Compound containing cyano-substituted azabenzene structure and organic electroluminescent device and display element using compound

Abstract

The invention discloses a compound containing a cyano-substituted aza-benzene structure and an organic electroluminescent device and a display element using the compound, and belongs to the technical field of semiconductor materials. The structure of the compound containing the cyano-substituted aza-benzene structure is shown in a general formula (1). A plurality of organic thin film layers are arranged between a first electrode and a second electrode of a # imgabs0 # organic light-emitting device, and at least one organic thin film layer is the compound containing the cyano-substituted aza-benzene structure. The display element contains the organic light-emitting device disclosed by the invention. The compound containing the cyano-substituted aza-benzene structure has the characteristics of relatively high glass transition temperature and molecular thermal stability, good electron mobility, relatively low evaporation temperature, proper HOMO / LUMO energy level and the like; and the driving voltage, the current efficiency and the service life of the device are remarkably improved.

Description

[0001] This divisional application of the present invention is based on the prior application with the application number: 2023104799101, the application date: April 28, 2023, and the invention title: An organic electroluminescent device and a display element comprising a compound with a cyanide-substituted azobenzene structure and its application. Technical Field

[0002] The present invention relates to the technical field of semiconductor materials, and in particular to an organic electroluminescent device and a display element comprising a compound with a cyanide-substituted azobenzene structure and its application. Background Art

[0003] The technology of organic electroluminescent devices (OLED: Organic Light Emission Diodes) can be used to manufacture new display products and new lighting products, and is expected to replace existing liquid crystal displays and fluorescent lamp lighting, with a very broad application prospect. An organic electroluminescent device has a sandwich-like structure, including electrode material layers and organic functional materials sandwiched between different electrode material layers. Various different organic functional materials are stacked together according to their uses to jointly form an organic electroluminescent device. As a current device, when a voltage is applied to the two electrodes of an organic electroluminescent device and positive and negative charges are acted on by an electric field in the organic layer functional material layer, the positive and negative charges further recombine in the light-emitting layer, thereby generating organic electroluminescence.

[0004] Currently, OLED display technology has been applied in the fields of smartphones, tablets, TVs, etc. However, compared with the actual product application requirements, the performance of organic electroluminescent devices, such as luminous efficiency and service life, still needs to be further improved. In order to continuously improve the performance of organic electroluminescent devices, it is necessary to continuously research and innovate organic optoelectronic functional materials to create higher-performance organic optoelectronic functional materials.

[0005] Organic optoelectronic functional materials applied to organic electroluminescent devices can be classified into two categories according to their uses, namely charge injection and transport materials and light-emitting materials. Further, the charge injection and transport materials can be further divided into electron injection and transport materials, electron blocking materials, hole injection and transport materials, and hole blocking materials. As charge transport materials, they are required to have good carrier mobility, high glass transition temperature, etc. For an organic electroluminescent device, electrons are injected from the cathode and then transferred to the host material through the electron transport layer, and recombine with holes in the host material to generate excitons. Therefore, improving the injection ability and transport ability of the electron transport layer is beneficial to reducing the device driving voltage and at the same time obtaining high-efficiency electron-hole recombination efficiency. Therefore, the electron transport layer is very important and requires high-efficiency electron injection ability, transport ability, and high electron durability.

[0006] For the device lifetime, the heat resistance of the material and the film stability are also important. Materials with low heat resistance are not only prone to decomposition during material evaporation, but also thermally decomposed by the heat generated by the device during device operation, leading to material degradation. When the phase state stability of the material film is poor, the material also crystallizes in a short time, resulting in direct layer separation of the organic film layer and device degradation. Therefore, the materials used are required to have high heat resistance and good film stability.

[0007] With the increasing demand for improving the performance of organic light-emitting devices, the requirements for material properties are also increasing. It is not only required to have good material stability, but also to achieve good efficiency and lifetime at low driving voltages. However, the current electron transport materials have insufficient heat and stability, and there are defects in the electron tolerance of the materials, resulting in phase separation or decomposition of the materials during device operation, and thus the device has a short lifetime. Summary of the Invention

[0008] In view of the above problems existing in the prior art, the present invention provides a compound containing a cyanide-substituted azobenzene structure, an organic light-emitting device and a display element using the same. The compound of the present invention is bridged by cyanide substitution with a specific structure, and the bridging structure is biphenyl or benzene, so that the compound has excellent electron injection and transport capabilities. When applied to an organic light-emitting device, it can effectively reduce the device operating voltage, improve the device luminous efficiency and operating lifetime.

[0009] A compound containing a cyanide-substituted azobenzene structure, the structure of the compound containing a cyanide-substituted azobenzene structure is shown in any one of Formulas (1-3) to (1-5):

[0010]

[0011] In Formulas (1-3) to (1-5), X 1 -X 6 each independently represents N or CH, wherein X 1 -X 3 at least one represents N, X 4 -X 6 at least one represents N;

[0012] The Ar 1 -Ar 4Respectively and independently represented as substituted or unsubstituted phenyl, substituted or unsubstituted biphenyl, substituted or unsubstituted naphthyl, substituted or unsubstituted terphenyl, substituted or unsubstituted anthryl, substituted or unsubstituted phenanthryl, substituted or unsubstituted pyridyl, substituted or unsubstituted pyrimidinyl, substituted or unsubstituted pyrazinyl, substituted or unsubstituted dibenzofuranyl, substituted or unsubstituted carbazolyl, substituted or unsubstituted N-phenylcarbazolyl, substituted or unsubstituted quinolinyl, substituted or unsubstituted isoquinolinyl;

[0013] The substituents of the substitutable groups are each independently selected from one or more of deuterium, tert-butyl, phenyl, biphenyl, naphthyl, terphenyl, anthryl, phenanthryl, pyridyl, carbazolyl, dibenzofuranyl.

[0014] Furthermore, the structure of the compound containing a cyano-substituted azobenzene structure is as shown in any one of general formulas (1-8) to (1-11):

[0015]

[0016]

[0017] In general formulas (1-8) to (1-11), Ar 1 -Ar 4 and X 1 -X 6 have the meanings defined in general formula (1).

[0018] Furthermore, the Ar 1 -Ar 4 is independently selected from any one of the following structures:

[0019]

[0020] Furthermore, X 1 , X 2 , X 3 , X 4 , X 5 , X 6 are each independently represented as N or CH, where at least two of X 1 -X 3 are represented as N, and at least two of X 4 -X 6 are represented as N.

[0021] Furthermore, X 1 , X 2 , X 3 are each independently represented as N, and X 4 , X 5 , X 6Each independently represents N or CH, X 4 -X 6 At least two represent N.

[0022] Furthermore, X 4 、X 5 、X 6 Each independently represents N, X 1 、X 2 、X 3 Each independently represents N or CH, X 1 -X 3 At least two represent N.

[0023] Furthermore, the specific structure of the compound containing a cyano-substituted azobenzene structure is any one of the following structures:

[0024]

[0025]

[0026]

[0027]

[0028]

[0029]

[0030]

[0031]

[0032] The present invention also discloses an organic electroluminescent device, comprising a first electrode and a second electrode, wherein there are multiple organic thin film layers between the first electrode and the second electrode of the organic electroluminescent device, and at least one organic thin film layer contains the compound containing a cyano-substituted azobenzene structure of the present invention.

[0033] Furthermore, the organic thin film layer includes an electron transport layer, and the electron transport layer contains the compound containing a cyano-substituted azobenzene structure of the present invention.

[0034] Furthermore, the organic thin film layer includes a hole transport region thin film layer, a light emitting region thin film layer, and an electron transport region thin film layer, and the electron transport region thin film layer contains the compound containing a cyano-substituted azobenzene structure of the present invention.

[0035] Furthermore, the electron transport region thin film layer includes an electron transport layer, and the electron transport layer contains the compound containing a cyano-substituted azobenzene structure of the present invention.

[0036] The present invention also discloses a display element, which comprises the organic electroluminescent device of the present invention.

[0037] Advantages of the present invention:

[0038] The compound of the present invention is based on an azaphenyl structure, and the azaphenyl structure group is connected by a specific cyano-substituted bridging group. Such compounds have good electron tolerance and stability, and have good electron injection and transport capabilities. Therefore, when used as an electron transport material for the OLED functional layer, it can effectively reduce the device driving voltage and improve the optoelectronic performance and device life of the OLED device.

[0039] Since the compound of the present invention contains a triazine or pyrimidine structure, it can further delocalize the LUMO electron cloud distribution of the material, improve the anti-electron characteristics of the material, and effectively improve the electron stability of the material. In addition, this parent nucleus can increase the weak interaction within the molecule, effectively reduce the evaporation temperature of the molecule, and improve the thermal durability of the material. Further, due to the ability of this parent nucleus to inhibit the π-π stacking between molecules, it significantly improves the electron mobility of the molecule and reduces the driving voltage of the device. And, due to the presence of the electron-withdrawing conjugation effect of this parent nucleus, it increases the glass transition temperature of the material and effectively improves the film stability of the material. Therefore, it can effectively reduce the device driving voltage, improve the device efficiency and working life.

[0040] In addition, under the action of an electric field or thermal energy, due to its strong electron-withdrawing conjugation effect, the compound of the present invention easily reduces and dissociates the lithium ions in the lithium complex, thereby improving the electron injection ability. Therefore, as an electron transport material, this type of compound has excellent electron transport ability and good electron injectability, and can effectively reduce the device driving voltage, improve the device efficiency and working life.

[0041] In summary, the compound of the present invention has characteristics such as a high glass transition temperature and molecular thermal stability, good electron mobility, a low evaporation temperature, and appropriate HOMO / LUMO energy levels. When the compound of the present invention is used as a material for an organic electroluminescent device, the driving voltage, current efficiency, and life of the device are significantly improved. Description of the Drawings

[0042] Figure 1 It is a schematic structural diagram of the OLED device described in the embodiment.

[0043] In the figure, 1, transparent substrate layer; 2, anode layer; 3, hole injection layer; 4, hole transport layer; 5, electron blocking layer; 6, light-emitting layer; 7, hole blocking layer; 8, electron transport layer; 9, electron injection layer; 10, cathode layer; 11, light extraction layer. Detailed Embodiments

[0044] The following provides a detailed description of the specific embodiments of the present invention. The present invention can be implemented in many other ways different from those described herein. Those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used are only for describing the specific embodiments and do not limit the present invention.

[0046] In the present application, unless otherwise specified, HOMO means the highest occupied molecular orbital of a molecule, and LUMO means the lowest unoccupied molecular orbital of a molecule. In addition, in the present invention, the HOMO and LUMO energy levels are represented by absolute values, and the comparison between the energy levels is also a comparison of the magnitudes of their absolute values. Those skilled in the art know that the greater the absolute value of the energy level, the lower the energy of that energy level.

[0047] In the append Figure 1 ices, for clarity, the dimensions of the layers and regions may be exaggerated. It will also be understood that when a layer or element is referred to as being "on" another layer or substrate, the layer or element may be directly on the other layer or substrate, or there may also be an intermediate layer. In addition, it will also be understood that when a layer is referred to as being "between" two layers, the layer may be the only layer between the two layers, or there may also be one or more intermediate layers. The same reference numerals throughout the text denote the same elements.

[0048] In the present application, when describing electrodes, organic electroluminescent devices, and other structures, the terms indicating directions such as "above" and "below" are only for indicating the directions in a certain specific state and do not mean that the relevant structures can only exist in the described directions; on the contrary, if the structure can be transformed in position, such as being inverted, the direction of the structure will be changed accordingly. Specifically, in the present invention, the "lower" side of the electrode refers to the side of the electrode close to the substrate during the preparation process, and the opposite side away from the substrate is the "upper" side.

[0049] Organic electroluminescent device:

[0050] In one embodiment of the present application, an organic electroluminescent device is provided, which includes a first electrode, a second electrode, and a multi-layer organic thin film layer located between the first electrode and the second electrode, wherein at least one organic thin film layer contains the compound having a cyanide-substituted azobenzene structure described in the present invention.

[0051] In a preferred embodiment of the present application, the organic thin film layer includes an electron transport layer, and the electron transport layer contains the compound with a cyano-substituted azobenzene structure described in the present invention. Preferably, in addition to the organic compound of the present invention, the electron transport layer further contains other electron transport materials, such as Liq (specific chemical structure can be seen in the examples).

[0052] In a preferred embodiment of the present invention, the organic electroluminescent device according to the present invention includes a substrate, a first electrode layer, an organic thin film layer, and a second electrode layer, wherein the organic thin film layer includes, but is not limited to: a light-emitting layer and a hole injection layer, a hole transport layer, an electron blocking layer, an electron transport layer, a hole blocking layer, and / or an electron injection layer.

[0053] The preferred device structure of the present invention adopts a top emitting form. Preferably, the anode layer of the organic electroluminescent device of the present invention uses an electrode with a high reflectivity, preferably ITO / Ag / ITO; the cathode layer uses a transparent electrode, preferably a mixed electrode of Mg:Ag = 1:9, so as to form a microcavity resonance effect, and the device emits light from the Mg:Ag electrode side.

[0054] In the following, Figure 1 the structure of the organic electroluminescent device in a specific embodiment of the present application will be described in detail.

[0055] As Figure 1 shown, according to a specific embodiment of the present application, the present invention provides an organic electroluminescent device, which sequentially includes a transparent substrate layer, an anode layer, a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer, a cathode layer, and a light extraction layer from bottom to top;

[0056] As the substrate of the organic electroluminescent device of the present invention, any substrate commonly used in organic electroluminescent devices can be used. Examples are transparent substrates, such as glass or transparent plastic substrates; opaque substrates, such as silicon substrates; flexible PI film substrates. Different substrates have different mechanical strengths, thermal stabilities, transparencies, surface smoothness, and water resistances. According to the properties of the substrate, their usage directions are different. In the present invention, a transparent substrate is preferably used. The thickness of the substrate is not particularly limited.

[0057] A first electrode is formed on the substrate, and the first electrode and the second electrode can be opposite to each other. The first electrode can be an anode or a cathode. The anode material is preferably a material with a high work function so that holes can be easily injected into the organic functional material layer. Non-limiting examples of the anode material include, but are not limited to, indium tin oxide (ITO), indium zinc oxide (IZO), tin oxide (SnO 2) Zinc oxide (ZnO), magnesium (Mg), aluminum (Al), silver (Ag), aluminum-lithium (Al-Li), calcium (Ca), magnesium-indium (Mg-In), and magnesium-silver (Mg-Ag). The first electrode may have a single-layer structure or a multi-layer structure including two or more layers. For example, the anode may have a three-layer structure of ITO / Ag / ITO, but is not limited thereto. Additionally, the thickness of the anode depends on the materials used and is typically 50 - 500 nm, preferably 70 - 300 nm, and more preferably 100 - 200 nm.

[0058] A hole injection layer, a hole transport layer, and an electron blocking layer may be provided between the first electrode and the light-emitting layer.

[0059] The structure of the hole injection layer is that the hole injection layer material is uniformly or non-uniformly dispersed in the hole transport layer. The hole injection material may be, for example, a P dopant. The P dopant may be selected from at least one compound selected from the following: quinone derivatives, metal oxides, or cyanide-containing compounds; the quinone derivative may be tetracyanoquinodimethane (TCNQ) or 2,3,5,6-tetrafluoro-tetracyano-1,4-benzoquinodimethane (F4-TCNQ); the metal oxide may be tungsten oxide or molybdenum oxide; the cyanide-containing compound may be the compounds P1, NDP, and F4-TCNQ shown below:

[0060]

[0061] In an embodiment of the present invention, P1 is preferably used as the P dopant. The mass ratio of the hole transport layer to the P dopant used in the present invention is 99:1 - 70:30, preferably 99:1 - 85:15, and more preferably 97:3 - 87:13.

[0062] The thickness of the hole injection layer of the present invention may be 1 - 100 nm, preferably 2 - 50 nm, and more preferably 5 - 20 nm.

[0063] The material of the hole transport layer is preferably a material with a high hole mobility, which enables holes to transfer from the anode or the hole injection layer to the light-emitting layer. The hole transport material can be phthalocyanine derivatives, triazole derivatives, triarylmethane derivatives, triarylamine derivatives, oxazole derivatives, oxadiazole derivatives, hydrazone derivatives, stilbene derivatives, pyridinoline derivatives, polysilane derivatives, imidazole derivatives, phenylenediamine derivatives, amino-substituted quinone derivatives, styryl anthracene derivatives, styrylamine derivatives and other styrene compounds, fluorene derivatives, spirofluorene derivatives, silazane derivatives, aniline copolymers, porphyrin compounds, carbazole derivatives, polyarylalkane derivatives, polyphenylene vinylene and its derivatives, polythiophene and its derivatives, poly-N-vinylcarbazole derivatives, thiophene oligomers and other conductive polymer oligomers, aromatic tertiary amine compounds, styrylamine compounds, triamines, tetraamines, benzidine compounds, propynediamine derivatives, p-phenylenediamine derivatives, m-phenylenediamine derivatives, 1,1'-bis(4-diarylaminophenyl)cyclohexane, 4,4'-bis(diarylamino)biphenyls, bis[4-(diarylamino)phenyl]methanes, 4,4''-bis(diarylamino)terphenyls, 4,4'''-bis(diarylamino)quaterphenyls, 4,4'-bis(diarylamino)diphenyl ethers, 4,4'-bis(diarylamino)diphenyl sulfides, bis[4-(diarylamino)phenyl]dimethylmethanes, bis[4-(diarylamino)phenyl]-bis(trifluoromethyl)methanes or 2,2-diphenylethylene compounds, etc.

[0064] The thickness of the hole transport layer of the present invention can be 5 - 200 nm, preferably 10 - 180 nm and more preferably 20 - 150 nm.

[0065] The electron blocking layer requires that the triplet (T1) energy level of the material is higher than the T1 energy level of the host material in the light-emitting layer, which can play a role in blocking the energy loss of the light-emitting layer material; the HOMO energy level of the electron blocking layer material is between the HOMO energy levels of the hole transport layer material and the host material of the light-emitting layer, which is conducive to the injection of holes from the positive electrode into the light-emitting layer. At the same time, it is required that the electron blocking layer material has a high hole mobility, which is conducive to hole transport and reduces the application power of the device; the LUMO energy level of the electron blocking layer material is higher than the LUMO energy level of the host material of the light-emitting layer, which plays a role in blocking electrons, that is, it is required that the electron blocking layer material has a wide bandgap (Eg). The electron blocking layer materials meeting the above conditions can be triarylamine derivatives, fluorene derivatives, spirofluorene derivatives, dibenzofuran derivatives, carbazole derivatives, etc. Among them, triarylamine derivatives are preferred, such as N4,N4-bis([1,1'-biphenyl]-4-yl)-N4'-phenyl-N4'-[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-fluoren-2-yl)-9,9'-spirobifluorene-2-amine; dibenzofuran derivatives, such as N,N-bis([1,1'-biphenyl]-4-yl)-3'-(dibenz[b,d]furan-4-yl)-[1,1'-biphenyl]-4-amine, but not limited thereto.

[0066] According to the present invention, the thickness of the electron blocking layer can be 1-200 nm, preferably 5-150 nm, and more preferably 5-100 nm.

[0067] According to the present invention, the light-emitting layer is located between the first electrode and the second electrode. The material of the light-emitting layer is a material that can emit visible light by respectively receiving holes from the hole transport region and electrons from the electron transport region and combining the received holes and electrons. The light-emitting layer may include a host material and a doping material. As the host material and the guest material of the light-emitting layer of the organic electroluminescent device of the present invention, among them, the host material can be one or a combination of two of anthracene derivatives, quinoxaline derivatives, triazine derivatives, xanthenone derivatives, benzophenone derivatives, carbazole derivatives, pyridine derivatives or pyrimidine derivatives. The guest material can be pyrene derivatives, boron derivatives, chrysene derivatives, spirofluorene derivatives, iridium complexes or platinum complexes.

[0068] 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.

[0069] The hole blocking layer can be disposed above the light-emitting layer. The triplet (T1) energy level of the hole blocking layer material is higher than that of the light-emitting layer host material, which can play a role in blocking the energy loss of the light-emitting layer material; the HOMO energy level of the material is lower than that of the light-emitting layer host material, playing a role in hole blocking. At the same time, it is required that the hole blocking layer material has a high electron mobility, which is conducive to electron transport and reduces the device application power; the hole blocking layer materials meeting the above conditions can be triazine derivatives, pyridine derivatives, etc. Among them, triazine derivatives are preferred; but not limited thereto.

[0070] The thickness of the hole blocking layer of the present invention can be 2-200 nm, preferably 5-150 nm, and more preferably 5-100 nm, but the thickness is not limited to this range.

[0071] The electron transport layer can be disposed above the hole blocking layer. The electron transport layer material is a material that can easily receive electrons from the cathode and transfer the received electrons to the light-emitting layer. The electron transport layer includes one or more compounds having a cyano-substituted pyridine structure described in the present invention. Preferably, the electron transport layer is composed of the compound having a cyano-substituted pyridine structure described in the present invention and other electron transport layer materials. More preferably, the other electron transport layer materials are commonly used electron transport materials in the art. Most preferably, the electron transport layer is composed of the compound having a cyano-substituted pyridine structure described in the present invention and Liq.

[0072] The thickness of the electron transport layer of the present invention can be 20-60 nm, preferably 30-50 nm, and more preferably 30-45 nm.

[0073] In the electron transport layer of the organic electroluminescent device according to the present invention, the ratio of the organic compound of the present invention to other electron transport layer materials is 1:9-9:1, preferably 2:8-8:2, more preferably 4:6-6:4, and most preferably 5:5.

[0074] As the electron transport compound of the present invention, one or more of the compounds having a cyano-substituted pyridine structure described in the present invention are preferably used.

[0075] In a preferred embodiment of the present invention, the electron injection layer material preferably has a material metal Yb with a low work function, so that electrons can be easily injected into the organic functional material layer. The thickness of the electron injection layer of the present invention can be 0.1-5 nm, preferably 0.5-3 nm, and more preferably 0.8-1.5 nm.

[0076] In one embodiment of the present invention, as described above, the second electrode can be a cathode or an anode. In the present invention, it is preferred to use the second electrode as the cathode. The material for forming the cathode can be a material with a low work function, such as a metal, an alloy, a conductive compound, or a mixture thereof. Non-limiting examples of the cathode material can include lithium (Li), ytterbium (Yb), magnesium (Mg), aluminum (Al), calcium (Ca), and aluminum-lithium (Al-Li), magnesium-indium (Mg-In), and magnesium-silver (Mg-Ag). The thickness of the cathode depends on the material used and is generally 5-100 nm, preferably 7-50 nm, and more preferably 10-25 nm.

[0077] Optionally, in order to improve the light extraction efficiency of the organic electroluminescent device, a light extraction layer (i.e., CPL layer) can also be added on top of the second electrode (i.e., the cathode) of the device. According to the principles of optical absorption and refraction, the refractive index of the CPL layer material should be as high as possible, and the light absorption coefficient should be as small as possible. Any material known in the art can be used as the CPL layer material, such as Alq3. The thickness of the CPL layer is generally 5-300 nm, preferably 20-100 nm, and more preferably 40-80 nm.

[0078] Optionally, the organic electroluminescent device may further include a packaging structure. The packaging structure can be a protective structure for preventing external substances such as moisture and oxygen from entering the organic layers of the organic electroluminescent device. The packaging structure can be, for example, a can, such as a glass can or a metal can; or a thin film covering the entire surface of the organic layer.

[0079] Method for preparing an organic electroluminescent device:

[0080] The present invention also relates to a method for preparing the above-mentioned organic electroluminescent device, which includes successively laminating a first electrode, a multi-layer organic thin film layer, and a second electrode on a substrate. Among them, the multi-layer organic thin film layer is formed by successively laminating a hole transport region, a light-emitting layer, and an electron transport region from bottom to top on the first electrode. The hole transport region is formed by successively laminating a hole injection layer, a hole transport layer, and an electron blocking layer from bottom to top on the first electrode. The electron transport region is formed by successively laminating a hole blocking layer, an electron transport layer, and an electron injection layer from bottom to top on the light-emitting layer. In addition, a CPL layer can also be laminated on the second electrode to improve the light extraction efficiency of the organic electroluminescent device.

[0081] Regarding lamination, methods such as vacuum deposition, vacuum evaporation, spin coating, casting, LB method, inkjet printing, laser printing, or LITI can be used, but are not limited thereto. Among them, vacuum evaporation means heating the material and depositing it on the substrate in a vacuum environment.

[0082] In the present invention, the vacuum evaporation method is preferably used to form each of the layers, where vacuum evaporation can be carried out at a temperature of about 100 - 500 °C, at a vacuum degree of about 10 -8 -10 -2 Torr and at a rate of about . The vacuum degree is preferably 10 -6 -10 -2 Torr, more preferably 10 -5 -10 -3 Torr.

[0083] The rate is about , more preferably about

[0084] In addition, it should be noted that the materials for forming each layer in the present invention can be formed into a film alone and used as a single layer, or can be formed into a film after being mixed with other materials and used as a single layer, and can also be a stacked structure between layers formed into a film alone, a stacked structure between layers formed into a film after being mixed, or a stacked structure of a layer formed into a film alone and a layer formed into a film after being mixed.

[0085] Display device:

[0086] The present invention also relates to a display device including the above-mentioned organic electroluminescent device, particularly a flat panel display device. In a preferred embodiment, the display device may include one or more of the above-mentioned organic electroluminescent devices, and in the case of including a plurality of devices, the devices are stacked horizontally or vertically. The display device may also include at least one thin film transistor. The thin film transistor may include a gate electrode, a source electrode, a drain electrode, a gate insulating layer, and an active layer, where one of the source electrode and the drain electrode may be electrically connected to the first electrode of the organic electroluminescent device. The active layer may include crystalline silicon, amorphous silicon, an organic semiconductor, or an oxide semiconductor, but is not limited thereto.

[0087] Exemplary embodiments have been disclosed herein. Although specific terms are used therein, these terms are used only and are to be construed only as having a general and descriptive meaning and not for the purpose of limitation. In some cases, as will be apparent to those of ordinary skill in the art upon the filing of the present application, unless specifically stated, the features, characteristics, and / or elements described in connection with a particular embodiment may be used alone or in combination with the features, characteristics, and / or elements described in connection with other embodiments. Accordingly, those skilled in the art will understand that various changes may be made in form and detail without departing from the spirit and scope of the present invention.

[0088] The following examples are intended to better explain the present invention, but the scope of the present invention is not limited thereto.

[0089] Examples

[0090] I. Preparation Examples of Compounds

[0091] The raw materials involved in the synthesis examples of the present invention can all be purchased from the market or prepared by conventional preparation methods in the art;

[0092] Preparation of Intermediate C1:

[0093]

[0094] Under nitrogen protection, in a round-bottom flask, successively add raw material A1 (10.75 g, 30 mmol), raw material B1 (9.52 g, 30 mmol), K 2 CO 3 (13.82 g, 100 mmol), tetrahydrofuran (180 mL), water (60 mL), purge with nitrogen for 50 min to displace air, add Pd(PPh 3 ) 4 (0.69 g, 0.6 mmol), and heat under reflux for 15 h under nitrogen protection. Take the reaction solution for TLC detection and find that raw material A1 has completely reacted. After the reaction is completed, naturally cool the reaction system to room temperature, rotary evaporate to remove the solvent, dissolve the residue in 150 ml of dichloromethane, wash with 120 ml of water, pour it into a separatory funnel, shake and then let it stand for layering. After liquid separation, extract the aqueous phase with dichloromethane (60 ml * 3). Combine the organic phases, add anhydrous magnesium sulfate for drying, filter, and rotary evaporate the filtrate to remove dichloromethane to obtain the crude product. The crude product is purified by a silica gel chromatography column to obtain Intermediate C1.

[0095] Other Intermediates C are prepared by the same synthesis method as Intermediate C1, with the difference being the raw materials. The raw materials A and B used are shown in Table 1;

[0096] Table 2

[0097]

[0098]

[0099] Preparation of Intermediate F1:

[0100]

[0101] Under nitrogen protection, in a round-bottom flask, successively add raw material D1 (6.34 g, 15 mmol), raw material E1 (4.58 g, 20 mmol), K 2 CO 3 (6.91 g, 50 mmol), tetrahydrofuran (150 mL), water (50 mL), purge with nitrogen for 35 min to displace air, add Pd(PPh 3 )4 (0.35 g, 0.3 mmol) was heated under reflux for 18 h under nitrogen protection. The reaction solution was taken for TLC detection and it was found that the raw material D1 had completely reacted. After the reaction was completed, the reaction system was naturally cooled to room temperature, and the solvent was removed by rotary evaporation. The residue was dissolved in 150 ml of dichloromethane, washed with 100 ml of water, poured into a separatory funnel, shaken and then allowed to stand for liquid separation. After liquid separation, the aqueous phase was extracted with dichloromethane (50 ml × 3). The combined organic phases were dried over anhydrous magnesium sulfate, filtered, and the filtrate was concentrated by rotary evaporation to remove dichloromethane to obtain a crude product. The crude product was purified by silica gel column chromatography to obtain intermediate F1.

[0102] Other intermediates F were prepared by the same synthetic method as intermediate F1, except that different raw materials were used. The raw materials D or intermediate C and raw material E used are shown in Table 2;

[0103] Table 2

[0104]

[0105]

[0106] Example 1: Synthesis of Compound 1

[0107]

[0108] Under nitrogen protection, in a round-bottom flask, intermediate F1 (4.45 g, 10 mmol), raw material G1 (4.31 g, 12 mmol), K 2 CO 3 (4.15 g, 30 mmol), tetrahydrofuran (50 mL), water (30 mL) were added in sequence. The air was displaced by passing nitrogen for 40 min. Palladium acetate (0.0225 g, 0.10 mmol) and 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl (0.0954 g, 0.20 mmol) were added. The mixture was heated under reflux for 26 h under nitrogen protection. The reaction solution was taken for TLC detection and it was found that intermediate F1 had completely reacted. After the reaction was completed, the reaction system was naturally cooled to room temperature, and the solvent was removed by rotary evaporation. The residue was dissolved in 180 ml of dichloromethane, washed with 120 ml of water, poured into a separatory funnel, shaken and then allowed to stand for liquid separation. After liquid separation, the aqueous phase was extracted with dichloromethane (80 ml × 3). The combined organic phases were dried over anhydrous magnesium sulfate, filtered, and the filtrate was concentrated by rotary evaporation to remove dichloromethane to obtain a crude product. The crude product was purified by silica gel column chromatography to obtain Compound 1.

[0109] Other compounds were prepared by the same synthetic method as Compound 1, except that different raw materials or intermediates were used. The raw materials or intermediates used are shown in Table 3;

[0110] Table 3

[0111]

[0112]

[0113]

[0114] II. Device Fabrication Examples

[0115] The application effects of the compounds containing a cyano-substituted azobenzene structure according to the present invention as an electron transport material in a device are described in detail below through Device Examples 1-4, 7-9, 11-13, 16-18 and Device Comparative Examples 1-11. Compared with Device Comparative Examples 1-11, the fabrication processes of the devices in Device Examples 1-4, 7-9, 11-13, 16-18 are exactly the same, and the same substrate material and electrode material are used, and the film thickness of the electrode material is also kept consistent. The difference is that the electron transport layer material in the device is changed. The device layer structure is shown in Table 4, and the performance test results of each device are shown in Table 5.

[0116] The molecular structural formulas of the related materials are as follows:

[0117]

[0118]

[0119] The structures of the comparative compounds ET-1, ET-2, ET-3, ET-4, ET-5, ET-6, ET-7, ET-8, ET-9, ET-10, ET-11 are shown above. All of the above materials are commercially available.

[0120] Device Example 1

[0121] The specific preparation process is as follows:

[0122] As Figure 1As shown, the transparent substrate layer 1 is transparent glass, and Ag (100 nm) is evaporated as the anode layer 2. On the anode layer 2, using a vacuum evaporation device, HT-1 and P-1 with a film thickness of 10 nm are evaporated as the hole injection layer 3, and the mass ratio of HT-1 to P-1 is 97:3. Then, HT-1 with a thickness of 130 nm is evaporated as the hole transport layer 4. Subsequently, EB-1 with a thickness of 5 nm is evaporated as the electron blocking layer 5. After the evaporation of the above electron blocking material is completed, the light-emitting layer 6 of the OLED light-emitting device is fabricated. Its structure includes BH-1 used as the host material and BD-1 used as the doping material in the OLED light-emitting layer 6, and the doping ratio of the doping material is 3% by weight, and the film thickness of the light-emitting layer is 20 nm. After the above light-emitting layer 6, HB-1 is continuously evaporated with a film thickness of 5 nm as the hole blocking layer 7. On the above hole blocking layer 7, ET-1 and Liq are continuously evaporated, and the mass ratio of ET-1 to Liq is 1:1. The vacuum evaporation film thickness of this material is 30 nm, and this layer is the electron transport layer 8. On the electron transport layer 8, a LiF layer with a film thickness of 1 nm is fabricated through a vacuum evaporation device, and this layer is the electron injection layer 9. On the electron injection layer 9, a Mg:Ag electrode layer with a film thickness of 16 nm is fabricated through a vacuum evaporation device, and the mass ratio of Mg to Ag is 1:9, and this layer is used as the cathode layer 10. On the cathode layer 10, 65 nm of CP-1 is vacuum-evaporated as the light extraction layer 11.

[0123] Device Examples 1-4, 7-9, 11-13, 16-18 and Device Comparative Examples 1-11 were prepared in a method similar to that of Device Example 1, and transparent glass was used for all substrates and Ag (100 nm) was used for all anodes, except that the parameters in Table 4 below were used.

[0124] Table 4

[0125]

[0126]

[0127]

[0128]

[0129] III. Device Test Examples

[0130] The devices prepared in II were tested for their driving voltage, current efficiency and LT95 lifetime. The voltage and current efficiency were tested using an IVL (current-voltage-brightness) test system (Suzhou Fushida Scientific Instruments Co., Ltd.), and the current density during the test was 10 mA / cm 2 . LT95 refers to the time when the device brightness decays to 95% of the initial brightness, and the current density during the test was 30 mA / cm2 ; The life test system is the EAS-62C type OLED device life tester from Nippon System Giken Co., Ltd.; the high-temperature life test temperature is 85°C, LT95 refers to the time taken for the device brightness to decay to 95% at a specific brightness, and the current density during the test is 20 mA / cm 2 .

[0131] The test results are shown in Table 5 below.

[0132] Table 5

[0133]

[0134]

[0135] It can be seen from the device test data results in Table 5 above that compared with the comparative devices using ET-1, ET-2, ET-3, ET-4, ET-5, ET-6, ET-7, ET-8, ET-9, ET-10, and ET-11 as the electron transport layer materials, the driving voltage of the device prepared using the compound of the present invention as the electron transport layer material is significantly reduced, while at the same time the current efficiency is improved, and the device life is extended. For example, its high-temperature life is basically more than 1.23 times that of the device comparative examples 1-11.

[0136] The structural formulas of the comparative compounds ET-1, ET-2, ET-3, ET-4, ET-5, ET-6, ET-7, ET-8, ET-9, ET-10, and ET-11 used in the comparative examples are similar to those of the present invention, with only slight differences, such as only the connection mode of the bridging group and the difference in the specific structure of the bridging group. However, unexpectedly, the compound of the present invention has achieved better technical effects than the comparative compounds as an electron transport material.

[0137] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, all possible combinations of the technical features in the above embodiments are not exhaustively listed. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0138] For those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. The protection scope of the present invention is subject to the appended claims.

Claims

1. A compound containing a cyano-substituted azobenzene structure, characterized in that, the structure of the compound containing a cyano-substituted azobenzene structure is shown as any one of general formula (1-3) to general formula (1-5): In General Formulas (1-3) to (1-5), X 1 -X 6 each independently represents N or CH, where X 1 -X 3 at least one represents N, X 4 -X 6 at least one represents N; The Ar 1 -Ar 4 are each independently represented by a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted naphthyl group, a substituted or unsubstituted terphenyl group, a substituted or unsubstituted anthryl group, a substituted or unsubstituted phenanthryl group, a substituted or unsubstituted pyridyl group, a substituted or unsubstituted pyrimidinyl group, a substituted or unsubstituted pyrazinyl group, a substituted or unsubstituted dibenzofuranyl group, a substituted or unsubstituted carbazolyl group, a substituted or unsubstituted N-phenylcarbazolyl group, a substituted or unsubstituted quinolinyl group, or a substituted or unsubstituted isoquinolinyl group; The substituents of the substitutable groups are each independently selected from one or more of deuterium, tert-butyl, phenyl, biphenyl, naphthyl, terphenyl, anthracenyl, phenanthryl, pyridyl, carbazolyl, dibenzofuranyl.

2. The compound containing a cyano-substituted azobenzene structure according to claim 1, characterized in that, the structure of the compound containing a cyano-substituted azobenzene structure is shown as any one of general formula (1-8) to general formula (1-11): In General Formulas (1-8) to (1-11), Ar 1 -Ar 4 and X 1 -X 6 have the meanings defined in General Formula (1).

3. The compound containing a cyano-substituted azobenzene structure according to claim 1, characterized in that, The Ar 1 -Ar 4 is independently selected from any one of the following structures:

4. The compound containing a cyano-substituted azobenzene structure according to claim 1, characterized in that, the specific structure of the compound containing a cyano-substituted azobenzene structure is any one of the following structures:

5. An organic electroluminescent device, comprising a first electrode and a second electrode, and having a plurality of organic thin film layers between the first electrode and the second electrode, characterized in that, at least one organic thin film layer contains the compound containing a cyano-substituted azobenzene structure according to any one of claims 1 to 4.

6. The organic electroluminescent device according to claim 5, characterized in that, the organic thin film layer includes an electron transport layer, and the electron transport layer contains the compound containing a cyano-substituted azobenzene structure according to any one of claims 1 to 4.

7. The organic electroluminescent device according to claim 5, characterized in that, the organic thin film layer includes a hole transport region thin film layer, a light emitting region thin film layer and an electron transport region thin film layer, and the electron transport region thin film layer contains the compound containing a cyano-substituted azobenzene structure according to any one of claims 1 to 4.

8. The organic electroluminescent device according to claim 7, characterized in that, the electron transport region thin film layer includes an electron transport layer, and the electron transport layer contains the compound containing a cyano-substituted azobenzene structure according to any one of claims 1 to 4.

9. A display element, characterized in that, the display element contains the organic electroluminescent device according to any one of claims 5 to 8.

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