An organic boron-nitrogen compound, a preparation method, a light-emitting layer, a light-emitting device, and a display device

Abstract

The application belongs to the field of electroluminescence, and discloses an organic boron-nitrogen compound, a preparation method, a light-emitting layer, a light-emitting device and a display device. The structure of the compound is shown in formula I; formula I; wherein A is a group with heavy atoms S or Se. The organic boron-nitrogen compound provided in the application has the characteristics of narrow spectral band, good solution processing characteristics, inhibition of molecular accumulation and low efficiency roll-off. The narrow spectral band characteristic is mainly realized by the boron-nitrogen multiple resonance skeleton in the parent nucleus, the good solubility, film uniformity and accumulation inhibition characteristics are mainly realized by the relatively twisted molecular structure, and the low efficiency roll-off is mainly realized by the introduction of heavy atoms.

Description

Technical Field

[0001] This application belongs to the field of electroluminescence, and specifically relates to an organoboron nitrogen compound and its preparation method, a light-emitting layer, a light-emitting device, and a display device. Background Technology

[0002] Organic light-emitting diodes (OLEDs), with their unique advantages such as ultra-high definition, ultra-thin form factor, high contrast, and flexibility, are gradually replacing liquid crystal display technology and occupying a dominant position in the small and medium-sized display panel field, especially in the mobile phone screen market. Currently, their penetration rate in the mobile phone panel market has exceeded 50%. From the perspective of OLED panel manufacturing processes, the mainstream technologies are currently divided into two categories: vacuum evaporation and inkjet printing. With the continuous iteration and upgrading of printed OLED technology and the significant investment in related industry chains, this technology has developed into a new OLED panel manufacturing solution capable of competing with vacuum evaporation technology. With its core advantages such as high material utilization, excellent panel aperture ratio, low equipment investment cost, and adaptability to large-area panel processing, printed OLED technology has become a research hotspot focusing on by both academia and industry.

[0003] The core structure of OLED devices consists of multiple stacked organic thin films. In the fabrication process of printed OLED displays, the hole injection layer, hole transport layer, and emissive layer are generally prepared using inkjet printing, while functional layers such as the hole blocking layer, electron transport layer, and cathode layer still require vacuum evaporation. Among all functional layers, the emissive layer plays a decisive role in the final performance of the panel. The emissive layer is composed of a host material and a guest emissive material, which places dual demands on both types of materials: on the one hand, they need to have good solubility in organic solvents; on the other hand, they need to maintain excellent film morphology and structural stability after film formation.

[0004] Multiple resonance thermally activated delayed fluorescence molecules with a boron-nitrogen (BN) framework at their core represent a class of organic light-emitting materials that simultaneously possess narrow-spectrum luminescence characteristics and high luminescent efficiency. However, these materials generally suffer from a rigid structure, leading to poor solubility and film-forming properties, and are highly susceptible to significant aggregation quenching effects, resulting in device efficiency roll-off. Currently, there is a severe shortage of boron-nitrogen luminescent materials suitable for solution processing that also exhibit low efficiency roll-off characteristics, highlighting the urgent need for breakthroughs in related research. Summary of the Invention

[0005] This application aims to improve at least one technical problem in the background art.

[0006] The first aspect of this application provides an organoboron-nitrogen compound, the structure of which is shown in Formula I: Formula I; Wherein, R1 is selected from one of hydrogen, C1~C12 alkyl, C1~C12 alkoxy, C3~C10 cycloalkyl, phenyl, aryl group substituted with at least one C1~C12 alkyl group, aryl group substituted with at least one C1~C12 alkoxy group, diphenylamino group, diphenylamino group substituted with at least one C1~C12 alkyl group, carbazole group, and carbazole group substituted with at least one C1~C12 alkyl group; A is a group containing a heavy atom (S or Se), and its structure is shown as in formula II-1, II-2, II-3 or II-4: ; Where X is either S or Se.

[0007] In some preferred embodiments, the structure of the above-mentioned organoboron nitrogen compound is any one of M1 to M20: .

[0008] More preferably, the structure of the aforementioned organoboron nitrogen compound is M20. When the structure is as shown in M20, its solubility in chlorobenzene is greater than 30 mg / mL, and its solubility in methyl benzoate is greater than 40 mg / mL; the maximum current efficiency of the organic electroluminescent device composed of it is 38.3 cd / A, and the current efficiency at 1000 nit brightness is 17.6 cd / A.

[0009] The second aspect of this application provides a method for preparing the above-mentioned organoboron nitrogen compound, including the following synthetic route: .

[0010] The specific process includes: Starting material 1 reacts with starting material 2 to generate intermediate A: Starting material 1 (2.1 eq), 1,3,5-tribromobenzene (1.0 eq), and potassium carbonate (4.2 eq) are dissolved in a mixed solution of water and 1,4-dioxane. Tetra(triphenylphosphine)palladium (0.05 eq) is added under nitrogen atmosphere, the temperature is raised to 70°C, and the mixture is stirred continuously for 12 hours. After the reaction is completed and cooled to room temperature, the mixture is washed three times each with dichloromethane and water. The organic phase is then purified by column chromatography (evolving solvent: petroleum ether) to obtain intermediate A.

[0011] Intermediate A (1.0 eq), starting material 2 (1.2 eq), cesium carbonate (1.5 eq), cuprous iodide (0.5 eq), and 1,10-phenanthroline (0.5 eq) were dissolved in o-dichlorobenzene. The mixture was heated to 180°C under nitrogen atmosphere and stirred continuously for 24 hours. After the reaction was completed and cooled to room temperature, the reaction solution was filtered and extracted. The organic phase was concentrated and purified by column chromatography (evolving solvent: dichloromethane / petroleum ether) to obtain the final product.

[0012] Wherein, the structure of raw material 1 mentioned above is any one of RM1-1 to RM1-4: ; The structure of raw material 2 mentioned above is any one of RM2-1 to RM2-5: .

[0013] A third aspect of this application provides a light-emitting layer, comprising a host material and a light-emitting guest material, wherein the light-emitting guest material includes the aforementioned organoboron-nitrogen compounds. These organoboron-nitrogen compounds possess excellent photophysical properties, such as high luminescence quantum yield and narrow emission spectrum. Using them as light-emitting guest materials can effectively improve the luminous efficiency, color purity, and lifespan of the light-emitting layer. Furthermore, these organoboron-nitrogen compounds generally exhibit good solubility, making them compatible with commonly used OLED printing processes such as spin coating and inkjet printing, reducing the difficulty of light-emitting layer fabrication, improving process feasibility, and facilitating their better application in printed OLED technology.

[0014] In some preferred embodiments, the content of the luminescent guest material is 0.1 wt% to 20 wt%. More preferably, the content of the luminescent guest material is 2 wt%.

[0015] A fourth aspect of this application provides an organic electroluminescent device, including an anode and a cathode, and further including a light-emitting layer as described above between the anode and the cathode. Applying the above-described light-emitting layer to the organic electroluminescent device can effectively improve the overall photoelectric performance of the device, specifically by increasing the luminous efficiency, improving color purity, and extending the device's lifespan.

[0016] More specifically, the aforementioned organic electroluminescent device sequentially comprises: an anode, a hole injection layer, an emissive layer, a hole blocking layer, an electron transport layer, an electron injection layer, and a cathode. The hole injection layer, located between the anode and the emissive layer, lowers the potential barrier for holes to inject from the anode into the emissive layer, thus improving hole injection efficiency. The hole blocking layer, located between the emissive layer and the electron transport layer, primarily prevents holes from diffusing from the emissive layer to the electron transport layer, ensuring sufficient recombination of holes and electrons within the emissive layer and improving carrier recombination efficiency. The electron transport layer and the electron injection layer respectively function to transport electrons and lower the electron injection barrier, ensuring efficient injection of electrons from the cathode and transport to the emissive layer for recombination with holes to emit light. The design of each layer in this organic electroluminescent device maximizes the functionality of each layer, further improving the device's luminous efficiency, stability, and lifespan, meeting the application requirements of high-performance organic electroluminescent devices.

[0017] The fifth aspect of this application provides a display device including the aforementioned organic electroluminescent device. The aforementioned organic electroluminescent device has advantages such as high luminous efficiency, good color purity, fast response speed, high contrast ratio, and long service life. Applying it to a display device can improve the display effect and user experience.

[0018] The beneficial effects of this application are as follows: The organoboron nitrogen compounds proposed in this application have narrow spectral characteristics and good solubility and solution processing performance. They can be formed into light-emitting layers through spin coating or inkjet printing processes and applied to printed OLED technology. The introduction of heavy atoms helps to reduce the efficiency roll-off performance of the device, thereby improving the efficiency of the device at the operating brightness. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of an organic electroluminescent device.

[0020] In the attached diagram: 1-Anode; 2-Hole injection layer; 3-Light emitting layer; 4-Hole blocking layer; 5-Electron transport layer; 6-Electron injection layer; 7-Cathode. Detailed Implementation

[0021] The following will provide a clear and complete description of the concept, specific structure, and resulting technical effects of this application in conjunction with embodiments and accompanying drawings, so as to fully understand the purpose, solution, and effects of this application. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0022] Unless otherwise specified, all experimental methods used in the following content are conventional methods; and all raw materials and reagents used are commercially available unless otherwise specified.

[0023] The structures of the organoboron nitrogen compounds involved in the following content are shown below: .

[0024] The synthetic routes for the above-mentioned organoboron nitrogen compounds are shown below: .

[0025] Wherein, the structure of raw material 1 mentioned above is any one of RM1-1 to RM1-4: ; The structure of raw material 2 mentioned above is any one of RM2-1 to RM2-5: .

[0026] The structures of PEDOT, PSS, mCP, TmPyPB, and Liq involved in the following content are shown below: .

[0027] The structures of the comparative compounds CM1-CM4 mentioned below are shown in the following text: .

[0028] In addition, the mass spectrometry data (Mass Spectra: MS) of molecules with a relative molecular weight below 1000 were obtained using a Thermo Fisher ITQ1100 ion trap gas chromatograph-mass spectrometer, while the mass spectrometry data of molecules with a relative molecular weight above 1000 were obtained using a Bruker Autoflex Speed ​​matrix-assisted laser desorption / ionization time-of-flight mass spectrometer. Elemental analysis of the final products was performed using an Elemental Analysis FlashEA1112 instrument.

[0029] Example 1 An organoboron nitrogen compound, the structure of which is shown in compound M11, specifically includes the following steps: Synthesis and characterization of intermediate A1: Starting material RM1-3 (22.6 g, 42.0 mmol), 1,3,5-tribromobenzene (6.3 g, 20.0 mmol), and potassium carbonate (11.61 g, 84.0 mmol) were dissolved in a mixed solution of 40 mL water and 160 mL 1,4-dioxane. Tetra(triphenylphosphine)palladium (1.16 g, 1 mmol) was added under nitrogen atmosphere. The mixture was heated to 70 °C and stirred continuously for 12 hours. After the reaction was complete and cooled to room temperature, the mixture was washed three times each with 500 mL dichloromethane and water. The organic phase was then purified by column chromatography (electrolyte: petroleum ether) to obtain 21.5 g of a white solid (yield: 75%). Mass spectrometry analysis confirmed this as the target product: MS: 1434.44 (calculated value: 1434.42).

[0030] Synthesis and characterization of compound M11: Intermediate A1 (14.34 g, 10.0 mmol), starting material RM2-3 (3.28 g, 12.0 mmol), cuprous iodide (0.95 g, 5.0 mmol), cesium carbonate (4.89 g, 15.0 mmol), and 1,10-phenanthroline (0.90 g, 5.0 mmol) were dissolved in 100 mL of o-dichlorobenzene. The mixture was heated to 180 °C under nitrogen atmosphere and stirred continuously for 24 hours. After the reaction was completed and cooled to room temperature, the mixture was filtered and the reaction solution was extracted with dichloromethane. The organic phase was concentrated and purified by column chromatography (evolving solvent: dichloromethane / petroleum ether) to give 7.5 g of blue-green solid (yield 66%). The product was confirmed as the target product by mass spectrometry and elemental analysis. MS: 1626.82 (calculated value: 1626.86); elemental analysis: C, 85.61; H, 6.76; N, 4.31 (calculated value: C, 85.64; H, 6.75; N, 4.30).

[0031] The following compounds were prepared using the same method as compound M11. The elemental analysis (percentage of C, H and N in the compounds) and mass spectrometry molecular weight data of the raw materials and products are shown in Table 1.

[0032] Table 1 Organic solvent solubility test Take 1 mL of solvent and add the corresponding mass x of boron nitrogen compound to it. After heating at 80 °C for 2 h, observe whether the solution is clear and transparent. If the solution is clear and transparent, it is considered to be completely dissolved; otherwise, it is considered not to be completely dissolved.

[0033] The solubility of the above compounds was compared with that of CM1~CM4. Two commonly used organic solvents in solution processing (chlorobenzene and methyl benzoate) were selected. These two organic solvents include low-boiling-point solvents (boiling point less than 180℃) and high-boiling-point solvents (boiling point greater than or equal to 180℃), which are representative. The test results are shown in Table 2.

[0034] Table 2 As shown in Table 2, the organic solvent solubility of the boron-nitrogen compounds with the specific structure proposed in this application is significantly better than that of the comparative compounds CM1, CM2 and CM4, which is more conducive to their application in printed OLED processes.

[0035] Example 2 A schematic diagram of the structure of an organic light-emitting diode (OLED device) is shown below. Figure 1 As shown, it includes, in sequence: ITO anode 1, hole injection layer 2, light-emitting layer 3, hole blocking layer 4, electron transport layer 5, electron injection layer 6, and metal cathode 7.

[0036] The following are methods for fabricating solution-processed OLED devices, including: The pre-fabricated ITO glass was ultrasonically cleaned sequentially with cleaning solution, deionized water, and isopropanol for 15 minutes and then dried in a 70°C oven. The dried ITO glass was then treated with a UV ozone cleaner for 15 minutes. Next, 200 μL of Pedot:PSS solution was added to the ITO glass, and the glass was spin-coated at 2000 rpm for 40 seconds, followed by annealing and drying at 150°C for 15 minutes to form a 40 nm thick hole injection layer. CBP was selected as the host material, and synthesized luminescent materials were used as luminescent guests. These materials were dissolved in chlorobenzene solvent at a specific mass ratio to form a first mixture with a concentration of 15 mg / mL. This first mixture was filtered through a 0.22 μm PTFE membrane to form a second mixture. 80 μL of this second mixture was added to the hole injection layer, and the glass was spin-coated at 3000 rpm for 30 seconds, followed by annealing and drying at 80°C for 60 minutes to form a hole injection layer approximately 40 nm thick. A light-emitting layer with a thickness of nm was formed; the unfinished device was transferred to the evaporation chamber and deposited at a depth of 3 × 10⁻⁶ nm. -5 Under a vacuum atmosphere of Pa, an electron transport layer with a thickness of 30 nm was formed at a rate of 0.05 nm / s, and TmPyPB was selected as the electron transport layer material; an electron injection layer with a thickness of 2 nm was formed at a rate of 0.01 nm / s, and (8-hydroxyquinoline)lithium was selected as the electron injection layer material; and a cathode layer was formed at a rate of 0.02 nm / s, and aluminum was selected as the cathode layer material.

[0037] Organic electroluminescent devices Device1 to Device12 were finally obtained. PEDOT:PSS was used as the hole injection layer. In the luminescent layer, the synthesized final products were used as the luminescent guest material (doping concentration of 2 wt%), CBP as the host material, TmPyPB as the electron transport material, (8-hydroxyquinoline)lithium as the electron injection layer, and Al as the metal cathode. The structure is [ITO / PEDOT:PSS (40 nm) / mCP:2.0wt%emitter (40 nm) / TmPyPB (30 nm) / Liq (2 nm) / Al (100 nm)].

[0038] Example 3 An organic electroluminescent device (OLED device) is prepared using the same method as the device in Example 2, except that M11 is selected as the light-emitting guest material and the doping concentration is changed to 5 wt% and 10 wt%. Finally, organic electroluminescent devices Device13 to Device14 are obtained.

[0039] Comparative Example 1 An organic electroluminescent device (OLED device) is prepared using the same method as the device in Application Example 1, except that the light-emitting guest material is selected as CM1~CM4, and comparative devices Compare1~Compare4 are obtained.

[0040] Comparative Example 2 An organic electroluminescent device (OLED device) is prepared using the same method as the device in Application Example 1, except that CM1 is selected as the light-emitting guest material, with doping concentrations of 5 wt% and 10 wt%, respectively. Comparative devices Compare5~Compare6 are obtained.

[0041] Performance testing of organic light-emitting diode (OLED) devices The organic electroluminescent devices Device1 to Device14 prepared in Examples 2-3 and the comparative devices Compare1 to Compare6 prepared in Comparative Examples 1-2 were tested. The current, voltage, brightness, and emission spectrum characteristics of the devices were simultaneously tested using a CS2000 spectrophotometer and a Keithley K2400 digital source meter system. The device performance tests were conducted at room temperature and under ambient atmosphere. The test results are shown in Table 3 below.

[0042] Table 3 By comparing the device performance of the examples and comparative examples in Table 3, the following conclusions can be drawn: When the boron nitrogen compound of the present application is used as the light-emitting guest material of the solution-processed OLED device, the prepared organic electroluminescent device achieves higher maximum efficiency and maintains better light color (half-maximum width at half maximum). At the same time, it can effectively suppress the spectral broadening and spectral redshift caused by the increase of doping concentration, which is beneficial to expanding the process window of the material in device fabrication, making it more applicable, with a smaller efficiency roll-off, and higher efficiency at 1000 nit brightness.

[0043] Furthermore, the maximum efficiency of the device decreases and the roll-off increases under high doping concentrations of the luminescent guest material. However, a comparison between Device 14 and Compare 6 shows that when the boron nitride compound of this application is used as the luminescent guest material, the efficiency degradation is less severe and the roll-off variation is smaller under high doping concentrations, while the full width at half maximum (FWHM) remains relatively stable. The boron nitride compound used in this application can effectively improve the device efficiency degradation and roll-off deterioration under high doping conditions, while avoiding spectral broadening defects and ensuring the purity of the emitted color.

[0044] The above description is merely a preferred embodiment of this application. This application is not limited to the above-described embodiments. Any embodiment that achieves the technical effect of this application using the same means should fall within the protection scope of this application. Within the protection scope of this application, the technical solutions and / or implementation methods can have various modifications and variations.

Claims

1. An organoboron nitrogen compound, characterized in that, Its structure is shown in Equation I: Formula I; Wherein, R1 is selected from one of hydrogen, C1~C12 alkyl, C1~C12 alkoxy, C3~C10 cycloalkyl, phenyl, aryl group substituted with at least one C1~C12 alkyl group, aryl group substituted with at least one C1~C12 alkoxy group, diphenylamino group, diphenylamino group substituted with at least one C1~C12 alkyl group, carbazole group, and carbazole group substituted with at least one C1~C12 alkyl group; The structure of A is shown in equations II-1, II-2, II-3, or II-4: ； Where X is S or Se.

2. The organoboron nitrogen compound according to claim 1, characterized in that, The organoboron nitrogen compound has any one of the structures M1 to M20: 。 3. The organoboron nitrogen compound according to claim 2, characterized in that, The structure of the organoboron nitrogen compound is M20.

4. A method for preparing an organoboron nitrogen compound as described in any one of claims 1-3, characterized in that, The following synthetic routes are included: 。 5. The method for preparing the organoboron nitrogen compound according to claim 4, characterized in that, The structure of raw material 1 is any one of RM1-1 to RM1-4: ； The structure of raw material 2 is any one of RM2-1 to RM2-5: 。 6. A light-emitting layer, characterized in that, It includes a host material and a luminescent guest material, wherein the luminescent guest material includes the organoboron nitrogen compound as described in any one of claims 1-3.

7. The light-emitting layer according to claim 6, characterized in that, The content of the luminescent guest material is 0.1 wt% to 20 wt%.

8. An organic electroluminescent device, characterized in that, It includes an anode and a cathode, and also includes a light-emitting layer as described in claim 6 or 7 between the anode and the cathode.

9. The organic electroluminescent device according to claim 8, characterized in that, In order, they include: The anode, hole injection layer, light-emitting layer, hole blocking layer, electron transport layer, electron injection layer, and cathode.

10. A display device, characterized in that, Including the organic electroluminescent device as described in claim 8 or 9.

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