JP2015046584A - Photoelectric conversion element, and solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoelectric conversion element which reduces variation of photoelectric conversion efficiency and exerts stable battery performance, and a solar cell having the same.SOLUTION: A photoelectric conversion element comprises: a first electrode having a porous layer provided on a conductive support and a photosensitive layer having a light absorption agent on a surface of the porous layer; a second electrode opposed to the first electrode; and a hole transport layer provided between the first electrode and the second electrode, and in the photoelectric conversion element, the light absorption agent contains a compound having the perovskite crystal structure containing a cation of a group I element in the periodic table or a cationic organic group A, a cation of a metal atom M other than the group I element in the periodic table and an anion of an anionic atom X. A film thickness of the porous layer is 15 to 100 μm, and a solar cell having the photoelectric conversion element is provided.

Description

  The present invention relates to a photoelectric conversion element and a solar cell.

  Photoelectric conversion elements are used in various optical sensors, copying machines, solar cells, and the like. Solar cells are expected to be put into full-scale practical use as non-depleting solar energy. Among these, a dye-sensitized solar cell using an organic dye or a Ru bipyridyl complex as a sensitizer has been actively researched and developed, and the photoelectric conversion efficiency has reached about 11%.

On the other hand, recently, research results have been reported that solar cells using metal halides as compounds having a perovskite crystal structure can achieve relatively high photoelectric conversion efficiency, and are attracting attention.
For example, Non-Patent Document 1 discloses that a compound having a perovskite crystal structure of CH ₃ NH ₃ PbX ₃ (X represents a bromine atom or an iodine atom) is adsorbed as nano-sized fine particles with a film thickness of 8 to 12 μm. A solar cell having a TiO ₂ film and an electrolyte solution is described.
Patent Document 1 discloses a lead complex having a perovskite crystal structure represented by CH ₃ NH ₃ MX ₃ (M represents Pb or Sn, and X represents a halogen atom) and a semiconductor having a thickness of 8.0 μm or less. A solar cell including a light absorbing layer including a fine particle layer and an electrolyte layer made of an electrolytic solution is described.
In addition, a solar cell using a compound having a perovskite crystal structure of CH ₃ NH ₃ PbI ₂ Cl and a hole transport material has been studied (Non-patent Document 2).

Korean Registered Patent No. 10-1172374

J. et al. Am. Chem. Soc. 2009, 131 (17), 6050-6051. Science, 338, 643 (2012)

As described above, the photoelectric conversion element and the solar cell using the compound having a perovskite crystal structure of a metal halide have achieved certain results in improving the photoelectric conversion efficiency. However, this photoelectric conversion element and solar cell have attracted attention in recent years, and little is known about battery performance other than photoelectric conversion efficiency.
In such a situation, when the above solar cell was repeatedly manufactured by the same manufacturing method using a metal halide compound having a perovskite crystal structure, there was a variation in photoelectric conversion efficiency between the obtained solar cells. It was found that the battery performance fluctuated greatly (hereinafter sometimes referred to as voltage fluctuation between solar cells) and the stability of the battery performance was not sufficient.

  Therefore, an object of the present invention is to provide a photoelectric conversion element that exhibits a small variation in photoelectric conversion efficiency and exhibits stable battery performance, and a solar cell including the photoelectric conversion element.

  In the solar cell using a compound having a perovskite-type crystal structure (sometimes referred to as a perovskite compound) (also referred to as a perovskite-sensitized solar cell), the inventors of the present invention are porous as a scaffold for providing a photosensitive layer containing a perovskite compound. It has been found that the film thickness of the layer has a great effect on fluctuations in photoelectric conversion efficiency when a hole transport material, particularly a solid hole transport material is used. As a result of further detailed investigation, when a porous layer having a film thickness set in a specific range and a hole transport material are used in combination, fluctuations in photoelectric conversion efficiency can be reduced, and the photoelectric conversion element and the solar cell are stable. It has been found that it demonstrates its performance. The present invention has been completed based on these findings.

That is, the above problem has been solved by the following means.
<1> a porous layer provided on a conductive support, a first electrode having a photosensitive layer provided with a light absorber on the surface of the porous layer, a second electrode facing the first electrode, A photoelectric conversion element having a hole transport layer provided between the first electrode and the second electrode,
A compound having a perovskite crystal structure in which the light absorber has a cation of a group 1 element of the periodic table or a cationic organic group A, a cation of a metal atom M other than a group 1 element of the periodic table, and an anion of an anionic atom X Including
The photoelectric conversion element whose film thickness of a porous layer is 15-100 micrometers.
<2> The photoelectric conversion element according to <1>, wherein the porous layer has a thickness of 15 to 50 μm.
<3> The photoelectric conversion element according to <1> or <2>, wherein the porous layer has a thickness of 15 to 30 μm.
<4> The porous layer contains at least one selected from the group consisting of titanium, tin, zinc, zirconium, aluminum and silicon oxides and carbon nanotubes, and any one of <1> to <3> The photoelectric conversion element as described in 2.
<5> The photoelectric conversion element according to any one of <1> to <4>, in which the porous layer contains titanium oxide or aluminum oxide.
<6> The photoelectric conversion element according to any one of <1> to <5>, wherein the compound having a perovskite crystal structure is a compound represented by the following formula (I).

Formula (I): A _a M _m X _x
In the formula, A represents a group 1 element of the periodic table or a cationic organic group. M represents a metal atom other than Group 1 elements of the periodic table. X represents an anionic atom. a represents 1 or 2, m represents 1, and a, m, and x satisfy a + 2m = x.

<7> The photoelectric conversion element according to any one of <1> to <6>, wherein the compound having a perovskite crystal structure includes a compound represented by the following formula (I-1).

Formula (I-1): AMX ₃
In the formula, A represents a group 1 element of the periodic table or a cationic organic group. M represents a metal atom other than Group 1 elements of the periodic table. X represents an anionic atom.

<8> The photoelectric conversion element according to any one of <1> to <7>, wherein the compound having a perovskite crystal structure includes a compound represented by the following formula (I-2).

Formula (I-2): A ₂ MX ₄
In the formula, A represents a group 1 element of the periodic table or a cationic organic group. M represents a metal atom other than Group 1 elements of the periodic table. X represents an anionic atom.

<9> The photoelectric conversion element according to any one of <6> to <8>, in which A is represented by the following formula (1).

Formula (1): R ^1a —NH ₃
In the formula, R ^1a represents a substituent.

<10> The photoelectric conversion element according to <9>, wherein R ^1a is an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, or a group that can be represented by the following formula (2).

In formula, ^Xa represents NR ^<1c> , an oxygen atom, or a sulfur atom. R ^1b and R ^1c each independently represent a hydrogen atom or a substituent. *** represents a bonding position with N in the formula (1).

<11> The photoelectric conversion device according to any one of <1> to <10>, wherein X is a halogen atom.
<12> The photoelectric conversion element according to any one of <1> to <11>, wherein M is Pb or Sn.
<13> A solar cell having the photoelectric conversion element according to any one of <1> to <12>.

In the present invention, the thickness of the porous layer is the lower layer surface on which the porous layer is formed along the linear direction intersecting at an angle of 90 ° with the surface of the conductive support in the cross section of the photoelectric conversion element. It is defined by the average distance from the surface of the porous layer.
Here, the “lower surface on which the porous layer is formed” means the interface between the conductive support and the porous layer. When another layer such as a blocking layer is formed between the conductive support and the porous layer, it means an interface between the other layer and the porous layer.
Further, the “surface of the porous layer” is a point of the porous layer located closest to the second electrode from the conductive support on a virtual straight line that intersects the surface of the conductive support at an angle of 90 ° ( (Intersection of virtual straight line and outline of porous layer).
The “average distance” is 10 in an observation area of a specific range in the cross section of the photoelectric conversion element along a horizontal (parallel) direction to the surface of the conductive support (for example, the horizontal direction in FIGS. 1 and 2). The longest distance from the lower layer surface to the surface of the porous layer is obtained for each equally divided section, and the average value of the longest distances of these 10 sections is obtained.
The film thickness of the porous layer can be measured by observing the cross section of the photoelectric conversion element with a scanning electron microscope (SEM).

In the present specification, each of the above formulas, in particular, the formula (1), the formula (2), and the formula (A ^am ) are partly shown as qualitative formulas in order to understand the chemical structure of a compound having a perovskite crystal structure. Sometimes written. Accordingly, in each formula, a partial structure is referred to as a group, a substituent, an atom, or the like. In this specification, these are element groups or elements constituting a group or a (substitution) group represented by the above formula. Means.

  In this specification, about the display of a compound (a complex and a pigment | dye are included), it uses for the meaning containing its salt and its ion besides the compound itself. In addition, it means that a part of the structure is changed as long as the desired effect is achieved. Furthermore, a compound that does not specify substitution or non-substitution is meant to include a compound having an arbitrary substituent as long as a desired effect is achieved. The same applies to substituents and linking groups (hereinafter referred to as substituents and the like).

  In this specification, when there are a plurality of substituents and the like indicated by a specific symbol, or when a plurality of substituents and the like are specified at the same time, the respective substituents are the same as or different from each other unless otherwise specified. May be. The same applies to the definition of the number of substituents and the like. Further, when a plurality of substituents and the like are close to each other (especially when they are adjacent to each other), they may be connected to each other to form a ring unless otherwise specified. In addition, a ring such as an alicyclic ring, an aromatic ring, or a heterocyclic ring may be further condensed to form a condensed ring.

  Further, in this specification, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

  INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a photoelectric conversion element that exhibits small fluctuations in photoelectric conversion efficiency and exhibits stable battery performance, and a solar cell including the photoelectric conversion element.

It is sectional drawing which showed typically about the preferable aspect of the photoelectric conversion element of this invention. It is sectional drawing which showed typically about the preferable aspect which has a thick photosensitive layer of the photoelectric conversion element of this invention. It is a figure explaining the crystal structure of a perovskite compound.

<< Photoelectric conversion element >>
The photoelectric conversion element of the present invention is provided between a first electrode having a conductive support, a porous layer and a photosensitive layer, a second electrode facing the first electrode, and the first electrode and the second electrode. And a hole transport layer. The porous layer, the photosensitive layer, the hole transport layer, and the second electrode are preferably provided on the conductive support in this order.
In the present invention, the porous layer is formed to a thickness of 15 to 100 μm. The photosensitive layer contains at least one perovskite compound provided on the surface of the porous layer. A hole transport layer is provided on the first electrode having the porous layer and the photosensitive layer. The photoelectric conversion element and the solar cell of the present invention having such a configuration exhibit reduced photoelectric conversion efficiency and stable battery performance.

The photoelectric conversion element of the present invention is not particularly limited in structure other than the structure defined in the present invention, and a known structure relating to the photoelectric conversion element and the solar cell can be adopted. Each layer constituting the photoelectric conversion element of the present invention is designed according to the purpose, and may be formed in a single layer or multiple layers, for example.
For example, in the present invention, the photosensitive layer may be a single layer or a laminate of two or more layers. When the photosensitive layer is a laminate, it may be a laminate of layers made of different light absorbers, and an intermediate layer made of a hole transport material may be provided between the photosensitive layer and the photosensitive layer.

Hereinafter, the preferable aspect of the photoelectric conversion element of this invention is demonstrated.
In FIG. 1 and FIG. 2, the same code | symbol means the same component (member).
1 and 2 show the size of the fine particles forming the porous layer with emphasis. These fine particles are preferably packed horizontally and vertically with respect to the conductive substrate to form a porous structure.

  In this specification, the term “photoelectric conversion element 10” means the photoelectric conversion elements 10A and 10B unless otherwise specified. The same applies to the system 100, the first electrode 1, the photosensitive layer 13, and the hole transport layer 3.

As a preferable aspect of the photoelectric conversion element of the present invention, for example, a photoelectric conversion element 10A shown in FIG. A system 100A shown in FIG. 1 is a system applied to a battery for causing an operation circuit M (for example, an electric motor) to perform work by the external circuit 6 using the photoelectric conversion element 10A.
The photoelectric conversion element 10A includes a first electrode 1A, a second electrode 2, and a hole transport layer 3A. 1 A of 1st electrodes have the electroconductive support body 11 which consists of the support body 11a and the transparent electrode 11b, the porous layer 12, and 13 A of photosensitive layers. In addition, the blocking layer 14 is preferably provided on the transparent electrode 11 b, and the porous layer 12 is formed on the blocking layer 14.

  The photoelectric conversion element 10B shown in FIG. 2 schematically shows a preferred embodiment in which the photosensitive layer 13A of the photoelectric conversion element 10A shown in FIG. In the photoelectric conversion element 10B, the hole transport layer 3B is thinly provided. The photoelectric conversion element 10B differs from the photoelectric conversion element 10A shown in FIG. 1 in the film thicknesses of the photosensitive layer 13B and the hole transport layer 3B, but is configured in the same manner as the photoelectric conversion element 10A except for these points. ing.

  In the present invention, the photosensitive layer can be formed in various forms on the surface of the porous layer depending on the shape of the porous layer, the amount of the light absorber provided, and the like. Therefore, in the present invention, the mode is not particularly limited as long as the photosensitive layer is provided on the surface of the porous layer. As a mode in which the photosensitive layer is formed on the surface of the porous layer, for example, a mode in which the photosensitive layer is provided in the form of a thin film or the like on the surface of the porous layer (see FIG. 1), a thickness provided on the surface of the porous layer (See FIG. 2). The photosensitive layer may be provided in a linear or dispersed form, but is preferably provided in a film form.

In the present invention, the system 100 to which the photoelectric conversion element 10 is applied functions as a solar cell as follows.
That is, in the photoelectric conversion element 10, light that has passed through the conductive support 11 or the second electrode 2 and entered the photosensitive layer 13 excites the light absorber. The excited light absorber has high-energy electrons, and these electrons reach the conductive support 11 from the photosensitive layer 13. At this time, the light absorber that has released electrons with high energy is an oxidant. Electrons reaching the conductive support 11 return to the photosensitive layer 13 via the second electrode 2 and then the hole transport layer 3 while working in the external circuit 6. The light absorber is reduced by the electrons returning to the photosensitive layer 13. The system 100 functions as a solar cell by repeating excitation and electron transfer of the light absorbing material.

The flow of electrons from the photosensitive layer 13 to the conductive support 11 differs depending on the presence and type of the porous layer 12 and the like. In the photoelectric conversion element 10, electron conduction occurs in which electrons move between perovskite compounds. Therefore, when providing the porous layer 12, the porous layer 12 can be formed with an insulator other than the conventional semiconductor. When the porous layer 12 is formed of a semiconductor, electron conduction in which electrons move inside or between the semiconductor particles of the porous layer 12 also occurs. On the other hand, when the porous layer 12 is formed of an insulator, electron conduction in the porous layer 12 does not occur.
Even when the blocking layer 14 as the other layer is formed of a conductor or a semiconductor, electron conduction in the blocking layer 14 occurs.

  The photoelectric conversion element and the solar cell of the present invention are not limited to the above-described preferred embodiments, and the configuration of each embodiment can be appropriately combined between the respective embodiments without departing from the spirit of the present invention.

  In the present invention, materials and components used for the photoelectric conversion element or solar cell are prepared by a conventional method except for the porous layer 12, the perovskite type light absorber as the sensitizer and the hole transport layer 3. Can do. For a photoelectric conversion element or a solar cell using a perovskite light absorber, for example, Patent Document 1 and Non-Patent Documents 1 and 2 can be referred to. As for the dye-sensitized solar cell, for example, JP-A No. 2001-291534, US Pat. No. 4,927,721, US Pat. No. 4,684,537, US Pat. No. 5,084, 365, US Pat. No. 5,350,644, US Pat. No. 5,463,057, US Pat. No. 5,525,440, JP-A-7-249790, JP 2004-220974 A and JP 2008-135197 A can be referred to.

  Hereinafter, the preferable aspect of the main member and compound of the photoelectric conversion element of this invention and a solar cell is demonstrated.

<First electrode 1>
The first electrode 1 includes a conductive support 11, a porous layer 12, and a photosensitive layer 13, and functions as a working electrode in the photoelectric conversion element 10.
The first electrode 1 preferably has a blocking layer 14.

− Conductive support 11 −
The conductive support 11 is not particularly limited as long as it has conductivity and can support the porous layer 12, the photosensitive layer 13, and the like. The conductive support is made of a conductive material, for example, a conductive support made of metal, or a glass or plastic support 11a and a conductive electrode as a transparent electrode 11b formed on the surface of the support 11a. A conductive support 11 having a membrane is preferred.

In particular, as shown in FIGS. 1 and 2, a conductive support 11 in which a transparent metal electrode 11b is formed by coating a conductive metal oxide on the surface of a glass or plastic support 11a is more preferable. . Examples of the support 11a made of plastic include a transparent polymer film described in paragraph No. 0153 of JP-A No. 2001-291534. As a material for forming the support 11a, ceramic (Japanese Patent Laid-Open No. 2005-135902) and conductive resin (Japanese Patent Laid-Open No. 2001-160425) can be used in addition to glass and plastic. As the metal oxide, tin oxide (TO) is preferable, and fluorine-doped tin oxide such as indium-tin oxide (tin-doped indium oxide; ITO) and fluorine-doped tin oxide (FTO) is particularly preferable. The coating amount of the metal oxide at this time is preferably 0.1 to 100 g per 1 m ² of the surface area of the support 11a. When the conductive support 11 is used, light is preferably incident from the support 11a side.

The conductive support 11 is preferably substantially transparent. In the present invention, “substantially transparent” means that the transmittance of light (wavelength 300 to 1200 nm) is 10% or more, preferably 50% or more, and particularly preferably 80% or more.
The thicknesses of the support 11a and the conductive support 11 are not particularly limited, and are set to appropriate thicknesses. For example, the thickness is preferably 0.01 μm to 10 mm, more preferably 0.1 μm to 5 mm, and particularly preferably 0.3 μm to 4 mm.
When providing the transparent electrode 11b, the film thickness of the transparent electrode 11b is not specifically limited, For example, it is preferable that it is 0.01-30 micrometers, It is more preferable that it is 0.03-25 micrometers, 0.05-20 micrometers It is particularly preferred that

  The conductive support 11 or the support 11a may have a light management function on the surface. For example, even if the surface of the conductive support 11 or the support 11a has an antireflection film in which high refractive films and low refractive index oxide films are alternately stacked as described in JP-A-2003-123859. The light guide function described in JP-A-2002-260746 may be provided.

− Blocking layer 14 −
In the present invention, a blocking layer 14 is preferably provided on the surface of the transparent electrode 11b, that is, between the conductive support 11 and the porous layer 12 or the hole transport layer 3 or the like.
In the photoelectric conversion element and the solar cell, when the hole transport layer 3 and the transparent electrode 11b are in direct contact, a reverse current is generated. The blocking layer 14 functions to prevent this reverse current. The blocking layer 14 is also referred to as a short circuit prevention layer.

The material for forming the blocking layer 14 is not particularly limited as long as it is a material capable of fulfilling the above function, but is a substance that transmits visible light and is an insulating substance for the conductive support 11 (transparent electrode 11b). Preferably there is. Specifically, the “insulating substance with respect to the conductive support 11 (transparent electrode 11b)” specifically refers to a material whose conduction band energy level forms the conductive support 11 (metal oxide forming the transparent electrode 11b). A compound (n-type semiconductor compound) that is higher than the energy level of the conduction band of the material and lower than the energy level of the conduction band of the material constituting the porous layer 12 and the ground state of the light absorber.
Examples of the material for forming the blocking layer 14 include silicon oxide, magnesium oxide, aluminum oxide, calcium carbonate, polyvinyl alcohol, and polyurethane. Moreover, the material generally used for the photoelectric conversion material may be used, and examples thereof include titanium oxide, tin oxide, niobium oxide, and tungsten oxide. Of these, titanium oxide, tin oxide, magnesium oxide, aluminum oxide and the like are preferable.
The film thickness of the blocking layer 14 is preferably 0.001 to 10 μm, more preferably 0.005 to 1 μm, and particularly preferably 0.01 to 0.1 μm.

− Porous layer 12 −
In the present invention, the porous layer 12 is formed on the transparent electrode 11b. When the blocking layer 14 is provided, the porous layer 12 is formed on the blocking layer 14.

The porous layer 12 is a layer that functions as a scaffold for carrying the photosensitive layer 13 on the surface. The porous layer 12 is preferably a fine particle layer having pores formed by depositing a porous material. The porous layer may be a layer in which one kind of porous material is deposited or a layer in which two or more kinds of porous materials are deposited.
The deposition state of the porous material is not particularly limited, and the porous material is preferably deposited so that the porous layer is a layer having pores. In the present invention, the deposited porous material is preferably in a state where a porous structure can be formed. The “state in which a porous layer can be formed” includes a state in which porous materials are gathered, a state in which the porous materials are further compressed or filled, and a state in which the porous materials are closely adhered, fused, or sintered.

When the porous layer 12 is a fine particle layer having pores, the amount of light absorbent supported (adsorption amount) can be increased. In the solar cell, in order to increase the light absorption efficiency, it is preferable to increase the surface area of at least a portion that receives light such as sunlight, and it is more preferable to increase the entire surface area of the porous layer 12.
In order to increase the surface area of the porous layer 12, it is preferable to increase the surface area of the individual fine particles constituting the porous layer 12. In the present invention, in a state where the fine particles forming the porous layer 12 are coated on the conductive support 11 or the like, the surface area of the fine particles is preferably 10 times or more, more than 100 times the projected area. It is more preferable. Although there is no restriction | limiting in particular in this upper limit, Usually, it is about 5000 times. The particle diameter of the fine particles forming the porous layer 12 is preferably 0.001 to 1 μm as the primary particle in the average particle diameter using the diameter when the projected area is converted into a circle. When the porous layer 12 is formed using a dispersion of fine particles, the average particle diameter of the fine particles is preferably 0.01 to 100 μm as the average particle diameter of the dispersion.

  The film thickness of the porous layer 12 is in the range of 15 to 100 μm. Even if the film thickness of the porous layer 12 is less than 15 μm or more than 100 μm, the photoelectric conversion efficiency may fluctuate greatly when the hole transport layer 3 is used. Further, when the blocking layer 14 is not provided, the first electrode 1 and the hole transport layer 3 are easily short-circuited when the thickness of the porous layer 12 is less than 15 μm. The film thickness of the porous layer 12 is preferably 15 to 50 μm, and more preferably 15 to 30 μm, from the viewpoint of effectively reducing fluctuations in photoelectric conversion efficiency.

The reason why the fluctuation in photoelectric conversion efficiency can be reduced when the film thickness of the porous layer 12 is set to 15 to 100 μm is not yet clear, but for example, the following reason is estimated.
In the solar cell, when the film thickness of the porous layer 12 is increased, the surface area of the porous layer 12 is increased, and the amount of the light absorbent supported is increased. This absorbs more incident light and increases the number of excited electrons. On the other hand, when the thickness of the porous layer 12 is increased, the electron transfer (charge transport) distance of the excited electrons injected into the porous layer 12 is increased. As a result, a reverse electron transfer amount occurs, and excited electrons are deactivated in the porous layer 12, so that the charge transport performance is lost and deteriorated. However, when the film thickness of the porous layer 12 is in the above range, it is considered that the loss of charge transport performance can be suppressed despite the fact that the surface area of the porous layer 12 can be increased. Thereby, it is considered that the loss of charge transport performance becomes relatively small with respect to the increased amount of excited electrons, and variation in photoelectric conversion efficiency can be suppressed.
Further, the contact area between the photosensitive layer 13 formed on the surface of the porous layer 12 and the hole transport layer 3 increases. As a result, the overall adhesion between the hole transport layer 3 and the photosensitive layer 13 is improved. Thereby, the influence of the interface defect that may occur at the interface between the photosensitive layer 13 and the hole transport layer 3 becomes relatively small with respect to the influence due to the increased contact area, and it is considered that variations in photoelectric conversion efficiency can be suppressed. .
The method for measuring the film thickness of the porous layer 12 is as described above.

The material for forming the porous layer 12 is not particularly limited with respect to conductivity, and may be an insulator (insulating material), a conductive material, or a semiconductor (semiconductive material). .
Examples of the material for forming the porous layer 12 include metal chalcogenides (eg, oxides, sulfides, selenides, etc.), compounds having a perovskite crystal structure (excluding a light absorber described later), and oxidation of silicon. An object (for example, silicon dioxide, zeolite), or carbon nanotube (including carbon nanowire and carbon nanorod) can be used.

  The metal chalcogenide is not particularly limited, but is preferably titanium, tin, zinc, tungsten, zirconium, hafnium, strontium, indium, cerium, yttrium, lanthanum, vanadium, niobium, aluminum or tantalum oxide, cadmium sulfide. , Cadmium selenide and the like. Examples of the crystal structure of the metal chalcogenide include an anatase type, brookite type and rutile type, and anatase type and brookite type are preferable.

  Although it does not specifically limit as a compound which has a perovskite type crystal structure, A transition metal oxide etc. are mentioned. For example, strontium titanate, calcium titanate, barium titanate, lead titanate, barium zirconate, barium stannate, lead zirconate, strontium zirconate, strontium tantalate, potassium niobate, bismuth ferrate, strontium barium titanate , Barium lanthanum titanate, calcium titanate, sodium titanate, bismuth titanate. Of these, strontium titanate, calcium titanate and the like are preferable.

  The carbon nanotube has a shape obtained by rounding a carbon film (graphene sheet) into a cylindrical shape. Carbon nanotubes are single-walled carbon nanotubes (SWCNT) in which one graphene sheet is wound in a cylindrical shape, double-walled carbon nanotubes (DWCNT) in which two graphene sheets are wound in a concentric shape, and multiple graphene sheets are concentric Are classified into multi-walled carbon nanotubes (MWCNT) wound in a shape. As the porous layer 12, any carbon nanotube is not particularly limited and can be used.

  Among these materials, the material forming the porous layer 12 is preferably titanium, tin, zinc, zirconium, aluminum or silicon oxide, or carbon nanotube, and more preferably titanium oxide or aluminum oxide.

  The porous layer 12 may be formed of at least one of the above-described metal chalcogenide, compound having a perovskite crystal structure, silicon oxide, and carbon nanotube, and may be formed of a plurality of types. .

  The material for forming the porous layer 12 is preferably used as fine particles as described later. The material forming the porous layer 12 includes a metal chalcogenide, a compound having a perovskite crystal structure, and a silicon oxide nanotube, nanowire or nanorod, a metal chalcogenide, a compound having a perovskite crystal structure, a silicon oxide. It can also be used with fine particles of carbon nanotubes.

− Photosensitive layer (light absorbing layer) 13 −
The photosensitive layer 13 is provided on the surface of the porous layer 12 (including the inner surface when the surface is uneven) using a perovskite compound described later as a light absorber. In the present invention, the light absorber only needs to contain at least one perovskite compound, and may contain two or more perovskite compounds. The light absorber may contain a light absorber other than the perovskite compound in combination with the perovskite compound. Examples of the light absorber other than the perovskite compound include metal complex dyes and organic dyes.

  The form in which the photosensitive layer 13 is formed on the conductive support 11 is as described above. The photosensitive layer 13 is preferably formed of the porous layer 12 so that excited electrons flow through the conductive support 11. Provided on the surface. At this time, the photosensitive layer 13 may be provided on the entire surface of the porous layer 12 or may be provided on a part of the surface.

The film thickness of the photosensitive layer 13 is appropriately set according to the mode in which the photosensitive layer 13 is formed on the conductive support 11 and is not particularly limited. For example, the film thickness of the photosensitive layer 13 is preferably 15 to 100 μm, more preferably 15 to 50 μm, and particularly preferably 15 to 30 μm as the total film thickness with the film thickness of the porous layer 12.
Here, as shown in FIG. 1, when the photosensitive layer 13 is a thin film, the thickness of the photosensitive layer 13 is the interface with the porous layer 12 along the direction perpendicular to the surface of the porous layer 12. And the distance between the hole transport layer 3 and the interface. Here, the film thickness of the photosensitive layer 13 (total film thickness with the film thickness of the porous layer 12) can be measured in the same manner as the film thickness of the porous layer 12.

  Note that the photoelectric conversion element 10B illustrated in FIG. 2 includes a photosensitive layer 13B having a greater thickness than the photosensitive layer 13A of the photoelectric conversion element 10A illustrated in FIG. In this case, the perovskite compound as the light absorber can be a hole transporting material, similar to the compound having the perovskite crystal structure as the material for forming the porous layer 12 described above.

(Light absorber)
The photosensitive layer 13 contains a perovskite compound having a periodic table group 1 element or a cationic organic group A, a metal atom M, and an anionic atom X as a light absorber.
In the perovskite compound, the periodic table group 1 element or the cationic organic group A, the metal atom M other than the periodic table group 1 element and the anionic atom X are each a cation (for convenience, the cation A in the perovskite crystal structure). ), Metal cations (sometimes referred to as cations M for convenience), and anions (sometimes referred to as anions X for convenience).
In the present invention, the cationic organic group means an organic group having a property of becoming a cation in the perovskite crystal structure, and the anionic atom means an atom having a property of becoming an anion in the perovskite crystal structure.
In the present invention, the light absorber only needs to contain at least one perovskite compound. In this case, one kind of perovskite compound may be used alone, or two or more kinds of perovskite compounds may be used in combination.

  The perovskite compound is not particularly limited as long as it is a compound capable of having a perovskite crystal structure containing the above constituent ions.

In the perovskite compound used in the present invention, the cation A is a cation of a group 1 element of the periodic table or an organic cation composed of a cationic organic group A. The cation A is preferably an organic cation.
The cation of the Group 1 element of the periodic table is not particularly limited, and for example, the cation (Li ⁺ , Na ⁺ , K ⁺ of each element of lithium (Li), sodium (Na), potassium (K), or cesium (Cs). Cs ⁺ ), and a cesium cation (Cs ⁺ ) is particularly preferable.
The organic cation is more preferably an organic cation of a cationic organic group represented by the following formula (1).
Formula (1): R ^1a —NH ₃

In the formula, R ^1a represents a substituent. R ^1a is not particularly limited as long as it is an organic group, but an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, or a group that can be represented by the following formula (2) preferable. Among these, an alkyl group and a group that can be represented by the following formula (2) are more preferable.

In formula, ^Xa represents NR ^<1c> , an oxygen atom, or a sulfur atom. R ^1b and R ^1c each independently represent a hydrogen atom or a substituent. *** represents a bonding position with N in the formula (1).

In the present invention, the organic cation of the cationic organic group A is preferably an organic ammonium cation composed of an ammonium cationic organic group A formed by bonding R ^1a and NH ₃ in the above formula (1). When the organic ammonium cation can have a resonance structure, the organic cation includes a cation having a resonance structure in addition to the organic ammonium cation. For example, in the group that can be represented by the above formula (2), when X ^a is NH (R ^1c is a hydrogen atom), the organic cation is bonded to the group that can be represented by the above formula (2) and NH _3. In addition to the organic ammonium cation of the ammonium cationic organic group, an organic amidinium cation which is one of the resonance structures of the organic ammonium cation is also included. Examples of the organic amidinium cation comprising an amidinium cationic organic group include a cation represented by the following formula (A ^am ). In this specification, for convenience the cation represented by the following formula ^{(A am),} may be referred to as ^{"R 1b C (= NH) -NH} 3 ".

The alkyl group is preferably an alkyl group having 1 to 18 carbon atoms, and examples thereof include methyl, ethyl, propyl, isopropyl, n-butyl, t-butyl, pentyl, hexyl and the like.
The cycloalkyl group is preferably a cycloalkyl group having 3 to 8 carbon atoms, and examples thereof include cyclopropyl, cyclopentyl, and cyclohexyl.

The alkenyl group is preferably an alkenyl group having 2 to 18 carbon atoms, and examples thereof include vinyl, allyl, butenyl and hexenyl.
The alkynyl group is preferably an alkynyl group having 2 to 18 carbon atoms, and examples thereof include ethynyl, butynyl and hexynyl.

The aryl group is preferably an aryl group having 6 to 14 carbon atoms, and examples thereof include phenyl.
The heteroaryl group includes a group consisting only of an aromatic heterocycle and a group consisting of a condensed heterocycle obtained by condensing an aromatic heterocycle with another ring such as an aromatic ring, an aliphatic ring or a heterocycle.
As a ring-constituting hetero atom constituting the aromatic hetero ring, a nitrogen atom, an oxygen atom and a sulfur atom are preferable. The number of ring members of the aromatic heterocycle is preferably a 5-membered ring or a 6-membered ring.
Examples of the condensed heterocycle including a 5-membered aromatic heterocycle and a 5-membered aromatic heterocycle include a pyrrole ring, an imidazole ring, a pyrazole ring, an oxazole ring, a thiazole ring, a triazole ring, a furan ring, and a thiophene ring. , Benzimidazole ring, benzoxazole ring, benzothiazole ring, indoline ring, and indazole ring. Examples of the condensed heterocycle including a 6-membered aromatic heterocycle and a 6-membered aromatic heterocycle include, for example, pyridine ring, pyrimidine ring, pyrazine ring, triazine ring, quinoline ring, and quinazoline ring. Is mentioned.

In the group that can be represented by the formula (2), Xa represents NR ^1c , an oxygen atom or a sulfur atom, and NR ^1c is preferable. Here, R ^1c is preferably a hydrogen atom, an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group or a heteroaryl group, and more preferably a hydrogen atom.
R ^1b represents a hydrogen atom or a substituent, and preferably a hydrogen atom. ^Examples of the substituent that R ^1b can take include a hydrogen atom, an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, and a heteroaryl group.
The alkyl group, cycloalkyl group, alkenyl group, alkynyl group, aryl group, and heteroaryl group that R ^1b and R ^1c can each have the same meanings as those of R ^1a , and the preferred ones are also the same.

Examples of the group that can be represented by the formula (2) include formimidoyl (HC (═NH) —), acetimidoyl (CH ₃ C (═NH) —), propionimidoyl (CH ₃ CH ₂ C). (= NH)-) and the like. Among these, formimidoyl is preferable.

The alkyl group, cycloalkyl group, alkenyl group, alkynyl group, aryl group, heteroaryl group and group that can be represented by the above formula (2), which can be represented by R ^1a , may have a substituent. Good. The substituent that R ^1a may have is not particularly limited, and examples thereof include an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, a heterocyclic group, an alkoxy group, an alkylthio group, an amino group, Examples include alkylamino group, arylamino group, acyl group, alkoxycarbonyl group, aryloxycarbonyl group, acylamino group, sulfonamido group, carbamoyl group, sulfamoyl group, halogen atom, cyano group, hydroxy group or carboxy group. Each substituent that R ^1a may have may be further substituted with a substituent.

  In the perovskite compound used in the present invention, the metal cation M is not particularly limited as long as it is a cation of a metal atom M other than a group 1 element of the periodic table and a cation of a metal atom capable of taking a perovskite crystal structure. Examples of such metal atoms include calcium (Ca), strontium (Sr), cadmium (Cd), copper (Cu), nickel (Ni), manganese (Mn), iron (Fe), cobalt (Co), Examples include metal atoms of palladium (Pd), germanium (Ge), tin (Sn), lead (Pb), ytterbium (Yb), europium (Eu), and indium (In). Among these, the metal atom M is particularly preferably Pb or Sn. The metal atom M may be one type of metal atom or two or more types of metal atoms. In the case of two or more kinds of metal atoms, two kinds of Pb and Sn are preferable. In addition, the ratio of the metal atom at this time is not specifically limited.

  In the perovskite compound used in the present invention, the anion X represents an anion of the anionic atom X. This anion is preferably an anion of a halogen atom. As a halogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc. are mentioned, for example. The anion X may be an anion of one kind of anionic atom or an anion of two or more kinds of anionic atoms. In the case of anions of two or more types of anionic atoms, two types of anions of halogen atoms, particularly anions of bromine atoms and iodine atoms are preferred. In addition, the ratio of the anion of the anionic atom at this time is not particularly limited.

  The perovskite compound used in the present invention is preferably a perovskite compound having a perovskite crystal structure having each of the above constituent ions and represented by the following formula (I).

Formula (I): A _a M _m X _x
In the formula, A represents a group 1 element of the periodic table or a cationic organic group. M represents a metal atom other than Group 1 elements of the periodic table. X represents an anionic atom.
a represents 1 or 2, m represents 1, and a, m, and x satisfy a + 2m = x. That is, x is 3 when a is 1 and 4 when a is 2.

  In the formula (I), the periodic table group 1 element or the cationic organic group A forms the cation A having a perovskite crystal structure. Accordingly, the Group 1 element of the periodic table and the cationic organic group A are not particularly limited as long as they are elements or groups that can form the perovskite crystal structure by becoming the cation A. The Periodic Table Group 1 element or the cationic organic group A has the same meaning as the Periodic Table Group 1 element or the cationic organic group described above for the cation A, and the preferred ones are also the same.

  The metal atom M is a metal atom that forms the metal cation M having a perovskite crystal structure. Therefore, the metal atom M is not particularly limited as long as it is an atom other than the Group 1 element of the periodic table and can form the perovskite crystal structure by becoming the metal cation M. The metal atom M is synonymous with the metal atom described in the metal cation M, and the preferred ones are also the same.

  The anionic atom X forms the anion X having a perovskite crystal structure. Therefore, the anionic atom X is not particularly limited as long as it is an atom that can form the perovskite crystal structure by becoming the anion X. The anionic atom X is synonymous with the anionic atom demonstrated with the said anion X, and its preferable thing is also the same.

When a is 1, the perovskite compound represented by the formula (I) is a perovskite compound represented by the following formula (I-1), and when a is 2, the following formula (I-2) It is a perovskite compound represented.
Formula (I-1): AMX ₃
Formula (I-2): A ₂ MX ₄

In formula (I-1) and formula (I-2), A represents a periodic table group 1 element or a cationic organic group, and is synonymous with A of the said formula (I), and its preferable thing is also the same.
M represents a metal atom other than the Group 1 element of the periodic table, and is synonymous with M in the above formula (I), and preferred ones are also the same.
X represents an anionic atom, and is synonymous with X of the said formula (I), and its preferable thing is also the same.

Here, the perovskite crystal structure will be described.
As described above, the perovskite crystal structure contains the cation A, the metal cation M, and the anion X as constituent ions.
FIG. 3A is a diagram showing a basic unit lattice of a perovskite crystal structure, and FIG. 3B is a diagram showing a structure in which the basic unit lattice is three-dimensionally continuous in the perovskite crystal structure. FIG. 3C is a diagram showing a layered structure in which inorganic layers and organic layers are alternately stacked in a perovskite crystal structure.
In the perovskite compound represented by the formula (I-1), as shown in FIG. 3A, a cation A is arranged at each apex, a metal cation M is arranged at the body center, and the metal cation M is the center. A cubic basic unit cell in which an anion X is arranged at each face center of the cubic crystal. As shown in FIG. 3 (b), one basic unit cell shares the cation A and the anion X with each of the other 26 adjacent basic unit cells (surrounding), and is three-dimensional. The basic unit cell has a continuous structure.

On the other hand, the perovskite compound represented by the formula (I-2) has an MX ₆ octahedron composed of a metal cation M and an anion X with respect to the perovskite compound represented by the formula (I-1). Same in respect, but different in basic unit cell and its arrangement. That is, the perovskite compound represented by the formula (I-2) is an inorganic layer formed by arranging MX ₆ octahedrons in a two-dimensional (planar) form as shown in FIG. And an organic layer formed by alternately inserting a cation A between the inorganic layers.
In such a layered structure, the basic unit cell shares the cation A and the anion X with other adjacent basic unit cells in the plane of the same layer. On the other hand, the basic unit cell does not share the cation A and the anion X in different layers. This layered structure has a two-dimensional layer structure in which the inorganic layer is divided by the organic group of the cation A. As shown in FIG. 3C, the organic group in the cation A functions as a spacer organic group between the inorganic layers.
For perovskite compounds having a layered structure, see, for example, New. J. et al. Chem. , 2008, 32, 1736.

In the perovskite compound, a possible crystal structure is determined by the cation A (group 1 element of the periodic table or cationic organic group A). For example, when the cation A is a cation of a group 1 element of the periodic table or an organic cation of a cationic organic group A having a substituent R ^1a having 1 carbon atom, the perovskite compound is represented by the formula (I-1) It is easy to take a cubic crystal structure. Examples of such a cation A include CH ₃ —NH ₃ and each cation such as HC (═NH) —NH ₃ among organic cations having a group that can be represented by the formula (2). .
On the other hand, when the cation A is a cation of a cationic organic group A having a substituent R ^1a having 2 or more carbon atoms, the perovskite compound is represented by the formula (I-2) and easily takes a layered crystal structure. As such a cation A, for example, an alkyl group having 2 or more carbon atoms, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, and the above formula (2) described as the substituent R ^1a are represented. And an organic cation of the cationic organic group A having a group capable of being substituted (provided that R ^1b and R ^1c are substituents).

  The perovskite compound used in the present invention may be either a compound represented by formula (I-1) or a compound represented by formula (I-2), or a mixture thereof. Therefore, in the present invention, at least one perovskite compound only needs to be present as a light absorber, and it is not necessary to clearly distinguish which compound is strictly based on the composition formula, molecular formula, crystal structure, and the like. .

  Specific examples of the perovskite compound used in the present invention are illustrated below, but the present invention is not limited thereby. In the following, the compound represented by the formula (I-1) and the compound represented by the formula (I-2) are described separately. However, even if it is a compound illustrated as a compound represented by a formula (I-1), depending on synthesis conditions etc., it may become a compound represented by a formula (I-2). In some cases, the mixture is a mixture of the compound represented by -1) and the compound represented by formula (I-2). Similarly, even if it is a compound illustrated as a compound represented by a formula (I-2), it may become a compound represented by a formula (I-1), and is represented by a formula (I-1). In some cases, the compound is a mixture of the compound represented by formula (I-2).

Specific examples of the compound represented by formula (I-1) include, for example, CH ₃ NH ₃ PbCl ₃ , CH ₃ NH ₃ PbBr ₃ , CH ₃ NH ₃ PbI ₃ , CH ₃ NH ₃ PbBrI ₂ , and CH ₃ NH _3. PbBr _{2 I,} include _{CH 3 NH 3 SnBr 3, CH} 3 NH 3 SnI 3, CH (= NH) NH 3 PbI 3.

Specific examples of the compound represented by the formula (I-2) include, for example, (C ₂ H ₅ NH ₃ ) ₂ PbI ₄ , (CH ₂ = CHNH ₃ ) ₂ PbI ₄ , (CH≡CNH ₃ ) ₂ PbI _{4 , (n-C 3 H 7} NH 3) 2 PbI 4, (n-C 4 H 9 NH 3) 2 PbI 4, (C 6 H 5 NH 3) 2 PbI 4, (C 6 H 3 F 2 NH 3 ) ₂ PbI ₄ , (C ₆ F ₅ NH ₃ ) ₂ PbI ₄ , (C ₄ H ₃ SNH ₃ ) ₂ PbI ₄ .
_{Here, C} 4 _{H 3} SNH 3 in _{(C 4 H 3 SNH 3)} 2 PbI 4 is aminothiophene.

The perovskite compound can be synthesized from MX ₂ and AX. For example, the said nonpatent literature 1 is mentioned. Also, Akihiro Kojima, Kenjiro Teshima, Yasuo Shirai, and Tsutomu Miyasaka, “Organometric Halide Perovskites as Visible Slightly.” Am. Chem. Soc. , 2009, 131 (17), 6050-6051.

  The amount of the light absorber used may be at least a part of the surface on which light is incident among the surfaces of the porous layer 12 or the blocking layer 14, and is preferably an amount covering the entire surface.

<Hole transport layer 3>
The hole transport layer 3 has a function of replenishing electrons to the oxidant of the light absorber. The hole transport layer 3 is provided between the first electrode 1 and the second electrode 2. The hole transport layer 3 is preferably provided between the photosensitive layer 13 and the second electrode 2, and at least a part of the hole transport layer 3 is provided in contact with the photosensitive layer 13. The hole transport layer 3 may be a liquid layer such as a liquid electrolyte, or may be a solid layer (solid layer). In the present invention, variation in photoelectric conversion efficiency can be reduced even if the hole transport layer is a solid layer. Therefore, a solid layer can be preferably selected as the hole transport layer.

  Although the film thickness of the positive hole transport layer 3 is not specifically limited, 50 micrometers or less are preferable, 1 nm-10 micrometers are more preferable, 5 nm-5 micrometers are further more preferable, and 10 nm-1 micrometer are especially preferable. The film thickness of the hole transport layer 3 corresponds to the distance between the second electrode 2 and the surface of the porous layer 12 or the surface of the photosensitive layer 13. This film thickness can be measured by observing the cross section of the photoelectric conversion element 10 using a scanning electron microscope (SEM) or the like.

  In the present invention, the total film thickness of the porous layer 12, the photosensitive layer 13, and the hole transport layer 3 is not particularly limited, but is preferably 15 to 100 μm, more preferably 15 to 50 μm, and further preferably 15 to 30 μm. preferable. The total film thickness of the porous layer 12, the photosensitive layer 13, and the hole transport layer 3 is determined by observing the cross section of the photoelectric conversion element 1 using a scanning electron microscope (SEM) or the like, Similarly, it is set as the average value of the longest distance of 10 sections.

The hole transport material for forming the hole transport layer 3 is not particularly limited, but is an inorganic material such as CuI or CuNCS, and the organic hole transport material described in JP-A-2001-291534, paragraphs 0209-0212. Etc. The organic hole transport material is preferably a conductive polymer such as polythiophene, polyaniline, polypyrrole and polysilane, a spiro compound in which two rings share a tetrahedral structure such as C and Si, and triarylamine. And aromatic amine compounds such as triphenylene compounds, nitrogen-containing heterocyclic compounds, and liquid crystalline cyano compounds.
The hole transport material is preferably an organic hole transport material that can be applied by a solution and becomes a solid. Specifically, 2,2 ′, 7,7′-tetrakis- (N, N-di-p-methoxyphenyl) is preferable. Amine) -9,9-spirobifluorene (also referred to as Spiro-OMeTAD), poly (3-hexylthiophene-2,5-diyl), 4- (diethylamino) benzaldehyde diphenylhydrazone, polyethylenedioxythiophene (PEDOT), etc. Is mentioned.

<Second electrode 2>
The second electrode 2 functions as a positive electrode in the solar cell. The 2nd electrode 2 will not be specifically limited if it has electroconductivity, Usually, it can be set as the same structure as the electroconductive support body 11. FIG. If the strength is sufficiently maintained, the support 11a is not necessarily required.
The structure of the second electrode 2 is preferably a structure having a high current collecting effect. In order for light to reach the photosensitive layer 13, at least one of the conductive support 11 and the second electrode 2 must be substantially transparent. In the solar cell of this invention, it is preferable that the electroconductive support body 11 is transparent and sunlight is entered from the support body 11a side. In this case, it is more preferable that the second electrode 2 has a property of reflecting light.

Examples of the material for forming the second electrode 2 include platinum (Pt), gold (Au), nickel (Ni), copper (Cu), silver (Ag), indium (In), ruthenium (Ru), palladium ( Examples thereof include metals such as Pd), rhodium (Rh), iridium (Ir), and osnium (Os), the above-described conductive metal oxides, and carbon materials. The carbon material may be a conductive material formed by bonding carbon atoms to each other, and examples thereof include fullerene, carbon nanotube, graphite, and graphene.
The second electrode 2 is preferably glass or plastic having a metal or conductive metal oxide thin film (including a thin film formed by vapor deposition), glass having a thin film of Au or Pt, or glass vapor-deposited with Pt. Is particularly preferred.

  The film thickness of the 2nd electrode 2 is not specifically limited, 0.01-100 micrometers is preferable, 0.01-10 micrometers is more preferable, 0.01-1 micrometer is especially preferable.

<Other configurations>
In the present invention, in order to prevent contact between the first electrode 1 and the second electrode 2, a spacer or a separator can be used instead of the blocking layer 14 or together with the blocking layer 14.
A hole blocking layer may be provided between the second electrode 2 and the hole transport layer 3.

<< Solar cell >>
The solar cell of this invention is comprised so that the photoelectric conversion element of this invention may work with respect to the external circuit 6, as FIG. 1 and FIG. 2 shows, for example. The external circuit connected to the first electrode 1 (conductive support 11) and the second electrode 2 can be used without particular limitation.
In the solar cell of the present invention, it is preferable to seal the side surface with a polymer, an adhesive or the like in order to prevent deterioration of the components and transpiration.
The solar cell to which the photoelectric conversion element of the present invention is applied is not particularly limited, and examples thereof include solar cells described in Patent Document 1, Non-Patent Documents 1 and 2.

  As described above, the photoelectric conversion element and the perovskite sensitized solar cell of the present invention have a porous layer having a film thickness of 15 to 100 μm, preferably a solid hole transport layer, and have an individual photoelectric conversion efficiency. Small difference and stable battery performance.

<< Photoelectric Conversion Element and Solar Cell Manufacturing Method >>
The photoelectric conversion element and solar cell of the present invention can be produced according to known production methods, for example, the methods described in Patent Document 1, Non-Patent Documents 1 and 2, and the like.
Below, the manufacturing method of the photoelectric conversion element and solar cell of this invention is demonstrated easily.

If desired, a blocking layer 14 and a porous layer 12 are formed on the surface of the conductive support 11.
The blocking layer 14 can be formed by, for example, a method of applying a dispersion containing the insulating material or a precursor compound thereof on the surface of the conductive support 11 and baking it, or a spray pyrolysis method.

The material forming the porous layer 12 is preferably used as fine particles, and more preferably used as a dispersion containing fine particles.
The method for forming the porous layer 12 is not particularly limited, and examples thereof include a wet method, a dry method, and other methods [for example, a method described in Chemical Review, Vol. 110, page 6595 (2010)]. Can be mentioned. In these methods, it is preferable that the dispersion (paste) is applied to the surface of the conductive support 11 and then baked at a temperature of 100 to 800 ° C. for 10 minutes to 10 hours. Thereby, microparticles | fine-particles can be stuck.
When firing is performed a plurality of times, the firing temperature other than the last firing (the firing temperature other than the last firing) is preferably performed at a temperature lower than the last firing temperature (the last firing temperature). For example, when a titanium oxide paste is used, the firing temperature other than the last can be set within a range of 50 to 300 ° C. Moreover, the last baking temperature can be set so that it may become higher than the baking temperature other than the last within the range of 100-600 degreeC. When a glass support is used as the support 11a, the firing temperature is preferably 60 to 500 ° C.

The amount of the porous material applied when forming the porous layer 12 is appropriately set according to the thickness of the porous layer 12 to be formed, the number of times of application, and the like, and is not particularly limited. The coating amount of the porous material per 1 m ² of the surface area of the conductive support 11 is preferably, for example, 0.5 to 500 g, and more preferably 5 to 100 g.

Next, the photosensitive layer 13 is provided.
First, a light absorber solution for forming a photosensitive layer is prepared. The light absorber solution contains MX ₂ and AX, which are raw materials for the perovskite compound. Here, A and X are synonymous with A and X in the above formula (I). M has the same ^meaning as M ^A1 and M ^{A2 in} the above formula (I). In this light absorber solution, the molar ratio of MX ₂ to AX is adjusted according to a or the like of the perovskite compound.
Next, the prepared light absorber solution is applied to the surface of the porous layer 12 and dried. Thereby, a perovskite compound is formed on the surface of the porous layer 12.

A hole transport material solution containing a hole transport material is applied onto the photosensitive layer 13 thus provided, and dried to form the hole transport layer 3.
The hole transport material solution is excellent in applicability and easily penetrates into the pores of the porous layer 12, and the concentration of the hole transport material is 0.1 to 1.0 M (mol / L). Is preferred.

  After forming the hole transport layer 3, the second electrode 2 is formed, and a photoelectric conversion element and a solar cell are manufactured.

  The film thickness of each layer can be adjusted by appropriately changing the concentration of each dispersion or solution and the number of coatings. For example, when the thick photosensitive layer 13B shown in FIG. 2 is provided, the dispersion may be applied and dried several times.

  Each of the dispersions and solutions described above may contain additives such as a dispersion aid and a surfactant, if necessary.

  Examples of the solvent or dispersion medium used in the method for manufacturing a photoelectric conversion element and a solar cell include, but are not limited to, the solvents described in JP-A No. 2001-291534. In the present invention, an organic solvent is preferable, and an alcohol solvent, an amide solvent, a nitrile solvent, a hydrocarbon solvent, a lactone solvent, and a mixed solvent of two or more of these are more preferable. As the mixed solvent, a mixed solvent of an alcohol solvent and a solvent selected from an amide solvent, a nitrile solvent, or a hydrocarbon solvent is preferable. Specifically, methanol, ethanol, γ-butyrolactone, chlorobenzene, acetonitrile, dimethylformamide (DMF) or dimethylacetamide, or a mixed solvent thereof is preferable.

  The application method of the solution or dispersant forming each layer is not particularly limited, and spin coating, extrusion die coating, blade coating, bar coating, screen printing, stencil printing, roll coating, curtain coating, spray coating, dip coating, inkjet A known coating method such as a printing method or a dipping method can be used. Of these, spin coating, screen printing, dipping, and the like are preferable.

  The solar cell is manufactured by connecting an external circuit to the first electrode 1 and the second electrode 2 of the photoelectric conversion element manufactured as described above.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.

Example 1
(Production of photoelectric conversion element and solar cell (sample No. 101))
The photoelectric conversion element 10A and the solar cell shown in FIG. 1 were manufactured by the following procedure. In addition, when the film thickness of the photosensitive layer 13 is large, it corresponds to the photoelectric conversion element 10B and the solar cell shown in FIG.

<Deposition of blocking layer 14>
A 15% by mass isopropanol solution of titanium diisopropoxide bis (acetylacetonate) (Aldrich) was diluted with 1-butanol to prepare a 0.02M blocking layer solution.

A fluorine-doped SnO ₂ conductive film (transparent electrode 11b) was formed on a glass substrate (support 11a, thickness 2.2 mm) to produce a conductive support 11. A blocking layer 14 (film thickness 50 nm) was formed on the SnO ₂ conductive film at 450 ° C. by spray pyrolysis using the prepared 0.02M blocking layer solution.

<Deposition of porous layer 12>

Ethyl cellulose, lauric acid and terpineol were added to an ethanol dispersion of titanium oxide (TiO ₂ , anatase, average particle size 20 nm) to prepare a titanium oxide paste.

The prepared titanium oxide paste was applied onto the blocking layer 14 by screen printing and baked. The titanium oxide paste was applied and fired twice. As the firing temperature, the first firing was performed at 130 ° C., and the second firing was performed at 500 ° C. for 1 hour. The obtained sintered body of titanium oxide was immersed in a 40 mM TiCl ₄ aqueous solution and then heated at 60 ° C. for 1 hour and subsequently at 500 ° C. for 30 minutes to form a porous layer 12 made of titanium oxide (TiO ₂ ). A film was formed.

<Formation of photosensitive layer 13A>
A 40% methanol solution of methylamine (27.86 mL) and an aqueous solution of 57% by mass of hydrogen iodide (hydroiodic acid, 30 mL) were stirred in a flask at 0 ° C. for 2 hours, and then concentrated to obtain CH _3. A crude NH ₃ I was obtained. The obtained crude CH ₃ NH ₃ I was dissolved in ethanol and recrystallized from diethyl ether. The precipitated crystals were collected by filtration and dried under reduced pressure at 60 ° C. for 24 hours to obtain purified CH ₃ NH ₃ I.
Next, the purified CH ₃ NH ₃ I and PbI ₂ were mixed at a molar ratio of 2: 1 and stirred and mixed in γ-butyrolactone at 60 ° C. for 12 hours, and then filtered through a polytetrafluoroethylene (PTFE) syringe filter. A light absorber solution A having a concentration of 40% by mass was prepared.

The prepared light absorbent solution A was applied on the porous layer 12 formed on the conductive support 11 by spin coating (at 2000 rpm for 60 seconds and then at 3000 rpm for 60 seconds). The applied light absorber solution A was dried on a hot plate at 100 ° C. for 40 minutes to provide a photosensitive layer 13 containing a perovskite compound represented by CH ₃ NH ₃ PbI ₃ .
In this way, the first electrode 1 was produced.

<Film Formation of Hole Transport Layer 3>
Spiro-OMeTAD (180 mg) as a hole transport material was dissolved in chlorobenzene (1 mL). To this chlorobenzene solution, an acetonitrile solution (37.5 μL) in which lithium-bis (trifluoromethanesulfonyl) imide (170 mg) was dissolved in acetonitrile (1 mL) and t-butylpyridine (TBP, 17.5 μL) were added. A hole transport material solution was prepared by mixing.

  Next, the prepared hole transport material solution is applied onto the photosensitive layer 13 of the first electrode 1 by a spin coating method, and the applied hole transport material solution is dried to obtain a solid hole transport layer 3 ( A film thickness of 0.1 μm) was formed.

<Preparation of the second electrode 2>
Gold was vapor-deposited on the hole transport layer 3 by the vapor deposition method, and the 2nd electrode 2 (film thickness of 0.3 micrometer) was produced.
Thus, the photoelectric conversion element and solar cell (sample No. 101) of this invention were manufactured.

(Production of photoelectric conversion element and solar cell (sample Nos. 102 to 108 and c101 to c103))
In the production of the photoelectric conversion element and the solar cell (sample No. 101), the present invention was carried out in the same manner as the photoelectric conversion element and the solar cell (sample No. 101) except that the number of times of applying and baking the titanium oxide paste was changed. Photoelectric conversion elements and solar cells (Sample Nos. 102 to 108), and photoelectric conversion elements and solar cells (Sample Nos. C101 to c103) for comparison were manufactured, respectively.
In addition, when the application and firing of titanium oxide were performed three times or more, the firing temperature of the titanium oxide paste was set to 130 ° C. except for the last, and the last firing temperature was set to 500 ° C.

(Manufacture of photoelectric conversion element and solar cell (sample No. 109))
In the manufacture of the photoelectric conversion element and the solar cell (sample No. 101), the following light absorbent solution B was used instead of the light absorbent solution A, and 160 of the light absorbent solution B applied on the porous layer 12 was used. A photoelectric conversion element and a solar cell (sample No. 109) of the present invention were produced in the same manner as the photoelectric conversion element and solar cell (sample No. 101) except that it was dried at 40 ° C. for 40 minutes.
The photosensitive layer of the manufactured photoelectric conversion element and solar cell (sample No. 109) contained a perovskite compound represented by CH (= NH) NH ₃ PbI ₃ .
<Light absorber solution B>
Formamidine acetate and an aqueous solution of 57% by mass hydrogen iodide containing 2 equivalents of hydrogen iodide with respect to formamidine acetate were stirred in a flask at 0 ° C. for 1 hour and then raised to 50 ° C. Warmed and stirred for an additional hour and mixed. The obtained solution was concentrated to obtain a crude formamidine hydrogen iodide. The obtained crude product was recrystallized with diethyl ether, and the precipitated crystals were collected by filtration and dried under reduced pressure at 50 ° C. for 10 hours to obtain purified formamidine hydrogen iodide salt. Next, purified formamidine hydrogen iodide and PbI ₂ were mixed at a molar ratio of 2: 1 and mixed in dimethylformamide (DMF) with stirring at 60 ° C. for 3 hours, and then a polytetrafluoroethylene (PTFE) syringe. It filtered with the filter and 40 mass% light absorber solution B was prepared.

(Manufacture of photoelectric conversion element and solar cell (sample No. 110))
In the manufacture of the photoelectric conversion element and the solar cell (sample No. 101), the following light absorbent solution C was used in place of the light absorbent solution A, and the light absorbent solution C applied on the porous layer 12 was 130. A photoelectric conversion element and a solar cell (sample No. 110) of the present invention were produced in the same manner as the photoelectric conversion element and solar cell (sample No. 101) except that the film was dried at 40 ° C. for 40 minutes.
The photosensitive layer of the manufactured photoelectric conversion element and solar cell (sample No. 110) contained a perovskite compound represented by (CH ₃ CH ₂ —NH ₃ ) ₂ PbI ₄ .
<Preparation of light absorber solution C>
A 40% ethanol solution of ethylamine and an aqueous solution of 57% by mass of hydrogen iodide were stirred in a flask at 0 ° C. for 2 hours and then concentrated to obtain a CH ₃ CH ₂ NH ₃ I crude product. The obtained crude product was dissolved in ethanol and recrystallized from diethyl ether. The precipitated crystals were collected by filtration and dried under reduced pressure at 60 ° C. for 12 hours to obtain purified CH ₃ CH ₂ NH ₃ I. Subsequently, purified CH ₃ CH ₂ NH ₃ I and PbI ₂ were mixed at a molar ratio of 3: 1 and mixed in dimethylformamide (DMF) with stirring at 60 ° C. for 5 hours, and then polytetrafluoroethylene (PTFE). It filtered with the syringe filter and prepared the light absorber solution C with a density | concentration of 40 mass%.

(Measurement of film thickness of porous layer)
The film thickness of the porous layer in the manufactured solar cells (Sample Nos. 101 to 110 and c101 to c103) was measured as follows based on the above measurement method. That is, the cross section of each solar cell was observed using a scanning electron microscope “SU-8030” (SEM, trade name, manufactured by Hitachi High-Technologies Corporation), and the observation area was horizontal (parallel) to the surface of the conductive support 11. It was divided into 10 equal parts along different directions. For each of these sections, the longest distance from the interface between the blocking layer 14 and the porous layer 14 to the surface of the porous layer 12 along the linear direction intersecting at an angle of 90 ° with respect to the surface of the conductive support 11. It was measured. The average value of the ten measured longest distances was determined and used as the film thickness of the porous layer 12 in each solar cell. The results are shown in Table 1.
The “surface of the porous layer” is as described above.

(Evaluation of variation in photoelectric conversion efficiency)
Sample No. of solar cell The variation in photoelectric conversion efficiency was evaluated as follows.
That is, each sample No. 15 samples of the solar cell were manufactured in the same manner as in the above manufacturing method, and a battery characteristic test was performed on each of the 10 samples to measure photoelectric conversion efficiency (η /%). The battery characteristic test was performed by irradiating 1000 W / m ² of pseudo-sunlight from a xenon lamp through an AM1.5 filter using a solar simulator “WXS-85H” (manufactured by WACOM). The current-voltage characteristics were measured using an IV tester, and the photoelectric conversion efficiency (η /%) was determined.

Numbers 1 to 15 were assigned in order from the one with the highest photoelectric conversion efficiency thus obtained, among which three samples Nos. 7 to 9 were selected, and the average value of the photoelectric conversion efficiencies of these three samples was calculated. The calculated average value (reference) was set to “1”. The photoelectric conversion efficiency (relative value) of each of the 15 solar cell samples with respect to the reference “1” was obtained, and the difference between the obtained photoelectric conversion efficiency (relative value) and the reference (absolute value) was 0.3 or more. The number of specimens was counted. The variation in photoelectric conversion efficiency was evaluated as follows according to the number of samples counted.
Evaluation is the first to sixth samples from which the obtained photoelectric conversion efficiency (relative value) is higher than the average value “1”, and the six samples (the obtained photoelectric conversion efficiency (relative value) is larger) (Sample group) and 6 groups (10th to 15th sample groups from the larger photoelectric conversion efficiency (relative value) obtained) having a photoelectric conversion efficiency lower than the average value “1”. And went.
In Table 1, “above average” represents the evaluation of 6 specimens (Nos. 1 to 6) that exhibited higher photoelectric conversion efficiency than the average value, and “below average” represents lower photoelectric conversion efficiency than the average value. It represents the evaluation of the specimen (No. 10-15) shown.
In the present invention, the variation evaluation of the photoelectric conversion efficiency is a target achievement level that each group is C or more, and is practically preferably B or more.
A: 1 or less B: 2 C: 3 D: 4 or more

As shown in Table 1, a solar cell (Sample Nos. 101 to 110) provided with a porous layer 12 having a film thickness of 15 to 100 μm, and further provided with a photosensitive layer made of a perovskite compound and a solid hole transport layer 3. ) All showed that variations in photoelectric conversion efficiency were reduced. In particular, it was found that when the film thickness of the porous layer 12 is 15 to 50 μm (sample Nos. 101 to 106, 109 and 110), the variation in photoelectric conversion efficiency is further reduced.
On the other hand, even when a photosensitive layer made of a perovskite compound and a solid hole transport layer are provided, when the film thickness of the porous layer is less than 15 μm (solar cell (sample No. c101 and c102)), In addition, when the film thickness of the porous layer exceeded 100 μm (solar cell (sample No. c103)), variations in photoelectric conversion efficiency were large in any case.

Example 2
(Manufacture of photoelectric conversion element and solar cell (sample No. 201))
In the manufacture of the photoelectric conversion element and the solar cell (sample No. 101), the number of coating and firing of the titanium oxide paste is changed to adjust the film thickness of the porous layer 12, and the light below instead of the light absorbent solution A is used. A photoelectric conversion element and a solar cell (sample No. 201) of the present invention were manufactured in the same manner as the manufacture of the photoelectric conversion element and the solar cell (sample No. 101) except that the absorbent solution D was used.
The photosensitive layer of the manufactured photoelectric conversion element and solar cell (sample No. 201) contained a perovskite compound represented by CH ₃ NH ₃ PbBr ₃ .
<Preparation of light absorber solution D>
A 40% methanol solution of methylamine (27.86 mL) and an aqueous solution of 57% by mass of hydrogen bromide (hydrobromic acid, 30 mL) were stirred in a flask at 0 ° C. for 2 hours, then concentrated, and CH ₃ A crude body of NH ₃ Br was obtained. The obtained crude CH ₃ NH ₃ Br was dissolved in ethanol and recrystallized from diethyl ether. The precipitated crystals were collected by filtration and dried under reduced pressure at 60 ° C. for 24 hours to obtain purified CH ₃ NH ₃ Br. Next, purified CH ₃ NH ₃ Br and PbBr ₂ were mixed at a molar ratio of 2: 1, stirred and mixed in γ-butyrolactone at 60 ° C. for 12 hours, filtered through a PTFF syringe filter, and light having a concentration of 40% by mass. Absorbent solution D was prepared.

(Manufacture of photoelectric conversion element and solar cell (sample No. 202))
In the manufacture of the photoelectric conversion element and the solar cell (sample No. 101), the number of coating and firing of the titanium oxide paste is changed to adjust the film thickness of the porous layer 12, and the light below instead of the light absorbent solution A is used. A photoelectric conversion element and a solar cell (sample No. 202) of the present invention were manufactured in the same manner as in the manufacture of the photoelectric conversion element and the solar cell (sample No. 101) except that the absorbent solution E was used.
The photosensitive layer of the produced photoelectric conversion element and solar cell (sample No. 202) contained a perovskite compound represented by CH ₃ NH ₃ PbI ₂ Cl.
<Preparation of light absorber solution E>
A 40% methanol solution of methylamine (27.86 mL) and an aqueous solution of 57% by mass of hydrogen iodide (hydroiodic acid, 30 mL) were stirred in a flask at 0 ° C. for 2 hours, and then concentrated to obtain CH _3. A crude NH ₃ I was obtained. The obtained crude CH ₃ NH ₃ I was dissolved in ethanol and recrystallized from diethyl ether. The precipitated crystals were collected by filtration and dried under reduced pressure at 60 ° C. for 24 hours to obtain purified CH ₃ NH ₃ I. Subsequently, purified CH ₃ NH ₃ I, PbI ₂ and PbCl ₂ were mixed at a molar ratio of 4: 1: 1 and stirred and mixed in γ-butyrolactone at 60 ° C. for 12 hours, and then filtered through a PTFE syringe filter to obtain a concentration. A 40 mass% light absorber solution E was prepared.

(Measurement of film thickness of porous layer)
The film thickness of the porous layer 12 in the thus produced solar cells (Sample Nos. 201 and 202) was measured in the same manner as in “Measurement of film thickness of porous layer” in Example 1. The results are shown in Table 2.

(Evaluation of variation in photoelectric conversion efficiency)
The variation in photoelectric conversion efficiency in the solar cells (Sample Nos. 201 and 202) was evaluated in the same manner as in “Evaluation of variation in photoelectric conversion efficiency” in Example 1. The results are shown in Table 2.

  As shown in Table 2, a solar cell (sample Nos. 201 and 202) provided with a porous layer 12 having a thickness of 20 μm, and further provided with a photosensitive layer made of a perovskite compound and a solid hole transport layer 3 was obtained. It was found that the variation in photoelectric conversion efficiency was small regardless of the type of light absorber.

1A, 1B First electrode 11 Conductive support 11a Support 11b Transparent electrode 12 Porous layer 13A, 13B Photosensitive layer (light absorption layer)
14 Blocking layer 2 Second electrode 3A, 3B Hole transport layer 6 External circuit (lead)
10A, 10B Photoelectric conversion element 100A, 100B System M applying photoelectric conversion element for battery use Electric motor

Claims (13)

A first electrode having a porous layer provided on a conductive support, and a photosensitive layer in which a light absorber is provided on the surface of the porous layer; a second electrode facing the first electrode; A photoelectric conversion element having a hole transport layer provided between the first electrode and the second electrode,
The light absorber has a perovskite crystal structure having a cation of a group 1 element of the periodic table or a cationic organic group A, a cation of a metal atom M other than the group 1 element of the periodic table, and an anion of an anionic atom X Containing a compound,
The photoelectric conversion element whose film thickness of the said porous layer is 15-100 micrometers.   The photoelectric conversion element according to claim 1, wherein the porous layer has a thickness of 15 to 50 μm.   The photoelectric conversion element according to claim 1, wherein the porous layer has a thickness of 15 to 30 μm.   4. The photoelectric device according to claim 1, wherein the porous layer includes at least one selected from the group consisting of titanium, tin, zinc, zirconium, aluminum and silicon oxides, and carbon nanotubes. 5. Conversion element.   The photoelectric conversion element according to claim 1, wherein the porous layer contains titanium oxide or aluminum oxide. The photoelectric conversion element according to claim 1, wherein the compound having a perovskite crystal structure is a compound represented by the following formula (I).
Formula (I): A _a M _m X _x
In the formula, A represents a group 1 element of the periodic table or a cationic organic group. M represents a metal atom other than the first group element of the periodic table. X represents an anionic atom. a represents 1 or 2, m represents 1, and a, m, and x satisfy a + 2m = x. The photoelectric conversion element according to claim 1, wherein the compound having a perovskite crystal structure includes a compound represented by the following formula (I-1).
Formula (I-1): AMX ₃
In the formula, A represents a group 1 element of the periodic table or a cationic organic group. M represents a metal atom other than the first group element of the periodic table. X represents an anionic atom. The photoelectric conversion element according to claim 1, wherein the compound having a perovskite crystal structure includes a compound represented by the following formula (I-2).
Formula (I-2): A ₂ MX ₄
In the formula, A represents a group 1 element of the periodic table or a cationic organic group. M represents a metal atom other than the first group element of the periodic table. X represents an anionic atom. The photoelectric conversion element according to any one of claims 6 to 8, wherein the A is represented by the following formula (1).
Formula (1): R ^1a —NH ₃
In the formula, R ^1a represents a substituent. The photoelectric conversion device according to claim 9, wherein R ^1a is an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, or a group that can be represented by the following formula (2).

In formula, ^Xa represents NR ^<1c> , an oxygen atom, or a sulfur atom. R ^1b and R ^1c each independently represent a hydrogen atom or a substituent. *** represents a bonding position with N in the formula (1).   The photoelectric conversion element according to claim 1, wherein X is a halogen atom.   The photoelectric conversion element according to claim 1, wherein the M is Pb or Sn.   The solar cell which has a photoelectric conversion element of any one of Claims 1-12.

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