JP5383016B2 - Methanofullerene derivative and photoelectric conversion element using the same - Google Patents

Description

  The present invention relates to a methanofullerene derivative. The methanofullerene derivative of the present invention is a material applicable as an organic semiconductor material to an electronic element such as an organic FET or an electroluminescence element, a solar cell, etc. The present invention also relates to a photoelectric conversion element using the same.

Photovoltaic power generation, which converts light energy such as sunlight into electrical energy, is an extremely clean power generation method because it does not involve CO ₂ emissions, and is a means of reducing greenhouse gases and solving global warming problems. As expected. Organic thin-film solar cells are considered to be promising next-generation solar cells because they can be expected to have a large-area, simple, and inexpensive manufacturing method, are lightweight, and are flexible. It has become an important issue for the future.
1992 Sariciftci showed that it is possible to efficiently charge separation by heterojunction cells of conductive polymer and fullerene _{C 60} is a hole transport material (Non-Patent Document 1, Patent Document 1).
Further, methanofullerene (phenyl C ₆₁ butyric acid methyl ester; PCBM) in which a phenyl group and a butyric acid ester group are cross-linked with methylene is synthesized for the purpose of enhancing the compatibility of fullerene with a hole transport material. MEH-PPV / PCBM system in which an alkoxy group is introduced into vinylene (poly [2-methoxy, 5- (2′-ethyl-hexoxyloxy) -para-phenylenevinylene]; MEH-PPV) and PCBM to form an active layer in the photoelectric conversion efficiency was greatly improved in comparison with C ₆₀ (see non-Patent Document 2).

Saricifci et al. Achieved an energy conversion efficiency of 3.5% in a bulk heterojunction structure composed of a mixed active layer of conjugated polymer poly (3-hexylthiophene); P3HT and methanofullerene derivative PCBM as a hole transport material. (Refer nonpatent literature 3).
Furthermore, Heeger and Carroll et al. Have independently reported an energy conversion efficiency of about 5% by heat treatment of the blend film element (see Non-Patent Documents 4 and 5).
Donor / acceptor composite film is PCBM is the synthesis for the purpose of enhancing the compatibility with the hole transport material of the fullerene is made, MEH-PPV / In PCBM system fact that the photoelectric conversion efficiency as compared with C ₆₀ was significantly improved As can be seen, the compatibility of the fullerene derivative with the hole transport material is extremely important. Further, as represented by P3HT as a hole transport material, high photoelectric conversion efficiency has been observed in thiophene polymers, and it is obvious that the compatibility of fullerene derivatives, which are electron transport material semiconductors, with thiophene polymers is important. It is.
For example, as an example of synthesizing a thiophene methanofullerene derivative having a thiophene substituent, 1- (3-methoxycarbonyl) propyl-1-thienyl- [6,6] -methanofullerene (ThCBM) shown in Non-Patent Document 6 However, the problem in terms of solubility during preparation of the coating solution and compatibility with the thiophene polymer has been insufficient.

US Pat. No. 5,331,183 N. S. Sariciftci, L. Smilowitz, A. J. Heeger, F. Wudl, “Science”, 1992, 258, p. 1474-1476 C. J. Brabec, F. Padinger, N.S. Sariciftci, J.C. Hummelen, “J. Appl. Phys.”, 1999, vol. 85, p. 6866 F. Padinger, R.S. Rittberger, N.S. Sariciftci, “Advanced Functional Material (Adv. Funct. Mater.)”, 2003, 13-1, p. 85-88 M. R-Reyes, K. Kim, D. L. Carroll, "Appl. Phy. Lett.", 2005, 87, 083506 W. Ma, C. Yang, X. Gong, K. Lee, A. J. Heeger, “Advanced Functional Material (Adv. Funct. Mater.)”, 2005, 15, p. 1617-1622 M. Popescu, P.V. Hof, A. B. Sieval, H. T. Jonkman, J. C. Hummelen, “Appl. Phy. Lett.”, 2006, 89, 213507

  As a result of intensive studies in view of the above-mentioned problems, the present inventors have succeeded in developing a methanofullerene derivative having a thiophene-based substituent and a high solubility in order to improve compatibility with a thiophene-based polymer. By using the novel methanofullerene derivative according to the present invention, a thiophene-based methanofullerene derivative having high solubility and compatibility with a polymer, excellent charge mobility and charge separation ability is provided, and excellent in electronic properties and durability. A photoelectric conversion element can be obtained.

The present invention relates to a methanofullerene derivative represented by the general formula (I).
(In the above general formula (I), FL represents fullerenes, and Tp represents a thiophene heterocyclic ring or a thiophene heterocyclic ring in which at least part of the hydrogen atoms are substituted with a halogen atom, an alkyl group, an alkoxy group or an aryl group. 1 to 8 mer of thiophene heterocycles or those in which up to 8 of these thiophene heterocycles are linked, X is hydrogen, halogen atom, Tp, alkyl group, cycloalkyl group, alkoxy group or aryl group FL, Tp and X are connected by a methylene group, and n represents an integer of 1 to 10.)

The present invention also relates to the methanofullerene derivative, wherein the Tp is a thiophene heterocycle represented by the following general formula (II).

The present invention also relates to the methanofullerene derivative, wherein the thiophene heterocycle has at least one substituent other than hydrogen.
The present invention also relates to a photoelectric conversion element using the methanofullerene derivative described above as an electron transport material.
The present invention also relates to the photoelectric conversion element, wherein the photoelectric conversion element includes a conjugated polymer compound including a thiophene ring as a hole transport material.

  The novel methanofullerene derivative of the present invention is a material applicable as an organic semiconductor material to an electronic device such as an organic FET or an electroluminescence device, a solar cell, or the like.

Hereinafter, the methanofullerene derivative of the present invention will be described.
The methanofullerene derivative of the present invention has a structure in which Tp and X are cross-linked with methylene, as indicated by the circled FL, the circled Tp, and the circled X in the above general formula (I). It is characterized by having.

In the present invention, FL in the general formula (I) represents fullerenes. Fullerenes are a general term for compounds having a three-dimensional closed nucleus structure in which Sp2-type carbon atoms are bonded in a spherical shape. Specifically, fullerenes, derivatives thereof, and metal atoms and compounds are included in the skeleton. You can list things. More specifically, examples of fullerene include C ₆₀ , C _70, C _76, C _78, C _82, C _84, C _{90, and} C ₉₆ as chemical formulas. Among these, C ₆₀ or C ₇₀ Is particularly preferred.

In the present invention, examples of Tp in the general formula (I) include thiophene heteroaromatic ring and aromatic ring, or thienothiophene and benzothiophene in which a plurality of heteroaromatic rings are condensed, preferably heteroaromatic ring compounds In particular, thiophene heteroaromatic compounds such as thiophene, benzothiophene, and thienothiophene containing sulfur are particularly preferable. These Tp can have a substituent for improving solubility in a solvent, improving compatibility with a hole transport material when used as a photoelectric conversion element, and improving durability.

  Examples of the substituent for Tp include a halogen atom or an alkyl group or alkoxy group having 1 to 30 carbon atoms, preferably 1 to 18 carbon atoms. Examples of the halogen atom include fluorine, chlorine, bromine and iodine. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an i-propyl group, a 2-ethylpropyl group, and a cyclohexyl group. Examples of the alkoxy group include a methoxy group, an ethoxy group, a propyloxy group, an i-propyloxy group, a butoxy group, a t-butyloxy group, a 2-ethylpropyloxy group, and a cyclohexyloxy group. Alternatively, part or all of the hydrogen of the alkyl group may be a group containing an unsaturated bond, a substituent containing an aromatic ring such as a phenyl group, or the like. The above alkyl group or the like may be bonded using a carbonyl group, a carbonyloxy group or an oxycarbonyl group, an amino group, or the like. The terminal of the alkyl group or the like may be a hydroxyl group, thiol group, carboxyl group, sulfonic acid group, cyano group, isocyanate group, aldehyde group, amino group, or the like. In the middle of the alkyl chain, an ester bond (—COO—), an acid amide bond (—NH—CO—), a urethane bond (—NH—COO—), an ether bond (—O—), and the like may be included. It may be an ethylene oxide group having 1 to 15 repeating units. Two substituents may form a bond at the terminal to form a ring. For example, cyclic ether, cyclic ester, acid anhydride, carbodiimide and the like can be mentioned. Further, a structure in which an aromatic ring is condensed may be used.

  As Tp, those in which at least a part of the hydrogen atoms of the thiophene heterocyclic ring or thiophene heterocyclic ring are substituted with an alkyl group, an alkoxy group or an aryl group, and oligomers thereof can be preferably used. The number of condensation of the thiophene heterocycle as an oligomer is not particularly limited, but preferably 30-mer or less, more preferably 20-mer or less, and particularly preferably 1-8 mer.

  In addition, when heteroaromatic rings such as thiophene heterocycles are used, it is known that the electron reactivity at the α-position (carbon adjacent to the heteroatom) is particularly high (Chemical Society of Japan, “Experimental Chemistry Course 4th Edition”). , 24, organic synthesis VI (heteroelement / typical metal element compound), p539-549). That is, this indicates that the reactivity at the α-position is high, and it is considered that the durability is lowered particularly when the carbon substituent is hydrogen. Therefore, when using a thiophene heterocycle or a derivative thereof, it is particularly desirable to introduce a substituent at the α-position.

  In the present invention, X in the general formula (I) represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 30, preferably 1 to 18 carbon atoms, a cycloalkyl group, an alkoxy group, an aryl group, or Tp shown above. Represent. Examples of the halogen atom include fluorine, chlorine, bromine and iodine. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an i-propyl group, a 2-ethylpropyl group, and a cyclohexyl group. Examples of the alkoxy group include a methoxy group, an ethoxy group, a propyloxy group, an i-propyloxy group, a butoxy group, a t-butyloxy group, a 2-ethylpropyloxy group, and a cyclohexyloxy group. Alternatively, part or all of the hydrogen of the alkyl group may be a group containing an unsaturated bond, a substituent containing an aromatic ring such as a phenyl group, or the like. The above alkyl group or the like may be bonded using a carbonyl group, a carbonyloxy group or an oxycarbonyl group, an amino group, or the like. The terminal of the alkyl group or the like may be a hydroxyl group, thiol group, carboxyl group, sulfonic acid group, cyano group, isocyanate group, aldehyde group, amino group, or the like. In the middle of the alkyl chain, an ester bond (—COO—), an acid amide bond (—NH—CO—), a urethane bond (—NH—COO—), an ether bond (—O—), and the like may be included. It may be an ethylene oxide group having 1 to 15 repeating units. Two substituents may form a bond at the terminal to form a ring. For example, cyclic ether, cyclic ester, acid anhydride, carbodiimide and the like can be mentioned. Further, a structure in which an aromatic ring is condensed may be used. The terminal of the alkyl group or the like may be a hydroxy group, a thiol group, a carboxyl group, a sulfonic acid group, a cyano group, an isocyanate group, an aldehyde group, an amino group, or the like. Further, an ester bond, an acid amide bond, a urethane bond, an ether bond, or the like may be included in the alkyl chain, and an ethylene oxide group having 1 to 15 repeating units may be used. Two substituents may form a bond at the terminal to form a ring. For example, cyclic ether, cyclic ester, acid anhydride, carbodiimide and the like can be mentioned. Further, a structure in which an aromatic ring is condensed may be used. The terminal may have a reactive substituent having a hetero element such as a hydroxyl group or an amino group, such as an ester group or an ether group.

  In the methanofullerene derivative of the present invention, the number of pairs of Tp and X bonded by a methylene bridge is not particularly limited as long as the object of the present invention can be achieved, but the number of substitutions n in the general formula (I) is 1. Is preferably an integer of from 1 to 10, more preferably from 1 to 5.

  Although an example of the synthesis | combining method of the methanofullerene derivative of this invention is described, it is not limited to these methods. That is, tosyl hydrazone (in the examples, 1a, 2a, 3a, 4a, 5a, 6a) and fullerene, which are precursors of the desired methanofullerene, in the presence of sodium methoxide in orthodichlorobenzene, pyridine solvent, 50 The target methanofullerene derivative can be obtained by refluxing at ˜150 ° C. for 1 to 12 hours.

Next, an electronic device manufactured using the methanofullerene derivative of the present invention will be described.
As an electronic device of the present invention, for example, a heterojunction having a photoelectric conversion layer formed on a substrate by using the methanofullerene derivative of the present invention as an electron transport material as an electron transport material and combining with an appropriate hole transport material. Type devices. The heterojunction type electronic device exhibits characteristics as a photoelectric conversion element in which, for example, a methanofullerene derivative and a hole transport material generate charges by light absorption, thereby taking out the light by light irradiation, that is, changing a current value.
As a specific structure of the heterojunction type electronic device of the present invention, for example, a structure having a structure in which the methanofullerene of the present invention, a photoelectric conversion layer by a hole transport material, and a counter electrode are sequentially laminated on a transparent conductive substrate. It is done.

  As the hole transport material, polythiophene, polypyrrole, polyaniline, polyfuran, polypyridine, polycarbazole and the like which are hole transport polymers can be used. Among them, it is preferable to use a polythiophene hole transport material as the hole transport material for the thiophene methanofullerene derivative which is the methanofullerene derivative of the present invention.

  As the polythiophene, those polymerized at the 2,5-positions with thiophene and substituted thiophene as monomer units can be suitably used. Specific examples of the substituted thiophene structure include alkyl-substituted thiophene and aryl-substituted thiophene. More specific polythiophene structures include poly (3-methylthiophene) and poly (3-butylthiophene). , Poly (3-hexylthiophene), poly (3-octylthiophene), poly (3-decylthiophene), poly (3-dodecylthiophene), poly (3-phenylthiophene), poly (3- (p-alkylphenyl) And thiophene)). Among these polythiophenes, those having particularly high mobility are preferable, and for example, those polymerized in a stereoregular manner can be used.

The photoelectric conversion layer is formed by mixing the methanofullerene derivative of the present invention, the hole transport material, and a solvent for dissolving them into a solution and applying the solution onto a substrate.
Examples of a method for producing a photoelectric conversion layer include a method in which the methanofullerene derivative of the present invention and the hole transport material are sandwiched between two smooth substrates.
The substrate to be used is not particularly limited as long as it is sufficiently smooth, and the material, thickness, dimensions, shape and the like can be appropriately selected according to the purpose. For example, colorless or colored glass, meshed glass, glass block, etc. Besides being used, a resin having colorless or colored transparency may be used. Specific examples of such resins include polyesters such as polyethylene terephthalate, polyamide, polysulfone, polyether sulfone, polyether ether ketone, polyphenylene sulfide, polycarbonate, polyimide, polymethyl methacrylate, polystyrene, cellulose triacetate, and polymethylpentene. Etc. In addition, the board | substrate in this invention has a smooth surface at normal temperature, The surface may be a plane or a curved surface, and may deform | transform by stress. Moreover, it may be opaque like a metal plate, for example, smooth metal plates, such as gold | metal | money, silver, chromium, copper, tungsten, aluminum, chromium, stainless steel, etc. are mentioned. When sandwiched between two substrates, heating and pressurization may be performed as necessary.

The mechanism by which the methanofullerene derivative of the present invention and the hole transport material function as a solar cell is described in, for example, S. Sun and N.M. S. Sarifitci, “Organic Photovoltaics” (Taylor and Francis) and the like. Usually, when a film in which methanofullerene and a hole transport material are mixed is prepared, they are phase-separated at a nanoscale to form an interleaved phase-separated structure, which is called a bulk heterojunction. Here, the methanofullerene derivative and the hole transport material each generate exciton (electron-hole pair) by light irradiation, and the exciton is separated by charge at the fullerene derivative / hole transport material interface, thereby free carriers (electrons and holes). ) Is generated. The generated free electrons and holes propagate through the methanofullerene phase and the hole transport material phase, which are electron-withdrawing and electron-donating, respectively, and reach a separate electrode, thereby obtaining a photovoltaic force. In this process, the exciton must be diffused to the interface between the methanofullerene derivative and the hole transport material layer in order to separate the charge. However, since the exciton has a lifetime (τ), the amount of exciton increases with time after light absorption. Decrease. If the time (τ) when the amount of exciton is 1 / e is defined as the lifetime of the exciton, the exciton diffusion constant is defined as D and the diffusion length of the exciton is defined as L _D = (D × τ) ^1/2 . In order to obtain a high-efficiency solar cell, it is necessary to charge-separate excitons into free carriers with high efficiency. Therefore, it is necessary to shorten the time for excitons generated by light absorption to be as short as possible. For this purpose, if the structure (domain) due to the phase separation of the methanofullerene phase and the hole transport material phase is too large, the exciton is separated by charge, and the average distance to be moved becomes long, so that the photoelectric conversion characteristics are deteriorated. . Therefore, in order to efficiently perform exciton charge separation and obtain a highly efficient solar cell element, it is necessary to increase the compatibility of the methanofullerene derivative and the hole transport material so as not to make the phase separation structure too large.

  The compatibility between the methanofullerene derivative and the hole transport material is a mixing characteristic of the methanofullerene derivative and the hole transport material in a solid film state in which the solvent is evaporated after coating. In order to obtain high photoelectric conversion characteristics, the methanofullerene derivative and the hole transport material must be appropriately phase-separated at the nanoscale. However, if the compatibility is poor, the phase separation between the methanofullerene derivative and the hole transport material becomes extremely high. Therefore, as described above, it becomes a cause of deteriorating device characteristics. In order to measure the compatibility in such a solid state, a direct image of the phase separation structure can be measured with an atomic force microscope with an average domain size by, for example, scattering characteristics or X-ray analysis.

In addition, a method is possible in which the methanofullerene derivative of the present invention and the hole transport material are dissolved in a soluble solvent to form a solution, which is applied to a substrate and then the solvent is removed. The solvent to be used is not particularly limited as long as it can dissolve both the methanofullerene derivative and the hole transport material. For example, benzene, toluene, xylene, chloroform, dichloromethane, tetrahydrofuran, dioxane, carbon tetrachloride, ethylbenzene, Examples include chlorobenzene, dichlorobenzene, propylbenzene, ethylene dichloride, and methyl chloride. Moreover, there is no restriction | limiting in particular about the density | concentration of the methanofullerene derivative and hole transport material in a solution, However, About 0.1-5 mass% is preferable from a viewpoint on preparation. If the methanofullerene derivative and the hole transport material are difficult to dissolve, operations such as stirring and heating may be performed.
The solution is then applied to the substrate surface. The substrate is the same as the substrate described above, and there is no problem as long as it has moderate smoothness. The method for applying the solution to the substrate surface is not particularly limited, and can be carried out by a method such as casting, spin coating, spray coating, or bar coating. Moreover, there is no restriction | limiting in particular about the application quantity, However Usually, about 0.002-0.1 ml per 1 cm < ² > of a board | substrate is preferable. Next, the photoelectric conversion layer can be formed by evaporating the solvent. Examples of the method for evaporating the solvent include a method of heating the substrate.

  A transparent conductive substrate is usually produced by laminating a transparent electrode layer on a transparent substrate. The transparent substrate is not particularly limited, and the material, thickness, dimensions, shape, and the like can be appropriately selected according to the purpose. For example, colorless or colored glass, meshed glass, glass block, etc. are used, and colorless. Alternatively, a colored transparent resin may be used. Specific examples of such resins include polyesters such as polyethylene terephthalate, polyamide, polysulfone, polyether sulfone, polyether ether ketone, polyphenylene sulfide, polycarbonate, polyimide, polymethyl methacrylate, polystyrene, cellulose triacetate, and polymethylpentene. Etc. In the present invention, the term “transparent” means having a transmittance of 10 to 100%, and the term “substrate” in the present invention has a smooth surface at room temperature, and the surface is flat or curved. It may be deformed by stress.

The transparent conductive film for forming the conductive layer of the transparent electrode is not particularly limited as long as it fulfills the object of the present invention. For example, a metal thin film such as gold, silver, chromium, copper, tungsten, Examples thereof include a conductive film made of a metal oxide. Examples of the metal oxide include Indium Tin Oxide (ITO (In ₂ O ₃ : Sn)), Fluorine doped Tin Oxide (FTO (SnO ₂ : F)) in which tin oxide or zinc oxide is slightly doped with another metal element. ), Aluminum doped Zinc Oxide (AZO (ZnO: Al)) and the like are preferably used. The film thickness is usually 1 nm to 50 μm, preferably 10 nm to 10 μm. The surface resistance (resistivity) is appropriately selected depending on the use of the substrate of the present invention, but is usually 0.01 to 500 Ω / sq, preferably 0.1 to 50 Ω / sq.

  As the counter electrode, a metal such as gold, platinum, silver, copper, aluminum, magnesium, lithium, and potassium, or a carbon electrode can be used. As a method for installing the counter electrode, the film may be formed by a known method such as a vacuum deposition method, an electron beam vacuum deposition method, a sputtering method, or applying metal fine particles dispersed in a solvent to volatilize and remove the solvent. In addition, before forming the counter electrode metal layer, various organic and inorganic materials can be formed in order to improve the adhesion and the exciton blocking property between the photoelectric conversion layer and the counter electrode metal layer. The material to be used is not particularly limited as long as it meets the object of the present invention. For example, a thin film layer of an organic compound such as phenanthroline or bathocuproine or an inorganic compound such as LiF or TiOx can be used.

  For the evaluation of the element characteristics, a current measurement terminal is attached to each of the transparent electrode and the counter electrode, and the change of the current value due to the presence or absence of light irradiation may be measured. For example, JIS C 8911-9, JIS C 8931-40 It is desirable to measure with reference to the above.

  In addition, various sealing processes can be performed in order to improve the durability of the element. The sealing method is not particularly limited as long as it meets the object of the present invention. For example, the element can be sealed using various materials having low gas permeability. As a sealing method with low gas permeability, the substrate material is utilized as a gas barrier layer, and the sealing process is performed by adhering to the device using an adhesive with low gas permeability. It is possible to improve.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 1
A methanofullerene derivative 1b (EThCBM) in which Tp is 5-ethylthiophen-2-yl and X is 3- (methoxycarbonyl) propyl was synthesized as follows.

The _{C 60} was added 50mg to 25mL pear-shaped flask, dissolved in dry o- dichlorobenzene (ODCB) 1.5 mL under argon, was sonicated for 60 minutes. In a 50 mL two-necked flask equipped with a Dimroth condenser and a stir bar, 56.7 mg of tosylhydrazone 1a and 8 mg of sodium methoxide were dissolved in 1 mL of dry pyridine in an argon atmosphere and stirred for 15 minutes. Thereafter, an ODCB solution of C ₆₀ was added from the pear-shaped flask and heated at 70 ° C. for 4 hours and further at 100 ° C. for 1.5 hours. The reaction solution was separated and purified by silica gel column chromatography (developing solvent: toluene) to obtain 29.5 mg of 1b (EThCBM) (yield 52.2%). Moreover, the obtained product was confirmed by high performance liquid chromatography and identified by ¹ H-NMR, ¹³ C-NMR, and IR.

<Analysis data>
IR (KBr) 2960, 1737 (C = O; s), 1456, 1428, 1376, 1263, 1186, 1170, 983, 885, 806, 741, 572, 562, 525 (s), 445, 432 cm ⁻¹ ; ¹ H-NMR (300 MHz; CDCl ₃ ) δ 7.27 (d, 1 H, 3.60 Hz), 6.78 (d, 1 H, 3.60 Hz), 3.69 (s, 3 H), 2.99-2 .90 (m, 4H), 2.58 (t, 2H, 7.5 Hz), 2.29-2.19 (m, 2H), 1.41 (t, 3H, 7.5 Hz); ¹³ C- NMR (75 MHz; CDCl ₃ ) δ 173.50 (C═O), 148.50, 148.40, 147.65, 145.74, 145.23, 145.20, 145.18, 145.13, 144. 81, 144 72, 144.64, 144.57, 144.47, 144.14, 143.82, 143.78, 143.10, 143.04, 143.00, 142.92, 142.90, 142.26, 142.17, 142.13, 142.11, 140.92, 140.70, 138.26, 138.10, 135.97, 131.77 ( C H), 122.20 ( C H), 80. 08 (bridge head), 51.66 (O C H ₃ ), 46.20 (bridge), 33.86 ( C H ₂ ), 33.71 ( C H ₂ ), 23.68 ( C H ₂ ), 22.52 ( C H ₂ ), 15.53 ( C H ₃ ).

(Comparative Example 1)
A methanofullerene derivative 2b (ThCBM) in which Tp is 2-thiophenyl and X is 3- (methoxycarbonyl) propyl was synthesized according to Non-Patent Document 6.

(Example 2)
A methanofullerene derivative 3b (TThCBM) in which Tp is thienothiophen-2-yl and X is 3- (methoxycarbonyl) propyl was synthesized as follows.

The _{C 60} was added 250mg to 30mL pear shaped flask under a nitrogen atmosphere was dissolved in dry o- dichlorobenzene (ODCB) 16 mL, it was sonicated for 60 minutes. In a 50 mL flask equipped with a stirrer, 182 mg of tosylhydrazone 3a and 26 mg of sodium methoxide were dissolved in 5 mL of dry pyridine under a nitrogen atmosphere and stirred for 15 minutes. Thereafter, an ODCB solution of C ₆₀ was added from the pear-shaped flask and heated at 100 ° C. for 4 hours. The reaction solution was separated and purified by silica gel column chromatography (developing solvent: toluene) to obtain 111 mg of 3b (TThCBM) (yield 33%). Moreover, the obtained product was confirmed by high performance liquid chromatography and identified by ¹ H-NMR, ¹³ C-NMR, and IR.

<Analysis data>
IR (KBr) 2943, 1735 (C═O; s), 1459, 1429, 1343, 1249, 1187, 1173, 1080, 1059, 905, 826, 799, 755, 742, 700 cm ⁻¹ ; ¹ H-NMR (300 MHz; CDCl ₃ ) δ 7.68 (s, 1H), 7.49 (d, 1H, 5.3 Hz), 7.34 (d, 1H, 5.1 Hz), 3.68 (s, 3H), 3.00 (t, 2H, 8.0 Hz), 2.58 (t, 2H, 7.5 Hz), 2.34-2.25 (m, 2H); ¹³ C-NMR (75 MHz, CDCl ₃ ) δ 173 .41 (C = O), 148.00, 147.29, 145.65, 145.27, 145.19, 145.05, 144.86, 144.70, 144.66, 144.57, 144. 24, 14 3.84, 143.81, 143.11, 143.05, 142.98, 142.96, 142.25, 142.17, 141.11, 141.02, 140.81, 139.42, 138. 38, 138.24, 137.62, 127.86 ( C H), 124.52 ( C H), 119.68 ( C H), 79.65 (bridge head), 51.70 (O C H ₃ ), 46.56 (bridge), 33.89 ( C H ₂ ), 33.70 ( C H ₂ ), 22.56 ( C H ₂ ).

(Example 3)
A methanofullerene derivative 4b (es-TThCBM) in which Tp was 5-carboethoxythienothiophen-2-yl and X was 3- (methoxycarbonyl) propyl was synthesized as follows.

30mL pear-shaped flask of _{C 60} was added 350mg to, dissolved in dry o- dichlorobenzene (ODCB) 20 mL under a nitrogen atmosphere and subjected to ultrasonic for 60 minutes. In a 50 mL flask equipped with a stir bar, 296 mg of tosylhydrazone 4a and 37 mg of sodium methoxide were dissolved in 7 mL of dry pyridine under a nitrogen atmosphere and stirred for 15 minutes. _Then added ODCB solution _{C 60} from pear-shaped flask, and heated at 100 ° C. 3.5 hours. The reaction solution was separated and purified by silica gel column chromatography (developing solvent; toluene, acetone) to obtain 214 mg of 4b (es-TThCBM) (yield 42%). Moreover, the obtained product was confirmed by high performance liquid chromatography and identified by ¹ H-NMR, ¹³ C-NMR, and IR.

<Analysis data>
IR (KBr) 2942, 1736 (C = O; s), 1707 (C = O; s), 1491, 1429, 1365, 1341, 1276, 1238, 1167, 1069, 1017, 747 cm ⁻¹ ; ¹ H-NMR (300 MHz; CDCl ₃ ) δ 8.04 (s, 1H), 7.70 (s, 1H), 4.42 (q, 2H, 7.2 Hz), 3.69 (s, 3H), 3.01 ( ¹³ C, t, 2H, 8.2 Hz), 2.59 (t, 2H, 7.4 Hz), 2.31-2.28 (m, 2H), 1.42 (t, 3H, 7.2 Hz); _{-NMR (75MHz, CDCl 3) δ173.31} (C = O), 162.47 (C = O), 147.64,146.95,145.52,145.27,144.95,144.85, 144.68, 144.61, 14 .29,143.81,143.06,143.01,142.13,141.06,140.86,138.71,138.28,138.24,135.80,125.69 (C H) , 124.77 ( C H), 79.28 (bridge head), 61.51 (O C H ₂ ), 51.73 (O C H ₃ ), 46.30 (bridge), 33.79 ( C H ₂ ), 33.63 ( C H ₂ ), 22.54 ( C H ₂ ), 14.40 ( C H ₃ ).

Example 4
A methanofullerene derivative 5b (2-BThCBM) in which Tp is benzothiophen-2-yl and X is 3- (methoxycarbonyl) propyl was synthesized as follows.

Was added 279mg of _{C 60} to 30mL pear shaped flask under a nitrogen atmosphere was dissolved in dry o- dichlorobenzene (ODCB) 19 mL, was sonicated for 60 minutes. In a 50 mL flask equipped with a stir bar, 200 mg of tosylhydrazone 5a and 29 mg of sodium methoxide were dissolved in 6 mL of dry pyridine in a nitrogen atmosphere and stirred for 15 minutes. Thereafter, an ODCB solution of C ₆₀ was added from the pear-shaped flask and heated at 100 ° C. for 4 hours. The reaction solution was separated and purified by silica gel column chromatography (developing solvent: toluene) to obtain 153 mg of 5b (2-BThCBM) (yield 39%). Moreover, the obtained product was confirmed by high performance liquid chromatography and identified by ¹ H-NMR, ¹³ C-NMR, and IR.

<Analysis data>
IR (KBr) 2941, 1736 (C = O; s), 1458, 1431, 1248, 1187, 1061, 833, 743, 723, 670 cm ^-1 ; ¹ H-NMR (300 MHz; CDCl ₃ ) δ 7.92-7 .87 (m, 2H), 7.72 (s, 1H), 7.47-7.39 (m, 2H), 3.67 (s, 3H), 3.02 (t, 2H, 8.0 Hz) ), 2.58 (t, 2H, 7.4 Hz), 2.32-2.23 (m, 2H); ¹³ C-NMR (75 MHz, CDCl ₃ ) δ 173.37 (C═O), 147.99 147.22, 145.66, 145.25, 145.17, 145.08, 144.84, 144.74, 144.68, 144.63, 144.56, 144.21, 143.82, 143 79, 143.13 143.09, 143.03, 142.97, 142.95, 142.22, 142.15, 141.02, 140.80, 140.15, 139.74, 138.73, 138.29, 138. 24,129.14 (C H), 125.04 ( C H), 124.67 (C H), 124.13 (C H), 122.45 (C H), 79.58 (bridge head), 51.67 (O C H ₃ ), 46.18 (bridge), 33.67 ( C H ₂ ), 33.45 ( C H ₂ ), 22.55 ( C H ₂ ).

(Example 5)
A methanofullerene derivative 6b (BiThCBM) in which Tp is 2,2′-bithienyl-5-yl and X is 3- (methoxycarbonyl) propyl was synthesized as follows.

The _{C 60} was added 500mg to 25mL pear-shaped flask, dissolved in dry o- dichlorobenzene (ODCB) 10 mL under argon, was sonicated for 60 minutes. In a 100 mL two-necked flask equipped with a Dimroth cooler and a stirrer, 500 mg of tosylhydrazone 6a and 40 mg of sodium methoxide were dissolved in 5 mL of dry pyridine in an argon atmosphere and stirred for 15 minutes. Thereafter, an ODCB solution of C ₆₀ was added from the pear-shaped flask and heated at 100 ° C. for 12 hours. The reaction solution was separated and purified by silica gel column chromatography (developing solvent; n-hexane 1: 3 toluene) to obtain 74.6 mg of 6b (BiThCBM) (yield 10.8%). Moreover, the obtained product was confirmed by high performance liquid chromatography and identified by ¹ H-NMR, ¹³ C-NMR, and IR.

<Analysis data>
IR (KBr) 1732 (C═O; s), 1541, 1507, 1428, 1186, 795, 689, 573, 553, 524 (s), 443, 416 cm ⁻¹ ; ¹ H-NMR (300 MHz; CDCl ₃ ) δ 7.39 (d, 1 H, 3.6 Hz), 7.27 (d, 1 H, 5.0 Hz), 7.18 (d, 1 H, 3.6 Hz), 7.09 (d, 1 H, 3.6 Hz) ), 7.05 (dd, 1H, 5.0 Hz, 3.6 Hz), 3.70 (s, 3H), 2.94 (t, 2H, 7.5 Hz), 2.58 (t, 2H, 7 .5 Hz), 2.26 (tt, 2H, 7.5 Hz); ¹³ C-NMR (75 MHz; CDCl ₃ ) δ 173.41 (C═O), 148.10, 147.76, 147.35, 147. 10, 145.55, 145.29, 145.2 145.25, 145.20, 148.08, 144.85, 144.70, 144.66, 144.62, 144.55, 144.29, 144.24, 143.82, 143.80, 143 .08, 143.05, 142.99, 142.97, 142.18, 142.14, 142.12, 141.02, 140.82, 140.69, 138.32, 138.28, 138.21 , 132.78 (C H), 132.46 (C H), 129.08 (C H), 128.21 (C H), 127.93 (C H), 124.85,124.17,79 .31 (bridge head), 51.72 (O C H ₃ ), 45.53 (bridge), 33.70 ( C H ₂ ), 33.63 ( C H ₂ ), 22.44 ( C H ₂ ) .

(Solubility test)
1 mg of a sample was weighed into a 10 mL volumetric flask with a lid using a precision electronic balance, dichloromethane was added to the marked line to obtain a standard solution, and the absorbance was measured in a wavelength region of 800 to 300 nm with an ultraviolet / visible absorptiometer. Each sample was then added to 2 mL of dichloromethane to supersaturation and centrifuged at 3500 rpm for 20 minutes. Thereafter, 1 mL of the supernatant solution was accurately weighed with a whole pipette and added to a 10 mL volumetric flask with a lid. When the measured absorbance exceeded 1, the comparison with the standard solution lacked accuracy. Therefore, the diluted solution was further diluted 5 times, compared with the standard solution, and the solubility was calculated and summarized in Table 1.

(Confirmation of compatibility)
(Example 6)
10 mg of fullerene derivative 4b and 15 mg of poly (3-hexylthiophene) (P3HT, manufactured by Aldrich) are dissolved in 1 mL of chlorobenzene, and about 50 μL is dropped onto a washed glass plate, followed by spin coating at 2000 rpm, 50 s. A thin film was formed from the derivative and P3HT. After vacuum drying, the surface of the thin film was observed with an atomic force microscope (5 μm × 5 μm). (FIG. 1 (b)). Moreover, the same thin film surface after heat-processing for 10 minutes at 140 degreeC was observed similarly (FIG.1 (e)).

(Example 7)
Using 5b as the fullerene derivative, surface observation was performed in the same manner as in Example 6 (5 μm × 5 μm). (FIG. 1 (a)). Moreover, the same thin film surface after heat-processing for 10 minutes at 140 degreeC was observed similarly (FIG.1 (d)).

(Comparative Example 2)
As a fullerene derivative, it was carried out using PCBM (synthesized according to documents J. C. Hummelen, B. W. Knight, F. LePeq, F. Wudl, J. Org. Chem., 60, 532 (1995)). Surface observation was performed in the same manner as in Example 6 (5 μm × 5 μm). (FIG. 1 (c)). Moreover, the same thin film surface after heat-processing for 10 minutes at 140 degreeC was observed similarly (FIG.1 (f)).

(Example 8)
(Measurement of photoelectric conversion characteristics)
Baytron P (manufactured by HC Stark) was spin-coated at 5000 rpm (50 s) on a glass substrate on which a cleaned ITO having a surface resistance of 15Ω / □ was formed by sputtering, and dried at 120 ° C. for 10 minutes. did. Using 1b as a methanofullerene derivative, it is mixed with poly (3-hexylthiophene) having a molecular weight of 17500 (manufactured by Aldrich) at a weight ratio of 0.8: 1.0, and dissolved in chlorobenzene so that the concentration of 1b is 1 wt%. As a result, both materials were completely dissolved into a uniform mixed solution. On the substrate, the mixed solution was spin-coated at 800 rpm (50 s) to form a photoelectric conversion layer. After the ITO / glass substrate on which the photoelectric conversion layer was formed was dried under nitrogen overnight, LiF was deposited at 0.5 nm and Al was deposited at 100 nm under a vacuum of about 10 ⁻⁵ torr to form a counter electrode to obtain a photoelectric conversion device. It was. The obtained photoelectric conversion device was sealed under nitrogen. A glass plate and an epoxy sealing material were used for sealing. The voltage-current characteristics of the sealed photoelectric conversion device were measured while irradiating 100 mW / cm ² simulated sunlight. The maximum efficiency was calculated from the voltage-current characteristics.

(Comparative Example 3)
The voltage-current characteristic of the photoelectric conversion device produced using 2b was measured in the same manner as in Example 8, and the maximum efficiency was calculated from the voltage-current characteristic.

(Comparative example 4) The voltage-current characteristic of the photoelectric conversion device produced using PCBM was measured similarly to Example 8, and the maximum efficiency was calculated from the voltage-current characteristic.

(Example 10)
[Durability test]
Using 1b as the methanofullerene derivative, the photoelectric conversion device prepared in Example 8 and the photoelectric conversion device similarly prepared using methanofullerene 2b were measured for changes in characteristics when left in a dark place at room temperature. Further, after about 20 hours, the photoelectric conversion characteristics were measured in the same manner as in Example 8. The result is shown in FIG. As shown in FIG. 2, when the initial characteristic was plotted as 1, it was confirmed that the durability of 1b was higher than 2b.

It is the photograph which observed the thin film surface with the atomic force microscope. It is a figure which shows a time-dependent change of a photoelectric conversion characteristic.

Claims (3)

A methanofullerene derivative represented by the general formula (I).
(In the general formula (I), FL represents a C60 fullerene, Tp represents 5-ethylthiophen-2-yl, benzothiophen-2-yl, or 5-carboethoxythienothiophen-2-yl; X represents a 3- (methoxycarbonyl) propyl group , FL, Tp and X are connected by a methylene group, and n represents 1 . A photoelectric conversion element comprising the methanofullerene derivative according to claim 1 as an electron transport material. The photoelectric conversion element according to claim 2 , comprising a conjugated polymer compound containing a thiophene ring as a hole transport material.