Light emitting device and method of fabricating the same

Abstract

The application belongs to the technical field of display, and particularly relates to a light-emitting device and a preparation method thereof. The light-emitting device comprises a first electrode, a hole functional layer, a light-emitting layer, an electron functional layer and a second electrode which are arranged in a stack, characterized in that the material of the light-emitting layer is a crystalline light-emitting material; the light-emitting device further comprises a first buffer layer arranged between the hole functional layer and the light-emitting layer, the material of the first buffer layer is a material with a work function greater than or equal to 5.0 eV; and / or the light-emitting device further comprises a second buffer layer arranged between the light-emitting layer and the electron functional layer, the material of the second buffer layer is a material with a work function less than or equal to 3.8 eV. The light-emitting device provided by the application improves the injection efficiency of holes and electrons by introducing the buffer layer, avoids the poor contact between the light-emitting layer adopting the crystalline light-emitting material and other layers, and thus influences the device performance, thereby improving the light-emitting efficiency of the device, and increasing the stability and service life of the device.

Description

Technical Field

[0001] This application relates to the field of display technology, and more specifically, to a light-emitting device and a method for fabricating the same. Background Technology

[0002] In the development of organic light-emitting diodes (OLEDs), solution processing technology has attracted much attention due to its low cost and potential for large-area production. However, solution-processed OLED devices mainly rely on amorphous organic materials, which have low carrier transport efficiency and insufficient thermal stability and oxidation resistance, resulting in problems such as low efficiency, short lifespan, and poor stability of OLED devices.

[0003] Crystalline organic light-emitting diodes (C-OLEDs) utilize crystalline organic semiconductor materials as the light-emitting layer. These materials possess high crystallinity and high fluorescence quantum efficiency, which can improve electroluminescence efficiency and brightness. Furthermore, the good thermal stability and oxidation resistance of crystalline organic semiconductor materials contribute to the stability and lifespan of C-OLED devices. Currently, C-OLED devices are mainly fabricated using vacuum evaporation, but the crystalline light-emitting layer is prone to poor contact with other layers, resulting in no light emission. Summary of the Invention

[0004] The technical problem to be solved by the embodiments of this application is how to avoid poor contact between the crystalline light-emitting layer and other layers, which would affect the device performance.

[0005] To address the aforementioned technical problems, this application provides a light-emitting device, employing the following technical solution:

[0006] A light-emitting device includes a first electrode, a hole-functional layer, a light-emitting layer, an electron-functional layer, and a second electrode stacked together, wherein the material of the light-emitting layer is a crystalline light-emitting material;

[0007] The light-emitting device further includes a first buffer layer disposed between the hole-functional layer and the light-emitting layer, wherein the material of the first buffer layer is a material with a work function greater than or equal to 5.0 eV; and / or,

[0008] The light-emitting device further includes a second buffer layer disposed between the light-emitting layer and the electronic functional layer, wherein the material of the second buffer layer is a material with a work function less than or equal to 3.8 eV.

[0009] To address the aforementioned technical problems, this application also provides a method for fabricating a light-emitting device, employing the following technical solution:

[0010] A method for fabricating a light-emitting device includes the following steps:

[0011] A substrate is provided, on which a first electrode is formed;

[0012] A hole-functional layer is formed on the first electrode;

[0013] A first buffer layer is formed on the hole functional layer, the first buffer layer comprising a first material with a work function greater than or equal to 5.0 eV;

[0014] A light-emitting layer is formed on the first buffer layer, the light-emitting layer comprising a crystalline light-emitting material;

[0015] A second buffer layer is formed on the light-emitting layer, the second buffer layer comprising a second material with a work function less than or equal to 3.8 eV;

[0016] An electronic functional layer is formed on the second buffer layer;

[0017] A second electrode is formed on the electronic functional layer to obtain a light-emitting device.

[0018] Compared with the prior art, the embodiments of this application have the following main advantages:

[0019] The light-emitting device provided in this application improves the injection efficiency of holes and electrons by introducing a buffer layer, avoiding poor contact between the light-emitting layer using crystalline light-emitting materials and other layers that could affect device performance, thereby improving the device's luminous efficiency, stability, and lifespan. Attached Figure Description

[0020] To more clearly illustrate the solutions in this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the specific structure of the light-emitting device in one embodiment of this application;

[0022] Figure 2 This is a schematic diagram of the specific structure of the light-emitting device in another embodiment of this application;

[0023] Figure 3 This is a flowchart of a method for fabricating a light-emitting device in one embodiment of this application;

[0024] Figure 4 This is a schematic diagram of the external quantum efficiency obtained by testing the light-emitting devices provided in Examples 1-18 and Comparative Example 1 of this application.

[0025] Figure label:

[0026] 1-First electrode; 2-Hole functional layer; 3-First buffer layer; 4-Light emitting layer; 5-Second buffer layer; 6-Electron functional layer; 7-Second electrode;

[0027] 8-Hole injection layer; 9-Hole transport layer;

[0028] 10-Electron injection layer; 11-Electron transport layer. Detailed Implementation

[0029] To facilitate understanding of the present invention, a more comprehensive description is provided below, along with preferred embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0030] It should be noted that when a component is said to be "on" another component, it can be directly on the other component or there may be an intervening component. When a component is said to be "connected" to another component, it can be directly connected to the other component or there may be an intervening component.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein in the specification of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification, claims, or foregoing description of the drawings are used to distinguish different objects, not to describe a particular order. The term "and / or" in the specification, claims, and foregoing description of the drawings includes any and all combinations of one or more of the associated listed items.

[0032] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0033] Please see Figure 1As shown, this application provides a light-emitting device, including: a first electrode 1, a hole functional layer 2, a light-emitting layer 4, an electronic functional layer 6, and a second electrode 7 stacked together, wherein the light-emitting material of the light-emitting layer 4 is a crystalline light-emitting material; in this embodiment, the light-emitting device further includes a first buffer layer 3 disposed between the hole functional layer 2 and the light-emitting layer 4, and a second buffer layer 5 disposed between the light-emitting layer 4 and the electronic functional layer 6.

[0034] In some embodiments, the light-emitting device is an upright light-emitting device, wherein the first electrode 1 is the anode and the second electrode 7 is the cathode.

[0035] In some embodiments, the glass transition temperature of the crystalline light-emitting material in the light-emitting layer 4 is 50°C to 100°C. In this embodiment, since the glass transition temperature of the crystalline light-emitting material is within the range, the light-emitting layer 4 exhibits a crystalline state after heat treatment, thereby improving the electroluminescence efficiency and brightness.

[0036] Optionally, the glass transition temperature of the crystalline light-emitting material is within the range of any one or two of 50°C, 52°C, 54°C, 56°C, 58°C, 60°C, 62°C, 64°C, 66°C, 70°C, 74°C, 78°C, 80°C, 85°C, 90°C, 95°C, 98°C, and 100°C. In this embodiment, the crystalline light-emitting material of the light-emitting layer 4 crystallizes at a relatively low heat treatment temperature, which helps to achieve efficient C-OLED fabrication at lower temperatures and reduces the risk of thermal damage and material deformation.

[0037] In some embodiments, the general formula of the crystalline luminescent material is:

[0038]

[0039] R1 or R2 is independently selected from one of the following structures:

[0040]

[0041] The asterisk (*) in the structure represents a connection site or fusion site.

[0042] Optionally, the crystalline light-emitting material is selected from one or more of MCP, CBP, NPB, TPD, and DPVB; these crystalline light-emitting materials crystallize at lower heat treatment temperatures, which helps to achieve efficient C-OLED fabrication at lower temperatures and reduces the risk of thermal damage and material deformation.

[0043] Specifically, the structures of MCP, CBP, NPB, TPD, and DPVB are as follows:

[0044]

[0045] In some embodiments, the thickness of the light-emitting layer 4 is 30 to 40 nm, for example, any one or any two of the following values: 30 nm, 32 nm, 34 nm, 36 nm, 38 nm, and 40 nm.

[0046] In some embodiments, the material of the first buffer layer 3 is a material with a work function greater than or equal to 5.0 eV. In this embodiment, a high work function material is introduced between the hole functional layer 2 and the light-emitting layer 4 as the first buffer layer 3, which helps to flatten the surface of the light-emitting layer 4 using crystalline light-emitting material and improve the contact with the light-emitting layer 4, avoid poor contact that affects device performance, and improve the efficiency of hole injection.

[0047] Furthermore, the work function of the material of the first buffer layer 3 is less than or equal to 9.0 eV.

[0048] Optionally, the work function of the material of the first buffer layer 3 is within the range of any one or two of 5.0 eV, 5.5 eV, 6.0 eV, 6.5 eV, 7.0 eV, 7.5 eV, 8.0 eV, 8.5 eV, and 9.0 eV. In this embodiment, the material of the first buffer layer 3 has a high work function, which can improve hole injection efficiency, thereby improving the overall electrical and optical performance of the device.

[0049] In some embodiments, the material of the first buffer layer 3 is a metal oxide material; optionally, the metal oxide material is selected from one or more of V2O5, MoO3, and WO3. These materials can improve hole injection efficiency, thereby improving the electrical and optical performance of the overall device.

[0050] In some embodiments, the thickness of the first buffer layer 3 is 1 to 10 nm, for example, any one of 1 nm, 3 nm, 5 nm, 7 nm, 9 nm, 10 nm or a range formed between any two values.

[0051] In some embodiments, the material of the second buffer layer 5 is an alkaline earth metal material with a work function less than or equal to 3.8 eV. In this embodiment, a low work function material is introduced between the light-emitting layer 4 and the electronic functional layer 6 as the second buffer layer 5. The low work function of the second buffer layer 5 helps to reduce the electron injection barrier and improve the efficiency of electron injection.

[0052] Furthermore, the work function of the material of the second buffer layer 5 is greater than or equal to 1.0 eV.

[0053] Optionally, the work function of the material of the second buffer layer 5 is within the range of any one or two of 1.0 eV, 1.5 eV, 2.0 eV, 2.5 eV, 3.0 eV, 3.1 eV, 3.2 eV, 3.3 eV, 3.4 eV, 3.5 eV, 3.6 eV, 3.7 eV, and 3.8 eV. In this embodiment, the material of the second buffer layer 5 has a low work function, which can improve electron injection efficiency, help improve the charge balance of the device, and further enhance device performance.

[0054] In some embodiments, the material of the second buffer layer 5 is an alkaline earth metal material. Optionally, the alkaline earth metal material is selected from one or more of (8-hydroxyquinoline)lithium, LiF, CsF, and NaF. These materials can improve electron injection efficiency, help improve the charge balance of the device, and further enhance the device performance.

[0055] In some embodiments, the thickness of the second buffer layer 5 is 1–5 nm, for example, any one or any two values ​​of 1 nm, 2 nm, 3 nm, 4 nm, and 5 nm. In this embodiment, inserting an ultrathin second buffer layer 5 between the light-emitting layer 4 and the electronic functional layer 6 facilitates the release of metal atoms at the organic / metal interface, forming n-type doping, thereby reducing the electron injection barrier.

[0056] The light-emitting device provided in this application improves the injection efficiency of holes and electrons by introducing a buffer layer, avoiding poor contact between the crystalline light-emitting layer and other layers that could affect device performance, thereby improving the device's luminous efficiency and increasing its stability and lifespan.

[0057] In other embodiments, the first electrode 1 and the second electrode 7 are each independently selected from one or more of metal electrodes, carbon electrodes, and doped or undoped metal oxide electrodes to form a composite electrode; wherein, the material of the metal electrode is selected from one or more of Al, Ag, Cu, Mo, Au, Ba, Ca, and Mg; the material of the carbon electrode is selected from one or more of graphite, carbon nanotubes, graphene, and carbon fibers; the material of the doped or undoped metal oxide electrode is selected from one or more of ITO, FTO, ATO, AZO, GZO, IZO, MZO, and AMO; and the material of the composite electrode is selected from one or more of AZO / Ag / AZO, AZO / Al / AZO, ITO / Ag / ITO, ITO / Al / ITO, ZnO / Ag / ZnO, ZnO / Al / ZnO, TiO2 / Ag / TiO2, TiO2 / Al / TiO2, ZnS / Ag / ZnS, ZnS / Al / ZnS, TiO2 / Ag / TiO2, and TiO2 / Al / TiO2.

[0058] Please see Figure 2As shown, in some embodiments, the hole functional layer 2 includes a hole injection layer 8 and a hole transport layer 9 stacked together, wherein the hole injection layer 8 is disposed on the side opposite to the first buffer layer 3.

[0059] In some embodiments, the materials of the hole injection layer 8 and the hole transport layer 9 are each independently selected from 4,4'-N,N'-dicarbazolyl-biphenyl, N,N'-diphenyl-N,N'-bis(1-naphthyl)-1,1'-biphenyl-4,4”-diamine, N,N'-diphenyl-N,N'-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine, N,N'-bis(3-methylphenyl)-N,N'-bis(phenyl)-spiro, N,N'-bis(4-(N,N'-diphenyl-amino)phenyl)-N,N'-diphenylbenzidine, 4,4',4'-tris(N-carbazolyl)-triphenylamine, 4,4',4'-tris(carbazolyl-9-yl)triphenylamine, trichloroisocyanuric acid, and terbium-doped phosphorus. Salt-based green luminescent materials, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazabenzphenanthrene, 4,4',4'-tris(N-3-methylphenyl-N-phenylamino)triphenylamine, poly[(9,9'-dioctylfluorene-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl)diphenylamine))], poly(4-butylphenyl-diphenylamine), poly[bis(4-phenyl)(4-butylphenyl)amine], polyaniline, polypyrrole, poly(p-phenylenevinylene), poly(phenylenevinylene), poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene], poly[2-methoxy-5-(3',7'-dimethyloctyloxy] [N,N'-1,4-phenylenevinylene], copper phthalocyanine, aromatic tertiary amines, polynuclear aromatic tertiary amines, 4,4'-bis(p-carbazolyl)-1,1'-biphenyl compounds, N,N,N',N'-tetraarylbenzidine, PEDOT, PEDOT:PSS and its derivatives, PEDOT:PSS derivatives doped with s-MoO3, poly(N-vinylcarbazole) and its derivatives, polymethacrylates and their derivatives, poly(9,9-octylfluorene) and its derivatives, poly(spirofluorene) and its derivatives, N,N'-di(naphthyl-1-yl)-N,N'-diphenylbenzidine, spiroNPB, nanocrystalline diamond, microcrystalline cellulose and tetracyanoquinone dimethane, doped graphene, undoped graphene, second-doped metal oxides The metal oxide particles are selected from one or more of the following: a second undoped metal oxide particle, a metal sulfide, a metal selenide, and a metal nitride. The metal oxides in the second doped metal oxide particles and the metal oxides in the second undoped metal oxide particles each independently include one or more of the following: MoO3, WO3, NiO, CrO3, CuO, Cu2O, and V2O5. The doping element in the second doped metal oxide particles includes one or more of the following: Mo, W, Ni, Cr, Cu, and V. The metal sulfide includes one or more of the following: CuS, MoS3, and WS3. The metal selenide includes one or more of the following: MoSe3 and WSe3. The metal nitride includes p-type gallium nitride.

[0060] In some embodiments, refer back Figure 2 The electronic functional layer 6 includes an electron injection layer 10 and an electron transport layer 11 stacked together, wherein the electron injection layer 10 is located on the side opposite to the second buffer layer 5.

[0061] In some embodiments, the material of the electron transport layer is selected from at least one of doped or undoped metal oxides and organic electron transport materials; the doped or undoped metal oxide is selected from at least one of doped or undoped zinc oxide, tin oxide, titanium oxide, and zirconium oxide, and the doped element includes at least one of aluminum, magnesium, lithium, manganese, yttrium, lanthanum, copper, nickel, zirconium, cerium, and gadolinium; the organic electron transport material is selected from organic fullerenes, 4,6-bis(3,5-di(3-pyridinyl)phenyl)-2-methylpyrimidine (B3PYMPM), 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBI), 1,3,5-tris[(3-pyridinyl)-3-phenyl]benzene (TmPyPB), 1,3-bis(3,5-dipyridinyl-3-ylphenyl)benzene (B3PyPB), bis[2-(2-pyridinyl)phenyl]benzene, etc. [Betray 2, 3-(biphenyl-4-yl)-5-(4-tert-butylphenyl)-4-phenyl-4H-1,2,4-triazole (TAZ), tri-(8-hydroxyquinoline)aluminum (Alq3), 2,9-dimethyl-4,7-biphenyl-1,10-phenanthroline (BCP), 4,7-diphenyl-1,10-phenanthroline (BPhen), 2,7-bis(diphenylphosphine)-9 The electron injection layer is selected from at least one of 9'-spirobis[fluorene] (SPPO13), diphenyl[4-(triphenylsilyl)phenyl]phosphine oxide (TSPO1), and 2-(4'-tert-butylphenyl)-5-(4'-biphenyl)-1,3,4-oxadiazole (PBD); the electron injection layer material is selected from at least one of Yb, yttrium fluoride, Li, LiF, NaF, CeF, CsCO3, Cs, KBH4, or KH.

[0062] This application also provides a method for fabricating a light-emitting device. Please refer to [link to relevant documentation]. Figure 3 As shown, in this embodiment, the light-emitting device is prepared through the following steps:

[0063] Step S100: Provide a substrate and form a first electrode on the substrate;

[0064] Step S200: A hole functional layer is formed on the first electrode;

[0065] Step S300: A first buffer layer is formed on the hole functional layer, the first buffer layer comprising a first material with a work function greater than or equal to 5.0 eV;

[0066] Step S400: A light-emitting layer is formed on the first buffer layer, the light-emitting layer comprising a crystalline light-emitting material;

[0067] Step S500: A second buffer layer is formed on the light-emitting layer, the second buffer layer comprising a second material with a work function less than or equal to 3.8 eV;

[0068] Step S600: An electronic functional layer is formed on the second buffer layer;

[0069] In step S700, a second electrode is formed on the electronic functional layer to obtain a light-emitting device.

[0070] The light-emitting device fabrication method provided in this application provides a light-emitting device that achieves bidirectional optimization through the introduction of a buffer layer, thereby improving the injection efficiency of holes and electrons and avoiding poor contact between the light-emitting layer using crystalline light-emitting materials and other layers, which would affect the device performance. This improves the luminous efficiency of the device and increases its stability and lifespan.

[0071] In some embodiments, the step of forming a first buffer layer on the hole functional layer specifically includes:

[0072] Step S301: Provide a first solution containing the first material;

[0073] Step S302: Deposit the first solution onto the cavitation functional layer and heat it for annealing to form the first buffer layer.

[0074] In some embodiments, the step of forming a light-emitting layer on the first buffer layer specifically includes:

[0075] Step S401: Provide a second solution containing the crystalline luminescent material;

[0076] Step S402: Deposit the second solution onto the first buffer layer and heat it for annealing to form the light-emitting layer.

[0077] In some embodiments, the step of forming a second buffer layer on the light-emitting layer specifically includes:

[0078] Step S501: Provide the second material;

[0079] Step S502: The second material is vapor-deposited onto the light-emitting layer to form the second buffer layer.

[0080] In some embodiments, the first material is a metal oxide material with a work function greater than or equal to 5.0 eV; further, the first material has a work function less than or equal to 9.0 eV.

[0081] Optionally, the glass transition temperature of the crystalline luminescent material is 50℃~100℃;

[0082] Optionally, the second material is an alkaline earth metal material with a work function less than or equal to 3.8 eV, and further, the work function of the second material is greater than or equal to 1.0 eV.

[0083] In some embodiments, the first material is selected from one or more of V2O5, MoO3, and WO3.

[0084] Optionally, the general formula of the crystalline luminescent material can be referred to in the above embodiments, and it can be selected from one or more of MCP, CBP, NPB, TPD, and DPVB.

[0085] Optionally, the second material is selected from one or more of (8-hydroxyquinoline)lithium, LiF, CsF, and NaF.

[0086] In some embodiments, the first solution is obtained by taking an appropriate amount of metal oxide material with a work function greater than or equal to 5.0 eV, adding an alcohol solvent and mixing to obtain the first solution.

[0087] In some embodiments, the second solution is obtained by taking an appropriate amount of crystalline luminescent material with a glass transition temperature of 50°C to 100°C, adding an alcohol solvent and mixing to obtain the second solution.

[0088] In some embodiments, the thickness of the light-emitting layer is 30 to 40 nm, for example: any one or any two values ​​of 30 nm, 32 nm, 34 nm, 36 nm, 38 nm, and 40 nm.

[0089] Optionally, the thickness of the first buffer layer is 1 to 10 nm, for example, any one of 1 nm, 3 nm, 5 nm, 7 nm, 9 nm, 10 nm or a range formed between any two values;

[0090] Optionally, the thickness of the second buffer layer is 1 to 5 nm, for example, any one of 1 nm, 2 nm, 3 nm, 4 nm, 5 nm or a range formed between any two values.

[0091] In other embodiments, the hole functional layer includes a hole injection layer and a hole transport layer stacked together, wherein the hole injection layer is disposed on the side away from the first buffer layer; the electronic functional layer includes an electron injection layer and an electron transport layer stacked together, wherein the electron injection layer is disposed on the side away from the second buffer layer.

[0092] Based on the fabrication method of the light-emitting device provided in the above embodiments, this application embodiment exemplarily provides a fabrication method for the light-emitting device described above, specifically including the following steps:

[0093] The patterned ITO substrate was placed in acetone, cleaning solution, deionized water and isopropanol in sequence for ultrasonic cleaning. Each ultrasonic cleaning step should last for 15 minutes. After ultrasonic cleaning is completed, the ITO substrate was placed in a clean oven to dry for later use.

[0094] The surface of the dried ITO substrate was treated with ultraviolet-ozone for 5 minutes to further remove organic matter attached to the surface of the ITO substrate and improve the work function of the ITO substrate.

[0095] A PEDOT:PSS layer with a thickness of 35 nm was deposited on an ITO substrate using a solution method as a hole injection layer. The ITO substrate was then heated on a heating stage at 150°C for 30 min to remove moisture.

[0096] A PVK layer with a thickness of 20 nm was deposited on the hole injection layer as a hole transport layer by solution method, and the ITO substrate was heated on a heating stage at 125°C for 15 min to remove organic solvents.

[0097] A first material with a thickness of 1 nm was deposited on the hole transport layer using a solution method as a first buffer layer, and the ITO substrate was heated on a heating stage at 100°C for 30 min to remove the organic solvent.

[0098] A crystalline luminescent material with a thickness of 35 nm was deposited on the first buffer layer using a solution method, and the ITO substrate was heated on a heating stage at 100°C for 20 minutes to make the luminescent layer crystalline.

[0099] The ITO substrate is transferred to the evaporation chamber, and a second material is thermally evaporated on the light-emitting layer through a mask as a second buffer layer with a thickness of 1 nm.

[0100] A 20nm thick TmPyPB electron transport layer is thermally vapor-deposited onto the second buffer layer using a mask.

[0101] A LiF layer with a thickness of 1 nm was thermally vapor-deposited on the electron transport layer using a mask as an electron injection layer.

[0102] A 100nm thick Ag layer is thermally deposited on the electron transport layer using a photomask to serve as the cathode, forming a light-emitting device.

[0103] This embodiment also provides a display device, which includes the light-emitting device as described above, or the light-emitting device prepared by the method described above.

[0104] The above solution will be further explained below with reference to specific embodiments. The embodiments of the present invention are described in detail below:

[0105] Example 1 of light-emitting device

[0106] (1) Provide an ITO substrate, with a transparent conductive thin film ITO as the anode and a thickness of 50nm;

[0107] (2) Preparation of the hole injection layer:

[0108] Hole injection material PEDOT:PSS was deposited on the anode layer to form a hole injection layer with a thickness of 35 nm, and then heated on a heating stage at 150 °C for 30 min to remove moisture.

[0109] (3) Preparation of hole transport layer:

[0110] Hole transport material PVK was deposited on the hole injection layer to form a hole transport layer with a thickness of 20 nm, and then heated on a heating stage at 125 °C for 15 min.

[0111] (4) Preparation of the first buffer layer:

[0112] A clear and transparent solution of 30 mg / ml was formed by dissolving MoO3 powder in ammonia water. This solution was deposited on the hole transport layer as the first buffer material to form a first buffer layer with a thickness of 1 nm. The solution was then heated on a heating stage at 150°C for 30 min to remove moisture.

[0113] (5) Fabrication of the light-emitting layer:

[0114] MCP was dissolved in methyl benzoate to form a clear and transparent solution of 20 mg / ml. This solution was then deposited on the first buffer layer as a light-emitting layer material to form a light-emitting layer with a thickness of 35 nm. The solution was then heated on a heating stage at 100 °C for 20 min to make the light-emitting layer crystalline.

[0115] (6) Preparation of the second buffer layer:

[0116] The ITO substrate was transferred to the evaporation chamber, and lithium (8-hydroxyquinoline) was deposited on the light-emitting layer as the second buffer material to form a second buffer layer with a thickness of 1 nm.

[0117] (7) Fabrication of electron transport layer:

[0118] Electron transport material TmPyPB was vapor-deposited onto the second buffer layer to form an electron transport layer with a thickness of 20 nm.

[0119] (8) Fabrication of electron transport layer:

[0120] The electron injection material LiF was deposited on the electron transport layer to form an electron injection layer with a thickness of 1 nm;

[0121] (9) Cathode layer preparation:

[0122] The cathode material Ag is vapor-deposited onto the electron transport layer to form a cathode layer with a thickness of 100 nm, thus forming a light-emitting device.

[0123] Example 2 of light-emitting device

[0124] The difference between this embodiment and embodiment 1 is that the thickness of the first buffer material in step (4) is 5 nm.

[0125] Example 3 of light-emitting device

[0126] The difference between this embodiment and embodiment 1 is that the thickness of the first buffer material in step (4) is 10 nm.

[0127] Example 4 of light-emitting device

[0128] The difference between this embodiment and embodiment 1 is that step (4) is not performed.

[0129] Example 5 of light-emitting device

[0130] The difference between this embodiment and embodiment 2 is that step (4) is not performed.

[0131] Example 6 of light-emitting device

[0132] The difference between this embodiment and embodiment 3 is that step (4) is not performed.

[0133] Example 7 of light-emitting device

[0134] The difference between this embodiment and embodiment 1 is that step (6) is not performed.

[0135] Example 8 of light-emitting device

[0136] The difference between this embodiment and embodiment 2 is that step (6) is not performed.

[0137] Example 9 of light-emitting device

[0138] The difference between this embodiment and embodiment 3 is that step (6) is not performed.

[0139] Example 10 of light-emitting device

[0140] The difference between this embodiment and embodiment 2 is that in step (4), V2O5 is used as the first buffer material and its concentration dissolved in ammonia water is 10 mg / ml.

[0141] Example 11 of light-emitting device

[0142] The difference between this embodiment and embodiment 2 is that in step (4), WO3 is used as the first buffer material and its concentration dissolved in ammonia water is 5 mg / ml.

[0143] Example 12 of light-emitting device

[0144] The difference between this embodiment and embodiment 2 is that CBP is used as the light-emitting layer material in step (5).

[0145] Example 13 of light-emitting device

[0146] The difference between this embodiment and embodiment 2 is that NPB is used as the light-emitting layer material in step (5).

[0147] Example 14 of light-emitting device

[0148] The difference between this embodiment and embodiment 2 is that TPD is used as the light-emitting layer material in step (5).

[0149] Example 15 of light-emitting device

[0150] The difference between this embodiment and embodiment 2 is that DPVBi is used as the light-emitting layer material in step (5).

[0151] Example 16 of light-emitting device

[0152] The difference between this embodiment and embodiment 1 is that LiF is used as the second buffer material in step (6).

[0153] Example 17 of light-emitting device

[0154] The difference between this embodiment and embodiment 1 is that CsF is used as the second buffer material in step (6).

[0155] Example 18 of light-emitting device

[0156] The difference between this embodiment and embodiment 1 is that NaF is used as the second buffer material in step (6).

[0157] Comparative Example 1 of Light Emitting Devices

[0158] The difference between Comparative Example 1 and Example 1 is that steps (4) and (6) were not performed.

[0159] Tests were conducted on the above-mentioned light-emitting devices in Examples 1 to 18 and Comparative Example 1.

[0160] Test Result Analysis:

[0161] Using the IVL testing system, at 2mA / cm 2 Under constant current drive, the luminous efficiency, performance, and stability of the light-emitting device were tested, and the test results are shown in Table 1 below:

[0162]

[0163]

[0164] Table 1

[0165] Among them, V@1cd / m 2 This indicates a brightness of 1 cd / m². 2 The corresponding driving voltage at that time; EQE max This indicates the maximum EQE (reference) when measuring the IVL curve. Figure 4 (As shown); T95(h)@1000cd / m 2 This indicates that the device has an initial brightness of 1000 cd / m². 2 The light continues to illuminate until the brightness decreases to 95% of the initial brightness (950 cd / m² in this case). 2 The higher the time elapsed, the more stable the light-emitting device. (Refer to Table 1 and...) Figure 4 By comparing the luminous efficiency, performance, and stability of the light-emitting devices in Examples 1-18 with those in Comparative Example 1, it can be seen that the introduction of a buffer layer in the light-emitting device achieves bidirectional optimization, improves the injection efficiency of holes and electrons, and avoids poor contact between the crystalline light-emitting layer and other layers, which would affect the device performance. Ultimately, this effectively improves the luminous efficiency, performance, and stability of the light-emitting device. In contrast, without a buffer layer, the crystalline light-emitting layer is prone to poor contact with other layers, resulting in a significant reduction in the luminous efficiency, performance, and stability of the light-emitting device.

[0166] Obviously, the embodiments described above are only some embodiments of this application, not all embodiments. The accompanying drawings show preferred embodiments of this application, but do not limit the patent scope of this application. This application can be implemented in many different forms; rather, the purpose of providing these embodiments is to provide a more thorough and comprehensive understanding of the disclosure of this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing specific embodiments, or make equivalent substitutions for some of the technical features. Any equivalent structures made using the content of this application's specification and drawings, directly or indirectly applied to other related technical fields, are similarly within the scope of patent protection of this application.

Claims

1. A light-emitting device, comprising a first electrode, a hole-functional layer, a light-emitting layer, an electron-functional layer, and a second electrode stacked together, characterized in that, The material of the light-emitting layer is a crystalline light-emitting material; The light-emitting device further includes a first buffer layer disposed between the hole-functional layer and the light-emitting layer, wherein the material of the first buffer layer is a material with a work function greater than or equal to 5.0 eV; and / or, The light-emitting device further includes a second buffer layer disposed between the light-emitting layer and the electronic functional layer, wherein the material of the second buffer layer is a material with a work function less than or equal to 3.8 eV.

2. The light-emitting device according to claim 1, characterized in that, The glass transition temperature of the crystalline luminescent material is 50℃~100℃; and / or, The material of the first buffer layer is a metal oxide material; and / or, The material of the second buffer layer is an alkaline earth metal; and / or, The work function of the material in the first buffer layer is less than or equal to 9.0 eV; and / or, The work function of the material in the second buffer layer is greater than or equal to 1.0 eV.

3. The light-emitting device according to claim 2, characterized in that, The general formula of the crystalline luminescent material is: R1 or R2 is independently selected from one of the following structures: The asterisk (*) in the structure represents a connection site or fusion site.

4. The light-emitting device according to claim 3, characterized in that, The crystalline luminescent material is selected from one or more of MCP, CBP, NPB, TPD, TAPC, and DPVB; The structural formula of the MCP is: The structural formula of the CBP is: The structural formula of the NPB is: The structural formula of the TPD is: The structural formula of the DPVB is:

5. The light-emitting device according to any one of claims 2 to 4, characterized in that, The metal oxide material is selected from one or more of V₂O₅, MoO₃, and WO₃; and / or, The alkaline earth metal material is selected from one or more of (8-hydroxyquinoline)lithium, LiF, CsF, and NaF.

6. The light-emitting device according to claim 1, characterized in that, The thickness of the light-emitting layer is 30–40 nm; and / or, The thickness of the first buffer layer is 1–10 nm; and / or, The thickness of the second buffer layer is 1–5 nm.

7. The light-emitting device according to claim 1, characterized in that, The hole functional layer includes a stacked hole injection layer and a hole transport layer, wherein the hole injection layer is located on the side opposite to the first buffer layer; and / or, The electronic functional layer includes an electron injection layer and an electron transport layer stacked together, wherein the electron injection layer is located on the side opposite to the second buffer layer.

8. The light-emitting device according to claim 7, characterized in that, The first electrode is the anode, and the second electrode is the cathode. The first electrode and the second electrode are each independently selected from one or more of the following: metal electrodes, carbon electrodes, and doped or undoped metal oxide electrodes to form a composite electrode. Specifically, the material of the metal electrode is selected from one or more of Al, Ag, Cu, Mo, Au, Ba, Ca, and Mg; the material of the carbon electrode is selected from one or more of graphite, carbon nanotubes, graphene, and carbon fibers; and the material of the doped or undoped metal oxide electrode is selected from ITO, FTO, ATO, etc. The composite electrode material is selected from one or more of AZO, GZO, IZO, MZO, and AMO; the material of the composite electrode is selected from one or more of AZO / Ag / AZO, AZO / Al / AZO, ITO / Ag / ITO, ITO / Al / ITO, ZnO / Ag / ZnO, ZnO / Al / ZnO, TiO2 / Ag / TiO2, TiO2 / Al / TiO2, ZnS / Ag / ZnS, ZnS / Al / ZnS, TiO2 / Ag / TiO2, and TiO2 / Al / TiO2; and / or, The materials of the hole injection layer and the hole transport layer are each independently selected from 4,4'-N,N'-dicarbazolyl-biphenyl, N,N'-diphenyl-N,N'-bis(1-naphthyl)-1,1'-biphenyl-4,4”-diamine, N,N'-diphenyl-N,N'-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine, N,N'-bis(3-methylphenyl)-N,N'-bis(phenyl)-spiro, N,N'-bis(4-(N,N'-diphenyl-amino)phenyl)-N,N'-diphenylbenzidine, 4,4',4'-tris(N-carbazolyl)-triphenylamine, 4,4',4'-tris(carbazolyl-9-yl)triphenylamine, trichloroisocyanuric acid, and terbium-doped phosphate-based green... Luminescent materials, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazabenzphenanthrene, 4,4',4'-tris(N-3-methylphenyl-N-phenylamino)triphenylamine, poly[(9,9'-dioctylfluorene-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl)diphenylamine))], poly(4-butylphenyl-diphenylamine), poly[bis(4-phenyl)(4-butylphenyl)amine], polyaniline, polypyrrole, poly(p-)phenylenevinylene, poly(phenylenevinylene), poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene], poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1, [4-Phenylenevinylene], copper phthalocyanine, aromatic tertiary amines, polynuclear aromatic tertiary amines, 4,4'-bis(p-carbazolyl)-1,1'-biphenyl compounds, N,N,N',N'-tetraarylbenzidine, PEDOT, PEDOT:PSS and its derivatives, PEDOT:PSS derivatives doped with s-MoO3, poly(N-vinylcarbazole) and its derivatives, polymethacrylate and its derivatives, poly(9,9-octylfluorene) and its derivatives, poly(spirofluorene) and its derivatives, N,N'-di(naphthyl-1-yl)-N,N'-diphenylbenzidine, spironolactone (NPB), nanocrystalline diamond, microcrystalline cellulose and tetracyanoquinone dimethane, doped graphene, undoped graphene, second-doped metal oxide particles, The second undoped metal oxide particle, metal sulfide, metal selenide, and metal nitride are selected from one or more of the following: metal oxide particles, metal sulfide, metal selenide, and metal nitride; the metal oxide in the second doped metal oxide particle and the metal oxide in the second undoped metal oxide particle are each independently selected from one or more of MoO3, WO3, NiO, CrO3, CuO, Cu2O, and V2O5; the doping element in the second doped metal oxide particle is selected from one or more of Mo, W, Ni, Cr, Cu, and V; the metal sulfide is selected from one or more of CuS, MoS3, and WS3; the metal selenide is selected from one or more of MoSe3 and WSe3; and the metal nitride is selected from p-type gallium nitride; and / or, The electron transport layer material is selected from at least one of doped or undoped metal oxides and organic electron transport materials; the doped or undoped metal oxide is selected from at least one of doped or undoped zinc oxide, tin oxide, titanium oxide, and zirconium oxide, and the doped element includes at least one of aluminum, magnesium, lithium, manganese, yttrium, lanthanum, copper, nickel, zirconium, cerium, and gadolinium; the organic electron transport material is selected from organic fullerenes, 4,6-bis(3,5-di(3-pyridinyl)phenyl)-2-methylpyrimidine (B3PYMPM), 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBI), 1,3,5-tris[(3-pyridinyl)-3-phenyl]benzene (TmPyPB), 1,3-bis(3,5-dipyridinyl-3-ylphenyl)benzene (B3PyPB), and bis[2-(2-pyridinyl)phenol. The electron injection layer is selected from at least one of beryllium (Bepp2), 3-(biphenyl-4-yl)-5-(4-tert-butylphenyl)-4-phenyl-4H-1,2,4-triazole (TAZ), tri-(8-hydroxyquinoline)aluminum (Alq3), 2,9-dimethyl-4,7-biphenyl-1,10-phenanthroline (BCP), 4,7-diphenyl-1,10-phenanthroline (BPhen), 2,7-bis(diphenylphosphineoxy)-9,9'-spirobis[fluorene] (SPPO13), diphenyl[4-(triphenylsilyl)phenyl]phosphineoxy (TSPO1), and 2-(4'-tert-butylphenyl)-5-(4'-biphenyl)-1,3,4-oxadiazole (PBD); the material of the electron injection layer is selected from at least one of Yb, yttrium fluoride, Li, LiF, NaF, CeF, CsCO3, Cs, KBH4, or KH.

9. A method for fabricating a light-emitting device, characterized in that, Includes the following steps: A substrate is provided, on which a first electrode is formed; A hole-functional layer is formed on the first electrode; A first buffer layer is formed on the hole functional layer, the first buffer layer comprising a first material with a work function greater than or equal to 5.0 eV; A light-emitting layer is formed on the first buffer layer, the light-emitting layer comprising a crystalline light-emitting material; A second buffer layer is formed on the light-emitting layer, the second buffer layer comprising a second material with a work function less than or equal to 3.8 eV; An electronic functional layer is formed on the second buffer layer; A second electrode is formed on the electronic functional layer to obtain a light-emitting device.

10. The method for fabricating a light-emitting device according to claim 9, characterized in that, The step of forming a first buffer layer on the hole functional layer specifically includes: providing a first solution containing the first material, depositing the first solution on the hole functional layer, and heating and annealing to form the first buffer layer; and / or, The step of forming a light-emitting layer on the first buffer layer specifically includes: providing a second solution containing the crystalline light-emitting material, depositing the second solution on the first buffer layer, and heating and annealing to form the light-emitting layer; and / or The step of forming a second buffer layer on the light-emitting layer specifically includes: providing the second material, depositing the second material onto the light-emitting layer by vapor deposition to form the second buffer layer; and / or, The first material is a metal oxide material; and / or, The glass transition temperature of the crystalline luminescent material is 50℃~100℃; and / or, The second material is an alkaline earth metal; and / or, The first material is selected from one or more of V2O5, MoO3, and WO3; and / or, The crystalline luminescent material is selected from one or more of MCP, CBP, NPB, TPD, and DPVB; and / or, The second material is selected from one or more of (8-hydroxyquinoline)lithium, LiF, CsF, and NaF; and / or, The thickness of the light-emitting layer is 30–40 nm; and / or, The thickness of the first buffer layer is 1–10 nm; and / or, The thickness of the second buffer layer is 1–5 nm; and / or, The work function of the material in the first buffer layer is less than or equal to 9.0 eV; and / or, The work function of the material in the second buffer layer is greater than or equal to 1.0 eV.

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