An electron transport layer, a preparation method therefor and use thereof

Abstract

The application provides an electron transport layer, a preparation method and application thereof, and the electron transport layer is prepared by a chemical bath deposition method, the preparation method does not perform an aging step, and the preparation method comprises the following steps: 1) mixing a binder, an electron transport layer precursor and a solvent to obtain a mother liquor of the electron transport layer, wherein the binder comprises a thiol-containing acid and urea; 2) diluting the mother liquor in step 1) to obtain a mother liquor diluent; immersing a substrate in the mother liquor diluent and heating, and then taking out and drying to obtain the electron transport layer. The electron transport layer with high quality and high density and uniformity is prepared by the improved chemical bath deposition method, the preparation process does not need to be aged, the charge transport capacity of the electron transport layer is improved, and the power conversion efficiency of the battery is improved. On this basis, an ionic liquid is introduced to perform interface modification, the charge extraction rate of the electron transport layer is improved, the recombination loss is reduced, and then the short-circuit current density and the power conversion efficiency of the battery are improved.

Description

Technical Field

[0001] This invention belongs to the field of solar cell technology, specifically relating to an electron transport layer, its preparation method, and its application. Background Technology

[0002] Perovskite solar cells use perovskite halides as the photosensitive material, offering advantages such as low production cost and high photovoltaic conversion efficiency, making them more commercially competitive than the currently leading crystalline silicon material. To increase the migration ability of photogenerated carriers in perovskite, transport layers are typically added above and below the perovskite to accelerate carrier transport. For even higher efficiency, an electron transport layer is currently essential. Its main functions are to extract and collect electrons and suppress carrier recombination. Common electron transport layer materials include TiO2, SnO2, and ZnO. Among them, SnO2 is a good transparent conductive material with good stability. Through continuous development, its properties have been utilized in perovskite solar cells, and today's high-efficiency cells mostly use SnO2 as the electron transport layer. SnO2 thin films are typically prepared using solution methods, chemical bath deposition, and atomic layer deposition. Compared to spin coating, chemical bath deposition is simpler, produces more uniform films, and the prepared SnO2 electron transport layer has lower series resistance loss.

[0003] However, in traditional methods, the mother liquor needs to be aged for 2-10 days, which greatly reduces the overall efficiency of the process and limits the further application of chemical bath deposition to some extent. In addition, the instability caused by the ambient temperature and aging time in the aging step is another shortcoming of this process. Although chemical bath deposition can prepare dense SnO2 electron transport layers, the SnO2 films prepared by existing chemical bath deposition processes still have unavoidable defects, which to some extent limits charge transport.

[0004] Therefore, how to improve the chemical bath deposition method for preparing high-quality electron transport layers and increase the charge transport rate of electron transport layers is an urgent problem to be solved. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide an electron transport layer, its preparation method, and its applications. This invention prepares an electron transport layer using a chemical bath deposition method. By adjusting the amount of thiol-containing acid and diluting the mother liquor, the process time is shortened, eliminating the need for aging, resulting in a dense, uniform, high-quality electron transport layer film. Furthermore, this method improves the charge transport capability of the electron transport layer, thereby increasing the efficiency of perovskite solar cells prepared based on it. In addition, introducing an ionic liquid interface to modify the chemically deposited electron transport layer not only improves the charge extraction rate of the electron transport layer but also reduces charge recombination losses, thereby increasing the short-circuit current density and power conversion efficiency of the perovskite solar cell.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing an electron transport layer, wherein the electron transport layer is prepared by chemical bath deposition, the preparation method does not involve an aging step, and the preparation method includes the following steps:

[0008] (1) The binder, the electron transport layer precursor and the solvent are mixed to obtain the mother liquor of the electron transport layer. The binder includes a mercapto-containing acid and urea. The amount of the mercapto-containing acid added is 50-200 μL / 100 mL of solvent, such as 50 μL / 100 mL solvent, 75 μL / 100 mL solvent, 100 μL / 100 mL solvent, 125 μL / 100 mL solvent, 150 μL / 100 mL solvent, 175 μL / 100 mL solvent or 200 μL / 100 mL solvent, etc.

[0009] (2) The mother liquor from step (1) is diluted to obtain a diluted mother liquor solution. The substrate is immersed in the diluted mother liquor solution and heated, then removed and dried to obtain an electron transport layer. In this invention, the addition of a binder to the mother liquor can promote the bonding between the electron transport layer and the substrate. The amount of thiol-containing acid added is adjusted to 50-200 μL / 100 mL of solvent, which helps the growth of the electron transport layer and improves its charge transport capability. Furthermore, diluting the mother liquor can slow down the rate of electron transport layer formation, thereby avoiding particle agglomeration and obtaining a thin, dense, and uniform electron transport layer.

[0010] In this invention, a high-quality electron transport layer is prepared by using an improved chemical bath deposition method. This method eliminates the need for aging, shortens the process time, and produces a dense and uniform electron transport layer that improves the charge transport rate. As a result, the efficiency of perovskite solar cells prepared based on this method is significantly improved.

[0011] In this invention, when the amount of thiol-containing acid added is less than 50 μL / 100 mL of solvent, the hydrolysis rate of stannous chloride will be accelerated, resulting in insufficient bonding between stannous chloride and the substrate, which will cause tin dioxide agglomeration and result in poor quality of the electron transport layer. When the amount of thiol-containing acid added is 200 μL / 100 mL of solvent, the excessive amount of thiol-containing acid will cause the hydrolysis rate of stannous chloride to be too slow, resulting in too thin a deposit of tin dioxide, which will cause leakage current in the device.

[0012] In this invention, the heating has a drying effect, and the drying is generally carried out by heating. The heating and the drying are generally two different steps.

[0013] In this invention, the electron transport layer covers the substrate.

[0014] Preferably, the thiol-containing acid in step (1) includes thioglycolic acid.

[0015] Preferably, the urea content in step (1) is 1-1.5g / 100mL solvent, such as 1g / 100mL solvent, 1.1g / 100mL solvent, 1.2g / 100mL solvent, 1.3g / 100mL solvent, 1.4g / 100mL solvent or 1.5g / 100mL solvent, etc.

[0016] Preferably, the electron transport layer precursor in step (1) includes any one or a combination of at least two of stannous chloride dihydrate, stannous tetrachloride pentahydrate, or tin powder, with stannous chloride dihydrate being the most preferred.

[0017] In this invention, compared to stannous chloride, stannous tetrachloride hydrolyzes too violently and requires a large amount of deionized water for dilution, while the tin in stannous chloride is divalent, and the hydrolysis process is mild and easy to control.

[0018] In this invention, the divalent Sn ions in stannous chloride dihydrate are oxidized to tetravalent Sn ions by the solution, and then further hydrolyzed to tin dioxide. Preferably, the concentration of the electron transport layer precursor in step (1) is 0.25-0.3 g / 100 mL solvent, such as 0.25 g / 100 mL solvent, 0.26 g / 100 mL solvent, 0.27 g / 100 mL solvent, 0.28 g / 100 mL solvent, 0.29 g / 100 mL solvent, or 0.3 g / 100 mL solvent, etc.

[0019] Preferably, the solvent in step (1) is water, such as deionized water or distilled water.

[0020] Preferably, the raw materials used in the mixing in step (1) further include a stabilizer, which includes hydrochloric acid.

[0021] In this invention, the hydrochloric acid can be concentrated hydrochloric acid, and the concentration of concentrated hydrochloric acid is generally 36-38%.

[0022] In this invention, hydrochloric acid of a certain concentration is used as a stabilizer to regulate the hydrolysis reaction.

[0023] Preferably, the amount of stabilizer added is 1-1.5 mL / 100 mL solvent, such as 1 mL / 100 mL solvent, 1.1 mL / 100 mL solvent, 1.2 mL / 100 mL solvent, 1.3 mL / 100 mL solvent, 1.4 mL / 100 mL solvent, or 1.5 mL / 100 mL solvent, etc.

[0024] Preferably, the diluent used in step (2) is water.

[0025] Preferably, in the dilution process described in step (2), the volume ratio of the mother liquor to the diluent is 1:(1-8), such as 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7 or 1:8, etc.

[0026] In this invention, if the volume ratio of mother liquor to diluent is too small during the dilution process, i.e., too much diluent, the concentration of stannous chloride will be too low, resulting in insufficient tin dioxide obtained from hydrolysis. Consequently, the prepared electron transport layer will not be dense. On the other hand, if the volume ratio of mother liquor to diluent is too large, there will be too little diluent, which will lead to agglomeration in the solution, producing large particles and affecting the quality of the electron transport layer.

[0027] Preferably, the heating temperature in step (2) is 60-90℃, such as 60℃, 70℃, 80℃ or 90℃, and the heating time is 2-8h, such as 2h, 3h, 4h, 5h, 6h, 7h or 8h.

[0028] In this invention, the solution in which the substrate is immersed is heated at a constant temperature. If the heating time is less than 2 hours, the reaction time will be insufficient and the tin dioxide layer formed will be too thin. If the heating temperature is higher than 8 hours, the tin dioxide layer formed will be too thick, leading to charge recombination in the device.

[0029] Preferably, the drying temperature in step (2) is 170-180℃, such as 170℃, 172℃, 174℃, 176℃, 178℃ or 180℃, and the drying time is 0.5-1.5h, such as 0.5h, 1h or 1.5h.

[0030] In a second aspect, the present invention provides an electron transport layer prepared using the preparation method described in the first aspect.

[0031] Preferably, the electron transport layer comprises a tin dioxide electron transport layer.

[0032] Thirdly, the present invention provides a method for interface modification of the electron transport layer described in the second aspect, the method comprising:

[0033] An ionic liquid is coated onto the surface of an electron transport layer, and after annealing, an interface-modified electron transport layer is obtained.

[0034] In this invention, ionic liquids are a class of molten salts that exist in liquid form at room temperature and are among the most promising materials for use as additives in perovskite solar cells. Unlike traditional inorganic salts, ionic liquids contain a large number of anions, which translates into weaker electrostatic attraction, resulting in lower melting points, typically below room temperature. This invention employs ionic liquid interface modification of the electron transport layer deposited in a chemical bath. The introduction of ionic liquids can passivate defects in the electron transport layer, improving the ohmic contact between the electron transport layer and the perovskite, which is beneficial for increasing the electron extraction rate and reducing recombination losses, thereby improving the short-circuit current density and power conversion efficiency of the device.

[0035] Preferably, the ionic liquid includes imidazolium-based ionic liquids.

[0036] Preferably, the cation of the solute in the ionic liquid is 1-benzyl-3-methylimidazole.

[0037] Preferably, the anion of the solute in the ionic liquid includes any one or a combination of at least two of chloride ions, bromide ions, tetrafluoroborate ions, hexafluorophosphate ions, or bis(trifluoromethanesulfonyl)imide ions, preferably 1-benzyl-3-methylimidazole chloride.

[0038] In this invention, the benzyl group of the imidazolium ionic liquid's cation plays a special role in the interface modification process; the benzene ring in the benzyl group can enhance the stability and conductivity of the ionic liquid. Preferably, the solvent of the ionic liquid includes any one or a combination of at least two of isopropanol, ethanol, or methanol.

[0039] Preferably, the concentration of the ionic liquid is 0.5-6 mg / mL, such as 0.5 mg / mL, 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, 5 mg / mL, 5.5 mg / mL, or 6 mg / mL.

[0040] In this invention, if the concentration of the ionic liquid used for interface modification is too high, the ionic liquid layer will be too thick, affecting charge transport. If the concentration of the ionic liquid is too low, the substrate surface will not be fully covered, and the charge transport effect will be weakened.

[0041] Preferably, the coating method includes spin coating.

[0042] Preferably, the spin coating rate is 2000-4000 rpm, such as 2000 rpm, 2500 rpm, 3000 rpm, 3500 rpm, or 4000 rpm.

[0043] In this invention, the spin coating speed affects the thickness of the ionic liquid and thus the performance of the device. When the spin coating speed is too low, the resulting ionic liquid layer is too thick, which reduces the charge transport rate. When the spin coating speed is too high, the resulting ionic liquid layer is too thin, resulting in poor interface modification.

[0044] Preferably, the spin coating time is 20-50s, such as 20s, 25s, 30s, 35s, 40s, 45s or 50s.

[0045] Preferably, the annealing temperature is 70-150℃, such as 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃ or 150℃.

[0046] Preferably, the annealing time is 10-60 minutes, such as 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, or 60 minutes.

[0047] In this invention, if the annealing time after coating with ionic liquid is longer than 60 minutes, it will affect the properties of the ionic liquid; while if the annealing time is less than 10 minutes, the solvent will not evaporate sufficiently due to the short time, which will affect the quality of the perovskite.

[0048] As a preferred technical solution, the method includes the following steps:

[0049] (1) An electron transport layer is prepared by chemical bath deposition, including the following steps:

[0050] (a) The binder, stabilizer, electron transport layer precursor and water are mixed to obtain the mother liquor of the electron transport layer;

[0051] (b) Dilute the mother liquor of the electron transport layer to obtain a diluted mother liquor solution with a dilution ratio of 1:(1-8); immerse the substrate in the diluted mother liquor solution and heat it at 60-90℃ for 2-8 hours, then remove it and dry it at 170-180℃ for 0.5-1.5 hours to obtain the electron transport layer.

[0052] (2) Imidazolium-based ionic liquids are spin-coated onto the surface of the electron transport layer at a speed of 2000-4000 rpm for 20-50 s, and then annealed at 70-150℃ for 10-60 min to obtain the interface-modified electron transport layer.

[0053] Fourthly, the present invention provides an interface-modified electron transport layer prepared by the method described in the third aspect, wherein the interface-modified electron transport layer comprises an electron transport layer and an interface modification layer.

[0054] Preferably, the thickness of the interface modification layer is 2-10nm, such as 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm or 10nm.

[0055] Fifthly, the present invention provides a perovskite solar cell, the perovskite solar cell comprising an electron transport layer as described in the second aspect or an interface-modified electron transport layer as described in the fourth aspect.

[0056] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0057] Compared with the prior art, the present invention has the following beneficial effects:

[0058] (1) The present invention prepares a high-quality electron transport layer by an improved chemical bath deposition method. The preparation process does not require aging, which shortens the process time. In addition, the prepared electron transport layer film is dense and uniform, and its charge transport capability is improved. Based on this, the efficiency of the perovskite solar cell is improved.

[0059] (2) Introducing an ionic liquid interface to modify the electron transport layer deposited in the chemical bath not only improves the charge extraction rate of the electron transport layer, but also reduces the loss of charge recombination, thereby improving the short-circuit current density and power conversion efficiency of perovskite solar cells. Attached Figure Description

[0060] Figure 1 This is a schematic diagram of a perovskite solar cell in a specific embodiment of the present invention.

[0061] Figure 2 This is a schematic diagram of the structure of a perovskite solar cell after interface modification in a specific embodiment of the present invention.

[0062] Among them, 1-FTO conductive glass; 2-electron transport layer; 3-perovskite layer; 4-hole transport layer; 5-metal electrode; 6-interface modification layer. Detailed Implementation

[0063] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0064] Example 1

[0065] This embodiment provides a method for fabricating an electron transport layer, the method comprising the following steps:

[0066] (1) The FTO glass was cleaned for 25 minutes each in an ultrasonic cleaner using detergent, deionized water, acetone, and ethanol. The specific cleaning process was as follows: the surface of the FTO glass substrate was wiped with a damp, lint-free cloth dipped in detergent, rinsed with deionized water, and then ultrasonically cleaned with deionized water, acetone, and ethanol for 25 minutes each time; the FTO glass was then dried with a dry nitrogen stream.

[0067] (2) Add 1.25g urea, 1.25mL hydrochloric acid (37wt%), 50μL mercaptoacetic acid, and 275mg stannous chloride dihydrate sequentially to 100mL of deionized water, and shake to dissolve evenly to obtain a chemical bath stock solution. Dilute the stock solution with deionized water at a ratio of 1:5 to obtain a mother liquor.

[0068] (3) After cleaning the FTO substrate in step (1) for 30 minutes, it was placed in the mother liquor and then heated in a constant temperature heating box at 90°C for 3 hours. The substrate glass was then ultrasonically cleaned with water and isopropanol for 5 minutes each. The substrate was then dried with a nitrogen gun and annealed at a constant temperature of 180°C for 1 hour to obtain the tin dioxide electron transport layer.

[0069] Example 2

[0070] This embodiment provides a method for fabricating an electron transport layer, the method comprising the following steps:

[0071] (1) The FTO glass was cleaned for 20 minutes each in an ultrasonic cleaner using detergent, deionized water, acetone, and ethanol. The specific cleaning process was as follows: the surface of the FTO glass substrate was wiped with a damp, lint-free cloth dipped in detergent, rinsed with deionized water, and then ultrasonically cleaned with deionized water, acetone, and ethanol for 20 minutes each time; the FTO glass was then dried with a dry nitrogen stream.

[0072] (2) Add 1g of urea, 1mL of hydrochloric acid (37wt%), 125μL of mercaptoacetic acid, and 250mg of stannous chloride dihydrate sequentially to 100mL of deionized water, and shake to dissolve evenly to obtain a chemical bath stock solution. Dilute the stock solution with deionized water at a ratio of 1:1 to obtain a mother liquor.

[0073] (3) After cleaning the FTO substrate in step (1) for 25 minutes, it was placed in the mother liquor and then heated in a 75°C constant temperature heating box for 5 hours. The substrate glass was then ultrasonically cleaned with water and isopropanol for 5 minutes each. The substrate was then dried with a nitrogen gun and annealed at a 175°C hot stage for 0.5 hours to obtain the tin dioxide electron transport layer.

[0074] Example 3

[0075] This embodiment provides a method for fabricating an electron transport layer, the method comprising the following steps:

[0076] (1) The FTO glass was cleaned for 30 minutes each in an ultrasonic cleaner using detergent, deionized water, acetone, and ethanol. The specific cleaning process was as follows: the surface of the FTO glass substrate was wiped with a damp, lint-free cloth dipped in detergent, rinsed with deionized water, and then ultrasonically cleaned with deionized water, acetone, and ethanol for 30 minutes each time; the FTO glass was then dried with a dry nitrogen stream.

[0077] (2) Add 1.5g urea, 1.5mL hydrochloric acid (37wt%), 200μL mercaptoacetic acid, and 300mg stannous chloride dihydrate sequentially to 100mL of deionized water, and shake to dissolve evenly to obtain a chemical bath stock solution. Dilute the stock solution with deionized water at a ratio of 1:8 to obtain a mother liquor.

[0078] (3) After cleaning the FTO substrate in step (1) for 20 minutes, it was placed in the mother liquor and then heated in a constant temperature heating box at 60°C for 8 hours. The substrate glass was then ultrasonically cleaned with water and isopropanol for 5 minutes each. The substrate was then dried with a nitrogen gun and annealed at 170°C for 1.5 hours to obtain the tin dioxide electron transport layer.

[0079] Example 4

[0080] This embodiment provides a method for fabricating an electron transport layer, the method comprising the following steps:

[0081] (1) The FTO glass was cleaned for 25 minutes each in an ultrasonic cleaner using detergent, deionized water, acetone, and ethanol. The specific cleaning process was as follows: the surface of the FTO glass substrate was wiped with a damp, lint-free cloth dipped in detergent, rinsed with deionized water, and then ultrasonically cleaned with deionized water, acetone, and ethanol for 25 minutes each time; the FTO glass was then dried with a dry nitrogen stream.

[0082] (2) Add 1.25g urea, 1.25mL hydrochloric acid (37wt%), 75μL mercaptoacetic acid, and 275mg stannous chloride dihydrate sequentially to 100mL of deionized water, and shake to dissolve evenly to obtain a chemical bath stock solution. Dilute the stock solution with deionized water at a ratio of 1:3 to obtain a mother liquor.

[0083] (3) After cleaning the FTO substrate in step (1) for 30 minutes, it was placed in the mother liquor and then heated in a constant temperature heating box at 90°C for 3.5 hours. The substrate glass was then ultrasonically cleaned with water and isopropanol for 5 minutes each. The substrate was then dried with a nitrogen gun and annealed at a constant temperature of 180°C for 1 hour to obtain the tin dioxide electron transport layer.

[0084] Example 5

[0085] This embodiment provides a method for fabricating an electron transport layer, the method comprising the following steps:

[0086] (1) The FTO glass was cleaned for 25 minutes each in an ultrasonic cleaner using detergent, deionized water, acetone, and ethanol. The specific cleaning process was as follows: the surface of the FTO glass substrate was wiped with a damp, lint-free cloth dipped in detergent, rinsed with deionized water, and then ultrasonically cleaned with deionized water, acetone, and ethanol for 25 minutes each time; the FTO glass was then dried with a dry nitrogen stream.

[0087] (2) Add 1.25g urea, 1.25mL hydrochloric acid (37wt%), 150μL mercaptoacetic acid, and 275mg stannous chloride dihydrate sequentially to 100mL of deionized water, and shake to dissolve evenly to obtain a chemical bath stock solution. Dilute the stock solution with deionized water at a ratio of 1:3 to obtain a mother liquor.

[0088] (3) After cleaning the FTO substrate in step (1) for 30 minutes, it was placed in the mother liquor and then heated in a constant temperature heating box at 90°C for 3.5 hours. The substrate glass was then ultrasonically cleaned with water and isopropanol for 5 minutes each. The substrate was then dried with a nitrogen gun and annealed at a constant temperature of 180°C for 1 hour to obtain the tin dioxide electron transport layer.

[0089] Example 6

[0090] The difference between this embodiment and embodiment 1 is that in step (2), the mother liquor is diluted with deionized water at a ratio of 1:0.5 to obtain the mother liquor.

[0091] The remaining preparation methods and parameters are consistent with those in Example 1.

[0092] Example 7

[0093] The difference between this embodiment and embodiment 1 is that in step (2), the mother liquor is diluted with deionized water at a ratio of 1:9 to obtain the mother liquor.

[0094] The remaining preparation methods and parameters are consistent with those in Example 1.

[0095] Example 8

[0096] The difference between this embodiment and embodiment 1 is that the constant temperature heating time in step (3) is 1 hour.

[0097] The remaining preparation methods and parameters are consistent with those in Example 1.

[0098] Example 9

[0099] The difference between this embodiment and embodiment 1 is that the constant temperature heating time in step (3) is 9 hours.

[0100] The remaining preparation methods and parameters are consistent with those in Example 1.

[0101] Example 10

[0102] This embodiment provides a method for preparing an interface-modified electron transport layer, which differs from Embodiment 1 in that the following step (4) is performed after step (3):

[0103] (4) Dissolve 1-benzyl-3-methylimidazolium chloride in isopropanol and stir until homogeneous to obtain an ionic liquid with a concentration of 1 mg / mL. Drop 200 μL of the ionic liquid onto the surface of a substrate with a tin dioxide electron transport layer, then rotate the sample at 3000 rpm for 30 seconds, followed by thermal annealing at 80 °C for 10 minutes to form a 6 nm thick interface modification layer.

[0104] Example 11

[0105] This embodiment provides a method for preparing an interface-modified electron transport layer, which differs from Embodiment 6 in step (4), specifically:

[0106] (4) Dissolve 1-benzyl-3-methylimidazolium chloride in isopropanol and stir until homogeneous to obtain an ionic liquid with a concentration of 3 mg / mL. Drop 200 μL of the ionic liquid onto the surface of a substrate with a tin dioxide electron transport layer, then rotate the sample at 2000 rpm for 20 seconds, followed by thermal annealing at 100 °C for 20 minutes to form a 10 nm thick interface modification layer.

[0107] Example 12

[0108] This embodiment provides a method for preparing an interface-modified electron transport layer, which differs from Embodiment 6 in step (4), specifically:

[0109] (4) Dissolve 1-benzyl-3-methylimidazolium chloride in isopropanol and stir until homogeneous to obtain an ionic liquid with a concentration of 6 mg / mL. Drop 200 μL of the ionic liquid onto the surface of a substrate with a tin dioxide electron transport layer, then rotate the sample at 4000 rpm for 40 seconds, followed by thermal annealing at 70 °C for 60 minutes to form a 2 nm thick interface modification layer.

[0110] Example 13

[0111] This embodiment provides a method for preparing an interface-modified electron transport layer, which differs from Embodiment 1 in that the following step (4) is performed after step (3):

[0112] (4) Dissolve 1-benzyl-3-methylimidazolium bromide in ethanol and stir until homogeneous to obtain an ionic liquid with a concentration of 0.5 mg / mL. Drop 200 μL of the ionic liquid onto the surface of a substrate with a tin dioxide electron transport layer, then rotate the sample at 3500 rpm for 50 seconds, followed by thermal annealing at 120 °C for 30 minutes to form a 4 nm thick interface modification layer.

[0113] Example 14

[0114] This embodiment provides a method for preparing an interface-modified electron transport layer, which differs from Embodiment 1 in that the following step (4) is performed after step (3):

[0115] (4) Dissolve 1-benzyl-3-methylimidazolium hexafluorophosphate in methanol and stir until homogeneous to obtain an ionic liquid with a concentration of 5 mg / mL. Drop 200 μL of the ionic liquid onto the surface of a substrate with a tin dioxide electron transport layer, then rotate the sample at 2500 rpm for 30 seconds, followed by thermal annealing at 150 °C for 10 minutes to form an 8 nm thick interface modification layer.

[0116] Example 15

[0117] The difference between this embodiment and embodiment 10 is that the concentration of the ionic liquid in step (4) is 0.3 mg / mL.

[0118] The remaining preparation methods and parameters are consistent with those in Example 10.

[0119] Example 16

[0120] The difference between this embodiment and embodiment 10 is that the concentration of the ionic liquid in step (4) is 7 mg / mL.

[0121] The remaining preparation methods and parameters are consistent with those in Example 10.

[0122] Example 17

[0123] The difference between this embodiment and embodiment 10 is that the heat annealing time in step (4) is 5 minutes.

[0124] The remaining preparation methods and parameters are consistent with those in Example 10.

[0125] Example 18

[0126] The difference between this embodiment and embodiment 10 is that the heat annealing time in step (4) is 35 minutes.

[0127] The remaining preparation methods and parameters are consistent with those in Example 10.

[0128] Example 19

[0129] The difference between this embodiment and Embodiment 10 is that the sample is rotated at 1000 rpm for 30 seconds.

[0130] Example 20

[0131] The difference between this embodiment and Embodiment 10 is that the sample is rotated at 6000 rpm for 30 seconds.

[0132] Application Example 1

[0133] This application example provides a method for fabricating a perovskite solar cell. Based on Example 1, the method further includes the following steps:

[0134] (A) Accurately weigh 5.37 mg methyl bromide, 17.61 mg lead bromide, 714.55 mg lead iodide, 33.76 mg chloromethylamine, and 266.67 mg formamidinium iodide into a small glass bottle, add 1 mL of a mixed solvent of N,N dimethylformamide and dimethyl sulfoxide with a volume ratio of 8:1, and shake overnight to completely dissolve.

[0135] (B) Filter the perovskite precursor solution. Then, place the glass substrate with the SnO2 layer prepared in step (3) onto the adsorption rubber ring of the spin coater. Turn on the vacuum pump, take 100 μL of the precursor solution and drop it onto the center of the substrate, evenly spreading the perovskite across the entire substrate surface. The substrate coated with the perovskite precursor is rotated at 1000 rpm and 5000 rpm for 10 s and 30 s respectively. At the 30th second of the spin coating process, use a 1 mL pipette to take 300 μL of ethyl acetate and evenly drop it onto the high-speed rotating substrate surface, obtaining a uniformly bright yellow transparent perovskite film. The substrate is then transferred to a heating stage at 120°C and annealed for 30 minutes. The substrate is then stored in a glass petri dish to cool.

[0136] (C) Weigh 73 mg of 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)hydro]-9,9'-spirobisulfonate (Spiro-OMeTAD) powder into a clean glass bottle, add 1 mL of chlorobenzene, then add 18 μL of prepared lithium bis(trifluoromethanesulfonyl)imide (Li-TFSI) solution (520 mg Li-TFSI dissolved in 1 mL acetonitrile), 29 μL of prepared FK209 solution (300 mg FK209 dissolved in 1 mL acetonitrile), and 30 μL of 4-tert-butylpyridine. After adding the reagents, place the bottle on a shaker and shake for 1 h to ensure complete dissolution. For spin coating, take out 30 μL of the dissolved Spiro-OMeTAD solution and gently drop it onto the perovskite film surface cooled to room temperature in step (5). The substrate rotation speed is 3000 rpm, and the time is 30 s.

[0137] (D) Scrape off the electrode portions at both ends of the substrate and transfer the substrate onto the mask of the coating machine. Place the mask carrying the substrate into the chamber, close the chamber door, and wait for the vacuum level inside the chamber to drop to 5 × 10⁻⁶. -4 Evaporation begins below Pa, with An Au electrode was deposited at an evaporation rate of 80 nm, with an effective area of ​​0.1 cm². 2 .

[0138] Figure 1 The perovskite solar cell fabricated in this application example is shown. The perovskite solar cell includes FTO conductive glass, an electron transport layer, a perovskite layer, a hole transport layer, and a metal electrode stacked sequentially. It can be seen that the electron transport layer is located between the FTO conductive glass and the perovskite layer.

[0139] Application Example 2

[0140] This application example provides a method for preparing a perovskite solar cell, which is based on Example 2, and further includes steps (A) to (D) as described in Application Example 1.

[0141] Application Example 3

[0142] This application example provides a method for preparing a perovskite solar cell, which is based on Example 3, and further includes steps (A) to (D) as described in Application Example 1.

[0143] Application Example 4

[0144] This application example provides a method for preparing a perovskite solar cell, which is based on Example 4, and further includes steps (A) to (D) as described in Application Example 1.

[0145] Application Example 5

[0146] This application example provides a method for preparing a perovskite solar cell, which is based on Example 5, and further includes steps (A) to (D) as described in Application Example 1.

[0147] Application Example 6

[0148] This application example provides a method for preparing a perovskite solar cell, which is based on Example 6, and further includes steps (A) to (D) as described in Application Example 1.

[0149] Application Example 7

[0150] This application example provides a method for preparing a perovskite solar cell, which is based on Example 7, and further includes steps (A) to (D) as described in Application Example 1.

[0151] Application Example 8

[0152] This application example provides a method for preparing a perovskite solar cell, which is based on Example 8, and further includes steps (A) to (D) as described in Application Example 1.

[0153] Application Example 9

[0154] This application example provides a method for preparing a perovskite solar cell, which is based on Example 9, and further includes steps (A) to (D) as described in Application Example 1.

[0155] Application Example 10

[0156] This application example provides a method for preparing a perovskite solar cell, which is based on Example 10, and further includes steps (A) to (D) as described in Application Example 1.

[0157] Figure 2 The diagram shows the layer structure of the perovskite solar cell prepared in this application example, including FTO conductive glass, electron transport layer, interface modification layer, perovskite layer, hole transport layer and metal electrode stacked in sequence. It can be seen that the interface modification layer is located between the electron transport layer and the perovskite layer, and plays the role of a bridge for electron transport.

[0158] Application Example 11

[0159] This application example provides a method for preparing a perovskite solar cell, which is based on Example 11, and further includes steps (A) to (D) as described in Application Example 1.

[0160] Application Example 12

[0161] This application example provides a method for preparing a perovskite solar cell, which is based on Example 12, and further includes steps (A) to (D) as described in Application Example 1.

[0162] Application Example 13

[0163] This application example provides a method for preparing a perovskite solar cell, which is based on Example 13, and further includes steps (A) to (D) as described in Application Example 1.

[0164] Application Example 14

[0165] This application example provides a method for preparing a perovskite solar cell, which is based on Example 14, and further includes steps (A) to (D) as described in Application Example 1.

[0166] Application Example 15

[0167] This application example provides a method for preparing a perovskite solar cell, which is based on Example 15, and further includes steps (A) to (D) as described in Application Example 1.

[0168] Application Example 16

[0169] This application example provides a method for preparing a perovskite solar cell, which is based on Example 16, and further includes steps (A) to (D) as described in Application Example 1.

[0170] Application Example 17

[0171] This application example provides a method for preparing a perovskite solar cell, which is based on Example 17, and further includes steps (A) to (D) as described in Application Example 1.

[0172] Application Example 18

[0173] This application example provides a method for preparing a perovskite solar cell, which is based on Example 18, and further includes steps (A) to (D) as described in Application Example 1.

[0174] Application Example 19

[0175] This application example provides a method for preparing a perovskite solar cell, which is based on Example 19, and further includes steps (A) to (D) as described in Application Example 1.

[0176] Application Example 20

[0177] This application example provides a method for preparing a perovskite solar cell, which is based on Example 20, and further includes steps (A) to (D) as described in Application Example 1.

[0178] Application Example 21

[0179] The difference between this application example and application example 10 is that the effective area of ​​the battery is 1 cm². 2 .

[0180] The remaining preparation methods and parameters are consistent with those in Application Example 10.

[0181] Application Comparative Example 1

[0182] The difference between this comparative example and application example 1 is that the amount of thioglycolic acid added in step (2) of example 1 is 40 μL.

[0183] The remaining preparation methods and parameters are consistent with those in Application Example 1.

[0184] Application Comparative Example 2

[0185] The difference between this comparative example and application example 1 is that the amount of thioglycolic acid added in step (2) of example 1 is 210 μL.

[0186] The remaining preparation methods and parameters are consistent with those in Application Example 1.

[0187] Application Comparative Example 3

[0188] The difference between this comparative example and application example 1 is that the mother liquor obtained in step (2) of example 1 is not diluted.

[0189] The remaining preparation methods and parameters are consistent with those in Application Example 1.

[0190] Application Comparative Example 4

[0191] The difference between this comparative example and application example 1 is that the mother liquor obtained in step (2) of example 1 was aged for 2 days.

[0192] The remaining preparation methods and parameters are consistent with those in Application Example 1.

[0193] Performance testing

[0194] The perovskite solar cells provided in Application Examples 1-21 and Comparative Examples 1-4 were subjected to JV testing. The test conditions were: solar intensity AM 1.5G, ambient temperature controlled at 25℃±2℃, and humidity 30%-40%. The results are shown in Table 1.

[0195] Table 1

[0196]

[0197]

[0198] analyze:

[0199] A comparison of the data results from Application Example 1 with Application Examples 6 and 7 shows that when the dilution ratio of the mother liquor is too high, the concentration of the mother liquor is too high, and the deposited tin dioxide is too thick, resulting in a lower open-circuit voltage and fill factor of the device. Conversely, when the dilution ratio of the mother liquor is too low, the concentration of the solution is too dilute, the hydrolysis rate of tin dioxide is too low, and the deposited tin dioxide is too thin, leading to leakage current and thus a lower open-circuit voltage of the device.

[0200] A comparison of the data results from Application Example 1 with Application Examples 8 and 9 shows that when the isothermal heating time is too short, the reaction will be insufficient, resulting in an excessively thin tin dioxide layer. This affects the open-circuit voltage and fill factor of the device, thus significantly reducing the device efficiency. Conversely, when the isothermal heating time is too long, the tin dioxide layer will be too thick, leading to severe charge recombination in the device. This results in a significant reduction in the open-circuit voltage and a sharp decrease in the fill factor, affecting the improvement of device efficiency.

[0201] A comparison of the data results from Application Example 1 and Application Example 10 shows that using ionic liquid interface modification of the tin dioxide layer is beneficial to improving the charge transport rate, resulting in a significant increase in the short-circuit current density of the obtained device, as well as improvements in its open-circuit voltage and fill factor. Therefore, ionic liquid interface modification can improve the photoelectric conversion efficiency of the device.

[0202] A comparison of the data results from Application Example 10 with Application Examples 15 and 16 shows that when the concentration of the ionic liquid is too low, it cannot play a role in charge transport and the improvement in short-circuit current density is not significant. When the concentration of the ionic liquid is too high, the resulting ionic liquid layer is too thick, which leads to charge recombination, reduces the device fill factor, and results in no significant improvement in device efficiency.

[0203] A comparison of the data results from Application Example 10 with Application Examples 17 and 18 shows that if the annealing time is too short after ionic liquid coating, the solvent will not evaporate sufficiently, affecting the quality of the interface modification layer and the subsequent spin-coated perovskite layer, resulting in a decrease in open-circuit voltage and device efficiency. On the other hand, if the annealing time is too long, it will affect the properties of the ionic liquid, leading to a significant decrease in the open-circuit voltage and efficiency of the resulting device.

[0204] A comparison of the data results from Application Example 10 with Application Examples 19 and 20 shows that the spin coating speed affects the device performance by influencing the thickness of the ionic liquid. When the speed is too low, the resulting ionic liquid layer is too thick, which reduces the charge transport rate and leads to a decrease in device performance. When the speed is too high, the resulting ionic liquid layer is too thin, making it difficult to exert the effect of interface modification, and therefore has little impact on improving device performance.

[0205] The data from Application Example 1 and Application Example 21 show that the improved process can also have a significant effect when applied to large-area devices.

[0206] A comparison of the data results from Application Example 1 with those from Comparative Examples 1 and 2 shows that the content of mercaptoacetic acid (MGA) is a crucial factor affecting device performance. When the concentration of MGA is too high, it hinders the hydrolysis of stannous chloride, resulting in an insufficiently dense electron transport layer and a lower open-circuit voltage. Conversely, when the concentration of MGA is too low, the hydrolysis rate of stannous chloride is too fast, resulting in an excessively thick electron transport layer, which affects charge transport and significantly reduces the open-circuit voltage and fill factor.

[0207] A comparison of the data results from Application Example 1 and Application Comparative Example 3 shows that the electron transport layer obtained without dilution of the mother liquor is too thick, which reduces the open-circuit voltage and conversion efficiency of the device.

[0208] A comparison of the data results from Application Example 1 and Application Comparison Example 4 shows that although the device performance has been improved, the process is time-consuming and unstable, and is easily affected by the external environment.

[0209] The applicant declares that the present invention is illustrated by the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in 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.

Claims

1. A method of interfacing a modified electron transport layer, characterized by, The method comprises: coating an ionic liquid on the surface of the electron transport layer, and obtaining an interface-modified electron transport layer after annealing; The electron transport layer is prepared by a chemical bath deposition method, the chemical bath deposition method does not perform an aging step, and the chemical bath deposition method comprises the following steps: (1) mixing a binder, an electron transport layer precursor, and a solvent to obtain a mother liquor of the electron transport layer, the binder comprising a thiol-containing acid and urea, and the thiol-containing acid being added in an amount of 50-200 μL / 100 mL of the solvent; (2) diluting the mother liquor of step (1) to obtain a diluted mother liquor, immersing a substrate in the diluted mother liquor and heating, and drying after taking out to obtain the electron transport layer.

2. The method of claim 1, wherein, The thiol-containing acid of step (1) comprises mercaptoacetic acid.

3. The method of claim 1, wherein, The content of the urea of step (1) is 1-1.5 g / 100 mL of the solvent.

4. The method of claim 1, wherein, The electron transport layer precursor of step (1) comprises any one or a combination of at least two of stannous chloride dihydrate, tin tetrachloride pentahydrate, or tin powder.

5. The method of claim 4, wherein, The electron transport layer precursor of step (1) is stannous chloride dihydrate.

6. The method of claim 1, wherein, The concentration of the electron transport layer precursor of step (1) is 0.25-0.3 g / 100 mL of the solvent.

7. The method of claim 1, wherein, The solvent of step (1) is water.

8. The method of claim 1, wherein, The raw materials used in the mixing of step (1) further comprise a stabilizer, and the stabilizer comprises hydrochloric acid.

9. The method of claim 8, wherein, The stabilizer is added in an amount of 1-1.5 mL / 100 mL of the solvent.

10. The method of claim 1, wherein, The diluent used in the dilution of step (2) is water.

11. The method of claim 1, wherein, The volume ratio of the mother liquor to the diluent in the dilution of step (2) is 1:(1-8).

12. The method of claim 1, wherein, The heating temperature of step (2) is 60-90 °C, and the heating time is 2-8 h.

13. The method of claim 1, wherein, The drying temperature of step (2) is 170-180 °C, and the drying time is 0.5-1.5 h.

14. The method of claim 1, wherein, The ionic liquid comprises an imidazolium ionic liquid.

15. The method of claim 1, wherein, The cation of the solute of the ionic liquid is a 1-benzyl-3-methyl imidazolium ion.

16. The method of claim 1, wherein, The anion of the solute of the ionic liquid comprises any one or a combination of at least two of a chloride ion, a bromide ion, a tetrafluoroborate ion, a hexafluorophosphate ion, or a bistrifluoromethanesulfonylimide ion.

17. The method of claim 14, wherein, The ionic liquid is 1-benzyl-3-methyl imidazole chloride.

18. The method of claim 1, wherein, The solvent of the ionic liquid comprises any one or a combination of at least two of isopropyl alcohol, ethanol, or methanol.

19. The method of claim 1, wherein, The concentration of the ionic liquid is 0.5-6 mg / mL.

20. The method of claim 1, wherein, The coating method comprises spin coating.

21. The method of claim 20, wherein, The spin coating rate is 2000-4000 rpm.

22. The method of claim 20, wherein, The spin coating time is 20-50 s.

23. The method of claim 1, wherein, The annealing temperature is 70-150 °C.

24. The method of claim 1, wherein, The annealing time is 10-60 min.

25. The method of claim 1, wherein, The method comprises the following steps: (1) preparing an electron transport layer by a chemical bath deposition method, comprising the following steps: (a) mixing a binder, a stabilizer, an electron transport layer precursor, and water to obtain a mother liquor of the electron transport layer; (b) diluting the mother solution of the electron transport layer to obtain a diluted mother solution, the dilution ratio being 1:(1-8); immersing the substrate in the diluted mother solution and heating at 60-90°C for 2-8h, and drying at 170-180°C for 0.5-1.5h after taking out, to obtain the electron transport layer; (2) spin-coating the imidazolium ionic liquid on the surface of the electron transport layer at a rotation speed of 2000-4000rpm, the spin-coating time being 20-50s, and then annealing at 70-150°C for 10-60min, to obtain the interface-modified electron transport layer.

26. An interfacially modified electron transport layer prepared by the method of any one of claims 1-25, wherein, The interface-modified electron transport layer comprises the electron transport layer and the interface-modified layer. The thickness of the interface-modified layer is 2-10nm.

27. A perovskite solar cell, characterized by, The perovskite solar cell comprises the interface-modified electron transport layer according to claim 26.

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