Isoreticular Contraction in Dicopper Paddle-Wheel-Based Metal-Organic Frameworks to Enhance CH/CO Separation.

Achieving a balance between high selectivity and uptake is a formidable challenge for the purification of acetylene from mixtures with carbon dioxide, particularly when seeking to maximize both CH adsorption capacity and CH/CO separation selectivity in crystalline porous materials. In this study, leveraging the principles of reticular chemistry, we selected two tetracarboxylate-based linkers and combined them with Cu ions to synthesize two isoreticular dicopper paddle-wheel-based metal-organic frameworks (MOFs): Cu-TPTC (terphenyl-3,3',5,5'-tetracarboxylic acid, HTPTC) and Cu-ABTC (3,3,5,5-azobenzenetetracarboxylic acid, HABTC). The structural and sorption analyses revealed that Cu-ABTC, despite having slightly smaller pores due to the strategic replacement of a phenyl ring with an azo group between two tetratopic ligands, maintains high porosity compared to Cu-TPTC.

A Propeller-Like Ligand-Directed Construction of a Tetranuclear Cerium-Organic Framework for Single-Step Ethylene Purification from Ternary C Mixtures.

The efficient single-step purification of ethylene from ternary C mixtures containing ethane and acetylene is challenging and demanding. Herein, we introduce a novel cerium-based metal-organic framework (MOF) of Ce-NTB- synthesized via a ligand-conformer strategy. The Ce-NTB- features a rare tetranuclear cerium cluster and 2D layers pillared by a 3D framework concomitant with an extraordinary (3,3,12)-c network.

Polynuclear Rare-Earth Cluster-Directed Self-Assembly of Highly Porous Zeolite-like Metal-Organic Frameworks with Methane Storage Property.

Due to their intrinsic structural features, the design and synthesis of a new type of zeolite-like metal-organic frameworks (ZMOFs) is highly desirable but challenging. Herein, solvothermal reactions between an angular dicarboxylate linker and rare-earth (RE) ions afforded two RE-MOFs, namely, Tb-ZMOF-2 and Tb-ZMOF-3, respectively. Structural analyses reveal that Tb-ZMOF-2 encompasses a novel [468] cage, while Tb-ZMOF-3 contains nonanuclear (i.

High-Performance Ultraviolet Light-Emitting Diodes Using n-ZnO/p-hBN/p-GaN Contact Heterojunctions.

Effective ultraviolet light-emitting diodes (LEDs) were fabricated by clamping the n-ZnO films on the top of p-hBN/p-GaN/sapphire substrates. An ultraviolet emission originating from ZnO was measured from the diode under a forward bias, the electroluminescence (EL) spectra of which show a peak wavelength of ∼376 nm with a narrow full-width at half maximum of ∼12 nm. Compared with the reference diode fabricated by directly growing n-ZnO on the p-hBN substrates using metal-organic chemical vapor deposition, the proposed diode showed a dramatic increment of the EL intensity; meanwhile, its emission onset lowered down considerably.

Synergetic Effect of the Surfactant and Silica Coating on the Enhanced Emission and Stability of Perovskite Quantum Dots for Anticounterfeiting.

Recently, the growing demand for optical anticounterfeiting technology has motivated intensive research in newly emerging halide perovskite quantum dots (QDs). However, the poor stability and unsatisfactory fluorescence efficiency of such materials are the main obstacles to the application of reliable anticounterfeiting. In this work, we performed a well-controlled investigation of the effect of the surfactant (l-α-phosphatidylcholine, LP) and silica encapsulation on the stability and emission of the CsPbBr QDs.

Silica coating enhances the stability of inorganic perovskite nanocrystals for efficient and stable down-conversion in white light-emitting devices.

Recently, inorganic halide perovskite (CsPbX3, X = Cl, Br, I) quantum dots (QDs) have attracted tremendous research interests because of their great potential for application in the fields of low-cost light sources and displays. However, the unsatisfactory structural and chemical stabilities of such materials are the main obstacles hindering reliable device operation significantly. In this study, we successfully prepared CsPbBr3/silica QD composites through a simple sol-gel reaction by using tetramethoxysilane as a single molecule precursor.

Carbon-Related Defects as a Source for the Enhancement of Yellow Luminescence of Unintentionally Doped GaN.

Yellow luminescence (YL) of unintentionally doped GaN (u-GaN) peaking at about 2.2 eV has been investigated for decades, but its origin still remains controversial. In this study, ten u-GaN samples grown via metalorganic chemical vapor deposition (MOCVD) are investigated.

Ultraviolet Photodetector Based on ITO/MgO/ZnO Structure Grown by Hydrothermal Process.

A simple two-step aqueous method was employed to grow MgO nanostructures on ZnO/sapphire at low temperature. The obtained thin MgO nanostructures were uniformly distributed on the surface of ZnO layer and showed the sheet-like structures. Meanwhile, an ultraviolet (UV) photodetector based on ITO/MgO/ZnO structures was fabricated by simple way.

Hole-Injection Layer-Free Perovskite Light-Emitting Diodes.

In this study, a dual-source vapor evaporation method was employed to fabricate the high-quality CsPbBr thin films with a good crystalline and high surface coverage. Temperature-dependent and excitation power-dependent photoluminescence measurements were performed to study the optical properties of the CsPbBr material. Further, based on the experimental data, the temperature sensitivity coefficient of band gap and exciton binding energy were estimated.

Anomalous electroluminescent blue-shift behavior induced by well widths variance and localization effect in InGaN/GaN multi-quantum wells.

Twelve InGaN MQW LED samples with varying well thickness grown via metal-organic chemical vaper deposition (MOCVD) are investigated. It is observed from electroluminescence (EL) measurement that at low current densities, the peak energy shifts to blue with increasing current, and when the current change by fixed increment, the peak energy shifts to blue end to different extent among samples. This blue shift was expected to be stronger when the well thickness increases, however, for well widths above 5 nm we observe a decrease in emission energy.

Self-powered SBD solar-blind photodetector fabricated on the single crystal of β-GaO.

A Schottky barrier diode (SBD) solar-blind photodetector was fabricated based on the single crystal β-GaO. Cu and Ti/Au were deposited on the top and bottom surface of GaO as Schottky and ohmic contacts, respectively. The SBD exhibits a higher rectification ratio of up to 5 × 10 at ±2 V.

Effect of carrier transfer process between two kinds of localized potential traps on the spectral properties of InGaN/GaN multiple quantum wells.

Two InGaN/GaN multiple-quantum-well (MQW) samples with identical epitaxial structures are grown at different growth rates via metal-organic chemical vapor deposition system. The room temperature photoluminescence intensity of the fast-grown sample is much stronger than that of the slow-grown one. In addition, the fast-grown sample has two luminescence peaks at low temperatures, and the height of main peak anomalously increases with increasing temperature below 100 K.

Strategy of Solution-Processed All-Inorganic Heterostructure for Humidity/Temperature-Stable Perovskite Quantum Dot Light-Emitting Diodes.

Recently, a pressing requirement of solid-state lighting sources with high performance and low cost has motivated increasing research in metal halide perovskites. However, the relatively low emission efficiency and poor operation stability of perovskite light-emitting diodes (LEDs) are still critical drawbacks. In this study, a strategy of solution-processed all-inorganic heterostructure was proposed to overcome the emission efficiency and operation stability issues facing the challenges of perovskite LEDs.

Vapor-Assisted Solution Approach for High-Quality Perovskite CHNHPbBr Thin Films for High-Performance Green Light-Emitting Diode Applications.

The vapor-assisted solution method was developed to prepare high-quality organic-inorganic halide perovskite CHNHPbBr (MAPbBr) thin films. We detailedly investigated the effect of evaporation time and temperature of MABr powder on the microstructure, crystallinity, and optical characterizations of MAPbBr thin films, and a controllable morphology evolution with varying surface coverage was observed. Temperature-dependent and time-resolved photoluminescence measurements were carried out to investigate the optical transition mechanisms and carrier recombination dynamics of MAPbBr thin films.

High-Efficiency and Air-Stable Perovskite Quantum Dots Light-Emitting Diodes with an All-Inorganic Heterostructure.

Perovskite light-emitting diodes (PeLEDs), because of its fundamental scientific importance and practical applications in the fields of low-cost light source or display applications, have drawn worldwide attention in recent years. However, PeLEDs available today suffer from a compromise in their emission efficiency and operation stability. In this study, we designed and fabricated a stacking all-inorganic multilayer structure by using inorganic perovskite CsPbBr quantum dots (QDs) as the emissive layer and inorganic n-type MgZnO and p-type MgNiO as the carrier injectors, respectively.

Electrically pumped ultraviolet lasing in polygonal hollow microresonators: investigation on optical cavity effect.

Electrically driven ultraviolet lasing was realized in two-dimensional ZnO nanowall networks from Au/MgO/n-ZnO/n-GaN/In structure, and whispering gallery type resonant modes are responsible for the lasing action. We present a comparative study on lasing action based on nanowall networks with different micro-hole sizes. The representative diode (Device II) with a moderate micro-hole size exhibits an ultralow threshold current density of 1.

Exciton localization and ultralow onset ultraviolet emission in ZnO nanopencils-based heterojunction diodes.

n-GaN/i-ZnO/p-GaN double heterojunction diodes were constructed by vertically binding p-GaN wafer on the tip of ZnO nanopencil arrays grown on n-GaN/sapphire substrates. An increased quantum confinement in the tip of ZnO nanopencils has been verified by photoluminescence measurements combined with quantitative analyses. Under forward bias, a sharp ultraviolet emission at ~375 nm due to localized excitons recombination can be observed in ZnO.

Near infrared electroluminescence of ZnMgO/InN core-shell nanorod heterostructures grown on Si substrate.

This paper presents a systematic investigation of a ZnMgO/InN core-shell nanorods heterojunction device on a p-Si substrate. Here we demonstrated the heteroepitaxial growth of the well-aligned ZnMgO/InN core-shell nanorods structure, which enabled an increased heterojunction area to improve the carrier injection efficiency of nanodevices by plasma-assisted molecular beam epitaxy combined with metal-organic chemical vapor deposition. In situ X-ray photoelectron spectroscopy measurements were performed on the ZnMgO nanorods, the interface of ZnMgO/InN and the InN core-shell nanorods to fully understand the structure and working mechanism of the heterojunction device.

Semi-transparent all-oxide ultraviolet light-emitting diodes based on ZnO/NiO-core/shell nanowires.

Semi-transparent all-oxide light-emitting diodes based on ZnO/NiO-core/shell nanowire structures were prepared on double-polished c-Al2O3 substrates. The entire heterojunction diode showed an average transparency of ∼65% in the ultraviolet and visible regions. Under forward bias, the diode displayed an intense ultraviolet emission at ∼382 nm, and its electroluminescence performance was remarkable in terms of a low emission onset, acceptable operating stability, and the ability to optically excite emissive semiconductor nanoparticle chromophores.

High-performance planar green light-emitting diodes based on a PEDOT:PSS/CH3NH3PbBr3/ZnO sandwich structure.

Unlabelled: Recently, perovskite-based light-emitting diodes based on organometal halide emitters have attracted much attention because of their excellent properties of high color purity, tunable emission wavelength and a low-temperature processing technique. As is well-known, organic light-emitting diodes have shown powerful capabilities in this field; however, the fabrication of these devices typically relies on high-temperature and high-vacuum processes, which increases the final cost of the product and renders them uneconomical for use in large-area displays. Organic/inorganic hybrid halide perovskites match with these material requirements, as it is possible to prepare such materials with high crystallinity through solution processing at low temperature.

The growth of ZnO on stainless steel foils by MOCVD and its application in light emitting devices.

Unlabelled: Direct fabrication of semiconductor light emitting devices on metal foils is beneficial, because it brings flexibility and good heat sink in the devices. In this work, we have grown ZnO on the commercially available stainless steel foils by metal-organic chemical vapor deposition for the first time. With the increase of growth temperature, the morphology changes from a thin film structure to closely stacked columns, and eventually to nanorods.

Photoluminescence performance enhancement of ZnO/MgO heterostructured nanowires and their applications in ultraviolet laser diodes.

Vertically aligned ZnO/MgO coaxial nanowire (NW) arrays were prepared on sapphire substrates by metal-organic chemical vapor deposition combined with a sputtering system. We present a comparative investigation of the morphological and optical properties of the produced heterostructures with different MgO layer thicknesses. Photoluminescence measurements showed that the optical performances of ZnO/MgO coaxial NWs were strongly dependent on the MgO layer thickness.

High-temperature continuous-wave laser realized in hollow microcavities.

Recently, an urgent requirement of ultraviolet (UV) semiconductor laser with lower cost and higher performance has motivated our intensive research in zinc oxide (ZnO) material owing to its wide direct band gap and large exciton binding energy. Here, we demonstrate for the first time continuous-wave laser in electrically-pumped hollow polygonal microcavities based on epitaxial ZnO/MgO-core/shell nanowall networks structures, and whispering gallery type resonant modes are responsible for the lasing action. The laser diodes exhibit an ultralow threshold current density (0.

Low Al-composition p-GaN/Mg-doped Al0.25Ga0.75N/n+-GaN polarization-induced backward tunneling junction grown by metal-organic chemical vapor deposition on sapphire substrate.

Low Al-composition p-GaN/Mg-doped Al0.25Ga0.75N/n(+)-GaN polarization-induced backward tunneling junction (PIBTJ) was grown by metal-organic chemical vapor deposition on sapphire substrate.

Electrically driven ultraviolet random lasing from an n-MgZnO/i-ZnO/SiO2/p-Si asymmetric double heterojunction.

Electrically pumped lasing action has been realized in ZnO from an n-MgZnO/i-ZnO/SiO2/p-Si asymmetric double heterostructure, an ultralow threshold of 3.9 mA was obtained. The mechanism of the laser is associated with the in-plane random resonator cavities formed in the ZnO films and the elaborate hollow-shaped SiO2 cladding pattern, which prevent the lateral diffusion of injection current and ultimately lower the threshold current of the laser diode.