JP2017143150A - Photoelectric conversion element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoelectric conversion element with high heat resistance.SOLUTION: A photoelectric conversion element is laminated with an electron transport layer, a photoelectric conversion layer 5, a hole transport layer 6, and an electrode 7 in this order on a conductive film 2. The electron transport layer comprises a first layer 3 containing a metal oxide, and a second layer 4 provided between the first layer and the photoelectric conversion layer. The second layer contains a first compound having at least one carboxylic acid group, and a second compound, which is a tertiary amine derivative having at least one pyridyl group.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a photoelectric conversion element. Here, the photoelectric conversion element means an element that converts light energy into electric energy or an element that converts electric energy into light energy, and specifically includes a solar cell, a photodiode, and the like.

  In recent years, driving power in electronic circuits has become very small, and various electronic components such as sensors can be driven even with weak power (μW order) for the coming IoT society. Furthermore, when utilizing the sensor, application to an environmental power generation element is expected as a self-supporting power source that can generate and consume on the spot. Among them, a photoelectric conversion element is attracting attention as an element that can generate power anywhere if there is light. In particular, there is a need for a photoelectric conversion element that can efficiently generate power even with weak light. Typical examples of weak light include LED lights and fluorescent lamps. Since they are mainly used indoors, they are called indoor light. The illuminance of these lights is about 20 Lux to 1000 Lux, which is very weak light compared to the direct sunlight (about 100000 Lux). In the environmental power generation element, an element capable of generating power efficiently with room light such as a fluorescent lamp and an LED lamp is required.

  As a photoelectric conversion element, a silicon-based solar cell is most popular, and many devices having high conversion efficiency under sunlight have been reported (for example, Non-Patent Document 1). However, it is generally known that silicon-based solar cells have excellent conversion efficiency under sunlight, but have low conversion efficiency under weak light (for example, Non-Patent Document 2). On the other hand, a dye-sensitized solar cell announced by Graetzel et al. Of Lausanne University of Technology in Switzerland has been reported to have a higher photoelectric conversion characteristic than a silicon solar cell under weak light (for example, Non-Patent Document 3). . It is also known that bulk heterojunction organic thin-film solar cells, which are a mixture of P-type organic semiconductors developed by Heeger et al. And N-type organic semiconductors typified by fullerenes, have a relatively high power generation capability under low light ( Non-patent document 4). However, it is known that the conversion efficiency of bulk heterojunction organic thin film solar cells is significantly reduced when placed at high temperatures (Non-patent Document 5). Thus, some means for improving heat resistance have been reported (Non-Patent Document 6), but these means are still insufficient. In particular, the characteristics under room light are more sensitive to heat than the characteristics under sunlight, and further improvement in heat resistance is desired.

  An object of this invention is to provide a photoelectric conversion element with high heat resistance.

The above problem is solved by the following invention 1).
1) A photoelectric conversion element in which an electron transport layer, a photoelectric conversion layer, a hole transport layer, and an electrode are sequentially stacked on a conductive film, wherein the electron transport layer includes a first layer containing a metal oxide, and A second layer provided between the first layer and the photoelectric conversion layer, the second layer comprising: a first compound having at least one carboxylic acid group; and at least one pyridyl. A photoelectric conversion element comprising a second compound which is a tertiary amine derivative having a group.

  According to the present invention, a photoelectric conversion element having high heat resistance can be provided.

The figure which shows an example of the laminated constitution of the photoelectric conversion element of this invention.

（上記式中、Ｒ１、Ｒ２は、炭素数１〜６の直鎖状又は分岐鎖状のアルキル基、又はベンジル基を表し、Ｘは、炭素数４〜６の２価の芳香族基、又は炭素数１〜４のアルキレン基を表す。また、Ｒ１とＲ２は、結合してヘテロ環を形成してもよい。）
３） 前記第一の化合物と前記第二の化合物の混合比が５０：５０〜９９：１（重量比）であることを特徴とする１）又は２）に記載の光電変換素子。
４） 前記金属酸化物が、酸化亜鉛又は酸化チタンであることを特徴とする１）〜３）のいずれかに記載の光電変換素子。 Hereinafter, the present invention 1) will be described in detail. However, since the following 2) to 4) are also included in the embodiment of the present invention 1), these will be described together.
2) Said 1st compound is what is represented by following General formula (1), The photoelectric conversion element as described in 1) characterized by the above-mentioned.
General formula (1)

(In the above formula, R 1 and R 2 represent a linear or branched alkyl group having 1 to 6 carbon atoms or a benzyl group, and X is a divalent aromatic group having 4 to 6 carbon atoms, or Represents an alkylene group having 1 to 4 carbon atoms, and R1 and R2 may combine to form a heterocycle.)
3) The photoelectric conversion element according to 1) or 2), wherein a mixing ratio of the first compound and the second compound is 50:50 to 99: 1 (weight ratio).
4) The photoelectric conversion element according to any one of 1) to 3), wherein the metal oxide is zinc oxide or titanium oxide.

An example of the layer structure of the photoelectric conversion element of the present invention is shown in FIG. 1, but the embodiment of the present invention is not limited to this.
In FIG. 1, a conductive film 2, an electron transport layer including a first layer 3 and a second layer 4, a photoelectric conversion layer 5, a hole transport layer 6, and an electrode 7 are provided on a substrate 1 in this order.
Hereinafter, each layer will be described.

<Electron transport layer>
The electron transport layer is composed of a first layer and a second layer.
There is no restriction | limiting in particular in the average thickness of an electron carrying layer, Although it can select suitably according to the objective, It is preferable to cover the whole surface thinly as much as possible, and 10-60 nm is more preferable.

≪First layer≫
The first layer forming the electron transport layer needs to contain a metal oxide in order to adsorb a basic carboxylic acid derivative contained in the second layer described later. Examples of metal oxides include zinc oxide, titanium oxide, and tin oxide.
Materials other than the metal oxide can be appropriately selected from known materials. For example, perylenetetracarboxylic acid anhydride, perylenetetracarboxylic acid diimide, oxazole derivative, triazole derivative, phenanthroline derivative, phosphine oxide derivative, fullerene compound , Carbon nanotubes (CNT), electron-accepting organic materials such as cyano-substituted polyphenylene vinylene (CN-PPV), and inorganic materials such as lithium fluoride and calcium metal.
The first layer can be manufactured by the sol-gel method or the sputtering method using the above material.

≪Second layer≫
The second layer forming the electron transport layer needs to contain a first compound having at least one carboxylic acid group and a second compound that is a tertiary amine derivative having at least one pyridyl group. .

[First compound having a carboxylic acid group]
The first compound having a carboxylic acid group contained in the second layer is adsorbed on the first layer. Among the first compounds, tertiary amine derivatives having a carboxylic acid group are preferred, and compounds represented by the general formula (1) are more preferred.
Examples of the linear or branched alkyl group having 1 to 6 carbon atoms related to R1 and R2 in the general formula (1) include an ethyl group, a propyl group, a butyl group, a pentyl group, and a hexyl group. Of these, a methyl group and an ethyl group are preferable.
X represents an aromatic group having 4 to 6 carbon atoms or an alkylene group having 1 to 4 carbon atoms. Examples thereof include a phenylene group, a thienylene group, a methylene group, and an ethylene group, preferably a phenylene group and a thienylene. It is a group.

As a result of intensive studies by the present inventors, the reason is not clear, but the first compound having a carboxylic acid group and the second compound which is a tertiary amine derivative having a pyridyl group are adsorbed to the first layer. As a result, a solar cell having high heat resistance even under weak light could be obtained.
It is known in dye-sensitized solar cells and the like that acidic groups typified by carboxylic acid groups are favorably adsorbed on metal oxides. It is also known that pyridyl groups are adsorbed at sites different from carboxylic acid groups on metal oxides. In the present invention, the first compound having a carboxylic acid group and the second compound which is a tertiary amine derivative having a pyridyl group are adsorbed to the first layer by skillfully utilizing the adsorptivity. Yes. A low molecular weight material having no carboxylic acid group or pyridyl group dissolves when the photoelectric conversion layer is applied, so it does not remain on the first layer and cannot exhibit the effect. Even if a polymer material having a tertiary amine is applied on the first layer, a basic layer can be provided between the photoelectric conversion layer and the first layer, but a polymer having a tertiary amine can be provided. Since the material is insulative, electron transport properties are hindered when the film thickness is increased. In addition, it is impossible to obtain a photoelectric conversion element having high heat resistance because the adhesion between the first layer and the basic layer is poor by simple application. On the other hand, the first compound having a carboxylic acid group and the second compound which is a tertiary amine derivative having a pyridyl group can be adsorbed to the first layer as a monomolecular layer. However, the effect of increasing the heat resistance is great because it is in close contact with a carboxylic acid group or a pyridyl group.

Here, although the specific example of a compound represented by the said General formula (1) is shown, it is not limited to these.

[Second compound which is a tertiary amine derivative having a pyridyl group]
The second compound is adsorbed on the first layer. Preferred examples include dimethylaminopyridine, 4- (pyrrolidino) pyridine, 1- (4-pyridyl) piperazine, 4- (4-pyridyl) morpholine, 9-azajulolidine, 1- (4-pyridyl) -4-piperazinone, N, N-diisopropylaminopyridine, N, N-dibenzylaminopyridine and the like can be mentioned. Particularly preferred is dimethylaminopyridine.

<Board>
The substrate is not particularly limited and a known material can be used, but a transparent material is preferable, and examples thereof include glass, a transparent plastic plate, a transparent plastic film, and an inorganic transparent crystal.

<Conductive film, electrode>
At least one of the conductive film and the electrode needs to be transparent to visible light, but the other may be transparent or opaque.
The material transparent to visible light is not particularly limited, and known materials used for ordinary photoelectric conversion elements and liquid crystal panels can be used. Examples include conductive metal oxides such as tin-doped indium oxide (ITO), fluorine-doped tin oxide (FTO), antimony-doped tin oxide (ATO), aluminum-doped zinc oxide (AZO), and gallium-doped zinc oxide (GZO). Is mentioned.
The average thickness of the conductive film or electrode transparent to visible light is preferably 5 nm to 10 μm, and more preferably 50 nm to 1 μm.
The conductive film transparent to visible light is preferably provided on a substrate made of a material transparent to visible light in order to maintain a certain hardness, and the electrode and the substrate are integrated. You can also. Examples thereof include FTO coated glass, ITO coated glass, zinc oxide: aluminum coated glass, FTO coated transparent plastic film, ITO coated transparent plastic film and the like.

The conductive film transparent to visible light has transparency such as a metal film provided on a glass substrate or the like having a structure capable of transmitting light such as a mesh shape or a stripe shape, carbon nanotube, graphene, or the like. It may be laminated to the extent. These may be used individually by 1 type, and 2 or more types may be mixed or laminated | stacked.
Furthermore, a metal lead wire or the like may be used for the purpose of reducing the substrate resistance. Examples of the material of the metal lead wire include metals such as aluminum, copper, silver, gold, platinum, and nickel. Examples of the method for providing the metal lead wire include a method in which deposition is performed on a substrate by vapor deposition, sputtering, pressure bonding, and the like, and ITO or FTO is provided thereon.
Examples of the material in the case where an opaque electrode is used for either the electron collector electrode or the hole collector electrode include metals such as platinum, gold, silver, copper, and Al, and graphite. The thickness of the opaque electrode is not particularly limited, and one type may be used alone, or two or more types may be used in a laminated configuration.

<Hole transport layer>
A hole transport layer may be provided to improve the hole collection efficiency. Specifically, conductive polymers such as PEDOT: PSS (polyethylenedioxythiophene: polystyrenesulfonic acid), hole transporting organic compounds such as aromatic amine derivatives, holes such as molybdenum oxide, vanadium oxide, and nickel oxide. An inorganic compound having a transporting property is formed by spin coating, a sol-gel method, sputtering, or the like. In the present invention, molybdenum oxide is preferred.
There is no restriction | limiting in particular in the average thickness of a hole transport layer, Although it can select suitably according to the objective, It is preferable to cover the whole surface as thinly as possible, and 1-50 nm is more preferable.

<Photoelectric conversion layer>
The photoelectric conversion layer is formed between the electron transport layer and the hole transport layer. A bulk heterojunction type photoelectric conversion layer in which a P-type organic semiconductor and an N-type organic semiconductor are mixed is preferable. A nano-sized PN junction is formed in the photoelectric conversion layer, and current is generated by utilizing photocharge separation generated at the junction surface. Get. The P-type organic semiconductor is composed of an electron-donating material, and the N-type semiconductor is composed of an electron-accepting material.
Examples of P-type organic semiconductors include polythiophene and derivatives thereof, arylamine derivatives, stilbene derivatives, oligothiophene and derivatives thereof, phthalocyanine derivatives, porphyrin and derivatives thereof, polyphenylene vinylene and derivatives thereof, polythienylene vinylene and derivatives thereof, benzo Conjugated polymers and low molecular weight compounds such as dithiophene derivatives and diketopyrrolopyrrole derivatives are exemplified, and these may be used in combination.
Preferred P-type organic semiconductors are polythiophene, which is a conductive polymer having π conjugation, and derivatives thereof. Polythiophene and its derivatives can ensure excellent stereoregularity and have relatively high solubility in solvents. Polythiophene and its derivatives are not particularly limited as long as they are compounds having a thiophene skeleton. Specific examples include polyalkylthiophenes such as poly-3-hexylthiophene, poly-3-hexylisothionaphthene, poly-3-octylisothionaphthene, and poly-3-decylisothionaphthene. Examples include thionaphthene; polyethylene dioxythiophene and the like.

Further, in recent years, PTB7 (poly ({4,8-bis [(2-ethylhexyl) oxy] benzo [1,2-b: 4,4,4), which is a copolymer of benzodithiophene, carbazole, benzothiadiazole, and thiophene. 5-b ′] dithiophene-2,6-diyl} {3-fluoro-2-[(2-ethylhexyl) carbonyl] thieno [3,4-b] thiophenezyl})) and PCDTBT (poly [N-9 ″ Derivatives such as -heptadecanyl-2,7-carbazole-alt-5,5- (4 ', 7'-di-2-thienyl-2', 1 ', 3'-benzothiadiazole)]) It is known as a compound that can obtain conversion efficiency.
Furthermore, not only a conjugated polymer but also a low molecular compound in which an electron donating unit and an electron withdrawing unit are combined is known, and a compound capable of obtaining excellent photoelectric conversion efficiency is known and can be used in the present invention. (See Non-Patent Document 6)

Examples of the N-type organic semiconductor material include fullerene and fullerene derivatives. Among these, fullerene derivatives are preferable from the viewpoint of charge separation and charge transport.
As said fullerene derivative, what was synthesize | combined suitably may be used or a commercial item may be used. Examples of commercially available products include PC71BM (phenyl C71 butyric acid methyl ester), PC61BM, fullerene indene 2-adduct, etc., manufactured by Frontier Carbon Corporation.

As a method for forming the photoelectric conversion layer, spin coating, blade coating, slit die coating, screen printing coating, bar coater coating, mold coating, print transfer method, dip pulling method, ink jet method, spray method, vacuum deposition method, etc. Is mentioned. From these, thickness control and orientation control can be appropriately selected according to the characteristics of the organic material thin film to be produced.
For example, when spin coating is performed, the concentration of the P-type organic semiconductor material and the N-type organic semiconductor material is preferably 5 to 40 mg / mL, and a uniform organic material thin film can be easily formed by using this concentration. Can be produced.
In order to remove the organic solvent from the produced organic material thin film, an annealing treatment may be performed under reduced pressure or under an inert atmosphere (in a nitrogen or argon atmosphere). The temperature of the annealing treatment is preferably 40 ° C to 300 ° C, more preferably 50 ° C to 200 ° C. Also, by performing the annealing treatment, the effective area where the stacked layers permeate and contact each other at the interface increases, and the short circuit current can be increased. Note that the annealing treatment may be performed after the electrodes are formed.

There is no restriction | limiting in particular as an organic solvent, According to the objective, it can select suitably. Examples include methanol, ethanol, butanol, toluene, xylene, o-chlorophenol, acetone, ethyl acetate, ethylene glycol, tetrahydrofuran, dichloromethane, chloroform, dichloroethane, chlorobenzene, dichlorobenzene, trichlorobenzene, chloronaphthalene, dimethylformamide, Examples thereof include dimethyl sulfoxide, N-methylpyrrolidone, and γ-butyrolactone. These may be used alone or in combination of two or more. Among these, chlorobenzene, chloroform, and orthodichlorobenzene are preferable.
In addition, an additive of 0.1 to 10% by weight may be added to the solvent for controlling the phase separation structure of the P-type organic semiconductor material and the N-type organic semiconductor material. Examples of additives include diiodoalkanes (1,8-diiodooctane, 1,6-diiodohexane, 1,10-diiododecane, etc.), alkanedithiols (1,8-octanedithiol, 1,6-hexane). Dithiol, 1,10-decanedithiol), 1-chloronaphthalene, polydimethylsiloxane derivatives and the like.

  The average thickness of the organic material thin film is preferably 50 to 400 nm, and more preferably 60 to 250 nm. If the average thickness is 50 nm or more, light absorption by the organic material thin film is small and carrier generation is not insufficient. If the average thickness is 400 nm or less, the transport efficiency of carriers generated by light absorption is further reduced. There is nothing wrong.

<Application>
The photoelectric conversion element of the present invention can be applied to a power supply device by combining with a circuit board for controlling the generated current. Examples of devices that use such a power supply device include an electronic desk calculator and a wristwatch. In addition, the power supply apparatus having the photoelectric conversion element of the present invention can be applied to a mobile phone, an electronic notebook, electronic paper, and the like. Moreover, the power supply device which has the photoelectric conversion element of this invention can also be used as an auxiliary power supply for extending the continuous use time of a rechargeable or dry battery type electric appliance. Furthermore, it can be applied as an image sensor.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further more concretely, this invention is not limited at all by these Examples.

Example 1
(Preparation of electron transport layer)
1 g of zinc acetate (manufactured by aldrich), 0.28 g of ethanolamine (manufactured by aldrich), and 10 mL of methoxyethanol (manufactured by Wako) were stirred overnight at room temperature to prepare a zinc oxide precursor solution. This zinc oxide precursor solution was applied onto an ITO substrate by spin coating so as to have a film thickness of 20 nm, and dried at 200 ° C. for 10 minutes to form a first layer.
4-Methylbenzoic acid (manufactured by TCI) and 4-dimethylaminopyridine were dissolved in ethanol so that each concentration was 1 mg / mL to prepare a mixed adsorption solution for the second layer. 0.02 mL of this mixed adsorbent is dropped on the first layer in a spin coater and left for 30 seconds, and then rotated at 5000 rpm for 30 seconds to form an electron transport layer composed of the first layer and the second layer. Was made.
The adsorbate on the first layer was measured by the following method.
The ITO substrate provided with the electron transport layer was immersed in 100 mL of THF for 10 minutes. THF was concentrated to 1 mL, and the concentrated solution was analyzed by high performance liquid chromatography (LC-2010 manufactured by Shimadzu Corporation). The results are shown in Table 1.

(Preparation of photoelectric conversion layer)
3 mg of the compound of the following structural formula A and 3 mg of PC61BM (manufactured by Aldrich) were dissolved in 0.4 mL of chloroform containing 1 vol% of 1-chloronaphthalene (manufactured by TCI) to prepare a solution for a photoelectric conversion layer. Next, this photoelectric conversion layer solution was applied on the electron transport layer by a spin coating method so as to have a film thickness of 100 nm, thereby preparing a photoelectric conversion layer.
Structural formula A

(Hole transport layer and electrode fabrication)
On the photoelectric conversion layer, molybdenum oxide (manufactured by Koyo Chemical Co., Ltd.) as a hole transport layer was formed to a thickness of 10 nm, and as an electrode, silver was formed to a thickness of 100 nm in this order by a vacuum deposition method to produce a photoelectric conversion element (solar cell).

The maximum output of the obtained solar cell under white LED irradiation (0.01 mW / cm ² ) was measured. Then, after putting in a 70 degreeC thermostat and hold | maintaining for 100 hours, after taking out and leaving to stand at room temperature for 2 hours, the maximum output after a heat test was measured.
Table 1 shows the maximum output retention rate after the heat resistance test calculated by the following equation.

Maximum output holding ratio = maximum output after holding / maximum output before holding

The white LED used was a desk lamp CDS-90α (study mode) manufactured by Cosmo Techno, and the output was measured using a solar cell evaluation system As-510-PV03 manufactured by NF Circuit Design Block.

Example 2
A solar cell was produced in the same manner as in Example 1 except that 4-dimethylaminobenzoic acid (manufactured by TCI) was used instead of 4-methylbenzoic acid in the production of the electron transport layer of Example 1. evaluated. The results are shown in Table 1.

Example 3
Instead of 4-methylbenzoic acid in the production of the electron transport layer of Example 1, 4-dimethylaminobenzoic acid (manufactured by TCI) was used, the concentration was 0.33 mg / mL, and 4-dimethylaminopyridine A solar cell was produced and evaluated in the same manner as in Example 1 except that the concentration was changed to 0.66 mg / mL. The results are shown in Table 1.

Example 4
Instead of 4-methylbenzoic acid in the preparation of the electron transport layer of Example 1, 4-dimethylaminobenzoic acid (manufactured by TCI) was used, the concentration was 0.99 mg / mL, and 4-dimethylaminopyridine A solar cell was produced and evaluated in the same manner as in Example 1 except that the concentration was changed to 0.01 mg / mL. The results are shown in Table 1.

Example 5
A solar cell was produced and evaluated in the same manner as in Example 1 except that 4- (pyrrolidino) pyridine (manufactured by TCI) was used instead of 4-dimethylaminopyridine in the production of the electron transport layer of Example 1. did. The results are shown in Table 1.

Example 6
A solar cell was produced in the same manner as in Example 1 except that 1- (4-pyridyl) piperazine (manufactured by TCI) was used in place of 4-dimethylaminopyridine in the production of the electron transport layer of Example 1. And evaluated. The results are shown in Table 1.

Example 7
A solar cell was produced in the same manner as in Example 1, except that 4- (4-pyridyl) morpholine (manufactured by TCI) was used instead of 4-dimethylaminopyridine in the production of the electron transport layer of Example 1. And evaluated. The results are shown in Table 1.

Example 8
A solar cell was produced and evaluated in the same manner as in Example 1 except that 9-azajulolidine (manufactured by TCI) was used instead of 4-dimethylaminopyridine in the production of the electron transport layer of Example 1. The results are shown in Table 1.

Example 9
A solar cell was produced and evaluated in the same manner as in Example 1 except that 4-diethylaminobenzoic acid (manufactured by TCI) was used instead of 4-methylbenzoic acid in the production of the electron transport layer of Example 1. did. The results are shown in Table 1.

Example 10
The same as Example 1 except that 4- (4-methylpiperazinyl) -benzoic acid (manufactured by TCI) was used instead of 4-methylbenzoic acid in the production of the electron transport layer of Example 1. A solar cell was prepared and evaluated. The results are shown in Table 1.

Example 11
A solar cell was produced in the same manner as in Example 1 except that 4-dibenzylaminobenzoic acid (manufactured by TCI) was used instead of 4-methylbenzoic acid in the production of the electron transport layer of Example 1. evaluated. The results are shown in Table 1.

Example 12
A solar cell was produced and evaluated in the same manner as in Example 2 except that the photoelectric conversion layer in Example 2 was changed to one produced as described below. The results are shown in Table 1.
(Preparation of photoelectric conversion layer)
10 mg of PTB7 (manufactured by aldrich) and 15 mg of ICBA (manufactured by N type organic semiconductor: frontier carbon) were dissolved in 1 mL of chlorobenzene containing 3 vol% diiodooctane (manufactured by TCI) to prepare a solution for a photoelectric conversion layer. did. Using this photoelectric conversion layer solution, a photoelectric conversion layer was formed on the electron transport layer in the same manner as in Example 1.

Example 13
A solar cell was produced in the same manner as in Example 2 except that the material of the first layer in the production of the electron transport layer of Example 2 was changed to titanium oxide and the first layer was formed as follows. evaluated. The results are shown in Table 1.
(Formation of the first layer of the electron transport layer)
A first layer made of titanium metal oxide was formed on the ITO glass substrate by reactive sputtering with oxygen gas using a target made of metal titanium. A sputtering device (DVD-Spinter) manufactured by UNAXIS was used for the sputtering film formation. The film thickness of the first layer was 10 nm.

Comparative Example 1
A solar cell was produced and evaluated in the same manner as in Example 1 except that the second layer was not formed in Example 1. The results are shown in Table 1.

Comparative Example 2
In Example 2, a solar cell was produced and evaluated in the same manner as in Example 2 except that 4-dimethylaminopyridine was not used for the second layer. The results are shown in Table 1.

Comparative Example 3
In Example 2, a solar cell was produced and evaluated in the same manner as in Example 2 except that 4-dimethylaminobenzoic acid was not used for the second layer. The results are shown in Table 1.

Comparative Example 4
A solar cell was produced and evaluated in the same manner as in Example 12 except that the second layer was not formed in Example 12. The results are shown in Table 1.

Comparative Example 5
In Example 12, a solar cell was produced and evaluated in the same manner as in Example 12 except that 4-dimethylaminobenzoic acid was not used for the second layer. The results are shown in Table 1.

Comparative Example 6
In Example 12, a solar cell was produced and evaluated in the same manner as in Example 12 except that 4-dimethylaminopyridine was not used for the second layer. The results are shown in Table 1.

Comparative Example 7
A solar cell was prepared and evaluated in the same manner as in Example 2 except that 4-t-butylpyridine (manufactured by TCI) was used instead of 4-dimethylaminopyridine in Example 2. The results are shown in Table 1.

Comparative Example 8
A solar cell was produced and evaluated in the same manner as in Example 13 except that the second layer was not formed in Example 13. The results are shown in Table 1.

Comparative Example 9
In Example 13, a solar cell was produced and evaluated in the same manner as in Example 13 except that 4-dimethylaminobenzoic acid was not used for the second layer. The results are shown in Table 1.

Comparative Example 10
In Example 13, a solar cell was produced and evaluated in the same manner as in Example 13 except that 4-dimethylaminopyridine was not used for the second layer. The results are shown in Table 1.

Comparative Example 11
A solar cell was produced and evaluated in the same manner as in Example 1 except that the first layer in the production of the electron transport layer of Example 1 was formed as follows. The results are shown in Table 1.
(Formation of the first layer of the electron transport layer)
An 80% ethoxylation solution of polyethyleneimine, 37 wt% in H ₂ O (molecular weight of polymer: 110000, manufactured by Aldrich) was diluted to 0.1% by weight with 2-methoxyethanol (manufactured by Wako). The solution was applied on the ITO substrate by spin coating so as to have a film thickness of 20 nm, and dried at 100 ° C. for 10 minutes to form a first layer.

  From Table 1, it can be seen that the solar cell of the example has a high maximum output retention rate even after the heat resistance test as compared with the comparative example and is a highly durable solar cell.

DESCRIPTION OF SYMBOLS 1 Substrate 2 Conductive film 3 First layer 4 Second layer 5 Photoelectric conversion layer 6 Hole transport layer 7 Electrode

Panasonic Electric Works Technical Report, 56 (2008) 87 Nature, 353 (1991) 737 J. et al. Am. Chem. Soc. , 115 (1993) 6382 Semicond. Sci. Technol. , 10 (1995) 1689 Toshiba review vol69 No6 2014 ACS Appl. Mater. Interfaces 2014, 6, 803-810

Claims (4)

  A photoelectric conversion element in which an electron transport layer, a photoelectric conversion layer, a hole transport layer, and an electrode are sequentially stacked on a conductive film, wherein the electron transport layer includes a first layer containing a metal oxide, and A second layer provided between the first layer and the photoelectric conversion layer, the second layer comprising: a first compound having at least one carboxylic acid group; and at least one pyridyl group. The photoelectric conversion element characterized by including the 2nd compound which is a tertiary amine derivative which has this. The photoelectric conversion element according to claim 1, wherein the first compound is represented by the following general formula (1).
General formula (1)

(In the above formula, R 1 and R 2 represent a linear or branched alkyl group having 1 to 6 carbon atoms or a benzyl group, and X is a divalent aromatic group having 4 to 6 carbon atoms, or Represents an alkylene group having 1 to 4 carbon atoms, and R1 and R2 may combine to form a heterocycle.)   3. The photoelectric conversion element according to claim 1, wherein a mixing ratio of the first compound and the second compound is 50:50 to 99: 1 (weight ratio).   The photoelectric conversion element according to claim 1, wherein the metal oxide is zinc oxide or titanium oxide.

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