Hybrid Metal Halide Research Articles

High Quantum Efficiency of Stable Sb‐Based Perovskite‐Like Halides toward White Light Emission and Flexible X‐Ray Imaging

AbstractAlthough low‐dimensional hybrid metal halides have emerged as promising light emitters due to their broadband emission originated from self‐trapped exciton (STE), the synthesis of lead‐free halides with high photoluminescence quantum yield remains a challenge. Herein, a series of new luminescent single crystals of antimony‐based metal halides [Na(DMSO)2]3SbBr6−xClx (x = 0, 2, 3, 4, 6) is synthesized. By optimizing the ratio of Br and Cl, [Na(DMSO)2]3SbBr3Cl3 exhibits an ultra‐broadband yellow light emission peaking at 606 nm with a full width at half‐maximum of 160 nm and a high photoluminescence quantum yield of 90.6%. Both experimental characterizations and theoretical calculations indicate that STE emission is responsible for the ultra‐broadband yellow light emission. Furthermore, blue LED chip‐pumped white light‐emitting diodes by using the yellow‐emitting [Na(DMSO)2]3SbBr3Cl3 are demonstrated, showing a correlated color temperature of 3948 K and a color rendering index of 85. Finally, a large‐size and flexible [Na(DMSO)2]3SbBr3Cl3 scintillator used for X‐ray imaging is prepared by a template assembled method, exhibiting a high spatial resolution of 15.5 lp mm−1 and a low detection limit of 285.8 nGyair s−1. This work highlights the potential of Sb‐based halides in solid‐state illumination and X‐ray imaging.

Organic Cation-Directed Modulation of Emissions in Zero-Dimensional Hybrid Tin Bromides.

Zero-dimensional hybrid metal halides (0D HMHs) are attractive due to their intriguing self-trapped exciton (STE) emission properties. However, the effect of organic cations on the emission of 0D HMHs is relatively underexplored. Herein, we report two types of 0D hybrid tin bromides, (BMe)2SnBr6 (BMe = C8N2H18) and (MeH)2SnBr6 (MeH = C7N2H16), which share similar structural features with different hydrogen bonding (HB) interactions between [SnBr6]4- anions and organic cations. The (BMe)2SnBr6 with weak HB interactions exhibits only STE emission, while the (MeH)2SnBr6 exhibits both STE and charge transfer exciton emissions owing to the strong HB interactions, resulting in an excitation-dependent emission at cryogenic conditions. Detailed structural analyses and Hirshfeld surface calculations confirm that the enhanced HB interactions are essential to obtain the multiple emissions in (MeH)2SnBr6.

Induction of Chiral Hybrid Metal Halides from Achiral Building Blocks.

Chiral hybrid organic-inorganic metal halides (HOMHs) with intrinsic noncentrosymmetry have shown great promise for broad applications in chiroptoelectronics, spintronics, and ferroelectronics. However, the construction strategies for chiral HOMHs often involve chiral building blocks in their frameworks, which greatly limit their chemical diversity. Here, we take advantage of a chiral induction approach and have successfully constructed a series of chiral HOMHs, DMA4MX7 (DMA = dimethylammonium, M = Sb or Bi, X = Cl or Br), based on achiral precursors. The resulting chiral products demonstrate a clear enantioenrichment, as confirmed by single-crystal X-ray diffraction analysis and solid-state circular dichroism (CD) spectroscopy. The induction of chiral HOMHs enables superior nonlinear optical performances with very high thermal stability and laser resistance. The successful employment of such a chiral induction approach might facilitate the construction of libraries of chiral HOMH crystals from diverse achiral precursors, in particular those into which it is not easy to introduce intrinsic chiral centers, and would thus pave a new way for rational preparation and application of chiral HOMH materials.

Charge Transport and Photoconductivity in a Hybrid Uranium(IV) Halide Perovskite.

Hybrid metal halide perovskites are extensively synthesized using p- and d-elements. However, the properties of hybrid halide perovskites involving 5f-elements are still elusive. Herein, we first report the semiconductive property of a uranium-bearing hybrid halide perovskite, [N(C2H5)4]2UCl6 (EAUCl). Single crystal X-ray crystallography demonstrates that EAUCl adopts a zero-dimensional molecular structure consisting of isolated [UCl6]2- anions and organic cations. The intrinsically semiconductive property endows EAUCl with obvious charge transport and photoconductivity, with a high carrier mobility lifetime (μτ) product of 9.91 × 10-4 cm2/V and a photocurrent on-off ratio of 380 under X-ray excitation. Theoretical calculations corroborate that the U 5f orbitals are involved in electron transitions and the formation of band structure.

Dimensional Control of Chiral Antimony Halide Compounds for Enhanced Circular Dichroism

Chiral organic–inorganic hybrid metal halides have a strong structure–property relationship, such as that the modification of their structural dimensionality can adjust their chiroptical properties. Here, based on chiral organic molecules R/S-methylbenzylamine (R/S-MBA), we synthesized new chiral antimony halides with structures from zero-dimensional (0D) (R/S-MBA)2SbI5to one-dimensional (1D) (R/S-MBA)SbI4. The chirality transfer from chiral ligands to the inorganic framework was analyzed based on the electrical dipole moment of R/S-MBA. The anisotropy factor of circular dichroism (gCD) of this 1D chiral (R/S-MBA)SbI4 is determined to be about ∼0.02, which is about 1 order of magnitude larger than that of the 0D (R/S-MBA)2SbI5.

The Pnictogen Bond, Together with Other Non-Covalent Interactions, in the Rational Design of One-, Two- and Three-Dimensional Organic-Inorganic Hybrid Metal Halide Perovskite Semiconducting Materials, and Beyond.

The pnictogen bond, a somewhat overlooked supramolecular chemical synthon known since the middle of the last century, is one of the promising types of non-covalent interactions yet to be fully understood by recognizing and exploiting its properties for the rational design of novel functional materials. Its bonding modes, energy profiles, vibrational structures and charge density topologies, among others, have yet to be comprehensively delineated, both theoretically and experimentally. In this overview, attention is largely centered on the nature of nitrogen-centered pnictogen bonds found in organic-inorganic hybrid metal halide perovskites and closely related structures deposited in the Cambridge Structural Database (CSD) and the Inorganic Chemistry Structural Database (ICSD). Focusing on well-characterized structures, it is shown that it is not merely charge-assisted hydrogen bonds that stabilize the inorganic frameworks, as widely assumed and well-documented, but simultaneously nitrogen-centered pnictogen bonding, and, depending on the atomic constituents of the organic cation, other non-covalent interactions such as halogen bonding and/or tetrel bonding, are also contributors to the stabilizing of a variety of materials in the solid state. We have shown that competition between pnictogen bonding and other interactions plays an important role in determining the tilting of the MX6 (X = a halogen) octahedra of metal halide perovskites in one, two and three-dimensions. The pnictogen interactions are identified to be directional even in zero-dimensional crystals, a structural feature in many engineered ordered materials; hence an interplay between them and other non-covalent interactions drives the structure and the functional properties of perovskite materials and enabling their application in, for example, photovoltaics and optoelectronics. We have demonstrated that nitrogen in ammonium and its derivatives in many chemical systems acts as a pnictogen bond donor and contributes to conferring stability, and hence functionality, to crystalline perovskite systems. The significance of these non-covalent interactions should not be overlooked, especially when the focus is centered on the rationale design and discovery of such highly-valued materials.

Tunable emission color of [(2-mb)tpp]2Cd1-xMnxCl4 (x = 0–1) solid solutions synthesized via mechanochemical method for anti-counterfeit luminescent paper and WLEDs

Zero-dimensional (0D) hybrid metal halides (HMHs) have received widespread concern due to their unique structures and splendid luminescent properties. However, the syntheses of HMHs primarily rely on crystal growth methods in solution or ion-thermal conditions, which are time-consuming and require extensive use of organic solvents. On the other hand, the reported HMHs usually exhibiting only one emission color hinder their further applications. Herein, we report a series of 0D HMHs solid solutions of [(2-mb)tpp]2Cd1-xMnxCl4 [(2-mb)tpp = (2-methylbenzyl)triphenylphosphine and x = 0–1] synthesized through a facile mechanochemical method. The emission color of [(2-mb)tpp]2Cd1-xMnxCl4 can be tuned from purplish-blue, bluish-green, to green light by adjusting the Cd/Mn molar ratio or excitation wavelength. Thus different luminescent panda and quick response (QR) code patterns can be designed with [(2-mb)tpp]2Cd1-xMnxCl4 as luminescent dyes for potential applications in multicolor imaging and anti-counterfeiting encryption. Moreover, owing to the excellent thermal stability, the as-fabricated white light emitting diode (WLED) with [(2-mb)tpp]2MnCl4 as the green phosphor possesses an applicable correlated color temperature (CCT = 5305 K), an ultrahigh color rendering index (CRI, Ra = 95.4), and the CIE chromaticity coordinates of (0.3386, 0.3864) corresponding to pure white light. This work provides guidance for the rapid, facile, economical, and large-scale synthesis of HMHs with multiple luminescent centers, and exhibits the development of these materials in potential applications such as anti-counterfeiting luminescent papers and WLEDs.

Organic Cation Modulation Triggered Second Harmonic Response in Manganese Halides with Bright Fluorescence.

Zero-dimensional (0D) hybrid manganese halides have been recently synthesized and exhibited rich functional properties including fluorescence, ferroelectrics, and ferromagnetism. However, few studies on second-harmonic generation (SHG) behaviors of manganese halide crystals have been reported, presumably owing to the d-d transitions. Here, we report three manganese bromides, [TEA]2MnBr4 (TEA+ = tetraethylammonium; 1), [BTEA]2MnBr4 (BTEA+ = benzyltriethylammonium; 2), and [BTMA]2MnBr4 (BTMA+= benzyltrimethylammonium; 3), with linear and nonlinear optical properties via benzyl or ethyl/methyl substitution strategies. They feature 0D structures containing isolated [MnBr4]2- anions and quaternary ammonium cations with different sizes inserted for charge balance. They all show green phosphorescence, and 2 possesses good luminescence efficiency with a quantum yield of 97.8%, which is larger than those of 1 (79%) and 3 (72%). Specifically, acentric 1 and 3 present effective SHG responses about 0.48 and 0.59 times that of KDP, respectively. The result throws light on the new properties of the hybrid manganese halides and provides a new way to develop novel nonlinear optical-active organic-inorganic hybrid metal halides.

Highly Distorted Antimony(III) Chloride [Sb2Cl8]2− Dimers for Near‐Infrared Luminescence up to 1070 nm

AbstractZero‐dimensional (0D) hybrid metal halides with unique compositional and structural tunability appear as an emerging class of luminescent materials, but near‐infrared (NIR) emitters therein are largely unexplored to date. This study presents three novel 0D hybrid antimony chlorines with edge‐sharing [Sb2Cl8]2− dimers, showing unusual room‐temperature broadband NIR emission with the maximum emission wavelength up to 1070 nm. Photoluminescence studies and density functional theory calculation demonstrate that the emissions originate from the highly localized excitons, and that the confined [Sb2Cl8]2− dimers in these structures show low symmetry and a large degree of structural freedom. These hybrid antimony chlorines with [Sb2Cl8]2− dimers expand the range of new NIR materials in 0D metal halides.

Zero-dimensional Hybrid Antimony Halide with Intrinsic Cyan Light Emission.

Recently, zero-dimensional (0D) hybrid metal halides have attracted intensive attention with wide applications in solid-state lighting and display diodes. Herein, by using a facile wet-chemistry method, we prepared one new 0D hybrid antimony halide of [HMHQ]2 SbCl5 ⋅ 2H2 O (MHQ=2-methyl-8-hydroxyquinoline) based on the discrete [SbCl5 ]2- unit. Remarkably, the bulk crystals of [HMHQ]2 SbCl5 ⋅ 2H2 O exhibit strong cyan light emission with a promising photoluminescence quantum yield (PLQY) of 18.92%. Systematical studies disclose that the cyan emission is mainly derived from the radiative recombination within conjugated organic cation. Benefiting from the promising luminescent performance, this 0D antimony halide can be utilized as an excellent down-conversion light emitting luminescent material to assemble white light-emitting diodes with high color rendering index (CRI) of 90.2.

Highly Distorted Antimony(III) Chloride [Sb2Cl8]2− Dimers for Near‐Infrared Luminescence up to 1070 nm

Zero-dimensional (0D) hybrid metal halides with unique compositional and structural tunability appear as an emerging class of luminescent materials, but near-infrared (NIR) emitters therein are largely unexplored to date. This study presents three novel 0D hybrid antimony chlorines with edge-sharing [Sb2 Cl8 ]2- dimers, showing unusual room-temperature broadband NIR emission with the maximum emission wavelength up to 1070 nm. Photoluminescence studies and density functional theory calculation demonstrate that the emissions originate from the highly localized excitons, and that the confined [Sb2 Cl8 ]2- dimers in these structures show low symmetry and a large degree of structural freedom. These hybrid antimony chlorines with [Sb2 Cl8 ]2- dimers expand the range of new NIR materials in 0D metal halides.

Enhanced Stokes Shift and Phase Stability by Cosynthesizing Perovskite Nanoparticles (MAPbI3/MAPbBr3) in a Single Solution

Herein, diblock copolymer reverse micelle templating (RMD) is used to control the reaction kinetics of metal halide hybrid perovskites formation to fabricate systems showing dual‐phase emission. Through micelle templating, desired compositions can be engineered which show high phase stability of mixtures of perovskite nanoparticles (NPs) through micellar shielding and stabilizing of the cage structure. In addition, Stokes shift of around 150 nm, one of the largest reported for perovskite systems, can be obtained with careful control over synthesis kinetics. Using an unconventional approach, that is, mixing methylammonium iodide (MAI) and lead bromide PbBr2, systems consisting of both green‐ and red‐emitting NPs are fabricated by a two‐step reaction process using RMD. By obtaining two stable phases in a single solution, the NP system can absorb in the ultraviolet region and emit in the red region, making them excellent candidates for downconversion to improve solar cells efficiency, as shown for two polymer active layers in organic bulk heretojunction solar cells (OPVs). Exploiting the phase stabilizing effect of the micelles, the reaction kinetics of perovskite formation can be tuned for various halide substitutions, opening up new avenues for coexisting perovskite phases for photovoltaic and light‐emitting applications.

Photoinduced large polaron transport and dynamics in organic–inorganic hybrid lead halide perovskite with terahertz probes

Organic-inorganic hybrid metal halide perovskites (MHPs) have attracted tremendous attention for optoelectronic applications. The long photocarrier lifetime and moderate carrier mobility have been proposed as results of the large polaron formation in MHPs. However, it is challenging to measure the effective mass and carrier scattering parameters of the photogenerated large polarons in the ultrafast carrier recombination dynamics. Here, we show, in a one-step spectroscopic method, that the optical-pump and terahertz-electromagnetic probe (OPTP) technique allows us to access the nature of interplay of photoexcited unbound charge carriers and optical phonons in polycrystalline CH3NH3PbI3 (MAPbI3) of about 10 μm grain size. Firstly, we demonstrate a direct spectral evidence of the large polarons in polycrystalline MAPbI3. Using the Drude–Smith–Lorentz model along with the Frӧhlich-type electron-phonon (e-ph) coupling, we determine the effective mass and scattering parameters of photogenerated polaronic carriers. We discover that the resulting moderate polaronic carrier mobility is mainly influenced by the enhanced carrier scattering, rather than the polaron mass enhancement. While, the formation of large polarons in MAPbI3 polycrystalline grains results in a long charge carrier lifetime at room temperature. Our results provide crucial information about the photo-physics of MAPbI3 and are indispensable for optoelectronic device development with better performance.

Large-Area Uniaxial-Oriented Growth of Free-Standing Thin Films at the Liquid-Air Interface with Millimeter-Sized Grains.

Manipulating materials at the atomic scale and assembling them into macroscopic structures with controlled dimensionalities and single-crystal quality are grand scientific challenges. Here, we report a general solvent evaporation method to synthesize large-area uniaxial-oriented growth of free-standing thin films at the liquid-air interface. Crystals nucleate at the solution surface and rotate into the same orientation under electrostatic interaction and then merge as large crystals and grow laterally into a large-area uniform thin film with millimeter-sized grains. The lateral dimension is confined only by the size of containers. The film thickness can be tuned by adjusting solvent evaporation rate (R) and solute diffusivity (D), and a characteristic length, , was derived to estimate the film thickness. Molecular dynamic (MD) simulations reveal a concentration spike at the liquid-air interface during fast solvent evaporation, leading to the lateral growth of thin films. The large-area uniaxial oriented films are demonstrated on both inorganic metal halides and hybrid metal halide perovskites. The solvent evaporation approach and the determination of key parameters enabling film thickness prediction are beneficial to the high throughput and scalable production of single crystal-quality thin film materials under controlled evaporation conditions.

Environmental-friendly lead-free chiral Mn-based metal halides with efficient circularly polarized photoluminescence at room temperature

In recent years, chiral organic-inorganic hybrid metal halides have attracted more and more attention from researchers. However, most chiral metal halides are based on toxic Pb elements. In this work, we first successfully prepared a pair of lead-free manganese-based metal halide enantiomers (R/S-1-PPA) 2 MnBr 4 (R/S-1-PPA=R/S-1-Phenylpropan-1-amine). Under the excitation of 365 nm UV light, (R/S-1-PPA) 2 MnBr 4 exhibited bright green emission, which can be attributed to the spin-forbidden d-d transition of Mn 2+ . In addition, the decay lifetimes were as high as 32.57 μs and 33.60 μs for (R-1-PPA) 2 MnBr 4 and (S-1-PPA) 2 MnBr 4 , respectively. (R/S-1-PPA) 2 MnBr 4 showed notable circular dichroism (CD) signals and displayed highly efficient circularly polarized photoluminescence (CPPL) at room temperature with the large g lum of − 0.01 and 0.008, respectively. The high g lum enables them to be a series of very promising materials for the development of chiral optoelectronic devices based on chiral hybrid metal halides. Finally, the white LED device constructed with (R-1-PPA) 2 MnBr 4 also showed a wide color gamut, as high as 107% of NTSC, and a "warm" white light-correlated color temperature of 6883 K, which indicated it has good competitiveness in the application of white light LED devices. • We synthesized a pair of Pb-free Mn-based chiral metal halides (R/S-1-PPA) 2 MnBr 4 . • The halides emitted green CPPL, with g lum of − 0.01 and 0.008 at room temperature. • The g lum represent the maximum of the reported Mn-based metal halides.

Frontispiece: Luminescent Organic‐Inorganic Hybrid Metal Halides: An Emerging Class of Stimuli‐Responsive Materials

Frontispiece: Luminescent Organic‐Inorganic Hybrid Metal Halides: An Emerging Class of Stimuli‐Responsive Materials

Two [Co(bipy)3]3+-Templated Silver Halobismuthate Hybrids: Syntheses, Structures, Photocurrent Responses, and Theoretical Studies.

Employing in situ-generated metal complexes as structural decorating agents, we, for the first time, isolated two [Co(bipy)3]3+-templated silver halobismuthate hybrids, namely [Co(bipy)3]2Ag4Bi2X16 (X = Br (1), I (2); bipy = 2,2'-bipyridine). Compounds 1 and 2 belong to the isomorphic phrases and exhibit the nonperovskite structures characteristic of the discrete [Ag4Bi2X16]6- anions. UV-vis absorption spectra analyses showed that the optical band gaps of compounds 1 and 2 are 2.40 and 1.95 eV, respectively, implying the visible light responding semiconductor properties. Moreover, under the alternate light illumination, the title compounds exhibited "on/off" photocurrent behaviors, with high photocurrent densities comparable to many metal halide hybrids. Presented in this work also involved the Hirshfeld surface analyses and X-ray photoelectron spectroscopy studies together with the theoretical band structures, density of states, and electron wave functions.

Structural Origin of Enhanced Circularly Polarized Luminescence in Hybrid Manganese Bromides

AbstractChiral hybrid metal halides with a high dissymmetry factor (glum) and a superior photoluminescence quantum yield (PLQY) are promising candidates for circularly polarized luminescence (CPL) light sources. Here, we report eight new chiral hybrid manganese halides, crystallizing in the non‐centrosymmetric space group P212121 and showing intense CPL emissions. Oppositely‐signed circular dichroism (CD) and CPL signals are detected according to the R‐ and S‐configurations of the chiral alkanolammonium cations. Time‐resolved PL spectra show long averaged decay lifetimes up to 1 ms for (R‐3‐quinuclidinol)MnBr3 (R‐1). The glum of polycrystalline samples for coordinated structures (23×10−3) is more than doubled compared with the non‐coordinated ones (8.5×10−3), due to the structural variations. R‐1 exhibit both a high glum and a high PLQY (50.2 %). The effective chirality transfer mechanism through coordination bonds, with strongly emissive MnII centers, enables a new class of high‐performance CPL materials.

Luminescent Organic‐Inorganic Hybrid Metal Halides: An Emerging Class of Stimuli‐Responsive Materials

Luminescent organic-inorganic metal halides (OIMHs) are well known as a new materials family in recent years. Novel materials and applications of luminescent OIMHs have been explored by changing either the organic component or the metal halide species. Thereinto, the stimuli-responsive (SR) phenomena in OIMHs have drawn much attention recently, for not only their attractive application potential but also the helpfulness in understanding the stability of OIMHs to the external environment. Herein, the luminescent OIMHs that are sensitive to external stimuli including contact, pressure, mechanical grinding, light, heat, and gas molecules, are reviewed, with an emphasis on analyses of the structural change during the SR process. The applications of SR luminescent OIMHs in widespread fields, including gas sensing, information encryption, and rewritable luminescent paper are summarized. Finally, the challenges that deserve to be further explored in this research field are discussed, which provides certain guidance for the future study of SR luminescent OIMHs.

Structural Origin of Enhanced Circularly Polarized Luminescence in Hybrid Manganese Bromides.

Chiral hybrid metal halides with a high dissymmetry factor (glum ) and a superior photoluminescence quantum yield (PLQY) are promising candidates for circularly polarized luminescence (CPL) light sources. Here, we report eight new chiral hybrid manganese halides, crystallizing in the non-centrosymmetric space group P21 21 21 and showing intense CPL emissions. Oppositely-signed circular dichroism (CD) and CPL signals are detected according to the R- and S-configurations of the chiral alkanolammonium cations. Time-resolved PL spectra show long averaged decay lifetimes up to 1 ms for (R-3-quinuclidinol)MnBr3 (R-1). The glum of polycrystalline samples for coordinated structures (23×10-3 ) is more than doubled compared with the non-coordinated ones (8.5×10-3 ), due to the structural variations. R-1 exhibit both a high glum and a high PLQY (50.2 %). The effective chirality transfer mechanism through coordination bonds, with strongly emissive MnII centers, enables a new class of high-performance CPL materials.