Display device, display panel and display device

Abstract

The invention provides a display device, a display panel and a display device, relates to the technical field of display, and is used for effectively improving the transverse leakage current problem of a charge generation layer. The display device includes: a first electrode; a first light emitting layer; the first charge generation layer is located on the side, away from the first electrode, of the first light emitting layer, and the first charge generation layer comprises at least one charge transport layer and at least one dopant layer; the second light-emitting layer is located on the side, away from the first light-emitting layer, of the first charge generation layer; the second electrode is located on the side, away from the first charge generation layer, of the second light-emitting layer.

Description

Technical Field

[0001] The present invention relates to the field of display technology, and in particular to a display device, a display panel and a display apparatus. Background Art

[0002] A stacked display device is a high-efficiency, long-life device structure formed by stacking at least two traditional display devices in series through a charge generation layer. However, in the panel structure using such a stacked display device, there is a problem of pixel stealing due to large lateral leakage of the charge generation layer.

[0003] At present, in order to solve this problem, the pixel definition layer is usually designed with grooves to reduce leakage by increasing the light-stealing path, but this will make the process more difficult and the production cost of the panel higher. Summary of the invention

[0004] Embodiments of the present invention provide a display device, a display panel and a display apparatus, which are used to effectively improve the lateral leakage problem of a charge generation layer.

[0005] In a first aspect, an embodiment of the present invention provides a display device, including: a first electrode; a first light-emitting layer; A first charge generation layer, located on a side of the first light-emitting layer away from the first electrode, the first charge generation layer comprising at least one charge transport layer and at least one dopant layer; a second light-emitting layer, located on a side of the first charge generating layer away from the first light-emitting layer; The second electrode is located at a side of the second light-emitting layer away from the first charge generating layer.

[0006] In a second aspect, based on the same inventive concept, an embodiment of the present invention further provides a display panel, comprising a plurality of the above-mentioned display devices, wherein the first charge generating layers in different display devices are arranged in a connected manner.

[0007] In a third aspect, based on the same inventive concept, an embodiment of the present invention further provides a display device, comprising the above-mentioned display panel.

[0008] The technical solution provided by the embodiment of the present invention has the following beneficial effects: The embodiment of the present invention proposes that the first charge generation layer can be designed as a stack of a charge transport layer and a dopant layer. In the first charge generation layer, the charge transport layer is formed by evaporation of a charge transport material, and the charge transport layer does not include a dopant material, and the dopant layer is formed by evaporation of a dopant material, and the dopant layer does not include a charge transport material.

[0009] Both charge transport materials and dopants are organic materials, which are mainly composed of carbon and hydrogen elements. Most organic substances are covalent compounds, which means that their atoms form chemical bonds by sharing electrons, rather than conducting electricity through the flow of free electrons. This structural characteristic determines that organic materials themselves do not contain free electrons or ions, so the flow of charge inside the material is restricted, resulting in very weak conductivity. In addition, there are no continuous energy bands in organic materials, and their conductivity depends on delocalized π electrons. These electrons are relatively free, but they are also confined within the molecule. Both charge transport materials and dopant materials are small molecule organic compounds with a low degree of conjugation and poor intrinsic conductivity. In summary, the charge transport layer and the dopant layer are limited by their molecular structure and chemical bonding method, which makes them lack freely moving electrons, thereby hindering the lateral flow of current.

[0010] In addition, under the stacked design of the charge transport layer and the dopant layer, the thickness of the charge transport layer and the dopant layer is very small. Both are thin layers with large lateral resistance. This structural characteristic of large lateral resistance can also inhibit the flow of lateral current, thereby further improving the lateral leakage problem of the first charge generation layer.

[0011] In the embodiment of the present invention, the first charge generating layer in the display device ensures the longitudinal transmission of charges while significantly suppressing the lateral current flow. Therefore, when it is applied in a display panel, it can effectively improve the pixel stealing problem at low grayscale. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative labor.

[0013] Figure 1 A schematic diagram of the structure of a display device provided by an embodiment of the present invention; Figure 2 Another schematic diagram of the structure of a display device provided by an embodiment of the present invention; Figure 3 A schematic diagram of another structure of a display device provided by an embodiment of the present invention; Figure 4 A schematic diagram of another structure of a display device provided by an embodiment of the present invention; Figure 5 A schematic diagram of a charge transfer path provided by an embodiment of the present invention; Figure 6A schematic diagram of another structure of a display device provided by an embodiment of the present invention; Figure 7 A schematic diagram of another structure of a display device provided by an embodiment of the present invention; Figure 8 A schematic diagram of another structure of a display device provided by an embodiment of the present invention; Fig. 9 A schematic diagram of the structure of a display panel provided by an embodiment of the present invention; Fig.10 A schematic diagram of the structure of a display device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0014] In order to better understand the technical solution of the present invention, the embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0015] It should be clear that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0016] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "said" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0017] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0018] An embodiment of the present invention provides a display device, which may be a tandem organic light-emitting diode (Tandem Organic Light-Emitting Diode, Tandem OLED) device.

[0019] like Figure 1 As shown, Figure 1 A schematic structural diagram of a display device provided in an embodiment of the present invention, the display device comprises a first electrode 1, a first light-emitting layer 2, a first charge generating layer 3, a second light-emitting layer 4 and a second electrode 5.

[0020] The first electrode 1 is an anode, which is used to receive an anode driving voltage. The first charge generation layer 3 is located on the side of the first light-emitting layer 2 away from the first electrode 1, and the first charge generation layer 3 includes at least one charge transport layer 31 and at least one dopant layer 32. The second light-emitting layer 4 is located on the side of the first charge generation layer 3 away from the first light-emitting layer 2. The second electrode 5 is located on the side of the second light-emitting layer 4 away from the first charge generation layer 3, and the second electrode 5 is a cathode, which is used to receive a cathode driving voltage.

[0021] In the related art, the first charge generation layer, such as the P-type charge generation layer, is formed by a co-evaporation process. In a vacuum environment, the charge transport material and the dopant material are heated simultaneously, so that they are vaporized and mixed separately, and then deposited together to form the first charge generation layer. In the first charge generation layer formed by this co-evaporation, the dopant material will adjust the energy level structure of the charge transport material, making it easier for the charge to be transferred in the material, thereby causing the first charge generation layer to have a higher lateral conductivity. Then, for a display panel using such a display device, when the first charge generation layers corresponding to multiple display devices are connected and arranged, the higher lateral conductivity of the first charge generation layer is prone to form a leakage path, thereby causing the problem of pixel stealing at low grayscales, resulting in display abnormalities.

[0022] In this regard, the embodiment of the present invention proposes that the first charge generation layer 3 may be designed as a stack of a charge transport layer 31 and a dopant layer 32. In the first charge generation layer 3, the charge transport layer 31 may be formed by evaporating a charge transport material, and the charge transport layer 31 does not include a dopant material, and the dopant layer 32 may be formed by evaporating a dopant material, and the dopant layer 32 does not include a charge transport material.

[0023] Both the charge transport material and the dopant are organic materials, which are mainly composed of carbon and hydrogen elements. Most organic substances are covalent compounds, which means that their atoms form chemical bonds by sharing electrons rather than conducting electricity through the flow of free electrons. This structural characteristic determines that the organic material itself does not contain free electrons or ions, so the flow of charge inside the material is restricted, resulting in very weak conductivity. In addition, there is no continuous energy band in the organic material, and its conductivity depends on delocalized π electrons. These electrons are relatively free, but they are only confined within the molecule. Both the charge transport material and the dopant material are small molecule organic compounds with a low degree of conjugation and poor intrinsic conductivity. In summary, the charge transport layer 31 and the dopant layer 32 are limited by their molecular structure and chemical bonding method, which makes them lack freely moving electrons, thereby hindering the lateral flow of current.

[0024] In addition, under the stacking design of the charge transport layer 31 and the dopant layer 32, the thickness of the charge transport layer 31 and the dopant layer 32 is very small, and both are thin layers with large lateral resistance. This structural characteristic of large lateral resistance can also inhibit the flow of lateral current, thereby further improving the lateral leakage problem of the first charge generation layer 3.

[0025] In the embodiment of the present invention, the first charge generating layer 3 in the display device ensures the longitudinal transmission of charges while significantly suppressing the lateral current flow. Therefore, when it is used in a display panel, it can effectively improve the pixel stealing problem at low grayscale.

[0026] In one possible implementation, see Figure 1 and Figure 2 , Figure 2 Another structural schematic diagram of a display device provided by an embodiment of the present invention, the first charge generation layer 3 includes m charge transport layers 31 and m dopant layers 32, the charge transport layers 31 and the dopant layers 32 are alternately arranged, and m is an integer greater than or equal to 2, for example, m can be equal to 2, 3, 4, etc. That is, the first charge generation layer 3 includes at least two repeating units 6 stacked, and each repeating unit 6 includes a charge transport layer 31 and a dopant layer 32.

[0027] Under the condition that the thickness of the first charge generation layer 3 is certain, m≥2, which means that the first charge generation layer 3 includes at least two charge transport layers 31 and at least two dopant layers 32. The number of charge transport layers 31 and dopant layers 32 in the first charge generation layer 3 is relatively large, the charge transport layers 31 and dopant layers 32 are thinner, the lateral resistance is larger, it is more difficult for charges to be transported laterally, and the leakage path will be blocked to a greater extent.

[0028] In a possible implementation, Figure 3~Figure 5 As shown, Figure 3 A schematic diagram of another structure of a display device provided by an embodiment of the present invention is shown in FIG. Figure 4 This is another structural schematic diagram of a display device provided by an embodiment of the present invention. Figure 5 A schematic diagram of a charge transfer path provided in an embodiment of the present invention, the first charge generation layer 3 is a P-type charge generation layer (P-CGL) 7, the charge transport layer 31 is a first hole transport layer (HTL) 8, and the dopant layer 32 is a P-type dopant layer (P-dopant) 9.

[0029] The display device further includes an N-type charge generation layer (N-CGL) 10 , which is located between the P-type charge generation layer 7 and the first light emitting layer 2 .

[0030] In the related art, the P-type charge generation layer is formed by co-evaporation of a hole transport material and a P-type dopant. In a vacuum environment, the hole transport material and the P-type dopant are heated simultaneously, so that they are vaporized and mixed separately, and then deposited together to form a P-type charge generation layer. As mentioned above, this P-type charge generation layer will have a higher lateral conductivity, resulting in a larger lateral leakage current.

[0031] In the embodiment of the present invention, the P-type charge generation layer 7 includes a first hole transport layer 8 and a P-type dopant layer 9 which are alternately stacked. The first hole transport layer 8 can be formed by evaporating a hole transport material, and the first hole transport layer 8 does not include a P-type dopant material. The P-type dopant layer 9 can be formed by evaporating a P-type dopant material, and the P-type dopant layer 9 does not include a hole transport material. Combined with the above analysis, the P-type charge generation layer 7 of this structure can also suppress the flow of lateral current and is not prone to lateral leakage.

[0032] The first hole transport layer 8 includes a hole transport material. In some optional embodiments, the molecular structure of the hole transport material may be as follows:

[0033]

[0034]

[0035]

[0036]

[0037]

[0038]

[0039]

[0040]

[0041]

[0042]

[0043]

[0044]

[0045] In some optional embodiments, the molecular formula of the material of the N-type charge generation layer 10 may be as follows:

[0046]

[0047] In one possible implementation, see again Figure 3 and Figure 4 The N-type charge generation layer 10 is in contact with the first hole transport layer 8 in the P-type charge generation layer 7 .

[0048] In this structure, the first hole transport layer 8 is spaced between the N-type charge generation layer 10 and the P-type dopant layer 9. The first hole transport layer 8 can block the active metal (Li, Yb, etc.) in the N-type charge generation layer 10 from undergoing redox reaction with the P-type dopant layer 9, thereby reducing the generation of the depletion layer and the drift voltage of the display device, thereby reducing the driving voltage of the display device to save power consumption.

[0049] In this regard, the inventors also conducted tests based on the display device A in the related art and the display device B provided in the embodiment of the present invention (in the display device B, the P-type charge generation layer 7 includes two first hole transport layers 8 and two P-type dopant layers 9).

[0050] From Table 1, it can be seen that when a current density of 10 J Base is provided to the display device and the brightness component CIE y is 0.04, the driving voltage of the display device B is less than the driving voltage of the display device A; the luminous efficiency of the display device B is equal to the luminous efficiency of the display device A; the time (LT95) taken for the display brightness of the display device B to decay to 95% of the initial brightness is greater than or equal to the time (LT95) taken for the display brightness of the display device A to decay to 95% of the initial brightness, that is, the life of the display device B is greater than the life of the display device A; the voltage offset of the display device B is less than the voltage offset of the display device A; compared with the display device B, the leakage current of the display device A is significantly reduced.

[0051] Table 1

[0052] Furthermore, if Figure 6 As shown, Figure 6This is another structural schematic diagram of a display device provided in an embodiment of the present invention, wherein the P-type charge generation layer 7 includes at least two first hole transport layers 8, wherein the thickness of the first hole transport layer 8 in contact with the N-type charge generation layer 10 is less than the thickness of other first hole transport layers 8.

[0053] The main purpose of the P-type charge generation layer 7 is to generate holes, but some side reactions or incomplete charge separation processes will occur while generating holes, which will also generate some electrons. In the P-type charge generation layer 7, each repeating unit 6 will generate free electrons. Under the action of the external electric field, the electrons are transferred between the LUMO orbital (lowest unoccupied molecular orbital) of the P-type doped layer and the HOMO orbital (highest occupied molecular orbital) of the first hole transport layer 8. When the first hole transport layer 8 in contact with the N-type charge generation layer 10 is thin, the potential barrier width is small, so it is easier for electrons to tunnel through the potential barrier to the LUMO orbital of the N-type charge generation layer 10, so that the longitudinal transfer of charges is not affected.

[0054] In one possible implementation, see Figure 6 To further ensure that electrons can tunnel to the N-type charge generation layer 10, the thickness d1 of the first hole transport layer 8 in the P-type charge generation layer 7 that contacts the N-type charge generation layer 10 is less than or equal to 2 nm. For example, in one structure, the thickness of the first hole transport layer 8 in the P-type charge generation layer 7 that contacts the N-type charge generation layer 10 may be greater than or equal to 10 Å and less than or equal to 15 Å.

[0055] In a feasible embodiment, the HOMO energy level of the first hole transport layer 8 in the P-type charge generation layer 7 is greater than or equal to -5.2 eV, that is, the highest occupied molecular orbital energy level of the first hole transport layer 8 is greater than or equal to -5.2 eV. For example, in one structure, the HOMO energy level of the first hole transport layer 8 in the P-type charge generation layer 7 is greater than or equal to -5.0 eV and less than or equal to -4.7 eV.

[0056] When the HOMO energy level of the first hole transport layer 8 in the P-type charge generation layer 7 is within the above range, it is beneficial to the injection and transport of holes. Holes can be more easily injected into the first hole transport layer 8 and continuously transported within the layer, reducing energy loss and providing sufficient hole carriers for subsequent composite luminescence in the light-emitting layer.

[0057] In a feasible embodiment, the LUMO energy level of the N-type charge generation layer 10 is greater than or equal to -2.7 ev, that is, the lowest unoccupied molecular orbital energy level of the N-type charge generation layer 10 is greater than or equal to -2.7 ev. For example, in one structure, the LUMO energy level of the N-type charge generation layer 10 is greater than or equal to -2.2 ev and less than or equal to -1.6 ev.

[0058] When the LUMO energy level of the N-type charge generation layer 10 is within the above range, it is more conducive to the injection and transmission of electrons, and provides sufficient electron carriers for the subsequent composite luminescence in the light-emitting layer.

[0059] In one possible implementation, see again Figure 6 The thickness d2 of the P-type dopant layer 9 is less than or equal to 1.5 nm, for example, 10 nm. At this time, the P-type dopant layer 9 is very thin, and the lateral resistance is very large, which can play a greater role in suppressing the lateral current.

[0060] In a possible implementation, Figure 7 and Figure 8 As shown, Figure 7 Another structural schematic diagram of a display device provided by an embodiment of the present invention is shown in FIG. Figure 8 This is another structural schematic diagram of a display device provided in an embodiment of the present invention. The display device also includes a hole injection layer (HIL) 11. The hole injection layer 11 is located between the first electrode 1 and the first light-emitting layer 2. The hole injection layer 11 includes at least two P-type dopants, that is, double PD doping is performed.

[0061] Different P-type dopants have different energy level characteristics. The hole injection layer 11 includes at least two P-type dopants, which can more finely adjust the energy level structure of the hole injection layer 11, so that the energy level matching between the hole injection layer 11 and the adjacent film layer is more optimized, such as optimizing the energy level matching with the first electrode 1, thereby helping to reduce the barrier of hole injection and transmission, and improve the injection efficiency and transmission performance of holes. Moreover, different P-type dopants can have different charge transfer characteristics. Through reasonable matching, the charge transfer capacity of the hole injection layer 11 can also be improved, so that holes can be transmitted in the hole injection layer 11 more quickly and effectively.

[0062] The P-type doping layer 9 in the P-type charge generation layer 7 has a high doping ratio, and the electrons in the repeating unit 6 closest to the hole injection layer 11 are majority carriers. The hole injection layer 11 is double-PD doped, which can adjust the carrier balance and improve the luminous efficiency.

[0063] In the embodiment of the present invention, the P-type dopant may include metal oxides such as molybdenum oxide and tungsten oxide, may include organic small molecules such as tetrafluorotetracyanoquinodimethane and hexacyanohexaazatriphenylene, and may include metal complexes such as copper phthalocyanine. The aforementioned P-type dopant layer 9 may be formed by using at least one of the aforementioned P-type dopants, and the hole injection layer 11 may be formed by using at least two of the aforementioned P-type dopants.

[0064] In addition, in the embodiments of the present invention, see Figure 3 and Figure 4The display device further includes a second hole transport layer 12 located between the first electrode 1 and the first light-emitting layer 2, an electron transport layer (ETL) 13 located between the first light-emitting layer 2 and the N-type charge generation layer 10, a third hole transport layer 14 located between the P-type charge generation layer 7 and the second light-emitting layer 4, a hole blocking layer (HBL) 15 located on a side of the second light-emitting layer 4 away from the third hole transport layer 14, and an electron injection layer (EIL) 16 located between the hole blocking layer 15 and the second electrode 5.

[0065] Based on the same inventive concept, an embodiment of the present invention further provides a display panel, such as Fig. 9 As shown, Fig. 9 A schematic diagram of the structure of a display panel provided by an embodiment of the present invention, the display panel comprises a plurality of the above-mentioned display devices 100, wherein the first charge generating layers 3 in different display devices are arranged in communication.

[0066] Combined with the above analysis, based on the specific structure of the display device, in the display panel, even if the first charge generation layers 3 in different display devices are connected, the lateral current in the first charge generation layer 3 can be effectively suppressed, and the problem of adjacent pixels stealing light can be effectively improved.

[0067] Based on the same inventive concept, an embodiment of the present invention further provides a display device, such as Fig.10 As shown, Fig.10 1 is a schematic diagram of a structure of a display device provided by an embodiment of the present invention, and the display device includes the above-mentioned display panel 1000. Of course, Fig.10 The display device shown is for illustration only, and the display device may be any electronic device with a display function, such as a mobile phone, a tablet computer, a laptop computer, an e-reader or a television.

[0068] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A display device, characterized in that: include: a first electrode; a first light-emitting layer; A first charge generation layer, located on a side of the first light-emitting layer away from the first electrode, the first charge generation layer comprising at least one charge transport layer and at least one dopant layer; a second light-emitting layer, located on a side of the first charge generating layer away from the first light-emitting layer; The second electrode is located at a side of the second light-emitting layer away from the first charge generating layer.

2. The display device according to claim 1, characterized in that The first charge generation layer includes m charge transport layers and m dopant layers, the charge transport layers and the dopant layers are alternately arranged, and m is an integer greater than or equal to 2.

3. The display device according to claim 1, characterized in that The first charge generation layer is a P-type charge generation layer, the charge transport layer is a first hole transport layer, and the dopant layer is a P-type dopant layer; The display device further includes an N-type charge generation layer located between the P-type charge generation layer and the first light emitting layer.

4. The display device according to claim 3, characterized in that The N-type charge generation layer contacts the first hole transport layer in the P-type charge generation layer.

5. The display device according to claim 4, characterized in that The P-type charge generation layer includes at least two first hole transport layers, wherein the thickness of the first hole transport layer in contact with the N-type charge generation layer is smaller than the thickness of the other first hole transport layers.

6. The display device according to claim 4, characterized in that In the P-type charge generation layer, the thickness of the first hole transport layer in contact with the N-type charge generation layer is less than or equal to 2 nm.

7. The display device according to claim 3, characterized in that: The HOMO energy level of the first hole transport layer in the P-type charge generation layer is greater than or equal to -5.2 eV.

8. The display device according to claim 3, characterized in that: The LUMO energy level of the N-type charge generation layer is greater than or equal to -2.7 eV.

9. The display device according to claim 3, characterized in that: The thickness of the P-type dopant layer is less than or equal to 1.5 nm.

10. The display device according to claim 3, characterized in that The display device further includes a hole injection layer, the hole injection layer is located between the first electrode and the first light-emitting layer, and the hole injection layer includes at least two P-type dopants.

11. A display panel, characterized in that: The device comprises a plurality of display devices as claimed in any one of claims 1 to 10, wherein the first charge generating layers in different display devices are arranged in a connected manner.

12. A display device, characterized in that: Comprising the display panel as claimed in claim 11.

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