Organic electroluminescent element

Abstract

The present invention provides an organic electroluminescent element. The organic electroluminescent element includes an anode, a cathode, a hole injection layer, a hole transport layer, a light-emitting layer, and an electron transport layer. The electron transport layer includes a bipyridine compound and a quinoxaline compound. The bipyridine compound has a chemical formula A, and the quinoxaline compound is any one of the compounds represented by chemical formula B1 and chemical formula B2. The bipyridine compound having the chemical formula A helps to reduce the driving voltage of the organic electroluminescent device, and the quinoxaline compound having the chemical formula B1 or chemical formula B2 is beneficial to improving the efficiency and lifespan of the organic electroluminescent device. By mixing the above-mentioned bipyridine compound and quinoxaline compound, the advantages of both are comprehensively utilized, and the disadvantages of both to the organic electroluminescent device are alleviated, thereby obtaining an organic electroluminescent device with both high efficiency, high lifespan, and low driving voltage.

Description

Technical Field

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

[0002] Due to its characteristics such as being thin, light, wide viewing angle, high contrast, low power consumption, high response speed, full-color display, and flexibility, organic electroluminescent elements (OLEDs) have currently been applied in fields such as smartphones, tablet computers, and vehicles, and are expanding towards large-size application fields such as televisions.

[0003] For an organic light-emitting diode to achieve a full-color display, the performance of the blue light device is crucial. An organic electroluminescent element generally includes multiple film layers such as a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, a hole blocking layer, an electron transport layer, and an electron injection layer. The glass transition temperature of the film layer, the energy level matching between film layers, the film formation quality and stability of the film layer, etc. will all affect the performance of the element. The performance of the electron transport layer material determines the electron transport efficiency, and further affects the combination efficiency of electrons and holes in the light-emitting layer. Therefore, the electron transport layer is a key film layer that affects the performance of the device. However, in actual applications, due to the limitations of the electron transport layer, it is difficult for organic electroluminescent elements to have both high efficiency, high lifespan, and low driving voltage. Summary of the Invention

[0004] The main object of the present invention is to provide an organic electroluminescent element to solve the problem in the prior art that it is difficult for organic electroluminescent devices to have both high efficiency, high lifespan, and low driving voltage.

[0005] To achieve the above object, according to one aspect of the present invention, there is provided an organic electroluminescent element, which includes an anode, a cathode, a hole injection layer, a hole transport layer, a light-emitting layer, and an electron transport layer. The electron transport layer includes a bipyridine compound and a quinoxaline compound. The bipyridine compound has chemical formula A, and the quinoxaline compound is any one of the compounds represented by chemical formula B1 and chemical formula B2.

[0006]

[0007]

[0008] Further, the mass ratio of the above bipyridine compound to the quinoxaline compound is 3 - 7:7 - 3.

[0009] Further, the above hole injection layer includes one or more arylamine compounds and one or more [n]cumulene derivatives, and the [n]cumulene derivatives are doped in the arylamine compounds.

[0010] Among them, the arylamine compound has general formula I: Ar1 、Ar 2 、Ar 3 、Ar 4 are each independently selected from substituted or unsubstituted aryl groups having C 6 to C 30 , substituted or unsubstituted heteroaryl groups having C 5 to C 30 , and any one of them is preferably Ar 1 and Ar 2 , Ar 3 and Ar 4 are each independently connected by any one of a single bond, a substituted or unsubstituted methylene group, an oxygen atom or a sulfur atom;

[0011] The [n]radialene derivative has the general formula II: wherein, Ar 5 is an aryl group having C 6 to C 18 substituted with an electron-withdrawing group, and preferably the electron-withdrawing group is fluorine or cyano.

[0012] Furthermore, in the above general formula I, Ar 1 , Ar 2 , Ar 3 , Ar 4 are each independently selected from substituted or unsubstituted aryl groups having C 6 to C 12 , substituted or unsubstituted heteroaryl groups having C 10 to C 15 , and further preferably, Ar 1 , Ar 2 , Ar 3 , Ar 4 are each independently selected from any one of substituted or unsubstituted phenyl, biphenyl, naphthyl, fluorenyl, carbazolyl.

[0013] Furthermore, in the above general formula II, Ar 5 is an aryl group having C 6 to C 12 substituted with an electron-withdrawing group, and further preferably, Ar 5 is a mono-substituted or multi-substituted phenyl or a mono-substituted or multi-substituted biphenyl, and each substituent is independently a cyano group or an F atom.

[0014] Furthermore, the mass ratio of the above arylamine compound to the [n]radialene derivative is 100:2 to 20, and further preferably 100:2 to 8.

[0015] Further, in a direction away from the above-mentioned hole injection layer, the hole transport layer includes a first hole transport layer and a second hole transport layer stacked in sequence. Preferably, the first hole transport layer includes any one or more arylamine compounds.

[0016] Further, the above-mentioned light-emitting layer is composed of a blend of at least one host matrix and at least one guest dopant.

[0017] Further, the above-mentioned host matrix is an anthracene compound represented by the general formula BH:

[0018]

[0019] Wherein, R 1 and R 2 are the same or different from each other, R 1 and R 2 each independently selected from hydrogen, substituted or unsubstituted C 1 ~C 6 alkyl, C 1 ~C 6 alkoxy, C 6 ~C 30 aryl, C 6 ~C 30 heteroaryl, any one or more of them; Ar 6 , Ar 7 each independently is an aryl selected from C 6 ~C 30 or a heteroaryl selected from C 6 ~C 30 ; a, b, c are each independently an integer from 1 to 4.

[0020] Further, the above-mentioned guest dopant is a fluorescent dye represented by the general formula BD,

[0021]

[0022] Wherein, R 3 to R 10 each independently selected from a hydrogen atom, a halogen atom, substituted or unsubstituted C 1 ~C 4 alkyl, substituted or unsubstituted C 3 ~C 10 cycloalkyl, substituted or unsubstituted silyl, cyano, substituted or unsubstituted C 6 ~C 30 aryl, any one of them; Ar 8 to Ar 11 each independently selected from substituted or unsubstituted C 6 ~C 30 aryl, substituted or unsubstituted C5 ~C 30 any one of the heteroaryl groups.

[0023] Applying the technical solution of the present invention, the bipyridine compound having the chemical formula A helps to reduce the driving voltage of the organic electroluminescent device, and the quinoxaline compound having the chemical formula B1 or the chemical formula B2 is beneficial to improving the efficiency and lifespan of the organic electroluminescent device. By mixing and using the above-mentioned bipyridine compound and quinoxaline compound, the advantages of both are comprehensively utilized, and the disadvantages of both to the organic electroluminescent device are alleviated, so as to obtain an organic electroluminescent device with high efficiency, long lifespan and low driving voltage. Description of the Drawings

[0024] The specification drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0025] Figure 1 shows a structural diagram of an organic electroluminescent device provided in Embodiment 1 of the present invention.

[0026] Among them, the above-mentioned drawings include the following reference numerals:

[0027] 1, anode; 2, hole injection layer; 3, hole transport layer; 4, light-emitting layer; 5, electron transport layer; 6, cathode. Detailed Embodiments

[0028] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the drawings and in combination with the embodiments.

[0029] As analyzed in the background art, there is a problem in the prior art that it is difficult for an organic electroluminescent device to have high efficiency, long lifespan and low driving voltage at the same time. To solve this problem, the present invention provides an organic electroluminescent element.

[0030] In a typical embodiment of this application, an organic electroluminescent element is provided. As Figure 1 shown, the organic electroluminescent element includes an anode 1, a cathode 6, a hole injection layer 2, a hole transport layer 3, a light-emitting layer 4 and an electron transport layer 5. The electron transport layer 5 includes a bipyridine compound and a quinoxaline compound. The bipyridine compound has the chemical formula A, and the quinoxaline compound is any one of the compounds represented by the chemical formula B1 and the chemical formula B2.

[0031]

[0032] The bipyridine compound with chemical formula A helps to reduce the driving voltage of the organic electroluminescent device, and the quinoxaline compound with chemical formula B1 or chemical formula B2 is beneficial to improving the efficiency and lifespan of the organic electroluminescent device. By using the above-mentioned bipyridine compound and quinoxaline compound in combination, the advantages of both are comprehensively utilized, and the disadvantages of both to the organic electroluminescent device are alleviated, thereby obtaining an organic electroluminescent device with high efficiency, long lifespan and low driving voltage.

[0033] To maximize the synergistic effect of the above-mentioned bipyridine compound and quinoxaline compound and obtain an organic electroluminescent device with higher efficiency, longer lifespan and lower driving voltage, the mass ratio of the above-mentioned bipyridine compound and quinoxaline compound is preferably 3 - 7:7 - 3.

[0034] In one embodiment of the present application, the hole injection layer includes one or more arylamine compounds and one or more [n]radialene derivatives, and the [n]radialene derivative is doped in the arylamine compound.

[0035] Among them, the arylamine compound has the general formula I: Ar 1 、Ar 2 、Ar 3 、Ar 4 are each independently selected from any one of substituted or unsubstituted aryl groups of C 6 ~C 30 and substituted or unsubstituted heteroaryl groups of C 5 ~C 30 Preferably, between Ar 1 and Ar 2 , between Ar 3 and Ar 4 are each independently connected by any one of a single bond, substituted or unsubstituted methylene, oxygen atom or sulfur atom;

[0036] The [n]radialene derivative has the general formula II: Among them, Ar 5 is an aryl group of C 6 ~C 18 substituted with an electron-withdrawing group, and preferably the electron-withdrawing group is fluorine or cyano.

[0037] The above arylamine compound as the main body of the hole injection layer ensures a low interface effect between the hole injection layer and the hole transport layer, and at the same time, the incorporation of the [n]radialene derivative utilizes its electron-withdrawing ability to improve the injection and transport ability of holes to the light-emitting layer, and increases the recombination probability of holes and electrons.

[0038] To further improve the synergistic effect of the arylamine compound and the [n]radialene derivative, preferably in the above general formula I, Ar 1 、Ar2 、Ar 3 、Ar 4 are each independently selected from a substituted or unsubstituted C 6 -C 12 aryl, a substituted or unsubstituted C 10 -C 15 heteroaryl, and further preferably Ar 1 、Ar 2 、Ar 3 、Ar 4 are each independently selected from any one of a substituted or unsubstituted phenyl, biphenyl, naphthyl, fluorenyl, carbazolyl. Further preferably, the above arylamine compound is selected from any one or more of the following compounds:

[0039]

[0040]

[0041] To further ensure a low interface effect between the hole injection layer and the hole transport layer, preferably in the above general formula II, the above Ar 5 is a C containing an electron-withdrawing group-substituted 6 -C 12 aryl, and further preferably Ar 5 is a mono-substituted or multi-substituted phenyl or a mono-substituted or multi-substituted biphenyl, and each substituent is independently a cyano group or an F atom. Further, the above annulene derivative can be selected from any one or more of the following compounds:

[0042]

[0043] To achieve a balance between the interface effect and the electron transport ability to obtain a more ideal luminescence efficiency, preferably in the above arylamine compound and annulene derivative, the mass ratio of the arylamine compound to the annulene derivative is 100:2 to 20, and further preferably 100:2 to 8.

[0044] In an embodiment of the present application, in the direction away from the hole injection layer, the hole transport layer includes a first hole transport layer and a second hole transport layer stacked in sequence, and preferably the first hole transport layer includes any one or more arylamine compounds.

[0045] Both the above first hole transport layer and the hole injection layer have arylamine compounds, so the interface effect between the two is weak. To further reduce the interface effect, it is preferred that the arylamine compounds of the two are the same.

[0046] To ensure excellent luminescence performance of the light-emitting layer, preferably the above light-emitting layer is composed of a blend of at least one host matrix and at least one guest dopant.

[0047] In an embodiment of the present application, the above-mentioned host matrix is an anthracene compound represented by the general formula BH:

[0048]

[0049] Wherein, R 1 and R 2 are the same as or different from each other, R 1 and R 2 each independently selected from hydrogen, substituted or unsubstituted C 1 to C 6 alkyl, C 1 to C 6 alkoxy, C 6 to C 30 aryl, C 6 to C 30 heteroaryl; Ar 6 , Ar 7 each independently is an aryl selected from C 6 to C 30 or a heteroaryl selected from C 6 to C 30 ; a, b, and c are each independently an integer from 1 to 4. Further, preferably, the above-mentioned anthracene compound can be selected from any one of the following compounds:

[0050]

[0051]

[0052] In order to further improve the luminescence efficiency and stability, preferably, the above-mentioned guest dopant is a fluorescent dye represented by the general formula BD,

[0053]

[0054] Wherein, R 3 to R 10 each independently selected from a hydrogen atom, a halogen atom, substituted or unsubstituted C 1 to C 4 alkyl, substituted or unsubstituted C 3 to C 10 cycloalkyl, substituted or unsubstituted silyl, cyano, substituted or unsubstituted C 6 to C 30 aryl; Ar 8 to Ar 11 each independently selected from substituted or unsubstituted C 6 to C 30 aryl, substituted or unsubstituted C 5 to C30 Any one of the heteroaryl groups. Further, the above fluorescent dye can be selected from any one of the following compounds:

[0055]

[0056]

[0057] The beneficial effects of the present application will be described below in conjunction with specific examples and comparative examples.

[0058] 1. Synthesis of Compound A

[0059] 1.1 Synthesis of Intermediate M1

[0060]

[0061] 2,4,6-Trichloropyridine (37.24 g, 204.6 mmol), phenylboronic acid (49 g, 402 mmol), 400 mL of tetrahydrofuran, sodium carbonate (85 g, 800 mmol), and 400 mL of water were added to a 1000 mL round-bottom flask. Under nitrogen protection, the mixture was stirred and heated to 40 °C, and 2.9 g of the catalyst PdCl 2 (PPh 3 ) 2 was added. The temperature was further raised to reflux and the reaction was stopped after 3 h. After cooling, the layers were separated. The organic phase was evaporated to dryness, 500 mL of toluene was added, and the mixture was heated through a short silica gel column for decolorization. Then, toluene was evaporated under reduced pressure. 200 mL of ethanol was added, and the mixture was heated to 80 °C until completely dissolved. Then, the mixture was stirred and cooled to precipitate a solid, which was filtered and dried to obtain 39.7 g of a white solid compound M1 with a yield of 73%. After the intermediate M1 was recrystallized once by the same method, the purity was 99.3%. The characterization results of the 1H NMR spectrum of this compound M1 were as follows: 1 1H NMR (400 MHz, CDCl 3 ) δ 8.10 (dt, J = 8.4, 1.9 Hz, 4H), 7.66 (s, 2H), 7.55–7.35 (m, 6H).

[0062] 1.2 Synthesis of Intermediate M2

[0063]

[0064] 2,4,6-Trichloropyridine (18.24 g, 100 mmol), 2-naphthaleneboronic acid (36.12 g, 210 mmol), 300 mL of toluene, sodium carbonate (31.8 g, 300 mmol), 150 mL of water, and 100 mL of ethanol were added to a 1000 mL round-bottom flask. Under nitrogen protection, the mixture was stirred and heated to 50 °C, and 3.4 g of the catalyst Pd(PPh 3 )4 , continue to heat up to reflux for 8 h and then stop the reaction. After cooling, filter and separate the liquid. Wash the organic phase with 100 mL of water twice, filter, combine the organic phases, add 500 mL of toluene, heat it to pass through a short silica gel column for decolorization, then rotary evaporate the toluene to 100 mL, stir and cool to precipitate solids, filter and dry to obtain 28.5 g of white solid compound M2 with a yield of 78%. After the intermediate M2 is recrystallized twice by the same method, the purity is 99.6%. The characterization results of the 1H NMR spectrum of this compound M2 are as follows: 1 H NMR(400MHz,CDCl 3 )δ8.62(d,J=1.1Hz,2H),8.33(dd,J=8.6,1.8Hz,2H),8.06–7.96(m,4H),7.95–7.88(m,2H),7.86(s,2H),7.63–7.49(m,4H).

[0065] 1.3 Synthesis of intermediate M3

[0066]

[0067] Add intermediate M1 (27.5 g, 103.4 mmol), bis(pinacolato)diboron (28.8 g, 113.8 mmol), 500 mL of toluene, and 13.2 g of potassium acetate into a 1000 mL round-bottom flask. Stir and heat up to 50 °C under nitrogen protection, add 0.59 g of catalyst Pd(dba) 2 and 0.95 g of 2-di-tert-butylphosphino-2',4',6'-triisopropylbiphenyl, continue to heat up to reflux for 6 h and then stop the reaction. Decolorize the organic phase by passing it through a short silica gel column while it is hot, then rotary evaporate the toluene. After cooling, add 50 mL of dichloromethane, heat to 40 °C until completely dissolved, then add 300 mL of n-hexane, stir and cool to precipitate solids, filter and dry to obtain 29.2 g of white solid compound M3 with a yield of 79% and a purity of 99.1%. The characterization results of the 1H NMR spectrum of this compound M3 are as follows: 1 H NMR(400MHz,CDCl 3 )δ8.41–8.14(m,4H),8.07(d,J=3.0Hz,2H),7.64–7.32(m,6H),1.39(s,12H).

[0068] 1.4 Synthesis of compound A

[0069]

[0070] Intermediate M2 (7.32 g, 20 mmol), intermediate M3 (7.5 g, 21 mmol), 80 mL of tetrahydrofuran, potassium carbonate (5.53 g, 40 mmol), and 20 mL of water were added to a 250 mL round-bottom flask. Under nitrogen protection, the mixture was stirred and heated to 40 °C. 45 mg of catalyst Pd(OAc) 2 , 0.19 g of 2-di-tert-butylphosphino-2',4',6'-triisopropylbiphenyl were added. The temperature was further raised to reflux and the reaction was carried out for 6 h, then the reaction was stopped. After cooling, filtration and liquid separation were carried out. The organic phase was dried by evaporation and combined with the filter residue. 500 mL of toluene was added and heated to pass through a short silica gel column for decolorization. Then, toluene was distilled off until a solid precipitated. The mixture was stirred and cooled to room temperature, filtered and dried to obtain a white solid compound A. Compound A was recrystallized twice by the same method and the purity was above 99.5%. It was further purified by vacuum sublimation twice and the purity was 99.98%. The characterization result of the 1H NMR spectrum of this compound A was as follows: 1 H NMR (400 MHz, CDCl 3 ) δ 8.65 (d, J = 1.1 Hz, 2H), 8.38 (dd, J = 8.6, 1.8 Hz, 2H), 8.20 (dd, J = 5.2, 3.3 Hz, 4H), 8.08 (s, 2H), 8.04–7.92 (m, 6H), 7.85 (dd, J = 8.2, 4.8 Hz, 2H), 7.58–7.38 (m, 10H).

[0071] 2. Synthesis of compound B1

[0072]

[0073] 2.1 Synthesis of intermediate M4

[0074] In a three-necked flask, 4-bromo-o-phenylenediamine (20 g, 0.106 mol), 2,3-butanedione (9.66 g, 0.112 mol), and toluene (200 mL) were added, and the mixture was heated to reflux for 3 h. After the reaction was completed, it was cooled to room temperature, filtered through a pad of silica gel, and the filtrate was evaporated to dryness under vacuum to obtain a crude product. The crude product was dissolved in n-hexane for decolorization and recrystallization to obtain 18.0 g of intermediate M4, which was a white solid powder with a yield of 71% and a purity of 99.91%.

[0075] 2.2 Synthesis of intermediate M5

[0076] In a three-necked flask, add intermediate I-1 (18.0 g, 76 mmol), 4-chloro-1-phenylboronic acid (15.68 g, 76 mmol), potassium carbonate (26.67 g, 152 mmol), tetrakis(triphenylphosphine)palladium(0) (0.88 g), toluene (300 mL), ethanol (76 mL) and water (76 mL), and heat under reflux for 3 hours under nitrogen protection. After the reaction is completed, cool to room temperature, extract with toluene and water, filter the organic layer through silica gel, evaporate the solvent in vacuo from the filtrate to obtain the crude product, and slurry the crude product with a mixed solvent of n-hexane / ethanol to obtain 16.34 g of intermediate M5, which is a white solid powder, with a yield of 80% and a purity of 99.30%.

[0077] 2.3 Synthesis of intermediate M6

[0078] In a three-necked flask, add intermediate I-2 (16.34 g, 60.8 mmol), bis(pinacolato)diboron (18.52 g, 72.96 mmol) and toluene (300 mL), stir under nitrogen for 15 minutes, then add potassium acetate (9.74 g, 91.2 mmol), tris(dibenzylideneacetone)dipalladium(0) (0.55 g), X-Phos (0.55 g), and heat under reflux for 7 hours. After the reaction is completed, cool to room temperature, filter through silica gel, evaporate the solvent in vacuo from the filtrate to obtain the crude product, slurry the crude product with n-hexane / dichloromethane (V:V = 10:1) for 1 hour, filter by suction, and wash twice with n-hexane to obtain 17.96 g of intermediate M6 as a white solid powder, with a yield of 82% and a purity of 98.9%.

[0079] 2.4 Synthesis of compound B1

[0080]

[0081] In a three-necked flask, add intermediate I-3 (11.35 g, 31.5 mmol), 2-chloro-4,6-bis(naphthalen-2-yl)-1,3,5-triazine (11.04 g, 30 mmol), potassium carbonate (12.44 g, 90 mmol), tetrakis(triphenylphosphine)palladium(0) (0.73 g), toluene (300 mL), ethanol (45 mL) and water (45 mL), and heat under reflux for 7 hours under nitrogen protection. After the reaction is completed, cool to room temperature, filter to obtain the crude product, dissolve the crude product in chlorobenzene, filter through silica gel while hot, and then wash twice with chlorobenzene. Evaporate the solvent in vacuo from the filtrate to obtain the crude product, and purify the crude product with chlorobenzene to obtain 17.08 g of compound B1 as a white solid powder, with a yield of 70% and a purity of 99.0%. The crude product is purified by vacuum sublimation once to a purity of 99.92%. The characterization results of the 1H NMR spectrum of this compound B1 are as follows: 1 H NMR(400MHz,CDCl 3)δ9.40(s,2H),8.99(d,J=8.4Hz,2H),8.89(dd,J=8.6,1.6Hz,2H),8.35(d,J=1.7Hz,1H),8.19–8.03(m,6H),8.00(d,J=8.4Hz,2H),7.98–7.91(m,2H),7.66–7.54(m,4H),2.78(d,J=2.3Hz,6H).

[0082] 3. Synthesis of Compound B2

[0083]

[0084] In a three-necked flask, add intermediate I-3 (9.45 g, 26.25 mmol), 2,4-bis([1,1'-biphenyl]-4-yl)-6-chloro-1,3,5-triazine (10.60 g, 25 mmol), potassium carbonate (10.37 g, 75 mmol), tetrakis(triphenylphosphine)palladium (0.58 g), toluene (250 mL), ethanol (40 mL) and water (40 mL). Heat under reflux for 7.5 hours under nitrogen protection. After the reaction is completed, cool to room temperature, filter to obtain the crude product. The crude product is dissolved in chlorobenzene, passed through silica gel while hot, and then rinsed twice with chlorobenzene. The filtrate is evaporated to dryness under vacuum to obtain the crude product. The crude product is purified by chlorobenzene to obtain 8.45 g of white solid powder of Compound B2, with a yield of 55% and a purity of 99.2%. The crude product is purified by vacuum sublimation once to a purity of 99.89%. The characterization results of the 1H NMR spectrum of this Compound B2 are as follows: 1 H NMR(400MHz,CDCl 3 )δ8.82(t,J=8.3Hz,6H),8.27(s,1H),8.02(dd,J=23.9,8.6Hz,2H),7.89(d,J=8.2Hz,2H),7.77(d,J=8.2Hz,4H),7.68(d,J=7.2Hz,4H),7.44(dt,J=31.3,7.3Hz,6H),2.74(s,6H).

[0085] Example 1

[0086] Reference Figure 1The structure of the organic electroluminescent device shown is used to fabricate the organic electroluminescent device with a Sunic sp1710 evaporation coater. The specific steps are as follows: A glass substrate (anode 1) (Corning glass 40mm * 40mm * 0.7mm) coated with ITO (indium tin oxide) with a thickness of 135nm is ultrasonically washed with isopropyl alcohol and pure water for 5 minutes respectively, and then cleaned with ultraviolet ozone. After that, the glass substrate is transferred to a vacuum deposition chamber; The hole transport material HT1 doped with 4% HD is thermally deposited on the transparent ITO electrode with a thickness of 20nm under vacuum (about 10 - 7 Torr) to form a hole injection layer 2. Then, a compound HT1 with a thickness of 120nm is vacuum deposited on the hole injection layer 2 as the first hole transport layer; Then, a 10nm second hole transport layer HT2 is vacuum deposited to form a hole transport layer 3; Then, 25nm of BH3 doped with 4% BD4 by mass fraction is vacuum deposited as the light-emitting layer 4; Then, a blend of compound A, compound B1, and Liq (mass ratio 25%: 25%: 50%) is vacuum deposited to form an electron transport layer 5 with a thickness of 30nm; Finally, a 2nm thick ytterbium metal (Yb, electron injection layer) and a magnesium-silver alloy with a doping ratio of 10:1 are deposited in sequence to form the cathode 6; Finally, the device is transferred from the deposition chamber to a glove box, and then encapsulated with a UV-curable epoxy resin and a glass cover plate containing a moisture absorbent to obtain the organic electroluminescent device. In the above manufacturing steps, the deposition rates of the organic material, ytterbium metal, and magnesium metal are maintained at 0.1nm / s, 0.05nm / s, and 0.2nm / s respectively. The structure of this organic electroluminescent device is expressed as: ITO(135nm) / HT1:4% HD(20nm) / HT1(120nm) / HT2(10nm) / BH3:4% BD4(25nm) / A:B1:Liq(25%: 25%: 50%,30nm) / Yb(2nm) / Mg:Ag(10:1,150nm).

[0087] The structural formulas of the above HD, HT1, HT2, BH3, BD4, and Liq are as follows:

[0088]

[0089]

[0090] Example 2

[0091] Example 2 is different from Example 1 in that, as the electron transport layer, Compound B2 is used instead of Compound B1, and finally an organic electroluminescent element is obtained. The structure of the organic electroluminescent element is represented as: ITO (135 nm) / HT1: 4% HD (20 nm) / HT1 (120 nm) / HT2 (10 nm) / BH3: 4% BD4 (25 nm) / A: B2: Liq (25%: 25%: 50%, 30 nm) / Yb (2 nm) / Mg: Ag (10:1, 150 nm).

[0092] Example 3

[0093] Example 3 is different from Example 1 in that

[0094] the mass ratio of Compound A, Compound B1, and Liq is 15%: 35%: 50%, and finally an organic electroluminescent element is obtained. The structure of the organic electroluminescent element is represented as: ITO (135 nm) / HT1: 4% HD (20 nm) / HT1 (120 nm) / HT2 (10 nm) / BH3: 4% BD4 (25 nm) / A: B1: Liq (15%: 35%: 50%, 30 nm) / Yb (2 nm) / Mg: Ag (10:1, 150 nm).

[0095] Example 4

[0096] Example 4 is different from Example 1 in that

[0097] the mass ratio of Compound A, Compound B1, and Liq is 35%: 15%: 50%, and finally an organic electroluminescent element is obtained. The structure of the organic electroluminescent element is represented as: ITO (135 nm) / HT1: 4% HD (20 nm) / HT1 (120 nm) / HT2 (10 nm) / BH3: 4% BD4 (25 nm) / A: B1: Liq (35%: 15%: 50%, 30 nm) / Yb (2 nm) / Mg: Ag (10:1, 150 nm).

[0098] Example 5

[0099] Example 5 is different from Example 1 in that

[0100] The mass ratio of Compound A, Compound B1, and Liq is 10%:40%:50%. Finally, an organic electroluminescent device is obtained, and the structure of the organic electroluminescent device is represented as: ITO (135 nm) / HT1:4% HD (20 nm) / HT1 (120 nm) / HT2 (10 nm) / BH3:4% BD4 (25 nm) / A:B1:Liq (10%:40%:50%, 30 nm) / Yb (2 nm) / Mg:Ag (10:1, 150 nm).

[0101] Example 6

[0102] The difference between Example 6 and Example 1 is that

[0103] The mass ratio of Compound A, Compound B1, and Liq is 40%:10%:50%. Finally, an organic electroluminescent device is obtained, and the structure of the organic electroluminescent device is represented as: ITO (135 nm) / HT1:4% HD (20 nm) / HT1 (120 nm) / HT2 (10 nm) / BH3:4% BD4 (25 nm) / A:B1:Liq (40%:10%:50%, 30 nm) / Yb (2 nm) / Mg:Ag (10:1, 150 nm).

[0104] Comparative Example 1

[0105] The difference between Comparative Example 1 and Example 1 is that Compound A:Liq (50%:50%) is used as the electron transport layer, and finally an organic electroluminescent device is obtained. The structure of the organic electroluminescent device is represented as: ITO (135 nm) / HT1:4% HD (20 nm) / HT1 (120 nm) / HT2 (10 nm) / BH3:4% BD4 (25 nm) / A:Liq (50%:50%, 30 nm) / Yb (2 nm) / Mg:Ag (10:1, 150 nm).

[0106] Comparative Example 2

[0107] The difference between Comparative Example 2 and Example 1 is that Compound B1:Liq (50%:50%) is used as the electron transport layer, and finally an organic electroluminescent device is obtained. The structure of the organic electroluminescent device is represented as: ITO (135 nm) / HT1:4% HD (20 nm) / HT1 (120 nm) / HT2 (10 nm) / BH3:4% BD4 (25 nm) / B1:Liq (50%:50%, 30 nm) / Yb (2 nm) / Mg:Ag (10:1, 150 nm).

[0108] Comparative Example 3

[0109] The difference between Comparative Example 3 and Example 1 is that compound B2:Liq (50%:50%) is used as the electron transport layer, and an organic electroluminescent device is finally obtained. The structure of the organic electroluminescent device is represented as: ITO (135 nm) / HT1:4%HD (20 nm) / HT1 (120 nm) / HT2 (10 nm) / BH3:4%BD4 (25 nm) / B2:Liq (50%:50%, 30 nm) / Yb (2 nm) / Mg:Ag (10:1, 150 nm).

[0110] The brightness, luminous efficiency, and EQE (external quantum efficiency) of the organic electroluminescent devices of Examples 1 to 6 and Comparative Examples 1 to 3 were respectively measured using Suzhou FushiDa FS-100GA4, and the lifetime LT98 (the time taken for the initial brightness of 4000 nits to decay to 3920 nits) of each organic electroluminescent device was measured using FushiDa FS-MP96. All measurements were completed in the ambient air at room temperature. The specific performance data of the organic electroluminescent devices, such as the ETM (bipyridine compound, quinoxaline compound, and their mass ratio), operating voltage (V), current efficiency (C.E.), power efficiency (P.E.), external quantum efficiency (EQE), and color coordinates (CIEx, CIEy) at a current density of 10 mA / cm2, are shown in Table 1.

[0111] Table 1

[0112]

[0113]

[0114] Compared with Comparative Example 1, the efficiency of the organic electroluminescent devices of Examples 1 to 6 was significantly improved, and the lifetime was also significantly improved. Compared with Comparative Example 2 and Comparative Example 3, the driving voltage of the organic electroluminescent devices of Examples 1 to 6 decreased significantly. Although the device lifetime decreased, the efficiency of the organic electroluminescent devices increased significantly. In addition, through the comparison of Examples 1, 3 to 6, it can be seen that when the mass ratio of the bipyridine compound to the quinoxaline compound is between 3:7 and 7:3, the performance of the organic electroluminescent device is better.

[0115] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0116] The bipyridine compound having Chemical Formula A helps to reduce the driving voltage of the organic electroluminescent device, and the quinoxaline compound having Chemical Formula B1 or Chemical Formula B2 is beneficial to improving the efficiency and lifetime of the organic electroluminescent device. By mixing the above bipyridine compound and quinoxaline compound, the advantages of both are comprehensively utilized, and the disadvantages of both to the organic electroluminescent device are alleviated, thereby obtaining an organic electroluminescent device with high efficiency, long lifetime, and low driving voltage.

[0117] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various changes and modifications. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An organic electroluminescent element, comprising an anode, a cathode, a hole injection layer, a hole transport layer, a light-emitting layer, and an electron transport layer, Characterized in that, The electron transport layer comprises a bipyridine compound and a quinoxaline compound, the bipyridine compound has chemical formula A, and the quinoxaline compound is any one of the compounds represented by chemical formula B1 and chemical formula B2, 2. The organic electroluminescent element according to claim 1, Characterized in that, The mass ratio of the bipyridine compound to the quinoxaline compound is 3 to 7:7 to 3.

3. The organic electroluminescent element according to claim 1, Characterized in that, The hole injection layer comprises one or more arylamine compounds and one or more annulene derivatives, and the annulene derivatives are doped in the arylamine compounds, Among them, the arylamine compound has the general formula I: Ar 1 , Ar 2 , Ar 3 , Ar 4 are each independently selected from any one of substituted or unsubstituted aryl groups having C 6 to C 30 , and substituted or unsubstituted heteroaryl groups having C 5 to C 30 ; The axylene derivative has the general formula II: wherein Ar 5 is an aryl group containing C 6 to C 18 substituted with an electron-withdrawing group.

4. The organic electroluminescent element according to claim 3, Characterized in that, The Ar 1 and the Ar 2 therebetween, the Ar 3 and the Ar 4 are each independently connected by any one of a single bond, a substituted or unsubstituted methylene group, an oxygen atom or a sulfur atom.

5. The organic electroluminescent element according to claim 3, Characterized in that, The electron-withdrawing group is fluorine or cyano.

6. The organic electroluminescent element according to claim 3, Characterized in that, In the general formula I, the Ar 1 , Ar 2 , Ar 3 , Ar 4 are each independently selected from any one of substituted or unsubstituted aryl having C 6 to C 12 and substituted or unsubstituted heteroaryl having C 10 to C 15 .

7. The organic electroluminescent element according to claim 6, Characterized in that, The described Ar 1 、Ar 2 、Ar 3 、Ar 4 Each independently selected from any one of substituted or unsubstituted phenyl, biphenyl, naphthyl, fluorenyl, carbazolyl.

8. The organic electroluminescent element according to any one of claims 3 to 7, Characterized in that, In the general formula II, the Ar 5 is an aryl group containing C 6 to C 12 substituted with an electron-withdrawing group.

9. The organic electroluminescent element according to claim 8, Characterized in that, The Ar 5 is a mono-substituted or multi-substituted phenyl group, or a mono-substituted or multi-substituted biphenyl group, and each substituent is independently a cyano group or an F atom.

10. The organic electroluminescent element according to any one of claims 3 to 7, Characterized in that, The mass ratio of the arylamine compound to the annulene derivative is 100:2 to 20.

11. The organic electroluminescent element according to claim 10, Characterized in that, The mass ratio of the arylamine compound to the annulene derivative is 100:2 to 8.

12. The organic electroluminescent element according to any one of claims 3 to 5, Characterized in that, In the direction away from the hole injection layer, the hole transport layer comprises a first hole transport layer and a second hole transport layer stacked in sequence.

13. The organic electroluminescent element according to claim 12, Characterized in that, The first hole transport layer comprises any one or more of the arylamine compounds.

14. The organic electroluminescent element according to claim 1, Characterized in that, The light-emitting layer is composed of a blend of at least one host matrix and at least one guest dopant.

15. The organic electroluminescent element according to claim 14, Characterized in that, The host matrix is an anthracene compound represented by the general formula BH: Among them, R 1 and R 2 are the same as or different from each other, and the said R 1 and R 2 each independently selected from any one or more of hydrogen, substituted or unsubstituted C 1 -C 6 alkyl, C 1 -C 6 alkoxy, C 6 -C 30 aryl, C 6 -C 30 heteroaryl; Ar 6 、Ar 7 Each independently is an aryl selected from C 6 ~C 30 or a heteroaryl of C 6 ~C 30 ; a, b, and c are each independently an integer from 1 to 4.

16. The organic electroluminescent element according to claim 14 or 15, Characterized in that, The guest dopant is a fluorescent dye represented by the general formula BD, Among them, R 3 to R 10 are each independently selected from a hydrogen atom, a halogen atom, a substituted or unsubstituted C 1 to C 4 alkyl group, a substituted or unsubstituted C 3 to C 10 cycloalkyl group, a substituted or unsubstituted silyl group, a cyano group, a substituted or unsubstituted C 6 to C 30 aryl group; Ar 8 to Ar 11 each independently selected from substituted or unsubstituted C 6 to C 30 aryl, substituted or unsubstituted C 5 to C 30 any one of heteroaryl.

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