Tin-based perovskite thin film, preparation method thereof and tin-based perovskite solar cell

Abstract

The invention provides a tin-based perovskite thin film, a preparation method thereof and a tin-based perovskite solar cell, and belongs to the technical field of solar cells. The preparation method of the tin-based perovskite thin film comprises the steps that tin-based perovskite powder is dissolved in an organic solvent, a tin-based perovskite precursor solution is obtained, and the organic solvent is composed of a low-boiling-point organic solvent and a high-boiling-point organic solvent; and blade-coating the tin-based perovskite precursor solution on a substrate, and carrying out annealing treatment to obtain the tin-based perovskite thin film. The invention also provides a tin-based perovskite solar cell using the prepared tin-based perovskite thin film as a light absorption layer. The high-quality tin-based perovskite thin film can be prepared, and better electrical properties can be obtained by applying the tin-based perovskite thin film to a tin-based perovskite solar cell.

Description

Technical Field

[0001] At least one embodiment of the present invention relates to a perovskite solar cell, and particularly to a tin-based perovskite thin film, a preparation method thereof, and a tin-based perovskite solar cell. Background Art

[0002] Based on the currently mature industrialized silicon-based solar cells, research on perovskite solar cells has been continuously making progress. At present, the photoelectric conversion efficiency of lead-based perovskite solar cells has increased from the initial 3.8% to 27%. However, lead-based perovskite solar cells contain heavy metal lead elements, which greatly limit the application scenarios of perovskite solar cells and also hinder their industrial development.

[0003] The tin-based perovskite system has become a strong competitor in the lead-free perovskite system due to its more suitable bandgap and better light absorption range. In the development of perovskite solar cells, spin coating has always played an important role in preparing perovskite thin films. However, as a traditional laboratory preparation method, spin coating has low preparation efficiency and is difficult to be applied industrially. Summary of the Invention

[0004] In view of this, in order to at least partially solve the above-mentioned technical problems, the present invention provides a tin-based perovskite thin film, a preparation method thereof, and a tin-based perovskite solar cell.

[0005] According to an embodiment of one aspect of the present invention, a preparation method of a tin-based perovskite thin film is provided, including: dissolving tin-based perovskite powder in an organic solvent to obtain a tin-based perovskite precursor solution, wherein the organic solvent is composed of a low-boiling organic solvent and a high-boiling organic solvent; and spin coating the tin-based perovskite precursor solution on a substrate, and obtaining a tin-based perovskite thin film after annealing treatment.

[0006] According to an embodiment of another aspect of the present invention, a tin-based perovskite thin film obtained by the above preparation method is provided.

[0007] According to an embodiment of still another aspect of the present invention, a tin-based perovskite solar cell is provided, including the above-mentioned tin-based perovskite thin film.

[0008] According to the preparation method of the tin-based perovskite thin film provided by the above embodiment of the present invention, a mixture of a low-boiling organic solvent and a high-boiling organic solvent is used as a solvent to prepare a tin-based perovskite precursor solution, and spin coating is used to prepare a tin-based perovskite thin film, which can be used to prepare high-quality tin-based perovskite thin films on a large scale and is conducive to industrial application. Applying the prepared high-quality tin-based perovskite thin film to a tin-based perovskite solar cell can obtain better electrical properties. Description of the Drawings

[0009] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description only relate to some embodiments of the present invention and do not limit the present invention.

[0010] Figure 1 Schematic flow chart of the preparation method of the tin-based perovskite thin film provided by the embodiment of the present invention;

[0011] Figure 2 Schematic diagram of the preparation of the tin-based perovskite thin film by the doctor blade method provided by the embodiment of the present invention;

[0012] Figure 3 Schematic diagram of the tin-based perovskite solar cell provided by the embodiment of the present invention;

[0013] Figure 4 Comparison chart of J-V curves of the tin-based perovskite solar cells provided for Examples 1-5;

[0014] Figure 5 Comparison chart of J-V curves of the tin-based perovskite solar cells provided for Examples 6-10;

[0015] Figure 6A SEM image of the tin-based perovskite thin film provided for Comparative Example 1;

[0016] Figure 6B SEM image of the tin-based perovskite thin film provided for Example 8 of the present invention;

[0017] Figure 7A In-situ photoluminescence spectrum of the tin-based perovskite thin film provided for Comparative Example 1;

[0018] Figure 7B In-situ photoluminescence spectrum of the tin-based perovskite thin film provided for Example 8 of the present invention;

[0019] Figure 8 Comparison chart of the storage stability of the tin-based perovskite solar cell of Comparative Example 1 and the tin-based perovskite solar cell provided for Example 8 of the present invention; and

[0020] Figure 9 Schematic diagram of the film formation principle of the tin-based perovskite thin film of Comparative Example 1 and the tin-based perovskite thin film of Example 8 of the present invention.

[0021] Explanation of reference numerals:

[0022] 1 - Conductive substrate;

[0023] 2 - Hole transport layer;

[0024] 3 - Tin-based perovskite thin film;

[0025] 4 - Electron transport layer;

[0026] 5 - Top electrode;

[0027] 10 - Substrate;

[0028] 20 - Tin - based perovskite precursor solution;

[0029] 30 - Doctor blade. Detailed implementation manners

[0030] To make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the following further elaborates the present invention in detail with reference to specific embodiments and the accompanying drawings. However, the present invention can be implemented in different forms and should not be construed as being limited to the embodiments presented herein. On the contrary, providing these embodiments will make the invention thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. In the drawings, for clarity, the dimensions and relative dimensions of layers and regions may be exaggerated, and the same reference numerals denote the same elements throughout.

[0031] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The terms "including", "comprising", etc. used herein indicate the presence of the described features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0032] Tin - based perovskite solar cells (FASnI 3 ) as a non - toxic alternative to high - efficiency lead - based perovskite solar cells have advantages such as a more suitable bandgap, better absorption spectrum, and non - toxicity. However, the intrinsic physical and chemical properties of tin - based perovskite materials determine that they have poor crystallization kinetics characteristics, with problems such as relatively fast crystallization speed and poor crystallization quality.

[0033] Specifically, the reasons for the poor crystallization kinetics of tin - based perovskite materials mainly include three aspects: First, the ionic radius of tin (Sn²⁺) (0.93 Å) is smaller than that of lead (Pb²⁺) (1.19 Å). The smaller ionic radius makes Sn²⁺ more likely to form a stable octahedral coordination structure with halogens (such as I⁻), reducing the nucleation energy barrier and thus accelerating crystallization. The rapid crystallization will result in a poor morphology of the tin - based perovskite thin film. Second, the Lewis acidity of Sn²⁺ is significantly stronger than that of Pb²⁺, resulting in a higher Zeta potential of colloidal particles in the tin - based perovskite precursor solution, weakening the solvation effect, thus accelerating the nucleation rate and inhibiting the ordered growth of crystals. This kinetic imbalance is likely to form a porous and defect - dense thin film. Third, the crystallization activation energy of tin - based perovskite materials is lower than that of lead - based perovskite materials, resulting in difficulty in effectively separating the nucleation stage and the growth stage of tin - based perovskite materials. The rapid crystallization increases the grain boundaries and pinhole defects.

[0034] According to the crystallization kinetics model, for the perovskite thin film in a perovskite solar cell, the process from the perovskite precursor solution to the perovskite thin film requires a nucleation and crystallization process, and these two processes need to be balanced. The common laboratory preparation method is spin coating. In the spin coating process, an anti-solvent can be used to well coordinate the nucleation and crystallization processes. Its advantage is that the prepared thin film has good quality, but its disadvantage is that it is extremely wasteful (about 90% is wasted. This is because about 90% of the solution spin-coated after the spin coater starts will be thrown out, and only 10% of the solution remains on the spin coating surface). Therefore, the spin coating method is difficult to be applied to industrial preparation.

[0035] The preparation of perovskite thin film by the blade coating method can achieve large-scale preparation, but the blade coating method cannot use an anti-solvent to balance the nucleation and crystallization processes. Specifically, in the spin coating preparation process, the anti-solvent can quickly mix evenly with the spin-coated perovskite precursor solution to play its role. However, in the blade coating process, the blade coating cannot evenly cover the anti-solvent on the substrate like spin coating by rotation, so it cannot be quickly mixed evenly and cannot play the role of quickly extracting the solvent.

[0036] In view of this, the present invention provides a method for preparing a tin-based perovskite thin film to large-scale prepare a high-quality tin-based perovskite thin film, which is beneficial to the industrial application of tin-based perovskite solar cells.

[0037] Figure 1 It is a schematic flow chart of the method for preparing a tin-based perovskite thin film provided by an embodiment of the present invention.

[0038] According to an exemplary embodiment of the present invention, the present invention provides a method for preparing a tin-based perovskite thin film. Referring to Figure 1 shown, it includes: step S1 to step S2.

[0039] Step S1, dissolving tin-based perovskite powder in an organic solvent to obtain a perovskite precursor solution, wherein the organic solvent is composed of a low-boiling organic solvent and a high-boiling organic solvent.

[0040] In some embodiments, the perovskite powder includes formamidinium hydroiodide (FAI), stannous iodide (SnI 2 ), stannous fluoride (SnF 2 ), and phenethylammonium bromide (PEABr).

[0041] In some embodiments, the molar ratio of FAI + PEABr, SnI 2 , SnF 2 is 1:1:(0 to 0.2), and the molar ratio of FAI and PEABr is (1:0) to (0.7:0.3).

[0042] In some embodiments, the molar ratio of FAI, PEABr, SnI 2 and SnF 2 can be, for example, 0.85:0.15:1:0.1.

[0043] In some embodiments, the high-boiling organic solvents include at least one of dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), and γ-butyrolactone (GBL).

[0044] In some embodiments, the low-boiling organic solvents have a boiling point lower than that of the high-boiling organic solvents, and the low-boiling organic solvents include at least one of acetonitrile (ACN), ethanol (EtOH), and dimethoxyethanol (2-ME).

[0045] In some embodiments, the volume ratio of the low-boiling organic solvent to the high-boiling organic solvent is (10 - 50):(2 - 17). The volume ratio can be, for example, 35:11, 35:13, 40:11, 45:11, 50:11, but is not limited to the recited values. If the volume ratio is too large (too much low-boiling organic solvent and too little high-boiling organic solvent), the tin-based perovskite powder cannot be dissolved in the organic solvent. If the volume ratio is too small (too little low-boiling organic solvent and too much high-boiling organic solvent), the prepared tin-based perovskite film will be porous and prone to bottom exposure, resulting in easy short-circuiting of the tin-based perovskite solar cell containing the tin-based perovskite film. By controlling the volume ratio within the above range, a high-quality tin-based perovskite film can be obtained, which helps to improve the photoelectric conversion efficiency and service life of the tin-based perovskite solar cell.

[0046] In some embodiments, the low-boiling organic solvent includes ACN, and the high-boiling organic solvents include DMF and DMSO, wherein the volume ratio of ACN, DMF, and DMSO is (10 - 50):(1 - 15):(1 - 2). The volume ratio can be, for example, 35:1:1, 35:4:1, 35:7:1, 35:10:1, 35:12:1, 30:10:1, 45:10:1, 50:10:1, but is not limited to the recited values; the volume ratio is preferably 40:10:1.

[0047] It should be noted that if the proportion of acetonitrile is too small, the prepared tin-based perovskite film will be porous and prone to bottom exposure, resulting in easy short-circuiting of the tin-based perovskite solar cell. If the proportion of acetonitrile is too large, it will be difficult to dissolve the tin-based perovskite powder. Adding dimethylformamide helps to dissolve the tin-based perovskite powder. If the proportion of dimethyl sulfoxide is too small, the crystallization is very poor. If the proportion of dimethyl sulfoxide is too large, the crystallization is too strong and dendritic crystals are obtained, which cannot form a film. By controlling the volume ratio of ACN, DMF, and DMSO within the above range, it helps to form a high-quality tin-based perovskite film.

[0048] In some embodiments, the concentration of the perovskite precursor solution is 0.2 - 1 M. For example, it can be 0.2 mol / L, 0.25 mol / L, 0.5 mol / L, 0.8 mol / L, 1 mol / L, but is not limited to the recited values; preferably it is 0.25 mol / L.

[0049] Step S2: Spin-coat the tin-based perovskite precursor solution on a substrate, and obtain a tin-based perovskite thin film after annealing treatment.

[0050] Figure 2 Schematic diagram of the method for preparing a tin-based perovskite thin film by spin-coating provided by the embodiments of the present invention.

[0051] In some embodiments, as shown in Figure 2 Figure, 20 drops or pour the tin-based perovskite precursor solution onto the substrate 10, and use a doctor blade 30 to evenly spread the tin-based perovskite precursor solution 20 on the substrate 10. Blow air on the evenly spread tin-based perovskite precursor solution 20, and quickly extract the organic solvent from the tin-based perovskite precursor solution by blowing air, so as to instantaneously increase the concentration of the tin-based perovskite precursor solution and improve the nucleation density. The doctor blade 30 is placed on the substrate 10, and the height of the doctor blade 30 (the distance between the doctor blade 30 and the substrate 10) is 20 μm. The spin-coating rate is 0.1 mm / s - 100 mm / s. For example, it can be 0.1 mm / s, 1 mm / s, 10 mm / s, 50 mm / s, 100 mm / s, but is not limited to the recited values. If the spin-coating rate is too high, it is difficult to form a uniform and dense tin-based perovskite thin film; if the spin-coating rate is too low, it is not conducive to large-scale industrial applications.

[0052] In some embodiments, the annealing temperature is 70°C - 120°C. For example, it can be 70°C, 80°C, 90°C, 100°C, 120°C, but is not limited to the recited values. The annealing time is 5 min - 20 min. For example, it can be 5 min, 10 min, 15 min, 20 min, but is not limited to the recited values. If the annealing temperature is too high, the perovskite material will decompose, resulting in an increase in defects; if the annealing temperature is too low, the perovskite material will not crystallize sufficiently, and the solvent (such as dimethyl sulfoxide) will remain in the crystallized perovskite, reducing the crystallization quality. By controlling the annealing temperature within the above range, the crystallization quality of the perovskite material can be improved, thereby improving the photoelectric conversion efficiency and service life of the tin-based perovskite solar cell.

[0053] According to an exemplary embodiment of the present invention, the present invention provides a tin-based perovskite thin film obtained by using the above preparation method.

[0054] According to an exemplary embodiment of the present invention, the present invention provides a tin-based perovskite solar cell, including the tin-based perovskite thin film prepared as above.

[0055] Figure 3 It is a schematic diagram of the tin-based perovskite solar cell provided by the embodiment of the present invention.

[0056] According to an exemplary embodiment of the present invention, the present invention provides a preparation method of a tin-based perovskite solar cell. Refer to Figure 3 as shown, including: step S01 to step S04.

[0057] Step S01, prepare a hole transport layer on the conductive substrate.

[0058] In some embodiments, the conductive substrate 1 can be, for example, indium tin oxide (ITO), and the hole transport layer 2 can be, for example, poly(3,4-ethylenedioxythiophene) / polystyrene sulfonate (PEDOT:PSS).

[0059] It should be noted that before preparing the hole transport layer 2 on the conductive substrate 1, the conductive substrate 1 is pretreated. Specifically, the ITO transparent glass substrate is ultrasonically cleaned with glass cleaner, deionized water, acetone, and isopropyl alcohol for 20 minutes each, dried in an oven, and then cleaned with an ultraviolet ozone machine for 15 minutes.

[0060] In some embodiments, preparing the hole transport layer 2 on the conductive substrate 1 includes: in an air atmosphere, spin-coating PEDOT:PSS on the ITO transparent glass substrate at a speed of 5000 r / min and annealing at 150 °C for 15 minutes.

[0061] Step S02, prepare a tin-based perovskite thin film 3 on the hole transport layer 2, and the tin-based perovskite thin film 3 serves as a light absorption layer.

[0062] According to the embodiment of the present invention, the tin-based perovskite thin film 3 is prepared on the hole transport layer 2 by using the above-mentioned preparation method of the tin-based perovskite thin film.

[0063] Step S03, prepare an electron transport layer 4 on the tin-based perovskite thin film 3.

[0064] In some embodiments, ICBA is prepared on the tin-based perovskite thin film 3 by spin-coating as the electron transport layer 4. Specifically, a 20 mg / ml ICBA solution is prepared, and the solvent is CB (chlorobenzene); the obtained solution is spin-coated on the tin-based perovskite thin film 3, where the spin-coating speed is 1000 r / min, the time is 30 s, and annealing treatment is carried out at 70 °C for 10 minutes to obtain an ICBA electron transport layer.

[0065] In some embodiments, C60 is prepared on the tin-based perovskite thin film 3 by thermal evaporation as the electron transport layer 4.

[0066] Step S04, a blocking layer 5 and a top electrode 6 are prepared on the electron transport layer 4.

[0067] In some embodiments, 5 nm of BCP is thermally evaporated on the electron transport layer 4 as the blocking layer 5, and then 100 nm of silver is prepared as the top electrode 6 by thermal evaporation.

[0068] The designed tin-based perovskite thin film, its preparation method, and the tin-based perovskite solar cell are schematically described below. It should be noted that this example is only a specific embodiment of the present invention and does not limit the protection scope of the present invention.

[0069] Comparative Example 1

[0070] A hole transport layer is prepared on ITO, and the hole transport layer is PEDOT:PSS.

[0071] A tin-based perovskite precursor solution is prepared. Specifically, FAI, SnI 2 , SnF 2 and PEABr are dissolved in an organic solvent to prepare a tin-based perovskite precursor solution with a concentration of 0.25 mol / L; wherein the molar ratio of FAI, PEABr, SnI 2 and SnF 2 is 0.85:0.15:1:0.1; the organic solvent includes DMF and DMSO, and the volume ratio of DMF to DMSO is 4:1.

[0072] The tin-based perovskite precursor solution is spin-coated on the hole transport layer. Specifically, the tin-based perovskite precursor solution is poured on the hole transport layer, and a doctor blade is used to evenly spread the tin-based perovskite precursor solution on the hole transport layer, and the evenly spread tin-based perovskite precursor solution is blown with air. Among them, the distance between the doctor blade and the hole transport layer is 20 μm, the spin-coating rate is 10 mm / s, and the evenly spread tin-based perovskite precursor solution is annealed at an annealing temperature of 80 °C for 10 min.

[0073] A 20-nm-thick C60 electron transport layer is prepared on the tin-based perovskite thin film by thermal evaporation.

[0074] A 5-nm BCP is prepared as the blocking layer and 100-nm-thick silver is used as the top electrode on the electron transport layer by thermal evaporation.

[0075] The performance of the tin-based perovskite solar cell prepared in Comparative Example 1 is tested, and the test results are shown in Table 1 for reference.

[0076] Example 1

[0077] The tin-based perovskite thin film was prepared by the same method as in Comparative Example 1, except that the organic solvent included ACN, DMF, and DMSO, and the volume ratio of ACN, DMF to DMSO was 35:1:1.

[0078] The performance of the tin-based perovskite solar cell prepared in Example 1 was tested, and the test results are shown in Table 1 for reference.

[0079] Example 2

[0080] The tin-based perovskite thin film was prepared by the same method as in Example 1, except that the volume ratio of ACN, DMF to DMSO was 35:4:1.

[0081] The performance of the tin-based perovskite solar cell prepared in Example 2 was tested, and the test results are shown in Table 1 for reference.

[0082] Example 3

[0083] The tin-based perovskite thin film was prepared by the same method as in Example 1, except that the volume ratio of ACN, DMF to DMSO was 35:7:1.

[0084] The performance of the tin-based perovskite solar cell prepared in Example 3 was tested, and the test results are shown in Table 1 for reference.

[0085] Example 4

[0086] The tin-based perovskite thin film was prepared by the same method as in Example 1, except that the volume ratio of ACN, DMF, and DMSO was 35:10:1.

[0087] The performance of the tin-based perovskite solar cell prepared in Example 4 was tested, and the test results are shown in Table 1 for reference.

[0088] Example 5

[0089] The tin-based perovskite thin film was prepared by the same method as in Example 1, except that the volume ratio of ACN, DMF, and DMSO was 35:12:1.

[0090] The performance of the tin-based perovskite solar cell prepared in Example 5 was tested, and the test results are shown in Table 1 for reference.

[0091] Figure 4 It is a comparison chart of the J-V curves of the tin-based perovskite solar cells provided for Examples 1 - 5.

[0092] Reference Figure 4As shown, according to the test results of Examples 1 - 5, it can be seen that compared with Examples 1 - 3 and Example 5, the perovskite solar cell based on tin prepared in Example 4 has the optimal photoelectric conversion efficiency. It can be seen that the volume ratio of ACN, DMF, and DMSO of 35:10:1 is relatively preferred.

[0093] Example 6

[0094] The tin - based perovskite thin film was prepared by the same method as in Example 1, except that the volume ratio of ACN, DMF, and DMSO was 30:10:1;

[0095] And the ICBA electron - transport layer was prepared on the tin - based perovskite thin film by spin - coating. Specifically, a 20 mg / ml ICBA solution was prepared with CB (chlorobenzene) as the solvent; the ICBA solution was spin - coated on the tin - based perovskite thin film, where the spin - coating speed was 1000 r / min, the time was 30 s, and annealing treatment was carried out at 70 °C for 10 min to obtain the ICBA electron - transport layer.

[0096] The performance of the perovskite solar cell based on tin prepared in Example 6 was tested, and the test results are shown in Table 1 for reference.

[0097] Example 7

[0098] The tin - based perovskite thin film was prepared by the same method as in Example 6, except that the volume ratio of ACN, DMF, and DMSO was 35:10:1.

[0099] The performance of the perovskite solar cell based on tin prepared in Example 7 was tested, and the test results are shown in Table 1 for reference.

[0100] Example 8

[0101] The tin - based perovskite thin film was prepared by the same method as in Example 6, except that the volume ratio of ACN, DMF, and DMSO was 40:10:1.

[0102] The performance of the perovskite solar cell based on tin prepared in Example 8 was tested, and the test results are shown in Table 1 for reference.

[0103] Example 9

[0104] The tin - based perovskite thin film was prepared by the same method as in Example 6, except that the volume ratio of ACN, DMF, and DMSO was 45:10:1.

[0105] The performance of the perovskite solar cell based on tin prepared in Example 9 was tested, and the test results are shown in Table 1 for reference.

[0106] Example 10

[0107] The tin-based perovskite thin film was prepared by the same method as in Example 6, except that the volume ratio of ACN, DMF and DMSO was 50:10:1.

[0108] The performance of the tin-based perovskite solar cell prepared in Example 10 was tested, and the test results are shown in Table 1 for reference.

[0109] Figure 5 It is a comparison chart of the J-V curves of the tin-based perovskite solar cells provided in Examples 6-10.

[0110] Reference Figure 5 As shown, according to the test results of Examples 6-10 of the present invention, compared with Examples 6-7 and Examples 9-10, the normalized photoelectric conversion efficiency of the tin-based perovskite solar cell prepared in Example 8 is the best, reaching 9.64%. It can be seen that the volume ratio of ACN, DMF and DMSO of 40:10:1 is more preferable.

[0111] Figure 6A It is the SEM image of the tin-based perovskite thin film provided for Comparative Example 1.

[0112] Figure 6B It is the SEM image of the tin-based perovskite thin film provided for Example 8 of the present invention.

[0113] Reference Figure 6A As shown, the tin-based perovskite thin film provided for Comparative Example 1 is loose and porous. Reference Figure 6B As shown, the tin-based perovskite thin film provided for Example 8 of the present invention is more uniform and dense, which indicates that a higher-quality tin-based perovskite thin film is prepared in Example 8 of the present invention.

[0114] Figure 7A It is the in-situ photoluminescence spectrum of the tin-based perovskite thin film provided for Comparative Example 1.

[0115] Figure 7B It is the in-situ photoluminescence spectrum of the tin-based perovskite thin film provided for Example 8 of the present invention.

[0116] Reference Figure 7A As shown, the nucleation time of the tin-based perovskite precursor solution in Comparative Example 1 is 2.5 s; reference Figure 7B As shown, the nucleation time of the tin-based perovskite precursor solution in Example 8 of the present invention is 9.12 s. That is to say, the nucleation density of the tin-based perovskite precursor solution in Comparative Example 1 is low, the crystallization rate is fast, the crystallization size of the obtained perovskite is large, and the perovskite thin film is non-uniform and non-dense; the nucleation density of the perovskite precursor solution in Example 8 of the present invention is large, the crystallization rate is slower, the crystallization size of the obtained perovskite is small, and the perovskite thin film is uniform and dense, obtaining a high-quality tin-based perovskite thin film.

[0117] Figure 8 Comparison graph of the storage stability between the tin-based perovskite solar cell of Comparative Example 1 and the tin-based perovskite solar cell provided in Example 8 of the present invention.

[0118] Reference Figure 8 As shown, the normalized photoelectric conversion efficiency of the tin-based perovskite solar cell of Comparative Example 1 decreased significantly after 200 h, while the normalized photoelectric conversion efficiency of the tin-based perovskite solar cell of Example 8 of the present invention could still remain above 80% after 600 h, indicating that the tin-based perovskite solar cell of Example 8 of the present invention has better storage stability.

[0119] Figure 9 Schematic diagram of the film-forming principle of the tin-based perovskite film of Comparative Example 1 and the tin-based perovskite film of Example 8 of the present invention.

[0120] Reference Figure 9 As shown, according to the Lamer model, when the concentration of the tin-based perovskite precursor solution is Cs, the tin-based perovskite precursor solution is in a stable state; when the organic solvent of the tin-based perovskite precursor solution is rapidly extracted, the concentration of the tin-based perovskite precursor solution exceeds Cmin, and the tin-based perovskite precursor solution begins to nucleate; the larger the Cmax of the tin-based perovskite precursor solution, the longer the nucleation time and the more the number of nuclei. Among them Figure 9 Cs represents the saturation concentration of the tin-based perovskite precursor solution, Cmin represents the nucleation concentration, and Cmax represents the maximum concentration of the tin-based perovskite precursor solution, where Cs < Cmin < Cmax.

[0121] Reference Figure 9 As shown, if the nucleation time of the tin-based perovskite precursor solution is too short, very few nuclei will form, and dendritic crystals will grow, making it impossible to form a film. Tin-based perovskite films are formed in both Comparative Example 1 and Example 8, but the tin-based perovskite film of Comparative Example 1 has poor uniformity and compactness, while the tin-based perovskite film of Example 8 of the present invention is uniform and dense, and a high-quality tin-based perovskite film is obtained in Example 8. This is because the nucleation time of the tin-based perovskite precursor solution in Comparative Example 1 is significantly shorter than that of the tin-based perovskite solution in Example 8 of the present application, that is, the number of nuclei of the tin-based perovskite solution in Comparative Example 1 is also significantly less than that of the tin-based perovskite solution in Example 8 of the present application. This is because in Example 8 of the present application, by using a low-boiling organic solvent to prepare the solvent, the organic solvent can be rapidly extracted from the tin-based perovskite precursor solution, the concentration of the tin-based perovskite precursor solution can be rapidly increased, so a large number of nuclei can be formed, and the formed grain size is small, thus a dense and high-quality tin-based perovskite film can be formed.

[0122] The test results of the above-mentioned examples and comparative examples are described as follows:

[0123] Table 1

[0124]

[0125] According to the above-mentioned examples and comparative examples of the present invention, by using a mixture of a low-boiling organic solvent and a high-boiling organic solvent as the solvent for formulating the tin-based perovskite precursor solution and regulating the ratio of the low-boiling organic solvent to the high-boiling organic solvent, a tin-based perovskite solar cell with a high open-circuit voltage, a high fill factor, and a high normalized photoelectric conversion efficiency can be obtained.

[0126] Among them, compared with Comparative Example 1, Examples 1 to 10 adopt a mixture of a low-boiling organic solvent and a high-boiling organic solvent as the solvent for formulating the tin-based perovskite precursor solution, resulting in a significant increase in the current density, open-circuit voltage, and fill factor of the prepared tin-based perovskite solar cell. Since the photoelectric conversion efficiency of the tin-based perovskite solar cell is related to the product of these three parameters, namely current density, open-circuit voltage, and fill factor, the photoelectric conversion efficiency of the tin-based perovskite solar cell is also better.

[0127] It is worth mentioning that the normalized photoelectric conversion efficiency of the tin-based perovskite solar cell prepared in Example 8 reaches 9.64%. Compared with Comparative Example 1 (using a high-boiling organic solvent), the normalized photoelectric conversion efficiency of the tin-based perovskite solar cell in Example 8 of the present invention is significantly improved, which indicates that by using a low-boiling solvent, the crystallization rate of the perovskite precursor solution can be reduced, a tin-based perovskite thin film with higher quality can be obtained, and better electrical properties can be obtained when the prepared tin-based perovskite thin film is applied to a tin-based perovskite solar cell.

[0128] The above-mentioned specific examples further elaborate on the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above are only specific examples of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a tin-based perovskite film, characterized in that: include: dissolving the tin-based perovskite powder in an organic solvent to obtain a tin-based perovskite precursor solution, wherein the organic solvent consists of a low-boiling point organic solvent and a high-boiling point organic solvent; and The tin-based perovskite precursor solution is scraped onto a substrate, and a tin-based perovskite film is obtained after annealing.

2. The preparation method according to claim 1, characterized in that: The low boiling point organic solvent includes at least one of acetonitrile, ethanol and dimethoxyethanol.

3. The preparation method according to claim 1, characterized in that: The high boiling point organic solvent includes at least one of dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone and γ-butyrolactone.

4. The preparation method according to claim 1, characterized in that: The volume ratio of the low boiling point organic solvent to the high boiling point organic solvent is (10~50):(2~17).

5. The preparation method according to claim 1, characterized in that: Low boiling point organic solvents include acetonitrile, and high boiling point organic solvents include dimethylformamide and dimethyl sulfoxide; The volume ratio of acetonitrile, dimethylformamide and dimethyl sulfoxide is (10~50):(1~15):(1~2).

6. The preparation method according to claim 1, characterized in that: The tin-based perovskite precursor solution is scraped onto the substrate at a scraping rate of 0.1 mm / s to 100 mm / s.

7. The preparation method according to claim 1, characterized in that: The annealing temperature of the annealing treatment is 70°C~120°C.

8. The preparation method according to claim 1, characterized in that: The tin-based perovskite powder includes formamidine hydroiodide, stannous iodide, stannous fluoride and phenethylammonium bromide.

9. A tin-based perovskite film obtained by the preparation method according to any one of claims 1 to 8.

10. A tin-based perovskite solar cell, characterized in that: Comprising the tin-based perovskite film as described in claim 9.

Images