Light-emitting devices and their fabrication methods, display panels, display devices

Abstract

A light-emitting device is provided. The light-emitting device includes a first electrode, a second electrode, a quantum dot light-emitting layer located between the first electrode and the second electrode, and a hole transport doping layer. The hole transport doping layer is located between the quantum dot light-emitting layer and the second electrode; the hole transport doping layer includes a mixture of at least two hole transport materials, wherein the highest occupied molecular orbital energy levels of the at least two hole transport materials are different.

Description

Technical Field

[0001] This disclosure relates to the fields of lighting and display technology, and in particular to a light-emitting device and its preparation method, a display panel, and a display device. Background Technology

[0002] Quantum dot light-emitting diodes (QLEDs) have gained widespread attention in the display field due to their advantages such as high color gamut, self-emissive nature, low start-up voltage, and fast response speed. The working principle of a quantum dot light-emitting diode substrate is as follows: electrons and holes are injected into both sides of the quantum dot light-emitting layer. These electrons and holes recombine in the quantum dot light-emitting layer to form excitons, which ultimately emit light. Summary of the Invention

[0003] On one hand, a light-emitting device is provided. The light-emitting device includes a first electrode, a second electrode, a quantum dot light-emitting layer located between the first electrode and the second electrode, and a hole transport doping layer. The hole transport doping layer is located between the quantum dot light-emitting layer and the second electrode; the hole transport doping layer includes a mixture of at least two hole transport materials, wherein the highest occupied molecular orbital energy levels of the at least two hole transport materials are different.

[0004] In some embodiments, the mobility of the at least two hole transport materials is different, and among any two hole transport materials, the mobility of the hole transport material with the lower highest occupied molecular orbital energy level is greater than the mobility of the hole transport material with the higher highest occupied molecular orbital energy level.

[0005] In some embodiments, the at least two hole transport materials include a first hole transport material and a second hole transport material, and the highest occupied molecular orbital energy level of the first hole transport material is lower than the highest occupied molecular orbital energy level of the second hole transport material; in the hole transport doped layer, the mass ratio of the first hole transport material to the second hole transport material is 1:5 to 5:1.

[0006] In some embodiments, in the hole transport doped layer, the mass ratio of the first hole transport material to the second hole transport material is 2:1.

[0007] In some embodiments, the thickness of the hole transport doped layer is 0.66 to 5 times the thickness of the quantum dot light-emitting layer.

[0008] In some embodiments, the thickness of the hole transport doped layer is 2.3 times the thickness of the quantum dot light-emitting layer.

[0009] In some embodiments, the thickness of the hole transport doped layer ranges from 20 nm to 50 nm.

[0010] In some embodiments, the light-emitting device further includes a first hole transport layer. The first hole transport layer is located between the quantum dot light-emitting layer and the hole transport doping layer; wherein the highest occupied molecular orbital energy level of the first hole transport layer is less than or equal to the highest occupied molecular orbital energy level of the first hole transport material, and greater than the highest occupied molecular orbital energy level of the quantum dot light-emitting layer.

[0011] In some embodiments, the mobility of the first hole transport layer is less than or equal to the mobility of the first hole transport material, and greater than the mobility of the quantum dot light-emitting layer.

[0012] In some embodiments, the first hole transport layer includes the first hole transport material.

[0013] In some embodiments, in the hole transport doped layer, the mass ratio of the first hole transport material to the second hole transport material is 2:1.

[0014] In some embodiments, the thickness of the hole transport doped layer is 0.33 to 5 times the thickness of the quantum dot light-emitting layer; the thickness of the first hole transport layer is 0.06 to 2 times the thickness of the hole transport doped layer.

[0015] In some embodiments, the thickness of the first hole transport layer is one-third of the thickness of the hole transport doped layer.

[0016] In some embodiments, the thickness of the hole transport doped layer is 10 nm to 50 nm; the thickness of the first hole transport layer is 3 nm to 20 nm.

[0017] In some embodiments, the light-emitting device further includes a second hole transport layer. The second hole transport layer is located between the hole transport doped layer and the second electrode; wherein the highest occupied molecular orbital energy level of the second hole transport layer is lower than the highest occupied molecular orbital energy level of the second electrode, and greater than or equal to the highest occupied molecular orbital energy level of the second hole transport material.

[0018] In some embodiments, the mobility of the second hole transport layer is less than the mobility of the second electrode, and greater than or equal to the mobility of the second hole transport material.

[0019] In some embodiments, the second hole transport layer includes a second hole transport material.

[0020] In some embodiments, in the hole transport doped layer, the mass ratio of the first hole transport material to the second hole transport material is 1:1.

[0021] In some embodiments, the thickness of the hole transport doped layer is 0.1 to 2 times the thickness of the quantum dot light-emitting layer; the thickness of the second hole transport layer is 0.5 to 16.66 times the thickness of the hole transport doped layer.

[0022] In some embodiments, the thickness of the second hole transport layer is three times the thickness of the hole transport doped layer.

[0023] In some embodiments, the thickness of the hole transport doped layer is 3 nm to 20 nm; the thickness of the second hole transport layer is 10 nm to 50 nm.

[0024] In some embodiments, the light-emitting device further includes: a first hole transport layer and a second hole transport layer. The first hole transport layer is located between the quantum dot light-emitting layer and the hole transport doped layer; wherein the highest occupied molecular orbital (HOO) energy level of the first hole transport layer is less than or equal to the HOC energy level of the first hole transport material, and greater than the HOC energy level of the quantum dot light-emitting layer. The second hole transport layer is located between the hole transport doped layer and the second electrode; wherein the HOC energy level of the second hole transport layer is less than the HOC energy level of the second electrode, and greater than or equal to the HOC energy level of the second hole transport material.

[0025] In some embodiments, the mobility of the first hole transport layer is less than or equal to the mobility of the first hole transport material and greater than the mobility of the quantum dot light-emitting layer; the mobility of the second hole transport layer is less than the mobility of the second electrode and greater than or equal to the mobility of the second hole transport material.

[0026] In some embodiments, the first hole transport layer includes the first hole transport material; the second hole transport layer includes the second hole transport material.

[0027] In some embodiments, in the hole transport doped layer, the mass ratio of the first hole transport material to the second hole transport material is 1:1.

[0028] In some embodiments, the thickness of the hole transport doped layer is 0.1 to 2 times the thickness of the quantum dot light-emitting layer; the thickness of the first hole transport layer is 0.15 to 6.67 times the thickness of the hole transport doped layer; and the thickness of the second hole transport layer is 0.5 to 16.67 times the thickness of the hole transport doped layer.

[0029] In some embodiments, the thickness of the first hole transport layer is 1 times the thickness of the hole transport doped layer; and the thickness of the second hole transport layer is 6 times the thickness of the hole transport doped layer.

[0030] In some embodiments, the thickness of the hole transport doped layer is 3nm to 20nm; the thickness of the first hole transport layer is 3nm to 20nm; and the thickness of the second hole transport layer is 10nm to 50nm.

[0031] In some embodiments, the hole transport doped layer includes multiple stacked sub-doped layers; in any two adjacent sub-doped layers, the mass ratio of the first hole transport material to the second hole transport material in the sub-doped layer closer to the quantum dot light-emitting layer is greater than the mass ratio of the first hole transport material to the second hole transport material in the sub-doped layer farther from the quantum dot light-emitting layer.

[0032] In some embodiments, the highest occupied molecular orbital energy level of the first hole transport material is 0.88 to 1.02 times that of the highest occupied molecular orbital energy level of the quantum dot emitting layer; and the highest occupied molecular orbital energy level of the second hole transport material is 0.82 to 0.97 times that of the highest occupied molecular orbital energy level of the quantum dot emitting layer.

[0033] In some embodiments, the highest occupied molecular orbital energy level of the first hole transport material ranges from -6.3 eV to -5.9 eV; the highest occupied molecular orbital energy level of the second hole transport material ranges from -6 eV to -5.5 eV.

[0034] In some embodiments, the mobility of the first hole transport material is 1 to 10 times the mobility of the quantum dot emitting layer. 3 The mobility of the second hole transport material is 10 times that of the quantum dot emitting layer. 2 Times ~ 10 4 times.

[0035] In some embodiments, the mobility of the first hole transport material ranges from 10. -5 cm 2 V -1 s -1 ~10 -3 cm 2 V -1 s -1 The mobility of the second hole transport material ranges from 10. - 3cm 2 V -1 s -1 ~10-2 cm 2 V -1 s -1 .

[0036] In some embodiments, the at least two hole transport materials include at least two of the following materials: 4,4-bis(carbazole-9-yl)biphenyl, 1,3-bis(carbazol-9-yl)benzene, 2,6-bis(3-(9H-carbazol-9-yl)phenyl)pyridine, 4,4',4”-tris(carbazol-9-yl)triphenylamine, 1,1-bis[4-[N,N'-di(p-tolyl)amino]phenyl]cyclohexane, and N,N'-bis(naphthalen-1-yl)-N,N'-bis(phenyl)benzidine.

[0037] In some embodiments, the light-emitting device further includes a hole injection layer and an electron transport layer. The hole injection layer is located between the second electrode and the hole transport doped layer; the electron transport layer is located between the first electrode and the quantum dot light-emitting layer.

[0038] On the other hand, a display panel is provided. The display panel includes a substrate and light-emitting devices as described in any of the above embodiments. The plurality of light-emitting devices are disposed on one side of the substrate.

[0039] In another aspect, a display device is provided. The display device includes a display panel as described in any of the above embodiments.

[0040] In another aspect, a method for fabricating a light-emitting device is provided, the method comprising: forming a quantum dot light-emitting layer on one side of a first electrode; forming a hole transport doping layer on the side of the quantum dot light-emitting layer away from the first electrode, wherein the hole transport doping layer comprises a mixture of at least two hole transport materials, wherein the highest occupied molecular orbital energy levels of the at least two hole transport materials are different; and forming a second electrode on the side of the hole transport doping layer away from the quantum dot light-emitting layer.

[0041] In some embodiments, the at least two hole transport materials include a first hole transport material and a second hole transport material, and the highest occupied molecular orbital energy level of the first hole transport material is lower than the highest occupied molecular orbital energy level of the second hole transport material; in the step of forming a hole transport doped layer on the side of the quantum dot light-emitting layer away from the first electrode, the first hole transport material and the second hole transport material are deposited simultaneously on one side of the first electrode using a dual-source co-evaporation method to form the hole transport doped layer.

[0042] In some embodiments, after the step of forming a quantum dot light-emitting layer on one side of the first electrode, the method further includes: forming a first hole transport layer on the side of the quantum dot light-emitting layer away from the first electrode. The step of forming a hole transport doped layer on the side of the quantum dot light-emitting layer away from the first electrode includes: forming the hole transport doped layer on the side of the first hole transport layer away from the first electrode.

[0043] In some embodiments, after the step of forming a hole transport doped layer on the side of the quantum dot light-emitting layer away from the first electrode, the method further includes: forming a second hole transport layer on the side of the hole transport doped layer away from the first electrode. The step of forming a second electrode on the side of the hole transport doped layer away from the quantum dot light-emitting layer includes: forming a second electrode on the side of the second hole transport layer away from the hole transport doped layer. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in this disclosure, the accompanying drawings used in some embodiments of this disclosure will be briefly described below. Obviously, the drawings described below are only drawings of some embodiments of this disclosure, and those skilled in the art can obtain other drawings based on these drawings. In addition, the drawings described below can be regarded as schematic diagrams and are not intended to limit the actual size of the product, the actual flow of the method, the actual timing of the signals, etc. involved in the embodiments of this disclosure.

[0045] Figure 1 This is a structural diagram of a display device according to some embodiments;

[0046] Figure 2 This is a structural diagram of a display panel according to some embodiments;

[0047] Figure 3 This is a cross-sectional view of a display panel according to some embodiments;

[0048] Figure 4 This is a structural diagram of a display panel according to one implementation method;

[0049] Figure 5This is a structural diagram of a display panel according to some embodiments;

[0050] Figure 6 This is a schematic diagram illustrating the variation of current efficiency with voltage according to some embodiments;

[0051] Figure 7 This is a structural diagram of a display panel according to some other embodiments;

[0052] Figure 8 This is a schematic diagram illustrating the current efficiency as a function of voltage according to some other embodiments;

[0053] Figure 9 This is a structural diagram of a display panel according to some other embodiments;

[0054] Figure 10 This is a schematic diagram illustrating the current efficiency as a function of voltage according to some other embodiments;

[0055] Figure 11 This is a structural diagram of a display panel according to some other embodiments;

[0056] Figure 12 This is a schematic diagram illustrating the variation of current efficiency with voltage according to some other embodiments;

[0057] Figure 13 A flowchart illustrating a method for fabricating a light-emitting device according to some embodiments;

[0058] Figure 14 A flowchart illustrating a method for fabricating a light-emitting device according to some embodiments;

[0059] Figure 15 A flowchart illustrating a method for fabricating a light-emitting device according to some embodiments;

[0060] Figure 16 This is a flowchart of a method for fabricating a light-emitting device according to some embodiments. Detailed Implementation

[0061] The technical solutions in some embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments provided in this disclosure are within the scope of protection of this disclosure.

[0062] Unless the context otherwise requires, throughout the specification and claims, the term "comprise" and its other forms, such as the third-person singular "comprises" and the present participle "comprising," are interpreted as open-ended and encompassing, meaning "including, but not limited to." In the description of the specification, terms such as "some embodiments," "example," or "some examples" are intended to indicate that a particular feature, structure, material, or characteristic associated with that embodiment or example is included in at least one embodiment or example of this disclosure. The illustrative representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics mentioned may be included in any suitable manner in any one or more embodiments or examples.

[0063] Hereinafter, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of this disclosure, unless otherwise stated, "a plurality of" means two or more.

[0064] The "difference between A and B" refers to the difference between the larger of A and B and the smaller of A and B.

[0065] It should be understood that when a layer or element is referred to as being on another layer or substrate, it can mean that the layer or element is directly on the other layer or substrate, or that there is an intermediate layer between the layer or element and the other layer or substrate.

[0066] This document describes exemplary embodiments with reference to cross-sectional views and / or plan views, which are idealized exemplary drawings. In the drawings, the thickness of layers and regions is enlarged for clarity. Therefore, variations in shape relative to the drawings are contemplated due to, for example, manufacturing techniques and / or tolerances. Thus, exemplary embodiments should not be construed as limited to the shapes of the regions shown herein, but rather include shape deviations due to, for example, manufacturing processes. For example, etched regions shown as rectangular would typically have curved features. Therefore, the regions shown in the drawings are schematic in nature, and their shapes are not intended to show the actual shapes of the regions of the device, nor are they intended to limit the scope of the exemplary embodiments.

[0067] Quantum dots (QDs), as novel light-emitting materials, possess advantages such as high light purity, high quantum efficiency, tunable color emission, and long lifespan, making them a current research hotspot for novel LED (Light Emitting Diode) materials. Therefore, quantum dot light-emitting diodes (QLEDs) using quantum dot materials as the light-emitting layer have become a major research direction for novel display devices.

[0068] The basic working principle of quantum dot light-emitting diodes is as follows: electrons and holes are injected into both sides of the quantum dot light-emitting layer, respectively. These electrons and holes recombine in the quantum dot light-emitting layer to form excitons, and finally emit light through the excitons.

[0069] However, the imbalance in the injection rates of electrons and holes into the quantum dot light-emitting layer causes the quantum dot light-emitting layer to be in a charged state. As a result, subsequent electrons and holes recombine in a non-radiative manner (Auger recombination), leading to low luminous efficiency of quantum dot light-emitting diodes.

[0070] In related technologies, the electron injection efficiency is greater than the hole injection efficiency, which leads to an imbalance in the injection rates of electrons and holes into the quantum dot light-emitting layer, resulting in low luminous efficiency of quantum dot light-emitting diodes.

[0071] Figure 1 This is a structural diagram of a display device 2000 according to some embodiments.

[0072] Please see Figure 1 Some embodiments of this disclosure provide a display device 2000, which includes a display panel 1000.

[0073] Among them, the display device 2000 can be a quantum dot organic light-emitting diode display device, and the corresponding display panel 1000 can be a quantum dot organic light-emitting diode display panel.

[0074] Figure 2 This is a structural diagram of a display panel 1000 according to some embodiments.

[0075] Please see Figure 2 Some embodiments of this disclosure provide a display panel 1000, which includes a display area AA and a peripheral area BB located at least on one side of the display area AA. In some examples, the peripheral area BB is arranged around the display area AA.

[0076] The aforementioned AA region includes sub-pixels P of multiple colors; these sub-pixels of multiple colors include at least a first-color sub-pixel, a second-color sub-pixel, and a third-color sub-pixel, wherein the first, second, and third colors are the three primary colors (e.g., red, green, and blue). The region of any sub-pixel P can be defined by a pixel delimitation layer.

[0077] For ease of explanation, the above-mentioned multiple sub-pixels P are illustrated in the form of a matrix arrangement. In this case, sub-pixels P arranged in a row along the first direction X are called sub-pixels in the same row, and sub-pixels P arranged in a row along the second direction Y are called sub-pixels in the same column.

[0078] Figure 3 This is a cross-sectional view of a display panel 1000 according to some embodiments.

[0079] Please see Figure 3 For a single sub-pixel P, a sub-pixel P includes a light-emitting device 100 and a pixel driving circuit 200. The pixel driving circuit 200 is generally composed of electronic devices such as thin-film transistors (TFTs) and capacitors (not shown in the figure). For example, the pixel driving circuit 200 can be a 2T1C structure pixel driving circuit consisting of two thin-film transistors (one switching TFT and one driving TFT) and one capacitor; of course, the pixel driving circuit 200 can also be a pixel driving circuit 200 consisting of two or more thin-film transistors (multiple switching TFTs and one driving TFT) and at least one capacitor. Regardless of the structure of the pixel driving circuit 200, it must include a driving TFT. The driving TFT can be connected to the anode of the light-emitting device 100.

[0080] The display panel 1000 includes multiple film layers, which are described below.

[0081] Please see Figure 2 The display panel 1000 includes a driving substrate 300, a light-emitting device 100, and an encapsulation layer 400 stacked in sequence.

[0082] The driving substrate 300 includes a substrate 310, a pixel driving circuit 200 located on one side of the substrate 310, and an insulating layer 320.

[0083] The light-emitting device 100 includes a first electrode 110, a second electrode 120, and a quantum dot light-emitting layer 130 located between the first electrode 110 and the second electrode 120.

[0084] The first electrode 110 can be a cathode, in which case the first electrode 110 can provide electrons. The second electrode 120 is an anode, in which case the second electrode 120 can provide holes.

[0085] In some examples, the first electrode 110 may be located on the side of the second electrode 120 away from the substrate 310.

[0086] In other examples, the first electrode 110 may be located between the second electrode 120 and the substrate 310.

[0087] The encapsulation layer 400 includes a first encapsulation inorganic film 410, an encapsulation organic film 420, and a second encapsulation inorganic film 430. In some examples, each of the first encapsulation inorganic film 410 and the second encapsulation inorganic film 430 may be made of silicon nitride, aluminum nitride, zirconium nitride, titanium nitride, hafnium nitride, tantalum nitride, silicon oxide, aluminum oxide, titanium oxide, tin oxide, cerium oxide, silicon oxynitride (SiON), lithium fluoride, etc. In some examples, the encapsulation organic film 420 may be made of acrylic resin, methacrylic resin, polyisoprene, vinyl resin, epoxy resin, urethane resin, cellulose resin, etc. The stacked structure of the encapsulation layer 400 may vary.

[0088] In addition, the display panel 1000 also includes a pixel defining layer 500, which is located on the side of the insulating layer 320 away from the substrate 310. Multiple pixel openings are formed in the pixel defining layer 500, and the quantum dot light-emitting layer 130 can be disposed in the pixel openings.

[0089] The light-emitting device 100 is described below.

[0090] Figure 4 This is a structural diagram of a display panel 1000 according to one implementation method.

[0091] Please see Figure 4 This disclosure provides a light-emitting device 100, which includes a first electrode 110, a second electrode 120, and a quantum dot light-emitting layer 130 located between the first electrode 110 and the second electrode 120.

[0092] In some examples, the first electrode 110 can be a cathode, which can be conductive glass, wherein the conductive glass can include materials such as indium tin oxide (ITO) or fluorine-doped tin oxide (FTO).

[0093] In some examples, the thickness of the first electrode 110 ranges from 90 nm to 150 nm. For example, the thickness of the first electrode 110 is 120 nm.

[0094] In some examples, the second electrode 120 can be an anode, which may include materials such as aluminum (Al), silver (Ag), and indium zinc oxide (IZO).

[0095] In some examples, the thickness of the second electrode 120 ranges from 80 nm to 150 nm. For example, the thickness of the second electrode 120 is 120 nm.

[0096] For example, the quantum dot emitting layer 130 includes CdS, CdSe, CdTe, ZnSe, InP, PbS, CuInS2, ZnO, CsPbCl3, CsPbBr3, CsPhI3, CdS / ZnS, CdSe / ZnS, ZnSe, InP / ZnS, PbS / ZnS, InAs, InGaAs, InGaN, GaNk, ZnTe, Si, Ge, C, and other nanoscale materials having the above components, such as nanorods and nanosheets. Preferably, the quantum dot emitting layer 130 is a cadmium-free quantum dot.

[0097] In one implementation, the light-emitting device 100 further includes a first hole transport layer 140 and a second hole transport layer 150. Both the first hole transport layer 140 and the second hole transport layer 150 are located between the second electrode 120 and the quantum dot light-emitting layer 130, with the first hole transport layer 140 located between the second hole transport layer 150 and the quantum dot light-emitting layer 130.

[0098] Among them, the HOMO (Highest Occupied Molecular Orbital) energy level of the second hole transport layer 150 is higher than the HOMO energy level of the first hole transport layer 140, while the HOMO energy level of the first hole transport layer 140 is higher than the energy level of the quantum dot emitting layer 130.

[0099] The greater the energy difference between two film layers, the greater the potential barrier between them. The greater the potential barrier, the more difficult it is for holes to jump from the film layer with the higher HOMO energy level to the film layer with the lower HOMO energy level. In other words, the fewer holes can jump from the film layer with the higher HOMO energy level to the film layer with the lower HOMO energy level.

[0100] Therefore, the potential barrier between the second hole transport layer 150 and the quantum dot emitting layer 130 is high, making it difficult for holes to jump from the second hole transport layer 150 to the quantum dot emitting layer 130.

[0101] In some of the above implementations, by setting a first hole transport layer 140 between the second hole transport layer 150 and the quantum dot emitting layer 130, holes can first jump from the second hole transport layer 150 to the first hole transport layer 140, and then jump from the first hole transport layer 140 to the quantum dot emitting layer 130. Since the potential barrier between the second hole transport layer 150 and the first hole transport layer 140 is low, it is easier for holes to jump from the second hole transport layer 150 to the first hole transport layer 140, resulting in a larger number of holes jumping into the first hole transport layer 140. Furthermore, the potential barrier between the first hole transport layer 140 and the quantum dot light-emitting layer 130 is relatively low. Therefore, it is easier for holes to jump from the first hole transport layer 140 to the quantum dot light-emitting layer 130. Consequently, the amount of holes jumping into the quantum dot light-emitting layer 130 is greater, thereby improving the efficiency of hole injection into the quantum dot light-emitting layer 130. This balances the injection rates of holes and electrons, thereby improving the luminous efficiency of the light-emitting device 100.

[0102] Figure 5 This is a structural diagram of a display panel 1000 according to some embodiments.

[0103] Please see Figure 5 In some embodiments of this disclosure, the light-emitting device 100 further includes a hole transport doped layer 160. The hole transport doped layer 160 is located between the quantum dot light-emitting layer 130 and the second electrode 120. The hole transport doped layer 160 includes a mixture of at least two hole transport materials, wherein the highest occupied molecular orbital energy levels of the at least two hole transport materials are different.

[0104] The greater the difference in HOMO energy levels between two film layers (or materials), the stronger the potential barrier between them, making it more difficult for holes to transition from the structure with the higher HOMO energy level to the structure with the lower HOMO energy level. In other words, fewer holes will transition from the structure with the higher HOMO energy level to the structure with the lower HOMO energy level. Conversely, the greater the difference in HOMO energy levels between two film layers (or materials), the weaker the potential barrier between them, and the more holes will transition from the structure with the higher HOMO energy level to the structure with the lower HOMO energy level.

[0105] In some embodiments of this disclosure, the hole transport doped layer 160 comprises a mixture of at least two hole transport materials. In this case, holes in the second electrode 120 can sequentially transition to the quantum dot emitting layer 130 via the at least two hole transport materials. In the hole transport doped layer 160, holes first pass through a hole transport material with a higher HOMO energy level, and then through a hole transport material with a lower HOMO energy level.

[0106] In the hole transport doped layer 160, since at least two hole transport materials are mixed, the contact area between two hole transport materials with similar HOMO energy levels is large. When a hole transitions from a hole transport material with a higher HOMO energy level to a hole transport material with a lower HOMO energy level, the hole transport rate is high, which can increase the rate of hole injection into the quantum dot light-emitting layer 130. This makes the injection rates of electrons and holes into the quantum dot light-emitting layer 130 more balanced, thereby improving the luminous efficiency of the light-emitting device 100.

[0107] In some examples, the hole transport doped layer 160 includes two, three, four or more hole transport materials.

[0108] In some embodiments, at least two hole transport materials have different mobilities, and in any two hole transport materials, the hole transport material with a lower HOMO energy level has a greater mobility than the hole transport material with a higher HOMO energy level.

[0109] Mobility is the average drift velocity of charge carriers under a unit electric field strength; it is a measure of how fast charge carriers move under the influence of an electric field. A high mobility means fast charge carrier movement; a low mobility means slow charge carrier movement.

[0110] The more similar the mobilities of the two materials (or membranes), the better they match. When charge carriers transition from one material (or membrane) to the other, the more similar their mobilities, the greater the amount of charge carriers that transition to the other material (or membrane), resulting in a higher carrier transport rate.

[0111] For example, the hole transport doped layer 160 includes two hole transport materials.

[0112] The second electrode 120 has a high mobility. During hole transport, the holes generated by the second electrode 120 preferentially pass through the hole transport material with a higher HOMO energy level. The hole transport material with a higher HOMO energy level has a higher mobility. Therefore, the mobility of the hole transport material with a higher HOMO energy level can match the mobility of the second electrode 120, thereby improving the hole transport efficiency between the second electrode 120 and the hole transport material with a higher HOMO energy level.

[0113] The mobility of the quantum dot light-emitting layer 130 is relatively low. In the hole transport doping layer 160, after holes are transported from the hole transport material with a higher HOMO energy level to the hole transport material with a lower HOMO energy level, the holes will be transported from the hole transport material with a lower HOMO energy level to the quantum dot light-emitting layer 130. Among them, the mobility of the quantum dot light-emitting layer 130 is relatively low, and the mobility of the hole transport material with a lower HOMO energy level is lower than that of the hole transport material with a higher HOMO energy level. Therefore, the mobility of the hole transport material with a lower HOMO energy level is more matched with the mobility of the quantum dot light-emitting layer 130, thereby improving the hole transport efficiency between the hole transport material with a lower HOMO energy level and the quantum dot light-emitting layer 130.

[0114] In summary, by improving the hole transport efficiency between the second electrode 120 and the hole transport material with a lower HOMO energy level, and the hole transport efficiency between the hole transport material with a higher HOMO energy level and the quantum dot light-emitting layer 130, the hole transport efficiency can be improved.

[0115] In some embodiments, the at least two hole transport materials include at least two of the following materials: 4,4-bis(carbazole-9-yl)biphenyl (abbreviation: CBP, Chinese name: 4,4'-bis(N-carbazolyl)-1,1'-biphenyl), 1,3-bis(carbazol-9-yl)benzene (abbreviation: mCP), 2,6-bis(3-(9H-carbazol-9-yl)phenyl)pyridine (abbreviation: 26DCzPPy), 4,4',4”-tris(carbazol-9-yl)triphenylamine (abbreviation: TCTA, Chinese name: tris(4-carbazol-9-yl)phenylamine), 1,1-bis[4-[N,N'-di(p-tolyl)amino]phenyl]cyclohexane (abbreviation: TAPC, Chinese name: 4,4'-cyclohexylbis[N,N-bis(4-methylphenyl)aniline]), N,N'-bis(naphthalen-1-yl)-N,N'-bis(phenyl)benzidine (abbreviation: NP B, Chinese name: N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine).

[0116] Exemplarily, the first hole transport material can be TCTA, and the second hole transport material can be NPB.

[0117] In some embodiments, the at least two hole transport materials include a first hole transport material and a second hole transport material, wherein the highest occupied molecular orbital energy level of the first hole transport material is lower than that of the second hole transport material. In the hole transport doped layer 160, the mass ratio of the first hole transport material to the second hole transport material ranges from 1:5 to 5:1, that is, in the hole transport doped layer 160, the mass of the first hole transport material is 0.2 to 5 times the mass of the second hole transport material.

[0118] The mobility of the first hole transport material is lower than that of the second hole transport material.

[0119] By ensuring that the mass ratio of the first hole transport material to the second hole transport material is greater than or equal to 1:5, i.e., the mass of the first hole transport material is greater than 0.2 times the mass of the second hole transport material, it is possible to avoid the content of the first hole transport material in the hole transport doping layer 160 being too low (e.g., less than 0.2 times the mass of the second hole transport material), which would result in an excessively small contact area between the first hole transport material and the quantum dot light-emitting layer 130, and consequently, an insufficient number of holes that jump from the first hole transport material to the quantum dot light-emitting layer 130.

[0120] Furthermore, by ensuring that the mass ratio of the first hole transport material to the second hole transport material is less than or equal to 5:1, i.e., the mass of the first hole transport material is less than 5 times the mass of the second hole transport material, it is possible to avoid the content of the second hole transport material in the hole transport doped layer 160 being too low, resulting in an excessively small contact area between the second hole transport material and the second electrode 120, which in turn leads to an insufficient amount of holes transitioning from the second electrode 120 to the quantum dot light-emitting layer 130 of the second hole transport material.

[0121] The light-emitting device 100 includes a hole transport section. In some embodiments, the hole transport section is a single-layer structure. In this case, the hole transport section only includes a hole transport doping layer 160. Based on this, the hole transport doping layer 160 will be described.

[0122] In some embodiments, the highest occupied molecular orbital (HMO) energy level of the first hole transport material is higher than that of the second hole transport material, and the mass ratio of the first hole transport material to the second hole transport material in the hole transport doped layer 160 is 2:1. In this case, the contact area between the second hole transport material and the second electrode 120 is sufficiently large, thereby enabling a higher hole transport efficiency between the two electrodes. Furthermore, the contact area between the first hole transport material and the quantum dot light-emitting layer 130 is sufficiently large, thereby enabling a higher hole transport efficiency between the two layers.

[0123] In summary, by ensuring a high hole transport efficiency between the second hole transport material and the second electrode 120, and simultaneously ensuring a high hole transport efficiency between the first hole transport material and the quantum dot light-emitting layer 130, the amount of holes entering the quantum dot light-emitting layer 130 can be guaranteed, thus ensuring the hole transport efficiency. This makes the injection rate of electrons and holes into the quantum dot light-emitting layer 130 more balanced, thereby improving the luminous efficiency of the light-emitting device 100.

[0124] Please see Figure 5 In some embodiments, the thickness H1 of the hole transport doped layer 160 is 0.66 to 5 times the thickness H2 of the quantum dot light-emitting layer 130, i.e., H2≤H1≤5H2.

[0125] The thickness H1 of the hole transport doped layer 140 is greater than or equal to 0.66H2. This avoids the hole transport doped layer 140 having a thickness H1 that is too small (e.g., less than 0.66H2), which would result in insufficient first hole transport material and second hole transport material in the hole transport doped layer 140. This, in turn, avoids the low hole transport efficiency caused by insufficient first hole transport material and second hole transport material, thereby ensuring the hole transport efficiency of the hole transport doped layer 140.

[0126] Furthermore, the thickness H1 of the empty transport doped layer 140 is ≤ 5H2, which can avoid the thickness H1 of the empty transport doped layer 140 being too large (e.g., greater than 5H2), resulting in an excessive amount of first hole transport material and second hole transport material in the empty transport doped layer 140, thereby avoiding material waste. At the same time, it can also avoid the thickness of the light-emitting device 100 being too large due to the thickness H1 of the empty transport doped layer 140 being too large.

[0127] In some embodiments, the thickness H1 of the hole transport doped layer 160 is A times the thickness H2 of the quantum dot light-emitting layer 130, i.e., H1 = 2.3H2.

[0128] By ensuring that H1 = 2.3H2, the hole transport doped layer 140 has sufficient thickness to guarantee the content of the first and second hole transport materials in the hole transport doped layer 140, thereby ensuring the hole transport efficiency of the hole transport doped layer 140. This also avoids the hole transport doped layer 160 having an excessively large thickness H1, which would lead to material waste and an excessively large thickness of the light-emitting device 100.

[0129] Please see Figure 5 In some embodiments, the thickness H1 of the hole transport doped layer 160 ranges from 20 nm to 50 nm, i.e., 20 nm ≤ H1 ≤ 50 nm.

[0130] The thickness H1 of the hole transport doped layer 140 is ≥20nm, which can prevent the thickness H1 of the hole transport doped layer 140 from being too small (e.g., less than 20nm), resulting in too little first hole transport material and second hole transport material in the hole transport doped layer 140. This can avoid the low hole transport efficiency caused by too little first hole transport material and second hole transport material, thereby ensuring the hole transport efficiency of the hole transport doped layer 140.

[0131] Furthermore, the thickness H1 of the empty transport doped layer 140 is ≤50nm, which can avoid the first hole transport material and the second hole transport material in the empty transport doped layer 140 being too large (e.g., greater than 50nm), thereby avoiding material waste. At the same time, it can also avoid the light-emitting device 100 being too large due to the excessive thickness H1 of the empty transport doped layer 140.

[0132] For example, the hole transport doped layer 160 has a thickness H1 of 35 nm.

[0133] In some examples, the thickness H2 of the quantum dot light-emitting layer 130 ranges from 10 nm to 30 nm, i.e., 10 nm ≤ H2 ≤ 30 nm.

[0134] For example, the thickness H2 of the quantum dot light-emitting layer 130 is 20 nm. Of course, the thickness of the quantum dot light-emitting layer can also be 15 nm, 17 nm, 23 nm, 25 nm, etc., which will not be listed here.

[0135] Please see Figure 5 In some embodiments, the light-emitting device 100 further includes a hole injection layer (HIL) 170 and an electron transport layer (ETL) 180, wherein the hole injection layer 170 is located between the second electrode 120 and the hole transport doped layer 160, and the electron transport layer 180 is located between the first electrode 110 and the quantum dot light-emitting layer 130.

[0136] By setting the hole injection layer 170, the hole transmission efficiency can be increased, thereby improving the luminous efficiency of the light-emitting device 100.

[0137] The hole injection layer 170 is made of PEDOT:PSS 4083 (poly(3,4-ethylenedioxythiophene / polystyrene sulfonate)). Alternatively, the hole injection layer 170 may also be made of molybdenum oxide.

[0138] In some examples, the thickness of the hole injection layer 170 ranges from 5 nm to 20 nm. For example, the thickness of the hole injection layer 170 is 7 nm.

[0139] By setting up an electron transport layer 180, the electron transport efficiency can be increased, thereby improving the luminous efficiency of the light-emitting device 100.

[0140] The electron transport layer 180 can be a zinc oxide-based nanoparticle film or a zinc oxide film. Furthermore, when the electron transport layer 180 is a zinc oxide-based nanoparticle film, the material of the electron transport layer 180 can also be ion-doped zinc oxide nanoparticles, such as magnesium (Mg), indium (In), aluminum (Al), or gallium (Ga) doped magnesium oxide nanoparticles.

[0141] In some examples, the thickness of the electron transport layer 180 ranges from 25 nm to 55 nm. For example, the thickness of the electron transport layer 180 is 40 nm.

[0142] In this disclosure, a reference light-emitting device and a test light-emitting device 1 are tested. The reference light-emitting device includes a first electrode 110, an electron transport layer 180, a quantum dot light-emitting layer 130, a first hole transport layer 140, a second hole transport layer 150, a hole injection layer 170, and a second electrode 120, which are sequentially stacked. The first hole transport layer 140 has a thickness of 10 nm and is made of TCTA. The second hole transport layer 150 has a thickness of 30 nm and is made of NPB.

[0143] The test light-emitting device 1 includes a first electrode 110, an electron transport layer 180, a quantum dot light-emitting layer 130, a hole transport doped layer 160, a hole injection layer 170, and a second electrode 120, which are stacked sequentially. The hole transport doped layer 160 has a thickness of 35 nm. The first hole transport material in the hole transport doped layer 160 is TCTA, and the second hole transport material is NPB, with a doping ratio of TCTA to NPB of 2:1.

[0144] It should be noted that in both the reference light-emitting device and the test light-emitting device 1, the first electrode 110 is made of ITO and has a thickness of 120 nm; the electron transport layer 180 is made of zinc oxide and has a thickness of 40 nm; the quantum dot light-emitting layer 130 is made of CdS (cadmium sulfide) and CdSe (cadmium selenide), with CdSe surrounding the CdS; the quantum dot light-emitting layer 130 has a thickness of 20 nm and is a red quantum dot light-emitting layer; the hole injection layer 170 is made of MoO3 (molybdenum oxide) and has a thickness of 7 nm; and the second electrode 120 is made of Ag and has a thickness of 120 nm.

[0145] After testing, the following results can be obtained: Figure 6 The diagram shows the current efficiency.

[0146] Depend on Figure 6 It can be seen that the current efficiency of the tested light-emitting device 1 is significantly higher than that of the reference light-emitting device. The higher the current efficiency, the higher the luminous efficiency of the device. Therefore, the luminous efficiency of the tested light-emitting device 1 is significantly higher than that of the reference light-emitting device. This shows that by providing a hole transport doping layer 160 in the light-emitting device 100, the luminous efficiency of the light-emitting device 100 can be effectively improved.

[0147] In some of the embodiments described above, an embodiment in which the hole transport section includes a hole transport-only doped layer 160 has been described.

[0148] Figure 7 This is a structural diagram of a display panel 1000 according to some other embodiments.

[0149] Please see Figure 7 In some embodiments, the light-emitting device 100 further includes a first hole transport layer 140. The first hole transport layer 140 is located between the quantum dot light-emitting layer 130 and the hole transport doped layer 160. The highest occupied molecular orbital energy level of the first hole transport layer 140 is less than or equal to the highest occupied molecular orbital energy level of the first hole transport material, and greater than the highest occupied molecular orbital energy level of the quantum dot light-emitting layer 130.

[0150] Specifically, by setting a first hole transport layer 140 between the quantum dot light-emitting layer 130 and the hole transport doping layer 160, holes will jump from the first hole transport material of the hole transport doping layer 160 into the first hole transport layer 140, and then jump from the first hole transport layer 140 to the quantum dot light-emitting layer 130.

[0151] When the HOMO energy level of the first hole transport layer 140 is lower than the HOMO energy level of the first hole transport material, the difference between the HOMO energy level of the first hole transport layer 140 and the HOMO energy level of the first hole transport material is smaller than the difference between the HOMO energy level of the quantum dot emitting layer 130 and the HOMO energy level of the first hole transport material. Therefore, the potential barrier between the first hole transport layer 140 and the first hole transport material is smaller than the potential barrier between the quantum dot emitting layer 130 and the first hole transport material. Thus, compared to a hole transitioning from the first hole transport material to the quantum dot emitting layer 130, it is easier for a hole to transition from the first hole transport material to the first hole transport layer 140. Similarly, the difference between the HOMO energy level of the quantum dot emitting layer 130 and the first hole transport layer 140 is smaller than the difference between the HOMO energy level of the quantum dot emitting layer 130 and the HOMO energy level of the first hole transport material. Therefore, the potential barrier between the quantum dot emitting layer 130 and the first hole transport layer 140 is smaller than the potential barrier between the quantum dot emitting layer 130 and the first hole transport material. Thus, it is easier for a hole to jump from the first hole transport layer 140 to the quantum dot emitting layer 130 than for a hole to jump from the first hole transport material to the quantum dot emitting layer 130.

[0152] Therefore, by setting a first hole transport layer 140 between the quantum dot light-emitting layer 130 and the hole transport doping layer 160, the hole transport efficiency can be increased, thereby making the injection rate of electrons and holes into the quantum dot light-emitting layer 130 more balanced, thus improving the luminous efficiency of the light-emitting device 100.

[0153] When the HOMO energy level of the first hole transport layer 140 is equal to the HOMO energy level of the first hole transport material, the first hole transport layer 140 can include the first hole transport material.

[0154] In some embodiments, the mobility of the first hole transport layer 140 is less than or equal to the mobility of the first hole transport material, and greater than the mobility of the quantum dot light-emitting layer 130.

[0155] When the mobility of the first hole transport layer 140 is less than the mobility of the first hole transport material, the difference between the mobility of the first hole transport layer 140 and the mobility of the first hole transport material is less than the difference between the mobility of the quantum dot emitting layer 130 and the mobility of the first hole transport material. Therefore, the mobility of the first hole transport layer 140 is more closely matched with the mobility of the first hole transport material, and holes are more likely to jump from the first hole transport material to the first hole transport layer 140 than from the first hole transport material to the quantum dot emitting layer 130.

[0156] Similarly, the difference between the mobility of the quantum dot emitting layer 130 and the mobility of the first hole transport layer 140 is smaller than the difference between the mobility of the quantum dot emitting layer 130 and the mobility of the first hole transport material. Therefore, the mobility of the first hole transport layer 140 is more matched with the mobility of the quantum dot emitting layer 130. Compared to holes jumping from the first hole transport material to the quantum dot emitting layer 130, holes are more likely to jump from the first hole transport layer 140 to the quantum dot emitting layer 130.

[0157] Therefore, by setting a first hole transport layer 140 between the quantum dot light-emitting layer 130 and the hole transport doping layer 160, the hole transport efficiency can be increased, thereby making the injection rate of electrons and holes into the quantum dot light-emitting layer 130 more balanced, thus improving the luminous efficiency of the light-emitting device 100.

[0158] When the mobility of the first hole transport layer 140 is equal to the mobility of the first hole transport material, the first hole transport layer 140 includes the first hole transport material.

[0159] In some embodiments, the first hole transport layer 140 includes a first hole transport material. Therefore, the energy level difference between the first hole transport layer 140 and the first hole transport material in the hole transport doped layer 160 is zero.

[0160] By including a first hole transport layer 140 in the first hole transport material, the contact area between the first hole transport material and the quantum dot light-emitting layer 130 can be increased, thereby increasing the hole transport efficiency. This makes the injection rates of electrons and holes into the quantum dot light-emitting layer 130 more balanced, thereby improving the luminous efficiency of the light-emitting device 100.

[0161] In some embodiments, when the light-emitting device 100 includes a first hole transport layer 140 and a hole transport doped layer 160, the mass ratio of the first hole transport material to the second hole transport material in the hole transport doped layer 160 is 2:1. In this case, the contact area between the second hole transport material in the hole transport doped layer 160 and the second electrode 120 is sufficiently large, thereby enabling a high hole transport efficiency between the second hole transport material and the second electrode 120. Furthermore, the sufficiently large contact area between the first hole transport material in the hole transport doped layer 160 and the first hole transport layer 140 allows a large number of holes to jump from the first hole transport material in the hole transport doped layer 160 to the first hole transport layer 140, and then a sufficient number of holes to jump from the first hole transport layer 140 to the quantum dot light-emitting layer 130, thereby ensuring a high mobility between the first hole transport material and the quantum dot light-emitting layer 130.

[0162] In summary, by ensuring a high hole transport efficiency between the second hole transport material and the second electrode 120, and simultaneously ensuring a high hole transport efficiency between the first hole transport material and the quantum dot light-emitting layer 130, the amount of holes entering the quantum dot light-emitting layer 130 can be guaranteed, thus ensuring the hole transport efficiency. This makes the injection rate of electrons and holes into the quantum dot light-emitting layer 130 more balanced, thereby improving the luminous efficiency of the light-emitting device 100.

[0163] Please see Figure 7 In some embodiments, when the light-emitting device 100 includes a hole transport doping layer 160 and a first hole transport layer 140, the thickness H1 of the hole transport doping layer 160 is 0.33 to 5 times the thickness of the quantum dot light-emitting layer 130, that is, 0.5H2≤H1≤5H2.

[0164] The thickness H1 of the hole transport doped layer 140 is greater than or equal to 0.33H2. This avoids the hole transport doped layer 140 having too small a thickness H1 (e.g., less than 0.33H2), which would result in too little first hole transport material and second hole transport material in the hole transport doped layer 140. This avoids the hole transport efficiency being too low due to insufficient first hole transport material and second hole transport material, thus ensuring the hole transport efficiency of the hole transport doped layer 140.

[0165] Furthermore, the thickness H1 of the empty transport doped layer 140 is ≤ 5H2, which can avoid the thickness H1 of the empty transport doped layer 140 being too large (e.g., greater than 5H2), resulting in an excessive amount of first hole transport material and second hole transport material in the empty transport doped layer 140, thereby avoiding material waste. At the same time, it can also avoid the thickness of the light-emitting device 100 being too large due to the thickness H1 of the empty transport doped layer 140 being too large.

[0166] Please see Figure 7 In some embodiments, when the light-emitting device 100 includes a hole transport doping layer 160 and a first hole transport layer 140, the thickness H3 of the first hole transport layer 140 is 0.06 to 2 times the thickness H1 of the hole transport doping layer 160, that is, 0.06H1≤H3≤2H1.

[0167] The thickness H3 of the first hole transport layer 140 is greater than or equal to 0.06H1. This avoids the situation where the thickness H3 of the first hole transport layer 140 is too small (e.g., less than 0.06H1), which would lead to the formation of nanoscale protrusions when forming the quantum dot light-emitting layer 130. If the thickness of the first hole transport layer 140 is too small, the surface of the first hole transport layer 140 would be uneven, which would be detrimental to the yield of the light-emitting device 100. Therefore, by ensuring that H3 is greater than or equal to 0.06H1, the first hole transport layer 140 has a sufficient thickness to ensure a smooth surface, thereby guaranteeing the yield of the light-emitting device 100.

[0168] Furthermore, the thickness H3 of the first hole transport layer 140 is less than or equal to 2H1, which can prevent the thickness H3 of the first hole transport layer 140 from being too large (e.g., greater than 2H1), thus avoiding the overall thickness of the light-emitting device 100 being too large.

[0169] Please see Figure 7 In some embodiments, when the light-emitting device 100 includes a hole transport doped layer 160 and a first hole transport layer 140, the thickness H3 of the first hole transport layer 140 is one-third of the thickness H1 of the hole transport doped layer 160. This ensures that the first hole transport layer 140 has sufficient thickness, guaranteeing a smooth surface and thus ensuring the yield of the light-emitting device 100. It also avoids the first hole transport layer 140 having an excessively large thickness H1, which would lead to material waste and an excessively large thickness of the light-emitting device 100.

[0170] Please see Figure 7 In some embodiments, when the light-emitting device 100 includes a hole transport doped layer 160 and a first hole transport layer 140, the thickness H1 of the hole transport doped layer 160 is 10 nm to 50 nm.

[0171] The thickness H1 of the hole transport doped layer 140 is ≥10nm, which can prevent the thickness H1 of the hole transport doped layer 140 from being too small (e.g., less than 10nm), resulting in too little first hole transport material and second hole transport material in the hole transport doped layer 140. This can avoid the low hole transport efficiency caused by too little first hole transport material and second hole transport material, thereby ensuring the hole transport efficiency of the hole transport doped layer 140.

[0172] Furthermore, the thickness H1 of the empty transport doped layer 140 is ≤50nm, which can avoid the first hole transport material and the second hole transport material in the empty transport doped layer 140 being too large (e.g., greater than 50nm), thereby avoiding material waste. At the same time, it can also avoid the light-emitting device 100 being too large due to the excessive thickness H1 of the empty transport doped layer 140.

[0173] For example, the hole transport doped layer 160 has a thickness H1 of 30 nm.

[0174] Please see Figure 7 In some embodiments, when the light-emitting device 100 includes a hole transport doping layer 160 and a first hole transport layer 140, the thickness H3 of the first hole transport layer 140 is 3nm to 20nm, that is, 3nm≤H3≤20nm.

[0175] The thickness H3 of the first hole transport layer 140 is ≥ 3 nm. This avoids the situation where the thickness H3 of the first hole transport layer 140 is too small (e.g., less than 3 nm), which would cause nanoscale protrusions to form when the quantum dot light-emitting layer 130 is formed. If the thickness of the first hole transport layer 140 is too small, the surface of the first hole transport layer 140 will be uneven, which is detrimental to the yield of the light-emitting device 100. Therefore, by ensuring that H3 ≥ 3 nm, the first hole transport layer 140 has a sufficient thickness to ensure that the first hole transport layer 140 has a smooth surface, thereby ensuring the yield of the light-emitting device 100.

[0176] In addition, the thickness H3 of the first hole transport layer 140 is ≤20nm, which can avoid the thickness H3 of the first hole transport layer 140 being too large (e.g., greater than 20nm), thus avoiding the overall thickness of the light-emitting device 100 being too large.

[0177] For example, the thickness H3 of the first hole transport layer 140 is 10 nm.

[0178] In some embodiments of this disclosure, a reference light-emitting device and a test light-emitting device 2 are tested. The reference light-emitting device includes a first electrode 110, an electron transport layer 180, a quantum dot light-emitting layer 130, a first hole transport layer 140, a second hole transport layer 150, a hole injection layer 170, and a second electrode 120, which are sequentially stacked. The first hole transport layer 140 has a thickness of 10 nm and is made of TCTA. The second hole transport layer 150 has a thickness of 30 nm and is made of NPB.

[0179] The hole transport section of the light-emitting device 2 includes a first electrode 110, an electron transport layer 180, a quantum dot light-emitting layer 130, a first hole transport layer 140, a hole transport doped layer 160, a hole injection layer 170, and a second electrode 120, which are stacked sequentially. The first hole transport layer 140 has a thickness of 10 nm and is made of TCTA. The hole transport doped layer 160 has a thickness of 30 nm. The first hole transport material in the hole transport doped layer 160 is TCTA, and the second hole transport material is NPB, with a TCTA to NPB doping ratio of 2:1.

[0180] It should be noted that in both the reference light-emitting device and the test light-emitting device 2, the first electrode 110 is made of ITO and has a thickness of 120 nm; the electron transport layer 180 is made of zinc oxide and has a thickness of 40 nm; the quantum dot light-emitting layer 130 is made of CdS (cadmium sulfide) and CdSe (cadmium selenide), with CdSe surrounding the CdS; the quantum dot light-emitting layer 130 has a thickness of 20 nm and is a red quantum dot light-emitting layer; the hole injection layer 170 is made of MoO3 (molybdenum oxide) and has a thickness of 7 nm; and the second electrode 120 is made of Ag and has a thickness of 120 nm.

[0181] After testing, the following results can be obtained: Figure 8 The diagram shows the current efficiency.

[0182] Depend on Figure 8 It can be seen that the current efficiency of the tested light-emitting device 2 is significantly higher than that of the reference light-emitting device. The higher the current efficiency, the higher the luminous efficiency of the device. Therefore, the luminous efficiency of the tested light-emitting device 2 is significantly higher than that of the reference light-emitting device. It can be concluded that by providing the first hole transport layer 140 and the hole transport doping layer 160 in the light-emitting device 100, the luminous efficiency of the light-emitting device 100 can be effectively improved.

[0183] In some of the embodiments described above, an embodiment in which the hole transport section includes a first hole transport layer 140 and a hole transport doped layer 160 has been described.

[0184] Figure 9 This is a structural diagram of a display panel 1000 according to some other embodiments.

[0185] Please see Figure 9In some other embodiments, the light-emitting device 100 further includes a second hole transport layer 150. The second hole transport layer 150 is located between the hole transport doped layer 160 and the second electrode 120. The highest occupied molecular orbital energy level of the second hole transport layer 150 is lower than the highest occupied molecular orbital energy level of the second electrode 120, and greater than or equal to the highest occupied molecular orbital energy level of the second hole transport material.

[0186] In the case where the light-emitting device 100 also includes a hole injection layer 170, the second hole transport layer 150 is located between the hole transport doped layer 160 and the second electrode 120.

[0187] Specifically, by providing a second hole transport layer 150 between the second electrode 120 and the hole transport doped layer 160, holes will jump from the second electrode 120 into the second hole transport layer 150, and then jump from the second hole transport layer 150 to the second hole transport material of the hole transport doped layer 160.

[0188] When the HOMO level of the second hole transport layer 150 is greater than the HOMO level of the second hole transport material, the difference between the HOMO level of the second hole transport layer 150 and the HOMO level of the second electrode 120 is less than the difference between the HOMO level of the second hole transport material and the HOMO level of the second electrode 120. Therefore, the potential barrier between the second hole transport layer 150 and the second electrode 120 is less than the potential barrier between the second hole transport material and the second electrode 120. Thus, compared to a hole transitioning from the second electrode 120 to the second hole transport material, it is easier for a hole to transition from the second electrode 120 to the second hole transport layer 150. Similarly, the difference between the HOMO level of the second hole transport material and the HOMO level of the second hole transport layer 150 is less than the difference between the HOMO level of the second hole transport material and the HOMO level of the second electrode 120. Therefore, the potential barrier between the second hole transport material and the second hole transport layer 150 is smaller than the potential barrier between the second hole transport material and the second electrode 120. Thus, compared to holes transitioning from the second electrode 120 to the second hole transport material, holes can more easily transition from the second hole transport layer 150 to the second hole transport material. Therefore, by placing the second hole transport layer 150 between the second electrode 120 and the hole transport doped layer 160, the hole transport efficiency can be increased, thereby making the injection rates of electrons and holes into the second electrode 120 more balanced, and thus improving the luminous efficiency of the light-emitting device 100.

[0189] When the HOMO energy level of the second hole transport layer 150 is equal to the HOMO energy level of the second hole transport material, the second hole transport layer 150 includes the second hole transport material.

[0190] In some embodiments, the mobility of the second hole transport layer 150 is less than the mobility of the second electrode 120, and greater than or equal to the mobility of the second hole transport material.

[0191] When the mobility of the second hole transport layer 150 is greater than the mobility of the second hole transport material, the difference between the mobility of the second hole transport layer 150 and the mobility of the second hole transport material is smaller than the difference between the mobility of the second electrode 120 and the mobility of the second hole transport material. Therefore, the mobility of the second hole transport layer 150 is more closely matched with the mobility of the second electrode 120, making it easier for holes to transition from the second hole transport layer 150 to the second hole transport material than from the second electrode 120 to the second hole transport material. Similarly, the difference between the mobility of the second electrode 120 and the mobility of the second hole transport layer 150 is smaller than the difference between the mobility of the second electrode 120 and the mobility of the second hole transport material. Therefore, the mobility of the second hole transport layer 150 is more closely matched with the mobility of the second electrode 120, making it easier for holes to transition from the second electrode 120 to the second hole transport material.

[0192] Therefore, by setting a second hole transport layer 150 between the second electrode 120 and the hole transport doping layer 160, the hole transport efficiency can be increased, thereby making the injection rates of electrons and holes into the second electrode 120 more balanced, and thus improving the luminous efficiency of the light-emitting device 100.

[0193] When the mobility of the second hole transport layer 150 is equal to the mobility of the second hole transport material, the second hole transport layer 150 includes the second hole transport material.

[0194] In some embodiments, the second hole transport layer 150 includes a second hole transport material. Therefore, the energy level difference between the second hole transport layer 150 and the second hole transport material in the hole transport doped layer 160 is zero.

[0195] By including a second hole transport layer 150 in the second hole transport material, the contact area between the second hole transport material and the second electrode 120 can be increased, thereby increasing the hole transport efficiency. This makes the injection rates of electrons and holes into the quantum dot light-emitting layer 130 more balanced, thereby improving the luminous efficiency of the light-emitting device 100.

[0196] In some embodiments, when the light-emitting device 100 further includes a second hole transport layer 150 and a hole transport doped layer 160, the mass ratio of the first hole transport material to the second hole transport material in the hole transport doped layer 160 is 1:1.

[0197] At this point, the contact area between the second hole transport material in the hole transport doped layer 160 and the second electrode 120 is large enough, allowing a large number of holes to jump from the second electrode 120 to the second hole transport layer 150 and the second hole transport material. Subsequently, sufficient holes jump from the second hole transport material to the first hole transport material, thus ensuring a high hole transport efficiency between the second electrode 120 and the second hole transport material. Furthermore, the contact area between the first hole transport material in the hole transport doped layer 160 and the quantum dot light-emitting layer 130 is large enough, further ensuring efficient hole transport between the first hole transport material and the quantum dot light-emitting layer 130.

[0198] In summary, by ensuring a high hole transport efficiency between the second hole transport material and the second electrode 120, and simultaneously ensuring a high hole transport efficiency between the first hole transport material and the quantum dot light-emitting layer 130, the amount of holes entering the quantum dot light-emitting layer 130 can be guaranteed, thus ensuring the hole transport efficiency. This makes the injection rate of electrons and holes into the quantum dot light-emitting layer 130 more balanced, thereby improving the luminous efficiency of the light-emitting device 100.

[0199] Please see Figure 9 In some embodiments, the light-emitting device 100 further includes a second hole transport layer 150 and a hole transport doped layer 160. The thickness H1 of the hole transport doped layer 160 is 0.1 to 2 times the thickness H2 of the quantum dot light-emitting layer 130, i.e., 0.1H2≤H1≤2H2.

[0200] The thickness H1 of the hole transport doped layer 140 is greater than or equal to 0.1H2. This avoids the hole transport doped layer 140 having too small a thickness H1 (e.g., less than 0.1H2), which would result in too little first hole transport material and second hole transport material in the hole transport doped layer 140. This avoids the hole transport efficiency being too low due to too little first hole transport material and second hole transport material, thus ensuring the hole transport efficiency of the hole transport doped layer 140.

[0201] Furthermore, the thickness H1 of the empty transport doped layer 140 is less than or equal to 2H2, which can prevent the thickness H1 of the empty transport doped layer 140 from being too large (e.g., greater than 2H2), resulting in an excessive amount of first hole transport material and second hole transport material in the empty transport doped layer 140. This can avoid material waste and also prevent the thickness of the light-emitting device 100 from being too large due to the thickness H1 of the empty transport doped layer 140 being too large.

[0202] Please see Figure 9In some embodiments, the light-emitting device 100 further includes a second hole transport layer 150 and a hole transport doped layer 160. The thickness H4 of the second hole transport layer 150 is 0.5 times to 16.66 times the thickness H1 of the hole transport doped layer 160, that is, 0.5H1≤H4≤16.66H1.

[0203] The thickness H4 of the second hole transport layer 150 is greater than or equal to 0.5H1. This avoids the second hole transport layer 150 having too small a thickness H4 (e.g., less than 0.5H1), which would result in too little second hole transport material and consequently, too low hole transport rate between the second hole transport material and the second electrode 120.

[0204] Furthermore, the thickness H4 of the second hole transport layer 150 is less than or equal to 16.66H1, which can prevent the thickness H4 of the second hole transport layer 150 from being too large (e.g., greater than 16.66H1), thus avoiding the overall thickness of the light-emitting device 100 being too large.

[0205] Please see Figure 9 In some embodiments, the light-emitting device 100 further includes a second hole transport layer 150 and a hole transport doped layer 160, wherein the thickness H4 of the second hole transport layer 150 is three times the thickness H1 of the hole transport doped layer 160, i.e., H4 = 3H1.

[0206] Please see Figure 9 In some embodiments, the light-emitting device 100 further includes a second hole transport layer 150 and a hole transport doped layer 160, wherein the thickness H1 of the hole transport doped layer 160 is 3nm to 20nm, i.e., 3nm≤H1≤20nm.

[0207] The thickness H1 of the hole transport doped layer 140 is ≥3nm, which can prevent the thickness H1 of the hole transport doped layer 140 from being too small (e.g., less than 3nm), resulting in too little first hole transport material and second hole transport material in the hole transport doped layer 140. This can avoid the low hole transport efficiency caused by too little first hole transport material and second hole transport material, thereby ensuring the hole transport efficiency of the hole transport doped layer 140.

[0208] Furthermore, the thickness H1 of the empty transport doped layer 140 is ≤20nm, which can avoid the empty transport doped layer 140 being too thick (e.g., greater than 20nm), resulting in too much first hole transport material and second hole transport material in the empty transport doped layer 140, thereby avoiding material waste. At the same time, it can also avoid the light-emitting device 100 being too thick due to the excessive thickness H1 of the empty transport doped layer 140.

[0209] For example, the hole transport doped layer 160 has a thickness H1 of 10 nm.

[0210] Please see Figure 9 In some embodiments, the light-emitting device 100 further includes a second hole transport layer 150 and a hole transport doped layer 160, wherein the thickness H4 of the second hole transport layer 150 is 10 nm to 50 nm, and 10 nm ≤ H4 ≤ 50 nm.

[0211] The thickness H4 of the second hole transport layer 150 is ≥10nm, which can prevent the thickness H4 of the second hole transport layer 150 from being too small (e.g., less than 10nm), resulting in too little second hole transport material, which in turn leads to too low hole transport rate between the second hole transport material and the second electrode 120.

[0212] In addition, the thickness H4 of the second hole transport layer 150 is ≤50nm, which can avoid the second hole transport layer 150 having an excessively large thickness H4 (e.g., greater than 50nm), thus avoiding the overall thickness of the light-emitting device 100 being too large.

[0213] For example, if the light-emitting device 100 further includes a second hole transport layer 150 and a hole transport doped layer 160, the thickness H4 of the second hole transport layer 150 is 30 nm.

[0214] In this disclosure, a reference light-emitting device and a test light-emitting device 3 are tested. The reference light-emitting device includes a first electrode 110, an electron transport layer 180, a quantum dot light-emitting layer 130, a first hole transport layer 140, a second hole transport layer 150, a hole injection layer 170, and a second electrode 120, which are sequentially stacked. The first hole transport layer 140 has a thickness of 10 nm and is made of TCTA. The second hole transport layer 150 has a thickness of 30 nm and is made of NPB.

[0215] The test light-emitting device 3 includes a first electrode 110, an electron transport layer 180, a quantum dot light-emitting layer 130, a hole transport doped layer 160, a second hole transport layer 150, a hole injection layer 170, and a second electrode 120, which are stacked sequentially. The hole transport doped layer 160 has a thickness of 10 nm, and the first hole transport material in the hole transport doped layer 160 is TCTA, the second hole transport material is NPB, and the mass ratio of TCTA to NPB is 1:1. The second hole transport layer 150 has a thickness of 30 nm and is made of NPB.

[0216] It should be noted that in both the reference light-emitting device and the test light-emitting device 3, the first electrode 110 is made of ITO and has a thickness of 120 nm; the electron transport layer 180 is made of zinc oxide and has a thickness of 40 nm; the quantum dot light-emitting layer 130 is made of CdS (cadmium sulfide) and CdSe (cadmium selenide), with CdSe surrounding the CdS; the quantum dot light-emitting layer 130 has a thickness of 20 nm and is a red quantum dot light-emitting layer; the hole injection layer 170 is made of MoO3 (molybdenum oxide) and has a thickness of 7 nm; and the second electrode 120 is made of Ag and has a thickness of 120 nm.

[0217] After testing, the following results can be obtained: Figure 10 The diagram shows the current efficiency.

[0218] Depend on Figure 10 It can be seen that the current efficiency of the tested light-emitting device 3 is significantly higher than that of the reference light-emitting device. The higher the current efficiency, the higher the luminous efficiency of the device. Therefore, the luminous efficiency of the tested light-emitting device 3 is significantly higher than that of the reference light-emitting device. It can be concluded that by providing a second hole transport layer 150 and a hole transport doping layer 160 in the light-emitting device 100, the luminous efficiency of the light-emitting device 100 can be effectively improved.

[0219] In some of the embodiments described above, an embodiment in which the hole transport section includes a second hole transport layer 150 and a hole transport doped layer 160 has been described.

[0220] Figure 11 This is a structural diagram of a display panel 1000 according to some other embodiments.

[0221] Please see Figure 11 In some embodiments, the light-emitting device 100 further includes a first hole transport layer 140 and a second hole transport layer 150. The first hole transport layer 140 is located between the quantum dot light-emitting layer 130 and the hole transport doped layer 160. The highest occupied molecular orbital (HOO) energy level of the first hole transport layer 140 is less than or equal to the HOC energy level of the first hole transport material, and greater than the HOC energy level of the quantum dot light-emitting layer 130. The second hole transport layer 150 is located between the hole transport doped layer 160 and the second electrode 120. The HOC energy level of the second hole transport layer 150 is less than the HOC energy level of the second electrode 120, and greater than or equal to the HOC energy level of the second hole transport material.

[0222] As can be seen from the above, by setting a first hole transport layer 140 between the quantum dot light-emitting layer 130 and the hole transport doping layer 160, and setting a second hole transport layer 150 between the second electrode 120 and the hole transport doping layer 160, the hole transport efficiency can be increased, thereby making the injection rate of electrons and holes into the quantum dot light-emitting layer 130 more balanced, and thus improving the luminous efficiency of the light-emitting device 100.

[0223] In some embodiments, when the light-emitting device 100 further includes a first hole transport layer 140, a second hole transport layer 150, and a hole transport doped layer 160, the mobility of the first hole transport layer 140 is less than or equal to the mobility of the first hole transport material, and greater than the mobility of the quantum dot light-emitting layer 130; the mobility of the second hole transport layer 150 is less than the mobility of the second electrode 120, and greater than or equal to the mobility of the second hole transport material. As can be seen from the above, this configuration can increase the hole transport efficiency, thereby making the injection rates of electrons and holes into the quantum dot light-emitting layer 130 more balanced, and thus improving the luminous efficiency of the light-emitting device 100.

[0224] In some embodiments, the first hole transport layer 140 includes a first hole transport material, and the second hole transport layer 150 includes a second hole transport material.

[0225] By including a first hole transport layer 140 in a first hole transport material, the contact area between the first hole transport material and the quantum dot light-emitting layer 130 can be increased, thereby increasing the hole transport efficiency. This makes the injection rates of electrons and holes into the quantum dot light-emitting layer 130 more balanced, thereby improving the luminous efficiency of the light-emitting device 100.

[0226] By including a second hole transport layer 150 in the second hole transport material, the contact area between the second hole transport material and the second electrode 120 can be increased, thereby increasing the hole transport efficiency. This makes the injection rates of electrons and holes into the quantum dot light-emitting layer 130 more balanced, thereby improving the luminous efficiency of the light-emitting device 100.

[0227] In some embodiments, when the light-emitting device 100 further includes a first hole transport layer 140, a second hole transport layer 150, and a hole transport doped layer 160, the mass ratio of the first hole transport material to the second hole transport material in the hole transport doped layer 160 is 1:1.

[0228] At this time, the contact area between the second hole transport material in the hole transport doped layer 160 and the second electrode 120 is large enough, so that more holes can jump from the second electrode 120 to the second hole transport layer 150 and the second hole transport material, and then enough holes can jump from the second hole transport material to the first hole transport material, thereby ensuring that the hole transport efficiency between the second electrode 120 and the second hole transport material is large.

[0229] Furthermore, the contact area between the first hole transport material in the hole transport doping layer 160 and the first hole transport layer 140 is large enough, so that a large number of holes can jump from the first hole transport material in the hole transport doping layer 160 to the first hole transport layer 140, and then enough holes can jump from the first hole transport layer 140 to the quantum dot light-emitting layer 130, thereby ensuring a large mobility between the first hole transport material and the quantum dot light-emitting layer 130.

[0230] In some embodiments, when the light-emitting device 100 further includes a first hole transport layer 140, a second hole transport layer 150, and a hole transport doped layer 160, the thickness H1 of the hole transport doped layer 160 is 0.1 to 2 times the thickness H2 of the quantum dot light-emitting layer 130, i.e., 0.1H2≤H1≤2H2.

[0231] The thickness H1 of the hole transport doped layer 140 is greater than or equal to 0.1H2. This avoids the hole transport doped layer 140 having too small a thickness H1 (e.g., less than 0.1H2), which would result in too little first hole transport material and second hole transport material in the hole transport doped layer 140. This avoids the hole transport efficiency being too low due to too little first hole transport material and second hole transport material, thus ensuring the hole transport efficiency of the hole transport doped layer 140.

[0232] Furthermore, the thickness H1 of the empty transport doped layer 140 is less than or equal to 2H2, which can prevent the thickness H1 of the empty transport doped layer 140 from being too large (e.g., greater than 2H2), resulting in an excessive amount of first hole transport material and second hole transport material in the empty transport doped layer 140. This can avoid material waste and also prevent the thickness of the light-emitting device 100 from being too large due to the thickness H1 of the empty transport doped layer 140 being too large.

[0233] When the light-emitting device 100 further includes a first hole transport layer 140, a second hole transport layer 150, and a hole transport doped layer 160, the thickness H3 of the first hole transport layer 140 is 0.15 to 6.67 times the thickness H1 of the hole transport doped layer 160, that is, 0.15H1≤H3≤6.67H1.

[0234] The thickness H3 of the first hole transport layer 140 is greater than or equal to 0.15H1. This avoids the situation where the thickness H3 of the first hole transport layer 140 is too small (e.g., less than 0.15H1), which would cause nanoscale protrusions to form when the quantum dot light-emitting layer 130 is formed. If the thickness of the first hole transport layer 140 is too small, the surface of the first hole transport layer 140 will be uneven, which is detrimental to the yield of the light-emitting device 100. Therefore, by ensuring that H3 is greater than or equal to 0.15H1, the first hole transport layer 140 has a sufficient thickness to ensure that it has a smooth surface, thereby ensuring the yield of the light-emitting device 100.

[0235] In addition, the thickness H3 of the first hole transport layer 140 is less than or equal to 6.67H1, which can prevent the thickness H3 of the first hole transport layer 140 from being too large (e.g., greater than 6.67H1), thus avoiding the overall thickness of the light-emitting device 100 being too large.

[0236] When the light-emitting device 100 further includes a first hole transport layer 140, a second hole transport layer 150, and a hole transport doped layer 160, the thickness H4 of the second hole transport layer 150 is 0.5 to 16.67 times the thickness H1 of the hole transport doped layer 160, that is, 0.5H1≤H4≤16.67H1.

[0237] The thickness H4 of the second hole transport layer 150 is greater than or equal to 0.5H1. This avoids the second hole transport layer 150 having too small a thickness H4 (e.g., less than 0.5H1), which would result in too little second hole transport material and consequently, too low hole transport rate between the second hole transport material and the second electrode 120.

[0238] Furthermore, the thickness H4 of the second hole transport layer 150 is less than or equal to 16.66H1, which can prevent the thickness H4 of the second hole transport layer 150 from being too large (e.g., greater than 16.66H1), thus avoiding the overall thickness of the light-emitting device 100 being too large.

[0239] In some embodiments, when the light-emitting device 100 further includes a first hole transport layer 140, a second hole transport layer 150, and a hole transport doped layer 160, the thickness H3 of the first hole transport layer 140 is twice the thickness H1 of the hole transport doped layer 160, i.e., H3 = H1. This ensures that the first hole transport layer 140 has sufficient thickness, guaranteeing a smooth surface and thus ensuring the yield of the light-emitting device 100. It also avoids the first hole transport layer 140 having an excessively large thickness H1, which would lead to material waste and an excessively large thickness of the light-emitting device 100.

[0240] In some embodiments, when the light-emitting device 100 further includes a first hole transport layer 140, a second hole transport layer 150, and a hole transport doped layer 160, the thickness H4 of the second hole transport layer 150 is 6 times the thickness H1 of the hole transport doped layer 160, i.e., H4 = 6H1.

[0241] In some embodiments, when the light-emitting device 100 further includes a first hole transport layer 140, a second hole transport layer 150, and a hole transport doped layer 160, the thickness H1 of the hole transport doped layer 160 is 3 nm to 20 nm.

[0242] The thickness H1 of the hole transport doped layer 140 is ≥3nm, which can prevent the thickness H1 of the hole transport doped layer 140 from being too small (e.g., less than 3nm), resulting in too little first hole transport material and second hole transport material in the hole transport doped layer 140. This can avoid the low hole transport efficiency caused by too little first hole transport material and second hole transport material, thereby ensuring the hole transport efficiency of the hole transport doped layer 140.

[0243] Furthermore, the thickness H1 of the empty transport doped layer 140 is ≤20nm, which can avoid the first hole transport material and the second hole transport material in the empty transport doped layer 140 being too large (e.g., greater than 20nm), thereby avoiding material waste. At the same time, it can also avoid the light-emitting device 100 being too large due to the excessive thickness H1 of the empty transport doped layer 140.

[0244] For example, when the light-emitting device 100 further includes a first hole transport layer 140, a second hole transport layer 150, and a hole transport doped layer 160, the thickness H1 of the hole transport doped layer 140 is 5 nm.

[0245] In some embodiments, when the light-emitting device 100 further includes a first hole transport layer 140, a second hole transport layer 150, and a hole transport doped layer 160, the thickness H3 of the first hole transport layer 140 is 3 nm to 20 nm.

[0246] The thickness H3 of the first hole transport layer 140 is ≥ 3 nm. This avoids the situation where the thickness H3 of the first hole transport layer 140 is too small (e.g., less than 3 nm), which would cause nanoscale protrusions to form when the quantum dot light-emitting layer 130 is formed. If the thickness of the first hole transport layer 140 is too small, the surface of the first hole transport layer 140 will be uneven, which is detrimental to the yield of the light-emitting device 100. Therefore, by ensuring that H3 ≥ 3 nm, the first hole transport layer 140 has a sufficient thickness to ensure that the first hole transport layer 140 has a smooth surface, thereby ensuring the yield of the light-emitting device 100.

[0247] In addition, the thickness H3 of the first hole transport layer 140 is ≤20nm, which can avoid the thickness H3 of the first hole transport layer 140 being too large (e.g., greater than 20nm), thus avoiding the overall thickness of the light-emitting device 100 being too large.

[0248] For example, when the light-emitting device 100 further includes a first hole transport layer 140, a second hole transport layer 150 and a hole transport doped layer 160, the thickness H3 of the first hole transport layer 140 is 5 nm.

[0249] In some embodiments, when the light-emitting device 100 further includes a first hole transport layer 140, a second hole transport layer 150, and a hole transport doped layer 160, the thickness H4 of the second hole transport layer 150 is 10 nm to 50 nm.

[0250] The thickness H4 of the second hole transport layer 150 is ≥10nm, which can prevent the thickness H4 of the second hole transport layer 150 from being too small (e.g., less than 10nm), resulting in too little second hole transport material, which in turn leads to too low hole transport rate between the second hole transport material and the second electrode 120.

[0251] In addition, the thickness H4 of the second hole transport layer 150 is ≤50nm, which can avoid the second hole transport layer 150 having an excessively large thickness H4 (e.g., greater than 50nm), thus avoiding the overall thickness of the light-emitting device 100 being too large.

[0252] For example, when the light-emitting device 100 further includes a first hole transport layer 140, a second hole transport layer 150 and a hole transport doped layer 160, the thickness H4 of the second hole transport layer 150 is 30 nm.

[0253] In this disclosure, a reference light-emitting device and a test light-emitting device 4 are tested. The reference light-emitting device includes a first electrode 110, an electron transport layer 180, a quantum dot light-emitting layer 130, a first hole transport layer 140, a second hole transport layer 150, a hole injection layer 170, and a second electrode 120, which are sequentially stacked. The first hole transport layer 140 has a thickness of 10 nm and is made of TCTA. The second hole transport layer 150 has a thickness of 30 nm and is made of NPB.

[0254] The test light-emitting device 4 includes a first electrode 110, an electron transport layer 180, a quantum dot light-emitting layer 130, a first hole transport layer 140, a hole transport doped layer 160, a second hole transport layer 150, a hole injection layer 170, and a second electrode 120, which are stacked sequentially. The first hole transport layer 140 has a thickness of 5 nm and is made of TCTA. The hole transport doped layer 160 has a thickness of 5 nm, and the first hole transport material in the hole transport doped layer 160 is TCTA, while the second hole transport material is NPB, with a TCTA to NPB doping ratio of 1:1. The second hole transport layer 150 has a thickness of 40 nm and is made of NPB.

[0255] It should be noted that in both the reference light-emitting device and the test light-emitting device 4, the first electrode 110 is made of ITO and has a thickness of 120 nm; the electron transport layer 180 is made of zinc oxide and has a thickness of 40 nm; the quantum dot light-emitting layer 130 is made of CdS (cadmium sulfide) and CdSe (cadmium selenide), with CdSe surrounding the CdS; the quantum dot light-emitting layer 130 has a thickness of 20 nm and is a red quantum dot light-emitting layer; the hole injection layer 170 is made of MoO3 (molybdenum oxide) and has a thickness of 7 nm; and the second electrode 120 is made of Ag and has a thickness of 120 nm.

[0256] After testing, the following results can be obtained: Figure 12 The diagram shows the current efficiency.

[0257] Depend on Figure 12 It can be seen that the current efficiency of the tested light-emitting device 4 is significantly higher than that of the reference light-emitting device. Higher current efficiency corresponds to higher luminous efficiency. Therefore, the luminous efficiency of the tested light-emitting device 4 is significantly higher than that of the reference light-emitting device. This demonstrates that by providing a first hole transport layer 140, a second hole transport layer 150, and a hole transport doping layer 160 in the light-emitting device 100, the luminous efficiency of the light-emitting device 100 can be effectively improved.

[0258] In some embodiments, the hole transport doped layer 160 includes multiple stacked sub-doped layers. In any two adjacent sub-doped layers, the mass ratio of the first hole transport material to the second hole transport material in the sub-doped layer closer to the quantum dot light-emitting layer 130 is greater than the mass ratio of the first hole transport material to the second hole transport material in the sub-doped layer farther from the quantum dot light-emitting layer 130.

[0259] Therefore, in the hole transport doping layer 160, the closer to the quantum dot light-emitting layer 130, the larger the proportion of the first hole transport material. This increases the contact area between the first hole transport material in the hole transport doping layer 160 and the quantum dot light-emitting layer 130, thereby increasing the hole transport rate between them. Consequently, the amount of holes injected into the quantum dot light-emitting layer 130 can be increased, improving the hole-electron injection balance and enhancing the luminous efficiency of the light-emitting device 100.

[0260] The closer to the second electrode 120, the greater the proportion of the second hole transport material. Therefore, the contact area between the second hole transport material and the second electrode 120 in the hole transport doped layer 160 can be increased, thereby increasing the hole transport rate between the second hole transport material and the second electrode 120. This, in turn, increases the amount of holes injected into the quantum dot light-emitting layer 130, improves the hole-electron injection balance, and enhances the luminous efficiency of the light-emitting device 100.

[0261] In some of the embodiments above, the film structure in the light-emitting device 100 has been described. Next, the first hole transport material and the second hole transport material will be described.

[0262] In some embodiments, the highest occupied molecular orbital energy level of the first hole transport material is 0.88 to 1.02 times that of the highest occupied molecular orbital energy level of the quantum dot luminescent layer 130.

[0263] Since both the HOMO energy level of the first hole transport material and the HOMO energy level of the quantum dot emitting layer 130 are negative, by making the HOMO energy level of the first hole transport material greater than or equal to 0.88 times the HOMO energy level of the quantum dot emitting layer 130, it is possible to avoid the HOMO energy level of the first hole transport material being too large, which would result in an excessively large difference between the HOMO energy level of the first hole transport material and the HOMO energy level of the quantum dot emitting layer 130, i.e., an excessively large potential barrier between the first hole transport material and the quantum dot emitting layer 130. This, in turn, avoids the hole transport efficiency between the first hole transport material and the quantum dot emitting layer 130 being too low.

[0264] Furthermore, since both the HOMO energy level of the first hole transport material and the HOMO energy level of the quantum dot emitting layer 130 are negative, by making the HOMO energy level of the first hole transport material less than or equal to 1.02 times the HOMO energy level of the quantum dot emitting layer 130, it is possible to avoid the HOMO energy level of the first hole transport material being too small, which would result in an excessively large difference between the HOMO energy levels of the first and second hole transport materials, leading to an excessively large potential barrier between them. This, in turn, prevents the hole transport efficiency between the first and second hole transport materials from being too low.

[0265] In some embodiments, the highest occupied molecular orbital energy level of the second hole transport material is 0.82 to 0.97 times that of the highest occupied molecular orbital energy level of the quantum dot luminescent layer 130.

[0266] Since both the HOMO energy level of the second hole transport material and the HOMO energy level of the quantum dot emitting layer 130 are negative, by making the HOMO energy level of the second hole transport material greater than or equal to 0.82 times the HOMO energy level of the quantum dot emitting layer 130, it is possible to avoid the HOMO energy level of the second hole transport material being too large, which would lead to an excessively large difference between the HOMO energy levels of the first and second hole transport materials, resulting in an excessively large potential barrier between them. This, in turn, prevents the hole transport efficiency between the first and second hole transport materials from being too low.

[0267] Furthermore, since both the HOMO energy level of the second hole transport material and the HOMO energy level of the quantum dot emitting layer 130 are negative, by making the HOMO energy level of the first hole transport material less than or equal to 0.97 times the HOMO energy level of the quantum dot emitting layer 130, it is possible to avoid the HOMO energy level of the second hole transport material being too small, resulting in an excessively large difference between the HOMO energy level of the second hole transport material and the second electrode 120, which would lead to an excessively large potential barrier between the second hole transport material and the second electrode 120. This, in turn, prevents the hole transport efficiency between the second hole transport material and the second electrode 120 from being too low.

[0268] In some embodiments, the highest occupied molecular orbital energy level of the first hole transport material ranges from -6.3 eV to -5.9 eV.

[0269] Specifically, by ensuring that the HOMO energy level of the first hole transport material is less than or equal to -5.9 eV, it is possible to avoid the HOMO energy level of the first hole transport material being too large (e.g., greater than -5.9 eV), which would result in an excessively large difference between the HOMO energy level of the first hole transport material and the HOMO energy level of the quantum dot emitting layer 130, thereby causing an excessively large potential barrier between the first hole transport material and the quantum dot emitting layer 130. This, in turn, can prevent the hole transport efficiency between the first hole transport material and the quantum dot emitting layer 130 from being too low.

[0270] Furthermore, by ensuring that the HOMO energy level of the first hole transport material is greater than or equal to -6.3 eV, it is possible to avoid the HOMO energy level of the first hole transport material being too small (e.g., less than -6.3 eV), which would result in an excessively large difference between the HOMO energy levels of the first and second hole transport materials, thereby causing an excessively large potential barrier between the first and second hole transport materials. This, in turn, can prevent the hole transport efficiency between the first and second hole transport materials from being too low.

[0271] In some embodiments, the highest occupied molecular orbital energy level of the second hole transport material ranges from -6 eV to -5.5 eV.

[0272] Specifically, by ensuring that the HOMO energy level of the second hole transport material is less than or equal to -5.5 eV, it is possible to avoid the HOMO energy level of the second hole transport material being too large (e.g., greater than -5.5 eV), which would result in an excessively large difference between the HOMO energy levels of the first and second hole transport materials, i.e., an excessively large potential barrier between the first and second hole transport materials. This, in turn, can prevent the hole transport efficiency between the first and second hole transport materials from being too low.

[0273] Furthermore, by ensuring that the HOMO energy level of the first hole transport material is greater than or equal to -6 eV, it is possible to avoid the HOMO energy level of the second hole transport material being too small (e.g., less than -6 eV), which would result in an excessively large difference between the HOMO energy level of the second hole transport material and the second electrode 120, thereby causing an excessively large potential barrier between the second hole transport material and the second electrode 120. This would prevent the hole transport efficiency between the second hole transport material and the second electrode 120 from being too low.

[0274] In some embodiments, the mobility of the first hole transport material is 1 to 10 times the mobility of the quantum dot emitting layer 130. 3 times.

[0275] Specifically, the mobility of the first hole transport material is made less than or equal to 10% of the mobility of the quantum dot emitting layer 130. 3This can avoid the first hole transport material having an excessively high mobility, which would lead to an excessively large difference between the mobility of the first hole transport material and the mobility of the quantum dot light-emitting layer 130, i.e., a mismatch between the first hole transport material and the quantum dot light-emitting layer 130. In turn, it can avoid the hole transport efficiency between the first hole transport material and the quantum dot light-emitting layer 130 being too low.

[0276] Furthermore, by ensuring that the mobility of the first hole transport material is greater than or equal to 1 times the mobility of the quantum dot emitting layer 130, it is possible to avoid the first hole transport material having too low a mobility, which would result in an excessively large difference between the mobility of the first hole transport material and the mobility of the second hole transport material, leading to a mismatch between the first and second hole transport materials. This, in turn, can prevent the hole transport efficiency between the first and second hole transport materials from being too low.

[0277] In some embodiments, the mobility of the second hole transport material is 10 times the mobility of the quantum dot light-emitting layer 130. 2 Times ~ 10 4 times.

[0278] Specifically, the mobility of the second hole transport material is made less than or equal to 10% of the mobility of the quantum dot emitting layer 130. 4 This can avoid the second hole transport material having an excessively high mobility, which would lead to an excessively large difference between the mobility of the second hole transport material and the mobility of the first hole transport material, thus causing a mismatch between the first and second hole transport materials. This can also avoid the hole transport efficiency between the first and second hole transport materials being too low.

[0279] Furthermore, by making the mobility of the first hole transport material greater than or equal to 10 times the mobility of the quantum dot light-emitting layer 130. 2 This can avoid the second hole transport material having too low a mobility, which would result in an excessively large difference between the mobility of the second hole transport material and the mobility of the second electrode 120, thus causing a mismatch between the second hole transport material and the second electrode 120. This can prevent the hole transport efficiency between the second hole transport material and the second electrode 120 from being too low.

[0280] In some embodiments, the mobility of the first hole transport material ranges from 10. -5 cm 2 V -1 s -1 ~10 - 3cm 2 V -1 s -1 .

[0281] Specifically, by making the mobility of the first hole transport material less than or equal to 10. -3 cm 2 V -1 s -1 This can avoid the mobility of the first hole transport material being too high (e.g., greater than 10). -3 cm 2 V -1 s -1 This results in an excessively large difference between the mobility of the first hole transport material and the mobility of the quantum dot light-emitting layer 130, i.e., a mismatch between the first hole transport material and the quantum dot light-emitting layer 130. This can prevent the hole transport efficiency between the first hole transport material and the quantum dot light-emitting layer 130 from being too low.

[0282] Furthermore, by making the mobility of the first hole transport material greater than or equal to 10 -5 cm 2 V -1 s -1 This can avoid the first hole transport material having too low a mobility (e.g., less than 10). -5 cm 2 V -1 s -1 This results in an excessively large difference between the mobility of the first hole transport material and the mobility of the second hole transport material, leading to a mismatch between the two materials. This, in turn, can prevent the hole transport efficiency between the two materials from being too low.

[0283] In some embodiments, the mobility of the second hole transport material ranges from 10. -3 cm 2 V -1 s -1 ~10 - 2 cm 2 V - 1s -1 .

[0284] Specifically, by making the mobility of the second hole transport material less than or equal to 10. -2 cm 2 V -1 s -1 This can prevent the mobility of the second hole transport material from being too high (e.g., greater than 10). -2 cm 2 V -1 s -1This results in an excessively large difference between the mobility of the second hole transport material and the mobility of the first hole transport material, leading to a mismatch between the two materials and thus preventing the hole transport efficiency between them from being too low.

[0285] Furthermore, by making the mobility of the first hole transport material greater than or equal to 10 -3 cm 2 V -1 s -1 This can avoid the second hole transport material having too low a mobility (e.g., less than 10). -3 cm 2 V -1 s -1 This results in an excessively large difference between the mobility of the second hole transport material and the mobility of the second electrode 120, which in turn causes a mismatch between the second hole transport material and the second electrode 120, thereby preventing the hole transport efficiency between the second hole transport material and the second electrode 120 from being too low.

[0286] In some embodiments, the hole transport material may be a material such as carbazole, triphenylamine, carbazole derivatives, and triphenylamine derivatives.

[0287] In summary, the light-emitting device 100 provided in some embodiments of this disclosure can effectively improve the efficiency of hole injection into the quantum dot light-emitting layer 130 by providing a hole transport doping layer 160 in the light-emitting device 100, thereby balancing the injection rates of holes and electrons and improving the luminous efficiency of the light-emitting device 100.

[0288] The display panel 1000 provided in some embodiments of this disclosure includes the light-emitting device 100 provided in the above embodiments. Therefore, all the beneficial effects of the display panel 1000 provided in some embodiments of this disclosure including the light-emitting device 100 provided in the above embodiments will not be repeated here.

[0289] The display device 2000 provided in some embodiments of this disclosure includes the display panel 1000 provided in the above embodiments. Therefore, all the beneficial effects of the display device 2000 provided in some embodiments of this disclosure including the display panel 1000 provided in the above embodiments will not be repeated here.

[0290] Some embodiments of this disclosure also provide a method for fabricating a light-emitting device, which is used in the light-emitting device 100 provided in the above embodiments.

[0291] Figure 13 This is a flowchart of a method for fabricating a light-emitting device according to some embodiments.

[0292] Please see Figure 13 The method for preparing the light-emitting device includes the following steps S1 to S3.

[0293] Please refer to it again. Figure 5 S1, A quantum dot light-emitting layer 130 is formed on one side of the first electrode 110.

[0294] The first electrode 110 can be conductive glass.

[0295] Before forming the quantum dot light-emitting layer 130, the conductive glass can be cleaned with water and isopropanol respectively, and then treated with ultraviolet light for 5 to 10 minutes.

[0296] Spin coating can be used to form the quantum dot light-emitting layer 130.

[0297] S2. A hole transport doped layer 160 is formed on the side of the quantum dot light-emitting layer 130 away from the first electrode 110, wherein the hole transport doped layer 160 comprises a mixture of at least two hole transport materials, wherein the highest occupied molecular orbital energy levels of the at least two hole transport materials are different.

[0298] In the hole transport doped layer 160, since at least two hole transport materials are mixed, the contact area between two hole transport materials with similar HOMO energy levels is large. When a hole transitions from a hole transport material with a higher HOMO energy level to a hole transport material with a lower HOMO energy level, the hole transport rate is high. This can increase the hole injection rate into the quantum dot light-emitting layer 130, making the injection rates of electrons and holes into the quantum dot light-emitting layer 130 more balanced, thereby improving the luminous efficiency of the light-emitting device 100.

[0299] For example, the hole transport doped layer 160 can be formed by a vapor deposition process.

[0300] S3. A second electrode 120 is formed on the side of the hole transport doped layer 160 away from the quantum dot light-emitting layer 130.

[0301] The second electrode 120 can be an aluminum film or a silver film, which can be formed by vapor deposition.

[0302] In addition, the second electrode 120 can also be indium zinc oxide (IZO), which can be formed by sputtering.

[0303] After step S3, the light-emitting device 100 can be encapsulated. For example, UV-curable adhesive can be used to encapsulate the light-emitting device 100.

[0304] In some embodiments, the at least two hole transport materials include a first hole transport material and a second hole transport material, and the HOMO energy level of the first hole transport material is lower than the HOMO energy level of the second hole transport material.

[0305] In step S2, forming a hole transport doped layer 160 on the side of the quantum dot light-emitting layer 130 away from the first electrode 110, a first hole transport material and a second hole transport material are deposited simultaneously on one side of the first electrode 110 using a dual-source co-evaporation method to form the hole transport doped layer 160.

[0306] The "dual-source co-evaporation method" refers to setting two evaporation sources in the coating chamber. One evaporation source is used to evaporate the first hole transport material, while the other evaporation source is used to evaporate the second hole transport material. The evaporation rate of the two materials can be changed by changing their evaporation temperatures.

[0307] For example, in step S2, the ratio of the evaporation rates of the first hole transport material and the second hole transport material is in the range of 1:5 to 5:1, so that the mass ratio of the first hole transport material and the second hole transport material in the hole transport doped layer 160 is in the range of 1:5 to 5:1.

[0308] In some examples, the hole transport section includes only a hole transport doped layer 160, and in step S2, the ratio of the evaporation rates of the first hole transport material and the second hole transport material is 2:1. In this case, the mass ratio of the first hole transport material to the second hole transport material in the hole transport doped layer 160 is 2:1.

[0309] Figure 14 This is a flowchart of a method for fabricating a light-emitting device according to some embodiments.

[0310] Please see Figure 14 And also refer to Figure 5 In some embodiments, before step S1, forming a quantum dot light-emitting layer 130 on one side of the first electrode 110, the method further includes: S01, forming an electron transport layer 180 on one side of the first electrode 110.

[0311] When the electron transport layer 180 is a zinc oxide-based nanoparticle film, zinc oxide nanoparticles can be spin-coated and heated to form a film at a temperature of 80℃ to 120℃. The spin coater speed is set to 500 rpm to 2500 rpm to adjust the film thickness.

[0312] When the electron transport layer 180 is a zinc oxide thin film, 1 g of zinc acetate (or zinc nitrate, etc.) is dissolved in 5 mL of a mixed solution of ethanolamine and n-butanol to form a zinc precursor solution.

[0313] The conductive glass was then placed in a spin coater, and 90 μL to 120 μL of a zinc precursor solution was dropped onto the conductive glass and spin-coated. The conductive glass was then placed on a hot plate at 250°C to 300°C for heating and solvent extraction.

[0314] Step S1, forming a quantum dot light-emitting layer 130 on one side of the first electrode 110, includes: S11, forming a quantum dot light-emitting layer 130 on the side of the electron transport layer 180 opposite to the first electrode 110.

[0315] In some embodiments, after step S2, forming a hole transport doped layer 160 on the side of the quantum dot light-emitting layer 130 away from the first electrode 110, the method further includes step S2A, forming a hole injection layer 170 on the side of the hole transport doped layer 160 away from the quantum dot light-emitting layer 130.

[0316] The hole injection layer 170 can be formed by spin coating.

[0317] For example, the hole injection layer 170 may include PEDOT:PSS 4083 (poly(3,4-ethylenedioxythiophene) / polystyrene sulfonate). The film-forming temperature of PEDOT is 130°C to 150°C. The thickness of the hole injection layer 170 can be adjusted according to the spin coater speed.

[0318] In addition, the hole injection layer 170 can also be formed by vapor deposition.

[0319] In the case including S2A, step S3, forming a second electrode 120 on the side of the hole transport doped layer 160 away from the quantum dot light-emitting layer 130, includes: S31, forming a second electrode 120 on the side of the hole injection layer 170 away from the hole transport doped layer 160.

[0320] Figure 15 This is a flowchart of a method for fabricating a light-emitting device according to some embodiments.

[0321] Please see Figure 15 In some embodiments, after step S1, forming a quantum dot light-emitting layer 130 on one side of the first electrode 110, the method further includes: S1A, forming a first hole transport layer 140 on the side of the quantum dot light-emitting layer 130 away from the first electrode 110.

[0322] For example, in step S1A, it can be done by The rate at which the first hole transport layer 140 is deposited on the side of the quantum dot light-emitting layer 130 away from the first electrode 110.

[0323] S2, the step of forming a hole transport doped layer 160 on the side of the quantum dot light-emitting layer 130 away from the first electrode 110 includes: S21, forming a hole transport doped layer 160 on the side of the first hole transport layer 140 away from the first electrode 110.

[0324] When the light-emitting device 100 includes a first hole transport layer 140 and a hole transport doped layer 160, in step S2, the ratio of the evaporation rates of the first hole transport material and the second hole transport material is 2:1. At this time, in the hole transport doped layer 160, the mass ratio of the first hole transport material to the second hole transport material is 2:1.

[0325] Figure 16 This is a flowchart of a method for fabricating a light-emitting device according to some embodiments.

[0326] Please see Figure 16 In some embodiments, after step S2, forming a hole transport doped layer 160 on the side of the quantum dot light-emitting layer 130 away from the first electrode 110, the method further includes: S2B, forming a second hole transport layer 150 on the side of the hole transport doped layer 160 away from the first electrode 110.

[0327] For example, in step S2B, it can be done by The rate at which the second hole transport layer 150 is deposited on the side of the quantum dot light-emitting layer 130 away from the first electrode 110.

[0328] When the light-emitting device 100 includes a second hole transport layer 150 and a hole transport doped layer 160, in step S2, the ratio of the evaporation rates of the first hole transport material and the second hole transport material is 1:1. At this time, in the hole transport doped layer 160, the mass ratio of the first hole transport material to the second hole transport material is 1:1.

[0329] When the light-emitting device 100 includes a first hole transport layer 140, a second hole transport layer 150, and a hole transport doped layer 160, in step S2, the ratio of the evaporation rates of the first hole transport material and the second hole transport material is 1:1. At this time, in the hole transport doped layer 160, the mass ratio of the first hole transport material to the second hole transport material is 1:1.

[0330] It is understood that, in the case where the light-emitting device 100 further includes a hole injection layer 170, the hole injection layer 170 is located between the second hole transport layer 150 and the second electrode 120.

[0331] S3, the step of forming a second electrode 120 on the side of the hole transport doped layer 160 away from the quantum dot light-emitting layer 130 includes: S32, forming a second electrode 120 on the side of the second hole transport layer 150 away from the hole transport doped layer 160.

[0332] The above description is merely a specific embodiment of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any variations or substitutions conceived by those skilled in the art within the scope of the technology disclosed in this disclosure should be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.

Claims

1. A light-emitting device, comprising: First electrode and second electrode; A quantum dot light-emitting layer located between the first electrode and the second electrode; as well as, A hole transport doped layer is located between the quantum dot light-emitting layer and the second electrode; the hole transport doped layer comprises a mixture of at least two hole transport materials, wherein the highest occupied molecular orbital energy levels of the at least two hole transport materials are different; the at least two hole transport materials include a first hole transport material and a second hole transport material, and the highest occupied molecular orbital energy level of the first hole transport material is lower than that of the second hole transport material; the mobility of the first hole transport material is greater than that of the second hole transport material. The light-emitting device further includes: A first hole transport layer is located between the quantum dot emitting layer and the hole transport doped layer; the mobility of the first hole transport layer is equal to the mobility of the first hole transport material and greater than the mobility of the quantum dot emitting layer; and / or, A second hole transport layer is located between the hole transport doped layer and the second electrode; the mobility of the second hole transport layer is less than the mobility of the second electrode and equal to the mobility of the second hole transport material.

2. The light-emitting device according to claim 1, wherein, The at least two hole transport materials have different mobilities, and among any two hole transport materials, the hole transport material with the lower highest occupied molecular orbital energy level has a higher mobility than the hole transport material with the higher highest occupied molecular orbital energy level.

3. The light-emitting device according to claim 2, wherein, In the hole transport doped layer, the mass ratio of the first hole transport material to the second hole transport material is 1:5 to 5:

1.

4. The light-emitting device according to claim 3, wherein, In the hole transport doped layer, the mass ratio of the first hole transport material to the second hole transport material is 2:

1.

5. The light-emitting device according to claim 4, wherein, The thickness of the hole transport doped layer is 0.66 to 5 times the thickness of the quantum dot light-emitting layer.

6. The light-emitting device according to claim 4, wherein, The thickness of the hole transport doped layer is 2.3 times the thickness of the quantum dot light-emitting layer.

7. The light-emitting device according to any one of claims 4 to 6, wherein, The thickness of the hole transport doped layer ranges from 20 nm to 50 nm.

8. The light-emitting device according to claim 3, wherein, In the case where the light-emitting device further includes the first hole transport layer but does not include the second hole transport layer, the highest occupied molecular orbital energy level of the first hole transport layer is less than or equal to the highest occupied molecular orbital energy level of the first hole transport material, and greater than the highest occupied molecular orbital energy level of the quantum dot light-emitting layer.

9. The light-emitting device according to claim 8, wherein, In the case where the light-emitting device further includes the first hole transport layer but does not include the second hole transport layer, The first hole transport layer includes the first hole transport material.

10. The light-emitting device according to claim 8 or 9, wherein, In the case where the light-emitting device further includes the first hole transport layer but does not include the second hole transport layer, In the hole transport doped layer, the mass ratio of the first hole transport material to the second hole transport material is 2:

1.

11. The light-emitting device according to claim 8 or 9, wherein, In the case where the light-emitting device further includes the first hole transport layer but does not include the second hole transport layer, The thickness of the hole transport doped layer is 0.33 to 5 times the thickness of the quantum dot light-emitting layer; The thickness of the first hole transport layer is 0.06 to 2 times the thickness of the hole transport doped layer.

12. The light-emitting device according to claim 8 or 9, wherein, In the case where the light-emitting device further includes the first hole transport layer but does not include the second hole transport layer, The thickness of the first hole transport layer is one-third of the thickness of the hole transport doped layer.

13. The light-emitting device according to claim 3, wherein, The light-emitting device further includes a second hole transport layer. In the absence of the first hole transport layer, the highest occupied molecular orbital energy level of the second hole transport layer is lower than the highest occupied molecular orbital energy level of the second electrode, and is greater than or equal to the highest occupied molecular orbital energy level of the second hole transport material.

14. The light-emitting device according to claim 13, wherein, In the case where the light-emitting device further includes a second hole transport layer, but does not include the first hole transport layer... The second hole transport layer includes a second hole transport material.

15. The light-emitting device according to claim 13 or 14, wherein, In the case where the light-emitting device further includes a second hole transport layer, but does not include the first hole transport layer... In the hole transport doped layer, the mass ratio of the first hole transport material to the second hole transport material is 1:

1.

16. The light-emitting device according to claim 13 or 14, wherein, In the case where the light-emitting device further includes a second hole transport layer, but does not include the first hole transport layer... The thickness of the hole transport doped layer is 0.1 to 2 times the thickness of the quantum dot light-emitting layer; The thickness of the second hole transport layer is 0.5 to 16.66 times the thickness of the hole transport doped layer.

17. The light-emitting device according to claim 13 or 14, wherein, In the case where the light-emitting device further includes a second hole transport layer, but does not include the first hole transport layer... The thickness of the second hole transport layer is three times the thickness of the hole transport doped layer.

18. The light-emitting device according to claim 3, wherein, In the case where the light-emitting device further includes the first hole transport layer and the second hole transport layer, The highest occupied molecular orbital energy level of the first hole transport layer is less than or equal to the highest occupied molecular orbital energy level of the first hole transport material, and greater than the highest occupied molecular orbital energy level of the quantum dot light-emitting layer. The highest occupied molecular orbital energy level of the second hole transport layer is lower than the highest occupied molecular orbital energy level of the second electrode, and is greater than or equal to the highest occupied molecular orbital energy level of the second hole transport material.

19. The light-emitting device according to claim 18, wherein, In the case where the light-emitting device further includes the first hole transport layer and the second hole transport layer, The first hole transport layer includes the first hole transport material; The second hole transport layer includes a second hole transport material.

20. The light-emitting device according to claim 18 or 19, wherein, In the case where the light-emitting device further includes the first hole transport layer and the second hole transport layer, In the hole transport doped layer, the mass ratio of the first hole transport material to the second hole transport material is 1:

1.

21. The light-emitting device according to claim 18 or 19, wherein, In the case where the light-emitting device further includes the first hole transport layer and the second hole transport layer, The thickness of the hole transport doped layer is 0.1 to 2 times the thickness of the quantum dot light-emitting layer; The thickness of the first hole transport layer is 0.15 to 6.67 times the thickness of the hole transport doped layer; The thickness of the second hole transport layer is 0.5 to 16.67 times the thickness of the hole transport doped layer.

22. The light-emitting device according to claim 18 or 19, wherein, In the case where the light-emitting device further includes the first hole transport layer and the second hole transport layer, The thickness of the first hole transport layer is 1 times the thickness of the hole transport doped layer; The thickness of the second hole transport layer is 6 times the thickness of the hole transport doped layer.

23. The light-emitting device according to any one of claims 3 to 6, 8, 9, 13, 14, 18, and 19, wherein, The hole transport doped layer includes multiple stacked sub-doped layers; in any two adjacent sub-doped layers, the mass ratio of the first hole transport material to the second hole transport material in the sub-doped layer closer to the quantum dot light-emitting layer is greater than the mass ratio of the first hole transport material to the second hole transport material in the sub-doped layer farther from the quantum dot light-emitting layer.

24. The light-emitting device according to any one of claims 3 to 6, 8, 9, 13, 14, 18, and 19, wherein, The highest occupied molecular orbital energy level of the first hole transport material is 0.88 to 1.02 times that of the highest occupied molecular orbital energy level of the quantum dot luminescent layer; The highest occupied molecular orbital energy level of the second hole transport material is 0.82 to 0.97 times that of the highest occupied molecular orbital energy level of the quantum dot luminescent layer.

25. The light-emitting device according to any one of claims 3 to 6, 8, 9, 13, 14, 18, and 19, wherein, The highest occupied molecular orbital energy level of the first hole transport material ranges from -6.3 eV to -5.9 eV; The highest occupied molecular orbital energy level of the second hole transport material ranges from -6eV to -5.5eV.

26. The light-emitting device according to any one of claims 3 to 6, 8, 9, 13, 14, 18 and 19, wherein, The mobility of the first hole transport material is 1 to 10 times the mobility of the quantum dot emitting layer. 3 times; The mobility of the second hole transport material is 10 times the mobility of the quantum dot emitting layer. 2 Times ~10 4 times.

27. The light-emitting device according to any one of claims 3-6, 8, 9, 13, 14, 18, and 19, wherein, The mobility range of the first hole transport material is: ~ ; The mobility range of the second hole transport material is as follows: ~ .

28. The light-emitting device according to any one of claims 1 to 6, 8, 9, 13, 14, 18 and 19, wherein, The at least two hole transport materials include at least two of the following materials: 4,4-bis(carbazole-9-yl)biphenyl, 1,3-bis(carbazol-9-yl)benzene, 2,6-bis(3-(9H-carbazol-9-yl)phenyl)pyridine, 4,4',4''-tris(carbaz ol-9-yl)triphenylamine, 1,1-bis[4-[N,N'-di(p-tolyl)amino]phenyl]cyclohexane, N,N'-bis(naphthalen-1-yl)-N,N'-bis(phenyl)benzidine.

29. The light-emitting device according to any one of claims 1 to 6, 8, 9, 13, 14, 18 and 19, further comprising: A hole injection layer is located between the second electrode and the hole transport doped layer; An electron transport layer is located between the first electrode and the quantum dot light-emitting layer.

30. A display panel, comprising: Substrate; as well as, The plurality of light-emitting devices as described in any one of claims 1 to 29, wherein the plurality of light-emitting devices are disposed on one side of the substrate.

31. A display device, comprising: The display panel as described in claim 30.

32. A method for fabricating a light-emitting device, comprising: A quantum dot light-emitting layer is formed on one side of the first electrode; A hole transport doped layer is formed on the side of the quantum dot light-emitting layer away from the first electrode, wherein the hole transport doped layer comprises a mixture of at least two hole transport materials, wherein the highest occupied molecular orbital energy levels of the at least two hole transport materials are different; A second electrode is formed on the side of the hole transport doping layer away from the quantum dot light-emitting layer; The at least two hole transport materials include a first hole transport material and a second hole transport material, wherein the highest occupied molecular orbital energy level of the first hole transport material is lower than the highest occupied molecular orbital energy level of the second hole transport material; and the mobility of the first hole transport material is greater than the mobility of the second hole transport material. The light-emitting device further includes: A first hole transport layer is located between the quantum dot emitting layer and the hole transport doped layer; the mobility of the first hole transport layer is equal to the mobility of the first hole transport material and greater than the mobility of the quantum dot emitting layer; and / or, A second hole transport layer is located between the hole transport doped layer and the second electrode; the mobility of the second hole transport layer is less than the mobility of the second electrode and equal to the mobility of the second hole transport material.

33. The method for fabricating a light-emitting device according to claim 32, wherein, The at least two hole transport materials include a first hole transport material and a second hole transport material, wherein the highest occupied molecular orbital energy level of the first hole transport material is lower than the highest occupied molecular orbital energy level of the second hole transport material. In the step of forming a hole transport doped layer on the side of the quantum dot light-emitting layer away from the first electrode, the first hole transport material and the second hole transport material are deposited simultaneously on one side of the first electrode using a dual-source co-evaporation method to form the hole transport doped layer.

34. The method for fabricating a light-emitting device according to claim 32 or 33, wherein, Following the step of forming a quantum dot light-emitting layer on one side of the first electrode, the method further includes: A first hole transport layer is formed on the side of the quantum dot light-emitting layer away from the first electrode; The step of forming a hole transport doped layer on the side of the quantum dot light-emitting layer away from the first electrode includes: The hole transport doped layer is formed on the side of the first hole transport layer away from the first electrode.

35. The method for fabricating a light-emitting device according to claim 32 or 33, wherein, After the step of forming a hole transport doped layer on the side of the quantum dot light-emitting layer away from the first electrode, the method further includes: A second hole transport layer is formed on the side of the hole transport doped layer away from the first electrode; The step of forming a second electrode on the side of the hole transport doped layer away from the quantum dot light-emitting layer includes: The second electrode is formed on the side of the second hole transport layer away from the hole transport doped layer.

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