JP2014189666A - Composition for forming semiconductor layer and solar cell element using the composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composition for forming a semiconductor layer which is for improving the productivity of a solar cell by increasing the film strength of a buffer layer on an active layer.SOLUTION: A composition for forming a semiconductor layer comprises a fullerene compound, a p-type semiconductor compound, and a solvent. A weight ratio of the p-type semiconductor compound to the fullerene compound is 2.1 or more and 11 or less.

Description

  The present invention relates to a composition for forming a semiconductor layer and a solar cell element using the same.

  Various methods for forming an active layer containing a p-type semiconductor compound and an n-type semiconductor compound have been studied in order to improve the performance of the photoelectric conversion element. For example, Patent Document 1 describes that an active layer is formed by mixing a p-type semiconductor compound and an n-type semiconductor compound in a weight ratio of 0.1 to 4.0: 1. Patent Document 2 describes an example in which poly-3-hexylthiophene, which is a p-type semiconductor compound, and fullerene derivative, which is an n-type semiconductor compound, are mixed at this weight ratio to form an active layer.

Special table 2013-504210 gazette JP 2009-084264 A

  In an organic thin film solar cell, it is considered to provide a buffer layer between an active layer and an upper electrode layer. However, according to studies by the present inventors, an upper buffer layer is applied on an active layer in which a p-type semiconductor compound and an n-type semiconductor compound are mixed at a weight ratio as described in Patent Document 1 or Patent Document 2. It has been found that when the film is formed, peeling of the upper buffer layer may occur at the manufacturing stage of the organic thin film solar cell. Specifically, when each layer of the solar cell is formed by the roll-to-roll method, the upper buffer layer and the roll are in contact with each other when forming the upper buffer layer or the upper electrode layer. As a result, the upper buffer layer is peeled off, resulting in a problem that productivity is lowered. The subject of this invention is providing the composition for semiconductor layer formation which raises the film | membrane intensity | strength of the upper buffer layer on an active layer, and improves the productivity of a solar cell.

The inventors of the present invention have made extensive studies and focused on a composition for forming a semiconductor layer for forming an active layer of an organic thin film solar cell (hereinafter sometimes simply referred to as a solar cell element or an element). The film strength of the upper buffer layer formed on the active layer can be increased by adjusting the p-type semiconductor compound and the fullerene compound, which is an n-type semiconductor compound, contained in the composition for forming a semiconductor layer to a specific weight ratio. The present invention was completed by discovering what can be done. That is, the gist of the present invention is as follows.
[1] A composition for forming a semiconductor comprising a fullerene compound, a p-type semiconductor compound, and a solvent, wherein the weight ratio of the fullerene compound to the p-type semiconductor compound is 2.1 or more and 11 or less. Composition.
[2] The composition for forming a semiconductor layer according to [1], wherein a HOMO energy level of the p-type semiconductor compound is −5.7 eV or more and −4.9 eV or less.
[3] The p-type semiconductor compound is a copolymer having a repeating unit represented by the following formula (IIIA) and a repeating unit represented by the following formula (IIIB) [1] or [2] The composition for forming a semiconductor layer as described in 1.

(In formula (IIIA), A represents an atom selected from Group 16 elements of the periodic table, and R ³ represents a hydrocarbon group optionally having a hetero atom.)

(In formula (IIIB), Q represents an atom selected from Group 14 elements of the periodic table, and R ⁴ and R ⁵ each independently represents a hydrocarbon group optionally having a hetero atom.)
[4] A step of forming an active layer using the composition for forming a semiconductor layer according to any one of [1] to [3], and a step of forming an upper buffer layer on the active layer by a coating method. The manufacturing method of the photovoltaic cell containing this.

  The present invention can provide a composition for forming a semiconductor layer that improves the film strength of the upper buffer layer.

It is sectional drawing of the solar cell element which concerns on embodiment of this invention. It is sectional drawing of the organic thin-film solar cell which concerns on embodiment of this invention. It is sectional drawing of the organic thin-film solar cell module which concerns on embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following description, and it is easily understood by those skilled in the art that modes and details can be variously changed without departing from the spirit and scope of the present invention. Note that in the structures of the present invention described below, the same portions or portions having similar functions are denoted by the same reference numerals in different drawings, and description thereof is not repeated.

<1. Composition for forming semiconductor layer>
The composition for forming a semiconductor layer according to the present invention includes a fullerene compound, a p-type semiconductor compound, and a solvent.

<1-1. Fullerene Compound>
The composition for forming a semiconductor layer according to the present invention includes a fullerene compound as an n-type semiconductor compound. In addition, there is no special restriction | limiting in the fullerene compound which can be used for this invention, 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 ) —C—C—C (R) with respect to two adjacent carbon atoms on the same 5-membered ring or 6-membered ring in the fullerene skeleton. ³² ) (R ³³ ) — are 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 group having 6 to 20 carbon atoms or an aromatic heterocyclic group having 2 to 20 carbon atoms, preferably A phenyl group, a naphthyl group, a biphenyl group, a thienyl group, a furyl group, a pyridyl group, a pyrimidyl group, a quinolyl group or a quinoxalyl group, more preferably a phenyl group, a thienyl group or a furyl group.

  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 represented by general formula (n5) which is a bicyclo structure which the aromatic group condensed is mentioned, for example.

F In the general formula (n5) has the same meaning as c, Z ² is two hydrogen atoms, an oxygen atom, a sulfur atom, an amino group, an alkylene group or an arylene group. The alkylene group preferably has 1 to 2 carbon atoms. The arylene group preferably has 5 to 12 carbon atoms, and examples thereof include a phenylene group. The amino group may be substituted with an alkyl group having 1 to 6 carbon atoms such as a methyl group or an ethyl group. The alkylene group is an alkoxy group having 1 to 6 carbon atoms such as a methoxy group, an aliphatic hydrocarbon group having 1 to 5 carbon atoms, an aromatic hydrocarbon group having 6 to 20 carbon atoms, or 2 to 20 carbon atoms. The aromatic heterocyclic group may be substituted. The arylene group is an alkoxy group having 1 to 6 carbon atoms such as a methoxy group, an aliphatic hydrocarbon group having 1 to 5 carbon atoms, an aromatic hydrocarbon group having 6 to 20 carbon atoms, or 2 to 20 carbon atoms. The aromatic heterocyclic group may be substituted.
The structure represented by the formula (n5) is particularly preferably a structure represented by the following formula (n6) or formula (n7).

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

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

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

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

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

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

  Note that when a preferable range of the solubility of the fullerene compound is given, 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. 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.

(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.

The LUMO energy level of the fullerene compound is not particularly limited, but for example, the value for the vacuum level calculated by a cyclic voltammogram measurement method is usually −3.85 eV or more, preferably −3.80 eV or more. In order to efficiently transfer electrons from the p-type semiconductor compound to the fullerene compound, the relative relationship of the LUMO energy levels of the p-type semiconductor compound and the fullerene compound is important. Specifically, the LUMO energy level of the p-type semiconductor compound is above the LUMO energy level of the fullerene compound by a predetermined value, in other words, the electron affinity of the fullerene compound is higher than the electron affinity of the p-type semiconductor compound. It is preferable that the energy is larger by a predetermined energy. 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 fullerene compound, increasing the LUMO energy level of the fullerene compound tends to increase the Voc. 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 fullerene compound, electrons tend to move and the short circuit current (Jsc) tends to increase.

  The HOMO energy level of the fullerene 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 fullerene compound is −7.0 eV or more from the viewpoint that light absorption of the fullerene 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 fullerene 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, and 5.0 × 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. It is preferable that the electron mobility of the fullerene compound is 1.0 × 10 ⁻⁶ cm ² / Vs or more from the viewpoint that effects such as improvement of the electron diffusion rate of the photoelectric conversion element, improvement of the short circuit current, and improvement of the conversion efficiency can be obtained. . 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).

<1-2. p-type semiconductor compound>
Although there is no special restriction | limiting in the p-type semiconductor compound contained in the composition which concerns on this invention, A high molecular p-type semiconductor compound is mentioned. Specifically, a semiconductor polymer obtained by copolymerizing two or more types of monomer units, for example, a polythiophene-thienothiophene copolymer described in Nature Materials, 2006, 5,328, and a polythiophene described in International Publication No. 2008/000664. A diketopyrrolopyrrole copolymer, Adv. Mater. , 2007, 4160, polythiophene copolymer such as PCPDTBT described in Nature Materials, 2007, 6,497, and imidothiophene described in International Publication No. 2011/028827. And a copolymer of thienothiophene and benzodithiophene described in International Publication No. 2011/011545. In addition, derivatives of these polymers and polymers that can be synthesized by combinations of the monomers listed here can also be used. The substituents of these polymers and monomers can be appropriately selected in order to control solubility, crystallinity, film formability, HOMO energy level, LUMO energy level, and the like.

The HOMO energy level of the above-mentioned p-type semiconductor compound is not particularly limited, but is usually −5.7 eV or more, more preferably −5.5 eV or more, on the other hand, −4.9 eV or less is preferable, and −4.8 eV or less. Is particularly preferred. 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 is −4.9 eV or less, the stability of the compound is improved. The open circuit voltage (Voc) is also improved. Further, the LUMO energy level of the p-type semiconductor compound is not particularly limited, but the LUMO energy level of the p-type semiconductor compound combined with the fullerene compound is usually −3.7 eV or more, preferably −3.6 eV or more. is there. 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 compound 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. On the other hand, when the LUMO energy level of the p-type semiconductor compound is −3.7 eV or more, electron transfer to the n-type semiconductor is likely to occur, and the short-circuit current density is improved. In the present invention, the HOMO energy level and the LUMO energy level of the p-type semiconductor compound mean values with respect to the vacuum order calculated by the cyclic voltammogram measurement method. Specifically, for example, it can be measured by a method described in a known document (International Publication No. 2011/016430).

  The p-type semiconductor compound is more preferably a copolymer A containing a repeating unit represented by the following formula (IIIA) and a repeating unit represented by the formula (IIIB). This copolymer A is preferable in that it has a good balance between solubility and crystallinity. Moreover, it is preferable at the point which absorbs light of a longer wavelength and has high light absorptivity.

(In formula (IIIA), A represents an atom selected from Group 16 elements of the periodic table, and R ³ represents a hydrocarbon group optionally having a hetero atom.)

(In formula (IIIB), Q represents an atom selected from Group 14 elements of the periodic table, and R ⁴ and R ⁵ each independently represents a hydrocarbon group optionally having a hetero atom.)

First, the repeating unit represented by the formula (IIIA) will be described. R ³ represents a hydrocarbon group which may have a hetero atom. Specific examples of R ³ include an alkyl group that may have a substituent, an alkenyl group that may have a substituent, or an aromatic group that may have a substituent.

The carbon number of the alkyl group is 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 or Examples include 1- (2-ethyl) hexyl-3-ethylheptyl group. 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 carbon number of the alkenyl group is usually 2 or more, preferably 3 or more, more preferably 4 or more, and is 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 vinyl, 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 carbon number of the aromatic group is usually 2 or more, and is 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. Group, thiazolyl group, oxazolyl group, triazolyl group, benzothiophenyl group, benzofuranyl group, benzothienyl group, benzothiazolyl group, benzooxazolyl group, or aromatic heterocyclic group such as benzotriazolyl group; . Of these, a phenyl group, a naphthyl group, a thienyl group, a pyridyl group, a pyrimidyl group, a thiazolyl group, or an oxazolyl group is preferable.

It is preferable to use R ³ as these groups because the solubility of the copolymer A in an organic solvent is improved and it can be advantageous in the coating film forming process. More preferably, R ³ 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. The linear alkyl group is preferable in that the crystallinity of the copolymer A can be improved and the mobility can be increased, and a linear alkyl group having 4 to 12 carbon atoms is particularly preferable. A branched alkyl group is preferable in that the solubility of the copolymer A can be improved. In addition, R ³ is an aromatic group which may have a substituent. This is because the copolymer A can absorb light having a longer wavelength and the crystallinity of the copolymer A can be improved. This is preferable in that the degree can be increased.

  The substituent that the alkyl group, alkenyl group, or aromatic group may have is not particularly limited as long as the effects of the present invention are not impaired, but preferably a halogen atom, a hydroxyl group, a cyano group, an amino group, a carboxyl group. Group, carbamoyl group, acyl group, alkoxycarbonyl group, aryloxycarbonyl group, alkylsulfonyl group, arylsulfonyl group, silyl group, boryl group, cyano group, nitro group, nitrile group, alkyl group, alkenyl group, alkynyl group, alkoxy Group, aryloxy group, alkylthio group, arylthio group, or aromatic group. These substituents may be linked with adjacent substituents to form a ring.

  In the formula (IIIA), 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. Specific examples of A include an oxygen atom, a sulfur atom, or a selenium atom. Of these, an oxygen atom or a sulfur atom is preferable. An oxygen atom is preferable in that the open circuit voltage (Voc) of the photoelectric conversion element can be improved, and a sulfur atom is preferable in that an intermolecular interaction between the copolymers A can be improved.

Next, the repeating unit represented by the formula (IIIB) will be described. Q represents an atom selected from Group 14 elements of the Periodic Table. Specific examples of Q include a carbon atom, a silicon atom, a germanium atom, and a tin atom. 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 that the crystallinity of the copolymer A can be improved, and a silicon atom is preferable in that the solubility of the copolymer A can be improved.

In formula (IIIB), R ⁴ and R ⁵ each independently represent a hydrocarbon group that may have a hetero atom. Examples of the hydrocarbon group which may have a hetero atom include the same as those mentioned for R ³ . These also include the same as those given for R ³ as the substituent which may have. Further, R ⁴ and R ⁵ may be bonded to each other to form a ring.

Among them, at least one of R ⁴ and R ⁵ is preferably an alkyl group which may have a substituent or an aromatic group which may have a substituent, and both of R ⁴ and R ⁵ Is more preferably an alkyl group which may have a substituent or an aromatic group which may have a substituent. The linear alkyl group is preferable in that the mobility can be increased by improving the crystallinity of the copolymer A, and the branched alkyl group is formed by a coating process by improving the solubility of the copolymer A. Is preferable in that it can be easily performed. The aromatic group is preferable in that the interaction between molecules is improved by the interaction between π electrons, and thus the mobility of the copolymer A tends to increase, and the stability of the skeleton represented by the formula (IIIB) It is preferable at the point which tends to improve.

In addition, it is preferable that at least one of R ⁴ and R ⁵ is an alkyl group which may have a substituent from the viewpoint that the copolymer A can absorb light having a longer wavelength. From these viewpoints, at least one of R ⁴ and R ⁵ is preferably an alkyl group having 1 to 20 carbon atoms, and particularly preferably an alkyl group having 6 to 20 carbon atoms. From the viewpoint of improving the durability of the copolymer A by increasing the steric hindrance around Q, which is an atom selected from Group 14 elements of the periodic table, R ⁴ and R ⁵ may have a substituent. It is preferably a good alkyl group, an alkenyl group which may have a substituent, or an aromatic group which may have a substituent.

  The ratio of the repeating unit represented by the formula (IIIA) in the repeating unit constituting the copolymer A is not particularly limited, but is usually 1 mol% or more, preferably 5 mol% or more, more preferably 15 mol%. As mentioned above, 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 (IIIB) in the repeating unit constituting the copolymer A is not particularly limited, but is usually 1 mol% or more, preferably 5 mol% or more, more preferably 15 mol%. As mentioned above, 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 (IIIB) to the repeating unit represented by the formula (IIIA) in the copolymer A is not particularly limited, but is usually 0.01 or more, preferably 0.1 or more, more Preferably it is 0.5 or more. On the other hand, it is usually 100 or less, preferably 10 or less, more preferably 2 or less.

Although there are a plurality of repeating units represented by the formulas (IIIA) and (IIIB), the copolymer A contains only one kind of each of the repeating units represented by the formulas (IIIA) and (IIIB). Alternatively, two or more kinds may be contained. In this case, the type of repeating unit contained in the copolymer A is not limited, but is usually 8 or less, preferably 5 or less.

  The arrangement state of the repeating units (IIIA) and (IIIB) of the present invention may be any of alternating, block and random. That is, the copolymer A may be any of an alternating copolymer, a block copolymer, and a random copolymer. Preferably, they are arranged alternately. In particular, the copolymer A is preferably a copolymer containing a repeating unit represented by the following formula (IV). By including a repeating unit represented by the following formula (IV), the charge separation state can be more easily maintained.

(In the formula (IV), A represents an atom selected from Group 16 elements of the periodic table, R ^{3 to} R ⁵ each independently represents a hydrocarbon group optionally having a hetero atom, and Q represents a period. (Represents an atom selected from Table 14 element)

Specific examples of A, Q, and R ^{3 to} R ⁵ in formula (IV) include the same as those described for formulas (IIIA) and (IIIB). From the viewpoints of solubility and light absorption, it is more preferable that Q is a silicon atom and A is a sulfur atom.

  The copolymer A may contain other repeating units as long as the effects of the present invention are not impaired. Examples of other repeating units include aromatic heterocyclic rings such as thiophenediyl group and thiazolediyl group.

  In this preferred example in which the copolymer A contains a repeating unit represented by the formula (IV), the ratio of the repeating unit represented by the formula (IV) to the repeating units constituting the copolymer A 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.

  Although there are a plurality of repeating units represented by the formula (IV), the copolymer A may contain only one type or two or more types of repeating units represented by the formula (IV). You may do it. In this case, the type of repeating unit contained in the copolymer A is not limited, but is usually 8 or less, preferably 5 or less.

Although the preferable specific example of the copolymer A is shown, it is not restricted to the following illustrations. C ₄ H ₉ , C ₈ H ₁₇ , and C ₁₂ H ₂₅ represent a linear alkyl group having a predetermined carbon number. Bu, Hex, and Oct represent an n-butyl group, an n-hexyl group, and an n-octyl group, respectively. When the copolymer A includes a plurality of repeating units, the ratio between the plurality of repeating units included is arbitrary.

  The copolymer A described above absorbs light in a long wavelength region (600 nm or more) and exhibits a high open-circuit voltage (Voc), and thus has an advantage of high photoelectric conversion characteristics. In particular, it is combined with a fullerene compound in a solar cell. When applied, it exhibits high solar cell characteristics. In addition, there is an advantage that the HOMO energy level is low and is not easily oxidized.

  Further, the copolymer A has an advantage of high solubility. When performing coating film formation, the copolymer A has high solubility in a solvent, and further, the range of choice of the solvent is widened. Therefore, it is easy to use a solvent that is optimal for the conditions, so that the film quality of the formed active layer can be improved. it can. This is also considered to be a factor that the solar cell using this copolymer exhibits high solar cell characteristics.

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

The polystyrene equivalent weight average molecular weight of the copolymer A 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. A copolymer (1 mg) to be measured is dissolved in chloroform (200 mg). BR> 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 of the copolymer A (Mn) is usually 1.0 × 10 ³ or more, on preferably 3.0 × 10 ^3, more preferably 5.0 × 10 ³ or more, more preferably 1.0 × 10 ⁴ More preferably, it is 1.5 × 10 ⁴ or more, still more preferably 2.0 × 10 ⁴ or more, and particularly preferably 2.5 × 10 ⁴ or more. On the other hand, it is preferably 1.0 × 10 ⁶ or less, more preferably 5.0 × 10 ⁵ or less, still more preferably 2.0 × 10 ⁵ or less, and particularly preferably 1.0 × 10 ⁵ or less. The number average molecular weight is preferably in this range from the viewpoint of increasing the light absorption wavelength and achieving high absorbance. The number average molecular weight of the copolymer A can be measured by the same method as the above weight average molecular weight.

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

The copolymer A preferably has a light absorption maximum wavelength (λ _max ) of usually 470 nm or more, preferably 480 nm or more, and is usually 1200 nm or less, preferably 1000 nm or less, more preferably 900 nm or less. Further, the half width is usually 10 nm or more, preferably 20 nm or more, and is usually 300 nm or less. It is desirable that the absorption wavelength region of the copolymer A is closer to the absorption wavelength region of sunlight.

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

The copolymer A is preferably one that interacts between molecules. In the present specification, the interaction between molecules means that the distance between polymer chains is shortened due to the interaction of π-π stacking between molecules. The stronger the interaction, the higher the mobility and / or crystallinity. That is, in a copolymer that interacts between molecules, electron transfer between molecules is likely to occur. Therefore, in the photoelectric conversion element, holes generated at the interface between the copolymer A and the fullerene compound in the active layer are efficiently used. It is thought that it can be well transported to the anode. 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 having a laminated structure in which molecules are arranged, and is preferable in that it tends to be easy to obtain an active layer having a sufficient thickness. 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 A 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 A is usually 1.0 × 10 ⁴ cm ² / Vs or less, preferably 1.0 × 10 ³ cm ² / Vs or less, and more preferably 1.0 × 10 ^2. cm ² / Vs or less. In order to obtain high conversion efficiency, the balance between the mobility of the n-type semiconductor compound and the mobility of the copolymer A is important. From the viewpoint of bringing the mobility of the copolymer A used as the p-type semiconductor compound close to the mobility of the fullerene compound used as the n-type semiconductor compound, the hole mobility of the copolymer A is preferably within this range. As a method for measuring the hole mobility, there is an FET method. The FET method can be performed by a method described in a known document (Japanese Patent Laid-Open No. 2010-045186).

  It is preferable that the impurities in the copolymer A are as small as possible. In particular, if a transition metal catalyst such as palladium or copper remains, an exciton trap due to the heavy atom effect of the transition metal occurs, which may hinder charge transfer, resulting in a decrease in photoelectric conversion efficiency of the photoelectric conversion element. is there. The concentration of the transition metal catalyst is usually 1000 ppm or less, preferably 500 pm or less, more preferably 100 ppm or less with respect to the copolymer A. 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 in the copolymer A (X ¹ and X ^{2 in} the formula (VA) and formula (VB) described later) is not particularly limited, but is usually 6000 ppm or less, preferably 4000 ppm or less, more preferably 3000 ppm or less, more preferably 2000 ppm or less, still more preferably 1000 ppm or less, particularly preferably 500 ppm or less, and most preferably 200 ppm or less. On the other hand, it is usually larger than 0 ppm and may be 1 ppm or more, or 3 ppm or more.

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

  The residual amount of halogen atoms in the copolymer A 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. 100 ppm or less. On the other hand, it is usually larger than 0 ppm, 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 ICP mass spectrometer (Agilent
It can be quantified by a calibration curve method using an ICP mass spectrometer (Model 7500ce) manufactured by Technologies.

(Method for producing copolymer A)
There is no particular limitation on the method for producing the copolymer A. For example, it can be produced by a known method using a compound represented by the following general formula (VA) and a compound represented by the following general formula (VB). Preferable methods include a method of polymerizing a compound represented by the following general formula (VA) and a compound represented by the following general formula (VB) in the presence of an appropriate catalyst if necessary. .

In formula (VA), R ³ and A are as defined above. In formula (VB), R ⁴ , R ⁵ and Q are as defined above.
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 (VA) or (VB) and ease of 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.

  As an alkenyl group, a C2-C12 alkenyl group is mentioned, for example.

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

When the Stille coupling reaction method is used, in the above general formula (VA) and general formula (VB), for example, X ¹ is a halogen atom and X ² is an alkylstannyl group, or X ¹ is alkylstannyl. It is preferable that X ² is a halogen atom.

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

Since the conversion characteristics of the photoelectric conversion element can be improved by increasing the purity of the copolymer A, the monomer before polymerization (compound represented by the general formula (VA) or (VB)) is distilled, sublimated and purified by column chromatography. Alternatively, the polymerization reaction is preferably performed after purification by a method such as recrystallization. The purity of the monomer before polymerization is usually 90% or more, preferably 95% or more. In the polymerization reaction, an alkali, a catalyst, a cocatalyst, an organic ligand, a phase transfer catalyst, or the like can be added to promote the reaction. These alkalis or catalysts may be selected according to the type of polymerization reaction, but are preferably sufficiently dissolved in the solvent used for the polymerization reaction. Examples of the alkali include inorganic bases such as potassium carbonate, sodium carbonate and cesium carbonate, and organic bases such as triethylamine. Examples of the catalyst include a palladium complex containing a phosphine compound such as tetrakis (triphenylphosphine) palladium (Pd (PPh ₃ ) ₄ ) as a ligand or a palladium (Pd) catalyst such as palladium acetate; Ni (dppp) Cl ₂ Or a nickel catalyst such as Ni (dppe) Cl ₂ ; an iron catalyst such as iron chloride; or a copper catalyst such as copper iodide.

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 ,} PdCl ₂ (PPh ₃ ) _{2 and the} like (wherein 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 as a usage-amount of the palladium complex with respect to the sum total of the compound represented by the compound represented by a formula (VA), and a formula (VB), Preferably It is 1.0 × 10 ⁻³ mol% or more, more preferably 1.0 × 10 ⁻² mol% or more, and usually 1.0 × 10 ² mol% or less, more preferably 5 mol% or less. It is preferable that the amount of the catalyst used be in this range because a higher molecular weight copolymer A 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.times.10.sup.- ³ mol%, relative to the compound represented by formula (VA). 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 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 (VA). 0.0 × 10 ⁻² mol% or more, and usually 5 mol% or less, more preferably 3 mol% or less. It is preferable that the amount of the phase transfer catalyst used be in this range because copolymer A tends to be obtained at a lower cost and in a higher yield.

  Examples of the solvent used in the polymerization reaction include saturated hydrocarbons such as pentane, hexane, heptane, octane, and cyclohexane; aromatic hydrocarbons such as benzene, toluene, ethylbenzene, and xylene; halogens such as chlorobenzene, dichlorobenzene, and trichlorobenzene. Aromatic hydrocarbons; alcohols such as methanol, ethanol, propanol, isopropanol, butanol or t-butyl alcohol; water; ethers such as dimethyl ether, diethyl ether, methyl t-butyl ether, tetrahydrofuran, tetrahydropyran or dioxane; DMF And aprotic organic solvents such as 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 (VA) and the compound represented by the formula (VB). × 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 longer, preferably 10 minutes or longer, on the other hand, usually 160 hours or shorter, preferably 120 hours or shorter, more preferably 100 hours or shorter. 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 A can be obtained by ordinary post-treatment such as quenching with water and extraction 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 after 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 of the copolymer is reduced. It is possible to reduce. This terminal treatment is preferable because a polymer 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 the copolymer is polymerized 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 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 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, Sn atoms in the alkylstannyl group, which are easily thermally decomposed, are not present 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 end treatment agent (aryl halide or aryltrimethyltin) 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. Do. Thereafter, the other end treatment agent (aryltrimethyltin 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 compound represented by the formula (VA) used as a raw material for the polymerization reaction is described in J. Org. Am. Chem. Soc. 2010, 132 (22), 7595-7597. The compound represented by the formula (VB) is described in J.P. Mater. Chem. , 2011, 21, 3895, and J.A. Am. Chem. Soc. 2008, 130, 16144-16145.

(Other p-type semiconductor compounds)
The composition for forming a semiconductor layer according to the present invention may contain a low molecular organic semiconductor compound as a p-type semiconductor compound. The active layer 103 may contain both a high molecular organic semiconductor compound and a low molecular organic semiconductor compound as a p-type semiconductor compound. As the low-molecular organic semiconductor compound, known compounds can be used, and specifically those described in known documents such as International Publication No. 2011-016430 can be adopted. The p-type semiconductor compound may have some self-organized structure in the deposited state, or may be in an amorphous state.

<1-3. Solvent>
The composition for forming a semiconductor layer according to the present invention is produced by dissolving the fullerene compound and the p-type semiconductor compound in a solvent. In addition, the composition for forming a semiconductor layer according to the present invention may be prepared by preparing a solution containing a fullerene compound and a solution containing a p-type semiconductor compound, respectively, and then mixing them.

  The solvent that can be used in the present invention is not particularly limited. For example, aliphatic hydrocarbons such as hexane, heptane, octane, isooctane, nonane or decane; toluene, xylene, mesitylene, cyclohexylbenzene, chlorobenzene, or orthodichlorobenzene, etc. Aromatic hydrocarbons such as cyclopentane, cyclohexane, methylcyclohexane, cycloheptane, cyclooctane, tetralin or decalin; lower alcohols such as methanol, ethanol or propanol; acetone, methyl ethyl ketone, cyclopenta Aliphatic ketones such as non- or cyclohexanone; aromatic ketones such as acetophenone or propiophenone; esters such as ethyl acetate, butyl acetate or methyl lactate Chloroform, methylene chloride, dichloroethane, halogenated hydrocarbons such as trichloroethane or trichlorethylene; ethers such as ethyl ether and tetrahydrofuran or dioxane; or an amide such as dimethylformamide or dimethylacetamide, and the like.

  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 Hydrogen; ketones such as acetone, methyl ethyl ketone, cyclopentanone or cyclohexanone; or ethers such as ethyl ether, tetrahydrofuran or dioxane. On the other hand, from the viewpoint of environmental burden, it is preferable not to use halogenated hydrocarbons such as chlorobenzene or diiodooctane.

  More preferably, non-halogen aromatic hydrocarbons such as toluene, xylene, mesitylene or cyclohexylbenzene; non-halogen ketones such as acetone, methyl ethyl ketone, cyclopentanone or cyclohexanone; aromatic ketones such as acetophenone or propiophenone Non-halogen alicyclic hydrocarbons such as tetrahydrofuran, cyclopentane, cyclohexane, methylcyclohexane, cycloheptane, cyclooctane, tetralin or decalin; or non-halogen aliphatic ethers such as 1,4-dioxane; . 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 solvents are used in combination, a low boiling point solvent having a boiling point of 60 ° C. or higher and 150 ° C. or lower under normal pressure and a high boiling point solvent having a boiling point of 180 ° C. or higher and 250 ° C. or lower under normal pressure. Is preferred. For example, examples of the high boiling point solvent include tetralin, decalin, and acetophenone, and examples of the low boiling point solvent include toluene, xylene, tetrahydrofuran, and ethyl methyl ketone. When using a combination of a high-boiling solvent and a low-boiling solvent in this way, when forming an active layer, the lower-volatile high-boiling solvent slowly volatilizes, which facilitates the organization of the semiconductor compound. The phase separation structure can be optimized. From the viewpoint of environmental load, these high-boiling solvents and low-boiling solvents are preferably non-halogen solvents.

  The ratio of the high boiling point solvent and the low boiling point solvent is not particularly limited, but the weight ratio (high boiling point solvent / low boiling point solvent) is preferably 1/20 or more, more preferably 1/15 or more, It is more preferable that it is 1/10 or more. On the other hand, it is preferably 10/1 or less, more preferably 2/1 or less, more preferably 1/1 or less, and particularly preferably 1/2 or less.

  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.

<1-4. Weight ratio of fullerene compound and p-type semiconductor compound>
In the composition for forming a semiconductor layer according to the present invention, the weight ratio of the fullerene compound to the p-type semiconductor compound is 2.1 or more and 11 or less. In the present invention, when the weight ratio of the p-type semiconductor compound to the p-type semiconductor compound contained in the composition for forming a semiconductor layer is 2.1 or more, the active layer formed using this composition for forming a semiconductor layer Thus, the film strength of the upper buffer layer formed can be improved. This is because when the weight ratio of the fullerene compound in the semiconductor-forming composition increases, there are many fullerene compound clusters on the surface of the active layer. It is thought that it contributes to the adhesiveness with the buffer layer interface. Therefore, by setting the weight ratio of the fullerene compound and the p-type semiconductor compound within the above range, even if the upper buffer layer is formed by the roll-to-roll method, film peeling hardly occurs and productivity is improved. . Moreover, if the said weight ratio is 11 or less, the quantity of the p-type semiconductor compound which has a long wavelength absorption region will not decrease too much, and conversion efficiency will be maintained.

  In addition, the weight ratio of the fullerene compound to the p-type semiconductor compound in the composition for forming a semiconductor layer is more preferably 2.2 or more, further preferably 2.3 or more, particularly preferably 2.5 or more, while 10 or less. More preferably, it is more preferably 8 or less, and particularly preferably 6 or less. Further, if the total weight ratio of the fullerene compound and the p-type semiconductor compound to the solvent is too small, the amount used is increased during film formation. On the other hand, if the weight ratio is too large, the fullerene compound and the p-type semiconductor compound are reduced. It will not dissolve sufficiently. Therefore, the total weight ratio of the fullerene compound and the p-type semiconductor compound to the solvent is preferably 1% or more, more preferably 2% or more, particularly preferably 3% or more, on the other hand, preferably 15% or less, It is more preferably 14% or less, and particularly preferably 13% or less.

<1-5. Other>
In addition to the above, the composition for forming a semiconductor layer according to the present invention may contain other materials without departing from the spirit of the present invention. For example, an additive may be included in the composition for forming a semiconductor layer. In the photoelectric conversion element, when the fullerene compound aggregates in the active layer, phase separation between the p-type semiconductor compound and the fullerene compound is promoted. In this case, since the contact area between the p-type semiconductor compound and the fullerene compound becomes small, it is considered that the electron transfer efficiency and / or the charge separation efficiency is lowered, leading to deterioration of the performance of the photoelectric conversion element. Therefore, if an additive is included in the active layer, the aggregation of the fullerene compound can be suppressed in the active layer through intermolecular interaction with the fullerene compound, and the performance deterioration of the photoelectric conversion element can be suppressed. it can. In particular, the additive improves the heat resistance of the photoelectric conversion element by preventing the fullerene compound from aggregating when the active layer or the photoelectric conversion element is exposed to heat. In addition, the additive makes it possible to heat the active layer while preventing the fullerene compound from aggregating, so that heat treatment promotes self-organization in the active layer and absorbs light of a long wavelength by the active layer. Can be possible. As the active layer absorbs light having a longer wavelength, sunlight having a wider wavelength range can be efficiently converted into electricity. Therefore, in this invention, it is effective that an additive is contained in the composition for semiconductor layer formation which forms an active layer. Hereinafter, a solar cell element using the composition for forming a semiconductor layer according to the present invention will be described with reference to FIG. In addition, although the formation method of each layer is demonstrated in detail below, a solar cell element is a process which forms an active layer using the composition for semiconductor layer formation which concerns on this invention, and an upper buffer on the said active layer. It is preferable to manufacture including a step of forming a layer by a coating method. Usually, when the upper buffer layer is formed by a coating method, the film formation rate is high, but the film strength of the formed upper buffer layer tends to be low. However, by forming the active layer using the composition for forming a semiconductor layer according to the present invention, the film strength of the upper buffer layer formed thereon is improved. Therefore, in the present invention, it is preferable to form the upper buffer layer by a coating method.

  In addition, each layer constituting the solar cell element may be formed by a sheet-to-sheet method (manyoba type) or a roll-to-roll method. The roll-to-roll method is a method in which a film-like substrate wound in a roll is fed out and processed intermittently or continuously while being wound up by a take-up roll. It is. Since it is possible to batch-process long substrates of km order, mass production can be easily performed. Therefore, the roll-to-roll method has an advantage of high mass productivity as compared with the sheet-to-sheet (sheet-fed) method. However, when each layer is formed by the roll-to-roll method, the back surface of the roll or the substrate and each layer constituting the solar cell element come into contact with each other, and as a result, the layer constituting the solar cell element is peeled off. There's a problem. In particular, as described above, when the upper buffer layer is formed on the active layer by a coating method, the formed upper buffer layer has a very weak film strength, which causes a problem that the upper buffer layer is easily peeled off. End up.

  However, when the active layer is formed using the composition for forming a semiconductor layer according to the present invention, the film strength of the upper buffer layer formed on the active layer is improved. Even if the buffer layer contacts, the upper buffer layer is unlikely to peel off. Therefore, in the present invention, it is preferable to form at least the upper buffer layer by a roll-to-roll method with excellent mass productivity.

<2-1. Substrate 106>
The material of the substrate 106 is not particularly limited as long as the effects of the present invention are not significantly impaired. Suitable examples of the substrate material include inorganic materials such as quartz, glass, sapphire, and titania; polyethylene terephthalate, polyethylene naphthalate, polyethersulfone, polyimide, nylon, polystyrene, polyvinyl alcohol, ethylene vinyl alcohol copolymer, fluorine Resin film, polyolefin such as vinyl chloride or polyethylene; organic material such as cellulose, polyvinylidene chloride, aramid, polyphenylene sulfide, polyurethane, polycarbonate, polyarylate, polynorbornene or epoxy resin; paper material such as paper or synthetic paper; stainless steel, Examples thereof include composite materials such as those obtained by coating or laminating a surface of a metal such as titanium or aluminum to impart insulation.

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

  There is no restriction | limiting in the shape of a board | substrate, 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 board | substrate 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 organic thin film solar cell 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 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 thickness of the substrate is 0.01 mm or more because the mechanical strength increases and it is difficult to break. Moreover, it is preferable that the film thickness of the substrate is 0.5 cm or less because the weight does not increase.

  Note that in the case of forming any layer by a roll-to-roll method, the substrate 106 is preferably a film that can be wound into a roll. Specifically, the thickness of the film-like material is usually 1 μm or more, preferably 5 μm or more, more preferably 10 μm or more, and usually 1 cm or less, preferably 5 mm or less, more preferably 1 mm or less. By being thicker than the above lower limit, the strength of the material can be maintained, and the degree of freedom in setting process conditions by the roll-to-roll method is increased. Moreover, the handleability at the time of winding in roll shape becomes high because it is thinner than the said upper limit.

<2-2. Lower electrode 101, upper electrode 105>
As described above, the solar cell element has a pair of electrodes of a lower electrode 101 and an upper electrode 105 described later. In the present invention, the lower electrode 101 means an electrode arranged at a position close to the substrate 31, and the upper electrode 105 means an electrode arranged at a position farther from the substrate 31 than the lower electrode 101.

  Usually, one of the pair of electrodes is an anode, and the other electrode is a cathode. In the present invention, when the lower electrode 101 is a cathode, the upper electrode 105 is an anode, and when the lower electrode 101 is an anode, the upper electrode 105 is a cathode. As for the lower electrode 101 and the upper electrode 105, at least one electrode should just have translucency, but both may have translucency. In the present invention, having translucency means that the average light transmittance of sunlight is 40% or more, but in order to make light sufficiently reach the organic active layer 38 described later, The average light transmittance is preferably 70% or more. The average light transmittance can be measured with a normal spectrophotometer.

  The materials used for the lower electrode 101 and the upper electrode 105 are different depending on whether it is an anode or a cathode. Specifically, the lower electrode 101 and the upper electrode 105 can be formed by the materials and methods described below. Whether 101 is a cathode or an anode, a metal oxide, a metal, or an alloy thereof is used.

  The anode is an electrode generally made of a conductive material having a work function higher than that of the cathode and having a function of smoothly extracting holes generated in the organic active layer 38.

  Examples of the anode material include 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; gold, Examples thereof include metals such as platinum, silver, chromium and cobalt or alloys thereof. These substances are preferable because they have a high work function, and further, a conductive polymer material represented by PEDOT: PSS in which a polythiophene derivative is doped with polystyrene sulfonic acid can be stacked. When laminating such a conductive polymer, the work function of this conductive polymer material is high, so even if it is not a material with a high work function as described above, it is suitable for cathodes such as Al and Mg. 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 is a transparent electrode, it is preferable to use a light-transmitting conductive metal oxide such as ITO, zinc oxide or tin oxide, and ITO is particularly preferable.

  The film thickness of the anode 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 thickness of the anode is 10 nm or more, the sheet resistance is suppressed, and when the thickness of the anode is 10 μm or less, light can be efficiently converted into electricity without decreasing the light transmittance. When the anode 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 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 the anode forming method 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.

  The cathode is generally composed of a conductive material having a low work function, and is an electrode having a function of smoothly extracting electrons generated in the organic active layer 38. For example, platinum, gold, Metals such as silver, copper, iron, tin, zinc, aluminum, indium, chromium, lithium, sodium, potassium, cesium, calcium or magnesium and their alloys; inorganic salts such as lithium fluoride and cesium fluoride; nickel oxide, oxide Examples thereof include metal oxides such as aluminum, lithium oxide, or cesium oxide. These materials are preferable because they are materials having a low work function. Similarly to the anode, a material having a high work function can be used for the cathode by using an n-type semiconductor such as titania having conductivity as the electron extraction layer. From the viewpoint of electrode protection, the cathode material is preferably a metal such as platinum, gold, silver, copper, iron, tin, aluminum, calcium or indium, or an alloy using these metals such as indium tin oxide.

  The film thickness of the cathode 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 is 10 nm or more, the sheet resistance is suppressed, and when the film thickness of the cathode is 10 μm or less, light can be efficiently converted into electricity without decreasing the light transmittance. When the cathode is 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 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, there are a vacuum film formation 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 and the cathode 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 and the cathode.

  After laminating the anode and cathode, the organic thin-film solar cell element is heated in a temperature range of usually 50 ° C. or higher, preferably 80 ° C. or higher, usually 300 ° C. or lower, preferably 280 ° C. or lower, more preferably 250 ° C. or lower. It is preferable to do this (this step may be referred to as an annealing treatment step). By performing the annealing treatment step at a temperature of 50 ° C. or higher, an effect of improving the adhesion between the layers of the organic thin film solar cell element, for example, the adhesion between the electron extraction layer and the cathode and / or the electron extraction layer and the active layer is obtained. Therefore, it is preferable. By improving the adhesion between the layers, the thermal stability and durability of the organic thin film solar cell element can be improved. It is preferable to set the temperature of the annealing treatment step to 300 ° C. or lower because the possibility that the organic compound in the active layer is thermally decomposed is reduced. In the annealing treatment step, stepwise heating may be performed within the above temperature range.

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

  As a heating method, the organic thin film solar cell element may be placed on a heat source such as a hot plate, or the organic thin film solar cell element may be placed in a heating atmosphere such as an oven. The heating may be performed batchwise or continuously.

<2-3. Upper Buffer Layer 102, Lower Buffer Layer 104>
The upper buffer layer 102 is formed on the lower electrode 101. Normally, when the lower electrode 101 is an anode, the upper buffer layer 102 is a hole extraction layer, and when the lower electrode 101 is a cathode, the upper buffer layer 102 is , An electron extraction layer. The lower buffer layer 104 means a hole extraction layer or an electron extraction layer formed on the organic active layer 38. When the upper electrode 105 is an anode, the lower buffer layer 104 is a hole extraction layer. When the upper electrode 105 is a cathode, the lower buffer layer 104 is an electron extraction layer. In the present invention, materials and the like that can be used differ depending on whether the upper buffer layer 102 and the lower buffer layer 104 are an electron extraction layer or a hole extraction layer. Specifically, although it can be formed by the following materials and methods, the upper buffer layer 102 is formed as described above regardless of whether the upper buffer layer 102 is an electron extraction layer or a hole extraction layer. Is preferably formed by a coating method.

  The electron extraction layer has a function of improving the efficiency of extracting electrons from the organic active layer 38 to the cathode. As long as it has such a function, a material that can be used for the electron extraction layer is not particularly limited, and examples thereof include inorganic compounds and organic compounds.

Examples of inorganic compound materials include alkali metal salts such as Li, Na, K or Cs; titanium oxide (TiOx), zinc oxide (ZnO), tin oxide (SnOx), niobium oxide (NbOx), or these. Examples thereof include n-type semiconductor metal oxides such as mixed (doped) mixed metal oxides. Among them, the alkali metal salt is preferably a fluoride salt such as LiF, NaF, KF or CsF, and the n-type semiconductor metal oxide is titanium oxide (TiO 2).
x) and zinc oxide (ZnO) are preferred. Although the operation mechanism of such a material is unknown, it is conceivable to reduce the work function of the cathode when combined with a cathode made of Al or the like and increase the voltage applied to the solar cell element.

  Examples of organic compound materials include, for example, phosphine compounds having a double bond between a phosphorus atom and a group 16 element such as triarylphosphine oxide compounds; bathocuproin (BCP) or bathophenanthrene (Bphen), A phenanthrene compound which may have a substituent and may be substituted at the 1-position and the 10-position with a heteroatom; a boron compound such as triarylboron; and (8-hydroxyquinolinato) aluminum (Alq3) Organometallic oxide; Compound having 1 or 2 ring structure which may have a substituent such as oxadiazole compound or benzimidazole compound; Naphthalenetetracarboxylic anhydride (NTCDA) or perylenetetracarboxylic acid Of dicarboxylic anhydrides, such as anhydrides (PTCDA) Aromatic compounds having Unachijimigo dicarboxylic acid structure.

  The LUMO energy level of the material of the electron extraction layer 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 for the electron extraction layer is −1.9 eV or less because charge transfer can be promoted. It is preferable that the LUMO energy level of the material for the electron extraction layer is −4.0 eV or more in terms of preventing reverse electron transfer to the n-type semiconductor material.

  The HOMO energy level of the material for the electron extraction layer 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 for the electron extraction layer 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, a cyclic voltammogram measurement method may be mentioned. For example, it can implement with reference to the method as described in well-known literature (International Publication 2011/016430).

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

  Among the compounds having a glass transition temperature of 55 ° C. or higher as measured by the DSC method, the glass transition temperature is preferably 65 ° C. or higher, more preferably 80 ° C. or higher, more preferably 110 ° C. or higher, particularly preferably. Compounds that are 120 ° C. or higher are desirable. On the other hand, the upper limit of the glass transition temperature is not particularly limited, but is usually 400 ° C. or lower, preferably 350 ° C. or lower, more preferably 300 ° C. or lower.

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

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

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

  There is no restriction | limiting in the formation method of an electronic taking-out layer. 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 the electron extraction layer is formed by a coating method, a surfactant may be further contained in the coating solution. By using the surfactant, the occurrence of dents due to adhesion of fine bubbles or foreign matters and / or uneven coating in the drying process is suppressed. Known surfactants (cationic surfactants, anionic surfactants, nonionic surfactants) can be used as the surfactant. Of these, silicon-based surfactants, acetylenic diol-based surfactants, and fluorine-based surfactants are preferable. In addition, as surfactant, only 1 type may be used and 2 or more types may be used together by arbitrary combinations and a ratio.

  Specifically, for example, when an alkali metal salt is used as a material for the electron extraction layer, the electron extraction layer can be formed by using a vacuum film formation method such as vacuum deposition or sputtering. Especially, it is desirable to form an electron taking-out layer by vacuum vapor deposition by resistance heating. By using vacuum deposition, damage to other layers such as an active layer can be reduced.

  On the other hand, for metal oxides of n-type semiconductors, for example, when zinc oxide ZnO is used as the material for the electron extraction layer, a vacuum film formation method such as sputtering can be used. It is desirable to form the extraction layer. For example, Sol-Gel Science, C.I. J. et al. Brinker, G.M. W. According to the sol-gel method described by Scherer, Academic Press (1990), an electron extraction layer composed of zinc oxide can be formed.

The hole extraction layer has a function of improving the efficiency of extracting holes from the active layer to the anode. The material that can be used for the hole extraction layer is not particularly limited as long as it has such a function. Specifically, polythiophene, polypyrrole, polyacetylene, triphenylenediamine, polyaniline, and the like, sulfonic acid and / or Conductive polymer doped with iodine, polythiophene derivative having sulfonyl group as a substituent, conductive organic compound such as arylamine, metal oxide such as copper oxide, nickel oxide, manganese oxide, molybdenum oxide, vanadium oxide or tungsten oxide Products, Nafion, p-type semiconductors described later, and the like. Among them, a conductive polymer doped with sulfonic acid is preferable, and (3,4-ethylenedioxythiophene) poly (styrenesulfonic acid) (PEDOT: PSS) in which a polythiophene derivative is doped with polystyrene sulfonic acid is more preferable. It is. 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.

  There is no restriction | limiting in the formation method of a positive hole taking-out layer. For example, when a material having sublimation property is used, it can be formed by a vacuum deposition method or the like. For example, when a material soluble in a solvent is used, it can be formed by a wet coating method such as a spin coating method or an ink jet method. When a semiconductor material is used for the hole extraction layer, the precursor may be converted into a semiconductor compound after forming the layer using the precursor, similarly to the low-molecular organic semiconductor compound of the organic active layer described later.

Especially, when using PEDOT: PSS as a material of a hole taking-out layer, it is preferable to form a hole taking-out layer by the method of apply | coating a dispersion liquid. PEDOT: The dispersion of PSS, and CLEVIOS ^TM series of Heraeus, Inc., include Agfa Corp. of ORGACON ^TM series and the like.

  When the hole extraction layer is formed by a coating method, a surfactant may be further contained in the coating solution. By using the surfactant, the occurrence of dents due to adhesion of fine bubbles or foreign matters and / or uneven coating in the drying process is suppressed. Known surfactants (cationic surfactants, anionic surfactants, nonionic surfactants) can be used as the surfactant. Of these, silicon-based surfactants, acetylenic diol-based surfactants, and fluorine-based surfactants are preferable. In addition, as surfactant, only 1 type may be used and 2 or more types may be used together by arbitrary combinations and a ratio.

<2-4. Active layer 103>
The active layer refers to a layer in which photoelectric conversion is performed, and is a bulk heterojunction type active layer having a layer (i layer) in which a p-type semiconductor compound and a fullerene compound are mixed.

The i layer has a structure in which a p-type semiconductor compound and a fullerene compound are phase-separated, carrier separation occurs on the general meeting surface, and the generated carriers (holes and electrons) are transported to the electrode. In addition to the layer in which the p-type semiconductor compound and the fullerene compound are mixed, at least one of the p-type semiconductor layer containing the p-type semiconductor compound and the n-type semiconductor layer containing the n-type semiconductor compound is stacked on the active layer. It may be. In the following description, the active layer has only the i layer.
The active layer can be formed by applying the semiconductor layer forming composition according to the present invention. As an application method, any method can be used. For example, spin coating method, ink jet 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.

  In addition, after apply | coating the composition for semiconductor layer formation, you may heat-dry. Heating can promote self-organization of the active layer. The heating temperature is usually 50 ° C. or higher, preferably 80 ° C. or higher, and is usually 300 ° C. or lower, preferably 280 ° C. or lower, more preferably 250 ° C. or lower. 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.

  There is no special restriction | limiting in the film thickness of an active layer, Usually, 5 nm or more, Preferably it is 10 nm or more, More preferably, it is 50 nm or more, More preferably, it is 120 nm or more. On the other hand, the film thickness of the active layer is 500 nm or less, preferably 400 nm or less, more preferably 300 nm or less. The thickness of the active layer is preferably 5 nm or more from the viewpoint of absorbing more light, and the thickness of the active layer is preferably 500 nm or less from the viewpoint of reducing the series resistance.

  Note that the active layer may further include a p-type semiconductor layer and an n-type semiconductor layer. There is no particular limitation on the p-type semiconductor layer and the n-type semiconductor layer. For example, Solar Energy Materials & Solar Cells 96 (2012) 155-159, International Publication No. 2011-016430, or JP 2012-191194 A, JP 2012-2012 A. An n-type semiconductor compound and a p-type semiconductor compound described in Japanese Patent No. 167241 can be used.

<3. Solar cell>
Although the organic thin film solar cell according to the present invention can be manufactured by the method described above, the organic thin film solar cell may include constituent members other than those described above.

  FIG. 2 is a cross-sectional view schematically showing the configuration of the organic thin-film solar cell 14 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 obtained by bonding a fluororesin film on 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. The materials, shapes, performances, and lamination methods of these encapsulant 5, backsheet 10 and various films are all as described in International Publication No. 2011/016430 or Japanese Patent Application Laid-Open No. 2012-191194. .

<4. Application>
There is no restriction | limiting in the use of the organic thin film solar cell 14 mentioned above, It is arbitrary. For example, as schematically shown in FIG. 3, a thin film solar cell 14 may be provided on some base material 12 and used at a place of use. As a specific example, when a building material plate is used as the base material 12, a thin-film solar cell 14 is produced on the surface of the plate material, and this solar cell panel is used on the outer wall of a building. That's fine.

  The substrate 12 is a support member that supports the solar cell element 6. Examples of the material for forming the substrate 12 include polyethylene terephthalate, polyethylene naphthalate, polyethersulfone, polyimide, nylon, polystyrene, polyvinyl alcohol, ethylene vinyl alcohol copolymer, fluororesin film, vinyl chloride, polyethylene, cellulose, Organic materials such as polyvinylidene chloride, aramid, polyphenylene sulfide, polyurethane, polycarbonate, polyarylate, polynorbornene; paper materials such as paper or synthetic paper; surface to impart insulation to metals such as stainless steel, titanium or aluminum Examples thereof include composite materials such as coated or laminated materials. In addition, 1 type may be used for the material of a base material, and 2 or more types may be used together by arbitrary combinations and a ratio. Moreover, carbon fiber may be included in these organic materials or paper materials to reinforce the mechanical strength.

  When the example of the field | area which applies the thin film solar cell of this invention is given, as it exists in international publication 2011/016430 or Unexamined-Japanese-Patent No. 2012-191194, for example, it is a solar cell for building materials, a solar cell for motor vehicles, and interior use. It is suitable for use in solar cells, railroad solar cells, marine solar cells, airplane solar cells, spacecraft solar cells, home appliance solar cells, mobile phone solar cells, toy solar cells, and the like.

Examples of the present invention will be described below. In addition, this invention is not limited to a following example, A design can be changed suitably in the range which does not deviate from the meaning of this invention.
(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 (trimethyl) obtained by referring to the methods described in known literature (Chem. Commun., 2011, 47, 4920-4922). Ruthin) -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.

(Preparation of semiconductor-forming composition 1)
The weight ratio of the copolymer A obtained in Synthesis Example 1 as a p-type semiconductor compound and the fullerene mixture (nanospectra-E124 (NS-E124) manufactured by Frontier Carbon Corporation) as an n-type semiconductor compound is 1: 1.5. The mixture was dissolved in a mixed solvent of orthoxylene and tetralin (weight ratio 9: 1) in a nitrogen atmosphere so that the mixture had a concentration of 2.25% by weight. This solution was stirred and mixed on a hot stirrer at a temperature of 40 ° C. for 1 hour. The solution after stirring and mixing was filtered through a polytetrafluoroethylene (PTFE) filter having a pore size of 5 μm to obtain a composition 1 for forming a semiconductor layer.

(Preparation of semiconductor layer forming composition 2)
Except that the copolymer A obtained in Synthesis Example 1 as a p-type semiconductor compound and the fullerene mixture (NS-E124 manufactured by Frontier Carbon Corporation) as an n-type semiconductor compound were mixed so that the weight ratio was 1: 2.5. A semiconductor layer forming composition 2 was prepared in the same manner as in the semiconductor layer forming composition 1.

(Preparation of semiconductor layer forming composition 3)
Except for mixing the copolymer A obtained in Synthesis Example 1 as a p-type semiconductor compound and the fullerene mixture (NS-E124 manufactured by Frontier Carbon Co.) as an n-type semiconductor compound so that the weight ratio is 1: 5, the semiconductor A semiconductor layer forming composition 3 was prepared in the same manner as the layer forming composition 1.

(Preparation of semiconductor layer forming composition 4)
The copolymer A obtained in Synthesis Example 1 as a p-type semiconductor compound and the fullerene mixture (NS-E124 manufactured by Frontier Carbon Co., Ltd.) as an n-type semiconductor compound are mixed so that the weight ratio is 1: 6, and the mixture is mixed. A semiconductor layer forming composition 4 was produced in the same manner as the semiconductor layer forming composition 1 except that the concentration was 5.91 wt% with respect to the solvent.

(Preparation of semiconductor layer forming composition 5)
The copolymer A obtained in Synthesis Example 1 as a p-type semiconductor compound and the fullerene mixture (NS-E124 manufactured by Frontier Carbon Co., Ltd.) as an n-type semiconductor compound are mixed so that the weight ratio is 1:10, and the mixture is mixed. A semiconductor layer forming composition 5 was produced in the same manner as the semiconductor layer forming composition 1 except that the concentration was 5.91 wt% with respect to the solvent.

(Example 1: Preparation of sample)
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 isopropyl alcohol, and then dried by nitrogen blowing.

  Next, the cleaned substrate was subjected to ultraviolet ozone treatment for 10 minutes using an ultraviolet ozone treatment apparatus (manufactured by Filgen). Thereafter, zinc acetate (II) dihydrate (manufactured by Wako Pure Chemical Industries, Ltd.) is mixed with 2-methoxyethanol (manufactured by Aldrich) and ethanolamine (manufactured by Aldrich) so that the concentration becomes 105 mg / mL. A solution (about 0.1 mL) dissolved in (volume ratio 100: 3) is spin-coated on a substrate at 3000 rpm and heated in an oven at 200 ° C. for 10 minutes, whereby the lower buffer layer (electron extraction layer) is formed. Formed. The film thickness of the formed electron extraction layer was 30 nm. Next, the substrate on which the lower buffer layer (electron extraction layer) was formed was brought into the glove box, and the semiconductor layer forming composition 2 (0.2 mL) produced by the above method was spin-coated at rpm 250, Then, heat treatment was performed at 140 ° C. for 10 minutes using a hot plate to form an active layer. The film thickness of the obtained active layer was 250 nm.

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

The samples prepared as described above were evaluated for scratch resistance using a continuous load-type scratch strength tester (manufactured by Shinto Kagaku Co., Ltd.). A pencil placed at 45 ° on a test machine loaded with a load of 750 g was scratched by about 7 mm, and the resistance to scratches was evaluated based on the presence or absence of scratches on the scratch marks. The pencils used were pencil hardnesses B to 2H made by Mitsubishi Pencil. 1 to 5 points were assigned to five levels of hardness from pencil hardness B to 2H, the test was repeated 5 times at each hardness, and when there was no scratch, the hardness was assigned as a score and the hardness score was determined. .

  Moreover, the same laminated body as the above-mentioned sample was produced, and 100 nm of silver was vapor-deposited by the vacuum evaporation method on the upper buffer layer, and the anode was formed. Thus, the produced solar cell element was evaluated with the following method. The results are shown in Table 1.

(Evaluation method of photoelectric conversion element)
A 6 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 and a source meter (type 2400, manufactured by Keithley) 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

(Example 2)
A sample and a photoelectric conversion element were produced and evaluated in the same manner as in Example 1 except that the semiconductor layer forming composition 3 was used instead of the semiconductor layer forming material 2 and spin coating was performed at rpm 200. went. The obtained results are shown in Table 1.

(Example 3)
A sample and a photoelectric conversion element were produced and evaluated in the same manner as in Example 1 except that the semiconductor layer forming composition 4 was used instead of the semiconductor layer forming material 2 and spin coating was performed at rpm 100. went. The obtained results are shown in Table 1.

Example 4
A sample and a photoelectric conversion element were prepared and evaluated in the same manner as in Example 1 except that the semiconductor layer forming composition 5 was used instead of the semiconductor layer forming material 2 and spin coating was performed at rpm 300. went. The obtained results are shown in Table 1.

(Comparative Example 1)
A sample and a photoelectric conversion element were produced and evaluated in the same manner as in Example 1 except that the semiconductor layer forming composition 1 was used instead of the semiconductor layer forming material 2 and spin coating was performed at rpm 250. went. The obtained results are shown in Table 1.

  Compared with the sample produced in Comparative Example 1, the pencil hardness test results of the samples produced in Examples 1 to 4 are B to F, indicating that the film strength of the upper buffer layer is high. Therefore, it can be seen that even when the upper buffer layer is formed by the roll-to-roll method and comes into contact with the back surface of the roll or the substrate, peeling of the upper buffer layer hardly occurs. Therefore, according to the present invention, it is possible to provide a photoelectric conversion element having high conversion efficiency as well as improvement in productivity.

DESCRIPTION OF SYMBOLS 1 Weatherproof protective film 2 UV cut film 3,9 Gas barrier film 4,8 Getter material film 5,7 Sealing material 6 Solar cell 101 Lower electrode 102 Lower buffer layer 103 Active layer 104 Upper buffer layer 105 Upper electrode 106 Substrate 107 Solar cell element

Claims (4)

  A composition for forming a semiconductor, comprising a fullerene compound, a p-type semiconductor compound, and a solvent, wherein the weight ratio of the fullerene compound to the p-type semiconductor compound is 2.1 or more and 11 or less.   2. The composition for forming a semiconductor layer according to claim 1, wherein a HOMO energy level of the p-type semiconductor compound is −5.7 eV or more and −4.9 eV or less. 3. The semiconductor according to claim 1, wherein the p-type semiconductor compound is a copolymer having a repeating unit represented by the following formula (IIIA) and a repeating unit represented by the following formula (IIIB). Layer forming composition.
(In formula (IIIA), A represents an atom selected from Group 16 elements of the periodic table, and R ³ represents a hydrocarbon group optionally having a hetero atom.)
(In formula (IIIB), Q represents an atom selected from Group 14 elements of the periodic table, and R ⁴ and R ⁵ each independently represents a hydrocarbon group optionally having a hetero atom.)   A solar battery cell comprising: a step of forming an active layer using the composition for forming a semiconductor layer according to claim 1; and a step of forming an upper buffer layer on the active layer by a coating method. Manufacturing method.