Layered trihalides exhibit distinctive band structures and physical properties due to the sixfold coordinated 3d or 4d transition metal site and partially occupied d orbitals,holding great potential in condensed matte...Layered trihalides exhibit distinctive band structures and physical properties due to the sixfold coordinated 3d or 4d transition metal site and partially occupied d orbitals,holding great potential in condensed matter physics and advanced electronic applications.Prior research focused on trihalides with highly symmetric honeycomb-like structures,such as CrI3 andα-RuCl_(3),while the role of crystal anisotropy in trihalides remains elusive.In particular,the trihalide MoCl_(3) manifests strong in-plane crystal anisotropy with the largest difference in Mo–Mo interatomic distances.Research on such material is imperative to address the lack of investigations on the effect of anisotropy on the properties of trihalides.Herein,we demonstrated the anisotropy of MoCl_(3) through polarized Raman spectroscopy and further tuned the phonon frequency via strain engineering.We showed the Raman intensity exhibits twofold symmetry under parallel configuration and fourfold symmetry under perpendicular configuration with changing the polarization angle of incident light.Furthermore,we found that the phonon frequencies of MoCl_(3) decrease gradually and linearly with applying uniaxial tensile strain along the axis of symmetry in the MoCl_(3) crystal,while those frequencies increase with uniaxial tensile strain applied perpendicularly.Our results shed light on the manipulation of anisotropic light-matter interactions via strain engineering,and lay a foundation for further exploration of the anisotropy of trihalides and the modulation of their electronic,optical,and magnetic properties.展开更多
Organolead trihalide perovskite materials have been attracting increasing attention due to their promising role in solid solar cells. Several advantages make them potential candidates for optoelectronics:(1) solution-...Organolead trihalide perovskite materials have been attracting increasing attention due to their promising role in solid solar cells. Several advantages make them potential candidates for optoelectronics:(1) solution- or/and vapor-processed preparation at low temperature;(2) tunable optical bandgap, wide absorption spectrum but narrow photoluminescence peaks;(3) long car-rier life time, large diffusion length and high charge mobility;(4) various nanostructures via tuning capping agents and sol-vents. In this review, we summarize recent attempts toward efficient LEDs based on organolead trihalide perovskite materials. The strategies of materials science, device design and interface engineering are highlighted. Recent development and future perspectives are summarized for practical perovskite light technologies.展开更多
The unique optical and electrical properties of two-dimensional(2D)materials provide a platform for novel van der Waals(vdW)heterojunction devices but the investigation of 2D magnetism is still limited.Recently,the em...The unique optical and electrical properties of two-dimensional(2D)materials provide a platform for novel van der Waals(vdW)heterojunction devices but the investigation of 2D magnetism is still limited.Recently,the emergence of long-range magnetic order atomically thin crystals expands 2D family,providing possibilities for the study of low-dimensional spin behavior and novel spintronics devices.As a specific member of magnetic van der Waals family,chromium trihalides(CrX_(3),X=Cl,Br,I)stimulated intensive interests on account of the newfangled magnetic properties.In this review,we briefly introduce the crystal structures,magnetism of the bulk and synthetic methods of 2D CrX_(3).Subsequently,the physical properties in atomically thin limit and magnetism manipulated by external field are presented.Next,some novel physical phenomena in CrX_(3) heterojunctions are discussed.Finally,the challenges and future directions are proposed.We focus on the intriguing physical phenomena in 2D magnetic CrX_(3) by combining related theoretical calculations and experimental results,providing a perspective on these emerging materials.展开更多
The Lewis acidity scale of boron trihalides BX3 (X=F, Cl, Br, I) and character of the boron-halogen bonds have been studied by means of DV-Xa approach. Present results show that the acid strength of boron trihalides i...The Lewis acidity scale of boron trihalides BX3 (X=F, Cl, Br, I) and character of the boron-halogen bonds have been studied by means of DV-Xa approach. Present results show that the acid strength of boron trihalides increases in the order BF3<BCl3<BBr3<BI3, in excellent agreement with experiments. Based on boron-halogen bonding character, the valence of boron atom in boron compounds can be considered as equal to five instead of three which seems to be more reasonable.展开更多
Because of the good thermal stability and superior carrier transport characteristics of formamidinium lead trihalide perovskite HC(NH_2)_2 PbX_3(FAPbX_3), it has been considered to be a better optoelectronic material ...Because of the good thermal stability and superior carrier transport characteristics of formamidinium lead trihalide perovskite HC(NH_2)_2 PbX_3(FAPbX_3), it has been considered to be a better optoelectronic material than conventional CH_3NH_3-PbX_3(MAPbX_3). Herein, we fabricated a FAPbBr_3 microcrystal-based photodetector that exhibited a good responsivity of 4000 A W-1 and external quantum efficiency up to 106% under one-photon excitation, corresponding to the detectivity greater than 1014 Jones. The responsivity is two orders of magnitude higher than that of previously reported formamidinium perovskite photodetectors. Furthermore, the FAPbBr_3 photodetector's responsivity to two-photon absorption with an 800-nm excitation source can reach 0.07 A W^(-1), which is four orders of magnitude higher than that of its MAPbBr_3 counterparts. The response time of this photodetector is less than 1 ms.This study provides solid evidence that FAPbBr_3 can be an excellent candidate for highly sensitive and fast photodetectors.展开更多
In this paper, undoped LaCl3 crystal growth was reported by modified Bridgman method.The starting materials used as charge for crystal growth was found to contain seven to three crystallized water molecules, and dehyd...In this paper, undoped LaCl3 crystal growth was reported by modified Bridgman method.The starting materials used as charge for crystal growth was found to contain seven to three crystallized water molecules, and dehydration will take place when heating the raw materials at about 230 ℃ for several hours.The oxidization of LaCl3 during dehydration and growth can be avoided by adding a special scanvenger into the growing system.The grown LaCl3 crystals are colorless and transparent, but very hygroscopic.Their optical cut-off edge was confirmed to be 220 nm.UV excited and X-ray induced emission spectra were measured at room temperature, whose peak is at 405 nm.展开更多
The orbital deletion procedure is introduced, which is suited to quantitatively investigating the electronic delocalization effect in carbocations and boranes. While the routineab initio molecular orbital methods can ...The orbital deletion procedure is introduced, which is suited to quantitatively investigating the electronic delocalization effect in carbocations and boranes. While the routineab initio molecular orbital methods can generate wavefunctions for real systems where all electrons are delocalized, the present orbital deletion procedure can generate wavefunctions for hypothetical reference molecules where electronic delocalization effect is deactivated. The latter wave-function normally corresponds to the most stable resonance structure in terms of the resonance theory. By comparing and analyzing the delocalized and the localized wavefunctions, one can obtain a quantitative and instinct picture to show how electronic delocalization inside a molecule affects the molecular structure, energy as well as other physical properties. Two examples are detailedly discussed. The first is related to the hyperconjugation of alkyl groups in carbocations and a comparison of the order of stability of carbocations is made. The second concerns the Lewis acidity of boron trihalides where the conjugation effect among the doubly-occupied π atomic orbitals on the halide atoms and the vacant π atomic rbital on the boron atom plays a dominant role in determining the relative acceptor properties. The results demonstrate that the orbital deletion procedure can be used to very successfully interpret some traditional chemical intuitions and concepts in a quantitative way.展开更多
基金supported by the National Natural Science Foundation of China(Nos.92365203,52072168,51861145201,and 523B1010)the National Key Basic Research Program of the Ministry of Science and Technology of China(No.2021YFA1202901)the Natural Science Foundation of Jiangsu Province(No.BK20200341).
文摘Layered trihalides exhibit distinctive band structures and physical properties due to the sixfold coordinated 3d or 4d transition metal site and partially occupied d orbitals,holding great potential in condensed matter physics and advanced electronic applications.Prior research focused on trihalides with highly symmetric honeycomb-like structures,such as CrI3 andα-RuCl_(3),while the role of crystal anisotropy in trihalides remains elusive.In particular,the trihalide MoCl_(3) manifests strong in-plane crystal anisotropy with the largest difference in Mo–Mo interatomic distances.Research on such material is imperative to address the lack of investigations on the effect of anisotropy on the properties of trihalides.Herein,we demonstrated the anisotropy of MoCl_(3) through polarized Raman spectroscopy and further tuned the phonon frequency via strain engineering.We showed the Raman intensity exhibits twofold symmetry under parallel configuration and fourfold symmetry under perpendicular configuration with changing the polarization angle of incident light.Furthermore,we found that the phonon frequencies of MoCl_(3) decrease gradually and linearly with applying uniaxial tensile strain along the axis of symmetry in the MoCl_(3) crystal,while those frequencies increase with uniaxial tensile strain applied perpendicularly.Our results shed light on the manipulation of anisotropic light-matter interactions via strain engineering,and lay a foundation for further exploration of the anisotropy of trihalides and the modulation of their electronic,optical,and magnetic properties.
基金supported by the National Basic Research Program of China (2011CB933300)the National Natural Science Foundation of China (91333107, 51573004)the fund from Shenzhen City (CXZZ20120618162051603)
文摘Organolead trihalide perovskite materials have been attracting increasing attention due to their promising role in solid solar cells. Several advantages make them potential candidates for optoelectronics:(1) solution- or/and vapor-processed preparation at low temperature;(2) tunable optical bandgap, wide absorption spectrum but narrow photoluminescence peaks;(3) long car-rier life time, large diffusion length and high charge mobility;(4) various nanostructures via tuning capping agents and sol-vents. In this review, we summarize recent attempts toward efficient LEDs based on organolead trihalide perovskite materials. The strategies of materials science, device design and interface engineering are highlighted. Recent development and future perspectives are summarized for practical perovskite light technologies.
基金financially supported by the National Key R&D Program of China(No.2017YFA0206301)the National Natural Science Foundation of China(Nos.51631001 and 52027801)+1 种基金the Natural Science Foundation of Beijing Municipality(No.2191001)the China-German Collaboration Project(No.M-0199)。
文摘The unique optical and electrical properties of two-dimensional(2D)materials provide a platform for novel van der Waals(vdW)heterojunction devices but the investigation of 2D magnetism is still limited.Recently,the emergence of long-range magnetic order atomically thin crystals expands 2D family,providing possibilities for the study of low-dimensional spin behavior and novel spintronics devices.As a specific member of magnetic van der Waals family,chromium trihalides(CrX_(3),X=Cl,Br,I)stimulated intensive interests on account of the newfangled magnetic properties.In this review,we briefly introduce the crystal structures,magnetism of the bulk and synthetic methods of 2D CrX_(3).Subsequently,the physical properties in atomically thin limit and magnetism manipulated by external field are presented.Next,some novel physical phenomena in CrX_(3) heterojunctions are discussed.Finally,the challenges and future directions are proposed.We focus on the intriguing physical phenomena in 2D magnetic CrX_(3) by combining related theoretical calculations and experimental results,providing a perspective on these emerging materials.
基金Project supported by the National Natural Science Foundation of China.
文摘The Lewis acidity scale of boron trihalides BX3 (X=F, Cl, Br, I) and character of the boron-halogen bonds have been studied by means of DV-Xa approach. Present results show that the acid strength of boron trihalides increases in the order BF3<BCl3<BBr3<BI3, in excellent agreement with experiments. Based on boron-halogen bonding character, the valence of boron atom in boron compounds can be considered as equal to five instead of three which seems to be more reasonable.
基金the National Key R@D Program of China (Grant 2017YFA0204800)the National Natural Science Foundation of China (Grant Nos: 21533010, 21321091, 21525315, 91333116 and 21173169) for their financial supports
文摘Because of the good thermal stability and superior carrier transport characteristics of formamidinium lead trihalide perovskite HC(NH_2)_2 PbX_3(FAPbX_3), it has been considered to be a better optoelectronic material than conventional CH_3NH_3-PbX_3(MAPbX_3). Herein, we fabricated a FAPbBr_3 microcrystal-based photodetector that exhibited a good responsivity of 4000 A W-1 and external quantum efficiency up to 106% under one-photon excitation, corresponding to the detectivity greater than 1014 Jones. The responsivity is two orders of magnitude higher than that of previously reported formamidinium perovskite photodetectors. Furthermore, the FAPbBr_3 photodetector's responsivity to two-photon absorption with an 800-nm excitation source can reach 0.07 A W^(-1), which is four orders of magnitude higher than that of its MAPbBr_3 counterparts. The response time of this photodetector is less than 1 ms.This study provides solid evidence that FAPbBr_3 can be an excellent candidate for highly sensitive and fast photodetectors.
文摘In this paper, undoped LaCl3 crystal growth was reported by modified Bridgman method.The starting materials used as charge for crystal growth was found to contain seven to three crystallized water molecules, and dehydration will take place when heating the raw materials at about 230 ℃ for several hours.The oxidization of LaCl3 during dehydration and growth can be avoided by adding a special scanvenger into the growing system.The grown LaCl3 crystals are colorless and transparent, but very hygroscopic.Their optical cut-off edge was confirmed to be 220 nm.UV excited and X-ray induced emission spectra were measured at room temperature, whose peak is at 405 nm.
基金Project supported by the National Natural Science Foundation of China (Grant No. 29892166)the Provincial Natural Science Foundation of Fujian (Grant No. B9810003)the State Key Laboratory for Physical Chemistry on Solid Surface at Xiamen Universit
文摘The orbital deletion procedure is introduced, which is suited to quantitatively investigating the electronic delocalization effect in carbocations and boranes. While the routineab initio molecular orbital methods can generate wavefunctions for real systems where all electrons are delocalized, the present orbital deletion procedure can generate wavefunctions for hypothetical reference molecules where electronic delocalization effect is deactivated. The latter wave-function normally corresponds to the most stable resonance structure in terms of the resonance theory. By comparing and analyzing the delocalized and the localized wavefunctions, one can obtain a quantitative and instinct picture to show how electronic delocalization inside a molecule affects the molecular structure, energy as well as other physical properties. Two examples are detailedly discussed. The first is related to the hyperconjugation of alkyl groups in carbocations and a comparison of the order of stability of carbocations is made. The second concerns the Lewis acidity of boron trihalides where the conjugation effect among the doubly-occupied π atomic orbitals on the halide atoms and the vacant π atomic rbital on the boron atom plays a dominant role in determining the relative acceptor properties. The results demonstrate that the orbital deletion procedure can be used to very successfully interpret some traditional chemical intuitions and concepts in a quantitative way.
