Light emitting device and display panel

Abstract

The present disclosure provides a light emitting device and a display panel. The light emitting device is configured by arranging a second P-type charge generation layer and a second N-type charge generation layer between a first P-type charge generation layer and a first N-type charge generation layer, so that a PN junction formed at the interface of the second P-type charge generation layer and the second N-type charge generation layer can prevent metal ions in the first N-type charge generation layer from diffusing into the first P-type charge generation layer. Meanwhile, the PN junction formed by the second P-type charge generation layer and the second N-type charge generation layer can also ensure that charges are effectively distributed to the light emitting stack, while playing a blocking role without affecting the current efficiency of the light emitting device.

Description

Technical Field

[0001] This disclosure relates to the field of displays, and more specifically, to a light-emitting device and a display panel using the light-emitting device for display. Background Technology

[0002] Tandem Organic Light-Emitting Diode (TOLED), also known as tandem organic electroluminescent device, is developed based on Organic Light-Emitting Diode (OLED). It not only has the advantages of traditional OLED such as light weight, ultra-thinness, low power consumption, flexibility, low operating voltage (3V-5V), transparency and environmental friendliness, but also has the device performance of high brightness and high efficiency.

[0003] However, current TOLEDs, limited by their structural design, are prone to material degradation or deterioration during operation, leading to reduced performance and lifespan. Therefore, it is necessary to provide a new light-emitting device to extend the lifespan of TOLED-structured light-emitting devices. Summary of the Invention

[0004] This disclosure provides a light-emitting device and a display panel. In the light-emitting device, a charge generation layer is disposed between a first P-type charge generation layer and a first N-type charge generation layer to prevent metal ions in the first N-type charge generation layer from diffusing into the first P-type charge generation layer, thereby extending the lifespan of the TOLED structure light-emitting device.

[0005] This disclosure provides a light-emitting device comprising a cathode, a first light-emitting stack, a first P-type charge-generating layer, a charge-generating layer, a first N-type charge-generating layer, and an anode arranged sequentially. The first N-type charge-generating layer is doped with a metal. The charge-generating layer is located between the first P-type charge-generating layer and the first N-type charge-generating layer, and includes a second P-type charge-generating layer and a second N-type charge-generating layer, wherein the second P-type charge-generating layer is located between the first P-type charge-generating layer and the second N-type charge-generating layer.

[0006] In this implementation, charge generation layers are provided in the first P-type charge generation layer and the first N-type charge generation layer. These charge generation layers extend the diffusion path of metal ions from the first N-type charge generation layer to the first P-type charge generation layer, thereby solving the problem of reduced TOLED lifetime caused by metal diffusion into the first P-type charge generation layer. The second P-type charge generation layer and the second N-type charge generation layer form a PN junction. This PN junction further prevents the diffusion of metal ions from the first N-type charge generation layer. Simultaneously, the PN junction ensures efficient charge distribution to the light-emitting stack, thus providing a blocking effect without affecting the current efficiency of the light-emitting device.

[0007] In one specific implementation of the first aspect of this disclosure, the HOMO energy level of the second P-type charge generation layer increases in the direction from the first P-type charge generation layer to the first N-type charge generation layer.

[0008] The HOMO energy level of the second P-type charge generation layer gradually increases from the first P-type charge generation layer to the first N-type charge generation layer, which can form a better band bending transition, reduce the potential barrier in the charge generation process, and achieve effective charge separation.

[0009] In one specific implementation of the first aspect of this disclosure, the LUMO energy level of the second N-type charge generation layer decreases in the direction from the first N-type charge generation layer to the first P-type charge generation layer.

[0010] The LUMO energy level of the second N-type charge generation layer gradually decreases from the first P-type charge generation layer to the first N-type charge generation layer, which can form a better band bending transition, reduce the potential barrier in the charge generation process, and achieve effective charge separation.

[0011] In one specific embodiment of the first aspect of this disclosure, the HOMO energy level of the second P-type charge generation layer is greater than -5.5 eV, and the LUMO energy level of the second N-type charge generation layer is less than -4.5 eV.

[0012] The energy level difference between the second P-type charge generation layer and the second N-type charge generation layer is less than ±1 eV, which can solve the problem of electron injection degradation in the first N-type charge generation layer caused by the large energy level difference between the first N-type charge generation layer and the first P-type charge generation layer, and improve the stability of the light-emitting device.

[0013] In one specific implementation of the first aspect of this disclosure, the thickness of the second P-type charge generation layer is 5 angstroms to 100 angstroms, and the thickness of the second N-type charge generation layer is 5 angstroms to 100 angstroms.

[0014] Setting the thickness of the second P-type charge generation layer 171 and the second N-type charge generation layer 172 to between 5 angstroms and 100 angstroms respectively can block the diffusion of metal ions without affecting the efficiency of electron transport.

[0015] In one specific implementation of the first aspect of this disclosure, the first light-emitting stack 130 includes a hole transport layer connected to a first P-type charge generation layer, wherein the HOMO energy level of the first P-type charge generation layer is located between the hole transport layer and the second P-type charge generation layer.

[0016] For example, further, the HOMO energy level of the first P-type charge generation layer increases in the direction from the first hole transport layer to the second P-type charge generation layer.

[0017] In the above embodiments, since the HOMO energy level of the first P-type charge generation layer gradually increases from the first hole transport layer to the second P-type charge generation layer, a better band bending transition can be formed, reducing the potential barrier in the charge generation process and achieving effective charge separation.

[0018] In one specific implementation of the first aspect of this disclosure, the second light-emitting stack includes an electron transport layer connected to the first N-type charge generation layer, wherein the LUMO energy level of the first N-type charge generation layer is located between the second electron transport layer and the second N-type charge generation layer.

[0019] For example, further, the LUMO energy level of the first N-type charge generation layer decreases in the direction from the second electron transport layer to the second N-type charge generation layer.

[0020] The LUMO energy level of the first N-type charge generation layer gradually decreases from the second electron transport layer to the second N-type charge generation layer, which can form a better band bending transition and reduce the potential barrier in the charge generation process, thus achieving effective charge separation.

[0021] In one specific implementation of the first aspect of this disclosure, the material of the first P-type charge generation layer is a strongly oxidizing material doped with an organic hole transport material.

[0022] For example, the doping concentration of the strong oxidizing material is further 3%-15%.

[0023] For example, further, the strong oxidizing materials include at least one of molybdenum oxide, tungsten oxide, vanadium oxide, and organic compounds containing cyano and / or fluorine groups, and the organic hole transport materials include at least one of materials such as poly(p-phenylenevinylene), polythiophene, polysilane, triphenylmethane, triarylamine, hydrazone, pyrazoline, chezolium, carbazole, and butadiene.

[0024] In one specific implementation of the first aspect of this disclosure, the material of the first N-type charge generation layer is a metal-doped organic electron transport material.

[0025] For example, the metal further includes at least one of alkali metals, alkaline earth metals, and transition metals, and the organic electron transport material includes at least one of phenanthroline derivatives and triazine derivatives.

[0026] For example, the doping concentration of the metal is further 1%-10%.

[0027] Excessive metal doping concentration reduces transport efficiency but also exacerbates metal ion diffusion. Therefore, the metal doping concentration is set to 1%-10% to minimize metal ion diffusion while maintaining transport efficiency.

[0028] A second aspect of this disclosure provides a display panel including a display area in which a plurality of light-emitting devices as described in the first aspect are disposed.

[0029] This disclosure involves placing a second P-type charge generation layer and a second N-type charge generation layer between a first P-type charge generation layer and a first N-type charge generation layer. The PN junction formed at the interface of the second P-type charge generation layer and the second N-type charge generation layer can prevent metal ions in the first N-type charge generation layer from diffusing into the P-type charge generation layer. Simultaneously, the PN junction formed by the second P-type charge generation layer and the second N-type charge generation layer can also ensure that charge is effectively distributed to the light-emitting stack, thus providing a blocking effect without affecting the current efficiency of the light-emitting device. Attached Figure Description

[0030] Figure 1 This is a cross-sectional schematic diagram of a light-emitting device provided in an embodiment of the present disclosure.

[0031] Figure 2 This is a cross-sectional schematic diagram of a light-emitting device provided in an embodiment of the present disclosure.

[0032] Figure 3 This is a schematic diagram of the energy levels of a portion of the film layer of a light-emitting device according to an embodiment of this disclosure.

[0033] Figure 4 This is a schematic diagram of a display panel provided in one embodiment of the present disclosure.

[0034] Figure 5 for Figure 4 A partial cross-sectional schematic diagram of a display panel. Detailed Implementation

[0035] The technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0036] It should be noted that in the embodiments of this disclosure, the HOMO energy level and LUMO energy level refer to the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), respectively. Electrons can only move in specific, discrete orbitals outside the atomic nucleus. Electrons in each orbital have discrete energies, and these energy values ​​are called energy levels. According to frontier orbital theory, the energy difference between the HOMO and LUMO is called the "band gap," and this energy difference is called the HOMO-LUMO energy level. It can sometimes be used to measure how easily a molecule is excited; the smaller the band gap, the easier the molecule is to be excited.

[0037] OLEDs are widely used in lighting and display devices. The working principle of OLEDs is as follows: under the action of an electric field, holes and electrons are injected from the anode and cathode respectively. After the holes and electrons migrate to the light-emitting layer, they meet to generate energy excitons, which in turn excite the light-emitting molecules in the light-emitting layer to produce visible light.

[0038] A TOLED comprises an anode, a cathode, at least two light-emitting layers located between the anode and cathode, and a charge generation layer located between the light-emitting layers. In other words, multiple light-emitting layers are connected in series via charge generation layers between the anode and cathode. The working principle of a TOLED is as follows: two or more independent light-emitting layers are connected by the intermediate charge generation layer. Under the action of an external electric field, the charge generation layer (CGL) generates holes and electrons. These holes and electrons are injected into the hole transport layer (HTL) and electron transport layer (ETL) of adjacent light-emitting layers, respectively, and combine with electrons from the cathode and holes from the anode in the light-emitting layers of the stack, causing the light-emitting layers to emit light.

[0039] The charge generation layer in a TOLED can employ a heterojunction structure. For example, the charge generation layer includes a P-type charge generation layer and an N-type charge generation layer stacked between two light-emitting layers. The N-type charge generation layer is used to inject electrons into the light-emitting layer connected to it, and the P-type charge generation layer is used to inject holes into the light-emitting layer connected to it. This ensures that charge is effectively distributed to the light-emitting layers while improving the current efficiency of the light-emitting layers in each light-emitting layer stack.

[0040] However, long-term operation of TOLEDs leads to the degradation or deterioration of the materials used in the charge generation layer. On the one hand, when the N-type charge generation layer is doped with metal, metal ions may diffuse into the P-type charge generation layer, resulting in a reduced lifetime of the TOLED. On the other hand, due to the energy level difference between the N-type and P-type charge generation layers, after long-term use, charges are generated at the interface between the P-type charge generation layer and the adjacent hole injection layer (HIL) or hole transport layer (HTL). Therefore, the charge accumulated at the interface between the P-type charge generation layer and the adjacent hole injection layer or hole transport layer prevents holes from being injected into the connected light-emitting stack. Consequently, the charge generation layer cannot effectively separate holes and electrons, leading to a deterioration in electron injection in the N-type charge generation layer. This results in a significant reduction in the electron injection efficiency from the interface between the P-type charge generation layer and the adjacent hole injection layer or hole transport layer to the N-type charge generation layer, and ultimately a significant reduction in the electron injection efficiency from the N-type charge generation layer to the adjacent electron transport layer, thus reducing the performance and lifetime of the TOLED.

[0041] In view of this, the present disclosure provides a light-emitting device that can solve the problem of degradation or deterioration of the material used for the charge generation layer due to long-term operation of TOLED, thereby extending the lifespan of TOLED.

[0042] Figure 1 This is a cross-sectional view of a light-emitting device provided in one embodiment of this disclosure. Figure 1 As shown, an embodiment of the present disclosure provides a light-emitting device 10 including a cathode 110, an anode 120, a first light-emitting stack 130, a first P-type charge-generating layer 150, a charge-generating layer 170, a first N-type charge-generating layer 160, and a second light-emitting stack 140 arranged sequentially from the cathode 110 to the anode 120. That is, the light-emitting device 10 includes a cathode 110, a first light-emitting stack 130, a first P-type charge-generating layer 150, a charge-generating layer 170, a first N-type charge-generating layer 160, a second light-emitting stack 140, and an anode 120 arranged sequentially from top to bottom.

[0043] In one implementation of this disclosure, the first N-type charge generation layer 160 is doped with a metal, and the first P-type charge generation layer 150 is doped with a strong oxidizing material. The charge generation layer 170 is used to prevent metal ions from diffusing from the first N-type charge generation layer 160 into the first P-type charge generation layer 150. Specifically, the charge generation layer 170 is made of an undoped material (either metal or a strong oxidizing material).

[0044] In this implementation, a charge generation layer 170 is provided between the first P-type charge generation layer 150 and the first N-type charge generation layer 160. The charge generation layer 170 can extend the diffusion path of metal ions in the first N-type charge generation layer 160 into the first P-type charge generation layer 150, thereby extending the time required for metal ions in the first N-type charge generation layer 160 to diffuse into the first P-type charge generation layer 150. This can solve the problem of reduced TOLED lifetime caused by metal potentially diffusing into the first P-type charge generation layer 150.

[0045] To avoid the impact of the charge generation layer 170 on the current efficiency of the light-emitting device, this disclosure provides another implementation. For example, the charge generation layer 170 includes a second P-type charge generation layer 171 and a second N-type charge generation layer 172, with the second P-type charge generation layer 171 located between the first P-type charge generation layer 150 and the second N-type charge generation layer. The material of the second P-type charge generation layer 171 is an undoped P-type organic semiconductor material, and the material of the second N-type charge generation layer 172 is an undoped N-type organic semiconductor material.

[0046] Specifically, the material of the second P-type charge generation layer 171 may include at least one of the following triphenylamine compounds: N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine (NPB), 4,4',4'-tris(carbazole-9-yl)triphenylamine (TCTA), N,N'-diphenyl-N,N'-di(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD), pentacene, and 4,4',4'-tris(N-3-methylphenyl-N-phenylamino)triphenylamine (MTDATA).

[0047] Specifically, the material of the second N-type charge-generating layer 172 may include at least one of the following: 4,7-diphenyl-1,10-phenanthroline, 8-hydroxyquinoline aluminum salt, 4,6-bis(3,5-di(pyridin-4-yl)phenyl)-2-methylpyriMidine, and 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene.

[0048] In this implementation, the charge generation layer 170 includes a second P-type charge generation layer 171 and a second N-type charge generation layer 172. The second P-type charge generation layer 171 and the second N-type charge generation layer 172 form a PN junction, that is, a space charge region (i.e., a depletion layer) is formed at the interface between the second P-type charge generation layer 171 and the second N-type charge generation layer 172. This creates a built-in electric field pointing from the second N-type charge generation layer 172 to the second P-type charge generation layer 171. Positively charged metal ions are subjected to a force in the built-in electric field pointing from the second P-type charge generation layer 171 to the second N-type charge generation layer 172. Therefore, the space charge region can further prevent metal ions in the first N-type charge generation layer 160 from diffusing into the first P-type charge generation layer 150. At the same time, the second P-type charge generation layer 171 and the second N-type charge generation layer 172 can ensure that holes and electrons are effectively distributed to the first light-emitting stack and the second light-emitting stack, respectively, preventing holes and electrons from moving in opposite directions. While acting as a barrier, it does not affect the current efficiency of the light-emitting device.

[0049] To improve the electrical performance of the light-emitting device 10 and avoid electron injection degradation caused by charge formation at the interface between the first P-type charge generation layer 150 and the adjacent hole transport layer, this disclosure provides another implementation. For example, the HOMO level of the second P-type charge generation layer 171 increases from the first P-type charge generation layer 150 to the first N-type charge generation layer 160. Specifically, the HOMO level of the second P-type charge generation layer 171 increases in a stepwise manner from the first P-type charge generation layer 150 to the first N-type charge generation layer 160.

[0050] In this implementation, the HOMO energy level of the second P-type charge generation layer 171 gradually increases from the first P-type charge generation layer 150 to the first N-type charge generation layer 160, which can form a better band bending transition and reduce the potential barrier in the charge generation process.

[0051] To improve the stability of the light-emitting device 10, this disclosure provides another implementation. For example, the LUMO energy level of the second N-type charge generation layer 172 decreases in the direction from the first N-type charge generation layer 160 to the first P-type charge generation layer 150. Specifically, the LUMO energy level of the second N-type charge generation layer 172 decreases in a stepwise manner in the direction from the first N-type charge generation layer 160 to the first P-type charge generation layer 150.

[0052] In this implementation, the LUMO energy level of the second N-type charge generation layer 172 gradually decreases from the first N-type charge generation layer 160 to the first P-type charge generation layer 150, which can further form a better band bending transition and reduce the potential barrier in the charge generation process.

[0053] In order to avoid the second P-type charge generation layer 171 and the second N-type charge generation layer 172 affecting the charge separation efficiency while blocking the diffusion of metal ions, this disclosure provides another implementation method.

[0054] In one implementation of this disclosure, the HOMO level of the second P-type charge generation layer 171 is greater than -5.5 eV, and the LUMO level of the second N-type charge generation layer 172 is less than -4.5 eV. Furthermore, the absolute value of the energy level difference between the second P-type charge generation layer 171 and the second N-type charge generation layer 172 is less than 1 eV.

[0055] In this implementation, the absolute value of the energy level difference between the second P-type charge generation layer 171 and the second N-type charge generation layer 172 is less than ±1 eV. Furthermore, the absolute value of the energy level difference between the second P-type charge generation layer 171 and the second N-type charge generation layer 172 is less than ±0.5 eV. Setting the energy level difference between the second P-type charge generation layer 171 and the second N-type charge generation layer 172 to a smaller value allows for a better bandgap transition, reducing the potential barrier during charge generation and achieving effective charge separation. Therefore, while solving the problem of metal ions diffusing from the first N-type charge generation layer 160 into the first P-type charge generation layer 150, it also solves the problem of electron injection degradation in the first N-type charge generation layer 160 caused by the large energy level difference between the first N-type charge generation layer 160 and the first P-type charge generation layer 150, thereby improving the stability of the light-emitting device.

[0056] In one implementation of this disclosure, a greater thickness of the second P-type charge generation layer 171 and the second N-type charge generation layer 172 results in a better blocking effect on metal ions. However, excessively large thicknesses of the second P-type charge generation layer 171 and the second N-type charge generation layer 172 can affect the efficiency of electron transport. Therefore, setting the thicknesses of the second P-type charge generation layer 171 and the second N-type charge generation layer 172 between 5 angstroms and 100 angstroms respectively can block the diffusion of metal ions without affecting the efficiency of electron transport. For example, the thickness of the second P-type charge generation layer 171 can be 10 angstroms, 20 angstroms, 50 angstroms, or 80 angstroms. Similarly, the thickness of the second N-type charge generation layer 172 can be 10 angstroms, 20 angstroms, 50 angstroms, or 80 angstroms.

[0057] In one implementation of this disclosure, the material of the first N-type charge generation layer 160 is a metal-doped organic electron transport material. Specifically, the metal doping concentration is 1%-10%. For example, the metal doping concentration is further 1%, 3%, 5%, and 8%, etc. More specifically, the metal includes at least one of alkali metals, alkaline earth metals, and transition metals. For example, the metal is further lithium, sodium, potassium, rubidium, cesium, francium, chromium, manganese, iron, cobalt, nickel, copper, zinc, lanthanides, and actinides, etc. The organic electron transport material includes at least one of phenanthroline derivatives and triazine derivatives. It should be understood that the organic electron transport material is not limited to the above materials. The thickness of the first N-type charge generation layer 160 is set between 50 angstroms and 100 angstroms.

[0058] Excessive metal doping concentration reduces transport efficiency but also exacerbates metal ion diffusion. Therefore, the metal doping concentration is set to 1%-10% to minimize metal ion diffusion while maintaining transport efficiency.

[0059] In one implementation of this disclosure, the material of the first P-type charge generation layer 150 is a strongly oxidizing material doped with an organic hole transport material. Specifically, the doping concentration of the strongly oxidizing material is 3%-15%. For example, the doping concentration of the strongly oxidizing material is further 1%, 3%, 5%, and 8%, etc. The strongly oxidizing material includes at least one of molybdenum oxide, tungsten oxide, vanadium oxide, and organic compounds containing cyano and / or fluorine groups. The organic hole transport material includes at least one of materials such as poly(p-phenylenevinyl)ethylene, polythiophene, polysilane, triphenylmethane, triarylamine, hydrazone, pyrazoline, chezolium, carbazole, and butadiene. It should be understood that the organic hole transport material is not limited to the above materials. The thickness of the first P-type charge generation layer 150 is set between 50 angstroms and 100 angstroms.

[0060] Figure 2 This is a cross-sectional schematic diagram of a light-emitting device according to an embodiment of this disclosure. Figure 2As shown, in an optional implementation of this embodiment, the light-emitting device 10 includes a cathode 110, a first light-emitting stack 130, a first P-type charge generation layer 150, a charge generation layer 170, a first N-type charge generation layer 160, a second light-emitting stack 140, and an anode 120 arranged from top to bottom.

[0061] For example, in one alternative implementation, the cathode 110 may be made of a conductive material, such as a conductive metal oxide. Examples of conductive metal oxides include zinc oxide, indium oxide, tin oxide, indium tin oxide (ITO), indium zinc oxide (IZO), or fluorine-doped tin oxide.

[0062] Specifically, the material of the anode 120 can be a conductive material such as a metal, a conductive metal oxide, a conductive polymer, or a combination thereof. Specifically, the material of the anode 120 can be a metal or its alloy, such as aluminum, magnesium, calcium, sodium, potassium, titanium, indium, yttrium, lithium, gadolinium, silver, gold, platinum, tin, lead, cesium, or barium. The material of the anode 120 can also be a multilayer material, but is not limited thereto. It should be noted that when the thickness of the metal film layer is relatively small (e.g., as small as a few hundred angstroms or less), the film layer will be transparent.

[0063] The first light-emitting stack 130 includes a first hole transport layer 133 connected to the first P-type charge generation layer 150, and the second light-emitting stack 140 includes a second electron transport layer 143 connected to the first N-type charge generation layer 160. Further, the first light-emitting stack 130 includes a first electron transport layer 131, a first light-emitting layer 132, and a first hole transport layer 133 sequentially stacked between the cathode 110 and the first P-type charge generation layer 150, and the second light-emitting stack 140 includes a second hole transport layer 141, a light-emitting layer 142, and a second electron transport layer 143 sequentially stacked between the anode 120 and the first N-type charge generation layer 160.

[0064] It should be understood that the emission colors of the first and second luminescent layers can be adaptively adjusted as needed.

[0065] In this embodiment, the light-emitting device is... Figure 1 and Figure 2 As an example, other implementations of this embodiment may also include other light-emitting layers, and the first and second light-emitting layers may respectively include electron blocking layers, electron injection layers, hole blocking layers, and hole injection layers.

[0066] Figure 3 This is a schematic diagram of the energy levels within a light-emitting device according to an embodiment of this disclosure. Figure 3As shown, the HOMO level of the first P-type charge generation layer 150 is between the HOMO level of the first hole transport layer 133 and the HOMO level of the second P-type charge generation layer 171. In an alternative implementation, the HOMO level of the first P-type charge generation layer 150 increases in the direction from the first hole transport layer 133 to the second P-type charge generation layer 171.

[0067] The LUMO level of the first N-type charge generation layer 160 is located between the second electron transport layer 143 and the second N-type charge generation layer 172. In an alternative implementation, the LUMO level of the first N-type charge generation layer 160 decreases in the direction from the second electron transport layer 143 to the second N-type charge generation layer 172.

[0068] In this implementation, by setting the HOMO energy level of the first P-type charge generation layer 150 to increase in the direction from the hole transport layer to the second P-type charge generation layer 171, and setting the LUMO energy level of the first N-type charge generation layer 160 to decrease in the direction from the second electron transport layer 143 to the second N-type charge generation layer 172, a better band bending transition can be formed, thereby reducing the potential barrier in the charge generation process.

[0069] At least one embodiment of this disclosure provides a display panel, which includes a display area in which a plurality of light-emitting devices as described in the above embodiments are disposed. For example, the display panel may further include an array substrate on which an array of light-emitting devices is arranged to form sub-pixels of the display panel. Exemplarily, the sub-pixels of the display panel may be in the form of R (red), G (green), and B (blue) sub-pixels.

[0070] Figure 4 This is a schematic diagram of a display panel provided according to an embodiment of the present disclosure. Figure 4 As shown, in one implementation, the display panel 20 is the display screen of a smartphone.

[0071] In other alternative implementations, the display panel can be any device with display functionality, such as the display screen of electronic products such as tablet computers, computer monitors, laptops, PDAs, in-vehicle electronic devices, game consoles, smart wearable devices, and televisions.

[0072] Figure 5 for Figure 4 A partial cross-sectional schematic diagram of a display panel. Figure 5 The cross-sectional structure in is Figure 4 A cross-sectional schematic diagram of region 201, as shown below. Figure 4 and Figure 5As shown, the display panel 20 may include an array substrate 210, on which thin-film transistors (TFTs) are disposed. Each TFT includes a control unit 230 for controlling different sub-pixels. An anode 120 is disposed on the TFT. A pixel definition layer (PDL) 220 is formed on the anode 120. The PDL 210 has multiple openings, in which the first light-emitting layer (not shown), charge-generating layer (not shown), and second light-emitting layer (not shown) of the light-emitting device 10 in the above embodiments of this disclosure are disposed. A cathode 110 of the display panel 20 is formed in the opening of the light-emitting device 10 and is electrically connected to the light-emitting layer. The cathode 110 may be a transparent metal, and the light-emitting side of the light-emitting device is the side where the cathode is located. To improve processing efficiency, the cathode layer covers the upper surface of the light-emitting layer and the upper surface of the pixel definition layer 210 in a common layer form. The display panel 20 also includes an encapsulation layer (not shown) disposed above the cathode 110. The encapsulation layer may be made of transparent plastic or glass, etc. In addition, the display panel 20 also includes conductive connecting wires (not shown) for connecting the control unit 230, cathode 110 and anode 120 to form a control circuit.

[0073] The light-emitting device provided according to any embodiment of this disclosure and the display panel provided according to the embodiments of this disclosure belong to the same inventive concept, and have corresponding film layer structures and beneficial effects. Details not described in detail in the embodiments of the display panel can be found in the embodiments of the light-emitting device, and will not be repeated here.

[0074] The above are merely preferred embodiments of this disclosure and are not intended to limit this disclosure. Any modifications or equivalent substitutions made within the spirit and principles of this disclosure should be included within the scope of protection of this disclosure.

Claims

1. A light emitting device, characterized by, The light emitting device comprises: a cathode and an anode; a first light emitting stack, a first P-type charge generation layer, a first N-type charge generation layer and a second light emitting stack arranged in sequence from the cathode to the anode, and the first N-type charge generation layer is doped with a metal; and a charge generation layer between the first P-type charge generation layer and the first N-type charge generation layer, and comprising a second P-type charge generation layer and a second N-type charge generation layer, the second P-type charge generation layer is between the first P-type charge generation layer and the second N-type charge generation layer; the HOMO energy level of the second P-type charge generation layer increases from the first P-type charge generation layer to the first N-type charge generation layer; the LUMO energy level of the second N-type charge generation layer decreases from the first N-type charge generation layer to the first P-type charge generation layer.

2. The light emitting device according to claim 1, wherein: the HOMO energy level of the second P-type charge generation layer is greater than -5.5 eV, and the LUMO energy level of the second N-type charge generation layer is less than -4.5 eV.

3. The light emitting device according to claim 1, wherein: the absolute value of the energy level difference between the second P-type charge generation layer and the second N-type charge generation layer is less than 1 eV.

4. The light emitting device according to claim 1, wherein: the absolute value of the energy level difference between the second P-type charge generation layer and the second N-type charge generation layer is less than ±0.5 eV.

5. The light emitting device of claim 1, wherein, the thickness of the second P-type charge generation layer is 5 angstroms-100 angstroms, and the thickness of the second N-type charge generation layer is 5 angstroms-100 angstroms.

6. The light emitting device according to any one of claims 1-5, wherein: the first light emitting stack comprises a first hole transport layer connected to the first P-type charge generation layer, and the HOMO energy level of the first P-type charge generation layer is between the first hole transport layer and the second P-type charge generation layer.

7. The light emitting device according to claim 6, wherein: the HOMO energy level of the first P-type charge generation layer increases from the first hole transport layer to the second P-type charge generation layer.

8. The light emitting device according to any one of claims 1-5, wherein: the second light emitting stack comprises a second electron transport layer connected to the first N-type charge generation layer, and the LUMO energy level of the first N-type charge generation layer is between the second electron transport layer and the second N-type charge generation layer.

9. The light emitting device according to claim 8, wherein: the LUMO energy level of the first N-type charge generation layer decreases from the second electron transport layer to the second N-type charge generation layer.

10. The light emitting device according to any one of claims 1-5, wherein: the material of the first P-type charge generation layer comprises a strong oxidizing material doped in an organic hole transport material.

11. The light emitting device according to claim 10, wherein: the doping concentration of the strong oxidizing material is 3%-15%.

12. The light emitting device according to claim 10, wherein: The strong oxidizing material includes at least one of molybdenum oxide, tungsten oxide, vanadium oxide, and an organic compound containing a cyano group and / or a fluorine group, and the organic hole transport material includes at least one of a poly(p-phenylenevinylene) compound, a polythiophene compound, a polysilane compound, a triphenylmethane compound, a triarylamine compound, a hydrazone compound, a pyrazoline compound, a diazoline compound, a carbazole compound, and a butadiene compound.

13. The light emitting device according to any one of claims 1-5, wherein The material of the first N-type charge generation layer includes a metal-doped organic electron transport material.

14. The light emitting device according to claim 13, wherein The doping concentration of the metal is 1-10%.

15. The light emitting device according to claim 13, wherein The metal includes at least one of an alkali metal, an alkaline earth metal, a lanthanide metal, an actinide metal, and a transition metal, and the organic electron transport material includes at least one of a phenanthroline derivative and a triazine derivative.

16. A display panel, characterized by A display area is provided with a plurality of light emitting devices as claimed in any one of claims 1-15.

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