An organic electroluminescent device

Abstract

The present invention relates to an organic electroluminescent device, in which a dual host material with a specific P:N ratio is used, and the energy level and mobility of the functional layer material are adjusted to be within a specific range, so that better device performance can be produced under a variety of P:N ratios, thereby providing more possibilities for device selection.

Description

Technical Field

[0001] The present invention relates to an organic electroluminescent device, in which a dual host material with a specific P:N ratio is used, and the energy level and mobility of the functional layer material are adjusted to be within a specific range, so that better device performance can be produced under a variety of P:N ratios, thereby providing more possibilities for device selection. Background of the Invention

[0003] In recent years, organic electroluminescent display (OLED) as a new type of flat panel display has gradually attracted more attention. Due to its characteristics of active light emission, high light brightness, high resolution, wide viewing angle, fast response speed, low energy consumption and flexibility, it has become a hot mainstream display product in the market.

[0004] With the continuous advancement of OLED technology, people are paying more attention to the research on high-efficiency organic materials and device performance that affect OLED. An organic electroluminescent device with high efficiency and long life is usually the result of an optimized combination of device structure and various organic materials. This provides great opportunities and challenges for the design and development of functional materials and device structures of various structures.

[0005] At present, most of the light-emitting devices based on phosphorescent host materials use dual-component host materials (dual hosts), one of which is an electron-type material (N-type) and the other is a hole-type material (P-type). After the electrons and holes are conducted through the two materials, they combine at the interface. Compared with bipolar materials, the two materials used in dual host materials are more widely available, and different materials can be combined to achieve better device performance.

[0006] However, the ratio of P-type and N-type in the dual-host material has a huge impact on the light-emitting layer and even the entire device. How to find the corresponding optimal matching relationship between the different ratios of P-type and N-type and other functional layers is of great significance to the device performance. Summary of the invention

[0007] The inventor surprisingly found during the experiment that when the phosphorescent dual host material changes in the P:N ratio, the performance of the device will be greatly affected, and the reason for the impact may be that as the P:N ratio changes, the exciton recombination area in the light-emitting layer will change. In particular, when the P:N ratio is greatly different, it is easy to cause the recombination area to shift in a certain direction, resulting in changes in efficiency and life. However, in addition to the P:N ratio, the factors affecting the exciton recombination area of ​​the light-emitting layer also include the relationship between the energy level and mobility between the functional layer and the main material of the light-emitting layer. Therefore, the present invention relates to an organic electroluminescent device, which defines the relationship between the P:N ratio in the light-emitting layer main body and the energy level and mobility of the functional layer material, so that it can produce better device performance under a variety of P:N ratios, thereby providing more possibilities for the selection of devices. In addition, it is surprisingly found that when the P:N ratio in the light-emitting layer main body is within a specific range, by setting the mobility of the hole transport layer and the electron transport layer so that it is within a specific range, better device performance can be produced.

[0008] Therefore, the present invention relates to an organic electroluminescent device in which a dual host material having a specific P:N ratio is used, and the energy level and mobility of the functional layer material are adjusted to be within a specific range.

[0009] Specifically, the present invention relates to an organic electroluminescent device, which includes an anode, a hole transport layer (HTL), an electron blocking layer (EBL), an emitting layer (EML), a hole blocking layer (HBL), an electron transport layer (ETL), and a cathode, wherein the emitting layer comprises at least one phosphorescent guest compound and at least two host materials, and the host materials are respectively an N-type material and a P-type material, wherein the weight ratio P:N of the N-type material to the P-type material is 1:5 to 5:1, characterized in that:

[0010] 0.02eV≤HOMO(HTL)-HOMO(EML)≤0.65eV,

[0011] Preferably,

[0012] 0.20eV≤HOMO(HTL)-HOMO(EML)≤0.60eV,

[0013] More preferably,

[0014] 0.35eV≤HOMO(HTL)-HOMO(EML)≤0.60eV.

[0015] In one embodiment of the present invention, it is characterized in that:

[0016] 0.25eV≤LUMO(EML)-LUMO(ETL)≤1.00eV,

[0017] Preferably,

[0018] 0.30eV≤LUMO(EML)-LUMO(ETL)≤0.60eV,

[0019] More preferably,

[0020] 0.25eV≤LUMO(EML)-LUMO(ETL)≤0.50eV.

[0021] In one embodiment of the present invention, it is characterized in that:

[0022] 0.01eV≤HOMO(HTL)-HOMO(EBL)≤0.28eV,

[0023] Preferably,

[0024] 0.03eV≤HOMO(HTL)-HOMO(EBL)≤0.25eV,

[0025] More preferably,

[0026] 0.05eV≤HOMO(HTL)-HOMO(EBL)≤0.20eV.

[0027] In one embodiment of the present invention, it is characterized in that:

[0028] 1.00eV≤LUMO(HBL)-LUMO(ETL)≤1.50eV,

[0029] Preferably,

[0030] 1.00eV≤LUMO(HBL)-LUMO(ETL)≤1.30eV,

[0031] More preferably,

[0032] 1.00eV≤LUMO(HBL)-LUMO(ETL)≤1.10eV.

[0033] In one embodiment of the present invention, it is characterized in that:

[0034] (3) HTL mobility is 5.0×10 -6 cm 2 / Vs to 1.0×10 -3 cm 2 / Vs;

[0035] The ETL mobility is 5.0×10 -8 cm 2 / Vs to 8.0×10 -6 cm2 / Vs,

[0036] Preferably,

[0037] (3) HTL mobility is 1.0×10 -5 cm 2 / Vs to 9.0×10 -4 cm 2 / Vs,

[0038] The ETL mobility is 8.0×10 -8 cm 2 / Vs to 6.0×10 -6 cm 2 / Vs;

[0039] More preferably,

[0040] (3) HTL mobility is 5.5×10 -4 cm 2 / Vs to 8.0×10 -4 cm 2 / Vs,

[0041] The ETL mobility is 1.0×10 -7 cm 2 / Vs to 3.0×10 -6 cm 2 / Vs;

[0042] Wherein the mobility is tested according to the SCLC method.

[0043] In one embodiment of the present invention, P:N is 1:4 to 4:1, preferably 1:3 to 3:1.

[0044] In yet another embodiment of the present invention, the present invention relates to an organic electroluminescent device, characterized in that:

[0045] When the P:N ratio is 7:3,

[0046] (1) 0.40eV≤HOMO(HTL)-HOMO(EML)≤0.55eV,

[0047] 0.28eV≤LUMO(EML)-LUMO(ETL)≤0.40eV;

[0048] When P:N is 6:4,

[0049] (1)0.45eV≤HOMO(HTL)-HOMO(EML)≤0.55eV,

[0050] 0.30eV≤LUMO(EML)-LUMO(ETL)≤0.40eV.

[0051] In one embodiment of the present invention, it is characterized in that:

[0052] When the P:N ratio is 7:3,

[0053] (2)0.05eV≤HOMO(HTL)-HOMO(EBL)≤0.15eV,

[0054] 1.00eV≤LUMO(HBL)-LUMO(ETL)≤1.10eV;

[0055] When P:N is 6:4,

[0056] (2)0.10eV≤HOMO(HTL)-HOMO(EBL)≤0.20eV,

[0057] 1.00eV≤LUMO(HBL)-LUMO(ETL)≤1.10eV.

[0058] In one embodiment of the present invention, it is characterized in that:

[0059] When the P:N ratio is 7:3,

[0060] (3) HTL mobility is 5.5×10 -4 cm 2 / Vs to 8.0×10 -4 cm 2 / Vs,

[0061] The ETL mobility is 1.0×10 -7 cm 2 / Vs to 7.0×10 -7 cm 2 / Vs;

[0062] When P:N is 6:4,

[0063] (3) HTL mobility is 5.5×10 -4 cm 2 / Vs to 8.0×10 -4 cm 2 / Vs,

[0064] The ETL mobility is 1.0×10 -7 cm 2 / Vs to 3.0×10 -7 cm 2 / Vs;

[0065] Wherein the mobility is tested according to the SCLC method.

[0066] In one embodiment of the present invention, it is characterized in that:

[0067] When the P:N ratio is 5:5,

[0068] (1)0.40eV≤HOMO(HTL)-HOMO(EML)≤0.50eV,

[0069] 0.25eV≤LUMO(EML)-LUMO(ETL)≤0.35eV.

[0070] In one embodiment of the present invention, it is characterized in that:

[0071] When the P:N ratio is 5:5,

[0072] (2)0.05eV≤HOMO(HTL)-HOMO(EBL)≤0.15eV,

[0073] 1.00eV≤LUMO(HBL)-LUMO(ETL)≤1.10eV.

[0074] In one embodiment of the present invention, it is characterized in that:

[0075] When the P:N ratio is 5:5,

[0076] (3) HTL mobility is 5.5×10 -4 cm 2 / Vs to 8.0×10 -4 cm 2 / Vs,

[0077] The ETL mobility is 5.0×10 -7 cm 2 / Vs to 8.0×10 -7 cm 2 / Vs;

[0078] Wherein the mobility is tested according to the SCLC method.

[0079] In one embodiment of the present invention, it is characterized in that:

[0080] When the P:N ratio is 4:6,

[0081] (1)0.45eV≤HOMO(HTL)-HOMO(EML)≤0.60eV,

[0082] 0.25≤LUMO(EML)-LUMO(ETL)≤0.40eV;

[0083] When the P:N ratio is 3:7,

[0084] (1)0.40eV≤HOMO(HTL)-HOMO(EML)≤0.55eV,

[0085] 0.27≤LUMO(EML)-LUMO(ETL)≤0.35eV.

[0086] In one embodiment of the present invention, it is characterized in that:

[0087] When the P:N ratio is 4:6,

[0088] (2)0.10eV≤HOMO(HTL)-HOMO(EBL)≤0.20eV,

[0089] 1.00≤LUMO(HBL)-LUMO(ETL)≤1.10eV;

[0090] When the P:N ratio is 3:7,

[0091] (2)0.10eV≤HOMO(HTL)-HOMO(EBL)≤0.20eV;

[0092] 0.50≤LUMO(HBL)-LUMO(ETL)≤1.0eV.

[0093] In one embodiment of the present invention, it is characterized in that:

[0094] When the P:N ratio is 4:6,

[0095] (3) HTL mobility is 5.5×10 -4 cm 2 / Vs to 8.0×10 -4 cm 2 / Vs,

[0096] The ETL mobility is 9.0×10 -7 cm 2 / Vs to 2.0×10 -6 cm 2 / Vs;

[0097] When the P:N ratio is 3:7,

[0098] (3) HTL mobility is 8.0×10 -5 cm 2 / Vs to 8.0×10 -4 cm 2 / Vs,

[0099] The ETL mobility is 1.0×10-7 cm 2 / Vs to 6.0×10 -7 cm 2 / Vs;

[0100] Wherein the mobility is tested according to the SCLC method.

[0101] In one embodiment of the present invention, the LUMO (EML) ≤ -2.0 eV and the HOMO (EML) ≥ -6.0 eV.

[0102] In one embodiment of the present invention, the total concentration of the phosphorescent guest compounds is 5-20 wt %, preferably 8-14 wt %, more preferably 9-12 wt %, based on the sum of the weights of the host material and the guest material.

[0103] The structure of the organic light emitting device of the present invention is known in the art. Figure 1 As shown, it includes an anode and a cathode located on a substrate, and an organic layer located between the anode and the cathode, and the organic layer can be a multilayer structure. For example, the organic material layer can include a hole transport layer, an electron blocking layer, a light-emitting layer, a hole blocking layer, and an electron transport layer. The organic material layer of the present invention can also include an electron injection layer.

[0104] The anode material can be transparent conductive materials such as indium tin oxide (ITO), indium zinc oxide (IZO), tin dioxide (SnO2), zinc oxide (ZnO) known in the prior art, or metal materials such as silver and its alloys, aluminum and its alloys, or organic conductive materials such as polydioxythiophene (PEDOT), as well as multilayer structures of the above materials.

[0105] The cathode material can be selected from, but not limited to, LiF / Al, ITO, metals, oxides and the like. The metal can be selected from Mg, Ag, Al and alloys thereof, preferably Mg / Ag alloys and Mg / Al alloys. The oxide can be selected from yttrium oxide, scandium oxide and rare earth metal oxides.

[0106] Located between the light emitting layer and the anode are a hole transport layer (HTL) and an electron blocking layer (EBL), and the materials thereof can be selected from but not limited to one or more combinations of HT-1 to HT-10 listed below.

[0107]

[0108]

[0109] The light-emitting layer may include a host material and a guest material, wherein the host material is a dual host, i.e., includes N-type and P-type host materials. In one embodiment of the present invention, the P-type material is selected from one or more of triarylamine derivatives, carbazole derivatives, fused carbazole derivatives, carbazole triphenylene derivatives, and dibenzofuran and benzofuranyl dibenzofuran derivatives; the N-type material is selected from one or more of triazine derivatives, pyrimidine derivatives, diazaphosphole derivatives, indole and carbazole derivatives substituted by electron-deficient heteroaromatic groups, and indenyl and carbazole derivatives substituted by electron-deficient heteroaromatic groups. Preferably, the N-type and P-type host materials include, but are not limited to, a combination of one or more conventional materials shown below:

[0110] P-type:

[0111]

[0112] N type:

[0113]

[0114] The guest material of the light-emitting layer may be selected from but not limited to one or more combinations of GD-1 to GD-10 listed below:

[0115]

[0116]

[0117] The materials of the electron transport layer (ETL) and the hole blocking layer (HBL) include but are not limited to one or more combinations of ET-1 to ET-10 listed below:

[0118]

[0119]

[0120] The material of the electron injection layer is selected from but not limited to LiF, Yb, LIQ, Mg:LiF and the like.

[0121] HTL and ETL can be evaporated separately or two or more materials can be evaporated together (doped).

[0122] The film thickness of each layer is known in the art, for example, respectively:

[0123] Anode: 10-300nm, preferably 50-250nm, more preferably 100-200nm;

[0124] Hole transport layer: 10-200nm, preferably 50-150nm, more preferably 80-120nm;

[0125] Electron blocking layer: 0.5-20 nm, preferably 0.8-10 nm, more preferably 0.8-5 nm;

[0126] Light-emitting layer: 5-100nm, preferably 10-50nm, more preferably 20-40nm;

[0127] Hole blocking layer: 0.5-20nm, preferably 0.8-10nm, more preferably 0.8-5nm;

[0128] Electron transport layer: 5-100nm, preferably 10-50nm, more preferably 20-40nm;

[0129] Electron injection layer: 0.5-20nm, preferably 0.8-10nm, more preferably 0.8-5nm;

[0130] Cathode: 10-300 nm, preferably 50-250 nm, more preferably 100-200 nm.

[0131] The present invention also relates to a method for preparing the OLED device of the present invention, which comprises stacking the layers in sequence. The layers of the OLED device of the present invention can be stacked by using an evaporation process.

[0132] In the embodiment of the present invention, the specific process of the evaporation process can be: using the method of electric current heating to evaporate the required material into atoms or molecules, these atoms and molecules will separate from the material itself due to thermal motion, move upward, contact the substrate during the movement, accumulate and condense on the substrate to form various film layers. Among them, the process of preparing each film layer by high-temperature evaporation is higher than 4×10 -4 Pa, preferably 1×10 -5 Pa to 1×10 -6 The evaporation rate is 0.01-10 nm / s, preferably 0.05-2 nm / s. BRIEF DESCRIPTION OF THE DRAWINGS

[0133] Figure 1 is a schematic diagram of the structure of an OLED device of the present invention, wherein:

[0134] 101 Anode

[0135] 102 Hole transport layer

[0136] 103 Electron blocking layer

[0137] 104 Luminescent Layer

[0138] 105 Hole blocking layer

[0139] 106 Electron Transport Layer

[0140] 107 cathode

[0141] Figure 2 It is the difference in efficiency and life span of the OLED device of the present invention under different proportions of PN components.

[0142] Figure 3 3 is the change of the exciton recombination area of ​​the OLED devices of Example 1 and Comparative Example 1. Example

[0143] The preparation process of organic electroluminescent device is as follows:

[0144] (1) ultrasonically treating the glass plate with ITO in a cleaning agent, rinsing in deionized water, ultrasonically degreasing in an acetone-ethanol mixed solvent, and baking in a clean environment until the water is completely removed;

[0145] (2) Place the glass substrate with the anode in a vacuum chamber and evacuate the chamber to a vacuum of 1×10 -6 Pa, vacuum evaporation of a hole transport layer on the above anode layer, the evaporation rate is 0.1nm / s, and the evaporation film thickness is 100nm; the hole transport material is shown in Table 1;

[0146] (3) Vacuum evaporating 3,3′-di(9H-carbazole-9-yl)-1,1′-biphenyl (mCBP) on the hole transport layer to form an electron blocking layer of the device. The evaporation rate is 0.05 nm / s and the film thickness is 1 nm.

[0147] (4) Vacuum evaporation of the light-emitting layer of the device on the electron blocking layer, the light-emitting layer includes dual host materials P-7 and N-1, and P:N=7:3 to 3:7, the guest material is GD-1, and the weight ratio of the host material to the guest material is 90:10 by multi-source co-evaporation method, the evaporation rate of the host material is adjusted to 0.1nm / s, and the evaporation rate of the guest material GD-1 is set according to 1 / 9 of the host material, and the total evaporation film thickness is 30nm;

[0148] (5) vacuum evaporating 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) on the light-emitting layer to form a hole blocking layer of the device, with an evaporation rate of 0.05 nm / s and a film thickness of 1 nm;

[0149] (6) The electron transport layer of the vacuum-deposited device on the hole blocking layer, the evaporation rate is 0.1 nm / s, and the total evaporation film thickness is 30 nm; the electron transport material is shown in Table 1;

[0150] (7) LiF was vacuum-deposited on the electron transport layer (ETL) to a thickness of 0.5 nm as an electron injection layer.

[0151] (8) The Al layer with a thickness of 150 nm serves as the cathode of the device.

[0152] Table 1

[0153]

[0154] The HOMO and LUMO of the HTL layer and ETL layer are as follows:

[0155] Table 2

[0156] HTL HOMO LUMO Mobility ETL HOMO LUMO Mobility HT-1 -5.23 -2.24 <![CDATA[5.3*10 -4 ]]> ET-1 -6.45 -3.20 <![CDATA[4.6*10 -7 ]]> HT-2 -5.44 -2.37 <![CDATA[6.8*10 -4 ]]> ET-5 -6.5 -3.26 <![CDATA[5.7*10 -7 ]]> HT-5 -5.37 -2.34 <![CDATA[6.4*10 -4 ]]> ET-4 -6.47 -3.30 <![CDATA[2.3*10 -7 ]]> HT-6 -5.35 -2.40 <![CDATA[7.2*10 -4 ]]> ET-8 -6.42 -3.28 <![CDATA[1.2*10 -6 ]]>

[0157] The HOMO and LUMO of the EML layer, HBL layer and EBL layer are as follows:

[0158] EML: HOMO=-5.90eV LUMO=-2.96eV

[0159] HBL: HOMO=-5.40eV LUMO=-2.25eV

[0160] EBL: HOMO=-5.53eV LUMO=-2.31eV

[0161] From Table 1-2 and Figure 3 It can be seen from the data that when the energy level and mobility between the light-emitting layer and the functional layer are effectively matched, it has a good impact on the exciton recombination area, the efficiency and life of the device.

Claims

1. An organic electroluminescent device, comprising an anode, a hole transport layer (HTL), an electron blocking layer (EBL), an emitting layer (EML), a hole blocking layer (HBL), an electron transport layer (ETL), and a cathode, wherein the emitting layer comprises at least one phosphorescent guest compound and at least two host materials, and the host materials are N-type materials and P-type materials, respectively, wherein the weight ratio of N-type material to P-type material is P:N of 1:5 to 5:1, characterized in that: 0.02eV≤HOMO(HTL)-HOMO(EML)≤0.65eV.

2. The organic electroluminescent device according to claim 1, characterized in that: 0.25eV≤LUMO(EML)-LUMO(ETL)≤1.00eV.

3. The organic electroluminescent device according to claim 1, characterized in that: 0.01eV≤HOMO(HTL)-HOMO(EBL)≤0.28eV.

4. The organic electroluminescent device according to claim 2, characterized in that: 0.01eV≤HOMO(HTL)-HOMO(EBL)≤0.28eV.

5. The organic electroluminescent device according to claim 3, characterized in that: 1.00eV≤LUMO(HBL)-LUMO(ETL)≤1.50eV.

6. The organic electroluminescent device according to claim 4, characterized in that: 1.00eV≤LUMO(HBL)-LUMO(ETL)≤1.50eV.

7. The organic electroluminescent device according to any one of claims 1 to 6, characterized in that: The HTL mobility is 5.0×10 -6 cm 2 / Vs to 1.0×10 -3 cm 2 / Vs, The ETL mobility is 5.0×10 -8 cm 2 / Vs to 8.0×10 -6 cm 2 / Vs, Wherein the mobility is tested according to the SCLC method.

8. The organic electroluminescent device according to any one of claims 1 to 6, wherein the weight ratio of P:N is 1:4 to 4:

1. 9 . The organic electroluminescent device as claimed in claim 8 , wherein the weight ratio of P:N is 1:3 to 3:

1.

10. The organic electroluminescent device according to any one of claims 1 to 6, characterized in that: When the P:N ratio is 7:3, (1) 0.40eV≤HOMO(HTL)-HOMO(EML)≤0.55eV, 0.28eV≤LUMO(EML)-LUMO(ETL)≤0.40eV; When P:N is 6:4, (1) 0.45eV≤HOMO(HTL)-HOMO(EML)≤0.55eV, 0.30eV≤LUMO(EML)-LUMO(ETL)≤0.40eV.

11. The organic electroluminescent device according to claim 10, characterized in that: When the P:N ratio is 7:3, (2) 0.05eV≤HOMO(HTL)-HOMO(EBL)≤0.15eV, 1.00eV≤LUMO(HBL)-LUMO(ETL)≤1.10eV; When P:N is 6:4, (2) 0.10eV≤HOMO(HTL)-HOMO(EBL)≤0.20eV, 1.00eV≤LUMO(HBL)-LUMO(ETL)≤1.10eV.

12. The organic electroluminescent device according to claim 10, characterized in that: When the P:N ratio is 7:3, (3) HTL mobility is 5.5×10 -4 cm 2 / Vs to 8.0×10 -4 cm 2 / Vs, The ETL mobility is 1.0×10 -7 cm 2 / Vs to 7.0×10 -7 cm 2 / Vs; When P:N is 6:4, (3) HTL mobility is 5.5×10 -4 cm 2 / Vs to 8.0×10 -4 cm 2 / Vs, The ETL mobility is 1.0×10 -7 cm 2 / Vs to 3.0×10 -7 cm 2 / Vs; Wherein the mobility is tested according to the SCLC method.

13. The organic electroluminescent device according to any one of claims 1 to 6, characterized in that: When the P:N ratio is 5:5, (1) 0.40eV≤HOMO(HTL)-HOMO(EML)≤0.50eV, 0.25eV≤LUMO(EML)-LUMO(ETL)≤0.35eV.

14. The organic electroluminescent device according to claim 13, characterized in that: When the P:N ratio is 5:5, (2) 0.05eV≤HOMO(HTL)-HOMO(EBL)≤0.15eV, 1.00eV≤LUMO(HBL)-LUMO(ETL)≤1.10eV.

15. The organic electroluminescent device according to claim 13, characterized in that: When the P:N ratio is 5:5, (3) HTL mobility is 5.5×10 -4 cm 2 / Vs to 8.0×10 -4 cm 2 / Vs, The ETL mobility is 5.0×10 -7 cm 2 / Vs to 8.0×10 -7 cm 2 / Vs; Wherein the mobility is tested according to the SCLC method.

16. The organic electroluminescent device according to any one of claims 1 to 6, characterized in that: When the P:N ratio is 4:6, (1) 0.45eV≤HOMO(HTL)-HOMO(EML)≤0.60eV, 0.25≤LUMO(EML)-LUMO(ETL)≤0.40eV; When the P:N ratio is 3:7, (1) 0.40eV≤HOMO(HTL)-HOMO(EML)≤0.55eV, 0.27≤LUMO(EML)-LUMO(ETL)≤0.35eV.

17. The organic electroluminescent device according to claim 16, characterized in that: When the P:N ratio is 4:6, (2) 0.10eV≤HOMO(HTL)-HOMO(EBL)≤0.20eV, 1.00≤LUMO(HBL)-LUMO(ETL)≤1.10eV; When the P:N ratio is 3:7, (2) 0.10eV≤HOMO(HTL)-HOMO(EBL)≤0.20eV; 0.50≤LUMO(HBL)-LUMO(ETL)≤1.0eV.

18. The organic electroluminescent device according to claim 16, characterized in that: When the P:N ratio is 4:6, (3) HTL mobility is 5.5×10 -4 cm 2 / Vs to 8.0×10 -4 cm 2 / Vs, The ETL mobility is 9.0×10 -7 cm 2 / Vs to 2.0×10 -6 cm 2 / Vs; When the P:N ratio is 3:7, (3) HTL mobility is 8.0×10 -5 cm 2 / Vs to 8.0×10 -4 cm 2 / Vs, The ETL mobility is 1.0×10 -7 cm 2 / Vs to 6.0×10 -7 cm 2 / Vs; Wherein the mobility is tested according to the SCLC method.

19. The organic electroluminescent device according to any one of claims 1 to 6, characterized in that: LUMO(EML)≤-2.0eV and HOMO(EML)≥-6.0eV.

20. The organic electroluminescent device according to any one of claims 1 to 6, characterized in that: The total concentration of the phosphorescent guest compound is 5-20% by weight based on the sum of the weights of the host material and the guest material.

21. The organic electroluminescent device according to any one of claims 1 to 6, characterized in that: The P-type material is selected from one or more of triarylamine derivatives, carbazole derivatives, fused carbazole derivatives, carbazole triphenylene derivatives, dibenzofuran and benzofuranyl dibenzofuran derivatives; the N-type material is selected from one or more of triazine derivatives, pyrimidine derivatives, diazaphosphole derivatives, indolecarbazole derivatives substituted by electron-deficient heteroaromatic groups, and indenylcarbazole derivatives substituted by electron-deficient heteroaromatic groups.

22. A method for preparing an organic electroluminescent device as claimed in any one of claims 1 to 21, comprising stacking the layers in sequence.

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