JP2014027174A - Photoelectric conversion element, solar cell module, and method of manufacturing photoelectric conversion element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoelectric conversion element of a reverse type configuration, which includes a hole extraction layer formable by a coating method and gives higher photoelectric conversion efficiency.SOLUTION: A photoelectric conversion element 107 has a structure in which a substrate 106, a cathode 101, an active layer 103, a hole extraction layer 104, and an anode 105 are arranged in this order. The hole extraction layer 104 contains a conductive polymer and an acetylene glycol-based compound.

Description

  The present invention relates to a photoelectric conversion element, a manufacturing method thereof, and a solar cell module using the photoelectric conversion element.

  The organic photoelectric conversion element has an electrode (anode) for collecting holes on the substrate side, and a hole extraction layer, an active layer, and an electrode (cathode) for collecting electrons are sequentially arranged on the anode. A forward-type component has been often used conventionally (for example, Patent Document 1). However, in recent years, attention has been focused on a reverse component in which a cathode is provided on the substrate side, and an active layer, a hole extraction layer, and an anode are sequentially arranged on the cathode (for example, Non-Patent Document 1).

  For example, Patent Document 1 describes a method for manufacturing a forward component. Specifically, a hole is formed by applying a conductive polymer paste containing PEDOT: PSS and fluoroalkylcarboxylic acid, which is a fluorosurfactant, to the ITO film on the PEN film substrate by spin coating. An extraction layer is formed. And a forward type | mold component is produced by laminating | stacking the bulk hetero type | mold active layer containing P3HT and PCBM on a positive hole taking-out layer.

  Non-Patent Document 1 describes a method for manufacturing an inverted component. Specifically, an electron extraction layer of titanium oxide (TiOx) and a bulk hetero type active layer containing P3HT and PCBM are sequentially formed on the ITO film on the PEN film substrate. And after performing oxygen plasma cleaning with respect to an active layer, hole extraction layer application | coating containing isopropyl alcohol (IPA) and / or Zonyl FS 300 which is a fluorine-type nonionic surfactant, and PEDOT: PSS is carried out. It describes that a hole extraction layer is formed on an active layer by depositing a solution by spin coating or gravure printing.

JP 2006-278582 A

Solar Energy Materials & Solar Cells 2011, 95, 731-734

  In order to put the organic photoelectric conversion element into practical use, further improvement in photoelectric conversion efficiency is required. Further, according to the study by the present inventors, when the coating solution for the hole extraction layer is applied on the active layer using the method of Patent Document 1 or Non-Patent Document 1, the wettability of the coating solution to the active layer is high. It has been found that there is a problem that it is not sufficient and it may be difficult to coat and form the hole extraction layer.

  An object of this invention is to provide the reverse type | mold photoelectric conversion element provided with the positive hole extraction layer which can be formed into a film by the apply | coating method, and giving higher photoelectric conversion efficiency.

In view of the above circumstances, the present inventors have intensively studied to produce a highly efficient photoelectric conversion element. As a result, the hole extraction layer of the photoelectric conversion element contains a conductive polymer and an acetylene glycol compound. The inventors have found that the object of the present invention can be achieved and completed the present invention.
That is, the gist of the present invention is as follows.

（式（Ｉ）中、Ｒ^１〜Ｒ^４は各々独立して置換基を有していてもよいアルキル基を表し、ｍ及びｎは、ｍとｎとの合計が０以上６０以下となる整数である。）
［３］前記活性層が、下記式（ＩＩＡ）で表される繰り返し単位と式（ＩＩＢ）で表される繰り返し単位とを含むコポリマーを含有することを特徴とする、［１］又は［２］に記載の光電変換素子。

（式（ＩＩＡ）中、Ａは周期表第１６族元素から選ばれる原子を表し、Ｒ^５はヘテロ原子を有していてもよい炭化水素基を表す。）

（式（ＩＩＢ）中、Ｑは周期表第１４族元素から選ばれる原子を表し、Ｒ^６及びＲ^７は各々独立して、水素原子、ハロゲン原子、又はヘテロ原子を有していてもよい炭化水素基を表し、Ｒ^６及びＲ^７は互いに結合して環を形成していてもよい。）
［４］前記コポリマーが下記式（ＩＩＩ）で表される繰り返し単位を含むコポリマーであることを特徴とする、［３］に記載の光電変換素子。

（式（ＩＩＩ）中、Ａは周期表第１６族元素から選ばれる原子を表し、Ｒ^５はヘテロ原子を有していてもよい炭化水素基を表し、Ｑは周期表第１４族元素から選ばれる原子を表し、Ｒ^６及びＲ^７は各々独立して、水素原子、ハロゲン原子、又はヘテロ原子を有していてもよい炭化水素基を表し、Ｒ^６及びＲ^７は互いに結合して環を形成していてもよい。）
［５］前記光電変換素子が太陽電池であることを特徴とする、［１］から［４］のいずれかに記載の光電変換素子。
［６］［５］に記載の光電変換素子を備えることを特徴とする、太陽電池モジュール。
［７］基材と、カソードと、活性層と、正孔取り出し層と、アノードと、がこの順に配置された構造を有する光電変換素子の製造方法であって、
導電性高分子とアセチレングリコール系化合物とを含有する塗布液を、前記活性層上に塗布することにより、前記正孔取り出し層を形成する工程を含むことを特徴とする、光電変換素子の製造方法。
［８］前記塗布液が、０．１重量％以上５重量％以下の前記アセチレングリコール系化合物を含有することを特徴とする、［７］に記載の光電変換素子の製造方法。 [1] A photoelectric conversion element having a structure in which a substrate, a cathode, an active layer, a hole extraction layer, and an anode are arranged in this order,
The hole extraction layer contains a conductive polymer and an acetylene glycol compound, The photoelectric conversion element characterized by the above-mentioned.
[2] The photoelectric conversion element according to [1], wherein the acetylene glycol compound is represented by the following formula (I).

(In formula (I), R ^{1 to} R ⁴ each independently represents an alkyl group which may have a substituent, and m and n are integers such that the sum of m and n is 0 or more and 60 or less. .)
[3] The active layer contains a copolymer containing a repeating unit represented by the following formula (IIA) and a repeating unit represented by the formula (IIB): [1] or [2] The photoelectric conversion element as described in 2.

(In the formula (IIA), A represents an atom selected from Group 16 elements of the periodic table, and R ⁵ represents a hydrocarbon group optionally having a hetero atom.)

(In Formula (IIB), Q represents an atom selected from Group 14 elements of the Periodic Table, and R ⁶ and R ⁷ are each independently a carbon atom that may have a hydrogen atom, a halogen atom, or a hetero atom. Represents a hydrogen group, and R ⁶ and R ⁷ may be bonded to each other to form a ring.
[4] The photoelectric conversion device according to [3], wherein the copolymer is a copolymer including a repeating unit represented by the following formula (III).

(In Formula (III), A represents an atom selected from Group 16 elements of the Periodic Table, R ⁵ represents a hydrocarbon group optionally having a hetero atom, and Q was selected from Group 14 Elements of the Periodic Table) R ⁶ and R ⁷ each independently represents a hydrogen atom, a halogen atom, or a hydrocarbon group optionally having a hetero atom, and R ⁶ and R ⁷ are bonded to each other to form a ring. (It may be formed.)
[5] The photoelectric conversion element according to any one of [1] to [4], wherein the photoelectric conversion element is a solar cell.
[6] A solar cell module comprising the photoelectric conversion element according to [5].
[7] A method for producing a photoelectric conversion element having a structure in which a substrate, a cathode, an active layer, a hole extraction layer, and an anode are arranged in this order,
A method for producing a photoelectric conversion element comprising the step of forming the hole extraction layer by applying a coating liquid containing a conductive polymer and an acetylene glycol-based compound on the active layer .
[8] The method for producing a photoelectric conversion element according to [7], wherein the coating liquid contains 0.1 wt% or more and 5 wt% or less of the acetylene glycol compound.

  ADVANTAGE OF THE INVENTION According to this invention, the reverse type | mold photoelectric conversion element provided with the positive hole extraction layer which can be formed into a film by the apply | coating method, and giving higher photoelectric conversion efficiency can be provided.

It is sectional drawing which shows typically the structure of the photoelectric conversion element as one Embodiment of this invention. It is sectional drawing which shows typically the structure of the solar cell as one Embodiment of this invention. It is sectional drawing which shows typically the structure of the solar cell module as one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail. The description of the constituent requirements described below is an example (representative example) of an embodiment of the present invention, and the present invention is not specified in these contents unless it exceeds the gist.

<1. Photoelectric conversion element>
The photoelectric conversion element according to the present invention has a structure in which a base material, a cathode, an active layer, a hole extraction layer, and an anode are arranged in this order. The hole extraction layer contains a conductive polymer and an acetylene glycol-based compound.

  A photoelectric conversion element 107 according to an embodiment of the present invention is shown in FIG. FIG. 1 shows a photoelectric conversion element used for a general organic thin film solar cell, but the photoelectric conversion element according to the present invention is not limited to the configuration of FIG.

  The photoelectric conversion element 107 has a structure in which a substrate 106, an electrode (cathode) 101, an active layer 103, a buffer layer (hole extraction layer) 104, and an electrode (anode) 105 are arranged in this order. . The photoelectric conversion element 107 may further include a buffer layer (electron extraction layer) 102 between the cathode 101 and the active layer 103. Hereinafter, each of these parts will be described.

<2. Hole Extraction Layer (104)>
The photoelectric conversion element 107 includes a buffer layer (hole extraction layer) 104 between the active layer 103 and the anode 105. The hole extraction layer 104 facilitates the movement of holes between the active layer 103 and the anode 105, and can prevent a short circuit between the electrodes 101 and 105. In order to fulfill this function, the hole extraction layer 104 is disposed in contact with the active layer 103 and the anode 105.

  The hole extraction layer 104 contains a conductive polymer and an acetylene glycol compound.

The acetylene glycol compound refers to a compound having a 2-butyne-1,4-diol structure which may have a substituent. Such an acetylene glycol compound is preferable in that it has a surface activity and improves the contact between the hole extraction layer 104 and the active layer 103. Further, such an acetylene glycol compound is preferable in that the function of the hole extraction layer 104 is not easily inhibited. An acetylene glycol compound which is an ethylene oxide adduct is preferred from the viewpoint of contact, and an example of a particularly preferred acetylene glycol compound is shown in the following formula (I).

  In the formula (I), m and n represent integers (m, n ≧ 0), and the sum of m and n is 0 or more and 60 or less. The total of m and n is preferably 2 or more and 50 or less, from the viewpoint that the affinity and solubility of an acetylene glycol compound in a general coating solvent are improved and the viscosity is easy to handle. More preferably, it is 40 or less.

In the formula (I), R ^{1 to} R ⁴ each independently represents an alkyl group which may have a substituent. The carbon number of the alkyl group is usually 1 or more, and is usually 10 or less, preferably 8 or less, more preferably 6 or less. When the carbon number of the alkyl group is in this range, the interface contact area between the active layer 103 and the hole extraction layer 104 is further improved. Specific examples of the alkyl group include a linear alkyl group such as a methyl group, n-propyl group, n-butyl group, n-hexyl group, n-octyl group or n-decyl group; 2-ethylhexyl group, 3 -Methylbutyl group, 1-ethylhexyl group, 1-ethyl-2-methylpropyl group, 1-ethyloctyl group, 1-propylhexyl group, 4-methyl-1-propylhexyl group, 1-ethyl-2-methylpentyl group Branched alkyl groups such as 1-butylhexyl group, 1-propylheptyl group, t-butyl group or 1,1-dimethylpropyl group.

R ^{1 to} R ⁴ may be the same or different. It is preferable that R ¹ and R ² are the same and R ³ and R ⁴ are the same, because an optical isomer is not generated in the compound synthesis process, and the cost is reduced in purification and the like.

  In the present specification, the term “optionally substituted” in the term “optionally substituted” is not particularly limited as long as the effects of the present invention are not impaired, but preferably a halogen atom. Hydroxyl group, cyano group, amino group, carboxyl group, carbamoyl group, acyl group, alkoxycarbonyl group, aryloxycarbonyl group, alkylsulfonyl group, arylsulfonyl group, silyl group, boryl group, cyano group, nitro group, nitrile group, Examples thereof include an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, and an aromatic group. These substituents may be linked with adjacent substituents to form a ring.

  The HLB value of the acetylene glycol compound is usually 1 or more, preferably 8 or more, more preferably 10 or more, and usually 20 or less, preferably 16 or less.

  The concentration of the acetylene glycol compound in the hole extraction layer 104 is not limited as long as the function of the hole extraction layer 104 is not impaired. Usually it is 0.001% by weight or more, preferably 0.01% by weight or more, while it is 10% by weight or less, preferably 5% by weight or less. It is preferable that the concentration of the acetylene glycol-based compound is in the above range in that the conductivity of the hole extraction layer 104 is not easily impaired. Concentrations of acetylene glycol compounds are known literatures ("Organic Mass Spectrometry" (by Kentaro Yamaguchi, Japan Analytical Chemistry Society) or "Identification Methods by Spectrum of Organic Compounds" (by Silverstein, Tokyo Kagaku Dojin)), etc. It can measure by the method of description.

  The conductive polymer is not particularly limited, but specifically, a conductive polymer in which polythiophene, polypyrrole, polyacetylene, triphenylenediamine polypyrrole, polyaniline, or the like is doped with sulfonic acid and / or iodine, or a sulfonyl group is substituted. Examples include conductive organic compounds such as polythiophene derivatives and arylamines in the group. Among them, preferred is a conductive polymer doped with sulfonic acid from the viewpoint of conductivity and chemical stability, and more preferred is (3,4-ethylenedioxythiophene) poly (polythiophene derivative) doped with polystyrene sulfonic acid. (Styrene sulfonic acid) (PEDOT: PSS).

  The LUMO energy level of the conductive polymer is not particularly limited, but is usually −4.0 eV or more, preferably −3.5 eV or more. On the other hand, it is usually −1.5 eV or less, preferably −2.0 eV or less. It is preferable that the LUMO energy level of the conductive polymer is −3.5 eV or more from the viewpoint that electrons can be prevented from moving.

  The HOMO energy level of the conductive polymer is not particularly limited, but is usually −6.5 eV or more, preferably −6.0 eV or more. On the other hand, it is usually −4.0 eV or less, preferably −4.5 eV or less. It is preferable that the HOMO energy level of the conductive polymer is −6.0 eV or more because the efficiency of extracting holes from the active layer 103 can be improved.

  As a calculation method of the HOMO energy level and the LUMO energy level of the conductive polymer, there are a theoretically calculated method and a method of actually measuring. The theoretically calculated values include semi-empirical molecular orbital methods and non-empirical molecular orbital methods. Examples of the actual measurement method include an ultraviolet-visible absorption spectrum measurement method and a cyclic voltammogram measurement method. Among them, the cyclic voltammogram measurement method is preferable, and the cyclic voltammogram measurement method is used in this specification. Specifically, it can measure by the method as described in well-known literature (International Publication 2011/016430), for example.

  In addition, the hole extraction layer 104 may be formed of a single layer or may have a stacked structure of two or more layers. For example, the hole extraction layer 104 may have a thin film of a metal such as gold, indium, silver, or palladium. When the hole extraction layer 104 has a stacked structure of two or more layers, the layer in contact with the active layer 103 preferably contains an acetylene glycol compound.

  The hole extraction layer 104 may contain a known surfactant (cationic surfactant, anionic surfactant, or nonionic surfactant) in addition to the acetylene glycol compound.

  The thickness of the hole extraction layer 104 is not particularly limited, but is usually 0.2 nm or more, preferably 0.5 nm or more, more preferably 1.0 nm or more. On the other hand, it is usually 400 nm or less, preferably 200 nm or less, more preferably 100 nm or less, and particularly preferably 70 nm or less. When the thickness of the hole extraction layer 104 is 0.2 nm or more, the function as a buffer layer is exhibited well, and when the thickness of the hole extraction layer 104 is 400 nm or less, the hole extraction efficiency is improved. In addition, the photoelectric conversion efficiency can be improved.

(Method for producing hole extraction layer)
The formation method of the hole extraction layer 104 is not particularly limited, but it is preferable that the hole extraction layer 104 is formed by applying a coating solution for the hole extraction layer in terms of easy film formation. . Since the hole extraction layer 104 is formed on the active layer 103, the hole extraction layer 104 is formed by the step of applying this coating liquid on the active layer 103.

  The coating solution for the hole extraction layer contains a conductive polymer and an acetylene glycol-based compound. Usually, the coating solution for the hole extraction layer contains a solvent in order to facilitate coating.

  Since the semiconductor compound contained in the active layer 103, particularly the copolymer II described later, is often highly soluble in a general hydrocarbon solvent, an aqueous solvent is used as a solvent for the coating solution in order not to dissolve the active layer 103. Alternatively, it is preferable to use an alcohol solvent. On the other hand, since the semiconductor compound contained in the active layer 103, particularly the copolymer II described later, is often highly hydrophobic, the wettability of the aqueous solvent or alcohol solvent with respect to the active layer 103 is not sufficient. The contact angle increases. For this reason, it is difficult to form a uniform film even when a coating liquid containing only a conductive polymer and an aqueous solvent or an alcohol solvent is applied.

  On the other hand, when the coating solution contains an acetylene glycol compound, the wettability of the coating solution with respect to the active layer 103 is improved, and the contact angle with the active layer 103 is reduced. Therefore, it is possible to uniformly apply the coating liquid on the active layer 103 and form a good hole extraction layer 104 with little coating unevenness through the drying process. Furthermore, the coating liquid containing an acetylene glycol compound has an advantage that bubbles are not easily generated, and can suppress the formation of a dent in the formed hole extraction layer 104 due to adhesion of minute bubbles or foreign matters. .

  Although there is no special restriction | limiting as a solvent, Nonpolar solvents, such as polar solvents, such as an aqueous solvent or an alcohol solvent, or a dioxane, are mentioned. Among these, it is preferable to use a polar solvent, particularly an aqueous solvent or an alcohol solvent, in that the active layer 103 is hardly eroded or dissolved.

  Examples of the aqueous solvent include water. Examples of the alcohol solvent include methanol, ethanol, 1-propanol, 2-propanol (isopropyl alcohol), ethylene glycol, propylene glycol, 1-methoxy-2-propanol, and 1-ethoxy-2-propanol. Other polar solvents include acetonitrile or N, N-dimethylformamide. Examples of the nonpolar solvent include dioxane and carbon tetrachloride. Among these solvents, one kind may be used alone, or two or more kinds may be used in combination.

  The coating solution for the hole extraction layer may contain a known surfactant (cationic surfactant, anionic surfactant or nonionic surfactant) in addition to the acetylene glycol compound.

  The coating solution for the hole extraction layer can be prepared, for example, by dissolving a conductive polymer and an acetylene glycol compound in a solvent. When preparing the coating solution for the hole extraction layer, a commercially available acetylene glycol surfactant containing an acetylene glycol compound may be used.

  The commercially available acetylene glycol-based surfactant is not particularly limited as long as it contains an acetylene glycol-based compound. For example, Surfynol 104, Surfynol 465, Olfine EXP. 4036, or Olfin EXP. 4200 (each manufactured by Nissin Chemical Co., Ltd.).

  The concentration of the conductive polymer in the coating solution for the hole extraction layer is usually 0.1% by weight or more, preferably 1% by weight or more, and usually 50% by weight or less, preferably 20% by weight or less. . It is preferable that the conductive polymer concentration is in the above range in that the conductive polymer is uniformly dispersed in the solution.

  The concentration of the acetylene glycol compound in the coating solution for the hole extraction layer is usually 0.001% by weight or more, preferably 0.01% by weight or more, more preferably 0.1% by weight or more, Usually, it is 10 wt% or less, preferably 5 wt% or less, and more preferably 3 wt% or less. When the concentration of the acetylene glycol compound is in the above range, the coating solution for the hole extraction layer has a viscosity suitable for coating, the wettability is improved, and the acetylene glycol compound remaining after the film formation is the hole extraction layer. It is preferable in that the conductivity of 104 is not impaired.

  The ratio of the amount of the acetylene glycol compound to the amount of the conductive polymer in the coating solution for the hole extraction layer is usually 0.01% by weight or more, preferably 0.1% by weight or more, while 10% by weight or less, Preferably it is 5 weight% or less. It is preferable that the ratio is in the above range from the viewpoint that the conductivity of the hole extraction layer 104 can be prevented from being lowered and the uniformity of the coating liquid can be maintained.

  The coating method of the coating solution for the hole extraction layer is not particularly limited. For example, spin coating method, ink jet method, doctor blade method, drop casting method, reverse roll coating method, kiss coating method, roll brush method, spray coating method. An air knife coating method, a wire barber coating method, a pipe doctor method, an impregnation / coating method, a curtain coating method, a gravure method, or a roll-to-roll method is preferable. Among them, the inkjet method, doctor blade method, spray coating method, gravure method, or roll-to-roll method is preferable in that a large area can be applied, and the roll can be reduced because the application speed is high and the cost can be reduced. A two-roll method or a gravure method is particularly preferable. You may perform the drying process by heating etc. after application | coating of a coating liquid.

<3. Active layer (103)>
The active layer 103 refers to a layer in which photoelectric conversion is performed, and usually contains a p-type semiconductor compound and an n-type semiconductor compound. A p-type semiconductor compound refers to a compound that functions as a p-type semiconductor material, and an n-type semiconductor compound refers to a compound that functions as an n-type semiconductor material. When the photoelectric conversion element 107 receives light, the light is absorbed by the active layer 103, electricity is generated at the interface between the p-type semiconductor compound and the n-type semiconductor compound, and the generated electricity is extracted from the cathode 101 and the anode 105.

  As the material of the active layer 103, either an inorganic compound or an organic compound may be used, but a layer that can be formed by a simple coating process is preferable. More preferably, the active layer 103 is an organic active layer made of an organic compound. In the following description, it is assumed that the active layer 103 is an organic active layer.

[3.1 Layer structure of active layer]
Examples of the layer structure of the active layer 103 include a thin film stacked type in which a p-type semiconductor compound and an n-type semiconductor compound are stacked, or a bulk heterojunction type having a layer in which a p-type semiconductor compound and an n-type semiconductor compound are mixed. It is done. Among these, a bulk heterojunction type active layer is preferable in that the photoelectric conversion efficiency can be further improved.

(Thin film type active layer)
The thin film stacked active layer has a structure in which a p-type semiconductor layer containing a p-type semiconductor compound and an n-type semiconductor layer containing an n-type semiconductor compound are stacked. The thin film stacked active layer can be formed by forming a p-type semiconductor layer and an n-type semiconductor layer, respectively. The p-type semiconductor layer and the n-type semiconductor layer may be formed by different methods.

(P-type semiconductor layer)
The p-type semiconductor layer is a layer containing a p-type semiconductor compound. There is no restriction | limiting in the film thickness of a p-type semiconductor layer, Usually, 5 nm or more, Preferably it is 10 nm or more, On the other hand, it is 500 nm or less normally, Preferably it is 200 nm or less. It is preferable that the thickness of the p-type semiconductor layer is 500 nm or less from the viewpoint of reducing the series resistance. The film thickness of the p-type semiconductor layer is preferably 5 nm or more from the viewpoint that more light can be absorbed.

  The p-type semiconductor layer can be formed by any method including a coating method and a vapor deposition method. However, it is preferable to use a coating method, preferably a wet coating method, because the p-type semiconductor layer can be formed more easily. .

  When a p-type semiconductor layer is produced by a coating method, a coating solution containing a p-type semiconductor compound may be prepared and applied. As an application method, any method can be used. For example, spin coating method, inkjet method, doctor blade method, drop casting method, reverse roll coating method, gravure coating method, kiss coating method, roll brush method, spray coating method , Air knife coating method, wire barber coating method, pipe doctor method, impregnation / coating method or curtain coating method. You may perform the drying process by heating etc. after application | coating of a coating liquid.

(N-type semiconductor layer)
The n-type semiconductor layer is a layer containing an n-type semiconductor compound described later. There is no special restriction | limiting in the film thickness of an n-type semiconductor layer, Usually, 5 nm or more, Preferably it is 10 nm or more, On the other hand, it is 500 nm or less normally, Preferably it is 200 nm or less. The film thickness of the n-type semiconductor layer is preferably 500 nm or less from the viewpoint of reducing the series resistance. The film thickness of the n-type semiconductor layer is preferably 5 nm or more from the viewpoint that more light can be absorbed.

  The n-type semiconductor layer can be formed by any method including a coating method and a vapor deposition method, but it is preferable to use the coating method because the n-type semiconductor layer can be more easily formed. When an n-type semiconductor layer is formed by a coating method, a coating solution containing an n-type semiconductor compound may be prepared and this coating solution may be applied. As a coating method, any method can be used, and for example, the methods mentioned as the method for forming the p-type semiconductor layer can be used. You may perform the drying process by heating etc. after application | coating of a coating liquid.

(Bulk heterojunction active layer)
The bulk heterojunction active layer has a layer (i layer) in which a p-type semiconductor compound and an n-type semiconductor compound are mixed. The i layer has a structure in which the p-type semiconductor compound and the n-type semiconductor compound are phase-separated, carrier separation occurs at the phase interface, and the generated carriers (holes and electrons) are transported to the electrode.

  There is no restriction | limiting in the film thickness of i layer, Usually, 5 nm or more, Preferably it is 10 nm or more, On the other hand, it is 500 nm or less normally, Preferably it is 300 nm or less. The film thickness of the i layer is preferably 500 nm or less from the viewpoint of reducing the series resistance. The film thickness of the i layer is preferably 5 nm or more from the viewpoint that more light can be absorbed.

  The i layer can be formed by any method including a coating method and a vapor deposition method (for example, a co-evaporation method). However, it is preferable to use the coating method because the i layer can be formed more easily. When the i layer is produced by a coating method, a coating solution containing a p-type semiconductor compound and an n-type semiconductor compound may be prepared, and this coating solution may be applied. The coating liquid containing the p-type semiconductor compound and the n-type semiconductor compound may be prepared by preparing and mixing a solution containing the p-type semiconductor compound and a solution containing the n-type semiconductor compound, respectively. The compound and the n-type semiconductor compound may be dissolved. Further, as described later, an i layer may be formed by preparing a coating liquid containing a semiconductor compound precursor, applying the coating liquid, and then converting the semiconductor compound precursor into a semiconductor compound. As a coating method, any method can be used, and for example, the methods mentioned as the method for forming the p-type semiconductor layer can be used. You may perform the drying process by heating etc. after application | coating of a coating liquid.

  When the bulk heterojunction active layer is formed by a coating method, an additive may be further added to the coating solution containing the p-type semiconductor compound and the n-type semiconductor compound. The phase separation structure of the p-type semiconductor compound and the n-type semiconductor compound in the bulk heterojunction active layer has an influence on the light absorption process, the exciton diffusion process, the exciton separation (carrier separation) process, the carrier transport process, etc. is there. Therefore, it is considered that good photoelectric conversion efficiency can be realized by optimizing the phase separation structure. When the coating liquid contains an additive having volatility different from that of the solvent, an active layer having a preferable phase separation structure can be obtained, and the photoelectric conversion efficiency can be improved.

  As an example of an additive, the compound etc. which are described in the international publication 2008/066933 are mentioned, for example. More specific examples of the additive include an aliphatic compound having a substituent or an aromatic compound such as naphthalene having a substituent. Substituents include aldehyde groups, oxo groups, hydroxy groups, alkoxy groups, thiol groups, thioalkyl groups, carboxyl groups, ester groups, amine groups, amide groups, halogen atoms, nitrile groups, epoxy groups, aromatic groups or arylalkyls. Groups and the like. There may be one or more, for example two, substituents. The substituent that the alkane has is preferably a thiol group or an iodine atom. Moreover, as a substituent which an aromatic compound like naphthalene has, Preferably they are a bromine atom or a chlorine atom.

  Since the additive preferably has a high boiling point, the aliphatic hydrocarbon used as the additive preferably has 6 or more carbon atoms, and more preferably 8 or more carbon atoms. Moreover, since it is preferable that an additive is liquid at normal temperature, carbon number of an aliphatic hydrocarbon has preferable 14 or less, and 12 or less is more preferable. For the same reason, the aromatic hydrocarbon used as an additive usually has 6 or more carbon atoms, preferably 8 or more, more preferably 10 or more, and usually 50 or less, preferably 30 or less, more preferably 20 or less. Similarly, the aromatic heterocyclic compound used as an additive generally has 2 or more carbon atoms, preferably 3 or more, more preferably 6 or more, and usually 50 or less, preferably 30 or less, more preferably 20 carbon atoms. It is as follows. The boiling point of the additive is usually 100 ° C. or higher, preferably 200 ° C. or higher at normal pressure (1 atm), and is usually 600 ° C. or lower, preferably 500 ° C. or lower.

  The amount of the additive contained in the coating solution containing the p-type semiconductor compound and the n-type semiconductor compound is preferably 0.1% by weight or more, and more preferably 0.5% by weight or more with respect to the entire coating solution. Moreover, 10 weight% or less is preferable with respect to the whole coating liquid, and 3 weight% or less is more preferable. When the amount of the additive is within this range, a preferable phase separation structure can be obtained while reducing the additive remaining in the active layer. As described above, a bulk heterojunction active layer can be formed by applying a coating liquid (ink) containing a p-type semiconductor compound, an n-type semiconductor compound, and, if necessary, an additive.

(Solvent for coating solution)
Examples of the solvent for the coating solution containing the p-type semiconductor compound, the coating solution containing the n-type semiconductor compound, and the coating solution containing the p-type semiconductor compound and the n-type semiconductor compound include p-type semiconductor compounds and / or n-type. Although it will not specifically limit if a semiconductor compound can be melt | dissolved uniformly, For example, aliphatic hydrocarbons, such as hexane, heptane, octane, isooctane, nonane, or decane; Toluene, xylene, mesitylene, cyclohexylbenzene, chlorobenzene, or orthodi Aromatic hydrocarbons such as chlorobenzene; cycloaliphatic hydrocarbons such as cyclopentane, cyclohexane, methylcyclohexane, cycloheptane, cyclooctane, tetralin or decalin; lower alcohols such as methanol, ethanol or propanol; acetone, methyl ethyl ketone Aliphatic ketones such as cyclohexane, cyclopentanone or cyclohexanone; aromatic ketones such as acetophenone or propiophenone; esters such as ethyl acetate, butyl acetate or methyl lactate; chloroform, methylene chloride, dichloroethane, trichloroethane, or trichloroethylene Halogen ethers of the above; ethers such as ethyl ether, tetrahydrofuran or dioxane; or amides such as dimethylformamide or dimethylacetamide.

  Among them, aromatic hydrocarbons such as toluene, xylene, mesitylene, cyclohexylbenzene, chlorobenzene or orthodichlorobenzene; cycloaliphatic carbonization such as cyclopentane, cyclohexane, methylcyclohexane, cycloheptane, cyclooctane, tetralin or decalin Hydrogens; ketones such as acetone, methyl ethyl ketone, cyclopentanone or cyclohexanone; halogen hydrocarbons such as chloroform, methylene chloride, dichloroethane, trichloroethane or trichloroethylene; or ethers such as ethyl ether, tetrahydrofuran or dioxane. More preferably, non-halogen aromatic hydrocarbons such as toluene, xylene, mesitylene or cyclohexylbenzene; non-halogen ketones such as cyclopentanone or cyclohexanone; aromatic ketones such as acetophenone or propiophenone; tetrahydrofuran, cyclohexane Alicyclic hydrocarbons such as pentane, cyclohexane, methylcyclohexane, cycloheptane, cyclooctane, tetralin or decalin; ketones such as acetone, methyl ethyl ketone, cyclopentanone or cyclohexanone; or non-halogens such as 1,4-dioxane Aliphatic ethers. Particularly preferred are non-halogen aromatic hydrocarbons such as toluene, xylene, mesitylene or cyclohexylbenzene.

  As the solvent, one kind of solvent may be used alone, or any two or more kinds of solvents may be used in any ratio. When two or more kinds of solvents are used in combination, it is preferable to combine a low boiling point solvent having a boiling point of 60 ° C. or higher and 150 ° C. or lower and a high boiling point solvent having a boiling point of 180 ° C. or higher and 250 ° C. or lower. Examples of combinations of low and high boiling solvents include non-halogen aromatic hydrocarbons and alicyclic hydrocarbons, non-halogen aromatic hydrocarbons and aromatic ketones, ethers and alicyclic carbonization. Examples thereof include hydrogens, ethers and aromatic ketones, aliphatic ketones and alicyclic hydrocarbons, or aliphatic ketones and aromatic ketones. Specific examples of preferred combinations include toluene and tetralin, xylene and tetralin, toluene and acetophenone, xylene and acetophenone, tetrahydrofuran and tetralin, tetrahydrofuran and acetophenone, methyl ethyl ketone and tetralin, methyl ethyl ketone and acetophenone, and the like.

[3.2 p-type semiconductor compound]
The p-type semiconductor compound contained in the active layer 103 is not particularly limited, but a copolymer containing a repeating unit represented by the following formula (IIA) and a repeating unit represented by the formula (IIB) (hereinafter referred to as copolymer II and Is a preferred example. Copolymer II is preferred in that it has a good balance between solubility and crystallinity. Further, it is preferable in that it absorbs light having a longer wavelength and has high light absorption.

（式（ＩＩＡ）中、Ａは周期表第１６族元素から選ばれる原子を表し、Ｒ^５はヘテロ原子を有していてもよい炭化水素基を表す。）

（式（ＩＩＢ）中、Ｑは周期表第１４族元素から選ばれる原子を表し、Ｒ^６及びＲ^７は各々独立して、水素原子、ハロゲン原子、又はヘテロ原子を有していてもよい炭化水素基を表し、Ｒ^６及びＲ^７は互いに結合して環を形成していてもよい。）

(In the formula (IIA), A represents an atom selected from Group 16 elements of the periodic table, and R ⁵ represents a hydrocarbon group optionally having a hetero atom.)

(In Formula (IIB), Q represents an atom selected from Group 14 elements of the Periodic Table, and R ⁶ and R ⁷ are each independently a carbon atom that may have a hydrogen atom, a halogen atom, or a hetero atom. Represents a hydrogen group, and R ⁶ and R ⁷ may be bonded to each other to form a ring.

  First, the repeating unit represented by the formula (IIA) will be described. A represents an atom selected from Group 16 elements of the Periodic Table. In this specification, the periodic table means an IUPAC 2005 recommended version. Specifically, an oxygen atom, a sulfur atom, a selenium atom, or the like. Of these, an oxygen atom or a sulfur atom is preferable. An oxygen atom is preferable in that an open circuit voltage (Voc) can be improved, and a sulfur atom is preferable in that an intermolecular interaction between copolymers can be improved.

R ⁵ represents a hydrocarbon group which may have a hetero atom. Specific examples of R ⁵ include an alkyl group which may have a substituent, an alkenyl group which may have a substituent, or an aromatic group which may have a substituent (aryl group). Is mentioned.

  The alkyl group generally has 1 or more carbon atoms, preferably 3 or more, more preferably 4 or more, and particularly preferably 6 or more, and usually 30 or less, preferably 25 or less, more preferably 20 or less. .

  Examples of the alkyl group include a methyl group, ethyl group, n-propyl group, iso-propyl group, cyclopropyl group, n-butyl group, iso-butyl group, tert-butyl group, 3-methylbutyl group, cyclobutyl group, Pentyl group, cyclopentyl group, hexyl group, 2-ethylhexyl group, cyclohexyl group, heptyl group, cycloheptyl group, octyl group, cyclooctyl group, nonyl group, cyclononyl group, decyl group, cyclodecyl group, lauryl group, cyclolauryl group, Alternatively, 1- (2-ethyl) hexyl-3-ethylheptyl group and the like can be mentioned. Among them, n-propyl group, iso-propyl group, cyclopropyl group, n-butyl group, iso-butyl group, tert-butyl group, 3-methylbutyl group, cyclobutyl group, pentyl group, cyclopentyl group, hexyl group, 2 -Ethylhexyl group, cyclohexyl group, heptyl group, cycloheptyl group, octyl group, cyclooctyl group, nonyl group, cyclononyl group, decyl group, cyclodecyl group, lauryl group, cyclolauryl group, or 1- (2-ethyl) hexyl- A 3-ethylheptyl group is preferred, and a butyl group, pentyl group, hexyl group, 2-ethylhexyl group, nonyl group, decyl group, or 1- (2-ethyl) hexyl-3-ethylheptyl group is more preferred.

  The alkenyl group has usually 2 or more, preferably 3 or more, more preferably 4 or more, and usually 20 or less, preferably 16 or less, more preferably 12 or less, and even more preferably 10 or less. Examples of such alkenyl groups include ethenyl, propenyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl, pentadecenyl Group, hexadecenyl group, heptadecenyl group, octadecenyl group, nonadecenyl group, icocenyl group or geranyl group. A propenyl group, a butenyl group, a pentenyl group, a hexenyl group, a heptenyl group, an octenyl group, a nonenyl group, a decenyl group, an undecenyl group or a dodecenyl group, more preferably a butenyl group, a pentenyl group, a hexenyl group, a heptenyl group , An octenyl group, a nonenyl group, or a decenyl group.

  The aromatic group usually has 2 or more carbon atoms, on the other hand, usually 60 or less, preferably 20 or less, more preferably 14 or less. Examples of such an aromatic group include an aromatic hydrocarbon group such as a phenyl group, a naphthyl group, an indanyl group, an indenyl group, a fluorenyl group, an anthracenyl group, or an azulenyl group; a thienyl group, a furyl group, a pyridyl group, and a pyrimidyl group. And aromatic heterocyclic groups such as a group, thiazolyl group, oxazolyl group, triazolyl group, benzothiophenyl group, benzofuranyl group, benzothienyl group, benzothiazolyl group, benzoxazolyl group, or benzotriazolyl group. Of these, a phenyl group, a naphthyl group, a thienyl group, a pyridyl group, a pyrimidyl group, a thiazolyl group, or an oxazolyl group is preferable.

It is preferable to use R ⁵ as these groups because the copolymer II tends to have excellent solubility in an organic solvent and can be advantageous in the coating film forming process. More preferably, R ⁵ is an alkyl group which may have a substituent or an aromatic group which may have a substituent. The alkyl group may be linear, branched or cyclic, but is preferably a linear or branched alkyl group. A linear alkyl group is preferable in that the crystallinity of the polymer can be improved, so that the carrier mobility can be increased, and a branched alkyl group is preferable in that the solubility of the polymer can be improved. In addition, R ⁵ is an aromatic group which may have a substituent. This means that the copolymer can absorb light having a longer wavelength and the crystallinity of the polymer can be improved, so that mobility is increased. This is preferable in that it can be increased.

  Next, the repeating unit represented by the formula (IIB) will be described. Q represents an atom selected from Group 14 elements of the Periodic Table. Specifically, a carbon atom, a silicon atom, a germanium atom, or a tin atom is mentioned. Among these, a carbon atom, a silicon atom or a germanium atom is preferable. More preferably, they are a carbon atom or a silicon atom. A carbon atom is preferable in terms of improving crystallinity, and a silicon atom is preferable in terms of improving solubility.

R ⁶ and R ⁷ each independently represents a hydrocarbon group optionally having a hydrogen atom, a halogen atom, or a hetero atom. Examples of the hydrocarbon group which may have a hetero atom include an alkyl group which may have a substituent, an alkenyl group which may have a substituent, or a substituent. An aromatic group (aryl group) is mentioned. The alkyl group, alkenyl group, and aromatic group can be the same as those listed for R ⁵ . Moreover, the substituent which the alkyl group, the alkenyl group, and the aromatic group may have may be the same as those mentioned for R ⁵ . R ⁶ and R ⁷ may be bonded to each other to form a ring.

Of these, at least one of R ⁶ and R ⁷ is preferably an alkyl group or an aromatic group which may have a substituent, and both R ⁶ and R ⁷ may have a substituent. More preferably, it is a good alkyl group or aromatic group. Straight chain alkyl groups are preferred in that the mobility can be increased by improving the crystallinity of the polymer, and branched alkyl groups can be easily formed by a coating process by improving the solubility of the polymer. It is preferable in that it can be. It is also preferable that at least one of R ⁶ and R ⁷ is an alkyl group from the viewpoint that the copolymer II can absorb light having a longer wavelength. From these viewpoints, at least one of R ⁶ and R ⁷ is preferably an alkyl group having 1 to 20 carbon atoms, and particularly preferably an alkyl group having 6 to 20 carbon atoms. An aromatic group is preferable in that the mobility tends to increase because the interaction between molecules is improved by the interaction between π electrons. Aromatic groups are also preferred in that they tend to improve the stability of the fused ring skeleton represented by formula (IIB).

From the viewpoint of improving the durability of the copolymer II by increasing the steric hindrance around Q, which is an atom selected from Group 14 elements of the periodic table, R ⁶ and R ⁷ may have a substituent. It is preferably a good alkyl group, an alkenyl group which may have a substituent, or an aromatic group which may have a substituent.

It is also preferred that at least one of R ⁶ and R ⁷ is a halogen atom. This is preferable in that the heat resistance, weather resistance, chemical resistance, water / oil repellency and the like of the copolymer II are improved.

  The ratio of the repeating unit represented by the formula (IIA) in the copolymer II is not particularly limited, but is usually 1 mol% or more, preferably 5 mol% or more, more preferably 15 mol% or more, and further preferably 30. More than mol%. On the other hand, it is usually 99 mol% or less, preferably 95 mol% or less, more preferably 85 mol% or less, and still more preferably 70 mol% or less.

  The ratio of the repeating unit represented by the formula (IIB) in the copolymer II is not particularly limited, but is usually 1 mol% or more, preferably 5 mol% or more, more preferably 15 mol% or more, and further preferably 30. More than mol%. On the other hand, it is usually 99 mol% or less, preferably 95 mol% or less, more preferably 85 mol% or less, and still more preferably 70 mol% or less.

  The ratio of the repeating unit represented by the formula (IIB) to the repeating unit represented by the formula (IIA) in the copolymer II is not particularly limited, but is usually 0.01 or more, preferably 0.1 or more, more Preferably it is 0.5 or more. On the other hand, it is usually 100 or less, preferably 10 or less, more preferably 2 or less.

  In the copolymer II, the arrangement state of the repeating units (IIA) and (IIB) may be any of alternating, block and random. That is, the copolymer II may be any of an alternating copolymer, a block copolymer, and a random copolymer. Preferably, they are arranged alternately.

  Among the copolymers including the repeating unit represented by the formula (IIA) and the repeating unit represented by the formula (IIB), the p-type semiconductor compound further preferably includes the repeating unit represented by the following formula (III). Copolymer (hereinafter referred to as Copolymer III). By including the repeating unit represented by formula (III), the charge separation state can be more easily maintained.

（式（ＩＩＩ）中、Ａは周期表第１６族元素から選ばれる原子を表し、Ｒ^５はヘテロ原子を有していてもよい炭化水素基を表し、Ｑは周期表第１４族元素から選ばれる原子を表し、Ｒ^６及びＲ^７は各々独立して、水素原子、ハロゲン原子、又はヘテロ原子を有していてもよい炭化水素基を表し、Ｒ^６及びＲ^７は互いに結合して環を形成していてもよい。）

(In Formula (III), A represents an atom selected from Group 16 elements of the Periodic Table, R ⁵ represents a hydrocarbon group optionally having a hetero atom, and Q was selected from Group 14 Elements of the Periodic Table) R ⁶ and R ⁷ each independently represents a hydrogen atom, a halogen atom, or a hydrocarbon group optionally having a hetero atom, and R ⁶ and R ⁷ are bonded to each other to form a ring. (It may be formed.)

In formula (III), specific examples of A, Q, and R ^{5 to} R ⁷ include the same as those described for formulas (IIA) and (IIB). From the viewpoints of solubility and light absorption, it is more preferable that Q is a silicon atom and A is a sulfur atom.

  The ratio of the repeating unit represented by the formula (III) in the copolymer III is not particularly limited, but is usually 10 mol% or more, preferably 25 mol% or more, more preferably 50 mol% or more, and further preferably 70 mol%. More than mol%. There is no upper limit in particular and it is 100 mol% or less.

  Further, the copolymer II or the copolymer III may contain other repeating units as long as the effects of the present invention are not impaired. Examples of other repeating units include aromatic heterocyclic rings such as thiophenediyl group and thiazolediyl group.

  The copolymer II may contain only one type of repeating units represented by the formulas (IIA) and (IIB). Moreover, 2 or more types of repeating units represented by Formula (IIA) may be included, and 2 or more types of repeating units represented by Formula (IIB) may be included. Although there is no restriction | limiting in the kind of repeating unit which the copolymer II contains, Usually, 8 or less, Preferably it is 5 or less. Similarly, the copolymer III may contain only 1 type among the repeating units represented by Formula (III), and may contain 2 or more types.

Preferred specific examples of copolymer II are shown below. However, the copolymer II is not limited to the following examples. In the following specific examples, C ₄ H ₉ and C ₈ H ₁₇ represent a linear alkyl group. Bu, Hex, and Oct represent an n-butyl group, an n-hexyl group, and an n-octyl group, respectively. When the copolymer II includes a plurality of repeating units, the ratio of the number of each repeating unit is arbitrary.

  Copolymer II has absorption in the long wavelength region (600 nm or more). Moreover, the photoelectric conversion element using the copolymer II shows a high open circuit voltage (Voc), and shows a high photoelectric conversion characteristic. Copolymer II exhibits high photoelectric conversion properties, particularly when combined with a fullerene compound. The copolymer II also has an advantage that it has a low HOMO energy level and is not easily oxidized.

  In addition, since the copolymer II exhibits high solubility, there is an advantage that coating film formation is easy. In addition, since the range of choice of solvent is widened when performing coating film formation, a solvent suitable for film formation can be selected, and the film quality of the formed active layer can be improved. This is also considered to be a factor that the photoelectric conversion element using the copolymer II exhibits high photoelectric conversion characteristics.

The weight average molecular weight (Mw) in terms of polystyrene of the copolymer II is usually 2.0 × 10 ³ or more, preferably 5.0 × 10 ³ or more, more preferably 1.0 × 10 ⁴ or more, and further preferably 3.0. × 10 ⁴ or more, more preferably 5.0 × 10 ⁴ or more, and particularly preferably 1.0 × 10 ⁵ or more. On the other hand, preferably 1.0 × 10 ⁷ or less, more preferably 5.0 × 10 ⁶ or less, even more preferably 3.0 × 10 ⁶ or less, still more preferably 2.0 × 10 ⁶ or less, and even more preferably. It is 1.0 × 10 ⁶ or less, particularly preferably 7.0 × 10 ⁵ or less, and particularly preferably 5.0 × 10 ⁵ or less. It is preferable that the weight average molecular weight is in this range from the viewpoint of increasing the light absorption wavelength, achieving high absorbance, and optimizing the phase separation structure.

  The polystyrene equivalent weight average molecular weight of the copolymer II can be determined by gel permeation chromatography (GPC). Specifically, two columns for Polymer Laboratories GPC (PLgel MIXED-B 10 μm, inner diameter 7.5 mm, length 30 cm) are connected in series as a column, and LC-10AT (manufactured by Shimadzu Corporation) is used as a pump. By using CTO-10A (manufactured by Shimadzu Corporation) as an oven, a differential refractive index detector (manufactured by Shimadzu Corporation: RID-10A), and a UV-vis detector (manufactured by Shimadzu Corporation: SPD-10A) as a detector. It can be measured. The copolymer to be measured (1 mg) is dissolved in chloroform (200 mg), and 1 μL of the resulting solution is injected onto the column. Measurement is performed at a flow rate of 1.0 mL / min using chloroform as the mobile phase. LC-Solution (Shimadzu Corporation) is used for the analysis.

The number average molecular weight (Mn) of the copolymer II is usually 1.0 × 10 ³ or more, preferably 3.0 × 10 ³ or more, more preferably 5.0 × 10 ³ or more, and further preferably 1.0 × 10 ^4. More preferably, it is 1.5 × 10 ⁴ or more, still more preferably 2.0 × 10 ⁴ or more, and particularly preferably 2.5 × 10 ⁴ or more. On the other hand, it is preferably 1.0 × 10 ⁶ or less, more preferably 5.0 × 10 ⁵ or less, still more preferably 2.0 × 10 ⁵ or less, and particularly preferably 1.0 × 10 ⁵ or less. The number average molecular weight is preferably within this range from the viewpoint of increasing the light absorption wavelength, from the viewpoint of realizing high absorbance, and from the viewpoint of optimizing the phase separation structure. The number average molecular weight of the copolymer II can be measured by the same method as the weight average molecular weight.

  The molecular weight distribution (PDI, (weight average molecular weight / number average molecular weight (Mw / Mn))) of the copolymer II is usually 1.0 or more, preferably 1.1 or more, more preferably 1.2 or more, and further preferably 1 .3 or more. On the other hand, it is preferably 20.0 or less, more preferably 15.0 or less, and still more preferably 10.0 or less. The molecular weight distribution is preferably in this range in that the solubility of the copolymer can be in a range suitable for coating. The molecular weight distribution of the copolymer II can be measured by the same method as the weight average molecular weight.

The copolymer II preferably has a light absorption maximum wavelength (λ _max ) of 470 nm or more, more preferably 480 nm or more, and is usually 1200 nm or less, preferably 1000 nm or less, more preferably 900 nm or less. Moreover, a half value width is 10 nm or more normally, Preferably it is 20 nm or more, on the other hand, it is 300 nm or less normally. Further, it is desirable that the absorption wavelength region of the copolymer II is closer to the absorption wavelength region of sunlight.

  The solubility of the copolymer II is not particularly limited, but preferably the solubility in chlorobenzene at 25 ° C. is usually 0.1% by weight or more, preferably 0.5% by weight or more, more preferably 1% by weight or more, Usually, it is 30% by weight or less, preferably 20% by weight. High solubility is preferable in that a thicker active layer can be formed.

  The copolymer II is preferably one that interacts between molecules. In the present specification, the interaction between molecules means that the distance between polymer chains is shortened due to the interaction of π-π stacking between molecules. The stronger the interaction, the more the copolymer tends to exhibit higher mobility and / or crystallinity. That is, in a copolymer that interacts between molecules, charge transfer between molecules is likely to occur. Therefore, holes generated at the interface between the copolymer II and the n-type semiconductor compound in the active layer 103 are efficiently generated. It can be considered that it can be transported to the extraction layer 104 and the anode 105.

  An example of a crystallinity measuring method is an X-ray diffraction method (XRD). In this specification, having crystallinity means that the diffraction peak of the copolymer is shown in the X-ray diffraction spectrum, and it is particularly preferable that the diffraction peak is shown in the vicinity of 2θ = 4.8 °. Having crystallinity is considered to mean that it has a laminated structure in which molecules are arranged, which is preferable in that it tends to be easier to obtain a thicker active layer. The X-ray diffraction method (XRD) can be performed based on a method described in a publicly known document (X-ray crystal analysis guide (applied physics selection book 4)).

The hole mobility of the copolymer II is usually 1.0 × 10 ⁻⁷ cm ² / Vs or more, preferably 1.0 × 10 ⁻⁶ cm ² / Vs or more, more preferably 1.0 × 10 ⁻⁵ cm ^2. / Vs or more, particularly preferably 1.0 × 10 ⁻⁴ cm ² / Vs or more. On the other hand, the hole mobility of the copolymer II is usually 1.0 × 10 ⁴ cm ² / Vs or less, preferably 1.0 × 10 ³ cm ² / Vs or less, and more preferably 1.0 × 10 ^2. cm ² / Vs or less. In order to obtain high conversion efficiency, the balance between the mobility of the n-type semiconductor compound and the mobility of the copolymer II is important. From the viewpoint of bringing the mobility of the copolymer II used as the p-type semiconductor compound close to the mobility of the n-type semiconductor compound, the hole mobility of the copolymer II is preferably within this range. As a method for measuring the hole mobility, there is an FET method. The FET method can be performed by a method described in a known document (Japanese Patent Laid-Open No. 2010-045186).

  It is preferable that the impurities in the copolymer II be as small as possible. In particular, if a transition metal catalyst such as palladium or copper remains, an exciton trap due to the heavy atom effect of the transition metal occurs, which may hinder charge transfer, resulting in a decrease in photoelectric conversion efficiency of the photoelectric conversion element. is there. Specifically, the concentration of the transition metal catalyst in the copolymer II is usually 1000 ppm or less, preferably 500 pm or less, more preferably 100 ppm or less. On the other hand, it is usually larger than 0 ppm and may be 1 ppm or more, or 3 ppm or more.

The residual amount of terminal residues (X ¹ and X ² in formula (IVA) and formula (IVB) described later) in copolymer II is not particularly limited, but is usually 6000 ppm or less, preferably 4000 ppm or less, more preferably 3000 ppm or less, more preferably 2000 ppm or less, still more preferably 1000 ppm or less, particularly preferably 500 ppm or less, and most preferably 200 ppm or less. On the other hand, it is usually larger than 0 ppm and may be 1 ppm or more, or 3 ppm or more.

  In particular, the residual amount of tin atoms in the copolymer II is usually 5000 ppm or less, preferably 4000 ppm or less, more preferably 2500 ppm or less, more preferably 1000 ppm or less, even more preferably 750 ppm or less, particularly preferably 500 ppm or less, most preferably. 100 ppm or less. On the other hand, it is usually larger than 0 ppm, 1 ppm or more, or 3 ppm or more. It is preferable to set the residual amount of tin atoms to 5000 ppm or less because the residual amount of tin atoms in the alkylstannyl group that is easily thermally decomposed is reduced, and higher stability can be obtained.

  The residual amount of halogen atoms in the copolymer II is usually 5000 ppm or less, preferably 4000 ppm or less, more preferably 2500 ppm or less, further preferably 1000 ppm or less, even more preferably 750 ppm or less, particularly preferably 500 ppm or less, most preferably. 100 ppm or less. On the other hand, it is usually larger than 0 ppm and may be 1 ppm or more, or 3 ppm or more. Setting the remaining amount of halogen atoms to 5000 ppm or less is preferable because the photoelectric conversion characteristics and durability of the photoelectric conversion element tend to be improved.

The residual amount of terminal residues (X ¹ and X ² described later) of the copolymer can be measured by the amount of elements other than carbon, hydrogen and nitrogen. As a measurement method, elemental analysis of the obtained copolymer can be carried out by ion chromatography or ICP mass spectrometry for bromine ion (Br ⁻ ) and iodine ion (I ⁻ ), and ICP for palladium and tin. It can be carried out by mass spectrometry.

  The ion chromatography method can be carried out by a method described in a known document (“ion chromatography”: Kyoritsu Shuppan Co., Ltd.). For example, it can be carried out by an ion chromatograph analyzer (Dionex Corporation ion chromatograph analyzer DX120 type or DX500 type).

ICP mass spectrometry can be carried out by a method described in a known document (“Plasma ion source mass spectrometry” (Academic Publishing Center)). Specifically, with respect to Pd and Sn, after wet decomposition of the sample, Pd and Sn in the decomposition solution are quantified by a calibration curve method using an ICP mass spectrometer (ICP mass spectrometer 7500ce type manufactured by Agilent Technologies). Can do. For Br ⁻ and I ⁻ , the sample is combusted with a sample combustion device (sample combustion device QF-02 type manufactured by Mitsubishi Chemical Analytech Co., Ltd.), and the combustion gas is absorbed in an alkaline absorbing liquid containing a reducing agent. Br ⁻ and I ⁻ in the medium can be quantified by a calibration curve method using an ICP mass spectrometer (ICP mass spectrometer 7500ce type manufactured by Agilent Technologies).

  There are no particular limitations on the method for producing Copolymer II. For example, it can be produced by a known method using a compound represented by the following general formula (IVA) and a compound represented by the following general formula (IVB). Preferable methods include a method of polymerizing a compound represented by the following general formula (IVA) and a compound represented by the following general formula (IVB) in the presence of an appropriate catalyst if necessary. .

In formula (IVA), A and R ⁵ have the same meaning as in formula (IIA). In formula (IVB), Q, R ⁶ and R ⁷ have the same meanings as in formula (IIB).

X ¹ and X ² are each independently a halogen atom, an alkylstannyl group, an alkylsulfo group, an arylsulfo group, an arylalkylsulfo group, a boric acid ester residue, a sulfonium methyl group, a phosphonium methyl group, a phosphonate methyl group, It represents a monohalogenated methyl group, a boric acid residue (—B (OH) ₂ ), a formyl group, an alkenyl group or an alkynyl group.

From the viewpoint of synthesis of the compound represented by the formula (IVA) or (IVB) and the viewpoint of easy reaction, X ¹ and X ² are each independently a halogen atom, an alkylstannyl group, a borate ester residue. It is preferably a group or a boric acid residue (—B (OH) ₂ ). In X ¹ and X ² , the halogen atom is preferably a bromine atom or an iodine atom.

Examples of the boric acid ester residue include a group represented by the following formula. In the following formulae, Me represents a methyl group, and Et represents an ethyl group.

Examples of the alkylstannyl group include a group represented by the following formula. In the following formulae, Me represents a methyl group, and Bu represents an n-butyl group.

  Examples of the alkenyl group include alkenyl groups having 2 to 12 carbon atoms.

As the reaction method used for the polymerization of the copolymer II, Suzuki-Miyaura cross-coupling reaction method, Stille coupling reaction method, Yamamoto coupling reaction method, Grignard reaction method, Heck reaction method, Sonogashira reaction method, oxidation of FeCl _{3 and the} like Examples include a reaction method using an agent, a method using an electrochemical oxidation reaction, a reaction method by decomposition of an intermediate compound having an appropriate leaving group, and the like. Among these, the Suzuki-Miyaura coupling reaction method, the Stille coupling reaction method, the Yamamoto coupling reaction method, or the Grignard reaction method is preferable in terms of easy structure control. In particular, the Suzuki-Miyaura cross-coupling reaction method, the Stille coupling reaction method, or the Grignard reaction method is preferable from the viewpoints of easy availability of materials and easy reaction operation. These reactions are described in "Cross Coupling-Fundamentals and Industrial Applications (CMC Publishing)", "Transition Metal Catalyzed Reactions for Organic Synthesis (edited by Jiro Jiro: edited by Organic Synthetic Chemistry Association)", "For Organic Synthesis" The reaction can be carried out according to a method described in known literature such as “catalytic reaction 103 (by Teijiro Hatakeyama: Tokyo Kagaku Dojin)”. The following describes the Stille coupling reaction method.

When the Stille coupling reaction method is used, in the above general formulas (IVA) and (IVB), X ¹ is a halogen atom and X ² is an alkylstannyl group, or X ¹ is an alkylstannyl group. X ² is preferably a halogen atom.

  The molar ratio (IVB / IVA) of the compound represented by the formula (IVB) to the compound represented by the formula (IVA) is usually 0.90 or more, preferably 0.95 or more. 3 or less, preferably 1.2 or less. It is preferable that the molar ratio is in the above range in that a copolymer having a higher molecular weight can be obtained with a higher yield.

  Since the conversion characteristics of the photoelectric conversion element can be improved by increasing the purity of the copolymer II, the monomer before polymerization (compound represented by the general formula (IVA) or (IVB)) is distilled, sublimated and purified by column chromatography. Alternatively, the polymerization reaction is preferably performed after purification by a method such as recrystallization. The purity of the monomer before polymerization is usually 90% or more, preferably 95% or more.

In the polymerization reaction, an alkali, a catalyst, a cocatalyst, an organic ligand, a phase transfer catalyst, or the like can be added to promote the reaction. These alkalis or catalysts may be selected according to the type of polymerization reaction, but are preferably sufficiently dissolved in the solvent used for the polymerization reaction. Examples of the alkali include inorganic bases such as potassium carbonate, sodium carbonate and cesium carbonate, and organic bases such as triethylamine. Examples of the catalyst include a palladium complex containing a phosphine compound such as tetrakis (triphenylphosphine) palladium (Pd (PPh ₃ ) ₄ ) as a ligand or a palladium (Pd) catalyst such as palladium acetate; Ni (dppp) Cl ₂ Alternatively, a nickel catalyst such as Ni (dppe) Cl ₂ ; an iron catalyst such as iron chloride; or a copper catalyst such as copper iodide may be used.

As a palladium complex containing a phosphine compound as a ligand, specifically, Pd (PPh ₃ ) ₄ , Pd (P (o-tolyl) ₃ ) ₄ , Pd (PCy ₃ ) ₂ , Pd ₂ (dba) ₃ Or PdCl ₂ (PPh ₃ ) ₂ (in the formula, Ph represents a phenyl group, Cy represents a cyclohexyl group, o-tolyl represents a 2-tolyl group, and dba represents dibenzylideneacetone). When a divalent Pd complex such as Pd ₂ (dba) ₃ or PdCl ₂ (PPh ₃ ) ₂ is used, it may be used in combination with an organic ligand such as PPh ₃ or P (o-tolyl) _3. desirable.

The usage-amount of a catalyst is 1.0x10 < ^-4 > mol% or more normally with respect to the sum total of the compound represented by the compound represented by Formula (IVA), and Formula (IVB), Preferably it is 1.0x. 10 ⁻³ mol% or more, more preferably 1.0 × 10 ⁻² mol% or more, and usually 1.0 × 10 ² mol% or less, more preferably 5 mol% or less. It is preferable that the amount of the catalyst used be in this range because a higher molecular weight copolymer II tends to be obtained at a lower cost and a higher yield.

Examples of the cocatalyst include inorganic salts such as cesium fluoride, copper oxide, and copper halide. The use amount of the cocatalyst is usually 1.0 × 10 ⁻⁴ mol% or more, preferably 1.0 × 10 ⁻³ mol% or more, more preferably 1. 0 × 10 ⁻² mol% or more, on the other hand, usually 1.0 × 10 ⁴ mol% or less, preferably 1.0 × 10 ³ mol% or less, more preferably 1.5 × 10 ² mol% or less. . It is preferable that the amount of the cocatalyst used be in this range because copolymer II tends to be obtained at a lower cost and with a higher yield.

Examples of the phase transfer catalyst include tetraethylammonium hydroxide and Aliquat 336 (manufactured by Aldrich). The amount of the phase transfer catalyst used is usually 1.0 × 10 ⁻⁴ mol% or more, preferably 1.0 × 10 ⁻³ mol% or more, more preferably 1 with respect to the compound represented by the formula (IVA). 0.0 × 10 ⁻² mol% or more, and usually 5 mol% or less, more preferably 3 mol% or less. It is preferable that the amount of the phase transfer catalyst used be in this range because copolymer II tends to be obtained at a lower cost and in a higher yield.

  Examples of the solvent used in the polymerization reaction include saturated hydrocarbons such as pentane, hexane, heptane, octane, and cyclohexane; aromatic hydrocarbons such as benzene, toluene, ethylbenzene, and xylene; halogens such as chlorobenzene, dichlorobenzene, and trichlorobenzene. Aromatic hydrocarbons; alcohols such as methanol, ethanol, propanol, isopropyl alcohol, butanol or t-butyl alcohol; water; ethers such as dimethyl ether, diethyl ether, methyl-t-butyl ether, tetrahydrofuran, tetrahydropyran or dioxane; Examples include aprotic organic solvents such as DMF. These solvents may be used alone or in combination of two or more.

The amount of the solvent used is usually 1.0 × 10 ⁻² mL or more, preferably 1.0 with respect to 1 g in total of the compound represented by the formula (IVA) and the compound represented by the formula (IVB). × 10 ⁻¹ mL or more, more preferably ¹ mL or more, while usually 1.0 × 10 ⁵ mL or less, preferably 1.0 × 10 ³ mL or less, more preferably 2.0 × 10 ² mL or less. is there.

  The reaction temperature of the Stille coupling reaction is usually 0 ° C. or higher, preferably 20 ° C. or higher, more preferably 40 ° C. or higher, and further preferably 60 ° C. or higher. On the other hand, it is usually 300 ° C. or lower, preferably 250 ° C. or lower, more preferably 200 ° C. or lower, further preferably 180 ° C. or lower, and particularly preferably 160 ° C. or lower.

  The heating method is not particularly limited, and examples thereof include oil bath heating, thermocouple heating, infrared heating, microwave heating, heating by contact using an IH heater, and the like.

  The reaction time is usually 1 minute or more, preferably 10 minutes or more, while it is usually 160 hours or less, preferably 120 hours or less, more preferably 100 hours or less. By carrying out the reaction under these reaction conditions, the copolymer can be obtained in a shorter time and with a higher yield.

  After the polymerization reaction, for example, the crude copolymer can be obtained by ordinary post-treatment such as quenching with water and then extracting the product with an organic solvent and distilling off the organic solvent. After the synthesis of the copolymer, it is preferable to carry out a purification treatment such as reprecipitation purification, purification using Soxhlet, gel permeation chromatography, or metal removal by a scavenger.

The Stille coupling reaction is preferably performed in a nitrogen (N ₂ ) or argon (Ar) atmosphere.

It is preferable to perform terminal treatment on the copolymer obtained by the polymerization reaction. By carrying out terminal treatment of the copolymer, the residual amount in the copolymer of terminal residues (X ¹ and X ² described above) such as halogen atoms such as bromine (Br) or iodine (I) or alkylstannyl groups is reduced. be able to. This terminal treatment is preferable because a copolymer having better performance in terms of efficiency and durability can be obtained.

  The method for terminal treatment of the copolymer is not particularly limited, but the following methods can be mentioned. When a copolymer is produced by a Stille coupling reaction, a terminal treatment can be performed on halogen atoms such as bromine (Br) and iodine (I) and alkylstannyl groups present at the terminal of the copolymer.

As a terminal treatment method for halogen atoms, aryltrialkyltin can be added to the reaction system as a terminal treating agent and then heated and stirred. Examples of the aryl trialkyl tin include phenyl trimethyl tin and thienyl trimethyl tin. Although there is no special restriction | limiting in the addition amount of a terminal processing agent, Usually ^1.0x10-2 equivalent or more with respect to the monomer which the halogen atom added to the terminal, Preferably it is 0.1 equivalent or more, More preferably, 1 equivalent On the other hand, it is usually 50 equivalents or less, preferably 20 equivalents or less, more preferably 10 equivalents or more. The heating time is not particularly limited, but is usually 30 minutes or longer, preferably 1 hour or longer, and is usually 50 hours or shorter, preferably 20 hours or shorter. By performing the reaction under these reaction conditions, the terminal treatment can be performed in a shorter time and with a higher conversion rate. Substitution of the halogen atom at the end of the copolymer with an aryl group by terminal treatment is preferred because the copolymer can be more stable due to the conjugate stability effect.

As a terminal treatment method for the alkylstannyl group, an aryl halide can be added as a terminal treatment agent to the reaction system, and then heated and stirred. Examples of the aryl halide include iodothiophene, iodobenzene, bromothiophene, and bromobenzene. Although there is no particular limitation on the amount of the end treatment agent added, it is usually 1.0 × 10 ⁻² equivalent or more, preferably 0.1 equivalent or more, more preferably, relative to the monomer having an alkylstannyl group added to the terminal. On the other hand, it is usually 50 equivalents or less, preferably 20 equivalents or less, more preferably 10 equivalents or less. The heating time is not particularly limited, but is usually 30 minutes or longer, preferably 1 hour or longer, and is usually 50 hours or shorter, preferably 10 hours or shorter. By performing the reaction under these reaction conditions, the terminal treatment can be performed in a shorter time and with a higher conversion rate. By substituting the alkylstannyl group at the end of the copolymer with an aryl group by terminal treatment, tin atoms in the alkylstannyl group, which are prone to thermal decomposition, do not exist in the copolymer, so that deterioration of the copolymer over time can be suppressed. Be expected. In addition, substitution of the alkylstannyl group at the terminal of the copolymer with an aryl group is also preferable in that the copolymer can be more stable due to the conjugate stability effect.

  Although there is no special restriction | limiting about reaction operation of terminal treatment, It is preferable to carry out each independently. For example, when the Stille coupling reaction is used, it is preferable that the terminal treatment of the halogen atom and the terminal treatment of the alkylstannyl group are performed independently. There is no particular limitation on the operation order of each end treatment, and the order can be selected as appropriate.

  The end treatment may be performed before the copolymer is purified or after the copolymer is purified. When the end treatment is performed after copolymer purification, the copolymer and one of the end treatment agents (aryl halide or aryltrialkyltin) are dissolved in an organic solvent, a transition metal catalyst such as a palladium catalyst is added, and the mixture is heated and stirred under nitrogen. I do. Thereafter, the other end treatment agent (aryltrialkyltin or aryl halide) is further added, and the end treatment can be performed by heating and stirring. The above treatment is preferable because the terminal residue can be efficiently removed in a short time.

The addition amount of the transition metal catalyst such as a palladium catalyst is not particularly limited, but is usually 5.0 × 10 ⁻³ equivalent or more, preferably 1.0 × 10 ⁻² equivalent or more, relative to the copolymer, On the other hand, it is usually 1.0 × 10 ⁻¹ equivalent or less, preferably 5.0 × 10 ⁻² equivalent or less. When the addition amount of the catalyst is within this range, the end treatment can be performed at a lower cost and at a higher conversion rate.

The addition amount of the alkylstannyl end-treating agent is not particularly limited, but is usually 1.0 × 10 ⁻² equivalent or more, preferably 1. 0 × 10 ⁻¹ equivalent or more, more preferably 1 equivalent or more, and usually 50 equivalents or less, preferably 20 equivalents or less, more preferably 10 equivalents or less. When the added amount of the end treatment agent is within this range, the end treatment can be performed at a lower cost and at a higher conversion rate.

The amount of the terminal-treating agent of the halogen group, but no particular restriction is not, based on the monomers halogen group is added to the ends, usually 1.0 × 10 ^-2 equivalents or more, preferably 1.0 × 10 ^{- 1} equivalent or more, more preferably 1 equivalent or more, and usually 50 equivalents or less, preferably 20 equivalents or less, more preferably 10 equivalents or less. When the added amount of the end treatment agent is within this range, the end treatment can be performed at a lower cost and at a higher conversion rate.

  The heating time is not particularly limited, but is usually 30 minutes or longer, preferably 1 hour or longer, and is usually 25 hours or shorter, preferably 10 hours or shorter.

  In addition, when the copolymer is polymerized by the Suzuki-Miyaura cross-coupling reaction method, the end treatment is performed by adding aryl boronic acid as the end treatment agent for the halogen group, adding the aryl boronic acid, and then stirring with heating. be able to.

  As described above, the copolymer after the terminal treatment can be purified by a method such as purification by Soxhlet, gel permeation chromatography, or metal removal by a scavenger.

  The method for producing the compound represented by the formula (IVA) used as a raw material for the polymerization reaction is not particularly limited. Am. Chem. Soc. 2010, 132 (22), 7595-7597. Further, the method for producing the compound represented by the formula (IVB) is not particularly limited. Mater. Chem. , 2011, 21, 3895 and J.A. Am. Chem. Soc. 2008, 130, 16144-16145.

(Other p-type semiconductor compounds)
The p-type semiconductor compound contained in the active layer 103 is not limited to the copolymer II and may be other organic semiconductor compounds. The active layer 103 can be used by mixing and / or laminating the copolymer II and another p-type semiconductor compound. Hereinafter, organic semiconductor compounds other than copolymer II that can be used as p-type semiconductor compounds, specifically, high-molecular organic semiconductor compounds and low-molecular organic semiconductor compounds will be described.

(High molecular organic semiconductor compounds)
The high molecular organic semiconductor compound that can be used as the p-type semiconductor compound is not particularly limited, and is a conjugated copolymer semiconductor compound such as polythiophene, polyfluorene, polyphenylene vinylene, polythienylene vinylene, polyacetylene, or polyaniline; an alkyl group or other substitution Examples thereof include copolymer semiconductor compounds such as oligothiophene having a substituted group. Moreover, the copolymer semiconductor compound which copolymerized 2 or more types of monomer units is also mentioned. Conjugated copolymers are described in, for example, Handbook of Conducting Polymers, 3 ^rd Ed. (2 volumes), 2007, Materials Science and Engineering, 2001, 32, 1-40, Pure Appl. Chem. Use a copolymer described in known literature such as 2002, 74, 2031-3044, Handbook of THIOPHENE-BASED MATERIALS (2 volumes), 2009, or a derivative thereof, and a copolymer that can be synthesized by a combination of the described monomers. Can do. The polymer organic semiconductor compound used as the p-type semiconductor compound may be a single compound or a mixture of a plurality of compounds.

  Specific examples of the polymer organic semiconductor compound that can be used as the p-type semiconductor compound include the following, but are not limited to the following.

(Low molecular organic semiconductor compounds)
The low-molecular organic semiconductor compound that can be used as the p-type semiconductor compound is not particularly limited, but specifically, a condensed aromatic hydrocarbon such as naphthacene, pentacene, or pyrene; a thiophene ring such as α-sexithiophene; Oligothiophenes containing 4 or more; those containing at least one of thiophene ring, benzene ring, fluorene ring, naphthalene ring, anthracene ring, thiazole ring, thiadiazole ring and benzothiazole ring, and a total of 4 or more linked; Examples thereof include macrocyclic compounds such as phthalocyanine compounds and metal complexes thereof, or porphyrin compounds such as tetrabenzoporphyrin and metal complexes thereof. Preferably, they are a phthalocyanine compound and its metal complex, or a porphyrin compound and its metal complex. More specifically, those described in known documents such as International Publication No. 2011/016430 can be employed.

  The p-type semiconductor compound that can be used is preferably a conjugated copolymer semiconductor compound such as polythiophene as the high molecular organic semiconductor compound, and a condensed aromatic carbonized compound such as naphthacene, pentacene, or pyrene as the low molecular organic semiconductor compound. Hydrogen, a phthalocyanine compound and a metal complex thereof, or a porphyrin compound such as tetrabenzoporphyrin (BP) and a metal complex thereof. One of the above compounds may be used, or a mixture of a plurality of compounds may be used.

  The p-type semiconductor compound may have some self-organized structure in the deposited state, or may be in an amorphous state.

  The HOMO (highest occupied molecular orbital) energy level of the p-type semiconductor compound is not particularly limited, and can be selected according to the type of the n-type semiconductor compound described later. In particular, when a fullerene compound is used as an n-type semiconductor compound, the HOMO energy level of the p-type semiconductor compound is usually −5.7 eV or more, more preferably −5.5 eV or more, on the other hand, usually −4.6 eV or less. Preferably it is -4.8 eV or less. When the HOMO energy level of the p-type semiconductor compound is −5.7 eV or more, the characteristics as a p-type semiconductor are improved, and when the HOMO energy level of the p-type semiconductor compound is −4.6 eV or less, Stability is improved and the open circuit voltage (Voc) is also improved.

  The LUMO (lowest unoccupied molecular orbital) energy level of the p-type semiconductor compound is not particularly limited, but can be selected according to the type of the n-type semiconductor compound described later. In particular, when a fullerene compound is used as an n-type semiconductor compound, the LUMO energy level of the p-type semiconductor compound is usually −3.7 eV or more, preferably −3.6 eV or more. On the other hand, it is usually −2.5 eV or less, preferably −2.7 eV or less. When the LUMO energy level of the p-type semiconductor is −2.5 eV or less, the band gap is adjusted, light energy having a long wavelength can be effectively absorbed, and the short-circuit current density is improved. When the LUMO energy level of the p-type semiconductor compound is −3.7 eV or more, electron transfer to the n-type semiconductor compound is likely to occur and the short-circuit current density is improved.

[3.3 N-type semiconductor compound]
The n-type semiconductor compound is not particularly limited. Specifically, the fullerene compound; a quinolinol derivative metal complex represented by 8-hydroxyquinoline aluminum; a condensed ring such as naphthalenetetracarboxylic acid diimide or perylenetetracarboxylic acid diimide Tetracarboxylic acid diimides; perylene diimide derivatives, terpyridine metal complexes, tropolone metal complexes, flavonol metal complexes, perinone derivatives, benzimidazole derivatives, benzoxazole derivatives, thiazole derivatives, benzthiazole derivatives, benzothiadiazole derivatives, oxadiazole derivatives, thiadiazoles Derivatives, triazole derivatives, aldazine derivatives, bisstyryl derivatives, pyrazine derivatives, phenanthroline derivatives, quinoxaline derivatives, benzoquinoline derivatives Bipyridine derivatives, borane derivatives; anthracene, pyrene, total fluoride condensed polycyclic aromatic hydrocarbons such as naphthacene or pentacene; single-walled carbon nanotubes, n-type polymer (n-type polymer semiconductor compound) and the like.

  Among them, fullerene compounds, borane derivatives, thiazole derivatives, benzothiazole derivatives, benzothiadiazole derivatives, N-alkyl-substituted naphthalenetetracarboxylic acid diimides, N-alkyl-substituted perylene diimide derivatives or n-type polymer semiconductor compounds are preferred. More preferred are fullerene compounds, N-alkyl-substituted perylene diimide derivatives, N-alkyl-substituted naphthalene tetracarboxylic acid diimides or n-type polymer semiconductor compounds. One of the above compounds may be used, or a mixture of a plurality of compounds may be used.

  The LUMO energy level of the n-type semiconductor compound is not particularly limited. For example, the value with respect to the vacuum level calculated by the cyclic voltammogram measurement method is usually −3.85 eV or more, preferably −3.80 eV or more. . In order to efficiently transfer electrons from a p-type semiconductor compound to an n-type semiconductor compound, the relative relationship of LUMO energy levels between the p-type semiconductor compound and the n-type semiconductor compound is important. Specifically, the LUMO energy level of the p-type semiconductor compound is above the LUMO energy level of the n-type semiconductor compound by a predetermined value, in other words, the electron affinity of the n-type semiconductor compound is p-type semiconductor compound. It is preferable that a predetermined energy is larger than the electron affinity. Since the open circuit voltage (Voc) depends on the difference between the HOMO energy level of the p-type semiconductor compound and the LUMO energy level of the n-type semiconductor compound, increasing the LUMO energy level of the n-type semiconductor compound tends to increase Voc. There is. On the other hand, the value of the LUMO energy level is usually −1.0 eV or less, preferably −2.0 eV or less, more preferably −3.0 eV or less, and further preferably −3.3 eV or less. By lowering the LUMO energy level of the n-type semiconductor compound, electrons tend to move and the short circuit current (Jsc) tends to increase.

  The HOMO energy level of the n-type semiconductor compound is not particularly limited, but is usually −5.0 eV or less, preferably −5.5 eV or less. On the other hand, it is usually −7.0 eV or more, preferably −6.6 eV or more. It is preferable that the HOMO energy level of the n-type semiconductor compound is −7.0 eV or more because light absorption of the n-type semiconductor compound can also be used for power generation. The HOMO energy level of the n-type semiconductor compound is preferably −5.0 eV or less from the viewpoint of preventing reverse movement of holes.

The electron mobility of the n-type semiconductor compound is not particularly limited, but is usually 1.0 × 10 ⁻⁶ cm ² / Vs or more, preferably 1.0 × 10 ⁻⁵ cm ² / Vs or more. 0 × 10 ⁻⁵ cm ² / Vs or more is more preferable, and 1.0 × 10 ⁻⁴ cm ² / Vs or more is more preferable. On the other hand, it is usually 1.0 × 10 ⁴ cm ² / Vs or less, preferably 1.0 × 10 ³ cm ² / Vs or less, and more preferably 5.0 × 10 ² cm ² / Vs or less. The fact that the electron mobility of the n-type semiconductor compound is 1.0 × 10 ⁻⁶ cm ² / Vs or more can provide effects such as improvement of the electron diffusion rate, improvement of short-circuit current, and improvement of conversion efficiency of the photoelectric conversion element. Is preferable. As a method for measuring the electron mobility, an FET method can be mentioned, which can be performed by a method described in a known document (Japanese Patent Laid-Open No. 2010-045186).

  The solubility of the n-type semiconductor compound in toluene at 25 ° C. is usually 0.5% by weight or more, preferably 0.6% by weight or more, and more preferably 0.7% by weight or more. On the other hand, it is usually preferably 90% by weight or less, more preferably 80% by weight or less, and further preferably 70% by weight or less. When the solubility of the n-type semiconductor compound in toluene at 25 ° C. is 0.5% by weight or more, the dispersion stability of the n-type semiconductor compound in the solution is improved, and aggregation, sedimentation, separation, and the like are less likely to occur. Therefore, it is preferable.

  Hereinafter, examples of preferable n-type semiconductor compounds will be described.

(Fullerene compound)
As a fullerene compound, what has the partial structure represented by general formula (n1), (n2), (n3), and (n4) is mentioned as a preferable example.

In the above formula, FLN represents fullerene, which is a carbon cluster having a closed shell structure. The carbon number of fullerene is not particularly limited as long as it is an even number of usually 60 or more and 130 or less. Examples of fullerenes include C ₆₀ , C ₇₀ , C ₇₆ , C ₇₈ , C ₈₂ , C ₈₄ , C ₉₀ , C ₉₄ , C ₉₆ and higher carbon clusters having more carbon than these. . Among these, _C60 or _C70 is preferable. As fullerenes, carbon-carbon bonds on some fullerene rings may be broken. Moreover, some of the carbon atoms constituting the fullerene may be replaced with other atoms. Further, the fullerene may include a metal atom, a non-metal atom, or an atomic group composed of these in a fullerene cage.

a, b, c and d are integers, and the sum of a, b, c and d is usually 1 or more, and usually 5 or less, preferably 3 or less. The partial structures in (n1), (n2), (n3) and (n4) are bonded to the same 5-membered ring or 6-membered ring in the fullerene skeleton. In the general formula (n1), —R ²¹ and — (CH ₂ ) _L are bonded to two adjacent carbon atoms on the same 5-membered ring or 6-membered ring in the fullerene skeleton. . In the general formula (n2), -C (R ²⁵ ) (R ²⁶ ) -N (R ²⁷ ) -C with respect to two adjacent carbon atoms on the same 5-membered ring or 6-membered ring in the fullerene skeleton. (R ²⁸ ) (R ²⁹ ) — are added to form a 5-membered ring. In the general formula (n3), —C (R ³⁰ ) (R ³¹ ) —Ar ¹ —C (R ³² ) with respect to two adjacent carbon atoms on the same 5-membered ring or 6-membered ring in the fullerene skeleton. ) (R ³³ ) — is added to form a 6-membered ring. In the general formula (n4), —C (R ³⁴ ) (R ³⁵ ) — is added to two adjacent carbon atoms on the same 5-membered ring or 6-membered ring in the fullerene skeleton to form a 3-membered ring. Forming.

  L is an integer of 1 to 8. L is preferably an integer of 1 to 4, more preferably an integer of 1 to 2.

R ²¹ in the general formula (n1) is an alkyl group having 1 to 14 carbon atoms which may have a substituent, an alkoxy group having 1 to 14 carbon atoms which may have a substituent, or a substituent. An aromatic group which may have a group.

  The alkyl group is preferably an alkyl group having 1 to 10 carbon atoms, more preferably a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group or an isobutyl group, and even more preferably a methyl group or an ethyl group. . The alkoxy group is preferably an alkoxy group having 1 to 10 carbon atoms, more preferably an alkoxy group having 1 to 6 carbon atoms, and particularly preferably a methoxy group or an ethoxy group. The aromatic group is preferably an aromatic hydrocarbon group having 6 to 20 carbon atoms or an aromatic heterocyclic group having 2 to 20 carbon atoms, more preferably a phenyl group, a thienyl group, a furyl group, or a pyridyl group. A group or a thienyl group is more preferred.

  Although it does not specifically limit as a substituent which said alkyl group, an alkoxy group, and an aromatic group may have, A halogen atom or a silyl group is preferable. As the halogen atom, a fluorine atom is preferable. The silyl group is preferably a diarylalkylsilyl group, a dialkylarylsilyl group, a triarylsilyl group or a trialkylsilyl group, more preferably a dialkylarylsilyl group, and even more preferably a dimethylarylsilyl group.

R ^{22 to} R ²⁴ in the general formula (n1) may each independently have a hydrogen atom, an alkyl group having 1 to 14 carbon atoms which may have a substituent, or a substituent. It is an aromatic group.

  As the alkyl group, an alkyl group having 1 to 10 carbon atoms is preferable, and a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, or an n-hexyl group is preferable. . The substituent that the alkyl group may have is preferably a halogen atom. As the halogen atom, a fluorine atom is preferable. The alkyl group substituted with a fluorine atom is preferably a perfluorooctyl group, a perfluorohexyl group or a perfluorobutyl group.

  The aromatic group is preferably an aromatic hydrocarbon group having 6 to 20 carbon atoms or an aromatic heterocyclic group having 2 to 20 carbon atoms, more preferably a phenyl group, a thienyl group, a furyl group, or a pyridyl group. A group or a thienyl group is more preferred. The substituent that the aromatic group may have is not particularly limited, but is a fluorine atom, an alkyl group having 1 to 14 carbon atoms, a fluorinated alkyl group having 1 to 14 carbon atoms, or a carbon atom having 1 to 14 carbon atoms. An alkoxy group or an aromatic group having 2 to 10 carbon atoms is preferable, a fluorine atom or an alkoxy group having 1 to 14 carbon atoms is more preferable, and a methoxy group, an n-butoxy group, or a 2-ethylhexyloxy group is further preferable. When the aromatic group has a substituent, the number is not limited, but is preferably 1 or more and 3 or less, and more preferably 1. When the aromatic group has a plurality of substituents, the types of the substituents may be different, but are preferably the same.

R ^{25 to} R ²⁹ in the general formula (n2) may each independently have a hydrogen atom, an alkyl group having 1 to 14 carbon atoms which may have a substituent, or a substituent. It is an aromatic group.

  The alkyl group is preferably a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, n-hexyl group or octyl group, and more preferably a methyl group. The substituent that the alkyl group may have is not particularly limited, but a halogen atom is preferable. As the halogen atom, a fluorine atom is preferable. The alkyl group substituted with a fluorine atom is preferably a perfluorooctyl group, a perfluorohexyl group or a perfluorobutyl group.

  As the aromatic group, an aromatic hydrocarbon group having 6 to 20 carbon atoms or an aromatic heterocyclic group having 2 to 20 carbon atoms is preferable, a phenyl group or a pyridyl group is more preferable, and a phenyl group is further preferable. Although it does not specifically limit as a substituent which an aromatic group may have, Preferably they are a fluorine atom, a C1-C14 alkyl group, or a C1-C14 alkoxy group. The alkyl group may be substituted with a fluorine atom. More preferably, it is an alkoxy group having 1 to 14 carbon atoms, and more preferably a methoxy group. When it has a substituent, the number is not limited, but it is preferably 1 or more and 3 or less, more preferably 1. The types of substituents may be different, but are preferably the same.

Ar ¹ in the general formula (n3) is an optionally substituted aromatic hydrocarbon ring having 6 to 20 carbon atoms or an aromatic heterocyclic ring having 2 to 20 carbon atoms, preferably benzene. A ring, a naphthalene ring, a biphenyl ring, a thiophene ring, a furan ring, a pyridine ring, a pyrimidine ring, a quinoline ring or a quinoxaline ring, and more preferably a benzene ring, a thiophene ring or a furan ring.

  Although there is no limitation as a substituent which you may have, a fluorine atom, a chlorine atom, a hydroxyl group, a cyano group, a silyl group, a boryl group, an amino group which may be substituted with an alkyl group, and having 1 to 14 carbon atoms An alkyl group, an alkoxy group having 1 to 14 carbon atoms, an alkylcarbonyl group having 2 to 14 carbon atoms, an alkylthio group having 1 to 14 carbon atoms, an alkenyl group having 2 to 14 carbon atoms, and 2 to 14 carbon atoms An alkynyl group, an ester group having 2 to 14 carbon atoms, an arylcarbonyl group having 3 to 20 carbon atoms, an arylthio group having 2 to 20 carbon atoms, an aryloxy group having 2 to 20 carbon atoms, and 6 or more carbon atoms An aromatic hydrocarbon group having 20 or less or a heterocyclic group having 2 to 20 carbon atoms is preferable, a fluorine atom, an alkyl group having 1 to 14 carbon atoms, or 1 or less carbon atoms. 4 an alkoxy group, having 2 to 14 ester groups carbons, an alkyl group or having 3 to 20 arylcarbonyl group carbons of 2 to 14 carbon atoms and more preferable. The alkyl group having 1 to 14 carbon atoms may be substituted with 1 or 2 or more fluorine atoms.

  The alkyl group having 1 to 14 carbon atoms is preferably a methyl group, an ethyl group or a propyl group. The alkoxy group having 1 to 14 carbon atoms is preferably a methoxy group, an ethoxy group, or a propoxy group. The alkylcarbonyl group having 2 to 14 carbon atoms is preferably an acetyl group. The ester group having 2 to 14 carbon atoms is preferably a methyl ester group or an n-butyl ester group. The arylcarbonyl group having 3 to 20 carbon atoms is preferably a benzoyl group.

  When it has a substituent, the number is not limited, but it is preferably 1 or more and 4 or less, more preferably 1 or more and 3 or less. When there are a plurality of substituents, the types may be different, but are preferably the same.

R ^{30 to} R ³³ in the general formula (n3) each independently have a hydrogen atom, an alkyl group which may have a substituent, an amino group which may have a substituent, or a substituent. It is an optionally substituted alkoxy group or an optionally substituted alkylthio group. R ³⁰ or R ³¹ may be bonded to any one of R ³² and R ³³ to form a ring. As a structure in the case of forming a ring, the structure represented by general formula (n5) which is a bicyclo structure which the aromatic group condensed is mentioned, for example.

F In the general formula (n5) has the same meaning as c, Z ² is two hydrogen atoms, an oxygen atom, a sulfur atom, an amino group, an alkylene group or an arylene group. The alkylene group preferably has 1 to 2 carbon atoms. The arylene group preferably has 5 to 12 carbon atoms, and examples thereof include a phenylene group. The amino group may be substituted with an alkyl group having 1 to 6 carbon atoms such as a methyl group or an ethyl group. The alkylene group is an alkoxy group having 1 to 6 carbon atoms such as a methoxy group, an aliphatic hydrocarbon group having 1 to 5 carbon atoms, an aromatic hydrocarbon group having 6 to 20 carbon atoms, or 2 to 20 carbon atoms. The aromatic heterocyclic group may be substituted. The arylene group is an alkoxy group having 1 to 6 carbon atoms such as a methoxy group, an aliphatic hydrocarbon group having 1 to 5 carbon atoms, an aromatic hydrocarbon group having 6 to 20 carbon atoms, or 2 to 20 carbon atoms. The aromatic heterocyclic group may be substituted.

  The structure represented by the formula (n5) is particularly preferably a structure represented by the following formula (n6) or formula (n7).

R ^{34 to} R ³⁵ in the general formula (n4) each independently have a hydrogen atom, an alkoxycarbonyl group, an alkyl group having 1 to 14 carbon atoms which may have a substituent, or a substituent. An aromatic group that may be present.

  The alkoxy group constituting the alkoxycarbonyl group is preferably an alkoxy group having 1 to 12 carbon atoms or a fluorinated alkoxy group having 1 to 12 carbon atoms, more preferably an alkoxy group having 1 to 12 carbon atoms, and a methoxy group. Ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, isobutoxy group, n-hexoxy group, octoxy group, 2-propylpentoxy group, 2-ethylhexoxy group, cyclohexylmethoxy group or benzyloxy group A methoxy group, an ethoxy group, an isopropoxy group, an n-butoxy group, an isobutoxy group or an n-hexoxy group is particularly preferable.

  As the alkyl group, a linear alkyl group having 1 to 8 carbon atoms is preferable, and an n-propyl group is more preferable. The substituent that the alkyl group may have is not particularly limited, but is preferably an alkoxycarbonyl group. The alkoxy group constituting the alkoxycarbonyl group is preferably an alkoxy group having 1 to 14 carbon atoms or a fluorinated alkoxy group, more preferably an alkoxy group having 1 to 14 carbon atoms, a methoxy group, an ethoxy group, or n-propoxy. Group, isopropoxy group, n-butoxy group, isobutoxy group, n-hexoxy group, octoxy group, 2-propylpentoxy group, 2-ethylhexoxy group, cyclohexylmethoxy group or benzyloxy group, more preferably methoxy group or n- A butoxy group is particularly preferred.

  As the aromatic group, an aromatic hydrocarbon group having 6 to 20 carbon atoms or an aromatic heterocyclic group having 2 to 20 carbon atoms is preferable, and a phenyl group, a biphenyl group, a thienyl group, a furyl group, or a pyridyl group is preferable. More preferred are a phenyl group and a thienyl group. The substituent that the aromatic group may have is preferably an alkyl group having 1 to 14 carbon atoms, a fluorinated alkyl group having 1 to 14 carbon atoms, or an alkoxy group having 1 to 14 carbon atoms. An alkoxy group having a number of 1 or more and 14 or less is more preferable, and a methoxy group or 2-ethylhexyloxy group is particularly preferable. When it has a substituent, the number is not limited, but it is preferably 1 or more and 3 or less, more preferably 1. The types of substituents may be different or the same, preferably the same.

As the structure of the general formula (n4), preferably R ³⁴ and R ³⁵ are both alkoxycarbonyl groups, R ³⁴ and R ³⁵ are both aromatic groups, or R ³⁴ is an aromatic group and R ^{And those in which 35} is a 3- (alkoxycarbonyl) propyl group.

  As the fullerene compound, one kind of the above compounds may be used, or a mixture of plural kinds of compounds may be used.

  In order to form a fullerene compound by a coating method, it is preferable that the fullerene compound itself can be applied in a liquid state, or that the fullerene compound is highly soluble in some solvent and can be applied as a solution. As a preferable range of solubility, the solubility in toluene at 25 ° C. is usually 0.1% by weight or more, preferably 0.4% by weight or more, more preferably 0.7% by weight or more. It is preferable that the solubility of the fullerene compound is 0.1% by weight or more because the dispersion stability of the fullerene compound in the solution increases and aggregation, sedimentation, separation, and the like are less likely to occur.

  The solvent for dissolving the fullerene compound is not particularly limited as long as it is a nonpolar organic solvent, but a non-halogen solvent is preferable. Although it is possible to use a halogen-based solvent such as dichlorobenzene, an alternative is demanded from the viewpoint of environmental load. Examples of non-halogen solvents include non-halogen aromatic hydrocarbons. Of these, toluene, xylene, cyclohexylbenzene, and the like are preferable.

(Method for producing fullerene compound)
Although there is no restriction | limiting in particular as a manufacturing method of a fullerene compound, For example, the synthesis | combination of the fullerene compound which has a partial structure (n1) is international publication 2008/059771 or J.N. Am. Chem. Soc. , 2008, 130 (46), 15429-15436.

  Synthesis of fullerene compounds having a partial structure (n2) is described in J. Org. Am. Chem. Soc. 1993, 115, 9798-9799, Chem. Mater. 2007, 19, 5363-5372 and Chem. Mater. It can be carried out according to the description of known documents such as 2007, 19, 5194-5199.

  Synthesis of a fullerene compound having a partial structure (n3) is described in Angew. Chem. Int. Ed. Engl. 1993, 32, 78-80, Tetrahedron Lett. It can be carried out according to the description of known documents such as 1997, 38, 285-288, WO 2008/018931 and WO 2009/086212.

  Synthesis of fullerene compounds having a partial structure (n4) is described in J. Org. Chem. Soc. Perkin Trans. 1, 1997 1595, Thin Solid Films 489 (2005) 251-256, Adv. Funct. Mater. 2005, 15, 1979-1987 and J. Org. Org. Chem. It can be carried out according to the description of known documents such as 1995, 60, 532-538.

  Moreover, as a commercially available fullerene compound, for example, PCBM (manufactured by Frontier Carbon Co.) including PC61BM and PC71BM, PCBNB (manufactured by Frontier Carbon Co., Ltd.) and the like can be suitably used.

(N-alkyl substituted perylene diimide derivatives)
N-alkyl-substituted perylene diimide derivatives are not particularly limited, and specifically, International Publication No. 2008/063609, International Publication No. 2009/115513, International Publication No. 2009/098250, International Publication No. Examples thereof include compounds described in 2009/000756 and International Publication No. 2009/091670. These compounds are preferable in that they have high electron mobility and can absorb light in the visible range, and thus can contribute to both charge transport and power generation.

(Naphthalene tetracarboxylic acid diimide)
The naphthalenetetracarboxylic acid diimide is not particularly limited, and specific examples thereof include compounds described in International Publication No. 2008/063609, International Publication No. 2007/146250 and International Publication No. 2009/000756. It is done. These compounds are preferable because they have high electron mobility, high solubility, and excellent coating properties.

(N-type polymer semiconductor compound)
The n-type polymer semiconductor compound is not particularly limited, but condensed ring tetracarboxylic acid diimides such as naphthalene tetracarboxylic acid diimide or perylene tetracarboxylic acid diimide, perylene diimide derivatives, benzimidazole derivatives, benzoxazole derivatives, thiazoles N-type polymer semiconductor comprising at least one of a derivative, a benzothiazole derivative, a benzothiadiazole derivative, an oxadiazole derivative, a thiadiazole derivative, a triazole derivative, a pyrazine derivative, a phenanthroline derivative, a quinoxaline derivative, a bipyridine derivative and a borane derivative Compounds and the like.

  Among them, a polymer having at least one of a borane derivative, a thiazole derivative, a benzothiazole derivative, a benzothiadiazole derivative, an N-alkyl-substituted naphthalenetetracarboxylic acid diimide and an N-alkyl-substituted perylene diimide derivative as a constituent unit is provided. Preferably, an n-type polymer semiconductor compound having at least one of N-alkyl-substituted perylene diimide derivative and N-alkyl-substituted naphthalenetetracarboxylic acid diimide as a constituent unit is more preferable. One of the above compounds may be used as the n-type polymer semiconductor compound, or a mixture of a plurality of compounds may be used.

  Specific examples of the n-type polymer semiconductor compound include compounds described in International Publication No. 2009/098253, International Publication No. 2009/098250, and International Publication No. 2010/0127710. Since these compounds can absorb light in the visible range, they can contribute to power generation, are preferred because of their high viscosity and excellent coating properties.

<4. Electrode (101, 105)>
The electrodes 101 and 105 have a function of collecting holes and electrons generated by light absorption. Therefore, it is preferable to use the electrode 101 (cathode) suitable for collecting electrons and the electrode 105 (anode) suitable for collecting holes as the pair of electrodes. Any one of the pair of electrodes may be translucent, and both may be translucent. Translucency means that sunlight passes through 40% or more. Moreover, it is preferable that the translucent transparent electrode has a solar ray transmittance of 70% or more in order to allow light to reach the active layer 103 through the transparent electrode. The light transmittance can be measured with a normal spectrophotometer.

  The cathode 101 is generally an electrode made of a conductive material having a work function smaller than that of the anode and having a function of smoothly extracting electrons generated in the active layer 103.

  Examples of the material of the cathode 101 include metals such as platinum, gold, silver, copper, iron, tin, zinc, aluminum, indium, chromium, lithium, sodium, potassium, cesium, calcium, and magnesium, and alloys thereof; Examples include inorganic salts such as lithium and cesium fluoride; metal oxides such as nickel oxide, aluminum oxide, lithium oxide, and cesium oxide. These materials are preferable because they are materials having a small work function. When an n-type semiconductor compound such as zinc oxide having conductivity is used as the material of the electron extraction layer 102, a material having a large work function suitable for the anode, such as ITO, is used as the material of the cathode 101. It can also be used. From the viewpoint of electrode protection, the cathode 101 is preferably made of a metal such as platinum, gold, silver, copper, iron, tin, aluminum, calcium, or indium and an alloy using these metals.

  The film thickness of the cathode 101 is not particularly limited, but is usually 10 nm or more, preferably 20 nm or more, more preferably 50 nm or more. On the other hand, it is usually 10 μm or less, preferably 1 μm or less, more preferably 500 nm or less. When the film thickness of the cathode 101 is 10 nm or more, the sheet resistance is suppressed, and when the film thickness of the cathode 101 is 10 μm or less, light can be efficiently converted into electricity without decreasing the light transmittance. it can. When the cathode 101 is used as a transparent electrode, it is necessary to select a film thickness that achieves both light transmittance and sheet resistance.

  The sheet resistance of the cathode 101 is not particularly limited, but is usually 1000Ω / □ or less, preferably 500Ω / □ or less, and more preferably 100Ω / □ or less. Although there is no restriction on the lower limit, it is usually 1Ω / □ or more.

  As a method for forming the cathode 101, there are a vacuum film-forming method such as an evaporation method or a sputtering method, or a wet coating method in which an ink containing nanoparticles or a precursor is applied to form a film.

  The anode 105 is an electrode generally made of a conductive material having a work function larger than that of the cathode and having a function of smoothly extracting holes generated in the active layer 103.

  Examples of the material of the anode 105 include conductive metal oxides such as nickel oxide, tin oxide, indium oxide, indium tin oxide (ITO), indium-zirconium oxide (IZO), titanium oxide, indium oxide, and zinc oxide. A metal such as gold, platinum, silver, chromium or cobalt or an alloy thereof; These substances are preferable because they have a large work function, and more preferably, a conductive polymer material represented by PEDOT: PSS in which a polythiophene derivative is doped with polystyrene sulfonic acid can be laminated. When laminating such a conductive polymer, the work function of this conductive polymer material is large, so it is suitable for cathodes such as aluminum and magnesium, even if it is not a material with a large work function as described above. Metals can also be widely used.

  PEDOT: PSS in which a polythiophene derivative is doped with polystyrene sulfonic acid, or a conductive polymer material in which polypyrrole, polyaniline, or the like is doped with iodine or the like can also be used as an anode material.

  When the anode 105 is a transparent electrode, it is preferable to use a light-transmitting conductive metal oxide such as ITO, zinc oxide, or tin oxide, and it is particularly preferable to use ITO.

  Although there is no restriction | limiting in particular in the film thickness of the anode 105, Usually, 10 nm or more, Preferably it is 20 nm or more, More preferably, it is 50 nm or more. On the other hand, it is usually 10 μm or less, preferably 1 μm or less, more preferably 500 nm or less. When the film thickness of the anode 105 is 10 nm or more, the sheet resistance is suppressed, and when the film thickness of the anode 105 is 10 μm or less, light can be efficiently converted into electricity without decreasing the light transmittance. it can. When the anode 105 is a transparent electrode, it is necessary to select a film thickness that can achieve both light transmittance and sheet resistance.

  The sheet resistance of the anode 105 is not particularly limited, but is usually 1Ω / □ or more, on the other hand, 1000Ω / □ or less, preferably 500Ω / □ or less, more preferably 100Ω / □ or less.

  Examples of a method for forming the anode 105 include a vacuum film forming method such as a vapor deposition method or a sputtering method, or a wet coating method in which an ink containing nanoparticles or a precursor is applied to form a film.

  Further, the cathode 101 and the anode 105 may have a stacked structure of two or more layers. Further, by performing surface treatment on the cathode 101 and the anode 105, characteristics (electric characteristics, wetting characteristics, etc.) may be improved.

<5. Substrate (106)>
The photoelectric conversion element 107 includes a base material 106 that serves as a support. That is, the electrodes 101 and 105, the active layer 103, and the hole extraction layer 104 are formed on the substrate.

  The material of the substrate 106 is not particularly limited as long as the effects of the present invention are not significantly impaired. Preferable examples of the material of the substrate 106 include inorganic materials such as quartz, glass, sapphire, and titania; polyethylene terephthalate, polyethylene naphthalate, polyethersulfone, polyimide, nylon, polystyrene, polyvinyl alcohol, ethylene vinyl alcohol copolymer Organic materials such as coalescence, fluororesin film, polyolefin such as vinyl chloride or polyethylene, cellulose, polyvinylidene chloride, aramid, polyphenylene sulfide, polyurethane, polycarbonate, polyarylate, polynorbornene or epoxy resin; paper material such as paper or synthetic paper And composite materials such as those obtained by coating or laminating a surface of a metal such as stainless steel, titanium or aluminum in order to impart insulation.

  Examples of the glass include soda glass, blue plate glass, and non-alkali glass. Among these, alkali-free glass is preferable in that there are few eluted ions from the glass.

  There is no restriction | limiting in the shape of the base material 106, For example, things, such as plate shape, a film form, or a sheet form, can be used. Moreover, although there is no restriction | limiting in the film thickness of the base material 106, Usually, it is 5 micrometers or more, Preferably it is 20 micrometers or more, On the other hand, it is 20 mm or less normally, Preferably it is 10 mm or less. It is preferable that the thickness of the substrate is 5 μm or more because the possibility that the strength of the photoelectric conversion element is insufficient is reduced. It is preferable that the thickness of the substrate is 20 mm or less because the cost is suppressed and the weight does not increase. When the material of the substrate 106 is glass, the film thickness is usually 0.01 mm or more, preferably 0.1 mm or more, and is usually 1 cm or less, preferably 0.5 cm or less. It is preferable that the glass substrate 106 has a film thickness of 0.01 mm or more because mechanical strength increases and it is difficult to break. Moreover, it is preferable that the film thickness of the glass substrate 106 is 0.5 cm or less because the weight does not increase.

<6. Electron Extraction Layer (102)>
The photoelectric conversion element 107 includes a buffer layer (electron extraction layer) 102 between the active layer 103 and the cathode 101. The electron extraction layer 102 facilitates the movement of electrons between the active layer 103 and the cathode 101, and can prevent a short circuit between the electrodes 101 and 105. In order to fulfill this function, the electron extraction layer 102 is disposed in contact with the active layer 103 and the cathode 101. However, the photoelectric conversion element 107 does not need to have the electron extraction layer 102. The electron extraction layer 102 may be composed of a plurality of different films.

  The material of the electron extraction layer 102 is not particularly limited as long as it is a material that improves the efficiency of extracting electrons from the active layer 103 to the cathode 101, and examples thereof include inorganic compounds and organic compounds.

  Preferable examples of the material of the inorganic compound include alkali metal salts such as lithium, sodium, potassium or cesium, or metal oxides. Among them, the alkali metal salt is preferably a fluoride salt such as lithium fluoride, sodium fluoride, potassium fluoride or cesium fluoride, and the metal oxide is titanium oxide (TiOx) or zinc oxide (ZnO). A metal oxide having n-type semiconductor characteristics such as Particularly preferred as a material for the inorganic compound is a metal oxide having n-type semiconductor characteristics such as zinc oxide (ZnO). The operation mechanism of such a material is unknown, but when combined with the cathode 101, it is conceivable to reduce the work function and increase the voltage applied to the solar cell element.

  Preferable examples of the material of the organic compound include a phosphine compound having a double bond between a phosphorus atom and a group 16 element such as a triarylphosphine oxide compound; bathocuproin (BCP) or bathophenanthrene (Bphen). A phenanthrene compound which may have a substituent and may be substituted at the 1-position and the 10-position with a heteroatom; a boron compound such as triarylboron; and (8-hydroxyquinolinato) aluminum (Alq3) Organometallic oxides; compounds having one or two ring structures which may have a substituent, such as oxadiazole compounds or benzimidazole compounds; naphthalenetetracarboxylic anhydride (NTCDA) or perylenetetracarboxylic Dicarboxylic acids such as acid anhydrides (PTCDA) Aromatic compounds and the like having a condensed dicarboxylic acid structure, such as anhydride.

  The LUMO energy level of the material of the electron extraction layer 102 is not particularly limited, but is usually −4.0 eV or more, preferably −3.9 eV or more. On the other hand, it is usually −1.9 eV or less, preferably −2.0 eV or less. It is preferable that the LUMO energy level of the material of the electron extraction layer 102 is −1.9 eV or less because charge transfer can be promoted. It is preferable that the LUMO energy level of the material of the electron extraction layer 102 is −4.0 eV or more because reverse electron transfer to the n-type semiconductor compound can be prevented.

  The HOMO energy level of the material of the electron extraction layer 102 is not particularly limited, but is usually −9.0 eV or more, preferably −8.0 eV or more. On the other hand, it is usually −5.0 eV or less, preferably −5.5 eV or less. The HOMO energy level of the material of the electron extraction layer 102 is preferably −5.0 eV or less from the viewpoint of preventing movement of holes. As a method for calculating the LUMO energy level and the HOMO energy level of the material of the electron extraction layer 102, the above-described cyclic voltammogram measurement method can be given.

  When the material of the electron extraction layer 102 is an organic compound, the glass transition temperature (hereinafter sometimes referred to as Tg) of this compound when measured by a DSC method is not particularly limited, but is not observed, Or it is preferable that it is 55 degreeC or more. That the glass transition temperature is not observed by the DSC method means that there is no glass transition temperature. Specifically, the determination is made based on the presence or absence of a glass transition temperature of 400 ° C. or lower. A material in which the glass transition temperature by the DSC method is not observed is preferable in that it has high thermal stability.

  Among the compounds having a glass transition temperature of 55 ° C. or higher as measured by the DSC method, the glass transition temperature is preferably 65 ° C. or higher, more preferably 80 ° C. or higher, more preferably 110 ° C. or higher, particularly preferably. Compounds that are 120 ° C. or higher are desirable. On the other hand, the upper limit of the glass transition temperature is not particularly limited, but is usually 400 ° C. or lower, preferably 350 ° C. or lower, more preferably 300 ° C. or lower. The material of the electron extraction layer 102 is preferably a material whose glass transition temperature by DSC method is not observed to be 30 ° C. or higher and lower than 55 ° C.

  The glass transition temperature in the present specification is defined as a point at which specific heat changes in an amorphous solid, which is a temperature at which local molecular motion is started by thermal energy. When the temperature rises further than Tg, the solid structure changes and crystallization occurs (the temperature at this time is defined as the crystallization temperature (Tc)). When the temperature rises further, it generally melts at the melting point (Tm) and changes to a liquid state. However, these phase transitions may not be observed due to molecular decomposition or sublimation at high temperatures.

  The DSC method is a thermophysical property measurement method (differential scanning calorimetry method) defined in JIS K-0129 “General Rules for Thermal Analysis”. In order to determine the glass transition temperature more clearly, it is desirable to measure after rapidly cooling a sample once heated to a temperature higher than the glass transition temperature. For example, the measurement can be carried out by a method described in a known document (International Publication No. 2011/016430).

  When the glass transition temperature of the compound used for the electron extraction layer is 55 ° C. or higher, the structure of this compound is difficult to change against external stress such as applied electric field, flowing current, stress due to bending or temperature change. It is preferable in terms of durability. Furthermore, since there is a tendency that the crystallization of the thin film of the compound does not proceed easily, the stability of the electron extraction layer is improved by making it difficult for the compound to change between the amorphous state and the crystalline state in the operating temperature range. Therefore, it is preferable in terms of durability. This effect becomes more prominent as the glass transition temperature of the material is higher.

  The thickness of the electron extraction layer 102 is not particularly limited, but is usually 0.01 nm or more, preferably 0.1 nm or more, more preferably 0.5 nm or more. On the other hand, it is usually 100 nm or less, preferably 70 nm or less, more preferably 40 nm or less, and particularly preferably 20 nm or less. When the film thickness of the electron extraction layer 102 is 0.01 nm or more, it functions as a buffer material. When the film thickness of the electron extraction layer 102 is 100 nm or less, electrons are easily extracted and photoelectric conversion is performed. Efficiency can be improved.

  There is no limitation on the method of forming the electron extraction layer 102. For example, when a material having sublimation property is used, it can be formed by a vacuum deposition method or the like. Further, for example, when a material soluble in a solvent is used, it can be formed by a wet coating method such as spin coating or inkjet. When a semiconductor compound is used for the electron extraction layer 102, the precursor may be converted into a semiconductor compound after forming a layer containing a semiconductor compound precursor, like the active layer 103.

<7. Manufacturing method of photoelectric conversion element>
The photoelectric conversion element 107 can be manufactured by sequentially stacking the base material 106, the cathode 101, the electron extraction layer 102, the active layer 103, the hole extraction layer 104, and the anode 105 in accordance with the method described above. A photoelectric conversion element having a different structure, for example, a photoelectric conversion element that does not include the electron extraction layer 102 can be manufactured by a similar method.

  As described above, the hole extraction layer 104 can be formed by a step of applying a hole extraction layer coating liquid onto the active layer 103. Since the coating solution for the hole extraction layer contains an acetylene glycol compound, the wettability of the coating solution with respect to the active layer 103 is high. For this reason, it is not essential to perform surface treatment such as oxygen plasma treatment after forming the active layer 103, and by directly applying a coating solution for the hole extraction layer on the active layer 103 formed by coating and drying. In addition, a good hole extraction layer 104 can be formed.

  After the cathode 101 and the anode 105 are laminated, the photoelectric conversion element is heated in a temperature range of usually 50 ° C. or higher, preferably 80 ° C. or higher, usually 300 ° C. or lower, preferably 280 ° C. or lower, more preferably 250 ° C. or lower. It is preferable to do this (this step is referred to as an annealing treatment step). Performing the annealing process at a temperature of 50 ° C. or higher improves adhesion between the layers of the photoelectric conversion element, for example, adhesion between the hole extraction layer 104 and the anode 105 and / or the hole extraction layer 104 and the active layer 103. This is preferable because the effect of By improving the adhesion between the layers, the thermal stability and durability of the photoelectric conversion element can be improved. Further, the self-organization of the active layer can be promoted by the annealing process. It is preferable to set the temperature of the annealing treatment step to 300 ° C. or lower because the possibility that the organic compound in the active layer 103 is thermally decomposed is reduced. In the annealing treatment step, stepwise heating may be performed within the above temperature range.

  The heating time is usually 1 minute or longer, preferably 3 minutes or longer, and usually 3 hours or shorter, preferably 1 hour or shorter. The annealing treatment step is preferably terminated when the open-circuit voltage, the short-circuit current, and the fill factor, which are parameters of the solar cell performance, reach a constant value. Further, the annealing treatment step is preferably performed under normal pressure and in an inert gas atmosphere.

  As a heating method, the photoelectric conversion element may be placed on a heat source such as a hot plate, or the photoelectric conversion element may be placed in a heating atmosphere such as an oven. The heating may be performed batchwise or continuously.

<8. Photoelectric conversion characteristics of photoelectric conversion element>
The photoelectric conversion characteristics of the photoelectric conversion element 107 can be obtained as follows. The photoelectric conversion element 107 is irradiated with light having an AM1.5G condition at a irradiance of 100 mW / cm ² by a solar simulator, and current-voltage characteristics are measured. From the obtained current-voltage curve, photoelectric conversion characteristics such as photoelectric conversion efficiency (PCE), short circuit current density (Jsc), open circuit voltage (Voc), fill factor (FF), series resistance, and shunt resistance can be obtained.

  The photoelectric conversion efficiency of the photoelectric conversion element according to the present invention is not particularly limited, but is usually 1% or more, preferably 1.5% or more, more preferably 2% or more. On the other hand, there is no particular limitation on the upper limit, and the higher the better.

Moreover, as a method for measuring the durability of the photoelectric conversion element, a method for obtaining a maintenance ratio of the photoelectric conversion efficiency before and after exposing the photoelectric conversion element to the atmosphere can be mentioned.
(Maintenance rate) = (Photoelectric conversion efficiency after N hours of atmospheric exposure) / (Photoelectric conversion efficiency immediately before atmospheric exposure)

  In order to put a photoelectric conversion element into practical use, it is important to have high photoelectric conversion efficiency and high durability in addition to simple and inexpensive manufacture. From this viewpoint, the maintenance rate of photoelectric conversion efficiency before and after exposure to the atmosphere for one week is preferably 60% or more, more preferably 80% or more, and the higher the better.

<9. Solar Cell According to the Present Invention>
The photoelectric conversion element 107 according to the present invention is preferably used as a solar cell, particularly a solar cell element of a thin film solar cell.

  FIG. 2 is a cross-sectional view schematically showing the configuration of a thin film solar cell as one embodiment of the present invention. As shown in FIG. 2, the thin film solar cell 14 of this embodiment includes a weather-resistant protective film 1, an ultraviolet cut film 2, a gas barrier film 3, a getter material film 4, a sealing material 5, and a solar cell element. 6, a sealing material 7, a getter material film 8, a gas barrier film 9, and a back sheet 10 are provided in this order. And light is irradiated from the side (downward in the figure) where the weather-resistant protective film 1 is formed, and the solar cell element 6 generates power. In addition, when using a highly waterproof sheet such as a sheet in which a fluororesin film is bonded to both surfaces of an aluminum foil as the back sheet 10 described later, the getter material film 8 and / or the gas barrier film 9 may not be used depending on the application. Good.

  For the above-described configuration and the manufacturing method thereof, a well-known technique can be used, and specifically, those described in known documents such as International Publication No. 2011/016430 can be adopted.

  There is no restriction | limiting in the use of the solar cell which concerns on this invention, especially the thin film solar cell 14 mentioned above, It can use for arbitrary uses. Examples of fields to which the thin-film solar cell according to the present invention can be applied include building material solar cells, automotive solar cells, interior solar cells, railroad solar cells, marine solar cells, airplane solar cells, and spacecrafts. Solar cells, solar cells for home appliances, solar cells for mobile phones, solar cells for toys, and the like.

  The solar cell according to the present invention, in particular, a thin film solar cell may be used as it is, or a solar cell may be installed on a substrate and used as a solar cell module. For example, as schematically shown in FIG. 3, a solar cell module 13 including a thin film solar cell 14 on a base material 12 is prepared and used at a place of use. For the base material 12, well-known techniques can be used, and specifically those described in publicly known documents such as International Publication No. 2011-016430 can be adopted.

  As a specific example, when a building material plate is used as the base material 12, a solar cell panel can be produced as the solar cell module 13 by providing the thin film solar cell 14 on the surface of the plate material.

  EXAMPLES Hereinafter, although the Example of this invention is shown and this invention is demonstrated more concretely, this invention is not limited to a following example, unless it deviates from the summary. Items described in the examples were measured by the following methods.

(Measurement method of weight average molecular weight and number average molecular weight)
The weight average molecular weight (Mw) and number average molecular weight (Mn) in terms of polystyrene were determined by gel permeation chromatography (GPC). Molecular weight distribution (PDI) represents Mw / Mn.

Gel permeation chromatography (GPC) measurement was performed under the following conditions.
Column: Polymer Laboratories GPC column (PLgel MIXED-B 10 μm, inner diameter 7.5 mm, length 30 cm) connected in series Pump: LC-10AT (manufactured by Shimadzu Corporation)
Oven: CTO-10A (manufactured by Shimadzu Corporation)
Detector: differential refractive index detector (manufactured by Shimadzu Corporation, RID-10A) and UV-vis detector (manufactured by Shimadzu Corporation, SPD-10A)
Sample: 1 μL of 1 mg sample dissolved in chloroform (200 mg)
Mobile phase: Chloroform Flow rate: 1.0 mL / min
Analysis: LC-Solution (manufactured by Shimadzu Corporation)

(Evaluation method of photoelectric conversion element)
A 4 mm square metal mask is attached to the photoelectric conversion element, a solar simulator with an air mass (AM) of 1.5 G and an irradiance of 100 mW / cm ² is used as an irradiation light source, and an ITO electrode is connected with a source meter (Keisley, Model 2400). The current-voltage characteristic between the aluminum electrode was measured. From this measurement result, open circuit voltage Voc (V), short circuit current density Jsc (mA / cm ² ), form factor FF, and photoelectric conversion efficiency PCE (%) were calculated.

Here, the open circuit voltage Voc is a voltage value when the current value = 0 (mA / cm ² ), and the short circuit current density Jsc is a current density when the voltage value = 0 (V). The form factor FF is a factor representing the internal resistance, and is represented by the following expression when the maximum output is Pmax.
FF = Pmax / (Voc × Jsc)
Further, the photoelectric conversion efficiency PCE is given by the following equation when the incident energy is Pin.
PCE = (Pmax / Pin) × 100
= (Voc x Jsc x FF / Pin) x 100

<Synthesis Example 1: Synthesis of Copolymer A>

  As a monomer, 1,3-dibromo-5-octyl-4H-thieno [3,4-c obtained by referring to a method described in known literature (J. Am. Chem. Soc. 2011, 133, 10062) ] Pyrrole-4,6- (5H) -dione (Compound E1, 86 mg, 0.204 mmol), obtained by referring to the method described in known literature (J. Am. Chem. Soc. 2011, 133, 10062). 4,4-bis (2-ethylhexyl) -2,6-bis (trimethyltin) -dithieno [3,2-b: 2 ′, 3′-d] silole (compound E2, 80 mg, 0.108 mmol), And 4,4-di-n-octyl-2,6-bis (tri-methyl ether) obtained by referring to the methods described in known literature (Chem. Commun., 2011, 47, 4920-4922). Tiltin) -dithieno [3,2-b: 2 ′, 3′-d] silole (compound E3, 80 mg, 0.108 mmol) was used to make known literature (J. Am. Chem. Soc. 2011, 133, 10062). The copolymer A was synthesized with reference to the method described in 1).

The weight average molecular weight Mw and PDI of the copolymer A were measured as described above, and were 3.69 × 10 ⁵ and 9.4, respectively.

<Example 1>
(Preparation of active layer coating liquid ink 1)
Copolymer A obtained in Synthesis Example 1 as a p-type semiconductor compound and PC71BM (NS-E112, manufactured by Frontier Carbon Co., Ltd.) as an n-type semiconductor compound are mixed so that the weight ratio is 1: 2, and the mixture is 2 It was dissolved in a mixed solvent of orthoxylene and tetralin (volume ratio 4: 1) in a nitrogen atmosphere so as to obtain a concentration by weight. This solution was stirred and mixed on a hot stirrer at a temperature of 80 ° C. for 1 hour. The solution after stirring and mixing was filtered through a polytetrafluoroethylene (PTFE) filter having a pore size of 1 μm to obtain ink 1 as an active layer coating solution.

(Preparation of photoelectric conversion element)
A glass substrate (manufactured by Geomat Co., Ltd.) on which an indium tin oxide (ITO) transparent conductive film (cathode) was patterned was subjected to ultrasonic cleaning with acetone, then ultrasonic cleaning with isopropyl alcohol, and then dried with nitrogen blowing.

  Next, the cleaned substrate was subjected to ultraviolet ozone treatment for 10 minutes using an ultraviolet ozone treatment apparatus (manufactured by Filgen). Thereafter, zinc acetate (II) dihydrate (manufactured by Wako Pure Chemical Industries, Ltd.) is mixed with 2-methoxyethanol (manufactured by Aldrich) and ethanolamine (manufactured by Aldrich) so that the concentration becomes 105 mg / mL. A solution (about 0.1 mL) dissolved in (volume ratio 100: 3) was spin-coated on a substrate at 3000 rpm, and heated in an oven at 200 ° C. for 10 minutes to form an electron extraction layer. The film thickness of the formed electron extraction layer was 30 nm.

  The substrate on which the electron extraction layer was formed was brought into a glove box, heat-treated at 150 ° C. for 3 minutes in a nitrogen atmosphere, and after cooling, spin-coated with ink 1 (0.2 mL) prepared as described above, A thick active layer was formed. Further, in the same glove box, heat treatment was performed at 140 ° C. for 10 minutes using a hot plate to complete the formation of the active layer.

  Next, a hole extraction layer was formed on the active layer as follows. First, in the atmosphere, PEDOT: PSS aqueous solution (AI4083, manufactured by Heraeus) was added to Olfin EXP. 2% by weight of 4200 (manufactured by Nissin Chemical Co., Ltd., containing 75% of an acetylene glycol compound) was added. The obtained liquid was further subjected to dispersion treatment by applying ultrasonic waves for 10 minutes, and filtered through a filter having a pore diameter of 0.45 μm to prepare a hole extraction layer coating liquid. This coating solution (500 μL) was spin-coated on the active layer at 5000 rpm for 15 seconds in the air, wiped the edge of the substrate, and transferred to a glove box in a nitrogen atmosphere. Next, heat treatment was performed for 10 minutes at a temperature of 140 ° C. using a hot plate in the glove box. It was confirmed by visual observation that the hole extraction layer was satisfactorily formed. The film thickness of the formed hole extraction layer was about 50 nm.

  Next, a silver film having a thickness of 100 nm was formed as an electrode (anode) layer by a resistance heating vacuum deposition method, and a 5 mm square photoelectric conversion element was produced.

(Evaluation of photoelectric conversion element)
The photoelectric conversion element produced in this way was evaluated as described above. The results are shown in Table 1.

<Comparative Example 1>
When preparing the hole extraction layer coating solution, Olfine EXP. Photoelectric conversion element in the same manner as in Example 1 except that 100 vol% isopropyl alcohol (IPA) was added to the PEDOT: PSS aqueous solution instead of adding 4200 (acetylene glycol surfactant). Were prepared and evaluated. The results are shown in Table 1. In Comparative Example 1, it was confirmed by visual observation that the hole extraction layer was satisfactorily formed.

<Comparative example 2>
When preparing the hole extraction layer coating solution, Olfine EXP. A photoelectric conversion element was produced and evaluated in the same manner as in Example 1 except that 4200 (acetylene glycol surfactant) was not added. The results are shown in Table 1. In Comparative Example 2, the contact angle of the hole extraction layer coating solution on the active layer was large and bounced, and it was confirmed by visual observation that almost no hole extraction layer was formed on the active layer. .

  As shown in Table 1, it was shown that the photoelectric conversion element obtained in Example 1 according to the present invention was superior in photoelectric conversion efficiency as compared with the photoelectric conversion element obtained in Comparative Example 1. . In Comparative Example 2, the hole extraction layer could not be formed on the active layer, and the obtained photoelectric conversion element was short-circuited. From this, it was shown that according to the manufacturing method of Example 1 according to the present invention, a hole extraction layer can be easily formed and a photoelectric conversion element free from defects can be obtained. As described above, it is shown that the method for manufacturing a photoelectric conversion element according to the present invention is a highly efficient method for manufacturing a photoelectric conversion element suitable for industrial use.

DESCRIPTION OF SYMBOLS 101 Cathode 102 Electron taking-out layer 103 Active layer 104 Hole taking-out layer 105 Anode 106 Base material 107 Photoelectric conversion element 1 Weather-resistant protective film 2 UV cut film 3, 9 Gas barrier film 4, 8 Getter material film 5, 7 Sealing material 6 Solar cell element 10 Back sheet 12 Base material 13 Solar cell module 14 Thin film solar cell

Claims (8)

A photoelectric conversion element having a structure in which a base material, a cathode, an active layer, a hole extraction layer, and an anode are arranged in this order,
The hole extraction layer contains a conductive polymer and an acetylene glycol compound, The photoelectric conversion element characterized by the above-mentioned. The photoelectric conversion element according to claim 1, wherein the acetylene glycol compound is represented by the following formula (I).

(In formula (I), R ^{1 to} R ⁴ each independently represents an alkyl group which may have a substituent, and m and n are integers such that the sum of m and n is 0 or more and 60 or less. .) The photoelectric conversion according to claim 1, wherein the active layer contains a copolymer including a repeating unit represented by the following formula (IIA) and a repeating unit represented by the formula (IIB). element.

(In the formula (IIA), A represents an atom selected from Group 16 elements of the periodic table, and R ⁵ represents a hydrocarbon group optionally having a hetero atom.)

(In Formula (IIB), Q represents an atom selected from Group 14 elements of the Periodic Table, and R ⁶ and R ⁷ are each independently a carbon atom that may have a hydrogen atom, a halogen atom, or a hetero atom. Represents a hydrogen group, and R ⁶ and R ⁷ may be bonded to each other to form a ring. The photoelectric conversion element according to claim 3, wherein the copolymer is a copolymer including a repeating unit represented by the following formula (III).

(In Formula (III), A represents an atom selected from Group 16 elements of the Periodic Table, R ⁵ represents a hydrocarbon group optionally having a hetero atom, and Q was selected from Group 14 Elements of the Periodic Table) R ⁶ and R ⁷ each independently represents a hydrogen atom, a halogen atom, or a hydrocarbon group optionally having a hetero atom, and R ⁶ and R ⁷ are bonded to each other to form a ring. (It may be formed.)   The photoelectric conversion element according to claim 1, wherein the photoelectric conversion element is a solar cell.   A solar cell module comprising the photoelectric conversion element according to claim 5. A method for producing a photoelectric conversion element having a structure in which a substrate, a cathode, an active layer, a hole extraction layer, and an anode are arranged in this order,
A method for producing a photoelectric conversion element comprising the step of forming the hole extraction layer by applying a coating liquid containing a conductive polymer and an acetylene glycol-based compound on the active layer .   The method for producing a photoelectric conversion element according to claim 7, wherein the coating solution contains 0.001 wt% or more and 10 wt% or less of the acetylene glycol-based compound.

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