A spiro-structured compound containing a boron-nitrogen coordination bond, an organic electroluminescent device

Abstract

The present invention belongs to the technical field of organic optoelectronic materials, and more specifically, relates to a boron-nitrogen coordination bond-containing spiro structure compound and an organic electroluminescent device. The boron-nitrogen coordination bond-containing spiro structure compound provided by the present invention has the structures shown in formulas (1), (2), (3), (4), (5) or (6), and has the advantages of simple synthesis method, short synthesis period, reproducibility in multiple syntheses, etc. Moreover, the ΔE of the above boron-nitrogen coordination bond-containing spiro structure compound ST is small, the PLQY is high, it has good solubility, excellent film-forming property and stable film morphology, and can be used as a solution-processable thermally activated delayed fluorescence material, which is suitable for preparing OLED devices by solution method. By applying the above boron-nitrogen coordination bond-containing spiro structure compound to an organic electroluminescent device through a solution processing method, a relatively high external quantum efficiency can be achieved, and the maximum external quantum efficiency can reach 38.21%. #imgabs0#

Description

Technical Field

[0001] The present invention relates to the technical field of organic optoelectronic materials, and more specifically, to a boron-nitrogen coordination bond-containing spiro structure compound and an organic light-emitting device. Background Art

[0002] Since C.W. Tang et al. first reported ultrathin multilayer organic light-emitting diodes (OLEDs) in 1987, OLEDs have received extensive attention in both academia and industry and have been successfully commercialized. As the third-generation organic light-emitting diode (OLED) materials, thermally activated delayed fluorescence (TADF) materials have attracted extensive attention in academia and industry because they do not contain expensive noble metals and can make full use of the characteristics of singlet and triplet excitons. Although significant progress has been made in the research of TADF materials and devices, new TADF materials are still urgently needed to be developed, especially the development and design of highly efficient TADF materials.

[0003] With the progress of people's understanding of molecular design criteria and photophysical principles, the maximum external quantum efficiency (EQE) of vacuum-evaporated TADF-OLED devices has exceeded 40%, approaching the level of phosphorescent devices. However, the equipment used for vacuum evaporation is complex, the equipment investment and maintenance costs are high, and the utilization rate of organic materials is low, etc., which increase the manufacturing cost and complexity of OLED devices and seriously affect the popularization and application of OLED displays. Solution processing technologies such as spin coating, inkjet printing, roll-to-roll, gravure printing, and screen printing, as an effective alternative strategy, have received extensive attention due to their high material utilization rate, simple manufacturing process, low equipment investment cost, and suitability for large-scale production. However, the solution processing method has very strict molecular requirements for TADF materials. Its molecules not only need to have a small ΔE ST and a high fluorescence quantum yield (PLQY), but also need to have good solubility and film-forming ability to meet its solution processability.

[0004] Small molecule TADF materials have advantages such as a definite molecular structure, easy synthesis and purification, and monodisperse molecular weight, making them promising solution-processable TADF materials. Most of the current solution-processable small molecule TADF materials are modified based on vapor-deposited TADF molecules to endow the TADF materials with good solution-processability. For example, by introducing flexible groups such as methyl, tert-butyl, fluorine atom, trifluoromethyl, sec-butoxy or adamantane into rigid TADF materials, the solubility and film-forming ability of small molecule TADF materials can be improved. However, the introduction of flexible groups will increase the non-radiative loss of the molecules and sacrifice the luminescence efficiency of the TADF materials themselves. Compared with numerous vapor-deposited TADF molecules, solution-processable high-efficiency small molecule TADF materials are still relatively few and have a low luminescence efficiency. Developing solution-processable small molecule TADF materials with high luminescence efficiency is a current research hotspot in the display field.

[0005] Nitrogen-containing aromatic heterocycles (pyridine, pyrimidine, pyrazine and triazine) are one of the most commonly used acceptor units for constructing small molecule TADF materials. Modifying their molecular structures by means of intramolecular hydrogen bonds or through fusion can improve the luminescence properties of TADF materials based on these molecules. However, the above modifications inevitably increase the planarity of the molecules to a certain extent, enhance the intermolecular interaction or crystallinity, and thus lead to poor solubility of the materials. Therefore, how to ensure its solubility while improving its luminescence properties is an urgent problem to be solved for this kind of materials. Summary of the Invention

[0006] Aiming at the defects of the prior art, the present invention provides a boron-nitrogen coordination bond-containing spiro structure compound and an organic electroluminescent device, which solve the problems of fewer existing solution-processable small molecule TADF materials and the need to improve the luminescence efficiency.

[0007] To achieve the above object, the present invention provides a boron-nitrogen coordination bond-containing spiro structure compound having a structure shown in formula (1), (2), (3), (4), (5) or (6),

[0008]

[0009] wherein, each occurrence of R1, R2, R3, R4, R5, R6, R7 is independently a hydrogen atom, a cyano group, a halogen, a C1-C20 alkoxy group, a C1-C20 alkylthio group, a C1-C20 alkylamino group, a C6-C50 aryloxy group, a C6-C50 arylthio group, a C6-C50 aryl group, a C6-C50 heteroaromatic group or a C6-C50 aromatic amine group.

[0010] Preferably, each occurrence of R1, R2, R3, R4, R5, R6, and R7 is independently methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, tert-butoxy, pentyloxy, isopentyloxy, neopentyloxy, tert-pentyloxy, hexyloxy, 2-methylpentyloxy, methylthio, ethylthio, propylthio, n-butylthio, sec-butylthio, tert-butylthio, methylamino, ethylamino, propylamino, butylamino, pentylamino, isopentylamino, neopentylamino, tert-pentylamino, hexylamino, dimethylamino, diethylamino, dipropylamino, dibutylamino, dipentylamino, diisopentylamino, dineopentylamino, ditert-pentylamino, or dihexylamino.

[0011] Preferably, each occurrence of R1, R2, R3, R4, R5, R6, and R7 is independently o-, m-, p-methylphenylamino, o-, m-, p-ethylphenylamino, o-, m-, p-propylphenylamino, o-, m-, p-isopropylphenylamino, o-, m-, p-methoxyphenylamino, o-, m-, p-ethoxyphenylamino, o-, m-, p-propoxyphenylamino, o-, m-, p-fluorophenylamino, o-, m-, p-chlorophenylamino, o-, m-, p-bromophenylamino, o-, m-, p-iodophenylamino, bis(o-, m-, p-methylphenyl)amino, bis(o-, m-, p-ethylphenyl)amino, bis(o-, m-, p-propylphenyl)amino, bis(o-, m-, p-isopropylphenyl)amino, bis(o-, m-, p-methoxyphenyl)amino, bis(o-, m-, p-ethoxyphenyl)amino, bis(o-, m-, p-propoxyphenyl)amino, bis(o-, m-, p-fluorophenyl)amino, bis(o-, m-, p-chlorophenyl)amino, bis(o-, m-, p-bromophenyl)amino, bis(o-, m-, p-iodophenyl)amino, or triphenylamino.

[0012] Preferably, each occurrence of R1, R2, R3, R4, R5, R6, and R7 is independently phenoxy, phenylthio, phenyl, diphenyl, triphenyl, tetraphenyl, pyrenyl, fluorene, spirofluorene, pyridine, pyrazine, pyrimidine, triazine, or tetrazine.

[0013] Preferably, R1, R2, R3, R4, R5, and R6 are all hydrogen atoms, and R7 is selected from C6-C50 aromatic amine groups.

[0014] Preferably, the C6-C50 aromatic amine group is selected from any one of the following groups:

[0015]

[0016]

[0017]

[0018]

[0019]

[0020] The present invention also provides a mixture, which comprises the boron-nitrogen coordination bond-containing spiral structure compound and at least one organic functional material, and the organic functional material is selected from a hole injection material, a hole transport material, an electron transport material, an electron injection material, an electron blocking material, a hole blocking material, a luminescent guest material, a luminescent host material or an organic dye.

[0021] The present invention also provides an application of the boron-nitrogen coordination bond-containing spiral structure compound or the mixture in an organic electroluminescent device prepared by a solution processing method.

[0022] The present invention also provides a composition, which comprises the boron-nitrogen coordination bond-containing spiral structure compound or the mixture, and at least one organic solvent.

[0023] The present invention also provides an organic electroluminescent device, which comprises at least one functional layer, the functional layer comprises the boron-nitrogen coordination bond-containing spiral structure compound or the mixture, or the functional layer is prepared from the composition.

[0024] Generally speaking, compared with the prior art by the above technical solution conceived by the present invention, at least the following beneficial effects can be achieved:

[0025] (1) The boron-nitrogen coordination bond-containing spiral structure compound provided by the present invention has a single structure, a determined molecular weight, and is easy to purify, and has the advantages of simple synthesis method, short steps, short synthesis period, and good reproducibility in multiple syntheses. The ΔE of the boron-nitrogen coordination bond-containing spiral structure compound provided by the present invention ST is small, the PLQY is high, it has good solubility, excellent film-forming property and stable film morphology, and can be used as a solution-processable thermally activated delayed fluorescence material, and is suitable for preparing large-area OLED devices by a solution method.

[0026] (2) By using the boron-nitrogen coordination mode, the nitrogen-containing aromatic heterocyclic receptor unit is combined with the rigid boron fluorene group with a large structure, which can not only regulate the geometric configuration and charge distribution of the molecule, but also effectively inhibit the intermolecular interaction and crystallinity. The electron-deficient characteristics of the nitrogen-containing aromatic heterocycle and the boron atom can realize the fusion of their electron-withdrawing effects, reduce its LUMO energy level, enhance the charge transfer characteristics from the donor unit to the pyrimidine π-conjugated skeleton, thereby regulating the luminescence characteristics of the material and reducing its ΔE STMoreover, the tetracoordinated configuration of the central boron atom can restrict the single-bond rotation between the pyrimidine and the benzene ring substituent, enhance the rigidity of the corresponding conjugated ligand unit, inhibit the non-radiative loss within the molecule, and thus improve the PLQY of the material. In addition, the rigidity and orthogonal structure of the spiro-structured compound containing boron-nitrogen coordination bonds can inhibit non-radiative energy dissipation and intermolecular interactions, resulting in loose molecular packing, making it easy for solvent molecules to enter between the molecules, thereby improving the solubility of the molecule.

[0027] (3) The spiro-structured compound containing boron-nitrogen coordination bonds of the present invention is applied to an organic electroluminescent device through a solution processing technology, which has the advantages of simple preparation method and low cost. Moreover, the maximum external quantum efficiency of the organic electroluminescent device is as high as 38.21%, and the color coordinates are (X = 0.23, Y = 0.53), showing good optoelectronic properties.

[0028] (4) The spiro-structured compound containing boron-nitrogen coordination bonds provided by the present invention can further improve its carrier transport characteristics and fluorescence quantum yield by changing the modifying groups on the aromatic structure; it can also effectively regulate the conjugation length, electrophilicity, film-forming property, and horizontal dipole orientation of the molecule by changing the connected chemical structure, so that it has good comprehensive performance when used as a small molecule TADF material in solution-processed organic electroluminescent devices. Description of the Drawings

[0029] Figure 1 is the electroluminescence spectrum of the organic electroluminescent device prepared in Example 2;

[0030] Figure 2 is the performance diagram of the organic electroluminescent device prepared in Example 2. Content (a) is the relationship diagram of current density - external quantum efficiency, and content (b) is the relationship diagram of current density - voltage - luminance;

[0031] Figure 3 is the atomic force micrograph of the film prepared by spin-coating the luminescent material P1 in Example 2. Detailed Embodiments

[0032] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0033] Unless otherwise specified, all technical terms and scientific terms used herein have the ordinary meanings in the field to which the claimed subject matter belongs. If there are multiple definitions for a certain term, the definition in this article shall prevail.

[0034] Unless otherwise specified, when disclosing or claiming any type of range (such as wavelength, full width at half maximum, and number of substituents), it is intended to disclose or claim separately each possible value that the range could reasonably cover, including any sub-ranges subsumed therein. For example, in this text, a numerical range defined for the number of carbon atoms in an alkoxy group such as 1 to 20, etc. indicates integers within that range.

[0035] The terms "group" and "chemical group" refer to specific fragments or functional groups in a molecule.

[0036] Unless otherwise specified, this application uses standard nomenclature and standard laboratory procedures and techniques in analytical chemistry, organic synthetic chemistry, and optics. In some cases, standard techniques are used for chemical synthesis, chemical analysis, and performance detection of light-emitting devices. Unless otherwise stated, this application uses traditional methods such as mass spectrometry and elemental analysis, and the procedures and conditions for each step can refer to the conventional operating procedures and conditions in the art.

[0037] The reagents and raw materials used in this application are commercially available or can be prepared by conventional chemical synthesis methods.

[0038] In this application, unless otherwise specified, the number of said "substitutions" can be one or more; when there are multiple substitutions, it can be 2, 3, or 4. And when the number of said "substitutions" is multiple, the "substitutions" can be the same or different. The position of the "substitution", unless otherwise specified, can be arbitrary.

[0039] The terms "ortho", "meta", and "para" refer to cases where there are exactly two hydrogen atoms on a benzene ring replaced by other groups. If it is at the 1, 2 positions, it is the ortho position; at the 1, 3 positions, it is the meta position; and at the 1, 4 positions, it is the para position.

[0040] The term "halogen" refers to fluorine, chlorine, bromine, or iodine.

[0041] The term "alkoxy group" refers to a group with the structure "-O-alkyl", that is, an alkyl group is connected to other groups via an oxygen atom. In some embodiments, the above alkoxy group is preferably a C1 - C20 alkoxy group, such as methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, tert-butoxy, pentyloxy, isopentyloxy, neopentyloxy, tert-pentyloxy, hexyloxy, 2-methylpentyloxy.

[0042] The term "alkylthio group" refers to a group with the structure "-S-alkyl", that is, an alkyl group is connected to other groups via a sulfur atom. In some embodiments, the above alkylthio group is preferably a C1 - C20 alkylthio group, such as methylthio, ethylthio, propylthio, n-butylthio, sec-butylthio, tert-butylthio.

[0043] The term "alkylamino" refers to a group with the structure "-N-alkyl", that is, an alkyl group is connected to other groups via an N atom. In some embodiments, the above alkylamino is preferably a C1-C20 alkylamino, such as methylamino, ethylamino, propylamino, butylamino, pentylamino, isopentylamino, neopentylamino, tert-pentylamino, hexylamino, dimethylamino, diethylamino, dipropylamino, dibutylamino, dipentylamino, diisopentylamino, dineopentylamino, ditert-pentylamino, dihexylamino.

[0044] The term "Cn-Cm aryloxy" refers to a group with a structure containing at least one benzene ring and an O-linked group, that is, the benzene ring is connected to other groups via an O atom. In some embodiments, the above aryloxy is phenoxy.

[0045] The term "Cn-Cm arylthio" refers to a group with a structure containing at least one benzene ring and an S-linked group, that is, the benzene ring is connected to other groups via an S atom. In some embodiments, the above arylthio is phenylthio.

[0046] The term "Cn-Cm aryl" refers to a monocyclic or polycyclic aromatic group (ring atoms are only carbon atoms) having n to m ring carbon atoms, which has at least one carbon ring with a conjugated π electron system. In some embodiments, the C6-C50 aryl is selected from phenyl, diphenyl, triphenyl, tetraphenyl, pyrenyl, fluorene or spirofluorene.

[0047] The term "Cn-Cm heteroaryl group" refers to an aromatic group whose ring atoms contain one or more (such as 1, 2, 3 and 4) heteroatoms selected from nitrogen, oxygen and sulfur, and the ring atoms are n to m, and the heteroaryl is a monocyclic, bicyclic, tricyclic or tetracyclic system, where at least one ring is an aromatic ring. In some embodiments, the C6-C50 heteroaryl group is selected from pyridine, pyrazine, pyrimidine, triazine, tetrazine.

[0048] The present invention provides a spiro-structured compound containing a boron-nitrogen coordination bond, having the structures shown in formula (1), (2), (3), (4), (5) or (6).

[0049]

[0050] Wherein, R1, R2, R3, R4, R5, R6, R7 are each independently a hydrogen atom, a cyano group, a halogen, a C1-C20 alkoxy group, a C1-C20 alkylthio group, a C1-C20 alkylamino group, a C6-C50 aryloxy group, a C6-C50 arylthio group, a C6-C50 aryl group, a C6-C50 heteroaryl group or a C6-C50 aromatic amine group.

[0051] In some embodiments, each occurrence of R1, R2, R3, R4, R5, R6, and R7 is independently methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, tert-butoxy, pentyloxy, isopentyloxy, neopentyloxy, tert-pentyloxy, hexyloxy, 2-methylpentyloxy, methylthio, ethylthio, propylthio, n-butylthio, sec-butylthio, tert-butylthio, methylamino, ethylamino, propylamino, butylamino, pentylamino, isopentylamino, neopentylamino, tert-pentylamino, hexylamino, dimethylamino, diethylamino, dipropylamino, dibutylamino, dipentylamino, diisopentylamino, dineopentylamino, ditert-pentylamino, dihexylamino.

[0052] In some embodiments, each occurrence of R1, R2, R3, R4, R5, R6, and R7 is independently o-, m-, p-methylphenylamino, o-, m-, p-ethylphenylamino, o-, m-, p-propylphenylamino, o-, m-, p-isopropylphenylamino, o-, m-, p-methoxyphenylamino, o-, m-, p-ethoxyphenylamino, o-, m-, p-propoxyphenylamino, o-, m-, p-fluorophenylamino, o-, m-, p-chlorophenylamino, o-, m-, p-bromophenylamino, o-, m-, p-iodophenylamino, bis(o-, m-, p-methylphenyl)amino, bis(o-, m-, p-ethylphenyl)amino, bis(o-, m-, p-propylphenyl)amino, bis(o-, m-, p-isopropylphenyl)amino, bis(o-, m-, p-methoxyphenyl)amino, bis(o-, m-, p-ethoxyphenyl)amino, bis(o-, m-, p-propoxyphenyl)amino, bis(o-, m-, p-fluorophenyl)amino, bis(o-, m-, p-chlorophenyl)amino, bis(o-, m-, p-bromophenyl)amino, bis(o-, m-, p-iodophenyl)amino, or triphenylamino.

[0053] In some embodiments, each occurrence of R1, R2, R3, R4, R5, R6, and R7 is independently phenoxy, phenylthio, phenyl, diphenyl, triphenyl, tetraphenyl, pyrenyl, fluorene, spirofluorene, pyridine, pyrazine, pyrimidine, triazine, or tetrazine.

[0054] In some embodiments, R1, R2, R3, R4, R5, and R6 are all hydrogen atoms, and R7 is selected from C6-C50 aromatic amine groups.

[0055] In some embodiments, the C6-C50 aromatic amine groups are selected from any one of the following groups:

[0056]

[0057]

[0058]

[0059]

[0060]

[0061] In some embodiments, the boron-nitrogen coordination bond-containing spiro structure compound of the present application can be used as an organic light-emitting material in the functional layer of an organic electroluminescent device, especially in the functional layer of an OLED device. The organic functional material can be, but is not limited to, a hole injection material (HIM), a hole transport material (HTM), an electron transport material (ETM), an electron injection material (EIM), an electron blocking material (EBM), a hole blocking material (HBM), a luminescent guest material (Gust Emitter), a luminescent host material (Host Emitter), and an organic dye.

[0062] The present application also provides a mixture comprising the above-mentioned boron-nitrogen coordination bond-containing spiro structure compound and at least one other organic functional material. It can be understood that the other organic functional material can be a small molecule organic material and a polymer material.

[0063] In some embodiments, the above-mentioned boron-nitrogen coordination bond-containing spiro structure compound or the above-mentioned mixture is used to prepare an organic electroluminescent device by a solution processing method. Among them, the above-mentioned solution processing method can be, but is not limited to, spin coating, inkjet printing, roll-to-roll, gravure printing, screen printing, etc.

[0064] The present application also relates to a composition comprising at least one of the above-mentioned boron-nitrogen coordination bond-containing spiro structure compound or mixture, and at least one organic solvent. In some embodiments, the above-mentioned organic solvent is selected from at least one of aromatic or heteroaromatic-based solvents, ester-based solvents, aromatic ketone-based solvents, aromatic ether-based solvents, aliphatic ketones, aliphatic ethers, cycloaliphatic compounds, olefinic compounds, borate compounds, and phosphate compounds.

[0065] In some embodiments, the above-mentioned composition is a solution. In still other embodiments, the above-mentioned composition is a suspension. The above-mentioned solution or the above-mentioned suspension can additionally include additives, where the above-mentioned additives are used to adjust viscosity, adjust film-forming properties, improve adhesion, etc.

[0066] In some embodiments, the above-mentioned additives can be, but are not limited to, at least one of a surface active compound, a lubricant, a wetting agent, a dispersant, a water repellent, and an adhesive.

[0067] It can be understood that the above-mentioned organic solvent can be used alone or as a mixed solvent of two or more organic solvents. The above-mentioned organic solvent can evaporate from the solvent system to form a thin film including organic compounds.

[0068] This application also relates to the use of the above-mentioned boron-nitrogen coordination bond-containing spiro structure compound, the above-mentioned mixture or the above-mentioned composition in an organic electroluminescent device.

[0069] This application also provides an organic electroluminescent device, which includes at least one functional layer, and the above-mentioned functional layer includes the above-mentioned boron-nitrogen coordination bond-containing spiro structure compound or the above-mentioned mixture, or the above-mentioned functional layer is prepared from the above-mentioned composition.

[0070] In some embodiments, the above-mentioned organic functional layer can be selected but not limited to a hole injection layer, a hole transport layer, a light-emitting layer, an electron blocking layer, an electron injection layer, an electron transport layer or a hole blocking layer. Preferably, the functional layer is a light-emitting layer, that is, the light-emitting layer contains at least one of the above-mentioned boron-nitrogen coordination bond-containing spiro structure compounds or the above-mentioned mixture, or the light-emitting layer is prepared from the above-mentioned composition.

[0071] In some embodiments, the above-mentioned light-emitting material is applied as a light-emitting layer in an organic electroluminescent device processed by a solution method. In some embodiments of the present invention, the above-mentioned light-emitting material is applied as a guest in an organic electroluminescent device processed by a solution method. In specific embodiments of the present invention, the light-emitting material is dissolved in an organic solvent, spin-coated at a certain rotation speed, and then annealed to finally prepare a uniform and smooth thin film, wherein the concentration of the light-emitting material is 5 mg / mL to 30 mg / mL, the doping concentration of the light-emitting material is 1 wt% to 30 wt%, the rotation speed of spin-coating is 500 r / min to 3000 r / min, the annealing temperature is 50 °C to 150 °C, and the annealing time is 10 min to 60 min.

[0072] In some embodiments, the above-mentioned organic electroluminescent device can be, but not limited to, an organic light-emitting diode (OLED), an organic photovoltaic cell (OPV), an organic light-emitting electrochemical cell (OLEEC), an organic field-effect transistor (OFET), an organic laser, an organic spintronic device, an organic sensor, and an organic plasmon emitting diode, etc. Particularly preferred are organic electroluminescent devices such as OLED, OLEEC, and organic light-emitting field-effect transistors. In a preferred embodiment, the above-mentioned organic electroluminescent device is an OLED.

[0073] In some embodiments, the organic electroluminescent device of the present application is a solution-type organic electroluminescent device, and one or more functional layers of the above-mentioned solution-type organic electroluminescent device are prepared by spin-coating. In specific embodiments of the present invention, the above-mentioned solution-type organic electroluminescent device is a solution-type OLED.

[0074] This application also relates to the application of the above-mentioned organic electroluminescent device in various electronic devices. Among them, the above-mentioned electronic devices can be, but are not limited to, display devices, lighting devices, light sources, sensors, etc.

[0075] The present invention combines a nitrogen-containing aromatic heterocyclic acceptor unit with a bulky boron fluorene group in a boron-nitrogen coordination manner to construct a novel vertical non-planar spiroboron acceptor unit, and combines it with a rigid acceptor unit to explore the influence of the introduction of the boron fluorene group on the luminescence properties, solubility, and solution-processed OLED device performance of nitrogen-containing aromatic heterocyclic TADF materials.

[0076] The present invention makes full use of the coordinatable characteristics of nitrogen atoms in the nitrogen-containing aromatic heterocyclic structure and introduces a rigid boron fluorene unit chelated with it, which can not only regulate the molecular geometry and charge distribution, but also effectively inhibit the intermolecular interaction and crystallinity. On the one hand, the electron-deficient characteristics of the nitrogen-containing aromatic heterocycle and the boron atom can realize the integration of their electron-withdrawing effects, reduce its LUMO energy level, and enhance the charge transfer characteristics from the donor unit to the pyrimidine π-conjugated backbone, thereby regulating the luminescence characteristics of the material and reducing its ΔE ST Moreover, the tetracoordinated configuration of its central boron atom can restrict the single-bond rotation between the pyrimidine and benzene ring substituents, enhance the rigidity of the corresponding conjugated ligand unit, inhibit the intramolecular non-radiative loss, and thus improve the PLQY of the material; on the other hand, the rigidity and orthogonal structure of the spiroboron molecule can inhibit the non-radiative energy dissipation and inhibit the intermolecular interaction resulting in loose molecular packing, making it easy for solvent molecules to enter between molecules, thereby improving the solubility of the molecule, and preparing a solution-processable small molecule TADF material with a small ΔE ST , high PLQY, and high EQE.

[0077] The ΔE of the spiro structure compound containing a boron-nitrogen coordination bond prepared by the present invention ST is 0.01 eV, and the PLQY is 96%. Applying the above spiro structure compound containing a boron-nitrogen coordination bond to an organic electroluminescent device prepared by a solution process, the organic electroluminescent device has good optoelectronic properties, its turn-on voltage is 3.4 V, the maximum current efficiency is 110.75 cd / A, and the maximum external quantum efficiency can reach 38.21%.

[0078] The following specifically illustrates this application through specific examples. The following examples are only part of the examples of this application and do not limit this application. This application is not limited to the following examples.

[0079] Example 1

[0080] Synthesize the luminescent material P1:

[0081]

[0082] (1) 2-Bromopyrimidine (0.477 g, 3.00 mmol) and (4-bromophenyl)-boronic acid (0.60 g, 3.00 mmol) were added to a two-necked flask. 20 mL of toluene solution was added and stirred until completely dissolved. Then 10 mL of aqueous Na2CO3 solution (0.32 g, 9.00 mmol) and 10 mL of absolute ethanol were added. After bubbling with Ar for 30 min, Pd(PPh3)4 (0.14 g, 0.12 mmol) was quickly added. Finally, under Ar protection, the mixture was heated at 70 °C for 12 h. After cooling to room temperature, it was extracted with dichloromethane and washed with water three times. The crude product was purified by silica gel column chromatography (eluent: petroleum ether / ethyl acetate = 7:1, V / V) to obtain 0.41 g of white solid 1 with a yield of 58%. 1 1H NMR (400 MHz, CDCl3) δ 8.71 (d, J = 4.8 Hz, 2H), 8.25 (d, J = 8.5 Hz, 2H), 7.54 (d, J = 8.5 Hz, 2H), 7.12 (dd, J = 5.8, 3.8 Hz, 1H).

[0083]

[0084] (2) The above white solid 1 (2.07 g, 8.81 mmol), i-Pr2EtN (1.25 g, 9.69 mmol) and 60 mL of absolute dichloromethane were added to a single-necked flask and purged with Ar three times. Then, at 0 °C, a 1 M solution of BBr3 in dichloromethane (26.43 mL, 26.43 mmol) was slowly added dropwise to the reaction solution. The mixture was stirred at room temperature for 24 h. Then the reaction mixture was concentrated under reduced pressure. The crude product was purified by silica gel column chromatography (eluent: petroleum ether / ethyl acetate = 2:1, V / V) to obtain 1.07 g of white solid 2 with a yield of 30%. 1 1H NMR (400 MHz, CDCl3) δ 9.07 (d, J = 4.8 Hz, 1H), 9.03 (d, J = 5.9 Hz, 1H), 7.94 (s, 1H), 7.88 (d, J = 8.1 Hz, 1H), 7.59–7.49 (m, 2H). 13 13C NMR (101 MHz, CDCl3) δ 164.34 (s), 163.00 (s), 151.37 (s), 133.78 (s), 132.57 (s), 131.08 (d, J = 18.3 Hz), 125.76 (s), 119.38 (s).

[0085]

[0086] (3) Dissolve the above-mentioned white solid 2 (1.11 g, 2.73 mmol) and 2,2'-bis(tributylstannyl)-1,1'-biphenyl (2.61 g, 3.55 mmol) in 5 mL of anhydrous dichloromethane. Replace the gas with Ar three times, and then quickly add anhydrous AlCl3 (0.11 mg, 1.09 mmol). Stir for 24 h under Ar protection, quench with water, extract with 10 mL of dichloromethane, wash with 3×10 mL of water, dry over anhydrous sodium sulfate, filter, concentrate the reaction mixture under reduced pressure, and purify the product by silica gel column chromatography (eluent: petroleum ether / dichloromethane = 1:1, V / V) to obtain 0.73 g of white solid 3 with a yield of 67%. 1 1H NMR (400 MHz, CDCl3) δ 8.94 (dd, J = 4.7, 2.1 Hz, 1H), 8.07 (d, J = 8.2 Hz, 1H), 7.96 (dd, J = 5.7, 2.1 Hz, 1H), 7.67 (d, J = 7.6 Hz, 2H), 7.51 (d, J = 1.6 Hz, 1H), 7.45 (s, 1H), 7.27–7.17 (m, 2H), 7.09 (t, J = 5.3 Hz, 1H), 6.95 (t, J = 7.2 Hz, 2H), 6.77 (d, J = 7.1 Hz, 2H). 13 13C NMR (101 MHz, CDCl3) δ 165.15, 160.54, 150.05, 149.41, 134.03, 132.58, 129.16, 128.17, 126.82, 125.73, 124.14, 118.56, 116.64.

[0087]

[0088] (4) Add the above-mentioned white solid 3 (0.65 g, 1.36 mmol), 10H-spiro[acridine-9,9'-fluorene] (SPAc) (0.57 g, 1.72 mmol), Pd(OAc)2 (0.037 g, 0.16 mmol), P(t-Bu)3HBF4 (0.047 g, 0.16 mmol), K2CO3 (0.68 g, 4.90 mmol) and 40 mL of anhydrous toluene solution to a two-necked flask. Replace the gas with Ar three times and reflux for 48 h under Ar protection. After cooling to room temperature, concentrate the filtrate under reduced pressure. Purify by silica gel column chromatography (eluent: petroleum ether / dichloromethane = 1:1, V / V) to obtain 0.60 g of pale yellow solid P1 with a yield of 53%. 11H NMR (400 MHz, CDCl3) δ 9.11 (dd, J = 4.7, 2.1 Hz, 1H), 8.64 (s, 1H), 8.12 (dd, J = 5.7, 2.0 Hz, 1H), 7.75 (d, J = 7.5 Hz, 4H), 7.56 (d, J = 8.7 Hz, 2H), 7.32 (ddd, J = 14.8, 9.8, 5.6 Hz, 6H), 7.24–7.16 (m, 3H), 7.06 (t, J = 7.2 Hz, 2H), 6.99 (d, J = 7.0 Hz, 2H), 6.87 (t, J = 7.7 Hz, 2H), 6.51 (t, J = 7.4 Hz, 2H), 6.35 (t, J = 8.1 Hz, 4H). 13 13C NMR (101 MHz, CDCl3) δ 166.16, 161.61, 156.71, 151.24, 150.60, 145.40, 141.02, 139.14, 136.35, 133.69, 130.17, 129.88, 128.42, 127.83, 127.47, 127.13, 126.86, 126.39, 125.93, 124.62, 120.50, 119.68, 117.74, 114.63, 56.75. HMS (ESI): m / z calcd for C 47 H 30 BN3 [M]+ 647.25, found 648.2611。

[0089]

[0090] By testing the light emission spectrum of the material at room temperature and the phosphorescence spectrum at low temperature, the singlet-triplet energy level difference of the luminescent material P1 in Example 1 above was calculated. The ΔE ST of the luminescent material in Example 1 is 0.01 eV. The ΔE ST of the luminescent material P1 is small, and it can achieve a good reverse intersystem crossing process.

[0091] The PLQY of the luminescent material in Example 1 is 96%.

[0092] The luminescent material in Example 1 has good solubility and is well soluble in common organic solvents such as chlorobenzene, dichloromethane, chloroform, toluene, and tetrahydrofuran.

[0093] The luminescent material in Example 1 has good thermal stability, and the thermal decomposition temperature is above 410 °C, which is beneficial to maintaining the stability of the compound when preparing optoelectronic devices.

[0094] Example 2

[0095] The luminescent material P1 in Example 1 was used to prepare an organic light-emitting device by solution processing method:

[0096] The ITO transparent conductive glass was ultrasonically treated in a cleaning agent, washed in deionized water, ultrasonically degreased in a mixed solvent of acetone:ethanol, baked in a clean environment until all moisture was removed, cleaned with ultraviolet light and ozone for 10 min, and bombarded with low-energy cations.

[0097] A layer of hole transport layer PEDOT:PSS was spin-coated on the above ITO glass.

[0098] The luminescent material P1 was dissolved in chlorobenzene solvent at a concentration of 10 mg / mL. On top of the hole transport layer, a luminescent layer with P1 as the guest, CzAcSF as the TADF sensitizer, and mCP as the host was further spin-coated (at a rotation speed of 900 r / min). The doping concentration of P1 was 1 wt% - 30 wt%, and then annealed at 60 °C for 30 min.

[0099] A layer of DPEPO was further evaporated as an exciton blocking layer; a layer of TmPyPB was evaporated as an electron transport layer; finally, a LiF layer and Al were sequentially evaporated on top of the above electron transport layer as the cathode layer of the device.

[0100] Device structure: ITO / PEDOT:PSS(40 nm) / CzAcSF:P1:mCP(30 nm) / DPEPO(9 nm) / TmPyPB(40 nm) / LiF(1.2 nm) / Al(120 nm).

[0101] The structural formulas of PEDOT:PSS, mCP, DPEPO, TmPyPB, and CzAcSF are as follows:

[0102]

[0103] The characteristics of the device such as current, voltage, brightness, and emission spectrum were tested using a PHOTORESEARCH Spectra Scan PR735 photometer and a KEITHLEY 2400 Source Meter constant current source. The performance test of the device was carried out at room temperature and ambient atmosphere. The external quantum efficiency (EQE) of the device was calculated using the Lambert distribution.

[0104] Specifically, the electroluminescence spectrum of the organic light-emitting device with a P1 doping concentration of 20% is as Figure 1 shown, and the current density-external quantum efficiency relationship and current density-voltage-brightness relationship of the organic light-emitting device are as in Figure 2 Content (a) and Figure 2As shown in content (b).

[0105] The formability of the film prepared by spin-coating the luminescent material P1 was evaluated using an atomic force microscope (AFM). As Figure 3 shown, the film prepared by spin-coating the luminescent material P1 is smooth and uniform, with a root mean square (RMS) roughness of 0.73 nm, and has excellent film-forming properties.

[0106] The device performance indicators are as follows:

[0107] Color coordinates: (X = 0.23, Y = 0.53);

[0108] Turn-on voltage: 3.4 V;

[0109] Current efficiency: 110.75 cd / A

[0110] External quantum efficiency: 38.21%.

[0111] It can be seen from the above content that the small molecule TADF material of the present invention has good solubility, high singlet-triplet energy levels, and excellent film-forming properties. The OLED prepared with the above small molecule luminescent material as the light-emitting layer exhibits excellent optoelectronic properties, with a low turn-on voltage and a high current efficiency. The turn-on voltage is 3.4 V, the maximum current efficiency is 110.75 cd / A, and the maximum external quantum efficiency can reach 38.21%. This performance can be comparable to that of traditional vacuum evaporation devices.

[0112] It is easy for those skilled in the art to understand that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention should be included within the protection scope of the present invention.

Claims

1. A spiro-structured compound containing a boron-nitrogen coordination bond, characterized in that, It has the structure shown in formula (1). Wherein, each occurrence of R1, R2, R3, R4, R5, R6, and R7 is independently a hydrogen atom, a cyano group, a halogen, a C1-C20 alkoxy group, a C1-C20 alkylthio group, a C1-C20 alkylamino group, a C6-C50 aryloxy group, a C6-C50 arylthio group, a C6-C50 aryl group, a C6-C50 heteroaryl group, or a C6-C50 aromatic amine group.

2. The boron-nitrogen coordination bond-containing spiro structure compound according to claim 1, characterized in that, Each occurrence of R1, R2, R3, R4, R5, R6, and R7 is independently methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, tert-butoxy, pentyloxy, isopentyloxy, neopentyloxy, tert-pentyloxy, hexyloxy, 2-methylpentyloxy, methylthio, ethylthio, propylthio, n-butylthio, sec-butylthio, tert-butylthio, methylamino, ethylamino, propylamino, butylamino, pentylamino, isopentylamino, neopentylamino, tert-pentylamino, hexylamino, dimethylamino, diethylamino, dipropylamino, dibutylamino, dipentylamino, diisopentylamino, dineopentylamino, ditert-pentylamino, or dihexylamino.

3. The boron-nitrogen coordination bond-containing spiro structure compound according to claim 1, characterized in that, Each occurrence of R1, R2, R3, R4, R5, R6, and R7 is independently o-, m-, p-methylphenylamino, o-, m-, p-ethylphenylamino, o-, m-, p-propylphenylamino, o-, m-, p-isopropylphenylamino, o-, m-, p-methoxyphenylamino, o-, m-, p-ethoxyphenylamino, o-, m-, p-propoxyphenylamino, o-, m-, p-fluorophenylamino, o-, m-, p-chlorophenylamino, o-, m-, p-bromophenylamino, o-, m-, p-iodophenylamino, bis(o-, m-, p-methylphenyl)amino, bis(o-, m-, p-ethylphenyl)amino, bis(o-, m-, p-propylphenyl)amino, bis(o-, m-, p-isopropylphenyl)amino, bis(o-, m-, p-methoxyphenyl)amino, bis(o-, m-, p-ethoxyphenyl)amino, bis(o-, m-, p-propoxyphenyl)amino, bis(o-, m-, p-fluorophenyl)amino, bis(o-, m-, p-chlorophenyl)amino, bis(o-, m-, p-bromophenyl)amino, bis(o-, m-, p-iodophenyl)amino, or triphenylamino.

4. The boron-nitrogen coordinated bond-containing spiral structure compound according to claim 1, wherein Each occurrence of R1, R2, R3, R4, R5, R6, and R7 is independently phenoxy, phenylthio, phenyl, diphenyl, triphenyl, tetraphenyl, pyrenyl, fluorene, spirofluorene, pyridine, pyrazine, pyrimidine, triazine, or tetrazine.

5. The boron-nitrogen coordinated bond-containing spiral structure compound according to claim 1, characterized in that, R, R1, R2, R3, R4, R5, and R6 are hydrogen atoms, and R7 is selected from C6-C50 aromatic amine groups.

6. The boron-nitrogen coordination bond-containing spiral structure compound according to claim 5, characterized in that, The C6-C50 aromatic amine groups are selected from any one of the following groups: 。 7. A mixture, characterized in that, The mixture includes a boron-nitrogen coordination bond-containing spiro-structured compound as described in any one of claims 1 to 6 and at least one organic functional material, and the organic functional material is selected from a hole injection material, a hole transport material, an electron transport material, an electron injection material, an electron blocking material, a hole blocking material, a light-emitting guest material, a light-emitting host material, or an organic dye.

8. Use of the spiro-structured compound containing a boron-nitrogen coordination bond according to any one of claims 1 to 6 or the mixture according to claim 7, characterized in that, It is applied to an organic electroluminescent device prepared by a solution processing method.

9. A composition, characterized in that, The composition includes a boron-nitrogen coordination bond-containing spiro-structured compound as described in any one of claims 1 to 6 or the mixture as described in claim 7, and at least one organic solvent.

10. An organic electroluminescent device, characterized in that, It includes at least one functional layer, and the functional layer includes a boron-nitrogen coordination bond-containing spiro-structured compound as described in any one of claims 1 to 6 or the mixture as described in claim 7, or the functional layer is prepared from the composition as described in claim 9.

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