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

Abstract

The present invention relates to the technical field of perovskite cells, and in particular to a method for preparing a perovskite film, a film, a perovskite cell, and a stacked cell. The preparation method comprises: preparing a buried substrate; the buried substrate comprising an alkali metal formate; forming a porous film containing a compound having a general chemical formula of BX2 on the buried substrate; and reacting the compound having a general chemical formula of BX2 in the porous film with a compound having a general chemical formula of 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. Under the combined action of the alkali metal ions and the formate ions, the metal halide film forms a well-oriented porous film, and the pores in the porous film serve as channels for the organic amine cations or alkali metal cations to enter the metal halide film, allowing the metal halide within the porous film to fully react.

Description

Technical Field

[0001] The present invention 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

[0002] Perovskite solar cells are solar cells that use perovskite-type compound semiconductors with the general organic chemical formula BX2 as light-absorbing materials.

[0003] Existing technology can use a two-step method to prepare perovskite films. During this two-step sequential deposition process, for example, the PbI2 film prepared 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. Summary of the Invention

[0004] In order to solve the above technical problems, the present application discloses a method for preparing a perovskite film, a film, a perovskite cell and a stacked cell, so as to solve the problem that in the current two-step sequential deposition process, the morphology of the PbI2 film prepared by multi-source evaporation is relatively dense, and the organic cations applied by spin coating are difficult to fully react with PbI2.

[0005] In a first aspect, an embodiment of the present application provides a method for preparing a perovskite thin film, the preparation method comprising:

[0006] preparing a buried bottom layer; the buried bottom layer comprises an alkali metal formate;

[0007] forming a porous film containing a compound having a chemical formula of BX2 on the buried bottom layer;

[0008] 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;

[0009] 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.

[0010] Furthermore, the step of making the buried bottom layer includes:

[0011] adding the alkali metal formate to a first solvent to obtain a first solution;

[0012] The first solution is coated on a substrate to obtain the buried layer.

[0013] Furthermore, the concentration of the alkali metal formate in the first solution is 1 mg / mL to 2 mg / mL;

[0014] And / or, the coating surface density of the first solution is 10 μL / cm 2 ~25μL / cm 2 ;

[0015] And / or, the first solvent includes at least one of ethanol or octanol.

[0016] Furthermore, the step of coating the first solution on a substrate to obtain the buried bottom layer comprises:

[0017] The first solution is spin-coated at a rotation speed of 3500 rpm to 4500 rpm for 25 s to 35 s and annealed at 95° C. to 105° C. for 8 min to 10 min.

[0018] Furthermore, the step of forming a porous film containing a compound having a chemical formula of BX2 on the buried bottom layer comprises:

[0019] The compound with the chemical formula BX2 is multi-source evaporated on the buried bottom layer to form a film layer; wherein the thickness of the film layer is 200nm to 400nm;

[0020] The membrane layer is annealed at 95° C. to 105° C. to form the porous film.

[0021] Furthermore, 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:

[0022] A second solution containing the compound with the general chemical formula AX is coated on the porous film.

[0023] Furthermore, the alkali metal in the alkali metal formate is any one of lithium, sodium, potassium, rubidium or cesium;

[0024] The alkali metal formate is selected from one or more of lithium formate, sodium formate, potassium formate, rubidium formate or cesium formate;

[0025] And / or, the metal cation is selected from Pb 2+ and Sn 2+ At least one of;

[0026] And / or, the organic amine cation is selected from CH3NH3 + and NH2CH=NH2 + At least one of;

[0027] And / or, the alkali metal cation is selected from Cs + and Rb + At least one of;

[0028] And / or, the halogen ion is selected from Cl - Br - and I - At least one of;

[0029] And / or, the anion of the pseudohalogen is selected from CN - 、SCN - 、OCN - and SeCN - At least one of .

[0030] 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.

[0031] In a third aspect, an embodiment of the present application provides a perovskite cell comprising the thin film as described in the second aspect.

[0032] In a fourth aspect, an embodiment of the present application provides a stacked battery comprising the perovskite battery described in the third aspect.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] The present invention provides a method for preparing a perovskite film. Before forming a metal halide film (a film containing a compound with the general chemical formula BX2), a buried bottom layer is prepared. The buried bottom layer contains alkali metal formate. Formate ions migrate upward when heated. Since the formate ions are relatively small, they can move through the grain boundaries in the metal halide during their upward migration, thereby forming a porous structure in the metal halide film. The alkali metal ions are conducive to oriented crystallization. Under the combined action of the alkali metal ions and the formate ions, the metal halide film forms a well-oriented porous film. The pores in the porous film serve as 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.

[0035] In addition, the production of the buried bottom layer 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0037] Figure 1 This is a flow chart of a method for preparing a perovskite film provided in an embodiment of the present application;

[0038] Figure 2 This is a flow chart of step S130 in a method for preparing a perovskite thin film provided in an embodiment of the present application;

[0039] Figure 3 This is a flow chart of step S150 in a method for preparing a perovskite thin film provided in an embodiment of the present application;

[0040] Figure 4 This is a SEM image of the PbI2 film of Comparative Example 1 of the present application;

[0041] Figure 5 is a SEM image of the PbI2 porous film of Example 1 of the present application;

[0042] Figure 6 is a SEM image of the perovskite film of Comparative Example 2 of the present application;

[0043] Figure 7 is a SEM image of the perovskite film of Example 1 of the present application;

[0044] Figure 8 is a SEM image of the perovskite film of Comparative Example 3 of the present application;

[0045] Figure 9 2 is a box plot of the photoelectric conversion efficiency of the perovskite cells of Example 2, Comparative Example 1, and Comparative Example 2 of the present application;

[0046] Figure 10 It 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

[0047] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0048] In the first aspect, the present invention provides a method for preparing a perovskite film. Figure 1 , the preparation method includes steps S110 to S150.

[0049] Step S110: preparing a buried bottom layer; the buried bottom layer comprises alkali metal formate.

[0050] In step S110, the formate ions in the formate contained in the buried layer are relatively small in size. Furthermore, the formate ions easily migrate when heated. During their upward migration, the formate ions can move through the grain boundaries of 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 is any one of lithium, sodium, potassium, rubidium, or cesium. That is, the alkali metal formate in the present application is selected from one or more of sodium formate, potassium formate, rubidium formate, or cesium formate, and "a plurality" refers to two or more. Preferably, the alkali metal formate is sodium formate.

[0051] Alkali metal ions facilitate oriented crystallization, leading to the subsequent formation of a well-oriented porous film. More specifically, alkali metal ions allow the pores in the porous film to penetrate the thickness of the film. Compared to interlaced pores, this well-oriented porous film is more conducive to the ingress of cations to the bottom during subsequent reactions. Under the combined action of alkali metal ions and formate ions, the metal halide film forms a well-oriented porous film. The pores in the porous film serve as pathways 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, even at the bottom of the porous film.

[0052] Further, see Figure 2 , step S110 includes step S111 and step S112:

[0053] Step S111, adding alkali metal formate to a first solvent to obtain a first solution;

[0054] 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.

[0055] If the formate concentration and / or coating density is too low, it will be difficult to form a porous and loose structure in the metal halide film, or the pore density will be too low. However, if the formate concentration is too high, it will damage the metal halide film, or even make the film too loose, which will adversely affect the performance of the final perovskite cell. Therefore, the concentration of the alkali metal formate in the first solution is preferably 1 mg / mL to 2 mg / mL; more preferably 1.2 mg / mL to 1.8 mg / mL, and even more preferably 1.3 mg / mL to 1.7 mg / mL. More specifically, the concentration of the alkali metal formate in the first solution is 1 mg / mL to 2 mg / mL, including any 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, and 2.0 mg / mL. Furthermore, the coating area density of the first solution is 10 μL / cm 2 ~25μL / cm 2 Any 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 .

[0056] Optionally, the first solvent includes at least one of ethanol or octanol. The first solvent may be ethanol, octanol, or a mixture of the two.

[0057] Furthermore, step S112 includes:

[0058] The first solution is spin-coated at a rotation speed of 3500 rpm to 4500 rpm for 25 s to 35 s and annealed at 95° C. to 105° C. for 8 min to 10 min.

[0059] Specifically, 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, and 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, and 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., and 105° C. The annealing time of the first solution is 8 min to 10 min, including any point value within the time range; for example, the annealing time of the first solution is 8 min, 9 min, and 10 min.

[0060] Step S130: forming a porous film containing a compound with a chemical formula of BX2 on the buried layer.

[0061] In step S130, B is a metal cation, and X is a halogen ion or a pseudohalogen anion. In some embodiments, the metal cation is selected from Pb 2+ and Sn 2+ At least one of; halogen ions selected from Cl - Br - and I - At least one of; the anion of the pseudohalogen is selected from CN - 、SCN - 、OCN - and SeCN - At least one of .

[0062] For example, BX2 is PbI2, PbCl2, PbBr2, SnI2, SnCl2, SnBr2, but is not limited to the above-mentioned compounds. Preferably, BX2 is PbI2. The porous film may contain only one or more compounds having the general chemical formula BX2.

[0063] In some embodiments, the porous film is formed by a vacuum method, such as thermal evaporation, close-space sublimation, vapor transport deposition, or chemical vapor deposition. Preferably, the porous film is formed by multi-source evaporation.

[0064] Preferably, see Figure 3 , step S130 includes:

[0065] Step S131 : forming a film layer by multi-source evaporation of a compound having a chemical formula of BX2 on the buried bottom layer.

[0066] The thickness of the film layer is 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;

[0067] Step S132 , annealing the film layer at 95° C. to 105° C. to form a porous film.

[0068] In more detail, the annealing temperature of step S132 is 95°C to 105°C, including any point value within 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.

[0069] 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.

[0070] 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.

[0071] 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 is selected from CH3NH3 + and NH2CH=NH2 + At least one of; alkali metal cations selected from Cs + and Rb + At least one of; halogen ions selected from Cl - Br - and I - At least one of; the anion of the pseudohalogen is selected from CN - 、SCN - 、OCN - and SeCN - At least one of .

[0072] Exemplarily, AX is 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 produces a perovskite material having the general chemical formula ABX3.

[0073] Further, step S150 includes step S151.

[0074] Step S151: coating a second solution on the porous film, wherein the second solution contains a compound with a chemical formula of AX.

[0075] Optionally, AX can be coated on a porous film by a solution method (such as spin coating, doctor blade coating, slit coating, screen printing, inkjet printing, spraying, ultrasonic atomization). Since the holes on the porous film become channels for organic amine cations or alkali metal cations to enter the metal halide film, the metal halide in the porous film can react fully.

[0076] In summary, the embodiment of the present application provides a method for preparing a perovskite film. Before forming a metal halide film (a film containing a compound with the general chemical formula BX2), a buried bottom layer is prepared. The buried bottom layer contains alkali metal formate. The formate ions move upward when heated, and the formate ions are small. During the upward movement, they can move through the grain boundaries in the metal halide, thereby forming a porous structure in the metal halide film. The alkali metal ions are conducive to oriented crystallization. Under the combined action of the alkali metal ions and the formate ions, the metal halide film will form a well-oriented porous film. The holes on the porous film become 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, even the metal halide located at the bottom of the porous film can fully react. Due to the full reaction of the metal halide, the performance of the perovskite solar cell is prevented from being affected by excessive unreacted metal halide.

[0077] In addition, the production of the buried bottom layer 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.

[0078] The preparation method provided in the present application can solve the problem that in the current two-step sequential deposition process, the morphology of the PbI2 film prepared by multi-source evaporation is relatively dense, and the organic cations coated 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 porous film.

[0079] Although a porous PbI2 layer with an ordered array structure can be prepared by combining succinamide (SA) additives with nanoimprinting technology, the preparation method is to introduce SA into a 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 this preparation method solves the density 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 future, and the process is too cumbersome. Compared with the above-mentioned preparation method, the preparation method provided in the present application is applicable to the preparation of PbI2 film by multi-source evaporation, and the process is simpler.

[0080] 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.

[0081] In a third aspect, an embodiment of the present application provides a perovskite cell comprising the thin film as described in the second aspect.

[0082] More specifically, the method for manufacturing the perovskite battery includes the following steps:

[0083] 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.

[0084] Taking the substrate as a crystalline silicon cell as an example, the method for manufacturing the perovskite cell further includes the following steps:

[0085] Sputtering a transmission layer on the crystalline silicon cell; wherein the buried bottom layer is formed on the transmission layer;

[0086] 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.

[0087] More specifically, the steps of sputtering the transport layer on the crystalline silicon cell include:

[0088] A transport layer is prepared by PVD sputtering a layer of hole transport material (such as nickel oxide, PEDOT:PSS, Cu2O, PTAA, poly-TPD and c-OTPD) or electron transport material on a crystalline silicon cell.

[0089] More specifically, a transmission layer is sputtered on the crystalline silicon cell, and then a passivation layer is formed on the transmission layer; wherein the step of forming the buried bottom layer on the passivation layer includes:

[0090] A transport layer is prepared by sputtering a layer of hole transport material or electron transport material on a substrate by PVD;

[0091] Then 2-PACz ([4-(9H-carbazol-9-yl)ethyl]phosphonic acid) or MeO-2PACz ([2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid) was added to the ethanol solution and spin-coated at 3500 rpm to 4500 rpm for 25 s to 35 s and annealed at 95°C to 105°C for 8 min to 10 min.

[0092] Optionally, the hole transport material is selected from 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]);

[0093] Specifically, 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, and 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, and 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, and 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, and 10 min.

[0094] 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.

[0095] 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.

[0096] The properties of the perovskite film prepared in this application will be introduced below with reference to the examples.

[0097] Example 1

[0098] The method for preparing the perovskite film of this embodiment includes:

[0099] The prepared crystalline silicon cell is sputtered with a layer of NiO by PVD x The film acts as a hole transport layer;

[0100] 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;

[0101] 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;

[0102] PbI2 was multi-source evaporated on the buried substrate and then annealed at 100°C to form a PbI2 porous film;

[0103] The PbI2 in the porous film is reacted with an organic amine salt to obtain a perovskite film.

[0104] Example 2

[0105] The preparation method of the perovskite battery provided in this embodiment comprises the following steps:

[0106] The perovskite film was prepared. The only difference between this step and Example 1 was that 1 mg of sodium formate was added to 1 mL of ethanol solution, i.e., the concentration of sodium formate in the ethanol solution was 1 mg / mL;

[0107] Preparation of electron transport layer on perovskite film;

[0108] preparing a buffer layer on the electron transport layer;

[0109] preparing a patterned transparent electrode on the buffer layer;

[0110] preparing a positive electrode on the transparent electrode;

[0111] A back electrode is prepared on the back of the crystalline silicon cell.

[0112] Example 3

[0113] The only difference between this embodiment and embodiment 1 is that the buried bottom layer is made of potassium formate.

[0114] Comparative Example 1

[0115] The preparation method of the perovskite battery provided in this comparative example comprises the following steps:

[0116] The prepared crystalline silicon cell is sputtered with a layer of NiO by PVD x The film acts as a hole transport layer;

[0117] 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;

[0118] A PbI2 thin film was formed on the passivation layer by multi-source evaporation of PbI2 followed by annealing at 100°C;

[0119] The PbI2 film reacts with an organic amine salt to obtain a perovskite film;

[0120] Preparation of electron transport layer on perovskite film;

[0121] preparing a buffer layer on the electron transport layer;

[0122] preparing a patterned transparent electrode on the buffer layer;

[0123] preparing a positive electrode on the transparent electrode;

[0124] A back electrode is prepared on the back of the crystalline silicon cell.

[0125] Comparative Example 2

[0126] The difference between this comparative example and Example 2 is that 0.1 mg of sodium formate was added to 1 mL of ethanol solution, that is, the concentration of sodium formate was 0.1 mg / mL.

[0127] Comparative Example 3

[0128] The difference between this comparative example and Example 1 is that 4 mg of sodium formate was added to 1 mL of ethanol solution, that is, the concentration of sodium formate was 4 mg / mL.

[0129] The PbI2 porous film of Example 1 and the PbI2 film obtained in Comparative Example 1 were scanned by a scanning electron microscope (SEM), and the images obtained were as follows: Figure 4 and Figure 5 As shown. Figure 4 It can be seen that there is almost no light and dark difference in the SEM image, and the overall image presents a nearly single color, indicating that the PbI2 film of Comparative Example 1 is relatively dense. Figure 5 , Figure 5 In the SEM image, there are many areas with different light and dark differences. The areas that are darker than the surrounding images are porous structures. It can be seen that the PbI2 porous film of Example 1 has an obvious 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.

[0130] The perovskite films obtained in Example 1, Comparative Example 2 and Comparative Example 3 were scanned by a scanning electron microscope (SEM), and the images obtained were as follows: Figures 6 to 8 See Figure 6 , Figure 6 This is an SEM image of the perovskite film from Comparative Example 2 of this application. The sodium formate solubility in Comparative Example 2 was only 0.1 mg / mL. When the sodium formate solubility is too low, the morphology of the resulting PbI2 film remains unchanged, resulting in excessive residual lead iodide in the final perovskite film. White patches are observed in the SEM image.

[0131] See also Figure 7 , Figure 7 This is a SEM image of the perovskite film of Example 1 of the present application. The solubility of sodium formate in Example 1 is 2 mg / mL. The prepared perovskite film is basically free of lead iodide residue, and the grain size is large and dense. Figure 6 , Figure 7 No white patches.

[0132] See also Figure 8 , Figure 8 This is a SEM image of the perovskite film of Comparative Example 3 of this application. The concentration of sodium formate in Comparative Example 3 is 4 mg / mL. If the concentration of sodium formate is too high, the PbI2 film will be too loose, resulting in hole defects in the prepared perovskite film. Figure 8 Pinhole-shaped hole defects appeared in the SEM images of the perovskite film, and these hole defects will affect the performance of the subsequent perovskite batteries.

[0133] The photoelectric conversion efficiency of the perovskite cells of Example 2, Comparative Example 1 and Comparative Example 2 was tested, and the test results were as follows: Figure 9As shown in the figure, it can be seen that in Comparative Example 1, the photoelectric conversion efficiency (PCE) of the final perovskite cell produced was low, indicating that the organic cations applied by spin coating were difficult to fully react with PbI2, and there would be too much PbI2 remaining at the bottom. The excess unreacted PbI2 would seriously affect the performance of the photovoltaic cell. Comparative Example 2 added a buried layer containing sodium formate, but the concentration of sodium formate was only 0.1 mg / mL. At this time, the photoelectric conversion efficiency (PCE) of the perovskite cell was improved to a certain extent compared with Comparative Example 1. In Example 2, the concentration of sodium formate is 1 mg / mL, which is higher than that of Comparative Example 2. The photoelectric conversion efficiency of the perovskite battery in Example 2 is also higher than that of Comparative Example 2. 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, so that the metal halide in the porous film can fully react, thereby further improving the photoelectric conversion efficiency of the perovskite battery.

[0134] Under the conditions of 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 tested and compared with time. Figure 10 It is known that excessive unreacted PbI2 will seriously affect the performance of photovoltaic cells and accelerate device degradation. In Comparative Example 1, a large amount of lead iodide will remain in the perovskite film, causing the device to age too quickly. However, in Example 2, there is almost no lead iodide remaining in the perovskite film, the device stability is better, and the device ages slowly.

[0135] 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 invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. 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 of the present invention and their core ideas: At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A method for preparing a perovskite thin film, characterized in that: The preparation method comprises: 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 bottom layer; 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; 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 steps of making the buried bottom layer include: adding the alkali metal formate 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 1 mg / mL to 2 mg / mL; And / or, the coating surface density of the first solution is 10 μL / cm 2 ~25μL / cm 2 ; And / or, the first solvent includes at least one of ethanol or octanol.

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

5. The method for preparing a perovskite thin film according to any one of claims 1 to 4, wherein: The step of forming a porous film containing a compound with a chemical formula of BX2 on the buried bottom layer comprises: The compound with the chemical formula BX2 is multi-source evaporated on the buried bottom layer to form a film layer; wherein the thickness of the film layer is 200nm to 400nm; The membrane layer is annealed at 95° C. to 105° C. to form the porous film.

6. The method for preparing a perovskite thin film according to any one of claims 1 to 4, 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 a perovskite film comprises: A second solution containing the compound with the general chemical formula AX is coated on the porous film.

7. The method for preparing a perovskite thin film according to any one of claims 1 to 4, wherein: The alkali metal in the alkali metal formate is any one of lithium, sodium, potassium, rubidium or cesium; The alkali metal formate is selected from one or more of lithium formate, sodium formate, potassium formate, rubidium formate or cesium formate; And / or, the metal cation is selected from Pb 2+ and Sn 2+ At least one of; And / or, the organic amine cation is selected from CH3NH3 + and NH2CH=NH2 + At least one of; And / or, the alkali metal cation is selected from Cs + and Rb + At least one of; And / or, the halogen ion is selected from Cl - Br - and I - At least one of; And / or, the anion of the pseudohalogen is selected from CN - 、SCN - 、OCN - and SeCN - At least one of .

8. A film, characterized in that The perovskite film is prepared by the preparation method of the perovskite film according to any one of claims 1 to 7.

9. A perovskite battery, characterized in that: Comprising the film according to claim 8.

10. A stacked battery, characterized in that: Comprising the perovskite cell as claimed in claim 9.

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