Four-arm non-fused ring electron acceptor as well as preparation method and application thereof

Abstract

The invention discloses a four-arm non-fused ring electron acceptor as well as a preparation method and application thereof, and belongs to the technical field of organic photovoltaic acceptor materials. The non-fused ring electron acceptor has a four-arm structure, and compared with a traditional two-arm structure, intermolecular dipole-dipole interaction sites are increased through a multi-side-chain design, and due to the action, a molecular skeleton is more closely stacked, and the interlayer distance is reduced, so that the charge transmission efficiency can be effectively improved. Besides, the four-arm structure effectively enhances the rigidity and planarity of a molecular skeleton through a multi-arm synergistic effect, the distortion problem caused by a C-C single bond in a non-condensed ring structure is inhibited, and the light absorption performance and the charge mobility can be improved by higher crystallinity. Moreover, the four-arm structure can optimize the light absorption range and energy level matching at the same time by regulating and controlling the side chain length and polarity, and the comprehensive performance of the device is further improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic photovoltaic acceptor materials, and in particular relates to a four-arm non-condensed ring electron acceptor and a preparation method and application thereof. Background Art

[0002] Organic solar cells (OSCs), as the third generation of photovoltaic power generation technology, have the advantages of being lightweight, semi-transparent, flexible, and able to be printed on paper backs over large areas, making them a hot topic in the field of organic semiconductors and batteries. Electron donors and electron acceptors are key materials for the bulk heterojunction active layer, and are crucial to the core research question of how to improve the efficiency of photoelectric energy conversion. As for electron acceptors, fullerenes and their derivatives have dominated early acceptor materials due to their excellent charge transport properties. However, due to their high structural symmetry, these acceptor materials suffer from poor light absorption, difficulty in controlling electronic energy levels, and unstable morphology, which limits the efficiency and stability of photovoltaic devices. Therefore, the upper limit of fullerene-based organic photovoltaic devices is only 13% in photoelectric conversion efficiency.

[0003] Compared to fullerene acceptors (FAs), non-fullerene acceptors (NFAs) offer greater structural versatility, superior light absorption properties, and easily tunable energy band gaps. Single-junction devices based on NFAs have already achieved efficiencies exceeding 20%, demonstrating their potential for commercialization and have garnered significant attention in recent years.

[0004] Non-fullerene acceptors are divided into fused ring electron acceptors (FREAs) and non-fused ring electron acceptors (NFREAs). Compared to fused ring electron acceptors, non-fused ring electron acceptors have simpler structures, lower synthesis costs, and are more environmentally friendly. Non-fused ring structures connect aromatic units via single bonds, allowing for free rotation or conjugation, making it easier to manipulate optoelectronic properties through molecular design. Currently, there are many patents for fused ring acceptors, but there is a lack of protection for the systematic design of four-arm non-fused ring structures (such as arm length, end group, and core selection). Summary of the Invention

[0005] In view of the above-mentioned prior art, the present invention provides a four-arm non-condensed ring electron acceptor and a preparation method and application thereof, so as to provide a non-condensed ring electron acceptor material with a completely new structure.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is to provide a four-arm non-condensed ring electron acceptor, the structural formula of the four-arm non-condensed ring electron acceptor is shown in Formula I,

[0007] ,

[0008] Among them, R 1-1 、R 1-2 and R2 is a long-chain alkyl group; R is a hydrogen atom or a fluorine atom; Ar is a benzene ring or a naphthalene ring.

[0009] On the basis of the above technical solution, the present invention can also be improved as follows.

[0010] Further, R 1-1 is a straight-chain alkyl group having 8 carbon atoms; R 1-2 is a straight-chain alkyl group having 6 carbon atoms; and R2 is a straight-chain alkyl group having 11 carbon atoms.

[0011] Furthermore, the four-arm non-fused ring electron acceptor has one of the following structural formulas:

[0012] 、

[0013] .

[0014] The present invention also discloses a method for preparing the four-arm non-condensed ring electron acceptor, comprising the following steps:

[0015] S1: Dissolving tetrabromohydroquinone and a first catalyst in a first solvent, and then adding an alkyl bromide to the resulting solution to obtain a first reaction system; then heating the first reaction system to 70-90° C. in an inert atmosphere and keeping the temperature to react for 14-20 hours, then extracting and purifying the product to obtain compound A;

[0016] S2: Compound A and 2-tributyl(7-alkyl-thiophen[3,2b']thiophene)tin reagent are co-dissolved in a second solvent, bubbling with nitrogen for 20 minutes, and then a second catalyst is added to obtain a second reaction system; the second reaction system is then heated to 90-110°C and kept warm for 36-50 hours, followed by filtration and purification to obtain compound B;

[0017] S3: Mix N,N-dimethylformamide with a third solvent, cool the mixture to -5-1°C, then add phosphorus oxychloride to the mixture, and stir and react for 0.5-2 hours to obtain a Vilsmeier reagent; dissolve compound B in the third solvent, and then add the resulting solution to the Vilsmeier reagent to obtain a third reaction system; heat the third reaction system to 60-80°C, reflux for 12-18 hours, and then extract and purify the product to obtain compound C;

[0018] S4: Compound C and the compound represented by Formula II are co-dissolved in a fourth solvent, and the resulting solution is heated to 50-60° C. after bubbling and exhausting with nitrogen for 20 minutes, and a third catalyst is added to obtain a fourth reaction system; the fourth reaction system is then heated to 55-70° C., refluxed for 10-15 hours, and then crystallized and purified to obtain;

[0019] ,

[0020] Here, Ar is a benzene ring or a naphthalene ring, and R is a hydrogen atom or a fluorine atom.

[0021] Furthermore, the molar ratio of tetrabromohydroquinone, alkyl bromide and the first catalyst is 1:1.5~3:2~4; the alkyl bromide is 7-(bromomethyl)pentadecane, and the first catalyst is cesium carbonate; the first solvent is N,N-dimethylformamide; and the concentration of tetrabromohydroquinone in the first reaction system is 0.05~1 mol / L.

[0022] Furthermore, the molar ratio of compound A, 2-tributyl(7-alkyl-thiophene[3,2b']thiophene)tin reagent and the second catalyst is 1:4~6:0.05~0.2; the 2-tributyl(7-alkyl-thiophene[3,2b']thiophene)tin reagent is 2-tributyl(7-undecylthiophene[3,2b']thiophene)tin reagent, and the second catalyst is at least one of tetrakistriphenylphosphine palladium, bistriphenylphosphine palladium dichloride, tris(dibenzylideneacetone)dipalladium and palladium acetate; the second solvent is toluene; and the feed concentration of compound A in the second reaction system is 0.02~0.06mol / L.

[0023] Furthermore, the volume ratio of N,N-dimethylformamide, the third solvent and phosphorus oxychloride in S3 is 8~9:100:10~12; the material-liquid ratio of compound B and the third solvent is 1g:40mL; and the third solvent is 1,2-dichloroethane.

[0024] Furthermore, the molar ratio of compound C, the compound shown in Formula II, and the third catalyst is 1:4~6:10~15; the third catalyst is pyridine, piperidine, or triethylamine; the fourth solvent is chloroform; and the concentration of compound C in the fourth reaction system is 0.005~0.02 mol / L.

[0025] The invention also discloses the application of the four-arm non-condensed ring electron acceptor in the preparation of photovoltaic devices.

[0026] Furthermore, the photovoltaic device is an organic solar cell; the organic solar cell is prepared by the following steps:

[0027] (1) Modifying an ITO glass substrate with PEDOT:PSS to obtain a substrate;

[0028] (2) dissolving the donor material and the four-arm non-fused ring electron acceptor in chloroform at a mass ratio of 1:1 to 1:1.2 to prepare a solution with a concentration of 10 mg / mL, and then spin-coating the resulting solution on a substrate to obtain an intermediate; the donor material is D18 or PM6;

[0029] (3) Spin-coat PDINN onto the intermediate, and then evaporate a silver electrode on the PDINN layer to obtain the result.

[0030] The beneficial effects of the present invention are:

[0031] 1. The non-condensed ring electron acceptor in the present invention has a 1,4-phenylenediether core, thieno[3,2-b]thiophene as a bridging unit, and a dicyanomethylene indigo derivative as an end group. The overall structure has a four-arm structure. Compared with the traditional two-arm structure, the four-arm structure in the present invention increases the intermolecular dipole-dipole interaction sites through the multi-side chain design (for example, the introduction of fluorinated side chains can form a stronger FO dipole effect). This effect promotes a closer packing of the molecular skeleton and reduces the interlayer spacing, thereby effectively improving the charge transfer efficiency. In addition, the four-arm structure effectively enhances the rigidity and planarity of the molecular skeleton through the multi-arm synergistic effect, suppresses the distortion problem caused by the CC single bond in the non-condensed ring structure, and the higher crystallinity can improve the light absorption performance and charge mobility. Furthermore, by regulating the length and polarity of the side chains, the four-arm structure can simultaneously optimize the light absorption range and energy level matching, further improving the overall performance of the device.

[0032] 2. The synthesis method provided by the present invention has a short synthesis route, high yield, mild reaction conditions, simple operation, and the preparation solvent includes an environmentally friendly solvent, which is easy to achieve scale-up production and can effectively reduce the production cost of the receptor material. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The synthetic route diagram of the four-arm non-fused ring electron acceptor;

[0034] Figure 2 This is a structural diagram of an organic solar cell device;

[0035] Figure 3 This is the IV curve of the organic solar cell device prepared in Experimental Example 1;

[0036] Figure 4 This is the IV curve of the organic solar cell device prepared in Experimental Example 2. DETAILED DESCRIPTION

[0037] The specific implementation methods of the present invention are described in detail below with reference to the embodiments.

[0038] Example 1

[0039] A four-arm non-condensed ring electron acceptor BO-TT-IC has the following structural formula:

[0040] .

[0041] The synthesis path of the four-arm non-fused ring electron acceptor BO-TT-IC in this embodiment is as follows: Figure 1 As shown, the specific synthesis method comprises the following steps:

[0042] (1) Synthesis of Compound A: Tetrabromohydroquinone (500 mg, 1.17 mmol, 1.00 equiv.) and cesium carbonate (1.15 g, 3.52 mmol, 3.00 equiv.) were added to a dry 100 mL single-necked flask, and 15 mL of anhydrous DMF was added for dissolution. 7-(Bromomethyl)pentadecane (0.811 mL, 2.58 mmol, 2.20 equiv.) was then added. The reaction apparatus was repeatedly degassed to remove oxygen (10 min), and then sealed with a PTFE stopper. Under the protection of inert gas (nitrogen), the reaction was placed in an oil bath and slowly heated to 80°C. The reaction was kept warm for 18 hours. After the reaction was completed, the reaction was cooled to room temperature, and a trace amount of the reactant was extracted and diluted with petroleum ether for thin-layer chromatography to confirm the completion of the reaction. Dichloromethane was then added, and the reaction solution was extracted with deionized water (50 mL x 3). After extraction, the reaction solution was dried over anhydrous sodium sulfate and then placed in a vacuum spin dryer for reduced pressure concentration of the crude product. After concentration to a certain degree, the crude product was purified by column chromatography using pure petroleum ether as the eluent to obtain compound A (897 mg, yield 87.32%). The hydrogen spectrum data of compound A are as follows:

[0043] 1 H NMR (600MHz, CDCl3) δ(TMS, ppm) = 3.85 (d, J = 6.0 Hz, 4H), 1.90-1.88 (t, J = 12 Hz, 2H), 1.58-1.53 ​​(m, 4H), 1.45-1.34(m, 12H), 1.33-1.23 (m,32H), 0.93-0.85 (m, 12H).

[0044] (2) Synthesis of Compound B: Compound A (720 mg, 0.82 mmol, 1.00 equiv.) and 2-tributyl(7-undecylthiophen[3,2b']thiophene)tin reagent (2.64 g, 4.52 mmol, 2.20 equiv.) were added to a dry 100 mL single-necked flask. 15 mL of anhydrous toluene was then added. Nitrogen was bubbled through the flask for 20 min, and then tetrakis(triphenylphosphine)palladium (100 mg, 0.197 mmol, 0.110 equiv.) was added rapidly. The oxygen in the reaction apparatus was removed by repeated bubbling (10 min), and then sealed with a PTFE stopper. Under the protection of inert gas (nitrogen), the flask was placed in an oil bath and slowly heated to 100°C. The reaction was then kept warm for 48 hours. After the reaction was completed, the flask was cooled to room temperature, a trace amount of the reactant was extracted, and diluted with petroleum ether for thin-layer chromatography to confirm the degree of reaction completion. The filter paper was then laid flat on the bottom of the filter funnel, filled with diatomaceous earth (2-4 cm), and filtered and flattened several times to compact the mixture. The reaction solution was then poured into a funnel and filtered, followed by spin drying and concentration. The crude product was purified by column chromatography using dichloromethane / petroleum ether (volume ratio 2:8) as the eluent to obtain compound B (1.06 g, yield 83.02%). The H spectral data of compound B are as follows:

[0045] 1 H NMR (600MHz, CDCl3) δ(TMS,ppm) = 7.12 (s,4H), 6.85 (s, 4H), 3.18(d, J = 6.0Hz, 4H), 2.63-2.60 (t, J = 18Hz, 8H), 1.63 -1.60 (m, 10H), 1.57-1.47 (m, 8H), 1.46-1.36 (m, 96H), 1.09-0.63 (m, 62H).

[0046] (3) Synthesis of Compound C: 1,2-dichloroethane (10 mL) and DMF (0.89 mL) were added to a dry 100 mL single-necked pressure flask. The reaction system temperature was controlled below 0°C, and phosphorus oxychloride (1.05 mL) was slowly added. The mixture was stirred in an ice bath for 1 h to generate Vilsmeier reagent. A 1,2-dichloroethane solution (20 mL) of compound B (500 mg, 0.286 mmol, 1.00 equiv.) was added to the above Vilsmeier reagent, and the temperature was slowly raised to 70°C and refluxed for 16 h. After the reaction was completed, the mixture was cooled to room temperature, 1 mol / L sodium hydroxide solution was added in an ice bath, and stirred for 2 h. The aqueous phase was then extracted with dichloromethane and concentrated to dryness to obtain a crude product. The crude product was purified by silica gel column chromatography using dichloromethane / petroleum ether (volume ratio 1:1) as eluent to obtain compound C (490 mg, yield 92%). The H NMR spectrum data of compound C are as follows:

[0047] 1 H NMR (600 MHz, CDCl3) δ (TMSppm) = 10.04 (s, 4H), 7.21 (s,4H), 3.20 (d, J = 6.0 Hz, 4H), 3.01 (t, J =6 Hz, 8H), 1.68-1,63 (m, 8H), 1.30-1.23 (m,74H), 1.06 - 0.97 (m, 18H), 0.86-0.79 (m, 25H), 0.79-0.74 (m, 13H), 0.68-0.63(m, 21H).

[0048] (4) Synthesis of the four-arm non-fused ring electron acceptor BO-TT-IC: Compound C (350 mg, 0.19 mmol, 1.00 equiv.) and 3-(dicyanomethylene)indone (203 mg, 1.05 mmol, 5.50 equiv.) were added to a dry 100 mL pressure-resistant reaction bottle, and then 20 mL of anhydrous chloroform was added. The mixture was bubbled with nitrogen for 20 min and then heated to 55°C. Pyridine (0.2 mL, 2.5 mmmol, 13.10 equiv.) was then quickly added, and the temperature was raised to 65°C and refluxed for 14 h. After the reaction was completed, the mixture was poured into 100 mL of anhydrous methanol to precipitate crystals. The mixture was filtered to obtain a purple-black crude product. The crude product was purified by column chromatography using dichloromethane and petroleum ether (1:1) as eluent to obtain the target compound BO-TT-IC (340 mg, yield: 56%). The hydrogen spectrum data of BO-TT-IC are as follows:

[0049] 1H NMR (600MHz, CDCl3) δ(TMS, ppm) = 9.09 (s, 4H), 8.71 (d, J = 6.0Hz, 4H), 7.92 (d, J = 6.0Hz, 4H), 7.78-7.72 (m, 8H), 7.32 (s, 4H), 3.27 (d, J =6.0Hz, 4H), 3.06-3.04 (t, J = 12Hz, 8H), 1.66-1.62 (m, 8H), 1.32-1.29 (m,10H), 1.25-1.17 (m, 64H), 1.06-0.97 (m, 18H), 0.86-0.79 (m, 25H), 0.79-0.74(m, 13H), 0.68-0.63(m, 21H).

[0050] Example 2

[0051] A four-arm non-condensed ring electron acceptor BO-TT-FIC has the following structural formula:

[0052] .

[0053] The synthesis path of the four-arm non-fused ring electron acceptor BO-TT-FIC in this embodiment is as follows: Figure 1 As shown, the specific synthesis method comprises the following steps:

[0054] Steps (1) to (3) are the same as in Example 1;

[0055] (4) Synthesis of the four-arm non-fused ring electron acceptor BO-TT-FIC: Compound C (350 mg, 0.19 mmol, 1.00 equiv.) and 5,6-difluoro-3-(dicyanomethylene)indone (203 mg, 1.05 mmol, 5.50 equiv.) were added to a dry 100 mL pressure-resistant reaction bottle, and then 20 mL of anhydrous chloroform was added. The mixture was bubbled with nitrogen for 20 min and then heated to 55°C. Pyridine (0.2 mL, 2.5 mmmol, 13.10 equiv.) was then quickly added, and the temperature was raised to 65°C and refluxed for 14 h. After the reaction was completed, the mixture was poured into 100 mL of anhydrous methanol to precipitate crystals. The mixture was filtered to obtain a purple-black crude product. The crude product was purified by column chromatography using dichloromethane and petroleum ether (1:1) as eluent to obtain the target compound BO-TT-FIC (310 mg, yield: 61%). The hydrogen spectrum data of BO-TT-IC are as follows:

[0056] 1H NMR (600MHz, CDCl3) δ(TMS ,ppm) = 9.07 (s, 4H), 8.57-8.54 (t, J =18Hz, 4H), 7.69-7.66 (t, J = 18Hz, 4H), 7.33 (s, 4H), 3.26 (d, J = 6.0Hz, 4H), 3.06-3.03 (t, J = 18Hz, 8H), 1.65-1.61 (m, 8H), 1.18-0.64 (m, 162H).

[0057] Example 3

[0058] A four-arm non-condensed ring electron acceptor BO-TT-ICB has the following structural formula:

[0059] .

[0060] The synthesis path of the four-arm non-fused ring electron acceptor BO-TT-ICB in this embodiment is as follows: Figure 1 As shown, the specific synthesis method comprises the following steps:

[0061] Steps (1) to (3) are the same as in Example 1;

[0062] (4) Synthesis of the four-arm non-fused ring electron acceptor BO-TT-FIC: Compound C (490 mg, 0.27 mmol, 1.00 equiv.) and 2-(3-oxo-2,3-dihydro-1H-cyclopenta[b]naphthalen-1-ylidene)malononitrile (357 mg, 1.46 mmol, 5.50 equiv.) were added to a dry 100 mL pressure-resistant reaction bottle. 20 mL of anhydrous chloroform was then added, and the mixture was bubbled with nitrogen for 20 min and heated to 55°C. Pyridine (0.2 mL, 2.5 mmol, 13.10 equiv.) was then quickly added, and the mixture was heated to 65°C and refluxed for 14 h. After the reaction was completed, the mixture was poured into 100 mL of anhydrous methanol to precipitate crystals. The mixture was filtered to obtain a purple-black crude product. The crude product was purified by column chromatography using dichloromethane and petroleum ether (1:1) as eluent to obtain the target compound BO-TT-ICB (410 mg, yield: 56%). The H spectral data of BO-TT-IC are as follows:

[0063] 1H NMR (600MHz, CDCl3) δ (TMS, ppm) = 9.16 (s, 8H), 8.33 (s, 8H), 8.05-8.02 (dd, J = 18Hz, 8H), 7.68 (s, 8H), 7.36 (s, 4H), 3.32-3.30 (t, J =12Hz, 4H), 3.10-3.08 (t, J = 12Hz, 8H), 1.68-1.65 (m, 8H), 1.36-1.33 (m, 9H), 1.19-1.15 (m, 62H), 1.02-0.99 (m, 18H), 0.87-0.81 (m, 38H), 0.68-0.64 (m, 21H).

[0064] Experimental Example 1

[0065] Prepare organic solar cell devices with four-arm non-condensed ring small molecules BO-TT series as receptors. The structure of the organic solar cell device is as follows Figure 2 As shown. Commercial D18 (CAS No.: 2433725-54-1) was used as the donor material, and the prepared four-arm non-condensed ring small molecule BO-TT series was used as the acceptor material. The mixture was mixed in a mass ratio of 1:1 and dissolved in chloroform to form a 10 mg / mL solution. The film was prepared by spin coating on an ITO glass substrate modified with a hole transport layer PEDOT:PSS. The electron transport layer PDINN was then spin coated, and a silver electrode was prepared as the anode by evaporation. Under white light 1.5G (100Mw / m 2 ) to test its photoelectric conversion efficiency.

[0066] The IV curves of organic solar cell devices containing the four-arm non-condensed ring acceptor small molecule BO-TT series are as follows: Figure 3 The photoelectric conversion efficiency is shown in Table 1. The blended donor material is D18.

[0067] Table 1 Photoelectric conversion efficiency of solar cell devices

[0068] Receptor material <![CDATA[V oc (V)]]> <![CDATA[Jsc(mA / cm 2 )]]> FF(%) PCE(%) BO-TT-IC 0.854(0.829 ± 0.02) 7.23(6.49 ± 0.74) 49.52(48.37 ± 1.15) 3.06(2.51± 0.55) BO-TT-FIC 0.842(0.835 ± 0.007) 10.11(10.03 ± 0.08) 76.25(75.91 ± 0.34) 6.49(6.37 ± 0.12) BP-TT-ICB 0.882(0.878 ± 0.005) 7.94(7.85 ± 0.09) 56.69(56.32 ± 0.37) 3.97(3.93 ± 0.04)

[0069] From the table Figure 3 As can be seen from Table 1, the photovoltaic device based on D18:BO-TT-ICB exhibits the highest open circuit voltage (V oc ), indicating that the energy level matching between the donor and BO-TT-ICB is optimal; while the photovoltaic device based on D18:BO-TT-FIC exhibits a significantly high circuit current density (J sc) and high fill factor (FF), and showed the best conversion efficiency, indicating that although the fluorinated end group caused a certain voltage loss in the device, the intermolecular FO dipole effect effectively promoted the charge separation and transfer, thereby improving the overall efficiency.

[0070] Experimental Example 2

[0071] Prepare organic solar cell devices with four-arm non-condensed ring small molecules BO-TT series as receptors. The structure of the organic solar cell device is as follows Figure 2 As shown. Commercial PM6 (CAS No.: 1802013-84-8) was used as the donor material, and the prepared four-arm non-condensed ring small molecule BO-TT series was used as the acceptor material. The mixture was mixed in a mass ratio of 1:1 and dissolved in chloroform to form a 10 mg / mL solution. The film was prepared by spin coating on an ITO glass substrate modified with a hole transport layer PEDOT:PSS. The electron transport layer PDINN was then spin coated, and a silver electrode was prepared as the anode by evaporation. Under white light 1.5G (100Mw / m 2 ) to test its photoelectric conversion efficiency.

[0072] The IV curves of organic solar cell devices containing the four-arm non-condensed ring acceptor small molecule BO-TT series are as follows: Figure 4 The photoelectric conversion efficiency is shown in Table 2. The blended donor material is PM6.

[0073] Table 2 Photoelectric conversion efficiency of solar cell devices

[0074] Receptor material <![CDATA[V oc (V)]]> <![CDATA[Jsc(mA / cm 2 )]]> FF(%) PCE(%) BO-TT-IC 0.949(0.942±0.006) 8.26(8.06±0.21) 56.58(56.81±0.53) 4.43(4.31±0.11) BO-TT-FIC 0.870(0.862±0.010) 11.22(10.92±0.22) 77.14(74.45±2.92) 7.53(7.02±0.42) BP-TT-ICB 0.882(0.937±0.002) 8.66(8.51±0.10) 52.15(51.00±1.42) 4.22(4.07±0.12)

[0075] From the table Figure 4 As can be seen in Table 2, when the blended donor material is replaced with PM6, the performance of photovoltaic devices based on all three acceptor materials improves. This indicates that compared to D18, the three acceptors are more compatible with the donor PM6. The photovoltaic devices based on PM6:BO-TT-IC and PM6:BO-TT-ICB exhibit similar high open-circuit voltages, indicating good energy level matching between these two acceptors and PM6. The fluorinated end groups of BO-TT-FIC are more conducive to the formation of intermolecular FO dipole interactions, promoting charge separation and transfer, and achieving optimal morphological compatibility with PM6.

[0076] Although the specific embodiments of the present invention have been described in detail in conjunction with the embodiments, this should not be construed as limiting the scope of protection of this patent. Within the scope described by the claims, various modifications and variations that can be made by those skilled in the art without creative work still fall within the scope of protection of this patent.

Claims

1. A four-arm non-fused ring electron acceptor, characterized in that: The structural formula of the four-arm non-fused ring electron acceptor is shown in Formula I, ， Among them, R 1-1 、R 1-2 and R2 is a long-chain alkyl group; R is a hydrogen atom or a fluorine atom; Ar is a benzene ring or a naphthalene ring.

2. The four-arm non-fused ring electron acceptor according to claim 1, characterized in that: The R 1-1 is a straight-chain alkyl group having 8 carbon atoms; 1-2 is a straight-chain alkyl group having 6 carbon atoms; and R2 is a straight-chain alkyl group having 11 carbon atoms.

3. The four-arm non-fused ring electron acceptor according to claim 2, characterized in that The four-arm non-fused ring electron acceptor has one of the following structural formulas: 、 、 。 4. The method for preparing the four-arm non-condensed ring electron acceptor according to any one of claims 1 to 3, wherein: The following steps are involved: S1: Dissolving tetrabromohydroquinone and a first catalyst in a first solvent, and then adding an alkyl bromide to the resulting solution to obtain a first reaction system; then heating the first reaction system to 70-90° C. in an inert atmosphere and keeping the temperature to react for 14-20 hours, then extracting and purifying the product to obtain compound A; S2: Compound A and 2-tributyl(7-alkyl-thiophen[3,2b']thiophene)tin reagent are co-dissolved in a second solvent, bubbling with nitrogen for 20 minutes, and then a second catalyst is added to obtain a second reaction system; the second reaction system is then heated to 90-110°C and kept warm for 36-50 hours, followed by filtration and purification to obtain compound B; S3: Mix N,N-dimethylformamide with a third solvent, cool the mixture to -5-1°C, then add phosphorus oxychloride to the mixture, and stir and react for 0.5-2 hours to obtain a Vilsmeier reagent; dissolve compound B in the third solvent, and then add the resulting solution to the Vilsmeier reagent to obtain a third reaction system; heat the third reaction system to 60-80°C, reflux for 12-18 hours, and then extract and purify the product to obtain compound C; S4: Compound C and the compound represented by Formula II are co-dissolved in a fourth solvent, and the resulting solution is heated to 50-60° C. after bubbling and exhausting with nitrogen for 20 minutes, and a third catalyst is added to obtain a fourth reaction system; the fourth reaction system is then heated to 55-70° C., refluxed for 10-15 hours, and then crystallized and purified to obtain; ， Here, Ar is a benzene ring or a naphthalene ring, and R is a hydrogen atom or a fluorine atom.

5. The preparation method according to claim 4, characterized in that: The molar ratio of the tetrabromohydroquinone, the alkyl bromide and the first catalyst is 1:1.5~3:2~4; the alkyl bromide is 7-(bromomethyl)pentadecane, and the first catalyst is cesium carbonate; the first solvent is N,N-dimethylformamide; and the concentration of tetrabromohydroquinone in the first reaction system is 0.05~1 mol / L.

6. The preparation method according to claim 4, characterized in that: The molar ratio of the compound A, 2-tributyl(7-alkyl-thiophene[3,2b']thiophene)tin reagent and the second catalyst is 1:4~6:0.05~0.2; the 2-tributyl(7-alkyl-thiophene[3,2b']thiophene)tin reagent is 2-tributyl(7-undecylthiophene[3,2b']thiophene)tin reagent, and the second catalyst is at least one of tetrakis(triphenylphosphine)palladium, bistriphenylphosphine palladium dichloride, tris(dibenzylideneacetone)dipalladium and palladium acetate; the second solvent is toluene; and the addition concentration of the compound A in the second reaction system is 0.02~0.06 mol / L.

7. The preparation method according to claim 4, characterized in that: The volume ratio of N,N-dimethylformamide, the third solvent and phosphorus oxychloride in S3 is 8~9:100:10~12; the material-liquid ratio of compound B to the third solvent is 1g:40mL; and the third solvent is 1,2-dichloroethane.

8. The preparation method according to claim 4, characterized in that: The molar ratio of the compound C, the compound represented by Formula II, and the third catalyst is 1:4-6:10-15; the third catalyst is pyridine, piperidine, or triethylamine; the fourth solvent is chloroform; and the concentration of the compound C in the fourth reaction system is 0.005-0.02 mol / L.

9. Use of the four-arm non-condensed ring electron acceptor according to any one of claims 1 to 3 in the preparation of photovoltaic devices.

10. The use according to claim 9, characterized in that The photovoltaic device is an organic solar cell; the organic solar cell is prepared by the following steps: (1) Modifying an ITO glass substrate with PEDOT:PSS to obtain a substrate; (2) dissolving a donor material and a four-arm non-fused ring electron acceptor in chloroform at a mass ratio of 1:1 to 1:1.2 to prepare a solution with a concentration of 10 mg / mL, and then spin-coating the resulting solution on a substrate to obtain an intermediate; the donor material is D18 or PM6; (3) Spin-coat PDINN onto the intermediate, and then evaporate a silver electrode on the PDINN layer to obtain the result.

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