Zero-dimensional perovskite single crystal and preparation method thereof

Abstract

The application belongs to the technical field of semiconductor material preparation, and relates to a zero-dimensional perovskite single crystal and a preparation method thereof. The chemical formula of the zero-dimensional perovskite single crystal material is (MPZ)2PbI6.2H2O, wherein MPZ is N-methylpiperazine, the zero-dimensional perovskite structure is formed by [PbI6] 4‑ octahedrons as basic units, the octahedrons are not connected with each other, N-methylpiperazine and water molecules are filled in the [PbI6] 4‑ octahedrons, the [PbI6] 4‑ octahedrons are effectively separated. The octahedrons of the material are completely separated by organic cations and water molecules; the material has the characteristics of low dark current and high resistivity, the optical band gap is 2.73 eV, the material has high radiation resistance to high-energy X rays, and the material can be used for X ray detection.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor material preparation, and in particular relates to a zero-dimensional perovskite single crystal and a preparation method thereof. Background Art

[0002] Zero-dimensional (0D) perovskites have attracted considerable attention due to their unique metal halide structure, which holds great promise for applications in fields such as white-light LEDs and solar cells, particularly in terms of environmental stability. In recent years, 0D perovskite materials have demonstrated tremendous potential for application in fields such as solar cells, thanks to their exceptional photoelectric conversion efficiency and stability. However, relatively few 0D perovskites have been reported, and most known 0D organic-inorganic hybrid perovskites are based on octahedral clusters, where the octahedra are connected corner- or edge-sharing. In contrast, completely isolated 0D perovskite structures, where the octahedra are not connected to each other, are extremely rare. Therefore, the development of novel 0D halide perovskites is of great significance. Summary of the Invention

[0003] The present invention aims to provide a zero-dimensional perovskite single crystal and a preparation method. The octahedrons of this material are completely separated by organic cations and water molecules, and it has high resistivity and can be used in the field of X-ray detection.

[0004] In a first aspect, the present invention provides a zero-dimensional perovskite single crystal material, wherein the chemical formula of the zero-dimensional perovskite single crystal material is (MPZ)2PbI6·2H2O, wherein: MPZ is N-methylpiperazine (C5H 12 N2), the zero-dimensional perovskite structure is composed of [PbI6] 4- Octahedron is the basic unit. The octahedrons are not connected to each other. N-methylpiperazine and water molecules are filled in [PbI6] 4- Between the octahedrons, [PbI6] 4- The octahedra are effectively spaced.

[0005] In a second aspect, the present invention provides a method for preparing the zero-dimensional perovskite single crystal material, comprising the following steps:

[0006] (1) First, prepare an acidified N-methylpiperazine solution, referred to as solution A.

[0007] (2) Subsequently, the lead-containing compound in a stoichiometric ratio is dissolved in a hydroiodic acid solution to form a solution B, wherein the molar ratio of N-methylpiperazine to the lead-containing compound is 1:7 to 7:1;

[0008] (3) Mixing liquid A and liquid B at room temperature to prepare a supersaturated precursor solution;

[0009] (4) heating the supersaturated precursor solution prepared in (3) above until the precipitate is completely dissolved;

[0010] (5) The solution obtained in (4) is slowly cooled until crystallization occurs, and the crystal growth is continued until it stops.

[0011] According to the above scheme, the preparation method of liquid A in step (1) is as follows: at room temperature, N-methylpiperazine is added to a hydroiodic acid solution according to a specific stoichiometric ratio to form liquid A, and the N-methylpiperazine is acidified. This process produces a large amount of white gas and is accompanied by heat release.

[0012] According to the above scheme, the molar ratio of N-methylpiperazine to the lead-containing compound is 1:3~2:1.

[0013] According to the above scheme, the lead-containing compound used in step (2) is one or more of lead iodide, lead acetate trihydrate or lead oxide.

[0014] According to the above scheme, 1-2 drops of hypophosphorous acid are added in step (2) to prevent oxidation by hydroiodic acid. The solution now appears light yellow.

[0015] According to the above scheme, the heating conditions of step (4) are: heating at 70-160°C for 3-5 hours. Heating is performed until the precipitate is completely dissolved to form an orange-yellow transparent solution.

[0016] According to the above scheme, the cooling rate of step (5) is 0.5~5℃ / h, and the temperature is slowly cooled to 43-53℃ and kept at this temperature until the crystals are completely precipitated. By cooling and crystallizing until the crystals are precipitated, a light yellow transparent crystal zero-dimensional perovskite single crystal material (MPZ) 2PbI6·2H2O is finally obtained.

[0017] According to the above scheme, 9-20 ml of hydroiodic acid solution is required to synthesize 1 mmol (MPZ) 2PbI 6 · 2H 2 O.

[0018] The present invention also provides application of zero-dimensional perovskite single crystal material (MPZ) 2PbI6·2H2O in X-ray detection.

[0019] The octahedron in the zero-dimensional perovskite single crystal material (MPZ) 2PbI6·2H2O of the present invention has a unique "discrete" structure, does not form a continuous electron band, retains the photophysical properties of a single octahedron, enriches the zero-dimensional perovskite quantum dot family, and provides a new sample for the theoretical research of zero-dimensional perovskites.

[0020] Beneficial effects of the present invention:

[0021] The zero-dimensional perovskite single crystal material (MPZ) 2PbI6·2H2O of the present invention is an organic-inorganic hybrid metal halide perovskite material with a large resistivity and a small dark current. The order of magnitude of its resistivity can reach 10, the dark current is small, and it has a certain response to X-rays; the optical band gap is 2.73eV, it has a high radiation resistance to high-energy X-rays, and can be used for X-ray detection.

[0022] The zero-dimensional perovskite single crystal material of the present invention is simple to prepare, and the prepared zero-dimensional perovskite single crystal material has high resistivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a physical picture of the (MPZ)2PbI6·2H2O crystal prepared in Example 1;

[0024] Figure 2 The resistivity of the (MPZ)2PbI6·2H2O crystal prepared in Example 1 is shown in FIG. It can be seen that the resistivity of the crystal of the present invention is relatively high.

[0025] Figure 3 The X-ray sensitivity of the (MPZ)2PbI6·2H2O crystal prepared in Example 1 at different bias voltages was measured. The crystal was exposed to X-rays, and the current was measured at different applied bias voltages. The X-ray sensitivity of the crystal of the present invention at different bias voltages was calculated by fitting. The resulting crystal of the present invention exhibits a moderate response to X-rays and has potential for application in X-ray detection.

[0026] Figure 4 This is the single crystal XRD analysis structure of the (MPZ)2PbI6·2H2O crystal prepared in Example 1. It can be seen that the (MPZ)2PbI6·2H2O crystal synthesized in the present invention has a zero-dimensional structure, and all octahedra are not connected to each other;

[0027] Figure 5 The powder XRD pattern of the prepared (MPZ)2PbI6·2H2O crystal is compared with the theoretically calculated XRD pattern. The XRD peak positions calculated theoretically are shown below.

[0028] Figure 6 The UV-visible absorption spectrum of the prepared (MPZ)2PbI6·2H2O crystal is shown in FIG. The band gap of the crystal of the present invention is calculated to be 2.73 eV by the Tauc plot method. DETAILED DESCRIPTION

[0029] The present invention will be further described below with reference to the accompanying drawings and specific implementation examples.

[0030] Example 1

[0031] First, 111 μL (1 mmol) of N-methylpiperazine solution was added to 1 mL of hydroiodic acid solution to prepare Solution A. Simultaneously, 1.383 g (3 mmol) of lead iodide was dissolved in 8 mL of hydroiodic acid solution, and two drops of hypophosphorous acid were added to prevent oxidation by the hydroiodic acid. After Solution A reacted completely, it was mixed with Solution B at room temperature, resulting in a precipitate. Subsequently, the solution was heated at 100°C for 3-4 hours to completely dissolve the precipitate, forming an orange-yellow transparent solution. After the reaction, the solution was slowly cooled from 100°C to 48°C on a hotplate at a rate of 1°C / h, eventually yielding pale yellow crystals with the molecular formula (MPZ)2PbI6·2H2O.

[0032] Example 2

[0033] Similarly, Solution A was prepared by adding 222 μL (2 mmol) of N-methylpiperazine solution to 2 mL of hydroiodic acid solution. Then, 0.461 g (1 mmol) of lead iodide was dissolved in 10 mL of hydroiodic acid solution, and two drops of hypophosphorous acid were added to prevent oxidation. After Solution A reacted completely, Solution A and Solution B were mixed at room temperature to produce a precipitate. Next, the solution was heated at 130°C for 3-4 hours to dissolve the precipitate, yielding a transparent orange-yellow solution. After the reaction was complete, the solution was cooled from 130°C to 48°C on a hot plate at a rate of 1°C / h, eventually yielding pale yellow crystals with the same molecular formula: (MPZ)2PbI6·2H2O.

[0034] The (MPZ)2PbI6·2H2O crystal obtained in Example 1 is shown in the figure below: Figure 1 ; The resistivity of (MPZ)2PbI6·2H2O crystal is as follows Figure 2 ; The sensitivity of (MPZ)2PbI6·2H2O crystal to X-rays at different bias voltages is as follows Figure 3 ; The structure of (MPZ)2PbI6·2H2O crystal is as follows Figure 4 ; XRD of (MPZ)2PbI6·2H2O crystal is as follows Figure 5 ; The UV-visible absorption spectrum of (MPZ)2PbI6·2H2O crystal is as follows Figure 6 .

[0035] Figure 1 This is a photo of the (MPZ)2PbI6·2H2O crystal produced by the present invention. It can be seen that the zero-dimensional perovskite has a two-dimensional growth trend on a macro scale, and the size can reach 3mm×20mm.

[0036] Figure 2 The resistivity of the prepared (MPZ)2PbI6·2H2O crystal was obtained by applying a certain external bias voltage to the measured current. It can be seen that the crystal of the present invention has a high resistivity and a small dark current, which makes it have certain application potential in photoelectric detection.

[0037] Figure 3 The sensitivity of the prepared (MPZ)2PbI6·2H2O crystal to X-rays under different bias voltages is determined. The crystal is placed under X-ray irradiation, and the current of the crystal under different applied bias voltages is measured, and the sensitivity of the crystal of the application to X-rays under different bias voltages is calculated by fitting. The obtained crystal of the application has a certain response to X-rays, and has application potential in detecting X-rays.

[0038] Figure 4 The structure of the prepared (MPZ)2PbI6·2H2O crystal is analyzed by single crystal XRD. It can be seen from the figure that the crystal of the application is indeed a zero-dimensional structure, and all the octahedrons are not connected to each other. The unit cell is monoclinic, and the unit cell parameters are a = 1.52 nm, b = 1.04 nm, c = 1.90 nm, α = 90, β = 107.760, γ = 90;

[0039] Figure 5 The powder XRD of the (MPZ)2PbI6·2H2O crystal prepared by grinding into powder is compared with the XRD pattern obtained by theoretical simulation. The XRD of the obtained crystal matches well with the theoretical simulation peak position, and has high purity;

[0040] Figure 6 The ultraviolet-visible absorption spectrum of the prepared (MPZ)2PbI6·2H2O crystal is shown. The band gap of the crystal of the application is calculated to be 2.73 eV by Tauc plot method, and the crystal has high radiation resistance to high-energy X-rays, and has application potential in detecting X-rays.

[0041] The above examples are only preferred schemes of the application, which are used to illustrate the principles of the application, and are not intended to limit the scope of application. Any technical solutions obtained by equivalent replacement or equivalent transformation shall be included in the protection scope of the application.

Claims

1. A zero-dimensional perovskite single crystal material, characterized by: The chemical formula of the zero-dimensional perovskite single crystal material is (MPZ)2PbI6·2H2O, wherein: MPZ is N-methylpiperazine, and the zero-dimensional perovskite structure is composed of [PbI6] 4- Octahedron is the basic unit. The octahedrons are not connected to each other. N-methylpiperazine and water molecules are filled in [PbI6] 4- Between the octahedrons, [PbI6] 4- The octahedra are effectively spaced.

2. The method for preparing a zero-dimensional perovskite single crystal material according to claim 1, wherein: (1) First, prepare an acidified N-methylpiperazine solution, referred to as solution A. (2) Subsequently, the lead-containing compound in a stoichiometric ratio is dissolved in a hydroiodic acid solution to form a solution B, wherein the molar ratio of N-methylpiperazine to the lead-containing compound is 1:7 to 7:1; (3) Mixing liquid A and liquid B at room temperature to prepare a supersaturated precursor solution; (4) heating the supersaturated precursor solution prepared in (3) above until the precipitate is completely dissolved; (5) The solution obtained in step (4) is slowly cooled until crystallization occurs, and the crystal growth is continued until it stops.

3. The preparation method according to claim 2, wherein: The preparation method of liquid A in step (1) is as follows: at room temperature, N-methylpiperazine is added to a hydroiodic acid solution to form liquid A, and the N-methylpiperazine is acidified.

4. The preparation method according to claim 2, wherein: The molar ratio of N-methylpiperazine to the lead-containing compound is 1:3 to 2:

1.

5. The preparation method according to claim 2, wherein: The lead-containing compound used in step (2) is one or more of lead iodide, lead acetate trihydrate or lead oxide.

6. The preparation method according to claim 2, wherein: In step (2), 1 to 2 drops of hypophosphorous acid are added to prevent oxidation by hydroiodic acid.

7. The preparation method according to claim 2, wherein: The heating conditions of step (4) are: heating at 70-160° C. for 3-5 hours.

8. The preparation method according to claim 2, wherein: The cooling rate of step (5) is 0.5-5°C / h, and the mixture is slowly cooled to 43-53°C and kept warm until the crystals are completely precipitated.

9. The preparation method according to claim 2, wherein: 1mmol per synthesis (MPZ)2PbI6·2H2O requires 9~20ml of hydroiodic acid solution.

10. Use of the zero-dimensional perovskite single crystal material (MPZ) 2PbI6·2H2O according to claim 1 in X-ray detection.

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