JP2016092293A - Photoelectric conversion element and solar battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a photoelectric conversion element arranged to use a perovskite compound as a light absorbent, which is enhanced in short circuit current density, and hard to cause the drop in photoelectric conversion efficiency even under a high-humidity environment; and a solar battery arranged by use of such a photoelectric conversion element.SOLUTION: A photoelectric conversion element comprises: a first electrode having a photosensitive layer including a light absorbent on a conductive support body; and a second electrode opposed to the first electrode. In the photoelectric conversion element, the photosensitive layer includes a nanorod made of a metal oxide and as the light absorbent, a compound having a perovskite type crystal structure; the aspect ratio of the nanorod is larger than one; and the compound having the perovskite type crystal structure is expressed by the following formula (I): Formula (I) AMX(where A represents an element of Group I of the periodic table or a cationic organic group; M represents a metal atom other than an element of Group I of the periodic table; and X represents an anionic atom). A solar battery comprises the photoelectric conversion element.SELECTED DRAWING: Figure 1

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, Patent Document 1 describes a photovoltaic device having a perovskite crystal structure including a first cation, a second cation, and at least one halide anion or chalcogenide anion. According to Patent Document 1, the first cation is represented by the formula: (R ₁ R ₂ R ₃ R ₄ N) ⁺ or the formula: (R ₅ R ₆ N═CH—R ₇ R ₈ ) ^+. It is an organic cation, and R _{1 to} R ₈ are each considered to be a hydrogen atom, a substituted or unsubstituted C _{1 to} C ₂₀ alkyl group, or a substituted or unsubstituted aryl group. Item 28 and 29).
Non-Patent Document 1 discloses that a solar cell having a compound having a perovskite crystal structure represented by CH ₃ NH ₃ PbI ₃ on a conductive glass substrate on which nanorods are formed has excellent photoelectric conversion efficiency. It has been described.

International Publication No. 2014/045021 Pamphlet

THE JOURNAL OF PHYSICAL CHEMISTRY, 2014, Vol. 118, p. 16567-16573

As described above, photoelectric conversion elements or solar cells using a compound having a perovskite crystal structure (hereinafter also referred to as “perovskite compound”) have attracted attention in recent years. The relationship between the composition and the photoelectric conversion efficiency (for example, the relationship between the short circuit current density and the open circuit voltage) is still unclear.
Moreover, in addition to high photoelectric conversion efficiency, the photoelectric conversion element and the solar cell are required to have durability capable of maintaining initial performance in a field environment where they are actually used. However, it is known that perovskite compounds are susceptible to damage in a high humidity environment. In fact, photoelectric conversion elements or solar cells using a perovskite compound as a light absorber have a reduced photoelectric conversion efficiency in a high humidity environment.
The present invention relates to a photoelectric conversion element using a perovskite compound as a light absorber, a short-circuit current density is increased, and a photoelectric conversion element in which photoelectric conversion efficiency is hardly reduced even in a high humidity environment, and the photoelectric conversion element It is an object to provide a solar cell using a conversion element.

  In the photoelectric conversion element or solar cell using the perovskite compound, the present inventors formed a photosensitive layer by coexisting a nanorod made of a metal oxide and a perovskite compound having a specific chemical composition on a conductive support. In this case, it has been found that a photoelectric conversion element or a solar cell having an increased short-circuit current density and excellent moisture resistance can be obtained. The present invention has been further studied based on these findings and has been completed.

That is, the above-described problems of the present invention have been solved by the following means.
[1]
A photoelectric conversion element having a first electrode having a photosensitive layer containing a light absorber on a conductive support, and a second electrode facing the first electrode,
The photosensitive layer includes a nanorod made of a metal oxide and a compound having a perovskite crystal structure as the light absorber,
The nanorod has an aspect ratio greater than 1,
The photoelectric conversion element in which the compound having the perovskite crystal structure is a compound represented by the following formula (I):
Formula (I) 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.
[2]
The photoelectric conversion element according to [1], wherein A is a cationic organic group represented by the following formula (1).
Formula (1) R ^1a —NH ₃
In the formula, R ^1a represents a substituent having 2 or more carbon atoms.
[3]
In the above formula (1), R ^1a is an alkyl group, an aralkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group or a group represented by the following formula (2): [2 ] The photoelectric conversion element of description.

In formula, ^Xa represents NR ^<1c> , an oxygen atom, or a sulfur atom. R ^1b represents a substituent. R ^1c represents a hydrogen atom or a substituent. * Represents a bonding position with the N atom in the formula (1).
[4]
The photoelectric conversion element according to any one of [1] to [3], wherein X is a halogen atom.
[5]
The photoelectric conversion element according to any one of [1] to [4], wherein M is a Pb atom or a Sn atom.
[6]
The photoelectric conversion element according to any one of [1] to [5], wherein a length of a long side of the nanorod is 1000 nm or less.
[7]
The photoelectric conversion element according to [6], wherein a length of a long side of the nanorod is 300 to 500 nm.
[8]
The photoelectric conversion element according to any one of [1] to [7], wherein the nanorod has an aspect ratio of 1.5 to 20.
[9]
The photoelectric conversion element according to [8], wherein the nanorod has an aspect ratio of 5 to 20.
[10]
The photoelectric conversion element according to any one of [1] to [9], wherein a length of a long side of the nanorod is 300 to 500 nm and an aspect ratio is 5 to 20.
[11]
The nanorods are titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, technetium, rhenium, iron, osmium, cobalt, nickel, copper, zinc, scandium, yttrium, lanthanum, cerium, praseody Mium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, boron, aluminum, gallium, indium, thallium, silicon, germanium, tin, lead, magnesium, calcium, The photoelectric conversion element according to any one of [1] to [10], comprising an oxide of a metal selected from the group consisting of strontium and barium.
[12]
The photoelectric conversion element according to [11], wherein the nanorod is made of a metal oxide selected from titanium oxide and zinc oxide.
[13]
The photoelectric conversion element according to any one of [1] to [12], wherein a major axis of the nanorod is oriented in a direction perpendicular to the surface of the conductive support.
[14]
The photoelectric conversion element according to any one of [1] to [13], which has a hole transport layer between the first electrode and the second electrode.
[15]
The solar cell using the photoelectric conversion element as described in any one of [1]-[14].

  In the present specification, a part of each chemical formula may be expressed as a formula for understanding the chemical structure of the perovskite compound. Accordingly, in each chemical formula, the partial structure is referred to as a (substituted) group, ion, atom, or the like. In this specification, these are represented by the above formula in addition to the (substituted) group, ion, atom, or the like. It may mean an element group or an element constituting a (substituent) group or ion.

  In the present specification, the term “compound” is used to mean not only the compound itself but also its salt and its ion. In addition, a group or compound that does not specify substitution or non-substitution is meant to include a group or compound having an arbitrary substituent within a range that exhibits a desired effect. 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.

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.
In this specification, “surface” of a conductive support, a seed layer, a photosensitive layer and the like constituting a photoelectric conversion element means a surface located on the second electrode side unless otherwise specified.

  The photoelectric conversion element and solar cell of the present invention use a perovskite compound as a light absorber, increase the short-circuit current density, and do not easily decrease the photoelectric conversion efficiency even in a high humidity environment.

It is sectional drawing which showed typically about the preferable aspect of the photoelectric conversion element of this invention.

<< Photoelectric conversion element >>
The photoelectric conversion element of the present invention includes a first electrode having a conductive support, a photosensitive material layer including a nanorod made of a metal oxide (hereinafter also simply referred to as “nanorod”) and a light absorber, and a first electrode. And a hole transport layer provided between the first electrode and the second electrode. The photosensitive layer and the second electrode are provided on the conductive support in this order. Moreover, when a photoelectric conversion element has a positive hole transport layer, the photosensitive layer, the positive hole transport layer, and the 2nd electrode are provided on the electroconductive support body in this order.
The light absorber contains at least one perovskite compound described later. 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.

  In the present invention, “having a photosensitive layer on a conductive support” means an embodiment having a photosensitive layer in contact with the surface of the conductive support, and another layer above the surface of the conductive support. The meaning includes an embodiment having a photosensitive layer.

  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.

  Hereinafter, the preferable aspect of the photoelectric conversion element of this invention is demonstrated.

As a preferable aspect of the photoelectric conversion element of the present invention, for example, a photoelectric conversion element 10 shown in FIG. A system 100 shown in FIG. 1 is a system applied to a battery application that causes an operation circuit M (for example, an electric motor) to perform work on the photoelectric conversion element 10 by an external circuit 6.
This photoelectric conversion element 10 has a first electrode 1, a second electrode 2, and a hole transport layer 3 containing a hole transport material described later between the first electrode 1 and the second electrode 2. .
The first electrode 1 has a conductive support 11 made of a support 11a and a transparent electrode 11b, and a photosensitive layer 13 containing a nanorod 12 made of a metal oxide and a light absorber containing a perovskite compound.

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 passed through 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. After the electrons that have reached the conductive support 11 work in the external circuit 6, via the second electrode 2 (if there is a hole transport layer 3, further via the hole transport layer 3), Return to the photosensitive layer 13. The light absorber is reduced by the electrons returning to the photosensitive layer 13. By repeating the cycle of excitation and electron transfer of the light absorber, the system 100 functions as a solar cell.
In the photoelectric conversion element 10, electron conduction occurs in which electrons move between perovskite compounds.

  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, the material and each member used for the photoelectric conversion element or the solar cell can be prepared by a conventional method except for the constitution specific to the present invention. For a photoelectric conversion element or a solar cell using a perovskite compound, for example, Patent Document 1 and Non-Patent Document 1 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 has a conductive support 11 and a photosensitive layer 13 and functions as a working electrode in the photoelectric conversion element 10.

− 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 includes a conductive material such as a metal, or a glass or plastic support 11a and a transparent electrode 11b as a conductive film formed on the surface of the support 11a. The structure which has is preferable.

In particular, as shown in FIG. 1, 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.

− Photosensitive layer (light absorbing layer) 13 −
The photosensitive layer 13 has a perovskite compound described later as a light absorber. That is, the light absorber exists so as to fill in the space between the nanorods 12 made of a metal oxide.
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 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, layers composed of different light absorbers may be laminated, and an intermediate layer containing a hole transport material is laminated between the photosensitive layer and the photosensitive layer. May be.

  The form having the photosensitive layer 13 on the conductive support 11 is as described above. The photosensitive layer 13 is preferably provided on the conductive support 11 so that excited electrons flow to the conductive support 11.

  The film thickness of the photosensitive layer 13 is appropriately set according to the size of the nanorods and the like, and is not particularly limited. For example, the thickness of the photosensitive layer 13 can be 0.1 to 5 μm, preferably 0.1 to 3 μm, and more preferably 0.2 to 1.5 μm.

  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.

[Nanorods 12 in the photosensitive layer 13]
The photosensitive layer 13 contains nanorods 12 made of a metal oxide. The nanorod in the present invention is a rod-shaped metal oxide structure having a nanometer size (that is, a long side and a short side to be described later are in the range of about 1 to 1000 nm). The nanorod 12 in the present invention has an aspect ratio, which will be described later, larger than 1. That is, the nanorod 12 in the present invention has a form in which the lengths of the long side and the short side are different.

Examples of the metal oxide constituting the nanorod 12 include titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, technetium, rhenium, iron, osmium, cobalt, nickel, copper, zinc, scandium, yttrium. , Lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, boron, aluminum, gallium, indium, thallium, silicon, germanium, tin And oxides of metals selected from the group consisting of lead, magnesium, calcium, strontium and barium.
Especially, it is preferable that the nanorod 12 is comprised with the titanium oxide or the zinc oxide from a viewpoint of the ease of shape control of a nanorod.

  There is no particular limitation on the form of the nanorods 12 in the photosensitive layer 13, and the nanorods may be present in the photosensitive layer 13 at random without unifying the major axis direction, but the major axis of the nanorods 12 is It is preferable to face in the direction perpendicular to the surface of the conductive support 11. More preferably, as shown in FIG. 1, the long axis of the nanorod 12 is oriented in the direction perpendicular to the surface of the conductive support 11, and one end of the nanorod 12 is connected to the conductive support 11 (conductive support). 11 is preferably connected to a seed layer when a seed layer described later is present on the surface.

In the present specification, the major axis of the nanorods is oriented in the direction perpendicular to the surface of the conductive support. More than 50% (more than half) of the nanorods present in the photosensitive layer are nanorods. It means that the angle formed between the major axis direction and the normal line of the surface of the conductive support 11 is between 0 and 45 degrees (this is described in the examples described later, “<Preparation of Titanium Oxide Nanorod Substrate”). > ”And“ <Preparation of Zinc Oxide Nanorod Substrate> ”).
In this specification, the “major axis direction of the nanorod” means a direction parallel to the longest straight line when the straight line connecting one end to the other end of the nanorod is the longest.
In this specification, the “long side of the nanorod” means the longest straight line when the straight line connecting one end to the other end of the nanorod is the longest.
In the present specification, the “short side of the nanorod” is a cross section obtained by cutting the nanorod perpendicularly to the long side, and the longest straight line connecting from one end to the other end of the cross section. This means the longest straight line.

  Moreover, when the nanorod 12 is connected to the conductive support 11 (including an embodiment where the nanorod 12 is connected to a seed layer described later), the end of the nanorod on the conductive support 11 side is the conductive support. From the surface of 11 (the seed layer surface when a seed layer is provided on the conductive support 11) from the surface of the conductive support 11 toward the second electrode side (in this case) The vertical direction in (means a direction of 90 ° with respect to the surface of the conductive support 11) is a portion located at a distance of 5 nm.

The nanorods 12 preferably have a long side length of 1000 nm or less, more preferably 100 to 800 nm, further preferably 200 to 700 nm, further preferably 200 to 600 nm, and 300 to 600 nm. More preferably, it is 500 nm. By setting the length of the long side of the nanorod 12 to the above-mentioned preferable length, the orientation of the perovskite compound is increased, and the short-circuit current density can be further improved.
Further, the aspect ratio (long side length / short side length) of the nanorods 12 is preferably 1.5 to 20, more preferably 5 to 20, further preferably 5 to 15, and further preferably 5 to 12. . By making the aspect ratio of the nanorods 12 within the above preferred range, a perovskite crystal structure is likely to grow in a direction substantially perpendicular to the major axis direction of the nanorods 12, the orientation of the crystal structure is aligned, the electron transfer is smooth, and the short-circuit current density Can be improved.
In this specification, the length of the long side of the nanorod 12 is obtained by measuring the length of the long side of each of the 20 nanorods randomly selected from the nanorods 12 present in the photosensitive layer 13. The average value of 20 measured values.
Further, in this specification, the aspect ratio of the nanorods 12 is the 20 measurements obtained by measuring the aspect ratios of 20 nanorods randomly selected from the nanorods 12 present in the photosensitive layer 13. The average value.

Examples of the method for causing the photosensitive layer 13 to contain nanorods include a method for forming the photosensitive layer 13 by containing nanorods in a light absorbent solution described later.
Also, a method of forming a metal oxide crystal on the conductive support 11 by growing a metal oxide crystal on the conductive support 11 in a direction substantially perpendicular to the surface of the conductive support 11. (Crystal growth method) can also be employed. In the present invention, it is preferable to form nanorods by a crystal growth method from the viewpoint of further improving the orientation of the perovskite crystal structure.

(Crystal growth method)
Crystal growth of the metal oxide by the crystal growth method can be performed by a conventional method. For example, THE JOURNAL OF PHYSICAL CHEMISTRY, 2014, Vol. 118, p. 16567-16573, J. Org. Am. Chem. Soc. 2009, 131, p. 3985-3990, Angew. Chem. Int. Ed. 2003, 42, p. With reference to the description in 3031-3034, a metal oxide crystal can be grown on the conductive support 11. In addition, as described in Examples described later, when a seed layer is formed on the surface of the conductive support 11, this seed layer constitutes the photosensitive layer 13.
In the present specification, the “seed layer” means a layer that serves as a scaffold for nanorod formation. The seed layer also has a function of preventing reverse current.

  In the present invention, the photosensitive layer 13 is preferably provided thicker than the length of the long side of the nanorod 12. By doing so, the light absorber can fill the space between the first electrode and the hole transport layer or the second electrode, so that the flow of electrons becomes smooth. The length of the long side of the nanorod 12 is preferably 1/2 or more of the thickness of the photosensitive layer 13. In this specification, the length of the long side of the nanorods 12 is equal to or greater than ½ of the thickness of the photosensitive layer 13, and the length of the nanorods 12 that are half or more of the nanorods 12 existing on the conductive support 11. It means that the length of the side is 1/2 or more of the thickness of the photosensitive layer 13.

  The volume of all nanorods in the photosensitive layer 13 is preferably 30 to 95% by volume and more preferably 50 to 70% by volume from the viewpoint of light absorption.

[Light absorber in photosensitive layer 13]
The photosensitive layer 13 has, as a light absorber, “Group 1 element or cationic organic group A of the periodic table”, “Metal atom M other than Group 1 element of the periodic table”, and “Anionic atom X”. And a perovskite compound represented by the formula (I) described later.
In the perovskite type crystal structure, the periodic table group 1 element or the cationic organic group A, the metal atom M, and the anionic atom X of the perovskite compound are each a cation (for convenience, sometimes referred to as cation A), a metal cation (for convenience). , Sometimes referred to as cation M) and anion (sometimes referred to as anion 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 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 having 2 or more carbon atoms. Examples of the substituent having 2 or more carbon atoms include alkyl groups (alkyl groups having 2 or more carbon atoms), aralkyl groups, cycloalkyl groups, alkenyl groups, alkynyl groups, aryl groups, heteroaryl groups (heteroaryls having 2 or more carbon atoms). Group) or a group that can be represented by the following formula (2). Of these, an alkyl group or an aralkyl group is preferable.

In formula, ^Xa represents NR ^<1c> , an oxygen atom, or a sulfur atom. R ^1b represents a substituent. R ^1c represents a hydrogen atom or a substituent. However, the number of carbon atoms of the group that can be represented by the above formula (2) is 2 or more. * Represents a bonding position with the N atom in the formula (1).

In the present invention, the organic cation of the cationic organic group A (that is, the organic cation when A is a cationic organic group) is an ammonium cation formed by bonding R ^1a in the above formula (1) and NH _3. An organic ammonium cation composed of a functional organic group A is preferred. 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 ".

When R ^1a is an alkyl group, the alkyl group may be linear or have a branched structure. When R ^1a is an alkyl group, the alkyl group preferably has 2 to 10 carbon atoms, more preferably 2 to 6 carbon atoms, and still more preferably 2 to 4 carbon atoms. Specific examples when R ^1a is an alkyl group include, for example, ethyl, propyl, isopropyl, butyl, tert-butyl, pentyl and hexyl.
When R ^1a is an aralkyl group, the aralkyl group preferably has 7 to 20 carbon atoms, more preferably 7 to 15 carbon atoms, and still more preferably 7 to 13 carbon atoms. The aryl group constituting the aralkyl group is preferably a phenyl group or a naphthyl group. Moreover, 1-5 are preferable, as for carbon number (carbon number except the aryl group which is a substituent) of the alkyl group (namely, alkyl group which has the said aryl group as a substituent) which comprises this aralkyl group, 1-3 are More preferred is methyl or ethyl.
When R ^1a is a cycloalkyl group, the cycloalkyl group is preferably a cycloalkyl group having 3 to 8 carbon atoms, and examples thereof include cyclopropyl, cyclopentyl, and cyclohexyl.

When R ^1a is an alkenyl group, the alkenyl group is preferably an alkenyl group having 2 to 18 carbon atoms, and examples thereof include vinyl, allyl, butenyl, hexenyl and the like.
When R ^1a is an alkynyl group, the alkynyl group is preferably an alkynyl group having 2 to 18 carbon atoms, and examples thereof include ethynyl, butynyl, and hexynyl.

When R ^1a is an aryl group, the aryl group is preferably an aryl group having 6 to 14 carbon atoms, and examples thereof include phenyl.
When R ^1a is a heteroaryl group, the heteroaryl group includes a group consisting only of an aromatic heterocycle, and a condensed heterocycle in which an aromatic heterocycle is condensed with another ring such as an aromatic ring, an aliphatic ring or a heterocycle. And a group consisting of a ring.
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), X ^a is preferably NR ^1c . Here, R ^1c is preferably a hydrogen atom, an alkyl group, an aralkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group or a heteroaryl group, and more preferably a hydrogen atom.
^Examples of the substituent that can be adopted as R ^1b include an alkyl group, an aralkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryl group, and a heteroaryl group.
1-10 are preferable, as for the alkyl group which R ^{< 1b>} and R ^<1c> can respectively take, 1-6 are more preferable, 1-4 are more preferable. Specific examples in the case of this alkyl group include, for example, methyl, ethyl, propyl, isopropyl, butyl, tert-butyl, pentyl and hexyl.
The aralkyl group, cycloalkyl group, alkenyl group, alkynyl group, aryl group and heteroaryl group which R ^1b and R ^1c can each take are the aralkyl group, cycloalkyl group, alkenyl group, alkynyl each of which R ^1a can take. It is synonymous with a group, an aryl group, and a heteroaryl group, and a preferable thing is also the same.

The alkyl group, aralkyl 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 taken as R ^1a , are all substituted. You may have. 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 palladium (Pd), germanium (Ge), tin (Sn), lead (Pb), ytterbium (Yb), europium (Eu), and indium (In). Among these, the metal atom M is particularly preferably a Pb atom or an Sn 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 atoms and Sn atoms 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 a perovskite compound represented by the following formula (I) having each of the above constituent ions.

Formula (I): 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.

  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. Therefore, the periodic table first group element and the cationic organic group constituting the cation A are not particularly limited as long as they are elements or groups that can form the perovskite crystal structure as 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.

As described above, the perovskite compound used in the present invention is a compound represented by A ₂ MX ₄ and not a compound represented by AMX ₃ . That is, the perovskite compound used in the present invention does not have a structure in which basic unit cells are three-dimensionally continuous, but has a layered structure in which inorganic layers and organic layers are alternately stacked.

In the present invention, specific examples of the perovskite compound used as the light absorber 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 , (C ₁₀ H ₇ CH ₂ CH ₂ NH ₃ ) ₂ PbI ₄ , (C ₆ H ₄ FCH ₂ NH _{3) 2} PbI ₄ and the like.
_Here, the _C 10 _{H 7} in _{(C 10 H 7 CH 2 CH} 2 NH 3) 2 PbI 4 _naphthyl, is _C 6 _{H 4} F is Fluorophenyl in _{(C 6 H 4 FCH 2 NH} 3) 2 PbI 4 .

The perovskite compound can be synthesized from MX ₂ and AX. For example, a perovskite compound can be synthesized with reference to Patent Document 1 and Non-Patent Document 1. Also, Akihiro Kojima, Kenjiro Teshima, Yasuo Shirai, and Tsutomu Miyasaka, “Organometric Halide Perovskites as Visible Slightly.” Am. Chem. Soc. , 2009, 131 (17), 6050-6051 as appropriate, a perovskite compound can be synthesized.

<Hole transport layer 3>
The photoelectric conversion element of the present invention preferably has a hole transport layer 3 between the first electrode and the second electrode.
The hole transport layer 3 has a function of replenishing electrons to the oxidant of the light absorber, 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.

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.

  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.

  In the present invention, the total film thickness of the photosensitive layer 13 and the hole transport layer 3 is not particularly limited, but is preferably 0.1 to 55 μm, more preferably 0.5 to 15 μm, and 0.5 to 7 μm, for example. Further preferred.

<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 a glass or plastic having a metal or conductive metal oxide thin film (including a thin film formed by vapor deposition), a glass having a gold or platinum thin film, or a glass vapor deposited with platinum. 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, a spacer or a separator can be used in order to prevent contact between the first electrode 1 and the second electrode 2.
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 using the photoelectric conversion element of this invention. For example, as shown in FIG. 1, a photoelectric conversion element 10 configured to cause the external circuit 6 to work 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 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 of this invention is not specifically limited, For example, the structure of the solar cell of patent document 1 and nonpatent literature 1 is employable except the structure peculiar to this invention.

<< Photoelectric Conversion Element and Solar Cell Manufacturing Method >>
The photoelectric conversion element and the solar cell of the present invention can be produced according to a known production method, for example, the method described in Patent Document 1 or Non-Patent Document 1 except for the configuration specific to the present invention.
Below, the manufacturing method of the photoelectric conversion element and solar cell concerning preferable embodiment (aspect of FIG. 1) of this invention is demonstrated easily.

A photosensitive layer 13 is provided on the surface of the conductive support 11.
<Formation of nanorods>
Nanorods can be formed by conventional methods as described above. For example, THE JOURNAL OF PHYSICAL CHEMISTRY, 2014, Vol. 118, p. 16567-16573 and J. Am. Chem. Soc. 2009, 131, p. 3985-3990, Angew. Chem. Int. Ed. 2003, 42, p. With reference to the description of 3031-3034, the metal oxide crystal can be formed on the conductive support 11 by growth.

<Preparation of light absorber solution>
The light absorber solution contains MX ₂ , AX, which is a raw material for the perovskite compound, and a solvent. Here, A is the above-described cationic organic group A, M is the above-described metal atom M, and X is the above-described anionic atom X. In this light absorber solution, the molar ratio of MX ₂ to AX is appropriately adjusted according to the purpose.
Next, the prepared light absorber solution is applied to the surface of the conductive support 11 (the seed layer surface) on which the nanorods 12 are formed, and is dried. Thereby, the photosensitive layer 13 having the nanorods 12 and the perovskite compound is formed.

A hole transport material solution containing a hole transport material is applied on the photosensitive layer 13 thus provided and dried to form the hole transport layer 3.
The hole transport material solution preferably has a hole transport material concentration of 0.1 to 1.0 M (mol / L) in terms of excellent coating properties.

  After forming the positive hole transport layer 3, the 2nd 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 (coating solution) and the number of coatings.

  Each of the above-mentioned coating liquids may contain additives such as a dispersion aid and a surfactant as 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 photoelectric conversion element produced as described above can be used as a solar cell by connecting an external circuit to the first electrode 1 and the second electrode 2.

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

[Manufacture and evaluation of photoelectric conversion elements]
<Preparation of titanium oxide nanorod substrate>
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. The surface of the obtained conductive support 11 was washed with ethanol, distilled water, and acetone, and then washed with UV ozone to remove organic substances.
An ethanol solution of titanium isopropoxide was dropped onto the washed conductive support 11 and spin-coated (20 seconds at 2000 rpm). After standing for 10 seconds, a titanium oxide seed layer was produced by firing at 500 ° C. for 30 minutes.
The conductive support 11 on which the seed layer was formed was immersed in a solution obtained by adding 20 ml of 37% by mass hydrochloric acid to 20 ml of distilled water and subjected to ultrasonic treatment for 5 minutes.
A conductive support 11 on which a titanium oxide seed layer was formed was placed in an autoclave, and 0.7 ml of titanium (IV) n-butoxide was added thereto. The autoclave was sealed and heated to 170 ° C. to form titanium oxide nanorods. The length of the long side of the titanium oxide nanorods 12 was adjusted by controlling the reaction time.
The aspect ratio of the titanium oxide nanorods 12 was adjusted by using ethylenediamine, ethylenediaminetetraacetic acid, sodium dodecyl sulfate, cetyltrimethylammonium bromide, polyvinylpyrrolidone, and sodium chloride as additives.
The obtained titanium oxide nanorods 12 had their major axis direction perpendicular to the surface of the conductive support 11.

<Preparation of zinc oxide nanorod substrate>
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. The surface of the obtained conductive support 11 was washed with ethanol, distilled water, and acetone, and then washed with UV ozone to remove organic substances.
An ethanol solution of 5 mM zinc acetate dihydrate (Aldrich) was dropped onto the washed conductive support 11 and spin-coated (20 seconds at 2000 rpm). After standing for 10 seconds, annealing was performed at 150 ° C. for 15 minutes. This operation was repeated three times to produce a zinc oxide seed layer.
A solution for forming zinc oxide nanorods was prepared by dissolving equivalent amounts of zinc nitrate hexahydrate and hexamethylenetetramine in distilled water.
The short side length of the zinc oxide nanorods was controlled by adjusting the solution concentration between 20-35 mM. The conductive support 11 on which the zinc oxide seed layer was formed was immersed in the above solution to form zinc oxide nanorods 12 on the seed layer.
The long side length of the zinc oxide nanorods was adjusted by controlling the immersion time.
The obtained zinc oxide nanorods 12 had their major axis direction perpendicular to the surface of the conductive support 11.

− Measurement of nanorod aspect ratio −
The aspect ratio of the nanorod was calculated by measuring the long side and the short side of the nanorod using a scanning electron microscope. The aspect ratios and long side lengths of the titanium oxide nanorods and zinc oxide nanorods 12 obtained above are shown in Tables 1 to 7 below.

Example 1
<Formation of photosensitive layer 13A>
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.
Next, 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 a polytetrafluoroethylene (PTFE) syringe. It filtered with the filter and 40 mass% light absorber solution was prepared.

Conductive support on which titanium oxide nanorods 12 (aspect ratio: 10, long side length: 1000 nm) are formed by spin coating (2000 rpm for 60 seconds, followed by 3000 rpm for 60 seconds) with the prepared light absorber solution 11 was applied. The applied light absorbent solution (a) was dried with a hot plate at 140 ° C. for 40 minutes to form a photosensitive layer 13 having a perovskite compound. The resulting perovskite compound was _{(CH 3 CH 2 -NH 3)} 2 PbI 4. The thickness of the photosensitive layer 13 including the seed layer was 1.2 μm.

<Formation of hole transport layer 3>
2,2 ′, 7,7′-Tetrakis [N, N-di (4-methoxyphenyl) amino] -9,9′-spirobifluorene (Spiro-OMeTAD, 180 mg) as a hole transport material in chlorobenzene (1 mL) Dissolved. 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, a hole transport material solution was applied onto the photosensitive layer 13 by spin coating, and the applied hole transport material solution was dried to form a hole transport layer 3 (film thickness 0.5 μm). .

<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 10 shown in FIG. 1 was manufactured.

Examples 2 to 12, Comparative Example 1
A photoelectric conversion element 10 shown in FIG. 1 was produced in the same manner as in Example 1 except that the titanium oxide nanorods 12 were changed as shown in Table 1 below.

Examples 13 to 24, Comparative Example 2
In the first _embodiment, to change the _{CH 3} CH 2 NH 3 I to _{C 10 H 7 CH 2 CH 2} NH 3 I, further, except for changing as described titanium oxide nanorod 12 in Table 2 below, The photoelectric conversion element 10 shown in FIG. 1 was manufactured in the same manner as Example 1.

Examples 25-36, Comparative Example 3
In Example 1, except that CH ₃ CH ₂ NH ₃ I was changed to C ₆ H ₄ FCH ₂ NH ₃ I, and titanium oxide nanorods 12 were changed as shown in Table 3 below, the examples 1 was manufactured in the same manner as in FIG.

Examples 37 to 46, Comparative Example 4
A photoelectric conversion element 10 shown in FIG. 1 was manufactured in the same manner as in Example 1, except that the titanium oxide nanorods 12 were changed to the zinc oxide nanorods described in Table 4 below.

Examples 47 to 56, Comparative Example 5
In the first _embodiment, to change the _{CH 3} CH 2 NH 3 I to _{C 10 H 7 CH 2 CH 2} NH 3 I, further, was changed to zinc oxide nanorods according titanium oxide nanorod 12 in Table 5 Produced the photoelectric conversion element 10 shown in FIG. 1 in the same manner as in Example 1.

Examples 57 to 66, Comparative Example 6
In Example 1 above, except that CH ₃ CH ₂ NH ₃ I was changed to C ₆ H ₄ FCH ₂ NH ₃ I, and the titanium oxide nanorods 12 were changed to zinc oxide nanorods described in Table 6 below, The photoelectric conversion element 10 shown in FIG. 1 was manufactured in the same manner as Example 1.

Comparative Examples 7 and 8
In the first _embodiment, to change the _{CH 3} CH 2 NH 3 I in _CH 3 NH ₃ I, and the purified _CH 3 NH ₃ I and PbI _2, in a molar ratio of 2: mixed as 1, further titanium oxide The photoelectric conversion element 10 shown in FIG. 1 was manufactured in the same manner as in Example 1 except that the nanorods 12 were changed to titanium oxide nanorods or zinc oxide nanorods described in Table 7.

In Examples 2 to 66 and Comparative Examples 1 to 8, the thickness of the photosensitive layer 13 including the seed layer was as follows.
1.2 μm when the long side of the nanorod is 1000 nm
When the long side of the nanorod is 800 nm, 1.0 μm
700 nm when the long side of the nanorod is 500 nm
500 nm when the long side of the nanorod is 300 nm
300 nm when the long side of the nanorod is 100 nm
250 nm when the long side of the nanorod is 50 nm

Test Example 1 Evaluation of Short-Circuit Current Density (Jsc) Using a solar simulator (manufactured by WACOM, WXS-85H), 1000 W / m ² simulated sunlight was irradiated from a xenon lamp that passed through an AM1.5 filter, and an I-V tester Jsc was measured by measuring current-voltage characteristics using Photoelectric conversion elements (Reference Examples 1 to 4 in Tables 1 to 7) in which a light absorbent solution was applied on a conductive support 11 on which nanorods were not formed and dried to form a photosensitive layer containing a perovskite compound. Using Jsc as a reference, the increase rate of Jsc relative to this reference was evaluated according to the following evaluation criteria. The results are shown in Table 1 below.
− Evaluation criteria for Jsc increase rate −
A: Jsc is more than 1.3 times the standard B: Jsc is more than 1.2 times the standard and 1.3 times or less C: Jsc is more than 1.1 times the standard and 1.2 times or less D: Jsc is the standard 1 .1 times or less

Test Example 2 Evaluation of moisture resistance-Measurement of initial photoelectric conversion efficiency-
Photoelectric conversion efficiency was evaluated as follows.
A battery characteristic test was performed on each of the photoelectric conversion elements prepared above, and the photoelectric conversion efficiency (η /%) was measured to obtain the initial photoelectric conversion efficiency (η /%). The battery characteristic test was performed by irradiating 1000 W / m ² of simulated 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.

− Evaluation of moisture resistance −
The moisture resistance of each photoelectric conversion element was evaluated as follows.
Each photoelectric conversion element whose initial photoelectric conversion efficiency was measured above was stored in a dark place at a temperature of 45 ° C. and a humidity of 60% RH for 80 hours, and then a battery characteristic test was performed in the same manner as described above to obtain a photoelectric conversion efficiency. (Η /%) was measured and taken as the photoelectric conversion efficiency (η /%) after storage.
From the rate of decrease in photoelectric conversion efficiency represented by the following formula, the moisture resistance of the photoelectric conversion element was evaluated based on the following evaluation criteria.

Decreasing rate (%) = 100− {100 × (photoelectric conversion efficiency after storage) / (initial photoelectric conversion efficiency)}

− Evaluation criteria for moisture resistance −
A: Reduction rate is less than 5% B: Reduction rate is 5% or more and less than 20% C: Reduction rate is 20% or more The results are shown in Tables 1 to 7 below.

From the above results, when the aspect ratio of the nanorod is 1 (when the long side and the short side have the same length, that is, when there is no distinction between the long side and the short side), the perovskite compound and the nanorod are contained in the photosensitive layer. Even if coexisting, Jsc of the photoelectric conversion element hardly increased, and the moisture resistance was inferior (Comparative Examples 1 to 6).
Further, even when the photosensitive layer contains nanorods having an aspect ratio larger than 1, when the perovskite compound contained in the photosensitive layer is represented by AMX ₃ , the Jsc of the photoelectric conversion element is almost improved. And the results were inferior in moisture resistance (Comparative Examples 7 and 8).
On the other hand, the photoelectric conversion element defined in the present invention having a photosensitive layer in which a nanorod having an aspect ratio of greater than 1 and a perovskite compound represented by A ₂ MX ₄ coexisted has an improved Jsc and excellent photoelectric conversion. It was shown that the device can realize the efficiency, and the moisture resistance was improved (Examples 1 to 66).

  From the above results, it was found that the photoelectric conversion element or the solar cell of the present invention can achieve excellent photoelectric conversion efficiency and also exhibits excellent moisture resistance.

DESCRIPTION OF SYMBOLS 1 1st electrode 11 Conductive support 11a Support 11b Transparent electrode 12 Nanorod (metal oxide)
13 Photosensitive layer (light absorption layer)
2 Second electrode 3 Hole transport layer 6 External circuit (lead)
10 Photoelectric conversion element 100 System M applying photoelectric conversion element for battery use Electric motor

Claims (15)

A photoelectric conversion element having a first electrode having a photosensitive layer containing a light absorber on a conductive support, and a second electrode facing the first electrode,
The photosensitive layer includes a nanorod made of a metal oxide, and a compound having a perovskite crystal structure as the light absorber,
The nanorod has an aspect ratio greater than 1,
The photoelectric conversion element in which the compound having the perovskite crystal structure is a compound represented by the following formula (I):
Formula (I) 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. The photoelectric conversion element according to claim 1, wherein A is a cationic organic group represented by the following formula (1).
Formula (1) R ^1a —NH ₃
In the formula, R ^1a represents a substituent having 2 or more carbon atoms. In the formula (1), R ^1a is an alkyl group, an aralkyl 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). 2. The photoelectric conversion element according to 2.

In formula, ^Xa represents NR ^<1c> , an oxygen atom, or a sulfur atom. R ^1b represents a substituent. R ^1c represents a hydrogen atom or a substituent. * Represents a bonding position with the N atom 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 M is a Pb atom or a Sn atom.   The photoelectric conversion element of any one of Claims 1-5 whose length of the long side of the said nanorod is 1000 nm or less.   The photoelectric conversion element according to claim 6 whose length of the long side of said nanorod is 300-500 nm.   The photoelectric conversion element of any one of Claims 1-7 whose aspect-ratio of the said nanorod is 1.5-20.   The photoelectric conversion element according to claim 8, wherein the nanorod has an aspect ratio of 5 to 20.   The photoelectric conversion element of any one of Claims 1-9 whose length of the long side of the said nanorod is 300-500 nm, and whose aspect-ratio is 5-20.   The nanorods are titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, technetium, rhenium, iron, osmium, cobalt, nickel, copper, zinc, scandium, yttrium, lanthanum, cerium, praseody Mium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, boron, aluminum, gallium, indium, thallium, silicon, germanium, tin, lead, magnesium, calcium, The photoelectric conversion element of any one of Claims 1-10 which consists of a metal oxide selected from the group which consists of strontium and barium.   The photoelectric conversion element according to claim 11, wherein the nanorod is made of a metal oxide selected from titanium oxide and zinc oxide.   The photoelectric conversion element of any one of Claims 1-12 in which the long axis of the said nanorod has faced the orthogonal | vertical direction with respect to the said electroconductive support body surface.   The photoelectric conversion element according to claim 1, further comprising a hole transport layer between the first electrode and the second electrode.   The solar cell using the photoelectric conversion element of any one of Claims 1-14.

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