Preparation of Fluorene-Benzothiadiazole Multichain BOLA Liquid Crystalline Compounds and Their Modification for Silicon-Based Solar Cells

Abstract

The present invention provides two types of fluorene-benzothiadiazole multi-chain BOLA liquid crystal compounds, their preparation methods, and their applications in solar cells. These compounds relate to the fields of liquid crystal materials and organic solar cells. These two types of molecules contain both fluorene and benzothiadiazole bifunctional groups and can self-assemble into complex honeycomb columnar and cubic phase liquid crystals by adjusting the conjugated linking groups and the length of the alkyl side chains. The short side chains of Fn form triangular honeycomb hexagonal columnar liquid crystals (Col hex△ / p 6 mm ), F18 with long side chains was observed to have a network cubic mesophase Cub / pm 3 n , low temperature is Col hex△ / p 6 mm Liquid crystal phase. Short side chain TFn can also form Col hex△ / p 6 mm Liquid crystal phase, TF18 with long side chains can form square honeycomb columnar liquid crystals at low temperatures squ / P 4 gm , high temperature is Col hex△ / p 6 mm Liquid crystals. Furthermore, the self-assembly properties of the compounds Fn and TFn were exploited to modify PEDOT:PSS thin films, resulting in the fabrication of highly efficient and practical PEDOT:PSS / n-Si heterojunction solar cell devices. These materials are expected to find widespread application in the field of organic optoelectronic materials.

Description

Technical Field

[0001] This invention relates to the field of fluorene-benzothiadiazole multi-chain BOLA liquid crystal materials, specifically methods for preparing BOLA liquid crystal compounds based on fluorene and benzothiadiazole (BTD) derivatives, and their application in organic / n-Si heterojunction solar cells. These compounds are expected to find widespread application in the field of organic optoelectronics. Background Art

[0002] Liquid crystal systems are a perfect example of how nature can self-assemble soft matter into well-defined structures. A particularly successful example is the multi-chain BOLA amphiphilic block molecule. These molecules consist of a π-conjugated rod-shaped aromatic core with glycerol end groups at each end and flexible side chains. Depending on the length of the conjugated core rods and the number and length of the side chains, these molecules can self-assemble into liquid crystal phases with complex honeycomb structures. Within this honeycomb structure, the π-conjugated rod-shaped aromatic core is connected by a hydrogen-bonded network formed by the glycerol end groups. The resulting prismatic units are filled with flexible side chains, with the π-conjugated rod-shaped aromatic core oriented perpendicular to the long axis of the column. Depending on the volume of the side chains and the length of the rigid rod-shaped core, different types of honeycomb phases, such as triangular, square, pentagonal, and hexagonal, are observed.

[0003] The present invention focuses on fluorene and benzothiadiazole because these units have been shown to be a class of organic optoelectronic materials with excellent properties. In particular, fluorene derivatives are known for their strong blue fluorescence emission and high thermal stability. 9-9 dialkylfluorene has been used as a π-conjugated linker to avoid molecular aggregation and inhibit charge recombination. Due to the sp 3 Hybridization, the two alkyl chains are almost perpendicular to the conjugated backbone, and the central fluorene unit usually distorts the π-conjugated coplanarity of the molecule. In this regard, finding a way to assemble such π-conjugated aromatic compounds into complex liquid crystals is of great significance. In particular, the self-healing ability of liquid crystals makes fluorene derivatives of great value as organic optoelectronic materials. Liquid crystal derivatives of fluorene form smectic and nematic liquid crystals in most cases, with only rare cases of multi-chain fluorene forming triangular honeycomb columnar phases. However, multi-chain BOLA liquid crystals containing both fluorene and benzothiadiazole dual functional groups have not been reported. Therefore, it is extremely important to expand this type of derivatives to produce more complex honeycomb liquid crystals and enrich the variety of BOLA compound liquid crystal libraries.

[0004] Organic / n-Si heterojunctions, consisting of a silicon-based absorber and an organic charge-selective functional layer, offer promising approaches for fabricating low-cost, high-power-to-photovoltaic (PCE) next-generation photovoltaic cells due to their unique properties of n-Si and simple device architecture. However, improvements in the performance of planar heterojunction solar cells are significantly hindered by nonideal interfacial contacts and low electrical conductivity of organic semiconductors. One promising approach is to further enhance device efficiency by controlling the interfacial contact and electrical conductivity of organic semiconductors. Poly(3,4-ethylenedioxythiophene):polystyrene (PEDOT:PSS) polymers are considered one of the most promising candidates for hole-selective functional layers in organic and perovskite solar cells due to their high transmittance and tunable optoelectronic properties. However, the very low electrical conductivity of pure PEDOT:PSS (PH-1000) films makes them difficult to use as charge-selective and collection functional layers in transparent conductive electrodes for high-efficiency organic / n-Si heterojunction solar cells. The short-circuit current and fill factor of PEDOT:PSS / n-Si heterojunction solar cells are lower than those of conventional homogeneous pn Si heterojunction solar cells. This means that the heterojunction's ability to separate photogenerated carriers remains weaker than that of conventional pn junctions. Improving electrical performance and energy-level alignment remains a significant challenge. This novel and feasible approach utilizes the self-assembly-inducing ability of liquid crystal molecules to modify the PEDOT:PSS thin film layer to improve the efficiency of organic / n-Si heterojunction solar cells. Summary of the Invention

[0005] The present invention provides a method for preparing these fluorene-benzothiadiazole multi-chain BOLA liquid crystal compounds. By introducing different conjugated groups into the BOLA amphiphilic molecules and adjusting the length of the C-9 side chain on the fluorene, a variety of liquid crystal materials with complex honeycomb columnar structures are obtained. Based on the self-assembly ability of liquid crystal materials, these BOLA liquid crystal compounds are doped into PEDOT:PSS / n-Si heterojunction solar cells, significantly improving the device's photoelectric conversion efficiency.

[0006] The multi-chain BOLA liquid crystal compound of the present invention is characterized in that the compound has the following structural formula:

[0007] The compound is Fn, wherein n is 12, 16, or 18;

[0008] The compound is TFn, wherein n is 12, 16, or 18.

[0009] The multi-chain BOLA liquid crystal compound is characterized in that the compound is prepared by the following steps:

[0010] 1. Step 1: 2,7-dibromofluorene and bromoalkane (bromododecadecane) were dissolved in dry tetrahydrofuran, potassium tert-butoxide was added under ice bath, and the mixture was reacted at room temperature for 3 hours to obtain compound 1 / n;

[0011] 2. Step 2: 1 / n and p-hydroxyphenylboronic acid were dissolved in tetrahydrofuran, and then a potassium carbonate solution dissolved in water was added to the tetrahydrofuran solution. Under nitrogen protection, after ultrasonic deoxygenation, a catalytic amount of tetrakis(triphenylphosphine)palladium was added, and the mixture was stirred and refluxed at 78°C for 12 hours to obtain 2 / n;

[0012] 3. Step 3: Dissolve the compound 2 / n obtained in step 2 in acetonitrile solution, add 2 equivalents of potassium carbonate, stir for 30 minutes, then add allyl bromide, and react at 70°C for 12 hours to obtain compound 3 / n;

[0013] 4. Step 4: Dissolve 3 / n in acetone, then add a catalytic amount of N-methylmorpholine-N-oxide (NMMNO) and an appropriate amount of osmium tetroxide (OsO4), and stir at 40°C for 3 hours to obtain 4 / n;

[0014] 5. Step 5: Compound 4 / n obtained in step 4 was dissolved in tetrahydrofuran, and pyridinium p-toluenesulfonate (PPTS) and acetone dimethyl acetal were added. The reaction was carried out at room temperature for 12 hours to complete the protection of the terminal vicinal diol to obtain compound 5 / n;

[0015] 6. Step 6: 5 / n and bis-pinacol borate were dissolved in 1,4-dioxane, followed by the addition of potassium acetate. Under nitrogen protection, after ultrasonic deoxygenation, a catalytic amount of 1,1'-bis(diphenylphosphino)ferrocenepalladium dichloride was added, and the mixture was stirred at 100°C for 12 hours to obtain 6 / n.

[0016] 7. Step 7: 6 / n and 4,7-dibromo-2,1,3-benzothiadiazole were dissolved in tetrahydrofuran, and then a potassium carbonate solution dissolved in water was added to the tetrahydrofuran solution. Under nitrogen protection, after ultrasonic deoxygenation, a catalytic amount of tetrakis(triphenylphosphine)palladium was added, and the mixture was stirred and refluxed at 78°C for 18 hours. After the reaction was completed, the solvent was removed, and the crude product was further directly dissolved in a tetrahydrofuran / methanol mixture without purification, and 10% HCl was added. After reacting at 70°C for 3 hours, a yellow solid Fn series product was obtained;

[0017] 8. Step 8: 6 / n and 4,4,7-bis(5-bromothiophen-2-yl)benzo[c][1,2,5]thiadiazole were dissolved in tetrahydrofuran, and then a potassium carbonate solution dissolved in water was added to the tetrahydrofuran solution. Under nitrogen protection, after ultrasonic deoxygenation, a catalytic amount of tetrakis(triphenylphosphine)palladium was added, and the mixture was stirred and refluxed at 78°C for 18 hours. After the reaction was completed, the solvent was removed. The crude product was further dissolved in a mixed solution of tetrahydrofuran / methanol without purification, and 10% HCl was added. After reacting at 70°C for 3 hours, a red solid TFn series product was obtained.

[0018] in,

[0019] Compound 1 / n is 1 / 12, 1 / 16, and 1 / 18, which are 2,7-dibromo-9,9-didodecanyl-9H-fluorene, 2,7-dibromo-9,9-dixadecanyl-9H-fluorene, and 2,7-dibromo-9,9-dioctadecanyl-9H-fluorene, respectively;

[0020] Compound 2 / n is 2 / 12, 2 / 16, and 2 / 18, which are 4-(7-bromo-9,9-didodecyl-9H-fluoren-2-yl)phenol, 4-(7-bromo-9,9-dixadecyl-9H-fluoren-2-yl)phenol, and 4-(7-bromo-9,9-dioctadecyl-9H-fluoren-2-yl)phenol, respectively;

[0021] Compounds 3 / n were 3 / 12, 3 / 16, and 3 / 18, which were 2-(4-(allyloxy)phenyl)-7-bromo-9,9-didodecanyl-9H-fluorene, 2-(4-(allyloxy)phenyl)-7-bromo-9,9-didecanyl-9H-fluorene, and 2-(4-(allyloxy)phenyl)-7-bromo-9,9-didecanyl-9H-fluorene, respectively;

[0022] Compounds 4 / n are 4 / 12, 4 / 16, and 4 / 18, which are 3-(4-(7-bromo-9,9-didodecanyl-9H-fluoren-2-yl))phenoxy)propane-1,2-diol, 3-(4-(7-bromo-9,9-dixadecanyl-9H-fluoren-2-yl))phenoxy)propane-1,2-diol, and 3-(4-(7-bromo-9,9-diodecyl-9H-fluoren-2-yl))phenoxy)propane-1,2-diol, respectively;

[0023] Compounds 5 / n were 5 / 12, 5 / 16, and 5 / 18, respectively, including 4-((4-(7-bromo-9,9-didecanyl-9H-fluoren-2-yl))phenoxy)methyl)-2,2-dimethyl-1,3-dioxolane, 4-((4-(7-bromo-9,9-didecanyl-9H-fluoren-2-yl))phenoxy)methyl)-2,2-dimethyl-1,3-dioxolane, and 4-((4-(7-bromo-9,9-didecanyl-9H-fluoren-2-yl))phenoxy)methyl)-2,2-dimethyl-1,3-dioxolane;

[0024] Compounds 6 / n are 6 / 12, 6 / 16, and 6 / 18, respectively, which are 2-(7-(4-((2,2-dimethyl-1,3-dioxolane-4-yl))methoxy)phenyl)-9,9-didodecanyl-9H-fluorene-2-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane, 2-(7-(4-((2,2-dimethyl-1,3-dioxolane-4-yl))methoxy)phenyl)-9,9-didecanyl-9H-fluorene-2-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane, and 2-(7-(4-((2,2-dimethyl-1,3-dioxolane-4-yl))methoxy)phenyl)-9,9-didecanyl-9H-fluorene-2-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane. -fluorene-2-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane.

[0025] In this new class of fluorene-benzothiadiazole multi-chain BOLA liquid crystal compounds, the molecules can self-assemble to form complex honeycomb columnar phases and cubic phases. For the Fn series, two different LC phases were observed. F12 and F16 with short side chains form triangular honeycomb hexagonal columnar liquid crystals (Col hex△ / p 6 mm ) and F18 with long alkyl side chains have cubic phase liquid crystal (Cub / pm 3 n ), forming triangular honeycomb hexagonal columnar liquid crystal in the low temperature range (Col hex△ / p 6 mm TF16 forms a triangular honeycomb hexagonal columnar liquid crystal (Col hex△ / p 6 mm The long-chain compound TF18 can form a square honeycomb columnar liquid crystal (Col squ / P 4 gm ), high temperature is still triangular honeycomb hexagonal columnar liquid crystal (Col hex△ / p 6 mm ). In addition, the self-assembly ability of compounds Fn and TFn was used to induce the modification of PEDOT:PSS thin films, and high-efficiency and practical PEDOT:PSS / n-Si heterojunction solar cell devices were prepared.

[0026] Figures in the specification

[0027] Figure 1 This is the preparation route of the present invention;

[0028] Figure 2 This is the columnar liquid crystal texture of compound F12 observed under a polarizing microscope at 120°C;

[0029] Figure 3 This is the columnar liquid crystal texture of compound F16 observed under a polarizing microscope at 120°C;

[0030] Figure 4 This is the columnar liquid crystal texture of compound F18 observed under a polarizing microscope at 100°C;

[0031] Figure 5 This is the columnar liquid crystal texture of compound TF16 observed under a polarizing microscope at 120°C;

[0032] Figure 6 This is the columnar liquid crystal texture of compound TF18 observed under a polarizing microscope at 100°C;

[0033] Figure 7 This is the columnar liquid crystal texture of compound TF18 observed under a polarizing microscope at 130°C;

[0034] Figure 8 is the XRD pattern of compound F16 at 120 °C;

[0035] Figure 9 is the XRD pattern of compound F18 at 100 °C;

[0036] Figure 10 is the XRD pattern of compound F18 at 130 °C;

[0037] Figure 11 is the XRD pattern of compound TF18 at 100 °C;

[0038] Figure 12 is the XRD pattern of compound TF18 at 130 °C;

[0039] Figure 13 The UV-visible absorption spectra of dichloromethane solutions and thin films of compounds F16 and TF16;

[0040] Figure 14Fluorescence emission spectra of dichloromethane solution and thin film of compounds F16 and TF16;

[0041] Figure 15 The JV current density voltage characteristic curves of solar cells with different dopants in PEDOT:PSS films;

[0042] Figure 16 Device photo of the prepared PEDOT:PSS:dopant / n-Si heterojunction solar cell;

[0043] Figure 17 H NMR characterization of compound F16;

[0044] Figure 18 The C NMR characterization of compound F16;

[0045] Figure 19 H NMR characterization of compound TF16;

[0046] Figure 20 This is the C NMR characterization of compound TF16. DETAILED DESCRIPTION

[0047] The present invention will be further described in detail below in conjunction with specific embodiments, but the protection scope of the present invention is not limited to the contents described above.

[0048] Example 1: Preparation and characterization of multi-chain bola liquid crystal compounds Fn and TFn

[0049] according to Figure 1 The preparation route of the invention is as follows:

[0050] 1. Step 1: Dissolve an appropriate amount of 2,7-dibromofluorene (15 mmol) in tetrahydrofuran. Add potassium tert-butoxide (30 mmol) under ice-cooling. Stir for 30 minutes, then add bromoalkane (31 mmol). Return to room temperature and allow to react for 3 hours. Quench the reaction with 40 ml of water. Extract three times with dichloromethane (30 ml x 3). Combine the organic layers, dry them over anhydrous magnesium sulfate, remove the organic solvent by distillation under reduced pressure, and recrystallize from ethanol. A white solid, 1 / n, is obtained with a yield of 96%.

[0051] The reaction formula is as follows:

[0052] .

[0053] 2. Step 2: Dissolve 1 / n (10 mmol) and p-hydroxyphenylboronic acid (10 mmol) in 40 mL of tetrahydrofuran, then add a 10 mL aqueous solution of potassium carbonate (20 mmol). Under N2 protection, deoxygenate by ultrasonication for 15 minutes. Rapidly add a catalytic amount of tetrakistriphenylphosphine palladium, and then reflux at 78°C for 12 hours. Monitor the reaction with thin-layer chromatography. After completion of the reaction, add 20 mL of water to the reaction system, extract three times with dichloromethane (20 mL x 3), combine the organic layers, dry them over anhydrous magnesium sulfate, and remove the organic solvent by distillation under reduced pressure. Purify the crude product by column chromatography using a 15:1 ratio of petroleum ether to ethyl acetate as the eluent to obtain 2 / n, a colorless liquid, in a yield of 45%.

[0054] The reaction formula is as follows:

[0055] .

[0056] 3. Step 3: Dissolve an appropriate amount of 2 / n (4 mmol) in acetonitrile, add potassium carbonate (8 mmol), stir for 30 minutes, add allyl bromide (4.2 mmol), react at 70°C for 12 hours, then quench the reaction with 20 ml of water. Extract with dichloromethane three times (20 ml x 3). Combine the organic layers, dry them over anhydrous magnesium sulfate, and remove the organic solvent by distillation under reduced pressure. Purify the crude product by column chromatography using a 15:1 ratio of petroleum ether to ethyl acetate as the eluent to obtain a colorless liquid 3 / n. Yield: 80%.

[0057] The reaction formula is as follows:

[0058] .

[0059] 4. Step 4: Dissolve an appropriate amount of 3 / n (3 mmol) in acetone, add catalytic amounts of N-methylmorpholine oxide and osmium tetroxide (3.3 mmol), react at 40°C for 3 hours, then add 20 ml of a saturated aqueous solution of sodium thiosulfate to quench the reaction. Extract with dichloromethane three times (20 ml x 3). Combine the organic layers, dry them over anhydrous magnesium sulfate, and remove the organic solvent by distillation under reduced pressure. Purify the crude product by column chromatography using a 1:1 ratio of petroleum ether to dichloromethane as the eluent to obtain 4 / n as a colorless liquid in a yield of 93%.

[0060] The reaction formula is as follows:

[0061] .

[0062] 5. Step 5: Dissolve an appropriate amount of 4 / n (2.5 mmol) in dry tetrahydrofuran, add acetone dimethyl acetal (10 mmol) and a catalytic amount of pyridinium p-toluenesulfonate, react at room temperature for 12 hours, then add 20 ml of water to quench the reaction, and extract three times with dichloromethane (20 ml x 3). Combine the organic layers, dry them over anhydrous magnesium sulfate, and remove the organic solvent by distillation under reduced pressure. The crude product is purified by column chromatography using a 1:1 ratio of petroleum ether to dichloromethane as the eluent to obtain a colorless liquid 5 / n with a yield of 75%.

[0063] The reaction formula is as follows:

[0064] .

[0065] 6. Step 6: Take an appropriate amount of 5 / n (1.5 mmol) and bis-pinacol borate (3 mmol) and dissolve them in dry 1,4-dioxane. Potassium acetate (6 mmol) is added. Under N2 protection, ultrasonic deoxygenation is carried out for 15 minutes. A catalytic amount of 1,1'-bis(diphenylphosphino)ferrocene]palladium dichloride is quickly added. The reaction is then refluxed at 100°C for 12 hours and monitored by thin-layer chromatography. After completion of the reaction, 20 ml of water is added to the reaction system to quench the reaction. The mixture is then extracted three times with dichloromethane (20 ml x 3). The organic layers are combined and dried over anhydrous magnesium sulfate. The organic solvent is removed by distillation under reduced pressure. The crude product is purified by column chromatography using a 2:1 ratio of petroleum ether to dichloromethane as the eluent to obtain 6 / n as a white solid. The yield is 85%.

[0066] The reaction formula is as follows:

[0067] .

[0068] 7. Step 7, 6 / n (0.5 mmol) and 4,7-dibromo-2,1,3-benzothiadiazole (0.24 mmol) were dissolved in 20 ml of tetrahydrofuran solution, and then 5 ml of an aqueous solution of potassium carbonate (1 mmol) was added thereto. Under N2 protection, ultrasonic deoxygenation was performed for 15 minutes, and a catalytic amount of tetrakistriphenylphosphine palladium was quickly added. The reaction was then refluxed at 78°C for 18 hours and monitored by thin layer chromatography. After the reaction was completed, 20 ml of water was added to the reaction system, and the mixture was extracted three times with dichloromethane (20 ml×3). The organic layers were combined and the organic solvent was removed by distillation under reduced pressure to obtain a crude product. The crude product did not need to be purified and was further dissolved in a 1:1 mixture of tetrahydrofuran and methanol. 8 ml of a 10% HCl solution was added and the reaction was carried out at 70°C for 3 hours and monitored by thin layer chromatography. After the reaction was completed, 20 ml of water was added to the reaction system and the mixture was extracted three times with dichloromethane (20 ml×3). ml×3), the organic layers were combined and dried over anhydrous magnesium sulfate, and the organic solvent was removed by distillation under reduced pressure. The crude product was purified by column chromatography using a dichloromethane:methanol ratio of 10:1 as eluent to obtain yellow solid Fn series products with a yield of 79%-84%;

[0069] The reaction formula is as follows:

[0070] .

[0071] 8. Step 8. Dissolve 6 / n (0.5 mmol) and 4,7-bis(5-bromothiophen-2-yl)benzo[c][1,2,5]thiadiazole (0.24 mmol) in 20 mL of tetrahydrofuran, and add 5 mL of an aqueous solution of potassium carbonate (1 mmol). Under N2 protection, deoxygenate by ultrasonication for 15 minutes. Rapidly add a catalytic amount of tetrakistriphenylphosphine palladium, and then reflux at 78°C for 18 hours. Monitor the reaction with thin-layer chromatography. After completion of the reaction, add 20 mL of water to the reaction system, and extract three times with dichloromethane (20 mL × 3). Combine the organic layers and distill under reduced pressure to remove the organic solvent. The crude product does not need to be purified. The crude product was dissolved in a 1:1 mixture of tetrahydrofuran and methanol, and 8 ml of 10% HCl solution was added. The reaction was allowed to proceed at 70°C for 3 hours, monitored by thin-layer chromatography. After completion of the reaction, 20 ml of water was added and the product was extracted three times with dichloromethane (20 ml x 3). The organic layers were combined and dried over anhydrous magnesium sulfate. The organic solvent was removed by distillation under reduced pressure. The crude product was purified by column chromatography using a 10:1 dichloromethane:methanol eluent to obtain a red solid TFn series product with a yield of 80%-83%.

[0072] The reaction formula is as follows:

[0073] .

[0074] All target compounds have similar NMR data, and representative compounds F16 and TF16 are selected to display their NMR data.

[0075] F16 NMR data such as Figure 17 、 Figure 18 As shown: 1 H NMR (CDCl3, 400 MHz), δ (ppm): 7.90-7.89 (d, 2H, J = 2.80 Hz), 7.87(s, 2H), 7.82-7.80 (d, 8H, J = 8.00 Hz), 7.65-7.62(d, 2H, J = 8.40 Hz), 7.58 (d, 4H, J = 1.20 Hz), 7.55(s, 4H), 7.05-7.03 (d, 4H, J =8.80Hz), 4.18-4.16 (m, 2H), 4.14-4.12 (m, 4H), 3.92-3.88 (m, 2H), 3.83-3.79(m, 2H), 2.69 (s, 2H), 2.14-2.01 (m, 10 H), 1.62 (s, 4H), 1.28-1.10 (m, 99H), 0.86 (t, 21H). 13 C NMR (CDCl3; 100 MHz): 157.9, 154.4, 152.1, 151.4, 141.1,139.7, 139.5, 136.1, 135.0, 133.6, 128.3, 128.2, 127.9, 125.7, 123.9, 121.2,120.2, 119.7, 114.9, 77.3, 77.2, 77.0, 76.7, 70.4, 69.4, 63.7, 55.3, 40.4,31.9, 30.1, 29.6, 29.3, 29.3, 24.0, 22.7, 14.1;

[0076] The NMR data of TF16 are as follows Figure 19 、 Figure 20 As shown: 1 H NMR (CDCl3, 400 MHz), δ (ppm): 8.16(s, 2H), 7.93 (s, 2H), 7.74-7.72 (d, 6H, J= 9.60 Hz), 7.68(s, 2H), 7.63-7.61(d, 4H, J = 8.80 Hz), 7.55-7.49 (m, 6H), 7.04-7.02 (d, 4H, J = 8.80Hz), 4.18-4.15(m, 2H), 4.13-4.11 (m, 4H), 3.91-3.88 (m, 2H), 3.82-3.78 (m, 2H), 2.70 (s,2H), 2.08-2.04 (m, 10 H), 1.63 (s, 4H), 1.27-1.07 (m, 98H), 0.87-0.73 (m, 22H). 13 C NMR (CDCl3; 100 MHz): 157.9, 152.7, 151.8, 151.7, 146.5, 140.8,139.7, 139.5, 138.3, 134.9, 132.8, 128.7, 128.3, 125.8, 125.7, 125.3, 124.9,123.9, 121.1, 120.1, 120.1, 120.0, 114.9, 77.3, 77.0, 76.8, 70.4, 69.4, 68.0,63.7, 55.4, 40.5, 31.9, 30.0, 29.7, 29.7, 29.7, 29.6, 29.4, 29.3, 25.6, 23.8,22.7, 14.1.

[0077] Example 2: Study on the optical properties of compounds Fn and TFn

[0078] The optical properties of Fn and TFn prepared in the above steps are not affected by the length of the alkyl chain. Therefore, the medium chain length compounds F16 and TF16 were selected to study their optical properties. -5 M) and the UV-visible absorption and fluorescence emission spectra of thin films were studied. Figure 13As shown in Figure 14, compound F16 exhibits maximum absorption wavelengths of 333 and 424 nm in dichloromethane solution and 340 and 436 nm in thin film form. Its maximum emission wavelengths are 551 nm in dichloromethane solution and 548 nm in thin film form, with fluorescence quantum yields of 62% and 85%, respectively. Compound TF16 exhibits maximum absorption wavelengths of 309, 370, and 514 nm in dichloromethane solution and 310, 377, and 530 nm in thin film form, exhibiting a wide absorption range (200-650 nm), making it more suitable for application in solar cells. Its maximum emission wavelengths are 650 nm in dichloromethane solution and 675 nm in thin film form, with fluorescence quantum yields of 32% and 36%, respectively.

[0079] Example 3: Study on the Liquid Crystal Properties of Compounds Fn and TFn

[0080] like Figure 2-12 As shown in Table 1, except for compound TF12, which is crystalline, the liquid crystal properties of the remaining compounds have been verified by polarizing microscopy (POM), differential scanning calorimetry (DSC), and X-ray diffractometry (XRD). For the Fn series, two distinct LC phases were observed. Compounds F12 with the shortest alkyl chain and F16 with a medium chain length only form triangular honeycomb hexagonal prisms in a specific temperature range (Col hex△ / p 6 mm The long alkyl chain F18 has a cubic phase liquid crystal (Cub / pm 3 n ), in the low temperature range, triangular honeycomb hexagonal columnar liquid crystals are formed (Col hex△ / p 6 mm Compound TF16 forms a triangular honeycomb hexagonal columnar liquid crystal (Col hex△ / p 6 mm The long-chain compound TF18 can form a square honeycomb columnar liquid crystal (Col squ / P 4 gm ), high temperature is still triangular honeycomb hexagonal columnar liquid crystal (Col hex△ / p 6 mm ).

[0081] Table 1: Phase transition temperatures and lattice constants of compounds Fn and TFn

[0082] Note: Cr: crystal; Col squ / p 4 gm : Tetragonal prism phase; Col hex△ / P 6 mm : hexagonal columnar phase; Cub / pm3n: with pm3 n Cubic phase of the crystal lattice; Iso: isotropic liquid. b Phase transition temperature determined by POM.

[0083] Example 4: Preparation of high-performance PEDOT:PSS / n-Si heterojunction solar cells

[0084] like Figure 15 、 16 As shown in Figure 2, a PEDOT:PSS / n-Si heterojunction solar cell was fabricated, consisting of a 200 nm Ag gate, a PEDOT:PSS:liquid crystal compound film (approximately 110 nm thick), an n-type Si wafer (300 μm thick, resistivity 0.05–0.10 Ω·cm), and an aluminum (Al) electrode (100 nm). Table 2 shows the changes in the conductive properties of PEDOT:PSS (PH-1000) as a function of F18 and TF18 doping in the PEDOT:PSS precursor solution film. The addition of 1.1% F18 significantly increased the conductivity of the PEDOT:PSS film. The film conductivity increased from 77.11 to 207.90 S·cm. -1 After adding 0.8% TF18, the conductivity of PEDOT:PSS film further increased to 268.92 S·cm -1 The carrier mobility also increases with the doping of F18 and TF18, from 5.68 to 6.18 and 10.70 cm 2 ·v -1 ·s -1 The carrier concentration of the film is improved with the doping of F18 and TF18, from 8.5×10 19 Increased to 1.5×10 20 and 2.1×10 20 cm -3 , which is exactly the same as the trend of increasing film conductivity, confirming that the main reason for the increase in PEDOT:PSS film conductivity is the increase in the carrier concentration inside the film. Figure 15 The JV photovoltaic characteristics of different types of PEDOT:PSS / n-Si heterojunction solar cells under AM1.5G simulated sunlight are given. The results show that when the F18 doping concentration is 1.1 wt%, the short-circuit current density J SC From 31.16 mA•cm -2 Increased to 32.75 mA•cm-2 , the fill factor FF increased from 59.12% to 64.23%, and the open circuit voltage V OC The voltage increased from 0.649 V to 0.653 V, and the PCE increased to 13.74%. When 0.8 wt% TF18 was doped in the PEDOT:PSS solution, the device performance was the best, with the PCE increased to 14.50%.

[0085] Therefore, based on the preparation of PEDOT:PSS / Si heterojunction solar cell devices, the PEDOT:PSS film was modified by doping BOLA liquid crystal compounds F18 and TF18 to prepare high-efficiency and practical PEDOT:PSS / n-Si heterojunction solar cell devices.

[0086] Table 2 Device performance parameters of PEDOT:PSS / n-Si heterojunction solar cells modified with different liquid crystal compounds

[0087] Note: The selected F18 and TF18 doping concentrations are already optimal.

[0088] The above describes the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A fluorene-benzothiadiazole multi-chain bola liquid crystal compound, characterized in that The compound has the following structural formula: Compound Fn, wherein n is 12, 16, or 18; Compound TFn, wherein n is 12, 16, or 18.

2. Use of the fluorene-benzothiadiazole multi-chain BOLA liquid crystal compound according to claim 1 as an organic liquid crystal material.

3. A use of the fluorene-benzothiadiazole multi-chain bola liquid crystal compound according to claim 1 to improve the photoelectric conversion efficiency of PEDOT:PSS / n-Si heterojunction solar cells.

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