Display panel and display apparatus

Abstract

The present application relates to a display panel and a display apparatus. The display panel comprises a tandem organic light-emitting device. The tandem organic light-emitting device comprises: a first electrode and a second electrode, which are arranged opposite each other; at least two organic light-emitting units, which are stacked and arranged between the first electrode and the second electrode; and a charge-generation layer, which connects two adjacent organic light-emitting units, wherein the charge-generation layer comprises a carrier supply layer and an electron trapping layer that are stacked, and the carrier supply layer is not doped. The display panel in the present application comprises a carrier supply layer and an electron trapping layer that are independently arranged in layers, such that the current of the tandem organic light-emitting device is increased, and the lateral conductivity of a charge-generation layer is weakened, thereby reducing a drive voltage and a lateral leakage current, thus solving the problems such as light leakage and afterimage of the display panel, which can better realize the generation and separation of carriers, and improve the performance of the display panel. Further provided in the present application is a display apparatus at least having the corresponding advantages of the display panel.

Description

Display panel and display device

[0001] Cross-reference to related applications

[0002] This application claims priority to Chinese Patent Application No. 202410918344.4, filed on July 9, 2024, entitled “Display Panel and Display Device”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of display technology, and more particularly to a display panel and a display device. Background Technology

[0004] With the rapid development of display technology, people have increasingly higher requirements for display panels. Display panels generally have advantages such as ultra-thinness, self-illumination, wide viewing angle, fast response, high luminous efficiency, good temperature adaptability, simple manufacturing process, low driving voltage, and low energy consumption. They have been widely used in industries such as flat panel displays, flexible displays, solid-state lighting, and automotive displays.

[0005] Display panels can incorporate various structures, such as stacked structures. In a stacked device structure, multiple layers of organic light-emitting units are stacked between the anode and cathode. Between adjacent light-emitting components is a charge-generation layer (CGL) for charge generation and movement; the charge-generation layer requires low driving voltage and high efficiency.

[0006] In the structure of traditional multilayer devices, the CGL layer often uses an organic material doped film to achieve the generation and separation of charge carriers. This results in large lateral leakage current and problems such as brightness skipping and ghosting in the product. Summary of the Invention

[0007] This application provides a display panel and a display device. The display panel includes a stacked organic light-emitting device, wherein the charge generation layer includes a carrier supply layer and an electron trapping layer that are independently arranged in layers. This increases the current in the stacked organic light-emitting device, weakens the lateral conductivity of the charge generation layer, reduces lateral leakage current, solves problems such as dim lighting and ghosting in the display panel, and can better realize the generation and separation of carriers, thereby improving the performance of the display panel.

[0008] In a first aspect, embodiments of this application provide a display panel including a stacked organic light-emitting device, the stacked organic light-emitting device comprising:

[0009] The first and second electrodes are positioned relative to each other;

[0010] At least two organic light-emitting units are stacked and disposed between the first electrode and the second electrode;

[0011] And a charge generation layer connecting two adjacent organic light-emitting units;

[0012] The charge generation layer includes a carrier supply layer and an electron trapping layer stacked together. The carrier supply layer is not doped and is used to provide holes and electrons. The electron trapping layer is used to receive electrons from the carrier supply layer and transfer the electrons to the electron transport layer of the organic light-emitting unit adjacent to the electron trapping layer.

[0013] Secondly, embodiments of this application provide a display device, including the display panel of the first aspect.

[0014] The display panel and display device of this application embodiment employ a stacked organic light-emitting device (CGL), which includes a charge generation layer connecting two adjacent organic light-emitting units. The charge generation layer comprises a carrier supply layer and an electron trapping layer, which are independently configured in layers. The carrier supply layer is undoped, changing the traditional organically doped CGL structure to a novel undoped CGL structure. The carrier supply layer in the charge generation layer provides holes and electrons. The electrons can be effectively captured and transported by the electron trapping layer, allowing them to be smoothly injected into adjacent organic light-emitting units and adjacent layers. Holes in the carrier supply layer can be smoothly injected into adjacent organic light-emitting units and adjacent layers through a layer on the opposite side of the electron trapping layer. This improves carrier generation and separation, facilitates carrier transport along the light emission direction, increases the current in the stacked organic light-emitting device, reduces the driving voltage, and further weakens carrier transport within the charge generation layer itself. This reduces lateral leakage current, solves problems such as screen flickering and ghosting in the display panel, and improves device efficiency. Attached Figure Description

[0015] The features, advantages, and technical effects of exemplary embodiments of this application will now be described with reference to the accompanying drawings.

[0016] Figure 1 shows a schematic diagram of a display panel structure provided in an embodiment of this application;

[0017] Figure 2 shows a schematic diagram of a stacked organic light-emitting device provided in an embodiment of this application;

[0018] Figure 3 shows a schematic diagram of another stacked organic light-emitting device provided in an embodiment of this application;

[0019] Figure 4 shows a schematic diagram of a charge generation layer structure provided in this application;

[0020] Figure 5 shows a schematic diagram of a charge generation layer structure provided in an embodiment of this application;

[0021] Figure 6 shows a schematic diagram of another charge generation layer structure provided in an embodiment of this application;

[0022] Figure 7 shows a schematic diagram of the structure of another stacked organic light-emitting device provided in an embodiment of this application;

[0023] Figure 8 shows a schematic diagram of the structure of another stacked organic light-emitting device provided in an embodiment of this application;

[0024] Figure 9 shows a top view of a display panel provided in an embodiment of this application;

[0025] Figure 10 shows the width of the first opening inside a subpixel and the width of the second opening between subpixels in the display panel provided in the embodiment of this application;

[0026] Figure 11 shows a schematic diagram of another display panel structure provided in an embodiment of this application;

[0027] Figure 12 shows a partial topographic view of the substrate used for lateral leakage current testing according to an embodiment of this application;

[0028] Figure 13 shows a comparison of leakage current in the embodiment and the comparative example.

[0029] Explanation of reference numerals in the attached figures: 100, display panel; 101, substrate; 102, encapsulation layer; 103, adhesive film; 104, dam-shaped insulating film; 105, passivation film; 200, multilayer organic light-emitting device; 2, anode; 3, hole injection layer; 4, first organic light-emitting unit; 41, first hole transport layer; 42, first buffer layer; 43, first light-emitting layer; 44, first hole blocking layer; 45, first electron transport layer; 5, charge generation layer; 501, N-type charge generation layer; 502, P-type charge generation layer; 50, metal layer; 5 1. Electron trapping layer; 52. Carrier supply layer; 6. Second organic light-emitting unit; 61. Second hole transport layer; 62. Second buffer layer; 63. Second light-emitting layer; 64. Second hole blocking layer; 65. Second electron transport layer; 7. Electron injection layer; 8. Cathode; 400. First charge generation layer; 500. Second charge generation layer; 600. Third organic light-emitting unit; 601. Third light-emitting layer; 700. Evaporation area; 800. Hollowed-out area; 9. Sub-pixel; 900. First solid portion; 910. Second solid portion.

[0030] In the accompanying drawings, the same parts use the same reference numerals. The drawings are not drawn to scale. Detailed Implementation

[0031] The features and exemplary embodiments of various aspects of this application will be described in detail below. To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain this application and not to limit it. For those skilled in the art, this application can be implemented without some of these specific details. The following description of the embodiments is merely to provide a better understanding of this application by illustrating examples.

[0032] It should be noted that in this article, the terms "first," "second," etc., are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features.

[0033] The terms “multiple,” “various,” and “several” refer to two or more (including two). Similarly, “multiple sets” refers to two or more (including two sets), and “multiple pieces” refers to two or more (including two pieces).

[0034] The terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase “comprising…” does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0035] To better understand this application, the display panel of the embodiment of this application will be described in detail below with reference to Figures 1 to 13.

[0036] Figure 1 shows a schematic diagram of the structure of a display panel as an example.

[0037] Please refer to Figure 1. The display panel 100 includes: a substrate 101 and an encapsulation layer 102 disposed opposite to each other, and a stacked organic light-emitting device disposed on the side of the substrate 101 facing the encapsulation layer 102. The stacked organic light-emitting device includes an anode 2, a cathode 8, a first organic light-emitting unit 4, a second light-emitting unit 6, and a charge-generating layer 5. The display panel 100 also includes:

[0038] An adhesive film 103 and a passivation film 105 are located between the cathode 8 and the encapsulation layer 102, with the passivation film 105 disposed on the side closer to the cathode 8;

[0039] A dam-shaped insulating film 104 is located between the anode 2 and the passivation film 105.

[0040] For example, the substrate 101 can be made of materials such as glass. Alternatively, it can be made of a flexible material, such as a light-transmitting material like polyimide (PI). A driving circuit is provided on one side of the surface of the substrate 101. The stacked organic light-emitting device can include electrodes, multiple organic light-emitting units, a charge generation layer, etc. The driving circuit is electrically connected to the stacked organic light-emitting device and controls the luminous intensity of the stacked organic light-emitting device.

[0041] Figure 2 is a schematic diagram of a stacked organic light-emitting device provided in an embodiment of this application.

[0042] Please refer to Figure 2. The stacked organic light-emitting device includes: an anode 2 and a cathode 8 disposed opposite to each other; at least two organic light-emitting units disposed in stack, namely a first organic light-emitting unit 4 and a second organic light-emitting unit 6; and a charge-generating layer 5 connecting two adjacent organic light-emitting units.

[0043] The first electrode or the second electrode can be arbitrarily anode 2. When the first electrode is anode 2, the corresponding second electrode is cathode 8.

[0044] In some alternative embodiments, the anode 2 material may include metals (e.g., copper, gold, silver, iron, chromium, nickel, manganese, palladium, platinum, etc., and alloys thereof), metal oxides (e.g., indium oxide, zinc oxide, indium tin oxide (ITO), indium zinc oxide (IZO), etc.), and conductive polymers (e.g., polyaniline, polypyrrole, poly(3-methylthiophene), etc.). In addition to the above materials and combinations thereof, other known materials suitable for anode 2 may also be included.

[0045] In some alternative embodiments, the cathode 8 may comprise a metallic material, such as aluminum, magnesium, silver, indium, tin, titanium, and alloys thereof. The cathode 8 may comprise a multilayer cathode 8 formed by a composite of one or more layers of metal oxides and metal halides (e.g., LiF / Al, LiO2 / Al, BaF2 / Al, etc.). In addition to the above materials and combinations thereof, other known materials suitable for making the cathode 8 are also included.

[0046] The stacked organic light-emitting device 200 may include multiple light-emitting units (EMLs) of the same color or multiple light-emitting units (EMLs) of different colors. When the organic light-emitting units emit light of the same color, a stacked organic light-emitting device with a single emission color can be obtained, such as a single blue, green, or red light; while when the organic light-emitting units in the stacked organic light-emitting device emit different colors, white light can be emitted by mixing the different colors of light emitted from different organic light-emitting units.

[0047] For example, the stacked organic light-emitting device 200 achieves white light by mixing blue light emitted from the first light-emitting unit and yellow-green light emitted from the second light-emitting unit. Thus, white light is generated by mixing the light emitted from each layer. Of course, organic light-emitting units of different colors can also be stacked as needed to achieve the stacked organic light-emitting device emitting more colors of light.

[0048] The stacked organic light-emitting device 200 is a top-emitting device that emits light from the first light-emitting unit and the second light-emitting unit along the bottom direction. However, the stacked organic light-emitting device 200 according to the embodiments of this application is not limited to the above example and may be a bottom-emitting type or a dual-emitting type.

[0049] The organic light-emitting unit includes an emissive layer (EML), and the organic light-emitting unit may optionally include one or more of the following: an electron transport layer (ET), a hole blocking layer (HBL), a hole transport layer (HTL), a buffer layer (Prime), and a hole injection layer (HIL).

[0050] The stacked organic light-emitting device 200 also includes a charge generation layer 5 between the organic light-emitting units. The material in the charge generation layer 5 (CGL) generates electrons and holes when stimulated by an electric field, thereby forming charge pairs. These charge pairs are then separated and injected into two adjacent organic light-emitting units respectively, exciting the organic molecules in these two organic light-emitting units, resulting in light emission.

[0051] Figure 3 illustrates a stacked organic light-emitting device 200 as an example, comprising a cathode 8, an electron injection layer 7 (EIL), a second organic light-emitting unit 6, a charge generation layer 5 (CGL), a first organic light-emitting unit 4, an anode 2, and a substrate 101 stacked sequentially. The second organic light-emitting unit 6 includes a second electron transport layer 65 (ET2), a second hole blocking layer 64 (HBL2), a second light-emitting layer 63 (EML2), a second buffer layer 62 (Prime2), and a second hole transport layer 61 (HTL2). The first organic light-emitting unit 4 includes a first electron transport layer 45 (ET1), a first hole blocking layer 44 (HBL1), a first light-emitting layer 43 (EML1), a first buffer layer 42 (Prime1), a first hole transport layer 41 (HTL1), and a first hole injection layer 3 (HIL1). The charge generation layer 5 includes an electron trapping layer 51 and a carrier supply layer 52.

[0052] The layer structures in the first organic light-emitting unit 4 and the second organic light-emitting unit 6 can be reasonably configured according to requirements, such as adjusting the thickness of any layer or removing any layer. For example, the thicknesses of the first electron transport layer 45 (ETL1), the first hole blocking layer 44 (HBL1), the first buffer layer 42 (Prime1), the first hole transport layer 41 (HTL1), the second electron transport layer 65 (ETL2), the second hole blocking layer 64 (HBL2), the second buffer layer 62 (Prime2), the second hole transport layer 61 (HTL2), and the first hole injection layer 3 (HIL1) are all easily achievable and will not be elaborated here. The thicknesses of the first hole blocking layer 4444 and the second hole blocking layer 64 can be adjusted according to carrier balance or one or both of the aforementioned hole blocking layers can be removed. The first hole blocking layer 4444 and the second hole blocking layer 64 can be 5nm.

[0053] In some alternative implementations, the sum of the thicknesses of HB1 and HB2 is a preset value, such as 50 Å. The thickness of either HB1 or HB2 can be adjusted or either layer can be removed as needed. For example, the thickness of HB1 is 50 Å, and HB2 is not specified.

[0054] In some alternative embodiments, the total thickness of the charge generation layer 5 and the second hole transport layer 61 is 65 nm. The thickness of either the charge generation layer 5 or the second hole transport layer 61 can be adjusted or removed as needed.

[0055] In some alternative embodiments, the first light-emitting layer 43 and the second light-emitting layer 63 may each contain one or more of the host material and the guest light-emitting material.

[0056] The host material is any material that can be used in the luminescent layer. The host material can coexist with the guest luminescent material in the luminescent layer to emit light. The absorption spectra of the host material and the guest luminescent material have a large overlap, so the host luminescent material can be mixed as a common luminescent material.

[0057] In some optional embodiments, the guest luminescent material may include one or more of fluorescent materials, phosphorescent materials, thermally activated delayed fluorescence materials, and aggregation-induced emission materials. Optionally, the guest material is a heavy metal complex electrophosphorescent material.

[0058] In existing technologies, charge generation layers often employ organic material doping to achieve carrier generation and separation, i.e., the film layer is prepared by mixing at least two types of materials.

[0059] Figure 4 shows a schematic diagram of the structure of a conventional charge generation layer 5. The conventional charge generation layer 5 generally includes an N-type charge generation layer 501 and a P-type charge generation layer 502. Specifically, the N-type charge generation layer 501 comprises an N-type material and a first dopant material. The N-type material contains compounds with sp2 hybridized N groups, such as pyridyl, o-phenanthroline (phenanthroline), pyrazinyl, pyrimidinyl, pyridazinyl, triazinyl, quinolinyl, isoquinolinyl, quinoxalinyl, quinazolinyl, and benzopyridazinyl. The first dopant material is generally any one or a combination of Yb, Li, Cs, and Cs₂CO₃. The P-type charge generation layer 502 comprises a P-type material and a second dopant material. The P-type material includes any one or a combination of at least two of aromatic amines and carbazole compounds. The second dopant material includes any one or a combination of at least two of the following groups: cyano, fluorine, chlorine, and trifluoromethyl. The P-type charge generation layer 501 is typically used to generate holes and electrons, with holes conducting to the adjacent organic light-emitting layer and electrons conducting to the N-type charge generation layer; the N-type charge generation layer 502 is typically used to transfer electrons transferred from the P-type charge generation layer to the adjacent organic light-emitting layer.

[0060] The conventional charge generation layer fabricated in this way has the following problems: The fabrication process requires complex multi-source vacuum co-evaporation, which introduces dopants that are prone to diffusion. As mass production and device operation time increase, dopants can diffuse to neighboring layers, altering the ratio of the two types of materials in the charge generation layer. This leads to CGL failure and device degradation during operation. In particular, the P-type charge generation layer, where the second dopant has strong diffusion properties, can affect the hole transport efficiency when it diffuses into adjacent organic light-emitting units (OLEDs), especially the hole transport layer. Furthermore, the diffusion of dopants alters the ratio of P-type material to the second dopant, affecting the electron and hole generation efficiency of the P-type charge generation layer, thus reducing the OLED's operating efficiency and further degrading device performance.

[0061] Further, as shown in Figure 2, the charge generation layer 5 (CGL) is located in the stacked organic light-emitting device 200 and can connect multiple organic light-emitting units. These units are discontinuous in the direction perpendicular to the light emission direction, while the charge generation layer 5 is continuous in this direction. Taking the light emission direction as the longitudinal direction, the direction perpendicular to the light emission direction is the transverse direction. Since different stacked organic light-emitting devices are connected to different driving circuits, and the light-emitting layers of different devices are disconnected, but the charge generation layer of different devices can be shared, it is a common layer. Therefore, the charge generation layer is usually continuous in the transverse direction. Because the material constituting the charge generation layer 5 itself has excellent carrier transport capability, especially the transverse carrier transport capability, and because the charge generation layer 5 is continuous in this direction, charge will transfer through this common layer to positions corresponding to other organic light-emitting units, thus causing changes in brightness or color of adjacent stacked organic light-emitting devices.

[0062] According to embodiments of this application, the charge generation layer 5 includes a stacked carrier supply layer 52 and an electron trapping layer 51. The carrier supply layer 52 provides holes and electrons and is not doped. The electron trapping layer 51 receives electrons from the carrier supply layer 52 and transfers them to the electron transport layer of the organic light-emitting unit adjacent to the electron trapping layer 51. In some optional embodiments, along the light emission direction of the stacked organic light-emitting device 200, the electron trapping layer 51 is disposed on the side of the carrier supply layer 52 away from the light emission direction.

[0063] Figure 5 shows a schematic diagram of the charge generation layer according to an embodiment of this application. The charge generation layer 5 includes a stacked carrier supply layer 52 and an electron trapping layer 51. The carrier supply layer 52 and the electron trapping layer 51 are prepared from different materials.

[0064] Research revealed that the charge generation layer 5 is formed by independently configuring the carrier supply layer 52 and the electron capture layer 51, neither of which is doped. Doping, as understood, involves introducing small amounts of other elements or compounds into the host material to improve its properties. Lack of doping means the absence of such elements or compounds. For example, the carrier supply layer 52 might be formed by vapor deposition of a single material or by vapor deposition of a mixture of several materials with similar properties or functions, but without doping. The same understanding applies to the electron capture layer, which will not be repeated here. It is important to note that impurities may appear in the carrier supply layer or electron capture layer due to material purity, the choice of vapor deposition environment, and the subsequent operation of the stacked light-emitting device. The impurity content can be controlled below 100 ppm.

[0065] The undoped carrier supply layer and the independent separation of the carrier supply layer and electron trapping layer avoid problems such as diffusion and doping ratio changes caused by doping with two types of materials in the same layer, thus improving the stability of the charge generation layer. The carrier supply layer 52 in the charge generation layer 5 provides holes and electrons. These electrons can be effectively captured and transported by the electron trapping layer 51, allowing them to be smoothly injected into adjacent organic light-emitting units or adjacent layers. Holes in the carrier supply layer 52 can be smoothly injected into adjacent organic light-emitting units or adjacent layers, thereby better realizing the generation and separation of carriers. Rapid vertical conduction of electrons and holes reduces lateral migration, thus weakening lateral conductivity, reducing lateral leakage current, solving problems such as screen flickering and ghosting in the display panel, and lowering the driving voltage. Reduced leakage current means more input electrical energy is effectively converted into light output, thereby improving the current efficiency and overall effectiveness of the device.

[0066] Furthermore, the carrier supply layer 52 and the electron capture layer 51 are set separately, which can improve the problem of reduced device stability caused by the instability of the charge generation layer 5, improve the stability of the stacked organic light-emitting device 200, and thus improve the performance of the display panel.

[0067] In some alternative implementations, the HOMO energy level of the carrier supply layer 52 is in the range of -5.2 eV to -4.6 eV, and can be selected as a HOMO energy level between -5.1 eV and -4.9 eV.

[0068] In some optional embodiments, the electron trapping layer 51 is a layer composed of p-type charge-doped material, and the LUMO energy level of the electron trapping layer 51 ranges from -5.5 eV to -4.9 eV. It can be selected as a LUMO energy level between -5.4 eV and -5.0 eV. The electron trapping layer 51 can be a transition metal compound or a compound containing phenyl or pyrrole groups. Specifically, it can be 2,3,5,6-tetrafluoro-7,7,8,-tetracyanodimethyl-p-benzoquinone (F4TCNQ), NDP-9 (2,3,5,6-tetramethyl-N-methylpyrrolo[3,2-6]pyrrolo[2',3':5,6]tetraazine-1,4-diamine), HATCN, or materials such as FeCl3, MoO3, and WO3. The materials used for the electron trapping layer 51 have deeper LUMO energy levels, which facilitates the electron trapping layer 51 in capturing electrons from the carrier supply layer 52, thereby achieving electron transport.

[0069] In some alternative implementations, the absolute value of the energy level difference α between the HOMO level of the carrier supply layer 52 and the LUMO level of the electron trapping layer 51 satisfies: |α|≤+0.3eV.

[0070] Optionally, the energy difference α between the HOMO energy level of the carrier supply layer 52 and the LUMO energy level of the electron trapping layer 51 can be any value or a range of combinations thereof from -0.30 eV, -0.25 eV, -0.20 eV, -0.15 eV, -0.10 eV, -0.05 eV, 0.05 eV, 0.10 eV, 0.15 eV, 0.20 eV, 0.25 eV, and 0.30 eV.

[0071] The HOMO energy level of the carrier supply layer 52 and the LUMO energy level of the electron trapping layer 51 can be determined or detected by the types of compounds contained in the carrier supply layer 52 or the electron trapping layer 51, respectively.

[0072] The absolute value of the energy level difference α between the HOMO energy level of the carrier supply layer 52 and the LUMO energy level of the electron trapping layer 51 is within the above range, which is conducive to the transition of electrons from the orbit of the carrier supply layer 52 to the orbit of the electron trapping layer 51, further improving the transmission of electrons in the light emission direction, and further weakening the lateral conductivity of the charge generation layer 5, thereby reducing lateral leakage current and solving problems such as dimming and ghosting in the display panel.

[0073] When the energy level difference 'a' is greater than 0.3 eV or less than -0.30 eV, the deviation between the HOMO energy level of the carrier supply layer 52 and the LUMO energy level of the electron trapping layer 51 increases. This indicates that electrons or holes encounter a large energy barrier when crossing the energy level gap, leading to reduced hole and electron injection efficiency and consequently affecting current transport. Lower injection efficiency results in less charge recombination, thus reducing luminescence efficiency. Furthermore, to overcome the large energy level difference, a higher voltage needs to be applied, which increases the device's operating voltage.

[0074] In some alternative implementations, the absolute value of the HOMO energy level of the carrier supply layer 52 is greater than the absolute value of the LUMO energy level of the electron trapping layer 51.

[0075] According to the embodiments of this application, the absolute value of the HOMO energy level of the carrier supply layer 52 is greater than the absolute value of the LUMO energy level of the electron trapping layer 51. This is beneficial for electrons in the carrier supply layer 52 to transition to the electron trapping layer 51, and also beneficial for the electron trapping layer 51 to trap electrons from the carrier supply layer 52. After receiving electrons, the electron trapping layer 51 conducts the electrons to the adjacent organic light-emitting units, and the holes in the carrier supply layer 52 are conducted to the adjacent organic light-emitting units, thereby increasing the supply of carriers to multiple organic light-emitting units, realizing the transfer of carriers, forming current, thereby reducing lateral leakage current and improving device efficiency.

[0076] In the embodiments of this application, the carrier supply layer 52 and the electron trapping layer 51 are prepared by using different compounds, so that the absolute value of the HOMO energy level of the carrier supply layer 52 is greater than the absolute value of the LUMO energy level of the electron trapping layer 51.

[0077] The HOMO energy level of the carrier supply layer 52 and the LUMO energy level of the electron trapping layer 51 can be detected using methods commonly used in the art. For example, the HOMO energy level can be measured by ultraviolet photoelectron spectroscopy; the LUMO energy level can be measured by photoelectron spectroscopy combined with inverse photoelectron spectroscopy; or the HOMO and LUMO energy levels of the organic molecular material in the stacked organic light-emitting device 200 can be predicted and calculated by cyclic voltammetry and density functional theory.

[0078] In some alternative embodiments, the charge carrier supply layer 52 comprises materials containing triarylamine, carbazole, and derivative groups thereof. Specifically, the charge carrier supply layer 52 comprises 4,4'4"-tris(3-methylphenylamino)triphenyl (MTDATA), 4,4',4"-tris(N,N-diphenyl-amino)triphenylamine (NATA), 4,4',4"-tris(N-(naphthyl-1-yl)-N-phenyl-amino)triphenylamine (1T-NATA), 4,4',4"-tris(N-(naphthyl-2-yl)-N-phenyl-amino)triphenylamine (2TNATA), 1,3,5-tris[4-(diphenylamino)phenyl]benzene (TDAPB), 2,2'-dimethyl-N,N'-di-1-naphthyl-N,N'-diphenyl[1,1'-biphenyl]-4,4'-diamine (α-N PD), 4,4',4”-tris(carbazole-9-yl)triphenylamine (TCTA), 1,3-dicarbazole-9-ylbenzene (mCP), 4,4'-di(9-carbazole)biphenyl (CBP), 3,3'-di(N-carbazole)-1,1'-biphenyl (mCBP), 4,4'-cyclohexylbis[N,N-di(4-methylphenyl)aniline (TAPC), N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine (α-NPB), N,N'-di(naphthyl-2-yl)-N,N'-di(phenyl)biphenyl-4,4'-diamine (NPB), poly(3,4-ethylenedioxythiophene) (PEDOT), N -(biphenyl-4-yl)-9,9-dimethyl-N-(4-(9-phenyl-9H-carbazole-3-yl)phenyl)-9H-fluorene-2-amine polyvinylcarbazole (PVK), 4,4'-bis(N-carbazole)-1,1'-biphenyl (CBP), poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)-benzidine] (poly-TPD), poly[(9,9-dioctylfluorene-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl)diphenylamine))] (TFB), 1,1-bis[4-(N,N'-di(p-tolyl)amino)phenyl)cyclohexane (TAPC), 3,5-bis(9H-carbazole-9-yl) -N,N-Diphenylaniline (DCDPA), N-(biphenyl-4-yl)-9,9-dimethyl-N-(4-(9-phenyl-9H-carbazol-3-yl)phenyl)-9H-fluorene-2-amine, N-(biphenyl-4-yl)-N-(4-(9-phenyl-9H-carbazol-3-yl)phenyl)biphenyl-4-amine, N-([1,1'-biphenyl]-4-yl)-9,9-dimethyl-N-(4-(9-phenyl-9H-carbazol-3-yl)phenyl)-9H-fluorene-2-amine, N4,N4,N4',N4'-tetra([1,1'-biphenyl]-4-yl)-[1,1'-biphenyl]-4,4'-diamine)9-phenyl-3,Materials such as 9-bicarbazole (CCP) and their combinations, but not limited to these materials, have shallow HOMO levels. After gaining sufficient energy in the carrier supply layer 52, electrons in these materials can easily undergo transitions.

[0079] In some alternative implementations, the thickness of the carrier supply layer 52 is [missing information]. to

[0080] In some alternative embodiments, the thickness of the electron trapping layer 51 is [missing information]. to

[0081] In some alternative embodiments, the sum of the thickness of the carrier supply layer 52 and the thickness of the electron trapping layer 51 is _____. Optional

[0082] Optionally, the sum of the thickness of the carrier supply layer 52 and the thickness of the electron trapping layer 51 can be [missing information]. Any ratio or range of values ​​in the range.

[0083] The sum of the thickness of the carrier supply layer 52 and the thickness of the electron trapping layer 51 is within the above range, which can effectively generate and inject electrons and holes into adjacent layers, helping to improve the luminous efficiency and brightness of the device; it can ensure a uniform electric field distribution, thereby promoting uniform charge transport; and it can also reduce interface defects, thereby improving the smoothness and efficiency of charge transport.

[0084] In some alternative implementations, the thickness of the carrier supply layer 52 is greater than the thickness of the electron trapping layer 51.

[0085] According to the embodiments of this application, the thickness of the carrier supply layer 52 is greater than the thickness of the electron trapping layer 51. On the one hand, this ensures efficient charge injection and transport in the carrier supply layer 52. For example, it can avoid the charge transport path in the carrier supply layer 52 being too long, thereby increasing the transport time and resistance, or the carrier supply layer 52 being too thin and not providing enough carriers, resulting in reduced injection efficiency. On the other hand, the thickness of the electron trapping layer 51 is appropriate, which is conducive to trapping and transporting electrons. This can improve the recombination efficiency of the charge generation layer 5, thereby improving the luminous efficiency and brightness, and reducing energy loss.

[0086] In some alternative embodiments, the ratio of the thickness of the carrier supply layer 52 to the thickness of the electron trapping layer 51 is 100:(20-45).

[0087] Optionally, the ratio of the thickness of the carrier supply layer 52 to the thickness of the electron trapping layer 51 can be any ratio or a range of combinations thereof from 100:20, 100:25, 100:26, 100:27, 100:28, 100:29, 100:30, 100:31, 100:32, 100:33, 100:34, 100:35, 100:36, 100:37, 100:38, 100:39, 100:40, 100:41, 100:42, 100:43, and 100:45.

[0088] According to the embodiments of this application, the ratio of the thickness of the carrier supply layer 52 to the thickness of the electron trapping layer 51 is within the above range, which can further improve the recombination efficiency of the charge generation layer 5, thereby improving the luminous efficiency and brightness and reducing energy loss.

[0089] In some alternative embodiments, the charge generation layer 5 further includes a carrier transport layer disposed on the side of the electron trapping layer 51 opposite to the carrier supply layer 52.

[0090] A carrier transport layer is disposed between the electron trapping layer 51 and the organic light-emitting unit. This carrier transport layer may include the N-type charge generation layer 501 found in conventional CGL structures. The primary function of the N-type charge generation layer 501 is to facilitate electron injection and transport. By doping with electronic materials, the N-type layer exhibits high electronic conductivity, enabling electrons to be effectively injected and transported to the light-emitting layer. N-type doping can significantly reduce the work function of the material, making it easier for electrons to be injected from the cathode into other organic layers, thereby improving device efficiency.

[0091] In some alternative implementations, the carrier transport layer may include a metal layer.

[0092] Figure 6 shows a schematic diagram of the charge generation layer 5 in another embodiment.

[0093] Referring to Figure 6, the charge generation layer 5 includes a stacked carrier supply layer 52, an electron trapping layer 51, and a metal layer 50. The carrier transport layer may include a metal layer 50, which is disposed on the side of the electron trapping layer 51 opposite to the carrier supply layer 52 and adjacent to the electron transport layer of the organic light-emitting unit. The metal layer 50 has free electrons and good electron conductivity. Its placement on the side of the electron trapping layer 51 opposite to the carrier supply layer 52 helps reduce the interface barrier between the light-emitting unit connected to the metal layer 50 and the electron trapping layer 51, thereby facilitating carrier transport. This configuration further reduces lateral leakage current, solves problems such as screen flickering and ghosting in the display panel, and further improves the current efficiency and overall effectiveness of the device.

[0094] In some alternative embodiments, the metal layer 50 has a discontinuous structure. As an example, the metal layer 50 in FIG6 includes columnar metal with gaps between the columnar metal, illustrating that the metal layer 50 has a discontinuous structure.

[0095] According to the embodiments of this application, the metal layer 50 has a discontinuous structure, which is beneficial to reduce the lateral conductivity of the metal layer 50 (current is formed by conduction within this layer), which is beneficial to solve the problem of lateral leakage current in the charge generation layer 5; it can also improve the carrier transport capability of the metal layer 50 in the light emission direction of the device, improve the stability of the stacked organic light-emitting device 200, and thus improve the performance of the display panel.

[0096] In some alternative implementations, the metal layer 50 includes multiple island-shaped regions.

[0097] According to embodiments of this application, the metal layer 50 may exist in an island-like (columnar) structure, rather than a continuous thin film, with certain gaps between the islands (columns). Alternatively, the metal layer 50 may have a continuous layered structure at the bottom, with uneven surfaces above the bottom, tending towards flatness, and certain gaps between the uneven surfaces.

[0098] In some alternative implementations, the discontinuous structure consists of multiple regions, the shapes of which include one or more of the following: strip-shaped, circular, elliptical, and regular polygonal.

[0099] According to embodiments of this application, a metal layer 50 with a discontinuous structure can further improve the electron transport capability in the light emission direction. The discontinuous structure reduces lateral leakage current; in other words, it allows current to be generated within the layer. The discontinuous structure can have many different morphologies. Having morphologies within the aforementioned range for multiple regions can further improve the electron transport capability of the metal layer 50 in the light emission direction and also reduce lateral leakage current.

[0100] In some alternative implementations, the work function M of the metal element in metal layer 50 is in the range of M≤4.3eV.

[0101] Optionally, the work function M can be any value or a range of combinations thereof from 0.1eV, 0.3eV, 0.5eV, 1.0eV, 1.5eV, 2.0eV, 2.5eV, 3.0eV, 3.5eV, 4.0eV, and 4.3eV.

[0102] According to the embodiments of this application, the work function M of the metal element in the metal layer 50 can be determined based on the type and content of the metal element in the metal layer 50. When the work function M of the metal element in the metal layer 50 is within the aforementioned range, it is beneficial to reduce the interface barrier between the light-emitting unit connected to the metal layer 50 and the electron trapping layer 51, thereby facilitating electron transitions and enabling electron transport.

[0103] The work function of a metallic element represents the minimum energy required to release an electron from the metal's surface. The work function of a metallic element can be obtained by examining relevant literature or detected using methods commonly used in the field, such as ultraviolet photoelectron spectroscopy (UVP) and Kelvin probe microanalysis.

[0104] In some alternative embodiments, the metal element of the metal layer 50 includes at least one of Ag, rare earth metals, Group IA metals, and Group IIA metals.

[0105] For example, the metal element of the metal layer 50 can be any value or range of the composition of Y, Gd, La, Ce, Ca, Mg, and Sr.

[0106] In some alternative embodiments, the metal layer 50 is composed of Ag. The Ag-formed metal layer 50 has a discontinuous structure, such as an island structure. During fabrication, when the Ag film is deposited at a relatively thin thickness, the surface morphology of silver islands naturally forms, achieving the silver island morphology without additional processes. The Ag-formed metal layer 50 is beneficial for enhancing electron injection and improving electron transport efficiency. The relatively thin metal layer 50 with a silver island morphology helps reduce the overall device thickness, lowers the overall device internal resistance, and also improves the overall device efficiency.

[0107] In some alternative implementations, the metal layer 50 is composed of Yb.

[0108] The metal layer 50 formed using Yb has a discontinuous structure, such as an island structure. During fabrication, the efficiency of electron transport is improved by utilizing the thinner Yb film deposition.

[0109] In some alternative embodiments, the metal layer 50 is composed of Ag and Yb.

[0110] The metal layer 50 formed using Ag and Yb has a discontinuous structure, such as an island structure. During preparation, Ag and Yb are co-evaporated. When the Ag film is deposited in a thin layer, the surface morphology of silver islands is naturally formed, achieving the silver island morphology without the need for additional processes. Ag plays the role of forming the island morphology, while Yb plays the role of electron injection light-emitting units.

[0111] According to an embodiment of this application, the metal layer 50 is composed of Ag and Yb. Ag helps to form a discontinuous structure, such as an island structure, which is beneficial to reduce the lateral conductivity of the metal layer 50 and to solve the problem of lateral leakage of charge generation layer 5.

[0112] In some alternative embodiments, the molar ratio of Ag to Yb in the metal layer 50 is (1-2):1.

[0113] For example, the molar ratio of Ag to Yb can be any ratio or range thereof from 1:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1, to 2:1. Controlling the molar ratio of Ag to Yb in the metal layer 50 within the above range helps to form a discontinuous structure, such as an island structure, which is beneficial to reducing the lateral conductivity of the metal layer 50, helping to solve the problem of lateral leakage current in the charge generation layer 5, and also improving the stability of the organic electroluminescent device.

[0114] Figure 7 illustrates a stacked organic light-emitting device (OLED) as an example. The stacked OLED 200 includes a cathode 8, an electron injection layer 7 (EIL), a second organic light-emitting unit 6, a charge generation layer 5 (CGL), a first organic light-emitting unit 4, an anode 2, and a substrate 101, stacked sequentially. The charge generation layer 5 includes a metal layer 50, an electron trapping layer 51, and a carrier supply layer 52.

[0115] In some optional embodiments, in order to further reduce the interface barrier between the light-emitting unit and the electron trapping layer 51 and realize electron transport, and in order to form a discontinuous structure and reduce the lateral leakage problem of the charge generation layer 5, the thickness d of the metal layer 50 is selected within the following range:

[0116] Optionally, the thickness d of the metal layer 50 can be... Any ratio or range of values ​​in the range.

[0117] In addition, the metal layer 50 with island-shaped regions is usually thinner, and the thin metal layer 50 can also reduce lateral leakage problems.

[0118] In this embodiment, the material, thickness, energy level, and other characteristics of any of the above-mentioned anode 2, first organic light-emitting unit 4, charge generation layer 5, second organic light-emitting unit 6, electron injection layer 7, cathode 8, metal layer 50, electron capture layer 51, and carrier supply layer 52 are independently applicable to this embodiment.

[0119] Figure 8 shows a stacked organic light-emitting device as an example. The stacked organic light-emitting device 200 includes a substrate 101, an anode 2, a first organic light-emitting unit 4, a first charge-generating layer 400, a second organic light-emitting unit 6, a second charge-generating layer 500, a third organic light-emitting unit 600, an electron injection layer 7, and a cathode 8 stacked sequentially.

[0120] In this embodiment, the material, thickness, energy level, and other characteristics of any of the above-mentioned anode 2, first organic light-emitting unit 4, second organic light-emitting unit 6, electron injection layer 7, cathode 8, metal layer 50, electron trapping layer 51, and carrier supply layer 52 are independently applicable to this embodiment. The charge generation layer 5 of the above embodiments is independently applicable to the first charge generation layer 400 and the second charge generation layer 500 of this embodiment. The first organic light-emitting unit 4 and the second organic light-emitting unit 6 of the above embodiments are independently applicable to the first organic light-emitting unit 4, the second organic light-emitting unit 6, and the third organic light-emitting unit 600 of this embodiment.

[0121] Figure 9 shows a top view of a color display panel 100 as an example. R, B, and G represent sub-pixels 9, where R represents the red sub-pixel 9, B represents the blue sub-pixel 9, and G represents the green sub-pixel 9. In the stacked organic light-emitting device 200, the organic light-emitting units are dispersed perpendicular to the light emission direction, thus the boundaries of these organic light-emitting units on the color display panel 100 are the sub-pixels R, B, and G 9.

[0122] In some alternative implementations, the display panel includes a plurality of sub-pixels 9, each sub-pixel 9 including a stacked organic light-emitting device 200, a metal layer 50 having a first opening inside the sub-pixel 9, and a second opening between two adjacent sub-pixels 9, the width of the second opening being greater than the width of the first opening.

[0123] Figure 10 shows a partial top view of a display panel according to an embodiment of this application.

[0124] Perpendicular to the light emission direction, the metal layer 50 in the multiple stacked organic light-emitting devices 200 is cut. Since the metal layer is a continuous common layer in the multiple stacked organic light-emitting devices 200, a partial top view of the display panel as shown in Figure 10 is obtained. In this top view, sub-pixels 9 and discontinuous structures within the metal layer 50 of the sub-pixels 9 can be observed on the surface of the display panel 100: The metal layer 50 includes a first solid portion 900 and a groove between the first solid portions 900. This groove is a gap in the original discontinuous structure of the metal layer. The width of the groove between two first solid portions 900 is the width d1 of the first opening. A metal layer 50 is included between two sub-pixels 9. This metal layer also has a second solid portion 910 and a groove between the second solid portions 910. The width of the groove between two second solid portions 910 is the width d2 of the second opening. The first solid portions 900 and the second solid portions 910 can be made of metal. In the display panel 100 or the stacked organic light-emitting devices 200, this metal layer 50 can connect multiple dispersed organic light-emitting units.

[0125] In some alternative embodiments, the internal metal layer 50 of the sub-pixel 9 is at least discontinuous. This discontinuous structure of the internal metal layer 50 of the sub-pixel 9 is advantageous in two ways: firstly, it further enhances the electron transport capability along the light emission direction within the sub-pixel 9; secondly, it reduces leakage current in the internal metal layer 50.

[0126] In some alternative embodiments, the display panel includes a plurality of sub-pixels 9, each sub-pixel 9 including a stacked organic light-emitting device 200, the plurality of sub-pixels 9 including a first sub-pixel 9 and a second sub-pixel 9 with different emission colors, and the first sub-pixel 9 and the second sub-pixel 9 including different numbers of stacked organic light-emitting units.

[0127] Please refer to Figure 9. The display panel includes multiple subpixels 9. A subpixel 9 can be understood as a unit displaying a color area in the display panel. For example, if a specific subpixel 9 needs to emit white light, multiple common red, blue, and green organic light-emitting units can be stacked to mix and emit light. For example, a white light emission effect can be achieved. Furthermore, referring to Figure 11, the light-emitting layers are dispersed or discontinuous in the direction perpendicular to the light emission direction. Therefore, the light emission effect of the display panel can be further adjusted by setting different numbers of organic light-emitting units or different numbers of light-emitting layers in the stacked organic light-emitting device 200.

[0128] Accordingly, the display panel includes a first sub-pixel and a second sub-pixel with different emission colors. The number of stacked first organic light-emitting units 4 and second organic light-emitting units 6 can be different, so that the first sub-pixel and the second sub-pixel have comparable display brightness when the emission colors are different.

[0129] For example, multiple sub-pixels 9 may have different emission colors, and the number of first organic light-emitting units 4 and second organic light-emitting units 6 stacked may differ. For example, if any sub-pixel 9 has low luminous efficiency, multiple organic light-emitting units can be stacked to improve its luminous efficiency.

[0130] In some optional implementations, the first sub-pixel includes a first organic light-emitting unit, the second sub-pixel includes a second organic light-emitting unit, the light emission color of the first sub-pixel is blue, and the number of stacked first organic light-emitting units 4 is greater than the number of stacked second organic light-emitting units 6.

[0131] Blue light emission requires higher energy and is generally less stable than red and green luminescent materials. Therefore, the external quantum efficiency and luminous efficiency of blue light are generally lower than those of red and green light.

[0132] When the first sub-pixel emits blue light and the second sub-pixel emits red, green, or other colors, the number of stacked first organic light-emitting units 4 can be greater than the number of stacked second organic light-emitting units 6, thereby improving the external quantum efficiency and luminous efficiency of blue and balancing the luminous effect of blue and other colors in the display panel.

[0133] In some optional embodiments, the display panel includes a plurality of sub-pixels 9, each sub-pixel including a stacked organic light-emitting device, the plurality of sub-pixels including a third sub-pixel and a fourth sub-pixel with different emission colors, the third sub-pixel including a third organic light-emitting unit 600, and the fourth sub-pixel including a fourth organic light-emitting unit; the third sub-pixel and the fourth sub-pixel include a common charge generation layer 50; along the light emission direction, the thickness of the charge generation layer 50 between two adjacent third organic light-emitting units 600 is greater than the thickness of the charge generation layer 50 between two adjacent fourth organic light-emitting units.

[0134] According to an embodiment of this application, the thickness of the charge generation layer 5 between two adjacent third organic light-emitting units 600 stacked sequentially along the light emission direction is greater than the thickness of the charge generation layer 5 between two adjacent fourth organic light-emitting units. This can be due to differences in the thickness of the electron trapping layer 51 or the carrier supply layer 52. Generally, when the charge generation layer 5 includes a metal layer 50, the thickness of the metal layer 50 can also vary, but the thickness of the metal layer 50 is generally relatively thin, which is beneficial for forming a discontinuous structure.

[0135] The thickness of the charge generation layer 5 between two adjacent third organic light-emitting units 600 is greater than the thickness of the charge generation layer 5 between two adjacent fourth organic light-emitting units. This setting can be based on the different total number of layers in the device; it can be based on the different efficiencies of electron and hole generation and transport, which have a certain impact on the light emission efficiency, thereby improving the light emission efficiency of the sub-pixel corresponding to the charge generation layer 5; this setting can also be based on the different light emission colors or light emission brightness of different sub-pixels, by setting different thicknesses of the charge generation layer 5 shared by different pixels 9, thereby balancing the light emission brightness and light emission effect of multiple sub-pixels, thus helping to solve the problem of different light transmittance and light emission brightness in different areas due to different light emission colors, solving the problem of the light emission effect of the third and fourth sub-pixels affecting the normal visual perception of the human eye, and thus balancing the light emission effect among multiple sub-pixels 9 of the display panel.

[0136] Figure 11 shows a schematic diagram of another display panel structure provided in one embodiment of this application.

[0137] Referring to Figure 11, and further, in conjunction with Figures 1 and 2, the display panel 100 includes a substrate 101, an anode 2, a cathode 8, a first light-emitting layer 43, a second light-emitting layer 63, and a third light-emitting layer 601. The first light-emitting layer 43, the second light-emitting layer 63, and the third light-emitting layer 601 are connected by any of the aforementioned connecting layers, which will not be elaborated further here. The first light-emitting layer 43, the second light-emitting layer 63, and the third light-emitting layer 601 are located in a microcavity structure. The first light-emitting layer 43, the second light-emitting layer 63, and the third light-emitting layer 601 are each located at a specific optical position within their respective microcavity structures. In some optional embodiments, the first light-emitting layer 43 (EML1) is placed at the λ / 4 position of the microcavity. This means that EML1 is located at one-quarter of the wavelength of light in the microcavity, at an antinode, where the light intensity is stronger, effectively enhancing the luminous efficiency of EML1. The second light-emitting layer 63 (EML2) is placed at the 3λ / 4 position of the microcavity. This means that EML2 is located at three-quarters of the wavelength of light in the microcavity, at the antinode, where the light intensity is also stronger, which can effectively enhance the luminous efficiency of EML2.

[0138] In summary, by placing the aforementioned light-emitting layer at the positions with the strongest light intensity (λ / 4 and 3λ / 4), the light field intensity is the strongest, and the number of excited photons is the largest, which can effectively improve the light emission efficiency. It can be used to emit light of different colors. By precisely adjusting the position and wavelength of the light-emitting layer, the color performance and brightness of the device can be optimized, thereby improving the overall light output efficiency.

[0139] In some alternative embodiments, the charge generation layer 5 includes a plurality of stacked carrier supply layers 52 and electron trapping layers 51.

[0140] Multiple carrier supply layers 52 and electron trapping layers 51 may be present in the charge generation layer 5, which includes multiple sets of carrier supply layers 52 and electron trapping layers 51. For example, 3-5 sets of carrier supply layers 52 and electron trapping layers 51 may be repeated. In some optional embodiments, the charge generation layer 5, consisting of multiple stacked carrier supply layers 52 and electron trapping layers 51, may have a thickness of 90-100 angstroms.

[0141] This can be understood as follows: the charge generation layer 5 is located between any two adjacent organic light-emitting units. The charge generation layer 5 may include multiple stacked carrier supply layers 52 and electron trapping layers 51. This arrangement is beneficial for improving electron transport, thereby further improving the recombination efficiency of the charge generation layer 5, and thus improving luminous efficiency and brightness while reducing energy loss; it can also improve the luminous efficiency and brightness of the device by stacking multiple organic light-emitting units.

[0142] In some alternative implementations, the third sub-pixel 9 emits light in blue.

[0143] For example, the third organic light-emitting unit 600 in the third sub-pixel 9 may include a first light-emitting layer 43, a second light-emitting layer 63, etc. When the light emitted by 90% to 100% of the light-emitting layers of the third organic light-emitting unit 600 is blue light, the color of the light emitted by the third sub-pixel 9 is blue.

[0144] In some alternative implementations, the display panel includes a plurality of sub-pixels 9, any one of which may include a substrate 101 and at least one stacked organic light-emitting device 200.

[0145] The multilayer organic light-emitting device 200 can be fabricated using methods known in the art. An exemplary fabrication method includes: forming an anode 2 on a substrate 101, forming a multilayer organic thin film layer on the anode 2, and forming a cathode 8 on the organic thin film layer. The organic thin film layer can be formed using known film-forming methods such as evaporation, sputtering, spin coating, dipping, and ion plating.

[0146] In this application, the thickness of the metal layer 50, the thickness of the carrier supply layer 52, and the thickness of the electron trapping layer 51 can be measured during the fabrication process or in the multilayer organic light-emitting device 200 product using methods known in the art, such as scanning electron microscopy, transmission electron microscopy, and elliptic polarization measurement.

[0147] It should be noted that the display device provided in this application embodiment has the beneficial effects of the display panel in any of the foregoing embodiments. For details regarding the beneficial effects of the display device, please refer to the foregoing description of the display panel; further details will not be repeated in this application embodiment.

[0148] Examples of display devices include, but are not limited to, mobile phones, computers, televisions, smartwatches, smart cars, VR or AR headsets, etc., and this application does not specifically limit them.

[0149] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on weight, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0150] Example 1

[0151] This embodiment provides a multilayer electroluminescent organic light-emitting device, the specific fabrication steps of which include:

[0152] (1) Cut the glass substrate into 50mm×50mm×0.7mm pieces, sonicate them in isopropanol and deionized water for 30min respectively, and then clean them under ozone for 10min; mount the glass substrate with ITO anode obtained by magnetron sputtering onto the vacuum deposition equipment.

[0153] (2) Preparation of hole injection layer: under a vacuum of 2×10 -6 At Pa, compounds HT-1 and PD-1 were vacuum-deposited on the ITO anode layer, with HT-1 as the host material and PD-1 as the dopant material. The mass ratio of HT-1 to PD-1 was 96:4, and the thickness was 10 nm, serving as a hole injection layer.

[0154] (3) Preparation of the first hole transport layer: The compound HTL-1 was vacuum-deposited on the hole injection layer as the first hole transport layer with a thickness of 20 nm.

[0155] (4) Vacuum evaporation of the first light-emitting layer on the first hole transport layer: organic compound BH-1 is used as the main material and BD-1 is used as the dopant material. The mass ratio of BH-1 to BD-1 is 98:2 and the thickness of the first light-emitting layer is 20nm.

[0156] (5) Preparation of the first hole blocking layer: Compound HB-1 is vacuum-deposited on the first light-emitting layer as the first hole blocking layer with a thickness of 5 nm;

[0157] (6) Preparation of the first electron transport layer: Vacuum evaporation of compounds ET-1 and Alq3 on the first hole blocking layer as the first electron transport layer, with a mass ratio of ET-1 to Alq3 of 1:1 and a thickness of 10 nm;

[0158] (7) Preparation of electron trapping layer: Compound P-1 was vacuum-deposited on the first electron transport layer as an electron trapping layer with a thickness of 30 Å;

[0159] (8) Preparation of carrier supply layer: Compound H-1 was vacuum-deposited on the electron trapping layer as a carrier supply layer with a thickness of 100 angstroms;

[0160] (9) Preparation of the second hole transport layer: Compound HT-1 is vacuum-deposited on the carrier supply layer as the second hole transport layer. In this embodiment, the total thickness of the carrier supply layer, the electron trapping layer and the second hole transport layer is controlled to be 65 nm.

[0161] (10) Preparation of the second light-emitting layer: Vacuum evaporation of the second light-emitting layer on the second hole transport layer, using compound BH-1 as the host material and BD-1 as the dopant material, with a mass ratio of BH-1 to BD-1 of 98:2 and a thickness of 20nm.

[0162] (11) Preparation of the second hole blocking layer: Compound HB-1 is vacuum-deposited on the second light-emitting layer as the second hole blocking layer with a thickness of 5 nm;

[0163] (12) Preparation of the second electron transport layer: Vacuum evaporation of compounds ET-1 and Alq3 on the second hole blocking layer as the second electron transport layer, with a mass ratio of ET-1 to Alq3 of 1:1 and a thickness of 30 nm;

[0164] (13) Preparation of electron injection layer: Yb is vacuum-deposited on the second electron transport layer as an electron injection layer with a thickness of 1 nm;

[0165] (14) Preparation of cathode: A magnesium-silver electrode is vacuum-deposited on the electron injection layer as the cathode, with a Mg to Ag mass ratio of 1:9 and a thickness of 14 nm;

[0166] (15) Preparation of capping layer: Compound CPL-1 with a thickness of 70 nm is vacuum evaporated on the cathode as a capping layer to obtain the Tandem OLED device.

[0167] Examples 2-1 to 2-3

[0168] The difference between this embodiment and embodiment 1 is that the compound H-1 used in the carrier supply layer in step (8) is replaced with equal amounts of H-2, H-3 and H-4, as shown in Table 1.

[0169] Examples 2-4 to Examples 2-6

[0170] The difference between this embodiment and embodiment 1 is that the compound P-1 used in the electron trapping layer in step (7) is replaced with equal amounts of P-2, P-3 and P-4, as shown in Table 1.

[0171] Examples 3-1 to 3-4

[0172] The difference between this embodiment and embodiment 1 is that the thickness of the carrier supply layer in step (8) or the electron trapping layer in step (7) is different, and the specific thickness is shown in Table 1.

[0173] Example 4-1

[0174] The difference between this embodiment and Embodiment 1 is that: after the first electron transport layer is prepared in step 6, silver is vacuum-deposited to obtain a metal layer with a thickness of 16 angstroms, which is a discontinuous structure. Then, compound P-1 with a thickness of 30 angstroms is vacuum-deposited on the metal layer as an electron trapping layer. Next, compound H-1 with a thickness of 100 angstroms is vacuum-deposited on the electron trapping layer as a carrier supply layer 52. This step is consistent with Embodiment 1. In this embodiment, the total thickness of the carrier supply layer, electron trapping layer, metal layer and second hole transport layer is controlled to be 65 nm.

[0175] Examples 4-2 to 5-4

[0176] The difference between this embodiment and embodiment 4-1 is that the composition or thickness of the metal layer is different. The specific composition and thickness are shown in Table 1. In this embodiment, the total thickness of the carrier supply layer, electron trapping layer, metal layer and second hole transport layer is controlled to be 65nm.

[0177] Comparative Example 1

[0178] The difference between this comparative example and Example 1 is that the preparation of the charge generation layer is different. The carrier supply layer 52 and the electron trapping layer 51 are not prepared. First, NCGL-1 and Yb are vacuum co-deposited on the first electron transport layer 45. The mass ratio of NCGL-1 to Yb is 97:3, and the thickness is 10 nm, which serves as the N-type charge generation layer. Then, compound P-1 and compound H-1 are co-deposited on the N-type charge generation layer. The mass ratio of P-1 to H-1 is 1:9, and the thickness is 10 nm, which serves as the P-type charge generation layer. The total thickness of the charge generation layer including the P-type charge generation layer and the N-type charge generation layer and the second hole transport layer is 65 nm, as shown in Table 2.

[0179] Comparative Example 2

[0180] The difference between this comparative example and Comparative Example 1 is as follows: After the first electron transport layer 45 is prepared in step 6, silver is vacuum-deposited to obtain a metal layer 50 with a thickness of 16 Å. Then, NCGL-1 and Yb are vacuum-deposited on Ag with a mass ratio of 97:3 and a thickness of 10 nm, serving as an N-type charge generation layer. Compounds P-1 and H-1 are co-deposited on the N-type charge generation layer with a mass ratio of 9:1 and a thickness of 10 nm, serving as a P-type charge generation layer. The total thickness of the charge generation layer and the second hole transport layer, including the P-type charge generation layer, the N-type charge generation layer, and the metal layer, is 65 nm, as shown in Table 2.

[0181] The compound structures used in the Tandem OLED devices of the above embodiments or comparative examples are as follows:

[0182] Device performance testing

[0183] 1) Operating voltage and current efficiency testing; the stacked organic light-emitting devices prepared in the examples and comparative examples were tested for current at different voltages using a Keithley 2365A digital nanovoltmeter, and then the current density of the devices at different voltages was obtained by dividing the current by the emitting area; the brightness and radiant energy flux density of the devices at different voltages were tested using a Konicaminolta CS-2000 spectroradiometer; based on the current density and brightness of the devices at different voltages, the efficiency at the same current density (10mA / cm²) was obtained. 2 The operating voltage V and current efficiency BI (Cd / A / CIEy) are used to determine the operating voltage V and current efficiency BI (Cd / A / CIEy).

[0184] The operating voltage of Comparative Example 1 is recorded as 100%. The value of the operating voltage of the embodiment or comparative example = operating voltage of the embodiment / operating voltage of Comparative Example 1 × 100%.

[0185] The current efficiency measured in Comparative Example 1 is recorded as 100%. The current efficiency value of the Example or Comparative Example = Current efficiency of the Example or Comparative Example / Current efficiency of Comparative Example 1 × 100.

[0186] A lower operating voltage means that the device requires less electrical energy to operate under the same conditions. This can reduce power consumption, improve energy efficiency, and extend battery life.

[0187] Current efficiency refers to the effective output of light or other forms of output that a device can produce given a current input. High current efficiency means that, with the same input current, the device can output more light or achieve higher performance.

[0188] Power consumption typically refers to the energy consumed or output by a device per unit time. For multilayer organic light-emitting devices (MLDs), a relatively lower operating voltage and relatively higher current efficiency can reduce the power consumption of MLDs, resulting in higher brightness or higher luminous efficiency.

[0189] 2) Device drift voltage: at 20mA / cm 2 The high-temperature lifetime LT95 of the device was tested at 85°C. The drift voltage (ΔV, the difference in operating voltage before and after lifetime LT95, where ΔV = operating voltage after lifetime - operating voltage before lifetime, in V) was calculated based on the 1sd operating voltage before and after lifetime LT95. With the drift voltage of Comparative Example 1 as 100%, the drift voltage value of the Example or Comparative Example = (drift voltage of Example or Comparative Example / drift voltage of Comparative Example 1) × 100%. The magnitude of the drift voltage reflects the stability of the device.

[0190] 3) Lateral leakage current test: The glass substrate of the multilayer electroluminescent device in the above embodiments or comparative examples was replaced with a substrate having the structure shown in Figure 12 for fabrication. The partial morphology of the substrate is shown in Figure 12, where the darker area represents the vapor deposition area 700 where each multilayer electroluminescent device is deposited; this vapor deposition area 700 is the solid portion. The lighter area represents the hollow area 800 of the substrate body. After device fabrication, a voltage of -10V to +10V was applied to both sides of the two electrodes. The current of the devices in the embodiments and comparative examples under different voltages was tested using a Keithley 2365A digital nanovoltmeter. The leakage current of Comparative Example 1 at 10V was recorded as 100%. The leakage current value of the embodiment or comparative example (relative magnitude of leakage current under the same conditions) = leakage current of the embodiment or comparative example / leakage current of Comparative Example 1 × 100%. The results are shown in Table 1 and Figure 13.

[0191] Based on the data from the embodiments and Comparative Example 1, it can be seen that the device with the novel CGL structure, which employs a layered and independently configured carrier supply layer and electron capture layer, exhibits a lower operating voltage and higher current efficiency, thus improving device performance. The embodiments show a smaller drift voltage compared to Comparative Example 1, indicating that this charge generation layered structure improves device stability. The embodiments also exhibit a smaller lateral leakage current compared to the comparative example, indicating that more input electrical energy is effectively converted into light output, improving the device's current efficiency and overall performance.

[0192] Furthermore, Examples 4-1 to 5-4 employ novel CGL structures consisting of a carrier supply layer, an electron trapping layer, and a metal layer. Compared to Example 1, the addition of the metal layer results in Example 4-1 exhibiting a lower operating voltage and higher current efficiency, thus improving device performance. Examples 4-1 to 5-4 also show lower lateral leakage current compared to Example 1, indicating that more input electrical energy is effectively converted into light output, thereby improving device current efficiency and overall performance. In Example 5-3, with Ag and Yb metal layers in a 1:1 mass ratio and a thickness of 10 angstroms, this device exhibits the lowest operating voltage and highest current efficiency among Examples 4-1 to 5-4, resulting in the highest overall device performance. Example 5-3 also shows the lowest lateral leakage current, demonstrating optimal current efficiency and overall performance.

[0193] Compared to Comparative Example 2, Example 4-1 employs a novel CGL structure with independently layered carrier supply and electron capture layers. Therefore, Example 4-1 exhibits a lower operating voltage and higher current efficiency, thus improving device performance. Example 4-1 also shows a smaller drift voltage compared to Comparative Example 2, indicating that this charge-generating layered structure improves device stability. Furthermore, Example 4-1 has a smaller lateral leakage current compared to the Comparative Example, demonstrating that more input electrical energy is effectively converted into light output, thereby improving the device's current efficiency and overall performance.

[0194] Figure 13 shows a comparison of leakage current for Embodiment 1, Embodiments 4-1 and 5-3, and Comparative Example 1, illustrating that the multilayer organic light-emitting devices of Embodiments 1, 4-1, and 5-3 of this application have relatively lower leakage current compared to the device of Comparative Example 1. In Embodiment 1, compared to the multilayer light-emitting device of Comparative Example 1, the charge generation layer is constructed by independently configuring the carrier supply layer and the electron capture layer, resulting in a relatively lower leakage current. The charge generation layer of the multilayer light-emitting device of Embodiment 4-1 includes a discontinuous metal layer, further reducing leakage current compared to Embodiment 1. In Embodiment 5-3, the metal layer uses Ag and Yb with a thickness of 16 angstroms, further reducing leakage current in the device.

[0195] Although this application has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of this application. In particular, the technical features mentioned in the various embodiments can be combined in any manner, provided there is no structural conflict. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A display panel, wherein, The device includes a stacked organic light-emitting device, wherein the stacked organic light-emitting device comprises: The first and second electrodes are positioned relative to each other; At least two organic light-emitting units are stacked and disposed between the first electrode and the second electrode; And a charge generation layer connecting two adjacent organic light-emitting units; The charge generation layer includes a carrier supply layer and an electron trapping layer stacked together. The carrier supply layer is not doped and is used to provide holes and electrons. The electron trapping layer is used to receive the electrons from the carrier supply layer and transfer the electrons to the electron transport layer of the organic light-emitting unit adjacent to the electron trapping layer.

2. The display panel according to claim 1, wherein, The absolute value of the energy level difference 'a' between the HOMO level of the carrier supply layer and the LUMO level of the electron trapping layer satisfies: |a|≤+0.3eV.

3. The display panel according to claim 1, wherein, The charge generation layer further includes a carrier transport layer, which is disposed on the side of the electron trapping layer opposite to the carrier supply layer.

4. The display panel according to claim 3, wherein, The carrier transport layer includes a metal layer disposed on the side of the electron trapping layer opposite to the carrier supply layer and adjacent to the electron transport layer of the organic light-emitting unit.

5. The display panel according to claim 4, wherein, The metal layer has a discontinuous structure.

6. The display panel according to claim 4, wherein, The work function M of the metal element in the metal layer has a range of M≤4.3eV.

7. The display panel according to claim 4, wherein, The metal elements in the metal layer include one or more of Ag, rare earth metals, Group IA metals, and Group IIA metals.

8. The display panel according to claim 7, wherein, The metal layer is composed of Ag and Yb.

9. The display panel according to claim 8, wherein, The molar ratio of Ag to Yb in the metal layer is (1-2):

1.

10. The display panel according to claim 4, wherein, The thickness d of the metal layer can be within the range that satisfies:

11. The display panel according to claim 1, wherein, The sum of the thickness of the carrier supply layer and the thickness of the electron trapping layer is 12. The display panel according to claim 11, wherein, The thickness of the carrier supply layer is greater than the thickness of the electron trapping layer.

13. The display panel according to claim 12, wherein, The ratio of the thickness of the carrier supply layer to the thickness of the electron trapping layer is 100:(20-45).

14. The display panel according to claim 4, wherein, The display panel includes a plurality of sub-pixels, each sub-pixel including a stacked organic light-emitting device, the metal layer having a first opening inside the sub-pixel, the metal layer having a second opening between two adjacent sub-pixels, the width of the second opening being greater than the width of the first opening.

15. The display panel according to claim 1, wherein, The charge generation layer includes multiple stacked carrier supply layers and electron trapping layers.

16. The display panel according to claim 1, wherein, The display panel includes multiple sub-pixels, each sub-pixel including stacked organic light-emitting devices. The multiple sub-pixels include a first sub-pixel and a second sub-pixel with different emission colors, and the number of stacked organic light-emitting units in the first sub-pixel and the second sub-pixel is different.

17. The display panel according to claim 16, wherein, The first sub-pixel includes a first organic light-emitting unit, the second sub-pixel includes a second organic light-emitting unit, the first sub-pixel emits blue light, and the number of stacked first organic light-emitting units is greater than the number of stacked second organic light-emitting units.

18. The display panel according to any one of claims 1-17, wherein, The display panel includes multiple sub-pixels, each sub-pixel including a stacked organic light-emitting device (OLED). The multiple sub-pixels include a third sub-pixel and a fourth sub-pixel with different emission colors. The third sub-pixel includes a third organic light-emitting unit (OLED), and the fourth sub-pixel includes a fourth OLED. The third sub-pixel and the fourth sub-pixel include a common charge generation layer. Along the light emission direction, the thickness of the charge generation layer between two adjacent third OLEDs is greater than the thickness of the charge generation layer between two adjacent fourth OLEDs.

19. The display panel according to claim 18, wherein, The third sub-pixel emits light in blue.

20. A display device, wherein, Includes the display panel as described in claims 1-19.

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