Nanometer Control of Ruddlesden-Popper Interlayers by Thermal Evaporation for Efficient Perovskite Photovoltaics.

Solution-processed Ruddlesden-Popper (RP) interlayers in lead halide perovskite solar cells (PSCs) present processing challenges due to fast film formation and uncontrolled growth of phases and layer thickness at interfaces. In this work, an alternative, solvent-free, thermal co-evaporation process is developed to deposit RP interlayers. The method provides precise control on interlayer thickness and enables understanding its role on charge-carrier extraction. Studying RP film growth reveals the development of heterointerfaces when deposited on three-dimensional (3D) perovskite layers. This allows a large thickness window with an optimum between 20 nm and 40 nm to improve the optoelectronic properties of the underlying 3D perovskite. Solar cells using evaporated interlayers achieve power conversion efficiency of 21.6%, compared to 19.6% for untreated devices, driven by improvements in the open-circuit voltage and fill factor. This work sheds light on the importance of phase and thickness control of passivation layers, which ultimately determine the solar cell performance in state-of-the-art PSCs.

Mathematical modelling of fracture waves in a blocky medium with thin compliant interlayers.

Physical mechanisms that contribute to the generation of fracture waves in condensed media under intensive dynamic impacts have not been fully studied. One of the hypotheses is that this process is associated with the blocky structure of a material. As the loading wave passes, the compliant interlayers between blocks are fractured, releasing the energy of self-balanced initial stresses in the blocks, which supports the motion of the fracture wave. We propose a new efficient numerical method for the analysis of the wave nature of the propagation of a system of cracks in thin interlayers of a blocky medium with complex rheological properties. The method is based on a variational formulation of the constitutive relations for the deformation of elastic-plastic materials, as well as the conditions for contact interaction of blocks through interlayers. We have developed a parallel computational algorithm that implements this method for supercomputers with cluster architecture. The results of the numerical simulation of the fracture wave propagation in tempered glass under the action of distributed pulse disturbances are presented. This article is part of the theme issue 'Non-smooth variational problems with applications in mechanics'.

Characterization of the Lithium/Solid Electrolyte Interface in the Presence of Nanometer-thin TiOx Layers for All-Solid-State Batteries.

It is unclear, which role space charge layers (SCLs) play within an all-solid-state battery during operation with high current densities, and to which extent they form. Herein, we use a solid electrolyte with a known SCL formation and investigate it in a symmetric cell under non-blocking conditions with Li metal electrodes. Since the used LICGC™ electrolyte is known for its instability against lithium, it is protected from rapid degradation by nanometer-thin layers of TiOx deployed by atomic layer deposition. Close attention is given to the interfacial properties, as now additional Li+ can traverse through the interface depending on the applied bias potential. The interlayer's impedance response shows efficient lithium-ion conduction for low bias potentials and a diffusion-limiting effect towards high positive and negative potentials. SCLs grow up to a thickness of 5.1 µm. Additionally, estimating the apparent rate constant of the charge transfer across the interface indicates that the potentials where kinetics are hindered coincide with the widest SCLs. In conclusion, the investigation under higher steady-state currents was only possible because of the improved stability due to the interlayer. No chemo-physical failure could be observed after 800+ hours of cycling. However, SEM study shows a new phase at the interface.

Conductive Polymer-Based Interlayers in Restraining the Polysulfide Shuttle of Lithium-Sulfur Batteries.

Lithium-sulfur batteries (LSBs) are considered a promising candidate for next-generation energy storage devices due to the advantages of high theoretical specific capacity, abundant resources and being environmentally friendly. However, the severe shuttle effect of polysulfides causes the low utilization of active substances and rapid capacity fading, thus seriously limiting their practical application. The introduction of conductive polymer-based interlayers between cathodes and separators is considered to be an effective method to solve this problem because they can largely confine, anchor and convert the soluble polysulfides. In this review, the recent progress of conductive polymer-based interlayers used in LSBs is summarized, including free-standing conductive polymer-based interlayers, conductive polymer-based interlayer modified separators and conductive polymer-based interlayer modified sulfur electrodes. Furthermore, some suggestions on rational design and preparation of conductive polymer-based interlayers are put forward to highlight the future development of LSBs.

Dependence of Interlayer or Sulfur Host on Hollow Framework of Lithium-Sulfur Battery.

Lithium-sulfur batteries are recognized as the next generation of high-specific energy secondary batteries owing to their satisfactory theoretical specific capacity and energy density. However, their commercial application is greatly limited by a series of problems, including disordered migration behavior, sluggish redox kinetics, and the serious shuttle effect of lithium polysulfides. One of the most efficient approaches to physically limit the shuttle effect is the rational design of a hollow framework as sulfur host. However, the influence of the hollow structure on the interlayers has not been clearly reported. In this study, the Mo2 C/C catalysts with hollow(H-Mo2 C/C) and solid(S-Mo2 C/C) frameworks are rationally designed to explore the dependence of the hollow structure on the interlayer or sulfur host. In contrast to the physical limitations of the hollow framework as host, the hollow structure of the interlayer inhibited lithium-ion diffusion, resulting in poor electrochemical properties at high current densities. Based on the superiority of the various frameworks, the H-Mo2 C/C@S | S-Mo2 C/C@PP | Li cells are assembled and displayed excellent electrochemical performance. This work re-examines the design requirements and principles of catalyst frameworks in different battery units.

Enhanced Stability and Highly Bright Electroluminescence of AgInZnS/CdS/ZnS Quantum Dots through Complete Isolation of Core and Shell via a CdS Interlayer.

An approach for synthesizing AgInZnS/CdS/ZnS core-shell-shell quantum dots (QDs) that demonstrate exceptional stability and electroluminescence (EL) performance is introduced. This approach involves incorporating a cadmium sulfide (CdS) interlayer between an AgInZnS (AIZS) core and a zinc sulfide (ZnS) shell to prevent the diffusion of Zn ions into the AIZS core and the cation exchange at the core-shell interface. Consequently, a uniform and thick ZnS shell, with a thickness of 2.9 nm, is formed, which significantly enhances the stability and increases the photoluminescence quantum yield (87.5%) of the QDs. The potential for AIZS/CdS/ZnS QDs in electroluminescent devices is evaluated, and an external quantum efficiency of 9.6% in the 645 nm is achieved. These findings highlight the importance of uniform and thick ZnS shells in improving the stability and EL performance of QDs.

In Situ Formed Tribofilms as Efficient Organic/Inorganic Hybrid Interlayers for Stabilizing Lithium Metal Anodes.

The practical application of Li metal anodes (LMAs) is limited by uncontrolled dendrite growth and side reactions. Herein, we propose a new friction-induced strategy to produce high-performance thin Li anode (Li@CFO). By virtue of the in situ friction reaction between fluoropolymer grease and Li strips during rolling, a robust organic/inorganic hybrid interlayer (lithiophilic LiF/LiC6 framework hybridized -CF2-O-CF2- chains) was formed atop Li metal. The derived interface contributes to reversible Li plating/stripping behaviors by mitigating side reactions and decreasing the solvation degree at the interface. The Li@CFO||Li@CFO symmetrical cell exhibits a remarkable lifespan for 5,600 h (1.0 mA cm-2 and 1.0 mAh cm-2) and 1,350 cycles even at a harsh condition (18.0 mA cm-2 and 3.0 mAh cm-2). When paired with high-loading LiFePO4 cathodes, the full cell lasts over 450 cycles at 1C with a high-capacity retention of 99.9%. This work provides a new friction-induced strategy for producing high-performance thin LMAs.

Demonstration of the threshold-switching memory devices using EMIm(AlCl3)Cl and ZnO for neuromorphic applications.

The threshold-switching behaviors of the synapses lead to energy-efficient operation in the neural computing system. Here, we demonstrated the threshold-switching memory devices by inserting the ZnO layer into the ionic synaptic devices. The EMIm(AlCl3)Cl is utilized as the electrolyte because its conductance can be tuned by the charge states of the Al-based ions. The redox reactions of the Al ions in the electrolyte can lead to the analog resistive switching characteristics, such as excitatory postsynaptic current, paired-pulse facilitation, potentiation, and depression. By inserting the ZnO layer into the EMIm(AlCl3)-based ionic synaptic devices, the threshold switching behaviors are demonstrated. Using the resistivity difference between ZnO and EMIm(AlCl3)Cl, the analog resistive switching behaviors are tunned as the threshold-switching behaviors. The threshold-switching behaviors are achieved by applying the spike stimuli to the device. Demonstration of the threshold-switching behaviors of the ionic synaptic devices has a possibility to achieve high energy-efficiency for the ion-based artificial synapses.

Design Strategies for Anodes and Interfaces Toward Practical Solid-State Li-Metal Batteries.

Solid-state Li-metal batteries (based on solid-state electrolytes) offer excellent safety and exhibit high potential to overcome the energy-density limitations of current Li-ion batteries, making them suitable candidates for the rapidly developing fields of electric vehicles and energy-storage systems. However, establishing close solid-solid contact is challenging, and Li-dendrite formation in solid-state electrolytes at high current densities causes fatal technical problems (due to high interfacial resistance and short-circuit failure). The Li metal/solid electrolyte interfacial properties significantly influence the kinetics of Li-metal batteries and short-circuit formation. This review discusses various strategies for introducing anode interlayers, from the perspective of reducing the interfacial resistance and preventing short-circuit formation. In addition, 3D anode structural-design strategies are discussed to alleviate the stress caused by volume changes during charging and discharging. This review highlights the importance of comprehensive anode/electrolyte interface control and anode design strategies that reduce the interfacial resistance, hinder short-circuit formation, and facilitate stress relief for developing Li-metal batteries with commercial-level performance.

Growing Electrocatalytic Conjugated Microporous Polymers on Self-Standing Carbon Nanotube Films Promotes the Rate Capability of Li-S Batteries.

Lithium-sulfur (Li-S) batteries hold great promise for widespread application on account of their high theoretical energy density (2600 Wh kg-1 ) and the advantages of sulfur. Practical use, however, is impeded by the shuttle effect of polysulfides along with sluggish cathode kinetics. it is reported that such deleterious issues can be overcome by using a composite film (denoted as V-CMP@MWNT) that consists of a conjugated microporous polymer (CMP) embedded with vanadium single-atom catalysts (V SACs) and a network of multi-walled carbon nanotubes (MWNTs). V-CMP@MWNT films are fabricated by first electropolymerizing a bidentate ligand designed to coordinate to V metals on self-standing MWNT films followed by treating the CMP with a solution containing V ions. Li-S cells containing a V-CMP@MWNT film as interlayer exhibit outstanding performance metrics including a high cycling stability (616 mA h g-1 at 0.5 C after 1000 cycles) and rate capability (804 mA h g-1 at 10 C). An extraordinary area-specific capacity of 13.2 mA h cm-2 is also measured at a high sulfur loading of 12.2 mg cm-2 . The underlying mechanism that enables the V SACs to promote cathode kinetics and suppress the shuttle effect is elucidated through a series of electrochemical and spectroscopic techniques.

Interlayer Tailoring of Ti-6Al-4V and 17-4PH Stainless Steel Joint by Tungsten Inert Gas Welding.

The development of robust and efficient methods for constructing and joining complex metal specimens with high bonding quality and durability is of paramount importance for various industries, e.g., aerospace, deep space, and automobiles. This study investigated the fabrication and characterization of two types of multilayered specimens prepared by tungsten inert gas (TIG) welding: Ti-6Al-4V/V/Cu/Monel400/17-4PH (Specimen 1) and Ti-6Al-4V/Nb/Ni-Ti/Ni-Cr/17-4PH (Specimen 2). The specimens were fabricated by depositing individual layers of each material onto a Ti-6Al-4V base plate, and subsequently welding them to the 17-4PH steel. The specimens exhibited an effective internal bonding without any cracks, accompanied by a high tensile strength, with Specimen 1 exhibiting a significantly higher tensile strength than Specimen 2. However, the substantial interlayer penetration of Fe and Ni in the Cu and Monel layers of Specimen 1 and the diffusion of Ti along the Nb and Ni-Ti layers in Specimen 2 resulted in a nonuniform elemental distribution, raising concerns about the lamination quality. This study successfully achieved elemental separation of Fe/Ti and V/Fe, which is vital for preventing the formation of detrimental intermetallic compounds, particularly in the fabrication of complex multilayered specimens, representing the prime novelty of this work. Our study highlights the potential of TIG welding for the fabrication of complex specimens with high bonding quality and durability.

Insight into Accelerating Polysulfides Redox Kinetics by BN@MXene Heterostructure for Li-S Batteries.

Sluggish redox kinetics and shuttle effect of polysulfides hinder the extensive application of the lithium-sulfur batteries (LSBs). Herein a functional heterostructure of boron nitride (BN) and MXene with an alternately layered structure (BN@MXene) is designed as separator interlayer. High efficiency Li+ transmission, uniform lithium deposition, strong adsorption, and efficient catalytic conversion activities of lithium polysulfides (LiPSs) realized by this heterostructure are confirmed by experiments and theoretical calculations. The alternately layered structure provides unblocked ion transmission channels and abundant active sites to accelerate the polysulfides redox kinetics with reduced energy barriers of oxidation and reduction reactions. As a result, the LSBs deliver an initial discharge capacity of up to 1273.9 mAh g-1 at 0.2 °C and a low decay of 0.058% per cycle in long-term cycling up to 700 cycles at 1 °C. This work provides an effective designing strategy to accelerate the polysulfides redox kinetics for advanced Li-S electrochemical system.

Uniform Zinc Deposition Regulated by a Nitrogen-Doped MXene Artificial Solid Electrolyte Interlayer.

The dendrite growth and side reactions of zinc metal anode in mildly acidic electrolytes seriously hinder the practical application of aqueous zinc-ion battery. To address these issues, an artificial protective layer of nitrogen-doped MXene (NMX) is used to protect the zinc anode. The NMX protective layer has high conductivity and uniformly distributed zincophilic sites, which can not only homogenize the local electric field on the electrode interface but also accelerate the kinetics for Zn deposition. As a result, the NMX protective layer induces uniform zinc deposition and reduces the overpotential of the electrode. Encouragingly, this NMX-protected Zn anode can cycle stably for 1900 h at 1 mA cm-2 and 1 mAh cm-2 . In asymmetric cells, it achieves high cycle reversibility with an average Coulomb efficiency of 99.79% for 4800 cycles at 5 mA cm-2 .

Enhancing Interfacial Strength and Wettability for Wide-Temperature Sodium Metal Batteries.

Development of high-performance sodium metal batteries (SMBs) with a wide operating temperature range (from -40 to 55 °C) is highly challenging. Herein, an artificial hybrid interlayer composed of sodium phosphide (Na3 P) and metal vanadium (V) is constructed for wide-temperature-range SMBs via vanadium phosphide pretreatment. As evidenced by simulation, the VP-Na interlayer can regulate redistribution of Na+ flux, which is beneficial for homogeneous Na deposition. Moreover, the experimental results confirm that the artificial hybrid interlayer possesses a high Young's modulus and a compact structure, which can effectively suppress Na dendrite growth and alleviate the parasitic reaction even at 55 °C. In addition, the VP-Na interlayer exhibits the capability to knock down the kinetic barriers for fast Na+ transportation, realizing a 30-fold decrease in impedance at -40 °C. Symmetrical VP-Na cells present a prolonged lifespan reaching 1200, 500, and 500 h at room temperature, 55 °C and -40 °C, respectively. In Na3 V2 (PO4 )3 ||VP-Na full cells, a high reversible capacity of 88, 89.8, and 50.3 mAh g-1 can be sustained after 1600, 1000, and 600 cycles at room temperature, 55 °C and -40 °C, respectively. The pretreatment formed artificial hybrid interlayer proves to be an effective strategy to achieve wide-temperature-range SMBs.

Integrated effect of bulk cations on nano-confined reactivity of clay-intercalated subnanoscale zero-valent iron in water-tetrahydrofuran mixtures.

Smectite clay-intercalated subnanoscale zero-valent iron (CSZVI) exhibits superior reactivity toward contaminants due to the small iron clusters (∼0.5 nm) under nano-confinement, which however is significantly influenced by the solution chemistry e.g., various cations, of polluted soil and water. This work was undertaken to elucidate the mechanisms of solution chemistry effects on dehalogenation ability of CSZVI in water-tetrahydrofuran solution using decabromodiphenyl ether as a model contaminant. By combined spectroscopic characterization and molecular dynamics simulation, it was revealed that bulk cations, i.e., Na+, K+, Mg2+ and Ca2+ collectively affected the interlayer distance, water content and Brønsted acidity of CSZVI and thus its degradation efficiency. Although causing inter-particle aggregation, Mg2+ induced optimal nano-confined interlayers at concentration of 20 mM, exhibiting a superior debromination efficiency with rate constant 9.84 times larger than that by the common nano-sized ZVI. Conversely, K+ rendered the interlayers less reactive, but protected CSZVI from corrosion loss with higher electron utilization efficiency, which was 1.7 times higher than CSZVI in presence of Mg2+. The findings provide new strategies to manipulate the reactivity of nano-confined CSZVI for effective wastewater and contaminated soil remediation.

Diazabicyclic Electroactive Ionenes for Efficient and Stable Organic Solar Cells.

Electroactive ionenes combining caged-shaped diazabicyclic cations and aromatic diimides were developed as interlayers in organic solar cells (OSCs). These ionenes reduce the work-function of air-stable metal electrodes (e.g., Ag, Cu and Au) by generating strong interfacial dipoles, and their optoelectronic and morphological characters can be modulated by aromatic diimides, leading to high conductivity and good compatibility with active layers. The optimal ionene exhibits superior charge-transport, desirable crystallinity, and weak visible-absorption, boosting the efficiency of benchmark PM6 : Y6-based OSCs up to 17.44 %. The corresponding normal devices show excellent stability at maximum power point test under one sun illumination for 1000 h. Replacing Y6 with L8-BO promotes the efficiency to 18.43 %, one of the highest in binary OSCs. Notably, high efficiencies >16 % are maintained as the interlayer thickness increasing to 105 nm, the best result with interlayer-thickness over 100 nm.

Effect of Geometry and Orientation on the Tensile Properties and Failure Mechanisms of Compliant Suture Joints.

Compliant sutures surrounded by stiff matrices are present in biological armors and carapaces, providing enhanced mechanical performance. Understanding the mechanisms through which these sutured composites achieve outstanding properties is key to developing engineering materials with improved strength and toughness. This article studies the impact of suture geometry and load direction on the performance of suture joints using a two-stage reactive polymer resin that enables facile photopatterning of mechanical heterogeneity within a single polymer network. Compliant sinusoidal sutures with varying geometries are photopatterned into stiff matrices, generating a modulus contrast of 2 orders of magnitude. Empirical relationships are developed connecting suture wavelength and amplitude to composite performance under parallel and perpendicular loading conditions. Results indicate that a greater suture interdigitation broadly improves composite performance when loading is applied perpendicular to suture joints but has deleterious effects when loading is applied parallel to the joint. Investigations into the failure mechanisms under perpendicular loading highlight the interplay between suture geometry and crack growth stability after damage initiation occurs. Our findings could enable a framework for engineering composites and bio-inspired structures in the future.

Reduced fatigue and leakage of ferroelectric TiN/Hf0.5Zr0.5O2/TiN capacitors by thin alumina interlayers at the top or bottom interface.

Hf0.5Zr0.5O2(HZO) thin films are promising candidates for non-volatile memory and other related applications due to their demonstrated ferroelectricity at the nanoscale and compatibility with Si processing. However, one reason that HZO has not been fully scaled into industrial applications is due to its deleterious wake-up and fatigue behavior which leads to an inconsistent remanent polarization during cycling. In this study, we explore an interfacial engineering strategy in which we insert 1 nm Al2O3interlayers at either the top or bottom HZO/TiN interface of sequentially deposited metal-ferroelectric-metal capacitors. By inserting an interfacial layer while limiting exposure to the ambient environment, we successfully introduce a protective passivating layer of Al2O3that provides excess oxygen to mitigate vacancy formation at the interface. We report that TiN/HZO/TiN capacitors with a 1 nm Al2O3at the top interface demonstrate a higher remanent polarization (2Pr∼ 42µC cm-2) and endurance limit beyond 108cycles at a cycling field amplitude of 3.5 MV cm-1. We use time-of-flight secondary ion mass spectrometry, energy dispersive spectroscopy, and grazing incidence x-ray diffraction to elucidate the origin of enhanced endurance and leakage properties in capacitors with an inserted 1 nm Al2O3layer. We demonstrate that the use of Al2O3as a passivating dielectric, coupled with sequential ALD fabrication, is an effective means of interfacial engineering and enhances the performance of ferroelectric HZO devices.

Influence of Acid-Doped Poly(ethylene imine) Interlayers on the Performance of Polymer:Nonfullerene Solar Cells.

This work reports that ultrathin polymeric films doped with organic acid molecules can act as an electron-transporting interfacial layer in polymer:nonfullerene solar cells. The polymeric interfacial layers, which consist of poly(ethylene imine) (PEI) doped with 3-hydroxypropane-1-sulfonic acid (HPSA) at various HPSA molar ratios, are introduced between transparent indium-tin oxide (ITO) electrodes and polymer:nonfullerene bulk heterojunction layers. The HPSA-doped PEI (PEI:HPSA) films are optically translucent in the wavelength range of ≈300-800 nm, while the acidity of PEI solutions reached ≈pH = 7 at HPSA = 30 mol%. The power conversion efficiency of solar cells is improved by doping 20 mol% HPSA due to the increased short circuit current density without open circuit voltage reduction. The improvement in solar cell performances is attributed to an adequate control of HPSA doping ratios, which spares undoped amine units of PEI for making sufficient net dipole layers with ITO surfaces and makes permanent charges for high electrical conductivity in the layers. The surface morphology and doped states are characterized with atomic force microscopy and X-ray photoelectron spectroscopy.

Ion Drift and Polarization in Thin SiO2 and HfO2 Layers Inserted in Silicon on Sapphire.

To reduce the built-in positive charge value at the silicon-on-sapphire (SOS) phase border obtained by bonding and a hydrogen transfer, thermal silicon oxide (SiO2) layers with a thickness of 50-310 nm and HfO2 layers with a thickness of 20 nm were inserted between silicon and sapphire by plasma-enhanced atomic layer deposition (PEALD). After high-temperature annealing at 1100 °C, these layers led to a hysteresis in the drain current-gate voltage curves and a field-induced switching of threshold voltage in the SOS pseudo-MOSFET. For the inserted SiO2 with a thickness of 310 nm, the transfer transistor characteristics measured in the temperature ranging from 25 to 300 °C demonstrated a triple increase in the hysteresis window with the increasing temperature. It was associated with the ion drift and the formation of electric dipoles at the silicon dioxide boundaries. A much slower increase in the window with temperature for the inserted HfO2 layer was explained by the dominant ferroelectric polarization switching in the inserted HfO2 layer. Thus, the experiments allowed for a separation of the effects of mobile ions and ferroelectric polarization on the observed transfer characteristics of hysteresis in structures of Si/HfO2/sapphire and Si/SiO2/sapphire.