Silver-based metal halide microcrystal, preparation method thereof and application of microcrystal in deep ultraviolet photoelectric detector

Abstract

The invention provides a silver-based metal halide microcrystal, a preparation method thereof and application of the microcrystal in a deep ultraviolet photoelectric detector, and belongs to the technical field of semiconductor nanomaterials. The preparation method comprises the following steps: dissolving cesium bromide and silver bromide by adopting dimethyl sulfoxide and N, N-dimethyl formamide to form a precursor saturated solution, coating the precursor saturated solution on the surface of a carrier, and in an anti-solvent evaporative crystallization process, influencing the supersaturation degree of the precursor saturated solution by utilizing methanol to drive the solute of the precursor saturated solution to separate out CsAgBr2 crystals, thereby obtaining the CsAgBr2 / CsAgBr2 / CsAgBr2 / CsAgBr2 / CsAgBr2 / CsAgBr2 composite material. Obtaining a carrier loaded with a precursor crystal; the carrier loaded with the precursor crystal is annealed, so that the internal stress of the precursor crystal can be released, the crystallinity of the precursor crystal is improved, and the crystallization quality of the silver-based metal halide microcrystal is improved. The method provided by the invention is simple and convenient to operate, does not need expensive equipment, ultrahigh vacuum and other harsh conditions, is easier to control and implement in the preparation process, and is beneficial to large-scale production.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor nanomaterials, and in particular to a silver-based metal halide microcrystal and a preparation method thereof, and application thereof in a deep ultraviolet photoelectric detector. Background Art

[0002] Photodetectors are high-performance devices that accurately convert light signals into electrical signals. They play a vital role in numerous fields, including optical communications, chemical analysis, optical imaging, and biosensing. Their operating principle is primarily based on the photoelectric effect of semiconductor materials: when the energy of an incident photon exceeds the band gap of a semiconductor material, the photon is absorbed by the material and excites electron-hole pairs. Under the influence of an electric field, these electrons and holes rapidly separate, forming a photocurrent. Among the numerous photodetection technologies, ultraviolet (UV) detection has been a key area of rapid development, following infrared laser detection. The key to UV detection lies in the semiconductor materials used in UV photodetectors. In recent years, perovskites, with their unique physical properties and outstanding performance, have rapidly attracted the attention of researchers worldwide. Among them, all-inorganic perovskite materials have attracted significant attention due to their excellent optoelectronic properties and potential as materials for light-emitting devices. However, the widespread application of conventional perovskite materials is hampered by the presence of the highly toxic heavy metal lead. Therefore, replacing lead with low- or non-toxic elements has become an effective approach to address the high toxicity of conventional all-inorganic perovskite materials.

[0003] CsAgBr2, a lead-free, low-dimensional metal halide, has a wide bandgap and effectively absorbs deep ultraviolet light, while being largely unresponsive to visible and near-infrared light. This avoids interference from visible light and improves the sensitivity and selectivity of deep ultraviolet detection. Furthermore, CsAgBr2 is chemically stable and environmentally friendly, resistant to decomposition in humid environments and exhibiting excellent stability, which is crucial for the long-term, stable operation of deep ultraviolet photodetectors in practical environments.

[0004] However, the conventional preparation method for CsAgBr2 is a high-temperature solid-phase melting method. For example, the related prior art discloses mixing cesium bromide and silver bromide at a molar ratio of 1:1 at room temperature, pressing the two into a sheet, heating them to 400°C under an argon atmosphere, and then slowly cooling them to room temperature. This method requires high temperature conditions to complete, consumes a lot of energy, and the cooling process is time-consuming and complicated. It is not suitable for large-scale production, and there are also problems such as poor quality of the prepared CsAgBr2 crystals. Summary of the Invention

[0005] The purpose of the present invention is to provide a silver-based metal halide microcrystal and a preparation method thereof and application in deep ultraviolet photodetectors. The method provided by the present invention is simple to operate and easy to control, and can be used to prepare high-quality CsAgBr2 crystals on a large scale.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing silver-based metal halide microcrystals, comprising:

[0008] Mixing cesium bromide, silver bromide, dimethyl sulfoxide and N,N-dimethylformamide to obtain a precursor saturated solution; the molar ratio of the cesium bromide to the silver bromide is 1 to 1.3:1;

[0009] coating the saturated precursor solution on the surface of a carrier to obtain a carrier coated with the saturated precursor solution;

[0010] placing the carrier coated with the saturated precursor solution in a container containing methanol, with the carrier coated with the saturated precursor solution being above the liquid level of the methanol, and then performing anti-solvent evaporation and crystallization to obtain a carrier loaded with precursor crystals;

[0011] The carrier carrying the precursor crystals is annealed to obtain silver-based metal halide microcrystals.

[0012] Preferably, the volume ratio of dimethyl sulfoxide to N,N-dimethylformamide is 1:2-4.

[0013] Preferably, the anti-solvent evaporation crystallization temperature and the annealing temperature are independently 60°C.

[0014] Preferably, the anti-solvent evaporation and crystallization time is 24 to 48 hours.

[0015] Preferably, the annealing time is 10 to 20 minutes.

[0016] The present invention also provides silver-based metal halide microcrystals prepared by the preparation method described in the above technical solution, and the chemical formula of the silver-based metal halide microcrystals is CsAgBr2.

[0017] The present invention also provides an application of the silver-based metal halide microcrystals described in the above technical solution in a deep ultraviolet photodetector. The deep ultraviolet photodetector includes interdigital electrodes and a silver-based metal halide microcrystal film grown on the interdigital electrodes.

[0018] Preferably, the thickness of the silver-based metal halide microcrystalline film is 1 to 2.5 μm.

[0019] Preferably, the method for preparing the deep ultraviolet photodetector comprises the following steps:

[0020] (1) mixing cesium bromide, silver bromide, dimethyl sulfoxide, and N,N-dimethylformamide to obtain a precursor saturated solution;

[0021] (2) coating the saturated precursor solution obtained in step (1) on the surface of the interdigital electrode to obtain an interdigital electrode coated with the saturated precursor solution;

[0022] (3) placing the interdigital electrode coated with the saturated precursor solution obtained in step (2) in a container containing methanol, wherein the interdigital electrode coated with the saturated precursor solution is located above the liquid surface of the methanol, and then performing anti-solvent evaporation crystallization to obtain an interdigital electrode loaded with precursor crystals;

[0023] (4) Annealing the interdigitated electrode loaded with the precursor crystal obtained in step (3) to obtain a deep ultraviolet photodetector.

[0024] Preferably, the interdigitated electrodes are silicon wafer interdigitated electrodes plated with SiO2.

[0025] The invention provides a method for preparing silver-based metal halide microcrystals, comprising: mixing cesium bromide, silver bromide, dimethyl sulfoxide and N,N-dimethylformamide to obtain a saturated precursor solution; coating the saturated precursor solution on a surface of a carrier to obtain a carrier coated with the saturated precursor solution; placing the carrier coated with the saturated precursor solution in a container containing methanol, wherein the carrier coated with the saturated precursor solution is located above the liquid surface of the methanol, and then performing anti-solvent evaporation and crystallization to obtain a carrier loaded with precursor crystals; and annealing the carrier loaded with the precursor crystals to obtain silver-based metal halide microcrystals. The present invention uses dimethyl sulfoxide and N,N-dimethylformamide as crystallization solvents to dissolve cesium bromide and silver bromide to form a saturated precursor solution. The saturated precursor solution is then coated on the surface of a carrier. Methanol is used as an anti-solvent in a container containing methanol. During the anti-solvent evaporation and crystallization process, methanol volatilizes and contacts dimethyl sulfoxide and N,N-dimethylformamide. Methanol affects the supersaturation of the saturated precursor solution, inducing the instantaneous formation of a large number of crystal nuclei, driving the solute in the saturated precursor solution to precipitate high-quality CsAgBr2 crystals, and obtaining a carrier loaded with the precursor crystals. The present invention anneals the carrier loaded with the precursor crystals to release the internal stress of the precursor crystals, improve the crystallinity of the precursor crystals, and enhance the quality of the silver-based metal halide microcrystals. The method provided by the present invention is simple to operate, does not require expensive equipment and harsh conditions such as ultra-high vacuum, and is easier to control and implement during the preparation process, which is conducive to large-scale production. The results of the examples show that the silver-based metal halide microcrystals prepared by the method of the present invention are CsAgBr2 crystals having a high-quality crystal structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The XRD spectrum of the silver-based metal halide microcrystals prepared in Example 1 of the present invention;

[0027] Figure 2 This is an absorption spectrum of the silver-based metal halide microcrystals prepared in Example 1 of the present invention;

[0028] Figure 3 The current-voltage curve of the deep ultraviolet photodetector prepared in Application Example 1 of the present invention at a wavelength of 265 nm;

[0029] Figure 4 The photocurrent response of the deep ultraviolet photodetector prepared in Application Example 1 of the present invention under different light intensities;

[0030] Figure 5 This is the time response curve of the deep ultraviolet photodetector prepared in Application Example 1 of the present invention under illumination. DETAILED DESCRIPTION

[0031] The present invention provides a method for preparing silver-based metal halide microcrystals, comprising:

[0032] Mixing cesium bromide, silver bromide, dimethyl sulfoxide and N,N-dimethylformamide to obtain a precursor saturated solution; the molar ratio of the cesium bromide to the silver bromide is 1 to 1.3:1;

[0033] coating the saturated precursor solution on the surface of a carrier to obtain a carrier coated with the saturated precursor solution;

[0034] placing the carrier coated with the saturated precursor solution in a container containing methanol, with the carrier coated with the saturated precursor solution being above the liquid level of the methanol, and then performing anti-solvent evaporation and crystallization to obtain a carrier loaded with precursor crystals;

[0035] The carrier carrying the precursor crystals is annealed to obtain silver-based metal halide microcrystals.

[0036] In the present invention, unless otherwise specified, the chemical reagents used in the present invention are all commercially available products well known to those skilled in the art.

[0037] The present invention mixes cesium bromide, silver bromide, dimethyl sulfoxide and N,N-dimethylformamide to obtain a precursor saturated solution.

[0038] In the present invention, the molar ratio of cesium bromide to silver bromide is 1 to 1.3:1. As an embodiment of the present invention, the molar ratio of cesium bromide to silver bromide can be 1:1, 1.1:1, 1.2:1, or 1.3:1. The present invention controls the molar ratio of cesium bromide to silver bromide to 1:1 to obtain CsAgBr2, which has a wide bandgap. This property enables it to effectively absorb deep ultraviolet light while being essentially unresponsive to visible light and near-infrared light, thereby avoiding interference from visible light and improving the sensitivity and selectivity of deep ultraviolet detection.

[0039] In the present invention, the volume ratio of dimethyl sulfoxide to N,N-dimethylformamide is preferably 1:2 to 4. As one embodiment of the present invention, the volume ratio of dimethyl sulfoxide to N,N-dimethylformamide can be 1:2, 1:3, or 1:4. By controlling the volume ratio of dimethyl sulfoxide to N,N-dimethylformamide within the above range, the present invention has better solubility for cesium bromide and silver bromide, and is more conducive to obtaining a high-quality precursor saturated solution.

[0040] In the present invention, the ratio of the total amount of cesium bromide and silver bromide to the total volume of dimethyl sulfoxide and N,N-dimethylformamide is preferably 0.01 mol:4 mL. Controlling the ratio of the total amount of cesium bromide and silver bromide to the total volume of dimethyl sulfoxide and N,N-dimethylformamide within the above range is more conducive to obtaining a high-quality precursor saturated solution.

[0041] In the present invention, the method for mixing cesium bromide, silver bromide, dimethyl sulfoxide, and N,N-dimethylformamide is preferably as follows: cesium bromide, silver bromide, dimethyl sulfoxide, and N,N-dimethylformamide are heated and mixed in the dark, and then filtered to obtain a saturated precursor solution. The present invention adopts this mixing method, which is more conducive to improving the solubility of cesium bromide and silver bromide in dimethyl sulfoxide and N,N-dimethylformamide and can prevent the decomposition of cesium bromide and silver bromide.

[0042] In the present invention, the temperature of the heating and mixing is preferably 60 to 80°C, more preferably 60 to 70°C. In the present invention, the time of the heating and mixing is preferably 2 to 3 hours. As an embodiment of the present invention, the time of the heating and mixing can be 2 hours, 2.5 hours or 3 hours. In the present invention, the heating and mixing is preferably carried out under stirring. The present invention does not specifically limit the rotation speed of the stirring, as long as it can promote the full dissolution of cesium bromide and silver bromide in dimethyl sulfoxide and N,N-dimethylformamide. The present invention performs heating and mixing at the above-mentioned temperature and time, which is more conducive to improving the solubility of cesium bromide and silver bromide in dimethyl sulfoxide and N,N-dimethylformamide.

[0043] The present invention has no particular limitation on the filtering method, and any conventional filtering method can be used. The present invention can remove undissolved solids after the mixture of cesium bromide, silver bromide, dimethyl sulfoxide and N,N-dimethylformamide by filtering, thereby obtaining a saturated precursor solution.

[0044] After obtaining the saturated precursor solution, the present invention coats the saturated precursor solution on the surface of the carrier to obtain the carrier coated with the saturated precursor solution.

[0045] The present invention does not particularly limit the material of the carrier; any material capable of supporting a saturated precursor solution is sufficient. In an embodiment of the present invention, the carrier can be a SiO2-coated silicon wafer interdigital electrode. The present invention utilizes SiO2-coated silicon wafer interdigital electrodes as a carrier, enabling the direct growth of silver-based metal halide microcrystals on the SiO2-coated silicon wafer interdigital electrodes for use as a deep ultraviolet photodetector.

[0046] In the present invention, the carrier is preferably cleaned and dried before coating. The cleaning and drying methods are not particularly limited in the present invention; conventional cleaning and drying methods can be used to fully remove impurities from the carrier surface. In an embodiment of the present invention, the cleaning and drying method may include ultrasonically cleaning the carrier in alcohol, acetone, and deionized water, followed by drying with air, and then cleaning with a plasma cleaner for 10 to 30 minutes.

[0047] The present invention does not particularly limit the coating method; a conventional coating method may be employed to form a uniform coating of the saturated precursor solution on the support. In the present invention, the coating method may be drop coating. The present invention does not particularly limit the coating amount of the saturated precursor solution; the amount may be adjusted based on the desired amount of silver-based metal halide microcrystals.

[0048] After obtaining the carrier coated with the saturated solution of the precursor, the present invention places the carrier coated with the saturated solution of the precursor in a container containing methanol, so that the carrier coated with the saturated solution of the precursor is above the liquid level of the methanol, and then performs anti-solvent evaporation and crystallization to obtain a carrier loaded with precursor crystals.

[0049] In the present invention, the carrier coated with the saturated solution of the precursor is placed in a container filled with methanol, and the method for the carrier coated with the saturated solution of the precursor to be located above the liquid level of the methanol is preferably: placing a supporting device in the container filled with methanol, and the upper surface of the supporting device is higher than the liquid level of the methanol; and then placing the carrier coated with the saturated solution of the precursor on the upper surface of the supporting device.

[0050] The present invention has no particular limitation on the supporting device, as long as it can support the carrier of the saturated solution of the coating precursor and be fixed in a container containing methanol. In an embodiment of the present invention, the supporting device can be a glass ring.

[0051] In the present invention, the height from the upper surface of the supporting device to the methanol liquid level is preferably 5 cm.

[0052] In the present invention, a glass sheet is preferably placed on the upper surface of the support device, and filter paper is preferably placed on the glass sheet. Placing a glass sheet on the upper surface of the support device, and preferably filter paper on the glass sheet, can prevent the saturated precursor solution on the carrier coated with the saturated precursor solution from overflowing during antisolvent evaporation and crystallization, thereby contaminating the glass ring and methanol.

[0053] In the present invention, the temperature of the anti-solvent evaporation crystallization is preferably 60°C. In the present invention, the time of the anti-solvent evaporation crystallization is preferably 24 to 48 hours. As an embodiment of the present invention, the time of the anti-solvent evaporation crystallization can be 24 hours, 26 hours, 28 hours, 30 hours, 32 hours, 34 hours, 36 hours, 38 hours, 40 hours, 42 hours, 46 hours or 48 hours. At the above temperature and time, the present invention can utilize methanol to affect the supersaturation of the precursor saturated solution, induce the instantaneous formation of a large number of crystal nuclei, drive the solute of the precursor saturated solution to precipitate CsAgBr2 crystals, and improve the precipitation speed and quality of CsAgBr2 crystals.

[0054] In the present invention, during the anti-solvent evaporation and crystallization process, the container containing methanol is preferably sealed with tin foil punctured with small holes. Sealing the container containing methanol with tin foil punctured with small holes can control the slow precipitation of crystals and prevent contamination by impurities. The number of small holes is not particularly limited in the present invention and is adjusted according to the crystal precipitation rate to enable the anti-solvent evaporation and crystallization to be completed within the above-mentioned time range.

[0055] After obtaining the carrier loaded with the precursor crystals, the present invention anneals the carrier loaded with the precursor crystals to obtain silver-based metal halide microcrystals.

[0056] In the present invention, the annealing temperature is preferably 60°C. In the present invention, the annealing time is preferably 10 to 20 minutes. As an embodiment of the present invention, the annealing time can be 10 minutes, 12 minutes, 14 minutes, 16 minutes, 18 minutes, or 20 minutes. In the present invention, annealing at the above temperature and time can further improve the quality of the silver-based metal halide microcrystals.

[0057] The method provided by the present invention is simple to operate, does not require expensive equipment and harsh conditions such as ultra-high vacuum, and the preparation process is easier to control and implement, which is conducive to large-scale production.

[0058] The present invention also provides silver-based metal halide microcrystals prepared by the preparation method described in the above technical solution, and the chemical formula of the silver-based metal halide microcrystals is CsAgBr2.

[0059] The silver-based metal halide microcrystals provided by the present invention have high-quality crystals, excellent stability, and strong absorption capacity for ultraviolet light.

[0060] The present invention also provides the use of the silver-based metal halide microcrystals described in the above technical solution in deep ultraviolet photodetectors.

[0061] In the present invention, the deep ultraviolet photodetector includes interdigital electrodes and a silver-based metal halide microcrystalline film grown on the interdigital electrodes.

[0062] In the present invention, the thickness of the silver-based metal halide microcrystalline film is preferably 1 to 2.5 μm, more preferably 1.5 to 2 μm. The present invention controls the thickness of the silver-based metal halide microcrystalline film within the above range, which can improve the selectivity and sensitivity of the deep ultraviolet photodetector.

[0063] In the present invention, the interdigital electrodes are preferably silicon wafer interdigital electrodes coated with SiO2. The present invention has no particular limitation on the thickness of the SiO2, and conventional silicon wafer interdigital electrodes coated with SiO2 can be used.

[0064] In the present invention, the thickness of SiO2 in the SiO2-coated silicon wafer interdigital electrode is preferably 100 nm. The present invention uses SiO2-coated silicon wafer interdigital electrodes and grows a silver-based metal halide microcrystalline film on the surface thereof to form a deep ultraviolet photodetector.

[0065] In an embodiment of the present invention, the number of pairs of the interdigital electrodes may be 5 pairs; the line width of the interdigital electrodes may be 5 μm; and the thickness of the interdigital electrodes may be 7 nm.

[0066] In the present invention, the method for preparing the deep ultraviolet photodetector preferably comprises the following steps:

[0067] (1) mixing cesium bromide, silver bromide, dimethyl sulfoxide, and N,N-dimethylformamide to obtain a precursor saturated solution;

[0068] (2) coating the saturated precursor solution on the surface of the interdigital electrode to obtain an interdigital electrode coated with the saturated precursor solution;

[0069] (3) placing the interdigital electrode coated with the precursor saturated solution in a container containing methanol, wherein the interdigital electrode coated with the precursor saturated solution is located above the liquid surface of the methanol, and then performing anti-solvent evaporation crystallization to obtain an interdigital electrode loaded with precursor crystals;

[0070] (4) Annealing the interdigitated electrodes loaded with the precursor crystals to obtain a deep ultraviolet photodetector.

[0071] In the present invention, cesium bromide, silver bromide, dimethyl sulfoxide and N,N-dimethylformamide are preferably mixed to obtain a precursor saturated solution.

[0072] In the present invention, the molar ratio of cesium bromide to silver bromide is 1 to 1.3:1. As an embodiment of the present invention, the molar ratio of cesium bromide to silver bromide can be 1:1, 1.1:1, 1.2:1, or 1.3:1. By controlling the molar ratio of cesium bromide to silver bromide within the above range, high-quality CsAgBr2 can be obtained, which can improve the sensitivity and selectivity of deep ultraviolet detection.

[0073] In the present invention, the volume ratio of dimethyl sulfoxide to N,N-dimethylformamide is preferably 1:2 to 4. As an embodiment of the present invention, the volume ratio of dimethyl sulfoxide to N,N-dimethylformamide may be 1:2, 1:3 or 1:4. In the present invention, the ratio of the total amount of cesium bromide and silver bromide to the total volume of dimethyl sulfoxide and N,N-dimethylformamide is preferably 0.01 mol: (1 to 4) mL.

[0074] In the present invention, the method for mixing cesium bromide, silver bromide, dimethyl sulfoxide and N,N-dimethylformamide is the same as the method for mixing cesium bromide, silver bromide, dimethyl sulfoxide and N,N-dimethylformamide described in the above technical solution, and will not be repeated here.

[0075] After obtaining the saturated precursor solution, the present invention preferably coats the saturated precursor solution on the surface of the interdigital electrode to obtain the interdigital electrode coated with the saturated precursor solution.

[0076] In the present invention, the interdigitated electrodes preferably use SiO2-coated silicon wafer interdigitated electrodes as a carrier, and silver-based metal halide microcrystals can be directly grown on the SiO2-coated silicon wafer interdigitated electrodes for use as deep ultraviolet photodetectors.

[0077] The present invention preferably cleans and dries the interdigitated electrodes before coating. In an embodiment of the present invention, the cleaning and drying method may be: ultrasonically cleaning the interdigitated electrodes with alcohol, acetone, and deionized water in sequence, then drying them with air, and then cleaning them with a plasma cleaner for 10 to 30 minutes.

[0078] The present invention does not particularly limit the coating method; a conventional coating method may be employed to form a uniform coating of the saturated precursor solution on the interdigitated electrodes. In the present invention, the coating method may be drop coating. The amount of the saturated precursor solution applied is not particularly limited; it may be adjusted based on the desired amount of silver-based metal halide microcrystals.

[0079] After obtaining the interdigitated electrode coated with a saturated solution of the precursor, the present invention places the interdigitated electrode coated with the saturated solution of the precursor in a container containing methanol, so that the interdigitated electrode coated with the saturated solution of the precursor is above the liquid surface of the methanol, and then performs anti-solvent evaporation and crystallization to obtain the interdigitated electrode loaded with the precursor crystal.

[0080] In the present invention, the interdigitated electrodes coated with a saturated solution of a precursor are placed in a container filled with methanol. The method for positioning the interdigitated electrodes coated with a saturated solution of a precursor above the liquid level of the methanol is preferably: placing a supporting device in the container filled with methanol, the upper surface of the supporting device being higher than the liquid level of the methanol; and then placing the interdigitated electrodes coated with a saturated solution of a precursor on the upper surface of the supporting device.

[0081] In an embodiment of the present invention, the supporting device may be a glass ring.

[0082] In the present invention, the height from the upper surface of the supporting device to the methanol liquid level is preferably 5 cm.

[0083] In the present invention, a glass sheet is preferably placed on the upper surface of the support device, and filter paper is preferably placed on the glass sheet. Placing a glass sheet on the upper surface of the support device and filter paper on the glass sheet can prevent the saturated precursor solution from overflowing from the interdigitated electrodes coated with the saturated precursor solution during antisolvent evaporation and crystallization, thereby contaminating the glass ring and methanol.

[0084] In the present invention, the temperature of the anti-solvent evaporation crystallization is preferably 60°C. In the present invention, the time of the anti-solvent evaporation crystallization is preferably 24 to 48 hours. As an embodiment of the present invention, the time of the anti-solvent evaporation crystallization can be 24 hours, 26 hours, 28 hours, 30 hours, 32 hours, 34 hours, 36 hours, 38 hours, 40 hours, 42 hours, 46 hours or 48 hours.

[0085] After obtaining the interdigital electrodes loaded with the precursor crystals, the present invention anneals the interdigital electrodes loaded with the precursor crystals to obtain silver-based metal halide microcrystals.

[0086] In the present invention, the anti-solvent evaporation crystallization preferably involves sealing the container containing methanol with tin foil punctured with small holes. Sealing the container containing methanol with tin foil punctured with small holes can control the slow precipitation of crystals and prevent contamination by impurities.

[0087] In the present invention, the annealing temperature is preferably 60°C. In the present invention, the annealing time is preferably 10 to 20 minutes. As an embodiment of the present invention, the annealing time can be 10 minutes, 12 minutes, 14 minutes, 16 minutes, 18 minutes, or 20 minutes. In the present invention, annealing at the above temperature and time can further improve the quality of the silver-based metal halide microcrystals.

[0088] The method provided by the present invention is simple to operate, does not require expensive equipment and harsh conditions such as ultra-high vacuum, and the preparation process is easier to control and implement, which is conducive to the large-scale production of deep ultraviolet photodetectors.

[0089] The present invention adopts dimethyl sulfoxide and N,N-dimethylformamide as crystallization solvents to dissolve cesium bromide and silver bromide to form a saturated precursor solution, and then coats the saturated precursor solution on the surface of an interdigitated electrode. In a container containing methanol, methanol is used as an anti-solvent. During the anti-solvent evaporation and crystallization process, methanol is used to influence the supersaturation of the saturated precursor solution, thereby inducing the instantaneous formation of a large number of crystal nuclei, driving the solute of the saturated precursor solution to precipitate, and growing CsAgBr2 crystals on the interdigitated electrodes. Annealing can release the internal stress of the precursor crystal, improve the crystallinity of the precursor crystal, and enhance the quality of the deep ultraviolet photodetector.

[0090] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0091] Example 1

[0092] A method for preparing silver-based metal halide microcrystals, comprising the following steps:

[0093] (1) 1.065 g of cesium bromide, 0.94 g of silver bromide, 1 mL of dimethyl sulfoxide, and 4 mL of N,N-dimethylformamide were stirred uniformly at 60 °C for 2 h in the dark, and filtered to obtain a saturated precursor solution;

[0094] (2) The SiO2-coated silicon wafer interdigitated electrode was cleaned sequentially with alcohol, acetone, and deionized water ultrasonically and dried, and then cleaned with a plasma cleaner for 20 minutes to obtain a carrier;

[0095] Drop-coating the saturated precursor solution obtained in step (1) on the surface of the carrier to obtain a carrier coated with the saturated precursor solution;

[0096] (3) Pour 100 mL of methanol into a beaker, place a glass ring in the beaker 5 cm above the methanol liquid level, place a clean glass sheet on the glass ring, and place a piece of filter paper on the glass sheet; place the carrier coated with the precursor saturated solution on the filter paper, and then seal the beaker with tin foil with small holes and keep it warm at 60°C for 36 hours to obtain a carrier loaded with precursor crystals;

[0097] (4) Annealing the carrier loaded with the precursor crystals at 60° C. for 15 min to obtain a silver-based metal halide microcrystalline film grown on the carrier, wherein the silver-based metal halide microcrystalline film is silver-based metal halide microcrystals.

[0098] Comparative Example 1

[0099] A method for preparing silver-based metal halide microcrystals, which differs from Example 1 in that the volume of dimethyl sulfoxide in step (1) is 1 mL, the volume of N,N-dimethylformamide is 1 mL, and the remaining steps and parameters are the same as those in Example 1.

[0100] Comparative Example 2

[0101] A method for preparing silver-based metal halide microcrystals, which differs from Example 1 in that the volume of dimethyl sulfoxide in step (1) is 1 mL, the volume of N,N-dimethylformamide is 2 mL, and the remaining steps and parameters are the same as those in Example 1.

[0102] Comparative Example 3

[0103] A method for preparing silver-based metal halide microcrystals, which differs from Example 1 in that the volume of dimethyl sulfoxide in step (1) is 1 mL, the volume of N,N-dimethylformamide is 3 mL, and the remaining steps and parameters are the same as those in Example 1.

[0104] Test Example 1

[0105] The presence of solute at the bottom of the reaction vessel was observed, and the color changed after being placed under natural light for a while, indicating the presence of unreacted AgBr. It can be seen from the observation that Comparative Examples 1 to 3 cannot obtain a good precursor saturated solution, while Example 1 can obtain a precursor saturated solution.

[0106] Comparative Example 4

[0107] A method for preparing silver-based metal halide microcrystals, which differs from Example 1 in that the temperature for evaporating the antisolvent in step (3) is 65° C., the temperature for annealing in step (4) is 65° C., and the remaining steps and parameters are the same as those in Example 1.

[0108] Comparative Example 5

[0109] A method for preparing silver-based metal halide microcrystals, which differs from Example 1 in that the temperature for evaporating the antisolvent in step (3) is 70° C., the temperature for annealing in step (4) is 70° C., and the remaining steps and parameters are the same as those in Example 1.

[0110] Test Example 2

[0111] The silver-based metal halide microcrystalline film prepared in Example 1 was tested, and the XRD spectrum of the silver-based metal halide microcrystalline was obtained as follows: Figure 1 As shown. Figure 1 In the example, PDF#38-0850 is the standard card of CsAgBr2; CsAgBr2 Sample is the silver-based metal halide microcrystalline film prepared in Example 1. Figure 1 It can be seen that the silver-based metal halide microcrystals obtained by the method of Example 1 of the present invention are CsAgBr2, and have excellent crystal quality.

[0112] The crystallinity of the silver-based metal halide microcrystals prepared in Comparative Examples 4 and 5 is inferior to that of the silver-based metal halide microcrystals prepared in Example 1. Therefore, the antisolvent evaporation temperature and the annealing temperature are key factors affecting the crystallinity of the silver-based metal halide microcrystals. When the antisolvent evaporation temperature and the annealing temperature are controlled at 60°C, high-quality silver-based metal halide microcrystals can be obtained.

[0113] Test Example 3

[0114] The silver-based metal halide microcrystalline film prepared in Example 1 was tested, and the absorption spectrum of the silver-based metal halide microcrystalline was obtained as shown in FIG. Figure 2 As shown. Figure 2 It can be seen that the silver-based metal halide microcrystals prepared in Example 1 have strong absorption in the deep ultraviolet region.

[0115] Application Example 1

[0116] A method for preparing a deep ultraviolet photodetector, comprising the following steps:

[0117] (1) 1.065 g of cesium bromide, 0.94 g of silver bromide, 1 mL of dimethyl sulfoxide, and 4 mL of N,N-dimethylformamide were stirred uniformly at 60 °C for 2 h in the dark, and filtered to obtain a saturated precursor solution;

[0118] (2) The SiO2-coated silicon wafer interdigital electrodes were sequentially cleaned with alcohol, acetone, and deionized water ultrasonically and dried, and then cleaned with a plasma cleaner for 20 minutes to obtain clean SiO2-coated silicon wafer interdigital electrodes; the number of pairs of interdigital electrodes was 5; the line width of the interdigital electrodes was 5 μm; and the thickness of the interdigital electrodes was 7 nm;

[0119] The saturated precursor solution obtained in step (1) is drop-coated on the surface of a clean silicon wafer interdigitated electrode coated with SiO2 (thickness of 100 nm) to obtain a carrier coated with the saturated precursor solution;

[0120] (3) Pour 100 mL of methanol into a beaker, place a glass ring in the beaker 5 cm above the methanol liquid level, place a clean glass sheet on the glass ring, and place a piece of filter paper on the glass sheet; place the carrier coated with the precursor saturated solution on the filter paper, and then seal the beaker with tin foil with small holes and keep it warm at 60°C for 36 hours to obtain a carrier loaded with precursor crystals;

[0121] (4) Annealing the carrier loaded with the precursor crystal at 60° C. for 15 min to obtain a deep ultraviolet photodetector, wherein the deep ultraviolet photodetector is composed of a silicon wafer interdigital electrode coated with SiO2 and a silver-based metal halide microcrystalline film grown on the silicon wafer interdigital electrode coated with SiO2.

[0122] Test Example 4

[0123] The deep ultraviolet photodetector prepared in Example 1 was tested and the current-voltage curve at a wavelength of 265nm was obtained as follows: Figure 3 As shown. Figure 3 It can be seen that as the light intensity increases from 0 to 2.29 mW / cm 2 As the power increases gradually, the photocurrent and the on-off ratio also increase gradually.

[0124] The deep ultraviolet photodetector prepared in Example 1 was tested and the photocurrent response under different light intensities was obtained as follows: Figure 4 As shown; the time response curve under light is as follows Figure 5 As shown. Figure 4 It can be seen that the deep ultraviolet photodetector prepared in Application Example 1 has good photocurrent response under different light intensities and exhibits good cycle stability. Figure 5 From the time response curve under illumination, it can be seen that the rise time and fall time are 512ms and 232ms respectively.

[0125] It can be seen from the above results that the deep ultraviolet photodetector prepared by the present invention has excellent accuracy and sensitivity. This is because the preparation method provided by the present invention can obtain silver-based metal halide microcrystals CsAgBr2 with a specific crystal structure. This structure gives it a suitable band gap width and good photoelectric conversion performance. Its crystal structure is conducive to the generation and transmission of photogenerated carriers (electron-hole pairs), and can efficiently convert deep ultraviolet light signals into electrical signals. In addition, the silver-based metal halide microcrystals CsAgBr2 in the deep ultraviolet photodetector prepared by the present invention have better selectivity for deep ultraviolet light, can accurately detect deep ultraviolet light signals in complex light environments, reduce interference from light in other bands, and improve detection accuracy and sensitivity. In addition, the method provided by the present invention is simple to operate and easy to control, and can prepare high-quality CsAgBr2 crystals on a large scale, which is conducive to the large-scale production of deep ultraviolet photodetectors.

[0126] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing silver-based metal halide microcrystals, characterized in that: include: mixing cesium bromide, silver bromide, dimethyl sulfoxide, and N,N-dimethylformamide to obtain a precursor saturated solution; The molar ratio of the cesium bromide to the silver bromide is 1 to 1.3:1; coating the saturated precursor solution on the surface of a carrier to obtain a carrier coated with the saturated precursor solution; placing the carrier coated with the saturated precursor solution in a container containing methanol, with the carrier coated with the saturated precursor solution being above the liquid level of the methanol, and then performing anti-solvent evaporation and crystallization to obtain a carrier loaded with precursor crystals; The carrier carrying the precursor crystals is annealed to obtain silver-based metal halide microcrystals.

2. The preparation method according to claim 1, characterized in that The volume ratio of the dimethyl sulfoxide to N,N-dimethylformamide is 1:2-4.

3. The preparation method according to claim 1, characterized in that The anti-solvent evaporation crystallization temperature and the annealing temperature are independently 60°C.

4. The preparation method according to claim 1 or 3, characterized in that The time for evaporation and crystallization of the anti-solvent is 24 to 48 hours.

5. The preparation method according to claim 1 or 3, characterized in that The annealing time is 10 to 20 minutes.

6. Silver-based metal halide microcrystals prepared by the preparation method according to any one of claims 1 to 5, wherein the chemical formula of the silver-based metal halide microcrystals is CsAgBr2.

7. Use of the silver-based metal halide microcrystals according to claim 6 in a deep ultraviolet photodetector, wherein the deep ultraviolet photodetector comprises interdigital electrodes and a silver-based metal halide microcrystal film grown on the interdigital electrodes.

8. The use according to claim 7, characterized in that The thickness of the silver-based metal halide microcrystalline film is 1 to 2.5 μm.

9. The use according to claim 7, characterized in that The method for preparing the deep ultraviolet photodetector comprises the following steps: (1) mixing cesium bromide, silver bromide, dimethyl sulfoxide, and N,N-dimethylformamide to obtain a precursor saturated solution; (2) coating the saturated precursor solution obtained in step (1) on the surface of the interdigital electrode to obtain an interdigital electrode coated with the saturated precursor solution; (3) placing the interdigital electrode coated with the saturated precursor solution obtained in step (2) in a container containing methanol, wherein the interdigital electrode coated with the saturated precursor solution is located above the liquid surface of the methanol, and then performing anti-solvent evaporation crystallization to obtain an interdigital electrode loaded with precursor crystals; (4) Annealing the interdigitated electrode loaded with the precursor crystal obtained in step (3) to obtain a deep ultraviolet photodetector.

10. The use according to claim 7, characterized in that The interdigital electrodes are silicon wafer interdigital electrodes plated with SiO2.

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