QLED device and preparation method and application thereof

Abstract

The invention relates to a QLED device and a preparation method and application thereof. The QLED device comprises a red sub-pixel unit, a green sub-pixel unit and a blue sub-pixel unit which are arranged on one side of a substrate, the red sub-pixel unit comprises a red quantum dot layer; in the direction perpendicular to the substrate, each green sub-pixel unit comprises a green quantum dot layer and a red quantum dot layer which are sequentially stacked; in the direction perpendicular to the substrate, each blue sub-pixel unit comprises a blue quantum dot layer, a green quantum dot layer and a red quantum dot layer which are sequentially stacked; the red quantum dot layer is located on the side, away from the substrate, of the green quantum dot layer. According to the QLED device adopting the technical scheme, the damage of development to the lower quantum dot layer in the overlay process can be avoided, the thickness reduction, the surface roughness increase and the like of the lower quantum dot layer are prevented, and the performance reduction of the QLED device is effectively avoided, so that the inverted QLED device with relatively good performance is obtained, and the wide application is facilitated.

Description

Technical Field

[0001] The present invention relates to the field of display technologies, and particularly to a quantum dot light-emitting layer of an inverted QLED device, a preparation method thereof, and an application thereof. Background Art

[0002] As a window for human-computer interaction, the performance of a display screen directly determines the user experience. Especially as the viewing distance decreases, people have higher and higher requirements for the display screen.

[0003] Due to features such as a wide color gamut, high brightness, low power consumption, flexibility, and low cost of wet processes, QLED has received extensive attention and research. However, there are still some problems in QLED devices, which are not conducive to wide applications. Summary of the Invention

[0004] Based on this, in view of the problem of how to improve the performance of QLED devices, it is necessary to provide a QLED device, a preparation method thereof, and an application thereof.

[0005] A QLED device includes: a red sub-pixel unit, a green sub-pixel unit, and a blue sub-pixel unit disposed on one side of a substrate;

[0006] The red sub-pixel unit includes a red quantum dot layer;

[0007] Along a direction perpendicular to the substrate, the green sub-pixel unit includes a green quantum dot layer and a red quantum dot layer stacked in sequence;

[0008] Along a direction perpendicular to the substrate, the blue sub-pixel unit includes a blue quantum dot layer, a green quantum dot layer, and a red quantum dot layer stacked in sequence;

[0009] The red quantum dot layer is located on a side of the green quantum dot layer away from the substrate.

[0010] The QLED device applying the technical solution of the present invention can avoid the damage to the lower-layer quantum dot layer caused by development during the lithography process, prevent the thickness of the lower-layer quantum dot layer from decreasing, the surface roughness from increasing, etc., effectively avoid the performance degradation of the QLED device, and thus obtain an inverted QLED device with better performance, which is conducive to wide applications.

[0011] In a feasible implementation manner, the absolute value of the valence band top energy level of the blue quantum dot layer > the absolute value of the valence band top energy level of the green quantum dot layer > the absolute value of the valence band top energy level of the red quantum dot layer;

[0012] Preferably, the absolute value of the conduction band bottom energy level of the blue quantum dot layer < the absolute value of the conduction band bottom energy level of the green quantum dot layer < the absolute value of the conduction band bottom energy level of the red quantum dot layer.

[0013] In a feasible implementation, the red quantum dot layer includes red quantum dots, the green quantum dot layer includes green quantum dots, and the blue quantum dot layer includes blue quantum dots. The red quantum dots, the green quantum dots, and the blue quantum dots all include a core and a shell layer coated on the surface of the core;

[0014] Preferably, the red quantum dots, the green quantum dots, and the blue quantum dots all have a quasi-type I energy level structure.

[0015] Preferably, in the quasi-type I energy level structure, the absolute value of the difference between the conduction band bottom energy level of the shell layer and the conduction band bottom energy level of the core is greater than the absolute value of the difference between the valence band top energy level of the shell layer and the valence band top energy level of the core;

[0016] Preferably, for the red quantum dots, the green quantum dots, and the blue quantum dots, the absolute value of the difference between the conduction band bottom energy level of the shell layer and the conduction band bottom energy level of the core is ≥ 0.3 eV; the absolute value of the difference between the valence band top energy level of the shell layer and the valence band top energy level of the core is 0 eV to 0.1 eV.

[0017] In a feasible implementation, the cores and the shell layers of the red quantum dots, the green quantum dots, and the blue quantum dots all have non-metallic elements with the same composition.

[0018] In a feasible implementation, the materials of the core and the shell layer of the red quantum dots are CdSe and Cd

[0015] ,

[0014] , 1-x4 , 1-y3 , 1-x3 , 1-y2 , 1-x2 , 1-y1 , 1-x1 , ,

[0018] , 1-x5 ,

[0017] ,

[0016] , , , x5 , x4 , x3 , y4 , x2 ,

[0020] , y3 , , x1 ,

[0019] , y2 , , y1 , , Zn 1-x1 Se, Cd x2 Zn 1-x2 Se and Cd<00000​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​1-y4 SeS and Cd y5 Zn 1-y5 SeS;

[0021] where 0 ≤ y1 < 1; 0 ≤ y3 < 0.4 < y2 < 1; 0 ≤ y5 < 0.6 < y4 < 1;

[0022] Preferably, the materials of the core and the shell layer of the blue quantum dots are successively Cd z1 Zn 1-z1 Se and Cd z2 Zn 1-z2 Se, Cd z3 Zn 1-z3 SeS and Cd z4 Zn 1-z4 SeS, Cd z5 Zn 1-z5 S and ZnS;

[0023] where 0 ≤ z2 < 0.3 < z1 < 1; 0 ≤ z4 < 0.5 < z3 < 1; 0 < z5 ≤ 1.

[0024] In a feasible implementation, the QLED device further includes:

[0025] A first electrode layer, respectively located between the substrate and the red sub-pixel unit, the green sub-pixel unit, and the blue sub-pixel unit;

[0026] A second electrode layer, respectively located on the side of the red sub-pixel unit, the green sub-pixel unit, and the blue sub-pixel unit away from the substrate;

[0027] A first functional layer, respectively located between the first electrode layer and the red sub-pixel unit, the green sub-pixel unit, and the blue sub-pixel unit; and

[0028] A second functional layer, respectively located between the second electrode layer and the red sub-pixel unit, the green sub-pixel unit, and the blue sub-pixel unit;

[0029] Preferably, the first electrode layer is a cathode, and the second electrode layer is an anode;

[0030] Preferably, the first functional layer includes an electron transport layer, and the second functional layer includes a hole transport layer and a hole injection layer stacked in sequence;

[0031] Preferably, the area outside the red sub-pixel unit, the green sub-pixel unit, and the blue sub-pixel unit includes a red quantum dot layer;

[0032] Preferably, there is no red quantum dot layer in the area other than the red sub-pixel unit, the green sub-pixel unit, and the blue sub-pixel unit.

[0033] In a feasible implementation, the QLED device is a bottom-emitting AMQLED or a top-emitting AMQLED.

[0034] A method for preparing a QLED device includes the following steps:

[0035] Provide a substrate, the substrate including a blue sub-pixel region, a green sub-pixel region, and a red sub-pixel region;

[0036] Coat a whole layer of blue quantum dot material on the substrate to obtain a blue quantum dot material layer, perform photolithography on the blue quantum dot material layer, and remove the blue quantum dot material in the area other than the blue sub-pixel region to obtain a blue quantum dot layer located in the blue sub-pixel region;

[0037] Coat a whole layer of green quantum dot material on the substrate and the blue quantum dot layer to obtain a green quantum dot material layer, perform photolithography on the green quantum dot material layer, and remove the green quantum dot material in the area other than the blue sub-pixel region and the green sub-pixel region to obtain a green quantum dot layer located in the blue sub-pixel region and the green sub-pixel region; and

[0038] Coat a whole layer of red quantum dot material on the substrate and the green quantum dot layer to obtain a red quantum dot material layer, perform photolithography on the red quantum dot material layer, and remove the red quantum dot material in the area other than the blue sub-pixel region, the green sub-pixel region, and the red sub-pixel region to obtain a red quantum dot layer located in the blue sub-pixel region, the green sub-pixel region, and the red sub-pixel region, and obtain a QLED device;

[0039] Preferably, after coating the whole layer of red quantum dot material on the substrate and the green quantum dot layer, obtain a red quantum dot material layer, cure the red quantum dot material layer to obtain a red quantum dot layer, and obtain a QLED device.

[0040] In the method for preparing a QLED device according to the technical solution of the present invention, during the process of patterning the quantum dot light-emitting layer by using the photolithography process, the quantum dot light-emitting layer above the existing quantum dot light-emitting layer is not deliberately removed, avoiding the damage to the quantum dot light-emitting layer caused by development during the overetching of the quantum dot light-emitting layer, preventing the reduction of the thickness of the lower quantum dot layer, the increase of the surface roughness, etc., effectively avoiding the reduction of the performance of the QLED device, thereby improving the performance and preparation yield of the QLED device.

[0041] In a feasible implementation, before forming the blue quantum dot layer, the following steps are further included:

[0042] forming a first electrode layer on the substrate; and

[0043] forming a first functional layer on the first electrode layer;

[0044] After forming the red quantum dot layer, the following steps are further included:

[0045] forming a second functional layer on the red quantum dot layer; and

[0046] A second electrode layer is formed on the second functional layer.

[0047] A display device includes the above-mentioned QLED device.

[0048] The display device of the technical solution of the present invention includes the above-mentioned QLED device, which can avoid damage to the underlying quantum dot layer caused by development during the overlay process, prevent the thickness of the underlying quantum dot layer from decreasing, prevent the surface roughness from increasing, etc., effectively avoid the performance degradation of the QLED device, thereby obtaining an inverted QLED device with better performance, which is conducive to wide application. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 1 is a side view of a QLED device according to one embodiment of the present invention;

[0050] Figure 2 1 is a top view of a QLED device according to one embodiment of the present invention;

[0051] Figure 3 This is a diagram illustrating the light-emitting principle of a blue sub-pixel unit of a quantum dot light-emitting layer of a QLED device according to one embodiment of the present invention;

[0052] Figure 4 This is a diagram illustrating the light-emitting principle of a green sub-pixel unit of a quantum dot light-emitting layer of a QLED device according to one embodiment of the present invention;

[0053] Figure 5 This is a light-emitting principle diagram of a red sub-pixel unit of a quantum dot light-emitting layer of a QLED device according to one embodiment of the present invention;

[0054] Figure 6 Schematic diagram of quasi-type I energy level structure;

[0055] Figure 7 Schematic diagram of the structure of a QLED device according to one embodiment of the present invention;

[0056] Figure 8 is a side view of a QLED device according to another embodiment of the present invention;

[0057] Figure 9 Schematic diagram of the device structure of a bottom-emitting AMQLED according to one embodiment of the present invention;

[0058] Figure 10 Schematic diagram of the device structure of a top-emitting AMQLED according to an embodiment of the present invention;

[0059] Figure 11 Flow chart of the preparation method of a QLED device according to an embodiment of the present invention;

[0060] Figure 12 Process diagram of the preparation method of a QLED device according to an embodiment of the present invention;

[0061] Figure 13 Flow chart of the preparation method of a QLED device according to another embodiment of the present invention;

[0062] Figure 14 Process diagram of the preparation method of a QLED device according to another embodiment of the present invention;

[0063] Figure 15 Flow chart of forming a first electrode layer and a first functional layer in the preparation method of a QLED device according to an embodiment of the present invention;

[0064] Figure 16 Flow chart of forming a second electrode layer and a second functional layer in the preparation method of a QLED device according to an embodiment of the present invention. Detailed Embodiments

[0065] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following describes the detailed embodiments of the present invention in conjunction with the accompanying drawings. Many specific details are set forth in the following description to fully understand the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0066] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0067] Please refer to Figure 1 and Figure 2, a QLED device 100 in an embodiment includes a red sub-pixel unit 120, a green sub-pixel unit 130, and a blue sub-pixel unit 140 disposed on one side of a substrate 110. The red sub-pixel unit 120 includes a red quantum dot layer RQD. Along a direction perpendicular to the substrate 110, the green sub-pixel unit 130 includes a green quantum dot layer GQD and a red quantum dot layer RQD stacked in sequence. Along a direction perpendicular to the substrate 110, the blue sub-pixel unit 140 includes a blue quantum dot layer BQD, a green quantum dot layer GQD, and a red quantum dot layer RQD stacked in sequence. Among them, the red quantum dot layer RQD is located on the side away from the substrate 110 of the green quantum dot layer GQD.

[0068] Among them, in the green sub-pixel unit 130, the green quantum dot layer GQD is disposed close to the substrate 110, and the red quantum dot layer RQD is disposed away from the substrate 110; in the blue sub-pixel unit 140, the blue quantum dot layer BQD is disposed close to the substrate 110, and the red quantum dot layer RQD is disposed away from the substrate 110.

[0069] Among them, the red quantum dot layer RQD of the red sub-pixel unit 120, the green quantum dot layer GQD of the green sub-pixel unit 130, and the blue quantum dot layer BQD of the blue sub-pixel unit 140 are located on the same substrate 110.

[0070] The QLED device in the above embodiment can avoid the damage to the lower quantum dot layer during the development process in the lithography process, prevent the reduction of the thickness of the lower quantum dot layer, the increase of the surface roughness, etc., effectively avoid the performance degradation of the QLED device, and thus obtain a QLED device with better performance, which is beneficial to wide application.

[0071] On the basis of the foregoing embodiment, the absolute value of the valence band top energy level of the blue quantum dot layer > the absolute value of the valence band top energy level of the green quantum dot layer > the absolute value of the valence band top energy level of the red quantum dot layer. Preferably, the absolute value of the conduction band bottom energy level of the blue quantum dot layer < the absolute value of the conduction band bottom energy level of the green quantum dot layer < the absolute value of the conduction band bottom energy level of the red quantum dot layer. It should be noted that the energy level relationship of each quantum dot layer in this embodiment is an absolute value, and both the valence band and the conduction band in the energy level diagram are negative values. Therefore, reflected in the energy level diagram, the smaller the absolute value, the higher the energy level.

[0072] In addition, the electron functional layer and the hole functional layer can be, for example, Figures 3 to 5The structure shown, wherein the bottom energy level of the conduction band of the electron transport layer (ETL) is lower than that of the blue quantum dot layer (BQD). The absolute value of the difference therebetween is preferably any value between 0.7 eV and 1.2 eV, for example, it can be 0.7 eV, 0.8 eV, 0.9 eV, 1.0 eV, 1.1 eV or 1.2 eV; the bottom energy level of the conduction band of the electron transport layer (ETL) is lower than that of the green quantum dot layer (GQD). The absolute value of the difference therebetween is preferably any value between 0.3 eV and 0.7 eV, for example, it can be 0.3 eV, 0.4 eV, 0.5 eV, 0.6 eV or 0.7 eV; the bottom energy level of the conduction band of the electron transport layer (ETL) is less than or equal to that of the red quantum dot layer (RQD). The absolute value of the difference therebetween is preferably any value between 0 and 0.3 eV, for example, it can be 0, 0.1 eV, 0.2 eV or 0.3 eV; the absolute value of the difference between the top energy level of the valence band of the hole transport layer (HTL) and the top energy levels of the valence bands of the blue quantum dot layer (BQD), the green quantum dot layer (GQD) and the red quantum dot layer (RQD) is small, preferably any value between 0 and 0.3 eV, for example, it can be 0, 0.1 eV, 0.2 eV or 0.3 eV; the hole injection layer (HIL) is a commonly used material in the art.

[0073] In this embodiment, for the blue sub-pixel unit 140, holes move from the anode through the hole injection layer (HIL), the hole transport layer (HTL), the red quantum dot layer (RQD), the green quantum dot layer (GQD) to the blue quantum dot layer (BQD) in sequence. Electrons accumulate at the interface between the electron transport layer (ETL) and the blue quantum dot layer (BQD), and are confined within the blue quantum dot layer (BQD). Electron-hole recombination basically occurs in the blue quantum dot layer (BQD), as Figure 3 shown; for the green sub-pixel, holes move from the anode through the hole injection layer (HIL), the hole transport layer (HTL), the red quantum dot layer (RQD) to the green quantum dot layer (GQD) in sequence. Electrons accumulate at the interface between the electron transport layer (ETL) and the green quantum dot layer (GQD), and are confined within the green quantum dot layer (GQD). Electron-hole recombination basically occurs in the green quantum dot layer (GQD), as Figure 4 shown; for the red sub-pixel unit 120, holes move from the anode through the hole injection layer (HIL), the hole transport layer (HTL) to the red quantum dot layer (RQD) in sequence. Electrons accumulate at the interface between the electron transport layer (ETL) and the red quantum dot layer (RQD). Electron-hole recombination basically occurs in the red quantum dot layer (RQD), as Figure 5 shown.

[0074] Based on the foregoing embodiments, the red quantum dot layer includes red quantum dots, the green quantum dot layer includes green quantum dots, and the blue quantum dot layer includes blue quantum dots. The red quantum dots, green quantum dots, and blue quantum dots all include a core and a shell layer coated on the surface of the core. Preferably, the red quantum dots, green quantum dots, and blue quantum dots all have a quasi-type I energy level structure, as Figure 6 shown. Preferably, in the quasi-type I energy level structure, the absolute value of the difference between the bottom energy level of the conduction band (CB) of the shell layer and the bottom energy level of the conduction band of the core is greater than the absolute value of the difference between the top energy level of the valence band (VB) of the shell layer and the top energy level of the valence band of the core. As Figure 6 shown, the depression degree of the top conduction band is greater than that of the bottom valence band. As Figure 3 shown, for the blue sub-pixel unit 140, when electrons migrate from the cathode to the blue quantum dot layer BQD, due to the large depression of the conduction band, the electrons can be confined within the blue quantum dot layer BQD and are not easily migrated to the green quantum dot layer GQD and the red quantum dot layer RQD; when holes migrate from the anode to the valence band of the red quantum dot layer RQD, due to the small depression of the valence band, they are more easily migrated to the green quantum dot layer GQD and then to the blue quantum dot layer BQD. As Figure 4 shown, for the green sub-pixel unit 130, when electrons migrate from the cathode to the green quantum dot layer GQD, due to the large depression of the conduction band, the electrons can be confined within the green quantum dot layer GQD and are not easily migrated to the red quantum dot layer RQD; when holes migrate from the anode to the valence band of the red quantum dot layer RQD, due to the small depression of the valence band, they are more easily migrated to the green quantum dot layer GQD. As Figure 5 shown, for the red sub-pixel unit 120, when electrons migrate from the cathode to the red quantum dot layer RQD, due to the large depression of the conduction band, the electrons can be confined within the red quantum dot layer RQD; when holes migrate from the anode, due to the small depression of the valence band, they are more easily migrated to the red quantum dot layer RQD.

[0075] Preferably, the absolute value of the difference between the bottom energy level of the conduction band of the shell layer of the red quantum dots, green quantum dots, and blue quantum dots and the bottom energy level of the conduction band of the core is ≥ 0.3 eV, and can be, for example, 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; the absolute value of the difference between the top energy level of the valence band of the shell layer of the red quantum dots, green quantum dots, and blue quantum dots and the top energy level of the valence band of the core is between 0 eV and 0.1 eV, and can be, for example, 0 eV, 0.1 eV, 0.2 eV, 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 time, holes can move freely in the red quantum dot layer, green quantum dot layer, and blue quantum dot layer, while the movement of electrons in the above-mentioned quantum dot light-emitting layer is restricted; this enables: for the blue sub-pixel unit 140, the recombination of electrons and holes basically occurs in the blue quantum dot layer, and the red quantum dot layer and green quantum dot layer basically do not participate in light emission, and the blue light emission spectrum has high purity; for the green sub-pixel unit 130, the recombination of electrons and holes basically occurs in the green quantum dot layer, and the red quantum dot layer basically does not participate in light emission, and the green light emission spectrum has high purity.

[0076] On the basis of the foregoing embodiments, the core and shell layers of the red quantum dots, green quantum dots, and blue quantum dots all have non-metallic elements of the same composition. This helps to make the absolute value of the difference between the bottom energy level of the conduction band of the shell layer of the red quantum dots, green quantum dots, and blue quantum dots and the bottom energy level of the conduction band of the core, as well as the absolute value of the difference between the top energy level of the valence band of the shell layer of the red quantum dots, green quantum dots, and blue quantum dots and the top energy level of the valence band of the core, satisfy the above relationships.

[0077] On the basis of the foregoing embodiments, the materials of the core and shell layers of the red quantum dots are CdSe and Cd x1 Zn 1-x1 Se, Cd x2 Zn 1-x2 Se and Cd x3 Zn 1-x3 Se, Cd x4 Zn 1-x4 SeS and Cd x5 Zn 1-x5 SeS; where 0 ≤ x1 < 1; 0 ≤ x3 < 0.5 < x2 < 1; 0 ≤ x5 < 0.7 < x4 < 1. Preferably, the materials of the core and shell layers of the green quantum dots are CdSe and Cd y1 Zn 1-y1 Se, Cd y2 Zn 1-y2 Se and Cd y3 Zn1-y3 Se, Cd y4 Zn 1-y4 SeS and Cd y5 Zn 1-y5 SeS; wherein, 0 ≤ y1 < 1; 0 ≤ y3 < 0.4 < y2 < 1; 0 ≤ y5 < 0.6 < y4 < 1. Preferably, the materials of the core and the shell layer of the blue quantum dots are Cd z1 Zn 1-z1 Se and Cd z2 Zn 1-z2 Se, Cd z3 Zn 1-z3 SeS and Cd z4 Zn 1-z4 SeS, Cd z5 Zn 1-z5 S and ZnS; wherein, 0 ≤ z2 < 0.3 < z1 < 1; 0 ≤ z4 < 0.5 < z3 < 1; 0 < z5 ≤ 1. In this embodiment, the red quantum dots, the green quantum dots and the blue - red quantum dots are carefully selected, so that in the blue sub - pixel unit 140, electron - hole recombination occurs in the blue quantum dot layer, in the green sub - pixel unit 130, electron - hole recombination occurs in the green quantum dot layer, and in the red sub - pixel unit 120, electron - hole recombination occurs in the red quantum dot layer, thereby maintaining high color purity and color gamut of the QLED.

[0078] Based on the foregoing embodiment, the QLED device 100 further includes a first electrode layer 150, a second electrode layer 160, a first functional layer 170 and a second functional layer 180, as Figure 7 shown. Among them, the first electrode layer 150 is respectively located between the substrate 110 and the red sub - pixel unit 120, the green sub - pixel unit 130 and the blue sub - pixel unit 140; the second electrode layer 160 is respectively located on the side of the red sub - pixel unit 120, the green sub - pixel unit 130 and the blue sub - pixel unit 140 away from the substrate 110; the first functional layer 170 is respectively located between the first electrode layer 150 and the red sub - pixel unit 120, the green sub - pixel unit 130 and the blue sub - pixel unit 140; the second functional layer 180 is respectively located between the second electrode layer 160 and the red sub - pixel unit 120, the green sub - pixel unit 130 and the blue sub - pixel unit 140.

[0079] Preferably, the first electrode layer 150 is a cathode, and the second electrode layer 160 is an anode. That is to say, the QLED device is an inverted structure.

[0080] Preferably, the first functional layer 170 includes an electron transport layer ETL, and the second functional layer 180 includes a hole transport layer HTL and a hole injection layer HIL which are sequentially stacked.

[0081] In the QLED device of the above-described embodiment, the materials of the functional layers such as the first electrode layer 150, the second electrode layer 160, the first functional layer 170, and the second functional layer 180 are selected from the materials commonly used in the relevant functional layers in the fields of QLED and OLED, and the present invention does not limit them.

[0082] Preferably, in the above QLED device 100, there is no red quantum dot layer RQD in the area other than the red sub-pixel unit 120, the green sub-pixel unit 130, and the blue sub-pixel unit 140. However, the structure of the QLED device of the present invention is not limited thereto.

[0083] Please refer to Figure 8 A QLED device 200 according to another embodiment of the present invention includes a red sub-pixel unit 220, a green sub-pixel unit 230, and a blue sub-pixel unit 240 disposed on one side of a substrate 210. The red sub-pixel unit 220 includes a red quantum dot layer RQD. Along the direction perpendicular to the substrate 210, the green sub-pixel unit 230 includes a green quantum dot layer GQD and a red quantum dot layer RQD stacked in sequence. Along the direction perpendicular to the substrate 210, the blue sub-pixel unit 240 includes a blue quantum dot layer BQD, a green quantum dot layer GQD, and a red quantum dot layer RQD stacked in sequence. Among them, the red quantum dot layer RQD is located on the side away from the substrate 210 of the green quantum dot layer GQD.

[0084] Among them, in the green sub-pixel unit 230, the green quantum dot layer GQD is disposed close to the substrate 210, and the red quantum dot layer RQD is disposed away from the substrate 210; in the blue sub-pixel unit 240, the blue quantum dot layer BQD is disposed close to the substrate 210, and the red quantum dot layer RQD is disposed away from the substrate 220.

[0085] Among them, the area other than the red sub-pixel unit 220, the green sub-pixel unit 230, and the blue sub-pixel unit 240 includes a red quantum dot layer RQD.

[0086] The QLED device applying the technical solution of the present invention can avoid the damage to the lower quantum dot layer during the development process in the lithography process, prevent the reduction of the thickness of the lower quantum dot layer, the increase of the surface roughness, etc., effectively avoid the reduction of the performance of the QLED device, and thus obtain an inverted QLED device with better performance, which is beneficial to wide application.

[0087] On the basis of the foregoing embodiment, the QLED device is a bottom-emitting AMQLED or a top-emitting AMQLED, as shown in Figure 9 and Figure 10 respectively.

[0088] Please refer to Figure 9, the bottom-emitting AMQLED 300 of one embodiment includes a substrate 310, and a first electrode layer 320, a first functional layer 330, a quantum dot light-emitting layer 340, a second functional layer 350, and a second electrode layer 360 that are sequentially stacked in a direction perpendicular to the substrate 310. Among them, the first electrode layer 320 is made of a transparent material, and the second electrode layer 360 can be made of an opaque material, and light is emitted in the direction of the first electrode layer 320 toward the substrate 310.

[0089] Among them, the first electrode layer 320 is a cathode, the first functional layer 330 is an electron transport layer ETL, the second functional layer 350 is a hole transport layer HTL, and the second electrode layer 360 is an anode. It should be noted that the first functional layer 330 and the second functional layer 350 are not limited to this. The second functional layer 350 may further include a hole injection layer HIL located between the hole transport layer and the second electrode layer 360.

[0090] Among them, the quantum dot light-emitting layer 340 includes a red sub-pixel unit 341, a green sub-pixel unit 342, and a blue sub-pixel unit 343. The red sub-pixel unit 341 includes a red quantum dot layer RQD. In a direction perpendicular to the substrate 310, the green sub-pixel unit 342 includes a green quantum dot layer GQD and a red quantum dot layer RQD that are sequentially stacked, and the green quantum dot layer GQD is close to the substrate 310, and the red quantum dot layer RQD is far from the substrate 310. In a direction perpendicular to the substrate 310, the blue sub-pixel unit 340 includes a blue quantum dot layer BQD, a green quantum dot layer GQD, and a red quantum dot layer RQD that are sequentially stacked, and the blue quantum dot layer BQD is close to the substrate 310, and the red quantum dot layer RQD is far from the substrate 310.

[0091] Please refer to Figure 10 , the top-emitting AMQLED 400 of one embodiment includes a substrate 410, and a first electrode layer 420, a first functional layer 430, a quantum dot light-emitting layer 440, a second functional layer 450, and a second electrode layer 460 that are sequentially stacked in a direction perpendicular to the substrate 410. Among them, the first electrode layer 420 serves as a reflective electrode and is made of an opaque material, and the second electrode layer 460 is made of a transparent material, and light is emitted in the direction of the second functional layer 450 toward the second electrode layer 460.

[0092] Among them, the first electrode layer 420 is a cathode, the first functional layer 430 is an electron transport layer ETL, the second functional layer 450 is a hole transport layer HTL, and the second electrode layer 460 is an anode. It should be noted that the first functional layer 430 and the second functional layer 450 are not limited to this. The second functional layer 450 may further include a hole injection layer HIL located between the hole transport layer and the second electrode layer 460.

[0093] The quantum dot light-emitting layer 440 includes a red sub-pixel unit 441, a green sub-pixel unit 442, and a blue sub-pixel unit 443. The red sub-pixel unit 441 includes a red quantum dot layer RQD. In a direction perpendicular to the substrate 410, the green sub-pixel unit 442 includes a green quantum dot layer GQD and a red quantum dot layer RQD stacked in sequence, with the green quantum dot layer GQD being located close to the substrate 410 and the red quantum dot layer RQD being located away from the substrate 410. In a direction perpendicular to the substrate 410, the blue sub-pixel unit 443 includes a blue quantum dot layer BQD, a green quantum dot layer GQD, and a red quantum dot layer RQD stacked in sequence, with the blue quantum dot layer BQD being located close to the substrate 410 and the red quantum dot layer RQD being located away from the substrate 410.

[0094] The QLED device of the technical solution of the present invention includes a quantum dot light-emitting layer of the above-mentioned structure, which can avoid damage to the underlying quantum dot layer during development during the overlay process, and helps to obtain an inverted QLED device with good performance such as high brightness, high efficiency, low driving voltage, and long life, which is conducive to wide application.

[0095] Please also see Figure 1 、 Figure 11 and Figure 12 A method for preparing a QLED device according to an embodiment of the present invention comprises the following steps:

[0096] S11 . Provide a substrate 110 , wherein the substrate 110 includes a blue sub-pixel region, a green sub-pixel region, and a red sub-pixel region.

[0097] The blue sub-pixel region is a region for forming a blue sub-pixel unit, the green sub-pixel region is a region for forming a green sub-pixel unit, and the red sub-pixel region is a region for forming a red sub-pixel unit.

[0098] S12. Coat a whole layer of blue quantum dot material on the substrate 110 to obtain a blue quantum dot material layer 121. Photolithography the blue quantum dot material layer 121 to remove the blue quantum dot material outside the blue sub-pixel area to obtain a blue quantum dot layer BQD located in the blue sub-pixel area.

[0099] The blue quantum dot material includes blue quantum dots and glue. The glue can be photoresist or other types of glue. The photoresist is suitable for photolithography (exposure and development).

[0100] In step S12, the photolithography operation of the blue quantum dot material layer 121 is: exposing and developing the blue quantum dot material layer 121. During the exposure process, a mask 122 can be used to block the non-exposed area.

[0101] S13. Coat the entire layer of green quantum dot material on the substrate 110 and the blue quantum dot layer BQD to obtain the green quantum dot material layer 131. Perform photolithography on the green quantum dot material layer 131 to remove the green quantum dot material in the regions other than the blue sub-pixel region and the green sub-pixel region, and obtain the green quantum dot layer GQD located in the blue sub-pixel region and the green sub-pixel region.

[0102] Among them, the green quantum dot material includes green quantum dots and glue. The glue can be photoresist or other types of glue. Among them, photoresist is suitable for photolithography (exposure, development).

[0103] In step S13, the operation of performing photolithography on the green quantum dot material layer 131 is: exposing and developing the green quantum dot material layer 131. During the exposure process, a mask 132 can be used to block the non-exposed regions.

[0104] S14. Coat the entire layer of red quantum dot material on the substrate 110 and the green quantum dot layer GQD to obtain the red quantum dot material layer 141. Perform photolithography on the red quantum dot material layer 141 to remove the red quantum dot material in the regions other than the blue sub-pixel region, the green sub-pixel region, and the red sub-pixel region, and obtain the red quantum dot layer RQD located in the blue sub-pixel region, the green sub-pixel region, and the red sub-pixel region, and obtain the QLED device 100.

[0105] Among them, the red quantum dot material includes red quantum dots and glue. The glue can be photoresist or other types of glue. Among them, photoresist is suitable for photolithography (exposure, development).

[0106] In step S14, the operation of performing photolithography on the red quantum dot material layer 141 is: exposing and developing the red quantum dot material layer 141. During the exposure process, a mask 142 can be used to block the non-exposed regions. It should be noted that in the method for preparing the QLED device of this embodiment, other feasible schemes can also be adopted to obtain the blue quantum dot layer BQD, the green quantum dot layer GQD, and the red quantum dot layer RQD.

[0107] The QLED device 100 obtained in step S14 includes a red sub-pixel unit 120, a green sub-pixel unit 130, and a blue sub-pixel unit 140 arranged on one side of a substrate 110. The red sub-pixel unit 120 is located in the red sub-pixel region, the green sub-pixel unit 130 is located in the green sub-pixel region, and the blue sub-pixel unit 140 is located in the blue sub-pixel region. The red sub-pixel unit 120 includes a red quantum dot layer RQD. In a direction perpendicular to the substrate 110, the green sub-pixel unit 130 includes a green quantum dot layer GQD and a red quantum dot layer RQD stacked in sequence. In a direction perpendicular to the substrate 110, the blue sub-pixel unit 130 includes a blue quantum dot layer BQD, a green quantum dot layer GQD, and a red quantum dot layer RQD stacked in sequence. The red quantum dot layer RQD is located on the side of the green quantum dot layer GQD away from the substrate 110.

[0108] Among them, in the green sub-pixel unit 130, the green quantum dot layer GQD is set close to the substrate 110, and the red quantum dot layer RQD is set away from the substrate 110; in the blue sub-pixel unit 140, the blue quantum dot layer BQD is set close to the substrate 110, and the red quantum dot layer RQD is set away from the substrate 110.

[0109] The red quantum dot layer RQD of the red sub-pixel unit 120 , the green quantum dot layer GQD of the green sub-pixel unit 130 , and the blue quantum dot layer BQD of the blue sub-pixel unit 140 are located on the same substrate 110 .

[0110] Please also see Figure 8 、 Figure 13 and Figure 14 A method for preparing a QLED device according to another embodiment of the present invention comprises the following steps:

[0111] S21 . Provide a substrate 210 , wherein the substrate 210 includes a blue sub-pixel region, a green sub-pixel region, and a red sub-pixel region.

[0112] The blue sub-pixel region is a region for forming a blue sub-pixel unit, the green sub-pixel region is a region for forming a green sub-pixel unit, and the red sub-pixel region is a region for forming a red sub-pixel unit.

[0113] S22. Coat a whole layer of blue quantum dot material on the substrate 210 to obtain a blue quantum dot material layer 221. Photolithography is performed on the blue quantum dot material layer 221 to remove the blue quantum dot material in areas outside the blue sub-pixel area to obtain a blue quantum dot layer BQD located in the blue sub-pixel area.

[0114] The blue quantum dot material includes blue quantum dots and glue. The glue can be photoresist or other types of glue. The photoresist is suitable for photolithography (exposure and development).

[0115] In step S22, the lithography operation on the blue quantum dot material layer 221 is as follows: the blue quantum dot material layer 221 is exposed and developed. During the exposure process, a mask 222 can be used to block the non-exposed area.

[0116] S23. Coat the entire layer of green quantum dot material on the substrate 210 and the blue quantum dot layer BQD to obtain the green quantum dot material layer 231. Perform lithography on the green quantum dot material layer 231 to remove the green quantum dot material in the areas other than the blue sub-pixel area and the green sub-pixel area, and obtain the green quantum dot layer GQD located in the blue sub-pixel area and the green sub-pixel area.

[0117] Among them, the green quantum dot material includes green quantum dots and glue. The glue can be a photoresist or other types of glue. Among them, the photoresist is suitable for lithography (exposure, development).

[0118] In step S23, the lithography operation on the green quantum dot material layer 231 is as follows: the green quantum dot material layer 231 is exposed and developed. During the exposure process, a mask 232 can be used to block the non-exposed area.

[0119] S24. After coating the entire layer of red quantum dot material on the substrate 210 and the green quantum dot layer GQD, obtain the red quantum dot material layer 241, cure the red quantum dot material layer 241 to obtain the red quantum dot layer RQD, and obtain the QLED device 200.

[0120] Among them, the red quantum dot material includes red quantum dots and glue. The glue can be types of glue such as photo-curing and thermal-curing, or other types of glue.

[0121] The QLED device 200 obtained in step S24 includes a red sub-pixel unit 220, a green sub-pixel unit 230, and a blue sub-pixel unit 240 disposed on one side of the substrate 210. The red sub-pixel unit 220 is located in the red sub-pixel area, the green sub-pixel unit 230 is located in the green sub-pixel area, and the blue sub-pixel unit 240 is located in the blue sub-pixel area; the red sub-pixel unit 220 includes the red quantum dot layer RQD; along the direction perpendicular to the substrate 210, the green sub-pixel unit 230 includes the green quantum dot layer GQD and the red quantum dot layer RQD stacked in sequence; along the direction perpendicular to the substrate 210, the blue sub-pixel unit 230 includes the blue quantum dot layer BQD, the green quantum dot layer GQD, and the red quantum dot layer RQD stacked in sequence. Among them, the red quantum dot layer RQD is located on the side of the green quantum dot layer GQD away from the substrate 210.

[0122] Among them, in the green sub-pixel unit 230, the green quantum dot layer GQD is disposed close to the substrate 210, and the red quantum dot layer RQD is disposed away from the substrate 210; in the blue sub-pixel unit 240, the blue quantum dot layer BQD is disposed close to the substrate 210, and the red quantum dot layer RQD is disposed away from the substrate 210.

[0123] Among them, the red quantum dot layer RQD of the red sub-pixel unit 220, the green quantum dot layer GQD of the green sub-pixel unit 230, and the blue quantum dot layer BQD of the blue sub-pixel unit 240 are located on the same substrate 210.

[0124] By using the preparation method of the QLED device according to this embodiment, after obtaining the red quantum dot material layer, the red quantum dot material layer is cured to obtain the red quantum dot layer RQD, thereby obtaining the QLED device. In this way, the steps of exposing and developing the red quantum dot material layer are omitted, and the production efficiency can be improved.

[0125] Please participate together Figure 15 , on the basis of the foregoing embodiments, before forming the blue quantum dot layer BQD, the following steps are further included:

[0126] S31. Form a first electrode layer on the substrate.

[0127] S32. Form a first functional layer on the first electrode layer.

[0128] Please participate together Figure 16 , on the basis of the foregoing embodiments, after forming the red quantum dot layer RQD, the following steps are further included:

[0129] S33. Form a second functional layer on the red quantum dot layer RQD.

[0130] S34. Form a second electrode layer on the second functional layer.

[0131] Preferably, the first electrode layer is a cathode, and the second electrode layer is an anode.

[0132] Preferably, the first functional layer includes an electron transport layer ETL, and the second functional layer includes a hole transport layer HTL and a hole injection layer HIL stacked in sequence.

[0133] In the preparation method of the QLED device according to the technical solution of the present invention, during the process of patterning the quantum dot light-emitting layer by using a photolithography process, the quantum dot light-emitting layer above the existing quantum dot light-emitting layer is not deliberately removed, avoiding the damage to the quantum dot light-emitting layer caused by development during the overlay process of the quantum dot light-emitting layer, preventing the reduction of the thickness of the lower quantum dot layer, the increase of the surface roughness, etc., effectively avoiding the reduction of the performance of the QLED device, and thus improving the performance and preparation yield of the QLED device.

[0134] A display device according to an embodiment includes any one of the above QLED devices.

[0135] The display device of the technical solution of the present invention includes the above QLED device, which can avoid the damage to the lower quantum dot layer during development in the lithography process, prevent the reduction of the thickness of the lower quantum dot layer, the increase of the surface roughness, etc., effectively avoid the performance degradation of the QLED device, and thus obtain an inverted QLED device with better performance, which is conducive to wide application.

[0136] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, 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, it should be considered as the scope recorded in this specification.

[0137] The above embodiments only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the invention patent should be subject to the appended claims.

Claims

1. A QLED device, characterized in that, Including: A red sub-pixel unit, a green sub-pixel unit, and a blue sub-pixel unit disposed on one side of a substrate; The red sub-pixel unit includes a red quantum dot layer; Along a direction perpendicular to the substrate, the green sub-pixel unit includes a green quantum dot layer and a red quantum dot layer stacked in sequence; Along a direction perpendicular to the substrate, the blue sub-pixel unit includes a blue quantum dot layer, a green quantum dot layer, and a red quantum dot layer stacked in sequence; The red quantum dot layer is located on a side of the green quantum dot layer away from the substrate.

2. The QLED device according to claim 1, wherein The absolute value of the valence band top energy level of the blue quantum dot layer > the absolute value of the valence band top energy level of the green quantum dot layer > the absolute value of the valence band top energy level of the red quantum dot layer; Preferably, the absolute value of the conduction band bottom energy level of the blue quantum dot layer < the absolute value of the conduction band bottom energy level of the green quantum dot layer < the absolute value of the conduction band bottom energy level of the red quantum dot layer.

3. The QLED device according to claim 1, wherein The red quantum dot layer includes red quantum dots, the green quantum dot layer includes green quantum dots, the blue quantum dot layer includes blue quantum dots, and the red quantum dots, the green quantum dots, and the blue quantum dots all include a core and a shell layer coated on the surface of the core; Preferably, the red quantum dots, the green quantum dots, and the blue quantum dots all have a quasi-type I energy level structure; Preferably, in the quasi-type I energy level structure, the absolute value of the difference between the conduction band bottom energy level of the shell layer and the conduction band bottom energy level of the core is greater than the absolute value of the difference between the valence band top energy level of the shell layer and the valence band top energy level of the core; Preferably, the absolute value of the difference between the conduction band bottom energy level of the shell layer and the conduction band bottom energy level of the core of the red quantum dots, the green quantum dots, and the blue quantum dots ≥ 0.3 eV; the absolute value of the difference between the valence band top energy level of the shell layer and the valence band top energy level of the core of the red quantum dots, the green quantum dots, and the blue quantum dots is 0 eV to 0.1 eV.

4. The QLED device according to claim 3, wherein The cores and the shell layers of the red quantum dots, the green quantum dots, and the blue quantum dots all have non-metallic elements with the same composition.

5. The QLED device according to claim 4, wherein, The materials of the core and the shell layer of the red quantum dots are CdSe and Cd x1 Zn 1-x1 Se, Cd x2 Zn 1-x2 Se and Cd x3 Zn 1-x3 Se, Cd x4 Zn 1-x4 SeS and Cd x5 Zn 1-x5 SeS; Wherein, 0 ≤ x1 < 1; 0 ≤ x3 < 0.5 < x2 < 1; 0 ≤ x5 < 0.7 < x4 < 1; Preferably, the materials of the core and the shell layer of the green quantum dots are CdSe and Cd y1 Zn 1-y1 Se, Cd y2 Zn 1-y2 Se and Cd y3 Zn 1-y3 Se, Cd y4 Zn 1-y4 SeS and Cd y5 Zn 1-y5 SeS; Wherein, 0 ≤ y1 < 1; 0 ≤ y3 < 0.4 < y2 < 1; 0 ≤ y5 < 0.6 < y4 < 1; Preferably, the materials of the core and the shell layer of the blue quantum dots are Cd z1 Zn 1-z1 Se and Cd z2 Zn 1- z2 Se, Cd z3 Zn 1-z3 SeS and Cd z4 Zn 1-z4 SeS, Cd z5 Zn 1-z5 S and ZnS; Wherein, 0 ≤ z2 < 0.3 < z1 < 1; 0 ≤ z4 < 0.5 < z3 < 1; 0 < z5 ≤ 1.

6. The QLED device according to claim 1, wherein, The QLED device further includes: A first electrode layer respectively located between the substrate and the red sub-pixel unit, the green sub-pixel unit, and the blue sub-pixel unit; A second electrode layer respectively located on a side of the red sub-pixel unit, the green sub-pixel unit, and the blue sub-pixel unit away from the substrate; A first functional layer respectively located between the first electrode layer and the red sub-pixel unit, the green sub-pixel unit, and the blue sub-pixel unit; and A second functional layer respectively located between the second electrode layer and the red sub-pixel unit, the green sub-pixel unit, and the blue sub-pixel unit; Preferably, the first electrode layer is a cathode and the second electrode layer is an anode; Preferably, the first functional layer includes an electron transport layer, and the second functional layer includes a hole transport layer and a hole injection layer which are stacked in sequence; Preferably, the region outside the red sub-pixel unit, the green sub-pixel unit, and the blue sub-pixel unit includes a red quantum dot layer; Preferably, there is no red quantum dot layer in the region outside the red sub-pixel unit, the green sub-pixel unit, and the blue sub-pixel unit.

7. The QLED device according to claim 1, characterized in that, The QLED device is a bottom-emitting AMQLED or a top-emitting AMQLED.

8. A method for preparing a QLED device, characterized in that, Including the following steps: Providing a substrate, the substrate including a blue sub-pixel region, a green sub-pixel region, and a red sub-pixel region; Coating a whole layer of blue quantum dot material on the substrate to obtain a blue quantum dot material layer, performing photolithography on the blue quantum dot material layer, and removing the blue quantum dot material in the region outside the blue sub-pixel region to obtain a blue quantum dot layer located in the blue sub-pixel region; Coating a whole layer of green quantum dot material on the substrate and the blue quantum dot layer to obtain a green quantum dot material layer, performing photolithography on the green quantum dot material layer, and removing the green quantum dot material in the region outside the blue sub-pixel region and the green sub-pixel region to obtain a green quantum dot layer located in the blue sub-pixel region and the green sub-pixel region; And Coating a whole layer of red quantum dot material on the substrate and the green quantum dot layer to obtain a red quantum dot material layer, performing photolithography on the red quantum dot material layer, and removing the red quantum dot material in the region outside the blue sub-pixel region, the green sub-pixel region, and the red sub-pixel region to obtain a red quantum dot layer located in the blue sub-pixel region, the green sub-pixel region, and the red sub-pixel region, and obtaining a QLED device; Preferably, after coating a whole layer of red quantum dot material on the substrate and the green quantum dot layer, a red quantum dot material layer is obtained, the red quantum dot material layer is cured to obtain a red quantum dot layer, and a QLED device is obtained.

9. The method for preparing a QLED device according to claim 8, wherein, Before forming the blue quantum dot layer, the following steps are further included: Forming a first electrode layer on the substrate; and Forming a first functional layer on the first electrode layer; After forming the red quantum dot layer, the following steps are further included: Forming a second functional layer on the red quantum dot layer; and Forming a second electrode layer on the second functional layer.

10. A display device, characterized in that, Including the QLED device according to any one of claims 1 to 7.

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