A four-armed non-fused ring electron acceptor, its preparation method and application

Abstract

This invention discloses a four-armed non-fused-ring electron acceptor, its preparation method, and its applications, belonging to the field of organic photovoltaic acceptor materials technology. The non-fused-ring electron acceptor of this invention has a four-arm structure. Compared to the traditional two-arm structure, this invention increases the number of intermolecular dipole-dipole interaction sites through a multi-side-chain design. This interaction promotes a more compact packing of the molecular backbone, reducing interlayer spacing and thus effectively improving charge transport efficiency. Furthermore, the four-arm structure, through multi-arm synergistic effects, effectively enhances the rigidity and planarity of the molecular backbone, suppressing the distortion problem caused by C-C single bonds in the non-fused-ring structure. Higher crystallinity improves light absorption performance and charge mobility. Moreover, by controlling the side-chain length and polarity, the four-arm structure can simultaneously optimize the light absorption range and energy level matching, further improving the overall device performance.

Description

Technical Field

[0001] This invention belongs to the field of organic photovoltaic acceptor materials technology, specifically relating to a four-armed non-fused ring electron acceptor, its preparation method, and its application. Background Technology

[0002] Organic solar cells (OSCs), as a third-generation photovoltaic power generation technology, possess advantages such as light weight, semi-transparency, flexibility, and the ability to be printed on paper backs over large areas, making them a research hotspot in the field of organic semiconductors and batteries. Electron donors and electron acceptors are key materials in the active layer of bulk heterojunctions, and are crucial to the core research question of how to improve photoelectric energy conversion efficiency. Regarding 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, limiting the improvement of photovoltaic device efficiency and stability. Therefore, the upper limit of photoelectric conversion efficiency for fullerene-based organic photovoltaic devices is only 13%.

[0003] Compared to fullerene acceptors (FAs), non-fullerene acceptors (NFAs) exhibit greater structural modifiability, superior light absorption performance, and easily tunable band gaps. NFA-based single-junction devices have already achieved efficiencies exceeding 20%, holding promise for commercial applications and thus attracting significant attention in recent years.

[0004] Non-fullerene acceptors are classified 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. The non-fused-ring structure connects aromatic units via single bonds, allowing for free rotation or conjugation, facilitating the modulation of photoelectric properties through molecular design. Currently, there are many patents on fused-ring acceptors, but systematic design of four-arm non-fused-ring structures (such as arm length, terminal groups, and core selection) lacks protection. Summary of the Invention

[0005] In view of the above-mentioned prior art, the present invention provides a four-armed non-fused ring electron acceptor, its preparation method and application, so as to provide a non-fused ring electron acceptor material with a novel structure.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is to provide a four-armed non-fused-ring electron acceptor, the structural formula of which is shown in Formula I.

[0007] ,

[0008] Among them, R 1-1 R 1-2 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] Based on the above technical solution, the present invention can be further improved as follows.

[0010] Furthermore, R 1-1 It is a straight-chain alkyl group with 8 carbon atoms; R 1-2 R1 is a straight-chain alkyl group with 6 carbon atoms; R2 is a straight-chain alkyl group with 11 carbon atoms.

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

[0012] , ,

[0013] .

[0014] This invention also discloses a method for preparing the above-mentioned four-armed non-fused ring electron acceptor, comprising the following steps:

[0015] S1: Tetrabromohydroquinone and the first catalyst are co-dissolved in the first solvent, and then alkyl bromide is added to the resulting solution to obtain the first reaction system; then the first reaction system is heated to 70~90℃ in an inert atmosphere and kept at the temperature for 14~20h, and then the product is extracted and purified to obtain compound A;

[0016] S2: Compound A and 2-tributyl(7-alkyl-thiophene[3,2b']thiophene)tin reagent are co-dissolved in a second solvent. After purging with nitrogen and bubbling for 20 min, a second catalyst is added to obtain a second reaction system. The second reaction system is then heated to 90~110℃ and kept at that temperature for 36~50 h. After filtration and purification, compound B is obtained.

[0017] S3: N,N-dimethylformamide is mixed with a third solvent, the mixture is cooled to -5 to 1°C, phosphorus oxychloride is added to the mixture, and the mixture is stirred and kept at this temperature for 0.5 to 2 hours to obtain Wilsmeier's reagent; compound B is dissolved in the third solvent, and the resulting solution is added to Wilsmeier's reagent to obtain the third reaction system; the third reaction system is heated to 60 to 80°C and refluxed for 12 to 18 hours, followed by extraction and purification of the product to obtain compound C;

[0018] S4: Compound C and the compound shown in Formula II are co-dissolved in a fourth solvent. After purging with nitrogen and bubbling for 20 min, the resulting solution is heated to 50-60 °C and a third catalyst is added to obtain a fourth reaction system. The fourth reaction system is then heated to 55-70 °C and refluxed for 10-15 h. After crystallization and purification, the product is obtained.

[0019] ,

[0020] Where 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, 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] Further, the molar ratio of compound A, 2-tributyl(7-alkyl-thiophene[3,2b']anthiophene)tin reagent, and the second catalyst is 1:4~6:0.05~0.2; the 2-tributyl(7-alkyl-thiophene[3,2b']anthiophene)tin reagent is 2-tributyl(7-undecylthiophene[3,2b']anthiophene)tin reagent, the second catalyst is at least one of tetra(triphenylphosphine)palladium, bis(triphenylphosphine)palladium dichloride, tris(dibenzylideneacetone)palladium, and palladium acetate; the second solvent is toluene; and the concentration of compound A in the second reaction system is 0.02~0.06 mol / 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 ratio of compound B to 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 present invention also discloses the application of the above-mentioned four-armed non-fused ring electron acceptor in the fabrication of photovoltaic devices.

[0026] Furthermore, the photovoltaic device is an organic solar cell; organic solar cells are fabricated through the following steps:

[0027] (1) Modify the ITO glass substrate with PEDOT:PSS to obtain the substrate;

[0028] (2) Dissolve the donor material and the four-armed 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. Then spin-coat the resulting solution onto the substrate to obtain the intermediate. The donor material is D18 or PM6.

[0029] (3) Spin-coat PDINN onto the intermediate, and then deposit silver electrodes on the PDINN layer to obtain the final product.

[0030] The beneficial effects of this invention are:

[0031] 1. The non-fused-ring electron acceptor in this invention uses 1,4-phenylenediether as the core, thieno[3,2-b]thiophene as the bridging unit, and dicyanomethyleneindone derivatives as end groups, exhibiting a four-arm structure. Compared to the traditional two-arm structure, the four-arm structure in this invention increases intermolecular dipole-dipole interaction sites through multi-side chain design (e.g., the introduction of fluorinated side chains can form stronger FO dipole interactions). This effect promotes a more compact packing of the molecular backbone, reducing interlayer spacing and thus effectively improving charge transport efficiency. Furthermore, the four-arm structure, through multi-arm synergistic effects, effectively enhances the rigidity and planarity of the molecular backbone, suppressing the distortion problem caused by CC single bonds in the non-fused-ring structure. Higher crystallinity improves light absorption performance and charge mobility. Moreover, by controlling the side chain length and polarity, the four-arm structure can simultaneously optimize the light absorption range and energy level matching, further enhancing the overall device performance.

[0032] 2. The synthesis method provided by this invention has a short synthesis route, high yield, mild reaction conditions, simple operation, and the preparation solvent includes environmentally friendly solvents, which can be easily scaled up for production and can effectively reduce the production cost of the receptor material. Attached Figure Description

[0033] Figure 1 This is a synthetic pathway diagram for a four-armed non-fused-ring electron acceptor;

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

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

[0036] Figure 4 The IV curve is shown for the organic solar cell device prepared in Experimental Example 2. Detailed Implementation

[0037] The specific embodiments of the present invention will be described in detail below with reference to examples.

[0038] Example 1

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

[0040] .

[0041] The synthetic pathway of the four-armed non-fused-ring electron acceptor BO-TT-IC in this embodiment is as follows: Figure 1 As shown, the specific synthesis method includes 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, followed by dissolution with 15 mL of anhydrous DMF. Then, 7-(bromomethyl)pentadecane (0.811 mL, 2.58 mmol, 2.20 equiv.) was added, and the reaction apparatus was repeatedly degassed to remove oxygen (10 min). The flask was then sealed with a PTFE stopper. Under the protection of an inert gas (nitrogen), the mixture was placed in an oil bath and slowly heated to 80 °C, and the reaction was maintained at this temperature for 18 hours. After the reaction was complete, the mixture was cooled to room temperature, and a small amount of the reactant was extracted, diluted with petroleum ether, and subjected to thin-layer chromatography to confirm the completion of the reaction. Then dichloromethane was added, and the reaction mixture was extracted with deionized water (50 mL × 3). After extraction, the mixture was dried over anhydrous sodium sulfate and then concentrated under reduced pressure using a vacuum rotary dryer. After concentration to a certain extent, 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 1H NMR spectrum of compound A is 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-undecylthiophene[3,2b']thiophene)tin reagent (2.64 g, 4.52 mmol, 2.20 equiv.) were added to a dry 100 mL single-necked flask, followed by 15 mL of anhydrous toluene. After purging with nitrogen and bubbling for 20 min, tetra(triphenylphosphine)palladium (100 mg, 0.197 mmol, 0.110 equiv.) was quickly added. Oxygen was repeatedly removed from the reaction apparatus by bubbling (10 min), and then the flask was sealed with a PTFE stopper. Under the protection of an inert gas (nitrogen), the flask was placed in an oil bath and slowly heated to 100 °C, and the reaction was maintained at this temperature for 48 hours. After the reaction was completed, the flask was cooled to room temperature, and a small amount of the reactant was extracted, diluted with petroleum ether, and spotted onto a thin-layer chromatography plate to confirm the degree of reaction completion. The filter paper was then laid flat at the bottom of the filter funnel, and diatomaceous earth (2-4 cm) was added. The mixture was then repeatedly filtered, flattened, and compacted. The reaction solution was then poured into the funnel and filtered again, followed by rotary evaporation for concentration. The crude product was purified by column chromatography using dichloromethane / petroleum ether (2:8 v / v) as the eluent to give compound B (1.06 g, yield 83.02%). The 1H NMR spectrum of compound B is 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 Wilsmeier's reagent. A 1,2-Dichloroethane solution (20 mL) of compound B (500 mg, 0.286 mmol, 1.00 equiv.) was added to the Wilsmeier's reagent. The mixture was slowly heated to 70 °C and refluxed for 16 h. After the reaction was completed, the mixture was cooled to room temperature, and 1 mol / L sodium hydroxide solution was added in an ice bath and stirred for 2 h. The aqueous phase was then removed by extraction with dichloromethane, and the product was concentrated by rotary evaporation to obtain the crude product. The crude product was purified by silica gel column chromatography, using dichloromethane / petroleum ether (volume ratio 1:1) as the eluent to obtain compound C (490 mg, yield 92%). The 1H 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-armed non-fused-ring electron acceptor BO-TT-IC: Compound C (350 mg, 0.19 mmol, 1.00 equiv.) and 3-(dicyanomethylene)indophenone (203 mg, 1.05 mmol, 5.50 equiv.) were added to a dry 100 mL pressure-resistant reaction flask, followed by 20 mL of anhydrous chloroform. The mixture was bubbled with nitrogen for 20 min and then heated to 55 °C. Pyridine (0.2 mL, 2.5 mmol, 13.10 equiv.) was then rapidly added, followed by reflux at 65 °C for 14 h. After the reaction was complete, the mixture was poured into 100 mL of anhydrous methanol to precipitate crystals. The mixture was filtered to obtain a crude product in a purplish-black color. 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 proton NMR data for 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-armed non-fused ring electron acceptor BO-TT-FIC has the following structural formula:

[0052] .

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

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

[0055] (4) Synthesis of the four-armed non-fused-ring electron acceptor BO-TT-FIC: Compound C (350 mg, 0.19 mmol, 1.00 equiv.) and 5,6-difluoro-3-(dicyanomethylene)indophenone (203 mg, 1.05 mmol, 5.50 equiv.) were added to a dry 100 mL pressure-resistant reaction flask, followed by 20 mL of anhydrous chloroform. The mixture was bubbled with nitrogen for 20 min and then heated to 55 °C. Pyridine (0.2 mL, 2.5 mmol, 13.10 equiv.) was then rapidly added, followed by reflux at 65 °C for 14 h. After the reaction was complete, the mixture was poured into 100 mL of anhydrous methanol to precipitate crystals. The mixture was filtered to obtain a crude product in a purplish-black color. 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 proton NMR data for 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-armed non-fused ring electron acceptor BO-TT-ICB has the following structural formula:

[0059] .

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

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

[0062] (4) Synthesis of the four-armed 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-cyclopentano[b]naphthalene-1-yl)malononitrile (357 mg, 1.46 mmol, 5.50 equiv.) were added to a dry 100 mL pressure-resistant reaction flask, followed by 20 mL of anhydrous chloroform. The mixture was bubbled with nitrogen for 20 min and then heated to 55 °C. Pyridine (0.2 mL, 2.5 mmol, 13.10 equiv.) was then rapidly added, followed by refluxing at 65 °C for 14 h. After the reaction was complete, the mixture was poured into 100 mL of anhydrous methanol to precipitate crystals. The mixture was filtered to obtain a crude product that was purplish-black. 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 1H NMR spectral data for BO-TT-ICB 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] Organic solar cell devices using four-armed non-fused-ring small molecules (BO-TT series) as acceptors were fabricated. The structure of the organic solar cell device is as follows: Figure 2 As shown. Using commercially available D18 (CAS No.: 2433725-54-1) as the donor material, and the prepared four-armed non-fused-ring small molecule BO-TT series as the acceptor material, they were mixed at a mass ratio of 1:1 and dissolved in chloroform to prepare a 10 mg / mL solution. A thin film was prepared by spin-coating on an ITO glass substrate modified with a hole transport layer PEDOT:PSS. Then, an electron transport layer PDINN was spin-coated, and a silver electrode was deposited as the anode. The film was tested under white light at 1.5 G (100 Mw / m²). 2 Under irradiation, its photoelectric conversion efficiency was tested.

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

[0067] Table 1. Photovoltaic conversion efficiency of solar cell devices

[0068] receptor materials <![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 relatively highest open-circuit voltage (V). oc This indicates that the donor and BO-TT-ICB have optimal energy level matching; while photovoltaic devices based on D18:BO-TT-FIC exhibit significantly higher circuit current density (J). scThe high fill factor (FF) and optimal conversion efficiency indicate that although the fluorinated end groups cause some voltage loss in the device, the intermolecular FO dipole interaction effectively promotes charge separation and transport, thereby improving the overall efficiency.

[0070] Experiment Example 2

[0071] Organic solar cell devices using four-armed non-fused-ring small molecules (BO-TT series) as acceptors were fabricated. The structure of the organic solar cell device is as follows: Figure 2 As shown. Using commercially available PM6 (CAS No.: 1802013-84-8) as the donor material, and the prepared four-armed non-fused-ring small molecule BO-TT series as the acceptor material, the materials were mixed at a mass ratio of 1:1 and dissolved in chloroform to prepare a 10 mg / mL solution. A thin film was then prepared by spin-coating on an ITO glass substrate modified with a hole transport layer PEDOT:PSS. An electron transport layer PDINN was then spin-coated, and a silver electrode was deposited as the anode. The film was then applied at 1.5 G (100 Mw / m²) white light. 2 Under irradiation, its photoelectric conversion efficiency was tested.

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

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

[0074] receptor materials <![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 shown in Table 2, the performance of photovoltaic devices based on all three acceptor materials improved when the blended donor material was replaced with PM6. This indicates that the three acceptors have better compatibility with the donor PM6 compared to D18. The photovoltaic devices based on PM6:BO-TT-IC and PM6:BO-TT-ICB exhibited similarly high open-circuit voltages, indicating good energy level matching between these two acceptors and PM6. Furthermore, the fluorinated end groups of BO-TT-FIC are more conducive to the formation of intermolecular FO dipole interactions, promoting charge separation and transport, and exhibiting the best morphological compatibility with PM6.

[0076] Although specific embodiments of the present invention have been described in detail with reference to examples, they should not be construed as limiting the scope of protection of this patent. Various modifications and variations that can be made by those skilled in the art without inventive effort within the scope described in the claims are still within the scope of protection of this patent.

Claims

1. A four-armed non-fused-ring electron acceptor, characterized in that: The structural formula of the four-armed non-fused ring electron acceptor is shown in Formula I. ， Among them, R 1-1 R 1-2 R2 is a long-chain alkyl group, wherein R 1-1 It is a straight-chain alkyl group with 8 carbon atoms; the R 1-2 R1 is a straight-chain alkyl group with 6 carbon atoms; R2 is a straight-chain alkyl group with 11 carbon atoms; R is a hydrogen atom or a fluorine atom; Ar is a benzene ring or a naphthalene ring.

2. The four-armed non-fused-ring electron acceptor according to claim 1, characterized in that, The four-armed non-fused ring electron acceptor has one of the following structural formulas: 、 、 。 3. The method for preparing the four-armed non-fused ring electron acceptor according to any one of claims 1 to 2, characterized in that, Includes the following steps: S1: Tetrabromohydroquinone and the first catalyst are co-dissolved in the first solvent, and then alkyl bromide is added to the resulting solution to obtain the first reaction system; then the first reaction system is heated to 70~90℃ in an inert atmosphere and kept at the temperature for 14~20h, and then the product is extracted and purified to obtain compound A; the structural formula of the alkyl bromide is shown in formula (1), and the structural formula of compound A is shown in formula (2). ， ， S2: Compound A and 2-tributyl(7-alkyl-thiophene[3,2b']thiophene)tin reagent are co-dissolved in a second solvent. After purging with nitrogen and bubbling for 20 min, a second catalyst is added to obtain a second reaction system. The second reaction system is then heated to 90~110℃ and kept at that temperature for 36~50 h. After filtration and purification, compound B is obtained. The structural formula of the 2-tributyl(7-alkyl-thiophene[3,2b']thiophene)tin reagent is shown in formula (3), and the structural formula of compound B is shown in formula (4). ， ， S3: Mix N,N-dimethylformamide with a third solvent, cool the mixture to -5~1℃, then add phosphorus oxychloride to the mixture, keep warm and stir for 0.5~2h to obtain Wilsmeer reagent; dissolve compound B in the third solvent, then add the resulting solution to Wilsmeer reagent to obtain a third reaction system; heat the third reaction system to 60~80℃, reflux for 12~18h, then extract the product and purify it to obtain compound C, the structural formula of compound C is shown in formula (5); ， Among them, R 1-1 R 1-2 R2 is as described in claim 1 or 2; S4: Compound C and the compound shown in Formula II are co-dissolved in a fourth solvent. After purging with nitrogen and bubbling for 20 min, the resulting solution is heated to 50-60 °C and a third catalyst is added to obtain a fourth reaction system. The fourth reaction system is then heated to 55-70 °C and refluxed for 10-15 h. After crystallization and purification, the product is obtained. ， Where Ar is a benzene ring or a naphthalene ring, and R is a hydrogen atom or a fluorine atom.

4. The preparation method according to claim 3, characterized in that: The molar ratio of tetrabromohydroquinone, alkyl bromide, and the first catalyst is 1:1.5~3:2~4; 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.

5. The preparation method according to claim 3, characterized in that: 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 second catalyst is at least one of tetra(triphenylphosphine)palladium, bis(triphenylphosphine)palladium dichloride, tris(dibenzylideneacetone)palladium, and palladium acetate; the second solvent is toluene; and the concentration of compound A in the second reaction system is 0.02~0.06 mol / L.

6. The preparation method according to claim 3, 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 ratio of compound B to the third solvent is 1g:40mL; the third solvent is 1,2-dichloroethane.

7. The preparation method according to claim 3, characterized in that: 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.

8. The use of the four-armed non-fused ring electron acceptor according to any one of claims 1 to 2 in the preparation of organic solar cells.

9. The application according to claim 8, characterized in that, The organic solar cell is prepared through the following steps: (1) Modify the ITO glass substrate with PEDOT:PSS to obtain the substrate; (2) Dissolve the donor material and the four-armed 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. Then spin-coat the resulting solution onto the substrate to obtain an intermediate. The donor material is D18 or PM6. (3) Spin-coat PDINN onto the intermediate, and then deposit silver electrodes on the PDINN layer to obtain the final product.

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