QLED device, preparation method thereof and display device

Abstract

The invention relates to a QLED device, a preparation method thereof and a display device. The QLED device includes: a substrate; the pixel unit is arranged on one side of the substrate; the hole function layer is arranged on one side, close to the substrate, of the pixel unit; the electronic function layer is arranged on one side, far away from the substrate, of the pixel unit; the pixel units comprise a first pixel unit, a second pixel unit and a third pixel unit, the light-emitting wavelength of the first pixel unit is larger than that of the second pixel unit, and the light-emitting wavelength of the second pixel unit is larger than that of the third pixel unit; the first pixel unit comprises a first quantum dot layer; in the direction perpendicular to the substrate, each second pixel unit comprises a second quantum dot layer and a first quantum dot layer which are stacked in sequence; in the direction perpendicular to the substrate, each third pixel unit comprises a third quantum dot layer, a second quantum dot layer and a first quantum dot layer which are sequentially stacked, and the first quantum dot layer is located on the side, away from the substrate, of the second quantum dot layer. The QLED device is good in performance and beneficial to wide application.

Description

Technical Field

[0001] This invention relates to the field of display technology, and in particular to a QLED device, its fabrication method, and a display apparatus. Background Technology

[0002] As a window for human-computer interaction, the performance of the display screen directly determines the user experience. In particular, as the viewing distance decreases, people's requirements for the display screen are getting higher and higher.

[0003] QLEDs have attracted widespread attention and research due to their wide color gamut, high brightness, low power consumption, flexibility, and low cost from wet processing. However, QLED devices still have some problems that hinder their widespread application. Summary of the Invention

[0004] Therefore, it is necessary to provide a QLED device, its fabrication method, and a display device to address the issue of how to improve the performance of QLED devices.

[0005] A QLED device, comprising:

[0006] Substrate;

[0007] A pixel unit disposed on one side of the substrate;

[0008] A hole functional layer is disposed on the side of the pixel unit near the substrate;

[0009] An electronic functional layer is disposed on the side of the pixel unit away from the substrate;

[0010] The pixel unit includes a first pixel unit, a second pixel unit, and a third pixel unit. The emission wavelength of the first pixel unit is greater than the emission wavelength of the second pixel unit, and the emission wavelength of the second pixel unit is greater than the emission wavelength of the third pixel unit.

[0011] The first pixel unit includes a first quantum dot layer;

[0012] Along a direction perpendicular to the substrate, the second pixel unit includes a second quantum dot layer and a first quantum dot layer stacked sequentially;

[0013] Along a direction perpendicular to the substrate, the third pixel unit includes a third quantum dot layer, a second quantum dot layer, and a first quantum dot layer stacked sequentially, wherein the first quantum dot layer is located on the side of the second quantum dot layer away from the substrate;

[0014] Wherein, the emission wavelength of the first quantum dot layer is greater than that of the second quantum dot layer, and the emission wavelength of the second quantum dot layer is greater than that of the third quantum dot layer.

[0015] The QLED device using the technical solution of this invention can avoid damage to the underlying quantum dot layer during the overlay process, prevent the thickness of the underlying quantum dot layer from decreasing and the surface roughness from increasing, effectively avoid the performance degradation of the QLED device, and thus obtain a high-performance upright QLED device, which is beneficial for its widespread application.

[0016] In one feasible implementation, the absolute value of the valence band top energy level of the third quantum dot layer is greater than the absolute value of the valence band top energy level of the second quantum dot layer, which is greater than the absolute value of the valence band top energy level of the first quantum dot layer.

[0017] Preferably, the absolute value of the conduction band bottom energy level of the third quantum dot layer is less than the absolute value of the conduction band bottom energy level of the second quantum dot layer, which is less than the absolute value of the conduction band bottom energy level of the first quantum dot layer.

[0018] In one feasible implementation, the first quantum dot layer includes a first quantum dot, the second quantum dot layer includes a second quantum dot, and the third quantum dot layer includes a third quantum dot. The emission wavelength of the first quantum dot is greater than that of the second quantum dot, and the emission wavelength of the second quantum dot is greater than that of the third quantum dot. The first quantum dot, the second quantum dot, and the third quantum dot all include a core and a shell layer covering the surface of the core.

[0019] In one feasible implementation, the first quantum dot, the second quantum dot, and the third quantum dot are all quasi-type I energy level structures;

[0020] Preferably, in the quasi-Type I energy level structure, the absolute value of the difference between the conduction band bottom energy level of the outer shell layer and the conduction band bottom energy level of the core is less than the absolute value of the difference between the valence band top energy level of the outer shell layer and the valence band top energy level of the core.

[0021] Preferably, the absolute value of the difference between the bottom conduction band level of the outer shell of the first quantum dot, the second quantum dot, and the third quantum dot and the bottom conduction band level of the core is 0 eV to 0.1 eV; the absolute value of the difference between the top valence band level of the outer shell of the first quantum dot, the second quantum dot, and the third quantum dot and the top valence band level of the core is ≥0.3 eV.

[0022] In one feasible implementation, the core and outer shell of the first quantum dot, the second quantum dot, and the third quantum dot all have the same composition of metallic elements;

[0023] Preferably, the first pixel unit is a red pixel unit, the second pixel unit is a green pixel unit, and the third pixel unit is a blue pixel unit; the first quantum dot layer is a red quantum dot layer, the second quantum dot layer is a green quantum dot layer, and the third quantum dot layer is a blue quantum dot layer; or the first quantum dot is a red quantum dot, the second quantum dot is a green quantum dot, and the third quantum dot is a blue quantum dot.

[0024] In one feasible implementation, the core and outer shell of the first quantum dot are made of CdSe and CdSe, respectively. x1 S 1-x1 CdSe x2 S 1-x2 and CdSe x3 S 1-x3 CdZnSe and CdZnSe x4 S 1-x4 、CdZnSe x5 S 1-x5 and CdZnSe x6 S 1-x6 ;

[0025] Where, 0≤x1<1, 0<x3<x2<1, 0≤x4<1, 0<x6<x5<1;

[0026] Preferably, the core and outer shell of the second quantum dot are made of CdSe, respectively. y1 S 1-y1 and CdSe y2 S 1-y2 CdZnSe and CdZnSe y3 S 1-y3 、CdZnSe y4 S 1-y4 and CdZnSe y5 S 1-y5 ;

[0027] Where, 0 < y2 < y1 < 1, 0 ≤ y3 < 1, 0 < y5 < y4 < 1;

[0028] Preferably, the core and outer shell of the third quantum dot are made of ZnSe and ZnSe, respectively. z1 S 1-z1 ZnSe z2 S 1-z2 andZnSe z3 S 1-z3 CdZnSe and CdZnSe z4 S 1-z4 、CdZnSe z5 S 1-z5 and CdZnSe z6S 1-z6 ;

[0029] Where 0≤z1<1, 0<z3<z2<1, 0≤z4<1, 0<z6<z5<1.

[0030] In one feasible implementation, the QLED device further includes:

[0031] The first electrode layer is located between the substrate and the hole functional layer;

[0032] The second electrode layer is located on the side of the electronic functional layer away from the substrate;

[0033] Wherein, the first electrode layer is the anode, and the second electrode layer is the cathode;

[0034] Preferably, the hole functional layer includes a hole injection layer and a hole transport layer sequentially stacked along a direction away from the substrate;

[0035] Preferably, the electronic functional layer includes an electronic transport layer;

[0036] Preferably, the valence band top energy level of the hole transport layer is greater than the valence band top energy level of the third quantum dot layer, and the absolute value of the difference between the valence band top energy level of the hole transport layer and the valence band top energy level of the third quantum dot layer is 1.0 eV to 1.5 eV;

[0037] Preferably, the valence band top energy level of the hole transport layer is greater than the valence band top energy level of the second quantum dot layer, and the absolute value of the difference between the valence band top energy level of the hole transport layer and the valence band top energy level of the second quantum dot layer is 0.5 eV to 1.0 eV;

[0038] Preferably, the valence band top energy level of the hole transport layer is greater than that of the first quantum dot layer, and the absolute value of the difference between the valence band top energy level of the hole transport layer and the valence band top energy level of the first quantum dot layer is 0 to 0.5 eV.

[0039] Preferably, the region other than the first pixel unit, the second pixel unit, and the third pixel unit includes a first quantum dot layer;

[0040] Preferably, the area outside the first pixel unit, the second pixel unit, and the third pixel unit has no first quantum dot layer.

[0041] A method for fabricating a QLED device includes the following steps:

[0042] A substrate is provided, the substrate comprising a third pixel region, a second pixel region, and a first pixel region;

[0043] A hole functional layer is formed in the third pixel region, the second pixel region, and the first pixel region on the substrate;

[0044] A full layer of third quantum dot material is coated on the substrate and the hole functional layer to obtain a third quantum dot material layer. The third quantum dot material layer is then photolithographically removed to remove the third quantum dot material outside the third sub-pixel region, thereby obtaining a third quantum dot layer located in the third pixel region.

[0045] A second quantum dot material with an emission wavelength greater than that of the third quantum dot material layer is coated on the substrate and the third quantum dot layer to obtain a second quantum dot material layer. The second quantum dot material layer is then photolithographically etched to remove the second quantum dot material in areas other than the third pixel region and the second pixel region, thereby obtaining a second quantum dot layer located in the third pixel region and the second pixel region.

[0046] A first quantum dot material with a wavelength greater than that of the second quantum dot material layer is coated onto the substrate and the second quantum dot layer to obtain a first quantum dot material layer. The first quantum dot material layer is then photolithographically etched to remove the first quantum dot material from the second pixel region, the area outside the second pixel region, and the first pixel region, resulting in a first quantum dot layer located in the third pixel region, the second pixel region, and the first pixel region. Alternatively, a first quantum dot material with a wavelength greater than that of the second quantum dot material layer is coated onto the substrate and the second quantum dot layer to obtain a first quantum dot material layer. The first quantum dot material layer is then cured to obtain a first quantum dot layer.

[0047] An electronic functional layer is formed on the first quantum dot layer.

[0048] The method for fabricating QLED devices according to the technical solution of the present invention does not intentionally remove the quantum dot emitting layer above the existing quantum dot emitting layer during the patterning process of the quantum dot emitting layer using photolithography. This avoids damage to the quantum dot emitting layer during the development process of quantum dot emitting layer overlay, prevents the thickness of the lower quantum dot layer from decreasing and the surface roughness from increasing, and effectively avoids the performance degradation of QLED devices, thereby improving the performance and fabrication yield of QLED devices.

[0049] In one feasible implementation, the following steps are included before forming the hole functional layer:

[0050] An anode is formed on the substrate;

[0051] After forming the electronic functional layer, the following steps are also included:

[0052] A cathode is formed on the electronic functional layer.

[0053] A display device comprising a QLED device as described in any of the preceding claims, or comprising a QLED device prepared by any of the preceding claims.

[0054] The display device of the present invention includes the above-mentioned QLED device, which can avoid damage to the lower quantum dot layer during the overlay process, prevent the thickness of the lower quantum dot layer from decreasing and the surface roughness from increasing, and effectively avoid the performance degradation of the QLED device, thereby obtaining a high-performance upright QLED device, which is beneficial for wide application. Attached Figure Description

[0055] Figure 1 This is a side view of a QLED device according to an embodiment of the present invention;

[0056] Figure 2 This is a top view of a QLED device according to an embodiment of the present invention;

[0057] Figure 3 A schematic diagram of the quasi-Type I energy level structure;

[0058] Figure 4 This is a schematic diagram of the light-emitting principle of the third pixel unit of the quantum dot light-emitting layer of a QLED device according to an embodiment of the present invention.

[0059] Figure 5 This is a schematic diagram of the light-emitting principle of the second pixel unit of the quantum dot light-emitting layer of a QLED device according to an embodiment of the present invention;

[0060] Figure 6 This is a schematic diagram of the light-emitting principle of the first pixel unit of the quantum dot light-emitting layer of a QLED device according to an embodiment of the present invention.

[0061] Figure 7 This is a schematic diagram of the structure of a QLED device according to an embodiment of the present invention;

[0062] Figure 8 This is a side view of a QLED device according to another embodiment of the present invention;

[0063] Figure 9 This is a schematic diagram of the device structure of a bottom-emitting AMQLED according to an embodiment of the present invention;

[0064] Figure 10 This is a schematic diagram of the device structure of a top-emitting AMQLED according to an embodiment of the present invention;

[0065] Figure 11 This is a flowchart of a method for fabricating a QLED device according to an embodiment of the present invention;

[0066] Figure 12 This is a process diagram of a method for fabricating a QLED device according to an embodiment of the present invention;

[0067] Figure 13 This is a flowchart illustrating a method for fabricating a QLED device according to another embodiment of the present invention;

[0068] Figure 14 This is a process diagram of a method for fabricating a QLED device according to another embodiment of the present invention. Detailed Implementation

[0069] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0070] It should be noted that when a component is said to be "fixed to" another component, it can be directly attached to the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0071] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0072] Please see Figure 1 and Figure 2 One embodiment of the QLED device 100 includes a substrate 110, a pixel unit 120 disposed on one side of the substrate 110, a hole functional layer 130 disposed on the side of the pixel unit 120 close to the substrate 110, and an electronic functional layer 140 disposed on the side of the pixel unit 120 away from the substrate 110. The pixel unit 120 includes a first pixel unit 121, a second pixel unit 122, and a third pixel unit 123. The emission wavelength of the first pixel unit 121 is greater than the emission wavelength of the second pixel unit 122, and the emission wavelength of the second pixel unit 122 is greater than the emission wavelength of the third pixel unit 123.

[0073] The first pixel unit 121 includes a first quantum dot layer 124. Along a direction perpendicular to the substrate 110, the second pixel unit 122 includes a second quantum dot layer 125 and a first quantum dot layer 124 stacked sequentially. Along a direction perpendicular to the substrate 110, the third pixel unit 123 includes a third quantum dot layer 126, a second quantum dot layer 125, and a first quantum dot layer 124 stacked sequentially, wherein the first quantum dot layer 124 is located on the side of the second quantum dot layer 125 away from the substrate 110. The emission wavelength of the first quantum dot layer 124 is greater than the emission wavelength of the second quantum dot layer 125, and the emission wavelength of the second quantum dot layer 125 is greater than the emission wavelength of the third quantum dot layer 126.

[0074] In the second pixel unit 122, the second quantum dot layer 125 is disposed close to the substrate 110, and the first quantum dot layer 124 is disposed away from the substrate 110; in the third pixel unit 123, the third quantum dot layer 126 is disposed close to the substrate 110, and the first quantum dot layer 124 is disposed away from the substrate 110.

[0075] The first quantum dot layer 124 of the first pixel unit 121, the second quantum dot layer 125 of the second pixel unit 122, and the third quantum dot layer 126 of the third pixel unit 123 are located on the same substrate 110.

[0076] The QLED device 100 of this embodiment can avoid damage to the underlying quantum dot layer during the overlay process, prevent the thickness of the underlying quantum dot layer from decreasing and the surface roughness from increasing, effectively avoid the performance degradation of the QLED device, and thus obtain a QLED device with better performance, which is beneficial for its widespread application.

[0077] Based on the aforementioned implementation, the absolute value of the valence band top energy level of the third quantum dot layer 126 is greater than the absolute value of the valence band top energy level of the second quantum dot layer 125, which is greater than the absolute value of the valence band top energy level of the first quantum dot layer 124. Preferably, the absolute value of the conduction band bottom energy level of the third quantum dot layer 126 is less than the absolute value of the conduction band bottom energy level of the second quantum dot layer 125, which is less than the absolute value of the conduction band bottom energy level of the first quantum dot layer 124. It should be noted that the energy level relationships of each quantum dot layer in this implementation are absolute values. Since both the valence band and conduction band are negative values ​​in the energy level diagram, the smaller the absolute value, the higher the energy level.

[0078] Based on the aforementioned embodiments, the first quantum dot layer 124 includes a first quantum dot, the second quantum dot layer 125 includes a second quantum dot, and the third quantum dot layer 126 includes a third quantum dot. The emission wavelength of the first quantum dot is greater than that of the second quantum dot, and the emission wavelength of the second quantum dot is greater than that of the third quantum dot. The first quantum dot, the second quantum dot, and the third quantum dot all include a core and an outer shell layer covering the surface of the core.

[0079] Based on the aforementioned implementation method, the first quantum dot, the second quantum dot, and the third quantum dot are all quasi-type I energy level structures, such as Figure 3 As shown. In the quasi-Type I energy level structure, the absolute value of the difference between the bottom conduction band (CB) level of the outer shell and the bottom conduction band level of the core is smaller than the absolute value of the difference between the top valence band (VB) level of the outer shell and the top valence band level of the core. From Figure 3 The results show that the indentation of the top conduction band is less than that of the bottom valence band. At this time, electrons can move freely in the first quantum dot layer 124, the second quantum dot layer 125, and the third quantum dot layer 126, while the movement of holes in the first quantum dot layer 124, the second quantum dot layer 125, and the third quantum dot layer 126 is restricted.

[0080] Figures 4-6 This is a schematic diagram of the light-emitting principle of the pixel unit in the quantum dot light-emitting layer, and at the same time... Figure 7 Using the QLED device structure diagram shown as an example, the light-emitting principle of the pixel unit in the quantum dot light-emitting layer will be explained.

[0081] Please see Figure 7 The QLED device 100 further includes a first electrode layer 150 and a second electrode layer 160. The first electrode layer 150 is located between the substrate 110 and the hole functional layer 130; the second electrode layer 160 is located on the side of the electron functional layer 140 away from the substrate 110. The first electrode layer 150 is the anode, and the second electrode layer 160 is the cathode. The hole functional layer 130 includes a hole injection layer 131 and a hole transport layer 132 sequentially stacked along the direction away from the substrate 110; the electron functional layer 140 includes an electron transport layer (ETL). The QLED device 100 in this embodiment has a positive orientation. Furthermore, in the QLED device of this embodiment, the first quantum dot, the second quantum dot, and the third quantum dot are all quasi-type I energy level structures, such as... Figure 3 As shown. In the quasi-Type I energy level structure, the absolute value of the difference between the bottom conduction band (CB) level of the outer shell and the bottom conduction band level of the core is smaller than the absolute value of the difference between the top valence band (VB) level of the outer shell and the top valence band level of the core. From Figure 3 The results show that the indentation of the top conduction band is less than that of the bottom valence band. At this time, electrons can move freely in the first quantum dot layer 124, the second quantum dot layer 125, and the third quantum dot layer 126, while the movement of holes in these layers is restricted. The QLED device of this embodiment avoids damage to the underlying quantum dot layer during the overlay process, preventing a decrease in the thickness and an increase in surface roughness of the underlying quantum dot layer, effectively preventing performance degradation of the QLED device, thus obtaining a high-performance upright QLED device.

[0082] In the QLED device described above, the materials of functional layers such as hole functional layer 130, electron functional layer 140, first electrode layer 150 and second electrode layer 160 are selected from materials commonly used in functional layers in the QLED and OLED fields, and the present invention does not impose any limitations.

[0083] Based on the aforementioned embodiments, the valence band top energy level of the hole transport layer 132 is greater than that of the third quantum dot layer 126, and the absolute value of the difference between the valence band top energy level of the hole transport layer 132 and the valence band top energy level of the third quantum dot layer 126 is preferably any value between 1.0 eV and 1.5 eV, for example, 1.0 eV, 1.1 eV, 1.2 eV, 1.3 eV, 1.4 eV, or 1.5 eV; the valence band top energy level of the hole transport layer 132 is greater than that of the second quantum dot layer 125, and the absolute value of the difference between the valence band top energy level of the hole transport layer 132 and the valence band top energy level of the second quantum dot layer 125 is preferably any value between 0.5 eV and 1.0 eV, for example, 0.5 eV, 0.6 eV, 0.7 eV, or 0.8 eV. The hole transport layer 132 has a valence band top energy level greater than or equal to that of the first quantum dot layer 124, and the absolute value of the difference between the valence band top energy level of the hole transport layer 132 and the valence band top energy level of the first quantum dot layer 124 is preferably any value between 0 and 0.5 eV, for example, 0, 0.1 eV, 0.2 eV, 0.3 eV, 0.4 eV, or 0.5 eV; the absolute value of the difference between the conduction band bottom energy level of the electron transport layer 132 and the conduction band bottom energy levels of the third quantum dot layer 126, the second quantum dot layer 125, and the first quantum dot layer 124 is small, preferably any value between 0 and 0.3 eV, for example, 0, 0.1 eV, 0.2 eV, or 0.3 eV; the hole injection layer 131 is a commonly used material in the art, wherein... Figures 4-6 The hole injection layer 131 in the example is only an example, and the energy level of the hole injection layer 131 in the technical solution of the present invention is not limited thereto.

[0084] Specifically, in this embodiment, for the third pixel unit 123, electrons move from the cathode 160 sequentially through the electronic functional layer 140, the first quantum dot layer 124, the second quantum dot layer 125, and then to the third quantum dot layer 126. Holes pass through the hole injection layer 131 and then accumulate at the interface between the hole transport layer 132 and the third quantum dot layer 126. Electron-hole recombination mainly occurs radiatively in the third quantum dot layer 126. Figure 4 As shown. Figure 4As shown, for the third pixel unit 123, when a hole migrates from the anode 150 to the third quantum dot layer 126, the large valence band depression confines the hole within the third quantum dot layer 126, making it difficult for it to migrate to the second quantum dot layer 125 and the first quantum dot layer 124. When an electron migrates from the cathode 160 to the conduction band of the first quantum dot layer 124, the small conduction band depression makes it easier for the electron to migrate to the second quantum dot layer 125 and then to the third quantum dot layer 126.

[0085] For the second pixel unit 122, electrons move from the cathode 160 through the electronic functional layer 140, the first quantum dot layer 124, and then to the second quantum dot layer 125. Holes pass through the hole injection layer 131 and then accumulate at the interface between the hole transport layer 132 and the second quantum dot layer 125. Electron-hole recombination is primarily radiative in the second quantum dot layer 125. Figure 5 As shown. Figure 5 As shown, for the second pixel unit 122, when a hole migrates from the anode 150 to the second quantum dot layer 125, the large valence band depression can confine the hole within the second quantum dot layer 125, making it difficult for it to migrate to the first quantum dot layer 124; when an electron migrates from the cathode 160 to the conduction band of the first quantum dot layer 124, the small conduction band depression makes it easier for it to migrate to the second quantum dot layer 125.

[0086] For the first pixel unit 121, electrons move from the cathode 160 through the electronic functional layer 140 to the first quantum dot layer 124, while holes pass through the hole injection layer 131 and then accumulate at the interface between the hole transport layer 132 and the first quantum dot layer 124. Electron-hole recombination is primarily radiative in the first quantum dot layer 124. Figure 6 As shown. Figure 6 As shown, for the first pixel unit 121, when a hole migrates from the anode 150 to the first quantum dot layer 124, the hole can be confined within the first quantum dot layer 124 because of the large valence band depression; when an electron migrates from the cathode 160, it is easier to migrate to the first quantum dot layer 124 because of the small conduction band depression.

[0087] Based on the aforementioned embodiments, the absolute value of the difference between the bottom conduction band energy level of the outer shell layer of the first quantum dot, the second quantum dot, and the third quantum dot and the bottom conduction band energy level of the core is 0 eV to 0.1 eV, for example, it can be 0 eV, 0.01 eV, 0.02 eV, 0.03 eV, 0.04 eV, 0.05 eV, 0.06 eV, 0.07 eV, 0.08 eV, 0.09 eV, or 0.1 eV; the absolute value of the difference between the top valence band energy level of the outer shell layer of the first quantum dot, the second quantum dot, and the third quantum dot and the top valence band energy level of the core is ≥0.3 eV, for example, it can be any value between 0.3 eV and 1 eV, including but not limited to 0.3 eV, 0.4 eV, 0.5 eV, 0.6 eV, 0.7 eV, 0.8 eV, 0.9 eV, or 1 eV. At this point, electrons can move freely in the first quantum dot layer 124, the second quantum dot layer 125, and the third quantum dot layer 126, while the movement of holes in the aforementioned quantum dot luminescent layers is restricted. This results in the following: for the third pixel unit 123, the recombination of electrons and holes is mainly in the third quantum dot layer 126, and the first quantum dot layer 124 and the second quantum dot layer 125 do not participate in luminescence, resulting in high purity of the blue luminescence spectrum; for the second pixel unit 122, the recombination of electrons and holes is mainly in the second quantum dot layer 125, and the first quantum dot layer 124 does not participate in luminescence, resulting in high purity of the green luminescence spectrum.

[0088] Based on the aforementioned embodiments, the core and outer shell of the first, second, and third quantum dots all contain the same metallic elements. This helps to ensure that the absolute values ​​of the differences between the bottom conduction band energy levels of the outer shells and the bottom conduction band energy levels of the cores of the first, second, and third quantum dots, as well as the absolute values ​​of the differences between the top valence band energy levels of the outer shells and the top valence band energy levels of the cores of the first, second, and third quantum dots, satisfy the aforementioned relationship.

[0089] Based on the aforementioned implementation, the first pixel unit 121 is a red pixel unit, the second pixel unit 122 is a green pixel unit, and the third pixel unit 123 is a blue pixel unit; the first quantum dot layer 124 is a red quantum dot layer RQD, the second quantum dot layer 125 is a green quantum dot layer GQD, and the third quantum dot layer 126 is a blue quantum dot layer BQD; the first quantum dot is a red quantum dot, the second quantum dot is a green quantum dot, and the third quantum dot is a blue quantum dot.

[0090] Based on the aforementioned implementation, the core and outer shell of the first quantum dot are made of CdSe and CdSe, respectively. x1 S 1-x1 CdSe x2 S 1-x2 and CdSe x3 S 1-x3CdZnSe and CdZnSe x4 S 1-x4 、CdZnSe x5 S 1-x5 and CdZnSe x6 S 1-x6 Wherein, 0 ≤ x1 < 1, 0 < x3 < x2 < 1, 0 ≤ x4 < 1, 0 < x6 < x5 < 1. Preferably, the core and outer shell of the second quantum dot are made of CdSe, respectively. y1 S 1-y1 and CdSe y2 S 1-y2 CdZnSe and CdZnSe y3 S 1-y3 、CdZnSe y4 S 1-y4 and CdZnSe y5 S 1-y5 Wherein, 0 < y2 < y1 < 1, 0 ≤ y3 < 1, 0 < y5 < y4 < 1. Preferably, the core and outer shell of the third quantum dot are made of ZnSe and ZnSe, respectively. z1 S 1-z1 ZnSe z2 S 1-z2 andZnSe z3 S 1-z3 CdZnSe and CdZnSe z4 S 1-z4 、CdZnSe z5 S 1-z5 and CdZnSe z6 S 1-z6 Wherein, 0≤z1<1, 0<z3<z2<1, 0≤z4<1, 0<z6<z5<1. This embodiment carefully selects the first quantum dot, the second quantum dot, and the first quantum dot so that in the third pixel unit 123, electrons and holes recombine in the third quantum dot layer 126; in the second pixel unit 122, electrons and holes recombine in the second quantum dot layer 125; and in the first pixel unit 121, electrons and holes recombine in the first quantum dot layer 124, thereby maintaining the high color purity and color gamut of QLED.

[0091] Preferably, in the QLED device 100 described above, the area other than the first pixel unit 121, the second pixel unit 122, and the third pixel unit 123 does not have the first quantum dot layer 124. However, the QLED device structure of the present invention is not limited to this.

[0092] Please see Figure 8Another embodiment of the QLED device 200 of the present invention includes a substrate 210, a pixel unit 220 disposed on one side of the substrate 210, a hole functional layer 230 disposed on the side of the pixel unit 220 closer to the substrate 210, and an electronic functional layer 240 disposed on the side of the pixel unit 220 away from the substrate 210. The pixel unit 220 includes a first pixel unit 221, a second pixel unit 222, and a third pixel unit 223. The emission wavelength of the first pixel unit 221 is greater than the emission wavelength of the second pixel unit 222, and the emission wavelength of the second pixel unit 222 is greater than the emission wavelength of the third pixel unit 223.

[0093] The first pixel unit 221 includes a first quantum dot layer 224. Along a direction perpendicular to the substrate 210, the second pixel unit 222 includes a second quantum dot layer 225 and a first quantum dot layer 224 stacked sequentially. Along a direction perpendicular to the substrate 210, the third pixel unit 223 includes a third quantum dot layer 226, a second quantum dot layer 225, and a first quantum dot layer 224 stacked sequentially, wherein the first quantum dot layer 224 is located on the side of the second quantum dot layer 225 away from the substrate 210. The emission wavelength of the first quantum dot layer 224 is greater than the emission wavelength of the second quantum dot layer 225, and the emission wavelength of the second quantum dot layer 225 is greater than the emission wavelength of the third quantum dot layer 226.

[0094] In the second pixel unit 222, the second quantum dot layer 225 is disposed close to the substrate 210, and the first quantum dot layer 224 is disposed away from the substrate 210; in the third pixel unit 223, the third quantum dot layer 226 is disposed close to the substrate 210, and the first quantum dot layer 224 is disposed away from the substrate 220.

[0095] In this embodiment, the area other than the first pixel unit 221, the second pixel unit 222 and the third pixel unit 223 includes the first quantum dot layer 224.

[0096] The QLED device using this embodiment can avoid damage to the underlying quantum dot layer during the overlay process, prevent the thickness of the underlying quantum dot layer from decreasing and the surface roughness from increasing, and effectively avoid the performance degradation of the QLED device, thereby obtaining a high-performance upright QLED device, which is beneficial for its widespread application.

[0097] Based on the aforementioned embodiments, the QLED device is a bottom-emitting AMQLED or a top-emitting AMQLED, as shown below. Figure 9 and Figure 10 As shown.

[0098] Please see Figure 9One embodiment of the bottom-emitting AMQLED 300 includes a substrate 310 and a first electrode layer 320, a hole function layer 330, a pixel unit 340, an electronic function layer 350, and a second electrode layer 360 sequentially stacked along a direction perpendicular to the substrate 310. The first electrode layer 320 is made of a transparent material, while the second electrode layer 360 can be made of an opaque material. Light is emitted along the first electrode layer 320 toward the substrate 310.

[0099] In this design, the first electrode layer 320 is the anode, the hole functional layer 330 includes a hole transport layer (HTL), the electron functional layer 350 includes an electron transport layer (ETL), and the second electrode layer 360 is the cathode. It should be noted that the hole functional layer 330 may also include a hole injection layer (HIL) located between the hole transport layer (HTL) and the first electrode layer 320.

[0100] Pixel unit 340 includes a first pixel unit 341, a second pixel unit 342, and a third pixel unit 343. The emission wavelength of the first pixel unit 341 is greater than that of the second pixel unit 342, and the emission wavelength of the second pixel unit 342 is greater than that of the third pixel unit 343. The first pixel unit 341 includes a first quantum dot layer 344. Along a direction perpendicular to the substrate 310, the second pixel unit 342 includes a second quantum dot layer 345 and a first quantum dot layer 344 stacked sequentially, with the second quantum dot layer 345 disposed close to the substrate 310 and the first quantum dot layer 344 disposed away from the substrate 310. Along a direction perpendicular to the substrate 310, the third pixel unit 340 includes a third quantum dot layer 346, a second quantum dot layer 345, and a first quantum dot layer 344 stacked sequentially, with the third quantum dot layer 346 disposed close to the substrate 310 and the first quantum dot layer 344 disposed away from the substrate 310. The first quantum dot layer 344 emits light at a wavelength greater than that of the second quantum dot layer 345, and the second quantum dot layer 345 emits light at a wavelength greater than that of the third quantum dot layer 346.

[0101] Please see Figure 10 One embodiment of a top-emitting AMQLED 400 includes a substrate 410 and a first electrode layer 420, a hole function layer 430, a pixel unit 440, an electronic function layer 450, and a second electrode layer 460 sequentially stacked along a direction perpendicular to the substrate 410. The first electrode layer 420 serves as a reflective electrode and is made of an opaque material, which facilitates upward light emission. The second electrode layer 460 is made of a transparent material, allowing light to be emitted from the electronic function layer 450 towards the second electrode layer 460.

[0102] In this design, the first electrode layer 420 is the anode, the hole functional layer 430 includes a hole transport layer (HTL), the electron functional layer 450 includes an electron transport layer (ETL), and the second electrode layer 460 is the cathode. It should be noted that the electron functional layer 450 may also include a hole injection layer (HIL) located between the hole transport layer (HTL) and the first electrode layer 420.

[0103] Pixel unit 440 includes a first pixel unit 441, a second pixel unit 442, and a third pixel unit 443. The emission wavelength of the first pixel unit 441 is greater than that of the second pixel unit 442, and the emission wavelength of the second pixel unit 442 is greater than that of the third pixel unit 443. The first pixel unit 441 includes a first quantum dot layer 444. Along a direction perpendicular to the substrate 410, the second pixel unit 442 includes a second quantum dot layer 445 and a first quantum dot layer 444 stacked sequentially, with the second quantum dot layer 445 disposed close to the substrate 410 and the first quantum dot layer 444 disposed away from the substrate 410. Along a direction perpendicular to the substrate 410, the third pixel unit 443 includes a third quantum dot layer 446, a second quantum dot layer 445, and a first quantum dot layer 444 stacked sequentially, with the third quantum dot layer 446 disposed close to the substrate 410 and the first quantum dot layer 444 disposed away from the substrate 410. The first quantum dot layer 444 emits light at a wavelength greater than that of the second quantum dot layer 445, and the second quantum dot layer 445 emits light at a wavelength greater than that of the third quantum dot layer 446.

[0104] The QLED device of the present invention includes a quantum dot light-emitting layer with the above-described structure, which can avoid damage to the underlying quantum dot layer during the overlay process. This helps to obtain a positive QLED device with good performance such as high brightness, high efficiency, low driving voltage, and long lifespan, which is beneficial for its wide application.

[0105] Please see also Figure 1 , Figure 11 and Figure 12 The method for fabricating a QLED device according to one embodiment of the present invention includes the following steps:

[0106] S11. A substrate 110 is provided, which includes a third pixel region, a second pixel region, and a first pixel region.

[0107] The third pixel region is the region used to form the third pixel unit, the second pixel region is the region used to form the second pixel unit, and the first pixel region is the region used to form the first pixel unit.

[0108] S12, A hole functional layer 130 is formed in the third pixel region, the second pixel region and the first pixel region on the substrate 110.

[0109] Hole functional layer 130 can be formed on the substrate 110 in the third pixel region, the second pixel region and the first pixel region using common techniques in the art.

[0110] S13. Coat an entire layer of third quantum dot material on the substrate 110 and the hole functional layer 130 to obtain a third quantum dot material layer 111. Perform photolithography on the third quantum dot material layer 111 to remove the third quantum dot material in the area outside the third pixel region to obtain a third quantum dot layer 126 located in the third pixel region.

[0111] The third quantum dot material includes third quantum dots and adhesive. The adhesive can be photoresist or other types of adhesive. Photoresist is suitable for photolithography (exposure and development).

[0112] In step S13, the photolithography operation on the third quantum dot material layer 111 involves exposing and developing the third quantum dot material layer 111. During the exposure process, a mask 171 can be used to block the non-exposed areas.

[0113] S14. Coat the entire layer of second quantum dot material with an emission wavelength greater than that of the third quantum dot material layer 111 on the substrate 110 and the third quantum dot layer 126 to obtain the second quantum dot material layer 112. Perform photolithography on the second quantum dot material layer 112 to remove the second quantum dot material in the areas outside the third pixel region and the second pixel region to obtain the second quantum dot layer 125 located in the third pixel region and the second pixel region.

[0114] The second quantum dot material includes a second quantum dot and an adhesive. The adhesive can be a photoresist or other types of adhesive. The photoresist is suitable for photolithography (exposure and development).

[0115] In step S14, the photolithography operation on the second quantum dot material layer 112 involves exposing and developing the second quantum dot material layer 112. During the exposure process, a mask 172 can be used to block the non-exposed areas.

[0116] S15. Coat the entire layer of first quantum dot material with a wavelength greater than that of the second quantum dot material layer 112 on the substrate 110 and the second quantum dot layer 125 to obtain the first quantum dot material layer 113. Perform photolithography on the first quantum dot material layer 113 to remove the first quantum dot material in areas other than the third pixel region, the second pixel region and the first pixel region, to obtain the first quantum dot layer 124 located in the third pixel region, the second pixel region and the first pixel region.

[0117] The first quantum dot material includes a first quantum dot and an adhesive. The adhesive can be a photoresist or other types of adhesive. The photoresist is suitable for photolithography (exposure and development).

[0118] In step S15, the photolithography operation on the first quantum dot material layer 113 involves exposing and developing the first quantum dot material layer 113. During the exposure process, a mask 173 can be used to block the non-exposed areas. It should be noted that in the QLED device fabrication method of this embodiment, other feasible methods can also be used to obtain the third quantum dot layer 126, the second quantum dot layer 125, and the first quantum dot layer 124.

[0119] S16. An electronic functional layer 140 is formed on the first quantum dot layer 124.

[0120] An electronic functional layer 140 can be formed on the first quantum dot layer 124 using methods commonly used in the field.

[0121] Combination Figure 1 The QLED device 100 obtained in step S16 includes a substrate 110, a pixel unit 120 disposed on one side of the substrate 110, a hole functional layer 130 disposed on the side of the pixel unit 120 close to the substrate 110, and an electronic functional layer 140 disposed on the side of the pixel unit 120 away from the substrate 110. The pixel unit 120 includes a first pixel unit 121, a second pixel unit 122, and a third pixel unit 123. The emission wavelength of the first pixel unit 121 is greater than the emission wavelength of the second pixel unit 122, and the emission wavelength of the second pixel unit 122 is greater than the emission wavelength of the third pixel unit 123.

[0122] The first pixel unit 121 includes a first quantum dot layer 124. Along a direction perpendicular to the substrate 110, the second pixel unit 122 includes a second quantum dot layer 125 and a first quantum dot layer 124 stacked sequentially. Along a direction perpendicular to the substrate 110, the third pixel unit 123 includes a third quantum dot layer 126, a second quantum dot layer 125, and a first quantum dot layer 124 stacked sequentially, wherein the first quantum dot layer 124 is located on the side of the second quantum dot layer 125 away from the substrate 110. The emission wavelength of the first quantum dot layer 124 is greater than the emission wavelength of the second quantum dot layer 125, and the emission wavelength of the second quantum dot layer 125 is greater than the emission wavelength of the third quantum dot layer 126.

[0123] In the second pixel unit 122, the second quantum dot layer 125 is disposed close to the substrate 110, and the first quantum dot layer 124 is disposed away from the substrate 110; in the third pixel unit 123, the third quantum dot layer 126 is disposed close to the substrate 110, and the first quantum dot layer 124 is disposed away from the substrate 110.

[0124] The first quantum dot layer 124 of the first pixel unit 121, the second quantum dot layer 125 of the second pixel unit 122, and the third quantum dot layer 126 of the third pixel unit 123 are located on the same substrate 110.

[0125] Please see also Figure 8 , Figure 13 and Figure 14 Another embodiment of the present invention provides a method for fabricating a QLED device, comprising the following steps:

[0126] S21. A substrate 210 is provided, which includes a third pixel region, a second pixel region, and a first pixel region.

[0127] The third pixel region is the region used to form the third pixel unit, the second pixel region is the region used to form the second pixel unit, and the first pixel region is the region used to form the first pixel unit.

[0128] S22, A hole functional layer 230 is formed in the third pixel region, the second pixel region and the first pixel region on the substrate 210.

[0129] Hole functional layer 230 can be formed on substrate 210 in the third pixel region, the second pixel region and the first pixel region using common techniques in the art.

[0130] S23. Coat an entire layer of third quantum dot material on the substrate 210 and the hole functional layer 130 to obtain a third quantum dot material layer 211. Perform photolithography on the third quantum dot material layer 211 to remove the third quantum dot material in the area outside the third pixel region to obtain a third quantum dot layer 226 located in the third pixel region.

[0131] The third quantum dot material includes third quantum dots and adhesive. The adhesive can be photoresist or other types of adhesive. Photoresist is suitable for photolithography (exposure and development).

[0132] In step S23, the photolithography operation on the third quantum dot material layer 211 involves exposing and developing the third quantum dot material layer 211. During the exposure process, a mask 271 can be used to block the non-exposed areas.

[0133] S24. Coat the entire layer of second quantum dot material with an emission wavelength greater than that of the third quantum dot material layer 211 on the substrate 210 and the third quantum dot layer 226 to obtain the second quantum dot material layer 212. Perform photolithography on the second quantum dot material layer 212 to remove the second quantum dot material in the areas outside the third pixel region and the second pixel region to obtain the second quantum dot layer 225 located in the third pixel region and the second pixel region.

[0134] The second quantum dot material includes a second quantum dot and an adhesive. The adhesive can be a photoresist or other types of adhesive. The photoresist is suitable for photolithography (exposure and development).

[0135] In step S24, the photolithography operation on the second quantum dot material layer 212 involves exposing and developing the second quantum dot material layer 212. During the exposure process, a mask 272 can be used to block the non-exposed areas.

[0136] S25. Coat the substrate 210 and the second quantum dot layer 225 with a first quantum dot material having a wavelength greater than that of the second quantum dot material layer 212 to obtain a first quantum dot material layer 213. Then, cure the first quantum dot material layer 213 to obtain a first quantum dot layer 224.

[0137] The first quantum dot material includes first quantum dots and adhesive. The adhesive can be a photocurable, thermocurable, or other type of adhesive.

[0138] S26. An electronic functional layer 240 is formed on the first quantum dot layer 224.

[0139] Combination Figure 8 The QLED device 200 obtained in step S26 includes a substrate 210, a pixel unit 220 disposed on one side of the substrate 210, a hole functional layer 230 disposed on the side of the pixel unit 220 closer to the substrate 210, and an electronic functional layer 240 disposed on the side of the pixel unit 220 away from the substrate 210. The pixel unit 220 includes a first pixel unit 221, a second pixel unit 222, and a third pixel unit 223. The emission wavelength of the first pixel unit 221 is greater than the emission wavelength of the second pixel unit 222, and the emission wavelength of the second pixel unit 222 is greater than the emission wavelength of the third pixel unit 223.

[0140] The first pixel unit 221 includes a first quantum dot layer 224. Along a direction perpendicular to the substrate 210, the second pixel unit 222 includes a second quantum dot layer 225 and a first quantum dot layer 224 stacked sequentially. Along a direction perpendicular to the substrate 210, the third pixel unit 223 includes a third quantum dot layer 226, a second quantum dot layer 225, and a first quantum dot layer 224 stacked sequentially, wherein the first quantum dot layer 224 is located on the side of the second quantum dot layer 225 away from the substrate 210. The emission wavelength of the first quantum dot layer 224 is greater than the emission wavelength of the second quantum dot layer 225, and the emission wavelength of the second quantum dot layer 225 is greater than the emission wavelength of the third quantum dot layer 226.

[0141] In the second pixel unit 222, the second quantum dot layer 225 is disposed close to the substrate 210, and the first quantum dot layer 224 is disposed away from the substrate 210; in the third pixel unit 223, the third quantum dot layer 226 is disposed close to the substrate 210, and the first quantum dot layer 224 is disposed away from the substrate 220.

[0142] In this embodiment, the area other than the first pixel unit 221, the second pixel unit 222 and the third pixel unit 223 includes the first quantum dot layer 224.

[0143] The QLED device fabrication method of this embodiment involves obtaining a first quantum dot material layer and then curing it to obtain a first quantum dot layer 224, thereby obtaining a QLED device. This eliminates the need for exposure and development steps on the first quantum dot material layer, thus improving production efficiency.

[0144] Based on the foregoing embodiments, before forming the hole functional layer, the method further includes the following step: forming an anode on a substrate. After forming the electronic functional layer, the method further includes the following step: forming a cathode on the electronic functional layer.

[0145] The method for fabricating QLED devices according to the technical solution of the present invention does not intentionally remove the quantum dot emitting layer above the existing quantum dot emitting layer during the patterning process of the quantum dot emitting layer using photolithography. This avoids damage to the quantum dot emitting layer during the development process of quantum dot emitting layer overlay, prevents the thickness of the lower quantum dot layer from decreasing and the surface roughness from increasing, and effectively avoids the performance degradation of QLED devices, thereby improving the performance and fabrication yield of QLED devices.

[0146] One embodiment of the display device includes any of the QLED devices described above.

[0147] The display device of the present invention includes the above-mentioned QLED device, which can avoid damage to the lower quantum dot layer during the overlay process, prevent the thickness of the lower quantum dot layer from decreasing and the surface roughness from increasing, and effectively avoid the performance degradation of the QLED device, thereby obtaining a high-performance upright QLED device, which is beneficial for wide application.

[0148] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0149] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A QLED device, characterized in that, include: Substrate; A pixel unit disposed on one side of the substrate; A hole functional layer is disposed on the side of the pixel unit near the substrate; An electronic functional layer is disposed on the side of the pixel unit away from the substrate; The pixel unit includes a first pixel unit, a second pixel unit, and a third pixel unit. The emission wavelength of the first pixel unit is greater than the emission wavelength of the second pixel unit, and the emission wavelength of the second pixel unit is greater than the emission wavelength of the third pixel unit. The first pixel unit includes a first quantum dot layer; Along a direction perpendicular to the substrate, the second pixel unit includes a second quantum dot layer and a first quantum dot layer stacked sequentially; Along a direction perpendicular to the substrate, the third pixel unit includes a third quantum dot layer, a second quantum dot layer, and a first quantum dot layer stacked sequentially, wherein the first quantum dot layer is located on the side of the second quantum dot layer away from the substrate; Wherein, the emission wavelength of the first quantum dot layer is greater than that of the second quantum dot layer, and the emission wavelength of the second quantum dot layer is greater than that of the third quantum dot layer.

2. The QLED device according to claim 1, characterized in that, The absolute value of the valence band top energy level of the third quantum dot layer is greater than the absolute value of the valence band top energy level of the second quantum dot layer, which is greater than the absolute value of the valence band top energy level of the first quantum dot layer. Preferably, the absolute value of the conduction band bottom energy level of the third quantum dot layer is less than the absolute value of the conduction band bottom energy level of the second quantum dot layer, which is less than the absolute value of the conduction band bottom energy level of the first quantum dot layer.

3. The QLED device according to claim 1, characterized in that, The first quantum dot layer includes a first quantum dot, the second quantum dot layer includes a second quantum dot, and the third quantum dot layer includes a third quantum dot. The emission wavelength of the first quantum dot is greater than that of the second quantum dot, and the emission wavelength of the second quantum dot is greater than that of the third quantum dot. The first quantum dot, the second quantum dot, and the third quantum dot all include a core and an outer shell layer covering the surface of the core.

4. The QLED device according to claim 3, characterized in that, The first quantum dot, the second quantum dot, and the third quantum dot are all quasi-type I energy level structures; Preferably, in the quasi-Type I energy level structure, the absolute value of the difference between the conduction band bottom energy level of the outer shell layer and the conduction band bottom energy level of the core is less than the absolute value of the difference between the valence band top energy level of the outer shell layer and the valence band top energy level of the core. Preferably, the absolute value of the difference between the bottom conduction band level of the outer shell of the first quantum dot, the second quantum dot, and the third quantum dot and the bottom conduction band level of the core is 0 eV to 0.1 eV; the absolute value of the difference between the top valence band level of the outer shell of the first quantum dot, the second quantum dot, and the third quantum dot and the top valence band level of the core is ≥0.3 eV.

5. The QLED device according to claim 3, characterized in that, The core and outer shell of the first quantum dot, the second quantum dot, and the third quantum dot all have the same metallic elements. Preferably, the first pixel unit is a red pixel unit, the second pixel unit is a green pixel unit, and the third pixel unit is a blue pixel unit; the first quantum dot layer is a red quantum dot layer, the second quantum dot layer is a green quantum dot layer, and the third quantum dot layer is a blue quantum dot layer; or the first quantum dot is a red quantum dot, the second quantum dot is a green quantum dot, and the third quantum dot is a blue quantum dot.

6. The quantum dot light-emitting layer according to claim 3, characterized in that, The core and outer shell of the first quantum dot are made of CdSe and CdSe, respectively. x1 S 1-x1 CdSe x2 S 1-x2 and CdSe x3 S 1-x3 CdZnSe and CdZnSe x4 S 1-x4 、CdZnSe x5 S 1-x5 and CdZnSe x6 S 1-x6 ; Where, 0≤x1<1, 0<x3<x2<1, 0≤x4<1, 0<x6<x5<1; Preferably, the core and outer shell of the second quantum dot are made of CdSe, respectively. y1 S 1-y1 and CdSe y2 S 1-y2 CdZnSe and CdZnSe y3 S 1-y3 、CdZnSe y4 S 1-y4 and CdZnSe y5 S 1-y5 ; Where, 0 < y2 < y1 < 1, 0 ≤ y3 < 1, 0 < y5 < y4 < 1; Preferably, the core and outer shell of the third quantum dot are made of ZnSe and ZnSe, respectively. z1 S 1-z1 ZnSe z2 S 1-z2 andZnSe z3 S 1-z3 CdZnSe and CdZnSe z4 S 1-z4 、CdZnSe z5 S 1-z5 and CdZnSe z6 S 1-z6 ; Where 0≤z1<1, 0<z3<z2<1, 0≤z4<1, 0<z6<z5<1.

7. The QLED device according to claim 1, characterized in that, The QLED device also includes: The first electrode layer is located between the substrate and the hole functional layer; The second electrode layer is located on the side of the electronic functional layer away from the substrate; Wherein, the first electrode layer is the anode, and the second electrode layer is the cathode; Preferably, the hole functional layer includes a hole injection layer and a hole transport layer sequentially stacked along a direction away from the substrate; Preferably, the electronic functional layer includes an electronic transport layer; Preferably, the valence band top energy level of the hole transport layer is greater than the valence band top energy level of the third quantum dot layer, and the absolute value of the difference between the valence band top energy level of the hole transport layer and the valence band top energy level of the third quantum dot layer is 1.0 eV to 1.5 eV; Preferably, the valence band top energy level of the hole transport layer is greater than the valence band top energy level of the second quantum dot layer, and the absolute value of the difference between the valence band top energy level of the hole transport layer and the valence band top energy level of the second quantum dot layer is 0.5 eV to 1.0 eV; Preferably, the valence band top energy level of the hole transport layer is greater than that of the first quantum dot layer, and the absolute value of the difference between the valence band top energy level of the hole transport layer and the valence band top energy level of the first quantum dot layer is 0 to 0.5 eV. Preferably, the region other than the first pixel unit, the second pixel unit, and the third pixel unit includes a first quantum dot layer; Preferably, the area outside the first pixel unit, the second pixel unit, and the third pixel unit has no first quantum dot layer.

8. A method for fabricating a QLED device, characterized in that, Includes the following steps: A substrate is provided, the substrate comprising a third pixel region, a second pixel region, and a first pixel region; A hole functional layer is formed in the third pixel region, the second pixel region, and the first pixel region on the substrate; A full layer of third quantum dot material is coated on the substrate and the hole functional layer to obtain a third quantum dot material layer. The third quantum dot material layer is then photolithographically removed to remove the third quantum dot material outside the third sub-pixel region, thereby obtaining a third quantum dot layer located in the third pixel region. A second quantum dot material with an emission wavelength greater than that of the third quantum dot material layer is coated on the substrate and the third quantum dot layer to obtain a second quantum dot material layer. The second quantum dot material layer is then photolithographically etched to remove the second quantum dot material in areas other than the third pixel region and the second pixel region, thereby obtaining a second quantum dot layer located in the third pixel region and the second pixel region. A first quantum dot material with a wavelength greater than that of the second quantum dot material layer is coated onto the substrate and the second quantum dot layer to obtain a first quantum dot material layer. The first quantum dot material layer is then photolithographically etched to remove the first quantum dot material from the second pixel region, the area outside the second pixel region and the first pixel region, to obtain a first quantum dot layer located in the third pixel region, the second pixel region and the first pixel region; or, a first quantum dot material with a wavelength greater than that of the second quantum dot material layer is coated onto the substrate and the second quantum dot layer to obtain a first quantum dot material layer. The first quantum dot material layer is then cured to obtain a first quantum dot layer. as well as An electronic functional layer is formed on the first quantum dot layer.

9. The method for fabricating a QLED device according to claim 8, characterized in that, The following steps are included before the formation of the hole functional layer: An anode is formed on the substrate; After forming the electronic functional layer, the following steps are also included: A cathode is formed on the electronic functional layer.

10. A display device, characterized in that, It includes the QLED device according to any one of claims 1 to 7, or the QLED device prepared by the preparation method according to claim 8 or 9.

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