JP6509342B2 - PHOTOELECTRIC CONVERSION ELEMENT, METHOD FOR MANUFACTURING PHOTOELECTRIC CONVERSION ELEMENT, AND SOLAR CELL - Google Patents

Description

  The present invention relates to a photoelectric conversion element, a method of manufacturing a photoelectric conversion element, and a solar cell.

  The photoelectric conversion element is used for various light sensors, copying machines, solar cells and the like. Solar cells are expected to be put into practical use as non-depleting solar energy. Among these, in the dye-sensitized solar cell using an organic dye or Ru bipyridyl complex as a sensitizer, research and development is actively promoted, and the photoelectric conversion efficiency has reached about 11%.

  On the other hand, in recent years, research results have been reported that solar cells using metal halides having a perovskite crystal structure as light absorbers can achieve relatively high photoelectric conversion efficiency, and are attracting attention (for example, Non Patent Literature 1). Non-Patent Document 1 describes a mode in which a layer (underlayer) of titanium oxide is provided on a conductive support, and a porous layer supporting a light absorbing agent is provided thereon.

Science, 2012, vol. 338, p. 643-647

  In a photoelectric conversion element using a compound having a perovskite crystal structure (hereinafter, also referred to as "perovskite compound") as a light absorber, certain achievements have been obtained for the improvement of photoelectric conversion efficiency. However, a photoelectric conversion element using a perovskite compound has attracted attention in recent years, and little is known about battery performance other than the photoelectric conversion efficiency.

In the practical application of photoelectric conversion elements, in addition to high photoelectric conversion efficiency, it is required to highly reduce variation in performance among manufactured elements. However, the photoelectric conversion element using the perovskite compound has many unknown points in the relation between the structure and the variation in performance, and the variation in photoelectric conversion efficiency between the elements has not been sufficiently reduced.
The present invention provides a photoelectric conversion element using a light absorbing agent containing a perovskite compound, which is excellent in photoelectric conversion efficiency and can highly reduce variations in photoelectric conversion efficiency between elements. To be a task. Moreover, this invention makes it a subject to provide the solar cell using the said photoelectric conversion element. Furthermore, this invention makes it a subject to provide the formation method of the base layer suitable for manufacture of the said photoelectric conversion element.

As a result of intensive investigations in view of the above problems, the inventors of the present invention have found that when manufacturing a photoelectric conversion element using a perovskite compound as a light absorber, the coating solution used for forming the underlayer on the conductive support is specific. By using a solvent, the maximum height roughness Rz of the formed underlayer can be reduced to a specific level, and a photosensitive layer containing a perovskite compound can be formed on the surface of such an underlayer, if necessary. It has been found that the above problems can be solved by providing
The present invention has been further studied based on these findings and has been completed.

That is, the above-mentioned subject of the present invention is solved by the following means.
[1]
A method of manufacturing a photoelectric conversion device , comprising: a first electrode having a base layer, a porous layer, and a photosensitive layer containing a light absorbing agent in this order on a conductive support; and a second electrode facing the first electrode. And
The light absorber includes a compound having a perovskite crystal structure having a cation or an organic cation of a periodic table first group element, a cation of a metal atom other than the periodic table first group element, and an anion,
Maximum height roughness Rz of the base layer surface Ri der less 250 nm,
The manufacturing method comprises the steps of applying a coating solution containing an inorganic semiconductor material or a precursor thereof onto the conductive support to form a coating film, and firing the coating film to form the underlayer. Including and
The solvent of the coating solution is a solvent S ₁ higher than the boiling point 0.99 ° C., boiling point is less than 0.99 ° C., and a boiling point above the boiling point of the solvent S ₁ is contained and low solvent S ₂ or 50 ° C., this The content of the solvent S _{1 in} the solvent is 1% by mass or more,
Formation of the underlying layer, the coating film, heated for 1 minute or more at a temperature higher than the low boiling point of the solvent S ₂ than the boiling point of the solvent S _1, then fired at a temperature higher than the boiling point of the solvent S ₁ The manufacturing method of the photoelectric conversion element performed by performing .
[2]
The manufacturing method of the photoelectric conversion element as described in [1] whose said Rz is 230 nm or less.
[3]
The manufacturing method of the photoelectric conversion element as described in [1] or [2] whose said Rz is 200 nm or less.
[4]
The manufacturing method of the photoelectric conversion element as described in any one of [1]-[3] in which the said base layer is formed with the inorganic semiconductor material .
[5 ]
The manufacturing method of the photoelectric conversion element according to any one of [1] to [4] , wherein the solvent in the coating solution contains 3 to 10% by mass of the solvent S ₁ .
[ 6 ]
Boiling point of the solvent S ₁ is at 250 ° C. or higher, (1) a method for manufacturing a photoelectric conversion device according to any one of to [5].

  In the present specification, the notations of the respective formulas may be partially indicated as the explicit formulas for the purpose of understanding the chemical structure of the compound. Accordingly, in each formula, a partial structure is referred to as a (substituted) group, an ion, an atom or the like, but in the present specification, in addition to the (substituted) group, an ion, an atom, etc., It may mean an element group or an element constituting an ion (substituted) group or ion.

  In the present specification, the notation of a compound is used to include the salt itself and the ion as well as the compound itself. Moreover, it is a meaning including what changed a part of structure in the range which show | plays the target effect. Furthermore, as for groups or compounds in which no substitution or substitution is specified, it is meant to include groups or compounds having any substituent, as long as the desired effects are exhibited.

  In the present specification, when there are a plurality of substituents or the like represented by a specific code, or when a plurality of substituents or the like are simultaneously defined, the respective substituents or the like may be identical to or different from each other unless otherwise specified. May be The same applies to the definition of the number of substituents and the like.

  Moreover, in this specification, the numerical range represented using "-" means the range which includes the numerical value described before and after "-" as a lower limit and an upper limit.

The photoelectric conversion element of the present invention is excellent in photoelectric conversion efficiency, and variation in photoelectric conversion efficiency between elements can be highly suppressed. In addition, the solar cell of the present invention is excellent in photoelectric conversion efficiency, and the variation in photoelectric conversion efficiency among the cells can be highly suppressed. Furthermore, according to the method for forming an underlayer according to the present invention, the photoelectric conversion device according to the present invention is applied to the manufacture of a photoelectric conversion device using a perovskite compound as a light absorbing agent, whereby the variation of photoelectric conversion efficiency among the devices is highly suppressed. It is possible to manufacture a conversion element.
The above and other features and advantages of the present invention will become more apparent from the following description with reference to the accompanying drawings as appropriate.

It is sectional drawing shown typically about the preferable aspect of the photoelectric conversion element of this invention. It is sectional drawing shown typically about the preferable aspect which has a thick photosensitive layer of the photoelectric conversion element of this invention. It is sectional drawing typically shown about another preferable aspect of the photoelectric conversion element of this invention. It is sectional drawing shown typically about another preferable aspect of the photoelectric conversion element of this invention. It is drawing which shows the positional relationship with respect to the whole base layer surface of the measurement area of Rz of a base layer.

<< photoelectric conversion element >>
The photoelectric conversion element of the present invention has a first electrode having a conductive support, an underlayer, and a photosensitive layer containing a light absorbing agent, and a second electrode opposed to the first electrode. Here, that the first electrode and the second electrode face each other means that the first electrode and the second electrode are stacked in contact with each other, and the first electrode and the second electrode are stacked via another layer. This means that both forms of the form (that is, the form in which the first electrode and the second electrode are provided to face each other with the other layer interposed therebetween) are included.
The photoelectric conversion device of the present invention preferably has a hole transport layer provided between the first electrode and the second electrode. The underlayer, the photosensitive layer and the second electrode are provided in this order on the conductive support. That is, when the photoelectric conversion element has a hole transport layer, the base layer, the photosensitive layer, the hole transport layer and the second electrode are provided in this order on the conductive support. It is also preferable that the photosensitive layer be provided on the porous layer, in which case a base layer, a porous layer, a photosensitive layer, (if necessary, a hole transport layer), and a second electrode are provided in this order. There is.
The light absorber contains at least one perovskite compound described later. The light absorbing agent may contain a light absorbing agent other than the perovskite compound in combination with the perovskite compound. Examples of light absorbers other than the perovskite compounds include metal complex dyes and organic dyes.
In the present invention, as an embodiment having a photosensitive layer on the porous layer, for example, an embodiment in which the photosensitive layer is provided in the form of a thin film on the surface of the porous layer (see FIG. 1) Aspects provided (see FIGS. 2 and 4) can be mentioned. The photosensitive layer may be provided directly on the surface of the underlayer (see FIG. 3). The photosensitive layer may be provided linearly or dispersedly, but is preferably provided in the form of a film.

  The configuration of the photoelectric conversion element of the present invention is not particularly limited except for the configuration specified in the present invention, and known configurations relating to the photoelectric conversion element and the solar cell can be adopted. Each layer which comprises the photoelectric conversion element of this invention may be designed according to the objective, for example, may be formed in a single | mono layer, or may be formed in multiple layers.

Hereinafter, the preferable aspect of the photoelectric conversion element of this invention is demonstrated.
In FIGS. 1 to 4, the same reference numerals indicate the same components (members).
FIGS. 1, 2 and 4 emphasize the size of the particles forming the porous layer 12. These fine particles are preferably clogged (deposited or closely attached) to the conductive support 11 in the horizontal and vertical directions to form a porous structure.

  In the present specification, the “photoelectric conversion element 10” simply means the photoelectric conversion elements 10A, 10B, 10C, and 10F unless otherwise specified. The same applies to the system 100 and the first electrode 1. Moreover, simply referring to “photosensitive layer 13” means photosensitive layers 13A, 13B and 13C unless otherwise specified. Similarly, the "hole transport layer 3" means the hole transport layers 3A and 3B unless otherwise specified.

As a preferable aspect of the photoelectric conversion element of this invention, 10 A of photoelectric conversion elements shown in FIG. 1 are mentioned, for example. The system 100A shown in FIG. 1 is a system in which the photoelectric conversion element 10A is applied to a battery application that causes the operation means M (for example, an electric motor) to work with the external circuit 6.
The photoelectric conversion element 10A includes a first electrode 1A, a second electrode 2, and a hole transport layer 3A including a hole transport material described later between the first electrode 1A and the second electrode 2 There is.
The first electrode 1A has a conductive support 11 composed of a support 11a and a transparent electrode 11b, a porous layer 12, and a photosensitive layer 13A on the porous layer 12. Further, the base layer 14 is provided on the transparent electrode 11 b, and the porous layer 12 is formed on the base layer 14. As described above, in the photoelectric conversion element 10A having the porous layer 12, the surface area of the photosensitive layer 13A is increased, so it is estimated that the charge separation and the charge transfer efficiency are improved.

  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. 1 is thickly provided. In the photoelectric conversion element 10B, the hole transport layer 3B is thinly provided. The photoelectric conversion element 10B is different from the photoelectric conversion element 10A shown in FIG. 1 in the film thickness (layer thickness) of the photosensitive layer 13B and the hole transport layer 3B, but the photoelectric conversion element 10A is different from the photoelectric conversion element 10A except these points. It is configured similarly.

  The photoelectric conversion element 10C shown in FIG. 3 schematically shows another preferable embodiment of the photoelectric conversion element of the present invention. The photoelectric conversion element 10C is different from the photoelectric conversion element 10B shown in FIG. 2 in that the porous layer 12 is not provided, but other than this point, the photoelectric conversion element 10C is configured in the same manner as the photoelectric conversion element 10B. That is, in the photoelectric conversion element 10C, the photosensitive layer 13C is formed on the surface of the base layer 14 in a thick film shape. In the photoelectric conversion element 10C, the hole transport layer 3B can be provided as thick as the hole transport layer 3A.

  The photoelectric conversion element 10F shown in FIG. 4 schematically shows still another preferable embodiment of the photoelectric conversion element of the present invention. The photoelectric conversion element 10F is different from the photoelectric conversion element 10B shown in FIG. 2 in that the hole transport layer 3B is not provided, but the photoelectric conversion element 10F is configured the same as the photoelectric conversion element 10B except this point.

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 10A, the light transmitted through the conductive support 11 or transmitted through the second electrode 2 and incident on the photosensitive layer 13 excites the light absorbing agent. The excited light absorber has high energy electrons and can emit the electrons. A light absorber that emits high energy electrons becomes an oxidant.

  In the photoelectric conversion elements 10A, 10B, 10C and 10F, electrons emitted from the light absorbing agent move between the light absorbing agents and reach the conductive support 11. At this time, the light absorbing agent that has emitted high-energy electrons is an oxidant. Electrons reaching the conductive support 11 work in the external circuit 6, and then pass through the second electrode 2 (if there is the hole transport layer 3, further via the hole transport layer 3), the photosensitive layer Return to 13. The light absorber is reduced by the electrons returned to the photosensitive layer 13.

In the photoelectric conversion element 10 of the present invention, the flow of electrons from the photosensitive layer 13 to the conductive support 11 differs depending on the presence or absence of the porous layer, the type thereof and the like. In the photoelectric conversion element 10 of the present invention, electron conduction occurs in which electrons move between light absorbers. Therefore, when the porous layer 12 is provided, the porous layer 12 can be formed of an insulator other than the conventional semiconductor. When the porous layer 12 is formed of a semiconductor, electron conduction in which electrons move between semiconductor fine particles in the porous layer 12 and between semiconductor fine particles 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. When the porous layer 12 is formed of an insulator, relatively high electromotive force (Voc) can be obtained by using fine particles of aluminum oxide (Al ₂ O ₃ ) as the insulator fine particles.
Note that electron conduction in the underlayer 14 also occurs when the underlayer 14 is formed of a conductor or a semiconductor.

  The photoelectric conversion element and the solar cell of the present invention are not limited to the above preferred embodiments, and the configurations and the like of the respective embodiments can be appropriately combined between the respective embodiments without departing from the spirit of the present invention. For example, in the photoelectric conversion element 10C, as in the photoelectric conversion element 10F, the hole transport layer 3B may not be provided.

  In the present invention, the materials and members used for the photoelectric conversion element or the solar cell can be prepared by an ordinary method except for the underlayer and the photosensitive layer. For a photoelectric conversion element or a solar cell using a perovskite compound, for example, Non-Patent Document 1 can be referred to. With respect to dye-sensitized solar cells, for example, JP-A 2001-291534, U.S. Pat. No. 4,927,721, U.S. Pat. No. 4,684,537, U.S. Pat. No. 5,084, No. 365, U.S. Pat. No. 5,350,644, U.S. Pat. No. 5,463,057, U.S. Pat. No. 5,525,440, JP-A-7-249790, and the like. JP 2004-220974 A and JP 2008-135197 A can be referred to.

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

<First electrode 1>
The first electrode 1 has a conductive support 11, an underlayer 14 and a photosensitive layer 13 and functions as a working electrode in the photoelectric conversion element 10.
It is also preferable that the first electrode 1 have a porous layer 12 in addition to the conductive support 11, the underlayer 14, and the photosensitive layer 13 as shown in FIGS.

-Conductive support 11-
The conductive support 11 is not particularly limited as long as it has conductivity and can support the photosensitive layer 13 and the like. The conductive support 11 is formed of a material having conductivity, for example, a metal, or a support 11a of glass or plastic and a transparent electrode 11b as a conductive film formed on the surface of the support 11a. The structure which it has is preferable.

Among them, as shown in FIGS. 1 to 4, the conductive support 11 in which the transparent electrode 11 b is formed by coating the conductive metal oxide on the surface of the support 11 a of glass or plastic is more preferable. . As the support body 11a formed with the plastics, the transparent polymer film as described in stage number 0153 of Unexamined-Japanese-Patent No. 2001-291534 is mentioned, for example. As materials 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 besides glass and plastic. As a 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 of this time, the surface area 1 m ² per 0.1~100g supports 11a are preferred. In the case of using the conductive support 11, 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 thickness of the support 11 a and the conductive support 11 is not particularly limited, and is set to an appropriate thickness. For example, 0.01 μm to 10 mm is preferable, 0.1 μm to 5 mm is more preferable, and 0.3 μm to 4 mm is particularly preferable.
When the transparent electrode 11 b is provided, the film thickness of the transparent electrode 11 b is not particularly limited, and is preferably, for example, 0.01 to 30 μm, further preferably 0.03 to 25 μm, and 0.05 to 20 μm. Is particularly preferred.

  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 the anti-reflection film in which high-refractive-index films and low-refractive-index oxide films are alternately laminated as described in JP-A 2003-123859. Well, you may have the light guide function of Unexamined-Japanese-Patent No. 2002-260746.

-Base layer 14-
In the present invention, as in the photoelectric conversion elements 10A, 10B, 10C and 10F, an undercoat layer is provided on the surface of the transparent electrode 11b, that is, between the conductive support 11 and the porous layer 12 or the photosensitive layer 13. There are fourteen.
In the photoelectric conversion element and the solar cell, for example, when the photosensitive layer 13 or the hole transport layer 3 and the transparent electrode 11 b are electrically connected, a reverse current is generated. The underlayer 14 functions to prevent this reverse current. The underlayer 14 is also called a blocking layer or a short circuit prevention layer.
This base layer may be provided also when the photoelectric conversion element has an electron transport layer. For example, in the embodiments of FIGS. 1, 2 and 4, an electron transport layer may be provided between the porous layer 14 and the underlayer. In the embodiment of FIG. 3, an electron transport layer may be provided between the photosensitive layer 13C and the underlayer 14.

The material for forming the base layer 14 is not particularly limited as long as it is a material capable of performing the above-mentioned function, but is a substance that transmits visible light and is an insulating substance for the conductive support 11 (transparent electrode 11b). Is preferred. Specifically, “the insulating support for the conductive support 11 (transparent electrode 11 b)” is a material in which the energy level of the conduction band forms the conductive support 11 (metal oxide for forming the transparent electrode 11 b) Compound) (n-type semiconductor compound) which is higher than the energy level of the conduction band of the substance) and lower than the energy level of the conduction band of the material constituting the porous layer 12 or the ground state of the light absorber.
Examples of the material forming the underlayer 14 include silicon oxide, magnesium oxide, aluminum oxide, calcium carbonate, polyvinyl alcohol, polyurethane and the like. The underlayer 14 may be made of a material generally used for photoelectric conversion materials, and may be made of, for example, titanium oxide, zinc oxide, tin oxide, niobium oxide, tungsten oxide or the like. Among them, the underlayer is preferably made of zinc oxide, titanium oxide, tin oxide, magnesium oxide, aluminum oxide or the like. In the present invention, from the viewpoint of durability, the underlayer is preferably formed of an inorganic semiconductor, and more preferably formed of titanium oxide, tin oxide, or the like.
In the present invention, the "underlayer" has a film thickness of 150 nm or less. Therefore, in the present invention, the "underlayer" is clearly different from the later-described "porous layer" having a film thickness of more than 150 nm in the film thickness.
10-150 nm is preferable, as for the film thickness of the base layer 14, 20-130 nm is more preferable, and 30-100 nm is especially preferable.

In the present invention, the film thickness of each layer can be measured by observing the cross section of the photoelectric conversion element 10 using a scanning electron microscope (SEM) or the like as described later.
In the present invention, the film thickness of the underlayer is usually smaller than the maximum height roughness Rz of the underlayer surface described later. This is because the film thickness of the underlayer is an average value of the measured values of the film thickness of the specific part of the underlayer. That is, as described later, the film thickness of the underlayer is calculated as an average value of the minimum values of the film thickness in a specific film thickness measurement section.

In the present invention, the maximum height roughness Rz of the surface of the underlayer 14 (surface on the photosensitive layer side) is 250 nm or less, preferably 230 nm or less, and more preferably 200 nm or less. By setting the Rz of the base layer surface of the photoelectric conversion element to 250 nm or less, variation in photoelectric conversion efficiency between the elements can be effectively reduced. Although the reason is not clear, the contact of the conductive support 11 with the light absorbing agent and the like can be more reliably suppressed by the structure of the underlayer, and the porous layer is provided on the underlayer. It can be considered that the contact between the porous layer and the second electrode or the hole transport layer which is the lower layer thereof can be effectively prevented, and the performance deterioration due to the occurrence of reverse electron transfer can be reduced.
The lower limit value of Rz of the surface of the underlayer 14 is not limited, and is preferably as small as possible, but usually Rz is 10 nm or more.
Rz is an index of surface roughness described in JIS B0601 2001, and can be measured, for example, by the method described in the examples described later. That is, on the surface of the base layer 14, five rectangular areas of 0.9 mm × 1.2 mm are randomly selected, and Rz in each area is measured. The average value of Rz (average value of five Rz) in each measurement area obtained is taken as Rz of the surface of the underlayer 14 defined in the present invention.
The method of forming the underlayer 14 will be described later.

-Porous layer 12-
In the present invention, like the photoelectric conversion elements 10A, 10B and 10F, preferably, the porous layer 12 is provided on the underlayer 14.
The porous layer 12 is a layer that functions as a scaffold supporting the photosensitive layer 13 on the surface. In the solar cell, in order to enhance the light absorption efficiency, it is preferable to increase the surface area of at least a portion receiving light such as sunlight, and it is preferable to increase the surface area of the porous layer 12 as a whole.

The porous layer 12 is preferably a fine particle layer having pores, in which fine particles of the material forming the porous layer 12 are deposited or in close contact. The porous layer 12 may be a fine particle layer formed by depositing two or more types of multi fine particles. When the porous layer 12 is a fine particle layer having pores, the amount of supported light (adsorbed amount) of the light absorber can be increased.
In order to increase the surface area of the porous layer 12, it is preferable to increase the surface area of each of the microparticles constituting the porous layer 12. In the present invention, in the 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 and 100 times or more the projected area. Is more preferred. The upper limit is not particularly limited, but is usually about 5000 times. The particle diameter of the fine particles forming the porous layer 12 is preferably 0.001 to 1 μm as primary particles in terms of the average particle diameter using the diameter when the projected area is converted to a circle. When forming the porous layer 12 using the dispersion of microparticles | fine-particles, 0.01-100 micrometers is preferable as said average particle diameter of microparticles | fine-particles as an average particle diameter of a dispersion.

The material forming the porous layer 12 (porous material) is not particularly limited in terms of conductivity, and even if it is an insulator (insulating material), the conductive material or semiconductor (semiconductive material) It may be
As the porous material, for example, metal chalcogenides (for example, oxides, sulfides, selenides and the like), compounds having a perovskite crystal structure (except for the light absorbing agent described later), oxides of silicon (for example, dioxide) Silicon, zeolite, or carbon nanotubes (including carbon nanowires and carbon nanorods) can be used.

  The metal chalcogenide is not particularly limited, but preferably titanium, tin, zinc, tungsten, zirconium, hafnium, strontium, indium, cerium, yttrium, lanthanum, vanadium, niobium, aluminum or tantalum oxide, cadmium sulfide And cadmium selenide. As a crystal structure of a metal chalcogenide, anatase type, brookite type or rutile type may be mentioned, 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 And barium lanthanum titanate, calcium titanate, sodium titanate, and bismuth titanate. Among these, strontium titanate, calcium titanate and the like are preferable.

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

  The porous material is preferably titanium, tin, zinc, zirconium, an oxide of aluminum or silicon, or a carbon nanotube, and more preferably titanium oxide or aluminum oxide.

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

  In the present invention, the "porous layer" has a thickness of more than 150 nm. The thickness of the porous layer 12 is preferably 160 nm to 100 μm, and more preferably 200 nm to 50 μm. Moreover, when using as a solar cell, 200 nm-30 micrometers of the film thickness of a porous layer are more preferable.

The film thickness of the porous layer 12 is from the lower layer surface on which the porous layer 12 is formed, along the linear direction intersecting the surface of the conductive support 11 at an angle of 90 ° in the cross section of the photoelectric conversion element 10 It is defined by the average distance to the surface of the porous layer 12. Here, “the lower surface on which the porous layer 12 is formed” means the interface between the underlayer 14 and the porous layer 12. When another layer is formed between the underlayer 14 and the porous layer 12, this means the interface between the other layer and the porous layer 12. In addition, “the surface of the porous layer 12” is a point (the virtual surface of the porous layer 12 located closest to the second electrode 2) on a virtual straight line that intersects the surface of the conductive support 11 at an angle of 90 °. The point of intersection of the straight line and the outline of the porous layer 12). The above "average distance" is determined as follows.
The photoelectric conversion element 10 is cut perpendicularly to the plane of the substrate, and the cross section thereof from end to end in a direction (horizontal direction in FIGS. 1 to 4) parallel to the surface of the conductive support 11 Of L from the one end, L × 1/12, L × 2/12, L × 3/12, ... L × 11/12 from the one end Measurement centers 1) to 11). The minimum distance from the surface of the lower layer to the surface of the porous layer 12 is determined in each of a total of 11 measurement ranges in a range of 2 μm in total of 1 μm from the measurement center to the left and right. For the 11 minimum distance values obtained, three measurements are made from 1 to 11 in order from the largest value (from the smallest distance) to 4th, 5th and 6th in order The average value of the three minimum distance values in the range is calculated to be the above average distance. The film thickness of the porous layer 12 is measured by observing the cross section of the photoelectric conversion element 10 with a scanning electron microscope (SEM).
In addition, unless it mentions in particular, it measures similarly about the film thickness of other layers, such as a base layer.
The film thickness of the other layers such as the underlayer is also determined in the same manner as the method of measuring the film thickness of the porous layer described above.

-Photosensitive layer (light absorbing layer) 13-
The photosensitive layer 13 is preferably provided with a perovskite compound described later on the surface of the underlayer 14 or the porous layer 12 (including the inner surface when the surface on which the photosensitive layer 13 is provided is uneven) as a light absorbing agent. .
In the present invention, the light absorber may contain at least one perovskite compound described later, and may contain two or more perovskite compounds.
The photosensitive layer 13 may be a single layer or a laminate of two or more layers. When the photosensitive layer 13 has a laminated structure of two or more layers, different light absorbing agents may be used for each photosensitive layer, and an intermediate layer containing a hole transport material may be interposed between the photosensitive layer and the photosensitive layer. You may provide.

The film thickness of the photosensitive layer 13 is not particularly limited, and is appropriately adjusted according to the purpose. For example, the film thickness of the photosensitive layer 13 can be 0.001 to 100 μm, preferably 0.01 to 10 μm, and more preferably 0.01 to 5 μm. As shown in FIG. 1, when the photosensitive layer 13 has a thin film shape, the thickness of the photosensitive layer 13 is in the direction perpendicular to the surface of the porous layer 12 and the interface with the porous layer 12 and the positive The distance to the interface with the hole transport layer 3 is referred to.
In the present invention, when the photosensitive layer is provided in the form of a thick film (photosensitive layers 13B and 13C), the light absorbing agent contained in the photosensitive layer may function as a hole transport material.

[Light Absorber for Photosensitive Layer]
The photosensitive layer 13 contains, as a light absorbing agent, a perovskite compound having a cation or an organic cation of a periodic table first group element, a cation of a metal atom other than the periodic table first group element, and an anion.

In the perovskite compound used in the present invention, the cation of the first group element of the periodic table is not particularly limited. For example, the cation of each element of lithium (Li), sodium (Na), potassium (K) or cesium (Cs) Li ^<+> , Na ^<+> , K ^<+> , Cs ^<+> ) is mentioned, Especially the cation of cesium (Cs ^<+> ) is preferable.
The organic cation is preferably an organic cation 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, and an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group or a group which can be represented by the following formula (2) is preferable. Among them, an alkyl group and a group which can be represented by the following formula (2) are more preferable.

In the formula, X ^a represents NR ^1c , an oxygen atom or a sulfur atom. Each of R ^1b and R ^1c independently represents a hydrogen atom or a substituent. *** represents a bond with the nitrogen atom of Formula (1).

In the present invention, the organic cation may contain a cation having a resonance structure in addition to the organic ammonium cation of the above formula (1). For example, in ^a group which can be represented by the above formula (2), an organic cation in which X ^a is NH (R ^1c is a hydrogen atom) is a group which can be represented by the above formula (2) and NH ₃ ⁺ is bonded In addition to the organic ammonium cation, the organic amidinium cation which is one of the resonance structures of this organic ammonium cation is also included. As an organic amidinium cation which consists of an amidinium cationic organic group, the cation represented by a following formula ( ^Aam ) is mentioned. 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 which can be taken as R ^1a is preferably an alkyl group having 1 to 18 carbon atoms, more preferably 1 to 6 alkyl groups, and still more preferably 1 to 3 alkyl groups. For example, methyl, ethyl, propyl, isopropyl, butyl, tert-butyl, pentyl, hexyl or decyl and the like can be mentioned.
The cycloalkyl group that can be taken as R ^1a is preferably a cycloalkyl group having a carbon number of 3 to 8, and examples thereof include cyclopropyl, cyclopentyl and cyclohexyl.

The alkenyl group which can be taken as R ^1a is preferably an alkenyl group having 2 to 18 carbon atoms, and more preferably an alkenyl group of 2 to 6 carbon atoms. For example, vinyl, allyl, butenyl or hexenyl and the like can be mentioned.
The alkynyl group which can be taken as R ^1a is preferably an alkynyl group having 2 to 18 carbon atoms, and more preferably an alkynyl group of 2 to 4 carbon atoms. For example, ethynyl, butynyl or hexynyl and the like can be mentioned.

The aryl group which can be taken as R ^1a is preferably an aryl group having 6 to 14 carbon atoms, more preferably an aryl group having 6 to 12 carbon atoms, and examples thereof include phenyl.
The heteroaryl group that can be taken out as R ^1a is a group consisting of only an aromatic heterocycle, and a group consisting of a fused heterocycle in which another ring such as an aromatic ring, an aliphatic ring or a heterocycle is fused to an aromatic heterocycle. Includes
As a ring-constituting hetero atom which comprises an aromatic heterocyclic 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 3- to 8-membered ring, more preferably a 5- or 6-membered ring.
Examples of the fused heterocycle containing 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. And each ring group of benzimidazole ring, benzoxazole ring, benzothiazole ring, indoline ring and indazole ring. Moreover, as a fused heterocycle containing a 6-membered aromatic heterocycle and a 6-membered aromatic heterocycle, for example, each ring group of a pyridine ring, a pyrimidine ring, a pyrazine ring, a triazine ring, a quinoline ring, and a quinazoline ring Can be mentioned.

In the group which can be represented by Formula (2), X ^a represents NR ^1c , an oxygen atom or a sulfur atom, and NR ^1c is preferable. Here, R ^1c represents a hydrogen atom or a substituent, 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, preferably a hydrogen atom. The substituent that R ^1b can adopt includes an amino group, an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group or an amino group.
An alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group and a heteroaryl group which R ^1b and R ^1c can be taken respectively are an alkyl group, a cycloalkyl group, an alkenyl group and an alkynyl group which can be taken respectively by the above R ^1a And aryl groups and heteroaryl groups, and preferred ones are also the same.
Examples of the group which can be represented by the formula (2) include (thio) acyl group, (thio) carbamoyl group, imidoyl group or amidino group.
The (thio) acyl group includes an acyl group and a thioacyl group. Acyl group, the total carbon number preferably an acyl group having 1 to 7, for example, formyl, acetyl _{(CH 3 C (= O)} -), propionyl, hexanoyl and the like. Thioacyl group, the total carbon number of preferably thioacyl group having 1 to 7, for example, thioformyl, thioacetyl _{(CH 3 C (= S)} -), thiopropionyl, and the like.
(Thio) carbamoyl group, a carbamoyl group _{(H 2 NC (= O)} -) and thiocarbamoyl group _{(H 2 NC (= S)} -) embraces.
Imidoyl ^{group, R 1b -C (= NR 1c} ) - is a group represented by ^is preferably a hydrogen atom or an alkyl group ^{R 1b} and ^{R 1c} are each alkyl groups are the same meaning as the above-described alkyl group ^{R 1a} Is more preferable. For example, formimidoyl (HC (= NH) -) , acetimidoyl _{(CH 3 C (= NH)} -), propionic imidoyl _{(CH 3 CH 2 C (=} NH) -) and the like. Among these, formimidoyl is preferable.
Amidino group as group which can be represented by the formula (2) is, ^{R 1c R 1b} of the imidoyl group at the amino group has the structure (-C (= NH) NH ₂₎ is a hydrogen atom.

The alkyl group, the cycloalkyl group, the alkenyl group, the alkynyl group, the aryl group, the heteroaryl group and the group which can be represented by the above formula (2), which R ^1a can adopt, may have a substituent. Good. The substituent W ^P which 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, and amino Group, alkylamino group, arylamino group, acyl group, alkylcarbonyloxy group, aryloxy group, alkoxycarbonyl group, aryloxycarbonyl group, acylamino group, sulfonamide group, carbamoyl group, sulfamoyl group, halogen atom, cyano group, A hydroxy group, a mercapto group or a carboxy group may be mentioned. Each substituent which R ^1a may have may further have a substituent.

  The perovskite compound used in the present invention has, in its crystal structure, a cation of a metal atom other than a periodic table first group element. As metal atoms other than the periodic table first group element, for example, calcium (Ca), strontium (Sr), cadmium (Cd), copper (Cu), nickel (Ni), manganese (Mn), iron (Fe), Cobalt (Co), palladium (Pd), germanium (Ge), tin (Sn), lead (Pb), ytterbium (Yb), europium (Eu), indium (In), titanium (Ti), bismuth (Bi), etc. Among these, Pb atoms, Cu atoms, Ge atoms or Sn atoms are particularly preferable, Pb atoms or Sn atoms are more preferable, and Pb atoms are particularly preferable. The perovskite compound used in the present invention may have one or two or more cations of metal atoms other than the elements of the first group of the periodic table in its crystal structure. When two or more types of cations of metal atoms other than the periodic table first group element are contained, it is preferable to have two types of Pb atoms and Sn atoms. When the perovskite compound has two or more cations of a metal atom other than the periodic table first group element, the abundance ratio of these two or more cations is not particularly limited.

The anion which comprises the perovskite compound used for this invention may be a single atom anion, and may be a polyatomic anion. As a single atom anion, the anion of a halogen atom is mentioned. Preferred examples of the polyatomic ^anion, NCS -, NCO ^- and COO ^- and the like. Among them, the anion constituting the perovskite compound is preferably an anion of a halogen atom. As a halogen atom, a fluorine atom, a chlorine atom, a bromine atom and an iodine atom are mentioned, and a bromine atom or an iodine atom is preferable.
The anion which comprises the perovskite compound used for this invention may be 1 type of anion, and 2 or more types of anions may be sufficient as it. When the anion constituting the perovskite compound is one kind, the anion of iodine atom is preferable. Moreover, when the anion which comprises a perovskite compound is 2 or more types, the form which has the anion of 2 or more types of halogen atoms is preferable, and the form which has 2 types of the anion of a chlorine atom and the anion of an iodine atom especially is more preferable. When the perovskite compound has two or more anions, the ratio is not particularly limited.

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

A _a M _m x _x formula (I)
In formula, A represents a periodic table group 1 element or a cationic organic group. M represents a metal atom other than a periodic table first group element. X represents an anionic atom or an anionic atom group.
a represents 1 or 2, m represents 1, and a, m and x satisfy a + 2 m = x.
In the present specification, a cationic organic group means an organic group present as a cation in a perovskite crystal structure, and an anionic atom means an atom present as a monoatomic anion in a perovskite crystal structure, an anion The sexing atom group means an atom group existing as a polyatomic anion in the perovskite crystal structure.

In the formula (I), the first group element A of the periodic table is present as a cation in the perovskite crystal structure.
In the formula (I), the cationic organic group A is present as the above-mentioned organic cation in the perovskite crystal structure.
In the formula (I), the metal atom M is present in the perovskite crystal structure as a cation of a metal atom other than the above-mentioned periodic table first group element.
In the formula (I), the anionic atom X is present in the perovskite crystal structure as the above-mentioned monoatomic anion.
In formula (I), the anionic atom group X is present as the polyatomic anion described above in the perovskite crystal structure.

  The perovskite compound used in the present invention may be a mixture of a perovskite compound in which a is 1 in the above formula (I) and a perovskite compound in which a is 2.

Specific examples of the perovskite compound used in the present invention 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 , CH ₃ NH ₃ PbBr ₂ I, CH ₃ NH ₃ SnBr ₃ , CH ₃ NH ₃ SnI ₃ , CH (= NH) NH ₃ PbI ₃ ,
(C ₂ H ₅ NH ₃ ) ₂ PbI ₄ , (CH ₂ CHCHNH 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 ₁₀ H ₂₁ NH ₃ ) ₂ PbI ₄ , (C ₆ H ₅ NH ₃ ) ₂ PbI ₄ , (C ₆ H ₅ CH ₂ CH ₂ 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 , (C ₄ H ₉ NH ₃ ) ₂ GeI _{4 And} (CH ₃ NH ₃ ) ₂ CuCl ₄ and (CH ₃ CH ₂ NH ₃ ) ₂ FeBr ₄ can be mentioned. _{Here, C} 4 _{H 3} SNH 3 in _{(C 4 H 3 SNH 3)} 2 PbI 4 is aminothiophene.

Perovskite compounds can be synthesized from MX ₂ and AX. For example, a perovskite compound can be synthesized with reference to Non-Patent Document 1 above. Also, Akihiro Kojima, Kenjiro Teshima, Yasuo Shirai, and Tsutomu Miyasaka, "Organometal Halide Perovskites as Visible-Light Sensitizers for Photovoltaic Cells", J. Am. Chem. Soc. 2009, 131 (17), 6050-6051 can also be referred to as appropriate to synthesize a perovskite compound.

  The amount of the light absorbing agent used may be at least a part of the surface of the porous layer 12 on which light is incident, and is preferably an amount covering the entire surface.

  The content of the perovskite compound in the photosensitive layer 13 is usually 1 to 100% by mass.

<Hole transport layer 3>
The photoelectric conversion element of the present invention preferably has the hole transport layer 3 between the first electrode and the second electrode.
The hole transport layer 3 has a function of replenishing the oxidant of the light absorber with electrons, and is preferably a solid layer. The hole transport layer 3 is preferably provided between the photosensitive layer 13 of the first electrode 1 and the second electrode 2.

Although the hole transport material which forms the hole transport layer 3 is not particularly limited, inorganic materials such as CuI and CuNCS, and the organic hole transport material described in paragraph Nos. 0209 to 0212 of JP 2001-291534 A Etc. As the organic hole transport material, preferably, conductive polymers such as polythiophene, polyaniline, polypyrrole and polysilane, spiro compounds in which two rings share a central atom having a tetrahedral structure such as C and Si, triarylamine And aromatic amine compounds, triphenylene compounds, nitrogen-containing heterocyclic compounds, or liquid crystalline cyano compounds.
The hole transport material is preferably an organic hole transport material which can be solution-coated and becomes solid, specifically, 2,2 ′, 7,7′-tetrakis- (N, N-di-p-methoxyphenyl) Amine) -9,9-spirobifluorene (also referred to as Spiro-OMeTAD), poly (3-hexylthiophene-2,5-diyl), 4- (diethylamino) benzaldehyde diphenylhydrazone, polyethylenedioxythiophene (PEDOT), etc. Can be mentioned.

  The thickness of the hole transport layer 3 is not particularly limited, but is preferably 50 μm or less, more preferably 1 nm to 10 μm, still more preferably 5 nm to 5 μm, and particularly preferably 10 nm to 1 μm.

  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 180 nm to 200 μm, more preferably 200 nm to 50 μm, and still more preferably 250 nm to 5 μm. preferable.

<Second electrode 2>
The second electrode 2 functions as a positive electrode in the solar cell. The second electrode 2 is not particularly limited as long as it has conductivity, and can generally have the same configuration as the conductive support 11. When 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 collection 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 the present invention, it is preferable that the conductive support 11 be transparent and that sunlight be incident from the side of the support 11a. In this case, it is more preferable that the second electrode 2 have 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), osmium (Os), aluminum (Al), the above-described conductive metal oxides, carbon materials, conductive polymers, and the like. The carbon material may be any material having conductivity, in which carbon atoms are bonded to each other, and examples thereof include fullerene, carbon nanotube, graphite, graphene, carbon black and the like.
The second electrode 2 is preferably a thin film (including a thin film formed by vapor deposition) of a metal or conductive metal oxide, or a glass substrate or a plastic substrate having the thin film. As a glass substrate or a plastic substrate, a glass having a thin film of gold or platinum or a glass on which platinum is vapor-deposited is preferable.

  The film thickness of the second electrode 2 is not particularly limited, and is preferably 0.01 to 100 μm, more preferably 0.01 to 10 μm, and particularly preferably 0.01 to 1 μm.

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

<< Solar cell >>
The solar cell of the present invention is configured using the photoelectric conversion element of the present invention. For example, as shown in FIGS. 1 to 4, the photoelectric conversion element 10 configured to work on the external circuit 6 can be used as a solar cell. The external circuit connected to the first electrode 1 (conductive support 11) and the second electrode 2 can be a known one without particular limitation.
The present invention is described, for example, in Non-Patent Document 1, J. Am. Chem. Soc. , 2009, 131 (17), p. 6050-6051 and Science, 338, p. It is applicable to each solar cell as described in 643 (2012).
In the solar cell of the present invention, it is preferable to seal the side with a polymer, an adhesive or the like in order to prevent deterioration and transpiration of the composition.

<< photoelectric conversion element and method of manufacturing solar cell >>
The photoelectric conversion element and the solar cell of the present invention can be manufactured according to known manufacturing methods, for example, the method described in Non-Patent Document 1 etc., except for the formation of the base layer 14.
Below, the manufacturing method of the photoelectric conversion element of this invention and a solar cell is demonstrated easily taking the case where the porous layer 12 and the positive hole transport layer 3 are provided as an example.

Underlayer 14 is formed on the surface of conductive support 11.
The underlayer 14 is formed, for example, by applying a coating solution containing an insulating material to the above-described conductive support 11 (transparent electrode 11 b) or a precursor compound thereof to the surface of the conductive support 11 to form a film. It is preferable to form this coating film by baking. The insulating material for the conductive support 11 (transparent electrode 11 b) is preferably an inorganic semiconductor material. The inorganic semiconductor material is preferably selected from titanium oxide, zinc oxide, silicon oxide, magnesium oxide, aluminum oxide, calcium carbonate, tin oxide, niobium oxide, tungsten oxide and the like.
Moreover, as a precursor compound of this inorganic semiconductor material, for example, alkoxides of the respective materials (preferably titanium ethoxide, titanium isopropoxide, titanium butoxide, titanium isopropoxide (diacetopropoxide (acetylacetonato)), aluminum triisopropoxide And one or more selected from diethoxy zinc), a halide (preferably one or more selected from titanium tetrachloride and zinc chloride), and a hydroxide (preferably from tetrahydroxy titanium and hydroxy zinc) 1 type or 2 types or more selected from 1 type or 2 types selected can be mentioned.
1-99 mass% is preferable in a coating liquid, and, as for content of the said insulating substance or its precursor compound, 1-50 mass% is more preferable.

The solvent used for the coating solution for forming the underlayer 14 preferably contains the solvent S ₁ having a boiling point of 150 ° C. or more, so that the solvent evaporates over a certain length of time even during baking. If the solvent in the coating solution is only a low boiling point solvent, the solvent is volatilized in a short time, and there is a tendency that the film is formed without correcting the coating unevenness (concave and convex). The solvent S ₁ contained in the coating solution may be _one kind or two or more kinds.
From the viewpoint of suppressing more the Rz of the base layer, the boiling point is preferably at least 200 ° C. The solvent _{S 1,} more preferably at least 215 ° C., more preferably above 230 ° C., more preferably above 240 ° C., and even more preferably 250 ° C.. Further, the boiling point of the solvent _{S 1} is preferably 400 ° C. or less, more preferably 350 ° C. or less, more preferably 300 ° C. or less.
The solvent in the coating solution preferably contains the solvent S ₁ or 1 wt%, and more preferably contains 3 to 10 wt%. If the proportion of the high boiling point solvent in the coating solution exceeds a certain amount, precipitation of TiO ₂ is likely to occur in a high temperature state or aggregation is likely to occur, and Rz is adjusted within the scope of the present invention. Tend to be difficult.
Solvent of the coating solution, the solvent constituting the remainder other than the solvent S _1, depending on the boiling point of the solvent S _1, preferably has a boiling point less than 140 ° C., more preferably less than 120 ° C., 100 More preferably, it is less than ° C.

Solvent of the coating solution for forming the undercoat layer 14, and the solvent S _1, a boiling point above the boiling point of the solvent S ₁ is preferably contains a low solvent S ₂ or 50 ° C.. The boiling point of the solvent S ₂ is less than 150 ° C., more preferably less than 140 ° C., still more preferably less than 120 ° C., and still more preferably less than 100 ° C. Boiling point of the solvent S ₂ is usually at 30 ° C. or higher, more preferably at least 50 ° C., more preferably 60 ° C. or higher.
Solvent S ₂ may be two or more solvents in one solvent. In this case, formation of the underlying layer 14 is formed by applying the coating liquid to form a coating film on a conductive support 11, the coating film, the lower the solvent S ₂ than the boiling point of the solvent S ₁ over 1 minute at a temperature higher than the boiling point (preferably 5 to 30 minutes) heated, then it is preferable to carry out by firing temperature higher than the boiling point of the solvent S _1. By so doing, the evaporation rate of the solvent can be adjusted to an appropriate level, and Rz on the surface of the underlayer 14 can be effectively reduced. During heating at a temperature higher than the boiling point of the solvent S ₂ lower than the boiling point of the solvent S _1, temperature may be varied at a constant. It is preferable that this temperature be constant or be heated.
Boiling point of the solvent _{S 2} is preferably less 50 to 200 ° C. than the boiling point of the solvent _{S 1,} and more preferably less 50 to 180 ° C., and even more preferably less 70 to 160 ° C..

Here, when "a solvent S _1, the solvent boiling point than the boiling point of S ₁ is containing a low solvent S ₂ or 50 ° C." refers containing two or more solvents as the solvent S ₁ is the the boiling point of the solvent S ₂ that is less 50 ° C. or higher than the boiling point of the lowest solvent boiling point of the solvent S _1.
Further, the above-mentioned “temperature lower than the boiling point of solvent S ₁ and higher than the boiling point of solvent S ₂ ” is the boiling point of solvent S ₁ (when S ₁ is a solvent of two or more types, the solvent having the lowest boiling point boiling point, hereinafter the same) 10-190 ° C. lower than, when the boiling point of the solvent _{S 2 (S 2} is 2 or more solvents, the most high boiling point solvent having a boiling point, than hereinafter the same) 10-190 It is preferred that the temperature is higher by 60 ° C. to 150 ° C. than the boiling point of the solvent S ₁ and more preferably 60 to 150 ° C. higher than the boiling point of the solvent S ₂ .
Moreover, "fired at a temperature higher than the boiling point of the solvent S _1", in the case as the solvent S ₁ comprising two or more solvents, the most high boiling point solvent having a boiling point above the temperature of the solvent S ₁ It means to bake. "A temperature above the boiling point of the solvent S _1" is the boiling point of the solvent S ₁ (if comprising two or more solvents, most high boiling point boiling point of the solvent of the solvent S ₁₎ 10 to 600 ° C. higher than the Is preferable, and 50 to 300 ° C. is more preferable.
When the solvent S ₁ is a solvent of two or more types, the proportion of the solvent having the highest boiling point in the solvent S ₁ is preferably 80 mass% or more, and more preferably 90 mass% or more. It is more preferable that it is 95 mass% or more, and it is further more preferable that it is 98 mass% or more.
Further, when the solvent S ₂ is two or more solvents, in a solvent S _2, and most preferably the ratio of the low boiling point solvent is 10 mass% or more, more not less than 20 wt% The content is preferably 40% by mass or more, more preferably 60% by mass or more, still more preferably 80% by mass or more, and still more preferably 90% by mass or more.
It is preferable that the solvent S ₁ is one solvent. Further, the solvent S ₂ is preferably composed of one or two solvents, more preferably one solvent. The coating solution preferably contains no solvent other than the solvents S ₁ and S ₂ .

As the solvent S ₁ , an oligoalkylene glycol (preferably an oligoalkylene glycol having 2 to 10 carbon atoms, specifically, one or two selected from triethylene glycol, dipropylene glycol, tripropylene glycol and tetraethylene glycol A glycol ether (preferably one or more selected from diethylene glycol monobutyl ether, diethylene glycol butyl methyl ether, tripropylene glycol dimethyl ether, diethylene glycol dibutyl ether and tetraethylene glycol dibutyl ether), an alcohol (preferably α-terpineol and 1 or 2 types selected from decanol, amides (preferably dimethylformamide, dimethylacetoamide) And one or more selected from N- methylpyrrolidone), and lactone (preferably it is preferred to use one or more selected from γ- butyrolactone). Among them, from the viewpoint of reducing Rz, it is preferable to use one or more solvents selected from α-terpineol, oligoalkylene glycol and glycol ether.

In addition, as the above-mentioned solvent S ₂ , alcohol (preferably one or more selected from methanol, ethanol, isopropanol and butanol), ester (preferably one or two selected from methyl acetate and ethyl acetate), Ketone (preferably one or more selected from acetone, methyl ethyl ketone, diethyl ketone and cyclopentanone), ether (preferably one or two selected from diethyl ether and tetrahydrofuran), hydrocarbon (substituted hydrocarbon) Preferably, it is preferable to use one or more solvents selected from one or more selected from hexane, methylene chloride, chloroform, benzene and toluene), and a nitrile (preferably acetonitrile).

The material forming the porous layer 12 is preferably used as fine particles, and more preferably 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, methods described in Chemical Review, Volume 110, page 6595 (2010)). Be In these methods, after the dispersion (paste) is applied to the surface of the conductive support 11 or the surface of the underlayer 14, baking may be performed, for example, in air for 10 minutes to 10 hours at a temperature of 100 to 800 ° C. preferable. Thereby, fine particles can be adhered to each other.
When the firing is performed a plurality of times, it is preferable to perform the temperature of the firing other than the final firing (the firing temperature other than the final) at a temperature lower than the temperature of the final firing (the final firing temperature). For example, when using a titanium oxide paste, the baking temperature other than the last can be set in the range of 50 to 300 ° C. In addition, the final baking temperature can be set to be higher than the baking temperature other than the final temperature in the range of 100 to 600 ° C. When using a glass support as the support 11a, 60-500 degreeC of baking temperature is preferable.

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

Next, the photosensitive layer 13 is provided.
The method of providing the photosensitive layer 13 includes a wet method and a dry method, and is not particularly limited. In the present invention, a wet method is preferred, and for example, a method of contacting with a light absorbent solution containing an absorbent is preferred. In this method, first, a light absorbing agent solution for forming the photosensitive layer 13 is prepared. The light absorbing agent solution contains MX ₂ and AX, which are raw materials of the above-mentioned perovskite compound. Here, A, M and X have the same meanings as A, M and X in the above formula (I). In this light absorbing agent solution, the molar ratio of MX ₂ to AX is appropriately adjusted according to the purpose. When forming a perovskite compound as a light absorber, the molar ratio of AX to MX ₂ is preferably 1: 1 to 10: 1. This light absorbing agent solution can be prepared by mixing AX and MX ₂ at a predetermined molar ratio and preferably heating. This forming solution is usually a solution, but may be a suspension. Although the conditions to heat are not specifically limited, 30-200 degreeC is preferable and 60-150 degreeC of heating temperature is more preferable. The heating time is preferably 0.5 to 100 hours, more preferably 1 to 3 hours. As the solvent or dispersion medium, those described later can be used.
Next, the prepared light absorbing agent solution is brought into contact with the surface of the layer forming the photosensitive layer 13 (for example, the porous layer 12) on the surface thereof. Specifically, it is preferable to apply or immerse a light absorbent solution. . Thereby, a perovskite compound is formed on the surface of the porous layer 12. The temperature for contact is preferably 5 to 100 ° C., the immersion time is preferably 5 seconds to 24 hours, and more preferably 20 seconds to 1 hour. When the applied light absorbing agent solution is dried, the drying is preferably performed by heat, and the drying is usually performed by heating to 20 to 300 ° C., preferably 50 to 170 ° C.
Moreover, a photosensitive layer can also be formed according to the synthesis method of the said perovskite compound.
Furthermore, a method of separately applying (including a dipping method) the AX solution containing the above AX and the MX ₂ solution containing the above MX ₂ and optionally drying it may also be mentioned. In this method, any solution may be applied first, but preferably the MX ₂ solution is applied first. The molar ratio of AX to MX _{2 in} this method, the coating conditions and the drying conditions are the same as the above method. In this method, AX or MX ₂ can be vapor deposited instead of the application of the AX solution and the MX ₂ solution.
Still another method is a dry method such as vacuum evaporation using a compound or a mixture from which the solvent of the light absorber solution has been removed. For example, the method of vapor-depositing said AX and said MX ₂ simultaneously or sequentially is also mentioned.
Thereby, a light absorbing agent is formed, and the photosensitive layer 13 is formed.

The hole transport layer 3 is preferably formed on the photosensitive layer 13 provided in this manner.
The hole transport layer 3 can be formed by applying and drying a hole transport material solution containing a hole transport material. The hole transport material solution has a concentration of the hole transport material at a concentration of 0.% because the hole transport material solution is excellent in coatability and easily penetrates into the pores of the porous layer 12 when it has the porous layer 12 and there are voids. It is preferable that it is 01-1.0 M (mol / L).

  After forming the hole transport layer 3, the second electrode 2 is formed, and the photoelectric conversion element and the 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 times of application. For example, in the case of providing the thick photosensitive layer 13B, the light absorbing agent solution may be applied and dried a plurality of times.

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

  As a solvent or dispersion medium used for the manufacturing method of a photoelectric conversion element and a solar cell, although the solvent of Unexamined-Japanese-Patent No. 2001-291534 is mentioned, it does not specifically limit to this. In the present invention, organic solvents are preferable, and alcohol solvents, amide solvents, nitrile solvents, hydrocarbon solvents, lactone solvents, halogen solvents, sulfide solvents, and mixed solvents of two or more of them are more preferable. The mixed solvent is preferably a mixed solvent of an alcohol solvent and a solvent selected from an amide solvent, a nitrile solvent or a hydrocarbon solvent. Specifically, methanol, ethanol, isopropanol, γ-butyrolactone, chlorobenzene, acetonitrile, dimethylformamide (DMF) or dimethylacetamide, or a mixed solvent thereof is preferable.

  The coating method of the solution or dispersant for forming each layer is not particularly limited, and spin coating, extrusion die coating, blade coating, blade coating, bar coating, screen printing, stencil printing, roll coating, curtain coating, spray coating, dip coating, inkjet Well-known coating methods, such as a printing method and an immersion method, can be used. Among them, spin coating, screen printing, immersion method and the like are preferable.

  The photoelectric conversion element produced as mentioned above can connect the external circuit 6 to the 1st electrode 1 and the 2nd electrode 2, and can use it as a solar cell.

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

Example, comparative example [manufacture of photoelectric conversion element]
The photoelectric conversion element 10A shown in FIG. 1 was manufactured by the procedure shown below. When the film thickness of the photosensitive layer 13 is large, it corresponds to the photoelectric conversion element 10B shown in FIG.

<Preparation of Conductive Support 11>
A fluorine-doped SnO ₂ conductive film (transparent electrode 11 b, film thickness 300 nm) is formed on a glass substrate (support 11 a, length × width × thickness = 25 mm × 25 mm × 2.2 mm), and conductive support 11 Was produced.

Preparation of Solution for Underlayer
Titanium (IV) isopropoxide (manufactured by Aldrich) was diluted with a mixed solvent of the following solvents (a) and (b) to prepare a 0.02 M underlayer solution.

<Formation of Base Layer 14>
The undercoat layer solution containing the prepared titanium (IV) isopropoxide at a concentration of 0.02 M was electroconductive by the spray method for Comparative Examples 1 to 3 and Example 1 and by the spin coating method for the other examples. It was coated on a SnO ₂ conductive film of the support 11.
Then, for Comparative Examples 1 to 4 and Examples 1 to 8, 10 and 11, after reaching 500 ° C. by heating from room temperature at 10 ° C./minute in air, the conductive support 11 is fired for 1 hour. The underlayer 14 (film thickness 50 nm) made of titanium oxide was formed on the conductive film of the above. In Example 9, the temperature was raised from room temperature to 10 ° C./minute in air, and after reaching 150 ° C., the temperature range was maintained at 150 ° C. ± 10 ° C. for 10 minutes. Thereafter, the temperature was raised at 10 ° C./min to reach 500 ° C., followed by firing for 30 minutes.

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

<Formation of Porous Layer 12>
The prepared titanium oxide paste was applied on the underlayer 14 by screen printing and baked. The application and firing of this titanium oxide paste were repeated twice. The baking temperature performed the 1st baking at 130 degreeC, and performed the 2nd baking at 500 degreeC for 1 hour. The obtained sintered body of titanium oxide is immersed in a 40 mM aqueous TiCl ₄ solution, heated at 60 ° C. for 1 hour, and then heated at 500 ° C. for 30 minutes to form a porous layer 12 (film thickness of TiO ₂₎ 300 nm).

<Formation of Photosensitive Layer 13A>
A solution of methylamine in 40% methanol (27.86 mL) and an aqueous solution of 57% by mass of hydrogen iodide (hydroiodic acid, 30 mL) are stirred in a flask at 0 ° C. for 2 hours and then concentrated to give CH 2 CH 2. A crude product of ₃ NH ₃ I was obtained. The resulting crude CH ₃ NH ₃ I was dissolved in ethanol and recrystallized with 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 are mixed at a molar ratio of 2: 1, mixed in γ-butyrolactone for 12 hours with stirring at 60 ° C., and then filtered with a polytetrafluoroethylene (PTFE) syringe filter Thus, a 40% by mass light absorber solution A was prepared.

The prepared light absorbing agent solution A is applied on the porous layer 12 by spin coating (2000 rpm for 60 seconds, then 3000 rpm for 60 seconds), and the applied light absorbing agent solution A is heated at 100 ° C. After drying for a minute, a photosensitive layer A (film thickness 350 nm (including the film thickness 300 nm of the porous layer 12)) as the photosensitive layer 13A having a perovskite compound was formed. The obtained perovskite compound was CH ₃ NH ₃ PbI ₃ .
Thus, the first electrode 1 was produced.

<Preparation of hole transport material solution>
Spiro-OMeTAD (180 mg) as a hole transport material was dissolved in chlorobenzene (1 mL). An acetonitrile solution (37.5 μL) in which lithium-bis (trifluoromethanesulfonyl) imide (170 mg) is dissolved in acetonitrile (1 mL) and t-butylpyridine (TBP, 17.5 μL) are added to this chlorobenzene solution. The solution was mixed to prepare a hole transport material solution.

<Formation of Hole Transport Layer 3>
Next, a hole transport material solution is applied on the photosensitive layer 13 of the first electrode 1 by spin coating, and the applied hole transport material solution is dried to form a hole transport layer 3 (film thickness 0.5 μm). Formed.

<Preparation of Second Electrode 2>
Gold was vapor-deposited on the hole transport layer 3 by vapor deposition to prepare a second electrode 2 (film thickness 0.3 μm).
Thus, photoelectric conversion elements 10 of Comparative Examples 1 to 4 and Examples 1 to 11 were manufactured.

[Measurement of Maximum Height Roughness Rz of Base Layer 14 Surface]
Using the sample after forming the underlayer 14 on the conductive support 11 as described above (before forming the photosensitive layer), the Rz of the surface of the underlayer 14 (the surface on which the photosensitive layer is formed) is calculated as follows: Was measured.
<Measurement method of Rz>
As shown in FIG. 5, Rz of the entire area was measured using a white light interferometer (Wyko, manufactured by Nippon Bico) for each of five measurement areas (1.2 mm × 0.9 mm). The Rz of the entire area herein refers to the result of measuring Rz (referred to as Rz ′) with a resolution of 5 μm in the direction of each of the XY axes. The average of the respective Rz values of the five measurement areas (average of five measurement values) was taken as Rz of the surface of the underlayer 14.
The five measurement areas shown in FIG. 5 are equivalent to five measurement areas randomly selected. Rz determined by five measurement areas selected at random can be regarded as Rz of the entire surface of the underlayer 14.

[Evaluation of variation of photoelectric conversion efficiency]
<Measurement of initial photoelectric conversion efficiency>
The photoelectric conversion efficiency was evaluated as follows.
Ten samples of each of the photoelectric conversion elements of the above Comparative Examples and Examples were produced, and a battery characteristic test was performed to measure the photoelectric conversion efficiency (η /%). The battery characteristic test was performed by irradiating 1000 W / m < ² > simulated sunlight from the xenon lamp which let the AM1.5 filter pass using solar simulator "WXS-85H" (made by WACOM). The current-voltage characteristic was measured using an IV tester to determine the photoelectric conversion efficiency (η /%).
The variation of the photoelectric conversion efficiency of 10 specimens was evaluated according to the following evaluation criteria for each comparative example and each example. The results are shown in the table below.
Here, Rz of the porous layer in each of the comparative examples and examples described in the following table is the highest Rz value among 10 specimens. That is, in each of the comparative examples and the examples, the Rz values of the 10 samples of porous layers were all equal to or less than the Rz values in the table.
Moreover, in each Example and the comparative example, the average value of the photoelectric conversion efficiency was 7% or more, and showed high photoelectric conversion efficiency.

(Evaluation standard of variation)
A: With respect to the average value (Av%) of the photoelectric conversion efficiency of 10 samples, the photoelectric conversion efficiency (%) of each of 10 samples is all [Av-0.5] (%) or more [Av + 0.5] (%) The following is satisfied.
B: The photoelectric conversion efficiency (%) of each of 10 samples is all [Av-0.6] (%) or more with respect to the average value (Av%) of photoelectric conversion efficiencies of 10 samples not satisfying the above A. [Av + 0.6] (%) or less is satisfied.
C: The photoelectric conversion efficiency (%) of each of 10 samples is all [Av-0.8] (%) or more with respect to the average value (Av%) of photoelectric conversion efficiencies of 10 samples which do not satisfy B above. [Av + 0.8] (%) or less is satisfied.
D: The photoelectric conversion efficiency (%) of each of 10 samples is all [Av-1.1] (%) or more with respect to the average value (Av%) of photoelectric conversion efficiencies of 10 samples which do not satisfy C. [Av + 1.1] (%) or less is satisfied.
E: With respect to the average value (Av%) of photoelectric conversion efficiencies of 10 samples, at least one of the photoelectric conversion efficiencies (%) of 10 samples is less than [Av-1.1] (%), or [ Av + 1.1] is over (%).

  In the following table, the proportions of solvents used are mass ratios. Moreover, when the solvent (a) consists of two types of solvents, the column of the boiling point of the solvent (a) showed the boiling point of the solvent having the highest boiling point among the solvents contained in the solvent (a).

  From the above results, it is understood that the photoelectric conversion device in which Rz of the underlayer is within the definition of the present invention is excellent in the photoelectric conversion efficiency and can highly reduce the variation of the photoelectric conversion efficiency between the devices (10 specimens). The

  While the present invention has been described with its embodiments and drawings, it is not intended that the invention be limited in any detail of the description unless otherwise specified, and the spirit and scope of the invention as set forth in the appended claims. Should be interpreted broadly without contradicting

  This application claims the priority of Japanese Patent Application No. 2015-124713 filed in Japan on June 22, 2015, which is incorporated herein by reference in its entirety. Capture as part.

1A, 1B, 1C, 1F first electrode 11 conductive support 11a support 11b transparent electrode 12 porous layer 13A, 13B, 13C photosensitive layer 14 base layer 2 second electrode 3A, 3B hole transport layer 6 external circuit ( Lead)
10A, 10B, 10C, 10F Photoelectric conversion device 100A, 100B, 100C, 100F System M that applies photoelectric conversion device to battery application Electric motor

Claims (6)

A method of manufacturing a photoelectric conversion device, comprising: a first electrode having a base layer, a porous layer, and a photosensitive layer containing a light absorbing agent in this order on a conductive support; and a second electrode facing the first electrode. And
The light absorber includes a compound having a perovskite crystal structure having a cation or an organic cation of a periodic table first group element, a cation of a metal atom other than the periodic table first group element, and an anion,
The maximum height roughness Rz of the base layer surface Ri der less 250 nm,
The manufacturing method comprises the steps of applying a coating solution containing an inorganic semiconductor material or a precursor thereof onto the conductive support to form a coating film, and firing the coating film to form the underlayer. Including and
The solvent of the coating solution is a solvent S ₁ higher than the boiling point 0.99 ° C., boiling point of less than 0.99 ° C., and a boiling point greater than the boiling point of the solvent S ₁ is contained and low solvent S ₂ or 50 ° C., the The content of the solvent S _{1 in} the solvent is 1% by mass or more,
Formation of the underlying layer, the coating film, the heated over 1 minute at a temperature higher than the boiling point of the solvent S ₂ lower than the boiling point of the solvent S _1, then fired in the solvent S ₁ above the boiling point temperature The manufacturing method of the photoelectric conversion element performed by performing . The manufacturing method of the photoelectric conversion element of Claim 1 whose said Rz is 230 nm or less. The manufacturing method of the photoelectric conversion element of Claim 1 or 2 whose said Rz is 200 nm or less. The manufacturing method of the photoelectric conversion element of any one of Claims 1-3 in which the said base layer is formed with the inorganic semiconductor material. The solvent in the coating solution, the solvent-containing S ₁ 3 to 10% by weight, method of manufacturing the photoelectric conversion device according to any one of claims 1-4. The boiling point of the solvent S ₁ is at 250 ° C. or higher, a method for manufacturing a photoelectric conversion device according to any one of claims 1 to 5.

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