Improving the operational stability of perovskite solar cells with cesium-doped graphene oxide interlayer

Perovskite solar cells(PSCs)have made great advances in terms of power conversion efficiency(PCE),yet their subpar stability continues to hinder their commercialization.The interface between the perovskite layer and the charge-carrier transporting layers plays a crucial role in undermining the stability of PSCs.In this work,we propose a strategy to stabilize high-performance PSCs with PCE over 23%by introducing a cesium-doped graphene oxide(GO-Cs)as an interlayer between the perovskite and hole-transporting material.The GO-Cs treated PSCs exhibit excellent operational stability with a projected T80(the time where the device PCE reduces to 80%of its initial value)of 2143 h of operation at the maximum powering point under one sun illumination.

Multifunctional SnO_(2) QDs/MXene Heterostructures as Laminar Interlayers for Improved Polysulfide Conversion and Lithium Plating Behavior

Poor cycling stability in lithium–sulfur(Li–S)batteries necessitates advanced electrode/electrolyte design and innovative interlayer architectures.Heterogeneous catalysis has emerged as a promising approach,leveraging the adsorption and catalytic performance on lithium polysulfides(LiPSs)to inhibit LiPSs shuttling and improve redox kinetics.In this study,we report an ultrathin and laminar SnO_(2)@MXene heterostructure interlayer(SnO_(2)@MX),where SnO_(2) quantum dots(QDs)are uniformly distributed across the MXene layer.The combined structure of SnO_(2) QDs and MXene,along with the creation of numerous active boundary sites with coordination electron environments,plays a critical role in manipulating the catalytic kinetics of sulfur species.The Li–S cell with the SnO_(2)@MX-modified separator not only demonstrates superior electrochemical performance compared to cells with a bare separator but also induces homogeneous Li deposition during cycling.As a result,an areal capacity of 7.6 mAh cm^(-2) under a sulfur loading of 7.5 mg cm^(-2) and a high stability over 500 cycles are achieved.Our work demonstrates a feasible strategy of utilizing a laminar separator interlayer for advanced Li–S batteries awaiting commercialization and may shed light on the understanding of heterostructure catalysis with enhanced reaction kinetics.

Laboratory study of fracture initiation and propagation in Barre granite under fluid pressure at stress state close to failure

Hydraulic fracturing is frequently used to increase the permeability of rock formations in energy extraction scenarios such as unconventional oil and gas extraction and enhanced geothermal systems(EGSs).The present study addresses uncertainties in the hydraulic fracturing process pertaining to EGSs in crystalline rock such as granite.Specifically,there is debate in the literature on the mechanisms(i.e.tensile and/or shear)by which these fractures initiate,propagate,and coalesce.We present experiments on Barre granite with pre-cut flaws where the material is loaded to high far-field stresses close to shear failure,and then the fluid pressure in the flaws is increased to move the Mohr’s circle to the left and observe the initiation and propagation of fractures using high-speed imaging and acoustic emissions(AEs).We find that the hydraulic fractures initiate as tensile microcracks at the flaw tips,and then propagate as a combination of tensile and shear microcracks.AE focal mechanisms also show elevated levels of tensional microfracturing near the flaw tips during pressurization and final failure.We then consider a numerical model of the experimental setup,where we find that fractures are indeed likely to initiate at flaw tips in tension even at relatively high far-field stresses of 40 MPa where shear failure is generally expected.

High-Performance Perovskite Solar Cells with Zwitterion-Capped-ZnO Quantum Dots as Electron Transport Layer and NH_(4)X(X=F,Cl,Br)Assisted Interfacial Engineering

The systematic advances in the power conversion efficiency(PCE)and stability of perovskite solar cells(PSCs)have been driven by the developments of perovskite materials,electron transport layer(ETL)materials,and interfacial passivation between the relevant layers.While zinc oxide(ZnO)is a promising ETL in thin film photovoltaics,it is still highly desirable to develop novel synthetic methods that allow both fine-tuning the versatility of ZnO nanomaterials and improving the ZnO/perovskite interface.Among various inorganic and organic additives,zwitterions have been effectively utilized to passivate the perovskite films.In this vein,we develop novel,well-characterized betaine-coated ZnO QDs and use them as an ETL in the planar n-i-p PSC architecture,combining the ZnO QDs-based ETL with the ZnO/perovskite interface passivation by a series of ammonium halides(NH_(4)X,where X=F,Cl,Br).The champion device with the NH4F passivation achieves one of the highest performances reported for ZnO-based PSCs,exhibiting a maximum PCE of~22%with a high fill factor of 80.3%and competitive stability,retaining~78%of its initial PCE under 1 Sun illumination with maximum power tracking for 250 h.

Interfacial engineering through lead binding using crown ethers in perovskite solar cells

In the domain of perovskite solar cells(PSCs),the imperative to reconcile impressive photovoltaic performance with lead-related issue and environmental stability has driven innovative solutions.This study pioneers an approach that not only rectifies lead leakage but also places paramount importance on the attainment of rigorous interfacial passivation.Crown ethers,notably benzo-18-crown-6-ether(B18C6),were strategically integrated at the perovskite-hole transport material interface.Crown ethers exhibit a dual role:efficiently sequestering and immobilizing Pb^(2+)ions through host-guest complexation and simultaneously establishing a robust interfacial passivation layer.Selected crown ether candidates,guided by density functional theory(DFT)calculations,demonstrated proficiency in binding Pb2+ions and optimizing interfacial energetics.Photovoltaic devices incorporating these materials achieved exceptional power conversion efficiency(PCE),notably 21.7%for B18C6,underscoring their efficacy in lead binding and interfacial passivation.Analytical techniques,including time-of-flight secondary ion mass spectrometry(ToF-SIMS),ultraviolet photoelectron spectroscopy(UPS),time-resolved photoluminescence(TRPL),and transient absorption spectroscopy(TAS),unequivocally affirmed Pb^(2+)ion capture and suppression of non-radiative recombination.Notably,these PSCs maintained efficiency even after enduring 300 h of exposure to 85%relative humidity.This research underscores the transformative potential of crown ethers,simultaneously addressing lead binding and stringent interfacial passivation for sustainable PSCs poised to commercialize and advance renewable energy applications.

New Opportunities for Lanthanide Luminescence

Trivalent lanthanide ions display fascinating optical properties. The discovery of the corresponding elements and their first industrial uses were intimately linked to their optical properties. This relationship has been kept alive until today when many high-technology applications of lanthanide-containing materials such as energy-saving lighting devices, displays, optical fibers and amplifiers, lasers, responsive luminescent stains for biomedical analyses and in cellulo sensing and imaging, heavily rely on the brilliant and pure-color emission of lanthanide ions. In this review we first outlined the basics of lanthanide luminescence with emphasis on f-f transitions, the sensitization mechanisms, and the assessment of the luminescence efficiency of lanthanide-containing emissive molecular edifices. Emphasis was then put on two fast developing aspects of lanthanide luminescence： materials for telecommunications and light emitting diodes, and biomedical imaging and sensing. Recent advances in NIR-emitting materials for plastic amplifiers and waveguides were described, together with the main solutions brought by researchers to minimize non-radiative deactivation of excited states. The demonstration in 1999 that erbium tris（8-hydroxyquinolinate） displayed a bright green emission suitable for organic light emitting diodes （OLEDs） was followed by realizing that in OLEDs, 25% of the excitation energy leads to singlet states and 75% to triplet states. Since lanthanide ions are good triplet quenchers, they now also play a key role in the development of these lighting devices. Luminescence analyses of biological molecules are among the most sensitive analytical techniques known. The long lifetime of the lanthanide excited states allows time-resolved spectroscopy to be used, suppressing the sample autofluorescence and reaching very low detection limits. Not only visible lanthanide sensors are now ubiquitously provided in medical diagnosis and in cell imaging, but the feasibility of using NIR emission of ions such as YbⅢ is now being tested because of deeper penetration in biological tissues.

Open cellular magnesium alloys for biodegradable orthopaedic implants

Replication processing using NaCl spaceholders offers the possibility to produce cellular structures for a range of Mg alloys. Four Mg alloys (AZ63, M2, ZM21 and MZX211) were processed into open cellular structures with a pore size near 500 μm and a porosity of 75% using an optimized NaCl leaching procedure. The production method was found to be robust and yielded samples of acceptable strength and stiffness. Their dissolution rate (by H2 release in simulated body fluid) and mechanical properties (by cyclic compression) were measured. For all 4 alloys the initial mechanical properties mimic those of cancellous bone;however, the dissolution rate is too high for direct use in the human body, leading to excessive hydrogen evolution and overly rapid degradation of mechanical properties. Further post-processing of the material is thus required.

Study of borohydride ionic liquids as hydrogen storage materials

Stability of borohydrides is determined by the localization of the negative charge on the boron atom.Ionic liquids(ILs) allow to modify the stability of the borohydrides and promote new dehydrogenation pathways with a lower activation energy. The combination of borohydride and IL is very easy to realize and no expensive rare earth metals are required. The composite of the ILs with complex hydrides decreases the enthalpy and activation energy for the hydrogen desorption. The Coulomb interaction between borohydride and IL leads to a destabilization of the materials with a significantly lower enthalpy for hydrogen desorption. Here, we report a simple ion exchange reaction using various ILs, such as vinylbenzyltrimethylammonium chloride([VBTMA][Cl]), 1-butyl-3-methylimidazolium chloride([bmim][Cl]), and 1-ethyl-1-methylpyrrolidinium bromide([EMPY][Br]) with NaBH4 to decrease the hydrogen desorption temperature. Dehydrogenation of 1-butyl-3-methylimidazolium borohydride([bmim][BH4]) starts below 100℃. The quantity of desorbed hydrogen ranges between 2.4 wt% and 2.9 wt%, which is close to the theoretical content of hydrogen. The improvement in dehydrogenation is due to the strong amine cation that destabilizes borohydride by charge transfer.

A Technical Review of Hydro-Project Development in China

This paper summarizes the development of hydro-projects in China,blended with an international perspective.It expounds major technical progress toward ensuring the safe construction of high dams and river harnessing,and covers the theorization of uneven non-equilibrium sediment transport,inter-basin water diversion,giant hydro-generator units,pumped storage power stations,underground caverns,ecological protection,and so on.

Correlating oriented grain number density of recrystallisation in particle-containing aluminium alloys

The recrystallized grain structure of Al-（Mn）-Fe-Si alloys after isothermal annealing was studied by electron backscatter diffraction（EBSD） technique. Statistical correlation suggests that the frequency of forming P-oriented（{011}？566？） grains at a particle larger than the critical diameter（about 1.1 μm） is about 2% when the effect of fine dispersoids and concurrent precipitation is negligible. The overall grain number density is correlated linearly with the number densities of P and Cube（{001}？100？） grains. The grain number densities of typical orientations（P, ND-rotated cube {001}？310？ and Cube） and the overall recrystallized grains increase as rolling strain increases, following a similar exponential law.

Second Harmonic Detection of Spin-Dependent Transport in Magnetic Nanostructures

Detection of the second harmonic response of magnetic nanostructures to an ac current is shown to be a very sensitive probe of the magnetization reversal process. A temperature oscillation is obtained by Joule heating instead of using a laser as the heat source, as in thermo-galvanic voltage measurements （TGV）. Joule heating is used to produce a large local temperature gradient in asymmetric Co/Cu/Co spin valves. Evidence is found for an effect of a heat current on magnetization.

Interplay of S and As in Mekong Delta sediments during redox oscillations

The cumulative effects of periodic redox cycling on the mobility of As,Fe,and S from alluvial sediment to groundwater were investigated in bioreactor experiments.Two particular sediments from the alluvial floodplain of the Mekong Delta River were investigated: Matrix A (14 m deep) had a higher pyrite concentration than matrix B (7 m deep) sediments.Gypsumwas present in matrix B but absent in matrix A.In the reactors,the sediment suspensions were supplemented with As(III) and SO4^2-,and were subjected to three full-redox cycles entailing phases of nitrogen/CO2,compressed air sparging,and cellobiose addition.Major differences in As concentration and speciation were observed upon redox cycling.Evidences support the fact that initial sediment composition is the main factor controlling arsenic release and its speciation during the redox cycles.Indeed,a high pyrite content associated with a low SO4^2- content resulted in an increase in dissolved As concentrations,mainly in the form of As(III),after anoxic half-cycles;whereas a decrease in As concentrations mainly in the form of As(V),was instead observed after oxic half-cycles.In addition,oxic conditions were found to be responsible for pyrite and arsenian pyrite oxidation,increasing the As pool available for mobilization.The same processes seem to occur in sediment with the presence of gypsum,but,in this case,dissolved As were sequestered by biotic or abiotic redox reactions occurring in the FeeS system,and by specific physico-chemical condition (e.g.pH).The contrasting results obtained for two sediments sampled from the same core show that many complexes and entangled factors are at work,and further refinement is needed to explain the spatial and temporal variability of As release to groundwater of the Mekong River Delta (Vietnam).

Design of a Fixed-Order Robust Controller to Damp Inter-Area Oscillations in Power Systems

This paper presents the design of a robust fixed-order H∞ controller to damp out the inter-area oscillations and to enhance the stability of the power system. The proposed H∞ approach is based on shaping the open-loop transfer function in the Nyquist diagram through minimizing the quadratic error between the actual and the desired open loop transfer functions in the frequency domain under linear constraints that guarantee robustness and stability. The proposed approach is robust with respect to multi-model uncertainty closed-loop sensitivity functions in the Nyquist diagram through the constraints on their infinity norm. The H∞ constraints are linearized with the help of a desired open-loop transfer function. The controller is designed using the convex optimization techniques in which the difference between the open-loop transfer function and the desired one is minimized. The two-area four-machine test system is selected to evaluate the performance of the designed controller under different load conditions as well as different levels of wind penetrations.

Design and Characterization of a Horizontal Double Impinging Jet Cell: Determination of Flow Modes at the Surface of a Flat Electrode

An electrochemical cell consisting of a double horizontal Impinging Jet Cell (IJC) has been conceived and characterized. The purpose of this system is the simultaneous electrodeposition of a composite metal/particle coating on both surfaces of a metal sheet. The silica particles imprint in the nickel matrix has allowed to distinguish four different flow areas onto the electrode namely the stagnation area, the radial flow area characterized by a higher flow speed, the return flow area that involves gravity effect, and the drainage area with a constant draining speed. Based on the limiting current evolution as a function of the Reynolds number, three flow modes were extracted: the Laminar Low Flow (LLF), the Laminar High Flow (LHF) and the Disturbance. The IJC investigated ensures a laminar flow for a large range of flow rate from a nozzle-to-sample distance of 19 mm and creates an laminar flow ovoid plan merged with the sample for the high flows.

Distributed media cooperation for enhanced video communication

The author designed two algorithms for distributed cooperation among multiple video streams sharing common communication resources. The algorithms take advantage of an optimization framework that characterizes video packets such that joint resource allocation can be implemented not only over the packets of a single stream, but also across packets of different streams. The first algorithm enables collaboration among multiple video senders in an 802.11 CSMA/CA wireless network such that their joint performance is maximized. Via the algorithm, the users cooperatively establish transmission priorities based on the assigned characterizations of their video packets. The second technique allows for low-complexity joint bandwidth adaptation of multiple video streams at intermediate network nodes in the Internet in order to maximize the overall network performance. The author analyzes the advantages of the proposed algorithms over conventional solutions employed in such scenarios. It is shown that depending on system parameters such as available network data rate the proposed techniques can provide substantial gains in end-to-end performance.

The INTERNODES Method for Non-conforming Discretizations of PDEs

INTERNODES is a general purpose method to deal with non-conforming discretizations of partial differential equations on 2D and 3D regions partitioned into two or several disjoint subdomains. It exploits two intergrid interpolation operators, one for transfering the Dirichlet trace across the interfaces, and the other for the Neumann trace. In this paper, in every subdomain the original problem is discretized by either the finite element method (FEM) or the spectral element method (SEM or hp-FEM), using a priori non-matching grids and piecewise polynomials of different degrees. Other discretization methods, however, can be used. INTERNODES can also be applied to heterogeneous or multiphysics problems, that is, problems that feature different differential operators inside adjacent subdomains. For instance, in this paper we apply the INTERNODES method to a Stokes- Darcy coupled problem that models the filtration of fluids in porous media. Our results highlight the flexibility of the method as well as its optimal rate of convergence with respect to the grid size and the polynomial degree.

The Use of Light Diffracted from Grating Etched onto the Backside Surface of an Atomic Force Microscope Cantilever Increases the Force Sensitivity

A reflecting diffraction grating has been etched onto the backside of a standard cantilever for atomic force microscopy, and the diffracted light has been used to monitor the angular position of the cantilever. It is shown experimentally that for small angles of incidence and for large reflection angles, the force sensitivity can be improved by few times when an appropriate detection scheme based on the position sensitive (duolateral) detector is used. The first demonstration was performed with a one micron period amplitude diffraction grating onto the backside of an Al-coated cantilever etched by a focused ion beam milling for the experiments in air and an analogous 600 nm-period grating for the experiments in air and in water.

An Innovative Architectural Strategy for the Integration of Energy Issues into the Design Process of a Commercial Center in Switzerland

In a context of growing efforts to develop sustainability strategies, energy-related issues occupy central stage in the built environment. Thus, the energy performance of housings has improved radically over the past decades. Yet other types of buildings, in particular commercial centers, haven’t received the same level of interest. As a result, there is a need for effective and practical measures to decrease their energy consumption, both for heating and electricity. The objective of the paper is to demonstrate that it is possible, through coherent strategies, to integrate energy issues and bioclimatic principles into the design process of commercial centers. It analyzes the exemplary case study of Marin Commercial Center (Switzerland). The interdisciplinary approach, based on integrated design strategies, aimed at increasing the energy efficiency while keeping the cost comparable to the market cost. The main design principles include natural ventilation, nighttime cooling with energy recovery and natural lighting, as well as optimization of mechanical systems. The results of the simulations show that Marin Center attains the best energy performance observed so far among Swiss commercial centers. It also meets the Swiss Minergie standard. The paper thus questions traditional design processes and outlines the need for interdisciplinary evaluation and monitoring approaches tailored for commercial centers. Even though most crucial decisions are taken during the early stages, all phases of the process require systematic optimization strategies, especially operating stages. Recommendations include legal measures, in particular in the fields of ventilation and air-conditioning, education, professional development and technology transfer, and financial incentives for the replacement of energy intensive installations.

An Analytical Model for the Electrolyser Performance Derived from Materials Parameters

Hydrogen is seen as a key element for the transition from a fossil fuel based economy to a renewable, sustainable economy. Hydrogen can be used either directly as an energy carrier or as a feedstock for the reduction of CO2 to synthetic hydrocarbons. Hydrogen can be produced by electrolysis, decomposing water in oxygen and hydrogen. This paper presents an overview of the three major electrolysis technologies: acidic (PEM), alkaline (AEL) and solid oxide electrolysis (SOEC). An updated list of existing electrolysers and commercial providers is provided. Most interestingly, the specific prices of commercial devices are also given when available. Despite tremendous development of the PEM technology in the past decades, the largest and most efficient electrolysers are still alkaline. Thus, this technology is expected to play a key role in the transition to the hydrogen society. A detailed description of the components in an alkaline electrolyser and an analytical model of the process are provided. The analytical model allows investigating the influence of the different operating parameters on the efficiency. Specifically, the effect of temperature on the electrolyte conductivity—and thus on the efficiency—is analyzed. It is found that in the typical range of operating temperatures for alkaline electrolysers of 65°C - 220°C, the efficiency varies by up to 3.5 percentage points, increasing from 80% to 83.5% at 65°C and 220°C, respectively.

Modelling of Predictive Hydraulic Impacts of a Potential Radioactive Waste Geological Repository on the Meuse/Haute-Marne Multilayered Aquifer System (France)

The French National Agency for Nuclear Waste Management (Andra) conducted a site investiga- tions program within the project of a deep geological disposal of radioactive waste in the Meuse/ Haute-Marne region. The construction of the tunnel of 5 Km length and the shafts of about 500 m depth to access the repository located in the clay host formation of Callovo-Oxfordian age, will lead to the perturbations of the groundwater flow fields. The prediction of the behaviour of these perturbations is needed to support: 1) the engineering and monitoring operations, and 2) the assessment of the consequences on groundwater resources. A variably-saturated flow model of a local multi-layered aquifer system is developed. It integrates the Oxfordian aquifer (limestone), the Kimmeridgianaquitard (marl) and the Barrois limestone aquifer including the karst conduits network. The variably-saturated flow Richard’s equation is solved with a finite element simulator. Prior to the simulation of the predictive repository impacts, a transient flow model is calibrated with respect to Underground Research Laboratory (URL) construction data. The results are analysed and evaluated by the use of performance measures.