A class of position isomer derivatives based on carbazole-triphenylamine and preparation method and application thereof

Abstract

The application belongs to the technical field of organic optoelectronics, and discloses a kind of position isomer derivatives based on carbazole-triphenylamine and a preparation method and application thereof, and belongs to the field of organic optoelectronics.The position isomer derivatives based on carbazole-triphenylamine have low crosslinking temperature, and can be crosslinked into film through a convenient thermal annealing process to form a functional film with excellent solvent erosion resistance.Meanwhile, the film has excellent hole transport capacity and high triplet energy level, and is very suitable for use as a hole transport layer of an organic electroluminescent device.The material of the application is highly compatible with solution process, and is convenient for preparing multilayer light-emitting devices.The obtained devices have excellent light-emitting characteristics, and have wide application prospects in the fields of solar cells and flexible light-emitting devices.

Description

Technical Field

[0001] This invention belongs to the field of organic optoelectronics and relates to a class of positional isomers based on carbazole-triphenylamine, their preparation methods and applications. Background Technology

[0002] Organic light-emitting diodes (OLEDs) have become a core technology in the display and lighting fields due to their superior image contrast, extremely fast response speed, thin and light form factor, and excellent energy-saving characteristics. In the architecture of multilayer OLED devices, the hole transport layer (HTL) plays a crucial role in regulating hole injection capability. An ideal hole transport material not only needs to possess highly matched frontier orbital levels (HOMO and LUMO) to promote efficient hole injection and block electron injection from the emissive layer to the anode, but also must have a sufficiently high triplet level to strictly confine excitons within the emissive layer, thereby improving the overall device efficiency.

[0003] In terms of device fabrication processes, current methods mainly rely on vacuum evaporation and solution processing. While vacuum evaporation can produce dense and uniform thin films, it suffers from stringent vacuum environment requirements, low material utilization, high manufacturing costs, and difficulty in producing large-area flexible devices. In contrast, solution processing significantly reduces energy consumption and cost, and is better suited to the needs of large-scale industrial production lines, thus gaining popularity in both academia and industry. However, solution processing of multilayer devices is prone to causing interlayer miscibility. Introducing crosslinkable groups and forming a solvent-resistant three-dimensional network through thermal curing is the mainstream strategy to solve this problem, and this method can also significantly improve the morphological stability of the film. Common crosslinking units include butane oxide and styrene. It should be noted that in recent research, while traditional butane oxide remains a classic crosslinking group, its thermal crosslinking typically requires high temperatures or photo-induced acid-generating agents. While the latter lowers the crosslinking temperature, it introduces impurities during the fabrication process, damaging the film morphology and molecular stacking. Similarly, styrene, as one of the most widely used crosslinking groups, typically requires processing temperatures as high as 180°C without the addition of additional initiators, which greatly limits its practical applications. Reducing the processing temperature required for thermal crosslinking is a core requirement for the development of this technology. Related studies have shown that excessively high thermal annealing temperatures severely damage the commonly used hole injection material (PEDOT:PSS) at the bottom layer, leading to a significant decrease in device luminous efficiency.

[0004] Therefore, it is particularly urgent to explore strategies to reduce the crosslinking temperature. Effectively reducing the crosslinking temperature can not only reduce manufacturing costs, but also significantly reduce thermal damage to organic molecules inside the device, thereby greatly expanding the practical application range of solution-processed semiconductor devices. Summary of the Invention

[0005] To address the technical bottlenecks caused by the aforementioned high-temperature crosslinking process, this invention provides a class of positional isomer derivatives based on carbazole-triphenylamine (VXCzTPA), their preparation method, and applications.

[0006] This invention introduces thermally polymerizable styrene units into different sites of carbazole, enabling rapid in-situ crosslinking of this type of material within a relatively low temperature range (110 °C) without relying on any external initiator. The resulting three-dimensional network film exhibits excellent solvent resistance and long-term morphological stability after curing. Furthermore, this series of novel crosslinked derivatives not only possesses HOMO energy levels highly matched to the anode but also extremely high triplet energy levels (greater than 2.80 eV). When used as a hole transport layer in solution-processed OLED devices, it effectively promotes hole injection and perfectly achieves exciton confinement within the emissive layer, thus successfully fabricating high-efficiency electroluminescent devices.

[0007] In a first aspect, the present invention provides a class of positional isomers based on carbazole-triphenylamine, the general structural formula of which is:

[0008] or ;

[0009] Either R1 or R2 is a substituent. The other is H, and n is a positive integer. Substituents As a crosslinkable group.

[0010] As a preferred embodiment of the isomeric derivative described in this application, the structure is selected from any one of the following compounds:

[0011]

[0012] V2CzTPA

[0013]

[0014] V3CzTPA

[0015]

[0016] V9CzTPA

[0017] Secondly, the present invention also provides a method for preparing the above-mentioned positional isomers of carbazole-triphenylamine;

[0018] (a) Preparation process of general formula I Figure 1 as follows:

[0019]

[0020] The specific preparation steps for Formula I are as follows:

[0021] Step 1: Preparation of intermediate compound BOVBr: 4-hydroxystyrene, Potassium carbonate was added to a reaction flask containing acetone solvent, and then the temperature was raised to 70 °C and reacted for 12 hours to obtain BOVBr;

[0022] In step 1, after the reaction is completed and cooled to room temperature, dichloromethane and water are added for liquid-liquid extraction. The organic phase is collected, dried over anhydrous magnesium sulfate, concentrated under reduced pressure, and finally purified by silica gel chromatography to obtain a colorless liquid, namely BOVBr.

[0023] Step 2, Preparation of Intermediate 1: X-bromo-9H-carbazole, sodium methoxide / methanol solution, cuprous iodide, and ultra-dry N,N-dimethylformamide were added to a dry three-necked flask. The mixture was stirred and reacted at 120 °C for 24 hours to obtain Intermediate 1; the X-bromo-9H-carbazole was 3-bromo-9H-carbazole or 2-bromo-9H-carbazole.

[0024] In step 2, after the reaction solution is cooled to room temperature, ice water is added, and the solid is obtained by filtration. The diatomaceous earth and the obtained solid are sequentially loaded into a Buchner funnel, and dichloromethane is added in batches to wash the solid repeatedly. The filtrate is collected, dried with anhydrous magnesium sulfate, and concentrated under reduced pressure. The crude product is purified by silica gel column chromatography to finally obtain intermediate 1.

[0025] Step 3, Synthesis of Intermediate 2: Intermediate 1, 1-bromo-3,5-difluorobenzene, potassium tert-butoxide and dimethyl sulfoxide were added to a dry three-necked flask and the mixture was stirred at 80 °C for 24 hours to obtain Intermediate 2;

[0026] In step 3, after the reaction solution cooled to room temperature, ice water was added, and a solid filter cake was obtained by filtration. Then, appropriate amounts of dichloromethane and water were added for extraction and separation. After three consecutive extractions, the organic phases were combined, dried over anhydrous magnesium sulfate, and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography to finally obtain intermediate 2.

[0027] Step 4, Synthesis of Intermediate 3: Under a nitrogen atmosphere, intermediate 2, diphenylamine, sodium tert-butoxide, tritert-butylphosphine tetrafluoroborate and tris(dibenzylacetone)dipalladium were added to a dry three-necked flask. After adding toluene, the reaction mixture was stirred at 110 °C for 24 hours to obtain intermediate 3.

[0028] In step 4, after the reaction mixture was cooled to room temperature, appropriate amounts of dichloromethane and water were added for extraction and separation. After three consecutive extractions, the organic phases were combined, dried over anhydrous magnesium sulfate, and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography to finally obtain a white solid intermediate 3.

[0029] Step 5, Synthesis of Intermediate 4: Intermediate 3 was added to a reaction flask containing dried dichloromethane. After the reaction flask was cooled to 0 °C in an ice-water bath, boron tribromide was slowly added dropwise. After the reaction was carried out in an ice-water bath for 2 hours, the reaction was transferred to room temperature for 6 hours to obtain intermediate 4.

[0030] In step 5, after the reaction is complete, excess water is added for quenching, and then saturated sodium bicarbonate solvent is added to adjust the pH of the reaction solution to neutral. Finally, dichloromethane and water are added for liquid-liquid extraction, the organic phase is collected, and the organic solvent is evaporated using a rotary evaporator to obtain a brown solid, which is intermediate 4.

[0031] Step 6: Preparation of compound of general formula I: Add the mixture of intermediate 4, potassium carbonate, tetrabutylammonium bromide, BOVBr and 50 g of acetonitrile to a dry three-necked flask, and stir the reaction mixture at 85 °C for 48 hours to obtain compound of general formula I.

[0032] In step 6, after the reaction is complete and cooled to room temperature, dichloromethane and an appropriate amount of water are added for extraction and separation. After three consecutive extractions, the organic phases are combined, dried over anhydrous magnesium sulfate, and concentrated under reduced pressure. The crude product is purified by silica gel column chromatography to finally obtain compound of general formula I.

[0033] (II) This invention provides a method for preparing general formula II:

[0034] The preparation flow chart of Formula II is as follows:

[0035]

[0036] The specific preparation steps for Formula I are as follows:

[0037] Step 1, Preparation of BOVBr: 4-hydroxystyrene, Potassium carbonate was added to a reaction flask containing acetone solvent, and then the temperature was raised to 70 °C and reacted for 12 hours to obtain BOVBr;

[0038] In step 1, after the reaction is completed and cooled to room temperature, dichloromethane and water are added for liquid-liquid extraction. The organic phase is collected, dried over anhydrous magnesium sulfate, concentrated under reduced pressure, and finally purified by silica gel chromatography to obtain a colorless liquid, namely BOVBr.

[0039] Step 2, Synthesis of intermediate 2': Carbazole, 1-bromo-3,5-difluorobenzene, potassium tert-butoxide and dimethyl sulfoxide were added to a dry three-necked flask and the mixture was stirred at 80 °C for 24 hours to obtain intermediate 2';

[0040] In step 2, after the reaction solution cooled to room temperature, ice water was added, and a solid filter cake was obtained by filtration. Then, appropriate amounts of dichloromethane and water were added for extraction and separation. After three consecutive extractions, the organic phases were combined, dried over anhydrous magnesium sulfate, and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography to finally obtain intermediate 2'.

[0041] Step 3, Synthesis of Intermediate 3': Under a nitrogen atmosphere, intermediate 2', Sodium tert-butoxide, tritert-butylphosphine tetrafluoroborate and tris(dibenzylacetone)palladium were added to a dry three-necked flask. After adding toluene, the reaction mixture was stirred at 110 °C for 24 hours to obtain intermediate 3'.

[0042] In step 3, after the reaction mixture was cooled to room temperature, appropriate amounts of dichloromethane and water were added for extraction and separation. After three consecutive extractions, the organic phases were combined, dried over anhydrous magnesium sulfate, and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography to finally obtain a white solid intermediate 3.

[0043] Step 4, Synthesis of intermediate 4': Intermediate 3' was added to a reaction flask containing dried dichloromethane. After the reaction flask was cooled to 0 °C in an ice-water bath, boron tribromide was slowly added dropwise. After the reaction was carried out in an ice-water bath for 2 hours, the reaction was transferred to room temperature for 6 hours to obtain intermediate 4'.

[0044] In step 4, after the reaction is complete, excess water is added for quenching, and then saturated sodium bicarbonate solvent is added to adjust the pH of the reaction solution to neutral. Finally, dichloromethane and water are added for liquid-liquid extraction, the organic phase is collected, and the organic solvent is evaporated using a rotary evaporator to obtain a brown solid, which is intermediate 4'.

[0045] Step 5: Preparation of compound of general formula II: Add the mixture of intermediate 4', potassium carbonate, tetrabutylammonium bromide, BOVBr and 50 g of acetonitrile to a dry three-necked flask, and stir the reaction mixture at 85 °C for 48 hours to obtain compound of general formula II.

[0046] In step 5, after the reaction is complete and cooled to room temperature, dichloromethane and an appropriate amount of water are added for extraction and separation. After three consecutive extractions, the organic phases are combined, dried over anhydrous magnesium sulfate, and concentrated under reduced pressure. The crude product is purified by silica gel column chromatography to finally obtain compound of general formula II.

[0047] Thirdly, the present invention provides the application of the above-mentioned carbazole-triphenylamine positional isomer derivative in the fabrication of a hole transport layer in an organic electroluminescent device. The organic electroluminescent device comprises, from anode to cathode, a metal cathode, an electron injection layer, an electron transport layer, a light-emitting layer, a hole transport layer, a hole injection layer, and an ITO anode. The hole transport layer is prepared by: coating the carbazole-based positional isomer derivative (dissolved in chloroform) onto the hole injection layer using a solution method, and then preparing a thin film structure by performing a thermal crosslinking reaction through annealing. The annealing temperature is not lower than 110°C, and the annealing time is not less than 30 minutes.

[0048] The carbazole-based positional isomers provided by this invention, as hole transport materials, possess high triplet energy levels and suitable highest occupied molecular orbital (HOMO) energy levels, enabling them to transport holes and block exciton overflow from the light-emitting layer. This allows them to be used as hole transport layers in organic electroluminescent devices. Furthermore, the carbazole-based positional isomers provided by this invention also have a low thermal crosslinking temperature, greatly optimizing the process conditions for solution-based electroluminescent device fabrication. When used to fabricate hole transport layers, they can improve the device efficiency of organic electroluminescent devices.

[0049] Beneficial effects: First, the carbazole-triphenylamine-based positional isomers provided in this application are constructed by introducing a thermally crosslinked functional group, styrene, into a molecular core with a high HOMO energy level through an alkyl chain. The constructed carbazole-triphenylamine-based positional isomers can still maintain a high HOMO energy level and also possess a high triplet energy level. In addition, characterization using photophysics, electrochemistry, and thermodynamics can verify that the carbazole-triphenylamine-based positional isomers provided in this application can be completely crosslinked as a thermally crosslinked hole transport material under thermal initiation, and the film formed after crosslinking has excellent solvent resistance and film-forming properties.

[0050] Secondly, the electroluminescent devices prepared based on carbazole-triphenylamine positional isomer derivatives as thermally crosslinked hole transport materials provided in this application have excellent device efficiency.

[0051] Finally, the positional isomeric derivative of carbazole-triphenylamine provided in this application can be used as a thermally crosslinked hole transport material to obtain a thin film with good solvent resistance and film-forming properties as a hole transport layer for electroluminescent devices under relatively low heat treatment conditions; thereby reducing the processing time of electroluminescent devices, making the process simple, efficient, and environmentally friendly.

[0052] Moreover, the thermally cross-linked hole transport material disclosed in this invention can be applied to the fabrication of large-area, large-scale devices in the field of optoelectronic information, and also has good application prospects in the fields of solar cells, flexible materials, and electrochromic materials. Attached Figure Description

[0053] Figure 1 This is a structural diagram of the organic electroluminescent device described in this invention;

[0054] Figure 2 The UV absorption, fluorescence, and low-temperature phosphorescence spectra of V3CzYPA solution are shown.

[0055] Figure 3 The oxidation curve of V3CzYPA;

[0056] Figure 4a Thermogravimetric analysis (TGA) curves of V3CzYPA after crosslinking;

[0057] Figure 4b The differential scanning calorimetry (DSC) curves of compound V3CzYPA after crosslinking are shown.

[0058] Figure 5 This is an atomic force microscopy (AFM) image of compound V3CzYPA after crosslinking.

[0059] Figure 6a Comparison of UV absorption spectra of V3CzTPA before and after film formation and elution after thermal crosslinking treatment at 110 °C;

[0060] Figure 6b Comparison of UV absorption spectra of OXE-TPA before and after film formation and elution after thermal crosslinking treatment at 120 °C;

[0061] Figure 6c Comparison of UV absorption spectra of OXE-TPA before and after film formation and elution after thermal crosslinking treatment at 140 °C;

[0062] Figure 6d Comparison of UV absorption spectra of OXE-TPA before and after film formation and elution after thermal crosslinking treatment at 160 °C; Figure 6e Comparison of UV absorption spectra of V4CzTPA before and after film formation and elution after thermal crosslinking treatment at 160 °C;

[0063] Figure 7 The elution retention diagram of VXCzTPA (V2CzYPA, V3CzYPA, V9CzYPA) after crosslinking at different temperatures (crosslinking degree diagram);

[0064] Figure 8a Current density-voltage-luminance characteristic curves of green light devices fabricated for V2CzYPA, V3CzYPA and green light devices without hole transport layer;

[0065] Figure 8bCurrent efficiency-luminance-external quantum efficiency characteristic curves of green light devices fabricated for V2CzYPA, V3CzYPA and green light devices without hole transport layer;

[0066] Figure 8c Electroluminescence spectra of green light devices fabricated for V2CzYPA, V3CzYPA, and green light devices without hole transport layers;

[0067] Figure 9a Current density-voltage-luminance characteristic curves of green light devices with hole transport layers of different thicknesses fabricated for V3CzYPA;

[0068] Figure 9b Current efficiency-luminance-external quantum efficiency characteristic curves of green light devices with hole transport layers of different thicknesses fabricated for V3CzYPA. Detailed Implementation

[0069] The technical solution of the present invention will be described in detail below through embodiments, but the scope of protection of the present invention is not limited to the embodiments described.

[0070] Example 1: Preparation of V3CzTPA

[0071] The synthetic route of V3CzTPA is shown below:

[0072]

[0073] Intermediate BOVBr: 5.0 g of 4-hydroxystyrene and 27.3 g of potassium carbonate (K₂CO₃) were added to a 250 mL three-necked flask, followed by 60 mL of acetone. The mixture was stirred at room temperature for 30 minutes, then 30.5 g of 1,6-dibromohexane was slowly added, and the mixture was heated to 70 °C and reacted for 12 h. After the reaction was complete, the mixture was cooled to room temperature, and 100 mL of dichloromethane and 100 mL of water were added for extraction. The collected organic phase was then evaporated to dryness and purified by silica gel column chromatography (petroleum ether:dichloromethane = 10:1, V:V) to obtain a colorless liquid, BOVBr, with a mass of 1.2 g and a yield of 10.2%. 1H NMR spectrum of BOVBr: 1H NMR (400 MHz, CDCl3) δ 7.40 – 7.30 (m, 2H), 6.92 – 6.83 (m, 2H), 6.68 (dd,J = 17.6, 10.9 Hz, 1H), 5.63 (d, J = 17.6 Hz, 1H), 5.15 (d, J = 11.9 Hz, 1H), 3.99 (t, J = 6.4 Hz, 2H), 3.45 (t, J = 6.8 Hz, 2H), 1.92 (p, J = 6.9 Hz, 2H), 1.82 (p, J = 6.4 Hz, 2H), 1.53 (p, J = 3.8 Hz, 4H).

[0074] Synthesis of Intermediate 1: 3-Bromo-9H-carbazole (5 g, 20.32 mmol), sodium methoxide / methanol solution (40 wt%, 20 mL), cuprous iodide (CuI) (3.82 g, 20 mmol), and 40 mL of ultra-dry N,N-dimethylformamide (DMF) were added to a dry 100 mL three-necked flask. The mixture was stirred at 120 °C for 24 hours. After the reaction solution cooled to room temperature, 300 mL of ice water was added, and the solid was obtained by vacuum filtration. Diatomaceous earth and the obtained solid were sequentially placed into a Buchner funnel, and the solid was washed repeatedly with dichloromethane (300 mL) in portions. The filtrate was collected, dried over anhydrous magnesium sulfate, and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography (eluent: petroleum ether / dichloromethane = 2:1, V / V) to give intermediate 1 (3.52 g, 17.78 mmol), a white powder with a yield of 87.5%. The 1H NMR spectrum of intermediate 1 is as follows: 1 H NMR (400 MHz, CDCl3) δ 8.04 (d, J = 7.9 Hz, 1H), 7.91 (s, 1H), 7.56 (d,J = 2.6 Hz, 1H), 7.40 (d, J = 4.4 Hz, 2H), 7.33 (d, J = 8.8 Hz, 1H), 7.21(dt, J = 8.0, 4.2 Hz, 1H), 7.07 (dd, J = 8.8, 2.5 Hz, 1H), 3.94 (s, 3H).

[0075] Synthesis of Intermediate 2: Intermediate 1 (5 g, 25.38 mmol), 1-bromo-3,5-difluorobenzene (3 g, 15.5 mmol), potassium tert-butoxide (t-BuOK, 3.5 g, 31.2 mmol), and 50 mL of dimethyl sulfoxide (DMSO) were added to a dry 100 mL three-necked flask. The mixture was stirred at 80 °C for 24 h. After the reaction solution cooled to room temperature, 300 mL of ice water was added, and a solid filter cake was obtained by suction filtration. Subsequently, appropriate amounts of dichloromethane (300 mL) and water (300 mL) were added for extraction and separation. After three consecutive extractions, the organic phases were combined, dried over anhydrous magnesium sulfate, and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography (eluent: petroleum ether / dichloromethane = 5:1, v / v) to finally obtain Intermediate 2 (4.7 g, 5.8 mmol) as a white solid, with a yield of 67.6%. The 1H NMR spectrum of intermediate 2: 1 H NMR(400 MHz, CDCl3) δ 8.02 (d, J = 7.8 Hz, 2H), 7.74 (d, J = 1.9 Hz, 2H), 7.68(t, J = 1.9 Hz, 1H), 7.53 (d, J = 2.5 Hz, 2H), 7.46 (d, J = 8.3 Hz, 2H), 7.37(t, J = 8.4 Hz, 4H), 7.22 (t, J = 7.5 Hz, 2H), 7.01 (dd, J = 8.9, 2.6 Hz,2H), 3.87 (s, 6H).

[0076] Synthesis of Intermediate 3: Under a nitrogen atmosphere, intermediate 2 (3 g, 5.5 mmol), diphenylamine (1.02 g, 6 mmol), sodium tert-butoxide (t-BuONa) (2 g, 20.8 mmol), tritert-tert-butylphosphine tetrafluoroborate (P(t-Bu)3BF4, 300 mg, 1 mmol), and tris(dibenzylacetone)palladium (Pd2(dba)3, 30 mg, 0.033 mmol) were added to a dry 100 mL three-necked flask. After adding 50 mL of toluene, the reaction mixture was stirred at 110 °C for 24 hours. After cooling the reaction mixture to room temperature, appropriate amounts of dichloromethane (300 mL) and water (300 mL) were added for extraction and separation. After three consecutive extractions, the organic phases were combined, dried over anhydrous magnesium sulfate, and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography (eluent: petroleum ether / dichloromethane = 3:1, v / v) to give intermediate 3 (3.28 g, 5.12 mmol) as a white solid, with a yield of 93.2%. The 1H NMR spectrum of intermediate 3 is shown below. 1 H NMR (400 MHz, DMSO) δ 8.21 (d, J =7.7 Hz, 2H), 7.80 (s, 2H), 7.56 (d, J = 8.4 Hz, 2H), 7.50 (d, J = 9.0 Hz,2H), 7.40 (dd, J = 21.3, 7.0 Hz, 11H), 7.25 (t, J = 7.5 Hz, 2H), 7.16 (t, J =7.2 Hz, 2H), 7.08 (d, J = 8.9 Hz, 2H), 7.01 (s, 2H), 3.86 (s, 6H).

[0077] Synthesis of Intermediate 4: Intermediate 3 (1.3 g, 2 mmol) and 50 mL of dichloromethane were added to a dry 100 mL three-necked flask. The reaction mixture was cooled to 0 °C, boron tribromide (1 M, 8 mL) was added, and the mixture was stirred for 2 hours, then allowed to continue the reaction at room temperature for 8 hours. After the reaction was complete, the reaction mixture was poured into water (300 mL) and stirred thoroughly. Then, an aqueous sodium hydroxide solution was added dropwise to neutralize the excess boron tribromide. Subsequently, dichloromethane (300 mL) was added for extraction and separation. After three consecutive extractions, the organic phases were combined, dried over anhydrous magnesium sulfate, and the mixture was concentrated under reduced pressure to give intermediate 4 (1.18 g, 16.5 mmol) as a white solid powder, in 82.3% yield. 1H NMR spectrum of intermediate 4: 1HNMR (400 MHz, CDCl3) δ 8.04 (d, J = 8.8 Hz, 2H), 7.52 (s, 4H), 7.36 (td, J =17.9, 8.0 Hz, 13H), 7.26 (s, 4H), 7.13 (d, J = 6.6 Hz, 2H), 6.98 (d, J = 7.6Hz, 2H), 4.74 (s, 2H).

[0078] Final product V3CzTPA: A mixture of compound 4 (1.8 g, 1.45 mmol), potassium carbonate (8 g, 58 mmol), tetrabutylammonium bromide (0.6 g, 1.9 mmol), compound 1-(6-bromohexyloxy)-4-vinylbenzene (1.58 g, 3.18 mmol), and 50 mL of acetonitrile was added to a dry 100 mL three-necked flask. The reaction mixture was stirred at 85 °C for 48 hours. After cooling to room temperature, dichloromethane (200 mL) and a suitable amount of water were added for extraction and separation. After three consecutive extractions, the organic phases were combined, dried over anhydrous magnesium sulfate, and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography (eluent: petroleum ether / dichloromethane = 10:1, v / v) to finally give V3CzTPA (0.76 g, white solid) in 51.8%.

[0079] The hydrogen NMR spectrum of V3CzTPA: 1 H NMR (400 MHz, Chloroform-d) δ 8.04 (d, J = 7.6Hz, 2H), 7.57 (s, 2H), 7.52 (d, J = 8.8 Hz, 2H), 7.46 – 7.38 (m, 4H), 7.38 –7.27 (m, 13H), 7.23 (d, J = 7.8 Hz, 4H), 7.09 (t, J = 6.8 Hz, 2H), 7.04 (d, J= 9.0 Hz, 2H), 6.85 (d, J = 6.9 Hz, 4H), 6.65 (dd, J = 17.5, 10.9 Hz, 2H),5.60 (d, J = 17.6 Hz, 2H), 5.11 (d, J = 11.0 Hz, 2H), 4.09 (t, J = 6.6 Hz, 4H), 3.98 (t, J = 6.5 Hz, 4H), 1.86 (dt, J = 13.9, 6.4 Hz, 8H), 1.59 (s, 8H).

[0080] C1NMR spectrum of V3CzTPA: 13 C NMR (101 MHz, Chloroform-d) δ 157.87, 152.84,145.88, 139.64, 138.90, 135.24, 134.12, 129.24, 128.61, 126.33, 124.94,124.28, 123.24, 123.03, 122.45, 119.27, 118.80, 117.02, 115.63, 114.54,113.46, 110.39, 109.60, 108.94, 103.17, 67.81, 66.85, 28.30, 24.91.

[0081] Other types of positionally isomeric carbazole hole transport materials, V2CzTPA and V9CzTPA, were prepared according to the method in Example 1. The positions of the substituent groups were changed to other positions in Example 1. Styrene crosslinked materials with different chain lengths were prepared according to the preparation process of BOVBr in Example 1. The structural formula of V2CzTPA is as follows:

[0082]

[0083] V2CzTPA

[0084] The steps for preparing V9CzTPA differ slightly from those in Example 1. The synthetic route for V9CzTPA is shown below:

[0085]

[0086] Example 2: Photophysical properties of V3CzTPA solution

[0087] Figure 2 The ultraviolet absorption spectrum, fluorescence spectrum and low-temperature phosphorescence spectrum of compound V3CzTPA in solution are presented.

[0088] The compound was dissolved in dichloromethane to prepare a solution with a concentration of 10. -5 A 0.7 mL solution of mol / L was pipetted into a cuvette, and absorption and emission spectra were measured using a UV-Vis spectrophotometer and a fluorophotometer. A 10 mol / L solution was prepared using 2-methyltetrahydrofuran as the solvent. -5A mol / L solution was prepared, and 2 mL of solvent was added to a sample tube. After cooling to 77 K with liquid nitrogen, the low-temperature phosphorescence spectrum was measured using a phosphorescence spectrophotometer. In solution, the ultraviolet absorption peaks of compound V3CzTPA were located at 300 and 347 nm, respectively, and the fluorescence spectrum peaks were located at 369 nm. The triplet energy level of V3CzTPA could be calculated to be 2.87 eV from the low-temperature phosphorescence spectrum. The compound V3CzTPA prepared in this embodiment has a high triplet energy level and can be used to fabricate a hole transport layer, which can effectively confine the excitons in the light-emitting layer, thereby improving the efficiency of organic semiconductor devices.

[0089] Example 3: Electrochemical performance testing of V3CzTPA

[0090] Figure 3 Oxidation curves of compound V3CzTPA are presented. Cyclic voltammetry was used to determine the energy levels of the compound. Dichloromethane was used during the oxidation process. Ag / AgNO3 solution was used as the reference electrode, and ferrocene solution (concentration greater than 10) was used as the standard solution. -3 (mol / L is sufficient). Based on the oxidation potential of compound V3CzTPA, the corresponding HOMO energy level can be calculated to be -5.21 eV, which is almost unchanged from the theoretically calculated HOMO energy level.

[0091] Example 4: Thermal stability test of V3CzTPA

[0092] Figure 4a Differential thermal scanning (DSC) curves of compound V3CzTPA are presented. It can be seen that the glass transition temperature of compound V3CzTPA is 150 ℃, indicating that the material has high film stability after crosslinking. Figure 4b Thermogravimetric analysis (TGA) of compound V3CzTPA is presented. The TGA shows that the material has a high thermal decomposition temperature of 405℃ and good thermal stability. The good thermal stability is attributed to the three-dimensional network structure formed after the styrene groups are cross-linked.

[0093] Example 5: Atomic force microscopy image of V3CzTPA after thermal cross-linking.

[0094] Figure 5 This is an atomic force microscope (AFM) image of compound V3CzTPA after crosslinking at 110°C for 30 minutes. Figure 5 The film formation of compound V3CzTPA before and after heat treatment at 110℃ is presented. It can be seen that the compound is completely cross-linked at 110℃ and no pinholes appear. The mean square roughness of the compound is less than 1 nm, indicating that V3CzTPA materials have excellent film morphology.

[0095] Example 6: Solvent resistance test of V3CzTPA and its absorbance test

[0096] Figure 6a The UV absorption spectra of compound V3CzTPA after crosslinking at 110°C and after elution with chlorobenzene are presented. To test the solvent resistance of the crosslinked film, compound V3CzTPA was coated onto PEDOT:PSS. For V3CzTPA molecules, complete crosslinking is achieved after only 30 minutes of heat treatment at 110°C. The crosslinked film was then eluted three times with chlorobenzene, and the UV absorption spectra before and after elution were measured. The results showed that the absorbance of the film after solvent elution after crosslinking remained almost unchanged, indicating that the material was completely crosslinked at this temperature and exhibited excellent solvent resistance. Figure 7 The retention rates of different materials, including V3CzTPA molecules, after annealing at different temperatures and washing with solvents are presented, reflecting the degree of crosslinking of the materials at different temperatures.

[0097] Oxe-DCzTPA (hereinafter referred to as Oxe-TPA), disclosed in patent literature "Class I Carbazole Derivatives Based on Butylene Oxide and Their Preparation Methods and Applications" (Publication No. CN114560851B), also requires heat treatment at 180°C for 60 minutes without an initiator to achieve complete crosslinking. After heat treatment of OXE-TPA molecules at 120°C, 140°C, and 160°C for 30 minutes each, followed by elution with chlorobenzene three times, the UV absorption spectra of the film before and after elution were measured. Figure 6b , 6c As shown in Figure 6d, the absorbance of the film after elution changed significantly, indicating that OXE-TPA was not fully crosslinked at temperatures of 120℃, 140℃, and 160℃. Therefore, the resulting film had poor solvent resistance. In another patent document, HTPA-VBCz (hereinafter referred to as V4CzTPA for ease of comparison), a class of styrene-hybridized carbazole derivatives and their preparation methods and applications (application number 202410098617), was also found to be not fully crosslinked at 110℃. Figure 6e As shown, the prepared films cannot completely resist solvent erosion. The structural formulas of OXE-TPA and V4CzTPA are as follows:

[0098] ;

[0099] .

[0100] V2CzTPA, V4CzTPA, and V9CzTPA were tested according to the methods in Examples 2-6, and the characterization results are shown in Table 1.

[0101] Table 1. Material Characterization of VXCzYPA

[0102] V2CzTPA 360 3.57 2.88 -5.26 -1.69 V3CzTPA 405 3.34 2.87 -5.21 -1.87 V4CzTPA 410 3.60 3.00 -5.25 -1.65 V9CzTPA 407 3.51 2.87 -5.11 -1.60

[0103] Test conditions: optical bandgap a Calculated from the onset edge of the UV-Vis absorption spectrum. HOMO b Measurements were obtained by cyclic voltammetric electrochemical scanning, calibrated using the ferrocene / ferrocene-onium redox pair as an internal standard. LUMO c It is calculated from the HOMO energy level value and the corresponding optical band gap.

[0104] Organic electroluminescent devices were fabricated using VXCzTPA prepared in Example 1 as a hole transport material, such as... Figure 1 As shown, the organic electroluminescent devices prepared in Examples 7 and 8 have the following structures from bottom to top: anode ITO glass (indium tin oxide), hole injection layer PEDOT:PSS, hole transport layer, light-emitting layer, electron transport layer TPBi, electron injection layer Ca, and metal cathode Ag. The organic electroluminescent devices emit green light. The metal cathode layer is made of Ag metal, and its thickness is 100 nm, prepared by vacuum evaporation. The electron injection layer is made of Ca metal, prepared by vacuum evaporation, and its thickness is 10 nm. The electron transport layer is 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)phenylTPBi, also prepared by vacuum evaporation, and its thickness is 35 nm. The light-emitting layer is prepared by solution method using 26DCzPPy and thermally activated delayed fluorescence material in different mass ratios. The light-emitting layer material is 26DCzPPy:4CzIPN, and the mass concentrations of 26DCzPPy and 4CzIPN are 90% and 10%, respectively. The hole transport layer is prepared using VXCzTPA prepared in this application. The hole injection layer is a poly(3,4-ethyldioxythiophene):polystyrene sulfonate PEDOT:PSS film, which is prepared by spin-coating on an ITO glass substrate using a solution process, and its thickness is approximately 30 nm. nm; The anode substrate is ITO glass, and ITO is a conductive anode. The required ITO glass substrate is cleaned, dried, and then subjected to ozone treatment.

[0105] Example 7: Fabrication of green light devices using V3CzTPA thin films as hole transport layers

[0106] The device structure in this embodiment can be simply represented as follows:

[0107] Device 1 (Green Light): ITO / PEDOT:PSS / V3CzTPA / 26DCzPPy:4CzIPN (90:10 wt%) / TPBi / Ca:Ag, wherein the transparent conductive substrate is the ITO glass substrate with the anode, PEDOT:PSS is the hole injection layer, V3CzTPA is the cross-linked hole transport layer, 26DCzPPy:4CzIPN (90:10 wt%) is the light-emitting layer, TPBi is the electron transport layer, Ca is the electron injection layer, and Ag is the cathode.

[0108] The specific fabrication steps of the device in this embodiment are as follows:

[0109] First, the ITO substrate was sonicated with dichloromethane for 20 min, then cleaned with detergent, followed by sonication with ultrapure water, acetone, and ethanol for 20 min each, and finally dried at 80 °C. After cleaning, the ITO substrate was treated with ozone for 20 min, and then a hole injection layer, PEDOT:PSS, was spin-coated at 3000 r / s for 30 s, followed by annealing at 120 °C for 20 min on a hot stage. Next, a hole transport layer was prepared using a solution method. All operations were performed inside a glove box. A chloroform solution of V3CzTPA (4 mg / mL) was spin-coated onto the hole injection layer at 3000 r / s for 30 s, then transferred to a hot stage and heat-treated at 110 °C for 30 min to prepare a V3CzTPA film (20 nm thick). The luminescent layer was also prepared using a solution method: the luminescent layer solution was prepared using a 4 mg / mL 26DCzPPy solution. A 4CzIPN chloroform solution was spin-coated onto the prepared cross-linked hole transport layer at 3000 r / s for 30 s, followed by annealing at 120 ℃ for 20 min on a hot stage to form a thin film. Finally, a vacuum evaporation process was performed: [The text abruptly ends here, so the translation stops as well.] -5 Below Pa pressure, the electron transport layer TPBi, the electron injection layer Ca, and the metal cathode Ag are deposited sequentially by vapor deposition.

[0110] Device 2 was prepared by replacing V3CzTPA with V2CzTPA, V4CzTPA, and V9CzTPA respectively, and device 3 without a hole transport layer was prepared by the above method.

[0111] like Figure 8a The figure shows the current density-voltage-brightness characteristic curves of organic electroluminescent devices prepared by V3CzTPA and V2CzTPA. It can be observed that with the addition of the cross-linked hole transport layer, although the turn-on voltage of the device increases slightly and the maximum brightness decreases, both still meet the requirements. Figure 8bThe figure shows the current efficiency-luminance-external quantum efficiency characteristic curves of green light devices fabricated with V3CzTPA and V2CzTPA. Compared with the device without a hole transport layer, the device with a cross-linked hole transport layer (the device fabricated with V3CzTPA) has a maximum current efficiency of 39.6 cd A. -1 Upgraded to 69.0 cd A -1 The external quantum efficiency increased from 12.2% to 21.4%, and the device exhibited excellent efficiency and stability; for example... Figure 8c The electroluminescence spectra of green light devices fabricated with V3CzTPA and V2CzTPA are shown. It can be observed that the addition of the hole transport layer has almost no effect on the light emission of the devices. In summary, V3CzTPA, as a thermally crosslinked hole transport layer, significantly improves the performance of green light devices, while requiring a lower fabrication temperature.

[0112] Example 8: Fabrication of green light devices using V3CzTPA thin films of different thicknesses as hole transport layers

[0113] This embodiment is identical to device 1 in embodiment 7 except for the thickness of the hole transport layer; all other structural components and preparation steps are the same. Therefore, the preparation process will not be described in detail. This embodiment prepares four devices with different V3CzTPA film thicknesses of 5nm, 10nm, 15nm, and 20nm.

[0114] like Figure 9a The figure shows the current density-voltage-brightness characteristic curves of the green light device in this embodiment. It can be seen from the figure that, compared to devices without hole transport layers, the start-up voltage of devices with hole transport layers of different thicknesses decreases as the thickness increases; for example... Figure 9b The diagram shows the current efficiency-luminance-external quantum efficiency characteristic curves of the green light device in this embodiment. Compared with the device without a hole transport layer, using V3CzTPA as the hole transport layer of different thicknesses significantly improves both current efficiency and external quantum efficiency, with the 10 nm thickness showing the greatest improvement and a maximum current efficiency of 77.9 cd A. -1 The external quantum efficiency is 24.0%.

[0115] Table 2 summarizes the performance of green optical devices using VXCzYPA as the hole transport layer:

[0116] Table 2. Performance of VXCzYPA as a green light device with hole transport layer

[0117]

[0118] Test conditions: Value 'a' is at a brightness of 1 cd / m. -2 The measured values ​​for b and c are both at a brightness of 1000 cd / m.-2 Measured.

[0119] As described above, although the invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the invention itself. Various changes in form and detail may be made without departing from the spirit and scope of the invention.

Claims

1. A class of positional isomers based on carbazole-triphenylamine, characterized in that, Its general structural formula is: or ; Either R1 or R2 is a substituent. The other is H, and n is a positive integer.

2. The positional isomer derivative based on carbazole-triphenylamine according to claim 1, characterized in that, The positional isomer derivative based on carbazole-triphenylamine has one of the following structures: ； ； 。 3. The method for preparing the positional isomer derivative based on carbazole-triphenylamine according to claim 1, characterized in that, The preparation flowchart of the compound with the structure shown in Formula I is as follows: ； The preparation steps are as follows: Step 1: Preparation of intermediate compound BOVBr: 4-hydroxystyrene, Potassium carbonate was added to a reaction flask containing acetone solvent, and then the temperature was raised to 70 °C and reacted for 12 hours to obtain BOVBr; Step 2, Preparation of Intermediate 1: X-bromo-9H-carbazole, sodium methoxide / methanol solution, cuprous iodide and ultra-dry N,N-dimethylformamide were added to a dry three-necked flask. The mixture was stirred at 120 °C for 24 hours to obtain Intermediate 1. Step 3, Synthesis of Intermediate 2: Intermediate 1, 1-bromo-3,5-difluorobenzene, potassium tert-butoxide and dimethyl sulfoxide were added to a dry three-necked flask and the mixture was stirred at 80 °C for 24 hours to obtain Intermediate 2; Step 4, Synthesis of Intermediate 3: Under a nitrogen atmosphere, intermediate 2, diphenylamine, sodium tert-butoxide, tritert-butylphosphine tetrafluoroborate and tris(dibenzylacetone)dipalladium were added to a dry three-necked flask. After adding toluene, the reaction mixture was stirred at 110°C for 24 hours to obtain intermediate 3. Step 5, Synthesis of Intermediate 4: Intermediate 3 was added to a reaction flask containing dried dichloromethane. After the reaction flask was cooled to 0 °C in an ice-water bath, boron tribromide was slowly added dropwise. After the reaction was carried out in an ice-water bath for 2 hours, the reaction was transferred to room temperature for 6 hours to obtain intermediate 4. Step 6: Preparation of compound of general formula I: Add the mixture of intermediate 4, potassium carbonate, tetrabutylammonium bromide, BOVBr and 50 g of acetonitrile to a dry three-necked flask, and stir the reaction mixture at 85 °C for 48 hours to obtain compound of general formula I.

4. The method for preparing the positional isomer derivative based on carbazole-triphenylamine according to claim 1, characterized in that, The preparation flowchart of the compound with the structure shown in Formula II is as follows: ； The preparation steps are as follows: Step 1, Preparation of BOVBr: 4-hydroxystyrene, Potassium carbonate was added to a reaction flask containing acetone solvent, and then the temperature was raised to 70 °C and reacted for 12 hours to obtain BOVBr; Step 2, Synthesis of intermediate 2': Carbazole, 1-bromo-3,5-difluorobenzene, potassium tert-butoxide and dimethyl sulfoxide were added to a dry three-necked flask and the mixture was stirred at 80 °C for 24 hours to obtain intermediate 2'; Step 3, Synthesis of Intermediate 3': Under a nitrogen atmosphere, intermediate 2', Sodium tert-butoxide, tritert-butylphosphine tetrafluoroborate and tris(dibenzylacetone)palladium were added to a dry three-necked flask. After adding toluene, the reaction mixture was stirred at 110 °C for 24 hours to obtain intermediate 3'. Step 4, Synthesis of intermediate 4': Intermediate 3' was added to a reaction flask containing dried dichloromethane. After the reaction flask was cooled to 0 °C in an ice-water bath, boron tribromide was slowly added dropwise. After the reaction was carried out in an ice-water bath for 2 hours, the reaction was transferred to room temperature for 6 hours to obtain intermediate 4'. Step 5: Preparation of compound of general formula II: Add the mixture of intermediate 4', potassium carbonate, tetrabutylammonium bromide, BOVBr and 50 g of acetonitrile to a dry three-necked flask, and stir the reaction mixture at 85 °C for 48 hours to obtain compound of general formula II.

5. The application of the positional isomeric derivative of carbazole-triphenylamine as described in claim 1 in the fabrication of the hole transport layer of an organic electroluminescent device.

6. The application according to claim 5, characterized in that, The method for preparing the hole transport layer is as follows: the carbazole-based positional isomer derivative is coated onto the hole injection layer using a solution method, and then a thin film structure is prepared by thermal crosslinking reaction through annealing treatment. The annealing treatment temperature is not lower than 110 ℃ and the annealing treatment time is not less than 30 minutes.

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