Transport Behavior Research Articles

Electronic structures and charge transport mobilities in hybrid organic-inorganic mixed Sn-Pb alloyed perovskites.

An all-perovskite tandem cell based on narrow-bandgap mixed tin-lead (Sn-Pb) alloyed perovskites is a potential photovoltaic device whose power conversion efficiency can exceed the Shockley-Queisser limit of a single-junction solar cell, 33%. However, comprehensive descriptions of the charge-carrier mobilities and transport mechanisms in the mixed Sn-Pb perovskite system remain elusive. Herein, we integrate density functional theory (DFT) calculations with charge transport models to provide more insight into the electronic structures and transport behaviors of these materials. We specifically employ a model using large polaron transport based on LO phonon scattering and ionized impurity scattering due to the oxidation of Sn2+ to Sn4+. DFT simulations revealed that there is a crossover in the electronic properties of pure-Sn and pure-Pb perovskites at Pb contents of more than 0.5, which causes increasing reduced effective mass as the Pb content increases. Theoretical calculations for charge-carrier mobility were in agreement with the experimental data between 23 and 89 cm2 V-1 s-1 at room temperature. In mixed Sn-Pb perovskites, LO phonon scattering predominates. However, in pure-Sn perovskites, transport scatterings based on LO phonon and ionized impurity scatterings are important. This discovery advances our knowledge of the transport mechanisms underlying the system of mixed Sn-Pb compounds.

Suspended sediment (SPS) triggers nitrogen retention by altering microbial network stability and electron transport behavior during the aerobic-anoxic transition.

NO3--N transformation, the vital biological process, determines nitrogen removal and retention in aquatic environment. Suspended sediment (SPS) ubiquitous in freshwater ecosystems can accelerate the transitions from aerobic to anoxic states, inevitably impacting NO3--N transformation. To elaborate on the microbial mechanism by which SPS content affected NO3--N transformation, we explored nitrogen removal and retention, microbial communities, co-occurrence networks, and electron transfer behavior under different SPS content during the aerobic-anoxic transition. We found that higher SPS concentration obviously increased NO3--N transformation rates but slightly affected TN removal, as the optimal SPS concentration boosting dissimilatory nitrate reduction to ammonium (DNRA) helped retain nitrogen during the transition. Microbial analysis suggested that the up-regulated SPS content slightly affected dominant bacteria abundance while progressively enhancing the essentiality of deterministic selection in microbial assembly and making microbial network more stable. Further investigations indicated that SPS content indirectly affected nitrogen retention via altering microbial network stability and electron transport system activity (ETSA) rather than bacterial abundance. Notably, elevating ETSA caused by SPS content directly promoted the potential for NO3--N being transformed through DNRA, enhancing nitrogen accumulation during the aerobic-anoxic transition. These results would provide supporting theories for the ecological restoration of micro-polluted water with higher SPS content.

Prediction methods for phonon transport properties of inorganic crystals: from traditional approaches to artificial intelligence.

In inorganic crystals, phonons are the elementary excitations describing the collective atomic motions. The study of phonons plays an important role in terms of understanding thermal transport behavior and acoustic properties, as well as exploring the interactions between phonons and other energy carriers in materials. Thus, efficient and accurate prediction of phonon transport properties such as thermal conductivity is crucial for revealing, designing, and regulating material properties to meet practical requirements. In this paper, typical strategies used to predict phonon transport properties in modern science and technologies are introduced, and relevant achievements are emphasized. Moreover, insights into the remaining challenges as well as future directions of phonon transport-related exploration are proposed. The viewpoints of this paper are expected to provide a valuable reference to the community and inspire relevant research studies on predicting phonon transport properties in the near future.

Role of multivalent state of B-site cations on the electrical transport behavior of Zn-substituted double perovskite: La2CuMnO6

The localization and delocalization of charge carriers considerably affect the ceramic's electrical transport characteristics. These phenomena depend on the cationic charge states, grain growth, crystal geometry, etc. Doping of similar cationic charge states and comparative ionic radii cations are expected to alter the crystal geometry only. In contrast, exciting features are reflected in the results when such substitution affects the cationic valance states. Our previous work reported the structural, electronic, dielectric, and magnetic behavior of Zn-doped La2CuMnO6 (LCM) [1]. A complex coordination state of B-site cations produced tilt in the crystal geometry, diffused relaxor behavior in dielectric response, and non-colinearity in the antiferromagnetic behavior of these oxides. However, the extents of cationic charge states were unraveled. This work reassembles the synergistic role of cationic charge states and their corresponding interactions on the electrical transport behavior of LCM, La2Cu0.5Zn0.5MnO6 (LCZM), and La2ZnMnO6 (LZM). The detailed analysis of AC- and DC- conductivity depicted the shift of long-range dynamics to short-range dynamics with Zn-substitution under the influence of temperature and frequency.

Applying multiple processes nonequilibrium model to investigate cesium transport in crushed granite

Abstract Understanding the movement of radionuclides (RN) in the subsurface environment is of paramount importance, particularly when it comes to the planning and assessment of facilities devoted to the disposal of radioactive waste. Comprehensive mathematical models serve as indispensable tools in this regard, demanding a profound and thorough understanding of the intricate mechanisms underlying radionuclide transport. The effective application of these models is contingent upon accurately determining the required input parameters. This is a critical aspect to consider given the inherent physical and chemical variations exhibited by the subsurface environment. These variations can induce significant effects on the movement of RNs below ground, potentially altering the predicted outcomes of radionuclide transport. This paper presents the findings of a comprehensive investigation that was conducted utilizing both advective-dispersive experiments (ADE) and multiple processes nonequilibrium (MPNE) inversion. These methodologies were employed using the advanced HYDRUS code, which is highly regarded in the field. The research specifically focuses on the transportation mechanisms of Cesium (Cs), a common radionuclide, in a medium of crushed granite. The study considers varying conditions, including different flow rates and column lengths, to provide a broad understanding of the behavior of Cs. The findings reveal that the transport behavior of Cs is not only influenced by the different flow rates and column lengths but is also significantly affected by the diffusive mass transfer and nonequilibrium sorption. These factors collectively contribute to our understanding of the complex processes involved in radionuclide transport.

Study of Optical, Thermoelectric, and Mechanical Behaviors of Double PerovskitesCs2SnVX6(X = Cl, Br, I) for Renewable Energy

Abstract Double perovskites are emerging materials for solar cells and renewable energy applications. Here this research emphasizes the optical, transport, and mechanical characteristics of Cs2SnVX6 (X = Cl, Br, I) for renewable energy. The structural and dynamic stabilities of these double perovskites in the cubic phase have been ensured by the tolerance factor (0.94, 0.93, 0.91) and the Ab initio molecular dynamic (AIMD) simulation. Furthermore, formation energy and elastic constants have also been reported, which provide evidence of thermodynamic and mechanical stability. The band gaps analyzed by TB-mBJ potential are 1.48 eV, 1.29 eV, and 0.22 eV for the Cs2SnVCl6, Cs2SnVBr6, and Cs2SnVI6, respectively. The band gap of Cs2SnVBr6 is standard for solar cells. The absorption band exists in the visible to infrared zone, with minimal optical losses. The transport behavior has been addressed through the BoltztraP code, whose large thermoelectric performance has been confirmed by the figure of merit (1.10, 0.90, 0.65) at 300K, and ultralow lattice thermal conductivity. From mechanical analysis, it is assumed that Cs2SnVCl6 has a ductile nature (B/G = 2.0) while Cs2SnVBr6 and Cs2SnVI6 have a brittle nature (B/G = 1.26, 0.94). Moreover, their hardness, large Debye, and melting temperature are also important for device fabrication.

Thickness-Dependent Electrical Simulation of Ternary Layer-by-Layer Organic Solar Cell

Recently, researchers have been interested in incorporating a third component into the active layer of organic solar cells (OSC). Introducing a third component aims to improve the efficiency of light absorption, charge separation, and transport within the solar cell. It is widely observed that varying active layer thicknesses result in different device competencies due to the behaviour of charge transportation and charge collection in such volume morphology of active layer. This paper incorporated layer-by-layer (LbL) devices based on BTR-Cl as donor and IT-2Cl as acceptor with Y6 acceptor as a third component in the active layer. These devices had been electrically characterized using organic and hybrid material nano (OghmaNano) simulation tool. A thickness ranging between 40 nm and 100 nm of each material in the active layer was evaluated in this simulation. This simulation shows the current-voltage (I-V) characteristics for ternary LbL OSC devices at various thicknesses. The short circuit current density (Jsc), open circuit voltage (Voc), and fill factor (FF) for each device's active layer thickness were also provided. At a thickness ratio of 50:60:50 nm (BTR-Cl to Y6 to IT-2Cl) and 100 mW cm-2, AM1.5 incident solar radiance, the maximum attainable efficiency, 12.1%, was found.

Enhanced giant magnetoresistance in Heusler alloy (Co2FeSi/Ag)N multilayers for read sensor applications

Abstract We theoretically investigate the spin transport behavior of multilayer [ Co 2 FeSi / Ag ] N structure for the application of next-generation read sensors in hard disk drive. To demonstrate the potential of the Heusler alloy-based current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) device, we employ an atomistic model coupled with a spin accumulation model including the effect of a diffuse interface. The dynamics of magnetization is observed in the atomistic model and the calculation of magnetoresistance (MR) and MR ratio of the magnetic structure can be achieved by the spin accumulation model enabling us to investigate the spin transport behavior within the structure. The MR value can be directly calculated from the gradient of spin accumulation and spin current. The effect of injected current density is first investigated. It is found that increasing the current density results in a high MR ratio. Subsequently, to achieve a high performance reader, the number of coupled layers (N) is varied up to 16 to study its effect on the MR ratio. The calculated results indicate that increasing the number of layers N gives rise to the enhancement of the resistance change and MR ratio. At the critical point N = 5, further increasing N does not affect the MR ratio, which remains relatively unchanged. Interestingly, the MR ratio is doubled for N > 5 compared to N = 1. Our results demonstrate the possibility of enhancing the performance of multilayer CPP-GMR devices.

Preparation of Aluminum-Based Dual-Gradient Surfaces for Directional Droplet Transport by Bioinspired Sarracenia Microstructures.

Inspired by the ultrafast directional water transport structure of Sarracenia trichomes, hierarchical textured surfaces with specific microgrooves were prepared based on laser processing combined with dip modification, in response to the growing problem of freshwater scarcity. The prepared surfaces were tested for droplet transport behavior to investigate the relationship between the surface structure and the driving force of directional water transport and their effects on the water transport distance and water transport velocity. The results showed that surfaces with a superhydrophobic background associated channels of multirib structures, and a dual-gradient surface of gradient hydrophobic background associated channels with gradient structure performed the best in terms of water transport efficiency. In addition, the water transport process of different samples under Mode II was simulated by CFD, and the dynamic evolution of water film mode formation was obtained to be divided into four phases, including film formation, transition state, mode formation, and stable water transport. This study provides a good reference for the development and preparation of surfaces for directional water transport.

Channel–molecule attraction mediated molecule transport in confined nanochannels of COF membranes for nanofiltration

AbstractPorous membranes, a type of material widely used in nanofiltration, are confronted with the limitation that the influence of channel–molecule interactions on transport behaviors has yet been investigated in detail. Herein, covalent organic framework membranes with adjustable pore sizes (⁓ 2.5 nm and ⁓ 1.2 nm) and chemical groups (−F, −OH, and −CO−) were prepared by interfacial polymerization. We demonstrate that strong channel–molecule attraction induces the formation of stable solvent layers along nanochannel walls, which protect central molecules from the attraction of chemical groups. Significantly, stable solvent layers permit fast transport of ethanol (245.6 L m−2 h−1 bar−1) with reactive black (RB) rejection of 96%. Likely, for membranes with weak channel–molecule attraction, no solvent layers are formed and molecules also transport smoothly. Interestingly, membranes that exhibit moderate channel–molecule attraction exert metastable solvent layers, thus displaying high transport resistance. This hindrance effect on molecule transport becomes more pronounced in smaller nanochannels.

Investigation of Hydrogen Transport Behavior in Polyethylene Terephthalate Membrane by Prolonged Hydrogen Exposure Treatments

Polyethylene terephthalate (PET) is one of the most used polymeric substances in production of packaging materials, fibers, textiles, coatings, and engineering materials. This paper elucidates the transport parameters of hydrogen gas through a PET membrane, which was selected to be a sufficiently permeable substrate for setting up an empirical strategy that aims at developing hydrogen barrier coatings. An examination of the structural degradation of PET by prolonged hydrogen exposure was performed. Hydrogen permeation tests were performed on a PET membrane with a thickness of 50 μm. To investigate the behavior of the material by prolonged hydrogen treatment, hydrogen-exposure experiments were carried out at a certain hydrogen pressure and time. Comparisons of the mechanical properties of the material were documented both before and after hydrogen exposure. A strong impact of comparatively transient hydrogen exposure on the mechanical and hydrogen transport properties of PET was observed. After 72 h of hydrogen exposure at 103 hPa and 300 K, the tensile strength decreased by 19%, the diffusion coefficients more than doubled, and material fracture behavior changed from ductile to distinctly brittle. This underlines the importance of developing effective hydrogen barrier coatings in case PET tubing is intended for use in hydrogen transport or storage.

Multiscale Mass Transport Across Membranes: From Molecular Scale to Nanoscale to Micron Scale.

Multiscale mass transport across membranes occurs ubiquitously in biological systems but is difficult to achieve and long-sought-after in abiotic systems. The multiscale transmembrane transport in abiotic systems requires the integration of multiscale transport channels and energy ergodicity, making multiscale mass transport a significant challenge. Herein, emulsion droplets with cell-like confinement are used as the experimental model, and multiscale mass transport is achieved from molecular scale to nanoscale to micron scale, reproducing rudimentary forms of cell-like transport behaviors. By adjustment of the magnetic dipole interactions between adjacent superparamagnetic nanoparticles (MNPs), the assembled structure at the interface of emulsion droplets is successfully modified, which constructs transport channels of various scales at the interface. Simultaneously, the assembly process of MNPs induces self-emulsification, which increases entropy and further reduces Gibbs free energy, ultimately realizing multiscale mass transport that evolves in time visiting all possible microscopic states (energy ergodicity). This work represents the comprehensive identification and realization of a multiscale transmembrane transport in abiotic droplet systems, which offers opportunities for the development of high-order cell-like characteristics in emulsion droplet-based communities, synthetic cells, microrobots, and drug carriers.

Signatures of ambient pressure superconductivity in thin film La3Ni2O7.

Recently, the bilayer nickelate La3Ni2O7 has been discovered as a new superconductor with transition temperature Tc near 80 K under high pressure1-3. Despite extensive theoretical and experimental work to understand the nature of its superconductivity4-29, the requirement of extreme pressure restricts the use of many experimental probes and limits its application potential. Here, we present signatures of superconductivity in La3Ni2O7 thin films at ambient pressure, facilitated by the application of epitaxial compressive strain. The onset Tc varies approximately from 26 K to 42 K, with higher Tc values correlating with smaller in-plane lattice constants. We observed the co-existence of other Ruddlesden-Popper phases within the films and dependence of transport behavior with ozone annealing, suggesting that the observed low zero resistance Tc of around 2 K can be attributed to stacking defects, grain boundaries, and oxygen stoichiometry. This finding initiates numerous opportunities to stabilize and study superconductivity in bilayer nickelates at ambient pressure, and to facilitate the broad understanding of the ever-growing number of high temperature and unconventional superconductors in the transition metal oxides.

A study of the transition to a turbulent shock using a coarse-graining approach to ion phase-space transport

ABSTRACT Shocks and turbulence are ubiquitous phenomena, responsible for particle acceleration to very high energies in a large collection of astrophysical systems. Using self-consistent, hybrid-kinetic simulations with and without pre-existing turbulence, we study the transition of a shock from ‘laminar’ to turbulent. We show that the changes in upstream proton transport behaviour are crucial to understand this transition, which we address quantitatively with a novel Eulerian approach. This method, based on the coarse-graining of the Vlasov equation originally introduced in one of our previous studies, gives consistent results for inertial range scales. The potential applications of the coarse-graining approach beyond the shock–turbulence system are outlined.

Different phase leads to different transport behavior in Pb9Cu(PO4)6O compounds

The recent claimed room-temperature superconductivity in Cu-doped lead apatite at ambient pressure is under debate. To identify its physical origin, we conducted a detailed analysis of the crystal structure, band structure, lattice dynamics and magnetic properties of the parent Pb[Formula: see text](PO4)6O compound and the two different phases of Pb9Cu(PO4)6O (LK-99) compound. Our results show that the parent Pb[Formula: see text](PO4)6O compound is an indirect band gap semiconductor, where Cu doping at the 4f site of Pb leads to a semiconducting to half-metallic transition. Two half-filled flat bands spanning the Fermi energy levels are present in the 4f phase of LK-99, which are mainly formed by hybridization of the d orbitals of Cu with the 2p orbitals of O. In addition, 6h phase of LK-99 always has spin polarization at the bottom of the conduction band and at the top of the valence band, making the material a magnetic semiconductor. Our theoretical research reveals recent experimental reports on the different transport properties of LK-99.

A Numerical Study on Impact of Coal Mining Activity and Mine Water Drainage on Flow and Transport Behavior in Groundwater

Under the dual carbon mission, more and more coal mines will face shutting down in the future and stop treating mine water drainage, which, if it escapes, may cause severe secondary damage to the local groundwater quality. Wudong Coal Mine is a currently active subsurface coal mine in Xinjiang, China, that shows high-salinity characteristics. To forecast and discuss future possible groundwater quality damages and potential solutions, we here introduce a model prediction study on the effects of water pollution by coal mine drainage. The study protocol first involves creating a calibrated 2D groundwater flow model by use of FEFLOW software, then designing several flow and solute transport prediction analyses under changing mine water drainage conditions, different pollution source areas and water treatment pumping wells to discuss future prominent flow and transport behavior, as well as water treatment-affecting factors. It has been shown that mine water drainage plays a critical role in maintaining the mine water solute distribution, as without mine draining, local flow and solute distribution change dramatically, altering the groundwater capture zone, and may change the plume-migrating direction from upstream to downstream. A larger pollution source could produce a higher concentration of pollutants and a larger pollution-coverage area. To reduce pollutant concentrations, mine water treatment pumping wells with higher pumping rates can be applied as a useful remedial measure to effectively prevent the pollutant plume front from reaching the important drinking and irrigation water source of the region, Urumqi River. The results of this study can give important suggestions and decision-making support for authorities focused on water treatment and environmental protection decision-making in the region.

Solution Processable Se-annulated Swallow Tail Perylene Bisimide Exhibiting Room Temperature Columnar Phase and Efficient Ambipolar Charge Carrier Mobility.

This study presents a selenium-annulated perylene bisimide (PBI-SeST) stabilizing room temperature columnar hexagonal phase with exceptionally low clearing temperature. The synthesis of this Se-annulated PBI (PBI-SeST) was accomplished using the reductive Cadogan cyclization method, with the introduction of swallow tails to reduce the clearing temperature and improve solubility. In addition, the charge carrier mobility of the Se-bay annulated PBI is assessed by space charge limited current (SCLC) technique and juxtaposed with PBI as well as nitrogen and sulphur-bay-annulated PBIs. It is noteworthy that all these PBIs exhibited ambipolar charge carrier mobility, a characteristic that diverges from the prevailing literature where predominantly electron transport behavior was observed for PBIs. This distinguishes them as an exclusive category of solution-processable, self-assembling organic semiconductors.

Effect of sulfur doping on superconductivity and charge density wave order in Kagome metal CsV3(Sb1−xSx)5

Abstract Recently, the coexistence and competition of superconductivity (SC) and charge density wave (CDW) have emerged in Kagome superconductor AV3Sb5 (A = K, Rb, Cs) under pressure, which has aroused widespread interest. Here, chemical substitution is used to introduce chemical pressure to further investigate the coexistence and competition between CDW and SC states. By preparing CsV3(Sb1−x S x )5 series single crystals and studying their crystal structure, chemical valence states, SC, and electronic transport behavior, it is found that S doping causes significant chemical pressure that is similar to axial mechanical pressure, resulting in suppression on the CDW and enhancement on SC. The T c−x relationship exhibits a double dome SC, similar to the behavior observed in the CsV3Sb5 under mechanical pressure. In addition, a negative correlation between T CDW and the disorder degree (measured by residual resistivity) is observed. This correlation is consistent with the observed translational jump in the ρ(T) curve before and after the CDW transition, that is, the temperature coefficient of resistivity does not change before and after the CDW phase transition, but only the resistivity curve shifts to a certain value. This phenomenon reveals that disorder is an important factor affecting the CDW transition of the system. Further, S doping also induces hole band filling effect that results in a decrease in the DOS at E F and consequently counterbalances the T c enhancement effect from chemical pressure to a certain extent. The electronic phase diagram of the CsV3(Sb1−x S x )5 system is accordingly established, which demonstrates the correlation between the SC, CDW, disorder degree, and other electronic nature of the system.

B─C Bonding Configuration Manipulation Strategy Toward Synergistic Optimization of Polarization Loss and Conductive Loss for Highly Efficient Electromagnetic Wave Absorption

AbstractIn non‐metallic atom‐doped carbonaceous materials, the disparity in electronegativity between the doped constituents and carbon atoms predetermines the bonding topology of covalent bonds and the distribution of electron density. This, consequently, influences the polarization and electron transport behavior within the doped domain and the electromagnetic wave attenuation attributes of the carbonaceous material. However, the influence of covalent bonds formed by doping with weakly electronegative atoms on electron density distribution, polarization effects, and electromagnetic wave attenuation remains uncharted. To address this deficiency, this study fabricates a porous carbonaceous material (NCP) and incorporates boron‐doped atoms to form a material with tunable B─C bonding configurations (B‐NCP). By modulating the B─C bonding configuration and proportion, it is feasible to achieve the synergistic optimization of conductive loss and polarization loss of the B‐NCP specimen. The optimized prototype B‐NCP‐1200 sample displays exceptionally efficient electromagnetic wave absorption capabilities with a minimum reflection loss (RLmin) of −52.03 dB and an effective absorption bandwidth (EAB) of 5.36 GHz. This study presents a conscientious model for comprehending the electromagnetic attenuation mechanisms associated with weakly electronegative atom doping in carbon‐based electromagnetic wave‐absorbing materials.

Distinctive adsorption and transport behaviors of short-chain versus long-chain perfluoroalkyl acids in a river sediment.

Perfluoroalkyl acids (PFAAs) embrace perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA), and other concerning chemicals of different chain length and terminal moieties. PFAAs can leach from municipal wastewater facilities as point sources discharging into rivers and receiving streams. In this study, we investigated the adsorption and transport behaviors of six select PFAAs in a Hudson River (USA) sediment in both batch and mesocosm studies. The adsorption capacities single and dual solute systems followed the order: PFBA < PFHxA ≈ PFBS < PFHxS < PFOA << PFOS. Mesocosm experiment that receives a continuous point source discharge of a mixture of these six PFAAs reached equilibrium after 4 weeks of operation. Total adsorbed PFAAs in the sediment was extracted and analyzed, following PFHxS (0.85 mg, 20.4%) ≈ PFBS (0.92 mg, 21.7%) < PFOA (1.02 mg, 27.3%) ≈ PFHxA (1.04 mg, 29.8%) < PFBA (1.12 mg, 30.1%) << PFOS (1.55 mg, 39.2%). PFOS showed highest adsorption, concentrating on the surface layer. Noticeably, two short-chain PFAAs, PFBA and PFHxA, were found with high vertical mobility, partitioning into deeper sediment. Two hotspots for PFAA sediment contamination were formed near the sediment surface downstream from the point source, providing new prospects to guide PFAA sediment cleanup and monitoring. Graphical abstract.