The Transition to Employment: An Analysis of Gross Flows from the House-hold Labour Force Survey

Following a steady increase over about five years, the number of people unemployed finally began to fall towards the end of 1991. Changes in unemployment numbers were reflected, to a degree, in employment numbers. Employment fell during most of the late 1980s, and a sustained rise in employment numbers did not occur until early in 1992. Falls in unemployment occur as the number of people moving into unemployment is exceeded by the number of people moving out of unemployment. Similarly, increases in employment result from a net inflow into employment. Of all the people who are not employed in one period, some have a higher probability than others of being employed in the next period. Using gross-flows data from all the 35 quarters of the Household Labour Force Survey, this paper examines the effect of selected characteristics on the probability of moving into employment, and how the effect of these characteristics has changed over time. Four characteristics are examined: occupation sought, job search method, length of time since last employment and educational attainment

Nitride MOVPE tops the bill

AbstractThe predominance of activity in the nitrides field and the emergence of in situ monitoring into mainstream metal organic vapour phase epitaxy were among the themes of the 8th European Workshop on MOVPE. The location of Prague close to the geographical centre of the united Europe did much to encourage participation from all corners of the continent, with over 200 delegates from 21 countries attending the workshop, held from 8–11 June 1999

Thin film cadmium telluride solar cells on ultra‐thin glass in low earth orbit—3 years of performance data on the AlSat‐1N CubeSat mission

This paper details 3 years of cadmium telluride (CdTe) photovoltaic performance onboard the AlSat‐1N CubeSat in low earth orbit. These are the first CdTe solar cells to yield I–V measurements from space and help to strengthen the argument for further development of this technology for space application. The data have been collected over some 17 000 orbits by the CubeSat with the cells showing no signs of delamination, no deterioration in short circuit current or series resistance. The latter indicating that the aluminium‐doped zinc oxide transparent front electrode performance remained stable over the duration. Effects of temperature on open circuit voltage (Voc) were observed with a calculated temperature coefficient for Voc of −0.19%/°C. Light soaking effects were also observed to increase the Voc. The fill factor decreased over the duration of the mission with a major contribution being a decrease in shunt resistance of all four of the cells. The decrease in shunt resistance is speculated to result from gold diffusion from the rear contacts into the absorber and through to the front interface. This has likely resulted in the formation of a deep trap state within the CdTe and micro shunts formed between the rear and front contact. Further development of this technology should therefore utilise more stable back contacting methodologies more commonly employed for terrestrial CdTe modules

A feasibility study towards ultra-thin PV solar cell devices by MOCDV based on a p-i-n structure incorporating pyrite

FeSx layers were deposited onto aluminosilicate glass substrates over a temperature range of 180°C to 500°C using a horizontal AP-MOCVD reactor. Fe(CO)5 was used as the Fe source in combination with t-Bu2S2 or t-BuSH as S precursor to control the rate of reaction and film stoichiometry. The Fe and S partial pressures were kept at 7.5 x 103 and 3.0 mbar, giving a gas phase S/Fe ratio of 400. Reactions followed a non-Arrhenius relationship at higher temperatures. XRD revealed mixed FeSx phases in the layers, which consisted mainly of FeS and Fe1-xS. Post growth annealing of the FeSx films using S powder in a static argon atmosphere and temperatures ranging from 250°C to 400°C was carried out using a 30 minute soak time. Characterisation by XRD confirmed a transitional phase change to FeS2 for the S anneal at 400°C. These films were highly absorbing in the visible region of the solar spectrum, which extended into the NIR. Devices with a p-i-n structure were produced using either a sulphurised or non-sulphurised FeSx i-layer, and compared to p-n devices without an i-layer. A non-sulphurised p-i-n device had the best I-V results, which was attributed to reduced lateral inhomogeneity across the device relative to the thinner p-n device structures. Devices with sulphurised FeSx i-layers performed least efficiently which is suspected to be due to a less defined FeSx/CdS junction caused by severe conditions during the S annealing process

Back contacts materials used in thin film CdTe solar cells—A review

CdTe is the leading commercial thin film photovoltaic technology with current record laboratory efficiency (22.1%). However, there is much potential for progress toward the Shockley‐Queisser limit (32%). The best CdTe devices have short‐circuit current close to the limit but open‐circuit voltage has much room for improvement. Back contact optimization is likely to play a key role in any improvement. Back contact material choice is also influenced by their applicability in more complex architectures such as bifacial and tandem solar cells, where high visible and/or near‐infrared transparency is required in conjunction with their electrical properties. The CdTe research community has employed many back contact materials and processes to realize them. Excellent reviews of back contacts were published by McCandless and Sites (2011) and Kumar and Rao (2014). There have been numerous publications on CdTe back contacts since 2014. This review includes both recent and older literature to give a comprehensive picture. It includes a categorization of back contact interface materials into groups such as oxides, chalcogenides, pnictides, halides, and organics. The authors attempt to identify the more promising material groups. Attention is drawn to parallels with back contact materials used on other thin film photovoltaics such as perovskites and kesterites

The Transition to Employment: An Analysis of Gross Flows from the House-hold Labour Force Survey

Following a steady increase over about five years, the number of people unemployed finally began to fall towards the end of 1991. Changes in unemployment numbers were reflected, to a degree, in employment numbers. Employment fell during most of the late 1980s, and a sustained rise in employment numbers did not occur until early in 1992. Falls in unemployment occur as the number of people moving into unemployment is exceeded by the number of people moving out of unemployment. Similarly, increases in employment result from a net inflow into employment. Of all the people who are not employed in one period, some have a higher probability than others of being employed in the next period. Using gross-flows data from all the 35 quarters of the Household Labour Force Survey, this paper examines the effect of selected characteristics on the probability of moving into employment, and how the effect of these characteristics has changed over time. Four characteristics are examined: occupation sought, job search method, length of time since last employment and educational attainment

Jumble Java Byte Code to Measure the Effectiveness of Unit Tests

Jumble is a byte code level mutation testing tool for Java which inter-operates with JUnit. It has been designed to operate in an industrial setting with large projects. Heuristics have been included to speed the checking of mutations, for example, noting which test fails for each mutation and running this first in subsequent mutation checks. Significant effort has been put into ensuring that it can test code which uses custom class loading and reflection. This requires careful attention to class path handling and coexistence with foreign class-loaders. Jumble is currently used on a continuous basis within an agile programming environment with approximately 370,000 lines of Java code under source control. This checks out project code every fifteen minutes and runs an incremental set of unit tests and mutation tests for modified classes. Jumble is being made available as open source

Interpretation of Absolute Laser Reflectance During Optical Monitoring of Polycrystalline GaAs Deposition on Quartz Using Metalorganic Chemical Vapor Deposition

Gallium arsenide was deposited by metal organic chemical vapor deposition in a horizontal quartz reactor tube using trimethylgallium and arsine at 400oC - 500oC. Nucleation time and deposition rate were monitored using in situ laser reflectometry. This allowed differentiation between film and parasitic growth, which was not possible with other optical techniques. An absolute reflectance model was developed using measurements prior to GaAs deposition, and then employed to calculate values for GaAs on quartz. Detected reflectance intensities during experimental GaAs deposition were low compared to the model due to 3-dimensional island growth, causing scattering of the incident laser radiation

Nanowire and core-shell-structures on flexible Mo Foil for CdTe solar cell applications

CdTe films, nanowires, film-nanowire combinations and CdS-CdTe core-shell structures have been fabricated in a preliminary survey of growth methods that will generate structures for PV applications. Selectivity between film, nanowire and film plus nanowire growth was achieved by varying the pressure of N2 gas present during Au-catalysed VLS growth of CdTe, on either Mo or Si substrates. Metamorphic growth of CdTe nanowires on sputtered CdTe films, deposited on glass substrates, was demonstrated. Coating of CdTe nanowires with CBD CdS gave conformal coverage whereas coating with MOCVD (Cd,Zn)S yielded highly crystallographic dendritic growth on the wires