Next-generation High Performance Research Articles

High-Performance Broadband Image Sensing Photodetector Based on MnTe/WS2 van der Waals Epitaxial Heterostructures.

Two-dimensional transition metal dichalcogenide (TMDC) heterostructure is receiving considerable attention due to its novel electronic, optoelectronic, and spintronic devices with design-oriented and functional features. However, direct design and synthesis of high-quality TMDC/MnTe heterostructures remain difficult, which severely impede further investigations of semiconductor/magnetic semiconductor devices. Herein, the synthesis of high-quality vertically stacked WS2/MnTe heterostructures is realized via a two-step chemical vapor deposition method. Raman, photoluminescence, and scanning transmission electron microscopy characterizations reveal the high-quality and atomically sharp interfaces of the WS2/MnTe heterostructure. WS2/MnTe-based van der Waals field effect transistors demonstrate high rectification behavior with rectification ratio up to 106, as well as a typical p-n electrical transport characteristic. Notably, the fabricated WS2/MnTe photodetector exhibits sensitive and broadband photoresponse ranging from UV to NIR with a maximum responsivity of 1.2 × 103 A/W, a high external quantum efficiency of 2.7 × 105%, and fast photoresponse time of ∼50 ms. Moreover, WS2/MnTe heterostructure photodetectors possess a broadband image sensing capability at room temperature, suggesting potential applications in next-generation high-performance and broadband image sensing photodetectors.

Guest Editor’s note: Special issue on challenges and solutions for porting applications to next-generation high performance computing systems

Guest Editor’s note: Special issue on challenges and solutions for porting applications to next-generation high performance computing systems

Lignin-derived lithiophilic nitrogen-doped three-dimensional porous carbon as lithium growth guiding layers for lithium-metal batteries

The growing demand for high-performance next-generation lithium (Li)-based batteries has brought Li-metal anodes into the spotlight, due to their high theoretical capacity (3,860 mAh g-1) and low electrochemical potential (-3.04 V vs. SHE). However, the practical application of Li-metal anodes faces formidable challenges, primarily associated with dendritic Li growth resulting from non-uniform ion flux. Although previous studies utilizing carbonaceous materials having pores and lithiophilic atoms have demonstrated powerful performances, the complex process involving pore creation and doping with heteroatoms still has limitations in terms of cost-effectiveness. This study introduces a lithiophilic nitrogen (N)-doped three-dimensional (3D) porous carbon (NLC) by simply reusing and carbonizing NH2-functionalized lignin (NL), an eco-friendly biopolymer derived from waste wood generated during the pulping process. The NLC offers macro-porous spaces with a rich array of N-doped sites, capable of accommodating and guiding Li deposition to facilitate uniform Li growth. The results demonstrate the effectiveness of the NLC as the Li growth guiding layer in Li-metal batteries. A full cell incorporating the NLC as a Li growth guiding layer, with NCM811 as cathodes, exhibits a remarkable capacity of 145. 57 mAh g-1 even at a high C-rate of 5C and capacity retention of 90.3% (167 mAh g-1) after 150 cycles at 1C. These findings represent significant advancements compared to conventional Li-metal batteries.

Synergistic enhancement of chemisorption and catalytic conversion in lithium-sulfur batteries via Co3Fe7/Co5.47N separator mediator

Lithium-sulfur batteries (LSBs) show considerable potential in next-generation high performance batteries, but the heavy shuttle effect and sluggish redox kinetics of polysulfide hinder their further applications. In this paper, to address these shortcomings of LSBs, Co3Fe7/Co5.47N heterostructure were prepared and constructed from their Fe-Co Prussian blue analogue precursors under the condition of high temperature pyrolysis. The obtained Co3Fe7/Co5.47N display excellent immobilization-diffusion-conversion performance for polysulfides by synergistic effect in successfully hindering the shuttle effect of polysulfides. When the Co3Fe7/Co5.47N heterostructure were applied to modify the commercial polypropylene (PP) separator, the batteries displayed fantastic rate capacity and cycling stability. Specifically, the Co3Fe7/Co5.47N-PP batteries exhibit an extremely satisfactory initial specific capacity of 1430 m Ah/g at 0.5C, wonderful rate capacity of around 780 m Ah/g at 3C and superior per cycle decaying rate of 0.08 % for 500 cycles at 0.5C. When the current density reaches to 2C, the batteries still exhibit 501 m Ah/g after 900 cycles with 0.015 % per cycle decay rate. Besides, even in the high loading of sulfur (3.0 mg cm−2) at 0.5C, the superior cycling stability (0.075 % per cycle decay rate after 200 cycles) and high specific capacity (741 mAh/g after 200 cycles) can still be performed. Thus, this work provides a facile method for high-powered and long-life Li-S batteries with eminent entrapping-conversion processes of polysulfides.

Controllable growth of wafer-scale PdS and PdS2 nanofilms via chemical vapor deposition combined with an electron beam evaporation technique

Palladium (Pd)-based sulfides have triggered extensive interest due to their unique properties and potential applications in the fields of electronics and optoelectronics. However, the synthesis of large-scale uniform PdS and PdS2 nanofilms (NFs) remains an enormous challenge. In this work, 2-inch wafer-scale PdS and PdS2 NFs with excellent stability can be controllably prepared via chemical vapor deposition combined with electron beam evaporation technique. The thickness of the pre-deposited Pd film and the sulfurization temperature are critical for the precise synthesis of PdS and PdS2 NFs. A corresponding growth mechanism has been proposed based on our experimental results and Gibbs free energy calculations. The electrical transport properties of PdS and PdS2 NFs were explored by conductive atomic force microscopy. Our findings have achieved the controllable growth of PdS and PdS2 NFs, which may provide a pathway to facilitate PdS and PdS2 based applications for next-generation high performance optoelectronic devices.

Condensation particle counters: Exploring the limits of miniaturisation

The measurement of airborne particles continues to attract increased interest for the detection and characterisation of air pollution, emissions, fire detection, occupational and climate impacts. Concerted efforts have reduced the size and cost of optical counters that have enabled widespread sensor deployment. Currently the World Health Organisation (WHO) enforces particle regulations that are mass-based which has resulted in an influx of low-cost portable optical particle counters (OPCs) calibrated to mass standards and widely utilised for research and personal monitoring. However, OPCs are incapable of measuring particles with diameters dp≲ 300 nm which misses ultrafine particles (≤ 100 nm) that often represent the majority of particles by number concentration. Condensation particle counters (CPCs) capable of measuring ultrafine particle number concentration with high instrument sensitivity, accuracy and precision have recently been targeted for miniaturisation.Herein, we explore the limitations of the miniaturisation of a CPC growth chamber (CPC-GC). Results presented in this work use water, but equivalent expressions can be obtained for other working fluids or design criteria using the same methods. Scaling analysis considers phenomenological constraints of supersaturation, heat transfer, particle penetration and droplet growth to establish limits during miniaturisation.The results showed that optimal thermal and saturation conditions are similar where the optimum device aspect ratio is L∗≥Lmin,s∗= 1.68 Re + 7.98 and L∗≥Lmin,th∗= 1.78 Re + 8.02 respectively. L∗ is the non-dimensional aspect ratio and Lmin∗ is the minimum non-dimensional device length required as a function of the flow Reynolds number Re. Higher Reynolds numbers lead to a convection-dominated regime, where the saturation and temperature profiles take a parabolic shape. As the Reynolds number approaches unity, the reduced mass and thermal Péclet numbers result in vapour and heat diffusing upstream of the condenser, creating ellipsoidal saturation and temperature profiles. To achieve a satisfactory performance, the heat and mass transport within the CPC-GC must be convection-dominated, leading to a minimum value of Re ≳2. Desired penetration P≥0.9 for particles with an initial diameter dpinit=10nm is achieved by designs with an aspect ratio, L∗≤Lmax,p∗= 2.5 Re. Together, these constraints define an allowable range of aspect ratios for a CPC-GC as a function of the Reynolds number.The final size of the grown droplets can be controlled by varying the interaction residence time τint, defined as the time a particle spends in the supersaturation profile. Having defined a target final droplet size for optical detection, and hence having fixed τint, the aspect ratio necessary to achieve the desired growth is a function of the Reynolds number and of the dimensional radius of the CPC-GC (Ricpc) according to: Lgrowth∗=γRe/(Ricpc)2 with γ= 2τintν, where ν is the kinematic viscosity of air. Selecting a value of Ricpc such that the line for Lgrowth∗ falls in the centre of the allowable operating region defined above will optimise the dimensional CPC-GC for the selected design criteria.Limits from this model were used to realising a prototype successfully tested experimentally against a reference commercial CPC within a laboratory environment. The outcome of the present work enables designers and researchers with a toolkit to optimise the next generation of high performance miniaturised CPC-GC designs.

Fabrication of carbon quantum dots modulated/polyindole(PIn/CDs) thin film by electrospray deposition for high-performance next-generation solid-state supercapacitor

A binder-free polyindole/carbon quantum dots (PIn/CDs) thin-film/layer electrode is synthesized by a hybrid-electrospray method. The synthesized CDs and PIn/CDs samples are used for furthercharacterization. Owing to the synergistic consequence of PIn and CDs, PIn/CDs display outstanding electrochemicalassets and cyclability, whichare deserved from the presence of robust interactions amongst polymeric chains and CDs. Further, CDs offer an electron allocation pathway owing to their extraordinary electricconductivity and high specific surface area. In a 3 M KOH aqueous-electrolyte, the Qs of PCDs-2is394 C/g at 6 A/g, which is higher than other comparative electrodes. The PCDs-2 film shows excellent cyclicretention of 75% at 20 Ag−1 up to 3000 cycles. The fabricated PIn/CDs-2//rGO asymmetric device shows the highest specific capacity of 54.5 C/g at 1 A/g with theenergy and power density of 15.9 Wh/kg and 955.6 W/kg. Theseresults demonstrate that PIn/CDs thin-film could be used as an efficient electrode for supercapacitor application.

Solid-state mechanochemistry advancing two dimensional materials for lithium-ion storage applications: A mini review

The vigorous development of two-dimensional (2D) materials brings about numerous opportunities for lithium-ion batteries (LIBs) due to their unique 2D layered structure, large specific surface area, outstanding mechanical and flexibility properties, etc. Modern technologies for production of 2D materials include but are not limited to mechanochemical (solid-state/liquid-phase) exfoliation, the solvothermal method and chemical vapor deposition. In this review, strategies leading to the production of 2D materials via solid-state mechanochemistry featuring traditional high energy ball-milling and Sichuan University patented pan-milling are highlighted. The mechanism involving exfoliation, edge selective carbon radical generation of the 2D materials is delineated and this is followed by detailed discussion on representative mechanochemical techniques for tailored and improved lithium-ion storage performance. In the light of the advantages of the solid-state mechanochemical method, there is great promise for the commercialization of 2D materials for the next-generation high performance LIBs.

Multifunctional cellulose-based aerogel for intelligent fire fighting

Multifunctional biomass-based aerogels with mechanically robust and high fire safety are urgently needed for the development of environmentally-friendly intelligent fire fighting but challenging. Herein, a novel polymethylsilsesquioxane (PMSQ)/cellulose/MXene composite aerogel (PCM) with superior comprehensive performance was fabricated by ice-induced assembly and in-situ mineralization. It exhibited light weight (16.2 mg·cm−3), excellent mechanical resilience, and rapidly recovered after being subjected to the pressure of 9000 times of its own weight. Moreover, PCM demonstrated outstanding thermal insulation, hydrophobicity and sensitive piezoresistive sensing. In addition, benefiting from the synergism of PMSQ and MXene, PCM displayed good flame retardancy and improved thermostability. The limiting oxygen index of PCM was higher than 45.0 %, and it quickly self-extinguished after being removed away from fire. More importantly, the rapid electrical resistance reduction of MXene at high temperature endowed PCM with sensitive fire-warning capability (trigger time was less than 1.8 s), which provided valuable time for people to evacuate and relief. This work provides new insights for the preparation and application of the next-generation high performance biomass-based aerogels.

Improved epitaxy of CsI(Tl) film on Si substrate buffered by graphene for X-ray detection

The growth of the CsI(Tl) scintillators deposited on glass substrates with proper wavelength matching the mainstream semiconductor circuits is crucial for X-ray imaging industry. But the coupling loss between the scintillators and silicon based photo sensors has limited the performance. So fabricating CsI(Tl) films on monocrystalline silicon is greatly important for next-generation high performance X-ray image devices. However, the lattice and thermal mismatch between CsI(Tl) and Si always deteriorates the morphology and structure, and thus degrades the property of the CsI(Tl) scintillation converters. Here, by utilizing crystalline graphene(Gr) as a buffer layer, the van der Waals epitaxial growth of CsI(Tl) film on Si(111) substrate is reported and its advanced applications are demonstrated. The introduced graphene buffer layer extremely frees the stress between CsI(Tl) and Si substrate. Therefore, the CsI(Tl) films show perfect micro-columnar and crystalline structures, and then, exhibit much higher light output and signal to noise ratio, and better modulation transfer functions and a bar pattern X-ray image compared to that on bare Si(111) substrate. This facile method not only lays the foundation for the epitaxy of the alkali halide crystals, including CsI(Tl), onto Si-based detectors and its applications in radiation detection, but also may broaden a new perspective of deposition of CsI(Tl) scintillators into flexible substrates.

Controlled and tunable growth of ambient stable 2D PtS2 thin film and its high-performance broadband photodetectors

PtS2, a group-10 transition metal dichalcogenide (TMDC), has recently attracted enormous interest owing to its tunable band gap (0.25–1.6 eV), high carrier mobility, and large current on-off ratio of the devices. In contrast to other TMDCs, the growth of PtS2 is more difficult, partly due to the nobility of Pt and partly due to the easier formation of the more stable PtS phase rather than PtS2. Herein, we investigate the effect of critical growth parameters like sulfur amount, Pt thickness and gas flow rate for the control and large area growth of PtS2 via thermal assisted conversion process in atmospheric chemical vapour deposition. The detailed characterization using Raman and X-ray photoelectron spectroscopy (XPS) suggests a controlled transition from PtS to PtS2, which can be obtained by fine tuning of these growth parameters. Furthermore, the optimized growth condition of PtS2 is highly reproducible and can be grown on varieties of substrates like SiO2/Si, sapphire, p-type Si, and even on flexible mica substrate. Finally, a high-performance PtS2 photodetector (PD) was fabricated on different substrates. The PD fabricated on SiO2/Si substrate with a detection range covering from visible to NIR region (400–1100 nm) showed a high responsivity and detectivity of 31.38 AW-1 and 3.92 × 1013 Jones, respectively, under 900 nm illumination at a low bias of 1 V. This work demonstrates an effective approach to control the growth of PtS2 on varieties of substrate for high-performance next-generation photodetector for NIR photodetection applications.

Nonvolatile Control of Metal-Insulator Transition in VO2 and Its Applications

With the advent of the 4th industrial revolution era, there has been a high demand for high-performance electronic devices capable of collecting, storing, and calculating vast amounts of data. Vanadium dioxide (VO<sub>2</sub>) is considered an attractive candidate for next-generation electronic devices as a prototypical strongly correlated material exhibiting a metal-insulator transition (MIT) accompanied by huge electrical resistivity changes in a few nanoseconds. The nonvolatile control of the MIT in VO<sub>2</sub> has recently been the subject of intensive research. In this report, we review recent advancements in the field of nonvolatile control of MIT in VO<sub>2</sub>, using electrochemical redox reactions, inverse piezoelectric effect, and ferroelectric polarization, and their potential to develop high-performance next-generation electronic devices.

Ultrafine Sb2O3 Nanoparticle-Decorated Reduced Graphene Oxide as an Anode Material for Lithium-Ion Batteries

Antimony (Sb)-based materials have shown great potential as anode materials for lithium-ion batteries (LIBs) owing to their high energy density as well as long lifespan. However, the huge volume variation upon cycling will result in severe capacity fading, thus hindering the practical application of Sb-based anode materials. Herein, an ultrafine Sb2O3 nanoparticle-decorated reduced graphene oxide (rGO) composite (denoted as Sb2O3/rGO) was developed through a facile thermal decomposition of antimony 2-ethylhexanoate on rGO in the air at low temperatures, where the ultrafine Sb2O3 nanoparticles are homogeneously anchored on the rGO substrate. Benefiting from the rich mesoporous structure, large specific surface area, moderate mass loading, and uniform dispersion of ultrafine Sb2O3 nanoparticles, the optimized Sb2O3/rGO-100 electrode showed enhanced electrode–electrolyte contact area and ion/electron transferability. When applied as an anode material for LIBs, the Sb2O3/rGO-100 electrode exhibited excellent cycling stability and rate performance, delivering a high reversible capacity of 513 mAh g–1 at 0.5 A g–1 after 300 cycles. Ex situ transmission electron microscopy reveals that the nanoscale configuration of rGO and Sb2O3 nanoparticles of Sb2O3/rGO-100 was well maintained, while the bulk Sb2O3 crushed into pieces after cycling, further confirming the robust structure of the composite. More importantly, the synthetic method may also be commonly applied to other metal oxides, which is promising for the development of high-performance next-generation electrochemical energy storage devices.

Nonvolatile Ferroelectric LiNbO3 Domain Wall Crossbar Memory

High-density domain wall memory based on crossbar architecture is a strong contender among next-generation high performance versatile memories due to its ultra-fast operation speed and excellent size scalability. Herein, we report 4 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 4 domain wall crossbar memory arrays fabricated on a LiNbO3 single crystal. Reversible creation and erasure of conducting domain walls between two antiparallel/parallel domains at bipolar write voltages enable the storage of digital “0” and “1” information. At the crosspoint of each word and bit lines, the memory cell can be accurately accessed, programmed and erased. The diode-like rectification of readout currents exhibited by all memory cells can inhibit read and write crosstalk. The electrical testing results in the crossbar memory array demonstrated the good stability of on/off currents and good uniformity of operating voltages, which can be reflected by the fact that the distribution of the coercive voltages is within 2.9 V and the “on”/ “off” current ratio is around 100 at a reading voltage of 3 V. Good data retention and fatigue resistance are also exhibited, making it possible to integrate domain wall random access memories in high density and reliability.

Electrocatalytic hydrogen and oxygen evolution reactions: Role of two-dimensional layered materials and their composites

Electrocatalytic hydrogen and oxygen evolution reactions (HER & OER) are the fundamental key processes of the overall water splitting towards sustainable hydrogen production. The reaction efficiency of these processes are majorly controlled by the characteristics (structure and properties) of the crucial components such as the electrocatalyst as well as the electrolyte system. In particular, the detailed investigation of the structure-property relationship of electrocatalyst along with reaction mechanism and electrokinetics supporting through computational calculations would boost the design and development of high-performance next-generation electrocatalytic systems. The electrocatalysts with higher electrical conductivity and more exposed active sites always exhibit better performance than the nonporous bulk materials. The transition-metal based 2D layered materials are highly suitable for this purpose due to their tunable interlayer spacing, edge-active sites and better electrical conductivity. In this review, the development of non-precious transition metal-based 2D layered materials including transition metal dichalcogenides, layered-double hydroxides, MXenes, and graphitic carbon nitride towards the HER & OER activities is discussed with very recent examples. The synthesis and electrocatalytic performance of these 2D layered materials and their composites are summarized along with the computational studies. Finally, the present challenges in the design of high-performance electrocatalysts together with the future perspectives are detailed in this review.

Electric Eel Biomimetics for Energy Storage and Conversion.

The electric eel is known as the most powerful creature to generate electricity with a discharge voltage up to 860V and peak current up to 1 A. These surprising properties are the results of billions of years of evolution on the electrical biological structure and bulk, and now have triggered great research interest in electric eel biomimetics for designing innovated configurations and components of energy storage and conversion devices. In this review, first, the bioelectrical behavior of electric eels is surveyed, followed by the physiological structure to reveal the discharge characteristics and principles of electric organs and electrocytes. Additionally, underlying electrochemical mechanisms and models for calculating the potential and current of electrocytes are presented. Central to this review is the recent progress of electric-eel-inspired innovations and applications for energy storage and conversion, particularly including novel power sources, triboelectric nanogenerators, and nanochannel ion-selective membranes for salinity gradient energy harvesting. Finally, insights on the challenges at the moment and the perspectives on the future research prospects are critically compiled. It is suggested that energy-related electric eel biomimetics will greatly boost the development of next-generation high performance, green, and functional electronics.

In-situ synthesis of Si@G@TiC double protective layer structure for enhancing cycling stability of lithium-ion batteries

Si-based materials are considered as the highly promising candidates for the next-generation high performance Li-ion batteries, and the development of Si/graphite anode is regarded as one of the common approaches to realize commercial application of it. Unfortunately, although the introduced graphite phase improves the electrical conductivity, the poor interfacial bonding strength as well as the limited ability to relieve the volume expansion of silicon still lead to the inferior cycle performance. Herein, a novel Si-based anode structure is constructed and modified with a double protective layer, in which the inner graphite is in close contact with silicon to improve the electrical conductivity while partially alleviating the volume expansion of silicon, and the outer rigid TiC layer further stabilizes the electrode structure as well as suppress the side reactions between active materials and electrolyte. Owing to the unique structural design, the cycling performance of the Si@G@TiC electrode is greatly improved, and the capacity retention of the electrode is high up to 85% after 300 cycles at 0.2 A g−1.

Facile synthesis of petal-like MnMoO4/Ni(OH)2 ultrathin nanosheets for high-performance asymmetric supercapacitor

Petal-like MnMoO4/Ni(OH)2 ultrathin nanosheets were synthesized via a facile hydrothermal method, and their electrochemical performance was evaluated. Electrochemical analysis indicated that the specific capacitance was 1999.6F/g at 1 A/g, with an excellent cycling stability of 97.2 % over 5000 cycles at 10 A/g. An asymmetric supercapacitor MnMoO4/Ni(OH)2//AC exhibited a good energy density of 60.2 W-h/kg at 800 W/kg. Hence, the MnMoO4/Ni(OH)2 electrode material is a potential candidate for the design of high-performance next-generation supercapacitors.

Validation of S(α, β) thermal neutron scattering libraries using pulsed-neutron die-away experiments

Validation of the accuracy of S(α, β) thermal scattering law (TSL) evaluations for moderator materials is an important task for the development of high-performance nuclear engineering systems. Many recent thermal neutron scattering evaluations have had limited experimental validation. Like other nuclear data, validation of TSL libraries has historically been by integral criticality benchmarks. While sufficient for general study, these benchmarks often have limited sensitivity to the tested TSLs, and compounding uncertainties from other nuclear data can make validation ambiguous. In some cases, no criticality benchmarks exist that are sensitive to the TSLs of interest. With the development of high-performance next-generation thermal nuclear reactors, alternative validation of applicable TSLs is of high importance. By performing thermal neutron measurements via pulsed-neutron die-away (PNDA) experiments, along with parallel simulations, the integral performance of various TSL evaluations can be compared to measured experimental data. An experimental testbed using a D-T neutron generator, moderator sample, and thermal neutron detector was assembled at Rensselaer Polytechnic Institute. A Thermo Scientific D211 Deuterium-Tritium Neutron generator is used to generate 10 μs neutron pulses. Various targets of different sizes and geometries are used to moderate the neutrons. Multiple detector types and configurations were tested to optimize the experiment. The room-temperature polyethylene TSL evaluation is well vetted and is similar across different evaluations. This makes it an ideal evaluation to compare with the experimental results.

Machine learning framework for the analysis and prediction of energy loss for non-fullerene organic solar cells

The efficiency of organic solar cells (OSCs) has been improved more than 19% recently with the development of non-fullerene acceptor materials. Further improvement is still attainable with the optimal combinations of donors and acceptors that provide minimal energy losses. In this work, a data-enabled machine-learning (ML) framework was employed to predict the energy losses in the polymer:non-fullerene acceptor based devices. Based on the collected experimental dataset, the prediction accuracies of various machine learning models were systematically compared by estimating mean absolute percentage errors (MAPE), root mean squared errors (RMSE), and person’s r coefficient. The Random Forest regression model showed the best performance in predicting the energy losses with a correlation coefficient of 0.83 and relative error in the range of 0 – 20%. The predictive ability of this model was further validated using the different parameters of devices with power conversion efficiency range of 6 – 18%. Three different donor–acceptor combinations were chosen for fabricating the photovoltaic devices to fit this model into practical devices and experimentally obtained energy loss values were compared with the predicted values. In addition, the device parameters with the molecular descriptors to understand the correlation and energy loss is highly correlated with the HOMO offset. This study demonstrates that the ML approach provide an effective method to predict and virtual screen of promising donor–acceptor pairs with minimal energy loss and would be useful for developing next-generation high performance solar cell materials.