JP5664200B2 - Conjugated polymer, electron donating organic material, photovoltaic device material and photovoltaic device using the same - Google Patents

Description

  The present invention relates to a conjugated polymer, an electron-donating organic material, a photovoltaic device material and a photovoltaic device using the conjugated polymer.

  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), was used C ₆₀ derivatives such other PCBM conductive polymer having semiconductor properties of n-type as the electron accepting organic material A photoelectric conversion material has been reported (for example, see Non-Patent Document 2).

  In addition, in order to efficiently absorb radiant energy over a wide range of the solar spectrum, a photoelectric conversion material using an organic semiconductor in which an electron-donating group and an electron-withdrawing group are introduced into the main chain to reduce the band gap has been reported. (For example, see Non-Patent Document 3). As this electron-donating group, a thiophene skeleton has been intensively studied, and as an electron-withdrawing group, a benzothiadiazole skeleton and a quinoxaline skeleton have been energetically studied (see, for example, Non-Patent Documents 3 to 14 and Patent Documents 1 and 2). However, sufficient photoelectric conversion efficiency has not been obtained.

JP 2004-534863 A (Claim 1) Japanese translation of PCT publication No. 2004-500464 (Claim 1)

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 G. Yu, J. et al. Gao, J .; C. Hummelen, F.M. Wudl, A.W. J. et al. Heeger, "Science", 1995, 270, 1789 E. Bundgaard, F.M. C. Krebs, "Solar Energy Materials & Solar Cells", 2007, 91, 954. A. Gadisa, W .; Mamo, L.M. M.M. Andersson, S.M. Admassie, F.A. Zhang, M.M. R. Andersson, O.D. Inganas, “Advanced Functional Materials”, 2007, 17: 3836-3842 W. Mammo, S .; Admassie, A.M. Gadisa, F .; Zhang, O .; Inganas, M.M. R. By Andersson, “Solar Energy Materials & Solar Cells”, 2007, 91, 1010-1018 R. S. Ashraf, H.M. Hoppe, M.M. Shahid, G.H. Gobsch, S.M. Sensfuss, E.M. Klemm, “Journal of Polymer Science: Part A: Polymer Chemistry”, 2006, 44, 6952-6916. CL. Liu, JH. Tsai, WY. Lee, WC. Chen, S.M. A. Jenekhe, “Macromolecules”, 2008, 41, 6952-6959. N. Blauin, A.M. Michaud, D.M. Gendron, S.M. Wakim, E .; Blair, R.A. Neagu-Plesu, M .; Bellette, G.M. Durocher, Y.M. Tao, M.C. Leclerc, "Journal of American Chemical Society", 2008, 130, 732-742. M.M. Sun, Q.D. Niu, B.A. Du, J. et al. Peng, W.H. Yang, Y. et al. Cao, “Macromolecular Chemistry and Physics”, 2007, 208, 988-993. W-Y. Lee, K-F. Chang, TF. Wang, CC. Chueh, WC. Chen, CS. Tuan, JL. Lin, “Macromolecular Chemistry and Physics”, 2007, 208, 1919-1927. A. Tsami, T .; W. Bunnagel, T .; Farrell, M.M. Scharber, S .; A. Choulis, C.I. J. et al. Brabec, U. Scherf, “Journal of Materials Chemistry”, 2007, Vol. 17, pp. 1353-1355. M.M. Lai, C.I. Chueh, W.H. Chen, J. et al. Wu, F.W. Chen, “Journal of Polymer Science (Part A: Polymer Chemistry)”, 2009, 47, 973-985, Journal of Polymer Science Part A, Polymer Chemistry (Part of Polymer Science: Part A: Polymer Chemistry). J. et al. Lee, W.H. Shin, J. et al. Haw, D.H. Moon, "Journal of Materials Chemistry", 2009, 19, 4938-4945 L. J. et al. Lindgren, F.M. Zhang, M.M. Andersson, S.M. Barrau, S .; Hellstrom, W.M. Mammo, E .; Perzon, O.M. Inganas, M.M. R. Andersson, “Chemistry of Materials”, 2009, 21, pp. 3491-3502.

  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 conjugated polymer having a structure represented by the following general formula (1), an electron donating organic material, a photovoltaic element material and a photovoltaic element using the conjugated polymer.

In the general formula (1), R ^{1 to} R ¹⁶ 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. A represents carbon, nitrogen or silicon. When A is nitrogen, the above R ¹⁶ does not exist. W, X, Y and Z may be the same or different and are selected from a single bond, an arylene group and a heteroarylene group excluding a thienothienylene group. n represents the range of 10 or more and 1000 or less.

  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 conjugated polymer of the present invention has a structure represented by the following general formula (1).

In the general formula (1), R ^{1 to} R ¹⁶ 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. A represents carbon, nitrogen or silicon. When A is nitrogen, the above R ¹⁶ does not exist. W, X, Y and Z may be the same or different and are selected from a single bond, an arylene group and a heteroarylene group excluding a thienothienylene group. n represents the range of 10 or more and 1000 or less.

  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. From the viewpoint of heat resistance, the alkyl group preferably has 30 or less carbon atoms, more preferably 20 or less. Examples of the substituent when substituted include the following alkoxy groups, aryl groups, heteroaryl groups, and halogens. 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. From the viewpoint of heat resistance, the alkoxy group preferably has 30 or less carbon atoms, more preferably 20 or less. Examples of the substituent when substituted include the following aryl groups, heteroaryl groups, and halogens. 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. The number of carbon atoms of the aryl group is preferably 6 or more and 30 or less from the viewpoint of processability. Examples of the substituent when substituted include the above alkyl group, alkoxy group, the following heteroaryl group, and halogen. The heteroaryl group is, for example, thienyl group, thienothienyl group, furyl group, pyrrolyl group, imidazolyl group, pyrazolyl group, oxazolyl group, pyridyl group, pyrazyl group, pyrimidyl group, quinolinyl group, isoquinolyl group, quinoxalyl group, acridinyl A heteroaromatic group having an atom other than carbon, such as a group, an indolyl group, a carbazolyl group, a benzofuran group, a dibenzofuran group, a benzothiophene group, a dibenzothiophene group, a benzodithiophene group, a silole group, a benzosilole group, or a dibenzosilole group This can be unsubstituted or substituted. Examples of the substituent in the case of substitution include the above alkyl group, alkoxy group, aryl group, and the following halogen. Halogen is any one of fluorine, chlorine, bromine and iodine.

  The arylene group is a divalent group of the aryl group (aromatic hydrocarbon group), and the heteroarylene group is a divalent group of the heteroaryl group (heteroaromatic group having an atom other than carbon). It is. However, when W, X, Y, or Z is a heteroarylene group, a thienothienylene group is excluded.

  N represents the degree of polymerization and is in the range of 10 to 1,000. The degree of polymerization can be determined from the weight average molecular weight. The weight average molecular weight can be determined by measuring using GPC (gel permeation chromatography) and converting to a polystyrene standard sample.

  Since the conjugated polymer represented by the general formula (1) is excellent in light absorption characteristics and carrier (especially hole) transporting ability, it can be preferably used as an electron donating organic material in a photovoltaic device.

  The photoelectric conversion efficiency of a photovoltaic element often correlates with the molecular weight of the electron donating organic material. In order to obtain high photoelectric conversion efficiency, it is preferable to use a conjugated polymer having a weight average molecular weight of 10,000 or more as the electron donating organic material, and more preferably a weight average molecular weight of 20,000 or more. However, in general, a conjugated polymer has low solubility because the main chain is rigid, and in order to obtain a polymer having high molecular weight and high solubility, usually an alkyl group having 6 or more carbon atoms. In addition, it is said that it is necessary to introduce an alkoxy group having 6 or more carbon atoms as a solubilizing group (for example, poly (3-hexylthiophene), PQTT described in Non-Patent Document 13, PQPDTT, PQTPDTT, etc.). On the other hand, as a technique for increasing the photoelectric conversion efficiency in terms of element configuration, a bulk heterojunction photovoltaic element that increases the bonding surface contributing to photoelectric conversion by mixing an electron-accepting organic material and an electron-donating organic material is used. Are known. In bulk heterojunction photovoltaic devices, the electron-donating organic material and the electron-accepting organic material are not completely compatible with each other in order to form a path for electrons and holes (carrier path). It is preferable to do. However, as described above, the solubilizing group introduced to increase the solubility of the electron-donating organic material enhances the compatibility with the electron-accepting organic material and inhibits the formation of a phase separation structure, or conversely. In many cases, the compatibility with the conductive organic material is lowered to cause phase separation on the micrometer scale, and the photoelectric conversion efficiency effect in the bulk heterojunction photovoltaic device cannot be sufficiently exhibited.

  As described above, it is difficult to achieve a high molecular weight while ensuring solubility and to impart a phase separation structure forming ability suitable for a bulk heterojunction photovoltaic device. The conjugated polymer having the structure represented by (1) enables this coexistence.

The main chain structure of the conjugated polymer having the structure represented by the general formula (1) includes a quinoxaline skeleton having R ¹ and R ² , ^two thienothiophene skeletons arranged on both sides of the quinoxaline skeleton, It has a divalent linking group (fluorene, silafluorene, or carbazole) linking thienothiophene-quinoxaline-thienothiophene triads.

The quinoxaline skeleton, which is the first component, has high planarity, so that it is likely to cause aggregation due to π-π stacking, and a phase separation structure suitable for the above-described bulk heterojunction is likely to be formed. Furthermore, when R ¹ and R ² have an optionally substituted alkyl group, an optionally substituted alkoxy group, an optionally substituted aryl group or an optionally substituted heteroaryl group It is preferable because it can be easily increased in molecular weight. Further, when the carbon number of the optionally substituted alkyl group and the optionally substituted alkoxy group is 5 or less, the compatibility with the above-described electron-accepting organic material should be adjusted to a more appropriate range. Is preferable. From such a viewpoint, R ¹ and R ² are each an optionally substituted alkyl group having 1 to 5 carbon atoms, an optionally substituted alkoxy group having 1 to 5 carbon atoms, and a substituted group. It is preferably an aryl group which may be substituted or a heteroaryl group which may be substituted. Here, the carbon number of the alkyl group and the alkoxy group does not include the carbon contained in the substituent when substituted.

  The second component, the thienothiophene skeleton, is combined with the quinoxaline skeleton to form a thienothiophene-quinoxaline-thienothiophene triad, thereby reducing the band gap of the main chain skeleton and This contributes to an increase in the short circuit current (Jsc). This effect is highest when thienothiophene and quinoxaline are bound directly. For this reason, it is preferable that said X and Y are a single bond.

The third constituent divalent linking group (fluorene, silafluorene or carbazole) is a skeleton that is effective for increasing the molecular weight and forming an appropriate nano-level phase separation structure. These linking groups have a feature that it is synthetically easy to introduce a solubilizing group required for high molecular weight. From the viewpoint of ensuring such solubility, R ¹⁵ and R ¹⁶ are preferably alkyl groups having 6 or more carbon atoms.

Of the above substituents, R ¹ and R ² are not only from the viewpoint of achieving both high molecular weight and ability to form a phase separation structure and ensuring solubility, but also from the viewpoint of ease of synthesis and synthesis yield. More preferably, it is an optionally substituted aryl group, R ^{3 to} R ¹⁴ are more preferably hydrogen or an alkyl group, W and Z are preferably a single bond, and A is carbon. Is preferred. When R ¹ and R ² are substituted aryl groups, the substituent is preferably an alkyl group having 1 to 5 carbon atoms or an alkoxy group having 1 to 5 carbon atoms, More preferably, it is an alkyl group having 1 to 3 carbon atoms or an alkoxy group having 1 to 3 carbon atoms.

  Examples of the conjugated polymer having the structure represented by the general formula (1) include the following structures. In the following structure, n is in the range of 10 to 1000.

  The electron donating organic material having the structure represented by the general formula (1) is described in, for example, a method similar to the method described in Non-Patent Document 4 or the Non-Patent Document 13. It can be synthesized by a method similar to the method.

The electron donating organic material of the present invention may be composed only of a conjugated polymer having a structure represented by the general formula (1), or may contain other electron donating organic materials. Examples of other electron-donating organic materials include polythiophene polymers, poly-p-phenylene vinylene polymers, poly-p-phenylene polymers, polyfluorene polymers, polypyrrole polymers, polyaniline polymers. Conjugated polymers such as polyacetylene polymers and polythienylene vinylene polymers, phthalocyanine derivatives such as H ₂ phthalocyanine (H ₂ Pc), copper phthalocyanine (CuPc), and 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- Triarylamine derivatives such as 4,4′-diphenyl-1,1′-diamine (NPD), 4,4′-di (carbazole-9) Yl) biphenyl (CBP) as an electroluminescent host carbazole derivatives such as, oligothiophene derivatives (terthiophene, quarter thiophene, sexithiophene include low molecular organic compound of octyl thiophene etc.) and the like.

  Since the conjugated polymer having the structure represented by the general formula (1) exhibits p-type semiconductor characteristics, an electron-accepting organic material (n-type) is required to obtain higher photoelectric conversion efficiency as a photovoltaic device material. It is preferable to combine with an organic semiconductor.

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- Triazole derivatives such as butylphenyl) -1,2,4-triazole (TAZ), phenanthroline derivatives, phosphine oxide derivatives, fullerene compounds (C ₆₀ , C ₇₀ , C ₇₆ , C ₇₈ , C ₈₂ , C ₈₄ , C ₉₀ , as unsubstituted, including C _94, [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), phenyl C85 butyric acid methyl ester (PC ₈₄ BM, etc.), carbon nanotubes (CNT), and derivatives in which a cyano group is introduced into a poly-p-phenylene vinylene polymer (CN-PPV). Among these, fullerene compounds are preferably used because of their high charge separation speed and electron transfer speed. Among the fullerene compounds, C ₇₀ derivatives (such as the PC 70 _BM) because excellent light absorption characteristics, it is possible to obtain a relatively high photoelectric conversion efficiency, more preferred.

  In the photovoltaic device material of the present invention, the content ratio (weight fraction) of the electron-donating organic material and the electron-accepting organic material is not particularly limited. The rate 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. It is preferable to use a mixture of an electron-donating organic material and an electron-accepting organic material. 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-mentioned content ratio is the content ratio of the electron-donating organic material and the electron-accepting organic material contained in the single layer. 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 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 method for removing impurities from the conjugated polymer having the structure represented by the general formula (1) and the electron-accepting organic material is not particularly limited, but column chromatography, recrystallization, Sublimation method, 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 purification of high molecular weight compounds, reprecipitation method, Soxhlet extraction method, molecular weight fractionation method by GPC is preferably used when removing low molecular weight components, and reprecipitation method or the like when removing metal components. A chelate method, an ion exchange method, and a column chromatography method are 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, an electron donating organic material including a conjugated polymer having a structure represented by the general formula (1) and an electron accepting organic material are included. These materials may be mixed or laminated, but are preferably mixed. The aforementioned “bulk heterojunction type” indicates this mixed type. When they are mixed, the electron-donating organic material and the electron-accepting organic material are compatible or phase-separated at the molecular level, but are preferably phase-separated at the nano-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 laminated, the layer having an electron-donating organic material exhibiting p-type semiconductor characteristics is preferably on the positive electrode side, and the layer having an electron-accepting organic material exhibiting n-type semiconductor characteristics is preferably on the 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 denotes a layer having an electron donating organic material containing a conjugated polymer having a structure represented by the general formula (1), and reference numeral 6 denotes 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 containing the conjugated polymer having the structure represented by the general formula (1) has a thickness of 1 nm to 400 nm among the above thicknesses. It is preferably 15 nm to 150 nm.

  The organic semiconductor layer 3 may contain a conjugated polymer having a structure represented by the general formula (1) 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.

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, tin and molybdenum, and composite metal oxides (indium tin oxide (ITO)). Indium zinc oxide (IZO) and the like are 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 with a low work function is a negative electrode, but as the conductive material with a low work function, alkali metal or alkaline earth metal, specifically lithium, magnesium, calcium, etc. are 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. In addition, it is possible to improve the extraction current by introducing a metal fluoride such as lithium fluoride or cesium fluoride or a metal carbonate such as cesium carbonate at 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 and an organic semiconductor layer can be laminated according to the type and application of the photoelectric conversion material, for example, inorganic materials such as alkali-free glass and 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 (H ₂ Pc, 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. Further, it is preferable to treat the hole transport layer with a fluorous compound (an organic compound having one or more fluorine atoms in the molecule), and the photoelectric conversion efficiency can be further improved. Examples of fluorous compounds include benzotrifluoride, hexafluorobenzene, 1,1,1,3,3,3-hexafluoro-2-propanol, perfluorotoluene, perfluorodecalin, perfluorohexane, 1H, 1H, 2H, 2H-hepta. Decafluoro-1-decanol (F-decanol) and the like can be mentioned. More preferably, benzotrifluoride, perfluorohexane, or F-decanol is used. As a treatment method, the above-mentioned fluorous compound is mixed in advance with the material for forming the hole-transporting layer and then the hole-transporting layer is formed, or the hole-transporting layer is formed and then the above-mentioned fluorous compound is contacted Examples thereof include spin coating, dip coating, blade coating, vapor deposition, and steam treatment.

  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, A compound exhibiting n-type semiconductor properties such as CNT and CN-PPV) and titanium oxide 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 of the organic semiconductor layers contains the material for a photovoltaic device of the present invention, and the other layers are represented by the general formula (1) in order not to reduce the short-circuit current. It is preferable to include an electron-donating organic material having a different band gap from the conjugated polymer having a structure. 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. Polymer, polyacetylene polymer, polythienylene vinylene polymer, benzothiadiazole polymer (for example, PCPDTBT (poly [2,6- (4,4-bis- (2-ethylhexyl) -4H-cyclopenta [ 2,1-b; 3,4-b ′] dithiophene) -alt-4,7- (2,1,3-benzothiadiazole)]) and PSBTBT (poly [(4,4-bis- (2-ethylhexyl)). ) Dithino [3,2-b: 2 ′, 3′-d] silole) − , 6-diyl-alt- (2,1,3 -benzothiadiazole) -4,7-diyl])) conjugated polymer or, _{H 2} phthalocyanine such as _(H 2 Pc), copper phthalocyanine (CuPc), zinc phthalocyanine Phthalocyanine derivatives such as (ZnPc), porphyrin derivatives, N, N′-diphenyl-N, N′-di (3-methylphenyl) -4,4′-diphenyl-1,1′-diamine (TPD), N, Triarylamine derivatives such as N′-dinaphthyl-N, N′-diphenyl-4,4′-diphenyl-1,1′-diamine (NPD), 4,4′-di (carbazol-9-yl) biphenyl ( Carbazole derivatives such as CBP), oligothiophene derivatives (terthiophene, quarterthiophene, sexithiophene, octithiophene, etc. Low molecular organic compounds and the like. 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, tin, molybdenum and titanium, composite metal oxides (indium tin oxide (ITO), indium zinc oxide (IZO), etc.), alloys composed of the above metals and the above metals Examples include laminates, polyethylenedioxythiophene (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, an example is given and demonstrated about the manufacturing method of the photovoltaic device of this invention. 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, a conjugated polymer having a structure represented by the general formula (1) and, if necessary, a material for a photovoltaic device including other electron donating organic materials and electron accepting organic materials are dissolved in a solvent. A solution is made and applied onto 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, photoelectric conversion efficiency can be improved more by containing the above-mentioned fluorous compound. Fluorous compounds (fluorus solvents) that are liquid at normal temperature and pressure are preferred, and the above-mentioned benzotrifluoride, perfluorohexane, and F-decanol are more preferably used. The content of the fluoro compound is preferably 0.01 to 20% by volume, more preferably 0.1 to 2% by volume, based on the total amount of the solvent. Further, the content of the fluorous solvent is preferably 0.01 to 30% by weight, more preferably 0.1 to 4% by weight in the total solvent.

  When an organic semiconductor layer is formed by mixing an electron-donating organic material containing an conjugated polymer having a structure represented by the general formula (1) and an electron-accepting organic material, the organic semiconductor layer is represented by the general formula (1). An electron-donating organic material containing a conjugated polymer having a structure and an electron-accepting organic material are added to a solvent at a desired ratio, and dissolved using a method such as heating, stirring, or ultrasonic irradiation to form a solution. Apply on a transparent electrode. In this case, the photoelectric conversion efficiency of the photovoltaic element can be improved by using a mixture of two or more solvents. This is presumably because the electron-donating organic material and the electron-accepting organic material undergo phase separation at the nano level, and a carrier path that forms a path for electrons and holes is formed. As the solvent to be combined, an optimal combination type can be selected depending on the types of the electron donating organic material and the electron accepting organic material to be used. When using an electron-donating organic material containing a conjugated polymer having a structure represented by the general formula (1), chloroform and chlorobenzene are mentioned as preferred solvents to be combined. In this case, the mixing volume ratio of each solvent is preferably in the range of chloroform: chlorobenzene = 5: 95 to 95: 5, more preferably in the range of chloroform: chlorobenzene = 10: 90 to 90:10. Further, when an organic semiconductor layer is formed by laminating an electron donating organic material containing a conjugated polymer having a structure represented by the general formula (1) and an electron accepting organic material, for example, an electron donating organic material After forming a layer having an electron-donating organic material by applying the above solution, 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 concentration of electron donating organic material including a conjugated polymer having the structure represented by the general formula (1) and the electron accepting organic material is 1 to 20 g / l (general Conjugation having the structure represented by the general formula (1) with respect to the volume of the solution containing the electron donating organic material, the electron accepting organic material and the solvent including the conjugated polymer having the structure represented by the formula (1) The weight of the electron-donating organic material and the electron-accepting organic material containing the polymer is preferable, and a homogeneous organic semiconductor layer having a thickness of 5 to 200 nm can be obtained by using this concentration. 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 treatment, 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 (such as fullerene derivatives) or an n-type inorganic semiconductor material (such as titanium oxide gel) is spin-coated on the organic semiconductor layer. After coating by a coating method, a casting method using a blade, a spray method, or the like, 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 devices (such as optical sensors, optical switches, phototransistors), optical recording materials (such as optical memories), and the like.

Hereinafter, the present invention will be described more specifically based on examples. 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 PC ₇₀ BM: phenyl C71 butyric acid methyl ester Eg: band gap HOMO: highest occupied molecular orbital Isc: short circuit current density Voc: open circuit voltage FF: fill Factor PCE: photoelectric conversion efficiency.

For ¹ H-NMR measurement, an FT-NMR apparatus (JEOL JNM-EX270 manufactured by JEOL Ltd.) was used. Moreover, the average molecular weight (number average molecular weight, weight average molecular weight) was calculated by an absolute calibration curve method using a GPC apparatus (manufactured by TOSOH Co., Ltd., to which chloroform was fed, high-speed GPC apparatus HLC-8220 GPC). The degree of polymerization n was calculated by the following formula.
Degree of polymerization n = [(weight average molecular weight) / (molecular weight of repeating unit)]
The light absorption edge wavelength is an ultraviolet-visible absorption spectrum (measurement wavelength) of a thin film formed on glass with a thickness of about 60 nm using a U-3010 spectrophotometer manufactured by Hitachi, Ltd. (Range: 300-900 nm). The band gap (Eg) was calculated from the light absorption edge wavelength by the following equation. The thin film was formed by spin coating using chloroform as a solvent.
Eg (eV) = 1240 / light absorption edge wavelength (nm)
In addition, the highest occupied molecular orbital (HOMO) level was determined by using a surface analyzer (in-air ultraviolet photoelectron spectrometer AC-2 type, manufactured by Riken Instruments Co., Ltd.) ). The thin film was formed by spin coating using chloroform as a solvent.

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

  Compound (1-a) (manufactured by Tokyo Chemical Industry Co., Ltd.) 4.3 g and bromine (manufactured by Wako Pure Chemical Industries, Ltd.) 10 g are added to 150 ml of 48% hydrobromic acid (manufactured by Wako Pure Chemical Industries, Ltd.). In addition, the mixture was stirred at 120 ° C. for 3 hours. After cooling to room temperature, the precipitated solid was filtered through a glass filter and washed with 1000 ml of water and 100 ml of acetone. The obtained solid was vacuum-dried at 60 ° C. to obtain 6.72 g of compound (1-b).

5.56 g of the above compound (1-b) is added to 180 ml of ethanol (manufactured by Wako Pure Chemical Industries, Ltd.), and 13.2 g of NaBH ₄ (manufactured by Wako Pure Chemical Industries, Ltd.) is added at 5 ° C. in a nitrogen atmosphere. After that, the mixture was stirred at room temperature for 2 days. After distilling off the solvent, 500 ml of water was added, and the solid was collected by filtration and washed with 1000 ml of water. The obtained solid was dissolved in 200 ml of diethyl ether, washed with 300 ml of water, and dried over magnesium sulfate. The solvent was distilled off to obtain 2.37 g of compound (1-c).

  2.37 g of the above compound (1-c) and 1.87 g of benzyl (manufactured by Wako Pure Chemical Industries, Ltd.) are added to 80 ml of chloroform, and methanesulfonic acid (manufactured by Wako Pure Chemical Industries, Ltd.) 3 is added in a nitrogen atmosphere. After adding the drops, the mixture was heated to reflux for 11 hours. The resulting solution was washed with an aqueous sodium bicarbonate solution and then dried over magnesium sulfate. The resulting solution was purified by column chromatography (filler: silica gel, eluent: chloroform) and washed with methanol to obtain 3.72 g of compound (1-d).

  1.26 g of compound (1-e) (manufactured by Tokyo Chemical Industry Co., Ltd.) was dissolved in 60 ml of tetrahydrofuran (manufactured by Wako Pure Chemical Industries, Ltd.) and cooled to -80 ° C. After adding 6.2 ml of n-butyllithium 1.6M hexane solution (made by Wako Pure Chemical Industries, Ltd.), the temperature was raised to room temperature and cooled to -90 ° C. 2.4 ml of 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (manufactured by Wako Pure Chemical Industries, Ltd.) was added, the temperature was raised to room temperature, and 4 in a nitrogen atmosphere. Stir for hours. To the resulting solution were added 100 ml of 1N aqueous ammonium chloride solution and 200 ml of ethyl acetate, the organic layer was separated, washed with 200 ml of water, and dried over magnesium sulfate. The solvent was distilled off from the resulting solution under reduced pressure to obtain 1.9 g of compound (1-f).

  7. 1.42 g of the above compound (1-d) and 1.9 g of the above compound (1-f) are added to 50 ml of dimethylformamide, and potassium phosphate (manufactured by Wako Pure Chemical Industries, Ltd.) under a nitrogen atmosphere. 15 g of [bis (diphenylphosphino) ferrocene] dichloropalladium (manufactured by Aldrich) 0.26 g was added, and the mixture was stirred at 100 ° C. for 4 hours. 200 ml of water was added to the resulting solution, and the deposited precipitate was collected by filtration and washed with water and methanol in this order. The obtained solid was purified by column chromatography (filler: silica gel, eluent: chloroform) to obtain 1.56 g of compound (1-g).

1.56 g of the above compound (1-g) is dissolved in 200 ml of dimethylformamide (manufactured by Wako Pure Chemical Industries, Ltd.), 1.04 g of N-bromosuccinimide (manufactured by Wako Pure Chemical Industries, Ltd.) is added, and room temperature is added. For 3 hours. The deposited precipitate was collected by filtration and washed with dimethylformamide, methanol, water and methanol in this order. The obtained solid was vacuum-dried at 60 degreeC, and 1.6g of compounds (1-h) were obtained. The ¹ H-NMR measurement result of the compound (1-h) is shown.
¹ H-NMR (CDCl ₃ , ppm): 8.16 (s, 2H), 8.00 (s, 2H), 7.73-7.69 (m, 4H), 7.43-7.41 ( m, 6H), 7.33 (s, 2H).

  220 mg of the above compound (1-h) and 154 mg of compound (1-i) (manufactured by Aldrich) were dissolved in 30 ml of toluene. 3 ml of water, 850 mg of potassium carbonate, 18 mg of tetrakis (triphenylphosphine) palladium (0) (manufactured by Tokyo Chemical Industry Co., Ltd.) and 1 drop of Aliquat 336 (manufactured by Aldrich) were added thereto, and 2 at 100 ° C. in a nitrogen atmosphere. Stir for hours. Subsequently, 100 mg of bromobenzene (manufactured by Tokyo Chemical Industry Co., Ltd.) was added and stirred at 100 ° C. for 2 hours. 400 ml of methanol was added to the resulting solution, and the generated solid was collected by filtration and washed with methanol, acetone, hot water, and hot acetone in this order. The obtained solid was added to 400 ml of acetone and heated to reflux for 30 minutes. The solid obtained by filtration while hot was dissolved in 300 ml of chloroform, passed through a silica gel short column (eluent: chloroform), concentrated, and reprecipitated with methanol to obtain 48 mg of compound A-1 (yield 18 %). The weight average molecular weight was 119700, the number average molecular weight was 7800, and the degree of polymerization n was 127. The light absorption edge wavelength was 660 nm, the band gap (Eg) was 1.88 eV, and the highest occupied molecular orbital (HOMO) level was −5.26 eV.

Synthesis example 2
Compound B-1 was synthesized by the method shown in Formula 2.

  93 mg of the compound (1-d) of Synthesis Example 1 and 118 mg of the compound (1-i) of Synthesis Example 1 were dissolved in 30 ml of toluene. 3 ml of water, 580 mg of potassium carbonate, tetrakis (triphenylphosphine) palladium (0) (manufactured by Tokyo Chemical Industry Co., Ltd.) 24 mg, and 1 drop of Aliquat 336 (manufactured by Aldrich) were added thereto, and 5 at 100 ° C. under a nitrogen atmosphere. Stir for hours. Subsequently, 100 mg of bromobenzene (manufactured by Tokyo Chemical Industry Co., Ltd.) was added and stirred at 100 ° C. for 1 hour. Next, 100 mg of phenylboronic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) was added, and the mixture was stirred at 100 ° C. for 4 hours. 100 ml of methanol was added to the obtained solution, and the generated solid was collected by filtration and washed with methanol, acetone, 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 with methanol to obtain 110 mg of compound B-1 (yield 78%). The weight average molecular weight was 84800, the number average molecular weight was 32900, and the polymerization degree n was 127. The light absorption edge wavelength was 487 nm, the band gap (Eg) was 2.55 eV, and the highest occupied molecular orbital (HOMO) level was −5.79 eV.

Synthesis example 3
Compound A-2 was synthesized by the method shown in Formula 3.

  Compound (2-a) (manufactured by Wako Pure Chemical Industries, Ltd.) 50.25 g and copper powder (manufactured by Wako Pure Chemical Industries, Ltd.) 25 g are added to 230 ml of dimethylformamide, and the nitrogen atmosphere is maintained at 130 ° C. for 7 hours. Stir. After distilling off the solvent under reduced pressure, 500 ml of toluene was added, filtered through Celite, washed with 400 ml of water and 200 ml of aqueous sodium hydrogencarbonate in this order, and then dried over magnesium sulfate. After the solvent was distilled off from the resulting solution, it was washed with 300 ml of isopropanol to obtain 26 g of compound (2-b).

  After 26 g of the above compound (2-b) was added to 320 ml of ethanol, 180 ml of 36% hydrochloric acid and 31 g of tin powder (manufactured by Wako Pure Chemical Industries, Ltd.) were added, followed by stirring at 100 ° C. for 4 hours in a nitrogen atmosphere. The obtained solution was put into 800 ml of water, and an aqueous sodium hydroxide solution was added to adjust the pH to about 10. The resulting precipitate was collected by filtration, dissolved in 1000 ml of chloroform, washed with 1000 ml of water, and dried over magnesium sulfate. The solvent was distilled off from the resulting solution to obtain 21.37 g of compound (2-c).

21.3 g of the above compound (2-c) was added to 75 ml of 36% hydrochloric acid and 85 ml of water, and a NaNO ₂ aqueous solution (NaNO ₂ 10.7 g / 55 ml of water) was added dropwise at 5 ° C. After stirring at 5 ° C. for 30 minutes, a KI aqueous solution (KI 104 g / water 200 ml) was added dropwise, and the mixture was stirred at 5 ° C. for 1 hour, at room temperature for 1 hour, and at 60 ° C. for 3 hours. The obtained solid was collected by filtration and purified by column chromatography (filler: silica gel, eluent: hexane) to obtain 4.27 g of compound (2-d).

  4.27 g of the above compound (2-d) was dissolved in 85 ml of tetrahydrofuran (manufactured by Wako Pure Chemical Industries, Ltd.) and cooled to -80 ° C. After adding 19 ml of n-butyllithium 1.6M hexane solution (made by Wako Pure Chemical Industries Ltd.) over 1 hour, it stirred at -80 degreeC for 30 minutes by nitrogen atmosphere. 5.2 ml of dichlorodioctylsilane (manufactured by Wako Pure Chemical Industries, Ltd.) was added, the temperature was raised to room temperature, and the mixture was stirred for 1 day in a nitrogen atmosphere. 50 ml of water was added to the resulting solution, and the solvent was distilled off. After adding 150 ml of diethyl ether, the organic layer was separated, washed with 400 ml of water, and dried over magnesium sulfate. The resulting solution was purified by column chromatography (filler: silica gel, eluent: hexane) to obtain 2.49 g of compound (2-e).

2.49 g of the above compound (2-e) and 2.58 g of bis (pinacolato) diboron (BASF) were added to 21 ml of 1,4-dioxane, and potassium acetate (Wako Pure Chemical Industries, Ltd.) was added under a nitrogen atmosphere. 2.6 g) [bis (diphenylphosphino) ferrocene] dichloropalladium (Aldrich) 648 mg was added, and the mixture was stirred at 80 ° C. for 5.5 hours. 200 ml of water and 200 ml of diethyl ether were added to the resulting solution, and the organic layer was separated, washed with 300 ml of water, and dried over magnesium sulfate. The resulting solution was purified by column chromatography (filler: Florisil, eluent: hexane / ethyl acetate) to obtain 2.6 g of compound (2-f). The ¹ H-NMR measurement result of the compound (2-f) is shown.
¹ H-NMR (CDCl ₃ , ppm): 8.04 (s, 2H), 7.90-7.83 (m, 4H), 1.37 (s, 24H), 1.35 to 1.17 ( m, 24H), 0.93 (t, 4H), 0.84 (t, 6H).

  290 mg of the above compound (2-f) and 310 mg of the compound (1-h) of Synthesis Example 1 were dissolved in 40 ml of toluene. 10 ml of water, 1.05 g of potassium carbonate, tetrakis (triphenylphosphine) palladium (0) (manufactured by Tokyo Chemical Industry Co., Ltd.) 25 mg, and 1 drop of Aliquat 336 (manufactured by Aldrich) were added to the mixture at 100 ° C. under a nitrogen atmosphere. And stirred for 6 hours. Subsequently, 150 mg of bromobenzene (manufactured by Tokyo Chemical Industry Co., Ltd.) was added and stirred at 100 ° C. for 1 hour. Subsequently, 150 mg of phenylboronic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) was added and stirred at 100 ° C. for 6 hours. 400 ml of methanol was added to the resulting solution, and the generated solid was collected by filtration and washed with methanol, acetone, hot water, and hot acetone in this order. The obtained solid was added to 400 ml of acetone and heated to reflux for 30 minutes. The solid obtained by filtration while hot was dissolved in 300 ml of chloroform, passed through a silica gel short column (eluent: chloroform), concentrated and reprecipitated with methanol to obtain 105 mg of compound A-2 (yield 25 %). The weight average molecular weight was 88700, the number average molecular weight was 9500, and the degree of polymerization n was 92.4. The light absorption edge wavelength was 670 nm, the band gap (Eg) was 1.85 eV, and the highest occupied molecular orbital (HOMO) level was −5.35 eV.

Synthesis example 4
Compound A-3 was synthesized by the method shown in Formula 4.

  When 125 ml of tetrahydrofuran was added to 6.15 g of ethyl formate (3-a) (manufactured by Tokyo Chemical Industry Co., Ltd.) and cooled to −78 ° C., a tetrahydrofuran solution of octylmagnesium bromide having a concentration of 1.0 M (Tokyo Chemical Industry Co., Ltd.) 250 ml of Kogyo) was added dropwise over 1 hour while keeping the reaction solution at -78 ° C. After completion of the dropwise addition, the reaction solution was stirred at room temperature for 5 hours. After adding 50 ml of methanol to crush excess octylmagnesium bromide, tetrahydrofuran was distilled off under reduced pressure. After adding 120 ml of diethyl ether, the mixture was washed with 100 ml of saturated aqueous ammonium chloride solution and then with 100 ml of saturated brine. After the organic layer was dried over anhydrous magnesium sulfate, the solvent was distilled off under reduced pressure. The residue was purified by column chromatography (filler: silica gel, eluent: hexane / ethyl acetate = 10/1) to obtain 16.0 g of compound (3-b) as a white solid.

  10.0 g of the above compound (3-b), 5.1 g of triethylamine (manufactured by Wako Pure Chemical Industries, Ltd.) and 5 ml of pyridine (manufactured by Wako Pure Chemical Industries, Ltd.) are added to 80 ml of dichloromethane and stirred at 0 ° C. 8.92 g of paratoluenesulfonyl chloride was added there. The reaction solution was stirred at 0 ° C. for 1 hour and then at room temperature for 12 hours. 50 ml of water was added and the mixture was further stirred at room temperature for 30 minutes, and then extracted twice with 80 ml of dichloromethane. The organic layer was dried over anhydrous magnesium sulfate, and the solvent was distilled off under reduced pressure. The residue was purified by column chromatography (filler: silica gel, eluent: hexane / ethyl acetate = 10/1) to obtain 9.2 g of compound (3-c) as a waxy solid.

  375 ml of acetic acid (manufactured by Wako Pure Chemical Industries, Ltd.) was added to 25.0 g of 4-4′-dibromobiphenyl (3-d) (manufactured by Tokyo Chemical Industry Co., Ltd.), and smoke was generated when stirring at 100 ° C. 120 ml of nitric acid (manufactured by Wako Pure Chemical Industries, Ltd.) was slowly added, followed by 10 ml of water to the reaction solution. The reaction solution was stirred at 100 ° C. for 1 hour, then cooled to room temperature and left at room temperature for 5 hours. The precipitated solid was collected by filtration, and then washed with water and then with ethanol. The crude product was recrystallized from ethanol to obtain 17.0 g of compound (3-e) as a pale yellow solid.

  40 ml of triethyl phosphite (manufactured by Wako Pure Chemical Industries, Ltd.) was added to 11.0 g of the compound (3-e), and the mixture was stirred at 150 ° C. for 10 hours. After distilling off triethyl phosphite under reduced pressure, the residue was purified by column chromatography (filler: silica gel, eluent: hexane / ethyl acetate = 5/1) to obtain 2.5 g of compound (3-f). Was obtained as a white solid.

  To 1.2 g of the above compound (3-f) are added 10 ml of dimethyl sulfoxide (manufactured by Wako Pure Chemical Industries, Ltd.) and 1.08 g of potassium hydroxide (manufactured by Wako Pure Chemical Industries, Ltd.), and the mixture is stirred at room temperature. Then, a dimethyl sulfoxide solution (6 ml) of 2.4 g of the compound (3-c) was added dropwise at room temperature over 1 hour. After completion of dropping, the mixture was stirred at room temperature for 5 hours. 50 ml of water was added to the reaction mixture, followed by extraction three times with 40 ml of hexane, the organic layer was dried over anhydrous magnesium sulfate, and the solvent was distilled off under reduced pressure. The residue was purified by column chromatography (filler: silica gel, eluent: hexane) to obtain 540 mg of the compound (3-g) as a white solid.

When 530 mg of the above compound (3-g) was dissolved in 10 ml of tetrahydrofuran and cooled to −78 ° C., 0.65 ml of n-butyllithium hexane solution having a concentration of 1.6 M (manufactured by Wako Pure Chemical Industries, Ltd.) was added dropwise. And stirred at −78 ° C. for 1 hour. The reaction solution was stirred for 30 minutes at 0 ° C. and then cooled again to −78 ° C., and 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (manufactured by Tokyo Chemical Industry Co., Ltd.). ) 440 mg was added. The reaction solution was further stirred at room temperature for 4 hours, and then water (10 ml) and then diethyl ether (50 ml) were added. The organic layer was washed 3 times with water (30 ml) and once with saturated brine (30 ml), and then dried over anhydrous magnesium sulfate, and the solvent was distilled off under reduced pressure. By recrystallization from a methanol / acetone mixed solvent, 390 mg of the compound (3-h) was obtained as a white solid. The ¹ H-NMR measurement result of the compound (3-h) is shown.

¹ H-NMR (CDCl ₃ , ppm): 8.12 (s, 2H), 8.02 (s, 1H), 7.89 (s, 1H), 7.66 (d, J = 7.6 Hz, 2H), 4.69 (m, 2H), 2.31 (m, 2H), 1.95 (m, 2H), 1.39 (s, 24H), 1.21-1.12 (m, 24H) ), 0.82 (t, J = 7.0 Hz, 6H).

  100 mg of the above compound (3-h) and 109 mg of the compound (1-h) of Synthesis Example 1 were dissolved in 20 ml of toluene. To this was added 5 ml of water, 500 mg of potassium carbonate, 9 mg of tetrakis (triphenylphosphine) palladium (0) (manufactured by Tokyo Chemical Industry Co., Ltd.) and 1 drop of Aliquat 336 (manufactured by Aldrich), and 6 at 100 ° C. under a nitrogen atmosphere. Stir for hours. Subsequently, 100 mg of bromobenzene (manufactured by Tokyo Chemical Industry Co., Ltd.) was added and stirred at 100 ° C. for 1 hour. Next, 100 mg of phenylboronic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) was added, and the mixture was stirred at 100 ° C. for 6 hours. 200 ml of methanol was added to the resulting solution, and the generated solid was collected by filtration and washed with methanol, acetone, hot water, and hot acetone in this order. The obtained solid was added to 200 ml of acetone and heated to reflux for 30 minutes. The solid obtained by filtration while hot was dissolved in 150 ml of chloroform, passed through a silica gel short column (eluent: chloroform), concentrated and reprecipitated with methanol to obtain 43 mg of compound A-3 (yield 30). %). The weight average molecular weight was 92800, the number average molecular weight was 8500, and the degree of polymerization n was 98. The light absorption edge wavelength was 670 nm, the band gap (Eg) was 1.85 eV, and the highest occupied molecular orbital (HOMO) level was −5.14 eV.

Example 1
1 mg of the above 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 cleaning machine (US-2 (trade name) manufactured by Inoue Seieido Co., Ltd.) The solution A was obtained by ultrasonic irradiation for 30 minutes in an output of 120 W).

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 using a hot plate, the above solution A was dropped onto the PEDOT: PSS layer, and an organic semiconductor layer having a thickness of 100 nm was formed by spin coating. Thereafter, the substrate on which the organic semiconductor layer is formed and the cathode mask are placed in a vacuum evaporation apparatus, and the vacuum is exhausted again until the degree of vacuum in the apparatus becomes 1 × 10 ⁻³ Pa or less. An aluminum layer was deposited to a thickness of 80 nm. As described above, a photovoltaic device having an area where the stripe-shaped ITO layer intersects with the aluminum layer 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 8.28 mA / cm ² , the open circuit voltage (value of the applied voltage when the current density is 0) is 0.840 V, and the fill factor (FF) was 0.460, and the photoelectric conversion efficiency calculated from these values was 3.20%. The fill factor and photoelectric conversion efficiency were calculated by the following equations.
Fill factor = IVmax (mW / cm ² ) / (Short-circuit current density (mA / cm ² ) × Open circuit voltage (V))
(Here, IVmax is the value of the product of the current density and the applied voltage at the point where the product of the current density and the applied voltage becomes maximum when the applied voltage is between 0 V and the open circuit voltage value.)
Photoelectric conversion efficiency = [(short circuit current density (mA / cm ² ) × open voltage (V) × fill factor) / pseudo sunlight intensity (100 mW / cm ² )] × 100 (%)
The fill factor and photoelectric conversion efficiency in the following comparative examples were all calculated by the above formula.

Example 2
A photovoltaic device was produced in the same manner as in Example 1 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 8.12 mA / cm ² , the open-circuit voltage was 0.830 V, the fill factor (FF) was 0.480, and the photoelectric conversion efficiency calculated from these values was 3.24%. .

Example 3
A photovoltaic device was produced in the same manner as in Example 1 except that A-3 was used instead of A-1, and current-voltage characteristics were measured. The short-circuit current density at this time was 8.30 mA / cm ² , the open-circuit voltage was 0.790 V, and the fill factor (FF) was 0.490, and the photoelectric conversion efficiency calculated from these values was 3.21%. .

Comparative Example 1
A photovoltaic device was produced in the same manner as in Example 1 except that B-1 was used instead of A-1, and current-voltage characteristics were measured. The short-circuit current density at this time was 0.13 mA / cm ² , the open circuit voltage was 0.680 V, the fill factor (FF) was 0.281, and the photoelectric conversion efficiency calculated from these values was 0.02%. .

Comparative Example 2
Instead of A-1, the following B-2 (synthesized by the method described in Journal of Materials Chemistry, 2009, Vol. 19, pages 4942-4943. The weight average molecular weight is 58200, and the number average molecular weight is 23900, the degree of polymerization n was 94.) A photovoltaic device was prepared in the same manner as in Example 1 except that was used, and the current-voltage characteristics were measured. The short-circuit current density at this time was 5.81 mA / cm ² , the open-circuit voltage was 0.710 V, the fill factor (FF) was 0.390, and the photoelectric conversion efficiency calculated from these values was 1.61%. .

Comparative Example 3
Instead of A-1, it was synthesized by the method described in the following B-3 (Macromolecules, 2003, Volume 36, page 4289. The weight average molecular weight was 39700, the number average molecular weight was 20200, and the polymerization degree n was A photovoltaic device was prepared in exactly the same manner as in Example 1 except that 7) was used, and current-voltage characteristics were measured. At this time, the short-circuit current density was 2.74 mA / cm ² , the open-circuit voltage was 0.880 V, and the fill factor (FF) was 0.410. The photoelectric conversion efficiency calculated from these values was 0.99%. .

DESCRIPTION OF SYMBOLS 1 Board | substrate 2 Positive electrode 3 Organic-semiconductor layer 4 Negative electrode 5 The layer which has an electron-donating organic material containing the conjugated polymer which has a structure represented by General formula (1) 6 The layer which has an electron-accepting organic material

Claims (6)

A conjugated polymer having a structure represented by the following general formula (1).

(R ^{1 to} R ¹⁶ may be the same or different and are selected from hydrogen, an alkyl group, an alkoxy group, an aryl group, a heteroaryl group, and halogen. A represents carbon, nitrogen, or silicon. A represents nitrogen. In this case, R ¹⁶ does not exist. W, X, Y and Z are single bonds . N represents a range of 10 or more and 1000 or less.) An electron donating organic material comprising the conjugated polymer according to claim 1. A material for a photovoltaic device comprising an electron-accepting organic material and the electron-donating organic material according to claim 2. The photovoltaic element material according to claim 3, wherein the electron-accepting organic material is a fullerene compound. The fullerene compound material for photovoltaic devices according to claim 4, wherein the C ₇₀ derivative. A photovoltaic element having at least a positive electrode and a negative electrode, wherein the photovoltaic element comprises the photovoltaic element material according to any one of claims 3 to 5 between the negative electrode and the positive electrode.

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