A method for preparing a perovskite thin film and a perovskite solar cell

Abstract

The application provides a preparation method of a perovskite film, which comprises the following steps: depositing a lead iodide solution on a substrate and then performing primary annealing to obtain a lead iodide film; soaking the lead iodide film in an anti-solvent and then performing secondary annealing to obtain a porous lead iodide film; and reacting the porous lead iodide film with an organic amine salt solution to obtain a perovskite film; and the lead iodide solution contains PMMA (polymethyl methacrylate). The application introduces an organic sacrificial material into the lead iodide layer, prepares a porous lead iodide, provides a channel for the diffusion and reaction of the organic amine salt, and promotes the complete conversion of the lead iodide into the perovskite.

Description

Technical Field

[0001] This invention belongs to the field of solar cell technology, and particularly relates to a method for preparing perovskite thin films and perovskite solar cells. Background Technology

[0002] In recent years, solar cell technology has made great progress. The photoelectric conversion efficiency of perovskite solar cells has now exceeded 25%, comparable to crystalline silicon solar cells. Perovskite solar cells utilize organic-metal halides with a perovskite lattice structure as the light-absorbing layer. This material possesses excellent photoelectric properties such as narrow band gap, strong light absorption, and high carrier mobility. Methods for preparing organic-metal halides typically include solution methods, vapor deposition methods, and liquid / vapor phase hybrid deposition methods. In solution methods, a two-step sequential deposition method can easily achieve the preparation of dense perovskite thin films, laying the foundation for high-performance perovskite solar cells. In the traditional two-step solution method, lead iodide is first deposited on the substrate, and then an organic amine salt solution is deposited on the lead iodide layer, contacting and reacting with the lead iodide to form the perovskite light-absorbing layer. However, the initially deposited lead iodide forms a dense film that cannot fully react with the organic amine salt, resulting in a large amount of residual lead iodide in the film, thus affecting device performance. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a method for preparing perovskite thin films and perovskite solar cells, so as to solve the problem that in the existing two-step perovskite thin film preparation process, the dense lead iodide film cannot react completely with organic amine salts, resulting in excessive lead iodide residue in the final perovskite film.

[0004] This invention provides a method for preparing perovskite thin films, comprising:

[0005] After depositing a lead iodide solution onto a substrate, an annealing process is performed to obtain a lead iodide film.

[0006] The lead iodide film was immersed in an antisolvent and then subjected to secondary annealing to obtain a porous lead iodide film.

[0007] The porous lead iodide film was reacted with an organic amine salt solution to obtain a perovskite film;

[0008] The lead iodide solution contains PMMA (polymethyl methacrylate).

[0009] In embodiments of the present invention, the lead iodide solution may include: lead iodide, PMMA, and a solvent; the concentration of lead iodide in the lead iodide solution may be selected from 0.5 to 1.5 mol / L, such as 0.8 mol / L, 1 mol / L, or 1.2 mol / L; the molar ratio of PMMA to lead iodide may be selected from (0.5% to 10%):1, such as 1%:1, 2%:1, 3%:1, 5%:1, or 8%:1; the solvent may be selected from at least one of DMF (N,N-dimethylformamide), DMSO (dimethyl sulfoxide), NMP (N-methylpyrrolidone), and GBL (γ-butyrolactone).

[0010] In embodiments of the present invention, the lead iodide solution deposition method can be selected from one or more of spin coating, blade coating, and coating, such as spin coating. The spin coating speed can be selected from 4500 to 5500 rpm, such as 4800 rpm, 5000 rpm, and 5200 rpm; the spin coating time can be selected from 20 to 40 s, such as 25 s, 30 s, and 35 s; and the deposition thickness can be selected from 200 to 500 nm, such as 300 nm and 400 nm.

[0011] In embodiments of the present invention, the substrate may include:

[0012] Substrate;

[0013] A SnO2 layer is disposed on the surface of the substrate.

[0014] In embodiments of the present invention, the substrate may be selected from transparent conductive glass, such as FTO or ITO; the substrate may be treated before the SnO2 layer is prepared; the treatment may include washing, drying and ultraviolet-ozone treatment; washing may be performed sequentially with acetone, isopropanol and water, and the water may be selected from deionized water; drying may be performed by blowing; the ultraviolet-ozone treatment time may be selected from 10 to 30 minutes, such as 15 minutes, 20 minutes and 25 minutes.

[0015] In embodiments of the present invention, the thickness of the SnO2 layer can be selected from 15 to 25 nm, such as 18 nm, 20 nm, or 22 nm; the method for preparing the SnO2 layer may include:

[0016] The SnO2 solution was spin-coated and then annealed to obtain a SnO2 layer.

[0017] In embodiments of the present invention, the SnO2 solution comprises SnO2 product and water. The SnO2 product may be selected from commercially available products, such as SnO2 dispersion; the water may be selected from deionized water; the volume ratio of SnO2 product to water may be selected from 1:(3-5), such as 1:4; the spin coating speed may be selected from 3500-4500 rpm, such as 3800 rpm, 4000 rpm, or 4200 rpm; the spin coating time may be selected from 15-25 s, such as 18 s, 20 s, or 22 s; the annealing temperature may be selected from 160-200℃, such as 170℃, 180℃, or 190℃; and the annealing time may be selected from 20-40 min, such as 25 min, 30 min, or 35 min.

[0018] In embodiments of the present invention, the temperature of a single annealing can be selected from 50 to 100°C, such as 60°C, 70°C, 80°C, or 90°C; the time of a single annealing can be selected from 30 to 300 seconds, such as 60 seconds, 120 seconds, 180 seconds, or 240 seconds.

[0019] In embodiments of the present invention, the thickness of the lead iodide film can be selected from 300 to 400 nm, such as 320 nm, 340 nm, 360 nm, and 380 nm.

[0020] In embodiments of the present invention, the antisolvent may be selected from at least one of chloroform, chlorobenzene, toluene, and dichloroethane.

[0021] In embodiments of the present invention, the soaking time can be selected from 30 to 300 seconds, such as 60 seconds, 120 seconds, 180 seconds, and 240 seconds.

[0022] In embodiments of the present invention, the temperature of the secondary annealing can be selected from 50 to 100°C, such as 60°C, 70°C, or 80°C; the time of the secondary annealing can be selected from 1 to 5 minutes, such as 2 minutes, 3 minutes, or 4 minutes.

[0023] In embodiments of the present invention, the organic amine salt solution may include: a solute and a solvent; the solute may be selected from at least one of formamidinium hydroiodate, formamidinium hydrobromide, methylamine hydroiodate, and methylamine hydrobromide; the solvent may be selected from isopropanol; the concentration of the solute in the organic amine salt solution may be selected from 60 to 100 mg / mL, such as 70 mg / mL, 80 mg / mL, or 90 mg / mL. In embodiments of the present invention, the organic amine salt solution may further include: an additive; the additive may be selected from methylamine chloride; the concentration of the additive in the organic amine salt solution may be selected from 5 to 15 mg / mL, such as 8 mg / mL, 9 mg / mL, or 12 mg / mL.

[0024] In embodiments of the present invention, the reaction method may include:

[0025] An organic amine salt solution was deposited on a porous lead iodide film and then annealed three times to obtain a perovskite film.

[0026] In embodiments of the present invention, the method for depositing organic amine salt solution can be selected from one or more of spin coating, blade coating, and coating; for example, it can be selected from spin coating, the spin coating speed can be selected from 2000 to 3000 rpm, such as 2500 rpm; the spin coating time can be selected from 20 to 40 s, such as 25 s, 30 s, 35 s.

[0027] In embodiments of the present invention, the volume ratio of lead iodide solution to organic amine salt solution can be selected from (0.5-1.5):1, such as (0.8-1.2):1, 1:1.

[0028] In embodiments of the present invention, the temperature of the three annealing processes can be selected from 100 to 150°C, such as 110°C, 120°C, 130°C, and 140°C; the time of the three annealing processes can be selected from 5 to 15 minutes, such as 8 minutes, 10 minutes, and 12 minutes.

[0029] In embodiments of the present invention, the thickness of the perovskite thin film can be selected from 350 to 450 nm, such as 380 nm, 400 nm, and 420 nm.

[0030] This invention provides a perovskite solar cell, comprising: a perovskite thin film;

[0031] The perovskite film is the perovskite film prepared by the method described in the above technical solution.

[0032] In embodiments of the present invention, the perovskite solar cell further includes:

[0033] Hole transport layer disposed on the surface of perovskite thin film;

[0034] Electrodes are placed on the surface of the coating.

[0035] In embodiments of the present invention, the thickness of the hole transport layer can be selected from 150 to 250 nm, such as 180 nm, 200 nm, or 220 nm; the method for preparing the hole transport layer may include:

[0036] Hole transport layer solution was spin-coated onto the surface of a perovskite thin film to prepare a hole transport layer.

[0037] In embodiments of the present invention, the hole transport layer solution comprises: a first solution and a second solution; the solute in the first solution comprises: Spiro-OMeTAD and 4-tert-butylpyridine; the ratio of Spiro-OMeTAD to 4-tert-butylpyridine can be selected from (65-75) mg:(35-45) μL, such as (68-73) mg:(38-42) μL, 72 mg:39 μL; the solvent in the first solution may include chlorobenzene; the ratio of Spiro-OMeTAD to chlorobenzene can be selected from (65-75) mg:1 mL, such as 68 mg:1 mL, 70 mg:1 mL, 72 mg:1 mL; the second solution is selected from bis(trifluoromethane). The concentration of the lithium sulfonylimide acetonitrile solution and the lithium bis(trifluoromethanesulfonylimide) acetonitrile solution can be selected from 500 to 550 mg / mL, such as 510 mg / mL, 520 mg / mL, 530 mg / mL, and 540 mg / mL; the volume ratio of Spiro-OMeTAD to the second solution can be selected from (65 to 75) mg: (20 to 25) μL, such as (68 to 73) mg: (22 to 24) μL, and 73 mg: 23 μL; the spin coating speed can be selected from 2500 to 3500 rpm, such as 2800 rpm, 300 rpm, and 3200 rpm; and the spin coating time can be selected from 25 to 35 s, such as 28 s, 30 s, and 32 s.

[0038] In embodiments of the present invention, the electrode can be selected from silver electrodes, and the electrode thickness can be selected from 60-80 nm, such as 65 nm, 70 nm, or 75 nm; the electrode can be prepared on the surface of the hole transport layer by vacuum evaporation; the vacuum degree of vacuum evaporation can be lower than 10. -4 Pa, the deposition rate can be selected from like

[0039] To address the problem of incomplete reaction between lead iodide at the bottom and organic amine salts, this invention introduces organic sacrificial materials into the lead iodide layer to prepare porous lead iodide, providing channels for the diffusion and reaction of organic amine salts, thus promoting the complete transformation of lead iodide into perovskite. Attached Figure Description

[0040] Figure 1 This is a SEM image of the perovskite thin film prepared in Example 1 of the present invention;

[0041] Figure 2 The current-voltage curve of the solar cell prepared in Example 1 of this invention;

[0042] Figure 3 This is a SEM image of the perovskite thin film prepared in Example 2 of the present invention;

[0043] Figure 4The current-voltage curve of the solar cell prepared in Example 2 of this invention;

[0044] Figure 5 This is a SEM image of the perovskite thin film prepared in Example 3 of the present invention;

[0045] Figure 6 The image shows the current-voltage curve of the solar cell prepared in Example 3 of this invention. Detailed Implementation

[0046] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] Example 1

[0048] The FTO glass substrate was cleaned sequentially with acetone, isopropanol, and deionized water, dried, and then treated with UV-ozone for 20 minutes. The SnO2 dispersion was mixed with deionized water at a volume ratio of 1:4, spin-coated onto the FTO substrate at 4000 rpm for 20 seconds, and annealed at 180°C for 30 minutes to obtain the SnO2 / FTO substrate.

[0049] Dissolve 1.5 mmol PbI2 and 0.15 mmol PMMA in 1 mL DMF to obtain solution A; dissolve 90 mg FAI (formamidinium hydroiodide) and 9 mg MACl (methylammonium chloride) in 1 mL IPA (isopropanol) to obtain solution B.

[0050] Take 50 μL of solution A and spin-coat it onto a SnO2 / FTO substrate at 5000 rpm for 30 s. Heat at 70 °C for 1 min to obtain a lead iodide film with a thickness of 360 nm (it is recommended to specify the specific thickness). Immerse the above lead iodide film in chlorobenzene for 60 seconds and then remove it. Anneal at 70 °C for 1 min. Take 50 μL of solution B and spin-coat it onto the lead iodide film at 2500 rpm for 30 s. Anneal at 150 °C for 10 min to obtain a perovskite film.

[0051] 72 mg of Spiro-OMeTAD and 39 μL of 4-tert-butylpyridine were dissolved in 1 mL of chlorobenzene. Then, 23 μL of a 520 mg / mL solution of lithium bis(trifluoromethanesulfonyl)imide in acetonitrile was added and mixed thoroughly. The mixture was then spin-coated onto a perovskite layer at 3000 rpm for 30 s. Finally, a 70 nm thick silver electrode was deposited on the hole transport layer surface using vacuum evaporation at a vacuum level below 10⁻⁴ Pa and a deposition rate of [missing information]. A solar cell was obtained.

[0052] In the perovskite solar cell prepared in Example 1, the thickness of the SnO2 layer is 20 nm, the thickness of the perovskite film is 400 nm, the thickness of the hole transport layer is 200 nm, and the thickness of the silver electrode is 70 nm.

[0053] Example 2

[0054] The perovskite film was prepared according to the method of Example 1, except that the amount of PMMA in solution A was 0.015 mmol.

[0055] Example 3

[0056] Perovskite films were prepared according to the method of Example 1, except that PMMA was not added to solution A.

[0057] Performance testing

[0058] The morphology of the perovskite films prepared in Examples 1-3 was characterized using scanning electron microscopy, and the results are as follows: Figure 1 , Figure 3 and Figure 5 As shown, the perovskite film prepared in Example 1 has a smooth surface with no lead iodide residue; the perovskite film prepared in Example 2 has a small amount of lead iodide residue on its surface; and the perovskite film prepared in Example 3 has a large amount of lead iodide residue.

[0059] Under room temperature conditions, using a 3A solar simulator at 100mW / cm², 2 The photoelectric conversion efficiency of the perovskite solar cells prepared in the examples was tested under varying light intensity. The effective area of ​​the perovskite solar cells was 0.09 cm². 2 ; test results as Figure 2 , Figure 4 and Figure 6 As shown; Figure 2 As shown, the short-circuit current density of the perovskite solar cell prepared in Example 1 is 25.73 mA / cm². 2 The open-circuit voltage is 1.137V, the fill factor is 80.33%, and the photoelectric conversion efficiency is 23.50%. Figure 4 As shown, the short-circuit current density of the perovskite solar cell prepared in Example 2 is 25.68 mA / cm². 2 The open-circuit voltage is 1.128V, the fill factor is 80.27%, and the photoelectric conversion efficiency is 23.23%. Figure 6 As shown, the short-circuit current density of the perovskite solar cell prepared in Example 3 is 25.60 mA / cm². 2 The open-circuit voltage is 1.067V, the fill factor is 77.93%, and the photoelectric conversion efficiency is 21.29%.

[0060] To address the problem of incomplete reaction between lead iodide at the bottom and organic amine salts, this invention introduces organic sacrificial materials into the lead iodide layer to prepare porous lead iodide, providing channels for the diffusion and reaction of organic amine salts, thus promoting the complete transformation of lead iodide into perovskite.

[0061] While the invention has been described and illustrated with reference to specific embodiments thereof, such description and illustration are not intended to limit the invention. It will be readily understood by those skilled in the art that various changes may be made to suit particular circumstances, materials, compositions, substances, methods, or processes to the objectives, spirit, and scope of this application without departing from the true spirit and scope of the invention as defined by the appended claims. All such modifications are intended to be within the scope of the appended claims. Although the methods disclosed herein have been described with reference to specific operations performed in a particular order, it should be understood that these operations may be combined, subdivided, or reordered to form equivalent methods without departing from the teachings of the invention. Therefore, unless specifically indicated herein, the order and grouping of operations are not a limitation of this application.

Claims

1. A method for preparing a perovskite thin film, comprising: After depositing a lead iodide solution onto a substrate, an annealing process is performed to obtain a lead iodide film. The lead iodide film was immersed in an antisolvent and then subjected to secondary annealing to obtain a porous lead iodide film. The porous lead iodide film was reacted with an organic amine salt solution to obtain a perovskite film; The lead iodide solution comprises: lead iodide, polymethyl methacrylate, and a solvent; the concentration of lead iodide in the lead iodide solution is selected from 0.5~1.5 mol / L; The antisolvent is selected from at least one of chloroform, chlorobenzene, toluene, and dichloroethane.

2. The preparation method according to claim 1, characterized in that, The molar ratio of polymethyl methacrylate to lead iodide is selected from (0.5%~10%):

1.

3. The preparation method according to claim 1, characterized in that, The solvent is selected from at least one of N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, and γ-butyrolactone.

4. The preparation method according to claim 1, characterized in that, The temperature of the first annealing is selected from 50~100℃, and the time of the first annealing is selected from 30~300 seconds.

5. The preparation method according to claim 1, characterized in that, The soaking time is selected from 30 to 300 seconds.

6. The preparation method according to claim 1, characterized in that, The temperature of the secondary annealing is selected from 50~100℃; the time of the secondary annealing is selected from 1~5 minutes.

7. The preparation method according to claim 1, characterized in that, The organic amine salt solution comprises: a solute and a solvent; The solute is selected from at least one of formamidine hydroiodide, formamidine hydrobromide, methylamine hydroiodide, and methylamine hydrobromide; The solvent is selected from isopropanol; The concentration of the solute in the organic amine salt solution is selected from 60 to 90 mg / mL.

8. A perovskite solar cell, comprising: The perovskite thin film prepared by the method of claim 1.

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