232 research outputs found
A real-time PCR method for quantification of the total and major variant strains of the Deformed wing virus
Funding: ELB was supported by a Biotechnology and Biological Sciences Research Council (BBSRC) EASTBIO Doctoral Training Partnership (http://www.bbsrc.ac.uk) [grant number BB/J01446X/1] and an Eastern Association Regional Studentship (EARS) and The Morley Agricultural Foundation awarded to ASB. CRC was supported by a KTN BBSRC CASE studentship (BB/M503526/1) (http://www.bbsrc.ac.uk), part-funded by the Scottish Beekeeping Association (https://www.scottishbeekeepers.org.uk/) and the Animal Health - Disease Prevention, Scottish Government awarded to ASB CRC. This project received funding from the European Unionâs Seventh Framework Programme for research, technological development and demonstration under grant agreement no 613960 (SMARTBEES) (http://www.smartbees-fp7.eu/) awarded to ASB. The funders had no role in study design, data collection and analysis decision to publish, or preparation of the manuscript. Acknowledgments The authors wish to thank Mr W. Thrale, Mr Z. Blackmore, Mr J. Quinlan, and Mr J. Palombo for sample collection from the South East of England and Margie Ramsey for Beinn Eighe National Nature Reserve sample collection.Peer reviewedPublisher PD
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Quantifying Photon Recycling in Solar Cells and Light-Emitting Diodes: Absorption and Emission Are Always Key.
Photon recycling has received increased attention in recent years following its observation in halide perovskites. It has been shown to lower the effective bimolecular recombination rate and thus increase excitation densities within a material. Here we introduce a general framework to quantify photon recycling which can be applied to any material. We apply our model to idealized solar cells and light-emitting diodes based on halide perovskites. By varying controllable parameters which affect photon recycling, namely, thickness, charge trapping rate, nonideal transmission at interfaces, and absorptance, we quantify the effect of each on photon recycling. In both device types, we demonstrate that maximizing absorption and emission processes remains paramount for optimizing devices, even if this is at the expense of photon recycling. Our results provide new insight into quantifying photon recycling in optoelectronic devices and demonstrate that photon recycling cannot always be seen as a beneficial process.ARB acknowledges funding from a Winton Studentship, Oppenheimer Studentship and the Engineering and Physical Sciences Research Council (EPSRC) Doctoral Training Centre in Photovoltaics (CDT-PV). MA acknowledges funding from the Marie SkĆodowska-Curie actions (grant agreement No. 841386) under the European Unionâs Horizon 2020 research and innovation programme. SDS acknowledges the Royal Society and Tata Group (UF150033). We thank Luis Pazos-OutĂłn for supplying data for MAPbI3 solar cells. This work was supported by EPSRC grant EP/S030638/1
Toward Empirical Constraints on the Global Redshifted 21 cm Brightness Temperature During the Epoch of Reionization
Preliminary results are presented from a simple, single-antenna experiment
designed to measure the all-sky radio spectrum between 100 and 200 MHz. The
system used an internal comparison-switching scheme to reduce non-smooth
instrumental contaminants in the measured spectrum to 75 mK. From the
observations, we place an initial upper limit of 450 mK on the relative
brightness temperature of the redshifted 21 cm contribution to the spectrum due
to neutral hydrogen in the intergalactic medium (IGM) during the epoch of
reionization, assuming a rapid transition to a fully ionized IGM at a redshift
of 8. With refinement, this technique should be able to distinguish between
slow and fast reionization scenarios. To constrain the duration of reionization
to dz > 2, the systematic residuals in the measured spectrum must be reduced to
3 mK.Comment: Submitted to ApJ. 9 pages including 6 figure
Interfacial Hot Carrier Collection Controls Plasmonic Chemistry
Harnessing non-equilibrium hot carriers from plasmonic metal nanostructures
constitutes a vibrant research field. It promises to enable control of activity
and selectivity of photochemical reactions, especially for solar fuel
generation. However, a comprehensive understanding of the interplay of
plasmonic hot carrier-driven processes in metal/semiconducting heterostructures
has remained elusive. In this work, we reveal the complex interdependence
between plasmon excitation, hot carrier generation, transport and interfacial
collection in plasmonic photocatalytic devices, uniquely determining the charge
injection efficiencies at the solid/solid and solid/liquid interfaces.
Interestingly, by measuring the internal quantum efficiency of ultrathin (14 to
33 nm) single-crystalline plasmonic gold (Au) nanoantenna arrays on titanium
dioxide substrates, we find that the performance of the device is governed by
hot hole collection at the metal/electrolyte interface. In particular, by
combining a solid- and liquid-state experimental approach with ab initio
simulations, we show a more efficient collection of high-energy d-band holes
traveling in [111] orientation, resulting in a stronger oxidation reaction at
the {111} surfaces of the nanoantenna. These results thus establish new
guidelines for the design and optimization of plasmonic photocatalytic systems
and optoelectronic devices
Spatially resolved photoluminescence analysis of Se passivation and defect formation in CdSeTe thin films
CdTe is the most commercially successful thin-film photovoltaic technology to
date. The recent development of Se-alloyed CdSeTe layers in CdTe
solar cells has led to higher device efficiencies, due to a lowered bandgap
improving the photocurrent, improved voltage characteristics and longer carrier
lifetimes. Evidence from cross-sectional electron microscopy is widely believed
to indicate that Se passivates defects in CdSeTe solar cells, and
that this is the reason for better lifetimes and voltages in these devices.
Here, we utilise spatially resolved photoluminescence measurements of
CdSeTe thin films on glass to study the effects of Se on carrier
recombination in the material, isolated from the impact of conductive
interfaces and without the need to prepare cross-sections through the samples.
We find further evidence to support Se passivation of grain boundaries, but
also identify an associated increase in below-bandgap photoluminescence that
indicates the presence of Se-enhanced luminescent defects. Our results show
that Se treatment, in tandem with Cl passivation, does increase radiative
efficiencies. However, the simultaneous enhancement of defects within the grain
interiors suggests that although it is overall beneficial, Se incorporation may
still ultimately limit the maximum attainable efficiency of
CdSeTe solar cells
RNAi gene knockdown in the poultry red mite, Dermanyssus gallinae (De Geer 1778), a tool for functional genomics
The authors gratefully acknowledge funding for this project from the Scottish Government Rural Affairs, Food and the Environment (RAFE) Strategic Research Portfolio 2016-2021. DRGP is supported by a research fellowship provided by the Moredun Foundation. WC is supported by a studentship provided by the University of Aberdeen and the Moredun Foundation.Peer reviewedPublisher PD
Quantum-mechanical effects in photoluminescence from thin crystalline gold films
Luminescence constitutes a unique source of insight into hot carrier
processes in metals, including those in plasmonic nanostructures used for
sensing and energy applications. However, being weak in nature, metal
luminescence remains poorly understood, its microscopic origin strongly
debated, and its potential for unravelling nanoscale carrier dynamics largely
unexploited. Here, we reveal quantum-mechanical effects emanating in the
luminescence from thin monocrystalline gold flakes. Specifically, we present
experimental evidence, supported by first-principles simulations, to
demonstrate its photoluminescence origin when exciting in the interband regime.
Our model allows us to identify changes to the measured gold luminescence due
to quantum-mechanical effects as the gold film thickness is reduced.
Excitingly, such effects are observable in the luminescence signal from flakes
up to 40 nm in thickness, associated with the out-of-plane discreteness of the
electronic band structure near the Fermi level. We qualitatively reproduce the
observations with first-principles modelling, thus establishing a unified
description of luminescence in gold and enabling its widespread application as
a probe of carrier dynamics and light-matter interactions in this material. Our
study paves the way for future explorations of hot-carriers and charge-transfer
dynamics in a multitude of material systems.Comment: Main text 21 pages and 4 figures. Supplemental Information 33 pages
and 17 figure
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Interactive ozone and methane chemistry in GISS-E2 historical and future climate simulations
The new generation GISS climate model includes fully interactive chemistry related to ozone in historical and future simulations, and interactive methane in future simulations. Evaluation of ozone, its tropospheric precursors, and methane shows that the model captures much of the largescale spatial structure seen in recent observations. While the model is much improved compared with the previous chemistry-climate model, especially for ozone seasonality in the stratosphere, there is still slightly too rapid stratospheric circulation, too little stratosphere-to-troposphere ozone flux in the Southern Hemisphere and an Antarctic ozone hole that is too large and persists too long. Quantitative metrics of spatial and temporal correlations with satellite datasets as well as spatial autocorrelation to examine transport and mixing are presented to document improvements in model skill and provide a benchmark for future evaluations. The difference in radiative forcing (RF) calculated using modeled tropospheric ozone versus tropospheric ozone observed by TES is only 0.016Wmâ»ÂČ. Historical 20th Century simulations show a steady increase in whole atmosphere ozone RF through 1970 after which there is a decrease through 2000 due to stratospheric ozone depletion. Ozone forcing increases throughout the 21st century under RCP8.5 owing to a projected recovery of stratospheric ozone depletion and increases in methane, but decreases under RCP4.5 and 2.6 due to reductions in emissions of other ozone precursors. RF from methane is 0.05 to 0.18Wmâ»ÂČ higher in our model calculations than in the RCP RF estimates. The surface temperature response to ozone through 1970 follows the increase in forcing due to tropospheric ozone. After that time, surface temperatures decrease as ozone RF declines due to stratospheric depletion. The stratospheric ozone depletion also induces substantial changes in surface winds and the Southern Ocean circulation, which may play a role in a slightly stronger response per unit forcing during later decades. Tropical precipitation shifts south during boreal summer from 1850 to 1970, but then shifts northward from 1970 to 2000, following upper tropospheric temperature gradients more strongly than those at the surfac
Relaxed Current Matching Requirements in Highly Luminescent Perovskite Tandem Solar Cells and Their Fundamental Efficiency Limits.
Perovskite-based tandem solar cells are of increasing interest as they approach commercialization. Here we use experimental parameters from optical spectroscopy measurements to calculate the limiting efficiency of perovskite-silicon and all-perovskite two-terminal tandems, employing currently available bandgap materials, as 42.0% and 40.8%, respectively. We show luminescence coupling between subcells (the optical transfer of photons from the high-bandgap to low-bandgap subcell) relaxes current matching when the high-bandgap subcell is a luminescent perovskite. We calculate that luminescence coupling becomes important at charge trapping rates (â€106 s-1) already being achieved in relevant halide perovskites. Luminescence coupling increases flexibility in subcell thicknesses and tolerance to different spectral conditions. For maximal benefit, the high-bandgap subcell should have the higher short-circuit current under average spectral conditions. This can be achieved by reducing the bandgap of the high-bandgap subcell, allowing wider, unstable bandgap compositions to be avoided. Lastly, we visualize luminescence coupling in an all-perovskite tandem through cross-section luminescence imaging.ARB acknowledges funding from a Winton Studentship, Oppenheimer Studentship the Engineering and Physical Sciences Research Council (EPSRC) Doctoral Training Centre in Photovoltaics (CDT-PV). ARB thanks Luis Pazos-OutĂłn for supplying data for MAPbI3 solar cells. FL acknowledges financial support from the Alexander Von Humboldt Foundation via the Feodor Lynen program and thanks Prof. Sir R. Friend for supporting his Fellowship at the Cavendish Laboratory. Y-HC acknowledges the funding from Taiwan Cambridge Scholarship. AJ-S gratefully acknowledges a postdoctoral scholarship from the Max Planck Society. KF acknowledges a George and Lilian Schiff Studentship, Winton Studentship, the Engineering and Physical Sciences Research Council (EPSRC) studentship, Cambridge Trust Scholarship, and Robert Gardiner Scholarship. GE was funded by NRELâs LDRD program. ER acknowledges the European Research Council (ERC) under the European Unionâs Horizon 2020 research and innovation programme (HYPERION, Grant Agreement Number 756962) and the EPSRC for a DTP Part Studentship. MA-J acknowledges funding support from EPSRC through the program grant: EP/M005143/1. MA-J thanks Cambridge Materials Limited for their funding and technical support. MA acknowledges funding from the European Research Council (ERC) (grant agreement No. 756962 [HYPERION]) and the Marie SkĆodowska-Curie actions (grant agreement No. 841386) under the European Unionâs Horizon 2020 research and innovation programme. BVL acknowledges funding from the Max Planck Society, the Cluster of Excellence e-conversion and the Center for Nanoscience (CeNS). SDS acknowledges the Royal Society and Tata Group (UF150033) and the EPSRC (EP/R023980/1, EP/T02030X/1, EP/S030638/1). We thank Axel Palmstrom and William Nemeth at NREL for depositing some of the layers in the tandem stack
Multimodal Microscale Imaging of Textured Perovskite-Silicon Tandem Solar Cells.
Halide perovskite/crystalline silicon (c-Si) tandem solar cells promise power conversion efficiencies beyond the limits of single-junction cells. However, the local light-matter interactions of the perovskite material embedded in this pyramidal multijunction configuration, and the effect on device performance, are not well understood. Here, we characterize the microscale optoelectronic properties of the perovskite semiconductor deposited on different c-Si texturing schemes. We find a strong spatial and spectral dependence of the photoluminescence (PL) on the geometrical surface constructs, which dominates the underlying grain-to-grain PL variation found in halide perovskite films. The PL response is dependent upon the texturing design, with larger pyramids inducing distinct PL spectra for valleys and pyramids, an effect which is mitigated with small pyramids. Further, optimized quasi-Fermi level splittings and PL quantum efficiencies occur when the c-Si large pyramids have had a secondary smoothing etch. Our results suggest that a holistic optimization of the texturing is required to maximize light in- and out-coupling of both absorber layers and there is a fine balance between the optimal geometrical configuration and optoelectronic performance that will guide future device designs
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