An organic ferroelectric eutectic material, a preparation method and application thereof

Abstract

This invention provides an organic ferroelectric eutectic material, its preparation method, and its applications, relating to the field of ferroelectric materials technology. The organic ferroelectric eutectic material constructs a crystal system with "rigid constraint and flexible adaptation coexisting, dipole order and controllable polarization synchronously" through "molecular selection-supramolecular assembly-crystal structure regulation," achieving a synergistic effect of high Curie temperature, strong polarization characteristics, and excellent flexibility. The preparation method of the organic ferroelectric eutectic material utilizes a simplified "solvent dissolution-solvent evaporation" process, leveraging the mediating effect of the solvent to promote the supramolecular self-assembly of donor and acceptor molecules. This achieves the preparation of an organic ferroelectric eutectic material possessing both high Curie temperature, strong polarization characteristics, and excellent flexibility. The preparation method has multiple advantages, including "stable process, low cost, and suitability for large-area processing," making it a simple, efficient, and universally applicable preparation method suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention relates to the field of ferroelectric materials technology, and more specifically, to an organic ferroelectric eutectic material, its preparation method, and its application. Background Technology

[0002] Ferroelectric materials, due to their switchable spontaneous polarization under an applied electric field, have demonstrated irreplaceable application value in electronic information fields such as information sensing, energy conversion and storage, and driving devices, becoming a research hotspot in the field of new materials. Among them, organic ferroelectric materials, with their unique advantages of solution processability (preparable through low-cost processes such as spin coating and printing), lightweight (low molecular weight and low density), and natural flexibility (adaptable to flexible substrates and resistant to bending deformation), perfectly meet the development needs of flexible and portable wearable electronic devices. They are regarded as ideal candidate materials for the core functional layer of wearable devices, with particularly outstanding application potential in scenarios such as flexible sensors, flexible energy storage capacitors, and micro flexible actuators.

[0003] Despite the aforementioned advantages of organic ferroelectric materials, their ferroelectric performance is significantly lacking, lagging considerably behind mature inorganic ferroelectric materials (such as barium titanate), severely limiting their industrial application scope and overall device performance. Specifically, the core performance defects of organic ferroelectric materials stem from inherent deficiencies at the crystal structure level: on the one hand, the dipoles within organic ferroelectric crystals are prone to partial cancellation due to local disorder or symmetrical distribution of molecular arrangement, leading to a significant reduction in macroscopic polarization intensity, failing to meet the performance requirements of high-end applications such as high energy density and high sensing sensitivity; on the other hand, the bonding between polar units in organic ferroelectrics is mostly weak interaction such as hydrogen bonds and π-π stacking, far weaker than the ionic / covalent bonds in inorganic ferroelectrics, making it difficult to maintain the long-range regular orientation of dipoles. At rising temperatures, thermal fluctuations easily disrupt the ordered arrangement of dipoles, causing their Curie temperature (T0) to rise. c The K values ​​are generally too low (far below the 393K of barium titanate), making it unsuitable for high-temperature working environments, which in turn causes the devices to degrade or even fail under complex operating conditions.

[0004] From the perspective of the fundamental structural requirements of ferroelectrics, materials must simultaneously meet three core conditions: First, they must possess polar units capable of generating dipole moments, such as polar ions, polar atomic groups, or polar molecules, which is the structural basis for ferroelectricity. Second, the dipoles of the polar units must achieve long-range periodic ordered arrangement; the interaction strength and arrangement between dipoles directly determine key performance parameters of the ferroelectric, such as the Curie temperature, polarization intensity, and coercive field. Third, the polarization direction of the long-range ordered dipoles must be reversibly controllable through an applied electric field; this is the core prerequisite for the functional applications of ferroelectric materials. For organic molecular-based ferroelectric materials, constructing polar units is less difficult, and the switchability of polarization direction can be achieved to a certain extent through molecular design; that is, these two fundamental requirements are relatively easy to meet. However, the efficient long-range ordered arrangement of dipoles has always been the core technical bottleneck restricting the preparation of high-performance organic ferroelectrics: on the one hand, the molecular stacking of organic lattices is prone to local symmetric structures, which cause the dipole moments to cancel each other out, directly reducing the macroscopic polarization intensity; on the other hand, weak bonding leads to poor orientation stability of polar units, and disordered arrangement at high temperatures will quickly disintegrate the long-range order of dipoles, resulting in a significant drop in Curie temperature.

[0005] Therefore, developing a high-performance organic ferroelectric material that can simultaneously achieve high Curie temperature and strong polarization characteristics, while also taking into account the inherent flexibility advantages of organic materials, has become an urgent need to break through the industry's technical bottlenecks and promote the industrialization of organic ferroelectric devices. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides an organic ferroelectric eutectic material, its preparation method, and its applications. The organic ferroelectric eutectic material possesses strong polarization characteristics, a high Curie temperature, and excellent flexibility. The preparation method of the organic ferroelectric eutectic material has the advantages of simplicity, high efficiency, and wide applicability, making it highly suitable for large-scale industrial production.

[0007] The specific technical solution of this invention is as follows:

[0008] In a first aspect, the present invention provides an organic ferroelectric eutectic material, formed by supramolecular self-assembly of donor molecules and acceptor molecules, and possessing a long-range ordered crystal structure; wherein, the donor molecules are π-conjugated organic molecules with non-centrosymmetric geometry and intrinsic molecular dipole moments; the acceptor molecules are π-conjugated organic molecules with planar rigid geometry and electron-withdrawing ability; in the crystal structure, donor molecule layers and acceptor molecule layers are alternately stacked along the CT axis, and each donor molecule is spatially sandwiched by two adjacent acceptor molecules, forming a sandwich unit; multiple sandwich units are periodically slid-stacked along a direction perpendicular to the CT axis, so that the dipole moments of the donor molecules are oriented, thereby generating macroscopic spontaneous polarization in the crystal; adjacent donor molecules can perform in-plane cooperative rotation within the confined space formed by the acceptor molecules under the action of an external electric field, thereby realizing the switching of the macroscopic spontaneous polarization direction.

[0009] In one possible implementation, the donor molecule is selected from molecules having the structure shown in general formula I.

[0010]

[0011] (I)

[0012] In Formula I, Y is one of O, S, Se and NR (R is H or C1-C4 alkyl), and X is H or F.

[0013] In one possible implementation, the donor molecule is selected from at least one of dinaphtho[2,1-B:1',2'-D]furan (DNF), dinaphtho[2,1-B:1',2'-D]thiophene (DNT), 3,11-difluorodinaphtho[2,1-B:1',2'-D]furan (3,11-FDNF), and dinaphtho[2,1-b:1',2'-d]selenophene (DNSe).

[0014] In one possible implementation, the acceptor molecule is at least one selected from 2,2'-(benzo[1,2-B;4,5-B']dithiophene-4,8-diylidene)malononitrile (DTTCNQ), 3,6-difluoro-DTTCNQ (F2-DTTCNQ), 3,6-dichloro-DTTCNQ (Cl2-DTTCNQ), 3,6-dicyano-DTTCNQ ((CN)2-DTTCNQ), 3,6-bis(2-ethylhexyl)-DTTCNQ (EH-DTTCNQ), and 2,2'-(benzo[1,2-b:4,5-b']dithiophene-4,8-diyl)bis(5-fluoro-1,3-benzothiazole) (F-BTZ).

[0015] In one possible implementation, the non-centrosymmetric geometry is V-shaped or bow-shaped, and the planar rigid geometry is planar or saddle-shaped.

[0016] In one possible implementation, the CT axis of the organic ferroelectric eutectic material is perpendicular to the c-axis of the crystal, and its spontaneous polarization intensity P along the c-axis of the crystal is... r ≥70 μC / cm 2 Spontaneous polarization intensity P along the a-axis of the crystal r ≥25 μC / cm 2 .

[0017] In one possible implementation, the CT axis direction of the organic ferroelectric eutectic material is perpendicular to the c-axis direction of the crystal, and its coercive field E along the c-axis of the crystal... c ≤0.5 MV / m, coercive field E along the a-axis of the crystal c ≤0.1 MV / m.

[0018] In one possible implementation, the Curie temperature T of the organic ferroelectric eutectic material is... c ≥479 K.

[0019] In one possible implementation, the rotation angle is 20° to 50°.

[0020] In a second aspect, the present invention provides a method for preparing the above-mentioned organic ferroelectric eutectic material, comprising the following steps:

[0021] S1. Dissolve the donor and acceptor molecules in an organic solvent to form a homogeneous solution;

[0022] S2. The solvent of the solution obtained in step S1 is evaporated to allow the donor molecules and acceptor molecules to co-crystallize, thereby obtaining an organic ferroelectric eutectic material.

[0023] In one possible implementation, the molar ratio of the donor molecule to the acceptor molecule is (0.8-1.2):1.

[0024] In one possible implementation, the organic solvent is selected from one or more of acetonitrile, chloroform, dichloromethane, tetrahydrofuran, and toluene.

[0025] Thirdly, the present invention provides a ferroelectric device, including a ferroelectric functional layer, wherein the ferroelectric functional layer contains the above-mentioned organic ferroelectric eutectic material.

[0026] In one possible implementation, the ferroelectric device is one of a non-volatile memory, a field-effect transistor, a sensor, an energy storage device, and a piezoelectric device.

[0027] The positive and progressive effects of this invention are as follows:

[0028] This invention provides an organic ferroelectric eutectic material, its preparation method, and its applications. The organic ferroelectric eutectic material, through a hierarchical design of "molecular selection-supramolecular assembly-crystal structure regulation," constructs a crystal system characterized by "coexistence of rigid constraints and flexible adaptation, and synchronous controllable polarization with dipole order." This enables the organic ferroelectric eutectic material to possess polarization intensity, high Curie temperature, and ultra-low coercive field approaching those of traditional inorganic ferroelectric materials, achieving a synergy of high Curie temperature, strong polarization characteristics, and excellent flexibility. Furthermore, the "sandwich layer unit" and "periodic slip stacking arrangement" stacking mode revealed by the organic ferroelectric eutectic material represent a universal supramolecular design strategy. By rationally selecting donor and acceptor molecules with specific shapes and electronic properties, the properties of this series of materials can be effectively regulated, exhibiting high scalability. The method for preparing the organic ferroelectric eutectic material uses a simplified process of "solvent dissolution-solvent evaporation" to promote the supramolecular self-assembly of donor and acceptor molecules through the medium effect of the solvent. This method achieves the preparation of organic ferroelectric eutectic materials that combine high Curie temperature, strong polarization characteristics, and excellent flexibility. The preparation method has multiple advantages such as "stable process, low cost, and suitability for large-area processing". It is a simple, efficient, and universally applicable preparation method that is very suitable for large-scale industrial production. Attached Figure Description

[0029] Figure 1 This is a schematic diagram showing the synthesis process, crystal packing structure, and dipole moment distribution of the DNF-DTTCNQ ferroelectric eutectic material in Example 1;

[0030] Figure 2 The graph shows the ferroelectric properties of the DNF-DTTCNQ ferroelectric eutectic material in Example 1.

[0031] Figure 3 The graph shows the high-temperature ferroelectric performance data of the DNF-DTTCNQ ferroelectric eutectic material in Example 1;

[0032] Figure 4 These are schematic diagrams of two energy-degenerate ferroelectric structures of the DNF-DTTCNQ ferroelectric eutectic material in Example 1;

[0033] Figure 5 This is a schematic diagram of the polarization switching mechanism of the DNF-DTTCNQ ferroelectric eutectic material in Example 1;

[0034] Figure 6 The curve showing the relationship between the polarization switching energy barrier of the DNF-DTTCNQ ferroelectric eutectic material in Example 1, predicted by theoretical calculation, and the change of rotation angle (φ).

[0035] Figure 7The DNF-DTTCNQ ferroelectric eutectic material in Example 1 and the P-type ferroelectric material of the previously reported ferroelectric materials are shown. r and 1 / E c Performance comparison chart;

[0036] Figure 8 This is a comparison of the XRD test curves and simulated curves of the DNT-DTTCNQ ferroelectric eutectic material in Example 1;

[0037] Figure 9 The room temperature hysteresis loop of the DNT-DTTCNQ ferroelectric eutectic material in Example 2;

[0038] Figure 10 The room temperature hysteresis loop of the 3,11-FDNF-DTTCNQ ferroelectric eutectic material in Example 3 is shown. Detailed Implementation

[0039] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. It should be noted that the following embodiments are only used to illustrate the implementation methods and typical parameters of the present invention, and are not intended to limit the parameter range described in the present invention. Reasonable variations derived therefrom are still within the protection scope of the present invention.

[0040] It should be noted that the endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0041] Unless otherwise defined, all terms, symbols, and other scientific terms used herein are intended to have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In some instances, terms having a conventional meaning are defined herein for clarification or ease of reference, and such definitions should not be construed as indicating a significant difference from conventional understanding in the art. The technical methods described or referenced herein are generally well understood by those skilled in the art and employed by conventional methods. Unless otherwise stated, the use of commercially available kits, reagents, and instruments shall be performed according to the manufacturer's instructions and parameters.

[0042] Terminology Explanation:

[0043] The CT axis is the primary direction of charge transfer. Electron clouds shift directionally along this axis from donor molecules to adjacent acceptor molecules, forming a one-dimensional or multi-dimensional charge transfer chain that runs through the eutectic crystal. In this invention, the CT axis refers to the dominant spatial axis along which charge transfer occurs between donor and acceptor molecules in the organic ferroelectric eutectic. It usually coincides with or is parallel to a major crystallographic axis of the organic ferroelectric eutectic (such as the c-axis of the ferroelectric eutectic, i.e., the direction of molecular stacking). It is the core extension direction of the periodic alternation of donor and acceptor molecules.

[0044] Cis-alignment: In the pairing of donor and acceptor, if the polarity directions of the two are aligned in the same direction or nearly aligned, it is cis-alignment; if the polarity directions are completely opposite, it is anti-alignment.

[0045] The specific technical solution of this invention is as follows:

[0046] In a first aspect, the present invention provides an organic ferroelectric eutectic material, formed by supramolecular self-assembly of donor molecules and acceptor molecules, and possessing a long-range ordered crystal structure; wherein, the donor molecules are π-conjugated organic molecules with non-centrosymmetric geometry and intrinsic molecular dipole moments; the acceptor molecules are π-conjugated organic molecules with planar rigid geometry and electron-withdrawing ability; in the crystal structure, donor molecule layers and acceptor molecule layers are alternately stacked along the CT axis, and each donor molecule is spatially sandwiched by two adjacent acceptor molecules, forming a sandwich unit; multiple sandwich units are periodically slid-stacked along a direction perpendicular to the CT axis, so that the dipole moments of the donor molecules are oriented, thereby generating macroscopic spontaneous polarization in the crystal; adjacent donor molecules can perform in-plane cooperative rotation within the confined space formed by the acceptor molecules under the action of an external electric field, thereby realizing the switching of the macroscopic spontaneous polarization direction.

[0047] The organic ferroelectric eutectic material provided by this invention, through a hierarchical design of "molecular selection - supramolecular assembly - crystal structure regulation," constructs a crystal system that achieves "coexistence of rigid constraint and flexible adaptation, and synchronous controllable polarization with dipole order," ultimately realizing a synergy of high Curie temperature, strong polarization characteristics, and excellent flexibility. Curie temperature (T0) cEssentially, the key to thermal stability in ferroelectric materials lies in the critical temperature at which the long-range ordered structure of dipoles resists thermal fluctuations. This organic ferroelectric eutectic material constructs a high-energy barrier through "spatial confinement + strong interactions," fundamentally enhancing thermal stability. The acceptor molecule possesses a planar rigid geometry, and its π-conjugated framework exhibits excellent structural stability, enabling it to tightly clamp the donor molecule in space. This strictly restricts the movement of the donor molecule within a confined space, effectively suppressing disordered flipping and shifting of the donor molecule that disrupts the dipole order as the temperature rises. Higher temperatures are required to overcome this spatial constraint, laying the structural foundation for high Curie temperatures. The donor and acceptor form a long-range ordered crystal structure through supramolecular self-assembly. Although supramolecular interactions are weaker than covalent bonds, they create a synergistic enhancement effect in periodic arrangement. Compared to the weak van der Waals forces relied upon by traditional organic ferroelectrics, the supramolecular interaction network in this scheme can more efficiently transmit intermolecular constraints, further enhancing the stability of the dipole arrangement. When the temperature rises, thermal fluctuations need to overcome the dual energy barriers of "spatial constraint + supramolecular network" in order to destroy the dipole order, thus making the Curie temperature of the eutectic much higher than that of traditional organic ferroelectric materials.

[0048] The macroscopic polarization intensity is jointly determined by the magnitude of the intrinsic dipole moment of the molecules and the degree of directional alignment of the dipoles. In the organic ferroelectric eutectic material provided by this invention, the asymmetric structure of the donor molecules has non-cancellable molecular dipoles, which are the core unit basis for forming macroscopic polarization. At the same time, the strong electron-withdrawing ability of the acceptor molecules will form a charge transfer interaction with the donor molecules, causing the electron cloud to shift directionally along the donor-acceptor direction, further strengthening the dipole moment of the donor molecules and guiding the dipole directions of adjacent donor molecules to tend to be consistent. The "sandwich layer unit" structure and "periodic slip stacking arrangement" force the intrinsic dipole moments of all non-centrosymmetric donor molecules to exhibit a highly consistent directional alignment, breaking the inversion symmetry of the crystal, maximizing the dipole alignment efficiency, and avoiding the problem of "partial cancellation caused by random dipole orientation" in traditional organic ferroelectrics. This dual protection allows the polarization intensity of the organic ferroelectric eutectic material to approach that of inorganic ferroelectrics.

[0049] The core of flexibility lies in the ability of a material to undergo reversible deformation under external force without compromising its core functional structure. This organic ferroelectric eutectic material achieves its flexible function through the characteristics of organic molecules and a layered stacking design, while avoiding interference with ferroelectric properties. Both the donor and acceptor are organic π-conjugated molecules. Although their molecular skeletons possess a certain degree of rigidity (ensuring ferroelectric order), the supramolecular interactions between molecules are "weak and reversible." Compared to the rigid ionic / covalent bonds in inorganic ferroelectrics, this "weak and reversible" interaction allows molecules to undergo minute relative displacements under force, enabling the eutectic to retain the natural flexibility of organic materials. The crystal structure is a layered structure of "alternating stacked donor and acceptor molecular layers." Molecules within each layer are tightly bound together through strong supramolecular interactions to maintain dipole order, while the interactions between layers are relatively weak. When organic ferroelectric eutectic materials are subjected to external forces such as bending and folding, slight slippage can occur between the layers to adapt to the deformation. This not only ensures the integrity of the core ferroelectric structure (orderly arrangement of dipoles) during the deformation process, but also gives the material excellent flexibility and bendability, perfectly meeting the application requirements of wearable electronic devices.

[0050] In one possible implementation, the donor molecule is selected from molecules having the structure shown in general formula I.

[0051]

[0052] (I)

[0053] In formula (I), Y is one of O, S, Se and NR (R is H or C1-C4 alkyl), and X is H or F.

[0054] In one possible implementation, the donor molecule is selected from at least one of dinaphtho[2,1-B:1',2'-D]furan (DNF), dinaphtho[2,1-B:1',2'-D]thiophene (DNT), 3,11-difluorodinaphtho[2,1-B:1',2'-D]furan (3,11-FDNF), and dinaphtho[2,1-b:1',2'-d]selenophene (DNSe). All of these donor molecules have a binaphthyl ring as their core, bridging with heterocyclic rings such as furan, thiophene, and selenophene to form a standard V-shaped geometric configuration. This asymmetric structure naturally generates an inherent molecular dipole, and the orientation of the V-shaped opening directly determines the dipole direction, satisfying the basic requirement of a ferroelectric "polar unit" without complex molecular modification. The edges of the naphthyl rings of all four types of molecules contain CH active sites capable of forming directional hydrogen bonds, which can precisely match the hydrogen bond acceptor sites of the acceptor molecules to form stable CH…N directional hydrogen bonds. This hydrogen bonding interaction forces donor and acceptor molecules to form a conformal arrangement, which not only locks the spatial orientation of donor molecules in the sandwich unit, but also provides supramolecular constraints for characteristic stacking modes such as "110.8° slip stacking", ensuring the breaking of crystal inversion symmetry and the construction of polar networks.

[0055] In one possible implementation, the acceptor molecule is at least one selected from 2,2'-(benzo[1,2-B;4,5-B']dithiophene-4,8-diylidene)dimalononitrile (DTTCNQ), 3,6-difluoro-DTTCNQ (F2-DTTCNQ), 3,6-dichloro-DTTCNQ (Cl2-DTTCNQ), 3,6-dicyano-DTTCNQ ((CN)2-DTTCNQ), 3,6-bis(2-ethylhexyl)-DTTCNQ (EH-DTTCNQ), and 2,2'-(benzo[1,2-b:4,5-b']dithiophene-4,8-diyl)bis(5-fluoro-1,3-benzothiazole) (F-BTZ). The aforementioned acceptor molecules all possess the core structural features of a "planar rigid framework + controllable interaction sites," enabling precise matching with donor molecules to construct stable sandwich-like units and gearbox-like crystal structures, providing the necessary spatial constraints and interaction support for ferroelectricity generation. DTTCNQ and its derivatives, as well as F-BTZ, all use benzo[1,2-b:4,5-b']dithiophene as their core framework. This structure is formed by the fusion of a benzene ring and two thiophene rings, with a well-developed conjugated system and fixed bond angles, resulting in a highly rigid planar structure. This rigid framework allows the acceptor molecule to act like a "clamp," stably clamping the donor molecule from both sides, constructing a uniformly sized cavity, and strictly restricting the movement of the donor molecule to in-plane rotation, avoiding ineffective movements such as out-of-plane flipping that could disrupt dipole order, thus providing structural assurance for high Curie temperatures in eutectic crystals. The malononitrile end group of DTTCNQ and its derivatives, and the benzothiazole end group of F-BTZ, both contain strongly electronegative atoms that can form directional hydrogen bonds with the CH active sites of the donor molecule. This hydrogen bonding can force the donor and acceptor to form a cis-aligned arrangement, ensuring that the dipoles are directionally superimposed along a specific direction.

[0056] In one possible implementation, the non-centrosymmetric geometry is V-shaped or bow-shaped, and the planar rigid geometry is planar or saddle-shaped. The V-shape consists of two conjugated rings connected by heterocyclic bridges forming a fixed angle, while the bow-shaped geometry is a curved structure formed by substituents or ring strain in a single conjugated system. Both configurations break the centrosymmetry of the molecule, causing an imbalance in the electron cloud distribution and naturally generating an inherent, non-cancellable molecular dipole. Compared to symmetric configurations, the basic requirement of a ferroelectric "polar unit" can be met without introducing additional complex substituents, simplifying molecular design while ensuring dipole stability. The planar acceptor constructs a completely planar molecular structure with conjugated rings, while the saddle-shaped acceptor forms a slightly curved, rigid structure resembling a saddle due to ring strain or substituents. The planar acceptor forms a regular cavity through parallel planes, while the saddle-shaped acceptor forms an arc-shaped cavity adapted to the bow-shaped donor through curved surfaces. Both methods confine the donor molecule within a fixed space, avoiding ineffective movements such as out-of-plane flipping, laying the structural foundation for high Curie temperatures. The symmetrical structure of the planar / saddle-shaped acceptor and the V-shaped / bow-shaped asymmetric structure of the donor form a complementary "symmetric-asymmetric" combination. This combination enables multiple donor-acceptor sandwich units to form a slip stacking mode when stacked; the symmetrical structure of the acceptor ensures the periodicity of the stacking, while the asymmetric structure of the donor breaks the inversion symmetry of the crystal, ensuring the realization of ferroelectric properties.

[0057] In one possible implementation, the CT axis of the organic ferroelectric eutectic material is perpendicular to the c-axis of the crystal, and its spontaneous polarization intensity P along the c-axis of the crystal is... r ≥70 μC / cm 2 Spontaneous polarization intensity P along the a-axis of the crystal r ≥25 μC / cm 2 The CT axis (charge transfer axis) is perpendicular to the crystal's c-axis, meaning that charge transfer between donor and acceptor molecules is dominated along the crystal's a / b axes, with the electron cloud shifting directionally to form a two-dimensional charge transfer network. This charge transfer, through the electronic coupling effect of the conjugated system, synchronously modulates the dipole orientation of donor molecules, enabling the intrinsic dipoles of a large number of donor molecules to achieve "co-alignment and efficient superposition" along the c-axis. This allows the P-axis along the crystal's c-axis to... r ≥70 μC / cm 2 This not only far surpasses traditional organic materials but also approaches the level of the classic inorganic ferroelectric material PbTiO3, significantly improving the charge storage capacity of organic eutectic within the same volume and greatly increasing the storage density of ferroelectric memory. (Along the crystal a-axis P) r ≥25 μC / cm 2 The strong polarization output enables the sensor made of organic ferroelectric eutectic material to generate significant electrical signal changes under minute deformation, greatly improving the sensitivity compared to traditional organic sensors.

[0058] In one possible implementation, the CT axis direction of the organic ferroelectric eutectic material is perpendicular to the c-axis direction of the crystal, and its coercive field E along the c-axis of the crystal... c ≤0.5 MV / m, coercive field E along the a-axis of the crystal c ≤0.1 MV / m. The CT axis (charge transfer axis) is perpendicular to the crystal's c-axis, meaning that the charge transfer between donor and acceptor molecules is dominated along the crystal's a / b axes. Lateral charge transfer makes the intermolecular interactions more uniformly dispersed, reducing the "site-specific resistance" during donor molecule rotation and providing a structural basis for polarization switching under low electric fields. The structure, with the CT axis perpendicular to the c-axis, places the donor molecules in an asymmetric interaction field of "lateral charge interaction + longitudinal stacking constraint" within the crystal. The weak lateral constraint reduces rotational resistance, while the moderate longitudinal constraint ensures high c-axis polarization while reducing the coercive field. The coercive field E along the crystal's c-axis... c With a coercivity of ≤0.5 MV / m and a coercive field Ec≤0.1 MV / m along the a-axis of the crystal, the a-axis polarization switching can be driven by low-voltage power sources such as button batteries and flexible piezoelectric power supply modules while significantly reducing energy consumption.

[0059] In one possible implementation, the Curie temperature T of the organic ferroelectric eutectic material is... c ≥479 K. Curie temperature T of organic ferroelectric eutectic materials. c At ≥479 K, organic ferroelectric eutectic has broken free from the limitation of being "only applicable to room temperature scenarios" and successfully entered the medium- and high-temperature application fields that traditional organic materials cannot reach, greatly enhancing its industrialization value.

[0060] In one possible implementation, the rotation angle is 20° to 50°. Compared to the nearly 180° flip required for the dipole in the conventional mechanism, a rotation angle of 20° to 50° only requires a small angle rotation of about a quarter turn to achieve polarization reversal, indicating that polarization reversal only requires overcoming an extremely low energy barrier.

[0061] In a second aspect, the present invention provides a method for preparing the above-mentioned organic ferroelectric eutectic material, comprising the following steps:

[0062] S1. Dissolve the donor and acceptor molecules in an organic solvent to form a homogeneous solution;

[0063] The homogeneous dissolution process in step S1 allows the donor and acceptor molecules to exist in a molecular-level dispersed state in the solvent.

[0064] S2. The solvent of the solution obtained in step S1 is evaporated to allow the donor molecules and acceptor molecules to co-crystallize, thereby obtaining an organic ferroelectric eutectic material.

[0065] During the solvent evaporation process in step S2, the medium effect of the solvent promotes the supramolecular self-assembly of donor and acceptor molecules. The molecular-level dispersion of donor and acceptor molecules allows each donor molecule to interact effectively with the surrounding acceptor molecules. The CH active sites of the donor molecules and the N / F hydrogen bonding sites of the acceptor molecules can be precisely identified and oriented to bind, spontaneously forming "sandwich sandwich units". The slow kinetics of solvent evaporation provides sufficient time for molecular self-assembly. As the molecular concentration gradually increases, the oriented interaction also causes the sandwich sandwich units to be arranged in an orderly manner along the same direction. The orderly arranged sandwich units gradually grow into a long-range ordered crystal structure.

[0066] The method for preparing organic ferroelectric eutectic materials provided by this invention achieves multiple advantages, including stable process, low cost, and suitability for large-area processing, through a simplified "solvent dissolution-solvent evaporation" process. The entire preparation process requires no high temperature, high pressure, or special catalysts; it can be completed using only conventional laboratory or industrial equipment, avoiding damage to the molecular structure under extreme conditions and ensuring process stability and repeatability. Equipment-wise, it eliminates the need for expensive specialized high-temperature furnaces and high-pressure reactors, resulting in low initial equipment investment costs, making it particularly suitable for technology transfer and mass production for small and medium-sized enterprises. A homogeneous solution is coated onto a flexible or rigid substrate using methods such as spin coating, blade coating, or inkjet printing, and then large-area ferroelectric thin films can be directly prepared through solvent evaporation. This "one-step film formation" characteristic allows the eutectic to be directly used in the fabrication of flexible displays, wearable sensors, and other devices.

[0067] In one possible implementation, the molar ratio of the donor molecule to the acceptor molecule is (0.8-1.2):1. Limiting the molar ratio of donor to acceptor molecules to (0.8-1.2):1 ensures that the vast majority of molecules in the reaction system can participate in the formation of a long-range ordered supramolecular structure, which is beneficial for improving the purity of the organic ferroelectric eutectic.

[0068] In one possible implementation, the organic solvent is selected from one or more of acetonitrile, chloroform, dichloromethane, tetrahydrofuran, and toluene. These solvents can fully dissolve the donor and acceptor molecules to form a homogeneous solution with molecular-level dispersion, without chemically reacting with the donor or acceptor, and without interfering with the predetermined key supramolecular interactions such as "directional hydrogen bonding" and "π-π stacking," thereby ensuring that the donor and acceptor molecules interact to form a long-range ordered crystal structure.

[0069] Thirdly, the present invention provides a ferroelectric device, including a ferroelectric functional layer, wherein the ferroelectric functional layer contains the above-mentioned organic ferroelectric eutectic material.

[0070] In one possible implementation, the ferroelectric device is one of a non-volatile memory, a field-effect transistor, a sensor, an energy storage device, and a piezoelectric device.

[0071] Based on common knowledge in the field, the above-described embodiments can be combined arbitrarily.

[0072] The technical solution of the present invention will be further described below with reference to specific embodiments. All reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing. The instruments used in the embodiments are also commercially available.

[0073] Example 1

[0074] This embodiment provides a DNF-DTTCNQ ferroelectric eutectic material with a layered structure formed by alternating stacking of DNF and DTTCNQ molecules along the CT axis. Each DNF molecule is sandwiched in a cavity formed by two adjacent DTTCNQ molecules, forming a sandwich unit. DNF and DTTCNQ molecules are bonded by directional hydrogen bonds to form a cis-donor-acceptor arrangement, and the rotation of DNF molecules is restricted by the steric hindrance of two adjacent DTTCNQ molecules. Multiple sandwich units are periodically slip-stacking and stacked along the CT axis, and DNF molecules in adjacent sandwich units rotate cooperatively under the action of an electric field.

[0075] It is prepared through the following steps:

[0076] S1, 12.8 mg of DNF and 15.09 mg of DTTCNQ were dissolved in 40 mL of acetonitrile to form a homogeneous mixed solution;

[0077] S2. Place the mixed solution obtained in step S1 in a test tube to evaporate the solvent. During the solvent evaporation process, DNF molecules and DTTCNQ molecules undergo co-crystallization through charge transfer to obtain a black, elongated DNF-DTTCNQ ferroelectric eutectic material.

[0078] Example 2

[0079] This embodiment provides a DNT-DTTCNQ ferroelectric eutectic material with a layered structure formed by alternating stacking of DNT and DTTCNQ molecules along the CT axis. Each DNT molecule is sandwiched in a cavity formed by two adjacent DTTCNQ molecules, forming a sandwich unit. The DNT and DTTCNQ molecules are bonded by directional hydrogen bonds to form a cis-donor-acceptor arrangement, and the rotation of the DNT molecules is restricted by the steric hindrance of the two adjacent DTTCNQ molecules. Multiple sandwich units are periodically slip-stackingly stacked along the CT axis, and the DNT molecules in adjacent sandwich units rotate cooperatively under the action of an electric field.

[0080] It is prepared through the following steps:

[0081] S1, 13.6 mg of DNT and 15.09 mg of DTTCNQ were dissolved in 40 mL of acetonitrile to form a homogeneous mixed solution;

[0082] S2. Place the mixed solution obtained in step S1 in a test tube to evaporate the solvent. During the solvent evaporation process, DNT molecules and DTTCNQ molecules undergo co-crystallization through charge transfer to obtain a black, elongated DNT-DTTCNQ ferroelectric eutectic material.

[0083] Example 3

[0084] This embodiment provides a 3,11-FDNF-DTTCNQ ferroelectric eutectic material, which has a layered structure formed by alternating stacking of 3,11-FDNF molecules and DTTCNQ molecules along the CT axis. Each 3,11-FDNF molecule is sandwiched in a cavity formed by two adjacent DTTCNQ molecules, and together they form a sandwich unit. The 3,11-FDNF molecules and DTTCNQ molecules form a cis-donor-acceptor arrangement through directional hydrogen bonding, and the rotation of the 3,11-FDNF molecules is restricted by the steric hindrance of the two adjacent DTTCNQ molecules. Multiple sandwich units are periodically slip-stackingly stacked along the CT axis, and the 3,11-FDNF molecules in adjacent sandwich units rotate cooperatively under the action of an electric field.

[0085] It is prepared through the following steps:

[0086] S1, 14.5 mg of 3,11-FDNF and 15.09 mg of DTTCNQ were dissolved in 40 mL of acetonitrile to form a homogeneous mixed solution;

[0087] S2. Place the mixed solution obtained in step S1 in a test tube to evaporate the solvent. During the solvent evaporation process, 3,11-FDNF molecules and DTTCNQ molecules undergo co-crystallization through charge transfer to obtain a black, elongated 3,11-FDNF-DTTCNQ ferroelectric eutectic material.

[0088] Example 4

[0089] This embodiment provides a DNSe-DTTCNQ ferroelectric eutectic material with a layered structure formed by alternating stacking of DNSe and DTTCNQ molecules along the CT axis. Each DNSe molecule is sandwiched in a cavity formed by two adjacent DTTCNQ molecules, forming a sandwich unit. DNSe and DTTCNQ molecules are bonded by directional hydrogen bonds to form a cis-donor-acceptor arrangement, and the rotation of DNSe molecules is restricted by the steric hindrance of two adjacent DTTCNQ molecules. Multiple sandwich units are periodically slip-stackingly stacked along the CT axis, and DNSe molecules in adjacent sandwich units rotate cooperatively under the action of an electric field.

[0090] It is prepared through the following steps:

[0091] S1, 16 mg of DNSe and 15.09 mg of DTTCNQ were dissolved in 40 mL of chloroform to form a homogeneous mixed solution;

[0092] S2. Place the mixed solution obtained in step S1 in a test tube to evaporate the solvent. During the solvent evaporation process, DNSe molecules and DTTCNQ molecules undergo co-crystallization through charge transfer to obtain a black, elongated DNSe-DTTCNQ ferroelectric eutectic material.

[0093] Example 5

[0094] This embodiment provides a DNF-F2-DTTCNQ ferroelectric eutectic material, which has a layered structure formed by alternating stacking of DNF molecules and F2-DTTCNQ molecules along the CT axis. Each DNF molecule is sandwiched in a cavity formed by two adjacent F2-DTTCNQ molecules, and together they form a sandwich unit. DNF molecules and F2-DTTCNQ molecules form a cis-donor-acceptor arrangement through directional hydrogen bonding, and the rotation of DNF molecules is restricted by the steric hindrance of two adjacent F2-DTTCNQ molecules. Multiple sandwich units are periodically slip-stackingly stacked along the CT axis, and DNF molecules in adjacent sandwich units rotate cooperatively under the action of an electric field.

[0095] It is prepared through the following steps:

[0096] S1, 12.8 mg of DNF and 16.66 mg of F2-DTTCNQ were dissolved in 40 mL of dichloromethane to form a homogeneous mixed solution;

[0097] S2. Place the mixed solution obtained in step S1 in a test tube to evaporate the solvent. During the solvent evaporation process, DNF molecules and F2-DTTCNQ molecules undergo co-crystallization through charge transfer to obtain a black, elongated DNF-F2-DTTCNQ ferroelectric eutectic material.

[0098] Example 6

[0099] This embodiment provides a DNT-Cl2-DTTCNQ ferroelectric eutectic material, which has a layered structure formed by alternating stacking of DNT molecules and Cl2-DTTCNQ molecules along the CT axis. Each DNT molecule is sandwiched in a cavity formed by two adjacent Cl2-DTTCNQ molecules, and together they form a sandwich unit. The DNT molecules and Cl2-DTTCNQ molecules form a cis-donor-acceptor arrangement through directional hydrogen bonding, and the rotation of the DNT molecules is restricted by the steric hindrance of the two adjacent Cl2-DTTCNQ molecules. Multiple sandwich units are periodically slip-stackingly stacked along the CT axis, and the DNT molecules in adjacent sandwich units rotate cooperatively under the action of an electric field.

[0100] It is prepared through the following steps:

[0101] S1, 13.6 mg of DNT and 18.1 mg of Cl2-DTTCNQ were dissolved in 40 mL of tetrahydrofuran solvent to form a homogeneous mixed solution;

[0102] S2. Place the mixed solution obtained in step S1 in a test tube to evaporate the solvent. During the solvent evaporation process, DNT molecules and Cl2-DTTCNQ molecules undergo co-crystallization through charge transfer to obtain a black, elongated DNT-Cl2-DTTCNQ ferroelectric eutectic material.

[0103] Example 7

[0104] This embodiment provides a 3,11-FDNF-(CN)2-DTTCNQ ferroelectric eutectic material, which has a layered structure formed by alternating stacking of 3,11-FDNF molecules and (CN)2-DTTCNQ molecules along the CT axis. Each 3,11-FDNF molecule is sandwiched in a cavity formed by two adjacent (CN)2-DTTCNQ molecules, and together they form a sandwich unit. The 3,11-FDNF molecules and (CN)2-DTTCNQ molecules are bonded by directional hydrogen bonds to form a cis-donor-acceptor arrangement, and the rotation of the 3,11-FDNF molecules is restricted by the steric hindrance of the two adjacent (CN)2-DTTCNQ molecules. Multiple sandwich units are arranged in a periodic sliding stack along the CT axis, and the 3,11-FDNF molecules in adjacent sandwich units rotate cooperatively under the action of an electric field.

[0105] It is prepared through the following steps:

[0106] S1, 14.5 mg of 3,11-FDNF and 17.27 mg of (CN)2-DTTCNQ were dissolved in 40 mL of toluene to form a homogeneous mixed solution;

[0107] S2. Place the mixed solution obtained in step S1 in a test tube to evaporate the solvent. During the solvent evaporation process, 3,11-FDNF molecules and (CN)2-DTTCNQ molecules undergo co-crystallization through charge transfer to obtain a black, elongated 3,11-FDNF-(CN)2-DTTCNQ ferroelectric eutectic material.

[0108] Example 8

[0109] This embodiment provides a DNF-EH-DTTCNQ ferroelectric eutectic material, which has a layered structure formed by alternating stacking of DNF molecules and EH-DTTCNQ molecules along the CT axis. Each DNF molecule is sandwiched in a cavity formed by two adjacent EH-DTTCNQ molecules, and together they form a sandwich unit. The DNF molecules and EH-DTTCNQ molecules form a cis-donor-acceptor arrangement through directional hydrogen bonding, and the rotation of the DNF molecules is restricted by the steric hindrance of the two adjacent EH-DTTCNQ molecules. Multiple sandwich units are arranged in a periodic sliding stack along the CT axis, and the DNF molecules in adjacent sandwich units rotate cooperatively under the action of an electric field.

[0110] It is prepared through the following steps:

[0111] S1, 12.8 mg of DNF and 24.91 mg of EH-DTTCNQ were dissolved in 40 mL of acetonitrile to form a homogeneous mixed solution;

[0112] S2. Place the mixed solution obtained in step S1 in a test tube to evaporate the solvent. During the solvent evaporation process, DNF molecules and EH-DTTCNQ molecules undergo co-crystallization through charge transfer to obtain a black, elongated DNF-EH-DTTCNQ ferroelectric eutectic material.

[0113] The performance of the ferroelectric crystals prepared in Examples 1-3 was tested, and the results are as follows:

[0114] Figure 1 This is a schematic diagram showing the synthesis process, crystal packing structure, and dipole moment distribution of the DNF-DTTCNQ ferroelectric eutectic material in Example 1. Figure 1 Figure A shows a schematic diagram of the synthesis process of DNF-DTTCNQ ferroelectric eutectic material. On the left side of the figure is the donor molecule DNF, which is a white powdery crystal, and in the middle is the acceptor molecule DTTCNQ, which is a brownish powder. DNF and DTTCNQ are dissolved in a solvent in a certain proportion. As the solvent slowly evaporates, the two self-assemble through charge transfer (CT) to form the DNF-DTTCNQ ferroelectric eutectic material on the right side, which is a black fibrous crystal.

[0115] Figure 1Figure B shows a side view of the molecular packing structure of the DNF-DTTCNQ ferroelectric eutectic material at 293 K. The crystallographic axes a, b, and c are marked in the figure. The donor DNF (containing a framework with red directional hydrogen bonds) and the acceptor DTTCNQ (containing a framework with yellow S and blue -CN bonds) sandwich the DNF from the top and bottom along the b-axis, forming a "sandwich unit". In other words, the DNF is nested in the spatial constraint of the DTTCNQ. Multiple "sandwich units" are arranged in an alternating pattern along the c-axis (corresponding to "110.8° slip packing"). The highly ordered packing forces the dipole orientation (the direction of the V-shaped opening) of all DNF molecules to be consistent, realizing the long-range ordered arrangement of dipoles and laying the foundation for the generation of strong macroscopic polarization.

[0116] Figure 1 Figure C shows a schematic diagram of the dipole moment distribution along the c-axis of the DNF-DTTCNQ ferroelectric eutectic material. In the diagram, the donor DNF (containing the framework of red oriented hydrogen bonds) is oriented along the c-axis. The blue arrows represent the dipole direction of a single DNF molecule (along the midline of the V-shaped opening). The dipole directions of all DNF molecules are consistent along the c-axis (without cancellation), forming a long-range ordered polar network. This results in a high spontaneous polarization intensity P along the c-axis in the DNF-DTTCNQ ferroelectric eutectic material. c It reaches 72 μC / cm² (marked below the figure), which is close to the level of inorganic ferroelectrics.

[0117] Figure 1 Figure D shows a schematic diagram of the dipole moment distribution along the a-axis of the DNF-DTTCNQ ferroelectric eutectic material. As can be seen from the figure, DNF molecules are arranged in an unequal-angled ordered manner along the a-axis, meaning adjacent DNF molecules have different tilt angles. The dipole components of the DNF molecules along the a-axis are oriented and superimposed, forming supramolecular dipoles; this results in the spontaneous polarization intensity P of the DNF-DTTCNQ ferroelectric eutectic material along the a-axis. a The coercive field is 24 μC / cm² (marked below the figure). In this direction, DNF molecules can rotate like gears, resulting in an extremely low coercive field.

[0118] Figure 2 The image shows the ferroelectric properties of the DNF-DTTCNQ ferroelectric eutectic material in Example 1. Figure 2 Figure A shows the differential scanning calorimetry (DSC) curve of the DNF-DTTCNQ ferroelectric eutectic material. During the heating process (red curve), a distinct endothermic peak appears between approximately 479 K and 492 K; during the cooling process (blue curve), a corresponding exothermic peak appears between approximately 450 K and 440 K. This pair of reversible endothermic / exothermic peaks indicates that the DNF-DTTCNQ ferroelectric eutectic material transforms from an ordered ferroelectric phase to a disordered paraelectric phase upon heating, and reverts to the ferroelectric phase upon cooling. This phase transition temperature is its ferroelectric Curie temperature T. cThe K value is approximately 479 K, which is much higher than room temperature and also higher than many classic inorganic ferroelectrics, proving that the DNF-DTTCNQ ferroelectric eutectic material has high-temperature ferroelectricity.

[0119] Figure 2 The figure shows the polarization-dependent dielectric loss tangent (SHG) response curve and the fitted curve of the DNF-DTTCNQ ferroelectric eutectic material at 0 K when B is 0 K. The polar plot shows the change of SHG signal intensity with the incident laser polarization angle (0-360°). The signal exhibits clear two-fold rotational symmetry, with two strong peaks and two weak peaks, resembling a "bow tie". The SHG effect can only occur in non-centrosymmetric materials, and this "bow tie" pattern clearly confirms that the DNF-DTTCNQ ferroelectric crystal does not have an inversion symmetry center.

[0120] Figure 2 In the figure, C represents the amplitude and phase hysteresis loop of the DNF-DTTCNQ ferroelectric eutectic material. The amplitude-voltage curve (blue) in the figure exhibits a typical "butterfly curve." When the applied DC bias voltage (Bias) scans from negative to positive, the amplitude of the piezoelectric vibration signal first decreases, reaches a minimum near the coercive field, and then rises, forming two symmetrical "wings." The phase-voltage curve (red) exhibits a typical "rectangular hysteresis loop." The phase signal stabilizes at a value in the negative voltage region, undergoes a near 180° abrupt change when the voltage sweeps across the coercive field, then stabilizes at another value in the positive voltage region, and experiences another 180° abrupt change during the reverse scan. The butterfly curve originates from the process where the piezoelectric response first cancels and then enhances when the ferroelectric domains flip under an electric field. The 180° phase flip directly proves that the polarization direction of the ferroelectric domains can be completely and reversibly controlled by an external voltage. The combination of these two factors confirms that the DNF-DTTCNQ ferroelectric eutectic material exhibits switchable spontaneous polarization at room temperature, thus demonstrating the ferroelectric properties of the DNF-DTTCNQ ferroelectric eutectic material.

[0121] Figure 2 Figure D shows the temperature dependence curve of the dielectric constant of the DNF-DTTCNQ eutectic. During the heating process, a sharp anomalous peak appears near approximately 479 K. Ferroelectric materials typically exhibit a maximum dielectric constant near the Curie temperature due to the dipole order-disorder phase transition. This peak is highly consistent with the endothermic peak temperature obtained by DSC, further verifying the Curie temperature determined by DSC from an electrical property perspective. The sharp peak shape indicates that the phase transition is first-order and the crystal quality is relatively good.

[0122] Figure 2E represents the polarization-electric field loop along the c-axis of the DNF-DTTCNQ ferroelectric eutectic material at room temperature, under conditions of 50 Hz frequency and 298 K temperature. The curve exhibits a typical hysteresis loop shape. When the electric field is parallel to the c-axis, the maximum polarization intensity P of the DNF-DTTCNQ ferroelectric eutectic material is... max >70 μC / cm², remanent polarization P r The value is approximately 58 μC / cm², indicating that the DNF-DTTCNQ ferroelectric eutectic material possesses high polarization intensity along the c-axis, with performance approaching that of inorganic ferroelectrics.

[0123] Figure 2 In the figure, F represents the polarization-electric field loop along the a-axis of the DNF-DTTCNQ ferroelectric eutectic material at room temperature, under the conditions of a frequency of 50 Hz and a temperature of 298 K. When the electric field is parallel to the a-axis, the loop also exhibits ferroelectric characteristics, but the coercive field E... c Extremely low, only about 0.022 MV / m; remanent polarization P r The value is approximately 12 μC / cm², indicating that the DNF-DTTCNQ ferroelectric eutectic material has low coercivity along the a-axis and low energy consumption for polarization switching.

[0124] Figure 3 The image shows the high-temperature ferroelectric performance data of the DNF-DTTCNQ ferroelectric eutectic material in Example 1. Figure 3 Figure A shows the polarization hysteresis loops of the DNF-DTTCNQ ferroelectric eutectic material at different temperatures. Even at a temperature as high as 508 K, the hysteresis loops maintain a typical "full" shape and do not collapse into linear or severely leaky curves. This proves that spontaneous polarization of the DNF-DTTCNQ ferroelectric eutectic material still exists at high temperatures and can be reversibly switched by an electric field.

[0125] Figure 3 In the figure, B represents the polarization temperature dependence of the DNF-DTTCNQ ferroelectric eutectic material, and E represents the coercive field. c (The blue curve) decreases monotonically with increasing temperature, which is typical behavior of ferroelectric materials because thermal fluctuations help overcome the energy barrier of polarization reversal; the maximum polarization intensity P max and residual polarization P r All values ​​decrease slowly with increasing temperature, but remain considerable even at temperatures far above room temperature. This indicates that the DNF-DTTCNQ ferroelectric eutectic material shows promise for stable operation in environments far above room temperature.

[0126] Figure 3 In the diagram, C represents the temperature dependence of the polarization intensity along the c-axis and a-axis of the DNF-DTTCNQ ferroelectric eutectic material, and P represents the polarization intensity along the c-axis. c The polarization of P along the a-axis decreases slowly with increasing temperature. aThe decay is more gradual, and both decrease rapidly to 0 only when approaching 500K; this indicates that the multiaxial polarization characteristics (high polarization of the c-axis and low coercivity of the a-axis) of the DNF-DTTCNQ ferroelectric eutectic material can be maintained over a wide temperature range, making it suitable for operation under complex temperature conditions.

[0127] Figure 3 The image shows the XRD patterns of the DNF-DTTCNQ ferroelectric eutectic material at different temperatures. Below 508 K, the positions and intensities of the characteristic diffraction peaks of the XRD remain basically stable, without significant broadening or shift. At high temperatures, the crystal structure of the eutectic does not undergo disordering or decomposition, indicating that the DNF-DTTCNQ ferroelectric eutectic material can maintain structural stability over a wide temperature range.

[0128] Figure 4 These are two energy-degenerate ferroelectric structures of the DNF-DTTCNQ ferroelectric eutectic material in Example 1, with arrows indicating the polarization direction. Figure 4 In A, the dipole direction of the DNF molecule is along the negative c-axis (red arrow), and at this time, the DNF-DTTCNQ ferroelectric eutectic material exhibits a "-polarized" ferroelectric state (-P state). Figure 4 In B, the dipole direction of the DNF molecule is along the positive c-axis (blue arrow). At this time, the DNF-DTTCNQ ferroelectric eutectic material exhibits a "+polarized" ferroelectric state (+P state). These two states are degenerate in energy (i.e., the energy is equal), but the polarization directions are opposite, which constitutes the basis of the bistable state of ferroelectric materials.

[0129] Figure 5 This is a schematic diagram of the polarization switching mechanism of the DNF-DTTCNQ ferroelectric eutectic material in Example 1. Figure 5 This diagram illustrates a gear-like rotation mechanism where two polarization orientations of DNF molecules along the c-axis switch under the influence of an electric field, representing the dynamic process of polarization transitioning from a -P state to a +P state. Under an applied electric field (E), adjacent DNF molecules rotate collaboratively in clockwise and counterclockwise directions, similar to the meshing rotation of gears. For example, upper-layer DNF molecules rotate clockwise, while lower-layer DNF molecules rotate counterclockwise. The rigid "box" formed by the DTTCNQ acceptor restricts the rotation axis and plane, forcing all DNF molecules to rotate collaboratively and uniformly, thus achieving efficient macroscopic polarization reversal. This "gear-like interlocking" rotation avoids spatial conflicts between molecules and achieves synchronous reversal of dipole orientations. Unlike the "flipping" of dipoles in traditional ferroelectrics, which requires overcoming a huge energy barrier, polarization switching in this invention is achieved through rotation within a confined plane of the donor molecules. This "rotation" mode requires much less energy than "flipping."

[0130] Figure 6The figure shows the polarization switching energy barrier of the DNF-DTTCNQ ferroelectric eutectic material as a function of rotation angle (φ), predicted by theoretical calculations (machine learning molecular dynamics). From "state A (-P)" to "state B (+P)," the energy first increases and then decreases, with the switching energy barrier being only about 56 meV / molecule, far lower than the out-of-plane flip energy barrier of traditional organic ferroelectrics. The rotation angle corresponding to the peak of the barrier (i.e., the transition state) is approximately 42°. This means that DNF molecules only need to rotate about 42° to cross the energy barrier and complete the switch from one polarization state to another. From an energy perspective, this proves that "planar rotation" is a low-barrier path, and the extremely low barrier corresponds to the extremely low coercive field E measured in the experiment. c .

[0131] Figure 7 For DNF-DTTCNQ ferroelectric eutectic materials and P of previously reported ferroelectric materials r and 1 / E c Performance comparison chart, residual polarization intensity P r The larger the value, the higher the charge density that the material can store, and the stronger its performance; the reciprocal of the coercive field 1 / E c The smaller the value, the easier the polarization switching. Compared to the data points in the figure representing different types of ferroelectric materials, the DNF-DTTCNQ ferroelectric eutectic material (red asterisk) is at a high P value. r and high 1 / E c It has the optimal region and the characteristics of strong polarization and easy switching, and its performance surpasses that of previously reported organic / organic-inorganic hybrid ferroelectric materials.

[0132] Figure 8 The image shows a comparison of the XRD test curves and simulated curves of the DNT-DTTCNQ ferroelectric eutectic material in Example 1. The diffraction peak positions (2θ) of the two curves are highly matched, with only slight differences in intensity. This indicates that the crystal structure of the actually synthesized DNT-DTTCNQ ferroelectric eutectic material is consistent with the theoretically designed "gearbox-like stacked structure"; and the synthesis process did not introduce impurities or structural defects, resulting in high purity and controllable structure of the DNT-DTTCNQ ferroelectric eutectic material.

[0133] Figure 9 The room-temperature hysteresis loop of the DNT-DTTCNQ ferroelectric eutectic material in Example 2 exhibits a typical "closed hysteresis loop," a hallmark characteristic of ferroelectrics. The extreme points at both ends of the curve correspond to the maximum polarization intensity P. max The remanent polarization intensity P is approximately 71 μC / cm when the applied electric field is 0. r The intersection of the curve and the vertical axis is approximately 55 μC / cm², representing the coercive field E required to reduce the polarization intensity to zero. n (The intersection of the curve and the horizontal axis) is approximately 0.46 MV / m. Pmax and P r The performance is at a high level, close to that of the DNF-DTTCNQ ferroelectric eutectic material in Example 1, indicating that DNT as a donor molecule can also achieve strong polarization; the curve morphology is regular and there is no obvious noise at room temperature, proving that the ferroelectric properties of this eutectic are stable at room temperature.

[0134] Figure 10 The room-temperature hysteresis loop of the 3,11-FDNF-DTTCNQ ferroelectric eutectic material in Example 3 exhibits a typical "closed hysteresis loop," a hallmark feature of ferroelectric materials, indicating that this eutectic possesses ferroelectric core properties with switchable polarization directions. The extreme points at both ends of the curve correspond to the maximum polarization intensity P. max The remanent polarization intensity P is approximately 75 μC / cm when the applied electric field is 0. r The intersection of the curve and the vertical axis is approximately 60 μC / cm², representing the coercive field E required to reduce the polarization intensity to zero. n The intersection of the curve and the horizontal axis is approximately 0.48 MV / m. 3,11-FDNF is a fluorine-substituted derivative of DNF. Compared to the DNF-DTTCNQ ferroelectric eutectic material of Example 1, the maximum polarization of the 3,11-FDNF-DTTCNQ ferroelectric eutectic material is slightly improved, possibly due to the strong electronegativity of fluorine atoms enhancing the molecular dipole moment, thus further increasing the macroscopic polarization intensity. Fluorine substitution did not disrupt the stability of the gearbox-like structure; the curve shape is regular and without significant distortion, indicating that the design concept of "introducing substituents to regulate performance" in the donor molecule of this application is feasible. The curve at room temperature shows no significant noise or broadening, proving that the eutectic exhibits stable ferroelectric properties under normal operating conditions, making it suitable for the working environment of most electronic devices.

[0135] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An organic ferroelectric eutectic material, characterized in that, The crystal structure is formed by supramolecular self-assembly of donor and acceptor molecules and has a long-range ordered crystal structure. The donor molecules are π-conjugated organic molecules with non-centrosymmetric geometry and intrinsic molecular dipole moments; the acceptor molecules are π-conjugated organic molecules with planar rigid geometry and electron-withdrawing ability. In the crystal structure, donor and acceptor molecule layers are alternately stacked along the CT axis, with each donor molecule spatially sandwiched between two adjacent acceptor molecules, forming a sandwich unit. Multiple sandwich units are periodically slid and stacked along a direction perpendicular to the CT axis, causing the dipole moments of the donor molecules to be oriented, thereby generating macroscopic spontaneous polarization in the crystal. The donor and acceptor molecules form a gearbox-like crystal structure, with the acceptor molecules forming the box. Adjacent donor molecules can perform in-plane cooperative rotation within the confined space formed by the acceptor molecules under the influence of an external electric field, thereby achieving the switching of the macroscopic spontaneous polarization direction. The donor molecule is selected from molecules having the structure shown in general formula I. （I） In formula (I), Y is one of O, S, Se and NR, R is H or C1-C4 alkyl, and X is H or F; The receptor molecule is selected from at least one of 2,2'-(benzo[1,2-B;4,5-B']dithiophene-4,8-diylidene)dimalononitrile, 3,6-difluoro-DTTCNQ, 3,6-dichloro-DTTCNQ, 3,6-dicyano-DTTCNQ, 3,6-bis(2-ethylhexyl)-DTTCNQ and 2,2'-(benzo[1,2-b:4,5-b']dithiophene-4,8-diyl)bis(5-fluoro-1,3-benzothiazole).

2. The organic ferroelectric eutectic material according to claim 1, characterized in that, The donor molecule is selected from at least one of dinaphtho[2,1-B:1',2'-D]furan, dinaphtho[2,1-B:1',2'-D]thiophene, 3,11-difluorodinaphtho[2,1-B:1',2'-D]furan, and dinaphtho[2,1-b:1',2'-d]selenophene.

3. The organic ferroelectric eutectic material according to claim 1, characterized in that, The non-centrosymmetric geometric configuration is V-shaped or bow-shaped, and the planar rigid geometric configuration is planar or saddle-shaped.

4. The organic ferroelectric eutectic material according to claim 1, characterized in that, The CT axis of the organic ferroelectric eutectic material is aligned with the c-axis of the crystal, and its spontaneous polarization intensity Pr along the c-axis is ≥70 μC / cm. 2 The spontaneous polarization intensity along the a-axis of the crystal is Pr ≥ 25 μC / cm 2 ; And / or, the CT axis direction of the organic ferroelectric eutectic material is the crystal c-axis direction, and the coercive field Ec of the organic ferroelectric eutectic material along the crystal c-axis is ≤0.5 MV / m, and the coercive field Ec along the crystal a-axis is ≤0.1 MV / m; And / or, the Curie temperature Tc of the organic ferroelectric eutectic material is ≥479 K.

5. The organic ferroelectric eutectic material according to claim 1, characterized in that, The rotation angle is between 20° and 50°.

6. A method for preparing an organic ferroelectric eutectic material as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Dissolve the donor and acceptor molecules in an organic solvent to form a homogeneous solution; S2. The solvent of the solution obtained in step S1 is evaporated to allow the donor molecules and acceptor molecules to co-crystallize, thereby obtaining an organic ferroelectric eutectic material.

7. The method for preparing the organic ferroelectric eutectic material according to claim 6, characterized in that, The molar ratio of the donor molecule to the acceptor molecule is (0.8-1.2):

1.

8. The method for preparing the organic ferroelectric eutectic material according to claim 6, characterized in that, The organic solvent is selected from one or more of acetonitrile, chloroform, dichloromethane, tetrahydrofuran, and toluene.

9. A ferroelectric device, comprising a ferroelectric functional layer, characterized in that, The ferroelectric functional layer contains the organic ferroelectric eutectic material as described in any one of claims 1-5.

10. The ferroelectric device according to claim 9, characterized in that, The ferroelectric device is one of the following: non-volatile memory, field-effect transistor, sensor, energy storage device, and piezoelectric device.

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