JP2015015461A - Photoelectric conversion element and organic thin-film solar cell using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a buffer layer provided on the cathode side at a low cost, and to provide a photoelectric conversion element and an organic thin-film solar cell which exhibit high photoelectric conversion efficiency by selecting a photoelectric conversion material excellent in compatibility with the buffer layer.SOLUTION: In the photoelectric conversion element, a photoelectric conversion layer is provided between two or more electrodes facing each other, and a buffer layer is provided between at least one of the electrodes and the photoelectric conversion layer. The photoelectric conversion layer contains a bibenzo[b]furan compound having at least one constituent unit represented by formula (1) or (2), and the buffer layer contains a fluorine-based surfactant. (In the formula, R13 and R14 each represent a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, an optionally substituted hydrocarbon group, or an optionally substituted heterocyclic group.)

Description

  The present invention relates to a photoelectric conversion element containing a specific surfactant as a buffer layer, and an organic thin film solar cell using the photoelectric conversion element.

In recent years, solar cells (solar power generation) that can be used continuously, do not deplete resources, and have low environmental pollution have been actively studied. Solar cells are roughly classified into Si-based and non-Si-based inorganic solar cells, and dye-sensitized and organic thin-film organic solar cells. Inorganic solar cells generally have high photoelectric conversion efficiency, but have a drawback of high manufacturing cost because high vacuum is required or high-temperature heat treatment is required. On the other hand, since the organic solar cell can be formed by a coating method, a printing method, or the like, the manufacturing cost is low and the film can be formed in a large area. Another advantage of organic solar cells is that they can be lighter than inorganic solar cells. In particular, an organic thin film type solar cell is said to be excellent in a printing method and easy to form a film or the like, so that it is easy to manufacture a flexible solar cell.
However, since many organic solar cells have low photoelectric conversion efficiency, increasing the photoelectric conversion efficiency is a problem.

  Currently, P3HT [poly (3-hexylthiophene)], which is a p-type organic semiconductor material, and PCBM [[6, 6], which is an n-type organic semiconductor material, as materials having high photoelectric conversion efficiency in organic thin-film solar cells. ] -Phenyl-C61-butyric acid methyl ester] and a bulk heterojunction made of a mixed material (see Non-Patent Document 1, etc.). In addition, a low molecular compound such as pentacene may be used as the p-type organic semiconductor material. However, it is generally considered that a high molecular weight material is more suitable for device manufacturing by coating, which can reduce cost and increase the screen size. It is considered easy.

A characteristic required for the p-type organic semiconductor material is that the material has a highly planar π-conjugated plane. This is because high π-π interaction and high carrier transport efficiency can be expected, and as a result, high photovoltaic power can be provided.
Patent Documents 1 to 3 disclose a polymer-type p-type organic semiconductor.
However, further improvement in photoelectric conversion efficiency of organic solar cells is desired.

  On the other hand, as a technique for improving the photoelectric conversion efficiency of an organic thin film solar cell, it is known that the efficiency of electron injection and electron extraction is improved by providing a buffer layer between an electrode and a photoelectric conversion layer. As an example, PEDOT / PSS (poly (3,4-ethylenedioxythiophene) / poly (styrenesulfonate)) is used as a buffer layer between a transparent electrode (anode) and a photoelectric conversion layer, and a metal electrode ( LiF (lithium fluoride), a metal oxide, or the like is used as a buffer layer between the cathode) and the photoelectric conversion layer. Among them, LiF is mainly used because of excellent photoelectric conversion efficiency.

  Since the buffer layer made of LiF provided on the cathode side is usually formed by a vacuum deposition method, there is a problem that the production cost is high. For this reason, it has been studied to use a polymer compound or a fluorosurfactant having an amino functional group or imino functional group at the end, which can be applied, instead of LiF (for example, Patent Document 4 and Non-Patent Document). 2).

JP 2008-042107 A JP 2009-155891 A JP 2011-116962 A JP 2012-186343 A

F. Padinger, et al., Adv. Funct. Mater., 13, 85 (2003) Ryo Ishikawa, et al., Appl. Phys. Express, 5 (2012) 121601

  An object of the present invention is to produce a buffer layer provided on the cathode side at a low cost, and further to select a photoelectric conversion material excellent in compatibility with the buffer layer, thereby showing a photoelectric conversion element and an organic thin film exhibiting high photoelectric conversion efficiency It is to provide a solar cell.

  As a result of intensive studies, the present inventors have used a fluorosurfactant for the buffer layer on the cathode side, and a bibenzo [b] furan compound having a specific structure as a p-type organic semiconductor. However, it has been found that it is possible to provide a photoelectric conversion element and an organic thin-film solar cell that are easy to manufacture, have low manufacturing costs, and exhibit high photoelectric conversion ability, and can solve the above problems.

（式中、Ｒ¹³及びＲ¹⁴は、水素原子、フッ素原子、塩素原子、臭素原子、ヨウ素原子、置換されていてもよい炭化水素基又は置換されていてもよい複素環基を表す。） This invention was made | formed based on the said knowledge, The photoelectric conversion element by which the photoelectric converting layer was provided between the two or more electrodes which oppose, and the buffer layer was provided between at least one electrode and the photoelectric converting layer Because
The photoelectric conversion layer contains a bibenzo [b] furan compound having at least one structural unit represented by the following formula (1) or (2),
The present invention provides a photoelectric conversion element characterized in that the buffer layer contains a fluorine-based surfactant.

(In the formula, R ¹³ and R ¹⁴ represent a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, an optionally substituted hydrocarbon group or an optionally substituted heterocyclic group.)

（式中、Ｒ¹及びＲ²は、水素原子、フッ素原子、塩素原子、臭素原子、ヨウ素原子、置換されていてもよい炭化水素基又は置換されていてもよい複素環基を表し、Ｙ¹及びＹ²は、単結合又は下記（Ｙ−１）〜（Ｙ−８）から選ばれる基を１〜５個組み合わせて連結した基であり、Ｚ¹及びＺ²は、単結合又は下記（Ｚ−１）〜（Ｚ−２１）から選ばれる基を表し、ｎは１以上１０００以下の整数を表す。）

（式中、Ｒ¹¹、Ｒ¹²、Ｒ¹³又はＲ¹⁴は、水素原子、フッ素原子、塩素原子、臭素原子、ヨウ素原子、置換されていてもよい炭化水素基又は置換されていてもよい複素環基を表し、Ｙ³及びＹ⁴は、単結合又は下記（Ｙ−１）〜（Ｙ−８）から選ばれる基を１〜５個組み合わせて連結した基であり、Ｚ³及びＺ⁴は、単結合又は下記（Ｚ−１）〜（Ｚ−２１）から選ばれる基を表し、ｍは１以上１０００以下の整数を表す。）

（式中、Ｘ¹及びＸ⁴はＳ、Ｏ又はＮＲ³を表し、ｋは１〜４の整数を表し、Ｒ³は置換されていてもよい炭化水素基を表し、（Ｙ−１）〜（Ｙ−４）及び（Ｙ−６）〜（Ｙ−８）基中の水素原子は、フッ素原子、塩素原子、臭素原子、ヨウ素原子、シアノ基、ニトロ基、水酸基、チオール基、−ＮＲ⁴Ｒ⁵基、置換されていてもよい炭化水素基又は置換されていてもよい複素環基で置換されていてもよく、Ｒ⁴及びＲ⁵は、置換されていてもよい炭化水素基を表す。）

（式中、Ｘ²はＳ、ＮＲ⁶又はＳｉＲ⁷Ｒ⁸を表し、Ｘ³はＳ、ＮＲ⁶、ＣＲ⁷Ｒ⁸又はＳｉＲ⁷Ｒ⁸を表し、Ｘ⁵はＳ、Ｏ又はＮＲ⁶を表し、Ｒ⁶、Ｒ⁷及びＲ⁸は、置換されていてもよい炭化水素基を表し、（Ｚ−１）〜（Ｚ−２１）基中の水素原子は、フッ素原子、塩素原子、臭素原子、ヨウ素原子、シアノ基、ニトロ基、水酸基、チオール基、−ＮＲ⁹Ｒ¹⁰基、置換されていてもよい炭化水素基又は置換されていてもよい複素環基で置換されていてもよく、Ｒ⁹及びＲ¹⁰は、置換されていてもよい炭化水素基を表す。） In addition, the present invention provides a photoelectric conversion element, wherein the bibenzo [b] furan compound is a bibenzo [b] furan compound represented by the following general formula (3) or (4). is there.

Wherein R ¹ and R ² represent a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, an optionally substituted hydrocarbon group or an optionally substituted heterocyclic group, Y ¹ And Y ² are a single bond or a group connected by combining 1 to 5 groups selected from the following (Y-1) to (Y-8), and Z ¹ and Z ² are a single bond or the following (Z -1) to (Z-21), and n represents an integer of 1 to 1000.

(Wherein R ¹¹ , R ¹² , R ¹³ or R ¹⁴ is a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, an optionally substituted hydrocarbon group or an optionally substituted heterocyclic ring. Represents a group, Y ³ and Y ⁴ are a single bond or a group connected by combining 1 to 5 groups selected from the following (Y-1) to (Y-8), and Z ³ and Z ⁴ are: Represents a single bond or a group selected from the following (Z-1) to (Z-21), and m represents an integer of 1 to 1,000.

(Wherein X ¹ and X ⁴ represent S, O or NR ³ , k represents an integer of 1 to 4, R ³ represents an optionally substituted hydrocarbon group, and (Y-1) to The hydrogen atoms in the groups (Y-4) and (Y-6) to (Y-8) are fluorine atom, chlorine atom, bromine atom, iodine atom, cyano group, nitro group, hydroxyl group, thiol group, —NR ^4. R ⁵ group, an optionally substituted hydrocarbon group or an optionally substituted heterocyclic group may be substituted, and R ⁴ and R ^{5 each} represents an optionally substituted hydrocarbon group. )

(Wherein X ² represents S, NR ⁶ or SiR ⁷ R ⁸ , X ³ represents S, NR ⁶ , CR ⁷ R ⁸ or SiR ⁷ R ⁸ , and X ⁵ represents S, O or NR ⁶ . , R ⁶ , R ⁷ and R ⁸ represent an optionally substituted hydrocarbon group, and the hydrogen atoms in the groups (Z-1) to (Z-21) are a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a nitro group, a hydroxyl group, a thiol group, -NR ⁹ R ¹⁰ groups, may be substituted at heterocyclic group is also substituted hydrocarbon group or a substituted substituted, R ⁹ And R ¹⁰ represents an optionally substituted hydrocarbon group.)

  Moreover, this invention provides the organic thin-film solar cell formed using the said photoelectric conversion element.

  ADVANTAGE OF THE INVENTION According to this invention, the photoelectric conversion element which can be manufactured at low cost and is excellent in photoelectric conversion efficiency can be provided.

FIG. 1A is a cross-sectional view showing an example of the configuration of the photoelectric conversion element of the present invention. FIG.1 (b) is sectional drawing which shows another example of a structure of the photoelectric conversion element of this invention. FIG.1 (c) is sectional drawing which shows another example of a structure of the photoelectric conversion element of this invention. FIG.1 (d) is sectional drawing which shows the tandem-type element which is another example of the structure of the photoelectric conversion element of this invention.

In the photoelectric conversion element of the present invention, if the photoelectric conversion layer 4 is provided between two or more electrodes facing each other and a buffer layer is provided between at least one of the electrodes and the photoelectric conversion layer 4, It is comprised similarly to a conventionally well-known photoelectric conversion element. For example, taking FIG. 1A as an example, the support 1, the transparent electrode 2, the anode buffer layer 3, the photoelectric conversion layer 4, the cathode buffer layer 5, and the electrode 6 are sequentially stacked. Moreover, as shown in FIG.1 (b), the structure except the anode buffer layer 3 may be sufficient.
Moreover, as shown in FIG.1 (c), the structure which replaced arrangement | positioning of the anode buffer layer 3 and the cathode buffer layer 5 may be sufficient.
Moreover, as shown in FIG.1 (d), after laminating | stacking in order of the anode buffer layer 3, the photoelectric converting layer 4, and the cathode buffer layer 5 on the transparent electrode 2, the anode buffer layer 3, the photoelectric converting layer 4 again. Alternatively, a tandem multilayer structure in which the cathode buffer layer 5 is laminated may be used.
Below, the material which comprises the photoelectric conversion element of this invention, a manufacturing method, etc. are demonstrated in detail based on preferable embodiment.

<Support>
If the support body 1 can hold | maintain the transparent electrode 2 on the surface stably, it will not be restrict | limited to a material or thickness, but it needs to have transparency. Therefore, the shape of the support may be plate or film. Transparency refers to the property of transmitting light in a predetermined wavelength region used in a photoelectric conversion element, for example, visible light region at a high rate. For the support 1, for example, glass, transparent polymer film (polyethylene terephthalate (PET), tetraacetyl cellulose (TAC), polycarbonate, polyethylene naphthalate, polyphenylene sulfide, polyester sulfone, syndiotactic polystyrene) or the like can be used. In addition, although it is preferable that the photoelectric conversion element of this invention is formed in the surface of the support body 1, when the transparent electrode 2 itself has a certain amount of hardness and has self-supporting property, the transparent electrode 2 supports the support body 1. In this case, the support 1 may be omitted.

<Transparent electrode and electrode>
Examples of the transparent electrode 2 and the electrode 6 include noble metals such as gold, platinum, and silver, zinc oxide, indium oxide, tin oxide (NESA), tin-doped indium oxide (ITO), and fluorine-doped tin oxide (FTO). Metal oxide, lithium, lithium-indium alloy, sodium, sodium-potassium alloy, calcium, magnesium, magnesium-silver alloy, magnesium-indium alloy, indium, ruthenium, titanium, manganese, yttrium, aluminum, aluminum-lithium alloy, aluminum -Calcium alloy, aluminum-magnesium alloy, chromium, graphite thin film, organic conductive compounds such as PEDOT-PSS, etc. can be used as appropriate. These electrode materials may be used alone or in combination. Since the transparent electrode 2 needs to have transparency, a transparent material such as zinc oxide, NESA, ITO, FTO, and PEDOT-PSS is used. The transparent electrode 2 and the electrode 6 can be formed by using a dry process or a wet process using these electrode materials in the same manner as the photoelectric conversion layer 4 described below. Further, it may be formed by firing by a sol-gel method or the like. The thickness of the electrode is generally about 5 to 1000 nm, more preferably about 10 to 500 nm for both the electrode 2 and the electrode 6, although depending on the material of the electrode substance used.

  In the present invention, the work functions of a pair of electrodes (electrode 2 and electrode 6) arranged opposite to each other may have a relative magnitude relationship with each other (that is, the work functions are different from each other). Therefore, it is sufficient that the work function of the electrode 2 is relatively larger than that of the electrode 6. In this case, the work function difference between the two electrodes is preferably 0.5 V or more. In addition, when a buffer layer is provided between each electrode and the semiconductor layer and the compound of the buffer layer on the electrode and the electrode are chemically bonded, these restrictions may be relaxed.

<Anode buffer layer>
The anode buffer layer 3 prevents the electrode material from entering and reacting with the photoelectric conversion layer 4, prevents recombination of charges separated by the photoelectric conversion layer 4, and efficiently moves the charge to the electrode 2. There is a role. Examples of the material include charge transfer materials such as PEDOT: PSS, PEO, V ₂ O ₅ , zinc oxide, lithium fluoride, TiOx, and naphthalenetetracarboxylic acid anhydride. The anode buffer layer 3 needs to have transparency. When the photoelectric conversion layer 4 is a bulk hetero type such as P3HT: PCBM, PEDOT: PSS is often used for the anode buffer layer 3. The anode buffer layer 3 can be formed using these charge transfer materials by a dry process method or a wet process method in the same manner as the photoelectric conversion layer 4 described below. The thickness of the anode buffer layer 3 is generally set to 0.01 to 100 nm, more preferably about 0.1 to 50 nm.

<Cathode buffer layer>
In the present invention, the cathode buffer layer 5 uses a fluorine-based surfactant, and can be formed by a wet process by using the material. The thickness of the cathode buffer layer 5 is usually about 0.01 to 100 nm, preferably about 0.1 to 50 nm. Fluorine surfactants include (1) anionic fluorine-containing surfactants, (2) cationic fluorine-containing surfactants, (3) amphoteric fluorine-containing surfactants, and (4) nonionic fluorine-containing surfactants. And (5) fluorine-containing oligomers and the like, and are not particularly limited and can be used. Specific examples of these are shown in [Chemical Formula 4] to [Chemical Formula 8] below.

In the above formulas (1) to (5), R _f and R _f ′ are linear or branched fluoroalkyl groups (preferably carbon atoms) in which part or all of the alkyl groups are replaced by fluorine atoms. 1 to 30 and more preferably 1 to 20), R ′ and R ″ represent a hydrogen atom or an alkyl group (1 to 40 carbon atoms, more preferably 1 to 10), and B represents —CO—. Or —SO ₂ —, Y and Y ′ represent a direct bond or an alkylene group (preferably having 1 to 40 carbon atoms, more preferably 1 to 20), A represents an ethylene group or a propylene group, and M represents Represents a hydrogen atom, —NH ₄ , an alkali metal (Li, Na, K, Cs, etc.) or an alkaline earth metal (Mg, Ca, Ba, etc.), and X is a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, iodine) Z is a direct bond, -N (R '' SO ₂ - or an -NHCO-, n represents 1 to 50, p is an integer of 1 to 3.

  Examples of the monomer (copolymerization component) that can form a copolymer with the polyfluoroalkyl group-containing (meth) acrylate in the (5) fluorine-containing oligomer include ethylene, vinyl acetate, vinyl chloride, vinyl fluoride, Vinylidene halide, styrene, α-methylstyrene, p-methylstyrene, (meth) acrylic acid and its alkyl ester, poly (oxyalkylene) (meth) acrylate, (meth) acrylimide, diacetone acrylamide, methylolated diacetone Acrylamide, N-methylolacrylamide, vinyl alkyl ether, halogenated alkyl vinyl ether, vinyl alkyl ketone, butadiene, isoprene, chloroprene, glycidyl acrylate, benzyl (meth) acrylate, cyclohexyl acrylate, Water maleic acid, aziridinyl (meth) acrylate, N- vinyl carbazole, and the like.

  The copolymerization ratio of these copolymer components to the polyfluoroalkyl group-containing (meth) acrylate is usually 1 to 70% by mass, preferably 10 to 50% by mass.

(1) Among the anionic fluorinated surfactant may, (i) -COO-M system, (ii) -OSO ₃ -M system, (iii) preferably having _-SO 3 -M system, in particular (i) - A COO-M system is preferred.
Among (2) cationic fluorine-containing surfactants, (ii) N ⁺ .X ⁻ system is preferable.
Among (3) amphoteric fluorine-containing surfactants, (iii) N ⁺ (R ′) ₂ —O ⁻ system is preferable.
Among (4) nonionic fluorine-containing surfactants, (ii) -O- type is preferable.
(5) Among fluorine-containing oligomers, methacrylate homopolymers or copolymers, acrylate homopolymers or copolymers, vinyl chloride homopolymers or copolymers, styrene homopolymers or copolymers In particular, a homopolymer or copolymer of methacrylate and acrylate is preferable.

  Commercially available fluorosurfactants include Zonyl FS-300 (manufactured by DuPont), Surflon S-211, Surflon S-221, Surflon S-231, Surflon S-241, Surflon S-242, Surflon S- 243, Surflon S-420, Surflon S-611, Surflon S-651, Surflon S-386, Surflon S-232, Surflon S-233 (manufactured by AGC Seimi Chemical Co., Ltd.), Aftergent 710FL, Aftergent 710FM, Aftergent 710FS , TF 730FL, FT 730LM (manufactured by Neos), Novec FC-4430, Novec FC-4432 (manufactured by Sumitomo 3M), and the like.

The above-mentioned fluorosurfactants may be used alone or as a mixture of a plurality of types. In the present invention, by using a fluorine-based surfactant, the cathode buffer layer 5 can be easily produced by a wet process. In the wet process, the fluorosurfactant alone may be applied or may be applied after being dissolved in a solvent or the like.
Here, the solvent to be used is not particularly limited as long as it can dissolve the fluorine-based surfactant uniformly. For example, the same solvent as used in the production of the photoelectric conversion layer 4 described below is used. Preferably, a solvent such as water, methanol, ethanol, n-propanol, or isopropanol can be used as one that hardly dissolves the previously applied layer.

  The concentration of the fluorosurfactant when used by dissolving in a solvent is not particularly limited as long as the cathode buffer layer thickness can be formed, but is 0.01 to 10% by mass, preferably 0.01 to 5% by mass. is there.

<Photoelectric conversion layer>
The photoelectric conversion layer 4 contains a p-type organic semiconductor material (A) and an n-type organic semiconductor material (B) (hereinafter collectively referred to as a photoelectric conversion material), and is an organic bulk which is a preferred embodiment. In addition to heterojunction elements, super-layer nanostructure junction elements, hybrid heterojunction elements, pin junction elements, and the like can be given. The film forming method is not particularly limited. For example, vapor deposition method, physical vapor deposition method (PVD), chemical vapor deposition method (CVD), atomic layer deposition method (ALD), atomic layer epitaxy method (ALE). , Dry processes such as molecular beam epitaxy (MBE), vapor phase epitaxy (VPE), sputtering, plasma polymerization, dip coating, casting, air knife coating, curtain coating, roller coating, wire bar A coating film is formed on a support by a wet process such as a coating method, a gravure coating method, a spin coating method, an LB method, an offset printing method, a screen printing method, a flexographic printing method, a dispenser printing method, an inkjet method, or an extrusion coating method. A method is mentioned. The material described below manufactured according to the present invention can be easily formed by a wet process.
Although the film thickness of a photoelectric converting layer is not specifically limited, Generally, it is preferable to set to about 5 nm-5 micrometers, and heat processing, such as annealing, may be performed.

  The p-type organic semiconductor material (A) contains a bibenzo [b] furan compound having at least one structural unit represented by the above formula (1) or (2). Note that * in the above formula (1) or (2) means that the group represented by these formulas is bonded to an adjacent group at the * portion (the same applies hereinafter).

Examples of the optionally substituted hydrocarbon group represented by R ¹³ and R ¹⁴ in the above formula (2) include an aromatic hydrocarbon group, an aromatic hydrocarbon group substituted with an aliphatic hydrocarbon, and an aliphatic hydrocarbon group. And those having 1 to 40 carbon atoms, particularly 4 to 22 carbon atoms are preferred.
Examples of the aromatic hydrocarbon group include phenyl, naphthyl, cyclohexylphenyl, biphenyl, terphenyl, fluoryl, thiophenylphenyl, furanylphenyl, 2′-phenyl-propylphenyl, benzyl, naphthylmethyl, and the like.
Examples of the aliphatic hydrocarbon group include methyl, ethyl, propyl, isopropyl, butyl, s-butyl, t-butyl, isobutyl, amyl, isoamyl, t-amyl, hexyl, heptyl, isoheptyl, t-heptyl, n. -Linear, branched and cyclic alkyl groups such as octyl, isooctyl, t-octyl, nonyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, etc., and these aliphatic hydrocarbon groups Is interrupted by —O—, —COO—, —OCO—, —CO—, —S—, —SO—, —SO ₂ —, —NR ¹⁵ —, —HC═CH— or —C≡C—. (Note that the interruption may interrupt the portion to which the aliphatic hydrocarbon group is bonded), and R ¹⁵ is substituted. Examples of the optionally substituted hydrocarbon group are the same groups as the optionally substituted hydrocarbon group represented by R ¹³ and R ¹⁴ , and among them, perfluoroalkyl ( Preferably 1 to 30 carbon atoms are preferred.
Examples of the aromatic hydrocarbon group substituted with the aliphatic hydrocarbon include phenyl, naphthyl, benzyl and the like substituted with the aliphatic hydrocarbon group.
Examples of the group that may substitute these hydrocarbon groups include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a nitro group, a hydroxyl group, a thiol group, and a —NR′R ″ group. 'And R ″ represent an optionally substituted hydrocarbon group, and the optionally substituted hydrocarbon group is the same group as the optionally substituted hydrocarbon group represented by R ¹³ and R ^14. Is mentioned.

Examples of the optionally substituted heterocyclic group represented by R ¹³ and R ¹⁴ in the above formula (2) include thiazolyl, imidazolyl, oxazolyl, pyridyl, pyrazinyl, pyrimidinyl, pyridazinyl, thiophenyl, furanyl, bithiophenyl, and terthiophenyl. Heterocyclic groups are mentioned, and those having 1 to 40, especially 4 to 22 carbon atoms are preferred.

  Among the bibenzo [b] furan compounds, those having 2 or more and 100 or less structural units represented by the above formula (1) or (2) are preferable because of excellent film forming properties. In addition, the bibenzo [b] furan compound may have a structural unit other than the structural unit represented by the above formula (1) or (2) (hereinafter also referred to as other structural unit). When the bibenzo [b] furan compound contains other structural units, the structural unit represented by the formula (1) or (2) is preferably 5 to 100 mol%, and 10 to 90 mol%. It is further more preferable and it is especially preferable that it is 20-80 mol%.

  The other structural unit is not particularly limited as long as it is a π-conjugated group, but examples include structural units selected from the following group Y or group Z. From the viewpoint of durability and light resistance of the material, (Y− 2), (Y-3), (Y-4) or group Z (especially (Z-1), (Z-2), (Z-6), (Z-8), (Z-9), A structural unit selected from (Z-21)) is preferred.

（式中、Ｘ¹及びＸ⁴はＳ、Ｏ又はＮＲ³を表し、ｋは１〜４の整数を表し、Ｒ³は置換されていてもよい炭化水素基を表し、群Ｙで表される構成単位中の水素原子は、フッ素原子、塩素原子、臭素原子、ヨウ素原子、シアノ基、ニトロ基、水酸基、チオール基、−ＮＲ⁴Ｒ⁵基、置換されていてもよい炭化水素基又は置換されていてもよい複素環基で置換されていてもよく、Ｒ⁴及びＲ⁵は、置換されていてもよい炭化水素基を表す。）

(Wherein X ¹ and X ⁴ represent S, O or NR ³ , k represents an integer of 1 to 4, R ³ represents an optionally substituted hydrocarbon group, and is represented by group Y) The hydrogen atom in the structural unit is a fluorine atom, chlorine atom, bromine atom, iodine atom, cyano group, nitro group, hydroxyl group, thiol group, —NR ⁴ R ⁵ group, an optionally substituted hydrocarbon group or a substituted group. (It may be substituted with an optionally substituted heterocyclic group, and R ⁴ and R ^{5 each} represents an optionally substituted hydrocarbon group.)

（式中、Ｘ²はＳ又はＮＲ⁶を表し、Ｘ³はＳ、ＮＲ⁶、ＣＲ⁷Ｒ⁸又はＳｉＲ⁷Ｒ⁸を表し、Ｘ⁵はＳ、Ｏ又はＮＲ⁶を表し、Ｒ⁶、Ｒ⁷及びＲ⁸は、置換されていてもよい炭化水素基を表し、群Ｚで表される構成単位中の水素原子は、フッ素原子、塩素原子、臭素原子、ヨウ素原子、シアノ基、ニトロ基、水酸基、チオール基、−ＮＲ⁹Ｒ¹⁰基、置換されていてもよい炭化水素基又は置換されていてもよい複素環基で置換されていてもよく、Ｒ⁹及びＲ¹⁰は、置換されていてもよい炭化水素基を表す。）

Wherein X ² represents S or NR ⁶ , X ³ represents S, NR ⁶ , CR ⁷ R ⁸ or SiR ⁷ R ⁸ , X ⁵ represents S, O or NR ⁶ , R ⁶ , R ⁷ and R ⁸ represent an optionally substituted hydrocarbon group, and the hydrogen atom in the structural unit represented by group Z is a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a nitro group, It may be substituted with a hydroxyl group, a thiol group, a —NR ⁹ R ¹⁰ group, an optionally substituted hydrocarbon group or an optionally substituted heterocyclic group, and R ⁹ and R ¹⁰ are substituted. Represents a good hydrocarbon group.)

A hydrocarbon group that may substitute a hydrogen atom in the structural unit represented by group Y or group Z, R ⁴ in the —NR ⁴ R ⁵ group, R ⁵ and R ⁹ in the —NR ⁹ R ¹⁰ group, R ¹⁰ and NR ³ representing X ¹ and X ⁴ in group Y, NR ⁶ representing X ² and X ⁵ in group Z, and NR ⁶ representing X ³ , R ^{3 of} CR ⁷ R ⁸ SiR ⁷ R ⁸ As the optionally substituted hydrocarbon group represented by R ⁶ , R ⁷ and R ^{8, the same} group as the optionally substituted hydrocarbon group represented by R ¹³ and R ¹⁴ in the above formula (2) is exemplified. Can be mentioned.
Examples of the heterocyclic group that may substitute a hydrogen atom in the structural unit represented by group Y or group Z include an optionally substituted heterocyclic group represented by R ¹³ and R ¹⁴ in formula (2) above. Similar groups are mentioned.

  When the bibenzo [b] furan compound contains a structural unit of the group Y or group Z, the bibenzo [b] furan compound is represented by the following general formula (1 ′) or (2 ′), and the general formula (1 ′ ) Or (2 ′), the arrangement of o, p, or q structural units is not particularly limited, and the effects of the present invention are achieved. Moreover, as a preferable ratio of each structural unit, when o which is a structural unit of Formula (1) or (2) is 1, p or q which is a structural unit of the group Y or the group Z is 1-10. is there. The value of p is more preferably 0 to 8 and still more preferably 1 to 5 from the viewpoint of high light absorption efficiency in the long wavelength region. Further, a more preferable value of q is 0 to 2, more preferably 1 or 2, particularly preferably 1, from the viewpoint of high light absorption efficiency in the long wavelength region.

（式中、Ｒ¹³及びＲ¹⁴は上記式（２）と同様の基を表し、Ｙは上記群Ｙから選ばれる基を表し、Ｚは上記群Ｚから選ばれる基を表し、ｏは１以上１０００以下の整数を表し、ｐ及びｑは、０以上１０００以下の整数を表す。）

(In the formula, R ¹³ and R ¹⁴ represent the same group as in the formula (2), Y represents a group selected from the group Y, Z represents a group selected from the group Z, and o is 1 or more. Represents an integer of 1000 or less, and p and q represent an integer of 0 or more and 1000 or less.)

  Preferable examples of the bibenzo [b] furan compound include compounds represented by the following general formula (3) or (4).

（式中、Ｒ¹及びＲ²は、水素原子、フッ素原子、塩素原子、臭素原子、ヨウ素原子、置換されていてもよい炭化水素基又は置換されていてもよい複素環基を表し、Ｙ¹及びＹ²は、単結合又は下記（Ｙ−１）〜（Ｙ−８）から選ばれる基を１〜５個組み合わせて連結した基であり、Ｚ¹及びＺ²は、単結合又は下記（Ｚ−１）〜（Ｚ−２１）から選ばれる基を表し、ｎは１以上１０００以下の整数を表す。）

Wherein R ¹ and R ² represent a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, an optionally substituted hydrocarbon group or an optionally substituted heterocyclic group, Y ¹ And Y ² are a single bond or a group connected by combining 1 to 5 groups selected from the following (Y-1) to (Y-8), and Z ¹ and Z ² are a single bond or the following (Z -1) to (Z-21), and n represents an integer of 1 to 1000.

（式中、Ｒ¹¹、Ｒ¹²、Ｒ¹³又はＲ¹⁴は、水素原子、フッ素原子、塩素原子、臭素原子、ヨウ素原子、置換されていてもよい炭化水素基又は置換されていてもよい複素環基を表し、Ｙ³及びＹ⁴は、単結合又は下記（Ｙ−１）〜（Ｙ−８）から選ばれる基を１〜５個組み合わせて連結した基であり、Ｚ³及びＺ⁴は、単結合又は下記（Ｚ−１）〜（Ｚ−２１）から選ばれる基を表し、ｍは１以上１０００以下の整数を表す。）

(Wherein R ¹¹ , R ¹² , R ¹³ or R ¹⁴ is a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, an optionally substituted hydrocarbon group or an optionally substituted heterocyclic ring. Represents a group, Y ³ and Y ⁴ are a single bond or a group connected by combining 1 to 5 groups selected from the following (Y-1) to (Y-8), and Z ³ and Z ⁴ are: Represents a single bond or a group selected from the following (Z-1) to (Z-21), and m represents an integer of 1 to 1,000.

（式中、Ｘ¹及びＸ⁴はＳ、Ｏ又はＮＲ³を表し、ｋは１〜４の整数を表し、Ｒ³は置換されていてもよい炭化水素基を表し、（Ｙ−１）〜（Ｙ−４）及び（Ｙ−６）〜（Ｙ−８）基中の水素原子は、フッ素原子、塩素原子、臭素原子、ヨウ素原子、シアノ基、ニトロ基、水酸基、チオール基、−ＮＲ⁴Ｒ⁵基、置換されていてもよい炭化水素基又は置換されていてもよい複素環基で置換されていてもよく、Ｒ⁴及びＲ⁵は、置換されていてもよい炭化水素基を表す。）

(Wherein X ¹ and X ⁴ represent S, O or NR ³ , k represents an integer of 1 to 4, R ³ represents an optionally substituted hydrocarbon group, and (Y-1) to The hydrogen atoms in the groups (Y-4) and (Y-6) to (Y-8) are fluorine atom, chlorine atom, bromine atom, iodine atom, cyano group, nitro group, hydroxyl group, thiol group, —NR ^4. R ⁵ group, an optionally substituted hydrocarbon group or an optionally substituted heterocyclic group may be substituted, and R ⁴ and R ^{5 each} represents an optionally substituted hydrocarbon group. )

（式中、Ｘ²はＳ、ＮＲ⁶又はＳｉＲ⁷Ｒ⁸を表し、Ｘ³はＳ、ＮＲ⁶、ＣＲ⁷Ｒ⁸又はＳｉＲ⁷Ｒ⁸を表し、Ｘ⁵はＳ、Ｏ又はＮＲ⁶を表し、Ｒ⁶、Ｒ⁷及びＲ⁸は、置換されていてもよい炭化水素基を表し、（Ｚ−１）〜（Ｚ−２１）基中の水素原子は、フッ素原子、塩素原子、臭素原子、ヨウ素原子、シアノ基、ニトロ基、水酸基、チオール基、−ＮＲ⁹Ｒ¹⁰基、置換されていてもよい炭化水素基又は置換されていてもよい複素環基で置換されていてもよく、Ｒ⁹及びＲ¹⁰は、置換されていてもよい炭化水素基を表す。）

(Wherein X ² represents S, NR ⁶ or SiR ⁷ R ⁸ , X ³ represents S, NR ⁶ , CR ⁷ R ⁸ or SiR ⁷ R ⁸ , and X ⁵ represents S, O or NR ⁶ . , R ⁶ , R ⁷ and R ⁸ represent an optionally substituted hydrocarbon group, and the hydrogen atoms in the groups (Z-1) to (Z-21) are a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a nitro group, a hydroxyl group, a thiol group, -NR ⁹ R ¹⁰ groups, may be substituted at heterocyclic group is also substituted hydrocarbon group or a substituted substituted, R ⁹ And R ¹⁰ represents an optionally substituted hydrocarbon group.)

As R ¹ and R ^{2 in} the general formula (3), R ¹¹ and R ¹² in the general formula (4), an optionally substituted hydrocarbon group or an optionally substituted heterocyclic group Includes the same groups as R ¹³ and R ¹⁴ in the above formula (2).

Among the compounds represented by the general formula (3), a compound in which at least one of Y ¹ , Y ² or Z ¹ is not a single bond is preferable because it is easy to produce, and the durability and light resistance of the material are preferred. Y ¹ or Y ² is a group selected from the group (Y-2), (Y-3), (Y-4), or Z ¹ or Z ² is the group (Z-1), A compound that is a group selected from (Z-2), (Z-6), (Z-8), (Z-9), and (Z-21) is preferable.
Among the compounds represented by the general formula (4), a compound in which at least one of Y ³ , Y ⁴ or Z ² is not a single bond is preferable because it is easy to produce, and the durability and light resistance of the material are preferred. From this point, Y ³ or Y ⁴ is a group selected from the group (Y-2), (Y-3) or (Y-4), or Z ³ or Z ⁴ is a group (Z-1 ), (Z-2), (Z-6), (Z-8), (Z-9), and a compound selected from (Z-21) are preferred.

Specific examples of the bibenzo [b] furan compound include the following compound No. 1-No. 80, but is not limited to these compounds. In the following compounds, R ¹ , R ² and n are the same as in the above general formula (3), and R ¹¹ , R ¹² and m are the same as in the above general formula (4).

  Any of the above-mentioned bibenzo [b] furan compounds are not limited to the production method, and can be obtained by a method using a known general reaction. An example of a method for producing the bibenzo [b] furan compound represented by the general formula (3) is given below.

First, the 3,4: 3′4′-bibenzo [b] furan skeleton in the bibenzo [b] furan compound represented by the above general formula (3) (n = 1, R ¹ and R ^{2 of} Compound No. ¹ are For example, as shown in the following reaction route, a hydrogen atom is produced from anthalphine through three steps of dietherification, hydrolysis, and cyclization.

Next, the obtained 3,4: 3′4′-bibenzo [b] furan is brominated to dibromobibenzo [b] furan (A).
Subsequently, a boronic acid pinacol ester derivative having a corresponding Y ¹ -or Y ² -is coupled to dibromobibenzo [b] furan (A) to obtain an intermediate (B), and then trimethylphenylammonium bromide is used. Bromination to give an intermediate (C), high molecular weight with a bisboronic acid pinacol ester derivative having the corresponding Z ¹ -or Z ^2- to give an intermediate (D), and capping the terminal, the above general formula (3 ) Can be obtained. In addition, when it quenches after the production | generation of an intermediate body (D), R < ¹ > and R < ² > becomes a hydrogen atom.

(式中、Ｒ¹、Ｒ²、Ｙ¹、Ｙ²、Ｚ¹、Ｚ²及びｎは上記一般式（３）と同様である。)

(In the formula, R ¹ , R ² , Y ¹ , Y ² , Z ¹ , Z ² and n are the same as those in the general formula (3).)

  In the above reaction formula, when the intermediate (C) is excessive in the reaction between the intermediate (C) and the bisboronic acid pinacol ester derivative, it is considered that the following bromine-substituted product (D ′) is also produced. Even if it is a bromine-substituted product (D ′), and is further reacted with a boronic acid pinacol ester derivative to obtain the following compound (3 ′), it is not particularly limited because the same effect is exhibited in the present invention.

In the above reaction formula, when performing various coupling reactions, the functional groups to which the intermediates (A), (B) and (C) are bonded are not only bromine but also corresponding halogen compounds, triflate bodies, boron compounds, silicon compounds, Bibenzofuran derivatives converted into zinc compounds and tin compounds may be used. Corresponding to the above intermediates, R ¹ -Br, R ² -Br, Bpin-Z ¹ -Bpin and Bpin-Z ² -Bpin are intermediates (A), (B) and (C) used. Corresponding to the present invention even when the target bibenzofuran derivative is synthesized with each intermediate converted to a halogen compound, triflate, boron compound, silicon compound, zinc compound, and tin compound In order to produce the effect of, it is not particularly limited.

(式中、Ｒ¹、Ｒ²、Ｙ¹、Ｙ²、Ｚ¹、Ｚ²及びｎは上記一般式（３）と同様である。)

(In the formula, R ¹ , R ² , Y ¹ , Y ² , Z ¹ , Z ² and n are the same as those in the general formula (3).)

  As a p-type organic-semiconductor material (A), what is necessary is just to contain at least 1 sort (s) of the said bibenzo [b] furan compound, and it can use it combining another well-known material. For example, phthalocyanine pigments, indigo or thioindigo pigments, quinacridone pigments, triarylmethane derivatives, triarylamine derivatives, oxazole derivatives, hydrazone derivatives, stilbene derivatives, pyrazoline derivatives, polysilane derivatives, polyphenylene vinylene and derivatives thereof (for example, polyphenylene vinylene) [2-Methoxy-5- (2-ethylhexyloxy) -1,4-phenylenevinylene]: MEH-PPV, poly [2-methoxy-5- (3 ′, 7′-dimethyloctyloxy) -1,4 -Phenylene vinylene]), polythiophene and derivatives thereof (for example, poly (3-dodecylthiophene), poly (3-hexylthiophene): P3HT, poly (3-octylthiophene)), poly-N-vinylcarbazole derivatives, and the like. It is done.

  When other known materials are used as the p-type organic semiconductor material (A), the content of the bibenzo [b] furan compound is preferably 1 to 99% by mass, more preferably 1 to 99% by mass in the p-type organic semiconductor material. 80% by mass.

  As the n-type organic semiconductor material (B), perylene pigments, perinone pigments, polycyclic quinone pigments, azo pigments, C60 fullerene, C70 fullerene, and derivatives thereof can be used. For example, tris (8-quinolinolato) aluminum, bis (10-benzo [h] quinolinolato) beryllium, beryllium salt of 5-hydroxyflavone, aluminum salt of 5-hydroxyflavone], oxadiazole derivative [for example, 1,3- Bis [5 ′-(p-tert-butylphenyl) -1,3,4-oxadiazol-2′-yl] benzene], triazole derivatives [eg 3- (4′-tert-butylphenyl) -4 -Phenyl-5- (4 ''-biphenyl) -1,2,4-triazole], phenanthroline derivatives [e.g. 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (basocproin, BCP)], triazine derivatives, quinoline derivatives, quinoxaline derivatives, diphenylquinone derivatives, nitro-substituted fluorenone derivatives, thiopyrandioxide derivatives, etc. It can also be used. Among the n-type organic semiconductor materials (B), C60 fullerene, C70 fullerene and derivatives thereof are preferable because they have high carrier mobility as n-type material and / or high charge separation efficiency. In addition, the compound quoted as an example as n-type organic-semiconductor material (B) may be used individually, or may be used together.

  Examples of the C60 fullerene, C70 fullerene, and derivatives thereof include the following C1 to C6 compounds. Among them, C1 PCBM (phenyl) is preferable because it has excellent electronic level matching and is easily available. -C61-butyric acid methyl ester) is preferably used.

  The weight ratio (the former: latter) of the p-type organic semiconductor material (A) and the n-type organic semiconductor material (B) is 10:90 to 90:10, preferably 10:90 to 70:30, more preferably. Is 20: 80-50: 50.

  In forming the photoelectric conversion layer, the photoelectric conversion material may be dissolved or dispersed in one or more solvents as necessary.

  The solvent is not particularly limited as long as it can dissolve or disperse the p-type organic semiconductor material (A) and the n-type organic semiconductor material (B). For example, water, alcohol solvent, diol solvent, ketone Solvent, ester solvent, ether solvent, aliphatic or alicyclic hydrocarbon solvent, aromatic hydrocarbon solvent, hydrocarbon solvent having cyano group, halogenated hydrocarbon solvent, other organic solvents, etc. Can be mentioned. A photoelectric conversion material using a solvent can be used as a coating solution.

  Examples of the alcohol solvent include methanol, ethanol, propanol, isopropanol, 1-butanol, isobutanol, 2-butanol, tertiary butanol, pentanol, isopentanol, 2-pentanol, neopentanol, and third. Pentanol, hexanol, 2-hexanol, heptanol, 2-heptanol, octanol, 2-ethylhexanol, 2-octanol, cyclopentanol, cyclohexanol, cycloheptanol, methylcyclopentanol, methylcyclohexanol, methylcycloheptanol , Benzyl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl Ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, 2- (N, N-dimethylamino) ethanol, 3 (N, N-dimethylamino) propanol, etc. Can be mentioned.

  Examples of the diol solvent include ethylene glycol, propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, isoprene glycol ( 3-methyl-1,3-butanediol), 1,2-hexanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,2-octanediol, octanediol (2-ethyl) -1,3-hexanediol), 2-butyl-2-ethyl-1,3-propanediol, 2,5-dimethyl-2,5-hexanediol, 1,2-cyclohexanediol, 1,4-cyclohexanediol 1,4-cyclohexanedimethanol and the like.

  Examples of the ketone solvent include acetone, ethyl methyl ketone, methyl isopropyl ketone, methyl butyl ketone, methyl isobutyl ketone, methyl amyl ketone, methyl hexyl ketone, ethyl butyl ketone, diethyl ketone, dipropyl ketone, diisobutyl ketone, and methyl. Examples include amyl ketone, cyclohexanone, and methylcyclohexanone.

  Examples of the ester solvent include methyl formate, ethyl formate, methyl acetate, ethyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate, second butyl acetate, third butyl acetate, amyl acetate, isoamyl acetate, and third amyl acetate. , Phenyl acetate, methyl propionate, ethyl propionate, isopropyl propionate, butyl propionate, isobutyl propionate, sec-butyl propionate, tert-butyl propionate, amyl propionate, isoamyl propionate, amyl propionate, Phenyl propionate, methyl 2-ethylhexanoate, ethyl 2-ethylhexanoate, propyl 2-ethylhexanoate, isopropyl 2-ethylhexanoate, butyl 2-ethylhexanoate, methyl lactate, ethyl lactate, methyl methoxypropionate Methyl ethoxypropionate, ethyl methoxypropionate, ethyl ethoxypropionate, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monopropyl ether acetate, ethylene glycol monoisopropyl ether acetate, ethylene glycol mono Butyl ether acetate, ethylene glycol mono secondary butyl ether acetate, ethylene glycol mono isobutyl ether acetate, ethylene glycol mono tertiary butyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monopropyl Pyrether acetate, Propylene glycol monoisopropyl ether acetate, Propylene glycol monobutyl ether acetate, Propylene glycol mono secondary butyl ether acetate, Propylene glycol monoisobutyl ether acetate, Propylene glycol mono tertiary butyl ether acetate, Butylene glycol monomethyl ether acetate, Butylene glycol monoethyl Ether acetate, butylene glycol monopropyl ether acetate, butylene glycol monoisopropyl ether acetate, butylene glycol monobutyl ether acetate, butylene glycol mono sec-butyl ether acetate, butylene glycol monoisobutyl ether acetate, butylene glycol mono Examples include tertiary butyl ether acetate, methyl acetoacetate, ethyl acetoacetate, methyl oxobutanoate, ethyl oxobutanoate, γ-lactone, dimethyl malonate, dimethyl succinate, propylene glycol diacetate, and δ-lactone.

  Examples of the ether solvent include tetrahydrofuran, tetrahydropyran, morpholine, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dipropylene glycol dimethyl ether, triethylene glycol dimethyl ether, dibutyl ether, diethyl ether, and dioxane.

  Examples of the aliphatic or alicyclic hydrocarbon solvents include pentane, hexane, cyclohexane, methylcyclohexane, dimethylcyclohexane, ethylcyclohexane, heptane, octane, decalin, solvent naphtha, turpentine oil, D-limonene, pinene, and minerals. Spirit, Swazol # 310 (Cosmo Matsuyama Oil Co., Ltd., Solvesso # 100 (Exxon Chemical Co., Ltd.)) and the like.

  Examples of the aromatic hydrocarbon solvent include benzene, toluene, ethylbenzene, xylene, mesitylene, diethylbenzene, cumene, isobutylbenzene, cymene, and tetralin.

  Examples of the hydrocarbon solvent having a cyano group include acetonitrile, 1-cyanopropane, 1-cyanobutane, 1-cyanohexane, cyanocyclohexane, cyanobenzene, 1,3-dicyanopropane, 1,4-dicyanobutane, , 6-dicyanohexane, 1,4-dicyanocyclohexane, 1,4-dicyanobenzene and the like.

  Examples of the halogenated hydrocarbon solvent include carbon tetrachloride, chloroform, dichloromethane, trichloroethylene, chlorobenzene, dichlorobenzene, and trichlorobenzene.

  Examples of the other organic solvents include N-methyl-2-pyrrolidone, dimethyl sulfoxide, dimethylformamide, aniline, triethylamine, pyridine, and carbon disulfide.

  Among these, preferable solvents include chloroform, dichloromethane, toluene, xylene, chlorobenzene, dichlorobenzene, trichlorobenzene and the like.

  When the above-mentioned solvent is included during the formation of the photoelectric conversion layer 4, the content is not particularly limited as long as it does not hinder the formation of the photoelectric conversion layer 4 using the photoelectric conversion material. The total amount of the photoelectric conversion material is preferably selected from the range of 0.1 to 20 parts by weight when 100 parts by weight, more preferably 1 to 10 parts by weight, and particularly preferably 3 to 7 parts by weight. It is desirable to select from the range.

  The photoelectric conversion element of this invention can be used for a photodiode, a photodetector, etc. other than the organic thin-film solar cell of this invention.

  Hereinafter, the present invention will be described in more detail with reference to synthesis examples, examples and comparative examples. However, the present invention is not limited by the following examples.

[Synthesis Example 1] Compound No. 1 Synthesis of 13 (R ¹ and R ² are phenyl groups) Under a nitrogen atmosphere, 147 mg (0.19 mmol) of BBF-3HTB shown below and N- (1-octylnonyl) carbazole-2,7-bis (pinacol boronate) Ester) 138 mg (0.21 mmol) and a solution charged with 15 ml of toluene were subjected to ultrasonic irradiation, and further to this solution, tetrakis (triphenylphosphine) palladium 22 mg (0.019 mmol) and sodium carbonate aqueous solution 8.0 ml (2 0.0M, 16.0 mmol) was added, and the mixture was reacted at 90 ° C. for 12 hours. After adding 232 mg (1.9 mmol) of phenylboronic acid and 11 mg (0.001 mmol) of tetrakis (triphenylphosphine) palladium and reacting at 90 ° C. for 4 hours, 298 mg (1.9 mmol) of phenylbromide and tetrakis ( Triphenylphosphine) palladium (11 mg, 0.001 mmol) was added and reacted at 90 ° C. for 4 hours. After cooling to room temperature, methanol was added for reprecipitation, and the resulting residue was washed with methanol and ultrapure water. Further, this residue was washed with acetone for 9 hours using a Soxhlet extractor, then dried, and compound No. 1 of black purple crystals was dried. 132 mg (yield 59%) of 13 (R ¹ and R ² are phenyl groups) was obtained. The obtained Compound No. The number average molecular weight (Mn) of 13 was 5142, the weight average molecular weight (Mw) was 9644, and Mw / Mn was 1.88.

[Synthesis Example 2] Compound No. 2 Synthesis of 29 (R ¹ and R ² are phenyl groups) Under a nitrogen atmosphere, a solution charged with 180 mg (0.25 mmol) of BBF-4HTB shown below and 10 ml of toluene was irradiated with ultrasonic waves. 97 mg (0.21 mmol) of (1-n-octylnonyl) carbazole-2,7-diboronate bis (pinacol), 11 mg (0.013 mmol) of tris (dibenzylideneacetone) dipalladium, tri (o-tolyl) phosphine 23 mg (0.075 mmol) and 1.7 ml (2.0 M, 3.4 mmol) of an aqueous sodium carbonate solution were added and reacted at 120 ° C. for 6 hours. Further, 11 mg (0.013 mmol) of tris (dibenzylideneacetone) dipalladium and 23 mg (0.075 mmol) of tri (o-tolyl) phosphine were added and reacted at 120 ° C. for 6 hours. Methanol was added for reprecipitation, and the resulting residue was washed with methanol and ultrapure water and refluxed in acetone. The solution was filtered, washed with acetone, dried, and the compound No. 126 mg of 29 (R ¹ and R ² are phenyl groups) was obtained (yield 99%). The obtained Compound No. The number average molecular weight (Mn) of 29 was 6082, the weight average molecular weight (Mw) was 10995, and Mw / Mn was 1.80.

[Synthesis Example 3] Compound No. Synthesis of 79 (R ¹ and R ² are phenyl groups) Under a nitrogen atmosphere, 100 mg (0.14 mmol) of the above BBF-4HTB, octyl-4,6-dibromo-3-fluorothieno [3,4-b] thiophene 2-carboxylate 16 mg (0.03 mmol), 2,5-bis (2-ethylhexyl) -3,6-bis (4- (4,4,5,5-tetramethyl-1,3,2-dioxaborane-2) -Yl) A solution charged with 132 mg (0.17 mmol) of phenyl-2,5-dihydropyrrolo [3,4-c] pyrrole-1,4-dione and 14 ml of toluene was irradiated with ultrasonic waves, and this solution was further subjected to tetrakis Add (triphenylphosphine) palladium 6.0 mg (0.005 mmol) and aqueous sodium carbonate 0.45 ml (2.0 M, 0.85 mmol) The mixture was reacted for 1 hour at 150 ° C. under microwave irradiation, and 105 mg (0.87 mmol) of phenylboronic acid and 2.0 mg (0.002 mmol) of tetrakis (triphenylphosphine) palladium were added and reacted at 150 ° C. for 15 minutes. Thereafter, 136 mg (0.87 mmol) of phenyl bromide was further added and reacted for 15 minutes at 150 ° C. After cooling to room temperature, methanol was added for reprecipitation, and the resulting residue was washed with methanol and ultrapure water. Further, this residue was washed with acetone using a Soxhlet extractor for 8 hours and then dried to obtain 121 mg of black purple crystal compound No. 79 (R ¹ and R ² are phenyl groups) (yield 68%). The number average molecular weight (Mn) of the obtained compound No. 79 is 13723, the weight average molecular weight (Mw) is 42172, Mw / Mn was 3.07.

[Synthesis Example 4] Compound No. Synthesis of 80 (R ¹ and R ² are phenyl groups) In a nitrogen atmosphere, 67 mg (0.09 mmol) of the above BBF-4HTB, 12 mg (0.04 mmol) of 2,5-dibromo-1- (5-hexenyl) pyrrole 2,5-bis (2-ethylhexyl) -3,6-bis (4- (4,4,5,5-tetramethyl-1,3,2-dioxaboran-2-yl) phenyl-2,5-dihydropyrrolo A solution charged with 100 mg (0.13 mmol) of [3,4-c] pyrrole-1,4-dione and 9 ml of toluene was subjected to ultrasonic irradiation. Further, 4.5 mg (0 of tetrakis (triphenylphosphine) palladium was added to this solution. 0.004 mmol) and 0.33 ml (2.0 M, 0.65 mmol) of an aqueous sodium carbonate solution were added, and the mixture was reacted at 150 ° C. for 1 hour under microwave irradiation. After adding 79 mg (0.65 mmol) of phenylboronic acid and 1.5 mg (0.001 mmol) of tetrakis (triphenylphosphine) palladium and reacting at 150 ° C. for 15 minutes, 103 mg (0.65 mmol) of phenyl bromide was further added. The mixture was allowed to react for 15 minutes at 150 ° C. After cooling to room temperature, methanol was added for reprecipitation, and the resulting residue was washed with methanol and ultrapure water, and the residue was further washed with acetone using a Soxhlet extractor for 8 hours. After washing, drying was performed to obtain 92 mg of black purple crystalline Compound No. 80 (R ¹ and R ² are phenyl groups) (yield: 74%), number average molecular weight (Mn) of the obtained Compound No. 80 Was 17038, the weight average molecular weight (Mw) was 36918, and Mw / Mn was 2.17.

Examples 1 to 27 and Comparative Examples 1 to 9 Production and Evaluation of Photoelectric Conversion Elements Photoelectric conversion elements having the layer configuration shown in FIG. 1A were produced by the following procedure.
First, a glass substrate (support 1) on which ITO is formed to a thickness of 150 nm as an electrode 2 is subjected to IPA boiling cleaning and UV-ozone cleaning, and then PEDOT: PSS (3,4-ethylenedioxythiophene: Polystyrene sulfonic acid) was formed into a film by a 20 nm spin coating method and dried under reduced pressure at 100 ° C. for 10 minutes.
Next, 20 mg of the p-type organic semiconductor material (A) described in [Table 1] and 80 mg of the n-type organic semiconductor material (B) are dissolved in 2 mL of 1,2-dichlorobenzene, respectively. Prepared. The prepared photoelectric conversion material was formed into a film by a spin coat method, and dried under reduced pressure at 100 ° C. for 30 minutes to obtain a photoelectric conversion layer 4.
Subsequently, on the photoelectric conversion layer 4 which is the obtained organic thin film layer, a solution prepared such that the material of the cathode buffer layer described in [Table 1] is 0.05 wt% -isopropyl alcohol is spin-coated. The cathode buffer layer 5 was coated by the above method and dried under reduced pressure under the conditions described in Table 1 for 30 minutes.
Finally, 100 nm of aluminum (electrode 6) was further vacuum-deposited on the obtained cathode buffer layer 5 to produce photoelectric conversion elements of Examples 1 to 27 and Comparative Examples 1 to 9, respectively.
The photoelectric conversion element thus obtained was irradiated with pseudo sunlight having an air mass of 1.5 G and 100 mW / cm ² from the ITO electrode side, and the photoelectric conversion characteristics (efficiency (%)) were measured. The results are shown in [Table 1].

上記式中、Ｏctはｎ−オクチル基を示す。 "FS-300", "S-221", "S-241", "S-232", "S-386", "S-243" used as surfactants in [Table 1] above , “FC-4430” and “FC-4432” and “Compound No. 29”, “Compound No. 13”, “Compound No. 79”, “Compound No. 80” used as p-type organic semiconductors, and The specific contents of “PCDTBT” are as follows.
FS-300: (Zonyl FS-300) Nonionic fluorine-containing surfactant manufactured by DuPont
S-221: (Surflon S-221) Cationic fluorine-containing surfactant manufactured by AGC Seimi Chemical Co., Ltd.
S-241: (Surflon S-241) Nonionic fluorine-containing surfactant manufactured by AGC Seimi Chemical Co., Ltd.
S-232: (Surflon S-232) Amphoteric fluorine-containing surfactant manufactured by AGC Seimi Chemical Co., Ltd.
S-386: (Surflon S-386) Nonionic fluorine-containing surfactant manufactured by AGC Seimi Chemical Co., Ltd.
S-243: (Surflon S-243) Nonionic fluorine-containing surfactant manufactured by AGC Seimi Chemical Co., Ltd.
FC-4430: (Novec FC-4430) Nonionic fluorine-containing surfactant manufactured by Sumitomo 3M Limited
FC-4432: (Novec FC-4432) Nonionic fluorine-containing surfactant compounds No. 13, 29, 79, 80 manufactured by Sumitomo 3M Limited: Compounds synthesized in Synthesis Examples 1 to 4 above
PCDTBT: a compound [weight average molecular weight (Mn: 20000 to 100,000)] having a constitutional unit represented by the following [Chemical Formula 31] manufactured by Aldrich.

In the above formula, Oct represents an n-octyl group.

  Based on the above results, a bibenzo [b] furan compound having at least one structural unit represented by the above formula (1) or (2) is used for the photoelectric conversion layer, and a fluorine-based surfactant is used for the cathode buffer layer. It is clear that the photoelectric conversion element of the invention has high thermal stability in the process of forming the cathode buffer layer and is excellent in photoelectric conversion characteristics of the element.

DESCRIPTION OF SYMBOLS 1 Support body 2 Transparent electrode 3 Anode buffer layer 4 Photoelectric conversion layer 5 Cathode buffer layer 6 Electrode

Claims (3)

A photoelectric conversion element in which a photoelectric conversion layer is provided between two or more electrodes facing each other, and a buffer layer is provided between at least one electrode and the photoelectric conversion layer,
The photoelectric conversion layer contains a bibenzo [b] furan compound having at least one structural unit represented by the following formula (1) or (2),
A photoelectric conversion element, wherein the buffer layer contains a fluorine-based surfactant.

(In the formula, R ¹³ and R ¹⁴ represent a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, an optionally substituted hydrocarbon group or an optionally substituted heterocyclic group.) 2. The photoelectric conversion element according to claim 1, wherein the bibenzo [b] furan compound is a bibenzo [b] furan compound represented by the following general formula (3) or (4).

Wherein R ¹ and R ² represent a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, an optionally substituted hydrocarbon group or an optionally substituted heterocyclic group, Y ¹ And Y ² are a single bond or a group connected by combining 1 to 5 groups selected from the following (Y-1) to (Y-8), and Z ¹ and Z ² are a single bond or the following (Z -1) to (Z-21), and n represents an integer of 1 to 1000.

(Wherein R ¹¹ , R ¹² , R ¹³ or R ¹⁴ is a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, an optionally substituted hydrocarbon group or an optionally substituted heterocyclic ring. Represents a group, Y ³ and Y ⁴ are a single bond or a group connected by combining 1 to 5 groups selected from the following (Y-1) to (Y-8), and Z ³ and Z ⁴ are: Represents a single bond or a group selected from the following (Z-1) to (Z-21), and m represents an integer of 1 to 1,000.

(Wherein X ¹ and X ⁴ represent S, O or NR ³ , k represents an integer of 1 to 4, R ³ represents an optionally substituted hydrocarbon group, and (Y-1) to The hydrogen atoms in the groups (Y-4) and (Y-6) to (Y-8) are fluorine atom, chlorine atom, bromine atom, iodine atom, cyano group, nitro group, hydroxyl group, thiol group, —NR ^4. R ⁵ group, an optionally substituted hydrocarbon group or an optionally substituted heterocyclic group may be substituted, and R ⁴ and R ^{5 each} represents an optionally substituted hydrocarbon group. )

(Wherein X ² represents S, NR ⁶ or SiR ⁷ R ⁸ , X ³ represents S, NR ⁶ , CR ⁷ R ⁸ or SiR ⁷ R ⁸ , and X ⁵ represents S, O or NR ⁶ . , R ⁶ , R ⁷ and R ⁸ represent an optionally substituted hydrocarbon group, and the hydrogen atoms in the groups (Z-1) to (Z-21) are a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a nitro group, a hydroxyl group, a thiol group, -NR ⁹ R ¹⁰ groups, may be substituted at heterocyclic group is also substituted hydrocarbon group or a substituted substituted, R ⁹ And R ¹⁰ represents an optionally substituted hydrocarbon group.) An organic thin-film solar cell using the photoelectric conversion element according to claim 1.

Images