Perovskite thin film and preparation method thereof, solar cell and preparation method and application thereof

Abstract

The invention provides a perovskite thin film and a preparation method thereof, and a solar cell and a preparation method and application thereof. The method for preparing the perovskite thin film comprises the following steps: dropwise adding a perovskite precursor solution on a substrate; based on the first spin-coating mode and the second spin-coating mode, spin-coating for a first preset time and a second preset time in sequence, and dropwise adding an anti-solvent in the process of the second spin-coating mode to obtain a prefabricated film; and annealing treatment is conducted on the prefabricated thin film, the perovskite thin film is obtained, the rotating speed in the first spin-coating mode is smaller than that in the second spin-coating mode, and the rotating speed in the first spin-coating mode is smaller than or equal to 1100 rpm. Under the action of small centrifugal force, the perovskite precursor solution is fully infiltrated on the surface of the substrate, good spreading and infiltrating are achieved, the coating performance is improved, and the film forming difficulty is reduced; and volatilizing the solvent in the perovskite precursor solution in a second spin-coating mode at a relatively high rotating speed to obtain a prefabricated thin film with good film-forming property, so as to obtain the perovskite thin film with good film-forming property and relatively good compactness and uniformity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solar cells, in particular to a perovskite thin film and a preparation method thereof, a solar cell and a preparation method and application thereof, and more particularly to a perovskite thin film and a preparation method thereof, a solar cell and a preparation method and a photovoltaic module. BACKGROUND

[0002] Perovskite solar cells (PSCs) have become a research hotspot in the field of photovoltaics due to their excellent photoelectric performance and low manufacturing cost. Perovskite materials have high light absorption coefficient, long carrier diffusion length, and adjustable band gap, and the laboratory efficiency of single-junction cells has broken through 26%, significantly surpassing traditional thin-film solar cells (such as CIGS, CdTe). However, the preparation of the perovskite thin film in the cell requires a high flatness of the substrate. If the flatness of the substrate surface is poor, the protrusions (such as protruding line marks) on the substrate surface will block the perovskite precursor solution, which may cause the perovskite precursor solution to accumulate in the gullies, insufficient grain growth, and micron-level line marks may also cause the perovskite thin film to be punctured, leading to the collapse of the device structure, and the lack of solution caused by the inability of the solution to cover the back side of the line mark will also lead to the formation of recombination centers, which seriously affects the performance of the device. SUMMARY

[0003] The present application aims to at least solve one of the technical problems in the related art. To this end, one object of the present application is to provide a method for preparing a perovskite thin film by spin coating, which has better compactness and uniformity, and is beneficial to improve the performance of the solar cell.

[0004] In one aspect of the present application, the present application provides a method for preparing a perovskite thin film by spin coating. According to an embodiment of the present application, the method for preparing a perovskite thin film comprises: dropping a perovskite precursor solution on a substrate, spin coating for a first predetermined time and a second predetermined time based on a first spin coating mode and a second spin coating mode in sequence, respectively, and dropping an anti-solvent during the second spin coating mode to obtain a pre-prepared thin film; and annealing the pre-prepared thin film to obtain the perovskite thin film, wherein the rotation speed in the first spin coating mode is less than the rotation speed in the second spin coating mode, and the rotation speed in the first spin coating mode is less than or equal to 1100 rpm. Thus, during the first spin coating mode with low rotation speed, the residence time of the perovskite precursor solution on the substrate is increased under the action of small centrifugal force, so that the perovskite precursor solution is fully infiltrated on the substrate surface, good spreading and infiltration are obtained, the coating performance is improved, the film forming difficulty is reduced, and even for the substrate surface with poor surface flatness (such as the surface with convex line marks), good coverage of the perovskite precursor solution can still be achieved, and no substrate surface exposure phenomenon occurs. Then, in the second spin coating mode with high rotation speed, the solvent in the perovskite precursor solution is volatilized to obtain a pre-prepared thin film with good film forming property, so as to obtain a perovskite thin film with good film forming property, compactness and uniformity.

[0005] According to an embodiment of the present application, the first spin coating mode comprises a first acceleration stage and a first uniform speed stage, and the second spin coating mode comprises a second acceleration stage and a second uniform speed stage, the rotation speed of the first uniform speed stage is 900-1100 rpm, and the rotation speed of the second uniform speed stage is 3500-4500 rpm.

[0006] According to an embodiment of the present application, the rotation speed of the first uniform speed stage is 1000 rpm, and the rotation speed of the second uniform speed stage is 4000 rpm.

[0007] According to an embodiment of the present application, the first predetermined time is 8-15 s, and / or the second predetermined time is 18-22 s.

[0008] According to an embodiment of the present application, the acceleration of the first acceleration stage is 450-550 rpm / s, and / or the acceleration of the second acceleration stage is 550-650 rpm / s.

[0009] According to an embodiment of the present application, the anti-solvent is dropped in the second uniform speed stage.

[0010] According to an embodiment of the present application, the temperature of the annealing treatment is 80-120℃, and the time is 15-25 min.

[0011] In another aspect of the present application, the present application provides a perovskite thin film. According to an embodiment of the present application, the perovskite thin film is prepared by the method described above. Thus, the perovskite thin film has good compactness and uniformity, and can well and uniformly cover the surface of the substrate. It can be understood by those skilled in the art that the perovskite thin film has all the features and advantages of the method described above, and will not be described in detail here.

[0012] In yet another aspect of the present application, the present application provides a method for preparing a solar cell. According to an embodiment of the present application, the method comprises: providing a substrate; forming a first charge transport layer on one side of the substrate; spin-coating a perovskite thin film on the side of the first charge transport layer away from the substrate by using the method described above; forming a second charge transport layer on the side of the perovskite thin film away from the substrate; and forming an electrode on the side of the second charge transport layer away from the substrate. Thus, in the solar cell, the perovskite thin film has better film formation quality and better coverage on the surface of the substrate, which helps to improve the cell efficiency of the solar cell; and the yield of the above preparation method is better.

[0013] According to an embodiment of the present application, the substrate comprises a crystalline silicon bottom cell and a composite layer between the crystalline silicon bottom cell and the first charge transport layer.

[0014] In yet another aspect of the present application, the present application provides a solar cell. According to an embodiment of the present application, the solar cell is prepared by the method described above, or comprises the perovskite thin film described above. Thus, the solar cell has higher cell efficiency.

[0015] In yet another aspect of the present application, the present application provides a photovoltaic module. According to an embodiment of the present application, the photovoltaic module comprises the solar cell described above. Thus, the photovoltaic module has better performance and efficiency.

[0016] Additional aspects and advantages of the present application will be in part apparent and in part pointed out hereinafter. BRIEF DESCRIPTION OF DRAWINGS

[0017] The above and / or additional aspects and advantages of the present application will become apparent and be readily appreciated from the following description, including the appended drawings.

[0018] Figure 1 is a flow chart of a method for preparing a perovskite thin film in an embodiment of the present application;

[0019] Figure 2 is a comparison chart of linear marks and non-linear marks on the surface of a silicon wafer in another embodiment of the present application;

[0020] Figure 3is Figure 2 A comparison of the surface of a silicon wafer with and without lines;

[0021] Figure 4 is a scanning electron microscope image of a silicon wafer with lines on the surface in some embodiments of the present application;

[0022] Figure 5 is a schematic diagram of a perovskite film prepared by spin coating on a substrate surface with and without lines in the prior art;

[0023] Figure 6 is a schematic diagram of a perovskite film prepared by spin coating on a substrate surface with lines in yet some other embodiments of the present application;

[0024] Figure 7 is a rotational speed curve of spin coating to prepare a perovskite film in yet another embodiment of the present application;

[0025] Figure 8 is a schematic diagram of a crystalline silicon-perovskite tandem cell in yet another embodiment of the present application;

[0026] Figure 9 is a schematic diagram of a crystalline silicon-perovskite tandem cell in yet another embodiment of the present application;

[0027] Figure 10 is a scanning electron microscope image of a perovskite film prepared in Examples 1-3 and Comparative Examples 1-2;

[0028] Figure 11 is a photograph of a perovskite film prepared in Examples 1-3 and Comparative Examples 1-2;

[0029] Figure 12 is a photoluminescence test diagram of a perovskite film prepared in Example 1 and Comparative Example 3. DETAILED DESCRIPTION

[0030] The present application will now be described in connection with the following examples. Those skilled in the art will appreciate that the following examples are intended to be illustrative only and are not meant to limit the scope of the present application. Unless otherwise indicated, the techniques or conditions described in the examples are intended to be the techniques or conditions as described in the literature or as recommended by the manufacturer of the products used. Unless otherwise indicated, the reagents or instruments used in the examples are commercially available and are conventional products.

[0031] The present application will now be described in connection with the following examples. Those skilled in the art will appreciate that the following examples are intended to be illustrative only and are not meant to limit the scope of the present application. Unless otherwise indicated, the techniques or conditions described in the examples are intended to be the techniques or conditions as described in the literature or as recommended by the manufacturer of the products used. Unless otherwise indicated, the reagents or instruments used in the examples are commercially available and are conventional products.

[0032] In one aspect of the present application, a method for spin coating a perovskite film is provided. According to embodiments of the present application, reference is made to Figure 1The method for preparing perovskite thin films includes:

[0033] S100: The perovskite precursor solution is dropped onto the substrate.

[0034] S200: Based on the first spin coating mode and the second spin coating mode, spin coating is performed sequentially for a first predetermined time and a second predetermined time, and an anti-solvent is added dropwise during the second spin coating mode to obtain a pre-formed film. The rotation speed in the first spin coating mode is less than the rotation speed in the second spin coating mode, and the rotation speed in the first spin coating mode is less than or equal to 1100 rpm.

[0035] S300: Anneal the pre-fabricated film to obtain a perovskite film.

[0036] According to an embodiment of the present invention, in the first spin coating mode at a low speed, the residence time of the perovskite precursor solution on the substrate is increased under the action of a smaller centrifugal force, so that the perovskite precursor solution is fully wetted on the substrate surface, resulting in good spreading and wetting, improving coating performance, reducing the difficulty of film formation, and even for substrate surfaces with poor surface smoothness (such as surfaces with raised lines), good coverage of the perovskite precursor solution can still be achieved, with no bare substrate surface appearing; then in the second spin coating mode at a higher speed, the solvent in the perovskite precursor solution is evaporated, resulting in a pre-formed film with good film-forming properties, so as to obtain a perovskite film with good film-forming properties, density, and uniformity.

[0037] In the fabrication of crystalline silicon-perovskite tandem solar cells, if the pre-cleaning or alkaline polishing stage of the silicon wafer is not properly handled during the crystalline silicon base cell process, raised lines (such as...) will appear on the silicon wafer surface. Figure 2 , Figure 3 and Figure 4 As shown, Figure 2 The left image shows a silicon wafer without traces, while the right image shows a silicon wafer with traces. Figure 3 (This is a cross-sectional view of the silicon wafer), resulting in poor surface flatness. The surface of the crystalline silicon substrate prepared in this way will also have line marks originating from the silicon wafer. The presence of these line marks 30 will severely affect the perovskite wet spin-coating process, for example, making it difficult for the perovskite precursor solution to form a film on the substrate 10 surface, resulting in uneven coverage (e.g., ...). Figure 5As shown in the figure, the left picture is a perovskite film 20 spin-coated on the surface of a substrate 10 without line trace, and the right picture is a perovskite film 20 spin-coated on the surface of a substrate 10 with micron-level line trace 30, which will pierce the perovskite film, resulting in a large defect density of the perovskite film 20, which is not conducive to the improvement of solar cell efficiency. In some embodiments of the present application, the perovskite film is prepared by the above-mentioned spin-coating method. Even if the surface of the substrate 10 has a certain line trace 30, the perovskite precursor solution can still relatively uniformly cover and infiltrate the substrate surface, the crystal grains grow uniformly, and a perovskite film 20 with good quality is formed, as shown in Figure 6 .

[0038] According to some embodiments of the present application, referring to Figure 7 , the first spin-coating mode includes a first acceleration stage S1 and a first uniform speed stage S2. The first acceleration stage S1 is a stage in which the rotation speed gradually increases from 0 (i.e., the start of rotation) to the rotation speed of the first uniform speed stage. The second spin-coating mode includes a second acceleration stage S3 and a second uniform speed stage S4. The second acceleration stage S3 is a stage in which the rotation speed increases from the rotation speed of the first uniform speed stage S2 to the rotation speed of the second uniform speed stage S4. After the second spin-coating mode ends, the spin-coating device is turned off, and a deceleration stage S5 is entered, in which the rotation speed gradually decreases from the rotation speed of the second uniform speed stage S4 to 0.

[0039] According to some embodiments of the present application, the rotation speed of the first uniform speed stage is 900-1100 rpm (such as 900 rpm, 950 rpm, 1000 rpm, 1050 rpm, 1100 rpm), and the rotation speed of the second uniform speed stage is 3500-4500 rpm (such as 3500 rpm, 3600 rpm, 3700 rpm, 3800 rpm, 3900 rpm, 4000 rpm, 4100 rpm, 4200 rpm, 4300 rpm, 4400 rpm, 4500 rpm, etc.). Thus, under the rotation speed conditions of the above-mentioned first spin-coating mode, the small centrifugal force increases the residence time of the perovskite precursor solution on the substrate, allowing the perovskite precursor solution to fully infiltrate the substrate surface, resulting in good spreading and infiltration, improving the coating performance, reducing the film-forming difficulty, and even for the substrate surface with poor flatness (such as the surface with protruding line traces), the perovskite precursor solution can still be well covered, and no substrate surface exposure occurs. Under the above-mentioned high-speed second spin-coating mode conditions, the solvent in the perovskite precursor solution can be effectively volatilized, and the centrifugal force will not be too large to cause the perovskite precursor solution to splash, thereby obtaining a pre-film with good film-forming properties, so as to obtain a perovskite film with good film-forming properties, compactness, and uniformity.

[0040] In some embodiments, the rotation speed of the first uniform stage is 1000 rpm, and the rotation speed of the second uniform stage is 4000 rpm. Thus, the prepared perovskite film has better compactness and uniformity, and can well cover the surface of the substrate.

[0041] According to some embodiments of the present application, the first predetermined time is 8-15 s, such as 8 s, 9 s, 10 s, 11 s, 12 s, 13 s, 14 s, 15 s, etc. Under the above conditions, the perovskite precursor solution has sufficient time to stay on the substrate during the first spin coating mode process, so that the perovskite precursor solution can fully infiltrate and cover the surface of the substrate; the second predetermined time is 18-22 s, such as 18 s, 19 s, 20 s, 21 s, 22 s, etc. Thus, during the second spin coating mode process within the above time, the solvent in the perovskite precursor solution can be sufficiently volatilized, and a perovskite film with small defect density, uniformity and compactness is formed.

[0042] According to some embodiments of the present application, the acceleration of the first acceleration stage is 450-550 rpm / s, such as 450 rpm / s, 460 rpm / s, 470 rpm / s, 480 rpm / s, 490 rpm / s, 500 rpm / s, 510 rpm / s, 520 rpm / s, 530 rpm / s, 540 rpm / s, 550 rpm / s, etc. Under the above acceleration conditions, the rotation speed of the spin coating process can be quickly and stably increased to the required rotation speed of the first uniform stage, and enter the first uniform stage. In other embodiments of the present application, the acceleration of the second acceleration stage is 550-650 rpm / s, such as 550 rpm / s, 560 rpm / s, 570 rpm / s, 580 rpm / s, 590 rpm / s, 600 rpm / s, 610 rpm / s, 620 rpm / s, 630 rpm / s, 640 rpm / s, 650 rpm / s, etc. Under the above acceleration conditions, the first uniform stage can quickly and stably enter the second uniform stage.

[0043] According to some embodiments of the present application, the anti-solvent is added dropwise in the second uniform stage. Thus, the anti-solvent is added dropwise in a stable state, which helps to improve the uniformity of the anti-solvent spreading, suppresses the splashing or edge accumulation of the solution, and further helps to accurately control the solvent evaporation rate and perovskite nucleation and crystallization behavior.

[0044] According to some embodiments of the present application, the annealing treatment is performed at a temperature of 80-120°C, such as 80°C, 90°C, 100°C, 110°C, 120°C, etc., for a time period of 15-25 min, such as 15 min, 16 min, 17 min, 18 min, 19 min, 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, etc. As a result, the above annealing conditions can effectively promote the growth of perovskite grains and optimize the crystallization, and are beneficial to eliminate and repair defects, release the stress between the perovskite film and the substrate, and reduce the risk of perovskite film cracking or peeling.

[0045] According to some embodiments of the present application, the perovskite layer comprises a perovskite material. In some embodiments, the perovskite material comprises at least one of a compound represented by [A][B][X]3, a compound represented by [A]2[C][D][X]6, wherein A comprises at least one of an inorganic or organic monovalent cation, B comprises at least one inorganic divalent cation, C comprises at least one inorganic monovalent cation, D comprises at least one inorganic trivalent cation, and X comprises at least one monovalent anion.

[0046] Exemplarily, the organic monovalent cation comprises at least one of (NR 14 R 15 R 16 R 17 ) + , (R 14 R 15 N=CR 16 R 17 ) + , (R 14 R 15 N-C(R 18 )=NR 16 R 17 ) + or (R 14 R 15 N-C(NR 18 R 19 )=NR 16 R 17 ) + , wherein R 14 , R 15 , R 16 , R 17 , R 18 and R 19 are each independently selected from H, substituted or unsubstituted C1-C20 alkyl, or substituted or unsubstituted aryl. For example, the organic monovalent cation comprises (H2N=CH-NH2) + (abbreviated as FA), CH3NH3 +at least one of Li

[0047] Exemplary inorganic monovalent cations include at least one of Li + , Na + , K + , Rb + , Cs + , Cu + , Ag + , Au + , or Hg + . Exemplary inorganic divalent cations include at least one of Pb 2+ , Sn 2+ , Be 2+ , Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , Zn 2+ , Ge 2+ , Fe 2+ , Co 2+ , Ni 2+ , Cd 2+ , Cu 2+ , Mn 2+ , Pd 2+ , Yb 2+ , or Eu 2+ . Exemplary inorganic trivalent cations include at least one of Bi 3+ , Sb 3+ , Cr 3+ , Fe 3+ , Co 3+ , Ga 3+ , As 3+ , Ru 3+ , Rh 3+ , In 3+ , Ir 3+ , Au 3+ , or Al 3+ . Exemplary monovalent anions include at least one of F - , Cl - , Br - , I - , SCN - , CNO - , OCN - , OSCN - , SH - , OH - , CN - , SeCN - .

[0048] According to some embodiments of the present application, the specific types of anti-solvents include, but are not limited to, chlorobenzene, chloroform, o-dichlorobenzene, toluene, anisole, diethyl ether, 2-propanol, n-butanol, isopropanol, ethyl acetate, butyl acetate, n-hexane, and the like.

[0049] In another aspect of the present application, the present application provides a perovskite thin film. According to embodiments of the present application, the perovskite thin film is prepared by the method described above. Thus, the perovskite thin film has good compactness, uniformity, and grain growth quality, and can uniformly cover the surface of the substrate. It is understood by those skilled in the art that the perovskite thin film has all the features and advantages of the method described above, and will not be described in more detail here.

[0050] In yet another aspect of the present application, the present application provides a method for preparing a solar cell. According to embodiments of the present application, the method comprises:

[0051] T10: providing a substrate 10.

[0052] According to some embodiments of the present application, the solar cell can be a single-junction perovskite solar cell, or a crystalline silicon-perovskite tandem cell.

[0053] In some embodiments of the present application, the solar cell can be a single-junction perovskite solar cell, and the substrate can be a transparent conductive glass substrate.

[0054] In other embodiments, the solar cell can be a crystalline silicon-perovskite tandem cell, and the substrate can be a crystalline silicon bottom cell. Figure 8 The substrate 10 comprises a crystalline silicon bottom cell 11 and a composite layer 12 between the crystalline silicon bottom cell 11 and the first charge transport layer 40. Thus, even if the crystalline silicon bottom cell has poor processing in the front cleaning or alkali etching stage of the silicon wafer, resulting in raised line marks on the surface of the silicon wafer (as shown in Figure 2 , Figure 3 and Figure 4 , Figure 2 the left image is a silicon wafer without line marks, and the right image is a silicon wafer with line marks, Figure 3 is a cross-sectional view of the silicon wafer), the surface of the crystalline silicon bottom cell substrate prepared in this way will also have line marks from the silicon wafer. In the process of preparing a perovskite top cell on a substrate surface with line marks, the spin coating method described above can be used to prepare the perovskite thin film in the subsequent steps, so that the perovskite precursor solution can relatively uniformly cover and infiltrate the substrate surface, promote uniform grain growth, and form a perovskite thin film with good quality.

[0055] In some embodiments, the specific cell type of the above-mentioned crystalline silicon bottom cell does not have special requirements, and those skilled in the art can flexibly select according to actual needs, such as heterojunction crystalline silicon bottom cell, TOPCon crystalline silicon bottom cell, BC crystalline silicon bottom cell, etc. In some specific embodiments, the crystalline silicon bottom cell is a TOPCon crystalline silicon bottom cell, i.e., the solar cell is a TOPCon-perovskite laminated cell, and the structure schematic diagram can refer to Figure 9 The TOPCon crystalline silicon bottom cell includes: a silicon wafer 101; a tunneling oxide layer 102 located on the side of the silicon wafer 101 close to the perovskite top cell; an n-type doped polysilicon layer 103 (such as phosphorus doping) located on the side of the tunneling oxide layer 102 close to the perovskite top cell; a p-type doped silicon layer 104 (such as boron doping) located on the side of the silicon wafer 101 away from the perovskite top cell; a passivation layer 105 located on the side of the p-type doped silicon layer 104 away from the perovskite top cell; an anti-reflection layer 106 located on the side of the passivation layer 105 away from the perovskite top cell; and a back electrode 107 in contact with the p-type doped silicon layer 104. The composite layer 12 is located on the surface of the n-type doped polysilicon layer 103 away from the silicon wafer 101.

[0056] T20: Forming a first charge transport layer 40 on one side of the substrate 10.

[0057] In some embodiments, one of the first charge transport layer in this step and the second charge transport layer in the subsequent step can be a hole transport layer, and the other can be an electron transport layer. In some specific embodiments, the first charge transport layer is a hole transport layer, and the second charge transport layer is an electron transport layer.

[0058] The hole transport material in the hole transport layer can include, but is not limited to, one or more of the following materials and their derivatives: nickel oxide (NiO xcopper iodide (Cul), cuprous oxide (Cu20), cuprous thiocyanate (CuSCN), 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene (Spiro-OMeTAD), 2,2',7,7'-tetra(di-p-tolylamino)spiro-9,9'-bifluorene (Spiro-TTB), poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), and [4-(3,6-dimethoxy-9H-carbazol-9-yl)butyl]phosphonic acid (MeO-4PACz), (4-(3,6-dimethyl-9H-carbazol-9-yl)butyl)phosphonic acid (Me-4PACz), [4-(9H-carbazol-9-yl)butyl]phosphonic acid (4PACz), (4-(3,6-dibromo-9H-carbazol-9-yl)butyl)phosphonic acid (Br-4PACz), [2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid (MeO-2PACz), (2-(3,6-dimethyl-9H-carbazol-9-yl)ethyl)phosphonic acid (Me-2PACz), (2-(9H-carbazol-9-yl)ethyl)phosphonic acid (2PACz), (2-(3,6-dibromo-9H-carbazol-9-yl)ethyl)phosphonic acid (Br-2PACz), 4-(7H-dibenzo(c,g)carbazol-7-yl)butylphosphonic acid (4PADCB), and the like.

[0059] The electron transport material in the electron transport layer can include, but is not limited to, one or more of the following materials and derivatives thereof: imide compounds, quinone compounds, fullerenes and derivatives thereof, methoxytriphenylamine-fluoroformamidine (OMeTPA-FA), calcium titanate (CaTi03), lithium fluoride (LiF), calcium fluoride (CaF2), poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid (PEDOT:PSS), poly 3-hexyl thiophene (P3HT), triptycene-core triphenylamine (H101), 3,4-ethylenedioxythiophene-methoxytriphenylamine (EDOT-OMeTPA), N-(4-phenyl)carbazole-spirobifluorene (CzPAF-SBF), polythiophene, metal oxides, silicon oxide (Si02), strontium titanate (SrTi03), cuprous thiocyanate (CuSCN), and the like.

[0060] In some embodiments, the first charge transport layer is a hole transport layer, which can be a self-assembled hole transport layer. The preparation method of the self-assembled hole transport layer is not limited, and a person skilled in the art can flexibly select according to the prior art. In some embodiments, when the self-assembled hole transport layer is prepared on a substrate with a line mark, the presence of the line mark can cause the anchoring effect of the monolayer serving as the hole transport layer on the substrate to be poor, such as poor local uniformity, missing, staggered growth, and the like, which directly affects the crystalline orientation and crystalline quality of the perovskite. The above-mentioned method for preparing a perovskite thin film by spin coating can significantly improve the crystalline orientation and crystalline quality of the perovskite.

[0061] T30: On the side of the first charge transport layer 40 away from the substrate 10, a perovskite thin film 20 is prepared by spin coating using the method described above.

[0062] T40: A second charge transport layer 50 is formed on the side of the perovskite thin film 20 away from the substrate 10.

[0063] In some embodiments, the second charge transport layer is an electron transport layer. The preparation method of the electron transport layer is not limited, and a person skilled in the art can flexibly select according to the prior art. In some specific embodiments, the electron transport layer can be a composite laminated structure of C60 and SnO2.

[0064] T50: An electrode 60 is formed on the side of the second charge transport layer 50 away from the substrate.

[0065] In some embodiments, the electrode can include a transparent electrode and / or a metal electrode.

[0066] According to embodiments of the present application, the solar cell prepared by the above-mentioned method has a perovskite thin film with good film formation quality and good coverage on the surface of the substrate, which helps to improve the cell efficiency of the solar cell. In addition, the yield of the above-mentioned preparation method is good.

[0067] In another aspect of the present application, a solar cell is provided. According to embodiments of the present application, the solar cell is prepared by the above-mentioned method, or includes the above-mentioned perovskite thin film. Therefore, the solar cell has high cell efficiency.

[0068] In another aspect of the present application, a photovoltaic module is provided. According to embodiments of the present application, the photovoltaic module includes the above-mentioned solar cell. Therefore, the photovoltaic module has good performance and efficiency.

[0069] Embodiments

[0070] Embodiment 1

[0071] A TOPCon crystalline silicon bottom cell is provided, which comprises: a silicon wafer 101; a tunneling oxide layer 102 located on one side of the silicon wafer 101 close to a perovskite top cell; an n-type doped polysilicon layer 103 (such as phosphorus doping) located on one side of the tunneling oxide layer 102 close to the perovskite top cell; a p-type doped silicon layer 104 (such as boron doping) located on one side of the silicon wafer 101 away from the perovskite top cell; a passivation layer 105 located on one side of the p-type doped silicon layer 104 away from the perovskite top cell; an anti-reflection layer 106 located on one side of the passivation layer 105 away from the perovskite top cell; and a back electrode 107 connected in contact with the p-type doped silicon layer 104. The surface of the silicon wafer has a certain line mark, such as Figure 2 and 3 As shown, the surface of the n-type doped polysilicon layer 103 of the TOPCon crystalline silicon bottom cell thus prepared still has a line mark derived from the silicon wafer.

[0072] An ITO composite layer 12 is formed on the surface of the n-type doped polysilicon layer 103 away from the silicon wafer 101 by magnetron sputtering.

[0073] The surface of the ITO composite layer is cleaned and treated with UV light and ozone to grow anchor groups on the surface of the ITO composite layer.

[0074] The above-mentioned semi-finished product with grown anchor groups is immersed in an ethanol solution of self-assembled hole material (4PADCB) for 19 minutes and then taken out to obtain a self-assembled hole transport layer, wherein the concentration of 4PADCB is 2.5 mg / ml. Due to the line mark on the surface of the n-type doped polysilicon layer 103 of the TOPCon crystalline silicon bottom cell.

[0075] Perovskite film is prepared by spin coating: 120 uL of 1.5 mmol / l perovskite precursor solution is added dropwise on the surface of the hole transport layer, the rotation speed is accelerated to 1000 rpm at an acceleration of 500 rpm / s, and then uniform rotation is performed at a rotation speed of 1000 rpm for a certain time. The total time of this first spin coating mode is 10 seconds; then the rotation speed is increased to 4000 rpm at an acceleration of 600 rpm / s, and then uniform rotation is performed for a certain time. The total time of this second spin coating mode is 20 seconds, and the anti-solvent ethyl acetate is added dropwise at the 15th second of the second spin coating; finally, the rotation is stopped, and the rotation speed gradually decreases to 0, completing the spin coating process. The temperature during the entire spin coating process is 20℃, and the humidity is 10%; finally, the prepared pre-film is annealed at 100℃ for 20 minutes to obtain a perovskite film Cs 0.22 FA 0.78 Pb(I 0.85 Br 0.15 )3, and its scanning electron microscope can refer to Figure 10 (corresponding to Figure 10 1000 rpm in the upper right corner), and the physical map can refer toFigure 11 .

[0076] A 15nm-thick C60 layer is prepared on the surface of the perovskite thin film by vacuum evaporation, and then a 8nm-thick tin oxide layer is deposited by ALD to obtain an electron transport layer.

[0077] An ITO layer with a thickness of 50nm is deposited on the surface of the electron transport layer by magnetron sputtering;

[0078] A silver electrode with a thickness of 100nm is deposited on the surface of the ITO layer by thermal evaporation, wherein the silver evaporation rate is 0.1nm / s;

[0079] An encapsulation film is prepared to obtain a perovskite top cell, and the preparation of the crystalline silicon-perovskite tandem cell is completed.

[0080] Example 2

[0081] The steps for preparing the crystalline silicon-perovskite tandem cell are basically the same as those in Example 1, except that in the preparation of the perovskite thin film by spin coating, the rotation speed of the first uniform speed stage in the first spin coating mode is 1100rpm. The scanning electron microscope of the prepared perovskite thin film can refer to Figure 10 (corresponding to Figure 10 the upper right corner of FIG. 11 100rpm), and the physical diagram can refer to Figure 11 .

[0082] Example 3

[0083] The steps for preparing the crystalline silicon-perovskite tandem cell are basically the same as those in Example 1, except that in the preparation of the perovskite thin film by spin coating, the rotation speed of the first uniform speed stage in the first spin coating mode is 900rpm. The scanning electron microscope of the prepared perovskite thin film can refer to Figure 10 (corresponding to Figure 10 the upper right corner of FIG. 9 900rpm), and the physical diagram can refer to Figure 11 .

[0084] Example 4

[0085] The steps for preparing the crystalline silicon-perovskite tandem cell are basically the same as those in Example 1, except that in the preparation of the perovskite thin film by spin coating, the time of the first spin coating mode is 7s.

[0086] Example 5

[0087] The steps for preparing the crystalline silicon-perovskite tandem cell are basically the same as those in Example 1, except that in the preparation of the perovskite thin film by spin coating, the time of the first spin coating mode is 8s.

[0088] Example 6

[0089] The steps for preparing the crystalline silicon-perovskite tandem cell are basically the same as those in Example 1, except that in the spin-coating for preparing the perovskite film, the time for the first spin-coating mode is 12 s.

[0090] Example 7

[0091] The steps for preparing the crystalline silicon-perovskite tandem cell are basically the same as those in Example 1, except that in the spin-coating for preparing the perovskite film, the time for the first spin-coating mode is 15 s.

[0092] Example 8

[0093] The steps for preparing the crystalline silicon-perovskite tandem cell are basically the same as those in Example 1, except that in the spin-coating for preparing the perovskite film, the rotation speed in the second uniform speed stage in the second spin-coating mode is 3400 rpm.

[0094] Example 9

[0095] The steps for preparing the crystalline silicon-perovskite tandem cell are basically the same as those in Example 1, except that in the spin-coating for preparing the perovskite film, the rotation speed in the second uniform speed stage in the second spin-coating mode is 3500 rpm.

[0096] Example 10

[0097] The steps for preparing the crystalline silicon-perovskite tandem cell are basically the same as those in Example 1, except that in the spin-coating for preparing the perovskite film, the rotation speed in the second uniform speed stage in the second spin-coating mode is 3800 rpm.

[0098] Example 11

[0099] The steps for preparing the crystalline silicon-perovskite tandem cell are basically the same as those in Example 1, except that in the spin-coating for preparing the perovskite film, the rotation speed in the second uniform speed stage in the second spin-coating mode is 4200 rpm.

[0100] Example 12

[0101] The steps for preparing the crystalline silicon-perovskite tandem cell are basically the same as those in Example 1, except that in the spin-coating for preparing the perovskite film, the rotation speed in the second uniform speed stage in the second spin-coating mode is 4500 rpm.

[0102] Example 13

[0103] The steps for preparing the crystalline silicon-perovskite tandem cell are basically the same as those in Example 1, except that in the spin-coating for preparing the perovskite film, the rotation speed in the second uniform speed stage in the second spin-coating mode is 4600 rpm.

[0104] Comparative Example 1

[0105] The steps for preparing the crystalline silicon-perovskite tandem cell are basically the same as those in Example 1, except that in the spin coating process for preparing the perovskite film, the rotation speed in the first uniform speed stage in the first spin coating mode is 1300 rpm. The scanning electron microscope of the prepared perovskite film can be referred to Figure 10 (corresponding to Figure 10 the upper right corner of the figure is labeled 1300 rpm), and the actual figure can be referred to Figure 11 .

[0106] Comparative Example 2

[0107] The steps for preparing the crystalline silicon-perovskite tandem cell are basically the same as those in Example 1, except that in the spin coating process for preparing the perovskite film, the rotation speed in the first uniform speed stage in the first spin coating mode is 1200 rpm. The scanning electron microscope of the prepared perovskite film can be referred to Figure 10 (corresponding to Figure 10 the upper right corner of the figure is labeled 1200 rpm), and the actual figure can be referred to Figure 11 .

[0108] Comparative Example 3

[0109] The steps for preparing the crystalline silicon-perovskite tandem cell are basically the same as those in Example 1, except that in the spin coating process for preparing the perovskite film: 1.5 mmol / l of perovskite precursor solution is added dropwise on the surface of the hole transport layer, the rotation speed is accelerated to 3500 rpm at an acceleration of 700 rpm / s, and then uniform rotation is maintained for a certain period of time, and the total time of the acceleration and uniform rotation is 30 seconds; then the rotation is stopped, and the rotation speed gradually decreases to 0, completing the spin coating process, wherein the temperature during the entire spin coating process is 20°C, and the humidity is 10%; finally, the pre-prepared film obtained by spin coating is annealed at 100°C for 20 min to obtain a perovskite film Cs 0.22 FA 0.78 Pb(I 0.85 Br 0.15 )3.

[0110] The crystalline silicon-perovskite tandem cells prepared in Examples 1-15 and Comparative Examples 1-2 above are tested for performance, and the specific test method is as follows: using a solar simulator and an I-V tester, the crystalline silicon-perovskite tandem cells obtained in the above examples and comparative examples are tested for electrical performance under 1 standard solar intensity by steady-state power output test, and the test results are shown in Table 1 (in the table, V1 represents the rotation speed of the uniform rotation in the first spin coating mode (i.e. the rotation speed in the first uniform speed stage), T1 represents the time of the first spin coating mode, and V2 represents the rotation speed of the uniform rotation in the second spin coating mode (i.e. the rotation speed in the second uniform speed stage)).

[0111] Table 1

[0112]

[0113]

[0114]

[0115] Photoluminescence tests were performed on the perovskite thin films prepared in Example 1 and Comparative Example 3, referring to... Figure 12 ,Depend on Figure 12 As can be seen, compared to Comparative Example 3, the peak photoluminescence intensity in Example 1 increased from 2.5*10⁻⁶. 5 Increased to 3.08*10 5 The peak intensity increased by 23%, and the spectral response was significantly enhanced.

[0116] Based on the test data from Examples 1-3 and Comparative Examples 1 and 2 above, and Figure 10 and Figure 11 visible:

[0117] In the segmented spin coating scheme, when the rotation speed in the first uniform speed stage of the first spin coating mode is 900-1100 rpm, the spin-coated perovskite film provides good coverage of the line marks, with no substrate or line mark exposure, resulting in good film quality. When the rotation speed in the first uniform speed stage is too high, the spreading effect of the perovskite precursor solution is relatively poor, which is not conducive to the good spreading of the perovskite precursor solution, leading to poor coverage of the line marks by the perovskite film.

[0118] As the spin coating time of the first spin coating mode increases, the efficiency shows a trend of first increasing and then decreasing. The maximum value still appears at the low-speed spin coating time of 10s. The efficiency increase before 10s is due to the significant improvement of the fill factor and voltage. This indicates that the increase of time has a good effect on the full wetting of the perovskite precursor solution on the surface of the bottom cell.

[0119] The test results for the spin coating speed in the second spin coating mode show that the spin coating speed increases the device efficiency up to 4000 rpm, and then decreases. This indicates that the spin coating speed significantly affects the crystallization process due to the different solvent evaporation processes at different speeds.

[0120] The terms "first" and "second" used in this document are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature marked "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0121] In the description of the specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are contained in at least one embodiment or example of the present application. In the specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the specification and the features of the different embodiments or examples without contradiction.

[0122] Although the embodiments of the present application have been shown and described above, it is understood that the above-described embodiments are exemplary and are not to be construed as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above-described embodiments within the scope of the present application.

Claims

1. A method for spin-coating a perovskite thin film, characterized by, The method comprises: dropping a perovskite precursor solution on a substrate; spinning a first predetermined time and a second predetermined time based on a first spinning mode and a second spinning mode respectively and dropping an anti-solvent during the second spinning mode to obtain a pre-prepared film; annealing the pre-prepared film to obtain the perovskite film; wherein the rotation speed of the first spinning mode is less than the rotation speed of the second spinning mode, and the rotation speed of the first spinning mode is less than or equal to 1100 rpm.

2. The method of claim 1, wherein, The first spinning mode comprises a first acceleration phase and a first uniform speed phase, and the second spinning mode comprises a second acceleration phase and a second uniform speed phase, the rotation speed of the first uniform speed phase is 900-1100 rpm, and the rotation speed of the second uniform speed phase is 3500-4500 rpm.

3. The method of claim 2, wherein, The rotation speed of the first uniform speed phase is 1000 rpm, and the rotation speed of the second uniform speed phase is 4000 rpm.

4. The method of claim 2, wherein, The first predetermined time is 8-15 s, and / or the second predetermined time is 18-22 s.

5. The method of claim 2, wherein, The acceleration of the first acceleration phase is 450-550 rpm / s, and / or the acceleration of the second acceleration phase is 550-650 rpm / s.

6. The method according to any one of claims 2 to 5, characterized in that, The anti-solvent is dropped during the second uniform speed phase.

7. The method according to any one of claims 1 to 5, characterized in that, The annealing temperature is 80-120℃, and the annealing time is 15-25 min.

8. A perovskite thin film, characterized by, The perovskite film is prepared by the method of any one of claims 1-7.

9. A method of fabricating a solar cell, characterized by, The method comprises: providing a substrate; forming a first charge transport layer on one side of the substrate; spinning to prepare a perovskite film on the side of the first charge transport layer away from the substrate by the method of any one of claims 1-7; forming a second charge transport layer on the side of the perovskite film away from the substrate; forming an electrode on the side of the second charge transport layer away from the substrate.

10. The method of claim 9, wherein, The substrate comprises a crystalline silicon bottom cell and a composite layer between the crystalline silicon bottom cell and the first charge transport layer.

11. A solar cell, characterized by, The solar cell is prepared by the method of claim 9 or 10, or comprises the perovskite film of claim 8.

12. A photovoltaic module, characterized by The solar cell of claim 11 is provided.

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