Quantum dot light emitting device and preparation method

Abstract

The display panel and the display device are provided, and the display panel comprises a first electrode layer, an electron transport layer, a light-emitting layer, a hole transport layer, a hole injection layer and a second electrode layer which are sequentially stacked, wherein the material of the hole injection layer comprises a first metal oxide and a second metal oxide, the first metal oxide and the second metal oxide contain the same metal element, but the number of outermost electrons of the metal element is different. In addition, the hole injection layer further comprises a metal M and a third metal oxide MOy, wherein the third metal oxide MOy is obtained by a redox reaction between the metal M and the first metal oxide. The hole injection layer can be a single layer or a multi-layer structure.

Description

Technical Field

[0001] This application relates to the field of display technology, and particularly to a display panel and a display device. Background Art

[0002] Quantum Dot Light Emitting Diodes (QLEDs) have shown great potential in the display field due to their advantages such as high color gamut, high color purity, wide viewing angle, long service life, and high luminous efficiency, and have become a favorable competitor for the next-generation display technology. One of the main problems currently faced by quantum dot light emitting diodes is the imbalance of carrier injection in the device.

[0003] A typical QLED device structure includes a cathode, an electron transport layer, a quantum dot light emitting layer, a hole transport layer, a hole injection layer, and an anode arranged in a stacked manner. Currently, the interface energy level barrier between the commonly used hole injection layer material and the anode is too high, so there is still a problem of low hole injection rate. Summary of the Invention

[0004] Embodiments of the present disclosure provide a hole injection layer material and structure, as well as a display panel and a display device, to achieve the purpose of improving the interface contact between the hole injection layer and the anode and enhancing the display performance of the QLED device. According to the first aspect of the embodiments of the present disclosure, a display panel is provided. The display panel includes: A first electrode layer, an electron transport layer, a light emitting layer, a hole transport layer, a hole injection layer, and a second electrode layer arranged in a stacked manner in sequence, wherein the material of the hole injection layer includes a first metal oxide and a second metal oxide, the metal elements included in the first metal oxide and the second metal oxide are the same, but the outermost electron numbers of the metal elements are different.

[0005] The material of the hole injection layer further includes a metal M and a third metal oxide MOy, where 0 < y ≤ 3 and y is a natural number or a decimal.

[0006] The total mass of the metal M and the third metal oxide MOy is less than the total mass of the first metal oxide and the second metal oxide.

[0007] In some embodiments, the mass ratio of the metal M to the third metal oxide MOy is 3:1 - 5:1. The mass percentage of the metal M in the hole injection layer is 5 - 10%, and the mass percentage of the third metal oxide MOy in the hole injection layer is 1 - 5%.

[0008] In some embodiments, the hole injection layer is a multilayer structure, with a first sublayer and a second sublayer sequentially disposed along a first direction, and a first reaction layer disposed between the first sublayer and the second sublayer. The material of the first sublayer includes the first metal oxide, the material of the second sublayer includes the metal M, and the material of the first reaction layer includes the second metal oxide and the third metal oxide MOy.

[0009] In some embodiments, the hole injection layer further includes n additional sublayers and (n+1) additional reaction layers disposed between the second sublayer and the second electrode layer, wherein the additional sublayers and the additional reaction layers are disposed sequentially at intervals and contain different materials, and the additional reaction layers are located on the side closer to the second sublayer, where n≥0 and is an integer.

[0010] In some embodiments, the material of the additional sublayer comprises metals and metal oxides, but is different from the materials contained in the first sublayer and the second sublayer, and the material of the additional reactive layer comprises metal oxides, but is different from the material contained in the first reactive layer.

[0011] In some embodiments, each of the additional sublayers contains a different material, and each of the additional reactive layers contains a different material.

[0012] In some embodiments, the roughness of the first reaction layer is less than that of the first sublayer, and the roughness of the additional reaction layer is less than that of the additional sublayer.

[0013] In some embodiments, the chemical activity of the metal element contained in the first metal oxide is lower than that of the metal M.

[0014] In some embodiments, the first reaction layer is generated by a redox reaction between the first sublayer and the second sublayer, and the additional reaction layer is generated by a redox reaction between adjacent additional sublayers.

[0015] In some embodiments, the first metal oxide contains at least one of molybdenum, vanadium, and tungsten, and the metal M contains at least one of magnesium, aluminum, copper, and silver.

[0016] In some embodiments, the first electrode layer may be a cathode or an anode, and correspondingly, the second electrode layer may be an anode or a cathode. The materials of the first electrode layer and the second electrode layer include at least one of silver, aluminum, indium tin oxide, and carbon nanotubes.

[0017] In some embodiments, the film thickness ratio of the first sublayer and the second sublayer ranges from 2:1 to 10:1.

[0018] In some embodiments, the thickness of the first sublayer is 5-10 nm, the thickness of the second sublayer is 1-5 nm, the thickness of the first reactive layer is 1-2 nm, and the thickness of the hole injection layer is 5-31 nm.

[0019] In some embodiments, the carrier mobility of the first reactive layer is greater than that of the first sublayer.

[0020] According to a second aspect of the present disclosure, a display device is provided, the display device including the display panel described above.

[0021] According to a third aspect of the present disclosure, a method for manufacturing a display panel is also provided, comprising the steps of: A substrate is provided, and a first electrode layer, an electron transport layer, a light-emitting layer, a hole transport layer, a hole injection layer, and a second electrode layer are sequentially fabricated on the substrate. The material of the hole injection layer comprises a first metal oxide and metal M; By applying a certain voltage between the first electrode layer and the second electrode layer, the first metal oxide undergoes a redox reaction with the metal M to generate a second metal oxide and a third metal oxide. The second metal oxide and the third metal oxide are located in the hole injection layer. The voltage is the operating voltage of the display panel.

[0022] In some embodiments, after applying a certain voltage between the first electrode layer and the second electrode layer, the display panel is then subjected to UV irradiation treatment, with the UV power ranging from 1 to 100 mW and the treatment time ranging from 1 to 20 min, in order to further promote the redox reaction between the first metal oxide and the metal M.

[0023] In some embodiments, forming the hole injection layer further includes the following steps: The first metal oxide and the metal M are deposited on the hole transport layer by co-evaporation. The metal M, the second metal oxide, and the third metal oxide are uniformly distributed in the first metal oxide.

[0024] In other embodiments, forming the hole injection layer further includes the following steps: The metal M is a metal nanowire, which is deposited on the hole transport layer by spin coating. The first metal oxide is deposited on the side of the metal M away from the hole transport layer by spin coating.

[0025] The main technical effects achieved by the embodiments of this disclosure are: The hole injection layer provided in this embodiment contains multiple components. By applying certain conditions, a redox reaction is induced in the hole injection layer, thereby improving the interfacial contact between the hole injection layer and the anode, and thus increasing the carrier transport rate at the interface. Furthermore, the addition of metal to the hole injection layer allows for a larger lateral current, resulting in more uniform conductivity and thermal conductivity of the device, thereby improving luminous efficiency, reducing power consumption, and extending lifespan. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings of the embodiments will be briefly described below. Obviously, the drawings described below only relate to some embodiments of this disclosure and are not intended to limit this disclosure.

[0027] Figure 1 This is a schematic diagram of the structure of a display panel provided in an exemplary embodiment of this disclosure.

[0028] Figure 2 is Figure 1 A schematic diagram of one structure of the hole injection layer described in the embodiment.

[0029] Figure 3 This is a schematic diagram of the structure of a display panel provided in another exemplary embodiment of this disclosure.

[0030] Figure 4 yes Figure 3 A schematic diagram of one structure of the first reaction layer in the embodiment.

[0031] Figure 5 This is a schematic diagram of the structure of a display panel provided in yet another exemplary embodiment of this disclosure.

[0032] Figure 6 yes Figure 5 A schematic diagram of an exemplary embodiment in which the hole injection layer includes multiple additional sublayers and multiple additional reaction layers.

[0033] Figure 7 This is a schematic diagram of the structure of a display panel provided in yet another exemplary embodiment of this disclosure.

[0034] Figure 8 yes Figure 7 A schematic diagram of an exemplary embodiment in which the hole injection layer includes multiple additional sublayers and multiple additional reaction layers.

[0035] Figure 9 This is a schematic diagram of the structure of a display panel provided in yet another exemplary embodiment of this disclosure.

[0036] Figure 10 This is a schematic diagram of the structure of a display panel provided in yet another exemplary embodiment of this disclosure.

[0037] Figure 11 This is a flowchart of a method for manufacturing a display panel provided in an exemplary embodiment of this disclosure.

[0038] Figure 12 This is a flowchart of a method for manufacturing a display panel provided in another exemplary embodiment of this disclosure.

[0039] Figure 13 This is a flowchart of a method for manufacturing a display panel provided in yet another exemplary embodiment of this disclosure.

[0040] Figure 14 This is a flowchart of a method for manufacturing a display panel provided in yet another exemplary embodiment of this disclosure.

[0041] Figure 15a This is a comparison graph showing the relationship between current and device efficiency of a display panel before and after UV irradiation treatment, provided by an exemplary embodiment of this disclosure.

[0042] Figure 15b This is a comparison graph showing the relationship between current and brightness of a display panel before and after UV irradiation treatment, provided by an exemplary embodiment of this disclosure.

[0043] Figure 15c This is a comparison graph showing the relationship between current density and device efficiency of a display panel before and after UV irradiation treatment when different metal materials are used as the first or second electrode layer, provided by an exemplary embodiment of this disclosure.

[0044] Figure 16 This is an impedance spectrum of a display panel prepared using different metal materials as the first or second electrode layer, provided by an exemplary embodiment of this disclosure.

[0045] Figure 17a This is a comparison graph showing the relationship between the thickness of the second sublayer and the device efficiency when the second sublayer material of the hole injection layer provided in some embodiments of this disclosure is Mg.

[0046] Figure 17b This is a comparison graph showing the relationship between the thickness of the second sublayer and the device efficiency when the second sublayer material of the hole injection layer provided in some embodiments of this disclosure is Al.

[0047] Figure 17c This is a comparison graph showing the relationship between the thickness of the second sublayer and the device efficiency when the second sublayer material of the hole injection layer provided in some embodiments of this disclosure is Ag.

[0048] Figure 17d This is a comparison graph showing the relationship between the material type of the second sublayer and the device efficiency when the thickness of the second sublayer of the hole injection layer provided in some embodiments of this disclosure is 1 nm.

[0049] Figure 17e This is a comparison graph showing the relationship between the thickness of the hole injection layer and the device efficiency provided in some embodiments of this disclosure.

[0050] Figure 18 This is a display device provided in an exemplary embodiment of the present disclosure.

[0051] Figure 19 This is a display device provided in another exemplary embodiment of the present disclosure.

[0052] In the diagram: 100 - Display panel; 1 - Substrate; 2 - First electrode layer; 3 - Electron transport layer; 4 - Light-emitting layer; 5 - Hole transport layer; 6 - Hole injection layer; 7 - Second electrode layer; 9 - Spacer (bank); 61 - Second reaction layer; 81 - Metal M; 82 - Third metal oxide; 83 - Second metal oxide; 84 - First metal oxide; 601 - First sublayer; 602 - First reaction layer; 603 - Second sublayer; 604 - Additional reaction layer; 605 - Additional sublayer; 110 - First light-emitting structure; 120 - Second light-emitting structure; 130 - Third light-emitting structure; 211 - First electrode layer of the first light-emitting structure; 212 - First electrode layer of the second light-emitting structure; 213 - First electrode layer of the third light-emitting structure Electrode layer; 311-Electron transport layer of the first light-emitting structure; 312-Electron transport layer of the second light-emitting structure; 313-Electron transport layer of the third light-emitting structure; 411-Light-emitting layer of the first light-emitting structure; 412-Light-emitting layer of the second light-emitting structure; 413-Light-emitting layer of the third light-emitting structure; 511-Hole transport layer of the first light-emitting structure; 512-Hole transport layer of the second light-emitting structure; 513-Hole transport layer of the third light-emitting structure; 611-Hole injection layer of the first light-emitting structure; 612-Hole injection layer of the second light-emitting structure; 613-Hole injection layer of the third light-emitting structure; 711-Second electrode layer of the first light-emitting structure; 712-Second electrode layer of the second light-emitting structure; 713-Second electrode layer of the third light-emitting structure. Detailed Implementation

[0053] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments 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.

[0054] The terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The singular forms “a,” “the,” and “the” as used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0055] It should be understood that although the terms first, second, third, etc., may be used in this disclosure to describe various information, such information should not be limited to these terms. These terms are used only to distinguish information of the same type from one another. For example, without departing from the scope of this disclosure, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0056] This disclosure provides a display panel, a display device, and a corresponding manufacturing method. The display panel and display device of this disclosure will be described in detail below with reference to the accompanying drawings. Unless otherwise specified, the features in the following embodiments can complement or combine with each other.

[0057] See Figure 1 Figure 8 This disclosure provides a QLED display panel 100, comprising a substrate 1, a first electrode layer 2, an electron transport layer 3, a light-emitting layer 4, a hole transport layer 5, a hole injection layer 6, and a second electrode layer 7, which are sequentially stacked. The hole injection layer 6 is made of a first metal oxide and a second metal oxide, wherein the first and second metal oxides contain the same metal element, but differ in the number of their outermost electrons, i.e., the valence states of the metal element are different. Optionally, the valence state of the metal element is two or more of +2, +3, +4, +5, and +6. Specifically, the metal element can be molybdenum (Mo), tungsten (W), or vanadium (V), and correspondingly, the first metal oxide can be molybdenum oxide, tungsten oxide, or vanadium oxide. It should be noted that the above oxides are only general terms. Taking molybdenum oxide as an example, the metal element molybdenum can have a +4 or +6 valence, i.e., in the hole injection layer 6, the first metal oxide can be molybdenum trioxide (MoO3), and the second metal oxide can be molybdenum dioxide (MoO2). In some embodiments, the mass of the first metal oxide contained in the hole injection layer 6 is greater than that of the second metal oxide.

[0058] The material of the hole injection layer 6 further includes a metal M and a third metal oxide MOy (0 < y ≤ 3, y is a natural number or a decimal). The total mass of the metal M and the third metal oxide MOy is less than the total mass of the first metal oxide and the second metal oxide. In some embodiments, the mass ratio of the metal M to the third metal oxide MOy is 3:1 - 5:1. The mass percentage of the metal M in the hole injection layer is 5 - 10%, and the mass percentage of the third metal oxide MOy in the hole injection layer is 1 - 5%.

[0059] In some embodiments, referring to Figure 1 , the metal M, the third metal oxide MOy, and the second metal oxide can be uniformly distributed in the first metal oxide, and the four together form the hole injection layer 6. Among them, the valence state of the metal M is one or more of +1, +2, and +3.

[0060] In some embodiments, the chemical activity of the metal M is higher than that of the metal element in the first metal oxide, that is, the metal M is more likely to react with oxygen. Or rather, under certain conditions, an oxidation-reduction reaction can occur between the metal M and the first metal oxide. The metal M loses electrons and undergoes an oxidation reaction to form the third metal oxide MOy, while the first metal oxide gains electrons and undergoes a reduction reaction to form the second metal oxide. That is to say, the second metal oxide and the third metal oxide MOy contained in the hole injection layer 6 are the products of the oxidation-reduction reaction between the metal M and the first metal oxide. Among them, the metal M can include magnesium, aluminum, and silver. Correspondingly, the third metal oxide MOy can include magnesium oxide (MgO), aluminum oxide (Al2O3), and silver oxide (MgO). Specifically, taking the first metal oxide as MoO3 and the metal as Al, the corresponding oxidation-reduction reaction formula is: Al + MoO3 → Al2O3 + MoOy (y < 3).

[0061] In related technologies, the hole injection layer 6 is made of MoO3, but the Fermi level of MoO3 is -5.48 eV, which is much lower than the level of the second electrode layer 7 (e.g., -4.2 eV). The interface energy barrier between the hole injection layer 6 and the second electrode layer 7 is too high, resulting in difficulties in hole injection and a low hole transport rate in QLED devices. This disclosure introduces a metal M into the hole injection layer 6 and sets certain conditions for the metal M to undergo a redox reaction with MoO3 to generate a third metal oxide MOy and low-valence or reduced molybdenum dioxide MoO2. This reduces the work function of molybdenum oxide in the hole injection layer 6, and the reduction of the work function means an increase in the Fermi level. This reduces the interface contact barrier between the hole injection layer 6 and the second electrode layer 7, making the interface closer to an ohmic contact. Furthermore, the decrease in the valence state of Mo in MoO3 means an increase in its conductivity. Therefore, electrons extracted from the hole transport layer 5 can be more easily transported to the second electrode layer 7 through the hole injection layer 6 and collected therein, which results in an improved hole injection capability.

[0062] In some embodiments, see Figure 1 and Figure 5 One of the first electrode layer 2 and the second electrode layer 7 can be an anode or a cathode, and the other can be a cathode or anode accordingly, which can be adjusted and selected according to the type of QLED device. Specifically, when the QLED device is an inverted structure, the first electrode layer 2 is the cathode and the second electrode layer 7 is the anode; when the QLED device is a normal structure, the first electrode layer 2 is the anode and the second electrode layer 7 is the cathode. The first electrode layer 2 and the second electrode layer 7 can be transparent electrodes or opaque electrodes (reflective electrodes), and the materials that can be selected include: metallic materials, such as aluminum, silver, gold, copper, etc.; transparent electrode materials, such as indium tin oxide (ITO), fluorine-doped tin oxide (FTO), graphene, carbon nanotube films, etc.

[0063] In some embodiments, substrate 1 is a rigid substrate, and the material of the rigid substrate may be glass, metal, etc. In other embodiments, substrate 1 may be a flexible substrate, and the material of the flexible substrate may include one or more of PI (polyimide), PET (polyethylene terephthalate), and PC (polycarbonate).

[0064] In some embodiments, see Figure 5The hole injection layer 6 has a multi-layer structure, comprising a first sub-layer 601, a second sub-layer 603, and a first reaction layer 602 disposed between the first sub-layer 601 and the second sub-layer 603, arranged sequentially along a first direction. The first sub-layer 601 is made of a first metal oxide, the second sub-layer 603 is made of metal M, and the first reaction layer 602 is made of a second metal oxide and a third metal oxide MOy. The first direction is along the path from the first electrode layer 2 to the second electrode layer 7.

[0065] In some embodiments, the hole injection layer 6 further includes n additional sublayers and n additional reaction layers disposed between the second sublayer 603 and the second electrode layer 7. The additional sublayers and the additional reaction layers are disposed sequentially at intervals and contain different materials. The additional reaction layers are located on the side closer to the second sublayer 603, and n ≥ 0 and is an integer.

[0066] In some embodiments, the material of the additional sublayer comprises metals and metal oxides, but is different from the metal oxides contained in the first sublayer 601 and the metal elements contained in the second sublayer 603; the material of the additional reaction layer comprises metal oxides, but is also different from the material contained in the first reaction layer 602.

[0067] In some embodiments, the materials contained in two adjacent additional sublayers may also be different, and the materials contained in two adjacent additional reactive layers may also be different. The specific materials may be selected according to different embodiments.

[0068] In this embodiment, the chemical reactivity of the metal element contained in the first metal oxide is lower than that of metal M. A redox reaction can occur at the interface between the first sublayer 601 and the second sublayer 603 to form a first reaction layer 602. Similarly, an additional reaction layer is generated by a redox reaction occurring at the contact interface between two adjacent additional sublayers.

[0069] In some embodiments, the thickness ratio of the first sublayer 601 and the second sublayer 603 ranges from 2:1 to 10:1. Specifically, the thickness of the first sublayer 601 is 5-10 nm, and the thickness of the second sublayer 603 is 1-5 nm. A redox reaction occurs at the interface between the first sublayer 601 and the second sublayer 603, resulting in a first reaction layer 603 with a thickness of 1-2 nm. The hole injection layer 6 can be a single-layer or multi-layer structure with a thickness ranging from 5-31 nm.

[0070] In some embodiments, the roughness of the first reaction layer 602 is less than that of the first sublayer 601, and the roughness of the additional reaction layer is less than that of the additional sublayer. The carrier mobility of the first reaction layer 602 is greater than that of the first sublayer 601.

[0071] This disclosure also provides a display device, which may include the display panel described above.

[0072] This disclosure also provides a method for manufacturing an inverted QLED display panel, comprising the following steps: A substrate 1 is provided, and a first electrode layer 2, an electron transport layer 3, a light-emitting layer 4, a hole transport layer 5, a hole injection layer 6, and a second electrode layer 7 are sequentially fabricated on the substrate 1, wherein the first electrode layer 2 serves as the cathode and the second electrode layer 7 serves as the anode. The material of hole injection layer 6 comprises a first metal oxide and metal M; By applying a certain voltage between the first electrode layer 2 and the second electrode layer 7, the first metal oxide in the hole injection layer 6 undergoes a redox reaction with the metal M to generate the second metal oxide and the third metal oxide MOy.

[0073] There are various methods for preparing the first metal oxide and metal M, such as: co-evaporation of the first metal oxide and metal M, sequential layer-by-layer evaporation of the first metal oxide and metal M, and sequential spin-coating of the first metal oxide and metal M.

[0074] As described above, the hole injection layer 6 provided in this embodiment contains multiple components, which improve the interfacial contact between the hole injection layer 6 and the second electrode layer 7 through redox reactions, thereby increasing the carrier transport rate at the interface. On the other hand, since metal is added to the hole injection layer 6, the lateral current of the hole injection layer 6 can be increased, which makes the conductivity and heat conduction of the device more uniform, thereby improving the luminous efficiency of the device, reducing power consumption, and improving lifespan. The following describes a specific embodiment of this disclosure with the first metal oxide being molybdenum trioxide (MoO3, element Mo with a +6 valence), the second metal oxide being molybdenum dioxide (MoO2, element Mo with a +4 valence), the metal M being magnesium (Mg) or aluminum (Al), the corresponding third metal oxide being magnesium oxide (MgO) or aluminum oxide (Al2O3), and the material of the second electrode layer 7 being aluminum (Al). Example 1

[0075] See Figure 1This embodiment employs an inverted QLED device, comprising, in sequence: a substrate 1, a first electrode layer 2, an electron transport layer 3, a light-emitting layer 4, a hole transport layer 5, a hole injection layer 6, and a second electrode layer 7. The hole injection layer 6 is made of a first metal oxide MoO3 and a second metal oxide MoO2, meaning both contain the same metal element, Mo, but with different valence states: +6 and +4, respectively. The hole injection layer 6 also includes small amounts of metal Al and a third metal oxide Al2O3. The total mass of metal Al and the third metal oxide Al2O3 is less than the total mass of the first metal oxide MoO3 and the second metal oxide MoO2; specifically, the sum of the masses of Al and Al2O3 accounts for 1-5% of the total mass of the hole injection layer 6.

[0076] See Figure 1 As shown in Figure 2, the hole injection layer 6 in this embodiment is a single-layer structure. Its main material is the first metal oxide MoO384, while metal Al81, the third metal oxide Al2O382, and the second metal oxide MoO283 are uniformly distributed within the first metal oxide. These four materials together constitute the hole injection layer 6. Specifically, metal Al and the first metal oxide MoO3 can be co-deposited on the side of the hole transport layer 5 away from the light-emitting layer 4 via co-evaporation. Under certain conditions, refer to... Figure 2a and Figure 2b A redox reaction can occur between metallic Al and the first metal oxide MoO3. Specifically, Al loses electrons and undergoes oxidation to generate the third metal oxide Al2O3, while the first metal oxide MoO3 gains electrons and undergoes reduction to generate the second metal oxide MoO2. In other words, the third metal oxide Al2O3 and the second metal oxide MoO2 contained in the hole injection layer 6 are generated through a chemical reaction between the first metal oxide MoO3 and metallic Al. Alternatively, the hole injection layer 6 can also be prepared by co-depositing metallic Al, the first metal oxide MoO3, and the second metal oxide MoO2. The principle is the same as the former and will not be elaborated here.

[0077] In this embodiment, since the material of the second electrode layer 7 is Al, it may also react with the first metal oxide MoO3. Therefore, at the S1 interface of the hole injection layer 6 near the second electrode layer 7, such as Figure 2a As shown, the concentration of the second metal oxide, MoO283, is relatively high. Example 2

[0078] See Figure 3 and Figure 4Compared to Example 1, in this embodiment, the metal M in the hole injection layer 6 is magnesium (Mg), which undergoes a redox reaction with the first metal oxide MoO3 to generate a third metal oxide MgO and a second metal oxide MoO2. That is, the material of the hole injection layer 6 includes the first metal oxide MoO3, the second metal oxide MoO2, metal Mg, and the third metal oxide MgO. Furthermore, a second reaction layer 61 is also included between the hole injection layer 6 and the second electrode layer 7. The material of the second reaction layer 61 includes Al2O383 and the second metal oxide MoO282. This is because the material of the second electrode layer 7 is Al, which can also undergo a redox reaction with the first metal oxide MoO3. Therefore, if there are remaining unreacted first metal oxide MoO3 at the interface of the hole injection layer 6 near the second electrode layer 7, it can undergo a redox reaction with the second electrode layer 7 to generate Al2O383 and the second metal oxide MoO282, thereby forming the second reaction layer 61. The thickness of the second reaction layer 61 is 1-2 nm, preferably 1 nm. Example 3

[0079] See Figure 5 The hole injection layer 6 has a multi-layer structure, comprising a first sub-layer 601, a second sub-layer 603, and a first reaction layer 602 disposed between the first sub-layer 601 and the second sub-layer 603, arranged sequentially along a first direction. The first sub-layer 601 is made of a first metal oxide MoO3, the second sub-layer 603 is made of metal Al, and correspondingly, the first reaction layer 602 is made of a second metal oxide MoO2 and a third metal oxide Al2O3. The first direction is along the path from the first electrode layer 2 to the second electrode layer 7.

[0080] Furthermore, the hole injection layer 6 also includes n additional sub-layers and n additional reaction layers disposed between the second sub-layer 603 and the second electrode layer 7. The additional sub-layers and the additional reaction layers are sequentially spaced apart and contain different materials. The additional reaction layers are located on the side closest to the second sub-layer 603, and n ≥ 0 and is an integer. (Refer to...) Figure 5 When n=1, the hole injection layer 6 includes one additional sublayer and one additional reaction layer.

[0081] In this embodiment, the material of the additional sublayer 605 is the same as that of the first sublayer 602, which is MoO3. Correspondingly, the materials of the additional reaction layers 604 and 606 are the same as those of the first reaction layer 602, both comprising the second metal oxide MoO2 and the third metal oxide Al2O3.

[0082] See Figure 6This embodiment may also include multiple additional sub-layers and additional reaction layers arranged sequentially at intervals. Each additional reaction layer 604 is made of the same material, and the materials of adjacent additional sub-layers are MoO3 and Al, respectively. Example 4

[0083] See Figure 7 and Figure 8 The difference between this embodiment and Embodiment 3 is that the materials of adjacent additional sublayers separated by an additional sublayer are not completely identical, and the materials of adjacent additional reaction layers separated by an additional reaction layer are not completely identical. In this embodiment, the material of additional sublayer 605 can be WO3, and correspondingly, the materials in the formed additional reaction layers 604 and 606 are different from the material of the first reaction layer 602. Example 5

[0084] See Figure 9 This embodiment employs a forward-mounted QLED device structure, primarily comprising a substrate 1, a second electrode layer 7, a hole injection layer 6, a hole transport layer 5, an electron transport layer 3, and a first electrode layer 2, stacked sequentially. The hole injection layer 6 is a multilayer structure, comprising a second sublayer 602, a first reaction layer 603, and a first sublayer 601, stacked sequentially in the direction away from the substrate 1. Specifically, the second sublayer 602 is made of metallic Al, the first sublayer 601 is made of MoO3, and the first reaction layer 603 is made of MoO2 and Al2O3. The second sublayer 602 and the first sublayer 601 are prepared sequentially by spin-coating. Example 6

[0085] See Figure 10 Compared to Embodiment 5, the hole injection layer 6 further includes multiple additional sublayers and multiple additional reaction layers disposed between the first sublayer 601 and the first electrode layer 2. The materials of each additional sublayer may not be completely identical; for example, the materials of the additional sublayer 604 may be V2O5, WO3, and MoO3 in sequence. Example 7

[0086] See Figure 11 This embodiment provides a method for manufacturing the inverted QLED display panel described in Embodiment 1, comprising the following steps: S1: Provide substrate 1, and sequentially fabricate first electrode layer 2, electron transport layer 3, and light-emitting layer 4 on substrate 1; S2: Hole transport layer 5 is prepared on light-emitting layer 4 by vacuum evaporation. The experimental conditions are: vacuum degree ≤ 10. - 4The evaporation rate is between 0.5 and 0.8 Å / s. Hole transport layer 5 can be an organic hole transport material, such as PVK (polyvinylcarbazole), TFM (poly(9,9-dioctylfluorene-CO-N-(4-butylphenyl)diphenylamine)) and TPD (N,N'-diphenyl-N,N'-Mis(3-methyllphenyl)-(1,1'-Miphenyl)-4,4-diamine) and their derivatives, or an inorganic hole transport material, such as nickel oxide (NiOy) and vanadium oxide (VOy). The thickness of hole transport layer 5 ranges from 10 to 60 nm. S3: Hole injection layer 6 is prepared by vacuum evaporation. Specifically, the first metal oxide MoO3 and metal Al are deposited on top of hole transport layer 5 by co-evaporation. The experimental conditions are: vacuum degree ≤ 10. -4 Pa, the evaporation rate is between 0.1 and 0.5 Å / s. Hole injection layer 6 is a monolayer structure, in which the mass percentage of metallic Al is 5-10%; S4: Next, a second electrode layer 7 is prepared above the hole injection layer 6. By applying a certain voltage (e.g., 2-6V) between the first electrode layer 2 and the second electrode layer 7, a redox reaction is induced between the first metal oxide MoO3 and metal Al in the hole injection layer 6 to generate the second metal oxide MoO2 and the third metal oxide Al2O3. The mass percentage of Al2O3 is 1-5%. Example 8

[0087] Reference Figure 12 Compared to Example 7, the hole injection layer 6 in this embodiment has a multi-layer structure, and correspondingly, the preparation process also includes the following steps: S31: After preparing the hole transport layer 5, a first metal oxide MoO3 with a thickness of 1-30 nm is deposited on the hole transport layer 5. The experimental conditions are: vacuum degree ≤10. -4 Pa, the evaporation rate is between 0.1 and 0.5 Å / s; S32: Next, a 1-30 nm thick layer of metallic Al was deposited on the first metal oxide MoO3. The experimental conditions were: vacuum degree ≤10. -4 Pa, the evaporation rate is between 1.2 and 2.0 Å / s; S33: Next, a first metal oxide MoO3 with a thickness of 1-30 nm is deposited on the metal Al; S4: Prepare the second electrode layer 7; S5: Apply a certain voltage (e.g., 2-6V) between the first electrode layer 2 and the second electrode layer 7 to induce a redox reaction between adjacent first metal oxide MoO3 and metal Al in the hole injection layer 6, generating second metal oxide MoO2 and third metal oxide Al2O3, which constitute the first reaction layer.

[0088] In other embodiments, the metal oxides deposited in steps S2 and S4 are different. For example, MoO3 is deposited in step S2 and WO3 is deposited in step S4. Accordingly, the materials contained in the first reaction layer and the additional reaction layer are different. Example 9

[0089] Reference Figure 13 This embodiment provides a method for fabricating the upright QLED device described in Embodiment 3. It includes the following steps: S1: Fabricate the second electrode layer 7 on the substrate; S2: Spin-coating a metal nanowire solution onto the second electrode layer. The experimental conditions were: 3000 r / min rotation speed and 40 s time. A metal nanowire film with a thickness of 5-10 nm was prepared. S3: Spin-coating a first metal oxide solution (e.g., molybdenum oxide solution) onto a metal nanowire thin film. The experimental conditions are: rotation speed 2000-3000 r / min, time 40 s, to prepare a first metal oxide thin film with a thickness of 5-10 nm. S4: Spin-coat quantum dot solution onto the first metal oxide film to prepare a light-emitting layer with a thickness of 20-40 nm; S5: An electron transport layer with a thickness of 10-60 nm is prepared by spin-coating on the light-emitting layer; S6: The first electrode layer is deposited on the electron transport layer with a thickness of 80-120nm. Example 10

[0090] Reference Figure 14 This embodiment relates to the preparation method in any one of Embodiments 7 to 9. The preparation steps further include: after applying a certain voltage between the first electrode layer and the second electrode layer, the display panel is then subjected to UV irradiation treatment. The UV power range is 1-100 mW and the treatment time range is 1-20 min, so as to further promote the redox reaction between the first metal oxide MoO3 and the metal Al. Example 11

[0091] Reference Figure 1 and Figure 3This embodiment adopts the QLED device structure described in Embodiment 1 or Embodiment 2. Specifically, the hole injection layer 6 is a single-layer structure; or it can undergo an oxidation-reduction reaction with the second electrode layer 7 to form a second reaction layer 61. The second electrode layer 7 is a metal electrode, and the metal material used can be one or more of Al, Ag, and Mg:Ag. Figure 15a and Figure 15b The graphs show a comparison of the relationship between current and device efficiency, and current and brightness of the display panel before and after UV irradiation treatment. The graphs show that after 1 minute of UV irradiation, the device efficiency of the display panel improves, and the brightness increases at the same current. On the other hand, Figure 15c The graph shows a comparison of the current density and device efficiency of display panels prepared with different metal materials for the second electrode layer before and after UV irradiation treatment. It can be seen from the graph that the device efficiency is improved to a certain extent after 2 minutes of UV irradiation. Figure 16 Impedance spectra of display panels fabricated using different metal materials for the second electrode layer are shown. It can be seen that, under the same voltage, the resistance is lowest when using the Mg:Ag electrode and highest when using the Ag electrode, indicating that different metal electrodes have different effects on current and device efficiency. Example 12

[0092] Reference Figure 5 and Figure 8 This embodiment employs the QLED device structure described in Embodiment 3 or Embodiment 5. Specifically, the hole injection layer 6 is a multilayer structure, including: a first sublayer 601, a first reaction layer 602, and a second sublayer 603. The material of the first sublayer 601 is MoO3, and the material of the second sublayer 603 is any one of Mg, Al, and Mg. The thickness of the first sublayer 601 is 1-10 nm, preferably 5 nm. The thickness of the second sublayer 603 is 1-10 nm, specifically, it can be 1 nm, 3 nm, or 5 nm. Figures 17a-17c The graphs show the relationship between device efficiency and thickness when the second sublayer 603 is made of different materials. The horizontal axis represents voltage (volts, V), and the vertical axis represents the device efficiency of the display panel (candela / ampere, cd / A). Experimental results show that when the voltage increases from 2V to 6V, the device efficiency exhibits a trend of first increasing and then decreasing. Furthermore, the device efficiency is inversely proportional to the thickness of the second sublayer 603; that is, as the thickness of the second sublayer 603 increases, the device efficiency decreases. Therefore, the device efficiency is highest when the thickness of the second sublayer 603 is 1nm. (Refer to...) Figure 17d When the thickness is 1nm, the device efficiency is relatively higher when the second sublayer 603 is Mg. Figure 17eThe graph shows the relationship between device efficiency and the thickness of the first sublayer MoO3, with the horizontal axis representing thickness (nanometers, nm) and the vertical axis representing device efficiency (candela / ampere, cd / A). Experimental results show that the device efficiency is relatively high when the thickness of the first sublayer is 5-7 nm. Example Thirteen See Figure 18 and Figure 19 These are the overall structure diagrams of inverted and upright QLED devices, respectively. (See also...) Figure 18 An inverted QLED device includes a first light-emitting element 110, a second light-emitting element 120, and a third light-emitting element 130, which can emit light of different colors. In some embodiments, the first light-emitting element 110 emits red light, the second light-emitting element 120 emits green light, and the third light-emitting element 130 emits blue light. The first light-emitting element 110 includes a first light-emitting layer 411, a first electron transport layer 311, and a first electrode layer 211; the first electrode layer 211 is in contact with the first electron transport layer 311, and when the first light-emitting element 110 emits light, the first electrode layer 211 provides electrons.

[0093] In some examples, the first light-emitting layer 411 may be a red quantum dot light-emitting layer. The material of the first light-emitting layer 411 may include cadmium selenide (CdSe), CdSe / ZnS core-shell quantum dot materials; it may also include cadmium-free quantum dot materials, such as indium phosphide (InP), InP / ZnS core-shell quantum dot materials, thereby reducing environmental pollution.

[0094] In some examples, the display device can be any product or component with a display function, such as a smartphone, tablet, television, monitor, laptop, digital photo frame, or navigator.

[0095] It should be noted that the dimensions of layers and regions may be exaggerated in the accompanying drawings for clarity. Furthermore, it is understood that when an element or layer is referred to as being "on" another element or layer, it can be directly on the other element, or there may be intermediate layers. Additionally, it is understood that when an element or layer is referred to as being "below" another element or layer, it can be directly below the other element, or there may be more than one intermediate layer or element. Furthermore, it is also understood that when a layer or element is referred to as being "between" two layers or two elements, it can be the only layer between the two layers or two elements, or there may be more than one intermediate layer or element. Similar reference numerals throughout indicate similar elements.

[0096] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the disclosure herein. This disclosure 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.

[0097] 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, comprising a first electrode layer, an electron transport layer, a light-emitting layer, a hole transport layer, a hole injection layer, and a second electrode layer sequentially stacked, wherein, The materials of the hole injection layer include a first metal oxide and a second metal oxide. The first metal oxide and the second metal oxide contain the same metal element, but the outermost electron numbers of the metal element are different; The materials of the hole injection layer further include a metal M and a third metal oxide MOy, where 0 < y ≤ 3 and y is a natural number or a decimal; The second metal oxide and the third metal oxide MOy are formed by an oxidation-reduction reaction of the first metal oxide and the metal M.

2. The display panel according to claim 1, wherein, The total mass of the metal M and the third metal oxide MOy is less than the total mass of the first metal oxide and the second metal oxide.

3. The display panel according to claim 2, wherein, The mass ratio range of the metal M to the third metal oxide MOy is 3:1 - 5:

1.

4. The display panel according to claim 3, wherein, The mass percentage of the metal M in the hole injection layer is 5 - 10%, and the mass percentage of the third metal oxide MOy in the hole injection layer is 1 - 5%.

5. The display panel according to claim 3, wherein, The hole injection layer is a multi-layer structure. Along a first direction, a first sub-layer and a second sub-layer are sequentially arranged, and a first reaction layer disposed between the first sub-layer and the second sub-layer. The material of the first sub-layer contains the first metal oxide, the material of the second sub-layer includes the metal M, and the material of the first reaction layer includes the second metal oxide and the third metal oxide MOy.

6. The display panel according to claim 5, wherein, The hole injection layer further includes n additional sub-layers and n additional reaction layers disposed between the second sub-layer and the second electrode layer. The additional sub-layers and the additional reaction layers are sequentially arranged at intervals and contain different materials. The additional reaction layer is located closer to the second sub-layer than the additional sub-layer, where n ≥ 0 and is an integer.

7. The display panel according to claim 6, wherein, The material of the additional sub-layer contains a metal and a metal oxide, but is different from the materials contained in the first sub-layer and the second sub-layer; the material of the additional reaction layer contains a metal oxide, but is different from the material contained in the first reaction layer.

8. The display panel according to claim 7, wherein, The materials contained in each additional sub-layer are different, and the materials contained in each additional reaction layer are different.

9. The display panel according to claim 6, wherein, The roughness of the first reaction layer is less than that of the first sub-layer, and the roughness of the additional reaction layer is less than that of the additional sub-layer.

10. The display panel according to claim 6, wherein, The chemical activity of the metal element contained in the first metal oxide is lower than that of the metal M.

11. The display panel according to claim 10, wherein, The first reaction layer is formed by an oxidation-reduction reaction of the first sub-layer and the second sub-layer, and the additional reaction layer is formed by an oxidation-reduction reaction of adjacent additional sub-layers.

12. The display panel according to claim 1, wherein, The metal element contained in the first metal oxide includes at least one of molybdenum, vanadium, and tungsten.

13. The display panel according to claim 1, wherein, The metal M includes at least one of magnesium, aluminum, copper, and silver.

14. The display panel according to claim 1, wherein, The first electrode layer can be a cathode or an anode. Correspondingly, the second electrode layer can be an anode or a cathode. The materials of the first electrode layer and the second electrode layer include at least one of silver, aluminum, indium tin oxide, and carbon nanotubes.

15. The display panel according to claim 5, wherein, The film thickness ratio range of the first sub-layer and the second sub-layer is 2:1 - 10:

1.

16. The display panel according to claim 15, characterized in that, The thickness of the first sublayer is 5-10 nm, the thickness of the second sublayer is 1-5 nm, and the thickness of the first reaction layer is 1-2 nm.

17. The display panel according to claim 1, wherein, The thickness of the hole injection layer is 5-31 nm.

18. The display panel according to claim 5, wherein, The carrier mobility of the first reaction layer is greater than that of the first sublayer.

19. A display device, wherein, Includes the display panel as described in any one of claims 1-18.

20. A method for manufacturing a display panel, wherein, Including the following steps: A substrate is provided, and a first electrode layer, an electron transport layer, a light-emitting layer, a hole transport layer, a hole injection layer, and a second electrode layer are sequentially fabricated on the substrate. The material of the hole injection layer comprises a first metal oxide, or a mixture of a first metal oxide and metal M; A certain voltage is applied between the first electrode layer and the second electrode layer, causing the first metal oxide to undergo a redox reaction with the metal M to generate a second metal oxide and a third metal oxide. The second metal oxide and the third metal oxide are located in the hole injection layer. The voltage is the operating voltage of the display panel.

21. The method for manufacturing a display panel according to claim 20, wherein, It also includes the following steps: After applying a certain voltage between the first electrode layer and the second electrode layer, the display panel is subjected to UV irradiation treatment, with the UV power ranging from 1 to 100 mW and the treatment time ranging from 1 to 20 min.

22. The method for manufacturing a display panel according to claim 20, wherein, It also includes the following steps: The first metal oxide and the metal M are deposited on the hole transport layer by co-evaporation. The metal M, the second metal oxide, and the third metal oxide are uniformly distributed in the first metal oxide.

23. The method for manufacturing a display panel according to claim 20, wherein, It also includes the following steps: The metal M is in the form of metal nanowires, which are deposited on the hole transport layer by spin coating. The first metal oxide is deposited on the side of the metal M away from the hole transport layer by spin coating.

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