Organic-inorganic Layered Perovskite Research Articles

Bis(dialkylammonium)-based hybrid organic–inorganic ionic materials as solid–solid phase change materials

The application of phase change materials (PCMs) in thermal energy storage (TES) systems is often restricted by challenges such as volume expansion, phase segregation, stability issues and potential leakage, particularly prominent in conventional solid–liquid PCMs. In response to these limitations, solid–solid PCMs have emerged as a promising alternative, garnering increasing attention. While both organic and inorganic solid–solid PCMs have been extensively studied, hybrid organic/inorganic materials represent a distinct class of solid–solid PCMs that have recently garnered significant interest due to their inherent properties such as high thermal stability, non-flammability or long cycle life. Organic-inorganic layered perovskites are emerging as potential good solid–solid PCMs as they present energetic solid–solid transitions and high thermal stability. In this work we propose the synthesis and thorough thermal characterization and cyclability of a series of new hybrid organic–inorganic ionic materials based on n-dialkylamines of different lengths (C8, C10, C12 and C18) with general formula of the type 2[(CnH2n+1)2NH2][MX4], using three different tetrachlorometalates anions ([FeCl4]2-, [MnCl4]2- and [CuCl4]2-). Among the new ionic materials prepared six of them have shown solid–solid transition enthalpies higher than 100 J/g. In particular, the 3 bearing the secondary n-dioctadecylamines as cations have shown unprecedent solid–solid transitions enthalpies ca. 90 °C, for this kind of ionic materials of 167.5 J/g, 157.7 J/g and 146.9 J/g for [DODA]2[MnCl4], [DODA]2[CuCl4] and [DODA]2[FeCl4] respectively. In addition, the latter ionic materials have undergone reliability tests showing excellent performance up to 500 heating/cooling cycles.

Understanding structural distortions in hybrid layered perovskites with the n = 1 Ruddlesden-Popper structure.

A symmetry mode analysis yields 47 symmetrically distinct patterns of octahedral tilting in hybrid organic-inorganic layered perovskites that adopt the n = 1 Ruddlesden-Popper (RP) structure. The crystal structures of compounds belonging to this family are compared with the predictions of the symmetry analysis. Approximately 88% of the 140 unique structures have symmetries that agree with those expected based on octahedral tilting alone, while the remaining compounds have additional structural features that further lower the symmetry, such as asymmetric packing of bulky organic cations, distortions of metal-centered octahedra or a shift of the inorganic layers that deviates from the a/2 + b/2 shift associated with the RP structure. The structures of real compounds are heterogeneously distributed amongst the various tilt systems, with only 9 of the 47 tilt systems represented. No examples of in-phase ψ-tilts about the a and/or b axes of the undistorted parent structure were found, while at the other extreme ∼66% of the known structures possess a combination of out-of-phase φ-tilts about the a and/or b axes and θ-tilts (rotations) about the c axis. The latter combination leads to favorable hydrogen bonding interactions that accommodate the chemically inequivalent halide ions within the inorganic layers. In some compounds, primarily those that contain either Pb2+ or Sn2+, favorable hydrogen bonding interactions can also be achieved by distortions of the octahedra in combination with θ-tilts.

Organic Chain Length Effect on Trap States of Lead Halide Perovskite Scintillators

Scintillators fabricated from organic–inorganic layered perovskites have attracted wide attention due to their excellent properties, including fast decay times, superior light yield, and high exciton binding energy. In relation to their optoelectronic properties, hybrid organic–inorganic perovskites are known for their tunability, which could be manipulated by modifying the organic cations. In this study, we investigate the optical and scintillation properties of lead halide perovskites A2PbBr4, where A vary from amylammonium (AA), hexylammonium (HA), octylammonium (OA), and benzylammonium (BZA) organic ligands. Photoluminescence (PL) spectra display dual peaks due to surface and bulk trap states contributions, while fast average decay times from time-resolved photoluminescence (TRPL) for all samples are within the range of 0.69 ± 0.11–0.99 ± 0.13 ns. The optical band gap of these hybrid perovskites is within ∼3 eV range, which fulfill the criteria of promising scintillators. Radioluminescence (RL) spectra show negative thermal quenching behavior (NTQ) in all samples, with the AA2PbBr4 peak intensity appearing at relatively lower temperature compared to other samples. Thermoluminescence (TL) measurement reveals trap-free states in AA2PbBr4, while other samples possess shallow traps (<40 meV) as well as low trap density, which is beneficial for fast-decay scintillators, X-ray detection and energy conversion for solar cells. Overall, our results demonstrate that the extension of linear organic chains in lead-based perovskite is a deterministic strategy for a fast response hybrid-based scintillator to date.

Revealing Giant Exciton Fine-Structure Splitting in Two-Dimensional Perovskites Using van der Waals Passivation.

Organic-inorganic layered perovskites are currently some of the most promising 2D van der Waals materials. Low crystal quality usually broadens the exciton line width, obscuring the fine structure of the exciton in conventional photoluminescence experiments. Here, we propose a mechanical approach to reducing the effect of spectral diffusion by means of hBN capping on layered perovskites, revealing the exciton fine structure. We used a stochastic model to link the reduction of the spectral line width with the population of charge fluctuation centers present in the organic spacer. van der Waals forces between both lattices cause the partial clamping of the perovskite organic spacer molecules, and hence the amplitude of the overall spectral diffusion effect is reduced. Our work provides a low-cost solution to the problem of accessing important fine-structure excitonic state information, along with an explanation of the important carrier dynamics present in the organic spacer that affect the quality of the optical emission.

Designing Ruddlesden–Popper Layered Perovskites through Their Organic Cations

Organic–inorganic layered perovskites were initially envisioned as materials for solar cells in view of their greater ambient stability compared to their 3D relatives. However, their major limitation was the insulating character of the bulky organic cations, especially in single-layer structures. This limitation was turned into an opportunity to explore organic molecules with different configurations, a journey that, to date, has delivered new materials for lighting, photocatalysis, chiro-optoelectronics, and ferroelectricity. In this Perspective, we aim to provide an outlook on the future challenges of using metal-halide Ruddlesden–Popper layered perovskites as scaffolds, including functional organic building blocks, for the creation of new hybrid materials. We envision that this research field can be empowered by establishing strong bridges with the organic chemistry and the machine-learning communities, which will help researchers to efficiently design new organic cations for exciting functionalities in this class of materials.

Reversible colossal barocaloric effect dominated by disordering of organic chains in (CH3–(CH2)n−1–NH3)2MnCl4 single crystals

Solid-state refrigeration based on the caloric effect is viewed as a promising efficient and clean refrigeration technology. Barocaloric materials were developed rapidly but have since encountered a general obstacle: the prominent caloric effect cannot be utilized reversibly under moderate pressure. Here, we report a mechanism of an emergent large, reversible barocaloric effect (BCE) under low pressure in the hybrid organic–inorganic layered perovskite (CH3–(CH2)n−1–NH3)2MnCl4 (n = 9,10), which show the reversible barocaloric entropy change as high as ΔSr ∼ 218, 230 J kg−1 K−1 at 0.08 GPa around the transition temperature (Ts ∼ 294, 311.5 K). To reveal the mechanism, single-crystal (CH3–(CH2)n−1–NH3)2MnCl4 (n = 10) was successfully synthesized, and high-resolution single-crystal X-ray diffraction (SC-XRD) was carried out. Then, the underlying mechanism was determined by combining infrared (IR) spectroscopy and density function theory (DFT) calculations. The colossal reversible BCE and the very small hysteresis of 2.6 K (0.1 K/min) and 4.0 K (1 K/min) are closely related to the specific hybrid organic–inorganic structure and single-crystal nature. The drastic transformation of organic chains confined to the metallic frame from ordered rigidity to disordered flexibility is responsible for the large phase-transition entropy comparable to the melting entropy of organic chains. This study provides new insights into the design of novel barocaloric materials by utilizing the advantages of specific organic–inorganic hybrid characteristics.

Magnetic–dielectric bistabilities and magnetodielectric coupling effects in a new layered hybrid perovskite: (C6H5(CH2)4NH3)2[MnCl4

A new organic–inorganic layered perovskite, (C6H5(CH2)4NH3)2[MnCl4], undergoes three reversible structural phase transitions accompanying with magnetic–dielectric dual-bistabilities, and exhibits an intrinsic magnetodielectric effect during the spin-flop transition.

Hydrogen-bonded and supramolecular ferroelectricity in a new hybrid (C12H25NH3)2CoCl4

A new organic-inorganic layered halide perovskite ((C12H25NH3)2CoCl4) has been synthesized and characterized by: chemical analysis, x-ray powder diffraction, differential scanning calorimetry, and differential thermal analysis thermographs. The dielectric and ferroelectric properties have been investigated. Analysis of the ac conductivity σac (ω, T) measured in the temperature interval from 110 K to 370 K and at selected frequencies in the range 1 kHz < f < 100 kHz and the results show that the Jonscher universal power law is accurately obeyed. The existence of ferroelectricity has been demonstrated by the hysteresis P-E loop. The collective data evidenced that the hybrid behaves as a proper ferroelectric rather than a relaxor one and undergoes an order-disorder ferroelectric phase transition at the Curie temperature Tc (Tc ≈ 360 K) accompanied with a structural distortion from an intercalated to non- intercalated state as the other Co and/or Zn hybrids. Since the room temperature space group of the hybrid is centrosymmetric (P21/c), the ferroelectricity should be due to the supramolecular interaction which results from the induced dipoles. The hydrogen bonding system of the type N–H….Cl plays the key role in the mechanism of supramolecular ferroelectricity.

Toward Increasing Micropore Volume between Hybrid Layered Perovskites with Silsesquioxane Interlayers.

Hybrid organic-inorganic layered perovskites are typically nonporous solids. However, the incorporation of silsesquioxanes with a cubic cage structure as interlayer materials creates micropores between the perovskite layers. In this study, we increase in the micropore volume in layered perovskites by replacing a portion of the silsesquioxane interlayers with organic amines. In the proposed method, approximately 20% of the silsesquioxane interlayers can be replaced without changing the layer distance owing to the size of the silsesquioxane. When small amines (e.g., ethylamine) are used in this manner, the micropore volume of the obtained hybrid layered perovskites increases by as much as 44%; when large amines (e.g., phenethylamine) are used, their micropore volume decreases by as much as 43%. Through the variation of amine fraction, the micropore volume can be adjusted in the range. Finally, the magnetic moment measurements reveal that the layered perovskites with mixed interlayers exhibit ferromagnetic ordering at temperature below 20 K, thus indicating that the obtained perovskites maintain their functions as layered perovskites.

Ppt-level benzene detection and gas sensing mechanism using (C4H9NH3)2PbI2Br2 organic–inorganic layered perovskite

Organic–inorganic layered perovskites employed as resistive gas sensing candidates for ppt-level benzene detection at a working temperature of 160 °C.

N-channel field-effect transistors with an organic-inorganic layered perovskite semiconductor

Large electron injection barriers and electrode degradation are serious issues that need to be overcome to obtain n-channel operation in field-effect transistors with an organic-inorganic layered perovskite (C6H5C2H4NH3)2SnI4 semiconductor. By employing low-work-function Al source/drain electrodes and by inserting C60 layers between the perovskite semiconductor and the Al electrodes to reduce the injection barrier and to suppress the electrode degradation, we demonstrate n-channel perovskite transistors with electron mobilities of up to 2.1 cm2/V s, the highest value ever reported in spin-coated perovskite transistors. The n-channel transport properties of these transistors are relatively stable in vacuum but are very sensitive to oxygen, which works as electron traps in perovskite and C60 layers. In addition, grazing-incidence X-ray scattering and thermally stimulated current measurements revealed that crystallite size and electron traps largely affect the n-channel transport properties.

Field-effect transistors with vacuum-deposited organic-inorganic perovskite films as semiconductor channels

Films of the organic-inorganic layered perovskite (C6H5C2H4NH3)2SnI4 were vacuum-deposited on substrates heated at various temperatures (Tsub) to investigate the influence of Tsub on their film quality and transistor performance (hole mobilities, threshold voltages, and current on/off ratios). Appropriate substrate heating at Tsub = 60 °C during vacuum deposition led to better-developed perovskite films with larger grains. These films exhibited the best transistor performance in comparison with films fabricated at the other Tsub. The transistor performance was further enhanced by reducing perovskite semiconductor thickness (t) because of a reduction of bulk resistance in a top-contact/bottom-gate transistor structure. By utilizing the optimized Tsub of 60 °C and t of 31 nm, we obtained the most improved hole mobility of 0.78 ± 0.24 cm2/V s, about 5000 times the hole mobilities of our initial transistors fabricated at Tsub = 24 °C and t = 50 nm.

Design and Prominent Dielectric Properties of a Layered Phase-Transition Crystal: (Cyclohexylmethylammonium)2CdCl4

Following our recent finding of interesting dielectric and ferroelectric properties in semiconducting organic–inorganic layered perovskites (benzylammonium)2PbCl4 and (cyclohexylammonium)2PbBr4–4xI4x (x = 0–1), we designed a new layered perovskite-type crystal (cyclohexylmethylammonium)2CdCl4. By systematic characterizations, including differential scanning calorimetry measurements, dielectric measurements, and variable-temperature structural analysis, this crystal was found to undergo a reversible first-order phase transition at around Tc = 342 K. The origin of the phase transition is associated with the order–disorder change of the organic cation as expected. The phase transition is accompanied by the anticipated large dielectric constant change and remarkable dielectric anisotropy. These dielectric performances reveal potential application of the crystal as a high-temperature dielectric material. More interesting dielectric crystals are expected to be tailored in the future by taking advantage of the r...

(CH3 NH3 )2 PdCl4 : A Compound with Two-Dimensional Organic-Inorganic Layered Perovskite Structure.

The synthesis of previously unknown perovskite (CH3 NH3 )2 PdCl4 is reported. Despite using an organic cation with the smallest possible alkyl group, a 2D organic-inorganic layered Pd-based perovskites was still formed. This demonstrates that Pd-based 2D perovskites can be obtained even if the size of the organic cation is below the size limit predicted by the Goldschmidt tolerance-factor formula. The (CH3 NH3 )2 PdCl4 phase has a bulk resistivity of 1.4 Ω cm, a direct optical gap of 2.22 eV, and an absorption coefficient on the order of 104 cm-1 . XRD measurements suggest that the compound is moderately stable in air, an important advantage over several existing organic-inorganic perovskites that are prone to phase degradation problems when exposed to the atmosphere. Given the recent interest in organic-inorganic perovskites, the synthesis of this new Pd-based organic-inorganic perovskite may be helpful in the preparation and understanding of other organic-inorganic perovskites.

Temperature-dependent time-resolved photoluminescence of (C6H5C2H4NH3)2PbX4 (X = Br and I)

This paper describes temperature-dependent time-resolved photoluminescence of two-dimensional organic–inorganic layered perovskite compounds, (C6H5C2H4NH3)2PbX4 (X=Br and I) prepared by solution-based self-assembly. (C6H5C2H4NH3)2PbX4 shows fluorescence from free-exciton even at room temperature. At low temperatures below 90K, the Stokes-shifted fluorescence from bound excitons appears in (C6H5C2H4NH3)2PbI4. In contrast, (C6H5C2H4NH3)2PbBr4 exhibits Stokes-shifted phosphorescence from the triplet excited state to the ground state. The local structure between the organic and inorganic layers plays a prominent role in the formation of triplet excitons.

Fabrication of Organic-Inorganic Nano-Hybrid Materials Containing Oligothiophene Derivatives

Oligothiophene derivatives, 4,4’-bis-(2-aminoethylthienyl)-3,4-ethylenedioxythiophene dihydrohalide (AET-EDOT·HX: X = I, Br), were synthesized by Grignard coupling reactions. The hybrid films of oligothiophene and lead halide were fabricated by casting and spin-coating methods. The effect of halogen species on the optical properties of the perovskites was investigated. The X-ray diffraction profiles of (AET-EDOT)PbX4 cast films indicated that the layered structures were formed by the self-organization. After hybridization of AET-EDOT·HX with PbX2, new absorption peaks due to the confined excitons were observed at 400 nm for (AET-EDOT)PbBr4 film, and at 395 nm for (AET-EDOT)PbI4 film. These results indicated that the diamino-type oligothiophenes were successfully incorporated into the organic-inorganic layered perovskites. AFM images of (AET-EDOT)PbX4 cast films showed polycrystalline grains, indicating that the polycrystalline structures covered on the substrate surface.

Synthesis and Characterization of Organic-Inorganic Layered Perovskite Compounds Using Fullerene Derivatives

Layered perovskite (RNH3)2PbI4 (R = organic cation), which contained the fullerene derivatives, [ethyl-3-tert-butoxycarbonylaminopropyl (1,2-methanofullerene C60)]-61,61-di carboxylate iodide (EAF-I) and di [3-tert-butoxycarbonylaminopropyl (1,2-methanofullerene C60)]- 61,61-dicarboxylate diiodide (DAF-I2) in the organic layers were fabricated and compared with previously reported perovkite compound containing N-methyl-2-(4-aminophenyl)-fulleropyrrolidine iodide (AmPF-I). Because the solvent solubilities of EAF-I and DAF-I2 to N,N-dimethylformamide (DMF) were higher than AmPF-I, the film processability of EAF-I and DAF-I2 was improved compared with AmPF-I. The X-ray diffraction patterns proved the construction of the perovskite structure in (EAF)2PbI4 and (AmPF)2PbI4 cast films. EAF was well-organized and closer-packing than AmPF in the perovskite structure. For the diamine-type fullerene, DAF-I2, it is difficult to form layered structure by spin-coated or cast methods. New sharp X-ray diffraction peaks were observed for DAF-I2 films dipped in PbI2 solution. The intercalations and formation of perovskite structure of (DAF)PbI4 were studied.

Synthesis and luminescence properties of lead-halide based organic–inorganic layered perovskite compounds (C nH 2 n+1 NH 3) 2PbI 4 ( n=4, 5, 7, 8 and 9)

This paper describes the synthesis and characterization of organic–inorganic layered perovskite compounds, (C n H 2 n+1 NH 3) 2PbI 4 ( n=4, 5, 7, 8 and 9). The effect of the number of carbon atoms on luminescence properties has been examined. Thin films of microcrystalline (C n H 2 n+1 NH 3) 2PbI 4 fabricated by spin-coating are highly oriented, with the c-axis perpendicular to the substrate surface. Temperature-dependent optical absorption spectra reveal that (C n H 2 n+1 NH 3) 2PbI 4 films ( n=4, 7, 8 and 9) show the structural phase transitions. The excitonic structures of (C n H 2 n+1 NH 3) 2PbI 4 vary with the number of carbon atoms of the alkyl chain length. At low temperatures below 100 K, the lowest-energy free-exciton band of (C n H 2 n+1 NH 3) 2PbI 4 ( n=7, 8 and 9) split into three fine-structure levels. In contrast to (C n H 2 n+1 NH 3) 2PbBr 4 films, (C n H 2 n+1 NH 3) 2PbI 4 ( n=7, 8 and 9) shows no triplet exciton emission, but it shows the Stokes-shifted emission from bound excitons.

Electroactive Organic-Inorganic Layered Perovskite Hybrids: Steric Interaction between Aminopyridine and Trivalent Ferricyanide and Use for Electrochemical Sensing Device

Steady organic-inorganic perovskite hybrids with (H22-Ap)3/2Fe(CN)6, (H23-Ap)3/2Fe(CN)6 and (H24-AP)3/2Fe(CN)6 (2-AP = 2-aminopyridine, 3-AP = 3- aminopyridine, 4-AP = 4- aminopyridine) were formed from aqueous solution. Each structure was an unusual layered organic-inorganic structural type. A device was designed to construct electrochemical sensing devices using above organic-inorganic perovskite hybrids. The sequence of redox activity is (H24-Ap)3/2Fe(CN)6 &gt; (H22-Ap)3/2Fe(CN)6 &gt; (H23-AP)3/2Fe(CN)6 and that of electrocatalytical activity is (H22-Ap)3/2Fe(CN)6 &gt; (H23-Ap)3/2Fe(CN)6 &gt; (H24-AP)3/2Fe(CN)6. The variation coefficients (RSD) of successive and interval assays are less than 2.0%. Three electrochemical sensing devices display a remarkable electrochemical sensitivity and stability.

Synthesis, structure and spectroscopic investigations of two new organic-inorganic hybrids NH3(C6H4)2NH3CuCl4 and NH3(C6H4)2NH3HgCl4

Two metal organic-inorganic hybrid compounds, NH3(C6H4)2NH3CuCl4, 1, and NH3(C6H4)2NH3HgCl4, 2, have been synthesized and structurally characterized by single-crystal X-ray diffraction. The two compounds crystallize in the monoclinic space groups P21/c and C2/c, respectively, with a = 14.3774 (7), b = 7.3472 (4), c = 7.1669 (3), β = 96.589 (3)°, Z = 2 and R1 = 0.037 for 1, and a = 6.2986 (4), b = 18.2911 (12), c = 28.5854 (17), β = 91.836 (2)°, Z = 8 and R1 = 0.049 for 2. The organic-inorganic layered perovskite structure of compound 1 features well-ordered sheets of corner-sharing distorted CuCl6 octahedra, due to the presence of Jahn-Teller effect in the d9 electronic system of Cu(II), separated by layers of benzidinium cations. The structure of compound 2 consists of anionic parallel layers built up from discrete tetrahedral HgCl42- species, alternating with layers of organic molecules [NH3(C6H4)2NH3]2+. The structures of the two compounds are stabilized by an extensive network of N-H…C1 hydrogen bonds. These compounds are also investigated by IR spectroscopy.