A highly stable thiopolar metal halide perovskite crystal, its preparation method and applications

Abstract

This invention discloses a highly stable thiocyanate polar metal halide perovskite crystal, its preparation method, and its applications, belonging to the field of artificial crystal materials within the functional crystal materials technology. The chemical formula of this crystal is (4-SP)4Pb3Br. 10 ·2H₂O belongs to the orthorhombic crystal system, space group Aea₂, with unit cell parameters of α=90°, β=90°, γ=90°, Z=4, and density of 2.842 g / cm³. 3 The preparation method involves mixing 4-aminothiophenol with lead acetate trihydrate, adding an aqueous HBr solution, heating and stirring until a colorless and clear solution is obtained, followed by post-treatment to obtain crystals. This crystal has potential applications in X-ray detectors.

Description

Technical Field

[0001] This invention belongs to the field of artificial crystal materials technology in the field of functional crystal materials, and particularly relates to a highly stable thiopolar metal halide perovskite crystal, its preparation method and uses. Background Technology

[0002] X-ray detection technology plays an indispensable role in medical testing, security inspection, and scientific research. Traditional X-ray detector materials are mainly based on silicon and α-Se, which have weak X-ray absorption and significant attenuation, resulting in low detection performance and greatly limiting their development. In recent years, metal halide perovskites have shown great potential in X-ray detection due to their strong X-ray absorption capabilities caused by the presence of heavy elements such as lead and halogens (bromine (Br) and iodine (I)). Two-dimensional perovskites, in particular, have attracted considerable attention due to their diverse structures and high designability. Currently, significant progress has been made in X-ray detectors based on two-dimensional metal halide perovskites, but the structural instability leading to detector instability remains a hurdle to overcome.

[0003] Currently, several effective approaches exist to improve the stability of materials, such as enhancing the interlayer interactions through halogen substitution and hydroxyl substitution. These interactions effectively promote carrier transport, thereby improving the X-ray detection performance of the material. However, these materials still exhibit large interlayer spacing, which is highly detrimental to carrier transport. Furthermore, the organic components are arranged in a bilayer configuration between the layers, and the upper and lower organic components are connected by weak van der Waals interactions, which significantly weakens the structural stability. In addition, unavoidable ion migration in perovskite materials remains a significant challenge, especially when the material operates continuously under high electric fields. Halogen vacancy-induced ion migration is particularly pronounced, with migrating ions accumulating at the electrode interface to form a space charge layer, causing a significant increase in dark current drift and baseline noise. Moreover, under prolonged high external electric fields, the irreversible accumulation of migrating ions leads to lattice distortion, further damaging the material structure. Therefore, suppressing ion migration is not only crucial for improving the detection performance of the material but also a key factor in enhancing its stability and lifespan. Recently, an effective method to suppress ion migration is to enable materials to operate without an external voltage, i.e., a self-driven detection mode. This detection mode requires the material to provide its own built-in electric field for separating and transporting charge carriers. Currently, the main materials that meet this condition are polar materials and heterojunction materials; however, the complex development process of heterojunction materials has slowed their progress in this field. Therefore, developing novel polar metal halide perovskite X-ray detection materials with both high performance and high stability, focusing on suppressing ion migration and promoting charge carrier transport efficiency, has significant theoretical and practical value. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a highly stable thiopolar metal halide perovskite crystal, its preparation method, and its applications.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] One objective of this invention is to provide a highly stable thiopolar metal halide perovskite crystal with the chemical formula (4-SP)4Pb3Br. 10 ·2H2O, molecular formula is C 24 H 36 N4O2S4Pb3Br 10 Wherein, 4-SP represents 4-aminothiophenol. Crystals of (4-SP)4Pb3Br were synthesized using a cooling crystallization method. 10 ·2H₂O, the chemical reaction formula is:

[0007] 4(4-SP)+3Pb(Ac)2·3H2O+10HBr→(4-SP)4Pb3Br 10 ·2H2O+6HAc+7H2O.

[0008] This invention utilizes a specific chemical composition to endow the crystal with high stability and excellent X-ray detection performance. The introduction of 4-aminothiophenol not only enhances the polarity of the crystal but also improves its structural stability by connecting it to the inorganic framework through two types of hydrogen bonds: NH···Br and SH···Br.

[0009] Furthermore, the thiocyanate polar metal halide perovskite crystal belongs to the orthorhombic crystal system with space group Aea2.

[0010] In this invention, the structural characteristics of the orthorhombic crystal system and the Aea2 polar space group help to understand the symmetry and arrangement of the crystal, which has a significant impact on the physical properties of the crystal (such as optical and electrical properties). In particular, the photovoltaic effect induced by the spontaneous polarization of this polar single crystal material can achieve efficient carrier separation and transport without external bias voltage, thereby realizing efficient self-driven X-ray detection.

[0011] Furthermore, the unit cell parameters of the thiopolar metal halide perovskite crystal are as follows: α=90°, β=90°, γ=90°, Z = 4, density is 2.842 g / cm³ 3 .

[0012] In this invention, these parameters precisely define the structure of the crystal, aiding in the understanding of its physical and chemical properties. For example, a larger unit cell volume and suitable density contribute to improved crystal stability and X-ray absorption capacity.

[0013] The second objective of this invention is to provide a method for preparing highly stable thiocyanate polar metal halide perovskite crystals, comprising the following steps: mixing 4-aminothiophenol and lead acetate trihydrate, then adding an aqueous HBr solution, heating and stirring until the solution is a colorless and clear solution; and performing a crystallization post-treatment on the obtained colorless and clear solution to obtain highly stable thiocyanate polar metal halide perovskite crystals.

[0014] In this invention, the method is simple and efficient, and can produce high-quality crystals. By controlling the reaction conditions, crystal growth can be optimized, thereby improving its stability and performance.

[0015] Furthermore, the specific operation steps of the post-crystallization treatment include: placing the obtained colorless and clear solution in a high-temperature oven at 120°C while it is still hot, and slowly cooling the solution to room temperature by a slow cooling growth method, with a cooling rate of 1°C per day.

[0016] In this invention, natural cooling is suitable for rapid preparation of microcrystals, while slow cooling growth can produce larger crystals, making it suitable for various applications. Slow cooling growth can further improve the quality and stability of the crystals.

[0017] Furthermore, the molar ratio of 4-aminothiophenol to lead acetate trihydrate is 1.5:1.

[0018] In this invention, the molar ratio ensures the complete progress of the reaction while optimizing the structure and properties of the crystal. An appropriate molar ratio can improve the stability and X-ray absorption capacity of the crystal.

[0019] Furthermore, the molar ratio of lead acetate trihydrate to HBr in the HBr aqueous solution is 1:(20-35).

[0020] In this invention, this molar ratio range ensures the complete progress of the reaction while avoiding side reactions caused by excess HBr. An appropriate molar ratio can improve the purity and quality of the crystals.

[0021] Furthermore, the HBr aqueous solution has a mass fraction of 48%.

[0022] In this invention, the 48% HBr aqueous solution concentration is appropriate, which can ensure the smooth progress of the reaction, while avoiding the corrosiveness and danger caused by excessively high concentrations.

[0023] Furthermore, the heating temperature is 80-120°C.

[0024] In this invention, this temperature range ensures efficient reaction while avoiding side reactions and crystal structure damage caused by excessively high temperatures. Appropriate temperatures can improve the growth quality and stability of the crystal.

[0025] The third objective of this invention is to provide an application of highly stable thiopolar metal halide perovskite crystals in the fabrication of X-ray detectors.

[0026] In this invention, the crystal exhibits excellent performance in the field of X-ray detection, such as high detection sensitivity, low detection limit, and high stability. These characteristics make it promising for wide applications in medical testing, security inspection, and scientific research.

[0027] Compared with the prior art, the present invention has the following advantages and technical effects:

[0028] This invention prepares a highly stable thiopolar metal halide perovskite crystal. When fabricated into an X-ray detector, this crystal enables efficient and stable X-ray detection under both zero and high bias voltages. The X-ray response performance of the single crystal was tested by irradiating it with different X-ray doses. The crystal exhibited a significant photoresponse when irradiated with different X-ray doses. These results indicate that this material has potential application value as an X-ray detection material. Attached Figure Description

[0029] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0030] Figure 1 (4-SP)4Pb3Br prepared in Example 2 of this invention 10 • A photograph of 2H2O crystals;

[0031] Figure 2 (4-SP)4Pb3Br prepared in Example 2 of this invention 10 • Packing diagram of 2H2O crystal structure;

[0032] Figure 3 (4-SP)4Pb3Br prepared in Example 2 of this invention 10 X-ray powder diffraction pattern of 2H2O crystal;

[0033] Figure 4 (4-SP)4Pb3Br prepared in Example 2 of this invention 10 • The ultraviolet-visible absorption spectrum of 2H2O crystals;

[0034] Figure 5 (4-SP)4Pb3Br prepared in Example 2 of this invention 10 • Thermal stability decomposition curve of 2H2O crystal;

[0035] Figure 6 (4-SP)4Pb3Br prepared in Example 2 of this invention 10 • The intensity of the nonlinear frequency doubling signal of the 2H2O crystal;

[0036] Figure 7 (4-SP)4Pb3Br prepared in Example 2 of this invention 10 • X-ray detection sensitivity of 2H2O crystal;

[0037] Figure 8 (4-SP)4Pb3Br prepared in Example 2 of this invention 10The X-ray detection limit of 2H2O crystals;

[0038] Figure 9 (4-SP)4Pb3Br prepared in Example 2 of this invention 10 • Dark current drift value of 2H2O crystal;

[0039] Figure 10 (4-SP)4Pb3Br prepared in Example 2 of this invention 10 Stability of 2H2O crystals under high X-ray irradiation dose;

[0040] Figure 11 (4-SP)4Pb3Br prepared in Example 2 of this invention 10 Comparison of the initial detection sensitivity of 2H2O crystals with the sensitivity two months later. Detailed Implementation

[0041] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0042] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0043] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0044] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0045] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0046] This invention provides a method for preparing highly stable thiocyanate polar metal halide perovskite crystals, comprising the following steps: mixing 4-aminothiophenol and lead acetate trihydrate, then adding an aqueous HBr solution, heating and stirring until the solution is a colorless and clear solution; and performing crystallization post-treatment on the obtained colorless and clear solution to obtain highly stable thiocyanate polar metal halide perovskite crystals.

[0047] In the following preferred embodiments of the present invention, the specific steps of the post-crystallization treatment include: placing the obtained colorless and clear solution in a high-temperature oven at 120°C while it is still hot, and slowly cooling the solution to room temperature using a slow cooling growth method at a cooling rate of 1°C per day. Only by using this post-treatment method can large-size single crystals of millimeter size or larger be obtained, and only such single crystals meet the preparation conditions for single-crystal X-ray detectors.

[0048] If the post-processing is carried out as follows: the obtained colorless and clear solution is naturally cooled to room temperature to obtain colorless blocky microcrystals, filtered, and dried; then extremely small microcrystals are obtained, which are mainly used for determining crystal structure and basic characterization such as ultraviolet absorption, but cannot be used to prepare X-ray detectors.

[0049] Method 2: Place the obtained colorless and clear solution in a high-temperature oven at 120°C while it is still hot, and slowly cool the solution to room temperature by a slow cooling growth method at a rate of 1°C per day.

[0050] In the following preferred embodiments of the present invention, the molar ratio of 4-aminothiophenol and lead acetate trihydrate is 1.5:1.

[0051] In the following preferred embodiments of the present invention, the molar ratio of lead acetate trihydrate to HBr in the HBr aqueous solution is 1:(20-35). As an example, in the following embodiments of the present invention, the molar ratio of lead acetate trihydrate to HBr in the HBr aqueous solution is more preferably 1:26.

[0052] In the following preferred embodiments of the present invention, the mass fraction of the HBr aqueous solution is 48%.

[0053] In the following preferred embodiments of the present invention, the heating temperature is 80-120°C. As an example, in the following embodiments of the present invention, the heating temperature is more preferably 105°C.

[0054] The application of the highly stable thiocyanate polar metal halide perovskite crystals in the fabrication of X-ray detectors. X-ray single-crystal diffraction results show that the molecular formula of this compound is C2. 24H 36 N4O2S4Pb3Br 10 The structural formula is (4-SP)4Pb3Br 10 ·2H₂O. Wherein, 4-SP represents 4-aminothiophenol. At room temperature, (4-SP)₄Pb₃Br 10 The 2H₂O crystal belongs to the orthorhombic crystal system, with space group Aea₂. The unit cell parameters of the crystal are: α=90°, β=90°, γ=90°, Z = 4, density is 2.842 g / cm³ 3 .

[0055] Unless otherwise specified, "room temperature" in this invention refers to 25±2℃.

[0056] All raw materials used in this invention were purchased from the market.

[0057] The technical solution of the present invention will be further illustrated by the following embodiments.

[0058] Example 1

[0059] A method for preparing highly stable thiocyanate polar metal halide perovskite crystals includes the following steps: 4-aminothiophenol and lead acetate trihydrate are placed in a beaker at a molar ratio of 1.5:1; then, a 48% (w / w) HBr aqueous solution is added to the beaker, wherein the molar ratio of lead acetate trihydrate to HBr in the HBr aqueous solution is 1:26; the mixture is heated to 105°C and stirred until the solution becomes a colorless and clear solution; the obtained colorless and clear solution is naturally cooled to room temperature to obtain colorless blocky microcrystals; these microcrystals are filtered and dried to obtain highly stable thiocyanate polar metal halide perovskite crystals ((4-SP)4Pb3Br). 10 ·2H2O).

[0060] Example 2

[0061] A method for preparing a highly stable thiocyanate polar metal halide perovskite crystal includes the following steps: 4-aminothiophenol and lead acetate trihydrate are placed in a beaker at a molar ratio of 1.5:1; then, a 48% (w / w) HBr aqueous solution is added to the beaker, wherein the molar ratio of lead acetate trihydrate to HBr in the HBr aqueous solution is 1:26; the mixture is heated to 105°C and stirred until the solution becomes a colorless and clear solution; the obtained colorless and clear solution is placed in a high-temperature oven at 120°C while still hot, and the solution is slowly cooled to room temperature by a slow cooling growth method at a cooling rate of 1°C per day, resulting in a crystal with dimensions of 5×3×2 mm. 3 Highly stable thiopolar metal halide perovskite crystals ((4-SP)4Pb3Br) 10·2H2O).

[0062] Figure 1 (4-SP)4Pb3Br prepared in Example 2 of this invention 10 Photograph of 2H2O crystals.

[0063] X-ray single-crystal diffraction results show that the molecular formula of this compound is C. 24 H 36 N4O2S4Pb3Br 10 The structural formula is (4-SP)4Pb3Br 10 ·2H₂O. Wherein, 4-SP represents 4-aminothiophenol. At room temperature, (4-SP)₄Pb₃Br 10 The 2H₂O crystal belongs to the orthorhombic crystal system, with space group Aea₂. The unit cell parameters of the crystal are: α=90°, β=90°, γ=90°, Z = 4, density is 2.842 g / cm³ 3 .

[0064] Figure 2 (4-SP)4Pb3Br prepared in Example 2 of this invention 10 Packing diagram of 2H₂O crystal structure. From... Figure 2 As can be seen from this, (4-SP)4Pb3Br 10 ·2H2O has the following structure: (4-SP)4Pb3Br 10 In ·2H₂O, the 4-aminobenzylthiophenol organic cations are neatly arranged in the interlayer, exhibiting a typical two-dimensional monolayer perovskite structure. Simultaneously, 4-aminobenzylthiophenol is directly connected to the PbBr₆ inorganic framework through strong NH…Br and SH…Br hydrogen bonds formed at both ends of the molecule. This not only shortens the interlayer spacing, which is beneficial for accelerating carrier transport efficiency, but also eliminates van der Waals interactions between organic components, thus resulting in higher structural stability.

[0065] X-ray powder diffraction analysis was performed on the (4-SP)4Pb3Br prepared in Example 2. 10 • Phase purity of 2H2O crystals (e.g.) Figure 3 As shown in the figure, the X-ray diffraction pattern obtained through structural simulation matches the experimental results.

[0066] The (4-SP)4Pb3Br prepared in Example 2 was analyzed by UV-Vis absorption spectroscopy. 10 The optical absorption of ·2H2O was analyzed, and the results are as follows: Figure 4 As shown. Figure 4The display shows (4-SP)4Pb3Br 10 The absorption cutoff edge of ·2H2O is 386 nm. Based on the Tauc formula, the optical band gap of this compound can be derived as 3.19 eV.

[0067] Figure 5 (4-SP)4Pb3Br prepared in Example 2 10 The thermal stability decomposition curve of 2H2O crystal, as shown by thermogravimetric analysis, reveals that (4-SP)4Pb3Br 10 The decomposition temperature of 2H2O is 207℃.

[0068] The (4-SP)4Pb3Br prepared in Example 2 10 The nonlinear frequency doubling signal of the 2H2O crystal was analyzed, and the results are as follows: Figure 6 As shown, Figure 6 This indicates that (4-SP)4Pb3Br 10 The nonlinear signal intensity of 2H2O is 1.1 times that of potassium dihydrogen phosphate (KDP).

[0069] Application Example 1

[0070] The (4-SP)4Pb3Br prepared in Example 2 was used... 10 • Single-crystal X-ray detectors are constructed using 2H₂O crystals. The specific method involves selecting crystals with a size of approximately 3×2×1mm. 3 A high-quality single crystal is placed on a glass slide, and Ag electrodes are uniformly coated on both ends of the crystal (along the polar axis: crystallographic c-axis). Then, wires are led out from both ends to form a complete current path.

[0071] The (4-SP)4Pb3Br prepared in Example 2 10 The detection performance of a single-crystal X-ray detector constructed from 2H2O crystals was tested, and the results are as follows: Figure 7 As shown, the test results indicate that (4-SP)4Pb3Br 10 The 2H₂O single-crystal X-ray detector exhibits excellent detection performance, with a power output of 278.1 μC Gy in self-driven mode. -1 cm -2 It exhibits high detection sensitivity; the sensitivity increases sequentially with increasing bias voltage, reaching a value of 10851.6 μC Gy at 100V. -1 cm -2 This value is the highest among single-layer metal halide perovskite single-crystal X-ray detector materials to date. Furthermore, as shown in Figure 8, the detection limits in self-driven mode and at a bias voltage of 100V are as low as 17.9 nGy s⁻¹. -1 and 368.3nGy s -1It is a commercially available α-Se (5500 nGy s) -1 307 times and 15 times that of ).

[0072] The (4-SP)4Pb3Br prepared in Example 2 10 The stability of the single-crystal X-ray detector constructed from 2H₂O crystal was tested. For example... Figure 9 As shown, the test results indicate that (4-SP)4Pb3Br 10 The dark current drift of the 2H₂O single-crystal X-ray detector is as low as 2.1 × 10⁻⁶ under a 100V bias voltage. -8 nAcm -1 s -1 V -1 It can effectively inhibit ion migration.

[0073] Figure 10 (4-SP)4Pb3Br prepared in Example 2 10 The stability of the 2H2O crystal tested under high X-ray irradiation doses shows that the detector can operate stably for a long time under high X-ray irradiation doses.

[0074] Figure 11 (4-SP)4Pb3Br prepared in Example 2 10 The comparison between the initial detection sensitivity of the 2H2O crystal and its sensitivity after two months shows that, even after being placed in a non-vacuum-sealed environment for two months, the detector's detection sensitivity under a 100V bias voltage can still maintain more than 95% of its initial efficiency.

[0075] All of the above demonstrates that the detection device has excellent stability.

[0076] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A highly stable thiopolar metal halide perovskite crystal, characterized in that, Its chemical formula is (4-SP)4Pb3Br 10 ·2H2O, where 4-SP represents 4-aminothiophenol; The thiopolar metal halide perovskite crystals belong to the orthorhombic crystal system with space group Aea2. The cell parameters of the thiopolar metal halide perovskite crystal are: a = 25.9985(14) Å, b = 9.0306(4) Å, c = 19.5276(12) Å, α = 90°, β = 90°, γ = 90°, V = 4584.7(4) Å. 3 Z=4, density is 2.842 g / cm³ 3 .

2. A method for preparing a highly stable thiopolar metal halide perovskite crystal as described in claim 1, characterized in that, The process includes the following steps: mixing 4-aminothiophenol and lead acetate trihydrate, then adding an aqueous HBr solution, heating and stirring until the solution becomes a colorless and clear solution; and then performing a crystallization process on the obtained colorless and clear solution to obtain highly stable thiopolar metal halide perovskite crystals.

3. The preparation method according to claim 2, characterized in that, The specific steps of the post-crystallization treatment include: placing the obtained colorless and clear solution in a high-temperature oven at 120°C while it is still hot, and slowly cooling the solution to room temperature by a slow cooling growth method at a rate of 1°C per day.

4. The preparation method according to claim 2, characterized in that, The molar ratio of 4-aminothiophenol to lead acetate trihydrate is 1.5:

1.

5. The preparation method according to claim 2, characterized in that, The molar ratio of HBr in the trihydrate lead acetate and HBr aqueous solution is 1:(20-35).

6. The preparation method according to claim 2, characterized in that, The HBr aqueous solution has a mass fraction of 48%.

7. The preparation method according to claim 2, characterized in that, The heating temperature is 80-120℃.

8. The application of the highly stable thiopolar metal halide perovskite crystal as described in claim 1 in the fabrication of X-ray detectors.

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