Non-fused ring electron acceptor containing asymmetric side chain and preparation method and application thereof

Abstract

The embodiment of the invention provides a non-fused ring electron acceptor containing an asymmetric side chain and a preparation method and application thereof, the non-fused ring electron acceptor containing the asymmetric side chain has the following structure: # imgabs0 #, R1, R2 and R3 comprise any one of branched chain type, straight chain type or cyclic alkyl containing 1-20 carbon atoms, and A is a strong electron withdrawing functional group. According to the non-fused ring electron acceptor containing the asymmetric side chain and the preparation method and application thereof provided by the embodiment of the invention, the aryl alkylamine asymmetric structure is introduced as the side chain, so that the molecular planarity of the non-fused ring electron acceptor can be maintained, and the molecular accumulation and solubility can be conveniently regulated and controlled. Therefore, the non-fused ring electron acceptor has the advantages of good solubility, strong crystallization, high mobility, good compatibility and easiness in processing into a film; when the electron acceptor material is used for preparing an organic solar cell, the photoelectric conversion efficiency of the device can reach 16%.

Description

Technical Field

[0001] The present application belongs to the field of organic photovoltaic technology, and in particular relates to a non-condensed ring electron acceptor containing an asymmetric side chain, and a preparation method and application thereof. Background Art

[0002] Organic solar cells are a promising renewable energy device that have attracted widespread attention over the past three decades because of their advantages such as lightness, flexibility and ease of mass production. Thanks to the rapid development of active layer materials and device engineering, especially the emergence of condensed ring electron acceptors, the power conversion efficiency (PCE) of organic solar cells has increased to more than 20%, approaching the threshold of commercialization. However, almost all high-performance organic photovoltaic materials currently have problems such as cumbersome synthesis steps, complex purification processes and low yields, which leads to high production costs and time costs for the active layer, hindering large-scale production.

[0003] To overcome the above limitations, non-condensed ring electron acceptors use conjugated units connected by single bonds to replace the central condensed ring structure of condensed ring electron acceptors, which can effectively avoid complex cyclization reactions in the synthesis steps. In addition, the conjugated units in non-condensed ring electron acceptors can also use intramolecular non-covalent interactions and steric hindrance to maintain molecular planarity. Therefore, non-condensed ring electron acceptors have simpler and lower-cost synthesis steps and photovoltaic performance similar to that of condensed ring electron acceptors. In addition, the modular molecular structure characteristics enable non-condensed ring electron acceptors to more flexibly and finely regulate molecular aggregation behavior through side chain engineering, which helps to improve their device performance. At present, the relevant technology introduces diphenylamine side chains into the central core of non-condensed ring molecules to inhibit excessive molecular aggregation. The solar cell device prepared by the synthesized non-condensed ring electron acceptor achieves a PCE of 15.44%. Although this type of diphenylamine structure can maintain the overall planarity of the molecule and inhibit excessive molecular aggregation by limiting the single bond rotation of the molecule through steric hindrance, for side chain engineering, the chemical modification sites of the structure are limited, and the degree of molecular aggregation that can be adjusted is limited. It is not enough to meet the current commercial needs. In order to further improve the photoelectric conversion efficiency of low-cost organic solar cells based on non-condensed ring electron acceptors, new molecular designs are needed to develop new non-condensed ring electron acceptors to further improve the photovoltaic performance of organic solar cells. Summary of the invention

[0004] In view of this, the embodiments of the present application provide a non-condensed ring electron acceptor containing an asymmetric side chain and a preparation method and application thereof, so as to solve the technical problem of low photoelectric conversion efficiency of the device when the existing electron acceptor materials are used in organic solar cells.

[0005] In a first aspect, the embodiments of the present application provide a non-condensed ring electron acceptor containing an asymmetric side chain, having the structure shown below:

[0006]

[0007] Wherein, R1, R2 and R3 include any one of branched, linear or cyclic alkyl groups containing 1 to 20 carbon atoms, and A is a strong electron-withdrawing functional group.

[0008] In some embodiments, the R2 and the R3 further include a cyclic alkoxy group containing 1 to 20 carbon atoms.

[0009] In some embodiments, the R3 further comprises a cyclic aromatic group containing 1 to 20 carbon atoms.

[0010] In some embodiments, A is any one of the following structural formulas:

[0011]

[0012] Here, R4 is any one of a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a carbonyl group, an ester group or a cyano group.

[0013] In a second aspect, the present invention provides a method for preparing a non-condensed ring electron acceptor containing an asymmetric side chain, comprising the following steps:

[0014] Compound 1 is subjected to an alkylation reaction with potassium carbonate to obtain compound 2;

[0015] The compound 2 is subjected to a coupling reaction with 3,6-dibromothiophene [3,2-B]thiophene to obtain compound 3;

[0016] The compound 3 is subjected to bromination reaction with N-bromosuccinimide (NBS) to obtain compound 4;

[0017] The compound 4 is coupled with the compound 5 to obtain the compound 6;

[0018] Compound 7 is obtained by subjecting compound 6 to a first reaction;

[0019] The compound 7 is subjected to a second reaction to obtain the non-condensed ring electron acceptor containing an asymmetric side chain as claimed in any one of claims 1 to 4;

[0020] Wherein, the structural formula of the compound 1 is: The structural formula of the compound 2 is: The structural formula of the compound 3 is: The structural formula of the compound 4 is: The structural formula of the compound 5 is: The structural formula of the compound 6 is:

[0021] The structural formula of the compound 7 is: The R5 is an alkyl group.

[0022] In some embodiments, the step of obtaining compound 7 by a first reaction of compound 6 comprises:

[0023] The first reaction is a Vilsmeier-Haack reaction, wherein the compound 6 reacts with N,N-dimethylformamide under the action of phosphorus oxychloride to generate the compound 7, the reaction temperature is 0°C ± 2°C, and the reaction time is 1h to 3h;

[0024] And / or, the compound 7 is subjected to a second reaction to obtain the non-condensed ring electron acceptor containing an asymmetric side chain, comprising:

[0025] The second reaction is a Knoevenagel reaction, wherein the compound 7 is dehydrated and condensed with 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile under the action of an alkaline catalyst to obtain the non-condensed ring electron acceptor containing an asymmetric side chain, the reaction temperature is 60°C to 80°C, and the reaction time is 1h to 3h.

[0026] In some embodiments, the reactions in all the steps are carried out under the protection of inert gas.

[0027] In a second aspect, an embodiment of the present application provides an organic solar cell, comprising a substrate, an anode, a hole transport layer, an active layer, an electron transport layer and a cathode arranged in sequence, wherein the active layer comprises a non-condensed ring electron acceptor containing an asymmetric side chain as described in any one of claims 1 to 4 and / or a non-condensed ring electron acceptor containing an asymmetric side chain prepared by the method described in any one of claims 5 to 7.

[0028] In some embodiments, the active layer further comprises an electron donor material matching the non-condensed ring electron acceptor containing an asymmetric side chain, wherein the electron donor material is any one of PM6, D18, PBDB-T, and PTB7-Th.

[0029] In some embodiments, the mass ratio of the non-condensed ring electron acceptor containing an asymmetric side chain to the electron donor material is 0.5 to 1:2.

[0030] The non-condensed ring electron acceptor containing asymmetric side chains provided in the embodiments of the present application, and its preparation method and application, by introducing an asymmetric side chain to replace the original diphenylamine structure, the newly introduced arylalkylamine structure provides a more flexible control site for the side chain engineering under the premise of maintaining the original molecular planarity, which is conducive to achieving more refined molecular aggregation control, thereby improving the power conversion efficiency of organic solar cells based on non-condensed ring electron acceptors. Specifically, its alkyl side chain has small steric hindrance, which can effectively improve the molecular planarity and enhance the intermolecular interaction, so that the non-condensed ring small molecule acceptor has better crystallinity and obtains a higher electron mobility. In addition, the asymmetric side chain structure gives the small molecule acceptor a richer structural property adjustability, which can effectively regulate its interfacial energy and obtain suitable compatibility with the electron donor material. Therefore, the active layer of the non-condensed ring electron acceptor molecule based on the asymmetric side chain of arylalkylamine can simultaneously achieve orderly molecular stacking and ideal phase separation morphology, and is applied to the light capture layer of organic solar cells, which is conducive to exciton dissociation and charge transfer, thereby achieving excellent photoelectric conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 is the chemical structural formula of a non-condensed ring electron acceptor containing an asymmetric side chain provided in the examples of the present application;

[0033] Figure 2 is the chemical structural formula of the non-condensed ring electron acceptor containing an asymmetric side chain prepared in Example 1 of the present application;

[0034] Figure 3 is the chemical structural formula of the non-condensed ring electron acceptor containing an asymmetric side chain prepared in Example 2 of the present application;

[0035] Figure 4 is the hydrogen nuclear magnetic resonance spectrum of the non-condensed ring electron acceptor containing an asymmetric side chain prepared in Example 1 of the present application;

[0036] Figure 5 is the UV-visible absorption spectrum of the non-condensed ring electron acceptor containing an asymmetric side chain prepared in Example 1 of the present application;

[0037] Figure 6 It is a current-voltage curve diagram of the organic solar cell in the application example of the present application under simulated sunlight. DETAILED DESCRIPTION

[0038] In the following description, specific details such as specific system structures, technologies, etc. are proposed for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present application. However, it should be clear to those skilled in the art that the embodiments of the present application can also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from hindering the description of the embodiments of the present application.

[0039] It should also be understood that the term “and / or” used in the description of the embodiments of the present application and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0040] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0041] It should be understood that the orientation or position relationship indicated by terms such as "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present application.

[0042] In addition, in the description of the embodiments of the present application and the appended claims, the terms "first", "second", "third", etc. are only used to distinguish the descriptions and cannot be understood as indicating or implying relative importance.

[0043] References to "some embodiments" or "some embodiments" etc. described in the specification of the embodiments of the present application mean that one or more embodiments of the embodiments of the present application include specific features, structures or characteristics described in conjunction with the embodiment. Thus, the statements "in some embodiments", "in some other embodiments", "in some other embodiments", etc. that appear in the different parts of this specification do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized in other ways. "Multiple" refers to two or more.

[0044] In a first aspect, the present invention provides a non-condensed ring electron acceptor containing an asymmetric side chain, such as Figure 1 As shown, it has the following structure:

[0045]

[0046] Wherein, R1, R2 and R3 include any one of branched, linear or cyclic alkyl groups containing 1 to 20 carbon atoms, and A is a strong electron-withdrawing functional group.

[0047] The non-condensed ring electron acceptor containing asymmetric side chains provided in the embodiments of the present application has an asymmetric side chain of an aryl alkylamine structure, wherein the alkyl side chain has a small steric hindrance, which can effectively improve the molecular planarity of the electron acceptor and enhance the intermolecular interaction, thereby making the non-condensed ring electron acceptor have better crystallinity and obtain a higher electron mobility. In addition, the asymmetric side chain structure gives the non-condensed ring electron acceptor a richer structural property adjustability, which can effectively regulate its interfacial energy and obtain suitable compatibility with the electron donor material. Therefore, the active layer of the non-condensed ring electron acceptor based on the asymmetric side chain of the aryl alkylamine can simultaneously achieve orderly molecular stacking and ideal phase separation morphology, and when applied to organic solar cells, it is beneficial to exciton dissociation and charge transfer, thereby obtaining excellent photoelectric conversion efficiency.

[0048] In the application, A is a strong electron-withdrawing functional group, which helps to improve the electron acceptance capacity of the entire electron acceptor molecule, thereby affecting the electrical properties of the material. Strong electron-withdrawing groups include but are not limited to cyano, nitro), ester groups, etc. Electron-withdrawing functional groups refer to those functional groups that can attract electrons from adjacent atoms or groups. These functional groups cause the electron cloud to shift toward them through inductive effects or conjugation effects, thereby affecting the electron distribution of the molecule. Common electron-withdrawing functional groups include but are not limited to: ester groups, ketone groups, cyano groups, and fluorine atoms. These functional groups usually reduce the electron density on adjacent carbon atoms, making some parts of the molecule more electrophilic (that is, more susceptible to attack by nucleophiles). Strong electron-withdrawing functional groups refer to those functional groups with stronger electron-withdrawing ability. They can not only significantly reduce the electron density on adjacent carbon atoms, but also affect the electron distribution at a greater distance. This is usually because these functional groups have a higher negative charge density or stronger electronegativity. Some typical strong electron-withdrawing functional groups include: Cyano: A very strong electron-withdrawing group because it contains a triple bond that can effectively attract electrons. Nitro group: Due to the presence of nitrogen-oxygen double bond, it becomes a very strong electron-withdrawing group. Fluorine atom: Although small in size, it is a very strong electron-withdrawing group due to the high electronegativity of fluorine. Sulfonic acid group: Through the high electronegativity of oxygen atom and the effect of sulfur-oxygen double bond, it becomes a strong electron-withdrawing group.

[0049] In some embodiments, R1, R2 and R3 include branched alkyl groups containing 1 to 20 carbon atoms. In other embodiments, R1, R2 and R3 include straight-chain alkyl groups containing 1 to 20 carbon atoms. In other embodiments, R1, R2 and R3 include cyclic alkyl groups containing 1 to 20 carbon atoms. Preferably, R1 is a straight-chain alkyl group or a branched alkyl group containing 4 to 10 carbon atoms. Such a substitution pattern helps to adjust the spatial conformation and solubility of the molecule, thereby affecting the processability and physical properties of the material. Preferably, R2 is a straight-chain alkyl group or a branched alkyl group containing 2 to 8 carbon atoms. It can increase the interaction force between molecules and change the polarity of the molecule. Preferably, R3 is a straight-chain alkyl group or a branched alkyl group containing 6 to 12 carbon atoms. This can further adjust the energy level structure and optical properties of the molecule, which is crucial for the development of high-performance organic optoelectronic devices.

[0050] In some embodiments, R2 and R3 further include a cyclic alkoxy group containing 1 to 20 carbon atoms. In other embodiments, R3 further includes a cyclic aryl group containing 1 to 20 carbon atoms. The newly introduced arylalkylamine structure provides a more flexible control site for side chain engineering while maintaining the original molecular planarity, which is conducive to achieving more refined molecular aggregation control.

[0051] In some embodiments, A is any one of the following structural formulas:

[0052]

[0053] Wherein, R4 is any one of a hydrogen atom, a halogen atom, an alkyl group containing 1 to 20 carbon atoms, an alkoxy group containing 1 to 20 carbon atoms, a carbonyl group, an ester group or a cyano group. The cyano group is a very strong electron-withdrawing group, which has high electronegativity and stability, and can enhance the electron-withdrawing ability of the molecule and improve the electrical properties of the material. The nitro group is also a strong electron-withdrawing group. It effectively disperses the negative charge through the resonance structure, thereby enhancing the electron-withdrawing ability. Halogen substituents, halogen substituents include fluorine (-F), chlorine (-Cl), bromine (-Br) and iodine (-I). The electron-withdrawing ability of these groups decreases with increasing atomic number, among which fluorine is the strongest electron-withdrawing group. Halogen substituents can significantly affect the polarity and solubility of the molecule. The carbonyl group is a medium-strength electron-withdrawing group. The ester group is a medium-strength electron-withdrawing group. The alkyl group can be a straight-chain, branched or cyclic alkyl group containing 1 to 20 carbon atoms. Although the alkyl group itself is not an electron-withdrawing group, when combined with other electron-withdrawing groups, it can affect the overall properties of the molecule. The alkoxy group can be a straight chain, branched chain or cyclic alkoxy group containing 1 to 20 carbon atoms. The alkoxy group usually has a moderate electron-withdrawing ability and can enhance the polarity and solubility of the molecule. It should be noted that the dotted line in the above structural formula is the connection point.

[0054] The present application also provides a method for preparing a non-condensed ring electron acceptor containing an asymmetric side chain, comprising the following steps:

[0055] S10, subjecting compound 1 to an alkylation reaction with potassium carbonate to obtain compound 2;

[0056] S20, coupling compound 2 with 3,6-dibromothiophene [3,2-B]thiophene to obtain compound 3;

[0057] S30, subjecting the compound 3 to a bromination reaction with N-bromosuccinimide (NBS) to obtain a compound 4;

[0058] S40, coupling reaction of the compound 4 and the compound 5 to obtain the compound 6;

[0059] S50, subjecting the compound 6 to a first reaction to obtain a compound 7;

[0060] S60, subjecting the compound 7 to a second reaction to obtain the non-condensed ring electron acceptor containing an asymmetric side chain as described in the first aspect;

[0061] Wherein, the structural formula of compound 1 is: The structural formula of compound 2 is: The structural formula of compound 3 is: The structural formula of compound 4 is: The structural formula of compound 5 is: The structural formula of compound 6 is:

[0062] The structural formula of compound 7 is:

[0063] R5 is an alkyl group. The preparation method provided in the embodiments of the present application has relatively mild reaction conditions, simpler synthesis steps, and low synthesis cost, which is conducive to large-scale production.

[0064] In the application, R5 is a branched or branched alkyl group, and R5 includes but is not limited to methane, ethyl, propane, n-butane, isobutane, etc.

[0065] In step S10, compound 1 is mixed with potassium carbonate for alkylation reaction, specifically comprising mixing compound 1, potassium carbonate and 1-bromooctane, adding anhydrous N, N-dimethylformamide, placing the reaction bottle in an oil bath under nitrogen protection, heating to 120°C, and stirring at this temperature for 8 hours. After the reaction is completed, the reaction bottle is taken out of the oil bath and naturally cooled to room temperature. After the reaction is completed, post-treatment is also included, specifically including adding an appropriate amount of water to the reaction mixture, quenching the reaction, extraction and separation: using a separatory funnel, extracting the reaction mixture with petroleum ether 3 times, each time using the same volume of petroleum ether. Collect the organic layer and combine the extracts. The combined organic layer is transferred to a rotary evaporator, concentrated under reduced pressure, and the solvent is removed to obtain a crude product. The crude product is purified by column chromatography, using silica gel as the stationary phase and dichloromethane: petroleum ether (1:2) as the eluent. Reaction principle: The active hydrogen (such as hydroxyl, amino, etc.) in compound 1 is deprotonated under the action of potassium carbonate to generate the corresponding anion. 1-Bromooctane is used as an alkylating agent to undergo a nucleophilic substitution reaction with the generated anion to generate the alkylated compound 2.

[0066] In step S20, compound 2 is coupled with 3,6-dibromothiophene [3,2-B] thiophene to obtain compound 3, specifically comprising: mixing compound 2, 3,6-dibromothiophene [3,2-B] thiophene and sodium tert-butoxide, adding o-xylene, adding tetrakis (triphenylphosphine) palladium and tri-tert-butylphosphine under nitrogen protection, heating and stirring in an oil bath, heating to 145 ° C, and reflux reaction at this temperature for 36 hours. After the reaction is completed, the reaction bottle is taken out of the oil bath and naturally cooled to room temperature. An appropriate amount of water is added to the reaction mixture to quench the reaction. Using a separatory funnel, the reaction mixture is extracted with dichloromethane 3 times, each time using the same volume of dichloromethane. Collect the organic layer and combine the extracts. The combined organic layer is transferred to a rotary evaporator, concentrated under reduced pressure, and the solvent is removed to obtain a crude product. The crude product is purified by column chromatography, using silica gel as the stationary phase and dichloromethane: petroleum ether (1:10) as the eluent. Reaction principle: The active hydrogen or functional group in compound 2 undergoes a coupling reaction with the bromine atom in 3,6-dibromothiophene [3,2-B]thiophene under the action of catalysts (Pd(PPh3)4 and P(t-Bu)3) and base (NaO(t-Bu)) to generate compound 3. Reaction conditions: High temperature (145°C) and long time (36 hours) help to increase the reaction rate and conversion rate. O-xylene as a solvent can dissolve all reactants, and nitrogen protection prevents oxidation and side reactions. Catalyst: Pd(PPh3)4 is a commonly used palladium catalyst used to promote carbon-carbon coupling reactions; P(t-Bu)3 as a co-catalyst can improve the selectivity and efficiency of the reaction.

[0067] In step S30, compound 3 is brominated with N-bromosuccinimide (NBS) to obtain compound 4, specifically comprising: mixing compound 3 and anhydrous DMF, adding N-bromosuccinimide under nitrogen protection, placing the reaction system under light-proof conditions, and stirring at room temperature for 6 hours. After the reaction is completed, the reaction bottle is taken out from the light-proof conditions and naturally cooled to room temperature. Add an appropriate amount of water to the reaction mixture to quench the reaction. Use a separatory funnel to extract the reaction mixture 3 times with petroleum ether, using the same volume of petroleum ether each time. Collect the organic layer and combine the extracts. Concentrate and purify: The combined organic layer is transferred to a rotary evaporator, concentrated under reduced pressure, and the solvent is removed to obtain a crude product. The crude product is purified by column chromatography, using silica gel as a stationary phase and petroleum ether as an eluent. Reaction principle: a specific position in compound 3 undergoes a bromination reaction under the action of N-bromosuccinimide (NBS) to generate compound 4.

[0068] In step S40, compound 4 and compound 5 undergo a coupling reaction to obtain compound 6, specifically including adding a palladium catalyst to catalyze the coupling reaction. Reaction principle: The bromine atom in compound 4 undergoes a coupling reaction with the active hydrogen or other functional groups in compound 5 under the action of a palladium catalyst (Pd(PPh3)4) to generate compound 6.

[0069] In step S50, compound 6 is reacted to obtain compound 7. In the application, the first reaction is a Vilsmeier-Haack reaction. Specifically, it includes preparing a Vilsmeier reagent: under nitrogen protection, phosphorus oxychloride and N,N-dimethylformamide are mixed, the reaction bottle is placed in an ice bath, the temperature is maintained at 0°C, and stirred at this temperature for 2 hours. The dissolved compound 6 solution is slowly dripped into the above-mentioned Vilsmeier reagent, and continued to stir at 0°C for 30 minutes. The reaction mixture is taken out of the ice bath, heated to 80°C, and stirred at this temperature for 12 hours. The reaction principle is: the Vilsmeier-Haack reaction is a reaction in which an imine salt intermediate is generated through a Vilsmeier reagent (a mixture of DMF and POCl3), and then a formal acylation reaction occurs with an aromatic ring to generate an aldehyde or ketone. In this process, a specific position in compound 6 is converted into an aldehyde group or a ketone group. After the reaction is completed, it also includes cooling and quenching: the reaction bottle is taken out of the oil bath and naturally cooled to room temperature. A saturated sodium acetate solution is added to the reaction mixture and stirred for 1 hour to quench the reaction. Extraction and separation: Using a separatory funnel, extract the reaction mixture three times with dichloromethane, using the same volume of dichloromethane each time. Collect the organic layer and combine the extracts. Concentration and purification: Transfer the combined organic layer to a rotary evaporator and concentrate under reduced pressure to remove the solvent to obtain a crude product. The crude product is purified by column chromatography using silica gel as the stationary phase and dichloromethane: petroleum ether (1:1) as the eluent.

[0070] In step S60, compound 7 is subjected to a second reaction to obtain a non-condensed ring electron acceptor containing an asymmetric side chain as described in the first aspect, wherein the second reaction is a Knoevenagel reaction. Specifically, the reactants are mixed first, compound 7 and 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile are added; a solvent and a catalyst are added: chloroform and 0 pyridine are added under nitrogen protection. Pyridine acts as a base to promote the reaction. Reaction principle: The Knoevenagel reaction is a condensation reaction of an aldehyde or ketone with an active methylene compound (such as malononitrile) under alkaline conditions to generate an α,β-unsaturated compound. In this process, the aldehyde group or ketone group in compound 7 undergoes a condensation reaction with 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile to generate an X1 acceptor material. Reaction conditions: Temperature (60℃~80℃) and time (1h~3h) help to improve the reaction rate and conversion rate. Chloroform as a solvent can dissolve all reactants, and nitrogen protection prevents oxidation and side reactions. Catalyst: Pyridine as a base promotes the deprotonation of aldehyde or ketone groups to generate carbon anions, which then react with malononitrile to undergo condensation reaction.

[0071] In some embodiments, all of the above steps are performed under an inert gas atmosphere. Specifically, they are performed under a nitrogen atmosphere. During each step of the reaction, the reaction system is pumped and charged with nitrogen three times to remove oxygen and moisture in the air to ensure that the reaction is performed under an inert atmosphere.

[0072] An embodiment of the present application also provides an organic solar cell, comprising a substrate, an anode, a hole transport layer, an active layer, an electron transport layer and a cathode arranged in sequence, wherein the active layer comprises the non-condensed ring electron acceptor containing asymmetric side chains described in the first aspect and / or the non-condensed ring electron acceptor containing asymmetric side chains prepared by the preparation method described in the second aspect.

[0073] In some embodiments, the active layer further comprises an electron donor material that matches the non-condensed ring electron acceptor containing an asymmetric side chain, wherein the electron donor material is any one of PM6, D18, PBDB-T, and PTB7-Th. The structural formula of the above electron donor material is as follows:

[0074]

[0075]

[0076] In a preferred embodiment, the electron donor material is D18. PM6 is a high-efficiency polymer donor material with good photoelectric properties and high crystallinity, suitable for preparing high-performance organic photovoltaic devices. D18 is a high-performance polymer donor material with high photoelectric conversion efficiency and good solubility, suitable for preparing high-efficiency organic photovoltaic devices. PBDB-T is a polymer donor material with high mobility and good solubility, suitable for preparing high-performance organic photovoltaic and organic field effect transistors. PTB7-Th is a high-performance polymer donor material with high photoelectric conversion efficiency and good solubility, suitable for preparing high-efficiency organic photovoltaic devices.

[0077] In some embodiments, the mass ratio of the non-condensed ring electron acceptor containing asymmetric side chains to the electron donor material is 0.5 to 1: 2. In some embodiments, the mass ratio of the non-condensed ring electron acceptor containing asymmetric side chains to the electron donor material can be any value within the range of 0.5 to 1: 2, such as 0.5: 2, 0.6: 2, 0.7: 2, 0.8: 2, 0.9: 2, 1: 2, etc.

[0078] Example

[0079] Example 1

[0080] The present invention provides a non-condensed ring electron acceptor containing an asymmetric side chain and a preparation method thereof, wherein the preparation method of the non-condensed ring electron acceptor containing an asymmetric side chain comprises the following steps:

[0081] S10, compound 1 is subjected to an alkylation reaction with potassium carbonate under nitrogen protection to obtain compound 2;

[0082] Specifically including: reactant mixing: compound 1 (2000mg, 13.4mmol) and K2CO3 (2037mg, 14.7mmol), 1-bromooctane (3109mg, 16.1mmol) and anhydrous N, N-dimethylformamide (DMF, 10mL) were added to a 100mL reaction bottle. Nitrogen protection: After nitrogen was pumped three times, the mixture was stirred at 120°C for 8 hours under nitrogen protection. Post-treatment: After cooling to room temperature, the reaction was quenched with water and extracted with petroleum ether 3 times. The organic layer was concentrated under reduced pressure, and the crude product was purified by column chromatography using dichloromethane: petroleum ether (1:2) as eluent to obtain compound 2 as a yellow oil (2122mg, 61%).

[0083] S20, compound 2 and 3,6-dibromothiophene [3,2-b] thiophene were subjected to coupling reaction under nitrogen protection to obtain compound 3;

[0084] Specifically include: reactant mixing: compound 2 (1569mg, 6.0mmol) and 3,6-dibromothiophene [3,2-b] thiophene (596mg, 2.0mmol), NaO (t-Bu) (865mg, 9.0mmol) and o-xylene (10mL) are added to a 100mL reaction bottle. Nitrogen protection: After nitrogen is pumped three times, Pd (PPh3) 4 (116mg, 0.10mmol) and P (t-Bu) 3 (101mg, 0.50mmol) are added under nitrogen protection, and the mixture is heated to 145 ° C and refluxed for 36h. Post-treatment: After cooling to room temperature, the reaction is quenched with water and extracted with dichloromethane 3 times. The organic layer is concentrated under reduced pressure, and the crude product is purified by column chromatography (silica gel) using dichloromethane: petroleum ether (1:10) as an eluent to obtain compound 3 as a yellow oil (422mg, 32%).

[0085] S30, compound 3 and N-bromosuccinimide (NBS) were subjected to bromination reaction under nitrogen protection to obtain compound 4;

[0086] Specifically include: reactant mixing: compound 3 (200mg, 0.30mmol) and anhydrous DMF (5mL) are added to a 50mL reaction bottle. Nitrogen protection: After nitrogen is pumped three times, NBS (125mg, 0.70mmol) is added under nitrogen protection. The mixture is reacted at room temperature for 6h under light-proof conditions. Post-treatment: The reaction is quenched with water and extracted with petroleum ether 3 times. The organic layer is concentrated under reduced pressure, and the crude product is purified by column chromatography (silica gel) using petroleum ether as eluent to obtain compound 4 as a yellow oil (208mg, 84%).

[0087] S40, compound 4 and compound 5 were subjected to coupling reaction under nitrogen protection to obtain compound 6;

[0088] Specifically including: reactant mixture: compound 4 (200 mg, 0.24 mmol), compound 5 (220 mg, 0.53 mmol), Pd (PPh3) 4 (35 mg, 0.03 mmol) and dry toluene (10 mL) were added to a 50 mL reaction bottle. Nitrogen protection: nitrogen was pumped and charged 3 times, and then reacted at 110 ° C for 18 hours under nitrogen protection. Post-treatment: After cooling to room temperature, the reaction was concentrated under reduced pressure, and the crude product was purified by column chromatography (silica gel) using dichloromethane: petroleum ether (1:2) as eluent to obtain compound 6 as a lemon yellow solid (230 mg, 81%).

[0089] S50, compound 6 was subjected to Vilsmeier-Haack reaction under nitrogen protection to obtain compound 7;

[0090] Specifically include: under nitrogen protection, add POCl3 (0.3mL) and DMF (3mL) in a 50ml flask and stir at 0°C for 2h. Add compound 6 (200mg, 0.17mmol) to 1,2-dichloroethane solution (5mL) to dissolve, and then drop into the reaction. After stirring at 80°C for 12h, cool to room temperature, add saturated CH3COONa solution and stir for 1h, and extract with dichloromethane 3 times. The organic layer is concentrated under reduced pressure, and the crude product is purified by column chromatography (silica gel) using dichloromethane: petroleum ether (1:1) as eluent to obtain an orange solid (160mg, yield 77%).

[0091] S60 and compound 7 are subjected to Knoevenagel reaction under nitrogen protection to obtain the non-condensed ring electron acceptor containing an asymmetric side chain;

[0092] Specifically include: Add compound 7 (150mg, 0.12mmol) and 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene) propanedinitrile (110mg, 0.48mmol) into a 25ml flask, and pump nitrogen three times. Add chloroform (5mL) and pyridine (0.02mL) under nitrogen protection. Heat the reaction mixture to 70°C and reflux and stir for 2 hours. After cooling to room temperature, the organic layer is concentrated under reduced pressure and purified by column chromatography (silica gel) using dichloromethane: petroleum ether (1:1) as eluent to obtain a dark blue solid product, which is a non-condensed ring electron acceptor containing an asymmetric side chain, weighing 131mg and a yield of 65%. The reaction formula is as follows Figure 2 shown.

[0093] The obtained non-condensed ring electron acceptor with asymmetric side chain was subjected to NMR and the following results were obtained: Figure 4 Based on the above spectrum characteristics, it can be inferred that the structure of the compound is X1:

[0094]

[0095] 1 H NMR (400MHz, CDCl3): δ9.03(s,2H),8.54(dd,J=10.0,6.5Hz,2H),7.66(t,J=7.6Hz,2H),7.39(s,2H),7.13(d,J=8.6Hz,4H),6.79(d,J=8.6Hz,4H) ,3.73-3.63(m,4H),3.05(t,J=7.7Hz,4H),2.61-2.54(m,4H),1.83-1.57 (m,12H),1.42-1.16(m,44H),0.93(t,J=7.3Hz,6H),0.90-0.81(m,12H).

[0096] UV-Vis absorption spectra of non-fused ring electron acceptors with asymmetric side chains Figure 5 The results show that the solution has a strong absorption peak in the wavelength range of 600-800nm, and the film has the strongest absorption at 770nm; the maximum absorption peak of the film is 62nm red-shifted than that of the solution.

[0097] Example 2

[0098] The present invention provides a non-condensed ring electron acceptor containing an asymmetric side chain and a preparation method thereof, wherein the preparation method of the non-condensed ring electron acceptor containing an asymmetric side chain comprises the following steps:

[0099] S10, compound 1 is subjected to an alkylation reaction with potassium carbonate under nitrogen protection to obtain compound 2;

[0100] Specifically include: reactant mixing: compound 1 (2000mg, 16.5mmol) and K2CO3 (2515mg, 18.2mmol), 1-bromooctane (3824mg, 19.8mmol) and anhydrous N, N-dimethylformamide (DMF, 10mL) are added to a 100mL reaction bottle. Nitrogen protection: After nitrogen is pumped three times, the mixture is stirred at 120°C for 8 hours under nitrogen protection. Post-treatment: After cooling to room temperature, the reaction is quenched with water and extracted with petroleum ether 3 times. The organic layer is concentrated under reduced pressure, and the crude product is purified by column chromatography (silica gel) using dichloromethane: petroleum ether (1:2) as eluent to obtain compound 2 as a yellow oil (2503mg, 65%).

[0101] S20, compound 2 and 3,6-dibromothiophene [3,2-b] thiophene were subjected to coupling reaction under nitrogen protection to obtain compound 3;

[0102] Specifically including: reactant mixing: compound 2 (1400mg, 6.0mmol) and 3,6-dibromothiophene [3,2-b] thiophene (596mg, 2.0mmol), NaO (t-Bu) (865mg, 9.0mmol) and o-xylene (10mL) were added to a 100mL reaction bottle. Nitrogen protection: After nitrogen was pumped three times, Pd (PPh3) 4 (116mg, 0.10mmol) and P (t-Bu) 3 (101mg, 0.50mmol) were added under nitrogen protection, and the mixture was heated to 145 ° C and refluxed for 36h. Post-treatment: After cooling to room temperature, the reaction was quenched with water and extracted with dichloromethane 3 times. The organic layer was concentrated under reduced pressure, and the crude product was purified by column chromatography using dichloromethane: petroleum ether (1:8) as an eluent to obtain compound 3 as a yellow oil (458mg, 38%).

[0103] S30, compound 3 and N-bromosuccinimide (NBS) were subjected to bromination reaction under nitrogen protection to obtain compound 4;

[0104] Specifically include: reactant mixing: compound 3 (400mg, 0.66mmol) and anhydrous DMF (5mL) are added to a 50ml reaction bottle. Nitrogen protection: After nitrogen is pumped three times, NBS (267mg, 1.5mmol) is added under nitrogen protection. The mixture is reacted at room temperature for 6h under light-proof conditions. Post-treatment: The reaction is quenched with water and extracted with petroleum ether 3 times. The organic layer is concentrated under reduced pressure, and the crude product is purified by column chromatography (silica gel) using petroleum ether as eluent to obtain compound 4 as a yellow oil (427mg, 85%).

[0105] S40, compound 4 and compound 5 were subjected to coupling reaction under nitrogen protection to obtain compound 6;

[0106] Specifically including: reactant mixture: compound 4 (400 mg, 0.53 mmol), compound 5 (498 mg, 1.2 mmol), Pd (PPh3) 4 (69 mg, 0.06 mmol) and dry toluene (10 mL) were added to a 50 mL reaction bottle. Nitrogen protection: nitrogen was pumped and charged 3 times, and then reacted at 110 ° C for 18 hours under nitrogen protection. Post-treatment: After cooling to room temperature, the reaction was concentrated under reduced pressure, and the crude product was purified by column chromatography (silica gel) using dichloromethane: petroleum ether (1:2) as eluent to obtain compound 6 as a lemon yellow solid (486 mg, 83%).

[0107] S50, compound 6 was subjected to Vilsmeier-Haack reaction under nitrogen protection to obtain compound 7;

[0108] Specifically include: under nitrogen protection, add POCl3 (0.3mL) and DMF (3mL) in a 50ml flask and stir at 0°C for 2h. Add compound 6 (400mg, 0.36mmol) to 1,2-dichloroethane solution (5mL) to dissolve, and then drop into the reaction. After stirring at 80°C for 12h, cool to room temperature, add saturated CH3COONa solution and stir for 1h, and extract with dichloromethane 3 times. The organic layer is concentrated under reduced pressure, and the crude product is purified by column chromatography (silica gel) using dichloromethane: petroleum ether (1:1) as eluent to obtain an orange solid (313mg, yield 75%).

[0109] S60 and compound 7 are subjected to Knoevenagel reaction under nitrogen protection to obtain the non-condensed ring electron acceptor containing an asymmetric side chain;

[0110] Specifically include: Add compound 7 (240mg, 0.20mmol) and 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene) propanedinitrile (184mg, 0.80mmol) into a 25ml flask, and pump nitrogen three times. Add chloroform (5mL) and pyridine (0.02mL) under nitrogen protection. Heat the reaction mixture to 70°C and reflux and stir for 2 hours. After cooling to room temperature, the organic layer is concentrated under reduced pressure and purified by column chromatography (silica gel) using dichloromethane: petroleum ether (1:1) as eluent to obtain a dark blue solid product, which is a non-condensed ring electron acceptor containing an asymmetric side chain, weighing 215mg and a yield of 68%. The reaction formula is as follows Figure 3 The structural formula X2 is shown below:

[0111]

[0112] 1 H NMR (400MHz, CDCl3): δ9.02(s,2H),8.54(dd,J=10.0,6.5Hz,2H),7.65(t,J=7.6Hz,2H),7.40(s,2H),7.10(d,J=8.6Hz,4H),6.77(d,J=8.6Hz,4H ),3.74-3.65(m,4H),3.04(t,J=7.7Hz,4H),2.64-2.59(m,4H),1.81-1. 56(m,8H),1.44-1.17(m,46H),0.94(t,J=7.3Hz,6H),0.91-0.83(m,6H).

[0113] Application Examples

[0114] This application example is used to explain the organic solar cell of the present invention.

[0115] The indium tin oxide (ITO) glass (purchased from Shenzhen CSG Float Glass Co., Ltd.) used as the anode was first cleaned with detergent, and then ultrasonically cleaned with deionized water, acetone, and isopropanol in sequence. After drying, a 30 nm thick PEDOT:PSS anode modification layer was spin-coated and dried at 150°C for 10 minutes for use.

[0116] 9.8 mg of the non-condensed ring acceptor molecules obtained in Example 1 and Example 2 were mixed with 0.7 mg of the polymer donor material D18 in 0.2 mL of chloroform to obtain a mixed solution, which was then spin-coated on the above-mentioned PEDOT:PSS layer. After drying, a light-harvesting active layer (effective area of ​​4 mm2) was obtained. 2 A 5 nm thick PDINN cathode modification layer was spin-coated on the active layer and vacuum (absolute pressure of 2×10 -5Pa) evaporated about 80nm of metal Ag as the cathode of the solar cell.

[0117] A solar light source was simulated using an AM1.5 filter (XES-70S1 model from SAN-EI ELECTRIC Co., Ltd.) at 100 mW / cm 2 The device was tested for photocurrent density under light intensity, and the light intensity was calibrated by a standard single-crystal silicon solar cell (purchased from VLSI Standards Inc). The resulting current-voltage curve was measured using a Keithley 2450 Source-Measure Unit and controlled by a computer using Labview software. Figure 6 Show.

[0118] The performance of the solar cell made of ITO / PEDOT:PSS / D18:X1 / PDINN / Ag was studied by using commercial D18 as the donor material and the non-condensed ring electron acceptor containing asymmetric side chains prepared in Example 1 and Example 2 as the acceptor material. Table 1 lists the performance parameters of the active layer composed of D18 and the electron acceptor X1 prepared in Example 1 and the electron acceptor X2 prepared in Example 2 in the solar cell.

[0119] Table 1 Parameters of solar cell devices prepared based on the acceptor materials

[0120]

[0121] As shown in the table above, the solar organic battery device prepared by using the non-condensed ring electron acceptor containing asymmetric side chains provided in the embodiment of the present application as the acceptor material has an open circuit voltage of about 0.9V and a short circuit current of 24mA / cm 2 The filling factor is above 73% and the energy conversion efficiency can reach 16%.

[0122] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0123] The above-described embodiments are only used to illustrate the technical solutions of the embodiments of the present application, rather than to limit them. Although the embodiments of the present application are described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the embodiments of the present application, and should all be included in the protection scope of the embodiments of the present application.

Claims

1. A non-condensed ring electron acceptor containing an asymmetric side chain, characterized in that: Has the following structure: Wherein, R1, R2 and R3 include any one of branched, linear or cyclic alkyl groups containing 1 to 20 carbon atoms, and A is a strong electron-withdrawing functional group.

2. The non-condensed ring electron acceptor containing an asymmetric side chain according to claim 1, characterized in that: The R2 and R3 also include a cyclic alkoxy group containing 1 to 20 carbon atoms.

3. The non-condensed ring electron acceptor containing an asymmetric side chain according to claim 1, characterized in that: The R3 also includes a cyclic aromatic group containing 1 to 20 carbon atoms.

4. The non-condensed ring electron acceptor containing an asymmetric side chain according to claim 1, characterized in that: The A is any one of the following structural formulas: Here, R4 is any one of a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a carbonyl group, an ester group or a cyano group.

5. A method for preparing a non-condensed ring electron acceptor containing an asymmetric side chain, characterized in that: The following steps are involved: Compound 1 is subjected to an alkylation reaction with potassium carbonate to obtain compound 2; The compound 2 is subjected to a coupling reaction with 3,6-dibromothiophene [3,2-B]thiophene to obtain compound 3; The compound 3 is subjected to bromination reaction with N-bromosuccinimide (NBS) to obtain compound 4; The compound 4 is coupled with the compound 5 to obtain the compound 6; Compound 7 is obtained by subjecting compound 6 to a first reaction; The compound 7 is subjected to a second reaction to obtain the non-condensed ring electron acceptor containing an asymmetric side chain as claimed in any one of claims 1 to 4; Wherein, the structural formula of the compound 1 is: The structural formula of the compound 2 is: The structural formula of the compound 3 is: The structural formula of the compound 4 is: The structural formula of the compound 5 is: The structural formula of the compound 6 is: The structural formula of the compound 7 is: The R5 is an alkyl group.

6. The preparation method according to claim 5, characterized in that: The step of obtaining compound 7 by subjecting compound 6 to a first reaction comprises: The first reaction is a Vilsmeier-Haack reaction, wherein the compound 6 reacts with N,N-dimethylformamide under the action of phosphorus oxychloride to generate the compound 7, the reaction temperature is 0°C ± 2°C, and the reaction time is 1h to 3h; And / or, the compound 7 is subjected to a second reaction to obtain the non-condensed ring electron acceptor containing an asymmetric side chain, comprising: The second reaction is a Knoevenagel reaction, wherein the compound 7 is dehydrated and condensed with 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile under the action of an alkaline catalyst to obtain the non-condensed ring electron acceptor containing an asymmetric side chain, the reaction temperature is 60°C to 80°C, and the reaction time is 1h to 3h.

7. The preparation method according to claim 5, characterized in that: All the reactions in the steps are carried out under the protection of inert gas.

8. An organic solar cell, characterized in that: The invention comprises a substrate, an anode, a hole transport layer, an active layer, an electron transport layer and a cathode arranged in sequence, wherein the active layer comprises a non-condensed ring electron acceptor containing an asymmetric side chain as described in any one of claims 1 to 4 and / or a non-condensed ring electron acceptor containing an asymmetric side chain prepared by the method described in any one of claims 5 to 7.

9. The organic solar cell according to claim 8, characterized in that The active layer also includes an electron donor material that matches the non-condensed ring electron acceptor containing an asymmetric side chain, wherein the electron donor material is any one of PM6, D18, PBDB-T, and PTB7-Th.

10. The organic solar cell according to claim 9, characterized in that The mass ratio of the non-condensed ring electron acceptor containing an asymmetric side chain to the electron donor material is 0.5 to 1:2.

Images