JP6878090B2 - Photoelectric conversion element - Google Patents

Description

The present invention relates to a photoelectric conversion element and a method for manufacturing the photoelectric conversion element.

In recent years, organic solar cells using organic materials for light absorption and photoelectric conversion have attracted attention. Typical organic solar cells include dye-sensitized solar cells and organic thin-film solar cells, and various studies have been conducted on these for improving light energy conversion efficiency and durability.

In recent years, perovskite-type solar cells using perovskite crystals, which are composite materials of inorganic and organic materials, have been rapidly attracting attention. It is known that a perovskite type solar cell has excellent light energy conversion efficiency and can easily produce a thin film by applying and drying a solution like an organic solar cell.

For example, in Patent Document 1, CH ₃ NH ₃ M ¹ X ₃ (in the formula, M ¹ is a divalent metal ion, and X is one or more selected from the group consisting of F, Cl, Br, and I. A photoelectric conversion element using a photosensitive material having a perovskite type crystal structure represented by.) Is disclosed.

Japanese Unexamined Patent Publication No. 2014-72227

However, it is known that a perovskite-type solar cell as described in Patent Document 1 is liable to deteriorate by reacting with moisture in the atmosphere. Therefore, improvement of durability is required for industrial application.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a photoelectric conversion element having high durability. Another object of the present invention is to provide a method for manufacturing a photoelectric conversion element capable of efficiently manufacturing such a highly durable photoelectric conversion element.

In order to solve the above problems, one aspect of the present invention includes a first electrode, a second electrode, and a photoelectric conversion layer sandwiched between the first electrode and the second electrode, and the photoelectric conversion layer is provided. The conversion layer _{contains particles made of a perovskite compound represented by ABX 3} as a forming material, and the average particle diameter of the particles is 0.10 μm or more and 0.30 μm or less, and the cubic crystal is obtained in the X-ray diffraction spectrum of the particles. A photoelectric conversion element in which the half-value width of the diffraction peak corresponding to the (111) peak is 2θ and is 0.12 ° or more and less than 0.14 °.
(In the formula, A is one or both of methylammonium ion and formamidinium ion. B is one or both ions of Pb and Sn. X consists of F, Cl, Br and I. One or more ions selected from the group.)

In one aspect of the present invention, an electron transport layer may be provided between the first electrode and the photoelectric conversion layer.

In one aspect of the present invention, the electron transport layer may be configured to use an inorganic material as a forming material.

In one aspect of the present invention, the electron transport layer may be configured to use a conductive oxide as a forming material.

In one aspect of the present invention, the electron transport layer may be configured to use zinc oxide as a forming material.

In another aspect of the present invention, a first solution containing a cation B, an anion X, an organic solvent and water is spin-coated on one main surface side of the electrode to form a BX ₂ layer. The BX ₂ layer is spin-coated with a second solution containing cations A and X _{to form an ABX 3} layer, wherein the A is a methylammonium ion and One or both of formamidinium ions, said B being one or both of Pb and Sn, and said X being selected from the group consisting of F, Cl, Br and I1 _{In the step of forming the BX 2} layer, the first solution contains more than 0% by volume and 2 volumes or less of the water, which is an ion of seeds or more, and the electrode is rotated when the electrode is rotated. spray the gas toward the upper side to the one main surface of, in the step of forming the ABX ₃ layers, dropping the second solution into the BX ₂ layer after immersing the BX ₂ layer to the second solution Provided is a method for manufacturing a photoelectric conversion element in which rotation of the electrode is started and spin coating is performed after a lapse of a predetermined time determined based on the crystal state of the BX ₂ particles constituting the BX _{2 layer.}

According to the present invention, it is possible to provide a photoelectric conversion element having high durability. Further, it is possible to provide a method for manufacturing a photoelectric conversion element capable of efficiently manufacturing such a highly durable photoelectric conversion element.

The schematic sectional view which shows the photoelectric conversion element of this embodiment. The flow chart explaining the manufacturing method of the photoelectric conversion element which concerns on this embodiment. The scatter diagram which shows the relationship between the half width of the diffraction peak corresponding to the (111) peak of a cubic crystal, and the conversion efficiency of the obtained photoelectric conversion element.

[Photoelectric conversion element]
Hereinafter, the photoelectric conversion element according to the present embodiment will be described with reference to FIG. In all the drawings below, the dimensions and ratios of the components are appropriately different in order to make the drawings easier to see.

FIG. 1 is a schematic cross-sectional view showing a photoelectric conversion element of the present embodiment. As shown in the figure, the photoelectric conversion element 10 of the present embodiment includes a first substrate 11, a second substrate 12, a first electrode 13, a second electrode 14, a hole transport layer 15, a photoelectric conversion layer 16, and an electron transport layer 17. , Has a sealing portion 18.

(1st board, 2nd board)
In the present embodiment, the first substrate 11 and the second substrate 12 mainly use a light-transmitting glass plate or resin as a forming material. As the first substrate 11 and the second substrate 12, films or sheets of these forming materials can be used.

Examples of the resin used for such a substrate include polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN); polyolefin resins such as polyethylene (PE), polypropylene (PP) and cyclic polyolefins; polyamide resins. Resins; polycarbonate-based resins; polystyrene-based resins; polyvinyl alcohol-based resins; saponified products of ethylene-vinyl acetate copolymers; polyacrylonitrile-based resins; acetal-based resins; polyimide-based resins.

Among these resins, polyester-based resins and polyolefin-based resins are preferable, and PET and PEN are particularly preferable, from the viewpoints of high heat resistance, high coefficient of linear expansion, and low manufacturing cost.

These resins may be used alone or in combination of two or more.

The thicknesses of the first substrate 11 and the second substrate 12 can be appropriately set in consideration of the stability when manufacturing the photoelectric conversion element of the present embodiment. The thickness of the first substrate 11 and the second substrate 12 is preferably in the range of 5 to 500 μm from the viewpoint that the substrate can be conveyed even in a vacuum.

Further, it is preferable that the first substrate 11 and the second substrate 12 are subjected to a surface activation treatment for cleaning the surface of the substrate from the viewpoint of adhesion to other layers to be laminated. Examples of such surface activation treatment include corona treatment, plasma treatment, and frame treatment.

When the first substrate 11 and the second substrate 12 are resin films or resin sheets, those having one or more thin film layers on the surface thereof are also preferable in order to improve the gas barrier property. Examples of the resin film provided with the thin film layer include the gas barrier laminated film described in JP-A-2011-73430, and a film in which the thin film layer is formed by a plasma CVD method using hexamethyldisiloxane or the like as a film-forming gas is preferable. In this case, the thickness of the substrate is more preferably in the range of 50 to 200 μm, and particularly preferably in the range of 50 to 150 μm.

The above-mentioned thin film layer may have the first substrate 11 and the second substrate 12 on one side, but it is preferable to have the first substrate 11 and the second substrate 12 on both sides.

When the first substrate 11 and the second substrate 12 have the above-mentioned thin film layer on only one side of the substrate, the formed thin film layer is formed by the first substrate 11, the second substrate 12, and the sealing portion 18. It is preferably arranged so as to face the space. With such a configuration, the gas barrier property of the obtained photoelectric conversion element can be improved.

(1st electrode)
The first electrode 13 is formed on the surface of the first substrate 11. The first electrode 13 takes in light and functions as an electrode in which the electric charge generated by the photoelectric conversion layer 16 flows in pairs with the second electrode 14. The first electrode 13 is preferably capable of transmitting visible light and infrared light and ultraviolet light in the vicinity of visible light.

The material of the first electrode 13 is not particularly limited, but _{conductive metal oxides such as In 2} O ₃ (indium oxide), SnO ₂ (tin oxide), and ZnO (zinc oxide) are preferable. Further, ITO (indium tin oxide), FTO (fluorinated tin oxide), IZO (indium zinc oxide), ATO (antimony-added tin oxide), AZO (aluminum-added zinc oxide), GZO (gallium-added zinc oxide), etc. Metal oxides, zinc oxide doped with indium, and zinc oxide doped with boron are also preferable.

Further, the first electrode 13 can also use a conductive polymer material as a material. Examples of the polymer material include polythiophene-based, polypyrrole-based, polyphenylene vinylene-based, and polyacetylene-based polymers.

The first electrode 13 is preferably a thin film formed by using the above metal oxide or polymer material. The first electrode 13 may have a single-layer structure or a laminated structure such as a two-layer structure.

The film thickness of the first electrode 13 is not particularly limited, but is preferably 0.1 to 1 μm.
Further, the first electrode 13 may be subjected to surface treatment such as ozone UV treatment from the viewpoint of adhesion to other layers.

(Hall transportation layer)
The hole transport layer 15 is a p-type semiconductor layer formed in contact with the first electrode 13 and electrically connected to the first electrode 13.
The material of the hole transport layer 15 is not particularly limited, and a known organic semiconductor compound can be used. Examples of the organic semiconductor compound include polymer compounds having a triphenylamine skeleton. The hole transport layer 15 can be produced by dissolving it in an organic solvent, coating or printing it on the first electrode 13, or on the photoelectric conversion layer 16 described later, and heating or firing it.

(2nd electrode)
The second electrode 14 is formed on the surface of the second substrate 12. The material of the second electrode 14 is not particularly limited, but is limited to metals such as gold, silver, platinum, aluminum, and calcium; conductive metal oxides such as _{ITO, FTO, SnO 2, and IZO; conductive.} A polymer material or the like can be used. It is preferable that the thin film formed by using these materials is used as the second electrode 14. The method for forming the thin film is not particularly limited, and the thin film can be formed by a conventional method such as thin film deposition or sputtering.
Among them, as the second electrode 14, a metal electrode or a metal oxide electrode is preferable.

(Electronic transport layer)
The electron transport layer 17 is an n-type semiconductor layer formed in contact with the second electrode 14 and electrically connected to the second electrode 14.

The material for forming the electron transport layer 17 is not particularly limited, and metal oxides such as titanium, tin, zinc, iron, tungsten, zirconium, strontium, indium, cerium, yttrium, lanthanum, vanadium, niobium, and tantalum can be used. Can be used. Among these, titanium oxide (TiO ₂ ), strontium titanate (SrTiO ₃ ), zinc oxide (ZnO), tin oxide (SnO ₂ ), tungsten oxide (WO ₃ ), or niobium oxide (Nb ₂ O ₅ ) Titanium oxide, strontium titanate or zinc oxide is more preferred, and titanium oxide or zinc oxide is particularly preferred.
As the material for forming the electron transport layer 17, zinc oxide formed by a vacuum vapor deposition method or a sputtering method is preferable, and zinc oxide formed by a vacuum vapor deposition method is more preferable.

(Photoelectric conversion layer)
The photoelectric conversion layer 16 is a layer sandwiched between the hole transport layer 15 and the electron transport layer 17 and electrically connected to the hole transport layer 15 and the electron transport layer 17. The photoelectric conversion layer 16 contains particles using a perovskite compound represented by the following formula (1) as a forming material.
ABX ₃ ... (1)

As used herein, the term "perovskite compound" refers to a compound having the same crystal structure as the ore "perovskite" (hereinafter referred to as "perovskite structure"), or a compound having a similar perovskite structure.

In the formula (1), A is one or both of ammonium ion _(CH ³ _NH 3 ⁺⁾ and formamidinium ion ^{_{((NH 2) 2 CH +}} ).

Methylammonium ions have two atoms other than hydrogen, one carbon and one nitrogen. On the other hand, formamidinium ions have a total of three atoms other than hydrogen, one carbon and two nitrogen atoms. Therefore, when the A site of a crystal having a perovskite structure is replaced with these ions, the volume of formamidinium ion occupying the A site is larger than that of methyl ammonium ion.

As a result, for example, the formumamidinium iodoide lead perovskite crystal has a larger crystal than the methylammonium iodide lead perovskite crystal, and the band gap becomes smaller. As a result, when formiodium amidineium lead perovskite crystals are used for the photoelectric conversion layer of the photoelectric conversion element, even infrared rays having a longer wavelength can be used for power generation, and the amount of current can be increased to improve the conversion efficiency.

On the other hand, if the bandgap becomes too small, the electromotive force of the photoelectric conversion element at the time of power generation becomes too small, and the performance may deteriorate.

Therefore, when examining a high-performance photoelectric conversion element, it is preferable to examine the balance between the amount of current and the electromotive force and to form a photoelectric conversion layer having an appropriate band gap that maximizes the conversion efficiency.

From this point of view, in the perovskite crystal constituting the photoelectric conversion layer 16, the above-mentioned methylammonium ion and formamidinium ion may be used in combination. By using methylammonium ion and formamidinium ion in combination and adjusting the ratio of both ions, the balance between the amount of current and the electromotive force of the photoelectric conversion element can be adjusted.

The electromotive force can be increased by increasing the content of methylammonium ions.
Increasing the content of formamidinium ion can increase the amount of current.
In the photoelectric conversion element of the present embodiment, the electromotive force and the amount of current are optimized by adjusting the content of methylammonium ion and formamidinium ion, and the photoelectric conversion element showing the maximum conversion efficiency is adjusted. Can be done.

For example, by using a perovskite crystal having methylammonium ion: formamidinium ion = 3: 2 in the photoelectric conversion layer, a photoelectric conversion element having higher conversion efficiency than using a perovskite crystal based only on methylammonium ion can be obtained. (See Non-Patent Document: Angew.Chem.Int.Ed., Vol.53, Page.3151-3157 (2014)).

In formula (1), B is an ion of either or both of Pb and Sn.

In formula (1), X is one or more ions selected from the group consisting of F, Cl, Br and I. X is preferably Br or I.

The film thickness of the photoelectric conversion layer 16 is not particularly limited, but is preferably 50 nm or more, and more preferably 100 nm or more. The film thickness of the photoelectric conversion layer 16 is preferably 1000 nm or less, more preferably 500 nm or less, and even more preferably 300 nm or less. The upper limit value and the lower limit value of the film thickness of the photoelectric conversion layer 16 can be arbitrarily combined.

In the photoelectric conversion layer 16 of the present embodiment, the average particle size of the particles using the perovskite compound as the forming material (hereinafter, may be referred to as “perovskite particles”) as described above adopts the value measured by the following method. To do.

For the SEM photograph of the perovskite particles, draw 10 straight lines extending in the longitudinal direction of the photograph. The 10 straight lines are evenly spaced. The magnification of the SEM photograph is appropriately adjusted so that one crystal particle does not overlap with two or more straight lines.

Next, in each straight line, the number of crystal grains overlapping the straight line is measured at the two crystal grain interfaces.
Next, in each straight line, the distance from the intersection on the farthest end side of the straight line to the intersection on the farthest end side of the straight line among the intersections between the straight line and the crystal grain interface is measured.
The average value is obtained by dividing the distance between the above-determined intersections by the number of crystal grains obtained earlier, and by multiplying the obtained average value by a conversion coefficient of 1.56, the average crystal grain size of the crystal particles is obtained. Find the value.

In one SEM photograph, the same processing was performed on each of the 10 straight lines, and further, the same processing was performed on SEM photographs of four different fields of view, and the average value of the crystal grain sizes of 40 points was obtained. Let these arithmetic mean be the "average particle size of perovskite crystal particles" to be obtained.

When the film thickness of the photoelectric conversion layer 16 is 100 nm or more and 300 nm or less, the average particle size of the perovskite particles is preferably 100 nm or more and 300 nm or less.

When the average particle size of the perovskite particles is 100 nm (0.10 μm) or more, the grain boundary resistance of the photoelectric conversion layer 16 in which a plurality of crystal grains are laminated does not become too high, and the current generated in the photoelectric conversion layer 16 easily flows. Become. As a result, the conversion efficiency is unlikely to decrease.

Further, when the average particle size of the perovskite particles is 300 nm (0.30 μm) or less, the generated perovskite particles are unlikely to become flat particles flattened in the plane direction of the photoelectric conversion layer 16. The flat particles have low crystallinity, and the strength of the photoelectric conversion layer 16 tends to decrease. However, when the perovskite particles are equal to or less than the upper limit of the average particle size, such a problem can be suppressed.

Further, in the present embodiment, when the X-ray diffraction spectrum of the perovskite particles of the photoelectric conversion layer 16 is measured, the half width of the diffraction peak corresponding to the (111) peak of the cubic crystal is 2θ, which is 0.12 ° or more. It is less than 14 °.

The "(111) peak" refers to a "diffraction peak on the crystal lattice plane represented by the Miller index (111)". The same applies to the notation using other Miller indexes.
Further, the "diffraction peak corresponding to the (111) peak of the cubic crystal" is the incident angle at which the (111) peak of the cubic crystal appears in the X-ray diffraction spectrum whose horizontal axis is the incident angle and the vertical axis is the diffraction intensity. It refers to the diffraction peak that appears at the same incident angle position (corresponding position) as (horizontal axis). In the following description, "diffraction peak corresponding to (111) peak of cubic crystal" may be abbreviated as "corresponding diffraction peak".

For the half width of the diffraction peak, the value measured as follows is adopted.

First, the X-ray diffraction spectrum is measured at 2θ from 10 degrees to 90 degrees by the X-ray diffraction method under the following conditions.
(Measurement condition 1)
Powder X-ray analyzer: X'Pert PRO MPD (manufactured by Spectris Co., Ltd.)
Radiation: Cu-Kα 1 line (λ = 0.154050 nm)
X-ray generated voltage: 45 kV
Current: 40mA
Step size: 0.0020889 degrees
Scan Speed: 0.021989 degrees / sec
Time per Step: 12.065 seconds Measurement time: 1 hour 2 minutes 17 seconds

Next, for the corresponding diffraction peak that appears near 25 degrees at 2θ, the range of 25 degrees ± 0.75 degrees at 2θ is measured under the following conditions. Other measurement conditions are the same as those in the above measurement condition 1.

(Measurement condition 2)
Time per Step: 30.355 seconds Measurement time: 1 hour 4 minutes 41 seconds

The full width at half maximum of the corresponding diffraction peak is calculated from the obtained X-ray diffraction spectrum using the X-ray diffraction pattern comprehensive analysis software JADE (MDI). The calculation process by the above software is performed based on the instruction manual of the above software (Jade (Ver.5) software, instruction manual, Rigaku Denki Co., Ltd.).
In this way, the half width of the corresponding diffraction peak is obtained.

As described above, in the photoelectric conversion element 10 of the present embodiment, in evaluating the crystallinity of the perovskite particles, the half width of the corresponding diffraction peak among the diffraction peaks of the X-ray diffraction spectrum is used.
Hereinafter, the "corresponding diffraction peak" will be described.

Normally, perovskite has a cubic crystal structure above the phase transition temperature called the Curie point. When the X-ray diffraction spectrum is measured for a cubic crystal, the diffraction peaks for the equivalent crystal lattice plane in the crystal appear at the same position. For example, the crystal lattice plane represented by the Miller index (plane index) (100) is equivalent to the crystal lattice plane represented by (010) and (001), and appears at the same position in the diffraction spectrum.

It can be evaluated that the diffraction peak measured in this way has higher crystallinity as the crystal has a narrower half width. In addition, "high crystallinity" means a crystal having few voids in the crystal and little variation in interatomic distance.

However, when the perovskite particles constituting the photoelectric conversion layer 16 are methyl ammonium iodide lead perovskite (CH ₃ NH ₃ PbI ₃ ), the crystal structure of the perovskite particles constituting the photoelectric conversion layer 16 undergoes a phase transition from cubic crystals. It occurs and becomes tetragonal at room temperature. At a lower temperature, a phase transition occurs from a tetragonal crystal at another phase transition temperature, resulting in a tetragonal crystal (orthorhombic crystal). Hereinafter, as an example, the perovskite particles will be described as cubic crystals.

In the orthorhombic system, the crystal lattice planes represented by the Miller index (plane index) (100), (010), and (001) are not equivalent. Therefore, the diffraction peaks of these crystal lattice planes corresponding to the (100) peak of the cubic crystal appear at positions close to each other but at different positions.

As a result, the diffraction peaks of the crystal lattice planes represented by (100), (010), and (001) overlap each other and appear as broad peaks. That is, the "diffraction peak corresponding to the (100) peak of the cubic crystal" is a broad peak. Such a broad peak is a result of overlapping of a plurality of peaks appearing at different positions, and does not indicate low crystallinity.

On the other hand, for cubic crystals, the crystal lattice plane represented by the Miller index (plane index) (111) is equivalent to the crystal lattice plane represented by (-111), (1-11), etc., and is diffracted. Appears at the same position in the spectrum. Further, in the orthorhombic system, the crystal lattice plane represented by the Miller index (plane index) (111) is also equivalent to the crystal lattice plane represented by (-111), (1-11), or the like. Appears at the same position in the diffraction spectrum.

Therefore, the full width at half maximum of the (111) peak of the orthorhombic crystal corresponding to the (111) peak of the cubic crystal reflects the crystallinity. For example, if the corresponding diffraction peak is a broad peak, it can be determined that the crystal has low crystallinity.

The above discussion also applies when methylammonium iodide lead perovskite (CH ₃ NH ₃ PbI ₃ ) exhibits tetragonal crystals at room temperature.

Similarly, methylammonium bromide lead perovskite (CH ₃ NH ₃ PbI ₃ ), which is cubic at room temperature, and formamidinium iodinium lead, which is trigonal at room temperature, have (111) peaks that are crystalline. You can make a judgment.

In the photoelectric conversion element 10 of the present embodiment, the perovskite particles having a half width of 2θ and 0.12 ° or more and less than 0.14 ° at the corresponding diffraction peak have crystallinity suitable as the photoelectric conversion layer 16 of the photoelectric conversion element 10. It has excellent durability. The half width is preferably 0.12 ° or more and 0.13 ° or less.

The photoelectric conversion layer 16 may have components other than the above-mentioned perovskite compound. For example, it may further contain some impurities or a compound having a composition similar to or similar to that of the perovskite compound described above, which is a compound having no perovskite structure.

(Sealing part)
The sealing portion 18 is located between the first substrate 11 and the second substrate 12, and is first so as to surround the first electrode 13, the second electrode 14, the hole transport layer 15, the photoelectric conversion layer 16, and the electron transport layer 17. It is arranged along the peripheral edge portion of the substrate 11 and the second substrate 12, and the first substrate 11 and the second substrate 12 are bonded together. As a result, the photoelectric conversion element 10 has a pair of electrodes, the first electrode 13, the second electrode 14, and the inside of the space formed by the first substrate 11, the second substrate 12, and the sealing portion 18. It has a structure in which a laminate composed of a hole transport layer 15, a photoelectric conversion layer 16 and an electron transport layer 17 is housed.

The sealing portion 18 is preferably made of an organic material having a reactive functional group.
Specifically, those having a vinyl group such as vinyltrimethoxysilane and vinyltriethoxysilane as a reactive functional group;
2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycid Those having an epoxy group such as xipropyltriethoxysilane as a reactive functional group;
Those having a styryl group such as p-styryltrimethoxysilane as a reactive functional group;
Those having a methacryl group such as 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane as a reactive functional group;
Those having an acrylic group such as 3-acryloxypropyltrimethoxysilane as a reactive functional group;
N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropyltriethoxysilane , 3-Aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, N-phenyl-3-aminopropyltrimethoxysilane, N -(Vinylbenzyl) -2-aminoethyl-3-aminopropyltrimethoxysilane having an amino group as a reactive functional group;
Those having a ureido group such as 3-ureidopropyltriethoxysilane as a reactive functional group;
Those having a mercapto group such as 3-mercaptopropylmethyldimethoxysilane and 3-mercaptopropyltrimethoxysilane as a reactive functional group;
Those having a sulfide group such as bis (triethoxysilylpropyl) tetrasulfide as a reactive functional group;
3-Isocyanate Propyl Triethoxysilane or other isocyanate group as a reactive functional group;
Those having a carboxy group as a reactive functional group;
Those having an aldehyde group as a reactive functional group can be mentioned.

As the photoelectric conversion element of the present embodiment, a glass substrate is used as the first substrate 11 and the second substrate 12, an ITO electrode is used as the first electrode 13, and a calcium electrode and a silver electrode are used as the second electrode 14. [Poly [bis (4-phenyl) (2,4,6-triphenylmethyl) amine]] is used as the transport layer 15, the perovskite compound as described above is used as the photoelectric conversion layer 16, and phenyl is used as the electron transport layer 17. with C ₆₁ butyric acid methyl ester, or zinc oxide, it is preferable to use an epoxy compound as the sealing portion 18.

According to the photoelectric conversion element having the above configuration, it is possible to provide a photoelectric conversion element having high durability.

The technical scope of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, the hole transport layer 15 and the electron transport layer 17 may not be provided separately, but may be replaced by a transport layer layer such as PCBM.
Further, the first substrate 11, the second substrate 12, and the sealing portion 18 can also be omitted if necessary.
Further, a buffer layer may be provided between the first electrode 13 and the hole transport layer 15. By providing the buffer layer, the first electrode 13 and the hole transport layer 15 can be isolated, and electrical contact can be reduced or suppressed. As the material of the buffer layer, a conductive material is preferable, and the above-mentioned metal oxide is more preferable.

[Manufacturing method of photoelectric conversion element]
In the method for producing a photoelectric conversion element of the present embodiment, a first solution containing a cation B, an anion X, an organic solvent and water is spin-coated on one main surface of an electrode to form _two BX layers. _{The BX 2} layer is spin-coated with a second solution containing cations A and X to form the BX ₃ layer.

A is either one or both of methylammonium ion and formamidinium ion.
B is an ion of either or both of Pb and Sn.
X is one or more ions selected from the group consisting of F, Cl, Br and I.

The first solution contains the water in an amount of more than 0% by volume and 2 volumes or less based on the organic solvent.

Further, _{in the step of forming the BX 2} layer, gas is sprayed from above the electrode toward the one main surface when the electrode is rotated.

Further, in the step of forming the ABX ₃ layer, after dropwise the second solution into the BX ₂ layer was dipped the BX ₂ layer to the second solution, start the rotation of the electrode after a predetermined time Let it spin coat.
Hereinafter, a method for manufacturing the photoelectric conversion element will be described in order.

(First solution)
As B contained in the first solution, only one kind may be contained, or two or more kinds may be contained. Examples of the _{B source include BX 2} which is a metal salt and _{B (OH) 2} which is a metal hydroxide.

As X contained in the first solution, only one kind may be contained, or two or more kinds may be contained. _{Examples of the X source include BX 2} which is a metal salt and HX which is an inorganic acid.

The organic solvent contained in the first solution is not particularly limited as long as it can dissolve _{BX 2 and other components.}
For example, esters such as methylformate, ethylformate, propylformate, pentylformate, methyl acetate, ethyl acetate, pentyl acetate;
Ketones such as γ-butyrolactone, N-methyl-2-pyrrolidone, acetone, dimethyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone, methylcyclohexanone;
Ethers such as diethyl ether, methyl-tert-butyl ether, diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, 4-methyldioxolane, tetrahydrofuran, methyl tetrahydrofuran, anisole, phenetol;
Methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, tert-butanol, 1-pentanol, 2-methyl-2-butanol, methoxypropanol, diacetone alcohol, cyclohexanol, 2-fluoro Alcohols such as ethanol, 2,2,2-trifluoroethanol, 2,2,3,3-tetrafluoro-1-propanol;
Glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monoethyl ether acetate, and triethylene glycol dimethyl ether;
Amide-based organic solvents such as N, N-dimethylformamide, acetamide, N, N-dimethylacetamide;
Nitrile-based organic solvents such as acetonitrile, isobutyronitrile, propionitrile, and methoxyacetonitrile;
Carboat organic solvents such as ethylene carbonate and propylene carbonate;
Halogenated hydrocarbon-based organic solvents such as methylene chloride, dichloromethane, and chloroform;
Hydrocarbon-based organic solvents such as n-pentane, cyclohexane, n-hexane, benzene, toluene, and xylene;
Examples thereof include dimethyl sulfoxide.

The organic solvent may have a branched structure or a cyclic structure, may have a plurality of functional groups such as −O−, −CO−, −COO−, and −OH, and the hydrogen atom may be fluorine or the like. It may be substituted with a halogen atom.

Only one kind of organic solvent may be contained, or two or more kinds may be contained.

The first solution may contain components other than the above-mentioned B, X and organic solvent. Other components that may be contained include one or more elements selected from the group consisting of Group 1, Group 2, Group 3, Group 11, Group 12, and Group 13 of the periodic table. Can be mentioned. Among them, as the component, Li, Na, Cu, Ag, Au, Mg, Ca, Sr, Ba, Sc, Y, La, Zn, B, Al, Ga and In are preferable.

(Second solution)
As A contained in the second solution, only one kind may be contained, or two kinds may be contained.

As the organic solvent contained in the second solution, the same solvent as those mentioned as the constituents of the first solution can be used. The organic solvent contained in the first solution and the organic solvent contained in the second solution may be the same or different.

FIG. 2 is a flow chart illustrating a method for manufacturing a photoelectric conversion element according to the present embodiment.

(Step S1)
In the method for manufacturing a photoelectric conversion element of the present embodiment, first, the first solution is spin-coated on one main surface side of an electrode provided on a substrate (step S1).

The composition and concentration of the first solution may be appropriately set and adjusted according to the configuration of the target photoelectric conversion element 10 (photoelectric conversion layer 16).

The spin coating conditions (rotation time, rotation speed) may be determined in advance by conducting a preliminary experiment.

When the photoelectric conversion element 10 has a hole transport layer 15 or an electron transport layer 17, the hole transport layer 15 or the electron transport layer 17 is formed on one main surface of the electrode and then used in step S1. When the electrode is the first electrode 13, it is preferable to use it in step S1 after forming the hole transport layer 15 on the first electrode 13. When the electrode is the second electrode 14, it is preferable to use it in step S1 after forming the electron transport layer 17 on the second electrode 14.

(Step S2)
Next, after a lapse of a predetermined time from the start of spin coating, spraying of gas toward the coating film of the first solution provided on one main surface side of the electrode is started (step S2). Step S1 and step S2 correspond to the "step of forming the _{BX 2 layer" in the present invention.}

As the gas, air or an inert gas can be used, and it is preferable to use air because it is inexpensive. Spraying gas toward one main surface of the electrode is referred to as "gas flow" in the following description.

The gas flow may be carried out along the normal direction of the one main surface toward the substantially center of one main surface of the electrode. As a result, the air blown toward the electrodes hits the coating film and then isotropically diffused from the center of the coating film toward the periphery. Therefore, the gas can be sprayed evenly over the entire coating film, and the unevenness of the treatment can be reduced.

The gas flow of the first solution to the coating film promotes evaporation (removal) of the solvent from the coating film. _{As a result, two} BX layers are formed on one main surface side of the electrode.

At this time, as described above, the first solution contains water in an amount of more than 0% by volume and 2 volumes or less with respect to the organic solvent. As a result, the solvent of the first solution becomes more polar and emphasizes the ionicity of the cation B and the anion X.

Further, as the removal of the organic solvent progresses in step S2, the water concentration is relatively increased, and the ionicity of the cation B and the anion X is further emphasized. When the ionicity is emphasized, the crystallization of the ionic crystal BX ₂ is promoted.

As a result, in the production method of the present embodiment, the crystal grains of _{BX 2} generated when the solvent is removed in step S2 are smaller than those in the case where the organic solvent of the first solution does not contain water.

Further, when the crystal grains become large, the chances of atomic defects (voids) in the crystal and variations in the interatomic distance increase in the process of crystal grain growth increase, and the crystal tends to have low crystallinity as a whole. On the other hand, in the production method of the present embodiment, since the crystal grains of _{BX 2} generated as described above are small, the crystallinity of the _{obtained BX 2 crystal tends to be relatively high.}

That is, in the method for producing a photoelectric conversion element of the present embodiment, since the first solution contains more than 0% by volume and 2 volumes or less of water with respect to the organic solvent, it is compared with the case where the solvent does not contain water. The crystal grain size becomes smaller.

Further, since the first solution contains more than 0% by volume and 2 volumes or less of water with respect to the organic solvent, _{the crystallinity of the BX 2} crystal becomes high and the half width becomes small in the X-ray diffraction spectrum.

Further, in the method for producing a photoelectric conversion element of the present embodiment, the particle size and crystallinity of the _{BX 2} crystal can be controlled by controlling the amount of water contained in the first solution within the above range. Increasing the amount of water contained in the solvent of the first solution, the crystal grain size of BX ₂ crystals is small and tends to half width is decreased in the X-ray diffraction spectrum of BX ₂ crystals.

(Step S3)
Next, the BX ₂ layer is immersed in the second solution, and after a lapse of a predetermined time, the rotation of the electrode is started (spin coated) (step S3). Step S3 corresponds to the "step of forming the _{ABX 3} layer" in the present invention.

The second solution is fed into BX ₂ layer by being dropped on the example BX ₂ layers. The second solution dropped, the immersion of the BX ₂ layers Shimiwatari in BX ₂ layers.

At this time, A, which is a cation contained in the second solution, invades the crystal of _{BX 2} to form a crystal structure of the perovskite structure of _{ABX 3.}

Here, the inventor thinks that in the reaction for forming the perovskite structure, _{the crystalline state of BX 2} , which is a precursor of the perovskite structure, contributes to the reactivity, which in turn affects the physical properties of the obtained photoelectric conversion layer. I arrived.

First, in a perovskite-type solar cell using a perovskite crystal, it is considered that the higher the crystallinity of the perovskite crystal, the higher the conversion efficiency and the better the durability. However, in the reaction for forming the perovskite structure, when A invades the crystal of _{BX 2 , it is considered that the crystal structure of BX 2} is disturbed and the crystallinity is lowered.

From this idea, considering the crystallinity that decreases in the reaction for forming the perovskite structure, it is considered _{that the higher the crystallinity of the precursor BX 2} , the higher the crystallinity of the obtained perovskite crystal. That is, it is considered that a better photoelectric conversion layer can be obtained _{when the precursor BX 2 has higher crystallinity. According to this idea, BX 2,} which is a precursor of perovskite crystals, preferably has high crystallinity.

On the other hand, in the reaction in which A contained in the second solution is _{brought into contact with BX 2} to obtain a perovskite crystal as _{described above, it is considered that the high crystallinity of BX 2} inhibits the invasion of A into the crystal. .. Therefore, when BX ₂ having high crystallinity is used as a precursor, the reaction for producing perovskite crystals may not proceed easily. As a result, in the obtained photoelectric conversion layer, unreacted BX ₂ may remain and the conversion efficiency may be low. According to this idea, when _{the crystallinity of BX 2} is high, the physical properties of the photoelectric conversion layer tend to be low.

As a result of examination by the inventor from these ideas, he came up with the idea of controlling the immersion time of the second solution according to the crystallinity of _{BX 2, which is a precursor of perovskite crystals, and completed the invention.}

That is, in the production method of the present embodiment, when the BX _{2 particles constituting the BX 2} layer have high crystallinity, the immersion time of the second solution is relatively long and the BX ₂ particles have low crystallinity. The immersion time of the second solution is relatively shortened. As a result, _{the invasion of A into the crystal of BX 2} can be ensured, and the reaction for forming the perovskite structure can be ensured. The crystallinity of the BX ₂ layers, can be determined from the half width of the X-ray diffraction spectrum of BX ₂ layers.

Further, for various BX ₂ particles (BX ₂ layers) having different crystallinity, it is advisable to confirm in advance the correspondence between the immersion time of the second solution and the physical properties of the obtained perovskite crystals. Thereby, the immersion time of the second solution can be appropriately set according to the crystallinity of the _{BX 2} particles obtained in step S2.

For example, when the predetermined time (gas flow start time) in step S2 is more than 0 seconds and 3 seconds or less, the immersion time (predetermined time) of the second solution may be 35 seconds or more and 50 seconds or less.

The second solution immersion time (predetermined time) can be determined in a guide crystalline PbI ₂ constituting the PbI ₂ layers. Crystalline PbI ₂ may measure the X-ray diffraction of PbI ₂ layers produced, the peak intensities of each peak is determined from the information of the half-value width, halo such as derived from amorphous each peak. When _{the crystallinity of PbI 2} is high, the peak intensity tends to be strong, the half width of the peak is narrow, and the halo tends to be small in the X-ray diffraction spectrum.

When _{the crystallinity of PbI 2} constituting the _{PbI 2} layer is high, the immersion time of the second solution may be set longer. When _{the crystallinity of PbI 2} is low, the immersion time of the second solution may be set short.

After the lapse of the immersion time of the second solution, the electrode (substrate) is rotated to perform spin coating. The spin coating conditions (rotation time, rotation speed) may be determined in advance by conducting a preliminary experiment.

After spin coating, it is preferable to dry the second solution if necessary to volatilize the organic solvent contained in the second solution. Drying may be carried out at room temperature or may be carried out by heating.

(Step S4)
Next, the whole is heat-treated (step S4). Step S4 corresponds to the "step of forming the _{ABX 3} layer" in the present invention.

In the heat treatment, for example, it is preferable to heat to 50 ° C. or higher and 200 ° C. or lower, and more preferably to 100 ° C. or higher and 200 ° C. or lower. By this heat treatment, the formation of a layer of perovskite crystals (ABX ₃ layer) is promoted, and a photoelectric conversion layer is preferably formed.

After that, another layer is laminated on the photoelectric conversion layer, and the periphery of the photoelectric conversion layer is sealed to manufacture the photoelectric conversion element.

In the method for manufacturing a photoelectric conversion element of the present embodiment as described above, first, in steps S1 and S2, a first solution containing a small amount of water is used to form a _{highly crystalline BX 2 layer.} Next, in steps S3 and S4, the second solution is _{immersed in the BX 2 layer for an appropriate time (predetermined time) according to the BX 2} layer having high crystallinity, whereby the perovskite crystal having high crystallinity and high durability ( Form a layer of ABX _3).

As a result, according to the method for manufacturing a photoelectric conversion element of the present embodiment, it is possible to efficiently manufacture a highly durable photoelectric conversion element.

Although preferred embodiments of the present invention have been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to such examples. The various shapes and combinations of the constituent members shown in the above-mentioned examples are examples, and can be variously changed based on design requirements and the like without departing from the gist of the present invention.

Hereinafter, the present invention will be described with reference to Examples, but the present invention is not limited to these Examples.

[Example 1]
A strip-shaped ITO film having a thickness of 150 nm and a width of 2 mm was provided on a 25 mm square glass substrate by a sputtering method, and then surface treatment was performed using ozone UV. The formed ITO film corresponds to the first electrode.

Next, it was dissolved in chlorobenzene so that the concentration of [poly [bis (4-phenyl) (2,4,6-triphenylmethyl) amine]] (PTAA) was 0.5% by weight. The obtained solution is filtered through a Teflon (registered trademark) filter having a pore size of 0.5 μm to prepare a coating solution, which is coated on the entire surface of the glass substrate by covering the ITO film with spin coating and heated at 120 ° C. in the air for 10 minutes. By doing so, a hole transport layer was formed.

_{Next, lead iodide (PbI 2} ) was weighed so as to form a 0.8 M solution, and dissolved in a DMF (N, N-dimethylformamide) solvent at 70 ° C. to prepare a solution. Further, 1% by volume of water was added to DMF to prepare a first solution.

A first solution at 70 ° C. at a rotation speed of 2000 rpm was applied by spin coating on the entire surface of the hole transport layer so as to cover the hole transport layer obtained above. From 2 seconds after the start of rotation of the substrate, air was blown from above in the normal direction of the substrate toward the surface to which the first solution was applied, and the coating film was dried to obtain a lead iodide layer. The rotation time of the substrate was 20 seconds.

Then, methylammonium iodide was dissolved in a solvent of dehydrated IPA (2-propanol) to prepare a 45 mg / ml methylammonium iodide solution (second solution).

The second solution was dropped onto the lead iodide layer obtained above, and the lead iodide layer was immersed in the second solution. After allowing to stand for 35 seconds, spin coating was performed at a rotation speed of 6000 rpm for 20 seconds to remove excess second solution.

Then, a photoelectric conversion layer was obtained by heating at 100 ° C. for 10 minutes in nitrogen at a dew point of −50 ° C.

Then, zinc oxide was vapor-deposited on the photoelectric conversion layer by a vacuum vapor deposition machine to provide a band-shaped zinc oxide layer having a thickness of 15 nm and a width of 2 mm. The formed zinc oxide layer corresponds to the electron transport layer in the present invention.

Further, gold was deposited on the zinc oxide layer, and a strip-shaped gold electrode having a thickness of 100 nm and a width of 2 mm was provided. The formed gold electrode corresponds to the second electrode in the present invention.

The zinc oxide layer and the gold electrode were formed so as to be orthogonal to the ITO film in the field of view from the normal direction of the glass substrate. Further, in the same field of view, the gold electrode was formed so as to just overlap the zinc oxide layer.

As described above, the photoelectric conversion element of Example 1 was produced. The degree of vacuum during the vapor deposition was 1-9 × ^10-5 Pa.

A glass substrate provided with a recess (hereinafter referred to as a glass cover) was prepared, and the photoelectric conversion element formed on the glass substrate was covered with a glass cover and sealed in nitrogen at a dew point of −50 ° C. Specifically, the glass cover is covered so that the photoelectric conversion element is arranged in the recess of the glass cover, and the glass substrate provided with the photoelectric conversion element and the glass cover are sealed with a UV curable resin. did. As a result, a sealing element for measuring conversion efficiency was produced.

(Examples 2 to 7, Comparative Examples 1 to 9)
Except for changing the time from the start of rotation of the substrate to the spraying of air during spin coating of the first solution and the time from the immersion of the lead iodide layer in the second solution to the start of spin coating. In the same manner as in Example 1, the photoelectric conversion elements of Examples 2 to 7 and Comparative Examples 1 to 9 were produced, and a sealing element was produced.

Each of the obtained photoelectric conversion elements was evaluated as follows.

[Conversion efficiency]
The photoelectric conversion elements obtained in Examples and Comparative Examples are irradiated with constant light using a solar simulator (manufactured by Spectrometer, trade name OTENTO-SUNII: AM1.5G filter, irradiance 100 mW / cm ^{2) to generate light.} Current and voltage were measured.

In the embodiment, the ratio of the areas converted maximum output for irradiance 100 mW / cm ² (maximum output in terms of 1 cm ²⁾ (percentage:%) and the conversion efficiency. The maximum output is a value obtained by multiplying the maximum current by the maximum voltage.

[Light resistance test]
The light resistance test was carried out as follows.
Using a xenon weather meter (“Atlas Ci4000” manufactured by Toyo Seiki Seisakusho Co., Ltd.), the light of a xenon lamp, which is pseudo-sunlight, is radiated at 100 mW / cm ² , the temperature is 65 ° C, and the relative humidity is 50%. The sealing elements obtained in Examples and Comparative Examples were irradiated for 2 weeks, and then the conversion efficiency was evaluated.
The conversion efficiency after irradiation for 2 weeks is shown in Table 1 as "durability evaluation" (unit:%).

[X-ray diffraction spectrum of perovskite crystal particles]
The photoelectric conversion element was taken out from the sealing element that had been subjected to the light resistance test, and the X-ray diffraction spectrum was measured so that the X-ray directly hits the photoelectric conversion layer as it is without disassembling the photoelectric conversion element.

The X-ray diffraction spectrum was measured at 2θ from 10 degrees to 90 degrees by the X-ray diffraction method under the following conditions.
(Measurement condition 1)
Powder X-ray analyzer: X'Pert PRO MPD (manufactured by Spectris Co., Ltd.)
Radiation: Cu-Kα 1 line (λ = 0.154050 nm)
X-ray generated voltage: 45 kV
Current: 40mA
Step size: 0.0020889 degrees
Scan Speed: 0.021989 degrees / sec
Time per Step: 12.065 seconds Measurement time: 1 hour 2 minutes 17 seconds

As a result of the measurement, it was confirmed that the corresponding diffraction peak appeared at around 25 degrees at 2θ.

Next, with respect to the confirmed corresponding diffraction peak, the range of 25 degrees ± 0.75 degrees at 2θ was measured under the following conditions. In that range, background measurements and baseline settings were performed. Other measurement conditions were the same as those in the above measurement condition 1.

(Measurement condition 2)
Time per Step: 30.355 seconds Measurement time: 1 hour 4 minutes 41 seconds

The full width at half maximum of the diffraction peak was calculated from the obtained X-ray diffraction spectrum using the X-ray diffraction pattern comprehensive analysis software JADE (MDI Corporation). The calculation process by the above software was performed based on the instruction manual of the above software (Jade (Ver.5) software, instruction manual, Rigaku Denki Co., Ltd.).

[Average particle size of perovskite crystal particles]
The photoelectric conversion element was taken out from the sealing element that had been subjected to the light resistance test, and gold sputtering was performed on the photoelectric conversion layer without disassembling the photoelectric conversion element, and SEM observation of the photoelectric conversion layer was performed. At the time of SEM observation, it was adjusted so that the electron beam directly hits the photoelectric conversion layer of the photoelectric conversion element.

The average particle size of the crystal particles was determined by the following method based on the SEM photograph taken.

First, for the SEM photograph, 10 straight lines extending in the longitudinal direction of the photograph were drawn. The 10 straight lines were evenly spaced. The magnification of the SEM photograph was appropriately adjusted so that one crystal particle did not overlap with two or more straight lines.

Next, in each straight line, the number of crystal grains overlapping the straight line was measured at the two crystal grain interfaces.
Next, in each straight line, the distance from the intersection on the most end side of the straight line to the intersection on the farthest end side of the straight line among the intersections between the straight line and the crystal grain interface was measured.
The average value is obtained by dividing the distance between the above-determined intersections by the number of crystal grains obtained earlier, and by multiplying the obtained average value by a conversion coefficient of 1.56, the average crystal grain size of the crystal particles is obtained. The value was calculated.

In one SEM photograph, the same processing was performed on each of the 10 straight lines, and further, the same processing was performed on SEM photographs of four different fields of view, and the average value of the crystal grain sizes of 40 points was obtained. The arithmetic mean of these was taken as the "average particle size of perovskite crystal particles" to be obtained.

The results of Examples and Comparative Examples are shown in Table 1. In Table 1, "the time from the start of rotation of the substrate to the blowing of air at the time of spin coating of the first solution" is set to "time 1", and "the spin coating is started after the lead iodide layer is immersed in the second solution". "Time to complete" is described as "time 2".

FIG. 3 is a scatter diagram showing the relationship between the half width of the diffraction peak (corresponding diffraction peak) corresponding to the (111) peak of the cubic crystal and the conversion efficiency of the obtained photoelectric conversion element. In FIG. 2, the full width at half maximum (unit: °) is shown on the horizontal axis, and the conversion efficiency (%) is shown on the vertical axis.

As shown in the figure, in the X-ray diffraction spectrum of perovskite particles, those having a half-value width of 2θ and 0.12 ° or more and less than 0.14 ° are more durable than those having a half-value width outside the range. It was confirmed that the sex was high.

From the above results, it was found that the present invention is useful.

10 ... photoelectric conversion element, 11 ... 1st substrate, 12 ... 2nd substrate, 13 ... 1st electrode, 14 ... 2nd electrode, 15 ... Hall transport layer, 16 ... Photoelectric conversion layer, 17 ... Electron transport layer,

Claims (5)

With the first electrode
With the second electrode
A photoelectric conversion layer sandwiched between the first electrode and the second electrode is provided.
The photoelectric conversion layer contains particles made of a perovskite compound represented by _{ABX 3 as a forming material.}
The average particle size of the particles is 0.10 μm or more and 0.30 μm or less.
A photoelectric conversion element in which the half width of the diffraction peak corresponding to the (111) peak of the cubic crystal in the X-ray diffraction spectrum of the particles is 2θ, which is 0.12 ° or more and less than 0.14 °.
(In the formula, A is either one or both of methylammonium ion and formamidinium ion.
B is an ion of either or both of Pb and Sn.
X is one or more ions selected from the group consisting of F, Cl, Br and I. ) The photoelectric conversion element according to claim 1, which has an electron transport layer between the first electrode and the photoelectric conversion layer. The photoelectric conversion element according to claim 2, wherein the electron transport layer is made of an inorganic material as a forming material. The photoelectric conversion element according to claim 3, wherein the electron transport layer is made of a conductive oxide as a forming material. The photoelectric conversion element according to claim 4, wherein the electron transport layer is made of zinc oxide as a forming material.

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