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Schematic illustration of energy transfer from the STE excitons, deep traps, and shallow traps to Mn2+. This simply and clearly explains the phenomenon of abnormal luminescence at high temperatures.

Broadband NIR phosphors as light sources are receiving increasing attention.

A novel green afterglow Na3(Y,Sc)Si3O9:Eu2+ phosphor is synthesized for optical data storage and latent fingerprint recognition.

Due to the simplicity of vacancy creation, Eu2+-doped melilite is an outstanding persistent luminescence (PersL) material with a continuing glow lifetime of more than several hours. In this paper, we...

Broadband emission with a large Stokes shift is important to obtain an excellent color rendering index of the solid-state lighting device. Among low-dimensional material and perovskite-like phosphors with broadband self-trapped emission, Sn-based phosphors have attracted much attention due to their high photoluminescence quantum yield (PLQY). However, the disadvantage is that the synthesis of Sn-based phosphors needs to be performed in a glovebox. Upon photoexcitation, the broadband emission of self-trapped excitons results from exciton-phonon coupling induced by the transient distortion of the lattice. Low-dimensional material structures often promote self-trapped emission because of more vibrational degrees of freedom and easier polarization under photoexcitation. Here, zero-dimensional (0D) SnX

Metal halide perovskites (MHPs) have shown unparalleled potential for optoelectronic applications. In particular, the quasi one-dimensional perovskite structures have attracted great attention due to their unique optoelectronic properties which can open up new possibilities for this exciting materials system. However, it is challenging to acquire one-dimensional cubic-phase MHPs in high yield due to their isotropic crystallization nature and instability towards conventional fabrication processes. Here, we demonstrate the feasibility of synthesizing single-crystalline perovskite microwires from an intrinsic 1D structured lattice framework which defines the size and shape of the resulting microwires. By incorporating the appropriate monovalent ions into the lattice of self-assembled PbBr2 microwires, single-crystal CH3NH3PbBr3 microwires are successfully synthesized. The excellent crystal quality of the microwires has led to a high carrier mobility of 36 cm2 V−1 s−1 and a long charge carrier lifetime of ∼100 ns. As a preliminary demonstration of their optoelectronics functionality, single CH3NH3PbBr3 microwire-based photodetectors are fabricated and the devices exhibit a fast response time (a rise time of 113 μs and a decay time of 295 μs), stable light switching behavior, high sensitivity, and good spatial resolution. The method described here proposes a novel and facile strategy for synthesizing single-crystal perovskite microwires with high yield and repeatability, showing the great promise of MHPs in micro-optoelectronic applications.

Among all the 2D-carbon materials, graphyne is currently one of the most interesting carbon allotropes besides graphene. It has potential applications in a wide variety of scientific fields owing to its unique sp–sp2 hybrid network, which endows desirable electronic properties towards energy-related applications. In this review, we summarize the recent progress in graphynes for electronic and energy applications from a theoretical point of view. The intrinsic electronic structure of graphyne and its chemical and mechanical properties are comprehensively described. It is hoped that this review could provide a strong theoretical understanding of graphynes, thus accelerating the design of robust and efficient graphyne-based advanced energy and electronic devices in the future.

Two-dimensional (2D) materials have attracted increasing interest in the past decades due to their unique physical and chemical properties for diverse applications. In this work, we present a first-principles design on a novel 2D family, MSi2CxN4−x (M = Cr, Mo, and W; x = 1 and 2), based on density-functional theory (DFT). We find that all MSi2CxN4−x monolayers are stable by investigating their mechanic, dynamic, and thermodynamic properties. Interestingly, we see that the alignment of magnetic moments can be tuned to achieve non-magnetism (NM), ferromagnetism (FM), anti-ferromagnetism (AFM) or paramagnetism (PM) by arranging the positions of carbon atoms in the 2D systems. Accordingly, their electronic properties can be controlled to obtain semiconductor, half-metal, or metal. The FM states in half-metallic 2D systems are contributed to the hole-mediated double exchange, while the AFM states are induced by super-exchange. Our findings show that the physical properties of 2D systems can be tuned by compositional and structural engineering, especially the layer of C atoms, which may provide guidance on the design and fabrication of novel 2D materials with projected properties for multi-functional applications.

Lead-free double perovskites have recently received increasing attention due to their variable band gap. In this work, tin was doped into Cs2BiAgCl6 successfully. The doping of Sn2+ cations can make the weak white luminescent host to produce pure blue emission peaking at around 464 nm. The internal carrier changes after Sn2+ doping and the origin of blue emission in Cs2BiAgCl6:Sn2+ was analyzed by ultrafast transient absorption (TA) techniques and time-resolved spectra. To further study the substitution feasibility of Sn2+–Sn4+ for Bi3+–Bi3+ pair cations, Rietveld refinement and density functional theory (DFT) calculations were performed, which proved that the crystal structures of Cs2BiAgCl6:Sn2+ can exist stably. Based on these observations, we introduced blue-emitting Cs2BiAgCl6:Sn2+ powder into a white LED fabricated by combining a 340 nm chip to generate stable white light with CIE coordinates of (0.31, 0.34) and a color rendering index value of 83. This work provides the methods to develop environmentally friendly blue emission from lead-free double perovskites at low cost.

As an important family of 2D materials, MXenes show great potential in various applications due to their specific physical and chemical properties, such as high conductivity and surface activity. Here, we investigate 54 phosphorus-functionalized MXenes (P-MXenes) and screen out 10 stable structures by analyzing their dynamical, thermal, and mechanical stabilities based on first-principles calculations. We find that these stable P-MXenes remain metallic and show weak magnetism. We show that they are effective as electrocatalysts for the hydrogen evolution reaction (HER) with near-zero Gibbs free energies of hydrogen adsorption, which are comparable to that of Pt. To understand the microkinetic process in the HER, an explicit water model is used to examine the Volmer–Heyrovsky (V–H) and Volmer–Tafel (V–T) pathways. We find that P-MXenes show a high HER performance along the V–H process due to the low activation barrier. Our systematic study confirms the possibility for the phosphorus-functionalization of MXenes, guides the design of novel electrocatalysts for the HER via surface-modification, and provides deep understanding on the HER mechanism.

Massively converting nitrogen gas to ammonia is a key process in modern agricultural and industrial fields. The conventional Haber–Bosch process for NH3 production has to be carried out under extre...

Ferroelectrics is expected to be an alternative to traditional solar cells, because its bulk photovoltaic effect (BPVE) may overcome the Shockley–Queisser limit. Here, we propose that a family of p...

Atomic catalysts (AC) are gaining extensive research interest as the most active new frontier in heterogeneous catalysis due to their unique electronic structures and maximum atom-utilization efficiencies. Among all the atom catalysts, atomically dispersed heteronuclear dual-atom catalysts (HDACs), which are featured with asymmetric active sites, have recently opened new pathways in the field of advancing atomic catalysis. In this review, the up-to-date investigations on heteronuclear dual-atom catalysts together with the last advances on their theoretical predictions and experimental constructions are summarized. Furthermore, the current experimental synthetic strategies and accessible characterization techniques for these kinds of atomic catalysts, are also discussed. Finally, the crucial challenges in both theoretical and experimental aspects, as well as the future prospects of HDACs for energy-related applications are provided. It is believed that this review will inspire the rational design and synthesis of the new generation of highly effective HDACs.

Interfacial quality of functional layers plays an important role in the carrier transport of sandwich-structured devices. Although the suppression of interface states is crucial to the overall device performance, our understanding on their formation and annihilation mechanism via direct characterization is still quite limited. Here, we present a thorough study on the interface states present in the electron transport layer (ETL) of blue quantum dot (QD) light-emitting diodes (QLEDs). A ZnO/ZnMgO bilayer ETL is adopted to enhance the electron injection into blue QDs. By probing the ETL band structure with photoelectron spectroscopy, we discover that substantial band bending exists at the ZnO/ZnMgO interface, elucidating the presence of a high density of interface states which hinder electron transport. By inserting a ZnO@ZMO interlayer composed of mixed ZnO and ZnMgO nanoparticles, the band bending and thus the interface states are observed to reduce significantly. We attribute this to the hybrid surface properties of ZnO@ZMO, which can annihilate the surface states of both the ZnO and ZnMgO layers. The introduction of a bridging layer has led to ∼40% enhancement in the power efficiency of blue QLEDs and noticeable performance boosts in green and red QLEDs. The findings here demonstrate a direct observation of interface states via detailed band structure studies and outline a potential pathway for eliminating these states for better performances in sandwich-structured devices.

Generating clean and sustainable hydrogen from water splitting processes represent a practical alternative to solve the energy crisis. Ultrathin two-dimensional materials exhibit attractive properties as catalysts for hydrogen production owing to their large surface-to-volume ratios and effective chemisorption sites. However, the catalytically inactive surfaces of the transition metal dichalcogenides (TMD) possess merely small areas of active chemical sites on the edge, thus decreasing their possibilities for practical applications. Here, we propose a new class of out-of-plane deformed TMD (cTMD) monolayer to anchor transition metal atoms for the activation of the inert surface. The calculated adsorption energy of metals (e.g., Pt) on curved MoS2 (cMoS2) can be greatly decreased by 72% via adding external compressions, compared to the basal plane. The enlarged diffusion barrier energy indicates that cMoS2 with an enhanced fixation of metals could be a potential candidate as a single atom catalyst (SAC). We made a well-rounded assessment of the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), which are two key processes in water splitting. The optimized Gibbs free energy of 0.02 for HER and low overpotential of 0.40 V for OER can be achieved when the proper compression and supported metals are selected. Our computational results provide inspiration and guidance towards the experimental design of TMD-based SACs.

Solution-processed ZnO nanoparticle thin film is widely used as the electron transport layers (ETLs) in quantum dot light emitting diodes (QLEDs). While the ZnO nanoparticles (NPs) synthesis proces...

Two-dimensional (2D) transition-metal dichalcogenides (TMDs) monolayers have found various applications spanning from electronics in physics to catalysis in chemistry due to their unique physical a...

Transition metal nitrides (TMNs)-based materials have attracted increasing attention in electrochemical nitrogen reduction reaction (eNRR) because of their unique structures and inherent electronic properties. However, the eNRR mechanism on such nitrogen contained catalysts is still unclear, for example, which part of the catalyst act as the active sites, and how to achieve the optimal efficiency is also challenging. In this work, a comprehensive study was conducted to unravel the reaction mechanisms of N

Two-dimensional (2D) materials have attracted increasing interest in the past decades due to their unique physical and chemical properties for diverse applications. In this work, we present a first-principles design on a novel 2D family, MSi

A class of new spatiotemporal solitary solution to nonlinear Schrodinger equation with a parabolic potential is investigated analytically and numerically using the F-expansion method and homogeneous balance principle. The propagation characteristics of soliton wave solutions are analyzed with/without spatial-temporal chirp. It is noteworthy that, by calculating spatial and temporal second-order intensity moment, several novel features of optical beam propagations are obtained, such as stable, oscillating, decaying and blowing up. Additionally, controllability of these solutions with the modulation depth of the parabolic potential is demonstrated.

The Goodenough-Kanamori-Anderson (GKA) rules have been widely applied for explaining the magnetic properties induced by super-exchange interaction. As conclusions of the super-exchange theory, they reveal the antiferromagnetic (ferromagnetic) ordering along with bond angle of 180 degrees (90 degrees) in the cation-anion-cation interaction path, in which the theory sets a pre-condition that the electronic states of cations in all paths are identical. We observed that the GKA rules are in fact not universal and even invalid to materials containing anions with different valence states, for example, the layered CrOCl crystal (with two valence states of anions: O2- and Cl-). In this study, we propose an extended super-exchange theory (ESET) related to superposed electronic states of cation in a specific path. ESET is capable of predicting not only the sign and relative magnitude of magnetic exchange constants in different cation-anion-cation paths, but also the magnetic ground state. Through our proposed theory, we conclude that the magnetic ordering along with bond angle of 90 degrees in Cr-Cl-Cr path is moderately antiferromagnetic and of 180 degrees in Cr-O-Cr path is strongly ferromagnetic, which are opposite to the contents of GKA rules. Moreover, we clarify that monolayer CrOCl has antiferromagnetic ordering rather than ferromagnetic as reported recently. The reliability of ESET is verified via first-principles calculation and previous experimental report as well, and its universality is also demonstrated. Thus, our theory is powerful to predict the magnetic properties, which makes it possible to design new high Curie temperature two-dimensional semiconducting ferromagnets with polyvalent anion materials., 18 pages, five figures(including TOC)

An oxide-based green emitting phosphor, SrAl2Si2O8: Mn2+ (SASO: Mn2+) deriving from the feldspar mineral model has been successfully synthesized by a facile solid-state reaction. Upon 450 nm blue-light excitation, brightness narrow-band green light peaking at 517 nm with a full-width at half-maximum (fwhm) of 26 nm can be obtained. Owing to the narrow band emission, the CIE chromaticity coordinates are (0.182, 0.745) and the color purity of SASO: Mn2+ is determined to be 78.3%. Meanwhile, the internal quantum efficiency (IQE) of the representative sample can reach up to 45.6% under 450 nm. In addition, the phosphor exhibits an extremely thermal stability, i.e., the integrated emission intensity at 420 K still remains 92% of the initial value. Furthermore, w-LED device fabricated from optimized phosphor SASO: Mn2+ (green), commercial phosphor KSF: Mn4+ (red) and blue LED chip can cover 120% National Television System Committee standard (NTSC) value. All these results suggest that the Mn2+ ion activated green emitting phosphor has great potential for wide gamut w-LEDs backlights.

We have proposed a switchable mode-locked fiber laser by means of carbon nanotube saturable absorber and fiber Bragg gratings (FBGs). The single-wavelength mode-locking operation can be switched between 1549.5 and 1559.5 nm, respectively, which correspond to the central wavelengths of two FBGs. With the appropriate setting of polarization controller, the stable dual-wavelength operation can be achieved due to the high stability of saturable absorber based on carbon nanotubes. Our method provides a simple, stable, low-cost, dual-wavelength ultrafast-pulsed source.

In this work, a rapid one-step process is developed to fabricate superhydrophobic cathodic surface by electrodepositing copper plate in an electrolyte solution containing manganese chloride (MnCl 2 ·4H 2 O), myristic acid (CH 3 (CH 2 ) 12 COOH) and ethanol. The superhydrophobic surfaces were characterized by means of scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The shortest electrolysis time for fabricating a superhydrophobic surface is about 1 min, the measured maximum contact angle is 163° and rolling angle is less than 3°. Furthermore, this method can be easily extended to other conductive materials. The approach is time-saving and cheap, and it is supposed to have a promising future in industrial fields.

Numerical simulation based on a new regularized phase field model was performed to describe the dendritic growth of an isothermal alloy with a strong anisotropy in the presence of a forced flow. These results indicate that a crystal grow into an equiaxial facet dendritic in the absence of a forced flow and into an asymmetrical facet dendritic in the presence of a forced flow. With increasing a flow velocity, the tip steady velocity of upstream dendritic arm increases, that of the downstream arm decreases, and that of the perpendicular arms increases at first, and then decreases, the perpendicular arms gradually grow toward the incoming flow direction. In the certain range of anisotropy parameter, when γ is larger than 0.14, dendritic tip steady velocities in all direction are expected to reach their own saturation values. In addition, the effect of a compound forced flow on an isothermal facet dendritic is similar to experimental results.

The reduction of the dipole moment of effective pair potentials of rigid water models enables accurate second virial coefficients to be determined over the whole temperature range. Subsequent Isothermal Isobaric (NPT) ensemble simulations of water vapour have shown that there is a significant difference in vapour densities between the modified water potentials.

We have proposed a nanotube-mode-locking fiber laser that can generate conventional solitons and stretched pulses in the same cavity. The net cavity dispersion of laser is slightly negative. The central wavelength and bandwidth of the conventional solitons are 1584.7 and 9.2 nm, respectively. The stretched pulse locates at 1572 nm with a bandwidth of 18.8 nm. The switchable mode-locking operation is mainly attributable to the bandwidth-dependent stretching factor that is tunable due to the spectral filtering effect induced by nonlinear polarization rotation.

We have experimentally observed the multiple bound states in a linear-cavity fiber laser mode-locked by a mixture of graphene and single-walled carbon nanotubes. The proposed laser can deliver the fundamental frequency soliton as well as the two and three bound-state solitons at suitable conditions. The numerical simulations confirm the experimental observations. Both the theoretical predictions and experimental results reveal that the spectral filtering effect plays a key role on the lasers.

We have proposed a compact dual-wavelength all-fiber pulse laser based on a single-walled carbon nanotube and chirped fiber Bragg gratings (CFBGs). A transmission filter is composed of a circulator and two CFBGs and is capable of controlling the operation of the proposed fiber laser. Mode-locking operations can be switched between 1551.2 and 1548.6 nm with the appropriate adjustment of polarization controller. Our laser delivers the pulses with the spectral bandwidth of about 0.6 nm and the pulse duration of about 7 ps. This work provides a low-cost, stable, and dual-wavelength ultrafast-pulsed laser source suitable for practical applications.