Quantum dot light-emitting device and preparation method thereof, and display panel

Abstract

The embodiments of the present invention disclose a quantum dot light-emitting device, a preparation method thereof, and a display panel. The quantum dot light-emitting device includes a first electrode and a second electrode spaced apart on a substrate, a first insulating layer, a hole functional layer and an electron functional layer arranged on the first insulating layer, a quantum dot light-emitting layer arranged on the hole functional layer and the electron functional layer, and a third electrode and a fourth electrode arranged on the quantum dot light-emitting layer, wherein the third electrode corresponds to the first electrode, and the fourth electrode corresponds to the second electrode. By adjusting the magnitude and positive and negative of the deflection voltage corresponding to the first electrode and the magnitude and positive and negative of the deflection voltage corresponding to the second electrode, the injection ability of holes and electrons can be enhanced or suppressed to varying degrees to achieve the optimal carrier injection state required for the quantum dot light-emitting device.

Description

Technical Field

[0001] The present invention relates to the field of display technology, and in particular to a quantum dot light-emitting device, a preparation method thereof, and a display panel. Background Art

[0002] In recent years, the emergence of quantum dot light-emitting diodes (QLEDs) has brought new breakthroughs to the fields of smart displays and lighting. Their light-emitting layer, composed of inorganic quantum dots, has a narrower emission spectrum, better stability, and even higher brightness than OLEDs (Organic Light-Emitting Diodes). The emission wavelength can be adjusted by changing the size of the quantum dots. Therefore, QLEDs are widely considered to be a strong competitor for future lighting and displays. However, in QLEDs, the hole mobility of the hole transport layer is typically much lower than the electron mobility of the electron transport layer, resulting in unbalanced charge injection and the occurrence of Auger recombination, which in turn leads to poor external quantum efficiency and stability of the device.

[0003] Therefore, promoting carrier balance is one of the important directions in QLED research. Researchers have conducted many studies to improve the carrier injection balance of quantum dot diodes, such as adding an electron blocking layer on the electron transport layer side or the hole transport layer side to prevent excessive electron injection into the quantum dot layer or the hole injection layer; or by setting up a multi-layer hole injection layer to step the injection barrier on the hole side to increase the injection of holes, thereby changing the hole injection ability of the device. However, the above methods only unilaterally change the carrier injection on one side. From existing research, it can be found that due to the different core-shell structures of the quantum dot layer and the different properties of the carrier transport layer materials, the device has different requirements for the degree of carrier injection balance on both sides. Therefore, it is of great significance to simultaneously control and change the carrier injection on both sides for quantum dot light-emitting devices.

[0004] However, based on the structure of existing quantum dot light-emitting devices, it is difficult to achieve the regulation of carrier injection capabilities on both sides. Summary of the Invention

[0005] The embodiments of the present invention provide a quantum dot light-emitting device, a preparation method thereof, and a display panel to solve the problem that the existing quantum dot light-emitting device structure is difficult to achieve the control of carrier injection capability on both sides.

[0006] To solve the above problems, the present invention provides the following technical solutions:

[0007] An embodiment of the present invention provides a quantum dot light-emitting device, comprising: a substrate, a first electrode and a second electrode spaced apart on the substrate; a first insulating layer disposed on the first electrode and the second electrode; a hole functional layer disposed on the first insulating layer and corresponding to the first electrode; an electron functional layer disposed on the first insulating layer and corresponding to the second electrode; a quantum dot light-emitting layer disposed on the hole functional layer and the electron functional layer; a third electrode disposed on the quantum dot light-emitting layer and corresponding to the first electrode; and a fourth electrode disposed on the quantum dot light-emitting layer and corresponding to the second electrode.

[0008] In at least one embodiment of the present invention, from the direction of the first electrode pointing to the quantum dot light-emitting layer, the hole functional layer includes a stacked first metal layer and a hole transport layer; from the direction of the second electrode pointing to the quantum dot light-emitting layer, the electron functional layer includes a stacked second metal layer and an electron transport layer.

[0009] In at least one embodiment of the present invention, the orthographic projection of the hole functional layer on the quantum dot light-emitting layer does not overlap with the orthographic projection of the electron functional layer on the quantum dot light-emitting layer.

[0010] In at least one embodiment of the present invention, a second insulating layer is provided between the hole functional layer and the electron functional layer.

[0011] In at least one embodiment of the present invention, the material of the first insulating layer and the material of the second insulating layer include any one of polymethyl methacrylate and aluminum oxide.

[0012] In at least one embodiment of the present invention, the quantum dot light-emitting device further includes: an anode, arranged on the surface of the first metal layer and spaced from the hole transport layer; and a cathode, arranged on the surface of the second metal layer and spaced from the electron transport layer.

[0013] In at least one embodiment of the present invention, both the first metal layer and the second metal layer are porous metal layers.

[0014] In at least one embodiment of the present invention, the material of the first metal layer and the second metal layer includes any one of carbon nanotubes and metal silver nanowires.

[0015] In at least one embodiment of the present invention, the material of the hole transport layer includes any one of NiO, WO3, and MoO3.

[0016] In at least one embodiment of the present invention, the material of the electron transport layer includes any one of ZnO, SnO2, and Mg:ZnO.

[0017] In at least one embodiment of the present invention, the material of the quantum dot light-emitting layer includes any one of CdZnSe / CdZnS, CdZnSe / ZnSe / ZnCdS, and CdZnSe / ZnSe / ZnS.

[0018] An embodiment of the present invention further provides a display panel, which includes the quantum dot light-emitting device in the above embodiment.

[0019] An embodiment of the present invention also provides a method for preparing the above-mentioned quantum dot light-emitting device, including: forming a first electrode and a second electrode spaced apart on a substrate; forming a first insulating layer on the first electrode and the second electrode; forming a hole functional layer in a region corresponding to the first electrode, and forming an electron functional layer in a region corresponding to the second electrode; forming a quantum dot light-emitting layer on the hole functional layer and the electron functional layer; and forming a third electrode corresponding to the first electrode and a fourth electrode corresponding to the second electrode on the quantum dot light-emitting layer.

[0020] In at least one embodiment of the present invention, the steps of forming a hole functional layer in the region corresponding to the first electrode and forming an electron functional layer in the region corresponding to the second electrode include: stacking a first metal layer and a hole transport layer in sequence on the first insulating layer to form the hole functional layer; stacking a second metal layer and an electron transport layer in sequence on the first insulating layer to form the electron functional layer; forming a second insulating layer between the hole functional layer and the electron functional layer; forming an anode on the surface of the first metal layer; and forming a cathode on the surface of the second metal layer.

[0021] The beneficial effects of the present invention are as follows: a hole functional layer and an electron functional layer are arranged on the same side of the quantum dot light-emitting layer, so that a first electrode and a third electrode can be respectively arranged on both sides of the hole functional layer, and a second electrode and a fourth electrode can be arranged on both sides of the electron functional layer. The electric field formed by the first electrode and the third electrode does not interfere with the electric field formed by the second electrode and the fourth electrode. By adjusting the size and positive and negative of the deflection voltage Vg1 corresponding to the first electrode, the hole injection ability can be enhanced or suppressed to varying degrees. By controlling the size and positive and negative of the deflection voltage Vg2 corresponding to the second electrode, the electron injection ability can be enhanced or suppressed to varying degrees, so as to achieve the optimal carrier injection state required by the quantum dot light-emitting device. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A schematic structural diagram of a display panel provided by an embodiment of the present invention;

[0023] Figure 2 for Figure 1 Schematic diagram of the structure of the AA section;

[0024] Figure 3 A schematic structural diagram of a quantum dot light-emitting device provided in an embodiment of the present invention;

[0025] Figure 4 A schematic structural diagram of a quantum dot light-emitting device provided in another embodiment of the present invention;

[0026] Figure 5 A flowchart of the steps of a method for preparing a quantum dot light-emitting device provided in an embodiment of the present invention;

[0027] Figures 6 to 11 A structural schematic diagram of the preparation process of a quantum dot light-emitting device provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the embodiments described are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative efforts are within the scope of protection of this application.

[0029] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the said features. In the description of the present application, "multiple" means two or more, unless otherwise clearly and specifically defined.

[0030] In the present application, unless otherwise clearly specified and limited, a first feature being "on" or "under" a second feature may include the first and second features being in direct contact, or the first and second features not being in direct contact but being in contact through another feature between them.

[0031] The disclosure below provides many different embodiments or examples for realizing different structures of the present application. In order to simplify the disclosure of the present application, the components and settings of specific examples are described below. Of course, they are merely examples and are not intended to limit the present application. In addition, the present application may repeat reference numbers and / or reference letters in different examples, and such repetition is for the purpose of simplicity and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present application provides examples of various specific processes and materials, but those of ordinary skill in the art will appreciate the application of other processes and / or the use of other materials.

[0032] The present invention addresses the problem that existing quantum dot light-emitting devices, due to the use of a structure of sequentially stacked hole transport layer, quantum dot light-emitting layer, and electron transport layer, are difficult to regulate the carrier injection capability on both sides of the quantum dot light-emitting layer. Instead, the carrier injection capability on only one side can be regulated, resulting in an unbalanced injection of carriers on both sides, and further leading to a low external quantum efficiency of the device. This embodiment is proposed to overcome this defect.

[0033] See also Figure 1 An embodiment of the present invention provides a display panel 1000, comprising a plurality of pixel units arranged in an array. Each pixel unit may include a plurality of sub-pixels of different colors, such as red, green, and blue sub-pixels. The display panel 1000 also comprises quantum dot light-emitting devices 100 arranged in an array. Each quantum dot light-emitting device 100 corresponds to a sub-pixel and can emit red, green, or blue light.

[0034] Among them, see Figure 2 and Figure 3 The quantum dot light emitting device 100 includes a substrate 10, a first electrode 20, a second electrode 30, a first insulating layer 40, a hole functional layer 50, an electron functional layer 60, a second insulating layer 70, a quantum dot light emitting layer 80, a third electrode 90, a fourth electrode 110, an anode 120, and a cathode 130. Figure 2 The quantum dot light-emitting devices 100 are disposed on a substrate 10. A third insulating layer 140 is disposed on the quantum dot light-emitting devices 100. The third insulating layer 140 covers the plurality of quantum dot light-emitting devices 100 to insulate and protect the quantum dot light-emitting devices 100. The material of the third insulating layer 140 can be epoxy resin or other filled insulating materials. Epoxy resin has good insulating properties.

[0035] The display panel 1000 further includes a pixel driving circuit (not shown in the figure), which is used to drive the quantum dot light-emitting device 100 to emit light.

[0036] In some embodiments, the driving circuit may include an array of thin film transistors, which may be disposed on the substrate 10 and electrically connected to the quantum dot light-emitting device 100 , specifically electrically connected to the anode 120 of the quantum dot light-emitting device 100 .

[0037] The thin film transistor may be any one of a metal oxide thin film transistor, a low temperature polysilicon thin film transistor and an amorphous silicon thin film transistor.

[0038] See also Figure 3 The first electrode 20 and the second electrode 30 are disposed on the substrate 10, and the first electrode 20 and the second electrode 30 are spaced apart from each other, that is, the first electrode 20 and the second electrode 30 are spaced apart from each other by a certain distance in the direction of the supporting surface of the substrate 10. The first insulating layer 40 is disposed on the first electrode 20 and the second electrode 30, specifically, the first insulating layer 40 covers the first electrode 20 and the second electrode 30.

[0039] The hole functional layer 50 is arranged on the first insulating layer 40 and corresponds to the first electrode 20. In other words, the hole functional layer 50 has an overlapping surface with the first electrode 20 in the thickness direction of the quantum dot light-emitting device 100. Specifically, the orthographic projection of the hole functional layer 50 on the first electrode 20 can be located in the area where the first electrode 20 is located; the electronic functional layer 60 is arranged on the first insulating layer 40 and corresponds to the second electrode pair 30. In other words, the electronic functional layer 60 has an overlapping surface with the second electrode 30 in the thickness direction of the quantum dot light-emitting device 100. Specifically, the orthographic projection of the electronic functional layer 60 on the second electrode 30 can be located in the area where the second electrode 30 is located.

[0040] The quantum dot light-emitting layer 80 is disposed on the hole functional layer 50 and the electron functional layer 60 .

[0041] The third electrode 90 is disposed on the quantum dot light-emitting layer 80 and corresponds to the first electrode 20. In other words, the third electrode 90 has an overlapping surface with the first electrode 20 in the thickness direction of the quantum dot light-emitting device 100. Specifically, the orthographic projection of the third electrode 90 on the first electrode 20 can be located in the region where the first electrode 20 is located. The fourth electrode 110 is disposed on the quantum dot light-emitting layer 80 and corresponds to the second electrode 30. In other words, the fourth electrode 110 has an overlapping surface with the second electrode 30 in the thickness direction of the quantum dot light-emitting device 100. Specifically, the orthographic projection of the fourth electrode 110 on the second electrode 30 can be located in the region where the second electrode 30 is located. The first electrode 20 and the third electrode 90 are used to form an electric field to control the injection amount of holes; the second electrode 30 and the fourth electrode 110 are used to form an electric field to control the injection amount of electrons.

[0042] In an embodiment of the present invention, the hole functional layer 50 and the electron functional layer 60 are arranged on the same side of the quantum dot light-emitting layer 80, so that the first electrode 20 and the third electrode 90 can be respectively arranged on both sides of the hole functional layer 50, and the second electrode 30 and the fourth electrode 110 can be arranged on both sides of the electron functional layer 60. The electric field formed by the first electrode 20 and the third electrode 90 does not interfere with the electric field formed by the second electrode 30 and the fourth electrode 110, and the hole injection ability can be changed by controlling the deflection voltage Vg1 corresponding to the first electrode 20, and the electron injection ability can be changed by controlling the deflection voltage Vg2 corresponding to the second electrode 30.

[0043] Specifically, in the direction from the first electrode 20 to the quantum dot light-emitting layer 80, the hole functional layer 50 includes a stacked first metal layer 51 and a hole transport layer 52. Due to the mismatch between the work function of the first metal layer 51 and the energy level of the material of the hole transport layer 52, the energy band of the hole transport layer 52 is bent at the interface where the first metal layer 51 and the hole transport layer 52 contact each other, forming a Schottky barrier at the interface. The Schottky barrier tends to be stable after the thermal motion equilibrium of the intrinsic carriers of the material, but it will change with the stimulation of external conditions (voltage, temperature, light, etc.). By applying a deflection voltage Vg1 to the first electrode 20 and the third electrode 90 and changing the voltage of the first electrode 20 and the third electrode 90, the Schottky barrier at the interface where the first metal layer 51 contacts the hole transport layer 52 is changed, thereby changing the hole injection capacity.

[0044] In the direction from the second electrode 30 to the quantum dot light-emitting layer 80, the electronic functional layer includes a stacked second metal layer 61 and an electron transport layer 62. Due to the mismatch between the work function of the second metal layer 61 and the energy level of the material of the electron transport layer 62, a Schottky barrier is formed at the interface between the second metal layer 61 and the electron transport layer 62. By applying a bias voltage Vg2 to the second electrode 30 and the fourth electrode 110 and changing the voltage of the second electrode 30 and the fourth electrode 110, the Schottky barrier at the interface between the second metal layer 61 and the electron transport layer 62 is changed, thereby changing the electron injection capability.

[0045] The voltage of Vg1 is equal to the difference between the potential of the first electrode 20 and the potential of the third electrode 90. For the hole side, when Vg1 is less than 0, holes accumulate at the interface of the first metal layer 51 / hole transport layer 52, the Schottky barrier becomes narrower, and hole injection is enhanced; the voltage of Vg2 is equal to the difference between the potential of the second electrode 30 and the potential of the fourth electrode 110. For the electron side, when Vg2 is greater than 0, electrons accumulate at the interface of the second metal layer 61 / electron transport layer 62, the Schottky barrier becomes narrower, and electron injection is enhanced.

[0046] It can be understood that when the applied voltage Vg1>0, the amount of hole injection can be suppressed; when the applied voltage Vg2<0, the electron injection ability can be suppressed. For the current problem of excessive electron injection, the amount of electron injection can be suppressed by applying the opposite voltage Vg2, which can also improve the overall performance of the quantum dot light-emitting device.

[0047] See also Figure 3 The anode 120 is arranged on the surface of the first metal layer 51 so that the holes generated by the anode 120 can be injected from the first metal layer 51, and the cathode 130 is arranged on the surface of the second metal layer 61 so that the electrons generated by the cathode 130 can be injected from the second metal layer 61.

[0048] Holes are injected from the anode 120, pass through the first metal layer 51, enter the hole transport layer 52, and reach the quantum dot light-emitting layer 80. Electrons are injected from the cathode 130, pass through the second metal layer 61, enter the electron transport layer 62, and reach the quantum dot light-emitting layer 80. Finally, the holes and electrons recombine in the quantum dot light-emitting layer 80 to emit light. The first electrode 20, the second electrode 30, the third electrode 90, and the fourth electrode 110 do not participate in the light-emitting process and are only used to adjust the size of the Schottky barrier to change the carrier injection capability.

[0049] The potential of the third electrode 90 and the potential of the fourth electrode 110 may be fixed potentials, so the voltage Vg1 and the voltage Vg2 may be changed correspondingly by simply changing the potential of the first electrode 20 and the potential of the second electrode 30 .

[0050] Since the first metal layer 51 needs to contact the anode 120 , an anode contact area can be reserved on the surface of the first metal layer 51 facing away from the first electrode 20 , and the anode 120 is disposed in the anode contact area.

[0051] It is understandable that the holes generated by the anode 120 need to first pass through the first metal layer 51 and then enter the hole transport layer 52 , so the anode 120 needs to be separated from the hole transport layer 52 .

[0052] Since the second metal layer 61 needs to contact the cathode 130 , a cathode contact area can be reserved on the surface of the second metal layer 61 facing away from the second electrode 30 , and the cathode 130 is disposed in the cathode contact area.

[0053] It is understandable that the electrons generated by the cathode 130 need to first pass through the second metal layer 61 and then enter the electron transport layer 62 , so the anode 120 needs to be separated from the hole transport layer 52 .

[0054] In one embodiment, the hole functional layer 50, the electron functional layer 60 and the quantum dot light-emitting layer 80 can be formed first, and then the hole transport layer 52, the electron transport layer 62 and part of the quantum dot light-emitting layer 80 on both sides of the quantum dot light-emitting device 100 are removed by etching or corrosion to expose part of the surface of the first metal layer 51 and part of the surface of the second metal layer 61, and an anode contact area and a cathode contact area are formed in the corresponding areas, and then an anode 120 is formed in the anode contact area, and a cathode 130 is formed in the cathode contact area.

[0055] The first metal layer 51 and the second metal layer 61 contain a large number of free electrons, which will shield the electric field to a certain extent. Therefore, the first metal layer 51 and the second metal layer 61 are preferably porous two-dimensional metal materials, which can allow the electric field to pass through the metal layer / carrier transport layer interface.

[0056] The material of the first metal layer 51 and the second metal layer 61 includes any one of carbon nanotubes (CNTs) and silver nanowires (AgNWs). The material of the first metal layer 51 is preferably CNTs, and the material of the second metal layer 61 is preferably AgNWs.

[0057] See also Figure 3 In this embodiment, the first insulating layer 40 is a continuous pattern, which not only covers the first electrode 20 and the second electrode 30 , but also fills the gap between the first electrode 20 and the second electrode 30 .

[0058] See also Figure 4In other embodiments, the first insulating layer 40 is a discontinuous pattern, which is disconnected at the gap between the first electrode 20 and the second electrode 30 , and the gap between the first electrode 20 and the second electrode 30 is filled by the second insulating layer 70 .

[0059] In order to prevent the hole functional layer 50 and the electron functional layer 60 from functionally interfering with each other, there should be no overlapping surface between the hole functional layer 50 and the electron functional layer 60, that is, the orthographic projection of the hole functional layer 50 on the quantum dot light-emitting layer 80 does not overlap with the orthographic projection of the electron functional layer 60 on the quantum dot light-emitting layer 80.

[0060] Furthermore, a second insulating layer 70 may be provided between the hole functional layer 50 and the electron functional layer 60. The second insulating layer 70 separates the hole functional layer 50 and the electron functional layer 60 so that the film layers on the left and right sides of the second insulating layer 70 are insulated from each other, thereby avoiding mutual interference between the electric fields formed on the left and right sides.

[0061] Specifically, the hole functional layer 50 , the electron functional layer 60 and the second insulating layer 70 are all disposed on the first insulating layer 40 in the same layer.

[0062] The surface of the hole transport layer 52 adjacent to the quantum dot light-emitting layer 80, the surface of the electron transport layer 62 adjacent to the quantum dot light-emitting layer 80, and the surface of the second insulating layer 70 adjacent to the quantum dot light-emitting layer 80 are flush with each other. The heights of the hole functional layer 50, the electron functional layer 60, and the second insulating layer 70 are kept consistent to provide a flat substrate, facilitating uniform spin coating of the quantum dot material on a flat surface.

[0063] The hole transport layer 52 may be made of any inorganic material such as NiO, WO 3 , or MoO 3 .

[0064] The material of the electron transport layer 62 includes any one of inorganic materials such as ZnO, SnO 2 , and Mg:ZnO.

[0065] The material of the second insulating layer 70 and the material of the first insulating layer 40 include any one of transparent insulating materials such as polymethyl methacrylate (PMMA) and aluminum oxide (Al 2 O 3 ).

[0066] Since it is necessary to maintain the same height for the hole functional layer 50, the electron functional layer 60, and the second insulating layer 70, atomic layer deposition (ALD) is a technique that forms a deposited film by alternately passing pulses of a gaseous precursor into a reactor and chemically adsorbing and reacting on a deposition substrate. The thickness of the deposited film can be controlled at the nanometer level. Therefore, ALD can solve the problem of maintaining the same film height. Since ALD has many restrictions on the deposited material, the material of the second insulating layer 70 in the embodiment of the present invention is preferably Al2O3.

[0067] The thickness of the first insulating layer 40 corresponding to the first electrode 20 and the second electrode 30 may be 120-200 nanometers to ensure that no current is generated between the first electrode 20 , the second electrode 30 and the anode 120 , the cathode 130 .

[0068] The first insulating layer 40 can be formed by spin coating, thermal evaporation or deposition, which is not limited here.

[0069] The quantum dot light-emitting layer 80 of the embodiment of the present invention is an electroluminescent layer, and its material is a core-shell quantum dot material. The material of the quantum dot light-emitting layer 80 can be any one of red quantum dot light-emitting material, blue quantum dot light-emitting material, and green quantum dot light-emitting material, including but not limited to any one of CdZnSe / CdZnS, CdZnSe / ZnSe / ZnCdS, and CdZnSe / ZnSe / ZnS.

[0070] The first electrode 20 and the second electrode 30 may be made of transparent indium tin oxide (ITO) material.

[0071] The substrate 10 is used as a base and can be a glass substrate or other transparent substrates, which is not limited here.

[0072] See also Figure 3 and Figure 5 Based on the quantum dot light-emitting device 100 in the above embodiment, the embodiment of the present invention also provides a preparation method of the above quantum dot light-emitting device 100, including: S10, forming a first electrode 20 and a second electrode 30 spaced apart on a substrate 10; S20, forming a first insulating layer 40 on the first electrode 20 and the second electrode 30; S30, forming a hole functional layer 50 in a region corresponding to the first electrode 20, and forming an electron functional layer 60 in a region corresponding to the second electrode 30; S40, forming a quantum dot light-emitting layer 80 on the hole functional layer 50 and the electron functional layer 60; S50, forming a third electrode 90 corresponding to the first electrode 20 and a fourth electrode 110 corresponding to the second electrode 30 on the quantum dot light-emitting layer 80.

[0073] The preparation of the hole functional layer 50 includes: sequentially forming a stacked first metal layer 51 and a hole transport layer 52 on the first insulating layer 40 .

[0074] The preparation of the electronic functional layer 60 includes: sequentially forming a stacked second metal layer 61 and an electron transport layer 62 on the first insulating layer 40 .

[0075] The preparation method further includes: forming a second insulating layer between the hole functional layer 50 and the electron functional layer 60 .

[0076] Specifically, see Figure 6 First, an ITO film layer is deposited on the substrate 10 , and then the ITO film layer is patterned to form a first electrode 20 and a second electrode 30 spaced apart.

[0077] The substrate 10, with the first electrode 20 and the second electrode 30 formed thereon, was then pretreated by ultrasonically cleaning the substrate 10 for 15 minutes using deionized water, acetone, and anhydrous ethanol. The cleaned substrate 10 was then subjected to an ultraviolet-ozone treatment for 13 to 17 minutes to further clean the substrate 10 and improve the surface activity and work function of the ITO electrode.

[0078] Then, a first insulating layer 40 is deposited on the first electrode 20 and the second electrode 30 . The first insulating layer 40 covers the first electrode 20 and the second electrode 30 and fills the gap between the first electrode 20 and the second electrode 30 .

[0079] The first insulating layer 40 may be made of transparent insulating materials such as PMMA and Al2O3, preferably Al2O3, and may be deposited by atomic layer deposition to form the first insulating layer 40. The thickness of the first insulating layer 40 may be 120-200 nm, preferably 150 nm.

[0080] See also Figure 7 A layer of first metal material 51' is deposited on the area of ​​the first insulating layer 40 corresponding to the first electrode 20, and a layer of second metal material 61' is deposited on the area of ​​the first insulating layer 40 corresponding to the second electrode 30. The order of deposition of the first metal material 51' and the second metal material 61' is not limited. The metal materials can be deposited using vacuum evaporation. When depositing one metal material in the corresponding area, a mask can be used to cover the other areas.

[0081] There is a certain distance between the deposited first metal material 51 ′ and the second metal material 61 ′ to avoid contact between the subsequently formed first metal layer and the second metal layer.

[0082] The metal materials may be deposited by vacuum evaporation. When one of the metal materials is deposited in the corresponding area, a mask may be used to cover the other areas.

[0083] The first metal material 51' and the second metal material 61' are both porous two-dimensional metal materials. The first metal material 51' and the second metal material 61' can be any one of CNTs and AgNWs. The first metal material 51' is preferably CNTs, and the second metal material 61' is preferably AgNWs.

[0084] See also Figure 8 Then, a hole transport material 52' is deposited on the first metal material 51', and an electron transport material 62' is deposited on the second metal material 61'. The order of depositing the hole transport material 52' and the electron transport material 62' is not limited. Vacuum evaporation can be used to deposit the carrier transport materials. When depositing one carrier transport material in a specific area, a mask can be used to cover other areas.

[0085] The deposited hole transport material 52 ′ and electron transport material 62 ′ are spaced a certain distance apart to avoid contact between the subsequently formed hole transport layer and electron transport layer.

[0086] The hole transport material 52 ′ includes inorganic materials such as NiO, WO 3 , and MoO 3 , preferably NiO. The deposition thickness of the hole transport material is preferably 40 nm.

[0087] The electron transport material 51 ′ includes inorganic materials such as ZnO, SnO 2 , and Mg:ZnO, and is preferably ZnO. The deposition thickness of the electron transport material 51 ′ is preferably 40 nm.

[0088] See also Figure 9 A second insulating layer 70 is deposited between the hole transport material 52' and the electron transport material 62'. The material of the second insulating layer 70 is preferably Al2O3. Al2O3 is deposited by atomic layer deposition, and the film thickness of the formed second insulating layer 70 can be controlled to reach the nanometer level, thereby controlling the upper surface of the second insulating layer 70 to be flush with the upper surface of the hole transport material 52' and the upper surface of the electron transport material 51', so as to provide a flat substrate for preparing the quantum dot light-emitting layer.

[0089] See also Figure 10A quantum dot luminescent material 80' is coated on the second insulating layer 70, the hole transport material 52', and the electron transport material 51'. The substrate coated with the quantum dot luminescent material 80' is then placed on a heating stage and annealed at 80°C for 10 minutes. The quantum dot luminescent material 80' is preferably CdZnSe / ZnSe / ZnCdS and can have a thickness of 40 nm.

[0090] See also Figure 11 , part of the hole transport material 52', the electron transport material 51' and the quantum dot light-emitting material 80' can be removed by etching or solution corrosion to form the anode contact area 101 and the cathode contact area 102, as well as the patterned hole transport layer 52, the electron transport layer 62 and the quantum dot light-emitting layer 80.

[0091] Specifically, taking the solution corrosion method as an example, the first end of the device having the hole transport material 52' is immersed in the decomposition solution until the hole transport material 52' and the quantum dot light-emitting material 80' at the first end are dissolved; the second end of the device having the electron transport material 62' is immersed in the decomposition solution until the electron transport material 62' and the quantum dot light-emitting material 80' at the second end are dissolved, and then the device is placed on a heating table and heated to evaporate the decomposition solution. The decomposition solution can be a chlorobenzene solution, which can well dissolve the substances in the carrier transport layer and the quantum dot light-emitting layer. The heating time is preferably 5 minutes, and the heating temperature is preferably 80°C.

[0092] The preparation method further includes: forming an anode 120 on the surface of the first metal layer 51 to generate holes; and forming a cathode 130 on the second metal layer 61 to generate electrons.

[0093] See also Figure 3 Specifically, after removing portions of the hole transport layer, electron transport layer, and quantum dot light-emitting layer, metals are deposited in corresponding areas using vacuum evaporation to form the anode 120, cathode 130, third electrode 90, and fourth electrode 110. The anode 120 is preferably Au metal, the cathode 130 is preferably Ag metal, the third electrode 90 and the fourth electrode 110 are preferably Al metal, and the thickness of each electrode is preferably 50 nm.

[0094] See also Figure 2 Finally, a third insulating layer 140 may be formed on each quantum dot light-emitting device 100 and in the gaps between the quantum dot light-emitting devices 100 to play an insulating and protective role.

[0095] The quantum dot light-emitting device 100 and its preparation method and display panel provided by the embodiments of the present invention have a hole functional layer 50 and an electron functional layer 60 arranged on the same side of the quantum dot light-emitting layer 80, so that a first electrode 20 and a third electrode 90 can be respectively arranged on both sides of the hole functional layer 50, and a second electrode 30 and a fourth electrode 110 can be arranged on both sides of the electron functional layer 60. The electric field formed by the first electrode 20 and the third electrode 90 does not interfere with the electric field formed by the second electrode 30 and the fourth electrode 110. By adjusting the size and positive and negative of the deflection voltage Vg1 corresponding to the first electrode 20, the hole injection ability can be enhanced or suppressed to varying degrees. By controlling the size and positive and negative of the deflection voltage Vg2 corresponding to the second electrode 30, the electron injection ability can be enhanced or suppressed to varying degrees, so as to achieve the optimal carrier injection state required by the quantum dot light-emitting device 100.

[0096] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0097] The above is a detailed introduction to a quantum dot light-emitting device, a preparation method thereof, and a display panel provided in an embodiment of the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the technical solutions and core ideas of the present invention. Ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A quantum dot light-emitting device, characterized in that: include: substrate; a first electrode and a second electrode spaced apart and arranged on the substrate; a first insulating layer, disposed on the first electrode and the second electrode; a hole functional layer, disposed on the first insulating layer and corresponding to the first electrode; an electronic functional layer, disposed on the first insulating layer and corresponding to the second electrode; A quantum dot light-emitting layer is provided on the hole functional layer and the electron functional layer; a third electrode, disposed on the quantum dot light-emitting layer and corresponding to the first electrode; as well as a fourth electrode, disposed on the quantum dot light-emitting layer and corresponding to the second electrode; Wherein, from the direction of the first electrode pointing to the quantum dot light-emitting layer, the hole functional layer includes a stacked first metal layer and a hole transport layer; from the direction of the second electrode pointing to the quantum dot light-emitting layer, the electron functional layer includes a stacked second metal layer and an electron transport layer; The quantum dot light emitting device further comprises: an anode, disposed on the surface of the first metal layer and spaced apart from the hole transport layer; and a cathode, disposed on a surface of the second metal layer and spaced apart from the electron transport layer; The first electrode, the second electrode, the third electrode and the fourth electrode do not participate in the light emitting process and are only used to adjust the size of the Schottky barrier.

2. The quantum dot light-emitting device according to claim 1, characterized in that The orthographic projection of the hole functional layer on the quantum dot light-emitting layer does not overlap with the orthographic projection of the electron functional layer on the quantum dot light-emitting layer; and a second insulating layer is provided between the hole functional layer and the electron functional layer.

3. The quantum dot light-emitting device according to claim 2, characterized in that The material of the first insulating layer and the material of the second insulating layer include any one of polymethyl methacrylate and aluminum oxide.

4. The quantum dot light-emitting device according to claim 1, characterized in that The first metal layer and the second metal layer are both porous metal layers, or the material of the first metal layer and the material of the second metal layer include any one of carbon nanotubes and metal silver nanowires.

5. The quantum dot light-emitting device according to claim 1, characterized in that The material of the hole transport layer includes any one of NiO, WO3, and MoO3; the material of the electron transport layer includes any one of ZnO, SnO2, and Mg:ZnO; and the material of the quantum dot light-emitting layer includes any one of CdZnSe / CdZnS, CdZnSe / ZnSe / ZnCdS, and CdZnSe / ZnSe / ZnS.

6. A display panel, characterized in that: A quantum dot light-emitting device comprising the quantum dot light-emitting device according to any one of claims 1 to 5.

7. A method for preparing a quantum dot light-emitting device, characterized in that: include: forming a first electrode and a second electrode spaced apart from each other on a substrate; forming a first insulating layer on the first electrode and the second electrode; forming a hole functional layer in a region corresponding to the first electrode and forming an electron functional layer in a region corresponding to the second electrode, comprising: sequentially stacking a first metal layer and a hole transport layer on the first insulating layer to form the hole functional layer; sequentially stacking a second metal layer and an electron transport layer on the first insulating layer to form the electron functional layer; forming a second insulating layer between the hole functional layer and the electron functional layer; forming an anode on a surface of the first metal layer; and forming a cathode on a surface of the second metal layer; forming a quantum dot light-emitting layer on the hole functional layer and the electron functional layer; forming a third electrode corresponding to the first electrode and a fourth electrode corresponding to the second electrode on the quantum dot light-emitting layer; The first electrode, the second electrode, the third electrode and the fourth electrode do not participate in the light emitting process and are only used to adjust the size of the Schottky barrier.

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