JP6984546B2 - Solar cells and their manufacturing methods - Google Patents

Description

The present invention relates to a solar cell and a method for manufacturing the same. More specifically, the present invention relates to a solar cell having a long life by suppressing an adverse effect of a halogen gas such as iodine gas generated in a solar cell using a perovskite compound, and a method for producing the same.

In recent years, single crystal silicon and amorphous silicon types of solar cells have become widespread, and solar parks and private homes have also become widespread. Although single crystal silicon and amorphous silicon solar cells, which are representative of inorganic solar cells, can obtain high conversion efficiency, they cannot be light-transmitting solar cells or flexible solar cells, so organic solar cells are attracting attention in order to seek their diversity. For example, it is disclosed in Non-Patent Document 1 and Patent Document 1.

Further, with the invention of the perovskite solar cell (also referred to as "perovskite type solar cell"), it has become possible to form by coating, and it has become possible to manufacture an ideal solar cell at low cost in terms of cost. It's coming.

However, although the perovskite solar cell has a high photoelectric conversion efficiency, there is a problem that the efficiency is lowered by light irradiation at the time of power generation, and an invention relating to measures such as deterioration promotion due to water and oxygen and distortion at the time of annealing is also disclosed. (See, for example, Patent Document 2).

For example, _{it has been found that perovskite solar cells using MAPbI 3} generate water, oxygen, and gaseous iodine generated in the power generation process, which themselves promote the deterioration of perovskite.

Specifically, when iodine gas (I ₂ ) reacts with the perovskite layer (MAPbl _{3 ), the reaction changes to PbI 2} and destroys the crystal structure of perovskite that contributes to power generation.

Further, in a perovskite solar cell using titanium oxide for an electron transport layer, many methods of applying a solution containing titanium alkoxide such as titanium isopropoxide and firing it are also disclosed (see, for example, Patent Document 3). ..

However, a method for suppressing or removing iodine gas has not been found, and when titanium alkoxide such as general titanium isopropoxide is formed, iodine generated during power generation can be obtained even if high luminous efficiency can be obtained at the initial stage. There is a problem that the amount of power generation is reduced due to the deterioration of the perovskite layer due to the gas.

Japanese Unexamined Patent Publication No. 2001-156307 International Publication 2016/152766 Japanese Unexamined Patent Publication No. 2016-82005

Tsutomu Miyasaka "The Appearance of Perovskite Solar Cells", Hyundai Kagaku March 2014, P24-29

The present invention has been made in view of the above problems and situations, and the problem to be solved is to suppress the adverse effects of halogen gas such as iodine gas generated during power generation in a solar cell using a perovskite compound to extend the life of the solar cell. And its manufacturing method.

In the process of investigating the cause of the above problem in order to solve the above problem, the present inventor captures halogens such as iodine gas generated during power generation in a solar cell using a perovskite compound by a specific organic metal oxide (trap). We found what we could do and came up with the present invention.

That is, the above-mentioned problem according to the present invention is solved by the following means.

1. 1. A solar cell including at least a first substrate, a first electrode, an electron transport layer, a photoelectric conversion layer, a hole transport layer, a second electrode, and a second substrate.
The photoelectric conversion layer contains a perovskite compound and
The solar cell (photoelectric cell) is characterized in that the electron transport layer contains at least two kinds of organometallic oxides having a structure represented by the following general formula (1) and the following general formula (2) and having different metal types. Conversion device).
General formula (1): R- [M ₁ (OR ₁ ) _y (O-) _x-y ] _n- R
General formula (2): R- [M ₂ (OR ₂ ) _y (O-) _xy ] _n- R
(In the formula, R represents a hydrogen atom, an alkyl group having one or more carbon atoms, an alkenyl group, an aryl group, a cycloalkyl group, an acyl group, an alkoxy group, or a heterocyclic group, where R is fluorine as a substituent. It may be a carbon chain containing an atom. M ₁ represents a metal atom selected from Cu, Ag and Au. M ₂ represents a metal atom selected from Ti, Zn, Sn, Al and Zr. _{OR 1} and OR. ₂ represents a fluorinated alkoxy group, x represents the valence of the metal atom, y represents an arbitrary integer between 1 and x, and n represents the degree of polycondensation.)

2. 2. The value of the molar ratio of organic metal oxide containing the metal species _{M 1} to the organic metal oxide containing the metal species _{M 2 (M 1 / M 2} ) is in the range of from 0.1 to 0.9 The solar cell according to paragraph 1, wherein the solar cell is characterized by the above.

3. 3. The organometallic oxide having the structure represented by the general formula (1) or the general formula (2) reacts with iodine gas or water, captures iodine gas, and releases a water-repellent or hydrophobic compound. The solar cell according to the first or second paragraph.

4. The solar cell according to any one of the items 1 to 3, wherein the perovskite compound has a structure represented by the following general formula (3).
General formula (3): R-MX ₃
(In the formula, R represents an organic molecule, M represents a metal atom, and X represents a halogen atom or a chalcogen atom.)

5. The solar cell according to any one of items 1 to 4, wherein the electron transport layer comprises a film in which a composition containing at least the organic metal oxide is sol-gel-transferred. ..

6. The method for manufacturing a solar cell according to any one of paragraphs 1 to 5, wherein the solar cell is manufactured.
A method for manufacturing a solar cell, which comprises a step of forming the electron transport layer using a mixed solution of a metal alkoxide or a metal carboxylate and a fluoroalcohol.

7. The method for manufacturing a solar cell according to Item 6, wherein the electron transport layer is formed by a wet coating method.

8. The method for manufacturing a solar cell according to item 7, wherein the wet coating method is an inkjet printing method.

According to the above means of the present invention, it is possible to provide a solar cell using a perovskite compound and a solar cell having a long life by suppressing the adverse effects of halogen gas such as iodine gas generated during power generation and a method for producing the same.

Although the mechanism of expression or the mechanism of action of the effect of the present invention has not been clarified, it is inferred as follows.

When a perovskite compound containing a halogen element is used in the photoelectric conversion layer according to the present invention, halogen gas such as iodine gas can be generated from the perovskite compound by a photochemical reaction in the process of irradiating sunlight to generate electricity. In such a case, if a compound containing silver that easily reacts with the halogen gas is present in the vicinity of the photoelectric conversion layer, it is considered that the halogen and silver can react with each other to produce silver halide.

In the present invention, by using an organic silver oxide or carboxylate as one of the constituents of the electron transport layer adjacent to the photoelectric conversion layer, a reaction that traps iodine occurs and the life of the solar cell of the present invention is extended. It is presumed that the effect was manifested.

Further, by using an organic metal oxide having an alkyl fluoride group or a carboxylate as one of the constituents of the electron transport layer, the reaction with water causes hydrolysis to generate water-repellent or hydrophobic fluoroalcohol. It is presumed that the water-repellent or hydrophobic effect is exhibited, and as a result, it contributes to the extension of the life of the solar cell of the present invention.

The details of the inferred reaction mechanism will be described later.

Basic Construct Diagram of the Solar Cell of the Present Invention The figure which shows the result of the light resistance test of a solar cell The figure which shows the result of the reliability test of a solar cell

The solar cell of the present invention is a solar cell including at least a first substrate, a first electrode, an electron transport layer, a photoelectric conversion layer, a hole transport layer, a second electrode, and a second substrate, and the photoelectric conversion layer is described. However, the perovskite compound is contained, and the electron transport layer contains at least two kinds of organic metal oxides having different metal types having the structures represented by the general formula (1) and the general formula (2). It is characterized by doing.

This feature is a technical feature common to or corresponding to each of the following embodiments.

In the embodiment of the present invention, from the viewpoint of exhibiting the effect of the present invention, the value of the molar ratio of the organometallic oxide containing the _{metal species M 1} to the organometallic oxide containing the _{metal species M 2 (M 1} /). It is preferable that M ₂ ) is in the range of 0.1 to 0.9. Further, the organometallic oxide having the structure represented by the general formula (1) or the general formula (2) reacts with iodine gas, captures iodine gas, and releases a water-repellent or hydrophobic compound. Is preferable.

In the embodiment of the present invention, it is preferable that the perovskite compound has a structure represented by the general formula (3) from the viewpoint of power generation efficiency. Further, it is preferable that the electron transport layer is composed of a film in which a composition containing at least the organometallic oxide is transferred to a sol-gel.

As the method for producing a solar cell of the present invention, it is preferable that the method includes a step of forming the electron transport layer using a mixed solution of a metal alkoxide or a metal carboxylate and a fluoroalcohol. The electron transport layer is preferably formed by a wet coating method, and the wet coating method is preferably an inkjet printing method.

Hereinafter, the present invention, its constituent elements, and modes and embodiments for carrying out the present invention will be described in detail. In the present application, "~" is used to mean that the numerical values described before and after it are included as the lower limit value and the upper limit value. In the description of each figure, the numbers in parentheses at the end of the components represent the symbols in each figure.

1. 1. Outline of Solar Cell The solar cell of the present invention is a solar cell including at least a first substrate, a first electrode, an electron transport layer, a photoelectric conversion layer, a hole transport layer, a second electrode and a second substrate. The photoelectric conversion layer contains a perovskite compound, and the electron transport layer has at least two different metal types having structures represented by the following general formulas (1) and the following general formula (2). It is characterized by containing an oxide.

General formula (1): R- [M ₁ (OR ₁ ) _y (O-) _x-y ] _n- R
General formula (2): R- [M ₂ (OR ₂ ) _y (O-) _xy ] _n- R
In the above general formulas (1) and (2), R represents a hydrogen atom, an alkyl group having one or more carbon atoms, an alkenyl group, an aryl group, a cycloalkyl group, an acyl group, an alkoxy group, or a heterocyclic group. However, R may be a carbon chain containing a fluorine atom as a substituent. M ₁ represents a metal atom selected from Cu, Ag and Au. M ₂ represents a metal atom selected from Ti, Zn, Sn, Al and Zr. OR ₁ and OR ₂ each represent a fluorinated alkoxy group. x represents the valence of the metal atom and y represents any integer between 1 and x. n represents the degree of polycondensation, respectively.

Details of the organometallic oxide will be described later.

Hereinafter, the basic configuration of the solar cell (1) of the present invention will be described with reference to FIG.

As shown in FIG. 1, the basic configuration of the solar cell of the present invention is at least a first substrate (2), a first electrode (3), an electron transport layer (4), and a photoelectric conversion layer (5). ), The hole transport layer (6), the second electrode (7), the sealing layer (8), the adhesive layer (9) and the second substrate (10), and the electron transport layer (4). ) Contains the organic metal oxide represented by the general formulas (1) and (2), and the photoelectric conversion layer (5) contains the perovskite compound.

Hereinafter, each of the above components will be described in detail.

2. 2. Components of Solar Cell [1] First Substrate As the first substrate (2), any material may be used as long as it has strength, durability, and light transmission, and synthetic resin, glass, or the like can be used. Examples of the synthetic resin include thermoplastic resins such as polyethylene naphthalate (PEN) film, polyethylene terephthalate (PET), polyesters, polycarbonates, polyolefins, polyimides, and fluororesins.

From the viewpoint of strength, durability, cost and the like, it is preferable to use a glass substrate.

As the first substrate, a metal foil may be used in addition to the above-mentioned base material. The metal foil may serve as a base material at the same time as one electrode of the flexible solar cell.

The metal constituting the metal foil is not particularly limited, and a metal having excellent durability and conductivity that can be used as an electrode is preferable, and for example, a metal such as aluminum, titanium, copper, or gold, or stainless steel. Alloys such as steel (SUS) can be used. These materials may be used alone or in combination of two or more.

Among them, the metal constituting the metal foil preferably contains stainless steel (SUS). By using stainless steel (SUS) as the metal constituting the metal foil, the metal foil becomes tough and the resistance to bending is improved, so that the variation in photoelectric conversion efficiency due to bending deformation can be suppressed. It is also preferable that the metal constituting the metal foil contains aluminum. By using aluminum as the metal constituting the metal foil, the difference in linear expansion coefficient between the metal foil and the photoelectric conversion layer containing the organic-inorganic perovskite compound becomes small, so that the occurrence of distortion during annealing is further suppressed. be able to.

The thickness of the metal foil is not particularly limited, but a preferable lower limit is 5 μm and a preferable upper limit is 500 μm. If the thickness of the metal foil is 5 μm or more, the mechanical strength of the obtained flexible solar cell is sufficient and the handleability is improved, and if it is 500 μm or less, the metal foil can be bent and the flexibility is achieved. Is improved. The more preferable lower limit of the thickness of the metal foil is 10 μm, and the more preferable upper limit is 100 μm.

When the metal foil is used as a base material for a flexible solar cell, the metal foil itself serves as both an electrode and a base material, and an electrode is provided on the surface of the metal foil on the photoelectric conversion layer side via an insulating layer. The mode of formation is conceivable.

The insulating layer is not particularly limited, but an insulating resin layer or an insulating layer made of a metal oxide layer is suitable. More specifically, it is preferable to form the insulating layer using an insulating resin such as a polyimide resin or a silicone resin, or a metal oxide such as zirconia, silica, or hafnium.

The preferable lower limit of the thickness of the insulating layer is 0.1 μm, and the preferable upper limit is 10 μm. When the thickness of the insulating layer is within this range, the metal foil and the electrode can be reliably insulated.

The electrode formed on the surface of the metal foil on the photoelectric conversion layer side via the insulating layer is not particularly limited, and a metal electrode usually used in a solar cell can be used.

[2] First electrode A transparent electrode is preferably used as the first electrode (3). As the material of the bright conductive layer 3 constituting the transparent electrode, for example, tin-added indium oxide (ITO) and fluorine-added tin oxide are used. Examples thereof include (FTO), tin oxide (SnO ₂ ), indium zinc oxide (IZO), zinc oxide (ZnO), and a polymer material having high conductivity.

Examples of the polymer material include polyacetylene-based, polypyrrole-based, polythiophene-based, and polyphenylene vinylene-based polymer materials. Further, a carbon-based thin film having high conductivity can also be used. Examples of the method for forming the transparent electrode include a sputtering method, a vapor deposition method, and a method of applying a dispersion.

[3] Electron transport layer The electron transport layer (4) according to the present invention has at least two kinds of organometallic oxides having structures represented by the general formula (1) and the pre-general formula (2) and different metal types. It is characterized by containing.

The organometallic oxide is a compound capable of capturing (trapping) iodine gas and releasing a water-repellent or hydrophobic substance by reacting with iodine gas or water.

As a method for producing an organic metal oxide having a structure represented by the general formula (1) and the previous general formula (2) according to the present invention, a metal alkoxide or a metal carboxylate is mixed with a fluoroalcohol. Manufacture is a preferred embodiment for obtaining the effects of the present invention.

The organic metal oxide according to the present invention is a polycondensate of an organic metal oxide or an organic metal oxide obtained by alcohol-decomposing a metal alkoxide or a metal carboxylate in the presence of an excess alcohol and substituting the metal with an alcohol. At that time, by using a long-chain alcohol in which a fluorine atom is substituted at the β-position of the hydroxy group, an organic metal oxide containing a fluorinated alkoxide is obtained, and the above-mentioned organic metal oxide according to the present invention is obtained.

On the other hand, the organic metal oxide can promote the sol-gel reaction and form a polycondensate by sintering or irradiating with ultraviolet rays. At that time, when a long-chain alcohol in which a fluorine atom is substituted at the β-position of the hydroxy group is used, the water-repellent effect of fluorine reduces the frequency factor of water present around the metal in the metal alkoxide, thereby reducing the hydrolysis rate. By utilizing this phenomenon, a three-dimensional polymerization reaction can be suppressed, and a uniform and dense organic thin film containing a desired organic metal oxide can be formed.

A more detailed description will be given below.

(Organic metal oxide)
The organometallic oxide according to the present invention is mainly an organometallic oxide having a structure represented by the following general formulas (1) and (2) produced from a compound represented by the following general formula (A). It is preferably contained as an ingredient. The "main component" is preferably the organic metal oxide in which 70% by mass or more of the total mass of the desiccant releases a hydrophobic substance, more preferably 80% by mass or more, and particularly preferably. It means that it is 90% by mass or more.

General formula (A) M (OR ₁ ) _y ( _{OR) xy}
In the formula, R represents a hydrogen atom, an alkyl group having one or more carbon atoms, an alkenyl group, an aryl group, a cycloalkyl group, an acyl group, an alkoxy group, or a heterocyclic group. However, R may be a carbon chain containing a fluorine atom as a substituent. M represents a metal atom. OR ₁ represents a fluorinated alkoxy group. x represents the valence of the metal atom and y represents any integer between 1 and x.

General formula (1): R- [M ₁ (OR ₁ ) _y (O-) _x-y ] _n- R
General formula (2): R- [M ₂ (OR ₂ ) _y (O-) _xy ] _n- R
In the formula, R represents a hydrogen atom, an alkyl group having one or more carbon atoms, an alkenyl group, an aryl group, a cycloalkyl group, an acyl group, an alkoxy group, or a heterocyclic group. However, R may be a carbon chain containing a fluorine atom as a substituent. M ₁ represents a metal atom selected from Cu, Ag and Au. M ₂ represents a metal atom selected from Ti, Zn, Sn, Al and Zr. OR ₁ and OR ₂ each represent a fluorinated alkoxy group. x represents the valence of the metal atom and y represents any integer between 1 and x. n represents the degree of polycondensation, respectively.

In the general formula (1) and the general formula (2), OR ₁ represents a fluorinated alkoxy group.

R ₁ represents an alkyl group, an aryl group, a cycloalkyl group, an acyl group, an alkoxy group, or a heterocyclic group substituted with at least one fluorine atom. Specific examples of each substituent will be described later.

R represents a hydrogen atom, an alkyl group having one or more carbon atoms, an alkenyl group, an aryl group, a cycloalkyl group, an acyl group, an alkoxy group, or a heterocyclic group. Alternatively, at least a part of hydrogen of each group may be substituted with halogen. It may also be a polymer.

Alkyl groups are substituted or unsubstituted, and specific examples thereof include methyl group, ethyl group, propyl group, butyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, heptyl group and octyl. Group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecil group, icosyl group, henicosyl group, docosyl and the like, but carbon is preferable. Those with a number of 8 or more are preferable. Further, these oligomers and polymers may be used.

The alkenyl group is substituted or unsubstituted, and specific examples thereof include a vinyl group, an allyl group, a butenyl group, a pentenyl group, a hexsenyl group and the like, and preferably one having 8 or more carbon atoms. Further, these oligomers or polymers may be used.

The aryl group is substituted or unsubstituted, and specific examples thereof include a phenyl group, a tolyl group, a 4-cyanophenyl group, a biphenyl group, o, m, p-terphenyl group, a naphthyl group, an anthranyl group, and a phenanthrenyl group. There are a fluorenyl group, a 9-phenylanthranyl group, a 9,10-diphenylanthranyl group, a pyrenyl group and the like, and those having 8 or more carbon atoms are preferable. Further, these oligomers or polymers may be used.

Specific examples of the substituted or unsubstituted alkoxy group include a methoxy group, an n-butoxy group, a tert-butoxy group, a trichloromethoxy group, a trifluoromethoxy group and the like, and preferably one having 8 or more carbon atoms. Further, these oligomers and polymers may be used.

Specific examples of the substituted or unsubstituted cycloalkyl group include a cyclopentyl group, a cyclohexyl group, a norbonan group, an adamantan group, a 4-methylcyclohexyl group, a 4-cyanocyclohexyl group, and the like, preferably those having 8 or more carbon atoms. Is good. Further, these oligomers or polymers may be used.

Specific examples of the substituted or unsubstituted heterocyclic group include a pyrrol group, a pyrrolin group, a pyrazole group, a pyrazoline group, an imidazole group, a triazole group, a pyridine group, a pyridazine group, a pyrimidine group, a pyrazine group, a triazine group, and an indol group. Benzimidazole group, purine group, quinoline group, isoquinoline group, quinoline group, quinoxalin group, benzoquinoline group, fluorenone group, dicyanofluorenone group, carbazole group, oxazole group, oxadiazole group, thiazole group, thiazyl group, benzoxazole group , Benzothiazole group, benzotriazole group, bisbenzoxazole group, bisbenzothiazole group, benzbenzimidazole group and the like. Further, these oligomers or polymers may be used.

Specific examples of the substituted or unsubstituted acyl group include a hole mill group, an acetyl group, a propionyl group, a butyryl group, an isobutyryl group, a valeryl group, an isovaleryl group, a pivaloyl group, a lauroyl group, a myritoyl group, a palmitoyl group and a stearoyl group. , Oxalyl group, malonyl group, succinyl group, glutalyl group, adipoil group, pimeroyl group, suberoyl group, azella oil group, sebacyl group, acryloyl group, propioloyl group, methacryloyl group, crotonoyle group, isocrotonoyle group, oleoyl group, eridoyl group, Male oil group, fumaroyl group, citraconoyl group, mesaconoyle group, camphoroyl group, benzoyl group, phthaloyl group, isophthaloyl group, terephthaloyl group, naphthoyl group, toluoil group, hydroatropoyl group, atropoyl group, cinnamoyl group, floyl group, tenoyl group. , Nicotinoyl group, isonicotinoyl group, glycoloyl group, lactyl group, glyceroyl group, tartronoyl group, maloyl group, tartaroyl group, tropoil group, benziloyl group, salicyloyl group, anisoyl group, vanilloyl group, veratroyl group, piperoniloyl group, protocatechuyl group. , Galoyl group, glyoxyloyl group, pyruvoyl group, acetoacetyl group, mesooxalyl group, mesooxalo group, oxalacetyl group, oxalacet group, levulinoyl group These acyl groups are replaced with fluorine, chlorine, bromine, iodine, etc. May be good. Preferably, the carbon of the acyl group is 8 or more. Further, these oligomers or polymers may be used.

Specific combinations of the metal alkoxide, the metal carboxylate, and the fluorinated alcohol for forming the organic metal oxide having the structure represented by the general formula (1) or (2) according to the present invention are exemplified below. do. However, the present invention is not limited to this.

The metal alkoxide, metal carboxylate and fluorinated alcohol (R'-OH) become the organic metal oxide according to the present invention by the following reaction scheme I. Here, as (R'-OH), the following structures of F-1 to F-16 are exemplified.

Examples of the metal alkoxide or metal carboxylate according to the present invention include the following _{compounds represented by M (OR) n} or M (OCOR) _n , and the organic metal oxide according to the present invention is the above-mentioned (R'-OH: F). When combined with -1 to F-16), it becomes a compound having the structure of the following Exemplified Compound Nos. 1 to 45 (see the following Exemplified Compound I). The organometallic oxide according to the present invention is not limited to this.

Specific examples of the metal alkoxide preferably used in the present invention include Ti (OiPr) ₄ , Ti (OiEt) ₄ , Ti (OMe) ₄ , Sn (OtBu) ₄ , Zr (OiPr) ₄ , and Al (OiPr). ) ₃ etc. can be mentioned.

Specific examples of the metal carboxylate include silver salts of fatty acids such _{as Ti (OCOCH 3} ) ₄ , CH ₃ COOAg, and AgOCO (CH ₂ ) ₂₀ CH _3.

(Reactivity of organometallic oxides)
The organometallic oxide according to the present invention exhibits reactivity as shown in the following reaction schemes II and III. In the structural formula of the polycondensate of the organic metal oxide after sintering, "M" in the "OM" portion further has a substituent, but is omitted.

For example, when two kinds of metal oxides having different metal species coexist, they have the reactivity as shown in the following reaction scheme III.

The organic thin film formed by polycondensing the organic metal oxide by sintering or irradiating with ultraviolet rays has reactivity as shown in the following reaction schemes IV and V.

For Reaction Scheme IV, hydrolyzed by moisture (H 2 _O) from the outside of the system, releasing the fluorinated alcohol is a water-repellent or hydrophobic materials (R'-OH). This fluorinated alcohol further prevents the permeation of water into the electronic device.

That is, in the organic metal oxide according to the present invention, since the fluorinated alcohol produced by hydrolysis is water-repellent or hydrophobic, in addition to the original drying property (desiccant property), a water-repellent function is added by reaction with water. Therefore, it has the characteristic of exerting a synergistic effect (synergistic effect) on the sealing property.

In the following structural formula, "M" in the "OM" part further has a substituent, but is omitted.

In the case of reaction scheme V, it reacts with corrosive iodine (I ₂ ) gas to trap iodine to produce silver iodide and relatively stable polyiodine ions (I ₃ ⁻ , I ₅ ⁻ and I). ₇ ^-) is generated.

(Manufacturing method of organometallic oxide)
The method for producing an organic metal oxide according to the present invention is characterized in that it is produced using a mixed solution of a metal alkoxide and a fluoroalcohol.

In the method for producing an organic metal oxide according to the present invention, after adding a fluoroalcohol to a metal alkoxide or a metal carboxylate and stirring and mixing as a mixture, water and a catalyst are added as necessary and reacted at a predetermined temperature. The method can be mentioned.

When the sol-gel reaction is carried out, a catalyst that can be a catalyst for the hydrolysis / polymerization reaction as shown below may be added for the purpose of promoting the hydrolysis / polycondensation reaction. What is used as a catalyst for the hydrolysis / polymerization reaction of the sol-gel reaction is "Technology for producing functional thin films by the latest sol-gel method" (written by Satoshi Hirashima, General Technology Center Co., Ltd., P29) and "Sol-gel". It is a catalyst used in a general sol-gel reaction described in "Science of Law" (written by Saio Sakuhana, Agne Shofusha, P154). For example, examples of the acid catalyst include inorganic and organic acids such as hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, acetic acid, oxalic acid, tartaric acid, and toluenesulfonic acid.

The amount of the catalyst used is preferably 2 mol equivalents or less, more preferably 1 mol equivalent or less, with respect to 1 mol of the metal alkoxide or metal carboxylate as a raw material of the organic metal oxide.

When the sol-gel reaction is carried out, the preferable amount of water added is 40 mol equivalents or less, more preferably 10 mol equivalents or less, with respect to 1 mol of the metal alkoxide or metal carboxylate as a raw material of the organic metal oxide. It is more preferably 5 mol equivalents or less.

In the present invention, the preferable reaction concentration, temperature, and time of the sol-gel reaction cannot be unequivocally determined because the type and molecular weight of the metal alkoxide or metal carboxylate used and the respective conditions are related to each other. That is, when the molecular weight of the alkoxide or metal carboxylate is high, or when the reaction concentration is high, if the reaction temperature is set high or the reaction time is set too long, the reaction product accompanies the hydrolysis and polycondensation reactions. The molecular weight of the alkoxide may increase, resulting in high viscosity and gelation. Therefore, the usual preferable reaction concentration is generally 1 to 50% by mass% of the solid content in the solution, more preferably 5 to 30%. The reaction temperature is usually 0 to 150 ° C., preferably 1 to 100 ° C., more preferably 20 to 60 ° C., and the reaction time is preferably about 1 to 50 hours, although it depends on the reaction time.

It is preferable that the fluorine ratio in the organic metal complex oxide according to the present invention satisfies the following formula (a).

Equation (a): 0.05 ≤ F / (C + F) ≤ 1.00
The measurement significance of the formula (a) is to quantify that the organic thin film produced by the sol-gel method requires a certain amount or more of fluorine atoms. F and C in the above formula (a) represent the concentrations of fluorine atoms and carbon atoms, respectively.

The preferred range of the formula (a) is 0.2 ≦ F / (C + F) ≦ 0.6.

The fluorine ratio is determined by applying the sol-gel solution used for forming an organic thin film onto a silicon wafer to prepare a thin film, and then applying the thin film to SEM / EDS (Energy Dispersive X-ray Spectrocopy: Energy Dispersive X-ray Analyzer). The concentrations of the fluorine atom and the carbon atom can be obtained by elemental analysis according to the above. As an example of the SEM / EDS device, JSM-IT100 (manufactured by JEOL Ltd.) can be mentioned.

SEM / EDS analysis has the characteristics of being able to detect elements at high speed, with high sensitivity and with high accuracy.

The organic metal oxide according to the present invention is not particularly limited as long as it can be produced by using the sol-gel method. For example, the metal and lithium introduced in "Science of sol-gel method" P13 and P20. , Sodium, copper, calcium, strontium, barium, zinc, boron, aluminum, gallium, ittrium, silicon, germanium, lead, phosphorus, antimony, vanadium, tantalum, tungsten, lanthanum, neodium, titanium, zirconium. As an example, a metal oxide containing the above-mentioned metal can be mentioned. Preferably, the metal atom represented by M is selected from titanium (Ti), zirconium (Zr), tin (Sn), zinc (Zn) and aluminum (Al) to obtain the effect of the present invention. Preferred from the point of view.

(Other materials for the electron transport layer, etc.)
The material of the electron transport layer according to the present invention is not particularly limited to the above-mentioned organic metal oxides, and for example, N-type conductive polymers, N-type low-molecular-weight organic semiconductors, N-type metal oxides, and N-type metal sulfides. , Alkali halide metal, alkali metal, surfactant and the like can be used in combination.

Specifically, for example, cyano group-containing polyphenylene vinylene, boron-containing polymer, vasocuproin, vasofenantrene, hydroxyquinolinatoaluminum, oxadiazole compound, benzoimidazole compound, naphthalenetetracarboxylic acid compound, perylene derivative, phosphine oxide compound, phosphine. Examples thereof include sulfide compounds, fluorogroup-containing phthalocyanine, titanium oxide, zinc oxide, indium oxide, tin oxide, gallium oxide, tin sulfide, indium sulfide, zinc sulfide and the like.

The thickness of the electron transport layer according to the present invention is preferably in the range of 1 to 2000 nm. If the thickness is 1 nm or more, holes can be sufficiently blocked. When the thickness is 2000 nm or less, it is unlikely to become a resistance during electron transport, and the photoelectric conversion efficiency becomes high. The thickness of the electron transport layer is more preferably in the range of 3 to 1000 nm, still more preferably in the range of 5 to 500 nm.

(Method of forming electron transport layer)
As a method for forming the electron transport layer, a coating liquid containing an organic metal oxide having the structures represented by the general formulas (1) and (2) is prepared, coated on the first electrode, and sintered or sintered. It can be formed by irradiating with ultraviolet rays and forming a film while polycondensing.

Examples of the organic solvent that can be used when preparing the coating liquid include hydrocarbon solvents such as aliphatic hydrocarbons, alicyclic hydrocarbons and aromatic hydrocarbons, halogenated hydrocarbon solvents, or , Aliphatic ethers, alicyclic ethers and other ethers can be used as appropriate.

The concentration of the organometallic oxide in the coating liquid varies depending on the target thickness and the pot life of the coating liquid, but is preferably about 0.2 to 35% by mass. In the present invention, a catalyst that promotes polymerization may be added to the coating liquid as long as the desired effect is not impaired.

The prepared coating liquid can be a spray coating method, a spin coating method, a blade coating method, a dip coating method, a casting method, a roll coating method, a bar coating method, a die coating method, or a printing method including an inkjet printing method. A wet forming method such as a method by patterning is mentioned, and it can be used depending on the material. Of these, the inkjet printing method is preferable. The inkjet printing method is not particularly limited, and a known method can be adopted.

The method of discharging the coating liquid from the inkjet head by the inkjet printing method may be either an on-demand method or a continuous method. The on-demand inkjet head is an electric-mechanical conversion system such as a single cavity type, a double cavity type, a bender type, a piston type, a shared mode type and a shared wall type, or a thermal inkjet type and a bubble jet (registered trademark). ) The electric-heat conversion method such as a mold may be used.

In order to immobilize the organic thin film after coating, it is preferable to use plasma, ozone or ultraviolet rays that can carry out a polymerization reaction at a low temperature.

Examples of the means for generating ultraviolet rays in the ultraviolet treatment include metal halide lamps, high-pressure mercury lamps, low-pressure mercury lamps, xenon arc lamps, carbon arc lamps, excimer lamps, UV light lasers, and the like.

The time required for ultraviolet irradiation is generally 0.1 seconds to 10 minutes, preferably 0.5 seconds to 3 minutes, although it depends on the base material used and the composition and concentration of the desiccant-containing coating liquid.

^{The energy received by the coating film surface is preferably 3.0 J / cm 2} or more, more preferably 3.5 J / cm ² or more, and 4.0 J from the viewpoint of forming a uniform and robust thin film. It is more preferably / cm ^2. Similarly, from the viewpoint of avoiding excessive ultraviolet radiation, it is preferably 14.0J / cm ² or less, more preferably 12.0J / cm ² or less, is 10.0J / cm ² or less Is even more preferable.

[4] Photoelectric conversion layer The photoelectric conversion layer (5) according to the present invention contains a perovskite compound. In the present invention, the "perovskite compound" refers to a compound having a perovskite structure. The perovskite compound is preferably a perovskite compound (a perovskite compound having an organic-inorganic hybrid structure) in which an organic substance and an inorganic substance are constituent elements of the perovskite structure.

In the present invention, it is preferable that the perovskite compound has a structure represented by the following general formula (3) from the viewpoint of photoelectric conversion efficiency.

General formula (3): R-MX ₃
(In the formula, R represents an organic molecule, M represents a metal atom, and X represents a halogen atom or a chalcogen atom.)
The site containing the perovskite compound represented by the general formula (3) is hereinafter also referred to as an organic-inorganic perovskite compound site.

The perovskite compound has a cubic structure in which a metal atom M is arranged at the center of the body, an organic molecule R is arranged at each apex, and a halogen atom or a chalcogen atom X is arranged at the face center when expressed by the general formula R-MX _3. It is preferable to have. Although the details are not clear, by having the above structure, the orientation of the octahedron in the crystal lattice can be easily changed, so that the electron mobility becomes high, so that high photoelectric conversion efficiency can be realized. It is estimated to be.

In the above general formula (3), R is an organic molecule, and _{it is preferable that R is a molecule represented by C l} N _m X _n (all l, m, and n are positive integers).

Specifically, R is methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, dipentylamine, dihexylamine, trimethylamine, triethylamine, tripropylamine, Tributylamine, tripentylamine, trihexylamine, ethylmethylamine, methylpropylamine, butylmethylamine, methylpentylamine, hexylmethylamine, ethylpropylamine, ethylbutylamine, imidazole, azole, pyrrole, aziridine, azirin, azetidine, Examples thereof include azeto, imidazoline, carbazole and ions thereof (for example, methylammonium (CH ₃ NH ₃ ) and the like), phenethylammonium and the like. Among them, methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine and their ions and phenethylammon are preferable, and methylamine, ethylamine, propylamine and these ions are more preferable.

M is a metal atom, and leads, tin, zinc, titanium, antimony, bismuth, nickel, iron, cobalt, silver, copper, gallium, germanium, magnesium, calcium, indium, aluminum, manganese, chromium, molybdenum, uropyum, etc. Can be mentioned. These elements may be used alone or in combination of two or more.

X is a halogen atom or a chalcogen atom, and examples thereof include chlorine, bromine, iodine, sulfur, and selenium. These elements may be used alone or in combination of two or more. Among them, a halogen atom is preferable because the inclusion of a halogen in the structure makes the perovskite compound soluble in an organic solvent and can be applied to an inexpensive printing method or the like. Further, iodine is more preferable because the energy band gap of the organic-inorganic perovskite compound is narrowed.

The photoelectric conversion layer according to the present invention may further contain an organic semiconductor or an inorganic semiconductor in addition to the above-mentioned perovskite compound as long as the effect of the present invention is not impaired. The organic semiconductor or the inorganic semiconductor referred to here may play a role as an electron transport layer or a hole transport layer.

Examples of the organic semiconductor include compounds having a thiophene skeleton such as poly (3-alkylthiophene). Further, for example, a conductive polymer having a polyparaphenylene vinylene skeleton, a polyvinylcarbazole skeleton, a polyaniline skeleton, a polyacetylene skeleton and the like can also be mentioned. Further, for example, a compound having a porphyrin skeleton such as a phthalocyanine skeleton, a naphthalocyanine skeleton, a pentacene skeleton, a benzoporphyrin skeleton, a spirobifluorene skeleton, and carbon-containing materials such as carbon nanotubes, graphene, and fullerene which may be surface-modified. Can also be mentioned.

As the inorganic semiconductor, e.g., titanium oxide, zinc oxide, indium oxide, tin oxide, gallium oxide, tin sulfide, indium sulfide, zinc _{sulfide, CuSCN, Cu 2 O, CuI} , MoO 3, V 2 O 5, WO 3, MoS ₂ , MoSe ₂ , Cu ₂ S and the like can be mentioned.

When the photoelectric conversion layer contains the organic semiconductor or the inorganic semiconductor, the photoelectric conversion layer may be a laminated body in which a thin-film organic semiconductor or an inorganic semiconductor moiety and a thin-film perovskite compound moiety are laminated, or the organic semiconductor or the inorganic semiconductor. It may be a composite film in which a site and a perovskite compound site are composited. A laminated body is preferable in terms of simple manufacturing method, and a composite film is preferable in that the charge separation efficiency in the organic semiconductor or the inorganic semiconductor can be improved.

The thickness of the thin-film organic-inorganic perovskite compound moiety is preferably in the range of 5 to 5000 nm. When the thickness is 5 nm or more, light can be sufficiently absorbed and the photoelectric conversion efficiency becomes high. Further, when the thickness is 5000 nm or less, it is possible to suppress the generation of a region where charge separation is not possible, which leads to improvement in photoelectric conversion efficiency.

A more preferable range of the thickness is 10 to 1000 nm, and more preferably 20 to 500 nm.

When the photoelectric conversion layer is a composite film in which an organic semiconductor or an inorganic semiconductor moiety and a perovskite compound moiety are composited, the thickness of the composite film is preferably in the range of 30 to 3000 nm. When the thickness is 30 nm or more, light can be sufficiently absorbed and the photoelectric conversion efficiency becomes high. When the thickness is 3000 nm or less, the electric charge easily reaches the electrode, so that the photoelectric conversion efficiency is high. A more preferable range of the thickness is 40 to 2000 nm, and even more preferably 50 to 1000 nm.

As a method for forming the photoelectric conversion layer, a method of forming a photoelectric conversion layer containing a perovskite compound on the electron transport layer and then performing a photoelectric conversion layer forming step of annealing at a temperature of 80 ° C. or higher is preferable.

The method for forming the photoelectric conversion layer on the electron transport layer is not particularly limited, and examples thereof include a vacuum vapor deposition method, a sputtering method, a vapor phase reaction method (CVD), an electrochemical deposition method, and a printing method. Above all, by adopting the printing method, it is possible to easily form a flexible solar cell capable of exhibiting high photoelectric conversion efficiency in a large area. Examples of the printing method include a spin coating method, a casting method, and the like, and examples of the method using the printing method include a roll-to-roll method.

As a method for forming the photoelectric conversion layer, specifically, for example, after laminating and coating a perovskite compound forming solution (a precursor solution of a perovskite compound) on the electron transport layer to form a thin-film perovskite compound site. , A method of forming the thin-film organic semiconductor moiety on the thin-film perovskite compound moiety and the like can be mentioned.

The annealing has a role of imparting light resistance to the photoelectric conversion layer containing the perovskite compound. It is considered that the crystallization increases the crystallinity of the perovskite compound, thereby exhibiting excellent light resistance. Further, as the crystallinity increases, the electron mobility increases and the photoelectric conversion efficiency improves.

For the above crystallinity, the scattering peak derived from the crystalline substance detected by the X-ray scattering intensity distribution measurement and the halo derived from the amorphous part are separated by fitting, and the intensity integration of each is obtained, and the crystal of the whole is obtained. It can be obtained by calculating the ratio of parts.

In the present invention, the preferable crystallinity of the perovskite compound is 30% or more. When the crystallinity is 30% or more, the electron mobility increases and the photoelectric conversion efficiency increases. The lower limit of the more preferable crystallinity is 50%, and the more preferable lower limit is 70%.

The annealing temperature is preferably 80 ° C. or higher. By annealing at a temperature of 80 ° C. or higher, the crystallinity of the organic-inorganic perovskite compound can be increased, so that a flexible solar cell having excellent light resistance and high photoelectric conversion efficiency can be obtained. The annealing temperature is more preferably 100 ° C. or higher, and even more preferably 120 ° C. or higher.

The upper limit of the annealing temperature is not particularly limited, but the effect of increasing the crystallinity does not change even if the temperature is higher than that, and since there is an adverse effect on other members, about 200 ° C. is a practical upper limit. be.

The heating time for the annealing is not particularly limited, but is preferably 3 minutes or more and 2 hours or less. When the heating time is 3 minutes or more, the crystallinity of the organic-inorganic perovskite compound can be sufficiently increased. If the heating time is within 2 hours, the heat treatment can be performed without thermally deteriorating the organic-inorganic perovskite compound.

These heating operations are preferably performed under vacuum or an inert gas, and the dew point temperature is preferably 10 ° C. or lower, more preferably 7.5 ° C. or lower, still more preferably 5 ° C. or lower.

[5] Hole transport layer The material of the hole transport layer (6) according to the present invention is not particularly limited, and is, for example, a P-type conductive polymer, a P-type low molecular weight organic semiconductor, and a P-type metal oxidation. Examples thereof include products, P-type metal sulfides, surfactants and the like. Specific examples thereof include polystyrene sulfonic acid adducts of polyethylenedioxythiophene, carboxy group-containing polythiophene, phthalocyanine, porphyrin, molybdenum oxide, vanadium oxide and oxidation. Examples thereof include tungsten, nickel oxide, copper oxide, tin oxide, molybdenum sulfide, tungsten sulfide, copper sulfide, tin sulfide and the like, fluorogroup-containing phosphonic acid, carbonyl group-containing phosphonic acid and the like.

As the hole transport layer, a hole transport layer containing an amorphous organic semiconductor is suitable. By using an amorphous organic semiconductor, high conversion efficiency can be obtained by relaxing the stress when the transparent electrode is formed.

Examples of the amorphous organic semiconductor include Poly (4-butylphenyl-diphenyl-amine) and the like.

The thickness of the hole transport layer is preferably in the range of 1 to 2000 nm. If the thickness is 1 nm or more, electrons can be sufficiently blocked. Further, when the thickness is 2000 nm or less, resistance during hole transport is unlikely to occur, and the photoelectric conversion efficiency becomes high. It is more preferably in the range of 3 to 1000 nm, and even more preferably in the range of 5 to 500 nm.

Examples of the method of forming the hole transport layer include a method of performing a hole transport layer forming step of forming a hole transport layer on the photoelectric conversion layer.

The method of forming the hole transport layer on the photoelectric conversion layer is not particularly limited, and for example, a method of applying a solution in which a hole transport material is dissolved in an organic solvent and then volatilizing the organic solvent, vapor deposition, sputtering, etc. Examples thereof include a method of forming a vacuum film.

[6] Second Electrode Examples of the second electrode (7) according to the present invention include _{oxide electrodes such as ITO, IZO, IWZO, ITZO, AZO, BZO, GZO, ZnO, and SnO 2} , and Au, Ag, and Ti. , Zn, Mo, Ta, AgNW, Na, NaK, Li, Mg, Al, MgAg, MgIn, AlLi, CuI and the like, and examples thereof include thin film metals, metal compounds and organic metals. It may be a stack of two or more types.

In addition, examples of the method for forming the second electrode include a CVD method, a sputtering method, a vapor deposition, and a coating method. The film thickness is not limited as long as it does not transmit light.

[7] Sealing layer The solar cell of the present invention is covered with the sealing layer (8) to protect the laminate including the photoelectric conversion layer from the external environment, especially gas such as water and oxygen, and has sufficient durability. Can be obtained, the photoelectric conversion efficiency is higher, and the durability can be improved.

The material of the sealing layer is not particularly limited, and a known material can be used, and it may be an organic material or an inorganic material.

Normally, the performance of the sealing layer is such that the water vapor permeability (environmental conditions: 25 ± 0.5 ° C., relative humidity (90 ± 2)% RH) is about 0.01 g / [m ² · day] or less, and oxygen permeation. A transparent insulating film having a degree of about 0.01 cm ³ / [m ² · day · atm] or less, a resistivity of 1 × 10 ¹² Ω · cm or more, and a gas barrier property is preferable.

In particular, a high barrier having an oxygen permeability of 0.001 cm ³ / [m ²・ day ・ atm] or less and a water vapor transmission rate of about 0.001 g / [m ²・ day] or less. It is preferably composed of a sex multilayer film. The "water vapor transmission rate" is a value measured by the infrared sensor method based on JIS (Japanese Industrial Standards) -K7129 (1992), and the "oxygen permeability" is JIS-K7126 (1987). It is a value measured by a coulometric method based on the year).

As the material for forming the sealing layer described above, any material can be used as long as it is a material that causes deterioration of the photoelectric conversion element, for example, a material that can suppress the infiltration of gas such as water or oxygen into the organic photoelectric conversion element. ..

For example, it can be composed of a film made of an inorganic material such as silicon oxide, silicon nitride, silicon nitride, silicon carbide, silicon carbide, aluminum oxide, aluminum nitride, titanium oxide, zirconium oxide, niobium oxide, and molybdenum oxide. In the organic photoelectric conversion element, the sealing layer is composed of an inorganic material coating containing a silicon compound such as silicon nitride or silicon oxide as a main raw material in consideration of gas barrier property, transparency, and splitting property at the time of division. Is preferable.

In addition to the above-mentioned inorganic material coating, a coating made of a composite material with an organic material or a hybrid coating obtained by laminating these coatings may be combined in order to improve the vulnerability of the sealing layer. .. In this case, the stacking order of the coating film made of an inorganic material and the coating film made of an organic material is arbitrary, but an organic material / an inorganic material may be used, or a plurality of both may be alternately laminated. This makes it possible to obtain a sealing layer having a good barrier function for avoiding damage to the organic photoelectric conversion element due to moisture or oxygen.

[8] Adhesive layer and second substrate As the second substrate (10), the same substrate as the first substrate can be used.

Further, a second substrate may be provided on the upper layer of the sealing layer to further block moisture. For example, it is preferable to form a second substrate that does not need to consider optical characteristics such as metal foil. Examples of the metal layer include a second substrate including an aluminum foil, a duralumin foil, a titanium foil, a copper foil, a phosphor bronze foil, a SUS304 foil, an inverse foil, a magnesium alloy foil, and a mixed foil thereof. Normally, if these metal foil foils are thin, they have defects such as pinholes. Therefore, by making them thick, it is possible to prevent these sealing defects. Preferably, by forming the metal foil to a thickness of about 5 to 50 μm, it is possible to prepare a foil from which pinholes and defects of the metal foil have been removed.

Further, it is preferable that the second substrate further forms an insulating layer for ensuring electrical insulation and preventing trauma in the direction facing the sealing layer.

Specifically, flexible resins are suitable, for example, polyolefins such as polyethylene, polypropylene, and cyclic olefin copolymers (COP), polyamides, polyimides, polyethylene terephthalates (PET), and polyethylene naphthalates (PEN). Such as polyester, cellophane, cellulose diacetate, cellulose acetate butyrate, cellulose acetate propionate (CAP), triacetyl cellulose (TAC), cellulose esters such as cellulose nitrate, polyvinylidene chloride, polyvinyl alcohol, polyethylene vinyl alcohol. Polymers (EVOH), syndiotactic polystyrene, polycarbonate, norbornene resin, polymethylpentene, polyether ketone, polyimide, polyethersulfone (PES), polyphenylene sulfide, polysulfones, polyetherimide, polyetherketoneimide, fluorine Resins, acrylic resins such as polymethylmethacrylate (PMMA), materials such as polyarylates, and derivatives thereof can be used. Further, for example, a cycloolefin resin called Arton (registered trademark: manufactured by JSR Corporation) or Apel (registered trademark: manufactured by Mitsui Chemicals, Inc.) can also be used.

Further, it is preferable that the second substrate and the sealing layer are connected via an adhesive, and there are thermosetting and ultraviolet (UV) curing, but when a metal foil is applied, a thermosetting type is preferable, and further. Since there is moisture intrusion from the adhesive bulk, the adhesive is preferably a material that delays the diffusion of water, or a material containing a filler or the like.

Examples thereof include acrylic acid-based oligomers, photocurable and thermosetting adhesives having a reactive vinyl group of methacrylic acid-based oligomers, and moisture-curable adhesives such as 2-cyanoacrylic acid ester. In addition, heat and chemical curing type (two-component mixing) such as epoxy type can be mentioned. Further, hot melt type polyamide, polyester and polyolefin can be mentioned. Further, a cation-curable type ultraviolet-curable epoxy resin adhesive can be mentioned.

In the case of the organic sealing layer, the thickness thereof is preferably in the range of 100 to 100,000 nm. When the thickness is 100 nm or more, the laminated body constituting the solar cell can be sufficiently covered with the organic sealing layer. When the thickness is 100,000 nm or less, the organic sealing layer can sufficiently block the water vapor infiltrating from the side surface.

It is more preferably in the range of 500 to 50,000 nm, and even more preferably in the range of 1000 to 20000 nm.

In the case of the inorganic sealing layer, its thickness is in the range of 30 to 3000 nm. When the thickness is 30 nm or more, the inorganic sealing layer can have a sufficient water vapor barrier property, and the durability of the solar cell is improved. When the thickness is 3000 nm or less, even if the thickness of the inorganic sealing layer is increased, the generated stress is small, so that peeling of the inorganic sealing layer, the electrode, the semiconductor layer, etc. can be suppressed. .. It is more preferably in the range of 50 to 1000 nm, and even more preferably in the range of 100 to 500 nm.

[9] Others The solar cell of the present invention may have various configurations depending on its purpose, usage conditions, and the like. For example, a gas barrier layer may be provided between the first substrate and the first electrode.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. Although the display of "parts" or "%" is used in the examples, it represents "parts by mass" or "% by mass" unless otherwise specified.

<Example 1>
The following steps (1) to (7) were carried out in order to prepare a perovskite solar cell.

(1) Preparation of First Electrode (FTO Electrode) An electrode consisting of a fluorine-doped tin oxide (FTO) layer provided on a glass substrate (first substrate) (manufactured by Asahi Glass Fabricec Co., Ltd., 25 mm × 25 mm × 1.8 mm) , Hereinafter referred to as “FTO electrode”) was etched with Zn powder and a 2 mol / L hydrochloric acid aqueous solution. Ultrasonic cleaning was performed with 1% by mass of neutral detergent, acetone, 2-propanol (IPA), and ion-exchanged water for 10 minutes each in this order. Further, immediately before the formation of the electron transport layer, the FTO electrode was placed in an ozone generator (ozone cleaner manufactured by Meiwaforsis Co., Ltd., PC-450UV) with the FTO surface facing up, and irradiated with ultraviolet rays for 30 minutes.

_{(2) Formation of electron transport layer 3% by mass dehydrated tetrafluoropropanol of titanium tetraisopropoxide (Ti (OiPr) 4} ) in a glove box under a dry nitrogen atmosphere with a water concentration of 1 ppm or less (exemplified compound F-1). Solution 1 is prepared, and silver acetate (CH ₃ CO ₂ Ag) is further dehydrated by 1% by mass. Tetrafluoropropanol (exemplified compound F-1) solution 2 is prepared, and then these are subjected to molars of titanium tetraisopropoxide and silver acetate. The solution was mixed and stirred so that the ratio (Ti / Ag) was 1.0 / 0.1, opened to the atmosphere at a humidity of 30% for 1 minute, and immediately returned to the glove box as a sol-gel solution. ..

Then, the same sol / gel solution is applied onto the FTO electrode by an inkjet method, post-baked (sintered) at 60 ° C. for 2 minutes, and then heat-treated at 400 ° C. for 30 minutes. The electron transport layer was formed so that the dry film thickness was 200 nm.

(3) Formation of photoelectric conversion layer In the glove box, lead iodide (PbI ₂ , for perobskite precursor, manufactured by Tokyo Kasei Kogyo Co., Ltd.) 0.114 g, methylamine iodide hydride (CH ₃ NH ₃ I) , Tokyo Kasei Kogyo Co., Ltd.) 0.035 g, dehydrated N, N-dimethylformamide (dehydrated DMF, manufactured by Wako Pure Chemical Industries, Ltd.) 1 mL were mixed, stirred at room temperature, and 0.3 M iodine-based perovskite (CH ₃ NH _3). PbI ₃ ) A DMF solution (colorless and transparent) as a raw material was prepared.

0.5 mL of the DMF solution of the iodine-based perovskite raw material was spin-coated on the electron transport layer using a spin coater (MS-100 manufactured by Mikasa Co., Ltd.) (5000 rpm × 30 sec). Immediately after spin coating, it was dried on a 100 ° C. hot plate for 10 minutes. The contact portion with the FTO was wiped off with a cotton swab soaked with DMF, and then dried at 70 ° C. for 60 minutes to form a photoelectric conversion layer. The formation of the perovskite compound was confirmed by X-ray diffraction pattern, absorption spectrum and electron microscopic observation.

(4) Formation of hole transport layer Bis (trifluoromethanesulfonyl) imidelithium (LiTFSI, manufactured by Wako Pure Chemical Industries, Ltd.) 9.1 mg, [Tris (2- (1H-pyrazole-1-yl) -4-tert) -Butyl pyridine) Cobalt (III) Tris (bis (trifluoromethylsulfonyl (imide)) (Co (4-tButylpyridyl-2-1H-pyrazole) 3.3TFSI, manufactured by Wako Pure Chemical Industries, Ltd.) 8.7 mg, 2 , 2', 7,7'-Tetrakiss [N, N-di-p-methoxyphenylamino] -9,9'-spirobifluorene (Spiro-OMeTAD, manufactured by Wako Pure Chemical Industries, Ltd.) 72.3 mg, chlorobenzene 1 mL (manufactured by Nakaraitesk Co., Ltd.) and 28.8 μL of tributylphosphine (TBP, manufactured by Sigma Aldrich) were mixed and stirred at room temperature to prepare a hole transporting agent (HTM) solution (black-purple transparent). Immediately before use. The HTM solution was filtered through a PTFE filter having a pore size of 0.45 μm. The HTM solution was spin-coated on the above-mentioned light absorption layer using a spin coater (Mikasa Co., Ltd., MS-100) (4000 rpm × 30 sec). After spin-coating. Immediately, it was dried on a 70 ° C. hot plate for 30 minutes. After drying, the contact portion with the FTO was wiped off with a cotton swab soaked with chlorobenzene, and then the entire back surface of the substrate was wiped off with a cotton swab soaked with DMF. Further, it was dried on a hot plate at 70 ° C. for several minutes to form a hole transport layer.

(5) Formation of the second electrode (gold electrode) Using a vacuum vapor deposition apparatus (VTR-060M / ERH manufactured by ULVAC Kiko Co., Ltd.), under vacuum (4 to 5 × 10 ^-3 Pa), on the hole transport layer described above. A second electrode was formed by depositing gold in 300 nm.

(6) Formation of Sealing Layer The sealing layer was supplied with silane gas and ammonia gas at a film forming pressure of 0.1 to 50 Pa to form a silicon nitride film having a diameter of 500 nm by a plasma CVD method. Specifically, the substrate formed up to the second electrode ^{is placed in a vacuum chamber reduced to 10 -4} Pa or less, the substrate temperature is adjusted to about 70 ° C., and the reaction gases are SiH ₄ gas, NH ₃ gas, and H. _Two gases were introduced at a ratio of 2: 1: 4, and the film was formed by a plasma CVD method having a high frequency power supply of 13.56 MHz while reducing the pressure to 50 Pa. Although the substrate temperature rises during film formation, the film was formed while controlling the substrate cooling so that the temperature reached 70 ° C. As a result, a SiN layer having a diameter of 500 nm was formed.

(7) Bonding of the second substrate As the second substrate, AlPET obtained by bonding 50 μm PET to a 25 μm aluminum foil is used, and 5% by mass of 5 to 10 μmφ talc is mixed with the ALPET as a filler to achieve epoxy thermosetting adhesion. It was bonded to the sealing layer via an agent (Elephant CS manufactured by Tomagawa Paper Co., Ltd.).

<Example 2>
In the formation of the (2) electron transport layer of Example 1, the molar ratio (Ti / Ag) of titanium tetraisopropoxide and silver acetate was adjusted to 1.0 / 0.3, except that it was the same as that of Example 1. An electron transport layer was formed in the same manner.

<Example 3>
In the formation of the (2) electron transport layer of Example 1, the molar ratio (Ti / Ag) of titanium tetraisopropoxide and silver acetate was adjusted to 1.0 / 0.5, but the same as that of Example 1. An electron transport layer was formed in the same manner.

<Example 4>
In the formation of the (2) electron transport layer of Example 1, the molar ratio (Ti / Ag) of titanium tetraisopropoxide and silver acetate was adjusted to 1.0 / 0.9, except that it was the same as that of Example 1. An electron transport layer was formed in the same manner.

<Comparative Example 1>
In the formation of the electron transport layer in (2) of Example 1, the electron transport layer was formed in the same manner as in Example 1 except that _{silver acetate (CH 3} CO _{2 Ag) was not used in combination.}

<Comparative Example 2>
In the formation of the electron transport layer in (2) of Example 1, the electron transport layer was formed in the same manner as in Example 1 except that propanol was used instead of tetrafluoisopropanol.

<Comparative Example 3>
The following steps (1) to (6) were carried out in order to produce a conventional type perovskite solar cell.

(1) Preparation of First Electrode (FTO Electrode) An FTO electrode was prepared in the same manner as in Example 1.

(2) Formation of electron transport layer A titanium oxide paste containing polyisobutyl methacrylate as an organic binder and titanium oxide (a mixture of an average particle diameter of 10 nm and 30 nm) is applied by a spin coating method and then dried at 150 ° C. for 10 minutes. I let you. Then, using a high-pressure mercury lamp (HLR100T-2 manufactured by Sen Special Light Source Co., Ltd.), ultraviolet rays were irradiated at a radiation intensity of 500 mW / cm ² for 15 minutes to form a porous electron transport layer having a thickness of 200 nm made of titanium oxide. Formed.

(3) Formation of photoelectric conversion layer Lead iodide was dissolved in N, N-dimethylformamide (DMF) to prepare a 1M solution, and a film was formed on the porous electron transport layer by a spin coating method. Further, methylammonium iodide as an amine compound was dissolved in 2-propanol to prepare a 1% by mass solution. By immersing the above-mentioned lead iodide-formed sample in this solution, a layer containing _{CH 3} NH ₃ PbI _{3 which is an organic-inorganic perovskite compound was formed.} Then, the obtained sample was annealed at 120 ° C. for 30 minutes to form a photoelectric conversion layer.

(4) Formation of Hole Transport Layer On the photoelectric conversion layer, a 1% by mass chlorobenzene solution of Poly (4-butylphenyl-diphenyl-amine) (manufactured by 1-Material) was added to a thickness of 50 nm by a spin coating method. They were laminated to form a hole transport layer.

(5) Formation of the second electrode (gold electrode) The same procedure as in Example 1 was performed.

(6) Formation of sealing layer The same procedure as in Example 1 was carried out.

(7) Arrangement of the Second Substrate A second substrate was provided after the completion of the steps (1) to (6) as in the first embodiment.

<Evaluation>
A power source (236 model manufactured by KEITHLEY) was connected between the electrodes of the flexible solar cell, and the photoelectric conversion efficiency was measured using a solar simulator (manufactured by Yamashita Denso Co., Ltd.) having an intensity of ^{300 mW / cm 2.} The obtained photoelectric conversion efficiency was used as the initial conversion efficiency.

The following evaluations were performed on various solar cells obtained as the above-mentioned Examples and Comparative Examples.

(1) Measurement of light conversion efficiency, etc. Using a solar simulator ^{, irradiation of a pseudo-sunlight spectrum with an incident light irradiance of 1000 W / m 2} and a spectrum of Air Mass (AM) of 1.5 G was performed in a room temperature environment of 25 ° C.

The solar simulator uses a pulsed light type SHSS-01 manufactured by Sharp, a device composed of an Xe lamp and a Ha lamp as a light source, and a panel having an opening of 2 cm x 2 cm with t = 0. By alumite-treating a 2 mm aluminum plate and blackening the surface, a light-shielding mask with a light-shielding part transmission rate of 0% is prepared, which is brought into close contact with the solar cell panel, and the IV curve and short-circuit current density under light irradiation ( Jsc), release voltage (Voc), maximum output (Pmax) and fill factor (FF) were measured, and the optical conversion efficiency and its maintenance rate or rate of change were calculated.

(2) Light resistance test Next, as a life test of the solar cell, an accelerated test was conducted under the condition of ^{3000 W / m 2 light irradiation and 80 ° C. dry condition using the above solar simulator to evaluate the initial characteristics.} The same measurement was performed to evaluate the light resistance.

(3) Reliability test The deterioration characteristics due to light irradiation were evaluated by conducting a light irradiation test for 3000 hours under the conditions of 85 ° C. and 85% based on the IEC standard by the same method as above.

The above evaluation results are shown in FIGS. 2 and 3.

From the above evaluation results, the conventional type solar cell (Comparative Example 3) significantly deteriorates in characteristics due to self-power generation, but the solar cell of the present invention suppresses the deterioration in all cases. I understood. Further, it can be seen that the more silver (Ag) alkoxide, the more the deterioration rate is suppressed, and the more the titanium (Ti) alkoxide having a fluorinated alkoxy group, the more the deterioration tends to be suppressed. From these results, the organic metal alkoxide reacts with iodine gas or water to trap iodine gas, and at the same time, water-repellent or hydrophobic compound is released by partial hydrolysis, and deterioration due to iodine gas or water is suppressed. It is presumed that it was done.

1 Solar cell 2 1st substrate 3 1st electrode 4 Electron transport layer 5 Photoelectric conversion layer 6 Hole transport layer 7 2nd electrode 8 Sealing layer 9 Adhesive layer 10 2nd substrate

Claims (8)

A solar cell including at least a first substrate, a first electrode, an electron transport layer, a photoelectric conversion layer, a hole transport layer, a second electrode, and a second substrate.
The photoelectric conversion layer contains a perovskite compound and
The solar cell (photoelectric cell) is characterized in that the electron transport layer contains at least two kinds of organometallic oxides having a structure represented by the following general formula (1) and the following general formula (2) and having different metal types. Conversion device).
General formula (1): R- [M ₁ (OR ₁ ) _y (O-) _x-y ] _n- R
General formula (2): R- [M ₂ (OR ₂ ) _y (O-) _xy ] _n- R
(In the formula, R represents a hydrogen atom, an alkyl group having one or more carbon atoms, an alkenyl group, an aryl group, a cycloalkyl group, an acyl group, an alkoxy group, or a heterocyclic group, where R is fluorine as a substituent. It may be a carbon chain containing an atom. M ₁ represents a metal atom selected from Cu, Ag and Au. M ₂ represents a metal atom selected from Ti, Zn, Sn, Al and Zr. _{OR 1} and OR. ₂ represents a fluorinated alkoxy group, x represents the valence of the metal atom, y represents an arbitrary integer between 1 and x, and n represents the degree of polycondensation.) The value of the molar ratio of organic metal oxide containing the metal species _{M 1} to the organic metal oxide containing the metal species _{M 2 (M 1 / M 2} ) is in the range of from 0.1 to 0.9 The solar cell according to claim 1, wherein the solar cell is characterized in that. An organic metal oxide having a structure represented by the general formula (1) or the general formula (2) reacts with iodine gas or water, captures iodine gas, and releases a water-repellent or hydrophobic compound. The solar cell according to claim 1 or claim 2. The solar cell according to any one of claims 1 to 3, wherein the perovskite compound has a structure represented by the following general formula (3).
General formula (3): R-MX ₃
(In the formula, R represents an organic molecule, M represents a metal atom, and X represents a halogen atom or a chalcogen atom.) The solar cell according to any one of claims 1 to 4, wherein the electron transport layer comprises a film in which a composition containing at least the organic metal oxide is sol-gel-transferred. .. The method for manufacturing a solar cell according to any one of claims 1 to 5, wherein the solar cell is manufactured.
A method for manufacturing a solar cell, which comprises a step of forming the electron transport layer using a mixed solution of a metal alkoxide or a metal carboxylate and a fluoroalcohol. The method for manufacturing a solar cell according to claim 6, wherein the electron transport layer is formed by a wet coating method. The method for manufacturing a solar cell according to claim 7, wherein the wet coating method is an inkjet printing method.

Images