Method for producing fullerene derivatives and method for producing deposited products

Abstract

This fullerene derivative has a structure represented by formula (1) or formula (2) (wherein Ar represents a substituted or unsubstituted aromatic ring, * represents a carbon atom at a linkage point with respect to a fullerene core, X represents O, S, Se, or Te, and R represents an organic group).

Description

[Technical Field]

[0001] This disclosure relates to fullerene derivatives, and more particularly to fullerene derivatives, methods for producing fullerene derivatives, deposited materials, films, and electronic devices containing fullerene derivatives. [Background technology]

[0002] Organic electronic devices using organic materials are in use. In electronic devices such as semiconductors, it is almost essential to make the material into a thin film. Methods for making organic materials into thin films include vacuum deposition and solution coating. Solution coating is low-cost, but the reliability of the product is generally lower compared to vacuum deposition. Therefore, currently, vacuum deposition, which can more reliably manufacture highly reliable products, is generally adopted.

[0003] Fullerene (C 60 Fullerenes are attracting attention as one of the few organic materials that can be used as electron acceptors or electron transport materials (see, for example, Patent Document 1). By introducing various substituents to fullerenes, it is expected that fullerene derivatives with suitable properties to match the purpose and specifications can be developed. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2019-99570 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, while fullerenes themselves can be deposited by both vacuum deposition and solution coating, fullerene derivatives generally undergo thermal decomposition during vacuum deposition, making them only suitable for deposition by solution coating.

[0006] This disclosure is made in view of these challenges, and its purpose is to provide fullerene derivatives having excellent properties. [Means for solving the problem]

[0007] To solve the above problems, one aspect of this disclosure is a fullerene derivative. This fullerene derivative is of formula (1) [ka] (Here, Ar is a substituted or unsubstituted aromatic ring, * is a carbon atom at the linking point with the fullerene core, X is O, S, Se, or Te, and R is an organic group.) It has this structure.

[0008] Another aspect of the present disclosure is a method for producing a fullerene derivative. This method is for producing a fullerene derivative having the structure of formula (1), and comprises: a first step of preparing a Grignard reagent by reaction of an aryl halide with magnesium; a second step of synthesizing an arylhydrofullerene by reaction of the Grignard reagent with fullerene; a third step of synthesizing an arylfullerene dimer by oxidation of the arylhydrofullerene in the presence of a base; and a fourth step of synthesizing a fullerene derivative having the structure of formula (1) by oxidation of the arylfullerene dimer.

[0009] Another aspect of this disclosure is a fullerene derivative. This fullerene derivative is of formula (2) [ka] It has the structure (where Ar is an aromatic ring, * is a carbon atom at the linking point with the fullerene core, and X is O, S, Se, or Te).

[0010] A further aspect of the present disclosure is a method for producing a fullerene derivative. This method is for producing a fullerene derivative having the structure of formula (2), and comprises the step of oxidizing a fullerene derivative having the structure of formula (1).

[0011] Still another aspect of the present disclosure is a method for manufacturing a vapor deposition product. This method includes a step of heating a fullerene derivative having the structure of formula (1) or formula (2) to a sublimation temperature or higher and vapor depositing it.

[0012] Still another aspect of the present disclosure is a film. This film contains a fullerene derivative having the structure of formula (1) or formula (2).

[0013] Still another aspect of the present disclosure is an electron transport material. This electron transport material contains a fullerene derivative having the structure of formula (1) or formula (2).

[0014] Still another aspect of the present disclosure is an electronic device. This electronic device includes the above film or the above electron transport material.

Advantages of the Invention

[0015] According to the present disclosure, a fullerene derivative having excellent properties can be provided.

Brief Description of the Drawings

[0016] [Figure 1] It is a diagram schematically showing the configuration of an organic solar cell according to an embodiment. [Figure 2] It is a diagram showing the result of vacuum vapor deposition of a fullerene derivative according to an embodiment. [Figure 3] FIGS. 3(a) and 3(b) are diagrams respectively showing the results of thermogravimetric analysis of fullerene derivatives of formula (1a) and formula (2a). [Figure 4] FIGS. 4(a) and 4(b) are electron micrographs of thin films of a fullerene derivative of formula (2a) formed by the spin coating method and the vacuum vapor deposition method, respectively. [Figure 5] FIGS. 5(a) and 5(b) are diagrams respectively showing the current-voltage characteristics of a fullerene derivative of formula (2a) formed by the spin coating method and the vacuum vapor deposition method. [Figure 6]Figures 6(a) and 6(b) show the electron mobility of vacuum-deposited films of C60 and the fullerene derivative of formula (2a), respectively. [Figure 7] Figures 7(a), (b), and (c) show examples of organic solar cells. [Modes for carrying out the invention]

[0017] As embodiments of this disclosure, a vapor-depositable fullerene derivative and a precursor fullerene derivative thereof are disclosed. For details on the synthesis method and electrical properties of the precursor fullerene derivative, please refer to the paper published by the inventors ("Highly Selective and Scalable Fullerene-Cation-Mediated Synthesis Accessing Cyclo

[60] fullerenes with Five-Membered Carbon Ring and Their Application to Perovskite Solar Cells", Hao-Sheng Lin, Il Jeon, Yingqian Chen, Xiao-Yu Yang, Takafumi Nakagawa, Shigeo Maruyama, Sergei Manzhos, Yutaka Matsuo, Chemistry of Materials, 2019, 31, 20, 8432-8439, published September 11, 2019).

[0018] The fullerene derivatives of this disclosure have the structure of formula (1). The fullerene derivatives having the structure of formula (1) are precursors to the fullerene derivatives having the structure of formula (2) described later, but the fullerene derivatives having the structure of formula (1) themselves also have excellent properties and can be used as electron acceptors or electron transport materials for organic semiconductors. [ka]

[0019] Here, Ar is an arbitrary aromatic ring. Ar may be, for example, a benzene ring, a condensed ring such as naphthalene, anthracene, phenanthrene, pyrene, or a heterocyclic ring such as furan, thiophene, pyrrole, pyrazole, imidazole, pyridine, pyridazine, pyrimidine, pyrazine. Ar may have any substituent such as an alkyl group, heteroalkyl group, alkenyl group, heteroalkenyl group, alkynyl group, heteroalkynyl group, cycloalkyl group, heterocycloalkyl group, aryl group, heteroaryl group, alkoxy group, carbonyl group, carboxy group, cyano group, hydroxy group, thiol group, amino group, imino group, nitro group, halogen, or may have no substituent.

[0020] * is a carbon atom at the connection point with the fullerene core. The fullerene core may be, for example, C 60 、C 70 、C 72 、C 74 、C 76 、C 78 、C 80 、C 82 、C 84 、C 86 、C 88 、C 90 and so on.

[0021] X is O, S, Se, or Te. X may also be C, N, P, etc.

[0022] R is an arbitrary organic group. R may be, for example, an alkyl group, heteroalkyl group, alkenyl group, heteroalkenyl group, alkynyl group, heteroalkynyl group, cycloalkyl group, heterocycloalkyl group, aryl group, heteroaryl group, alkoxy group, carbonyl group, imino group, or a combination thereof.

[0023] A method for producing a fullerene derivative having the structure of formula (1) comprises: a first step of preparing a Grignard reagent by reaction of an aryl halide with magnesium; a second step of synthesizing an aryl hydrofullerene by reaction of the Grignard reagent with fullerene; a third step of synthesizing an aryl fullerene dimer by oxidation of the aryl hydrofullerene in the presence of a base; and a fourth step of synthesizing a fullerene derivative having the structure of formula (1) by oxidation of the aryl fullerene dimer.

[0024] In the second step, a solvent containing a planar organic substance such as 1,3-dimethyl-2-imidazolidinone (DMI) as a cosolvent may be used. This allows for highly selective generation of arylhydrofullerenes.

[0025] In the third step, a strong base with low nucleophilicity may be used as the base, such as a metal alkoxide like potassium tert-butoxide (t-BuOK), a metal amide like lithium diisopropylamide (LDA), potassium hexamethyldisilazide (KHMDS), or lithium-2,2,6,6-tetramethylpiperidide (LiTMP). N-bromosuccinimide (NBS) may also be used as the oxidizing agent.

[0026] In step 4, CuBr2 may be used as the oxidizing agent. In step 4, the aryl fullerene dimer may be heated in the presence of the oxidizing agent. The heating temperature may be, for example, 100°C, and the heating time may be, for example, 3 hours.

[0027] In each step, the product may be isolated and purified before proceeding to the next step, or the product may be proceeded to the next step without isolation or purification. For example, the aryl fullerene dimer produced in step 3 may be proceeded to step 4 without isolation, and a fullerene derivative having the structure of formula (1) may be synthesized by adding an oxidizing agent and heating it as is.

[0028] The vapor-depositable fullerene derivative of this disclosure has the structure of formula (2). [ka]

[0029] Here, Ar is any aromatic ring. For example, Ar may be a benzene ring, a condensed ring such as naphthalene, anthracene, phenanthrene, or pyrene, or a heterocycle such as furan, thiophene, pyrrole, pyrazole, imidazole, pyridine, pyridazine, pyrimidine, or pyrazine. Ar may have any substituents such as alkyl groups, heteroalkyl groups, alkenyl groups, heteroalkenyl groups, alkynyl groups, heteroalkynyl groups, cycloalkyl groups, heterocycloalkyl groups, aryl groups, heteroaryl groups, alkoxy groups, carbonyl groups, carboxyl groups, cyano groups, hydroxyl groups, thiol groups, amino groups, imino groups, nitro groups, halogens, etc., or it may not have any substituents.

[0030] * represents the carbon atom at the link point with the fullerene core. The fullerene core is C 60 , C 70 , C 72 , C 74 , C 76 , C 78 , C 80 , C 82 , C 84 , C 86 , C 88 , C 90 You can also use these.

[0031] X is O, S, Se, or Te. X may also be C, N, P, etc.

[0032] A method for producing a fullerene derivative having the structure of formula (2) includes the step of oxidizing the fullerene derivative of formula (1). In the oxidation step, CuBr2 may be used as the oxidizing agent. In the oxidation step, the fullerene derivative of formula (1) may be heated in the presence or absence of the oxidizing agent. The heating temperature may be, for example, 80 to 130°C, and the heating time may be, for example, 1 to 6 hours. The heating temperature may also be higher than the sublimation temperature of the fullerene derivative of formula (1). [ka]

[0033] Since the fourth step of the method for producing the fullerene derivative of formula (1) and the steps of the method for producing the fullerene derivative of formula (2) are both oxidation reactions, these steps may be performed consecutively. For example, CuBr2 may be added to the aryl fullerene dimer as an oxidizing agent, heated at 100°C for 3 hours to synthesize the fullerene derivative of formula (1), and then, without isolating the fullerene derivative of formula (1), the mixture may be further heated at 130°C for 6 hours to synthesize the fullerene derivative of formula (2). The heating temperature in the step of synthesizing the fullerene derivative of formula (2) may be higher than the heating temperature in the step of synthesizing the fullerene derivative of formula (1). Also, the heating time in the step of synthesizing the fullerene derivative of formula (2) may be longer than the heating time in the step of synthesizing the fullerene derivative of formula (1). The heating temperature when synthesizing the fullerene derivative of formula (2) after isolating and purifying the fullerene derivative of formula (1) may be lower than the heating temperature when synthesizing the fullerene derivative of formula (2) without isolating and purifying the fullerene derivative of formula (1), for example, it may be 100°C. The heating time when synthesizing the fullerene derivative of formula (2) after isolating and purifying the fullerene derivative of formula (1) may be shorter than the heating time when synthesizing the fullerene derivative of formula (2) without isolating and purifying the fullerene derivative of formula (1), for example, it may be 3 hours.

[0034] As shown in the examples below, fullerene derivatives having the structure of formula (2) can be deposited with almost no decomposition. Generally, when fullerene derivatives are deposited, many of them undergo thermal decomposition, and decomposition products such as fullerene cores are deposited. The fullerene derivative of formula (2) has a structure in which a stable five-membered carbon ring is bonded to a fullerene core, and since there are no relatively weak and easily decomposed CH bonds within the five-membered carbon ring, it is thought that it can be deposited without thermal decomposition even when heated to temperatures above the sublimation temperature.

[0035] As shown in the examples below, when a fullerene derivative with the structure of formula (1) is deposited, some of it is thermally decomposed into a fullerene core, but some of it is converted into a fullerene derivative having the structure of formula (2) and deposited. Therefore, even by depositing a fullerene derivative having the structure of formula (1), a deposited material containing a fullerene derivative having the structure of formula (2) can be produced.

[0036] The method for producing a deposited product containing the fullerene derivative of this disclosure comprises the step of heating a fullerene derivative having the structure of formula (2) to a sublimation temperature or higher to deposit it. This makes it possible to efficiently produce a high-purity deposited product of a fullerene derivative with excellent properties.

[0037] The method for producing a deposited product containing a fullerene derivative according to this disclosure comprises the step of heating a fullerene derivative having the structure of formula (1) to a sublimation temperature or higher to deposit it. This makes it possible to efficiently produce a deposited product containing a fullerene derivative with excellent properties.

[0038] The film of this disclosure comprises a fullerene derivative having the structure of formula (1) or formula (2). This film may be manufactured by any film deposition technique such as vacuum deposition or solution coating. This makes it possible to provide a thin film with excellent properties.

[0039] The electron transport material of this disclosure includes a fullerene derivative having the structure of formula (1) or formula (2). This makes it possible to provide an electron transport material with excellent properties.

[0040] The electronic device of this disclosure comprises a film or electron transport material containing a fullerene derivative having the structure of formula (1) or formula (2). The electronic device may be, for example, an organic semiconductor or an organic solar cell. This makes it possible to manufacture electronic devices with excellent properties at a high yield.

[0041] Figure 1 schematically shows the configuration of an organic solar cell according to an embodiment. The organic solar cell 1 comprises a cathode 2, an electron transport material layer 3, an electron acceptor / electron donor layer 4, a hole transport material layer 5, an anode 6, a cathode terminal 7, and an anode terminal 8. The cathode 2 and anode 6 are formed from electrically conductive metals, alloys, inorganic materials, organic materials, etc. The electron transport material layer 3 is a thin film containing a fullerene derivative having the structure of formula (1) or formula (2). The electron acceptor / electron donor layer 4 is a layer of a mixture of electron acceptors and electron donors. The hole transport material layer 5 is a thin film containing any hole transport material. These thin films may be formed by solution coating or by vapor deposition. In the case of solution coating, a solution of a fullerene derivative having the structure of formula (1) or formula (2) that functions as an electron acceptor molecule and an electron donor molecule may be coated onto a transparent electrode substrate such as indium tin oxide (ITO) to form the film. In the case of vapor deposition, a fullerene derivative having the structure of formula (1) or formula (2) and an electron donor molecule may be deposited separately onto a transparent electrode substrate, or they may be deposited by co-deposition. An organic solar cell 1 is manufactured by forming a cathode 2 on the substrate thus prepared by vapor deposition or the like, connecting a cathode terminal 7 to the cathode 2 and an anode terminal 8 to the anode 6.

[0042] When light such as sunlight strikes the organic solar cell 1, mainly electron donor molecules absorb the light and become excited, generating excitons. The generated excitons move to the electron acceptor / electron donor layer 4, where electrons flow from electron donor molecules to electron acceptor molecules, forming a charge-separated state. That is, the electron donor molecules transfer electrons to the electron acceptor molecules and become cations (holes), while the electron acceptor molecules accept electrons and become anions. In the hole transport material layer 5, holes flow to the anode 6, and in the electron transport material layer 3, electrons flow to the cathode 2, causing current to flow to the external circuit via the cathode terminal 7 and anode terminal 8.

[0043] [Examples] As examples of this disclosure, fullerene derivatives (1a) to (1e) having the structure of formula (1) and fullerene derivatives (2a) to (2e) having the structure of formula (2) were synthesized. Unless otherwise specified, all reactions were carried out using a dry solvent in heated and dried glass products under an argon atmosphere using standard vacuum line technology. [ka] [ka]

[0044] [Synthesis of aryl bromides] Methanol (20.0 mL) was slowly added to sodium (517.5 mg, 22.5 mmol) at 0°C. After the sodium had completely reacted with methanol, benzyl bromide (15 mmol) with various functional groups was added to the reaction mixture and left at room temperature for 5 hours. Subsequently, the reaction suspension was quenched with 10 mL of water and extracted with dichloromethane (10 × 3 mL). The organic layer was dried over magnesium sulfate, and the solvent was removed under reduced pressure to obtain the crude product. The product was purified by silica gel column chromatography using n-hexane / ethyl acetate (10 / 1, v / v) as the eluent to obtain a colorless oily product.

[0045] [Step 1: Synthesis of Grignard Reagents] Under an argon atmosphere at 0°C, a trace amount of iodine was used as an initiator to slowly add a 10.0 mL solution of aryl bromide (10 mmol) in anhydrous tetrahydrofuran (THF) to polished magnesium powder (360.0 mg, 15 mmol) dropwise. After vigorous stirring for 1 hour, the prepared Grignard solution was transferred to a Schlenk bottle by the Schlenk operation and stored. Before use, the concentration was confirmed by anhydrous titration under an argon atmosphere using a trace amount of 1,10-phenanthroline as the indicator and menthol as the titrant.

[0046] [Step 2: Aryl hydrofullerene (ArC 60 [Synthesis of H] C 60 (300.0 mg, 0.417 mmol) was dissolved in anhydrous o-dichlorobenzene (o-DCB) (50.0 mL) containing 1,3-dimethyl-2-imidazolidinone (DMI) (1.4 mL, 12.5 mmol) as a cosolvent. Subsequently, the Grignard reagent synthesized above was added to the solution under an argon atmosphere at 25°C. After stirring for 15 minutes, acetic acid (0.1 mL, 1.75 mmol) was added to quench the reaction, and the solvent was evaporated under vacuum. The residue was dissolved in CS2 and purified using a silica gel column with CS2 / dichloromethane as the eluent to obtain the product.

[0047] [Step 3: Aryl fullerene dimer (ArC 60 -C 60 [Ar synthesis] The monoadduct (0.048 mmol) synthesized in step 2 was dissolved in 5.0 mL of anhydrous o-DCB solution. Then, t-BuOK THF solution (58 μL, 0.058 mmol, 1 M) was added, and the mixture was vigorously stirred at room temperature under an argon atmosphere for 15 minutes. Next, N-bromosuccinimide (NBS) (34.2 mg, 0.192 mmol) was added. The reaction mixture was vigorously stirred at room temperature under an argon atmosphere for 12 hours. Then, the resulting brown suspension was quenched with 1.0 mL of water, and the product was precipitated by adding an excess amount of methanol. Finally, the aryl

[60] fullerene dimer was recovered as a residue by filtration without the need for further purification.

[0048] [Step 4: Synthesis of the fullerene derivative of formula (1)] 0.030 mmol of aryl

[60] fullerene dimer was dissolved in 10.0 mL of anhydrous o-DCB solution containing CuBr2 (26.8 mg, 0.120 mmol) as an oxidizing agent. After vigorous stirring at 100°C for 3 hours, the resulting mixture was filtered directly through a silica gel plug to remove insoluble salts, and then the solvent was removed by evaporation under vacuum. Next, the residue was purified using a silica gel column with CS2 as the eluent to obtain the product. The yields of fullerene derivatives (1a) to (1d) were 93%, 90%, 86%, and 73%, respectively.

[0049] [Synthesis of fullerene derivatives of formula (2)] The fullerene derivative of formula (1) was dissolved in 5.0 mL of anhydrous o-DCB solution containing CuBr2 (4.0 eq.) as an oxidizing agent. After vigorous stirring at 130°C for 6 hours, the resulting mixture was purified to obtain the product. The yields of fullerene derivatives (2a) to (2d) were 94%, 92%, 90%, and 82%, respectively.

[0050] [Properties of fullerene derivatives] Figure 2 shows the results of vacuum deposition of fullerene derivatives of formulas (1) and (2). Figure 2(a) is a high-performance liquid chromatograph (HPLC) chart of the deposition source before deposition. Figure 2(b) is an HPLC chart of the deposited material and residue after deposition. The deposited material with the fullerene derivative of formula (2) shows the same peak as the fullerene derivative of formula (2) before deposition, and there are almost no peaks originating from other substances. Therefore, it was shown that the fullerene derivative of formula (2) can be deposited almost 100% without thermal decomposition.

[0051] The deposited material containing the fullerene derivative of formula (1) shows numerous peaks, including a large peak at the same position as the fullerene derivative of formula (2). Furthermore, the residue remaining after the deposition of the fullerene derivative of formula (1) also shows a large peak at the same position as the fullerene derivative of formula (2). Therefore, it was shown that the fullerene derivative of formula (2) is produced by heating the fullerene derivative of formula (1) to a temperature above its sublimation temperature, and that a deposited material containing the fullerene derivative of formula (2) is produced by depositing the fullerene derivative of formula (1).

[0052] Figures 3(a) and 3(b) show the results of thermogravimetric analysis of the fullerene derivatives of formula (1a) and formula (2a), respectively. The samples were heated under a nitrogen atmosphere and the change in mass was measured. The fullerene derivative of formula (1a) began to decompose at around 250°C, while the fullerene derivative of formula (2a) remained stable up to around 400°C.

[0053] Figures 4(a) and 4(b) show electron microscope images of thin films of the fullerene derivative of formula (2a) deposited by spin coating and vacuum deposition, respectively. The thin film deposited by vacuum deposition was a homogeneous amorphous thin film. The thin film deposited by spin coating was a crystalline thin film. Figures 5(a) and 5(b) show the current-voltage characteristics of the fullerene derivative of formula (2a) deposited by spin coating and vacuum deposition, respectively. The thin film deposited by vacuum deposition had less charge trapping than the thin film deposited by spin coating. From the above, it is possible to produce organic thin films with better properties by depositing the fullerene derivative of formula (2a) by vacuum deposition.

[0054] Figures 6(a) and 6(b) are, respectively, C 60 The electron mobility of vacuum-deposited films of the fullerene derivative of formula (2a) is shown. The electron mobility of each vacuum-deposited film was measured by the Space Charge Limited Current (SCLC) method. The electron mobility of the vacuum-deposited film of the fullerene derivative of formula (2a) is C 60 The electron mobility was equivalent to that of the vacuum-deposited film.

[0055] Figures 7(a), 7(b), and 7(c) show examples of organic solar cells. Figure 7(a) shows the structure of the organic solar cell according to the example. A fullerene derivative of formula (2a) was vacuum deposited on an ITO electrode as an electron transport layer, and then a perovskite compound, methylammonium lead iodide (MAPbI3), was deposited on top of it. Furthermore, spiro-OMeTAD was deposited as a hole transport layer, and an Au electrode was formed to fabricate an organic solar cell. In addition, as a comparative example, C was used as the electron transport layer. 60 Organic solar cells were fabricated by vacuum deposition. Figure 7(b) shows the output characteristics of the organic solar cell of the example, and Figure 7(c) shows the output characteristics of the organic solar cell of the comparative example. Table 1 shows the open-circuit voltage V of the organic solar cells of the example and comparative example. OC , short-circuit current density J SCThe values ​​for the shape factor FF and the energy conversion efficiency PCE are shown. The energy conversion efficiency of the organic solar cell in the example was 13.5%, which was higher than the 10.5% of the comparative example. [Table 1]

[0056] The present disclosure has been explained above based on examples. These examples are illustrative, and it will be understood by those skilled in the art that various modifications are possible in combinations of their components and processing processes, and that such modifications are also within the scope of the present disclosure. [Industrial applicability]

[0057] This disclosure is applicable to fullerene derivatives, methods for producing fullerene derivatives, deposited materials containing fullerene derivatives, films, and electronic devices. [Explanation of symbols]

[0058] 1. Organic solar cell, 2. Cathode, 3. Electron transport material layer, 4. Electron acceptor / electron donor layer, 5. Hole transport material layer, 6. Anode, 7. Cathode terminal, 8. Anode terminal.

Claims

【Request Item 1】 【Chemistry 1】 (Here, * represents the carbon atom at the linkage point with the fullerene core.) A method for producing a fullerene derivative having any of the following structures: 【Chemistry 2】 (Here, * represents the carbon atom at the linkage point with the fullerene core.) A method comprising the step of oxidizing a fullerene derivative having any of the following structures.

2. A step of producing a fullerene derivative by the method described in claim 1, The steps include heating the obtained fullerene derivative above the sublimation temperature to deposit it, A method for producing a deposited material.

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