Low refractive index capping layer, capping layer structure and organic light emitting device

Abstract

The invention discloses a low-refractive-index covering layer, a covering layer structure and an organic light-emitting device, and the low-refractive-index covering layer is formed by a compound represented by a formula I and / or a formula II: in the formula, A is selected from substituted or unsubstituted C6-C30 aryl and substituted or unsubstituted C3-C30 heteroaryl; r is selected from hydrogen, deuterium, and the following substituted or unsubstituted groups: a C1-C30 alkyl group, a C3-C30 cycloalkyl group, a C1-C30 heteroalkyl group, a C1-C30 heterocycloalkyl group, a C1-C10 fluoroalkyl group, a C1-C10 fluorocycloalkyl group, a C6-C30 aryl group, and a C3-C30 heteroaryl group; a1 and A2 are the same or different and are independently selected from a five-membered ring or a six-membered ring. A relatively strong peeling adhesive force exists between the low-refractive-index covering layer formed by the compound shown in the formula I and / or the formula II and the cathode, and meanwhile, a relatively high glass transition temperature is also achieved. When the covering layer structure jointly formed by the low-refractive-index covering layer and the high-refractive-index covering layer is applied to the organic light-emitting device, the device can have high light-emitting efficiency and color purity at the same time.

Description

Technical Field

[0001] This application relates to the field of organic light-emitting materials technology, specifically to a low-refractive-index capping layer, a capping layer structure, and an organic light-emitting device. Background Technology

[0002] Organic light-emitting devices (OLEDs) are widely used in various main displays and other applications, and their practical application has made significant progress. Although research on organic electroluminescence (OLEDs) has progressed very rapidly, many problems still need to be solved, such as improving the external quantum efficiency (EQE). For OLEDs, the luminescent quantum efficiency is a comprehensive reflection of various factors and is also an important indicator for measuring device quality.

[0003] Currently, some organic light-emitting materials have been commercially applied due to their excellent performance. They use amine derivatives with specific structures and high refractive indices or materials that meet specific parameter requirements as capping materials to improve light extraction efficiency and color purity. However, the problem of balancing luminous efficiency and color purity has not yet been solved, especially in the case of preparing blue light-emitting elements.

[0004] In response, researchers have found that using a stack of high-refractive-index and low-refractive-index layers in the capping layer can improve light extraction efficiency and color purity, as illustrated by Chinese authorized patent CN111316461B. However, existing low-refractive-index materials generally contain fluorine atoms. While the introduction of fluorine atoms and their derivatives can reduce the refractive index of the material, it also weakens the adhesion between the material and the device cathode (Ag), making it prone to interlayer delamination. In addition, the introduction of fluorine atoms also weakens the intermolecular forces of the compound, thereby lowering the glass transition temperature (Tg) of the material and reducing the lifespan of the device. Summary of the Invention

[0005] The technical problem solved by this application is to improve the peel adhesion between the capping layer and the cathode and the glass transition temperature of the capping layer material while maintaining a low refractive index.

[0006] To address the aforementioned technical problems, a first aspect of this application provides a low refractive index capping layer formed from compounds represented by Formula I and / or Formula II: In Formulas I and II, A is selected from substituted or unsubstituted C6-C30 aryl groups and substituted or unsubstituted C3-C30 heteroaryl groups; R is selected from hydrogen, deuterium, substituted or unsubstituted C1-C30 alkyl groups, substituted or unsubstituted C3-C30 cycloalkyl groups, substituted or unsubstituted C1-C30 heteroalkyl groups, substituted or unsubstituted C1-C30 heterocycloalkyl groups, substituted or unsubstituted C1-C10 fluoroalkyl groups, substituted or unsubstituted C1-C10 fluorocycloalkyl groups, substituted or unsubstituted C6-C30 aryl groups, and substituted or unsubstituted C3-C30 heteroaryl groups; A1 and A2 may be the same or different and are independently selected from five-membered or six-membered rings; Ak1 and Ak2 may be the same as or different from other alkyl groups of C1 to C30, heteroalkyl groups of C1 to C30, cycloalkyl groups of C3 to C30, heterocycloalkyl groups of C2 to C30, alkylamino groups of C1 to C30, heteroalkylamino groups of C1 to C30, cycloaminoalkyl groups of C3 to C30, or heterocycloalkylamino groups of C2 to C30, or rings formed by bonds with adjacent atoms; Ar1 ​​and Ar2 may be the same as or different from other aryl groups of C6 to C24, or heteroaryl groups of C3 to C24, substituted or unsubstituted.

[0007] A second aspect of this application provides a capping layer structure, comprising: the aforementioned low-refractive-index capping layer and a high-refractive-index capping layer located on the low-refractive-index capping layer, wherein the high-refractive-index capping layer has a refractive index of 1.90 or higher for 460nm wavelength light.

[0008] A third aspect of this application provides an organic light-emitting device comprising a first electrode, an organic layer, a second electrode, and a low-refractive-index capping layer as described in the first aspect of this application or a capping layer structure as described in the second aspect of this application, stacked sequentially.

[0009] The capping layer formed by the compounds shown in Formula I and / or Formula II has a low refractive index and strong peel adhesion to the cathode, while also possessing a high glass transition temperature. Furthermore, when the capping layer structure composed of this low-refractive-index capping layer and the high-refractive-index capping layer is applied to an organic light-emitting device, the device can achieve both high luminous efficiency and color purity. Attached Figure Description

[0010] The following accompanying drawings describe in detail the exemplary embodiments disclosed in this application. The same reference numerals denote similar structures in several views of the drawings. Those skilled in the art will understand that these embodiments are non-limiting and exemplary, and the drawings are for illustrative purposes only and are not intended to limit the scope of this application. Other embodiments may similarly fulfill the inventive intent of this application. It should be understood that the drawings are not drawn to scale. Wherein:

[0011] Figure 1 This is a schematic diagram of the structure of the organic light-emitting device prepared in Example 25 of this application. Detailed Implementation

[0012] The following description provides specific application scenarios and requirements for this application, intended to enable those skilled in the art to make and use the content of this application. Various partial modifications to the disclosed embodiments will be apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments and applications without departing from the spirit and scope of this application. Therefore, this application is not limited to the embodiments shown, but rather to the widest scope consistent with the claims.

[0013] Driven by the urgent need to improve the peel adhesion between the capping layer and the cathode, as well as the glass transition temperature of the capping layer material, the inventors of this application conducted extensive research and discovered that when heteroatoms (such as O, N, S, etc.) are introduced into the material molecules to form a cyclic imide structure, even if the material molecules also contain fluorine atoms or their derivatives, the capping layer formed by this material and the cathode still exhibit strong adhesion, making interlayer peeling less likely, and the material possesses a high glass transition temperature. The reason for this is that heteroatoms contain lone pairs of electrons, which can form weak interactions with the cathode, thereby improving the peel adhesion between the capping layer and the cathode. Simultaneously, the cyclic imide structure is a planar rigid structure, which facilitates intermolecular stacking, thus possessing strong intermolecular forces, resulting in a high glass transition temperature for the material.

[0014] The following is a detailed explanation of the terms used in this application:

[0015] Substitution or non-substitution: refers to substitution with one or more substituents, or no substitution. Unless otherwise specified, substituents may be selected from the following: deuterium, halogen groups, fluorine atoms, trifluoromethyl, cyano, nitro, hydroxyl, carbonyl, ester, imide, amino, phosphoxy, alkoxy, aryloxy, sulfone, sulfoxide, alkylthio, arylthio, alkylsulfonyl, arylsulfonyl, silyl, boron, alkyl, cycloalkyl, alkenyl, aryl, heteroaryl, aralkyl, arylenyl, alkylaryl, alkylamine, aralkylamine, heteroarylamine, arylamine, arylphosphinyl, heterocyclic, carboxyl derivative groups; or substitution with substituents that connect to two or more substituents listed above. For example, "substituents that connect to two or more substituents" may include biphenyl, i.e., biphenyl may be aryl, or a substituent that connects to two phenyl groups. When substituted with two or more substituents, adjacent substituents may also bond to form a ring. As an example, cyclization can be achieved through chemical bonding or through fusion.

[0016] Aryl group: Not particularly limited, it can be monocyclic or polycyclic aryl. In some embodiments, monocyclic aryl includes, but is not limited to, phenyl, biphenyl, terphenyl, tetraphenyl, pentaphenyl, etc. Polycyclic aryl includes, but is not limited to, naphthyl, anthracene, phenanthryl, pyrene, perylene, fluorene, etc. The fluorene group can be substituted, such as 9,9'-dimethylfluorenel, 9,9'-dibenzofluorenel, etc. In addition, two of the substituents can combine with each other to form a spirocyclic structure, such as 9,9'-spirodifluorenel, etc.

[0017] The above description of aryl groups can be applied to aryl groups in the following categories: aryloxy, arylthio, arylsulfonyl, arylphosphinyl, aralkyl, arylalkylamine, arylenyl, alkylaryl, arylamine, and arylheteroarylamine.

[0018] Heteroaryl groups: Containing one or more of B, N, O, P, S, Si, and Se as heteroatoms. Heteroaryl groups include, but are not limited to, pyridinyl, pyrrolyl, pyrimidinyl, pyridazinyl, furanyl, thiopheneyl, imidazolyl, pyrazolyl, azole, isozolyl, thiazolyl, isothiazolyl, triazolyl, diazolyl, thiadiazolyl, dithiazolyl, tetrazolyl, pyranyl, thiaranyl, pyrazinyl, azinyl, thiazolyl, dioxazinyl, dioxazinyl, triazinyl, tetraazinyl, quinolinyl, isoquinolinyl, quinolinyl, quinazolinyl, quinoxalinyl, naphridinyl, acridineyl, xanthyl, phenanthridineyl, diazanaphthyl, triazaindenyl, indoleyl, dihydroindoleyl, nitro-indenyl, phthalazinyl, pyridopyrimidinyl, pyridopyrazinyl, pyrazinyl Pyrazinyl, benzothiazolyl, benzoxazolyl, benzoimidazolyl, benzothiophene, benzofuranyl, dibenzothiophene, dibenzofuranyl, carbazoleyl, benzocarbazoleyl, dibenzocarbazoleyl, indolocarbazoleyl, indocarbazoleyl, phenazinyl, imidazopyridyl, phenazinyl, phenanthrinyl, phenthiazolyl, imidazopyridyl, imidazophenanthrinyl, benzoimidazoquinazolinyl, benzoimidazophenanthrinyl, spiro[fluorene-9,9'-oxazanthracene], phenylbinaphthyl, dinaphthofuranyl, naphthobenzofuranyl, dinaphthiophene, naphthobenzothiophene, triphenylphosphine oxide, triphenylborane, etc.

[0019] The above description of heteroaryl groups can be applied to heteroaryl groups in heteroaryl amines and aryl heteroaryl amines.

[0020] Alkyl groups: may be straight-chain or branched, including but not limited to methyl, ethyl, propyl, n-propyl, isopropyl, butyl, n-butyl, isobutyl, tert-butyl, sec-butyl, 1-methyl-butyl, 1-ethyl-butyl, pentyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, hexyl, n-hexyl, 1-methylpentyl, 2-methylpentyl, 4-methyl-2-pentyl, 3,3-dimethylbutyl, 2-ethylbutyl, heptyl, n-heptyl, 1-methylhexyl, cyclopentylmethyl, cyclohexylmethyl, octyl, n-octyl, tert-octyl, 1-methylheptyl, 2-ethylhexyl, 2-propylpentyl, n-nonyl, 2,2-dimethylheptyl, 1-ethyl-propyl, 1,1-dimethyl-propyl, isohexyl, 4-methylhexyl, 5-methylhexyl.

[0021] The above description of alkyl groups can also be used for alkyl groups in aralkyl, aralkylamino, alkylaryl, and alkylamino (alkylamino) groups.

[0022] Heteroalkyl: Can be a straight-chain or branched alkyl group containing heteroatoms, and the number of carbon atoms is not particularly limited. In some embodiments, heteroalkyl includes, but is not limited to, alkoxy, alkylthio, alkylsulfonyl, etc. Alkoxy may include, for example, methoxy, ethoxy, n-propoxy, isopropoxy, i-propyloxy, n-butoxy, isobutoxy, tert-butoxy, sec-butoxy, n-pentoxy, neopentoxy, isopentoxy, n-hexyloxy, 3,3-dimethylbutoxy, 2-ethylbutoxy, n-octoxy, n-nonoxy, n-decoxy, benzyloxy, p-methylbenzyloxy, etc. Alkylthio groups can include, for example, methylthio, ethylthio, n-propylthio, isopropylthio, isopropylthio, n-butylthio, isobutylthio, tert-butylthio, sec-butylthio, n-pentylthio, neopentylthio, isopentylthio, n-hexylthio, 3,3-dimethylbutylthio, 2-ethylbutylthio, n-octylthio, n-nonylthio, n-decylthio, benzylthio, etc. The above description of heteroalkyl groups can also be applied to heteroalkyl groups within heteroalkylamine groups.

[0023] Cycloalkyl groups: also known as cyclic saturated hydrocarbon groups, such as cyclopropyl, cyclobutyl, cyclopentyl, 3-methylcyclopentyl, 2,3-dimethylcyclopentyl, cyclohexyl, 3-methylcyclohexyl, 4-methylcyclohexyl, 2,3-dimethylcyclohexyl, 3,4,5-trimethylcyclohexyl, 4-tert-butylcyclohexyl, cycloheptyl, cyclooctyl, etc. The above description of cycloalkyl groups can also be applied to cycloalkyl groups within cycloamine alkyl groups.

[0024] Heterocyclic alkyl groups: cycloalkyl groups containing heteroatoms, for example: The above description of heterocyclic alkyl groups can also be applied to heterocyclic alkyl groups in heterocyclic alkylamine groups.

[0025] This application provides a low refractive index capping layer formed from compounds represented by Formula I and / or Formula II:

[0026]

[0027] In Formulas I and II, A is selected from substituted or unsubstituted C6-C30 aryl groups and substituted or unsubstituted C3-C30 heteroaryl groups. R is a substituent of A, which can be monosubstituted or polysubstituted at any substituted position on A. R can be selected from hydrogen, deuterium, substituted or unsubstituted straight-chain or branched C1-C30 alkyl groups, substituted or unsubstituted C3-C30 cycloalkyl groups, substituted or unsubstituted C1-C30 heteroalkyl groups, substituted or unsubstituted C1-C30 heterocycloalkyl groups, substituted or unsubstituted C1-C10 fluoroalkyl groups, substituted or unsubstituted C1-C10 fluorocycloalkyl groups, substituted or unsubstituted C6-C30 aryl groups, and substituted or unsubstituted C3-C30 heteroaryl groups.

[0028] A fuses with A1 and A2 to form rings. A1 and A2 may be the same or different, and are independently selected from five-membered or six-membered rings.

[0029] In Formula I, Ak1 is a substituent of A1 and is attached to the nitrogen atom (N) in A1, and Ak2 is a substituent of A2 and is attached to the nitrogen atom (N) in A2. Ak1 and Ak2 may be the same or different and are independently selected from substituted or unsubstituted C1-C30 alkyl groups, substituted or unsubstituted C1-C30 heteroalkyl groups, substituted or unsubstituted C3-C30 cycloalkyl groups, substituted or unsubstituted C2-C30 heterocycloalkyl groups, substituted or unsubstituted C1-C30 alkylamine groups, substituted or unsubstituted C1-C30 heteroalkylamine groups, substituted or unsubstituted C3-C30 cycloaminealkyl groups, substituted or unsubstituted C2-C30 heterocycloalkylamine groups, or formed a ring with adjacent atomic bonds.

[0030] In Formula II, Ar1 is a substituent of A1 and is attached to the nitrogen atom (N) in A1, and Ar2 is a substituent of A2 and is attached to the nitrogen atom (N) in A2. Ar1 and Ar2 may be the same or different and are independently selected from substituted or unsubstituted C6-C24 aryl groups and substituted or unsubstituted C3-C24 heteroaryl groups.

[0031] Because the core of the compounds shown in Formulas I and II contains nitrogen (N) and oxygen (O) atoms, the capping layer formed by the compound has a strong adhesion to the cathode. At the same time, the core of the compound has a planar rigid cyclic imide structure, which can give the material a high glass transition temperature.

[0032] In some preferred embodiments, the compound represented by Formula I is selected from:

[0033]

[0034] The compound represented by formula II is selected from:

[0035]

[0036] And A, R, Ak1, Ak2, Ar1 and Ar2 are the same as described above.

[0037] In some preferred embodiments, when at least one of A, R, Ak1, Ak2, Ar1, and Ar2 is substituted, the substituents are independently selected from one or more combinations of fluorine atoms, trifluoromethyl, cyano, nitro, phosphoxy, sulfone, sulfoxide, aryl, azaaryl, dimethyl, tert-butyl, isopropyl, and carboxyl derivative groups.

[0038] In some preferred embodiments, A is selected from the following groups, whether substituted or unsubstituted:

[0039]

[0040] In some preferred embodiments, Ar1 and Ar2 are independently selected from the following groups, whether substituted or unsubstituted:

[0041]

[0042]

[0043] Where * represents the connection site, that is, the connection site with the nitrogen atom in A1 and A2 of Formula II.

[0044] In some preferred embodiments, Ak1 and Ak2 are independently selected from methyl, ethyl, propyl, isopropyl, butyl, tert-butyl, sec-butyl, pentyl, isopentyl, hexyl, cyclohexyl, adamantyl, and substituted or unsubstituted groups:

[0045]

[0046] Wherein, * represents the linking site, that is, the linking site with the nitrogen atom in A1 and A2 of Formula I; (C)n represents an alkyl group having n carbon atoms, and n is selected from 1, 2, 3, 4, 5, 6; Ar3 is selected from substituted or unsubstituted C6-C12 aryl groups and substituted or unsubstituted C3-C12 heteroaryl groups.

[0047] In some preferred embodiments, the compound represented by Formula I is selected from the group consisting of:

[0048]

[0049]

[0050]

[0051] And Ar2 is selected from the following groups:

[0052]

[0053] Where * represents a connection site;

[0054] The compounds represented by Formula II are selected from the following group:

[0055]

[0056] And Ak2 is selected from the following groups:

[0057] adamantyl, The asterisk (*) represents a connection site.

[0058] In some more preferred embodiments, the compound represented by formula II is selected from the group consisting of:

[0059]

[0060] The compound represented by formula I is selected from the following group:

[0061]

[0062] This application also provides a capping layer structure, comprising: the aforementioned low-refractive-index capping layer and a high-refractive-index capping layer located on the low-refractive-index capping layer, wherein the high-refractive-index capping layer has a refractive index of 1.90 or higher for 460nm wavelength light. When this capping layer structure is applied to an organic light-emitting device, it can effectively improve the luminous efficiency and color purity of the device.

[0063] In some preferred embodiments, the refractive index of the low-refractive-index capping layer for 460nm wavelength light is 1.40–1.70. For example, the refractive index of the low-refractive-index capping layer can be 1.40, 1.41, 1.42, 1.43, 1.44, 1.45, 1.46, 1.47, 1.48, 1.49, 1.50, 1.51, 1.52, 1.53, 1.54, 1.55, 1.56, 1.57, 1.58, 1.59, 1.60, 1.61, 1.62, 1.63, 1.64, 1.65, 1.66, 1.67, 1.68, 1.69, or 1.70, or a specific value within a sub-range formed by any of the above values. More preferably, the refractive index of the low-refractive-index capping layer is 1.50–1.65. More preferably, the refractive index of the low refractive index capping layer is 1.52 to 1.61.

[0064] In some preferred embodiments, the high refractive index capping layer has a refractive index of 1.90 to 2.50 for 460 nm wavelength light. For example, it can be 1.90, 1.95, 1.95, 2.00, 2.10, 2.15, 2.20, 2.25, 2.30, 2.35, 2.40, 2.45, 2.50, or a specific value within a sub-range formed by any of the above values. More preferably, the refractive index of the high refractive index capping layer is 2.20.

[0065] In some preferred embodiments, the high refractive index capping layer is formed of at least one of an inorganic compound and an organic compound, wherein the inorganic compound includes at least one of SiOx, SiNy, ZnS, ZnSe, ZrO, and TiO2, and x and y are independently selected from integers from 1 to 4. The organic compound includes at least one of aromatic amine derivatives, carbazole derivatives, benzimidazole derivatives, and triazole derivatives. More preferably, the organic compound includes at least one of the following compounds:

[0066]

[0067] This application also provides an organic light-emitting device, comprising a first electrode, an organic layer, a second electrode, and the aforementioned low-refractive-index capping layer or capping layer structure stacked sequentially.

[0068] In some preferred embodiments, the first electrode is the anode, the second electrode is the cathode, and the low-refractive-index capping layer is located between the cathode and the high-refractive-index capping layer. The cathode can be one or more layers. The organic layer can be a single-layer structure or a multilayer tandem structure with two or more organic layers laminated together. The organic layer can include at least one of a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, a hole blocking layer, an electron transport layer, and an electron injection layer.

[0069] In some preferred embodiments, the organic layer includes a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, and an electron injection layer stacked sequentially.

[0070] In some specific embodiments, the structure of the organic light-emitting device can be selected from one of the following:

[0071] (1) An organic light-emitting device comprises an anode, a hole injection layer, a first hole transport layer, a light-emitting layer, a first electron transport layer, a cathode, and a capping layer stacked sequentially, i.e., anode / hole injection layer / first hole transport layer / light-emitting layer / first electron transport layer / cathode / capping layer. The device structure will be expressed in this simplified manner below.

[0072] (2) Anode / hole injection layer / second hole transport layer / first hole transport layer / light-emitting layer / first electron transport layer / cathode / capping layer.

[0073] (3) Anode / hole injection layer / second hole transport layer / first hole transport layer / light-emitting layer / first electron transport layer / second electron transport layer / cathode / capping layer.

[0074] (4) Anode / hole injection layer / second hole transport layer / first hole transport layer / light-emitting layer / first electron transport layer / second electron transport layer / electron injection layer / cathode / capping layer.

[0075] (5) Anode / hole injection layer / second hole transport layer / first hole transport layer / light-emitting layer / first electron transport layer / second electron transport layer / multilayer cathode / capping layer.

[0076] (6) Anode / hole injection layer / first hole transport layer / first light-emitting layer / carrier generation layer / first hole transport layer / second light-emitting layer / first electron transport layer / cathode / capping layer.

[0077] (7) Anode / hole injection layer / first hole transport layer / first light-emitting layer / carrier generation layer / first hole transport layer / second light-emitting layer / first electron transport layer / second electron transport layer / cathode / capping layer.

[0078] (8) Anode / hole injection layer / second hole transport layer / first hole transport layer / first light-emitting layer / carrier generation layer / first hole transport layer / second light-emitting layer / first electron transport layer / cathode / capping layer.

[0079] (9) Anode / hole injection layer / second hole transport layer / first hole transport layer / first light-emitting layer / carrier generation layer / first hole transport layer / second light-emitting layer / first electron transport layer / second electron transport layer / cathode / capping layer.

[0080] (10) Anode / hole injection layer / hole transport layer / electron blocking layer / light emitting layer / electron transport layer / electron injection layer / cathode / capping layer.

[0081] (11) Anode / hole injection layer / first hole transport layer / second hole transport layer / light-emitting layer / hole blocking layer / electron transport layer / cathode / capping layer.

[0082] (12) Anode / hole injection layer / hole transport layer / electron blocking layer / light emission layer / electron transport layer / cathode / capping layer.

[0083] (13) Anode / hole injection layer / hole transport layer / electron blocking layer / light emitting layer / hole blocking layer / electron transport layer / cathode / capping layer.

[0084] (14) Anode / hole injection layer / hole transport layer / light emission layer / electron transport layer / electron injection layer / cathode / capping layer.

[0085] The following will describe some of the specific functional layers in the organic light-emitting device.

[0086] Substrate:

[0087] The substrate is generally located below the anode. The substrate can be made of plastic or glass, and can be rigid or flexible. The substrate has a driving unit that can drive the corresponding pixel to emit light.

[0088] anode:

[0089] Anodes typically need to meet requirements such as good conductivity, smooth surface, and resistance to cracking. They also have certain requirements for work function, mainly to match the hole injection layer and achieve the hole injection effect.

[0090] When using a top-emitting method (cathode-side light emission), the anode is a metal compound with a work function of 4.2 eV or higher, such as indium tin oxide, tin oxide, indium zinc oxide, gold, silver, platinum, copper, carbon nanotubes, carbon nanowires, graphene, etc. The thickness is 10 nm to 200 nm, preferably 10 nm to 50 nm. A reflective electrode is placed below the anode (near the substrate end). The reflective electrode is generally made of metal or metal alloy, such as silver, copper, aluminum, gold, or alloys of these metals with other metals. The reflective electrode has high reflectivity, requiring a reflectivity of over 90%, and its thickness is typically between 100 nm and 500 nm, preferably in the range of 80 nm to 150 nm.

[0091] The anode can be made by forming a thin film from the electrode material using methods such as vapor deposition, sputtering, or coating.

[0092] Hole injection layer:

[0093] The thickness of the hole injection layer is typically 3 nm to 20 nm. The hole injection layer uses a mixture of P-type and hole transport materials. The purpose of using P-type materials is to accept holes from the anode and transfer them to the hole transport material. The weight percentage of P-type materials in the hole injection layer is typically 0.5% to 10%. When the weight percentage is 0.5% to 3%, the absolute value of the difference between the lowest unoccupied molecular orbital (LUMO) energy level of the P-type material and the highest occupied molecular orbital (HOMO) energy level of the HTL material must not exceed 0.3 eV. When the weight percentage is 3% to 5%, the absolute value of the difference between the lowest unoccupied molecular orbital (LUMO) energy level of the P-type material and the highest occupied molecular orbital (HOMO) energy level of the HTL material must not exceed 0.5 eV. When the weight percentage is 5% to 10%, the absolute value of the difference between the lowest unoccupied molecular orbital (LUMO) energy level of the P-type material and the highest occupied molecular orbital (HOMO) energy level of the HTL material must not exceed 1 eV.

[0094] P-type materials can be metal oxides, such as molybdenum oxide, vanadium oxide, and tungsten oxide; they can also be organic compounds, such as 4,4',4”-((1E,1'E,1”E)-cyclopropane-1,2,3-trimethylenetris(cyanoformyl))tris(2,3,5,6-tetrafluorobenzyl) (PD1, CAS No.: 1224447-88-4), tetracyanoquinone dimethyl (TCNQ), 2,3,5,6-tetrafluoro-tetracyano-1,4-benzoquinone dimethyl (F4-TCNQ), 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (HAT-CN), and are not limited to these. The hole transport material paired with the P-type material can be selected from the material of the second hole transport layer, and can be the same as or different from the material of the second hole transport layer.

[0095] Second hole transport layer:

[0096] The thickness of the second hole transport layer is typically 40 nm to 150 nm, and it often uses aromatic amine compounds, such as monoaryl amines or polyaryl amines. Hole transport materials are required to have high hole mobility, reduce driving voltage, and have a glass transition temperature exceeding 100°C to avoid crystallization at high temperatures.

[0097] First hole transport layer:

[0098] The thickness of the first hole transport layer is typically 3 nm to 150 nm. When there is no second hole transport layer, the thickness of the first hole transport layer is typically 40 nm to 150 nm; when there is a second hole transport layer, the thickness of the first hole transport layer is typically 3 nm to 40 nm.

[0099] Electron blocking layer:

[0100] The electron blocking layer can simultaneously possess both hole transport and electron blocking functions. Furthermore, the higher triplet excitation energy level of the electron blocking layer can confine excitons generated in the emissive layer within it, thereby improving the device's luminous efficiency.

[0101] Emissive layer:

[0102] The material of the light-emitting layer generally includes a host material and a guest dopant material, wherein the content of the host material is greater than that of the guest dopant material. Optionally, the mass percentage of the guest dopant material in the light-emitting layer is 1% to 20%.

[0103] Guest dopants used as luminescent materials can include phosphorescent or fluorescent materials or thermally activated delayed fluorescence materials. Red, green, and blue light can be selected from these three types of guest dopants. For example, the guest dopant material for the luminescent layer corresponding to a red luminescent unit and the luminescent layer corresponding to a green luminescent unit is a phosphorescent material, while the guest dopant material for the luminescent layer corresponding to a blue luminescent unit is a fluorescent material.

[0104] For example, the guest doping material of the light-emitting layer corresponding to the light-emitting unit with a red emission color and the light-emitting layer corresponding to the light-emitting unit with a green emission color is a phosphorescent material, and the guest doping material of the light-emitting layer corresponding to the light-emitting unit with a blue emission color is a phosphorescent material.

[0105] For example, the guest doping material of the light-emitting layer corresponding to the light-emitting unit with a red emission color and the light-emitting layer corresponding to the light-emitting unit with a green emission color is a thermally activated delayed fluorescence material, and the guest doping material of the light-emitting layer corresponding to the light-emitting unit with a blue emission color is a fluorescent material.

[0106] For example, the guest doping material of the light-emitting layer corresponding to the light-emitting unit with a red emission color and the light-emitting layer corresponding to the light-emitting unit with a green emission color is a thermally activated delayed fluorescence material, and the guest doping material of the light-emitting layer corresponding to the light-emitting unit with a blue emission color is a phosphorescent material.

[0107] To reduce the power consumption of organic light-emitting display panels in organic electroluminescent devices, guest doping materials with superior luminescent properties can be selected. Optionally, the light-emitting unit with a red emission color has a luminous intensity of 1000 cd / m². 2 A green light-emitting unit with a current efficiency greater than 35 cd / A and a luminous intensity of 6000 cd / m² is used. 2 A blue light-emitting unit with a current efficiency greater than 100 cd / A and a luminous intensity of 1000 cd / m² 2 Using an external quantum efficiency greater than 8% as a standard, suitable guest doping materials are selected.

[0108] As the main light-emitting material, one or two main light-emitting materials can be selected.

[0109] Cavity blocking layer:

[0110] To enhance the balance between hole and electron concentrations, a hole blocking layer is inserted to balance carrier concentration and prevent exciton quenching. Typically, the hole blocking layer is located between the emitting layer and the electron transport layer, and the hole blocking layer material must meet conditions such as high stability, good film-forming properties, and a sufficiently high highest molecular occupied orbital.

[0111] First electron transport layer:

[0112] The thickness of the first electron transport layer can typically be 3nm–40nm, 3nm–10nm, 10nm–20nm, 20nm–30nm, 30nm–40nm, or 20nm–40nm. When there is no second electron transport layer, the thickness of the first electron transport layer is typically 20nm–40nm; when there is a second electron transport layer, the thickness of the first electron transport layer is typically 30nm–20nm. The first electron transport layer is in direct contact with the emitting layer, and therefore, similar to the first hole transport layer, it also undergoes electronic changes during electron transport, leading to increased molecular vibration and deformation. Furthermore, the interaction between the excitons of the emitting layer and the polarons of the electron transport material can easily generate reactive free radicals, which can damage the electron transport material. Electron transport materials can be single compounds or mixtures with other metal compounds, such as Liq.

[0113] Second electron transport layer:

[0114] The thickness of the second electron transport layer is generally 10 nm to 40 nm. The material of the second electron transport layer may include a mixture of organic electron transport materials and metal compounds, or a mixture of organic electron transport materials and metals.

[0115] When organic electron transport materials are mixed with metal compound materials, such as alkali metal compounds, alkaline earth metal compounds, and rare earth metal compounds, more specifically, they can be mixed with lithium metal compounds, calcium metal compounds, Mg metal compounds, samarium metal compounds, ytterbium metal compounds, etc., and even more specifically, they can be mixed with lithium 8-hydroxyquinoline, lithium fluoride, magnesium fluoride, ytterbium fluoride, calcium fluoride, etc. When used in combination with metal compounds, the mass percentage of the organic electron transport material can be 20%–80%, 20%–40%, 40%–60%, or 60%–80%, etc.

[0116] When organic electron transport materials are used in combination with metals, such as alkali metals, alkaline earth metals, and rare earth metals, or more specifically, with lithium metal, magnesium metal, calcium metal, ytterbium metal, and samarium metal, the mass ratio of the organic electron transport material can be 80%–99%, 80%–89%, 89%–99%, 80%–85%, 85%–90%, 90%–95%, or 95%–99%, etc.

[0117] Charge generation layer:

[0118] When a single-layer light-emitting device is used, holes and electrons are injected from the anode and cathode respectively, eliminating the need for a charge generation layer. When using double or multiple light-emitting layers, a charge generation layer is required between the light-emitting layers to achieve charge generation, injection, and transport. This charge generation layer is located between the two light-emitting layers and is typically composed of two P / N type materials. The P-type material is selected from the hole injection materials mentioned earlier, while the N-type material is a mixture of organic electron transport materials and metals. The organic electron transport layer material is selected from the second electron transport layer mentioned earlier, and the metal is selected from alkali metals, alkaline earth metals, and rare earth metals. More specifically, examples include lithium, magnesium, calcium, ytterbium, and samarium. When organic electron transport materials are mixed with metals, the mass percentage of the organic electron transport material can be 80%–99%, 80%–89%, 89%–99%, 80%–85%, 85%–90%, 90%–95%, or 95%–99%, etc.

[0119] cathode:

[0120] The cathode requires materials with good electrical conductivity and a smooth surface. To improve electron injection capability, materials with a low work function are typically chosen. Cathode materials can be single-layer, double-layer, or multi-layer cathodes, generally made of metals or metal alloys. For single-layer cathodes, silver, copper, aluminum, gold, or alloys of these metals with other metals, such as rare earth metals, alkali metals, and alkaline earth metals, can be used. Examples include magnesium-indium alloys, magnesium-aluminum alloys, aluminum-potassium alloys, aluminum-scandium-potassium alloys, magnesium-silver alloys, silver-ytterbium alloys, and silver-samarium alloys. If a double-layer metal cathode is used, the cathode layer closer to the light-emitting layer can be made of alkali metals, alkaline earth metals, or rare earth metals, such as lithium, calcium, magnesium, and ytterbium, to increase electron injection capability. The cathode layer farther from the light-emitting side is mainly used to improve conductivity, and generally uses silver, copper, aluminum, gold, or alloys of these metals with other metals, such as alloys with rare earth metals, alkali metals, or alkaline earth metals. Examples include magnesium-indium alloys, magnesium-aluminum alloys, aluminum-potassium alloys, aluminum-scandium-potassium alloys, magnesium-silver alloys, silver-ytterbium alloys, and silver-samarium alloys. The cathode can also be formed into a thin film using methods such as vapor deposition or sputtering.

[0121] When light comes out from the anode side, the cathode must be opaque, and a cathode with a thickness greater than 100 nm can be deposited. When light comes out from the cathode side, the cathode must be transparent, with a transmittance greater than 40% and a thickness of 10 nm to 20 nm.

[0122] Overlay:

[0123] The capping layer is formed after the semi-transparent cathode of the OLED display panel is away from the substrate, enabling the stack formed by the capping layer and the semi-transparent cathode to have a light transmittance of ≥65% in the 450nm-650nm range, such as 68%, 69%, 73%, 77%, 79%, 83%, 88%, 93%, etc. A suitable capping layer material can improve the luminous efficiency of the device, while also achieving a more balanced light extraction efficiency and viewing angle for red, green, and blue light.

[0124] In some preferred embodiments, two cover layers are used, and the total thickness can be 50nm to 90nm, for example: 50nm, 55nm, 57nm, 59nm, 62nm, 64nm, 67nm, 68nm, 70nm, 75nm, 77nm, 79nm, 80nm, 82nm, 85nm, 88nm, 90nm, etc.

[0125] In some preferred embodiments, the capping layer near the cathode side is a low-refractive-index capping layer, and the thickness can be 5nm to 40nm, for example: 5nm, 7nm, 10nm, 12nm, 15nm, 18nm, 20nm, 22nm, 25nm, 27nm, 30nm, 32nm, 34nm, 36nm, 38nm, 40nm, etc.

[0126] In some preferred embodiments, the capping layer away from the cathode side is a high-refractive-index capping layer, and the thickness can be 35nm to 85nm, for example: 35nm, 40nm, 43nm, 45nm, 48nm, 50nm, 55nm, 57nm, 59nm, 62nm, 64nm, 67nm, 68nm, 70nm, 75nm, 77nm, 79nm, 80nm, 82nm, 85nm, etc.

[0127] The technical solution of this application will be clearly and completely described below with reference to the embodiments of this application. Unless otherwise specified, the reagents and raw materials used can be purchased commercially. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards. If there is no corresponding national standard, then general international standards, conventional methods and conditions, or conditions recommended by the manufacturer, or the product instructions shall be followed.

[0128] The initial raw materials and solvents in the following examples were purchased from Sinopharm, and some commonly used OLED intermediates were purchased from domestic OLED intermediate manufacturers; HPLC data were determined using a Shimadzu LC 20AD high-performance liquid chromatograph; LC-MS (liquid chromatography-mass spectrometry) was performed on a Waters Corporation H-class+SQD2 instrument.

[0129] Compound preparation examples

[0130] Example 1

[0131] Preparation of Compound 1

[0132]

[0133] 21.8 g (100 mmol) of pyromellitic dianhydride 1-A and acetic acid (AcOH, 250 mL) were placed in a reaction flask and cooled to 5 °C in an ice bath. Compound 1-B (50.38 g, 220 mmol) was slowly added. After the addition was complete, the mixture was heated to 130 °C and reacted for 4 hours. The reaction mixture was then slowly poured into 250 mL of water, resulting in the precipitation of a large amount of solid. The mixture was filtered, and the filter cake was washed with water. The solid was recrystallized from ethanol, filtered, and dried to give 58.2 g of a white solid product, yield 91%, HPLC purity: 99.9%, and the product was confirmed as the target product. LC MS: M / Z 640.03 (M+).

[0134] Examples 2 to 24

[0135] Compounds 2-20 and compounds 22-25, as shown in the table below, were prepared according to the preparation method in Example 1.

[0136] Table 1 Reactants and Products

[0137]

[0138]

[0139]

[0140] 90° peel performance test

[0141] The coating is performed according to the following structure: ITO substrate (40mm*40mm) / Ag (200nm) / compound film (1200nm). The material of the compound film is selected from compounds 1 to 20, compounds 22 to 25, CPL-1, and CPL-3 of this application. For the molecular structures of CPL-1 and CPL-3, please refer to the device fabrication example.

[0142] One side of the test tape (model: 3M681) was adhered to the coating layer and rolled evenly 10 times with a roller. The other side of the tape was then clamped with a fixture, and the test was conducted at a speed of 200 mm / min. After the measurement began, the first 5 mm length of measurement was ignored. Then, a 2 mm length was peeled off from the ITO substrate, and three parallel tests were performed. The average value of the adhesive force measurement was taken and set as the peel adhesion value. The test results are shown in Table 2.

[0143] Table 2. Peeling performance test results

[0144]

[0145]

[0146] As shown in Table 2, compared with compounds CPL-1 and CPL-3, the peel adhesion between compounds 1-20 and compounds 22-25 of this application and the cathode Ag has been significantly improved. Therefore, the capping layer prepared using compounds 1-20 and compounds 22-25 of this application is not prone to interlayer peeling with the cathode Ag.

[0147] Tg test

[0148] The samples of compounds 1-20, compounds 22-25, CPL-1, and CPL-3 of this application were tested using a differential scanning calorimeter (DSC25, TA Instruments, USA) to determine their glass transition temperatures (Tg). The test results are shown in Table 3.

[0149] Table 3 Tg Test Results

[0150]

[0151]

[0152] As shown in Table 3, compared with compounds CPL-1 and CPL-3, compounds 1-20 and 22-25 of this application have higher Tg. When these compounds 1-20 and 22-25 are used to prepare organic light-emitting devices, the device lifespan can be improved.

[0153] Device fabrication examples

[0154] Example 25

[0155] refer to Figure 1 The method for preparing an organic light-emitting device in this embodiment includes the following steps:

[0156] (1) After ultrasonically washing the alkali-free glass 1 in isopropanol for 15 minutes, it is treated with ultraviolet ozone in the atmosphere for 30 minutes. Then, a 100nm silver (Ag) film and a 10nm ITO film (not distinguished in the figure) are formed on the alkali-free glass 1 by means of the photometric method to form the reflective anode 2.

[0157] (2) The reflective anode 2 is subjected to ultraviolet ozone washing treatment for 10 minutes. The hole injection layer 3 (NPD and F4-TCNQ with a weight ratio of 97:3, 50nm), hole transport layer 4 (NPD, 80nm), blue light emitting layer 5 (BH and BD with a weight ratio of 97:3, 20nm), electron transport layer 6 (Alq3, 35nm), and electron injection layer 7 (LiF, 1nm) are sequentially deposited on the reflective anode 2. Then, Mg and Ag (weight ratio of 10:1, 15nm) are co-deposited as a semi-transparent cathode 8.

[0158] (3) On the semi-transparent cathode 8, the compound 1 prepared in Example 1 is vapor-deposited to form a low refractive index capping layer 91 with a film thickness of 10 nm, and the compound CPL-2 is vapor-deposited on the low refractive index capping layer 91 to form a high refractive index capping layer 92 with a thickness of 50 nm.

[0159] (4) An organic light-emitting device is prepared by packaging an alkali-free glass sealing plate with epoxy resin adhesive in a glove box under a dry nitrogen atmosphere.

[0160] Examples 26-48

[0161] Except that when forming the low refractive index capping layer 91, compounds 2-20 and 22-25 prepared in the aforementioned examples were used to replace compound 1, the organic light-emitting device was prepared using the same method as in Example 25.

[0162] Comparative Example 1

[0163] The only difference from Example 25 is that the low refractive index capping layer 91 is not provided.

[0164] Comparative Example 2

[0165] The only difference from Example 25 is that the high refractive index capping layer 92 is not provided.

[0166] Comparative Example 3

[0167] The only difference from Example 25 is that the material of the low refractive index capping layer 91 is compound CPL-1.

[0168] Comparative Example 4

[0169] The only difference from Example 25 is that the material of the low refractive index capping layer 91 is compound CPL-3.

[0170] The compounds involved in the above device fabrication examples are shown below:

[0171]

[0172] Device performance testing

[0173] The refractive index of the capping layer was measured using elliptic polarization spectroscopy (JAWoollam Co.Inc M-2000). A 10 mA / cm² load was applied to the organic light-emitting device prepared above at room temperature and pressure. 2 The luminance and color purity of the device were tested using a luminance meter (CS1000, Konica Minolta Corporation) with a spectral radiation sealing plate and a DC current. The luminous efficiency and color purity were obtained from the test results, as shown in Table 4.

[0174] Table 4. Results of luminous efficiency and color purity

[0175]

[0176]

[0177] In Table 4, n1 refers to the refractive index of the low-refractive-index capping layer for 460nm wavelength light, and n2 refers to the refractive index of the high-refractive-index capping layer for 460nm wavelength light. According to the results of Comparative Examples 1 and 2, the luminous efficiency of the device is low and the color purity is not high when using either a high-refractive-index capping layer or a low-refractive-index capping layer alone. According to the results of Examples 25-48 and Comparative Examples 3-4 of this application, although Comparative Examples 3 and 4 simultaneously used both high-refractive-index and low-refractive-index capping layers, which improved the luminous efficiency of the device, the color purity of the device was still not high. However, by keeping the material of the high-refractive-index capping layer unchanged and using the compound of this application to prepare the low-refractive-index capping layer, not only can the luminous efficiency of the device be improved, but the color purity is also enhanced.

[0178] In summary, the compounds of this application can be used to prepare a low-refractive-index capping layer, which exhibits strong adhesion to the cathode, is not prone to interlayer delamination, and possesses a high Tg. Furthermore, when used together with a high-refractive-index capping layer to form the capping layer structure of an organic light-emitting device, it can significantly improve the device's luminous efficiency and color purity.

[0179] The above description of the embodiments is intended to enable those skilled in the art to understand and apply this application. It will be apparent to those skilled in the art that various modifications can be easily made to these embodiments, and the general principles described herein can be applied to other embodiments without creative effort. Therefore, this application is not limited to the embodiments described herein, and any improvements and modifications made by those skilled in the art based on the disclosure of this application without departing from the scope and spirit of this application are within the scope of this application.

Claims

1. A low-refractive-index coating layer, characterized in that, Formed from compounds represented by Formula I and / or Formula II: In Formula I and Formula II, A is selected from substituted or unsubstituted C6-C30 aryl groups and substituted or unsubstituted C3-C30 heteroaryl groups; R is selected from hydrogen, deuterium, substituted or unsubstituted C1-C30 alkyl, substituted or unsubstituted C3-C30 cycloalkyl, substituted or unsubstituted C1-C30 heteroalkyl, substituted or unsubstituted C1-C30 heterocycloalkyl, substituted or unsubstituted C1-C10 fluoroalkyl, substituted or unsubstituted C1-C10 fluorocycloalkyl, substituted or unsubstituted C6-C30 aryl, substituted or unsubstituted C3-C30 heteroaryl; A1 and A2 may be the same or different, and are independently selected from pentagonal or hexaagonal rings; Ak1 and Ak2 may be the same or different, and are independently selected from substituted or unsubstituted C1-C30 alkyl, substituted or unsubstituted C1-C30 heteroalkyl, substituted or unsubstituted C3-C30 cycloalkyl, substituted or unsubstituted C2-C30 heterocycloalkyl, substituted or unsubstituted C1-C30 alkylamine, substituted or unsubstituted C1-C30 heteroalkylamine, substituted or unsubstituted C3-C30 cycloaminealkyl, substituted or unsubstituted C2-C30 heterocycloalkylamine, or formed a ring with adjacent atomic bonds; Ar1 and Ar2 may be the same or different, and are independently selected from substituted or unsubstituted C6-C24 aryl groups and substituted or unsubstituted C3-C24 heteroaryl groups.

2. The low refractive index capping layer according to claim 1, characterized in that, The compound represented by formula I is selected from: The compound represented by formula II is selected from: Furthermore, the definitions of A, R, Ak1, Ak2, Ar1, and Ar2 are the same as those in claim 1.

3. The low refractive index capping layer according to claim 2, characterized in that, When at least one of A, R, Ak1, Ak2, Ar1, and Ar2 is substituted, the substituents are independently selected from one or more combinations of fluorine atoms, trifluoromethyl, cyano, nitro, phosphoxy, sulfone, sulfoxide, aryl, azaaryl, dimethyl, tert-butyl, isopropyl, and carboxyl derivative groups.

4. The low refractive index capping layer according to claim 3, characterized in that, A is selected from the following groups, whether substituted or unsubstituted:

5. The low refractive index capping layer according to claim 3, characterized in that, Ar1 and Ar2 are independently selected from the following groups, whether substituted or unsubstituted: In this context, * represents a connection site.

6. The low refractive index capping layer according to claim 3, characterized in that, Ak1 and Ak2 are independently selected from methyl, ethyl, propyl, isopropyl, butyl, tert-butyl, sec-butyl, pentyl, isopentyl, hexyl, cyclohexyl, adamantyl, and the following substituted or unsubstituted groups: Wherein, * represents a linking site; (C)n represents an alkyl group having n carbon atoms, and n is selected from an integer from 1 to 6; Ar3 is selected from substituted or unsubstituted C6 to C12 aryl groups and substituted or unsubstituted C3 to C12 heteroaryl groups.

7. The low refractive index capping layer according to claim 3, characterized in that, The compound represented by formula I is selected from the following group: And Ar2 is selected from the following groups: Where * represents a connection site; The compounds represented by Formula II are selected from the following group: And Ak2 is selected from the following groups: adamantyl, The asterisk (*) represents a connection site.

8. The low refractive index capping layer according to claim 7, characterized in that, The compound represented by formula II is selected from the following group: The compound represented by formula I is selected from the following group:

9. A cover layer structure, characterized in that, include: The low refractive index capping layer according to any one of claims 1 to 8 and the high refractive index capping layer located on the low refractive index capping layer, wherein the high refractive index capping layer has a refractive index of 1.90 or higher for light with a wavelength of 460 nm.

10. The cover layer structure according to claim 9, characterized in that, The high refractive index capping layer is formed of at least one of an inorganic compound and an organic compound, wherein the inorganic compound includes at least one of SiOx, SiNy, ZnS, ZnSe, ZrO, and TiO2, and x and y are independently selected from integers from 1 to 4; the organic compound includes at least one of an aromatic amine derivative, a carbazole derivative, a benzimidazole derivative, and a triazole derivative; preferably, the organic compound includes at least one of the following compounds:

11. An organic light-emitting device, characterized in that, It includes a first electrode, an organic layer, a second electrode, and a low-refractive-index capping layer as described in any one of claims 1 to 8, or a capping layer structure as described in claim 9 or 10, stacked sequentially.

12. The organic light-emitting device according to claim 11, characterized in that, The organic layer includes at least one of a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, a hole blocking layer, an electron transport layer, and an electron injection layer. Preferably, the organic layer comprises a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, and an electron injection layer stacked sequentially.

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