Functional layer for improving stability of perovskite thin film and preparation method and application thereof

Abstract

The invention belongs to the technical field of perovskite. The invention provides a functional layer for improving the stability of a perovskite thin film and a preparation method and application thereof. The functional layer comprises a novel covalent organic framework material (COFs material). The structures of the COFs materials can form fine micro / nano-scale pore diameters, and the COFs materials not only have high surface area, but also have stable non-polar vinyl bonds. In the COFs material, an azine unit of a lone electron pair is completely exposed to provide a strong hydrogen bond accepting site in a one-dimensional channel, so that the COFs material has excellent water absorption performance. The functional layer containing the COFs material can significantly reduce the erosion of water vapor to the perovskite film, and the stability of the perovskite device is greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of perovskite technology, and relates to a functional layer for improving the stability of perovskite thin films, its preparation method and application. Background Technology

[0002] With the continuous progress and development of human society, the demand for energy is increasing. Traditional energy sources, such as oil, natural gas, and coal, are non-renewable resources with limited availability and rising extraction costs. More seriously, the large-scale use of these fossil fuels has led to a series of environmental problems, including increased air pollution and greenhouse gas emissions, posing a significant threat to the Earth's ecosystem. Therefore, finding and developing renewable, clean, and efficient green new energy sources is particularly urgent and important.

[0003] Among numerous renewable energy sources, solar energy stands out for its inexhaustible and pollution-free nature, becoming one of the most promising alternative energy sources. Research on solar energy applications has made significant progress in recent years, with continuous advancements in the development of various new types of solar cells aimed at improving conversion efficiency, reducing costs, and enhancing environmental adaptability. Perovskite solar cells (PSCs) have attracted considerable attention due to their unique performance advantages. Since their first report in 2009, the photoelectric conversion efficiency of PSCs has rapidly increased from an initial 3.8% to over 26.4%, almost on par with traditional silicon-based solar cells. This remarkable progress is attributed to the unique physicochemical properties of perovskite materials, such as broad-spectrum absorption, long carrier diffusion length, and low manufacturing cost, making them a key candidate for future solar energy technologies.

[0004] However, despite the remarkable achievements of perovskite saturated carbon (PSCs) in photoelectric conversion efficiency, they still face numerous challenges in practical applications, particularly the lack of long-term stability. Studies have shown that PSCs exhibit significant performance degradation under extreme conditions such as high temperature, light, and humidity, with moisture having the most severe impact. Specifically, water molecules can form hydrogen bonds with non-coordinated iodine atoms on the perovskite surface, promoting non-radiative recombination processes and thus reducing the cell's photoelectric conversion efficiency. Furthermore, water molecules can penetrate the surface and boundaries, infiltrating into the perovskite lattice to form hydrated substances such as MAPbI3·H2O and MAPbI3·2H2O. These intermediate products not only weaken the interaction between organic cations and the inorganic framework but may also lead to the degradation and disintegration of the perovskite structure. In addition, moisture can trigger the protonation reaction of iodides, generating volatile halide acids, further exacerbating material corrosion and degradation. Of particular note is that wide-bandgap perovskite materials, such as CsPbI3, are extremely sensitive to moisture; even under low humidity conditions, a black-to-yellow phase transition may occur, severely affecting cell performance.

[0005] Therefore, how to effectively prevent moisture from corroding perovskite materials and improve the long-term stability of PSCs has become the focus and challenge of current research. Summary of the Invention

[0006] In view of the problems existing in the prior art, the purpose of this invention is to provide a functional layer for improving the stability of perovskite thin films, a method for its preparation, and its applications. The functional layer includes a novel covalent organic framework material (COFs). These COFs materials have structures that can form fine micro / nanoscale pores, possessing not only high surface area but also stable nonpolar vinyl bonds. In this COF material, azazine units with fully exposed lone pairs of electrons provide strong hydrogen bond accepting sites within one-dimensional channels, giving the COF material excellent water absorption properties. Functional layers containing this COF material can significantly reduce the erosion of perovskite thin films by moisture, greatly improving the stability of perovskite devices.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a functional layer for improving the stability of perovskite thin films, the functional layer being disposed on at least one side of the perovskite thin film, the functional layer comprising a COFs material having a unit cell structure as shown in Formula I:

[0009]

[0010] Among them, X1, X2, X3 and X4 are each independently selected from N or CH, and at least one of them is N;

[0011] R is selected from any one of hydrogen, methyl, ethyl, hydroxyl, methoxy, or halogen; n is 1, 2, or 3;

[0012] The dashed line indicates the connection point with another unit structure.

[0013] This invention provides a novel covalent organic framework (COF) material. These COF materials possess finely customized micro / nanoscale pore sizes, high surface area, and stable nonpolar vinyl bonds. The one-dimensional channels in this COF material have strong hydrogen bond accepting sites derived from modified azazine units with fully exposed lone pairs of electrons, giving the prepared COF material excellent water absorption properties. The introduction of a functional layer containing this COF material can significantly reduce the erosion of the perovskite layer by moisture, greatly improving the stability of perovskite solar cells.

[0014] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following technical solutions.

[0015] In Formula I, at least one of X1, X2, X3 and X4 is N, where the number of N can be 1, 2, 3 or 4.

[0016] As a preferred embodiment of the present invention, the functional layer comprises a COFs material having the following unit structure:

[0017]

[0018]

[0019]

[0020] As a preferred embodiment of the present invention, the functional layer is disposed on the surface of the perovskite film to directly contact the perovskite film.

[0021] The main function of the COFs material of this invention is to prevent water from intruding into the perovskite film. Therefore, it can only be disposed on one side of the perovskite film in the form of a functional layer. However, it is not necessarily limited to being disposed on the side of the perovskite film near the electron transport layer. It can also be disposed on the side of the perovskite film near the hole transport layer, either selectively or simultaneously. However, it cannot be directly mixed into the perovskite layer. Preferably, it is in direct contact with the perovskite film, that is, there are no other layer structures between it and the perovskite film. This is because the COFs material contains some groups that are beneficial to passivation, which can achieve perovskite passivation and help to further improve performance.

[0022] As a preferred technical solution of the present invention, the thickness of the functional layer is 20 to 100 nm, such as 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm or 100 nm, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0023] In a second aspect, a method for preparing a functional layer for improving the stability of perovskite thin films as described in the first aspect involves preparing a COFs material having a unit structure as shown in Formula I as a coating solution, and then sequentially coating and annealing it to obtain the functional layer.

[0024] As a preferred embodiment of the present invention, the solvent in the coating solution includes any one of isopropanol, ethanol, butanol, methanol, or acetone.

[0025] As a preferred technical solution of the present invention, the concentration of the coating solution is 1 to 5 mg / mL, such as 1 mg / mL, 1.5 mg / mL, 2 mg / mL, 2.5 mg / mL, 3 mg / mL, 3.5 mg / mL, 4 mg / mL, 4.5 mg / mL or 5 mg / mL, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0026] As a preferred technical solution of the present invention, the coating method includes spin coating; the spin coating speed is 3000-5000 rpm, such as 3000 rpm, 3300 rpm, 3500 rpm, 3800 rpm, 4000 rpm, 4300 rpm, 4500 rpm, 4800 rpm or 5000 rpm, etc., and the time is 20-40 s, such as 20 s, 23 s, 25 s, 28 s, 30 s, 33 s, 35 s, 38 s or 40 s, etc., but is not limited to the listed values, and other unlisted values ​​within the above range are also applicable.

[0027] As a preferred technical solution of the present invention, the annealing temperature is 60-100℃, such as 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃ or 100℃, and the time is 5-8min, such as 5min, 5.5min, 6min, 6.5min, 7min, 7.5min or 8min, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0028] As a preferred embodiment of the present invention, the method for preparing the COFs material having the unit structure shown in Formula I includes:

[0029] The raw material compound III, raw material compound II, benzoic acid and benzoic anhydride are mixed and subjected to a Knoevenagel condensation reaction to generate a COFs material with the unit structure shown in Formula I.

[0030]

[0031] Among them, X1, X2, X3 and X4 are each independently selected from N or CH, and at least one of them is N;

[0032] R is selected from any one of hydrogen, methyl, ethyl, hydroxyl, methoxy, or halogen; n is an integer between 1 and 3;

[0033] The dashed line indicates the connection point with another unit structure.

[0034] As a preferred embodiment of the present invention, the raw material compound III comprises a compound having the following structure:

[0035]

[0036] That is, compound IIIa is 3,6-dimethyl-1,2,4,5-tetraazine; compound IIIb is 3,6-dimethyl-1,2,4-triazine; compound IIIc is 3,6-dimethylpyridazine; compound IIId is 2,5-dimethylpyrazine; compound IIIe is 2,5-dimethylpyrimidine; and compound IIIf is 2,5-dimethylpyridine.

[0037] As a preferred embodiment of the present invention, the raw material compound II comprises a compound having the following structure:

[0038]

[0039] That is, compound IIa is 1,3,5-benzanthraldehyde (TB); compound IIb is 2-hydroxy-1,3,5-benzanthraldehyde; compound IIc is trialdehyde-resorcinol; compound IId is 2,4,6-trichloro-1,3,5-benzanthraldehyde; and compound IIe is 1,3,5-trimethoxy-2,4,6-tricarboxymethylbenzene.

[0040] As a preferred technical solution of the present invention, the molar ratio of the raw material compound III to the raw material compound II is (1-2):1, for example 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1 or 2:1, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0041] As a preferred technical solution of the present invention, the molar ratio of the benzoic anhydride to the raw material compound II is (1-3):1, for example 1:1, 1.3:1, 1.5:1, 1.8:1, 2:1, 2.2:1, 2.4:1, 2.6:1 or 3:1, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0042] As a preferred technical solution of the present invention, with the amount of the raw material compound II being 1 mmol, the amount of benzoic acid is 0.5 to 3 mL, for example, 0.5 mL, 0.8 mL, 1 mL, 1.3 mL, 1.5 mL, 1.8 mL, 2 mL, 2.2 mL, 2.5 mL, 2.8 mL or 3 mL, etc., but not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0043] As a preferred technical solution of the present invention, the mixture is subjected to a freeze-thaw cycle before the Knoevenagel condensation reaction begins.

[0044] As a preferred technical solution of the present invention, the temperature of the Knoevenagel condensation reaction is 180-220°C, such as 180°C, 185°C, 190°C, 195°C, 200°C, 205°C, 210°C, 215°C, or 220°C, and the time is 96-144h, such as 96h, 100h, 104h, 108h, 112h, 116h, 120h, 124h, 128h, 132h, 136h, 140h, or 144h, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0045] As a preferred technical solution of the present invention, after the Knoevenagel condensation reaction is completed, the reactants are purified.

[0046] As a preferred embodiment of the present invention, the purification process includes first soaking the obtained reactants in a first mixed solution consisting of methanol and 1 mol / L NaOH aqueous solution in a volume ratio of 1:(0.5-2), such as 1:0.5, 1:0.8, 1:1, 1:1.3, 1:1.5, 1:1.8, or 1:2, for 60-80 hours, such as 60 hours, 65 hours, 70 hours, 75 hours, or 810 hours. Then, the reactants are purified sequentially with water, methanol, and dichloromethane, and finally purified with a second mixed solution consisting of methanol and acetone. Soxhlet extraction is performed for 48–96 hours, for example, 48 hours, 56 hours, 64 hours, 72 hours, 80 hours, 88 hours, or 96 hours. The deep yellow solid is collected and dried at 50–70°C, for example, 50°C, 55°C, 60°C, 65°C, or 70°C, for 6–18 hours, for example, 6 hours, 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, or 18 hours, to obtain the COFs material having the unit structure shown in Formula I. However, it is not limited to the values ​​listed, and other unlisted values ​​within the above range are also applicable.

[0047] Thirdly, the present invention provides a perovskite device, wherein the perovskite device contains the functional layer for improving the stability of the perovskite thin film as described in the first aspect, or contains the functional layer for improving the stability of the perovskite thin film obtained by the preparation method described in the second aspect.

[0048] Apart from the functional layer that enhances the stability of the perovskite thin film, this invention does not specifically limit the type of perovskite device or its other film layers or film layer structures, film layer materials, specifications (such as layer thickness), and preparation methods. These should be reasonably adjusted and selected according to actual design and needs. The following is an exemplary solution for a perovskite solar cell.

[0049] As a preferred embodiment of the present invention, the perovskite device includes a perovskite solar cell.

[0050] Preferably, when the perovskite solar cell has a nip structure, the nip structure includes a conductive substrate, an electron transport layer, a perovskite thin film, a functional layer for improving the stability of the perovskite thin film, a hole transport layer, and a back electrode stacked sequentially; or, the nip structure includes a conductive substrate, an electron transport layer, a functional layer for improving the stability of the perovskite thin film, a perovskite thin film, a hole transport layer, and a back electrode stacked sequentially; or, the nip structure includes a conductive substrate, an electron transport layer, a functional layer for improving the stability of the perovskite thin film, a perovskite thin film, a functional layer for improving the stability of the perovskite thin film, a hole transport layer, and a back electrode stacked sequentially.

[0051] Preferably, when the perovskite solar cell has a pin structure, the pin structure includes a conductive substrate, a hole transport layer, a perovskite thin film, a functional layer for improving the stability of the perovskite thin film, an electron transport layer, and a back electrode stacked sequentially; or, the pin structure includes a conductive substrate, a hole transport layer, a functional layer for improving the stability of the perovskite thin film, a perovskite thin film, an electron transport layer, and a back electrode stacked sequentially; or, the pin structure includes a conductive substrate, a hole transport layer, a functional layer for improving the stability of the perovskite thin film, a perovskite thin film, a functional layer for improving the stability of the perovskite thin film, an electron transport layer, and a back electrode stacked sequentially.

[0052] Preferably, the conductive substrate includes at least one of ITO, FTO, or AZO.

[0053] Preferably, the material of the hole transport layer includes poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene (Spiro-OMeTAD), poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), 4-butyl-N,N-diphenylaniline homopolymer (Ploy-TPD), polyvinylcarbazole (PVK), NiO x At least one of CuI, CuSCN, (2-(9H-carbazole-9-yl)ethyl)phosphonic acid (2PACz) and its derivatives is obtained.

[0054] Preferably, the perovskite material of the perovskite thin film has the general formula ABX3, where A is CH3NH3. + CH(NH2)2 + Cs + or Rb + At least one of them; B is Pb 2+ Sn 2+ Or Ge 2+ At least one of them, X is Cl -,Br - Or I - At least one of them.

[0055] Preferably, the thickness of the perovskite thin film is 300–700 nm, such as 300 nm, 330 nm, 350 nm, 380 nm, 400 nm, 430 nm, 450 nm, 480 nm, 500 nm, 530 nm, 550 nm, 580 nm, 600 nm, 630 nm, 650 nm, 680 nm, or 700 nm, but is not limited to the listed values; other unlisted values ​​within the above range are also applicable.

[0056] Preferably, the material of the electron transport layer includes C. 60 At least one of PCBM, BCP, TiO2, SnO2, ZnO, or ZnO-ZnS.

[0057] Preferably, the material of the back electrode includes at least one of common metal electrodes such as Au, Ag, Al, or carbon electrodes.

[0058] Preferably, the method for manufacturing the perovskite solar cell includes:

[0059] S1. Prepare a hole transport layer on a conductive substrate;

[0060] S2. Prepare a perovskite precursor solution, coat it onto the hole transport layer and heat it for annealing to generate a perovskite film.

[0061] S3. Spin-coating the perovskite film to prepare the functional layer that enhances the stability of the perovskite film;

[0062] S4. An electron transport layer is formed based on the above functions;

[0063] S5. Finally, prepare the back electrode.

[0064] Preferably, in step S2, the solvent of the perovskite precursor solution includes at least one of N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), γ-butyrolactone (GBL), 1,3-dimethyl-2-imidazolinone (DMI), dimethylacetamide (DMAC), N,N-dimethylpropenylurea (DMPU), acetonitrile (ACN), or 2-mercaptoethanol (ME).

[0065] Compared with existing technical solutions, the present invention has at least the following beneficial effects:

[0066] This invention provides a novel covalent organic framework (COF) material. These COF materials possess finely customized micro / nanoscale pore sizes, high surface area, and stable nonpolar vinyl bonds. The one-dimensional channels in this COF material have strong hydrogen bond accepting sites derived from modified azazine units with fully exposed lone pairs of electrons, giving the prepared COF material excellent water absorption properties. The introduction of a functional layer containing this COF material can significantly reduce the erosion of the perovskite layer by moisture, greatly improving the stability of perovskite solar cells. Attached Figure Description

[0067] Figure 1 The JV curves are shown for the perovskite solar cell with the functional layer of Example 1 in Application Example 1 and the perovskite solar cell without the functional layer in Comparative Example 2.

[0068] Figure 2 This is a comparison chart of the stability of perovskite solar cells in Application Example 1 containing functional layers from Examples 1, 9, and 10, and the perovskite solar cell without functional layers in Comparative Example 2. Detailed Implementation

[0069] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0070] Those skilled in the art will understand that the embodiments described are merely illustrative of the invention and should not be construed as limiting the invention.

[0071] Example 1

[0072] This embodiment provides a functional layer for improving the stability of perovskite thin films. The functional layer is disposed on one side surface of the perovskite thin film and has a thickness of 60 nm. The functional layer is composed of COFs material with a unit structure shown in Formula Ia (dashed lines indicate connection sites with another unit structure). Formula Ia is:

[0073]

[0074] The method for preparing the functional layer that enhances the stability of perovskite thin films includes:

[0075] (1) Preparation of the COFs material having the unit structure shown in Formula I:

[0076] Specifically, a mixture of 0.3 mmol of 3,6-dimethyl-1,2,4,5-tetraazine (reagent compound IIIa), 0.2 mmol of 1,3,5-benzyltrialdehyde (reagent compound IIa), and benzoic anhydride (0.4 mmol) was added to 1 mL of benzoic acid in a 5 mL Pyrex heat-resistant glass tube. After a freeze-pump-thaw cycle, the heat-resistant glass tube was sealed. The heat-resistant glass tube was placed in a muffle furnace and stored at 200 °C for 5 days to carry out the Knoevenagel condensation reaction. The resulting reactants were soaked in a first mixed solution of 1 mol / L NaOH aqueous solution and methanol (v / v, 1 / 1) for 72 h, then purified sequentially with water, methanol, and dichloromethane, and then subjected to Soxhlet extraction for 3 days with a second mixed solution of methanol and acetone. The deep yellow solid was collected and dried overnight at 60 °C to obtain COFs materials with the unit structure shown in Formula Ia.

[0077]

[0078] (2) The COFs material with the unit structure shown in Formula Ia is prepared with the solvent isopropanol to form a coating solution with a concentration of 3 mg / mL. The solution is spin-coated at a speed of 4000 rpm for 30 s and then annealed at 80 °C for 6 min to obtain the functional layer.

[0079] Example 2

[0080] This embodiment provides a functional layer for improving the stability of perovskite thin films. The functional layer is composed of COFs material with a unit structure shown in Formula Ib (dashed lines indicate connection sites with another unit structure). Formula Ib is:

[0081]

[0082] That is, in step 1 of the method for preparing the functional layer that improves the stability of the perovskite thin film, 3,6-dimethyl-1,2,4,5-tetraazine (raw material compound IIIa) is replaced with 3,6-dimethyl-1,2,4-triazine (raw material compound IIIb).

[0083] Apart from the above, all other conditions are exactly the same as in Example 1.

[0084] Example 3

[0085] This embodiment provides a functional layer for improving the stability of perovskite thin films. The functional layer is composed of COFs material with a unit structure shown in Formula Ic (dashed lines indicate connection sites with another unit structure). Formula Ic is:

[0086]

[0087] That is, in step 1 of the method for preparing the functional layer that improves the stability of the perovskite thin film, 3,6-dimethyl-1,2,4,5-tetraazine (raw material compound IIIa) is replaced with 3,6-dimethylpyridazine (raw material compound IIIc).

[0088] Apart from the above, all other conditions are exactly the same as in Example 1.

[0089] Example 4

[0090] This embodiment provides a functional layer for improving the stability of perovskite thin films. The functional layer is composed of COFs material with a unit structure shown in Formula Id (dashed lines indicate connection sites with another unit structure). Formula Id is:

[0091]

[0092] That is, in step 1 of the method for preparing the functional layer that improves the stability of the perovskite thin film, 3,6-dimethyl-1,2,4,5-tetraazine (raw material compound IIIa) is replaced with 2,5-dimethylpyrazine (raw material compound IIId).

[0093] Apart from the above, all other conditions are exactly the same as in Example 1.

[0094] Example 5

[0095] This embodiment provides a functional layer for improving the stability of perovskite thin films. The functional layer is composed of COFs material with a unit structure shown in Formula Ie (dashed lines indicate connection sites with another unit structure), where Formula Ie is:

[0096]

[0097] That is, in step 1 of the method for preparing the functional layer that improves the stability of the perovskite thin film, 3,6-dimethyl-1,2,4,5-tetraazine (raw material compound IIIa) is replaced with 2,5-dimethylpyrimidine (raw material compound IIIe).

[0098] Apart from the above, all other conditions are exactly the same as in Example 1.

[0099] Example 6

[0100] This embodiment provides a functional layer for improving the stability of perovskite thin films. The functional layer is composed of COFs material with a unit structure shown in Formula If (dashed lines indicate connection sites with another unit structure), where Formula If is:

[0101]

[0102] That is, in step 1 of the method for preparing the functional layer that improves the stability of the perovskite film, 3,6-dimethyl-1,2,4,5-tetraazine (raw material compound IIIa) is replaced with 2,5-dimethylpyridine (raw material compound IIIf).

[0103] Apart from the above, all other conditions are exactly the same as in Example 1.

[0104] Example 7

[0105] This embodiment provides a functional layer to improve the stability of perovskite thin films, wherein the thickness of the functional layer is adjusted from 60 nm to 20 nm.

[0106] That is, in step 2 of the method for preparing the functional layer that enhances the stability of the perovskite film, the concentration of the coating solution is adjusted from 3 mg / mL to 1 mg / mL, and the spin coating speed is adjusted from 4000 rpm to 4500 rpm.

[0107] Apart from the above, all other conditions are exactly the same as in Example 1.

[0108] Example 8

[0109] This embodiment provides a functional layer to improve the stability of perovskite thin films, wherein the thickness of the functional layer is adjusted from 60 nm to 100 nm.

[0110] That is, in step 2 of the method for preparing the functional layer that enhances the stability of the perovskite film, the concentration of the coating solution is adjusted from 3 mg / mL to 5 mg / mL, and the spin coating speed is adjusted from 4000 rpm to 3500 rpm.

[0111] Apart from the above, all other conditions are exactly the same as in Example 1.

[0112] Example 9

[0113] This embodiment provides a functional layer to improve the stability of perovskite thin films, wherein the thickness of the functional layer is adjusted from 60 nm to 10 nm.

[0114] That is, in step 2 of the method for preparing the functional layer that improves the stability of the perovskite film, the concentration of the coating solution is adjusted from 3 mg / mL to 0.5 mg / mL, and the spin coating speed is adjusted from 4000 rpm to 5000 rpm;

[0115] Apart from the above, all other conditions are exactly the same as in Example 1.

[0116] Example 10

[0117] This embodiment provides a functional layer to improve the stability of perovskite thin films, wherein the thickness of the functional layer is adjusted from 60 nm to 120 nm.

[0118] That is, in step 2 of the method for preparing the functional layer that enhances the stability of the perovskite film, the concentration of the coating solution is adjusted from 3 mg / mL to 7 mg / mL, and the spin coating speed is adjusted from 4000 rpm to 3000 rpm.

[0119] Apart from the above, all other conditions are exactly the same as in Example 1.

[0120] Example 11

[0121] This embodiment provides a functional layer for improving the stability of perovskite thin films. The functional layer is composed of COFs material with a unit structure shown in Formula Ig (dashed lines indicate connection sites with another unit structure). Formula Ig is:

[0122]

[0123] That is, in step 1 of the method for preparing the functional layer that improves the stability of the perovskite thin film, 3,6-dimethyl-1,2,4,5-tetraazine (raw material compound IIIa) is replaced with 3,6-dimethylpyridazine (raw material compound IIIc); and 1,3,5-benzyltrialdehyde (raw material compound IIa) is replaced with trialdehyde-resorcinol (raw material compound IIc).

[0124] Apart from the above, all other conditions are exactly the same as in Example 1.

[0125] Example 12

[0126] This embodiment provides a functional layer for improving the stability of perovskite thin films. The functional layer is composed of COFs material with a unit structure shown in Formula Ih (dashed lines indicate connection sites with another unit structure), where Formula Ih is:

[0127]

[0128] That is, in step 1 of the method for preparing the functional layer that enhances the stability of the perovskite thin film, 3,6-dimethyl-1,2,4,5-tetraazine (raw material compound IIIa) is replaced with 3,6-dimethyl-1,2,4-triazine (raw material compound IIIb); and 1,3,5-benzyltrialdehyde (raw material compound IIa) is replaced with 2,4,6-trichloro-1,3,5-benzyltricarboxaldehyde (raw material compound IId).

[0129] Apart from the above, all other conditions are exactly the same as in Example 1.

[0130] Example 13

[0131] This embodiment provides a functional layer for improving the stability of perovskite thin films. The functional layer is composed of COFs material with a unit structure shown in Formula Ii (dashed lines indicate connection sites with another unit structure), where Formula Ii is:

[0132]

[0133] That is, in step 1 of the method for preparing the functional layer that enhances the stability of the perovskite thin film, 3,6-dimethyl-1,2,4,5-tetraazine (raw material compound IIIa) is replaced with 2,5-dimethylpyridine (raw material compound IIIf); and 1,3,5-benzyltrialdehyde (raw material compound IIa) is replaced with 1,3,5-trimethoxy-2,4,6-tricarboxyphenyl (raw material compound IIe).

[0134] Apart from the above, all other conditions are exactly the same as in Example 1.

[0135] Comparative Example 1

[0136] Comparative Example 1 provides a COFs material thin film layer, wherein the COFs material has a unit cell structure as shown in the following formula (dashed lines indicate connection sites with another unit cell structure), which is:

[0137]

[0138] That is, in step 1 of the method for preparing the functional layer that improves the stability of the perovskite thin film, 3,6-dimethyl-1,2,4,5-tetraazine (raw material compound IIIa) is replaced with p-xylene (CAS#:106-42-3);

[0139] Apart from the above, all other conditions are exactly the same as in Example 1.

[0140] Application Example 1

[0141] This application example provides a perovskite solar cell, comprising a conductive substrate, a hole transport layer, a perovskite thin film, a functional layer for improving the stability of the perovskite thin film, an electron transport layer, and a back electrode stacked sequentially.

[0142] The manufacturing method of the perovskite solar cell is as follows:

[0143] S1. Clean the transparent conductive glass, specifically by ultrasonic cleaning with detergent, deionized water, acetone and anhydrous ethanol respectively, and then drying it with a nitrogen gun; wherein, the ultrasonic cleaning power is 100Hz and the ultrasonic cleaning time is 15min.

[0144] A hole transport layer solution with a concentration of 0.5 mg / mL, prepared from [2-(3,6-dimethoxy-9H-carbazole-9-yl)ethyl]phosphonic acid (meo-2PACz), was dropwise added to the transparent conductive glass and spin-coated at 3000 rpm for 30 s. The solution was then annealed at 100 °C for 10 min to obtain a hole transport layer with a thickness of approximately 2 nm on the surface of the transparent conductive glass.

[0145] S2. 108.33 mg CsI, 1218.34 mg FAI, 132.50 mg MAI, 4033.76 mg PbI2, and 83.27 mg MACl were added to a vial containing 4200 μL DMF and 840 μL LDMSO, and stirred thoroughly for at least 12 hours. The final perovskite concentration was 1.67 mol / L. 0.05 MA 0.1 FA 0.85 PbI3 perovskite precursor solution;

[0146] The perovskite precursor solution was spin-coated onto the hole transport layer at 5000 rpm for 50 s with an acceleration of 1000 rpm. At the 35th second, 200 μL of chlorobenzene was added dropwise. Finally, the mixture was annealed at 120 °C for 15 min to crystallize and form a Cs layer with a thickness of approximately 450 nm. 0.05 MA 0.1 FA 0.85 PbI3 perovskite light-absorbing layer;

[0147] S3. Prepare (set) the functional layers for improving the stability of perovskite thin films as described in Examples 1-10 on the perovskite light-absorbing layer;

[0148] S4. An electron transport layer C is deposited on the surface of the functional layer by vacuum evaporation. 60 The evaporation is carried out under a vacuum of 5×10⁻⁶. -4 The process was carried out under Pa conditions, with an evaporation rate of 0.15 A / s and a thickness of approximately 20 nm.

[0149] In electron transport layer C 60 An electron transport layer (BCP) is then deposited on the surface using a vacuum evaporation method, wherein the evaporation is performed at a vacuum degree of 5 × 10⁻⁶. -4 The process was carried out under Pa conditions, with an evaporation rate of 0.2 A / s and a thickness of approximately 8 nm.

[0150] S5. In a metal evaporation chamber, a 90 nm thick silver electrode is formed on the surface of the electron transport layer BCP using a PVD thermal evaporation process to serve as the back electrode (cathode); wherein the vacuum degree of the evaporation chamber is 5 × 10⁻⁶. -4 Pa, evaporation rate is 2A / s.

[0151] Application Comparative Example 1

[0152] This application example provides a perovskite solar cell, comprising a conductive substrate, a hole transport layer, a perovskite thin film, a COFs material thin film layer, an electron transport layer, and a back electrode stacked sequentially.

[0153] That is, in step S3 of the method for manufacturing perovskite solar cells, a COFs material thin film layer of Comparative Example 1 is prepared (set) on the perovskite light-absorbing layer as a functional layer.

[0154] Apart from the above, all other conditions are exactly the same as in Application Example 1.

[0155] Application Comparative Example 2

[0156] This application example provides a perovskite solar cell, comprising a conductive substrate, a hole transport layer, a perovskite thin film, an electron transport layer, and a back electrode stacked sequentially.

[0157] That is, the manufacturing method of the perovskite solar cell skips step S3 and directly proceeds to step S4 to directly prepare an electron transport layer on the perovskite light-absorbing layer.

[0158] Apart from the above, all other conditions are exactly the same as in Application Example 1.

[0159] The perovskite solar cells obtained in corresponding use case 1 and application comparison examples 1 and 2 were tested, and the results are shown in Table 1.

[0160] Table 1

[0161]

[0162]

[0163] As can be seen from Table 1:

[0164] Figure 1 The table shows the JV curves of the perovskite solar cell with the functional layer of Example 1 in Application Example 1 and the perovskite solar cell without the functional layer in Comparative Example 2. As can be seen from Table 1, the perovskite solar cell formed by introducing the functional layer for improving the stability of the perovskite thin film described in this invention has significantly improved open-circuit voltage, short-circuit current, fill factor and photoelectric conversion efficiency.

[0165] When the upper functional layer is too thin (Example 9), the number of hydrogen bond accepting sites in the one-dimensional channels of the COFs material decreases, leading to a weakening of the COFs material's water absorption capacity and a reduction in battery stability. Furthermore, the reduction in nitrogen-containing functional groups also affects Pb... 2+ The passivation effect of defects will also be weakened, resulting in poor film quality and reduced battery efficiency; when the thickness of the above-mentioned functional layer is too thick (Example 8), it may hinder carrier transport and thus affect battery efficiency.

[0166] Figure 2This is a stability comparison chart of the perovskite solar cells in Application Example 1 containing the functional layers of Examples 1, 9, and 10, and the perovskite solar cell without a functional layer in Comparative Example 2. The results show that the perovskite solar cell treated with the functional layer formed by the COFs material described in this invention retains more than 90% of its initial stability after 1000 hours, while the solar cell without a functional layer degrades faster. This is mainly because the one-dimensional channels in the COFs material have strong hydrogen bond accepting sites. These sites originate from modified azazine units with fully exposed lone pairs of electrons, giving the prepared COFs material excellent water absorption properties and improving cell stability.

[0167] As can be seen from the above, by using the COFs material with finely formed micro / nano-scale pores, the present invention not only possesses a high surface area but also stable nonpolar vinyl bonds. Furthermore, the azazine units with fully exposed lone pairs in the COFs material provide strong hydrogen bond accepting sites within the one-dimensional channels, giving the COFs material excellent water absorption properties. The functional layer containing this COFs material can significantly reduce the erosion of perovskite films by moisture, greatly improving the stability of perovskite devices.

[0168] The present invention illustrates the process flow through the above embodiments, but the present invention is not limited to the detailed process flow described above, that is, it does not mean that the present invention must rely on the detailed process flow described above to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0169] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0170] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0171] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A functional layer for improving the stability of perovskite thin films, characterized in that, The functional layer is disposed on at least one side of the perovskite thin film, and the functional layer comprises a COFs material having a unit structure shown in Formula I: Among them, X1, X2, X3 and X4 are each independently selected from N or CH, and at least one of them is N; R is selected from any one of hydrogen, methyl, ethyl, hydroxyl, methoxy, or halogen; n is an integer between 1 and 3; The dashed line indicates the connection point with another unit structure.

2. The functional layer for improving the stability of perovskite thin films according to claim 1, characterized in that, The functional layer comprises COFs materials having the following unit structure:

3. The functional layer for improving the stability of perovskite thin films according to claim 1, characterized in that, The functional layer is disposed on the surface of the perovskite film to be in direct contact with the perovskite film.

4. The functional layer for improving the stability of perovskite thin films according to claim 1, characterized in that, The thickness of the functional layer is 20–100 nm.

5. A method for preparing a functional layer for improving the stability of perovskite thin films according to any one of claims 1-4, characterized in that, A COFs material with the unit structure shown in Formula I is prepared as a coating solution, and then coated and annealed sequentially to obtain the functional layer.

6. The method for preparing the functional layer for improving the stability of perovskite thin films according to claim 5, characterized in that, The solvent in the coating solution includes any one of isopropanol, ethanol, butanol, methanol, or acetone; the concentration of the coating solution is 1–5 mg / mL; the coating method includes spin coating; the spin coating speed is 3000–5000 rpm and the time is 20–40 s; the annealing temperature is 60–100 °C and the time is 5–8 min.

7. The method for preparing the functional layer for improving the stability of perovskite thin films according to claim 5, characterized in that, The method for preparing the COFs material having the unit structure shown in Formula I includes: The raw material compound III, raw material compound II, benzoic acid and benzoic anhydride are mixed and subjected to a Knoevenagel condensation reaction to generate a COFs material with the unit structure shown in Formula I. Among them, X1, X2, X3 and X4 are each independently selected from N or CH, and at least one of them is N; R is selected from any one of hydrogen, methyl, ethyl, hydroxyl, methoxy, or halogen; n is an integer between 1 and 3; The dashed line indicates the connection point with another unit structure.

8. The method for preparing the functional layer for improving the stability of perovskite thin films according to claim 7, characterized in that, The raw material compound III includes compounds having the following structures: The raw material compound II includes compounds having the following structure: The molar ratio of raw material compound III to raw material compound II is (1-2):1; The molar ratio of the benzoic anhydride to the raw material compound II is (1-3):1; Based on the amount of raw material compound II being 1 mmol, the amount of benzoic acid being used is 0.5 to 3 mL.

9. The method for preparing the functional layer for improving the stability of perovskite thin films according to claim 7, characterized in that, Before the Knoevenagel condensation reaction begins, the mixture is subjected to a freeze-thaw cycle. The Knoevenagel condensation reaction was carried out at a temperature of 180–220 °C for 96–144 h. After the Knoevenagel condensation reaction is completed, the reactants are purified. The purification process involves first soaking the obtained reactants in a first mixed solution consisting of methanol and 1 mol / L NaOH aqueous solution at a volume ratio of 1:(0.5-2) for 60-80 h, then purifying them sequentially with water, methanol, and dichloromethane, followed by Soxhlet extraction with a second mixed solution consisting of methanol and acetone for 48-96 h, collecting the deep yellow solid, and drying it at 50-70 °C for 6-18 h to obtain the COFs material having the unit structure shown in Formula I.

10. A perovskite device, characterized in that, The perovskite device contains the functional layer for improving the stability of the perovskite thin film as described in claims 1-4, or contains the functional layer for improving the stability of the perovskite thin film obtained by the preparation method described in claims 5-9. The perovskite device includes a perovskite solar cell; The perovskite solar cell has a nip structure, which includes a conductive substrate, an electron transport layer, a perovskite thin film, a functional layer for improving the stability of the perovskite thin film, a hole transport layer, and a back electrode stacked sequentially; or, the nip structure includes a conductive substrate, an electron transport layer, a functional layer for improving the stability of the perovskite thin film, a perovskite thin film, a hole transport layer, and a back electrode stacked sequentially; or, the nip structure includes a conductive substrate, an electron transport layer, a functional layer for improving the stability of the perovskite thin film, a perovskite thin film, a functional layer for improving the stability of the perovskite thin film, a hole transport layer, and a back electrode stacked sequentially. The perovskite solar cell has a pin structure, which includes a conductive substrate, a hole transport layer, a perovskite thin film, a functional layer for improving the stability of the perovskite thin film, an electron transport layer, and a back electrode stacked sequentially; or, the pin structure includes a conductive substrate, a hole transport layer, a functional layer for improving the stability of the perovskite thin film, a perovskite thin film, an electron transport layer, and a back electrode stacked sequentially; or, the pin structure includes a conductive substrate, a hole transport layer, a functional layer for improving the stability of the perovskite thin film, a perovskite thin film, a functional layer for improving the stability of the perovskite thin film, an electron transport layer, and a back electrode stacked sequentially.

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