A phosphorescent host material and its preparation method, and an organic electroluminescent device.

Abstract

This invention belongs to the technical field of organic electroluminescent materials, and provides a phosphorescent host material and its preparation method, as well as an organic electroluminescent device. The general structural formula of the phosphorescent host material described in this invention is shown in the specification. The phosphorescent host material provided by this invention, as a material in the light-emitting layer of an organic electroluminescent device, can not only improve luminous efficiency but also significantly increase device lifetime and reduce driving voltage.

Description

Technical Field

[0001] This invention belongs to the field of organic electroluminescent materials technology, specifically relating to a phosphorescent host material and its preparation method, and an organic electroluminescent device. Background Technology

[0002] Organic light-emitting displays (OLEDs) are active-matrix display devices. Currently, small and medium-sized OLED displays have been widely used in high-end smartphones from companies such as Huawei, Xiaomi, and Samsung. Achieving optimal luminous efficiency of the device under low operating voltage conditions is a common requirement in the OLED field.

[0003] OLED light emission occurs in two ways: fluorescence and phosphorescence. In phosphorescence, to suppress the backflow of triplet energy from the guest to the host, the triplet excitons are confined within the emitting layer. This requires the triplet energy level of the host material to be higher than that of the phosphorescent guest. For example, for red light, the triplet energy level needs to be higher than 2.0 eV; while for blue phosphorescence, it needs to exceed 2.7 eV. The triplet energy level is related to the triplet energy level of each constituent unit in the structure and the conjugation of the entire molecule. Furthermore, the HOMO energy level of the host material should match that of the adjacent hole transport material; otherwise, an excessively low HOMO energy level of the host material will create a large hole injection barrier, increasing the device's driving voltage. Therefore, the host material significantly affects the efficiency and performance of organic light-emitting devices, making the development of a novel host material that meets practical requirements crucial. Summary of the Invention

[0004] In view of this, the present invention provides a phosphorescent host material and its preparation method, as well as an organic electroluminescent device. When the phosphorescent host material described in the present invention is applied to a specific light-emitting device, it has the advantages of low driving voltage, high luminous efficiency and long service life.

[0005] It should be noted that the present invention provides an organic electroluminescent device prepared from a compound centered on dibenzofuran, with a six-membered nitrogen heterocycle with strong electron-withdrawing properties connected at position 7, a carbazole connected at position 2, and an aryl group substituted at position 6, 8, or 9. This compound has the technical effects of improving luminous efficiency, significantly increasing lifetime, and reducing driving voltage.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] The first technical objective of this invention is to provide a phosphorescent host material having the structure shown in general formula I:

[0008]

[0009] in,

[0010] Z1-Z3 are each independently selected from N or C, and Z1-Z3 contains at least one N;

[0011] R1 and R2 are each independently selected from substituted or unsubstituted C6-C24 aryl groups and substituted or unsubstituted C3-C24 heteroaryl groups;

[0012] L1 is selected from chemical bonds, phenyl, naphthyl, biphenyl, and terphenyl;

[0013] Ar1 is an independent aryl group selected from C6-C24.

[0014] Furthermore, Equation I has the structure shown in Equations I-1 to I-3:

[0015]

[0016] Z1-Z3 contain at least 2 N;

[0017] R1 and R2 are each independently selected from phenyl, naphthyl, biphenyl, terphenyl, naphthyl-substituted phenyl, phenanthryl, dimethylfluorenyl, dibenzofuranyl, dibenzothiopheneyl, 9-phenylcarbazoyl, pyridyl, phenylpyridyl, methylphenyl, phenyl-substituted dimethylfluorenyl, phenyl-substituted dibenzofuranyl, and phenyl-substituted dibenzothiopheneyl.

[0018] Ar1 is selected from phenyl, naphthyl, biphenyl, terphenyl, and phenyl-substituted naphthyl.

[0019] In the terms “substituted or unsubstituted”, the number of carbon atoms in the substituents indicates the number of carbon atoms that constitute the unsubstituted form, without taking into account the number of carbon atoms in the substituents.

[0020] The term "substituted or unsubstituted" means substituted with one, two or more substituents selected from the following:

[0021] Methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, cyclopentane, cyclohexane, phenyl, biphenyl, naphthyl, fluorenyl, dimethylfluorenyl, phenanthryl, anthracene, indene, phenylenetriene, pyrene, The substituent may be substituted with a substituent consisting of benzofuranyl, furanyl, thiophenyl, pyrroleyl, pyridyl, benzofuranyl, benzothiophenyl, isobenzofuranyl, dibenzofuranyl, dibenzothiophenyl, benzimidazolyl, benzothiazolyl, benzoisothiazolyl, benzoisooxazolyl, benzooxazolyl, isoindolyl, indolyl, benzoindolyl, indazoleyl, benzothiadiazolyl, carbazoleyl, benzocarbazoleyl, or a substituent connected to two or more of the substituents shown above, or may not have any substituents.

[0022] Aryl refers to monocyclic aromatic hydrocarbon groups and polycyclic aromatic ring systems. Polycyclic systems can have two or more rings in which two carbons are shared by two adjacent rings (the rings are "fused").

[0023] Heteroaryl groups include monocyclic aromatic groups and polycyclic aromatic ring systems with at least one heteroatom, including but not limited to O, S, N, P, B, Si, and Se.

[0024] The substitution positions of dibenzofurans are defined as follows:

[0025]

[0026] Furthermore, the phosphorescent host material is selected from any of the following structures:

[0027]

[0028]

[0029]

[0030]

[0031]

[0032]

[0033]

[0034] The above only lists some specific structural forms, but this series of phosphorescent host materials is not limited to the above molecular structures. Other specific molecular structures can be obtained by simply changing some simple groups and their substituted groups and substitution positions, which will not be elaborated here.

[0035] A second objective of this invention is to provide a method for preparing the aforementioned phosphorescent host material. The phosphorescent host material of this invention can be prepared by synthetic methods known to those skilled in the art. Alternatively, the following reaction process is preferred for preparation, and the specific synthetic route is as follows:

[0036]

[0037] The limitations in the above formula are the same as those mentioned above, and will not be repeated here.

[0038] In particular, compared to complex raw materials that have not been disclosed before, the invention will employ classic Suzuki coupling reaction, Buchwald-Hartwig coupling reaction and lithiation reaction for synthesis.

[0039] Furthermore, the series of palladium-catalyzed coupling reactions performed in this invention utilize the difference in reactivity between I and Br (which is greater than that of Cl) and the reaction sites are controlled by adjusting the reaction conditions. The reactions are then purified using column chromatography or a silica gel funnel to remove byproducts, yielding the target compound. References to common general knowledge are as follows:

[0040] Organometallic Chemistry (6th Edition), Robert H. Crabtree, published by East China University of Science and Technology Press, Shanghai, September 00, 2017, ISBN: 978-7-5628-5111-0, page 388.

[0041] Organic Chemistry and Optoelectronic Materials Experiment Tutorial, Chen Runfeng, Publisher: Southeast University Press, Publication Date: 2019-11-00, ISBN: 9787564184230, Page 174.

[0042] Specific preparation method:

[0043] Step 1:

[0044] Under N2 protection, reactants Al (1.0 eq), BI (1.0-1.2 eq), Pd(PPh3)4 (0.01-0.04 eq), and NaOH (2.0-2.4 eq) were dissolved in 1,4-dioxane / H2O (volume ratio 3-5:1) and heated to 100-120 °C for 24 h. After the reaction was complete, the product was extracted by introducing distilled water and DCM at room temperature, and the solvent was removed by rotary evaporation after drying the organic layer with MgSO4. The intermediate CI was purified by column chromatography.

[0045] Step 2:

[0046] Under N2 protection, intermediates CI (1.0 eq) and BBr3 (2.1-2.4 eq) were dissolved in DCM and heated to reflux for 1-3 h. After the reaction was complete, the product was extracted by introducing distilled water and DCM at room temperature, and the solvent was removed by rotary evaporation after drying the organic layer with MgSO4. The intermediate DI was purified by column chromatography.

[0047] Step 3:

[0048] Intermediate DI (1.0 eq) and K₂CO₃ (2.1–2.5 eq) were dissolved in DMF and heated to reflux for 4–8 h. After the reaction was complete, the product was extracted by introducing distilled water and DCM at room temperature, and the solvent was removed by rotary evaporation after drying the organic layer with MgSO₄. Intermediate EI was purified by column chromatography.

[0049] Step 4:

[0050] Under N2 protection, intermediate EI (1.0 eq), reactant FI (1.1-1.4 eq), Pd(PPh3)4 (0.01-0.05 eq), and K2CO3 (2.1-2.4 eq) were dissolved in a mixed solvent of toluene, ethanol, and water (volume ratio 2-4:1:1). The mixture was heated to 85-95℃ and reacted for 8-12 h. After the reaction was complete, the product was extracted by introducing distilled water and DCM at room temperature. After drying the organic layer with MgSO4, the solvent was removed using a rotary evaporator. The intermediate GI was purified by column chromatography. Step 5:

[0051] Under N2 protection, intermediate GI (1.0 eq) and reactant HI (1.1-1.3 eq) dissolved in xylene were added to a reaction vessel. Then, under nitrogen protection, Pd(OAc)2 (0.01-0.05 eq), X-Phos (0.02-0.15 eq), and t-BuONa (2.0-2.4 eq) were added. After addition, the reaction temperature was slowly increased to 130-140 °C, and the mixture was stirred for 8-12 h. The product was extracted by introducing distilled water and ethyl acetate at room temperature. After drying the organic layer with MgSO4, the solvent was removed by rotary evaporation, and the product was purified by column chromatography to obtain compound I.

[0052] A third objective of this invention is to provide the application of the aforementioned phosphorescent host material in organic electroluminescent devices.

[0053] An electroluminescent device comprising the aforementioned phosphorescent host material. The organic electroluminescent device includes: a first electrode, a second electrode, and an organic layer disposed between the two electrodes, wherein the organic layer comprises at least one or more of the following: a hole injection layer, a hole transport layer, a hole transport auxiliary layer, an electron blocking layer, a light-emitting auxiliary layer, a light-emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer, and a capping layer.

[0054] Specifically, the organic electroluminescent device includes a light-emitting layer containing the phosphorescent host material described in this invention.

[0055] The light-emitting layer of the organic electroluminescent device includes a host material and a dopant material. The host material is the phosphorescent host material described in this invention, and the mixing ratio of the host material and the dopant material is 90-99.5:0.5-10.

[0056] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects:

[0057] 1) This invention retains the advantage of the high triplet energy level of dibenzofuran, and on this basis, the phenyl group substituted at the 6, 8 or 9 position bends the overall structure and extends the molecular conjugated system, avoiding the localization of carrier migration. At the same time, the phenyl substitution on the rigid group of dibenzofuran gives it higher thermal stability and film-forming properties when evaporating devices, which is beneficial to improving the life of the device.

[0058] 2) As a light-emitting layer, it needs to have high mobility for both holes and electrons. Carbazole linked at the 2-position of dibenzofuran is an electron-rich ammonia-containing heterocyclic compound. The electrophilic nitrogen atom of carbazole absorbs electrons from the carbon-carbon double bond through an inductive effect, and at the same time, it has a P-π conjugation effect, which increases the hole transport rate and improves efficiency. Triazine and pyrimidine six-membered nitrogen heterocycles linked at the 7-position of dibenzofuran enhance the electron mobility of organic molecules. The N atom in it has good electron transport performance, which enhances the conductivity of the material. As a whole, the compound has the technical effects of reducing driving voltage, extending lifetime, and improving luminescence efficiency. Attached Figure Description

[0059] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0060] Figure 1 This is the hydrogen nuclear magnetic resonance spectrum of intermediate C-16 of the present invention.

[0061] Figure 2 This is the hydrogen nuclear magnetic resonance spectrum of intermediate E-16 of the present invention.

[0062] Figure 3 This is the 1H NMR spectrum of compound 16 of the present invention. Detailed Implementation

[0063] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0064] The present invention discloses a method for preparing a phosphorescent host material.

[0065] Additionally, it should be noted that the values ​​given in the following embodiments are as accurate as possible. However, those skilled in the art will understand that due to unavoidable measurement errors and experimental issues, each number should be understood as an approximation rather than an absolutely accurate value.

[0066] Example 1: Synthesis of Compound 16

[0067]

[0068] CAS: Reactant A-16: 2756407-80-2

[0069] CAS: Reactant B-16: 116272-42-5

[0070] CAS: Reactant F-16: 1672704-46-9

[0071] CAS: Reactant H-16: 1547492-13-6

[0072] Step 1:

[0073] Under N2 protection, reactants A-16 (1.0 eq), B-16 (1.2 eq), Pd(PPh3)4 (0.02 eq), and NaOH (2.4 eq) were dissolved in 1,4-dioxane / H2O (volume ratio 4:1) and heated to 100 °C for 24 h. After the reaction was complete, the product was extracted by introducing distilled water and DCM at room temperature, and the solvent was removed by rotary evaporation after drying the organic layer with MgSO4. The intermediate C-16 was purified by column chromatography (yield: 61.2%, MS (ESI, m / Z): [M+H]+=390.14).

[0074] Step 2:

[0075] Under N2 protection, intermediate C-16 (1.0 eq) and BBr3 (2.3 eq) were dissolved in DCM and heated to reflux for 2 h. After the reaction was complete, the product was extracted by introducing distilled water and DCM at room temperature, and the solvent was removed by rotary evaporation after drying the organic layer with MgSO4. The intermediate D-16 was purified by column chromatography (yield: 88.9%, MS (ESI, m / Z): [M+H]+=376.20).

[0076] Step 3:

[0077] Intermediate D-16 (1.0 eq) and K2CO3 (2.2 eq) were dissolved in DMF and heated to reflux for 4 h. After the reaction was complete, the product was extracted by introducing distilled water and DCM at room temperature, and the solvent was removed by rotary evaporation after drying the organic layer with MgSO4. Intermediate E-16 was purified by column chromatography (yield: 53.4%, MS (ESI, m / Z): [M+H]+=356.06).

[0078] Step 4:

[0079] Under N2 protection, intermediate E-16 (1.0 eq), reactant F-16 (1.1 eq), Pd(PPh3)4 (0.01 eq), and K2CO3 (2.1 eq) were dissolved in a mixed solvent of toluene, ethanol, and water (volume ratio 3:1:1). The mixture was heated to 85 °C and reacted for 8 h. After the reaction was complete, the product was extracted by introducing distilled water and DCM at room temperature. After drying the organic layer with MgSO4, the solvent was removed by rotary evaporation. The intermediate G-16 was purified by column chromatography (yield: 81.7%, MS (ESI, m / Z): [M+H]+=661.31).

[0080] Step 5:

[0081] Under N2 protection, intermediate G-16 (1.0 eq) and reactant H-16 (1.2 eq) dissolved in xylene were added to a reaction vessel. Then, under nitrogen protection, Pd(OAc)2 (0.02 eq), X-Phos (0.05 eq), and t-BuONa (2.4 eq) were added. After the addition, the reaction temperature was slowly increased to 130 °C and the mixture was stirred for 8 h. The product was extracted by introducing distilled water and ethyl acetate at room temperature. After drying the organic layer with MgSO4, the solvent was removed by rotary evaporation and purified by column chromatography to obtain compound 16 (yield: 86.5%, MS (ESI, m / Z): [M+H]+=868.53).

[0082] Characterization:

[0083] HPLC purity: >99.8%.

[0084] Elemental analysis:

[0085] Theoretical values: C, 87.07; H, 4.64; N, 6.45; O, 1.84

[0086] Test values: C, 86.78; H, 4.86; N, 6.51; O, 1.91

[0087] The proton NMR spectrum of intermediate C-16 is as follows: Figure 1 As shown.

[0088] The proton NMR spectrum of intermediate E-16 is as follows: Figure 2 As shown.

[0089] The proton NMR spectrum of compound 16 is as follows: Figure 3 As shown.

[0090] Example 2: Synthesis of Compound 90

[0091]

[0092] CAS: Reactant F-90: 2864367-66-6

[0093] CAS: Reactant H-90: 2364378-54-9

[0094] Step 1:

[0095] Intermediate E-90 was prepared as in Example 1, intermediate E-16.

[0096] Step 2:

[0097] Under N2 protection, intermediate E-90 (1.0 eq), reactant F-90 (1.2 eq), Pd(PPh3)4 (0.01 eq), and K2CO3 (2.2 eq) were dissolved in a mixed solvent of toluene, ethanol, and water (volume ratio 3:1:1). The mixture was heated to 90 °C and reacted for 12 h. After the reaction was complete, the product was extracted by introducing distilled water and DCM at room temperature. After drying the organic layer with MgSO4, the solvent was removed by rotary evaporation. The intermediate G-90 was purified by column chromatography (yield: 76.2%, MS (ESI, m / Z): [M+H]+=675.40).

[0098] Step 3:

[0099] Under N2 protection, intermediate G-90 (1.0 eq) and reactant H-90 (1.1 eq) dissolved in xylene were added to a reaction vessel. Then, under nitrogen protection, Pd(OAc)2 (0.02 eq), X-Phos (0.04 eq), and t-BuONa (2.2 eq) were added. After addition, the reaction temperature was slowly increased to 130 °C, and the mixture was stirred for 8 h. The product was extracted by introducing distilled water and ethyl acetate at room temperature. After drying the organic layer with MgSO4, the solvent was removed by rotary evaporation. The product was purified by column chromatography to obtain compound 90 (yield: 80.5%, MS (ESI, m / Z): [M+H]+=958.48).

[0100] Characterization:

[0101] HPLC purity: >99.8%.

[0102] Elemental analysis:

[0103] Theoretical values: C, 86.41; H, 4.41; N, 5.84; O, 3.34

[0104] Test values: C, 86.24; H, 4.54; N, 5.89; O, 3.38

[0105] Example 3: Synthesis of Compound 117

[0106]

[0107] CAS: Reactant a-117: 99770-93-1

[0108] CAS: Reactant b-117: 2437221-56-0

[0109] CAS: Reactant H-117: 1914125-21-5

[0110] Step 1:

[0111] Intermediate E-117 was prepared as in Example 1, intermediate E-16.

[0112] Step 2:

[0113] Under N2 protection, reactants a-117 (1.0 eq) and b-117 (1.3 eq) were dissolved in xylene in a reaction vessel. Then, under nitrogen protection, Pd(OAc)2 (0.01 eq), X-Phos (0.04 eq), and t-BuONa (2.2 eq) were added. After addition, the reaction temperature was slowly raised to 135 °C and the mixture was stirred for 12 h. The product was extracted by introducing distilled water and ethyl acetate at room temperature. After drying the organic layer with MgSO4, the solvent was removed by rotary evaporation and purified by column chromatography to obtain reactant 117 (yield: 87.1%, MS (ESI, m / Z): [M+H]+=601.36).

[0114] Step 3:

[0115] Under N2 protection, intermediate E-117 (1.0 eq), reactant F-117 (1.1 eq), Pd(PPh3)4 (0.02 eq), and K2CO3 (2.3 eq) were dissolved in a mixed solvent of toluene, ethanol, and water (volume ratio 3:1:1). The mixture was heated to 95 °C and reacted for 10 h. After the reaction was complete, the product was extracted by introducing distilled water and DCM at room temperature. After drying the organic layer with MgSO4, the solvent was removed by rotary evaporation. The intermediate G-117 was purified by column chromatography (yield: 79.5%, MS (ESI, m / Z): [M+H]+=751.42).

[0116] Step 4:

[0117] Under N2 protection, intermediate G-117 (1.0 eq) and reactant H-117 (1.3 eq) dissolved in xylene were added to a reaction vessel. Then, under nitrogen protection, Pd(OAc)2 (0.01 eq), X-Phos (0.04 eq), and t-BuONa (2.2 eq) were added. After addition, the reaction temperature was slowly increased to 135 °C and the mixture was stirred for 12 h. The product was extracted by introducing distilled water and ethyl acetate at room temperature. After drying the organic layer with MgSO4, the solvent was removed by rotary evaporation and purified by column chromatography to obtain compound 117 (yield: 82.9%, MS (ESI, m / Z): [M+H]+=1008.52).

[0118] Characterization:

[0119] HPLC purity: >99.7%.

[0120] Elemental analysis:

[0121] Theoretical values: C, 88.07; H, 4.79; N, 5.55; O, 1.59

[0122] Test values: C, 87.94; H, 4.86; N, 5.61; O, 1.63

[0123] Examples 4-55

[0124] The following compounds were synthesized using the synthesis method described in the above embodiments, and their molecular formulas and mass spectra are shown in Table 1 below. The mass spectrometer used in this application was a Waters XEVO TQD, a low-precision ESI source.

[0125] Table 1 Molecular formulas and mass spectra

[0126]

[0127]

[0128] In addition, it should be noted that other compounds in this application can be obtained by referring to the synthesis methods of the embodiments listed above, so they will not be listed one by one here.

[0129] This invention provides an organic electroluminescent device that can have a structure comprising an organic layer, a hole injection layer, a hole transport layer, a hole transport auxiliary layer, an electron blocking layer, a light-emitting auxiliary layer, a light-emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer, and a capping layer. However, the structure of the organic light-emitting element is not limited to this and can contain fewer or more organic layers.

[0130] According to one embodiment of this specification, the main material in the light-emitting layer is the compound of Formula I prepared according to this invention.

[0131] According to one embodiment of this specification, the green light-emitting host material prepared by the present invention is Formula I.

[0132] Regarding the compound represented by Formula I above, the organic layer can be formed using either vacuum evaporation or solution coating when manufacturing organic light-emitting elements. Solution coating methods include, but are not limited to, spin coating, dip coating, blade coating, inkjet printing, screen printing, spray coating, and roller coating.

[0133] Depending on the material used, the organic light-emitting element of the present invention can be a top-emitting type, a bottom-emitting type, or a bidirectional-emitting type.

[0134] The devices described in this invention can be used in organic light-emitting devices, including but not limited to flat panel displays, computer monitors, a medical monitor, a television set, billboards, a lamp for internal or external lighting and / or signaling, head-up displays, fully transparent or partially transparent displays, flexible displays, a laser printer, a telephone, a mobile phone, tablets, a photo album, a personal digital assistant (PDA), a wearable device, a laptop computer, a digital camera, a camcorder, a viewfinder, a microdisplay, a 3D display, a virtual reality or augmented reality display, vehicles, video walls comprising multiple displays tiled together, theater or stadium screens, phototherapy devices, and signs.

[0135] As an anode material, a material with a high work function is preferred in order to facilitate the injection of holes into the organic layer. Specific examples of anode materials that can be used in this invention include metals such as vanadium, chromium, copper, zinc, and gold, or their alloys; metal oxides such as zinc oxide, indium oxide, indium tin oxide (ITO), and indium zinc oxide (IZO); combinations of metals and oxides such as ZnO:Al or SnO2:Sb; and conductive polymers such as polypyrrole and polyaniline.

[0136] The hole injection layer is preferably a p-doped hole injection layer, which means a hole injection layer doped with a p-doped agent. A p-doped agent is a material that can impart p-type semiconductor characteristics. P-type semiconductor characteristics refer to the characteristics of injecting or transporting holes at the HOMO energy level, that is, the characteristics of a material with high hole conductivity.

[0137] P-dopers can be illustrated by the following compounds, but are not limited to them.

[0138]

[0139] Hole transport layers, hole transport auxiliary layers, electron blocking layers, and luminescent auxiliary layers are placed between the anode and the luminescent layer. These layers can promote hole injection and / or hole transport, or prevent electron leakage. They can be selected from aryl amine derivatives, conductive polymers, and block copolymers containing both conjugated and non-conjugated portions. Specifically, the hole transport layer, hole transport auxiliary layer, electron blocking layer, and luminescent auxiliary layer are selected from the following compounds, but are not limited to these.

[0140]

[0141]

[0142]

[0143] The luminescent material in the luminescent layer is a substance that can receive holes and electrons from the hole transport layer and the electron transport layer respectively, and combine them to emit light in the visible light region.

[0144] The light-emitting layer consists of a host material and doped materials.

[0145] The mass ratio of the main material to the dopant material is 90-99.5:0.5-10.

[0146] The main material of the light-emitting layer of this invention is a single green light material or a dual green light material.

[0147] The electron transport region may include at least one of an electron buffer layer, a hole blocking layer, an electron transport layer, and an electron injection layer, and preferably at least one of an electron transport layer and an electron injection layer. The electron transport region is a layer capable of mitigating the degradation of luminous brightness caused by changes in the current characteristics of the device when the device is exposed to high temperatures during the panel manufacturing process, and it can control charge flow characteristics.

[0148] Materials for the electron transport layer (hole blocking layer) include derivatives of oxazole, imidazole, thiazole, triazine, etc., metal chelates, quinoline derivatives, oxaloline derivatives, diazanthracene derivatives, diphenanthroline derivatives, silicon-containing heterocyclic compounds, perfluorinated oligomers, etc. Specifically, electron transport layer materials are selected from the following compounds, but are not limited to them.

[0149]

[0150]

[0151] In some embodiments of the present invention, the material of the electron injection layer includes oxazole, oxadiazole, triazole, imidazole, perylenetetracarboxylic acid, fluorenemethane, anthrone and its derivatives, magnesium, calcium, sodium, potassium, titanium, indium, yttrium, lithium, gadolinium, aluminum, silver, tin, ytterbium and other metals or their alloys, metal complexes or nitrogen-containing 5-membered ring derivatives, etc., but is not limited thereto.

[0152] The cathode material is preferably a material with a low work function, which facilitates the injection of electrons into the organic layer. Specific examples of cathode materials include metals or alloys such as magnesium, calcium, sodium, potassium, titanium, indium, yttrium, lithium, gadolinium, aluminum, silver, tin, and lead; multilayered materials such as LiF / Al or LiO2 / Al, and Mg / Ag.

[0153] Apart from the main material disclosed herein being the compound shown in Formula I, there are no special restrictions on other layer materials in OLED devices, and existing hole injection materials, hole transport materials, dopant materials, hole blocking layer materials, electron transport layer materials, and electron injection materials can be used.

[0154] The following detailed description, in conjunction with specific embodiments, illustrates an organic electroluminescent composition and an organic electroluminescent device provided by the present invention.

[0155] [Application Example] Fabrication of Green Organic Light Emitting Devices:

[0156] A method for fabricating a green organic electroluminescent device includes the following steps:

[0157] a. ITO anode: ITO (indium tin oxide)-Ag-ITO (indium tin oxide) glass substrates with coating thicknesses of 14nm / 150nm / 14nm are cleaned twice in distilled water, ultrasonically washed for 30 minutes, then repeatedly cleaned twice in distilled water, ultrasonically washed for 10 minutes, and baked in a vacuum oven at 220℃ for 2 hours. After baking, the substrates are cooled down before use. Using this substrate as the anode, the device is deposited using a vapor deposition machine, and other functional layers are deposited sequentially on it.

[0158] b. HIL (Hole Injection Layer): The evaporation rate of the vacuum evaporation hole injection layer materials HT1-27 and P-5 is as follows; the evaporation rate ratio of HT1-27 and P-5 is 95:5, and the thickness is 10nm.

[0159] c. HTL (Hole Transport Layer): At the evaporation rate, 125nm HT 1-27 was vacuum-deposited on the hole injection layer as a hole transport layer;

[0160] d. Prime (Emitting Assist Layer): with The evaporation rate was such that 45nm HT 1-24 was vacuum-deposited on the hole transport layer as a light-emitting auxiliary layer;

[0161] e. EML (Emitting Layer): On the emitting auxiliary layer, with... The evaporation rate of the vacuum evaporation of a host material (GH + compound I of the present invention) and a dopant material (Dopant) with a total thickness of 40 nm, wherein GH and compound I are co-evaporated as dual host materials with the dopant material, the ratio of GH and compound I is 50%:50%, and the evaporation rate ratio of host material to dopant is 88:12.

[0162] f. HBL (Hole Blocking Layer): with The evaporation rate was high, and a hole-blocking layer ET-5 with a thickness of 5.0 nm was vacuum-deposited.

[0163] g. ETL (Electron Transport Layer): The evaporation rate was determined, and ET-25 and Liq with a thickness of 30 nm were vacuum-deposited as electron transport layers; the evaporation rate ratio of ET-25 to Liq was 1:1.

[0164] h, EIL (Electron Injection Layer): with The evaporation rate was such that a Yb film layer of 1.0 nm was deposited to form an electron injection layer;

[0165] i. Cathode: with The evaporation rate ratio of magnesium and silver is 1:9, which is used to form a cathode;

[0166] j. Optical extraction layer: with The evaporation rate was used to vacuum evaporate a 60 nm thick CPL layer on the cathode as a light extraction layer.

[0167] k. Encapsulate the vapor-deposited substrate; use a coating equipment to coat the cleaned cover plate with UV adhesive, move the coated cover plate to the pressing section, place the vapor-deposited substrate on the top of the cover plate, and bond the substrate and cover plate together under the action of the bonding equipment, while simultaneously completing the UV adhesive photocuring.

[0168] The material structures involved in device fabrication are as follows:

[0169]

[0170] Application Example 1-55

[0171] Organic electroluminescent devices of application examples 1-55 were prepared according to the above-described method for preparing organic electroluminescent devices, except that the compounds of formula I in the application examples were replaced with the corresponding compounds in Table 2.

[0172] Comparative Examples 1-16

[0173] Organic electroluminescent devices are prepared according to the above-described method, except that the compound of formula I in the application examples is replaced with comparative compounds 1-16.

[0174]

[0175] The driving voltage, luminous efficiency, and lifetime of the organic electroluminescent devices obtained in Examples 1-55 and Comparative Examples 1-16 were characterized at a brightness of 15000 nits. The test results are shown in Table 2 below.

[0176] Table 2 Device Test Results

[0177]

[0178]

[0179]

[0180] In summary, the present invention retains the advantage of the high triplet energy level of dibenzofuran. Furthermore, by substituting phenyl groups at positions 6, 8, or 9, the overall structure is bent, and the molecular conjugation system is extended. As a luminescent layer, it needs to have high mobility for both holes and electrons. The carbazole linked at position 2 of dibenzofuran is an electron-rich ammonia-containing heterocyclic compound. The electrophilic nitrogen atom of carbazole absorbs electrons from the carbon-carbon double bond through an inductive effect, while also exhibiting a p-π conjugation effect, increasing the hole transport rate and improving efficiency. The triazine or pyrimidine six-membered nitrogen heterocycle linked at position 7 of dibenzofuran enhances the electron mobility of the organic molecule. The N atom in this heterocycle has excellent electron transport properties, enhancing the conductivity of the material. Overall, the compound exhibits the technical effects of reducing driving voltage, extending lifetime, and improving luminescence efficiency.

[0181] As shown in Table 2, the test results indicate that Compound 1 and Compound 2 are parallel comparisons. The difference is that Compound 1 does not have phenyl substitution on dibenzofuran. The compound of the present invention can effectively extend the molecular conjugated system and avoid carrier migration localization. At the same time, the phenyl substitution on the rigid group of dibenzofuran gives it higher thermal stability and film-forming properties when evaporating devices, which is beneficial to improving the lifespan of the device.

[0182] Comparative compounds 6, 10, and 3 are compared in parallel, differing only in the substitution positions of carbazole and triazine. The compounds of this invention are more favorable for carrier balance. Among similar substances, the substitution position and the type of substituent both affect the triplet energy level and mobility, thus influencing the device performance in organic electroluminescence. Although the structures of the compounds in this invention are similar to those in the prior art, compounds conforming to Formula I of this invention have a significant performance advantage in improving lifetime.

[0183]

[0184] Furthermore, the dibenzofuran of the present invention is connected to a six-membered nitrogen heterocycle with strong electron-withdrawing properties at the 7 position, to a carbazole at the 2 position, and to an aryl group at the 6, 8, or 9 position. The organic electroluminescent device prepared from the resulting compound has the technical effects of improving luminous efficiency, significantly increasing lifetime, and reducing driving voltage.

[0185] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A phosphorescent host material, characterized in that, It has the structure shown in general formula I: ； in, Z1-Z3 are each independently selected from N or C, and Z1-Z3 contains at least one N; R1 and R2 are each independently selected from phenyl, naphthyl, biphenyl, terphenyl, naphthyl-substituted phenyl, phenanthryl, dimethylfluorenyl, dibenzofuranyl, dibenzothiophene, 9-phenylcarbazoyl, pyridyl, phenylpyridyl, methylphenyl, phenyl-substituted dimethylfluorenyl, phenyl-substituted dibenzofuranyl, and phenyl-substituted dibenzothiophene. L1 is selected from chemical bonds, phenyl, naphthyl, biphenyl, and terphenyl; Ar1 is an independent aryl group selected from C6-C24.

2. The phosphorescent host material according to claim 1, characterized in that, Equation I has the structure shown in Equations I-1 to I-3: 。 3. The phosphorescent host material according to claim 1 or 2, characterized in that, Z1-Z3 contain at least 2 Ns.

4. The phosphorescent host material according to claim 3, characterized in that, Ar1 is selected from phenyl, naphthyl, biphenyl, terphenyl, and phenyl-substituted naphthyl.

5. A phosphorescent host material, characterized in that, The phosphorescent host material is selected from any one of the compounds shown in the following structural formulas: 。 6. A method for preparing the phosphorescent host material as described in claim 1, characterized in that, The method specifically includes the following steps: Step 1: Under N2 protection, 1.0 eq reactant Al, 1.0-1.2 eq reactant BI, 0.01-0.04 eq Pd(PPh3)4 and 2.0-2.4 eq NaOH were dissolved in 1,4-dioxane / H2O and heated to 100-120℃ for 24 h. After the reaction was completed, the product was extracted by introducing distilled water and DCM at room temperature, the organic layer was dried with MgSO4, the solvent was removed by rotary evaporation, and the product was purified by column chromatography to obtain intermediate CI. Step 2: Under N2 protection, 1.0 eq intermediate CI and 2.1-2.4 eq BBr3 were dissolved in DCM and heated to reflux for 1-3 h. After the reaction was complete, the product was extracted by introducing distilled water and DCM at room temperature, the organic layer was dried with MgSO4, the solvent was removed by rotary evaporation, and the product was purified by column chromatography to obtain intermediate DI. Step 3: 1.0 eq intermediate DI and 2.1-2.5 eq K2CO3 were dissolved in DMF and heated to reflux for 4-8 h. After the reaction was complete, the product was extracted by introducing distilled water and DCM at room temperature, and the organic layer was dried with MgSO4. The solvent was removed by rotary evaporation and purified by column chromatography to obtain intermediate EI. Step 4: Under N2 protection, 1.0 eq intermediate EI, 1.1-1.4 eq reactant FI, 0.01-0.05 eq Pd(PPh3)4 and 2.1-2.4 eq K2CO3 were dissolved in a mixed solvent of toluene, ethanol and water in a volume ratio of 2-4:1:

1. The mixture was heated to 85-95℃ and reacted for 8-12 h. After the reaction was completed, the product was extracted by introducing distilled water and DCM at room temperature, and the organic layer was dried with MgSO4. The solvent was removed by rotary evaporation, and the product was purified by column chromatography to obtain intermediate GI. Step 5: Under N2 protection, 1.0 eq of intermediate GI and 1.1-1.3 eq of reactant HI dissolved in xylene were added to a reaction vessel. Then, under nitrogen protection, 0.01-0.05 eq of Pd(OAc)2, 0.02-0.15 eq of X-Phos, and 2.0-2.4 eq of t-BuONa were added. After the addition, the reaction temperature was slowly increased to 130-140℃, and the mixture was stirred for 8-12 h. The product was extracted by introducing distilled water and ethyl acetate at room temperature, and the organic layer was dried with MgSO4. The solvent was removed by rotary evaporation, and the product was purified by column chromatography to obtain compound I. The specific synthesis route is as follows: ； Wherein, Z1-Z3, R1, R2, L1, and Ar1 are as described in claim 1.

7. An organic electroluminescent device, characterized in that, The organic electroluminescent device includes a first electrode, a second electrode, and an organic layer disposed between the first electrode and the second electrode; and... The organic layer includes at least one or more of the following: a hole injection layer, a hole transport layer, a hole transport auxiliary layer, an electron blocking layer, a light-emitting auxiliary layer, a light-emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer, and a capping layer; and, The light-emitting layer comprises the phosphorescent host material as described in claim 1.

8. The organic electroluminescent device according to claim 7, characterized in that, The light-emitting layer includes a host material and a dopant material, wherein the host material is the phosphorescent host material.

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