High-Performance and Self-Powered X-Ray Detectors Made of Smooth Perovskite Microcrystalline Films with 100 μm Grains

Perovskite single crystals and polycrystalline films have complementary merits and deficiencies in X-ray detection and imaging. Herein, we report preparation of dense and smooth perovskite microcrystalline films with both merits of single crystals and polycrystalline films through polycrystal-induced growth and hot-pressing treatment (HPT). Utilizing polycrystalline films as seeds, multi-inch-sized microcrystalline films can be in situ grown on diverse substrates with maximum grain size reaching 100 μm, which endows the microcrystalline films with comparable carrier mobility-lifetime (μτ) product as single crystals. As a result, self-powered X-ray detectors with impressive sensitivity of 6.1×10⁴ μC Gy_air⁻¹ cm⁻² and low detection limit of 1.5 nGy_air s⁻¹ are achieved, leading to high-contrast X-ray imaging at an ultra-low dose rate of 67 nGy_air s⁻¹. Combining with the fast response speed (186 μs), this work may contribute to the development of perovskite-based low-dose X-ray imaging.     

Centimeter-Sized Single Crystal of Two-Dimensional Halide Perovskites Incorporating Straight-Chain Symmetric Diammonium Ion for X-Ray Detection

Two-dimensional (2D) AA′_n−1M_nX_3n+1 type halide perovskites incorporating straight-chain symmetric diammonium cations define a new type of structure, but their optoelectronic properties are largely unexplored. Reported here is the synthesis of a centimeter-sized AA′_n−1M_nX_3n+1 type perovskite, BDAPbI₄ (BDA=NH₃C₄H₈NH₃), single crystal and its charge-transport properties under X-ray excitation. The crystal shows a staggered configuration of the [PbI₆]⁴⁻ layers, a band gap of 2.37 eV, and a low trap density of 3.1×10⁹ cm⁻³. The single-crystal X-ray detector exhibits an excellent sensitivity of 242 μC Gy_air⁻¹ cm⁻² under the 10 V bias (0.31 V μm⁻¹), a detection limit as low as 430 nGy_air s⁻¹, ultrastable response current, a stable baseline with the lowest dark current drift of 6.06×10⁻⁹ nA cm⁻¹ s⁻¹ V⁻¹, and rapid response time of τ_rise=7.3 ms and τ_fall=22.5 ms. These crystals are promising candidates for the next generation of optoelectronic devices.     

Dimensional and Optoelectronic Tuning of Lead-free Perovskite Cs3Bi2I9−nBrn Single Crystals for Enhanced Hard X-ray Detection

Inorganic Bi-based perovskites have shown great potential in X-ray detection for their large absorption to X-rays, diverse low-dimensional structures, and eco-friendliness without toxic metals. However, they suffer from poor carrier transport properties compared to Pb-based perovskites. Here, we propose a mixed-halogen strategy to tune the structural dimensions and optoelectronic properties of Cs₃Bi₂I_9−nBr_n (0≤n≤9). Ten centimeter-sized single crystals are successfully grown by the Bridgman technique. Upon doping bromine to zero-dimensional Cs₃Bi₂I₉, the crystal transforms into a two-dimensional structure as the bromine content reaches Cs₃Bi₂I₈Br. Correspondingly, the optoelectronic properties are adjusted. Among these crystals, Cs₃Bi₂I₈Br exhibits negligible ion migration, moderate resistivity, and the best carrier transport capability. The sensitivities in 100 keV hard X-ray detection are 1.33×10⁴ and 1.74×10⁴ μC Gy_air⁻¹ cm⁻² at room temperature and 75 °C, respectively, which are the highest among all reported bismuth perovskites. Moreover, the lowest detection limit of 28.6 nGy_air s⁻¹ and ultralow dark current drift of 9.12×10⁻⁹ nA cm⁻¹ s⁻¹ V⁻¹ are obtained owing to the high ionic activation energy. Our work demonstrates that Br incorporation is an effective strategy to enhance the X-ray detection performance by tuning the dimensional and optoelectronic properties.     

Tailored Engineering of an Unusual (C4H9NH3)2(CH3NH3)2Pb3Br10 Two‐Dimensional Multilayered Perovskite Ferroelectric for a High‐Performance Photodetector

Two‐dimensional (2D) layered hybrid perovskites have shown great potential in optoelectronics, owing to their unique physical attributes. However, 2D hybrid perovskite ferroelectrics remain rare. The first hybrid ferroelectric with unusual 2D multilayered perovskite framework, (C₄H₉NH₃)₂(CH₃NH₃)₂Pb₃Br₁₀ ( 1 ), has been constructed by tailored alloying of the mixed organic cations into 3D prototype of CH₃NH₃PbBr₃. Ferroelectricity is created through molecular reorientation and synergic ordering of organic moieties, which are unprecedented for the known 2D multilayered hybrid perovskites. Single‐crystal photodetectors of 1 exhibit fascinating performances, including extremely low dark currents (ca. 10⁻¹² A), large on/off current ratios (ca. 2.5×10³), and very fast response rate (ca. 150 μs). These merits are superior to integrated detectors of other 2D perovskites, and compete with the most active CH₃NH₃PbI₃.     

Hydrogen Bonds Strengthened Metal-Free Perovskite for Degradable X-ray Detector with Enhanced Stability,Flexibility and Sensitivity

Metal-free perovskites (MFPs) with flexible and degradable properties have been adopted in flexible X-ray detection. For now, figuring out the key factors between structure and device performance are critical to guide the design of MFPs. Herein, MPAZE-NH₄I₃ ⋅ H₂O was first designed and synthesized with improved structural stability and device performance. Through theoretical calculations, the introducing methyl group benefits modulating tolerance factor, increases dipole moment and strengthens hydrogen bonds. Meanwhile, H₂O increases the hydrogen bond formation sites and synergistically realizes the band nature modulation, ionic migration inhibition and structural stiffness optimization. Spectra analysis also proves that the improved electron-phonon coupling and carrier recombination lifetime contribute to enhanced performance. Finally, a flexible and degradable X-ray detector was fabricated with the highest sensitivity of 740.8 μC Gy_air⁻¹ cm⁻² and low detection limit (0.14 nGy_air s⁻¹).     

Self‐Template‐Directed Synthesis of Porous Perovskite Nanowires at Room Temperature for High‐Performance Visible‐Light Photodetectors

The unique optoelectronic properties and promising photovoltaic applications of organolead halide perovskites have driven the exploration of facile strategies to synthesize organometal halide perovskites and corresponding hybrid materials and devices. Currently, the preparation of CH₃NH₃PbBr₃ perovskite nanowires, especially those with porous features, is still a great challenge. An efficient self‐template‐directed synthesis of high‐quality porous CH₃NH₃PbBr₃ perovskite nanowires in solution at room temperature using the Pb‐containing precursor nanowires as both the sacrificial template and the Pb²⁺ source in the presence of CH₃NH₃Br and HBr is now presented. The initial formation of CH₃NH₃PbBr₃ perovskite layers on the surface of the precursor nanowires and the following dissolution of the organic component of the latter led to the formation of mesopores and the preservation of the 1D morphology. Furthermore, the perovskite nanowires are potential materials for visible‐light photodetectors with high sensitivity and stability.     

Hydrothermal synthesis and crystal structure of a 3D supramolecular compound [H3NCH2CH2NH3]3H4[H2W12O42] · 2.5H2O

A 3D supramolecular compound [NH₃CH₂CH₂NH₃]³H₄[H₂W₁₂O₄₂] · 2.5H₂O (I) was synthesized hydrothermally and characterized by elemental analyses, IR, UV, TG analyses, and X-ray single-crystal diffraction. The X-ray diffraction experiment indicates that compound I exhibits a 3D network through electrostatic interactions and hydrogen bonding interactions between protonated ethylenediamine molecules, [H₂W₁₂O₄₀]¹⁰⁻ polyanions, and water molecules.     

A novel chain-like molybdenum phosphate: hydrothermal synthesis,crystal structure and characterization of [NH3(CH2CH2)2NH3]3[NH3(CH2CH2)2NH2]-Na5[Mo6O12(OH)3(PO4)(HPO4)3]2·4H2O

A novel organic/inorganic hybrid molybdenum phosphate, [NH₃(CH₂CH₂)₂NH₃]₃[NH₃(CH₂CH₂)₂NH₂]Na₅-[Mo₆O₁₂(OH)₃(PO₄)(HPO₄)₃]₂·4H₂O (1), involving molybdenum presented in V oxidation, has been hydrothermally prepared and characterized by elemental analysis, i.r., u.v.–vis., x.p.s., t.g. and single crystal X-ray diffraction. The structure of the title compound (1) may be considered to consist of two [Mo₆O₁₂(OH)₃(PO₄)(HPO₄)₃] units bonded together with NaO₆ octahedra, forming dimers. Further, these dimers connect with each other through four Na⁺ cations as bridges, giving rise to novel one-dimensional chain-like skeleton. Piperazines exist among inorganic chains acting as charge balancing cations.     

[NH4][(CH3)2NH2]2[Ta(C2O4)4]·2H2O: the first (oxalato)tantalate(V) complex structurally characterized

Abstract  The compound [NH₄][(CH₃)₂NH₂]₂[Ta(C₂O₄)₄]·2H₂O has been synthesized and characterized by elemental and TG/DTA analyses, IR spectroscopy and by the single-crystal X-ray diffraction study. The structure comprises the [Ta(C₂O₄)₄]³⁻ anion, NH₄ ⁺ and [(CH₃)₂NH₂]⁺ cations and crystallization water molecules. The Ta atom is octacoordinated by oxygen atoms from four bidentate oxalate groups forming a coordination polyhedron close to the triangular dodecahedron. The charge-assisted hydrogen bonds from both cations connect the [Ta(C₂O₄)₄]³⁻ anions into a three-dimensional framework. Graphical Abstract  The synthesis and properties of [NH₄][(CH₃)₂NH₂]₂[Ta(C₂O₄)₄]·2H₂O, the first structurally characterized compound with the tetra(oxalato)tantalate(V) anion, is reported.      

Crystal structure and magnetic properties of a thiocyanato-bridged dinuclear Cr(III)Cu(II) complex [(HL)Cu(SCN)Cr(NCS)3(NH3)2]·DMF

The complex [(HL)Cu(SCN)Cr(NCS)₃(NH₃)₂]·DMF [H₂L=3,3′-trimethylenedinitrilobis(2-butanoneoxime), DMF=N,N′-dimethylformamide] has been synthesized and the structure determined by single-crystal X-ray diffraction. The structure consists of a dinuclear thiocyanato-bridged Cr(III)Cu(II) unit and a DMF molecule as crystal solvate. The chromium ion is six-coordinated with two NH₃ molecules in axial positions and four nitrogen atoms, from four NCS⁻, in equatorial positions. One of the NCS⁻ bridges the Cr and Cu ions, the S atom of which occupies the apex of the square-pyramidal coordination at Cu with the tetradentate HL ligand in the basal site. Cryomagnetic measurement revealed a weak antiferromagnetic coupling between the heterometal ions with J=−0.63 cm⁻¹ based on the spin Hamiltonian H=−2JS₁S₂.     

Two Chain Like B-Type-Anderson-Based Hybrids Synthesized in Choline Chloride/Urea Eutectic Mixture

Two new chain like B-Anderson type polyoxomolybdates based hybrids {Na[(CH₃)₃N(CH₂)₂OH]₂}[Al(OH)₆Mo₆O₁₈]·2(NH₂CONH₂)·6H₂O (1) and {Na[(CH₃)₃N(CH₂)₂OH]₂}[Cr(OH)₆Mo₆O₁₈]·2(NH₂CONH₂)·6H₂O (2) were synthesized in choline chloride/urea eutectic mixture and characterized by element analysis, IR, UV–vis, TG, single-crystal X-ray analysis, and power X-ray diffraction. Through the linkage [Na(H₂O)₂(NH₂CONH₂)₂]⁺, the [X(OH)₆Mo₆O₁₈]³⁻ (X = Al, Cr) units are arranged into a chain. Considering hydrogen bonding interactions between the chains, compound 1 and 2 are all well-arranged into 3-D supermolecular assembly. The structure is first obtained in the choline chloride/urea eutectic mixture.     

Polyoxomolybdates functionalized with aminomethylene phosphonate

A new organic-inorganic hybrid Strandberg-type polyoxomolybdate derivative [(n-C₄H₉)₄N]₂[(NH₂CH₂PO₃)₂Mo₅O₁₅] · (CH₃NHCH₃)₂ · H₂O (I) has been synthesized and structurally characterized by elemental analysis, IR spectrum, UV spectrum, TG analysis, cyclic voltammetry, and single-crystal X-ray diffraction. The hybrid polyoxoanion [(NH₂CH₂PO₃)₂Mo₅O₁₅]²⁻ consists of a ring-shaped {Mo₅O₂₁} cluster with two [NH₂CH₂PO₃]⁻ groups incorporating into the opposite sides of the ring. The UV spectrum studied at different times reveals that I remains stable in CH₃CN-H₂O solvents (volume ratio = 1 : 2) for one day, and the electrochemical measurement indicates that I can exist in a pH range of 4.12–4.72.     

Halogen in materials design: Revealing the nature of hydrogen bonding and other non-covalent interactions in the polymorphic transformations of methylammonium lead tribromide perovskite

Methylammonium lead tribromide (CH₃NH₃PbBr₃) perovskite as a photovoltaic material has attracted a great deal of recent interest. Factors that are important in their application in optoelectronic devices include their fractional contribution of the composition of the materials as well as their microscopic arrangement that is responsible for the formation of well-defined macroscopic structures. CH₃NH₃PbBr₃ assumes different polymorphs (orthorhombic, tetragonal and cubic) depending on the evolution temperature of the bulk material. An understanding of the structure of these compounds will assist in rationalizing how halogen-centered non-covalent interactions play an important role in the rational design of these materials. Density functional theory (DFT) calculations have been performed on polymorphs of CH₃NH₃PbBr₃ to demonstrate that the H atoms on C of the methyl group in CH₃NH₃⁺ entrapped within a PbBr₆^4? perovskite cage are not electronically innocent, as is often contended. We show here that these H atoms are involved in attractive interactions with the surrounding bromides of corner-sharing PbBr₆^4? octahedra of the CH₃NH₃PbBr₃ cage to form Br?H(C) hydrogen bonding interactions. This is analogous to the way the H atoms on N of the NH₃⁺ group in CH₃NH₃⁺ form Br?H(N) hydrogen bonding interactions to stabilize the structure of CH₃NH₃PbBr₃. Both these hydrogen bonding interactions are shown to persist regardless of the nature of the three polymorphic forms of CH₃NH₃PbBr₃. These, together with the Br?C(N) carbon bonding, the Br?N(C) pnictogen bonding, and the Br?Br lump-hole type intermolecular non-covalent interactions identified for the first time in this study, are shown to be collectively responsible for the eventual emergence of the orthorhombic geometry of the CH₃NH₃PbBr₃ system. These conclusions are arrived at from a systematic analysis of the results obtained from combined DFT, Quantum Theory of Atoms in Molecules (QTAIM), and Reduced Density Gradient Non-Covalent Interaction (RDG-NCI) calculations carried out on the three temperature-dependent polymorphic geometries of CH₃NH₃PbBr₃.     

A novel hybrid material based on two symmetrically independent Keggin polyoxoanions: [NH3-CH(CH3)COOH][H3O]8[PMo12O40]3.4NH3CH(CH3)COO

Novel polyoxometalate-based organic-inorganic hybrid [NH₃-CH(CH₃)COOH][H₃O]₈[PMo₁₂O₄₀]₃.4NH₃CH(CH₃)COO was synthesized and characterized by ³¹P, ¹H, ¹³C NMR and IR spectroscopies, elemental analysis and single crystal X-ray determination. Two of the PMo₁₂O₄₀ ^3? anions in the title hybrid are symmetrically equivalent. They are crystallographically independent from the third PMo₁₂O₄₀ ^3? polyoxoanion, in the case of various interactions with neighboring components in the crystal network (i.e. ⁺NH_3-CH(CH₃)-COOH and H₃O⁺ cations, ₊NH₃CH(CH₃)COO^? zwitterions and polyoxoanions). The compound crystallizes in an orthorhombic C222 space group with a = 16.0392(16) Å, b = 34.480(4) Å, c = 12.8968(13) Å and Z = 2.     

Understanding the Impact of Bismuth Heterovalent Doping on the Structural and Photophysical Properties of CH3NH3PbBr3 Halide Perovskite Crystals with Near-IR Photoluminescence

A comprehensive study unveiling the impact of heterovalent doping with Bi³⁺ on the structural, semiconductive, and photoluminescent properties of a single crystal of lead halide perovskites (CH₃NH₃PbBr₃) is presented. As indicated by single-crystal XRD, a perfect cubic structure in Bi³⁺-doped CH₃NH₃PbBr₃ crystals is maintained in association with a slight lattice contraction. Time-resolved and power-dependent photoluminescence (PL) spectroscopy illustrates a progressively quenched PL of visible emission, alongside the appearance of a new PL signal in the near-infrared (NIR) regime, which is likely to be due to energy transfer to the Bi sites. These optical characteristics indicate the role of Bi³⁺ dopants as nonradiative recombination centers, which explains the observed transition from bimolecular recombination in pristine CH₃NH₃PbBr₃ to a dominant trap-assisted monomolecular recombination with Bi³⁺ doping. Electrically, it is found that the mobility in pristine perovskite crystals can be boosted with a low Bi³⁺ concentration, which may be related to a trap-filling mechanism. Aided by temperature (T)-dependent measurements, two temperature regimes are observed in association with different activation energies (E_a) for electrical conductivity. The reduction of E_a at lower T may be ascribed to suppression of ionic conduction induced by doping. The modified electrical properties and NIR emission with the control of Bi³⁺ concentration shed light on the opportunity to apply heterovalent doping of perovskite single crystals for NIR optoelectronic applications.     

Unusual potassium-oxalate coordination in the two-dimensional trimetallic [CoCl(NH3)5][KCr(C2O4)3]·0.5H2O complex

A new heterometallic compound, [CoCl(NH₃)₅][KCr(C₂O₄)₃]·0.5H₂O (1), has been synthesized and characterized by elemental analysis, IR and electronic spectra, thermal analysis, variable temperature magnetic susceptibility measurements, and single crystal X-ray diffraction. Compound 1 consists of two-dimensional [{KCr(C₂O₄)₃}_n]^2n? layers, [CoCl(NH₃)₅]²⁺ ions and water molecules. Within the 2-D layer, three different types of oxalate coordination modes are present. Each K cation is coordinated by eight oxygen atoms from oxalate groups and also weakly interacts with the ninth oxygen atom. The extensive network of hydrogen bond is formed between the [KCr(C₂O₄)₃]^2? layer and the [CoCl(NH₃)₅]²⁺ ions. These interactions involve all hydrogen atoms of ammonia ligads and water molecule.     

Structural phase transition,thermal analysis,and spectroscopic studies in an organic–inorganic hybrid crystal: [(CH3)2NH2]2ZnBr4

An organic–inorganic hybrid compound [(CH₃)₂NH₂]₂ZnBr₄ has been prepared at room temperature under the slow evaporation method. Its structure was solved at 150 K using the single-crystal X-ray diffraction method. [(CH₃)₂NH₂]₂ZnBr₄ crystallizes in the monoclinic system – a = 8.5512 (12) Å, b = 11.825 (2) Å, c = 13.499 (2) Å, β = 90.358 (6)°, V = 1365 (4) ų, and Z = 4, space group P2₁/n. In the structure of [(CH₃)₂NH₂]₂ZnBr₄, tetrabromozincate anions are connected to organic cations through N–H⋯ Br hydrogen bonds. Differential scanning calorimetry (DSC) measurements indicate that [(CH₃)₂NH₂]₂ZnBr₄ undergoes four phase transitions at T₁ = 281 K, T₂ = 340 K, T₃ = 377 K, and T₄ = 408 K. Meanwhile, several studies including DSC measurements and variable-temperature structural analyses were performed to reveal the structural phase transition at T = 281 K in [(CH₃)₂NH₂]₂ZnBr₄. Conductivity and dielectric study as a function of temperature (378 < T [K] < 423) and frequency (10⁻¹ < f [Hz] < 10⁶) were investigated. Analysis of equivalent circuit, alternating current conductivity, and dielectric studies confirmed the phase transition at T₄. Conduction takes place by correlated barrier hopping in each phase.     

Poly[tetraamminecopper(II) bis[tris(μ2‐cyanido‐κ2C,N)dicuprate(I)]]: a unique CuI–CuII mixed‐valence complex containing anionic cuprous cyanide layers and [Cu(NH3)4]2+ cations

The title compound, {[Cu(NH₃)₄][Cu(CN)₃]₂}_n, features a Cu^I–Cu^II mixed‐valence CuCN framework based on {[Cu₂(CN)₃]⁻}_n anionic layers and [Cu(NH₃)₄]²⁺ cations. The asymmetric unit contains two different Cu^I ions and one Cu^II ion which lies on a centre of inversion. Each Cu^I ion is coordinated to three cyanide ligands with a distorted trigonal–planar geometry, while the Cu^II ion is ligated by four ammine ligands, with a distorted square‐planar coordination geometry. The interlinkage between Cu^I ions and cyanide bridges produces a honeycomb‐like {[Cu₂(CN)₃]⁻}_n anionic layer containing 18‐membered planar [Cu(CN)]₆ metallocycles. A [Cu(NH₃)₄]²⁺ cation fills each metallocyclic cavity within pairs of exactly superimposed {[Cu₂(CN)₃]⁻}_n anionic layers, but there are no cations between the layers of adjacent pairs, which are offset. Pairs of N—H...N hydrogen‐bonding interactions link the N—H groups of the ammine ligands to the N atoms of cyanide ligands.     

SEMICONDUCTOR COPPER(II) MACROCYCLIC COMPLEXES. SYNTHESIS,CHARACTERIZATION AND ELECTRICAL PROPERTIES OF COPPER(II) COMPLEXES OF THE TYPE [Cu(TAABL)](NO3) · nH2O WITH L = NH(CH2)2NH2, NH(CH2)4NH2, NH(CH2)12NH2, AND THE COMPLEX [Cu(TAAB(C14H9N2O2)2)] · 4H2O

Abstract

The complexes [Cu(TAABNH(CH₂)₂NH₂)](NO₃) · 2H₂O, (1) [Cu(TAABNH(CH₂)₄NH₂)] (NO₃)·4H₂O, (2), [Cu(TAABNH(CH₂)₁₂NH₂](NO₃)·4H₂O,(3) and [Cu(TAAB(C₁₄H₁₀ N₂O₂)₂]·4H₂O, (4) have been synthesized and characterized by IR, mass spectroscopy, electronic spectroscopy, thermogravimetric analysis and elemental analysis. Electrical conductivity and activation energy evaluation were obtained from study of the temperature dependence of the electrical current (in tablet and thin film). Refraction and reflectance indices, absorption coefficient and optical activation energy were established through ellipsometry and UV-Vis spectroscopy. The electrical conductivity values at room temperature were within the range of semiconducting molecular solids (10^?6?10¹Ω^?1cm^?1).     

Colloidal Synthesis of CH3NH3PbBr3 Nanoplatelets with Polarized Emission through Self‐Organization

We report a combined experimental and theoretical study of the synthesis of CH₃NH₃PbBr₃ nanoplatelets through self‐organization. Shape transformation from spherical nanodots to square or rectangular nanoplatelets can be achieved by keeping the preformed colloidal nanocrystals at a high concentration (3.5 mg mL⁻¹) for 3 days, or combining the synthesis of nanodots with self‐organization. The average thickness of the resulting CH₃NH₃PbBr₃ nanoplatelets is similar to the size of the original nanoparticles, and we also noticed several nanoplatelets with circular or square holes, suggesting that the shape transformation experienced a self‐organization process through dipole–dipole interactions along with a realignment of dipolar vectors. Additionally, the CH₃NH₃PbBr₃ nanoplatelets exhibit excellent polarized emissions for stretched CH₃NH₃PbBr₃ nanoplatelets embedded in a polymer composite film, showing advantageous photoluminescence properties for display backlights.