JP2011168747A - Conjugated polymer, and organic thin film solar cell using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conjugated polymer which is excellent in film-forming properties and also excellent in the light absorption characteristics in a region of long wavelengths and which is capable of achieving a high open voltage value between this polymer and fullerenes; and an organic thin film solar cell provided with the photoelectric conversion layer using this conjugated polymer. <P>SOLUTION: The conjugated polymer comprises a repeating unit expressed by formula (1) and a repeating unit expressed by formula (2). In formula (1), R is a hydrogen atom or a univalent organic group. In formula (2), X is a divalent conjugated linkage group which is different from the repeating unit expressed by formula (1). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a conjugated polymer and an organic thin film solar cell using the conjugated polymer. More specifically, the present invention relates to a conjugated polymer including a thiophene group having an imide ring and a linking group having a divalent conjugated structure, and an organic thin-film solar cell obtained using the conjugated polymer. .

  The organic thin film solar cell has a simple element structure in which a p-type (electron donor property) organic semiconductor material and an n-type (electron acceptor property) organic semiconductor material are combined. Unlike a wet solar cell typified by a dye-sensitized solar cell, this battery is excellent in workability because it does not use an electrolyte and can be formed into a desired shape. In addition, since the battery can be much lighter than a silicon solar battery or a dye-sensitized solar battery, it can be applied to various installation locations. Furthermore, since there are no resource restrictions such as the use of high-purity silicon or precious metals, it is estimated that the cost can be significantly reduced as the market share increases.

  One of the problems of organic thin film solar cells is improvement of energy conversion efficiency (photoelectric conversion efficiency). In order to improve the photoelectric conversion efficiency, it is important to improve the open-circuit voltage value. The open-circuit voltage value of the organic thin film solar cell greatly depends on the combination of the electron donating material and the electron accepting material, and a breakthrough is necessary for optimization of the material used.

  Currently, in a series of organic thin film solar cell researches that are being promoted around the world, fullerenes (for example, fullerene derivatives such as PCBM) are considered to be optimal as n-type semiconductor materials. It is known that HOMO (maximum occupied molecular orbital) of PCBM is 6.0 eV and LUMO (lowest unoccupied molecular orbital) is 4.2 eV (Non-patent Document 1).

  On the other hand, a p-type semiconductor material currently most commonly used includes a conjugated polymer compound of a polythiophene derivative (for example, P3HT: poly-3-hexylthiophene-2,5-diyl). It is known that the HOMO (maximum occupied molecular orbital) of this P3HT is 3.2 eV and the LUMO (lowest unoccupied molecular orbital) is 5.2 eV.

Barry C. Thompson and one other, Angewandte Chemie International Edition, 2008, Vol. 47, pp. 58-77.

On the other hand, as shown in Non-Patent Document 1, P3HT did not necessarily show ideal HOMO levels and LUMO levels with respect to fullerenes which are n-type semiconductor materials (see FIG. 17). Actually, in an organic thin-film solar cell including a photoelectric conversion layer containing P3HT and PCBM, the open-circuit voltage value is not always satisfactory from a practical viewpoint, and further improvement is necessary.
As a method for improving the open-circuit voltage value, a means for lowering the HOMO level of the p-type semiconductor material is conceivable. In this case, the band gap (difference between the LUMO level and the HOMO level) of the p-type semiconductor material is widened and long It becomes impossible to absorb light in the wavelength region. That is, there is a drawback in that the light absorption efficiency on the long wavelength side in the visible light region is reduced, the incident light cannot be used effectively, and as a result, the energy conversion efficiency does not increase.
As described above, the open-circuit voltage value and the light absorption in the long wavelength region often have a trade-off relationship, and it has been difficult to achieve both at a higher level.

  In view of the above circumstances, the present invention provides a conjugated polymer that is excellent in film formability, excellent in light absorption characteristics in a long wavelength region, and capable of realizing a high open-circuit voltage value with fullerenes, and An object of the present invention is to provide an organic thin-film solar cell including a photoelectric conversion layer using a conjugated polymer.

As a result of intensive studies, the present inventors have found that the above problem can be solved by using a conjugated polymer having a thiophene structure having a predetermined imide ring and a π-conjugated linking group.
That is, the present inventors have found that the above problem is solved by the following configuration.

<1> A conjugated polymer having a repeating unit represented by the following general formula (1) and a repeating unit represented by the following general formula (2).
<2> X in the general formula (1) is a divalent aromatic hydrocarbon group, a divalent aromatic heterocyclic group, — (CH═CH) —, — (C≡C) —, or The conjugated polymer according to <1>, which is a combined group.
<3> A first electrode layer and a second electrode layer that is an electrode facing the first electrode layer,
An organic thin-film solar cell comprising a photoelectric conversion layer containing at least a conjugated polymer and a fullerene according to <1> or <2> between the first electrode layer and the second electrode layer.

  ADVANTAGE OF THE INVENTION According to this invention, it is excellent in film forming property, is excellent in the light absorption characteristic in a long wavelength region, and can provide a high open circuit voltage value with fullerenes, and this conjugated polymer An organic thin-film solar cell provided with a photoelectric conversion layer using can be provided.

It is typical sectional drawing of 1st Embodiment of the organic thin-film solar cell of this invention. It is typical sectional drawing of 2nd Embodiment of the organic thin-film solar cell of this invention. It is typical sectional drawing of 3rd Embodiment of the organic thin-film solar cell of this invention. It is typical sectional drawing of 4th Embodiment of the organic thin-film solar cell of this invention. FIG. 5A shows ¹ H NMR measurement results of PDT, FIG. 5B shows IR measurement results, and FIG. 5C shows UV measurement and fluorescence measurement results. 6A shows the ¹ H NMR measurement results of POT, FIG. 6B shows the IR measurement results, and FIG. 6C shows the UV measurement and fluorescence measurement results. 7A shows the results of ¹ H NMR measurement of PHOT, FIG. 7B shows the results of IR measurement, and FIG. 7C shows the results of UV measurement. FIG. 8A shows PHHT ¹ H NMR measurement results, FIG. 8B shows IR measurement results, and FIG. 8C shows UV measurement and fluorescence measurement results. 9A shows the results of ¹ H NMR measurement of PPHT, FIG. 9B shows the results of IR measurement, and FIG. 9C shows the results of UV measurement and fluorescence measurement. FIG. 10 shows the ¹ H NMR measurement result of PTPF. FIG. 11 shows the results of UV measurement and fluorescence measurement of PTPB. It is an absorption spectrum figure of the chloroform solution of PDT and P3HT. It is an energy level diagram of the conjugated polymer of the present invention. FIG. 14A is a top view of an organic thin-film solar cell used in Examples, and FIG. 14B is a schematic cross-sectional view. It is an absorption spectrum figure of a PDT: PCBM film | membrane and a P3HT: PCBM film | membrane. It is a photocurrent action spectrum figure of the organic thin film solar cell of Example 3. 2 is an energy level diagram of P3HT and PCMB described in Non-Patent Document 1. FIG.

Below, the conjugated polymer which has the repeating unit represented by General formula (1) based on this invention and the repeating unit represented by General formula (2), and the photoelectric converting layer using this conjugated polymer An organic thin film solar cell comprising:
First, the configuration of the conjugated polymer and the production method thereof will be described in detail.

<Conjugated polymer>
The conjugated polymer of the present invention is a polymer having a repeating unit represented by the following general formula (1) and a repeating unit represented by the following general formula (2) in the main chain.
The imide ring part in the repeating unit represented by the general formula (1) has an electron-withdrawing function, and by containing this part in a conjugated polymer, a more preferable electronic state for fullerenes Is presumed to be realized. Usually, when polymerization is performed using a compound in which an electron-withdrawing group is introduced at two β-positions in the thiophene skeleton, the molecular weight of the resulting polymer does not increase, and the desired film formability is often not obtained. The conjugated polymer of the present invention has satisfactory film forming properties from a practical viewpoint.
In addition, in the polymer obtained only from the repeating unit represented by the general formula (1) described in the publicly known literature, the molecular weight does not increase and does not have sufficient film formability to be applicable to an organic thin film solar cell. . Moreover, the LUMO level is calculated to be about 6 ev, and it can be said that the energy level is inappropriate for application to organic thin-film solar cells together with fullerenes.

(Repeating unit represented by general formula (1))
In general formula (1), R represents a hydrogen atom or a monovalent organic group.
Although it does not specifically limit as a monovalent organic group, For example, the group etc. which combined the alkyl group, the alkenyl group, the alkynyl group, the aryl group, the heterocyclic group, the alkoxy group, the aryloxy group, etc. are mentioned.
These exemplified groups may have a substituent. The type of the substituent is not particularly limited as long as the effect of the present invention is not impaired. For example, halogen atom, nitro group, cyano group, sulfonic acid group, carbonyloxy group, carboxyl group, amino group, alkyl group, alkenyl group, alkynyl group, aryl group, heterocyclic group, alkoxy group, aryloxy group, carboxylic acid Examples include esters, sulfonic acid ester groups, and amide groups.
Further, the organic group may contain a divalent linking group moiety such as —O—, —S—, —SO ₂ —, —CO—, —NH—, etc., as long as the effects of the present invention are not impaired. Good.

The organic group is preferably an aliphatic hydrocarbon group such as an alkyl group, an alkenyl group, and an alkynyl group, more preferably an alkyl group, from the viewpoint of excellent film forming properties.
The aliphatic hydrocarbon group may be linear, branched or cyclic, preferably has 6 to 30 carbon atoms, and more preferably has 8 to 20 carbon atoms.
Specific examples of the alkyl group include hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group and the like.

  In addition, when the repeating unit represented by several general formula (1) is contained in a conjugated polymer, R may be the same or different in each repeating unit.

(Repeating unit represented by general formula (2))
In the general formula (2), X represents a divalent conjugated linking group different from the repeating unit structure (linking group) represented by the general formula (1). The conjugated linking group means a linking group having a π-conjugated structure. By the presence of a linking group having such a π-conjugated structure in the polymer, the π-conjugated plane spreads throughout the polymer, and the properties as a p-type semiconductor material are further improved.
In addition, when the repeating unit represented by several general formula (2) is contained in a conjugated polymer, several X may be same or different.

  X will not be specifically limited if it is a bivalent coupling group which consists of conjugated structures other than the repeating unit represented by General formula (1). Among them, a divalent aromatic hydrocarbon group, a divalent aromatic heterocyclic group, — (CH═CH) —, —, in which the synthesis is simple and the effects of the present invention such as film forming properties are more excellent. (C≡C) — or a linking group formed by combining two or more groups selected from these is preferable. Of these, an aromatic linking group selected from a divalent aromatic hydrocarbon group, a divalent aromatic heterocyclic group, and a group obtained by combining them is preferable because the effects of the present invention are more excellent.

Although carbon number of an aromatic hydrocarbon group is not specifically limited, From a synthetic viewpoint, C5-C40 is preferable, C6-C20 is more preferable, An arylene group etc. are mentioned.
As the aromatic hydrocarbon group, for example, benzene ring group, naphthalene ring group, anthracene ring group, tetralin ring group, phenanthrene ring group, fluorene ring group, azulene ring group, pyrene ring group, chrysene ring group, triphenylene ring group, Perylene ring group, pentalene ring group, indacene ring group, phenalene ring group, fluoranthene ring group, acephenanthrylene ring group, asanthrylene ring group, naphthacene ring group, preaden ring group, pentaphen ring group, pentacene ring group, Examples include a tetraphenylene ring group, a hexaphen ring group, and a hexacene ring group. Of these, a fluorene ring group, a benzene ring group, and a naphthalene ring group are preferable. In addition, a bond is formed in any of the bondable portions in the group.

Although carbon number of an aromatic heterocyclic group is not specifically limited, From a synthetic viewpoint, C5-C40 is preferable, C6-C20 is more preferable, Nitrogen-containing or a sulfur-containing aromatic heterocyclic ring etc. are mentioned. .
Examples of the aromatic heterocyclic group include pyrrole ring group, indole ring group, isoindole ring group, carbazole ring group, furan ring group, coumarone ring group, isobenzofuran ring group, thiophene ring group, benzothiophene ring group, dibenzo Thiophene ring group, pyrazole ring group, indazole ring group, imidazole ring group, benzimidazole ring group, oxazole ring group, benzoxazole ring group, benzoxazoline ring group, isoxazole ring group, benzoisoxazole ring group, thiazole ring group, Benzothiazole ring group, benzothiazoline ring group, isothiazole ring group, benzoisothiazole ring group, triazole ring group, benzotriazole ring group, oxadiazole ring group, thiadiazole ring group, benzooxadiazole ring group, benzothiadiazole ring Group, tetrazole ring group, Ring group, pyridine ring group, quinoline ring group, isoquinoline ring group, acridine ring group, phenanthridine ring group, benzoquinoline ring group, benzoisoquinoline ring group, naphthyridine ring group, phenanthroline ring group, pyridazine ring group, pyrimidine ring Group, pyrazine ring group, phthalazine ring group, quinoxaline ring group, quinazoline ring group, cinnoline ring group, phenazine ring group, perimidine ring group, triazine ring group, tetrazine ring group, pteridine ring group, benzoxazine ring group, phenoxazine ring Group, benzothiazine ring group, phenothiazine ring group, oxadiazine ring group, thiadiazine ring group, benzodioxole ring group, benzodioxane ring group, pyran ring group, chromene ring group, xanthene ring group, chroman ring group, isochroman ring group, etc. Is mentioned. Of these, a thiophene ring group, a benzothiadiazole ring group, and the like are preferable. In addition, a bond is formed in any of the bondable portions in the group.

  The conjugated linking group represented by X may have a substituent, and examples of the substituent include a substituent that the organic group represented by R described above may have.

  The conjugated linking group may be a linking group formed by combining two or more of the above-described linking groups, and a group obtained by combining two or three of the linking groups described above is more preferable. For example, aromatic carbonization such as-(aromatic hydrocarbon group)-(aromatic hydrocarbon group)-,-(aromatic hydrocarbon group)-(aromatic hydrocarbon group)-(aromatic hydrocarbon group)- A group in which two or more hydrogen groups are linked,-(aromatic heterocyclic group)-(aromatic heterocyclic group)-,-(aromatic heterocyclic group)-(aromatic heterocyclic group)-(aromatic heterocyclic group) )-Or a group in which two or more aromatic heterocyclic groups are linked,-(aromatic hydrocarbon group)-(aromatic heterocyclic group)-,-(aromatic hydrocarbon group)-(CH = CH)- ,-(Aromatic heterocyclic group)-(CH = CH)-,-(aromatic heterocyclic group)-(aromatic hydrocarbon group)-(aromatic heterocyclic group)- Group and the like.

The content ratio (molar ratio) between the repeating unit represented by the general formula (1) and the repeating unit represented by the general formula (2) in the conjugated polymer is not particularly limited as long as the effects of the invention are not impaired.
Among these, from the point that the light absorption characteristics of the conjugated polymer and the open circuit voltage value in the organic thin film solar cell are larger, the content ratio of both repeating units (repeating unit represented by the general formula (1) / general formula ( The repeating unit represented by 2)) (molar ratio) is preferably 0.2 to 5, and more preferably 0.5 to 2.

In the conjugated polymer of the present invention, the content of the repeating unit represented by the general formula (1) is not particularly limited as long as the effects of the present invention are not impaired. Of these, the content of the repeating unit is preferably 10 to 90 mol%, more preferably 30 to 70 mol% with respect to the total repeating units (100 mol%) in that the effect of the present invention is more excellent.
In the conjugated polymer of the present invention, the content of the repeating unit represented by the general formula (2) is not particularly limited as long as the effects of the present invention are not impaired. Of these, the content of the repeating unit is preferably 10 to 90 mol%, more preferably 30 to 70 mol% with respect to the total repeating units (100 mol%) in that the effect of the present invention is more excellent.

In the conjugated polymer of the present invention, the repeating unit represented by the general formula (1) and the repeating unit represented by the general formula (2) are preferably main components.
More specifically, the total amount of both repeating units is preferably 80 mol% or more, more preferably 90 mol% or more, based on all repeating units (100 mol%). As an upper limit, it is 100 mol%.

  In the conjugated polymer of the present invention, the bonding mode of the repeating unit represented by the general formula (1) and the repeating unit represented by the general formula (2) is not particularly limited, and a random copolymer, a block A copolymer, an alternating copolymer, etc. are mentioned.

(Preferred embodiment of conjugated polymer)
A preferred embodiment of the conjugated polymer of the present invention is a conjugated polymer having a structure in which the repeating unit represented by the general formula (1) and the repeating unit represented by the general formula (2) are alternately bonded. Molecules (alternate copolymer type conjugated polymers) are preferred. In the case of the conjugated polymer, the sterically bulky thiophene skeleton represented by the general formula (1) is separated via the repeating unit represented by the general formula (2), and therefore the polymer It is expected that the flatness of the polymer becomes higher and the packing between the polymers in the film is improved.

In the conjugated polymer of the present invention, the content of the structure in which the repeating unit represented by the general formula (1) and the repeating unit represented by the general formula (2) are alternately bonded has the effect of the present invention. There is no particular limitation as long as it is not impaired.
Especially, it is preferable that this structure is substantially contained as a main component from the point which the light absorption characteristic of a conjugated polymer and the open circuit voltage value in an organic thin-film solar cell are larger. More specifically, the content of the structure is preferably 80 mol% or more, more preferably 90 mol% or more, based on all repeating units (100 mol%). As an upper limit, it is 100 mol%.

In addition, when the conjugated polymer of the present invention is the above alternating copolymer type, the repeating unit represented by the general formula (1) and the general formula (2) are represented within the range not impairing the effects of the present invention. It may have a repeating unit having a conjugated structure other than the structure in which the repeating unit is alternately bonded.
For example, a structure obtained by connecting repeating units represented by the general formula (2) may be included in part.

The number average molecular weight (M _n ) of the conjugated polymer of the present invention is not particularly limited, but is preferably 2000 to 150,000, and more preferably 2500 to 100,000, because it is more excellent in solubility in a solvent and film formability.
Further, the molecular weight distribution (M _w / M _n ) of the conjugated polymer is not particularly limited, but 1 to 8 is preferable and 1 to 5 is more preferable from the viewpoint of superior solubility in a solvent and film formability.

The method for synthesizing the conjugated polymer of the present invention is not particularly limited, and can be synthesized by combining known methods. For example, the method of polymerizing the thiophene compound which has the imide ring mentioned above and the compound which has a structure represented by X through a coupling reaction (for example, Stille coupling reaction) is mentioned.
Specifically, it can be synthesized by referring to documents such as Nielsen, CB; Bjornholm, T. Org. Lett. 2004, 6, 3381.

<Organic thin film solar cell and manufacturing method thereof>
The organic thin film solar cell of the present invention includes a first electrode layer, a photoelectric conversion layer containing at least the conjugated polymer and fullerenes described above, and a second electrode layer.
Below, the form of the organic thin-film solar cell of this invention and its manufacturing method are explained in full detail.

<Organic thin film solar cell (first embodiment)>
FIG. 1 is a schematic cross-sectional view of a first embodiment of the organic thin-film solar cell of the present invention.
The organic thin film solar cell 10 shown in the figure has a laminated structure in which a transparent substrate 12, a transparent electrode layer 14, a hole transport layer 16, a photoelectric conversion layer 18, an electron transport layer 20, and a counter electrode layer 22 are laminated in this order. Have. The solar cell corresponds to a so-called bulk heterojunction organic thin film solar cell in which the photoelectric conversion layer 18 is a mixed layer in which a p-type organic semiconductor material and an n-type organic semiconductor material are mixed. The thickness of each layer is not limited depending on the figure.
Below, each layer is explained in full detail.

<Transparent substrate>
As the transparent substrate 12, any material can be used as long as it supports and reinforces an electrode layer, a photoelectric conversion layer, and the like described later. The substrate does not have to be included in the organic thin film solar cell of the present invention as long as the transparent electrode layer 14 described later has sufficient strength.
Examples of the transparent substrate 12 include glass, heat-resistant polymer films such as polyimide, PET, PEN, PES, and Teflon (registered trademark), and ceramics. The transparent substrate 12 preferably has high transparency, and examples thereof include glass. Note that the surface of the transparent substrate 12 may be flat or may have irregularities.
The thickness of the transparent substrate 12 can be any thickness, and is preferably 0.05 mm to 3 mm.

<Transparent electrode layer (first electrode layer)>
The transparent electrode layer 14 is a first electrode layer provided on one side of the photoelectric conversion layer 18 described later. In the present embodiment, the transparent electrode layer 14 is provided via the hole transport layer 16, but may be provided in contact with the photoelectric conversion layer 18. The transparent electrode layer 14 can be made of any material as long as it can form an ohmic contact with the photoelectric conversion layer 18 and transmits the irradiation light.
For example, a transparent conductive material such as ITO, SnO ₂ , ZnO, In ₂ O ₃ , or fluorine-doped tin oxide (SnO ₂ : F), antimony-doped tin oxide (SnO ₂ : Sb), tin-doped indium oxide (In ₂₎ O ₃ : Sn), Al-doped zinc oxide (ZnO: Al), Ga-doped zinc oxide (ZnO: Ga), and the like, which are formed by doping the transparent conductive material with impurities.
The transparent electrode layer 14 may be composed of a single layer made of the above material, or may be composed of a laminate in which a plurality of layers are laminated. The layer thickness of the transparent electrode layer 14 is not particularly limited as long as it functions as an electrode, but is usually 3 nm to 10 μm. In addition, the transparent electrode layer 14 may have a flat surface or may have irregularities on the surface.

<Hole transport layer>
The hole transport layer 16 is disposed between the transparent electrode layer 14 and a photoelectric conversion layer 18 described later, and contributes to improvement of hole extraction efficiency. The hole transport layer 16 also functions as an electron blocking effect that suppresses leakage of electrons from the photoelectric conversion layer 18 to the transparent electrode layer 14 and a buffer layer that smoothes the unevenness of the transparent electrode layer 14. In addition, this hole transport layer 16 is installed as needed, and does not need to be contained in the organic thin-film solar cell of this invention.
The hole transport layer 16 is a substance having a hole transport property such as poly- (3,4-ethylenedioxythiophene) / polyethylene sodium sulfonate (commonly known as PEDOT-PSS), and has the highest occupied molecular orbital (HOMO). If the energy level is lower than that of the transparent electrode layer 14 as compared with the vacuum level, there is no particular limitation. Examples of the material include conductive organic compounds such as doped polyaniline, polyphenylene vinylene, polypyrrole, polyparaphenylene, polyacetylene, and triphenyldiamine (TPD).
The layer thickness of the hole transport layer 16 is not particularly limited, but is preferably about 5 to 500 nm.

<Photoelectric conversion layer>
The photoelectric conversion layer 18 of this embodiment is a bulk hetero type photoelectric conversion layer (bulk hetero type mixed layer) in which a p-type organic semiconductor material (acceptor) and an n-type semiconductor material (donor) are mixed in one layer. In this embodiment, a conjugated polymer having the repeating unit represented by the general formula (1) and the repeating unit represented by the general formula (2) is used as the p-type organic semiconductor material, and the n-type organic semiconductor is used. Fullerenes are mainly used as the material.
Hereinafter, the materials used will be described in detail.

As the p-type organic semiconductor material, the conjugated polymer described above is used, but other known materials may be used in combination.
Known p-type organic semiconductor materials include N, N′-bis (3-tolyl) -N, N′-diphenylbenzidine (mTPD), N, N′-dinaphthyl-N, N′-diphenylbenzidine (NPD). , 4,4 ′, 4 ″ -tris (phenyl-3-tolylamino) triphenylamine (MTDATA) and the like; phthalocyanine (Pc), copper phthalocyanine (CuPc), zinc phthalocyanine (ZnPc), titanyl phthalocyanine (TiOPc) ); Phthalocyanines such as octaethylporphyrin (OEP), platinum octaethylporphyrin (PtOEP), zinc tetraphenylporphyrin (ZnTPP); polyhexylthiophene (P3HT), methoxyethylhexyloxyphenylene vinylene (MEHPPV), etc. Lord of Examples thereof include polymer compounds such as chain-type conjugated polymers and side-chain polymers such as polyvinyl carbazole.

Fullerenes are used as the n-type organic semiconductor material. The fullerene is a concept including fullerene, a derivative thereof (fullerene derivative), a metal inclusion thereof, and the like.
Examples of fullerenes include carbon clusters having various three-dimensional structures, for example, fullerenes such as C ₆₀ , C ₇₀ , C ₇₄ , C ₇₆ , C ₇₈ , C ₈₂ , C ₈₄ , C ₇₂₀ , and C ₈₆₀ . Examples of the form of fullerene include a soccer ball shape and a bucky ball shape.

  The fullerene derivative means a compound that is surface-modified by introducing a substituent into the fullerene skeleton. The modification method is not particularly limited, and for example, a carbon 5-membered ring portion rich in fullerene reactivity can be chemically modified. The type of the substituent is not particularly limited, and for example, an alkyl group (alkyl group such as a methyl group having 1 to 10 carbon atoms, a t-butyl group), an aryl group (phenyl group, etc.), an aralkyl group (benzyl group, etc.). ), A dioxolane unit, a halogen atom, or an oxygen atom. Moreover, it may be modified by introducing a liquid crystal polymer, pigments, polyethylene oxide or the like. The modification of fullerene enables solubilization in solvents and polymers, improved affinity, and alignment or orientation of fullerenes.

  The metal-encapsulated fullerene is doped with various metals such as 1A group elements (K, Na, Rb, etc.), 2A group elements, lanthanoid elements (La, etc.) of the periodic table. An example is fullerene.

Among the above, as the n-type organic semiconductor material, [6,6] -phenyl-C ₆₁ butylcarboxylic acid methyl ester (PCBM) is preferably exemplified.

  As long as the effects of the present invention are not impaired, other known n-type organic semiconductor materials such as perylene derivatives, polycyclic quinones, and quinacridones may be used in combination.

  The mixing ratio of the p-type organic semiconductor material and the n-type organic semiconductor material is not particularly limited, but the mass ratio of the two (p-type organic semiconductor material / n-type organic semiconductor material) from the point that the performance of the obtained organic thin film solar cell is more excellent ) Is preferably 0.3 to 1.8, more preferably 0.5 to 1.5.

  Although the thickness in particular of the photoelectric converting layer 18 is not restrict | limited, 100-400 nm is preferable and 150-300 nm is more preferable from the point which the performance of the organic thin-film solar cell obtained is more excellent.

<Electron transport layer>
The electron transport layer 20 is disposed between the photoelectric conversion layer 18 and the counter electrode layer 22 and contributes to an improvement in electron extraction efficiency. In addition, this electron carrying layer 20 is installed as needed, and does not need to be contained in the organic thin film solar cell of this invention.
As the electron transport layer 20, for example, an alkali metal such as lithium fluoride, a halide of an alkaline earth metal, an oxide, or the like can be used. An inorganic semiconductor such as titanium oxide can also be used.
Although there is no restriction | limiting in particular about the layer thickness of the electron carrying layer 20, About 5-100 nm is preferable.

<Counter electrode layer (second electrode layer)>
The counter electrode layer 22 is a second electrode layer provided on the other surface side of the photoelectric conversion layer 18. The other side refers to the side opposite to the transparent electrode layer 14 with respect to the photoelectric conversion layer 18. In the present embodiment, the counter electrode layer 22 is provided via the electron transport layer 20, but may be provided in contact with the photoelectric conversion layer 18.
The material constituting the counter electrode layer 22 desirably has a work function capable of effectively collecting charges from the semiconductor of the photoelectric conversion layer 18. When the transparent electrode layer 14 collects holes, aluminum, magnesium, calcium, or the like that easily collects electrons is used as the counter electrode layer 22.
The thickness of the counter electrode layer 22 is not particularly limited as long as the sheet resistance that can sufficiently transmit the generated photocharge to the external circuit can be obtained. Although there is no restriction | limiting in particular about the layer thickness of the counter electrode layer 22, 1-100 nm is preferable.

<Method for producing organic thin-film solar cell>
The method for forming each layer of the organic thin film solar cell of the present invention is not particularly limited, and is a dry film forming method such as vacuum deposition, sputtering, plasma, ion plating, spin coating, dip coating, casting, roll coating, flow coating, A wet film forming method such as an ink jet can be employed.
More specifically, first, the transparent substrate 12 is installed, and the transparent electrode layer 14 is formed on the transparent substrate 12. There is no restriction | limiting in the shape and dimension of a board | substrate, It can install arbitrarily. The transparent electrode layer 14 can be formed by any method, and examples thereof include a dry process such as vacuum deposition and sputtering, and a wet process such as a sol-gel method.
Next, the hole transport layer 16 is formed on the surface of the transparent electrode layer 14. The hole transport layer 16 can be formed by dissolving a material to be used in a solvent and using the solution to form an arbitrary method such as spin coating, dip coating, or cast coating.
Next, the photoelectric conversion layer 18 is formed on the surface of the transparent electrode layer 14 by a wet film forming method using the above-described solution containing the conjugated polymer and the n-type organic semiconductor material.
Further, the electron transport layer 20 is formed on the surface of the photoelectric conversion layer 18. The electron transport layer 20 can be formed using a method such as a dry process such as vacuum deposition or a wet process such as a sol-gel method.
Finally, the counter electrode layer 22 is formed on the surface of the electron transport layer 20. The counter electrode layer 22 can be formed by any method such as vacuum deposition or laser transfer.

When the dry film forming method is employed, it is preferable to heat and evaporate the material using a resistance heating method. Moreover, when forming a mixed layer, the film-forming method by simultaneous vapor deposition from a several evaporation source is preferable, for example. During film formation, it is preferable to control the substrate temperature to be constant.
In the case of applying a wet film formation method, a thin film is formed after preparing a solution by dissolving or dispersing materials in an appropriate solvent. As such a solvent, any solvent can be used, for example, halogenated hydrocarbon solvents such as dichloromethane, dichloroethane, chloroform, carbon tetrachloride, tetrachloroethane, trichloroethane, chlorobenzene, dichlorobenzene, chlorotoluene; dibutyl ether, tetrahydrofuran, dioxane. , Ether solvents such as anisole; alcohol solvents such as methanol, ethanol, propanol, butanol, pentanol, hexanol, cyclohexanol, methyl cellosolve, ethyl cellosolve, ethylene glycol; benzene, toluene, xylene, ethylbenzene, hexane, octane, Examples thereof include hydrocarbon solvents such as decane and tetralin; ester solvents such as ethyl acetate, butyl acetate and amyl acetate. These solvents may be used alone or in combination.
The material concentration in the solution is appropriately selected according to the material used.

In the present invention, in any layer of the organic thin film solar cell, an appropriate resin or additive may be contained in order to improve the film formability and prevent pinholes in the film. Usable resins include polystyrene, polycarbonate, polyarylate, polyester, polyamide, polyurethane, polysulfone, polymethyl methacrylate, polymethyl acrylate, cellulose and other insulating resins and copolymers thereof; poly-N-vinylcarbazole And photoconductive resins such as polysilane; and conductive resins such as polythiophene and polypyrrole.
Examples of the additive include an antioxidant, an ultraviolet absorber, and a plasticizer.

<Organic thin film solar cell (second embodiment)>
FIG. 2 is a schematic view showing a second embodiment of the organic thin-film solar cell of the present invention.
The organic thin film solar cell 110 shown in FIG. 2 is configured by sequentially laminating a counter electrode layer 22, a photoelectric conversion layer 18, and a transparent electrode layer 14 on a substrate 12A. In this configuration, the order of stacking from the substrate 12A is reversed from that shown in FIG. The counter electrode layer 22 is provided on the substrate 12 </ b> A, and the transparent electrode layer 14 is provided on the outermost surface of the organic thin film solar cell 110.
In the present embodiment, the substrate 12A is not necessarily transparent, and substrates of various materials such as metal, ceramics, and plastic can be used.
The component of each layer in this embodiment and the preparation method of a coating liquid can be made the same as that of 1st embodiment. The manufacturing method of the organic thin film solar cell of this embodiment is the point which laminates | stacks in order of the counter electrode layer 22, the electron carrying layer 20, the photoelectric converting layer 18, the positive hole transport layer 16, and the transparent electrode layer 14 on the board | substrate 12A. Different from the first embodiment. With this configuration, compared to the configuration shown in FIG. 1, a metal thin film is used in many cases, and the counter electrode layer 22 formed by vacuum deposition can be formed before forming the organic film. The effect that it is possible to suppress the damage to the organic film due to is obtained.

<Organic thin-film solar cell (third embodiment)>
FIG. 3 is a schematic view showing a third embodiment of the organic thin film solar cell of the present invention.
The organic thin film solar cell 120 shown in FIG. 3 has a laminated structure in which a transparent substrate 12, a transparent electrode layer 14, a hole transport layer 16, a photoelectric conversion layer 18A, an electron transport layer 20, and a counter electrode layer 22 are laminated in this order. The photoelectric conversion layer 18A has a two-layer structure (bi-layer structure) of a p layer 24 made of a p-type organic semiconductor material and an n layer 26 made of an n-type organic semiconductor material.
The component of each layer in this embodiment and the preparation method of a coating liquid can be made the same as that of 1st embodiment. As a method for manufacturing the photoelectric conversion layer 18A, first, the p layer 24 is formed by a wet film formation method using a solution containing a p-type organic semiconductor material, and then a solution containing an n-type organic semiconductor material is used. A method of forming the n-layer 26 by a wet film forming method is included.

<Organic thin film solar cell (fourth embodiment)>
FIG. 4 is a schematic view showing a fourth embodiment of the organic thin film solar cell of the present invention.
The organic thin film solar cell 130 shown in FIG. 4 has a laminated structure in which the transparent substrate 12, the transparent electrode layer 14, the hole transport layer 16, the photoelectric conversion layer 18B, the electron transport layer 20, and the counter electrode layer 22 are laminated in this order. A photoelectric conversion layer 18B having a p layer 24 made of a p-type organic semiconductor material, a mixed layer 28 of a p-type organic semiconductor material and an n-type organic semiconductor material, and an n layer 26 made of an n-type organic semiconductor material. It has a three-layer structure.
The component of each layer in this embodiment and the preparation method of a coating liquid can be made the same as that of 1st embodiment. As a method of manufacturing the photoelectric conversion layer 18B, first, the p layer 24 is formed by a wet film formation method using a solution containing a p-type organic semiconductor material, and then the p-type organic semiconductor material and the n-type organic semiconductor material are used. And the n-layer 26 is formed by a wet film formation method using a solution containing an n-type organic semiconductor material.

  The organic thin film solar cell using the organic thin film solar cell material obtained in the present invention is effectively used for devices such as a solar cell module, a photovoltaic power generation panel, a watch, a portable information terminal, and a personal computer.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these.

(Measurement conditions, etc.)
For GPC measurement, SHIMADZU Prominence was used, column temperature was 25 ° C., chloroform was used as an elution solvent, and the number average molecular weight was calculated using a calibration curve prepared using standard polystyrene.
Nuclear magnetic resonance ( ¹ H NMR) spectra were measured using JEOL JNM-EX400.
Infrared absorption (IR) spectra were measured using JASCO FT / IR-470 Plus.
Cyclic voltammetry was measured using ALS 630a as a measuring device, an ITO electrode coated with a conjugated polymer described later as a working electrode, a Pt line as a counter electrode, and an Ag / AgNO ₃ electrode as a reference electrode. The sweep rate during this measurement was 10 to 100 mV / sec, and the scanning potential region was −2.0 V to 1.6 V. The reduction potential and the oxidation potential were measured by immersing a conjugated polymer film described later in an acetonitrile solution in which 0.1 mol / L of tetrabutylammonium hexafluorophosphate was dissolved as a supporting electrolyte.

<Synthesis Example 1>
N-dodecylimide-fused thiophene (compound 5) was synthesized according to the method described previously (Nielsen, CB; Bjornholm, T. Org. Lett. 2004, 6, 3381) (Scheme 1).

(2,5-Diiodo (N-dodecyldioxopyrrolothiophene)) (Compound 6)
The compound 5 (0.838 g, 2.70 mmol) was dissolved in a mixed solution of concentrated sulfuric acid (4.2 ml) and trifluoroacetic acid (14 ml). Next, N-iodosuccinimide (NIS) (2.44 g, 10.8 mmol) was added to the reaction solution in two portions, and the reaction solution was stirred at room temperature for 24 hours. The resulting purple solution was added to ice water (150 ml) and extracted with dichloromethane. The obtained organic layer was washed with a 10% aqueous sodium thiosulfate solution and dried over anhydrous magnesium sulfate, and then the solvent was removed by an evaporator to obtain a brown crude product. The crude product was purified by column chromatography using silica gel and dichloromethane / hexane solution (1: 1) as an eluent, and further recrystallized with ethanol to obtain Compound 6 (0.868 g, 1.51 mmol, yield 56%). The results of ¹ H NMR measurement of Compound 6 were as follows.
¹ H NMR (300 Mhz, CDCl ₃ ): δ 3.59 (dd, 2H), 1.62 (quintet, 2H), 1.25 (m, 18H), 0.88 (t, 3H).

(2,5-Bis (tributylstannyl) thiophene) (Compound 7)
2,5-bis (tributylstannyl) thiophene (compound 7) was prepared by the previously reported method (Hou, J .; Tan, Z .; Yan, Y .; He, Y .; Yang, C .; Li, YJ Am. Chem. Soc. 2006, 128, 4911) (Scheme 2).

(Poly [(N-dodecyldioxopyrrolothiophene) -alt- (thiophene)]) (PDT)
Furthermore, to a dry Schlenk tube purged with argon, compound 6 (30 mg, 0.052 mmol), compound 7 (38 mg, 0.057 mmol), dichlorobis (triphenylphosphine) palladium (II) (3.7 g, 0.0053 mmol), And distilled toluene (1 ml) was added (Scheme 3). The reaction mixture was then stirred at 120 ° C. for 72 hours. After completion of the stirring, the cooled reaction mixture was added to methanol, and the resulting black precipitate was recovered with a membrane filter (ADVANTEC). The product was washed with methanol and hexane, and then purified using preparative chromatography (LC-908 JAi) to obtain black PDT (8) (5.6 mg, 27% yield). FIG. 5A shows the results of ¹ H NMR measurement of the obtained polymer, FIG. 5B shows the results of IR measurement, and FIG. 5C shows the results of UV measurement and fluorescence measurement. By cyclic voltammetry measurement, the oxidation onset (E _{OX, ONSET} , onset of the oxidation potential) is 0.81V, and the reduction onset (E _{RED, ONSET} , onset of the reduction potential) is −1.11V. there were.
The number average molecular weight (M _n ) of PDT (8) was 87,000, and the molecular weight distribution (PDI) was 4.1.

<Synthesis Example 2>
(4-Octadecylcarbamoylthiophene-3-carboxylic acid) (Compound 9)
As shown in Scheme 4, the thiophene-3,4-carboxylic anhydride (Compound 3) (468 mg, 3.04 mmol) synthesized in Synthesis Example 1 and n-octadecylamine (873 mg, 3.24 mmol) were distilled from toluene. (50m) and the reaction was refluxed for 24 hours. The crude product was recovered from the cooled reaction solution by filtration. The filtrate was washed with a 5% aqueous hydrochloric acid solution to precipitate a crude product, extracted with chloroform, and then the solvent was removed to recover the crude product from the filtrate. Next, the recovered crude product was recrystallized from toluene to obtain Compound 9 as white crystals (1.21 g, 2.86 mmol, yield 94%). The results of ¹ H NMR measurement of Compound 9 were as follows.
¹ H NMR (300 MHz, CDCl ₃ ): δ 8.40 (d, 1H), 7.73 (d, 1H), 6.46 (broad s, 1H), 3.41 (t, 2H), 1.58 (quintet, 2H), 1.46- 0.76 (m, 33H).

(Octadecyldioxopyrrolothiophene) (Compound 10)
Compound 9 (1.21 g, 2.86 mmol) was added to thionyl chloride (100 ml), and the reaction solution was refluxed for 3 hours. The reaction solution was concentrated to obtain a light brown oil, which was further dried to obtain light yellow crystals. Next, the crystal was recrystallized in hexane to obtain Compound 10 as a white crystal (903 mg, 2.23 mmol, yield 78%). The results of ¹ H NMR measurement of Compound 10 were as follows.
¹ H NMR (300 MHz, CDCl ₃ ): δ 7.80 (s, 2H), 3.60 (t, 2H), 1.63 (quintet, 2H), 1.54-0.86 (m, 33H).

(1,3-Dibromooctadecyldioxopyrrolothiophene) (Compound 11)
The obtained compound 10 (887 mg, 2.19 mmol) was dissolved in a mixed solution of concentrated sulfuric acid (3.4 ml) and trifluoroacetic acid (11.3 ml). Next, N-bromosuccinimide (NBS) (1.56 g, 4.67 mmol) was added to the reaction solution in two portions, and the reaction solution was stirred at 55 ° C. for 24 hours. The resulting brown solution was diluted with water (120 ml) and extracted with dichloromethane (150 ml). The obtained organic layer was dried over anhydrous magnesium sulfate, and then the solvent was removed by an evaporator to obtain an orange crude product. The crude product was purified by column chromatography using silica gel and chloroform as the eluent, and further recrystallized with ethanol to obtain Compound 11 as white crystals (716 mg, 1.27 mmol, yield 58). %). The results of ¹ H NMR measurement of Compound 11 were as follows.
¹ H NMR (400 MHz, CDCl ₃ ): δ 3.58 (t, 2H), 1.62 (quintet, 2H), 1.53-086 (m, 33H).

(Poly [(N-octadecyldioxopyrrolothiophene) -alt- (thiophene)]) (POT)
Compound 11 (200 mg, 0.355 mmol) synthesized above was dissolved in chloroform (5 ml) under an argon atmosphere (Scheme 5). Next, Compound 7 (243 mg, 0.367 mmol) and dichlorobis (triphenylphosphine) palladium (II) (12.5 mg, 0.018 mmol) were added to the reaction solution, and the mixture was stirred at 65 ° C. for 96 hours. The cooled reaction solution was added to 500 ml of methanol, and the precipitate was collected by filtration. Thereafter, the precipitate was washed with methanol and hexane to obtain a crude product POT as a black solid (160 mg, yield 93%). The crude product was purified by chromatography using chloroform as an eluent and then reprecipitated with chloroform / methanol to obtain POT (12) (131 mg, yield 76%). The result of ¹ H NMR measurement of the obtained polymer is shown in FIG. 6A, the result of IR measurement is shown in FIG. 6B, and the results of UV measurement and fluorescence measurement are shown in FIG. 6C. By cyclic voltammetry measurement, the oxidation onset (E _{OX, ONSET} , onset of the oxidation potential) is 0.57V, and the reduction onset (E _{RED, ONSET} , onset of the reduction potential) is −1.31V. there were.
The number average molecular weight (M _n ) of POT (12) was 39,000, and the molecular weight distribution (PDI) was 1.5.

<Synthesis Example 3>
(4- (2-Heptyloctyl) carbamoylthiophene-3-carboxylic acid) (Compound 13)
As shown in Scheme 6, compound 3 (1.00 g, 6.49 mmol) synthesized in Synthesis Example 1 and 2-heptyloctylamine (1.57 g, 6.92 mmol) were added to distilled toluene (100 ml), and the reaction was performed. The solution was refluxed for 24 hours. The cooled reaction solution was filtered to recover the crude product. The filtrate was washed with a 5% aqueous hydrochloric acid solution to precipitate a crude product, extracted with chloroform, and then the solvent was removed to recover the crude product from the filtrate. Further, the recovered crude product was dried in vacuum, and then compound 13 was obtained as a pale yellow liquid (2.05 g, 5.39 mmol, yield 83%). The results of ¹ H NMR measurement of Compound 13 were as follows.
¹ H NMR (300 MHz, CDCl ₃ ): δ 8.49 (d, 1H), 7.97 (d, 1H), 6.70 (broad s, 1H), 4.11 (m, 1H), 1.57 (m, 4H), 1.26 (m, 20H), 0.87 (t, 6H).

(2-Heptyloctyldioxopyrrolothiophene) (Compound 14)
Compound 13 (1.51 g, 3.96 mmol) was added to thionyl chloride (150 ml), and the reaction solution was refluxed for 4 hours. The reaction solution was concentrated to obtain a light brown liquid, which was further dried to obtain light yellow crystals. Furthermore, after drying in vacuo, compound 14 was obtained as a light brown liquid (1.14 g, 3.13 mmol, 79% yield). The results of ¹ H NMR measurement of Compound 14 were as follows.
¹ H NMR (300 MHz, CDCl ₃ ): δ 7.78 (s, 2H), 4.11 (m, 1H), 1.85 (m, 4H), 1.23 (m, 20H), 0.85 (t, 6H).

(1,3-Dibromo (2-heptyloctyl) dioxopyrrolothiophene) (Compound 15)
The obtained compound 14 (1,000 g, 2.75 mmol) was dissolved in a mixed solution of concentrated sulfuric acid (4.3 ml) and trifluoroacetic acid (14.2 ml). Next, N-bromosuccinimide (NBS) (1.96 g, 5.86 mmol) was added in two portions to the reaction solution, and the reaction solution was stirred at room temperature for 24 hours. The resulting brown solution was diluted with water (150 ml) and extracted with dichloromethane (200 ml). The obtained organic layer was dried over anhydrous magnesium sulfate, and then the solvent was removed by an evaporator to obtain an orange crude product. The crude product was purified by column chromatography using silica gel and chloroform as the eluent to give compound 15 as a brown liquid (816 mg, 1.56 mmol, 57% yield). The results of ¹ H NMR measurement of Compound 15 were as follows.
¹ H NMR (400 MHz, CDCl ₃ ): δ 4.14 (m, 1H), 1.83 (m, 4H), 1.23 (m, 20H), 0.86 (t, 6H).

(Poly [(N- (2-heptyloctyl) dioxopyrrolothiophene) -alt- (thiophene)]) (PHOT)
Compound 15 (50 mg, 0.096 mmol) synthesized above was dissolved in chloroform (1 ml) under an argon atmosphere (Scheme 7). Next, Compound 7 (67 mg, 0.10 mmol) and dichlorobis (triphenylphosphine) palladium (II) (3.4 mg, 0.005 mmol) were added to the reaction solution, and the mixture was stirred at 65 ° C. for 48 hours. The cooled reaction solution was added to 500 ml of methanol, and the precipitate was collected by filtration. Thereafter, the precipitate was washed with methanol and hexane to obtain PHOT (16) as a black solid (37 mg, yield 86%). The result of ¹ H NMR measurement of the obtained polymer is shown in FIG. 7A, the result of IR measurement is shown in FIG. 7B, and the result of UV measurement is shown in FIG. 7C.
The number average molecular weight (M _n ) of PHOT (16) was 3900, and the molecular weight distribution was 1.3.

<Synthesis Example 4>
(4- (2-Hexylheptyl) carbamoylthiophene-3-carboxylic acid) (Compound 17)
As shown in Scheme 8, Compound 3 (1.64 g, 10.6 mmol) synthesized in Synthesis Example 1 and 2-hexylheptylamine (2.25 g, 11.3 mmol) were added to distilled toluene, and the reaction solution was converted to 24. Reflux for hours. The cooled reaction solution was filtered to recover the crude product. The filtrate was washed with a 5% aqueous hydrochloric acid solution to precipitate a crude product, extracted with chloroform, and then the solvent was removed to recover the crude product from the filtrate. Further, the recovered crude product was dried in vacuum, and then compound 17 was obtained as a pale yellow liquid (3.52 g, yield 94%). The results of ¹ H NMR measurement of Compound 17 were as follows.
¹ H NMR (400 MHz, CDCl ₃ ): δ8.46 (d, 1H), 7.87 (d, 1H), 6.42 (broad s, 1H), 4.11 (m, 1H), 1.56 (m, 4H), 1.28 (m, 16H), 0.87 (t, 6H).

(2-Hexylheptyldioxopyrrolothiophene) (Compound 18)
Compound 17 (3.52 g, 9.96 mmol) was added to thionyl chloride (200 ml) and the reaction was refluxed for 8 hours. The reaction solution was concentrated to obtain a light brown liquid, which was further dried to obtain light yellow crystals. Further, after drying in vacuo, compound 18 was obtained as a pale yellow solid (2.82 g, 8.41 mmol, 85% yield). The results of ¹ H NMR measurement of Compound 18 were as follows.
¹ H NMR (400 MHz, CDCl ₃ ): δ 7.84 (s, 2H), 4.11 (m, 1H), 1.60 (m, 4H), 1.28 (m, 16H), 0.86 (t, 6H).

(1,3-Diiodo (2-hexylheptyl) dioxopyrrolothiophene) (Compound 19)
The obtained compound 18 (3.15 g, 9.39 mmol) was dissolved in a mixed solution of concentrated sulfuric acid (15 ml) and trifluoroacetic acid (50 ml). Next, N-iodosuccinimide (NIS) (4.23 g, 18.7 mmol) was added to the reaction solution in two portions, and the reaction solution was stirred at room temperature for 12 hours. The resulting brown solution was diluted with water and extracted with dichloromethane. The obtained organic layer was dried over anhydrous magnesium sulfate, and then the solvent was removed by an evaporator to obtain an orange crude product. The crude product was purified by column chromatography using silica gel and chloroform as the eluent to give compound 19 as white crystals (3.09 g, 5.26 mmol, 58% yield). The result of ¹ H NMR measurement of Compound 19 was as follows.
¹ H NMR (400 MHz, CDCl ₃ ): δ 4.09 (m, 1H), 1.83 (m, 4H), 1.24 (m, 12H), 0.86 (t, 6H).

(Poly [(N- (2-hexylheptyl) dioxopyrrolothiophene) -alt- (thiophene)]) (PHHT)
Compound 19 (58 mg, 0.10 mmol) synthesized above was dissolved in dimethylformamide (1 ml) under an argon atmosphere (Scheme 9). Next, Compound 7 (66 mg, 0.10 mmol) and tetrakis (triphenylphosphine) palladium (0) (3 mg, 0.005 mmol) were added to the reaction solution, and the mixture was stirred at 110 ° C. for 48 hours. The cooled reaction solution was added to 500 ml of methanol, and the precipitate was collected by filtration. Thereafter, the precipitate was washed with methanol and hexane to obtain PHHT (20) as a black solid (27 mg, yield 64%). FIG. 8A shows the results of ¹ H NMR measurement of the obtained polymer, FIG. 8B shows the results of IR measurement, and FIG. 8C shows the results of UV measurement and fluorescence measurement. In addition, the reduction onset (ERED _{, ONSET} , onset of the reduction potential) was -1.18V by cyclic voltammetry measurement.
The number average molecular weight (M _n ) of PHHT (20) was 4300, and the molecular weight distribution (PDI) was 1.1.

<Synthesis Example 5>
(4- (2-Pentylhexyl) carbamoylthiophene-3-carboxylic acid) (Compound 21)
As shown in Scheme 10, compound 3 (1.54 g, 11.3 mmol) synthesized in Synthesis Example 1 and 2-pentylhexylamine (1.83 g, 10.7 mmol) were added to distilled toluene (100 ml), and the reaction was performed. The solution was refluxed for 24 hours. The cooled reaction solution was filtered to recover the crude product. The filtrate was washed with a 5% aqueous hydrochloric acid solution to precipitate a crude product, extracted with chloroform, and then the solvent was removed to recover the crude product from the filtrate. Furthermore, after the recovered crude product was dried in vacuum, compound 21 was obtained (3.60 g, 11.1 mmol, yield 98%). The results of ¹ H NMR measurement of Compound 21 were as follows.
¹ H NMR (400 MHz, CDCl ₃ ): δ8.43 (d, 1H), 8.07 (d, 1H), 6.95 (broad s, 1H), 4.11 (m, 1H), 1.56 (m, 4H), 1.30 (m, 12H), 0.87 (t, 6H).

(2-Pentylhexyldioxopyrrolothiophene) (Compound 22)
Compound 21 (3.22 g, 9.90 mmol) was added to thionyl chloride (200 ml) and the reaction was refluxed for 8 hours. The reaction solution was concentrated to obtain a light brown liquid, which was further dried to obtain light yellow crystals. Further, after drying in vacuo, compound 22 was obtained as a pale yellow solid (2.80 g, 9.11 mmol, 92% yield). The results of ¹ H NMR measurement of Compound 22 were as follows.
¹ H NMR (400 MHz, CDCl ₃ ): δ 7.84 (s, 2H), 4.11 (m, 1H), 1.60 (m, 4H), 1.28 (m, 16H), 0.86 (t, 6H).

(1,3-Diiodo (2-pentylhexyl) dioxopyrrolothiophene) (Compound 23)
The obtained compound 22 (2.80 g, 9.11 mmol) was dissolved in a mixed solution of concentrated sulfuric acid (14 ml) and trifluoroacetic acid (47 ml). Next, N-iodosuccinimide (NIS) (4.10 g, 18.2 mmol) was added in two portions to the reaction solution, and the reaction solution was stirred at room temperature for 12 hours. The resulting brown solution was diluted with water and extracted with dichloromethane. The obtained organic layer was dried over anhydrous magnesium sulfate, and then the solvent was removed by an evaporator to obtain an orange crude product. The crude product was purified by column chromatography using silica gel and chloroform as the eluent to give compound 23 as white crystals (3.11 g, 5.56 mmol, 61% yield). The results of ¹ H NMR measurement of Compound 23 were as follows.
¹ H NMR (400 MHz, CDCl ₃ ): δ 4.09 (m, 1H), 1.83 (m, 4H), 1.24 (m, 12H), 0.86 (t, 6H).

(Poly [(N- (2-pentylhexyl) dioxopyrrolothiophene) -alt- (thiophene)]) (PPHT)
Compound 23 (56 mg, 0.10 mmol) synthesized above was dissolved in dimethylformamide (1 ml) under an argon atmosphere (Scheme 11). Next, Compound 7 (66 mg, 0.10 mmol) and tetrakis (triphenylphosphine) palladium (0) (3 mg, 0.005 mmol) were added to the reaction solution, and the mixture was stirred at 110 ° C. for 48 hours. The cooled reaction solution was added to 500 ml of methanol, and the precipitate was collected by filtration. Thereafter, the precipitate was washed with methanol and hexane to obtain PPHT (24) as a black solid (28 mg, yield 71%). FIG. 9A shows the results of ¹ H NMR measurement of the obtained polymer, FIG. 9B shows the results of IR measurement, and FIG. 9C shows the results of UV measurement and fluorescence measurement. In addition, the reduction onset (ERED _{, ONSET} , onset of the reduction potential) was -1.20V by cyclic voltammetry measurement.
The number average molecular weight (M _n ) of PPHT (24) was 2700, and the molecular weight distribution (PDI) was 1.3.

<Synthesis Example 6>
(2,5-dithieno (N-pentadecyldioxopyrrolothiophene)) (Compound 27)
As shown in Scheme 12, 2,5-dibromo (N-pentadecyldioxopyrrolothiophene) (547 mg, 1.05 mmol) (Compound 25), 2- (tributylstannyl) thiophene (783 mg, 2 .10 mmol) (Compound 26) and tetrakis (triphenylphosphine) palladium (0) (121 mg) were dissolved in dimethylformamide (20 ml), and the reaction solution was stirred at 110 ° C. for 24 hours. The cooled reaction solution was added to methanol, and a yellow precipitate was collected. The precipitate was purified by column chromatography using silica gel and a chloroform / hexane (1: 1) solution as the eluent to give compound 27 as a yellow solid (274 mg, 0.51 mmol, 50% yield). ). The result of ¹ H NMR measurement of Compound 27 was as follows.
¹ H NMR (400 MHz, CDCl ₃ ): δ 8.02 (d, 2H), 7.44 (d, 2H), 7.13 (t, 2H), 3.66 (dd, 2H), 1.68 (m, 2H), 1.24 (m , 24H), 0.88 (t, 3H).

(2,5-Bis (5-bromothiophen-2-yl) (N-pentadecyldioxopyrrolothiophene)) (Compound 28)
Compound 27 (270 mg, 0.51 mmol) was dissolved in a mixture of chloroform (4 ml) and acetic acid (4 ml). Next, N-iodosuccinimide (NIS) (191 mg, 1.07 mmol) was added to the reaction solution, and the mixture was stirred at room temperature for 12 hours. The resulting solution was added to ice water (100 ml) and extracted with chloroform. The obtained organic layer was dried over anhydrous magnesium sulfate, and the solvent was removed by an evaporator to obtain a yellow crude product. The crude product was purified by column chromatography using silica gel and chloroform / hexane (1: 1) solution as eluent to give compound 28 as yellow crystals (224 mg, 0.33 mmol, yield). 64%). The results of ¹ H NMR measurement of Compound 28 were as follows.
¹ H NMR (400 MHz, CDCl ₃ ): δ 7.65 (d, 2H), 7.07 (d, 2H), 3.65 (dd, 2H), 1.67 (m, 2H), 1.24 (m, 24H), 0.88 (t , 3H).

  Compound 30 was synthesized by a previously reported method (Ranger, M .; Rondeau, D .; Leclerc, M. Macromolecules 1997, 30, 7686.).

As shown in Scheme 13, compound 28 (36 mg, 0.05 mmol), compound 30 (34 mg, 0.05 mmol), and tetrakis (triphenylphosphine) palladium (0) (3 mg, 0.05 eq) were added to toluene (0. 57 ml). Further, an aqueous sodium carbonate solution (0.12 ml) and Aliquat 336 (17 mg of Aliquat 336 in 1 ml of 2M sodium carbonate solution) were added to the reaction solution, and the mixture was stirred at 100 ° C. for 60 hours. The cooled solution was added to methanol and neutralized with 1M aqueous hydrochloric acid. The red precipitate was collected and washed with methanol and hexanes to give PTPF (31) as a red solid. The result of ¹ H NMR measurement of the obtained polymer is shown in FIG.
The number average molecular weight (M _n ) of PTPF (31) was 13,000, and the molecular weight distribution (PDI) was 1.9.

<Synthesis Example 7>
(2,5-Bis (5-tributylstannylthiophen-2-yl) (N-pentadecyldioxopyrrolothiophene)) (Compound 29)
As shown in Scheme 14, compound 27 (181 mg, 0.34 mmol) was dissolved in hexane (5 ml) under a nitrogen atmosphere. Next, butyl lithium (0.54 ml, 0.86 mmol, 1.6 mol / l in hexane) was added dropwise to the reaction solution, and the reaction solution was refluxed for 1 hour. The reaction solution was cooled to −78 ° C., tributyltin chloride (57 mg, 0.21 mmol) was added, and the mixture was further stirred at room temperature for 12 hours. After completion of the stirring, the reaction solution was added to water (20 ml), the organic layer was separated, and the aqueous layer was extracted with hexane (20 ml). The collected organic layer was dried over anhydrous magnesium sulfate, and then the solvent was removed to obtain Compound 29. The results of ¹ H NMR measurement of Compound 29 were as follows.
¹ H NMR (400 MHz, CDCl ₃ ): δ 7.65 (d, 2H), 7.07 (d, 2H), 3.65 (dd, 2H), 1.68 -0.88 (m, 85H).

As shown in Scheme 15, Compound 29 (54 mg, 0.048 mmol), Compound 32 (14 mg, 0.047 mmol), and dichlorobis (triphenylphosphine) palladium (II) (2 mg, 0.05 eq) in chloroform (1 ml) The reaction solution was heated at 65 ° C. for 72 hours. The cooled reaction solution was added to methanol, and the precipitate was collected. Thereafter, the precipitate was washed with methanol and hexane to obtain PTPB (33) as a black solid (26 mg, 0.039 mmol, yield 83%). The results of UV measurement and fluorescence measurement of the obtained polymer are shown in FIG. By cyclic voltammetry measurement, the oxidation onset (E _{OX, ONSET} , onset of the oxidation potential) is 0.57V, and the reduction onset (E _{RED, ONSET} , onset of the reduction potential) is −1.31V. there were.
The number average molecular weight (M _n ) of PTPB (33) was 9,800, and the molecular weight distribution (PDI) was 1.4.

<Synthesis Example 8>
N-octylimide-fused thiophene (compound 34) was synthesized according to a previously reported method (Nielsen, CB; Bjornholm, T. Org. Lett. 2004, 6, 3381).

  As shown in Scheme 16, under an argon atmosphere, compound 34 (42 mg, 0.10 mmol), compound 7 (73 mg, 0.11 mmol), dichlorobis (triphenylphosphine) palladium (II) (0.1 eq), and distilled toluene (1 ml) was put into a Schlenk tube, and the reaction solution was stirred at 110 ° C. for 96 hours. The cooled reaction solution was added to methanol, and a black precipitate was collected with a membrane filter (ADVANTEC). Thereafter, the precipitate was washed with methanol and hexane, and the solvent was removed with an evaporator to obtain black P8T (35) (18 mg, 38% yield).

<Absorption spectrum measurement>
PDT synthesized above and P3HT (poly-3-hexylthiophene-2,5-diyl (resiregular)) (Aldrich, Poly (3-hexylthiophene-2,5-diyl), weight average, which is a known material And a solution having the same concentration (27 mg / L) were prepared, and absorption spectrum measurement was performed (FIG. 12).
From FIG. 12, it was found that PDT is superior in absorption characteristics in the long wavelength region than P3HT, which is a known material. As can be seen from the figure, PDT showed better light absorption characteristics in the range of 550 to 750 nm. For example, the absorption coefficient at a wavelength of 650 nm, PDT is 29L g ^-1 cm ^-1, was 0.30 L g ^-1 cm ^-1 in P3HT. As the absorption coefficient at a wavelength of 550 nm, PDT is 26L g ^-1 cm ^-1, was 3.1 L g ^-1 cm ^-1 in P3HT.

<HOMO-LUMO energy level>
FIG. 13 shows the energy levels of the conjugated polymer of the present invention, the known material P3HT, and PCBM's highest occupied molecular orbit (HOMO) and lowest unoccupied molecular orbit (LUMO). FIG.
As can be seen from the figure, HOMO and LUMO of the conjugated polymers (PDT and PTPB) of the present invention were lower than those of P3HT as a known material. That is, the conjugated polymer of the present invention was a material having a more appropriate energy level with respect to fullerenes (PCBM) as compared with the conventionally known materials as can be seen from FIG.
The HOMO and LUMO levels of the conjugated polymer of the present invention are values converted from the results of cyclic voltammetry measurement, UV measurement, etc. described above. Moreover, the energy level of P3HT and PCBM referred to the value described in Non-Patent Document 1.

<Production and evaluation of organic thin-film solar cells>
PDT and PCBM are used for the photoelectric conversion layer material, and literature has already been reported (Umeyama, T .; Takamatsu, T .; Tezuka, N .; Matano, Y .; Araki, Y .; Wada, T .; Yoshikawa, O .; Sagawa, T .; Yoshikawa, S .; Imahori, HJ Phys. Chem. C 2009, 113, 10798-10806.) Organic thin film solar cells were fabricated and evaluated.
More specifically, first, a glass substrate (manufactured by Geomatec: surface resistance is 5Ω / □) coated with ITO (indium tin oxide) (thickness: 300 nm) was prepared. Next, the glass substrate was ultrasonically washed successively in acetone and ethanol. After the substrate was blown dry and treated with UV ozone, an aqueous solution of poly (3,4-ethylenedioxythiophene) / polystyrene sulfonic acid (PEDOT: PSS, BaytronP) was spin-coated on the substrate at 4000 rpm, Heat drying at 200 ° C. for 10 minutes. Furthermore, the PDT: PCBM layer (thickness: 170 nm) was produced by spin-coating the chloroform solution of PDT and PCBM synthesized above at 1000 rpm on the PEDOT: PSS layer in a nitrogen atmosphere. Thereafter, an ethanol solution of titanium tetraisopropoxide (Wako Pure Chemical Industries, Ltd.) was spin-coated on the PDT: PCBM layer at 2000 rpm and left for 30 minutes to allow hydrolysis of titanium tetraisopropoxide to proceed, and the TiOx layer ( (Thickness: 5 nm). Finally, under vacuum (5 × 10 ⁻³ Pa), an aluminum layer (manufactured by NilacoCorp) (thickness: 100 nm) is deposited by thermal evaporation, and ITO / PEDOT: PSS / conjugated polymer: PCBM / TiOx / Al An organic thin film solar cell having the following structure was obtained (FIG. 14).
AM1.5, simulated sunlight is irradiated at a light intensity of 100 mW / m ² , the IV characteristics are measured, the open circuit voltage value (V _OC ), the short circuit current density (J _SC ), the fill factor (FF) The conversion efficiency (η) was determined. The results are shown in Table 1.
In Table 1, the PDT and PCBM concentrations (g / L) mean the concentrations in the chloroform solution described above.

As can be seen from Table 1, in the organic thin-film solar cell using the conjugated polymer of the present invention, a high open circuit voltage of 0.70 V or higher was realized.
On the other hand, when the above organic thin-film solar cell was produced using P3HT (manufactured by Aldrich, Poly (3-hexylthiophene-2,5-diyl), weight average molecular weight 60000) instead of PDT in Example 1, its release. The voltage was about 0.6 V, and it was confirmed that the PDT of the present invention shows a higher open circuit voltage value.

FIG. 15 is a light absorption spectrum diagram of the PDT: PCBM film and the P3HT: PCBM film. The PDT: PCBM film is a film obtained by spin-coating PDT / PCBM (10 mg / 10 mg in 1 mL chloroform) on a glass substrate at 750 rpm. The P3HT: PCBM film is a film obtained by spin-coating P3HT / PCBM (15 mg / 7.5 mg in 1 mL chlorobenzene) on a glass substrate at 750 rpm and annealing at 150 ° C. for 6 minutes. . In addition, as P3HT (Poly (3-hexylthiophene-2,5-diyl)), the thing of the weight average molecular weight 60000 (made by Aldrich) was used.
As can be seen from the figure, the PDT: PCBM film, which is a photoelectric conversion layer using the conjugated polymer of the present invention, is superior in absorption characteristics in the long wavelength region of visible light compared to the case of using P3HT. I understood.

  FIG. 16 is a photocurrent action spectrum diagram of the organic thin-film solar cell of Example 3. The photocurrent action spectrum is the result of measuring the photoelectric conversion efficiency (IPCE; Incident Photon-to-Current Efficiency) per incident monochromatic light. As can be seen from the figure, the absorption edge of the spectrum extends to the long wavelength region, which suggests that there is a possibility that high-efficiency photoelectric conversion may be realized by effectively using light of a wide wavelength.

10, 110, 120, 130 Organic thin film solar cell 12 Transparent substrate 12A Substrate 14 Transparent electrode layer 16 Hole transport layer 18, 18A, 18B Photoelectric conversion layer 20 Electron transport layer 22 Counter electrode layer 24 p layer 26 n layer 28 Mixed layer

Claims (3)

A conjugated polymer having a repeating unit represented by the general formula (1) and a repeating unit represented by the general formula (2).

(In general formula (1), R represents a hydrogen atom or a monovalent organic group.
In General Formula (2), X represents a divalent conjugated linking group different from the repeating unit represented by General Formula (1). )   X in the general formula (1) is a divalent aromatic hydrocarbon group, a divalent aromatic heterocyclic group, — (CH═CH) —, — (C≡C) —, or a combination thereof. The conjugated polymer according to claim 1, wherein A first electrode layer, and a second electrode layer that is an electrode facing the first electrode layer,
An organic thin-film solar cell comprising a photoelectric conversion layer containing at least the conjugated polymer and fullerenes according to claim 1 or 2 between the first electrode layer and the second electrode layer.