A solar cell based on two-dimensional / three-dimensional perovskite heterojunction thin film and a preparation method thereof

Abstract

The application relates to the technical field of photoelectric materials and devices, in particular to a solar cell based on a two-dimensional / three-dimensional perovskite heterojunction film and a preparation method thereof; an electron transport layer and a three-dimensional perovskite photoelectric conversion layer are sequentially deposited on a transparent conductive substrate; an organic amine halide solution is sprayed on the surface of the heated three-dimensional perovskite photoelectric conversion layer, in-situ reaction and non-uniform crystallization occur to form a two-dimensional perovskite, a two-dimensional / three-dimensional perovskite heterojunction film is obtained; a hole transport layer is deposited on the two-dimensional / three-dimensional perovskite heterojunction film, and the hole transport layer is subjected to oxidation treatment; finally, a metal electrode is deposited to obtain a perovskite solar cell; by forming a locally covered two-dimensional / three-dimensional perovskite heterojunction structure, the surface defects of the three-dimensional perovskite are passivated, the environmental stability is improved, the adverse influence of the two-dimensional perovskite structure on carrier transport is reduced, and therefore the photoelectric conversion efficiency and humidity stability of the perovskite solar cell are improved.

Description

Technical Field

[0001] This invention relates to the field of optoelectronic materials and devices, specifically to a solar cell based on a two-dimensional / three-dimensional perovskite heterojunction thin film and its fabrication method. Background Technology

[0002] In recent years, organic-inorganic hybrid three-dimensional perovskite solar cells have attracted widespread attention due to their excellent photoelectric performance. Three-dimensional perovskite materials possess characteristics such as long charge carrier diffusion length, high light absorption coefficient, high carrier mobility, and tunable optical bandgap. Combined with low-cost fabrication methods such as solution processing, they show promising application prospects in the field of solar cells. However, three-dimensional perovskite materials are quite sensitive to external environmental factors, and their performance is prone to degradation under the influence of moisture, oxygen, heat, and light. Their long-term stability remains a significant factor limiting practical applications. The performance degradation of three-dimensional perovskite solar cells is usually related to factors such as surface defects in the photoelectric conversion layer, grain boundary defects, and non-radiative recombination at the interface. To address these issues, researchers have proposed various methods, including interface engineering, additive engineering, component control, and molecular modification. Among these, introducing low-dimensional perovskite structures onto the surface of the three-dimensional perovskite photoelectric conversion layer, utilizing the hydrophobic properties and passivation effect of the organic components in the low-dimensional perovskite on surface defects to improve device performance and stability, is a technical solution that has gained attention in recent years.

[0003] However, there is still room for further optimization of existing low-dimensional / three-dimensional perovskite heterojunction structures. On the one hand, the large-volume organic amine cations introduced into two-dimensional perovskites can enhance their hydrophobicity and suppress ion migration, but at the same time, they also make carrier transport anisotropic. Two-dimensional perovskites usually tend to grow parallel to the substrate during crystallization. This orientation means that the insulating organic amine cation spacer layer will hinder the longitudinal transport of carriers from the three-dimensional perovskite layer to the electron transport layer, thereby significantly increasing the interfacial cross-resistance, reducing the device fill factor and photocurrent, and limiting the improvement of device efficiency. On the other hand, existing solution processing methods usually require the solution containing organic amine halides to be in full contact with the three-dimensional perovskite surface. During the processing, component exchange or local dissolution may occur between the solvent and the three-dimensional perovskite layer, which will affect the surface morphology and defect state of the film and ultimately introduce additional surface defects. In addition, a complete and continuous two-dimensional perovskite layer is formed, which completely covers the surface of the three-dimensional perovskite layer, which is not conducive to the longitudinal transport of carriers.

[0004] In summary, how to further optimize the formation state of low-dimensional perovskites and the structural features of low-dimensional / three-dimensional heterostructures to achieve a synergistic improvement in device efficiency and stability remains a problem to be solved in this field. Summary of the Invention

[0005] To address the aforementioned shortcomings of existing technologies, this invention provides a solar cell based on a two-dimensional / three-dimensional perovskite heterojunction thin film and its fabrication method. This effectively solves the problems of carrier transport obstruction caused by continuous low-dimensional perovskite coverage in existing low-dimensional / three-dimensional perovskite heterojunctions, and the difficulty in balancing device photoelectric performance and stability during traditional solution processing, which can easily damage the three-dimensional perovskite surface.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] In a first aspect, the present invention provides a method for fabricating a solar cell based on a two-dimensional / three-dimensional perovskite heterojunction thin film, the method comprising:

[0008] (1) Depositing an electron transport layer on a transparent conductive substrate;

[0009] (2) A three-dimensional perovskite photoelectric conversion layer is deposited on the electron transport layer;

[0010] (3) The organic amine halide solution is sprayed onto the heated surface of the three-dimensional perovskite photoelectric conversion layer, and an in-situ reaction occurs, which does not result in uniform crystallization to form a two-dimensional perovskite, thus obtaining a two-dimensional / three-dimensional perovskite heterojunction film.

[0011] (4) Deposit a hole transport layer on the two-dimensional / three-dimensional perovskite heterojunction film and oxidize the hole transport layer;

[0012] (5) Deposit a metal electrode on the hole transport layer after oxidation treatment to obtain a two-dimensional / three-dimensional perovskite heterojunction solar cell.

[0013] Furthermore, the transparent conductive substrate is either ITO glass or ITO-PEN substrate.

[0014] Furthermore, the electron transport layer is made of SnO2.

[0015] Furthermore, step (2) includes:

[0016] A three-dimensional perovskite precursor solution was coated onto the electron transport layer and subjected to thermal annealing and crystallization to form a three-dimensional polycrystalline perovskite film with mixed formamidinium and cesium ions.

[0017] Furthermore, the three-dimensional perovskite precursor solution is obtained by dissolving lead iodide, formamidine iodide, cesium iodide and methylamine chloride in a mixed solvent of N,N-dimethylformamide and dimethyl sulfoxide, followed by heating, stirring and filtration.

[0018] Furthermore, in the three-dimensional perovskite precursor solution, the concentration of lead iodide is 1.5 M, the concentration of formamidine iodide is 1.36 M, the concentration of cesium iodide is 0.09 M, the concentration of methylamine chloride is 0.15 M, and the volume ratio of N,N-dimethylformamide to dimethyl sulfoxide is 4:1.

[0019] Further, in step (3), the mass concentration of the organic amine halide solution is 0.5–10 mg / mL. Preferably, the mass concentration of the organic amine halide solution is 1 mg / mL.

[0020] Furthermore, the organic amine halide is selected from CH3(CH2). n1 NH3X, (CH2) n2 (NH3)2X2, C6H5(CH2) n3 NH3X, C6H4(CH2) n4 One of (NH3)2X2, NH2C(=NH)NH2.HX, and the fluorine-containing derivatives of the above-mentioned organic amine halides;

[0021] Wherein, n1 is an integer ≥ 1; n2 is an integer ≥ 2; n3 is an integer ≥ 1; n4 is an integer ≥ 2; and X is one of CI, Br, and I. Preferably, the organic amine halide is 4-(trifluoromethyl)phenylethylamine hydrochloride.

[0022] Furthermore, the solvent for the organic amine halide solution is an alkyl alcohol solvent, preferably isopropanol.

[0023] In step (3), the organic amine halide solution is sprayed by gas atomization spraying. During the spraying process, the spraying is carried out by controlling the distance between the nozzle and the substrate, the injection speed of the organic amine halide solution, the atomizing gas pressure, and the moving speed of the nozzle relative to the three-dimensional perovskite photoelectric conversion layer.

[0024] Furthermore, the spraying process is carried out in an air environment with a relative humidity of 30% to 70%. The organic amine halide solution is injected into the spray chamber. The distance between the nozzle and the three-dimensional perovskite photoelectric conversion layer is 10 to 30 cm. The injection speed is 0.2 to 1 mm / min. The atomizing gas is nitrogen with a pressure of 0.2 to 0.8 MPa. The moving speed of the nozzle relative to the three-dimensional perovskite photoelectric conversion layer is 50 to 100 mm / min.

[0025] Furthermore, in step (3), the heating temperature of the three-dimensional perovskite photoelectric conversion layer is 70-100 ℃, preferably 80 ℃;

[0026] After the spraying is completed, a further heating treatment is performed for 5 minutes.

[0027] Furthermore, step (4) includes:

[0028] A hole transport layer solution is coated onto the two-dimensional / three-dimensional perovskite heterojunction film, and the hole transport layer is formed after the solvent evaporates.

[0029] The substrate with the hole transport layer deposited thereon was then placed in an environment with a relative humidity of less than 20% and an oxygen content of more than 80% and left to stand to oxidize the hole transport layer.

[0030] The hole transport layer solution is prepared by adding an acetonitrile solution of 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene and lithium bis(trifluoromethanesulfonyl)imide, an acetonitrile solution of tri[4-tert-butyl-2-(1H-pyrazol-1-yl)pyridine]cobalttrix(1,1,1-trifluoro-N-[(trifluoromethyl)sulfonyl]methanesulfonamide salt] and 4-tert-butylpyridine to a chlorobenzene solvent.

[0031] Furthermore, the two-dimensional perovskite is discontinuously distributed on the surface of the three-dimensional perovskite photoelectric conversion layer, i.e., locally covered, and the surface of the three-dimensional perovskite photoelectric conversion layer has areas not covered by the two-dimensional perovskite.

[0032] Furthermore, in step (5), the metal electrode material is Au, Ag or Cu.

[0033] In a second aspect, the present invention also provides a solar cell based on a two-dimensional / three-dimensional perovskite heterojunction thin film, wherein the solar cell is fabricated according to the method described in the first aspect, and comprises, in sequence, a transparent conductive substrate, an electron transport layer, a three-dimensional perovskite photoelectric conversion layer, a two-dimensional / three-dimensional perovskite heterojunction locally covering the three-dimensional perovskite photoelectric conversion layer, a hole transport layer, and a metal electrode.

[0034] The technical solution provided by this invention has the following advantages compared with the known prior art:

[0035] 1. This invention applies an organic amine halide solution to the surface of a three-dimensional perovskite photoelectric conversion layer using a spraying method, allowing the organic amine halide to react in situ on the three-dimensional perovskite surface to form a locally covered two-dimensional / three-dimensional perovskite heterojunction structure. This locally covered structure utilizes the two-dimensional perovskite to control and protect the defects on the three-dimensional perovskite surface, while reducing the adverse effects of the continuous two-dimensional perovskite layer on carrier transport, thereby improving the photoelectric conversion performance of solar cells based on this heterojunction film.

[0036] 2. This invention prepares two-dimensional / three-dimensional perovskite heterostructures by spraying. Compared with traditional solution deposition methods such as spin coating or blade coating, it can reduce the coverage and residence time of organic amine halide solution on the three-dimensional perovskite surface. At the same time, the three-dimensional perovskite film is heated during the spraying process, so that the sprayed droplets evaporate quickly after contacting the film and promote in-situ crystallization, thereby reducing the adverse effects of alcohol solvents on the components of the three-dimensional perovskite surface and facilitating the acquisition of a stable heterostructure.

[0037] 3. This invention forms a local two-dimensional perovskite structure on the surface of a three-dimensional perovskite photoelectric conversion layer. By utilizing the hydrophobic properties of the organic components in the two-dimensional perovskite and the defect passivation effect, the adverse effects of three-dimensional perovskite surface defects on device performance are reduced, and the environmental stability of two-dimensional / three-dimensional perovskite heterojunction films is improved.

[0038] 4. When the two-dimensional / three-dimensional perovskite heterojunction thin film prepared by this invention is applied to solar cells, it has higher photoelectric conversion efficiency and better humidity stability compared with three-dimensional perovskite solar cells without a two-dimensional / three-dimensional heterojunction structure. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0040] Figure 1 This is a schematic diagram of the fabrication process of the two-dimensional / three-dimensional perovskite heterojunction thin film and solar cell in Embodiment 1 of the present invention;

[0041] Figure 2 This is a SEM image of the locally covered two-dimensional / three-dimensional perovskite heterojunction film prepared in Example 1 of the present invention;

[0042] Figure 3 Box plots showing the photoelectric conversion efficiency of the solar cells of Example 1 and Comparative Example 1;

[0043] Figure 4 The graph shows the normalized photoelectric conversion efficiency of the solar cells in Example 1 and Comparative Example 1 as a function of time. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0045] 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 are 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. The terms “comprising,” “including,” “having,” “containing,” etc., as used herein are open-ended terms, meaning that they include but are not limited to. Unless the context clearly indicates otherwise, the expressions “a” and “an” as used herein include plural references. It should be noted that “first,” “second,” etc., are used merely for convenience of description and distinction and should not be construed as indicating or implying relative importance. The term “about” as used herein indicates a range of ±20% of the following numerical value. In some embodiments, the term “about” indicates a range of ±10% of the following numerical value. In some embodiments, the term “about” indicates a range of ±5% of the following numerical value. The invention is further described below with reference to embodiments.

[0046] Example: Refer to Figures 1 to 4 .

[0047] Example 1:

[0048] A method for fabricating solar cells based on two-dimensional / three-dimensional perovskite heterojunction thin films is provided, and the process diagram is shown below. Figure 1 As shown, the specific steps include:

[0049] Step 1: Clean the surface of the ITO conductive glass: Sonicate the glass for 10 minutes in each of the four cleaning solutions: detergent, deionized water, acetone and isopropanol. Then discard the cleaning solution and dry the cleaned ITO conductive glass in an oven at 70 ℃ for 1 hour to obtain clean ITO conductive glass.

[0050] Step 2: Deposition of the electron transport layer: A 15 wt% SnO2 colloidal solution was mixed with deionized water at a volume ratio of 1:5 and stirred at room temperature for 1 h to obtain a diluted SnO2 colloidal aqueous solution. Clean ITO conductive glass was treated with UV ozone for 20 min, cooled to room temperature, and then placed on a spin coater tray. The diluted SnO2 colloidal aqueous solution was dropped onto its surface, and spin coating was immediately performed at 4000 rpm for 30 s. After the spin coating process, the ITO conductive glass was placed on a heating stage and annealed at 150 ℃ for 20 min to form a dense electron transport layer with a thickness of approximately 25 nm.

[0051] Step 3: Deposit a three-dimensional perovskite photoelectric conversion layer on the surface of the electron transport layer: First, dissolve 1.5 M lead iodide, 1.36 M formamidinium iodide, 0.09 M cesium iodide and 0.15 M methylamine chloride in a mixed solvent of N,N-dimethylformamide and dimethyl sulfoxide in a volume ratio of 4:1, stir at 60 °C for 12 h, and filter to obtain a three-dimensional perovskite precursor solution. The substrate with the electron transport layer deposited was transferred to a glove box filled with nitrogen atmosphere, and a three-dimensional perovskite photoelectric conversion layer was deposited by spin coating. In the preparation, the three-dimensional perovskite precursor solution was first dropped onto the electron transport layer. The spin coater was set to a rotation speed of 1000 rpm for 10 s in the first stage and a rotation speed of 4000 rpm for 30 s in the second stage. In the last 15 s of the second stage of spin coating, 200 µL of ethyl acetate was dropped onto the film. After the spin coating process was completed, the three-dimensional perovskite wet film was placed on a heating stage and annealed at 120 °C for 30 min to form a three-dimensional perovskite photoelectric conversion layer with a thickness of about 400 nm.

[0052] Step 4: Prepare locally covered two-dimensional / three-dimensional perovskite heterojunctions on the surface of the three-dimensional perovskite photoelectric conversion layer using a spraying method. Specifically, first, prepare an organic amine halide solution for spraying; in this example, C6H5(CH2) is used. n3 4-Trifluoromethylphenylethylamine hydrochloride, a fluorinated derivative of NH3X organic amine halide, was used as the solute, and isopropanol as the solvent, with a solution concentration of 1 mg / mL. The spraying process was as follows: the prepared 4-trifluoromethylphenylethylamine hydrochloride solution was injected into the spray chamber. The spraying process was carried out in air with a relative humidity of 30%–50%, the distance between the nozzle and the substrate was 20 cm, the nitrogen atomization pressure was 0.3 MPa, the injection speed was 0.4 mm / min, and the nozzle moving speed was 60 mm / min. During the organic amine halide solution spraying, the three-dimensional perovskite photoelectric conversion layer was heated on a heating stage at 80 °C. After spraying, heating continued for 5 min to allow the organic amine halide to react in situ with the surface of the three-dimensional perovskite photoelectric conversion layer and crystallize to form a two-dimensional perovskite, resulting in a locally distributed two-dimensional / three-dimensional perovskite heterojunction film. SEM images are shown below. Figure 2 As shown.

[0053] Step 5: Deposit a hole transport layer on the perovskite layer that locally covers the two-dimensional / three-dimensional heterostructure and perform an oxidation treatment on the hole transport layer. Specifically, first, prepare a hole transport layer solution by taking 72.3 mg of 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene, 17.5 µL of acetonitrile solution of lithium bis(trifluoromethanesulfonate) (concentration 520 mg / mL), 19 µL of acetonitrile solution of tris[4-tert-butyl-2-(1H-pyrazol-1-yl)pyridine]cobalttrium(1,1,1-trifluoro-N-[(trifluoromethyl)sulfonyl]methanesulfonamide salt (concentration 200 mg / mL), and 29 µL of 4-tert-butylpyridine, and add them to 1 mL of chlorobenzene solvent. Stir at room temperature to obtain the hole transport layer solution. The hole transport layer solution was spin-coated onto a three-dimensional perovskite photoelectric conversion layer containing locally covered two-dimensional / three-dimensional perovskite heterostructures at a spin speed of 4000 rpm for 30 s. After solvent evaporation, a completely covered hole transport layer film was formed. The deposited hole transport layer was then placed in an environment with a relative humidity of less than 20% and an oxygen content of more than 80% for 24 h to obtain an oxidized hole transport layer.

[0054] Step 6: Deposit metal electrodes on the hole transport layer. Specifically, transfer the substrate with each functional layer deposited to the vacuum deposition system, using Ag particles as the evaporation source, until the vacuum level reaches 5 × 10⁻⁶. -4 Below Pa, 70 nm of metallic Ag is thermally evaporated at a rate of 0.5 Å / s, and the effective area of ​​the cell is controlled to be 0.04 cm² using a mask. 2 .

[0055] This invention leverages the non-uniform film formation characteristic of spray coating (i.e., high-pressure atomized droplets cannot simultaneously and completely cover the surface of a three-dimensional perovskite layer upon landing). It forms a locally covered two-dimensional / three-dimensional perovskite heterojunction by spraying an organic amine halide solution onto the surface of a three-dimensional perovskite film. Compared to traditional two-dimensional / three-dimensional perovskite heterojunction films with complete two-dimensional perovskite layer coverage, this locally covered two-dimensional / three-dimensional perovskite heterojunction structure has less impact on charge interfacial transport efficiency. Charge carriers can be transported through the partially exposed three-dimensional perovskite layer, thus eliminating the need for precise control of the crystal growth direction of the two-dimensional perovskite. Compared to traditional solution deposition methods (such as blade coating and spin coating), the spray coating method used in this invention requires less material. Furthermore, by heating the three-dimensional perovskite film substrate in real time during spraying, the atomized droplets immediately crystallize in situ upon contact with the three-dimensional perovskite film surface, thereby avoiding the dissolution and damage to the three-dimensional perovskite surface components caused by alcohol solvent penetration.

[0056] Comparative Example 1:

[0057] Comparative Example 1 uses the same method as Example 1 to prepare each functional layer (i.e., transparent conductive substrate, electron transport layer, three-dimensional perovskite photoelectric conversion layer, hole transport layer, and metal electrode). The difference from Example 1 is that the three-dimensional perovskite layer in Comparative Example 1 does not use the method in step 4 to form a two-dimensional / three-dimensional perovskite heterojunction on its upper surface.

[0058] Results analysis:

[0059] Using an AM 1.5G standard solar simulator as the light source, at an illumination intensity of 100 mW / cm²... 2 The photoelectric conversion efficiency of each solar cell in Example 1 and Comparative Example 1 was measured under simulated sunlight irradiation.

[0060] The solar cells of Example 1 and Comparative Example 1 were placed in an air environment with room temperature and relative humidity of 50 ± 5% for long-term storage stability testing, and the change in photoelectric conversion efficiency over time was recorded.

[0061] like Figure 3 The figure shows a box plot of the photoelectric conversion efficiency of the perovskite solar cells of Example 1 and Comparative Example 1. The results show that the average efficiency of the device in Example 1 is significantly improved compared with that of the device in Comparative Example 1.

[0062] like Figure 4 The normalized photoelectric conversion efficiency of the devices in Example 1 and Comparative Example 1 is shown as a function of time. The results show that the humidity stability of the device in Example 1 is significantly improved compared with that of the device in Comparative Example 1.

[0063] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the protection scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for fabricating a solar cell based on a two-dimensional / three-dimensional perovskite heterojunction thin film, characterized in that the method... include: (1) Depositing an electron transport layer on a transparent conductive substrate; (2) A three-dimensional perovskite photoelectric conversion layer is deposited on the electron transport layer; (3) The organic amine halide solution is sprayed onto the heated surface of the three-dimensional perovskite photoelectric conversion layer, and an in-situ reaction occurs, which does not result in uniform crystallization to form a two-dimensional perovskite, thus obtaining a two-dimensional / three-dimensional perovskite heterojunction film. (4) Deposit a hole transport layer on the two-dimensional / three-dimensional perovskite heterojunction film and oxidize the hole transport layer; (5) Deposit a metal electrode on the hole transport layer after oxidation treatment to obtain the solar cell.

2. The method for fabricating a solar cell based on a two-dimensional / three-dimensional perovskite heterojunction thin film according to claim 1, characterized in that, Step (2) includes: A three-dimensional perovskite precursor solution was coated onto the electron transport layer and subjected to thermal annealing and crystallization to form a three-dimensional polycrystalline perovskite film with mixed formamidinium and cesium ions.

3. The method for fabricating a solar cell based on a two-dimensional / three-dimensional perovskite heterojunction thin film according to claim 2, characterized in that, The three-dimensional perovskite precursor solution is obtained by dissolving lead iodide, formamidine iodide, cesium iodide and methylamine chloride in a mixed solvent of N,N-dimethylformamide and dimethyl sulfoxide, followed by heating, stirring and filtration.

4. The method for fabricating a solar cell based on a two-dimensional / three-dimensional perovskite heterojunction thin film according to claim 1, characterized in that, In step (3), the mass concentration of the organic amine halide solution is 0.5–10 mg / mL.

5. A method for fabricating a solar cell based on a two-dimensional / three-dimensional perovskite heterojunction thin film according to claim 1 or 4, characterized in that, In step (3), the organic amine halide is selected from CH3(CH2). n1 NH3X, (CH2) n2 (NH3)2X2, C6H5(CH2) n3 NH3X, C6H4(CH2) n4 One of (NH3)2X2, NH2C(=NH)NH2.HX, and the fluorine-containing derivatives of the above-mentioned organic amine halides; Where n1 is an integer ≥ 1; n2 is an integer ≥ 2; n3 is an integer ≥ 1; n4 is an integer ≥ 2; and X is one of CI, Br, and I.

6. The method for fabricating a solar cell based on a two-dimensional / three-dimensional perovskite heterojunction thin film according to claim 1, characterized in that, In step (3), the organic amine halide solution is sprayed by gas atomization spraying. During the spraying process, the spraying is carried out by controlling the distance between the nozzle and the substrate, the injection speed of the organic amine halide solution, the atomizing gas pressure, and the moving speed of the nozzle relative to the three-dimensional perovskite photoelectric conversion layer.

7. A method for fabricating a solar cell based on a two-dimensional / three-dimensional perovskite heterojunction thin film according to claim 1 or 4, characterized in that, In step (3), the heating temperature of the three-dimensional perovskite photoelectric conversion layer is 70-100 °C; After the spraying is completed, a further heating treatment is performed for 5 minutes.

8. The method for fabricating a solar cell based on a two-dimensional / three-dimensional perovskite heterojunction thin film according to claim 1, characterized in that, Step (4) includes: A hole transport layer solution is coated onto the two-dimensional / three-dimensional perovskite heterojunction film, and the hole transport layer is formed after the solvent evaporates. The substrate with the hole transport layer deposited thereon was then placed in an environment with a relative humidity of less than 20% and an oxygen content of more than 80% and left to stand to oxidize the hole transport layer. The hole transport layer solution is prepared by adding an acetonitrile solution of 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene and lithium bis(trifluoromethanesulfonyl)imide, an acetonitrile solution of tri[4-tert-butyl-2-(1H-pyrazol-1-yl)pyridine]cobalttrix(1,1,1-trifluoro-N-[(trifluoromethyl)sulfonyl]methanesulfonamide salt] and 4-tert-butylpyridine to a chlorobenzene solvent.

9. The method for fabricating a solar cell based on a two-dimensional / three-dimensional perovskite heterojunction thin film according to claim 1, characterized in that, The two-dimensional perovskite is discontinuously distributed on the surface of the three-dimensional perovskite photoelectric conversion layer, and the surface of the three-dimensional perovskite photoelectric conversion layer has areas not covered by the two-dimensional perovskite.

10. A solar cell based on a two-dimensional / three-dimensional perovskite heterojunction thin film, characterized in that, The solar cell is fabricated by the method according to any one of claims 1-9, comprising a transparent conductive substrate, an electron transport layer, a three-dimensional perovskite photoelectric conversion layer, a two-dimensional / three-dimensional perovskite heterojunction locally covering the three-dimensional perovskite photoelectric conversion layer, a hole transport layer, and a metal electrode arranged sequentially.

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