Perovskite heterojunction solar cell and preparation method thereof

Abstract

The application relates to the technical field of photovoltaic cells, in particular to a perovskite heterojunction solar cell and a preparation method thereof. The preparation method comprises the following steps: performing chemical polishing treatment on one side of a three-dimensional perovskite active layer which is away from a hole transport layer; evaporating lead iodide on the one side of the three-dimensional perovskite active layer which is away from the hole transport layer, coating a benzyldimethylamine hydrobromide solution, and performing annealing treatment to obtain a two-dimensional perovskite covering layer. The three-dimensional perovskite active layer is treated by means of chemical polishing, the surface properties of the three-dimensional perovskite active layer are changed, the growth mode of the lead iodide deposited thereon is changed, a uniform and dense two-dimensional perovskite covering layer is prepared on the surface of the three-dimensional perovskite active layer, the interface defects between the three-dimensional perovskite active layer and the two-dimensional perovskite covering layer are inhibited, and the performance and stability of the finally prepared perovskite heterojunction solar cell are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photovoltaic cells, and particularly relates to a perovskite heterojunction solar cell and a preparation method thereof. BACKGROUND

[0002] Perovskite solar cells (PSCs) have attracted much attention due to their low manufacturing cost and excellent optoelectronic performance. To date, the certified power conversion efficiency (PCE) of small-area single-junction PSCs has reached 26.1%. However, due to the inhomogeneity of charge extraction and the inherent instability of perovskite absorber in large-area thin-film PSCs, developing high-performance, long-term stable perovskite solar cells suitable for commercial deployment remains a formidable challenge.

[0003] In the prior art, the performance and stability of three-dimensional PSCs are usually enhanced by constructing two-dimensional / three-dimensional perovskite heterojunctions. Most of the current two-dimensional / three-dimensional perovskite heterojunctions are prepared by a solution cation exchange strategy, in which a long-chain organic cation salt solution is spin-coated on the top of the three-dimensional perovskite, and a heterojunction is formed by proton transfer between the three-dimensional and two-dimensional perovskite. However, the two-dimensional / three-dimensional perovskite formed by solution cation exchange will form a gradient junction due to the mutual diffusion of cations, and this gradient junction interface is considered to be a decomposition pathway of the two-dimensional / three-dimensional perovskite, which adversely affects the stability of the heterojunction solar cell. In addition, the cation exchange strategy will produce two-dimensional perovskite with multiple n values, leading to inhomogeneous charge extraction in solar modules.

[0004] Another way to construct two-dimensional / three-dimensional perovskite heterojunctions is by a gas-phase assisted growth strategy. By controlling the thickness of the vapor-deposited lead iodide (PbI2), a uniform and dense two-dimensional perovskite cover layer can be formed on the surface of the three-dimensional perovskite, enhancing the uniform charge extraction capability. However, the thickness of the two-dimensional perovskite cover layer required by this method varies depending on the solar cell structure. In a trans structure (p-i-n), the thickness of the vapor-deposited PbI2 should be controlled at the nanometer level, and achieving good coverage at such a thin thickness is still a challenge. Considering the significant volume expansion during the transformation from PbI2 to two-dimensional perovskite, there are challenges in preparing a uniform and thin two-dimensional perovskite cover layer on the surface of the three-dimensional perovskite. Although there has been extensive research on two-dimensional / three-dimensional perovskite heterojunctions, there has been little research on the influence of the surface state of the three-dimensional perovskite. The surface state of the three-dimensional perovskite, including the surface energy and lattice parameters, determines the growth mode of the vapor-deposited PbI2 thin film. In addition, since the vapor-deposited PbI2 is directly deposited in physical contact with the three-dimensional perovskite, the surface defects of the three-dimensional perovskite will be retained and act as interface defects between the two-dimensional / three-dimensional perovskite heterojunction, increasing the recombination of carriers.

[0005] Therefore, the prior art still needs to be improved. SUMMARY

[0006] In view of the deficiencies of the prior art described above, the purpose of the present application is to provide a perovskite heterojunction solar cell and a preparation method thereof, aiming to solve the problem of interface defects between two-dimensional / three-dimensional perovskite heterojunctions in the prior art perovskite heterojunction solar cell.

[0007] The technical solution of the present application is as follows:

[0008] The first aspect of the present application provides a preparation method of a perovskite heterojunction solar cell, comprising the steps of: performing chemical polishing treatment on the side of a three-dimensional perovskite active layer away from a hole transport layer; evaporating lead iodide on the side of the three-dimensional perovskite active layer subjected to chemical polishing treatment to obtain a lead iodide layer, coating a phenethylamine hydrobromide solution on the surface of the lead iodide layer, and performing annealing treatment to prepare a two-dimensional perovskite covering layer.

[0009] Optionally, the step of polishing treatment comprises spin-coating a polishing solution on the side of the three-dimensional perovskite active layer away from the hole transport layer and performing annealing treatment; wherein the polishing solution comprises at least one of isopropyl alcohol and dimethyl sulfoxide, dimethyl formamide, N-acetyl pyrrolidone, and gamma-butyrolactone.

[0010] Optionally, the volume ratio of the dimethyl sulfoxide and the isopropyl alcohol is 1:100-1:500.

[0011] Optionally, the thickness of the evaporated lead iodide is 3-8 nm.

[0012] Optionally, the concentration of phenethylamine hydrobromide in the phenethylamine hydrobromide solution is 1-3 mg / mL, and the solvent is isopropyl alcohol.

[0013] Optionally, the preparation method further comprises the steps of: providing a conductive substrate; preparing a hole transport layer on one side of the conductive substrate; and preparing a three-dimensional perovskite active layer on the side of the hole transport layer away from the conductive substrate, before the step of polishing the side of the three-dimensional perovskite active layer away from the hole transport layer.

[0014] Optionally, the preparation method further comprises the steps of: preparing an electron transport layer on the side of the two-dimensional perovskite covering layer away from the three-dimensional perovskite active layer; and preparing a metal electrode layer on the side of the electron transport layer away from the two-dimensional perovskite covering layer to obtain a perovskite heterojunction solar cell, after the step of preparing the two-dimensional perovskite covering layer.

[0015] Optionally, the method further comprises, after the two-dimensional perovskite cover layer is prepared, the steps of: preparing a passivation layer on a side of the two-dimensional perovskite cover layer away from the three-dimensional perovskite active layer; preparing an electron transport layer on a side of the passivation layer away from the two-dimensional perovskite cover layer; and preparing a metal electrode layer on a side of the electron transport layer away from the two-dimensional perovskite cover layer.

[0016] In a second aspect, the present application provides a perovskite heterojunction solar cell prepared by the method described above.

[0017] Optionally, the perovskite heterojunction solar cell comprises, in sequence, a conductive substrate, a hole transport layer, a three-dimensional perovskite active layer, a two-dimensional perovskite cover layer, a passivation layer, an electron transport layer, and a metal electrode layer.

[0018] Compared with the prior art, the present application has the following advantages:

[0019] In the present application, the surface of the three-dimensional perovskite active layer is treated by chemical polishing to change its surface properties. Lead iodide is evaporated on the surface of the three-dimensional perovskite active layer to make the lead iodide grow layer by layer on the surface and form a uniform and dense two-dimensional perovskite cover layer. In addition, chemical polishing reduces the surface defect concentration of the three-dimensional perovskite active layer and suppresses the interface defects between the three-dimensional perovskite active layer and the two-dimensional perovskite cover layer, thereby improving the certified power conversion efficiency (PCE) and stability of the finally prepared perovskite heterojunction solar cell. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced as follows.

[0021] Figure 1 A flowchart of the preparation method of the perovskite heterojunction solar cell provided in the embodiments of the present application;

[0022] Figure 2 A structure diagram of the perovskite heterojunction solar cell provided in the embodiments of the present application;

[0023] Figure 3 An interface scanning electron microscope image of the perovskite heterojunction solar cell provided in the embodiments of the present application:

[0024] (a) is a perovskite heterojunction solar cell without chemical polishing, and (b) is a perovskite heterojunction solar cell with chemical polishing;

[0025] Figure 4 An X-ray diffraction pattern of the perovskite heterojunction solar cell provided in the embodiments of the present application:

[0026] Figure 5 A J-V test curve of the perovskite heterojunction solar cell provided by the embodiment of the application is shown in the following figure;

[0027] Figure 6 A stability test graph of the perovskite heterojunction solar cell provided by the embodiment of the application is shown in the following figure. DETAILED DESCRIPTION

[0028] In order to make the objectives, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the accompanying drawings and embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application. The following embodiments and features in the embodiments can be combined with each other without conflict.

[0029] It should be noted that if the description of "first", "second" and the like is involved in the embodiments of the present application, the "first", "second" and the like are only for the purpose of description, and cannot be understood as indicating or implying the relative importance and implicitly indicating the number of the indicated technical features. Therefore, the features with "first", "second" can explicitly or implicitly include at least one of the features. In addition, the technical solutions of each embodiment can be combined with each other, but the combination of the technical solutions must enable the person skilled in the art to realize the basis, and when the combination of the technical solutions appears contradictory or unachievable, it should be considered that the combination of the technical solutions does not exist, and is not within the scope of protection claimed by the present application.

[0030] In a first aspect of the embodiments of the present application, a preparation method of a perovskite heterojunction solar cell is provided, comprising the steps of:

[0031] The side of the three-dimensional perovskite active layer away from the hole transport layer is subjected to chemical polishing treatment; lead iodide is evaporated on the side of the three-dimensional perovskite active layer away from the hole transport layer to obtain a lead iodide layer, a phenylethylamine hydrobromide solution is coated on the surface of the lead iodide layer, and annealing treatment is performed to obtain a two-dimensional perovskite covering layer.

[0032] The surface of the three-dimensional perovskite active layer is treated by chemical polishing to change the surface state (surface energy, surface defects, etc.) of the three-dimensional perovskite active layer. When lead iodide is evaporated, the increased surface energy of the three-dimensional perovskite active layer can match the lattice of lead iodide, promoting the Frank-van der Merwe growth (layer-by-layer growth) of the evaporated lead iodide, and thus a dense two-dimensional perovskite covering layer is finally formed on the surface of the three-dimensional perovskite active layer.

[0033] In addition, the chemical polishing reduces the surface defect concentration of the three-dimensional perovskite active layer, inhibits the interface recombination between the three-dimensional perovskite active layer and the two-dimensional perovskite covering layer, eliminates the interface defects, and improves the certified power conversion efficiency (PCE) and stability of the perovskite heterojunction solar cell.

[0034] In some embodiments, the step of the chemical polishing treatment comprises:

[0035] A polishing solution is spin-coated on the side of the three-dimensional perovskite active layer away from the hole transport layer, and an annealing treatment is performed.

[0036] Preferably, the polishing solution is selected from dimethyl sulfoxide and isopropyl alcohol. Dimethyl sulfoxide has strong polarity and can better dissolve perovskite, thereby reconstructing the surface of perovskite. In some embodiments, the volume ratio of dimethyl sulfoxide and isopropyl alcohol is 1:100-1:500. For example, the volume ratio of dimethyl sulfoxide and isopropyl alcohol is 1:100, 1:200, 1:300, 1:400, or 1:500, etc. Preferably, the volume ratio of dimethyl sulfoxide and isopropyl alcohol is 1:200.

[0037] In some embodiments, the thickness of the evaporated lead iodide is 3-8 nm. For example, the thickness of the evaporated lead iodide is 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, or 8 nm, etc. Preferably, the thickness of the evaporated lead iodide is 4 nm. The two-dimensional perovskite covering layer formed by the subsequent preparation of the lead iodide of this thickness can completely cover the surface of the three-dimensional perovskite active layer and does not hinder the extraction of electrons.

[0038] In some embodiments, the concentration of phenethylamine hydrobromide in the phenethylamine hydrobromide solution is 1.5 mg / mL, and the solvent is isopropyl alcohol.

[0039] In some embodiments, referring to Figure 1 , the perovskite heterojunction solar cell and the preparation method thereof comprise the steps of:

[0040] S101, providing a conductive substrate;

[0041] S102, preparing a hole transport layer on one side of the conductive substrate;

[0042] S103, preparing a three-dimensional perovskite active layer on the side of the hole transport layer away from the conductive substrate;

[0043] S104, performing a chemical polishing treatment on the side of the three-dimensional perovskite active layer away from the hole transport layer;

[0044] S105, evaporating lead iodide on the side of the three-dimensional perovskite active layer away from the hole transport layer to obtain a lead iodide layer, coating the surface of the lead iodide layer with a phenylethylamine hydrobromide solution, and performing annealing treatment to obtain a two-dimensional perovskite covering layer;

[0045] S106, preparing a passivation layer on the side of the two-dimensional perovskite covering layer away from the three-dimensional perovskite active layer;

[0046] S107, preparing an electron transport layer on the side of the passivation layer away from the two-dimensional perovskite covering layer;

[0047] S108, preparing a metal electrode layer on the side of the electron transport layer away from the passivation layer to obtain a perovskite heterojunction solar cell. By arranging the passivation layer, the surface defects of the two-dimensional perovskite covering layer are further passivated, and thus the performance of the perovskite heterojunction solar cell is improved.

[0048] In a second aspect, the present application provides a perovskite heterojunction solar cell prepared by the above method.

[0049] In some embodiments, referring to Figure 2 , the perovskite heterojunction solar cell comprises a conductive substrate, a hole transport layer, a three-dimensional perovskite active layer, a two-dimensional perovskite covering layer, a passivation layer, an electron transport layer and a metal electrode layer arranged in sequence.

[0050] The application will be further described in the following specific examples.

[0051] Example 1

[0052] (1) Clean the ITO conductive substrate. The ITO conductive substrate is ultrasonically cleaned with sodium dodecyl benzene sulfonate, deionized water and isopropyl alcohol for 30 min respectively. After cleaning, it is placed on a hot plate for drying. Then the conductive substrate is placed in an ultraviolet ozone cleaning machine for ozone treatment for 30 min.

[0053] (2) Prepare a hole transport layer on the ITO conductive substrate. The specific method is as follows: 0.4 mg of [4-(3,6-dimethyl-9H-carbazol-9-yl)butyl]phosphonic acid (Me-4PACz) is dissolved in an ethanol solution and shaken for 1 hour. 50 μL of Me-4PACz solution is spin-coated on the ITO conductive substrate at a rotation speed of 3000 rpm, and the spin-coating time is 30 s. Finally, it is placed on a 100℃ hot plate for annealing treatment, and the holding time is 10 min. After cooling, further spin-coat aluminum oxide dispersion (Al2O3) at a rotation speed of 5000 rpm for 30 s. Finally, it is placed on a 100℃ hot plate for annealing treatment, and the holding time is 10 min.

[0054] (3) Preparation of three-dimensional perovskite active layer. The specific method is as follows: 1.52M Cs 0.05 MA 0.1 FA 0.85 PbI 2.9 Br 0.1 The perovskite is dissolved in a mixed solution of dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) with a volume ratio of 3:1, and the solution is fully stirred and dissolved uniformly to prepare a perovskite solution. 40 μL of the perovskite solution is spin-coated on the hole transport layer prepared in step (2) at a speed of 4700 rpm for 45 s, and 200 uL of anti-solvent chlorobenzene (CB) is added dropwise at the 20th second. After the film is formed, it is annealed on a hot stage at 65°C for 5 min, and then annealed on a hot stage at 105°C for 20 min to obtain a three-dimensional perovskite active layer.

[0055] (4) Chemical polishing of the surface of the three-dimensional perovskite active layer. 5 uL of DMSO and 1 mL of isopropanol are fully mixed and uniformly prepared to obtain a polishing solution. 70 uL of the polishing solution is spin-coated on the surface of the three-dimensional perovskite active layer, and annealed on a hot stage at 100°C for 5 min.

[0056] (5) Preparation of a two-dimensional perovskite cover layer. The film prepared in (4) is transferred to a vacuum coating device, and 4 nm thick PbI2 is evaporated. After removal, 70 uL of phenethylamine hydrobromide (PEABr) solution (the concentration of PEABr is 1.5 mg / mL, and the solution is isopropanol) is spin-coated on the surface of the evaporated PbI2, and annealed on a hot stage at 100°C for 5 min.

[0057] (6) Preparation of a passivation layer. 1 mg of polymethyl methacrylate (PMMA) is dissolved in 1 mL of chlorobenzene, fully stirred and dissolved, and then spin-coated on the film prepared in step (5) at a speed of 5000 rpm for 30 s.

[0058] (7) Preparation of an electron transport layer on the passivation layer. 10 mg of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) is dissolved in 1 mL of chlorobenzene, fully shaken and dissolved to prepare a PCBM solution. 30 μL of the PCBM solution is spin-coated on the film prepared in step (6) at a speed of 3000 rpm for 30 s. Then, it is transferred to an evaporation device, and 10 nm of carbon 60 (C 60 ) is evaporated. After completion, the film is transferred to an atomic deposition system to deposit a 10 nm SnO x buffer layer.

[0059] (8) Evaporation of a metal electrode on the electron transport layer. A metal electrode is evaporated on the electron transport layer by an evaporation process to form a metal electrode. A silver electrode with a thickness of 100 nm was evaporated on the thin film prepared in step (7), and a perovskite heterojunction solar cell was prepared after packaging.

[0060] Comparative Example 1

[0061] A perovskite heterojunction solar cell of Comparative Example 1 was prepared by using almost the same method as that of Example 1, but without chemical polishing treatment (step 4).

[0062] Test Example 1

[0063] (1) The perovskite heterojunction solar cells prepared in Example 1 and Comparative Example 1 were observed by using a scanning electron microscope (SEM) for cross-section, and the results are shown in FIG. 1. As can be seen from FIG. 1, the two-dimensional perovskite covering layer of the perovskite heterojunction solar cell prepared in Example 1 can completely cover the three-dimensional perovskite active layer, indicating that the surface of the three-dimensional perovskite active layer is changed by chemical polishing, and the lead iodide is grown layer by layer on the surface of the three-dimensional perovskite active layer by evaporating lead iodide on the surface of the three-dimensional perovskite active layer, which is conducive to the formation of a uniform and dense two-dimensional perovskite covering layer. Figure 3 Figure 3 (2) The perovskite heterojunction solar cells prepared in Example 1 and Comparative Example 1 were analyzed by X-ray diffraction, and the results are shown in FIG. 2. As can be seen from FIG. 2, the two-dimensional perovskite covering layer with n = 1 can be formed in the thin film of Example 1, while no diffraction peak of the two-dimensional perovskite covering layer can be detected in Comparative Example 1, indicating that the n value of the thin film formed in Comparative Example 1 is not uniform, and further indicating that a uniform and dense two-dimensional perovskite covering layer is formed in the perovskite heterojunction solar cell prepared by the preparation method in the present application.

[0064] Test Example 2 Figure 4 Figure 4 (1) The J-V curves of the perovskite heterojunction solar cells prepared in Example 1 and Comparative Example 1 were determined, and the results are shown in FIG. 3. As can be seen from FIG. 3 in combination with the calculation, the PCE of the perovskite heterojunction solar cell prepared in Example 1 is 31% at a band gap of 1.57 eV, which is significantly higher than that of the perovskite heterojunction solar cell prepared in Comparative Example 1, indicating that the perovskite heterojunction solar cell prepared by the preparation method in the present application has an extremely high certified power conversion efficiency.

[0065] (2) The stability of the perovskite heterojunction solar cells prepared in Example 1 and Comparative Example 1 was determined, and the results are shown in FIG. 4. As can be seen from FIG. 4, the perovskite heterojunction solar cell prepared in Example 1 has a higher stability than that of the perovskite heterojunction solar cell prepared in Comparative Example 1.

[0066] (2) The stability of the perovskite heterojunction solar cells prepared in Example 1 and Comparative Example 1 was determined, and the results are shown in FIG. 4. As can be seen from FIG. 4, the perovskite heterojunction solar cell prepared in Example 1 has a higher stability than that of the perovskite heterojunction solar cell prepared in Comparative Example 1. Figure 5 Figure 5 (2) The stability of the perovskite heterojunction solar cells prepared in Example 1 and Comparative Example 1 was determined, and the results are shown in FIG. 4. As can be seen from FIG. 4, the perovskite heterojunction solar cell prepared in Example 1 has a higher stability than that of the perovskite heterojunction solar cell prepared in Comparative Example 1.

[0067] (2) The stability of the perovskite heterojunction solar cells prepared in Example 1 and Comparative Example 1 was determined, and the results are shown in FIG. 4. As can be seen from FIG. 4, the perovskite heterojunction solar cell prepared in Example 1 has a higher stability than that of the perovskite heterojunction solar cell prepared in Comparative Example 1. Figure 6 Figure 6 ​​​​It can be seen that the perovskite heterojunction solar cell prepared in Example 1 is subjected to maximum power point (MPP) tracking under ISOS-L-1 standard, and the normalized efficiency is about 98.2% after light irradiation for 500 h, and the perovskite heterojunction solar cell prepared in Comparative Example 1 has a normalized efficiency of about 90.7% after light irradiation for 400 h, indicating that the perovskite heterojunction solar cell prepared by the preparation method in the application has excellent stability.

[0068] In summary, the surface of the three-dimensional perovskite active layer is treated by chemical polishing in the application, the surface properties are changed, lead iodide is evaporated on the surface of the three-dimensional perovskite active layer, and the lead iodide grows layer by layer on the surface to form a uniform and dense two-dimensional perovskite cover layer. In addition, chemical polishing reduces the surface defect concentration of the three-dimensional perovskite active layer, suppresses the interface defects between the three-dimensional perovskite active layer and the two-dimensional perovskite cover layer, and improves the certified power conversion efficiency (PCE) and stability of the finally prepared perovskite heterojunction solar cell.

[0069] It should be understood that the application of the application is not limited to the above examples, and those skilled in the art can make improvements or changes according to the above description, and all these improvements and changes shall belong to the protection scope of the claims attached to the application.

Claims

1. A method for preparing a perovskite heterojunction solar cell, characterized by, The method comprises the steps of: carrying out chemical polishing treatment on a side of a three-dimensional perovskite active layer away from a hole transport layer; evaporating lead iodide on the side of the three-dimensional perovskite active layer subjected to the chemical polishing treatment to obtain a lead iodide layer, coating a phenethylamine hydrobromide solution on a surface of the lead iodide layer, and carrying out annealing treatment to prepare a two-dimensional perovskite covering layer. The step of the chemical polishing treatment comprises: spinning a polishing solution on the side of the three-dimensional perovskite active layer away from the hole transport layer and carrying out annealing treatment. The polishing solution comprises at least one of isopropyl alcohol and dimethyl sulfoxide, dimethyl formamide, N-acetyl pyrrolidone, and gamma-butyrolactone.

2. The production method according to claim 1, characterized by, The volume ratio of the dimethyl sulfoxide to the isopropyl alcohol is 1:100-1:

500.

3. The preparation method according to claim 1, characterized in that The thickness of the lead iodide layer is 3-8 nm.

4. The method of claim 1, wherein, The concentration of phenethylamine hydrobromide in the phenethylamine hydrobromide solution is 1-3 mg / mL, and the solvent is isopropyl alcohol.

5. The preparation method according to claim 1, characterized in that Before the step of carrying out polishing treatment on the side of the three-dimensional perovskite active layer away from the hole transport layer, the method further comprises the steps of: providing an electrically conductive substrate; preparing a hole transport layer on a side of the electrically conductive substrate; preparing a three-dimensional perovskite active layer on a side of the hole transport layer away from the electrically conductive substrate.

6. The method of claim 1, wherein, After the step of preparing the two-dimensional perovskite covering layer, the method further comprises the steps of: preparing an electron transport layer on a side of the two-dimensional perovskite covering layer away from the three-dimensional perovskite active layer; preparing a metal electrode layer on a side of the electron transport layer away from the two-dimensional perovskite covering layer to obtain a perovskite heterojunction solar cell.

7. The preparation method according to claim 1, characterized in that After the step of preparing the two-dimensional perovskite covering layer, the method further comprises the steps of: preparing a passivation layer on a side of the two-dimensional perovskite covering layer away from the three-dimensional perovskite active layer; preparing an electron transport layer on a side of the passivation layer away from the two-dimensional perovskite covering layer; preparing a metal electrode layer on a side of the electron transport layer away from the passivation layer to obtain a perovskite heterojunction solar cell.

8. A perovskite heterojunction solar cell prepared by the preparation method according to any one of claims 1 to 7.

9. The perovskite heterojunction solar cell according to claim 8, characterized in that, The perovskite heterojunction solar cell comprises an electrically conductive substrate, a hole transport layer, a three-dimensional perovskite active layer, a two-dimensional perovskite covering layer, a passivation layer, an electron transport layer, and a metal electrode layer which are sequentially stacked.

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