Zero-dimensional perovskite single crystal and preparation method thereof

Abstract

The invention 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, MPZ is N-methyl piperazine, the zero-dimensional perovskite structure takes [PbI6] 4-octahedrons as a basic unit, the octahedrons are not connected with each other, the N-methyl piperazine and water molecules are filled among the [PbI6] 4-octahedrons, and the [PbI6] 4-octahedrons are effectively separated. 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, has an optical band gap of 2.73 eV, has high radiation resistance to high-energy X-rays, and 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 much attention due to their unique metal halide structure, which makes them have broad application prospects in white light LEDs, solar cells and other fields, especially in terms of environmental stability. In recent years, zero-dimensional perovskite materials have shown great application potential in fields such as solar cells due to their excellent photoelectric conversion efficiency and stability. However, there are not many zero-dimensional perovskites reported so far, and most of the currently known zero-dimensional (0D) organic-inorganic hybrid perovskites are based on octahedral clusters as basic units, in which the octahedra are connected at the same corners or edges. In contrast, the octahedra are not connected to each other, and the completely isolated zero-dimensional perovskite structure is very rare. Therefore, it is of great significance to develop new zero-dimensional halide perovskites. Summary of the invention

[0003] The purpose of the present invention is to provide a zero-dimensional perovskite single crystal and a preparation method thereof. The octahedrons of the material are completely separated by organic cations and water molecules; the material has the characteristics of high resistivity and can be applied to the field of X-ray detection. 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.

[0004] In a second aspect, the present invention provides a method for preparing the zero-dimensional perovskite single crystal material, comprising the following steps: (1) First, prepare an acidified N-methylpiperazine solution, referred to as solution A; (2) Subsequently, a stoichiometric lead-containing compound 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 the above (4) is slowly cooled until crystallization occurs, and the crystal growth is continued until it stops.

[0005] According to the above scheme, the preparation method of liquid A in step (1) is: at room temperature, N-methylpiperazine is added to a hydroiodic acid solution according to a specific stoichiometric ratio to form liquid A, and N-methylpiperazine is acidified. This process generates a large amount of white gas and is accompanied by heat release.

[0006] According to the above scheme, the molar ratio of N-methylpiperazine to the lead-containing compound is 1:3~2:1.

[0007] 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.

[0008] According to the above scheme, 1-2 drops of hypophosphorous acid are added in step (2) to prevent oxidation by hydroiodic acid. At this time, the solution is light yellow.

[0009] 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.

[0010] According to the above scheme, the cooling rate of step (5) is 0.5-5°C / h, and the temperature is slowly cooled to 43-53°C and kept warm 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.

[0011] According to the above scheme, 9-20 ml of hydroiodic acid solution is required to synthesize 1 mmol (MPZ) 2PbI6·2H2O.

[0012] The present invention also provides application of zero-dimensional perovskite single crystal material (MPZ) 2PbI6·2H2O in X-ray detection.

[0013] 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 study of zero-dimensional perovskites.

[0014] Beneficial effects of the present invention: The zero-dimensional perovskite single crystal material (MPZ) 2PbI6·2H2O of the present invention is an organic-inorganic hybrid metal halide perovskite material, which has 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.

[0015] The zero-dimensional perovskite single crystal material of the present invention is easy to prepare, and the prepared zero-dimensional perovskite single crystal material has a large resistivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a physical picture of the (MPZ)2PbI6·2H2O crystal prepared in Example 1; Figure 2 The resistivity of the (MPZ)2PbI6·2H2O crystal obtained in Example 1. It can be seen that the resistivity of the crystal of the present invention is relatively high; Figure 3 The sensitivity of the (MPZ)2PbI6·2H2O crystal obtained in Example 1 to X-rays at different bias voltages. The crystal is placed under X-ray irradiation, and the current of the crystal under different applied bias voltages is measured. The sensitivity of the crystal of the present invention to X-rays at different bias voltages is obtained by fitting calculation. The obtained crystal of the present invention has a certain response to X-rays and has application potential in detecting X-rays; 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 is a zero-dimensional structure, and all octahedrons are not connected to each other; Figure 5 The powder XRD of the prepared (MPZ)2PbI6·2H2O crystal is compared with the XRD obtained by theoretical calculation. The XRD peak position calculated theoretically is shown below. Figure 6 The UV-visible absorption spectrum of the prepared (MPZ)2PbI6·2H2O crystal is shown in Figure 1. The band gap of the crystal of the present invention is 2.73 eV as calculated by the Tauc plot method. DETAILED DESCRIPTION

[0017] The present invention is further described below in conjunction with the accompanying drawings and specific implementation examples.

[0018] Example 1 First, 111 μL (1 mmol) of N-methylpiperazine solution was added to 1 ml of hydroiodic acid solution to prepare liquid A; at the same time, 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 hydroiodic acid oxidation. After liquid A reacted completely, liquid A was mixed with liquid B at room temperature, and a precipitate was immediately generated. Subsequently, the solution was heated at 100 ° C for 3-4 hours to completely dissolve the precipitate and form an orange-yellow transparent solution. After the reaction was completed, the solution was slowly cooled from 100 ° C to 48 ° C on a cooling hot plate at a rate of 1 ° C / h, and finally light yellow crystals were generated, and its molecular formula was (MPZ) 2PbI6 · 2H2O.

[0019] Example 2 Similarly, 222 μL (2 mmol) of N-methylpiperazine solution was added to 2 ml of hydroiodic acid solution to prepare solution A; 0.461 g (1 mmol) of lead iodide was then 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. Then, the precipitate was dissolved by heating at 130 ° C for 3-4 hours to obtain an orange-yellow transparent solution. After the reaction was completed, the solution was cooled from 130 ° C to 48 ° C on a cooling hot plate at a rate of 1 ° C / h, and finally light yellow crystals were generated, and its molecular formula was also (MPZ) 2PbI6 · 2H2O.

[0020] The actual picture of (MPZ)2PbI6·2H2O crystal prepared in Example 1 is as follows 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 .

[0021] Figure 1 This is a real picture of the (MPZ)2PbI6·2H2O crystal prepared by the present invention. It can be seen that the zero-dimensional perovskite has a two-dimensional growth trend in macroscopic terms, and the size can reach 3mm×20mm.

[0022] Figure 2 The resistivity is obtained by fitting after applying a certain external bias voltage to the prepared (MPZ)2PbI6·2H2O crystal and testing its current size. 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.

[0023] Figure 3 The sensitivity of the prepared (MPZ)2PbI6·2H2O crystal to X-rays under different bias voltages is measured. The crystal is placed under X-ray irradiation, and the current size of the crystal under different external bias voltages is measured. The sensitivity of the crystal of the present invention to X-rays under different bias voltages is obtained by fitting calculation. The obtained crystal of the present invention has a certain response to X-rays and has application potential in detecting X-rays.

[0024] Figure 4The single crystal XRD analysis structure of the prepared (MPZ)2PbI6·2H2O crystal is shown in the figure. It can be seen from the figure that the crystal of the present invention is indeed a zero-dimensional structure, and all the octahedra are not connected to each other. Its unit cell is a monoclinic system, and the unit cell parameters are a=1.52nm, b=1.04nm, c=1.90nm, α=90, β=107.760, γ=90; Figure 5 The powder XRD pattern of the (MPZ)2PbI6·2H2O crystal obtained by grinding it into powder is compared with the XRD pattern obtained by theoretical simulation. The lower part is the result of theoretical simulation. It can be seen that the XRD peak position of the obtained crystal matches well with the theoretical simulation peak position, and has a high purity. Figure 6 The ultraviolet-visible absorption spectrum of the prepared (MPZ)2PbI6·2H2O crystal is shown in Figure 1. The band gap of the crystal of the present invention is 2.73 eV calculated by the Tauc plot method, and the crystal has a high radiation resistance to high-energy X-rays and has the potential for application in detecting X-rays.

[0025] The above embodiments are only preferred solutions of the present invention, which are used to illustrate the principle of the present invention and are not intended to limit its scope of application. Any technical solution obtained by equivalent replacement or equivalent transformation should be included in the protection scope of the present invention.

Claims

1. A zero-dimensional perovskite single crystal material, characterized in that: 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, characterized in that: (1) First, prepare an acidified N-methylpiperazine solution, referred to as solution A; (2) Subsequently, a stoichiometric lead-containing compound 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 the above (4) is slowly cooled until crystallization occurs, and the crystal growth is continued until it stops.

3. The preparation method according to claim 2, characterized in that: The preparation method of liquid A in step (1) is: 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.

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

8. The preparation method according to claim 2, characterized in that: 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, characterized in that: 9~20ml of hydroiodic acid solution is required to synthesize 1mmol (MPZ) 2PbI6·2H2O.

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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