Organic light emitting device and display apparatus

Abstract

The present disclosure provides an organic light-emitting device and a display device, and belongs to the technical field of display. The organic light-emitting device comprises at least one light-emitting layer, the light-emitting layer comprises at least one first light-emitting layer and at least one second light-emitting layer, and the first light-emitting layer and the second light-emitting layer are alternately stacked; the material of the first light-emitting layer comprises a first host material and a thermally activated delayed fluorescence sensitized material, and the material of the second light-emitting layer comprises a second host material and a fluorescent guest material; the first host material and the second host material are the same; the thickness of the first light-emitting layer is 1-15 nm, and the thickness of the second light-emitting layer is 1-15 nm. The present disclosure increases the distance between the TADF sensitized material and the fluorescent guest material to a certain extent, reduces the probability of Dexter energy transfer from T1 TADF →T1 Dopant , reduces the loss of excitons, and improves the device efficiency.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of display, and in particular to an organic light-emitting device and a display device. BACKGROUND

[0002] Thermal active delay fluorescent (TADF) material can be used as a sensitizing material to sensitize the luminescence of a fluorescent guest material. In the prior art, T1 TADF → T1 Dopant (T1 TADF : the lowest triplet energy of the TADF sensitizing material; T1 Dopant : the lowest triplet energy of the guest material) Dexter energy transfer occurs in the TADF sensitizing device. Since the T1 TADF of the fluorescent luminescent material cannot radiate transition light, it will cause loss of excitons and reduction of device efficiency.

[0003] The above information disclosed in the background section is only intended to strengthen the understanding of the background of the present disclosure, and therefore it can include information that does not constitute the prior art known to those of ordinary skill in the art. SUMMARY

[0004] The purpose of the present disclosure is to provide an organic light-emitting device and a display device to improve the efficiency of the light-emitting device.

[0005] To achieve the above-mentioned purposes, the present disclosure adopts the following technical solutions:

[0006] According to a first aspect of the present disclosure, an organic light-emitting device is provided, comprising at least one light-emitting layer, the light-emitting layer comprising at least one first light-emitting layer and at least one second light-emitting layer, the first light-emitting layer and the second light-emitting layer being arranged alternately in layers;

[0007] The material of the first light-emitting layer comprises a first host material and a thermal active delay fluorescent sensitizing material, and the material of the second light-emitting layer comprises a second host material and a fluorescent guest material;

[0008] The first host material and the second host material are the same;

[0009] The thickness of the first light-emitting layer is 1-15 nm, and the thickness of the second light-emitting layer is 1-15 nm.

[0010] In an exemplary embodiment of the present disclosure, the material of the first light-emitting layer comprises the first host material with a doping concentration of 40-85%, and the thermal active delay fluorescent sensitizing material with a doping concentration of 15-60%;

[0011] The material of the second light-emitting layer comprises the first host material with a doping concentration of 98%-99.5% and the fluorescent guest material with a doping concentration of 0.5%-2%.

[0012] In an exemplary embodiment of the present disclosure, the thickness of the light-emitting layer is 20-50 nm.

[0013] In an exemplary embodiment of the present disclosure, the total number of layers of the first light-emitting layer and the second light-emitting layer is 3-45 layers.

[0014] In an exemplary embodiment of the present disclosure, the first host material, the second host material, the thermally activated delayed fluorescence sensitizing material and the fluorescent guest material satisfy the following relationship:

[0015] S1 Host > S1 TADF > S1 Dopant ;

[0016] wherein S1 Host represents the lowest singlet energy of the first host material or the second host material, S1 TADF represents the lowest singlet energy of the thermally activated delayed fluorescence sensitizing material, S1 Dopant represents the lowest singlet energy of the fluorescent guest material.

[0017] In an exemplary embodiment of the present disclosure, the first host material, the second host material, the thermally activated delayed fluorescence sensitizing material and the fluorescent guest material satisfy the following relationship:

[0018] T1 Host > T1 TADF > T1 Dopant ;

[0019] wherein T1 Host represents the lowest triplet energy of the first host material or the second host material, T1 TADF represents the lowest triplet energy of the thermally activated delayed fluorescence sensitizing material, T1 Dopant represents the lowest triplet energy of the fluorescent guest material.

[0020] In an exemplary embodiment of the present disclosure, the first host material, the second host material and the thermally activated delayed fluorescence sensitizing material satisfy the following relationship:

[0021] | HOMO TADF |<| HOMO Host ;

[0022] | LUMOTADF | LUMO Host |;

[0023] HOMO TADF represents a highest occupied molecular orbital energy level of the thermally activated delayed fluorescence sensitizing material, HOMO Host represents a highest occupied molecular orbital energy level of the first host material or the second host material;

[0024] LUMO TADF represents a lowest unoccupied molecular orbital energy level of the thermally activated delayed fluorescence sensitizing material, LUMO Host represents a lowest unoccupied molecular orbital energy level of the first host material or the second host material.

[0025] In an exemplary embodiment of the present disclosure, the organic light-emitting device is a single light-emitting device containing one layer of the light-emitting layer or a tandem light-emitting device containing two or more layers of the light-emitting layer.

[0026] According to a second aspect of the present disclosure, a method for manufacturing an organic light-emitting device is provided, comprising:

[0027] heating the first host material and the thermally activated delayed fluorescence sensitizing material to co-evaporate to form the first light-emitting layer;

[0028] heating the second host material and the fluorescent guest material to co-evaporate to form the second light-emitting layer;

[0029] wherein the first host material and the second host material are the same;

[0030] the thickness of the first light-emitting layer is 1 nm-15 nm, and the thickness of the second light-emitting layer is 1 nm-15 nm.

[0031] According to a third aspect of the present disclosure, a display device is provided, comprising the organic light-emitting device according to the first aspect.

[0032] The organic light-emitting device provided by the present disclosure has the TADF sensitizing material and the fluorescent guest material in the first light-emitting layer and the second light-emitting layer, respectively, which helps to reduce the probability of contact between the two, thereby increasing the distance between the TADF sensitizing material and the fluorescent guest material to a certain extent, reducing the probability of Dexter energy transfer of T1 TADF → T1 Dopant between the two, reducing the loss of excitons, and improving the device efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0033] The above and other features and advantages of the present disclosure will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings.

[0034] Figure 1 is a schematic diagram of an energy transfer structure of a light emitting layer in the related art;

[0035] Figure 2 is a schematic diagram of a structure of an organic light emitting device in an exemplary embodiment of the present disclosure;

[0036] Figure 3 is a schematic diagram of a structure of an organic light emitting device in another exemplary embodiment of the present disclosure;

[0037] Figure 4 is a schematic diagram of an energy transfer structure of a light emitting layer in an exemplary embodiment of the present disclosure.

[0038] Reference signs of main elements in the drawings are explained as follows.

[0039] 10 - first electrode; 20 - second electrode; 310 - first hole injection layer; 320 - first hole transport layer; 330 - first electron blocking layer; 350 - first hole blocking layer; 360 - first electron transport layer; 370 - electron generation layer; 410 - hole generation layer; 420 - second hole transport layer; 430 - second electron blocking layer; 450 - second hole blocking layer; 460 - second electron transport layer; 470 - second electron injection layer;

[0040] 100 - anode; 200 - hole injection layer; 300 - hole transport layer; 400 - electron blocking layer; 500 - light emitting layer; 510 - first light emitting layer; 520 - second light emitting layer; 600 - hole blocking layer; 700 - electron transport layer; 800 - electron injection layer; 900 - cathode. DETAILED DESCRIPTION

[0041] Example embodiments now will be described more fully hereinafter with reference to the accompanying drawings; however, the example embodiments can be implemented in many different forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the example embodiments to those skilled in the art. The features, structures, or characteristics described in connection with the embodiments can be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of embodiments of the present disclosure.

[0042] In the drawings, the thicknesses of regions and layers can be exaggerated for clarity. Like reference numerals in different drawings denote like elements, and thus their detailed descriptions will be omitted.

[0043] The described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of embodiments of the disclosure. One skilled in the relevant art will recognize, however, that the techniques described can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail in order to avoid obscuring aspects of the disclosure.

[0044] When an element (e.g., a layer or region) is referred to as being "on" another element, it can be directly on the other element or intervening elements can also be present. In contrast, when an element is referred to as being "directly on" another element, there are no intervening elements present. It will be understood that when an element is referred to as being "connected" to or "coupled" to another element, it can be directly connected or coupled or intervening elements can be present. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0045] The singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprises," "comprising," "includes," and "including" are intended to be open-ended terms that mean "including, but not limited to," and thus specify the presence of stated elements or integers, but do not preclude the presence or addition of one or more other elements or integers. The term "first," "second," and the like do not denote any order, quantity, or importance, but rather are used to distinguish one element from another.

[0046] Organic Light Emitting Device (OLED) is an active light-emitting device, which has the advantages of light-emitting, ultra-thin, wide viewing angle, high brightness, high contrast, low power consumption, extremely high response speed, etc., and has gradually become the next generation display technology with great development prospects. An OLED includes an anode, a cathode, and an organic light-emitting layer disposed between the anode and the cathode. The light-emitting principle is that holes and electrons are injected into the light-emitting layer from the anode and the cathode, respectively. When the holes and the electrons meet in the light-emitting layer, the holes and the electrons recombine in the light-emitting layer to generate excitons. These excitons emit light while changing from an excited state to a ground state.

[0047] TADF materials are known as the third generation of organic light-emitting materials. The energy difference between the lowest triplet state (T1) and the lowest singlet state (S1) is small (S1 – T1≤ 0.3 eV), and T1 can be converted to S1 through the reverse intersystem crossing (RISC) process with the aid of environmental heat, and then emit light. Compared with fluorescent materials, TADF materials can utilize T1 to emit light, and the internal quantum efficiency can theoretically reach 100%. Compared with phosphorescent materials, TADF sensitized materials do not contain noble metal elements, and the cost is lower.

[0048] The TADF material can be used as a sensitizing material to sensitize the fluorescent material to emit light. In the related art, the light-emitting layer (EML) of the TADF sensitized device structure is formed by mixing a host material, a TADF sensitizing material, and a fluorescent guest material, and then forming a film through a film forming process. Among them, the proportion of the host material and the TADF sensitizing material is relatively high, and the proportion of the fluorescent guest material is relatively low. As shown in FIG. Figure 1 Due to the high doping concentration of the TADF sensitizing material, and the highest occupied molecular orbital HOMO (TADF) and the lowest unoccupied molecular orbital LUMO (TADF) energy levels of the sensitizing material are usually between the host materials, the holes and electrons are mainly recombined on the TADF sensitizing material to form excitons, including 25% S1 TADF and 75% T1 TADF . The T1 TADF can be converted to S1 TADF through the reverse intersystem crossing (RISC) process, and the S1 TADF can transfer energy to the fluorescent guest material S1 Dopant through Forster energy transfer, and then radiate light. Since the actual light-emitting material is the fluorescent guest material, which has strong molecular rigidity, the electroluminescent spectrum is narrow. However, in this device structure, the TADF sensitizing material and the fluorescent guest material are in direct contact, and Dexter energy transfer from T1 TADF to T1 Dopant is inevitable. Since the T1 Dopant of the fluorescent light-emitting material cannot radiate transition light, it will cause loss of excitons and reduction of device efficiency. A common improvement scheme is to reduce the doping concentration of the fluorescent guest material, but this will cause incomplete Forster energy transfer from S1 TADF to S1 Dopant , resulting in the appearance of the light-emitting peak of the TADF sensitizing material in the electroluminescent spectrum, affecting the light-emitting color of the device.

[0049] As shown in FIG. Figure 2 , the present disclosure provides an organic light-emitting device, which comprises at least one light-emitting layer, the light-emitting layer comprises at least one first light-emitting layer 510 and at least one second light-emitting layer 520, the first light-emitting layer 510 and the second light-emitting layer 520 are alternately stacked; the material of the first light-emitting layer 510 comprises a first host material and a thermally activated delayed fluorescence (TADF) sensitizing material, and the material of the second light-emitting layer 520 comprises a second host material and a fluorescent guest material; the first host material and the second host material are the same; the thickness of the first light-emitting layer 510 is 1-15 nm, and the thickness of the second light-emitting layer 520 is 1-15 nm.

[0050] The organic light-emitting device provided by the present disclosure, the TADF sensitization material and the fluorescent guest material are respectively located in the first light-emitting layer 510 and the second light-emitting layer 520, so as to help reduce the probability of contact between the two, thereby increasing the distance between the TADF sensitization material and the fluorescent guest material to a certain extent, reducing the probability of Dexter energy transfer of T1 TADF → T1 Dopant , reducing the loss of excitons and improving the efficiency of the device.

[0051] The components of the organic light-emitting device provided by the embodiments of the present disclosure will be described in detail below in combination with the drawings:

[0052] As shown in Figure 2 , the organic light-emitting device provided by the present disclosure comprises an anode 100, a cathode 900 and at least one light-emitting layer 500, and the light-emitting layer 500 is arranged between the anode 100 and the cathode 900. The light-emitting layer comprises at least one first light-emitting layer 510 and at least one second light-emitting layer 520, and the first light-emitting layer 510 and the second light-emitting layer 520 are arranged in an alternating stack.

[0053] The organic light-emitting device provided by the present disclosure can be a single light-emitting device or a series light-emitting device.

[0054] In some embodiments of the present disclosure, the organic light-emitting device is a single light-emitting device, which comprises one light-emitting layer 500. In this embodiment, the organic light-emitting device further comprises a hole injection layer (HIL) 200, a hole transport layer (HTL) 300, an electron blocking layer (EBL) 400, a hole blocking layer (HBL) 600, an electron transport layer (ETL) 700 and an electron injection layer (EIL) 800. The hole injection layer 200 (HIL), the hole transport layer (HTL) 300 and the electron blocking layer (EBL) 400 are located between the anode 100 and the light-emitting layer 500, and the hole blocking layer (HBL) 600, the electron transport layer (ETL) 700 and the electron injection layer (EIL) 800 are located between the light-emitting layer 500 and the cathode 900. The hole injection layer 200 is used to reduce the potential barrier for injecting holes from the anode, so that the holes can be effectively injected from the anode 100 to the light-emitting layer 500, thereby improving the hole injection efficiency. The hole transport layer 300 is used to realize the controllable migration of the injected holes in a directional and orderly manner. The electron blocking layer 400 is used to form a migration potential barrier for electrons or excitons, so as to prevent the migration of electrons or excitons out of the light-emitting layer 500. The light-emitting layer 500 is used to form excitons by recombination of electrons and holes, thereby emitting light. The hole blocking layer 600 is used to form a migration potential barrier for holes or excitons, so as to prevent the migration of holes or excitons out of the light-emitting layer 500. The electron transport layer 700 is used to realize the controllable migration of the injected electrons in a directional and orderly manner. The electron injection layer 800 is used to reduce the potential barrier for injecting electrons from the cathode, so that the electrons can be effectively injected from the cathode 900 to the light-emitting layer 500.

[0055] In exemplary embodiments, the anode 100 can employ a material with a high work function. For a bottom emission OLED, the anode 100 can employ a transparent oxide material, such as indium tin oxide (ITO) or indium zinc oxide (IZO), etc., and the thickness of the anode 100 can be about 80 nm to 200 nm. For a top emission OLED, the anode 100 can employ a composite structure of metal and transparent oxide, such as Ag / ITO or Ag / IZO, etc., and the thickness of the metal layer in the anode 100 can be about 80 nm to 100 nm, and the thickness of the transparent oxide in the anode 100 can be about 5 nm to 20 nm, so that the average reflectivity of the anode 100 in the visible light region is about 85% to 95%.

[0056] In exemplary embodiments, for a top emission OLED, the cathode 900 can employ a metal material, formed by a vapor deposition process, and the metal material can employ magnesium (Mg), silver (Ag), or aluminum (Al), or an alloy material, such as an alloy of Mg:Ag, with a ratio of Mg:Ag of about 3:7 to 1:9, and the thickness of the cathode 900 can be about 10 nm to 20 nm, so that the average transmittance of the cathode 900 at a wavelength of 530 nm is about 50% to 60%. For a bottom emission OLED, the cathode 900 can employ magnesium (Mg), silver (Ag), aluminum (Al), or an alloy of Mg:Ag, and the thickness of the cathode 900 can be greater than about 80 nm, so that the cathode 900 has good reflectivity.

[0057] In exemplary embodiments, the hole injection layer 200 can employ a single material, such as 4-isopropyl-4'-methyl diphenyl iodonium tetra(pentafluorophenyl) borate and / or dipyrazino[2,3-f:2',3'-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile (HAT-CN), CuPc, etc., or can employ a doped material, such as p-type doping of a hole transport material, with a p-doping ratio of about 0.5% to 10%, such as N,N'-di(naphthalen-1-yl)-N,N'-diphenyl-benzidine (NPB): 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanoquinodimethane (F4-TCNQ), 4,4'-cyclohexylidenebis[N,N-bis(4-methylphenyl)benzenamine] (TAPC): MnO3, etc. The thickness of the hole injection layer 200 can be about 5 nm to 20 nm.

[0058] In exemplary embodiments, the hole transport layer 300 can employ a material with a high hole mobility, such as carbazole, methylfluorene, spirofluorene, dithiophene, or furan, etc., formed by a vapor deposition process, and the thickness of the hole transport layer 300 can be about 100 nm to 140 nm.

[0059] In an exemplary embodiment, the electron blocking layer 400 can be formed by an evaporation process using a material with a high LUMO level, such as 3,3'-[5'-[3-(3-pyridyl)phenyl][1,1':3',1''-terphenyl]-3,3''-diyl]dipyridine (TmPyPB) or 2,7-bis(diphenylphosphine oxide)-9,9'-spirobifluorene (SPPO13), etc. The thickness of the electron blocking layer 400 can be about 5 nm to 90 nm, configured to pass holes, block electrons, and block excitons generated in the light emitting layer.

[0060] In an exemplary embodiment, the hole blocking layer 600 can be formed by an evaporation process using a material such as 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) or tris-2,3,5,6-tetramethylphenylboron (TPbB). The thickness of the hole blocking layer 600 can be about 2 nm to 10 nm, configured to block holes and block excitons generated in the light emitting layer.

[0061] In an exemplary embodiment, the electron transport layer 700 can be prepared by blending with lithium quinolate at a ratio of about 30% to 70% using a thiophene derivative, an imidazole derivative, or an azine derivative, etc. The thickness of the electron transport layer 700 can be about 20 nm to 70 nm.

[0062] In an exemplary embodiment, the electron injection layer 800 can be formed by an evaporation process using a material such as lithium fluoride (LiF), lithium 8-hydroxyquinolate (LiQ), ytterbium (Yb), or calcium (Ca). The thickness of the electron injection layer 800 can be about 0.5 nm to 2 nm.

[0063] Continuing as in Figure 2As shown, the light-emitting layer 500 includes at least one first light-emitting layer 510 and at least one second light-emitting layer 520, which are arranged in an alternating stack. The number of the first light-emitting layer 510 and the second light-emitting layer 520 is not particularly limited, and the first light-emitting layer 510 and the second light-emitting layer 520 can be arranged in any order. The layer closest to the anode 100 or the cathode 900 in the light-emitting layer 500 can be the first light-emitting layer 510 or the second light-emitting layer 520. The number of the first light-emitting layer 510 can be equal to, greater than, or less than the number of the second light-emitting layer 520, which is determined by the arrangement of the first light-emitting layer 510 and the second light-emitting layer 520. The total number of layers of the first light-emitting layer 510 and the second light-emitting layer 520 is 3-45, which can be 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36, 39, 40, 41, 42, 43, 44, or 45, but is not limited thereto.

[0064] The material of the first light-emitting layer 510 includes a first host material and a thermally activated delayed fluorescence (TADF) sensitizing material, and the material of the second light-emitting layer 520 includes a second host material and a fluorescent guest material. The first host material and the second host material are the same.

[0065] The first host material and the second host material can be selected from single materials such as 8-hydroxyquinoline aluminum (Alq3), 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBi), 3-(biphenyl-4-yl)-5-(4-tert-butylphenyl)-4-phenyl-4H-1,2,4-triazole (TAZ1), or 4,4'-bis(N-carbazolyl)-9,9'-spirobifluorene (CFL), or a blended combination of these materials.

[0066] In an exemplary embodiment, the TADF sensitizing material can be a material such as 2,4,5,6-tetrakis(9-carbazolyl)-isophthalonitrile (4CzIPN) or bis(4-(9,9-dimethyl-acetyl-10(9H)-yl)phenyl) ketone (DMAC-BP).

[0067] In an exemplary embodiment, the fluorescent guest material can be a material such as 6,13-diphenylpentacene (DPP) or 4-(dicyanovinyl)-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidinyl-4-vinyl)-4H-pyrane (DCJTB).

[0068] The thickness of the first light-emitting layer 510 is 1 nm-15 nm, and the thickness of the second light-emitting layer 520 is 1 nm-15 nm. Specifically, the thickness of the first light-emitting layer 510 can be 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, or 15 nm; and the thickness of the second light-emitting layer 520 can be 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, or 15 nm, but is not limited thereto. The thickness of the light-emitting layer 500 as a whole is 20 nm-50 nm, and specifically can be 20 nm, 22 nm, 24 nm, 26 nm, 28 nm, 30 nm, 32 nm, 34 nm, 36 nm, 38 nm, 40 nm, 42 nm, 44 nm, 46 nm, 48 nm, or 50 nm. But is not limited thereto.

[0069] In some embodiments of the present disclosure, the material of the first light-emitting layer 510 contains the first host material with a doping concentration of 40%-85%, and specifically can be 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60%, 62%, 64%, 66%, 68%, 70%, 72%, 73%, 74%, 75%, 80%, or 85%, but is not limited thereto. The doping concentration of the thermally activated delayed fluorescence sensitizing material is 15%-60%, and specifically can be 60%, 58%, 56%, 54%, 52%, 50%, 48%, 46%, 44%, 42%, 40%, 38%, 36%, 34%, 32%, 30%, 28%, 27%, 26%, or 25%, but is not limited thereto.

[0070] The material of the second light-emitting layer 520 contains the second host material with a doping concentration of 98%-99.5%, and specifically can be 98%, 98.1%, 98.2%, 98.3%, 98.4%, 98.5%, 98.6%, 98.7%, 98.8%, 98.9%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, or 99.5%, but is not limited thereto. The doping concentration of the fluorescent guest material is 0.5%-2%. Specifically, it can be 2%, 1.9%, 1.8%, 1.7%, 1.6%, 1.5%, 1.4%, 1.3%, 1.2%, 1.1%, 1%, 0.9%, 0.8%, 0.7%, 0.6%, or 0.5%, but is not limited thereto.

[0071] In some embodiments of the present disclosure, the first host material, the second host material, the thermally activated delayed fluorescence sensitizing material, and the fluorescent guest material satisfy the following relationship:

[0072] S1 Host > S1 TADF > S1 Dopant ;

[0073] Among them, S1 Host S1 represents the lowest singlet energy of either the first or second host material. TADF S1 represents the lowest singlet energy of the thermally activated delayed fluorescence sensitized material. Dopant This represents the lowest singlet energy of the fluorescent guest material.

[0074] The first host material, the second host material, the thermally activated delayed fluorescence sensitizing material, and the fluorescent guest material satisfy the following relationship:

[0075] T1 Host > T1 TADF > T1 Dopant ;

[0076] Among them, T1 Host T1 represents the lowest triplet energy of either the first or second host material. TADF T1 represents the lowest triplet energy of the thermally activated delayed fluorescence sensitized material. Dopant This represents the lowest triplet energy of the fluorescent guest material.

[0077] Furthermore, the first host material, the second host material, and the thermally activated delayed fluorescence sensitizing material satisfy the following relationship:

[0078] | HOMO TADF |<| HOMO Host |; such as HOMO TADF = -5.2 eV, HOMO Host = -5.5 eV;

[0079] | LUMO TADF |>| LUMO Host |; such as LUMO TADF = -2.5 eV, LUMO Host = -2.4 eV;

[0080] Among them, HOMO TADF The highest occupied molecular orbital energy level (HOMO) of the thermally activated delayed fluorescence sensitized material is indicated. Host This indicates the highest occupied molecular orbital energy level of the first host material or the second host material;

[0081] LUMO TADFThe lowest unoccupied molecular orbital energy level, LUMO, represents the thermally activated delayed fluorescence sensitized material. Host This indicates the lowest unoccupied molecular orbital energy level of either the first or second host material.

[0082] The emission spectrum of the TADF-sensitized material overlaps well with the absorption spectrum of the fluorescent guest material to ensure S1 TADF → S1 Dopant Forster energy transfer occurs effectively. Because the HOMO level of the TADF-sensitized material is higher than that of the host materials (first and second host materials), and the LUMO level of the TADF-sensitized material is lower than that of the host materials, holes and electrons mainly recombine on the TADF-sensitized material to form excitons, including 25% of the S1 excitons. TADF and 75% of T1 TADF In this disclosure, because most TADF-sensitized materials and fluorescent guest materials are spatially separated and do not directly contact each other, the occurrence of T1 is reduced. TADF → T1 Dopant The Dexter energy transfer probability is reduced, and exciton loss is avoided. Furthermore, since the Forest energy transfer is a long-range energy transfer, it can still occur within a 10 nm range, therefore S1... TADF → S1 Dopant The Forster energy transfer can occur normally, thus improving the efficiency of TADF sensitized devices.

[0083] In other embodiments of this disclosure, the organic light-emitting device is a tandem light-emitting device, which may include two or more light-emitting layers.

[0084] like Figure 3 As shown, the organic light-emitting device includes a first electrode 10, a first hole injection layer 310, a first hole transport layer 320, a first electron blocking layer 330, a light-emitting layer 500, a first hole blocking layer 350, a first electron transport layer 360, a charge generation layer, a second hole transport layer 420, a second electron blocking layer 430, a light-emitting layer 500, a second hole blocking layer 450, a second electron transport layer 460, a second electron injection layer 470, and a second electrode 20, stacked sequentially. The charge generation layer includes an electron generation layer (NCGL) 370 and a hole generation layer (PCGL) 410. The first electrode 10 can be an anode, and the second electrode 20 can be a cathode.

[0085] The first hole injection layer 310 is used to enhance the ability to inject holes into the first hole transport layer 320. The specific material selection can refer to the hole injection layer 200 in the above embodiment.

[0086] The material selection of the first hole transport layer 320 and the second hole transport layer 420 can refer to the hole transport layer 300 in the above-described embodiments. The material selection of the first hole blocking layer 350 and the second hole blocking layer 450 can refer to the hole blocking layer 600 in the above-described embodiments. The material selection of the first electron blocking layer 330 and the second electron blocking layer 430 can refer to the electron blocking layer 400 in the above-described embodiments. The material selection of the first electron transport layer 360 and the second electron transport layer 460 can refer to the electron transport layer 700 in the above-described embodiments.

[0087] As shown in Figure 2 and Figure 3 The present disclosure further provides a manufacturing method of an organic light-emitting device, comprising the following steps:

[0088] In step S100, a first host material and a thermally activated delayed fluorescence sensitized material are heated and co-evaporated to form a first light-emitting layer.

[0089] In step S200, a second host material and a fluorescent guest material are heated and co-evaporated to form a second light-emitting layer.

[0090] The first host material and the second host material are the same.

[0091] The thickness of the first light-emitting layer 510 is 1-15 nm, and the thickness of the second light-emitting layer 520 is 1-15 nm.

[0092] It should be noted that steps S100 and S200 are alternately repeated to form the light-emitting layer. Comparative Example

[0093] As shown in Figure 2 A glass plate provided with an anode 100 (ITO) is placed in a vacuum chamber, and vacuumed to 1×10 -5 ~ 1×10 -6 A hole injection material is vacuum evaporated on the side of the ITO away from the glass plate to form a hole injection layer 200.

[0094] A hole transport material is evaporated on the side of the hole injection layer 200 away from the ITO to form a hole transport layer 300.

[0095] An electron blocking material is vacuum evaporated on the side of the hole transport layer 300 away from the hole injection layer 200 to form an electron blocking layer 400.

[0096] A light-emitting layer 500 is formed by vacuum evaporation of light-emitting layer materials on the side of the electron blocking layer 400 away from the hole transport layer 300. The light-emitting layer materials include host materials and guest materials. The light-emitting layer materials include host materials with a doping concentration of 40-85%, TADF sensitization materials with a doping concentration of 15-60%, and fluorescent guest materials with a doping concentration of 0.5-2%, totaling 100%.

[0097] A hole blocking layer 600 is formed by vacuum evaporation of hole blocking materials on the side of the light-emitting layer 500 away from the electron blocking layer 400.

[0098] An electron transport layer 700 is formed by vacuum evaporation of electron transport materials on the side of the hole blocking layer 600 away from the light-emitting layer 500.

[0099] An electron injection layer 800 is formed by vacuum evaporation of an inorganic material (LiF) with a thickness of 2 nm as an electron injection material on the side of the electron transport layer 700 away from the hole blocking layer 600.

[0100] A cathode 900 is formed on the side of the electron injection layer 800 away from the electron transport layer.

[0101] A cover layer is formed by vacuum evaporation of a material with a thickness of 60 nm on the side of the cathode 900 away from the electron injection layer 800.

[0102] The device structure is: anode / hole injection layer (10 nm) / hole transport layer (120 nm) / electron blocking layer (85 nm) / light-emitting layer (45 nm) / hole blocking layer (5 nm) / electron transport layer (30 nm) / electron injection layer (2 nm) / cathode (14 nm) / cover layer (60 nm). Embodiment

[0103] In the comparative example, when forming the light-emitting layer, the first host material and the thermally activated delayed fluorescence sensitization material are heated and co-evaporated to form the first light-emitting layer, the second host material and the fluorescent guest material are heated and co-evaporated to form the second light-emitting layer, and then the first host material and the thermally activated delayed fluorescence sensitization material are heated and co-evaporated to form the first light-emitting layer, followed by the formation of a new second light-emitting layer and a first light-emitting layer. The first light-emitting layer includes host materials with a doping concentration of 40-85%, and the thermally activated delayed fluorescence sensitization material with a doping concentration of 15-60%, and the second light-emitting layer includes host materials with a doping concentration of 98-99.5%, and the fluorescent guest material with a doping concentration of 0.5-2%. In the embodiment, all the materials are selected to be the same as in the comparative example.

[0104] The device structure is: anode / hole injection layer (10 nm) / hole transport layer (120 nm) / electron blocking layer (85 nm) / first light-emitting layer (9 nm) / second light-emitting layer (9 nm) / first light-emitting layer (9 nm) / second light-emitting layer (9 nm) / first light-emitting layer (9 nm) / hole blocking layer (5 nm) / electron transport layer (30 nm) / electron injection layer (2 nm) / cathode (14 nm) / cover layer (60 nm).

[0105] The current efficiency of the organic light-emitting devices in the comparative examples and the examples is tested and compared, and the results show that the current efficiency of the examples can be increased by about 5%~12% compared with the comparative examples. Therefore, it can be illustrated that the distribution of the TADF sensitizing material and the fluorescent guest material in the first light-emitting layer and the second light-emitting layer respectively in the present disclosure helps to improve the device efficiency.

[0106] It should be understood that the present disclosure does not limit its application to the detailed structure and arrangement of the components presented in the specification. The present disclosure can have other implementations and can be implemented and executed in various ways. The foregoing variations and modifications fall within the scope of the present disclosure. It should be understood that the present disclosure disclosed and defined in the specification extends to all alternative combinations of two or more individual features mentioned or obvious from the text and / or drawings. All these different combinations constitute multiple alternative aspects of the present disclosure. The embodiments of the specification illustrate the best mode currently known for implementing the present disclosure and will enable those skilled in the art to utilize the present disclosure.

Claims

1. An organic light emitting device, characterized by, The light-emitting layer comprises at least one first light-emitting layer and at least one second light-emitting layer, which are alternately stacked; The material of the first light-emitting layer comprises a first host material and a thermally activated delayed fluorescence sensitizing material, and the material of the second light-emitting layer comprises a second host material and a fluorescent guest material; The first host material and the second host material are the same; The thickness of the first light-emitting layer is 1-15 nm, and the thickness of the second light-emitting layer is 1-15 nm; The first host material, the second host material, the thermally activated delayed fluorescence sensitizing material, and the fluorescent guest material satisfy the following relationship: T1 Host T1 TADF T1 Dopant ; wherein T1 Host represents the lowest triplet energy of the first host material or the second host material, T1 TADF represents the lowest triplet energy of the thermally activated delayed fluorescence sensitizing material, T1 Dopant represents the lowest triplet energy of the fluorescent guest material.

2. The organic light emitting device according to claim 1, characterized in that, The material of the first light-emitting layer comprises a first host material and a thermally activated delayed fluorescence sensitizing material, and the material of the second light-emitting layer comprises a second host material and a fluorescent guest material; The material of the second light-emitting layer comprises a second host material and a fluorescent guest material, and the doping concentration of the second host material is 98-99.5%, and the doping concentration of the fluorescent guest material is 0.5-2%.

3. The organic light-emitting device according to claim 1, characterized in that, The thickness of the light-emitting layer is 20-50 nm.

4. The organic light emitting device of claim 1, wherein, The total number of layers of the first light-emitting layer and the second light-emitting layer is 3-45 layers.

5. The organic light-emitting device according to claim 1, characterized in that, The first host material, the second host material, the thermally activated delayed fluorescence sensitizing material, and the fluorescent guest material satisfy the following relationship: S1 Host S1 TADF S1 Dopant ; wherein S1 Host represents the lowest singlet energy of the first host material or the second host material, S1 TADF represents the lowest singlet energy of the thermally activated delayed fluorescence sensitizing material, S1 Dopant represents the lowest singlet energy of the fluorescent guest material.

6. The organic light emitting device of claim 1, wherein The first host material, the second host material, the thermally activated delayed fluorescence sensitizing material satisfy the following relationship: | HOMO TADF |<| HOMO Host |; | LUMO TADF |>| LUMO Host |; wherein HOMO TADF represents the highest occupied molecular orbital energy level of the thermally activated delayed fluorescence sensitizing material, HOMO Host represents the highest occupied molecular orbital energy level of the first host material or the second host material; LUMO TADF represents the lowest unoccupied molecular orbital energy level of the thermally activated delayed fluorescence sensitizing material, LUMO Host represents the lowest unoccupied molecular orbital energy level of the first host material or the second host material.

7. The organic light-emitting device according to claim 1, characterized in that, The organic light-emitting device is a single light-emitting device or a tandem light-emitting device, the single light-emitting device comprises one light-emitting layer, and the tandem light-emitting device comprises two or more light-emitting layers.

8. A method for manufacturing an organic light emitting device, characterized by, The first host material and the thermally activated delayed fluorescence sensitizing material are heated and co-evaporated to form a first light-emitting layer; The second host material and the fluorescent guest material are heated and co-evaporated to form a second light-emitting layer; The first host material and the second host material are the same; The thickness of the first light-emitting layer is 1-15 nm, the thickness of the second light-emitting layer is 1-15 nm, and the first host material, the second host material, the thermally activated delayed fluorescence sensitizing material, and the fluorescent guest material satisfy the following relationship: The organic light-emitting device comprises the organic light-emitting device according to any one of claims 1-7. T1 Host > T1 TADF > T1 Dopant ; wherein T1 Host represents the lowest triplet energy of the first host material or the second host material, T1 TADF represents the lowest triplet energy of the thermally activated delayed fluorescence sensitizing material, T1 Dopant represents the lowest triplet energy of the fluorescent guest material.

9. A display device, characterized by comprising: ​

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