Perovskite composition and photoelectric conversion device

Abstract

The present disclosure aims to provide a perovskite composition that can obtain a crystalline film that is flat, free of voids, and has high power generation efficiency. [Solution] The perovskite composition according to this embodiment comprises a perovskite compound precursor, a first component which is a solvent for the perovskite compound precursor, and at least one second component selected from the group consisting of nitrogen-containing pyridines and 4-tert-butylpyridine. The nitrogen-containing pyridines are compounds in which a first nitrogen-containing group is bonded to one of the ortho, meta, or para positions of a pyridine ring, and a hydrogen atom is bonded to a position other than the position to which the first nitrogen-containing group is bonded, or at least one of the positions other than the position to which the first nitrogen-containing group is bonded is bonded to one selected from the group consisting of a carbon-containing group, a second nitrogen-containing group, and an alkoxy group.

Description

[Technical Field]

[0001] This disclosure relates to perovskite compositions and photoelectric conversion devices. [Background technology]

[0002] Conventionally, lead-containing lead perovskite solar cells are known (see, for example, Patent Document 1). In recent years, due to concerns about environmental impact, tin perovskite solar cells have been proposed in which tin is substituted for part or all of the lead (see, for example, Patent Documents 2 to 4). Patent Document 2 discloses a so-called antisolvent method in which a dimethyl sulfoxide solution of a perovskite compound precursor is applied to an FTO glass equipped with a titanium oxide thin film by spin coating, toluene is dropped onto it while it is rotating to obtain a perovskite precursor thin film, and then it is heated to form a perovskite layer.

[0003] Patent Document 3 discloses a technique for improving crystallinity by adding a first compound, such as a pyridine derivative, to a perovskite composition. During the drying process of the liquid coating film of the perovskite composition, the first compound remains in the film, facilitating the alignment of crystalline regions. Patent Document 4 describes how a perovskite layer containing a specific compound having a pyridine skeleton and Brønsted acidic groups reduces the enthalpy of the perovskite compound precursor, stabilizing it, slowing the crystal growth rate of the perovskite compound, and increasing the grain size. This reduces grain boundaries that induce charge recombination, thereby improving the fill factor of the photoelectric conversion device. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-78207 [Patent Document 2] Japanese Patent Publication No. 2018-56473 [Patent Document 3] Japanese Patent Publication No. 2022-75064 [Patent Document 4] Japanese Patent Publication No. 2023-128266 [Overview of the project] [Problems that the invention aims to solve]

[0005] Perovskite compositions have generally been studied using anti-solvent deposition methods with spin coaters. However, spin coaters have poor mass productivity, and anti-solvent deposition methods are unsuitable for mass production due to the large amount of organic solvents used. Therefore, methods that do not use anti-solvent deposition and offer superior mass productivity, such as roll-to-roll deposition, are being investigated. In recent years, due to concerns about environmental impact, tin perovskite solar cells have been proposed in which tin is substituted for part or all of the lead. However, perovskite compositions using tin crystallize faster than those using lead, and methods other than anti-solvent deposition have the problem of making it difficult to obtain flat films without voids. Therefore, we have developed a crystallization-delaying ink that can be used in a highly mass-producible deposition method applicable to both lead perovskite solar cells and tin perovskite solar cells.

[0006] The present disclosure aims to provide a perovskite composition and a photoelectric conversion device that can obtain a crystalline film that is flat, free of voids, and has high power generation efficiency without using an antisolvent method as a film formation process. [Means for solving the problem]

[0007] The perovskite composition according to the present invention comprises a perovskite compound precursor, a first component which is a solvent for the perovskite compound precursor, and at least one second component selected from the group consisting of nitrogen-containing pyridines and 4-tert-butylpyridine, wherein the nitrogen-containing pyridines are compounds in which a first nitrogen-containing group is bonded to one of the ortho, meta, or para positions of a pyridine ring, and hydrogen atoms are bonded to positions other than those to which the first nitrogen-containing group is bonded, or compounds in which a first nitrogen-containing group is bonded to one of the ortho, meta, or para positions of a pyridine ring, and at least one of the positions other than those to which the first nitrogen-containing group is bonded is bonded to one selected from the group consisting of a carbon-containing group, a second nitrogen-containing group, and an alkoxy group.

[0008] In the perovskite composition according to the present invention, it is preferable that the film formed under the following condition 1 contains less than 100 ppm of the second component. The second component may affect the efficiency. Condition 1: Distribute the perovskite composition at a rate of 0.25 g / m² on a 20 mm square glass substrate. 2 The wet coating film applied is then blown with 50 L / min of nitrogen gas for 90 seconds through a 6 mm diameter nozzle with a fixed distance of 20 mm between the glass substrate and the nozzle, followed by annealing on a hot plate heated to 100°C for 15 minutes to complete the film formation.

[0009] In the perovskite composition according to the present invention, the first nitrogen-containing group is preferably an aminoalkyl group bonded to the ortho or meta position of the pyridine ring. Because it has a low melting point and is liquid at room temperature, it can be volatilized more efficiently and is less likely to reduce the power generation efficiency of the resulting film.

[0010] In the perovskite composition according to the present invention, the latent heat of vaporization of the second component is preferably 50 kJ / mol or less. This allows the second component to be volatilized more efficiently, thus reducing the likelihood of a decrease in the power generation efficiency of the resulting film.

[0011] In the perovskite composition according to the present invention, it is preferable that the latent heat of vaporization of the first component is smaller than the latent heat of vaporization of the second component. Since the first component volatilizes prior to the second component, the precipitation and grain growth of microcrystals of the perovskite compound by the second component can be carried out more efficiently, so that a flat film without voids can be obtained more efficiently.

[0012] In the perovskite composition according to the present invention, it is preferable that the boiling point of the second component is 280 °C or lower. Since the second component can be volatilized more efficiently, there is a low possibility of reducing the power generation efficiency of the obtained film.

[0013] The perovskite composition according to the present invention preferably does not contain dimethyl sulfoxide or the addition amount of dimethyl sulfoxide is at most 5.0 vol% with respect to the total volume of the first component and the second component. Oxidation of tin (II) ions can be suppressed and a decrease in the power generation efficiency of the obtained film can be suppressed.

[0014] The perovskite film according to the present invention is characterized by being a dry film of the perovskite composition according to the present invention.

[0015] The photoelectric conversion device according to the present invention is characterized by having a dry film of the perovskite composition according to the present invention.

Effects of the Invention

[0016] According to the present disclosure, it is possible to provide a perovskite composition and a photoelectric conversion device capable of obtaining a crystalline film that is flat without voids and has high power generation efficiency without using an anti-solvent method as a film forming step.

Brief Description of the Drawings

[0017] [Figure 1] It is a microscopic observation image of the perovskite film of Example 1. [Figure 2] It is a microscopic observation image of the perovskite film of Comparative Example 1.

Embodiments for Carrying Out the Invention

[0018] Hereinafter, an aspect of the present invention will be described with reference to the accompanying drawings. The embodiments described below are examples of the present invention, and the present invention is not limited to the following embodiments. In the present specification and drawings, components having the same reference numerals indicate the same components. As long as the effects of the present invention are achieved, various modifications may be made.

[0019] The perovskite composition according to the present embodiment includes a perovskite compound precursor, a first component that dissolves the perovskite compound precursor, and at least one second component selected from the group consisting of pyridines having a nitrogen-containing group and 4-tert-butylpyridine. The pyridines having a nitrogen-containing group are compounds in which, as the nitrogen-containing group, a first nitrogen-containing group is bonded to any one of the ortho-position, meta-position, or para-position of the pyridine ring, and a hydrogen atom is bonded to a position other than the position where the first nitrogen-containing group of the pyridine ring is bonded, or as the nitrogen-containing group, a first nitrogen-containing group is bonded to any one of the ortho-position, meta-position, or para-position of the pyridine ring, and at least one of the positions other than the position where the first nitrogen-containing group of the pyridine ring is bonded is bonded to one selected from the group consisting of a carbon-containing group, a second nitrogen-containing group, and an alkoxy group.

[0020] The perovskite composition according to the present embodiment is a composition for forming a film containing a perovskite compound (hereinafter, sometimes also referred to as a perovskite film) by film formation, and is suitable, for example, as a composition for forming an active layer of a photoelectric conversion device. The photoelectric conversion device can be used, for example, in a perovskite solar cell.

[0021] Perovskite compounds are compounds having a perovskite structure. A perovskite structure is a type of crystal structure, and refers to the same crystal structure as perovskite (CaTiO3). Perovskite compounds are not particularly limited, but for example, they are compounds represented by the general formula AMX3 or A2MX4. In the general formula, A represents a monovalent cation, and for example, it is a cation containing elements of Group 1 and Groups 13-16 of the periodic table, and is preferably a cesium ion, rubidium ion, potassium ion, ammonium ion, or phosphonium ion. The ammonium ion or phosphonium ion may have substituents, for example, formamidium ion (CH(NH2)2) + It is preferable that ) is present. In the general formula, M represents a divalent cation, for example, a divalent metal cation or a divalent metalloid cation, and lead cation (Pb 2+ ), tin cation (Sn 2+ ) or germanium cation (Ge 2+ It is preferable that the divalent cation M is a lead cation (Pb). These divalent cations M may be used individually or in combination of two or more. From the viewpoint of environmental impact, the divalent cation M is preferably a lead cation (Pb 2+It is preferable that the following are not included. In the general formula, X represents a monovalent anion, for example, a halide ion, acetate ion, nitrate ion, sulfate ion, borate ion, acetylacetonate ion, carbonate ion, citrate ion, sulfur ion, tellurium ion, thiocyanate ion, titanate ion, zirconate ion, 2,4-pentanedionato ion, or fluorosilica ion. In one embodiment of the present invention, X is preferably a halide ion, or a combination of a halide ion and other anions. X may be one type or two or more types in any combination and ratio. Here, the band gap of the active layer can be adjusted to a preferred range by selecting the type and combination of X. In this embodiment, the perovskite compound is preferably a metal halide perovskite compound. Since the band gap of the active layer tends to be moderately narrowed, X is preferably a halide ion such as chloride ion, bromide ion, and iodide ion, and more preferably bromide ion and iodide ion.

[0022] A perovskite compound precursor is a compound that becomes a perovskite compound in a perovskite film, and more specifically, a compound that becomes a perovskite compound after coating and drying a perovskite composition. The perovskite compound precursor is not particularly limited, but preferably includes, for example, a compound represented by the general formula AX and a compound represented by the general formula MX2. In the general formula, A, M, and X are the same as A, M, and X described in the general formula of the perovskite compound. In this embodiment, the perovskite compound precursor may be a lead-containing lead perovskite compound precursor or a tin-containing tin perovskite compound precursor, but it is preferable that it is a tin perovskite compound precursor and is lead-free. A preferred specific example of the perovskite compound precursor is a form that includes CH(NH2)2I and SnI2.

[0023] The first component is a solvent for the perovskite compound precursor. Here, the solvent for the perovskite compound precursor refers to a liquid medium capable of dissolving the perovskite compound precursor, and includes both a solvent consisting of one type of liquid medium (hereinafter sometimes referred to as a single solvent) and a solvent consisting of two or more types of liquid mediums (hereinafter sometimes referred to as a mixed solvent). The first component preferably has a solubility of 0.2 mol / l (M) or higher for the perovskite compound precursor at 25°C, more preferably 0.5 mol / l or higher, and particularly preferably 1.0 mol / l or higher. The first component is of a different type from the second component. The solubility of the perovskite compound precursor in the first component was defined as the upper limit of the concentration at which the perovskite precursor solution was visually transparent.

[0024] The case where the first component is a single solvent will be described below. The single solvent consists of a liquid medium (hereinafter sometimes referred to as the soluble liquid medium) that can dissolve the perovskite compound precursor on its own, and is preferably an organic solvent, and more preferably a polar organic solvent. The soluble liquid medium that can be used as the single solvent is not particularly limited, but is preferably, for example, dimethylformamide (DMF), dimethylacetamide, dimethyl sulfoxide (DMSO), N-methylpyrrolidone, 2-methoxyethanol, 2-methoxyethylamine, N,N-diethylformamide, N,N-diethylformamide, N-methylformamide, N-methylacetamide, trimethyl phosphate, or γ-butyrolactone, and more preferably dimethylformamide (DMF). The solubility of perovskite compound precursors at 25°C is, for example, 3.0 mol / l for dimethylformamide (DMF), 3.0 mol / l for dimethylacetamide, 1.0 mol / l for dimethyl sulfoxide (DMSO), 2.0 mol / l for N-methylpyrrolidone, and 1.0 mol / l for 2-methoxyethanol.

[0025] When the first component is a mixed solvent containing two or more soluble liquid media, the soluble liquid media that can be incorporated into the mixed solvent are not particularly limited, but include, for example, the soluble liquid media listed as soluble liquid media that can be used as a single solvent.

[0026] The first component is a solvent for dissolving the perovskite compound precursor, and is preferably a solvent for dissolving compounds represented by the general formula AX and compounds represented by the general formula MX2. The first component is not particularly limited, but is preferably an organic solvent such as dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methylpyrrolidone, or 2-methoxyethanol, and more preferably dimethylformamide (DMF). These solvents may be used individually or in combination of two or more.

[0027] The perovskite composition according to this embodiment preferably does not contain dimethyl sulfoxide, or if DMSO is added, the amount of DMSO added is preferably a maximum of 5.0 vol% relative to the total volume of the first and second components. While it is preferable that the perovskite composition according to this embodiment does not contain DMSO, DMSO may be added as long as it does not impair the effects of the present invention. DMSO has the effect of delaying crystallization and increasing particle size, and in conventional perovskite compositions, DMSO was essential for the formation of a perovskite film. However, the inventors were concerned that dimethyl sulfoxide oxidizes tin(II) ions to tin(IV) ions, thus reducing power generation efficiency. In contrast, the perovskite composition according to this embodiment, by containing the second component, can form a perovskite film even if the composition does not contain DMSO. Therefore, the reduction in power generation efficiency caused by DMSO can be suppressed. When DMSO is added to the perovskite composition, the amount of DMSO added is preferably 2.0 Vol% or less, more preferably 0.5 Vol% or less, and even more preferably 0.1 Vol% or less, relative to the total volume of the first and second components.

[0028] The second component is preferably at least one selected from the group consisting of pyridines having nitrogen-containing groups and 4-tert-butylpyridine, and is liquid at 100°C or below. The second component may be liquid at room temperature or solid at room temperature, but it is more preferably liquid at room temperature.

[0029] The second component is preferably a compound having a melting point below the heating temperature in the annealing treatment described later. The melting point of the second component is preferably 100°C or lower, and more preferably 80°C or lower. If the second component is solid at room temperature, it may be heated above its melting point to become liquid and then incorporated into the composition, or the second component may be dissolved in the first component, or it may be incorporated as a solid and melted by the annealing treatment described later. Of these, it is preferable that the second component dissolves in the first component, and it is more preferable that the second component dissolves in the first component, and after the first component volatilizes in the blowing process described later, the second component evaporates before the blowing process and the annealing treatment described later.

[0030] The second component is preferably a compound that dissolves the perovskite compound precursor. In this case, the perovskite composition is a composition containing the perovskite compound precursor and a mixed solvent containing the first component as the main solvent and the second component as a secondary solvent.

[0031] In the perovskite composition according to this embodiment, the latent heat of vaporization of the second component is preferably 50 kJ / mol or less, and more preferably 45 kJ / mol or less. If the latent heat of vaporization of the second component exceeds 50 kJ / mol or less, it may not be possible to volatilize the second component in the annealing treatment described later. By setting the latent heat of vaporization of the second component within the above range, the second component can be more reliably volatilized, preventing a decrease in the power generation efficiency of the resulting film. The lower limit of the latent heat of vaporization of the second component is not particularly limited, but from the viewpoint of not impairing coating workability, it is preferably 28 kJ / mol or more, and more preferably 35 kJ / mol or more.

[0032] In the perovskite composition according to this embodiment, it is preferable that the latent heat of vaporization of the first component is smaller than that of the second component. Since the first component volatilizes before the second component, the precipitation and grain growth of microcrystals of the perovskite compound by the second component can be performed more efficiently, thus allowing for the more efficient acquisition of a flat film without voids. Furthermore, if the first component is a mixed solvent, it is preferable that the latent heat of vaporization of each solvent constituting the mixed solvent is smaller than that of the second component. The method for determining the latent heat of vaporization is not particularly limited and may be, for example, a value obtained by searching various chemical substance databases such as Chemspider. The latent heat of vaporization of the first component is not particularly limited, but is preferably 50 kJ / mol or less, and more preferably 45 kJ / mol or less. The latent heat of vaporization of the first component exemplified above is, for example, 39.0 kJ / mol for dimethylformamide (DMF), 40.3 kJ / mol for dimethylacetamide, 40.8 kJ / mol for dimethyl sulfoxide (DMSO), 43.8 kJ / mol for N-methylpyrrolidone, and 37.5 kJ / mol for 2-methoxyethanol.

[0033] In the perovskite composition according to this embodiment, the boiling point of the second component is preferably 330°C or lower, more preferably 280°C or lower, and particularly preferably 260°C or lower. If the boiling point of the second component exceeds 330°C, it may not be possible to efficiently volatilize the second component. By setting the boiling point of the second component within the above range, the second component can be more reliably volatilized, preventing a decrease in the power generation efficiency of the resulting film. The lower limit of the boiling point of the second component is not particularly limited, but from the viewpoint of not impairing coating workability, it is preferably 80°C or higher, and more preferably 100°C or higher.

[0034] The second component, pyridines having a nitrogen-containing group, is either a monosubstituted pyridine in which a first nitrogen-containing group is bonded to one of the ortho, meta, or para positions of the pyridine ring, and hydrogen atoms are bonded to positions other than those to which the first nitrogen-containing group is bonded, or a polysubstituted pyridine in which a first nitrogen-containing group is bonded to one of the ortho, meta, or para positions of the pyridine ring, and at least one of the positions other than those to which the first nitrogen-containing group is bonded is bonded to one selected from the group consisting of a carbon-containing group, a second nitrogen-containing group, and an alkoxy group. The second component may be used alone or in combination of two or more types.

[0035] A nitrogen-containing group is a group containing a nitrogen atom, preferably with the nitrogen atom bonded to the carbon of the pyridine ring. Examples of nitrogen-containing groups include amino groups, imino groups, nitrilo groups, hydrazino groups, nitroso groups, or nitro groups. Nitrogen-containing groups may have substituents, such as alkylamino groups. The alkyl group in the alkylamino group is, for example, a linear alkyl group, a branched alkyl group, or a cyclic alkyl group, which may be further substituted with halogens or the like. Examples of alkylamino groups include methylamino groups, dimethylamino groups, diethylamino groups, or ethylmethylamino groups.

[0036] Among the pyridine compounds containing nitrogen-containing groups, monosubstituted pyridine compounds are compounds in which only one first nitrogen-containing group is bonded to the carbon of the pyridine ring. Monosubstituted pyridine compounds include compounds in which the first nitrogen-containing group is bonded to the ortho position of the pyridine ring, compounds in which the first nitrogen-containing group is bonded to the meta position of the pyridine ring, and compounds in which the first nitrogen-containing group is bonded to the para position of the pyridine ring. Of these, monosubstituted pyridine compounds are more preferably compounds in which the first nitrogen-containing group is bonded to the ortho position of the pyridine ring or to the meta position of the pyridine ring. The first nitrogen-containing group is preferably an alkylamino group or an amino group, and more preferably a methylamino group, a dimethylamino group, or an amino group.

[0037] In the perovskite composition according to this embodiment, the first nitrogen-containing group is preferably an aminoalkyl group bonded to the ortho or meta position of the pyridine ring. Because it has a low melting point and is liquid at room temperature, it can be volatilized more efficiently and is less likely to reduce the power generation efficiency of the resulting film.

[0038] Examples of monosubstituted pyridines include 2-(methylamino)pyridine (latent heat of vaporization 43.8 kJ / mol, boiling point 201°C), 3-(methylaminopyridine) (latent heat of vaporization 45.0 kJ / mol, boiling point 110°C / 7 mmHg (251°C)), 2-dimethylaminopyridine (latent heat of vaporization 43.2 kJ / mol, boiling point 191°C), 4-(methylaminopyridine) (latent heat of vaporization 45.3 kJ / mol, It is preferable that the pyridine monosubstituted is 2-(methylamino)pyridine, 3-(methylaminopyridine), or 2-dimethylaminopyridine, which are liquids at room temperature.

[0039] Among the pyridine compounds containing nitrogen-containing groups, polysubstituted pyridines are compounds in which, in addition to a first nitrogen-containing group, at least one selected from the group consisting of a carbon-containing group, a second nitrogen-containing group, and an alkoxy group is bonded to the carbon of the pyridine ring. Polysubstituted pyridines include compounds in which the first nitrogen-containing group is bonded to the ortho position of the pyridine ring, compounds in which the first nitrogen-containing group is bonded to the meta position of the pyridine ring, and compounds in which the first nitrogen-containing group is bonded to the para position of the pyridine ring. In polysubstituted pyridines, only one of the carbon-containing group, second nitrogen-containing group, or alkoxy group may be bonded, or two or more may be bonded. Furthermore, in polysubstituted pyridines, one of the carbon-containing group, second nitrogen-containing group, or alkoxy group may be bonded to multiple positions on the carbon of the pyridine ring. In polysubstituted pyridines, examples and preferred forms of the first nitrogen-containing group are the same as those for monosubstituted pyridines. The carbon-containing group is a group containing a carbon atom, preferably with the carbon atom bonded to the carbon of the pyridine ring. Examples of carbon-containing groups include alkyl groups, alkylene groups, cycloalkyl groups, alkenyl groups, cycloalkenyl groups, or aryl groups, with alkyl groups being preferred and methyl groups being more preferred. The second nitrogen-containing group can be appropriately selected from the nitrogen-containing groups described above. The alkoxy group is a group having a structure in which an alkyl group is bonded to an oxygen atom, with the oxygen atom bonded to the carbon of the pyridine ring. Examples of alkoxy groups include methoxy groups, ethoxy groups, or propyloxy groups, with methoxy groups being preferred. The polysubstituted pyridine is preferably, for example, 2-amino-5-methylpyridine, 6-amino-2,4-lutidine, or 2-amino-5-methoxypyridine.

[0040] The perovskite composition preferably contains 0.26 mol to 5.0 mol of the second component per mol of the perovskite compound precursor, and more preferably 0.50 mol to 2.0 mol. If the content of the second component is less than 0.26 mol, there may be areas where the crystallization of the perovskite compound cannot be delayed, resulting in a porous film and potentially lower power generation efficiency. If the content of the second component exceeds 5.0 mol, the solubility stability of the perovskite compound precursor decreases, and precipitation may occur in the solution.

[0041] In the perovskite composition according to this embodiment, the film formed under the following condition 1 preferably contains less than 100 ppm of the second component, more preferably 50 ppm or less, and most preferably 0 ppm, i.e., the second component does not remain in the film. If the content of the second component exceeds 100 ppm, the movement of electrons and holes may be inhibited by the second component, which may reduce the power generation efficiency. Condition 1: Distribute the perovskite composition at a rate of 0.25 g / m² on a 20 mm square glass substrate. 2 The wet coating film applied is then blown with 50 L / min of nitrogen gas for 90 seconds through a 6 mm diameter nozzle with a fixed distance of 20 mm between the glass substrate and the nozzle, followed by annealing on a hot plate heated to 100°C for 15 minutes to complete the film formation.

[0042] In condition 1, the glass substrate is not particularly limited, but is preferably, for example, ITO (Indium Tin Oxide) glass or FTO (Fluorine doped tin oxide) glass. Alternatively, the glass substrate may be a glass substrate coated with a conductive polymer. The conductive polymer is not particularly limited, but is preferably, for example, PEDOT:PPS (Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate). For example, if the glass substrate is ITO glass coated with PEDOT:PPS, the perovskite composition is applied on the PEDOT:PPS coating of the glass substrate.

[0043] In Condition 1, the method for applying the perovskite composition can be any known method and is not particularly limited, but examples include spin coating, inkjet coating, doctor blade coating, drop casting, reverse roll coating, gravure coating, kiss coating, roll brushing, spray coating, air knife coating, bar coating, pipe doctor coating, impregnation coating, or curtain coating. 0.25 g / m² in Condition 1 2 This is the amount of wet coating.

[0044] In condition 1, the method of blowing nitrogen gas is not particularly limited as long as nitrogen gas can be directly blown onto the surface of the wet coating film, but for example, a system is used in which nitrogen gas is supplied from a nitrogen gas supply device such as a high-pressure nitrogen gas cylinder or a nitrogen generator, and the flow rate of the gas can be controlled using a needle valve or a flow meter. Furthermore, it is preferable to fix the nozzle so that the direction of nitrogen gas discharge is perpendicular to the surface of the glass substrate.

[0045] In condition 1, the annealing method is, for example, a method in which a glass substrate having a wetted film after blowing is placed on a hot plate heated to 100°C for 15 minutes.

[0046] The content of the second component in the film can be confirmed, for example, using a Fourier transform infrared spectrometer (FT-IR).

[0047] The second component plays a role in delaying the crystallization rate of the perovskite compound precursor. By incorporating it into the composition, grain growth can be carried out after the precipitation of numerous microcrystals of the perovskite compound, thereby obtaining a void-free, flat crystalline film. In this invention, the second component volatilizes after a sufficient number of microcrystals of the perovskite compound have precipitated, through the blowing and annealing processes described later. The resulting crystalline film of the perovskite compound becomes a void-free, flat film due to the crystallization-delaying second component, thus achieving high conversion efficiency.

[0048] The method for manufacturing the photoelectric conversion device according to this embodiment is not particularly limited as long as it can form a film of the perovskite compound, and known methods for manufacturing photoelectric conversion devices using perovskite compounds can be applied. The method for manufacturing the film of the perovskite compound is not particularly limited, and for example, it is a method of coating and then drying the perovskite composition according to this embodiment. Conventional drying methods can be used, such as blow drying, reduced pressure drying, annealing, IR (near-infrared) drying, drying in a constant temperature bath, and hot air blow drying.

[0049] The method for producing a perovskite film according to this embodiment includes a coating step of applying the perovskite composition according to this embodiment to form a coated film, and a film formation step of forming a dried film containing a perovskite compound from the coated film.

[0050] In the coating process, the composition is preferably a liquid paint in which a perovskite compound precursor is dissolved in at least the first component, and more preferably a liquid paint in which a perovskite compound precursor is dissolved in both the first and second components. The method of coating the composition is not particularly limited and includes, for example, spin coating, inkjet coating, doctor blade coating, drop casting, reverse roll coating, gravure coating, kiss coating, roll brushing, spray coating, air knife coating, bar coating, pipe doctor coating, impregnation coating, or curtain coating.

[0051] The coating film formed in the coating process is a wet film containing at least a first component as a solvent. The coating film may also contain a second component in addition to the first component as a solvent. The amount of coating film applied is not particularly limited, but it is preferable to adjust it so that the film after crystallization is 50 nm to 600 nm in thickness.

[0052] The substrate to which the composition is applied can be selected according to the application and is not particularly limited, but for example, when a perovskite film is used as the active layer of a photoelectric conversion device, a glass substrate coated with a conductive polymer or a transparent conductive flexible substrate is preferred. In this case, the composition is applied to the side of the glass substrate on which the conductive polymer is applied. The glass substrate is not particularly limited and is, for example, ITO (Indium Tin Oxide) glass or FTO (Fluorine doped tin oxide) glass. The conductive polymer is not particularly limited and is, for example, preferably PEDOT:PPS (Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate). When the glass substrate is glass with an ITO film, the conductive polymer is applied on the ITO film.

[0053] The film formation process involves volatilizing the first and second components in the coated film to obtain a perovskite film as a dried film. The film formation process can also be described as the process of crystallizing the perovskite compound precursor in the coated film to form a crystalline film of the perovskite compound. The film formation process may be an antisolvent method in which a poor solvent for perovskite is dropped onto the perovskite to precipitate perovskite crystal nuclei when the composition is coated by spin coating in the coating process, or it may be a film formation method other than the antisolvent method. In this embodiment, a film formation method other than the antisolvent method is more preferable because it allows for the adoption of more efficient manufacturing methods such as a roll-to-roll method for the photoelectric conversion device.

[0054] Next, an example of a film formation method other than the antisolvent method will be described. In the method for producing a perovskite film according to this embodiment, the film formation step preferably includes a blow step in which an inert gas is supplied toward the coated film, and an annealing step in which the coated film is heated after the blow step. This makes it possible to increase the area and can be applied to manufacturing methods that improve mass productivity, such as the roll-to-roll method.

[0055] The blowing process is a process for precipitating microcrystals of the perovskite compound. The inert gas is not particularly limited and may be, for example, nitrogen gas or argon gas. The amount of inert gas supplied is not particularly limited. In the blowing process, some or all of the first and / or second components may be removed as a by-product. The method of blowing the inert gas is not particularly limited as long as the inert gas can be directly blown onto the surface of the coating film, but may be, for example, a system in which the inert gas is supplied from an inert gas supply device such as a high-pressure inert gas cylinder or an inert gas generator, and the flow rate of the gas can be controlled using a needle valve or a flow meter.

[0056] In the blowing process, by using a component with a lower latent heat of vaporization than the second component as the first component, the first component can be preferentially volatilized over the second component. This allows for more efficient precipitation of microcrystals of the perovskite compound by the second component and grain growth in the subsequent annealing process, thus enabling the more efficient acquisition of a flat film without voids.

[0057] The annealing process involves heating the film after the blowing process to promote grain growth of the microcrystals precipitated during the blowing process. The heating temperature for the annealing process is preferably 50 to 130°C, and more preferably 70 to 100°C. The heating and holding time for the annealing process is preferably 5 to 60 minutes, and more preferably 10 to 30 minutes. The heating method for the annealing process is not particularly limited; for example, a substrate on which a coated film has been formed after the blowing process is placed on a hot plate and heated. In the annealing process, all of the first and second components remaining in the film after the blowing process are incidentally removed. The heating temperature for the annealing process is preferably, for example, 70°C to 100°C, and it is preferable to volatilize all of the first and second components during the annealing process.

[0058] The surface of the dried film of the perovskite composition according to this embodiment is preferably mirror-like.

[0059] The surface roughness of the dried film of the perovskite composition according to this embodiment is preferably in the range of 15% or less, more preferably in the range of 10% or less, and even more preferably in the range of 5% or less, relative to the film thickness of the dried film of the perovskite composition. The lower limit of the surface roughness is not particularly limited, but it is preferable to have as little as possible. The film thickness and surface roughness were measured using a white light interference microscope (BW-501, Nikon Corporation) on a perovskite film deposited on a glass substrate.

[0060] The thickness of the perovskite film can be selected according to the application and is not particularly limited. For example, when the perovskite film is used as the active layer of a photoelectric conversion device, the thickness of the perovskite film is preferably 10 to 1000 nm, and more preferably 50 to 500 nm.

[0061] The photoelectric conversion device according to this embodiment has a dried film of the perovskite composition according to this embodiment.

[0062] The photoelectric conversion device according to this embodiment comprises a dry film, i.e., a perovskite film, as an active layer, and it is preferable that the active layer is positioned between two electrodes. The active layer is sometimes called a perovskite layer. The structure of the photoelectric conversion device is not particularly limited, and known structures can be adopted. Next, an example of a photoelectric conversion device will be described, but the present invention is not limited thereto. The photoelectric conversion device may be, for example, a sequential structure comprising a conductive substrate, an electron transport layer, an active layer (perovskite layer), a hole transport layer, and an electrode layer, or an inverse structure comprising a conductive substrate, a hole transport layer, an active layer (perovskite layer), an electron transport layer, and an electrode layer in that order.

[0063] The conductive substrate acts as an electrode and is a transparent conductive substrate, not particularly limited, but for example, ITO glass, FTO glass, or other transparent conductive material. Alternatively, the conductive substrate may be a transparent conductive flexible substrate. The conductive substrate collects electrons from the electron transport layer and flows them to the external circuit.

[0064] The hole transport layer is, for example, PEDOT:PPS (Poly3,4-EthyleneDiOxyThiophene / Poly4-StyreneSulfonate) or nickel oxide. The hole transport layer collects holes generated in the active layer while hindering the flow of electrons.

[0065] The active layer (perovskite layer) is a film formed using the perovskite composition according to this embodiment, and is the layer where photoelectric conversion takes place. When the photoelectric conversion device receives light, the active layer absorbs the light and generates electrons and holes. The photoelectric conversion device sandwiches the active layer between an electron transport layer and a hole transport layer, causing electrons to move to the electron transport layer and holes to move to the hole transport layer. As a result, electrons flow and electricity is generated.

[0066] The electron transport layer is, for example, a metal oxide such as titanium dioxide, tin oxide, zinc oxide, aluminum oxide, niobium oxide, or yttrium oxide, or a fullerene derivative such as C60 (fullerene) or PCBM ((6,6)-phenylC61 methyl butyrate). The electron transport layer collects electrons generated in the active layer while hindering the flow of holes.

[0067] The electrode layer is made of a metal such as gold, silver, copper, or aluminum, or a conductive transparent material such as tin oxide or ITO. The electrode layer collects holes from the hole transport layer and supplies them to the external circuit. [Examples]

[0068] The present invention will be described in more detail below based on examples, but the present invention is not limited in any way to these examples. In the examples, "parts" and "%" refer to "parts by mass" and "% by mass," respectively, unless otherwise specified. The number of added parts is the value on a solid content basis.

[0069] (Example 1) As a perovskite compound precursor, 0.3725 g of tin iodide (SnI2) and 0.1720 g of formamidinium iodide (FAI) were added with 0.90 ml of dimethylformamide as the first component and 0.10 ml of 2-(methylamino)pyridine as the second component, and stirred for 2 hours to obtain a perovskite composition. ITO glass coated with PEDOT:PPS was prepared as a substrate, and the perovskite composition was coated on the coated surface of PEDOT:PPS using a bar coater. The wet coating amount was 0.25 g / m 2 2. After coating, nitrogen gas as an inert gas was applied at 50 L / min for 30 seconds (blowing step), and annealing was performed at 70 °C for 15 minutes using a hot plate (annealing step) to obtain a perovskite film. The film thickness of the perovskite film was 170 nm. The content of the second component relative to 1 mol of the perovskite compound precursor was 0.98 mol.

[0070] (Example 2) A perovskite film was obtained in the same manner as in Example 1, except that 0.10 ml of 3-(methylamino)pyridine was used instead of 0.10 ml of 2-(methylamino)pyridine as the second component. The content of the second component relative to 1 mol of the perovskite compound precursor was 0.98 mol.

[0071] (Example 3) A perovskite film was obtained in the same manner as in Example 1, except that 0.10 ml of 2-dimethylaminopyridine was used instead of 0.10 ml of 2-(methylamino)pyridine as the second component. The content of the second component relative to 1 mol of the perovskite compound precursor was 0.83 mol.

[0072] (Example 4) A perovskite film was obtained in the same manner as in Example 1, except that 0.0941 g of 3-aminopyridine was used instead of 0.10 ml of 2-(methylamino)pyridine as the second component. The content of the second component relative to 1 mol of the perovskite compound precursor was 1.0 mol.

[0073] (Example 5) A perovskite film was obtained in the same manner as in Example 1, except that 0.10 ml of 2-(methylamino)pyridine was replaced with 0.1082 g of 2-amino-5-methylpyridine as the second component, and the annealing conditions were changed from 70°C for 15 minutes to 80°C for 15 minutes. The content of the second component per 1 mol of perovskite compound precursor was 1.0 mol.

[0074] (Example 6) A perovskite film was obtained in the same manner as in Example 1, except that 0.1222 g of 6-amino-2,4-lutidine was used instead of 0.10 ml of 2-(methylamino)pyridine as the second component. The content of the second component per 1 mol of perovskite compound precursor was 1.0 mol.

[0075] (Example 7) A perovskite film was obtained in the same manner as in Example 1, except that 0.1242 g of 2-amino-5-methoxypyridine was used instead of 0.10 ml of 2-(methylamino)pyridine as the second component. The content of the second component per 1 mol of perovskite compound precursor was 1.0 mol.

[0076] (Example 8) A perovskite film was obtained in the same manner as in Example 1, except that the amount of the second component, 2-(methylamino)pyridine, was changed from 0.10 ml to 0.05 ml. The content of the second component per 1 mol of perovskite compound precursor was 0.49 mol.

[0077] (Example 9) A perovskite film was obtained in the same manner as in Example 1, except that the amount of the second component, 2-(methylamino)pyridine, was changed from 0.10 ml to 0.20 ml. The content of the second component per 1 mol of perovskite compound precursor was 1.96 mol.

[0078] (Example 10) A perovskite film was obtained in the same manner as in Example 1, except that 0.40 ml of 4-tert-butylpyridine was used instead of 0.10 ml of 2-(methylamino)pyridine as the second component. The content of the second component per 1 mol of perovskite compound precursor was 2.72 mol.

[0079] (Example 11) A perovskite film was obtained in the same manner as in Example 1, except that 0.90 ml of 2-methoxyethanol was used instead of 0.90 ml of dimethylformamide as the first component. The content of the second component per 1 mol of perovskite compound precursor was 0.98 mol.

[0080] (Example 12) A perovskite film was obtained in the same manner as in Example 1, except that a mixed solvent of 0.45 ml of dimethylformamide and 0.45 ml of 2-methoxyethanol was used instead of 0.90 ml of dimethylformamide as the first component. The content of the second component per 1 mol of perovskite compound precursor was 0.98 mol.

[0081] (Example 13) A perovskite film was obtained in the same manner as in Example 1, except that 0.90 ml of dimethylacetamide was used instead of 0.90 ml of dimethylformamide as the first component. The content of the second component per 1 mol of perovskite compound precursor was 0.98 mol.

[0082] (Example 14) A perovskite film was obtained in the same manner as in Example 1, except that 0.10 ml of 2-(methylamino)pyridine was replaced with 0.1081 g of 3-amino-5-methylpyridine as the second component. The content of the second component per 1 mol of perovskite compound precursor was 0.98 mol.

[0083] (Comparative Example 1) A perovskite film was obtained in the same manner as in Example 1, except that 0.20 ml of dimethyl sulfoxide was used instead of 0.10 ml of 2-(methylamino)pyridine, which is the second component.

[0084] (Comparative Example 2) A perovskite film was obtained in the same manner as in Example 1, except that 0.10 ml of 2-propylpyridine was used instead of 0.10 ml of 2-(methylamino)pyridine, which is the second component. The content of the second component per 1 mol of perovskite compound precursor was 0.76 mol.

[0085] (Comparative Example 3) A perovskite film was obtained in the same manner as in Example 1, except that 0.10 ml of 3-ethylpyridine was used instead of 0.10 ml of 2-(methylamino)pyridine, which is the second component. The content of the second component per 1 mol of perovskite compound precursor was 0.88 mol.

[0086] (Comparative Example 4) A perovskite film was obtained in the same manner as in Example 1, except that 0.10 ml of 4-propylpyridine was used instead of 0.10 ml of 2-(methylamino)pyridine, which is the second component. The content of the second component per 1 mol of perovskite compound precursor was 0.77 mol.

[0087] (Comparative Example 5) A perovskite film was obtained in the same manner as in Example 1, except that 0.10 ml of 2-methoxypyridine was used instead of 0.10 ml of 2-(methylamino)pyridine, which is the second component. The content of the second component per 1 mol of perovskite compound precursor was 0.96 mol.

[0088] (Comparative Example 6) A perovskite film was formed in the same manner as in Example 1, except that 0.10 ml of pyrrolidine was used instead of 0.10 ml of 2-(methylamino)pyridine, the second component, but no film was formed. The content of the second component per 1 mol of perovskite compound precursor was 1.21 mol.

[0089] (Time until crystal precipitation) For Example 1 and Comparative Example 1, the time from the start of the blowing process after applying the perovskite composition until the crystals of the perovskite compound began to precipitate was measured and defined as the time to crystal precipitation. The start of crystal precipitation was defined as the time when the coating film began to change to brown, as observed visually. Crystal precipitation occurred when the crystallization region gradually expanded after the start of the blowing process until a crystalline film was completed. Therefore, the start of crystal precipitation was defined as the time when a part of the coating film began to change to brown. As a result, the time to crystal precipitation was 15 seconds for Example 1 and less than 3 seconds for Comparative Example 1. From these results, it was confirmed that the crystallization of the perovskite compound can be delayed by incorporating the second component in the perovskite composition of the examples.

[0090] (Surface state of perovskite film) The surface condition of the perovskite films of the examples and comparative examples was observed visually and with a microscope (model: VHX-6000, manufactured by Keyence Corporation) at a magnification of 2000x. As representative examples, Figure 1 shows a microscope image of the perovskite film of Example 1, and Figure 2 shows a microscope image of the perovskite film of Comparative Example 1. Visual observation confirmed that the perovskite film of Example 1 had a completely flat, mirror-like surface, and as shown in Figure 1, no voids between crystals were observed, confirming high coverage. Examples 2 to 11 also had completely flat, mirror-like surfaces and high coverage, similar to Example 1. On the other hand, visual observation of the perovskite film of Comparative Example 1 revealed significant irregularities, no mirror-like surface, and many voids between crystals, as shown in Figure 2. Similarly, Comparative Examples 2 to 5 also had significant irregularities and were not mirror-like, confirming low coverage, similar to Comparative Example 1. No film was formed from the composition of Comparative Example 6. From these results, it was confirmed that the perovskite composition of the example can produce a perovskite film with high coverage and flatness even without using the antisolvent method as a film formation step.

[0091] The perovskite films of the examples were evaluated as follows, and the evaluation results are shown in Tables 1 and 2. The perovskite films of the comparative examples were evaluated for their surface condition, and as a result, their surface condition was poor and they did not generate electricity. Therefore, evaluations other than surface condition evaluation and power generation efficiency were not performed.

[0092] [Table 1]

[0093] [Table 2]

[0094] (Presence or absence of voids) In the observation of the "surface condition of the perovskite film" described above, the presence or absence of voids was confirmed based on the results of microscopic observation. (film thickness) The film thickness was measured using a white light interference microscope (BW-501, Nikon Corporation) on a perovskite film deposited on a glass substrate. (Surface roughness) The surface roughness of the perovskite film was measured using a white light interference microscope (BW-501, Nikon Corporation) on a perovskite film deposited on a glass substrate. (Surface roughness relative to film thickness) The surface roughness relative to the film thickness is the value obtained by dividing the "surface roughness" value by the "film thickness" value and expressing the result as a percentage. (Amount of the second component or its substitute component remaining in the membrane) For the perovskite films of the examples, the residual amount of the second component in the film was measured. For the perovskite films of the comparative examples, the presence or absence of residual amounts of the component added in place of the second component (sometimes called the second component substitute) in the film was measured. The residual amounts in the film were measured using the ATR method with a Fourier transform infrared spectrometer (IRTracer-100, Shimadzu Corporation) on perovskite films deposited on a glass substrate. An MCT detector was used to measure trace amounts of substances. (Power generation efficiency) Using a solar simulator (HAL-320, manufactured by Asahi Spectroscopy Co., Ltd.) and a PV power analyzer (VK-PA-1000, manufactured by SPD Laboratory Co., Ltd.), we obtained voltage-current density curves for the fabricated photoelectric conversion element. From the obtained voltage-current density curves, we can determine photoelectric conversion characteristics such as photoelectric conversion efficiency (PCE), short-circuit current density (JSc), open-circuit voltage (VOc), and fill factor (FF). Here, short-circuit current density (JSc) is the current density when the voltage value = 0 (V), and open-circuit voltage (VOc) is the current value = 0 (mA / cm²). 2 This is the voltage value at that time. The fill factor (FF) is a factor that represents the internal resistance. The fill factor (FF) is expressed by the following formula, where PmaX is the maximum output. FF = PmaX / (VOc × JSc) Furthermore, the power generation efficiency (PCE) is calculated by the amount of incident energy in PiN (mW / cm²). 2 If we let ), then it is given by the following equation: PCE = (PmaX / PiN) × 100 = (VOc × JSc × FF / PiN) × 100 The power generation efficiency (PCE) is calculated by dividing the output (maximum output) at the optimal operating point of the current-voltage curve of the photoelectric conversion device, measured with a predetermined irradiation light, by the total energy contained in that irradiation light (%). In this patent, the total energy of the irradiated light is 100 mW / cm² because it uses simulated sunlight with an intensity of AM.15. 2 This is the result.

[0095] As can be seen from Tables 1 and 2, the perovskite films in the examples were all flat and free of voids, resulting in high power generation efficiency. The perovskite films in the comparative examples all lacked the second component, and therefore had voids between crystals. For this reason, the perovskite films of Comparative Examples 1 to 6 were all considered to generate no power.

Claims

1. The material comprises a perovskite compound precursor, a first component which is a solvent for the perovskite compound precursor, and at least one second component selected from the group consisting of nitrogen-containing pyridines and 4-tert-butylpyridine. The aforementioned pyridines having nitrogen-containing groups are The compound is such that the first nitrogen-containing group is bonded to one of the ortho, meta, or para positions of the pyridine ring, and hydrogen atoms are bonded to positions other than those to which the first nitrogen-containing group is bonded on the pyridine ring, or A perovskite composition characterized in that the first nitrogen-containing group is bonded to one of the ortho, meta, or para positions of a pyridine ring, and at least one of the positions other than the one to which the first nitrogen-containing group is bonded to the pyridine ring is a compound selected from the group consisting of a carbon-containing group, a second nitrogen-containing group, and an alkoxy group.

2. The perovskite composition according to claim 1, characterized in that the film formed under the following condition 1 contains less than 100 ppm of the second component. Condition 1: Distribute the perovskite composition at a rate of 0.25 g / m² on a 20 mm square glass substrate. ２ The wet coating film applied is then blown with 50 L / min of nitrogen gas for 90 seconds through a 6 mm diameter nozzle with a fixed distance of 20 mm between the glass substrate and the nozzle, and then annealed for 15 minutes on a hot plate heated to 100°C to form the final film.

3. The perovskite composition according to claim 1, characterized in that the first nitrogen-containing group is an aminoalkyl group bonded to the ortho or meta position of the pyridine ring.

4. The perovskite composition according to claim 1, characterized in that the latent heat of vaporization of the second component is 50 kJ / mol or less.

5. The perovskite composition according to claim 1, characterized in that the latent heat of vaporization of the first component is smaller than the latent heat of vaporization of the second component.

6. The perovskite composition according to claim 1, characterized in that the boiling point of the second component is 280°C or lower.

7. The perovskite composition according to claim 1, characterized in that the perovskite composition does not contain dimethyl sulfoxide, or the amount of dimethyl sulfoxide added is a maximum of 5.0 vol% relative to the total volume of the first component and the second component.

8. A perovskite film characterized by being a dried film of a perovskite composition described in any one of claims 1 to 7.

9. A photoelectric conversion device characterized by having a dried film of a perovskite composition according to any one of claims 1 to 7.

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