Organic electroluminescent device and display substrate

Abstract

An organic electroluminescent device includes a substrate (1), an anode (2) on the substrate, at least one light emitting unit (3) on a side of the anode (1) away from the substrate (1), and a cathode (4) on a side of the light emitting unit (3) away from the substrate (1), where the light emitting unit (3) includes a light emitting layer (32) and a light emitting auxiliary layer (31), where the light emitting auxiliary layer (31) is located between the anode (2) and the light emitting layer (32), and where the cathode (4) is located between the anode (2) and the light emitting layer (32). The material of the light-emitting layer (32) and the material of the light-emitting auxiliary layer (31) are different, the light-emitting layer (32) comprises a first host material and a first guest material, and the light-emitting auxiliary layer (31) comprises the first host material.

Description

Organic electroluminescent device and display substrate Technical Field

[0001] The present disclosure relates to the field of display, and more particularly to an organic electroluminescent device and a method for preparing the organic electroluminescent device. Background Art

[0002] Sensitized fluorescence technology fully utilizes the high efficiency of sensitizers (such as phosphorescent or thermally-activated delayed fluorescence (TADF) materials) while combining the advantages of high color purity of fluorescent emitters. Therefore, compared with traditional fluorescent and phosphorescent technologies, it has more advantages in the display field.

[0003] Summary of the Invention

[0004] An embodiment of the present invention provides an organic electroluminescent device. The organic electroluminescent device includes: an anode, at least one light-emitting unit located on the anode, and a cathode located on a side of the light-emitting unit away from the anode. The light-emitting unit includes: a light-emitting layer and a light-assisting layer. The light-assisting layer is located between the anode and the light-emitting layer. The material of the light-emitting layer and the material of the light-assisting layer are different. The light-emitting layer includes a first host material and a first guest material, and the light-assisting layer includes the first host material.

[0005] In some embodiments, the light-emitting layer includes a green light-emitting layer and the green light-emitting layer includes the first guest material, the light-emitting auxiliary layer includes a green light-emitting auxiliary layer and the green light-emitting auxiliary layer includes the first host material, and wherein the projection of the green light-emitting layer on the anode at least partially overlaps with the projection of the green light-emitting auxiliary layer on the anode.

[0006] In some embodiments, the first host material comprises a void-type host material.

[0007] In some embodiments, the green light emitting auxiliary layer further includes the first guest material.

[0008] In some embodiments, the green light emitting layer further includes a sensitizer, and wherein the green light emitting auxiliary layer further includes the sensitizer.

[0009] In some embodiments, the organic electroluminescent device satisfies:

[0010] T1 (hole-type host material)-T1 (sensitizer) ≥ 0.1eV,

[0011] Wherein, T1(hole-type host material) is the energy of the first excited triplet state of the hole-type host material, and T1(sensitizer) is the energy of the first excited triplet state of the sensitizer.

[0012] In some embodiments, the organic electroluminescent device satisfies:

[0013] |LUMO(sensitizer)|<|LUMO(hole-type host material)|,

[0014] Wherein, LUMO (sensitizer) is the lowest unoccupied molecular orbital energy level of the sensitizer, and LUMO (sensitizer) is the lowest unoccupied molecular orbital energy level of the hole-type host material.

[0015] In some embodiments, |LUMO(hole-type host material)|−|LUMO(sensitizer)|>0.3 eV.

[0016] In some embodiments, the sensitizer comprises a thermally activated delayed phosphorescent (TADF) material, the first guest material comprises a fluorescent guest material, and under normalized conditions, an overlap area between an emission spectrum of the TADF material and an absorption spectrum of the first guest material / an absorption spectrum area of ​​the first guest material is ≥ 60%.

[0017] In some embodiments, the hole-type host material includes a carbazole material, and the fluorescent guest material includes a boron-containing organic compound.

[0018] In some embodiments, the light-emitting unit further includes: a hole transport layer between the anode and the light-emitting auxiliary layer, and the organic electroluminescent device satisfies:

[0019] |HOMO(hole transport layer)-HOMO(first host material)|≤0.3eV,

[0020] HOMO (hole transport layer) is the highest occupied molecular orbital energy level of the hole transport layer material, and HOMO (host material) is the highest occupied molecular orbital energy level of the first host material.

[0021] In some embodiments, the light emitting unit further comprises: a hole injection layer, the hole injection layer being located between the anode and the hole transport layer;

[0022] a hole blocking layer, the hole blocking layer being located on a side of the light-emitting layer away from the anode;

[0023] an electron transport layer, the electron transport layer being located on a side of the hole blocking layer away from the anode;

[0024] An electron injection layer is located on a side of the electron transport layer away from the anode.

[0025] In some embodiments, for the electron transport layer and the hole blocking layer of the same light-emitting unit, the following conditions are satisfied:

[0026] |LUMO (electron transport layer)|>|LUMO (hole blocking layer)|,

[0027] The LUMO (electron transport layer) is the lowest unoccupied molecular orbital energy level of the material of the electron transport layer, and the LUMO (hole blocking layer) is the lowest unoccupied molecular orbital energy level of the material of the hole blocking layer.

[0028] In some embodiments, the light-emitting layer further includes: a blue light-emitting layer and a red light-emitting layer, wherein the blue light-emitting layer, the red light-emitting layer, and the green light-emitting layer are spaced apart from each other;

[0029] The light-emitting auxiliary layer includes a blue light-emitting auxiliary layer and a red light-emitting auxiliary layer, wherein the blue light-emitting auxiliary layer, the red light-emitting auxiliary layer and the green light-emitting auxiliary layer are spaced apart from each other.

[0030] wherein the projection of the blue light emitting layer on the substrate at least partially overlaps with the projection of the blue light emitting auxiliary layer on the substrate, and wherein the projection of the red light emitting layer on the substrate at least partially overlaps with the projection of the red light emitting auxiliary layer on the substrate.

[0031] In some embodiments, the light-emitting layer further includes: a blue light-emitting layer and a red light-emitting layer, wherein at least two of the projection of the blue light-emitting layer on the anode, the projection of the red light-emitting layer on the anode, and the projection of the green light-emitting layer on the anode partially overlap.

[0032] In some embodiments, the red light-emitting auxiliary layer includes at least two sublayers, and the HOMO absolute values ​​of the materials of the at least two sublayers increase sequentially in a direction away from the anode and toward the cathode. The mobility of the material of the red light-emitting auxiliary sublayer closer to the cathode is lower than the mobility of the material of the red light-emitting auxiliary sublayer farther from the cathode, and the difference between the two is at least 5 times.

[0033] In some embodiments, the anode includes a plurality of sub-anodes, wherein a voltage applied to a sub-anode corresponding to the red light emitting layer is different from a voltage applied to a sub-anode corresponding to the blue light emitting layer.

[0034] In some embodiments, the voltage applied to the sub-anode corresponding to the red light emitting layer, the voltage applied to the sub-anode corresponding to the blue light emitting layer, and the voltage applied to the sub-anode corresponding to the green light emitting layer are all different.

[0035] In some embodiments, the organic electroluminescent device satisfies:

[0036] T1(hole blocking layer)>T1(TADF),

[0037] Wherein, T1(hole blocking layer) is the energy of the first excited triplet state of the material of the hole blocking layer, and T1(TADF) is the energy of the first excited triplet state of the thermally activated delayed phosphorescent material.

[0038] In some embodiments, the organic electroluminescent device satisfies: |LUMO (hole blocking layer)|<|LUMO (light-emitting layer)| min

[0039] LUMO (hole blocking layer) is the lowest unoccupied molecular orbital energy level of the material of the hole blocking layer, |LUMO (light-emitting layer)| min It is the smallest one among the absolute values ​​of the lowest unoccupied molecular orbital energy levels of all materials of the light-emitting layer.

[0040] In some embodiments, |LUMO(light-emitting layer)| min -|LUMO (hole blocking layer)|≥0.2 eV.

[0041] In some embodiments, the organic electroluminescent device satisfies:

[0042] |HOMO (hole transport layer)|<|HOMO (blue light emitting auxiliary layer)|<|HOMO (blue light emitting host material)|,

[0043] Wherein, HOMO (blue light emitting auxiliary layer) is the highest occupied molecular orbital energy level of the material of the blue light emitting auxiliary layer, and HOMO (blue light emitting host material) is the highest occupied molecular orbital energy level of the blue light emitting host material; and

[0044] S1 (blue light emitting auxiliary layer) > S1 (blue light emitting layer),

[0045] Wherein, S1 (blue light emitting auxiliary layer) is the energy of the first singlet state of the material of the blue light emitting auxiliary layer, and S1 (blue light emitting layer) is the energy of the first singlet state of the main material of the blue light emitting layer.

[0046] In some embodiments, the blue light emitting layer includes at least one second host material and at least one second guest material. Under normalized conditions, the overlapping area of ​​the emission spectrum of the second host material and the absorption spectrum of the second guest material / the area of ​​the absorption spectrum of the second guest material is ≥60%; in some possible embodiments, the second host material has TADF characteristics or phosphorescence characteristics.

[0047] The red light emitting layer includes at least one third host material, at least one fourth host material, and at least one third guest material, wherein the third host material and the fourth host material are different.

[0048] In some embodiments, the second host material includes at least one of the following: anthracenes, fluorenes, pyrenes and derivatives thereof, DLA structure, polycarbazole structure materials or metal complex materials.

[0049] The second guest material includes at least one of the following: a pyrene-based organic compound and a boron-containing organic compound;

[0050] The blue light emitting auxiliary layer includes carbazole and its derivatives;

[0051] The third main material is an N-type material, and the fourth main material is a P-type material;

[0052] The third guest material includes at least one of a fluorescent material and a phosphorescent material;

[0053] The red light emitting auxiliary layer includes carbazole and its derivatives.

[0054] In some embodiments, the material of the hole transport layer includes at least one of the following: carbazole and its derivatives;

[0055] The material of the hole injection layer includes at least one of the following:

[0056] (1) at least one of CuPc, HATCN, and MnO3; and

[0057] (2) the material of the hole transport layer and a P-type dopant, wherein the P-type dopant comprises an oxide-based inorganic material and / or a radialene-based organic material;

[0058] The materials of the electron transport layer include: electron transport material and doping material, wherein the doping material includes at least one of LIQ3, Li, and Ca.

[0059] In some embodiments, the organic electroluminescent device includes at least two light-emitting units.

[0060] In some embodiments, the organic electroluminescent device further comprises:

[0061] at least one charge generation layer located between two adjacent light-emitting units of the at least two light-emitting units;

[0062] A capping layer is provided on a surface of the cathode remote from the substrate.

[0063] In some embodiments, the refractive index of the cover layer at a wavelength of 550 nm is greater than 1.8, and the thickness of the cover layer is in the range of 50 nm to 100 nm.

[0064] An embodiment of the present invention further provides a method for preparing the organic electroluminescent device as described above, which comprises stacking various layers in sequence.

[0065] An embodiment of the present invention further provides a display substrate. The display substrate comprises: an organic electroluminescent device on a substrate, the organic electroluminescent device comprising the organic electroluminescent device according to any one of claims 1 to 28; and

[0066] A pixel circuit is used to control the light emission of the organic electroluminescent device. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments will be briefly described below. It should be noted that the drawings described below only relate to some embodiments of the present invention and are not intended to limit the present invention.

[0068] FIG1 is a schematic diagram of an organic electroluminescent device according to an embodiment of the present disclosure;

[0069] FIG2 is a schematic diagram of an organic electroluminescent device according to an embodiment of the present disclosure;

[0070] FIG3 is a schematic diagram of an organic electroluminescent device according to an embodiment of the present disclosure;

[0071] FIG4 is a schematic diagram of an organic electroluminescent device according to an embodiment of the present disclosure;

[0072] FIG5 is a schematic diagram of an organic electroluminescent device according to an embodiment of the present disclosure.

[0073] FIG6 is a schematic diagram of an organic electroluminescent device according to some embodiments of the present disclosure;

[0074] FIG7 is a schematic diagram of an organic electroluminescent device according to an embodiment of the present disclosure;

[0075] FIG. 8 is a schematic diagram of a display substrate according to an embodiment of the present invention. DETAILED DESCRIPTION

[0076] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work also fall within the scope of protection of the present invention.

[0077] When introducing elements of the present invention and the embodiments thereof, the articles "a," "an," "the," and "said" are intended to mean that there are one or more elements. The terms "comprising," "including," "containing," and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements.

[0078] For the purpose of the following description, the terms "upper," "lower," "left," "right," "vertical," "horizontal," "top," "bottom," and their derivatives shall refer to the invention as it is oriented in the accompanying drawings. The terms "overlying," "on top of," "positioned on," or "positioned on top of" mean that a first element, such as a first structure, is present on a second element, such as a second structure, wherein an intermediate element, such as an interface structure, may be present between the first and second elements. The term "contacting" means connecting a first element, such as a first structure, and a second element, such as a second structure, with or without other elements at the interface between the two elements.

[0079] FIG1 is a schematic diagram of an organic electroluminescent device according to an embodiment of the present disclosure. As shown in FIG1 , the organic electroluminescent device according to an embodiment of the present disclosure may include: an anode 2, at least one light-emitting unit 3 located on the anode 2, and a cathode 4 located on a side of the light-emitting unit away from the substrate 1. As shown in FIG1 , the light-emitting unit 3 may include: a light-emitting layer 32 and a light-emitting auxiliary layer 31, wherein the light-emitting auxiliary layer 31 is located between the anode 2 and the light-emitting layer 32, and the material of the light-emitting layer and the light-emitting auxiliary layer are different. The light-emitting layer may include a first host material and a first guest material, and the light-emitting auxiliary layer 32 includes the first host material.

[0080] The difference between the materials of the light-emitting layer and the light-assisting layer here refers to the fact that the two layers contain different materials. The light-assisting layer can be used to prevent excitons in the light-emitting layer from diffusing into other layers. For example, the light-assisting layer can prevent excitons in the light-emitting layer from diffusing into the hole transport layer. As a result, the light-assisting layer can improve device efficiency and stability.

[0081] Conventional techniques often require four evaporation sources to prepare two different light-assisted layers to assist the light-emitting layer. Using only one light-assisted layer results in unsatisfactory light-emitting efficiency. However, in the embodiments of the present disclosure, by providing the light-assisted layer with the first host material that also includes the light-emitting layer, the number of evaporation sources and evaporation chambers can be reduced, enabling the light-emitting layer to be assisted by only one light-assisted layer while maintaining good light-emitting efficiency, thus reducing manufacturing difficulty and cost.

[0082] The organic electroluminescent device may not include a substrate, or may include a substrate as required. The following description will take the organic electroluminescent device including a substrate as an example.

[0083] Figure 2 is a schematic diagram of an organic electroluminescent device according to an embodiment of the present disclosure. As shown in Figure 2, in an embodiment of the present disclosure, the light-emitting layer may include a green light-emitting layer 32G, and the green light-emitting layer 31G includes the first guest material; the light-emitting auxiliary layer may include a green light-emitting auxiliary layer 31G, and the green light-emitting auxiliary layer includes the first host material, and wherein the projection of the green light-emitting layer 32G on the substrate at least partially overlaps with the projection of the green light-emitting auxiliary layer 31G on the substrate 1. The thickness of the green light-emitting layer can be used to adjust the green light optical cavity length. The green light-emitting auxiliary layer can prevent excitons in the adjacent light-emitting layer from diffusing to the hole transport layer, thereby improving efficiency and device stability.

[0084] The first host material may include a hole-type material. The hole-type host material has good hole transport properties. For example, the first host material may include TGM (TADF green matrix). In some embodiments, the hole-type host material may include a carbazole material. The carbazole material may include mCP and CBP, etc.

[0085] In some embodiments, the green light emitting auxiliary layer may further include the aforementioned first guest material. Such a solution can provide a device with lower power consumption.

[0086] In some embodiments, the green light emitting layer may include a first host material, a first guest material, and a sensitizer. The first guest material may include GD (green dopant). For example, the first guest material may include a fluorescent guest material.

[0087] In some embodiments, the sensitizer may include a TGH (TADF green host). For example, the sensitizer may include a thermally activated delayed phosphorescence (TADF) material. The thermally activated delayed phosphorescence (TADF) material may include a polycarbazole material having a DLA structure.

[0088] In some embodiments, the activated delayed phosphorescent material and the first guest material can be configured such that the emission spectrum of the activated delayed phosphorescent material and the absorption spectrum of the first guest material have a significant overlap area. For example, under normalized conditions, the overlap area between the emission spectrum of the thermally activated delayed phosphorescent material and the emission spectrum of the first guest material / the absorption spectrum area of ​​the first guest material is ≥ 60%.

[0089] In some embodiments, the energy of the first excited triplet state of the hole-type host material is higher than the energy of the first excited triplet state of the sensitizer, such as TADF.

[0090] In some embodiments, the organic electroluminescent device satisfies:

[0091] T1 (hole-type host material)-T1 (sensitizer) ≥ 0.1eV,

[0092] Here, T1(hole-type host material) is the energy of the first excited triplet state of the hole-type host material, and T1(sensitizer) is the energy of the first excited triplet state of the sensitizer.

[0093] In some embodiments, the organic electroluminescent device satisfies:

[0094] |LUMO(sensitizer)|<|LUMO(hole-type host material)|,

[0095] Wherein, LUMO (sensitizer) is the lowest unoccupied molecular orbital energy level of the sensitizer, and LUMO (sensitizer) is the lowest unoccupied molecular orbital energy level of the hole-type host material.

[0096] In some embodiments, |LUMO(hole-type host material)|−|LUMO(sensitizer)|>0.3 eV.

[0097] Figure 3 is a schematic diagram of an organic electroluminescent device according to an embodiment of the present disclosure. As shown in Figure 3, the organic electroluminescent device according to an embodiment of the present disclosure may further include a hole transport layer (HTL) between the anode 2 and the light-emitting auxiliary layer 31. For top-emitting devices, the optical thickness of the organic layer between the cathode and anode must meet the optical path requirements of the optical microresonator to achieve optimal light output intensity and the desired color. The internal optical path of the top-emitting device is generally adjusted by varying the thickness of the hole transport layer, which has a minimal effect on voltage.

[0098] In some embodiments, the organic electroluminescent device satisfies:

[0099] |HOMO(hole transport layer)-HOMO(first host material)|≤0.3eV,

[0100] HOMO (hole transport layer) is the highest occupied molecular orbital energy level of the material of the hole transport layer, and HOMO (first host material) is the highest occupied molecular orbital energy level of the first host material.

[0101] By using such a hole transport material with a relatively "deep" HOMO, the device voltage can be reduced, especially the green light voltage (for example, it can be significantly reduced by 0.8eV), and the luminous efficiency of red and blue light can be improved, thereby reducing power consumption.

[0102] The hole transport layer can include a material with excellent hole transport properties, i.e., a material with high hole mobility. For example, the hole mobility of the hole transport layer material can be two orders of magnitude higher than its electron mobility. Specifically, for example, the hole transport layer material can include at least one of the following: carbazole, aniline, and its derivatives. In some embodiments, the thickness of the hole transport layer can be in the range of approximately 1 nm to 200 nm. For top-emitting devices, the blue light optical cavity length can be adjusted by adjusting the thickness of the hole transport layer.

[0103] FIG4 is a schematic diagram of an organic electroluminescent device according to an embodiment of the present disclosure. As shown in FIG4 , the light-emitting unit of the organic electroluminescent device according to an embodiment of the present disclosure may further include: a hole injection layer (HIL), a hole blocking layer (HBL), an electron transport layer (ETL), and an electron injection layer (EIL). As shown in FIG4 , the hole injection layer (HIL) is located between the anode 2 and the hole transport layer (HTL), the hole blocking layer (HBL) is located on the side of the light-emitting layer (32R, 32B, 32R) away from the anode 2, the electron transport layer (ETL) is located on the side of the hole blocking layer (HBL) away from the anode 2, and the electron injection layer (EIL) is located on the side of the electron transport layer (ETL) away from the anode 2.

[0104] The hole blocking layer can have a thickness ranging from 5 nm to 30 nm. The electron injection layer can be formed by evaporation using low-work-function metals such as Li, Ca, Yb, or metal salts such as LiF and LiQ3. The thickness of the electron injection layer can range from 0.5 nm to 2 nm.

[0105] For the electron transport layer (ETL) and hole blocking layer (HBL) of the same light-emitting unit, the following conditions must be met:

[0106] |LUMO (electron transport layer)|>|LUMO (hole blocking layer)|,

[0107] The LUMO (electron transport layer) is the lowest unoccupied molecular orbital energy level of the material of the electron transport layer, and the LUMO (hole blocking layer) is the lowest unoccupied molecular orbital energy level of the material of the hole blocking layer.

[0108] The material of the hole transport layer may include at least one of the following: carbazole and its derivatives.

[0109] The material of the hole injection layer may include at least one of the following:

[0110] (1) at least one of CuPc, HATCN, and MnO3; and

[0111] (2) the material of the hole transport layer and a P-type dopant, wherein the P-type dopant comprises an oxide-based inorganic material and / or a radialene-based organic material;

[0112] The material of the electron transport layer may include: an electron transport material and a dopant material, wherein the dopant material includes at least one of LIQ3, Li, and Ca. In some embodiments, the electron mobility of the electron transport material is at least two orders of magnitude higher than its hole mobility.

[0113] As shown in FIG4 , the light-emitting layer of the organic electroluminescent device may further include a blue light-emitting layer 32B and a red light-emitting layer 32R, wherein the blue light-emitting layer 32B, the red light-emitting layer 32R, and the green light-emitting layer 32G are spaced apart from each other. The light-emitting auxiliary layer 31 may include a blue light-emitting auxiliary layer 31B and a red light-emitting auxiliary layer 31R, wherein the blue light-emitting auxiliary layer 31B, the red light-emitting auxiliary layer 31R, and the green light-emitting auxiliary layer 31G are spaced apart from each other. The projection of the blue light-emitting layer 32B on the substrate 1 at least partially overlaps with the projection of the blue light-emitting auxiliary layer 31B on the substrate 1, and the projection of the red light-emitting layer 32R on the substrate 1 at least partially overlaps with the projection of the red light-emitting auxiliary layer 31R on the substrate 1.

[0114] It should be noted that the red light emitting layer 32B and the green light emitting layer 32G are shown as examples in which they are not in contact with the film layer above them (e.g., the hole blocking layer HBL). They can be arranged to be in contact with the film layer above them as needed. In other embodiments, at least two of the projection of the blue light emitting layer on the anode (or substrate), the projection of the red light emitting layer on the anode (or substrate), and the projection of the green light emitting layer on the anode (or substrate) partially overlap.

[0115] The anode and the cathode correspond to the sub-light-emitting layer (for example, a green light-emitting layer, a red light-emitting layer, and a blue light-emitting layer) of the light-emitting unit to control the light emission of the sub-light-emitting layer. At least one of the anode and the cathode may include a plurality of sub-electrodes spaced apart from each other (for example, 41' and 21' in Figures 2 and 4). These sub-electrodes may correspond one-to-one with the sub-light-emitting layers of the light-emitting layer through independent patterning designs, and different signals may be input to these sub-electrodes. In some embodiments, at least one of the anode and the cathode is configured to be formed through a whole-layer process, which can achieve the effect of saving process costs.

[0116] In some embodiments, the anode includes a plurality of sub-anodes, wherein the voltage applied to the sub-anode corresponding to the red light emitting layer is different from the voltage applied to the sub-anode corresponding to the blue light emitting layer. In some embodiments, the voltage applied to the sub-anode corresponding to the red light emitting layer, the voltage applied to the sub-anode corresponding to the blue light emitting layer, and the voltage applied to the sub-anode corresponding to the green light emitting layer are all different.

[0117] The red light-emitting auxiliary layer can be used to reduce the transport barrier of holes from the adjacent hole transport layer to the red light-emitting layer, while ensuring that excitons in the light-emitting layer do not overflow. For top-emitting structures, the red light-emitting auxiliary layer can also be used to adjust the optical cavity length. In some embodiments, the red light-emitting auxiliary layer can include at least two sublayers, and the absolute HOMO values ​​of the materials of the at least two sublayers increase in a direction away from the anode and toward the cathode.

[0118] In some embodiments, the T1 energy of the hole blocking layer material needs to be greater than the T1 energy of the TADF material in the green light emitting layer connected thereto, that is, the organic electroluminescent device satisfies:

[0119] T1(hole blocking layer)>T1(TADF),

[0120] Wherein, T1(hole blocking layer) is the energy of the first excited triplet state of the material of the hole blocking layer, and T1(TADF) is the energy of the first excited triplet state of the thermally activated delayed phosphorescent material.

[0121] In some embodiments, the organic electroluminescent device satisfies:

[0122] |LUMO(hole blocking layer)|<|LUMO(light-emitting layer)|min

[0123] LUMO (hole-blocking layer) is the lowest unoccupied molecular orbital energy level of the material of the hole-blocking layer, |LUMO (light-emitting layer)| min It is the smallest absolute value of the lowest unoccupied molecular orbital energy level of all materials in the light-emitting layer.

[0124] In some embodiments, |LUMO(light-emitting layer)| min -|LUMO (hole blocking layer)|≥0.2 eV.

[0125] The blue-light emitting auxiliary layer can be used to reduce the hole transport barrier from the adjacent hole injection layer to the blue-light emitting layer. Therefore, in some embodiments, the highest occupied molecular orbital (HOMO) energy level of the molecules of the material in this layer should be between the HOMO of the adjacent hole transport layer and the HOMO of the main body of the blue-light emitting layer, that is, |HOMO(hole transport layer)| <|HOMO(blue-light emitting auxiliary layer)| <|HOMO(blue-light emitting main material)|. HOMO(blue-light emitting auxiliary layer) is the highest occupied molecular orbital energy level of the material of the blue-light emitting auxiliary layer, and HOMO(blue-light emitting main material) is the highest occupied molecular orbital energy level of the main material of the blue-light emitting layer.

[0126] The blue light-emitting auxiliary layer also has an exciton-blocking effect. In some embodiments, the singlet first excited state energy S1 of the material of this layer is greater than S1 of the material of the blue light-emitting layer, that is, S1(blue light-emitting auxiliary layer)>S1(blue light-emitting layer). Wherein, S1(blue light-emitting auxiliary layer) is the energy of the first singlet state of the material of the blue light-emitting auxiliary layer, and S1(blue light-emitting layer) is the energy of the first singlet state of the material of the blue light-emitting layer.

[0127] In some embodiments, the blue light emitting layer includes at least one second host material and at least one second guest material (for example, a fluorescent guest material). Under normalized conditions, the overlapping area of ​​the emission spectrum of the second host material and the absorption spectrum of the second guest material / the area of ​​the absorption spectrum of the second guest material is ≥60%. In some possible embodiments, the second host material has TADF characteristics or phosphorescent characteristics. The second host material may include at least one of the following: anthracenes, fluorenes, pyrenes and their derivatives, materials with DLA structures, polycarbazole structures, or metal complex materials. The second guest material may include at least one of the following: pyrene organic matter and boron-containing organic matter. The doping concentration of the second guest material may be in the range of 0.5 to 5% (mass). The main emission peak wavelength of the second guest in the blue light emitting layer is between 450 nm and 480 nm.

[0128] In some embodiments, the red light-emitting layer includes at least one third host material, at least one fourth host material, and at least one third guest material, wherein the third host material and the fourth host material are different. The third host material can be an N-type material, and the fourth host material can be a P-type material. The third guest material can include at least one of a fluorescent material and a phosphorescent material. The red light-emitting auxiliary layer can include carbazole and its derivatives. The thickness of the red light-emitting layer can be between 30 nm and 80 nm.

[0129] The organic electroluminescent device may further include a capping layer (CPL) 5 on the surface of cathode 4 facing away from substrate 1. The capping layer can be used to improve optical output. The capping layer can be formed by evaporating a high-refractive-index small-molecule material. For example, for 550nm light, the refractive index of the capping layer is greater than 1.8. The thickness of the capping layer can be between 50nm and 100nm.

[0130] The substrate may include various substrate materials, such as glass, sapphire, polyimide, silicon wafer, etc. For a bottom-emitting device, the substrate transmittance needs to be greater than 85% for a wavelength of 550 nm.

[0131] The anode can be a high work function electrode material, such as (1) transparent oxides such as ITO and IZO, with a thickness of 80 to 200 nm; (2) composite electrodes formed of Ag / ITO, Al / ITO, Ag / IZO, and Al / IZO, with a metal thickness of generally 10 to 100 nm and an oxide layer thickness of generally 5 to 20 nm. If the transparent conductive material in (1) is used as the anode, the device has a bottom emission structure; if the reflective composite electrode in (2) is used, the device has a top emission structure.

[0132] The cathode can include a metal with a low work function (e.g., Al, Ag, Mg, etc.) or an alloy containing a low work function metal material. For bottom-emitting devices, the cathode thickness can exceed 80nm to ensure good reflectivity (e.g., >85% @ 550nm). For top-emitting devices, the cathode thickness can be in the range of 10-20nm to ensure a certain transmittance (e.g., >45% @ 550nm).

[0133] The organic electroluminescent device may further include an encapsulation layer, such as a UV sealant or a thin film encapsulation (TFE).

[0134] In some embodiments, the organic electroluminescent device may be a tandem light-emitting structure, that is, the organic electroluminescent device may include at least two light-emitting units. For example, the organic electroluminescent device may include two, three, four, or more light-emitting units. In some embodiments, these multiple light-emitting units may be the same. In other embodiments, these multiple light-emitting units are different. For example, the hole transport layer of one light-emitting unit may be different from the hole transport layer of another light-emitting unit. For example, the thickness of the layer may be different, the type of material contained in the layer may be different, or the proportion of the material contained in the layer may be different.

[0135] FIG5 is a schematic diagram of an organic electroluminescent device according to an embodiment of the present disclosure. As shown in FIG5 , in some embodiments, the organic electroluminescent device may further include at least one charge generation layer 6 located between two adjacent light-emitting units of at least two light-emitting units. The charge generation layer may include an n-type charge generation layer and / or a p-type charge generation layer. The n-type charge generation layer may be formed by doping an ET (electron transport) material with a low work function active metal (e.g., Li, Ca, Yb, etc.), and the p-type charge generation layer may generally be formed by doping an HT (hole transport) material with a P-type dopant (molybdenum oxide, etc.).

[0136] The embodiments of the present invention further provide a method for preparing the organic electroluminescent device as described above, which comprises stacking various layers in sequence.

[0137] It should be noted that the emission spectrum of a material refers to the luminescence spectrum obtained when a single-layer bottom-emitting OLED device is prepared by doping the material at a relatively low ratio (e.g., 1% to 10%) into a host material, with power applied. The device reference structure is ITO anode / HIL / HTL / EBL / EML (host: test material) / HB / ETL / EIL / Mg:Ag (9:1); or the photoemission spectrum of a solid-state doped film of the material in a wide-bandgap host, with a reference doping concentration of 0.5% to 10%. The descriptions of the S1 and T1 of the host material, if the host material is in the form of an exciplex containing two components, refer to the S1 and T1 of the exciplex. Subsequent descriptions of the HOMO and LUMO of the host material, if the host material is in the form of an exciplex, refer to the HOMO with the smaller absolute value and the LUMO with the larger absolute value, respectively, of the two components forming the exciplex.

[0138] The present invention will be further described below with reference to specific embodiments.

[0139] Comparative Example 1

[0140] In Comparative Example 1, a dual-light-emitting unit structure is adopted. The R / G / B composition strategy of Comparative Example 1 adopts a series top emission scheme of a common structure. The B color is determined by the thickness of the hole transport layer of the hole transport material (HT1) including the shallow HOMO of the two light-emitting units, and the R color is jointly adjusted by the red light-emitting auxiliary layer (R prime) of the two light-emitting units. The green light-emitting auxiliary layer (G prime) requires two film layers, namely, a layer of G prime 1 and a layer of G prime 2. The materials of G prime 1 and G prime 2 are different. Among them, G prime 1 is used to adjust the G color, and G prime2 has a high T1, which is used for exciton blocking to improve efficiency. However, due to the use of a double-layer green light-emitting auxiliary layer, the process is relatively complicated, and 4 evaporation sources (corresponding to 2 evaporation chambers of mass production equipment) are required to prepare two double-layer green light-emitting auxiliary layer structures.

[0141] Comparative Example 2

[0142] Compared to Comparative Example 1, Comparative Example 2 eliminates one green light-emitting auxiliary layer, employing only one green light-emitting auxiliary layer (G prime 2) per light-emitting unit. While the materials and evaporation sources used in the actual EV process are reduced compared to Comparative Example 1, the evaporation chamber requirements for mass production remain the same. This is because, to improve the green light luminous efficiency, Comparative Example 2 requires a green light-emitting layer with lower mobility for color compensation.

[0143] Example 1

[0144] FIG. 6 is a schematic diagram of an organic electroluminescent device according to some embodiments of the present invention.

[0145] The main difference between Example 1 and the comparative example lies in the configuration of the green light-emitting auxiliary layer. In Example 1, the anode includes a 100 nm thick silver layer and an 8 nm thick ITO layer. The hole injection layer (HIL1) is 10 nm thick and comprises the same hole transport material as that contained in the hole transport layer and a p-type dopant. The p-type dopant accounts for 3% by weight of the hole injection layer. The hole transport layer uses a conventional hole transport material.

[0146] The green light emitting layer (32G) includes a host material TGM, a sensitizer TGH, and a guest material GD, wherein the mass ratio of TGM, TGH, and GD is 69%:30%:1.0%. The green light emitting auxiliary layer (31G) is 5 nm thick and includes TGM.

[0147] The red light-emitting layer (32R) includes two host materials (RH-p and RH-n) and a guest material (RD), wherein the mass ratio of RH-p, RH-n, and RD is 52%:45%:3%. The blue light-emitting layer (32B) includes a host material (BH) and a guest material (BD), wherein the mass ratio of BD to the blue light-emitting layer is 3%. The blue light-emitting auxiliary layer (31B) is 5nm thick.

[0148] The hole blocking layer (HBL1) is 5 nm thick. An n-type charge generation layer (nCG) is provided on the hole blocking layer. The charge generation layer (nCG) is doped with Yb, and the mass percentage of Yb in the n-type charge generation layer is 1%.

[0149] A further hole injection layer (HIL2) is provided above the charge generation layer (nCG). The material of this hole injection layer (HIL2) is the same as that of the underlying hole injection layer (HIL), but its p-type doping concentration is different from that of the underlying hole injection layer (HIL). The p-type dopant in this further hole injection layer (HIL2) accounts for 10% by weight of the hole injection layer.

[0150] A further hole transport layer (HTL2) is provided on the further hole injection layer (HIL2). In this embodiment, the material of the further hole transport layer (HTL2) is the same as that of the underlying hole transport layer (HTL1).

[0151] The green light emitting layer (32G') includes a host material TGM, a sensitizer TGH, and a guest material GD, wherein the mass ratio of TGM, TGH, and GD is 69%:30%:1.0%. The green light emitting auxiliary layer (31G') is 5 nm thick and includes TGM.

[0152] The red light-emitting layer (32R') includes two host materials (RH-p and RH-n) and a guest material (RD), where the mass ratio of RH-p, RH-n, and RD is 52%:45%:3%. The blue light-emitting layer (32B') includes a host material (BH) and a guest material (BD), where BD accounts for 3% of the blue light-emitting layer by mass. The blue light-emitting auxiliary layer (31B') is 5nm thick.

[0153] The hole blocking layer (HBL2) was 5 nm thick.

[0154] The electron transport layer (ETL) is 35 nm thick and includes an electron transport material and a doping material LiQ, and the mass percentage of the electron transport material and the doping material LiQ is 50%:50%.

[0155] The electron injection layer (EIL) was 1 nm thick.

[0156] The cathode includes Mg and Ag, and the thickness of the cathode is 15 nm.

[0157] In this first embodiment, the green light-emitting auxiliary layer is a single layer. This reduces material usage compared to conventional solutions. Because the green light-emitting auxiliary layer utilizes the main material of the green light-emitting layer, it can be formed in the same evaporation chamber as the green light-emitting layer. This eliminates the need for two evaporation chambers compared to conventional solutions, significantly reducing both material costs and process complexity.

[0158] Example 2

[0159] Example 2 further optimizes the hole transport layer and the hole injection layer. As shown in the subsequent Table 1, the HOMO of the hole transport material of Example 2 (denoted as HT2) is deeper than that of Example 1. In Example 2, as shown in the following Table 2, the device voltage of Example 2, especially the green light voltage, dropped significantly by 0.8V, which is an acceptable level, and the device efficiency and lifespan are both good. At the same time, after using the deep HOMO hole transport material, the efficiency of R / B light is improved to a certain extent. Although the luminous lifetime of B light decreases by 13%, considering the benefits brought by the efficiency improvement in actual industrial applications (reduced power consumption and little loss of brightness life), the decrease in lifespan is acceptable.

[0160] Example 3

[0161] Compared to Example 2, Example 3 modified the configuration of the green light-emitting auxiliary layer. In Example 3, the green light-emitting auxiliary layer included a host luminescent material TGM and a guest luminescent material GD. In Example 3, the mass of the guest luminescent material GD accounted for 1.5% of the mass of the green light-emitting auxiliary layer. The green light-emitting auxiliary layer was 5 nm thick.

[0162] Compared with Example 2, Example 3 uses two green light emitting layer materials, TGM and GD, as the green light emitting auxiliary layer. Its device characteristics are similar to those of Example 2 and also achieve good technical effects.

[0163] Example 4

[0164] Figure 7 is a schematic diagram of an organic electroluminescent device according to an embodiment. As shown in Figure 7, compared to Example 2, Example 4 includes an additional electron transport layer (ETL 1), located between the charge generation layer (nCG) and the hole blocking layer (HBL 1). The ETL 1 includes an electron transport material and a dopant material, with the dopant material including LiQ (8-hydroxyquinolinolate lithium).

[0165] Compared with the solution of Example 2, the device voltage of Example 4 is significantly reduced, while the device efficiency and lifespan are also maintained at a good level.

[0166] Example 5

[0167] Compared to Example 2, Example 5 changes the configuration of the green light-emitting auxiliary layer. In Example 5, the green light-emitting auxiliary layer (31G, 31G') includes the main luminescent material TGM of the green light-emitting layer (32G, 32G') and the sensitizer material TGH of the green light-emitting layer. In Example 5, the sensitizer material TGH accounts for 30% of the mass of the green light-emitting auxiliary layer. The green light-emitting auxiliary layer is 5 nm thick.

[0168] Compared to Example 2, Example 5 uses two green light-emitting materials, TGM and TGH, as the green light-emitting auxiliary layer. This results in a slight decrease in green light-emitting device efficiency. This decrease is due to TGH acting as a triplet generation center, causing exciton leakage. However, this solution also offers a lifespan advantage, making it useful in certain scenarios where lifespan is crucial.

[0169] Example 6

[0170] Compared to Example 5, the materials of the two green light-emitting auxiliary layers of the two light-emitting units in Example 6 are different. The green light-emitting auxiliary layer 31G, closer to the anode, includes the same luminescent host material TGM as the green light-emitting layer 32G and the same sensitizer material TGH as the green light-emitting layer 32G. The sensitizer material TGH accounts for 30% of the mass of the green light-emitting auxiliary layer. The thickness of the green light-emitting auxiliary layer 31G is 5 nm. The green light-emitting auxiliary layer 31G', closer to the cathode, does not include the material of the green light-emitting layer 32G'.

[0171] Compared to Solution 2, Example 6 shows a slight decrease in green light voltage, while maintaining essentially the same efficiency and lifespan. However, compared to Example 2, this solution requires an additional evaporation source for the green light-emitting auxiliary layer 31G', increasing the process complexity. However, compared to the comparative example, the process in Example 6 is still somewhat simplified.

[0172] The characteristic parameters of some materials are as follows:

[0173] Table 1 Molecular energy orbitals and excited state energies of some materials involved

[0174] Among them, the S1 and T1 of the material are derived from the energy corresponding to the peak of the fluorescence spectrum and phosphorescence spectrum obtained from the dilute solution of the material at ≤77K.

[0175] The properties of Comparative Examples 1-2 and Examples 1-6 are shown in the following table:

[0176] Table 2 Device characteristics

[0177] Figure 8 is a schematic diagram of a display substrate according to an embodiment of the present invention. As shown in Figure 8, the display substrate may include an organic electroluminescent device 200 and a pixel circuit 300 on a substrate 1. The organic electroluminescent device 200 may be the organic electroluminescent device shown in Figures 1-7, and the pixel circuit 300 is used to control the light emission of the organic electroluminescent device. In some embodiments, the pixel circuit 300 may be located on the same side of the substrate as the organic electroluminescent device 200. In other embodiments, the pixel circuit 300 and the organic electroluminescent device 200 are located on different sides of the substrate.

[0178] While certain specific embodiments have been described, these embodiments have been presented by way of example only and are not intended to limit the scope of the invention. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions, and changes in the form of the embodiments described herein may be made without departing from the spirit of the invention. The appended claims and their equivalents are intended to cover such forms or modifications as fall within the scope and spirit of the invention.

Claims

1. An organic electroluminescent device, comprising: An anode, at least one light-emitting unit located on the anode, and a cathode located on a side of the light-emitting unit away from the anode, wherein the light-emitting unit includes: a light-emitting layer and a light-emitting auxiliary layer, wherein the light-emitting auxiliary layer is located between the anode and the light-emitting layer, the material of the light-emitting layer is different from the material of the light-emitting auxiliary layer, the light-emitting layer includes a first main material and a first guest material, and the light-emitting auxiliary layer includes the first main material.

2. The organic electroluminescent device according to claim 1, wherein: The multiple light-emitting units include a green light-emitting unit, the green light-emitting unit includes a green light-emitting layer and the green light-emitting layer includes the first guest material, the light-emitting auxiliary layer includes a green light-emitting auxiliary layer and the green light-emitting auxiliary layer includes the first host material, and wherein a projection of the green light-emitting layer on the anode at least partially overlaps with a projection of the green light-emitting auxiliary layer on the anode.

3. The organic electroluminescent device according to claim 2, wherein: The first host material includes a void-type host material.

4. The organic electroluminescent device according to claim 3, wherein: The green light emitting auxiliary layer further includes the first guest material.

5. The organic electroluminescent device according to claim 3, wherein: The green light emitting layer further includes a sensitizer, and wherein the green light emitting auxiliary layer also includes the sensitizer.

6. The organic electroluminescent device according to claim 5, which satisfies: T1(hole-type host material)-T1(sensitizer)≥0.1eV, in, T1(hole-type host material) is the energy of the first excited triplet state of the hole-type host material, and T1(sensitizer) is the energy of the first excited triplet state of the sensitizer.

7. The organic electroluminescent device according to claim 5, satisfying: |LUMO(sensitizer)|<|LUMO(hole-type host material)|, in, LUMO(sensitizer) is the lowest unoccupied molecular orbital energy level of the sensitizer, and LUMO(sensitizer) is the lowest unoccupied molecular orbital energy level of the hole-type host material.

8. The organic electroluminescent device according to claim 7, wherein: |LUMO(hole-type host material)|-|LUMO(sensitizer)|>0.3eV.

9. The organic electroluminescent device according to claim 5, wherein: The sensitizer includes a thermally activated delayed phosphorescence (TADF) material. Under normalized conditions, the first guest material includes a fluorescent guest material. The overlapping area of ​​the emission spectrum of the thermally activated delayed phosphorescence material and the emission spectrum of the first guest material / the absorption spectrum area of ​​the first guest material is ≥60%.

10. The organic electroluminescent device according to claim 9, wherein: The hole-type host material includes a carbazole material, and the fluorescent guest material includes a boron-containing organic substance.

11. The organic electroluminescent device according to claim 1, wherein the light emitting unit further comprises: In the hole transport layer between the anode and the light-emitting auxiliary layer, the organic electroluminescent device satisfies: |HOMO(hole transport layer)-HOMO(first host material)|≤0.3eV, HOMO(hole transport layer) is the highest occupied molecular orbital energy level of the material of the hole transport layer, and HOMO(host material) is the highest occupied molecular orbital energy level of the first host material.

12. The organic electroluminescent device according to claim 11, wherein the light emitting unit further comprises: A hole injection layer, the hole injection layer is located between the anode and the hole transport layer; a hole blocking layer, the hole blocking layer being located on a side of the light-emitting layer away from the anode; An electron transport layer, the electron transport layer is located on a side of the hole blocking layer away from the anode; An electron injection layer is located on a side of the electron transport layer away from the anode.

13. The organic electroluminescent device according to claim 12, wherein for the electron transport layer and the hole blocking layer of the same light-emitting unit, the following conditions are satisfied: |LUMO (electron transport layer)|>|LUMO (hole blocking layer)|, in, LUMO (electron transport layer) is the lowest unoccupied molecular orbital energy level of the material of the electron transport layer, and LUMO (hole blocking layer) is the lowest unoccupied molecular orbital energy level of the material of the hole blocking layer.

14. The organic electroluminescent device according to claim 12, wherein the light-emitting layer further comprises: a blue light-emitting layer and a red light-emitting layer, wherein: The blue light emitting layer, the red light emitting layer and the green light emitting layer are spaced apart from each other; The light-emitting auxiliary layer includes: a blue light-emitting auxiliary layer and a red light-emitting auxiliary layer, and the blue light-emitting auxiliary layer, the red light-emitting auxiliary layer and the green light-emitting auxiliary layer are spaced apart from each other. wherein the projection of the blue light emitting layer on the anode at least partially overlaps with the projection of the blue light emitting auxiliary layer on the anode, and wherein the projection of the red light emitting layer on the anode at least partially overlaps with the projection of the red light emitting auxiliary layer on the anode.

15. The organic electroluminescent device according to claim 12, wherein the light-emitting layer further comprises: A blue light emitting layer and a red light emitting layer, wherein at least two of a projection of the blue light emitting layer on the anode, a projection of the red light emitting layer on the anode, and a projection of the green light emitting layer on the anode partially overlap.

16. The organic electroluminescent device according to claim 14 or 15, wherein: The red light emitting auxiliary layer includes at least two sub-layers, and in a direction away from the anode and toward the cathode, the HOMO absolute values ​​of the materials of the at least two sub-layers increase sequentially.

17. The organic electroluminescent device according to claim 14 or 15, wherein: The anode includes a plurality of sub-anodes, wherein a voltage applied to a sub-anode corresponding to the red light emitting layer is different from a voltage applied to a sub-anode corresponding to the blue light emitting layer.

18. The organic electroluminescent device according to claim 17, wherein: The voltage applied to the sub-anode corresponding to the red light emitting layer, the voltage applied to the sub-anode corresponding to the blue light emitting layer, and the voltage applied to the sub-anode corresponding to the green light emitting layer are all different.

19. The organic electroluminescent device according to claim 9, satisfying: T1(hole blocking layer)>T1(TADF), in, T1(hole blocking layer) is the energy of the first excited triplet state of the material of the hole blocking layer, and T1(TADF) is the energy of the first excited triplet state of the thermally activated delayed phosphorescent material.

20. The organic electroluminescent device according to claim 19, satisfying: |LUMO (hole blocking layer)|<|LUMO (light-emitting layer)| min LUMO (hole blocking layer) is the lowest unoccupied molecular mass of the material of the hole blocking layer. Orbital energy level, |LUMO (luminescent layer)| min It is the smallest one among the absolute values ​​of the lowest unoccupied molecular orbital energy levels of all materials of the light-emitting layer.

21. The organic electroluminescent device according to claim 20, wherein: |LUMO(luminescent layer)| min -|LUMO (hole blocking layer)|≥0.2 eV.

22. The organic electroluminescent device according to claim 14 or 15, satisfying: |HOMO (hole transport layer)|<|HOMO (blue light emitting auxiliary layer)|<|HOMO (blue light emitting main material)|, in, HOMO (blue light emitting auxiliary layer) is the highest occupied molecular orbital energy level of the material of the blue light emitting auxiliary layer, and HOMO (blue light emitting main material) is the highest occupied molecular orbital energy level of the blue light emitting main material; as well as S1 (blue light emitting auxiliary layer) > S1 (blue light emitting layer), Among them, S1 (blue light emitting auxiliary layer) is the energy of the first singlet state of the material of the blue light emitting auxiliary layer, and S1 (blue light emitting layer) is the energy of the first singlet state of the main material of the blue light emitting layer.

23. The organic electroluminescent device according to claim 14 or 15, wherein: The blue light emitting layer comprises at least one second host material and at least one second guest material, the overlapping area of ​​the absorption spectrum of the second host material and the absorption spectrum of the second guest material / the area of ​​the absorption spectrum of the second guest material is ≥ 60%, and the second host material has at least one of the characteristics of a thermally activated delayed phosphorescent material and a phosphorescent material; The red light emitting layer includes at least one third host material, at least one fourth host material and at least one third guest material, wherein the third host material and the fourth host material are different.

24. The organic electroluminescent device according to claim 23, wherein: The second main material includes at least one of the following: anthracene, fluorene, pyrene and derivatives thereof, DLA structure, polycarbazole structure material or metal complex material; The second guest material includes at least one of the following: pyrene-based organic matter and boron-containing organic matter; The blue light emitting auxiliary layer comprises carbazole and its derivatives; The third main material is an N-type material, and the fourth main material is a P-type material; The third guest material includes at least one of a fluorescent material and a phosphorescent material; The red light emitting auxiliary layer comprises carbazole and its derivatives.

25. The organic electroluminescent device according to claim 11, wherein: The material of the hole transport layer includes at least one of the following: carbazole and its derivatives; The material of the hole injection layer includes at least one of the following: (1) at least one of CuPc, HATCN and MnO3; and (2) the material of the hole transport layer and a P-type dopant, wherein the P-type dopant includes an oxide-based inorganic material and / or a radialene-based organic material; The materials of the electron transport layer include: electron transport material and doping material, wherein the doping material includes at least one of LIQ3, Li, and Ca.

26. The organic electroluminescent device according to any one of claims 1-15, 19-21, and 24, wherein: The organic electroluminescent device includes at least two light-emitting units.

27. The organic electroluminescent device according to claim 26, further comprising: at least one charge generation layer located between two adjacent light emitting units of the at least two light emitting units; A covering layer is provided on a surface of the cathode remote from the light emitting unit.

28. The organic electroluminescent device according to claim 24, wherein: The refractive index of the cover layer for a wavelength of 550 nm is greater than 1.8, and the thickness of the cover layer is in the range of 50 nm to 100 nm.

29. A display substrate, comprising: An organic electroluminescent device on a substrate, the organic electroluminescent device comprising the organic electroluminescent device according to any one of claims 1 to 28; as well as A pixel circuit is used to control the light emission of the organic electroluminescent device.

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