Organic electroluminescent device, display panel, and display apparatus

Abstract

The present application discloses an organic electroluminescent device, a display panel, and a display apparatus. The organic electroluminescent device comprises: a first electrode; a first light-emitting layer, the first light-emitting layer being located on one side of the first electrode; a second light-emitting layer, the second light-emitting layer being located on the side of the first light-emitting layer away from the first electrode; a third light-emitting layer, the third light-emitting layer being located on the side of the second light-emitting layer away from the first electrode; and a second electrode, the second electrode being located on the side of the third light-emitting layer away from the first electrode. The first to third light-emitting layers contain dye-sensitized light-emitting materials, and the first to third light-emitting layers each contain first to third materials. The first material has hole transport properties, the second material has at least one among electron transport properties and thermally activated delayed fluorescence properties, and the third material has thermally activated delayed fluorescence properties.

Description

Organic electroluminescent device, display panel, and display device

[0001] This application claims priority to Chinese patent application number 202311685579.5 filed on December 8, 2023, entitled “Organic electroluminescent device, display panel and display device,” the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of display technology, and in particular, to organic electroluminescent devices, display panels and display apparatuses. Background Art

[0003] In recent years, organic light-emitting diode (OLED)-based luminescent display technology has gradually been recognized by the industry and applied to a wide range of application scenarios due to its advantages such as soft light emission, fast response speed, rich color and wide viewing angle.

[0004] OLED top-emitting devices have gained widespread application due to their larger light-emitting area. However, compared to other display devices, these devices suffer from significant color shift and brightness degradation at wide viewing angles. Specifically, at wide viewing angles, JNCD (Just Noticeable Color Difference) increases significantly, while brightness decreases significantly.

[0005] Therefore, current organic electroluminescent devices, display panels, and display apparatuses still need to be improved.

[0006] Public content

[0007] The present application aims to solve at least one of the technical problems in the related art to a certain extent. To this end, one purpose of the present application is to propose an organic electroluminescent device that can effectively improve the existing problems.

[0008] In one aspect, an organic electroluminescent device is provided, comprising:

[0009] a first electrode;

[0010] a first light-emitting layer, wherein the first light-emitting layer is located on one side of the first electrode;

[0011] a second light-emitting layer, the second light-emitting layer being located on a side of the first light-emitting layer away from the first electrode;

[0012] a third light-emitting layer, the third light-emitting layer being located on a side of the second light-emitting layer away from the first electrode;

[0013] a second electrode, the second electrode being located on a side of the third light-emitting layer away from the first electrode,

[0014] The first light-emitting layer, the second light-emitting layer, and the third light-emitting layer are all dye-sensitized light-emitting material systems, and the first light-emitting layer, the second light-emitting layer, and the third light-emitting layer all contain a first material, a second material, and a third material. The first material has hole transport properties, the second material has electron transport properties and at least one of thermally activated delayed fluorescence properties, and the third material has thermally activated delayed fluorescence properties.

[0015] In some possible implementations, the organic electroluminescent device satisfies at least one of the following conditions:

[0016] The mass percentage of the second material in the third light-emitting layer is greater than the mass percentage of the second material in the second light-emitting layer;

[0017] The thickness of the second light-emitting layer is greater than that of the first light-emitting layer and the third light-emitting layer;

[0018] The total thickness of the film layer containing the luminescent guest material is greater than or equal to 80% of the thickness of the film layer with electron transport function arranged closest to the electrode, and the luminescent guest material includes at least one of the second material and the third material.

[0019] In some possible implementations, the first material of the first light-emitting layer, the second light-emitting layer, and the third light-emitting layer are the same or different, the second material is the same or different, and the third material is the same or different;

[0020] The first material includes at least one of a carbazole compound and a polycarbazole compound;

[0021] The second material includes at least one of a triazine compound and a polycarbazole compound;

[0022] The third material includes at least one of a coumarin compound, an anthracene compound, a boron-containing organic compound, and a metal complex.

[0023] In some possible implementations, the first material in the first light-emitting layer has hole transport properties, the second material has electron transport properties or thermally activated delayed fluorescence properties, and the third material has thermally activated delayed fluorescence properties;

[0024] The first material in the second light-emitting layer has hole transport properties, the second material has electron transport properties or thermally activated delayed fluorescence properties, and the third material has thermally activated delayed fluorescence properties;

[0025] The first material in the third light-emitting layer has hole transport properties or thermally activated delayed fluorescence properties, the second material has electron transport properties, and the third material has thermally activated delayed fluorescence properties.

[0026] In some possible implementations, the first material, the second material, and the third material satisfy at least one of the following conditions:

[0027] Under normalized conditions, the second material and the third material in the first light-emitting layer, the second light-emitting layer, and the third light-emitting layer, in a light-emitting system consisting of the first material, the second material, and the third material, the emission spectrum of the third material accounts for at least 70% of the emission spectrum area of ​​the light-emitting system;

[0028] From the first light-emitting layer, the second light-emitting layer to the third light-emitting layer, the wavelength of the photoemission spectrum of the first material, the second material and the third material of each layer is red-shifted in sequence;

[0029] The mass percentage X of the second material in the first light-emitting layer and the second light-emitting layer in a single light-emitting layer satisfies X ≥ 15%;

[0030] When the first material in the third light-emitting layer has thermally activated delayed fluorescence characteristics, the mass percentage X' of the second material in the third light-emitting layer satisfies X'≥15%;

[0031] The mass percentage Y of the third material in the first light-emitting layer, the second light-emitting layer and the third light-emitting layer in a single light-emitting layer satisfies 0.1%≤Y≤15%;

[0032] In the first light-emitting layer and the second light-emitting layer, when the third material is a fluorescent material, the emission spectrum of the second material and the absorption spectrum of the third material satisfy the following normalization: the overlap area between the two in the visible light region is greater than or equal to 60% of the absorption spectrum area of ​​the third material;

[0033] In the third light-emitting layer, when the third material is a fluorescent material, after normalization, the emission spectrum of the first material and the absorption spectrum of the third material satisfy that the overlapping area in the visible light region is greater than or equal to 60% of the absorption spectrum area of ​​the third material.

[0034] In some possible implementations, at least one of the first light-emitting layer, the second light-emitting layer, and the third light-emitting layer further includes a fourth material, where the fourth material is an exciton-consuming material, and the exciton-consuming material includes a material having fluorescent or phosphorescent properties. The fourth material contained in the first light-emitting layer, the second light-emitting layer, and the third light-emitting layer is the same or different, the mass percentage of the fourth material in a single light-emitting layer is less than or equal to 5%, and the fourth material satisfies:

[0035] The absolute value of the difference between the T1 energy level of the fourth material and the T1 of at least one of the first material, the second material, and the third material is less than or equal to 0.3 eV,

[0036] Alternatively, an overlapping region between the absorption spectrum of the fourth material and the emission spectrum of at least one of the first material, the second material and the third material under normalized conditions occupies greater than or equal to 20% of the area of ​​the absorption spectrum of the fourth material.

[0037] In some possible implementations, in the first light-emitting layer and the second light-emitting layer, an overlapping area between the absorption spectrum of the fourth material and the emission spectrum of at least one of the first material, the second material and the third material in the layer under normalized conditions is greater than or equal to 30% of the absorption spectrum area of ​​the fourth material.

[0038] In some possible implementations, the organic electroluminescent device further satisfies at least one of the following conditions:

[0039] In the first light-emitting layer, when the second material is a fluorescent material, the photoemission spectrum wavelengths λ1, λ2, λ3 and λ4 of the first material, the second material, the third material and the fourth material satisfy: λ1<λ2<λ4, and λ3<λ4;

[0040] In the second light-emitting layer, when the first material is a fluorescent material, the photoemission spectrum wavelengths λ1, λ2, λ3 and λ4 of the first material, the second material, the third material and the fourth material satisfy: λ1<λ2<λ4, and λ3<λ4;

[0041] In the third light-emitting layer, the wavelengths λ1, λ2, λ3 and λ4 of the photoemission spectra of the first material, the second material, the third material and the fourth material satisfy: λ1<λ2<λ4, and λ3<λ4.

[0042] In some possible implementations, the mass percentages of the second material in the first light-emitting layer, the second light-emitting layer, and the third light-emitting layer decrease in sequence.

[0043] In some possible implementations, in the first light-emitting layer, there is at least one material that satisfies the requirement that hole mobility is greater than electron mobility; and / or

[0044] In the third light-emitting layer, there is at least one material satisfying that electron mobility is greater than hole mobility.

[0045] In some possible implementations, under normalized conditions, the third material in the second light-emitting layer satisfies at least one of the following conditions:

[0046] The overlapping area between the emission spectrum of the third material and the emission spectrum of the organic electroluminescent device is greater than or equal to 80% of the emission spectrum area of ​​the third material in the second light-emitting layer;

[0047] In the visible light region, the overlapping area between the emission spectrum of the third material and the emission spectrum of the organic electroluminescent device is greater than 70% of the emission spectrum area of ​​the third material;

[0048] The electroluminescence ratio of the second light-emitting layer is greater than or equal to 50% of the light emitted by the organic electroluminescent device.

[0049] In some possible implementations, when the second material in the second light-emitting layer is a fluorescent material, the emission spectrum of the second material in the first light-emitting layer and the absorption spectrum of the second material in the second light-emitting layer satisfy: under normalized conditions, the overlapping area of ​​the emission spectrum of the second material in the first light-emitting layer and the absorption spectrum of the second material in the second light-emitting layer is greater than or equal to 60% of the absorption spectrum area of ​​the second material in the second light-emitting layer; and / or

[0050] The emission spectrum of the second material in the third light-emitting layer and the absorption spectrum of the second material in the second light-emitting layer satisfy: under normalized conditions, the overlapping area of ​​the emission spectrum of the second material in the third light-emitting layer and the absorption spectrum of the second material in the second light-emitting layer is greater than or equal to 60% of the absorption spectrum area of ​​the second material in the second light-emitting layer.

[0051] In some possible implementations, the organic electroluminescent device satisfies at least one of the following conditions:

[0052] |HOMO(A)-HOMO(E)|≤0.3eV, and |HOMO(E)-HOMO(J)|≤0.3eV;

[0053] |HOMO(A)|≤|HOMO(B)|, |HOMO(E)|≤|HOMO(F)|, |HOMO(J)|≤|HOMO(K)|;

[0054] |HOMO(A)-HOMO(E)|≤0.3eV;

[0055] |HOMO(E)-HOMO(K)|≤0.3eV;

[0056] |T1(A)-T1(E)|≤0.2eV, |T1(E)-T1(J)|≤0.2eV; and,

[0057] T1(A)>T1(B), T1(E)>T1(F), T1(J)>T1(K),

[0058] Wherein, HOMO(A) is the highest occupied energy level orbital of the first material in the first light-emitting layer, HOMO(E) is the highest occupied energy level orbital of the first material in the second light-emitting layer, HOMO(J) is the highest occupied energy level orbital of the first material in the third light-emitting layer, HOMO(B) is the highest occupied energy level orbital of the second material in the first light-emitting layer, HOMO(F) is the highest occupied energy level orbital of the second material in the second light-emitting layer, HOMO(K) is the highest occupied energy level orbital of the second material in the third light-emitting layer, T1(A) is the triplet first excited state energy level of the first material in the first light-emitting layer, T1(B) is the triplet first excited state energy level of the second material in the first light-emitting layer, T1(E) is the triplet first excited state energy level of the first material in the second light-emitting layer, T1(F) is the triplet first excited state energy level of the second material in the second light-emitting layer, T1(J) is the triplet first excited state energy level of the first material in the third light-emitting layer, and T1(K) is the triplet first excited state energy level of the second material in the third light-emitting layer.

[0059] In some possible implementations, the organic electroluminescent device further includes:

[0060] a hole transport layer located between the first electrode and the first light-emitting layer, wherein the first light-emitting layer is located closest to the hole transport layer relative to the other film layers;

[0061] The electron transport layer is located between the second electrode and the third light-emitting layer, and the third light-emitting layer is arranged closest to the electron transport layer relative to other film layers.

[0062] In some possible implementations, the organic electroluminescent device further includes an auxiliary light-emitting layer, and the auxiliary light-emitting layer is located between the hole transport layer and the first light-emitting layer;

[0063] The auxiliary light-emitting layer comprises a fifth material, and the fifth material comprises at least one hole transport material.

[0064] In some possible implementations, the auxiliary light-emitting layer satisfies at least one of the following conditions:

[0065] The thickness of the auxiliary light-emitting layer is greater than 1 / 3 of the total thickness of the film layers containing the light-emitting guest material, wherein the light-emitting guest material includes at least one of the second material and the third material;

[0066] The T1 energy level of the fifth material is at least greater than or equal to the T1 energy level of the material with the second largest content in the first light-emitting layer, and the absolute value of the difference between the HOMO value of the fifth material and the HOMO value of the material with the largest absolute HOMO value in the first light-emitting layer is less than or equal to 0.3 eV;

[0067] The fifth material includes a carbazole compound, and the mass percentage of the fifth material in the auxiliary light-emitting layer is 55wt% to 100wt%;

[0068] The auxiliary light-emitting layer further includes a sixth material, the sixth material including at least one of an anthracene compound, a boron nitrogen compound, and a metal complex, and the mass percentage of the sixth material in the auxiliary light-emitting layer is 0 to 15 wt %;

[0069] The auxiliary light-emitting layer further includes a seventh material, the seventh material includes a polycarbazole compound, and the mass percentage of the seventh material in the auxiliary light-emitting layer is 0 to 45 wt %;

[0070] The seventh material has thermally activated delayed fluorescence characteristics, and under normalized conditions, the emission spectrum of the seventh material must overlap with the absorption spectrum of the light-emitting guest with the least content in the first light-emitting layer by at least 60% of the emission spectrum area of ​​the seventh material;

[0071] The organic electroluminescent device further comprises an electron blocking layer, wherein the T1 energy level of the electron blocking layer is at least 0.1 eV higher than the T1 energy level of the seventh material.

[0072] In some possible implementations, a plurality of light-emitting units are included between the first electrode and the second electrode, and each of the light-emitting units includes at least the first light-emitting layer, the second light-emitting layer, and the third light-emitting layer;

[0073] A charge generation layer is provided between different light-emitting units.

[0074] In some possible implementations, the organic electroluminescent device satisfies at least one of the following conditions:

[0075] The organic electroluminescent device comprises an electron blocking layer, which is located between the first electrode and the first light-emitting layer and in contact with the first light-emitting layer or the auxiliary light-emitting layer, and the electron blocking layer satisfies:

[0076] |HOMO(EBL)-HOMO(EML) max |<0.3eV, HOMO(EBL) is the HOMO energy level of the electron blocking layer, HOMO(EML) max The HOMO energy level of the material with the largest highest occupied orbital in the first light-emitting layer or the auxiliary light-emitting layer in contact with the electron blocking layer;

[0077] The organic electroluminescent device comprises a hole blocking layer, which is located between the second electrode and the third light-emitting layer and contacts the third light-emitting layer, and the hole blocking layer satisfies:

[0078] T1(HBL)>T1(EML3 M ), T1(HBL) is the triplet first excited state energy level of the hole blocking layer, T1(EML3 M ) is the triplet first excited state energy level of the third material in the third light-emitting layer.

[0079] In another aspect of the present application, a display panel is provided, which includes the organic electroluminescent device described above.

[0080] In another aspect of the present application, a display device is provided, which includes the display panel described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0081] FIG1 shows a schematic structural diagram of an organic electroluminescent device according to an example of the present application;

[0082] FIG2 shows a schematic structural diagram of an organic electroluminescent device according to another example of the present application;

[0083] FIG3 shows a schematic structural diagram of an organic electroluminescent device according to another example of the present application;

[0084] FIG4 shows the emission spectrum of TH-1 and the absorption spectrum of D-1 in the embodiment;

[0085] FIG5 shows the emission spectrum of GD-1 and the emission spectrum of the luminescence system composed of TM-1:TH-1:GD-1 in the embodiment. DETAILED DESCRIPTION

[0086] The following embodiments of the present invention are described in detail. The embodiments described below are exemplary and are only used to explain the present invention and are not to be construed as limiting the present invention. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in the art or in the product specifications shall be followed.

[0087] In one aspect, the present application provides an organic electroluminescent device. Referring to FIG1 , the organic electroluminescent device includes a first electrode 100, a first light-emitting layer 310, a second light-emitting layer 320, a third light-emitting layer 330, and a second electrode 200. The first light-emitting layer 310, the second light-emitting layer 320, and the third light-emitting layer 330 are all dye-sensitized luminescent material systems. For example, the first light-emitting layer 310 is located on one side of the first electrode 100, the second light-emitting layer 320 is located on the side of the first light-emitting layer 310 away from the first electrode 100, the third light-emitting layer 330 is located on the side of the second light-emitting layer 320 away from the first electrode 100, and the second electrode 200 is located on the side of the third light-emitting layer 330 away from the first electrode 100. The first light-emitting layer 310, the second light-emitting layer 320, and the third light-emitting layer 330 each contain a first material, a second material, and a third material. The first material has hole transport properties, the second material has at least one of electron transport properties and thermally activated delayed fluorescence properties, and the third material has thermally activated delayed fluorescence properties.

[0088] The organic electroluminescent device has at least one of the advantages of a simple overall device structure, a wider range of material selection, and high device stability.

[0089] For ease of understanding, the following briefly explains the principle by which the device can achieve the above-mentioned beneficial effects:

[0090] In order to improve the luminescent properties of organic electroluminescent devices, sensitizers, such as phosphorescent or molecules with thermally activated delayed fluorescence (TADF) properties, are used to prepare the light-emitting layer of organic electroluminescent devices (OLEDs). Sensitized fluorescence technology can fully utilize the high efficiency characteristics of luminescent materials while having the advantages of high color purity of fluorescent light emitters. Therefore, compared with traditional fluorescence and phosphorescent technologies, this type of material has more technical advantages in the display field. However, the current sensitized fluorescent material system also faces many problems, such as poor efficiency and stability, and has not yet reached the same level as phosphorescence. The organic electroluminescent device proposed in this application has multiple light-emitting layers, and by introducing multiple materials in the multiple light-emitting layers, such as the aforementioned first material, second material and third material, the stacked structure of the device as a whole can be better adjusted, and the carrier balance of the device as a whole can be improved, so that the materials of each layer can be selected more flexibly to form an organic electroluminescent device with better stability, lifespan and efficiency.

[0091] In some examples, in the organic electroluminescent device proposed in the present application, the first light-emitting layer 310, the second light-emitting layer 320, and the third light-emitting layer 330 are all dye-sensitized light-emitting material systems, that is, the constituent materials of the first light-emitting layer 310, the second light-emitting layer 320, and the third light-emitting layer 330 contain dye-sensitized light-emitting materials.

[0092] To achieve good device stability, maintain good luminous efficiency, a low driving voltage, and a long device luminous lifetime, in some examples, the mass percentage of the second material in the third luminescent layer 330 can be greater than the mass percentage of the second material in the second luminescent layer 320. For the first luminescent layer 310, the second luminescent layer 320, and the third luminescent layer 330, the thickness of the second luminescent layer 320 can be greater than the thicknesses of the first luminescent layer 310 and the third luminescent layer 330. In some examples, the total thickness of the layers containing the luminescent guest material can be greater than or equal to 80% of the thickness of the layer with electron transport functionality located closest to the electrode. The luminescent guest material can include at least one of the second material and the third material. The "layer with electron transport functionality" mentioned above can be an electron transport layer, an electron injection layer, or a hole blocking layer. In some examples, the electron transport layer is in contact with the electrode. In this case, the total thickness of the layers containing the luminescent guest material can be greater than or equal to 80% of the thickness of the electron transport layer. In other examples, the electron injection layer is in contact with the electrode, and the total thickness of the film layer containing the light-emitting guest material is greater than or equal to 80% of the thickness of the electron injection layer.

[0093] In some examples, the first light-emitting layer 310 and the third light-emitting layer 330 serve as interface layers to improve the carrier balance of the device. For example, the OLED device may include a hole transport layer located between the first electrode 100 and the first light-emitting layer 310, with the first light-emitting layer 310 positioned closest to the hole transport layer relative to the other layers. The device may also include an electron transport layer located between the second electrode 200 and the third light-emitting layer 330, with the third light-emitting layer 330 positioned closest to the electron transport layer relative to the other layers.

[0094] In some examples, the first material in the first light-emitting layer 310, the second light-emitting layer 320, and the third light-emitting layer 300 can be the same or different (for different situations, the first materials of the three light-emitting layers can be different, or the first materials of two of the light-emitting layers can be the same, and both are different from the first material of the other light-emitting layer), the second material in the first light-emitting layer 310, the second light-emitting layer 320, and the third light-emitting layer 300 can also be the same or different (the layout of the second material in each light-emitting layer can refer to the above-mentioned first material), and the third material in the first light-emitting layer 310, the second light-emitting layer 320, and the third light-emitting layer 300 can be the same or different (the layout of the third material in each light-emitting layer can refer to the above-mentioned first material).

[0095] In some examples, the first material includes at least one of a carbazole compound and a polycarbazole compound, the second material includes at least one of a triazine compound and a polycarbazole compound, and the third material includes at least one of a coumarin compound, an anthracene compound, a boron-containing organic compound, and a metal complex (for example, a complex of a metal such as Ir or Pt).

[0096] The carbazole compounds, polycarbazole compounds (such as 4CzPIN, etc.), triazine compounds, polycarbazole compounds, coumarin compounds, anthracene compounds, boron-containing organic compounds, and metal complexes currently used in organic electroluminescent devices are all suitable for the embodiments of the present application as long as they can meet the setting conditions of each light-emitting layer specified in the present application.

[0097] Those skilled in the art can select materials that meet the above-mentioned compound types as the first material, the second material and the third material based on the specific materials and interface conditions selected for the remaining film layers that are matched with the first light-emitting layer 310, the second light-emitting layer 320 and the third light-emitting layer 300, such as but not limited to the hole injection layer, the electron injection layer, the hole transport layer, the electron transport layer, the hole blocking layer, the electron blocking layer, etc.

[0098] In a specific example, the first material A in the first light-emitting layer 310 has hole transport properties, the second material B has electron transport properties or thermally activated delayed fluorescence properties, and the third material C has thermally activated delayed fluorescence properties. The first material E in the second light-emitting layer 320 has hole transport properties, the second material F has electron transport properties or thermally activated delayed fluorescence properties, and the third material G has thermally activated delayed fluorescence properties. The first material J in the third light-emitting layer 330 has hole transport properties, the second material K has electron transport properties, and the third material M has thermally activated delayed fluorescence properties.

[0099] For example, in the first light-emitting layer 310, the second light-emitting layer 320, and the third light-emitting layer 300, under normalized conditions, the emission spectrum of the third material in the light-emitting system formed by the first, second, and third materials accounts for at least 70% of the emission spectrum area of ​​the light-emitting system. The wavelengths of the photoemission spectra of the first, second, and third materials in each layer are sequentially red-shifted from the first light-emitting layer 310, the second light-emitting layer 320, and the third light-emitting layer 300. In the first light-emitting layer 310 and the second light-emitting layer 320, the mass percentage X of the second material in a single light-emitting layer (i.e., the second material of the first light-emitting layer is in the first light-emitting layer, and the second material of the second light-emitting layer is in the second light-emitting layer) satisfies X ≥ 15%. In the third light-emitting layer, when the first material J exhibits thermally activated delayed fluorescence, the mass percentage X' of the second material L in the third light-emitting layer satisfies X' ≥ 15%. The mass percentage Y of the third material (ie, C, G, and M) in the first light-emitting layer 310 , the second light-emitting layer 320 , and the third light-emitting layer 300 in a single light-emitting layer satisfies 0.1%≤Y≤15%.

[0100] In some examples, when the third material in the first and second light-emitting layers is a fluorescent material, the emission spectrum of the second material in the layer and the absorption spectrum of the third material satisfy the following normalization condition: the overlap area between the two in the visible light region is greater than or equal to 60% of the absorption spectrum area of ​​the third material. When the third material M in the third light-emitting layer is a fluorescent material, the emission spectrum of the first material J in the third light-emitting layer and the absorption spectrum of the third material M satisfy the following normalization condition: the overlap area between the two in the visible light region is greater than or equal to 60% of the absorption spectrum area of ​​the third material M.

[0101] To further improve device performance, at least one of the first light-emitting layer 310, the second light-emitting layer 320, and the third light-emitting layer 300 may further include a fourth material, which is an exciton-depleting material. Exciton-depleting materials include materials having fluorescent or phosphorescent properties. The fourth material contained in the first light-emitting layer 310, the second light-emitting layer 320, and the third light-emitting layer 300 may be the same or different.

[0102] The mass percentage of the fourth material in a single light-emitting layer is relatively small, specifically, less than or equal to 5%. In a single light-emitting layer, that is, in any one of the first light-emitting layer 310, the second light-emitting layer 320, and the third light-emitting layer 300, the absolute value of the difference between the T1 energy level of the fourth material and the T1 of at least one of the first material, the second material, and the third material in the layer is less than or equal to 0.3 eV, or the overlap region between the absorption spectrum of the fourth material and the emission spectrum of at least one of the first material, the second material, and the third material in the layer under normalized conditions accounts for greater than or equal to 20% of the area of ​​the absorption spectrum of the fourth material, that is, the area of ​​the overlap region accounts for greater than or equal to 20% of the area of ​​the absorption spectrum of the fourth material.

[0103] In a specific example, in the first light-emitting layer 310 and the second light-emitting layer 320, the fourth material may also meet the following conditions: the overlapping area of ​​the absorption spectrum of the fourth material and the emission spectrum of at least one of the first material, the second material and the third material in the layer under normalized conditions accounts for greater than or equal to 30% of the area of ​​the absorption spectrum of the fourth material, that is, the area of ​​the above-mentioned overlapping area accounts for greater than or equal to 30% of the area of ​​the absorption spectrum of the fourth material.

[0104] In a specific example, when the second material in the first light-emitting layer 310 is a fluorescent material, the photoemission spectrum wavelengths λ1, λ2, λ3 and λ4 of the first material, the second material, the third material and the fourth material may satisfy: λ1<λ2<λ4, and λ3<λ4.

[0105] In a specific example, when the first material in the second light-emitting layer 320 is a fluorescent material, the photoemission spectrum wavelengths λ1, λ2, λ3 and λ4 of the first material, the second material, the third material and the fourth material satisfy: λ1<λ2<λ4, and λ3<λ4.

[0106] In a specific example, the photoemission spectrum wavelengths λ1, λ2, λ3 and λ4 of the first material, the second material, the third material and the fourth material in the third light emitting layer 330 satisfy: λ1<λ2<λ4, and λ3<λ4.

[0107] In a specific embodiment, the weight percentage of the second material in the first light-emitting layer 310, the second light-emitting layer 320, and the third light-emitting layer 330 may decrease in sequence. That is, the weight percentage of the second material in the first light-emitting layer 310 is lower than the weight percentage of the second material in the second light-emitting layer 320, and the weight percentage of the second material in the second light-emitting layer 320 is lower than the weight percentage of the second material in the third light-emitting layer 330.

[0108] In a specific example, the first light-emitting layer 310 may contain at least one material satisfying that hole mobility is greater than electron mobility. For example, the hole mobility may be at least one order of magnitude greater than the electron mobility. The third light-emitting layer 330 may contain at least one material satisfying that electron mobility is greater than hole mobility. For example, the electron mobility may be at least one order of magnitude greater than the hole mobility.

[0109] In some examples, under normalized conditions, the emission spectrum of the third material G in the second light-emitting layer 320 has a large overlap area with the emission spectrum of the organic electroluminescent device as a whole. Specifically, the overlap area may be greater than or equal to 80% of the emission spectrum area of ​​the third material G in the second light-emitting layer 320.

[0110] In some examples, in the visible light region, the overlap area between the emission spectrum of the third material G and the overall emission spectrum of the organic electroluminescent device may also be relatively large, specifically greater than 70% of the emission spectrum area of ​​the third material G. In this OLED device, the electroluminescence of the second light-emitting layer 320 may account for greater than or equal to 50% of the light emitted by the organic electroluminescent device.

[0111] In some examples, when the second material F in the second light-emitting layer 320 is a fluorescent material, the emission spectrum of the second material B in the first light-emitting layer 310 and the absorption spectrum of the second material F in the second light-emitting layer 320, under normalized conditions, may have an overlapping area greater than or equal to 60% of the absorption spectrum area of ​​the second material F in the second light-emitting layer 320. The emission spectrum of the second material K in the third light-emitting layer 330 and the absorption spectrum of the second material F in the second light-emitting layer 320, under normalized conditions, may have an overlapping area greater than or equal to 60% of the absorption spectrum area of ​​the second material F in the second light-emitting layer 320.

[0112] In order to further improve the device performance of the OLED, the energy level relationship of each material in the three light-emitting layers may satisfy at least one of the following conditions:

[0113] |HOMO(A)-HOMO(E)|≤0.3eV, and |HOMO(E)-HOMO(J)|≤0.3eV;

[0114] |HOMO(A)|≤|HOMO(B)|, |HOMO(E)|≤|HOMO(F)|, |HOMO(J)|≤|HOMO(K)|;

[0115] |HOMO(A)-HOMO(E)|≤0.3eV;

[0116] |HOMO(E)-HOMO(K)|≤0.3eV;

[0117] |T1(A)-T1(E)|≤0.2eV, |T1(E)-T1(J)|≤0.2eV; and,

[0118] T1(A)>T1(B), T1(E)>T1(F), T1(J)>T1(K).

[0119] Among them, HOMO(A) is the highest occupied energy level orbital of the first material A in the first light-emitting layer 310, HOMO(E) is the highest occupied energy level orbital of the first material E in the second light-emitting layer 320, HOMO(J) is the highest occupied energy level orbital of the first material J in the third light-emitting layer 330, HOMO(B) is the highest occupied energy level orbital of the second material B in the first light-emitting layer 310, HOMO(F) is the highest occupied energy level orbital of the second material F in the second light-emitting layer 320, and HOMO(K) is the highest occupied energy level orbital of the second material K in the third light-emitting layer 330.

[0120] T1(A) is the triplet first excited state energy level of the first material in the first light-emitting layer 310, T1(B) is the triplet first excited state energy level of the second material in the first light-emitting layer 310, T1(E) is the triplet first excited state energy level of the first material in the second light-emitting layer 320, T1(F) is the triplet first excited state energy level of the second material F in the second light-emitting layer 320, T1(J) is the triplet first excited state energy level of the first material J in the third light-emitting layer 330, and T1(K) is the triplet first excited state energy level of the second material K in the third light-emitting layer 330.

[0121] In order to further improve the performance of the device, referring to Figure 2, taking the first electrode 100 as the anode and the second electrode 200 as the cathode as an example, the organic electroluminescent device proposed in this application may further have, including but not limited to, a hole injection layer 400, a hole transport layer 500, an electron blocking layer 600, a hole blocking layer 700, an electron transport layer 800 and an electron injection layer 900.

[0122] For example, the anode can be made of a high-work-function electrode material, such as a transparent conductive oxide such as ITO or IZO. Alternatively, a composite electrode formed by stacking a metal and a transparent conductive oxide, such as Ag / ITO, Al / ITO, Ag / IZO, or Al / IZO, can be used. Those skilled in the art will appreciate that when a transparent conductive material is used as the anode, the device has a bottom-emitting structure. When a reflective composite electrode containing a metal such as Ag or Al is used, the device has a top-emitting structure.

[0123] The hole injection layer 400 may contain injection materials such as CuPc, HATCN, MnO3, and may also be formed by p-type doping in a hole transport material. The optional p-type dopant may be an oxide-based inorganic material or a radiallyne-based organic material. The layer may have a thickness of 1 to 30 nm and may be formed by methods including but not limited to multi-source co-evaporation.

[0124] The hole transport layer 500 can contain a material with excellent hole transport properties and have a thickness ranging from 1 to 200 nm. In devices where the light-emitting layer emits green or red light, the hole transport layer 500 can be formed by stacking two layers of hole transport materials with increasing HOMO absolute values ​​to achieve a lower hole transport barrier. Materials for the hole transport layer may include, but are not limited to, carbazole or aniline compounds with high hole mobility.

[0125] The material of the electron blocking layer 600 can be adjusted according to the HOMO energy level of the material in contact with it to reduce the hole transport barrier. The thickness of the electron blocking layer 600 can be 1 to 90 nm.

[0126] In some examples, the OLED may include an auxiliary light-emitting layer 340. Auxiliary light-emitting layer 340 is located between the hole transport layer 500 and the first light-emitting layer 310. Auxiliary light-emitting layer 340 includes a fifth material, which includes at least one hole-transporting material. The thickness of auxiliary light-emitting layer 340 can be relatively large, for example, greater than one-third of the total thickness of the layers containing the light-emitting guest material, where the light-emitting guest material includes at least one of the second material and the third material.

[0127] To further improve the overall performance of the device, the fifth material is selected to have a T1 energy level at least equal to or greater than the T1 energy level of the material with the next highest content in the first light-emitting layer. Furthermore, the absolute difference between the HOMO value of the fifth material and the HOMO value of the material with the highest absolute HOMO value in the first light-emitting layer can be controlled to be less than or equal to 0.3 eV. For example, the fifth material comprises a carbazole compound, and its mass percentage in the auxiliary light-emitting layer can be relatively high, specifically 55 wt% to 100 wt%.

[0128] In some examples, the auxiliary light-emitting layer 340 may further include at least one of a sixth material and a seventh material. The sixth material may include at least one of an anthracene compound, a boron nitrogen compound, and a metal complex, and the mass percentage of the sixth material in the auxiliary light-emitting layer 340 is 0 to 15 wt% (may not be 0). The seventh material includes a polycarbazole compound, and the mass percentage of the seventh material in the auxiliary light-emitting layer 340 is 0 to 45 wt% (may not be 0). Exemplarily, the seventh material may have thermally activated delayed fluorescence characteristics, and under normalized conditions, the emission spectrum of the seventh material must have a large overlapping area with the absorption spectrum of the light-emitting guest material with the least content in the first light-emitting layer 310. For example, the overlapping area may account for at least 60% of the emission spectrum area of ​​the seventh material.

[0129] When the device has an auxiliary light-emitting layer 340, the material of the electron blocking layer 600 can be adjusted according to the seventh material of the auxiliary light-emitting layer 340. For example, the selected electron blocking layer material can make the T1 energy level of the electron blocking layer 600 greater than the T1 energy level of the seventh material, and the difference between the two can be greater than 0.1 eV.

[0130] In some examples, when the device does not have the auxiliary light-emitting layer 340, the electron blocking layer 600 may be in contact with the first light-emitting layer. To further improve device performance, the material of the electron blocking layer 600 may be selected based on the material of the film layer in contact with it. For example, the electron blocking layer 600 may satisfy: |HOMO(EBL)-HOMO(EML max )|<0.3eV. Wherein, HOMO(EBL) is the HOMO energy level of the electron blocking layer, HOMO(EML max ) is the HOMO energy level of the material with the largest highest occupied orbital in the first light-emitting layer or the auxiliary light-emitting layer in contact with the electron blocking layer.

[0131] In some examples, the hole blocking layer 700 may be in contact with the third light emitting layer. The material of the hole blocking layer 700 and the third material in the third light emitting layer may directly satisfy: T1(HBL)>T1(EML3 M ), wherein T1(HBL) is the triplet first excited state energy level of the hole blocking layer, T1(EML3 M ) is the triplet first excited state energy level of the third material in the third light-emitting layer. More specifically, the HOMO absolute value of the material in the hole blocking layer 700 can be greater than the HOMO absolute value of the material in the third light-emitting layer with the largest HOMO absolute value. For example, the difference between the two can be greater than or equal to 0.2 eV.

[0132] The electron transport layer 800 may include a material with good electron transport properties, for example, it may be formed by methods including but not limited to evaporation. Alternatively, it may be formed by doping an electron transport material in a certain proportion, such as LIQ3, Li, Ca, etc. The specific thickness of this layer is not particularly limited, for example, it may be 10 to 70 nm. The electron injection layer 900 may be formed of a low work function metal, such as Li, Ca, Yb, or a metal salt LiF, LiQ3, etc., formed by evaporation. The thickness of the electron injection layer 900 may be 0.5 to 2 nm.

[0133] When the second electrode 200 is a cathode, it can be formed of a metal with a low work function, such as Al, Ag, Mg, or an alloy containing a low work function metal. Those skilled in the art will appreciate that if the OLED is a bottom-emitting device, the thickness of the second electrode 200 must exceed 80 nm to ensure good reflectivity, such as a reflectivity of at least 85% at 550 nm. If the OLED is a top-emitting device, the thickness of the second electrode 200 can be within the range of 10 to 20 nm to ensure a certain transmittance. For example, a transmittance of greater than 45% can be achieved at 550 nm.

[0134] In some examples, the surface of the second electrode 200, that is, the surface away from the light-emitting layer, may further have an optical capping layer (CPL) and an encapsulation layer (not shown in the figure). The optical capping layer can improve the optical output and can be formed by a small amount of material with a higher refractive index including but not limited to evaporation. For example, the thickness of the optical capping layer can be 50 to 100 nm, and the refractive index at 550 nm is greater than 1.8. The encapsulation layer can adopt a structure such as UV sealant or thin film encapsulation (TFE).

[0135] In some examples, if the OLED is a top-emitting device, at least one of the material type and thickness of each layer between the first electrode 100 and the second electrode 200 can be adjusted to ensure that the optical thickness of the organic layer between the first electrode 100 and the second electrode 200 meets the optical path requirements of the optical microresonator, thereby achieving optimal light output intensity and the desired color. For example, the optical path within the top-emitting device can be adjusted by changing the thickness of the hole transport layer (HTL), which has a relatively low voltage impact.

[0136] Referring to Figure 3 , the organic electroluminescent device proposed in this application can also be a stacked device, that is, a plurality of light-emitting units (as shown in 10A and 10B in the figure) are included between the first electrode 100 and the second electrode 200. Each light-emitting unit includes at least a first light-emitting layer, a second light-emitting layer, and a third light-emitting layer (as shown in 310A / B-340A / B in the figure). A charge generation layer is provided between different light-emitting units. The charge generation layer may include an N-type sublayer 350A and a P-type sublayer 350B. Each light-emitting unit may also include structures including, but not limited to, a hole / charge transport layer and a hole / charge blocking layer.

[0137] In another aspect of the present application, a display panel is provided. The display panel includes the aforementioned organic electroluminescent device. Thus, the display panel possesses all the features and advantages of the aforementioned electroluminescent device, which are not further elaborated here. For example, the display panel exhibits at least one of the following advantages: good stability, high efficiency, long device life, and high color purity.

[0138] In another aspect of the present application, a display device is provided. The display device includes the display panel described above. Thus, the display device possesses all the features and advantages of the display panel described above, which are not further elaborated here. For example, the display device has at least one of the following advantages: good stability, high efficiency, long device life, and high color purity.

[0139] Example

[0140] Devices 1 through 13 were prepared. Each of these devices was a top-emitting OLED device with an Ag / ITO anode. The percentages for each material are by weight. All other layers, unless otherwise specified, were constructed from conventional materials in the art. For layers not specifically specified, the same materials were used. The arrangement of the layers in Devices 1 through 13 can be found in the following description. Unless otherwise specified, the English and English abbreviations used in the devices of the following examples have the following meanings:

[0141] HIL: hole injection layer; HTL: hole transport layer; EBL: electron blocking layer; a-EML: auxiliary light-emitting layer; EML: light-emitting layer; HBL: hole blocking layer; ETL: electron transport layer; EIL: electron injection layer; CPL: optical cover layer.

[0142] Device 1:

[0143] Ag(100nm) / ITO(8nm) / HIL / HTL1 / HTL2 / EBL(5nm) / EML: (TM-1:TH-1:D-1)(40nm, 60%:39%:1%) / HBL / ETL / EIL(1nm) / Mg:Ag(15nm) / CPL.

[0144] Device 2:

[0145] Ag(100nm) / ITO(8nm) / HIL / HTL1 / HTL2 / a-EML: (TM-1:D-1)(5nm, 1.0%) / EML: (TM-1:TH-1:D-1)(34nm, 60%:39%:1%) / HBL / ETL / EIL(1nm) / Mg:Ag(15nm) / CPL.

[0146] Device 3:

[0147] Ag(100nm) / ITO(8nm) / HIL / HTL1 / HTL2 / EBL(5nm) / a-EML: (TM-1:TH-1) (5nm, 70%:30%) / EML: (TM-1:TH-1:D-1) (34nm, 60%:39%:1%) / HBL / ETL / EIL (1nm) / Mg:Ag (15nm) / CPL.

[0148] Device 4:

[0149] Ag(100nm) / ITO(8nm) / HIL / HTL1 / HTL2 / a-EML: (TM-1:TH-1)(5nm, 70%:30%) / EML: (TM-1:TH-1:D-1)(34nm, 60%:39%:1%) / HBL / ETL / EIL(1nm) / Mg:Ag(15nm) / CPL.

[0150] Device 5:

[0151] Ag(100nm) / ITO(8nm) / HIL / HTL1 / HTL2 / TM-1:TD-1(5nm,1.0%) / TM-1:TH1:D-1)(3nm,75%:24.2%:0.8%) / EML:(TM-1: TH-1:D-1) (34nm, 60%:39.2%:0.8%) / TM-1:TH-1:D-1 (3nm, 75%:24.2%:0.8%) / HBL / ETL / EIL (1nm) / Mg:Ag (15nm) / CPL.

[0152] Device 6:

[0153] Ag(100nm) / ITO(8nm) / HIL / HTL1 / HTL2 / a-EML: (TM-1:TD-1)(5nm, 1.0%) / EML1: (TM-1:TH1:D-1)(3nm, 75%:24.2%:0.8%) / EML 2: (TM-1:TH-1:D-1)(34nm, 60%:39.2%:0.8%) / EML 3: (TM-1:TH-1:D-1)(3nm, 45%:54.2%:0.8%) / HBL / ETL / EIL(1nm) / Mg:Ag(15nm) / CPL。

[0154] Device 7:

[0155] Ag(100nm) / ITO(8nm) / HIL / HTL1 / HTL2 / a-EML: (TM-1:TD-1)(5nm, 1.0%) / EML1: (TM-1:TH1:D-1)(3nm, 45%:54.2%:0.8%) / EML2: (TM-1:TH-1:D-1)(34nm, 60%:39.2%:0.8%) / EML3: (TM-1:TH-1:D-1)(3nm, 75%:24.2%:0.8%) / HBL / ETL / EIL(1nm) / Mg:Ag(15nm) / CPL。

[0156] Device 8:

[0157] Ag(100nm) / ITO(8nm) / HIL / HTL1 / HTL2 / a-EML: (TM-1:TD-1)(5nm, 1.0%) / EML1: (TM-1:TH1:D-1)(3nm, 45%:54.2%:0.8%) / EML2: (TM-1:TH-1:D-1)(34nm, 60%:39.2%:0.8%) / EML3: (TM-1:TH-1:D-1)(3nm, 45%:54.2%:0.8%) / HBL / ETL / EIL(1nm) / Mg:Ag(15nm) / CPL。

[0158] Device 9:

[0159] Ag(100nm) / ITO(8nm) / HIL / HTL1 / HTL2 / a-EML: (TM-1:TD-1)(5nm, 1.0%) / EML1: (TM-1:TH-1:D-1)(3nm, 65%:34.2%:0.8%) / EML2: (T M-1:TH-1:D-1) (34nm, 60%:39.2%:0.8%) / EML3: (TM-1:TH-1:D-1) (3nm, 45%:54.2%:0.8%) / HBL / ETL / EIL (1nm) / Mg:Ag (15nm) / CPL.

[0160] Device 10:

[0161] Ag(100nm) / ITO(8nm) / HIL / HTL1 / HTL2 / a-EML: (TM-1:TD-1)(10nm, 1.0%) / EML1: (TM-1:TH-1:D-1)(3nm, 65%:34.2%:0.8%) / EML2: ( TM-1:TH-1:D-1)(29nm, 60%:39.2%:0.8%) / EML3: (TM-1:TH-1:D-1)(3nm, 45%:54.2%:0.8%) / HBL / ETL / EIL(1nm) / Mg:Ag(15nm) / CPL.

[0162] Device 11:

[0163] Ag(100nm) / ITO(8nm) / HIL / HTL1 / HTL2 / a-EML: (TM-1:TD-1)(15nm, 1.0%) / EML1: (TM-1:TH-1:D-1)(3nm, 65%:34.2%:0.8%) / EML2: ( TM-1:TH-1:D-1)(24nm, 60%:39.2%:0.8%) / EML3: (TM-1:TH-1:D-1)(3nm, 45%:54.2%:0.8%) / HBL / ETL / EIL(1nm) / Mg:Ag(15nm) / CPL.

[0164] In the above examples, TM-1 is a hole-transporting host material with a hole mobility / electron mobility ratio > 30; TH-1 is an electron-transporting material with TADF properties with an electron mobility / hole mobility ratio > 10; and D-1 is a guest with fluorescent luminescence characteristics. The characteristic parameters of some materials are shown in Table 1 below:

[0165] Table 1

[0166] The emission spectrum of TH-1 and the absorption spectrum of D-1 are shown in Figure 4 (normalized intensity on the vertical axis). The TH-1 emission spectrum is obtained from the emission spectrum of a TM-1:TH-1 (90%:10%) doped film under 350nm excitation conditions, while the D-1 absorption spectrum is measured using a pure film. The emission spectrum of GD-1 and the emission spectrum of the TM-1:TH-1:GD-1 system are shown in Figure 5 (normalized intensity on the vertical axis).

[0167] The spectrum test is performed using a bottom-emitting device structure, specifically:

[0168] GD-1 spectrum test device structure: ITO / HIL / HTL1 / HTL2 / EBL / TM-1:D-1 (20nm, 60%:39%:1%) / HBL / ETL / EIL / Mg:Ag (100nm).

[0169] Light-emitting layer spectrum test device: ITO / HIL / HTL1 / HTL2 / EBL / TM-1:TH-1:D-1 (40nm, 60%:39%:1%) / HBL / ETL / EIL / Mg:Ag (100nm).

[0170] The performance test results of devices 1-11 are shown in Table 2 below:

[0171] Table 2

[0172] The test results in Table 2 show that compared to Device 1, Device 2 features an auxiliary light-emitting layer formed by a hole-type high-T1 host and a fluorescent guest (TM-1:D-1), achieving similar efficiency and lifetime to Device 1. However, due to the presence of the auxiliary light-emitting layer, Device 2 uses HT3 with a lower T1 instead of the HT2 / EBL combination. While achieving similar efficiency, lifetime, and voltage, Device 2 offers a more flexible material selection strategy for its hole-transport layer, simplifying the device material composition.

[0173] Compared to device 1, device 3 features an auxiliary light-emitting layer formed of TM-1 and TH-1, a material with TADF characteristics. The TH-1 concentration in the first light-emitting layer is 30%, less than the 39% in the second light-emitting layer. Device 4 differs from device 3 in that device 4 uses HT3 instead of the HT2 / EBL combination. HT3's T1 is similar to that of TH-1, while device 3's EBL has a higher T1 energy. Device 3 exhibits superior efficiency and lifetime characteristics to device 1, while device 4 exhibits a significant performance degradation. This indicates that the presence of TADF material in the auxiliary light-emitting layer requires a high T1 energy in the associated hole transport layer.

[0174] In summary, the auxiliary light-emitting layer structure of TM-1:D-1 adopted in device 2 simplifies the overall device material composition, provides a more flexible strategy for the selection of HT, and the device characteristics are no different from those of device 1 with a standard structure.

[0175] Device 5, based on Device 2, features a three-layer luminescent layer. The concentration of the electron-transporting TH-1 in the two luminescent layers near the EBL and HBL is significantly lower than that in the middle luminescent layer (the concentrations in the first, second, and third luminescent layers are 24.2%, 39.2%, and 24.2%, respectively). The device's efficiency and voltage are essentially the same as those of Device 1.

[0176] Device 6 builds on the foundation of device 5 by increasing the TH-1 concentration in the third light-emitting layer, near the HBL, to a higher level than in the second light-emitting layer. The TH-1 concentration distribution in the three light-emitting layers increases sequentially (24.2%, 39.2%, and 54.2%). Compared to device 1, device 6 exhibits slightly lower voltage and efficiency, while significantly improving lifetime. These changes can be attributed to the new structure's more optimized charge transfer pathways and improved carrier balance, which in turn enhances device stability.

[0177] Based on device 5, device 7 increases the TH-1 concentration in the first light-emitting layer close to the EBL and makes it higher than that in the second light-emitting layer. The concentration distribution of TH-1 in the three light-emitting layers decreases successively (54.2%, 39.2%, and 24.2%). Compared with device 1, the device voltage increases, the device efficiency decreases, and the device life is also significantly reduced under this structure.

[0178] Based on device 5, device 8 increases the TH-1 thickness of the first and third light-emitting layers and makes them higher than the second light-emitting layer. The concentration distribution of TH-1 in the three light-emitting layers is (54.2%, 39.2%, and 54.2%), respectively. Compared with device 1, the device voltage increases under this structure, the efficiency decreases significantly, and the device life is significantly improved.

[0179] Based on device 5, device 9 reduces the TH-1 content in the first light-emitting layer. The TH-1 concentrations are (34.2%, 39.2%, and 54.2%), respectively. The device efficiency is improved compared to device 8, and the device life is also significantly improved compared to standard device 1.

[0180] Combining the test results of Devices 1, 6, 8, and 9, we can see that reducing the TH-1 concentration in the first light-emitting layer improves device efficiency, while increasing the TH-1 concentration in the third light-emitting layer increases device life. Therefore, the three-light-emitting layer structure proposed in this application provides more flexible device characteristic adjustment compared to the standard structure. Furthermore, Device 6 also exhibits better overall characteristics than the standard Device 1.

[0181] Compared to device 9, devices 10 and 11 increased the proportion of the auxiliary light-emitting layer relative to the total thickness of the film containing the luminescent guest D-1. This reduced device efficiency but improved device lifetime. In device 11, the TH-1 thickness accounted for one-third of the total light-emitting layer thickness, resulting in a reduction in efficiency of over 5%.

[0182] Based on the above results, tandem top-emitting devices 12 and 13 were prepared. Both devices adopted a top-emitting structure and had an Ag / ITO anode. Unless otherwise specified, all other layers were constructed from conventional materials in the art, and the corresponding layers in each embodiment, where materials are not specifically specified, used the same materials. Unless otherwise specified, the abbreviations in the devices of the following embodiments have the same meanings as those in devices 1-11, where n-CGL and p-CGL represent charge generation layers.

[0183] Device 12:

[0184] Ag(100nm) / ITO(8nm) / HIL / HTL1 / HTL2 / EBL(5nm) / EMLA: (TM-1:TH-1:D-1)(40nm, 60%:39%:1%) / ETL / n-CGL / p-CGL / HTL1 / HTL2 / EBL(5nm) / EMLB: (TM-1:TH-1:D-1)(40nm, 60%:39%:1%) / EIL(1nm) / Mg:Ag(15nm) / CPL.

[0185] Device 13:

[0186] Ag(100nm) / ITO(8nm) / HIL / HTL1 / HTL2 / a-EMLA: (TM:D-1)(1.0%) / EML1A: (TM-1:TH-1:D-1)(3nm, 70%:29.2%:0.8%) / EML2A: (TM-1:TH-1:D-1)(34nm, 60%:39%:1.0%) / EML3A: (TM-1:TH-1:D-1)(3nm, 45%:54.2%:0.8%) / ETL / n-CGL / p- CGL / HTL1 / HTL2 / EBL(5nm) / a-EMLB: (TM:D-1)(1.0%) / EML1B: (TM-1:TH-1:D-1)(3nm, 70%:29.2%:0.8%) / EML2B: (TM) -1:TH-1:D-1)(34nm, 60%:39%:1%) / EML3B: (TM-1:TH-1:D-1)(3nm, 45%:54.2%:0.8%) / EIL(1nm) / Mg:Ag(15nm) / CPL.

[0187] The performance test results of devices 12-13 are shown in Table 3 below:

[0188] Table 3

[0189] Device 12 is a tandem sensitized fluorescent device with a standard TM-1:TH-1:D-1 structure. Device 13, in which both units are connected in series, has a three-emission layer structure. The TH-1 concentration increases from the first to the third layer (29.2%, 39%, and 54.2%). Compared to device 12 with the standard structure, device 13 exhibits a slight decrease in efficiency but a significant 10% improvement in lifetime. This demonstrates that the three-emission layer structure is also suitable for improving the performance and tunability of tandem devices.

[0190] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, "plurality" means two or more, unless otherwise specifically specified.

[0191] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of this specification. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0192] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. An organic electroluminescent device, wherein: include: a first electrode; a first light-emitting layer, wherein the first light-emitting layer is located on one side of the first electrode; a second light-emitting layer, the second light-emitting layer being located on a side of the first light-emitting layer away from the first electrode; a third light-emitting layer, the third light-emitting layer being located on a side of the second light-emitting layer away from the first electrode; a second electrode, the second electrode being located on a side of the third light-emitting layer away from the first electrode, The first light-emitting layer, the second light-emitting layer, and the third light-emitting layer are all dye-sensitized light-emitting material systems, and the first light-emitting layer, the second light-emitting layer, and the third light-emitting layer all contain a first material, a second material, and a third material. The first material has hole transport properties, the second material has electron transport properties and at least one of thermally activated delayed fluorescence properties, and the third material has thermally activated delayed fluorescence properties.

2. The organic electroluminescent device according to claim 1, wherein: The organic electroluminescent device satisfies at least one of the following conditions: The mass percentage of the second material in the third light-emitting layer is greater than the mass percentage of the second material in the second light-emitting layer; The thickness of the second light-emitting layer is greater than the thickness of the first light-emitting layer and the third light-emitting layer; The total thickness of the film layer containing the luminescent guest material is greater than or equal to 80% of the thickness of the film layer with electron transport function arranged closest to the electrode, and the luminescent guest material includes at least one of the second material and the third material.

3. The organic electroluminescent device according to claim 1 or 2, wherein: The first material of the first light-emitting layer, the second light-emitting layer and the third light-emitting layer is the same or different, the second material is the same or different, and the third material is the same or different; The first material includes at least one of a carbazole compound and a polycarbazole compound; The second material includes at least one of a triazine compound and a polycarbazole compound; The third material includes at least one of coumarin compounds, anthracene compounds, boron-containing organic compounds, and metal complexes.

4. The organic electroluminescent device according to claim 3, wherein: The first material in the first light-emitting layer has hole transport properties, the second material has electron transport properties or thermally activated delayed fluorescence properties, and the third material has thermally activated delayed fluorescence properties; The first material in the second light-emitting layer has hole transport properties, the second material has electron transport properties or thermally activated delayed fluorescence properties, and the third material has thermally activated delayed fluorescence properties; The first material in the third light-emitting layer has a hole transport property or a thermally activated delayed fluorescence property, the second material has an electron transport property, and the third material has a thermally activated delayed fluorescence property.

5. The organic electroluminescent device according to claim 4, wherein: The first material, the second material, and the third material satisfy at least one of the following conditions: Under normalized conditions, the second material and the third material in the first light-emitting layer, the second light-emitting layer and the third light-emitting layer, in a light-emitting system composed of the first material, the second material and the third material, the emission spectrum of the third material accounts for at least 70% of the emission spectrum area of ​​the light-emitting system; From the first light-emitting layer, the second light-emitting layer to the third light-emitting layer, the wavelength of the photoemission spectrum of the first material, the second material and the third material of each layer is red-shifted in sequence; The mass percentage X of the second material in the first light-emitting layer and the second light-emitting layer in a single light-emitting layer satisfies X ≥ 15%; When the first material in the third light-emitting layer has a thermally activated delayed fluorescence characteristic, the mass percentage X' of the second material in the third light-emitting layer satisfies X'≥15%; The mass percentage content Y of the third material in the first light-emitting layer, the second light-emitting layer and the third light-emitting layer in a single light-emitting layer satisfies 0.1%≤Y≤15%; In the first light-emitting layer and the second light-emitting layer, when the third material is a fluorescent material, the emission spectrum of the second material and the absorption spectrum of the third material satisfy the normalization, and the overlapping area of ​​the two in the visible light region is greater than or equal to 60% of the absorption spectrum area of ​​the third material; In the third light-emitting layer, when the third material is a fluorescent material, after normalization, the emission spectrum of the first material and the absorption spectrum of the third material have an overlapping area in the visible light region greater than or equal to 60% of the absorption spectrum area of ​​the third material.

6. The organic electroluminescent device according to claim 3, wherein: At least one of the first light-emitting layer, the second light-emitting layer and the third light-emitting layer further comprises a fourth material, the fourth material is an exciton-consuming material, the exciton-consuming material comprises a material having a fluorescent property or a phosphorescent property, the fourth material contained in the first light-emitting layer, the second light-emitting layer and the third light-emitting layer is the same or different, the mass percentage of the fourth material in a single light-emitting layer is less than or equal to 5%, and the fourth material satisfies: The absolute value of the difference between the T1 energy level of the fourth material and the T1 of at least one of the first material, the second material and the third material is less than or equal to 0.3 eV, Alternatively, an overlapping region between the absorption spectrum of the fourth material and the emission spectrum of at least one of the first material, the second material and the third material under normalized conditions occupies greater than or equal to 20% of the area of ​​the absorption spectrum of the fourth material.

7. The organic electroluminescent device according to claim 6, wherein: In the first light-emitting layer and the second light-emitting layer, the overlapping area of ​​the absorption spectrum of the fourth material and the emission spectrum of at least one of the first material, the second material and the third material in the layer under normalized conditions is greater than or equal to 30% of the absorption spectrum area of ​​the fourth material.

8. The organic electroluminescent device according to claim 6, wherein: The organic electroluminescent device further satisfies at least one of the following conditions: In the first light-emitting layer, when the second material is a fluorescent material, the wavelengths λ1, λ2, λ3 and λ4 of the photoemission spectra of the first material, the second material, the third material and the fourth material satisfy: λ1<λ2<λ4, and λ3<λ4; In the second light-emitting layer, when the first material is a fluorescent material, the wavelengths λ1, λ2, λ3 and λ4 of the photoemission spectra of the first material, the second material, the third material and the fourth material satisfy: λ1<λ2<λ4, and λ3<λ4; In the third light-emitting layer, the wavelengths λ1, λ2, λ3 and λ4 of the photoemission spectra of the first material, the second material, the third material and the fourth material satisfy: λ1<λ2<λ4, and λ3<λ4.

9. The organic electroluminescent device according to claim 1, wherein: The mass percentage of the second material in the first light-emitting layer, the second light-emitting layer and the third light-emitting layer decreases in sequence.

10. The organic electroluminescent device according to claim 1, wherein: In the first light-emitting layer, there is at least one material satisfying that hole mobility is greater than electron mobility; and / or In the third light-emitting layer, there is at least one material satisfying that electron mobility is greater than hole mobility.

11. The organic electroluminescent device according to claim 1, wherein: Under normalized conditions, the third material in the second light-emitting layer satisfies at least one of the following conditions: The overlapping area between the emission spectrum of the third material and the emission spectrum of the organic electroluminescent device is greater than or equal to 80% of the emission spectrum area of ​​the third material in the second light-emitting layer; In the visible light region, the overlap area between the emission spectrum of the third material and the emission spectrum of the organic electroluminescent device is greater than 70% of the emission spectrum area of ​​the third material; The electroluminescence ratio of the second light-emitting layer is greater than or equal to 50% of the light emitted by the organic electroluminescent device.

12. The organic electroluminescent device according to claim 1, wherein: When the second material in the second light-emitting layer is a fluorescent material, the emission spectrum of the second material in the first light-emitting layer and the absorption spectrum of the second material in the second light-emitting layer satisfy: under normalized conditions, the overlapping area of ​​the emission spectrum of the second material in the first light-emitting layer and the absorption spectrum of the second material in the second light-emitting layer is greater than or equal to 60% of the absorption spectrum area of ​​the second material in the second light-emitting layer; and / or The emission spectrum of the second material in the third light-emitting layer and the absorption spectrum of the second material in the second light-emitting layer satisfy: under normalized conditions, the overlapping area of ​​the emission spectrum of the second material in the third light-emitting layer and the absorption spectrum of the second material in the second light-emitting layer is greater than or equal to 60% of the absorption spectrum area of ​​the second material in the second light-emitting layer.

13. The organic electroluminescent device according to any one of claims 1 to 12, wherein: The organic electroluminescent device satisfies at least one of the following conditions: |HOMO(A)-HOMO(E)|≤0.3eV, and |HOMO(E)-HOMO(J)|≤0.3eV; |HOMO(A)|≤|HOMO(B)|, |HOMO(E)|≤|HOMO(F)|, |HOMO(J)|≤|HOMO(K)|; |HOMO(A)-HOMO(E)|≤0.3eV; |HOMO(E)-HOMO(K)|≤0.3eV; |T1(A)-T1(E)|≤0.2eV, |T1(E)-T1(J)|≤0.2eV; and, T1(A)>T1(B), T1(E)>T1(F, T1(J)>T1(K), Wherein, HOMO(A) is the highest occupied energy level orbital of the first material in the first light-emitting layer, HOMO(E) is the highest occupied energy level orbital of the first material in the second light-emitting layer, HOMO(J) is the highest occupied energy level orbital of the first material in the third light-emitting layer, HOMO(B) is the highest occupied energy level orbital of the second material in the first light-emitting layer, HOMO(F) is the highest occupied energy level orbital of the second material in the second light-emitting layer, HOMO(K) is the highest occupied energy level orbital of the second material in the third light-emitting layer, T1(A) is the triplet first excited state energy level of the first material in the first light-emitting layer, T1(B) is the highest occupied energy level of the second material in the third light-emitting layer, The triplet first excited state energy level T1(E) of the second material in a light-emitting layer is the triplet first excited state energy level of the first material in the second light-emitting layer, T1(F) is the triplet first excited state energy level of the second material in the second light-emitting layer, T1(J) is the triplet first excited state energy level of the first material in the third light-emitting layer, and T1(K) is the triplet first excited state energy level of the second material in the third light-emitting layer.

14. The organic electroluminescent device according to any one of claims 1 to 13, wherein: The organic electroluminescent device further comprises: A hole transport layer located between the first electrode and the first light-emitting layer, wherein the first light-emitting layer is disposed closest to the hole transport layer relative to other film layers; The electron transport layer is located between the second electrode and the third light emitting layer, and the third light emitting layer is arranged closest to the electron transport layer relative to other film layers.

15. The organic electroluminescent device according to claim 14, wherein: The organic electroluminescent device further comprises an auxiliary light-emitting layer, wherein the auxiliary light-emitting layer is located between the hole transport layer and the first light-emitting layer; The auxiliary light emitting layer has a fifth material, and the fifth material includes at least one hole transport material.

16. The organic electroluminescent device according to claim 15, wherein: The auxiliary light-emitting layer satisfies at least one of the following conditions: The thickness of the auxiliary light-emitting layer is greater than 1 / 3 of the total thickness of each film layer containing the light-emitting guest material, wherein the light-emitting guest material includes at least one of the second material and the third material; The T1 energy level of the fifth material is at least greater than or equal to the T1 energy level of the material with the second largest content in the first light-emitting layer, and the absolute value of the difference between the HOMO value of the fifth material and the HOMO value of the material with the largest HOMO absolute value in the first light-emitting layer is less than or equal to 0.3 eV; The fifth material includes a carbazole compound, and the mass percentage of the fifth material in the auxiliary light-emitting layer is 55wt% to 100wt%; The auxiliary light-emitting layer further includes a sixth material, the sixth material includes at least one of an anthracene compound, a boron nitrogen compound and a metal complex, and the mass percentage of the sixth material in the auxiliary light-emitting layer is 0 to 15 wt %; The auxiliary light-emitting layer further comprises a seventh material, the seventh material comprises a polycarbazole compound, and the mass percentage of the seventh material in the auxiliary light-emitting layer is 0 to 45 wt %; The seventh material has a thermally activated delayed fluorescence characteristic. Under normalized conditions, the seventh material The emission spectrum of the seventh material must overlap with the absorption spectrum of the light-emitting guest with the least content in the first light-emitting layer, and the overlap area must account for at least 60% of the emission spectrum area of ​​the seventh material; The organic electroluminescent device further has an electron blocking layer, wherein a T1 energy level of the electron blocking layer is at least 0.1 eV higher than a T1 energy level of the seventh material.

17. The organic electroluminescent device according to any one of claims 1 to 16, wherein: A plurality of light-emitting units are included between the first electrode and the second electrode, and each of the light-emitting units includes at least the first light-emitting layer, the second light-emitting layer and the third light-emitting layer; A charge generation layer is provided between different light-emitting units.

18. The organic electroluminescent device according to any one of claims 1 to 17, wherein: The organic electroluminescent device satisfies at least one of the following conditions: The organic electroluminescent device comprises an electron blocking layer, which is located between the first electrode and the first light-emitting layer and in contact with the first light-emitting layer or the auxiliary light-emitting layer, and the electron blocking layer satisfies: |HOMO(EBL)-HOMO(EML) max |<0.3eV, HOMO(EBL) is the HOMO energy level of the electron blocking layer, HOMO(EML) max The HOMO energy level of the material with the largest highest occupied orbital in the first light-emitting layer or the auxiliary light-emitting layer in contact with the electron blocking layer; The organic electroluminescent device comprises a hole blocking layer, which is located between the second electrode and the third light-emitting layer and in contact with the third light-emitting layer, and the hole blocking layer satisfies: T1(HBL)>T1(EML3 M ), T1(HBL) is the triplet first excited state energy level of the hole blocking layer, T1(EML3 M ) is the triplet first excited state energy level of the third material in the third light-emitting layer.

19. A display panel, wherein: The display panel comprises the organic electroluminescent device according to any one of claims 1 to 18.

20. A display device, wherein: The display device comprises the display panel according to claim 19.

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