Conjugated polymer, method for producing conjugated polymer, electron-donating organic material, material for photovoltaic element, and photovoltaic element

Abstract

This conjugated polymer has a structure represented by formula 1. In formula 1, Ar represents an arylene group optionally having a substituent, a heteroarylene group optionally having a substituent, or a vinylene group optionally having a substituent, R1 represents an alkyl group optionally having a substituent, an aryl group optionally having a substituent, or a heteroaryl group optionally having a substituent, and n represents the degree of polymerization and falls within a range of 2-1,000.

Description

Conjugated polymer, method for producing conjugated polymer, electron-donating organic material, material for photovoltaic device, and photovoltaic device

[0001] The present invention relates to a conjugated polymer, a method for producing a conjugated polymer, an electron-donating organic material, a material for a photovoltaic device, and a photovoltaic device.

[0002] In recent years, organic thin-film solar cells, which use organic semiconductor materials in the power generation layer, have been attracting attention. Compared to solar cells made from inorganic semiconductor materials, organic thin-film solar cells have the advantage of being thinner and more flexible. For this reason, research and development of various organic thin-film solar cells is being conducted. The conversion efficiency of organic thin-film solar cells has been greatly improved thanks to the development of new materials such as polymer-based electron-donating organic materials (polymer donors) and non-fullerene-based electron-accepting organic materials (non-fullerene acceptors = NFA), which are organic semiconductors.

[0003] For example, organic thin-film solar cells using PM6 as a polymer donor have been reported to have a conversion efficiency of over 18% (Non-Patent Document 1). Furthermore, organic thin-film solar cells using the polymer donor PTzBTE, which has a thiazolothiazole, have been reported to have a conversion efficiency of approximately 15% (Non-Patent Document 2). Polymer donors used in highly efficient organic thin-film solar cells have molecular structures consisting of multiple different fused ring skeletons, and because fluorine atoms are further introduced, they are synthesized using a complex, multi-step synthetic method. For example, as shown in Non-Patent Document 3, PM6, a typical polymer donor, is synthesized through a total of 15 steps. Furthermore, PTzBTE, as described in Non-Patent Document 2, is synthesized through a total of 12 steps.

[0004] L. Zhu, et al., Nat. Mater. 2022, 21, 656-663.K. Yamanaka, et al., Adv. Energy Mater. 2023, 13, 2203443.S. Pang, et al., Angew. Chem. Int. Ed. 2021, 60, 8813-8817.

[0005] As described above, polymer donors are synthesized using a complex, multi-step synthesis method, which increases material costs and poses a major problem for the social adoption of organic thin-film solar cells.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a conjugated polymer that can be synthesized in a small number of steps and exhibits good conversion efficiency, a method for producing the conjugated polymer, an electron-donating organic material, a material for a photovoltaic device, and a photovoltaic device.

[0007] A conjugated polymer according to a first aspect of the present invention has a structure represented by formula 1: (In Formula 1, Ar represents an arylene group which may have a substituent, a heteroarylene group which may have a substituent, or a vinylene group which may have a substituent; R １ represents an alkyl group which may have a substituent, an aryl group which may have a substituent, or a heteroaryl group which may have a substituent, and n represents the degree of polymerization and is in the range of 2 to 1,000.

[0008] In addition, in the formula 1, Ar is preferably represented by any one of the formulas 11 to 43. (In Formulas 13 to 17, 19, and 21 to 43, R ２ represents an alkyl group which may have a substituent, an aryl group which may have a substituent, or a heteroaryl group which may have a substituent.

[0009] A method for producing a conjugated polymer according to a second aspect of the present invention comprises reacting a compound represented by formula 50 with a compound represented by formula 60 to synthesize a polymer represented by formula 1. (In Formula 1 and Formula 50, R １represents an optionally substituted alkyl group, an optionally substituted aryl group, or an optionally substituted heteroaryl group. In formulas 1 and 60, Ar represents an optionally substituted arylene group, an optionally substituted heteroarylene group, or an optionally substituted vinylene group. In formula 1, n represents the degree of polymerization and is in the range of 2 to 1,000. In formula 50, Z represents hydrogen, halogen, a trialkylstannyl group, or a boronic acid ester group, and in formula 60, Y has the same meaning as Z in formula 50.

[0010] An electron-donating organic material according to a third aspect of the present invention is characterized by comprising the conjugated polymer according to the first aspect of the present invention.

[0011] A material for a photovoltaic device according to a fourth aspect of the present invention is characterized by comprising the electron donating organic material and the electron accepting organic material according to the third aspect of the present invention.

[0012] The electron-accepting organic material preferably includes a non-fullerene electron-accepting organic material.

[0013] A photovoltaic element according to a fifth aspect of the present invention is a photovoltaic element having at least an anode and a cathode, characterized in that it has an organic power generation layer between the anode and the cathode, which contains the material for photovoltaic elements according to the fourth aspect of the present invention.

[0014] According to the present invention, it is possible to provide a conjugated polymer that can be synthesized in a small number of steps and exhibits good conversion efficiency, a method for producing a conjugated polymer, an electron-donating organic material, a material for a photovoltaic device, and a photovoltaic device.

[0015] 1 is a schematic cross-sectional view showing one aspect of a photovoltaic element according to the present embodiment; 2 is a graph showing the current density-voltage characteristics of elements A-1, B, and C in Examples; 3 is a graph showing the current density-voltage characteristics of element A-2 in Examples;

[0016] (Conjugated Polymer) The conjugated polymer has a structure represented by formula 1.

[0017]

[0018] In Formula 1, Ar represents an optionally substituted arylene group, an optionally substituted heteroarylene group, or an optionally substituted vinylene group. The arylene group refers to a divalent aromatic hydrocarbon group, and the heteroarylene group refers to a divalent heteroaromatic ring group having atoms other than carbon.

[0019] Examples of the arylene group include divalent groups corresponding to aryl groups such as a phenyl group, a naphthyl group, a biphenyl group, a phenanthryl group, an anthryl group, and a terphenyl group, and these may be unsubstituted or substituted. Examples of the substituent in the substituted group include an alkyl group, an alkoxy group, a halogen atom, and a heteroaryl group. From the viewpoint of further improving the solubility of the conjugated polymer, the number of carbon atoms in the arylene group is preferably 6 or more and 12 or less.

[0020] Examples of heteroarylene groups include divalent groups corresponding to heteroaromatic ring groups such as thienyl, furyl, pyrrolyl, imidazolyl, pyrazolyl, oxazolyl, pyridyl, pyrazyl, pyrimidyl, and thienothienyl groups, and these may be unsubstituted or substituted. Examples of the substituent in the substituted group include alkyl groups, alkoxy groups, halogens, and the aforementioned aryl groups. From the viewpoint of further improving the solubility and crystallinity of the conjugated polymer, the number of carbon atoms in the heteroarylene group is preferably 4 or more and 6 or less.

[0021] In Formula 1, specific examples of Ar are shown in Formulas 11 to 43. In Formulas 13 to 17, Formula 19, and Formulas 21 to 43, R ２ is R in Formula 1 described below. １ is synonymous with.

[0022]

[0023]

[0024] In formula 1, R １represents an alkyl group which may have a substituent, an aryl group which may have a substituent, or a heteroaryl group which may have a substituent. Examples of the alkyl group include monovalent saturated aliphatic hydrocarbon groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, ethylhexyl, butyloctyl, hexyldecyl, and octyldodecyl. The alkyl group may be linear, branched, or cyclic, and may be unsubstituted or substituted. From the viewpoint of further improving the solubility of the conjugated polymer in organic solvents, the alkyl group preferably has 4 or more carbon atoms, more preferably 6 or more carbon atoms. By improving the solubility of the conjugated polymer in organic solvents, the conjugated polymer can be suitably applied to wet processes such as spin coating and slit coating. From the viewpoint of further improving the carrier mobility and photoelectric conversion efficiency of the conjugated polymer, the alkyl group preferably has 24 or less carbon atoms, more preferably 20 or less, and even more preferably 16 or less carbon atoms. In the present invention, the number of carbon atoms in each group does not include the number of carbon atoms contained in the substituent.

[0025] In Formula 1, n represents the degree of polymerization and is an integer ranging from 2 to 1,000. From the viewpoints of further improving the carrier mobility of the conjugated polymer, more easily forming an effective carrier path in a bulk heterojunction type power generation layer, and further improving the photoelectric conversion efficiency, n is preferably 5 or more. On the other hand, from the viewpoint of ease of synthesis, n is preferably less than 200. Here, the degree of polymerization n can be determined from the weight average molecular weight. The weight average molecular weight can be measured using GPC (gel permeation chromatography) and calculated using a polystyrene standard sample.

[0026] (Method for Producing Conjugated Polymer) The conjugated polymer represented by formula 1 can be obtained by synthesis by reacting a compound represented by formula 50 with a compound represented by formula 60.

[0027]

[0028] R in Formula 50 １ Ar in Formula 60 is R in Formula 1 above１ , Ar are synonymous with each other. In Formula 50, Z represents hydrogen, a halogen, a trialkylstannyl group, or a boronate ester group. Examples of halogens include bromine and chlorine. Examples of trialkylstannyl groups include trimethylstannyl groups, triethylstannyl groups, tributylstannyl groups, and trihexylstannyl groups. Examples of boronate ester groups include dialkoxyboryl groups such as dimethoxyboryl groups, diisopropoxyboryl groups, and dibutoxyboryl groups, and cyclic boronate ester groups such as pinacolatoboryl groups. In Formula 60, Y is synonymous with Z in Formula 50. When a compound in Formula 50 where Z represents a halogen is used, it is preferable to combine it with a compound in Formula 60 where Y represents hydrogen, a trialkylstannyl group, or a boronate ester group. When a compound in Formula 50 where Z represents a hydrogen, a trialkylstannyl group, or a boronate ester group is used, it is preferable to combine it with a compound in Formula 60 where Y represents a halogen.

[0029] The synthesis of the compound represented by formula 50 will be described in detail in the Examples below. However, as described below, among the compounds represented by formula 50, compounds in which Z is hydrogen (hereinafter referred to as compounds represented by formula 50a) can be synthesized through four steps (S1 to S4), and among the compounds represented by formula 50, compounds in which Z is halogen, a trialkylstannyl group, or a boronic acid ester group (hereinafter referred to as compounds represented by formula 50b) can be synthesized through five steps (S1 to S5). Note that in formulas 51, 52, 55, 50a, and 50b, R １ is R in the above formula 1 １ In addition, in formula 52, X is a halogen, and examples of the halogen include bromine and chlorine.

[0030]

[0031] In step S1, an alcohol represented by formula 51 is halogenated to synthesize an alkyl halide represented by formula 52. This can be achieved by reacting the alcohol with a halogen such as bromine using a reactant such as triphenylphosphine in a solvent such as dichloromethane. Purification can be easily achieved by distillation rather than using a silica gel column.

[0032] In step S2, the second position of 3-thiophenecarboxaldehyde represented by formula 53 is formylated to synthesize a compound represented by formula 54. The compound represented by formula 53 can be formylated using a base such as lithium diisopropylamide and a formylating reagent such as N-formylpiperidine in a solvent such as tetrahydrofuran. The compound is then recrystallized and purified.

[0033] In step S3, the compound represented by formula 54 is reacted with the alkyl halide represented by formula 52 in a solvent such as dimethylformamide to substitute the hydrogen atom of the carboxyl group of the compound represented by formula 54 with an alkyl group, thereby synthesizing the compound represented by formula 55. Purification can be easily performed by a liquid separation process without using a silica gel column or recrystallization.

[0034] In step S4, the compound represented by formula 55 is reacted with rubeanic acid in a solvent such as dimethylformaldehyde to synthesize the compound represented by formula 50a. Purification can be easily performed by liquid separation without using a silica gel column.

[0035] In step S5, the compound represented by formula 50a is reacted with a halogen such as bromine in a solvent such as a mixed solvent of chloroform and acetic acid to halogenate the compound, thereby synthesizing a compound represented by formula 50b in which Z is a halogen. In step S5, the compound represented by formula 50a is reacted with a base such as lithium diisopropylamide, followed by a stannylation reagent such as trimethyltin chloride to stannylate the compound, thereby synthesizing a compound represented by formula 50b in which Z is a trialkylstannyl group. In step S5, the compound represented by formula 50a is borylated by reacting with a borylation reagent such as pinacol isopropoxyboronate to synthesize a compound represented by formula 50b in which Z is a trialkylstannyl group or a boronic acid ester group. Purification can be easily performed by recrystallization, solvent washing, and activated carbon treatment without using a silica gel column.

[0036] Furthermore, when Y of the compound represented by formula 60 is a trialkylstannyl group, it can be synthesized in one step by referring to Macromolecules 2010, 43, 697-708. For example, it can be synthesized by reacting a compound represented by formula 61 with a trialkyltin halide such as trimethyltin chloride. Note that Ar in formula 61 has the same meaning as Ar in formula 1. Furthermore, X in formula 61 represents hydrogen or a halogen such as bromine or chlorine.

[0037]

[0038] In this way, the compound represented by formula 50a can be synthesized in four steps, the compound represented by formula 50b can be synthesized in five steps, and the compound represented by formula 60 can be synthesized in one step. The conjugated polymer represented by formula 1 can be synthesized by reacting the compound represented by formula 50a or formula 50b with the compound represented by formula 60. Therefore, the conjugated polymer represented by formula 1 can be synthesized in a small number of steps, a total of six or seven steps. Furthermore, the compounds represented by formulas 52, 55, 50a, and 50b, respectively, can be purified without using a silica gel column, i.e., during purification in steps S1, S3, S4, and S5, and therefore can be synthesized easily. This allows for a reduction in the production cost of the conjugated polymer represented by formula 1.

[0039] (Electron-donating organic material, material for photovoltaic device, and photovoltaic device) The electron-donating organic material according to this embodiment includes a conjugated polymer having a structure represented by the above formula 1. An electron-donating organic material using a conjugated polymer having a structure represented by the above formula 1 exhibits p-type semiconductor properties. Other electron-donating organic materials may be included together with such an electron-donating organic material.

[0040] The electron-donating organic material according to the present embodiment can be applied to organic transistors by taking advantage of its high carrier mobility. It can also be applied to various photoelectric conversion devices that utilize its photoelectric conversion function, optical rectification function, and the like. For example, it is useful in photovoltaic elements (solar cells), electronic elements (image sensors, optical sensors, optical switches), optical recording materials (optical memories, etc.), imaging elements, and the like, and can be particularly suitably used as a material for photovoltaic elements.

[0041] The material for a photovoltaic device according to this embodiment includes the above-described electron-donating organic material and electron-accepting organic material. The electron-accepting organic material preferably exhibits n-type semiconductor properties.

[0042] Examples of electron-accepting organic materials that exhibit n-type semiconductor properties include phenyl C61 butyric acid methyl ester (PC ６０ BM) and phenyl C71 butyric acid methyl ester (PC７０ fullerene-type organic materials such as 2,2'-((2Z,2'Z)-((12,13-bis(2-ethylhexyl)-3,9-(2-butyloctyl)-12,13-dihydro-[1,2,5]thiadiazolo[3,4-e]thieno[2",3":4',5']thieno[2',3':4,5]pyrrolo[3,2-g]thieno[2',3':4,5]thieno[3,2-b]indole-2,10-d iyl)bis(methanylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile (hereinafter referred to as L8 -BO) or 2,2'-((2Z,2'Z)-((12,13-bis(2-ethylhexyl)-3,9-diundecyl-12,13-dihydro-[1,2,5]thiadiazolo[3,4-e]thien o[2”,3”:4',5']thieno[2',3':4,5]pyrrolo[3,2-g]thieno[2',3':4,5]thieno[3,2-b]indole-2,10-diyl)bis(methanylyl idene)) bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile (hereinafter referred to as Y6) and 2,2'-[[6,6,12 , 12-Tetrakis(4-hexylphenyl)-6,12-dihydrodithioeno[2,3-d:2',3'-d']-s-indaceno[1,2-b:5,6-b']dithiophene-2,8-diyl]bis[methyldyne(3-oxo-1H-indene-2,1(3H)-diylidene)]]bis[propanedinitrile] (ITIC) are examples of non-fullerene organic materials.

[0043] In the photovoltaic element material according to this embodiment, the content ratio of the electron-donating organic material to the electron-accepting organic material (donor-acceptor ratio) is preferably in the range of 1:99 to 99:1, more preferably in the range of 20:80 to 60:40, and further preferably in the range of 40:60 to 50:50.

[0044] In order to further improve the photoelectric conversion efficiency, it is preferable to remove as many impurities as possible that may trap carriers. In this embodiment, methods for removing impurities from the electron-donating organic material and the electron-accepting organic material include, for example, column chromatography, recrystallization, sublimation, reprecipitation, Soxhlet extraction, molecular weight fractionation by GPC, filtration, ion exchange, and chelation. Two or more of these methods may be combined.

[0045] Next, a photovoltaic element according to the present embodiment will be described. The photovoltaic element according to the present embodiment has at least an anode and a cathode, and an organic power generation layer containing the material for photovoltaic elements according to the present embodiment between them. A hole transport layer may be present between the organic power generation layer and the anode, or an electron transport layer may be present between the organic power generation layer and the cathode. FIG. 1 shows a schematic cross-sectional view of one aspect of the photovoltaic element according to the present embodiment. The photovoltaic element has an anode, an organic power generation layer containing the material for photovoltaic elements according to the present embodiment, and a cathode, in this order, on a substrate. Alternatively, the photovoltaic element may have a cathode / organic power generation layer containing the material for photovoltaic elements according to the present embodiment / anode, in this order, on a substrate, inversely to FIG. 1.

[0046] Next, each layer will be described. The organic power generation layer contains a photovoltaic device material according to this embodiment. That is, it contains an electron-donating organic material using a conjugated polymer having a structure represented by Formula 1, and an electron-accepting organic material. These materials may be mixed or laminated, but are preferably mixed. A bulk heterojunction organic power generation layer formed by mixing an electron-donating organic material and an electron-accepting organic material can increase the interface between the electron-donating organic material and the electron-accepting organic material, which contributes to photoelectric conversion, thereby achieving superior charge separation and charge transport capabilities. In a bulk heterojunction organic power generation layer, it is preferable that the electron-donating organic material and the electron-accepting organic material are phase-separated on a nanometer scale and that a carrier path to the electrode is formed continuously. The domain size of this phase-separated structure is not particularly limited, but is typically 1 nm or more and 50 nm or less.

[0047] In the photovoltaic element according to the present embodiment, it is preferable that the anode or cathode has optical transparency, that is, is transparent or semi-transparent. The optical transparency of the electrode is not particularly limited as long as it allows incident light to reach the organic power generation layer and generate an electromotive force. Here, the optical transparency in the present invention is defined as the transmitted light intensity (W / m ２ ) / incident light intensity (W / m ２ ) × 100 (%). The thickness of the electrode may be in a range that provides light transparency and conductivity, and although it differs depending on the electrode material, a thickness of 20 nm to 300 nm is preferable. Note that the other electrode does not necessarily need to be light transparent as long as it is conductive, and there are no particular restrictions on its thickness.

[0048] Examples of conductive materials for forming electrodes include metals such as gold, platinum, silver, copper, iron, zinc, tin, aluminum, indium, chromium, nickel, cobalt, scandium, vanadium, yttrium, cerium, samarium, europium, terbium, and ytterbium, and alloys thereof; metal oxides such as indium, tin, molybdenum, and nickel; composite metal oxides such as indium tin oxide (ITO), indium zinc oxide (IZO), aluminum zinc oxide (AZO), and gallium zinc oxide (GZO); alkali metals or alkaline earth metals such as lithium, magnesium, sodium, potassium, calcium, strontium, and barium; carbon-containing materials such as graphite, graphite intercalation compounds, carbon nanotubes, and graphene; and organic compounds such as polyaniline and its derivatives, polythiophene and its derivatives. Two or more of these may be used, and electrodes made of laminates of these materials are also preferably used.

[0049] Here, the conductive material used in the anode preferably forms an ohmic junction with the organic power generation layer. Furthermore, when a hole transport layer is used, the conductive material used in the anode preferably forms an ohmic junction with the hole transport layer. Furthermore, the conductive material used in the cathode preferably forms an ohmic junction with the organic power generation layer or the electron transport layer. Here, an electron extraction layer may be introduced into the cathode, which can improve the junction between the cathode and the organic power generation layer or the electron transport layer and increase the extracted current. This can further improve the photoelectric conversion efficiency. Examples of materials for forming the electron extraction layer include metal fluorides such as lithium fluoride (LiF) and cesium fluoride.

[0050] The substrate may be a substrate on which an electrode material or an organic power generation layer can be laminated depending on the type and application of the photoelectric conversion material, and examples thereof include films or plates made by any method from inorganic materials such as alkali-free glass, quartz glass, and alloys of aluminum, iron, copper, stainless steel, etc.; and organic materials such as polyester, polycarbonate, polyolefin, polyamide, polyimide, polyphenylene sulfide, polyparaxylene polymethyl methacrylate, epoxy resin, fluorine-based resin, etc. When used with light incident from the substrate side, the substrate preferably has a light transmittance of 80% or more.

[0051] Examples of materials for forming the hole transport layer include conductive polymers such as polythiophene polymers, poly-p-phenylene vinylene polymers, polyfluorene polymers, polypyrrole polymers, polyaniline polymers, polyfuran polymers, polypyridine polymers, and polycarbazole polymers, and phthalocyanine derivatives (H ２ Pc, CuPc, ZnPc, etc.), porphyrin derivatives, acene compounds (tetracene, pentacene, etc.), and other low-molecular-weight organic compounds exhibiting p-type semiconductor properties; carbon compounds such as graphene and graphene oxide; and MoO ３ Molybdenum oxide (MoO ｘ ), W.O. ３ Tungsten oxide (WO ｘ ), nickel oxides such as NiO (NiO ｘ ), V ２ O ５ Vanadium oxide (VO ｘ ), ZrO ２ Zirconium oxide (ZrO ｘ ), Cu ２ Copper oxides such as CuO ｘ ), copper iodide, RuO ４ Ruthenium oxide (RuO ｘ ), Re ２ O ７ Rhenium oxide (ReO) ｘ) and other inorganic compounds. Two or more of these may be used, or these may be laminated. Among these, polythiophene-based polymers such as polyethylene dioxythiophene (PEDOT) and PEDOT with polystyrene sulfonate (PSS), molybdenum oxide, vanadium oxide, and tungsten oxide are preferably used. The thickness of the hole transport layer is preferably 10 nm or more and 200 nm or less.

[0052] The material for forming the electron transport layer is preferably a material exhibiting n-type semiconductor properties, such as TiO ２ Titanium oxide (TiO ｘ ) and zinc oxide such as ZnO (ZnO ｘ Inorganic materials such as PEI (Polyethylenenimine) and PDINO (2,9-bis[3-(dimethyloxideamino)propyl]anthra[2,1,9-def:6,5,10-d'e'f']diisoquinoline-1,3,8,10(2H,9H)-tetrone), poly[[2,7-bis(2-ethylhexyl)-1,2,3,6,7,8-hexahydro-1,3,6,8-tetraoxobenzo[lmn][3,8]phenanthroline-4,9-diyl]-2,5-thiophenediyl[9,9-bis[3'((N,N-dimethyl)-N-ethylammonium)]-propyl]-9H-furan] Preferred examples of such an organic material include poly[[2,7-bis(2-ethylhexyl)-1,2,3,6,7,8-hexahydro-1,3,6,8-tetraoxobenzo[lmn][3,8]phenanthroline-4,9-diyl]-2,5-thiophenediyl[9,9-bis[3-(dimethylamino)propyl]-9H-fluorene-2,7-diyl]-2,5-thiophenediyl] (PNDIT-F3N-Br) and poly[[2,7-bis(2-ethylhexyl)-1,2,3,6,7,8-hexahydro-1,3,6,8-tetraoxobenzo[lmn][3,8]phenanthroline-4,9-diyl]-2,5-thiophenediyl[9,9-bis[3-(dimethylamino)propyl]-9H-fluorene-2,7-diyl]-2,5-thiophenediyl] (PNDIT-F3N); and organic-inorganic hybrid materials such as PEI-Zn (Polyethyleneimine-Zn).

[0053] Next, an example of a method for manufacturing a photovoltaic element according to this embodiment will be described. A transparent electrode (corresponding to the anode in this case) such as ITO is formed on a substrate by sputtering or the like. Next, a solution of a photovoltaic element material containing an electron-donating organic material using a conjugated polymer having a structure represented by Formula 1 and, if necessary, an electron-accepting organic material dissolved in an organic solvent is applied to the transparent electrode to form an organic power generation layer. The organic solvent is not particularly limited as long as it can appropriately dissolve or disperse the electron-donating organic material and the electron-accepting organic material, but from the viewpoint of ease of handling, an organic solvent with a boiling point of 50°C or higher is preferred.

[0054] Examples of methods for forming the organic power generation layer include spin coating, blade coating, slit die coating, screen printing, bar coater coating, mold coating, print transfer, dipping and pulling, inkjet printing, spraying, and vacuum deposition. It is preferable to select a formation method depending on the desired properties of the organic power generation layer, such as film thickness control and orientation control. Any additive may be added to optimize the phase separation structure of the organic power generation layer. Preferred additives include 1,8-diiodooctane, 1-chloronaphthalene, and 1-phenylnaphthalene.

[0055] Next, a metal electrode (corresponding to a cathode in this case) made of Al, Ag, or the like is formed on the organic power generation layer by vacuum deposition or sputtering. When a low-molecular organic material is used for the electron transport layer by vacuum deposition, it is preferable to subsequently form the metal electrode while maintaining the vacuum.

[0056] When a hole transport layer is provided between the anode and the organic power generation layer, a solution of a desired p-type organic semiconductor material (e.g., PEDOT) is applied to the anode, and the solvent is then removed to form the hole transport layer. Examples of application methods include spin coating, bar coating, and blade casting. Examples of solvent removal methods include heating using a vacuum thermostatic bath or a hot plate. When using low-molecular-weight organic materials such as phthalocyanine derivatives or porphyrin derivatives, vacuum deposition using a vacuum deposition machine can also be used.

[0057] When an electron transport layer is provided between the organic power generation layer and the cathode, a solution of a desired n-type organic semiconductor material (such as a fullerene derivative) or n-type inorganic semiconductor material (such as titanium oxide gel) is applied to the organic power generation layer, and then the solvent is removed to form the electron transport layer. Examples of the application method and solvent removal method include the methods exemplified for forming the hole transport layer. For example, a phenanthroline derivative or C ６０ When using a low molecular weight organic material such as the above, it is also possible to apply a vacuum deposition method using a vacuum deposition machine.

[0058] Polymer compounds 1a to 1c were synthesized stepwise as shown in the following scheme. Compound 6 was synthesized with reference to Macromolecules 2010, 43, 697-708.

[0059]

[0060] (Synthesis of Compound 2) A 500 mL three-neck flask was flame-dried and purged with argon, and then compound 1 (128 mg, 1 mmol) and ultra-dehydrated tetrahydrofuran (10 mL) were added. Lithium diisopropylamide (78 mmol) was added dropwise to the reaction solution at room temperature, and the mixture was stirred at room temperature for 1 hour. N-formylpiperidine (8.7 mL, 78 mmol) was then added, and the mixture was stirred at room temperature for 1 hour. Hydrochloric acid was added to the reaction solution, and the mixture was extracted with ether. The organic layer was washed with dilute hydrochloric acid and water and dried over anhydrous magnesium sulfate. The mixture was then filtered, concentrated, and purified by recrystallization using a mixed solvent of hexane and dichloromethane to obtain compound 2 (142 mg, 0.91 mmol, 91% yield). The physical property data of compound 2 are as follows. 1 H NMR (500 MHz, CDCl3) δ 10.50 (s, 1H), 7.76 - 7.69 (m, 2H).

[0061] (Synthesis of Compound 3a) Compound 2 (4.0 g, 25.6 mmol), 1-bromo-2-hexyldecane (6.3 g, 20.5 mmol), sodium carbonate (27 g, 256 mmol), and dimethylformamide (150 mL) were added to a 300 mL recovery flask and stirred at 90°C for 12 hours. The sodium carbonate was removed by filtration, and the mixture was extracted with hexane. The extracted solution was washed with water and methanol and dried over anhydrous magnesium sulfate. After that, the mixture was filtered and concentrated to obtain Compound 3a (7.41 g, 19.5 mmol, yield 95.0%). The physical property data of Compound 3a are as follows: 1 H NMR (500 MHz, CDCl3) δ 10.63 (d, J = 1.2 Hz, 1H), 7.64 (dd, J = 5.1, 1.2 Hz, 1H), 7.57 (d, J = 5.1 Hz, 1H), 4.27 (d, J = 5.7 Hz, 2H), 1.77 (h, J = 5.9 Hz, 1H), 1.36 - 1.26 (m, 24H), 0.89 - 0.86 (m, 6H).

[0062] (Synthesis of Compound 3b) Compound 2 (1.0 g, 6.4 mmol), 1-bromo-2-octyldodecane (1.6 g, 5.1 mmol), sodium carbonate (6.8 g, 64 mmol), and dimethylformamide (50 mL) were added to a 300 mL recovery flask and stirred at 90°C for 12 hours. The sodium carbonate was removed by filtration, and the mixture was extracted with hexane. The extracted solution was washed with water and methanol and dried over anhydrous magnesium sulfate. After that, the mixture was filtered and concentrated to obtain Compound 3b (2.1 g, 4.7 mmol, yield 92.0%). The physical property data of Compound 3b are as follows: 1 H NMR (500 MHz, CDCl3) δ 10.63 (d, J = 1.2 Hz, 1H), 7.64 (dd, J = 5.1, 1.2 Hz, 1H), 7.57 (d, J = 5.1 Hz, 1H), 4.27 (d, J = 5.7 Hz, 2H), 1.77 (h, J = 5.9 Hz, 1H), 1.44 - 1.18 (m, 32H), 0.87 (m, 6H).

[0063] (Synthesis of Compound 3c) Compound 2 (193 mg, 1.24 mmol), 1-bromo-5-hexyltridecane (344 mg, 0.992 mmol), sodium carbonate (1.31 g, 12.4 mmol), and dimethylformamide (15 mL) were added to a 300 mL recovery flask and stirred at 90°C for 12 hours. The sodium carbonate was removed by filtration, and the mixture was extracted with hexane. The extracted solution was washed with water and methanol and dried over anhydrous magnesium sulfate. After filtration and concentration, compound 3c (407 mg, 0.96 mmol, yield 97.0%) was obtained. The physical property data of compound 3c are as follows: 1 H NMR (400 MHz, CDCl3) δ 10.63 (d, J = 1.1 Hz, 1H), 7.63 (dd, J = 5.1, 1.1 Hz, 1H), 7.58 (d, J = 5.1 Hz, 1H), 4.36 (t, J = 6.8 Hz, 2H), 1.76 (p, J = 7.0 Hz, 2H), 1.39 (m, 2H), 1.36 - 1.26 (m, 27H), 0.89 - 0.86 (m, 6H).

[0064] (Synthesis of Compound 5a) Compound 3a (7.41 g, 19.5 mmol), rubeanic acid (1.17 g, 9.74 mmol), and dimethylformamide (25 mL) were added to a 100 mL recovery flask and stirred at 140°C for 12 hours. The reaction solution was cooled to room temperature and extracted with hexane. The extracted solution was washed with water and methanol and dried over anhydrous magnesium sulfate. It was then filtered and concentrated to obtain a black solid containing compound 4a. The resulting solid was dissolved in a mixed solvent of chloroform and acetic acid (chloroform:acetic acid = 1:1) and cooled to 0°C. Bromine (2.0 mL, 38.7 mmol) was added dropwise to the solution, and the mixture was heated to room temperature and stirred for 8 hours. Aqueous sodium thiosulfate was poured into the reaction solution, which was then extracted with chloroform, washed with water and aqueous sodium thiosulfate, and dried over anhydrous magnesium sulfate. The resulting solid was washed with isopropanol, dissolved in hexane, added with activated carbon, and stirred at 50°C for 3 hours. The activated carbon was removed by filtration, and the hexane was removed under reduced pressure. The resulting solid was purified by recrystallization using a mixed solvent of ethanol and hexane to obtain compound 5a (4.23 g, 4.23 mmol, yield 43%). The physical properties of compound 5a are as follows: 1 H NMR (400 MHz, CDCl3) δ 7.45 (s, 2H), 4.26 (d, J = 5.7 Hz, 4H), 1.78 (h, J = 5.8 Hz, 2H), 1.37 - 1.25 (m, 48H), 0.88 (m, 12H).

[0065] (Synthesis of Compound 5b) Compound 3b (2.05 g, 4.7 mmol), rubeanic acid (1.17 g, 2.8 mmol), and dimethylformamide (10 mL) were added to a 100 mL recovery flask and stirred at 140°C for 12 hours. The reaction solution was cooled to room temperature and extracted with hexane. The extracted solution was washed with water and methanol and dried over anhydrous magnesium sulfate. It was then filtered and concentrated to obtain a black solid containing compound 4b. The resulting solid was dissolved in a mixed solvent of chloroform and acetic acid (chloroform:acetic acid = 1:1) and cooled to 0°C. Bromine (0.97 mL, 18.8 mmol) was added dropwise to the solution, and the mixture was heated to room temperature and stirred for 8 hours. Aqueous sodium thiosulfate was poured into the reaction solution, which was then extracted with chloroform, washed with water and aqueous sodium thiosulfate, and dried over anhydrous magnesium sulfate. The resulting solid was washed with isopropanol, dissolved in hexane, added with activated carbon, and stirred at 50°C for 3 hours. The activated carbon was removed by filtration, and the hexane was removed under reduced pressure. The resulting solid was purified by recrystallization using a mixed solvent of ethanol and hexane to obtain compound 5b (0.44 g, 0.94 mmol, yield 40%). The physical properties of compound 5b are as follows: 1 H NMR (400 MHz, CDCl3) δ 7.45 (s, 2H), 4.26 (d, J = 5.7 Hz, 4H), 1.78 (h, J = 5.8 Hz, 2H), 1.36 - 1.26 (m, 64H), 0.90 (m, 12H).

[0066] (Synthesis of Compound 5c) Compound 3c (407 mg, 0.96 mmol), rubeanic acid (69 mg, 0.58 mmol), and dimethylformamide (2 mL) were added to a 10 mL recovery flask and stirred at 140°C for 12 hours. The reaction solution was cooled to room temperature and extracted with hexane. The extracted solution was washed with water and methanol and dried over anhydrous magnesium sulfate. It was then filtered and concentrated to obtain a black solid containing compound 4c. The resulting solid was dissolved in a mixed solvent of chloroform and acetic acid (chloroform:acetic acid = 1:1) and cooled to 0°C. Bromine (0.10 mL, 1.92 mmol) was added dropwise thereto, and the mixture was heated to room temperature and stirred for 8 hours. Aqueous sodium thiosulfate was poured into the reaction solution, which was then extracted with chloroform, washed with water and aqueous sodium thiosulfate, and dried over anhydrous magnesium sulfate. The resulting solid was washed with isopropanol, dissolved in hexane, added with activated carbon, and stirred at 50°C for 3 hours. The activated carbon was removed by filtration, and the hexane was removed under reduced pressure. The resulting solid was purified by recrystallization using a mixed solvent of ethanol and hexane to obtain compound 5c (314 mg, 0.29 mmol, yield 60%). The physical properties of compound 5c are as follows: 1 H NMR (400 MHz, CDCl3) δ 7.48 (s, 2H), 4.36 (t, J = 6.7 Hz, 4H), 1.76 (p, J = 7.0 Hz, 4H), 1.39 (m, 4H), 1.34 - 1.15 (m, 54H), 0.88 - 0.86 (m, 12H).

[0067] (Synthesis of Polymer Compound 1a) A Schlenk flask was flame-dried and purged with argon, and then compound 5a (50.0 mg, 0.050 mmol), compound 6 (20.5 mg, 0.050 mmol), tris(dibenzylideneacetone)dipalladium(0)-chloroform adduct (1.04 mg, 1 μmmol), tri(o-tolyl)phosphine (2.44 mg, 8 μmmol), and chlorobenzene (1 mL) were added and stirred at room temperature for 30 minutes. The mixture was then stirred at 120°C for 24 hours, and the reaction solution was poured into methanol and stirred for 2 hours. The resulting solid was subjected to Soxhlet extraction with methanol, hexane, dichloromethane, and chloroform, in that order, and the chloroform-soluble component was dried to obtain polymer compound 1a (43 mg, yield 90%).

[0068] (Synthesis of Polymer Compound 1b) After flame drying and purging with argon, compound 5b (55.5 mg, 0.050 mmol), compound 6 (20.5 mg, 0.050 mmol), tris(dibenzylideneacetone)dipalladium(0)-chloroform adduct (1.04 mg, 1 μmmol), tri(o-tolyl)phosphine (2.44 mg, 8 μmmol), and chlorobenzene (1 mL) were added and stirred at room temperature for 30 minutes. The mixture was then stirred at 120°C for 24 hours, and the reaction solution was poured into methanol and stirred for 2 hours. The resulting solid was subjected to Soxhlet extraction with methanol, hexane, dichloromethane, and chloroform, in that order, and the chloroform-soluble component was dried to obtain polymer compound 1b (41 mg, yield 77%).

[0069] (Synthesis of Polymer Compound 1c) After flame drying and purging with argon, compound 5c (54.3 mg, 0.050 mmol), compound 6 (20.5 mg, 0.050 mmol), tris(dibenzylideneacetone)dipalladium(0)-chloroform adduct (1.04 mg, 1 μmmol), tri(o-tolyl)phosphine (2.44 mg, 8 μmmol), and chlorobenzene (1 mL) were added and stirred at room temperature for 30 minutes. The mixture was then stirred at 120°C for 24 hours, and the reaction solution was poured into methanol and stirred for 2 hours. The resulting solid was subjected to Soxhlet extraction with methanol, hexane, dichloromethane, and chloroform, in that order, and the chloroform-soluble component was dried to obtain polymer compound 1c (38 mg, yield 73%).

[0070] (Cyclic voltammetry measurement of polymer compounds 1a, 1b, and 1c) First, 5 mg / mL chloroform solutions of polymer compounds 1a, 1b, and 1c were prepared. Next, a working electrode was immersed in each of the chloroform solutions and then dried to prepare a thin film of each of the polymer compounds on the working electrode. Then, the prepared thin films were measured, and the obtained current-potential curves were analyzed to determine the redox potentials.

[0071] The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels of polymer compounds 1a, 1b, and 1c were calculated using the oxidation and reduction potentials determined by cyclic voltammetry. These values ​​are summarized in Table 1.

[0072]

[0073] (UV-vis absorption spectrum measurement of solutions using polymer compounds 1a, 1b, and 1c) First, 1 mg of polymer compounds 1a, 1b, and 1c were each dissolved in 10 mL of chlorobenzene. This chlorobenzene solution was further diluted 10 times with chlorobenzene to prepare a measurement solution.

[0074] (UV-vis absorption spectrum measurement of thin films using polymer compounds 1a, 1b, and 1c) A glass substrate was thoroughly washed and then subjected to UV ozone treatment. Next, a chloroform solution of polymer compounds 1a, 1b, and 1c adjusted to a concentration of 4 mg / mL was spin-coated at 2500 rpm for 20 seconds to prepare a thin film for measurement.

[0075] The maximum absorption wavelength and absorption edge of each chloroform solution and thin film were evaluated by UV-vis absorption spectroscopy. These values ​​are summarized in Table 2.

[0076]

[0077] (Evaluation of Organic Thin-Film Solar Cell Elements Using Polymer Compounds 1a, 1b, and 1c) Subsequently, organic thin-film solar cell elements were fabricated using the synthesized polymer compounds 1a, 1b, and 1c, and the photoelectric conversion efficiency was evaluated. After thoroughly cleaning the glass substrate on which the ITO film had been patterned, UV ozone treatment was performed. Next, PEDOT:PSS was spin-coated at 5,000 rpm for 30 seconds as a hole transport layer. The substrate was heated at 150°C for 15 minutes to form a hole transport layer. The substrate on which the hole transport layer had been formed was brought into a glove box, and a chloroform solution containing polymer compound 1a and Y12 (compound shown in the formula below) (weight ratio of polymer compound 1a / Y12 = 1 / 1.5) was spin-coated at 2,500 rpm for 30 seconds to form a power generation layer (film thickness 100 nm). This thin film was heated at 90°C for 5 minutes under a nitrogen atmosphere. Furthermore, an electron transport layer was formed on the power generation layer by spin-coating a solution of 2 mg of PNDIT-F3N (Poly[[2,7-bis(2-ethylhexyl)-1,2,3,6,7,8-hexahydro-1,3,6,8-tetraoxobenzo[lmn][3,8]phenanthroline-4,9-diyl]-2,5-thiophenediyl[9,9-bis[3-(dimethylamino)propyl]-9H-fluorene-2,7-diyl]-2,5-thiophenediyl]) in a mixed solvent of 2 mL of methanol and 0.5 mL of acetic acid at 2000 rpm for 30 seconds. Next, a silver film having a thickness of 150 nm was formed as an electrode layer by vacuum deposition to prepare a 4 mm square organic thin-film solar cell element (hereinafter referred to as element A-1).

[0078]

[0079] Organic thin-film solar cell elements (hereinafter referred to as element B and element C, respectively) were prepared in the same manner as above, except that polymer compounds 1b and 1c were used instead of polymer compound 1a.

[0080] In addition, an organic thin-film solar cell element (hereinafter referred to as element A-2) using polymer compound 1a was produced in the same manner as above, except that 2PACz ([2-(9H-Carbazol-9-yl)ethyl]phosphonic Acid) was used in place of PEDOT:PSS as the hole transport layer.

[0081] Each of the obtained elements was subjected to a solar simulator (AM1.5G filter, irradiance 100 mW / cm ２ ) was used to irradiate a certain amount of light, and the generated current and voltage were measured. Figure 2 shows the current density-voltage characteristics of Devices A-1, B, and C. Figure 3 shows the current density-voltage characteristics of Device A-2.

[0082] From the obtained Figures 2 and 3, the short-circuit current density (J ｓｃ (mAcm －２ The photoelectric conversion efficiency (η (%)) of each element was calculated using the formula η = (J ｓｃ ×V ｏｃ The results are summarized in Table 3.

[0083]

[0084] The present invention allows various embodiments and modifications without departing from the broad spirit and scope of the present invention. Furthermore, the above-described embodiments are intended to explain the present invention and do not limit the scope of the present invention. That is, the scope of the present invention is defined by the claims, not the embodiments. Various modifications made within the scope of the claims and the meaning of the invention equivalent thereto are considered to be within the scope of the present invention.

[0085] This application is based on Japanese Patent Application No. 2024-77674, filed on May 13, 2024. The entire specification, claims, and drawings of Japanese Patent Application No. 2024-77674 are incorporated herein by reference.

[0086] The conjugated polymer according to the present invention can be used as an electron-donating organic material, a material for a photovoltaic device, or a photovoltaic device.

Claims

1. Having a structure represented by Formula 1: (In Formula 1, Ar represents an arylene group which may have a substituent, a heteroarylene group which may have a substituent, or a vinylene group which may have a substituent; R １ represents an alkyl group which may have a substituent, an aryl group which may have a substituent, or a heteroaryl group which may have a substituent, and n represents a degree of polymerization which is in the range of 2 or more and 1,000 or less.

2. In the formula 1, Ar is represented by any one of formulas 11 to 43. (In Formulas 13 to 17, 19, and 21 to 43, R ２ represents an alkyl group which may have a substituent, an aryl group which may have a substituent, or a heteroaryl group which may have a substituent. The conjugated polymer according to claim 1, 3. Reacting a compound represented by formula 50 with a compound represented by formula 60 to synthesize a polymer represented by formula 1; (In Formula 1 and Formula 50, R １ represents an optionally substituted alkyl group, an optionally substituted aryl group, or an optionally substituted heteroaryl group. In formulas 1 and 60, Ar represents an optionally substituted arylene group, an optionally substituted heteroarylene group, or an optionally substituted vinylene group. In formula 1, n represents a degree of polymerization and is in the range of 2 or more and 1,000 or less. In formula 50, Z represents hydrogen, halogen, a trialkylstannyl group, or a boronic acid ester group, and in formula 60, Y has the same meaning as Z in formula 50.

4. An electron-donating organic material comprising the conjugated polymer according to claim 1 or 2.

5. A material for a photovoltaic device, comprising the electron donating organic material and the electron accepting organic material according to claim 4.

6. The material for a photovoltaic device according to claim 5, wherein the electron-accepting organic material includes a non-fullerene type electron-accepting organic material.

7. A photovoltaic device having at least an anode and a cathode, characterized in that it has an organic power generation layer between the anode and the cathode, which contains the material for photovoltaic devices according to claim 5.

8. A photovoltaic element having at least an anode and a cathode, characterized in that it has an organic power generation layer between the anode and the cathode, which contains the material for photovoltaic elements according to claim 6.

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