A boron-nitrogen heterocyclic compound, a preparation method thereof, and an organic electroluminescent device

Abstract

The present invention discloses a boron-nitrogen hetero-compound, a preparation method thereof, and an organic electroluminescent device. The molecular structural formula of the boron-nitrogen hetero-compound is provided by the present invention. The boron-nitrogen hetero-organic compound is obtained by modifying the periphery of a boron-nitrogen hetero-fused ring skeleton with multiple resonance effects with an electron-withdrawing group. On the one hand, connecting the electron-withdrawing group to the periphery of the boron-nitrogen hetero-fused ring skeleton can adjust the energy level of the material and provide adjustable light color. On the other hand, introducing heavy atoms on the peripheral electron-withdrawing group can improve the reverse intersystem crossing rate while ensuring the narrow-band emission of the multiple resonance skeleton. The organic electroluminescent device prepared with the boron-nitrogen hetero-compound has the advantages of narrow-band emission, high color purity, high efficiency, low roll-off, and long lifespan at the same time.

Description

Technical Field

[0001] The present invention relates to the field of thermally activated delayed fluorescence materials, and particularly to a boron-nitrogen heterocyclic compound, a preparation method thereof, and an organic electroluminescent device. Background Art

[0002] Organic electroluminescent diodes (OLEDs) have been widely used due to their advantages such as low cost, low power consumption, high contrast ratio, and flexible wide viewing angle. Since Adachi et al. reported highly efficient electroluminescent devices based on pure organic thermally activated delayed fluorescence (TADF) compounds in 2012, such materials have been widely studied. Due to their theoretically up to 100% exciton utilization efficiency, organic electroluminescent devices using such materials as the light-emitting layer have reached device efficiencies similar to those of phosphorescent materials.

[0003] Traditional D-A type TADF materials have a relatively broad spectrum (full width at half maximum greater than 70 nm) due to large structural relaxation, and the corresponding OLED devices have low color purity, which cannot meet the requirements of high color purity display. In 2016, Hatakeyama et al. reported a new type of TADF material based on a boron / nitrogen multiple resonance structure. Such materials have characteristics such as high quantum yield and narrow emission spectrum. Electroluminescent devices prepared using such materials as the light-emitting layer have both high efficiency and high color purity.

[0004] However, the currently reported multiple resonance type TADF materials often have a long delayed fluorescence lifetime, which is caused by a small reverse intersystem crossing rate from the triplet state to the singlet state. This makes the exciton utilization efficiency of electroluminescent devices based on such materials seriously decline at high brightness, with very serious efficiency roll-off. Recent studies have shown that embedding heavy atoms into the boron-nitrogen heterocyclic multiple resonance framework can enhance the coupling between the singlet and triplet states, promote the reverse intersystem crossing process, and thus reduce the efficiency roll-off of its OLED devices. However, this method generally has the problem of increasing the full width at half maximum of the luminescent material, which is not conducive to high color purity display.

[0005] Therefore, the prior art still needs to be improved and developed. Summary of the Invention

[0006] In view of the above deficiencies of the prior art, the purpose of the present invention is to provide a boron-nitrogen heterocyclic compound, a preparation method thereof, and an organic electroluminescent device, aiming to solve the problem of serious efficiency roll-off of multiple resonance type thermally activated delayed fluorescence materials in the prior art.

[0007] The technical solutions adopted by the present invention to solve the above technical problems are as follows:

[0008] In a first aspect, the present invention discloses a boron-nitrogen heterocyclic compound, whose molecular structure is shown in the following formula:

[0009]

[0010] Among them, X 1 and X 2 are independently selected from one of hydrogen, deuterium, halogen, sulfone group, substituted or unsubstituted C 1 -C 10 alkyl, substituted or unsubstituted C 1 -C 10 alkoxy, substituted or unsubstituted C 6 -C 60 aryl, substituted or unsubstituted C 3 -C 60 heteroaryl, or substituted or unsubstituted diarylamino; R 1 -R 23 are independently selected from one of hydrogen, deuterium, halogen, sulfone group, substituted or unsubstituted C 1 -C 10 alkyl, substituted or unsubstituted C 1 -C 10 alkoxy, substituted or unsubstituted C 6 -C 60 aryl, substituted or unsubstituted C 3 -C 60 heteroaryl, substituted or unsubstituted diarylamino, substituted or unsubstituted diheteroarylamino, or substituted or unsubstituted arylheteroarylamino; Y 1 is selected from one of O, S, Se, Te, C(R 24 )(R 25 ), Si(R 26 )(R 27 ), Ge(R 28 )(R 29 ), Sn(R 30 )(R 31 ), carbonyl, sulfoxide, sulfone, selenoxide, or selenone; R 24 -R 31 are independently selected from alkyl or aryl; Y 2 is selected from one of carbonyl, sulfoxide, sulfone, selenoxide, or selenone.

[0011] In a second aspect, the present invention discloses a method for preparing a boron-nitrogen heterocompound, which includes the steps of: mixing a first reactant with a second reactant or a third reactant, and reacting to obtain a first product;

[0012] mixing the first product with butyllithium, adding boron tribromide for reaction, and then adding N,N-diisopropylethylamine for reaction to obtain a second product;

[0013] mixing the second product with a catalyst and bis(pinacolato)diboron for reaction to obtain a third product;

[0014] Mix the third product with a fourth reactant, and react to obtain the boron-nitrogen heterocyclic compound;

[0015] Among them, the structural formula of the first reactant is: The structural formula of the second reactant is: The structural formula of the third reactant is: The structural formula of the first product is: The structural formula of the second product is: The structural formula of the third product is: The structural formula of the fourth reactant is:

[0016] In a third aspect, the present invention discloses an organic electroluminescent device, including a light-emitting layer, characterized in that the light-emitting layer is obtained by co-doping a host material and a guest material, wherein the structural formula of the host material is: The guest material is the boron-nitrogen heterocyclic compound of the present invention.

[0017] Beneficial effects: The present invention discloses a boron-nitrogen heterocyclic compound, its preparation method, and an organic electroluminescent device. An electron-withdrawing group is introduced at the para-position of the boron atom in the boron-nitrogen heterocyclic compound. On the one hand, it changes the HOMO and LUMO energy level gaps of the material to adjust the light color. On the other hand, heavy atoms are introduced into the electron-withdrawing group. While ensuring the narrow-band emission characteristics of the material, through the heavy atom effect, the orbital coupling between the triplet state and the singlet state in the excited state of the compound is enhanced, promoting the reverse intersystem crossing process, accelerating the conversion of triplet excitons to singlet excitons, and thus obtaining a smaller delay lifetime and higher exciton utilization rate. The device based on it as a light-emitting material not only takes into account the advantages of traditional multi-resonant TADF materials, but also has extremely high external quantum efficiency at high brightness, effectively improving the serious problem of efficiency roll-off of traditional multi-resonant TADF materials. Moreover, the boron-nitrogen heterocyclic compound provided in the present invention has a nearly 100% photoluminescence quantum yield and narrow-band emission. The device prepared based on it as a light-emitting material has the advantages of high efficiency, high brightness, high color purity, and low roll-off. Description of the Drawings

[0018] Figure 1 It is a structural diagram of the organic electroluminescent device provided by the present invention.

[0019] Figure 2 It is an emission wavelength diagram of Application Examples 1 and 3 of the present invention.

[0020] Figure 3 It is an emission wavelength diagram of Application Example 9 of the present invention.

[0021] Figure 4This is the external quantum efficiency graph of Application Examples 3 and 9 of the present invention.

[0022] Figure 5 This is the external quantum efficiency graph of Application Examples 1 and 3 of the present invention. Detailed implementation manners

[0023] The present invention provides a boron-nitrogen hetero compound, a preparation method thereof, and an organic electroluminescent device. To make the objectives, technical solutions, and effects of the present invention clearer and more definite, the present invention is further described in detail below. 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.

[0024] The present invention provides a boron-nitrogen hetero compound, and the general formula of its molecular structure is as follows:

[0025]

[0026] Among them, X 1 , X 2 are independently selected from one of hydrogen, deuterium, halogen, sulfone group, substituted or unsubstituted C 1 -C 10 alkyl, substituted or unsubstituted C 1 -C 10 alkoxy, substituted or unsubstituted C 6 -C 60 aryl, substituted or unsubstituted C 3 -C 60 heteroaryl, substituted or unsubstituted diarylamino; R 1 -R 23 are independently selected from one of hydrogen, deuterium, halogen, sulfone group, substituted or unsubstituted C 1 -C 10 alkyl, substituted or unsubstituted C 1 -C 10 alkoxy, substituted or unsubstituted C 6 -C 60 aryl, substituted or unsubstituted C 3 -C 60 heteroaryl, substituted or unsubstituted diarylamino, substituted or unsubstituted diheteroarylamino, substituted or unsubstituted arylheteroarylamino; Y 1 is selected from O, S, Se, Te, C(R 24 )(R 25 ), Si(R 26 )(R 27 ), Ge(R 28 )(R 29 ), Sn(R 30 )(R 31), carbonyl, sulfoxide, sulfone, selenoxide, selenone; R 24 -R 31 is independently selected from alkyl or aryl; Y 2 is selected from one of carbonyl, sulfoxide, sulfone, selenoxide, selenone.

[0027] The present invention provides a boron-nitrogen heterocyclic compound, which is a multi-resonance type thermally activated delayed fluorescence material. In the boron-nitrogen heterocyclic compound of the present invention, an electron-withdrawing group is introduced at the para-position of the boron atom. On the one hand, the HOMO and LUMO energy level gaps of the material are changed to adjust the light color. On the other hand, heavy atoms are introduced into the electron-withdrawing group. While ensuring the narrow-band emission characteristics of the material, the orbital coupling between the triplet state and the singlet state in the excited state of the compound is enhanced through the heavy atom effect, promoting the reverse intersystem crossing process, accelerating the conversion of triplet excitons to singlet excitons, and thus obtaining a smaller delay lifetime and higher exciton utilization rate. The device based on it as a luminescent material not only takes into account the advantages of traditional multi-resonance type TADF materials, but also has extremely high external quantum efficiency even at high brightness, effectively improving the serious problem of efficiency roll-off of traditional multi-resonance type TADF materials. Moreover, the boron-nitrogen heterocyclic compound provided in the present invention has a nearly 100% photoluminescence quantum yield and narrow-band emission. The device prepared based on it as a luminescent material has the advantages of high efficiency, high brightness, high color purity and low roll-off.

[0028] Optionally, the substituted C 1 -C 10 alkyl, substituted C 1 -C 10 alkoxy, substituted C 6 -C 60 aryl, substituted C 3 -C 60 heteroaryl, substituted diarylamino, substituted diheteroarylamino, substituted arylheteroarylamino contains 1-10 substituents, and the substituents are selected from deuterium, halogen, nitro, C 1 -C 4 alkyl, C 1 -C 4 alkoxy, C 6 -C 12 aryl, C 6 -C 12 aryloxy, C 6 -C 12 arylamino, C 3 -C 12 heteroaryl and C 3 -C 12 heteroarylamino.

[0029] Optionally, the heteroatom in the heteroaryl may be one or more of O, S, N, Se, Te, Ge, and Sn.

[0030] Optionally, the C 1 -C 10 alkyl groups include but are not limited to methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, 2-methylbutyl, n-pentyl, sec-pentyl, cyclopentyl, neopentyl, n-hexyl, cyclohexyl, neohexyl, n-heptyl, cycloheptyl, n-octyl, cyclooctyl, 2-ethylhexyl, trifluoromethyl, pentafluoroethyl, 2,2,2-trifluoroethyl, and adamantyl; the C 1 -C 4 alkyl group is an alkyl group having 1 to 4 carbon atoms among the above alkyl groups.

[0031] Optionally, the aryl or C 6 -C 60 aryl groups include but are not limited to phenyl, naphthyl, anthracenyl, benzanthracenyl, phenanthryl, benzophenanthryl, pyrenyl, chrysenyl, perylenyl, tetracenyl, pentacenyl, benzopyrenyl, biphenyl, terphenyl, triphenyl, tetraphenyl, fluorene, spirobifluorene, dihydrophenanthryl, dihydropyrenyl, tetrahydropyrenyl, cis- or trans-indeno[1,2-b]fluorene, truxene, isotruxene, spirotruxene, and spiroisotruxene; the C 6 -C 12 aryl group is an aryl group having 6 to 12 carbon atoms among the above aryl groups.

[0032] Optionally, the C 3 -C 60The heteroaryl groups include, but are not limited to, furyl, benzofuryl, isobenzofuryl, dibenzofuryl, thienyl, benzothienyl, isobenzothienyl, dibenzothienyl, pyrrolyl, isoindolyl, carbazolyl, indolocarbazolyl, pyridyl, quinolinyl, isoquinolinyl, acridinyl, phenanthridinyl, benzo-5,6-quinolyl, benzo-6,7-quinolyl, benzo-7,8-quinolyl, pyrazolyl, indazolyl, imidazolyl, benzimidazolyl, naphthimidazolyl, phenanthrimidazolyl, pyridinimidazolyl, pyrazinimidazolyl, quinoxalinimidazolyl, anthrazolyl, benzanthrazolyl, naphthanthrazolyl, anthrancanthrazolyl, phenanthrancanthrazolyl, 1,2-thiazolyl, 1,3-thiazolyl, benzothiazolyl, pyridazinyl, benzopyridazinyl, pyrimidinyl, benzopyrimidinyl, quinoxalinyl, 1,5-diazaanthracenyl, 2,7-diazapyrenyl, 2,3-diazapyrenyl, 1,6-diazapyrenyl, 1,8-diazapyrenyl, 4,5-diazapyrenyl, 4,5,9,10-tetraazaperopyrenyl, pyrazinyl, phenazinyl, naphthyridinyl, azacarbazolyl, benzocarbazolyl, phenanthroline, 1,2,3-triazolyl, 1,2,4-triazolyl, benzotriazolyl, 1,2,3-oxadiazolyl, 1,2,4-oxadiazolyl, 1,2,5-oxadiazolyl, 1,2,3-thiadiazolyl, 1,2,4-thiadiazolyl, 1,2,5-thiadiazolyl, 1,3,4-thiadiazolyl, 1,3,5-triazinyl, 1,2,4-triazinyl, 1,2,3-triazinyl, tetrazolyl, 1,2,4,5-tetrazinyl, 1,2,3,4-tetrazinyl, 1,2,3,5-tetrazinyl, purinyl, pteridinyl, indolizinyl, benzothiadiazolyl, 9,9-dimethylacridinyl, triarylamine, fluorophenyl, methylphenyl, trimethylphenyl, pyrrolidine, piperidine, methoxy, silyl, phenothiazinyl, phenoxazinyl, phenol, naphthol, and thiophenol; C 3 -C 12 The heteroaryl group of -C is a heteroaryl group having 3 to 12 carbon atoms among the above heteroaryl groups.

[0033] Optionally, the boron-nitrogen heterocompound has the structure shown below:

[0034]

[0035]

[0036]

[0037]

[0038]

[0039] The present invention also provides a method for preparing a boron-nitrogen heterocompound, which includes the steps:

[0040] S1. Mix the first reactant (compound a) with the second reactant (compound b) or the third reactant (compound c), and react to obtain the first product (compound d);

[0041] S2. Mix the first product (compound d) with butyllithium, add boron tribromide to react, and then add N,N - diisopropylethylamine to react to obtain the second product (compound e);

[0042] S3. Mix the second product (compound e) with a catalyst and bis(pinacolato)diboron, and react to obtain the third product (compound f);

[0043] S4. Mix the third product (compound f) with the fourth reactant (compound g), and react to obtain the boron - nitrogen heterocyclic compound.

[0044] In this embodiment, the catalyst is methoxy(cycloocta - 1,5 - diene)iridium dimer.

[0045] The synthetic route of the boron - nitrogen heterocyclic compound is as follows:

[0046]

[0047] In some embodiments, in step S1, the synthesis steps of compound d:

[0048] Heat and stir the N,N - dimethylformamide mixture of compound a, compound b, compound c and cesium carbonate, and after reaction, cool, extract, distill, and then subject the residue to column chromatography separation to obtain compound d.

[0049] In some embodiments, the heating temperature is 140 - 160 °C and the stirring time is 12 - 24 hours.

[0050] In some embodiments, in step S2, the steps of compound e include:

[0051] Mix compound d with butyllithium, perform a lithium - halogen exchange reaction on the halogen atom using butyllithium, then, add boron tribromide to perform a lithium - boron exchange reaction, and then add N,N - diisopropylethylamine, thereby performing a bora - Friedel - Crafts reaction to obtain compound e.

[0052] Specifically, dissolve the compound d described in step S1 in ultra - dry xylene, successively add tert - butyllithium, boron tribromide, and N,N - diisopropylethylamine to react, and after reaction, subject the residue to column chromatography separation to obtain the compound containing e.

[0053] In some embodiments, in step S3, the synthesis steps of compound f are as follows:

[0054] A tetrahydrofuran mixture of compound e, bis(pinacolato)diboron, 4,4'-di-tert-butyl-2,2'-bipyridine, and iridium(III) dimethoxy(1,5-cyclooctadiene) dimer was heated under reflux for 24 hours, cooled, distilled, and the residue was separated by column chromatography to obtain the compound f.

[0055] In some embodiments, in step S4, the synthesis step of the boron-nitrogen heterocyclic compound is as follows:

[0056] The compound f and compound g were subjected to a Suzuki cross coupling reaction to obtain the boron-nitrogen heterocyclic compound.

[0057] Specifically, a toluene / ethanol / water mixed solution of compound f, compound g, potassium carbonate, and tetrakis(triphenylphosphine)palladium was heated and stirred. After the reaction, it was cooled, extracted, distilled, and the residue was separated by column chromatography to obtain the boron-nitrogen heterocyclic compound.

[0058] In some embodiments, the reaction heating temperature is 70 - 100 °C, and the stirring time is 12 - 24 hours.

[0059] The present invention also provides an organic electroluminescent device. Refer to Figure 1 , the organic electroluminescent device includes a light-emitting layer (6), and the light-emitting layer (6) is obtained by co-doping a host material and a guest material; wherein, the guest material is one or more of the above-mentioned boron-nitrogen heterocyclic compounds, and the doping amount of the guest material accounts for 0.5 - 5 wt% of the total mass of the host material and the guest material. Further preferably, the doping ratio of the guest material can be 1 wt%, 3 wt%, and 5 wt%.

[0060] In some embodiments, refer to Figure 1 , the organic electroluminescent device includes an anode layer (2), a hole injection layer (3), a hole transport layer (4), an electron blocking layer (5), a light-emitting layer (6), a hole blocking layer (7), an electron transport layer (8), an electron injection layer (9), and a cathode layer (10) which are sequentially arranged on a substrate (1) from bottom to top.

[0061] Preferably, in some embodiments, the material of the anode layer (2) is ITO; the thickness of the hole injection layer (3) is 5 - 30 nm; the thickness of the hole transport layer (4) is 5 - 500 nm; the thickness of the light-emitting layer (6) is 1 - 200 nm; the thickness of the electron transport layer (8) is 5 - 300 nm; the material of the cathode layer (10) is metallic aluminum. In this embodiment, by applying a DC voltage with the ITO electrode and the aluminum electrode as the anode and the cathode respectively, the brightness, electroluminescence spectrum, full width at half maximum, and efficiencies such as energy, current, and external quantum of the device can be measured. The time when the brightness decays to half during continuous operation of the device at a certain brightness can be measured and calculated, and it is used to evaluate the device lifetime.

[0062] Preferably, in some embodiments, the structure of the organic electroluminescent device is ITO / HI(30 nm) / HT(15 nm) / EBL(10 nm) / EML(50 nm) / HBL(20 nm) / ET(30 nm) / EI(2 nm) / Al(100 nm). Specifically, ITO is the anode material, HI is the hole injection layer material, HT is the hole transport layer material, ET is the electron transport layer material, EI is the electron injection layer, and Al is the cathode material. Further, the molecular structures of HI, HT, EBL, HBL, ET, and EI are as follows:

[0063]

[0064] In some embodiments, the preparation method of the organic electroluminescent device includes the steps:

[0065] S10. Use a glass substrate with a certain thickness of ITO deposited by evaporation as the transparent support substrate;

[0066] S20. Sequentially deposit a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer, and an aluminum film on the transparent support substrate.

[0067] Specifically, the organic electroluminescent device is prepared by vacuum evaporation. Use a glass substrate with a certain thickness of ITO deposited by evaporation as the transparent support substrate; fix the transparent support substrate on the substrate holder of the evaporation device, and install molybdenum evaporation boats containing the electroplating materials and the light-emitting material for each layer respectively; install tungsten evaporation boats containing lithium 8-hydroxyquinoline and aluminum respectively; sequentially deposit a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer, and an aluminum film on the ITO film of the transparent support substrate.

[0068] In some embodiments, the ratio of the host material, sensitizing material, and light-emitting material in the light-emitting layer can be adjusted to reach the expected doping ratio by the evaporation rate.

[0069] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments, and are only used to illustrate the present invention and in no way limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0070] Example 1

[0071] This example provides a boron-nitrogen heterocyclic compound 1, and its synthesis route is as follows:

[0072]

[0073] The preparation method of compound 1 specifically includes the following steps:

[0074] (1) Synthesis of intermediate m3

[0075] Under argon protection, a mixed solution of compound m1 (2.06 g, 10.7 mmol), compound m2 (6.13 g, 21.9 mmol) and cesium carbonate (10.4 g, 31.9 mmol) in N,N-dimethylformamide (50 mL) was heated and stirred at 150 °C for 24 hours. After the reaction system was cooled to room temperature, dichloromethane was added for extraction, the organic layer was collected, dried, and distilled under reduced pressure. The residue was separated by column chromatography to obtain intermediate m3 (5.10 g, 67%); m / z 710.52 [M + .

[0076] (2) Synthesis of intermediate m4

[0077] The above-prepared intermediate m3 (4.50 g, 6.32 mmol) was dissolved in 60 mL of ultra-dry xylene, cooled to -40 °C, and n-butyllithium (3.20 mL, 2.4 M, 7.59 mmol) was slowly added to the above solution. The mixture was allowed to warm to room temperature naturally and stirred for 2 hours. Then it was cooled to 0 °C, and boron tribromide (0.78 mL, 8.21 mmol) was added dropwise, and the reaction was carried out at room temperature for 1 hour. Then it was cooled to 0 °C again, and N,N-diisopropylethylamine (1.36 mL, 8.22 mmol) was slowly added to the reaction system, and then the temperature was raised to 120 °C and stirred for 20 hours. The heating was stopped, and after the system was cooled to room temperature, the organic solvent and volatile substances were evaporated to dryness. The residue was separated by column chromatography to obtain intermediate m4 (2.8 g, 69%); m / z 640.45 [M + .

[0078] (3) Synthesis of intermediate m5

[0079] Under argon protection, a mixed solution of compound m4 (2.05 g, 3.20 mmol), 4,4'-di-tert-butyl-2,2'-bipyridine (0.0258 g, 0.096 mmol), methoxy(cyclooctadiene)iridium dimer (0.0424 g, 0.064 mmol) and bis(pinacolato)diboron (0.975 g, 3.84 mmol) in tetrahydrofuran was heated under reflux for 24 hours, cooled, distilled, and the residue was separated by column chromatography to obtain intermediate m5 (1.65 g, 67%); m / z 766.74 [M + .

[0080] (4) Synthesis of target compound 1

[0081] A mixed solution of compound m5 (0.400 g, 0.521 mmol), compound m6 (0.176 g, 0.521 mmol), potassium carbonate (0.361 g, 2.61 mmol) and palladium tetrakis(triphenylphosphine) (0.030 g, 0.0261 mmol) in toluene / ethanol / water was heated to 120 °C and stirred for 20 hours. Heating was stopped, and after the system cooled to room temperature, extraction and distillation were carried out, and the residue was separated by column chromatography to obtain target product 1 (0.310 g, 66%). 1 H NMR (500 MHz, Chloroform-d) δ 9.15 (d, J = 1.8 Hz, 2H), 8.91 (d, J = 8.2 Hz, 1H), 8.74 (d, J = 8.0 Hz, 1H), 8.56 (s, 2H), 8.50 (d, J = 1.8 Hz, 2H), 8.44 (d, J = 8.9 Hz, 2H), 8.29 (d, J = 2.1 Hz, 2H), 8.14 (s, 1H), 8.04 (d, J = 8.3 Hz, 1H), 7.75–7.69 (m, 3H), 7.61 (t, J = 6.8 Hz, 1H), 7.54 (t, J = 7.4 Hz, 1H), 1.69 (s, 18H), 1.54 (s, 18H). HRMS (ESI) m / z: 899.3699 [M+H] + .

[0082] Example 2

[0083] This example provides a boron-nitrogen heterocyclic compound 5, and its synthesis route is as follows:

[0084]

[0085] The preparation method of compound 5 specifically includes the following steps:

[0086] (1) Synthesis of intermediate m3

[0087] Under argon protection, a mixed solution of compound m1 (2.06 g, 10.7 mmol), compound m7 (6.17 g, 21.9 mmol) and cesium carbonate (10.4 g, 31.9 mmol) in N,N-dimethylformamide (50 mL) was heated and stirred at 150 °C for 24 hours. After the reaction system was cooled to room temperature, dichloromethane was added for extraction, and the organic layer was collected, dried and distilled under reduced pressure. The residue was separated by column chromatography to obtain intermediate m8 (5.04 g, 66%); m / z 714.52 [M + .

[0088] (2) Synthesis of intermediate m9

[0089] The above-prepared intermediate m8 (4.52 g, 6.32 mmol) was dissolved in 60 mL of ultra-dry xylene, and the temperature was lowered to -40 °C. n-Butyllithium (3.20 mL, 2.4 M, 7.59 mmol) was slowly added to the above solution, and the temperature was naturally raised to room temperature and stirred for 2 hours. Then the temperature was lowered to 0 °C, and boron tribromide (0.78 mL, 8.21 mmol) was added dropwise and reacted at room temperature for 1 hour. Then the temperature was lowered to 0 °C again, and N,N-diisopropylethylamine (1.36 mL, 8.22 mmol) was slowly added to the reaction system, and then the temperature was raised to 120 °C and stirred for 20 hours. The heating was stopped, and after the system was cooled to room temperature, the organic solvent and volatile substances were rotary evaporated. The residue was separated by column chromatography to obtain intermediate m9 (1.67 g, 41%); m / z 644.63 [M + .

[0090] (5) Synthesis of intermediate m10

[0091] Under argon protection, a mixed solution of compound m9 (2.06 g, 3.20 mmol), 4,4'-di-tert-butyl-2,2'-bipyridine (0.0258 g, 0.096 mmol), methoxy(cyclooctadiene)iridium dimer (0.0424 g, 0.064 mmol) and bis(pinacolato)diboron (0.975 g, 3.84 mmol) in tetrahydrofuran was heated under reflux for 24 hours, cooled and distilled. The residue was separated by column chromatography to obtain intermediate m10 (1.65 g, 67%); m / z 771.52 [M + .

[0092] (6) Synthesis of target compound 5

[0093] A mixed solution of compound m10 (0.401 g, 0.521 mmol), compound m6 (0.176 g, 0.521 mmol), potassium carbonate (0.361 g, 2.61 mmol) and tetrakis(triphenylphosphine)palladium (0.030 g, 0.0261 mmol) in toluene / ethanol / water was heated to 120 °C and stirred for 20 hours. The heating was stopped, and after the system cooled to room temperature, extraction and distillation were carried out. The residue was then separated by column chromatography to obtain the target product 5 (0.357 g, 76%). 1 H NMR (500 MHz, Chloroform-d) δ 9.15 (d, J = 1.8 Hz, 2H), 8.91 (d, J = 8.2 Hz, 2H), 8.74 (d, J = 8.0 Hz, 2H), 8.44 (d, J = 8.9 Hz, 1H), 8.29 (d, J = 2.1 Hz, 4H), 8.09 (d, J = 8.8 Hz, 1H), 8.04 (d, J = 8.3 Hz, 4H), 7.75–7.69 (m, 3H), 7.61 (t, J = 6.8 Hz, 1H), 7.54 (t, J = 7.4 Hz, 1H), 1.65 (s, 18H), 1.54 (s, 18H). HRMS (ESI) m / z: 902.3889 [M+H] + 。

[0094] Example 3

[0095] This example provides a boron-nitrogen heterocyclic compound 9, and its synthetic route is as follows:

[0096]

[0097] The preparation method of compound 9 specifically includes the following steps:

[0098] (1) Synthesis of intermediate m12

[0099] Under argon protection, a mixed solution of compound m1 (2.06 g, 10.7 mmol), compound m11 (6.13 g, 21.9 mmol) and cesium carbonate (10.4 g, 31.9 mmol) in N,N-dimethylformamide (50 mL) was heated and stirred at 150 °C for 24 hours. After the reaction system cooled to room temperature, dichloromethane was added for extraction, and the organic layer was collected, dried, and distilled under reduced pressure. The residue was separated by column chromatography to obtain intermediate m12 (5.52 g, 61%); m / z 794.37 [M + .

[0100] (2) Synthesis of intermediate m13

[0101] The intermediate product m12 (5.00 g, 6.32 mmol) prepared above was dissolved in 60 mL of ultra-dry xylene, and the temperature was lowered to -40 °C. n-Butyllithium (3.20 mL, 2.4 M, 7.59 mmol) was slowly added to the above solution, and the temperature was naturally raised to room temperature and stirred for 2 hours. Then the temperature was lowered to 0 °C, and boron tribromide (0.78 mL, 8.21 mmol) was added dropwise, and the reaction was carried out at room temperature for 1 hour. Then the temperature was lowered to 0 °C again, and N,N-diisopropylethylamine (1.36 mL, 8.22 mmol) was slowly added to the reaction system, and then the temperature was raised to 120 °C and stirred for 20 hours. The heating was stopped, and after the system was cooled to room temperature, the organic solvent and volatile substances were rotary evaporated. The residue was separated by column chromatography to obtain intermediate m13 (2.70 g, 59%); m / z 724.42 [M + .

[0102] (7) Synthesis of intermediate m14

[0103] Under argon protection, a mixed solution of compound m13 (2.32 g, 3.20 mmol), 4,4'-di-tert-butyl-2,2'-bipyridine (0.0258 g, 0.096 mmol), methoxy(cyclooctadiene)iridium dimer (0.0424 g, 0.064 mmol) and bis(pinacolato)diboron (0.975 g, 3.84 mmol) in tetrahydrofuran was heated under reflux for 24 hours, cooled, distilled, and the residue was separated by column chromatography to obtain intermediate m14 (1.55 g, 57%); m / z 850.51 [M + .

[0104] (8) Synthesis of target compound 9

[0105] A mixed solution of compound m14 (0.400 g, 0.521 mmol), compound m6 (0.202 g, 0.521 mmol), potassium carbonate (0.361 g, 2.61 mmol) and palladium tetrakis(triphenylphosphine) (0.030 g, 0.0261 mmol) in toluene / ethanol / water was heated to 120 °C and stirred for 20 hours. The heating was stopped, and after the system was cooled to room temperature, it was extracted and distilled, and the residue was separated by column chromatography to obtain the target product 9 (0.303 g, 61%). 11H NMR (500 MHz, Chloroform-d) δ 9.14 (d, J = 1.8 Hz, 2H), 8.90 (d, J = 8.2 Hz, 1H), 8.76 (d, J = 8.0 Hz, 1H), 8.57 (s, 2H), 8.52 (d, J = 1.8 Hz, 2H), 8.42 (d, J = 8.9 Hz, 2H), 8.27 (d, J = 2.1 Hz, 2H), 8.14 (s, 1H), 8.04 (d, J = 8.3 Hz, 1H), 7.74–7.69 (m, 3H), 7.64 (t, J = 6.8 Hz, 1H), 7.54 (t, J = 7.4 Hz, 1H), 1.68 (s, 18H), 1.58 (s, 12H), 1.54 (s, 18H). HRMS (ESI) m / z: 982.4515 [M+H] + 。

[0106] Example 4

[0107] This example provides a boron-nitrogen heterocyclic compound 11, and its synthesis route is as follows:

[0108]

[0109] The preparation method of compound 11 specifically includes the following steps:

[0110] (1) Synthesis of intermediate m3

[0111] Under argon protection, a mixed solution of compound m1 (2.06 g, 10.7 mmol), compound m2 (6.13 g, 21.9 mmol) and cesium carbonate (10.4 g, 31.9 mmol) in N,N-dimethylformamide (50 mL) was heated and stirred at 150 °C for 24 hours. After the reaction system was cooled to room temperature, dichloromethane was added for extraction, and the organic layer was collected, dried, and distilled under reduced pressure. The residue was separated by column chromatography to obtain intermediate m3 (5.10 g, 67%); m / z 710.52 [M + .

[0112] (2) Synthesis of intermediate m4

[0113] The intermediate product m3 (4.50 g, 6.32 mmol) prepared above was dissolved in 60 mL of ultradry xylene, and the temperature was lowered to -40 °C. n-Butyllithium (3.20 mL, 2.4 M, 7.59 mmol) was slowly added to the above solution, and the temperature was naturally raised to room temperature. The mixture was stirred for 2 hours, then cooled to 0 °C, and boron tribromide (0.78 mL, 8.21 mmol) was added dropwise. The reaction was carried out at room temperature for 1 hour, then cooled to 0 °C again. N,N-Diisopropylethylamine (1.36 mL, 8.22 mmol) was slowly added to the reaction system, and then the temperature was raised to 120 °C and stirred for 20 hours. Heating was stopped, and after the system cooled to room temperature, the organic solvent and volatile substances were evaporated. The residue was separated by column chromatography to obtain intermediate m4 (2.8 g, 69%); m / z 640.45 [M + .

[0114] (9) Synthesis of intermediate m5

[0115] Under argon protection, a mixed solution of compound m4 (2.05 g, 3.20 mmol), 4,4'-di-tert-butyl-2,2'-bipyridine (0.0258 g, 0.096 mmol), methoxy(cyclooctadiene)iridium dimer (0.0424 g, 0.064 mmol) and bis(pinacolato)diboron (0.975 g, 3.84 mmol) in tetrahydrofuran was heated under reflux for 24 hours, cooled, and distilled. The residue was separated by column chromatography to obtain intermediate m5 (1.65 g, 67%); m / z 766.74 [M + .

[0116] (10) Synthesis of target compound 11

[0117] A mixed solution of compound m5 (0.400 g, 0.521 mmol), compound m15 (0.202 g, 0.521 mmol), potassium carbonate (0.361 g, 2.61 mmol) and tetrakis(triphenylphosphine)palladium (0.030 g, 0.0261 mmol) in toluene / ethanol / water was heated to 120 °C and stirred for 20 hours. Heating was stopped, and after the system cooled to room temperature, extraction and distillation were carried out. The residue was separated by column chromatography to obtain the target product 11 (0.303 g, 61%). 11H NMR (500 MHz, Chloroform-d) δ 9.14 (d, J = 1.8 Hz, 2H), 8.90 (d, J = 8.2 Hz, 1H), 8.76 (d, J = 8.0 Hz, 1H), 8.57 (s, 2H), 8.52 (d, J = 1.8 Hz, 2H), 8.42 (d, J = 8.9 Hz, 2H), 8.27 (d, J = 2.1 Hz, 2H), 8.14 (s, 1H), 8.04 (d, J = 8.3 Hz, 1H), 7.74–7.69 (m, 3H), 7.64 (t, J = 6.8 Hz, 1H), 7.54 (t, J = 7.4 Hz, 1H), 1.68 (s, 18H), 1.54 (s, 18H). HRMS (ESI) m / z: 948.3466 [M+H] + 。

[0118] Example 5

[0119] This example provides a boron-nitrogen heterocyclic compound 20, and its synthesis route is as follows:

[0120]

[0121] The preparation method of compound 20 specifically includes the following steps:

[0122] (1) Synthesis of intermediate m3

[0123] Under argon protection, a mixture of compound m1 (2.06 g, 10.7 mmol), compound m2 (6.13 g, 21.9 mmol) and cesium carbonate (10.4 g, 31.9 mmol) in N,N-dimethylformamide (50 mL) was heated and stirred at 150 °C for 24 hours. After the reaction system was cooled to room temperature, dichloromethane was added for extraction, and the organic layer was collected, dried, and distilled under reduced pressure. The residue was separated by column chromatography to obtain intermediate m3 (5.10 g, 67%); m / z 710.52 [M + .

[0124] (2) Synthesis of intermediate m4

[0125] The intermediate m3 (4.50 g, 6.32 mmol) prepared above was dissolved in 60 mL of ultra-dry xylene, and the temperature was lowered to -40 °C. n-Butyllithium (3.20 mL, 2.4 M, 7.59 mmol) was slowly added to the above solution, and the temperature was allowed to rise to room temperature naturally. The mixture was stirred for 2 hours, then the temperature was lowered to 0 °C, and boron tribromide (0.78 mL, 8.21 mmol) was added dropwise. The reaction was carried out at room temperature for 1 hour, then the temperature was lowered to 0 °C again. N,N-Diisopropylethylamine (1.36 mL, 8.22 mmol) was slowly added to the reaction system, and then the temperature was raised to 120 °C and stirred for 20 hours. The heating was stopped, and after the system cooled to room temperature, the organic solvent and volatile substances were removed by rotary evaporation. The residue was separated by column chromatography to obtain intermediate m4 (2.8 g, 69%); m / z 640.45 [M + .

[0126] (11) Synthesis of intermediate m5

[0127] Under argon protection, a mixture of compound m4 (2.05 g, 3.20 mmol), 4,4'-di-tert-butyl-2,2'-bipyridine (0.0258 g, 0.096 mmol), methoxy(cyclooctadiene)iridium dimer (0.0424 g, 0.064 mmol) and bis(pinacolato)diboron (0.975 g, 3.84 mmol) in tetrahydrofuran was heated under reflux for 24 hours, cooled, and distilled. The residue was separated by column chromatography to obtain intermediate m5 (1.65 g, 67%); m / z 766.74 [M + .

[0128] (12) Synthesis of target compound 20

[0129] A mixed solution of compound m5 (0.400 g, 0.521 mmol), compound m16 (0.152 g, 0.521 mmol), potassium carbonate (0.361 g, 2.61 mmol) and tetrakis(triphenylphosphine)palladium (0.030 g, 0.0261 mmol) in toluene / ethanol / water was heated to 120 °C and stirred for 20 hours. The heating was stopped, and after the system cooled to room temperature, it was extracted and distilled. The residue was further separated by column chromatography to obtain the target product 20 (0.306 g, 69%). 11H NMR (400 MHz, Chloroform-d) δ 9.08 (d, J = 2.0 Hz, 2H), 8.57–8.49 (m, 3H), 8.49–8.36 (m, 5H), 8.26 (d, J = 2.1 Hz, 2H), 7.97 (d, J = 1.4 Hz, 1H), 7.89 (d, J = 8.3 Hz, 1H), 7.80 (t, J = 7.7 Hz, 1H), 7.69 (dd, J = 8.8, 2.1 Hz, 2H), 7.61 (d, J = 8.4 Hz, 1H), 7.47 (t, J = 7.4 Hz, 1H), 1.65 (s, 18H), 1.53 (s, 18H). HRMS (ESI) m / z: 850.4132 [M+H] + 。

[0130] Application Example 1

[0131] This example provides an organic electroluminescent device, as Figure 1 shown, including an anode layer 2, a hole injection layer 3, a hole transport layer 4, an electron blocking layer 5, a light-emitting layer 6, a hole blocking layer 7, an electron transport layer 8, an electron injection layer 9, and a cathode layer 10, which are sequentially arranged on a substrate 1 from bottom to top; the device structure is ITO / HI(30 nm) / HT(15 nm) / EBL(10 nm) / EML(50 nm) / HBL(20 nm) / ET(30 nm) / EI(2 nm) / Al(100 nm).

[0132] The device is prepared by vacuum evaporation, and the evaporation environment is 2×10 -5 Pa. The evaporation rates of the hole injection layer 3, the hole transport layer 4, the electron blocking layer 5, the light-emitting layer 6, the hole blocking layer 7, the electron transport layer 8, and the electron injection layer 9 are The evaporation rate of the cathode layer 10 is

[0133] Among them, the anode layer 2 is made of ITO material, that is, indium tin oxide material;

[0134] The hole injection layer 3, the hole transport layer 4, the electron blocking layer 5, the hole blocking layer 7, the electron transport layer 8, and the electron injection layer 9 are sequentially selected from the following structural compounds:

[0135]

[0136] The light-emitting layer 6 is formed by co-doping a host material and a guest material. Among them, the host material is selected as the compound DMIZ-TRZ, and the guest material is selected as the boron-nitrogen heterocyclic compound 1 of the present invention. The doping amount of the guest material accounts for 1 wt% of the total mass of the host material and the guest material; the chemical structure of DMIC-TRZ is as follows:

[0137]

[0138] Application Example 2

[0139] The structure of Application Example 2 is the same as that of Application Example 1, and the doping amount of the guest material is changed from 1 wt% to 3 wt%.

[0140] Application Example 3

[0141] The structure of Application Example 3 is the same as that of Application Example 1, and the doping amount of the guest material is changed from 1 wt% to 5 wt%.

[0142] Application Example 4

[0143] This example provides an organic electroluminescent device, as Figure 1 shown, including an anode layer 2, a hole injection layer 3, a hole transport layer 4, an electron blocking layer 5, a light emitting layer 6, a hole blocking layer 7, an electron transport layer 8, an electron injection layer 9 and a cathode layer 10 which are sequentially arranged on a substrate 1 from bottom to top; the device structure is ITO / HI(30nm) / HT(15nm) / EBL(10nm) / EML(50nm) / HBL(20nm) / ET(30nm) / EI(2nm) / Al(100nm).

[0144] The device is prepared by vacuum evaporation, and the evaporation environment is 2×10 -5 Pa. The evaporation rates of the hole injection layer 3, the hole transport layer 4, the electron blocking layer 5, the light emitting layer 6, the hole blocking layer 7, the electron transport layer 8 and the electron injection layer 9 are The evaporation rate of the cathode layer 10 is

[0145] Among them, the anode layer 2 is made of ITO material, that is, indium tin oxide material;

[0146] The hole injection layer 3, the hole transport layer 4, the electron blocking layer 5, the hole blocking layer 7, the electron transport layer 8 and the electron injection layer 9 are sequentially made of the following structural compounds:

[0147]

[0148] The light emitting layer 6 is formed by co-doping a host material and a guest material. Among them, the host material is compound DMIZ-TRZ, the guest material is the boron-nitrogen heterocyclic compound 11 of the present invention, and the doping amount of the guest material accounts for 1 wt% of the total mass of the host material and the guest material; the chemical structure of DMIC-TRZ is as follows:

[0149]

[0150] Application Example 5

[0151] The structure of Application Example 5 is the same as that of Application Example 4, and the doping amount of the guest material is changed from 1 wt% to 3 wt%.

[0152] Application Example 6

[0153] The structure of Application Example 5 is the same as that of Application Example 4, and the doping amount of the guest material is changed from 1 wt% to 5 wt%.

[0154] Application Example 7

[0155] This embodiment provides an organic electroluminescent device, as Figure 1 shown, which includes an anode layer 2, a hole injection layer 3, a hole transport layer 4, an electron blocking layer 5, a light emitting layer 6, a hole blocking layer 7, an electron transport layer 8, an electron injection layer 9, and a cathode layer 10 that are sequentially arranged on a substrate 1 from bottom to top; the device structure is ITO / HI(30nm) / HT(15nm) / EBL(10nm) / EML(50nm) / HBL(20nm) / ET(30nm) / EI(2nm) / Al(100nm).

[0156] The device is prepared by vacuum evaporation, and the evaporation environment is 2×10 -5 Pa. The evaporation rates of the hole injection layer 3, the hole transport layer 4, the electron blocking layer 5, the light emitting layer 6, the hole blocking layer 7, the electron transport layer 8, and the electron injection layer 9 are The evaporation rate of the cathode layer 10 is

[0157] Among them, the anode layer 2 is made of ITO material, that is, indium tin oxide material;

[0158] The hole injection layer 3, the hole transport layer 4, the electron blocking layer 5, the hole blocking layer 7, the electron transport layer 8, and the electron injection layer 9 are sequentially selected from the following structural compounds:

[0159]

[0160] The light emitting layer 6 is formed by co-doping a host material and a guest material. Among them, the host material is selected as the compound DMIZ-TRZ, the guest material is selected as the boron-nitrogen heterocyclic compound 20 of the present invention, and the doping amount of the guest material accounts for 1 wt% of the total mass of the host material and the guest material; the chemical structure of DMIC-TRZ is as follows:

[0161]

[0162] Application Example 8

[0163] The structure of Application Example 8 is the same as that of Application Example 7, and the doping amount of the guest material is changed from 1 wt% to 3 wt%.

[0164] Application Example 9

[0165] The structure of Application Example 9 is the same as that of Application Example 7, and the doping amount of the guest material is changed from 1 wt% to 5 wt%.

[0166] Application Example 10

[0167] This embodiment provides an organic light-emitting device, as Figure 1 shown, including an anode layer 2, a hole injection layer 3, a hole transport layer 4, an electron blocking layer 5, a light-emitting layer 6, a hole blocking layer 7, an electron transport layer 8, an electron injection layer 9, and a cathode layer 10 which are sequentially arranged on a substrate 1 from bottom to top; the device structure is ITO / HI(30 nm) / HT(15 nm) / EBL(10 nm) / EML(50 nm) / HBL(20 nm) / ET(30 nm) / EI(2 nm) / Al(100 nm).

[0168] The device is prepared by vacuum evaporation, and the evaporation environment is 2×10 -5 Pa. The evaporation rates of the hole injection layer 3, the hole transport layer 4, the electron blocking layer 5, the light-emitting layer 6, the hole blocking layer 7, the electron transport layer 8, and the electron injection layer 9 are The evaporation rate of the cathode layer 10 is

[0169] Among them, the anode layer 2 is made of ITO material, that is, indium tin oxide material;

[0170] The hole injection layer 3, the hole transport layer 4, the electron blocking layer 5, the hole blocking layer 7, the electron transport layer 8, and the electron injection layer 9 are sequentially made of the following structural compounds:

[0171]

[0172] The light-emitting layer 6 is formed by co-doping a host material, a sensitizer, and a guest material. Among them, the host material is compound DMIZ-TRZ, the sensitizer is compound 5TBuCzBN, and the guest material is the boron-nitrogen heterocyclic compound 1 of the present invention. The doping amount of the sensitizer accounts for 25 wt% of the total mass of the host material, the sensitizer, and the guest material, and the doping amount of the guest material accounts for 1 wt% of the total mass of the host material, the sensitizer, and the guest material; the chemical structure of DMIC-TRZ is as follows: The chemical structure of compound 5TBuCzBN is as follows

[0173] A DC voltage is applied to the organic light-emitting devices provided in Application Examples 1-10, and their device performances are measured. Table 1 shows some of their parameters, including the maximum external quantum efficiency (EQE max) and an external quantum efficiency (EQE 2 ), emission wavelength, full width at half maximum, and color coordinates at a luminance of 1000 cd / m 1000 .

[0174] Table 1 - Electroluminescence performance test results of Application Examples 1 - 10

[0175]

[0176] The results in Table 1 show that the boron - nitrogen heterocyclic compounds described in the present invention all possess thermally activated delayed fluorescence characteristics, and compared with traditional multiple - resonance thermally activated delayed fluorescence materials, they have shorter delayed fluorescence lifetimes and faster RISC processes. The devices in the present invention not only have ultra - high external quantum efficiency, energy efficiency, and luminance, but more importantly, the device performance is still very excellent at high luminance. At an appropriate doping ratio, the maximum external quantum efficiency of the device can be as high as or even higher than 40%, and at a high luminance such as 1000 cd / m 2 , the external quantum efficiency can still be maintained at more than 30%. The y - value of the color coordinates of the green - light device can be as high as 0.70, having very high color purity. Therefore, the present invention not only further improves the device efficiency of thermally activated delayed fluorescence materials, but also solves the problem of serious efficiency roll - off at high luminance based on multiple - resonance thermally activated delayed fluorescence materials, while ensuring the narrow - band emission characteristics of the luminescent materials, and is expected to promote the practical application of narrow - band luminescent materials in the OLED field.

[0177] In summary, the present invention provides a boron - nitrogen heterocyclic compound, which is obtained by modifying the periphery of a boron - nitrogen hetero - fused ring skeleton with multiple resonance effects with electron - withdrawing groups. On the one hand, the connection of electron - withdrawing groups to the periphery of the boron - nitrogen hetero - fused ring skeleton can adjust the energy level of the material and provide tunable light colors; on the other hand, introducing heavy atoms on the peripheral electron - withdrawing groups can, while ensuring the narrow - band emission of the multiple - resonance skeleton, increase the reverse intersystem crossing rate of the material. Due to the introduction of heavy atoms, the presence of the heavy - atom effect significantly enhances the orbital coupling between the triplet and singlet states in the excited state of the compound, greatly promoting the reverse intersystem crossing process, accelerating the conversion of triplet excitons to singlet excitons, significantly reducing the delay lifetime, thereby effectively improving the exciton utilization rate and also increasing the device efficiency. At the same time, the method of introducing heavy atoms peripherally avoids the participation of heavy atoms in the structural relaxation of the emitting group, ensuring the narrow - band emission characteristics of the multiple - resonance skeleton. Further, the organic electroluminescent device provided by the present invention not only takes into account the advantages of traditional multiple - resonance TADF materials, but also has extremely high external quantum efficiency at high luminance, which effectively improves the problem of serious efficiency roll - off of traditional multiple - resonance TADF materials.

[0178] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A boron-nitrogen hetero compound, characterized in that, the boron-nitrogen hetero compound is selected from any one of the following compounds: 。 2. An organic electroluminescent device comprising a light-emitting layer, characterized in that, The light-emitting layer is obtained by co-doping a host material and a guest material, wherein the structural formula of the host material is: ; the guest material is the boron-nitrogen heterocyclic compound described in claim 1.

3. The organic electroluminescent device according to claim 2, characterized in that, the doping amount of the guest material is 0.5-5 wt% of the total mass of the host material and the guest material.

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