Organic solar cell acceptor material based on benzothiazole non-condensed ring A-D-A '-D-A type and preparation method and application thereof

Abstract

The invention discloses a benzothiazole non-condensed ring A-D-A '-D-A type organic solar cell acceptor material and a preparation method and application thereof, a benzothiazole unit is used as a central nuclear electron withdrawing unit (A-unit), and then the benzothiazole unit, the central nuclear electron withdrawing unit (A-unit), an electron donating unit (D-unit) and a terminal group are synthesized into the organic solar cell acceptor material with an A-D-A'-D-A structure. Wherein benzothiazole as an asymmetric central core structure can enhance the dipole moment of molecules, optimize the accumulation among the molecules and improve the blending property of a donor and an acceptor, and the characteristics can jointly promote charge transfer to inhibit the bimolecular recombination condition. The molecular morphology is regulated and controlled by connecting different structural groups to a top branched chain, and meanwhile, different atoms can be introduced into a benzene ring to regulate and control the chemical energy level. In addition, the polymer also has the characteristics that the aggregation behavior and the light absorption range of molecules can be adjusted by accessing different terminal groups. The benzothiazole-based non-fused ring A-D-A '-D-A type acceptor material provided by the invention is few in synthesis and preparation steps, simple in purification process and high in yield.

Description

Technical Field

[0001] This application relates to the field of organic solar cell technology, and more specifically, to an organic solar cell acceptor material based on a benzothiazole non-fused ring AD-A'-DA type, its preparation method, and its application. Background Technology

[0002] In recent years, the country has vigorously promoted the construction of large-scale photovoltaic bases, placing unprecedented emphasis on new energy sources. However, maximizing the conversion efficiency of solar energy, the most stable energy source, has always been a challenge. Organic solar cells (OSCs) have become a research hotspot for third-generation solar cells due to their advantages such as being lightweight, flexible, solution-processable, and suitable for large-scale fabrication. In recent years, non-fullerene acceptors (NFAs), with their advantages of highly designable molecular structures, wide light absorption range, flexible energy level control, and tunable crystallinity, have gradually replaced traditional fullerene acceptors, driving the photoelectric conversion efficiency of organic solar cells to exceed 21%.

[0003] Among them, the ADA-type (receptor-donor-receptor) fused-ring acceptor is one of the most widely studied and highest-performing systems. However, existing acceptors of this system still face several technical bottlenecks: limited light absorption range leading to low photon capture efficiency; and insufficient open-circuit voltage. V OC Limited capacity may exacerbate carrier recombination; the preparation process is complex, and some acceptor materials rely on expensive monomers or harsh reaction conditions, making large-scale production difficult. Summary of the Invention

[0004] To overcome at least one problem existing in the prior art, the primary objective of this application is to provide an organic solar cell acceptor material based on a benzothiazole non-fused ring AD-A'-DA type. By modifying the atoms of the benzothiazole structural units and end groups, the electronic structure of the material is controlled, achieving a decrease in the highest occupied molecular orbital (HOMO) energy level, a broadening of the spectral absorption range, and improved energy level matching with typical donor materials. The four small-molecule acceptor materials prepared have advantages such as simple synthetic routes, tunable optical band gaps, and suitable energy level matching, which contribute to improving the photoelectric conversion efficiency of organic solar cells. This method provides a new design strategy for developing efficient, stable, and process-friendly acceptor materials.

[0005] The second objective of this application is to provide a method for preparing the above-mentioned organic solar cell acceptor material based on the benzothiazole non-fused ring AD-A'-DA type.

[0006] The third objective of this application is to provide the application of the above-mentioned organic solar cell acceptor material based on the benzothiazole non-fused ring AD-A'-DA type.

[0007] To achieve the above objectives, this application provides the following solution: This application provides an organic solar cell acceptor material based on the benzothiazole non-fused ring AD-A'-DA type, the structure of which is shown in general formula (Ⅰ): ; (I); Among them, R1 is independently selected from C1–C 100 Alkyl groups and their alkyl derivatives; wherein one or more carbon atoms are substituted with oxygen, alkenyl, alkynyl, aryl, hydroxyl, amino, carbonyl, carboxyl, ester, cyano, or nitro, or one or more hydrogen atoms are substituted with fluorine, oxygen, alkenyl, alkynyl, aryl, hydroxyl, amino, carbonyl, carboxyl, ester, cyano, or nitro; X1 and X2 are independently selected from hydrogen, fluorine, chlorine, bromine, cyano, and nitro; D1 and D2 are electron-donating units; A1 and A2 are electron-withdrawing units.

[0008] Preferably, D1 and D2 are selected from any one of the following structural formulas: ; Where X3 is independently selected from any one of hydrogen, fluorine, chlorine, bromine, and iodine atoms; R represents an alkyl chain that is a straight or branched chain with 1 to 100 carbon atoms, wherein one or more carbon atoms may be replaced by oxygen atoms, alkenyl, alkynyl, aryl, hydroxyl, amino, carbonyl, carboxyl, ester, cyano, or nitro groups, and hydrogen atoms may be replaced by fluorine atoms, oxygen atoms, alkenyl, alkynyl, aryl, hydroxyl, amino, carbonyl, carboxyl, ester, cyano, or nitro groups.

[0009] Preferably, A1 and A2 are selected from any one of the following structural formulas: ; Wherein X4 is independently selected from sulfur, oxygen, and selenium atoms; X5 is independently selected from hydrogen, fluorine, chlorine, bromine, and iodine atoms; the alkyl chain represented by R is a straight or branched chain of 1 to 100 carbon atoms, wherein one or more carbon atoms may be replaced by oxygen atoms, alkenyl, alkynyl, aryl, hydroxyl, amino, carbonyl, carboxyl, ester, cyano, or nitro groups, and hydrogen atoms may be replaced by fluorine atoms, oxygen atoms, alkenyl, alkynyl, aryl, hydroxyl, amino, carbonyl, carboxyl, ester, cyano, or nitro groups.

[0010] This application also provides a method for preparing the above-mentioned organic solar cell acceptor material based on the benzothiazole non-fused ring AD-A'-DA type, including the following steps: S1. Synthetic intermediates B1 and B2: A benzothiazole-containing trimethyl-stanane with a D-unit was coupled under tetra(triphenylphosphine)palladium catalysis to yield 4,7-bis[4,4-bis(2-ethylhexyl)-4H-cyclopentano[2,1-b:3,4-b']dithiophene-2-yl]-2-heptylbenzo[d]thiazole B1; 4,7-dibromo-5,6-difluoro-2-heptylbenzo[d]thiazole and [4,4- The coupling reaction of bis(2-ethylhexyl)-4H-cyclopentadiene[2,1-b:3,4-b']dithiophene-2-yl]trimethyl-stanane under tetra(triphenylphosphine)palladium catalysis yielded 4,7-bis[4,4-bis(2-ethylhexyl)-4H-cyclopento[2,1-b:3,4-b']dithiophene-2-yl]-5,6-difluoro-2-heptylbenzo[d]thiazole B2; S2. Synthesize monomers M1 and M2: Introducing an aldehyde group into B1 in S1 via a Vilsmeier-Haack reaction yields 6,6'-(2-heptylbenzo[d]thiazol-4,7-diyl)bis(4,4-bis(2-ethylhexyl)-4H-cyclopentano[2,1-b:3,4-b']dithiophene-2-carboxaldehyde)M1; Introducing an aldehyde group into B2 in S2 via a Vilsmeier-Haack reaction yields 6,6'-(5,6-difluoro-2-heptylbenzo[d]thiazol-4,7-diyl)bis(4,4-bis(2-ethylhexyl)-4H-cyclopentano[2,1-b:3,4-b']dithiophene-2-carboxaldehyde)M2; S3. Synthesize small molecule receptors Z1~Z2: M1 in S2 was reacted with 5,6-difluoro-3-(dicyanomethylene)indophenone in chloroform as a solvent under pyridine catalysis. The reaction was followed by Soxhlet extraction and recrystallization to obtain the final high-purity product Z1. Similarly, M1 in S2 was reacted with 5,6-difluoro-3-(dicyanomethylene)indophenone in chloroform as a solvent under pyridine catalysis. The reaction was followed by Soxhlet extraction and recrystallization to obtain the final high-purity product Z2. The structural formulas of Z1 and Z2 are as follows: .

[0011] Preferably, the molar ratio of 4,7-dibromo-2-heptylbenzo[d]thiazole and [4,4-bis(2-ethylhexyl)-4H-cyclopentadiene[2,1-b:3,4-b']dithiophene-2-yl]trimethyl-stanane in tetra(triphenylphosphine)palladium catalysis is 1:(2.0-2.1):(0.04-0.06); the molar ratio of 4,7-dibromo-5,6-difluoro-2-heptylbenzo[d]thiazole and [4,4-bis(2-ethylhexyl)-4H-cyclopentadiene[2,1-b:3,4-b']dithiophene-2-yl]trimethyl-stanane in tetra(triphenylphosphine)palladium catalysis is 1:(2.0-2.1):(0.04-0.06).

[0012] More preferably, the reaction is carried out under the protection of organic solvent and nitrogen, at a temperature of 110–115ºC, and for a time of 12–14 h.

[0013] Preferably, in S2, the molar ratio of B1 to Vilsmeier-Haack reagent (a mixed solution of phosphorus oxychloride and N,N-dimethylformamide) is 1:(20-25):(20-25); the molar ratio of B2 to Vilsmeier-Haack reagent (a mixed solution of phosphorus oxychloride and N,N-dimethylformamide) is 1:(20-25):(20-25); the reaction is carried out under the protection of organic solvent and nitrogen, at room temperature in the dark, and the reagent is added first at -1 to 1ºC and then the temperature is raised to 95 to 100ºC for 3 to 4 hours.

[0014] Preferably, the molar ratio of M1 to 5,6-difluoro-3-(dicyanomethylene)indoketone in S3 is 1:(4.5-5); the molar ratio of M2 to 5,6-difluoro-3-(dicyanomethylene)indoketone is 1:(4.5-5); the reaction is carried out in the dark at 0.3 mmol in 25-30 ml of chloroform solvent and under nitrogen protection, the amount of pyridine added is 0.5-0.7 mL, the reaction temperature is 65-70ºC, and the reaction time is 9 h.

[0015] Preferably, the Soxhlet extraction described in S3 involves, after the reaction is complete and the mixture is cooled to room temperature, precipitated with methanol, and then purified using a Soxhlet extractor with methanol, petroleum ether, and dichloromethane to remove unreacted raw materials and residual catalyst. The solution is then evaporated and concentrated, and recrystallized using methanol as a poor solvent and dichloromethane as a good solvent. The solid is collected by filtration and dried under vacuum to obtain four organic solar cell acceptor materials based on the benzothiazole non-fused ring AD-A'-DA type.

[0016] This application also provides the application of the above-mentioned benzothiazole non-fused ring AD-A'-DA type organic solar cell acceptor material in the fabrication of organic solar cell devices.

[0017] Compared with the prior art, the beneficial effects of this application are: In the first aspect, this application uses benzothiazole non-fused ring AD-A'-DA type organic solar cell acceptor material to achieve a deeper highest occupied molecular orbital (HOMO) energy level by introducing different atoms in benzothiazole and the end group, thereby broadening the optical absorption range and obtaining higher device performance.

[0018] Secondly, the benzothiazole non-fused ring AD-A'-DA type organic solar cell acceptor material provided in this application has readily available raw materials, simple synthesis and purification processes, high yield, and can be synthesized on a large scale. Organic solar cell devices based on this material exhibit high open-circuit voltage, with optimal device efficiency reaching 10.89%. Attached Figure Description

[0019] Figure 1 The UV absorption spectra of the solution and thin film of Z1 prepared in Example 1 of this application are shown. Figure 2 The UV absorption spectra of the solution and thin film of Z2 prepared in Example 2 of this application are shown. Figure 3 The cyclic voltammetry curves are of the Z1-Z2 chloroform solutions prepared in Examples 1-2 of this application. Figure 4 Thermogravimetric analysis (TGA) diagrams of Z1-Z2 prepared in Examples 1-2 of this application; Figure 5 The organic solar cell device structure prepared when Z1 to Z2 prepared in Examples 1 to 2 of this application are used as donor materials; Figure 6 This is a graph showing the current density-voltage performance parameters of the organic solar cell in this application. Figure 7 A diagram showing the specific chemical structure of PM6, the donor material used in this application; Figure 8 The image shows the proton NMR spectrum of the monomer Z1 prepared in this application.

[0020] Figure 9 The image shows the hydrogen nuclear magnetic resonance spectrum of the monomer Z2 prepared in this application. Detailed Implementation

[0021] The embodiments of this application will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of this application. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0022] It should be noted that: Unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined to form new technical solutions.

[0023] In this application, unless otherwise stated, the various reactions or operation steps may be performed sequentially or in a particular order. Preferably, the reaction methods described herein are performed sequentially.

[0024] Unless otherwise stated, the technical and scientific terms used herein have the same meanings as those familiar to a person skilled in the art. Furthermore, any methods or materials similar to or equivalent to those described herein may also be used in this application.

[0025] In our research, we discovered that benzothiazole derivatives possess strong electron affinity, a favorable planar conjugated structure, and excellent thermal stability, making them ideal building blocks for acceptor units. Introducing benzothiazole into the acceptor backbone allows for the modulation of molecular energy levels through its strong electron-withdrawing ability, while the planar structure enhances intermolecular π-π stacking, thereby improving carrier mobility. Currently, there are no reports on the design and synthesis of AD-A'-DA type acceptors using benzothiazole as the core acceptor unit. This structure, by introducing an intermediate auxiliary acceptor A' unit, can further optimize intramolecular charge transfer efficiency and broaden the light absorption range.

[0026] To address the shortcomings of the existing technologies, this invention provides an organic solar cell acceptor material based on the benzothiazole non-fused ring AD-A'-DA type. Through precise molecular structure design and optimized preparation process, it achieves a synergistic improvement in broad-spectrum absorption, superior energy level matching, and ease of processing, thereby promoting the industrialization of organic solar cells.

[0027] This application provides an organic solar cell acceptor material based on the benzothiazole non-fused ring AD-A'-DA type, the structure of which is shown in general formula (Ⅰ): ; (I); Among them, R1 is independently selected from C1–C 100 Alkyl groups and their alkyl derivatives; wherein one or more carbon atoms are substituted with oxygen, alkenyl, alkynyl, aryl, hydroxyl, amino, carbonyl, carboxyl, ester, cyano, or nitro, or one or more hydrogen atoms are substituted with fluorine, oxygen, alkenyl, alkynyl, aryl, hydroxyl, amino, carbonyl, carboxyl, ester, cyano, or nitro; X1 and X2 are independently selected from hydrogen, fluorine, chlorine, bromine, cyano, and nitro; D1 and D2 are electron-donating units; A1 and A2 are electron-withdrawing units.

[0028] In some preferred embodiments, D1 and D2 are selected from any of the following structural formulas: ; Where X3 is independently selected from any one of hydrogen, fluorine, chlorine, bromine, and iodine atoms; R represents an alkyl chain that is a straight or branched chain with 1 to 100 carbon atoms, wherein one or more carbon atoms may be replaced by oxygen atoms, alkenyl, alkynyl, aryl, hydroxyl, amino, carbonyl, carboxyl, ester, cyano, or nitro groups, and hydrogen atoms may be replaced by fluorine atoms, oxygen atoms, alkenyl, alkynyl, aryl, hydroxyl, amino, carbonyl, carboxyl, ester, cyano, or nitro groups.

[0029] In some preferred embodiments, A1 and A2 are selected from any of the following structural formulas: ; Wherein X4 is independently selected from sulfur, oxygen, and selenium atoms; X5 is independently selected from hydrogen, fluorine, chlorine, bromine, and iodine atoms; the alkyl chain represented by R is a straight or branched chain of 1 to 100 carbon atoms, wherein one or more carbon atoms may be replaced by oxygen atoms, alkenyl, alkynyl, aryl, hydroxyl, amino, carbonyl, carboxyl, ester, cyano, or nitro groups, and hydrogen atoms may be replaced by fluorine atoms, oxygen atoms, alkenyl, alkynyl, aryl, hydroxyl, amino, carbonyl, carboxyl, ester, cyano, or nitro groups.

[0030] This application also provides a method for preparing the above-mentioned organic solar cell acceptor material based on the benzothiazole non-fused ring AD-A'-DA type, including the following steps: S1. Synthetic intermediates B1 and B2: A benzothiazole-containing trimethyl-stanane with a D-unit was coupled under tetra(triphenylphosphine)palladium catalysis to yield 4,7-bis[4,4-bis(2-ethylhexyl)-4H-cyclopentano[2,1-b:3,4-b']dithiophene-2-yl]-2-heptylbenzo[d]thiazole B1; 4,7-dibromo-5,6-difluoro-2-heptylbenzo[d]thiazole and [4,4- The coupling reaction of bis(2-ethylhexyl)-4H-cyclopentadiene[2,1-b:3,4-b']dithiophene-2-yl]trimethyl-stanane under tetra(triphenylphosphine)palladium catalysis yielded 4,7-bis[4,4-bis(2-ethylhexyl)-4H-cyclopento[2,1-b:3,4-b']dithiophene-2-yl]-5,6-difluoro-2-heptylbenzo[d]thiazole B2; S2. Synthesize monomers M1 and M2: Introducing an aldehyde group into B1 in S1 via a Vilsmeier-Haack reaction yields 6,6'-(2-heptylbenzo[d]thiazol-4,7-diyl)bis(4,4-bis(2-ethylhexyl)-4H-cyclopentano[2,1-b:3,4-b']dithiophene-2-carboxaldehyde)M1; Introducing an aldehyde group into B2 in S2 via a Vilsmeier-Haack reaction yields 6,6'-(5,6-difluoro-2-heptylbenzo[d]thiazol-4,7-diyl)bis(4,4-bis(2-ethylhexyl)-4H-cyclopentano[2,1-b:3,4-b']dithiophene-2-carboxaldehyde)M2; S3. Synthesize small molecule receptors Z1~Z2: M1 in S2 was reacted with 5,6-difluoro-3-(dicyanomethylene)indophenone in chloroform as a solvent under pyridine catalysis. The reaction was followed by Soxhlet extraction and recrystallization to obtain the final high-purity product Z1. Similarly, M1 in S2 was reacted with 5,6-difluoro-3-(dicyanomethylene)indophenone in chloroform as a solvent under pyridine catalysis. The reaction was followed by Soxhlet extraction and recrystallization to obtain the final high-purity product Z2. The structural formulas of Z1 and Z2 are as follows: .

[0031] In some preferred embodiments, the molar ratio of 4,7-dibromo-2-heptylbenzo[d]thiazole and [4,4-bis(2-ethylhexyl)-4H-cyclopentadiene[2,1-b:3,4-b']dithiophene-2-yl]trimethyl-stanane in tetra(triphenylphosphine)palladium catalysis is 1:(2.0-2.1):(0.04-0.06); the molar ratio of 4,7-dibromo-5,6-difluoro-2-heptylbenzo[d]thiazole and [4,4-bis(2-ethylhexyl)-4H-cyclopentadiene[2,1-b:3,4-b']dithiophene-2-yl]trimethyl-stanane in tetra(triphenylphosphine)palladium catalysis is 1:(2.0-2.1):(0.04-0.06).

[0032] In some preferred embodiments, the reaction is carried out under the protection of organic solvent and nitrogen, at a temperature of 110–115ºC, and for a time of 12–14 h.

[0033] In some preferred embodiments, the molar ratio of B1 and Vilsmeier-Haack reagent (a mixed solution of phosphorus oxychloride and N,N-dimethylformamide) in S2 is 1:(20-25):(20-25); the molar ratio of B2 and Vilsmeier-Haack reagent (a mixed solution of phosphorus oxychloride and N,N-dimethylformamide) is 1:(20-25):(20-25); the reaction is carried out under the protection of organic solvent and nitrogen, at room temperature in the dark, and the reaction time is 3-4 h after adding the reagent at -1 to 1ºC and then raising the temperature to 95 to 100ºC.

[0034] In some preferred embodiments, the molar ratio of M1 to 5,6-difluoro-3-(dicyanomethylene)indoketone in S3 is 1:(4.5-5); the molar ratio of M2 to 5,6-difluoro-3-(dicyanomethylene)indoketone is 1:(4.5-5); the reaction is carried out in the dark at 0.3 mmol in 25-30 ml of chloroform solvent and under nitrogen protection, the amount of pyridine added is 0.5-0.7 mL, the reaction temperature is 65-70ºC, and the reaction time is 9 h.

[0035] In some preferred embodiments, the Soxhlet extraction described in S3 involves, after the reaction is complete and the mixture is cooled to room temperature, precipitated with methanol, and then purified using a Soxhlet extractor with methanol, petroleum ether, and dichloromethane to remove unreacted raw materials and residual catalyst. The solution is then evaporated and concentrated, and recrystallized using methanol as a poor solvent and dichloromethane as a good solvent. The solid is collected by filtration and dried under vacuum to obtain four organic solar cell acceptor materials based on the benzothiazole non-fused ring AD-A'-DA type.

[0036] This application also provides the application of the above-mentioned benzothiazole non-fused ring AD-A'-DA type organic solar cell acceptor material in the fabrication of organic solar cell devices.

[0037] Next, specific embodiments will be used to describe in detail the preparation method of the organic solar cell acceptor material based on the benzothiazole non-fused ring AD-A'-DA type and the preparation method of the organic solar cell.

[0038] Example 1 The synthetic route of the benzothiazole non-fused-ring AD-A'-DA type acceptor material in this application is as follows: ; The preparation method of the benzothiazole non-fused ring AD-A'-DA type receptor material in this application embodiment is as follows: Synthesis of monomer B1: 4,7-Dibromo-2-heptylbenzo[d]thiazole (782.3 mg, 2.00 mmol), [4,4-bis(2-ethylhexyl)-4H-cyclopentadiene[2,1-b:3,4-b']dithiophene-2-yl]trimethyl-stanane (2.54 g, 4.5 mmol), and Pd(PPh3)4 (115.6 mg, 0.10 mmol) were placed in a pressure-resistant flask reactor and dissolved in 5 mL of DMF. The mixture was heated to 110ºC under nitrogen protection and then refluxed with stirring for 12 hours. After the reaction was completed, the mixture was cooled to room temperature and extracted three times with dichloromethane. The organic phases were combined, dried over anhydrous sodium sulfate, concentrated by rotary evaporation, and purified by silica gel column chromatography (eluent: 100% petroleum ether) to give a brown oil B1 (1.68 g, 81% yield).

[0039] Synthesis of monomer M1: B1 (1.03 g, 1 mmol) was dissolved in 1,2-dichloroethane (20 mL). Under nitrogen protection, a mixture of Vilsmeier-Haack reagent, namely phosphorus oxychloride (0.2 mL) and N,N-dimethylformamide (1.0 mL), was slowly added dropwise at 0ºC. After the addition was complete, the temperature was raised to 95ºC and the reaction was allowed to proceed for 3 hours. After the reaction was completed, saturated sodium carbonate aqueous solution was added to quench the reaction, the pH was adjusted to neutral, and the mixture was extracted with dichloromethane. The organic phase was dried, concentrated, and purified by silica gel column chromatography (eluent: petroleum ether / ethyl acetate = 30:1, v / v) to give an orange-red oily intermediate M1 (829.0 mg, yield 76%).

[0040] Synthesis of small molecule receptor Z1: M1 (327.2 mg, 0.3 mmol) and 5,6-difluoro-3-(dicyanomethylene)indophenone (345.3 mg, 1.5 mmol) were added to a reaction vessel, followed by chloroform (30 mL), and then pyridine (1 mL) was slowly added as a catalyst. The mixture was refluxed at 65°C for 9 h under nitrogen protection. After the reaction was completed, the mixture was cooled to room temperature, and the solution was added dropwise to methanol using a glass dropper to allow precipitation. The solid was collected by filtration through a funnel. The crude product was purified by Soxhlet extraction with methanol and petroleum ether to remove unreacted raw materials and residual catalyst. Finally, the product was collected from dichloromethane. The solution was then evaporated and concentrated, and recrystallized from dichloromethane using methanol as a poor solvent and dichloromethane as a good solvent. The solid was collected by filtration and dried under vacuum to obtain the final high-purity dark blue solid, Z1 (377.2 mg, yield 83%). The monomer Z1 was characterized by nuclear magnetic resonance (NMR). The data in the figure are as follows: 1 H NMR (400MHz, Chloroform-d) δ 8.92 (d, J= 5.2 Hz, 2H), 8.54 – 8.48 (m, 2H), 7.96 (s,1H), 7.92 – 7.90 (m, 1H), 7.69 – 7.63 (m, 5H), 7.54 – 7.52 (m, 1H), 3.28 (t, J = 6.0 Hz, 2H), 2.09 – 2.00 (m, 10H), 1.59 – 1.34 (m, 10H), 1.05 – 0.91 (m, 34H), 0.77 – 0.64 (m, 27H), the 1H NMR spectrum of the small molecule acceptor Z1 is shown in [reference needed]. Figure 8 .

[0041] Example 2 The synthetic route of the benzothiazole non-fused-ring AD-A'-DA type acceptor material in this application is as follows: ; The preparation method of the benzothiazole non-fused ring AD-A'-DA type receptor material in this application embodiment is as follows: Synthesis of monomer B2: 4,7-Dibromo-5,6-difluoro-2-heptylbenzo[d]thiazole (854.3 mg, 2.00 mmol), [4,4-bis(2-ethylhexyl)-4H-cyclopentadiene[2,1-b:3,4-b']dithiophene-2-yl]trimethyl-stanane (2.54 g, 4.5 mmol), and Pd(PPh3)4 (115.6 mg, 0.10 mmol) were placed in a pressure-resistant flask reactor and dissolved in 5 mL of DMF. The mixture was heated to 110ºC under nitrogen protection and then refluxed with stirring for 12 hours. After the reaction was completed, the mixture was cooled to room temperature and extracted three times with dichloromethane. The organic phases were combined, dried over anhydrous sodium sulfate, concentrated by rotary evaporation, and purified by silica gel column chromatography (eluent: 100% petroleum ether) to give a brown oil B2 (1.76 g, 82% yield).

[0042] Synthesis of monomer M2: B2 (1.07 g, 1 mmol) was dissolved in 1,2-dichloroethane (20 mL). Under nitrogen protection, a mixture of Vilsmeier-Haack reagent, namely phosphorus oxychloride (0.2 mL) and N,N-dimethylformamide (1.0 mL), was slowly added dropwise at 0ºC. After the addition was complete, the temperature was raised to 95ºC and the reaction was allowed to proceed for 3 hours. After the reaction was completed, saturated sodium carbonate aqueous solution was added to quench the reaction, the pH was adjusted to neutral, and the mixture was extracted with dichloromethane. The organic phase was dried, concentrated, and purified by silica gel column chromatography (eluent: petroleum ether / ethyl acetate = 30:1, v / v) to give an orange-red oily intermediate M2 (856.3 mg, yield 76%).

[0043] Synthesis of small molecule receptor Z2: M2 (338.0 mg, 0.3 mmol) and 5,6-difluoro-3-(dicyanomethylene)indophenone (345.3 mg, 1.5 mmol) were added to a reaction vessel, followed by chloroform (30 mL), and then pyridine (1 mL) was slowly added as a catalyst. The mixture was refluxed at 65°C for 9 h under nitrogen protection. After the reaction was completed, the mixture was cooled to room temperature, and the solution was added dropwise to methanol using a glass dropper to allow precipitation. The solid was collected by filtration through a funnel. The crude product was purified by Soxhlet extraction with methanol and petroleum ether to remove unreacted raw materials and residual catalyst. Finally, the product was collected from dichloromethane. The solution was then evaporated and concentrated, and recrystallized from dichloromethane using methanol as a poor solvent and dichloromethane as a good solvent. The solid was collected by filtration and dried under vacuum to obtain the final high-purity dark blue solid, Z2 (395.5 mg, yield 85%). The monomer Z2 was characterized by nuclear magnetic resonance (NMR). The data in the figure are as follows: 1 H NMR (400MHz, Chloroform-d) δ 8.93 (d, J = 3.2 Hz, 2H), 8.54 – 8.52 (m, 2H), 8.11 (s,1H), 7.72 – 7.62 (m, 5H), 3.26 (t, J = 7.6 Hz, 2H), 2.06 – 2.04 (m, 10H), 1.59– 1.36 (m, 10H), 1.01 – 0.91 (m, 34H), 0.77 – 0.66 (m, 27H). The 1H NMR spectrum of the small molecule acceptor Z2 is shown in [reference needed]. Figure 9 .

[0044] Performance testing This application provides physical and chemical performance tests of the small molecule receptors in Examples 1-2, including: 1. UV-Vis spectra of the benzothiazole non-fused-ring AD-A'-DA type acceptor materials in Examples 1 and 2: 5 mg of the benzothiazole non-fused-ring AD-A'-DA type acceptor materials Z1-Z2 prepared in Examples 1-2 were weighed and added to 0.5 ml of chloroform to obtain a polymer solution of 10 mg / ml. 3 μl of each solution was diluted 1000 times using a pipette, and its absorption in chloroform solution was measured using a Shimadzu 2400 spectrometer. Thin-film absorption was performed by spin-coating 20 μl of the above acceptor solution onto a quartz slide at 3000 rpm to obtain thin-film quartz slides carrying the acceptor material. The thin-film absorption results were measured using a Shimadzu 2400 spectrometer. The test results are shown in Table 1, and the test spectra are shown in […]. Figure 1 and Figure 2 .

[0045] Table 1: Absorbance test data of small molecule acceptor materials in solutions and films described in Examples 1-2 ; pass Figure 1 and Figure 2 As shown in Table 1, the benzothiazole non-fused ring AD-A'-DA type acceptor material obtained in this application has an absorption range of 560 nm to 800 nm in its solution, which can complement the absorption range of commercial donor materials, greatly increasing the ability to capture sunlight and greatly helping the device to obtain high short-circuit current.

[0046] 2. Cyclic voltammetry tests of benzothiazole non-fused-ring AD-A'-DA type acceptor materials in Examples 1 and 2: Cyclic voltammetry measurements were performed on a Metrohm Autolab PGSTAT302N electrochemical workstation using a three-electrode system: a glassy carbon electrode as the working electrode, a platinum wire as the counter electrode, and an Ag / Ag reference electrode. + The electrode was used at a scan rate of 100 mV / s under nitrogen atmosphere. The electrolyte was tetrabutylammonium hexafluorophosphate (Bu4NPF6, 0.1 mol / L) dissolved in HPLC-grade acetonitrile, with ferrocene (Fc / Fc) as the electrolyte. + Use as an internal standard. Add 10 mg / ml chloroform solutions of Z1-Z2 to a platinum-carbon electrode and determine the energy levels using the three-electrode method. Specific data are shown in Table 2, and the obtained spectra are shown below. Figure 3 .

[0047] Table 2: Electrochemical Energy Level Tests of Small Molecule Acceptors Described in Examples 1-2 ; The small molecule acceptor materials Z1 to Z2, as measured by the data, all have low highest occupied orbitals. Among them, the highest-performing material has an energy level of -5.67 eV, which will bring a larger open-circuit voltage and is crucial for improving the performance of organic solar cells.

[0048] 3. Thermogravimetric analysis of benzothiazole non-fused ring AD-A'-DA type acceptor materials in Examples 1 and 2: The thermodynamic properties of the acceptor material in this application were tested using a NETZSCH STA449F5 thermogravimetric analyzer under nitrogen atmosphere at a heating rate of 10ºC / min. Specific data are shown in Table 3, and the obtained spectra are shown below. Figure 4 .

[0049] Table 3: Thermogravimetric analysis of small molecule receptors described in Examples 1-2 ; As can be seen from Table 3, the 5% thermal weight loss temperature of Examples 1-2 under nitrogen conditions all exceeded 300ºC, indicating a high decomposition temperature, which effectively ensures that no qualitative change occurs during high-temperature thermal annealing.

[0050] Application Examples (1) Pretreatment of ITO glass anode: First, the quartz glass sheet sputtered with ITO was cleaned under ultrasonic conditions. The cleaning solution in sequence was conductive glass cleaning solution, deionized water, acetone and ethanol. The glass was then dried in an oven for 12 h at a temperature of 60ºC. Before coating with PEDOT:PSS film, the ITO glass was cleaned with oxygen plasma for 30 min. Subsequently, PEDOT:PSS solution was spin-coated at 4000 rpm for 30 s, followed by annealing at 150ºC for 20 min.

[0051] (2) Device fabrication: A traditional upright device structure of ITO / PEDOT:PSS / active layer / PDIN / Ag was adopted. The active layer blend solution was spin-coated onto PEDOT:PSS in a glove box under nitrogen atmosphere at a spin speed of 3000 rpm for 30 s. Then, it was placed on a hot plate for thermal annealing at 90ºC for 10 min. A methanol solution of PDIN (2 mg / ml) was coated onto the stationary active layer surface. Spin-coating was started at an acceleration of 500 rpm / s and continued for 30 s at a rotation speed of 3000 rpm to complete the electron transport layer spin-coating. The vacuum was reduced to 2×10⁻⁶ in a high-vacuum evaporation apparatus. -4 Pa deposited a 100 nm silver layer on the surface of the electron transport layer.

[0052] (3) Device packaging: The fabricated device is sealed in a nitrogen atmosphere glove box, and the effective area is covered with glue and a sealing cap and then sealed by UV curing.

[0053] The light source was calibrated using a silicon reference cell from an AM 1.5 G global solar simulator (Oriel model 91192), with an intensity of 100 mW cm⁻¹. -2 In current-voltage ( J - V Before testing, a device with a precise area of ​​4 mm was used. 2 The device area is defined by a physical mask of the aperture. See the specific device structure for details. Figure 5 The use of the body see Figure 7 The corresponding solar cell parameters are shown in Table 4, and the corresponding test spectra are shown in Table 5. Figure 6 .

[0054] Table 4: Test parameters of solar energy devices using the small molecule acceptors described in Examples 1-2 ; As shown in Table 4, Example 1 has the highest open-circuit voltage of 0.95 V, which ensures that its energy conversion efficiency is not too low, and its short-circuit current density is 16.52 mA / cm². 2 With a fill factor of 59.19%, the final energy conversion efficiency is 9.30%. Example 2 has the best energy conversion efficiency—10.98%, attributed to its open-circuit voltage of 0.93 V and short-circuit current density of 18.99 mA / cm². 2 The fill factor is 62.36%.

[0055] By introducing different substitutions in benzothiazole, the energy levels of the acceptor material can be tuned, and its absorption range can be effectively improved, thus broadening the photon-trapping capability. This further enhances the commercial potential of the benzothiazole non-fused ring AD-A'-DA type acceptor material in organic solar cells.

[0056] This application provides an organic solar cell acceptor material based on the benzothiazole non-fused ring AD-A'-DA type, the structure of which is shown in general formula (Ⅰ): ; (I); Among them, R1 is independently selected from C1–C 100Alkyl groups and their alkyl derivatives; wherein one or more carbon atoms are substituted with oxygen, alkenyl, alkynyl, aryl, hydroxyl, amino, carbonyl, carboxyl, ester, cyano, or nitro, or one or more hydrogen atoms are substituted with fluorine, oxygen, alkenyl, alkynyl, aryl, hydroxyl, amino, carbonyl, carboxyl, ester, cyano, or nitro; X1 and X2 are independently selected from hydrogen, fluorine, chlorine, bromine, cyano, and nitro; D1 and D2 are electron-donating units; A1 and A2 are electron-withdrawing units.

[0057] This application modulates the electronic structure of benzothiazole structural units and end groups by atomic modification, achieving a decrease in the highest occupied molecular orbital (HOMO) energy level, a broadening of the spectral absorption range, and improved energy level matching with typical donor materials. The four small-molecule acceptor materials prepared possess advantages such as simple synthetic routes, tunable optical band gaps, and suitable energy level matching, contributing to improved photoelectric conversion efficiency in organic solar cells. This method provides a new design strategy for developing efficient, stable, and process-friendly acceptor materials.

[0058] Compared with the prior art, this application has the following technical advantages: In the first aspect, this application uses benzothiazole non-fused ring AD-A'-DA type organic solar cell acceptor material to achieve a deeper highest occupied molecular orbital (HOMO) energy level by introducing different atoms in benzothiazole and the end group, thereby broadening the optical absorption range and obtaining higher device performance.

[0059] Secondly, the benzothiazole non-fused ring AD-A'-DA type organic solar cell acceptor material provided in this application has readily available raw materials, simple synthesis and purification processes, high yield, and can be synthesized on a large scale. Organic solar cell devices based on this material exhibit high open-circuit voltage, with optimal device efficiency reaching 10.89%.

[0060] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0061] Although several embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. An organic solar cell acceptor material based on the benzothiazole non-fused ring AD-A'-DA type, characterized in that: Its structure is shown in general formula (Ⅰ): ； （Ⅰ）； Among them, R1 is independently selected from C1 – C 100 Alkyl groups and their alkyl derivatives; wherein one or more carbon atoms are substituted with oxygen, alkenyl, alkynyl, aryl, hydroxyl, amino, carbonyl, carboxyl, ester, cyano, or nitro, or one or more hydrogen atoms are substituted with fluorine, oxygen, alkenyl, alkynyl, aryl, hydroxyl, amino, carbonyl, carboxyl, ester, cyano, or nitro; X1 and X2 are independently selected from hydrogen, fluorine, chlorine, bromine, cyano, and nitro; D1 and D2 are electron-donating units; A1 and A2 are electron-withdrawing units.

2. The organic solar cell acceptor material based on the benzothiazole non-fused ring AD-A'-DA type according to claim 1, characterized in that: D1 and D2 are selected from any of the following structural formulas: ； Where X3 is independently selected from any one of hydrogen, fluorine, chlorine, bromine, and iodine atoms; R represents an alkyl chain that is a straight or branched chain with 1 to 100 carbon atoms, wherein one or more carbon atoms may be replaced by oxygen atoms, alkenyl, alkynyl, aryl, hydroxyl, amino, carbonyl, carboxyl, ester, cyano, or nitro groups, and hydrogen atoms may be replaced by fluorine atoms, oxygen atoms, alkenyl, alkynyl, aryl, hydroxyl, amino, carbonyl, carboxyl, ester, cyano, or nitro groups.

3. The organic solar cell acceptor material based on the benzothiazole non-fused ring AD-A'-DA type according to claim 1, characterized in that: A1 and A2 are selected from any of the following structural formulas: ； Wherein X4 is independently selected from sulfur, oxygen, and selenium atoms; X5 is independently selected from hydrogen, fluorine, chlorine, bromine, and iodine atoms; the alkyl chain represented by R is a straight or branched chain of 1 to 100 carbon atoms, wherein one or more carbon atoms may be replaced by oxygen atoms, alkenyl, alkynyl, aryl, hydroxyl, amino, carbonyl, carboxyl, ester, cyano, or nitro groups, and hydrogen atoms may be replaced by fluorine atoms, oxygen atoms, alkenyl, alkynyl, aryl, hydroxyl, amino, carbonyl, carboxyl, ester, cyano, or nitro groups.

4. The method for preparing the organic solar cell acceptor material based on the benzothiazole non-fused ring AD-A'-DA type according to claims 1-3, characterized in that: Includes the following steps: S1. Synthetic intermediates B1 and B2: A benzothiazole-containing trimethyl-stanane with a D-unit was coupled under tetra(triphenylphosphine)palladium catalysis to yield 4,7-bis[4,4-bis(2-ethylhexyl)-4H-cyclopentano[2,1-b:3,4-b']dithiophene-2-yl]-2-heptylbenzo[d]thiazole B1; 4,7-dibromo-5,6-difluoro-2-heptylbenzo[d]thiazole and [4,4- The coupling reaction of bis(2-ethylhexyl)-4H-cyclopentadiene[2,1-b:3,4-b']dithiophene-2-yl]trimethyl-stanane under tetra(triphenylphosphine)palladium catalysis yielded 4,7-bis[4,4-bis(2-ethylhexyl)-4H-cyclopento[2,1-b:3,4-b']dithiophene-2-yl]-5,6-difluoro-2-heptylbenzo[d]thiazole B2; S2. Synthesize monomers M1 and M2: Introducing an aldehyde group into B1 in S1 via a Vilsmeier-Haack reaction yields 6,6'-(2-heptylbenzo[d]thiazol-4,7-diyl)bis(4,4-bis(2-ethylhexyl)-4H-cyclopentano[2,1-b:3,4-b']dithiophene-2-carboxaldehyde)M1; Introducing an aldehyde group into B2 in S2 via a Vilsmeier-Haack reaction yields 6,6'-(5,6-difluoro-2-heptylbenzo[d]thiazol-4,7-diyl)bis(4,4-bis(2-ethylhexyl)-4H-cyclopentano[2,1-b:3,4-b']dithiophene-2-carboxaldehyde)M2; S3. Synthesize small molecule receptors Z1~Z2: M1 in S2 was reacted with 5,6-difluoro-3-(dicyanomethylene)indophenone in chloroform as a solvent under pyridine catalysis. The reaction was followed by Soxhlet extraction and recrystallization to obtain the final high-purity product Z1. Similarly, M1 in S2 was reacted with 5,6-difluoro-3-(dicyanomethylene)indophenone in chloroform as a solvent under pyridine catalysis. The reaction was followed by Soxhlet extraction and recrystallization to obtain the final high-purity product Z2. The structural formulas of Z1 and Z2 are as follows: 。 5. The method for preparing the organic solar cell acceptor material based on the benzothiazole non-fused ring AD-A'-DA type according to claim 4, characterized in that: The molar ratio of 4,7-dibromo-2-heptylbenzo[d]thiazole and [4,4-bis(2-ethylhexyl)-4H-cyclopentadiene[2,1-b:3,4-b']dithiophene-2-yl]trimethyl-stanane in tetra(triphenylphosphine)palladium catalysis is 1:(2.0-2.1):(0.04-0.06); the molar ratio of 4,7-dibromo-5,6-difluoro-2-heptylbenzo[d]thiazole and [4,4-bis(2-ethylhexyl)-4H-cyclopentadiene[2,1-b:3,4-b']dithiophene-2-yl]trimethyl-stanane in tetra(triphenylphosphine)palladium catalysis is 1:(2.0-2.1):(0.04-0.06).

6. The method for preparing the organic solar cell acceptor material based on the benzothiazole non-fused ring AD-A'-DA type according to claim 5, characterized in that: The reaction was carried out under the protection of organic solvent and nitrogen, at a temperature of 110–115ºC, for a time of 12–14 h.

7. The method for preparing the organic solar cell acceptor material based on the benzothiazole non-fused ring AD-A'-DA type according to claim 4, characterized in that: The molar ratio of B1 and Vilsmeier-Haack reagent (a mixed solution of phosphorus oxychloride and N,N-dimethylformamide) in S2 is 1:(20-25):(20-25); the molar ratio of B2 and Vilsmeier-Haack reagent (a mixed solution of phosphorus oxychloride and N,N-dimethylformamide) is 1:(20-25):(20-25); the reaction is carried out under the protection of organic solvent and nitrogen, at room temperature in the dark, and the reagent is added first at -1 to 1ºC and then the temperature is raised to 95 to 100ºC for 3 to 4 hours.

8. The method for preparing the organic solar cell acceptor material based on the benzothiazole non-fused ring AD-A'-DA type according to claim 4, characterized in that: The molar ratio of M1 to 5,6-difluoro-3-(dicyanomethylene)indoketone in S3 is 1:(4.5–5); the molar ratio of M2 to 5,6-difluoro-3-(dicyanomethylene)indoketone is 1:(4.5–5); the reaction is carried out in the dark at 0.3 mmol in 25–30 ml of chloroform solvent under nitrogen protection, with 0.5–0.7 mL of pyridine added, at a reaction temperature of 65–70ºC, and for 9 h.

9. The method for preparing the organic solar cell acceptor material based on the benzothiazole non-fused ring AD-A'-DA type according to claim 7, characterized in that: The Soxhlet extraction described in S3 involves, after the reaction is complete and the mixture is cooled to room temperature, precipitated with methanol, and then purified using a Soxhlet extractor with methanol, petroleum ether, and dichloromethane to remove unreacted raw materials and residual catalyst. The solution is then evaporated and concentrated, and recrystallized using methanol as a poor solvent and dichloromethane as a good solvent. The solid is collected by filtration and dried under vacuum to obtain four organic solar cell acceptor materials based on the benzothiazole non-fused ring AD-A'-DA type.

10. The application of the benzothiazole non-fused ring AD-A'-DA type organic solar cell acceptor material as described in claims 1 to 3 in the fabrication of organic solar cell devices.

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