Unraveling the mechanochemical synthesis and luminescence in MnⅡ-based two-dimensional hybrid perovskite（C4H9NH3）2PbCl4

The mechanochemical route is a facile and fast way and has received much attention for developing versatile advanced functional materials. Herein, we reported a mechanochemical synthesis for incorporating divalent manganese ions (Mn^Ⅱ) into a two-dimensional (2D) hybrid perovskite (C4H9NH3)2PbCl4. The mild external stimuli originating from the grinding at room temperature enabled the formation of Mn^Ⅱ-doped 2D hybrid perovskites, and rapidly changed the luminescence characteristics. The photoluminescence analyses show that the violet and orange emissions are attributed to (C4H9NH3)2Pb1-xMnxCl4 band-edge emission and the T1→^6A1 transition of Mn^2+ resulting from an efficient energy transfer process, respectively. Site preference and distribution of the doped Mn^2+ cations on the locations of Pb^2+ were analyzed. The formation energy calculated by the density functional theory (DFT) indicates that the Mn^2+ ions can rapidly enter the crystal lattice due to the unique 2D crystal structure of the hybrid perovskite. Such a case of mechanochemical synthesis for the 2D hybrid perovskite motivates many novel emerging materials and the related applications.

High-performance photodetectors based on two-dimensional perovskite crystals with alternating interlayer cations

Organic-inorganic halide perovskite,as a low-cost,solution-processable material with remarkable optoelectronic properties,is ideal candidate to fabricate high-performance photodetectors and is expected to significantly reduce device costs.Compared to the common Dion-Jacobson and Ruddlesden-Popper two-dimensional(2D)layered hybrid perovskite compounds,the perovskites with alternating cations in the interlayer(ACI)phase show higher crystal symmetry and narrower optical bandgaps,which exhibit great potential for excellent photodetection performance.Herein,we report a high-performance photodetector based on the 2D bilayered hybrid lead halide perovskite single crystal with the ACI phase(GAMA_(2)Pb_(2)I_(7);GA=C(NH_(2))_(3)and MA=CH_(3)NH_(3)).The single-crystal photodetector exhibits high photoresponsivity of 1.56,2.54,and 2.60 A/W for incident light wavelengths of 405,532,and 635 nm under 9.82 nW,respectively,together with the correspondingly high detectivity values of 1.86×10^(12),3.04×10^(12),and 3.11×10^(12)Jones under the same operating conditions.Meanwhile,a high-resolution imaging sensor is built based on the GAMA_(2)Pb_(2)I_(7)single-crystal photodetector,confirming the high stability and photosensitivity of the imaging system.These results show that the 2D hybrid lead halide perovskites with alternating interlayer cations are promising for high-performance visible light photodetectors and imaging systems.

Strong circularly polarized luminescence from quantum dots/2D chiral perovskites composites

Chiral perovskites(CPs)have attracted enormous attentions since they have combined chirality and optoelectrical properties well which is promising in circularly polarized luminescence(CPL)application and of great importance for future spin-optoelectronics.However,there is a key contradiction that in chiral perovskites chirality distorts the crystal structure,leading to poor photoluminescence(PL)properties.Achieving the balance between chirality and PL is a major challenge for strong CPL from chiral perovskites.Differently,two-dimensional(2D)chiral perovskite has shown fascinating chiral induced spin selectivity(CISS)effect which can act as spin injector under ambient conditions.Here,we propose an effective strategy to achieve high CPL activity generated from quantum dots(QDs)by introducing 2D chiral perovskite as a chiral source,providing spin polarized carriers through the CISS effect.The as-synthesized QDs/CP composites exhibit dissymmetry factors(glum)up to 9.06×10^(−3).For the first time,we performed grazing incident wide angle X-ray scattering(GIWAXS)measurements,showing the chirality originates from the distorted lattices caused by the large chiral organic cations.Besides,time-resolved PL(TR-PL)measurements verify the enhanced CPL activity should be attributed to the charge transport between two components.These findings provide a useful method to achieve CPL in QDs/2D chiral perovskite heterojunctions which could be promising in spinoptoelectronics application.

Research Advances of Ferroelectric Semiconductors of 2D Hybrid Perovskites toward Photoelectronic Applications

Ferroelectric materials, characterized by the switchable spontaneous polarization(Ps) through reversing the directions of external electric field, exhibit versatile physical attributes that have been extensively used for practical device applications. Two-dimensional(2D) organic-inorganic hybrid perovskites are recently emerging as a robust family of candidate ferroelectrics, termed ferroelectric semiconductors. In particular, the coexistence and/or coupling of ferroelectric polarization with their semiconducting properties enables new physical concepts, thus providing a potential platform for the development of new multifunctional optoelectronic devices. This review primarily describes the structural origin of symmetry breaking for generating ferroelectric orders in 2D hybrid perovskites, and then presents the combination of ferroelectric Ps with other semiconducting optoelectronic activities. Regarding the emergence of new photoelectric behaviors, the prospects for this 2D family of ferroelectric semiconductors are further discussed, along with their development tendency for the future photoelectronic device applications.

Rational alloying of secondary and aromatic ammonium cations in a metal-halide perovskite toward crystal-array photodetection

Two-dimensional(2D)hybrid perovskites with the Ruddlesden-Popper lattice(A')_(2)(A)_(n-1)M_(n)X_(3n+1)are emerging as the promising optoelectronic candidates,both the inorganic and organic ingredients of which can be tailored to modulate the physical properties.Nevertheless,there is a scarcity of 2D multilayered motifs with the A-site large-size cations occupying perovskite cavities.Here,by rational mixedcation alloying,we present a new 2D hybrid perovskite,(4-TFBMA)_(2)(DMA)Pb_(2)I_(7)(1),in which the secondary cation of CH_(3)NH_(2)CH_(3)^(+)(DMA)is located inside the perovskite cage while the aromatic 4-(trifluoromethyl)benzylammonium(4-TFBMA)cation acts as a spacer moiety.Benefiting from the quantum structure of alternating organic spacers and inorganic networks,crystal-array detectors of 1 show fascinating in-plane photodetection responses of large detectivity(~2.95×10^(12)Jones)and responsivity(~1.97AW^(-1)),comparable to those of some inorganic 2D counterparts.In addition,a fast response rate(~264μs)and a low dark current are also realized,related to the high crystalline quality and suppression of the hopping barrier due to the insulating organic spacing layers.This result sheds light on the further exploration of new 2D hybrid perovskites toward high-performance photodetector applications.

层状有机-无机杂化钙钛矿(C_7H_(12)N_2)PbBr_4的合成、结构及发光性质

通过向杂化体系中引入特殊的有机配体2-(2-氨基乙基)吡啶,利用溶液冷却技术,合成了一种二维层状有机-无机杂化钙钛矿结构材料的化合物(C7H12N2)PbBr4的晶体。X射线单晶衍射结果表明,化合物(C7H12N2)PbBr4的单晶结构属于正交晶系,Pbca空间群,a=1.7023 nm,b=0.8289 nm,c=2.022 4 nm,Z=8。无机部分是由共顶点的PbBr6金属卤化物八面体组成的二维平面片层。采用了相对扭曲构型的有机胺阳离子与二维无机片层通过氢键作用组成了杂化钙钛矿结构。对其光学性质进行了测试。荧光光谱的特征发射峰出现在422 nm处。

Brightening thiocyanate-anion layered perovskite through internal stress modulated nano phase segregation

Thiocyanate-anion(SCN−)two-dimensional(2D)layered perovskite with internal stress-controlled nano phase segregation has been firstly demonstrated as a promising material system for luminescence applications.An interesting energy band structure is found as well as charge transfer process caused by nano phase segregation,which provide an alternative route to overcome the indirect-bandgap luminescence limit of SCN layered perovskites.It is revealed that,within the SCN layered framework,the segregated nano phases exist in a quantum well form,possessing much higher carrier localization and second-order radiative recombination abilities.With the help of internal stress modulation,these advantages can be significantly enhanced and finally contribute to high luminescence performances in visible-red regions.This work provides more potential opportunities for 2D layered perovskite materials in the future optoelectronic applications.

无机杂化钙钛矿团簇材料:介尺度钙钛矿材料发光性质研究

近年来,介尺度钙钛矿材料体系中钙钛矿魔幻尺寸团簇(PMSCs)材料因具有优异的半导体特性而在新兴光电器件领域极具潜力。然而,介尺度PMSCs容易在合成过程中生成尺寸较大的介尺度钙钛矿量子点(PQDs),难以满足实际应用的需求。本研究采用配体辅助再沉淀(LAPR)方法,通过调节戊酸(VA)和油胺(OAm)配体比例制备了不同发光性质的无机杂化介尺度钙钛矿材料CsPbBr_(3) PMSCs、CsPbBr_(3) PMSCs/CsPbBr_(3) PQDs混合物和CsPbBr_(3) PQDs,研究并分析了PQDs和PMSCs的光学性质、形貌结构、稳定性和介尺度结构演变机理。研究发现,表面协同钝化配体VA和OAm的比例是反应能否生成介尺度纯相CsPbBr_(3) PMSCs的关键。而且,当VA和OAm配体的表面钝化效果越佳越易生成发光性质优异的纯相CsPbBr_(3) PMSCs。

The first 2D organic-inorganic hybrid relaxor-ferroelectric single crystal

Inorganic relaxor ferroelectric solid solution single crystals are spurring new generations of high performance electromechanical devices,including transducers,sensors,and actuators,due to their ultrahigh electric field induced strain,large piezoelectric constant,high electromechanical coupling factor and low dielectric loss.However,relaxor ferroelectric single crystals found in organic-inorganic hybrid perovskites are very limited,but achieving these superior properties in them will be of great significance in the design of modern functional materials.Fortunately,here the first two-dimensional(2D)organic-inorganic hybrid relaxor ferroelectric single crystal,[Br(CH_(2))_(3)NH_(3)]_(2)PbBr_(4)(BPA_(2)-PbBr_(4),BPA=3-bromopropylamine),achieves some of superior properties.Interestingly,BPA_(2)-PbBr_(4)reveals a successive relaxor ferroelectric-ferroelectric-paraelectric phase transitions accompanying by a large degree of relaxationΔT_(relax)=61 K and ultralow energy loss(tanδ<0.001).Meanwhile,it exhibits a superior second harmonic generation(SHG)effect with maximum value accounts for 95%of the standard KDP due to great deformation of structure(3.2302×10^(-4)).In addition,temperature dependent luminescence spectra(80-415 K)exhibit fluorescence and phosphorescence overlapping emission originated from inorganic and organic components with the nanosecond-scale short lifetime and the millisecond-scale long lifetime,respectively,and the color of the emitted light is continuously adjustable,which is the first to achieve luminescence and relaxor ferroelectricity compatibility.

CH3NH3PbBr3钙钛矿纳米晶的室温合成及发光性能研究

有机-无机杂化钙钛矿材料因光吸收系数大、带隙直接且可调、载流子迁移率高、载流子扩散长度长等优势在光电器件领域显现巨大的应用前景.采用低温合成工艺,实现光学性能调控,对于扩展其应用具有重要研究价值.本文开发了一种室温下合成CH3NH3PbBr3纳米晶的简便方法,研究了反应时间对钙钛矿纳米晶的晶体结构和发光性能的影响.结果表明,当反应时间为24 h时,CH3NH3PbBr3纳米晶的结晶质量好,发光性能最优.

铜源对铜掺杂MAPbI3薄膜结构和光学性质的影响

有机-无机杂化钙钛矿(MAPbI3)材料已成为光电器件领域的先进材料,但铅元素的存在带来的环境污染问题严重影响钙钛矿材料的实际应用.以无毒性金属元素部分取代铅元素是推进其应用进程的途径之一.选用氯化铜和醋酸铜作为铜元素掺杂源,利用一步法合成铜掺杂钙钛矿薄膜,研究不同铜源对MAPbI3薄膜成膜质量和光学性质的影响,并揭示影响机制.

前驱体溶液老化时间对Mg掺杂MAPbI_3薄膜的形貌、结构及发光性质的影响

采用一步旋涂法在硅片基底上制备Mg掺杂MAPbI_3薄膜,探究溶液老化时间对Mg掺杂MAPbI_3薄膜成膜质量和发光性质的影响规律.利用SEM、XRD、PL等表征手段对薄膜的形貌、结构、光学特性进行研究,结果表明随着钙钛矿前驱体溶液老化时间的延长,薄膜形貌由致密薄膜逐渐演变为树枝状微米结构,发光强度降低.