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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 (VO2) 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 VO2 has recently been the subject of intensive research. In this report, we review recent advancements in the field of nonvolatile control of MIT in VO2, using electrochemical redox reactions, inverse piezoelectric effect, and ferroelectric polarization, and their potential to develop high-performance next-generation electronic devices.

The performance of halide perovskite-based electronic and optoelectronic devices is often related to interfacial charge transport. To shed light on the underlying physical and chemical properties of CH3NH3PbI3 (MAPbI3) in direct contact with common electrodes Al, Ti, Cr, Ag, and Au, the evolution of interfacial properties and Fermi level pinning is systematically studied. Given a unique experimental facility, pristine interfaces without any exposure to ambient air were prepared. We observe aggregation of substantial amounts of metallic lead (Pb0) at the metal/MAPbI3 interface, resulting from the interfacial reaction between the deposited metal and iodine ions from MAPbI3. It is found that the Schottky barrier height at the metal/MAPbI3 interface is independent of the metal work function due to strong Fermi level pinning, possibly due to the metallic Pb0 aggregates, which act as interfacial trap sites. The charge neutrality level of MAPbI3 is consistent with the energy level of Pb0-related defects, indicating that Pb0 interfacial trap states can be nonradiative recombination sites. This work underlines that control of chemical bonding at interfaces is a key factor for designing future halide perovskite-based devices.

Controlling phase transitions in correlated materials yields emergent functional properties, providing new aspects to future electronics and a fundamental understanding of condensed matter systems. With vanadium dioxide (VO

As the BO6 octahedral structure in perovskite oxide is strongly linked with electronic behavior, it is actively studied for various fields such as metal–insulator transition, superconductivity, and...

Palladium (Pd) has been the key element for several C–C bond-forming reactions, especially the Nobel-acclaimed Suzuki, Heck, and Sonogashira cross-coupling reactions, among others. This review arti...

Direct consideration for both, the catalytically active species and the host materials provides highly efficient strategies for the architecture design of nanostructured catalysts. The conventional wet chemical methods have limitations in achieving such unique layer-by-layer design possessing one body framework with many catalyst parts. Herein, an innovative physical method is presented that allows the well-regulated architecture design for an array of functional nanocatalysts as exemplified by layer-by-layer adornment of Pd nanoparticles (NPs) on the highly arrayed silica nanorods. This spatially confined catalyst exhibits excellent efficiency for the hydrogenation of nitroarenes and widely deployed Suzuki cross-coupling reactions; their facile separation from the reaction mixtures is easily accomplished due to the monolithic structure. The generality of this method for the introduction of other metal source has also been demonstrated with Au NPs. This pioneering effort highlights the feasibility of physically controlled architecture design of nanostructured catalysts which may stimulate further studies in the general domain of the heterogeneous catalytic transformations.

Organic redox compounds are potential substitutes for transition-metal-oxide electrode materials in rechargeable batteries because of their low cost, minimal environmental footprint, and chemical diversity. However, their inherently low electrical conductivity and high solubility in organic solvents are serious impediments to achieving performance comparable to that of currently used inorganic-based electrode materials. Herein, we report organic charge-transfer complexes as a novel class of electrode materials with intrinsically high electrical conductivity and low solubility that can potentially overcome the chronic drawbacks associated with organic electrodes. The formation of the charge-transfer complexes, phenazine–7,7,8,8-tetracyanoquinodimethane and dibenzo-1,4-dioxin–7,7,8,8-tetracyanoquinodimethane, via a room-temperature process leads to enhancement in the electrical conductivity and reduction in the dissolution resulting in the high power and cycle performances that far outperform those of each single-moiety counterpart. This finding demonstrates the general applicability of the charge-transfer complex to simultaneously improve the electrical conductivity and mitigate the shortcomings of existing single-moiety-based organic electrode materials, and opens up an uncharted pathway toward the development of high-performance organic electrode materials via the exploration of various combinations of donor–acceptor monomers with different stoichiometry.

Metal–insulator transition (MIT) in strongly correlated electronic materials has enormous potential with scientific and technological impacts in future oxide nanoelectronic devices. Although photo-induced MIT can provide opportunities to extend the novel functionality of strongly correlated electronic materials, there have rarely been reports on it. Here, we report MIT provoked by visible–near-infrared light in Ag-decorated VO2 nanorod arrays (NRs) because of localized surface plasmon resonance (LSPR) and its application to broadband photodetectors. Our simulation results based on the finite-difference time-domain method show that the electric field resulting from LSPR can be generated at the interface between Ag nanoparticles and VO2 layers under vis NIR illumination. Using high-resolution transmission electronic microscopy and Raman spectroscopy, we observe the MIT and structural phase transition in the Ag-decorated VO2 NRs due to the LSPR effect. The optoelectronic measurements confirm that high, fast,...

In order to develop high performance chemoresistive gas sensors for Internet of Everything applications, low power consumption should be achieved due to the limited battery capacity of portable devices. One of the most efficient ways to reduce power consumption is to lower the operating temperature to room temperature. Herein, we report superior gas sensing properties of SnS2 nanograins on SiO2 nanorods toward NO2 at room temperature. The gas response is as high as 701% for 10 ppm of NO2 with excellent recovery characteristics and the theoretical detection limit is evaluated to be 408.9 ppb at room temperature, which has not been reported for SnS2-based gas sensors to the best of our knowledge. The SnS2 nanograins on the template used in this study have excessive sulfur component (Sn:S = 1:2.33) and exhibit p-type conduction behavior. These results will provide a new perspective of nanostructured two-dimensional materials for gas sensor applications on demand.

Recently, organometallic and all-inorganic halide perovskites (HPs) have become promising materials for resistive switching (RS) nonvolatile memory devices with low power consumption because they show current-voltage hysteresis caused by fast ion migration. However, the toxicity and environmental pollution potential of lead, a common constituent of HPs, has limited the commercial applications of HP-based devices. Here, RS memory devices based on lead-free all-inorganic cesium tin iodide (CsSnI3) perovskites with temperature tolerance are successfully fabricated. The devices exhibit reproducible and reliable bipolar RS characteristics in both Ag and Au top electrodes (TEs) with different switching mechanisms. The Ag TE devices show filamentary RS behavior with ultralow operating voltages (

The multilayered ceramic capacitor (MLCC) is a key component of electronic equipment, such as smartphones, portable PCs and electric vehicles, which contain a number of MLCCs. As MLCCs distribute and control the amount of current flowing through circuits, remove noise, and prevent malfunction, MLCCs play a key role in enabling electronic devices to have high performance, multi-functionality, and high integration. This review highlights the critical issues and recent progress in developing highly volumetric-efficient and high capacitance MLCCs from the viewpoint of designing a BaTiO3-based dielectric layer. After a brief introduction of MLCCs and dielectric materials, we summarize the current issues in developing BaTiO3-based dielectric materials for MLCCs with high performance and reliability and describe the strategies to optimize dielectric properties through nano/microstructure control, chemical modification and doping. Finally, we provide an outlook on the development and future application of MLCCs. It is anticipated that this review can serve as an overview and evaluation of state-of-the-art synthesis and design of BaTiO3-based dielectric materials for MLCC applications.

As the BO

Organometallic and all-inorganic halide perovskites (HPs) have recently emerged as promising candidate materials for resistive switching (RS) nonvolatile memory due to their current-voltage hysteresis caused by fast ion migration. Lead-free and all-inorganic HPs have been researched for non-toxic and environmentally friendly RS memory devices. However, only HP-based devices with electrochemically active top electrode (TE) exhibit ultra-low operating voltages and high on/off ratio RS properties. The active TE easily reacts to halide ions in HP films, and the devices have a low device durability. Herein, RS memory devices based on an air-stable lead-free all-inorganic dual-phase HP (AgBi2 I7 -Cs3 Bi2 I9 ) are successfully fabricated with inert metal electrodes. The devices with Au TE show filamentary RS behavior by conducting-bridge involving Ag cations in HPs with ultra-low operating voltages ( 107 ), multilevel data storage, and long retention times (>5 × 104 s). The use of a closed-loop pulse switching method improves reversible RS properties up to 103 cycles with high on/off ratio above 106 . With an extremely small bending radius of 1 mm, the devices are operable with reasonable RS characteristics. This work provides a promising material strategy for lead-free all-inorganic HP-based nonvolatile memory devices for practical applications.

Vertically ordered hematite nanotubes decorated with Au nanoparticles are synthesized by a facile electrochemical anodization method and self-agglomeration of Au films. Au decoration significantly enhances the response of hematite nanotubes to acetone at 350 °C and the response to acetone is 2.4 times higher than the response to ethanol, the counterpart target gas. The Au nanoparticles decorated hematite nanotubes exhibit unprecedentedly high and selective responses to acetone at 350 °C with 50% relative humidity condition (calibrated at room temperature, 25 °C). The enhanced gas sensing properties in a humid condition were attributed to the spillover effect by Au nanoparticles and high porosity of hematite nanotubes with a large surface-to-volume ratio. These results indicate that Au nanoparticles decorated hematite nanotubes are promising for use in high quality sensor materials for breath analyzers to diagnose diabetes mellitus.

We synthesized the reproducible heterogeneous catalyst of graphene oxide (GO)-supported palladium nanoparticles (NPs) via a simple and green process. The structure, morphology and physicochemical properties of the synthesized heterogeneous catalyst were characterized by the latest techniques such as high-resolution transmission electron microscopy (TEM), scanning TEM, energy-dispersive X-ray spectroscopy, X-ray diffraction analysis, and X-ray photoelectron spectroscopy. The GO-supported Pd NPs (Pd/GO nanocatalyst) exhibited excellent catalytic activity for the reduction of nitroaromatics to aminoaromatics in aqueous sodium borohydride. The nitroaromatics were converted to corresponding aminoaromatics with high yields (up to 99%) using Pd/GO nanocatalyst in aqueous solution. The hybrid heterogeneous catalyst showed 83% of conversion after six cycles in the reduction of nitrobenzene to aminobenzene. These features ensured the high catalytic activity of the introduced graphene oxide supported Pd nanocatalysts.

Despite its abundant, nontoxicity and photochemical stability, titanium dioxide shows low solar water oxidation performance due to low photogenerated carrier transport and wide optical band gap, which results in substantially low photogenerated carrier density that impair the solar to hydrogen conversion efficiency. Herein, highly enhanced water oxidation performance of high-aspect-ratio TiO2 nanorods doped with dual heteroatoms, sulfur and nitrogen, for photoelectrochemical solar water oxidation is demonstrated. The codoped TiO2 NRs have shown enhanced optical absorption coefficient due to the induced impurities energy states near to the top of the valance band and result in a red shift in the optical absorption edges. Consequently, a 2.82 mAcm−2 photocurrent density at 1.23 V vs. RHE is obtained from the sulfur and nitrogen codoped TiO2 nanorods, and pristine TiO2 nanorods photoanode shows 0.7 mAcm−2. The applied bias photon-to-current conversion efficiency and external quantum efficiency of the codoped TiO2 nanorods are 1.49% and 97.0% at λ = 360 nm and 0.69% and 19.1% at λ = 370 nm for pristine TiO2 nanorods, respectively. Our study offers experimental and theoretical evidence for codoping of sulfur and nitrogen improve the optical and electrical properties of TiO2 for efficient photoelectrochemical solar water oxidation.

The hydrothermal method is a facile route for the synthesis of TiO2 nanostructured materials, but it requires accurate process optimizations and adjustments to circumvent the undesirable morphology products. In this study, systematically controlled experimental studies are carried out under thermodynamic and kinetic considerations to understand the formation of well-aligned TiO2 nanorods during the hydrothermal reaction. In this regard, TiO2 nanorods are synthesized on various types of substrates, including single crystal TiO2 and sapphire, fluorine doped tin oxide, and silicon. Variable growth parameters are classified and investigated for their effects on the morphological evolution of TiO2 nanorods. The preferred morphology of TiO2 nanorods with the {110} facet is confirmed based on the crystallographic results for TiO2 nanorods acquired by extensive transmission electron microscopy studies during the entire growth processes. The presence of the seeds on the substrates is found to be mandatory for the ...

The utilization of edge sites in two-dimensional materials including transition-metal dichalcogenides (TMDs) is an effective strategy to realize high-performance gas sensors because of their high catalytic activity. Herein, we demonstrate a facile strategy to synthesize the numerous edge sites of vertically aligned MoS2 and larger surface area via SiO2 nanorod (NRs) platforms for highly sensitive NO2 gas sensor. The SiO2 NRs encapsulated by MoS2 film with numerous edge sites and partially vertical-aligned regions synthesized using simple thermolysis process of [(NH4)2MoS4]. Especially, the vertically aligned MoS2 prepared on 500 nm thick SiO2 NRs (500MoS2) shows approximately 90 times higher gas-sensing response to 50 ppm NO2 at room temperature than the MoS2 film prepared on flat SiO2, and the theoretical detection limit is as low as ∼2.3 ppb. Additionally, it shows reliable operation with reversible response to NO2 gas without degradation at an operating temperature of 100 °C. The use of the proposed fa...

Two-dimensional transition-metal dichalcogenides (TMDCs) are very promising for photovoltaic (PV) applications due to their excellent light absorption properties and appropriate bandgap energy, Although multifunctional applications of TMDCs in photovoltaic devices have been achieved, the photovoltaic conversion efficiency under 1 sun is still very low with small active area because of their inexpedient high sheet resistance and limitation of synthesis techniques. In this study, we demonstrate uniform synthesis of 4-in. wafer-scale MoS2 thin films by thermal decomposition of solution precursors. The solar cells are fabricated by transferring n-MoS2 thin films on p-Si substrates to form p-n heterojunctions and then transferring Au nanomeshes prepared in a novel surface treatment as transparent top electrodes onto MoS2. The circular n-MoS2/p-Si heterojunction solar cell exhibited a power conversion efficiency of 5.96% at a diameter of 0.3 in. and proved to be easily scalable to 1-in. diameter with 5.18% efficiency. To the best of our knowledge, the solar cells of this study are the most efficient and the largest in all types of solar cells based on TMDC reported so far. Finally, based on finite difference time-domain simulation, we proposed a strategy for implementing n-MoS2/p-Si heterojunction solar cell with efficiency higher than 15% by introducing optimal doping control of n-MoS2 and efficient anti-reflection layers.

Insulation resistance (IR) degradation in BaTiO3 is a key issue for developing miniaturized multilayer ceramic capacitors (MLCCs) with high capacity. Despite rapid progress in BaTiO3-based MLCCs, the mechanism of IR degradation is still controversial. In this study, we demonstrate the Al doping effect on IR degradation behavior of BaTiO3 MLCCs by electrical measurements and scanning Kelvin probe microscopy (SKPM). As the Al doping concentration in BaTiO3 increases, IR degradation of MLCCs seems to be suppressed from electrical characterization results. However, SKPM results reveal that the conductive regions near the cathode become lager with Al doping after IR degradation. The formation of conducting regions is attributed to the migration of oxygen vacancies, which is the origin of IR degradation in BaTiO3, in dielectric layers. These results imply that acceptor doping in BaTiO3 solely cannot suppress the IR degradation in MLCC even though less asymmetric IR characteristics and IR degradation in MLCCs with higher Al doping concentration are observed from electrical characterization. Our results strongly suggest that observing the surface potential distribution in IR degraded dielectric layers using SKPM is an effective method to unravel the mechanism of IR degradation in MLCCs.

Halide perovskites are emerging materials for future optoelectronics and electronics due to their remarkable advantages such as a high light absorption coefficient, long charge carrier diffusion length, facile synthesis method, and low cost. As polycrystalline halide perovskite thin films, which have been studied so far, have crucial limitations, low-dimensional halide perovskites have attracted attention due to their unique optical properties and charge transport properties, which have not been observed before. This review highlights the limitations of polycrystalline halide perovskites thin films and the unique characteristics of low-dimensional halide perovskite nanostructures including their electrical, optical, and chemical properties. After introducing the recent developments of various low-dimensional halide perovskite nanostructures including the synthesis methods, their properties, and applications, a brief overview of the challenges of low-dimensional halide perovskites as candidates for future optoelectronics and electronic devices is provided.

Herein, we describe the fabrication of a magnetically retrievable nanocomposite adorned with highly active Pd nanoparticles (NPs) (MRN-Pd), which is useful for the efficient reduction of nitroaromatics in aqueous solution. The polymerization of pyrrole as the monomer in the presence of Pd salt and iron nanopowder generates Pd nanocatalysts and localizes the resultant Pd NPs discretely and uniformly on the polypyrrole framework comprising strongly magnetic MRN-Pd catalyst without the need for any reducing agent. The nitrogen-containing polymer enhances the interaction between the decorated Pd nanocatalysts and the polymer scaffold, endowing stability to the Pd NPs and maintaining their monodispersity. This prevents the possible aggregation of the MRN-Pd catalyst and promotes its reactivity for fast reduction processes. The unique features exhibited by the MRN-Pd catalyst result in excellent catalytic activity for the expeditious reduction of nitroaromatics under green reaction conditions at room temperature. Furthermore, the pronounced magnetic characteristics of the MRN-Pd catalyst allow its convenient separation and recycling from the reaction mixture. In addition, the MRN-Pd catalyst can be completely separated and recycled using a small magnet and reused for seven consecutive cycles of high-yield reduction of nitrobenzene (99–95%) in water, thus affording a highly retrievable and sustainable magnetic nanocomposite catalyst suitable for environmentally friendly processes. The MRN-Pd catalyst also presents high catalytic activity in other typical catalytic transformations requiring Pd nanocatalysts, such as the Suzuki and Heck cross-coupling reactions.

Transferable 2-dimensional (2D) MoS2 thin films have a versatile potential for constructing highly efficient photoelectrodes when combined with conventional semiconductor light absorbers, taking advantage of its optical transparency and high electrochemical activity. Here, we firstly report fully vertically aligned MoS2 (VMS)/p-Si heterostructure photocathode for photoelectrochemical (PEC) water splitting. Furthermore, 3D iron-nickel sulfide nanoparticles of tailored atomic composition are formed simultaneously during the synthesis of VMS via one-step sulfurization to build 3D/2D transition metal sulfide (TMD) heterostructure thin film catalyst. The spectroscopic results reveal that the Fe-doped Ni3S2 nanoparticles on VMS/p-Si photocathode induce the electrochemically-benign band bending in the overall heterostructure, enabling a significant improvement in PEC performance and long-term stability. Scanning photoelectrochemical microscopy is used to vividly visualize the photocurrent enhancement by the various 3D/2D TMD heterostructures. This work provides promising strategies in developing high performance TMD-based electrocatalysts for practical applications in a wide variety of electrochemical energy conversion processes.

It was demonstrated that organolead halide perovskites (OHPs) show a resistive switching behavior with an ultralow electric field of a few kilovolts per centimeter. However, a slow switching time and relatively short endurance remain major obstacles for the realization of the next-generation memory. Here, we report a performance-enhanced OHP resistive switching device. To fabricate topologically and electronically improved OHP thin films, we added hydroiodic acid solution (for an additive) in the precursor solution of the OHP. With drastically improved morphology such as small grain size, low peak-to-valley depth, and precise thickness, the OHP thin films showed an excellent performance as insulating layers in Ag/CH3NH3PbI3/Pt cells, with an endurance of over 103 cycles, a high on/off ratio of 106, and an operation speed of 640 μs and without electroforming. We suggest plausible resistive switching and conduction mechanisms with current–voltage characteristics measured at various temperatures and with dif...

We demonstrate the tungsten disulfide (WS2) thin film catalysts prepared by the sulfurization of vacuum deposited WO3 thin films for efficient hydrogen production with over 90% Faradaic efficiency. The 23-nm-thick WS2 thin film catalyst heterojunction with p-type silicon photocath-ode could exhibit a photocurrent density of 8.3 mA/cm2 at 0 V versus a reversible hydrogen electrode (RHE), a low onset potential of 0.2 V versus RHE when photocurrent density reaches -1 mA/cm2 and long-term stability over 10 h. The enhanced catalytic activities of WS2/p-Si photocathodes compared with the bare p-Si photocathode originate from a number of edge sites in the synthesized polycrystalline thin films, which could act as hydrogen evolution catalyst.

We synthesized transferrable and transparent anion-engineered molybdenum disulfide thin-film catalysts through a simple thermolysis method by using [(NH4)2MoS4] solution and powder precursors with different sulphur/phosphorus weight ratios. The synthesized sulphur-doped molybdenum phosphide (S:MoP) thin film changed from a two-dimensional van der Waals structure to a three-dimensional hexagonal structure by introduction of phosphorus atoms in the MoS2 thin film. The S:MoP thin film catalyst, which is composed of cheap and earth abundant elements, could provide the lowest onset potential and the highest photocurrent density for planar p-type Si photocathodes. The density functional theory calculations indicate that the surface of S:MoP thin films absorb hydrogen better than that of MoS2 thin films. The structurally engineered thin film catalyst facilitates the easy transfer of photogenerated electrons from the p-Si light absorber to the electrolyte. Anion-engineering of the MoS2 thin film catalyst would be an efficient way to enhance the catalytic activity for photoelectrochemical water splitting.

In order to develop high performance chemoresistive gas sensors for Internet of Everything applications, low power consumption should be achieved due to the limited battery capacity of portable devices. One of the most efficient ways to reduce power consumption is to lower the operating temperature to room temperature. Herein, we report superior gas sensing properties of SnS

Vertically ordered hematite nanotubes are considered to be promising photoactive materials for high-performance water-splitting photoanodes. However, the synthesis of hematite nanotubes directly on conducting substrates such as fluorine-doped tin oxide (FTO)/glass is difficult to be achieved because of the poor adhesion between hematite nanotubes and FTO/glass. Here, we report the synthesis of hematite nanotubes directly on FTO/glass substrate and high-performance photoelectrochemical properties of the nanotubes with NiFe cocatalysts. The hematite nanotubes are synthesized by a simple electrochemical anodization method. The adhesion of the hematite nanotubes to the FTO/glass substrate is drastically improved by dipping them in nonpolar cyclohexane prior to postannealing. Bare hematite nanotubes show a photocurrent density of 1.3 mA/cm(2) at 1.23 V vs a reversible hydrogen electrode, while hematite nanotubes with electrodeposited NiFe cocatalysts exhibit 2.1 mA/cm(2) at 1.23 V which is the highest photocurrent density reported for hematite nanotubes-based photoanodes for solar water splitting. Our work provides an efficient platform to obtain high-performance water-splitting photoanodes utilizing earth-abundant hematite and noble-metal-free cocatalysts.

Atomically thin two-dimensional materials such as MoS2, WS2, and graphene oxide (GO) are used as hole extraction layers (HEL) in organolead halide perovskites solar cells (PSCs) instead of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) HEL. MoS2 and WS2 layers with a polycrystalline structure were synthesized by a chemical deposition method using a uniformly spin-coated (NH4)MoS4 and (NH4)WS4 precursor solution. GO was synthesized by the oxidation of natural graphite powder using Hummers' method. The work functions of MoS2, WS2, and GO are measured to be 5.0, 4.95, and 5.1 eV, respectively. The X-ray diffraction spectrum indicated that the synthesized perovskite material is CH3NH3PbI3−xClx. The PSCs with the p-n junction structure were fabricated based on the CH3NH3PbI3−xClx perovskite layer. The power conversion efficiencies of the MoS2, WS2, and GO-based PSCs were 9.53%, 8.02%, and 9.62%, respectively, which are comparable to those obtained from PEDOT:PSS-based devices (9.93%). These results suggest that two-dimensional materials such as MoS2, WS2, and GO can be promising candidates for the formation of HELs in the PSCs.

Organolead halide perovskites are used for low-operating-voltage multilevel resistive switching. Ag/CH3 NH3 PbI3 /Pt cells exhibit electroforming-free resistive switching at an electric field of 3.25 × 10(3) V cm(-1) for four distinguishable ON-state resistance levels. The migration of iodine interstitials and vacancies with low activation energies is responsible for the low-electric-field resistive switching via filament formation and annihilation.

Organolead halide perovskites (OHPs) have attracted extensive attention as light harvesting materials for solar cells recently, because of their high charge carrier mobility, high photoconversion efficiencies, low cost, and simple methodology. Despite these advantages, the OHPs exhibit sweep-dependent hysteresis behavior in current–voltage characteristics films, deteriorating the reliability of devices based on the OHPs. This study demonstrates reliable high on/off ratio (Ion/Ioff = 104) CH3NH3PbI3 broadband photodetectors with buffer layer-free simple metal/semiconductor/metal lateral structure. At high external bias, poor on/off ratios and spikes in dark current and photocurrent are observed due to the migration of charged defect ions. The ion migration can be effectively inhibited at low external bias, and thus the devices show high Ion/Ioff ratios and spike-free dark current and photocurrent. In addition, prevention of the prepoling in the CH3NH3PbI3 films by operating at the low external bias results in pronouncedly enhanced signal-to-noise ratios even under low intensity incident light. These results strongly propose that inhibiting the migration of charged defect ions in CH3NH3PbI3 films is a key in developing reliable high performance CH3NH3PbI3-based devices.

We demonstrate that wafer-scale, transferable, and transparent thin-film catalysts based on MoS2, which consists of cheap and earth abundant elements, can provide a low onset potential of 1 mA cm−2 at 0.17 V versus a reversible hydrogen electrode and the high photocurrent density of 24.6 mA cm−2 at 0 V for a p-type Si photocathode. c-Domains with vertically stacked (100) planes in the transferable 2H-MoS2 thin films, which are grown via a thermolysis method, act as active sites for the hydrogen evolution reaction, and photogenerated electrons are efficiently transported through the n-MoS2/p-Si heterojunction.

The utilization of edge sites in two-dimensional materials including transition-metal dichalcogenides (TMDs) is an effective strategy to realize high-performance gas sensors because of their high catalytic activity. Herein, we demonstrate a facile strategy to synthesize the numerous edge sites of vertically aligned MoS

Fascinating characteristics of halide perovskites (HPs), which cannot be seen in conventional semiconductors and metal oxides, have boosted the application of HPs in electronic devices beyond optoelectronics such as solar cells, photodetectors, and light-emitting diodes. Here, recent advances in HP-based memory and logic devices such as resistive-switching memories (i.e., resistive random access memory (RRAM) or memristors), transistors, and artificial synapses are reviewed, focusing on inherently exotic properties of HPs: i) tunable bandgap, ii) facile majority carrier control, iii) fast ion migration, and iv) superflexibility. Various fabrication techniques of HP thin films from solution-based methods to vacuum processes are introduced. Up-to-date work in the field, emphasizing the compositional flexibility of HPs, suggest that HPs are promising candidates for next-generation electronic devices. Taking advantages of their unique electrical properties, low-cost and low-temperature synthesis, and compositional and mechanical flexibility, HPs have enormous potential to provide a new platform for future electronic devices and explosively intensive studies will pave the way in finding new HP materials beyond conventional silicon-based semiconductors to keep up with "More-than-Moore" times.

We synthesized transferrable and transparent anion-engineered molybdenum disulfide thin-film catalysts through a simple thermolysis method by using [(NH4)2MoS4] solution and powder precursors with different sulphur/phosphorus weight ratios. The synthesized sulphur-doped molybdenum phosphide (S:MoP) thin film changed from a two-dimensional van der Waals structure to a three-dimensional hexagonal structure by introduction of phosphorus atoms in the MoS2 thin film. The S:MoP/p-Si heterojunction photocathodes showed a high photocurrent density (33.13 mA/cm2 at 0 V vs. the RHE), large overpotential shift (0.9 V at 10 mA/cm2), and long-term stability (over 10000 s). The characterization of the S:MoP/p-Si photocathodes revealed that they could act not only as surface active catalysts owing to their low hydrogen adsorption Gibbs free energy but also as passivation layers owing to their 3D tight bonding between molybdenum and sulphur or phosphorus atoms. Anion-engineering of the MoS2 thin film catalyst would be an efficient way to enhance the catalytic activity for photoelectrochemical water splitting. Figure 1