Preparation method for perovskite thin film, thin film, perovskite cell, and stacked cell

Abstract

A preparation method for a perovskite thin film, a thin film, a perovskite cell, and a stacked cell. The preparation method comprises: fabricating a buried layer, wherein the buried layer comprises a formate of an alkali metal; forming a porous thin film containing a compound with a general chemical formula of BX2 on the buried layer; and reacting the compound with a general chemical formula of BX2 in the porous thin film with a compound with a general chemical formula of AX, so as to obtain a perovskite thin film.

Description

Preparation method of perovskite film, film, perovskite battery and stacked battery

[0001] Related applications

[0002] This application claims priority to Chinese patent application number CN202311289096.3, filed on October 7, 2023, entitled “Method for preparing perovskite film, film, perovskite cell and stacked cell,” the entire text of which is hereby incorporated by reference. Technical Field

[0003] The present application relates to the technical field of perovskite cells, and in particular to a method for preparing a perovskite film, the film, a perovskite cell, and a stacked cell. Background Art

[0004] Perovskite solar cells are solar cells that use perovskite-type compound semiconductors with the general organic chemical formula BX2 as light-absorbing materials.

[0005] Traditionally, perovskite thin films can be prepared using a two-step process. For example, in this two-step sequential deposition process, the PbI2 film produced by multi-source evaporation has a relatively dense morphology. This makes it difficult for the organic cations applied by spin coating to fully react with the PbI2 during the subsequent perovskite film preparation, resulting in excessive PbI2 remaining at the bottom. This excess unreacted PbI2 can seriously affect photovoltaic cell performance and accelerate device degradation.

[0006] Summary of the Invention

[0007] According to various embodiments of the present application, a method for preparing a perovskite thin film, a thin film, a perovskite battery, and a stacked battery are provided.

[0008] In a first aspect, an embodiment of the present application provides a method for preparing a perovskite thin film, the preparation method comprising:

[0009] preparing a buried bottom layer; the buried bottom layer comprises an alkali metal formate;

[0010] forming a porous film containing a compound having a general chemical formula of BX2 on the buried bottom layer; and,

[0011] reacting the compound with the general chemical formula BX2 with the compound with the general chemical formula AX in the porous film to obtain a perovskite film;

[0012] Wherein, B is a metal cation; A is an organic amine cation or an alkali metal cation; and X is a halogen ion or a pseudohalogen anion.

[0013] In some embodiments, the step of preparing the buried bottom layer includes:

[0014] adding the alkali metal formate to a first solvent to obtain a first solution;

[0015] The first solution is coated on a substrate to obtain the buried layer.

[0016] In some embodiments, the concentration of the alkali metal formate in the first solution is about 1 mg / mL to 2 mg / mL.

[0017] In some embodiments, the coating area density of the first solution is about 10 μL / cm 2 ~25μL / cm 2 .

[0018] In some embodiments, the first solvent comprises at least one of ethanol and octanol.

[0019] In some embodiments, the step of coating the first solution on a substrate to obtain the buried bottom layer comprises:

[0020] The first solution is spin-coated at a rotation speed of about 3500 rpm to 4500 rpm for about 25 seconds to 35 seconds and annealed at about 95° C. to 105° C. for about 8 minutes to 10 minutes.

[0021] In some embodiments, the step of forming a porous film containing a compound having a chemical formula of BX2 on the buried bottom layer comprises:

[0022] forming a film layer by multi-source evaporation of the compound with the chemical formula BX2 on the buried bottom layer; wherein the thickness of the film layer is about 200nm to 400nm;

[0023] The membrane layer is annealed at about 95° C. to 105° C. to form the porous film.

[0024] In some embodiments, the step of reacting the compound with the general chemical formula BX2 in the porous film with the compound with the general chemical formula AX to obtain a perovskite film comprises:

[0025] A second solution containing the compound with the general chemical formula AX is coated on the porous film.

[0026] In some embodiments, the alkali metal in the alkali metal formate includes at least one of lithium, sodium, potassium, rubidium, and cesium.

[0027] In some embodiments, the alkali metal formate includes at least one of lithium formate, sodium formate, potassium formate, rubidium formate, and cesium formate.

[0028] In some embodiments, the metal cation comprises Pb 2+ and Sn 2+ At least one of .

[0029] In some embodiments, the organic amine cation comprises CH3NH3 + and NH2CH=NH2 + At least one of .

[0030] In some embodiments, the alkali metal cation comprises Cs + and Rb + At least one of .

[0031] In some embodiments, the halide ion comprises Cl - Br - and I - At least one of .

[0032] In some embodiments, the pseudohalogen anion comprises CN - 、SCN - 、OCN - and SeCN - At least one of .

[0033] In a second aspect, an embodiment of the present application provides a thin film, comprising a perovskite thin film prepared by the preparation method of the perovskite thin film as described in the first aspect.

[0034] In a third aspect, an embodiment of the present application provides a perovskite cell comprising the thin film as described in the second aspect.

[0035] In a fourth aspect, an embodiment of the present application provides a stacked battery comprising the perovskite battery described in the third aspect.

[0036] The details of one or more embodiments of the present application are set forth in the following drawings and description. Other features, objects, and advantages of the present application will become apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the conventional technology, the following briefly introduces the drawings required for use in the embodiments or the conventional technology descriptions. Obviously, the drawings described below are merely embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the disclosed drawings without any creative work.

[0038] FIG1 is a flow chart of a method for preparing a perovskite thin film according to an embodiment of the present application;

[0039] FIG2 is a flow chart of step S130 in a method for preparing a perovskite thin film according to an embodiment of the present application;

[0040] FIG3 is a flow chart of step S150 in a method for preparing a perovskite thin film according to an embodiment of the present application;

[0041] FIG4 is a SEM image of the PbI2 film of Comparative Example 1 of the present application;

[0042] FIG5 is a SEM image of the PbI2 porous film of Example 1 of the present application;

[0043] FIG6 is a SEM image of the perovskite film of Example 4 of the present application;

[0044] FIG7 is a SEM image of the perovskite film of Example 1 of the present application;

[0045] FIG8 is a SEM image of the perovskite film of Example 5 of the present application;

[0046] FIG9 is a box plot of the photoelectric conversion efficiency of the perovskite cells of Example 2, Comparative Example 1, and Example 4 of the present application;

[0047] FIG10 is a schematic diagram of the aging test results of the perovskite cells of Example 2 and Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0048] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0049] Traditionally, perovskite thin films can be prepared using a two-step process. For example, in this two-step sequential deposition process, the PbI2 film produced by multi-source evaporation has a relatively dense morphology. This makes it difficult for the organic cations applied by spin coating to fully react with the PbI2 during the subsequent perovskite film preparation, resulting in excessive PbI2 remaining at the bottom. This excess unreacted PbI2 can seriously affect photovoltaic cell performance and accelerate device degradation.

[0050] Based on this, in the first aspect, an embodiment of the present application provides a method for preparing a perovskite thin film. Referring to FIG. 1 , the preparation method includes step S110 , step S130 , and step S150 .

[0051] Step S110: preparing a buried bottom layer; the buried bottom layer comprises alkali metal formate.

[0052] In step S110, the formate ions in the formate contained in the buried layer are relatively small in size. At the same time, the formate ions are easily migrated when heated. In the process of moving upward, the formate ions can move through the grain boundaries in the metal halide, thereby forming a porous structure in the metal halide film. In some embodiments, the alkali metal in the formate of the present application includes any one of lithium, sodium, potassium, rubidium and cesium. Optionally, the alkali metal formate in the present application includes one or more of sodium formate, potassium formate, rubidium formate and cesium formate, and multiple refers to two or more. Further optionally, the above-mentioned alkali metal formate includes sodium formate.

[0053] Alkali metal ions are conducive to oriented crystallization, allowing the subsequent formation of a well-oriented porous film. More specifically, the alkali metal ions allow the holes on the porous film to penetrate the thickness of the porous film. Compared with holes that are staggered with each other, this well-oriented porous film is more conducive to the cations entering its bottom during subsequent reactions. In this application, under the combined action of alkali metal ions and formate ions, the metal halide film will form a well-oriented porous film. The holes on the porous film can become channels for organic amine cations or alkali metal cations to enter the metal halide film, allowing the metal halide of the porous film to fully react, even the metal halide located at the bottom of the porous film can fully react.

[0054] In some embodiments, referring to FIG2 , step S110 includes step S111 and step S112:

[0055] Step S111, adding alkali metal formate to a first solvent to obtain a first solution; and,

[0056] Step S112: coating the first solution on the substrate to obtain a buried layer. It is understood that the buried layer can be directly or indirectly formed on the substrate.

[0057] In some embodiments, the concentration of the alkali metal formate in the first solution is about 1 mg / mL to 2 mg / mL; optionally 1.2 mg / mL to 1.8 mg / mL, and further optionally 1.3 mg / mL to 1.7 mg / mL. In more detail, the concentration of the alkali metal formate in the first solution is 1 mg / mL to 2 mg / mL, including any point value within this numerical range, for example, the concentration of the alkali metal formate in the first solution is 1 mg / mL, 1.1 mg / mL, 1.2 mg / mL, 1.3 mg / mL, 1.4 mg / mL, 1.5 mg / mL, 1.6 mg / mL, 1.7 mg / mL, 1.8 mg / mL, 1.9 mg / mL or 2.0 mg / mL. In some embodiments, the coating surface density of the first solution is about 10 μL / cm 2 ~25μL / cm 2Any point within this numerical range is included. For example, the coating area density of the first solution is 10 μL / cm 2 , 12μL / cm 2 , 15μL / cm 2 , 18μL / cm 2 , 20μL / cm 2 , 22μL / cm 2 , 24μL / cm 2 or 25 μL / cm 2 .

[0058] The formate concentration and / or coating density are selected as described above in the present application to achieve a moderate pore density and pore structure in the metal halide film, thereby ensuring the performance of the prepared perovskite cell. If the formate concentration and / or coating density are relatively low, the pore density of the metal halide film may be too low, or it may be difficult to form a porous and loose structure. If the formate concentration is relatively high, it may damage the metal halide film or even cause the film layer to be too loose, adversely affecting the performance of the final perovskite cell.

[0059] Optionally, the first solvent includes at least one of ethanol and octanol. The first solvent may be ethanol, octanol, or a mixture of the two.

[0060] In some embodiments, step S112 includes:

[0061] The first solution is spin-coated at a rotation speed of about 3500 rpm to 4500 rpm for about 25 seconds to 35 seconds and annealed at about 95° C. to 105° C. for about 8 minutes to 10 minutes.

[0062] In some embodiments, the spin coating speed of the first solution is 3500 rpm to 4500 rpm, including any value within this numerical range; for example, the spin coating speed of the first solution is 3500 rpm, 3600 rpm, 3700 rpm, 3800 rpm, 3900 rpm, 4000 rpm, 4200 rpm, or 4500 rpm. The spin coating time of the first solution is 25 s to 35 s, including any value within this time range; for example, the spin coating time of the first solution is 25 s, 26 s, 28 s, 30 s, 32 s, 34 s, or 35 s. The annealing temperature of the first solution is 95° C. to 105° C., including any value within this temperature range; for example, the annealing temperature of the first solution is 95° C., 98° C., 100° C., 102° C., 104° C., or 105° C. The annealing time of the first solution is 8 min to 10 min, including any point value within this time range; for example, the annealing time of the first solution is 8 min, 9 min or 10 min.

[0063] Step S130: forming a porous film containing a compound with a chemical formula of BX2 on the buried layer.

[0064] In step S130, B is a metal cation, and X is a halogen ion or a pseudohalogen anion. In some embodiments, the metal cation includes Pb 2+ and Sn 2+ At least one of; halogen ions include Cl - Br - and I - At least one of; pseudohalogen anions include CN - 、SCN - 、OCN - and SeCN - At least one of .

[0065] For example, BX2 can be at least one of PbI2, PbCl2, PbBr2, SnI2, SnCl2, and SnBr2, but is not limited to the compounds listed above. Alternatively, BX2 includes PbI2. The porous film can contain only one or more compounds having the general chemical formula BX2.

[0066] In some embodiments, the porous film can be formed by a vacuum method, such as thermal evaporation, close-space sublimation, vapor transport deposition, or chemical vapor deposition. Alternatively, the porous film can be formed by multi-source evaporation.

[0067] In some embodiments, referring to FIG3 , step S130 includes:

[0068] Step S131 : forming a film layer by multi-source evaporation of a compound having a chemical formula of BX2 on the buried bottom layer.

[0069] In some embodiments, the thickness of the film layer is about 200 nm to 400 nm, including any value within the thickness range, for example, the thickness of the film layer is 200 nm, 220 nm, 250 nm, 280 nm, 300 nm, 320 nm, 350 nm, 380 nm or 400 nm;

[0070] Step S132 , annealing the film layer at about 95° C. to 105° C. to form a porous film.

[0071] In some embodiments, the annealing temperature of step S132 is 95°C to 105°C, including any point in this temperature range, for example, the annealing temperature of the film layer is 95°C, 98°C, 99°C, 100°C, 101°C, 103°C or 105°C.

[0072] It should be noted that in step S131, the temperature of the position where the substrate is located is relatively low, and generally, the carrier temperature will not exceed 75°C. In step S132, during the annealing process, formate ions can migrate in the compound with the general chemical formula BX2 at a temperature of 95°C to 105°C to form a porous film. Another reason why the present application uses alkali metal formates as the material for making the buried bottom layer is that formate ions are small molecules with low melting and boiling points, and can migrate in large quantities at a temperature of 95°C to 105°C. If other acid ions are used, for example, sodium propionate is used to make the buried bottom layer, since the molecular weight of the propionate ion is larger than that of the formate ion, it is difficult for the propionate ion to move at the grain boundary in the metal halide. On the other hand, it is difficult for the propionate ion to migrate at a temperature of 95°C to 105°C, resulting in the inability to form a porous film.

[0073] Step S150 : reacting the compound with the chemical formula BX2 in the porous film with the compound with the chemical formula AX to obtain a perovskite film.

[0074] In step S150, A is an organic amine cation or an alkali metal cation; X is a halogen ion or a pseudohalogen anion. In some embodiments, the organic amine cation includes CH3NH3 + and NH2CH=NH2 + At least one of; alkali metal cations including Cs + and Rb + At least one of; halogen ions include Cl - Br - and I - At least one of; pseudohalogen anions include CN - 、SCN - 、OCN - and SeCN - At least one of .

[0075] For example, AX can be at least one of methylamine iodine, methylamine bromide, formamidine iodine, and formamidine bromide, but is not limited to the aforementioned compounds. AX that reacts with BX2 can be one or more compounds. The reaction of AX and BX2 can produce a perovskite material having the general chemical formula ABX3.

[0076] In some embodiments, step S150 includes step S151.

[0077] Step S151: coating a second solution on the porous film, wherein the second solution contains a compound with a chemical formula of AX.

[0078] Alternatively, AX can be coated on a porous film by a solution method (e.g., spin coating, blade coating, slit coating, screen printing, inkjet printing, spraying, ultrasonic atomization), and the pores on the porous film serve as channels for organic amine cations or alkali metal cations to enter the metal halide film, enabling the metal halide in the porous film to fully react.

[0079] In summary, the embodiment of the present application provides a method for preparing a perovskite film, in which a buried bottom layer is prepared before forming a metal halide film (a film containing a compound with the general chemical formula BX2), and the buried bottom layer contains alkali metal formate. The formate ions move upward when heated, and the formate ions are small. In the process of moving upward, they can move through the grain boundaries in the metal halide, thereby forming a porous structure of the metal halide film, and the alkali metal ions are conducive to oriented crystallization. Under the joint action of alkali metal ions and formate ions, the metal halide film will form a porous film with good orientation. The holes on the porous film can become channels for organic amine cations or alkali metal cations to enter the metal halide film, so that the metal halide in the porous film can fully react, even the metal halide located at the bottom of the porous film can fully react. The metal halide in the perovskite film prepared by the present application fully reacts, avoiding the effect of excessive unreacted metal halide on the performance of the perovskite solar cell.

[0080] In addition, the preparation of the buried bottom layer in this application will not affect the metal halide film preparation process, and no additional process steps need to be added subsequently. The process flow is simpler and more suitable for industrial production.

[0081] The preparation method provided in the present application can solve the problem that the morphology of the PbI2 film prepared by multi-source evaporation in the current two-step sequential deposition process is relatively dense, and the organic cations applied by spin coating are difficult to fully react with PbI2, so that the organic amine cations or alkali metal cations can fully react with the metal halide (such as PbI2) through the pores of the porous film.

[0082] Although the conventional technology can also prepare a porous PbI2 layer with an ordered array structure by combining succinamide (SA) additives with nanoimprinting technology, the preparation method is to introduce SA into the PbI2 precursor solution to form hydrogen bonds, thereby forming a porous PbI2-SA film, and then by nanoimprinting technology to obtain an ordered array structure of PbI2-SA. Therefore, although the preparation method solves the compactness problem of the PbI2 film, it is contrary to the use of multi-source evaporation to prepare the PbI2 film in industrial production. It is also necessary to combine with nanoimprinting technology in the follow-up, and the process is too cumbersome. Compared with the above-mentioned preparation method, the preparation method provided in the present application is more suitable for preparing PbI2 film by multi-source evaporation, and the process is simpler.

[0083] In a second aspect, embodiments of the present application provide a thin film comprising a perovskite thin film prepared by the method for preparing a perovskite thin film as described in the first aspect. It is understood that the thin film may be solely a perovskite thin film, or a combination of a perovskite thin film and other thin films.

[0084] In a third aspect, an embodiment of the present application provides a perovskite cell comprising the thin film as described in the second aspect.

[0085] In some embodiments, the method for manufacturing the perovskite cell comprises the following steps:

[0086] A substrate is provided; the substrate can be any substrate known in the art suitable for forming a perovskite thin film thereon to prepare a perovskite cell. Examples include a transparent conductive substrate, a transport layer (hole transport layer or electron transport layer), or a combination of a transport layer and other structures (e.g., a crystalline silicon cell and / or a passivation layer). The substrate can be planar or textured.

[0087] Taking the substrate as a crystalline silicon cell as an example, the method for manufacturing the perovskite cell further includes the following steps:

[0088] Sputtering a transmission layer on the crystalline silicon cell; wherein the buried bottom layer is formed on the transmission layer;

[0089] Alternatively, a transmission layer is sputtered on the crystalline silicon cell, and then a passivation layer is formed on the transmission layer; wherein the buried bottom layer is formed on the passivation layer.

[0090] In some embodiments, the step of sputtering a transport layer on a crystalline silicon cell includes:

[0091] A transport layer is prepared by PVD sputtering a layer of hole transport material (eg nickel oxide, PEDOT:PSS, Cu2O, PTAA, poly-TPD or c-OTPD) or electron transport material on a crystalline silicon cell.

[0092] In some embodiments, a transport layer is sputtered on a crystalline silicon cell, and then a passivation layer is formed on the transport layer; wherein the step of forming the buried bottom layer on the passivation layer includes:

[0093] A transport layer is prepared by sputtering a layer of hole transport material or electron transport material on a substrate by PVD;

[0094] Then, 2-PACz ([4-(9H-carbazol-9-yl)ethyl]phosphonic acid) and / or MeO-2PACz ([2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid) are added to the ethanol solution and spin-coated at a rotation speed of about 3500 rpm to 4500 rpm for about 25 s to 35 s and annealed at about 95° C. to 105° C. for about 8 min to 10 min.

[0095] Optionally, the hole transport material includes at least one of nickel oxide, PEDOT:PSS (poly(3,4-ethylenedioxythiophene):polystyrenesulfonic acid), cuprous oxide, PTAA (poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine]), and poly-TPD (poly[bis(4-phenyl)(4-butylphenyl)amine]);

[0096] In some embodiments, the spin coating speed of the 2-PACz ethanol solution is 3500 rpm to 4500 rpm, including any value within this numerical range; for example, the spin coating speed of the 2-PACz ethanol solution is 3500 rpm, 3600 rpm, 3700 rpm, 3800 rpm, 3900 rpm, 4000 rpm, 4200 rpm, or 4500 rpm. The spin coating time of the 2-PACz ethanol solution is 25 to 35 seconds, including any value within this time range; for example, the spin coating time of the 2-PACz ethanol solution is 25 seconds, 26 seconds, 28 seconds, 30 seconds, 32 seconds, 34 seconds, or 35 seconds. The annealing temperature of the 2-PACz ethanol solution is 95°C to 105°C, including any value within this temperature range; for example, the annealing temperature of the 2-PACz ethanol solution is 95°C, 98°C, 100°C, 102°C, 104°C, or 105°C. The annealing time of the ethanol solution of 2-PACz is 8 min to 10 min, including any point value within this time range; for example, the annealing time of the ethanol solution of 2-PACz is 8 min, 9 min or 10 min.

[0097] Exemplarily, the perovskite cell includes a transparent conductive substrate, an electron transport layer, a perovskite film, a hole transport layer and a top electrode. The perovskite cell can be nip type (also called formal or cis) or pin type (also called trans), but is not limited to the above structure.

[0098] In a fourth aspect, embodiments of the present application provide a tandem cell comprising the perovskite cell described in the third aspect. Exemplarily, the tandem cell may be a crystalline silicon / perovskite tandem cell, a full perovskite tandem cell, or a thin film cell (e.g., copper indium gallium selenide) / perovskite tandem cell.

[0099] The following examples will describe the performance of the perovskite film prepared in this application. It should be understood that these examples are only used to illustrate this application and are not intended to limit the scope of this application. For experimental methods in the following examples where specific conditions are not specified, please refer to the instructions given in this application first. Alternatively, you can follow the experimental manuals or conventional conditions in this field, or the conditions recommended by the manufacturer, or refer to experimental methods known in the art.

[0100] Example 1

[0101] The method for preparing the perovskite film of this embodiment includes:

[0102] The prepared crystalline silicon cell is sputtered with a layer of NiO by PVD x The film acts as a hole transport layer;

[0103] Then, 1 mg of 2-PACz was added to 1 mL of ethanol solution and spin-coated at 4000 rpm for 30 s and annealed to obtain a passivation layer;

[0104] Then, 2 mg of sodium formate was added to 1 mL of ethanol solution and spin-coated at 4000 rpm for 30 s. The coating density of the sodium formate ethanol solution was 20 μL / cm 2 , annealing at 100 ° C for 10 min to obtain the buried bottom layer;

[0105] Multi-source evaporation of PbI2 on the buried substrate followed by annealing at 100° C. to form a PbI2 porous thin film; and,

[0106] The PbI2 in the porous film is reacted with an organic amine salt to obtain a perovskite film.

[0107] Example 2

[0108] The preparation method of the perovskite battery provided in this embodiment comprises the following steps:

[0109] The perovskite film was prepared. The difference between this step and Example 1 is that 1 mg of sodium formate was added to 1 mL of ethanol solution, that is, the concentration of sodium formate in the ethanol solution was 1 mg / mL;

[0110] Preparation of electron transport layer on perovskite film;

[0111] preparing a buffer layer on the electron transport layer;

[0112] preparing a patterned transparent electrode on the buffer layer;

[0113] preparing a positive electrode on the transparent electrode; and,

[0114] A back electrode is prepared on the back of the crystalline silicon cell.

[0115] Example 3

[0116] The difference between this embodiment and embodiment 1 is that the buried bottom layer is made of potassium formate.

[0117] Example 4

[0118] The difference between this embodiment and embodiment 2 is that 0.1 mg of sodium formate is added to 1 mL of ethanol solution, that is, the concentration of sodium formate is 0.1 mg / mL.

[0119] Example 5

[0120] The difference between this embodiment and embodiment 1 is that 4 mg of sodium formate is added to 1 mL of ethanol solution, that is, the concentration of sodium formate is 4 mg / mL.

[0121] Comparative Example 1

[0122] The preparation method of the perovskite battery provided in this comparative example comprises the following steps:

[0123] The prepared crystalline silicon cell is sputtered with a layer of NiO by PVD x The film acts as a hole transport layer;

[0124] Then, 1 mg of 2-PACz was added to 1 mL of ethanol solution and spin-coated at 4000 rpm for 30 s and annealed to obtain a passivation layer;

[0125] A PbI2 thin film was formed on the passivation layer by multi-source evaporation of PbI2 followed by annealing at 100°C;

[0126] The PbI2 film reacts with an organic amine salt to obtain a perovskite film;

[0127] Preparation of electron transport layer on perovskite film;

[0128] preparing a buffer layer on the electron transport layer;

[0129] preparing a patterned transparent electrode on the buffer layer;

[0130] preparing a positive electrode on the transparent electrode; and,

[0131] A back electrode is prepared on the back of the crystalline silicon cell.

[0132] The PbI2 porous film of Example 1 and the PbI2 film obtained in Comparative Example 1 were scanned by scanning electron microscopy (SEM), and the images obtained are shown in Figures 4 and 5. As shown in Figure 4, there are almost no light and dark difference areas in the SEM image, and the overall image presents an approximately single color, indicating that the PbI2 film of Comparative Example 1 is relatively dense. Referring to Figure 5, in the SEM image of Figure 5, there are more light and dark difference areas, among which the darker areas than the surrounding images are porous structures. It can be seen that the PbI2 porous film of Example 1 has a significant porous structure. The holes in the figure are channels for organic amine cations or alkali metal cations to enter the metal halide film, allowing the metal halide in the porous film to fully react.

[0133] The perovskite films obtained in Example 1, Example 4, and Example 5 were scanned by scanning electron microscopy (SEM), and the images obtained are shown in Figures 6 to 8. Referring to Figure 6, Figure 6 is an SEM picture of the perovskite film of Example 4 of the present application. The solubility of sodium formate in Example 4 is 0.1 mg / mL, and the solubility of sodium formate is relatively small, which may result in no significant change in the morphology of the obtained PbI2 film, resulting in residual lead iodide in the final perovskite film. White patches were found in the SEM picture.

[0134] See Figure 7, which is a SEM image of the perovskite film of Example 1 of the present application. The sodium formate concentration in Example 1 was 2 mg / mL. The resulting perovskite film is essentially free of lead iodide residue and exhibits large, dense grains. Compared to Figure 6, Figure 7 shows no white patches.

[0135] See Figure 8, which is an SEM image of the perovskite film of Example 5 of the present application. In Example 5, the concentration of sodium formate is 4 mg / mL. The relatively high concentration of sodium formate may make the PbI2 film too loose, resulting in some hole defects in the prepared perovskite film. As shown in Figure 8, pinhole-shaped hole defects appear in the SEM image of the perovskite film. These hole defects may affect the performance of the subsequently produced perovskite battery.

[0136] The photoelectric conversion efficiency of the perovskite cells of Example 2, Comparative Example 1, and Example 4 was tested, and the test results are shown in Figure 9. As can be seen from the figure, Comparative Example 1 does not add a buried layer containing sodium formate, and the photoelectric conversion efficiency (PCE) of the perovskite cell finally produced is low, indicating that the organic cations applied by spin coating are difficult to fully react with PbI2, and there will be too much PbI2 remaining at the bottom. Excessive unreacted PbI2 will seriously affect the performance of the photovoltaic cell. Example 4 adds a buried layer containing sodium formate, but the concentration of sodium formate is 0.1 mg / mL. At this time, the photoelectric conversion efficiency (PCE) of the perovskite cell has been improved to a certain extent relative to Comparative Example 1. In Example 2, the concentration of sodium formate is 1 mg / mL, which is higher than that of Example 4. The photoelectric conversion efficiency of the perovskite cell in Example 2 is also higher than that of Example 4. It can be understood that by increasing the concentration of sodium formate within an appropriate range, the prepared PbI2 porous film has a more obvious porous structure. The porous structure is a channel for organic amine cations or alkali metal cations to enter the metal halide film, allowing the metal halide in the porous film to fully react, thereby further improving the photoelectric conversion efficiency of the perovskite cell.

[0137] At room temperature of 25°C and humidity of 10%, the normalized photoelectric conversion efficiency of the perovskite cells prepared in Example 2 and Comparative Example 1 was measured over time. As shown in Figure 10 , it is known that excessive unreacted PbI2 can severely affect photovoltaic cell performance and accelerate device degradation. In Comparative Example 1, a significant amount of lead iodide remained in the perovskite film, causing the device to age rapidly. In contrast, in Example 2, virtually no lead iodide remained in the perovskite film, resulting in better device stability and slower device aging.

[0138] The above is a detailed introduction to the preparation method of a perovskite film, the film, the perovskite battery and the stacked battery disclosed in the embodiments of the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the preparation method of a perovskite film, the film, the perovskite battery and the stacked battery and their core ideas of the present application: At the same time, for general technical personnel in this field, according to the ideas of the present application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

[0139] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0140] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A method for preparing a perovskite film, the method comprising: preparing a buried bottom layer; the buried bottom layer comprises an alkali metal formate; forming a porous film containing a compound having a chemical formula of BX2 on the buried layer; and, Reacting the compound with the chemical formula BX2 in the porous film with the compound with the chemical formula AX to obtain a perovskite film; Wherein, B is a metal cation; A is an organic amine cation or an alkali metal cation; and X is a halogen ion or a pseudohalogen anion.

2. The method for preparing a perovskite thin film according to claim 1, wherein the step of preparing the buried bottom layer comprises: adding the alkali metal formate salt to a first solvent to obtain a first solution; The first solution is coated on a substrate to obtain the buried layer. 3 . The method for preparing a perovskite thin film according to claim 2 , wherein the concentration of the alkali metal formate in the first solution is about 1 mg / mL to 2 mg / mL.

4. The method for preparing a perovskite thin film according to claim 2 or 3, wherein the coating surface density of the first solution is about 10 μL / cm 2 ~25μL / cm 2 .

5. The method for preparing a perovskite thin film according to any one of claims 2 to 4, wherein the first solvent comprises at least one of ethanol and octanol.

6. The method for preparing a perovskite thin film according to any one of claims 2 to 5, wherein the step of coating the first solution on a substrate to obtain the buried layer comprises: The first solution is spin-coated at a rotation speed of about 3500 rpm to 4500 rpm for about 25 s to 35 s and annealed at about 95° C. to 105° C. for about 8 min to 10 min.

7. The method for preparing a perovskite film according to any one of claims 1 to 6, wherein the step of forming a porous film containing a compound having a chemical formula of BX2 on the buried layer comprises: Forming a film layer by multi-source evaporation of the compound with the chemical formula BX2 on the buried bottom layer; wherein the thickness of the film layer is about 200nm to 400nm; The membrane layer is annealed at about 95° C. to 105° C. to form the porous film.

8. The method for preparing a perovskite film according to any one of claims 1 to 7, wherein the step of reacting the compound with the chemical formula BX2 in the porous film with the compound with the chemical formula AX to obtain the perovskite film comprises: A second solution is coated on the porous film, wherein the second solution contains the compound with the chemical formula AX.

9. The method for preparing a perovskite thin film according to any one of claims 1 to 8, wherein the alkali metal in the alkali metal formate comprises at least one of lithium, sodium, potassium, rubidium and cesium.

10. The method for preparing a perovskite thin film according to any one of claims 1 to 9, wherein the alkali metal formate comprises at least one of lithium formate, sodium formate, potassium formate, rubidium formate and cesium formate.

11. The method for preparing a perovskite film according to any one of claims 1 to 10, wherein the metal cation comprises Pb 2+ Sn 2+ At least one of .

12. The method for preparing a perovskite film according to any one of claims 1 to 11, wherein the organic amine cation comprises CH3NH3 + and NH2CH=NH2 + At least one of .

13. The method for preparing a perovskite film according to any one of claims 1 to 12, wherein the alkali metal cation comprises Cs + and Rb + At least one of .

14. The method for preparing a perovskite film according to any one of claims 1 to 13, wherein the halogen ions include Cl - Br - and I - At least one of .

15. The method for preparing a perovskite film according to any one of claims 1 to 14, wherein the pseudohalogen anion comprises CN - 、SCN - 、OCN - and SeCN - At least one of .

16. A film, comprising a perovskite film prepared by the method for preparing a perovskite film according to any one of claims 1 to 15.

17. A perovskite cell comprising the thin film according to claim 16.

18. A stacked cell comprising the perovskite cell according to claim 17.

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