Hybrid Ferroelectrics Research Articles

Organic‐Inorganic Hybrid Ferroelectric and Antiferroelectric with Afterglow Emission

AbstractLuminescent ferroelectrics are holding exciting prospect for integrated photoelectronic devices due to potential light‐polarization interactions at electron scale. Integrating ferroelectricity and long‐lived afterglow emission in a single material would offer new possibilities for fundamental research and applications, however, related reports have been a blank to date. For the first time, we here achieved the combination of notable ferroelectricity and afterglow emission in an organic‐inorganic hybrid material. Remarkably, the presented (4‐methylpiperidium)CdCl3 also shows noticeable antiferroelectric behavior. The implementation of cationic customization and halogen engineering not only enables a dramatic enhancement of Curie temperature of 114.4 K but also brings a record longest emission lifetime up to 117.11 ms under ambient conditions, realizing a leapfrog improvement of at least two orders of magnitude compared to reported hybrid ferroelectrics so far. This finding would herald the emergence of novel application potential, such as multi‐level density data storage or multifunctional sensors, towards the future integrated optoelectronic devices with multitasking capabilities.

Organic-Inorganic Hybrid Ferroelectric and Antiferroelectric with Afterglow Emission.

Luminescent ferroelectrics are holding exciting prospect for integrated photoelectronic devices due to potential light-polarization interactions at electron scale. Integrating ferroelectricity and long-lived afterglow emission in a single material would offer new possibilities for fundamental research and applications, however, related reports have been a blank to date. For the first time, we here achieved the combination of notable ferroelectricity and afterglow emission in an organic-inorganic hybrid material. Remarkably, the presented (4-methylpiperidium)CdCl3 also shows noticeable antiferroelectric behavior. The implementation of cationic customization and halogen engineering not only enables a dramatic enhancement of Curie temperature of 114.4 K but also brings a record longest emission lifetime up to 117.11 ms under ambient conditions, realizing a leapfrog improvement of at least two orders of magnitude compared to reported hybrid ferroelectrics so far. This finding would herald the emergence of novel application potential, such as multi-level density data storage or multifunctional sensors, towards the future integrated optoelectronic devices with multitasking capabilities.

Large Enhancement of Polarization in a Layered Hybrid Perovskite Ferroelectric Semiconductor via Molecular Engineering.

Switchable spontaneous polarization is the vital property of ferroelectrics, which leads to other key physical properties such as piezoelectricity, pyroelectricity, and nonlinear optical effects, etc. Recently, organic-inorganic hybrid perovskites with 2D layered structure have become an emerging branch of ferroelectric materials. However, most of the 2D hybrid ferroelectrics own relatively low polarizations (<15µC cm-2 ). Here, a strategy to enhance the polarization of these hybrid perovskites by using ortho-, meta-, para-halogen substitution is developed. Based on (benzylammonium)2 PbCl4 (BZACL), the para-chlorine substituted (4-chlorobenzylammonium)2 PbCl4 (4-CBZACL) ferroelectric semiconductor shows a large spontaneous polarization (23.3µCcm-2 ), which is 79% larger than the polarization of BZACL. This large enhancement of polarization is successfully explained via ab initio calculations. The study provides a convenient and efficient strategy to promote the ferroelectric property in the hybrid perovskite family.

Facile Control of Ferroelectricity Driven by Ingenious Interaction Engineering.

Construction of ferroelectric and optimization of macroscopic polarization has attracted tremendous attention for next generation light weight and flexible devices, which brings fundamental vitality for molecular ferroelectrics. However, effective molecular tailoring toward cations makes ferroelectric synthesis and modification relatively elaborate. Here, the study proposes a facile method to realize triggering and optimization of ferroelectricity. The experimental and theoretical investigation reveals that orientation and alignment of polar cations, dominated factors in molecular ferroelectrics, can be controlled by easily processed anionic modification. In one respect, ferroelectricity is induced by strengthened intermolecular interaction. Moreover, ≈50% of microscopic polarization enhancement (from 8.07 to 11.68µCcm-2 ) and doubling of equivalent polarization direction (from 4 to 8) are realized in resultant ferroelectric FEtQ2ZnBrI3 (FEQZBI, FEtQ = N-fluoroethyl-quinuclidine). The work offers a totally novel platform for control of ferroelectricity in organic-inorganic hybrid ferroelectrics and a deep insight of structure-property correlations.

High‐Tc Realization of Lead‐Free Halide Hybrid Ferroelectrics via Steric Confinement Modulation

AbstractHybrid organic–inorganic perovskite (HOIP) ferroelectrics with high Curie temperature (Tc), typified by the lead halide hybrid perovskite ferroelectrics, are developing rapidly owing to their maneuverable ferroelectricity at high temperatures. However, acquiring high‐Tc lead‐free HOIP ferroelectrics via rational strategy still needs development. In this study, a brand‐new program by modulating the steric confinement in a cuplike cavity to design high‐Tc bismuth‐halide ferroelectrics [H2mdap]BiX5 (H2mdap = N‐Methyl‐1,3‐Propanediamine, X = Cl (1), Br (2), I(3)) is proposed. Emphatically, the Tc enhanced dramatically from 264 K of 3 to 318 K of 2 and 377 K of 1, induced by the substitution of Br and Cl to I, accompanied with an interesting transition from second‐order phase transition (for 3) to the first‐order one (for 1 and 2). The extent of Tc increase is up to 113 K, which far outweighs that of reported Pb‐halide hybrid ferroelectrics. Structural and computational analyses elucidate that this unprecedented improvement of Tc is due to the higher phase transition energy barriers induced by modulating the steric confinement of cuplike cavity via halogen substitution. These results will provide new inspiration for designing high‐Tc lead‐free HOIP ferroelectrics.

Self‐Powered Visible‐Infrared Polarization Photodetection Driven by Ferroelectric Photovoltaic Effect in a Dion–Jacobson Hybrid Perovskite

AbstractFerroelectric materials, particularly the emerging layered hybrid ferroelectrics, have shown great potential for high‐sensitive polarization photodetection owing to their striking bulk photovoltaic effect (BPVE). Despite recent great achievements, the linear photoresponse range based on single‐mode BPVE is still limited in the shortwave region due to the large intrinsic bandgaps. Herein, first, the realization of self‐powered visible–infrared polarization photodetection by exploiting dual‐modal BPVE in a newly developed layered Dion–Jacobson (D‐J) hybrid ferroelectric (BDA)(EA)2Pb3Br10 (1, BDA is 1,4‐butadiammonium, EA is ethylammonium) is reported. Crystallographic investigations indicate that 1 adopts a typical trilayered D‐J perovskite structure with a fascinating ferroelectric feature and a giant two‐photon absorption coefficient as giant as 4.73 cm MW–1. Meanwhile, the bulk single crystal device of 1 exhibits excellent self‐powered direct detection performance under both visible light (405 nm) and near‐infrared light (800 nm), with a current on/off ratio as high as 103. More intriguingly, the device displays high sensitivity to the polarization of illuminated light, showing a considerable anisotropy up to 4.2 (405 nm) and 4.8 (800 nm), which are much larger than the detectors achieved by geometry anisotropy. The realization of self‐powered visible‐infrared dual‐modal polarization photodetection in 1 indicates the tremendous potential of hybrid ferroelectrics in various optoelectronic applications.

Chiral Zn‐Based Organic‐Inorganic Hybrid Ferroelectrics with Large Polarization and Luminescence

AbstractMulti‐functionalized lead‐free organic‐inorganic hybrid ferroelectrics have recently realized diverse applications especially for optoelectronics and photovoltaics. Herein, the chiral Zn‐based organic−inorganic hybrids are discovered: [(R)‐(−)‐2‐methylpiperazine‐1,4‐diium][Zn(H2O)6]•(SO4)2 (RMPZnS2, space group P21) and [(S)‐(+)‐2‐methylpiperazine‐1,4‐diium]2[Zn(H2O)6]•(SO4)3 (SMP2ZnS3, space group P21212). Through experimental and computational investigations, it is found that RMPZnS2 is a ferroelectric with considerable large polarization value (P ≈ 9.5 µC cm−2) along b–axis, and its ferroelectric‐paraelectric phase transition is switched by rotation of organic cations. Meanwhile, it also possesses a fascinating photovoltaic effect driven by the polar charges at solar‐blind UV region, endowing it with the potential of self‐driven photodetection. In addition, white‐light emissions of the RMPZnS2 and SMP2ZnS3 are observed. The enhanced luminescence by heating is especially suitable for the application in white light‐emitting diodes. Overall, these chiral emission ferroelectrics at the supramolecular level will largely expand their applications in multidisciplinary fields.

An Organic-Inorganic Hybrid Pyrrolidinium Ferroelectric Based on Solvent Selective Effect.

Organic-inorganic hybrid ferroelectrics (OIHFs) have fueled enormous interest benefiting from their less environmental pollution, performance-tailored functionality, low product costs as well as tunability of structures. However, the lack of material synthesis approaches and diverse targeted molecular design is a stumbling block for designing novel OIHFs rationally. Here, we report a unique organic-inorganic hybrid ferroelectric (3,3-difluoropyrrolidine)2CdCl4 1 and another novel nonferroelectric crystal (3,3-difluoropyrrolidine)2Cd2Cl6 2 by changing various crystallization solvents. Significantly, 1 presents a ferroelectric phase transition behavior at ∼367 K, and the distinct symmetry breaking, i.e., mmmFm, sets up a biaxial ferroelectric with four equivalent directions of polarization, which has a Pr ∼ 0.77 μC/cm2. Systematic studies prove that ferroelectricity can be ascribed to the synergistic effects of the distortion of the inorganic anion skeleton and the ordering of organic cations. This work reveals the potential of constructing novel ferroelectrics based on the solvent selective effect and pyrrolidinium as organic cations.

Ferroelastic-switching-driven large shear strain and piezoelectricity in a hybrid ferroelectric.

Materials that can produce large controllable strains are widely used in shape memory devices, actuators and sensors1,2, and great efforts have been made to improve the strain output3-6. Among them, ferroelastic transitions underpin giant reversible strains in electrically driven ferroelectrics or piezoelectrics and thermally or magnetically driven shape memory alloys7,8. However, large-strain ferroelastic switching in conventional ferroelectrics is very challenging, while magnetic and thermal controls are not desirable for practical applications. Here we demonstrate a large shear strain of up to 21.5% in a hybrid ferroelectric, C6H5N(CH3)3CdCl3, which is two orders of magnitude greater than that in conventional ferroelectric polymers and oxides. It is achieved by inorganic bond switching and facilitated by structural confinement of the large organic moieties, which prevents undesired 180° polarization switching. Furthermore, Br substitution can soften the bonds, allowing a sizable shear piezoelectric coefficient (d35 ≈ 4,830 pm V-1) at the Br-rich end of the solid solution, C6H5N(CH3)3CdBr3xCl3(1-x). The electromechanical properties of these compounds suggest their potential in lightweight and high-energy-density devices, and the strategy described here could inspire the development of next-generation piezoelectrics and electroactive materials based on hybrid ferroelectrics.

Three-Dimensional Lead Bromide Hybrid Ferroelectric Realized by Lattice Expansion.

Three-dimensional (3D) organic-inorganic lead halide hybrids have become a hot academic topic because of their various functional properties. However, 3D lead halide hybrid ferroelectrics are still very rare until now. Here, we report a new 3D lead halide perovskite-related ferroelectric, (EATMP)Pb2Br6 [EATMP = (2-aminoethyl)trimethylphosphanium]. Based on nonferroelectric CH3NH3PbBr3, by replacing PbBr6 octahedra with a Pb2Br10 dimer of edge-sharing octahedra as the basic building unit, the expanded 3D lead bromide perovskite analog was formed with the large [EATMP]2+ cations occupying the voids of framework. Notably, (EATMP)Pb2Br6 displays a direct bandgap of 2.81 eV, four polarization directions, and a high Curie temperature (Tc) of 518 K (much beyond that of BaTiO3, 393 K), which is the highest among all reported 3D organic-inorganic hybrid ferroelectrics. Such a high Tc may result from the high rotational energy barrier of cations induced by a larger molecular volume and relatively low crystal symmetry. Our work provides an efficient avenue to construct new 3D organic-inorganic lead halide hybrids and would inspire the further exploration of 3D lead halide ferroelectrics.

Photo-degradation organic dyes by Sb-based organic-inorganic hybrid ferroelectrics

The organic-inorganic hybrid halide compounds have emerged as one of the most promising photoelectric material for their superior optoelectronic properties and hold great prospects for renewable energy substitutes and environmental protection as photocatalysis. Here, we report the optical properties of the Sb-based organic-inorganic hybrid ferroelectric materials: pyridine-4-aminium tetrachloroantimonate ((C5H7N2)SbCl4, sample 1), piperidin-1-aminium tetrachloroantimonate ((C5H13N2)SbCl4, sample 2) and tris(trimethylammonium) nonachlorodiantimonate (((CH3)3NH)3Sb2Cl9, sample 3), which are a kind of exploited efficient photocatalysts. Samples 2 and 3 exhibit distinct photoelectric respond, which are mainly ascribed to their minor narrow band-gap compared with sample 1. For the ferroelectrics, the intrinsic of spontaneous polarization of sample 3 at room temperature is favourable for the separation of photogenerated electrons and holes within the photorespond process. Moreover, sample 3 shows the highest efficiency of photo-decomposed Rhodamine B (90.2% within 80 min) and Methyl Orange (MO) (97.4% within 50 min), thanks to the photo-excited electrons and holes promoting the formation of oxidative radical species during the photo-redox progress. These findings prove that the development of a novel Sb-based organic-inorganic hybrid halide compounds with good stability in the degradation of organic dyes paves a way to designing new photocatalyst.

Piezoelectric Energy Harvesting from a Ferroelectric Hybrid Salt [Ph3 MeP]4 [Ni(NCS)6 ] Embedded in a Polymer Matrix.

Organic-inorganic hybrid ferroelectrics are an exciting class of molecular materials with promising applications in the area of energy and electronics. The synthesis, ferroelectric and piezoelectric energy harvesting behavior of a 3d metal ion-containing A4 BX6 type organic-inorganic hybrid salt [Ph3 MeP]4 [Ni(NCS)6 ] (1) is now presented. P-E hysteresis loop studies on 1 show a remnant ferroelectric polarization value of 18.71 μC cm-2 , at room temperature. Composite thermoplastic polyurethane (TPU) devices with 5, 10, 15 and 20 wt % compositions of 1 were prepared and employed for piezoelectric energy harvesting studies. A maximum output voltage of 19.29 V and a calculated power density value of 2.51 mW cm-3 were observed for the 15 wt % 1-TPU device. The capacitor charging experiments on the 15 wt % 1-TPU composite device shows an excellent energy storage performance with the highest stored energies and measured charges of 198.8 μJ and 600 μC, respectively.

Piezoelectric Energy Harvesting from a Ferroelectric Hybrid Salt [Ph3MeP]4[Ni(NCS)6] Embedded in a Polymer Matrix

AbstractOrganic–inorganic hybrid ferroelectrics are an exciting class of molecular materials with promising applications in the area of energy and electronics. The synthesis, ferroelectric and piezoelectric energy harvesting behavior of a 3d metal ion‐containing A4BX6 type organic–inorganic hybrid salt [Ph3MeP]4[Ni(NCS)6] (1) is now presented. P‐E hysteresis loop studies on 1 show a remnant ferroelectric polarization value of 18.71 μC cm−2, at room temperature. Composite thermoplastic polyurethane (TPU) devices with 5, 10, 15 and 20 wt % compositions of 1 were prepared and employed for piezoelectric energy harvesting studies. A maximum output voltage of 19.29 V and a calculated power density value of 2.51 mW cm−3 were observed for the 15 wt % 1‐TPU device. The capacitor charging experiments on the 15 wt % 1‐TPU composite device shows an excellent energy storage performance with the highest stored energies and measured charges of 198.8 μJ and 600 μC, respectively.

Precise Molecular Design Toward Organic-Inorganic Zinc Chloride ABX3 Ferroelectrics.

Organic-inorganic ABX3 (A, B = cations, X = anion) hybrids with perovskite structure have recently attracted tremendous interest due to their structural tunability and rich functional properties, such as ferroelectricity. However, ABX3 hybrid ferroelectrics with other structures have rarely been reported. Here, we successfully designed an ABX3 hybrid ferroelectric [(CH3)3NCH2F]ZnCl3 with a spontaneous polarization of 4.8 μC/cm2 by the molecular modification of [(CH3)4N]ZnCl3 through hydrogen/halogen substitution. It is the first zinc halide ABX3 ferroelectric, which contains one-dimensional [ZnCl3]-n chains of corner-sharing ZnCl4 tetrahedra, distinct from the anionic framework of corner-sharing or face-sharing BX6 octahedra in the ABX3 perovskites. From zero dimension to one dimension, the high symmetry of ZnCl4 tetrahedra is broken, and all of them align along one direction to form a polar [ZnCl3]-n chain, beneficial to the generation of ferroelectricity. This finding provides an efficient polar anionic framework for enriching the family of hybrid ferroelectrics by assembling with various cations and should inspire further exploration of new classes of organic-inorganic ABX3 ferroelectrics.

The First 2D Hybrid Perovskite Ferroelectric Showing Broadband White‐Light Emission with High Color Rendering Index

AbstractLuminescent ferroelectrics have attracted considerable attention in terms of integrated photoelectronic devices, most of which are focused on the multicomponent systems of rare‐earth doping ferroelectric ceramics. However, bulk ferroelectricity with coexistence of strong white‐light emission, especially in the single‐component system, remains quite rare. Here, a new organic–inorganic hybrid ferroelectric of (C4H9NH3)2PbCl4 (1) is reported, adopting a 2D layered perovskite architecture, which exhibits an unprecedented coexistence of notable ferroelectricity and intrinsic white‐light emission. Decent above‐room‐temperature spontaneous polarization of ≈2.1 µC cm−2 is confirmed for 1. Particularly, it also exhibits brilliant broadband white‐light emission with a high color‐rendering‐index up to 86 under UV excitation. Structural analyses indicate that ferroelectricity of 1 originates from molecular reorientation of dynamic organic cations, as well as significant structural distortion of PbCl6 octahedra that also contribute to its white‐light emission. This work paves an avenue to design new hybrid ferroelectrics for multifunctional application in the photoelectronic field.

Towards a Spectrally Customized Photoresponse from an Organic–Inorganic Hybrid Ferroelectric

AbstractPhotosensitive organic–inorganic hybrid ferroelectrics are emerging as a new class of promising materials with a broad spectral response (e.g., visible light, UV light, and IR light) for optoelectronic applications. However, spectrally customized photoresponses in ferroelectrics have not been achieved. Herein, we report a photosensitive organic–inorganic hybrid ferroelectric, (diisobutylammonium)3ClCoCl4 (1), with a notable spontaneous polarization of approximately 4.6 μC cm−2 and high Curie temperature (Tc=372.5 K). More interestingly, it features spectrally selective absorption at specific wave bands ranging from 550 to 700 nm with a large absorption coefficient, which was assigned to the d–d transition of Co2+ from the 4A2 to the 4T1 (P) state. It is emphasized that 1 shows spectrally customized photosensitivity with distinct photocurrent generation under light illumination at 550–700 nm. This is the first hybrid photosensitive ferroelectric with a spectrally customized photoresponse. This finding should lead to innovative applications of hybrid photosensitive ferroelectrics, especially towards spectrally selective optoelectronic devices.

Towards a Spectrally Customized Photoresponse from an Organic-Inorganic Hybrid Ferroelectric.

Photosensitive organic-inorganic hybrid ferroelectrics are emerging as a new class of promising materials with a broad spectral response (e.g., visible light, UV light, and IR light) for optoelectronic applications. However, spectrally customized photoresponses in ferroelectrics have not been achieved. Herein, we report a photosensitive organic-inorganic hybrid ferroelectric, (diisobutylammonium)3 ClCoCl4 (1), with a notable spontaneous polarization of approximately 4.6 μC cm-2 and high Curie temperature (Tc =372.5 K). More interestingly, it features spectrally selective absorption at specific wave bands ranging from 550 to 700 nm with a large absorption coefficient, which was assigned to the d-d transition of Co2+ from the 4 A2 to the 4 T1 (P) state. It is emphasized that 1 shows spectrally customized photosensitivity with distinct photocurrent generation under light illumination at 550-700 nm. This is the first hybrid photosensitive ferroelectric with a spectrally customized photoresponse. This finding should lead to innovative applications of hybrid photosensitive ferroelectrics, especially towards spectrally selective optoelectronic devices.

Bilayered Hybrid Perovskite Ferroelectric with Giant Two-Photon Absorption

Perovskite ferroelectrics with prominent nonlinear optical absorption have attracted great attention in the field of photonics. However, they are traditionally dominated by inorganic oxides and exhibit relatively small nonlinear optical absorption coefficients, which hinder their further applications. Herein, we report a new organic-inorganic hybrid bilayered perovskite ferroelectric, (C4H9NH3)2(NH2CHNH2)Pb2Br7 (1), showing an above-room-temperature Curie temperature (∼322 K) and notable spontaneous polarization (∼3.8 μC cm-2). Significantly, the unique quantum-well structure of 1 results in intriguing two-photon absorption properties with a giant nonlinear optical absorption coefficient as high as 5.76 × 103 cm GW-1, which is almost two-orders of magnitude larger than those of mostly traditional all-inorganic perovskite ferroelectrics. To our best knowledge, 1 is the first example of hybrid ferroelectrics with giant two-photon absorption coefficient. The mechanisms for ferroelectric and two-photon absorption are revealed. This work will shed light on the design of new ferroelectrics with two-photon absorption and promote their potentials in the photonic application.

Unmasking the Mechanism of Structural Para- to Ferroelectric Phase Transition in (NH4)2SO4.

New nontoxic and biocompatible ferroelectric materials are a subject undergoing intense study. One of the most promising research branches is focused on H-bonded organic or hybrid ferroelectrics. The engineering of these materials is based on mimicking the phase transition mechanisms of the well-known inorganic ferroelectrics. In our study, a coupled experimental and theoretical methodology was used for a precise investigation of the ferroelectric phase transition mechanism in ammonium sulfate (AS). A series of single-crystal X-ray diffraction measurements were performed in the temperature range between 273 and 163 K. The detailed inspection of the obtained static structural data, in the above-mentioned temperature range, allowed us to reveal dynamical effects at the ferroelectric phase transition. Accurate analysis of all geometrical features within the obtained crystal structures was carried out. The results were discussed in the view of previously discovered physical properties. X-ray studies were complemented by the use of quantum theory of atoms in molecules calculations and Hirshfeld surface analysis. Valence shell charge concentration analysis allowed us to find the subtle changes between charge density distribution within SO42- in para- and ferroelectric phases. H-bond interactions, geometrically classified in both AS phases, were all confirmed by the appropriate critical points. The interaction energies were estimated for the structures at 273, 233, 213, 183, and 163 K. Correlation between the geometrical approach and the results of theoretical calculations enabled us to discover the differences in interaction equilibrium between the AS phases. The mechanism of the phase transition originates from the disruption of the vibrational lattice mode between sulfate anions. Our studies resolved the problem, which was under discussion for more than 60 years.

A semiconducting molecular ferroelectric with a bandgap much lower than that of BiFeO3

Ferroelectrics have been attracting increasing attention as good candidates for multifunctional materials because of their fascinating properties. However, their large bandgap has been a roadblock limiting their application in optoelectronics and photovoltaics, among other applications. Hybrid ferroelectrics have the potential to combine the advantages of both molecular materials and ferroelectrics. In this context, we designed a hybrid ferroelectric: (2-(ammoniomethyl)pyridinium)SbI5. It shows an above-room-temperature Curie temperature (Tc=360 K), a large spontaneous polarization (Ps=4 μC cm−2) and a small bandgap (2.03 eV) that is much smaller than the recently reported 2.7–3.65 eV for the lead-halide perovskite ferroelectrics. The implementation of ferroelectricity in hybrid semiconducting materials may be a feasible way to realize high-performance ferroelectric optoelectronic and photovoltaic devices.