CsCu2I3 / porous GaN heterojunction and preparation method and application thereof
By combining thermal decomposition and spin coating methods to prepare CsCu2I3/porous GaN heterojunctions, the problem of small contact area of CsCu2I3/GaN heterojunctions was solved, the charge transport channels were increased and the stability of heterojunctions was improved, and the carrier mobility was significantly improved.
Patent Information
- Application Number
- CN202511398239.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-28
- Publication Date
- 2026-01-09
AI Technical Summary
In existing CsCu2I3/GaN heterojunction structures, the contact area between CsCu2I3 and GaN is small, resulting in fewer charge transport channels, higher charge transport resistance, and poor heterojunction stability.
Porous GaN was prepared by thermal decomposition and CsCu2I3 film was formed on the surface of porous GaN by spin coating. By optimizing the precursor solution ratio and spin coating process parameters, CsCu2I3/porous GaN heterojunction was prepared.
The contact area between CsCu2I3 and GaN was significantly increased, improving the charge transport channel and the stability of the heterojunction, and the carrier mobility was increased to 13.3–115 cm2/Vs.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor materials technology, and in particular to a CsCu2I3 / porous GaN heterojunction, its preparation method, and its application. Background Technology
[0002] Currently, semiconductor materials are widely used in ultraviolet photodetectors due to their excellent photoelectric properties. Among them, GaN and halide perovskite materials have attracted much attention as leading semiconductor materials. GaN has a hexagonal wurtzite structure and has received great attention from researchers due to its large band gap, high electron mobility, and excellent thermal stability. It has also made significant progress in applications such as lasers, transistors, and ultraviolet detectors. Compared with two-dimensional thin-film GaN, three-dimensional porous GaN has a larger specific surface area, further expanding the application range of GaN-based materials.
[0003] In recent years, although lead-based perovskites have experienced rapid development, the instability and toxicity of lead severely limit their further development and application. Therefore, it is necessary to identify alternative metal elements to replace lead. Among lead-free metal halide perovskites, CsCu₂I₃ exhibits high stability in air due to its unique one-dimensional electronic structure and excellent photovoltaic properties, demonstrating broadband photoluminescence and high photoluminescence quantum yield. This makes CsCu₂I₃ a promising candidate for applications in high-brightness LEDs, photodetectors, and other electronic devices.
[0004] In semiconductor devices, the pn junction, as an interface structure composed of p-type and n-type semiconductor materials, provides an important theoretical foundation for the design and performance optimization of semiconductor devices due to its unique band arrangement and carrier behavior. The pn junction is a fundamental structure in semiconductor materials, its advantage lying in its ability to form an internal electric field, achieving effective separation of electrons and holes, thus exhibiting unidirectional conductivity. This characteristic makes the pn junction play a crucial role in electronic devices. Pn junctions are widely used in diodes, transistors, solar cells, and photodetectors. By rationally selecting semiconductor materials and constructing corresponding heterostructures, the advantages of multiple components can be integrated, significantly improving the operating efficiency of related devices.
[0005] CsCu₂I₃ is a p-type conductive material, and the fabrication of its n-type form is relatively difficult. Typically, it is combined with other n-type wide-bandgap semiconductor materials to form heterojunctions. Since the growth technology of n-GaN is relatively mature, it can be used to fabricate CsCu₂I₃ / porous GaN heterojunctions. The fabrication process usually involves first growing a GaN layer, and then growing CsCu₂I₃ on the GaN layer. However, current heterojunctions fabricated using these two materials are all traditional two-dimensional heterostructures, which are detrimental to charge transport and heterojunction stability. Therefore, researching how to fabricate novel CsCu₂I₃ / GaN heterojunctions that significantly enhance the efficiency of related devices is of great significance. Summary of the Invention
[0006] The purpose of this invention is to provide a CsCu2I3 / porous GaN heterojunction, its preparation method, and its application, in order to solve the shortcomings of existing CsCu2I3 / GaN heterojunction structures, such as small contact area between CsCu2I3 and GaN, resulting in fewer charge transport channels, high charge transport resistance, and poor heterojunction stability.
[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:
[0008] This invention provides a method for preparing a CsCu2I3 / porous GaN heterojunction, comprising the following steps:
[0009] (1) A GaN buffer layer, a u-GaN layer, and an n-GaN layer are sequentially grown on a sapphire substrate to obtain the substrate;
[0010] (2) The substrate is decomposed at high temperature in a mixture of hydrogen and inert gas to obtain porous GaN;
[0011] (3) Dissolve CuI and CsI in a solvent and react to obtain a precursor solution;
[0012] (4) Spin-coat the precursor solution onto the porous GaN surface and add antisolvent during the spin-coating process. After spin-coating, anneal the obtained sample to form a CsCu2I3 film, thereby obtaining a CsCu2I3 / porous GaN heterojunction.
[0013] Optionally, the gallium source of the GaN buffer layer is TMGa, the nitrogen source is NH3, the growth temperature of the GaN buffer layer is 500-570℃, and the thickness of the GaN buffer layer is 20-30nm.
[0014] Optionally, the gallium source of the u-GaN layer is TMGa, the nitrogen source is NH3, the growth temperature of the u-GaN layer is 1000-1100℃, and the thickness of the u-GaN layer is 1.8-2.7μm.
[0015] Optionally, the gallium source of the n-GaN layer is TMGa, the silicon source is SiH4, the growth temperature of the n-GaN layer is 950-1100℃, and the thickness of the n-GaN layer is 1.7-2.4μm.
[0016] Optionally, in step (2), the volume ratio of hydrogen to inert gas is 1:9; the thermal decomposition temperature in step (2) is 900-1100℃ and the time is 30-140 min.
[0017] Optionally, the molar ratio of CsI to CuI is 1:2; the solvent is dimethylformamide and dimethyl sulfoxide; and the volume ratio of dimethylformamide to dimethyl sulfoxide is 4:1 to 1:1.
[0018] The reaction temperature in step (3) is 50-80℃ and the reaction time is 3-7h.
[0019] Optionally, the thickness of the CsCu2I3 thin film is 240–460 nm;
[0020] The spin coating method is a one-step spin coating method; the spin coating process parameters are: first spin coating at 500-1500 rpm for 5 seconds, then spin coating at 2000-4000 rpm for 60 seconds; after spin coating for 30-50 seconds, the anti-solvent is added dropwise; the anti-solvent is ethyl acetate.
[0021] Optionally, the annealing temperature in step (4) is 50–150°C and the time is 30–80 min.
[0022] The present invention also provides a CsCu2I3 / porous GaN heterojunction prepared by the above preparation method.
[0023] The present invention also provides the application of the above-mentioned CsCu2I3 / porous GaN heterojunction in ultraviolet detectors.
[0024] Compared with the prior art, the present invention has the following beneficial effects:
[0025] 1. This invention combines two methods—thermal decomposition for preparing porous GaN and spin coating for preparing CsCu2I3 thin films—to prepare a CsCu2I3 / porous GaN heterojunction. This method is simple to operate, low in cost, and significantly increases the specific surface area of the CsCu2I3 / porous GaN heterojunction, increases the contact area between CsCu2I3 and GaN, thereby increasing the charge transport channels and improving the stability of the heterojunction.
[0026] 2. This invention can improve the crystallinity of CsCu2I3 films by optimizing the solvent ratio in the precursor solution, thereby increasing the carrier mobility of the heterojunction, which ranges from 13.3 to 115 cm⁻¹. 2 / Vs.
[0027] 3. The method for preparing a CsCu2I3 / porous GaN heterojunction according to the present invention, wherein the thickness of the CsCu2I3 thin film can be controlled by the spin coating time and spin coating speed. Attached Figure Description
[0028] Figure 1 This is a flowchart of the steps involved in preparing the CsCu2I3 / porous GaN heterojunction according to Example 1 of the present invention.
[0029] Figure 2 The XRD pattern of the CsCu2I3 / porous GaN heterojunction prepared in Example 1 of this invention;
[0030] Figure 3 A top-view scanning electron microscope image of the porous GaN prepared in Example 1 of this invention;
[0031] Figure 4 A top-view scanning electron microscope image of the CsCu2I3 / porous GaN heterojunction prepared in Example 1 of this invention;
[0032] Figure 5 A top-view scanning electron microscope image of the CsCu2I3 / porous GaN heterojunction prepared in Example 4 of this invention;
[0033] Figure 6 The UV-Vis absorption spectrum of the CsCu2I3 / porous GaN heterojunction prepared in Example 1 of this invention;
[0034] Figure 7 The photoluminescence spectrum of the CsCu2I3 / porous GaN heterojunction prepared in Example 1 of this invention is shown. Detailed Implementation
[0035] 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.
[0036] 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.
[0037] 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.
[0038] 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 obvious to those skilled in the art. This application specification and embodiments are merely exemplary.
[0039] 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.
[0040] All raw materials used in this invention can be obtained commercially or prepared using existing technologies.
[0041] This invention provides a method for preparing a CsCu2I3 / porous GaN heterojunction, comprising the following steps:
[0042] (1) A GaN buffer layer, a u-GaN layer, and an n-GaN layer are sequentially grown on a sapphire substrate to obtain the substrate;
[0043] (2) The substrate is decomposed at high temperature in a mixture of hydrogen and inert gas to obtain porous GaN;
[0044] (3) Dissolve CuI and CsI in a solvent and react to obtain a precursor solution;
[0045] (4) Spin-coat the precursor solution onto the porous GaN surface and add antisolvent during the spin-coating process. After spin-coating, anneal the obtained sample to form a CsCu2I3 film, thereby obtaining a CsCu2I3 / porous GaN heterojunction.
[0046] Step (1) of this invention is to use an MOCVD system to sequentially grow a GaN buffer layer, a u-GaN layer, and an n-GaN layer on a substrate to obtain a substrate;
[0047] In this invention, the substrate is a sapphire substrate, and a GaN buffer layer, a u-GaN layer, and an n-GaN layer are sequentially grown on the c-surface of the sapphire substrate.
[0048] In this invention, the gallium source of the GaN buffer layer is TMGa, the nitrogen source is NH3, and the growth temperature of the GaN buffer layer is 500-570℃, for example, 500℃, 510℃, 520℃, 530℃, 540℃, 550℃, 560℃ or 570℃, etc.; the thickness of the GaN buffer layer is 20-30nm, preferably 22-28nm, and more preferably 23-27nm.
[0049] In this invention, the gallium source of the u-GaN layer is TMGa, the nitrogen source is NH3, and the growth temperature of the u-GaN layer is 1000-1100℃, for example, 1010℃, 1020℃, 1030℃, 1050℃, 1060℃, 1080℃ or 1100℃, etc.; the thickness of the u-GaN layer is 1.8-2.7μm, preferably 2.0-2.5μm, and more preferably 2.3-2.4μm.
[0050] In this invention, the gallium source of the n-GaN layer is TMGa, the silicon source is SiH4, and the growth temperature of the n-GaN layer is 950 to 1100°C, for example, 950°C, 960°C, 970°C, 980°C, 990°C, or 1000°C; the thickness of the n-GaN layer is 1.7 to 2.4 μm, preferably 1.9 to 2.1 μm.
[0051] In this invention, the substrate obtained in step (1) is further subjected to ultrasonic cleaning and nitrogen drying in sequence to remove organic contaminants from the surface.
[0052] The ultrasonic cleaning involves sequentially ultrasonically treating acetone, ethanol, and deionized water for 10–15 minutes each, for example, 10 minutes, 11 minutes, 12 minutes, 13 minutes, 14 minutes, or 15 minutes.
[0053] Step (2) of the present invention involves thermally decomposing the substrate obtained in step (1) in a mixture of hydrogen and inert gas to obtain porous GaN.
[0054] In this invention, the volume ratio of hydrogen to inert gas in step (2) is 1:9; the thermal decomposition temperature in step (2) is 900 to 1100°C, for example, 900°C, 940°C, 1000°C, 1050°C, 1090°C, or 1100°C; and the time is 30 to 140 minutes, for example, 30 minutes, 40 minutes, 50 minutes, 60 minutes, 70 minutes, 80 minutes, 90 minutes, 100 minutes, 110 minutes, 120 minutes, 130 minutes, or 140 minutes.
[0055] In this invention, the inert atmosphere includes nitrogen, argon, or helium.
[0056] This invention achieves the preparation of porous GaN with uniformly distributed pores and regular morphology by controlling the temperature and time of thermal decomposition within the above-mentioned range, which is beneficial to obtaining CsCu2I3 / porous GaN heterojunction with a large specific surface area.
[0057] Step (3) of this invention involves dissolving CuI and CsI in a solvent and heating and stirring with a magnetic stirrer until the precursor is completely dissolved to obtain a precursor solution.
[0058] In this invention, the molar ratio of CsI to CuI is 1:2; the solvent is dimethylformamide and dimethyl sulfoxide; the volume ratio of dimethylformamide to dimethyl sulfoxide is 4:1 to 1:1, for example, it can be 4:1, 3:1, 2:1, 1:1, etc.
[0059] The heating and stirring temperature in step (3) is 50 to 80°C, for example, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C; the time is 3 to 7 hours, for example, 3 hours, 4 hours, 5 hours, 6 hours or 7 hours.
[0060] This invention, by controlling the heating and stirring temperature and reaction time, can ensure that the precursor solution is fully dissolved, the reaction is uniform and stable, thus laying the foundation for the preparation of high-quality CsCu2I3 thin films.
[0061] Step (4) of the present invention is to apply the precursor solution to the porous GaN surface obtained in step (2), and add antisolvent during the application process. After the application is completed, the obtained sample is annealed to obtain a CsCu2I3 film with high crystal quality, thereby forming a CsCu2I3 / porous GaN heterojunction.
[0062] In this invention, the thickness of the CsCu2I3 thin film is 240-460 nm, for example, it can be 240 nm, 250 nm, 300 nm, 330 nm, 350 nm, 400 nm, 450 nm or 460 nm.
[0063] The application method is a one-step spin coating method; the spin coating process parameters are as follows: first, spin coating at 500-1500 rpm, for example, 500 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm, 1000 rpm, 1100 rpm, 1200 rpm, 1300 rpm, 1400 rpm, or 1500 rpm, for 5 seconds; then spin coating at 2000-4000 rpm, for example, 2000 rpm, 2200 rpm, 2400 rpm, 2500 rpm, 2800 rpm, 3000 rpm, 3200 rpm, 3400 rpm, 3500 rpm, 3800 rpm, or 4000 rpm, for 60 seconds; after spin coating for 30-50 seconds, for example, 30 seconds, 35 seconds, 40 seconds, 45 seconds, or 50 seconds, an anti-solvent is dropped onto the center of the rotating substrate;
[0064] The antisolvent is ethyl acetate;
[0065] The volume ratio of the antisolvent to the precursor solution is 2:1.
[0066] This invention achieves a dense and uniform film formation effect by controlling the spin coating speed and antisolvent drop time within the above-mentioned range, thereby ensuring that the film has good crystallinity and optical properties.
[0067] In this invention, the annealing temperature in step (4) is 50 to 150°C, for example, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C or 150°C, and the time is 30 to 80 minutes, for example, 30 minutes, 40 minutes, 50 minutes, 60 minutes, 70 minutes or 80 minutes.
[0068] By controlling the annealing temperature and annealing time within the above-mentioned range, this invention can improve the crystal quality of the film, reduce lattice defects, and optimize the morphology of the film, making it more uniform and dense.
[0069] The present invention also provides a CsCu2I3 / porous GaN heterojunction prepared by the above preparation method.
[0070] The present invention also provides the application of the above-mentioned CsCu2I3 / porous GaN heterojunction in ultraviolet detectors.
[0071] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.
[0072] According to the embodiments Figure 1 The steps are shown in the flowchart.
[0073] Example 1
[0074] (1) In the MOCVD system, sapphire is used as the substrate, and a GaN buffer layer with a thickness of 25 nm, a u-GaN layer with a thickness of 2.5 μm and an n-GaN layer with a thickness of 2 μm are sequentially stacked on the c surface of the sapphire substrate to obtain the substrate;
[0075] The growth temperature of the GaN buffer layer is 550℃, the growth temperature of the u-GaN layer is 1080℃, and the growth temperature of the n-GaN layer is 950℃.
[0076] The gallium source for growing the GaN buffer layer and the u-GaN layer is TMGa, and the nitrogen source is NH3. The gallium source for growing the n-GaN layer is TMGa, and the silicon source is SiH4.
[0077] (2) The substrate was subjected to ultrasonic treatment in acetone, ethanol and deionized water for 15 min in sequence, and then dried with nitrogen to obtain the pretreated substrate.
[0078] (3) The pretreated substrate obtained in step (2) is placed in a tube furnace and decomposed at 1000°C for 50 minutes in a mixture of hydrogen and nitrogen to obtain porous GaN; the volume ratio of hydrogen to nitrogen in the mixture of hydrogen and nitrogen is 1:9.
[0079] (4) Dissolve 0.33 mmol of CsI and 0.66 mmol of CuI in 1.5 mL of a mixed solution of DMF and DMSO with a volume ratio of 4:1. Heat and stir at 70 °C for 4 h. After cooling, filter to obtain the precursor solution.
[0080] (5) The precursor solution obtained in step (4) is spin-coated onto the surface of the sample prepared in step (5) using a one-step spin-coating method, and ethyl acetate is added dropwise during the spin-coating process. The spin-coating process is as follows: first spin-coat at a speed of 500 rpm for 5 s, then spin-coat at a speed of 3000 rpm for 60 s, and after spin-coating for 45 s, 100 μL of ethyl acetate antisolvent is added dropwise.
[0081] (6) The sample obtained in step (5) is annealed at 100°C for 60 min to obtain a CsCu2I3 thin film with high crystal quality, and then a CsCu2I3 / porous GaN heterojunction is formed.
[0082] The thickness of the CsCu2I3 thin film is 330 nm; the carrier mobility of the heterojunction is 115 cm⁻¹. 2 / Vs.
[0083] Example 2
[0084] The porous CsCu2I3 / porous GaN heterojunction was prepared according to the method of Example 1, except that the spin coating process in step (5) was as follows: first spin coating at 500 rpm for 5 s, then spin coating at 2000 rpm for 60 s, and finally adding ethyl acetate as a solvent after spin coating for 45 s. The thickness of the CsCu2I3 film was 460 nm.
[0085] Example 3
[0086] The porous CsCu2I3 / porous GaN heterojunction was prepared according to the method of Example 1, except that the spin coating process in step (5) was as follows: first spin coating at 500 rpm for 5 s, then spin coating at 4000 rpm for 60 s, and finally adding ethyl acetate as a solvent after spin coating for 45 s. The thickness of the CsCu2I3 film was 240 nm.
[0087] Example 4
[0088] A porous CsCu₂I₃ / porous GaN heterojunction was prepared according to the method of Example 1, except that the volume ratio of DMF to DMSO in step (4) was 2:1. The carrier mobility of the heterojunction was 17.26 cm⁻¹. 2 / Vs.
[0089] Figure 2 The XRD pattern of the CsCu2I3 / porous GaN heterojunction is shown. The diffraction peak at 34.3° belongs to the (002) plane of the GaN film. There is a set of diffraction peaks at 10.721°, 13.421°, 21.621°, 26.141° and 27.121°, which belong to the (110), (020), (220), (221) and (040) planes of the orthorhombic CsCu2I3, respectively. The diffraction peaks at other positions also correspond well with the standard card. No other impurities were found, which further indicates that the CsCu2I3 / porous GaN heterojunction was successfully prepared.
[0090] Figure 3 This is a top-view scanning electron microscope image of the porous GaN prepared in this invention. Figure 3 It can be seen that many small pores are formed on the GaN surface, indicating that porous n-GaN has been successfully prepared. The prepared porous n-GaN has an average pore size of 210 nm and a pore density of 2.61 × 10⁻⁶. 8 cm -2 .
[0091] Figure 4 This is a top-view scanning electron microscope image of the CsCu2I3 / porous GaN heterojunction prepared in Example 1 of this invention. Figure 4It can be seen that the CsCu2I3 prepared on the porous n-GaN substrate is dendritic and the film is very dense and uniform, indicating that the CsCu2I3 film prepared by this method has good crystal quality.
[0092] Figure 5 This is a top-view scanning electron microscope image of the CsCu2I3 / porous GaN heterojunction prepared in Example 4 of this invention. Figure 5 It can be seen that CsCu2I3 prepared on porous n-GaN substrate is dendritic, but the film is not dense and uniform and has a large number of defects. The solvent ratio in the surface precursor solution will seriously affect the crystallization quality of CsCu2I3 film.
[0093] Figure 6 The UV-Vis absorption spectrum of the CsCu2I3 / porous GaN heterojunction is shown below. Figure 6 It can be seen that the sample exhibits absorption edges at 320nm and 361nm, corresponding to the absorption edges of CsCu2I3 and GaN, respectively. Moreover, the absorption edges are very steep and rapidly decay to a low level in the visible light region, indicating that the heterojunction has excellent ultraviolet selective absorption capability.
[0094] Figure 7 The photoluminescence spectrum of the CsCu2I3 / porous GaN heterojunction is shown below. Figure 7 It can be seen that the sample exhibited emission peaks at 361 nm and 570 nm, which correspond to the emission peaks of CsCu2I3 and GaN, respectively.
[0095] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for preparing a CsCu₂I₃ / porous GaN heterojunction, characterized in that, Includes the following steps: (1) A GaN buffer layer, a u-GaN layer, and an n-GaN layer are sequentially grown on a sapphire substrate to obtain the substrate; (2) The substrate is decomposed at high temperature in a mixture of hydrogen and inert gas to obtain porous GaN; (3) Dissolve CuI and CsI in a solvent and react to obtain a precursor solution; (4) Spin-coat the precursor solution onto the porous GaN surface and add antisolvent during the spin-coating process. After spin-coating, anneal the obtained sample to form a CsCu2I3 film, thereby obtaining a CsCu2I3 / porous GaN heterojunction.
2. The preparation method according to claim 1, characterized in that, The GaN buffer layer uses TMGa as the gallium source and NH3 as the nitrogen source. The growth temperature of the GaN buffer layer is 500–570℃, and the thickness of the GaN buffer layer is 20–30 nm.
3. The preparation method according to claim 1, characterized in that, The gallium source of the u-GaN layer is TMGa, the nitrogen source is NH3, the growth temperature of the u-GaN layer is 1000~1100℃, and the thickness of the u-GaN layer is 1.8~2.7μm.
4. The preparation method according to claim 1, characterized in that, The gallium source of the n-GaN layer is TMGa, the silicon source is SiH4, the growth temperature of the n-GaN layer is 950~1100℃, and the thickness of the n-GaN layer is 1.7~2.4μm.
5. The preparation method according to claim 1, characterized in that, In step (2), the volume ratio of hydrogen to inert gas is 1:9; the thermal decomposition temperature in step (2) is 900-1100℃ and the time is 30-140min.
6. The preparation method according to claim 1, characterized in that, The molar ratio of CsI to CuI is 1:2; the solvent is dimethylformamide and dimethyl sulfoxide; the volume ratio of dimethylformamide to dimethyl sulfoxide is 4:1 to 1:1; The reaction temperature in step (3) is 50-80℃ and the reaction time is 3-7h.
7. The preparation method according to claim 1, characterized in that, The thickness of the CsCu2I3 thin film is 240–460 nm; The spin coating method is a one-step spin coating method; the spin coating process parameters are: first spin coating at 500-1500 rpm for 5 seconds, then spin coating at 2000-4000 rpm for 60 seconds; after spin coating for 30-50 seconds, the anti-solvent is added dropwise; the anti-solvent is ethyl acetate.
8. The preparation method according to claim 1, characterized in that, The annealing temperature in step (4) is 50-150℃ and the time is 30-80 min.
9. The CsCu2I3 / porous GaN heterojunction prepared by the preparation method according to any one of claims 1 to 8.
10. The application of the CsCu2I3 / porous GaN heterojunction as described in claim 9 in an ultraviolet detector.