3,265 research outputs found
Development of Highly Bendable Transparent Window Electrodes Based on MoOx, SnO2, and Au Dielectric/Metal/Dielectric Stacks: Application to Indium Tin Oxide (ITO)-Free Perovskite Solar Cells
Indium-doped tin oxide (ITO) is the transparent conductive material of choice for a wide range of optoelectronic devices such as sensors, light-emitting diodes, and solar cells. However, its brittle nature, high cost, scarcity as well as aggressive deposition via sputtering determine the need to find cheap alternatives with high optical transparency, low sheet resistance, and mechanical flexibility. Dielectric/metal/dielectric (D/M/D) electrodes fulfill all these requirements and are deposited via low embodied energy low-temperature processing. We developed D/M/D multilayered electrodes based on thermally evaporated MoOx or solution-processed SnO2 seed layers, a thermally evaporated ultrathin Au film, and a spin-coated SnO2 top layer on rigid glass substrates. We first systematically unraveled the role of each layer on the resistance-transmittance properties of the full D/M/D electrode structure. By optimizing the thickness of the seed, metal, and the top layer, we obtained electrodes with transmittance of 72% at 550 nm and a minimum sheet resistance of similar to 9 omega sq(-1). Subsequently, these optimized multilayered stacks were employed as bottom electrodes for perovskite solar cells (PSC) with glass/D/M/D/mesoporous-TiO2/CH3NH3PbI3/spiro-MeOTAD/Au device architecture, delivering power conversion efficiencies (PCE) of 10.7%. Further, we deposited and characterized D/M/D electrodes on flexible polyethylene terephthalate (PET) films, achieving a maximum PCE of 7.6%. The difference in performance compared to rigid glass devices can be ascribed to the different wetting of the active layer on PET substrates. Flexible D/M/D electrodes displayed excellent mechanical properties compared to commercial PET/ITO, showing completely stable sheet resistance after repeated bending even down to 1.5 mm of curvature radius, whereas PET/ITO showed one order of magnitude increase in sheet resistance in the same mechanical test, due to formation of cracks in the conductive oxide. Our optimized D/M/D stacks on glass and especially on PET or other types of flexible substrates are therefore excellent alternatives to ITO as transparent window electrodes for low-cost, light-weight, and conformal optoelectronics applications
The European Migration System and Global Justice. A First Appraisal
Migration is at the heart of the current political debate in Europe. Moreover,
the migration crisis has disclosed a number of normative and ethical issues
connected to the current management of migration in the EU. This report provides
a preliminary insight into the EU’s policy on migration. It looks specifically
at the terms the EU chooses, the definitions it devises and the concepts and
understandings it endorses in its migration policies. In order to grasp the actual
working of an emerging EU Migration System of Governance (EUMSG), the
same terms, concepts and definitions are also examined with reference to a set
of national cases: Italy, France, Germany, United Kingdom, Hungary, Greece
and Norway
Mathematical Structure of Rabi Oscillations in the Strong Coupling Regime
In this paper we generalize the Jaynes--Cummings Hamiltonian by making use of
some operators based on Lie algebras su(1,1) and su(2), and study a
mathematical structure of Rabi floppings of these models in the strong coupling
regime. We show that Rabi frequencies are given by matrix elements of
generalized coherent operators (quant--ph/0202081) under the rotating--wave
approximation.
In the first half we make a general review of coherent operators and
generalized coherent ones based on Lie algebras su(1,1) and su(2). In the
latter half we carry out a detailed examination of Frasca (quant--ph/0111134)
and generalize his method, and moreover present some related problems.
We also apply our results to the construction of controlled unitary gates in
Quantum Computation. Lastly we make a brief comment on application to Holonomic
Quantum Computation.Comment: Latex file, 24 pages. I added a new section (Quantum Computation), so
this paper became self-contained in a certain sens
Chow's theorem and universal holonomic quantum computation
A theorem from control theory relating the Lie algebra generated by vector
fields on a manifold to the controllability of the dynamical system is shown to
apply to Holonomic Quantum Computation. Conditions for deriving the holonomy
algebra are presented by taking covariant derivatives of the curvature
associated to a non-Abelian gauge connection. When applied to the Optical
Holonomic Computer, these conditions determine that the holonomy group of the
two-qubit interaction model contains . In particular, a
universal two-qubit logic gate is attainable for this model.Comment: 13 page
Multiresistant Salmonella enterica serovar 4,[5],12:i:- in Europe: a new pandemic strain?
A marked increase in the prevalence of S. enterica serovar 4,[5],12:i:- with resistance to ampicillin, streptomycin, sulphonamides and tetracyclines (R-type ASSuT) has been noted in food-borne infections and in pigs/pig meat in several European countries in the last ten years. One hundred and sixteen strains of S. enterica serovar 4,[5],12:i:- from humans, pigs and pig meat isolated in England and Wales, France, Germany, Italy, Poland, Spain and the Netherlands were further subtyped by phage typing, pulsed-field gel electrophoresis and multilocus variable number tandem repeat analysis to investigate the genetic relationship among strains. PCR was performed to identify the fljB flagellar gene and the genes encoding resistance to ampicillin, streptomycin, sulphonamides and tetracyclines. Class 1 and 2 integrase genes were also sought. Results indicate that genetically related serovar 4,[5],12:i:- strains of definitive phage types DT193 and DT120 with ampicillin, streptomycin, sulphonamide and tetracycline resistance encoded by blaTEM, strA-strB, sul2 and tet(B) have emerged in several European countries, with pigs the likely reservoir of infection. Control measures are urgently needed to reduce spread of infection to humans via the food chain and thereby prevent the possible pandemic spread of serovar 4,[5],12:i:- of R-type ASSuT as occurred with S. Typhimurium DT104 during the 1990s
Anisotropic in-plane optical conductivity in detwinned Ba(Fe1-xCox)2As2
We study the anisotropic in-plane optical conductivity of detwinned
Ba(Fe1-xCox)2As2 single crystals for x=0, 2.5% and 4.5% in a broad energy range
(3 meV-5 eV) across their structural and magnetic transitions. For temperatures
below the Neel transition, the topology of the reconstructed Fermi surface,
combined with the distinct behavior of the scattering rates, determines the
anisotropy of the low frequency optical response. For the itinerant charge
carriers, we are able to disentangle the evolution of the Drude weights and
scattering rates and to observe their enhancement along the orthorhombic
antiferromagnetic a-axis with respect to the ferromagnetic b-axis. For
temperatures above Ts, uniaxial stress leads to a finite in-plane anisotropy.
The anisotropy of the optical conductivity, leading to a significant dichroism,
extends to high frequencies in the mid- and near-infrared regions. The
temperature dependence of the dichroism at all dopings scales with the
anisotropy ratio of the dc conductivity, suggesting the electronic nature of
the structural transition. Our findings bear testimony to a large nematic
susceptibility that couples very effectively to the uniaxial lattice strain. In
order to clarify the subtle interplay of magnetism and Fermi surface topology
we compare our results with theoretical calculations obtained from density
functional theory within the full-potential linear augmented plane-wave method.Comment: 17 pages, 9 figure
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