Inorganic Sheets Research Articles

Tuning the Circular Dichroism and Circular Polarized Luminescence Intensities of Chiral 2D Hybrid Organic-Inorganic Perovskites through Halogenation of the Organic Ions.

Through the incorporation of various halogen-substituted chiral organic cations, the effects of chiral molecules on the chiroptical properties of hybrid organic-inorganic perovskites (HOIPs) are investigated. Among them, the HOIP having a Cl-substituted chiral cation exhibits the highest circular dichroism (CD) and circular polarized luminescence (CPL) intensities, indicating the existence of the largest rotatory strength, whereas the F-substituted HIOP shows the weakest intensities. The observed modulation can be correlated to the varied magnetic transition dipole of HOIPs, which is sensitive to the d-spacing between inorganic layers and the halogen-halogen interaction between organic cations and the inorganic sheets. These counteracting effects meet the optimal CD and CPL intensity with chlorine substitution, rendering the rotatory strength of HOIPs arranged in the order of (ClMBA)2 PbI4 >(BrMBA)2 PbI4 >(IMBA)2 PbI4 >(MBA)2 PbI4 >(FMBA)2 PbI4 .

Incorporating Guanidinium as Perovskitizer-Cation of Two-Dimensional Metal Halide for Crystal-Array Photodetectors.

Two-dimensional (2D) hybrid perovskites are recently emerging as a potential family of semiconductors for versatile optoelectronic applications. Currently, the "perovskitizer" moieties are rigidly limited to small-size cations, while few 2D metal-halides containing guanidinium cations inside perovskite cages have been studied for photodetection. Herein, we present a new 2D hybrid perovskite, (i-BA)2 (G)Pb2 I7 (where G is guanidinium and i-BA is isobutylammonium), which adopts a bilayered framework of {GPb2 I7 }. Single-crystal structure analyses disclose that G cations act as the perovskitizer, confined in the flexible perovskite cages formed by the distorted PbI6 octahedra. Such inorganic sheets are crucial to the superior semiconducting properties and optical bandgap, as verified by the density functional theory calculation. Furthermore, its planar crystal-array photodetector shows fascinating photoelectric performance, including a quite low dark current (∼4.6×10-11 A), a large current switching ratio (∼1.0×103 ), and a notable photo-responsivity of ∼0.72 A W-1 , suggesting great potential of (i-BA)2 (G)Pb2 I7 for photodetection.

Progress and perspective in Dion-Jacobson phase 2D layered perovskite optoelectronic applications

2D organic-inorganic halide perovskites have recently become the “next big thing” as promising candidates in optoelectronics. They possess higher moisture stability and lower ion migration compared to 3D perovskites due to the incorporation of bulky organic spacers. Compared to 2D Ruddlesden-Popper (RP) phase with two monoammoniums, 2D Dion-Jacobson (DJ) phase containing one diammonium has achieved a tighter connection between inorganic sheets due to formation of hydrogen bonds, resulting in higher crystal stability and more favorable charge transfer. RP phase solar cell has increased from 4.73% to 18.24% within six years, whereas DJ phase device shows a steep efficiency rise from 7.32% to 17.9% within only one year. Herein, this review provides in-depth understandings on optical property, orientation and charge transport, and energy band alignment of DJ phase perovskites, and raise perspectives that how they are affected by n value and diammoniums characteristics. The recent advances in solar cells, light-emitting diodes, and photodetectors have also been summarized. Finally, we discuss the remaining challenges of boosting device efficiency and try to answer the key scientific question that how to narrow phase distribution and engineer vertical orientation achieving the favorable energy alignment.

Effect of Compatibilizers on the Structure and Dynamics at Polymer Blend Interfaces

We use coarse grained Molecular Dynamics simulations to determine the effect of diblock copolymers and inorganic sheet like compatibilizers at polymer blend interfaces. Previous studies have shown that the interfacial region is prone to slip if an external shear force is applied to the polymer blend. While a number of theoretical and computational studies have examined the effect of copolymer compatibilizers, the effect of adding sheet-like compatilibilizers (for e.g. nanoclay) has not been investigated computationally. Thus, while experiments have shown that sheet-like filler are effective, the exact mechanisms are unknown. Our results indicate that sheet like fillers that have equal affinity to either polymer in a binary blend can produce a larger reduction of interfacial tension when compared to diblock copolymers at equal volume fractions. However, the localization of sheet fillers at the interface can be a possible limiting factor. We also show that sheet fillers reduce slip, thus providing for improved stress transfer across the interface, leading to a stronger blend.

New Radical Cation Salts Based on BDH-TTP Donor: Two Stable Molecular Metals with a Magnetic [ReF6]2− Anion and a Semiconductor with a [ReO4]− Anion

Three radical cation salts of BDH-TTP with the paramagnetic [ReF6]2− and diamagnetic [ReO4]− anions have been synthesized: κ-(BDH-TTP)4ReF6 (1), κ-(BDH-TTP)4ReF6·4.8H2O (2) and pseudo-κ″-(BDH-TTP)3(ReO4)2 (3). The crystal and band structures, as well as the conducting properties of the salts, have been studied. The structures of the three salts are layered and characterized by alternating κ-(1, 2) and κ″-(3) type organic radical cation layers with inorganic anion sheets. Similar to other κ-salts, the conducting layers in the crystals of 1 and 2 are formed by BDH-TTP dimers. The partial population of positions of Re atoms and disorder in the anionic layers of 1–3 are their distinctive features. Compounds 1 and 2 show the metallic character of conductivity down to low temperatures, while 3 is a semiconductor. The ac susceptibility of crystals 1 was investigated in order to test the possible slow relaxation of magnetization associated with the [ReF6]2− anion.

A Universal Approach for Controllable Synthesis of n-Specific Layered 2D Perovskite Nanoplates.

2D perovskites with chemical formula A'2 An-1 Bn X3n+1 have recently attracted considerable attention due to their tunable optical and electronic properties, which can be attained by varying the chemical composition. While high color-purity emitting perovskite nanomaterials have been accomplished through changing the halide composition, the preparation of single-phase, specific n-layer 2D perovskite nanomaterials is still pending because of the fast nucleation process of nanoparticles. We demonstrate a facile, rational and efficacious approach to synthesizing single-phase 2D perovskite nanoplates with a designated n number for both lead- and tin-based perovskites through kinetic control. Casting carboxylic acid additives in the reaction medium promotes selective formation of the kinetic product-multilayer 2D perovskite-in preference to the single-layer thermodynamic product. For the n-specific layered 2D perovskites, decreasing the number of octahedral layers per inorganic sheet leads to an increase of photoluminescence energy, radiative decay rate, and a significant boost in photostability.

A Universal Approach for Controllable Synthesis of n‐Specific Layered 2D Perovskite Nanoplates

Abstract2D perovskites with chemical formula A′2An−1BnX3n+1 have recently attracted considerable attention due to their tunable optical and electronic properties, which can be attained by varying the chemical composition. While high color‐purity emitting perovskite nanomaterials have been accomplished through changing the halide composition, the preparation of single‐phase, specific n‐layer 2D perovskite nanomaterials is still pending because of the fast nucleation process of nanoparticles. We demonstrate a facile, rational and efficacious approach to synthesizing single‐phase 2D perovskite nanoplates with a designated n number for both lead‐ and tin‐based perovskites through kinetic control. Casting carboxylic acid additives in the reaction medium promotes selective formation of the kinetic product—multilayer 2D perovskite—in preference to the single‐layer thermodynamic product. For the n‐specific layered 2D perovskites, decreasing the number of octahedral layers per inorganic sheet leads to an increase of photoluminescence energy, radiative decay rate, and a significant boost in photostability.

Strong Self-Trapped Exciton Emissions in Two-Dimensional Na-In Halide Perovskites Triggered by Antimony Doping.

Soft lattice and strong exciton-phonon coupling have been demonstrated in layered double perovskites (LDPs) recently; therefore, LDPs represents a promising class of compounds as excellent self-trapped exciton (STE) emitters for applications in solid-state lighting. However, few LDPs with outstanding STE emissions have been discovered, and their optoelectronic properties are still unclear. Based on the three-dimensional (3D) Cs2 NaInCl6 , we synthesized two 2D derivatives (PEA)4 NaInCl8 :Sb (PEA=phenethylamine) and (PEA)2 CsNaInCl7 :Sb with monolayer and bilayer inorganic sheets by a combination of dimensional reduction and Sb-doping. Bright broadband emissions were obtained for the first time under ambient temperature and pressure, with photoluminescence quantum efficiency (PLQE) of 48.7 % (monolayer) and 29.3 % (bilayer), superior to current known LDPs. Spectroscopic characterizations and first-principles calculations of excited state indicate the broadband emissions originate from STEs trapped at the introduced [SbCl6 ]3- octahedron.

Strong Self‐Trapped Exciton Emissions in Two‐Dimensional Na‐In Halide Perovskites Triggered by Antimony Doping

AbstractSoft lattice and strong exciton–phonon coupling have been demonstrated in layered double perovskites (LDPs) recently; therefore, LDPs represents a promising class of compounds as excellent self‐trapped exciton (STE) emitters for applications in solid‐state lighting. However, few LDPs with outstanding STE emissions have been discovered, and their optoelectronic properties are still unclear. Based on the three‐dimensional (3D) Cs2NaInCl6, we synthesized two 2D derivatives (PEA)4NaInCl8:Sb (PEA=phenethylamine) and (PEA)2CsNaInCl7:Sb with monolayer and bilayer inorganic sheets by a combination of dimensional reduction and Sb‐doping. Bright broadband emissions were obtained for the first time under ambient temperature and pressure, with photoluminescence quantum efficiency (PLQE) of 48.7 % (monolayer) and 29.3 % (bilayer), superior to current known LDPs. Spectroscopic characterizations and first‐principles calculations of excited state indicate the broadband emissions originate from STEs trapped at the introduced [SbCl6]3− octahedron.

A new organic–inorganic hybrid compound (NH3(CH2)C6H4CO2H)[SnCl6]: Synthesis, crystal structure, vibrational, optical, magnetic properties and theoretical study

A new organic-inorganic hybrid (NH3(CH2)C6H4CO2H)[SnCl6] crystallizes in a triclinic system (P-1 space group) at room temperature, with unit cell parameters of a = 6.8643(2) Å, b = 6.9777(2) Å, c = 14.0056(5) Å, α = 91.120(2)°, β = 97.232(2)°, γ = 118.476(2) and Z = 2. Its structure is determined by single-crystal X-ray diffraction, revealing that the crystal structure is stabilized by hydrogen bonding between +[NH3CH2C6H4CO2H] cations and isolated [SnCl6]− anions to form organic and inorganic sheets parallel to the (a,b) plane and stacked along the c-axis. Hirshfeld surface analysis and fingerprint plots were utilized to elucidate the intermolecular interactions. X-ray photoelectron spectroscopy (XPS) is employed to confirm the phase purity, and micro-Raman spectroscopy is employed to probe the vibration modes. In addition, the compound is characterised by vibrating sample magnetometer (VSM) measurements as well as UV–visible absorption spectroscopy. The Raman and UV–visible spectra predicted by density functional theory (DFT) are in good agreement with the experimental Raman and UV–visible spectra.

Tuning the Excitonic Properties of the 2D (PEA)2(MA)n-1PbnI3n+1 Perovskite Family via Quantum Confinement.

In atomically thin two-dimensional (2D) crystals, the excitonic properties and band structure scale strongly with the thickness, providing a new playground for the investigation of exciton physics in the ultimate confinement regime. Here, we demonstrate the evolution of the fundamental excitonic properties, such as reduced mass, wave function extension, and exciton binding energy, in the 2D perovskite (PEA)2(MA)n-1PbnI3n+1, for n = 1, 2, 3. These parameters are experimentally determined using optical spectroscopy in a high magnetic field up to 65 T. The observation of the interband Landau level transitions provides direct access to the reduced effective mass μ and band gap Eg. We show that μ increases with the number of inorganic sheets n, reaching the value of three-dimensional (3D) MAPbI3 already for n = 3. Our experimental observations contradict the general expectation that quantum confinement leads to an enhanced carrier mass, showing another aspect of the unprecedented flexibility in the design of the electronic properties of 2D perovskites.

Synthesis and characterization of montmorillonite/polyaniline composites and its usage to modify a commercial separator

Composites of montmorillonite (MMT) and polyaniline (PANI) were synthetized through a facile and inexpensive method. Two samples with different MMT:PANI ratios were studied and deeply characterized by XRD, TG, zeta potential, FTIR and XPS measurements. On one hand, the sample with ratio MMT:PANI = 87:13 was an intercalated composite, were polyaniline resides between the inorganic layers of the clay at a regular distance. On the other hand, the sample with ratio MMT:PANI = 12:88 was an exfoliated composite, where the inorganic sheets are immersed in an amorphous polymeric matrix. FTIR and XRD results indicated that in both samples, the emeraldine form of polyaniline was obtained. The composites were used to modify -by dr. blade technique- a commercial separator for lithium-ion batteries (LIBs) with the aim of increasing its wettability, ionic conductivity and electrochemical performance. The three-dimensional and multilayered network structure of the MMT/PANI composites led to an enhancement of the electrolyte uptake capacity (from 32% in bare separator to 137% and 168% for MMT/PANI_87/13 and MMT/PANI_12/88 modified separators, respectively, after 3 h). The presence of the coating membrane also led to an increase of the ionic conductivity by one order of magnitude in the modified separators respect to the unmodified one. These coated and non-coated separators were used to assemble full cells with LiNi1.5Mn0.5O4 as cathode active material. The capacity fade after 200 cycles was 20% lower in the cell with MMT/PANI_12/88 membrane in comparison with the bare separator. The enhancement of the electrochemical performance of the cells with the coated separator suggests that is a promising strategy to be used in LIBs.

Giant and Broadband Multiphoton Absorption Nonlinearities of a 2D Organometallic Perovskite Ferroelectric.

Multiphoton absorption (MPA) has been utilized for important technological applications. High-order multiphoton harvesting (e.g., five-photon absorption, 5PA) exhibits unique properties that could benefit biophotonics. Within this field, perovskite oxide ferroelectrics (e.g., BaTiO3 ) enable low-order optical nonlinearities of 2PA/3PA processes. However, it is challenging to obtain efficient, high-order 5PA effects. Herein, for the first time, giant and broadband MPA properties are presented in the 2D hybrid perovskite ferroelectric (IA)2 (MA)2 Pb3 Br10 (1; IA = isoamylammonium and MA = methylammonium), where multiphoton-excited optical nonlinearities related to different MPA mechanisms over a broadband range of 550-2400 nm are observed. Strikingly, its 5PA absorption cross-section (σ5 ) reaches up to 1.2 × 10-132 cm10 s4 photon-4 (at 2400 nm), almost 10 orders larger than some state-of-the-art organic molecules and a record-high value among all known ferroelectrics. This unprecedented 5PA effect results from the quantum-confined motif of inorganic trilayer sheets (wells) and organic cations (barriers) in 1. Moreover, its large ferroelectric polarization of 5 µC cm-2 could promote modulation of MPA effects under external electric fields. As far as it is known, this is the first report on giant, broadband high-order MPA properties in ferroelectrics, which provides potential, novel electric-ordered materials for next-generation biophotonic applications.

Tunable exciton binding energy in 2D hybrid layered perovskites through donor-acceptor interactions within the organic layer.

The strength of electrostatic interactions within semiconductors strongly affects their performance in optoelectronic devices. An important target is the tuning of a material's exciton binding energy-the energy binding an electron-hole pair through the electrostatic Coulomb force-independent of its electronic band gap. Here, we report on the doping of a family of two-dimensional hybrid perovskites, in which inorganic lead halide sheets alternate with naphthalene-based organic layers, with tetrachloro-1,2-benzoquinone (TCBQ). For four out of seven n = 1 perovskites, the incorporation of the electron-accepting TCBQ dopant into the organic sublattice containing the electron-donating naphthalene species enabled the tuning of the materials' 1s exciton binding energy. The naphthalene-TCBQ electron donor-acceptor interactions increased the electrostatic screening of the exciton, in turn lowering its binding energy relative to the undoped perovskite-by almost 50% in one system. Structural and optical characterization showed that the inorganic lattice is not significantly perturbed even though the layer-to-layer spacing increases upon molecular dopant incorporation.

Room-Temperature Ferroelectric Material Composed of a Two-Dimensional Metal Halide Double Perovskite for X-ray Detection.

Although two-dimensional (2D) metal-halide double perovskites display versatile physical properties due to their huge structural compatibility, room-temperature ferroelectric behavior has not yet been reported for this fascinating family. Here, we designed a room-temperature ferroelectric material composed of 2D halide double perovskites, (chloropropylammonium)4 AgBiBr8 , using an organic asymmetric dipolar ligand. It exhibits concrete ferroelectricity, including a Curie temperature of 305 K and a notable spontaneous polarization of ≈3.2 μC cm-2 , triggered by dynamic ordering of the organic cation and the tilting motion of heterometallic AgBr6 /BiBr6 octahedra. Besides, the alternating array of inorganic perovskite sheets and organic cations endows large mobility-lifetime product (μτ=1.0×10-3 cm2 V-1 ) for detecting X-ray photons, which is almost tenfold higher than that of CH3 NH3 PbI3 wafers. As far as we know, this is the first study on an X-ray-sensitive ferroelectric material composed of 2D halide double perovskites. Our findings afford a promising platform for exploring new ferroelectric materials toward further device applications.

Room‐Temperature Ferroelectric Material Composed of a Two‐Dimensional Metal Halide Double Perovskite for X‐ray Detection

AbstractAlthough two‐dimensional (2D) metal–halide double perovskites display versatile physical properties due to their huge structural compatibility, room‐temperature ferroelectric behavior has not yet been reported for this fascinating family. Here, we designed a room‐temperature ferroelectric material composed of 2D halide double perovskites, (chloropropylammonium)4AgBiBr8, using an organic asymmetric dipolar ligand. It exhibits concrete ferroelectricity, including a Curie temperature of 305 K and a notable spontaneous polarization of ≈3.2 μC cm−2, triggered by dynamic ordering of the organic cation and the tilting motion of heterometallic AgBr6/BiBr6 octahedra. Besides, the alternating array of inorganic perovskite sheets and organic cations endows large mobility‐lifetime product (μτ=1.0×10−3 cm2 V−1) for detecting X‐ray photons, which is almost tenfold higher than that of CH3NH3PbI3 wafers. As far as we know, this is the first study on an X‐ray‐sensitive ferroelectric material composed of 2D halide double perovskites. Our findings afford a promising platform for exploring new ferroelectric materials toward further device applications.

Dimensional Reduction of Cs2 AgBiBr6 : A 2D Hybrid Double Perovskite with Strong Polarization Sensitivity.

By dimensional reduction of the 3D motif of Cs2 AgBiBr6 , a lead-free 2D hybrid double perovskite, (i-PA)2 CsAgBiBr7 (1, i-PA=isopentylammonium), was successfully designed. It adopts a quantum-confined bilayered structure with alternating organic and inorganic sheets. Strikingly, the unique 2D architecture endows it highly anisotropic nature of physical properties, including electric conductivity and optical absorption (the ratio αb /αc =1.9 at 405 nm). Such anisotropy attributes result in the strong polarization-sensitive responses with large dichroic ratios up to 1.35, being comparable to some 2D inorganic materials. This is the first study on the hybrid double perovskites with strong polarization sensitivity. A crystal device of 1 also exhibits rapid response speed (ca. 200 μs) and excellent stabilities. The family of 2D hybrid double perovskites are promising optoelectronic candidates, and this work paves a new pathway for exploring new green polarization-sensitive materials.

Dimensional Reduction of Cs2AgBiBr6: A 2D Hybrid Double Perovskite with Strong Polarization Sensitivity

AbstractBy dimensional reduction of the 3D motif of Cs2AgBiBr6, a lead‐free 2D hybrid double perovskite, (i‐PA)2CsAgBiBr7 (1, i‐PA=isopentylammonium), was successfully designed. It adopts a quantum‐confined bilayered structure with alternating organic and inorganic sheets. Strikingly, the unique 2D architecture endows it highly anisotropic nature of physical properties, including electric conductivity and optical absorption (the ratio αb/αc=1.9 at 405 nm). Such anisotropy attributes result in the strong polarization‐sensitive responses with large dichroic ratios up to 1.35, being comparable to some 2D inorganic materials. This is the first study on the hybrid double perovskites with strong polarization sensitivity. A crystal device of 1 also exhibits rapid response speed (ca. 200 μs) and excellent stabilities. The family of 2D hybrid double perovskites are promising optoelectronic candidates, and this work paves a new pathway for exploring new green polarization‐sensitive materials.

Two-dimensional organic–inorganic superlattice-like heterostructures for energy storage applications

Recent progress in 2D organic–inorganic superlattices by alternate stacking of organic layers and inorganic sheets is reviewed.

Protein–inorganic nano hybrid sheets of Pd embedded BSA as a robust catalyst in water for oxidase mimic activity and C–C coupling reactions, and as a sustainable material for micromolar sensing of dopamine

A new nano-hybrid sheet material using palladium and BSA protein (Pd_NP@BSAsheet) was developed as a sustainable catalyst for C–C coupling reactions in water, as an oxidase enzyme mimic and for the detection of dopamine in buffer, human serum and urine.