 (x = 1) and CZ0.75F0.25TS (x = 0.75) phases are present with good crystallinity. Transmittance and reflectance spectra revealed that the films are homogenous mostly for x = 0.75 and 1. Structural and optical parameters like crystallite size, absorption coefficient and band gaps were estimated for all the x values

Prevalence and risk factors for urinary and anal incontinence in Tunisian middle aged women

Objectives: To estimate the prevalence of urinary incontinence and anal incontinence in Tunisian women and to identify their risk factors.Subjects and methods: A cross-sectional study was conducted among 402 female doctors and nurses randomly selected from 3 large hospitals in the center of Tunisia. The prevalence of urinary incontinence and anal incontinence were measured using validated questionnaires.Results: Overall 45.3% of women experienced incontinence (urinary incontinence or anal incontinence). The overall prevalence of urinary incontinence, anal incontinence and double incontinence were 45%, 6.3% and 6%, respectively. Factors associated with incontinence were postpartum urinary incontinence (OR 11.91, CI 4:72–30:04, P < 0.001), menopausal status (OR 11.72, CI 3:8–36:07, P < 0.001), arterial hypertension (OR 4.17, CI 1:61–10.81, P = 0.003), nurse occupation (OR 3.22, CI 1:62–6:36, P = 0.001) and constipation (OR 1.71, CI 1:02–2:87, P = 0.041). Medical help seeking was taken only by 21% of the incontinent women.Conclusion: Forty five percent of Tunisian women suffered from urinary or anal incontinence. A primary prevention for modifiable risk factors, such as postpartum pelvic floor physiotherapy and hypertension control, should be advised to women in order to optimize their quality of life

Structural and optical studies on antimony and zinc doped CuInS2 thin films

AbstractThe influence of Zn and Sb impurities on the structural, optical and electrical properties of CuInS2 thin films on corning 7059 glass substrates was studied. Undoped and Zn or Sb doped CuInS2 thin films were deposited by thermal evaporation method and annealed in vacuum at temperature of 450 ∘C Undoped thin films were grown from CuInS2 powder using resistively heated tungsten boats. Zn species was evaporated from a thermal evaporator all together to the CuInS2 powder and Sb species was mixed in the starting powders. The amount of the Zn or Sb source was determined to be in the range 0–4 wt% molecular weight compared with the CuInS2 alloy source. The films were studied by means of X-ray diffraction (XRD), Optical reflection and transmission and resistance measurements. The films thicknesses were in the range 450–750 nm. All the Zn: CuInS2 and Sb: CuInS2 thin films have relatively high absorption coefficient between 104 cm−1 and 105 cm−1 in the visible and the near-IR spectral range. The bandgap energies are in the range of 1.472–1.589 eV for Zn: CuInS2 samples and 1.396–1.510 eV for the Sb: CuInS2 ones. The type of conductivity of these films was determined by the hot probe method. Furthermore, we found that Zn and Sb-doped CuInS2 thin films exhibit P type conductivity and we predict these species can be considered as suitable candidates for use as acceptor dopants to fabricate CuInS2-based solar cells

Study of the beneficial effects of sodium doping Cu2ZnSnS4 material

International audienc