Showing papers in "Communications materials in 2022"
TL;DR: Graph Neural Networks (GNNs) as mentioned in this paper are one of the fastest growing classes of machine learning models and play an increasingly important role in many areas of chemistry and materials science, being used to predict materials properties, accelerate simulations, design new structures, and predict synthesis routes of new materials.
Abstract: Abstract Machine learning plays an increasingly important role in many areas of chemistry and materials science, being used to predict materials properties, accelerate simulations, design new structures, and predict synthesis routes of new materials. Graph neural networks (GNNs) are one of the fastest growing classes of machine learning models. They are of particular relevance for chemistry and materials science, as they directly work on a graph or structural representation of molecules and materials and therefore have full access to all relevant information required to characterize materials. In this Review, we provide an overview of the basic principles of GNNs, widely used datasets, and state-of-the-art architectures, followed by a discussion of a wide range of recent applications of GNNs in chemistry and materials science, and concluding with a road-map for the further development and application of GNNs.
45 citations
TL;DR: In this article , the authors demonstrate that UTe 2 single crystals displaying an optimal superconducting transition temperature at 2 K exhibit a single transition and remarkably high quality supported by their large residual resistance ratio and small residual heat capacity.
Abstract: Abstract UTe 2 is a newly-discovered unconventional superconductor wherein multicomponent topological superconductivity is anticipated based on the presence of two superconducting transitions and time-reversal symmetry breaking in the superconducting state. The observation of two superconducting transitions, however, remains controversial. Here we demonstrate that UTe 2 single crystals displaying an optimal superconducting transition temperature at 2 K exhibit a single transition and remarkably high quality supported by their large residual resistance ratio and small residual heat capacity in the superconducting state. Our results shed light on the intrinsic superconducting properties of UTe 2 and bring into question whether UTe 2 is a multicomponent superconductor at ambient pressure.
35 citations
TL;DR: In this article , the main degradation mechanisms of perovskite solar cells and key results for achieving sufficient stability to meet IEC standards are summarized and limitations for evaluating solar cell stability and commercialization potential under the current IEC standard.
Abstract: Abstract Commercialization is widely believed to be achievable for metal halide perovskite solar cells with high efficiency and low fabrication cost. However, stability remains a key obstacle for them to compete with established photovoltaic technologies. The photovoltaic community relies on the International Electrotechnical Commission (IEC) standard for the minimum stability assessment for any commercialized solar cell. In this review, we summarize the main degradation mechanisms of perovskite solar cells and key results for achieving sufficient stability to meet IEC standards. We also summarize limitations for evaluating solar cell stability and commercialization potential within the framework of the current IEC standard, and discuss the importance of outdoor testing.
25 citations
TL;DR: In this article , different 2D and quasi-2D perovskite materials have demonstrated significant improvements in the device stability compared to 3D materials due to their increased hydrophobicity and suppressed ion migration.
Abstract: Abstract Different 2D and quasi-2D perovskite materials have demonstrated significant improvements in the device stability compared to 3D perovskites due to their increased hydrophobicity and suppressed ion migration. However, fundamental investigations of these materials have been scarce and consequently detailed understanding of the processes responsible for experimental phenomena are often lacking despite huge interest in these materials. Even more importantly, there have been a limited number of structure-property studies for different material compositions, and research is generally by trial and error rather than by design. Here we discuss different stability issues in these materials and identify questions which need to be answered to design materials with further stability improvements.
25 citations
TL;DR: A review of the use of Hall effect measurements to probe chiral spin textures can be found in this article , focusing on the SrRuO 3 as a model system, where the ambiguity between Hall effects due to topological sources has led to disagreement in the interpretation of experimental results and casts doubts on the effectiveness of these techniques for investigating chiral spyrmions.
Abstract: Abstract Chiral spin textures such as skyrmions are of interest to the field of spintronics for their potential use in future computing devices. Hall effect measurements are a simple and powerful method to probe the electronic and magnetic properties of materials. The topological Hall effect, which appears as anomalies in Hall resistance versus magnetic field measurements compared to magnetic measurements, has frequently been used to establish the occurrence of chiral spin textures. However, in addition to experimental issues, intrinsic electronic mechanisms combined with inhomogeneity in materials and at interfaces can lead to an inhomogeneous anomalous Hall effect which could be mistaken for a topological Hall signal. This review covers recent research using Hall effect measurements to probe chiral spin textures, focusing on SrRuO 3 as a model system. The ambiguity between Hall effects due to topological sources has led to disagreement in the interpretation of experimental results and casts doubts on the effectiveness of these techniques for investigating chiral spin textures.
20 citations
TL;DR: In this paper , a new generation of complementary metal oxide semiconductor (sCMOS) X-ray cameras with an uncoated image sensor which has fast image transfer and high quantum efficiency at the carbon K-edge was reported.
Abstract: Abstract Ptychography is a coherent diffraction imaging technique that measures diffraction patterns at many overlapping points on a sample and then uses an algorithm to reconstruct amplitude and phase images of the object and probe. Here, we report imaging, spectroscopy and linear dichroism ptychographic measurements at the carbon K-edge. This progress was achieved with a new generation of scientific Complementary Metal Oxide Semiconductor (sCMOS) X-ray cameras with an uncoated image sensor which has fast image transfer and high quantum efficiency at the carbon K-edge. Reconstructed amplitude and phase contrast images, C 1s spectral stacks, and X-ray linear dichroism of carbon nanotubes at the carbon K-edge were measured with ptychography. Ptychography and conventional Scanning Transmission X-ray Microscopy (STXM) are compared using results acquired from the same area. Relative to STXM, ptychography provides both improved spatial resolution and improved image quality. We used defocus ptychography, with an X-ray beam spot size of 1.0 micron, in order to reduce radiation damage and carbon deposition. Comparable spatial resolution was achieved to that of ptychography performed with a focused beam. Ptychography at the carbon K-edge offers unique opportunities to perform high resolution spectromicroscopy on organic materials important in medicine, biology, environmental science and energy materials.
18 citations
TL;DR: In this paper , the authors present a discussion of recurring errors and inaccuracies in battery research, including electrolyte ideality, ion conduction and transference, Sand's time and lithium-dendrite, cycle number and reversibility, and capacity and energy calculations.
Abstract: Abstract The field of battery research is highly active with an ever-increasing number of publications. This makes it extremely challenging for researchers to stay on top of the latest developments. In addition, and particularly challenging for those new to the battery field, a number of fundamental errors or inaccuracies frequently occur in published papers, creating additional barriers to understanding an already complicated field. Such errors and inaccuracies are potentially problematic given how battery research is focused toward those materials with promising performance metrics, which subsequently influences where research efforts are placed. This discussion seeks to clarify a few such recurring errors and inaccuracies, including electrolyte ideality, ion conduction and transference, Sand’s time and lithium-dendrite, cycle number and reversibility, and capacity and energy calculations. This discussion is intended to encourage researchers to follow rigorous reporting standards when publishing their battery research, which will help to ensure that findings can be reproduced by others.
17 citations
TL;DR: In this article , a dual-phase Mg-Li-Al alloy was designed to be durable via friction stir processing followed by liquid CO 2 quenching, which suppressed the formation of the detrimental AlLi phase, and an aluminium-rich protective surface layer also formed.
Abstract: Abstract Magnesium is the lightest structural metal, and alloying with lithium makes it even lighter. However, multi-phase Mg-Li alloys typically undergo rapid corrosion, and their strength decreases at room temperature due to natural age-softening. Here, we engineer a rapidly degrading dual-phase Mg-Li-Al alloy to be durable via friction stir processing followed by liquid CO 2 quenching. The best performing alloy has a low electrochemical degradation rate of 0.72 mg·cm −2 · day −1 , and high specific strength of 209 kN·m·kg −1 . We attribute this electrochemical and mechanical durability to its microstructure, which consists of a refined grain size of approximately 2 µm and dense nanoprecipitates. This microstructure suppressed the formation of the detrimental AlLi phase, and an aluminium-rich protective surface layer also formed. This processing route might be useful for designing lightweight and durable engineering alloys.
16 citations
TL;DR: In this article , the authors summarize procedures for conducting reliable impedance measurements on a battery system, including cell configurations, readiness of a system for impedance testing, validation of the data in an impedance spectrum, deconvolution of electrochemical processes based on the distribution of relaxation time and equivalent circuit fitting of the impedance spectrum.
Abstract: Abstract Electrochemical impedance spectroscopy provides information on the steady state of an electrochemical redox reaction and its kinetics. For instance, impedance is a very useful technique to investigate kinetics in batteries, such as diffusion processes or charge-transfer reaction dynamics during battery operation. Here, we summarize procedures for conducting reliable impedance measurements on a battery system, including cell configurations, readiness of a system for impedance testing, validation of the data in an impedance spectrum, deconvolution of electrochemical processes based on the distribution of relaxation time and equivalent circuit fitting of the impedance spectrum. The aim of this paper is to discuss key parameters for accurate and repeatable impedance measurements of batteries.
14 citations
TL;DR: Wang et al. as mentioned in this paper used photo-initiated polymerization of polypseudorotaxane with acrylamide in-situ, and further crosslinked by 1,4-butanediol diglycidyl ether in sodium hydroxide solution to form a slide-ring supramolecular hydrogel.
Abstract: Abstract Slide-ring materials with movable cross-links have received attention due to their excellent mechanical properties. However, due to the poor solubility of polyrotaxane and low synthesis efficiency, their applications are hindered. Here, we use hydroxypropyl-modified α-cyclodextrin (Hy-α-CD) and Acrylamide-PEG 20000 -Acrylamide (ACA-PEG 20000 -ACA) to construct a polypseudorotaxane with good water solubility. Through photo-initiated polymerization of polypseudorotaxane with acrylamide in-situ, the capped polyrotaxane was easily obtained and further cross-linked by 1,4-butanediol diglycidyl ether in sodium hydroxide solution to form a slide-ring supramolecular hydrogel. The hydrogel can be stretched to 25.4 times its original length, which recovers rapidly on unloading, and the addition of Ca 2+ ions during crosslinking enhances ionic conductivity. The Ca 2+ -doped hydrogels are used to prepare wearable strain sensors for monitoring human motion.
14 citations
TL;DR: In this article , the authors report the development of pivotally interconnected polygons based on even-numbered modules, which, in contrast to odd-numbered ones, are not straightforward to generalize.
Abstract: Abstract Mechanical metamaterials are man-made structures capable of achieving different intended mechanical properties through their artificial, structural design. Specifically, metamaterials with negative Poisson’s ratio, known as auxetics, have been of widespread interest to scientists. It is well-known that some pivotally interconnected polygons exhibit auxetic behaviour. While some hierarchical variations of these structures have been proposed, generalising such structures presents various complexities depending on the initial configuration of their basic module. Here, we report the development of pivotally interconnected polygons based on even-numbered modules, which, in contrast to odd-numbered ones, are not straightforward to generalize. Particularly, we propose a design method for such assemblies based on the selective removal of rotational hinges, resulting in fully-deployable structures, not achievable with previously known methods. Analytical and numerical analyses are performed to evaluate Poisson’s ratio, verified by prototyping and experimentation. We anticipate this work to be a starting point for the further development of such metamaterials.
TL;DR: In this paper , the authors use deep learning algorithms to identify rare-event designs for 3D printing of metamaterials with not only complex geometries but also arbitrary distributions of multiple materials within those geometry, yielding unique combinations of elastic properties.
Abstract: Abstract Emerging multi-material 3D printing techniques enables the rational design of metamaterials with not only complex geometries but also arbitrary distributions of multiple materials within those geometries, yielding unique combinations of elastic properties. However, discovering the rare designs that lead to highly unusual combinations of material properties, such as double-auxeticity and high elastic moduli, remains a non-trivial crucial task. Here, we use computational models and deep learning algorithms to identify rare-event designs. In particular, we study the relationship between random distributions of hard and soft phases in three types of planar lattices and the resulting mechanical properties of the two-dimensional networks. By creating a mapping from the space of design parameters to the space of mechanical properties, we are able to reduce the computational time required for evaluating each design to ≈2.4 × 10 −6 s, and to make the process of evaluating different designs highly parallelizable. We then select ten designs to be 3D printed, mechanically test them, and characterize their behavior using digital image correlation to validate the accuracy of our computational models. Our simulation results show that our deep learning-based algorithms can accurately predict the mechanical behavior of the different designs and that our modeling results match experimental observations.
TL;DR: In this article , the authors systematically discuss the stability of inverted perovskite solar cells, including each functional layer, interface and entire device, and consider environmental and operational stressors.
Abstract: Abstract Inverted perovskite solar cells (IPSCs) have great potential for commercialization, in terms of compatibility with flexible and multijunction solar cells. However, non-ideal stability limits their entry into the market. To shed light on the unstable origins of IPSCs, an analysis of recent research progress is needed. Here, we systematically discuss the stability of IPSCs, including each functional layer, interface and entire device, and consider environmental and operational stressors. We summarize a range of strategies for improving device stability and discuss the significance of stability test protocols. Finally, we highlight the shortcomings of current approaches for stability improvement and assessment, and provide recommendations for improving the stability of IPSCs.
TL;DR: In this paper , angle-resolved photoemission spectroscopy of KV3Sb5 and demonstrate a substantial reconstruction of Fermi surface in the CDW state that accompanies the formation of small three-dimensional pockets.
Abstract: Kagome lattices offer a fertile ground to explore exotic quantum phenomena associated with electron correlation and band topology. The recent discovery of superconductivity coexisting with charge-density wave (CDW) in the kagome metals KV3Sb5, RbV3Sb5, and CsV3Sb5 suggests an intriguing entanglement of electronic order and superconductivity. However, the microscopic origin of CDW, a key to understanding the superconducting mechanism and its possible topological nature, remains elusive. Here, we report angle-resolved photoemission spectroscopy of KV3Sb5 and demonstrate a substantial reconstruction of Fermi surface in the CDW state that accompanies the formation of small three-dimensional pockets. The CDW gap exhibits a periodicity of undistorted Brillouin zone along the out-of-plane wave vector, signifying a dominant role of the in-plane inter-saddle-point scattering to the mechanism of CDW. The characteristics of experimental band dispersion can be captured by first-principles calculations with the inverse star-of-David structural distortion. The present result indicates a direct link between the low-energy excitations and CDW, and puts constraints on the microscopic theory of superconductivity in alkali-metal kagome lattices.
TL;DR: In this paper , the same authors apply this approach to study the stability of halide perovskites and find that halide alloys experience three different degradation mechanisms depending on halogen content.
Abstract: Abstract The conventional approach to search for new materials is to synthesize a limited number of candidates. However, this approach might delay or prevent the discovery of better-performing materials due to the narrow composition space explored. Here, we fabricate binary alloy films with a composition gradient in a single shot in less than one minute. We apply this approach to study the stability of halide perovskites. We synthesize all possible binary compositions from MAPbI 3 and MAPbBr 3 and then study their optical properties, structure, and environmental stability in a high-throughput manner. We find that perovskite alloys experience three different degradation mechanisms depending on halogen content: bromine-rich perovskites degrade by hydration, iodine-rich perovskites by the loss of the organic component, and all other intermediate alloys by phase segregation. The proposed method offers an avenue for discovering new materials and processing parameters for a wide range of applications that rely on compositional engineering.
TL;DR: In this article , structural heterogeneity is used to characterize the dynamical behavior of semi-ordered soft-matter systems at a mesoscopic level and track their time-evolution, ultimately detecting the order-disorder transition at the microscopic scale.
Abstract: Abstract Persistent homology is an effective topological data analysis tool to quantify the structural and morphological features of soft materials, but so far it has not been used to characterise the dynamical behaviour of complex soft matter systems. Here, we introduce structural heterogeneity, a topological characteristic for semi-ordered materials that captures their degree of organisation at a mesoscopic level and tracks their time-evolution, ultimately detecting the order-disorder transition at the microscopic scale. We show that structural heterogeneity tracks structural changes in a liquid crystal nanocomposite, reveals the effect of confined geometry on the nematic-isotropic and isotropic-nematic phase transitions, and uncovers physical differences between these two processes. The system used in this work is representative of a class of composite nanomaterials, partially ordered and with complex structural and physical behaviour, where their precise characterisation poses significant challenges. Our developed analytic framework can provide both a qualitative and quantitative characterisation of the dynamical behaviour of a wide range of semi-ordered soft matter systems.
TL;DR: In this paper , the size control of MS2 bacteriophage VLPs was achieved via insertion of amino acid sequences in an external loop to shift morphology to significantly larger forms.
Abstract: Virus-like particles (VLPs) have significant potential as artificial vaccines and drug delivery systems. The ability to control their size has wide ranging utility but achieving such controlled polymorphism using a single protein subunit is challenging as it requires altering VLP geometry. Here we achieve size control of MS2 bacteriophage VLPs via insertion of amino acid sequences in an external loop to shift morphology to significantly larger forms. The resulting VLP size and geometry is controlled by altering the length and type of the insert. Cryo electron microscopy structures of the new VLPs, in combination with a kinetic model of their assembly, show that the abundance of wild type (T = 3), T = 4, D3 and D5 symmetrical VLPs can be biased in this way. We propose a mechanism whereby the insert leads to a change in the dynamic behavior of the capsid protein dimer, affecting the interconversion between the symmetric and asymmetric conformers and thus determining VLP size and morphology.
TL;DR: In this article , a model fluorescent material, 9-phenylcarbazole-3-yl)-10-(naphthalene-1-yl)anthracene, revealing that TTU can lower the threshold current densities required to achieve lasing under current injection, but to achieve the best performance, the singlet-triplet annihilation (STA) must be simultaneously minimized.
Abstract: Abstract Significant progress has recently been made in the field of organic solid-state lasers. However, achieving lasing action from organic semiconductors under electrical excitation remains challenging due to losses introduced by triplet excitons. Here, we report experimental and theoretical results that confirm a positive contribution of triplet excitons for electrically-driven organic lasing via a bimolecular triplet-triplet upconversion (TTU) mechanism. We study a model fluorescent material, 9-(9-phenylcarbazole-3-yl)-10-(naphthalene-1-yl)anthracene, revealing that TTU can lower the threshold current densities required to achieve lasing under current injection. However, to achieve the best performance, the singlet-triplet annihilation (STA) must be simultaneously minimized. Hence, an experimental strategy to simultaneously obtain high TTU with low STA is demonstrated in host-guest system with coumarin 545T as the guest laser dye. This system has a low amplified spontaneous emission threshold of 1.7 µJ cm − 2 under nanosecond optical pumping, and a more than three orders of magnitude improvement in J 50 in organic light-emitting diodes as compared to a reference blend.
TL;DR: In this article , the authors studied the chemistry and distribution of various species and the integrity of the functional layers in high-performance inverted perovskite solar cells, with and without an electric field.
Abstract: Abstract What causes the instability of perovskite solar cells has been a puzzling problem impeding the development of commercial panels. So far there is limited evidence on the link between device instability and the various materials in each of the stacked layers. Here, we study the chemistry and distribution of various species and the integrity of the functional layers in high-performance inverted perovskite solar cells, with and without an electric field. The distribution of the diffusion species and its impact on the chemical and electronic structures through the transporting layers are measured by photoemission spectroscopy combined with damage-free ion beam sputtering. We find that various species, such as I 2 and PbI 2 , are distributed throughout the organic transporting layers toward the electrode interface. These species are found to be charge neutral, have no impact on the Fermi level, and react little with copper. An electric field, however, can catalyze the electro-decomposition of the perovskite, causing chemical heterogeneity and degradation in device performance.
TL;DR: In this paper , the authors exploit non-local effects as a powerful design tool by introducing a versatile effectively two-dimensional metamaterial platform for airborne sound and elastic waves, and analytically show that the lowest band can be engineered by Fourier synthesis.
Abstract: Abstract The interior of the synthetic unit cells and their interactions determine the wave properties of metamaterials composed of periodic lattices of these cells. While local interactions with the nearest neighbors are well appreciated, nonlocal beyond-nearest-neighbor interactions are often considered as a nuisance. Here, by introducing a versatile effectively two-dimensional metamaterial platform for airborne sound and elastic waves, we exploit nonlocal effects as a powerful design tool. Within a simplified discrete model, we analytically show that the lowest band can be engineered by Fourier synthesis, where the $$N$$ N -th order Fourier coefficient is determined by the $$N$$ N -th nearest-neighbor interaction strength. Roton-like dispersion relations are an example. The results of the discrete model agree well with a refined model and with numerical calculations. In addition, we engineer the passage of waves from a local metamaterial into a nonlocal metamaterial by carefully tailoring the transition region between the two.
TL;DR: In this paper , the authors employ a dimer Kresling origami system consisting of unit cells with opposite chirality, which couples longitudinal and rotational degrees of freedom in elastic waves.
Abstract: Abstract Topological mechanical metamaterials have been widely explored for their boundary states, which can be robustly isolated or transported in a controlled manner. However, such systems often require pre-configured design or complex active actuation for wave manipulation. Here, we present the possibility of in-situ transfer of topological boundary modes by leveraging the reconfigurability intrinsic in twisted origami lattices. In particular, we employ a dimer Kresling origami system consisting of unit cells with opposite chirality, which couples longitudinal and rotational degrees of freedom in elastic waves. The quasi-static twist imposed on the lattice alters the strain landscape of the lattice, thus significantly affecting the wave dispersion relations and the topology of the underlying bands. This in turn facilitates an efficient topological state transfer from one edge to the other. This simple and practical approach to energy transfer in origami-inspired lattices can thus inspire a new class of efficient energy manipulation devices.
TL;DR: In this article , a flexible and light thermoelectric generator made of polymeric composites and heat sink fabrics is presented. But the performance of the generator depends on the temperature distribution of temperature difference across the generator.
Abstract: Abstract Light and flexible thermoelectric generators working around room temperature and within a small temperature range are much desirable for numerous applications of wearable microelectronics, internet of things, and waste heat recovery. Herein, we report a high performance flexible thermoelectric generator made of polymeric thermoelectric composites and heat sink fabrics. The thermoelectric composites comprise n- and p-type Bi 2 Te 3 particles and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate, exhibiting a synergic effect that results in Seebeck coefficients higher than those of the constituent alloys and conductive polymer. The flexible and light thermoelectric generator produces an output power of 9.0 mW, a specific output power of 2.3 mW/g, and an areal power density of 6.5 W/m 2 at Δ T = 45 K. By using the heat sink fabrics to maintain a large and uniform distribution of temperature difference across the generator, a three-fold increment of the output power is obtained.
TL;DR: In this paper , the authors show that the two-qubit gates CROT, CPHASE and SWAP can be executed in less than 100 ns and, by theoretically analyzing the experimental noise sources, they predict control fidelities exceeding 99% even for operation above one Kelvin.
Abstract: Abstract Spin qubits in quantum dots define an attractive platform for quantum information because of their compatibility with semiconductor manufacturing, their long coherence times, and the ability to operate above one Kelvin. However, despite demonstrations of SWAP oscillations, the integration of this two-qubit gate together with single-qubit control to create a universal gate set as originally proposed for single spins in quantum dots has remained elusive. Here, we show that we can overcome these limitations and execute a multitude of native two-qubit gates, together with single-qubit control, in a single device, reducing the operation overhead to perform quantum algorithms. We demonstrate single-qubit rotations, together with the two-qubit gates CROT, CPHASE, and SWAP, on a silicon double quantum dot. Furthermore, we introduce adiabatic and diabatic composite sequences that allow the execution of CPHASE and SWAP gates on the same device, despite the finite Zeeman energy difference. Both two-qubit gates can be executed in less than 100 ns and, by theoretically analyzing the experimental noise sources, we predict control fidelities exceeding 99%, even for operation above one Kelvin.
TL;DR: In this paper , a weak degree of anisotropy in the fracture toughness, G c (armchair) / G c(zigzag) , of 0.94 was determined, which aligns with previous predictions from first-principles calculations and observed growth kinetics of graphene crystals.
Abstract: Abstract The two-dimensional nature of graphene offers a number of interesting mechanical properties. Amongst these, fracture toughness has received substantial interest, yet computational works have not reached a consensus regarding anisotropy in its fracture energy when graphene is loaded in armchair or zigzag directions. Here, we resolve the steps involved during fracture of graphene by carrying out in situ tensile tests. Embryo cracks nucleated from the graphene edges are observed to deflect into major cracks with local kinking features, as explained by an evolving stress intensity factor during crack advance. Extended finite element analysis with the maximum energy release rate criterion is used to model the fracture process. We determine a weak degree of anisotropy in the fracture toughness, G c(armchair) / G c(zigzag) , of 0.94, which aligns with previous predictions from first-principles calculations and observed growth kinetics of graphene crystals in experiments.
TL;DR: In this paper , the authors review and analyse strategies in the literature and the most promising solutions to identify the factors that limit the power conversion efficiency and long-term stability of lead-free tin-based perovskite solar cells.
Abstract: Abstract Due to their outstanding optoelectronic properties, lead-based halide perovskite materials have been applied as efficient photoactive materials in solution-processed solar cells. Current record efficiencies offer the promise to surpass those of silicon solar cells. However, uncertainty about the potential toxicity of lead-based halide perovskite materials and their facile dissolution in water requires a search for new alternative perovskite-like materials. Thanks to the foresight of scientists and their experience in lead-based halide perovskite preparation, remarkable results have been obtained in a short period of time using lead-free perovskite compositions. However, the lower solar-to-energy conversion efficiency and long-term stability issues are serious drawbacks that hinder the potential progression of these materials. Here, we review and analyse strategies in the literature and the most promising solutions to identify the factors that limit the power conversion efficiency and long-term stability of lead-free tin-based perovskite solar cells. In the light of the current state-of-the-art, we offer perspectives for further developing these promising materials.
TL;DR: In this paper , the phase diagram of the (110) surface was determined using a combination of density functional theory calculations and X-ray photoelectron spectroscopy experiments, and it was shown that in the 0-1000 K temperature range, the surface is dominated by a highly stable phase of coexisting and adjacent carbonyl and ether groups.
Abstract: Abstract Diamond-based materials have unique properties that are exploited in many electrochemical, optical, thermal, and quantum applications. When grown via chemical vapor deposition (CVD), the growth rate of the (110) face is typically much faster than the other two dominant crystallographic orientations, (111) and (100). As such, achieving sufficiently large-area and high-quality (110)-oriented crystals is challenging and typically requires post-growth processing of the surface. Whilst CVD growth confers hydrogen terminations on the diamond surface, the majority of post-growth processing procedures render the surface oxygen-terminated, which in turn impacts the surface properties of the material. Here, we determine the oxygenation state of the (110) surface using a combination of density functional theory calculations and X-ray photoelectron spectroscopy experiments. We show that in the 0–1000 K temperature range, the phase diagram of the (110) surface is dominated by a highly stable phase of coexisting and adjacent carbonyl and ether groups, while the stability of peroxide groups increases at low temperatures and high pressures. We propose a mechanism for the formation of the hybrid carbonyl-ether phase and rationalize its high stability. We further corroborate our findings by comparing simulated core-level binding energies with experimental X-ray photoelectron spectroscopy data on the highest-quality (110)-oriented diamond crystal surface reported to date.
TL;DR: In this paper , the grain boundaries are shown to stabilize nanocrystalline alloys at high temperatures via thermodynamic and kinetic effects, and both grain boundary and bulk high-entropy effects can reduce grain boundary energy with increasing temperature for saturated multicomponent alloys.
Abstract: Abstract As high-entropy alloys receive an increasing amount of attention, an interesting scientific question arises: can grain boundaries be “high entropy”? In 2016, we proposed “high-entropy grain boundaries” as the grain boundary counterparts to high-entropy materials. Here, we discuss the underlying interfacial thermodynamics to elaborate relevant concepts. We emphasize that “high-entropy grain boundaries” are neither equivalent to grain boundaries in high-entropy materials nor simply “compositionally complex grain boundaries”, but they should possess specific thermodynamic characters. Using a simplified segregation model, we illustrate that both grain boundary and bulk high-entropy effects can reduce grain boundary energy with increasing temperature for saturated multicomponent alloys, where the effective grain boundary entropy can be positive and increase with the number of components. We show that high-entropy grain boundaries can stabilize nanocrystalline alloys at high temperatures via thermodynamic and kinetic effects. Grain boundary structural disordering and transitions may offer further opportunities to attain higher effective grain boundary entropies.
TL;DR: In this paper , a low-disorder, oxide-free interface between high-mobility planar germanium and a germanosilicide parent superconductor is proposed.
Abstract: The co-integration of spin, superconducting, and topological systems is emerging as an exciting pathway for scalable and high-fidelity quantum information technology. High-mobility planar germanium is a front-runner semiconductor for building quantum processors with spin-qubits, but progress with hybrid superconductor-semiconductor devices is hindered because obtaining a superconducting gap free of subgap states (hard gap) has proven difficult. Here we solve this challenge by developing a low-disorder, oxide-free interface between high-mobility planar germanium and a germanosilicide parent superconductor. This superconducting contact is formed by the thermally-activated solid phase reaction between a metal (Pt) and the semiconductor heterostructure (Ge/SiGe). Electrical characterization reveals near-unity transparency in Josephson junctions and, importantly, a hard induced superconducting gap in quantum point contacts. Furthermore, we demonstrate phase control of a Josephson junction and study transport in a gated two-dimensional superconductor-semiconductor array towards scalable architectures. These results expand the quantum technology toolbox in germanium and provide new avenues for exploring monolithic superconductor-semiconductor quantum circuits towards scalable quantum information processing.
TL;DR: In this paper , the key factors and parameters which influence cell fabrication and testing, including electrode uniformity, component dryness, electrode alignment, internal and external pressure, electrolyte amount control, and cell fixture with pressure control, are discussed.
Abstract: Abstract Improved lithium batteries are in high demand for consumer electronics and electric vehicles. In order to accurately evaluate new materials and components, battery cells need to be fabricated and tested in a controlled environment. For the commonly used coin and small pouch cells, certain key factors and parameters substantially influence the final cell quality and performance. Therefore, to achieve accurate and reliable data on new materials for batteries, repeatability, and quality of cell fabrication are critical to ensure reproducible findings. Here, we discuss the key factors and parameters which influence cell fabrication and testing, including electrode uniformity, component dryness, electrode alignment, internal and external pressure, electrolyte amount control, and cell fixture with pressure control. We also provide general guidelines for reliable cell preparation.