46 research outputs found
Effects of different needles and substrates on CuInS2 deposited by electrostatic spray deposition
Copper indium disulphide (CuInS2) thin films were deposited using the electrostatic spray deposition method. The effects of applied voltage and solution flow rate on the aerosol cone shape, film composition, surface morphology and current conversion were investigated. The effect of aluminium substrates and transparent fluorine doped tin oxide (SnO2:F) coated glass substrates on the properties of as-deposited CuInS2 films were analysed. An oxidation process occurs during the deposition onto the metallic substrates which forms an insulating layer between the photoactive film and substrate. The effects of two different spray needles on the properties of the as-deposited films were also studied. The results reveal that the use of a stainless steel needle results in contamination of the film due to the transfer of metal impurities through the spray whilst this is not seen for the glass needle. The films were characterised using a number of different analytical techniques such as X-ray diffraction, scanning electron microscopy, Rutherford back-scattering and secondary ion mass spectroscopy and opto-electronic measurements
Use of combinatorial analysis for the study of new material for solar cells applications
This paper presents a combinatorial method for the deposition and
characterization of new metallic precursors for photovoltaic materials.
Onedimensional thin film alloy âlibrariesâ were electrodeposited on Mo-coated
glass. The library elements were deposited in two consecutive baths and then
heated in a reducing atmosphere to promote interdiffusion of the elements. At
the end of this process, the libraries possessed a composition gradient along
their lengths, with single elements at their two opposite ends and one or more
alloys and/or a solid state solution in between. This continuous range of
compositions can therefore be considered a collection of specific precursors
that can be interrogated by examining their corresponding locations, with the
crystallographic structure along the library changing in accordance with the
phase diagram for the metals. The libraries were then sulphurised or selenised
by heating in a sulphur-rich or selenium rich atmosphere; this converted the
metallic precursors in a continuous range of materials, candidates for potential
solar cells absorbers. The libraries were analysed by X-ray diffraction and
energy dispersive X-ray spectrometry. The X-ray diffraction results show phase
changes across the libraries, which can be correlated with the original
precursor concentration at that particular p
MOCVD of ultra-thin PV solar cell devices using a pyrite based p-i-n structure
Ultra-thin photovoltaic (PV) devices were produced by atmospheric pressure metal organic chemical vapour deposition (AP-MOCVD) incorporating a highly absorbing intermediate sulphurised FeSâ layer into a CdS/CdTe structure. X ray diffraction (XRD) confirmed a transitional phase change to pyrite FeSâ after post growth sulphur (S) annealing of the FeSâ layer between 400â°C and 500â°C. Devices using a superstrate configuration incorporating a sulphurised or non sulphurised FeSâ layer were compared to p-n devices with only a CdS/CdTe structure. Devices with sulphurised FeSâ layers performed least efficiently, even though pyrite fractions were present. Rutherford back scattering (RBS) confirmed deterioration of the CdS/FeSâ interface due to S inter-diffusion during the annealing process
Effects of different needles and substrates on CuInS2 deposited by electrostatic spray deposition
The Global Durum Wheat Panel (GDP): An International Platform to Identify and Exchange Beneficial Alleles
Representative, broad and diverse collections are a primary resource to dissect genetic diversity and meet pre-breeding and breeding goals through the identification of beneficial alleles for target traits. From 2,500 tetraploid wheat accessions obtained through an international collaborative effort, a Global Durum wheat Panel (GDP) of 1,011 genotypes was assembled that captured 94-97% of the original diversity. The GDP consists of a wide representation of Triticum turgidum ssp. durum modern germplasm and landraces, along with a selection of emmer and primitive tetraploid wheats to maximize diversity. GDP accessions were genotyped using the wheat iSelect 90K SNP array. Among modern durum accessions, breeding programs from Italy, France and Central Asia provided the highest level of genetic diversity, with only a moderate decrease in genetic diversity observed across nearly 50 years of breeding (1970-2018). Further, the breeding programs from Europe had the largest sets of unique alleles. LD was lower in the landraces (0.4 Mbp) than in modern germplasm (1.8 Mbp) at r 2 = 0.5. ADMIXTURE analysis of modern germplasm defined a minimum of 13 distinct genetic clusters (k), which could be traced to the breeding program of origin. Chromosome regions putatively subjected to strong selection pressure were identified from fixation index (F st ) and diversity reduction index (DRI) metrics in pairwise comparisons among decades of release and breeding programs. Clusters of putative selection sweeps (PSW) were identified as co-localized with major loci controlling phenology (Ppd and Vrn), plant height (Rht) and quality (gliadins and glutenins), underlining the role of the corresponding genes as driving elements in modern breeding. Public seed availability and deep genetic characterization of the GDP make this collection a unique and ideal resource to identify and map useful genetic diversity at loci of interest to any breeding program
Severe asthma: One disease and multiple definitions
Introduction: There is, so far, no universal definition of severe asthma. This definition usually relies on: number of exacerbations, inhaled therapy, need for oral corticosteroids, and respiratory function. The use of such parameters varies in the different definitions used. Thus, according to the parameters chosen, each patient may result in having severe asthma or not. The aim of this study was to evaluate how the choice of a specific definition of severe asthma can change the allocation of patients. Methods: Data collected from the Severe Asthma Network Italy (SANI) registry were analyzed. All the patients included were then reclassified according to the definitions of U-BIOPRED, NICE, WHO, ATS/ERS, GINA, ENFUMOSA, and TENOR. Results: 540 patients, were extracted from the SANI database. We observed that 462 (86%) met the ATS/ERS criteria as well as the GINA criteria, 259 (48%) the U-Biopred, 222 (41%) the NICE, 125 (23%) the WHO, 313 (58%) the Enfumosa, and 251 (46%) the TENOR criteria. The mean eosinophil value were similar in the ATS/ERS, U-Biopred, and Enfumosa (528, 532 and 516 cells/mcl), higher in WHO and Tenor (567 and 570 cells/mcl) and much higher in the NICE classification (624 cells/mcl). Lung function tests resulted similarly in all groups, with WHO (67%) and ATS/ERS-GINA (73%), respectively, showing the lower and upper mean FEV1 values. Conclusions: The present observations clearly evidence the heterogeneity in the distribution of patients when different definitions of severe asthma are used. However, the recent definition of severe asthma, provided by the GINA document, is similar to that indicated in 2014 by ATS/ERS, allowing mirror reclassification of the patients examined. This lack of homogeneity could complicate the access to biological therapies. The definition provided by the GINA document, which reflects what suggested by ATS/ERS, could partially overcome the problem
A study of electrostatically sprayed CuInS2 and ZnS thin films
The investigation of ternary compounds for the fabrication of thin film solar cells is well
documented but the production of thin films by electrostatic spray deposition (ESD) is still limited.
This thesis represents the first attempt to deposit photovoltaic thin films using this novel method.
The lack of information regarding the deposition of CuInS2 by ESD required a statistical
investigation of the effects of different deposition variables. To achieve this, a new image analysis
method was developed to calculate the variation of the thickness of the as-deposited films using
their optical density. The thickness variation across the sample was then used to define its
uniformity.
Once the conditions for the best uniformity were defined, different needle and substrate materials
were investigated to try and improve the performance of the ESD method for potential large scale
production.
A formation of precipitates was observed during the preparation of the chloride precursor solutions
(prepared from CuCl2, InCl3 and thiourea salts). A possible reaction mechanism was proposed and
the chemical composition of precipitates analysed. An explanation of the absence of the precipitate
during the preparation of a nitrate starting solution (from Cu(NO3)2, In(NO3)3 and thiourea salts)
was reported.
The behaviour of the aerosol cone for the two different starting solutions (nitrate and chloride) was
established using the laser-based particle image velocimetry (PIV) measurement technique. The
properties of as-deposited films sprayed by the two precursor solutions were thoroughly
investigated using a number of techniques including X-ray diffraction (XRD), Rutherford backscattering
(RBS), optoelectronic characterisation and miniSIMS.
The effect of different precursor molar ratios on the properties of as-deposited films was studied for
both the nitrate and chloride based solutions using the above techniques.
ZnS films were also deposited using ESD for the first time. Using the information acquired during
the deposition of the CuInS2, a fully comprehensive analysis of the effect of different deposition
conditions and starting solution properties was performed.
Finally, CdS/CuInS2 and ZnS/CuInS2 junctions were prepared and tested using EQE measurements
in solution. Substrate and superstrate device configurations were used to prepare complete solar
cells which were analysed using IV measurements
An approach to high-throughput X-ray diffraction analysis of combinatorial polycrystalline thin film libraries
With the demand for higher rates of discovery in the materials field,
characterization techniques that are capable of rapidly and reliably surveying
the characteristics of large numbers of samples are essential. A chemical
combinatorial approach using thin films can provide detailed phase diagrams
without the need to produce multiple, individual samples. This is achieved with
compositional gradients forming high-density libraries. Conventional raster
scanning of chemical or structural probes is subsequently used to interrogate
the libraries. A new, alternative approach to raster scanning is introduced to
provide a method of high-throughput data collection and analysis using an X-ray
diffraction probe. Libraries are interrogated with an extended X-ray source and
the scattering data collected using an area detector. A simple technique of
'partitioning' this scattering distribution enables determination of information
comparable to conventional raster scanned results but in a dramatically reduced
collection time. The technique has been tested using synthetic X-ray scattering
distributions and those obtained from contrived samples. In all cases, the
partitioning algorithm is shown to be robust and to provide reliable data;
discrimination along the library principal axis is shown to be similar to 500 mm
and the lattice parameter resolution to be similar to 10(-3) A angstrom mm(-1).
The limitations of the technique are discussed and future potential applications
described
When does a particle arrive?
We compare the proposals that have appeared in the literature to describe a measurement of the time of arrival of a quantum particle at a detector. We show that there are multiple regimes where different proposals give inequivalent, experimentally discriminable, predictions. This analysis paves the way for future experimental tests