Accelerated Sequential Deposition Reaction via Crystal Orientation Engineering for Low-Temperature,High-Efficiency Carbon-Electrode CsPbBr_(3) Solar Cells

Low-temperature,ambient processing of high-quality CsPbBr_(3)films is demanded for scalable production of efficient,low-cost carbon-electrode perovskite solar cells(PSCs).Herein,we demonstrate a crystal orientation engineering strategy of PbBr_(2)precursor film to accelerate its reaction with CsBr precursor during two-step sequential deposition of CsPbBr_(3)films.Such a novel strategy is proceeded by adding CsBr species into PbBr_(2)precursor,which can tailor the preferred crystal orientation of PbBr_(2)film from[020]into[031],with CsBr additive staying in the film as CsPb_(2)Br_(5)phase.Theoretical calculations show that the reaction energy barrier of(031)planes of PbBr_(2)with CsBr is lower about 2.28 eV than that of(O2O)planes.Therefore,CsPbBr_(3)films with full coverage,high purity,high crystallinity,micro-sized grains can be obtained at a low temperature of 150℃.Carbon-electrode PSCs with these desired CsPbBr_(3)films yield the record-high efficiency of 10.27%coupled with excellent operation stability.Meanwhile,the 1 cm^(2)area one with the superior efficiency of 8.00%as well as the flexible one with the champion efficiency of 8.27%and excellent mechanical bending characteristics are also achieved.

Effect of Rigid Pitch Motion on Flexible Vibration Characteristics of a Wind Turbine Blade

Adynamic pitch strategy is usually adopted to improve the aerodynamic performance of the blade of awind turbine.The dynamic pitch motion will affect the linear vibration characteristics of the blade.However,these influences have not been studied in previous research.In this paper,the influences of the rigid pitch motion on the linear vibration characteristics of a wind turbine blade are studied.The blade is described as a rotating cantilever beam with an inherent coupled rigid-flexible vibration,where the rigid pitch motion introduces a parametrically excited vibration to the beam.Partial differential equations governing the nonlinear coupled pitch-bend vibration are proposed using the generalized Hamiltonian principle.Natural vibration characteristics of the inherent coupled rigid-flexible system are analyzed based on the combination of the assumed modes method and the multi-scales method.Effects of static pitch angle,rotating speed,and characteristics of harmonic pitch motion on flexible natural frequencies andmode shapes are discussed.It shows that the pitch amplitude has a dramatic influence on the natural frequencies of the blade,while the effects of pitch frequency and pith phase on natural frequencies are little.

Interfacial Voids Trigger Carbon-Based, All-Inorganic Cs Pb IBr2 Perovskite Solar Cells with Photovoltage Exceeding 1.33 V

A novel interface design is proposed for carbon-based,all-inorganic CsPbIBr2 perovskite solar cells(PSCs)by introducing interfacial voids between TiO2 electron transport layer and CsPbIBr2 absorber.Compared with the general interfacial engineering strategies,this design exempts any extra modification layer in final PSC.More importantly,the interfacial voids produced by thermal decomposition of 2-phenylethylammonium iodide trigger three beneficial e ects.First,they promote the light scattering in CsPbIBr2 film and thereby boost absorption ability of the resulting CsPbIBr2 PSCs.Second,they suppress recombination of charge carriers and thus reduce dark saturation current density(J0)of the PSCs.Third,interfacial voids enlarge built-in potential(Vbi)of the PSCs,awarding increased driving force for dissociating photo-generated charge carriers.Consequently,the PSC yields the optimized e ciency of 10.20%coupled with an open-circuit voltage(Voc)of 1.338 V.The Voc achieved herein represents the best value among CsPbIBr2 PSCs reported earlier.Meanwhile,the non-encapsulated PSCs exhibit an excellent stability against light,thermal,and humidity stresses,since it remains^97%or^94%of its initial e ciency after being heated at 85℃for 12 h or stored in ambient atmosphere with relative humidity of 30–40%for 60 days,respectively.

Inactivation of Staphylococcus aureus and Enterococcus faecalis by a direct-current,cold atmospheric-pressure air plasma microjet

Objective： A direct-current, cold atmospheric-pressure air plasma microjet （PMJ） was performed to inactivate Staphylococcus aureus （S. aureus） and Enterococcusfaecalis （E. faecalis） in air. The process of sterilization and morphology of bacteria was observed. We wish to know the possible inactivation mechanisms of PMJ and explore a potential application in dental and other temperature sensitive treatment. Methods： In this study, we employed a direct current, atmospheric pressure, cold air PMJ to inactivate bacterias. Scanning electron microscopy was employed to evaluate the morphology of S. aureus and showed rupture of cell walls after the plasma treatment and Optical emission spectrum （OES） were used to understand the possible inactivation mechanisms of PMJ. Re- suits＂ The inactivation rates could reach 100% in 5 min. When the distance between the exit nozzle of the PMJ device and Petri dish was extended from 1 cm to 3 cm, effective inactivation was also observed with a similar inactivation curve. Conclusion： The inactivation of bacteria is attributed to the abundant reactive oxygen and nitrogen species, as well as ultroviolet radiation in the plasma. Different life spans and defensibilities of these killing agents may hold the key to understanding the different inactivation curves at different treatment distances.

氮化碳负载铂催化剂的制备、表征及对肉桂醛加氢的催化性能

通过尿素的高温聚合制备了片层状氮化碳g-C3N4,采用乙二醇还原法载铂得到Pt/g-C3N4催化剂。以X射线衍射(XRD)、X射线光电子能谱(XPS)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、傅里叶变换红外光谱(FT-IR)、比表面与孔隙度分析和电感耦合等离子体原子发射光谱(ICP-AES)等对所制备催化剂进行了表征,并在肉桂醛加氢反应中考察了其催化性能。结果表明,载体g-C3N4含有大量的含N基团,能有效稳定金属纳米粒子;Pt纳米粒子均匀分散在g-C3N4表面,且Pt粒径在2~3 nm之间;载体煅烧温度对催化剂的择性加氢性能有明显影响,550℃煅烧后的g-C3N4,所负载Pt在较温和的条件下表现出较明显的活性,肉桂醛转化率为30%,肉桂醇选择性为66%左右。重复使用3次,催化剂活性基本不变,具有良好的稳定性。

Dynamical modeling and non-planar coupled behavior of inclined CFRP cables under simultaneous internal and external resonances

A dynamic model for an inclined carbon ?ber reinforced polymer(CFRP)cable is established, and the linear and nonlinear dynamic behaviors are investigated in detail. The partial differential equations for both the in-plane and out-of-plane dynamics of the inclined CFRP cable are obtained by Hamilton's principle. The linear eigenvalues are explored theoretically. Then, the ordinary differential equations for analyzing the dynamic behaviors are obtained by the Galerkin integral and dimensionless treatments.The steady-state solutions of the nonlinear equations are obtained by the multiple scale method(MSM) and the Newton-Raphson method. The frequency-and force-response curves are used to investigate the dynamic behaviors of the inclined CFRP cable under simultaneous internal(between the lowest in-plane and out-of-plane modes) and external resonances, i.e., the primary resonances induced by the excitations of the in-plane mode,the out-of-plane mode, and both the in-plane mode and the out-of-plane mode, respectively. The effects of the key parameters, e.g., Young's modulus, the excitation amplitude,and the frequency on the dynamic behaviors, are discussed in detail. Some interesting phenomena and results are observed and concluded.

Slope Stability Considering the Top Building Load

Slope stability is one of the most important subjects of geotechnics. The slope top-loading plays a key role in the stability of slopes in hill slope areas. When the building load is too large or the point of action from the shoulder is too close, the shear stress of the slope will be significantly greater than its shear strength, resulting in reduced slope stability. Therefore, it is of great importance to study the relationship between the building load and the stability of the slope. This study aims to analyze the influence of different building loads applied at different distances on the top of the slope and deduces their effects on the slope stability. For this purpose, a three-dimensional slope model under different building loads with different distances to the slope shoulder was established using the finite-difference analysis software Flac3D. The results show that the loads applied at different distances on the top of the slope have different effects on the slope stability. The slope factor of safety (FOS) increases with the increase of the distance between the top-loading and the slope shoulder;it varies from 1.37 to 1.53 for the load P = 120 KPa, 1.27 to 1.53 for the load P = 200 KPa, and from 1.18 to 1.44 for P = 300 KPa, resulting in the decrease of the coincidence area between the load-deformation and the potential sliding surface. The slope is no longer affected by the potential risk of sliding at approximately 20 m away from the slope shoulder.

A Breakthrough in the Industrialization of Manufacturing Technology for New Mainstream Low-GWP Refrigerants in China

Hydrofluoroolefins （HFOs）： New-generation refrigerants and foaming agents Hydrofluorocarbons （HFCs）, which represent the third genera- tion of refrigerants and foaming agents, do not contribute to ozone depletion; that is, their ozone-depleting potential （ODP） is zero. However, HFCs are listed as greenhouse gases by the Kyoto Protocol because of their relatively high global-warming potential （GWP）.

Cobalt-nanoparticle catalysts derived from zeolitic imidazolate framework@MXene composites for efficient oxidative self-coupling of benzylamines

In this study,we synthesize a catalyst comprising cobalt nanoparticles supported on MXene by pyrolyzing a composite in a N2 environment.Specifically,the composite comprises a bimetallic Zn/Co zeolitic imidazole framework grown in situ on the outer surface of MXene.The catalytic efficiency of the catalyst is tested for the self-coupling of 4-methoxybenzylamine to produce value-added imine,where atmospheric oxygen(1 atm)is used as the oxidant.Based on the results,the catalyst displayed impressive catalytic activity,achieving 95.4%yield of the desired imine at 383 K for 8 h.Furthermore,the catalyst showed recyclability and tolerance toward benzylamine substrates with various functional groups.The outstanding performance of the catalyst is primarily attributed to the synergetic catalytic effect between the cobalt nanoparticles and MXene support,while also benefiting from the three-dimensional porous structure.Additionally,a preliminary investigation of potential reaction mechanisms is conducted.

Graded Heterojunction Improves Wide-Bandgap Perovskite for Highly Efficient 4-Terminal Perovskite/Silicon Tandem Solar Cells

Wide-bandgap(WBG)perovskite solar cells(PSCs)are essential for highly efficient and stable silicon/perovskite tandem solar cells.In this study,we adopted a synthetic strategy with lead thiocyanate(Pb(SCN)_(2))additive and methylammonium chloride(MACl)posttreatment to enhance the crystallinity and improve the interface of WBG perovskite films with a bandgap of 1.68 eV.The excessive PbI_(2)was formed at grain boundaries and converted into MAPbI_(3-x)Cl_(x)perovskites,which are utilized to form the graded heterojunction(GHJ)and compressive strain.This is beneficial for passivating nonradiative recombination defects,suppressing halide phase segregation,and facilitating carrier extraction.Subsequently,the device with GHJ delivered a champion efficiency of 20.30%and superior stability in ambient air and under 85℃.Finally,we achieved a recorded efficiency of 30.91%for 4-terminal WBG perovskite/TOPCon tandem silicon solar cells.Our findings demonstrate a promising approach for fabricating efficient and stable WBG PSCs through the formation of GHJ.

Ultrahigh fill-factor all-inorganic CsPbBr_(3)perovskite solar cells processed from two-step solution method and solvent additive strategy

All-inorganic CsPbBr_(3)perovskite solar cells(PSCs)have attracted more attentions due to the excellent environmental stability,however,the wide bandgap and relatively poor crystallinity of CsPbBr_(3)have been the main obstacle to improve their power conversion efficiency(PCE).Herein,we proposed an efficient and simple strategy of precursor additive in the two-step aqueous-solution method,the resulted CsPbBr_(3)film has achieved more uniform grain size,almost pure perovskite phase,smoother surface,less defects,enhanced light absorption and longer carrier lifetime.This is due to the rapid evaporation of additive(IPA and CH_(3)OH)in the CsBr/H_(2)O precursor leads to a relatively higher local CsBr concentration on the surface of PbBr_(2),which can provide more nucleation sites and accelerate the crystallization of perovskite.Further,when utilizing the optimal additive of 5%(in volume)IPA,the HTM-free carbonbased CsPbBr_(3)PSCs obtained a PCE improvement from 9.09%to 10.29%,and an ultrahigh fill factor(FF)of 85.21%.What is more,by adding 0.1 mol/L PbCl_(2)into the PbBr_(2)solution in the first step,the open circuit voltage of device has increased from 1.36 V to 1.48 V,the champion PCE reached 10.37%(steady output PCE of 10.17%),and the non-encapsulated device could maintain 85%of its initial efficiency after 50 d in the air.This work provides a cost-effective approach to grow CsPbBr_(3)film and boosts the efficiency benchmark of the CsPbBr_(3)PSCs to more than 10%,it is desirable that the highly efficient and stable CsPbBr_(3)PSCs can be developed in future.

Strategies for improving the photocatalytic performance of metal-organic frameworks for CO_(2) reduction: A review

Photocatalytic CO_(2)reduction is an appealing strategy for mitigating the environmental effects of greenhouse gases while simultaneously producing valuable carbon-neutral fuels.Numerous attempts have been made to produce effective and efficient photocatalysts for CO_(2)reduction. In contrast, the selection of competitive catalysts continues to be a substantial hindrance and a considerable difficulty in the development of photocatalytic CO_(2)reduction. It is vital to emphasize different techniques for building effective photocatalysts to improve CO_(2)reduction performance in order to achieve a long-term sustainability. Metalorganic frameworks(MOFs) are recently emerging as a new type of photocatalysts for CO_(2)reduction due to their excellent CO_(2)adsorption capability and unique structural characteristics. This review examines the most recent breakthroughs in various techniques for modifying MOFs in order to improve their efficiency of photocatalytic CO_(2)reduction. The advantages of MOFs using as photocatalysts are summarized, followed by different methods for enhancing their effectiveness for photocatalytic CO_(2)reduction via partial ion exchange of metal clusters, design of bimetal clusters, the modification of organic linkers,and the embedding of metal complexes. For integrating MOFs with semiconductors, metallic nanoparticles(NPs), and other materials, a number of different approaches have been also reviewed. The final section of this review discusses the existing challenges and future prospects of MOFs as photocatalysts for CO_(2)reduction. Hopefully, this review can stimulate intensive research on the rational design and development of more effective MOF-based photocatalysts for visible-light driven CO_(2)conversion.

Visible-light-induced photocatalytic CO_(2)reduction over zirconium metal organic frameworks modified with different functional groups

The reduction of CO_(2)into high value-added chemicals and fuels by a photocatalytic technology can relieve energy shortages and the environmental problems caused by greenhouse effects.In the current work,an amino-functionalized zirconium metal organic framework(Zr-MOF)was covalently modified with different functional groups via the condensation of Zr-MOF with 2-pyridinecarboxaldehyde(PA),salicylaldehyde(SA),benzaldehyde(BA),and trifluoroacetic acid(TA),named Zr-MOF-X(X=PA,SA,BA,and TA),respectively,through the post-synthesis modification.Compared with Zr-MOF and Zr-MOF-TA,the introduction of PA,SA,or BA into the framework of Zr-MOF can not only enhance the visible-light harvesting and CO_(2)capture,but also accelerate the photogenerated charge separation and transfer,thereby improving the photocatalytic ability of Zr-MOF for CO_(2)reduction.These results indicate that the modification of Zr-MOF with electron-donating groups can promote the photocatalytic CO_(2)reduction.Therefore,the current work provides an instructive approach to improve the photocatalytic efficiency of CO_(2)reduction through the covalent modification of MOFs.

Wide-range-adjusted threshold voltages for E-mode AlGaN/GaN HEMT with a p-SnO cap gate

p-GaN cap layer has been recognized as a commercial technology to manufacture enhanced-mode(E-mode)AlGaN/GaN high electron mobility transistor(HEMT);however,the difficult activation of Mg doping and etching damage of p-GaN limit the further improvement of device performance.Thus,the more cost-effective cap layer has attracted wide attention in GaN-based HEMT.In this paper,p-type tin monoxide(p-SnO)was firstly investigated as a gate cap to realize E-mode AlGaN/GaN HEMT by both Silvaco simulation and experiment.Simulation results show that by simply adjusting the thickness(50 to 200 nm)or the doping concentration(3×10^(17)to 3×10^(18)cm^(-3))of p-SnO,the threshold voltage(V_(th))of HEMT can be continuously adjusted in the range from zero to 10 V.Simultaneously,the device demonstrated a drain current density above 120 mA mm^(-1),a gate breakdown voltage(V_(BG))of 7.5 V and a device breakdown voltage(V_(B))of 2470 V.What is more,the etching-free AlGaN/GaN HEMT with sputtered p-SnO gate cap were fabricated,and achieved a positive V_(th) of 1 V,V_(BG) of 4.2 V and V_(B) of 420 V,which confirms the application potential of the p-SnO film as a gate cap layer for E-mode GaN-based HEMT.This work is instructive to the design and manufacture of p-oxide gate cap E-mode AlGaN/GaN HEMT with low cost.

Discovery of a high-altitude ecotype and ancient lineage of Arabidopsis thaliana from Tibet

Arabidopsis thaliana（A, thaliana） has long been a model species for dicotyledon study, and was the first flowering plant to get its genome completed sequenced . Although most wild A. thaliana are collected in Europe, several studies have found a rapid A. thaliaria west-east expansion from Central Asia . The Qinghai-Tibet Plateau （QTP） is close to Central Asia and known for its high altitude, unique environments and biodiversity . However, no wild-type A. thaliana had been either discovered or sequenced from QTP. Studies on the A. thaliana populations collected under 2000 m asl have shown that the adaptive variations associated with climate and altitudinal gradients .

Uniform Non-Bernoulli Sequences Oriented Locating Method for Reliability-Critical Gates

Hardening reliability-critical gates in a circuit is an important step to improve the circuit reliability at a low cost.However,accurately locating the reliability-critical gates is a key prerequisite for the efficient implementation of the hardening operation.In this paper,a probabilistic-based calculation method developed for locating the reliabilitycritical gates in a circuit is described.The proposed method is based on the generation of input vectors and the sampling of reliability-critical gates using uniform non-Bernoulli sequences,and the criticality of the gate reliability is measured by combining the structure information of the circuit itself.Both the accuracy and the efficiency of the proposed method have been illustrated by various simulations on benchmark circuits.The results show that the proposed method has an efficient performance in locating accuracy and algorithm runtime.

Reduced-order modeling of train-curved-slab-track dynamics with the effects of fastening failures

Fastening failures have frequently been found on China high-speed railway curved tracks in recent years.Thus the influence of fastening failures on high-speed train-track interaction in curved track needs to be analyzed.A train-curved slab track interaction model is built,in which the real shape of the curved rail is considered and modeled with reduced beam model(RBM)and curved beam theory,and the slabs are modeled with four-nodes Kirchhoff-Love plate elements.The present model is validated at first with different traditional models.Then the influence of fastening failure in curved slab track on train-track interaction dynamics is studied.A different number of failed fastenings is assumed to occur at the curved track,and different types of fastening failure including the fatigue fracture of the clip structure and failure of the rail pad are considered.Based on the calculation results,the fatigue fracture of the clip structure has little influence on train-track interaction dynamics.But when rail pad failure happens and its equivalent vertical stiffness and damping are less than one-tenth of its original,the fastening failure seriously affects the high-speed train operation safety,and it must be prevented.

PdZn intermetallic compound stabilized on ZnO/nitrogendecorated carbon hollow spheres for catalytic semihydrogenation of alkynols

Enhancing the selectivity of noble metal catalysts through electronic modulation is important for academic research and chemical industrial processes.Herein,we report a facile sacrificial template strategy for the synthesis of PdZn intermetallic compound(3-4 nm)highly distributed in ZnO/nitrogen-decorated carbon hollow spheres(PdZn-ZnO/NCHS)to optimize the selectivity of Pd catalysts,which involves carbonization of a core-shell structured polystyrene(PS)@ZIF-8 precursor in an inert atmosphere,impregnation Pd precursor,and subsequent H2 reduction treatment.Due to the unique structural and compositional features,the developed PdZn-ZnO/NCHS delivers an excellent catalytic performance for the semihydrogenation of 2-methyl-3-butyn-2-ol(MBY)to 2-methyl-3-buten-2-ol(MBE)with high activity(>99%),high selectivity(96%),and good recyclability,outperforming the analog Pd on ZnO(Pd/ZnO)as well as the supported Pd nanoparticles(Pd/C and Pd/NC).Density functional theory(DFT)calculations reveal that the presence of Znδ+species in PdZn-ZnO/NCHS alters the adsorption modes of reactant and product,leading to a decrease of the adsorption strength and an enhancement of the energy barrier for overhydrogenation,which results in a kinetic favor for the selective transformation of MBY to MBE.In addition,PdZn-ZnO/NCHS was also very effective for the partial hydrogenation of dehydrolinalool to hydrolinalool.

Slow halide exchange in CsPbIBr_(2) films for high-efficiency,carbon-based,all-inorganic perovskite solar cells

Halide exchange offers a versatile way to modify the properties of halide perovskites,but it is particularly challenging to slow the reaction rate to restrain defect growth in the products.Herein,we propose a slow halide exchange strategy to simultaneously fine-tune the optical and microstructural characteristics of CsPbIBr_(2) films by physically pairing CsPbIBr_(2) and CH_(3)NH_(3)PbI_(3) films.Once a proper heating treatment is applied,halide exchange of Br^(-)and I^(-)ions between the films is activated,and the reaction rate can be well-controlled by the heating recipe,in which a high temperature can accelerate the exchange reaction,while a low temperature slows or stops it.By using an optimal halide exchange temperature(110℃)and time(2 h),the parent CsPbIBr_(2) film was transformed into high-quality CsPbI_(1+x)Br_(2-x) film,featuring an extended absorption onset from 590 to 625 nm,coarsened grains,improved crystallinity,reduced surface roughness,suppressed halide phase segregation,and identical stability to the pristine film.Accordingly,the efficiency of a carbon-based,all-inorganic perovskite solar cell(PSC)was boosted to 10.94%,which was much higher than that of the pristine CsPbIBr_(2) film(8.21%).The CsPbI_(1+x)Br_(2-x) PSC also possessed excellent tolerance against heat and moisture stresses.

Construction of isolated Ni sites on nitrogen-doped hollow carbon spheres with Ni-N_(3) configuration for enhanced reduction of nitroarenes

Designing and synthesizing high-efficiency non-precious metal-based catalysts having uniform active sites increases the reactivity and selectivity of materials and provides a platform for an in-depth understanding of their catalytic reaction mechanism.In this study,we provided an approach for fabricating isolated nickel single-atom sites(Ni SAs)with high loading(4.9 wt.%)stabilized on nitrogen-doped hollow carbon spheres(NHCS)using a core–shell structured Zn/Ni bimetallic zeolitic imidazolate framework(ZIF)composite as the sacrificial template.The as-fabricated Ni SAs/NHCS catalyst shows superior activity,selectivity,and recycling durability for the catalytic transfer hydrogenation of nitrobenzene to aniline,thus achieving 100%yield of aniline with a turn-over frequency(TOF)value as high as 29.9 h^(−1) under mild conditions.This TOF value is considerably superior to the supported Ni nanoparticle catalysts.The experiments designed show that the hollow structure feature of NHCS facilitates accessible active sites and mass transfer,which thus contributes to the enhancement of the catalytic performance of Ni SAs/NHCS.Density functional theory calculations show the high chemo-selectivity and activity of the Ni SAs catalyst,arising from the unique role of the single Ni-N3 site on simultaneously activating the H donor(N_(2)H_(4))and substrate,as well as the hydrogenation of the–NOH group as the rate-determining step.