Small molecular material taking p-dibenzo [b] thienyl benzene as substrate, preparation method thereof and application of small molecular material in OLED (Organic Light Emitting Diode)

Abstract

The invention relates to a small molecular material taking p-dibenzo [b] thienyl benzene as a substrate, a preparation method thereof and application of the small molecular material in an OLED (Organic Light Emitting Diode), belonging to the technical field of new materials. The substrate p-dibenzo [b] thienyl benzene and the derivative thereof have a larger conjugate plane structure, can induce stronger intermolecular interaction, not only can reduce a hole transport energy barrier and significantly optimize hole migration performance, but also can promote molecules to form more ordered accumulation on an ITO substrate, so that the hole transport efficiency is improved. Therefore, the problems of aggregation and grain boundary blockage of the material in the film forming process are avoided; a phosphoric acid anchoring group is introduced into the material, so that firm combination of the hole transport material and the surface of an ITO substrate can be realized, and the HOMO energy level better matched with other layers of the device is further guaranteed. When the material is used as a core component of an OLED hole transport layer, molecular aggregation can be effectively inhibited, the thermal stability of a film is enhanced, the conductivity and the hole injection capability are improved, and finally the brightness, the efficiency and the long-term stability of an OLED device are remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of new materials technology and relates to the preparation of functional materials for organic light-emitting diodes (OLEDs). In particular, it relates to a small molecule material based on p-dibenzo[b]thiophenebenzene, its preparation method and application. Specifically, the small molecule material is used as a core component of the hole transport layer (HTL) in OLED devices, thereby improving the charge transport efficiency, thermal stability and long-term operational reliability of the devices. Background Technology

[0002] Organic light-emitting diode (OLED) technology, with its inherent advantages such as self-illumination, wide viewing angle, and the ability to achieve flexible and ultra-thin forms, has established its core position in the fields of next-generation displays and solid-state lighting. In this typical multilayer thin-film device architecture, the hole transport layer, as a key functional layer, is of paramount importance in terms of material properties. High-performance hole transport materials not only need to possess high hole mobility to ensure efficient carrier transport, but also need to be able to precisely control the energy level structure, aiming to achieve efficient hole injection from the anode to the light-emitting layer from a low barrier. At the same time, its higher-order lowest unoccupied molecular orbital energy level can construct a barrier to block electrons, thereby confining the electron-hole recombination region within the light-emitting layer and maximizing exciton formation efficiency. However, traditional small-molecule materials (NPB, TCTA, etc.) generally suffer from inherent defects such as poor thin-film morphological stability (prone to crystallization during long-term operation), insufficient hole mobility, insufficient thermal stability, and poor matching between the highest occupied molecular orbital energy level and the anode / light-emitting layer. Therefore, developing novel small-molecule hole transport materials with excellent thermal stability, high-efficiency charge transport performance, and energy level matching is key to breaking through the performance bottlenecks of existing OLED devices and promoting their large-scale application in high-end display and lighting fields. It has significant academic value and promising industrial application prospects. Summary of the Invention

[0003] The purpose of this invention is to provide a small molecule material based on p-dibenzo[b]thiophenebenzene. This invention uses this small molecule material as a core component of the hole transport layer in OLED devices. Compared with traditional NBP-type hole transport materials, it exhibits superior thermal stability, stronger molecular stacking characteristics, and a more matched HOMO energy level. It can effectively suppress molecular aggregation, enhance thin film thermal stability, improve electrical conductivity and hole injection capability, and significantly improve the brightness, efficiency, and long-term stability of OLED devices. This invention is based on a small molecule material with p-dibenzo[b]thiophenebenzene as its base. It is a hole transport material for OLEDs constructed with p-dibenzo[b]thiophenebenzene as its core. This material has a novel structure and high stability, and can solve the performance shortcomings of traditional hole transport materials in OLED applications. It is a highly promising organic optoelectronic functional material.

[0004] This invention is achieved through the following technical solution: A small molecule material based on p-dibenzo[b]thiophenebenzene has the following structural formula:

[0005] A further improvement to the present invention is as follows: A method for preparing a small molecule material based on p-dibenzo[b]thiophenebenzene includes the following steps: (1) Compound 1 or 1,4-dibromobutane undergoes a substitution reaction to generate compound 2; (2) Compound 2 is substituted with benzo[b]thiophene-2-boronic acid to generate compound 3; (3) Compound 3 undergoes a substitution reaction with triethyl phosphite to generate compound 4; (4) Compound 4 undergoes a hydrolysis reaction with trimethylbromosilane to generate compound GT1; The reaction route is shown below:

[0006] Furthermore, the substitution reaction in step (1) is carried out in the presence of potassium carbonate, with acetone as the solvent, and the molar ratio of compound 1 to 1,4-dibromobutane is 1:10~40.

[0007] Furthermore, the temperature of the substitution reaction in step (1) is 60~100℃ and the time is 6~10h.

[0008] Furthermore, the substitution reaction in step (2) uses tetra(triphenylphosphine)palladium as a catalyst and toluene as a solvent, and the molar ratio of compound 2 to benzo[b]thiophene-2-boronic acid is 1:2~3.

[0009] Furthermore, the temperature of the substitution reaction in step (2) is 60~140℃ and the time is 4~12h.

[0010] Furthermore, the substitution reaction in step (3) is carried out in the presence of triethyl phosphite, and the molar ratio of compound 3 to triethyl phosphite is 1:5~60. Furthermore, the temperature of the substitution reaction in step (3) is 100~200℃ and the time is 6~20h.

[0011] Furthermore, the hydrolysis reaction in step (4) is carried out in the presence of trimethylbromosilane and methanol, with 1,4-dioxane as the solvent, and the molar ratio of compound 4 to trimethylbromosilane is 1:10~30.

[0012] Furthermore, the temperature of the substitution reaction in step (4) is 10~40℃ and the time is 20~30h.

[0013] Furthermore, the reactions in steps (1) to (4) are all carried out in an argon atmosphere; the reactions in steps (1) to (4) also include post-processing steps.

[0014] A further improvement of the present invention is as follows: The above-mentioned small molecule materials based on p-dibenzo[b]thiophenebenzene are used in OLEDs.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: The small-molecule material based on p-dibenzo[b]thiophenebenzene provided by this invention is a hole transport material for OLED devices. The p-dibenzo[b]thiophenebenzene substrate and its derived large conjugated planar structure induce stronger intermolecular interactions, reduce the hole transport energy barrier, significantly optimize hole migration performance, and promote more ordered molecular stacking on the ITO substrate, preventing aggregation and blockage at grain boundaries during film formation. Simultaneously, phosphate acts as an anchoring group, enabling a firm bond between the hole transport material and the ITO substrate surface. Attached Figure Description

[0016] Figure 1 The hydrogen NMR spectrum of formula GT1 prepared in this invention; Figure 2 The liquid UV test pattern of the GT1 prepared in this invention shows that the material has a characteristic absorption peak in the 250-450 nm range, indicating that the molecular conjugation system is good and the electron delocalization is excellent, which lays the foundation for low-barrier hole transport. Compared with traditional triarylamine materials, it is more conducive to improving charge transport efficiency. Figure 3 Thermogravimetric analysis test diagram of formula GT1 prepared in this invention; Figure 4 This is a schematic diagram of an organic light-emitting diode (OLED) made from the material of Example 1; from bottom to top, the layers are a glass substrate, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, an electron injection layer, and a cathode. Detailed Implementation

[0017] The present invention will now be described in detail with reference to specific embodiments.

[0018] Example 1: Synthesis of the small molecule material GT1

[0019] The specific synthetic route is as follows: (1) Synthesis of compound 2

[0020] Compound 1 (2 g, 7.47 mmol) and potassium carbonate (3.71 g, 26.88 mmol) were added to a two-necked flask, followed by the addition of 1,4-dibromobutane (4.03 g, 18.66 mmol) and acetone (20 mL). The mixture was stirred at 80 °C for 8 hours under argon protection. After the reaction was complete, the mixture was extracted with dichloromethane, and the organic layer was dried over anhydrous sodium sulfate and the solvent was removed by vacuum distillation. The crude product was purified by column chromatography (eluent: petroleum ether:dichloromethane = 5:1) to give 3.19 g of a white solid (79.39% yield).

[0021] The structural characterization data of compound 2 are as follows: 1 H NMR (400 MHz, DMSO) δ 7.37 (s, 2H), 4.05(t, J = 6.2 Hz, 4H), 3.63 (t, J = 6.7 Hz, 4H), 2.04 – 1.94 (m, 4H), 1.83 (dq, J =12.8, 6.3 Hz, 4H). In some embodiments of the present invention, the molar ratio of compound 1 to 1,4-dibromobutane in this step can be selected in the range of 1:10 to 40.

[0022] In some embodiments of the present invention, the temperature of the substitution reaction in this step can be selected from 60 to 100°C, and the time can be selected from 6 to 10 hours.

[0023] (2) Synthesis of compound 3

[0024] Compound 2 (2 g, 3.72 mmol), benzo[b]thiophene-2-boronic acid (1.39 g, 7.81 mmol), tetrakis(triphenylphosphine)palladium (0.64 g, 0.56 mmol), and potassium carbonate (4.11 g, 29.74 mmol) were added to a two-necked flask, followed by dissolution in 25 mL of toluene. The reaction mixture was stirred at 100 °C for 10 hours. After the reaction was complete, the reaction mixture was filtered, and the filtrate was extracted with dichloromethane. The organic layer was dried over anhydrous sodium sulfate. The crude product was purified by column chromatography (eluent: petroleum ether / dichloromethane = 5:3) to give 1.4 g of a yellow solid (yield 58.33%).

[0025] The structural characterization data of compound formula 3 are as follows: 1 H NMR (400 MHz, DMSO) δ 8.11 (s, 2H), 7.97(d, J= 7.7 Hz, 2H), 7.91 – 7.86 (m, 2H), 7.62 (s, 2H), 7.44 – 7.34 (m, 4H), 4.30 (t, J = 6.0 Hz, 4H), 3.70 (t, J = 6.4 Hz, 4H), 2.17 – 2.01 (m, 8H). In some embodiments of the present invention, the molar ratio of compound 2 to benzo[b]thiophene-2-boronic acid in this step can be selected in the range of 1:2 to 3.

[0026] In some embodiments of the present invention, the temperature of the substitution reaction in this step can be selected from 60 to 140°C, and the time can be selected from 4 to 12 hours.

[0027] (3) Synthesis of compound 4

[0028] Compound 3 (1.4 g, 2.17 mmol) was dissolved in triethyl phosphite (20.21 g, 121.65 mmol), and the reaction mixture was heated at 170 °C for 8 hours. After the reaction was complete, the solvent was removed by vacuum distillation. The crude product was purified by column chromatography (eluent was a mixture of petroleum ether and ethyl acetate in a 1:2 ratio) to give 0.9 g of a yellow oil (yield 54.55%).

[0029] The structural characterization data of compound 4 are as follows: 1 H NMR (400 MHz, DMSO) δ 8.11 (s, 2H), 7.97(t, J = 6.2 Hz, 2H), 7.92 – 7.86 (m, 2H), 7.61 (s, 2H), 7.43 – 7.33 (m, 4H), 4.28 (t, J = 6.2 Hz, 4H), 4.01 – 3.90 (m, 8H), 2.06 – 1.96 (m, 4H), 1.93 – 1.72(m, 8H), 1.18 (q, J = 6.8 Hz, 12H). In some embodiments of the present invention, the molar ratio of compound 3 to triethyl phosphite in this step can be selected in the range of 1:5 to 60.

[0030] In some embodiments of the present invention, the temperature of the substitution reaction in this step can be selected from 100 to 200°C, and the time can be selected from 6 to 20 hours.

[0031] (5) Synthesis of compound GT1

[0032] Compound 4 (0.9 g, 1.46 mmol) was dissolved in anhydrous 1,4-dioxane (5 mL) under argon protection, and trimethylbromosilane (3.63 mL, 23.72 mmol) was slowly added dropwise. The reaction mixture was stirred at room temperature under argon atmosphere for 24 hours. Subsequently, some of the solvent was removed by vacuum distillation, and the remaining liquid was dissolved in methanol (5 mL). Then, distilled water (50 mL) was slowly added dropwise until the solution became cloudy. The product was collected by filtration and washed with water to give 0.69 g of white solid product (yield 89.97%).

[0033] The structural characterization data of compound GT1 are as follows: 1 H NMR (400 MHz, DMSO) δ 8.11 (s, 2H),7.97 (dd, J = 7.9, 4.1 Hz, 2H), 7.89 (d, J = 7.8 Hz, 2H), 7.61 (s, 2H), 7.44 –7.33 (m, 4H), 4.26 (dd, J = 9.7, 5.6 Hz, 4H), 2.06 – 1.95 (m, 4H), 1.91 – 1.60 (m, 8H). In some embodiments of the present invention, the molar ratio of compound 4 to trimethylbromosilane in this step can be selected in the range of 1:10 to 30.

[0034] In some embodiments of the present invention, the temperature of the substitution reaction in this step can be selected from 10 to 40°C, and the time can be selected from 20 to 30 hours. This embodiment prepares a small molecule material based on p-dibenzo[b]thiophenebenzene, and its 1H NMR spectrum is as follows: Figure 1 As shown. Simultaneously, the molecule exhibits characteristic absorption peaks in the 250-450 nm range, indicating a well-developed conjugated molecular system and excellent electron delocalization, laying the foundation for low-barrier hole transport. Compared to traditional triarylamine materials, this is more conducive to improving charge transport efficiency. Figure 2 As shown). Its 5% thermal decomposition temperature reaches 344℃, and it has a high glass transition temperature, enabling it to withstand the heat generated during vacuum evaporation and long-term operation. Figure 3 (As shown). The device's brightness and efficiency are significantly improved. During long-term operation, material crystallization and phase separation are suppressed, interface defects are reduced, and device reliability is ensured.

[0035] The small molecule material based on p-dibenzo[b]thiophenebenzene prepared in this embodiment can be used in light-emitting diodes (OLEDs). Figure 4 A schematic diagram of the organic light-emitting diode (OLED) structure fabricated from the material obtained in this embodiment is shown; from bottom to top, it consists of a glass substrate, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, an electron injection layer, and a cathode. Its 5% thermal decomposition temperature reaches 344°C, and its high glass transition temperature allows it to withstand the heat generated by vacuum evaporation and long-term operation. The device's brightness and efficiency are significantly improved, and material crystallization and phase separation are suppressed during long-term operation, reducing interface defects and ensuring device reliability.

[0036] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent transformations or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A small molecule material based on p-dibenzo[b]thiophenebenzene, characterized in that, The structure is shown in equation GT1: 。 2. The method for preparing a small molecule material based on p-dibenzo[b]thiophenebenzene according to claim 1, characterized in that, Includes the following steps: (1) Compound 1 or 1,4-dibromobutane undergoes a substitution reaction to generate compound 2; (2) Compound 2 is substituted with benzo[b]thiophene-2-boronic acid to generate compound 3; (3) Compound 3 undergoes a substitution reaction with triethyl phosphite to generate compound 4; (4) Compound 4 undergoes a hydrolysis reaction with trimethylbromosilane to generate compound GT1; the reaction route is shown below: 。 3. The method for preparing a small molecule material based on p-dibenzo[b]thiophenebenzene according to claim 2, characterized in that: The substitution reaction in step (1) is carried out in the presence of potassium carbonate and acetone as solvent. The molar ratio of compound 1 to 1,4-dibromobutane is 1:10~40. The substitution reaction is carried out at a temperature of 60-100℃ for 6-10 hours.

4. The method for preparing a small molecule material based on p-dibenzo[b]thiophenebenzene according to claim 2, characterized in that: The substitution reaction in step (2) uses tetra(triphenylphosphine)palladium as a catalyst and toluene as a solvent. The molar ratio of compound 2 to benzo[b]thiophene-2-boronic acid is 1:2~3. The substitution reaction is carried out at a temperature of 60~140℃ for 4~12h.

5. The method for preparing a small molecule material based on p-dibenzo[b]thiophenebenzene according to claim 2, characterized in that: The substitution reaction in step (3) is carried out under the action of triethyl phosphite, and the molar ratio of compound 3 to triethyl phosphite is 1:5~60; The substitution reaction is carried out at a temperature of 100-200℃ for 6-20 hours.

6. The method for preparing a small molecule material based on p-dibenzo[b]thiophenebenzene according to claim 2, characterized in that: The hydrolysis reaction in step (4) is carried out in the presence of trimethylbromosilane and methanol, with 1,4-dioxane as the solvent, and the molar ratio of compound 4 to trimethylbromosilane is 1:10~30; The substitution reaction is carried out at a temperature of 10~40℃ for 20~30h.

7. The method for preparing a small molecule material based on p-dibenzo[b]thiophenebenzene according to claim 2, characterized in that: The reactions in steps (1) to (4) are all carried out in an argon atmosphere.

8. The application of the small molecule material based on p-dibenzo[b]thiophenebenzene as described in claim 1 in organic light-emitting diodes.

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