Organic ferroelastic enantiomers with high Tc and large dielectric switching ratio triggered by order-disorder and displacive phase transition

Molecular-based ferroelastics with dielectric switching properties are highly desirable for their applications on microelectronic dielectric switches,sensors,data storage,and so on.However,the current reports mostly focus on organic-inorganic hybrids containing toxic heavy metal atoms,and the relatively low phase transition temperature limits their application.In this paper,low-toxic organic salt ferroelastic enantiomers(R/S)-4-fluoro-1-azabicyclo[3.2.1]octonium chloride[(R/S)-F-321]were designed and synthesized under the introducing chirality strategy.They undergo a 432F422-type ferroelastic phase transition with a high Curie temperature(Tc)of 470 K,simultaneously exhibiting excellent dielectric switching characteristics.In addition to the ordered-disordered movement of cations,the significant displacement of anions is also responsible for such high Tc and large dielectric switching ratios,which is very rare in molecular-based switching materials.This work enriches the development of molecular ferroelastic switching materials and gives inspiration for the exploration of environmentally friendly high Tc organic salt ferroelastics with prominent switching performances.

(Benzimidazolium)_(2)GeI_(4):A layered two-dimensional perovskite with dielectric switching and broadband near-infrared photoluminescence

Two-dimensional(2D)lead halide perovskites have attracted tremendous attention due to their outstanding physical properties.However,the presence of toxic lead is a major problem for large-scale applications.Here,we report the synthesis,phase transition,dielectric and photoluminescence(PL)properties of a lead-free 2D Ge-based perovskite(BIM)_(2)GeI_(4)(BIM=benzimidazolium)which experiences a phase transition at 405 K accompanied by an order-disorder change of organic spacer.Moreover,the step-like dielectric transition near the phase transition temperature makes it suitable for dielectric switching.Meanwhile,(BIM)_(2)GeI_(4)has a direct bandgap of 2.23 eV and broadband emission from 550 to 1000 nm,implying its unique optical property for potential near-infrared lighting and displaying.This work provides a fresh example for the development of lead-free 2D Ge-based perovskite with potential applications in the fields of optoelectronics and high temperature dielectric switching.

A chiral lead-free tin(Ⅳ)-based halide organic-inorganic semiconductor with dielectric switching and phase transition

Chiral organic-inorganic metal halide semiconductors(OIMHSs)have recently attracted numerous interests due to their unique chirality,structural tunability,and extensive physical properties.However,most reported chiral OIMHSs contain toxic lead,which will be a potential obstacle to their further applications.Herein,we successfully synthesized a novel chiral lead-free tin(IV)-based OIMHS[(R)-3-hydroxyquinuclidinium]_(2)SnCl_(6)([R-HQ]_(2)SnCl_(6)).It exhibits a wide band gap(Eg)of about 4.11 eV.Moreover,[R-HQ]_(2)SnCl6 undergoes a phase transition around 330 K(Tc)and shows distinct dielectric switching characteristics with good repeatability.This work enriches the chiral lead-free OIMHS family and stimulates further exploration of chiral lead-free OIMHS switching materials.

Hybrid perovskite shows temperature-dependent photoluminescence and dielectric response triggered by halogen substitution

Materials exhibiting dielectric switching response and photoluminescence(PL)are promising for sensors and information storage.In previous research,we synthesized a series of materials with red or green PL and dielectric switching capabilities by incorporating luminescent metal halides into organic ammonium compounds.However,effective modification to synthesize organic-inorganic hybrid materials with dielectric switching response and orange PL continues to be a challenge in the respective fields.Orange PL materials are valuable for switching and sensors,and most orange light sources are derived from rare earth elements,making them harder to obtain.We have successfully synthesized two organic-inorganic hybrid materials([CMPD]PbBr_(3)(1)and[BMPD]PbBr_(3)(2),CMPD=N-ClCH_(2)-N-methylpiperidine,BMPD=N-BrCH_(2)-N-methylpiperidine)that exhibit both orange PL and dielectric switching response.When Cl in compound 1 is substituted by Br in compound 2,the phase transition temperature of the compound is elevated by 45 K.These compounds exhibit captivating orange light emission when exposed to ultraviolet lamps.This research provides insights into exploring multifunctional materials with orange PL and dielectric switching response and provides proof for halogen substitution strategies to design materials with higher phase transition temperatures.

Lead-free hybrid two-dimensional double perovskite with switchable dielectric phase transition

Molecular dielectric switches constitute a type of intelligent materials that are highly coveted for their distinctive advantages of switchable dielectric responses,lightweight,and mechanical flexibility.Twodimensional(2D)hybrid perovskites have demonstrated excellent promise for assembling dielectric switches,in which the dynamic motions of organic moieties afford driving force to trigger switchable dielectric phase transition.Here,we successfully assembled a new lead-free hybrid double perovskite,(CHA)4Cu Bi Br8(1,CHA=cyclohexylammonium),adopting a typical 2D structural motif,which shows dielectric anisotropy and bistable behaviors during the reversible phase transition near T_(c)=378 K(the Curie temperature).That is,its dielectric constants could be switched and tuned between high-dielectric and low-dielectric states.Structure analyses reveal that the ordered-disordered transformation of the organic CHA+moiety and distortion of inorganic framework account for its phase transition.This result will stimulate further exploration of molecular dielectric switches in this 2D environmentally friendly family.

X-site doping in ABX_(3) triggers phase transition and higher T_(c) of the dielectric switch in perovskite

Material stability is always the key factor for applied materials especially the working environment that requires higher temperature sensitivity or temperature fluctuation range.In which,the stimulus-response perovskite materials are just sensitive to stability to ensure the accuracy and stability of the signals,in the applied devices of batteries and memory storage devices and so on.However,it is still a tremendous challenge to improve the stability of perovskite materials,and maintain reliability in the devices.Here,a novel ABX_(2)X'_(1)(X-site doping in an ABX_(3))compound[CEMP]-[CdBr_(2)(SCN)](1,CEMP=1-(2-chloro-ethyl)-1-methyl-piperidine)with remarkable high-temperature reversible dielectric switching behavior was proposed.The strategy of[SCN]^(−)doping in perovskite for improving the stability was successfully achieved.Meanwhile,the steric hindrance is increased while the energy barrier is also increased by replacing hydrogen with flexible groups,which leads to a high-temperature reversible phase transition.The new finding provides a new direction to enrich new applications and design ideas of perovskite materials.Especially the X-site strategy of doping or substitution in the ABX_(3),it will promote ingenious and perfect experimental results in material synthesis and performance improvement by chemistry disciplines.

High-temperature dielectric switch and second harmonic generation integrated in a stimulus responsive material

Stimulus re s ponsive materials can provide a variety of desirable properties in one equipment unit,such as optoelectronic devices,data communications,actuators,memories,sensors and capacitors.However,it remains a large challenge to design such stimulus responsive materials,especially functional materials having both dielectric switch and second harmonic generation(SHG).Here,a new stimuli-responsive switchable material [(CH_(3))_(3)N(CH_(2))_(2)Cl]_(2)]Mn(SCN)_(4)(H_(2)O)_(2)] was discovered as a potential secondharmonic generation(SHG) dielectric switch.It is worth noting that it has SHG characteristics before and after undergoing reversible high-temperature phase transitions.In this work,we successfully refined the tetramethylammonium cation to obtain a quasi-spherical cation,which is tetramethylchloroethylamine(TMCEM) cation.By substituting H with a halogen,the increased steric hindrance of the molecular makes energy barrier increased,resulting in the reversible high-temperature phase transition.At the same time,the interactions of quasi-spherical cations and [Mn(SCN)_(4)(H_(2)O)_(2)]^(2-) anions affect a noncentrosymmetric structure to induce the SHG effect.These findings provide a new approach to design novel functional switch materials.

Structural phase transition in a new organic-inorganic hybrid post-perovskite:(N,N-dimethylpyrrolidinium)[Mn(N(CN)_(2))_(3)]

In the realm of molecular phase transition research,particularly for applications in sensors,data storage and switching technologies,the role of organic-inorganic hybrid perovskite materials has been increasingly recognized for their significant potential.Nevertheless,hybrid post-perovskites,as a critical subclass of perovskites,have not been thoroughly studied and mainly limit in the instances based on polyatomic bridging agents like dicyanamide(dca^(-))and non-cyclic organic cations.Herein,a polar cyclic quaternary ammonium cation,N,N-dimethylpyrrolidinium(DMP^(+)),was used to assemble a new hybrid post-perovskite,(DMP)[Mn(dca)_(3)](1),which undergoes a phase transition from orthorhombic Bmmb to monoclinic P2_(1)/n space group at 249 K.By employing multiple techniques such as differential scanning calorimetry,variable-temperature single-crystal X-ray analysis,dielectric measurements,and Hirshfeld surface analysis,we disclosed the role of polar cyclic quaternary ammonium DMP^(+)in elevating the phase-transition temperature by 48 K,generating significant dielectric switching effect and facilitating interlayer sliding of inorganic framework.

厘米级无铅卤化物双钙钛矿单晶实现铁弹性相变触发介电开关性质

在铅基卤化物钙钛矿突破性发展的推动下,卤化物双钙钛矿因其环境友好、丰富的物理化学性能和结构可调性而成为杰出的多用途材料.尽管卤化物双钙钛矿的研究取得了飞速的进展,但在这个吸引人的钙钛矿家族中对可切换电介质的探索仍然很少.本工作通过溶液冷却法成功地生长了单层卤化物双钙钛矿(3-溴丙胺)_(4)AgBiBr_(8)(1)的大尺寸单晶,其尺寸达20 mm×17 mm×5 mm.它经历了由Aizu符号定义的mmm F2/m的铁弹性相变,通过结构分析可知该铁弹相变是八面体畸变和柔性分子运动协同作用的结果.值得注意的是,它在373 K附近具有理想的铁弹性相变触发的可切换电介质性能,可以在两个稳定的电介质状态之间切换.而且,1展现出间接带隙半导体特性和X射线响应,其中在40 V的偏压下1的灵敏度高达517μC Gy_(air)^(-1)cm^(-2).这项工作为具有智能功能的无铅卤化物双钙钛矿提供了一条有效的应用路径.

Thermal-Induced Ferroelastics in Two Lead-Free Organic-Inorganic Hybrid Perovskites

Lead-based organic-inorganic hybrids occupy a niche in the field of optoelectronics due to exceptional semiconducting properties and potential ferroelasticity.Nevertheless,the possible toxicity of lead restricts their widespread application to a certain extent.Herein,two new lead-free ferroelastic semiconductors are reported:[DMMClEA]_(3)Bi_(2)Br_(9)(compound 1)and[DMMClEA]_(3)Sb_(2)Br_(9)(compound 2)(DMMClEA=N-(chloromethyl)-N,N-dimethylethylammonium),in which the inorganic framework neatly arranges with[Bi_(2)Br_(9)]^(3−)/[Sb_(2)Br_(9)]^(3−)polyhedrons shared by face,forming an A_(3)B_(2)X_(9)-type structure.Both compounds 1 and 2 possess two-step phase transitions,including a3mF2/m-type ferroelastic phase transition,based on the Aizu rule.In addition,dual dielectric switches endow the application toward sensor devices.This finding enriches A_(3)B_(2)X_(9)-type zero-dimensional hybrid ferroelastics and provides an approach to designing high-performance,lead-free perovskite semiconductors with dielectric functionality.