Boron-nitrogen fused ring compound as well as preparation method and application thereof

Abstract

The invention discloses a boron-nitrogen fused ring compound as well as a preparation method and application thereof. Belongs to the technical field of organic electroluminescence. The boron-nitrogen fused ring compound provided by the invention has a structure as shown in formula 1, and in the formula 1, R1 and R2 are any one of substituted or unsubstituted methyl, tertiary butyl, phenyl, carbazolyl, diphenylamino and dibenzofuranyl. The organic electroluminescent material disclosed by the invention can be applied to a solution processing 0LED process as a narrow-spectrum luminescent material, effectively improves the aggregation-induced fluorescence quenching effect caused by a boron-nitrogen condensed ring rigid plane structure and the defect that the half-peak width is increased due to aggregation, and reduces the half-peak width, so that in the luminescence process, the luminous efficiency of the organic electroluminescent material is greatly improved. And the luminescent property and the color purity of the device are not reduced and are also well improved.

Description

Technical Field

[0001] The present invention relates to the technical field of organic electroluminescence, and in particular to a boron-nitrogen condensed ring compound and a preparation method and application thereof. Background Art

[0002] Organic electroluminescent materials and devices have broad application prospects in the fields of flat panel display and solid-state lighting. Among them, the multi-resonance thermally activated delayed fluorescence molecule based on the boron nitrogen (BN) skeleton is an organic light-emitting material with narrow spectrum luminescence characteristics and high efficiency. This kind of organic light-emitting material has important application value in the future ultra-high-definition display application field.

[0003] Today, the preparation of boron-nitrogen organic light-emitting materials based on vacuum evaporation is relatively mature, but there are relatively few boron-nitrogen materials that can be applied to solution processing, which deserves attention and research. This is mainly because boron-nitrogen light-emitting materials generally have a rigid molecular structure, which is not conducive to their dissolution and solution processing into films, and easily causes strong molecular aggregation, resulting in red shift and broadening of their emission spectrum. In the field of organic electroluminescence, light-emitting materials are the key factor in determining the performance of OLED devices. At present, there are few types of solution-processed MR-TADF light-emitting materials, and more breakthroughs are urgently needed.

[0004] In solution-processed OLED devices, the hole injection layer, hole transport layer and light-emitting layer are generally formed on the anode in sequence by spin coating or inkjet printing, while the hole blocking layer, electron transport layer, electron injection layer and cathode are generally deposited by evaporation. The light-emitting layer generally includes a host material and a light-emitting material. The light-emitting materials suitable for solution-processed OLED technology or the light-emitting materials that can be applied to both vacuum evaporation and solution processing technology need to have good solubility in organic solvents, and in order to reduce the efficiency roll-off of the device and suppress the red shift and spectrum broadening of the emission, the light-emitting materials are required not to be seriously accumulated when forming a thin film. However, there are few types of solution-processed MR-TADF light-emitting materials that meet the above requirements, and related organic electroluminescent materials and devices need to receive attention and in-depth research. Summary of the invention

[0005] The present invention aims to solve the defects and shortcomings of the above-mentioned prior art and propose a boron nitrogen condensed ring compound and its preparation method and application. The OLED prepared by using the new TADF material achieves higher photoelectric conversion efficiency, longer service life and lower cost. The present invention has the characteristics of easy modification, can control the overall molecular weight, and can be applied to the preparation of OLED by spin coating process.

[0006] The technical solution adopted by the present invention to solve its technical problem is:

[0007] As one aspect, the present invention provides a boron-nitrogen condensed ring compound, wherein the boron-nitrogen condensed ring compound has a structure shown in Formula 1:

[0008]

[0009] Here, R1 and R2 are any one of substituted or unsubstituted methyl, tert-butyl, phenyl, carbazolyl, diphenylamino, and dibenzofuranyl.

[0010] As another aspect, the present invention provides an organic electroluminescent composition, which comprises the above-mentioned boron-nitrogen fused-ring compound or the boron-nitrogen fused-ring compound obtained by the preparation method of the above-mentioned boron-nitrogen fused-ring compound.

[0011] As another aspect, the present invention provides an organic electroluminescent device, which includes an anode, a cathode, and an organic thin film layer disposed between the anode and the cathode; the organic thin film layer includes a light-emitting layer, a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer; wherein the light-emitting layer comprises the above-mentioned boron-nitrogen condensed ring compound or the boron-nitrogen condensed ring compound obtained by the preparation method of the above-mentioned boron-nitrogen condensed ring compound or the above-mentioned organic electroluminescent composition.

[0012] As yet another aspect, the present invention provides an application of the organic electroluminescent device as described above, wherein the organic electroluminescent device is used as a narrow spectrum OLED device in a solution processing process.

[0013] The technical solution provided by the embodiment of the present invention has the following advantages:

[0014] The boron nitrogen condensed ring compound provided by the embodiment of the present invention connects multiple BN luminescent skeleton core units to the pyrene group, so that the molecular structure of the boron nitrogen condensed ring compound presents a special twisted structure. The twisted structure of the boron nitrogen condensed ring compound molecule can improve the solubility of organic materials in organic solvents on the one hand, and can be applied to solution processing technology; on the other hand, it is conducive to inhibiting the accumulation of luminescent molecules, thereby reducing the efficiency roll-off of the device and the spectral red shift and spectral broadening caused by molecular accumulation. In addition, the boron nitrogen condensed ring compound of the embodiment of the present invention has a BN molecular core skeleton, has the characteristics of narrow-band luminescence, and can effectively improve the color purity of the device.

[0015] The boron nitrogen condensed ring compound of the embodiment of the present invention connects multiple BN light-emitting skeleton core units together through a pyrene group to obtain a boron nitrogen condensed ring compound with a twisted molecular structure. Compared with the unconnected boron nitrogen condensed ring compound, the solubility of the boron nitrogen condensed ring compound with a twisted molecular structure of the embodiment of the present invention is improved; when the boron nitrogen condensed ring compound with a twisted molecular structure of the embodiment of the present invention is used as a guest in an organic electroluminescent device, its spectrum broadening and red shift are suppressed, and the efficiency roll-off is also suppressed.

[0016] The TADF material provided by the present invention has good thermal stability, a glass transition temperature greater than 120°C, and a thermal decomposition temperature greater than 500°C. At the same time, blue light-emitting devices can be prepared by spin coating, expanding the processing methods of TADF materials. Therefore, the new TADF material provided by the present invention has broad market application prospects and is easily applicable to industrial large-scale preparation.

[0017] Furthermore, the present invention includes an organic electroluminescent device, which includes an anode, a cathode and an organic layer, wherein the organic layer includes a TADF material of a boron-nitrogen condensed ring compound.

[0018] Furthermore, the organic electroluminescent device of the present invention comprises an anode, a cathode and an organic thin film layer disposed between the anode and the cathode; the organic thin film layer comprises a light-emitting layer, a hole injection layer, a hole transport layer, an electron transport layer and an electron injection layer.

[0019] Wherein, the light-emitting layer comprises a boron-nitrogen condensed ring compound or a boron-nitrogen condensed ring compound obtained by a preparation method of a boron-nitrogen condensed ring compound.

[0020] Furthermore, the present invention includes the application of organic electroluminescent devices in organic light-emitting diodes, organic photovoltaic cells, organic light-emitting cells, organic field effect transistors, organic light-emitting field effect transistors, organic lasers, organic spin electronic devices, organic sensors, and organic exciton emitting diodes.

[0021] Beneficial effects:

[0022] 1. The present invention achieves higher photoelectric conversion efficiency, longer service life and lower costs.

[0023] 2. The present invention has the characteristics of being easy to modify, being able to control the overall molecular weight, and being able to be applied to the preparation of OLEDs by spin coating process.

[0024] 3. The organic electroluminescent material of the present invention can be applied to solution-processed 0LED technology as a narrow-spectrum luminescent material, and can effectively improve the aggregation-induced fluorescence quenching effect caused by the rigid planar structure of the boron nitrogen fused ring and the shortcomings of widening the half-peak width caused by aggregation, thereby reducing the half-peak width, so that during the luminescence process, the luminescence performance and color purity of the device are not only not reduced but also greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the structure of the organic electroluminescent device in an embodiment of the present invention.

[0026] In the figure, 1-transparent substrate layer; 2-transparent anode electrode layer; 3-hole transport layer; 4-light-emitting layer; 5-electron transport layer; 6-electron injection layer. DETAILED DESCRIPTION

[0027] For ease of understanding, the technical solutions and implementation methods of the present invention are further described clearly, completely and in detail through specific examples. It should be noted that the embodiments described in the present invention are implemented on the premise of the technical solutions of the present invention, and detailed implementation methods and specific operating processes are given, but they are only part of the embodiments of the present invention, not all of the embodiments. The specific implementation methods described are limited to explaining and interpreting the present invention, and do not limit the present invention. Based on the embodiments in the present invention, all other implementation methods obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods, and the materials, reagents, etc. used in the examples are all available from commercial sources unless otherwise specified.

[0029] According to an embodiment of the present invention, a boron-nitrogen fused ring compound is provided, and the boron-nitrogen fused ring compound has a structure shown in formula (I):

[0030]

[0031] The boron-nitrogen fused ring compound of the embodiment of the present invention connects multiple BN luminescent skeleton core units to a pyrene group, so that the molecular structure of the boron-nitrogen fused ring compound presents a special twisted structure. On the one hand, this twisted structure of the boron-nitrogen fused ring compound can improve the solubility of organic materials in organic solvents, and thus can be applied to solution processing technology; on the other hand, it is beneficial to inhibit the accumulation of luminescent molecules, thereby reducing the efficiency roll-off of the device and the spectral red shift and spectral broadening caused by molecular accumulation.

[0032] In some embodiments of the present invention, the boron-nitrogen fused ring compound is selected from any one of the following compounds:

[0033]

[0034]

[0035]

[0036]

[0037] According to an embodiment of the present invention, there is provided a method for preparing the above-mentioned boron-nitrogen fused ring compound, comprising:

[0038] The raw material 1 undergoes a boroesterification reaction to generate an intermediate 1, which is then reacted with the raw material 2 through a Suzuki coupling reaction to generate the final product 1. The reaction formula is as follows:

[0039] Intermediate 1 and raw material 2 undergo Suzuki coupling reaction to generate final product Formula 1, the reaction formula is as follows:

[0040]

[0041] In some embodiments of the present invention, the reaction conditions for synthesizing intermediate 1 are:

[0042] The catalyst [Ir(COD)(OCH3)]2 (0.01eq), 4,4-di-tert-butylbipyridine (dtbpy) (0.02eq), raw material 1 (1.0eq) and bis(pinacolato)diboron (B2Pin) (1.0eq) were added to an ultra-dry tetrahydrofuran solvent, and then nitrogen was bubbled for 5 minutes, and then heated to reflux and stirred for 24 hours under a nitrogen atmosphere. After cooling to room temperature, the mixture was purified by column chromatography to obtain intermediate 1.

[0043] In some embodiments of the present invention, the reaction conditions of the synthesis formula 1 are:

[0044] Intermediate 1 (2.2 eq), raw material 2 (1.0 eq), appropriate amount of tetrabutylammonium bromide and tetrakis(triphenylphosphine)palladium were added to aqueous potassium carbonate solution and tetrahydrofuran, heated under reflux for 8 hours under nitrogen atmosphere, extracted and separated by column chromatography to obtain the final product of formula 1.

[0045] According to an embodiment of the present invention, an organic electroluminescent material is provided. The organic electroluminescent material comprises the above-mentioned boron-nitrogen condensed ring compound or the boron-nitrogen condensed ring compound obtained by the preparation method of the above-mentioned boron-nitrogen condensed ring compound.

[0046] According to an embodiment of the present invention, an organic electroluminescent device is provided, which includes an anode, a cathode and an organic thin film layer disposed between the anode and the cathode; the organic thin film layer includes a light-emitting layer, a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer; wherein the light-emitting layer comprises the above-mentioned boron-nitrogen condensed ring compound or the boron-nitrogen condensed ring compound obtained by the preparation method of the above-mentioned boron-nitrogen condensed ring compound or the above-mentioned organic electroluminescent composition.

[0047] In some embodiments of the present invention, an organic electroluminescent device comprises an anode and a cathode and an organic thin film layer disposed between the anode and the cathode, wherein the organic thin film layer comprises a light-emitting layer, an optional hole injection layer, an optional hole transport layer, an optional electron transport layer, and an optional electron injection layer. The light-emitting layer comprises a host material and a light-emitting material. The light-emitting layer, the hole injection layer, and the hole transport layer are prepared using a spin coating process or an inkjet printing process, and the electron transport layer, the electron injection layer, and the cathode are prepared using a vacuum evaporation process.

[0048] In some embodiments of the present invention, the compound having the structure shown in Formula 1 can be used as a luminescent guest material in the luminescent layer. The luminescent layer also contains a host material.

[0049] In some embodiments of the present invention, the organic electroluminescent device may further include an optional hole blocking layer, an optional electron blocking layer, an optional capping layer, and the like.

[0050] In some embodiments of the present invention, the boron nitrogen fused ring compound can be used as a luminescent guest material in a light-emitting layer in an organic electroluminescent device, wherein the organic electroluminescent device comprises a hole injection layer, optionally a hole transport layer, one or more electron transport layers, and a light-emitting layer. Further, when the compound of the present invention is used as a guest luminescent material of the light-emitting layer, the mass ratio of the compound in the light-emitting layer is 0.1 to 20%.

[0051] According to an embodiment of the present invention, there is provided an application of the organic electroluminescent device as described above, wherein the organic electroluminescent device is used as a narrow spectrum OLED device in a solution processed OLED process.

[0052] In order to further illustrate the effect of the present invention, specific embodiments are used for illustration below.

[0053] The synthesis examples of the present invention include the following:

[0054] Taking the boron nitrogen condensed ring compound structure 2 as an example, the synthesis route of the boron nitrogen condensed ring compound of the embodiment of the present invention is described, and the specific steps are as follows:

[0055] (1) Catalyst [Ir(COD)(OCH3)]2 (43.1 mg, 0.065 mmol), 4,4-di-tert-butyl bipyridine (dtbpy) (34.9 mg, 0.13 mmol), raw material 1-2 (4.69 g, 6.5 mmol) and bis(pinacolato)diboron (B2Pin) (1.68 g, 6.6 mmol) were added to a 250 mL two-necked bottle, and 60 mL of ultra-dry tetrahydrofuran was added thereto. After bubbling with nitrogen for 5 minutes, the mixture was heated under reflux and stirred for 24 hours under a nitrogen atmosphere. After cooling to room temperature, the reaction solution was concentrated under reduced pressure and purified by column chromatography using dichloromethane and petroleum ether to obtain intermediate 1-2 (4.8 g) with a yield of 87%. MS (MALDI-TOFMS): m / z 848.37 ([M+H]+).

[0056] (2) The catalyst tetrakistriphenylphosphine palladium (350 mg, 0.3 mmol), tetrabutylammonium bromide (0.1 mg, 0.3 mmol), the above intermediate 1-2 (14.93 g, 17.6 mmol), the raw material 2 (3.1 g, 8 mmol) and 50 mL of a 1 mol / L potassium carbonate aqueous solution were added to a 250 mL double-necked flask, and then 50 mL of ultra-dry tetrahydrofuran was added thereto. The mixture was heated to reflux and stirred for 8 hours under a nitrogen atmosphere. After cooling to room temperature, the reaction solution was extracted and concentrated under reduced pressure. The product was purified by column chromatography using dichloromethane and petroleum ether to obtain the final product of structural formula 2 (10.1 g) with a yield of 72%.

[0057] In the embodiment of the present invention, the specific raw materials used to synthesize the structural formula 2 are as follows:

[0058]

[0059] The following compounds were prepared by the same synthesis method as that of Structural Formula 2. The elemental analysis (C, H and N percentages in the compounds) and mass spectrometry molecular weight data of the raw materials and products are shown in Table 1.

[0060] Table 1 Preparation raw materials and product analysis of structural formula 1-35:

[0061]

[0062]

[0063] The organic solvent solubility test of the present invention includes the following:

[0064] Take 1 mL of solvent and add the corresponding mass x of boron-nitrogen fused ring compound thereto. After heating at 80°C for 2 hours, 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 to be incompletely dissolved.

[0065] Compounds 2, 16, 30, 31, and BN were selected for solubility comparison. The solvents selected were two organic solvents commonly used in solution processing (chlorobenzene and methyl benzoate). These two organic solvents included low boiling point solvents (boiling point less than 180°C) and high boiling point solvents (boiling point greater than or equal to 180°C), which were representative. The test results are shown in Table 2.

[0066] The structural formula of the comparative compound BN is as follows:

[0067]

[0068] Table 2 Comparison of organic solvent solubility test of compounds 2, 16, 30, 31 and BN

[0069] Structural formula Solubility in chlorobenzene (mg / mL) Solubility in methyl benzoate (mg / mL) 2 x>20 x>40 16 x>20 x>40 30 x>20 x>40 31 x>20 x>40 BN 15<x<20 25<x<40

[0070] The boron nitrogen condensed ring compound of the embodiment of the present invention connects multiple BN luminescent skeleton core units together through a pyrene group to obtain a boron nitrogen condensed ring compound with a distorted molecular structure. Compared with the unconnected boron nitrogen condensed ring compound (such as BN), the solubility of the boron nitrogen condensed ring compound with a distorted molecular structure (such as 2, 16, 30) of the embodiment of the present invention is significantly improved.

[0071] Electroluminescent device embodiments

[0072] Device Example 1:

[0073] The prefabricated ITO glass was ultrasonically cleaned with cleaning solution, deionized water, and isopropanol for 15 minutes in sequence and dried in a 70°C oven; the dried ITO glass was treated with an ultraviolet ozone cleaner for 15 minutes; then 200 microliters of PEDOT:PSS solution was dripped onto the ITO glass, spin-coated at a speed of 2000 rpm / min for 40 seconds, and then annealed and dried at a temperature of 150°C for 15 minutes to form a hole injection layer with a thickness of 40 nm;

[0074] Compound α was selected as the main material, and the above-mentioned luminescent material structure 1 was selected as the luminescent guest, and dissolved in chlorobenzene solvent according to a certain mass ratio to form a first mixed solution, the concentration of the first mixed solution was 15 mg / ml, and it was filtered using a PTFE filter membrane with a filter diameter of 0.22 microns to form a second mixed solution, 100 microliters of the second mixed solution was dripped onto the hole injection layer, and the rotation speed was 1500 rpm / min for 30 seconds, and the temperature was annealed and dried at 80°C for 60 minutes to form a luminescent layer with a thickness of 40 nm; the unfinished device was transferred to the evaporation chamber, and the 3×10 -5In a Pa vacuum atmosphere, an electron transport layer is formed at a rate of 0.05 nm / s with a thickness of 30 nm, where TmPyPB is selected as the electron transport layer material; an electron injection layer is formed at a rate of 0.01 nm / s with a thickness of 2 nm, where (8-hydroxyquinoline) lithium is selected as the electron injection layer material; a cathode layer is formed at a rate of 0.02 nm / s, where metal aluminum is selected as the cathode layer. An organic electroluminescent device is obtained.

[0075]

[0076] Device Examples 2 to 12:

[0077] The difference between Examples 2 to 12 and Device Example 1 is that the main material of the light-emitting layer of the electroluminescent device is Compound 1, 2, 5, 16, 25, 30 of the present invention.

[0078] Table 3 Performance test results of organic electroluminescent devices in device examples 1-35 and comparative example CN

[0079]

[0080]

[0081] By comparing the device performance of the embodiment and the comparative example in Table 3, the following conclusions can be drawn:

[0082] When the boron nitrogen fused ring compound of the embodiment of the present invention is used as a light-emitting guest material for solution-processed OLED devices, it has better solubility than the comparative material BN, and the organic electroluminescent device obtains a higher maximum efficiency and maintains a better light color (half-peak width), while maintaining a higher efficiency at a higher brightness. At the same time, it can effectively suppress the spectral width broadening caused by increasing the doping concentration, which is beneficial to expanding the process window of the material in device preparation and has stronger applicability.

[0083] The boron nitrogen condensed ring compound of the embodiment of the present invention connects multiple BN light-emitting skeleton core units together through a pyrene group to obtain a boron nitrogen condensed ring compound with a distorted molecular structure. Compared with the unconnected boron nitrogen condensed ring compound (such as BN), the boron nitrogen condensed ring compound with a distorted molecular structure of the embodiment of the present invention, when used as a guest in an organic electroluminescent device, the spectrum broadening and red shift of the organic electroluminescent device are suppressed, and the efficiency roll-off is also suppressed.

[0084] In summary, the boron-nitrogen fused ring compound provided in the embodiment of the present invention can be used as an organic electroluminescent material in the solution-processed OLED process as a narrow-spectrum luminescent material, and the corresponding solution-processed organic electroluminescent device has a significant improvement in color purity.

[0085] It should be noted that, in the present invention, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0086] The above description is only a specific embodiment of the present invention, so that those skilled in the art can understand or implement the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined in the present invention can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments described in the present invention, but should conform to the widest scope consistent with the principles and novel features disclosed in the present invention.

Claims

1. A boron-nitrogen fused ring compound, characterized in that: The boron-nitrogen fused ring compound has a structure shown in Formula 1: Wherein R1 and R2 are any one of substituted or unsubstituted methyl, tert-butyl, phenyl, carbazolyl, diphenylamino, and dibenzofuranyl.

2. A boron-nitrogen fused ring compound according to claim 1, characterized in that: The compound is any one of the following structures:

3. A method for preparing a boron-nitrogen fused ring compound according to any one of claims 1 to 2, characterized in that: include: The raw material 1 undergoes a boroesterification reaction to generate an intermediate 1, which is then reacted with the raw material 2 through a Suzuki coupling reaction to generate the final product 1. The reaction formula is as follows:

4. An application of a boron-nitrogen fused ring compound as claimed in claim 1, characterized in that: The invention comprises an organic electroluminescent device, which comprises an anode, a cathode and an organic layer, wherein the organic layer comprises a TADF material of a boron-nitrogen condensed ring compound.

5. An organic electroluminescent device applied to a boron-nitrogen fused ring compound, characterized in that: The organic electroluminescent device comprises an anode, a cathode and an organic thin film layer disposed between the anode and the cathode; The organic thin film layer includes a light-emitting layer, a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer; wherein the light-emitting layer contains a boron-nitrogen condensed ring compound or a boron-nitrogen condensed ring compound obtained by a preparation method of a boron-nitrogen condensed ring compound.

6. A use of the organic electroluminescent device as claimed in claim 5, characterized in that: Including the application of organic electroluminescent devices in organic light emitting diodes, organic photovoltaic cells, organic light emitting cells, organic field effect transistors, organic light emitting field effect transistors, organic lasers, organic spin electronic devices, organic sensors, and organic plasma emitting diodes.

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