JP5299023B2 - Material for photovoltaic element and photovoltaic element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a material for a photovoltaic element, which contains a rubicene compound and to provide the photovoltaic element using the material and having high photoelectric conversion efficiency. <P>SOLUTION: The photovoltaic element uses the photovoltaic element material containing the rubicene compound represented by the shown formula (2). In the formula (2), A represents a rubicene skeleton, B represents a bivalent coupling group, m is 0 or 1, and n is included in a range of 2 to 1,000. In the formula (2), X<SP>1</SP>and X<SP>2</SP>may be identical or different and are selected from hydrogen, alkyl, alkoxy, aryl, and hetero aryl groups, and halogens. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a photovoltaic element material and a photovoltaic element using the same.

  Solar cells are attracting attention as an environmentally friendly electrical energy source and an influential energy source for increasing energy problems. Currently, inorganic materials such as single crystal silicon, polycrystalline silicon, amorphous silicon, and compound semiconductors are used as semiconductor materials for photovoltaic elements of solar cells. However, solar cells manufactured using inorganic semiconductors have not been widely used in ordinary households because of high costs compared with power generation methods such as thermal power generation and nuclear power generation. The high cost factor is mainly in the process of manufacturing a semiconductor thin film under vacuum and high temperature. Therefore, organic solar cells using organic semiconductors and organic dyes such as conjugated polymers and organic crystals are being studied as semiconductor materials expected to simplify the manufacturing process.

  However, an organic solar cell using a conjugated polymer or the like has the biggest problem that the photoelectric conversion efficiency is lower than that of a conventional solar cell using an inorganic semiconductor, and has not yet been put into practical use. The photoelectric conversion efficiency of organic solar cells using conventional conjugated polymers is mainly due to the low solar absorption efficiency and the excitons that are difficult to separate the electrons and holes generated by sunlight. This is because a state is formed and a trap for trapping carriers (electrons and holes) is easily formed, so that the generated carriers are easily trapped in the trap and the mobility of carriers is slow.

  Conventional photoelectric conversion elements using organic semiconductors can be generally classified into the following element configurations at present. A Schottky type that joins an electron-donating organic material (p-type organic semiconductor) and a metal having a low work function, and an electron-accepting organic material (n-type organic semiconductor) and an electron-donating organic material (p-type organic semiconductor). Heterojunction type. In these elements, only the organic layer (about several molecular layers) at the junction contributes to the photocurrent generation, so that the photoelectric conversion efficiency is low, and its improvement is a problem.

As a method for improving photoelectric conversion efficiency, a bulk heterojunction in which an electron-accepting organic material (n-type organic semiconductor) and an electron-donating organic material (p-type organic semiconductor) are mixed to increase the bonding surface contributing to photoelectric conversion There is a type (for example, see Non-Patent Document 1). Among them, the conjugated polymer used as the electron donating organic material (p-type organic semiconductor), a fullerene or a carbon nanotube, such as other C ₆₀ of the conductive polymer having the semiconductor characteristics of the n-type as the electron accepting organic material The used photoelectric conversion material is reported (for example, refer nonpatent literatures 2-3 and patent documents 1-2).

  As electron donating organic materials (p-type organic semiconductors), poly (3-hexylthiophene) is used as a conjugated polymer, and heterocyclic organic semiconductors represented by copper phthalocyanine are used as low-molecular materials. On the other hand, hydrocarbon condensed ring organic semiconductors that do not contain heteroatoms in the main skeleton of the chromophore have also been reported (see, for example, Non-Patent Documents 4 to 5). The hydrocarbon-based condensed ring is a skeleton that can be expected to be excellent in thermal and electrochemical stability and light resistance. However, no material showing a high photoelectric conversion efficiency has been found so far.

JP 2003-347565 A (Claims 1 and 3) JP 2004-165474 A (Claims 1 and 3)

J. et al. J. et al. M.M. Halls, C.I. A. Walsh, N .; C. Greenham, E.I. A. Marsegla, R.M. H. Frind, S.M. C. Moratti, A.M. B. Homes, "Nature", 1995, 376, 498 E. Kymakis, G .; A. J. et al. Amaruntunga, "Applied Physics Letters" (USA), 2002, 80, 112. G. Yu, J. et al. Gao, J .; C. Hummelen, F.M. Wudl, A.W. J. et al. Heeger, "Science", 1995, 270, 1789 K. Hirota, K. et al. Tajima, K .; Hashimoto, “Synthetic Metals”, 2007, 157, 290 L. Valentini, D.C. Bagnis, A.M. Marrochi, M.M. Seri, A.M. Taticchi, J. et al. M.M. Kenny, “Chemistry of Materials”, 2008, 20, 32

  As described above, all of the conventional organic solar cells have a problem of low photoelectric conversion efficiency. An object of this invention is to provide a photovoltaic device with high photoelectric conversion efficiency.

That is, the present invention is a rubicene compound represented by the following general formula (2), wherein the divalent linking group represented by B in the following general formula (2) may be substituted, A photovoltaic device material containing a rubicene compound which is a heteroarylene group, vinylene group or phenylene vinylene group , and a photovoltaic device using the same.

  According to the present invention, a photovoltaic device with high photoelectric conversion efficiency can be provided.

The schematic diagram which showed the one aspect | mode of the photovoltaic device of this invention. The schematic diagram which showed another aspect of the photovoltaic element of this invention.

  The photovoltaic device material of the present invention is characterized by containing a rubicene compound. A rubicene compound is characterized by having a wide light absorption wavelength region and high carrier mobility, which are important characteristics as a material for a photovoltaic device. For this reason, the photoelectric conversion efficiency of the photovoltaic device using the photovoltaic device material of the present invention can be greatly improved.

  As the rubicene compound having the above-described characteristics, a compound having a structure represented by the following general formula (1) or (2) is preferable. In order to apply the photovoltaic element material of the present invention to a wet process such as spin coating or blade coating, a uniform thin film can be formed. Therefore, an oligomer or polymer containing two or more rubicene skeletons is used. Preferably, it has a structure represented by the following general formula (2). A bulk heterojunction element with efficient photoelectric conversion is mainly manufactured by a wet process. For this reason, in order to obtain a high photoelectric conversion efficiency, a compound having a structure represented by the following general formula (2) that is more suitable for device fabrication by a wet process is more preferably used.

In the general formula (1), R ^{1 to} R ¹⁴ may be the same or different, and represent hydrogen, alkyl group, alkenyl group, alkynyl group, alkoxy group, aryl group, heteroaryl group, halogen, and adjacent substituent. It is selected from cyclic structures formed between them.

In the general formula (2), A represents a rubicene skeleton, and B represents a divalent linking group. m is 0 or 1. n is in the range of 2 to 1000. X ¹ and X ² may be the same or different and are selected from hydrogen, an alkyl group, an alkoxy group, an aryl group, a heteroaryl group, and a halogen.

  Here, the alkyl group is, for example, a saturated aliphatic group such as methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group. The hydrocarbon group may be linear, branched, or cyclic, and may be unsubstituted or substituted. Examples of the substituent when substituted include the following alkenyl groups, alkynyl groups, alkoxy groups, aryl groups, heteroaryl groups, and halogens. The number of carbon atoms of the alkyl group is preferably 10 or less when applied to a dry process such as vacuum deposition, and is preferably 4 or more when applied to a wet process such as spin coating.

  Further, the alkenyl group is an unsaturated aliphatic hydrocarbon group containing a C═C double bond, which may be linear, branched or cyclic, and may be substituted even if unsubstituted. It does not matter. Examples of the substituent in the case of substitution include the following alkynyl group, alkoxy group, aryl group, heteroaryl group, and halogen. The preferable carbon number range of the alkenyl group is the same as that of the alkyl group described above.

  An alkynyl group is an unsaturated aliphatic hydrocarbon group containing a C≡C triple bond, which may be unsubstituted or substituted. Examples of the substituent in the case of substitution include the above alkenyl group, the following alkoxy group, aryl group, heteroaryl group, and halogen. The preferred carbon number range of the alkynyl group is the same as that of the alkyl group described above.

  The alkoxy group refers to, for example, an aliphatic hydrocarbon group via an ether bond such as a methoxy group, an ethoxy group, a propoxy group, or a butoxy group, and the aliphatic hydrocarbon group may be unsubstituted or substituted. Absent. Examples of the substituent in the case of substitution include the above alkenyl group, alkynyl group, the following aryl group, heteroaryl group, and halogen. The range of the preferable carbon number of the said alkoxy group is the same as the case of the above-mentioned alkyl group.

  The aryl group represents, for example, an aromatic hydrocarbon group such as a phenyl group, a naphthyl group, a biphenyl group, a phenanthryl group, an anthryl group, a terphenyl group, a pyrenyl group, a fluorenyl group, and a perylenyl group, which is unsubstituted. But it can be replaced. Examples of the substituent in the case of substitution include the above alkyl group, the following heteroaryl group, and halogen.

  The heteroaryl group includes, for example, thienyl group, furyl group, pyrrolyl group, imidazolyl group, pyrazolyl group, oxazolyl group, pyridyl group, pyrazyl group, pyrimidyl group, quinolinyl group, isoquinolyl group, quinoxalyl group, acridinyl group, indolyl group. Group, carbazolyl group, benzofuran group, dibenzofuran group, benzothiophene group, dibenzothiophene group, benzodithiophene group, silole group, benzosilole group, dibenzosilole group and other heteroaromatic ring groups having atoms other than carbon, It can be unsubstituted or substituted. Examples of the substituent in the case of substitution include the above alkyl group, aryl group, and the following halogen.

  The halogen is any one of fluorine, chlorine, bromine and iodine.

  Further, the cyclic structure formed between adjacent substituents may be an aliphatic ring or an aromatic ring, which may be unsubstituted or substituted. Examples of the substituent when substituted include the above alkyl group, alkoxy group, aryl group, heteroaryl group, and halogen.

In order to obtain a high photovoltaic current in the photovoltaic device, it is desirable to further expand the light absorption wavelength region. From such a viewpoint, R ^{1 to} R ¹⁴ in the general formula (1) are preferably a cyclic structure formed between an aryl group, a heteroaryl group, and an adjacent substituent, and contribute to the conjugated expansion of rubicene. . In particular, when applied to dry processes such as vacuum deposition, in order to suppress thermal modification (decomposition, multimerization, isomerization, etc.), the above-mentioned aryl group, heteroaryl group, and adjacent substituents It is desirable to keep the number of substituents having a relatively large molecular weight such as the cyclic structure formed in (1) to a minimum. From this viewpoint, R ^{1 to} R ¹⁴ are preferably hydrogen.

  The following structure is mentioned as a rubicene compound which has a structure represented by said General formula (1).

In the above general formula (2), A represents a rubicene skeleton and may be substituted. Examples of the rubicene skeleton of A include divalent groups derived from compounds exemplified as the rubicene compound having the structure represented by the general formula (1). B represents a divalent linking group. In order to further improve the photoelectric conversion efficiency of the photovoltaic device, a structure in which the conjugated structure of rubicene is expanded is preferable. Examples of such a linking group include arylene, heteroarylene, vinylene, and phenylene vinylene. These groups may be substituted, and examples of the substituent include an alkyl group and an alkoxy group. m is 0 or 1, and 1 is more preferable. n is in the range of 2 to 1000. From the viewpoint of ease of synthesis, a range of 2 to 50 is preferred. X ¹ and X ² may be the same or different and are selected from hydrogen, an alkyl group, an alkoxy group, an aryl group, a heteroaryl group, and a halogen. From the viewpoint of contributing to the expansion of the conjugated structure and further improving the photoelectric conversion efficiency of the photovoltaic device, aryl and heteroaryl groups are more preferable.

  Specific examples of the rubicene compound having the structure represented by the general formula (2) include the following structures. However, m shows the range of 0-1, and n shows 2 or more and 1000 or less.

  The rubicene compound can be synthesized, for example, by the method described in European Journal of Organic Chemistry 1998, Vol. 12, pages 2769-2773. For example, a method in which hydrochloric acid is allowed to act on a 1,5-dichloro-9,10-diphenylanthracene derivative to cyclize is exemplified. The rubicene compound having the structure represented by the general formula (2) can be obtained by a hetero-coupling reaction such as a Suzuki-Miyaura reaction or a Stille reaction. For example, a coupling reaction between a disubstituted rubicene derivative in which the 5,12-position of rubicene is substituted with a boronic acid derivative or a tin compound and a disubstituted aryl halide can be mentioned.

  A rubicene compound is excellent in light absorption characteristics and has a feature of high hole mobility and can be suitably used as an electron donating organic material.

The photovoltaic element material of the present invention may be composed of only the rubicene compound or may contain other electron donating organic materials. Examples of other electron donating organic materials include polythiophene polymers, benzothiadiazole-thiophene derivatives, benzothiadiazole-thiophene copolymers, poly-p-phenylene vinylene polymers, poly-p-phenylene polymers. Conjugated polymers such as polyfluorene polymer, polypyrrole polymer, polyaniline polymer, polyacetylene polymer, polythienylene vinylene polymer, H ₂ phthalocyanine (H ₂ Pc), copper phthalocyanine (CuPc) ), Phthalocyanine derivatives such as zinc phthalocyanine (ZnPc), porphyrin derivatives, N, N′-diphenyl-N, N′-di (3-methylphenyl) -4,4′-diphenyl-1,1′-diamine (TPD) ), N, N′-dinaphthyl-N, N′-diphenyl-4,4′-diphenyl Triarylamine derivatives such as -1,1′-diamine (NPD), carbazole derivatives such as 4,4′-di (carbazol-9-yl) biphenyl (CBP), oligothiophene derivatives (terthiophene, quarterthiophene, Cithiophene, octithiophene, etc.).

  Since the rubicene compound exhibits an electron donating property (p-type semiconductor characteristics), the photovoltaic device material of the present invention preferably further contains an electron-accepting organic material (n-type organic semiconductor). By combining the rubicene compound and the electron-accepting organic material, the photoelectric conversion efficiency of the photovoltaic element can be further improved.

The electron-accepting organic material used in the present invention is an organic material exhibiting n-type semiconductor characteristics. For example, 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA), 3,4,9,10- Perylenetetracarboxylic dianhydride (PTCDA), 3,4,9,10-perylenetetracarboxylic bisbenzimidazole (PTCBI), N, N′-dioctyl-3,4,9,10-naphthyltetracarboxydiimide (PTCDI) -C8H), 2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole (PBD), 2,5-di (1-naphthyl) -1,3 , 4-oxadiazole (BND) and other oxazole derivatives, 3- (4-biphenylyl) -4-phenyl-5- (4-t - butylphenyl) -1,2,4-triazole (triazole derivatives such as TAZ), phenanthroline derivatives, phosphine oxide derivatives, fullerene compounds _{(C 60, C 70, C} 76, C 78, C 82, C 84, C 90 , C ₉₄ and the like, [6,6] -phenyl C61 butyric acid methyl ester ([6,6] -PCBM), [5,6] -phenyl C61 butyric acid methyl ester ( [5,6] -PCBM), [6,6] -phenyl C61 butyric acid hexyl ester ([6,6] -PCBH), [6,6] -phenyl C61 butyric acid dodecyl ester ([6,6 ] -PCBD), phenyl C71 butyric acid methyl ester _(PC 70 BM), Fe Le C85 butyric acid methyl ester _(PC 84 BM), etc.), carbon nanotubes (CNT), poly -p- phenylene vinylene-based polymer derivatives obtained by introducing cyano group into (CN-PPV) and the like. Among these, fullerene compounds are preferably used because of their high charge separation speed and electron transfer speed.

  In the photovoltaic device material of the present invention, the content ratio (weight fraction) of the electron-donating organic material containing the rubicene compound and the electron-accepting organic material is not particularly limited, but the electron-donating organic material: electron-accepting organic material The material weight fraction is preferably in the range of 1 to 99:99 to 1, more preferably in the range of 10 to 90:90 to 10, still more preferably in the range of 20 to 60:80 to 40. is there. The electron-donating organic material and the electron-accepting organic material may be used as a mixture or laminated. Although it does not specifically limit as a mixing method, After adding to a solvent in a desired ratio, the method of making it melt | dissolve in a solvent combining 1 type or multiple types of methods, such as a heating, stirring, and ultrasonic irradiation, is mentioned. . As will be described later, when the photovoltaic element material forms a single organic semiconductor layer, the above-described content ratios of the electron-donating organic material and the electron-accepting organic material of the present invention contained in the single layer are included. When the organic semiconductor layer has a laminated structure of two or more layers, it means the content ratio of the electron donating organic material and the electron accepting organic material of the present invention in the whole organic semiconductor layer.

  In order to further improve the photoelectric conversion efficiency, it is preferable to remove impurities that can trap carriers as much as possible. In the present invention, the above-mentioned rubicene compound, an electron-donating organic material containing the compound, and a method for removing impurities from the electron-accepting organic material are not particularly limited, but column chromatography, recrystallization, sublimation, reprecipitation Method, Soxhlet extraction method, molecular weight fractionation method by GPC (gel permeation chromatography), filtration method, ion exchange method, chelate method and the like can be used. In general, a column chromatography method, a recrystallization method, and a sublimation method are preferably used for purification of a low molecular weight organic material. On the other hand, for the purification of high molecular weight compounds, when removing low molecular weight components, reprecipitation, Soxhlet extraction, or molecular weight fractionation by GPC (gel permeation chromatography) is preferably used to remove metal components. In such a case, a reprecipitation method, a chelate method, or an ion exchange method is preferably used. A plurality of these methods may be combined.

  Next, the photovoltaic element of the present invention will be described. The photovoltaic device of the present invention has at least a positive electrode and a negative electrode, and includes the photovoltaic device material of the present invention between them. FIG. 1 is a schematic view showing an example of the photovoltaic element of the present invention. In FIG. 1, reference numeral 1 is a substrate, reference numeral 2 is a positive electrode, reference numeral 3 is an organic semiconductor layer containing the photovoltaic element material of the present invention, and reference numeral 4 is a negative electrode.

  The organic semiconductor layer 3 contains the photovoltaic element material of the present invention. That is, it includes an electron-donating organic material containing an rubicene compound and an electron-accepting organic material. These materials are preferably mixed, and the electron-donating organic material and the electron-accepting organic material are preferably compatible or phase-separated at the molecular level. The domain size of this phase separation structure is not particularly limited, but is usually 1 nm or more and 50 nm or less. When the electron donating organic material and the electron accepting organic material are laminated, the layer having the electron donating organic material exhibiting p-type semiconductor characteristics is on the positive electrode side, and the electron accepting organic material exhibiting n-type semiconductor characteristics It is preferable that the layer having a negative electrode side. An example of the photovoltaic element in the case where the organic semiconductor layer 3 is laminated is shown in FIG. Reference numeral 5 is a layer having a rubicene compound, and reference numeral 6 is a layer having an electron-accepting organic material. The organic semiconductor layer preferably has a thickness of 5 nm to 500 nm, more preferably 30 nm to 300 nm. When laminated, the layer having the electron-donating organic material of the present invention preferably has a thickness of 1 nm to 400 nm, more preferably 15 nm to 150 nm.

  Further, the organic semiconductor layer 3 may contain the rubicene compound of the present invention and an electron donating organic material (p-type organic semiconductor) other than the electron accepting organic material. Examples of the electron donating organic material (p-type organic semiconductor) used here include those exemplified above as other compounds of the electron donating organic material.

In the photovoltaic device of the present invention, it is preferable that either the positive electrode 2 or the negative electrode 4 has light transmittance. The light transmittance of the electrode is not particularly limited as long as incident light reaches the organic semiconductor layer 3 and an electromotive force is generated. Here, the light transmittance in the present invention is a value obtained by [transmitted light intensity (W / m ² ) / incident light intensity (W / m ² )] × 100 (%). The thickness of the electrode may be in a range having light transparency and conductivity, and is preferably 20 nm to 300 nm, although it varies depending on the electrode material. The other electrode is not necessarily light-transmitting as long as it has conductivity, and the thickness is not particularly limited.

  As an electrode material, it is preferable to use a conductive material having a high work function for one electrode and a conductive material having a low work function for the other electrode. An electrode using a conductive material having a large work function is a positive electrode. Conductive materials with a large work function include metals such as gold, platinum, chromium and nickel, transparent metal oxides such as indium and tin, composite metal oxides (indium tin oxide (ITO), indium Zinc oxide (IZO) or the like is preferably used. Here, the conductive material used for the positive electrode 2 is preferably one that is in ohmic contact with the organic semiconductor layer 3. Furthermore, when a hole transport layer described later is used, it is preferable that the conductive material used for the positive electrode 2 is in ohmic contact with the hole transport layer.

  An electrode using a conductive material having a low work function serves as a negative electrode. As the conductive material having a low work function, alkali metal or alkaline earth metal, specifically, lithium, magnesium, or calcium is used. Tin, silver, and aluminum are also preferably used. Furthermore, an electrode made of an alloy made of the above metal or a laminate of the above metal is also preferably used. Further, it is possible to improve the extraction current by introducing a metal fluoride such as lithium fluoride or cesium fluoride into the interface between the negative electrode 4 and the electron transport layer. Here, the conductive material used for the negative electrode 4 is preferably one that is in ohmic contact with the organic semiconductor layer 3. Furthermore, when an electron transport layer described later is used, it is preferable that the conductive material used for the negative electrode 4 is in ohmic contact with the electron transport layer.

  The substrate 1 is a substrate on which an electrode material or an organic semiconductor layer can be laminated according to the type and application of the photoelectric conversion material, for example, an inorganic material such as alkali-free glass or quartz glass, polyester, polycarbonate, polyolefin, polyamide, polyimide, polyphenylene A film or plate produced by an arbitrary method from an organic material such as sulfide, polyparaxylene, epoxy resin or fluorine resin can be used. When light is incident from the substrate side and used, it is preferable that each substrate described above has a light transmittance of about 80%.

  In the present invention, a hole transport layer may be provided between the positive electrode 2 and the organic semiconductor layer 3. As a material for forming the hole transport layer, conductive polymers such as polythiophene polymers, poly-p-phenylene vinylene polymers, polyfluorene polymers, phthalocyanine derivatives (H2Pc, CuPc, ZnPc, etc.), Low molecular organic compounds exhibiting p-type semiconductor properties such as porphyrin derivatives are preferably used. In particular, polyethylenedioxythiophene (PEDOT), which is a polythiophene polymer, or PEDOT to which polystyrene sulfonate (PSS) is added is preferably used. The hole transport layer preferably has a thickness of 5 nm to 600 nm, more preferably 30 nm to 200 nm.

  In the photovoltaic device of the present invention, an electron transport layer may be provided between the organic semiconductor layer 3 and the negative electrode 4. The material for forming the electron transport layer is not particularly limited, but the above-described electron-accepting organic materials (NTCDA, PTCDA, PTCDI-C8H, oxazole derivatives, triazole derivatives, phenanthroline derivatives, phosphine oxide derivatives, fullerene compounds, An organic material exhibiting n-type semiconductor characteristics such as CNT and CN-PPV is preferably used. The thickness of the electron transport layer is preferably 5 nm to 600 nm, more preferably 30 nm to 200 nm.

  In the photovoltaic device of the present invention, two or more organic semiconductor layers may be stacked (tandemized) via one or more intermediate electrodes to form a series junction. For example, a laminated structure of substrate / positive electrode / first organic semiconductor layer / intermediate electrode / second organic semiconductor layer / negative electrode can be given. By laminating in this way, the open circuit voltage can be improved. Note that the hole transport layer described above may be provided between the positive electrode and the first organic semiconductor layer and between the intermediate electrode and the second organic semiconductor layer, and between the first organic semiconductor layer and the intermediate electrode. The hole transport layer described above may be provided between the second organic semiconductor layer and the negative electrode.

In the case of such a laminated structure, at least one layer of the organic semiconductor layer contains the photovoltaic device material of the present invention, and the other layer does not reduce the short-circuit current. It preferably contains an electron donating organic material having a different band gap. Examples of such an electron-donating organic material include the polythiophene polymer, poly-p-phenylene vinylene polymer, poly-p-phenylene polymer, polyfluorene polymer, polypyrrole polymer, polyaniline described above. Conjugated polymers such as polymer, polyacetylene polymer, polythienylene vinylene polymer, phthalocyanine derivatives such as H ₂ phthalocyanine (H ₂ Pc), copper phthalocyanine (CuPc), zinc phthalocyanine (ZnPc), porphyrin Derivatives, N, N′-diphenyl-N, N′-di (3-methylphenyl) -4,4′-diphenyl-1,1′-diamine (TPD), N, N′-dinaphthyl-N, N ′ -Triarylamine derivatives such as diphenyl-4,4'-diphenyl-1,1'-diamine (NPD), 4,4'-di ( Carbazole-9-yl) carbazole derivatives, such as biphenyl (CBP), oligothiophene derivatives (terthiophene, quarter thiophene, sexithiophene, etc. oct thiophene) include low molecular weight organic compounds, such as.

  In addition, the material for the intermediate electrode used here is preferably a material having high conductivity, for example, the above-mentioned metals such as gold, platinum, chromium, nickel, lithium, magnesium, calcium, tin, silver, aluminum, and transparent Metal oxides such as indium and tin, composite metal oxides (indium tin oxide (ITO), indium zinc oxide (IZO), etc.), alloys composed of the above metals and laminates of the above metals, polyethylene Examples include dioxythiophene (PEDOT) and those obtained by adding polystyrene sulfonate (PSS) to PEDOT. The intermediate electrode preferably has a light transmission property, but even a material such as a metal having a low light transmission property can often ensure a sufficient light transmission property by reducing the film thickness.

  Next, the example of the manufacturing method of the photovoltaic element of this invention is demonstrated. A transparent electrode such as ITO (corresponding to a positive electrode in this case) is formed on the substrate by sputtering or the like. Next, the photoelectric conversion element material containing the rubicene compound of the present invention and the electron-accepting organic material is dissolved in a solvent to form a solution, which is applied on the transparent electrode to form an organic semiconductor layer. The solvent used at this time is preferably an organic solvent. For example, methanol, ethanol, butanol, toluene, xylene, o-chlorophenol, acetone, ethyl acetate, ethylene glycol, tetrahydrofuran, dichloromethane, chloroform, dichloroethane, chlorobenzene, dichlorobenzene, Examples include chlorobenzene, chloronaphthalene, dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, and γ-butyrolactone. Two or more of these may be used. Moreover, the photoelectric conversion efficiency can be further improved by containing a fluorous solvent (an organic solvent having one or more fluorine atoms in the molecule). Examples of such a fluorous solvent include benzotrifluoride, hexafluorobenzene, 1,1,1,3,3,3-hexafluoro-2-propanol, perfluorotoluene, perfluorodecalin and the like. More preferably, benzotrifluoride is used. The content of the fluorous solvent is preferably 0.01 to 20% by volume, more preferably 0.1 to 5% by volume with respect to the total amount of solvent.

  When an organic semiconductor layer is formed by mixing an electron-donating organic material and an electron-accepting organic material containing the rubicene compound of the present invention, for example, the electron-donating organic material and the electron-accepting organic material are used in a solvent in a desired ratio. The solution is added and dissolved using a method such as heating, stirring and ultrasonic irradiation to form a solution, which is applied on the transparent electrode. In the case of forming an organic semiconductor layer by laminating an electron-donating organic material and an electron-accepting organic material, for example, after applying a solution of the electron-donating organic material to form a layer having the electron-donating organic material Then, a layer of the electron-accepting organic material is applied to form a layer. Here, when the electron-donating organic material and the electron-accepting organic material are low molecular weight substances having a molecular weight of about 1000 or less, it is possible to form a layer using a vapor deposition method.

  For organic semiconductor layer formation, spin coating, blade coating, slit die coating, screen printing coating, bar coater coating, mold coating, printing transfer method, dip pulling method, ink jet method, spray method, vacuum deposition method, etc. This method may be used, and the formation method may be selected according to the characteristics of the organic semiconductor layer to be obtained, such as film thickness control and orientation control. For example, when spin coating is performed, the electron donating organic material and the electron accepting organic material have a concentration of 1 to 20 g / l (relative to the volume of the solution containing the electron donating organic material, the electron accepting organic material, and the solvent). The weight of the electron-donating organic material and the electron-accepting organic material) is preferable, and by setting this concentration, a homogeneous organic semiconductor layer having a thickness of 5 to 500 nm, more preferably 30 to 300 nm can be obtained. . In order to remove the solvent, the formed organic semiconductor layer may be subjected to an annealing treatment under reduced pressure or in an inert atmosphere (in a nitrogen or argon atmosphere). A preferable temperature for the annealing treatment is 40 ° C to 300 ° C, more preferably 50 ° C to 200 ° C. Further, by performing the annealing process, the effective area where the stacked layers permeate and contact each other at the interface increases, and the short-circuit current can be increased. This annealing treatment may be performed after the formation of the negative electrode.

  Next, a metal electrode such as Al (corresponding to a negative electrode in this case) is formed on the organic semiconductor layer by vacuum deposition or sputtering. When the metal electrode is vacuum-deposited using a low molecular organic material for the electron transport layer, it is preferable that the metal electrode is continuously formed while maintaining the vacuum.

  When a hole transport layer is provided between the positive electrode and the organic semiconductor layer, a desired p-type organic semiconductor material (such as PEDOT) is applied on the positive electrode by spin coating, bar coating, blade casting, or the like. Then, the solvent is removed using a vacuum thermostat or a hot plate to form a hole transport layer. In the case of using a low molecular organic material such as a phthalocyanine derivative or a porphyrin derivative, it is also possible to apply a vacuum vapor deposition method using a vacuum vapor deposition machine.

When an electron transport layer is provided between the organic semiconductor layer and the negative electrode, a desired n-type organic semiconductor material (fullerene derivative, etc.) is applied onto the organic semiconductor layer by spin coating, bar coating, blade casting, or spraying. Then, the solvent is removed using a vacuum thermostat or a hot plate to form an electron transport layer. When using a low molecular organic material such as a phenanthroline derivative or C _60, it is also possible to apply a vacuum deposition method using a vacuum deposition machine.

  The photovoltaic element of the present invention can be applied to various photoelectric conversion devices using a photoelectric conversion function, an optical rectification function, and the like. For example, it is useful for photovoltaic cells (such as solar cells), electronic elements (such as optical sensors, optical switches, and phototransistors), optical recording materials (such as optical memories), and the like.

Hereinafter, the present invention will be described more specifically based on examples. Here, the first embodiment is an embodiment according to the claims deleted by the correction of the claims. In addition, this invention is not limited to the following Example. Of the compounds used in the examples and the like, those using abbreviations are shown below.
ITO: indium tin oxide PEDOT: polyethylene dioxythiophene PSS: polystyrene sulfonate 2,6-dibromo-4,4-bis (2-ethylhexyl) -4H-cyclopentadithiophene (1-f ), And 4,4-bis (2-ethylhexyl) -4H-cyclopentadithiophene (2-a) are the methods described in Macromolecules 2007, 41, 1981-1986. Was synthesized. The disubstituted rubicene derivative (1-d) was synthesized with reference to the method described in European Journal of Organic Chemistry 1998, Vol. 12, pages 2769-2773. Compound (2-c) was synthesized by the method described in Helvetica Chimica Acta 2002, 85, 2195-2212.

^Further, using JEOLJNM-EX270FT-NMR apparatus manufactured by JEOL, Ltd. in the 1 H-NMR measurement. A 10 mg sample was dissolved in chloroform-d ₁ (0.6 ml) containing 0.05% (v / v) tetramethylsilane, placed in an NMR measurement tube, and measured at room temperature using the above apparatus.

Synthesis example 1
Compound A-1 was synthesized by the method shown in Formula 1.

  A normal butyl lithium hexane solution (1.6 M, 45.0 ml) was added to an ether solution (200 ml, manufactured by Wako Pure Chemical Industries, Ltd.) of 4-bromobenzene (14.4 g, 75.0 mmol, manufactured by Tokyo Chemical Industry Co., Ltd.). 70 mmol (manufactured by Tokyo Chemical Industry Co., Ltd.) was added dropwise at 0 ° C. After completion of dropping, the mixture was stirred at room temperature for 15 minutes. 1,5-Dichloroanthraquinone (1-a) (6.9 g, 25 mmol, manufactured by Tokyo Chemical Industry Co., Ltd.) was added to the obtained 4-chlorophenyllithium solution at 0 ° C., and the mixture was stirred at room temperature for 2 hours. After completion of stirring, water (100 ml) was added, and the aqueous layer was extracted twice with ether (100 ml). The organic layer was dried over anhydrous magnesium sulfate, and the solvent was distilled off under reduced pressure. Toluene (100 ml) was added to the residue, and the precipitated solid was collected by filtration and washed with hexane to obtain compound (1-b) as a white solid (4.8 g, yield 38%).

  Potassium iodide (9.0 g, 54 mmol, Wako Pure Chemical Industries, Ltd.) was added to an acetic acid solution (60 ml, Wako Pure Chemical Industries, Ltd.) of the above compound (1-b) (3.0 g, 6.0 mmol). Product) and sodium hypophosphite monohydrate (9.0 g, 75 mol, manufactured by Wako Pure Chemical Industries, Ltd.) were added at room temperature, and the mixture was heated to reflux for 1 hour. After cooling the reaction mixture to room temperature, the resulting precipitate was collected by filtration. The obtained yellow solid was dried with water, methanol and acetone, and dried to obtain compound (1-c) as a yellow solid (2.1 g, yield 75%).

  Potassium hydroxide (6.0 g) was added to a quinoline suspension solution (40 ml, manufactured by Wako Pure Chemical Industries, Ltd.) of the above compound (1-c) (2.0 g, 4.27 mmol), and a silicon bath temperature of 200. The mixture was stirred at 30 ° C. for 30 minutes. The reaction mixture was cooled to room temperature, poured into 1M sulfuric acid (600 ml) little by little, and the resulting red solid was collected by filtration. The obtained crude product was extracted with toluene using a Soxhlet extractor, and the solvent was distilled off under reduced pressure to obtain compound (1-d) as a yellow solid (1.22 g, yield 73%).

In a 100 ml two-necked flask, the above compound (1-d) (600 mg, 1.5 mmol), bis (dibenzylideneacetone) palladium complex (80 mg, 0.14 mol, manufactured by Aldrich), S-phos ligand (100 mg) 0.24 mol, manufactured by Aldrich), potassium acetate (730 mg, 7.5 mmol, manufactured by Wako Pure Chemical Industries, Ltd.) and bis (pinacolato) diboron (1.93 g, 7.5 mmol, manufactured by BASF) were added, After the flask was purged with nitrogen, dioxane (80 ml, manufactured by Wako Pure Chemical Industries, Ltd.) was added, and the reaction mixture was stirred at 90 ° C. for 10 hours. After completion of the stirring, the solvent was distilled off under reduced pressure, and the residue was purified by silica gel column chromatography (eluent: toluene) to obtain compound (1-e) as a light red solid (310 mg, yield 36%). The measurement result of ¹ H-NMR of the obtained compound (1-e) is shown below.
¹ H-NMR (270 MHz, CDCl ₃ ): 8.58 (d, J = 8.6 Hz, 2H), 8.32 (d, J = 7.0 Hz, 2H), 8.04 (d, J = 6) .6 Hz, 2H), 7.93 (d, J = 8.6 Hz, 2H), 7.78 (d, J = 6.6 Hz, 2H), 7.75 (d, J = 7.0 Hz, 2H) , 1.44 (s, 24H) ppm.

  To a toluene (25 ml) solution of the above compound (1-e) (108 mg, 0.19 mmol) and compound (1-f) (105 mg, 0.19 mmol), 1M aqueous potassium carbonate solution (4 ml), Alquat 336 (1 drop, Aldrich) and tetrakis (triphenylphosphine) palladium complex (10 mg, manufactured by Tokyo Chemical Industry Co., Ltd.) were added and stirred at 90 ° C. for 10 hours. Subsequently, 40 mg of bromobenzene (manufactured by Tokyo Chemical Industry Co., Ltd.) was added and stirred at 90 ° C. for 1 hour. Subsequently, 60 mg of phenylboronic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) was added and stirred at 90 ° C. for 1 hour. The reaction mixture was cooled to room temperature, poured into methanol (200 ml), and the resulting precipitate was collected by filtration. The crude product was washed on the filter paper with water, methanol, and then acetone to obtain a black solid. Chloroform (200 ml) was added to the crude product, and the mixture was heated to reflux for 1 hour, and a polymer insoluble in chloroform was filtered off. After the solvent was distilled off under reduced pressure, the compound (A-1) was obtained as a black solid by reprecipitation with methanol. The weight average molecular weight was 4000, the number average molecular weight was 3000, and the degree of polymerization n was 6. The light absorption edge wavelength was 760 nm, the band gap (Eg) was 1.63 eV, and the highest occupied molecular orbital (HOMO) level was -4.96 eV.

Synthesis example 2
Compound A-2 was synthesized by the method shown in Formula 2.

  A dry tetrahydrofuran solution (40 ml) of compound (2-a) (2.4 g, 6.0 mmol) was cooled to −78 ° C., and an n-butyllithium hexane solution (concentration: 1.6 M, manufactured by Tokyo Chemical Industry Co., Ltd.) 6.0 ml, 9.6 mmol) was added dropwise. The reaction solution was kept at −78 ° C. and stirred for 30 minutes. Subsequently, 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (2.2 g, 12 mmol, manufactured by Tokyo Chemical Industry Co., Ltd.) was added at −78 ° C., and the mixture was stirred at room temperature for 2 hours. Stir. After completion of stirring, diethyl ether (50 m) was added, and the mixture was washed 3 times with water and once with saturated brine. After drying over anhydrous magnesium sulfate, the solvent was distilled off under reduced pressure. The residue was purified by column chromatography (filler: silica gel, eluent: chloroform: hexane: triethylamine = 200: 300: 1), whereby compound (2-b) (2.0 g, yield 63%) was colorless. Obtained as an oil.

Compound (2-b) (2.0 g, 3.8 mmol), Compound (2-c) (440 mg, 1.0 mmol) and K ₃ PO ₄ (1.2 g, 6.0 mol, Wako Pure Chemical Industries, Ltd.) Dimethylformamide (20 ml) is added to (Industry) and [1,1′-bis (diphenylphosphino) ferrocene] dichloropalladium (Pd (dppf) Cl ₂ , Aldrich, 200 mg, 0.25 mol) is added with stirring. The mixture was added at room temperature and stirred at 90 ° C. for 5 hours. After completion of stirring, the reaction mixture was cooled to room temperature, diethyl ether (50 ml) and water (50 ml) were added, and the organic layer was washed several times with water. After drying over anhydrous magnesium sulfate, the solvent was distilled off under reduced pressure, and the residue was purified by silica gel column chromatography (eluent: chloroform: hexane = 1: 2) to give compound (2-d) (490 mg, yield 45%) Was obtained as a black solid. The measurement result of ¹ H-NMR of the compound (2-d) is shown below.
¹ H-NMR (270 MHz, CDCl ₃ ): 8.08 (s, 2H), 7.84 (s, 2H), 7.75 (m, 4H), 7.41 (m, 6H), 7.15 (D, J = 4.9 Hz, 2H), 6.95 (d, J = 4.9 Hz, 2H), 1.95 (m, 8H), 1.02-0.95 (m, 60H) ppm.

The above compound (2-d) (490 mg, 0.45 mmol) was dissolved in dimethylformamide (20 ml) and stirred at 0 ° C., and N-bromosuccinimide (176 mg, 0.99 mmol, manufactured by Wako Pure Chemical Industries, Ltd.) And stirred at 0 ° C. for 4 hours. After completion of the stirring, 5% Na ₂ SO ₃ aqueous solution (20 ml) and diethyl ether (60 ml) were added, and the organic layer was washed several times with water and once with saturated brine. After the solvent was dried over anhydrous magnesium sulfate, the solvent was distilled off under reduced pressure. The residue was washed with methanol and then dried under reduced pressure to obtain compound (2-e) (470 mg, 84% yield) as a black solid. The measurement result of ¹ H-NMR of the compound (2-e) is shown below.
¹ H-NMR (270 MHz, CDCl ₃ ): 8.10 (s, 2H), 7.77 (s, 2H), 7.73-7.54 (m, 4H), 7.44-7.42 ( m, 6H), 6.98 (s, 2H), 2.0-1.8 (m, 8H), 1.02-0.59 (m, 60H) ppm.

  Compound (1-e) (58 mg, 0.10 mmol) and compound (2-e) (124 mg, 0.10 mmol) were dissolved in toluene (5 ml), and then concentrated 1M aqueous potassium carbonate (1 ml), Alquat 336 (1 drop) And Aldrich) and tetrakis (triphenylphosphine) palladium catalyst (6 mg, manufactured by Tokyo Chemical Industry Co., Ltd.) at room temperature, and stirred at 90 ° C. for 6 hours in a nitrogen atmosphere. Subsequently, 40 mg of bromobenzene (manufactured by Tokyo Chemical Industry Co., Ltd.) was added and stirred at 90 ° C. for 1 hour. Subsequently, 60 mg of phenylboronic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) was added and stirred at 90 ° C. for 1 hour. After completion of the stirring, the reaction mixture was cooled to room temperature and poured into 200 ml of methanol. The precipitated solid was collected by filtration and washed with methanol, water, and acetone in this order. The obtained solid was dissolved in 100 ml of chloroform, passed through a silica gel short column (eluent: chloroform), concentrated, and reprecipitated in methanol to obtain A-2 (90 mg). The weight average molecular weight was 10,000, the number average molecular weight was 7,300, and the degree of polymerization n was 7. The light absorption edge wavelength was 775 nm, the band gap (Eg) was 1.60 eV, and the highest occupied molecular orbital (HOMO) level was −5.16.

Example 1
A photovoltaic device was produced by a dry process method as shown below. A glass substrate on which an ITO transparent conductive layer serving as a positive electrode having a thickness of 120 nm was deposited by sputtering was cut into 38 mm × 46 mm, and then ITO was patterned into a 38 mm × 13 mm rectangular shape by photolithography. The obtained substrate was subjected to ultrasonic cleaning for 10 minutes with an alkali cleaning solution (“Semico Clean” EL56 (trade name), manufactured by Furuuchi Chemical Co., Ltd.), and then washed with ultrapure water. After this substrate was UV / ozone treated for 30 minutes, a PEDOT: PSS aqueous solution (0.8% by weight of PEDOT, 0.5% by weight of PPS) serving as a hole transport layer was formed on the substrate to a thickness of 60 nm by spin coating. did. After heating and drying at 200 ° C. for 5 minutes with a hot plate, the substrate was placed in a vacuum deposition apparatus and evacuated until the degree of vacuum in the apparatus was 1 × 10 ⁻³ Pa or less. Rubicene (manufactured by ACROS ORGANICS) represented by the formula was deposited to a thickness of 30 nm to form a p-type organic semiconductor layer.

Next, fullerene C ₆₀ (manufactured by Tokyo Chemical Industry Co., Ltd.), which is an n-type organic semiconductor, was deposited to a thickness of 40 nm by a resistance heating method without breaking the vacuum, thereby forming an n-type organic semiconductor layer.

A cathode mask is placed in a vacuum deposition apparatus, and the vacuum inside the apparatus is exhausted again until the vacuum level becomes 1 × 10 ⁻³ Pa or less, and an aluminum layer serving as a negative electrode is deposited to a thickness of 80 nm by resistance heating. did. The extraction electrode was taken out from the upper and lower electrodes, and a photovoltaic device having an area where the stripe-like ITO layer and the aluminum layer intersect each other was 5 mm × 5 mm was produced.

The positive and negative electrodes of the photovoltaic device thus fabricated were connected to a picoammeter / voltage source 4140B manufactured by Hewlett-Packard Co., and simulated sunlight (from Yamashita Denso Co., Ltd., simplified) from the ITO layer side in the atmosphere. Type solar simulator YSS-E40, spectrum shape: AM1.5, intensity: 100 mW / cm ² ), and the current value was measured when the applied voltage was changed from −1V to + 2V. At this time, the short-circuit current density (value of the current density when the applied voltage is 0 V) is 1.84 mA / cm ² , the open circuit voltage (value of the applied voltage when the current density is 0) is 0.71 V, and the fill factor (FF) was 0.435, and the photoelectric conversion efficiency calculated from these values was 0.57%. The fill factor and photoelectric conversion efficiency were calculated by the following equations.
Fill factor = JVmax / (Short-circuit current density × Open-circuit voltage)
(Here, JVmax is the product of the current density and the applied voltage at the point where the product of the current density and the applied voltage is maximum when the applied voltage is between 0 V and the open circuit voltage value.)
Photoelectric conversion efficiency = [(short circuit current density × open circuit voltage × fill factor) / pseudo sunlight intensity (100 mW / cm ² )] × 100 (%)
The fill factor and photoelectric conversion efficiency in the following examples and comparative examples were all calculated by the above formula.

Comparative Example 1
A photovoltaic device was produced in the same manner as in Example 1 except that copper phthalocyanine represented by the following formula was used instead of rubicene, and current-voltage characteristics were measured. The short-circuit current density at this time was 2.72 mA / cm ² , the open-circuit voltage was 0.38 V, the fill factor (FF) was 0.275, and the photoelectric conversion efficiency calculated from these values was 0.29%. .

Comparative Example 2
A photovoltaic device was prepared in the same manner as in Example 1 except that coronene represented by the following formula was used instead of rubicene, and current-voltage characteristics were measured. The short-circuit current density at this time was 0.67 mA / cm ² , the open-circuit voltage was 0.77 V, the fill factor (FF) was 0.163, and the photoelectric conversion efficiency calculated from these values was 0.08%. .

Comparative Example 3
A photovoltaic device was produced in the same manner as in Example 1 except that decacyclene represented by the following formula was used instead of rubicene, and current-voltage characteristics were measured. The short-circuit current density at this time was 0.81 mA / cm ² , the open-circuit voltage was 0.65 V, the fill factor (FF) was 0.245, and the photoelectric conversion efficiency calculated from these values was 0.13%. .

Comparative Example 4
A photovoltaic device was produced in the same manner as in Example 1 except that 9,10-bis (phenylethynyl) anthracene represented by the following formula was used instead of rubicene, and current-voltage characteristics were measured. The short-circuit current density at this time was 1.05 mA / cm ² , the open circuit voltage was 0.72 V, the fill factor (FF) was 0.315, and the photoelectric conversion efficiency calculated from these values was 0.24%. .

  Table 1 shows the evaluation results of Example 1 and Comparative Examples 1 to 4 in which photovoltaic elements were produced by a dry process.

  As is clear from Table 1, the photovoltaic device (Example 1) produced by a dry process using a rubicene compound was produced under the same conditions using a compound having a similar skeleton not containing a rubicene structure. Compared with the photovoltaic elements (Comparative Examples 1 to 4), the photoelectric conversion efficiency was remarkably high.

Example 2
A photovoltaic device was produced by the wet process method as shown below. 1 mg of the above compound (A-1) and 4 mg of PC ₇₀ BM (manufactured by Solen) are added to a sample bottle containing 0.25 ml of chlorobenzene, and an ultrasonic washer (US-2 manufactured by Inoue Seieido Co., Ltd.) Name), and output 120W) for 30 minutes to obtain a solution A.

  In the same manner as in Example 1, an ITO transparent conductive layer and a hole transport layer (PEDOT: PSS layer) were formed on a glass substrate. The solution A was dropped on the PEDOT: PSS layer, and an organic semiconductor layer having a thickness of 100 nm was formed by a spin coating method. Thereafter, the substrate on which the organic semiconductor layer is formed and the cathode mask are placed in a vacuum deposition apparatus to form a negative electrode in the same manner as in Example 1, and the area of the portion where the stripe-like ITO layer and the aluminum layer intersect A photovoltaic device having a size of 5 mm × 5 mm was produced.

The photovoltaic device thus produced was measured for current-voltage characteristics in the same manner as in Example 1. At this time, the short-circuit current density was 5.89 mA / cm ² , the open-circuit voltage was 0.66 V, and the fill factor (FF) was 0.490, and the photoelectric conversion efficiency calculated from these values was 1.90%. .

Example 3
A photovoltaic device was produced in the same manner as in Example 2 except that A-2 was used in place of A-1, and current-voltage characteristics were measured. At this time, the short-circuit current density was 7.95 mA / cm ² , the open-circuit voltage was 0.69 V, the fill factor (FF) was 0.445, and the photoelectric conversion efficiency calculated from these values was 2.44%. .

Comparative Example 5
A photovoltaic device was prepared in exactly the same manner as in Example 2 except that B-1 weight average molecular weight: 2500, number average molecular weight: 2000, polymerization degree n: 4) was used instead of A-1. -Voltage characteristics were measured. B-1 is the same as A-1, except that a compound obtained by converting the bromo group of (2-c) into a boronic acid pinacol ester is used instead of (1-e) in the synthesis method of A-1. Was synthesized. At this time, the short-circuit current density was 3.10 mA / cm ² , the open circuit voltage was 0.59 V, and the fill factor (FF) was 0.279, and the photoelectric conversion efficiency calculated from these values was 0.51%. .

Comparative Example 6
A photovoltaic device was prepared in exactly the same manner as in Example 2 except that the following B-2 (weight average molecular weight: 25000, number average molecular weight: 16000, polymerization degree n: 18) was used instead of A-1. Current-voltage characteristics were measured. B-2 is the same as A-2 except that 9,9-Dioctylfluorene-2,7-bis (trimethyleneborate) (Aldrich) was used instead of (1-e) in the synthesis method of A-2. The method was synthesized. The short-circuit current density at this time was 3.55 mA / cm ² , the open-circuit voltage was 0.72 V, the fill factor (FF) was 0.558, and the photoelectric conversion efficiency calculated from these values was 1.43%. .

Comparative Example 7
A photovoltaic device was produced in the same manner as in Example 2 except that the following B-3 (weight average molecular weight: 16000, number average molecular weight: 11000, polymerization degree n: 12) was used instead of A-1. Current-voltage characteristics were measured. B-3 is 3,6-bis (4,4,5,5-tetramethyl-1,3,2-dioxabolan-2-yl) -9 instead of (1-e) in the synthesis method of A-2. The synthesis was performed in the same manner as in A-2 except that -octylcarbazole was used. At this time, the short-circuit current density was 3.46 mA / cm ² , the open-circuit voltage was 0.64 V, the fill factor (FF) was 0.458, and the photoelectric conversion efficiency calculated from these values was 1.01%. .

  Table 2 shows the evaluation results of Examples 2 to 3 and Comparative Examples 5 to 7 in which photovoltaic elements were produced by a wet process.

  As is clear from Table 2, photovoltaic devices (Examples 2 to 3) produced by a wet process using a rubicene compound were produced under the same conditions using a polymer having a similar skeleton that does not contain a rubicene structure. As compared with the other photovoltaic elements (Comparative Examples 5 to 7), high photoelectric conversion efficiency was exhibited.

DESCRIPTION OF SYMBOLS 1 Substrate 2 Positive electrode 3 Organic semiconductor layer 4 Negative electrode 5 Layer having a rubicene compound 6 Layer having an electron-accepting organic material

Claims (5)

A rubicene compound represented by the following general formula (2), divalent linking group, optionally substituted arylene group, heteroarylene group represented by Medium B following general formula (2), vinylene A photovoltaic device material comprising a rubicene compound which is a phenylene vinylene group .

(In the general formula (2), A represents a rubicene skeleton, B represents a divalent linking group, m is 0 or 1. n is in the range of 2 to 1000. X ¹ and X ^2. May be the same or different and are selected from hydrogen, an alkyl group, an alkoxy group, an aryl group, a heteroaryl group, and a halogen.) The photovoltaic device material according to claim 1, wherein the rubicene compound is an electron-donating organic material. The material for a photovoltaic device according to claim 2, further comprising an electron-accepting organic material. The material for a photovoltaic device according to claim 3 , wherein the electron-accepting organic material is a fullerene compound. A photovoltaic element having at least positive and negative, a photovoltaic element comprising a photovoltaic device material according to any one of claims 1 to 4 between the anode and cathode.

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