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

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Journal of Materiomics 2023年第4期9卷 717-724页

作者： Dazheng Chen Yibing He Gang Fan Zeyang Zhang Weidong Zhu He Xi Long Zhou Chunfu Zhang Jincheng Zhang Yue Hao State Key Discipline Laboratory of Wide Band Gap Semiconductor Technology&Shaanxi Joint Key Laboratory of Graphene School of MicroelectronicsXidian UniversityXi'anShaanxi710071China

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.

关键词： CsPbBr_(3) Aqueous solution two-step method Solvent additive High fill factor

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A two-step machine learning method for casualty prediction under emergencies

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Journal of Safety Science and Resilience 2022年第3期3卷 243-251页

作者： Xiaofeng Hu Jinming Hu Miaomiao Hou School of Information Technology and Cyber Security People’s Public Security University of ChinaBeijing 100038China

Casualty prediction is meaningful to the emergency management of natural hazards and human-induced disasters.In this study,a two-step machine learning method,including classification step and regression step,is proposed to predict the number of casualties under emergencies.In the classification step,whether there are casualties under an incident is firstly predicted,then in the regression step,samples predicted to have casualties are used to further predict the exact number of the casualties.Using an open-source dataset,this two-step method is validated.The results show that the two-step model performs better than the original regression models.Back propagation(BP)neural network combined with Random Forest performs the best in terms of the death toll and the number of injuries.Among all the two-step models,the lowest mean absolute error(MAE)for the death toll is 1.67 while that for the number of injuries is 4.13,which indicates that this method can accurately predict the number of casualties under emergencies.This study’s results are expected to provide support for decision-making on rapid resource allocation and other emergency responses.

关键词： Emergencies Machine learning Casualty prediction two-step method

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Temperature-dependent photoluminescence on organic inorganic metal halide perovskite CH3NH3Pb I3-xClx prepared on ZnO/FTO substrates using a two-step method

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Chinese Physics B 2017年第1期26卷 482-487页

作者：庄仕伟徐德前徐佳新伍斌张源涛董鑫李国兴张宝林杜国同 State Key Laboratory on Integrated Optoelectronics College of Electronic Science and Engineering Jilin University Changchun 130012 China

Temperature-dependent photoluminescence characteristics of organic-inorganic halide perovskite CH3NH3Pb I3-xClx films prepared using a two-step method on ZnO/FTO substrates were investigated. Surface morphology and absorption characteristics of the films were also studied. Scanning electron microscopy revealed large crystals and substrate coverage. The orthorhombic-to-tetragonal phase transition temperature was-140 K. The films＇ exciton binding energy was 77.6 ± 10.9 meV and the energy of optical phonons was 38.8 ± 2.5 meV. These results suggest that perovskite CH3NH3Pb I（3-x）Clx films have excellent optoelectronic characteristics which further suggests their potential usage in perovskitebased optoelectronic devices.

关键词： perovskite temperature-dependent photoluminescence two-step method ZnO

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A two-step method for estimating high-dimensional Gaussian graphical models

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Science China Mathematics 2020年第6期63卷 1203-1218页

作者： Yuehan Yang Ji Zhu School of Statistics and Mathematics Central University of Finance and EconomicsBeijing 100081China Department of Statistics University of MichiganAnn ArborMI 48109USA

The problem of estimating high-dimensional Gaussian graphical models has gained much attention in recent years. Most existing methods can be considered as one-step approaches, being either regression-based or likelihood-based. In this paper, we propose a two-step method for estimating the high-dimensional Gaussian graphical model. Specifically, the first step serves as a screening step, in which many entries of the concentration matrix are identified as zeros and thus removed from further consideration. Then in the second step, we focus on the remaining entries of the concentration matrix and perform selection and estimation for nonzero entries of the concentration matrix. Since the dimension of the parameter space is effectively reduced by the screening step,the estimation accuracy of the estimated concentration matrix can be potentially improved. We show that the proposed method enjoys desirable asymptotic properties. Numerical comparisons of the proposed method with several existing methods indicate that the proposed method works well. We also apply the proposed method to a breast cancer microarray data set and obtain some biologically meaningful results.

关键词： covariance estimation graphical model penalized likelihood sparse regression two-step method

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Fully discrete two-step mixed element method for the symmetric regularized long wave equation

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International Journal of Modeling, Simulation, and Scientific Computing 2014年第3期5卷 88-103页

作者： Meng Zhao Yang Liu Hong Li School of Mathematical Sciences Inner Mongolia University Hohhot 010021 P.R.China

A numerical method based on the explicit two-step method in time direction and the mixed finite element method in spatial direction is presented for the symmetric regularized long wave(SRLW)equation.The optimal a priori error estimates(O((∆t)^(2)+h^(m+1)+h^(k+1)))for fully discrete explicit two-step mixed scheme are derived.Moreover,a numerical example is provided to confirm our theoretical results.

关键词： SRLW equation two-step method mixed finite element method a priori error estimates optimal convergence

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In-depth understanding of ionic liquid assisted perovskite film formation mechanism for two-step perovskite photovoltaics

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Journal of Energy Chemistry 2022年第10期31卷 599-606,I0015页

作者： Fei Wang Patrick Wai-Keung Fong Zhiwei Ren Hai-Lun Xia Kang Zhou Kai Wang Jiajie Zhu Xiaoxi Huang Xiao-Yuan Liu Hao Wang Yumeng Shi Haoran Lin Quanyao Zhu Gang Li Hanlin Hu Hoffman Institute of Advanced Materials Shenzhen PolytechnicShenzhen 518055GuangdongChina Department of Electronic and Information Engineering Research Institute for Smart Energy(RISE)The Hong Kong Polytechnic UniversityHong Kong 999077China State Key Laboratory of Advanced Technology for Materials Synthesis and Processing School of Materials Science and EngineeringWuhan University of TechnologyWuhan 43007HubeiChina International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology of Ministry of Education Institute of Microscale OptoelectronicsShenzhen UniversityShenzhen 518060GuangdongChina The Hong Kong Polytechnic University Shenzhen Research Institute Shenzhen 518057GuangdongChina Institute of Flexible Electronics Northwestern Polytechnical UniversityXi’an 710072ShannxiChina School of Physics Science and Engineering Tongji UniversityShanghai 200092China

Ionic liquids(ILs)have been widely applied in the one-step fabrication of perovskite with noticeable enhancement in the device performance.However,in-depth mechanism of ionic-liquid-assisted perovskite film formation is not well understood for also important two-step perovskite fabrication method,with better control of crystallization behavior.In this work,we introduced ionic liquid methylammonium formate(MAFa)into organic salt to produce perovskite film via a two-step method.Systematic investigations on the influence of MAFa on the perovskite thin film formation mechanism were performed.Ionic liquid is shown to assist lowering the perovskite formation enthalpy upon the density functional theory(DFT)calculation,leading to an accelerated crystallization process evidenced by in-situ UV-Vis absorption measurement.A gradient up-down distribution of ionic liquid has been confirmed by timeof-flight SIMS.Importantly,besides the surface passivation,we found the HCOO-can diffuse into the perovskite crystals to fill up the halide vacancies,resulting in significant reduction of trap states.Uniform perovskite films with significantly larger grains and less defect density were prepared with the help of MAFa IL,and the corresponding device efficiency over 23%was obtained by two-step process with remarkably improved stability.This research work provides an efficient strategy to tune the morphology and opto-electronic properties of perovskite materials via ionic-liquid-assisted two-step fabrication method,which is beneficial for upscaling and application of perovskite photovoltaics.

关键词： Halide vacancies Perovskite solar cells two-step method Ionic liquid

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Synthesis of CA_(6)/AlON composite with enhanced slag resistance

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International Journal of Minerals,Metallurgy and Materials 2023年第4期30卷 756-765页

作者： Yunsong Liu Enhui Wang Linchao Xu Tao Yang Zhijun He Tongxiang Liang Xinmei Hou Beijing Advanced Innovation Center for Materials Genome Engineering Collaborative Innovation Center of Steel TechnologyUniversity of Science and Tech-nology BeijingBeijing 10083China School of Materials and Metallurgy University of Science and Technology LiaoningAnshan 114051China School of Materials Science and Engineering Jiangxi University of Science and TechnologyGanzhou 341000China

Different amounts of AlON have been introduced in calcium hexaaluminate(CA_(6)) using two approaches, that is, one-step and twostep methods, to improve the slag resistance of CA_(6). A one-step method can directly sinter the mixtures combining Al_(2)O_(3), CaCO_(3), and Al in flowing nitrogen, in which AlON clusters are always formed because of the poor wettability of Al by Al_(2)O_(3), leading to the high porosity of CA_(6)/AlON composite. In a two-step method, CA_(6)and AlON are prepared separately and then mixed and sintered in flowing nitrogen. Compared with the sample prepared by the one-step method, CA_(6)and AlON in composite by the two-step method are more uniformly distributed,and the optimized amount of AlON added is 10wt%. The slag corrosion and penetration test shows that the CA_(6)/AlON composite using the two-step method exhibits superior slag corrosion protection. The promoted effect of AlON on slag penetration and corrosion resistance is also discussed.

关键词： CA_(6)/AlON composite two-step method wettability slag resistance

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Nuclear design of an integrated small modular reactor based on the APR-1400 for RO desalination purposes

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Nuclear Science and Techniques 2022年第8期33卷 1-15页

作者： Reem Rashed Alnuaimi Bassam Khuwaileh Muhammad Zubair Donny Hartanto Department of Mechanical and Nuclear Engineering University of SharjahP.O.BOX 27272SharjahUAE Oak Ridge National Laboratory 1 Bethel Valley RoadOak RidgeTN 37830USA

The United Arab Emirates lacks conventional water resources and relies primarily on desalination plants powered by fossil fuels to produce fresh water.Nuclear desalination is a proven technology,cost-competitive,and sustainable option capable of integrating the existing largescale desalination plants to produce both freshwater and electricity.However,Small Modular Reactors(SMRs)are promising designs with advanced simplified configurations and inherent safety features.In this study,an Integrated Desalination SMR that produces thermal energy compatible with the capacity of a fossil fuel-powered desalination plant in the UAE was designed.First,the APR-1400 reactor core was used to investigate two 150 MWthconceptual SMR core designs,core A and core B,based on two-dimensional parameters,radius,and height.Then,the CASMO-4 lattice code was used to generate homogenized few-group constants for optimized fuel assembly loading patterns.Finally,to find the best core configuration,SIMULATE-3 was used to calculate the core key physics parameters such as power distribution,reactivity coefficients,and critical boron concentration.In addition,different reflector materials were investigated to compensate for the expected high leakage of the small-sized SMR cores.The pan shape core B model(142.6132 cm diameter,100 cm height,and radially reflected by Stainless Steel)was selected as the best core configuration based on its calculated physics parameters.Core B met the design and safety criteria and indicated low total neutron leakage of 11.60%and flat power distribution with 1.50 power peaking factor.Compared to core A,it has a more negative MTC value of-6.93 pcm/°F with lower CBC.In a 2-batch scheme,the fuel is discharged at 42.25 GWd/MTU burnup after a long cycle length of 1.58 years.The core B model offers the highest specific power of 36.56 kW/kgU while utilizing the smallest heavy metal mass compared with the SMART and NuScale models.

关键词： Nuclear desalination Small modular reactor(SMR) APR-1400 CASMO-4 SIMULATE-3 two-step method Homogenized cross sections Optimization

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Excess PbI_(2)evolution for triple-cation based perovskite solar cells with 21.9%efficiency

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Journal of Energy Chemistry 2022年第3期31卷 152-160,I0005页

作者： Zhu Ma Dejun Huang Qianyu Liu Guangyuan Yan Zheng Xiao Dong Chen Jiaxuan Zhao Yan Xiang Changtao Peng Haijin Li Meng Zhang Wenfeng Zhang Lianfeng Duan Yuelong Huang Institute of Photovoltaic Southwest Petroleum UniversityChengdu 610500SichuanChina Department of Chemistry Shantou UniversityShantou 515063GuangdongChina

The triple cation mixed perovskites(Cs FAMA)are known as one of the most efficient candidates for perovskite solar cells(PSCs).It is found that the power conversion efficiency(PCE)of triple-cation based devices would increase with the test time extending,and the maximum efficiency is normally obtained after several days aging storage.Here,the relationship between enhanced device performance,excess PbI_(2)and its evolution in triple cation perovskite films of initial days was systematically explored.The Cs FAMA-PSCs are prepared by two-step methods under two environmental conditions,including in the glove box and the ambient air(30%humidity).After 7 days testing,the maximum PCE of PSCs under two conditions dramatically increased 12.4%and 12.2%,reached 21.68%and 21.89%,respectively.At initial days,the XRD peak intensities of perovskite phase gradually decreased and those corresponding to PbI_(2)increased.Along with time-resolved photoluminescence(TRPL)and kelvin probe force microscopy(KPFM),it was found that the defects were passivated with the evolution of PbI_(2).This work reveals the excess PbI_(2)and its evolution in perovskite film,which can further supplement the understanding of PbI_(2)defect passivation.

关键词： Evolution of PbI_(2) Defect passivation two-step method Triple cation Perovskite solar cells

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A facile two-step pretreatment method for delignification of cornstalk by combining choline hydroxide and 1-ethyl-3-methylimidazolium dimethylphosphate

A facile two-step pretreatment method for delignification of...

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第十七届全国化学热力学和热分析学术会议

作者： Junli Xu Xingmei Lu Suojiang Zhang Beijing Key Laboratory of Ionic Liquids Clean Process Key Laboratory of Green Process and Engineering State Key Laboratory of Multiphase Complex Systems Institute of Process Engineering Chinese Academy of Sciences College of Chemistry and Chemical Engineering Graduate University of Chinese Academy of Sciences

Ionic liquids are recognized as solvents with great potential for cellulose dissolution and biomass pretreatment.1, 2 The aim of this work was to develop efficient cornstalk pretreatment methods with low energy cost. An effectively two-step method combining choline hydroxide（ChOH） and 1-ethyl-3-methylimidazolium dimethyl phosphate（[Emim][DMP]） was developed for delignification of cornstalk under mild conditions. In this two-step method, cornstalk sample was first soaked in ChOH aqueous solution for 3 hours, and then the residue was dissolved completely by [Emim][DMP] in 10 minutes. As compared to cornstalk sample, most lignin was removed and cellulose content was greatly increased in the regenerated cellulose rich material（CRM）, which was obtained from [Emim][DMP] solution by adding anti-solvent. Meanwhile, the CRM was converted into HMF with a high yield of 87.21 %. This two-step method enhanced the cornstalk pretreatment by increasing the dissolution of cornstalk and shortening the dissolving time at high pretreated temperature, which indicated that the two-step method for cornstalk was effective and eco-friendly.

关键词： Cornstalk two-step method Pretreatment Ionic liquids

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