Preparation of MXene-based hybrids and their application in neuromorphic devices

The traditional von Neumann computing architecture has relatively-low information processing speed and high power consumption,making it difficult to meet the computing needs of artificial intelligence(AI).Neuromorphic computing systems,with massively parallel computing capability and low power consumption,have been considered as an ideal option for data storage and AI computing in the future.Memristor,as the fourth basic electronic component besides resistance,capacitance and inductance,is one of the most competitive candidates for neuromorphic computing systems benefiting from the simple structure,continuously adjustable conductivity state,ultra-low power consumption,high switching speed and compatibility with existing CMOS technology.The memristors with applying MXene-based hybrids have attracted significant attention in recent years.Here,we introduce the latest progress in the synthesis of MXene-based hybrids and summarize their potential applications in memristor devices and neuromorphological intelligence.We explore the development trend of memristors constructed by combining MXenes with other functional materials and emphatically discuss the potential mechanism of MXenes-based memristor devices.Finally,the future prospects and directions of MXene-based memristors are briefly described.

Toluene Processed All-Polymer Solar Cells with 18%Efficiency and Enhanced Stability Enabled by Solid Additive:Comparison Between Sequential-Processing and Blend-Casting

The emergence of polymerized small molecule acceptors(PSMAs)has significantly improved the performance of all-polymer solar cells(all-PSCs).However,the pace of device engineering lacks behind that of materials development,so that a majority of the PSMAs have not fulfilled their potentials.Furthermore,most high-performance all-PSCs rely on the use of chloroform as the processing solvent.For instance,the recent highperformance PSMA,named PJ1-γ,with high LUMO,and HOMO levels,could only achieve a PCE of 16.1%with a high-energy-level donor(JD40)using chloroform.Herein,we present a methodology combining sequential processing(SqP)with the addition of 0.5%wt PC_(71)BM as a solid additive(SA)to achieve an impressive efficiency of 18.0%for all-PSCs processed from toluene,an aromatic hydrocarbon solvent.Compared to the conventional blend-casting(BC)method whose best efficiency(16.7%)could only be achieved using chloroform,the SqP method significantly boosted the device efficiency using toluene as the processing solvent.In addition,the donor we employ is the classic PM6 that has deeper energy levels than JD40,which provides low energy loss for the device.We compare the results with another PSMA(PYF-T-o)with the same method.Finally,an improved photostability of the SqP devices with the incorporation of SA is demonstrated.

Dual‑Donor‑Induced Crystallinity Modulation Enables 19.23% Efficiency Organic Solar Cells

Trap-assisted charge recombination is one of the primary limitationsof restricting the performance of organic solar cells. However, effectivelyreducing the presence of traps in the photoactive layer remains challenging.Herein, wide bandgap polymer donor PTzBI-dF is demonstrated as an effectivemodulator for enhancing the crystallinity of the bulk heterojunction active layerscomposed of D18 derivatives blended with Y6, leading to dense and orderedmolecular packings, and thus, improves photoluminescence quenching properties.As a result, the photovoltaic devices exhibit reduced trap-assisted charge recombinationlosses, achieving an optimized power conversion efficiency of over 19%.Besides the efficiency enhancement, the devices comprised of PTzBI-dF as athird component simultaneously attain decreased current leakage, improved chargecarrier mobilities, and suppressed bimolecular charge recombination, leading toreduced energy losses. The advanced crystalline structures induced by PTzBI-dFand its characteristics, such as well-aligned energy level, and complementaryabsorption spectra, are ascribed to the promising performance improvements.Our findings suggest that donor phase engineering is a feasible approach to tuning the molecular packings in the active layer, providingguidelines for designing effective morphology modulators for high-performance organic solar cells.

Step-scheme ZnO@ZnS hollow microspheres for improved photocatalytic H_(2) production performance

Constructing a step-scheme heterojunction at the interface between two semiconductors is an efficient way to optimize the redox ability and accelerate the charge carrier separation of a photocatalytic system for achieving high photocatalytic performance.In this study,we prepared a hierarchical ZnO@ZnS step-scheme photocatalyst by incorporating ZnS into the outer shell of hollow ZnO microspheres via a simple in situ sulfidation strategy.The ZnO@ZnS step-scheme photocatalysts had a large surface area,high light utilization capacity,and superior separation efficiency for photogenerated charge carriers.In addition,the material simulation revealed that the formation of the step-scheme heterojunction between ZnO and ZnS was due to the presence of the built-in electric field.Our study paves the way for design of high-performance photocatalysts for H_(2) production.

g-C_(3)N_(4)/CoTiO_(3) S-scheme heterojunction for enhanced visible light hydrogen production through photocatalytic pure water splitting

Photocatalytic hydrogen(H_(2))production via water splitting in the absence of sacrificial agents is a promising strategy for producing clean and sustainable hydrogen energy from solar energy.However,the realization of a photocatalytic pure water splitting system with desirable efficiency is still a huge challenge.Herein,visible light photocatalytic H_(2) production from pure water splitting was successfully achieved using a g-C_(3)N_(4)/CoTiO_(3) S-scheme heterojunction photocatalyst in the absence of sacrificial agents.An optimum hydrogen evolution rate of 118μmol∙h^(−1)∙g^(−1) was reached with the addition of 1.5 wt%CoTiO_(3).The remarkably promoted hydrogen evolution rate was attributed to the intensified light absorption coupled with the synergistic effect of visible light responsive CoTiO_(3),the promoted efficiency in charge separation,and the reserved strong redox capacity induced by the S-scheme charge transfer mechanism.This work provides an alternative to visible light-responding oxidation photocatalysts for the construction of S-scheme heterojunctions and high-efficiency photocatalytic systems for pure water splitting.

Air-Processed Efficient Organic Solar Cells from Aromatic Hydrocarbon Solvent without Solvent Additive or Post-Treatment:Insights into Solvent Effect on Morphology

Most of the recent organic solar cells(OSCs)with top-of-the-line efficiencies are processed from organic solvents with a high vapor pressure such as CF in nitrogen-filled glovebox,which is not feasible for large-area manufacturing.Herein,we cast active layers with both aromatic hydrocarbon solvents and halogenated solvents without any solvent additive or post-treatment,as well as interlayers with water and methanol in air(35%relative humidity)for efficient OSCs,except cathode electrode's evaporation is in vacuum.Compared to the PM6:Y6 system that is processed from CF,the PM6:BTP-ClBr2 system demonstrates good efficiency of 16.28%processed from CB and the device based on PM6:BTP-4Cl achieves 16.33%using TMB as its solvent for the active layer.These are among the highest efficiencies for CB-and TMB-processed binary OSCs to date.The molecular packing and phase separation length scales of each combination depend strongly on the solvent,and the overall morphology is the result of the interplay between solvent evaporation(kinetics)and materials miscibility(thermodynamics).Different solvents are required to realize the optimal morphology due to the different miscibility between the donor and acceptor.Finally,17.36%efficiency was achieved by incorporating PC71BM for TMB-processed devices.Our result provides insights into the effect of processing solvent and shows the potential of realizing high-performance OSCs in conditions relevant for industrial fabrication.

Bifunctional PdPt bimetallenes for formate oxidation-boosted water electrolysis

Small-molecule electrooxidation-boosted water electrolysis(WE)is an energy-saving method for hydrogen(H2)production.Herein,PdPt bimetallenes(PdPt BMLs)are obtained through the simple galvanic replacement reaction.PdPt BMLs reveal 2.93-fold enhancement in intrinsic electroactivity and 4.53-fold enhancement in mass electroactivity for the formate oxidation reaction(FOR)with respect to Pd metallenes(Pd MLs)at 0.50 V potential due to the synergistic effect.Meanwhile,the introduction of Pt atoms also considerably increases the electroactivity of PdPt BMLs for hydrogen evolution reaction(HER)with respect to Pd MLs in an alkaline medium,which even exceeds that with the use of commercial Pt nanocrystals.Inspired by the outstanding FOR and HER electroactivity of bifunctional PdPt BMLs,a two-electrode FOR-boosted WE system(FOR-WE)is constructed by using PdPt BMLs as the cathode and the anode.The FOR-WE system only requires an operational voltage of 0.31 V to achieve H2 production,which is 1.48 V lower than that(ca.1.79 V)with the use of the traditional WE system.

Pressure manipulation of ultrafast carrier dynamics in monolayer WS_(2)

Two-dimensional transition metal dichalcogenides(TMDs)have intriguing physic properties and offer an exciting platform to explore many features that are important for future devices.In this work,we synthesized monolayer WS_(2)as an example to study the optical response with hydrostatic pressure.The Raman results show a continuous tuning of the lattice vibrations that is induced by hydrostatic pressure.We further demonstrate an efficient pressure-induced change of the band structure and carrier dynamics via transient absorption measurements.We found that two time constants can be attributed to the capture process of two kinds of defect states,with the pressure increasing from 0.55 GPa to 2.91 GPa,both of capture processes were accelerated,and there is an inflection point within the pressure range of 1.56 GPa to 1.89 GPa.Our findings provide valuable information for the design of future optoelectronic devices.

Interfacial engineering of holey platinum nanotubes for formic acid electrooxidation boosted water splitting

Both structure and interface engineering are highly effective strategies for enhancing the catalytic activity and selectivity of precious metal nanostructures.In this work,we develop a facile pyrolysis strategy to synthesize the high-quality holey platinum nanotubes(Pt-H-NTs)using nanorods-like Pt^(Ⅱ)-phenanthroline(PT)coordination compound as self-template and self-reduction precursor.Then,an up-bottom strategy is used to further synthesize polyallylamine(PA)modified Pt-H-NTs(Pt-HNTs@PA).PA modification sharply promotes the catalytic activity of Pt-H-NTs for the formic acid electrooxidation reaction(FAEOR)by the direct reaction pathway.Meanwhile,PA modification also elevates the catalytic activity of Pt-H-NTs for the hydrogen evolution reaction(HER)by the proton enrichment at electrolyte/electrode interface.Benefiting from the high catalytic activity of Pt-H-NTs@PA for both FAEOR and HER,a two-electrode FAEOR boosted water electrolysis system is fabricated by using Pt-H-NTs@PA as bifunctio nal electrocatalysts.Such FAEOR boosted water electrolysis system only requires the operational voltage of 0.47 V to achieve the high-purity hydrogen production,showing an energy-saving hydrogen production strategy compared to traditional water electrolysis system.

Ultrafast charge transfer in dual graphene-WS_2 van der Waals quadrilayer heterostructures

Using dual graphene–WS2 quadrilayer heterostructures as an example, we find that the ultrafast transfer of electrons from WS2 to graphene takes place within 114 fs, and the Coulomb field of the charge can effectively affect the interlayer electron transfer. This effect illustrates that the charge transfer in such van der Waals heterostructures may be controlled by an externally applied electric field for promising applications in photoelectric devices.

Spontaneous decoration of ionic compounds at perovskite interfaces to achieve 23.38% efficiency with 85% fill factor in NiO_X-based perovskite solar cells

Inorganic hole transport materials, particularly NiO_X, have shown considerable promise in boosting the efficiency and stability of perovskite solar cells. However, a major barrier to commercialization of NiO_X-based perovskite solar cells with positive-intrinsic-negative architectures is their direct contact with the absorbing layer, which can lead to losses of photovoltage and fill factor. Furthermore, highly positive under-coordinated Ni cations degrade the perovskite at the interface. Here, we address these issues with the use of an ionic compound(QAPyBF_(4)) as an additive to passivate defects throughout the perovskite layer and improve carrier conduction and interactions with under-coordinated Ni cations. Specifically,the highly electronegative inorganic anion [BF_(4)]~- interacts with the NiO_x/perovskite interface to passivate under-coordinated cations(Ni^(≥3+)). Accordingly, the decorated cells achieved a power conversion efficiency of 23.38% and a fill factor of 85.5% without a complex surface treatment or NiO_X doping.

Enhanced Photovoltage for Inverted Perovskite Solar Cells Using Delafossite CuCrO_(2) Hole Transport Material

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS)has been widely adopted as hole transport material(HTM)in inverted perovskite solar cells(PSCs),due to high optical transparency,good mechanical flexibility,and high thermal stability;however,its acidity and hygroscopicity inevitably hamper the long-term stability of the PSCs and its energy level does not match well with perovskite materials with a relatively low open-circuit voltage.In this work,p-type delafossite CuCrO_(2)nanoparticles synthesized through hydrothermal method was employed as an alternative HTM for triple cation perovskite[(FAPbI_(3))_(0.87)(MAPbBr_(3))_(0.13)]_(0.92)(CsPbI_(3))_(0.08)(possessing better photovoltaic performance and stability than conventional CH3NH3PbI3)based inverted PSCs.The average open-circuit voltage of PSCs increases from 908 mV of the devices with PEDOT:PSS HTM to 1020 m V of the devices with CuCrO_(2)HTM.Ultraviolet photoemission spectroscopy demonstrates the energy band alignment between CuCrO_(2)and perovskite is better than that between PEDOT:PSS and perovskite,the electrochemical impedance spectroscopy indicates CuCrO_(2)-based PSCs exhibit larger recombination resistance and longer charge carrier lifetime than PEDOT:PSS-based PSCs,which contributes to the high VOCof CuCrO_(2)HTM-based PSCs.

Photonic crystal-connected bidirectional micro-ring resonator array for duplex mode and wavelength channel(de)multiplexing

The progress of on-chip optical communication relies on integrated multi-dimensional mode(de)multiplexers to enhance communication capacity and establish comprehensive networks.However,existing multi-dimensional(de)multiplexers,involving modes and wavelengths,face limitations due to their reliance on single-directional total internal reflection and multi-level mode conversion based on directional coupling principles.These constraints restrict their potential for full-duplex functionality and highly integrated communication.We solve these problems by introducing a photonic-like crystal-connected bidirectional micro-ring resonator array(PBMRA)and apply it to duplex mode-wavelength multiplexing communication.The directional independence of total internal reflection and the cumulative effect of the subwavelength-scale pillar within the single-level photonic crystal enable bidirectional mode and wavelength multiplexed signals to transmit among multi-pair nodes without interference,improving on-chip integration in single-level mode conversion.As a proof of concept,we fabricated a nine-channel bidirectional multi-dimensional(de)multiplexer,featuring three wavelengths and three TE modes,compactly housed within a footprint of 80μm×80μm,which efficiently transmits QPSK-OFDM signals at a rate of 216 Gbit/s,achieving a bit error rate lower than 10^(-4).Leveraging the co-ring transmission characteristic and the orthogonality of the mode-wavelength channel,this(de)multiplexer also enables a doubling of communication capacity using two physical transmission channels.

Phase separation and domain crystallinity control enable open-air-printable highly efficient and sustainable organic photovoltaics

Organic solar cells(OSCs)have emerged as a promising solution for sustainable energy production,offering advantages such as a low carbon footprint,short energy payback period,and compatibility with eco-solvents.However,the use of hazardous solvents continues to dominate the best-performing OSCs,mainly because of the challenges of controlling phase separation and domain crystallinity in eco-solvents.In this study,we combined the solvent vapor treatment of CS2 and thermal annealing to precisely control the phase separation and domain crystallinity in PM6:M-Cl and PM6:O-Cl systems processed with the eco-solvent o-xylene.This method resulted in a maximum power conversion efficiency(PCE)of 18.4%,which is among the highest values reported for sustainable binary OSCs.Furthermore,the fabrication techniques were transferred from spin coating in a nitrogen environment to blade printing in ambient air,retaining a PCE of 16.0%,showing its potential for high-throughput and scalable production.In addition,a comparative analysis of OSCs processed with hazardous and green solvents was conducted to reveal the differences in phase aggregation.This work not only underscores the significance of sustainability in OSCs but also lays the groundwork for unlocking the full potential of open-air-printable sustainable OSCs for commercialization.

2D materials for conducting holes from grain boundaries in perovskite solar cells

Grain boundaries in organic-inorganic halide perovskite solar cells(PSCs)have been found to be detrimental to the photovoltaic performance of devices.Here,we develop a unique approach to overcome this problem by modifying the edges of perovskite grain boundaries with flakes of high-mobility two-dimensional(2D)materials via a convenient solution process.A synergistic effect between the 2D flakes and perovskite grain boundaries is observed for the first time,which can significantly enhance the performance of PSCs.We find that the 2D flakes can conduct holes from the grain boundaries to the hole transport layers in PSCs,thereby making hole channels in the grain boundaries of the devices.Hence,2D flakes with high carrier mobilities and short distances to grain boundaries can induce a more pronounced performance enhancement of the devices.This work presents a cost-effective strategy for improving the performance of PSCs by using high-mobility 2D materials.

MXenes and MXene-based composites for energy conversion and storage applications

MXenes have received extensive attention from scholars due to their unique layered structure,significant electrical conductivity,and excellent mechanical properties.In addition to their pristine forms,they could also be incorporated with other components for attaining hybrids and nanocomposites,accompanying with amplified functionalities.It has been widely used in lithium batteries,supercapacitors,electromagnetic shielding,tumor therapy,biosensors,photocatalysis,and other fields,and has shown great application potential in energy conversion and storage.The purpose of this article is to encyclopaedically overview the latest progress in synthesis and characterization of MXenes,while their potential applications in energy conversation such as water splitting and solar cells,as well as in energy storage such as Li-ion batteries,supercapacitors,and hydrogen energy will be comprehensively elaborated.Development opportunities and challenges are summarized.

An overview on transparent ceramics with pyrochlore and fluorite structures

Transparent ceramics have potential applications in various areas,including aerospace,relativistic optics industries,medical cares and defense.Specifically,they can be used as laser gain media,armor windows,IR domes,solid-state phosphors,scintillators and electro-optical components.From crystal structure point of view,transparent ceramic materials should have high crystallographic symmetries(cubic,tetragonal and hexagonal),which have minimal birefringent effect.Currently,transparent ceramics are dominantly based on oxide materials,although there are also nonoxides,such as fluorides and nitrides(oxynitrides).Transparent ceramics with pyrochlore and fluorite structures have attracted much attention in recent years,whereas fluorides are not well described in the open literature.Therefore,this paper is aimed to deliver an overview on the progress of the two categories of transparent ceramics,from material processing and characterization point of view.

High-power, ultra-broadband supercontinuum source based upon 1/1.5 μm dual-band pumping

We experimentally demonstrate an all-fiber supercontinuum source that covers the spectral region ranging from visible to mid-infrared. The ultra-broadband supercontinuum is realized by pumping a cascaded photonic crystal fiber and a highly nonlinear fiber with a 1/1.5 μm dual-band pump source. A maximum output power of 9.01 W is achieved using the system,which is the highest power ever achieved from a supercontinuum source spanning from the visible to mid-infrared.

Zeolite templated carbon nanodots for broadband ultrafast pulsed fiber laser generation

Carbon nanodots(C-dots) with a uniform size of about 2 nm are synthesized via in situ pyrolysis of n-propylamine that is confined in the nanochannels of zeolite Linde Type A(LTA). The as-synthesized C-dots@LTA composite shows nonlinear optical saturable absorption properties in a broad wavelength band and can be used as saturable absorber(SA) to generate ultrafast pulsed fiber lasers. By inserting a zeolite LTA single crystal hosting C-dots into the fiber laser cavity, mode-locked fiber lasers with long-term operation stability at 1.5 μm and 1 μm are achieved. These results show that the C-dots@LTA are a promising SA material for ultrafast pulsed fiber laser generation in a broad wavelength band. To the best of our knowledge, this is the first demonstration of a C-dots@LTA-based mode-locked fiber laser.

Tunable Filtering of Orbital Angular Momentum Modes via Spatial Depth-Dependent Mode Transformation

Advancements in orbital angular momentum (OAM) mode-multiplexing communication networks requiretunable mode filters for selective channel demultiplexing and downloading. In this study, we propose a spatialdepth-dependent mode transformation strategy for the tunable filtering of OAM modes. By integrating the spiralphase and lens phase modulations, we achieved mode conversions that varied with the transmission depth,enabling selective demultiplexing in predetermined axial planes. This approach facilitates tunable mode filteringby adjusting spatial depths. As a proof of concept, we fabricated a mode filter using two-photon polymerizationlithography (TPL) technology, successfully filtering five OAM modes with mode crosstalk below −10.9 dB.Additionally, the filter was applied in a mode-multiplexing communication link, achieving tunable demultiplexingof five mode channels with bit error rates below 10^(−6). These results highlight the efficacy and flexibilityof our strategy for OAM mode filtering and offer promising insights for the development of mode-multiplexingcommunication networks and channel interconnections.