Conjugated polymers, conjugated compounds, electron-donating organic materials using the same, materials for photovoltaic elements, and photovoltaic elements

Abstract

To provide a photovoltaic device with high photoelectric conversion efficiency.SOLUTION: The invention provides a conjugated polymer with a structure represented by the general formula (1) in the figure, and an electron-donating organic material, a photovoltaic device material and a photovoltaic device that employ the polymer. (In the general formula (1), Ra, Rb, and R3 to R6 are each H, an alkyl group, an alkoxy group, an alkanoyl group, an alkoxycarbonyl group, a halogen, an aryl group, or a heteroaryl group; Ra and Rb may be fused to form an aryl ring or heteroaryl ring; A is an arylene group or a heteroarylene group; x and y are integers from 0 to 4 inclusive; and n indicates a polymerization degree and represents the range from 2 to 1,000 inclusive.)SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a conjugated polymer, a conjugated compound, an electron-donating organic material using the same, a material for a photovoltaic device, and a photovoltaic device.

Background Art

[0002] Solar cells have received great attention as an energy source contributing to the realization of a recycling-based society. Currently, as semiconductor materials used in photovoltaic devices such as solar cells, inorganic substances such as single crystal silicon, polycrystalline silicon, amorphous silicon, and compound semiconductors are used. However, solar cells manufactured using inorganic semiconductors have not been widely popularized because of one reason that the manufacturing cost is high. The factor of high cost mainly lies in the process of forming a semiconductor thin film under vacuum and high temperature. Therefore, organic solar cells using organic semiconductors such as conjugated polymers and organic crystals, and organic dyes, which are expected to simplify the manufacturing process, have been developed. In such organic solar cells, since the semiconductor material layer can be formed by a coating method, the manufacturing process can be greatly simplified.

[0003] However, organic solar cells using conjugated polymers and the like have not yet been put into practical use because their photoelectric conversion efficiency is lower than that of conventional solar cells using inorganic semiconductors. Further improvement of the photoelectric conversion efficiency is essential for the practical use of organic solar cells.

[0004] As one method of improving the photoelectric conversion efficiency of organic solar cells, a power generation layer 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 of a bulk heterojunction type has been reported (for example, see Non-Patent Document 1).

[0005] To further improve the photoelectric conversion efficiency of organic solar cells, electron-donating organic materials that can increase the open-circuit voltage (Voc), one of the element characteristics of solar cells, are desired. In order to increase the open-circuit voltage, electron-donating organic materials need to have deep HOMO (Highest Occupied Molecular Orgital) levels, and heteroconjugated compounds in which nitrogen atoms or sulfur atoms are incorporated into a π-conjugated system and fused into rings have been reported as electron-donating organic materials having such deep HOMO levels (see, for example, Patent Documents 1-2 and Non-Patent Document 2). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] International Public Gazette No. 2011 / 156478 [Patent Document 2] International Public Gazette No. 2019 / 023025 [Non-patent literature]

[0007] [Non-Patent Document 1] Chemical Reviews, 2015, Vol. 115, pp. 12666-12731 [Non-Patent Document 2] "Advanced Materials," 2016, Vol. 28, pp. 4734-4739. [Overview of the project] [Problems that the invention aims to solve]

[0008] Although electron-donating organic materials containing heteroconjugated compounds incorporating nitrogen atoms into the conjugated system, as described in Patent Documents 1 and 2, yield high open-circuit voltages, the low carrier mobility results in low short-circuit current (Jsc) and fill factor (FF), preventing sufficient photoelectric conversion efficiency. Similarly, electron-donating organic materials with expanded conjugated systems through ring fusion of sulfur-containing thiophene ring derivatives, as described in Non-Patent Document 2, also failed to achieve sufficient photoelectric conversion efficiency. In view of the above problems, the present invention aims to provide a conjugated polymer capable of obtaining a photovoltaic element with high photoelectric conversion efficiency. [Means for solving the problem]

[0009] It is known that the photoelectric conversion efficiency of conjugated polymers with extended planarity varies greatly depending on the main chain structure, side chain structure, and substituent structure. The inventors of this invention hypothesized that the photoelectric conversion efficiency of photovoltaic elements could be improved by using conjugated polymers that possess both high carrier mobility and deep HOMO levels. To achieve the above objective, they diligently investigated the chemical structure of such conjugated polymers and found that a conjugated polymer containing benzo[1,2-d:4,3-d']bisthiazole can provide a photovoltaic element with high photoelectric conversion efficiency, thus completing the present invention.

[0010] In other words, the present invention is represented by the following general formula (2) The present invention provides a conjugated polymer having a structure represented by [the given formula], an electron-donating organic material using the same, a material for a photovoltaic element, and a photovoltaic element.

[0011] [ka]

[0012] (In the above general formula (2), R 1 ~R 6x and y may be the same or different and represent hydrogen, alkyl group, alkoxy group, alkanoyl group, alkoxycarbonyl group, halogen, aryl group, or heteroaryl group. A represents an arylene group or heteroarylene group. x and y may be the same or different and represent integers between 0 and 4 (inclusive). If x or y is 2 or greater, there are x R 3 and R 4 y R 5 and R 6 These can be the same or different. n represents the degree of polymerization, in the range of 2 to 1,000.

[0013] The present invention also provides a conjugated compound having a structure represented by the following general formula (3).

[0014] [ka]

[0015] (In the above general formula (3), R 7 ~R 10 (These may be the same or different, and represent hydrogen, alkyl group, alkoxy group, alkoxycarbonyl group, halogen, aryl group, or heteroaryl group.) [Effects of the Invention]

[0016] The conjugated polymer of the present invention can provide a photovoltaic element with excellent photoelectric conversion efficiency. [Brief explanation of the drawing]

[0017] [Figure 1] This is a schematic cross-sectional view showing one embodiment of the photovoltaic element of the present invention. [Figure 2] This is a current density-voltage curve graph of the organic thin-film solar cell obtained in Example 1. [Figure 3] This graph shows the spectral sensitivity characteristics of the organic thin-film solar cell obtained in Example 1. [Figure 4]This is a current density-voltage curve graph of the organic thin-film solar cell obtained in Example 2. [Figure 5] This graph shows the spectral sensitivity characteristics of the organic thin-film solar cell obtained in Example 2. [Figure 6] This is a current density-voltage curve graph of the organic thin-film solar cell obtained in Example 3. [Figure 7] This graph shows the spectral sensitivity characteristics of the organic thin-film solar cell obtained in Example 3. [Figure 8] This is a current density-voltage curve graph of the organic thin-film solar cell obtained in Example 4. [Figure 9] This graph shows the spectral sensitivity characteristics of the organic thin-film solar cell obtained in Example 4. [Figure 10] This is a current density-voltage curve graph of the organic thin-film solar cell obtained in Comparative Example 1. [Figure 11] This graph shows the spectral sensitivity characteristics of the organic thin-film solar cell obtained in Comparative Example 1. [Modes for carrying out the invention]

[0018] The conjugated polymer of the present invention has a structure represented by the following general formula (1). In general formula (1), the benzo[1,2-d:4,3-d']bisthiazole skeleton, in which two thiazole skeletons are fused to a benzene ring, exhibits high planarity and improved packing properties, thereby increasing carrier mobility in thin films and improving short-circuit current and fill factor. Furthermore, the benzo[1,2-d:4,3-d']bisthiazole skeleton allows for the introduction of a bent structure into the polymer main chain while maintaining high planarity, thereby improving solubility in organic solvents. Moreover, the nitrogen atom in the benzobisthiazole in general formula (1) has the effect of deepening the HOMO level of the conjugated polymer, thereby improving the open-circuit voltage of the photovoltaic element. For these reasons, a conjugated polymer having the structure represented by general formula (1) can improve the photoelectric conversion efficiency of a photovoltaic element.

[0019] [Chemical formula] (In the above general formula (1), R a , R b and R 3 ~R 6 may be the same or different and represent hydrogen, an alkyl group, an alkoxy group, an alkanoyl group, an alkoxycarbonyl group, a halogen, an aryl group or a heteroaryl group. R a and R b may be condensed to form an aryl ring or a heteroaryl ring. A represents an arylene group or a heteroarylene group. x and y may be the same or different and represent an integer of 0 or more and 4 or less. When x or y is 2 or more, x R 3 and R 4 , y R 5 and R 6 may each be the same or different. n represents the degree of polymerization and represents a range of 2 or more and 1,000 or less.) The structure represented by the general formula (1) may be a structure represented by the following general formula (2). In the general formula (2), it is possible to introduce a substituent that enhances solubility into the thienobenzobisthiazole skeleton obtained by condensing thiophene with the benzobisthiazole skeleton, and the solubility in an organic solvent can be further improved while maintaining high planarity. [Chemical formula] ​​​​​​​​​​​​In the present invention, alkyl groups are monovalent saturated aliphatic hydrocarbon groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, and dodecyl groups, and may be linear, branched, or cyclic, and may be unsubstituted or substituted. Examples of substituents when substituted include alkoxy groups, aryl groups, heteroaryl groups, and halogens, which will be described later. From the viewpoint of further improving the solubility of the conjugated polymer in organic solvents, the number of carbon atoms in the alkyl group is preferably 4 or more, and more preferably 6 or more. By improving the solubility of the conjugated polymer in organic solvents, it 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 of the conjugated polymer and further improving the photoelectric conversion efficiency, 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 included in substituents.

[0022] In this invention, the alkoxy group refers to a monovalent aliphatic hydrocarbon group via an ether bond, such as a methoxy group, ethoxy group, propoxy group, or butoxy group, and the aliphatic hydrocarbon group may be unsubstituted or substituted. Examples of substituents when substituted include aryl groups, heteroaryl groups, halogens, etc., which will be described later. The preferred range of carbon atoms for the alkoxy group is the same as for alkyl groups described above.

[0023] In this invention, the alkanoyl group refers to an alkyl group mediated by a ketone group. The preferred range of carbon atoms for the alkanoyl group is the same as that for the alkyl group described above.

[0024] In this invention, the alkoxycarbonyl group refers to an alkyl group via an ester bond. The preferred range of carbon atoms for the alkoxycarbonyl group is the same as that for the alkyl group described above.

[0025] In this invention, the halogen is any one of fluorine, chlorine, bromine, or iodine.

[0026] In this invention, the aryl group refers to a monovalent aromatic hydrocarbon group such as a phenyl group, naphthyl group, biphenyl group, phenanthryl group, anthryl group, or terphenyl group, which may be unsubstituted or substituted. Examples of substituents when substituted include the alkyl groups, alkoxy groups, halogens mentioned above, and the heteroaryl groups described later. From the viewpoint of further improving the solubility and crystallinity of the conjugated polymer, the number of carbon atoms in the aryl group is preferably 6 to 12.

[0027] In the present invention, the heteroaryl group refers to a monovalent heteroaromatic ring group having an atom other than carbon, such as a thienyl group, furyl group, pyrrolyl group, imidazolyl group, pyrazolyl group, oxazolyl group, pyridyl group, pyrimidyl group, or thienothenyl group, and may be unsubstituted or substituted. Examples of substituents when substituted include the alkyl groups, alkoxy groups, halogens, and the aryl groups mentioned above. From the viewpoint of further improving the solubility and crystallinity of the conjugated polymer, the number of carbon atoms in the heteroaryl group is preferably 4 to 6.

[0028] R in general formula (1) a and R b To maintain the planarity of the conjugated system, hydrogen, alkyl groups, or fused heteroaryl groups are preferred. R in general formulas (1) and (2) 3 ~R 6 R in general formula (2) is preferably hydrogen or an alkyl group, and it is preferable that at least a portion of it be an alkyl group in order to improve solubility in organic solvents while maintaining the planarity of the conjugated polymer. 1 From the viewpoint of improving solubility in organic solvents while maintaining the planarity of the conjugated polymer, alkyl groups are preferred. 2 To maintain planarity, hydrogen or halogens with small atomic radii are preferably used. 1 ~R 6When the alkyl group is preferred, the number of carbon atoms is 4 to 28, more preferably 6 to 12, and particularly preferred 7 to 10.

[0029] In the above general formulas (1) or (2), x and y represent the number of thiophene rings, and may be the same or different, and represent integers between 0 and 4. To improve the planarity of the conjugated polymer, thereby improving carrier mobility and further increasing photoelectric conversion efficiency, it is preferable that x and y are 1. In the above general formula (1) or (2), A represents an arylene group or a heteroarylene group.

[0030] In this invention, an arylene group refers to a divalent aromatic hydrocarbon group, and a heteroarylene group refers to a divalent heteroaromatic ring group having atoms other than carbon. Examples of arylene groups include divalent groups corresponding to the aryl groups exemplified earlier, and examples of heteroarylene groups include divalent groups corresponding to the heteroaryl groups exemplified earlier. These may be unsubstituted or substituted. In order to improve the planarity of the conjugated polymer and enhance carrier mobility, it is preferable that A is a heteroarylene group having a benzodithiophene ring. As substituents on the benzodithiophene ring, thienyl groups are particularly preferred as they can further enhance planarity. Here, when a thienyl group is present on the benzodithiophene ring, the thienyl group is preferably substituted, and examples of substituents include alkyl groups or halogens. The number of carbon atoms in the alkyl group is preferably 4 to 28, and more preferably 6 to 12, in order to achieve both solubility and planarity. For halogens, fluorine, which has a small atomic radius, is preferably used to maintain planarity. Since the number of synthesis steps is reduced, thienyl groups substituted only with alkyl groups are particularly preferred as substituents on benzodithiophene.

[0031] In the above general formulas (1) or (2), n represents the degree of polymerization and is an integer in the range of 2 to 1,000. From the viewpoint of further improving the carrier mobility of the conjugated polymer and more easily forming effective carrier paths in the bulk heterojunction type power generation layer described above, and further improving the photoelectric conversion efficiency, n is preferably 5 or higher. On the other hand, from the perspective 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 converted to a standard sample of polystyrene.

[0032] Examples of structures represented by the above general formula (1) or (2) include the following:

[0033] [ka]

[0034] [ka]

[0035] [ka]

[0036] [ka]

[0037] [ka]

[0038] [ka]

[0039] [ka]

[0040] [ka]

[0041] Furthermore, conjugated polymers having a structure represented by general formula (1) or (2) can be synthesized from the corresponding monomers by polymerization reactions such as Stille coupling, and can be synthesized, for example, by a method similar to the one described in Patent Document 2.

[0042] Examples of monomers corresponding to conjugated polymers having the structure represented by general formula (2) include conjugated compounds having the structure represented by the following general formula (3).

[0043] [ka]

[0044] In the above general formula (3), R 7 ~R 10 R may be the same or different, and represents hydrogen, alkyl group, alkoxy group, alkoxycarbonyl group, halogen, aryl group, or heteroaryl group. 7 This is R in general formula (2). 1 Corresponds to R 8 This is R in general formula (2). 2 It corresponds to.

[0045] The electron-donating organic material of the present invention includes a conjugated polymer having a structure represented by the general formula (1) or (2). The electron-donating organic material using the conjugated polymer of the present invention having a structure represented by the general formula (1) or (2) exhibits p-type semiconductor properties. Other electron-donating organic materials may be included along with such electron-donating organic material.

[0046] The electron-donating organic material of the present invention can be applied to organic transistors by taking advantage of its high carrier mobility. Furthermore, it can be applied to various photoelectric conversion devices utilizing photoelectric conversion and optical rectification functions. For example, it is useful in photovoltaic elements (solar cells), electronic elements (image sensors, light sensors, optical switches), optical recording materials (optical memory, etc.), and image sensors, and is particularly suitable for use as a material for photovoltaic elements.

[0047] The photovoltaic element material of the present invention includes the electron-donating organic material of the present invention described above and an electron-accepting organic material. The electron-accepting organic material preferably exhibits n-type organic semiconductor properties.

[0048] Examples of electron-accepting organic materials exhibiting n-type semiconductor properties include phenyl C61 butyric acid methyl ester (PC). 60 BM) and phenyl C71 butyric acid methyl ester (PC 70 Fullerene-type organic materials such as BM) and 2,2'-((2Z,2'Z)-((12,13-bis(2-ethylhexyl)-3,9-diundecyl-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-diyl)bis(methanylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1 Examples of non-fullerene-type organic materials include H-indene-2,1-diylidene))dimalononitrile (Y6) and 2,2′-[[6,6,12,12-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).

[0049] The electron-donating organic material of the present invention is preferably combined with a non-fullerene type electron-accepting organic material having a band gap of 1.2 eV to 1.7 eV. Compared to fullerene type electron-accepting organic materials, it can absorb solar energy over a wider wavelength range, thereby further improving photoelectric conversion efficiency.

[0050] In the photovoltaic element material of the present invention, the content ratio (donor-acceptor ratio) of electron-donating organic material to electron-accepting organic material is preferably in the range of 1:99 to 99:1, and more preferably in the range of 20:80 to 60:40.

[0051] To further improve photoelectric conversion efficiency, it is preferable to remove as many impurities as possible that can trap carriers. In the present invention, methods for removing impurities from electron-donating organic materials and electron-accepting organic materials 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.

[0052] Next, the photovoltaic element of the present invention will be described. The photovoltaic element of the present invention has at least an anode and a cathode, and an organic semiconductor layer containing the photovoltaic element material of the present invention is provided between them. A hole transport layer may be provided between the organic semiconductor layer and the anode, or an electron transport layer may be provided between the organic semiconductor layer and the cathode. Figure 1 shows a schematic cross-sectional view of one embodiment of the photovoltaic element of the present invention. On a substrate 1, there is an anode 2, an organic semiconductor layer 3 containing the photovoltaic element material of the present invention, and a cathode 4 in this order. Alternatively, conversely to Figure 1, the substrate may have a cathode / organic semiconductor layer containing the photovoltaic element material of the present invention / anode in this order.

[0053] Next, I will explain each layer. The organic semiconductor layer includes the photovoltaic element material of the present invention. Specifically, it includes an electron-donating organic material using a conjugated polymer having a structure represented by general formula (1) or (2), and an electron-accepting organic material. These materials may be mixed or laminated, but mixing is preferred. A bulk heterojunction type organic semiconductor layer, which increases the junction surface between the electron-donating organic material and the electron-accepting organic material that contribute to photoelectric conversion by mixing the electron-donating organic material and the electron-accepting organic material, is preferred because it has superior charge separation ability and charge transport ability. In the organic semiconductor layer which is a bulk heterojunction type 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 co-continuous carrier path to the electrode is formed. The domain size of this phase-separated structure is not particularly limited, but is usually between 1 nm and 50 nm.

[0054] In the photovoltaic element of the present invention, it is preferable that the anode or cathode is light-transmitting, that is, transparent or semi-transparent. The light transmittance of the electrode is not particularly limited as long as incident light reaches the organic semiconductor layer and generates an electromotive force. Here, the light transmittance in the present invention is defined as [transmitted light intensity (W / m²)]. 2 ) / incident light intensity (W / m 2 This value is calculated by multiplying (%) by 100 (%). The electrode thickness can be any range that has both light transmittance and conductivity, and although it varies depending on the electrode material, 20 nm to 300 nm is preferred. The other electrode does not necessarily need to be light transmittance as long as it is conductive, and its thickness is not particularly limited.

[0055] Examples of conductive materials for forming electrodes include metals and alloys thereof such as gold, platinum, silver, copper, iron, zinc, tin, aluminum, indium, chromium, nickel, cobalt, scandium, vanadium, yttrium, cerium, samarium, europium, terbium, and ytterbium; 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.

[0056] Here, it is preferable that the conductive material used for the anode forms an ohmic junction with the organic semiconductor layer. Furthermore, when a hole transport layer is used, it is preferable that the conductive material used for the anode forms an ohmic junction with the hole transport layer. In addition, it is preferable that the conductive material used for the cathode forms an ohmic junction with the organic semiconductor layer or the electron transport layer. Here, an electron extraction layer may be introduced into the cathode, and the cathode and the organic semiconductor layer Alternatively, the junction with the electron transport layer can be improved, increasing the extraction current. This allows for a further improvement in photoelectric conversion efficiency. Examples of materials for forming the electron extraction layer include metallic fluorides such as lithium fluoride (LiF) and cesium fluoride.

[0057] The substrate can be a film or plate made by any method from an inorganic material such as alkali-free glass, quartz glass, aluminum, iron, copper, stainless steel alloys, etc., on which electrode materials and organic semiconductor layers can be laminated, depending on the type and application of the photoelectric conversion material. Examples include films or plates made from organic materials such as polyester, polycarbonate, polyolefin, polyamide, polyimide, polyphenylene sulfide, polyparaxylene polymethyl methacrylate, epoxy resin, and fluororesin. When light is incident from the substrate side, it is preferable that the substrate has a light transmittance of 80% or more.

[0058] Materials that form the hole transport layer include, for example, 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 oxide (MoO3) such as MoO3. x ), tungsten oxide such as WO3 (WO x ), nickel oxide such as NiO (NiO x ), vanadium oxide (VO2O5), etc. x ), Zirconium oxide such as ZrO2 (ZrO x ), copper oxide such as Cu2O (CuO x ), copper iodide, ruthenium oxide (RuO4), etc. x ), rhenium oxide (ReO2O7) such as Re2O7 x Examples include inorganic compounds such as ). Two or more of these may be used, and they may be laminated. Among these, polyethylenedioxythiophene (PEDOT), which is a polythiophene polymer, or PEDOT to which polystyrene sulfonate (PSS) has been added, molybdenum oxide, vanadium oxide, and tungsten oxide are preferably used. Furthermore, the thickness of the hole transport layer is preferably 10 nm to 200 nm.

[0059] As the material for forming the electron transport layer, a material exhibiting n-type semiconductor properties is preferred, such as titanium oxide (TiO2). x ) and zinc oxide such as ZnO (ZnO x Inorganic materials such as PEI (Polyethylenimine) 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)-tetron), poly[[2,7-bis(2-ethylhexyl)-1,2,3,6,7,8-hexahydro-1,3,6,8-tetraoxobenzo[lm Organic materials such as n[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](PNDIT-F3N-Br) and organic-inorganic hybrid materials such as PEI-Zn (Polyethyleneimine-Zn) are preferably used.

[0060] Next, the method for manufacturing the photovoltaic element of the present invention will be explained with an example. A transparent electrode (corresponding to the anode in this case) made of ITO or the like 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 general formula (1) or (2), and optionally an electron-accepting organic material, is dissolved in an organic solvent and coated onto the transparent electrode to form an organic semiconductor layer. The organic solvent is not particularly limited as long as it can adequately 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.

[0061] Methods for forming an organic semiconductor layer include, for example, spin coating, blade coating, slit die coating, screen printing, bar coating, template coating, print transfer, immersion and pulling, inkjet, spray, and vacuum deposition. It is preferable to select a formation method according to the characteristics of the organic semiconductor layer to be obtained, such as film thickness control and orientation control. In addition, any additive that optimizes the phase separation structure of the organic semiconductor layer may be added. Preferred additives include 1,8-diiodoctane, 1-chloronaphthalene, and 1-phenylnaphthalene.

[0062] Next, a metal electrode (corresponding to the cathode in this case), such as Al, is formed on the organic semiconductor layer by vacuum deposition or sputtering. If a low-molecular-weight organic material is used for the electron transport layer and vacuum deposition is performed, it is preferable to continue forming the metal electrode while maintaining the vacuum.

[0063] When a hole transport layer is to be provided between the anode and the organic semiconductor layer, a solution of the desired p-type organic semiconductor material (such as PEDOT) is applied to the anode, and then the solvent is 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 bath or 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 applied.

[0064] When an electron transport layer is to be provided between the organic semiconductor layer and the cathode, a solution of the desired n-type organic semiconductor material (such as a fullerene derivative) or n-type inorganic semiconductor material (such as titanium dioxide gel) is applied to the organic semiconductor layer, and then the solvent is removed to form the electron transport layer. Examples of application and solvent removal methods include those exemplified for the formation of the hole transport layer. Phenanthroline derivatives and C 60 When using low-molecular-weight organic materials such as those mentioned above, it is also possible to apply a vacuum deposition method using a vacuum deposition machine. [Examples]

[0065] The present invention will be described in more detail below based on examples. However, the present invention is not limited to the following examples. Furthermore, abbreviations used for the compounds in the examples are listed below.

[0066] Jsc: Short-circuit current density Voc: Open-circuit voltage FF: Fill Factor (Shape Factor) ITO: Indium tin oxide Y6 acceptor: A compound having the structure represented by the following formula.

[0067] [ka]

[0068] (Synthesis Example 1) The starting material, 2,2'-bistriisopropylsilyl-4,4'-dibromo-5,5'-bithiazole (compound 1), was synthesized based on the information provided by Xugang Guo et al., "Chemistry of Materials," 2018, Vol. 30, pp. 7988-8001. Additionally, 2-(2-ethylhexyl)-5-trimethylstanylthiophene (compound 2) was synthesized based on the information provided by Qichun Zhang et al., "Journal of Materials Chemistry C," 2016, Vol. 4, pp. 3809-3814.

[0069] [ka]

[0070] (Synthesis of compound 3a) Under an argon atmosphere, compound 1 (2.5 g, 3.93 mmol), 2-(2-ethylhexyl)-5-trimethylstanylthiophene (compound 2) (1.45 g, 5.89 mmol), tetrakis(triphenylphosphine)palladium (0) (Tokyo Chemical Industries, Ltd.) (454 mg, 5.89 mmol), and dimethylformamide (80 mL) were added to a reaction vessel and reacted at 90°C for 12 hours. After cooling to room temperature, water was added to the reaction solution, and the mixture was extracted with hexane. The organic layer was washed with water. The organic layer was dried over anhydrous sodium sulfate, filtered, and the solvent was removed under reduced pressure. The resulting reaction mixture was separated and purified by silica gel column chromatography using hexane:dichloromethane (3:1) as the mobile phase to obtain compound 3a as a pale yellow liquid (2.1 g, yield 71%). The physical properties of the obtained compound 3a are as follows:

[0071] 1 HNMR (400 MH) z ,CDCl3,TMS)δ=7.05(d,1H),δ=6.60(d,1H),δ=2.65(d,2H),δ=1.45(m,7H),δ=1.26(m,8H),δ=1.20(d,18H),δ=1.17(d,18H),δ=0.85(m,6H)

[0072] (Synthesis of compound 3b) The raw material, 2-octyl-5-trimethylstanylthiophene, was synthesized based on the information provided in Qichun Zhang et al., "Journal of Materials Chemistry C," 2016, Vol. 4, pp. 3809-3814.

[0073] Compound 3b was obtained as a pale yellow liquid by the same synthetic method as compound 3a, except that 2-(2-ethylhexyl)-5-trimethylstanylthiophene was replaced with 2-octyl-5-trimethylstanylthiophene. (620 mg, yield 67%) The physical properties of the obtained compound 3b are as follows.

[0074] 1 HNMR (400 MH)z ,CDCl3,TMS)δ=7.00(d,1H),δ=6.62(d,1H),δ=2.72(t,2H),δ=1.60(m,2H),δ=1. 47(m,6H),δ=1.25-1.30(m,10H),δ=1.20(d,18H),δ=1.17(d,18H),δ=0.87(t,3H)

[0075] [ka]

[0076] (Synthesis of compound 4a) Under an argon atmosphere, compound 3a (2.1 g, 2.65 mmol), palladium(II) acetate (Tokyo Chemical Industries, Ltd.) (30 mg, 5 mol%), tricyclohexylphosphonium tetrafluoroborate (Tokyo Chemical Industries, Ltd.) (98 mg, 10 mol%), cesium carbonate (Nacalai Tesque Corporation) (1.7 g, 5.3 mmol), and 1,4-dioxane (30 mL) were added to a reaction vessel and reacted at 140°C for 4 hours. After cooling to room temperature, water was added to the reaction solution and extracted with dichloromethane, and the organic layer was washed with water. The organic layer was dried over anhydrous sodium sulfate, filtered, and the solvent was removed under reduced pressure. The resulting reaction mixture was separated and purified by silica gel column chromatography using hexane:dichloromethane (3:1) as the mobile phase to obtain compound 4a as a pale yellow liquid (1.7 g, yield 95%). The physical properties of the obtained compound 4a are as follows:

[0077] 1 HNMR (400 MH) z ,CDCl3,TMS)δ=7.81(s,1H),δ=2.99(d,2H)δ=1.81(m,1H),δ=1.24(d,18H),δ=1.22(d,18H),δ=1.5-1.6(m,8H),δ=0.80-1.00(m,6H)

[0078] (Synthesis of compound 4b) Compound 4b was obtained as a pale yellow liquid by the same synthesis method as compound 4a. (1.47g, yield 87%) The physical properties of the obtained compound 4b are as follows:

[0079] 1 HNMR (400 MH) z ,CDCl3,TMS)δ=7.82(s,1H),δ=3.05(t,2H),δ=1.86(m,2H),δ=1.55(m,6H ),δ=1.25-1.35(m,10H),δ=1.23(d,18H),δ=1.21(d,18H),δ=0.87(t,3H)

[0080] [ka]

[0081] (Synthesis of compound 5a) Under an argon atmosphere, compound 4a (1.2 g, 1.78 mmol) and tetrahydrofuran (15 mL) were added to a reaction vessel and cooled to 0°C using an ice bath. Tetrabutylammonium fluoride (Tokyo Chemical Industries, Ltd.) (7.12 mL, 7.12 mmol) was added dropwise and the mixture was reacted for 1 hour. Water was added to the reaction solution, and the mixture was extracted with ethyl acetate. The organic layer was washed with water. The organic layer was dried over anhydrous sodium sulfate, filtered, and the solvent was removed under reduced pressure. The resulting reaction mixture was separated and purified by silica gel column chromatography using hexane:ethyl acetate (3:1) as the mobile phase to obtain compound 5a as a pale yellow solid (490 mg, yield 76%). The physical properties of the obtained compound 5a are as follows:

[0082] 1 HNMR (400 MH) z ,CDCl3,TMS)δ=9.05(s,1H),δ=9.03(s,1H),δ=7.75(s,1H),δ=2.99(d,2H),δ=1.78(m,1H),δ=1.39(m,8H),δ=0.91(m,6H)

[0083] (Synthesis of compound 5b) Compound 5b was obtained as a pale yellow solid by synthesis using the same method as compound 5a. (260 mg, yield 98%) The physical properties of the obtained compound 5b are as follows:

[0084] 1 HNMR (400 MH) z ,CDCl3,TMS)δ=9.09(s,1H),δ=9.06(s,1H),δ=7.79(s,1H),δ=3.06(t,2H),δ=1.86(m,2H),δ=1.20-1.50(m,10H),δ=0.88(t,3H)

[0085] [ka]

[0086] (Synthesis of compound 6a) Under an argon atmosphere, compound 5a (200 mg, 0.55 mmol), 1,2-dibromo-1,1,2,2-tetrachloroethane (Tokyo Chemical Industries, Ltd.) (465 mg, 1.43 mmol), and tetrahydrofuran (10 mL) were added to a reaction vessel and cooled to -78°C. Lithium hexamethyldisilazide (Sigma-Aldrich) (1.1 mL, 1.1 mmol) was added dropwise and the mixture was reacted for 30 minutes. After raising the temperature to room temperature, water was added to the reaction solution, and the organic layer was extracted with chloroform and washed with water. The organic layer was dried over anhydrous sodium sulfate, filtered, and the solvent was removed under reduced pressure. The resulting reaction mixture was separated and purified by silica gel column chromatography using hexane:chloroform (1:1) as the mobile phase to obtain compound 6a as a white solid (248 mg, yield 87%). The physical properties of the obtained compound 6a are as follows:

[0087] 1 HNMR (400 MH) z ,CDCl3,TMS)δ=7.69(s,1H),δ=2.96(d,2H),δ=1,74(m,1H),δ=1.35(m,8H),δ=0.91(m,6H)

[0088] (Synthesis of compound 6b) Compound 6b was obtained as a white solid by synthesis using the same method as compound 6a. (615 mg, yield 93%) The physical properties of the obtained compound 6b are as follows:

[0089] 1 HNMR (400 MH) z ,CDCl3,TMS)δ=7.70(s,1H),δ=3.02(t,2H),δ=1.83(m,2H),δ=1.20-1.50(m,10H),δ=0.87(t,3H)

[0090] [ka]

[0091] (Synthesis of compound 8a) The raw material, 3-(2-ethylhexyl)-5-trimethylstanylthiophene (compound 7a), can be synthesized by referring to Qichun Zhang et al., "Journal of Materials Chemistry C," 2016, Vol. 4, pp. 3809-3814.

[0092] Under an argon atmosphere, compound 6a (248 mg, 0.48 mmol), 3-(2-ethylhexyl)-5-trimethylstanylthiophene (compound 7a) (433 mg, 1.2 mmol), tetrakis(triphenylphosphine)palladium (0) (Tokyo Chemical Industries, Ltd.) (24 mg, 4.4 mol%), toluene (5 mL), and dimethylformamide (5 mL) were added to a reaction vessel and reacted at 90°C for 4 hours. After cooling to room temperature, water was added to the reaction solution and extracted with hexane, and the organic layer was washed with water. The organic layer was dried over anhydrous sodium sulfate, filtered, and the solvent was removed under reduced pressure. The resulting reaction mixture was separated and purified by silica gel column chromatography using hexane:ethyl acetate (30:1) as the mobile phase to obtain compound 8a as a yellow liquid (220 mg, yield 62%). The physical properties of the obtained compound 8a are as follows:

[0093] 1 HNMR (400 MH) z,CDCl3,TMS)δ=7.75(s,1H),δ=7.51(dd,2H),δ=7.09(s,2H),δ=2.98(d,2H),δ=2.59 (d,4H),δ=1.79(m,1H),δ=1.61(m,2H),δ=1.35-1.45(m,24H),δ=0.80-1.00(m,18H)

[0094] (Synthesis of compound 8b) Compound 8b was obtained as a yellow liquid by synthesis using the same method as compound 8a. (370 mg, yield 80%) The physical properties of the obtained compound 8b are as follows:

[0095] 1 HNMR (400 MH) z ,CDCl3,TMS)δ=7.76(d,1H),δ=7.50(t,2H),δ=7.09(s,2H),δ=3.04(t,2H),δ=2 .59(d,4H),δ=1.85(m,2H),1.62(m,2H),δ=1.20-1.50(m,26H),0.80-0.95(15H)

[0096] [ka]

[0097] (Synthesis of compound 9a) Under an argon atmosphere, compound 8a (100 mg, 0.13 mmol), chloroform (3 mL), and acetic acid (2.3 mL) were added to a reaction vessel, and the mixture was cooled to 0°C using an ice bath while protected from light. N-bromosuccinimide (Tokyo Chemical Industries, Ltd.) (48 mg, 0.26 mmol) was then added and the mixture was reacted for 2 hours. Water was added to the reaction solution, and the mixture was extracted with chloroform. The organic layer was washed with water. The organic layer was dried over anhydrous sodium sulfate, filtered, and the solvent was removed under reduced pressure. The resulting reaction mixture was separated and purified by silica gel column chromatography using hexane:chloroform (3:1) as the mobile phase to obtain compound 9a as a yellow solid (70 mg, yield 62%). The physical properties of the obtained compound 9a are as follows:

[0098] 1 HNMR (400 MH) z ,CDCl3,TMS)δ=7.71(s,1H),δ=7.33(s,1H),δ=7.32(s,1H),δ=2.98(d,2H),δ=2.55 (d,4H),δ=1.78(m,1H),δ=1.68(m,2H),δ=1.30-1.50(m,24H),δ=0.88-0.98(m,18H)

[0099] (Synthesis of compound 9b) Compound 9b was obtained as a yellow solid by synthesis using the same method as compound 9a. (355 mg, yield 82%) The physical properties of the obtained compound 9b are as follows:

[0100] 1 HNMR (400 MH) z ,CDCl3,TMS)δ=7.72(s,1H),δ=7.32(s,1H),δ=7.31(s,1H),δ=3.04(t,2H),δ=2.55 (d,4H),δ=1.85(m,2H),δ=1.67(m,2H),δ=1.20-1.50(m,26H),δ=0.85-0.95(m,15H)

[0101] (Example 1) [ka]

[0102] (Synthesis of conjugated polymer P1) Compound 9a (45.3 mg, 0.05 mmol), compound 10 (45.3 mg, 0.05 mmol), tetrakis(triphenylphosphine)palladium (0) (Tokyo Chemical Industries, Ltd.) (1.15 mg, 2 mol%), and toluene (2.0 mL) were added to a reaction vessel, and the mixture was reacted at 200 °C for 2 hours using a microwave reactor (Biotage, Initiator). After cooling to room temperature, the reaction mixture was added to methanol (50 mL) and stirred for 2 hours. After filtration, Soxhlet extraction was performed using methanol, hexane, and dichloromethane as solvents to remove low molecular weight components. The residue was extracted with chloroform, and after removing the solvent under reduced pressure, methanol was added and the mixture was filtered to obtain the conjugated polymer P1 as a red solid (59 mg, yield 89%, number average molecular weight: 98,400, molecular weight dispersion: 5.4). The number average molecular weight was calculated as the molecular weight equivalent to standard polystyrene using Tosoh HLC-8321GPC / HT.

[0103] (Evaluation of solar cell devices using conjugated polymer P1) A glass substrate patterned with an ITO film was ultrasonically cleaned for 10 minutes in the following order: neutral detergent, deionized water, acetone, and isopropyl alcohol, followed by UV ozone treatment. Next, an aqueous dispersion of poly(3,4-ethylenedioxythiophene) / poly(4-styrenesulfonic acid) (Heraeus, Clevios® P VP Al 4083) was spin-coated at 5000 rpm for 30 seconds. The hole extraction layer was formed by heating the substrate at 120°C for 10 minutes. The substrate with the hole extraction layer was brought into a glove box, and a photoactive layer was formed by spin-coating using a chloroform solution containing the conjugated polymer P1 and the n-type material Y6 (weight ratio of polymer compound P1 / Y6 = 1 / 1.2) (film thickness 100 nm). Y6 was synthesized and used based on Joule, 2019, Vol. 3, p. 1140. Furthermore, a methanol solution (2 mg / mL) of 2,9-bis[3-(dimethyloxideamino)propyl]anthra[2,1,9-def:6,5,10-d'e'f']diisoquinoline-1,3,8,10(2H,9H)-tetron was spin-coated onto the active layer at 3000 rpm for 30 seconds as an electron extraction layer. The 2,9-bis[3-(dimethyloxideamino)propyl]anthra[2,1,9-def:6,5,10-d'e'f']diisoquinoline-1,3,8,10(2H,9H)-tetron was purchased from 1-Material. Next, a 220 nm thick silver film was sequentially deposited as an electrode layer using a resistance heating vacuum deposition method to fabricate a 4 mm square organic thin-film solar cell element.

[0104] The resulting organic thin-film solar cell was subjected to a solar simulator (SAN-EI Electric XES-40S1) (AM1.5G filter, irradiance 100mW / cm²). 2 A constant amount of light was irradiated using (), and the generated current and voltage were measured. Figure 2 shows the current density-voltage characteristics graph, and Figure 3 shows the spectral sensitivity characteristics.

[0105] From the obtained Figure 2, the short-circuit current density Jsc (mA / cm²) 2), the open-circuit voltage Voc (V) and the shape factor FF were calculated, and Jsc = 25.3 mA / cm 2 The voltages were Voc = 0.84V and FF = 0.69V. The photoelectric conversion efficiency (η) was calculated using the formula η = (Jsc × Voc × FF) / 100, and was found to be 14.9%.

[0106] (Example 2) (Synthesis of conjugated polymer P2) Conjugated polymer P2 was obtained as a red solid by synthesizing it using the same method as conjugated polymer P1. (46 mg, yield 66%, number-average molecular weight: 51,100, molecular weight dispersion: 2.3)

[0107] (Evaluation of solar cell devices using conjugated polymer P2) An organic thin-film solar cell was fabricated in the same manner as in Example 1 (film thickness 100 nm) except that a photoactive layer was formed by spin coating using a chloroform solution containing the conjugated polymer P2 and the n-type material Y6 (weight ratio of polymer compound P2 / Y6 = 1 / 1.2), and its properties were evaluated. The current density-voltage characteristics shown in Figure 4 were obtained, with Jsc = 22.5 mA / cm². 2 The values ​​were Voc = 0.88V and FF = 0.67. η was 13.5%. Figure 5 shows the spectral sensitivity characteristics.

[0108] (Example 3) [ka]

[0109] (Synthesis of conjugated polymer P3) Conjugated polymer P3 was obtained as a red solid by synthesizing it using the same method as conjugated polymer P1. (23 mg, yield 35%, number average molecular weight: 56,800, molecular weight dispersion: 3.36)

[0110] (Evaluation of solar cell devices using conjugated polymer P3) An organic thin-film solar cell was fabricated in the same manner as in Example 1 (film thickness 100 nm) except that a photoactive layer was formed by spin coating using a chloroform solution containing the conjugated polymer P3 and the n-type material Y6 (weight ratio of conjugated compound P3 / Y6 = 1 / 1.2), and its properties were evaluated. The current density-voltage characteristics shown in Figure 6 were obtained, with Jsc = 22.6 mA / cm². 2 The values ​​were Voc = 0.80V and FF = 0.64. η was 11.6%. Figure 7 shows the spectral sensitivity characteristics.

[0111] (Synthesis Example 2) The starting material, 2,2'-bistriisopropylsilyl-4,4'-dibromo-5,5'-bithiazole (compound 11), was synthesized based on the information in "Chemistry of Materials" by Xugang Guo et al., 2018, Vol. 30, pp. 7988-8001.

[0112] [ka]

[0113] (Synthesis of Compound 12) Under an argon atmosphere, compound 11 (3.80 g, 6.00 mmol) and tetrahydrofuran (72 mL) were added to a reaction vessel and cooled to -78°C. n-butyllithium (Tokyo Chemical Industries, Ltd.) (11.2 mL, 18.0 mmol) was added dropwise, and the mixture was stirred for 2 hours. 1-formylpiperidine (Tokyo Chemical Industries, Ltd.) (2.13 mL, 19.2 mmol) was added, and the mixture was stirred overnight while increasing the temperature to room temperature. Water was added to the reaction solution, and the mixture was extracted with hexane. The organic layer was washed with water. The organic layer was dried over anhydrous sodium sulfate, filtered, and the solvent was removed under reduced pressure. The resulting reaction mixture was separated and purified by silica gel column chromatography using dichloromethane as the mobile phase to obtain compound 12 as a yellow liquid (2.7 g, yield 84%). The physical properties of compound 12 obtained are as follows:

[0114] 1HNMR(400MHz,CDCl3,TMS)δ=10.5(s,2H),δ=1.49(m,6H),δ=1.19(d,36H)

[0115] [ka]

[0116] (Synthesis of Compound 13) Under an argon atmosphere, zinc (Tokyo Chemical Industries, Ltd.) (3.90 g, 60.3 mmol) and tetrahydrofuran (200 mL) were added to a reaction vessel and cooled to 0°C using an ice bath. Titanium tetrachloride (Nacalai Tesque) (3.30 mL, 30.0 mmol) was added dropwise, and the mixture was stirred at 80°C for 1 hour. Compound 12 (2.7 g, 5.0 mmol) in a tetrahydrofuran solution (100 mL) was added dropwise, and the mixture was stirred for 24 hours. After cooling to room temperature, an aqueous sodium carbonate solution was added to the reaction solution, and the mixture was filtered using Celite. Hexane was added to the filtrate for extraction, and the organic layer was washed with water. The organic layer was dried over anhydrous sodium sulfate, filtered, and the solvent was removed under reduced pressure. Compound 13 was obtained as a yellow solid by separating and purifying the resulting reaction mixture using silica gel column chromatography with dichloromethane as the mobile phase (1.77 g, yield 70%). The physical properties of compound 13 obtained are as follows:

[0117] 1 HNMR(400MHz,CDCl3,TMS)δ=8.25(s,2H),δ=1.55(m,6H),δ=1.20(d,36H)

[0118] [ka] (Synthesis of Compound 14) Under an argon atmosphere, compound 13 (1.77 g, 3.50 mmol) and tetrahydrofuran (30 mL) were added to a reaction vessel and cooled to 0°C using an ice bath. Tetrabutylammonium fluoride (Tokyo Chemical Industries, Ltd.) (10.5 mL, 10.5 mmol) was added dropwise and the mixture was reacted for 1 hour. Water was added to the reaction solution and extracted with dichloromethane, and the organic layer was washed with water. The organic layer was dried over anhydrous sodium sulfate, filtered, and the solvent was removed under reduced pressure. The resulting reaction mixture was separated and purified by silica gel column chromatography using chloroform:ethyl acetate (7:1) as the mobile phase to obtain compound 14 as a white solid (505 mg, yield 75%). The physical properties of compound 14 obtained are as follows:

[0119] 1 HNMR(400MHz,CDCl3,TMS)δ=9.06(s,2H),δ=8.26(s,2H)

[0120] [ka]

[0121] (Synthesis of Compound 15) Under an argon atmosphere, compound 14 (100 mg, 0.52 mmol), 1,2-dibromo-1,1,2,2-tetrachloroethane (Tokyo Chemical Industries, Ltd.) (390 mg, 1.20 mmol), and tetrahydrofuran (12 mL) were added to a reaction vessel and cooled to -78°C. Lithium hexamethyldisilazide (Sigma-Aldrich) (1.04 mL, 1.04 mmol) was added dropwise and the mixture was reacted for 30 minutes. After raising the temperature to room temperature, water was added to the reaction solution, and compound 15 was obtained as a white solid by filtration and washing with ethanol. (168 mg, yield 92%) The physical properties of compound 15 obtained are as follows:

[0122] 1 HNMR(400MHz,CDCl3,TMS)δ=8.06(s,2H)

[0123] [ka]

[0124] (Synthesis of Compound 17) The raw material, 3-(2-butyloctyl)-5-trimethylstanylthiophene (compound 16), was synthesized based on the information provided in Qichun Zhang et al., "Journal of Materials Chemistry C," 2016, Vol. 4, pp. 3809-3814. Under an argon atmosphere, compound 15 (350 mg, 1.00 mmol), 3-(2-butyloctyl)-5-trimethylstanylthiophene (compound 16) (955 mg, 2.3 mmol), tetrakis(triphenylphosphine)palladium (0) (Tokyo Chemical Industries, Ltd.) (50.8 mg, 4.4 mol%), toluene (13 mL), and dimethylformamide (13 mL) were added to a reaction vessel and reacted at 90°C for 5 hours. After cooling to room temperature, water was added to the reaction solution and extracted with hexane, and the organic layer was washed with water. The organic layer was dried over anhydrous sodium sulfate, filtered, and the solvent was removed under reduced pressure. The resulting reaction mixture was separated and purified by silica gel column chromatography using hexane:ethyl acetate (10:1) as the mobile phase to obtain compound 17 as a yellow liquid (600 mg, yield 87%). The physical properties of compound 17 obtained are as follows:

[0125] 1 HNMR(400MHz,CDCl3,TMS)δ=8.06(s,2H),δ=7.48(d,2H),δ=7.09(d,2H),δ=2.59(d,4H),δ=1.65(m,2H),δ=1.30(m,32H),δ=0.88(m,12H)

[0126] [ka]

[0127] (Synthesis of Compound 18) Under an argon atmosphere, compound 17 (580 mg, 0.84 mmol), chloroform (17 mL), and acetic acid (11 mL) were added to a reaction vessel, and the mixture was cooled to 0°C using an ice bath while protected from light. N-bromosuccinimide (Tokyo Chemical Industries, Ltd.) (330 mg, 1.84 mmol) was then added and the mixture was reacted for 5 hours. Water was added to the reaction solution, and the mixture was extracted with chloroform. The organic layer was washed with water. The organic layer was dried over anhydrous sodium sulfate, filtered, and the solvent was removed under reduced pressure. The resulting reaction mixture was separated and purified by silica gel column chromatography using hexane:chloroform (1:2) as the mobile phase to obtain compound 18 as a yellow solid (600 mg, yield 84%). The physical properties of compound 18 obtained are as follows:

[0128] 1 HNMR(400MHz,CDCl3,TMS)δ=8.04(s,2H),δ=7.30(s,2H),δ=2.54(d,4H),δ=1.70(m,2H),δ=1.30(m,32H),δ=0.88(m,12H)

[0129] (Example 4) [ka]

[0130] (Synthesis of conjugated polymer P4) Compound 18 (42.55 mg, 0.05 mmol), Compound 19 (45.3 mg, 0.05 mmol), Tetrakis(triphenylphosphine)palladium (0) (Tokyo Chemical Industries, Ltd.) (1.15 mg, 2 mol%), and Toluene (2.0 mL) were added to a reaction vessel, and the mixture was reacted at 200°C for 2 hours using a microwave reactor (Biotage, Initiator). After cooling to room temperature, the reaction mixture was added to methanol (50 mL) and stirred for 2 hours. After filtration, Soxhlet extraction was performed using methanol, hexane, and dichloromethane as solvents to remove low molecular weight components. The residue was extracted with chloroform, and after removing the solvent under reduced pressure, methanol was added and the mixture was filtered to obtain high molecular weight compound P4 as a red solid (60 mg, yield 95%, number average molecular weight: 81,300, molecular weight dispersion: 1.9). The number average molecular weight was calculated as the molecular weight equivalent to standard polystyrene using Tosoh HLC-8321GPC / HT.

[0131] (Evaluation of solar cell devices using conjugated polymer P4) An organic thin-film solar cell was fabricated in the same manner as in Example 1 (film thickness 100 nm) except that a photoactive layer was formed by spin coating using a chloroform solution containing the conjugated polymer P4 and the n-type material Y6 (weight ratio of polymer compound P4 / Y6 = 1 / 1.2), and its properties were evaluated. The current density-voltage characteristics shown in Figure 8 were obtained, with Jsc = 24.4 mA / cm². 2 The values ​​were Voc = 0.83V and FF = 0.70. η was 14.2%. Figure 9 shows the spectral sensitivity characteristics.

[0132] (Comparative Example 1) (Fabrication and evaluation of solar cell devices using conjugated polymer P5) Solar cell elements were fabricated and evaluated using P5 (FlexPV), a commercially available p-type polymer.

[0133] [ka]

[0134] (Evaluation of solar cell devices using conjugated polymer P5) An organic thin-film solar cell was fabricated in the same manner as described above, except that a photoactive layer was formed by spin coating using a chloroform solution containing the conjugated polymer P5 and the n-type material Y6 (weight ratio of conjugated polymer P4 / Y6 = 1 / 1.2), and its properties were evaluated. The current density-voltage characteristics shown in Figure 10 were obtained, with Jsc = 24.9 mA / cm². 2 The values ​​were Voc = 0.78V and FF = 0.58. η was 11.4%. Figure 11 shows the spectral sensitivity characteristics.

[0135] The evaluation results for Examples 1-4 and Comparative Example 1 are summarized in Table 1. It can be seen that organic thin-film solar cells fabricated using the conjugated polymer (P1-P4) of the present invention having a structure represented by general formula (1) or (2) have higher open-circuit voltage and photoelectric conversion efficiency, and exhibit better characteristics compared to organic thin-film solar cells obtained using the conjugated polymer P5.

[0136] [Table 1] [Explanation of Symbols]

[0137] 1 circuit board 2 Anode 3. Organic semiconductor layer 4 cathode

Claims

1. A conjugated polymer having a structure represented by the following general formula (2). 【Chemistry 1】 (In the above general formula (2), R １ ~R ６ x and y may be the same or different and represent hydrogen, alkyl group, alkoxy group, alkanoyl group, alkoxycarbonyl group, halogen, aryl group, or heteroaryl group. A represents an arylene group or heteroarylene group. x and y may be the same or different and represent integers between 0 and 4. If x or y is 2 or greater, there are x R ３ and R ４ y R ５ and R ６ These can be the same or different. n represents the degree of polymerization, in the range of 2 to 1,000.

2. In the above general formula (2), R １ ~R ６ The conjugated polymer according to claim 1, wherein is hydrogen, halogen, or alkyl group.

3. The conjugated polymer according to claim 1 or 2, wherein A in the general formula (2) has a benzodithiophene structure.

4. A conjugated compound having a structure represented by the following general formula (3). 【Chemistry 2】 (In the above general formula (3), R ７ to R １０ may be the same or different and each represents hydrogen, an alkyl group, an alkoxy group, an alkoxycarbonyl group, a halogen, an aryl group or a heteroaryl group.)

5. An electron-donating organic material comprising a conjugated polymer according to any one of claims 1 to 3.

6. A material for a photovoltaic element comprising the electron-donating organic material and the electron-accepting organic material described in claim 5.

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

8. 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 containing the photovoltaic element material described in claim 6 or 7.

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