Manufacturing method for perovskite-type solar cell

Abstract

To provide a manufacturing method for a perovskite-type solar cell that can suppress deterioration of a photoelectric conversion layer.SOLUTION: The present invention relates to a manufacturing method for a perovskite-type solar cell having a photoelectric conversion layer containing a perovskite compound, the manufacturing method including a step of applying a silver nanowire solution onto an electron transport layer or a hole transport layer formed on the photoelectric conversion layer, wherein a solvent of the silver nanowire solution is an alcohol having 3 or more carbon atoms.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a perovskite solar cell. [Background technology]

[0002] Solar cells are widely used as an energy source with low environmental impact. Known types of solar cells include silicon (Si) solar cells, which use silicon in the photoelectric conversion layer, and perovskite solar cells, whose photoelectric conversion layer is mainly composed of perovskite compounds.

[0003] Known perovskite solar cells include, for example, a substrate, a first electrode layer, a first carrier layer (e.g., a hole transport layer or an electron transport layer), a photoelectric conversion layer containing a perovskite compound, a second carrier layer (e.g., an electron transport layer or a hole transport layer), and a second electrode layer.

[0004] Transparent conductive films are widely used as electrodes for solar cells. Known transparent conductive films include indium oxide-based (indium tin oxide (ITO), indium zinc oxide (IZO), etc.) transparent conductive films. Indium oxide-based transparent conductive films are usually formed by sputtering.

[0005] In the manufacture of perovskite solar cells using an indium oxide-based transparent conductive film as the second electrode layer, the indium oxide-based transparent conductive film must be deposited by sputtering at low temperatures to avoid thermal damage to underlying layers such as the photoelectric conversion layer, electron transport layer, and hole transport layer. However, indium oxide-based transparent conductive films have low crystallinity when deposited at low temperatures, making it difficult to obtain low-resistance films. Furthermore, there are concerns about the volatilization of film components when the photoelectric conversion layer, an organic film containing a perovskite compound, is exposed to a vacuum. Furthermore, the sputtering method, which is a vacuum process, has the problem of high manufacturing costs.

[0006] As a transparent conductive film other than indium oxide-based transparent conductive films, transparent conductive films made of metal nanowires such as silver nanowires have also attracted attention. Transparent conductive films made of silver nanowires can be formed at low cost by applying a silver nanowire solution. Furthermore, transparent conductive films made of silver nanowires have performance comparable to that of indium oxide-based transparent conductive films. Thus, transparent conductive films made of silver nanowires were expected to be promising for solving the above-mentioned problems with indium oxide-based transparent conductive films.

[0007] As described in Patent Document 1, silver nanowire ink typically contains a mixed solvent of water and alcohol. However, perovskite compounds are known to have low resistance to polar solvents such as water. For this reason, the perovskite compound in the photoelectric conversion layer deteriorates when it comes into direct contact with a polar solvent such as water, or when it comes into contact with polar solvent molecules such as water that have diffused through an adjacent layer and reached the photoelectric conversion layer. Therefore, when a perovskite solar cell is manufactured using conventional silver nanowire ink, there is a risk of deterioration of the photoelectric conversion layer. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 6723343 Summary of the Invention [Problem to be solved by the invention]

[0009] As described above, conventional methods for manufacturing perovskite solar cells using silver nanowire solutions have been known to involve the risk of deterioration of the photoelectric conversion layer. Therefore, an object of the present invention is to provide a method for manufacturing perovskite solar cells that can suppress deterioration of the photoelectric conversion layer. [Means for solving the problem]

[0010] The present inventors have discovered that the use of a specific alcohol as a solvent for a silver nanowire solution in the production of a perovskite solar cell can suppress deterioration of the photoelectric conversion layer, and have completed the present invention.

[0011] That is, the gist of the present invention is as follows. (1) A method for manufacturing a perovskite solar cell having a photoelectric conversion layer containing a perovskite compound, the method comprising the step of applying a silver nanowire solution onto an electron transport layer or a hole transport layer formed on the photoelectric conversion layer, wherein the solvent for the silver nanowire solution is an alcohol having three or more carbon atoms. (2) A method for producing a perovskite solar cell according to (1), comprising the step of applying the silver nanowire solution onto an electron transport layer containing a fullerene compound, wherein the solvent for the silver nanowire solution is an alcohol having 5 or less carbon atoms. (3) A method for manufacturing a perovskite solar cell according to (1) or (2), comprising the step of applying the silver nanowire solution by an inkjet method, wherein the solvent for the silver nanowire solution is an alcohol having 4 or more carbon atoms. [Effects of the Invention]

[0012] The present invention makes it possible to provide a method for manufacturing a perovskite solar cell that can suppress deterioration of the photoelectric conversion layer. [Brief explanation of the drawings]

[0013] [Figure 1] Photographs of the appearance of samples on which perovskite material films were formed after being immersed in each solvent for a predetermined period of time. [Figure 2] This is a photograph of the appearance of a silver nanowire layer fabricated on PCBM using a silver nanowire ink in 1-hexanol solvent. [Figure 3] 1 is a flowchart showing a manufacturing process of a perovskite solar cell in Examples 1 and 2. [Figure 4]1 is a photograph showing the appearance of a silver nanowire layer produced using a silver nanowire ink with a 1-butanol solvent. [Figure 5] 1 is a graph showing the dielectric constant and boiling point of various solvents. DETAILED DESCRIPTION OF THE INVENTION

[0014] Preferred embodiments of the present invention will now be described in detail.

[0015] The present invention relates to a method for producing a perovskite solar cell having a photoelectric conversion layer containing a perovskite compound.

[0016] The perovskite solar cell obtained by the production method of the present invention (hereinafter also referred to as the solar cell of the present invention) has a photoelectric conversion layer containing a perovskite compound.

[0017] In one embodiment, the solar cell of the present invention comprises, in this order, a substrate, a first electrode layer (substrate-side electrode), a first carrier transport layer, a photoelectric conversion layer containing a perovskite compound, a second carrier transport layer, and a second electrode layer (substrate counter electrode). In this embodiment, the second electrode layer is a silver nanowire layer.

[0018] In one embodiment, the first carrier transport layer is a hole transport layer (HTL) and the second carrier transport layer is an electron transport layer (ETL), and in another embodiment, the first carrier transport layer is an electron transport layer and the second carrier transport layer is a hole transport layer.

[0019] The first electrode layer and the second electrode layer can be an anode or a cathode. In one embodiment, the first electrode layer is an anode, the first carrier transport layer is a hole transport layer, the second electrode layer is a cathode, and the second carrier transport layer is an electron transport layer. In another embodiment, the first electrode layer is a cathode, the first carrier transport layer is an electron transport layer, the second electrode layer is an anode, and the second carrier transport layer is a hole transport layer.

[0020] In a first embodiment of the solar cell of the present invention, the solar cell has a substrate, a first electrode layer, an electron transport layer, a photoelectric conversion layer, a hole transport layer, and a second electrode layer (silver nanowire layer) in this order.

[0021] In a second embodiment of the solar cell of the present invention, the solar cell has a substrate, a first electrode layer, a hole transport layer, a photoelectric conversion layer, an electron transport layer, and a second electrode layer (silver nanowire layer) in this order.

[0022] The material of the substrate is not particularly limited, and examples thereof include inorganic materials such as glass, organic materials such as polyethylene, polyethylene terephthalate, polyethylene naphthalate, polyimide, polyamide, polyamideimide, liquid crystal polymer, cycloolefin polymer, and metal materials such as stainless steel, silicon, etc. The substrate material is preferably glass.

[0023] The substrate may be transparent or opaque. When light is incident from the surface of the substrate, a transparent substrate is used. As the transparent substrate, a substrate made of glass, polyethylene terephthalate, polyethylene naphthalate, polyimide, polyamide, polyamideimide, or cycloolefin polymer can be used. When light is incident from the opposite side of the substrate, the substrate can be opaque. The thickness of the substrate is usually several tens of μm to several mm.

[0024] The first electrode layer can be made of any of the following materials: metals such as aluminum (Al), silver (Ag), and gold (Au); transparent conductive films such as indium tin oxide (ITO), indium zinc oxide (IZO), aluminum-doped zinc oxide (AZO), and fluorine-doped tin oxide (FTO); and carbon nanotubes, all of which are known materials for solar cell electrodes. The first electrode layer is preferably made of ITO, IZO, or FTO. The thickness of the first electrode layer is typically 50 nm to 500 nm.

[0025] The material of the second electrode layer is a transparent conductive film containing silver nanowires (silver nanowire layer), preferably a transparent conductive film made of silver nanowires. The second electrode layer is formed by applying a silver nanowire solution onto the electron transport layer or hole transport layer. The silver nanowires may have a wire length of several μm to 100 μm and a wire diameter of several nm to several tens of nm. The thickness of the second electrode layer is usually several tens of nm to 1 μm.

[0026] The hole transport layer transports holes generated by photoelectric conversion in the photoelectric conversion layer to the first electrode layer or the second electrode layer. Known organic or inorganic materials suitable for hole transport layers can be used as the material for the hole transport layer. Examples of organic materials include, but are not limited to, 2,2',7,7'-tetrakis-(N,N-di-4-methoxyphenylamino)-9,9'-spirobifluorene (Spiro-OMeTAD), polyethylenedioxythiophene:polystyrenesulfonic acid (PEDOT:PSS), poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), and [2-(3,6-dimethoxy-9H-carbazol-9H-yl)ethyl]phosphonic acid (MeO-2PACz). Examples of inorganic materials include, but are not limited to, nickel oxide, copper oxide, cobalt oxide, and copper iodide. In the first embodiment of the solar cell of the present invention, the material of the hole transport layer is preferably Spiro-OMeTAD, PTAA, and nickel oxide. In the second embodiment of the solar cell of the present invention, the material of the hole transport layer is preferably PEDOT:PSS, PTAA, and nickel oxide. The thickness of the hole transport layer is usually 1 nm to 1000 nm.

[0027] The electron transport layer has a function of transporting electrons generated by photoelectric conversion in the photoelectric conversion layer to the first electrode layer or the second electrode layer. The material of the electron transport layer can be any known organic or inorganic material that can be used for electron transport layers. Examples of organic materials include, but are not limited to, fullerene compounds, phenanthroline derivatives (e.g., bathocuproine), and polyethyleneimines. Examples of fullerene compounds include fullerenes (e.g., C60 fullerene, C70 fullerene), and derivatives of fullerenes with a substituent added (e.g., [6,6]-phenyl-C 61 -methyl butyrate (also known as PCBM or

[60] PCBM), [6,6]-phenyl-C 71 Examples of inorganic materials include titanium oxide, tin oxide, and zinc oxide. In the first embodiment of the solar cell of the present invention, the material of the electron transport layer is preferably fullerene, PCBM, bathocuproine, polyethyleneimines, titanium oxide, and tin oxide. In the second embodiment of the solar cell of the present invention, the material of the electron transport layer is preferably fullerene, PCBM, bathocuproine, and polyethyleneimines. In one embodiment, the electron transport layer contains a fullerene compound, and preferably consists of a fullerene compound. The content of the fullerene compound in the electron transport layer is usually 60% by weight or more, preferably 80% by weight or more, more preferably 90% by weight or more, particularly preferably 95% by weight or more, and most preferably 100% by weight. The thickness of the electron transport layer is usually 1 nm to 1,000 nm.

[0028] The photoelectric conversion layer contains a perovskite compound, preferably contains a perovskite compound as a main component, and more preferably consists of a perovskite compound. The content of the perovskite compound in the photoelectric conversion layer is usually 60% by weight or more, preferably 80% by weight or more, more preferably 90% by weight or more, particularly preferably 95% by weight or more, and most preferably 100% by weight. The thickness of the photoelectric conversion layer is usually 50 nm to 1000 nm, more preferably 200 nm to 600 nm.

[0029] A perovskite compound is a compound having a perovskite-type crystal structure. The perovskite-type crystal structure typically consists of ions A, B, and X. The perovskite-type crystal structure has a cubic unit cell, with A located at each vertex of the cubic crystal, B located at the body center, and X located at each face center of the cubic crystal centered on A. Whether a compound has a perovskite-type crystal structure can be confirmed, for example, by X-ray diffraction measurement.

[0030] The perovskite compound can be represented by, for example, the following formula (1). ABX3(1) (wherein A is a monovalent cation, B is a divalent cation, and X is a monovalent anion.)

[0031] In one embodiment, in formula (1), A is at least one selected from the group consisting of a monovalent organic ammonium ion, a monovalent amidinium ion, and a monovalent metal ion. Examples of the monovalent organic ammonium ion include CH3NH3 + (Methylammonium ion: MA), C2H5NH3 + , C3H7NH3 + and C4H9NH3 + Examples of monovalent amidinium ions include HC(NH2)2 + (formamidinium ion: FA). Examples of monovalent metal ions include rubidium ion (Rb + ) and cesium ions (Cs + In formula (1), A may be a combination of a monovalent organic ammonium ion, a monovalent amidinium ion, and a monovalent metal ion. In formula (1), A is preferably MA, FA, or Cs + and combinations of two or three of these. + or Cs + If it contains Rb relative to the total amount of A + or Cs + The content is usually 10 atomic % or less.

[0032] In one embodiment, in formula (1), B is a divalent metal ion, for example, a lead ion (Pb 2+ ), tin ions (Sn 2+ ) and combinations thereof, more preferably Pb 2+ is.

[0033] In one embodiment, in formula (1), X is a halogen ion, for example, a fluoride ion (F - ), chloride ions (Cl - ), bromide ion (Br - ) and iodide ion (I - ) and at least one selected from Cl - , Br - and I - is preferred.

[0034] The solar cell of the present invention can be used alone or in combination with other solar cells such as silicon (Si) solar cells. When used in combination with other solar cells, for example, a tandem solar cell can be formed by stacking the other solar cell on the second electrode layer side (counter electrode of the substrate) of the solar cell of the present invention.

[0035] The method for producing a perovskite solar cell of the present invention includes a step of applying a silver nanowire solution onto an electron transport layer or a hole transport layer (second carrier transport layer). As described above for the solar cell of the present invention, the electron transport layer or the hole transport layer is formed on a photoelectric conversion layer. The electron transport layer or the hole transport layer may be laminated directly on the photoelectric conversion layer, or may be laminated on the photoelectric conversion layer via another layer.

[0036] The silver nanowire solution can be applied onto the electron transport layer or the hole transport layer by a known method. The method for applying the silver nanowire solution is not particularly limited, and examples thereof include spin coating, inkjet coating, spray coating, blade coating, and die coating. The inkjet coating and spray coating are preferred, and the inkjet coating is more preferred.

[0037] The silver nanowire solution can usually be applied in the atmosphere at a temperature of 15°C to 35°C.

[0038] The silver nanowire solution is prepared by dissolving or dispersing silver nanowires in a solvent. The wire length and wire diameter of the silver nanowires are as described above for the silver nanowire layer. The concentration of silver nanowires in the silver nanowire solution is typically 5% by weight or less, and preferably 1% by weight or less. In one embodiment, when the silver nanowire solution is applied by an inkjet method, the concentration of silver nanowires in the silver nanowire solution is preferably 0.5% by weight or less.

[0039] The solvent for the silver nanowire solution is an alcohol having 3 or more carbon atoms. Using an alcohol having 3 or more carbon atoms as the solvent for the silver nanowire solution suppresses deterioration of the photoelectric conversion layer present below the electron transport layer or hole transport layer to which the silver nanowire solution is applied. The alcohol having 3 or more carbon atoms as the solvent for the silver nanowire solution can be a monohydric or polyhydric alcohol, but a monohydric alcohol is preferred because it can further suppress deterioration of the photoelectric conversion layer. The alcohol having 3 or more carbon atoms as the solvent for the silver nanowire solution may be either a linear alcohol or a branched alcohol, and may be either a saturated alcohol or an unsaturated alcohol. The solvent for the silver nanowire solution is preferably an alcohol having 6 or less carbon atoms. The solvent for the silver nanowire solution is preferably an alcohol having 3 to 6 carbon atoms, more preferably 1-propanol, 1-butanol, 1-pentanol, or 1-hexanol. The alcohols may be used alone or in combination of two or more.

[0040] In one embodiment, when the electron transport layer contains a fullerene compound, the solvent of the silver nanowire solution is preferably an alcohol having 5 or less carbon atoms (i.e., an alcohol having 3 to 5 carbon atoms), more preferably 1-propanol, 1-butanol, or 1-pentanol. When the solvent of the silver nanowire solution is an alcohol having 3 to 5 carbon atoms, deterioration of the photoelectric conversion layer and the electron transport layer can be suppressed.

[0041] In one embodiment, when the silver nanowire solution is applied by an inkjet method, the solvent of the silver nanowire solution is preferably an alcohol having four or more carbon atoms, from the viewpoint of preventing clogging of the inkjet nozzle.

[0042] In one embodiment, when the electron transport layer contains a fullerene compound and the silver nanowire solution is applied by an inkjet method, the solvent of the silver nanowire solution is preferably an alcohol having 4 to 5 carbon atoms, more preferably 1-butanol or 1-pentanol, from the viewpoint of suppressing deterioration of the photoelectric conversion layer and the electron transport layer and suppressing clogging of the inkjet nozzle.

[0043] The manufacturing method of the present invention may include a step of drying the applied silver nanowire solution. The drying step can be carried out by heating at a temperature of usually 80°C to 150°C.

[0044] In the manufacturing method of the present invention, layers other than the silver nanowire layer can be formed by known film formation methods. [Example]

[0045] The present invention will be described in more detail below using examples, although the technical scope of the present invention is not limited to these examples.

[0046] <Solvent study for silver nanowire ink 1> We investigated solvents for silver nanowire inks that can be used for photoelectric conversion layers containing perovskite compounds.The solvents used were dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), water, methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, and 1-hexanol.

[0047] A film of perovskite material (CsFAMAPbI3) was formed on a glass substrate, and a small piece of the material was used as a sample. The sample was immersed in each solvent and the change in appearance was observed after 10 minutes. When the solvent was water, the change in appearance was observed after 10 seconds. Figure 1 shows photographs of the appearance of the sample after immersion in each solvent for a predetermined time. As shown in Figure 1, the perovskite material dissolved immediately after immersion in DMSO, NMP, and DMF. Furthermore, the perovskite material turned yellow after short immersion in water, methanol (not shown), and ethanol. This is thought to be due to the decomposition of the perovskite compound, resulting in the production of yellow lead iodide. On the other hand, the perovskite material did not change appearance even after immersion for 10 minutes in alcohols with three or more carbon atoms (1-propanol, 1-butanol, 1-pentanol, and 1-hexanol). This confirms that perovskite materials are sufficiently resistant to alcohols with three or more carbon atoms.

[0048] <Solvent study for silver nanowire ink 2> [6,6]-phenyl-C 61 We investigated solvents for silver nanowire inks suitable for electron transport layers containing poly(methyl butyl phosphate) (PCBM). Various primary alcohols were used as the solvents for the silver nanowire inks. First, silver nanowires were dispersed in various primary alcohols to prepare silver nanowire inks. Next, the silver nanowire inks were spin-coated onto PCBM, and the presence or absence of corrosion of the underlying PCBM was confirmed by optical microscopy. When the silver nanowire ink solvent was 1-hexanol, PCBM dissolution was confirmed. Figure 2 shows a photograph of the appearance of a silver nanowire layer fabricated on PCBM using silver nanowire ink in 1-hexanol solvent. As shown in Figure 2, when the silver nanowire ink solvent was 1-hexanol, numerous holes were observed in the underlying PCBM. On the other hand, alcohols with a carbon number of 5 or less had no effect on PCBM.

[0049] <Fabrication of perovskite solar cells> Example 1 A perovskite solar cell was fabricated using the process shown in Figure 3. The perovskite layer (photoelectric conversion layer), electron transport layer (ETL), and silver nanowire layer (counter electrode) were fabricated as follows.

[0050] Perovskite layer A CsFAMAPbI3 solution was prepared using chlorobenzene as a poor solvent. The CsFAMAPbI3 solution was first applied to a hole transport layer (HTL) by spin coating, followed by application of a poor solvent. The HTL was then heated on a hot plate at 100 °C for 1 hour to dry.

[0051] Electron transport layer (ETL) [6,6]-phenyl-C 61 PCBM ink was prepared at a concentration of 30 mg / ml by dissolving PCBM (P2682, manufactured by Tokyo Chemical Industry Co., Ltd., purity by HPLC: >99.5%) in 1-chlorobenzene. The PCBM ink was spin-coated onto the perovskite layer at 1000 rpm for 30 seconds and then dried on a hot plate at 100 °C for 10 minutes.

[0052] Silver nanowire layer (counter electrode, transparent electrode) Silver nanowire ink (Seiko PMC Corporation, wire length: 4 μm, wire diameter: 25 nm, solvent: 1-butanol (purity: >95%), solid content: ≦1 wt%) was spin-coated onto the ETL at 1000 rpm for 10 seconds, and then dried by heating on a hot plate at 100°C for 5 minutes.

[0053] The silver nanowire layer of the resulting solar cell was observed using an optical microscope. Figure 4 shows a photograph of the appearance of the silver nanowire layer produced using a silver nanowire ink with a 1-butanol solvent. As shown in Figure 4, when the solvent for the silver nanowire ink was 1-butanol, the resulting silver nanowire layer was confirmed to be free of nanowire aggregation and anisotropy, and no PCBM dissolution occurred.

[0054] Example 2 A silver nanowire layer was formed by inkjet printing on a cell using the same perovskite layer and ETL as in Example 1, with the solvent of the silver nanowire ink changed. The silver nanowire ink was prepared in the same manner as the silver nanowire ink used in Example 1, except that the solvent was changed to 1-pentanol (>95%) or 1-propanol (>95%) and the solids concentration was changed to ≦0.5 wt%.

[0055] Figure 5 shows the dielectric constant and boiling point of various solvents. In Figure 5, the dielectric constant indicates the relative permittivity at 20°C. As confirmed in Section 1, perovskite materials are sufficiently resistant to alcohols with three or more carbon atoms. Here, in the inkjet method, using a solvent with a higher boiling point can prevent clogging of the inkjet nozzle, so it is considered desirable to use a solvent with a boiling point of 100°C or higher. However, even when 1-propanol, which has a boiling point slightly lower than 100°C, was used as the solvent for the silver nanowire ink, we were able to form a silver nanowire layer and fabricate a solar cell using the inkjet method. Furthermore, when 1-pentanol was used as the solvent for the silver nanowire ink, we were able to form a silver nanowire layer and fabricate a solar cell using the inkjet method.

Claims

1. A method for producing a perovskite solar cell having a photoelectric conversion layer containing a perovskite compound, comprising: a step of applying a silver nanowire solution onto an electron transport layer or a hole transport layer formed on the photoelectric conversion layer, The solvent of the silver nanowire solution is an alcohol having 3 or more carbon atoms. A method for manufacturing perovskite solar cells.

2. applying the silver nanowire solution onto an electron transport layer containing a fullerene compound; The solvent of the silver nanowire solution is an alcohol having 5 or less carbon atoms. A method for producing the perovskite solar cell according to claim 1.

3. applying the silver nanowire solution by an inkjet method; The solvent of the silver nanowire solution is an alcohol having 4 or more carbon atoms.

3. A method for producing a perovskite solar cell according to claim 1 or 2.

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