Organic electroluminescent devices

Abstract

This invention provides an organic electroluminescent device comprising red, green, and blue emitting layers and two capping layers. This organic electroluminescent device can optimize the light extraction efficiency of red, green, and blue light, thereby improving image quality and reducing the degree of color variation depending on the viewing angle.

Description

Technical Field

[0001] This invention relates to an organic electroluminescent device, and more specifically, to an organic electroluminescent device comprising red, green, and blue light-emitting layers and two capping layers. Background Technology

[0002] An organic light-emitting device (OLED) comprises multiple pixels consisting of red (R), green (G), and blue (B) sub-pixels. Each sub-pixel has an organic light-emitting device (OLED) and pixel circuitry located within the sub-pixel. The OLED includes two electrodes (anode and cathode) and an organic light-emitting layer located between the two electrodes. The pixel circuitry includes at least two thin-film transistors and at least one capacitor.

[0003] Typically, an organic light-emitting layer consists of a red light-emitting layer, a green light-emitting layer, and a blue light-emitting layer located in each of the red, green, and blue sub-pixels.

[0004] In top-emitting organic electroluminescent devices, the metal cathode layer and the bottom metal reflective layer form a resonant cavity (also called a microcavity), resulting in both constructive and destructive interference. As the viewing angle changes, the distance between the metal cathode layer and the bottom metal reflective layer (i.e., the cavity length of the microcavity) changes accordingly. This leads to significant differences in brightness and color observed at different viewing angles, severely impacting product performance.

[0005] In such light-emitting elements, when light emitted from the light-emitting layer is incident on other films at an angle greater than a certain value, total internal reflection will occur at the interface between the light-emitting layer and other films. Therefore, only a portion of the emitted light can be utilized. In recent years, to improve light extraction efficiency and reduce color shift, light-emitting elements with a high-refractive-index "capping layer" placed on the outside of a semi-transparent electrode with a low refractive index have been proposed. Red, green, and blue light have different requirements for their respective capping layer materials. Therefore, it is necessary to deposit the corresponding capping layer material separately for each extremely small sub-pixel region of different emission colors, requiring complex patterning techniques. (See...) Figure 1 (a). Summary of the Invention

[0006] Therefore, in order to overcome the problems of the prior art, this application provides an organic electroluminescent device including red, green, and blue light-emitting layers and two capping layers. Its advantages are: significantly improved light extraction efficiency, improved device polarization and angular dependence of emitted light, reduced patterning technology requirements, and significantly reduced process requirements and costs, thereby achieving easy manufacturing and high resolution.

[0007] The purpose of this invention is to provide an OLED device that has a balanced improvement in light extraction efficiency and color shift reduction for blue, green and red light, and is also inexpensive.

[0008] The object of this invention is achieved by providing an organic electroluminescent device having the following structure, comprising:

[0009] The substrate includes multiple sub-pixel regions, the multiple sub-pixel regions including a red sub-pixel region, a green sub-pixel region and a blue sub-pixel region;

[0010] A plurality of first electrodes are arranged on the substrate to correspond to each of the plurality of sub-pixel regions;

[0011] Red, green and blue light-emitting layers are formed on their respective first electrodes;

[0012] The second electrode covers the red, green, and blue light-emitting layers;

[0013] A first covering layer covers the second electrode;

[0014] The second overlay layer covers the first overlay layer within the red sub-pixel region and / or the green sub-pixel region;

[0015] The refractive index (n1@450nm) of the first capping layer within the blue sub-pixel region is 1.8 to 2.4, preferably 1.8 to 2.3, and most preferably 1.9 to 2.3; and

[0016] The refractive index (n2@620nm) of the second capping layer in the red subpixel region is 1.9 to 2.7, preferably 1.9 to 2.6, and most preferably 2.0 to 2.6;

[0017] Within the green sub-pixel region, the refractive index (n2@525nm) of the second capping layer is 2.0 to 2.7, preferably 2.0 to 2.6, and most preferably 2.1 to 2.6.

[0018] The organic electroluminescent device according to the present invention optimizes the light extraction efficiency of red, green and blue light, thereby improving image quality; at the same time, it reduces the degree of color change with viewing angle. Attached Figure Description

[0019] Features will become apparent to those skilled in the art from a detailed description of exemplary embodiments with reference to the accompanying drawings, in which:

[0020] Figure 1The following are examples of patterning masks required for depositing a capping layer: (a) a patterning mask in the prior art; (b) a patterning mask required for depositing a first capping layer in this invention; (c) a patterning mask required for depositing a second capping layer in the organic light-emitting device 1 of this invention; (d) a patterning mask required for depositing a second capping layer in the organic light-emitting device 2 of this invention; and (e) a patterning mask required for depositing a second capping layer in the organic light-emitting device 3 of this invention.

[0021] Figure 2 A schematic cross-sectional view of an organic electroluminescent device according to a first exemplary embodiment is shown, wherein the second capping layer 401 in the green sub-pixel region is made of a different material than the second capping layer 402 in the red sub-pixel region.

[0022] Figure 3 A schematic cross-sectional view of an organic electroluminescent device according to a second exemplary embodiment is shown, wherein the second capping layer 403 in the green and red sub-pixel regions uses the same material.

[0023] Figure 4 A schematic cross-sectional view of an organic electroluminescent device according to a third exemplary embodiment is shown, wherein the second overlay layer 404 is only present in the red sub-pixel region.

[0024] Figure 5 A schematic cross-sectional view of an organic light-emitting device (OLED) 200 is shown. Detailed Implementation

[0025] definition

[0026] Throughout this specification, unless explicitly stated otherwise, the term "including" any component will be understood to imply the inclusion of other components, not to exclude any other components. Furthermore, it should be understood that throughout this specification, when an element such as a layer, film, region, or substrate is referred to as being "on" or "above" another element, it may be "directly on" the other element, or there may be intermediate elements present. Additionally, "on" or "above" means located above the target portion, and not necessarily above it in the direction of gravity.

[0027] A subpixel region refers to the area where a subpixel is located.

[0028] A pixel region refers to the area where a single pixel is located.

[0029] A pixel is composed of the three primary colors: red, blue, and green (RGB). Each color on a pixel is called a "subpixel".

[0030] In this paper, the refractive index of a material is expressed by first listing the first capping layer, represented by n1, or the second capping layer, represented by n2, in parentheses, followed by the wavelength of the incident light; therefore, the refractive index is expressed as, for example, (n1@450nm), which means the refractive index of the first capping layer material relative to vacuum for light with a wavelength of 450nm.

[0031] In this document, the term "covering layer" without the prefixes "first" or "second" refers to the entire covering layer including its respective sub-pixel region. For example, within the red sub-pixel region, both the first and second covering layers are included. Correspondingly, the term "refractive index of the covering layer" without the prefixes "first" or "second" refers to the combined refractive index of the entire covering layer.

[0032] In this paper, the term "refractive index in the blue sub-pixel region" refers to the refractive index of the first capping material relative to vacuum for blue light at a wavelength of 450 nm, denoted as n1@450nm; the term "refractive index in the green sub-pixel region" refers to the refractive index of the first and / or second capping material relative to vacuum for green light at a wavelength of 525 nm; and the term "refractive index in the red sub-pixel region" refers to the refractive index of the first and / or second capping material relative to vacuum for red light at a wavelength of 620 nm.

[0033] This invention provides an organic electroluminescent device, the display comprising: a substrate including a plurality of sub-pixel regions, the plurality of sub-pixel regions including a red sub-pixel region, a green sub-pixel region, and a blue sub-pixel region; a plurality of first electrodes arranged on the substrate corresponding to each of the plurality of sub-pixel regions; red, green, and blue light-emitting layers formed on the respective corresponding first electrodes; a second electrode covering the red, green, and blue light-emitting layers; a first cover layer covering the second electrode; and a second cover layer covering the first cover layer within the red sub-pixel region and / or the green sub-pixel region.

[0034] The refractive index (n1@450nm) of the first capping layer within the blue sub-pixel region is 1.8 to 2.4, preferably 1.8 to 2.3, and most preferably 1.9 to 2.3; and

[0035] The refractive index (n2@620nm) of the second capping layer in the red subpixel region is 1.9 to 2.7, preferably 1.9 to 2.6, and most preferably 2.0 to 2.6;

[0036] Within the green sub-pixel region, the refractive index (n2@525nm) of the second capping layer is 2.0 to 2.7, preferably 2.0 to 2.6, and most preferably 2.1 to 2.6.

[0037] In this design, the first electrode can be a positive electrode, i.e., a hole injection electrode, and the second electrode can be a negative electrode, i.e., an electron injection electrode; or the first electrode can be a negative electrode, i.e., an electron injection electrode, and the second electrode can be a positive electrode, i.e., a hole injection electrode. When the first electrode is a positive electrode, at least one of the hole injection layer (HIL), the hole transport layer (HTL), and the electron blocking layer (EBL) can be disposed between the first electrode and the light-emitting layer. Furthermore, at least one of the hole blocking layer (HBL), the electron transport layer (ETL), and the electron injection layer (EIL) can be disposed between the light-emitting layer and the second electrode.

[0038] Cover layer

[0039] The capping layer is an organic material with a refractive index ≥1.8 under visible light. The capping layer comprises a first capping layer and / or a second capping layer.

[0040] First covering layer

[0041] The same organic material is used as the first cover layer in the red, green, and blue sub-pixel regions.

[0042] The organic material of the first capping layer is an organic compound with a core composed of monoamine, diamine, carbazole, carbazole cyclohexane, pyromellitic acid, aziridine, oxanthrone, dibenzofuran, spirofluorene, fluorene, or oxaspirene, and branched with one or more combinations of aryl, heteroaryl, or amino groups. Preferably, the organic material of the first capping layer is an organic compound with a core composed of benzidine, triphenylamine, pyridine, carbazole, carbazole cyclohexane, 1,3,5-triphenylbenzene, spirofluorene, oxanthrone, or oxaspirene, and branched with phenyl, naphthyl, biphenyl, benzoxazolyl, dibenzofuranyl, amino, or benzothiazolyl groups, wherein the branched groups may be unsubstituted or substituted with groups selected from phenyl or carbazole groups.

[0043] The preferred organic material for the first capping layer is selected from compounds with the structures shown in CP1-1 to CP1-16 below:

[0044]

[0045] The aforementioned organic materials CP1-1 to CP1-16 are commercially available or prepared according to the methods disclosed in patent publication numbers CN109761967A and CN109928962A. For example, CP1-2 can be purchased from Wuhan Shangsai Optoelectronic Technology Co., Ltd., CP1-6 can be prepared according to Example 1 described in CN109761967A, and CP1-8 can be prepared according to Example 2 described in CN109928962A.

[0046] When the same material is used as the first capping layer in the blue, green, and red sub-pixel regions, the refractive index is the highest in the blue sub-pixel region, followed by the green sub-pixel region, and the lowest in the red sub-pixel region; that is, n1@450nm > n1@525nm > n1@620nm.

[0047] The first cover layer has a refractive index (n1@450nm) of 1.8 to 2.4 in the blue sub-pixel region, preferably 1.8 to 2.3, and most preferably 1.9 to 2.3 in the green sub-pixel region; and a refractive index (n1@525nm) of 1.8 to 2.3 in the green sub-pixel region, preferably 1.8 to 2.2, and most preferably 1.9 to 2.2.

[0048] The difference between the refractive index of the first cover layer in the blue sub-pixel region (n1@450nm) and the refractive index in the green sub-pixel region (n1@525nm) is greater than 0 and less than or equal to 0.2, preferably greater than 0 and less than or equal to 0.15.

[0049] The first cover layer has the same thickness in the red sub-pixel region, green sub-pixel region and blue sub-pixel region, which is 20-120nm, preferably 30-100nm, and most preferably 30-85nm.

[0050] Second covering layer

[0051] The second overlay can cover both the red sub-pixel region and the green sub-pixel region of the first overlay, or it can only cover the red sub-pixel region of the first overlay.

[0052] When the second cover layer simultaneously covers the first cover layer in both the red sub-pixel region and the green sub-pixel region, the organic materials used in the second cover layer in the red sub-pixel region and the green sub-pixel region can be the same or different.

[0053] The organic material of the second capping layer is an organic compound with a monoamine, diamine, carbazole, carbazole cyclohexane, pyromellitic acid, or aziridine as the parent core and one or more combinations of aryl, heteroaryl, or amino groups as branches; preferably, the organic material of the second capping layer is an organic compound with a benzidine, triazine, 1,3-diphenylbenzene, terphenyldiamine, pyridine, triphenylamine, carbazole, or carbazole cyclohexane as the parent core and phenyl, xanthonone, dibenzofuran, benzoxazol, benzothiazolyl, N-phenylcarbazole, or amino groups as branches, wherein the branches can be unsubstituted or phenyl-substituted groups; in particular, the organic material of the second capping layer is characterized in that at least one of the branched groups contains a group selected from xanthonone, dibenzofuran, benzoxazol, or benzothiazolyl.

[0054] The preferred organic material for the second capping layer is selected from compounds with the structures shown in CP2-1 to CP2-11 below:

[0055]

[0056] The aforementioned organic materials CP2-1 to CP2-11 are commercially available or prepared according to the methods disclosed in patent publication numbers CN109206420A and CN109824659A. For example, CP2-2 can be prepared according to Example 3 of CN109206420A, and CP2-8 can be prepared according to Example 1 of CN109824659A.

[0057] The refractive index (n2@620nm) of the second capping layer in the red subpixel region is 1.9 to 2.7, preferably 1.9 to 2.6, and most preferably 2.0 to 2.6. In the green subpixel region, the refractive index (n2@525nm) of the second capping layer is 2.0 to 2.7, preferably 2.0 to 2.6, and most preferably 2.1 to 2.6.

[0058] When the second overlay layer covers the first overlay layer within the green subpixel region and the red subpixel region, the materials of the first and second overlay layers should be selected such that n1@450nm-n2@620nm≤0.2 and n1@450nm-n2@525nm≤0.2, preferably n1@450nm-n2@620nm≤0.1 and n1@450nm-n2@525nm≤0.1, more preferably n1@450nm-n2@620nm≤0 and n1@450nm-n2@525nm≤0, and most preferably n1@450nm-n2@620nm<0 and n1@450nm-n2@525nm<0. 525nm < 0; In other words, the difference between the refractive index of the first capping layer in the blue sub-pixel region (n1@525nm) and the refractive index of the second capping layer in the green and red sub-pixel regions (n2@525nm and n2@620nm) is less than or equal to 0.2, preferably less than or equal to 0.1, more preferably less than or equal to 0, and most preferably the refractive index of the organic material of the first capping layer under blue light is less than the refractive index of the organic material of the second capping layer under red and / or green light. For example, -0.25 ≤ n1@450nm - n2@525nm ≤ -0.05; -0.2 ≤ n1@450nm - n2@620nm ≤ -0.04.

[0059] When the second capping layer covers both the green and red sub-pixel regions, the material of the second capping layer should be selected such that the difference between the refractive index (n2@525nm) of the second capping layer in the green sub-pixel region and the refractive index (n2@620nm) in the red sub-pixel region is less than or equal to 0.1, preferably less than or equal to 0, and more preferably less than or equal to 0. Alternatively, the refractive index (n2@525nm) of the second capping layer in the green sub-pixel region is less than that in the red sub-pixel region. This can also be expressed as n2@525nm-n2@620nm≤0.1, preferably n2@525nm-n2@620nm≤0, and more preferably n2@525nm-n2@620nm<0, for example, -0.2≤n2@525nm-n2@620nm≤-0.05.

[0060] When the second capping layer only covers the first capping layer within the red sub-pixel region, the material of the second capping layer should be selected such that n1@450nm-n2@620nm≤0.2, preferably n1@450nm-n2@620nm≤0.1, more preferably n1@450nm-n2@620nm≤0, and most preferably n1@450nm-n2@620nm<0. Specifically, the difference between the refractive index of the first capping layer in the blue sub-pixel region (n1@525nm) and the refractive index of the second capping layer in the red sub-pixel region (n2@620nm) is less than or equal to 0.2, preferably less than or equal to 0.1, more preferably less than or equal to 0, and most preferably the refractive index of the organic material of the first capping layer under blue light is less than the refractive index of the organic material of the second capping layer under green light, for example -0.2≤n1@450nm-n2@620nm≤-0.04.

[0061] The thickness of the second cover layer in the green sub-pixel region is 10-100nm, preferably 10-90nm, and most preferably 10-80nm;

[0062] The thickness of the second cover layer in the red sub-pixel region is 10-100nm, preferably 10-90nm, and most preferably 10-80nm;

[0063] The thickness of the second cover layer in the red sub-pixel region and the green sub-pixel region can be the same or different; preferably, the thickness of the second cover layer in the green sub-pixel region is less than the thickness of the second cover layer in the red sub-pixel region.

[0064] Hole injection layer (HIL), hole transport layer (HTL), electron blocking layer (EBL)

[0065] The material of the hole injection layer (HIL) is typically preferably a material with a high work function, which facilitates hole injection into the light-emitting layer. The thickness of the hole injection layer in this invention can be 5-100 nm, preferably 5-50 nm, and more preferably 5-20 nm.

[0066] The hole transport layer (HTL) is preferably made of a material with high hole mobility, which enables holes to transfer from the anode or hole injection layer to the light-emitting layer. The thickness of the hole transport layer of the present invention can be 5-200 nm, preferably 10-150 nm.

[0067] An electron blocking layer (EBL) can be disposed above a hole injection layer / hole transport layer. The thickness of the electron blocking layer in this invention can be 1-200 nm, preferably 10-100 nm.

[0068] As for the hole injection layer, hole transport layer, and electron blocking layer materials, any material can be selected from known materials used in OLED devices.

[0069] Examples of the aforementioned materials include phthalocyanine derivatives, triazole derivatives, triarylmethane derivatives, triarylamine derivatives, oxazole derivatives, oxadiazole derivatives, hydrazone derivatives, stilbene derivatives, pyridinium derivatives, polysilane derivatives, imidazole derivatives, phenylenediamine derivatives, amino-substituted quinone derivatives, styrene-based anthracene derivatives, styrene-based amine derivatives, styrene compounds, fluorene derivatives, spirofluorene derivatives, silazane derivatives, aniline copolymers, porphyrin compounds, carbazole derivatives, polyaryl alkane derivatives, polyphenylene oxide and its derivatives, polythiophene and its derivatives, poly-N-vinylcarbazole derivatives, thiophene oligomers and other conductive polymers, aromatic tertiary amine compounds, and styrene aminations. Compounds, triamines, tetraamines, benzidines, propyne diamine derivatives, p-phenylenediamine derivatives, m-phenylenediamine derivatives, 1,1'-bis(4-diarylaminophenyl)cyclohexane, 4,4'-bis(diarylamine)biphenyls, bis[4-(diarylamino)phenyl]methanes, 4,4”-bis(diarylamino)terphenyls, 4,4”-bis(diarylamino)tetraphenyls, 4,4'-bis(diarylamino)diphenyl ethers, 4,4'-bis(diarylamino)diphenylsulfanes, bis[4-(diarylamino)phenyl]dimethylmethanes, bis[4-(diarylamino)phenyl]-bis(trifluoromethyl)methanes, or 2,2-diphenylethylene compounds, etc.

[0070] At least one of the hole injection layer (HIL) and hole transport layer (HTL) may further include a charge-generating material for improving conductivity. The charge-generating material may be a p-dopant. Non-limiting compounds of p-dopants include: quinone derivatives, such as tetracyanoquinone dimethyl (TCNQ) and 2,3,5,6-tetrafluoro-tetracyano-1,4-benzoquinone dimethyl (F4-TCNQ); or hexaazatriphenyl derivatives, such as 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenyl (HAT-CN); or cyclopropane derivatives, such as 4,4′,4″-((1E,1′E,1″E)-cyclopropane-1,2,3-trimethylenetris(cyanoformyl))tris(2,3,5,6-tetrafluorobenzyl); or metal oxides, such as tungsten oxide and molybdenum oxide, but not limited thereto.

[0071] In the electron blocking layer (EBL), the triplet (T1) energy level of the material is required to be higher than the T1 energy level of the host material in the emissive layer 202, thus blocking energy loss from the emissive layer material. The HOMO energy level of the EBL material is between the HOMO energy level of the hole transport layer (HTL) material and the HOMO energy level of the host material in the emissive layer 202, facilitating hole injection from the positive electrode into the emissive layer. Simultaneously, the EBL material is required to have high hole mobility to facilitate hole transport and reduce the power consumption of the device. The LUMO energy level of the EBL material is higher than the LUMO energy level of the host material in the emissive layer 202, serving as an electron blocker; that is, the EBL material is required to have a wide bandgap (Eg). EBL materials meeting these conditions can be triarylamine derivatives, fluorene derivatives, spirofluorene derivatives, dibenzofuran derivatives, carbazole derivatives, etc. Preferred are triarylamine derivatives, such as N4,N4-bis([1,1′-biphenyl]-4-yl)-N4′-phenylN4′-[1,1′:4′,1″-terphenyl]-4-yl-[1,1′-biphenyl]-4,4′-diamine; spirofluorene derivatives, such as N-([1,1′-diphenyl]-4-yl)-N-(9,9-dimethyl-9H-furan-2-yl)-9,9′-spirodifluorene-2-amine; dibenzofuran derivatives, such as N,N-bis([1,1′-biphenyl]-4-yl)-3′-(dibenzo[b,d]furan-4-yl)-[1,1′-biphenyl]-4-amine, but not limited thereto.

[0072] Emissive layer

[0073] The light-emitting layer can be disposed above the hole transport region. The thickness of the light-emitting layer of the present invention can be 5-60 nm, preferably 10-50 nm, and more preferably 20-45 nm.

[0074] To obtain a high-efficiency OLED device, its emissive layer can use the same doping material or multiple doping materials. The doping materials can be simple fluorescent materials, delayed fluorescence (TADF) materials, or phosphorescent materials, or a combination of different fluorescent materials, TADF materials, and phosphorescent materials. The emissive layer can be a single emissive layer material or a composite emissive layer material stacked laterally or vertically.

[0075] The host material of the luminescent layer constituting the aforementioned OLED light emitter not only needs to possess bipolar charge transport characteristics, but also needs to have an appropriate energy level to effectively transfer the excitation energy generated by electron-hole recombination to the guest luminescent material, i.e., the doped material. Examples of host materials are selected from, but not limited to, stilbene arylene derivatives, stilbene derivatives, carbazole derivatives, triarylamine derivatives, anthracene derivatives, pyrene derivatives, triazine derivatives, xanthones, triphenylene derivatives, azirbenzene derivatives, hexabenzobenzene derivatives, or bis(2-methyl-8-quinoline)(p-phenylphenol)aluminum (BAlq), etc.

[0076] As a guest material capable of producing blue fluorescence, blue phosphorescence, green fluorescence, green phosphorescence, and blue-green fluorescence, it not only needs to possess extremely high fluorescence quantum luminescence efficiency but also needs to have an appropriate energy level to effectively absorb the excitation energy of the host material and emit light. There are no particular limitations on such materials. They are selected from, but not limited to, stilbene amine derivatives, pyrene derivatives, anthracene derivatives, triazine derivatives, xanthone derivatives, benzoxazole derivatives, benzothiazole derivatives, benzimidazole derivatives, chrysodium derivatives, diazoxide-phenanthroline derivatives, stilbeneylbenzene derivatives, or tetraphenylbutadiene derivatives, etc. Among them, 4,4'-bis[2-(9-ethylcarbazole-2-yl)-vinyl]biphenyl (BCzVBi), perylene, etc. can be used. Other examples include tetraphenyl compounds, diphenyl compounds, benzimidazole compounds, benzoxazole compounds, benzoxadiazole compounds, styrene-based compounds, bistyrene-pyrazine compounds, butadiene compounds, naphthalene-dicarboximide compounds, perillene compounds, aldehyde-azo compounds, cyclopentadiene compounds, pyrrolopyrrole-based compounds, styrene-based compounds, coumarin compounds, aromatic xylene-theophylline compounds, metal coordination compounds with 8-quinolinephenol as ligands, or polyphenylene compounds, either alone or in combination of two or more. Specific examples that can be listed are aromatic xylene-theophylline compounds, such as 4,4'-bis(2,2-di-1-butylphenylvinyl)bisphenyl (abbreviated as: DTBBBi) or 4,4'-bis(2,2-diphenylvinyl)bisphenyl (abbreviated as: DPVBi) and their derivatives.

[0077] The content (doping amount) of fluorescent guest material relative to the fluorescent host material is preferably 0.01% to 20% by weight, more preferably 0.1% to 10% by weight.

[0078] The emitting layer 340 included in the aforementioned OLED device can use not only the fluorescent emitting material but also the phosphorescent material. Compared to fluorescent materials, phosphorescent materials can utilize both singlet and triplet excitons during the luminescence process, theoretically achieving an internal quantum efficiency of 100%, thereby significantly improving the luminescence efficiency of the emitting device.

[0079] As a blue phosphorescent dopant, any substance possessing blue phosphorescence emission function is acceptable, without particular limitation. Examples include metal complexes of iridium, titanium, platinum, rhenium, palladium, etc. Preferably, at least one ligand of the aforementioned metal complex has a phenylpyridine backbone, a dipyridine backbone, a porphyrin backbone, etc. More specifically, examples include bis[4,6-difluorophenylpyridine-N,C2']-methylpyridine iridium, tris[2-(2,4-difluorophenyl)pyridine-N,C2']iridium, bis[2-(3,5-trifluoromethyl)pyridine-N,C2']-methylpyridine iridium, or bis[4,6-difluorophenylpyridine-N,C2']acetylacetone iridium.

[0080] As a green phosphorescent dopant, any substance with green phosphorescent emission function is acceptable, without particular limitations. For example, metal complexes of iridium, niobium, platinum, rhenium, palladium, etc. can be cited. Furthermore, complexes with at least one ligand of the aforementioned metal complexes having a phenylpyridine backbone, a dipyridine backbone, a porphyrin backbone, etc., can also be cited as green phosphorescent dopants. More specifically, facet-tris(2-phenylpyridine)iridium (Ir(ppy)3), bis[2-phenylpyridine-N,C2']-acetylacetone iridium, or facet-tris[5-fluoro-2-(5-trifluoromethyl-2-pyridine)phenyl-C,N]iridium, etc., can be cited.

[0081] Examples of red phosphorescent doped materials include octaethylporphyrin platinum(II) (PtOEP), tris(2-phenylisoquinoline)iridium (Ir(piq)3), and bis(2-(2'-benzothiophene)-pyridine-N,C3')iridium (acetylacetonate) (Btp2Ir(acac)).

[0082] The content (doping amount) of phosphorescent dopant material relative to the phosphorescent host material is preferably 0.01% to 30% by weight, more preferably 0.1% to 20% by weight. When using green phosphorescent dopant material, the content is preferably 0.1% to 20% by weight relative to the phosphorescent host material.

[0083] Furthermore, as the host material for phosphorescence, any material whose triplet energy is greater than that of the phosphorescent dopant can be used; there are no particular limitations. Examples include carbazole derivatives, diazophenanthrene derivatives, triazine derivatives, triazole derivatives, and hydroxyquinoline metal complexes. Specifically, examples include 4,4',4”-tris(9-carbazolyl)triphenylamine, 4,4'-bis(9-carbazolyl)-2,2'-dimethylbiphenyl, 2,9-dimethyl-4,7-diphenyl-1,10-o-diazophenanthrene (BCP), 3-phenyl-4-(1'-naphthyl)-5-phenylcarbazole, tris(8-hydroxyquinoline)aluminum (Alq3), or bis-(2-methyl-8-hydroxyquinoline-4-(phenylphenol)aluminum), etc.

[0084] In addition to the fluorescent or phosphorescent host-guest materials used in the light-emitting layer, the light-emitting layer material can also be a non-host-guest doped system material, such as excitocomplex energy transfer and interfacial luminescence; the light-emitting layer material can also be a host-guest material with thermally activated delayed fluorescence (TADF) function, as well as a combination of TADF functional materials and the aforementioned fluorescent and phosphorescent materials.

[0085] Hole blocking layer (HBL), electron transport layer (ETL)

[0086] A hole blocking layer (HBL) is a layer that prevents holes injected from the anode from passing through the light-emitting layer and entering the cathode, thereby extending the device lifetime and improving the device performance. The hole blocking layer of this invention can be disposed above the light-emitting layer. The thickness of the hole blocking layer of this invention can be 2-200 nm, preferably 5-150 nm, and more preferably 10-100 nm.

[0087] An electron transport layer (ETL) may be disposed above the light-emitting layer or (if present) a hole-blocking layer. The electron transport layer material is one that readily receives electrons from the cathode and transfers them to the light-emitting layer. A material with high electron mobility is preferred. The thickness of the electron transport layer of the present invention can be 10-80 nm, preferably 20-60 nm, and more preferably 25-45 nm.

[0088] The materials used to form the hole blocking layer and electron transport layer of the OLED device can be any material selected from those used in OLEDs that have electron transport properties. Examples of such materials include 1,3-bis[5'-(p-tert-butylphenyl)-1,3,4-oxadiazole-2'-yl]benzene, 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole and other oxadiazole derivatives, 3-(4'-tert-butylphenyl)-4-phenyl-5-(4"-biphenyl)-1,2,4-triazole and other triazole derivatives, triazine derivatives, quinoline derivatives, quinoxaline derivatives, dibenzoquinone derivatives, nitro-substituted linone derivatives, thiam dioxide derivatives, anthraquinone dimethane derivatives, thiam dioxide derivatives, naphthylperylene and other heterocyclic tetrahydric anhydrides, carbodiimide, lin derivatives, anthraquinone dimethane derivatives, anthrone derivatives, stilbene pyrazine derivatives, silicone heterocyclic pentabenzene derivatives, diazonium phenanthrene derivatives, or imidazopyridine derivatives, etc.

[0089] In addition, examples include organometallic complexes such as bis(10-benzo[h]hydroxyquinoline) beryllium, beryllium salts of 5-hydroxyflavone, and aluminum salts of 5-hydroxyflavone, or metal complexes of 8-hydroxyquinoline or its derivatives, such as tris(8-hydroxyquinoline)aluminum (Alq), tris(5,7-dichloro-8-hydroxyquinoline)aluminum, bis(2-methyl-8-hydroxyquinoline)(p-phenylphenol)aluminum (BAlq), and tris(5,7-dibromo-8-hydroxyquinoline)aluminum. Metal chelating agent compounds containing chelating agents are also included, such as hydroxyquinoline metal complexes containing plant hormones (generally 8-hydroxyquinoline) such as tris(2-methyl-8-hydroxyquinoline)aluminum. Furthermore, examples include metal complexes in which the central metal is replaced by beryllium, indium, magnesium, copper, calcium, tin, zinc, or aluminum. Non-metals, metal phthalocyanines, or substances whose ends are replaced by alkyl, sulfonyl, or other similar groups are preferred. 2,9-Dimethyl-4,7-diphenyl-1,10-o-diazaphenanthroline (BCP) and 3-phenyl-4-(1'-naphthalene)-5-phenyl-1,2,4-triazole (TAZ) can also be used.

[0090] The hole blocking layer (HBL) requires that the triplet state (T1) energy level of the material be higher than that of the main material in the light-emitting layer 202, so as to block energy loss from the light-emitting layer material. The HOMO energy level of the hole blocking layer (HBL) material is lower than that of the main material in the light-emitting layer 202, thus blocking holes. Simultaneously, the hole blocking layer (HBL) material is required to have high electron mobility to facilitate electron transport and reduce the power consumption of the device. Hole blocking layer (HBL) materials meeting these conditions can be triazine derivatives, azirene derivatives, etc., with triazine derivatives being preferred; however, they are not limited to this.

[0091] Electron Injection Layer (EIL)

[0092] An electron injection layer (EIL) may be disposed above the electron transport layer. The electron injection layer material is typically preferably a material with a low work function, allowing electrons to be easily injected into the organic functional material layer. The thickness of the electron injection layer of this invention can be 0.1-5 nm, preferably 0.5-3 nm, and more preferably 0.8-1.5 nm.

[0093] The electron injection layer (EIL) can be formed from one or more of the following substances: alkali metals; alkaline earth metals; halides of alkali metals and alkaline earth metals; oxides of alkali metals and alkaline earth metals; carbonates of alkali metals and alkaline earth metals; oxalates of alkali metals and alkaline earth metals; or fluoroaluminates of alkali metals and alkaline earth metals. Examples include Li, Ca, Sr, LiF, CsF, BaO, Li₂CO₃, CaCO₃, Li₂C₂O₄, Cs₂C₂O₄, and CsAlF₄. In some embodiments, the electron injection layer (EIL) may include at least one metal, such as one or more of Yb, Sc, V, Y, In, Ce, Sm, Eu, or Tb.

[0094] The advantages of the present invention will now be explained with reference to the accompanying drawings and specific embodiments.

[0095] Figure 2 A schematic cross-sectional view of an organic electroluminescent device 1 according to a first exemplary embodiment is shown.

[0096] refer to Figure 2 The organic light-emitting device 1 of the first exemplary embodiment includes a substrate 100, a plurality of organic light-emitting devices (OLEDs) 200, a first cover layer 300, a second cover layer 400, and an encapsulation layer 500.

[0097] The substrate 100 can be made of glass, quartz, ceramic, polymer film, metal plate, etc. The substrate 100 has multiple pixel regions thereon. Each pixel region can be divided into a red sub-pixel region, a green sub-pixel region, and a blue sub-pixel region. Pixel circuitry (not shown) and an organic light-emitting diode (OLED) 200 are arranged for each sub-pixel region.

[0098] The pixel circuit includes at least two thin-film transistors (a switching thin-film transistor and a driving thin-film transistor) and at least one capacitor. The switching thin-film transistor is a switching device used to select a sub-pixel to emit light, and the driving thin-film transistor applies a driving power supply to the corresponding sub-pixel, causing the selected sub-pixel to emit light.

[0099] Figure 2One of the pixel regions comprising three sub-pixel regions is shown (pixel circuitry will be omitted for convenience). Pixels with the same configuration are arranged parallel to each other along the column and row directions on the substrate 100, and the combination of light emitted from multiple pixels realizes an image.

[0100] The organic light-emitting device (OLED) 200 includes a first electrode 201, a light-emitting layer 202, and a second electrode 203. The first electrode 201 is formed individually for each sub-pixel region and is electrically connected to the driving thin-film transistor of the corresponding sub-pixel region. The second electrode 203 is formed over the entire substrate 100.

[0101] A pixel-defining film 110 having a lattice structure can be disposed between the first electrodes 201. The pixel-defining film 110 forms openings for exposing each of the first electrodes 201 and delineates sub-pixel regions. The pixel-defining film 110 can be made of an organic film, such as polyimide.

[0102] The light-emitting layer 202 includes a red light-emitting layer 202R, a green light-emitting layer 202G, and a blue light-emitting layer 202B. The red light-emitting layer 202R is formed on the first electrode 201 of the red sub-pixel region, the green light-emitting layer 202G is formed on the first electrode 201 of the green sub-pixel region, and the blue light-emitting layer 202B is formed on the first electrode 201 of the blue sub-pixel region.

[0103] The first electrode 201 can be a positive electrode, i.e., a hole injection electrode, and the second electrode 203 can be a negative electrode, i.e., an electron injection electrode; alternatively, the first electrode 201 can be a negative electrode, i.e., an electron injection electrode, and the second electrode 203 can be a positive electrode, i.e., a hole injection electrode. When the first electrode 201 is a positive electrode, at least one of the hole injection layer 20210 (HIL), the hole transport layer 20220 (HTL), and the electron blocking layer 20230 (EBL) can be arranged between the first electrode 201 and the light-emitting layer 202. Furthermore, at least one of the hole blocking layer 20240 (HBL), the electron transport layer 20250 (ETL), and the electron injection layer 20260 (EIL) can be arranged between the light-emitting layer 202 and the second electrode 203, such as... Figure 5 As shown.

[0104] The first electrode 201, used as the anode, may comprise at least one metal, such as silver (Ag), nickel (Ni), molybdenum (Mo), gold (Au), platinum (Pt), tungsten (W), and copper (Cu) having a work function of 4.2 eV or higher. It may be formed from indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), aluminum zinc oxide (AZO), indium gallium oxide (IGO), indium oxide (In₂O₃), or tin oxide (SnO₂); or it may be formed from a combination of metals and oxides, such as ITO / Ag / ITO, IGO / Al / IGO, or AZO / Ag / AZO. The thickness of the first electrode 201 depends on the material used, and its thickness typically ranges from 5 nm to 1 μm, preferably from 10 nm to 1 μm, more preferably from 10 nm to 500 nm, particularly preferably from 10 nm to 300 nm, and most preferably from 10 nm to 250 nm.

[0105] The second electrode 203, used as the cathode, may include at least one metal, such as lithium (Li), magnesium (Mg), calcium (Ca), zinc (Zn), and aluminum (Al), which have a work function (i.e., 4.2 eV or less) smaller than that of the first electrode 201. The thickness of the second electrode 203 depends on the material used and is typically 5-40 nm, preferably 5-30 nm, and more preferably 5-20 nm.

[0106] Holes injected from the first electrode 201 and electrons injected from the second electrode 203 combine with each other in the light-emitting layer 202 to generate excitons, and emit various colors of light when the energy from the excitons is released.

[0107] The first electrode 201 can be formed of a reflective film, and the second electrode 203 can be formed of a semi-permeable film or a transparent conductive film. In this case, the light emitted from the light-emitting layer 202 is reflected by the first electrode 201 and transmitted through the second electrode 203, the first cover layer 300, the second cover layer 400 and the encapsulation layer 500 to emit light to the outside.

[0108] The encapsulation layer 500 can be integrally bonded to the substrate 100 using a sealant (not shown). The encapsulation layer 500 seals the organic electroluminescent device 200, protecting it from external environments containing moisture or oxygen, thereby suppressing degradation of the organic electroluminescent device 200 due to moisture or oxygen. The encapsulation layer 500 can be made of glass, polymer film, or the like. When both the substrate 100 and the encapsulation layer 500 are made of polymer film, the organic electroluminescent device 1 can be flexible.

[0109] The encapsulation layer 500 can also be deposited onto the substrate 100, the first capping layer 300, and the second capping layer 400. The encapsulation layer 500 can be formed by alternating deposition of inorganic and organic materials. In this case, a protective layer can be placed between the encapsulation layer 500 and the first capping layer 300 and the second capping layer 400 to prevent damage to the first capping layer 300 and the second capping layer 400 from high-energy plasma, secondary electrons, or strong ultraviolet radiation. This protective layer can be made of materials such as LiF or MgF2. When the substrate 100 is made of a polymer film, the organic electroluminescent device 1 can be flexible.

[0110] Additionally, an optical film (not shown) may be disposed on the outer surface of the encapsulation layer 500 to reduce light reflection from external light.

[0111] A first capping layer 300 is formed on the second electrode 203 and is arranged in the path through which red, green, and blue light are transmitted toward the encapsulation layer 500. The first capping layer 300 is an organic material with a refractive index (n1@450nm) of 1.8 to 2.4 in the blue sub-pixel region, preferably in the range of 1.8 to 2.3, and most preferably in the range of 1.9 to 2.3. The organic material is selected from the specific compounds CP1-1 to CP1-16 listed above.

[0112] The second capping layer 401 is formed on the first capping layer 300 within the green sub-pixel region and is arranged in the path through which green light is transmitted toward the encapsulation layer 500. Within the green sub-pixel region, the refractive index (n2@525nm) of the organic material of the second capping layer 401 is greater than the refractive index (n1@525nm) of the first capping layer 300, and the difference in refractive index is in the range of 0.1-0.8, preferably in the range of 0.1-0.5, and more preferably in the range of 0.1-0.35.

[0113] The second capping layer 402 is formed on the first capping layer 300 within the red sub-pixel region and is arranged in the path through which red light is transmitted toward the encapsulation layer 500. Within the red sub-pixel region, the refractive index (n2@620nm) of the organic material of the second capping layer 402 is greater than the refractive index (n1@620nm) of the first capping layer 300, and the difference in refractive index is in the range of 0.1-0.8, preferably in the range of 0.1-0.5, and more preferably in the range of 0.1-0.4.

[0114] The second capping layers 401 and 402 are composed of different organic materials selected from the specific compounds CP2-1 to CP2-11 listed above.

[0115] Because the refractive index of the first capping layer 300 is greater than that of the material inside the organic light-emitting device (OLED) 200; in the green sub-pixel region, the refractive index of the second capping layer 401 is greater than that of the first capping layer 300; in the red sub-pixel region, the refractive index of the second capping layer 402 is greater than that of the first capping layer 300; this difference in refractive index reduces the amount of light lost due to total internal reflection at the boundary surface of the light generated inside the organic light-emitting device (OLED) 200, increases the amount of transmitted light, and improves the light extraction efficiency, thereby improving the device's apparent polarization and the angle dependence of the emitted light.

[0116] It should be noted that Figure 2 The second overlay layer 401 in the green sub-pixel region uses a different material than the second overlay layer 402 in the red sub-pixel region.

[0117] Figure 3 A schematic cross-sectional view of an organic electroluminescent device 2 according to a second exemplary embodiment is shown.

[0118] Reference Figure 3 Except for the use of the same material in the second cover layer 403 within the red and green sub-pixel regions, the organic electroluminescent device 2 according to the second exemplary embodiment has the same configuration as the organic electroluminescent device 1 of the first exemplary embodiment described above. The same reference numerals will be used for components that are the same as in the first exemplary embodiment. The different configurations between the second and first exemplary embodiments will be described below.

[0119] The second capping layer 403 is formed simultaneously on the first capping layer 300 in both the green and red sub-pixel regions, and is arranged in the paths through which green and red light are transmitted toward the encapsulation layer 500. In the green and red sub-pixel regions, the refractive index of the second capping layer 403 (n2@525nm, n2@620nm) is greater than the refractive index of the first capping layer 300 in the same region (n1@525nm, n1@620nm), with the difference in refractive index ranging from 0.1 to 0.8, preferably from 0.1 to 0.5, and more preferably from 0.1 to 0.4. The material of the second capping layer 403 is selected from the specific compounds CP2-1 to CP2-11 listed above.

[0120] In the green sub-pixel region and the red sub-pixel region, the thickness of the second cover layer 403 and the first cover layer 300 may be the same or different; the thickness of the second cover layer 403 in the green sub-pixel region is the same as that in the red sub-pixel region.

[0121] Because the refractive index of the first capping layer 300 is greater than that of the material in the organic light-emitting device (OLED) 200; in the green and red sub-pixel regions, the refractive index of the second capping layer 403 is greater than that of the first capping layer 300; this difference in refractive index reduces the amount of light lost due to total internal reflection at the boundary surface of the light generated in the organic light-emitting device (OLED) 200, increases the amount of transmitted light, and improves the light extraction efficiency, thereby improving the device's apparent polarization and the angle dependence of the emitted light.

[0122] Compared to the organic electroluminescent device 1 of the first exemplary embodiment, the organic electroluminescent device 2 of the second exemplary embodiment requires a simpler patterning technique when depositing the second capping layer 403. Figure 1 ), because in organic electroluminescent devices 1 ( Figure 2 In organic electroluminescent devices (OLEDs), the photomask used for vapor deposition needs to have finer holes drilled for 401 and 402. The smaller the holes and the more holes there are, the higher the cost. Figure 3 In this process, only relatively larger and fewer holes need to be made for 403, thus reducing the manufacturing cost.

[0123] Figure 4 A schematic cross-sectional view of an organic electroluminescent device 3 according to a third exemplary embodiment is shown.

[0124] Reference Figure 4 Except for having a second overlay layer 404 only in the red sub-pixel region, the organic electroluminescent device 3 according to the third exemplary embodiment has the same configuration as the organic electroluminescent device 1 of the first exemplary embodiment described above. The same reference numerals will be used for components that are the same as in the first exemplary embodiment. The different configurations between the third exemplary embodiment and the first exemplary embodiment will be described below.

[0125] A second capping layer 404 is formed on the first capping layer 300 within the red sub-pixel region and is disposed in the path through which red light is transmitted toward the encapsulation layer 500. Within the red sub-pixel region, the refractive index of the second capping layer 404 (n2@620nm) is greater than the refractive index of the first capping layer 300 (n1@620nm), with the difference in refractive index ranging from 0.1 to 0.8, preferably from 0.1 to 0.5, and more preferably from 0.1 to 0.4. The second capping layer 404 is selected from the specific compounds CP2-1 to CP2-11 listed above.

[0126] Because the refractive index of the first capping layer 300 is greater than that of the material in the organic light-emitting device (OLED) 200; in the red sub-pixel region, the refractive index of the second capping layer 404 is greater than that of the first capping layer 300; this difference in refractive index reduces the amount of light lost due to total internal reflection at the boundary surface of the light generated in the organic light-emitting device (OLED) 200, increases the amount of transmitted light, and improves the light extraction efficiency, thereby improving the device's apparent polarization and the angle dependence of the emitted light.

[0127] Compared to the organic electroluminescent device 1 of the first exemplary embodiment, the organic electroluminescent device 3 of the third exemplary embodiment requires a simpler patterning technique when depositing the second capping layer 404. Figure 1 ), because in organic electroluminescent devices 1 ( Figure 2 In organic electroluminescent devices (OECDs), the photomask used for vapor deposition needs to have finer holes for 401 and 402. The smaller the holes and the more holes there are, the higher the cost. Figure 4 In this process, only half the number of holes of the same size as those in 404 stainless steel are needed, thus reducing the manufacturing cost.

[0128] In the organic electroluminescent devices 1, 2 and 3 according to the first exemplary embodiment, the second exemplary embodiment and the third exemplary embodiment, the first capping layer 300, the second capping layer 400 (including 401, 402), 403 and 404 can be formed by deposition method, laser thermal transfer imaging method and the like.

[0129] The deposition method utilizes a deposition mask with multiple openings, each corresponding to a sub-pixel region of a specific color. The laser thermal transfer imaging method prepares a donor film comprising a photothermal conversion layer and a transfer layer on a substrate film. Then, by irradiating the donor film with a laser, a portion of the photothermal conversion layer and a portion of the transfer layer in contact with the photothermal conversion layer expand, thereby transferring the transfer layer onto a second electrode.

[0130] The exemplary embodiments described above provide an organic light-emitting device that can improve the light extraction efficiency of each of the red, green and blue sub-pixels and reduce the degree of color variation with viewing angle in the organic light-emitting device (OLED).

[0131] This organic electroluminescent device can optimize the light extraction efficiency of red, green and blue light, thereby improving image quality and reducing the degree of color variation with viewing angle.

[0132] The exemplary embodiments of this application will be described in more detail below through examples. However, the scope of this application is not limited to the embodiments disclosed below.

[0133] Example

[0134] The capping material of the present invention: CP1-2 was purchased from Wuhan Shangsai Optoelectronic Technology Co., Ltd., CP1-8 can be prepared according to Example 2 described in CN109928962A, CP2-2 can be prepared according to Example 3 described in CN109206420A, and CP2-8 can be prepared according to Example 1 described in CN109824659A.

[0135] Determination methods

[0136] (Comprehensive) Methods for measuring refractive index, current efficiency, CIE, and the determination of perceptible color difference (JNCD):

[0137] The current efficiency (cd / A), CIEx, CIEy, and perceptible color difference of the OLED devices in the following examples and comparative examples were measured using an IVL (current-voltage-luminance) testing system (Suzhou Fosker Scientific Instruments Co., Ltd.). The refractive index of the single-film device (tested in an atmospheric environment) made of the capping layer (CPL) material described in the following device examples and comparative examples was measured using an ellipsometer testing system (JAWoollam Co., USA, model: ALPHA-SE). The data are shown in Table 1 below:

[0138] Table 1

[0139]

[0140] Application Examples

[0141] Device Example 1

[0142] Transparent substrate layer 100 / Anode layer 201 (i.e., first electrode, ITO (15nm) / Ag (150nm) / ITO (15nm)) / Hole injection layer 20210 (HT-1:P-1 = 97:3 mass ratio, thickness 10nm) / Hole transport layer 20220 (HT-1, thickness 120nm) / Electron blocking layer 20230 (EB-1, thickness 10nm) / Blue emitting layer 202B (BH-1:BD-1 = 97:3 mass ratio, thickness 20nm) / Electron transport layer 20250 (ET-1:Liq = 1:1 mass ratio, thickness 30nm) / Electron injection layer 20260 (LiF, thickness 1nm) / Cathode layer 203 (i.e., second electrode, Mg:Ag = 1:9 mass ratio, thickness 16nm) / First capping layer 300 (CP1-2, thickness 70nm).

[0143] The specific preparation process is as follows:

[0144] like Figure 1As shown, the transparent substrate layer 100 is a PI film (polyimide film). The ITO (15nm) / Ag (150nm) / ITO (15nm) anode layer 201 (i.e., the first electrode) is washed sequentially by alkaline washing, pure water washing, drying, and then ultraviolet-ozone washing to remove organic residues on the surface of the anode layer. After the above washing, a 10nm thick HT-1 and P-1 layer is deposited on the anode layer 201 using a vacuum evaporation apparatus as a hole injection layer 20210, with a mass ratio of HT-1 to P-1 of 97:3. Next, a 120nm thick HT-1 layer is deposited as a hole transport layer 20220. Subsequently, a 10nm thick EB-1 layer is deposited as an electron blocking layer 20230. After the electron blocking material is deposited, the blue emitting layer 202B of the OLED light-emitting device is fabricated. Its structure includes BH-1 as the main material and BD-1 as the dopant material, with a doping ratio of 3% by weight. The thickness of the emitting layer is 20 nm. Following the emitting layer 202B, ET-1 and Liq are vacuum-deposited at a mass ratio of 1:1, resulting in a thickness of 30 nm. This layer is the electron transport layer 20250. On the electron transport layer 20250, a 1 nm thick LiF layer is fabricated using a vacuum evaporation apparatus. This layer is the electron injection layer 20260. On the electron injection layer 20260, a 16 nm thick Mg:Ag electrode layer is fabricated using a vacuum evaporation apparatus, with a Mg:Ag mass ratio of 1:9. This layer is used as the cathode layer 203 (i.e., the second electrode). On the cathode layer 203, CP1-2 of 70 nm is vacuum-deposited as the first capping layer 300.

[0145] Device Example 2

[0146] Transparent substrate layer 100 / Anode layer 201 (i.e., first electrode, ITO (15nm) / Ag (150nm) / ITO (15nm)) / Hole injection layer 20210 (HT-1∶P-1=97∶3 mass ratio, thickness 10nm) / Hole transport layer 20220 (HT-1, thickness 120nm) / Electron blocking layer 20230 (EB-2, thickness 30nm) / Green light emitting layer 202G (GH-1∶GH-2∶G D-1 (47:47:6 mass ratio, 30nm thickness) / Electron transport layer 20250 (ET-1:Liq = 1:1 mass ratio, 30nm thickness) / Electron injection layer 20260 (LiF, 1nm thickness) / Cathode layer 203 (i.e., second electrode, Mg:Ag = 1:9 mass ratio, 16nm thickness) / First capping layer 300 (CP1-2, 70nm thickness) / Second capping layer 401 (CP2-8, 30nm thickness).

[0147] Device Example 3

[0148] Transparent substrate layer 100 / Anode layer 201 (i.e., first electrode, ITO (15nm) / Ag (150nm) / ITO (15nm)) / Hole injection layer 20210 (HT-1:P-1 = 97:3 mass ratio, thickness 10nm) / Hole transport layer 20220 (HT-1, thickness 120nm) / Electron blocking layer 20230 (EB-3, thickness 80nm) / Red emitting layer 202R (RH-1:RD) -1=97∶3 mass ratio, thickness 30nm) / Electron transport layer 20250 (ET-1∶Liq=1∶1 mass ratio, thickness 30nm) / Electron injection layer 20260 (LiF, thickness 1nm) / Cathode layer 203 (i.e., second electrode, Mg∶Ag=1∶9 mass ratio, thickness 16nm) / First capping layer 300 (CP1-2, thickness 70nm) / Second capping layer 402 (CP2-2, thickness 50nm).

[0149] Device Example 4:

[0150] The preparation method of device embodiment 4 is the same as that of device embodiment 2, except that CP2-2 is used instead of CP2-8.

[0151] Device Example 5:

[0152] The preparation method of device embodiment 5 is the same as that of device embodiment 2, except that CP2-8 is deleted.

[0153] Comparative Example 1:

[0154] The preparation method of Comparative Example 1 is the same as that of Example 1.

[0155] Comparative Example 2:

[0156] The preparation method of Comparative Example 2 is the same as that of Example 2, except that CP2-8 is deleted.

[0157] Comparative Example 3:

[0158] The preparation method of Comparative Example 3 is the same as that of Example 3, except that CP2-2 is deleted.

[0159] Comparative Example 4:

[0160] The apparatus of Comparative Example 4 was prepared in the same manner as that of Apparatus Example 2, except that CP1-8 was used instead of CP2-8.

[0161] Comparative Example 5:

[0162] The apparatus of Comparative Example 5 was prepared in the same manner as that of Apparatus Example 3, except that CP1-8 was used instead of CP2-2.

[0163] The organic electroluminescent device of the present invention

[0164] The organic electroluminescent device 1 includes device embodiment 1 in the blue sub-pixel region, device embodiment 2 in the green sub-pixel region, and device embodiment 3 in the red sub-pixel region.

[0165] The difference between organic electroluminescent device 2 and 1 is that device embodiment 4 is used in the green sub-pixel region.

[0166] The organic electroluminescent device 3 differs from 1 in that it uses device embodiment 5 in the green sub-pixel region.

[0167] Comparative examples of organic electroluminescent devices

[0168] Comparative Example 1 of an organic electroluminescent device includes Comparative Example 1 of a device in the blue sub-pixel region, Comparative Example 2 of a device in the green sub-pixel region, and Comparative Example 3 of a device in the red sub-pixel region; that is, only the first cover layer is included in the blue, green and red sub-pixel regions.

[0169] Comparative Example 2 of the organic electroluminescent device includes Comparative Example 1 of the device in the blue sub-pixel region, Comparative Example 4 of the device in the green sub-pixel region, and Comparative Example 5 of the device in the red sub-pixel region; that is, only a first capping layer is included in the blue sub-pixel region, and two capping layers are included in the green and red sub-pixel regions, and the materials of the two capping layers are selected from the organic materials of the first capping layer described above.

[0170] The structural formulas of the organic materials involved in the above implementation process are shown below:

[0171]

[0172]

[0173] After completing the fabrication of the electroluminescent device according to the above steps, the current efficiency (CIE) and perceptible color difference of the device were measured, and the results are shown in Table 2.

[0174] Table 2

[0175]

[0176] Note: Index = Current efficiency / CIEy, and is only applied to blue light devices; the efficiency of blue light devices is generally not determined by current efficiency, but by Index (industry standard);

[0177] Perceptible color difference, unit: JNCD; 1 JNCD = 0.004;

[0178] It should be understood that the smaller the perceptible color difference (@30°, @45°, @60°), the smaller the amount of color change, indicating that the angle dependence of the emitted light wavelength of the organic electroluminescent device is suppressed better.

[0179] As can be seen from the results in Table 2, for the organic electroluminescent devices 1, 2, and 3 of the present invention, in the same device, compared with the refractive index of the capping layer in the blue sub-pixel region, the refractive index of the capping layer (including the first and second capping layers) in the green and / or red sub-pixel regions is comparable to or greater. For the organic electroluminescent devices 1 and 2 of the present invention, compared with the refractive index of the capping layer in the blue sub-pixel region, the refractive index of the capping layer (including the first and second capping layers) in the green and / or red sub-pixel regions is smaller.

[0180] Comparing the organic electroluminescent devices 1, 2, and 3 of the present invention with comparative displays 1 and 2, for devices including a green emitting layer 202G, the refractive index of the capping layer in device embodiments 2 and 4 of the present invention is higher than that in comparative devices 2 and 4, and the device embodiments of the present invention are significantly superior to the comparative devices in terms of current efficiency and perceptible color difference; in particular, the current efficiency of the device embodiments of the present invention is improved by at least 9.7%. For devices including a red emitting layer 202R, the refractive index of the capping layer in device embodiment 3 of the present invention is higher than that in comparative devices 3 and 5, and the current efficiency and perceptible color difference of the device embodiments of the present invention are also superior to the comparative examples; in particular, in terms of current efficiency, the device embodiments of the present invention are improved by 9.9% and 9.5% respectively compared to comparative examples 3 and 5.

[0181] Taking the organic electroluminescent device including blue, green, and red sub-pixel regions as an example, compared with Comparative Example 1 of the display, the current efficiency of green light in the organic electroluminescent device 1 of the present invention—where the second capping layer is a different compound of the present invention—is improved by 9.7% and the current efficiency of red light is improved by 9.9%; the current efficiency of green light in the organic electroluminescent device 2 of the present invention—where the second capping layer is the same compound of the present invention—is improved by 11.0% and the current efficiency of red light is improved by 9.9%.

[0182] Similarly, compared to Comparative Example 2 of the display, the current efficiency of green light in the organic electroluminescent device 1 of the present invention is increased by 8.3% and the current efficiency of red light is increased by 9.5%; the current efficiency of green light in the organic electroluminescent device 2 of the present invention is increased by 9.7% and the current efficiency of red light is increased by 9.5%.

[0183] The above results show that the two-layer capping layer prepared according to the present invention and the display of the present invention containing the same layer have significantly improved current efficiency for both green and red light, and the improvement in current efficiency is comparable. Therefore, the light extraction efficiency of the display for green and red light is also improved accordingly.

[0184] Meanwhile, compared with Comparative Examples 1 and 2 of the displays, the organic electroluminescent device including the cover layer prepared according to the present invention has less perceptible color difference in blue light, green light and red light, and therefore less angle dependence.

[0185] Example embodiments have been disclosed herein, and although specific terminology has been used, it is used and interpreted in a general and descriptive sense only, and not for limiting purposes. In some instances, it will be apparent to those skilled in the art, as of the filing of this application, that features, characteristics, and / or elements described in connection with particular embodiments may be used alone or in conjunction with features, characteristics, and / or elements described in connection with other embodiments, unless expressly indicated otherwise. Therefore, those skilled in the art will understand that various changes in form and detail may be made without departing from the spirit and scope of the invention as set forth in the claims.

Claims

1. An organic electroluminescent device, comprising: The substrate includes multiple sub-pixel regions, the multiple sub-pixel regions including a red sub-pixel region, a green sub-pixel region and a blue sub-pixel region; A plurality of first electrodes are arranged on the substrate to correspond to each of the plurality of sub-pixel regions; Red, green and blue light-emitting layers are formed on their respective first electrodes; The second electrode covers the red, green, and blue light-emitting layers; A first covering layer covers the second electrode; The second overlay layer covers the first overlay layer within the red sub-pixel region and / or the green sub-pixel region; The first overlay layer in the blue sub-pixel region has a refractive index (n1@450nm) of 1.8 to 2.4 for light with a wavelength of 450nm. The refractive index (n2@620nm) of the second overlay layer in the red subpixel region for light at a wavelength of 620nm is 1.9 to 2.7; Within the green sub-pixel region, the refractive index (n2@525nm) of the second capping layer for light at a wavelength of 525nm is 2.0 to 2.7; The first and second capping layers are organic materials with a refractive index ≥1.8 under visible light; and Within the green sub-pixel region, the refractive index of the second capping layer for 525nm wavelength light (n2@525nm) is greater than that of the first capping layer for 525nm wavelength light (n1@525nm), with the difference in refractive index ranging from 0.1 to 0.

35. Within the red sub-pixel region, the refractive index of the second capping layer for 620nm wavelength light (n2@620nm) is greater than that of the first capping layer for 620nm wavelength light (n1@620nm), with the difference in refractive index ranging from 0.1 to 0.

4.

2. The organic electroluminescent device according to claim 1, characterized in that, The first overlay in the blue subpixel region has a refractive index (n1@450nm) of 1.8 to 2.3 for light at a wavelength of 450nm.

3. The organic electroluminescent device according to claim 1, characterized in that, The first overlay in the blue subpixel region has a refractive index (n1@450nm) of 1.9 to 2.3 for light at a wavelength of 450nm.

4. The organic electroluminescent device according to claim 1, characterized in that, The refractive index (n2@620nm) of the second overlay layer in the red subpixel region is 1.9 to 2.6 for light at a wavelength of 620nm.

5. The organic electroluminescent device according to claim 1, characterized in that, The refractive index (n2@620nm) of the second overlay layer in the red subpixel region is 2.0 to 2.6 for light at a wavelength of 620nm.

6. The organic electroluminescent device according to claim 1, characterized in that, Within the green sub-pixel region, the refractive index (n2@525nm) of the second overlay layer for light at a wavelength of 525nm is 2.0 to 2.

6.

7. The organic electroluminescent device according to claim 1, characterized in that, Within the green sub-pixel region, the refractive index (n2@525nm) of the second overlay layer for light at a wavelength of 525nm is 2.1 to 2.

6.

8. The organic electroluminescent device according to claim 1, characterized in that, The organic material of the first covering layer is an organic compound with biphenyl diamine, triphenylamine, pyridine, carbazole, carbazole ring, 1,3,5-triphenylbenzene, spirofluorene, oxanthrone or oxaspirene as the parent core and phenyl, naphthyl, biphenyl, benzoxazolyl, dibenzofuranyl, amino or benzothiazolyl as the branch chain, wherein the branch chain group can be unsubstituted or substituted by a group selected from phenyl or carbazole group; The organic material of the second covering layer is an organic compound with a parent nucleus of benzidine, triazine, 1,3-diphenylbenzene, triphenyldiamine, pyridine, triphenylamine, carbazole or carbazole ring, and branches of phenyl, xanthonone, dibenzofuran, benzoxazolyl, benzothiazolyl, N-phenylcarbazole or amino groups, wherein the branches can be unsubstituted or phenyl-substituted groups.

9. The organic electroluminescent device according to claim 8, characterized in that, The organic material of the first capping layer is selected from compounds with the structures shown in CP1-1 to CP1-16 below:

10. The organic electroluminescent device according to claim 8, characterized in that, At least one of the branched groups of the organic material in the second covering layer contains a group selected from xanthone, dibenzofuran, benzoxazol, or benzothiazolyl.

11. The organic electroluminescent device according to claim 8, characterized in that, The organic material of the second capping layer is selected from compounds with the structures shown in CP2-1 to CP2-11 below:

12. The organic electroluminescent device according to any one of claims 1 to 11, characterized in that, The first overlay layer has a refractive index (n1@525nm) of 1.8 to 2.3 for light with a wavelength of 525nm within the green sub-pixel.

13. The organic electroluminescent device according to claim 12, characterized in that, The first overlay layer has a refractive index (n1@525nm) of 1.8 to 2.2 for light with a wavelength of 525nm within the green sub-pixel.

14. The organic electroluminescent device according to claim 12, characterized in that, The first overlay layer has a refractive index (n1@525nm) of 1.9 to 2.2 for light at a wavelength of 525nm within the green sub-pixel.

15. The organic electroluminescent device according to any one of claims 1 to 11, characterized in that, The organic material of the first capping layer is the same in the red, green, and blue sub-pixel regions. The difference between the refractive index (n1@450nm) of the first capping layer for light with a wavelength of 450nm in the blue sub-pixel region and the refractive index (n1@525nm) for light with a wavelength of 525nm in the green sub-pixel region is greater than 0 and less than or equal to 0.

2.

16. The organic electroluminescent device according to claim 15, characterized in that, The organic material of the first capping layer is the same in the red, green, and blue sub-pixel regions. The difference between the refractive index of the first capping layer for light with a wavelength of 450nm (n1@450nm) in the blue sub-pixel region and the refractive index for light with a wavelength of 525nm (n1@525nm) in the green sub-pixel region is greater than 0 and less than or equal to 0.

15.

17. The organic electroluminescent device according to any one of claims 1 to 11, characterized in that, The organic materials used for the second capping layer in the red and green subpixel regions can be the same or different.

18. The organic electroluminescent device according to any one of claims 1 to 11, characterized in that, When the second overlay layer covers the first overlay layer within the green subpixel region and the red subpixel region, n1@450nm-n2@620nm≤0.2 and n1@450nm-n2@525nm≤0.

2.

19. The organic electroluminescent device according to claim 18, characterized in that, When the second overlay layer covers the first overlay layer within the green subpixel region and the red subpixel region, n1@450nm-n2@620nm≤0.1 and n1@450nm-n2@525nm≤0.

1.

20. The organic electroluminescent device according to claim 18, characterized in that, When the second overlay layer covers the first overlay layer within the green subpixel region and the red subpixel region, n1@450nm-n2@620nm≤0 and n1@450nm-n2@525nm≤0.

21. The organic electroluminescent device according to claim 18, characterized in that, When the second overlay layer covers the first overlay layer within the green sub-pixel region and the red sub-pixel region, n1@450nm-n2@620nm<0 and n1@450nm-n2@525nm<0.

22. The organic electroluminescent device according to claim 18, characterized in that, The difference between the refractive index (n2@525nm) of the second cover layer for light with a wavelength of 525nm in the green sub-pixel region and the refractive index (n2@620nm) for light with a wavelength of 620nm in the red sub-pixel region is less than or equal to 0.

1.

23. The organic electroluminescent device according to claim 22, characterized in that, The difference between the refractive index (n2@525nm) of the second cover layer for light with a wavelength of 525nm in the green sub-pixel region and the refractive index (n2@620nm) for light with a wavelength of 620nm in the red sub-pixel region is less than or equal to 0.

24. The organic electroluminescent device according to claim 22, characterized in that, The refractive index of the second cover layer for 525nm wavelength light (n2@525nm) in the green sub-pixel region is less than that for 620nm wavelength light (n2@620nm) in the red sub-pixel region.

25. The organic electroluminescent device according to any one of claims 1 to 11, characterized in that, When the second overlay layer only covers the first overlay layer within the red sub-pixel area, n1@450nm-n2@620nm≤0.

2.

26. The organic electroluminescent device according to claim 25, characterized in that, When the second overlay layer only covers the first overlay layer within the red sub-pixel area, n1@450nm-n2@620nm≤0.

1.

27. The organic electroluminescent device according to claim 25, characterized in that, When the second overlay layer only covers the first overlay layer within the red sub-pixel area, n1@450nm-n2@620nm≤0.

28. The organic electroluminescent device according to claim 25, characterized in that, When the second overlay layer only covers the first overlay layer within the red sub-pixel area, n1@450nm-n2@620nm<0.

29. The organic electroluminescent device according to any one of claims 1 to 11, characterized in that, The first cover layer has the same film thickness of 20-120nm in the red sub-pixel region, green sub-pixel region and blue sub-pixel region; The thickness of the second cover layer in the green sub-pixel region is 10-100 nm; the thickness of the second cover layer in the red sub-pixel region is 10-100 nm.

30. The organic electroluminescent device according to claim 29, characterized in that, The first cover layer has the same thickness of 30-100nm in the red sub-pixel region, green sub-pixel region and blue sub-pixel region.

31. The organic electroluminescent device according to claim 29, characterized in that, The first cover layer has the same thickness of 30-85nm in the red sub-pixel region, green sub-pixel region and blue sub-pixel region.

32. The organic electroluminescent device according to claim 29, characterized in that, The thickness of the second cover layer in the green sub-pixel region is 10-90 nm.

33. The organic electroluminescent device according to claim 29, characterized in that, The thickness of the second cover layer in the green sub-pixel region is 10-80 nm.

34. The organic electroluminescent device according to claim 29, characterized in that, The thickness of the second overlay layer in the red sub-pixel region is 10-90 nm.

35. The organic electroluminescent device according to claim 29, characterized in that, The thickness of the second overlay layer in the red sub-pixel region is 10-80 nm.

36. The organic electroluminescent device according to claim 29, wherein the thickness of the second cover layer in the green sub-pixel region is less than the thickness of the second cover layer in the red sub-pixel region.

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