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

Abstract

To provide a conjugated polymer, an electron-donating organic material, a material for a photovoltaic element, and a photovoltaic element that exhibit a short π-stack distance in a thin-film state.SOLUTION: A conjugated polymer has a structure represented by formula 1, wherein, in formula 1, X represents carbon, oxygen, sulfur, selenium, nitrogen, or a vinylene group, R1 represents an alkyl group, Ar represents an arylene group or a heteroarylene group, m represents an integer of 0 to 10, and n represents a degree of polymerization and represents a range of 2 to 1000.SELECTED DRAWING: Figure 5

Description

[Technical Field]

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

[0002] Solar cells have attracted considerable attention as an energy source that contributes to the realization of a recycling-oriented society. Currently, inorganic materials such as single-crystal silicon, polycrystalline silicon, amorphous silicon, and compound semiconductors are used as semiconductor materials in photovoltaic devices such as solar cells. However, solar cells manufactured using inorganic semiconductors have the drawback of being expensive to manufacture. This cost is primarily due to the process of forming semiconductor thin films under vacuum and high temperatures. Therefore, organic solar cells using organic semiconductors such as conjugated polymers and organic crystals, as well as organic dyes, have been developed as semiconductor materials that are expected to simplify the manufacturing process. In such organic solar cells, the semiconductor material layer can be fabricated by a coating method, significantly simplifying the manufacturing process.

[0003] As a method for improving the photoelectric conversion efficiency of organic solar cells, a power generation layer has been reported in which an electron-donating organic material (p-type organic semiconductor) and an electron-accepting organic material (n-type organic semiconductor) are mixed, and the junction surface contributing to photoelectric conversion is made into a bulk heterojunction type. For example, it has been reported that an organic power generation layer using D18 as the electron-donating organic material and Y6 as the electron-accepting organic material exhibits high photoelectric conversion efficiency (e.g., Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Qishi Liu et al., "18% Efficiency organic solar cells", Science Bulletin, Vol. 65, 272-275 (2020). Summary of the Invention [Problem to be solved by the invention]

[0005] Although various electron-donating organic materials have been developed, material development is still in its infancy. One way to improve photovoltaic conversion efficiency is to shorten the π-stack distance when thinning the material.

[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 has a short π-stack distance when formed into a thin film, an electron-donating organic material, a material for a photovoltaic device, and a photovoltaic device. [Means for solving the problem]

[0007] The conjugated polymer according to the first aspect of the present invention comprises: having a structure represented by formula 1: [ka] (In Formula 1, X represents carbon, oxygen, sulfur, selenium, nitrogen, or a vinylene group. R 1 represents an alkyl group. Ar represents an arylene group or a heteroarylene group. m represents an integer of 0 to 10. n represents the degree of polymerization, and is in the range of 2 to 1,000. It is characterized by:

[0008] The electron donating organic material according to the second aspect of the present invention comprises: A polymer comprising the conjugated polymer according to the first aspect of the present invention. It is characterized by:

[0009] A material for a photovoltaic device according to a third aspect of the present invention comprises: An electron donating organic material according to the second aspect of the present invention and an electron accepting organic material, It is characterized by:

[0010] The electron-accepting organic material preferably includes a non-fullerene electron-accepting organic material.

[0011] A photovoltaic element according to a fourth aspect of the present invention comprises: A photovoltaic element having at least an anode and a cathode, wherein the photovoltaic element has an organic power generation layer between the anode and the cathode, the photovoltaic element comprising the material for photovoltaic elements according to the third aspect of the present invention. It is characterized by: [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a conjugated polymer having a short π-stack distance when formed into a thin film, an electron-donating organic material, a material for a photovoltaic device, and a photovoltaic device. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic cross-sectional view showing one aspect of a photovoltaic element according to an embodiment of the present invention. [Figure 2] FIG. 2(A) is a graph showing the cyclic voltammetry of polymer compounds P1 and P5, and FIG. 2(B) is a graph showing the results of photoelectron yield spectroscopy measurements of polymer compounds P1 and P5. [Figure 3] FIG. 3(A) is a graph showing the UV-Vis absorption spectra of solutions of polymer compounds P1 and P5, and FIG. 3(B) is a graph showing the UV-Vis absorption spectra of thin films of polymer compounds P1 and P5. [Figure 4] FIG. 4(A) is a graph showing the temperature-variable absorption spectrum of a solution of polymer compound P1, and FIG. 4(B) is a graph showing the temperature-variable absorption spectrum of a solution of polymer compound P5. [Figure 5] FIG. 5(A) is a photograph showing an X-ray diffraction image of a thin film of polymer compound P1, and FIG. 5(B) is a photograph showing an X-ray diffraction image of a thin film of polymer compound P5. [Figure 6]FIG. 6(A) is a graph showing the current density-voltage characteristics of organic thin-film solar cell elements fabricated using polymer compounds P1 and P5, and FIG. 6(B) is a graph showing the external quantum efficiency of organic thin-film solar cell elements fabricated using polymer compounds P1 and P5. DETAILED DESCRIPTION OF THE INVENTION

[0014] The conjugated polymer according to this embodiment is represented by formula 1. In formula 1, X represents carbon, oxygen, sulfur, selenium, nitrogen, or a vinylene group, which may have a substituent.

[0015] [ka]

[0016] In formula 1, R 1 represents an alkyl group. 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, and hexyldecyl. The alkyl group may be linear, branched, or cyclic, and may be unsubstituted or substituted. The number of carbon atoms in the alkyl group is preferably 4 or more, more preferably 6 or more, from the viewpoint of further improving the solubility of the conjugated polymer in organic solvents. By improving the solubility of the conjugated polymer in organic solvents, the polymer can be suitably applied to wet processes such as spin coating and slit coating. On the other hand, from the viewpoint of further improving the carrier mobility and photoelectric conversion efficiency of the conjugated polymer, the number of carbon atoms in the alkyl group is preferably 28 or less, more preferably 12 or less, and even more preferably 10 or less. In the present invention, the number of carbon atoms in each group does not include the number of carbon atoms contained in the substituent.

[0017] 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 the 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 determined by measuring using GPC (gel permeation chromatography) and converting it into a polystyrene standard sample.

[0018] In Formula 1, Ar represents an arylene group or a heteroarylene 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 phenyl, naphthyl, biphenyl, phenanthryl, anthryl, and terphenyl, which may be unsubstituted or substituted. Examples of the substituent in the substituted group include alkyl groups, alkoxy groups, halogens, and heteroaryl groups. From the viewpoint of further improving the solubility and crystallinity of the conjugated polymer, the number of carbon atoms in the arylene group is preferably 6 to 12.

[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 to 6.

[0021] In addition, in formula 1, m represents an integer of 0 to 10. The above arylene group and heteroarylene group may have a plurality of the same groups bonded thereto, or a plurality of different groups bonded thereto, or a plurality of groups may be condensed.

[0022] Specific examples of Ar in Formula 1 include the following structures. 2 is R in the above formula 1 1 is synonymous with.

[0023] [ka]

[0024] In the conjugated polymer represented by Formula 1, a thiophene is bonded to each thiazole at both ends of the dithiazolobenzene backbone. This creates a non-bonding interaction between the nitrogen atom of the thiazole and the sulfur atom of the adjacent thiophene. This non-bonding interaction makes it difficult for the bond between the dithiazolobenzene backbone and the thiophene to twist, thereby increasing the planarity of the polymer backbone. The improved planarity shortens the π-stacking distance when the conjugated polymer represented by Formula 1 is thin-filmed, resulting in high crystallinity.

[0025] In addition, in the conjugated polymer represented by formula 1, the electron-withdrawing ability is enhanced by the nitrogen of each thiazole in the dithiazolobenzene-containing skeleton. Therefore, when the conjugated polymer is used in a photovoltaic device such as an organic thin-film solar cell, the HOMO (Highest Occupied Molecular Orbital) level of the donor is lowered, and the open-circuit voltage is increased.

[0026] As a result, when the conjugated polymer represented by formula 1 is used as a photovoltaic element such as an organic thin-film solar cell, an improvement in photoelectric conversion efficiency can be expected.

[0027] The above-mentioned conjugated polymer can be synthesized, for example, by referring to the following examples.

[0028] 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.

[0029] 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.

[0030] The material for a photovoltaic device according to this embodiment includes the above-mentioned electron-donating organic material and electron-accepting organic material. The electron-accepting organic material preferably exhibits n-type semiconductor properties.

[0031] 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 (PC 70Fullerene-type organic materials such as BM) and 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) 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 Examples of non-fullerene organic materials include 12-Tetrakis(4-hexylphenyl)-6,12-dihydrodithieno[2,3-d:2',3'-d']-s-indaceno[1,2-b:5,6-b']dithiophene-2,8-diyl]bis[methylidyne(3-oxo-1H-indene-2,1(3H)-diylidene)]]bis[propanedinitrile](ITIC).

[0032] In the material for photovoltaic devices according to this embodiment, the content ratio (donor-acceptor ratio) of the electron-donating organic material to the electron-accepting organic material is preferably in the range of 1:99 to 99:1, more preferably 20:80 to 60:40.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] In the photovoltaic element according to this 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 The thickness of the electrode is not limited as long as it has optical transparency and electrical conductivity, and is preferably 20 nm to 300 nm, although this varies depending on the electrode material. The other electrode does not necessarily need to be optically transparent as long as it has electrical conductivity, and there are no particular limitations on its thickness.

[0037] 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, as well as 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 preferred.

[0038] Here, the conductive material used for 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 for the anode preferably forms an ohmic junction with the hole transport layer. Furthermore, the conductive material used for 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.

[0039] 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, and fluorine-based resin. When light is incident from the substrate side, the substrate preferably has a light transmittance of 80% or more.

[0040] 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; low-molecular-weight organic compounds exhibiting p-type semiconductor properties, such as phthalocyanine derivatives (H2Pc, CuPc, ZnPc, etc.), porphyrin derivatives, and acene compounds (tetracene, pentacene, etc.); carbon compounds such as graphene and graphene oxide; and molybdenum oxides (MoO3) such as MoO3. x ), tungsten oxide such as WO3 (WO x ), nickel oxides such as NiO (NiO x ), vanadium oxides such as V2O5 (VO x), zirconium oxide such as ZrO2 (ZrO x ), copper oxides such as CuO (CuO x ), copper iodide, ruthenium oxides such as RuO4 (RuO x ), rhenium oxides such as Re2O7 (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 polyethylenedioxythiophene (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.

[0041] The material for forming the electron transport layer is preferably a material that exhibits n-type semiconductor properties, and titanium oxide (TiO) such as TiO x ) and zinc oxide such as ZnO (ZnO x ), inorganic materials such as PEI (Polyethylenimine), 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 Organic materials such as 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) are preferably used.

[0042] 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 standpoint of ease of handling, an organic solvent with a boiling point of 50°C or higher is preferred.

[0043] 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, immersion and lifting, 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.

[0044] Next, a metal electrode (corresponding to the cathode in this case) made of Al or the like is formed on the organic power generation layer by vacuum deposition or sputtering. If 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.

[0045] When a hole transport layer is provided between the anode and the organic power generation layer, a solution of the desired p-type organic semiconductor material (such as 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 chamber 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.

[0046] 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 application and solvent removal methods 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. [Example]

[0047] The synthesis and properties of dithiazolobenzothiadiazole and polymer compounds (organic semiconductor materials) based on it, as well as the characteristics of organic thin-film solar cells using the polymer compounds in the organic power generation layer will be described below based on examples. The present invention is not limited to these examples.

[0048] (Synthesis example) The starting material, benzo[c][1,2,5]thiadiazole-4,7-diamine (compound 1), was synthesized with reference to "Yoshiro Yamashita et al., The Journal of Organic Chemistry, 2001, Vol. 66, pp. 8954-8960." Also, 4-(2-butyloctyl)thiophene-2-carbonyl chloride (compound 2a) and 4-(2-hexyldecyl)thiophene-2-carbonyl chloride (compound 2b) were synthesized with reference to "Wen-Chang Chen et al., Macromolecules, 2012, Vol. 45, pp. 9046-9055." The copolymerization units (4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene-2,6-diyl)bis(trimethylstannane) (compound 9) and (4,8-bis(5-(2-butyloctyl)thiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene-2,6-diyl)bis(tributylstannane) (compound 10) were synthesized with reference to Yongsheng Chen et al., Journal of the American Chemical Society, 2013, Vol. 135, pp. 8484-8487.

[0049] [ka]

[0050] (Synthesis of Compound 3a) Under an argon atmosphere, compound 2a (4.45 g, 15.0 mmol) and 1,4-dioxane (40 mL) were added to a 200 mL three-neck flask and cooled to 0 °C. Subsequently, oxalyl chloride (12.9 mL, 150 mmol) and N,N-dimethylformamide (1 drop) were added and stirred at 0 °C for 30 minutes, then warmed to room temperature and stirred for 12 hours. The solvent was removed under reduced pressure, and the mixture was placed under an argon atmosphere. 1,4-dioxane (40 mL) was added and cooled to 0 °C. Compound 1 (0.831 g, 5.00 mmol) and pyridine (3.3 mL, 40 mmol) were added and stirred at 0 °C for 30 minutes, then stirred at room temperature for an additional 1 hour. The solvent was removed under reduced pressure, followed by extraction with ethyl acetate, and the organic layer was washed with brine. The separated organic layer was dried over anhydrous sodium sulfate, filtered, and the solvent was removed by evaporation. The crude product was purified by silica gel column chromatography (developing solvent: a mixed solvent of n-hexane:chloroform=1:4) to obtain Compound 3a (3.07 g, 4.25 mmol, yield 85%). The physical property data of compound 3a are as follows: 1 H NMR (500 MHz, CDCl3): δ 8.83 (s, 2H), 8.61 (s, 2H), 7.55 (d, J = 1.5 Hz, 2H), 7.18 (d, J = 1.5 Hz, 2H), 2.60 (d, J = 7.0 Hz, 4H), 1.69-1.62 (m, 2H), 1.30-1.27 (m, 32H), 0.91-0.87 (m, 12H).

[0051] (Synthesis of Compound 3b) Under an argon atmosphere, compound 2b (0.71 g, 2.01 mmol) and 1,4-dioxane (7.5 mL) were added to a 100 mL three-neck flask and cooled to 0 °C. Next, oxalyl chloride (1.7 mL, 2 mmol) and N,N-dimethylformamide (1 drop) were added and stirred at 0 °C for 30 minutes, followed by stirring at room temperature for 12 hours. The solvent was removed under reduced pressure, and then the mixture was placed under an argon atmosphere. 1,4-dioxane (15 mL) was added and cooled to 0 °C. Compound 1 (0.140 g, 0.84 mmol) and pyridine (0.65 mL, 8.1 mmol) were added and stirred at 0 °C for 1 hour, then heated to 140 °C and stirred for an additional hour. After distilling off the solvent, the mixture was extracted with chloroform, and the organic layer was washed with brine. The separated organic layer was dried over anhydrous magnesium sulfate, filtered, and the solvent was evaporated. The crude product was purified by silica gel column chromatography (developing solvent: a mixed solvent of n-hexane and chloroform (1:1)) to obtain Compound 3b (0.575 g, 0.688 mmol, yield 82%). The physical property data of compound 3b are as follows: 1 H NMR (500 MHz, CDCl3): δ 8.83 (s, 2H), 8.61 (s, 2H), 7.55 (d, J = 1.5 Hz, 2H), 7.17 (d, J = 1.5 Hz, 2H), 2.60 (d, J = 7.0 Hz, 4H), 1.66-1.63 (m, 2H), 1.32-1.26 (m, 48H), 0.89-0.86 (m, 12H).

[0052] (Synthesis of Compound 4a) Under an argon atmosphere, compound 3a (3.50 g, 4.84 mmol) and 1,4-dioxane (97 mL) were added to a 200 mL three-neck flask and stirred at room temperature. Next, Lawesson's reagent (5.87 g, 14.51 mmol) was added and stirred at 100 °C for 12 hours. After cooling to room temperature, the solvent was distilled off. The crude product was purified by silica gel column chromatography (developing solvent: n-hexane:chloroform = 1:1 mixed solvent) to obtain compound 4a (3.45 g, 4.57 mmol, yield 94%). The physical property data of compound 4a are as follows: 1 H NMR (500 MHz, CDCl3): δ 10.21 (s, 2H), 9.49 (s, 2H), 7.44 (d, J = 1.5 Hz, 2H), 7.19 (d, J = 1.5 Hz, 2H), 2.58 (d, J = 7.0 Hz, 4H), 1.66-1.64 (m, 2H), 1.32-1.28 (m, 32H), 0.92-0.87 (m, 12H).

[0053] (Synthesis of Compound 4b) Under an argon atmosphere, compound 3b (0.553 g, 0.662 mmol) and 1,4-dioxane (13.2 mL) were added to a 100 mL three-neck flask and stirred at room temperature. Next, Lawesson's reagent (0.803 g, 1.985 mmol) was added and stirred at 100 °C for 12 hours. After cooling to room temperature, the solvent was distilled off. The crude product was purified by silica gel column chromatography (developing solvent: n-hexane:chloroform = 1:1 mixed solvent) to obtain compound 4b (0.560 g, 0.646 mmol, 98% yield). The physical property data of compound 4b are as follows: 1 H NMR (500 MHz, CDCl3): δ 10.24 (s, 2H), 9.54 (s, 2H), 7.47 (d, J = 1.5 Hz, 2H), 7.20 (d, J = 1.5 Hz, 2H), 2.58 (d, J = 7.0 Hz, 4H), 1.66-1.63 (m, 2H), 1.33-1.24 (m, 48H), 0.90-0.86 (m, 12H).

[0054] (Synthesis of Compound 5a) Compound 4a (3.43 g, 4.54 mmol) and tetrahydrofuran (454 mL) were added to a 200 mL three-neck flask under an argon atmosphere and stirred at room temperature. Next, chloranil (3.35 g, 13.62 mmol) was added and stirred for 12 hours under monochromatic light irradiation at 450 nm. After distilling off the solvent, the crude product was washed with n-hexane. After distilling off the solvent from the filtrate, the crude product was purified by silica gel column chromatography (developing solvent: n-hexane:chloroform = 1:1 mixed solvent) to obtain compound 5a (3.04 g, 4.05 mmol, 89% yield). The physical property data of compound 5a are as follows: 1 H NMR (500 MHz, CDCl3): δ 7.57 (d, J = 1.5 Hz, 2H), 7.12 (d, J = 1.5 Hz, 2H), 2.59 (d, J = 7.0 Hz, 4H), 1.66-1.62 (m, 2H), 1.33-1.27 (m, 32H), 0.92-0.87 (m, 12H).

[0055] (Synthesis of Compound 5b) Compound 4b (0.538 g, 0.620 mmol) and tetrahydrofuran (62 mL) were added to a 100 mL three-neck flask under an argon atmosphere and stirred at room temperature. Next, chloranil (0.457 g, 1.859 mmol) was added and stirred for 7 hours under monochromatic light irradiation at 450 nm. After distilling off the solvent, the crude product was washed with n-hexane. After distilling off the solvent from the filtrate, the crude product was purified by silica gel column chromatography (developing solvent: n-hexane:chloroform = 1:1 mixed solvent) to obtain compound 5b (0.532 g, 0.616 mmol, yield 99%). The physical property data of compound 5b are as follows: 1H NMR (500 MHz, CDCl3): δ 7.58 (d, J = 1.5 Hz, 2H), 7.12 (d, J = 1.5 Hz, 2H), 2.59 (d, J = 7.0 Hz, 4H), 1.68-1.65 (m, 2H), 1.34-1.25 (m, 48H), 0.90-0.86 (m, 12H).

[0056] (Synthesis of Compound 6a) Compound 5a (1.00 g, 1.33 mmol), chloroform (50 mL), and acetic acid (17 mL) were added to a 200 mL three-neck flask and cooled to 0 °C. Next, N-bromosuccinimide (0.437 g, 2.66 mmol) was added at 0 °C and stirred at room temperature for 10 hours. After the reaction was completed, the mixture was cooled to 0 °C and quenched by adding aqueous sodium bicarbonate solution dropwise. After extraction with chloroform, the organic layer was washed with brine. The organic layer was dried over anhydrous sodium sulfate, filtered, and the solvent was evaporated. The crude product was purified by silica gel column chromatography (developing solvent: a 1:1 mixture of n-hexane and chloroform) to obtain compound 6a (1.06 g, 2.66 mmol, yield 88%). The physical property data of compound 6a are as follows: 1 H NMR (500 MHz, CDCl3): δ 7.39 (s, 2H), 2.54 (d, J = 7.0 Hz, 4H), 1.74-1.68 (m, 2H), 1.33-1.28 (m, 32H), 0.92-0.87 (m, 12H).

[0057] (Synthesis of Compound 6b) Compound 5b (0.173 g, 0.20 mmol), chloroform (7.5 mL), and acetic acid (2.5 mL) were added to a 30 mL two-neck flask and cooled to 0 °C. Next, N-bromosuccinimide (71.2 mg, 0.40 mmol) was added and stirred at 60 °C overnight. After the reaction was completed, the mixture was cooled to 0 °C and quenched by adding aqueous sodium bicarbonate solution dropwise. After extraction with chloroform, the organic layer was washed with brine. The separated organic layer was dried over anhydrous sodium sulfate, filtered, and the solvent was evaporated. The crude product was purified by silica gel column chromatography (developing solvent: n-hexane:chloroform = 1:1 mixed solvent) to obtain compound 6b (0.173 g, 0.17 mmol, 85% yield). The physical property data of compound 6b are as follows: 1 H NMR (500 MHz, CDCl3): δ 7.39 (s, 2H), 2.54 (d, J = 7.0 Hz, 4H), 1.74-1.68 (m, 2H), 1.37-1.24 (m, 48H), 0.90-0.85 (m, 12H).

[0058] [ka]

[0059] (Synthesis of Compound 7) Compound 5a (0.751 g, 1.000 mmol), 1,4-dioxane (50 mL), and acetic acid (50 mL) were added to a 200 mL three-neck flask under an argon atmosphere, followed by argon bubbling for 15 minutes. Next, zinc (1.31 g, 20.0 mmol) was added at 150 °C, followed by refluxing for 10 minutes. After cooling to room temperature, the supernatant liquid was transferred to a 500 mL three-neck flask previously conditioned under an argon atmosphere. 2,3-butanedione (0.215 g, 2.50 mmol) was added and stirred at room temperature for 10 minutes. After the reaction, the mixture was cooled to 0 °C and quenched by the dropwise addition of aqueous sodium bicarbonate. The mixture was then extracted with chloroform, and the organic layer was washed with brine. The removed organic layer was dried over anhydrous sodium sulfate, filtered, and the solvent was evaporated. The crude product was purified by silica gel column chromatography (developing solvent: chloroform) to obtain Compound 7 (0.498 g, 0.644 mmol, yield 64%). The physical property data of Compound 7 are as follows: 1 H NMR (500 MHz, CDCl3): δ 7.61 (d, J = 1.5 z, 2H), 7.10 (d, J = 1.5 Hz, 2H), 2.90 (s, 6 H), 2.57 (d, J = 7.0 Hz, 4H), 1.67-1.63 (m, 2H), 1.29-1.26 (m, 32H), 0.90-0.86 (m, 12H).

[0060] (Synthesis of Compound 8) Compound 7 (0.451 g, 0.583 mmol), chloroform (22 mL), and acetic acid (7 mL) were added to a 100 mL three-neck flask and cooled to 0°C. Next, N-bromosuccinimide (0.208 g, 1.17 mmol) was added and stirred at 0°C for 2 hours. After the reaction, aqueous sodium bicarbonate solution was added dropwise at 0°C to quench the reaction. The mixture was then extracted with chloroform, and the organic layer was washed with brine and dried over anhydrous sodium sulfate. After filtration, the solvent was distilled off. The crude product was purified by silica gel column chromatography (developing solvent: chloroform) to obtain compound 8 (0.515 g, 0.553 mmol, yield 95%). The physical property data of Compound 8 are as follows: 1 H NMR (500 MHz, CDCl3): 7.48 (s, 2H), 2.93 (s, 6H), 2.55 (d, J = 7.0 Hz, 4H), 1.76-1.70 (m, 2H), 1.32-1.28 (m, 32H), 0.91-0.87 (m, 12H).

[0061] [ka]

[0062] (Synthesis of polymer compound P1) Compound 6a (27.3 mg, 0.030 mmol), compound 9 (27.1 mg, 0.030 mmol), tetrakis(triphenylphosphine)palladium (0.69 mg, 0.0006 mmol), and chlorobenzene (1.2 mL) were placed in a reaction vial, sealed with nitrogen, and stirred at 100 °C for 17 hours. After cooling to room temperature, the reaction solution was poured into a 5% hydrochloric acid / methanol solution and stirred for 2 hours. The precipitated solid was collected by filtration and washed with methanol, n-hexane, and dichloromethane using a Soxhlet extractor, followed by extraction with chloroform. The resulting solution was concentrated and reprecipitated in methanol to obtain polymer compound P1 (17.5 mg, 44% yield) as a dark red solid (number average molecular weight 19,900).

[0063] [ka]

[0064] (Synthesis of polymer compound P2) Compound 6a (28.5 mg, 0.031 mmol), compound 10 (39.8 mg, 0.031 mmol), tetrakis(triphenylphosphine)palladium (0.72 mg, 0.0006 mmol), and chlorobenzene (1.2 mL) were placed in a reaction vial, sealed with nitrogen, and stirred at 100 °C for 4 hours. After cooling to room temperature, the reaction solution was poured into a 5% hydrochloric acid / methanol solution and stirred for 2 hours. The precipitated solid was collected by filtration and washed with methanol, n-hexane, and dichloromethane using a Soxhlet extractor, followed by extraction with chloroform. The resulting solution was concentrated and reprecipitated in methanol to obtain polymer compound P2 (24.0 mg, 53% yield) as a dark red solid (number average molecular weight 38,100).

[0065] [ka]

[0066] (Synthesis of polymer compound P3) Compound 6b (34.4 mg, 0.034 mmol), compound 9 (30.5 mg, 0.034 mmol), tris(dibenzylideneacetone)(chloroform)dipalladium (0.70 mg, 0.0007 mmol), tri(o-toluyl)phosphine (1.64 mg, 0.0054 mmol), and toluene (1.35 mL) were placed in a reaction vial, blanketed with nitrogen, and stirred at 130 °C for 11 hours. After cooling to room temperature, the reaction solution was poured into a 5% hydrochloric acid / methanol solution and stirred for 2 hours. The precipitated solid was collected by filtration and washed with methanol, n-hexane, and dichloromethane using a Soxhlet extractor. It was then extracted with chloroform. The resulting solution was concentrated and reprecipitated in methanol to obtain polymer compound P3 (32.2 mg, 67% yield) as a dark red solid (number average molecular weight 26,000).

[0067] [ka]

[0068] (Synthesis of polymer compound P4) Compound 8 (27.9 mg, 0.030 mmol), compound 9 (27.1 mg, 0.030 mmol), tetrakis(triphenylphosphine)palladium (0.69 mg, 0.0006 mmol), and toluene (1.2 mL) were placed in a reaction vial, sealed with nitrogen, and sealed. The reaction was carried out at 200 °C for 2 hours using a microwave reactor. After cooling to room temperature, the reaction solution was poured into a 5% hydrochloric acid / methanol solution and stirred for 2 hours. The precipitated solid was collected by filtration and washed with methanol, acetone, and n-hexane using a Soxhlet extractor. It was then extracted with dichloromethane. The resulting solution was concentrated and reprecipitated in methanol to obtain polymer compound P4 (35.1 mg, 87% yield) as a red solid (number average molecular weight 19,900).

[0069] (Cyclic voltammetry measurements of polymer compounds P1 and P5) First, a 1 mg / mL chloroform solution of polymer compound P1 was prepared. For comparison, a 1 mg / mL chloroform solution of polymer compound P5, represented by the following formula, was also prepared. Next, a working electrode was dipped into each chloroform solution to prepare a thin film. The thin film was then measured, and the redox potential was determined by analyzing the resulting current-potential curve.

[0070] [ka]

[0071] The highest occupied molecular orbital (HOMO) level, lowest unoccupied molecular orbital (LUMO) level, and band gap of polymer compounds P1 and P5 were evaluated by cyclic voltammetry (CV) measurements (Figure 2(A)). The HOMO levels of polymer compounds P1 and P5 were also evaluated by photoelectron yield spectroscopy (PYS) measurements (Figure 2(B)). Table 1 shows these values.

[0072] [Table 1]

[0073] CV and PYS measurements showed that polymer P1, which does not have electron-withdrawing fluorine atoms, exhibited a deeper HOMO level than polymer P5, which does. This is thought to be due to the higher electron deficiency of the dithiazolobenzothiadiazole skeleton of polymer P1 compared to the dithienobenzothiadiazole skeleton of polymer P5. Furthermore, polymer P1 exhibited a significantly lower LUMO level than polymer P5, which is also thought to be due to the higher electron deficiency of the dithiazolobenzothiadiazole skeleton.

[0074] (UV-vis absorption spectrum evaluation of solutions using polymer compounds P1 and P5) First, approximately 1 mg of polymer compounds P1 and P5 was weighed out and dissolved in 20 mL of chlorobenzene, and then diluted five-fold with chlorobenzene to prepare solutions to be evaluated.

[0075] (UV-vis absorption spectrum evaluation of thin films using polymer compounds P1 and P5) After thorough cleaning, the glass substrate was subjected to UV ozone treatment, and then a 5 mg / mL chloroform solution of each of the polymer compounds P1 and P5 was spin-coated at 3000 rpm for 30 seconds to form a thin film.

[0076] The UV-vis absorption spectra of the solutions and thin films of polymer compounds P1 and P5 were measured. The results are shown in Figures 3(A) and 3(B), and the maximum absorption wavelengths and absorption edges are listed in Table 2.

[0077] [Table 2]

[0078] The absorption region of polymer compound P1 was slightly shifted to shorter wavelengths than that of polymer compound P5.

[0079] The temperature-variable absorption spectra of the solutions of polymer compounds P1 and P5 were measured. Figures 4(A) and 4(B) show the temperature-variable absorption spectra of the solutions of polymer compounds P1 and P5, respectively.

[0080] 4(A) and (B), polymer compound P1 exhibits smaller changes in the shape of the absorption spectrum at high temperatures than polymer compound P5, which indicates that polymer compound P1 has a more rigid polymer main chain or a higher degree of cohesion between the polymer main chains than polymer compound P5.

[0081] (Glancing incidence X-ray diffraction evaluation of polymer compounds P1 and P5) After thorough cleaning, the glass substrate was subjected to UV ozone treatment. Next, a 5 mg / mL chloroform solution of each of polymer compounds P1 and P5 was spin-coated at 3000 rpm for 30 seconds to prepare a thin film. Each thin film was then heated at 100°C for 5 minutes under a nitrogen atmosphere. X-ray diffraction images of each thin film were taken. Figure 5(A) shows the X-ray diffraction image of the thin film obtained using polymer compound P1, and Figure 5(B) shows the X-ray diffraction image of the thin film obtained using polymer compound P5.

[0082] The thin film structures of polymer compounds P1 and P5 were evaluated from the X-ray diffraction images shown in Figures 5(A) and (B). The lamellar distance (d L ) and π stack distance (d π ) are shown in Table 3. Polymer compound P1 exhibits diffraction due to π-π stacking in the out-of-plane direction, and d π = 3.63 Å, d L = 19.5 Å. The corresponding crystallite size was L π = 16.2, and L L = 52.6 Å. Polymer compound P5 exhibits diffraction due to π-π stacking in the out-of-plane direction, and d π = 3.73 Å, d L = 20.6 Å. The corresponding crystallite size was L π = 17.7, and L L=65.3 Å.

[0083] [Table 3]

[0084] (Evaluation of solar cell elements using polymer compound P1) Solar cell devices were fabricated using polymer compound P1, and their photoelectric conversion efficiency was evaluated. Glass substrates patterned with an ITO (indium tin oxide) film were thoroughly cleaned and then subjected to UV ozone treatment. Next, PEDOT:PSS (poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)) was spin-coated at 4000 rpm for 30 seconds. The substrates were heated at 150°C for 15 minutes to form an electron extraction layer. The substrates with the electron extraction layer were then placed in a glove box, and a chloroform solution containing polymer compounds P1, P2, or P4 and Y6 (polymer compound P1 / Y6 weight ratio = 1 / 1.2) was spin-coated to form an organic power generation layer (100 nm thick). The thin film was then heated at 100°C for 5 minutes under a nitrogen atmosphere. A hole extraction layer was formed on the organic power generation layer by spin-coating 1 mg of PNDIT-F3N-Br (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-fluorene-2,7-diyl]-2,5-thiophenediyl]) in 1 mL of methanol at 2000 rpm for 60 seconds. A 150 nm thick silver film was then deposited as an electrode layer by resistance heating vacuum deposition, completing a 4 mm square organic thin-film solar cell.

[0085] (Evaluation of solar cell elements using polymer compound P5) Solar cells were fabricated using polymer compound P5, and their photoelectric conversion efficiency was evaluated. Glass substrates with patterned ITO films were thoroughly cleaned and then subjected to UV ozone treatment. Next, PEDOT:PSS was spin-coated at 4000 rpm for 30 seconds. The substrates were heated at 150°C for 15 minutes to form an electron extraction layer. The substrates with the electron extraction layer were then brought into a glove box, and a chloroform solution containing polymer compounds P5 and Y6 (polymer compound P5 / Y6 weight ratio = 1 / 1.6) was spin-coated to form an organic power generation layer (100 nm thick). This thin film was then heated at 85°C for 5 minutes under a nitrogen atmosphere. A solution of 1 mg of PNDIT-F3N-Br dissolved in 1 mL of methanol was spin-coated at 3000 rpm for 30 seconds on the organic power generation layer to form a hole extraction layer. A 110 nm thick silver film was then deposited as an electrode layer using resistance heating vacuum deposition, resulting in the fabrication of 4 mm square organic thin-film solar cells.

[0086] [ka]

[0087] Each of the fabricated organic thin-film solar cell elements was placed under a solar simulator (AM1.5G filter, irradiance 100 mW / cm 2 The generated current and voltage were measured by irradiating a constant amount of light using a 1000 kV IR laser. Figure 6 shows the current density-voltage characteristics and external quantum efficiency (EQE).

[0088] From Figure 6, the short-circuit current density (J SC (mAcm -2 )), open circuit voltage (V OC (V)) and fill factor (FF) were calculated. Then, the photoelectric conversion efficiency (η (%)) was calculated as η = (J SC ×V OC The results are shown in Table 4.

[0089] [Table 4]

[0090] The organic thin-film solar cell device fabricated using polymer compound P1 exhibited a significantly higher open-circuit voltage than the organic thin-film solar cell device fabricated using polymer compound P5, due to the deep HOMO level. [Industrial Applicability]

[0091] 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: 【Chemistry 1】 (In Formula 1, X represents carbon, oxygen, sulfur, selenium, nitrogen, or a vinylene group. R １ represents an alkyl group. Ar represents an arylene group or a heteroarylene group. m represents an integer of 0 to 10. n represents the degree of polymerization, and is in the range of 2 to 1,000. A conjugated polymer characterized by:

2. The conjugated polymer according to claim 1, 1. An electron-donating organic material comprising:

3. The electron donating organic material according to claim 2 and the electron accepting organic material are included. A material for a photovoltaic element, characterized in that:

4. the electron-accepting organic material comprises a non-fullerene electron-accepting organic material; The material for a photovoltaic device according to claim 3 .

5. A photovoltaic element having at least an anode and a cathode, the photovoltaic element having an organic power generation layer between the anode and the cathode, the photovoltaic element comprising the material for photovoltaic elements according to claim 3 or 4. A photovoltaic element characterized by:

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