Perovskite solar cells, their fabrication methods, and electrical devices

Abstract

This application provides a perovskite solar cell, which structurally comprises, in sequence, a transparent electrode, an electron transport layer, a perovskite layer, a hole transport layer, and a second electrode. The perovskite layer includes a main perovskite layer and a two-dimensional perovskite coating layer covering its surface and surrounding edges. The two-dimensional perovskite coating layer includes: a first capping layer located between the main perovskite layer and the electron transport layer; a second capping layer located between the main perovskite layer and the hole transport layer; and a third capping layer covering the surrounding edges of the main perovskite layer. The perovskite solar cell provided by this application exhibits high energy conversion efficiency and good stability.

Description

Technical Field

[0001] This application relates to a perovskite solar cell. Furthermore, this application also relates to a method for fabricating the perovskite solar cell and an electrical device for using it. Background Technology

[0002] In recent years, global energy shortages and environmental pollution have become increasingly prominent, leading to growing attention on solar cells as an ideal renewable energy source. Solar cells, also known as photovoltaic cells, are devices that directly convert light energy into electrical energy through the photoelectric effect or photochemical effect. Perovskite solar cells are a type of novel solar cell that is currently under extensive research. Within a few years of their development, they rapidly achieved high photoelectric conversion efficiencies, with the highest exceeding 25%, demonstrating promising application prospects.

[0003] Due to the significant advancements in perovskite solar cells, higher demands have been placed on energy conversion efficiency and long-term stability. However, existing perovskite thin films inevitably exhibit various intrinsic defects during their fabrication process. Furthermore, perovskite materials themselves are unstable and readily decompose under the influence of light, heat, water, and oxygen, thus affecting the performance of perovskite solar cells. Therefore, existing perovskite solar cells still require improvement. Summary of the Invention

[0004] This application is made in view of the above-mentioned problems, and its purpose is to provide a perovskite solar cell with high energy conversion efficiency and good stability.

[0005] To achieve the above objectives, the first aspect of this application provides a perovskite solar cell, which structurally comprises, in sequence, a transparent electrode, an electron transport layer, a perovskite layer, a hole transport layer, and a second electrode.

[0006] The perovskite layer comprises a main perovskite layer and a two-dimensional perovskite coating layer covering its surface and surrounding areas, the two-dimensional perovskite coating layer comprising:

[0007] The first capping layer located between the main perovskite layer and the electron transport layer;

[0008] The second capping layer is located between the main perovskite layer and the hole transport layer; and

[0009] A third capping layer covering the periphery of the main perovskite layer.

[0010] By fully covering the main perovskite layer, that is, covering the top and bottom surfaces and all four sides, the resulting battery device can achieve better long-term stability compared to perovskite covering only the top and bottom surfaces.

[0011] In any embodiment, in the perovskite solar cell, the thickness of the first capping layer, the second capping layer, and the third capping layer is independently 1 nm to 30 nm, and can be selected as 3 nm to 10 nm.

[0012] When the thicknesses of the first, second, and third capping layers are within the aforementioned range, the photoelectric conversion efficiency of perovskite solar cells can be improved.

[0013] The thicker the third capping layer, the better the stability of the perovskite solar cell.

[0014] In addition, the thickness of each capping layer can also affect its HOMO and LUMO energy levels. Therefore, the HOMO and LUMO energy levels can be controlled by adjusting their thickness to achieve better energy level matching with the host perovskite and charge transport layer.

[0015] In any embodiment, in the perovskite solar cell, the LUMO energy level of the first capping layer is less than or equal to the LUMO energy level of the main perovskite layer, and

[0016] The absolute value of the difference between the LUMO energy level of the first capping layer and the LUMO energy level of the main perovskite layer is in the range of 0 to 0.5 eV, and can be selected in the range of 0.05 eV to 0.3 eV.

[0017] In any embodiment, in the perovskite solar cell, the LUMO energy level of the first capping layer is greater than or equal to the LUMO energy level of the electron transport layer, and

[0018] The absolute value of the difference between the LUMO energy level of the first capping layer and the LUMO energy level of the electron transport layer is in the range of 0 to 0.5 eV, and can be selected in the range of 0.05 eV to 0.5 eV.

[0019] The LUMO energy levels between the first capping layer and the main perovskite layer, and between the first capping layer and the electron transport layer, have the relationships described above. This facilitates the smoother passage of electrons from the main perovskite layer to the electron transport layer, thereby ensuring the cell's turn-on voltage and improving the photoelectric conversion efficiency of the solar cell.

[0020] The LUMO energy level of the first capping layer can also be adjusted by adjusting its thickness and material.

[0021] In any embodiment, in the perovskite solar cell, the HOMO energy level of the second capping layer is greater than or equal to the HOMO energy level of the host perovskite layer, and

[0022] The absolute value of the difference between the HOMO energy level of the second capping layer and the HOMO energy level of the main perovskite layer is in the range of 0 to 0.3 eV, and can be selected in the range of 0.05 eV to 0.2 eV.

[0023] In any embodiment, in the perovskite solar cell, the HOMO level of the second capping layer is less than or equal to the HOMO level of the hole transport layer, and

[0024] The absolute value of the difference between the HOMO energy level of the second capping layer and the HOMO energy level of the hole transport layer is in the range of 0 to 0.3 eV, and can be selected in the range of 0.05 eV to 0.15 eV.

[0025] The HOMO energy levels between the second capping layer and the main perovskite layer, as well as between the second capping layer and the hole transport layer, have the relationships described above. This facilitates the smoother passage of holes from the main perovskite layer to the hole transport layer, thereby ensuring the cell's on-state voltage and influencing the cell's photoelectric conversion efficiency.

[0026] In any embodiment, in the perovskite solar cell, the covering material of the first capping layer, the second capping layer, and the third capping layer is each independently a halide salt selected from at least one of the following substances or derivatives thereof:

[0027] Ethylamine, propylamine, butylamine, pentylamine, hexylamine, isobutylamine, isopentylamine, 3-buten-1-amine, 3-butyn-1-amine, 2-(methylthio)ethylamine, 2-hydroxyethylamine, 2-chloroethylamine, 2-bromoethylamine, 2-iodoethylamine, 2-fluoroethylamine, 2,2-difluoroethylamine, 2,2,2-trifluoroethylamine;

[0028] H3NC m H 2m+1 , where m is selected from 7 to 10, 12, 14, 16, 18;

[0029] Methylhydrazine;

[0030] Cyclopropylamine, cyclobutylamine, cyclopentylamine, cyclohexylamine;

[0031] Benzylamine, phenethylamine, 2-naphthylmethylamine, 2-naphthylethylamine;

[0032] 2-(1-Naphthoxy)ethylamine, 2-(1-Naphthoxy)propylamine, 2-(1-Naphthoxy)butylamine;

[0033] 2-(1-Methoxypyrene)ethylamine, 2-(1-Methoxypyrene)propylamine, 2-(1-Methoxypyrene)butylamine;

[0034] Peryloxyethylamine;

[0035] 3-Phenylacet-2-propen-1-amine;

[0036] 9-Anthracenemethylamine, 4-fluorophenylethylamine, 2-fluorophenylethylamine, 3-fluorophenylethylamine, 4-fluorophenylethylamine, perfluorophenylethylamine, 2-chlorophenylethylamine, 2-bromophenylethylamine, 4-fluorobenzylamine, 4-chlorobenzylamine, 4-bromobenzylamine, 4-iodobenzylamine, 3-aminopyrrolidine, piperazine, 1-ethylpiperazine, 1H-imidazol-4-ethylamine, 1-(3-aminopropyl)-1-imidazolium, 3-(2-aminoethyl)-1-imidazolium, 3-(aminomethyl)piperidine, 4-(aminomethyl)piperidine, 3-(aminomethyl)pyridine, 4-(aminomethyl)pyridine, 4-(aminoethyl)pyridine, phenylene dimethylamine, iodoformamidin, imidazole, 1-methylimidazolium, 1,2,4-triazole.

[0037] The halogen salt can be an iodized salt, a bromine salt, or a chloride salt, and can be an iodized salt.

[0038] In practice, the material used to coat the main perovskite layer is in the form of an ionic compound. Therefore, the coating material can be made in the form of a salt; theoretically, any salt that does not affect operation is acceptable, with halide salts being the most suitable. Then, the salt is brought into direct contact with the main perovskite layer.

[0039] The cations in the capping material are mainly embedded as A-site ions in the host perovskite or in the BX (B and X in perovskite ABX3, such as lead iodide) framework. They are hydrophobic organic cations, which are not easily volatilized and therefore have good stability.

[0040] In any embodiment, in the perovskite solar cell, one of the first capping layer and the second capping layer is formed of the aforementioned capping material and a metal halide salt. Optionally, the molar ratio of the capping material to the metal halide salt is in the range of 1:0.9 to 1:1.3, and more preferably in the range of 1:1.05 to 1:1.2.

[0041] The molar ratio of the capping material to the halide metal salt (e.g., lead iodide) affects the energy level of the formed capping layer, and thus the performance of the solar cell. Therefore, the energy level of the capping layer can be adjusted within the aforementioned molar ratio range to achieve better solar cell performance.

[0042] In any embodiment, the halide metal salt is selected from at least one of lead iodide, lead bromide or lead chloride, and may be lead iodide.

[0043] A second aspect of this application provides a method for fabricating a perovskite solar cell, comprising: a step of fabricating or preparing a transparent electrode; a step of fabricating an electron transport layer; a step of fabricating a perovskite layer; a step of fabricating a hole transport layer; and a step of fabricating a second electrode, wherein...

[0044] The perovskite layer comprises a main perovskite layer and a two-dimensional perovskite coating layer covering its surface and surrounding areas, wherein the two-dimensional perovskite coating layer comprises:

[0045] The first capping layer located between the main perovskite layer and the electron transport layer;

[0046] The second capping layer is located between the main perovskite layer and the hole transport layer; and

[0047] A third capping layer covering the periphery of the main perovskite layer.

[0048] The description of perovskite solar cells above in this application is also applicable to methods for fabricating perovskite solar cells.

[0049] In any embodiment, the steps for preparing the perovskite layer include the following operations:

[0050] (1) A capping layer material and a halide metal salt are coated onto the electron transport layer or hole transport layer to obtain the bottom capping layer.

[0051] (2) Coat the underlying capping layer with the material used to prepare the main perovskite layer to obtain the main perovskite layer.

[0052] (3) Coating the main perovskite layer with a capping material to obtain a surface capping layer.

[0053] Either the bottom cover layer or the top cover layer is a first cover layer, and the other is a second cover layer.

[0054] (4) Apply a protective layer material to the surface coating layer to obtain the protective layer.

[0055] (5) Add a solution of the capping layer material to the protective layer, allowing it to flow to the perimeter of the main perovskite layer and the protective layer to completely cover the perimeter. Heat the solution to obtain a perimeter capping layer, which is the third capping layer.

[0056] (6) Remove the protective layer.

[0057] In the preparation of the third capping layer of perovskite solar cells, this application creatively employs a protective layer, which makes the preparation of the third capping layer more controllable and easier to adjust in terms of thickness and material.

[0058] The perovskite solar cell described in this application can be fabricated using conventional techniques in the art. Optionally, at least one of the following methods can be used to prepare the perovskite layer (including three capping layers and a main perovskite layer): chemical bath deposition, electrochemical deposition, chemical vapor deposition, physical epitaxial growth, co-evaporation, atomic layer deposition, spin coating of precursor solution, slot coating of precursor solution, blade coating of precursor solution, mechanical pressing, etc.; wherein, thermal evaporation and precursor solution coating (spin coating) methods are optional.

[0059] In any embodiment, in the method for preparing a perovskite solar cell, the capping material in (1), (3), and (5) is each independently a halide salt selected from at least one of the following substances or derivatives thereof:

[0060] Ethylamine, propylamine, butylamine, pentylamine, hexylamine, isobutylamine, isopentylamine, 3-buten-1-amine, 3-butyn-1-amine, 2-(methylthio)ethylamine, 2-hydroxyethylamine, 2-chloroethylamine, 2-bromoethylamine, 2-iodoethylamine, 2-fluoroethylamine, 2,2-difluoroethylamine, 2,2,2-trifluoroethylamine;

[0061] H3NC m H 2m+1 , where m is selected from 7 to 10, 12, 14, 16, 18;

[0062] Methylhydrazine;

[0063] Cyclopropylamine, cyclobutylamine, cyclopentylamine, cyclohexylamine;

[0064] Benzylamine, phenethylamine, 2-naphthylmethylamine, 2-naphthylethylamine;

[0065] 2-(1-Naphthoxy)ethylamine, 2-(1-Naphthoxy)propylamine, 2-(1-Naphthoxy)butylamine;

[0066] 2-(1-Methoxypyrene)ethylamine, 2-(1-Methoxypyrene)propylamine, 2-(1-Methoxypyrene)butylamine;

[0067] Peryloxyethylamine;

[0068] 3-Phenylacet-2-propen-1-amine;

[0069] 9-Anthracenemethylamine, 4-fluorophenylethylamine, 2-fluorophenylethylamine, 3-fluorophenylethylamine, 4-fluorophenylethylamine, perfluorophenylethylamine, 2-chlorophenylethylamine, 2-bromophenylethylamine, 4-fluorobenzylamine, 4-chlorobenzylamine, 4-bromobenzylamine, 4-iodobenzylamine, 3-aminopyrrolidine, piperazine, 1-ethylpiperazine, 1H-imidazol-4-ethylamine, 1-(3-aminopropyl)-1-imidazolium, 3-(2-aminoethyl)-1-imidazolium, 3-(aminomethyl)piperidine, 4-(aminomethyl)piperidine, 3-(aminomethyl)pyridine, 4-(aminomethyl)pyridine, 4-(aminoethyl)pyridine, phenylene dimethylamine, iodoformamidin, imidazole, 1-methylimidazolium, 1,2,4-triazole.

[0070] In any embodiment, in the method of preparing a perovskite solar cell, in (1), the molar ratio of the capping material to the halide metal salt is in the range of 1:0.9 to 1:1.3, and optionally in the range of 1:1.05 to 1:1.2.

[0071] In any embodiment, in the method of preparing a perovskite solar cell, the halide metal salt is selected from at least one of lead iodide, lead bromide or lead chloride, and may be lead iodide.

[0072] In any embodiment, the coating is performed by spin coating, co-evaporation or vapor deposition. Optionally, in (4), the coating is performed by spin coating, and after spin coating is completed, heating is performed to obtain a protective layer.

[0073] In any embodiment, in (6), a solvent is used to dissolve the protective layer, optionally trifluoroethanol; then the protective layer and the substances on the protective layer are spun off.

[0074] In any embodiment, the protective layer material is lead pyridine-2-carboxylate.

[0075] A third aspect of this application provides an electrical device comprising a perovskite solar cell as described in this application or a perovskite solar cell prepared according to the method for preparing a perovskite solar cell as described in this application. Attached Figure Description

[0076] Figure 1 This is a schematic diagram of a perovskite solar cell. From bottom to top, the diagram includes a transparent electrode, a charge transport layer, a perovskite host layer (i.e., the host perovskite layer), a two-dimensional perovskite cladding layer surrounding it, a charge transport layer, and a second electrode. The two charge transport layers are different, being either an electron transport layer or a hole transport layer, respectively. This schematic diagram shows the two-dimensional perovskite cladding layer completely covering the upper and lower surfaces and the surrounding area of ​​the perovskite host layer.

[0077] Figure 2 This is an X-ray diffraction pattern of the surface layer (second capping layer) of the two-dimensional perovskite coating layer prepared in Example I-1 of this application. The first peak in the figure is the structural peak of the two-dimensional perovskite layer, and the subsequent peaks are all structural peaks of the main perovskite layer. Detailed Implementation

[0078] Hereinafter, embodiments of perovskite solar cells are specifically disclosed in detail with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0079] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is also expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-6. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0080] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0081] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0082] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, optionally sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0083] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0084] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0085] The fabrication of perovskite solar cells involves the preparation of the perovskite layer. However, the surface of typically prepared perovskite films inevitably exhibits intrinsic defects such as vacancy defects, interstitial defects, and antisite defects. These defects can cause the migration, escape, and degradation of component ions in the perovskite, particularly A-site ions such as methylamine and formamidinium. Furthermore, water, oxygen, and ultraviolet radiation from the air or environment can penetrate the charge transport layers (electron transport layer and / or hole transport layer) and reach the perovskite layer. Contact with these substances can lead to perovskite alteration and decomposition. These problems make the perovskite structure susceptible to damage and can easily cause solar cell device failure.

[0086] Based on research into the aforementioned problems, it is now believed that suppressing defects and ion migration on the perovskite surface, and blocking water, oxygen, and ultraviolet radiation from the environment, are key to solving these problems. Encapsulating the perovskite surface (for ease of description, the uncovered perovskite will be referred to as the "main perovskite") with a two-dimensional perovskite coating layer is an ideal solution. The intrinsic stability of the two-dimensional perovskite coating layer is superior, even higher than that of the two-dimensional perovskite material itself. Simultaneously, the two-dimensional perovskite coating layer, covering the main perovskite surface, can block water, oxygen, and ultraviolet radiation, and forms an interface with the main perovskite layer, improving interface stability. Furthermore, fully covering the top, bottom, and sides of the main perovskite layer can significantly improve the stability of perovskite solar cells.

[0087] Therefore, the first aspect of this application provides a perovskite solar cell, which structurally comprises, in sequence, a transparent electrode, an electron transport layer, a perovskite layer, a hole transport layer, and a second electrode.

[0088] The perovskite layer comprises a main perovskite layer and a two-dimensional perovskite coating layer covering its surface and surrounding areas, the two-dimensional perovskite coating layer comprising:

[0089] The first capping layer located between the main perovskite layer and the electron transport layer;

[0090] The second capping layer is located between the main perovskite layer and the hole transport layer; and

[0091] A third capping layer covering the periphery of the main perovskite layer.

[0092] The perovskite solar cell described in this application may, from bottom to top, sequentially include a transparent electrode, an electron transport layer, a perovskite layer, a hole transport layer, and a second electrode, such as... Figure 1 As shown, sunlight enters through the transparent electrode below; alternatively, the structure can be arranged from top to bottom as follows: transparent electrode, hole transport layer, perovskite layer, electron transport layer, and second electrode. The transparent electrode is used for light incident.

[0093] Structurally, perovskites can be divided into layered and non-layered types. Layered perovskites consist of periodically arranged single or multiple inorganic layers, with the Ruddlesden-Popper (RP) and Dion-Jacobson (DJ) stacking configurations being the most representative. These configurations exhibit better environmental stability and structural tunability than non-layered perovskites. Changes in the perovskite structure can affect its overall physical properties, such as band gap width and exciton binding energy. Therefore, the overall physical properties are typically adjusted by modifying the perovskite structure. Single-layer or few-layer perovskites are defined as a novel class of two-dimensional materials. Unlike traditional two-dimensional inorganic materials, single-layer perovskites are composed of flexible, dynamically changeable lattices, and their chemical structures are highly tunable. This allows for the acquisition of a large number of novel two-dimensional materials with customizable features, providing greater diversity for layered perovskites.

[0094] In this application, a two-dimensional perovskite coating layer is used to fully cover the host perovskite.

[0095] First-principles calculations show that the band gap of two-dimensional perovskites is larger than that of three-dimensional perovskites. Furthermore, the band gap gradually increases as the number of layers in a two-dimensional perovskite decreases, thus enabling it to absorb high-energy ultraviolet photons and protect the underlying three-dimensional perovskite layer. In addition, the formation energy of two-dimensional perovskites is lower than that of three-dimensional perovskites, resulting in higher thermodynamic stability. Moreover, the formation energy gradually decreases as the number of layers in a two-dimensional perovskite decreases, further improving its thermodynamic stability.

[0096] In addition to the advantages mentioned above, the two-dimensional perovskite coating layer described in this application can block external water and oxygen erosion and inhibit the migration of perovskite ions, thereby reducing the degradation effect of light on perovskite. Furthermore, the two-dimensional perovskite layer exhibits excellent intrinsic stability, and when it forms an interface with the host perovskite surface, it can improve the interface's stability against water, oxygen, ultraviolet radiation, etc. Therefore, the perovskite layer described in this application is suitable for use in conjunction with electron transport layers or hole transport layers that have poor blocking capabilities against water, oxygen, and ultraviolet radiation.

[0097] Compared to one-dimensional perovskite layers, two-dimensional perovskite coatings exhibit superior electrical conductivity. The formation process and mechanism of the two-dimensional perovskite coatings described in this application are as follows:

[0098] Taking co-evaporated PbI2 and hexylammonium iodide as an example, in the process of preparing the bottom capping layer using, for example, thermal evaporation, the solid powders of these two salts are used as the evaporation source. Under certain vacuum and temperature conditions, the two salts are evaporated in molecular form, meet in the air or above the substrate, and undergo a chemical reaction to form a two-dimensional layered perovskite structure and deposit it on the substrate surface. In the process of preparing the surface capping layer and the surrounding capping layer using, for example, spin coating, hexylammonium iodide is spin-coated onto the surface and surrounding areas of the main perovskite layer, and then heated and annealed. Since there is an excess of PbI2 in the main perovskite layer, it can combine with the hexylammonium iodide embedded in the shallow surface to form a two-dimensional layered perovskite structure.

[0099] Figure 2 The image in the middle is an X-ray diffraction pattern of the surface layer (second capping layer) of the two-dimensional perovskite coating layer prepared in Example I-1 of this application, which confirms that the layer formed in this application is a two-dimensional perovskite coating layer.

[0100] Furthermore, by fully covering the main perovskite layer—that is, covering the top and bottom surfaces and all four sides—the resulting battery device achieves better long-term stability compared to perovskite layers that are only covered on the top and bottom surfaces.

[0101] In some embodiments, in the perovskite solar cell, the thickness of the first capping layer, the second capping layer, and the third capping layer is independently 1 nm to 30 nm, and can be selected as 3 nm to 10 nm.

[0102] When the thicknesses of the first, second, and third capping layers are within the aforementioned range, the photoelectric conversion efficiency of perovskite solar cells can be improved.

[0103] The thicker the third capping layer, the better the stability of the perovskite solar cell.

[0104] In addition, the thickness of each capping layer can also affect its HOMO and LUMO energy levels. Therefore, the HOMO and LUMO energy levels can be controlled by adjusting their thickness to better match them with the host perovskite and charge transport layer.

[0105] After using the two-dimensional perovskite coating layer described in this application, a passivation layer may be omitted from the main perovskite layer.

[0106] In some embodiments, in the perovskite solar cell, the LUMO energy level of the first capping layer is less than or equal to the LUMO energy level of the host perovskite layer, and

[0107] The absolute value of the difference between the LUMO energy level of the first capping layer and the LUMO energy level of the main perovskite layer is in the range of 0 to 0.5 eV, and can be selected in the range of 0.05 eV to 0.3 eV.

[0108] In some embodiments, in the perovskite solar cell, the LUMO level of the first capping layer is greater than or equal to the LUMO level of the electron transport layer, and

[0109] The absolute value of the difference between the LUMO energy level of the first capping layer and the LUMO energy level of the electron transport layer is in the range of 0 to 0.5 eV, and can be selected in the range of 0.05 eV to 0.5 eV.

[0110] The LUMO energy levels between the first capping layer and the main perovskite layer, and between the first capping layer and the electron transport layer, have the relationships described above. This facilitates the smoother passage of electrons from the main perovskite layer to the electron transport layer, ensuring the cell's turn-on voltage and improving the photoelectric conversion efficiency of the solar cell.

[0111] The LUMO energy level of the first capping layer can also be adjusted by adjusting its thickness and material.

[0112] In some embodiments, in the perovskite solar cell, the HOMO level of the second capping layer is greater than or equal to the HOMO level of the host perovskite layer, and

[0113] The absolute value of the difference between the HOMO energy level of the second capping layer and the HOMO energy level of the main perovskite layer is in the range of 0 to 0.3 eV, and can be selected in the range of 0.05 eV to 0.2 eV.

[0114] In some embodiments, in the perovskite solar cell, the HOMO level of the second capping layer is less than or equal to the HOMO level of the hole transport layer, and

[0115] The absolute value of the difference between the HOMO energy level of the second capping layer and the HOMO energy level of the hole transport layer is in the range of 0 to 0.3 eV, and can be selected in the range of 0.05 eV to 0.15 eV.

[0116] The HOMO energy levels between the second capping layer and the main perovskite layer, as well as between the second capping layer and the hole transport layer, have the relationships described above. This facilitates the smoother movement of holes from the main perovskite layer to the hole transport layer, thereby ensuring the cell's on-state voltage and influencing the cell's photoelectric conversion efficiency.

[0117] In some embodiments, in the perovskite solar cell, the covering materials of the first capping layer, the second capping layer, and the third capping layer are each independently a halide salt selected from at least one of the following substances or derivatives thereof:

[0118] Ethylamine, propylamine, butylamine, pentylamine, hexylamine, isobutylamine, isopentylamine, 3-buten-1-amine, 3-butyn-1-amine, 2-(methylthio)ethylamine, 2-hydroxyethylamine, 2-chloroethylamine, 2-bromoethylamine, 2-iodoethylamine, 2-fluoroethylamine, 2,2-difluoroethylamine, 2,2,2-trifluoroethylamine;

[0119] H3NC m H 2m+1 , where m is selected from 7 to 10, 12, 14, 16, 18;

[0120] Methylhydrazine;

[0121] Cyclopropylamine, cyclobutylamine, cyclopentylamine, cyclohexylamine;

[0122] Benzylamine, phenethylamine, 2-naphthylmethylamine, 2-naphthylethylamine;

[0123] 2-(1-Naphthoxy)ethylamine, 2-(1-Naphthoxy)propylamine, 2-(1-Naphthoxy)butylamine;

[0124] 2-(1-Methoxypyrene)ethylamine, 2-(1-Methoxypyrene)propylamine, 2-(1-Methoxypyrene)butylamine;

[0125] Peryloxyethylamine;

[0126] 3-Phenylacet-2-propen-1-amine;

[0127] 9-Anthracenemethylamine, 4-fluorophenylethylamine, 2-fluorophenylethylamine, 3-fluorophenylethylamine, 4-fluorophenylethylamine, perfluorophenylethylamine, 2-chlorophenylethylamine, 2-bromophenylethylamine, 4-fluorobenzylamine, 4-chlorobenzylamine, 4-bromobenzylamine, 4-iodobenzylamine, 3-aminopyrrolidine, piperazine, 1-ethylpiperazine, 1H-imidazol-4-ethylamine, 1-(3-aminopropyl)-1-imidazolium, 3-(2-aminoethyl)-1-imidazolium, 3-(aminomethyl)piperidine, 4-(aminomethyl)piperidine, 3-(aminomethyl)pyridine, 4-(aminomethyl)pyridine, 4-(aminoethyl)pyridine, phenylene dimethylamine, iodoformamidin, imidazole, 1-methylimidazolium, 1,2,4-triazole.

[0128] The halogen salt can be an iodized salt, a bromine salt, or a chloride salt, and can be selected as an iodized salt.

[0129] In practice, the material used to coat the main perovskite layer is in the form of an ionic compound. Therefore, the coating material can be made in the form of a salt; theoretically, any salt that does not affect operation is acceptable, with halide salts being the most suitable. Then, the salt is brought into direct contact with the main perovskite layer.

[0130] The cations in the capping material are mainly embedded as A-site ions in the host perovskite or in the BX (e.g., Pb-I) framework. They are hydrophobic organic cations, which are not easily volatilized and therefore have good stability.

[0131] As described above, by introducing certain specific cations (such as those with alkyl chains or hydrocarbon functional groups) as A-site ions to embed into the shallow layer of a three-dimensional perovskite layer (i.e., the host perovskite layer) and enter the BX (e.g., Pb-I) framework, a two-dimensional structure can be formed. Since the band gap and band position of the two-dimensional perovskites formed by different A-site ions are tunable, this property can also be used to optimize the energy level matching inside the battery by changing the type and amount of introduced cations.

[0132] In some embodiments, in the perovskite solar cell, one of the first capping layer and the second capping layer is formed of the aforementioned capping material and a metal halide salt. Optionally, the molar ratio of the capping material to the metal halide salt is in the range of 1:0.9 to 1:1.3, and more preferably in the range of 1:1.05 to 1:1.2.

[0133] The molar ratio of the capping material and the halide metal salt (e.g., lead iodide) affects the energy level of the formed capping layer, and thus the performance of the solar cell. Therefore, the energy level of the capping layer can be tuned within the aforementioned molar ratio range to achieve better performance.

[0134] When one of the first and second capping layers is formed by the aforementioned capping material and a metal halide salt, the other layer is formed by the capping material, without the need for a metal halide salt. In practice, the first layer prepared is the bottom layer. During the preparation of the bottom layer, a two-dimensional perovskite structure is optionally formed using a co-evaporation method with the capping material and the metal halide salt. The next layer prepared is the top layer. During the preparation of the top layer, only the capping material is used, without the need for a metal halide salt. This is because the prepared main perovskite layer usually contains excess X anions, which can interact with the capping material to form the top capping layer. If the prepared main perovskite layer does not contain excess X anions or has insufficient X anions, an X anion salt, such as a metal halide salt, can be added as appropriate during the preparation of the top layer.

[0135] In some embodiments, the halide metal salt is selected from at least one of lead iodide, lead bromide, or lead chloride, and may be lead iodide.

[0136] A second aspect of this application provides a method for fabricating a perovskite solar cell, comprising: a step of fabricating or preparing a transparent electrode; a step of fabricating an electron transport layer; a step of fabricating a perovskite layer; a step of fabricating a hole transport layer; and a step of fabricating a second electrode, wherein...

[0137] The perovskite layer comprises a main perovskite layer and a two-dimensional perovskite coating layer covering its surface and surrounding areas, wherein the two-dimensional perovskite coating layer comprises:

[0138] The first capping layer located between the main perovskite layer and the electron transport layer;

[0139] The second capping layer is located between the main perovskite layer and the hole transport layer; and

[0140] A third capping layer covering the periphery of the main perovskite layer.

[0141] The description of perovskite solar cells above in this application is also applicable to methods for fabricating perovskite solar cells.

[0142] In some embodiments, the steps for preparing the perovskite layer include the following operations:

[0143] (1) A capping layer material and a halide metal salt are coated onto the electron transport layer or hole transport layer to obtain the bottom capping layer.

[0144] (2) Coat the underlying capping layer with the material used to prepare the main perovskite layer to obtain the main perovskite layer.

[0145] (3) Coating the main perovskite layer with a capping material to obtain a surface capping layer.

[0146] Either the bottom cover layer or the top cover layer is a first cover layer, and the other is a second cover layer.

[0147] (4) Apply a protective layer material to the surface coating layer to obtain the protective layer.

[0148] (5) Add a solution of the capping layer material to the protective layer, allowing it to flow to the perimeter of the main perovskite layer and the protective layer to completely cover the perimeter. Heat the solution to obtain a perimeter capping layer, which is the third capping layer.

[0149] (6) Remove the protective layer.

[0150] Optionally, the thickness of the protective layer is 1 nm to 10 nm.

[0151] In the preparation of the third capping layer of perovskite solar cells, this application creatively employs a protective layer, which makes the preparation of the third capping layer more controllable and easier to adjust in terms of thickness and material.

[0152] The perovskite solar cells described in this application can be fabricated using conventional techniques in the art. Optionally, the perovskite layer (including three capping layers and a main perovskite layer) can be prepared using at least one of the following methods: chemical bath deposition, electrochemical deposition, chemical vapor deposition, physical epitaxial growth, co-evaporation, atomic layer deposition, spin coating of precursor solution, slot coating of precursor solution, blade coating of precursor solution, mechanical pressing, etc.; wherein, thermal evaporation and precursor solution coating (spin coating) methods are optional. This application does not impose specific limitations on the preparation method of the perovskite layer, as long as the desired purpose can be achieved. Optionally, the "coating" described in this application is performed using the above-mentioned methods.

[0153] Optionally, the coating in (1) is performed using a co-evaporation method. The "co-evaporation" described in this application can be performed by using powders of two or more substances as evaporation sources. Taking the formation of perovskite as an example, under certain vacuum and temperature conditions, the powders of the corresponding substances are used as evaporation sources to evaporate in molecular form. These molecules meet in the air or on the substrate, undergo a chemical reaction to form a perovskite structure, and are deposited on the substrate surface.

[0154] In some embodiments, in the method of preparing perovskite solar cells, the capping material in (1), (3), and (5) is each independently a halide salt selected from at least one of the following substances or derivatives thereof:

[0155] Ethylamine, propylamine, butylamine, pentylamine, hexylamine, isobutylamine, isopentylamine, 3-buten-1-amine, 3-butyn-1-amine, 2-(methylthio)ethylamine, 2-hydroxyethylamine, 2-chloroethylamine, 2-bromoethylamine, 2-iodoethylamine, 2-fluoroethylamine, 2,2-difluoroethylamine, 2,2,2-trifluoroethylamine;

[0156] H3NC m H 2m+1 , where m is selected from 7 to 10, 12, 14, 16, 18;

[0157] Methylhydrazine;

[0158] Cyclopropylamine, cyclobutylamine, cyclopentylamine, cyclohexylamine;

[0159] Benzylamine, phenethylamine, 2-naphthylmethylamine, 2-naphthylethylamine;

[0160] 2-(1-Naphthoxy)ethylamine, 2-(1-Naphthoxy)propylamine, 2-(1-Naphthoxy)butylamine;

[0161] 2-(1-Methoxypyrene)ethylamine, 2-(1-Methoxypyrene)propylamine, 2-(1-Methoxypyrene)butylamine;

[0162] Peryloxyethylamine;

[0163] 3-Phenylacet-2-propen-1-amine;

[0164] 9-Anthracenemethylamine, 4-fluorophenylethylamine, 2-fluorophenylethylamine, 3-fluorophenylethylamine, 4-fluorophenylethylamine, perfluorophenylethylamine, 2-chlorophenylethylamine, 2-bromophenylethylamine, 4-fluorobenzylamine, 4-chlorobenzylamine, 4-bromobenzylamine, 4-iodobenzylamine, 3-aminopyrrolidine, piperazine, 1-ethylpiperazine, 1H-imidazol-4-ethylamine, 1-(3-aminopropyl)-1-imidazolium, 3-(2-aminoethyl)-1-imidazolium, 3-(aminomethyl)piperidine, 4-(aminomethyl)piperidine, 3-(aminomethyl)pyridine, 4-(aminomethyl)pyridine, 4-(aminoethyl)pyridine, phenylene dimethylamine, iodoformamidin, imidazole, 1-methylimidazolium, 1,2,4-triazole.

[0165] In this application, "covering material" and "covering material" are used synonymously.

[0166] In some embodiments, in the method of preparing perovskite solar cells, in (1), the molar ratio of the capping material and the halide metal salt is in the range of 1:0.9 to 1:1.3, and optionally in the range of 1:1.05 to 1:1.2.

[0167] In some embodiments, in the method of preparing a perovskite solar cell, the halide metal salt is selected from at least one of lead iodide, lead bromide, or lead chloride, and may be lead iodide.

[0168] In some embodiments, the coating is performed by spin coating, co-evaporation or vapor deposition. Optionally, in (4), the coating is performed by spin coating, and after spin coating is completed, heating is performed to obtain a protective layer.

[0169] In some embodiments, in (6), a solvent is used to dissolve the protective layer, optionally trifluoroethanol; then the protective layer and the substances on the protective layer are spun off.

[0170] In some embodiments, the protective layer material is lead pyridine-2-carboxylate.

[0171] In some alternative embodiments, a protective layer may not be used when preparing the four-sided capping layer (i.e., the third capping layer). The four-sided capping layer can be prepared simultaneously with the surface capping layer, in which case the A-site ions of the surface two-dimensional perovskite capping layer and the four-sided two-dimensional perovskite capping layer are the same. A specific operational example is as follows: When preparing the surface capping layer, an excess of a capping material solution (e.g., an isopropanol solution of hexylammonium iodide) is added (which can be added by spin coating) so that it not only covers the main perovskite layer but also flows to and fully covers the periphery of the main perovskite layer. Then, it is heated and annealed to simultaneously obtain a two-dimensional perovskite surface capping layer and a four-sided capping layer.

[0172] A third aspect of this application provides an electrical device comprising a perovskite solar cell as described in this application or a perovskite solar cell prepared according to the method for preparing a perovskite solar cell as described in this application.

[0173] The following is a brief description of the main perovskite layer, electron transport layer, hole transport layer, and electrode structure of a perovskite solar cell, but this application is not limited thereto.

[0174] Main perovskite layer

[0175] It can be prepared using any perovskite material conventionally used in the art.

[0176] Optionally, this application uses an ABX3 type host perovskite, wherein A is an inorganic, organic, or mixed organic-inorganic cation, B is an inorganic, organic, or mixed organic-inorganic cation, and X is an inorganic, organic, or mixed organic-inorganic anion. As an example, the ion at the A site can be, for example, a methylamine cation MA. + Formamidinium cation FA + Cs + and their mixtures; the B-site ion can be, for example, Pb2+ Sn 2+ And their mixture; the X-site ion can be a halide ion, COO - And their mixtures.

[0177] Alternatively, the host perovskite layer can be prepared by vapor deposition, for example, by depositing FAPbI3 single crystals.

[0178] Transparent electrode and second electrode

[0179] The transparent electrode and the second electrode described in this application can be any electrode used in the art. Optionally, the electrode materials of the transparent electrode and the second electrode are organic, inorganic, or a mixture of organic and inorganic conductive materials. As an example, the organic conductive material can be a conductive polymer, such as poly(3,4-ethylenedioxythiophene) (PEDOT), polythiophene, polyacetylene, etc.; the inorganic conductive material can be: transparent conductive oxides, such as fluorine-doped tin oxide (FTO), indium tin oxide (ITO), aluminum-doped zinc oxide (AZO), etc.; metals; carbon derivatives, etc.

[0180] Transparent electrodes are used for light incident. Transparent conductive oxides are typically used. Generally, the transparent conductive oxide consists of a glass substrate and an oxide thin film (TCO) conductive layer. Commonly used TCOs include ITO, FTO, and AZO, but this application is not limited to these.

[0181] Conductive glass needs to be cleaned before use, for example, by ultrasonic cleaning with cleaning agents (including but not limited to surfactants), ethanol, acetone, isopropanol and deionized water.

[0182] The second electrode, used to collect charge carriers, is selected from metals or carbon derivatives and is prepared using techniques known in the art, such as thermal evaporation, with a thickness of 20 nm to 1000 nm. In a specific embodiment of this application, metallic silver is used as the second electrode, prepared by evaporation, with a thickness of 50 nm to 120 nm.

[0183] Hole transport layer

[0184] The hole transport layer is used to collect and extract holes from the perovskite layer. Any hole transport layer material conventionally used in the art can be used, and optionally, a hole transport layer material that satisfies the above-described HOMO energy level matching relationship can be used.

[0185] Optionally, for example, the material of the hole transport layer is at least one of the following materials and their derivatives: poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene (Spiro-OMeTAD), poly3-hexylthiophene (P3HT), triphenylamine with a triphenylene core (H101), 3,4-ethylenedioxythiophene-methoxytriphenylamine (EDOT-OMeTPA), N-(4-aniline)carbazole-spirobifluorene (CzPAF-SBF), poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS), polythiophene, nickel oxide (NiOx), molybdenum oxide (MoO3), cuprous iodide (CuI), cuprous oxide (Cu2O), etc.

[0186] The thickness of the hole transport layer can range from 5nm to 300nm, or optionally from 100nm to 200nm.

[0187] Electron transport layer

[0188] The electron transport layer is used to collect and extract electrons from the perovskite layer. Any electron transport layer material used in the art can be used, and optionally, an electron transport layer material that satisfies the aforementioned HOMO energy level matching relationship can be used.

[0189] Optionally, for example, the material of the electron transport layer is at least one of the following materials and their derivatives: [6,6]-phenyl-C 61 methyl butyrate (PC) 61 BM), [6,6]-phenyl-C 71 methyl butyrate (PC) 71 BM), fullerene C60 (C60), fullerene C70 (C70), tin dioxide (SnO2), zinc oxide (ZnO), titanium dioxide (TiO2), etc.

[0190] The thickness of the electron transport layer can range from 5nm to 200nm, or optionally from 20nm to 100nm.

[0191] Both the hole transport layer and the electron transport layer can be prepared using methods commonly used in this field.

[0192] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0193] I. Fabrication of Perovskite Solar Cells

[0194] Example I-1

[0195] Transparent Electrode

[0196] The surface of an FTO conductive glass with dimensions of 2.0cm×2.0cm was cleaned twice with acetone and isopropanol, then immersed in deionized water and ultrasonically treated for 10 minutes. After drying in a forced-air drying oven, it was placed in a glove box (N2 atmosphere) for later use. This is a transparent electrode.

[0197] Electron transport layer

[0198] A 3% by weight SnO2 nanocolloid aqueous solution was spin-coated onto the FTO thin film layer of the transparent electrode using a spin coater (LEBO EZ6-S, hereinafter the same). The spin coating time was 30 seconds. Afterwards, the layer was heated at 150°C for 15 minutes on a constant temperature stage to obtain an electron transport layer with a thickness of 30 nm.

[0199] [Perovskite layer]

[0200] Step 1: Prepare a two-dimensional perovskite substrate (first capping layer)

[0201] The sample with the transparent electrode and electron transport layer already formed was placed in a vacuum coating machine and coated at 5×10⁻⁶. -4 Under vacuum conditions of Pa, hexylammonium iodide and PbI2 with a molar ratio of 1:1.1 were co-deposited on the surface of the electron transport layer to form a perovskite structure and deposit it on the sample surface. The evaporation rate ratio of the two substances was 1:1 (evaporation rate of 0.1 Å / s), resulting in a two-dimensional perovskite underlayer with a thickness of 5 nm.

[0202] Step 2: Preparation of the main perovskite layer

[0203] Next, the evaporation source was changed to FAPbI3 single crystal, and FAPbI3 main perovskite layer with a thickness of 500nm was deposited on the surface of the two-dimensional perovskite bottom layer obtained in step 1.

[0204] Step 3: Prepare a two-dimensional perovskite surface layer (second capping layer)

[0205] Next, a solution of hexylammonium iodide in isopropanol with a concentration of 5 mg / mL was spin-coated onto the surface of the FAPbI3 host perovskite layer at a speed of 5000 rpm for 30 s. Then, the layer was heated at 100 °C for 10 min on a constant temperature hot plate to obtain a two-dimensional perovskite surface with a thickness of 5 nm.

[0206] Step 4: Add a protective layer

[0207] Next, a 5 mg / mL solution of lead pyridine-2-carboxylate in trifluoroethanol was spin-coated onto the two-dimensional perovskite surface prepared in step 3 at a speed of 5000 rpm to completely cover the surface. Then, the surface was heated at 100 °C for 10 min on a constant temperature hot plate to obtain a protective layer.

[0208] Step 5: Add a three-layer cover (third cover) around the perimeter.

[0209] Next, the protective layer and perovskite layer of the sample obtained in step 4 were polished and cleaned using an electric mill (Bosch GSR120). The width of the protective layer / perovskite layer removed from the four sides was 1 mm. Then, a 5 mg / mL solution of hexylammonium iodide in isopropanol was spin-coated onto the surface of the protective layer of the obtained sample at 5000 rpm, so that it could flow to the polished edges and completely cover the edges. The sample was then heated at 100 °C for 10 min on a constant temperature hot plate to obtain a two-dimensional perovskite coating layer with a thickness of about 5 nm.

[0210] Next, 100 μL of excess trifluoroethanol solution was added to dissolve the protective layer. Then, a spin coater was used to spin the protective layer and the material on it at 6000 rpm to remove the protective layer. Finally, the mixture was heated at 100°C for 5 minutes on a constant temperature hot plate.

[0211] The final result is a perovskite layer completely covered by two-dimensional perovskite.

[0212] Hole transport layer

[0213] A chlorobenzene solution of Spiro-OMeTAD with a concentration of 73 mg / mL was spin-coated onto the obtained heterojunction perovskite layer at a speed of 5000 rpm for 20 seconds to obtain a hole transport layer with a thickness of 150 nm.

[0214] [Second Electrode]

[0215] The sample, which already has a transparent electrode, electron transport layer, perovskite layer, and hole transport layer, is placed in a vacuum coating machine and coated at 5 × 10⁻⁶. -4 Under vacuum conditions of Pa, Ag is vapor-deposited on the surface of the obtained hole transport layer to obtain an Ag electrode with a thickness of 80 nm, which serves as the second electrode.

[0216] Thus, the perovskite solar cell of Example I-1 was obtained.

[0217] Examples I-2 to I-7 and Comparative Examples

[0218] Examples I-2 to I-7 and the comparative examples are prepared similarly to Example I-1, except that the thickness of the surrounding capping layer in step 5 of the preparation of the [perovskite layer] is shown in Table 1.

[0219] II. Examination of energy level matching in the second capping layer

[0220] Examples II-1 to II-11

[0221] Examples II-1 to II-11 are similar to Example I-1, with the differences shown in Table 2. The thicknesses of the three covering layers are consistent and are all the thickness values ​​in Table 2.

[0222] III. Examination of energy level matching in the first capping layer

[0223] Examples III-1 to III-13

[0224] Examples III-1 to III-13 are similar to Example II-1, with the differences shown in Table 3. The thicknesses of the three cover layers are consistent and are all the thickness values ​​in Table 3.

[0225] IV. Battery Performance Testing

[0226] The performance of the perovskite solar cells in the various embodiments and comparative examples was tested.

[0227] 1. Energy conversion efficiency test

[0228] The energy conversion efficiency of the perovskite solar cells in each embodiment and comparative example was measured. Under atmospheric conditions, an AM1.5G standard light source was used as the simulated sunlight source. The current-voltage characteristic curve of the cell under the illumination of the light source was measured using a four-channel digital source meter (Keithley 2440) to obtain the cell's open-circuit voltage Voc, short-circuit current density Jsc, and fill factor FF. The energy conversion efficiency Eff of the cell was then calculated.

[0229] Energy conversion efficiency is calculated as follows: Eff = Pout / Popt

[0230] =Voc×Jsc×(Vmpp×Jmpp) / (Voc×Jsc)

[0231] =Voc×Jsc×FF

[0232] Where Pout, Popp, Vmpp, and Jmpp are the battery's operating output power, incident light power, battery's maximum power point voltage, and maximum power point current, respectively.

[0233] In this test, the open-circuit voltage Voc is the battery open-circuit voltage shown in Tables 2-3.

[0234] 2. Battery stability test

[0235] The stability performance of the perovskite solar cells in each embodiment and comparative example was tested. The cells were placed in air conditions with a relative humidity of 75% to 80% and an ambient temperature of 25°C to 30°C for at least 800 hours without protection from light. The energy conversion efficiency before and after placement was determined according to the above test method. The ratio of the cell efficiency after 800 hours to the initial efficiency was calculated as the cell stability performance parameter.

[0236] 3. Energy level testing

[0237] The band distribution of each capping layer was measured at room temperature and pressure using an Escalab 250Xi X-ray ultraviolet photoelectron spectrometer (XPS-UPS) from Thermo Scientific.

[0238] 4. Thickness testing of each coating layer

[0239] Under normal temperature and vacuum conditions, a dual-beam system (FIB-SEM) coupled with a focused ion beam (FIB) and a high-resolution scanning electron microscope (SEM) was used to fix and thin the sample, prepare a cross-section, and perform thickness testing.

[0240] The test results are shown in Tables 1-3.

[0241] Table 1: The impact of the thickness of the four-sided cover layer (i.e., the third cover layer) on battery performance

[0242]

[0243]

[0244] The results in the table above show that:

[0245] Compared to a comparative example without a capping layer on all four sides, having a capping layer on all four sides significantly improves the stability of perovskite solar cells.

[0246] The thicker the surrounding cover layer (third cover layer), the better the stability of the solar cell;

[0247] When the thickness of the surrounding cover layer is in the range of 1nm to 30nm, or more preferably in the range of 3nm to 10nm, better energy conversion efficiency and battery stability can be achieved.

[0248]

[0249] The results in the table above indicate that:

[0250] The HOMO energy level of the surface layer (i.e., the second capping layer) of the two-dimensional perovskite coating is related to its thickness; the greater the thickness, the greater the HOMO energy level.

[0251] The HOMO energy level of the surface layer (i.e., the second capping layer) of the two-dimensional perovskite coating is related to the type of material. At the same thickness, the HOMO energy level is higher when using 3-(aminomethyl)piperidinium or benzylamine cations than when using hexylammonium cations.

[0252] The HOMO energy level of the surface layer (i.e., the second capping layer) of the two-dimensional perovskite coating is greater than or equal to the HOMO energy level of the host perovskite layer, and the absolute value of the difference between the two is in the range of 0 to 0.3 eV, and can be selected in the range of 0.05 eV to 0.20 eV to achieve better energy conversion efficiency and battery opening voltage.

[0253] The HOMO energy level of the surface layer (i.e., the second capping layer) of the two-dimensional perovskite coating is less than or equal to the HOMO energy level of the hole transport layer, and the absolute value of the difference between the two is in the range of 0 to 0.3 eV, or preferably in the range of 0.05 eV to 0.15 eV, which can achieve better energy conversion efficiency and battery opening voltage.

[0254]

[0255] The results in Table 3 show that:

[0256] The LUMO energy level of the surface layer (i.e., the first capping layer) of the two-dimensional perovskite coating is related to its thickness; the greater the thickness, the smaller the LUMO energy level.

[0257] When the thickness of the two-dimensional perovskite substrate is 1nm to 30nm, or optionally 3nm to 10nm, better energy conversion efficiency and battery opening voltage can be achieved.

[0258] The LUMO energy level of the surface layer (i.e., the first capping layer) of a two-dimensional perovskite coating is related to the type of material it is made of.

[0259] The LUMO energy level of the surface layer (i.e., the first capping layer) of the two-dimensional perovskite coating is related to the molar ratio of its material to lead iodide. The smaller the molar ratio, the smaller the LUMO energy level. When the molar ratio of the material of the two-dimensional perovskite bottom layer to lead iodide is 1:0.9 to 1:1.3, or optionally 1:1.05 to 1:1.2, better energy conversion efficiency and battery opening voltage can be achieved.

[0260] When the LUMO energy level of the surface layer (i.e., the first capping layer) of the two-dimensional perovskite coating is lower than that of the LUMO energy level of the main perovskite layer, and the absolute value of the difference between the two is in the range of 0 to 0.5 eV, or can be selected in the range of 0.05 eV to 0.3 eV, better energy conversion efficiency and battery opening voltage are achieved.

[0261] When the LUMO energy level of the surface layer (i.e., the first capping layer) of the two-dimensional perovskite coating is greater than that of the LUMO energy level of the electron transport layer, and the absolute value of the difference between the two is in the range of 0 to 0.5 eV, or can be selected in the range of 0.05 eV to 0.5 eV, better energy conversion efficiency and battery opening voltage are achieved.

[0262] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A perovskite solar cell, which structurally comprises, in sequence, a transparent electrode, an electron transport layer, a perovskite layer, a hole transport layer, and a second electrode. The perovskite layer comprises a main perovskite layer and a two-dimensional perovskite coating layer covering its surface and surrounding areas, the two-dimensional perovskite coating layer comprising: The first capping layer located between the main perovskite layer and the electron transport layer; A second capping layer located between the main perovskite layer and the hole transport layer; and A third capping layer covering the periphery of the main perovskite layer; The LUMO energy level of the first capping layer is greater than or equal to the LUMO energy level of the electron transport layer, and The absolute value of the difference between the LUMO energy level of the first capping layer and the LUMO energy level of the electron transport layer is in the range of 0~0.5 eV.

2. The perovskite solar cell of claim 1, wherein The thickness of the first cover layer, the second cover layer, and the third cover layer is independently 1~30 nm.

3. The perovskite solar cell according to claim 1 or 2, wherein The thickness of the first cover layer, the second cover layer, and the third cover layer is independently 3~10 nm.

4. The perovskite solar cell according to claim 1 or 2, wherein The LUMO energy level of the first capping layer is less than or equal to the LUMO energy level of the host perovskite layer, and The absolute value of the difference between the LUMO energy level of the first capping layer and the LUMO energy level of the main perovskite layer is in the range of 0~0.5eV.

5. The perovskite solar cell of claim 4, wherein, The absolute value of the difference between the LUMO energy level of the first capping layer and the LUMO energy level of the main perovskite layer is in the range of 0.05~0.3 eV.

6. The perovskite solar cell of claim 1, wherein, The absolute value of the difference between the LUMO energy level of the first capping layer and the LUMO energy level of the electron transport layer is in the range of 0.05~0.5 eV.

7. The perovskite solar cell according to claim 1 or 2, wherein, The HOMO energy level of the second capping layer is greater than or equal to the HOMO energy level of the host perovskite layer, and The absolute value of the difference between the HOMO energy level of the second capping layer and the HOMO energy level of the main perovskite layer is in the range of 0~0.3eV.

8. The perovskite solar cell of claim 7, wherein, The absolute value of the difference between the HOMO energy level of the second capping layer and the HOMO energy level of the main perovskite layer is in the range of 0.05~0.2 eV.

9. The perovskite solar cell according to claim 1 or 2, wherein, The HOMO level of the second capping layer is less than or equal to the HOMO level of the hole transport layer, and The absolute value of the difference between the HOMO energy level of the second capping layer and the HOMO energy level of the hole transport layer is in the range of 0~0.3 eV.

10. The perovskite solar cell according to claim 9, wherein, The absolute value of the difference between the HOMO energy level of the second capping layer and the HOMO energy level of the hole transport layer is in the range of 0.05~0.15 eV.

11. The perovskite solar cell of claim 1, wherein the covering material of the first capping layer, the second capping layer, and the third capping layer is each independently a halide salt selected from at least one of the following substances or derivatives thereof: Ethylamine, propylamine, butylamine, pentylamine, hexylamine, isobutylamine, isopentylamine, 3-buten-1-amine, 3-butyn-1-amine, 2-(methylthio)ethylamine, 2-hydroxyethylamine, 2-chloroethylamine, 2-bromoethylamine, 2-iodoethylamine, 2-fluoroethylamine, 2,2-difluoroethylamine, 2,2,2-trifluoroethylamine; H3NC m H 2m+1 wherein m is selected from 7-10, 12, 14, 16, 18; Methylhydrazine; Cyclopropylamine, cyclobutylamine, cyclopentylamine, cyclohexylamine; Benzylamine, phenethylamine, 2-naphthylmethylamine, 2-naphthylethylamine; 2-(1-Naphthoxy)ethylamine, 2-(1-Naphthoxy)propylamine, 2-(1-Naphthoxy)butylamine; 2-(1-Methoxypyrene)ethylamine, 2-(1-Methoxypyrene)propylamine, 2-(1-Methoxypyrene)butylamine; Peryloxyethylamine; 3-Phenylacet-2-propen-1-amine; 9-Anthracenemethylamine, 4-fluorophenylethylamine, 2-fluorophenylethylamine, 3-fluorophenylethylamine, 4-fluorophenylethylamine, perfluorophenylethylamine, 2-chlorophenylethylamine, 2-bromophenylethylamine, 4-fluorobenzylamine, 4-chlorobenzylamine, 4-bromobenzylamine, 4-iodobenzylamine, 3-aminopyrrolidine, piperazine, 1-ethylpiperazine, 1H-imidazol-4-ethylamine, 1-(3-aminopropyl)-1-imidazolium, 3-(2-aminoethyl)-1-imidazolium, 3-(aminomethyl)piperidine, 4-(aminomethyl)piperidine, 3-(aminomethyl)pyridine, 4-(aminomethyl)pyridine, 4-(aminoethyl)pyridine, phenylene dimethylamine, iodoformamidin, imidazole, 1-methylimidazolium, 1,2,4-triazole.

12. The perovskite solar cell of claim 11, wherein one of the first capping layer and the second capping layer is formed of the capping material and a metal halide salt.

13. The perovskite solar cell of claim 12, wherein, The molar ratio of the covering material to the halide metal salt is in the range of 1:0.9 to 1:1.

3.

14. The perovskite solar cell of claim 13, wherein, The molar ratio of the covering material to the halide metal salt is in the range of 1:1.05 to 1:1.

2.

15. The perovskite solar cell according to claim 14, wherein the halide metal salt is selected from at least one of lead iodide, lead bromide or lead chloride.

16. A method for fabricating a perovskite solar cell, comprising the steps of fabricating or preparing a transparent electrode, fabricating an electron transport layer, fabricating a perovskite layer, fabricating a hole transport layer, and fabricating a second electrode, wherein, The perovskite layer comprises a main perovskite layer and a two-dimensional perovskite coating layer covering its surface and surrounding areas, wherein the two-dimensional perovskite coating layer comprises: The first capping layer located between the main perovskite layer and the electron transport layer; The second capping layer is located between the main perovskite layer and the hole transport layer; and A third capping layer covering the periphery of the main perovskite layer; The LUMO energy level of the first capping layer is greater than or equal to the LUMO energy level of the electron transport layer, and the absolute value of the difference between the LUMO energy level of the first capping layer and the LUMO energy level of the electron transport layer is in the range of 0~0.5 eV.

17. The method of preparing a perovskite solar cell according to claim 16, wherein, The steps for preparing the perovskite layer include the following operations: (1) A capping layer material and a halide metal salt are coated onto the electron transport layer or hole transport layer to obtain the bottom capping layer. (2) Coating the underlying capping layer with the material used to prepare the main perovskite layer to obtain the main perovskite layer. (3) A capping material is coated onto the main perovskite layer to obtain a surface capping layer. Either the bottom cover layer or the top cover layer is a first cover layer, and the other is a second cover layer. (4) Apply a protective layer material to the surface coating layer to obtain the protective layer. (5) Add a solution of the capping material to the protective layer, allowing it to flow to the periphery of the main perovskite layer and the protective layer to completely cover the periphery. Heat the solution to obtain a periphery capping layer, which is the third capping layer. (6) Remove the protective layer.

18. The method for preparing a perovskite solar cell according to claim 17, wherein the capping material in (1), (3), and (5) is each independently a halide salt selected from at least one of the following substances or derivatives thereof: Ethylamine, propylamine, butylamine, pentylamine, hexylamine, isobutylamine, isopentylamine, 3-buten-1-amine, 3-butyn-1-amine, 2-(methylthio)ethylamine, 2-hydroxyethylamine, 2-chloroethylamine, 2-bromoethylamine, 2-iodoethylamine, 2-fluoroethylamine, 2,2-difluoroethylamine, 2,2,2-trifluoroethylamine; H3NCmH2m+1, where m is selected from 7~10, 12, 14, 16, 18; Methylhydrazine; Cyclopropylamine, cyclobutylamine, cyclopentylamine, cyclohexylamine; Benzylamine, phenethylamine, 2-naphthylmethylamine, 2-naphthylethylamine; 2-(1-Naphthoxy)ethylamine, 2-(1-Naphthoxy)propylamine, 2-(1-Naphthoxy)butylamine; 2-(1-Methoxypyrene)ethylamine, 2-(1-Methoxypyrene)propylamine, 2-(1-Methoxypyrene)butylamine; Peryloxyethylamine; 3-Phenylacet-2-propen-1-amine; 9-Anthracenemethylamine, 4-fluorophenylethylamine, 2-fluorophenylethylamine, 3-fluorophenylethylamine, 4-fluorophenylethylamine, perfluorophenylethylamine, 2-chlorophenylethylamine, 2-bromophenylethylamine, 4-fluorobenzylamine, 4-chlorobenzylamine, 4-bromobenzylamine, 4-iodobenzylamine, 3-aminopyrrolidine, piperazine, 1-ethylpiperazine, 1H-imidazol-4-ethylamine, 1-(3-aminopropyl)-1-imidazolium, 3-(2-aminoethyl)-1-imidazolium, 3-(aminomethyl)piperidine, 4-(aminomethyl)piperidine, 3-(aminomethyl)pyridine, 4-(aminomethyl)pyridine, 4-(aminoethyl)pyridine, phenylene dimethylamine, iodoformamidin, imidazole, 1-methylimidazolium, 1,2,4-triazole.

19. The method of preparing a perovskite solar cell according to claim 17, wherein, In (1), the molar ratio of the coating material to the halide metal salt is in the range of 1:0.9 to 1:1.

3.

20. The method of preparing a perovskite solar cell according to claim 19, wherein, In (1), the molar ratio of the coating material and the halide metal salt is in the range of 1:1.05 to 1:1.

2.

21. The method of preparing a perovskite solar cell according to claim 17, wherein, The halide metal salt is selected from at least one of lead iodide, lead bromide, or lead chloride.

22. The method of preparing a perovskite solar cell according to claim 17, wherein, The coating is performed by spin coating, co-evaporation or evaporation. In (4), the coating is performed by spin coating. After spin coating is completed, the coating is heated to obtain the protective layer.

23. The method of preparing a perovskite solar cell according to claim 17, wherein, In (6), a solvent is used to dissolve the protective layer, and the solvent for dissolving the protective layer is trifluoroethanol; then the protective layer and the substances on the protective layer are removed by rotating.

24. The method of preparing a perovskite solar cell according to claim 17, wherein, The protective layer material is lead pyridine-2-carboxylate.

25. An electrical device comprising a perovskite solar cell according to any one of claims 1-15 or a perovskite solar cell prepared by any one of claims 16-24.

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