JP2014027175A - Method for manufacturing photoelectric conversion element, photoelectric conversion element, solar cell, and solar cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a photoelectric conversion element using a practical method while achieving higher photoelectric conversion efficiency.SOLUTION: The method for manufacturing a photoelectric conversion element having at least a pair of electrodes, an active layer located between the electrodes, and an electron extraction layer located between the active layer and one of the electrodes includes a step of forming the electron extraction layer by a sputtering method. The active layer contains a copolymer containing a repeating unit represented by formula (IA) and a repeating unit represented by formula (IB).

Description

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

  As a next-generation solar cell, an organic thin-film solar cell using an organic compound as a semiconductor material has been actively developed. Organic thin-film solar cells usually have an active layer and a pair of electrodes that sandwich the active layer. Non-Patent Document 1 discloses an organic thin film solar cell including a bulk heterojunction type active layer containing a copolymer having an imidothiophene skeleton and a dithienosilole skeleton and a fullerene derivative (PCBM), and a zinc oxide (ZnO) layer as an electron extraction layer. Is described. In Non-Patent Document 1, the zinc oxide layer is formed by a sol-gel method.

In Non-Patent Document 2, a bulk heterojunction type active layer containing P3HT and PCBM which are conjugated polymer polymers is used as an active layer, and zinc oxide (ZnO) is doped with aluminum oxide (Al ₂ O ₃ ) as an electron extraction layer. Organic thin-film solar cells comprising a metal oxide layer (AZO) are described. The metal oxide layer (AZO) is formed by performing solution etching with a 0.1% hydrochloric acid solution after forming a film by a sputtering method. It is described that the surface roughness of AZO is increased by solution etching, and the photoelectric conversion efficiency is improved.

J. et al. Am. Chem. Soc. 133, 10062 (2011) App. Phys. Lett. 98,023102 (2011)

  In order to put the photoelectric conversion element into practical use, it is required to achieve higher photoelectric conversion efficiency.

  Further, as a result of the study by the inventors of the present application, the sol-gel method used in Non-Patent Document 1 requires a high temperature and a long process, and thus it is difficult to use as a practical large-area coating method such as a roll-to-roll method. I understood that.

  An object of the present invention is to provide a practical method for manufacturing a photoelectric conversion element while realizing higher photoelectric conversion efficiency.

As a result of intensive studies to solve the above problems, the present inventors have found that the object of the present invention can be achieved by forming the electron extraction layer by a specific method, and have completed the present invention.
That is, the gist of the present invention is as follows.

（式（ＩＡ）中、Ａは周期表第１６族元素から選ばれる原子を表し、Ｒ^１はヘテロ原子を有していてもよい炭化水素基を表す。）

（式（ＩＢ）中、Ｑは周期表第１４族元素から選ばれる原子を表し、Ｒ^２及びＲ^３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^２及びＲ^３は互いに結合して環を形成していてもよい。）
［２］前記電子取り出し層が酸化亜鉛又は酸化チタンを含有することを特徴とする、［１］に記載の光電変換素子の製造方法。
［３］前記コポリマーが下記式（ＩＩ）で表される繰り返し単位を含むことを特徴とする、［１］又は［２］に記載の光電変換素子の製造方法。

（式（ＩＩ）中、Ａは周期表第１６族元素から選ばれる原子を表し、Ｒ^１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^２及びＲ^３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^２及びＲ^３は互いに結合して環を形成していてもよい。）
［４］前記光電変換素子は、基材と、前記電極の一方であるカソードと、前記電子取り出し層と、前記活性層と、前記電極の他方であるアノードと、がこの順に配置された構造を有することを特徴とする、［１］から［３］のいずれかに記載の光電変換素子の製造方法。
［５］［１］から［４］のいずれかに記載の光電変換素子の製造方法により得られることを特徴とする、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。
［７］［６］に記載の太陽電池を備えることを特徴とする、太陽電池モジュール。 [1] A method for producing a photoelectric conversion element comprising at least a pair of electrodes, an active layer positioned between the electrodes, and an electron extraction layer positioned between the active layer and one of the electrodes,
Including a step of forming the electron extraction layer by a sputtering method,
The active layer contains a copolymer containing a repeating unit represented by the following formula (IA) and a repeating unit represented by the formula (IB).

(In formula (IA), A represents an atom selected from Group 16 elements of the periodic table, and R ¹ represents a hydrocarbon group optionally having a hetero atom.)

(In formula (IB), Q represents an atom selected from Group 14 elements of the periodic table, and R ² and R ³ each independently represents a carbon atom that may have a hydrogen atom, a halogen atom, or a hetero atom. Represents a hydrogen group, and R ² and R ³ may be bonded to each other to form a ring.
[2] The method for producing a photoelectric conversion element according to [1], wherein the electron extraction layer contains zinc oxide or titanium oxide.
[3] The method for producing a photoelectric conversion element according to [1] or [2], wherein the copolymer includes a repeating unit represented by the following formula (II).

(In the formula (II), A represents an atom selected from Group 16 elements of the periodic table, R ¹ represents a hydrocarbon group optionally having a hetero atom, and Q was selected from Group 14 elements of the periodic table. R ² and R ³ each independently represents a hydrogen atom, a halogen atom, or a hydrocarbon group optionally having a hetero atom, and R ² and R ³ are bonded to each other to form a ring. (It may be formed.)
[4] The photoelectric conversion element has a structure in which a base material, a cathode that is one of the electrodes, the electron extraction layer, the active layer, and an anode that is the other of the electrodes are arranged in this order. The method for producing a photoelectric conversion element according to any one of [1] to [3], comprising:
[5] A photoelectric conversion element obtained by the method for manufacturing a photoelectric conversion element according to any one of [1] to [4].
[6] A solar cell comprising the photoelectric conversion element according to [5].
[7] A solar cell module comprising the solar cell according to [6].

  According to the present invention, it is possible to manufacture a photoelectric conversion element by a practical method while realizing higher photoelectric conversion efficiency.

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.

（式（ＩＡ）中、Ａは周期表第１６族元素から選ばれる原子を表し、Ｒ^１はヘテロ原子を有していてもよい炭化水素基を表す。）

（式（ＩＢ）中、Ｑは周期表第１４族元素から選ばれる原子を表し、Ｒ^２及びＲ^３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^２及びＲ^３は互いに結合して環を形成していてもよい。） <1. Photoelectric conversion element>
Hereinafter, a method for manufacturing a photoelectric conversion element having at least a pair of electrodes, an active layer positioned between the electrodes, and an electron extraction layer positioned between the active layer and one of the electrodes will be described. This manufacturing method includes a step of forming an electron extraction layer by a sputtering method. The active layer contains a copolymer (hereinafter referred to as a copolymer according to the present invention) containing a repeating unit represented by the following formula (IA) and a repeating unit represented by the following formula (IB), which will be described later. .

(In formula (IA), A represents an atom selected from Group 16 elements of the periodic table, and R ¹ represents a hydrocarbon group optionally having a hetero atom.)

(In formula (IB), Q represents an atom selected from Group 14 elements of the periodic table, and R ² and R ³ each independently represents a carbon atom that may have a hydrogen atom, a halogen atom, or a hetero atom. Represents a hydrogen group, and R ² and R ³ may be bonded to each other to form a ring.

  A photoelectric conversion element 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 includes a pair of electrodes 101 and 105, an active layer 103 positioned between the electrodes 101 and 105, and a buffer layer (electron extraction layer) 102 positioned between the active layer 103 and the electrode 101. . Here, the electrode 101 is a cathode (an electrode for collecting electrons), and the electrode 105 is an anode (an electrode for collecting holes). Further, the photoelectric conversion element 107 may have a buffer layer (hole extraction layer) 104 between the active layer 103 and the anode 105.

  Further, the photoelectric conversion element 107 may have a base material 106. For example, the photoelectric conversion element 107 may have a structure in which a base material 106, a cathode 101, an electron extraction layer 102, an active layer 103, and an anode 105 are arranged in this order. Such a structure is preferable in that the hole extraction layer 104 and the anode 105, which are often unstable with respect to air, can be protected from air. However, the photoelectric conversion element 107 may have a structure in which the cathode 101, the electron extraction layer 102, the active layer 103, the anode 105, and the base material 106 are arranged in this order.

<1.1 Electron extraction layer (102)>
The photoelectric conversion element 107 includes an electron extraction layer 102 between the active layer 103 and the cathode 101. By providing the electron extraction layer 102, electrons can be easily transferred between the active layer 103 and the cathode 101, and a short circuit between the electrodes can be prevented. The electron extraction layer 102 is usually disposed so as to be in contact with the active layer 103 and the cathode 101. The electron extraction layer 102 may include a plurality of films having different material configurations or formed by different methods.

  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 electrode 101. Examples of the electron extraction layer material contained in the electron extraction layer 102 include an inorganic compound material and an organic compound material.

  Examples of inorganic compound materials that are preferably used in combination with the copolymer according to the present invention include alkali metal salts such as lithium, sodium, potassium, and cesium; or titanium oxide (TiOx), zinc oxide (ZnO), and oxide. Examples thereof include metal oxides having n-type semiconductor characteristics such as tin, aluminum oxide, silicon oxide, cerium oxide, lead oxide, zirconium oxide, or gallium oxide. 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 preferably zinc oxide, titanium oxide, or tin oxide. More preferable as the material of the inorganic compound is titanium oxide (TiOx) or zinc oxide (ZnO) from the viewpoint that the film formation stability is excellent and the production cost can be reduced. Particularly preferred is 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.

  Examples of the material of the organic compound that is preferably used in combination with the copolymer according to the present invention include, for example, a phosphine compound having a double bond between a phosphorus atom and a group 16 element such as a triarylphosphine oxide compound; bathocuproin A phenanthrene compound such as (BCP) or bathophenanthrene (Bphen), which may have a substituent and optionally substituted at the 1-position and the 10-position with a heteroatom; a boron compound such as triarylboron; Organic metal oxides such as 8-hydroxyquinolinato) aluminum (Alq3); compounds having one or two ring structures which may have a substituent such as oxadiazole compounds or benzimidazole compounds; naphthalene Tetracarboxylic anhydride (NTCDA) or perylene tetraca Such as carbon anhydride (PTCDA), aromatic compounds having a condensed dicarboxylic acid structure, such as dicarboxylic acid 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 material 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, there are a theoretically calculated method and a actually measured method. 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.

  The thickness of the electron extraction layer 102 is not particularly limited, but is usually 0.1 nm or more, preferably 0.5 nm or more, more preferably 1.0 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 0.1 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.

  The surface roughness of the electron extraction layer 102 is not particularly limited, but is usually 0.1 nm or more, preferably 0.2 nm or more, particularly preferably 0.5 nm or more. On the other hand, it is usually 50 nm or less, preferably 30 nm or less, particularly preferably 20 nm or less. When the surface roughness is in the above-described range, even when the active layer 103 is relatively thin, defects that cause a short circuit between the two electrodes hardly occur. As a result, the yield of the photoelectric conversion element or the solar cell module can be improved. In this specification, the surface roughness refers to the arithmetic average roughness Ra specified in JIS B 0601.

The surface resistivity of the electron extraction layer 102 is not particularly limited, but is usually 1.0 × 10 ⁻⁵ Ω · cm or more, preferably 5.0 × 10 ⁻⁵ Ω · cm or more, particularly preferably 1.0 × 10. ^-4 Ω · cm or more. On the other hand, it is usually 1.0 × 10 ⁻¹ Ω · cm or less, preferably 5.0 × 10 ⁻² Ω · cm or less, particularly preferably 1.0 × 10 ⁻² Ω · cm or less. When the surface resistivity is in the above-described range, it is possible to suppress the loss when taking out the charges generated in the photoelectric conversion element, and to obtain an effect that it is difficult to cause a short circuit between the two electrodes.

(Method for forming the electron extraction layer)
The electron extraction layer 102 is formed by a sputtering method. The use of the sputtering method makes it possible to produce a film having a stronger adhesion to the substrate compared to a coating film forming method, a vacuum evaporation method, etc., and to form a film with extremely high smoothness. The film speed can be precisely controlled, the film can be formed while maintaining the target composition ratio, the film can be formed even with a substance having a high melting point, and the gas composition in the sputtering atmosphere is controlled. Therefore, it is preferable in that a thin film of oxide, nitride or the like can be formed.

  When a photoelectric conversion element having a large area is manufactured, a short circuit between the electrodes becomes a problem. Therefore, it is preferable to manufacture a stacked structure so that the short circuit hardly occurs. For this purpose, it is required to control the thickness of each layer to be as uniform as possible. In particular, when the active layer 103 containing the copolymer according to the present invention is produced by a roll-to-roll coating process or the like, film thickness control in units of several nm to several tens of nm is required. This can be a limiting factor in the coating speed of each layer such as the active layer 103, the electron extraction layer 102, and the hole extraction layer 104.

  In particular, in the process of forming the electron extraction layer 102 prior to the active layer 103, it is relatively difficult to uniformly form the electron extraction layer having a film thickness of less than 100 nm by a coating method. For example, it is not easy to form a thinner and more uniform electron extraction layer by the sol-gel method used in Non-Patent Document 1.

  As another method for forming the electron extraction layer, there is a method of applying a nanoparticle dispersion, for example, a metal oxide nanoparticle dispersion. However, in this method, since the particle size distribution of the nanoparticles in the dispersion dominates the film thickness of the electron extraction layer, the surface roughness of the electron extraction layer cannot be controlled within a certain range, or the surface roughness becomes large. End up. If the surface roughness of the electron extraction layer cannot be controlled, there may be a problem that a short circuit between the electrodes tends to occur. For example, when an active layer is formed on an electron extraction layer, particularly when the active layer is applied and formed, if the surface roughness of the electron extraction layer cannot be controlled, there is a high possibility that unevenness will occur in the active layer. Defects are likely to occur in the element. Furthermore, since the commercially available nanoparticle dispersion is expensive, it causes a problem when a large-area film is produced.

  On the other hand, according to the sputtering method, the thin electron extraction layer 102 can be formed while the film thickness is uniform. From the viewpoint of promoting hole transport from the active layer 103 to the cathode 101, the electron extraction layer 102 is preferably thinner. On the other hand, as described above, the thinner the electron extraction layer 102, the easier the short circuit occurs. By using the sputtering method, the photoelectric conversion element 107 with higher conversion efficiency can be manufactured while suppressing a short circuit.

  When the electron extraction layer 102 is formed by sputtering, the interface between the electron extraction layer 102 and the active layer 103 becomes smoother, so that the contact area between the electron extraction layer 102 and the active layer 103 is reduced, and charge transport efficiency is reduced. Is considered to be reduced. For example, in Non-Patent Document 2, in order to increase the contact area, the surface roughness of the electron extraction layer is increased by hydrochloric acid etching. In order to perform such a process, it is considered that the electron extraction layer needs to have a certain thickness or more.

  On the other hand, when the active layer 103 contains the copolymer according to the present invention as a semiconductor material, it has been found that sufficient photoelectric conversion efficiency can be obtained without performing hydrochloric acid etching treatment. Thus, in the case where the active layer 103 contains the copolymer according to the present invention as a semiconductor material, it is possible to use the thinner electron extraction layer 102 obtained by the sputtering method, resulting in higher conversion efficiency and a short circuit. A difficult photoelectric conversion element 107 can be manufactured.

  As described above, when the photoelectric conversion element 107 having the active layer 103 containing the copolymer according to the present invention is manufactured, the photoelectric conversion efficiency can be increased by forming the electron extraction layer 102 by a sputtering method. .

  Moreover, when forming an electron taking-out layer using the sol-gel method used by the nonpatent literature 1, it heats normally for 10 minutes or more at the high temperature of 180 degreeC or more. Under such a high temperature condition, the constituent elements of the photoelectric conversion element 107 may be dissolved. For example, when a flexible substrate is used as the substrate 106, the Tg (glass transition temperature) of the flexible substrate is often equal to or lower than the processing temperature (180 ° C.), and the substrate is likely to be dissolved. For this reason, when producing the photoelectric conversion element using a flexible base material, it is thought that it is difficult to form an electron extraction layer using a sol-gel method.

  Moreover, when producing an electron taking-out layer by a sol-gel method, an organic solvent such as 2-methoxyethanol is often used. However, these solvents tend to be avoided especially in recent years due to reasons such as high environmental load when coating a large area film.

  When the electron extraction layer 102 is formed by a sputtering method, heating is not essential and a solvent is not required. Therefore, it is possible to solve these problems and to manufacture a large-area photoelectric conversion element.

  The sputtering conditions are not particularly limited, and for example, a DC sputtering method, an RF sputtering method, a magnetron sputtering method, an ECR sputtering method, a reactive sputtering method, or the like can be used. Among these, the RF sputtering method is preferable in that high electron extraction efficiency is easily obtained and the photoelectric conversion efficiency is easily improved.

  In particular, when a metal oxide is used as the electron extraction layer material, it is preferable to use a sputtering method. The reason for this is that when zinc oxide (ZnO) is taken as an example, zinc metal or zinc oxide is used as a target, and a zinc oxide film is produced in an oxygen gas atmosphere without polluting the interior of the container as compared with vapor deposition. The film can be mentioned. Another reason is that the kinetic energy of the sputtered particles is much larger than that in the case of thermal evaporation, so that a metal oxide polycrystalline film can be produced while maintaining the substrate at a low temperature.

  The temperature at the time of sputtering is not particularly limited, but is preferably −50 ° C. or higher, more preferably 0 ° C. or higher, and further preferably 10 ° C. or higher. On the other hand, it is preferably 150 ° C. or lower, more preferably 100 ° C. or lower, and further preferably 80 ° C. or lower. By performing sputtering in this temperature range, plasma generation during sputtering can be stably controlled, and the film formation rate and film formation components can be controlled to be more uniform.

  The pressure at the time of sputtering is not particularly limited, but is preferably 0.001 Pa or more, more preferably 0.01 Pa or more, and further preferably 0.1 Pa or more. On the other hand, it is preferably 10 Pa or less, more preferably 5 Pa or less, and even more preferably 1 Pa or less. By performing sputtering in this pressure range, it is possible to control the deposition rate and deposition components to be more uniform.

  The atmosphere at the time of sputtering is preferably an argon atmosphere or an oxygen atmosphere. Although depending on the target to be used, an argon atmosphere is more preferable when using a ZnO target. This is because the composition of the thin film to be formed can be directly controlled by the target component.

<1.2 Active layer (103)>
The active layer 103 refers to a layer in which photoelectric conversion is performed, and contains the copolymer according to the present invention. The active layer 103 usually includes 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. The copolymer according to the present invention is usually used as a p-type semiconductor compound. 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 electrodes 101 and 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.

[1.2.1 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. . The bulk heterojunction active layer includes a p-type semiconductor compound including a p-type semiconductor compound, an n-type semiconductor layer including an n-type semiconductor compound, in addition to a layer in which a p-type semiconductor compound and an n-type semiconductor compound are mixed. You may have at least one of these. In terms of photoelectric conversion efficiency, the active layer 103 is preferably a bulk heterojunction type.

(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 the copolymer according to the present invention. The p-type semiconductor layer may further contain a p-type semiconductor compound described later. There is no limitation on the film thickness of the p-type semiconductor layer. However, it is usually 5 nm or more, preferably 10 nm or more, and usually 500 nm or less, preferably 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. . The copolymer according to the present invention is preferable in that it has solubility in a solvent and is excellent in coating film formation.

  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.

  Of the p-type semiconductor compounds contained in the p-type semiconductor layer, usually 50% by weight or more, preferably 70% by weight or more, more preferably 90% by weight or more is the copolymer according to the present invention. Since the copolymer according to the present invention has properties suitable as a p-type semiconductor compound, it is particularly preferable that the p-type semiconductor layer contains only the copolymer according to the present invention as a p-type semiconductor compound.

(N-type semiconductor layer)
The n-type semiconductor layer is a layer containing an n-type semiconductor compound described later. Although 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.

  Of the p-type semiconductor compounds contained in the i layer, 50% by weight or more, preferably 70% by weight or more, more preferably 90% by weight or more is the copolymer according to the present invention. Since the copolymer according to the present invention has suitable properties as a p-type semiconductor compound, it is particularly preferable that the i layer contains only the copolymer according to the present invention as a p-type semiconductor compound.

  There is no restriction | limiting in the film thickness of i layer. However, it is usually 5 nm or more, preferably 10 nm or more, and usually 500 nm or less, preferably 200 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), but it is preferable to use the coating method because the i layer can be formed more easily. Since the copolymer according to the present invention has solubility in a solvent, it is preferable from the viewpoint of excellent coating film-forming properties. 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. It may be prepared by dissolving the compound and the n-type semiconductor compound. 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 the coating method, 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.

[1.2.2 p-type semiconductor compound]
The active layer 103 contains at least the copolymer according to the present invention as a p-type semiconductor compound.

  The copolymer according to the present invention includes a repeating unit represented by the following formula (IA) and a repeating unit represented by the formula (IB). The copolymer according to the present invention is preferable in that it has a good balance between solubility and crystallinity. The copolymer according to the present invention is preferable in that it absorbs light having a longer wavelength and has high light absorption.

（式（ＩＡ）中、Ａは周期表第１６族元素から選ばれる原子を表し、Ｒ^１はヘテロ原子を有していてもよい炭化水素基を表す。）

(In formula (IA), A represents an atom selected from Group 16 elements of the periodic table, and R ¹ represents a hydrocarbon group optionally having a hetero atom.)

（式（ＩＢ）中、Ｑは周期表第１４族元素から選ばれる原子を表し、Ｒ^２及びＲ^３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^２及びＲ^３は互いに結合して環を形成していてもよい。）

(In formula (IB), Q represents an atom selected from Group 14 elements of the periodic table, and R ² and R ³ each independently represents a carbon atom that may have a hydrogen atom, a halogen atom, or a hetero atom. Represents a hydrogen group, and R ² and R ³ may be bonded to each other to form a ring.

  First, the repeating unit represented by the formula (IA) 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 ¹ represents a hydrocarbon group which may have a hetero atom. Specific examples of R ¹ include an optionally substituted alkyl group, an optionally substituted alkenyl group, or an optionally substituted aromatic group (aryl group). Is mentioned.

  The alkyl group has usually 1 or more, preferably 3 or more, more preferably 4 or more, 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 that R ¹ is these groups because the copolymer according to the present invention tends to have excellent solubility in an organic solvent and can be advantageous in a coating film forming process. More preferably, R ¹ 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 ¹ is an aromatic group which may have a substituent. This indicates 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.

  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.

  Next, the repeating unit represented by the formula (IB) 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 ² and R ³ each independently represent a hydrogen atom, a halogen atom, or a hydrocarbon group that may have 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. Specific examples of the alkyl group, alkenyl group, and aromatic group include the same groups as those described for R ¹ . In addition, the substituent that the alkyl group, alkenyl group, and aromatic group may have may be the same as those described for R ¹ . R ² and R ³ may be bonded to each other to form a ring.

Of these, at least one of R ² and R ³ is preferably an alkyl group or an aromatic group which may have a substituent, and both R ² and R ³ 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 ² and R ³ is an alkyl group from the viewpoint that the copolymer according to the present invention can absorb light having a longer wavelength. From these viewpoints, at least one of R ² and R ³ 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 (IB).

From the viewpoint of improving the durability of the copolymer according to the present invention by increasing the steric hindrance around Q, which is an atom selected from Group 14 elements, R ² and R ^{3 each} have a substituent. It is preferably an 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 ² and R ³ 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 according to the present invention are improved.

  The ratio of the repeating unit represented by the formula (IA) in the copolymer according to the present invention is not particularly limited, but is usually 1 mol% or more, preferably 5 mol% or more, more preferably 15 mol% or more, Preferably it is 30 mol% or more. 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 (IB) in the copolymer according to the present invention is not particularly limited, but is usually 1 mol% or more, preferably 5 mol% or more, more preferably 15 mol% or more, Preferably it is 30 mol% or more. 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 (IB) to the repeating unit represented by the formula (IA) in the copolymer according to the present invention is not particularly limited, but is usually 0.01 or more, preferably 0.1 Above, more preferably 0.5 or more. On the other hand, it is usually 100 or less, preferably 10 or less, more preferably 2 or less.

  The arrangement state of the repeating units (IA) and (IB) in the copolymer according to the present invention may be alternating, block or random. That is, the copolymer according to the present invention may be any of an alternating copolymer, a block copolymer, and a random copolymer. Preferably, they are arranged alternately.

（式（ＩＩ）中、Ａは周期表第１６族元素から選ばれる原子を表し、Ｒ^１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^２及びＲ^３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^２及びＲ^３は互いに結合して環を形成していてもよい。） In particular, the copolymer according to the present invention is preferably a copolymer containing a repeating unit represented by the following formula (II). By including a repeating unit represented by the following formula (II), the charge separation state can be more easily maintained.

(In the formula (II), A represents an atom selected from Group 16 elements of the periodic table, R ¹ represents a hydrocarbon group optionally having a hetero atom, and Q was selected from Group 14 elements of the periodic table. R ² and R ³ each independently represents a hydrogen atom, a halogen atom, or a hydrocarbon group optionally having a hetero atom, and R ² and R ³ are bonded to each other to form a ring. (It may be formed.)

Specific examples of A, Q, and R ^{1 to} R ³ in formula (II) include the same as those described for formulas (IA) and (IB). From the viewpoints of solubility and light absorption, it is more preferable that Q is a silicon atom and A is a sulfur atom.

  In a preferred example in which the copolymer according to the present invention includes a repeating unit represented by the formula (II), the ratio of the repeating unit represented by the formula (II) in the copolymer according to the present invention is not particularly limited. Usually, it is 10 mol% or more, preferably 25 mol% or more, more preferably 50 mol% or more, and further preferably 70 mol% or more. There is no upper limit in particular and it is 100 mol% or less.

  Moreover, the copolymer which concerns on this invention may contain the other repeating unit in the range which does not impair the effect of this invention. Examples of other repeating units include aromatic heterocyclic rings such as thiophenediyl group and thiazolediyl group.

  The copolymer according to the present invention may contain only one type of each of the repeating units represented by the formulas (IA) and (IB). Moreover, 2 or more types of repeating units represented by Formula (IA) may be included, and 2 or more types of repeating units represented by Formula (IB) may be included. Although there is no restriction | limiting in the kind of repeating unit which the copolymer based on this invention contains, Usually, it is 8 or less, Preferably it is 5 or less. Similarly, the copolymer which concerns on this invention may contain only 1 type among the repeating units represented by Formula (II), and may contain 2 or more types.

Preferred specific examples of the copolymer according to the present invention are shown below. However, the copolymer according to the present invention is not limited to the following examples. In the following specific examples, C ₄ H ₉ , C ₈ H ₁₇ , and C ₁₂ H ₂₅ 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 according to the present invention includes a plurality of repeating units, the ratio of the number of each repeating unit is arbitrary.

  The copolymer according to the present invention has absorption in a long wavelength region (600 nm or more). Moreover, the photoelectric conversion element using the copolymer which concerns on this invention shows a high open circuit voltage (Voc), and shows a high photoelectric conversion characteristic. The copolymer according to the present invention exhibits high photoelectric conversion characteristics particularly when combined with a fullerene compound. Further, the copolymer according to the present invention has an advantage that it has a low HOMO energy level and is hardly oxidized.

  Further, since the copolymer according to the present invention 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 according to the present invention exhibits high photoelectric conversion characteristics.

The polystyrene-equivalent weight average molecular weight (Mw) of the copolymer according to the present invention is usually 2.0 × 10 ³ or more, preferably 5.0 × 10 ³ or more, more preferably 1.0 × 10 ⁴ or more, and still more preferably. It is 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 weight average molecular weight in terms of polystyrene of the copolymer according to the present invention 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 according to the present invention 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 or more, more preferably 1.5 × 10 ⁴ or more, even 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 according to the present invention 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 according to the present invention is usually 1.0 or more, preferably 1.1 or more, more preferably 1.2 or more, Preferably it is 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 according to the present invention can be measured by the same method as the weight average molecular weight.

The copolymer according to the present invention 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 according to the present invention is closer to the absorption wavelength region of sunlight.

  The solubility of the copolymer according to the present invention 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. On the other hand, it is usually 30% by weight or less, preferably 20% by weight. High solubility is preferable in that a thicker active layer can be formed.

  The copolymer according to the present invention preferably 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 according to the present invention and the n-type semiconductor compound in the active layer 103 are efficiently used. It is thought that it can be transported to the anode 105 well.

  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 according to the present invention 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 according to the present invention is usually 1.0 × 10 ⁴ cm ² / Vs or less, preferably 1.0 × 10 ³ cm ² / Vs or less, more preferably 1.0. × 10 ² cm ² / Vs or less. In order to obtain high conversion efficiency, it is important to balance the mobility of the n-type semiconductor compound and the mobility of the copolymer according to the present invention. From the viewpoint of bringing the mobility of the copolymer according to the present invention used as the p-type semiconductor compound closer to the mobility of the n-type semiconductor compound, the hole mobility of the copolymer according to the present invention 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).

  The impurities in the copolymer according to the present invention are preferably as few 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 according to the present invention 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 (IIIA) and formula (IIIB) described later) in the copolymer according to the present invention is not particularly limited, but is usually 6000 ppm or less, preferably 4000 ppm or less, More preferably, it is 3000 ppm or less, More preferably, it is 2000 ppm or less, More preferably, it is 1000 ppm or less, Especially preferably, it is 500 ppm or less, Most preferably, it is 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 according to the present invention 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, it is 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.

  Further, the residual amount of halogen atoms in the copolymer according to the present invention is usually 5000 ppm or less, preferably 4000 ppm or less, more preferably 2500 ppm or less, further preferably 1000 ppm or less, still more preferably 750 ppm or less, particularly preferably 500 ppm or less, Most preferably, it is 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).

(Method for producing copolymer according to the present invention)
There is no limitation in particular in the manufacturing method of the copolymer based on this invention. For example, it can be produced by a known method using a compound represented by the following general formula (IIIA) and a compound represented by the following general formula (IIIB). Preferable methods include a method of polymerizing a compound represented by the following general formula (IIIA) and a compound represented by the following general formula (IIIB) in the presence of an appropriate catalyst if necessary. .

In formula (IIIA), A and R ¹ are the same as defined in formula (IA). In formula (IIA), Q, R ² and R ³ are the same as defined in formula (IB).

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 (IIIA) or (IIIB) 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 formula, 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 formula, 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.

Reaction methods used for polymerization of the copolymer according to the present invention include Suzuki-Miyaura cross-coupling reaction method, Stille coupling reaction method, Yamamoto coupling reaction method, Grignard reaction method, Heck reaction method, Sonogashira reaction method, FeCl ₃ A reaction method using an oxidizing agent such as an electrochemical oxidation method, 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 general formulas (IIIA) and (IIIB), 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 (IIIB / IIIA) of the compound represented by the formula (IIIB) to the compound represented by the formula (IIIA) 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.

  By increasing the purity of the copolymer according to the present invention, the conversion characteristics of the photoelectric conversion element can be improved. It is preferable to carry out the polymerization reaction after purification by a method such as column chromatography or 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 Formula (IIIA), and the compound represented by Formula (IIIB), 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 within this range in that the copolymer according to the present invention having a higher molecular weight 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 amount of the cocatalyst used 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 the copolymer according to the present invention 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 (IIIA). 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 is within this range because the copolymer according to the present invention tends to be obtained at a lower cost and with 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, isopropanol, butanol or t-butyl alcohol; water; ethers such as dimethyl ether, diethyl ether, methyl t-butyl ether, tetrahydrofuran, tetrahydropyran or dioxane; N , N-dimethylformamide (DMF) and the like aprotic organic solvents. 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 (IIIA) and the compound represented by the formula (IIIB). × 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 (IIIA) used as a raw material for the polymerization reaction is not particularly limited. Am. Chem. Soc. 2010, 132 (22), 7595-7597. Further, the production method of the compound represented by the formula (IIIB) 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 active layer 103 contains at least the copolymer according to the present invention. However, other organic semiconductor materials can also be used as a p-type semiconductor compound by mixing and / or laminating with the copolymer according to the present invention. Hereinafter, organic semiconductor materials that can be used in combination, for example, 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 in combination 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 And a copolymer semiconductor compound such as oligothiophene substituted with a 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 in combination as the p-type semiconductor compound may be a single compound or a mixture of a plurality of types of compounds.

  Specific examples of the polymer organic semiconductor compound that can be used in combination 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 in combination 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 Including 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 four or more linked A macrocyclic compound such as a phthalocyanine compound and a metal complex thereof, or a porphyrin compound such as tetrabenzoporphyrin and a metal complex 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.

  As the p-type semiconductor compound that can be used in combination with the copolymer according to the present invention, the high-molecular organic semiconductor compound is preferably a conjugated copolymer semiconductor compound such as polythiophene, and the low-molecular organic semiconductor compound may be naphthacene, pentacene, or pyrene. Condensed aromatic hydrocarbons such as phthalocyanine compounds and metal complexes thereof, or porphyrin compounds such as tetrabenzoporphyrin (BP) and metal complexes 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.

[1.2.3 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 increases Voc. Tend. On the other hand, 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 may have, an amino group which may be substituted with a fluorine atom, a chlorine atom, a hydroxyl group, a cyano group, a silyl group, a boryl group or an alkyl group, 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, 1 or less carbon atoms 1 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 shown to the general formula (n5) which is a bicyclo structure which the aromatic ring 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)
There are no particular restrictions on the n-type polymer semiconductor compound, but condensed ring tetracarboxylic acid diimides such as naphthalenetetracarboxylic acid diimide and perylenetetracarboxylic 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. These compounds are preferable in that they can absorb light in the visible range, can contribute to power generation, have high viscosity, and are excellent in coatability.

<1.3 Electrodes (101, 105)>
The electrodes 101 and 105 have a function of collecting holes and electrons generated by light absorption, and a pair of electrodes are an electrode (cathode) 101 for collecting electrons and an electrode (anode) 105 for collecting holes. And classified. Any one of the pair of electrodes 101 and 105 may be translucent, and both may be translucent. Translucency means that sunlight passes through 40% or more. Moreover, it is preferable that the sunlight transmittance of the transparent electrode is 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. Similarly to the anode 105, the cathode 101 can be made of a material having a large work function suitable for the anode 105 by using an n-type semiconductor such as titania having conductivity as the electron extraction layer 104. From the viewpoint of electrode protection, the material of the cathode 101 is preferably a metal such as platinum, gold, silver, copper, iron, tin, aluminum, calcium or indium, or these metals such as ITO (indium tin oxide). Alloy.

  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 that it is suitable for cathodes such as aluminum or 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.

  The film thickness of the anode 105 is not particularly limited, but is usually 10 nm or more, preferably 20 nm or more, and 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 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.

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

<1.4 Hole Extraction Layer (104)>
The photoelectric conversion element 107 may have a hole extraction layer 104 between the active layer 103 and the anode 105. By providing the hole extraction layer 102, holes can be easily transferred between the active layer 103 and the anode 105, and a short circuit between the electrodes can be prevented. The hole extraction layer 104 is usually disposed so as to be in contact with the active layer 103 and the anode 105. The hole extraction layer 104 may be configured by a plurality of films having different material configurations or formed by different methods.

  The material of the hole extraction layer 104 is not particularly limited as long as it is a material capable of improving the efficiency of extracting holes from the active layer 103 to the anode 105. Specifically, conductive polymers in which polythiophene, polypyrrole, polyacetylene, triphenylenediamine, polyaniline or the like is doped with sulfonic acid and / or iodine, polythiophene derivatives having a sulfonyl group as a substituent, conductive organic materials such as arylamine Examples include compounds, metal oxides such as molybdenum trioxide, and the above-described p-type semiconductor compounds. Among them, a conductive polymer doped with sulfonic acid is preferable, and poly (3,4-ethylenedioxythiophene) poly (styrenesulfonic acid) (PEDOT: PSS) in which a polythiophene derivative is doped with polystyrene sulfonic acid is more preferable. . Another preferred example is a metal oxide having semiconductor characteristics such as molybdenum trioxide. A thin film of metal such as gold, indium, silver or palladium can also be used. A thin film of metal or the like may be formed alone or in combination with the above organic material.

  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 film thickness of the hole extraction layer 104 is 0.2 nm or more, it functions as a buffer material, and when the film thickness of the hole extraction layer 104 is 400 nm or less, holes are easily extracted. The photoelectric conversion efficiency can be improved.

  There is no limitation on the formation method of the hole extraction layer 104. 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 as the material of the hole extraction layer 104, the precursor may be converted into a semiconductor compound after forming a layer containing the semiconductor compound precursor, as in the active layer 103.

<1.5 Substrate (106)>
The photoelectric conversion element 107 has a base material 106 that usually serves as a support. That is, the electrodes 101 and 105, the electron extraction layer 102, and the active layer 103 are formed on the substrate. But the photoelectric conversion element which concerns on this invention does not need to have the base material 106. FIG.

  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.

  An organic material is preferably used as the material of the substrate 106 in that a lightweight and flexible photoelectric conversion element 107 can be obtained. Although the organic material may be melted under high temperature conditions, it is not essential to perform heating when the electron extraction layer 102 is formed by a sputtering method. It is prevented from melting.

  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.

<1.6 Manufacturing Method of Photoelectric Conversion Element>
The photoelectric conversion element 107 is manufactured by a manufacturing method including a step of forming the electron extraction layer 102 by a sputtering method. Specifically, 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 above-described method. it can. A photoelectric conversion element having a different structure, for example, a photoelectric conversion element that does not include at least one of the base 106 and the hole extraction layer 104 can be manufactured by a similar method.

  After laminating the cathode 101 and the anode 105, it is preferable to heat the photoelectric conversion element usually at 50 ° C. or higher, preferably 80 ° C. or higher (this step is referred to as an annealing treatment step). Performing the annealing process at a temperature of 50 ° C. or higher improves the adhesion between the layers of the photoelectric conversion element, for example, the adhesion between the electron extraction layer 102 and the cathode 101 and / or the electron extraction layer 102 and the active layer 103. Is preferable. 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. 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.

<1.7 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 an irradiation intensity of 100 mW / cm ^{2 using 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.

<2. 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 the field to which the thin-film solar cell according to the present invention is applied include building material solar cells, automobile solar cells, interior solar cells, railway 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 substrate 12 can be prepared and used at a place of use. A well-known thing can be used as the base material 12, Specifically, the thing as described in well-known literatures, such as international publication 2011/016430, can be employ | 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 were mixed so that the weight ratio was 1: 2, and the mixture was 2 wt. % In a nitrogen atmosphere and dissolved in a mixed solvent of orthoxylene and tetralin (volume ratio 4: 1). 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 1)
A glass substrate (manufactured by Geomatic Co., Ltd.) on which an indium tin oxide (ITO) transparent conductive film (cathode) was patterned was subjected to ultrasonic cleaning with acetone, followed by ultrasonic cleaning with isopropanol, and then dried with nitrogen blowing.

  Next, on a glass substrate after cleaning, an electron is formed by RF sputtering using a zinc oxide (ZnO) target (manufactured by Kojundo Chemical Laboratory Co., Ltd., 99.99%) in an argon atmosphere (argon flow rate 20 sccm). A zinc oxide film (thickness 20 nm) was formed as the extraction layer.

  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.

Further, a molybdenum trioxide (MoO ₃ ) film having a thickness of 1.5 nm as a hole extraction layer and a silver film having a thickness of 100 nm as an electrode (anode) layer are sequentially formed on the active layer by resistance heating vacuum deposition. Film formation was performed to produce a 5 mm square photoelectric conversion element.

(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 the electron extraction layer was formed, a photoelectric conversion element was produced and evaluated in the same manner as in Example 1 except that a zinc oxide film was formed using a sol-gel method instead of a sputtering method. The results are shown in Table 1.

  Specifically, in Comparative Example 1, the glass substrate after washing was subjected to ultraviolet ozone treatment for 10 minutes using an ultraviolet ozone treatment apparatus (manufactured by Filgen), and zinc acetate (II) dihydrate (Wako Pure Chemical Industries, Ltd.) was obtained. Solution (about 0.1 mL) dissolved in a mixed solvent (volume ratio 100: 3) of 2-methoxyethanol (Aldrich) and ethanolamine (Aldrich) to a concentration of 105 mg / mL Was spin-coated on a substrate at 3000 rpm and heated in an oven at 200 ° C. for 40 minutes to form an electron extraction layer. The film thickness of the formed electron extraction layer was 30 nm. Furthermore, in order to remove moisture in the glove box, the glass substrate after the heat treatment was returned to the glove box and subjected to additional heat at 150 ° C. for 3 minutes.

  As shown in Table 1, in Example 1 according to the present invention, an electron extraction layer can be formed at a lower film formation temperature than in Comparative Example 1, and the photoelectric conversion efficiency of the produced photoelectric conversion element is improved. ing. As described above, according to the present invention, by using a sputtering method that can be used to fabricate a large-area photoelectric conversion element, higher photoelectric conversion efficiency can be realized without using the high temperature conditions used in the sol-gel method. The photoelectric conversion element to be manufactured can be manufactured.

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 (7)

A method for producing a photoelectric conversion element comprising at least a pair of electrodes, an active layer positioned between the electrodes, and an electron extraction layer positioned between the active layer and one of the electrodes,
Including a step of forming the electron extraction layer by a sputtering method,
The active layer contains a copolymer containing a repeating unit represented by the following formula (IA) and a repeating unit represented by the formula (IB).

(In formula (IA), A represents an atom selected from Group 16 elements of the periodic table, and R ¹ represents a hydrocarbon group optionally having a hetero atom.)

(In formula (IB), Q represents an atom selected from Group 14 elements of the periodic table, and R ² and R ³ each independently represents a carbon atom that may have a hydrogen atom, a halogen atom, or a hetero atom. Represents a hydrogen group, and R ² and R ³ may be bonded to each other to form a ring.   The method for producing a photoelectric conversion element according to claim 1, wherein the electron extraction layer contains zinc oxide or titanium oxide. The method for producing a photoelectric conversion element according to claim 1, wherein the copolymer includes a repeating unit represented by the following formula (II).

(In the formula (II), A represents an atom selected from Group 16 elements of the periodic table, R ¹ represents a hydrocarbon group optionally having a hetero atom, and Q was selected from Group 14 elements of the periodic table. R ² and R ³ each independently represents a hydrogen atom, a halogen atom, or a hydrocarbon group optionally having a hetero atom, and R ² and R ³ are bonded to each other to form a ring. (It may be formed.)   The photoelectric conversion element has a structure in which a base material, a cathode that is one of the electrodes, the electron extraction layer, the active layer, and an anode that is the other of the electrodes are arranged in this order. The method for producing a photoelectric conversion element according to any one of claims 1 to 3, wherein the method is characterized in that:   A photoelectric conversion element obtained by the method for manufacturing a photoelectric conversion element according to any one of claims 1 to 4.   A solar cell comprising the photoelectric conversion element according to claim 5.   A solar cell module comprising the solar cell according to claim 6.

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