Enhancement of electroluminescent properties of organic optoelectronic integrated device by doping phosphorescent dye

Organic optoelectronic integrated devices（OIDs） with ultraviolet（UV） photodetectivity and different color emitting were constructed by using a thermally activated delayed fluorescence（TADF） material 4, 5-bis（carbazol-9-yl）-1, 2-dicyanobenzene（2 CzPN） as host. The OIDs doping with typical red phosphorescent dye [tris（1-phenylisoquinoline）iridium（Ⅲ）, Ir（piq）3], orange phosphorescent dye {bis[2-（4-tertbutylphenyl）benzothiazolato-N,C-（2＇）]iridium（acetylacetonate）,（tbt）2 Ir（acac）}, and blue phosphorescent dye [bis（2, 4-di-fluorophenylpyridinato）-tetrakis（1-pyrazolyl）borate iridium（Ⅲ）, FIr6] were investigated and compared. The（tbt）2 Ir（acac）-doped orange device showed better performance than those of red and blue devices, which was ascribed to more effective energy transfer. Meanwhile, at a low dopant concentration of 3 wt.%, the（tbt）2 Ir（acac）-doped OIDs showed the maximum luminance, current efficiency, power efficiency of 70786 cd/m^2, 39.55 cd/A, and 23.92 lm/W, respectively, and a decent detectivity of 1.07 × 10^11 Jones at a bias of -2 V under the UV-350 nm illumination. This work may arouse widespread interest in constructing high efficiency and luminance OIDs based on doping phosphorescent dye.

Stability and optoelectronic property of lead-free halide double perovskite Cs_(2)B′BiI_(6)(B′=Li,Na and K)

Although lead-based perovskite solar cells have achieved more than 25%power conversion efficiency,the toxicity of lead and instability are still urgent problems faced in industrial application.Lead-free halide double perovskite(DP)materials are promising candidates to resolve these issues.Based on the density functional theory,we explore the geometric stability,thermodynamic stability,mechanical stability,electronic structures,and optical properties of theCs_(2)B 0BiI_(6)(B 0=Li,Na and K)DP materials.By analyzing the tolerance factor and octahedral factor,we find the geometric stabilities ofCs_(2)NaBiI_(6) andCs_(2)KBiI_(6) DPs are better thanCs_(2)LiBiI_(6).By calculating the total energy,formation energy and decomposition energy,we propose that the most favorable structure ofCs_(2)B 0BiI_(6) is the orthorhombic phase,andCs_(2)LiBiI_(6) is less stable relative to the other two counterparts from an energetic viewpoint.Mechanical stability evaluations reveal that the orthorhombicCs_(2)LiBiI_(6) material is less stable relative to the isostructuralCs_(2)NaBiI_(6) andCs_(2)KBiI_(6) DPs.The mechanical property calculations indicate that theCs_(2)B 0BiI_(6) DPs possess good ductility,which can be used as flexible materials.Electronic structures and optical property calculations show that the orthorhombicCs_(2)B 0BiI_(6) DPs have suitable band gap values,weaker exciton binding energies,and excellent optical absorption performance in the visible-light range.Based on the above comprehensive assessments,we can conclude that the orthorhombic Cs_(2)NaBiI_(6) and Cs_(2)KBiI_(6) DPs with good stability are promising candidates for solar cell applications.

Semiannual oscillation,annual oscillation,quasibiennial oscillation,and solar cycle variation of the OH airglow emission in the mesopause region

The vertically integrated emission rate,centroid altitude,peak emission rate,and peak height of the hydroxyl(OH)airglow were calculated from Thermosphere Ionosphere Mesosphere Energetics and Dynamics(TIMED)/Sounding of the Atmosphere using Broadband Emission Radiometry(SABER)observations to study the seasonal and interannual variations in the intensity and location of the OH emission.The emission rate is inversely proportional to the height of the emission,with the semiannual oscillation dominating at low latitudes and the annual oscillation dominating at higher latitudes.The OH emission is modulated by the quasibiennial oscillation at the equator,and the quasibiennial oscillation signal is weak at other latitudes.We represented the vertical transport of atomic oxygen by using atomic oxygen concentrations obtained from a global atmospheric model,the Specified Dynamics Whole Atmosphere Community Climate Model with thermosphere and ionosphere eXtension simulations.Compared with the amplitudes of the migrating diurnal tide(DW1)calculated from temperature data observed by TIMED/SABER,we found that both the vertical transport of atomic oxygen and DW1 amplitudes in the equatorial region exhibit semiannual oscillation and quasibiennial oscillation,which have a strong correlation with the variations in the amplitude and phase of semiannual oscillation and quasibiennial oscillation in OH emission.It is likely that the DW1 affects the vertical transport of atomic oxygen that is involved in the reaction to produce O3,thus affecting the OH emission.We analyzed the relationship between OH emission and solar activity by using the solar radio flux at 10.7 cm as a proxy for solar activity.The results showed that the OH emission is well correlated with solar activity,and the modulation of OH emission by solar activity has a significant latitudinal variation.The small correlation between emission height and solar activity indicates that solar activity modulates OH emission mainly through chemical rather than dynamic processes.

Analysis and inversion of target polarization characteristics based on pBRDF

Imaging detection is an important means to obtain target information.The traditional imaging detection technology mainly collects the intensity information and spectral information of the target to realize the classification of the target.In practical applications,due to the mixed scenario,it is difficult to meet the needs of target recognition.Compared with intensity detection,the method of polarization detection can effectively enhance the accuracy of ground object target recognition(such as the camouflage target).In this paper,the reflection mechanism of the target surface is studied from the microscopic point of view,and the polarization characteristic model is established to express the relationship between the polarization state of the reflected signal and the target surface parameters.The polarization characteristic test experiment is carried out,and the target surface parameters are retrieved using the experimental data.The results show that the degree of polarization(DOP)is closely related to the detection zenith angle and azimuth angle.The(DOP)of the target is the smallest in the direction of light source incidence and the largest in the direction of specular reflection.Different materials have different polarization characteristics.By comparing their DOP,target classification can be achieved.

Harmonic splitting phenomenon of bright-dark pulse pairs in a passive mode-locked Thulium-Holmium co-doped fiber laser

This study reports a passive mode-locked Thulium-Holmium co-doped fiber laser featuring a figure-9 shaped resonator structure.The laser utilizes a nonlinear amplifying loop mirror(NALM)as the mode-locking device.By increasing pump power,the laser’s output evolution was experimentally observed,showing that bright-dark pulse pairs first split into double pulses and then into a second harmonic state.Additionally,the time intervals between bright and dark pulses and between double pulses increased with higher pump power.The RF spectrum of the bright-dark pulse pairs exhibited envelope modulation,with a modulation frequency approximately equal to the reciprocal of the time interval between bright and dark pulses.When the pump power increased from 0.46 W to 0.72 W,the reciprocal of the modulation frequency showed a linear growth trend.These findings contribute to understanding the evolution patterns of bright-dark pulse pairs in passive mode-locked fiber lasers.

Generation of subwavelength inverted pin beam via fiber end integrated plasma structure

A pin-like beam is a kind of structured light with a special intensity distribution that can be against diffraction,which can be seen as a kind of quasi-nondiffracting beam(Q-NDB).Due to its wide applications,recently,numerous researchers have used optical lenses or on-chip integrated optical diffractive elements to generate this kind of beam.We theoretically verify and experimentally demonstrate an all-fiber solution to generate a subwavelength inverted pin beam by integrating a simple plasma structure on the fiber end surface.The output beams generated by two kinds of plasma structures,i.e.,nanoring slot and nanopetal structure,are investigated and measured experimentally.The results show that both the structures are capable of generating subwavelength beams,and the beam generated using the nanopetal structure has the sidelobe suppression ability along the x-axis direction.Our all-fiber device can be flexibly inserted into liquid environments such as cell cultures,blood,and biological tissue fluids to illuminate or stimulate biological cells and molecules in them.It provides a promising fiber-integrated solution for exploring light–matter interaction with subwavelength resolution in the field of biological research.

Numerical design of an efficient Ho^(3+)-doped InF3 fiber laser at~3.2μm

In this work,we theoretically unlock the potential of Ho^(3+)-doped InF3 fiber for efficient~3.2μm laser generation(from the ^(5)F_(4),^(5)S_(2)→^(5)F_(5) transition),by employing a novel dual-wavelength pumping scheme at 1150 nm and 980 nm,for the first time.Under clad-coupled 1150 nm pumping of 5 W,~3.2μm power of 3.6 W has been predicted with the optical-to-optical efficiency of 14.4%.Further efficient power scaling,however,is blocked by the output saturation with 980 nm pumping.To alleviate this behavior,the cascaded ^(5)I_(5)→^(5)I_(6) transition,targeting~3.9μm,has been activated simultaneously,therefore accelerating the population circulation between the laser upper level ^(5)F_(4),^(5)S_(2) and long-lived ^(5)I_(6) level under 980 nm pumping.As a result,enhanced~3.2μm power of 4.68 W has been obtained with optical-to-optical efficiency of 15.6%.Meanwhile the~3.9μm laser,yielding power of 2.76 W with optical-to-optical efficiency of 9.2%,is theoretically achievable as well with a moderate heat load,of which the performance is even better than the prior experimentally and theoretically reported Ho^(3+)-doped InF3 fiber lasers emitting at~3.9μm alone.This work demonstrates a versatile platform for laser generation at~3.2μm and~3.9μm,thus providing the new opportunities for many potential applications,e.g.,polymer processing,infrared countermeasures,and free-space communications.

Lithiophilic CoF_(2)@C hollow spheres towards spatial lithium deposition for stable lithium metal batteries

Lithium metal(LM)is a promising anode for next-generation batteries due to its high theoretical capacity and low electrode potential.Nonetheless,side reactions,volume change,and unwanted lithium dendrite growth seriously limit the practical application of LM.Herein,with the aid of a hard template approach,a novel lithiophilic CoF_(2)-carbon hollow sphere(CoF_(2)@C-HS)composite material is successfully prepared via a facile in-situ fluorination and etching strategy.The lithiophilic CoF_(2) acts as nucleation sites to reduce nucleation overpotential as well as induces the spatial Li deposition and the formation of LiFrich solid electrolyte interphase(SEI),and the hollow carbon matrix can enhance the electrical conductivity and offer free space for LM deposition.Theoretical simulations reveal that the synergistic effect of lithiophilic CoF_(2) and hollow carbon matrix homogenizes the electric field distribution and Li~+flux.Benefiting from these advantages,the CoF_(2)@C-HS-modified copper substrate electrode delivers an enhanced Coulombic efficiency(CE)of 93.7%for 280 cycles at 1 mA cm^(-2)and 1 mA h cm^(-2).The symmetrical cell using CoF_(2)@C-HS can stably cycle more than 1800 h with a low voltage hysteresis of 11 mV at a current density of 0.5 MA cm^(-2)and an areal capacity of 0.5 mA h cm^(-2).Moreover,the Li@CoF_(2)@C-HS composite anode enables more than 300 stable cycles at 1 C with a capacity retention of 95%in LiFePO_(4)-based full cell and 110 stable cycles at 1 C in LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811)-based highvoltage full cell.This work might shed a new light on designing lithiophilic hosts to spatially confine LM deposition,realizing dendrite-free LM anodes and the practical applications of LM batteries.

Exploring negative ion behaviors and their influence on properties of DC magnetron sputtered ITO films under varied power and pressure conditions

We deposited indium-tin-oxide(ITO)films on silicon and quartz substrates by magnetron sputtering technology in pure argon.Using electrostatic quadrupole plasma diagnostic technology,we investigate the effects of discharge power and discharge pressure on the ion flux and energy distribution function of incidence on the substrate surface,with special attention to the production of high-energy negative oxygen ions,and elucidate the mechanism behind its production.At the same time,the structure and properties of ITO films are systematically characterized to understand the potential effects of high energy oxygen ions on the growth of ITO films.Combining with the kinetic property analysis of sputtering damage mechanism of transparent conductive oxide(TCO)thin films,this study provides valuable physical understanding of optimization of TCO thin film deposition process.

Theoretical simulation study of laser-induced plasma bombardment on bacteria

With the rapid advancement of laser decontamination technology and growing awareness of microbial hazards,it becomes crucial to employ theoretical model to simulate and evaluate decontamination processes by laser-induced plasma.This study employs a two-dimensional axisymmetric fluid dynamics model to simulate the power density of plasma bombardment on bacteria and access its decontamination effects.The model considers the transport processes of vapor plasma and background gas molecules.Based on the destructive impact of high-speed moving particles in the plasma on bacteria,we investigate the bombardment power density under various conditions,including different laser spot sizes,wavelengths,plate's tilt angles,and plate-target spacing.The results reveal that the bombardment power density increases with a decrease in laser spot size and wavelength.For instance,when the plate is parallel to the target surface with a 1 mm spacing,the bombardment power density triples as the laser spot size decreases from 0.8 mm to 0.5 mm and quadruples as the wavelength decreases from 1064 nm to 266 nm.Notably,when the plate is parallel to the target with a relatively close spacing of 0.5 mm,the bombardment power density at 0°inclination increases sevenfold compared to 45°.This simulation study is essential for optimizing optical parameters and designing component layouts in decontamination devices using laser-induced plasma.The reduction of laser spot size,wavelength,plate-target spacing and aligning the plate parallel to the target,collectively contribute to achieving precise and effective decontamination.

Effects of power on ion behaviors in radio-frequency magnetron sputtering of indium tin oxide(ITO)

This study delves into ion behavior at the substrate position within RF magnetron discharges utilizing an indium tin oxide(ITO)target.The positive ion energies exhibit an upward trajectory with increasing RF power,attributed to heightened plasma potential and initial emergent energy.Simultaneously,the positive ion flux escalates owing to amplified sputtering rates and electron density.Conversely,negative ions exhibit broad ion energy distribution functions(IEDFs)characterized by multiple peaks.These patterns are clarified by a combination of radiofrequency oscillation of cathode voltage and plasma potential,alongside ion transport time.This elucidation finds validation in a one-dimensional model encompassing the initial ion energy.At higher RF power,negative ions surpassing 100 e V escalate in both flux and energy,posing a potential risk of sputtering damages to ITO layers.

Oriented structural design of MXene electrodes for lithium sulfur catalysis

The lithium-sulfur reaction can contribute to the chemical electrical energy conversion capacity due to the multi-level ion/electron transfer process. However, the appearance of soluble intermediate products prevents efficient electron transfer, making it impossible to achieve stable cycling and capacity contribution. Restricted catalysis provides a solution for inhibiting the shuttle of soluble lithium polysulfides.Herein, MXene aerogel with optimized channel utilization is designed as S host according to the polysulfide control strategy of localization, adsorption, and catalysis. With the help of the results of oriented channels, the polysulfide conversion process is optimized, providing a comprehensive scheme for inhibiting the shuttle effect. Lithium sulfur catalytic batteries have achieved high capacity and stable cycling.This system provides a comprehensive solution for lithium sulfur reaction catalysis and a new perspective for the functional application of MXene based lithium sulfur batteries.

Investigation on Breakdown Characteristics of Various Surface Terminal Structures for GaN-Based Vertical P-i-N Diodes

GaN-based vertical P-i-N diode with mesa edge terminal structure due to electric field crowding effect, the breakdown voltage of the device is significantly reduced. This work investigates three terminal structures, including deeply etched, bevel, and stepped-mesas terminal structures, to suppress electric field crowding effects at the device and junction edges. Deeply-etched mesa terminal yields a breakdown voltage of 1205 V, i.e., 89% of the ideal voltage. The bevel-mesa terminal achieves about 89% of the ideal breakdown voltage, while the step-mesa terminal is less effective in mitigating electric field crowding, at about 32% of the ideal voltage. This work can provide an important reference for the design of high-power, high-voltage GaN-based P-i-N power devices, finding a terminal protection structure suitable for GaNPiN diodes to further enhance the breakdown performance of the device and to unleash the full potential of GaN semiconductor materials.

Progress in Analytical Methods of Halogenated Disinfection By-Products

Ensuring the health and safety of drinking water is crucial for both nations and their citizens.Since the 20th century,the disinfection of drinking water,effectively controlling pathogens in water sources,has become one of the significant advances in public health.However,the disinfectants used in the process,such as chlorine and chlorine dioxide,react with natural organic matter in the water to produce disinfection by-products(DBPs).Most of these DBPs contain chlorine,and if the source water contains bromine or iodine,brominated or iodinated DBPs,collectively referred to as Halogenated disinfection byproducts(X-DBPs),are formed.Numerous studies have found that X-DBPs pose potential risks to human health and the environment,leading to widespread concern.Mass spectrometry has become an important means of discovering new types of X-DBPs.This paper focuses on the study of methods for analyzing X-DBPs in drinking water using mass spectrometry.

Study on the Performance of PECVD Silicon Nitride Thin Films

Mechanical properties and corrosion resistance of Si3N4 films are studied by using different experiment parameters, such as plasma enhanced chemical vapor deposition(PECVD) RF power, ratio of reaction gas, reaction pressure and working temperature. The etching process of Si3N4 is studied by inductively coupled plasma (ICP) with a gas mixture of SF6 and O2. The influence of the technique parameters, such as ICP power, DC bias, gas composition, total flow rate, on the etching selectivity of Si3N4/EPG533 which is used as a mask layer and the etching rate of Si3N4 is studied, in order to get a better etching selectivity of Si3N4/EPG533 with a faster etching rate of Si3N4. The optimized process parameters of etching Si3N4 by ICP are obtained after a series of experiments and analysis. Under the conditions of total ICP power of 250 W, DC bias of 50W, total flow rate of 40 sccm and O2 composition of 30%, the etching selectivity of 2.05 can be reached when Si3N4 etching rate is 336 nm/min.

Generation of cavity-birefringence-dependent multi-wavelength bright-dark pulse pair in a figure-eight thulium-doped fiber laser

We experimentally demonstrated a stable multi-wavelength bright-dark pulse pair in a mode-locked thulium-doped fiber laser(TDFL).The nonlinear polarization rotation(NPR)and nonlinear optical loop mirror(NOLM)were employed in a figure-eight cavity to allow for multi-wavelength mode-locking operation.By incorporating different lengths of high birefringence polarization-maintaining fiber(PMF),the fiber laser could operate stably in a multi-wavelength emission state.Compared with the absence of the PMF,the birefringence effect caused by PMF resulted in rich multi-wavelength optical spectra and better intensity symmetry and stability of the bright-dark pulse pair.

Study of nanocrystalline VO_2 thin films prepared by magnetron sputtering and post-oxidation

Nanocrystalline VO2 thin films were deposited onto glass slides by direct current magnetron sputtering and postoxidation. These films undergo semiconductor-metal transition at 70 ℃, accompanied by a resistance drop of two magnitude orders. The crystal structures and surface morphologies of the VO2 films were characterized by x-ray diffraction （XRD） and atomic force microscope （AFM）, respectively. Results reveal that the average grain size of VO2 nanograins measured by XRD is smaller than those measured by AFM. In addition, Raman characterization indicates that stoichiometric VO2 and oxygen-rich VO2 phases coexist in the films, which is supported by x-ray photoelectron spectroscopy （XPS） results. Finally, the optical properties of the VO2 films in UV-visible range were also evaluated. The optical band gap corresponding to 2p-3d inter-band transition was deduced according to the transmission and reflection spectra. And the deduced value, Eopt2p-3d ： 1.81 eV, is in good agreement with that previously obtained by theoretical calculation.

Simulation of GaN micro-structured neutron detectors for improving electrical properties

Nowadays,the superior detection performance of semiconductor neutron detectors is a challenging task.In this paper,we deal with a novel GaN micro-structured neutron detector(GaN-MSND)and compare three different methods such as the method of modulating the trench depth,the method of introducing dielectric layer and p-type inversion region to improve the width of depletion region(W).It is observed that the intensity of electric field can be modulated by scaling the trench depth.On the other hand,the electron blocking region is formed in the detector enveloped with a dielectric layer.Furthermore,the introducing of p-type inversion region produces new p/n junction,which not only promotes the further expansion of the depletion region but also reduces the intensity of electric field produced by main junction.It can be realized that all these methods can considerably enhance the working voltage as well as W.Of them,the improvement on W of GaN-MSND with the p-type inversion region is the most significant and the value of W could reach 12.8μm when the carrier concentration of p-type inversion region is 10^17 cm^-3.Consequently,the value of W is observed to improve 200%for the designed GaN-MSND as compared with that without additional design.This work ensures to the researchers and scientific community the fabrication of GaN-MSND having superior detection limit in the field of intense radiation.

Effects of Defocus Distance on Three-Beam Laser Internal Coaxial Wire Cladding

Three-beam laser internal coaxial wire feeding cladding is regarded as a promising additive manufacturing technique because it is highly efficient and controllable.In this study,the effects of the defocus distance on cladding using a three-beam laser with internal wire feeding are experimentally and numerically studied.A process map indicating the surface characteristics at different defocus distances with various parameter combinations was developed.The transmission characteristics including laser intensity,beam size,and laser spot distance of the three-beam laser at different defocus distances were analyzed using TracePro software.Based on the TracePro results as heat source,a three-dimensional transient finite element(FE)thermal model was formulated to predict the thermal field,temperature history and molten pool shape at different defocus distances.A molten pool with a flat bottom and low melting depth is generated when the defocus distance is−2.5 mm,whereas when this distance is−1.5 mm,a pool with a valley-shaped bond and high melting depth is formed.The simulated results of the temperature cycle and clad geometry are both validated and found to well agree with experimental measurements.The influence of the defocus distance on the microstructure and microhardness are discussed based on the temperature history and cooling rate.With the increase in the absolute defocus distance,the height and dilution of the clad decreased,whereas the width increased.In addition,the effects of defocus distance with various parameter combinations on clad geometry were explored using the formulated FE model.

Theoretical study and optimization of a high power mid-infrared erbium-doped ZBLAN fibre laser

Based on the rate equations describing the erbium-doped fluoride glass （ZBLAN） fibre lasers with different pumping configurations being taken into account, this paper presents theoretical calculations related to the dynamic population density and the operation performance of a high power mid-infrared all-fibre erbium-doped ZBLAN fibre laser. It shows that the ground-state absorption, excited-state absorption and energy-transfer-upconversion processes co-exist and produce a population balance, causing the laser to operate stably at a continuous wave state. A good agreement between the theoretical results and recent experimental measurement is obtained. Furthermore, the laser structure parameters including fibre length, reflectance of output fibre Bragg grating and pumping configurations are quantitatively optimised to achieve the best performance. The results show, as expected, that the slope efficiency of the fibre laser can be improved significantly through optimisation, which then provides an important guide for the design of high-performance mid-infrared erbium-doped ZBLAN fibre lasers.