A lead-based molecular ferroelectric and a method of making the same
The hydrothermal synthesis of lead-based molecular ferroelectrics solves the preparation problems in existing technologies, and achieves the preparation of lead-based molecular ferroelectrics with high crystallinity and high purity. These ferroelectric photovoltaics exhibit ferroelectric properties and are suitable for optoelectronic devices and information storage.
Patent Information
- Application Number
- CN202311725121.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-14
- Publication Date
- 2026-01-30
- Estimated Expiration
- 2043-12-14
AI Technical Summary
Existing technologies make it difficult to prepare highly crystalline and high-purity organic-inorganic hybrid lead halide ferroelectric molecules easily and quickly, and conventional methods require extreme reaction conditions and high costs.
Lead-based molecular ferroelectrics were synthesized by a hydrothermal method. Organic ligand A was added to the solution of oxide PbO in an excess of halogen aqueous solution, followed by a hydrothermal reaction, and then the mixture was washed and dried to prepare lead-based molecular ferroelectrics A2PbQ4 with a layered structure.
A simple and mild preparation process was achieved, resulting in lead-based molecular ferroelectrics with high crystallinity and high purity, exhibiting significant ferroelectric photovoltaic properties, which can be widely used in optoelectronic devices and information storage fields.
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Figure CN117720568B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a lead-based molecular ferroelectric and its preparation method, belonging to the field of molecular ferroelectric materials technology. Background Technology
[0002] Among various ferroelectric materials, molecular ferroelectric materials are highly favored in the field due to their advantages such as structural tunability, light weight, ease of environmentally friendly processing, and mechanical flexibility. Inorganic semiconductor ferroelectric materials, such as BiFeO3, have shown great potential in photovoltaics and photocatalysts due to their large photovoltage and switchable photocurrent, exceeding their band gap by several times; however, their extremely low conversion efficiency limits their applications. In contrast, organic-inorganic hybrid lead halide molecular ferroelectrics possess advantages such as good structural tunability, large spontaneous polarization, and high piezoelectric response, showing broad application prospects in ferroelectric memories, piezoelectric devices, capacitors, sensors, and optoelectronics, attracting considerable interest. However, the ferroelectricity of some lead halide molecular ferroelectrics remains controversial. Furthermore, there is currently no very simple synthetic method to prepare homogeneous organic-inorganic hybrid lead halide molecular ferroelectrics. Conventional solid-state methods typically require extreme reaction conditions and high costs, while solvent evaporation methods result in uneven reaction temperatures.
[0003] Therefore, it is of great significance to find a simpler, faster, and milder hydrothermal synthesis route to prepare highly crystalline and pure lead-based molecular ferroelectrics and to study their properties. Summary of the Invention
[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a lead-based molecular ferroelectric and its preparation method.
[0005] To achieve the above objectives, the present invention provides a lead-based molecular ferroelectric, wherein the general chemical formula of the lead-based molecular ferroelectric is A2PbQ4, wherein A is at least one of the organic ligands 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane and 1,8-diaminooctane, and Q is at least one of the halogen elements Cl, Br and I.
[0006] Preferably, the lead-based molecular ferroelectric has a layered structure, with each Pb atom coordinated with six Q atoms to form a (slightly) distorted PbQ6 octahedron. The PbQ6 octahedrons are connected by common vertices to form an octahedral layer, and A cations are intercalated in the interlayer spaces to form a layered structure.
[0007] The present invention also provides a method for preparing the above-mentioned lead-based molecular ferroelectric, comprising the following steps:
[0008] Step 1: Dissolve the oxide PbO in an excess of aqueous HQ solution;
[0009] Step 2: After all the solution has dissolved, add organic ligand A, stir and mix evenly, then transfer to a reaction vessel for hydrothermal reaction;
[0010] Step 3: After the reaction is complete, collect the precipitate obtained from the reaction, wash and dry it to obtain the lead-based molecular ferroelectric sample.
[0011] Preferably, the HQ in step 1 is at least one of HCl, HBr, and HI.
[0012] Preferably, the mass fraction of the aqueous solution of HQ is 30-50%.
[0013] Preferably, the molar ratio of PbO to A is 1:1.
[0014] Preferably, the hydrothermal reaction in step 2 is carried out at a temperature of 100–150°C for 10–15 hours.
[0015] The present invention also provides a molecular ferroelectric thin film material, the structure of which, from bottom to top, comprises a transparent conductive substrate, a molecular ferroelectric thin film, and a transparent conductive substrate; the molecular ferroelectric thin film is prepared using the above-mentioned molecular ferroelectric material.
[0016] This invention also provides applications of the above-mentioned molecular ferroelectrics in the fields of information storage, optoelectronic devices, or ferroelectric photovoltaics.
[0017] Compared with the prior art, the present invention has the following beneficial effects:
[0018] (1) The present invention uses a mild and simple hydrothermal method to prepare lead-based molecular ferroelectrics. The samples prepared by the hydrothermal method have good quality and relatively regular morphology.
[0019] (2) The lead-based molecular ferroelectric A2PbQ4 of the present invention can change the direction of photocurrent by adjusting the polarization voltage direction, indicating that the sample has obvious ferroelectric photovoltaic characteristics. It can be widely used in next-generation optoelectronic devices, has high economic value, and has broad application prospects in information storage, ferroelectric photovoltaic and other fields. Attached Figure Description
[0020] Figure 1 The [C4H] prepared in Example 1 of this invention 13 Powder XRD pattern and structural diagram of N2]2PbI4 molecular ferroelectric;
[0021] Figure 2 The [C4H] prepared in Example 1 of this invention 13 Crystal morphology, SEM, and EDS images of the N2]2PbI4 molecular ferroelectric;
[0022] Figure 3The [C4H] prepared in Example 1 13 Absorption and band gap diagrams of N2]2PbI4 molecular ferroelectric powder;
[0023] Figure 4 The [C4H] prepared in Example 2 13 I-T curves of N2]2PbI4 molecular ferroelectric thin films under different positive polarization voltages;
[0024] Figure 5 The [C4H] prepared in Example 2 13 I-T curves of N2]2PbI4 molecular ferroelectric thin films under different negative polarization voltages;
[0025] Figure 6 This is a schematic diagram of the structure of the molecular ferroelectric thin film material of the present invention. Detailed Implementation
[0026] To make the present invention more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings.
[0027] Example 1
[0028] A lead-based molecular ferroelectric [C4H] 13 The hydrothermal synthesis method of N2]2PbI4 specifically includes:
[0029] 1) Dissolve 0.01 mol PbO in 25 ml of hydroiodic acid and stir magnetically;
[0030] 2) After complete dissolution, add 1 mL of 1,4-diaminobutane to the above solution and continue magnetic stirring for a few minutes. The solution will become viscous and yellow.
[0031] 3) Then, fill the 50mL reaction vessel with the above mixture, make sure it is level and tightened, react in a 120℃ oven for 12 hours, then cool the reaction vessel to room temperature and depressurize it.
[0032] 4) After the vessel is cooled and depressurized, slowly pour off the supernatant, keeping the yellow precipitate. Use a disposable pipette to transfer the precipitate to a 50mL centrifuge tube. Use a pipette to pick up ethyl acetate and centrifuge to wash the crystal sample, being careful not to contaminate the ethyl acetate reagent.
[0033] 5) Repeatedly centrifuge the yellow sample, discarding the supernatant after each centrifugation, retaining the precipitate, and repeating the previous step by adding ethyl acetate to continue washing until the solvent is clear after centrifugation;
[0034] 6) Dry the washed yellow precipitate in a drying oven at 60°C to obtain the molecular ferroelectric [C4H]. 13 [N2]2PbI4.
[0035] Example 2
[0036] A lead-based molecular ferroelectric [C4H] 13 The preparation method of N2]2PbI4 thin film specifically includes:
[0037] 1) Weigh out 0.7g of [C4H] 13 [N2]2PbI4 crystal powder was dissolved in 650 μL of DMF to obtain a mixed solution;
[0038] 2) Stir the above mixture evenly on a magnetic stirrer at a speed of 240 r / min;
[0039] 3) After stirring evenly, spin coat the solution onto ITO using a spin coater at a speed of 3000 rpm for 20 seconds.
[0040] 4) Then dry the prepared film in an oven at 60°C;
[0041] 5) After drying, the film is transferred to a tube furnace for annealing to improve crystallinity. The specific process of vacuum annealing is to heat to 120°C at a rate of 1°C / min, calcine for 30 min, and then cool to room temperature under vacuum.
[0042] 6) After annealing, remove the film from the tube furnace. The resulting film is [C4H] 13 [N2]2PbI4 molecular ferroelectric thin film, the structure of which from bottom to top includes a transparent conductive substrate, molecular ferroelectric [C4H] 13 [N2]2PbI4 thin film, transparent conductive substrate, such as Figure 6 As shown.
[0043] Example 3
[0044] A lead-based molecular ferroelectric [C4H] 13 The hydrothermal synthesis method of N2]2PbBr4 specifically includes:
[0045] 1) Dissolve 0.01 mol PbO in 25 ml of hydrobromic acid and stir magnetically;
[0046] 2) After all the solution is dissolved, add 1 mL of 1,4-diaminobutane to the above solution and continue to stir magnetically for a few minutes. The solution will become viscous and milky white.
[0047] 3) Then, fill the 50mL reaction vessel with the above mixture, make sure it is level and tightened, react in a 120℃ oven for 12 hours, then cool the reaction vessel to room temperature and depressurize it.
[0048] 4) After the vessel is cooled and depressurized, slowly pour off the supernatant, keeping the white precipitate. Use a disposable pipette to transfer the precipitate to a 50mL centrifuge tube. Use a pipette to pick up ethyl acetate and centrifuge to wash the crystal sample, being careful not to contaminate the ethyl acetate reagent.
[0049] 5) Repeatedly centrifuge the white sample, discarding the supernatant after each centrifugation, retaining the precipitate, and repeating the previous step by adding ethyl acetate to continue washing until the solvent is clear after centrifugation;
[0050] 6) Dry the washed white precipitate in a drying oven at 60°C to obtain the molecular ferroelectric [C4H]. 13 [N2]2PbBr4.
[0051] Example 4
[0052] A lead-based molecular ferroelectric [C4H] 13 The hydrothermal synthesis method of N2]2PbCl4 specifically includes:
[0053] 1) Dissolve 0.01 mol PbO in 25 ml of hydrochloric acid and stir magnetically;
[0054] 2) After all the solution is dissolved, add 1 mL of 1,4-diaminobutane to the above solution and continue to stir magnetically for a few minutes. The solution will become viscous and milky white.
[0055] 3) Then, fill the 50mL reaction vessel with the above mixture, make sure it is level and tightened, react in a 120℃ oven for 12 hours, then cool the reaction vessel to room temperature and depressurize it.
[0056] 4) After the vessel is cooled and depressurized, slowly pour off the supernatant, keeping the white precipitate. Use a disposable pipette to transfer the precipitate to a 50mL centrifuge tube. Use a pipette to pick up ethyl acetate and centrifuge to wash the crystal sample, being careful not to contaminate the ethyl acetate reagent.
[0057] 5) Repeatedly centrifuge the white sample, discarding the supernatant after each centrifugation, retaining the precipitate, and repeating the previous step by adding ethyl acetate to continue washing until the solvent is clear after centrifugation;
[0058] 6) Dry the washed white precipitate in a drying oven at 60°C to obtain the molecular ferroelectric [C4H]. 13 [N2]2PbCl4.
[0059] Example 5
[0060] A lead-based molecular ferroelectric [C5H] 15 The hydrothermal synthesis method of N2]2PbI4 is described in Example 1, except that 1,5-diaminopentane is used instead of 1,4-diaminobutane.
[0061] Example 6
[0062] A lead-based molecular ferroelectric [C6H] 17 The hydrothermal synthesis method of N2]2PbI4 is described in Example 1, except that 1,6-diaminohexane is used instead of 1,4-diaminobutane.
[0063] Example 7
[0064] A lead-based molecular ferroelectric [C8H] 21 The hydrothermal synthesis method of N2]2PbI4 is described in Example 1, except that 1,8-diaminooctane is used instead of 1,4-diaminobutane.
[0065] Example 8
[0066] A lead-based molecular ferroelectric [C5H] 15 The hydrothermal synthesis method of N2]2PbBr4 is described in Example 3, except that 1,5-diaminopentane is used instead of 1,4-diaminobutane.
[0067] Example 9
[0068] A lead-based molecular ferroelectric [C6H] 17 The hydrothermal synthesis method of N2]2PbBr4 is described in Example 3, except that 1,6-diaminohexane is used instead of 1,4-diaminobutane.
[0069] Example 10
[0070] A lead-based molecular ferroelectric [C8H] 21 The hydrothermal synthesis method of N2]2PbBr4 is described in Example 3, except that 1,8-diaminooctane is used instead of 1,4-diaminobutane.
[0071] Example 11
[0072] A lead-based molecular ferroelectric [C5H] 15 The hydrothermal synthesis method of N2]2PbCl4 is described in Example 4, except that 1,5-diaminopentane is used instead of 1,4-diaminobutane.
[0073] Example 12
[0074] A lead-based molecular ferroelectric [C6H] 17 The hydrothermal synthesis method of N2]2PbCl4 is described in Example 4, except that 1,6-diaminohexane is used instead of 1,4-diaminobutane.
[0075] Example 13
[0076] A lead-based molecular ferroelectric [C8H] 21 The hydrothermal synthesis method of N2]2PbCl4 is described in Example 4, except that 1,8-diaminooctane is used instead of 1,4-diaminobutane.
[0077] Performance testing:
[0078] (1) X-ray diffraction was used to detect the molecular ferroelectric [C4H] prepared in Example 1. 13 The powder crystal structure of N2]2PbI4 and its XRD pattern are shown below. Figure 1 As shown, the obtained sample is a pure phase with high crystallinity. Structurally, each Pb atom coordinates with six Q atoms to form a slightly distorted PbQ6 octahedron. These PbQ6 octahedrons are connected by shared vertices to form octahedral layers. A cations are intercalated in the interlayer spaces to form a layered structure. The PbQ6 octahedral distortion caused by the organic ligands is the source of the sample's ferroelectricity. Figure 1 As shown.
[0079] (2) For molecular ferroelectrics [C4H 13 The crystal morphology, SEM, and EDS of N2]2PbI4 were measured, as shown below. Figure 2 As shown, the sample has a regular rod-shaped morphology; the prepared molecular ferroelectric [C4H] was analyzed using a UV-Vis-NIR spectrophotometer. 13 The N2]2PbI4 powder was subjected to absorption tests, and its band gap was calculated to be 2.30 eV. Figure 3 As shown.
[0080] (3) The molecular ferroelectric [C4H] prepared in Example 2 was tested using a KEITHLEY 2450 Source Meter. 13 The photoelectric properties of the N2]2PbI4 thin film, as shown by the IT curves, are as follows: Under a positive polarization voltage of 0 to 11V, the photocurrent gradually increases, reaching a maximum of 15.2 nA at 11V, and then gradually decreases. Under a negative polarization voltage of 0 to -9V, the photocurrent gradually increases, reaching a maximum of 16.8 nA at -9V, and then gradually decreases. The direction of the photocurrent can be changed by adjusting the polarization voltage, indicating that the sample exhibits significant ferroelectric photovoltaic characteristics. Figure 4 As shown in Figure 5.
[0081] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any form or substance. It should be noted that those skilled in the art can make several improvements and additions without departing from the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.
Claims
1. A method of preparing a lead-based molecular ferroelectric, characterized by, The chemical general formula of the lead-based molecular ferroelectric is A2PbQ4, wherein A is at least one of monohydrogen cations of organic ligands 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane and 1,8-diaminooctane, and Q is at least one of halogen elements Cl, Br and I. The preparation method comprises the following steps: Step 1: dissolving oxide PbO in an aqueous solution of excess HQ; Step 2: after complete dissolution, adding organic ligand A, stirring and mixing uniformly, then transferring to a reaction kettle and performing hydrothermal reaction; Step 3: collecting the precipitate obtained after the reaction, washing and drying to obtain the lead-based molecular ferroelectric sample.
2. The method for preparing lead-based molecular ferroelectrics as described in claim 1, characterized in that, The lead-based molecular ferroelectric has a layered structure, each Pb atom is coordinated with six Q atoms to form a distorted PbQ6 octahedron, the PbQ6 octahedrons are connected by common vertices to form an octahedral layer, and A cations are inserted into the interlayer space to form the layered structure.
3. The method for preparing lead-based molecular ferroelectrics as described in claim 1, characterized in that, The HQ in step 1 is at least one of HCl, HBr and HI.
4. The method for preparing lead-based molecular ferroelectrics as described in claim 3, characterized in that, The mass fraction of the aqueous solution of HQ is 30-50%.
5. The method for preparing lead-based molecular ferroelectrics as described in claim 1, characterized in that, The molar ratio of PbO to A is 1:
1.
6. The method for preparing lead-based molecular ferroelectrics as described in claim 1, characterized in that, The temperature of the hydrothermal reaction in step 2 is 100-150 DEG C, and the time is 10-15 h.
7. A molecular ferroelectric thin film material, characterized by, The structure comprises, from bottom to top, a transparent conductive substrate, a molecular ferroelectric film and a transparent conductive substrate; the molecular ferroelectric film is prepared from the lead-based molecular ferroelectric prepared by the preparation method in any one of claims 1-6.
8. Application of the lead-based molecular ferroelectric prepared by the preparation method in any one of claims 1-6 in the fields of information storage, optoelectronic devices or ferroelectric photovoltaics.