Most widely used piezoelectric ceramics are based on Pb(Zr,Ti)O3(PZT)composition which has adverse environmental and health effects due to its high lead content.Environmental and safety concerns with respect to the ut...Most widely used piezoelectric ceramics are based on Pb(Zr,Ti)O3(PZT)composition which has adverse environmental and health effects due to its high lead content.Environmental and safety concerns with respect to the utilization,recycling,and disposal of lead-based piezoelectric ceramics have induced a new surge in developing lead-free piezoelectric ceramics.Among all the lead-free ceramics,(K,Na)NbO3(KNN)has drawn increasing attention because of its well-balanced piezoelectric properties and better environmental compatibility.On basis of the author’s work,this review summarizes the progress that has been made in recent years on development of KNN-based piezoelectric ceramics,including crystallographic structure and phase transition analysis,pressurized solid-state sintering as well as liquid-phase-assisted sintering process,and poling treatment for property enhancement.All in all,KNN is a promising lead-free system,but more research is still required both from academic and industrial interests.展开更多
Heterogeneous catalytic combustion provides a feasible technique for high efficient methane utilization.Perovskites ABO_3-type materials have received renewed attention as a potential alternative for noble metals supp...Heterogeneous catalytic combustion provides a feasible technique for high efficient methane utilization.Perovskites ABO_3-type materials have received renewed attention as a potential alternative for noble metals supported catalysts in catalytic methane combustion due to excellent hydrothermal stability and sulfur resistance. Recently, the emergence of nanostructured perovskite oxides（such as threedimensional ordered nanostructure, nano-array structure） with outstanding catalytic activity has further driven methane catalytic combustion research into spotlight. In this review, we summarize the recent development of nanostructured perovskite oxide catalysts for methane combustion, and shed some light on the rational design of high efficient nanostructured perovskite catalysts via lattice oxygen activation,lattice oxygen mobility and materials morphology engineering. The emergent issues needed to be addressed on perovskite catalysts were also proposed.展开更多
Metal halide perovskites are crystalline materials originally developed out of scientific curiosity. They have shown great potential as active materials in optoelectronic applications. In the last 6 years, their certi...Metal halide perovskites are crystalline materials originally developed out of scientific curiosity. They have shown great potential as active materials in optoelectronic applications. In the last 6 years, their certified photovoltaic efficiencies have reached 22.1%. Compared to bulk halide perovskites, low-dimensional ones exhibited novel physical properties. The photoluminescence quantum yields of perovskite quantum dots are close to 100%. The external quantum efficiencies and current efficiencies of perovskite quantum dot light-emitting diodes have reached 8% and 43 cd A^(-1),respectively, and their nanowire lasers show ultralow-threshold room-temperature lasing with emission tunability and ease of synthesis. Perovskite nanowire photodetectors reached a responsivity of 10 A W^(-1)and a specific normalized detectivity of the order of 10^(12 )Jones. Different from most reported reviews focusing on photovoltaic applications, we summarize the rapid progress in the study of low-dimensional perovskite materials, as well as their promising applications in optoelectronic devices. In particular, we review the wide tunability of fabrication methods and the state-of-the-art research outputs of low-dimensional perovskite optoelectronic devices. Finally, the anticipated challenges and potential for this exciting research are proposed.展开更多
Organic-inorganic halide perovskites(OHPs)have been intensively studied for application in solar cells with high conversion efficiency exceeding 22%.The unique electrical and optical properties of OHPs have led to the...Organic-inorganic halide perovskites(OHPs)have been intensively studied for application in solar cells with high conversion efficiency exceeding 22%.The unique electrical and optical properties of OHPs have led to their use in optoelectronic device applications beyond photovoltaics,such as light-emitting diodes,photodetectors,transistors.New information storage technologies and computing architectures are being researched extensively with the aim of addressing the growing challenge of approaching end of Moore's law and von Neumann bottleneck.As the fourth basic circuit element,memristor is a leading candidate with powerful capabilities in information storage and neuromorphic computing applications.Recently,OHPs have received growing attention as promising materials for memristors.In particular,their mixed ionic-electronic conduction ability paired with light sensitivity provide OHPs with the opportunity to display novel functions such as optical-erase memory,optogenetics-inspired synaptic functions,and lightaccelerated learning capability.This review covers recent advances in OHP-based memristors development including memristive mechanism and analytical models,universal memristive characteristics for memory and neuromorphic computing applications,and novel multi-functionalization.Challenges and future prospects of OHP-based memristors are also discussed.展开更多
Owing to its nice performance, low cost, and simple solution-processing, organic-inorganic hybrid perovskite solar cell(PSC) becomes a promising candidate for next-generation high-efficiency solar cells.The power conv...Owing to its nice performance, low cost, and simple solution-processing, organic-inorganic hybrid perovskite solar cell(PSC) becomes a promising candidate for next-generation high-efficiency solar cells.The power conversion efficiency(PCE) has boosted from 3.8% to 25.2% over the past ten years. Despite the rapid progress in PCE, the device stability is a key issue that impedes the commercialization of PSCs. Recently, all-inorganic cesium lead halide perovskites have attracted much attention due to their better stability compared with their organic-inorganic counterpart. In this progress report, we summarize the properties of CsPb(IxBr1-x)3 and their applications in solar cells. The current challenges and corresponding solutions are discussed. Finally, we share our perspectives on CsPb(IxBr1-x)3 solar cells and outline possible directions to further improve the device performance.展开更多
ABO_(3)perovskites,owning unique properties,have great research prospect in electromagnetic wave absorption field.Normally,doping can significantly regulate the dielectric loss,whereas the magnetic loss can be ignored...ABO_(3)perovskites,owning unique properties,have great research prospect in electromagnetic wave absorption field.Normally,doping can significantly regulate the dielectric loss,whereas the magnetic loss can be ignored.In this work,the crystal structure and electromagnetic properties can be regulated systematically by the K,Fe co-doping for LaCoO_(3)perovskites(LKCFO)under the condition of fixed F content.In addition,the obtained samples show the obvious interfacial polarization effect on accounting to the small size effect,which is conducive to the effective microwave absorption.By analyzing the evolution of the positron annihilation lifetime and the first-principles calculation of the oxygen density of states for the series of LKCFO perovskites,it is found that the charge transport characteristics will be controlled by the point defect generated by allelic doping.The point defect content decreases and then increases as the doping level rises.The prepared perovskite exhibits the lowest defect density and the largest dielectric loss capability,which indicates that the lower point defects promote electron migration and thus enhance the dielectric loss;thus,the electromagnetic wave absorption bandwidth up to 6.2 GHz is reached.In contrast,both insufficient and excessive K doping are detrimental to the enhancement of microwave absorption.Especially,the practical application value was investigated using Computer Simulation Technology(CST)simulations.The LKCFO-2 exhibits the smallest RCS value(below-10 dBm^(2))at almost-90°-90°with a thickness of 2 mm,providing an effective method for study excellent microwave absorption and scattering property.展开更多
Metal halide perovskites have shown great performance for various applications,including solar cells,light emitting diodes,and radiation detectors,but they still suffer from the toxicity of lead and instability.Here w...Metal halide perovskites have shown great performance for various applications,including solar cells,light emitting diodes,and radiation detectors,but they still suffer from the toxicity of lead and instability.Here we report the use of lanthanide series as trivalent metals to obtain low toxicity and highly stable double perovskites(Cs_2NaLnCl_6,Ln=Tb or Eu)with high scintillation light yield.The crystals exhibit typical f-f transitions of lanthanide cations,while Cs_2NaTbCl_6exhibits strong green photoluminescence,and Cs_2NaEuCl_6exhibits red photoluminescence.Under X-ray radiations,the light yield of Cs_2NaTbCl_6reaches46600 photons MeV^(-1),much higher than that of the commercially used(Lu,Y)_2SiO_5:Ce^(3+)crystals(LYSO,28500 photons MeV^(-1)),and previously reported lead-based perovskites(14000 photons MeV^(-1)).As a new member of lead-free perovskites,lanthanide-based double perovskites open up a new route toward radiation detections and potential medical imaging.展开更多
La1-x Cax MnO3 （x=0-0.3） perovskite-type oxides were synthesized by citrate sol-gel method. The physical and chemical properties were characterized by X-ray diffraction （XRD）, Brumauer-Emmett-Teller method （BET）...La1-x Cax MnO3 （x=0-0.3） perovskite-type oxides were synthesized by citrate sol-gel method. The physical and chemical properties were characterized by X-ray diffraction （XRD）, Brumauer-Emmett-Teller method （BET）, X-ray photoelectron spectroscopy （XPS）, NO＋O2 -TPD （temperature-programmed desorption）, activated oxygen evaluation and H2 -TPR （temperature-programmed reduction） technologies. The results showed that NO catalytic oxidation activity was significantly improved by Ca substitution, especially for lower temperature activity. The La0.9 Ca0.1 MnO 3 sample showed the maximum conversion of 82% at 300 oC. The monodentate nitrates played a crucial role for the formation of NO2 . The reducibility of Mn 4＋ ions and reactivity of activated oxygen were favorable for the catalytic performances of NO oxidation.展开更多
The empirical relation of between the transition temperature of optimum doped superconductors T<sub>co</sub> and the mean cationic charge , a physical paradox, can be recast to strongly support fractal the...The empirical relation of between the transition temperature of optimum doped superconductors T<sub>co</sub> and the mean cationic charge , a physical paradox, can be recast to strongly support fractal theories of high-T<sub>c</sub> superconductors, thereby applying the finding that the optimum hole concentration of σ<sub>o</sub> = 0.229 can be linked with the universal fractal constant δ<sub>1</sub> = 8.72109… of the renormalized quadratic Hénon map. The transition temperature obviously increases steeply with a domain structure of ever narrower size, characterized by Fibonacci numbers. However, also conventional BCS superconductors can be scaled with δ<sub>1</sub>, exemplified through the energy gap relation k<sub>B</sub>T<sub>c</sub> ≈ 5Δ<sub>0</sub>/δ<sub>1</sub>, suggesting a revision of the entire theory of superconductivity. A low mean cationic charge allows the development of a frustrated nano-sized fractal structure of possibly ferroelastic nature delivering nano-channels for very fast charge transport, in common for both high-T<sub>c</sub> superconductor and organic-inorganic halide perovskite solar materials. With this backing superconductivity above room temperature can be conceived for synthetic sandwich structures of less than 2+. For instance, composites of tenorite and cuprite respectively tenorite and CuI (CuBr, CuCl) onto AuCu alloys are proposed. This specification is suggested by previously described filamentary superconductivity of “bulk” CuO1﹣x samples. In addition, cesium substitution in the Tl-1223 compound is an option.展开更多
Perovskite LaCoO_(3)is of great potential in electromagnetic wave absorption considering its outstanding dielectric loss as well as the existing magnetic response with the magnetic doping.However,the dissipation mecha...Perovskite LaCoO_(3)is of great potential in electromagnetic wave absorption considering its outstanding dielectric loss as well as the existing magnetic response with the magnetic doping.However,the dissipation mechanism of the magnetic doping on the microwave absorption is lack of sufficient investigated.In this paper,LaCo_(1-x)Fe_(x)O_(3)(x=0,0.05,0.1,0.15,0.2,0.25,0.3,LCFOs)perovskites with different Fe doping amounts were prepared successfully by the sol-gel method and subsequent heat treatment in the air atmosphere.The structure characterization carried out by the frst-principles calculations shows the effect of Fe doping on the dielectric and magnetic properties of LCFOs and the strong hybridization of Co/Fe-3d with O-2p in the LCFOs system was successfully demonstrated.Particularly,when x=0.1 and the thickness is only 1.95 mm,the LaCo_(0.9)Fe_(0.1)O_(3)exhibits the best microwave absorption performance with the minimum reflection loss(RL)value of about-41 dB.The typical samples achieve a broad effective absorption bandwidth(EAB)of 5.16 GHz(7.92-13.08 GHz),which covers the total X band(8-12 GHz).Considering that,the especial Fe doping perovskite is promising to be a candidate as efficient microwave absorbers.展开更多
Metal-halide perovskites are novel optoelectronic materials that are considered good candidates for solar harvesting and light emitting applications. In this study, we develop a reproducible and low-cost approach for ...Metal-halide perovskites are novel optoelectronic materials that are considered good candidates for solar harvesting and light emitting applications. In this study, we develop a reproducible and low-cost approach for synthesizing high- quality cesium lead halide perovskite （CsPbX3, X = CI, Br, and I or C1/Br and I/Br） nanocrystals （NCs） by direct heating of precursors in octadecene in air. Experimental results show that the particle size and composition of as-prepared CsPbX3 nanocrystals can be successfully tuned by a simple variation of reaction temperature. The emission peak positions of the as-prepared nanocrystals can be conveniently tuned from the UV to the NIR （360-700 nm） region, and the quantum yield of the as-obtained samples （green and red emissions） can reach up to 87%. The structures and chemical compositions of the as-obtained NCs were characterized by transmission electron microscopy, X-ray diffraction, and elemental analysis. This proposed synthetic route can yield large amounts of high-quality NCs with a one-batch reaction, usually on the gram scale, and could pave the way for further applications of perovskite-based light-emitting and photovoltaic solar cells.展开更多
Two-dimensional Ruddlesden-Popper(2DRP)perovskites have attracted intense research interest for optoelectronic applications,due to their tunable optoelectronic properties and better environmental stability than their ...Two-dimensional Ruddlesden-Popper(2DRP)perovskites have attracted intense research interest for optoelectronic applications,due to their tunable optoelectronic properties and better environmental stability than their threedimensional counterparts.Furthermore,high-performance photodetectors based on single-crystal and polycrystalline thin-films 2DRP perovskites have shown great potential for practical application.However,the complex growth process of single-crystal membranes and uncontrollable phase distribution of polycrystalline films hinder the further development of 2DRP perovskites photodetectors.Herein,we report a series of high-performance photodetectors based on single-crystal-like phase-pure 2DRP perovskite films by designing a novel spacer source.Experimental and theoretical evidence demonstrates that phase-pure films substantially suppress defect states and ion migration.These highly sensitive photodetectors show I_(light)/I_(dark) ratio exceeding 3×10^(4),responsivities exceeding 16 A/W,and detectivities exceeding 3×10^(13) Jones,which are higher at least by 1 order than those of traditional mixed-phase thinfilms 2DRP devices(close to the reported single-crystal devices).More importantly,this strategy can significantly enhance the operational stability of optoelectronic devices and pave the way to large-area flexible productions.展开更多
Metal halide perovskites(MHPs),emerging as innovative and promising semiconductor materials with prominent optoelectronic properties,has been pioneering a new era of light management(ranging from emission,absorption,m...Metal halide perovskites(MHPs),emerging as innovative and promising semiconductor materials with prominent optoelectronic properties,has been pioneering a new era of light management(ranging from emission,absorption,modulation,to transmission)for next-generation optoelectronic technology.Notably,the exploration of fundamental characteristics of MHPs and their devices is the main research theme during the past decade,while in the next decade,it will be primarily critical to promote their implantation in the next-generation optoelectronics.In this review,we first retrospect the historical research milestones of MHPs and their optoelectronic devices.Thereafter,we introduce the origin of the unique optoelectronic features of MHPs,based on which we highlight the tunability of these features via regulating the phase,dimensionality,composition,and geometry of MHPs.Then,we show that owing to the convenient property control of MHPs,various optoelectronic devices with target performance can be designed.At last,we emphasize on the revolutionary applications of MHPs-based devices on the existing optoelectronic systems.This review demonstrates the key role of MHPs played in the development of modern optoelectronics,which is expected to inspire the novel research directions of MHPs and promote the widespread applications of MHPs in the next-generation optoelectronics.展开更多
Halide perovskites have emerged as the next generation of optoelectronic materials and their remarkable performances have been attractive in the fields of solar cells,light-emitting diodes,photodetectors,etc.In additi...Halide perovskites have emerged as the next generation of optoelectronic materials and their remarkable performances have been attractive in the fields of solar cells,light-emitting diodes,photodetectors,etc.In addition,halide perovskites have been reported as an attractive new class of X-ray direct detecting materials recently,owning to the strong X-ray stopping capacity,excellent carrier transport,high sensitivity,and cost-effective manufacturing.Meanwhile,perovskite based direct Xray imagers have been successfully demonstrated as well.In this review article,we firstly introduced some fundamental principles of direct X-ray detection and imaging,and summarized the advances of perovskite materials for these purposes and finally put forward some needful and feasible directions.展开更多
The progress made by the scientific community in emerging photovoltaic technologies over the past two decades has been outstanding. Numerous methods have been developed for the preparation of hybrid organic–inorganic...The progress made by the scientific community in emerging photovoltaic technologies over the past two decades has been outstanding. Numerous methods have been developed for the preparation of hybrid organic–inorganic perovskite solar cells. The power conversion efficiency has been up to 14% by a one-step vacuum deposition technique. A serious concern is the toxicity of the materials. In this review, several methods aimed at resolving these problems to some extent have been compiled, including eco-friendly synthesis. Further efficiency enhancements are expected following optimization, and a better fundamental understanding of the internal electron charge transfer, electron–hole diffusion to the corresponding layers, flexibility, and stability-dependent bandgaps is reported. This paper explores the green synthesis of organic–inorganic perovskites for industrialization. Concerning the above facts, a simple low-cost model called‘‘dispersed photovoltaic cells' ' is presented.展开更多
Despite the impressive power conversion efficiency(PCE)beyond 25.5%,perovskite solar cells,especially the Sn-based variants,are poorly stable under normal operating conditions compared with the market-dominant silicon...Despite the impressive power conversion efficiency(PCE)beyond 25.5%,perovskite solar cells,especially the Sn-based variants,are poorly stable under normal operating conditions compared with the market-dominant silicon solar cells that can last for over 25 years.2D3D hybrid perovskite materials are one of the best options to overcome the instability chal-lenge without compromising efficiency.Indeed,a record performance of 1 year was reported in Pb-based 2D3D planar per-ovskite devices.However,the reaction between 2 and 3D perovskite molecules requires high temperatures(-300°C)and increased reaction time(-24 h)to achieve high-quality 2D3D hybrid perovskites.Herein,we base on the ability of chlorine to displace iodine from its ionic compounds in solutions to utilize chloride ions as catalysts for speeding up the reaction between iodine-based 2D and 3D perovskite molecules.The approach reduces the reaction time to-20 min and the reaction temperature to-100°C with the formation of high-quality 2D3D hybrid perovskites,free from pure 2D traces.Integrating the synthesized 2D3D hybrid perovskite material with 50%chlorine doping in a fiber-shaped solar cell architecture yielded the highest reported PCE of 11.96%in Sn-based fiber-shaped perovskite solar cells.The unencapsulated and encapsulated fiber-shaped solar cells could maintain 75%and 95.5%of their original PCE,respectively,after 3 months under room light and relative humidity of 35–40%,revealing the champion stability in Sn-based perovskite solar devices.The solar yarn also demonstrated constant energy output under changing light incident angles(0–180°).展开更多
基金Tsinghua University Initiative Scientific Research Program and National Nature Science Foundation of China(Grant Nos.50921061 and 51028202).
文摘Most widely used piezoelectric ceramics are based on Pb(Zr,Ti)O3(PZT)composition which has adverse environmental and health effects due to its high lead content.Environmental and safety concerns with respect to the utilization,recycling,and disposal of lead-based piezoelectric ceramics have induced a new surge in developing lead-free piezoelectric ceramics.Among all the lead-free ceramics,(K,Na)NbO3(KNN)has drawn increasing attention because of its well-balanced piezoelectric properties and better environmental compatibility.On basis of the author’s work,this review summarizes the progress that has been made in recent years on development of KNN-based piezoelectric ceramics,including crystallographic structure and phase transition analysis,pressurized solid-state sintering as well as liquid-phase-assisted sintering process,and poling treatment for property enhancement.All in all,KNN is a promising lead-free system,but more research is still required both from academic and industrial interests.
基金the financial support from the Recruitment Program of Global Young Experts Start-up Fundthe Program of Introducing Talents of Discipline to Universities of China(111 Program, No. B17019)
文摘Heterogeneous catalytic combustion provides a feasible technique for high efficient methane utilization.Perovskites ABO_3-type materials have received renewed attention as a potential alternative for noble metals supported catalysts in catalytic methane combustion due to excellent hydrothermal stability and sulfur resistance. Recently, the emergence of nanostructured perovskite oxides（such as threedimensional ordered nanostructure, nano-array structure） with outstanding catalytic activity has further driven methane catalytic combustion research into spotlight. In this review, we summarize the recent development of nanostructured perovskite oxide catalysts for methane combustion, and shed some light on the rational design of high efficient nanostructured perovskite catalysts via lattice oxygen activation,lattice oxygen mobility and materials morphology engineering. The emergent issues needed to be addressed on perovskite catalysts were also proposed.
基金supported by the Doctoral Program of Higher Education(20130142120075)the Fundamental Research Funds for the Central Universities(HUST:2016YXMS032)National Key Research and Development Program of China(Grant No.2016YFB0700702)
文摘Metal halide perovskites are crystalline materials originally developed out of scientific curiosity. They have shown great potential as active materials in optoelectronic applications. In the last 6 years, their certified photovoltaic efficiencies have reached 22.1%. Compared to bulk halide perovskites, low-dimensional ones exhibited novel physical properties. The photoluminescence quantum yields of perovskite quantum dots are close to 100%. The external quantum efficiencies and current efficiencies of perovskite quantum dot light-emitting diodes have reached 8% and 43 cd A^(-1),respectively, and their nanowire lasers show ultralow-threshold room-temperature lasing with emission tunability and ease of synthesis. Perovskite nanowire photodetectors reached a responsivity of 10 A W^(-1)and a specific normalized detectivity of the order of 10^(12 )Jones. Different from most reported reviews focusing on photovoltaic applications, we summarize the rapid progress in the study of low-dimensional perovskite materials, as well as their promising applications in optoelectronic devices. In particular, we review the wide tunability of fabrication methods and the state-of-the-art research outputs of low-dimensional perovskite optoelectronic devices. Finally, the anticipated challenges and potential for this exciting research are proposed.
基金supported by the National Natural Science Foundation of China(NSFC)for Excellent Young Scholars(No.51422201)the NSFC Program(Nos.51701037,51732003,61774031,51872043,and 61574031)+3 种基金the“111”Project(No.B13013)the Fund from People's Government of Jilin Province(Nos.20180520186JH,and JJKH20190275KJ)the Project Funded by China Postdoctoral Science Foundation(No.2017M621189)Fundamental Research Funds for the Central Universities(No.JGPY201909).
文摘Organic-inorganic halide perovskites(OHPs)have been intensively studied for application in solar cells with high conversion efficiency exceeding 22%.The unique electrical and optical properties of OHPs have led to their use in optoelectronic device applications beyond photovoltaics,such as light-emitting diodes,photodetectors,transistors.New information storage technologies and computing architectures are being researched extensively with the aim of addressing the growing challenge of approaching end of Moore's law and von Neumann bottleneck.As the fourth basic circuit element,memristor is a leading candidate with powerful capabilities in information storage and neuromorphic computing applications.Recently,OHPs have received growing attention as promising materials for memristors.In particular,their mixed ionic-electronic conduction ability paired with light sensitivity provide OHPs with the opportunity to display novel functions such as optical-erase memory,optogenetics-inspired synaptic functions,and lightaccelerated learning capability.This review covers recent advances in OHP-based memristors development including memristive mechanism and analytical models,universal memristive characteristics for memory and neuromorphic computing applications,and novel multi-functionalization.Challenges and future prospects of OHP-based memristors are also discussed.
基金the National Key Research and Development Program of China(2017YFA0206600)the National Natural Science Foundation of China(51773045,21572041 and 21772030)for the financial support
文摘Owing to its nice performance, low cost, and simple solution-processing, organic-inorganic hybrid perovskite solar cell(PSC) becomes a promising candidate for next-generation high-efficiency solar cells.The power conversion efficiency(PCE) has boosted from 3.8% to 25.2% over the past ten years. Despite the rapid progress in PCE, the device stability is a key issue that impedes the commercialization of PSCs. Recently, all-inorganic cesium lead halide perovskites have attracted much attention due to their better stability compared with their organic-inorganic counterpart. In this progress report, we summarize the properties of CsPb(IxBr1-x)3 and their applications in solar cells. The current challenges and corresponding solutions are discussed. Finally, we share our perspectives on CsPb(IxBr1-x)3 solar cells and outline possible directions to further improve the device performance.
基金We are thankful for the financial support from the National Nature Science Foundation of China(No.51971111).
文摘ABO_(3)perovskites,owning unique properties,have great research prospect in electromagnetic wave absorption field.Normally,doping can significantly regulate the dielectric loss,whereas the magnetic loss can be ignored.In this work,the crystal structure and electromagnetic properties can be regulated systematically by the K,Fe co-doping for LaCoO_(3)perovskites(LKCFO)under the condition of fixed F content.In addition,the obtained samples show the obvious interfacial polarization effect on accounting to the small size effect,which is conducive to the effective microwave absorption.By analyzing the evolution of the positron annihilation lifetime and the first-principles calculation of the oxygen density of states for the series of LKCFO perovskites,it is found that the charge transport characteristics will be controlled by the point defect generated by allelic doping.The point defect content decreases and then increases as the doping level rises.The prepared perovskite exhibits the lowest defect density and the largest dielectric loss capability,which indicates that the lower point defects promote electron migration and thus enhance the dielectric loss;thus,the electromagnetic wave absorption bandwidth up to 6.2 GHz is reached.In contrast,both insufficient and excessive K doping are detrimental to the enhancement of microwave absorption.Especially,the practical application value was investigated using Computer Simulation Technology(CST)simulations.The LKCFO-2 exhibits the smallest RCS value(below-10 dBm^(2))at almost-90°-90°with a thickness of 2 mm,providing an effective method for study excellent microwave absorption and scattering property.
基金supported by the Major State Basic Research Development Program of China (2016YFB0700702)the National Natural Science Foundation of China (5171101030, 51602114)+1 种基金the HUST Key Innovation Team for Interdisciplinary Promotion (2016JCTD111)the Open Fund of State Key Laboratory of Luminescence and Applications (SKLA-2016-08)
文摘Metal halide perovskites have shown great performance for various applications,including solar cells,light emitting diodes,and radiation detectors,but they still suffer from the toxicity of lead and instability.Here we report the use of lanthanide series as trivalent metals to obtain low toxicity and highly stable double perovskites(Cs_2NaLnCl_6,Ln=Tb or Eu)with high scintillation light yield.The crystals exhibit typical f-f transitions of lanthanide cations,while Cs_2NaTbCl_6exhibits strong green photoluminescence,and Cs_2NaEuCl_6exhibits red photoluminescence.Under X-ray radiations,the light yield of Cs_2NaTbCl_6reaches46600 photons MeV^(-1),much higher than that of the commercially used(Lu,Y)_2SiO_5:Ce^(3+)crystals(LYSO,28500 photons MeV^(-1)),and previously reported lead-based perovskites(14000 photons MeV^(-1)).As a new member of lead-free perovskites,lanthanide-based double perovskites open up a new route toward radiation detections and potential medical imaging.
基金Project supported by National High Technology Research and Development Program of China(863Program,2011AA03A405)
文摘La1-x Cax MnO3 （x=0-0.3） perovskite-type oxides were synthesized by citrate sol-gel method. The physical and chemical properties were characterized by X-ray diffraction （XRD）, Brumauer-Emmett-Teller method （BET）, X-ray photoelectron spectroscopy （XPS）, NO＋O2 -TPD （temperature-programmed desorption）, activated oxygen evaluation and H2 -TPR （temperature-programmed reduction） technologies. The results showed that NO catalytic oxidation activity was significantly improved by Ca substitution, especially for lower temperature activity. The La0.9 Ca0.1 MnO 3 sample showed the maximum conversion of 82% at 300 oC. The monodentate nitrates played a crucial role for the formation of NO2 . The reducibility of Mn 4＋ ions and reactivity of activated oxygen were favorable for the catalytic performances of NO oxidation.
文摘The empirical relation of between the transition temperature of optimum doped superconductors T<sub>co</sub> and the mean cationic charge , a physical paradox, can be recast to strongly support fractal theories of high-T<sub>c</sub> superconductors, thereby applying the finding that the optimum hole concentration of σ<sub>o</sub> = 0.229 can be linked with the universal fractal constant δ<sub>1</sub> = 8.72109… of the renormalized quadratic Hénon map. The transition temperature obviously increases steeply with a domain structure of ever narrower size, characterized by Fibonacci numbers. However, also conventional BCS superconductors can be scaled with δ<sub>1</sub>, exemplified through the energy gap relation k<sub>B</sub>T<sub>c</sub> ≈ 5Δ<sub>0</sub>/δ<sub>1</sub>, suggesting a revision of the entire theory of superconductivity. A low mean cationic charge allows the development of a frustrated nano-sized fractal structure of possibly ferroelastic nature delivering nano-channels for very fast charge transport, in common for both high-T<sub>c</sub> superconductor and organic-inorganic halide perovskite solar materials. With this backing superconductivity above room temperature can be conceived for synthetic sandwich structures of less than 2+. For instance, composites of tenorite and cuprite respectively tenorite and CuI (CuBr, CuCl) onto AuCu alloys are proposed. This specification is suggested by previously described filamentary superconductivity of “bulk” CuO1﹣x samples. In addition, cesium substitution in the Tl-1223 compound is an option.
基金fnancial support from the National Natural Science Foundation of China(No.51971111)。
文摘Perovskite LaCoO_(3)is of great potential in electromagnetic wave absorption considering its outstanding dielectric loss as well as the existing magnetic response with the magnetic doping.However,the dissipation mechanism of the magnetic doping on the microwave absorption is lack of sufficient investigated.In this paper,LaCo_(1-x)Fe_(x)O_(3)(x=0,0.05,0.1,0.15,0.2,0.25,0.3,LCFOs)perovskites with different Fe doping amounts were prepared successfully by the sol-gel method and subsequent heat treatment in the air atmosphere.The structure characterization carried out by the frst-principles calculations shows the effect of Fe doping on the dielectric and magnetic properties of LCFOs and the strong hybridization of Co/Fe-3d with O-2p in the LCFOs system was successfully demonstrated.Particularly,when x=0.1 and the thickness is only 1.95 mm,the LaCo_(0.9)Fe_(0.1)O_(3)exhibits the best microwave absorption performance with the minimum reflection loss(RL)value of about-41 dB.The typical samples achieve a broad effective absorption bandwidth(EAB)of 5.16 GHz(7.92-13.08 GHz),which covers the total X band(8-12 GHz).Considering that,the especial Fe doping perovskite is promising to be a candidate as efficient microwave absorbers.
基金This work was supported by the National Natural Science Foundation of China （Nos. 21373097 and 51072067）.
文摘Metal-halide perovskites are novel optoelectronic materials that are considered good candidates for solar harvesting and light emitting applications. In this study, we develop a reproducible and low-cost approach for synthesizing high- quality cesium lead halide perovskite （CsPbX3, X = CI, Br, and I or C1/Br and I/Br） nanocrystals （NCs） by direct heating of precursors in octadecene in air. Experimental results show that the particle size and composition of as-prepared CsPbX3 nanocrystals can be successfully tuned by a simple variation of reaction temperature. The emission peak positions of the as-prepared nanocrystals can be conveniently tuned from the UV to the NIR （360-700 nm） region, and the quantum yield of the as-obtained samples （green and red emissions） can reach up to 87%. The structures and chemical compositions of the as-obtained NCs were characterized by transmission electron microscopy, X-ray diffraction, and elemental analysis. This proposed synthetic route can yield large amounts of high-quality NCs with a one-batch reaction, usually on the gram scale, and could pave the way for further applications of perovskite-based light-emitting and photovoltaic solar cells.
基金Shenzhen-Hong Kong-Macao Science and Technology Innovation Project(Category C),Grant/Award Number:SGDX2020110309360100Fundo para o Desenvolvimento das Ciências e da Tecnologia,Grant/Award Numbers:FDCT-0044/2020/A1,0034/2021/APD+3 种基金Guangdong-Hong Kong-Macao Joint Laboratory of Optoelectronic and Magnetic Functional Materials,Grant/Award Number:2019B121205002Natural Science Foundation of Guangdong Province,Grant/Award Number:2019A1515012186National Natural Science Foundation of China,Grant/Award Numbers:61935017,62175268,62105292UM's research fund,Grant/Award Numbers:MYRG2018-00148-IAPME,MYRG2020-00151-IAPME。
文摘Two-dimensional Ruddlesden-Popper(2DRP)perovskites have attracted intense research interest for optoelectronic applications,due to their tunable optoelectronic properties and better environmental stability than their threedimensional counterparts.Furthermore,high-performance photodetectors based on single-crystal and polycrystalline thin-films 2DRP perovskites have shown great potential for practical application.However,the complex growth process of single-crystal membranes and uncontrollable phase distribution of polycrystalline films hinder the further development of 2DRP perovskites photodetectors.Herein,we report a series of high-performance photodetectors based on single-crystal-like phase-pure 2DRP perovskite films by designing a novel spacer source.Experimental and theoretical evidence demonstrates that phase-pure films substantially suppress defect states and ion migration.These highly sensitive photodetectors show I_(light)/I_(dark) ratio exceeding 3×10^(4),responsivities exceeding 16 A/W,and detectivities exceeding 3×10^(13) Jones,which are higher at least by 1 order than those of traditional mixed-phase thinfilms 2DRP devices(close to the reported single-crystal devices).More importantly,this strategy can significantly enhance the operational stability of optoelectronic devices and pave the way to large-area flexible productions.
基金financially supported by the Natural Science Foundation of China(Grants 51972172,61705102,and 51802253)the China Postdoctoral Science Foundation(Grants 2021M692630)+6 种基金Natural Science Basic Research Plan in Shaanxi Province of China(2022JQ-629,2021JLM-43)the Joint Research Funds of Department of Science&Technology of Shaanxi Province and Northwestern Polytechnical University(2020GXLH-Z-007 and 2020GXLH-Z-014)Natural Science Foundation of Jiangsu Province for Distinguished Young Scholars,China(Grant BK20200034)the Innovation Project of Optics Valley Laboratory(OVL2021BG006)the Open Project Program of Wuhan National Laboratory for Optoelectronics(2021WNLOKF003)the Young 1000 Talents Global Recruitment Program of Chinathe Fundamental Research Funds for the Central Universities.
文摘Metal halide perovskites(MHPs),emerging as innovative and promising semiconductor materials with prominent optoelectronic properties,has been pioneering a new era of light management(ranging from emission,absorption,modulation,to transmission)for next-generation optoelectronic technology.Notably,the exploration of fundamental characteristics of MHPs and their devices is the main research theme during the past decade,while in the next decade,it will be primarily critical to promote their implantation in the next-generation optoelectronics.In this review,we first retrospect the historical research milestones of MHPs and their optoelectronic devices.Thereafter,we introduce the origin of the unique optoelectronic features of MHPs,based on which we highlight the tunability of these features via regulating the phase,dimensionality,composition,and geometry of MHPs.Then,we show that owing to the convenient property control of MHPs,various optoelectronic devices with target performance can be designed.At last,we emphasize on the revolutionary applications of MHPs-based devices on the existing optoelectronic systems.This review demonstrates the key role of MHPs played in the development of modern optoelectronics,which is expected to inspire the novel research directions of MHPs and promote the widespread applications of MHPs in the next-generation optoelectronics.
文摘Halide perovskites have emerged as the next generation of optoelectronic materials and their remarkable performances have been attractive in the fields of solar cells,light-emitting diodes,photodetectors,etc.In addition,halide perovskites have been reported as an attractive new class of X-ray direct detecting materials recently,owning to the strong X-ray stopping capacity,excellent carrier transport,high sensitivity,and cost-effective manufacturing.Meanwhile,perovskite based direct Xray imagers have been successfully demonstrated as well.In this review article,we firstly introduced some fundamental principles of direct X-ray detection and imaging,and summarized the advances of perovskite materials for these purposes and finally put forward some needful and feasible directions.
基金CONACYT for a postdoctoral research fellowship (Fellowship:24641)support by CONACYT (Grant: 240011)UANL-FCQ
文摘The progress made by the scientific community in emerging photovoltaic technologies over the past two decades has been outstanding. Numerous methods have been developed for the preparation of hybrid organic–inorganic perovskite solar cells. The power conversion efficiency has been up to 14% by a one-step vacuum deposition technique. A serious concern is the toxicity of the materials. In this review, several methods aimed at resolving these problems to some extent have been compiled, including eco-friendly synthesis. Further efficiency enhancements are expected following optimization, and a better fundamental understanding of the internal electron charge transfer, electron–hole diffusion to the corresponding layers, flexibility, and stability-dependent bandgaps is reported. This paper explores the green synthesis of organic–inorganic perovskites for industrialization. Concerning the above facts, a simple low-cost model called‘‘dispersed photovoltaic cells' ' is presented.
基金thank the Shenzhen-Hong Kong-Macao Science and Technology Plan Project(Category C,Grant No.ZGCP)Research Grants Council of Hong Kong(Grant No.15302121)+4 种基金National Natural Science Foundation of China(21975214)National Key R&D Program of China(Grant No.2018YFC2000900)Seed Fund of Research Institute of Intelligent Wearable Systems(Grant No.CD45)Start-up Fund of The Hong Kong Polytechnic University(Grant No.BE1H)Departmental General Research Fund of The Hong Kong Polytechnic University(Grant No.UAME),and The Hong Kong Ph.D.Fellowship Scheme.
文摘Despite the impressive power conversion efficiency(PCE)beyond 25.5%,perovskite solar cells,especially the Sn-based variants,are poorly stable under normal operating conditions compared with the market-dominant silicon solar cells that can last for over 25 years.2D3D hybrid perovskite materials are one of the best options to overcome the instability chal-lenge without compromising efficiency.Indeed,a record performance of 1 year was reported in Pb-based 2D3D planar per-ovskite devices.However,the reaction between 2 and 3D perovskite molecules requires high temperatures(-300°C)and increased reaction time(-24 h)to achieve high-quality 2D3D hybrid perovskites.Herein,we base on the ability of chlorine to displace iodine from its ionic compounds in solutions to utilize chloride ions as catalysts for speeding up the reaction between iodine-based 2D and 3D perovskite molecules.The approach reduces the reaction time to-20 min and the reaction temperature to-100°C with the formation of high-quality 2D3D hybrid perovskites,free from pure 2D traces.Integrating the synthesized 2D3D hybrid perovskite material with 50%chlorine doping in a fiber-shaped solar cell architecture yielded the highest reported PCE of 11.96%in Sn-based fiber-shaped perovskite solar cells.The unencapsulated and encapsulated fiber-shaped solar cells could maintain 75%and 95.5%of their original PCE,respectively,after 3 months under room light and relative humidity of 35–40%,revealing the champion stability in Sn-based perovskite solar devices.The solar yarn also demonstrated constant energy output under changing light incident angles(0–180°).
