Light-emitting device, preparation method and display device

Abstract

The invention provides a light-emitting device, a preparation method and a display device. The light-emitting device comprises a first electrode, a second electrode, a light-emitting layer and at least one light-emitting auxiliary function layer, the first electrode and the second electrode are oppositely arranged, the light-emitting layer and the light-emitting auxiliary function layer are clamped between the first electrode and the second electrode, at least one of the light-emitting layer and the light-emitting auxiliary function layer is provided with a network structure, and materials forming the network structure comprise cross-linkable molecules.

Description

Technical Field

[0001] The present disclosure relates to the field of display technology, and in particular to a light-emitting device and a preparation method thereof, and a display apparatus. Background Art

[0002] With the development of display technology, organic light-emitting diodes (OLED) and quantum dot light-emitting diodes (QLED) are widely used in the display field. However, light-emitting diodes based on solution processes, especially quantum dot light-emitting diodes, are difficult to apply to large-area display panels. The solution process requires coating a solution containing a luminescent material or other material on a substrate and drying to form various layers of thin films of the light-emitting device. When the size of the display panel is large, the uniformity of the thickness of the solution-supported film is difficult to guarantee.

[0003] Therefore, the current light emitting devices, preparation methods and display devices still need to be improved. Summary of the invention

[0004] In one aspect of the present application, the present application discloses a light-emitting device. The light-emitting device includes: a first electrode and a second electrode arranged opposite to each other, and a light-emitting layer and at least one light-emitting auxiliary functional layer sandwiched between the first and second electrodes, wherein at least one of the light-emitting layer and the light-emitting auxiliary functional layer has a network structure, and a material forming the network structure includes cross-linkable molecules.

[0005] Furthermore, the content of the cross-linkable molecules in each layer does not exceed 20 wt %.

[0006] Furthermore, the light-emitting device further includes a substrate, and the light-emitting auxiliary function layer includes at least one of the following structures: a hole injection layer, the hole injection layer is arranged on one side of the substrate; a hole transport layer, the hole transport layer is arranged on a side of the hole injection layer away from the substrate; an electron transport layer, the electron transport layer is arranged on a side of the light-emitting layer away from the hole transport layer; and an electron injection layer, the electron injection layer is arranged on a side of the electron transport layer away from the substrate.

[0007] Furthermore, the cross-linkable molecules include at least two cross-linkable groups, the cross-linkable molecules include at least one of photo-cross-linking molecules and thermal-cross-linking molecules, the photo-cross-linking molecules include reversible photo-cross-linking molecules, the thermal-cross-linking molecules include: at least one of diformamide compounds, melamine compounds, and epoxy resin compounds; the photo-cross-linking molecules include at least one of benzophenone compounds, thioxanthone compounds, and camphorquinone compounds.

[0008] Furthermore, the reversible photocrosslinking molecules include at least one of coumarin compounds, cinnamic acid compounds, stilbene compounds and anthracene compounds.

[0009] Furthermore, the light-emitting layer includes light-emitting quantum dot materials or organic light-emitting materials.

[0010] In another aspect of the present application, the present application proposes a method for preparing the above-mentioned light-emitting device. The method includes the operation of forming a light-emitting layer and a plurality of light-emitting auxiliary functional layers between a first electrode and a second electrode, and the operation of forming the light-emitting layer and at least one of the plurality of light-emitting auxiliary functional layers includes: coating a solution containing cross-linkable molecules to form a wet film, treating the wet film to form a network structure containing the cross-linkable molecules; and drying the treated wet film.

[0011] Furthermore, the solution is coated on one side of a substrate to form a wet film, and the size of the substrate is not less than 4 cm*4 cm.

[0012] Furthermore, the cross-linkable molecules are reversibly photocross-linkable molecules. After the wet film that has undergone the cross-linking treatment is dried to form a dry film, the method further includes: irradiating a predetermined area of ​​the dry film with light having a specific wavelength, and removing the dry film in the predetermined area. The specific wavelength is a wavelength that causes the reversible photocross-linkable molecules to de-cross-link.

[0013] In another aspect of the present application, the present application provides a display device, which includes: the light-emitting device described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the multiple drawings represent the same or similar parts or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings only depict some embodiments according to the present disclosure and should not be regarded as limiting the scope of the present disclosure.

[0015] Figure 1 is a schematic structural diagram of a light emitting device according to an embodiment of the present disclosure;

[0016] Figure 2 is a schematic structural diagram of a light emitting device according to another embodiment of the present disclosure;

[0017] Figure 3 A flow chart of a method for preparing a light-emitting device according to an embodiment of the present disclosure;

[0018] Figure 4 The present invention is a flow chart of a method for preparing a light-emitting device according to another embodiment of the present invention. DETAILED DESCRIPTION

[0019] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present disclosure, and different embodiments may be combined arbitrarily without conflict. Therefore, the drawings and descriptions are considered to be illustrative in nature and not restrictive.

[0020] In the description of this application, regardless of whether the words "about" or "approximately" are used, all the numbers disclosed herein are approximate values. The value of each number may differ by less than 10% or a reasonable difference considered by those skilled in the art, such as 1%, 2%, 3%, 4% or 5%.

[0021] As a first aspect of the application, the present application provides a light emitting device. Figure 1 , the light-emitting device may include a first electrode 100, a second electrode 200, a light-emitting layer 300 and at least one light-emitting auxiliary function layer 400. At least one of the light-emitting layer 300 and the plurality of light-emitting auxiliary function layers 400 has a network structure (not shown in the figure) formed by cross-linking of cross-linkable molecules. The network structure can limit and hinder the flow of materials such as solutes in the coating ink when the corresponding film layer structure is prepared by a solution process, thereby reducing the uneven thickness and other defects caused by the flow of solutes due to uneven solvent evaporation speed, and improving the uniformity and quality of the film layer. In addition, the grid structure can also improve the solvent resistance of the corresponding film layer, thereby improving the display performance and use performance of the light-emitting device.

[0022] The following is a detailed explanation of the principle by which the organic light-emitting display substrate according to the embodiment of the present disclosure can achieve the above beneficial effects.

[0023] As mentioned above, the film prepared by the solution process is suitable for large-size light-emitting devices (such as those with an area greater than 1 cm 2 ), the uneven solvent evaporation rate leads to solute flow and long drying time, which can easily lead to uneven thickness of the final film and cause mura defects.

[0024] In particular, most of the current QLED devices based on quantum dots as luminescent materials are based on very small luminous areas (e.g., luminous area < 1 cm 2), this type of device only needs to meet the requirements of film quality on a very small scale, such as no mura, film thickness meets the standard, and film thickness is uniform everywhere. However, for the preparation of large-size devices, the resolution of methods such as inkjet printing is difficult to further improve, so other coating methods still need to be developed to form devices. However, the formation of the final dry film in the solution process is determined by the two steps of wet film coating and wet film drying, that is, the solution is first coated into a continuous and uniform liquid film, and then a solid film is formed by controlling its drying process. In the process of liquid film drying, the flow and volatilization of the solvent in the liquid film will cause the migration of the solute, resulting in mura defects in the formed dry film, affecting the quality and display performance of the prepared QLED substrate.

[0025] The inventors have found through in-depth research that when preparing a large-size substrate by coating, cross-linkable molecules are added to the coating ink, and a network structure can be formed by the cross-linkable molecules before the wet film is dried. The network structure can limit and hinder the solute flow in the wet film in the wet film state after coating, thereby reducing the solvent volatilization rate and the mura caused by the solute flow during the preparation of large-area thin films, thereby improving the uniformity and quality of large-area thin films. In addition, the polymer network structure formed by cross-linking the cross-linkable molecules exists in the entire film, which can also make the film more solvent-resistant and further improve the performance of the light-emitting device.

[0026] In the present application, the type of luminescent material in the luminescent layer is not particularly limited. For example, it can be an organic luminescent material or a quantum dot luminescent material. Electroluminescent quantum dot devices (QLEDs) have the advantages of high color gamut, self-luminescence, low starting voltage, fast response speed, and long life. With the development of the materials themselves, the continuous optimization of the device structure, and the continuous deepening of research on effective charge transport, QLED is expected to become the next generation of mainstream display technology. Further adoption of new processes and technologies to achieve its industrialization has become a future trend. Below, taking the luminescent material of the luminescent layer as quantum dots as an example, the structure of each layer of the luminescent device is described in detail:

[0027] The area of ​​the light emitting device is not particularly limited. For example, the light emitting device can be a large-sized device or a small-sized device. In particular, when the area of ​​the ink applied to the light emitting device is large during the preparation process, the aforementioned network structure can also ensure that the obtained film layer has a good film flatness.

[0028] In some examples, the light-emitting device may include a substrate. The first electrode may be disposed on one side of the substrate. In the present application, the specific types of the first and second electrodes are not particularly limited, for example, one may be an anode and the other may be a cathode. The number and position of the light-emitting auxiliary functional layer may not be particularly limited, and those skilled in the art may adjust them according to actual needs and device performance parameter requirements. For example, the light-emitting auxiliary functional layer may include a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer. In some specific examples, reference Figure 2 Taking the first electrode 100 as an anode as an example, the light-emitting device may include a hole injection layer 410, a hole transport layer 420, a light-emitting layer 300, a hole blocking layer 440, an electron transport layer 450, and an electron injection layer 460 stacked in sequence. The second electrode 200 is a cathode and may further include a covering layer 210. The light-emitting layer 300 may be provided with quantum dots having an electroluminescent function.

[0029] It should be noted that the present application only shows the structure and position of part of the auxiliary light-emitting functional layer, and those skilled in the art can add or reduce the relevant auxiliary light-emitting functional layer according to actual needs. For example, the light-emitting device may further have an electron blocking layer. Alternatively, the light-emitting device may also have only Figure 2 Those skilled in the art will appreciate that when the light emitting device only has Figure 2 When only part of the film layers are shown in FIG, the remaining film layers can be arranged in a manner familiar to those skilled in the art.

[0030] In other embodiments, the light-emitting device may also have a tandem structure, in which the light-emitting material in the light-emitting layer may be an electro-induced organic light-emitting material. When the light-emitting device is a tandem device, it may have multiple, for example two, light-emitting layers. Each light-emitting layer has multiple light-emitting regions with different colors, such as red, green, and blue light-emitting regions. In addition, in order to improve the device performance of the tandem device, the light-emitting layer may also have a light-emitting sublayer and a light-emitting auxiliary sublayer stacked once, and the light-emitting auxiliary sublayer is arranged close to the first electrode. Between the two light-emitting layers, there may be further structures such as a charge generation layer.

[0031] In some specific embodiments, at least one of the hole injection layer, hole transport layer, light-emitting layer and electron transport layer has a network structure formed by cross-linking of cross-linkable molecules. Thus, when the aforementioned layers are prepared by coating, the network structure can limit and hinder the flow of hole injection materials, hole transport materials, light-emitting layer materials, electron transport materials, and especially the corresponding solutes in the coating ink, thereby reducing the uneven thickness caused by the flow of solutes due to the uneven solvent evaporation rate, improving the uniformity and quality of the prepared hole injection layer, hole transport layer, light-emitting layer, and electron transport layer, and improving the solvent resistance of each layer, thereby improving the display performance and use performance of the light-emitting element.

[0032] In one embodiment, the content of the network structure contained in each layer structure is not more than 20% of the mass of the film layer. Specifically, the organic light-emitting display functional material can be the hole injection material, hole transport material, light-emitting layer material, electron transport material, etc. mentioned above. Specifically, the content of the network structure can be 15%, 12%, 10%, 8%, 5%, 3%, etc. of the total mass of the corresponding film layer. Therefore, when the content of the network structure is within the above range, it can better limit and hinder the flow of the wet film formed by the coating ink, and then reduce the solute flow caused by the uneven solvent evaporation rate, improve the uniformity and quality of the film layer, and improve its solvent resistance, and it will not significantly affect the electrical properties of the film layer, and will not significantly increase the resistance of the film layer.

[0033] In some examples, the content of the network structure can be controlled by controlling the amount of cross-linkable molecules added to the ink. For example, the content of cross-linkable molecules in the ink used for coating to form a wet film can be controlled to not exceed 20% of the solid content of the ink. The content of cross-linkable molecules in each film layer formed after film formation can be determined by, including but not limited to, thermogravimetric analysis: subjecting a specific film layer material to a programmed temperature treatment, testing the weight loss of the film layer when heated to a specific temperature, to determine the mass of the material that decomposes at a specific temperature. The specific temperature can be the temperature at which the cross-linkable molecules decompose.

[0034] In one embodiment, the specific chemical composition of the materials forming each layer is not particularly limited, and those skilled in the art can select as needed. For example, the material of the hole injection layer may include one or more of PEDOT:PSS, CuPc, F4-TCNQ, HATCN, etc.; the material forming the hole transport layer may include an organic hole transport material or an inorganic hole transport material, and the organic hole transport material forming the hole transport layer may include one or more of TFB, PVK, poly-TPD, PFB, TCTA, CBP, TPD, NPB, P3HT, etc.; the inorganic hole transport material forming the hole transport layer may include MoO x , VO x , WOx CrO x , CuO, MoS2, MoSe2, WS2, WSe2, CuS, etc., wherein x can be determined according to the valence of the inorganic substance that forms a compound with the O atom. The luminescent material forming the luminescent layer can be a quantum dot material, and specifically can include: one or more of CdS@ZnSZnS, CdSe@ZnS, InP@ZnS, PbS@ZnS, CsPbCl3@ZnS, CsPbBr3@ZnS, CsPbI3@ZnS, CdS@ZnS, and CdSe@ZnS. The quantum dot material can further have a quantum dot ligand, for example, a long-chain alkane ligand, such as a saturated alkane of C10 or more. More specifically, it can include one or more of trioctylphosphine, tributylphosphine, oleic acid, stearic acid, oleylamine, long-chain alkylamine, long-chain alkylphosphine, and long-chain alkylphosphonic acid. The material forming the electron transport layer 40 may include one or more of ZnO, TiO2, SnO, ZnMgO, AlZnO, ZnSnO, InSnO, Alq3, LiF, etc. The above materials have good performance and can easily form a light-emitting device with a high degree of energy level matching, thereby further improving the display performance of the light-emitting device.

[0035] In the present application, the specific components of the coating ink used to form the above-mentioned film layers are not particularly limited, as long as they have good dispersibility for cross-linkable molecules and can form a wet film through processes including but not limited to coating processes. Those skilled in the art can select the solvent and the content of each component in the ink according to actual conditions. The materials forming the network structure include cross-linkable molecules. For example, the network structure can be formed by cross-linking the cross-linkable molecules alone, or by the cross-linkable molecules and the materials in each film layer. For example, specifically, the cross-linkable molecules can be molecules that can form a network structure through free radical polymerization. When the network structure is formed by cross-linkable molecules and other materials, the other materials may include ligand materials for quantum dots, or other materials that are prone to free radical polymerization, such as materials containing unsaturated bonds.

[0036] In one embodiment, the crosslinkable molecule includes at least two crosslinkable groups, so that the crosslinkable molecule can be crosslinked to form a network structure. In one embodiment, the crosslinkable molecule may include at least one of a photocrosslinkable molecule and a thermal crosslinkable molecule. By exposure or heating, the crosslinkable molecules can be easily crosslinked to form a network structure, thereby improving the uniformity and solvent resistance of the wet film. Specifically, crosslinkable molecules of different chain lengths can be selected according to the molecular size of the functional material. For example, when the core material (such as a luminescent material, a hole transport / blocking material, an electron transport / blocking material, etc.) in the film layer of the wet film is small, a crosslinkable molecule with a shorter chain length can be selected. Thus, the grid of the network structure formed by crosslinking is also small, which can better hinder the flow of the organic light-emitting display functional material; on the contrary, when the core material molecule is large, a crosslinkable molecule with a longer or shorter chain length can be selected, and the grid of the network structure formed by crosslinking can also better hinder the flow of the organic light-emitting display functional material.

[0037] In one embodiment, the aforementioned cross-linkable molecules may include at least one of photo-cross-linking molecules and thermal cross-linking molecules. Specifically, the thermal cross-linking molecules may include at least one of diformamide molecules, melamine molecules, and epoxy resin molecules. Thus, by heat treatment, the thermal cross-linking molecules can form a network structure. Specifically, thermal cross-linking reaction is an important chemical reaction, which can change the physical and chemical properties of polymer materials, thereby giving them better performance. The principle of thermal cross-linking reaction is to react the cross-linking agent in the polymer material by heating, thereby forming a cross-linking structure, so that a three-dimensional network structure is formed between the molecular chains of the polymer material.

[0038] In one embodiment, the photocrosslinking molecules may include a photoinitiator and a monomer. Specifically, a photoinitiator is a light-initiated chemical substance that absorbs light and participates in polymerization reactions. It can produce active intermediates (free radicals and ions) with the ability to initiate polymerization through primary or subsequent reactions alone or involving one or more additional compounds. Photoinitiators account for a relatively small proportion of photopolymerization formulas, but they play a major role in polymerization. A photoinitiator or photoinitiator system is defined as a molecule or a combination of molecules that, once light is absorbed, begins to polymerize, causing the system to crosslink and cure from a liquid to a solid state. After the photoinitiator molecules are irradiated with light, they transition from a stable ground state to an excited state (an excited singlet state or a certain degree of excited triplet state), and the excited photoinitiator molecules produce active substances that can initiate polymerization of the system through a chemical process. Specifically, the photoinitiator may include free radicals, ions or ionic free radicals, etc. Free radical photoinitiators may include cleavage-type free radical photoinitiators and hydrogen abstraction-type free radical photoinitiators, and cleavage-type photoinitiators may include aromatic carbonyl compounds with appropriate substitutions, such as: benzoin, benzil, acetophenone, α-hydroxybenzophenone and its derivatives, and acylphosphine oxides, etc. As shown in the following formula, after absorbing light, the single-molecule photoinitiator undergoes homolytic bond cleavage to generate active free radicals.

[0039]

[0040] Specifically, hydrogen abstraction type photoinitiators may include ketone compounds, such as benzophenone, thioxanthone, camphorquinone, etc., which exhibit bimolecular photobehavior in the formation of free radicals. This characteristic behavior mainly comes from the photoinitiator generating active free radicals through hydrogen extraction or electron transfer mechanism between the photoinitiator and the co-initiator by absorbing light and generating a long-lived excited triplet state. As described in the following formula, the hydrogen abstraction type photoinitiator generates active free radicals after absorbing light.

[0041]

[0042] In one embodiment, the monomer of the photo-crosslinking molecule may include at least one of a benzophenone compound, a thioxanthone compound, and a camphorquinone compound.

[0043] In one embodiment, the photocrosslinking molecules may also include reversible photocrosslinking molecules. Specifically, the reversible photocrosslinking molecules may include coumarins, cinnamic acids, diphenylethylenes, anthracenes, etc. Specifically, when the prepared organic light-emitting functional part film needs to be patterned, reversible photocrosslinking molecules can be used. After the ink is coated, the wet film can be exposed using band 1 to crosslink the reversible photocrosslinking molecules to form a network structure, and then the film is dried; then the patterned area is exposed using band 2 to decrosslink the network structure in the film in the exposed area and return to reversible photocrosslinking molecules, so that the film layer in the non-patterned area can be removed to obtain a predetermined pattern.

[0044] In one embodiment, referring to the following formula, the reversible photocrosslinking molecule can be a coumarin, which generally undergoes photocrosslinking at wavelengths greater than 320 nm and undergoes de-crosslinking at wavelengths less than 280 nm. R1 and R2 of the coumarin compound can be any substituents, and when the substituents are different, the wavelengths at which reversible crosslinking occurs can be slightly different.

[0045]

[0046] In one embodiment, the reversible photocrosslinkable molecule may be cinnamic acid. Cinnamic acid compounds generally undergo photocrosslinking at wavelengths greater than 300 nm, and decrosslinking occurs when the wavelength is less than 260 nm. Similarly, R1 and R2 in cinnamic acid compounds may be any substituents, and when the substituents are different, the wavelengths at which reversible crosslinking occurs may also be slightly different.

[0047]

[0048] In one embodiment, referring to the following formula, the reversible photocrosslinkable molecule can be a diphenylethylene compound. The diphenylethylene compound generally undergoes photocrosslinking when the wavelength is greater than 300nm, and decrosslinking occurs when the wavelength is less than 280nm. R1, R2, R3, and R4 of the diphenylethylene compound can be any substituent. When the substituents are different, the wavelength at which the reversible crosslinking occurs can be slightly different.

[0049]

[0050] In one embodiment, referring to the following formula, the reversible photocrosslinking molecule can be an anthracene compound. Anthracene compounds generally undergo photocrosslinking at wavelengths greater than 300 nm, and de-crosslinking occurs when the wavelength is less than 280 nm. R1 and R2 of the compound can be any substituents. When the substituents are different, the wavelengths at which reversible crosslinking occurs may be slightly different. Specifically, anthracene reversible photocrosslinking molecules can also undergo de-crosslinking at temperatures above 150°C, and have a high efficiency of use.

[0051]

[0052] As a second aspect of the embodiments of the present disclosure, the embodiments of the present disclosure provide a method for preparing a light-emitting device. Specifically, the light-emitting device prepared by the method can be the light-emitting device described above. Therefore, the light-emitting device prepared by the method has all the characteristics and advantages of the light-emitting device described above, which will not be described in detail here. In general, the thin film uniformity and solvent resistance of the light-emitting device prepared by the method are good, and it has good display performance and usage performance.

[0053] According to an embodiment of the present application, the method may include an operation of forming a light-emitting layer and a plurality of light-emitting auxiliary function layers between a first electrode and a second electrode. Specifically, the operation of forming the light-emitting layer and at least one of the plurality of light-emitting auxiliary function layers may include coating a solution containing cross-linkable molecules to form a wet film, and performing an exposure treatment on the wet film to form a network structure containing the cross-linkable molecules. The wet film subjected to the exposure treatment is then dried.

[0054] Specifically, refer to Figure 3 and Figure 4 , the method comprising:

[0055] S100 provides substrate

[0056] In this step, a substrate is provided. Specifically, the substrate can be a common substrate material, such as glass, polyimide, etc. In this step, the substrate can also be cleaned, for example, by ultrasonic treatment with deionized water, isopropanol and acetone for 20 minutes respectively, and then treated with UV-Ozone for 15 minutes.

[0057] As mentioned above, since the present application adds cross-linkable molecules to the ink, a larger substrate can be used and the uniformity of the film thickness can be ensured. In some specific examples, the size of the substrate may be no less than 4 cm*4 cm. For example, the size of the substrate may be no less than 370 mm*470 mm.

[0058] It should be noted here that the feature of "the size of the substrate is not less than" means that the edge length of the substrate is greater than the aforementioned value in any one of the two dimensions of length and width.

[0059] S200: Coating ink

[0060] In this step, ink is applied on one side of the substrate described above to form a wet film. The ink contains cross-linkable molecules. The specific materials and contents of other components of the ink can be adjusted according to the specific materials of the light-emitting function auxiliary layer and / or the light-emitting layer to be formed. For example, the ink applied in this step can be the hole injection material ink, hole transport material ink, quantum dot light-emitting layer material ink, electron transport material ink, etc. described above. The cross-linkable molecules can be the photo-cross-linkable molecules, thermal cross-linkable molecules, etc. described above, which will not be repeated here.

[0061] Specifically, the coating method may include but is not limited to at least one of blade coating, inkjet printing, slit coating, and spray coating, for example, slit coating. The coating method can be any method that can ensure that a wet film with good thickness uniformity is obtained in the coating step. Specifically, taking slit coating as an example, refer to Figure 4 In step (a), the ink can be added to the slit coater and subjected to defoaming treatment, and then the coating parameters are set and the coating is performed.

[0062] In the present application, the solid content of the ink is not particularly limited. In some examples, the solid content of the ink used in this step can be relatively low. For example, the solid content can be less than 10%, more specifically, less than 8%, less than 5%. In a specific example, the solid content of the ink can be 0.1%-2%.

[0063] As mentioned above, in the ink, the content of cross-linkable molecules may not be greater than 20% of the solid content of the ink. Specifically, the mass content of the cross-linkable molecules may be 15%, 12%, 10%, 8%, 5%, 3%, etc. of the solid content. When the content of the cross-linkable molecules is within the above range, the network structure formed by the subsequent cross-linking treatment can better restrict and hinder the flow of materials such as solutes in the coating ink, thereby reducing the solute flow caused by the uneven solvent evaporation rate, uneven thickness after drying, etc., improve the uniformity and quality of the prepared film layer, and improve its solvent resistance, while ensuring that the electrical and luminescent properties of the film layer are not significantly affected.

[0064] It is understood by those skilled in the art that, before applying the ink, the method may further include operations such as forming a first electrode layer. The first electrode layer may be patterned to form the first electrode before applying the ink. Alternatively, if the shape of the first electrode of the light-emitting device is consistent with the shape of the light-emitting layer and the light-emitting auxiliary function layer having a network structure, the patterning of the first electrode layer may not be performed before applying the ink.

[0065] S300: Forming a network structure

[0066] In this step, the wet film formed previously is treated to form a network structure containing at least cross-linkable molecules. Specifically, depending on the type of cross-linkable molecules, the treatment in this step may be an exposure treatment (see Figure 4 The specific wavelength of light or heating temperature is determined according to the properties of the selected cross-linkable molecules. Thus, the network structure formed by exposure and other treatments in this step can better limit and hinder the flow of solutes in the coating ink, improve the uniformity and quality of the prepared film layer, and improve its solvent resistance. Specifically, the wet film coated on the substrate in the previous step can be transferred to an exposure chamber and exposed with light of a certain wavelength to cross-link the cross-linkable molecules to form a network structure.

[0067] S400: Drying

[0068] In this step, the wet film treated as described above is dried. Figure 4In (c), the wet film with a network structure formed by exposure treatment in the previous step can be transferred to a vacuum cooling and drying device (VCD) for film drying, and then further high-temperature baking can be performed to form a corresponding film layer (reference Figure 4 (d) in the above). The specific drying temperature and the like can be determined according to the material in the film layer.

[0069] In one embodiment, the method may specifically include the following operations:

[0070] Formation of hole injection layer

[0071] In this step, a hole injection material ink is coated on one side of the first electrode and subjected to a first drying treatment. Specifically, the hole injection material may be as described above and will not be described in detail here, for example, it may be PEDOT:PSS, etc. The specific hole injection material ink may contain cross-linkable molecules. After wet film coating, the wet film may be exposed or heated to cross-link the cross-linkable molecules in the wet film to generate a network structure, and then a first drying treatment is performed to remove the solvent.

[0072] Formation of hole transport layer

[0073] In this step, the hole transport material ink is coated on the side of the hole injection layer formed in the previous step away from the substrate, and then subjected to a second drying treatment. Specifically, the hole transport material may be as described above, which will not be described in detail here, for example, it may be TFB, etc. Specifically, the hole transport material ink may contain cross-linkable molecules, and after wet film coating, the wet film may be exposed or heated to cross-link the cross-linkable molecules in the wet film to generate a network structure, and then a second drying treatment is performed to remove the solvent.

[0074] Forming a light-emitting layer

[0075] In this step, the light-emitting layer material ink having quantum dots is coated on the side of the hole transport layer formed in the previous step away from the hole injection layer, and then subjected to a third drying process. Specifically, the light-emitting layer material can be as described above, which will not be described in detail here.

[0076] In some embodiments, the method may further include the step of preparing luminescent quantum dots. For example, the luminescent quantum dots may be InP@ZnS quantum dots. The specific preparation method may include: in a glove box vacuum environment, weighing a certain amount of indium bromide (InBr3) and zinc bromide (ZnBr2) with an electronic balance and adding them to a three-necked flask, then adding oleylamine (OLA) thereto, evacuating for 30 minutes and heating to about 100°C, until there is no water vapor, then introducing argon (Ar), and heating to about 215°C. Inject a certain amount of a mixed solution of tri(dimethylamino)phosphine [(DMA)3P] and oleylamine (OLA) therein, and keep the temperature at this temperature for 20 minutes. Allow it to react fully at an appropriate stirring speed, and then quickly add dodecanethiol and stearic acid-ODE solution (zinc stearate dissolved in ODE) with a syringe. Heat to about 300°C for reaction, and take samples from the reactor at 10 minutes, 20 minutes, 30 minutes, and 40 minutes, respectively. After reacting for 40 minutes, stop heating. After the solution is cooled to 70-80°C, a certain amount of n-hexane is added and centrifuged at 10,000 rpm to precipitate the zinc stearate. A certain amount of n-hexane and anhydrous ethanol are added and centrifuged at 10,000 rpm to precipitate the InP / ZnS nanocrystals. After that, the InP / ZnS nanocrystals are dried with N2. The obtained InP / ZnS nanocrystals can be well dissolved in the n-hexane solution and then characterized and analyzed. During the reaction process, the color of the solution changes from colorless and transparent to brown, and then gradually changes to yellow-green. The amount of each reactant, ligand, and solvent added in the operation of synthesizing quantum dots can be determined according to the chemical composition of the quantum dots.

[0077] Subsequently, cross-linkable molecules and solvents can be added to the quantum dot material to form a light-emitting layer ink. After wet film coating, the wet film can be exposed or heated to cross-link the cross-linkable molecules in the wet film to produce a network structure, and then a third drying process is performed to remove the solvent.

[0078] Forming an electron transport layer

[0079] In this step, the electron transport material ink is coated on the side of the light-emitting layer away from the hole transport layer formed in the previous step, and then subjected to the fourth drying treatment. Specifically, the electron transport material can be as described above, which will not be described here, for example, it can be ZnO, etc. Specifically, the electron transport material ink can contain cross-linkable molecules. After wet film coating, the wet film can be exposed or heated to cross-link the cross-linkable molecules in the wet film to generate a network structure, and then the fourth drying treatment is performed, and the electron transport layer is formed after the solvent is removed.

[0080] The method may also include preparing an electron blocking layer, an electron injection layer, a hole blocking layer, etc. When the above layers are prepared by a coating method, the coating ink may also contain cross-linkable molecules, which will not be described in detail here.

[0081] In one embodiment, if the aforementioned film layer does not need to be patterned, operations such as forming a second electrode and encapsulation can be performed after the first to fourth or more drying processes to obtain a light-emitting device.

[0082] In other embodiments, if the aforementioned film layer needs to be patterned, the method may further include the operation of patterning the aforementioned film layer. In some examples, irreversibly cross-linkable molecules may be used, and etching techniques including but not limited to dry etching or wet etching may be used to pattern part or all of the aforementioned film layer, for example, the light-emitting layer may be patterned while the shape of the remaining light-emitting auxiliary function layer remains unchanged, or the light-emitting layer and the light-emitting auxiliary function layer may be etched simultaneously using the same etching process.

[0083] Alternatively, reversible photocrosslinking molecules may be used as crosslinkable molecules. After each film layer is dried, a predetermined area in the dry film obtained by drying is irradiated with light having a specific wavelength, and the dry film in the predetermined area is removed. The specific wavelength is a wavelength at which the reversible photocrosslinking molecules are de-crosslinked. The wavelengths at which different types of crosslinkable molecules are de-crosslinked have been described in detail above and will not be repeated here. Alternatively, those skilled in the art may also determine the specific value or range of the specific wavelength based on the material of the specific crosslinkable molecule.

[0084] For example, taking coumarin compounds as reversible photocrosslinkable molecules, when crosslinking treatment is performed in the previous step, it can be performed under light greater than 320nm, and when patterning is required, the film layer is de-crosslinked under light with a wavelength less than 280nm. After de-crosslinking and development treatment, the network structure is de-crosslinked, and the film material at the de-crosslinked part can be removed to form a patterned film layer.

[0085] Similarly, the de-crosslinking light treatment can be performed after all the film layers containing cross-linkable molecules are formed. Alternatively, in order to improve the efficiency of the cross-linkable molecules receiving de-crosslinking light, each film layer can be de-crosslinked after being formed by drying.

[0086] As a third aspect of the embodiments of the present disclosure, the present disclosure provides a display device. The display device includes: the light-emitting device described above. Therefore, the organic light-emitting display device has all the features and advantages of the light-emitting device described above, which will not be repeated here. In general, the display performance of the display device is good.

[0087] In this application, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this disclosure, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0088] In the present disclosure, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or a communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present disclosure can be understood according to specific circumstances.

[0089] In the present disclosure, unless otherwise clearly specified and limited, a first feature being “above” or “below” a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being “above”, “above”, and “above” a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being “below”, “below”, and “below” a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0090] The disclosure above provides many different embodiments or examples to implement different structures of the present disclosure. In order to simplify the present disclosure, the components and settings of specific examples are described above. Of course, they are only examples, and the purpose is not to limit the present disclosure. In addition, the present disclosure can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplification and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed.

[0091] The above are only specific embodiments of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any technician familiar with the technical field can easily think of various changes or substitutions within the technical scope disclosed in the present disclosure, which should be included in the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be based on the protection scope of the claims.

Claims

1. A light emitting device, characterized in that: include: A first electrode and a second electrode are arranged opposite to each other, and a light-emitting layer and at least one light-emitting auxiliary functional layer are sandwiched between the first and second electrodes. At least one of the light-emitting layer and the light-emitting functional layer has a network structure, and a material forming the network structure includes cross-linkable molecules.

2. The light emitting device according to claim 1, wherein The content of the cross-linkable molecules in each layer does not exceed 20 wt%.

3. The light emitting device according to claim 1, wherein The light-emitting device further includes a substrate, and the light-emitting auxiliary function layer includes at least one of the following structures: a hole injection layer, the hole injection layer being disposed on one side of the substrate; a hole transport layer, the hole transport layer being arranged on a side of the hole injection layer away from the substrate; an electron transport layer, the electron transport layer being arranged on a side of the light-emitting layer away from the hole transport layer; An electron injection layer is provided on a side of the electron transport layer away from the substrate.

4. The light emitting device according to claim 1, wherein The cross-linkable molecules include at least two cross-linkable groups, the cross-linkable molecules include at least one of photo-cross-linkable molecules and thermal-cross-linkable molecules, and the photo-cross-linkable molecules include reversible photo-cross-linkable molecules. The thermal cross-linking molecules include: at least one of diformamide compounds, melamine compounds, and epoxy resin compounds; The photo-crosslinking molecules include at least one of benzophenone compounds, thioxanthone compounds, and camphorquinone compounds.

5. The light emitting device according to claim 4, characterized in that The reversible photocrosslinking molecules include at least one of coumarin compounds, cinnamic acid compounds, stilbene compounds and anthracene compounds. The light emitting device according to claim 1 , wherein: The light-emitting layer includes light-emitting quantum dot materials or organic light-emitting materials.

7. A method for preparing the light-emitting device according to any one of claims 1 to 6, characterized in that: The method includes forming a light-emitting layer and a plurality of light-emitting auxiliary functional layers between a first electrode and a second electrode, wherein the forming of the light-emitting layer and at least one of the plurality of light-emitting auxiliary functional layers includes: coating a solution containing cross-linkable molecules to form a wet film, and treating the wet film to form a network structure containing the cross-linkable molecules; The wet film that has undergone the treatment is dried.

8. The method according to claim 7, characterized in that The solution is coated on one side of a substrate to form a wet film, and the size of the substrate is not less than 4 cm*4 cm.

9. The method according to claim 7, characterized in that The cross-linkable molecules are reversibly photocross-linkable molecules. After the cross-linked wet film is dried to form a dry film, the method further comprises: irradiating a predetermined area of ​​the dry film with light having a specific wavelength and removing the dry film from the predetermined area. The specific wavelength is a wavelength that causes the reversibly photocrosslinkable molecules to decrosslink.

10. A display device, characterized in that: include: The light-emitting device according to any one of claims 1 to 6.

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