Non-fused ring electron acceptors containing asymmetric side chains, methods of making and use thereof

Abstract

The embodiment of the present application provides a kind of non-fused ring electron acceptor containing asymmetric side chain and its preparation method and application, wherein the non-fused ring electron acceptor containing asymmetric side chain has the structure as shown in the following: Wherein R1, R2 And R3 Include any one of branched alkyl, straight-chain or cyclic alkyl containing 1-20 carbon atoms, A is strong electron-withdrawing functional group.The non-fused ring electron acceptor containing asymmetric side chain and its preparation method and application provided by the embodiment of the present application, by introducing arylalkylamine asymmetric structure as side chain, it is conducive to keeping the molecular planarity of non-fused ring electron acceptor, easy to control molecular packing and solubility.Therefore, the non-fused ring electron acceptor has good solubility, strong crystallization, high mobility, good compatibility, easy to process into film;When the electron acceptor material is used to prepare organic solar cell, the device photoelectric conversion efficiency can reach 16%.

Description

Technical Field

[0001] This application belongs to the field of organic photovoltaic technology, and in particular relates to a non-fused ring electron acceptor containing asymmetric side chains, its preparation method and application. Background Technology

[0002] Organic solar cells are a highly promising renewable energy utilization device that has attracted widespread attention over the past three decades due to their advantages such as portability, flexibility, and ease of large-scale production. Thanks to rapid advancements in active layer materials and device engineering, particularly the emergence of fused-ring electron acceptors, the power conversion efficiency (PCE) of organic solar cells has increased to over 20%, approaching the threshold for commercialization. However, almost all high-performance organic photovoltaic materials currently suffer from cumbersome synthesis steps, complex purification processes, and low yields. This results in high production costs and time for the active layer, hindering large-scale production.

[0003] To overcome the aforementioned limitations, non-fused-ring electron acceptors utilize single-bonded conjugated units to replace the central fused-ring structure of fused-ring electron acceptors, effectively avoiding complex cyclization reactions during synthesis. Furthermore, the conjugated units in non-fused-ring electron acceptors can maintain molecular planarity through intramolecular non-covalent interactions and steric hindrance. Therefore, non-fused-ring electron acceptors offer a simpler and lower-cost synthesis process while exhibiting photovoltaic performance similar to fused-ring electron acceptors. Moreover, the modular molecular structure allows for more flexible and precise control of molecular aggregation behavior through side-chain engineering, thereby contributing to improved device performance. Currently, related techniques introduce diphenylamine side chains into the central core of non-fused-ring molecules to suppress excessive molecular aggregation, achieving a PCE of 15.44% in solar cells fabricated from synthesized non-fused-ring electron acceptors. While such diphenylamine structures can maintain overall molecular planarity and suppress excessive molecular aggregation by restricting single-bond rotation through steric hindrance, the limited chemical modification sites and tunable degree of molecular aggregation limit the potential for side-chain engineering. Insufficient to meet current commercial needs, new molecular designs are needed to develop novel non-fused-ring electron acceptors in order to further improve the photoelectric conversion efficiency of low-cost organic solar cells based on non-fused-ring electron acceptors, thereby further enhancing the photovoltaic performance of organic solar cells. Summary of the Invention

[0004] In view of this, embodiments of this application provide a non-fused-ring electron acceptor with asymmetric side chains, its preparation method and application, to solve the technical problem of low photoelectric conversion efficiency of existing electron acceptor materials when used in organic solar cells.

[0005] In a first aspect, embodiments of this application provide a non-fused-ring electron acceptor containing an asymmetric side chain, having the following structure:

[0006]

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

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

[0009] In some embodiments, R3 further includes a cyclic aryl group containing 1 to 20 carbon atoms.

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

[0011]

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

[0013] Secondly, embodiments of this application provide a method for preparing a non-fused-ring electron acceptor containing an asymmetric side chain, comprising the following steps:

[0014] Compound 1 was alkylated with potassium carbonate to obtain compound 2;

[0015] Compound 2 was coupled with 3,6-dibromothiophene[3,2-B]thiophene to obtain compound 3;

[0016] Compound 3 was subjected to a bromination reaction with N-bromosuccinimide (NBS) to obtain compound 4;

[0017] Compound 4 and compound 5 were coupled together to obtain compound 6;

[0018] Compound 6 was subjected to a first reaction to obtain compound 7;

[0019] The compound 7 was subjected to a second reaction to obtain the non-fused-ring electron acceptor with an asymmetric side chain as described in any one of claims 1 to 4;

[0020] The structural formula of compound 1 is as follows: 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:

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

[0022] In some embodiments, obtaining compound 7 from compound 6 through a first reaction includes:

[0023] The first reaction is a Vilsmeier-Haack reaction, in which compound 6 reacts with N,N-dimethylformamide in the presence of phosphorus oxychloride to generate compound 7. The reaction temperature is 0℃±2℃ and the reaction time is 1h~3h.

[0024] And / or, the step of obtaining the non-fused-ring electron acceptor containing asymmetric side chains by passing the compound 7 through a second reaction includes:

[0025] The second reaction is the Knoevenagel reaction, in which compound 7 undergoes dehydration condensation with 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-yl)malononitrile under the action of an alkaline catalyst to obtain the non-fused-ring electron acceptor with asymmetric side chains. The reaction temperature is 60℃~80℃ and the reaction time is 1h~3h.

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

[0027] In a second aspect, embodiments of this application provide an organic solar cell, comprising a substrate, an anode, a hole transport layer, an active layer, an electron transport layer, and a cathode arranged sequentially. The active layer comprises a non-fused-ring electron acceptor with asymmetric side chains as described in any one of claims 1 to 4 and / or a non-fused-ring electron acceptor with asymmetric side chains prepared by the method described in any one of claims 5 to 7.

[0028] In some embodiments, the active layer further includes an electron donor material that matches the non-fused-ring electron acceptor with asymmetric side chains, 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-fused-ring electron acceptor material with asymmetric side chains to the electron donor material is 0.5 to 1:2.

[0030] The non-fused-ring electron acceptor with asymmetric side chains, its preparation method, and its application provided in this application, by introducing asymmetric side chains to replace the original diphenylamine structure, introduces a new arylalkylamine structure that, while maintaining the original molecular planarity, provides more flexible control sites for side chain engineering. This facilitates more refined molecular aggregation control, thereby improving the power conversion efficiency of organic solar cells based on non-fused-ring electron acceptors. Specifically, its alkyl side chains have low steric hindrance, which can effectively improve molecular planarity and enhance intermolecular interactions, thus giving the non-fused-ring small molecule acceptor better crystallinity and higher electron mobility. In addition, the asymmetric side chain structure endows the small molecule acceptor with richer structural property tunability, which can effectively control its interface energy and obtain suitable compatibility with electron donor materials. Therefore, the active layer of the non-fused-ring electron acceptor molecule based on the asymmetric side chains of arylalkylamine can simultaneously achieve ordered molecular stacking and ideal phase separation morphology. When applied to the light-harvesting layer of organic solar cells, it is beneficial for exciton dissociation and charge transport, thereby achieving excellent photoelectric conversion efficiency. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 The chemical structural formula of the non-fused-ring electron acceptor containing asymmetric side chains provided in the embodiments of this application is as follows:

[0033] Figure 2 This is the chemical structural formula of the non-fused-ring electron acceptor containing asymmetric side chains prepared in Example 1 of this application;

[0034] Figure 3 This is the chemical structural formula of the non-fused-ring electron acceptor containing asymmetric side chains prepared in Example 2 of this application;

[0035] Figure 4 This is the 1H NMR spectrum of the non-fused-ring electron acceptor with asymmetric side chains prepared in Example 1 of this application;

[0036] Figure 5 This is the UV-Vis absorption spectrum of the non-fused-ring electron acceptor with asymmetric side chains prepared in Example 1 of this application;

[0037] Figure 6 This is a current-voltage curve of the organic solar cell in the application example of this application under simulated sunlight. Detailed Implementation

[0038] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that the embodiments of this application can also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of the embodiments of this application with unnecessary detail.

[0039] It should also be understood that the term "and / or" as used in the specification of embodiments of this application and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

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

[0041] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0042] Furthermore, in the description of the embodiments and the appended claims of this application, the terms "first," "second," "third," etc., are used only for distinguishing descriptions and should not be construed as indicating or implying relative importance.

[0043] In the description of embodiments in this application, references to "some embodiments" or "some embodiments" mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in some embodiments," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiments, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized. "A plurality" refers to two or more.

[0044] The first aspect of this application provides a non-fused-ring electron acceptor containing an asymmetric side chain, such as... Figure 1 As shown, it has the following structure:

[0045]

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

[0047] The non-fused-ring electron acceptor with asymmetric side chains provided in this application has an arylalkylamine structure. The alkyl side chains have low steric hindrance, which effectively improves the molecular planarity of the electron acceptor and enhances intermolecular interactions, thereby giving the non-fused-ring electron acceptor better crystallinity and higher electron mobility. Furthermore, the asymmetric side chain structure endows the non-fused-ring electron acceptor with richer structural property tunability, allowing for effective control of its interfacial energy and achieving suitable compatibility with electron donor materials. Therefore, the active layer of the non-fused-ring electron acceptor based on the arylalkylamine asymmetric side chains can simultaneously achieve ordered molecular stacking and ideal phase separation morphology. When applied to organic solar cells, this facilitates exciton dissociation and charge transport, resulting in excellent photoelectric conversion efficiency.

[0048] In applications, A represents a strong electron-withdrawing functional group. This part helps to improve the electron-accepting ability 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, and ester groups. Electron-withdrawing functional groups are those functional groups that can attract electrons from neighboring atoms or groups. These functional groups cause the electron cloud to shift towards them through inductive or conjugation effects, thereby affecting the electron distribution of the molecule. Common electron-withdrawing functional groups include, but are not limited to, ester, ketone, cyano, and fluorine atoms. These functional groups usually reduce the electron density on neighboring carbon atoms, making certain parts of the molecule more electrophilic (i.e., more susceptible to nucleophilic attacks). Strong electron-withdrawing functional groups are those functional groups with even stronger electron-withdrawing capabilities. They can not only significantly reduce the electron density on neighboring carbon atoms but also affect the electron distribution over greater distances. 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 the nitrogen-oxygen double bond, it becomes a very strong electron-withdrawing group. Fluorine atom: Although small in size, due to the high electronegativity of fluorine, it is a very strong electron-withdrawing group. Sulfonic acid group: Through the high electronegativity of the oxygen atom and the interaction of the sulfur-oxygen double bond, it becomes a strong electron-withdrawing group.

[0049] In some embodiments, R1, R2, and R3 comprise branched alkyl groups containing 1 to 20 carbon atoms. In other embodiments, R1, R2, and R3 comprise straight-chain alkyl groups containing 1 to 20 carbon atoms. In still other embodiments, R1, R2, and R3 comprise 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 substitution modes help 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. This can increase intermolecular forces 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 tune the energy level structure and optical properties of the molecule, which is crucial for developing 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 more flexible regulatory sites for side-chain engineering while maintaining the original molecular planarity, which is beneficial for achieving more precise molecular aggregation control.

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

[0052]

[0053] In this group, R4 can be any one of a hydrogen atom, a halogen atom, an alkyl group containing 1–20 carbon atoms, an alkoxy group containing 1–20 carbon atoms, a carbonyl group, an ester group, or a cyano group. The cyano group is a very strong electron-withdrawing group with high electronegativity and stability, enhancing the electron-withdrawing ability of the molecule and improving the electrical properties of the material. The nitro group is also a strong electron-withdrawing group. It effectively disperses the negative charge through resonance structure, thereby enhancing the electron-withdrawing ability. Halogen substituents include fluorine (-F), chlorine (-Cl), bromine (-Br), and iodine (-I). The electron-withdrawing ability of these groups decreases with increasing atomic number, with fluorine being the strongest electron-withdrawing group. Halogen substituents can significantly affect the polarity and solubility of the molecule. The carbonyl group is a moderately strong electron-withdrawing group. The ester group is a moderately strong electron-withdrawing group. Alkyl groups can be straight-chain, branched, or cyclic alkyl groups containing 1–20 carbon atoms. Although alkyl groups themselves are not electron-withdrawing groups, they can affect the overall properties of the molecule when combined with other electron-withdrawing groups. Alkoxy groups can be straight-chain, branched, or cyclic alkoxy groups containing 1 to 20 carbon atoms. Alkoxy groups typically have moderate electron-withdrawing ability, which can enhance the polarity and solubility of the molecule. It should be noted that the dashed lines in the above structural formulas represent connection sites.

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

[0055] S10. Compound 1 is alkylated with potassium carbonate to obtain compound 2;

[0056] S20. Compound 2 is coupled with 3,6-dibromothiophene[3,2-B]thiophene to obtain compound 3;

[0057] S30. The compound 3 is subjected to a bromination reaction with N-bromosuccinimide (NBS) to obtain compound 4;

[0058] S40. Compound 4 and compound 5 are coupled together to obtain compound 6;

[0059] S50, Compound 6 is subjected to a first reaction to obtain Compound 7;

[0060] S60. The compound 7 is subjected to a second reaction to obtain a non-fused-ring electron acceptor with an asymmetric side chain as described in the first aspect;

[0061] The structural formula of compound 1 is as follows: 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 this application has relatively mild reaction conditions, simpler synthesis steps, and lower synthesis cost, which is conducive to large-scale production.

[0064] In applications, R5 is a branched or branched alkyl group, including but not limited to methane, ethane, propane, n-butane, isobutane, etc.

[0065] In step S10, compound 1 is mixed with potassium carbonate for an alkylation reaction. Specifically, compound 1, potassium carbonate, and 1-bromooctane are mixed, anhydrous N,N-dimethylformamide is added, and under nitrogen protection, the reaction flask is placed in an oil bath and heated to 120°C, stirred at this temperature for 8 hours. After the reaction is complete, the reaction flask is removed from the oil bath and allowed to cool naturally to room temperature. Post-treatment is also included, specifically adding an appropriate amount of water to the reaction mixture to quench the reaction, followed by extraction and separation: using a separatory funnel, the reaction mixture is extracted three times with the same volume of petroleum ether each time. The organic layers are collected, and the extracts are combined. The combined organic layers are transferred to a rotary evaporator, concentrated under reduced pressure, and the solvent is removed to obtain the 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: Active hydrogens (such as hydroxyl and amino groups) in compound 1 are deprotonated by potassium carbonate, generating the corresponding anions. 1-Bromooctane, as an alkylating agent, undergoes a nucleophilic substitution reaction with the generated anion to produce alkylated compound 2.

[0066] In step S20, compound 2 undergoes a coupling reaction with 3,6-dibromothiophene[3,2-B]thiophene to obtain compound 3. Specifically, this involves mixing compound 2, 3,6-dibromothiophene[3,2-B]thiophene, and sodium tert-butoxide, adding o-xylene, and under nitrogen protection, adding tetra(triphenylphosphine)palladium and tri-tert-butylphosphine. The mixture is heated and stirred in an oil bath to 145°C and refluxed at this temperature for 36 hours. After the reaction is complete, the reaction flask is removed from the oil bath and allowed to cool naturally to room temperature. An appropriate amount of water is added to the reaction mixture to quench the reaction. The reaction mixture is extracted three times with dichloromethane using a separatory funnel, each time using the same volume of dichloromethane. The organic layers are collected, and the extracts are combined. The combined organic layers are transferred to a rotary evaporator, concentrated under reduced pressure, and the solvent is removed to obtain the 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 a base (NaO(t-Bu)), to generate compound 3. Reaction Conditions: High temperature (145℃) and long reaction time (36 hours) help improve the reaction rate and conversion. o-xylene, as a solvent, can dissolve all reactants. Nitrogen protection prevents oxidation and side reactions. Catalysts: 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 undergoes a bromination reaction with N-bromosuccinimide (NBS) to yield compound 4. Specifically, compound 3 is mixed with anhydrous DMF, and under nitrogen protection, N-bromosuccinimide is added. The reaction system is placed under light-protected conditions and stirred at room temperature for 6 hours. After the reaction is complete, the reaction flask is removed from the light-protected environment and allowed to cool naturally to room temperature. An appropriate amount of water is added to the reaction mixture to quench the reaction. The reaction mixture is extracted three times with petroleum ether using a separatory funnel, with the same volume of petroleum ether used each time. The organic layers are collected, and the extracts are combined. Concentration and purification: The combined organic layers are transferred to a rotary evaporator, concentrated under reduced pressure, and the solvent is removed to obtain the crude product. The crude product is purified by column chromatography using silica gel as the stationary phase and petroleum ether as the 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 involving the addition of a palladium catalyst to catalyze the coupling reaction. The reaction principle is as follows: bromine atoms in compound 4, under the action of a palladium catalyst (Pd(PPh3)4), undergo a coupling reaction with active hydrogen or other functional groups in compound 5 to generate compound 6.

[0069] In step S50, compound 6 is converted to compound 7 via a first reaction. In practice, the first reaction is the Vilsmeier-Haack reaction. Specifically, this involves preparing the Vilsmeier reagent: under nitrogen protection, phosphoryl chloride and N,N-dimethylformamide are mixed, the reaction flask is placed in an ice bath, the temperature is maintained at 0°C, and the mixture is stirred at this temperature for 2 hours. The dissolved compound 6 solution is slowly added dropwise to the aforementioned Vilsmeier reagent, and stirring continues at 0°C for 30 minutes. The reaction mixture is removed from the ice bath, heated to 80°C, and stirred at this temperature for 12 hours. The reaction principle is as follows: the Vilsmeier-Haack reaction is a reaction in which an imine salt intermediate is generated via the Vilsmeier reagent (a mixture of DMF and POCl3), which then undergoes a formal acylation reaction with an aromatic ring to generate an aldehyde or ketone. In this process, a specific position in compound 6 is converted to an aldehyde or ketone group. After the reaction is complete, cooling and quenching are also included: the reaction flask is removed from the oil bath and allowed to cool naturally to room temperature. A saturated sodium acetate solution is added to the reaction mixture, and the mixture is stirred for 1 hour to quench the reaction. Extraction and separation: The reaction mixture was extracted three times with dichloromethane using a separatory funnel, each time using the same volume of dichloromethane. The organic layers were collected, and the extracts were combined. Concentration and purification: The combined organic layers were transferred to a rotary evaporator and concentrated under reduced pressure to remove the solvent, yielding the crude product. The crude product was 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 undergoes a second reaction to obtain a non-fused-ring electron acceptor with an asymmetric side chain as described in the first aspect, wherein the second reaction is a Knoevenagel reaction. Specifically, this includes: mixing the reactants, adding compound 7 and 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-1-yl)malononitrile; adding a solvent and catalyst: under nitrogen protection, adding chloroform and 0-pyridine. Pyridine acts as a base to promote the reaction. The reaction principle is as follows: the Knoevenagel reaction is a condensation reaction between an aldehyde or ketone and an active methylene compound (such as malononitrile) under basic conditions to generate an α,β-unsaturated compound. In this process, the aldehyde or ketone group in compound 7 undergoes a condensation reaction with 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-1-yl)malononitrile to generate the X1 acceptor material. Reaction conditions: Temperature (60℃~80℃) and time (1h~3h) help improve the reaction rate and conversion. 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 carbanions, which then undergo a condensation reaction with malononitrile.

[0071] In some embodiments, all the above steps are carried out under an inert gas atmosphere. Specifically, they are carried out under a nitrogen atmosphere. During each reaction step, the reaction system is purged three times with nitrogen to remove oxygen and moisture from the air, ensuring that the reaction proceeds under an inert atmosphere.

[0072] This 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 sequentially. The active layer includes the non-fused-ring electron acceptor with asymmetric side chains as described in the first aspect and / or the non-fused-ring electron acceptor with asymmetric side chains prepared by the preparation method described in the second aspect.

[0073] In some embodiments, the active layer further includes an electron donor material matched with a non-fused-ring electron acceptor containing asymmetric side chains, wherein the electron donor material is any one of PM6, D18, PBDB-T, and PTB7-Th. The structural formulas of the above electron-donating materials are shown below:

[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 fabricating high-performance organic photovoltaic devices. D18 is a high-performance polymer donor material with high photoelectric conversion efficiency and good solubility, suitable for fabricating high-efficiency organic photovoltaic devices. PBDB-T is a polymer donor material with high mobility and good solubility, suitable for fabricating high-performance organic photovoltaics and organic field-effect transistors. PTB7-Th is a high-performance polymer donor material with high photoelectric conversion efficiency and good solubility, suitable for fabricating high-efficiency organic photovoltaic devices.

[0077] In some embodiments, the mass ratio of the non-fused-ring electron acceptor material with asymmetric side chains to the electron donor material is 0.5 to 1:2. In some embodiments, the mass ratio of the non-fused-ring electron acceptor material with 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, or 1:2.

[0078] Example

[0079] Example 1

[0080] This application provides a non-fused-ring electron acceptor with asymmetric side chains and a method for preparing the same. The method for preparing the non-fused-ring electron acceptor with asymmetric side chains includes the following steps:

[0081] S10, compound 1 and potassium carbonate under nitrogen protection undergo alkylation reaction to obtain compound 2;

[0082] Specifically, the reaction mixture consisted of: Compound 1 (2000 mg, 13.4 mmol) and K₂CO₃ (2037 mg, 14.7 mmol), 1-bromooctane (3109 mg, 16.1 mmol), and anhydrous N,N-dimethylformamide (DMF, 10 mL) added to a 100 mL reaction flask. Nitrogen protection: After purging with nitrogen 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 three times with petroleum ether. 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 give Compound 2 as a yellow oil (2122 mg, 61%).

[0083] S20, compound 2 and 3,6-dibromothiophene[3,2-b]thiophene were coupled under nitrogen protection to give compound 3;

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

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

[0086] Specifically, the reaction mixture consisted of: Compound 3 (200 mg, 0.30 mmol) and anhydrous DMF (5 mL) added to a 50 mL reaction flask. Nitrogen protection was applied: After purging with nitrogen three times, NBS (125 mg, 0.70 mmol) was added under nitrogen protection. The mixture was reacted at room temperature for 6 hours in the dark. Post-treatment: The reaction was quenched with water and extracted three times with petroleum ether. The organic layer was concentrated under reduced pressure, and the crude product was purified by column chromatography (silica gel) using petroleum ether as eluent to give Compound 4 as a yellow oil (208 mg, 84%).

[0087] S40, compound 4 and compound 5 under nitrogen protection undergo a coupling reaction to give compound 6;

[0088] Specifically, the reaction mixture consisted of: Compound 4 (200 mg, 0.24 mmol), Compound 5 (220 mg, 0.53 mmol), Pd(PPh3)4 (35 mg, 0.03 mmol), and dried toluene (10 mL) added to a 50 mL reaction flask. Nitrogen protection: After purging with nitrogen three times, the reaction was carried out at 110 °C for 18 h under nitrogen protection. Post-treatment: After cooling to room temperature, the reaction was concentrated under reduced pressure. The crude product was purified by column chromatography (silica gel) using dichloromethane:petroleum ether (1:2) as the eluent to give Compound 6 as a lemon-yellow solid (230 mg, 81%).

[0089] S50 and compound 6 were reacted under nitrogen protection via the Vilsmeier-Haack reaction to give compound 7;

[0090] Specifically, the reaction proceeded as follows: Under nitrogen protection, POCl3 (0.3 mL) and DMF (3 mL) were added to a 50 mL flask and stirred at 0 °C for 2 h. Compound 6 (200 mg, 0.17 mmol) was dissolved in 5 mL of 1,2-dichloroethane solution and then added dropwise to the reaction mixture. After stirring at 80 °C for 12 h, the mixture was cooled to room temperature, and a saturated CH3COONa solution was added and stirred for 1 h. The mixture was then extracted three times with dichloromethane. The organic layer was concentrated under reduced pressure, and the crude product was purified by column chromatography (silica gel) using dichloromethane:petroleum ether (1:1) as the eluent to give an orange solid (160 mg, 77% yield).

[0091] S60 and compound 7 were reacted under nitrogen protection by the Knoevenagel reaction to obtain the non-fused-ring electron acceptor with asymmetric side chains;

[0092] Specifically, the reaction mixture consisted of: adding compound 7 (150 mg, 0.12 mmol) and 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-yl)malononitrile (110 mg, 0.48 mmol) to a 25 mL flask, followed by purging with nitrogen three times. Chloroform (5 mL) and pyridine (0.02 mL) were added under nitrogen protection. The reaction mixture was heated to 70 °C and refluxed with stirring for 2 hours. After cooling to room temperature, the organic layer was concentrated under reduced pressure and purified by column chromatography (silica gel) using dichloromethane:petroleum ether (1:1) as the eluent to obtain a dark blue solid product, which was the non-fused-ring electron acceptor with an asymmetric side chain, weighing 131 mg, with a yield of 65%. The reaction formula is as follows. Figure 2 As shown.

[0093] Nuclear magnetic resonance imaging of the obtained non-fused-ring electron acceptor with asymmetric side chains yielded results such as... Figure 4 The proton NMR spectrum. Based on the above spectral characteristics, the structure of the compound can be deduced to be 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] The UV-Vis absorption spectrum of a non-fused-ring electron acceptor with asymmetric side chains is as follows: Figure 5 The results show that the solution has a strong absorption peak in the wavelength range of 600-800 nm, while the thin film has the strongest absorption at 770 nm; the maximum absorption peak of the thin film is redshifted by 62 nm compared to that of the solution.

[0097] Example 2

[0098] This application provides a non-fused-ring electron acceptor with asymmetric side chains and a method for preparing the same. The method for preparing the non-fused-ring electron acceptor with asymmetric side chains includes the following steps:

[0099] S10, compound 1 and potassium carbonate under nitrogen protection undergo alkylation reaction to obtain compound 2;

[0100] Specifically, the reaction mixture consisted of: Compound 1 (2000 mg, 16.5 mmol) and K₂CO₃ (2515 mg, 18.2 mmol), 1-bromooctane (3824 mg, 19.8 mmol), and anhydrous N,N-dimethylformamide (DMF, 10 mL) added to a 100 mL reaction flask. Nitrogen protection: After purging with nitrogen 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 three times with petroleum ether. The organic layer 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 give Compound 2 as a yellow oil (2503 mg, 65%).

[0101] S20, compound 2 and 3,6-dibromothiophene[3,2-b]thiophene were coupled under nitrogen protection to give compound 3;

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

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

[0104] Specifically, the reaction mixture consisted of: Compound 3 (400 mg, 0.66 mmol) and anhydrous DMF (5 mL) added to a 50 mL reaction flask. Nitrogen protection was applied: After purging with nitrogen three times, NBS (267 mg, 1.5 mmol) was added under nitrogen protection. The mixture was reacted at room temperature for 6 hours in the dark. Post-treatment: The reaction was quenched with water and extracted three times with petroleum ether. The organic layer was concentrated under reduced pressure, and the crude product was purified by column chromatography (silica gel) using petroleum ether as eluent to give Compound 4 as a yellow oil (427 mg, 85%).

[0105] S40, compound 4 and compound 5 under nitrogen protection undergo a coupling reaction to give compound 6;

[0106] Specifically, the reaction mixture consisted of: Compound 4 (400 mg, 0.53 mmol), Compound 5 (498 mg, 1.2 mmol), Pd(PPh3)4 (69 mg, 0.06 mmol), and dried toluene (10 mL) added to a 50 mL reaction flask. Nitrogen protection: After purging with nitrogen three times, the reaction was carried out at 110 °C for 18 h under nitrogen protection. Post-treatment: After cooling to room temperature, the reaction was concentrated under reduced pressure. The crude product was purified by column chromatography (silica gel) using dichloromethane:petroleum ether (1:2) as the eluent to give Compound 6 as a lemon-yellow solid (486 mg, 83%).

[0107] S50 and compound 6 were reacted under nitrogen protection via the Vilsmeier-Haack reaction to give compound 7;

[0108] Specifically, the reaction proceeded as follows: Under nitrogen protection, POCl3 (0.3 mL) and DMF (3 mL) were added to a 50 mL flask and stirred at 0 °C for 2 h. Compound 6 (400 mg, 0.36 mmol) was dissolved in 5 mL of 1,2-dichloroethane solution and then added dropwise to the reaction mixture. After stirring at 80 °C for 12 h, the mixture was cooled to room temperature, and a saturated CH3COONa solution was added and stirred for 1 h. The mixture was then extracted three times with dichloromethane. The organic layer was concentrated under reduced pressure, and the crude product was purified by column chromatography (silica gel) using dichloromethane:petroleum ether (1:1) as the eluent to give an orange solid (313 mg, 75% yield).

[0109] S60 and compound 7 were reacted under nitrogen protection by the Knoevenagel reaction to obtain the non-fused-ring electron acceptor with asymmetric side chains;

[0110] Specifically, the reaction mixture consisted of: adding compound 7 (240 mg, 0.20 mmol) and 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-yl)malononitrile (184 mg, 0.80 mmol) to a 25 mL flask, followed by purging with nitrogen three times. Chloroform (5 mL) and pyridine (0.02 mL) were added under nitrogen protection. The reaction mixture was heated to 70 °C and refluxed with stirring for 2 hours. After cooling to room temperature, the organic layer was concentrated under reduced pressure and purified by column chromatography (silica gel) using dichloromethane:petroleum ether (1:1) as the eluent to obtain a dark blue solid product, which was the non-fused-ring electron acceptor with an asymmetric side chain, weighing 215 mg, with a yield of 68%. The reaction formula is as follows. Figure 3 As shown. 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 illustrates the organic solar cell of the present invention.

[0115] The indium tin oxide (ITO) glass (purchased from Shenzhen Nanbo 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 30nm thick PEDOT:PSS anode modification layer was spin-coated and dried at 150℃ for 10 minutes for later use.

[0116] 9.8 mg of the non-fused-ring acceptor molecule obtained in Examples 1 and 2 was mixed with 0.7 mg of polymer donor material D18 in 0.2 mL of chloroform to obtain a mixture, which was then spin-coated onto the above 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 onto the active layer under vacuum (absolute pressure 2 × 10⁻⁶). -5A metallic Ag of approximately 80 nm is deposited by vapor deposition (Pa) as the cathode of a solar cell.

[0117] A simulated solar light source was used with an AM1.5 filter (SAN-EI ELECTRIC Co., Ltd. model XES-70S1), at 100mW / cm². 2 The photocurrent density of the device was measured under varying light intensity, calibrated using a standard monocrystalline silicon solar cell (purchased from VLSI Standards Inc.). The resulting current-voltage curves were measured using a Keithley 2450 Source-Measure Unit, controlled by a computer via LabVIEW software. The resulting current-voltage curves are shown below. Figure 6 Show.

[0118] Using commercially available D18 as the donor material and the non-fused-ring electron acceptor with asymmetric side chains prepared in Examples 1 and 2 as the acceptor material, the performance of solar cells fabricated according to the ITO / PEDOT:PSS / D18:X1 / PDINN / Ag ratio was discussed. Table 1 lists the performance parameters exhibited by the active layers in the solar cells composed of D18 and electron acceptor X1 prepared in Example 1 and electron acceptor X2 prepared in Example 2, respectively.

[0119] Table 1. Parameters of solar cell devices fabricated based on the aforementioned acceptor material

[0120]

[0121] As shown in the table above, the solar organic cell device prepared using the non-fused-ring electron acceptor with asymmetric side chains provided in the embodiments of this application as the acceptor material has an open-circuit voltage of approximately 0.9V and a short-circuit current of 24mA / cm. 2 With a fill factor of over 73%, the energy conversion efficiency can reach 16%.

[0122] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0123] The above-described embodiments are only used to illustrate the technical solutions of the embodiments of this application, and are not intended to limit them. Although the embodiments of this application have been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of the embodiments of this application.

Claims

1. A non-fused-ring electron acceptor containing an asymmetric side chain, characterized in that, It has one of the following structures: 。 2. A method for preparing the non-fused-ring electron acceptor containing asymmetric side chains as described in claim 1, characterized in that, Includes the following steps: Compound 1 was alkylated with 1-bromooctane to give compound 2; Compound 2 was coupled with 3,6-dibromothiophene[3,2-B]thiophene to obtain compound 3; Compound 3 was subjected to a bromination reaction with N-bromosuccinimide (NBS) to obtain compound 4; Compound 4 and compound 5 were coupled together to obtain compound 6; Compound 6 was subjected to a first reaction to obtain compound 7; the first reaction was a Vilsmeier-Haack reaction, in which compound 6 reacted with N,N-dimethylformamide in the presence of phosphorus oxychloride to generate compound 7, the reaction temperature was 0℃±2℃, and the reaction time was 1h~3h. The compound 7 is subjected to a second reaction to obtain the non-fused-ring electron acceptor with an asymmetric side chain as described in claim 1; the second reaction is a Knoevenagel reaction, in which the compound 7 is dehydrated and condensed with 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-yl)malononitrile under the action of an alkaline catalyst to obtain the non-fused-ring electron acceptor with an asymmetric side chain, the reaction temperature is 60℃~80℃, and the reaction time is 1h~3h; The structural formula of compound 1 is as follows: ; 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: ； The structural formula of compound 7 is: ； The R5 is as shown in claim 1.

3. The preparation method according to claim 2, characterized in that, All reactions were carried out under the protection of an inert gas.

4. An organic solar cell, characterized in that, It includes a substrate, an anode, a hole transport layer, an active layer, an electron transport layer, and a cathode arranged sequentially, wherein the active layer includes a non-fused-ring electron acceptor with asymmetric side chains as described in claim 1.

5. The organic solar cell according to claim 4, characterized in that, The active layer further includes an electron donor material that matches the non-fused-ring electron acceptor with asymmetric side chains, wherein the electron donor material is any one of PM6, D18, PBDB-T, and PTB7-Th.

6. The organic solar cell according to claim 5, characterized in that, The mass ratio of the non-fused-ring electron acceptor material with asymmetric side chains to the electron donor material is 0.5~1:2.

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