An organic electroluminescent element

Abstract

The present invention provides an organic electroluminescent element. The organic electroluminescent element comprises a hole injection layer, a hole transport layer, a light-emitting layer and an electron transport layer stacked in sequence, wherein the main body of the light-emitting layer is composed of compound A and compound B: the electron transport layer comprises compound C: the compound C in the electron transport layer of the organic electroluminescent element and the compound A in the main body of the light-emitting layer have two identical fragments, so the interface effect between the film layers is weakened, which is conducive to the rapid transmission of electrons to the light-emitting layer; since the main material of the light-emitting layer is composed of an electron-type main material A and a hole-type main material B, the transmission capacity of holes and electrons is further balanced, so the efficiency of the organic electroluminescent element is significantly improved by combining the mutual synergistic effect of the above-mentioned substances.

Description

Technical Field

[0001] The present invention relates to the technical field of electroluminescence, and in particular to an organic electroluminescent element. Background Art

[0002] Organic electroluminescent elements have been used in smart phones, tablet computers, and automotive fields due to their characteristics of lightness, wide viewing angle, high contrast, low power consumption, high response speed, full-color display, and flexibility, and are expanding to large-size application areas such as televisions.

[0003] Organic electroluminescent elements usually include 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 other film layers. Holes and electrons are injected from the anode and cathode respectively, enter the light-emitting layer through the transport layer, and recombine with each other to emit light. The efficiency of the element depends on the recombination probability of holes and electrons, so regulating the balance of carriers at both ends is the key. The main means of regulation are: improving the injection and transport properties of holes and electrons, thereby increasing the probability of hole-electron recombination; improving the blocking properties of holes and electrons, thereby confining the generated excitons in the light-emitting layer to obtain high luminous efficiency; or co-evaporating electron-transporting materials and hole-transporting materials to form dual-host materials, so that electrons and holes can be transmitted at the same time, so that the two are balanced, reducing exciton quenching, and thus improving luminous efficiency.

[0004] The selection of dual-host materials requires many factors to be considered. It is not a simple mixture of two materials. It requires not only the energy level matching between the materials, but also the balance of electron and hole transport capabilities and the stability of the materials. In addition, the materials on both sides must also match them to achieve the purpose of optimizing device performance. Summary of the invention

[0005] The main purpose of the present invention is to provide an organic electroluminescent element to solve the problem of low luminescence efficiency of the device caused by the difficulty in balancing holes and electrons in the electroluminescent element in the prior art, while reducing the material source in the evaporation operation.

[0006] In order to achieve the above object, according to one aspect of the present invention, an organic electroluminescent element is provided, the organic electroluminescent element comprising a hole injection layer, a hole transport layer, a light-emitting layer and an electron transport layer stacked in sequence, the main body of the light-emitting layer is composed of compound A and compound B,

[0007]

[0008] The electron transport layer comprises compound C:

[0009]

[0010] Furthermore, the hole injection layer comprises any one or more arylamine compounds and any one or more radialene derivatives doped therein.

[0011] The arylamine compounds have the general formula I: wherein Ar1 to Ar4 are each independently a substituted or unsubstituted C6-C 30 Aryl, substituted or unsubstituted C5-C 30 Heteroaryl, the substituents on Ar1 and Ar2, Ar3 and Ar4 may be bonded to each other to form a ring via a single bond, a substituted or unsubstituted methylene, an oxygen atom or a sulfur atom, and n is any integer from 0 to 4;

[0012] The radialene derivatives have the general formula II: Wherein Ar6 is a C6-C 18 The electron withdrawing group is preferably fluorine or cyano.

[0013] Furthermore, in the above general formula I, Ar1 to Ar4 are each independently selected from any one of substituted or unsubstituted phenyl, biphenyl, naphthyl, fluorenyl or carbazole.

[0014] Furthermore, in the above general formula II, Ar6 is selected from phenyl or biphenyl containing at least one cyano group or F atom substituted.

[0015] Furthermore, in the above-mentioned arylamine compound and the radialene derivative, the doping mass ratio of the radialene derivative is 2% to 20%.

[0016] Furthermore, the hole transport layer comprises a first hole transport layer and a second hole transport layer which are sequentially stacked away from the hole injection layer, and the first hole transport layer comprises any one or more aromatic amine compounds.

[0017] Furthermore, the second hole transport layer comprises any one or more triarylamine compounds represented by general formula III:

[0018]

[0019] wherein Ar7, Ar8 and Ar9 are each independently a substituted or unsubstituted C6-C 30 Aryl, substituted or unsubstituted C5-C 30 Any of the heteroaryl groups.

[0020] Furthermore, in the above general formula III, Ar7, Ar8 and Ar9 are each independently selected from any one of biphenyl, fluorenyl, dibenzofuranyl, phenyl-substituted naphthyl, phenyl-substituted dibenzofuranyl or phenyl-substituted carbazolyl.

[0021] Furthermore, the guest of the light-emitting layer is any one or more phosphorescent green dyes represented by general formula IV:

[0022]

[0023] Wherein, R1, R2, R3, R4, R5, R6, and R7 are each independently selected from substituted or unsubstituted hydrogen, deuterium, a halogen atom, a C1-C10 alkyl group, a substituted or unsubstituted C6-C30 aryl group, or a substituted or unsubstituted C5-C30 heteroaryl group.

[0024] Furthermore, in the general formula IV, R1 is H, R2 is H, methyl, ethyl or propyl, R3 is H, methyl, ethyl, propyl, butyl, phenyl, methylphenyl or deuterium-substituted phenyl, R4, R6 and R7 are H, R5 is H, methyl, ethyl, isopropyl, isobutyl, phenyl, dimethylphenyl, diethylphenyl, dipropylphenyl or fluorophenyl, and the phosphorescent green dye is preferably the following compound:

[0025]

[0026] By applying the technical solution of the present invention, the compound C in the electron transport layer of the organic electroluminescent element is the same fragment as the compound A in the main body of the light-emitting layer, so the interface effect between the film layers is weakened, which is conducive to the rapid transmission of electrons to the light-emitting layer; in addition, since the main material of the light-emitting layer is a dual-main material, the transmission capacity of holes and electrons is further balanced, so the efficiency of the organic electroluminescent element is significantly improved by combining the synergistic effect of the above-mentioned substances. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0028] Figure 1 A schematic structural diagram of an OLED element provided according to an embodiment of the present invention is shown;

[0029] Figure 2 The current density-external quantum efficiency test graphs of the devices prepared in the device examples and device comparison examples of the present invention are shown.

[0030] The above drawings include the following reference numerals:

[0031] 1. Anode layer; 2. Hole injection layer; 3. First hole transport layer; 4. Second hole transport layer; 5. Light-emitting layer; 6. Electron transport layer; 7. Electron injection layer; 8. Cathode layer. DETAILED DESCRIPTION

[0032] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0033] As analyzed in the background technology of this application, in the prior art, although it is theoretically possible to combine fragments with electron activity and fragments with hole activity to form a bipolar host material, thereby being able to simultaneously transmit electrons and holes, balance the two, reduce exciton quenching, and thus improve luminescence efficiency. However, in practice, due to the influence of the application environment, etc., not all bipolar host materials with the above characteristics can achieve the effect of improving luminescence efficiency. Based on this, in order to improve the luminescence efficiency of an electroluminescent element, the present application provides an organic electroluminescent element, the organic electroluminescent element comprising a hole injection layer, a hole transport layer, a light-emitting layer and an electron transport layer stacked in sequence, the host of the light-emitting layer comprising compound A or compound B,

[0034]

[0035] The electron transport layer comprises compound C:

[0036]

[0037] The compound C in the electron transport layer of the organic electroluminescent element of the present application has the same fragments as the compounds A and B in the main body of the light-emitting layer, so the interface effect between the film layers is weakened, which is conducive to the rapid transmission of electrons to the light-emitting layer; in addition, since the main material of the light-emitting layer has bipolar characteristics, the transmission capacity of holes and electrons is further balanced, so the efficiency of the organic electroluminescent element is significantly improved by combining the synergistic effects of the above-mentioned substances.

[0038] In one embodiment of the present application, in order to reduce the interface effect between the hole injection layer and the hole transport layer, the hole injection layer preferably includes any one or more arylamine compounds and any one or more radialene derivatives doped therein.

[0039] The arylamine compounds have the general formula I: wherein Ar1 to Ar4 are each independently a substituted or unsubstituted C6-C 30 Aryl, substituted or unsubstituted C5-C 30 Heteroaryl, the substituents on Ar1 and Ar2, Ar3 and Ar4 may be bonded to each other to form a ring via a single bond, a substituted or unsubstituted methylene, an oxygen atom or a sulfur atom, and n is any integer from 0 to 4;

[0040] The radialene derivatives have the general formula II: Wherein Ar6 is a C6-C18 The electron withdrawing group is preferably fluorine or cyano.

[0041] The above aromatic amino compound is used as the main body of the hole injection layer to ensure a low interface effect between the hole injection layer and the hole transport layer, and at the same time, the electron-withdrawing ability of the axialene derivative is utilized to improve the injection and transport ability of holes to the light-emitting layer, thereby increasing the recombination probability of holes and electrons.

[0042] In a preferred embodiment, in the above general formula I, Ar1 to Ar4 are each independently selected from any one of substituted or unsubstituted phenyl, biphenyl, naphthyl, fluorenyl, phenyl or carbazole. Further, it is preferred that the above arylamine compound is selected from any one or more of the following compounds:

[0043]

[0044] Preferably, in the above general formula II, Ar6 is selected from a phenyl or biphenyl group containing at least one cyano group or F atom substituted. Further, the above radialene derivative can be selected from any one or more of the following compounds:

[0045]

[0046] In order to achieve a balance between the interface effect and the electron transport capability to obtain a more ideal luminescence efficiency, it is preferred that the doping mass ratio of the arylamine compound and the radium derivative is 2% to 20%, and it is further preferred that the doping mass ratio of the radium derivative is 2% to 8%.

[0047] In one embodiment of the present application, the hole transport layer comprises a first hole transport layer and a second hole transport layer stacked sequentially away from the hole injection layer, and the first hole transport layer comprises an arylamine compound. Both the first hole transport layer and the hole injection layer comprise an arylamine compound, so the interface effect between the two is weak. In order to further reduce the interface effect, it is preferred that the arylamine compounds of the two are the same.

[0048] In one embodiment, the second hole transport layer comprises any one or more triarylamine compounds represented by general formula III:

[0049]

[0050] wherein Ar7, Ar8 and Ar9 are each independently a substituted or unsubstituted C6-C 30 Aryl, substituted or unsubstituted C5-C 30 The triarylamine compound enables the second hole transport layer to assist in further hole transport on the one hand, and on the other hand, to confine electrons in the light-emitting layer to improve the light-emitting efficiency.

[0051] Further, in the above general formula III, Ar7, Ar8 and Ar9 are each independently selected from any one of biphenyl, fluorenyl, dibenzofuranyl, phenyl-substituted naphthyl, phenyl-substituted dibenzofuranyl or phenyl-substituted carbazole. Preferably, the above triarylamine compound can be selected from any one or more of the following compounds:

[0052]

[0053] In order to further improve the luminous efficiency and stability, it is preferred that the guest of the above-mentioned luminescent layer is any one or more phosphorescent green dyes represented by general formula IV:

[0054]

[0055] wherein R1, R2, R3, R4, R5, R6, and R7 are each independently selected from substituted or unsubstituted C1-C 10 Alkyl, substituted or unsubstituted C6-C 30 Aryl, or substituted or unsubstituted C5-C 30 The phosphorescent green dye having the above structure cooperates with the main material in the light-emitting layer to achieve a better electron and hole recombination effect.

[0056] Further, preferably in the general formula IV, R1 is H, R2 is H, methyl, ethyl or propyl, R3 is H, methyl, ethyl, propyl, butyl, phenyl, methylphenyl or deuterium-substituted phenyl, R4, R6 and R7 are H, R5 is H, methyl, ethyl, isopropyl, isobutyl, phenyl, dimethylphenyl, diethylphenyl, dipropylphenyl or fluorophenyl, and the above-mentioned phosphorescent green dye is preferably selected from any one or more of the following compounds:

[0057]

[0058] The beneficial effects of the present application will be further illustrated below in combination with embodiments and comparative examples.

[0059] Synthesis Example

[0060] 1. Synthesis of Compound A

[0061] 1.1 Synthesis of intermediate M1

[0062]

[0063] In a 500ml three-necked flask, add 6-bromo-2,3-dimethylquinoxaline (9.48g, 40mmol), 3-chlorophenylboronic acid (6.88g, 44mmol), sodium carbonate (8.48g, 80mmol), tetrakis-(triphenylphosphine) palladium (0.46g), toluene (200ml), ethanol (60ml) and water (40ml), and heat under reflux for 6 hours under nitrogen protection. After the reaction is completed, cool to room temperature, extract with toluene and water, filter the organic layer with silica gel pad, and vacuum evaporate the filtrate to remove the solvent to obtain a crude product, which is recrystallized with n-hexane to obtain 8.38g of intermediate M1, which is an off-white solid powder with a yield of 78% and a purity of 99.3%.

[0064] 1.2 Synthesis of Compound A

[0065]

[0066] In a 250ml three-necked flask, add intermediate M1 (8.06g, 30mmol), 2-[3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]-4,6-diphenyl-1,3,5-triazine (13.06g, 30mmol), potassium carbonate (12.44g, 90mmol), palladium acetate (0.13g), X-Phos (0.57g), tetrahydrofuran (130ml) and water (45ml), and heat under reflux for 8 hours under nitrogen protection. After the reaction is completed, cool to room temperature and directly filter by suction to obtain an off-white filter cake. The filter cake is washed with ethanol / water / ethanol to obtain a crude product. The crude product is dissolved in toluene for decolorization and recrystallization to obtain 11.7g of compound A, which is a white solid powder with a yield of 72% and a purity of 99.3%. Compound A was purified twice by vacuum sublimation with a purity of 99.91%.

[0067] The structural characterization results of compound A are as follows:

[0068] 1H NMR (400MHz, CDCl3) δ8.97(t,J=1.6Hz,1H),8.80–8.67(m,5H),8.26(d,J=1.8Hz,1H),8.07–7.94(m, 3H),7.82(ddd,J=10.2,5.7,4.2Hz,1H),7.77–7.68(m,2H),7.64–7.48(m,8H),2.70(d,J=1.1Hz,6H).

[0069] 2. Synthesis of Compound B

[0070]

[0071] In a 2000ml three-necked flask, add m-bromoiodobenzene (88.7g, 0.31mol), dibenzofuran-4-boric acid (70g, 0.33mol), potassium carbonate (86.7g, 0.62mol), tetrakis-(triphenylphosphine) palladium (1.8g), toluene (480ml), ethanol (70ml) and water (240ml), and heat under reflux for 6 hours under nitrogen protection. After the reaction is completed, cool to room temperature, extract with toluene and water, filter the organic layer with silica gel pad, and vacuum evaporate the filtrate to remove the solvent to obtain 100g of oily substance, which is recrystallized with n-hexane to obtain 60g of intermediate M2, which is an off-white solid powder with a yield of 60% and a purity of 98.4%.

[0072] In a 2000ml three-necked flask, add intermediate M2 (50g, 0.15mol), 4-chlorophenylboronic acid (25.4g, 0.16mol), potassium carbonate (41.5g, 0.3mol), bis(triphenylphosphine)palladium dichloride (0.55g), toluene (500ml), ethanol (125ml) and water (250ml), and heat under reflux for 6 hours under nitrogen protection. After the reaction is completed, cool to room temperature, extract with toluene and water, filter the organic layer with silica gel pad, and vacuum evaporate the filtrate to remove the solvent to obtain 55g of oily substance, which is recrystallized with n-hexane to obtain 43g of intermediate M3, which is an off-white solid powder with a yield of 80% and a purity of 97.7%.

[0073]

[0074] Add 300ml toluene and sodium tert-butoxide (12g, 175mmol) to a 500ml three-necked flask, reflux for half an hour under nitrogen; then cool to 80 degrees, add intermediate M3 (30g, 84.5mmol), di(4-biphenyl)amine (27.2g, 84.5mmol), tris[dibenzylideneacetone]dipalladium (0.5g) / tri-tert-butylphosphine (1.5g) in sequence, stir for 15min and turn on the heating, heat to reflux for 4 hours. After the reaction is completed, turn off the heating, stir to about 60℃, wash with water twice, separate the liquids; filter the organic layer with silica gel pad, vacuum evaporate the solvent from the filtrate, and obtain 65g of oily substance, which is recrystallized three times with toluene / ethanol to obtain 37.5g of compound B, which is an off-white solid powder with a yield of 69.4% and a purity of 99.1%. Compound B is purified by vacuum sublimation twice with a purity of 99.84%.

[0075] The structural characterization results of compound B are as follows:

[0076] 1H NMR (400MHz, DMSO) δ8.22–8.07(m,3H),7.83(t,J=10.0Hz,1H),7.80–7.67(m,5H),7.66–7.55(m,9 H),7.55–7.45(m,2H),7.41(t,J=7.6Hz,5H),7.30(ddd,J=6.7,4.5,1.1Hz,2H),7.22–7.09(m,6H).

[0077] 3. Synthesis of Compound C

[0078]

[0079] In a 500mL three-necked flask, add 4-bromo-o-phenylenediamine (20g, 0.106mol), 2,3-butanedione (9.66g, 0.112mol) and toluene (200ml), and heat to reflux for 3 hours. After the reaction is completed, cool to room temperature, filter with silica gel pad, and use vacuum to evaporate the solvent in the filtrate to obtain a crude product. The crude product is dissolved and decolorized with n-hexane and recrystallized to obtain 18.0g of intermediate M3, which is an off-white solid powder with a yield of 71%. The purity is 99.95%.

[0080] In a three-necked flask, add intermediate M3 (10g, 0.042mol), 2,4-diphenyl-6-[4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]-1,3,5-triazine (18.36g, 0.042mol), potassium carbonate (11.65g, 0.084mol), tetrakis-(triphenylphosphine)palladium (0.49g), toluene (150ml), ethanol (45ml) and water (30ml), and heat under reflux for 8 hours under nitrogen protection. After the reaction is completed, cool to room temperature, extract with toluene and water, filter the organic layer with silica gel pad, and vacuum evaporate the solvent in the filtrate to obtain a crude product, which is dissolved in toluene for decolorization and recrystallization to obtain 13.3g of compound C, which is a white solid powder with a yield of 68% and a purity of 99.93%. Compound C was purified twice by vacuum sublimation with a purity of 99.96%.

[0081] The structural characterization results of compound C are as follows:

[0082] 1H NMR (400MHz, CDCl3) δ8.89 (d, J = 8Hz, 2H), 8.80 (d, J = 7.2Hz, 4H), 8.32 (s, 1H), 8. 06(dd,J=21.4,8.6Hz,2H),7.95(d,J=8Hz,2H),7.65-7.58(m,6H),2.77(s,6H).

[0083] 5. Synthesis of Compound ET1

[0084] 5.1 Synthesis of intermediate N

[0085]

[0086] 1-Bromo-2-iodobenzene (70.7 g, 250 mmol), phenylacetylene (25.5 g, 250 mmol) and 350 mL of triethylamine were added to a three-necked flask. After nitrogen protection for 10 min, CuI (0.48 g, 2.5 mmol) and 0.7 g of Pd(PPh3)2Cl2 were added. The reaction was stirred at room temperature for 0.5 h and then stopped. A large amount of solid was obtained by filtration. The solid was washed with triethylamine and concentrated below 35°C to remove triethylamine. 100 mL of dichloromethane was added to dissolve the solid. The solid was washed with dilute hydrochloric acid solution until it was nearly neutral. Then, the solid was concentrated and dried to obtain 46.8 g of yellow oil N1 with a yield of 96%.

[0087] N1 (15.4 g, 60 mmol), 4-chlorophenylboronic acid (10.3 g, 66 mmol), potassium carbonate (16.6 g, 120 mmol) were added to a three-necked flask, and then 90 mL of toluene, 45 mL of THF and 45 mL of deionized water were added. After blowing nitrogen for 10 min, 0.31 g of Pd(PPh3)2Cl2 was added and heated to reflux. After reacting for 5 h, it was cooled, separated, washed with water until neutral, concentrated by rotary evaporation, and then ethanolamine phosphate was added to dissolve the solution. The solution was passed through a silica gel column, rinsed with ethanolamine phosphate, and concentrated by rotary evaporation to obtain 18.2 g of yellow oily liquid N2 with a yield of 71%.

[0088] N2 (14.5 g, 60 mmol) and 350 mL of dichloromethane were added to a three-necked flask, and the temperature was cooled to 0°C in an ice bath. 11.6 g of iodine chloride was dissolved in 90 mL of dichloromethane and then added dropwise to the three-necked flask (dropwise addition for 0.5 h). The reaction was stirred for 0.5 h, and sodium sulfite solution was added dropwise to quench the reaction until neutral. The reaction was separated, dried, and concentrated by rotary evaporation. The mixture was passed through a silica gel column with phosphoethanolamine, concentrated by rotary evaporation, and dried to obtain 15.6 g of light yellow-green solid N3 with a yield of 54%.

[0089] N3 (17.3g, 35mmol), 3-pyridine boronic acid pinacol ester (10.9g, 53mmol), potassium carbonate (14.5g, 105mmol) were added to a three-necked flask, and then 105mL toluene, 35mL ethanol and 35mL deionized water were added. After nitrogen protection for 10min, 0.87g Pd(PPh3)2Cl2 was added, heated to reflux, reacted for 6h and then cooled, separated, washed with water, precipitated solid, filtered, washed with water to neutrality, washed with ethanol, and dried. 200mL toluene was hot-dissolved, passed through a silica gel column while hot, rinsed with dichloromethane, concentrated by rotary evaporation to about 50mL, cooled and crystallized, and dried to obtain 10.7g light yellow solid N4 with a yield of 38%.

[0090] Intermediate N4 (18.3g, 50mmol), biboric acid pinacol ester (15.2g, 60mmol), potassium acetate (14.7g, 150mmol) and 180mL dioxane were placed in a 500ml round-bottom flask and stirred while heating. Pd(dba)2 (0.57g, 1mmol) and tricyclohexylphosphine (0.56g, 2mmol) were added under reflux and stirred for 6 hours. After cooling to room temperature, 50ml water was added and stirred. The organic layer was separated and dried over anhydrous magnesium sulfate, then concentrated by rotary evaporation, and purified by silica gel column to obtain 21.8g intermediate N with a yield of 65%.

[0091]

[0092] The intermediate N (7.3 g, 20 mmol), (3-(4,6-diphenyl-1,3,5-triazine-2-)phenyl)boric acid (7.4 g, 21 mmol), potassium carbonate (8.3 g, 60 mmol) were added to a three-necked flask, and then 70 mL of toluene, 35 mL of THF and 35 mL of deionized water were added. After blowing nitrogen for 10 min, 0.22 g of Pd(OAc)2 and 0.44 g of X-phos were added, and the mixture was heated to 78 ° C for 1 h to precipitate a large amount of solids. The solids were filtered while hot, washed with water until nearly neutral, washed with ethanol and dried, and then refluxed with 150 mL of dichloromethane to dissolve the solids, passed through silica gel, rinsed with dichloromethane, concentrated to about 50 mL, stirred at room temperature for crystallization, filtered, and rinsed with dichloromethane. The filter cake obtained was recrystallized with 150 mL of dichloromethane to obtain 3.4 g of white solid product 2-9 with a yield of 23%. The product ET1 was further purified twice by vacuum sublimation with a purity of 99.96% and MS [M+H] + = 638.16.

[0093] The physicochemical properties of compound A, compound B and compound C were characterized. The absorption wavelength of the material was measured using a Shimadzu UV-2600 ultraviolet spectrophotometer. The solvent was THF and the material concentration was about 10 ppm. g =1240 / UVonset ; Vertex.C.EIS electrochemical workstation was used, the working electrode was a glassy carbon electrode, the reference electrode was a saturated calomel electrode-saturated potassium chloride solution, the counter electrode was a platinum wire electrode, and the solvent was 50% dichloromethane + 50% acetonitrile (the material concentration was about 5×10 -4 mol / L), the electrolyte is 0.1M tetrabutylammonium hexafluorophosphate, the standard is ferrocene, and the measurement starts after nitrogen is passed for 10 minutes at room temperature. The scanning condition is rate = 0.1V / s, and the redox potential of the material is measured and finally converted into LUMO and HOMO energy poles. The characterization results are shown in Table 1.

[0094] Table 1

[0095]

[0096]

[0097] 3. Preparation of organic electroluminescent elements

[0098] The actual effect of the organic electroluminescent device prepared by the material combination adopted in the present invention is described in detail below through specific examples and comparative examples.

[0099] Device Example 1

[0100] Reference Figure 1 The structure shown in the figure is used to manufacture the OLED element using a Sunic sp1710 evaporation machine. The specific steps are as follows: a glass substrate (Corning glass 40mm*40mm*0.7mm) coated with ITO (indium tin oxide, as the anode layer 1) with a thickness of 135nm is ultrasonically cleaned with isopropyl alcohol and pure water for 5 minutes respectively, and then cleaned with ultraviolet ozone, and then the glass substrate is transferred to a vacuum deposition chamber; HT1 and HD mixed (HD doping mass ratio is 4%) are vacuum (about 10 -7 Torr) thermal deposition of 20nm thickness to form a hole injection layer 2; then vacuum depositing 90nm thickness HT1 on the hole injection layer as the first hole transport layer 3; then vacuum depositing 10nm thickness HT2 to form a second hole transport layer 4; then vacuum depositing 30nm of compound A and compound B (mass fraction 48%:48%) doped with 4% phosphorescent green guest GD1; then vacuum depositing 50% LiQ (8-hydroxyquinoline lithium) doped ET1 to form an electron transport layer 6 with a thickness of 30nm; finally, depositing 2nm thick metal ytterbium (Yb, as an electron injection layer 7) and a magnesium-silver alloy doped with a ratio of 10:1 in sequence to form a cathode layer 8; finally, the component is transferred from the deposition chamber to a glove box and then encapsulated with a UV-curable epoxy resin and a glass cover containing a desiccant.

[0101] In the above manufacturing steps, the deposition rates of the organic material, metal ytterbium, and metal Mg were maintained at 0.1 nm / s, 0.05 nm / s, and 0.2 nm / s, respectively.

[0102]

[0103]

[0104] The structure of the element is represented as: ITO (135nm) / HT1:4%HD (20nm) / HT1 (90nm) / HT2 (10nm) / Compound A: Compound B: GD1 (48%:48%:4%) / Compound C: LiQ (5:5, 30nm) / Yb (2nm) / Mg:Ag (10:1, 150nm).

[0105] Device Example 2

[0106] The experiment was conducted in the same manner as in Example 1, except that GH1 and GH2 were used as dual hosts (mass fraction 48%:48%).

[0107] The structure of the device is represented as: ITO (135nm) / HT1:4%HD (20nm) / HT1 (90nm) / HT2 (10nm) / GH1:GH2:GD1 (48%:48%:4%) / Compound C:LiQ (5:5, 30nm) / Yb (2nm) / Mg:Ag (10:1, 150nm).

[0108] Device Comparison Example 1

[0109] The experiment was conducted in the same manner as in Example 1, except that ET1 was used instead of Compound C as the electron transport layer.

[0110] The structure of the element is represented as: ITO (135nm) / HT1:4%HD (20nm) / HT1 (90nm) / HT2 (10nm) / Compound A: Compound B: GD1 (48%:48%:4%) / ET1: LiQ (5:5, 30nm) / Yb (2nm) / Mg: Ag (10:1, 150nm).

[0111] Device Comparison Example 2

[0112] The experiment was conducted in the same manner as in Example 2, except that ET1 was used instead of Compound C as the electron transport layer.

[0113] The component structure is represented as: ITO (135nm) / HT1:4%HD (20nm) / HT1 (90nm) / HT2 (10nm) / GH1:GH2:GD1 (48%:48%:4%) / ET1:LiQ (5:5, 30nm) / Yb (2nm) / Mg:Ag (10:1, 150nm).

[0114] Device Comparison Example 3

[0115] The experiment was conducted in the same manner as in Example 1, except that Compound C and Compound B were used as dual hosts (mass fraction 48%:48%).

[0116] The component structure is represented as:

[0117] ITO (135nm) / HT1:4%HD (20nm) / HT1 (90nm) / HT2 (10nm) / Compound C: Compound B: GD1 (48%:48%:4%) / Compound C: LiQ (5:5, 30nm) / Yb (2nm) / Mg:Ag (10:1, 150nm).

[0118] The brightness, luminous efficiency, and EQE (external quantum efficiency) of the components were tested by Suzhou Fushida FS-100GA4. All measurements were completed in the room temperature atmosphere. 2 The specific performance data of the working voltage (V), current efficiency (CE), external quantum efficiency (EQE) and color coordinates (CIEx, CIEy) under current density are shown in Table 2. The trend of external quantum efficiency changing with current density is shown in Figure 2 .

[0119] Table 2

[0120]

[0121] It can be seen from the table that the above embodiments of the present invention achieve the following technical effects:

[0122] It can be seen from the comparison between device example 2 and device comparative example 2 that compound C is more suitable as an electron transport material than ET1, and the device efficiency is higher; it can be seen from the comparison between device example 1 and device comparative example 3 that compound A is more suitable than compound C as an electron-type hole host to be used in combination with compound B, the energy levels are more matched, the device efficiency is significantly improved, and the light color is greener; it can be seen from the comparison between device example 1 and device example 2 that compound A and compound B are more efficient when used as a dual host, mainly because compound A and compound B contain two identical fragments, which leads to a weakening of the film interface effect of the light-emitting layer and the electron transport layer, which is conducive to the rapid transmission of electrons to the light-emitting layer; since the main material of the light-emitting layer is composed of an electron-type main material A and a hole-type main material B, the transmission capacity of holes and electrons is further balanced, so the synergistic effect of the above-mentioned substances is combined to significantly improve the efficiency of the organic electroluminescent element.

[0123] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An organic electroluminescent element, comprising a hole injection layer, a hole transport layer, a light-emitting layer and an electron transport layer stacked in sequence, characterized in that: The main body of the light-emitting layer is composed of compound A and compound B: The electron transport layer comprises compound C:

2. The organic electroluminescent element according to claim 1, characterized in that: The hole injection layer comprises any one or more arylamine compounds and any one or more radialene derivatives doped therein, The arylamine compound has the general formula I: wherein Ar1 to Ar4 are each independently a substituted or unsubstituted C6-C 30 Aryl, substituted or unsubstituted C5-C 30 Heteroaryl, the substituents on both Ar1 and Ar2, and both Ar3 and Ar4 may be combined to form a ring via a single bond, a substituted or unsubstituted methylene, an oxygen atom or a sulfur atom, and n is any integer from 0 to 4; The radialene derivative has the general formula II: Wherein Ar6 is a C6-C 18 The aromatic group.

3. The organic electroluminescent element according to claim 2, characterized in that: The electron withdrawing group is fluorine or cyano.

4. The organic electroluminescent element according to claim 2, characterized in that: In the general formula I, Ar1 to Ar4 are each independently selected from any one of a substituted or unsubstituted phenyl group, a biphenyl group, a naphthyl group, a fluorenyl group or a carbazole group.

5. The organic electroluminescent element according to claim 2, characterized in that: In the general formula II, Ar6 is selected from a phenyl or biphenyl group containing at least one cyano group or F atom substituted.

6. The organic electroluminescent element according to any one of claims 2 to 5, characterized in that: Among the plurality of aromatic amine compounds and the radialene derivative, the doping mass ratio of the radialene derivative is 2% to 20%.

7. The organic electroluminescent element according to any one of claims 2 to 4, characterized in that: The hole transport layer includes a first hole transport layer and a second hole transport layer which are sequentially stacked away from the hole injection layer, and the first hole transport layer includes any one or more of the arylamine compounds.

8. The organic electroluminescent element according to claim 7, characterized in that: The second hole transport layer includes any one or more triarylamine compounds represented by general formula III: wherein Ar7, Ar8 and Ar9 are each independently a substituted or unsubstituted C6-C 30 Aryl, substituted or unsubstituted C5-C 30 Any of the heteroaryl groups.

9. The organic electroluminescent element according to claim 6, characterized in that: In the general formula III, Ar7, Ar8 and Ar9 are each independently selected from any one of biphenyl, fluorenyl, dibenzofuranyl, phenyl-substituted naphthyl, phenyl-substituted dibenzofuranyl or phenyl-substituted carbazolyl.

10. The organic electroluminescent element according to claim 1, characterized in that: The guest of the light-emitting layer is any one or more phosphorescent green dyes represented by general formula IV: wherein R1, R2, R3, R4, R5, R6, and R7 are each independently selected from hydrogen, deuterium, a halogen atom, a substituted or unsubstituted C1-C 10 Alkyl, substituted or unsubstituted C6-C 30 Aryl, or substituted or unsubstituted C5-C 30 Heteroaryl.

11. The organic electroluminescent element according to claim 10, characterized in that: In the general formula IV, R1 is H, R2 is H, methyl, ethyl or propyl, R3 is H, methyl, ethyl, propyl, butyl, phenyl, methylphenyl or deuterium-substituted phenyl, R4, R6 and R7 are H, and R5 is H, methyl, ethyl, isopropyl, isobutyl, phenyl, dimethylphenyl, diethylphenyl, dipropylphenyl or fluorophenyl.

12. The organic electroluminescent element according to claim 11, characterized in that: The phosphorescent green dye is the following compound:

Images