WO2016039063A1

WO2016039063A1 - Photoelectric conversion element and organic semiconductor compound used in same

Info

Publication number: WO2016039063A1
Application number: PCT/JP2015/072746
Authority: WO
Inventors: 淳志若宮; 光田中; 一剛萩谷; 濱本　史朗
Original assignee: 東洋紡株式会社
Priority date: 2014-09-11
Filing date: 2015-08-11
Publication date: 2016-03-17
Also published as: JPWO2016039063A1; JP6699545B2

Abstract

The present invention provides a photoelectric conversion element achieving a high open circuit voltage with use of a polymer compound into which various skeletons and substituents can be introduced. A photoelectric conversion element which has a structure wherein a base, an anode, an active layer and a cathode are sequentially arranged in this order, and which is characterized in that the active layer contains a polymer compound that has a benzobisthiazole structure unit represented by formula (1). (In formula (1), each of A¹ and A² independently represents an alkoxy group, a thioalkoxy group, a thiophene ring which may be substituted by a hydrocarbon group, a thiazole ring which may be substituted by a hydrocarbon group or an organosilyl group, or a phenyl group which may be substituted by a hydrocarbon group, an alkoxy group, a thioalkoxy group, an organosilyl group, a halogen atom or a trifluoromethyl group.)

Description

Photoelectric conversion element and organic semiconductor compound used therefor

The present invention relates to a photoelectric conversion element having a structure in which a substrate, an anode, an active layer, and a cathode are arranged in this order, and a photoelectric conversion containing a polymer compound having a specific structural unit of a benzobisthiazole skeleton It relates to an element.

Organic semiconductor compounds are one of the most important materials in the field of organic electronics, and can be classified into electron-donating p-type organic semiconductor compounds and electron-accepting n-type organic semiconductor compounds. Various elements can be manufactured by appropriately combining a p-type organic semiconductor compound and an n-type organic semiconductor compound. For example, such elements include excitons (recombination of electrons and holes) It is applied to organic electroluminescence that emits light by the action of excitons), organic thin-film solar cells that convert light into electric power, and organic thin-film transistors that control the amount of current and voltage.

Among these, organic thin-film solar cells are useful for environmental conservation because they do not release carbon dioxide into the atmosphere, and demand is increasing because they are easy to manufacture with a simple structure. However, the photoelectric conversion efficiency of the organic thin film solar cell is still not sufficient. The photoelectric conversion efficiency η is calculated by the product “η = open circuit voltage (Voc) × short circuit current density (Jsc) × curve factor (FF)” of the short circuit current density (Jsc), the open circuit voltage (Voc), and the fill factor (FF). In order to increase the photoelectric conversion efficiency, it is necessary to improve the short circuit current density (Jsc) and the fill factor (FF) in addition to the improvement of the open circuit voltage (Voc).

The open circuit voltage (Voc) is proportional to the energy difference between the HOMO (highest occupied orbital) level of the p-type organic semiconductor compound and the LUMO (lowest unoccupied orbital) level of the n-type organic semiconductor compound. In order to improve (Voc), it is necessary to deepen (lower) the HOMO level of the p-type organic semiconductor.

The short circuit current density (Jsc) correlates with the amount of energy received by the organic semiconductor compound. In order to improve the short circuit current density (Jsc) of the organic semiconductor compound, from the visible region to the near infrared region. It is necessary to absorb light in a wide wavelength range. Of the light that can be absorbed by the organic semiconductor compound, the wavelength of the light with the lowest energy (the longest wavelength) is the absorption edge wavelength, and the energy corresponding to this wavelength corresponds to the band gap energy. Therefore, in order to absorb light in a wider wavelength range, it is necessary to narrow the band gap (energy difference between the HOMO level and the LUMO level of the p-type semiconductor).

On the other hand, research on p-type organic semiconductor compounds is also actively conducted. For example, Non-Patent Document 1 describes the co-polymerization of 4,4′-bis (2-ethylhexyl) dithieno [3,2-b; 2 ′, 3 ′,-d] silole and 2,1,3-benzothiadiazole. Coalescence has been proposed. However, the p-type organic semiconductor compound described in Non-Patent Document 1 may not have a sufficiently deep HOMO level. Non-Patent Document 2 proposes a p-type organic semiconductor compound having a benzodithiophene skeleton. However, the p-type organic semiconductor compound described in Non-Patent Document 2 is limited in the skeleton and substituents that can be introduced due to problems in the synthesis method.
Further, Patent Documents 1 and 2 each propose a compound having a benzobisthiazole skeleton, but the conversion efficiency is not clear.

JP 2007-238530 A JP 2010-053093 A

An object of the present invention is to provide a photoelectric conversion element that exhibits a high open circuit voltage. In addition, the capability of the photoelectric conversion element depends on the type and combination of the organic semiconductor compound, and since HOMO and the open circuit voltage are closely related to each other, more various skeletons and substituents can be introduced. It is providing the photoelectric conversion element using a high molecular compound.

In order to improve the short-circuit current density (Jsc) while improving the open circuit voltage (Voc) in order to fabricate a photoelectric conversion element with high conversion efficiency, the present inventors have applied a wide wavelength to a p-type organic semiconductor compound. It has been found that the HOMO level is moderately deep while absorbing a range of light. And earnestly examined paying attention to the correlation of the HOMO level and chemical structure in a p-type organic-semiconductor compound. As a result, by using an organic semiconductor compound having a polymer compound with a specific structure, the HOMO level and the LUMO level can be adjusted to appropriate ranges, so that a photoelectric conversion element with a high open-circuit voltage (Voc) can be manufactured. The headline and the present invention were completed.

That is, the present invention is a photoelectric conversion element having a structure in which a substrate, an anode, an active layer, and a cathode are arranged in this order, and the active layer has a specific benzox represented by the formula (1). It contains a polymer compound having a structural unit of a bisthiazole skeleton (hereinafter sometimes referred to as “polymer compound (1)”).

[In Formula (1),
A ¹ and A ² are each independently an alkoxy group, a thioalkoxy group, a thiophene ring optionally substituted with a hydrocarbon group, a thiazole ring optionally substituted with a hydrocarbon group or an organosilyl group, or It represents a phenyl group which may be substituted with a hydrocarbon group, an alkoxy group, a thioalkoxy group, an organosilyl group, a halogen atom, or a trifluoromethyl group. ]
In the above formula (1), each of A ¹ and A ² is preferably a group represented by the following formula.

[In the formulas (a1) to (a4), R ²¹ to R ²⁵ each independently represents a hydrocarbon group having 8 to 30 carbon atoms. * Represents a bond bonded to the benzene ring of benzobisthiazole. ]

The polymer compound (1) used in the photoelectric conversion element of the present invention is preferably a donor-acceptor type semiconductor polymer.

The active layer preferably further contains an n-type organic semiconductor compound, and the n-type semiconductor compound is preferably fullerene or a derivative thereof.

The photoelectric conversion element of the present invention preferably has a hole transport layer between the anode and the active layer, and preferably has an electron transport layer between the cathode and the active layer. The anode is preferably a transparent electrode, and the cathode is preferably a metal electrode.

The polymer compound (1) used in the present invention has a deep HOMO level and can absorb a wide range of light from the visible region to the near infrared region. Thereby, the photoelectric conversion element having the element structure shown in FIG. 1 can obtain a high open circuit voltage (Voc), and can obtain a high photoelectric conversion efficiency η. In addition, it is possible to introduce various substituents as substituents into the benzobisthiazole skeleton constituting the polymer compound (1) used in the present invention, and materials that have various influences on the characteristics of photoelectric conversion elements Characteristics (crystallinity, film-forming property, absorption wavelength) can be controlled.

FIG. 1 shows an element structure of a photoelectric conversion element in which a substrate, an anode, an active layer, and a cathode are arranged in this order.

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

1. Photoelectric Conversion Element The photoelectric conversion element according to the present invention is a photoelectric conversion element having a structure in which a substrate, an anode, an active layer, and a cathode are arranged in this order, and the active layer is represented by the formula (1). A polymer compound having a benzobisthiazole structural unit represented is contained.

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

The photoelectric conversion element (VII) has a structure in which a substrate (I), an electrode (anode) (II), an active layer (IV), and an electrode (cathode) (VI) are arranged in this order. The photoelectric conversion element (VII) preferably further has a buffer layer (hole transport layer) (III) and a buffer layer (electron transport layer) (V). That is, the photoelectric conversion element (VII) includes a base material (I), an anode (II), a buffer layer (hole transport layer) (III), an active layer (IV), and a buffer layer (electron transport layer) (V ) And the cathode (VI) are preferably arranged in this order. However, the photoelectric conversion element according to the present invention may not have the hole transport layer (III) and the electron transport layer (V). Hereinafter, each of these parts will be described.

<1.1 Active layer (IV)>
The active layer (IV) refers to a layer in which photoelectric conversion is performed, and usually includes a single or a plurality of p-type semiconductor compounds and a single or a plurality of n-type semiconductor compounds. Specific examples of the p-type semiconductor compound include, but are not limited to, the polymer compound (1) and the organic semiconductor compound (10) described later. In the present invention, it is necessary to use at least the polymer compound (1) as the p-type semiconductor compound. When the photoelectric conversion element (VII) receives light, the light is absorbed by the active layer (IV), electricity is generated at the interface between the p-type semiconductor compound and the n-type semiconductor compound, and the generated electricity is the anode (II) and It is taken out from the cathode (VI). In the present invention, the polymer compound (1) is used as a p-type semiconductor compound.

The film thickness of the active layer (IV) is not particularly limited, but is preferably 70 nm or more, more preferably 90 nm or more, and may be 100 nm or more. On the other hand, the thickness of the active layer (IV) is preferably 1000 nm or less, more preferably 750 nm or less, and further preferably 500 nm or less.

When the film thickness of the active layer (IV) is 70 nm or more, the conversion efficiency of the photoelectric conversion element (VII) can be expected to be improved. Moreover, it is also preferable that the film thickness of the active layer (IV) is 70 nm or more in that a through short circuit in the film can be prevented. It is preferable that the thickness of the active layer (IV) is 1000 nm or less because the internal resistance is small and the distance between the electrodes (II) and (VI) is not too far and the charge diffusion is good. Furthermore, it is preferable that the film thickness of the active layer (IV) be 70 nm or more and 1000 nm or less because the reproducibility in the process of producing the active layer (IV) is improved.

In general, the thicker the active layer, the longer the distance traveled by the charge generated in the active layer to the electrode or the electron transport layer or hole transport layer, thus hindering the transport of charge to the electrode. It is done. As described above, when the active layer (IV) is thick, the region capable of absorbing light is increased, but it is difficult to transport charges generated by light absorption, so that the photoelectric conversion efficiency is lowered. Therefore, it is preferable that the thickness of the active layer (IV) is 70 nm or more and 500 nm or less from the viewpoint of securing voltage and improving conversion efficiency.

[1.1.1 Layer structure of active layer]
As the layer structure of the active layer (IV), a thin film stacked type in which a p-type semiconductor compound and an n-type semiconductor compound are stacked, a bulk heterojunction type having a layer in which a p-type semiconductor compound and an n-type semiconductor compound are mixed, or the like. Is mentioned. Among these, a bulk heterojunction type active layer is preferable in that the photoelectric conversion efficiency can be further improved.

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

Of the p-type semiconductor compound contained in the i layer, usually 50% by weight or more, preferably 70% by weight or more, more preferably 90% by weight or more is represented by the benzobisthiazole structural unit represented by the formula (1) and It is the high molecular compound (1) which consists of a copolymerization component (2) to do. Since the polymer compound (1) has properties suitable as a p-type semiconductor compound, it is particularly preferable that the p-type semiconductor compound contains only the polymer compound (1).

The weight ratio of the p-type semiconductor compound to the n-type semiconductor compound in the i layer (p-type semiconductor compound / n-type semiconductor compound) is 0 from the viewpoint of improving the photoelectric conversion efficiency by obtaining a good phase separation structure. .5 or more is preferable, more preferably 1 or more, while 4 or less is preferable, 3 or less is more preferable, and 2 or less is particularly preferable.

The i layer can be formed by any method including a coating method and a vapor deposition method (for example, a co-evaporation method), but it is preferable to use the coating method because the i layer can be formed more easily. Since the polymer compound (1) according to the present invention has solubility in a solvent, it is preferable from the viewpoint of excellent coating film-forming properties. When the i layer is produced by a coating method, a coating solution containing a p-type semiconductor compound and an n-type semiconductor compound may be prepared, and this coating solution may be applied. The coating liquid containing the p-type semiconductor compound and the n-type semiconductor compound may be prepared by preparing and mixing a solution containing the p-type semiconductor compound and a solution containing the n-type semiconductor compound, respectively. The compound and the n-type semiconductor compound may be dissolved.

The total concentration of the p-type semiconductor compound and the n-type semiconductor compound in the coating solution is not particularly limited, but is 1.0% by weight or more based on the entire coating solution from the viewpoint of forming an active layer having a sufficient film thickness. In view of sufficiently dissolving the semiconductor compound, it is preferably 4.0% by weight or less based on the entire coating solution.

As an application method, any method can be used. For example, spin coating method, inkjet method, doctor blade method, drop casting method, reverse roll coating method, gravure coating method, kiss coating method, roll brush method, spray coating method , Air knife coating method, wire barber coating method, pipe doctor method, impregnation / coating method or curtain coating method. You may perform the drying process by heating etc. after application | coating of a coating liquid.

The solvent of the coating solution is not particularly limited as long as it can uniformly dissolve the p-type semiconductor compound and the n-type semiconductor compound. For example, aliphatic hydrocarbons such as hexane, heptane, octane, isooctane, nonane or decane. Aromatic hydrocarbons such as toluene, xylene, mesitylene, cyclohexylbenzene, chlorobenzene, or orthodichlorobenzene; alicyclic hydrocarbons such as cyclopentane, cyclohexane, methylcyclohexane, cycloheptane, cyclooctane, tetralin, or decalin; methanol Lower alcohols such as ethanol or propanol; aliphatic ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone (MIBK), cyclopentanone or cyclohexanone; acetophenone Or aromatic ketones such as propiophenone; esters such as ethyl acetate, isopropyl acetate, butyl acetate or methyl lactate; halogen hydrocarbons such as chloroform, methylene chloride, dichloroethane, trichloroethane or trichloroethylene; ethyl ether, tetrahydrofuran, Examples include ethers such as cyclopentyl methyl ether and dioxane; and amides such as dimethylformamide and dimethylacetamide.

Among them, aromatic hydrocarbons such as toluene, xylene, mesitylene, cyclohexylbenzene, chlorobenzene or orthodichlorobenzene; cycloaliphatic carbonization such as cyclopentane, cyclohexane, methylcyclohexane, cycloheptane, cyclooctane, tetralin or decalin Hydrogen; ketones such as acetone, methyl ethyl ketone, cyclopentanone or cyclohexanone; or ethers such as ethyl ether, tetrahydrofuran or dioxane.

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

The additive is preferably solid or has a high boiling point in that the additive is less likely to be lost from the active layer (IV).

Specifically, when the additive is solid, the melting point (1 atm) of the additive is usually 35 ° C. or higher, preferably 50 ° C. or higher, more preferably 80 ° C. or higher, more preferably 150 ° C. or higher. Particularly preferably, the temperature is 200 ° C. or higher.

When the additive is liquid, the boiling point (1 atm) is 80 ° C. or higher, more preferably 100 ° C. or higher, and particularly preferably 150 ° C. or higher.

Examples of the additive include aliphatic hydrocarbons having 10 or more carbon atoms or aromatic compounds if solid. Specific examples include naphthalene compounds, and compounds in which 1 to 8 substituents are bonded to naphthalene are particularly preferable. Substituents bonded to naphthalene are halogen atoms, hydroxyl groups, cyano groups, amino groups, amide groups, carbonyloxy groups, carboxyl groups, carbonyl groups, oxycarbonyl groups, silyl groups, alkenyl groups, alkynyl groups, alkoxy groups. , Aryloxy group, alkylthio group, arylthio group or aromatic group.

If the additive is liquid, examples thereof include aliphatic hydrocarbons or aromatic compounds having 8 or more carbon atoms. Specific examples include dihalogen hydrocarbon compounds, and compounds in which 1 to 8 substituents are bonded to octane are particularly preferable. Examples of the substituent bonded to octane include a halogen atom, a hydroxyl group, a thiol group, a cyano group, an amino group, an amide group, a carbonyloxy group, a carboxyl group, a carbonyl group, or an aromatic group. Another example of the additive is a benzene compound to which 4 or more and 6 or less halogen atoms are bonded.

The amount of the additive contained in the coating solution containing the p-type semiconductor compound and the n-type semiconductor compound is preferably 0.1% by weight or more, and more preferably 0.5% by weight or more with respect to the entire coating solution. Moreover, 10 weight% or less is preferable with respect to the whole coating liquid, and 5 weight% or less is more preferable. When the amount of the additive is within this range, a preferable phase separation structure can be obtained.

[1.1.2 p-type semiconductor compound]
The active layer (IV) contains at least the polymer compound (1) as a p-type semiconductor compound.

(Polymer compound (1))
The polymer compound used in the photoelectric conversion element of the present invention (hereinafter sometimes referred to as “polymer compound (1)”) is a kind of p-type semiconductor compound, and is a benzoate represented by the formula (1). It has a bis-thiazole structural unit (hereinafter sometimes referred to as “structural unit represented by formula (1)”).

[In Formula (1),
A ¹ and A ² are each independently an alkoxy group, a thioalkoxy group, a thiophene ring optionally substituted with a hydrocarbon group, a thiazole ring optionally substituted with a hydrocarbon group or an organosilyl group, or It represents a phenyl group which may be substituted with a hydrocarbon group, an alkoxy group, a thioalkoxy group, an organosilyl group, a halogen atom, or a trifluoromethyl group. ]

The polymer compound used in the photoelectric conversion element of the present invention has a benzobisthiazole structural unit represented by the formula (1). Therefore, the band gap can be narrowed while deepening the HOMO level, which is advantageous in increasing the photoelectric conversion efficiency. The polymer compound (1) is preferably a donor-acceptor type semiconductor polymer obtained by copolymerizing a structural unit represented by the formula (1) and a copolymerization component (2) described later. The donor-acceptor type semiconductor polymer means a polymer compound in which donor units and acceptor units are alternately arranged. The donor unit means an electron donating structural unit, and the acceptor unit means an electron accepting structural unit. The donor-acceptor type semiconductor polymer is preferably a polymer compound in which a structural unit represented by the formula (1) and a copolymer component (2) described later are alternately arranged. With such a structure, it can be suitably used as a p-type semiconductor compound.

In the benzobisthiazole structural unit represented by the formula (1), A ¹ and A ² may be the same or different from each other, but are preferably the same from the viewpoint of easy production.
In the benzobisthiazole structural unit represented by the formula (1), A ¹ and A ² are each preferably groups represented by the following formulas (a1) to (a4). When A ¹ and A ² are groups represented by the following formulas (a1) to (a4), light of a short wavelength can be absorbed, so that the photoelectric conversion efficiency can be further improved.

R ²¹ to R ²⁵ are each a hydrocarbon group having 8 to 30 carbon atoms, preferably a branched hydrocarbon group, and more preferably a branched saturated hydrocarbon group. Since the hydrocarbon group of R ²¹ to R ²⁵ has a branch, the solubility in an organic solvent can be increased, and appropriate crystallinity can be obtained. As the carbon number of the hydrocarbon group of A ¹ and A ² increases, the solubility in an organic solvent can be improved. However, if the carbon number is too large, the reactivity in the coupling reaction described later decreases. The synthesis of 1) may be difficult. Therefore, the carbon number of the hydrocarbon group of A ¹ and A ² is preferably 8 to 25, more preferably 8 to 20, and still more preferably 8 to 16.

Examples of the hydrocarbon group having 8 to 30 carbon atoms represented by R ²¹ to R ²⁵ include an n-octyl group, 1-n-butylbutyl group, 1-n-propylpentyl group, 1-ethylhexyl group, 2- Such as ethylhexyl, 3-ethylhexyl, 4-ethylhexyl, 1-methylheptyl, 2-methylheptyl, 6-methylheptyl, 2,4,4-trimethylpentyl, 2,5-dimethylhexyl, etc. An alkyl group having 8 carbon atoms; n-nonyl group, 1-n-propylhexyl group, 2-n-propylhexyl group, 1-ethylheptyl group, 2-ethylheptyl group, 1-methyloctyl group, 2-methyloctyl group An alkyl group having 9 carbon atoms such as a group, 6-methyloctyl group, 2,3,3,4-tetramethylpentyl group, 3,5,5-trimethylhexyl group; n-decyl group, 1 -N-pentylpentyl group, 1-n-butylhexyl group, 2-n-butylhexyl group, 1-n-propylheptyl group, 1-ethyloctyl group, 2-ethyloctyl group, 1-methylnonyl group, 2- C10 alkyl groups such as methylnonyl group and 3,7-dimethyloctyl group; n-undecyl group, 1-n-butylheptyl group, 2-n-butylheptyl group, 1-n-propyloctyl group, 2- an alkyl group having 11 carbon atoms such as n-propyloctyl group, 1-ethylnonyl group, 2-ethylnonyl group; n-dodecyl group, 1-n-pentylheptyl group, 2-n-pentylheptyl group, 1-n-butyl 12 alkyl groups such as octyl, 2-n-butyloctyl, 1-n-propylnonyl, 2-n-propylnonyl, n-tridecyl, 1-n-pe An alkyl group having 13 carbon atoms such as tiloctyl group, 2-n-pentyloctyl group, 1-n-butylnonyl group, 2-n-butylnonyl group, 1-methyldecyl group, 2-methyldecyl group; n-tetradecyl group, 1- an alkyl group having 14 carbon atoms such as n-heptylheptyl group, 1-n-hexyloctyl group, 2-n-hexyloctyl group, 1-n-pentylnonyl group, 2-n-pentylnonyl group; n-pentadecyl group Alkyl groups having 15 carbon atoms such as 1-n-heptyloctyl group, 1-n-hexylnonyl group and 2-n-hexylnonyl group; n-hexadecyl group, 1-n-octyloctyl group, 1-n- C16 alkyl group such as heptylnonyl group, 2-n-heptylnonyl group, 2-n-hexyldecyl group; n-heptadecyl group, 1-n-octylnonyl group, etc. An alkyl group having 17 carbon atoms; an alkyl group having 18 carbon atoms such as an n-octadecyl group and a 1-n-nonylnonyl group; an alkyl group having 19 carbon atoms such as an n-nonadecyl group; a carbon group having 20 carbon atoms such as an n-eicosyl group An alkyl group; an alkyl group having 21 carbon atoms such as an n-heneicosyl group; an alkyl group having 22 carbon atoms such as an n-docosyl group; an alkyl group having 23 carbon atoms such as an n-tricosyl group; an n-tetracosyl group, 2-decyl; And an alkyl group having 24 carbon atoms such as a tetradecyl group. An alkyl group having 8 to 20 carbon atoms is preferable, an alkyl group having 8 to 16 carbon atoms is more preferable, a branched alkyl group having 8 to 16 carbon atoms is further preferable, and n-octyl is particularly preferable. Group, 2-ethylhexyl group, 3,7-dimethyloctyl group, 2-n-butyloctyl, 2-n-hexyldecyl group. It is preferable that R ²¹ to R ²⁵ are the above groups because the solubility of the polymer compound (1) in an organic solvent is improved and it has appropriate crystallinity.

In the benzobisthiazole structural unit represented by the formula (1), A ¹ and A ² are each independently an alkoxy group, a thioalkoxy group, a hydrocarbon group, a thiophene ring, a hydrocarbon group or A thiazole ring optionally substituted with an organosilyl group, or a phenyl group optionally substituted with a hydrocarbon group, an alkoxy group, a thioalkoxy group, an organosilyl group, a halogen atom, or a trifluoromethyl group It is preferable. In particular, when the groups A ¹ and A ² are groups represented by the following formulas (a1) to (a4), the structural unit represented by the formula (1) has high planarity, so that Since π-π stacking is formed, the conversion efficiency can be further improved, which is more preferable.

[In formulas (a1) to (a4), * represents a bond, and R ²¹ to R ²⁴ represent the same groups as described above. * Represents a bond bonded to the benzene ring of benzobisthiazole. ]

A ¹ and A ² are more preferably a group represented by the formula (a1) or (a3) from the viewpoint of excellent planarity as a whole structural unit represented by the formula (1). Groups represented by formulas (a1-5) and (3-1) to (3-10) are more preferred. Formulas (a1-1) to (a1-3), (a3-1) to (a3-6) ) Is particularly preferred. In the formula, * represents a bond bonded to the benzene ring of benzobisthiazole.

Examples of the structural unit represented by the formula (1) include a group represented by the following formula.

(Copolymerization component (2))
The polymer compound (1) used in the present invention preferably contains a copolymer component (2) in combination with the structural unit represented by the formula (1). As the copolymerization component (2), a conventionally known structural unit can be used as a structural unit (donor unit or acceptor unit) that forms a donor-acceptor type semiconductor polymer. Although not particularly limited, specific examples include the following structural units, which can be used alone or in combination of two or more.

[In the formulas (b1) to (b22), R ³⁰ to R ⁴⁹ each independently represents the same group as R ²¹ to R ^25, and A ³⁰ and A ³¹ each independently represent A ¹ , A ² And j represents an integer of 1 to 4. ● represents a bond bonded to the thiazole ring of the structural unit represented by the formula (1). ]

The groups represented by the above formulas (b1) to (b12) are groups that act as acceptor units, and the groups represented by formulas (b14) to (b22) are groups that act as donor units. It is. The group represented by the formula (b13) may act as an acceptor unit or may act as a donor unit depending on the types of A ³⁰ and A ³¹ .

The repeating ratio of the structural unit represented by the formula (1) in the polymer compound (1) used in the present invention is not particularly limited, but is usually 1 mol% or more, preferably 5 mol% or more, more preferably It is 15 mol% or more, more preferably 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 of the copolymer component (2) in the polymer compound (1) is not particularly limited, but is usually 1 mol% or more, preferably 5 mol% or more, more preferably 15 mol% or more, Preferably it is 30 mol% or more. On the other hand, it is usually 99 mol% or less, preferably 95 mol% or less, more preferably 85 mol% or less, and still more preferably 70 mol% or less.

In the polymer compound (1) according to the present invention, the arrangement state of the structural unit represented by the formula (1) of the repeating unit and the copolymer component (2) may be any of alternating, block and random. That is, the polymer compound (1) according to the present invention may be an alternating copolymer, a block copolymer, or a random copolymer. Preferably, they are arranged alternately.

In the polymer compound (1), the structural unit represented by the formula (1) and the copolymer component (2) may each contain only one type. Moreover, 2 or more types of structural units represented by Formula (1) may be included, and 2 or more types of copolymerization components (2) may be included. Although there is no restriction | limiting in the kind of the structural unit represented by Formula (1) and the copolymerization component (2), Usually, it is 8 or less, Preferably it is 5 or less. Particularly preferred is a polymer compound (1) containing one type of structural unit represented by formula (1) and one type of copolymer component (2) alternately, and most preferred is formula (1). ) And a polymer compound (1) containing only one type of copolymer component (2) alternately.

Preferred specific examples of the polymer compound (1) are shown below. However, the polymer compound (1) according to the present invention is not limited to the following examples. In the following specific examples, R ³⁰ to R ⁴⁹ represent n-octyl group, 2-ethylhexyl group, 3,7-dimethyloctyl group, 2-n-butyloctyl, 2-n-hexyldecyl group. When the polymer compound (1) includes a plurality of repeating units, the ratio of the number of each repeating unit is arbitrary.

The polymer compound (1) used in the present invention has absorption in a long wavelength region (600 nm or more). Moreover, the photoelectric conversion element using a high molecular compound (1) shows a high open circuit voltage (Voc), and shows a high photoelectric conversion characteristic. When the polymer compound (1) is a p-type organic semiconductor compound and the fullerene compound is combined as an n-type organic semiconductor compound, particularly high photoelectric conversion characteristics are exhibited. Further, the polymer compound (1) according to the present invention has an advantage that it has a low HOMO energy level and is not easily oxidized.

Also, since the polymer compound (1) exhibits high solubility in a solvent, there is an advantage that coating film formation is easy. In addition, since the range of choice of solvent is widened when performing coating film formation, a solvent suitable for film formation can be selected, and the film quality of the formed active layer can be improved. This is also considered to be a factor that the photoelectric conversion element using the polymer compound (1) according to the present invention exhibits high photoelectric conversion characteristics.

In general, the weight average molecular weight and number average molecular weight of the polymer compound (1) of the present invention are preferably 2,000 or more and 1,000,000 or less, more preferably 3,000 or more, 500,000 or less. 000 or less. The weight average molecular weight and number average molecular weight of the polymer compound (1) of the present invention can be calculated based on a calibration curve prepared using polystyrene as a standard sample using gel permeation chromatography.

The polymer compound (1) according to the present invention preferably has a light absorption maximum wavelength (λmax) of 400 nm or more, more preferably 450 nm or more, and is usually 1200 nm or less, preferably 1000 nm or less, more preferably 900 nm or less. is there. Moreover, a half value width is 10 nm or more normally, Preferably it is 20 nm or more, on the other hand, it is 300 nm or less normally. Moreover, it is desirable that the absorption wavelength region of the polymer compound (1) according to the present invention is closer to the absorption wavelength region of sunlight.

The solubility of the polymer compound (1) according to the present invention is not particularly limited, but preferably the solubility in chlorobenzene at 25 ° C. is usually 0.1% by weight or more, more preferably 0.4% by weight or more, more preferably On the other hand, it is usually 30% by weight or less, preferably 20% by weight. High solubility is preferable in that a thicker active layer can be formed.

The polymer compound (1) according to the present invention preferably interacts between molecules. In the present invention, the interaction between molecules means that the distance between polymer chains is shortened due to the interaction of π-π stacking between molecules of the polymer compound. The stronger the interaction, the higher the polymer compound tends to exhibit higher carrier mobility and / or crystallinity. That is, in a polymer compound that interacts between molecules, charge transfer between molecules is likely to occur. Therefore, the p-type semiconductor compound (polymer compound (1)) in the active layer (IV) and the n-type semiconductor compound It is considered that holes generated at the interface can be efficiently transported to the anode (II).

(Production method of polymer compound (1))
The production method of the polymer compound (1) used in the present invention is not particularly limited. For example, a compound represented by the formula (3) using benzobisthiazole as a starting material,

[In Formula (3), R ¹ to R ⁶ each independently represents an aliphatic hydrocarbon group having 1 to 20 carbon atoms or an aromatic hydrocarbon group having 6 to 10 carbon atoms. ]
A compound represented by formula (4),

[In the formula (4), X and R ¹ to R ⁶ represent the same groups as described above. ]
A compound represented by formula (5),

[In the formula (5), A ¹ , A ² and R ¹ to R ⁶ each represent the same group as described above. ]
A compound represented by formula (6), and

[In the formula (6), A ¹ and A ² each represent the same group as described above. ]
Compound represented by formula (7)

[In the formula (7), A ¹ and A ² each represent the same group as described above. M ¹ and M ² each independently represents a boron atom or a tin atom. R ⁷ to R ¹⁰ each independently represents an aliphatic hydrocarbon group having 1 to 6 carbon atoms, a hydroxyl group, an alkoxy group having 1 to 6 carbon atoms, or an aryloxy group having 6 to 10 carbon atoms. R ⁷ and R ⁸ may form a ring together with M ¹ , and R ⁹ and R ¹⁰ may form a ring together with M ² . m and n each represents an integer of 1 or 2. When m and n are 2, the plurality of R ⁷ and R ⁹ may be the same or different. ]
It is possible to manufacture by the manufacturing method which passes through.

The carbon number of the aliphatic hydrocarbon group of R ¹ to R ⁶ is preferably 1 to 18, more preferably 1 to 8. Examples of the aliphatic hydrocarbon group represented by R ¹ to R ⁶ include a methyl group, an ethyl group, an isopropyl group, a tert-butyl group, an isobutyl group, an octyl group, and an octadecyl group. The carbon number of the aromatic hydrocarbon group of R ¹ to R ⁶ is preferably 6 to 8, more preferably 6 to 7, and particularly preferably 6. Examples of the aromatic hydrocarbon group represented by R ¹ to R ⁶ include a phenyl group. Among these, as R ¹ to R ⁶ , an aliphatic hydrocarbon group is preferable, an aliphatic hydrocarbon group having a branch is more preferable, and an isopropyl group is particularly preferable.

The compound of the above formula (7) can be produced, for example, as follows.
First step: A step of reacting a benzobisthiazole with a base and a halogenated silane compound to obtain a compound represented by formula (3) Second step: A base and a halogenating reagent for the compound represented by formula (3) And a step of obtaining a compound represented by the formula (4)

Furthermore, it is possible to obtain the compound represented by Formula (7) by including the following third step, fourth step and fifth step.
Third step: reacting the compound represented by formula (4) with the compound represented by formula (8) and / or (9),

[In the formulas (8) and (9), A ¹ and A ² each represent the same group as described above. R ¹¹ and R ¹² each independently represents a hydrogen atom or * -M ³ (R ¹³ ) _k R ¹⁴ . R ¹³ and R ¹⁴ each independently represents an aliphatic hydrocarbon group having 1 to 6 carbon atoms, a hydroxyl group, an alkoxy group having 1 to 6 carbon atoms, or an aryloxy group having 6 to 10 carbon atoms. M ³ represents a boron atom or a tin atom. R ¹³ and R ¹⁴ may form a ring together with M ³ . k represents an integer of 1 or 2. When k is 2, the plurality of R ¹³ may be the same or different. * Represents a bond to A ¹ or A ^1,,. The compound represented by formula (4) is reacted to obtain a compound represented by formula (4) Fourth step: The compound represented by formula (5) is treated with an acid or a base to obtain a compound represented by formula (6) Step 5 for obtaining a compound represented by formula: Step for obtaining a compound represented by formula (7) by reacting a compound represented by formula (6) with a tin halide compound

Coupling reaction Furthermore, the polymer compound (1) is combined with the structural unit represented by the formula (1) and the copolymerization component (2) alternately by a coupling reaction to form a donor-acceptor type. It can be produced as a polymer compound.

The coupling reaction can be performed by reacting the compound represented by the formula (6) with any one of the compounds represented by the following formulas (B1) to (B21) in the presence of a metal catalyst.

[In formulas (B1) to (B22), R ³⁰ to R ⁴⁹ each independently represents the same group as R ²¹ to R ^25, and A ³⁰ and A ³¹ each independently represent A ¹ , A ² Represents the same group. X represents a halogen atom. j represents an integer of 1 to 4. ]

(Other p-type semiconductor compounds)
The active layer (IV) contains at least the polymer compound (1) according to the present invention as a p-type semiconductor compound. However, a p-type semiconductor compound different from the polymer compound (1) can be mixed and / or laminated with the polymer compound (1). Although it does not specifically limit as another p-type semiconductor compound which can be used together, An organic-semiconductor compound (10) is mentioned. Hereinafter, the organic semiconductor compound (10) will be described. The organic semiconductor compound (10) may be a high molecular organic semiconductor compound or a low molecular organic semiconductor compound, but is preferably a high molecular organic semiconductor.

(Organic semiconductor compound (10))
The organic semiconductor compound (10) is not particularly limited, and is a conjugated copolymer semiconductor compound such as polythiophene, polyfluorene, polyphenylene vinylene, polythienylene vinylene, polyacetylene, or polyaniline; an oligothiophene substituted with an alkyl group or other substituent. And copolymer semiconductor compounds such as Moreover, the copolymer semiconductor compound which copolymerized 2 or more types of monomer units is also mentioned. Conjugated copolymers are described in, for example, Handbook of Conducting Polymers, 3rd Ed. (2 volumes in total), 2007, J.M. Polym. Sci. Part A: Polym. Chem. 2013, 51, 743-768, J. MoI. Am. Chem. Soc. 2009, 131, 13886-13887, Angew. Chem. Int. Ed. 2013, 52, 8341-8344, Adv. Mater. Copolymers that can be synthesized by a combination of a copolymer described in publicly known documents such as 2009, 21, 2093-2097, derivatives thereof, and the monomers described can be used. The organic semiconductor compound (10) may be a single compound or a mixture of a plurality of compounds. By using the organic semiconductor compound (10), an increase in the amount of light absorption due to the addition of the absorption wavelength band can be expected.

Specific examples of the organic semiconductor compound (10) include the following, but are not limited to the following.

The HOMO (highest occupied molecular orbital) energy level of the p-type semiconductor compound is not particularly limited and can be selected according to the type of the n-type semiconductor compound described later. In particular, when a fullerene compound is used as an n-type semiconductor compound, the HOMO energy level of the p-type semiconductor compound is usually −5.9 eV or more, more preferably −5.7 eV or more, while usually −4.6 eV or less. Preferably, it is −4.8 eV or less. When the HOMO energy level of the p-type semiconductor compound is −5.9 eV or more, the characteristics as a p-type semiconductor are improved, and when the HOMO energy level of the p-type semiconductor compound is −4.6 eV or less, the p-type semiconductor compound has p-type characteristics. The stability of the semiconductor compound is improved and the open circuit voltage (Voc) is also improved.

The LUMO (lowest unoccupied molecular orbital) energy level of the p-type semiconductor compound is not particularly limited, but can be selected according to the type of the n-type semiconductor compound described later. In particular, when a fullerene compound is used as an n-type semiconductor compound, the LUMO energy level of the p-type semiconductor compound is usually −4.5 eV or more, preferably −4.3 eV or more. On the other hand, it is usually −2.5 eV or less, preferably −2.7 eV or less. When the LUMO energy level of the p-type semiconductor is −2.5 eV or less, the band gap is adjusted, light energy of a long wavelength can be effectively absorbed, and the short-circuit current density is improved. When the LUMO energy level of the p-type semiconductor compound is −3.9 eV or more, electron transfer to the n-type semiconductor compound is likely to occur, and the short-circuit current density is improved.

As a method for calculating the LUMO energy level and the HOMO energy level, there are a theoretically calculated method and a method of actually measuring. The theoretically calculated values include semi-empirical molecular orbital methods and non-empirical molecular orbital methods. Examples of the actual measurement method include ultraviolet-visible absorption spectrum measurement or measurement of ionization potential with an ultraviolet photoelectron analyzer (“AC-3”, manufactured by Riken Keiki Co., Ltd.) under normal temperature and normal pressure.
Among them, AC-3 measurement is preferable, and the AC-3 measurement method is used in the present invention.

[1.1.3 n-type semiconductor compound]
The n-type organic semiconductor compound is not particularly limited, but is generally a π-electron conjugated compound having a lowest unoccupied orbital (LUMO) level of 3.5 to 4.5 eV, such as fullerene or Perfluoro derivatives (eg, perfluoropentacene or perfluorophthalocyanine) in which hydrogen atoms of p-type organic semiconductor compounds are substituted with fluorine atoms, such as derivatives thereof, octaazaporphyrins, naphthalene tetracarboxylic acid anhydrides, naphthalene tetracarboxylic acid diimides, Examples thereof include aromatic carboxylic acid anhydrides such as perylenetetracarboxylic acid anhydride and perylenetetracarboxylic acid diimide, and polymer compounds containing the imidized product as a skeleton.

Among these n-type organic semiconductor compounds, fullerene or a derivative thereof is preferable because charge separation can be performed at high speed and efficiently from the polymer compound (1) (p-type organic semiconductor compound) having the specific structural unit of the present invention.
As fullerenes and derivatives thereof, C60 fullerene, C70 fullerene, C76 fullerene, C78 fullerene, C84 fullerene, C240 fullerene, C540 fullerene, mixed fullerene, fullerene nanotubes, and some of them are hydrogen atoms, halogen atoms, substituted or non-substituted. Examples include fullerene derivatives substituted with a substituted alkyl group, alkenyl group, alkynyl group, aryl group, heteroaryl group, cycloalkyl group, silyl group, ether group, thioether group, amino group, silyl group, and the like.

As the fullerene derivative, phenyl-C61-butyric acid ester, diphenyl-C62-bis (butyric acid ester), phenyl-C71-butyric acid ester, phenyl-C85-butyric acid ester or thienyl-C61-butyric acid ester is preferable. The carbon number of the alcohol moiety is preferably 1-30, more preferably 1-8, still more preferably 1-4, and most preferably 1.

Examples of preferred fullerene derivatives include phenyl-C61-butyric acid methyl ester ([60] PCBM), phenyl-C61-butyric acid n-butyl ester ([60] PCBnB), phenyl-C61-butyric acid isobutyl ester ([60] PCBiB). Phenyl-C61-butyric acid n-hexyl ester ([60] PCBH), phenyl-C61-butyric acid n-octyl ester ([60] PCBO), diphenyl-C62-bis (butyric acid methyl ester) (bis [60] PCBM) Phenyl-C71-butyric acid methyl ester ([70] PCBM), phenyl-C85-butyric acid methyl ester ([84] PCBM), thienyl-C61-butyric acid methyl ester ([60] ThCBM), C60 pyrrolidine tris acid, C60 pyrrolidine Tris acid ethyl ester N-methylfulleropyrrolidine (MP-C60), (1,2-methanofullerene C60) -61-carboxylic acid, (1,2-methanofullerene C60) -61-carboxylic acid t-butyl ester, JP2008- Metallocene fullerenes such as No. 130889, and fullerenes having a cyclic ether group such as US Pat. No. 7,329,709.

<1.2 Anode (II), Cathode (VI)>
The anode (II) and the cathode (VI) have a function of collecting holes and electrons generated by light absorption. Therefore, it is preferable to use an electrode (VI) (cathode) suitable for collecting electrons and an electrode (II) (anode) suitable for collecting holes for the pair of electrodes. Any one of the pair of electrodes may be translucent, and both may be translucent. Translucency means that sunlight passes through 40% or more. Moreover, it is preferable that the translucent transparent electrode has a sunlight transmittance of 70% or more in order to allow light to reach the active layer (IV) through the transparent electrode. The light transmittance can be measured with a normal spectrophotometer.

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

Examples of the material of the cathode (VI) include metals such as platinum, gold, silver, copper, iron, tin, zinc, aluminum, indium, chromium, lithium, sodium, potassium, cesium, calcium or magnesium and alloys thereof; Examples include inorganic salts such as lithium fluoride and cesium fluoride; metal oxides such as nickel oxide, aluminum oxide, lithium oxide, and cesium oxide. These materials are preferable because they are materials having a small work function. In addition, when an n-type semiconductor compound such as zinc oxide having conductivity is used as a material for the electron transport layer (V), a material having a large work function suitable for an anode, such as indium tin oxide (ITO). Can also be used as a material for the cathode (VI). From the viewpoint of electrode protection, the material of the cathode 1 (VI) is preferably a metal such as platinum, gold, silver, copper, iron, tin, aluminum, calcium or indium and an alloy using these metals.

The film thickness of the cathode (VI) 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 thickness of the cathode (VI) is 10 nm or more, the sheet resistance is suppressed, and when the thickness of the cathode (VI) is 10 μm or less, the light is efficiently supplied without reducing the light transmittance. Can be converted. When the cathode (VI) is used as a transparent electrode, it is necessary to select a film thickness that achieves both light transmittance and sheet resistance.

The sheet resistance of the cathode (VI) is not particularly limited, but is usually 1000Ω / sq or less, preferably 500Ω / sq or less, more preferably 100Ω / sq or less. Although there is no restriction | limiting in a lower limit, Usually, it is 1 ohm / sq or more.

As a method for forming the cathode (VI), there are 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 anode (II) is an electrode generally made of a conductive material having a work function larger than that of the cathode and having a function of smoothly extracting holes generated in the active layer (IV).

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

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

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

The film thickness of the anode (II) 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 anode (II) is 10 nm or more, the sheet resistance is suppressed, and when the film thickness of the anode (II) is 10 μm or less, the light is efficiently transferred without reducing the light transmittance. Can be converted. When the anode (II) 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 (II) is not particularly limited, but is usually 1Ω / sq or more, on the other hand, 1000Ω / sq or less, preferably 500Ω / sq or less, more preferably 100Ω / sq or less.

Examples of the method for forming the anode (II) include a vacuum film forming method such as an evaporation method or a sputtering method, or a wet coating method in which an ink containing nanoparticles and a precursor is applied to form a film.

Furthermore, the cathode (VI) and the anode (II) may have a laminated structure of two or more layers. Further, the characteristics (electrical characteristics, wetting characteristics, etc.) may be improved by performing a surface treatment on the cathode (VI) and the anode (II).

<1.3 Substrate (I)>
A photoelectric conversion element (VII) has the base material (I) which becomes a support body normally. That is, the electrodes (II) and (VI) and the active layer (IV) are formed on the substrate.

The material for the substrate (I) is not particularly limited as long as the effects of the present invention are not significantly impaired. Preferable examples of the material of the substrate (I) include inorganic materials such as quartz, glass, sapphire and titania; polyethylene terephthalate, polyethylene naphthalate, polyethersulfone, polyimide, nylon, polystyrene, polyvinyl alcohol, ethylene vinyl alcohol Organic materials such as copolymers, fluororesin films, polyolefins such as vinyl chloride or polyethylene, cellulose, polyvinylidene chloride, aramid, polyphenylene sulfide, polyurethane, polycarbonate, polyarylate, polynorbornene, or epoxy resins; paper or synthetic paper Paper materials; composite materials such as those obtained by coating or laminating a surface of a metal such as stainless steel, titanium, or aluminum to provide insulation;

Examples of 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 base material (I), 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 base material (I), it is 5 micrometers or more normally, 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. The film thickness of the substrate (I) is preferably 5 μm or more because the possibility that the strength of the photoelectric conversion element is insufficient is reduced. It is preferable that the film thickness of the substrate (I) is 20 mm or less because the cost is suppressed and the weight does not increase. When the material of the substrate (I) 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 film thickness of the glass substrate (I) 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 glass substrate (I) is 0.5 cm or less because the weight does not increase.

<1.4 Buffer layer (III, V)>
The photoelectric conversion element (VII) includes an active layer (IV), an anode (II) (hereinafter also referred to as “electrode (II)”), and a cathode (VI) (hereinafter also referred to as “electrode (VI)”). It is preferable to have buffer layers (III) and (V) between them. The buffer layer can be classified into an electron transport layer (V) and a hole transport layer (III). By providing the buffer layer, electrons or holes can be easily transferred between the active layer (IV) and the anode (II), and a short circuit between the electrodes can be prevented. However, in the present invention, the buffer layers (III) and (V) may not exist.

The electron transport layer (V) and the hole transport layer (III) are arranged so as to sandwich the active layer (IV) between the pair of electrodes (II) and (VI). That is, when the photoelectric conversion element (VII) according to the present invention includes both the electron transport layer (V) and the hole transport layer (III), the cathode (VI), the electron transport layer (V), and the active layer (IV) , Hole transport layer (III), and anode (II) are arranged in this order. When the photoelectric conversion element (VII) according to the present invention includes the electron transport layer (V) and does not include the hole transport layer (III), the cathode (VI), the electron transport layer (V), the active layer (IV), and The anode (II) is arranged in this order.

[1.4.1 Electron Transport Layer (V)]
The electron transport layer (V) is a layer for extracting electrons from the active layer (IV) to the cathode (VI), and is not particularly limited as long as it is an electron transport material that improves the efficiency of electron extraction. A compound or an inorganic compound may be used, but an inorganic compound is preferable.

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

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

The HOMO energy level of the material of the electron transport layer (V) 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. It is preferable that the HOMO energy level of the material of the electron transport layer (V) is −5.0 eV or less from the viewpoint that holes can be prevented from moving. As a method for calculating the LUMO energy level and the HOMO energy level of the material of the electron transport layer (V), a cyclic voltammogram measurement method may be mentioned.

The film thickness of the electron transport layer (V) is not particularly limited, but is usually 0.1 nm or more, preferably 0.5 nm or more, more preferably 1.0 nm or more. On the other hand, it is usually 100 nm or less, preferably 70 nm or less, more preferably 40 nm or less, and particularly preferably 20 nm or less. When the film thickness of the electron transport layer (V) is 0.1 nm or more, it functions as a buffer material. When the film thickness of the electron transport layer (V) is 100 nm or less, electrons are easily taken out. Thus, the photoelectric conversion efficiency can be improved.

[1.4.2 Hole transport layer (III)]
The hole transport layer (III) is a layer that extracts holes from the active layer (IV) to the anode (II), and any material that can improve the hole extraction efficiency can be used. There is no particular limitation. Specifically, conductive polymers in which polythiophene, polypyrrole, polyacetylene, triphenylenediamine, polyaniline or the like is doped with sulfonic acid and / or iodine, polythiophene derivatives having a sulfonyl group as a substituent, conductive organic materials such as arylamine Examples include compounds, metal oxides having p-type semiconductor properties such as molybdenum trioxide, vanadium pentoxide, or nickel oxide, and the above-described p-type semiconductor compounds. Among them, a conductive polymer doped with sulfonic acid is preferable, and poly (3,4-ethylenedioxythiophene) poly (styrenesulfonic acid) (PEDOT: PSS) in which a polythiophene derivative is doped with polystyrene sulfonic acid is more preferable. . A thin film of metal such as gold, indium, silver or palladium can also be used. A thin film of metal or the like may be formed alone or in combination with the above organic material.

The film thickness of the hole transport layer (III) is not particularly limited, but is usually 0.2 nm or more, preferably 0.5 nm or more, more preferably 1.0 nm or more. On the other hand, it is usually 400 nm or less, preferably 200 nm or less, more preferably 100 nm or less, and particularly preferably 70 nm or less. When the thickness of the hole transport layer 104 is 0.2 nm or more, it functions as a buffer material. When the thickness of the hole transport layer (III) is 400 nm or less, holes are easily extracted. The photoelectric conversion efficiency can be improved.

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

<1.5 Manufacturing Method of Photoelectric Conversion Element>
Although there is no restriction | limiting in particular in the manufacturing method of a photoelectric conversion element (VII), According to the following method, base material (I), anode (II), hole transport layer (III), active layer (IV), electron transport layer (V ) And the cathode (VI) can be sequentially laminated. For example, an indium tin oxide (ITO) transparent conductive film (cathode) patterned glass substrate (manufactured by Geomatic) is ultrasonically cleaned with acetone, then ultrasonically cleaned with ethanol, and then dried with nitrogen blow. Ozonation is performed to make a substrate with an anode. Next, PEDOT-PSS ([poly (3,4-ethylenedioxythiophene) -poly (styrenesulfonic acid)) used as a hole transport layer was applied with a spin coater (5000 rpm for 50 seconds) and then annealed at 200 ° C. for 10 minutes. And a hole transport layer can be formed. The active layer can be formed by carrying it in a glove box later, spin-coating a mixed solution of donor material and acceptor material in an inert gas atmosphere, and performing annealing treatment or drying under reduced pressure on a hot plate. Next, an electron transport layer in which tetraisopropyl orthotitanate in ethanol (about 0.3 v%) is spin-coated in the atmosphere and converted into titanium oxide by moisture in the atmosphere can be produced. Finally, aluminum as an electrode is vapor-deposited to form a cathode, and a photoelectric conversion element can be obtained.
In addition, photoelectric conversion elements having different configurations, for example, a photoelectric conversion element that does not have at least one of the hole transport layer (III) and the electron transport layer (V) can be manufactured by a similar method.

<1.6 Photoelectric conversion characteristics>
The photoelectric conversion characteristics of the photoelectric conversion element (VII) can be obtained as follows. The photoelectric conversion element (VII) is irradiated with AM1.5G light with a solar simulator at an irradiation intensity of 100 mW / cm 2 and current-voltage characteristics are measured. From the obtained current-voltage curve, photoelectric conversion characteristics such as photoelectric conversion efficiency (PCE), short circuit current density (Jsc), open circuit voltage (Voc), fill factor (FF), series resistance, and shunt resistance can be obtained.

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

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

<2. Organic Thin Film Solar Cell According to the Present Invention>
The photoelectric conversion element (VII) according to the present invention is preferably used as a solar cell, particularly a solar cell element of an organic thin film solar cell.

The use of the organic thin-film solar cell according to the present invention is not limited and can be used for any purpose. Examples of fields to which the organic thin film solar cell according to the present invention can be applied include building material solar cells, automotive solar cells, interior solar cells, railway solar cells, marine solar cells, airplane solar cells, and spacecrafts. Solar cells for home appliances, solar cells for home appliances, solar cells for mobile phones, solar cells for toys, and the like.

The organic thin film solar cell according to the present invention may be used as it is, or may be used as a solar cell module by installing a solar cell on the substrate (I). If a specific example is given, when using the board | plate material for building materials as a base material, a solar cell panel can be produced as a solar cell module by providing a thin film solar cell on the surface of this board | plate material.

The measurement method used in the synthesis example is as follows.

(NMR spectrum measurement)
About the benzobis thiazole compound, NMR spectrum measurement was performed using the NMR spectrum measuring apparatus (Agilent (formerly Varian), "400MR", and Bruker, "AVANCE500").

(High-resolution mass spectrum measurement)
The benzobisthiazole compound was subjected to high-resolution mass spectrum measurement (APCI: atmospheric pressure chemical ionization method) using a mass spectrometer (manufactured by Bruker Daltnics, “MicOTOF”).

(Gel permeation chromatography (GPC))
The molecular weight of the benzobisthiazole compound was measured using gel permeation chromatography (GPC). In the measurement, the benzobisthiazole compound was dissolved in a mobile phase solvent (chloroform) so as to have a concentration of 0.5 g / L, measured under the following conditions, and based on a calibration curve prepared using polystyrene as a standard sample. By converting, the weight average molecular weight of the benzobisthiazole compound was calculated. The GPC conditions in the measurement are as follows.
Mobile phase: Chloroform flow rate: 0.6 ml / min
Apparatus: HLC-8320GPC (manufactured by Tosoh Corporation)
Column: TSKgel (registered trademark) SuperHM-H´2 + TSKgel (registered trademark) SuperH2000 (manufactured by Tosoh Corporation)

(IR spectrum)
With respect to the benzobisthiazole compound, IR spectrum measurement was performed using an infrared spectrometer (manufactured by JASCO, “FT / IR-6100”).

(UV-visible absorption spectrum)
The obtained benzobisthiazole compound was dissolved in chloroform so as to have a concentration of 0.03 g / L, and an ultraviolet / visible spectroscope (manufactured by Shimadzu Corporation, “UV-2450”, “UV-3150”), and The UV-visible absorption spectrum was measured using a cell having an optical path length of 1 cm.

(Melting point measurement)
The melting point of the benzobisthiazole compound was measured using a melting point measurement apparatus (manufactured by Buchi, “M-560”).

(Ionization potential measurement)
A benzobisthiazole compound was formed on a glass substrate so as to have a thickness of 50 nm to 100 nm. The ionization potential of this membrane was measured with an ultraviolet photoelectron analyzer (“AC-3” manufactured by Riken Keiki Co., Ltd.) at room temperature and normal pressure.

An example of the synthesis of the polymer compound (1) used in this patent is shown below. The polymer compound (1) used in the present invention is not limited by the following synthesis examples, and the synthesis method itself may be synthesized with appropriate modifications within a range that can meet the purpose described above and below. Of course it is possible. In the following, “part” means “part by mass” and “%” means “mass%” unless otherwise specified.

(Synthesis Example 1)
Synthesis of DBTH-DT (2,6-bis-triisopropylsilanylbenzo [1,2-d; 4,5-d ′] bisthiazole)

Under a nitrogen atmosphere, DBTH (benzo [1,2-d; 4,5-d ′] bisthiazole, 4 g, 20.8 mmol) and tetrahydrofuran (160 mL) were added to a 200 mL flask, cooled to −40 ° C., and lithium diisopropylamide was added. The solution (1.5M solution, 29.1 mL, 43.7 mmol) was added dropwise. Thereafter, after stirring at −40 ° C. for 1 hour, triisopropyl chloride (8.8 mL, 41.6 mmol) was added dropwise, and the mixture was warmed to room temperature and stirred for 2 hours. After completion of the reaction, the aqueous layer obtained by adding 10% brine and separating the layers was extracted once with ethyl acetate, and then the organic layers were combined, washed with saturated brine, and dried over anhydrous magnesium sulfate. Next, the crude product obtained by filtration and concentration is purified by column chromatography (silica gel, chloroform) to give DBTH-DT (2,6-bis-triisopropylsilanylbenzo [1,2-d; 4,5-d '] Bisthiazole) was obtained as a white solid in 7.14 g (68% yield). ¹ H-NMR measurement, ¹³ C-NMR measurement, melting point measurement, and high-resolution mass spectrum analysis confirmed that the target compound was produced.

(Synthesis Example 2)
Synthesis of DI-DBTH-DT (4,8-diiodo-2,6-bis-triisopropylsilanylbenzo [1,2-d; 4,5-d ′] bisthiazole)

In a 200 mL flask under nitrogen atmosphere, DBTH-DT (2,6-bis-triisopropylsilanylbenzo [1,2-d; 4,5-d ′] bisthiazole, 3 g, 5.88 mmol), N, N, N ′, N′-tetramethylethylenediamine (1.84 mL, 12.4 mmol) and tetrahydrofuran (60 mL) were added and cooled to −40 ° C. to obtain a lithium diisopropylamide solution (1.5 M solution, 8.24 mL, 12.4 mmol). Was dripped. Thereafter, the mixture was stirred at 0 ° C. for 30 minutes, then cooled to −80 ° C., iodine (7.47 g, 29.4 mmol) was added, and the mixture was warmed to room temperature and stirred for 2 hours. After completion of the reaction, a 10% aqueous sodium hydrogen sulfite solution was added to separate the aqueous layer, and the aqueous layer was extracted once with ethyl acetate. The organic layers were combined and washed with 5% aqueous sodium bicarbonate and then with saturated brine. Dry using magnesium sulfate. The crude product obtained by filtration and concentration was purified by column chromatography (silica gel, chloroform / hexane = 1/1) to obtain DI-DBTH-DT (4,8-diiodo-2,6-bis-triisopropylsilanylbenzo [1,2-d; 4,5-d ′] bisthiazole) was obtained as a white solid in 1.95 g (44% yield). ¹ H-NMR measurement, ¹³ C-NMR measurement, melting point measurement, and high-resolution mass spectrum analysis confirmed that the target compound was produced.

(Synthesis Example 3)
Synthesis reaction of DBTH-C8THO (4,8-bis (5-octylthiophen-2-yl) benzo [1,2-d; 4,5-d ′] bisthiazole)

In a 50 mL flask under nitrogen atmosphere, DI-DBTH-DT (4,8-diiodo-2,6-bis-triisopropylsilanylbenzo [1,2-d; 4,5-d ′] bisthiazole, 500 mg, 0 .66 mmol), tributyl (5-octylthiophen-2-yl) stannane (962 mg, 1.98 mmol), tris (dibenzylideneacetone) dipalladium (0) -chloroform adduct (62 mg, 0.06 mmol), tris (2 -Furyl) phosphine (28 mg, 0.12 mmol) and N, N-dimethylformamide (10 mL) were added, and the mixture was heated to 60 ° C. and reacted for 18 hours. Then, it cooled to room temperature, the tetrabutylammonium fluoride solution (1M tetrahydrofuran solution, 2.0 mL, 1.98 mmol) was added, and it reacted for 3 hours. After completion of the reaction, water was added and the organic layer obtained by extraction twice with chloroform was washed with water and dried over anhydrous magnesium sulfate. The crude product obtained by filtration and concentration was purified by column chromatography (silica gel, chloroform / hexane = 1/1) to give DBTH-C8THO (4,8-bis (5-octylthiophen-2-yl) benzo [1, 2-d; 4,5-d ′] bisthiazole) was obtained as a yellow solid in 323 mg (84% yield). ¹ H-NMR measurement, IR spectrum measurement, and high-resolution mass spectrum analysis confirmed that the target DBTH-C8THO was produced.

(Synthesis Example 4)
Similarly to Synthesis Example 3, DBTH-EHT (4,8-bis [5- (2-ethylhexyl) thiophen-2-yl] benzo [1,2-d; 4,5-d ′] bisthiazole) was obtained. It was. The yield was 72 to 84%.

(Synthesis Example 5)
Synthesis of DBTH-C8THO-DSM (4,8-bis (5-octylthiophen-2-yl) -2,6-bistrimethylstannylbenzo [1,2-d; 4,5-d ′] bisthiazole) (Dinning reaction of DBTH-C8THO)

In a nitrogen atmosphere, DBTH-C8THO (180 mg, 0.31 mmol) and tetrahydrofuran (6 mL) were added to a 30 mL flask, cooled to 0 ° C., and a lithium diisopropylamide solution (2 M solution, 0.33 mL, 0.65 mmol) was added dropwise. Thereafter, the mixture was stirred at 0 ° C. for 30 minutes, cooled to −80 ° C., trimethyltin chloride (0.65 mL, 0.65 mmol) was added, and the mixture was warmed to room temperature and stirred for 2 hours. After completion of the reaction, water was added and the organic layer obtained by extraction once with toluene was washed with saturated brine and dried over anhydrous magnesium sulfate. When the crude product obtained by filtration and concentration was purified by GPC-HPLC (JAIGEL-1H, 2H, chloroform), DBTH-C8THO-DSM (4,8-bis (5-octylthiophen-2-yl) -2,6 -Bistrimethylstannylbenzo [1,2-d; 4,5-d ′] bisthiazole) was obtained as a solid in 93 mg (33% yield).

(Synthesis Example 6)
As in Synthesis Example 5, DBTH-EHT-DSM (4,8-bis [5- (2-ethylhexyl) thiophen-2-yl] -2,6-bistrimethylstannylbenzo [1,2-d; 4 , 5-d ′] bisthiazole). The yield was 70%.

(Synthesis Example 7)
Synthesis of P-DBTH-C8TH-O-DPP

In a 30 mL flask under nitrogen atmosphere, DBTH-C8THO-DSM (92 mg, 0.10 mmol), O-DPP-DB (3,6-bis (5-bromothiophen-2-yl) -2,5-dioctyl-2 , 5-dihydropyrrolo [3,4-c] pyrrole-1,4-dione, 69 mg, 0.10 mmol), tris (dibenzylideneacetone) dipalladium (0) -chloroform adduct (4.2 mg, 4.1 μmol) ), Tris (o-tolyl) phosphine (4.9 mg, 16 μmol) and chlorobenzene (6 mL) were added and reacted at 110 ° C. for 46 hours. After completion of the reaction, the reaction solution was added to methanol (35 mL), the precipitated solid was collected by filtration, and the obtained solid was washed with Soxhlet (methanol, acetone, hexane). Subsequent extraction with Soxhlet (chloroform) gave 42 mg (37%) of P-DBTH-C8TH-O-DPP as a black solid.

(Synthesis Examples 8 to 9)
In the same manner as in Synthesis Example 7, P-DBTH-EHT-EH-DPP (Synthesis Example 8) and P-DHD-DBTH-O-IMTHT (Synthesis Example 9) were obtained. Yields were 27-83%.

(Synthesis Example 10)
Synthesis reaction of DHD-DBTH (4,8-bis (2-hexyldecyloxy) benzo [1,2-d; 4,5-d ′] bisthiazole)

In a 50 mL flask under a nitrogen atmosphere, DI-DBTH-DT (4,8-diiodo-2,6-bis-triisopropylsilanylbenzo [1,2-d; 4,5-d ′] bisthiazole, 3 g, 4.0 mmol), 2-hexyldecanol (5.8 g, 23.8 mmol), copper (I) iodide (151 mg, 0.79 mmol), 1,10-PHT (1,10-phenanthroline, 286 mg, 1.59 mmol) , T-butoxy sodium (1.14 g, 11.9 mmol) and 1,4-dioxane (30 mL) were added and reacted under reflux for 23 hours. After cooling to room temperature, tetrabutylammonium fluoride (1M-tetrahydrofuran solution, 12.0 mL, 11.9 mmol) was added, and the mixture was further reacted at room temperature for 3 hours. After completion of the reaction, water was added and the organic layer obtained by extraction twice with chloroform was washed with water and dried over anhydrous magnesium sulfate. The crude product obtained by filtration and concentration was purified by column chromatography (silica gel, chloroform / hexane = 1/1) to obtain DHD-DBTH (4,8-bis (2-hexyldecyloxy) benzo [1,2-d ; 4,5-d '] bisthiazole) was obtained as a brown oil in 1.30 g (49% yield).

(Synthesis Examples 11 to 12)
As in Synthesis Example 10, DEH-DBTH (4,8-bis (2-ethylhexyloxy) benzo [1,2-d; 4,5-d ′] bisthiazole) (Synthesis Example 11), DDMO-DBTH (4,8-bis (3,7-dimethyloctyloxy) benzo [1,2-d; 4,5-d ′] bisthiazole) (Synthesis Example 12) was obtained. The yield was 49-60%.

(Synthesis Example 13)
Synthesis of DHD-DBTH-DSB (4,8-bis (2-hexyldecyloxy) -2,6-bistributylstannylbenzo [1,2-d; 4,5-d ′] bisthiazole) (DHD- DBTH stannation reaction)

Under a nitrogen atmosphere, in a 30 mL flask was added DHD-DBTH (4,8-bis (2-hexyldecyloxy) benzo [1,2-d; 4,5-d ′] bisthiazole, 1 g, 1.49 mmol) and tetrahydrofuran ( 20 mL) was added, the mixture was cooled to −80 ° C., and n-butyllithium (1.6 M hexane solution, 1.95 mL, 3.12 mmol) was added dropwise. After stirring for 30 minutes, tributyltin chloride (0.87 mL, 3.19 mmol) was added, and the mixture was warmed to room temperature and stirred for 2 hours. After completion of the reaction, water was added and the organic layer obtained by extraction once with toluene was washed with saturated brine and dried over anhydrous magnesium sulfate. The crude product obtained by filtration and concentration was purified by GPC-HPLC (JAIGEL-1H, 2H, chloroform) to obtain DHD-DBTH-DSB (4,8-bis (2-hexyldecyloxy) -2,6-bistributyl. Stannylbenzo [1,2-d; 4,5-d ′] bisthiazole) was obtained as a brown oil in 1.12 g (yield 63%). It was confirmed by ¹ H-NMR measurement that the target compound was produced.

(Synthesis Examples 14 to 15)
As in Synthesis Example 13, DEH-DBTH-DSB (4,8-bis (2-ethylhexyloxy) -2,6-bistributylstannylbenzo [1,2-d; 4,5-d ′] bis Thiazole) (Synthesis Example 14), DDMO-DBTH-DSB (4,8-bis (3,7-dimethyloctyloxy) -2,6-bistributylstannylbenzo [1,2-d; 4,5-d '] Bisthiazole) (Synthesis Example 15) was obtained. The yield was 33-70%.

(Synthesis Example 16)
Synthesis of P-DHD-DBTH-O-IMTHT

In a 20 mL flask under nitrogen atmosphere, DHD-DBTH-DSB (4,8-bis (2-hexyldecyloxy) -2,6-bistributylstannylbenzo [1,2-d; 4,5-d ′] Bisthiazole, 0.14 mmol), O-IMTHT-DB (1,3-dibromo-5-octylthieno [3,4-c] pyrrole-4,6-dione, 0.14 mmol), tris (dibenzylideneacetone) di Palladium (0) -chloroform adduct (5.6 mg, 5.4 μmol), tris (o-tolyl) phosphine (6.2 mg, 22 μmol) and chlorobenzene (12 mL) were added and reacted at 120 ° C. for 24 hours. After completion of the reaction, the reaction solution was added to methanol (60 mL), the precipitated solid was collected by filtration, and the obtained solid was subjected to Soxhlet washing (methanol, acetone). Subsequently, P-DHD-DBTH-O-IMTHT was obtained as a solid with a yield of 75% by Soxhlet extraction (chloroform).

(Synthesis Examples 17 to 21)
Similar to Synthesis Example 16, P-DHD-DBTH-TDZT (Synthesis Example 17), P-DHD-DBTH-DMO-DPP (Synthesis Example 18), P-DHD-DBTH-3HTDZT (Synthesis Example 19), P- DEH-DBTH-EH-DPP (Synthesis Example 20) and P-DDMO-DBTH-EH-BDT (Synthesis Example 21) were obtained. Yields were 19-99%.

(Evaluation method of photoelectric conversion element)
A 0.0550 mm square metal mask is attached to the photoelectric conversion element, a solar simulator (CEP2000, AM1.5G filter, radiation intensity 100 mW / cm ² , manufactured by Spectrometer) is used as an irradiation light source, and a source meter (type 2400 manufactured by Keithley, Inc.). ) To measure the current-voltage characteristics between the ITO electrode and the aluminum electrode. From this measurement result, open circuit voltage Voc (V), short circuit current density Jsc (mA / cm 2), fill 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 curve 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

(Preparation of mixed solution of p-type semiconductor compound and n-type semiconductor compound)
As the p-type semiconductor compound, a polymer compound having a structure of P-DBTH-C8TH-O-DPP [Chem. 28] was used.
PC61BM (phenyl C61 butyric acid methyl ester, manufactured by Frontier Carbon Corporation, NS-) as an n-type semiconductor compound is dissolved in chlorobenzene at a total concentration of 1.6 wt%, p-type semiconductor compound: n-type semiconductor compound = 1: 1 (weight). I let you. This solution was stirred and mixed for 2 hours or more at a temperature of 100 ° C. on a hot stirrer. The solution after stirring and mixing was filtered through a 0.45 μm filter to obtain a mixed solution of a p-type semiconductor compound and an n-type semiconductor compound.

(Preparation of photoelectric conversion element)
A glass substrate (manufactured by Geomatic Co., Ltd.) on which an indium tin oxide (ITO) transparent conductive film (cathode) was patterned was ultrasonically cleaned with acetone, then ultrasonically cleaned with ethanol, and then dried by nitrogen blowing.

After performing UV-ozone treatment, after applying PEDOT-PSS ([poly (3,4-ethylenedioxythiophene) -poly (styrenesulfonic acid)) used as a hole transport layer with a spin coater (5000 rpm, 60 seconds) Annealed at 200 ° C. for 10 minutes.

搬 carried into the glove box, spin-coated with a mixed solution of p-type semiconductor compound and n-type semiconductor compound in an inert gas atmosphere, and dried under reduced pressure.

In the air, an ethanol solution of tetraisopropyl orthotitanate (about 0.3 v%) was spin-coated, and a film converted into titanium oxide by moisture in the atmosphere was created. Then, aluminum which is an electrode was vapor-deposited to make a device. The obtained device evaluated the said photoelectric conversion element. The results are shown in Table 1.

As the p-type semiconductor compound, a high molecular compound having a structure of P-DBTH-EHT-EH-DPP [Chemical 29] was used.
Using PCBM (C61) as an n-type semiconductor compound, p-type semiconductor compound: n-type semiconductor compound = 1: 1 (weight), dissolved in chlorobenzene at a total concentration of 1.6 wt%, and passed through a 0.45 μm filter. A mixed solution was obtained. Using the obtained mixed solution, a device was produced in the same manner as in Example 1. The obtained device evaluated the said photoelectric conversion element. The results are shown in Table 1.

As the p-type semiconductor compound, a polymer compound having a structure of P-DHD-DBTH-O-IMTHT [Chemical Formula 30] was used.
Using PCBM (C61) as an n-type semiconductor compound, p-type semiconductor compound: n-type semiconductor compound = 1: 2 (weight), 6% (v / v) 1,8-di at a total concentration of 3.0 wt% It was dissolved in orthodichlorobenzene containing iodooctane and passed through a 0.45 μm filter to obtain a mixed solution. Using the obtained mixed solution, a device was produced in the same manner as in Example 1. The obtained device evaluated the said photoelectric conversion element. The results are shown in Table 1.

As the p-type semiconductor compound, a polymer compound having a structure of P-DHD-DBTH-TDZT [Chemical Formula 31] was used.
Using PCBM (C61) as an n-type semiconductor compound, p-type semiconductor compound: n-type semiconductor compound = 1: 1.5 (weight), and dissolved in chlorobenzene at a total concentration of 2.0 wt% to form a 0.45 μm filter. A mixed solution was obtained. Using the obtained mixed solution, a device was produced in the same manner as in Example 1. The obtained device evaluated the said photoelectric conversion element. The results are shown in Table 1.

As the p-type semiconductor compound, a polymer compound having a structure of P-DHD-DBTH-DMO-DPP [Chemical Formula 32] was used.
Using PCBM (C61) as an n-type semiconductor compound, p-type semiconductor compound: n-type semiconductor compound = 1: 1.5 (weight), and dissolved in chlorobenzene at a total concentration of 2.5 wt% to form a 0.45 μm filter. A mixed solution was obtained. Using the obtained mixed solution, a device was produced in the same manner as in Example 1. The obtained device evaluated the said photoelectric conversion element. The results are shown in Table 1.

As the p-type semiconductor compound, a polymer compound having a structure of P-DHD-DBTH-3HTDZT [Chemical Formula 33] was used.
Using PCBM (C61) as an n-type semiconductor compound, p-type semiconductor compound: n-type semiconductor compound = 1: 2 (weight), and dissolved in orthodichlorobenzene at a total concentration of 3.0 wt% to form a 0.45 μm filter. A mixed solution was obtained. Using the obtained mixed solution, a device was produced in the same manner as in Example 1. The obtained device evaluated the said photoelectric conversion element. The results are shown in Table 1.

As the p-type semiconductor compound, a polymer compound having a structure of P-DEH-DBTH-EH-DPP [Chemical Formula 34] was used.
Using PCBM (C61) as an n-type semiconductor compound, p-type semiconductor compound: n-type semiconductor compound = 1: 1.5 (weight), and dissolved in chlorobenzene at a total concentration of 2.0 wt% to form a 0.45 μm filter. A mixed solution was obtained. Using the obtained mixed solution, a device was produced in the same manner as in Example 1. The obtained device evaluated the said photoelectric conversion element. The results are shown in Table 1.

As the p-type semiconductor compound, a polymer compound having a structure of P-DDMO-DBTH-EH-BDT [Chemical Formula 35] was used.
Using PCBM (C61) as an n-type semiconductor compound, p-type semiconductor compound: n-type semiconductor compound = 1: 2.0 (weight), dissolved in orthodichlorobenzene at a total concentration of 3.0 wt%, 0.45 μm The solution was passed through a filter. Using the obtained mixed solution, a device was produced in the same manner as in Example 1. The obtained device evaluated the said photoelectric conversion element. The results are shown in Table 1.

As the p-type semiconductor compound, a polymer compound having a structure of P-DHD-DBTH-TDZT [Chemical Formula 31] was used.
Using PCBM (C61) as an n-type semiconductor compound, p-type semiconductor compound: n-type semiconductor compound = 1: 1.5 (weight), and dissolved in chlorobenzene at a total concentration of 2.0 wt% to form a 0.45 μm filter. As a result, a mixed solution of p-type semiconductor compound and n-type semiconductor compound was obtained.

Lithium fluoride as an electron transfer layer was vapor-deposited with a vapor deposition machine, and then aluminum as an electrode was vapor-deposited to obtain a device. The obtained device evaluated the said photoelectric conversion element. The results are shown in Table 1.

After the UV-ozone treatment, PEDOT-PSS ([poly (3,4-ethylenedioxythiophene) -poly (styrenesulfonic acid)) used as a hole transport layer was applied with a spin coater (5000 rpm for 60 seconds). Annealed at 200 ° C. for 10 minutes.

Calcium which is an electron transfer layer was vapor-deposited with a vapor deposition machine, and then aluminum which was an electrode was vapor-deposited to obtain a device. The obtained device evaluated the said photoelectric conversion element. The results are shown in Table 1.

As the p-type semiconductor compound, a polymer compound having a structure of P-DDMO-DBTH-EH-BDT [Chemical Formula 35] was used.
Using PCBM (C61) as an n-type semiconductor compound, p-type semiconductor compound: n-type semiconductor compound = 1: 2.0 (weight), dissolved in orthodichlorobenzene at a total concentration of 3.0 wt%, 0.45 μm The solution was passed through a filter. A device was produced in the same manner as in Example 9 using the obtained mixed solution. The obtained device evaluated the said photoelectric conversion element. The results are shown in Table 1.

As described above, it was confirmed that most of the photoelectric conversion elements made of the polymer compound used in the present invention showed a high voltage of 0.7 V or more because the HOMO level was moderately deep. Furthermore, it is confirmed that the polymer compound used in the present invention can introduce various skeletons and substituents according to the production method, and fine adjustment of Voc of the photoelectric conversion element is possible.

(VII) Photoelectric conversion element (VI) Cathode (V) Electron transport layer
(IV) Active layer (III) Hole transport layer (II) Anode (I) Base material

Claims

A photoelectric conversion element having a structure in which a base material, an anode, an active layer, and a cathode are arranged in this order, wherein the active layer has a benzobisthiazole structural unit represented by formula (1) A photoelectric conversion element comprising a molecular compound.

[In Formula (1),
A 1 and A 2 are each independently an alkoxy group, a thioalkoxy group, a thiophene ring optionally substituted with a hydrocarbon group, a thiazole ring optionally substituted with a hydrocarbon group or an organosilyl group, or It represents a phenyl group which may be substituted with a hydrocarbon group, an alkoxy group, a thioalkoxy group, an organosilyl group, a halogen atom, or a trifluoromethyl group. ]
2. The photoelectric conversion element according to claim 1 , wherein A 1 and A 2 of the polymer compound are groups represented by the following formulas (a1) to (a4), respectively.

[In the formulas (a1) to (a4),
R 21 to R 25 each independently represents a hydrocarbon group having 8 to 30 carbon atoms. * Represents a bond bonded to the benzene ring of benzobisthiazole. ]
3. The photoelectric conversion element according to claim 1, wherein the polymer compound is a donor-acceptor type semiconductor polymer.
The photoelectric conversion element according to any one of claims 1 to 3, wherein the active layer further contains an n-type organic semiconductor compound.
The photoelectric conversion element according to claim 4, wherein the n-type organic semiconductor compound is fullerene or a derivative thereof.
6. The photoelectric conversion element according to claim 1, further comprising a hole transport layer between the anode and the active layer.
The photoelectric conversion device according to any one of claims 1 to 6, further comprising an electron transport layer between the cathode and the active layer.
The photoelectric conversion element according to any one of claims 1 to 7, wherein the anode is a transparent electrode.
The photoelectric conversion element according to any one of claims 1 to 8, wherein the cathode is a metal electrode.
An organic thin film solar cell comprising the photoelectric conversion device according to any one of claims 1 to 9.