Display panel, display device and electronic equipment

Abstract

The invention provides a display panel, a display module and electronic equipment, the display panel comprises a plurality of light-emitting devices arranged at intervals and an electric connection layer, each light-emitting device comprises a cathode layer, an anode layer and at least two light-emitting units, the cathode layer is arranged in a stacked mode, the anode layer is arranged on a substrate, and the at least two light-emitting units are arranged between the cathode layer and the anode layer; wherein a charge generation layer is arranged between every two adjacent light-emitting units, and every two adjacent light-emitting devices are spaced through an isolation structure. The electrical connection layer covers the cathode layers of the plurality of light-emitting devices, and the plurality of cathode layers are electrically connected through the electrical connection layer. In the display panel, the plurality of light-emitting devices are arranged at intervals through the isolation structures, so that transverse leakage current between pixels can be reduced, and the problem of pixel crosstalk of the display panel can be relieved; according to the display panel, the cathode layers of the light-emitting devices arranged at intervals are electrically connected through the electric connection layer, so that the cathodes of the display panel have low resistance, the potential has good continuity, the voltage of the light-emitting devices is reduced, and the display panel has good display performance.

Description

Technical Field

[0001] This disclosure relates to the field of display technology, and more particularly to a display panel, display device, and electronic device. Background Technology

[0002] Compared to traditional OLEDs (Organic Light Emitting Diodes), Tandem OLEDs are formed by connecting multiple traditional OLEDs in series through a charge generating layer (CGL). They have advantages such as high luminous efficiency, long lifespan, and low power consumption.

[0003] Because lateral leakage current between pixels is prone to occur in tandem OLEDs, which can lead to pixel crosstalk in low-brightness scenarios, isolation structures are usually set between adjacent light-emitting devices to isolate the charge generation layers of adjacent light-emitting devices and reduce lateral leakage current between pixels.

[0004] However, because the thickness of tandem OLEDs is relatively small, and the thickness of the isolation structure cannot be stably controlled within a small range, the isolation structure is very likely to penetrate the cathodes that connect adjacent light-emitting devices, causing the operating voltage of the tandem OLED to rise and resulting in the display panel failing to display properly. Summary of the Invention

[0005] To overcome the problems existing in the related technologies, this disclosure provides a display panel, a display device, and an electronic device.

[0006] According to a first aspect of this disclosure, a display panel is provided, the display panel comprising:

[0007] A plurality of spaced-apart light-emitting devices are provided, each of the light-emitting devices including a stacked cathode layer, an anode layer disposed on the substrate, and at least two light-emitting units disposed between the cathode layer and the anode layer, wherein a charge-generating layer is disposed between adjacent light-emitting units; wherein adjacent light-emitting devices are spaced apart by an isolation structure.

[0008] An electrical connection layer covers the cathode layers of a plurality of light-emitting devices, and the plurality of cathode layers are electrically connected through the electrical connection layer.

[0009] In some embodiments of this disclosure, the electrical connection layer includes at least one transparent conductive layer.

[0010] In some embodiments of this disclosure, the electrical connection layer further includes a light extraction layer disposed on the side of the electrical connection layer away from the cathode layer.

[0011] In some embodiments of this disclosure, in each of the light-emitting devices, the charge generation layer includes a first charge generation layer near the anode layer and a second charge generation layer near the cathode layer;

[0012] Each pair of adjacent light-emitting units includes a first light-emitting unit near the anode layer and a second light-emitting unit near the cathode layer. The first light-emitting unit includes a first electron transport layer, and the second light-emitting unit includes a first hole transport layer.

[0013] The first charge generation layer is disposed adjacent to the first electron transport layer, and the first charge generation layer and the first electron transport layer are homojunction structures; the second charge generation layer is disposed adjacent to the first hole transport layer, and the second charge generation layer and the first hole transport layer are homojunction structures.

[0014] In some embodiments of this disclosure, the first charge generation layer and the first electron transport layer have the same first host material, and the first charge generation layer further includes a first doped guest material;

[0015] The second charge generation layer has the same second host material as the first hole transport layer, and the second charge generation layer further includes a second doped guest material;

[0016] The first doped guest material is different from the second doped guest material.

[0017] In some embodiments of this disclosure, the first host material includes one of lithium 8-hydroxyquinoline, 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene, 2,9-dimethyl-4,7-biphenyl-1,10-o-diazaphenanthroline, 3-(biphenyl-4-yl)-5-(4-tert-butylphenyl)-4-phenyl-4H-1,2,4-triazole, 1,3,5-tris[(3-pyridyl)-3-phenyl]benzene, tris[2,4,6-trimethyl-3-(3-pyridyl)phenyl]borane, and diphenylbis(4-(pyridyl-3-yl)phenyl)silane;

[0018] The first doped guest material includes one of lithium, potassium, rubidium, cesium, magnesium, calcium, sodium, cesium carbonate, lithium fluoride, lithium carbonate, sodium chloride, ferric chloride, iron tetroxide, fullerene, and phthalocyanine derivatives.

[0019] The doping concentration of the first doped guest material is 1wt%-3wt%.

[0020] In some embodiments of this disclosure, the second host material includes one of N,N'-diphenyl-N,N'-di(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine, N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine, N,N”-di(naphthyl-2-yl)-N,N”-di(phenyl)biphenyl-4,4”-diamine, N,N,N',N'-tetra(2-naphthyl)-1,1'-biphenyl-4,4'-diamine, and 4-[1-[4-[di(4-methylphenyl)amino]phenyl]cyclohexyl]-N-(3-methylphenyl)-N-(4-methylphenyl)aniline;

[0021] The second doped guest material includes one of the following: molybdenum trioxide, vanadium pentoxide, tungsten trioxide, ferric chloride, iron tetroxide, pentacene, tetrafluorotetracyanoquinone dimethane, and phthalocyanine derivatives.

[0022] The doping concentration of the second doped guest material is 6wt%-10wt%.

[0023] In some embodiments of this disclosure, when the first light-emitting unit is adjacent to the anode layer, the first light-emitting unit includes: a hole injection layer, a second hole transport layer, a first light-emitting layer, and a first electron transport layer sequentially disposed from one side of the anode layer to one side of the cathode layer;

[0024] When the second light-emitting unit is adjacent to the cathode layer, the second light-emitting unit includes: an electron injection layer, a second electron transport layer, a second light-emitting layer and the first hole transport layer, which are sequentially disposed from one side of the cathode layer to the one side of the anode layer.

[0025] The hole injection layer and the second hole transport layer are homogeneous junction structures.

[0026] In some embodiments of this disclosure, the first light-emitting unit includes a first buffer layer, which is disposed between the second hole transport layer and the first light-emitting layer;

[0027] The second light-emitting unit includes a second buffer layer, which is disposed between the first hole transport layer and the second light-emitting layer.

[0028] In some embodiments of this disclosure, the material of the electrical connection layer includes at least one of indium tin oxide, indium zinc oxide, polyethylene dioxythiophene, carbon nanotubes, metal nanowires, graphene, and graphene carbon nanotubes.

[0029] According to a second aspect of this disclosure, a display device is provided, the display device including the display panel provided in the first aspect of this disclosure.

[0030] According to a third aspect of this disclosure, an electronic device is provided, the electronic device including the display device provided in the second aspect of this disclosure.

[0031] The technical solutions provided by the embodiments of this disclosure may include the following beneficial effects: multiple light-emitting devices are arranged at intervals through an isolation structure, which can reduce the lateral leakage current between pixels and alleviate the problem of pixel crosstalk in the display panel; by setting an electrical connection layer to electrically connect the cathode layers of multiple spaced light-emitting devices, the cathode layers that are easily penetrated by the isolation structure have low resistance and good potential continuity, thereby reducing the voltage of the light-emitting devices and thus enabling the display panel to have good display performance.

[0032] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0033] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure.

[0034] Figure 1 This is a schematic diagram of the structure of a display panel.

[0035] Figure 2 This is a schematic diagram of the structure of a display panel according to some embodiments of the present disclosure.

[0036] Figure 3 This is a schematic diagram of the structure of a display panel according to some other embodiments of the present disclosure.

[0037] Figure 4 This is a schematic diagram of the structure of a display panel according to some other embodiments of the present disclosure.

[0038] Figure 5 This is a schematic diagram of the structure of a display panel according to some other embodiments of the present disclosure. Detailed Implementation

[0039] Some embodiments of this disclosure will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description refers to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following examples of this disclosure do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0040] A series-connected OLED display panel includes multiple arrays of light-emitting devices of different colors, as shown in the reference. Figure 1 As shown, Figure 1This is a display panel 100. The light-emitting devices 10 typically include a cathode layer 40, an anode layer 50, and multiple light-emitting units 20 connected in series via charge-generating layers 30. The cathode layers 40 of the multiple light-emitting devices 10 are interconnected. The anode layer 50 of each light-emitting device 10 is connected to a substrate 60. The substrate 60 contains transistors corresponding to each light-emitting device 10. When the display panel 100 is operating, the cathode layer 40 is negatively charged, and the substrate 60 causes the anode layer 50 of the light-emitting device 10 that needs to emit light to be positively charged, thereby selectively controlling the light-emitting devices 10 in the display panel 100 to emit light for display. In order to achieve good exciton separation and carrier injection in the charge generation layer 30, the charge generation layer 30 is usually doped with chemically active materials to improve carrier mobility. However, the doping process of active materials cannot use fine masks, which makes it easy for the charge generation layers 30 in adjacent light-emitting devices 10 to form electrical connections. This can easily lead to increased lateral leakage current in adjacent light-emitting devices 10, and the display panel 100 is prone to pixel crosstalk in low-brightness display scenarios, affecting the user experience.

[0041] To address the issue of inter-pixel lateral leakage current in the display panel 100, refer to Figure 1 As shown, an isolation structure 80 is typically provided between adjacent light-emitting devices 10 to isolate the charge-generating layer 30 in adjacent light-emitting devices 10, thereby reducing lateral leakage current between pixels. However, due to the small thickness of the display panel 100 and the inability to stably control the thickness of the isolation structure 80 within a small range, the isolation structure 80 can easily penetrate the cathode layer 40 that connects adjacent light-emitting devices 10, resulting in discontinuous cathode potential of the display panel 100, increased operating voltage of the display panel 100, and the inability of the display panel 100 to display normally.

[0042] To address the aforementioned technical problems, this disclosure provides a display panel comprising a plurality of spaced-apart light-emitting devices and an electrical connection layer. The electrical connection layer covers the cathode layers of the plurality of light-emitting devices, and the plurality of cathode layers are electrically connected through the electrical connection layer. In this disclosure, the spaced-apart arrangement of the plurality of light-emitting devices reduces lateral leakage current between pixels, mitigating pixel crosstalk issues in the display panel. By providing the electrical connection layer to electrically connect the cathode layers of the spaced-apart light-emitting devices, the cathodes of the display panel exhibit low resistance and good potential continuity, reducing the voltage of the light-emitting devices and thereby enabling the display panel to achieve excellent display performance.

[0043] An exemplary embodiment of this disclosure provides a display panel, with reference to... Figure 2As shown, the display panel 100 includes a plurality of spaced light-emitting devices 10 and an electrical connection layer 70. The light-emitting devices 10 can emit red, green or blue light. The plurality of light-emitting devices 10 of different colors can be arranged in an array in a certain way in the display panel 100, so that the display panel 100 can display patterns, pictures, text, videos, etc.

[0044] Each light-emitting device 10 may include a cathode layer 40, an anode layer 50 stacked together, and at least two light-emitting units 20 disposed between the cathode layer 40 and the anode layer 50. The cathode layer 40 may be formed of a material with a low work function, such as conductive metals, conductive alloys, doped composite materials, etc., and is used to generate electrons under the action of an electric field. The anode layer 50 may be formed of a material with a high work function, such as gold, silver, platinum, silicon, ITO (Indium Tin Oxide), IZO (Indium Zinc Oxide), etc., and is used to generate holes under the action of an electric field.

[0045] An anode layer 50 is disposed on a substrate 60, which may include a substrate 61, a driving circuit layer 62, and a planarization layer 63 stacked together. The anode layer 50 is disposed on the planarization layer 63. The substrate 61 may be formed of a rigid material, such as glass or PMMA (polymethyl methacrylate), or a flexible material, such as PET (polyethylene terephthalate), PI (polyimide), or PEN (polyethylene naphthalate dimethyl methacrylate), etc. The substrate 61 is used to provide support for various devices disposed on the display panel 100.

[0046] The driving circuit layer 62 includes multiple arrayed light-emitting device driving circuits. When the anode layer 50 of each light-emitting device 10 is disposed on the substrate 60, the anode layer 50 of each light-emitting device 10 is connected to a corresponding light-emitting device driving circuit in the driving circuit layer 62, so that the driving circuit layer 62 can control the light emission of multiple light-emitting devices 10. For example, the light-emitting device driving circuit may include multiple thin-film transistors and capacitors. The planarization layer 63 can perform planarization to make the alignment more uniform, while shielding the electric field generated by the driving circuit layer 62, reducing electric field interference between the driving circuit layer 62 and the multiple light-emitting devices 10, and reducing coupling capacitance.

[0047] It should be noted that one of the cathode layer 40 and the anode layer 50 is a transparent electrode, and the other is a highly reflective electrode, so that light can be emitted. In some examples, when the display panel 100 is a bottom-emitting panel, the anode layer 50 is set as a transparent anode, and the cathode layer 40 is set as a highly reflective cathode with light reflectivity. In some examples, when the display panel 100 is a top-emitting panel, the cathode layer 40 is set as a translucent cathode, and the anode layer 50 is set as a highly reflective anode with light reflectivity.

[0048] When the display panel 100 is a top-emitting panel, in order to ensure that the cathode layer 40 simultaneously possesses low sheet resistance, high reflectivity, low absorption, high stability, and good electron injection characteristics, a combination of various materials can be used in the cathode layer 40, and / or the cathode layer 40 can be configured as a multi-layer structure. For example, an aluminum / silver double-layer structure, a cadmium / silver double-layer structure, a cesium fluoride / ytterbium / silver triple-layer structure, a ytterbium / magnesium-silver alloy double-layer structure, etc., can be used. In some examples, the cathode layer 40 can be configured as a ytterbium / magnesium-silver alloy double-layer structure, where the thickness of the ytterbium metal layer can be between 0.8 nm and 1.5 nm, and the thickness of the magnesium-silver alloy layer can be between 9 nm and 15 nm. In the magnesium-silver alloy, the mass ratio of the two elements can be expressed as magnesium:silver = 1:9~10. The anode layer 50 can be configured as an ITO / Ag / ITO sandwich structure. The ITO layer on the side closer to the substrate 60 is used for electrical connection with the driving circuit layer 62 in the substrate 60, and the ITO layer on the side closer to the light-emitting unit 20 is used for hole injection. The silver metal layer serves as a light-reflecting layer so that light is emitted from one side of the cathode layer 40. For example, the thickness of the ITO layer can be between 3nm and 12nm, and the thickness of the silver metal layer can be between 80nm and 120nm.

[0049] In each light-emitting device 10, at least two light-emitting units 20 may be disposed between the cathode layer 40 and the anode layer 50. Each light-emitting unit 20 may contain a light-emitting material that emits red, green, or blue light. Under the action of an electric field, holes and electrons move to the light-emitting layer of the light-emitting unit 20 to form excitons. The excitons excite the light-emitting material in the light-emitting unit 20 to emit visible light. A charge-generating layer 30 is disposed between adjacent light-emitting units 20. The charge-generating layer 30 is used to connect adjacent light-emitting units 20 in the same light-emitting device 10 in series, so that under the action of an electric field, electrons generated by the cathode layer 40 can be transferred not only to the adjacent light-emitting unit 20, but also to the light-emitting unit 20 away from the cathode layer 40 through the charge-generating layer 30. Similarly, holes generated by the anode layer 50 can be transferred not only to the adjacent light-emitting unit 20, but also to the light-emitting unit 20 away from the anode layer 50 through the charge-generating layer 30. Thus, each light-emitting unit 20 in the light-emitting device 10 has excitons formed by holes and electrons in its light-emitting layer, enabling each light-emitting unit 20 in the light-emitting device 10 to emit light. This improves the brightness and luminous efficiency of the display panel 100, and further extends the lifespan of the display panel 100. It should be noted that at least two light-emitting units 20 in the same light-emitting device 10 have the same color.

[0050] Multiple light-emitting devices 10 are spaced apart, and adjacent light-emitting devices 10 can be separated by isolation structures 80. Each isolation structure 80 may include a pixel definition layer 81 and an isolation pillar 82 stacked together. The pixel definition layer 81 is disposed on the substrate 60 and is used to define the position of each light-emitting device 10. The isolation pillar 82 is used to isolate the charge generation layer 30 in adjacent light-emitting devices 10, thereby reducing lateral leakage current between adjacent light-emitting devices 10. The pixel definition layer 81 and the isolation pillar 82 allow adjacent light-emitting devices 10 to be spaced apart and isolate the charge generation layer 30 in adjacent light-emitting devices 10, thereby reducing color mixing between adjacent light-emitting devices 10 and reducing or eliminating the probability of pixel crosstalk problems in the display panel 100.

[0051] Since the light emission of each light-emitting device 10 is achieved through the driving circuits of each light-emitting device in the driving circuit layer 62 of the control substrate 60, the cathode layers 40 of each light-emitting device 10 should be interconnected to maintain a continuous potential. This is necessary so that when the anode layer 50 of a specific light-emitting device 10 is connected to a positive potential, the display panel 100 can be lit up and the specific light-emitting device 10 can be controlled to emit light. However, due to the uncontrollable thickness of the isolation pillars 82, the cathode layers 40 that should be interconnected between adjacent light-emitting devices 10 can easily penetrate, causing the potential of the cathode layers 40 of each light-emitting device 10 to become discontinuous, resulting in the display panel 100 failing to light up normally.

[0052] By providing a conductive electrical connection layer 70 to cover the cathode layers 40 of multiple light-emitting devices 10, the multiple cathode layers 40 that are disconnected by the isolation pillar 82 are electrically connected through the electrical connection layer 70. In this way, the potential of the cathode layers 40 of all light-emitting devices 10 of the display panel 100 is continuous and the resistance is low, so that the voltage of the display panel 100 is low when it is lit, thereby improving the display performance of the display panel 100, extending the service life of the display panel 100, and improving the user experience.

[0053] Exemplarily, the electrical connection layer 70 can be a single-layer structure or a multi-layer structure, as long as the material of the side of the electrical connection layer 70 close to the cathode layer 40 is conductive, so that the cathode layers 40 of multiple light-emitting devices 10 can be electrically connected to each other. In some examples, when the cathode layer 40 is a high-reflectivity electrode and the anode layer 50 is a transparent electrode, i.e., when the display panel 100 is a bottom-emitting panel, since the light is emitted from the anode layer 50, the electrical connection layer 70 covering the cathode layer 40 will not affect the light emission. The electrical connection layer 70 may include one or more layers of transparent and / or opaque conductive material, and the material of each layer may be the same or different. Exemplarily, the forming material of the electrical connection layer 70 may include at least one of indium tin oxide, indium zinc oxide, polyethylene dioxythiophene, carbon nanotubes, metal nanowires, graphene, and graphene carbon nanotubes. The forming material of the electrical connection layer 70 may also include conductive materials such as metals and alloys. The thickness of the electrical connection layer 70 may be between 50 nm and 1000 nm.

[0054] In an exemplary embodiment, when the cathode layer 40 of each light-emitting device 10 is a semi-transparent electrode and the anode layer 50 is a highly reflective electrode, i.e., when the display panel 100 is a top-emitting panel, since the light is emitted from the cathode layer 40, the electrical connection layer 70 covering the cathode layer 40 will affect the light emission. The electrical connection layer 70 may include one or more transparent conductive materials, and the materials of each layer may be the same or different. Furthermore, in a top-emitting panel, the light emission of the display panel 100 is not affected by the driving circuit and metal wires in the substrate 60, meaning the light-emitting area of ​​the display panel 100 is larger, and the operating voltage of the display panel 100 is lower at the same brightness, thus the display panel 100 can have a longer service life.

[0055] refer to Figure 3 As shown, the electrical connection layer 70 for connecting multiple light-emitting devices 10 may include one or more transparent conductive layers 71. Figure 3 Figure 3The illustration exemplarily depicts an electrical connection layer 70 comprising two transparent conductive layers 71. It is understood that the number of transparent conductive layers 71 can be determined based on the transmittance, conductivity, and stability of the electrical connection layer 70. The materials forming the transparent conductive layers 71 include transparent conductive materials. The material forming each transparent conductive layer 71 may include at least one of indium tin oxide, indium zinc oxide, polyethylene dioxythiophene, carbon nanotubes, metal nanowires, graphene, and graphene carbon nanotubes. The materials of different transparent conductive layers 71 may be the same or different.

[0056] In one exemplary embodiment, reference Figure 4 As shown, when the electrical connection layer 70 is transparent, in addition to at least one transparent conductive layer 71, the electrical connection layer 70 may also include a light extraction layer 72. When the light extraction layer 72 is not conductive, it can be disposed in the electrical connection layer 70 on the side away from the cathode layer 40. Since light, after being reflected by the highly reflective anode layer 50, passes through at least two light-emitting units 20, the charge-generating layer 30, the cathode layer 40, and at least one transparent conductive layer 71 in the light-emitting device 10, the light is prone to total internal reflection within these stacked structures. The totally reflected light is completely attenuated within these stacked structures and cannot be emitted, resulting in low light extraction efficiency of the display panel 100.

[0057] The light extraction layer 72 is configured to complement the refractive index of at least two light-emitting units 20, the charge-generating layer 30, the cathode layer 40, and at least one transparent conductive layer 71 in the light-emitting device 10. This increases the critical angle between the light extraction layer 72 and the medium of these stacked structures, thereby increasing the incident angle of light in these stacked structures. This allows most of the total internally reflected light that would otherwise be unable to exit these stacked structures to be refracted, thus greatly improving the light extraction efficiency of the display panel 100. Therefore, the material of the light extraction layer 72 is a material with a high refractive index.

[0058] Exemplarily, the material of the light extraction layer 72 includes at least one organic compound such as triarylamines, cyclic ureas, acyl compounds, dibenzothiophenes, dibenzofurans, and carbazoles. The material of the light extraction layer 72 also includes lithium fluoride. It is understood that the material of the light extraction layer 72 can be selected based on the refractive index of the materials of the various layered structures in the light-emitting device 10.

[0059] In one exemplary embodiment, reference Figure 4 and Figure 5As shown, in each light-emitting device 10, for every two adjacent light-emitting units 20, the light-emitting unit 20 closer to the anode layer 50 is designated as the first light-emitting unit 21, and the light-emitting unit closer to the cathode layer 40 is designated as the second light-emitting unit 22. For example, when the light-emitting device 10 includes two light-emitting units 20, the one closer to the anode layer 50 is designated as the first light-emitting unit 21, and the one closer to the cathode layer 40 is designated as the second light-emitting unit 22. As another example, when the light-emitting device 10 includes three light-emitting units 20, in the direction from the anode layer 50 to the cathode layer 40, the one closest to the anode layer 50 is designated as the first light-emitting unit 21, and the light-emitting unit 20 adjacent to the first light-emitting unit 21 and located in the middle position is designated as the second light-emitting unit 22; in the direction from the cathode layer 40 to the anode layer 50, the one closest to the cathode layer 40 is designated as the second light-emitting unit 22, and the light-emitting unit 20 adjacent to the second light-emitting unit 22 and located in the middle position is designated as the first light-emitting unit 21.

[0060] A charge generation layer 30 is provided between each pair of adjacent light-emitting units 20. The charge generation layer 30 may include a first charge generation layer 31 near the anode layer 50 and a second charge generation layer 32 near the cathode layer 40. When the light-emitting device 10 is under the action of an electric field, the charge generation layer 30 can generate electron-hole pairs under the action of the electric field. The first charge generation layer 31, which is close to the anode layer 50, can transfer electrons to the first light-emitting unit 21, and the second charge generation layer 32, which is close to the cathode layer 40, can transfer holes to the second light-emitting unit 22, thereby achieving current multiplication.

[0061] In each pair of adjacent light-emitting units 20, the first light-emitting unit 21 closest to the anode layer 50 includes a first electron transport layer 211. Since the anode layer 50 is used to inject holes, the first electron transport layer 211 is used to transport electrons to the first light-emitting unit 21. The first electron transport layer 211 is close to or adjacent to the first charge generation layer 31. The first charge generation layer 31 in the charge generation layer 30 can transfer electrons to the first electron transport layer 211, and the first electron transport layer 211 further transports electrons to the light-emitting material of the first light-emitting unit 21.

[0062] In each pair of adjacent light-emitting units 20, the second light-emitting unit 22 closest to the cathode layer 40 includes a first hole transport layer 221. Since the cathode layer 40 is used to inject electrons, the first hole transport layer 221 is used to transport holes to the second light-emitting unit 22. The first hole transport layer 221 is close to or adjacent to the second charge generation layer 32. The second charge generation layer 32 in the charge generation layer 30 can transfer holes to the first hole transport layer 221, and the first hole transport layer 221 further transfers holes to the light-emitting material of the second light-emitting unit 22.

[0063] In each pair of adjacent light-emitting units 20, the first charge-generating layer 31 of the charge-generating layer 30 and the first electron transport layer 211 of the adjacent first light-emitting unit 21 form a homojunction structure, and the second charge-generating layer 32 and the first hole transport layer 221 of the adjacent second light-emitting unit 22 form a homojunction structure. In the homojunction structure, the film layers use the same host material, the energy level barrier between the film layers is low, and the carrier injection and transport efficiency is high, thereby reducing the driving voltage and operating voltage of the light-emitting device 10 including multiple light-emitting units 20.

[0064] In some examples, reference Figure 5 As shown, the first charge generation layer 31 and the adjacent first electron transport layer 211 are homojunction structures. The first charge generation layer 31 and the first electron transport layer 211 have the same first host material. Since the first charge generation layer 31 and the adjacent first electron transport layer 211 are both used to transfer and transport electrons, the first host material can be a material with good electron mobility. For example, the first host material may include 8-hydroxyquinolinolato-lithium (Liq), 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBI), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), 3-(biphenyl-4-yl)-5-(4-tert-butylphenyl)-4-phenyl-4H-1,2,4-triazole (3-(4-biphenyl)-4-p One of the following: henyl-5-tert-butylphenyl-1,2,4-triazole (TAZ), 1,3,5-tri[(3-pyridyl)-3-phenyl]benzene (TmTyPB), tri[2,4,6-trimethyl-3-(3-pyridin-3-yl)phenyl]borane (3TPYMB), and diphenylbis(4-(pyridin-3-yl)phenyl)silane (DPPS).

[0065] Since the charge generation layer 30 can generate electron-hole pairs, and the first charge generation layer 31 is used for electron transfer, the first charge generation layer 31 includes a first doped guest material, which may include a metal, a metal compound, or an organic compound. In some examples, the first charge generation layer 31 may be N-type doped, such that the free electron concentration in the first charge generation layer 31 is much greater than the hole concentration. Under the action of an electric field, the first charge generation layer 31 conducts electricity electronically, thereby allowing electrons to transfer to the adjacent first electron transport layer 211. Exemplarily, the first doped guest material in the first charge generation layer 31 may include one of lithium, potassium, rubidium, cesium, magnesium, calcium, sodium, cesium carbonate, lithium fluoride, lithium carbonate, sodium chloride, ferric chloride, iron tetroxide, fullerene, or phthalocyanine derivatives. In the first charge generation layer 31, the doping concentration of the first doped guest material is proportional to the concentration of free electrons, and the doping concentration of the first doped guest material may be between 1 wt% and 3 wt%. For example, the thickness of the first charge generation layer 31 can be between 10 nm and 15 nm.

[0066] Since the first electron transport layer 211 is used to transport electrons, it may not contain any guest material and may only include a first host material with high electron mobility. Of course, the first host material may also be doped in the first electron transport layer 211, and this is not limited here. For example, the thickness of the first electron transport layer 211 may be between 14 nm and 16 nm.

[0067] In some examples, reference Figure 5As shown, the second charge generation layer 32 of the charge generation layer 30 and the adjacent first hole transport layer 221 are homojunction structures. The second charge generation layer 32 and the first hole transport layer 221 have the same second host material. Since both the second charge generation layer 32 and the first hole transport layer 221 are used to transfer and transport holes, the second host material can be a material with good hole mobility. For example, the second host material may include N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (N,N'-bis(3-methylphenyl)-N,N'-bis(phenyl)-benzidine, TPD), N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine (N,N'-bis(naphthalen-1-yl)-N,N'-bis(phenyl)-benzidine, NPB), N,N'”-bis(naphthalen-2-yl)-N,N'”-bis(phenyl)biphenyl-4,4”-diamine (N,N'-bis(naphthalen-2-yl)-N,N'-b One of the following: is(phenyl)-benzidine (β-NPB), N,N,N',N'-tetra-naphthalen-2-yl-benzidine (β-TNB), and 4-[1-[4-[bis(4-methylphenyl)amino]phenyl]cyclohexyl]-N-(3-methylphenyl)-N-(4-methylphenyl)aniline (TAPC).

[0068] Since the charge generation layer 30 can generate electron-hole pairs, and the second charge generation layer 32 is used to transfer holes, the second charge generation layer 32 includes a second doped guest material, which may include a metal compound or an organic material. The second doped guest material in the second charge generation layer 32 may be different from the first doped guest material in the first charge generation layer 31. In some examples, the second charge generation layer 32 may be p-type doped, such that the hole concentration in the second charge generation layer 32 is much greater than the concentration of free electrons. Under the action of an electric field, the second charge generation layer 32 conducts electricity through holes, thereby allowing holes to be transferred to the adjacent first hole transport layer 221. Exemplarily, the second doped guest material in the second charge generation layer 32 may include one of molybdenum trioxide, vanadium pentoxide, tungsten trioxide, ferric chloride, iron tetroxide, pentacene, tetrafluorotetracyanoquinone dimethane, or phthalocyanine derivatives. In the second charge generation layer 32, the doping concentration of the second doped guest material is proportional to the hole concentration, and the doping concentration of the second doped guest material can be between 6 wt% and 10 wt%. For example, the thickness of the second charge generation layer 32 can be between 10 nm and 15 nm.

[0069] Since the first hole transport layer 221 is used to transport holes, it may not contain any guest material and may only include a second host material with high hole mobility. Of course, the second host material may also be doped in the first hole transport layer 221; this is not a limitation. For example, the thickness of the first hole transport layer 221 may be between 18 nm and 27 nm.

[0070] refer to Figure 5 As shown, the film structure of the first light-emitting unit 21 and the second light-emitting unit 22 can be the same. For example, when the first light-emitting unit 21 is not adjacent to the anode layer 50 and the second light-emitting unit 22 is not adjacent to the cathode layer 40, that is, when both the first light-emitting unit 21 and the second light-emitting unit 22 are located in the middle region of the light-emitting device 10, the first light-emitting unit 21 may include a second hole transport layer 213, a first light-emitting layer 212, and a first electron transport layer 211 arranged sequentially from the anode layer 50 side to the cathode layer 40 side, and the second light-emitting unit 22 may include a first hole transport layer 221, a second light-emitting layer 222, and a second electron transport layer 223 arranged sequentially from the anode layer 50 side to the cathode layer 40 side. In the first light-emitting unit 21, the second hole transport layer 213 and the first electron transport layer 211 respectively transport holes and electrons to the first light-emitting layer 212 to combine and form excitons, so that the first light-emitting unit 21 emits light. In the second light-emitting unit 22, the first hole transport layer 221 and the second electron transport layer 223 respectively transport holes and electrons to the second light-emitting layer 222 to combine and form excitons, so that the second light-emitting unit 22 emits light.

[0071] In some possible implementations, refer to Figure 5 As shown, when the first light-emitting unit 21 is adjacent to the anode layer 50, the first light-emitting unit 21 includes: a hole injection layer 214, a second hole transport layer 213, a first light-emitting layer 212, and a first electron transport layer 211, sequentially disposed from the anode layer 50 side to the cathode layer 40 side. The anode layer 50 provides holes. Due to the high hole injection barrier between the anode layer 50 and the hole transport material forming the second hole transport layer 213, the device voltage is high. Therefore, a hole injection layer 214 is disposed between the anode layer 50 and the second hole transport layer 213 as a buffer to reduce the hole injection barrier between them. Simultaneously, because the hole injection layer 214 has a relatively uniform film and strong adhesion, it facilitates the bonding between the anode layer 50 and the first light-emitting unit 21, reducing interface defects.

[0072] In some examples, the hole injection layer 214 and the second hole transport layer 213 can be configured as a homojunction structure, using the same host material. This results in a lower energy level barrier between them, improving the hole transport efficiency between the anode layer 50 and the second hole transport layer 213. Exemplarily, the host material used in the hole injection layer 214 and the second hole transport layer 213 can be the second host material with good hole mobility as described in the above embodiments. The hole injection layer 214 can include a doped material, which can be the second doped guest material as described in the above embodiments. The hole injection layer 214 can be p-type doped. Exemplarily, the doping concentration of the second doped guest material in the hole injection layer 214 can be between 0.5 wt% and 5.0 wt%, and the thickness of the hole injection layer 214 can be between 5 nm and 20 nm.

[0073] The second hole transport layer 213 is used to transport holes to the first light-emitting layer 212. The second hole transport layer 213 may not contain any guest material, but only a second host material with a high hole mobility. Of course, the second host material can also be doped into the second hole transport layer 213; this is not a limitation. It is understood that because the second hole transport layer 213 has a high hole mobility and a low electron mobility, it can also trap electrons from the first charge generation layer 31 in the first light-emitting layer 212, thereby improving the luminous efficiency of the first light-emitting layer 212. For example, the thickness of the second hole transport layer 213 can be between 15 nm and 30 nm.

[0074] The first electron transport layer 211 is used to transport electrons to the first light-emitting layer 212. The material and thickness of the first electron transport layer 211 can be the same as those of the first electron transport layer 211 described in the above embodiments.

[0075] The host material of the first light-emitting layer 212 can be an organic small molecule material with a certain electron mobility, especially a material containing electron-withdrawing groups. For example, electron-withdrawing groups can include one or more of nitrogen-containing heterocycles, oxygen atoms, amide groups, and acyloxy groups. Alternatively, the host material of the first light-emitting layer 212 can be an organic small molecule material with a certain hole mobility, especially a material containing electron-donating groups. For example, electron-donating groups can include one or more of fluorene, carbazole, and aromatic amines. The first light-emitting layer 212 also includes a dopant material, which can be a fluorescent dopant material or a phosphorescent dopant material, and the doping concentration of the dopant material in the first light-emitting layer 212 can be between 2 wt% and 10 wt%.

[0076] Depending on the doped material, the first light-emitting layer 212 can emit red, green, or blue light. For example, based on the resonant wavelengths of different colors of light, when the first light-emitting layer 212 is red, its thickness can be between 38 nm and 42 nm. When the first light-emitting layer 212 is green, its thickness can be between 28 nm and 32 nm. When the first light-emitting layer 212 is blue, its thickness can be between 18 nm and 22 nm.

[0077] Continue to refer to Figure 5 When the second light-emitting unit 22 is adjacent to the cathode layer 40, the second light-emitting unit 22 includes: an electron injection layer 224, a second electron transport layer 223, a second light-emitting layer 222, and a first hole transport layer 221, sequentially disposed from one side of the cathode layer 40 to the other side of the anode layer 50. The cathode layer 40 provides electrons. Due to the high electron injection barrier between the cathode layer 40 and the electron transport material forming the second electron transport layer 223, the device voltage is high. Therefore, an electron injection layer 224 is disposed between the cathode layer 40 and the second electron transport layer 223 as a buffer to reduce the electron injection barrier between them.

[0078] In some examples, the electron injection layer 224 and the second electron transport layer 223 can be configured as a homojunction structure, using the same host material. This results in a lower energy level barrier between them, improving the electron transport efficiency of the cathode layer 40 and the second electron transport layer 223. Exemplarily, the host material used in the electron injection layer 224 and the second electron transport layer 223 can be the first host material with good electron mobility as described in the above embodiments. The electron injection layer 224 can include a doped material, which can be the first doped guest material as described in the above embodiments. The electron injection layer 224 can be N-type doped. In some examples, the electron injection layer 224 can include two dopants, one of which is Liq, with a Liq mass percentage between 40wt% and 20wt%. Exemplarily, the thickness of the electron injection layer 224 can be between 25nm and 35nm.

[0079] The second electron transport layer 223 is used to transport electrons to the second light-emitting layer 222. The second electron transport layer 223 may not contain any guest material, only a first host material with high electron mobility. Of course, the first host material can also be doped into the second electron transport layer 223; this is not a limitation. It is understood that, due to the high electron mobility and low hole mobility of the second electron transport layer 223, it can also trap holes from the second charge generation layer 32 in the second light-emitting layer 222, thereby improving the luminous efficiency of the second light-emitting layer 222. For example, the thickness of the second electron transport layer 223 can be between 15 nm and 30 nm.

[0080] The first hole transport layer 221 is used to transport holes to the second light-emitting layer 222. The material and thickness of the first hole transport layer 221 can be the same as those of the first hole transport layer 221 described in the above embodiments. The material and thickness of the second light-emitting layer 222 can be the same as those of the first light-emitting layer 212, and the light emission color of the second light-emitting layer 222 is the same as that of the first light-emitting layer 212.

[0081] In some possible implementations, refer to Figure 4 and Figure 5 As shown, since the light-emitting unit 20 and the charge generation layer 30 in the light-emitting device 10 are both formed of organic small molecule materials, the light-emitting device 10 has a wide emission spectrum and low emission color purity due to the non-uniform expansion of transitions and sideband vibration problems of organic small molecule materials, which is not conducive to the color display of the display panel 100.

[0082] Since one of the anode layer 50 and the cathode layer 40 is a total internal reflection electrode and the other is a semi-transparent electrode, after light is generated in the light-emitting layer of the light-emitting device 10, part of the light penetrates the semi-transparent electrode and enters the user's eye, while part of the light is reflected back into the light-emitting device 10 at the semi-transparent electrode. Therefore, the light-emitting device 10 constitutes an optical microcavity, which exhibits a microcavity effect. In the light-emitting device 10, these reflected lights interfere with each other, causing constructive interference and producing a resonance phenomenon.

[0083] Since the total optical thickness of the microcavity device is related to the peak wavelength of the microcavity emission, a first buffer layer 215 is provided between the second hole transport layer 213 and the first emission layer 212 in the first light-emitting unit 21, and a second buffer layer 225 is provided between the first hole transport layer 221 and the second emission layer 222 in the second light-emitting unit 22. This allows the thickness of the microcavity formed by the light-emitting device 10 to reach the required wavelength, resulting in a narrower emission spectrum and better color saturation.

[0084] For example, since different colors of light have different wavelengths, the thicknesses of the first buffer layer 215 and the second buffer layer 225 used to adjust the microcavity thickness are different in light-emitting devices 10 of different colors. The thickness of the first buffer layer 215 and the second buffer layer 225 in the blue light-emitting device 10 is less than the thickness of the first buffer layer 215 and the second buffer layer 225 in the green light-emitting device 10, which is less than the thickness of the first buffer layer 215 and the second buffer layer 225 in the red light-emitting device 10. For example, in the blue light-emitting device 10, the thickness of the first buffer layer 215 and the second buffer layer 225 can be 20nm-28nm. In the green light-emitting device 10, the thickness of the first buffer layer 215 and the second buffer layer 225 can be 30nm-40nm. In the red light-emitting device 10, the thickness of the first buffer layer 215 and the second buffer layer 225 can be 70nm-85nm.

[0085] In some examples, the materials of the first buffer layer 215 and the second buffer layer 225 can be the same as those of the second hole transport layer 213 or the first hole transport layer 221. During the formation of the first light-emitting unit 21, the thickness of the second hole transport layer 213 can be increased during its formation, and the first buffer layer 215 can be fabricated concurrently. Similarly, during the formation of the second light-emitting unit 22, the thickness of the first hole transport layer 221 can be increased during its formation, and the second buffer layer 225 can be fabricated concurrently, thereby reducing the number of process steps. For example, in the blue light-emitting device 10, the total thickness of the second hole transport layer 213 and the first buffer layer 215 can be 40nm-50nm, and / or, the total thickness of the first hole transport layer 221 and the second buffer layer 225 can be 40nm-50nm. In the green light-emitting device 10, the total thickness of the second hole transport layer 213 and the first buffer layer 215 can be 55nm-65nm, and / or, the total thickness of the first hole transport layer 221 and the second buffer layer 225 can be 55nm-65nm. In the red light-emitting device 10, the total thickness of the second hole transport layer 213 and the first buffer layer 215 can be 95nm-105nm, and / or, the total thickness of the first hole transport layer 221 and the second buffer layer 225 can be 95nm-105nm.

[0086] In some examples, to protect multiple light-emitting devices 10 from external moisture and oxygen, an encapsulation layer (not shown) can be formed on the surface of the electrical connection layer 70 to seal the display panel 100. The encapsulation layer may include stacked organic and inorganic materials. Inorganic materials may include, for example, alumina, silicon nitride, etc. The inorganic material layer can be formed on the surface of the electrical connection layer 70 using plasma chemical vapor deposition or atomic layer deposition to reduce damage to the electrical connection layer 70. Furthermore, inkjet printing technology can be used to form an organic material layer on the surface of the inorganic material to enhance moisture sealing and release stress between the inorganic material layers. An additional inorganic material layer is then formed on the surface of the organic material layer using plasma chemical vapor deposition or atomic layer deposition to form the encapsulation layer.

[0087] In one exemplary embodiment, this disclosure provides a display screen including the display panel described above, which improves problems such as pixel crosstalk, high voltage, and screen failure to light up normally, thereby enhancing the display effect of the display screen.

[0088] In one exemplary embodiment, this disclosure provides an electronic device including the aforementioned display screen, which improves issues such as pixel crosstalk, high voltage, and screen malfunction, thereby enhancing the display performance of the electronic device. The electronic device may include, for example, a smartphone, wearable device, computer, television, in-vehicle infotainment system, etc.

[0089] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the following claims.

[0090] It should be understood that this disclosure is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this disclosure is limited only by the appended claims.

Claims

1. A display panel, characterized in that, The display panel includes: A plurality of spaced-apart light-emitting devices are provided, each of the light-emitting devices including a cathode layer stacked on a substrate, an anode layer disposed on a substrate, and at least two light-emitting units disposed between the cathode layer and the anode layer, wherein a charge-generating layer is disposed between adjacent light-emitting units; wherein adjacent light-emitting devices are spaced apart by an isolation structure. An electrical connection layer covers the cathode layers of a plurality of light-emitting devices, and the plurality of cathode layers are electrically connected through the electrical connection layer.

2. The display panel according to claim 1, characterized in that, The electrical connection layer includes at least one transparent conductive layer.

3. The display panel according to claim 2, characterized in that, The electrical connection layer includes a light extraction layer, which is disposed on the side of the electrical connection layer away from the cathode layer.

4. The display panel according to any one of claims 1-3, characterized in that, In each of the light-emitting devices, the charge generation layer includes a first charge generation layer near the anode layer and a second charge generation layer near the cathode layer; Each pair of adjacent light-emitting units includes a first light-emitting unit near the anode layer and a second light-emitting unit near the cathode layer. The first light-emitting unit includes a first electron transport layer, and the second light-emitting unit includes a first hole transport layer. The first charge generation layer is disposed adjacent to the first electron transport layer, and the first charge generation layer and the first electron transport layer are homojunction structures; the second charge generation layer is disposed adjacent to the first hole transport layer, and the second charge generation layer and the first hole transport layer are homojunction structures.

5. The display panel according to claim 4, characterized in that, The first charge generation layer and the first electron transport layer have the same first host material, and the first charge generation layer further includes a first doped guest material; The second charge generation layer has the same second host material as the first hole transport layer, and the second charge generation layer further includes a second doped guest material; The first doped guest material is different from the second doped guest material.

6. The display panel according to claim 5, characterized in that, The first host material includes one of the following: lithium 8-hydroxyquinoline, 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene, 2,9-dimethyl-4,7-biphenyl-1,10-o-diazaphenanthroline, 3-(biphenyl-4-yl)-5-(4-tert-butylphenyl)-4-phenyl-4H-1,2,4-triazole, 1,3,5-tris[(3-pyridyl)-3-phenyl]benzene, tris[2,4,6-trimethyl-3-(3-pyridyl)phenyl]borane, and diphenylbis(4-(pyridyl-3-yl)phenyl)silane; The first doped guest material includes one of lithium, potassium, rubidium, cesium, magnesium, calcium, sodium, cesium carbonate, lithium fluoride, lithium carbonate, sodium chloride, ferric chloride, iron tetroxide, fullerene, and phthalocyanine derivatives. The doping concentration of the first doped guest material is 1wt%-3wt%.

7. The display panel according to claim 5, characterized in that, The second main material includes one of N,N'-diphenyl-N,N'-di(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine, N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine, N,N”-di(naphthyl-2-yl)-N,N”-di(phenyl)biphenyl-4,4”-diamine, N,N,N',N'-tetra(2-naphthyl)-1,1'-biphenyl-4,4'-diamine, and 4-[1-[4-[di(4-methylphenyl)amino]phenyl]cyclohexyl]-N-(3-methylphenyl)-N-(4-methylphenyl)aniline; The second doped guest material includes one of the following: molybdenum trioxide, vanadium pentoxide, tungsten trioxide, ferric chloride, iron tetroxide, pentacene, tetrafluorotetracyanoquinone dimethane, and phthalocyanine derivatives. The doping concentration of the second doped guest material is 6wt%-10wt%.

8. The display panel according to claim 4, characterized in that, When the first light-emitting unit is adjacent to the anode layer, the first light-emitting unit includes: a hole injection layer, a second hole transport layer, a first light-emitting layer and a first electron transport layer sequentially disposed from one side of the anode layer to one side of the cathode layer; When the second light-emitting unit is adjacent to the cathode layer, the second light-emitting unit includes: an electron injection layer, a second electron transport layer, a second light-emitting layer and the first hole transport layer, which are sequentially disposed from one side of the cathode layer to the one side of the anode layer. The hole injection layer and the second hole transport layer are homogeneous junction structures.

9. The display panel according to claim 8, characterized in that, The first light-emitting unit includes a first buffer layer, which is disposed between the second hole transport layer and the first light-emitting layer; The second light-emitting unit includes a second buffer layer, which is disposed between the first hole transport layer and the second light-emitting layer.

10. The display panel according to claim 1, characterized in that, The material of the electrical connection layer includes at least one of indium tin oxide, indium zinc oxide, polyethylene dioxythiophene, carbon nanotubes, metal nanowires, graphene, and graphene carbon nanotubes.

11. A display device, characterized in that, The display device includes the display panel as described in any one of claims 1-10.

12. An electronic device, characterized in that, The electronic device includes the display device as described in claim 11.

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