Light-emitting device and manufacturing method therefor, and display apparatus

Abstract

The present invention provides a light-emitting device and a manufacturing method therefor, and a display apparatus. The light-emitting device comprises: a substrate; a hole transport layer located on the substrate; a quantum dot light-emitting layer located on the side of the hole transport layer distant from the substrate; and first wavelength light absorption molecules located on the side of the hole transport layer distant from the substrate, the first wavelength light absorption molecules being configured to absorb first wavelength light capable of causing a cross-linking reaction of the hole transport layer.

Description

Light-emitting device, manufacturing method thereof, and display device Technical Field

[0001] The present disclosure relates to the field of display technology, and in particular to a light-emitting device and a method for manufacturing the same, and a display device including the light-emitting device. Background Art

[0002] Light emitting diodes (LEDs) emit light by releasing energy through the recombination of electrons and holes. Light emitting diodes include but are not limited to organic light emitting diodes (OLEDs) and quantum dot light emitting diodes (QLEDs). Quantum dots are a type of semiconductor nanomaterial that can bind excitons in three-dimensional space. Due to their excellent properties such as high quantum efficiency, narrow excitation spectrum, high photostability, long fluorescence lifetime, and good solution processing compatibility, they have great application potential in high-quality displays. Quantum dot light emitting diodes are devices that use quantum dots as light-emitting materials. Compared with organic light emitting diodes, they have outstanding advantages such as lower energy consumption, higher color purity, and a wider color gamut. Therefore, quantum dot light emitting technology has become the most promising next-generation self-luminous display technology.

[0003] Summary of the Invention

[0004] According to one aspect of the present disclosure, a light-emitting device is provided, comprising: a substrate; a hole transport layer located on the substrate; a quantum dot light-emitting layer located on a side of the hole transport layer away from the substrate; and first wavelength light-absorbing molecules located on a side of the hole transport layer away from the substrate, the first wavelength light-absorbing molecules being configured to absorb first wavelength light that can cause a cross-linking reaction in the hole transport layer.

[0005] In some embodiments, the light-emitting device further comprises a first wavelength light-blocking layer, wherein the first wavelength light-blocking layer is located between the hole transport layer and the quantum dot light-emitting layer or on a side of the quantum dot light-emitting layer away from the hole transport layer, and the first wavelength light-blocking layer comprises the first wavelength light-absorbing molecules.

[0006] In some embodiments, the first wavelength light blocking layer includes an azide group or a benzophenone group.

[0007] In some embodiments, the first wavelength light absorbing molecule includes a single azide group or a double azide group.

[0008] In some embodiments, the hole transport layer includes a cross-linked structure formed by cross-linking a first cross-linking agent with a hole transport material.

[0009] In some embodiments, the content ratio of the first wavelength light absorbing molecules in the first wavelength light blocking layer is greater than the content ratio of the first cross-linking agent in the hole transport layer.

[0010] In some embodiments, the first wavelength light blocking layer further comprises polymer molecules.

[0011] In some embodiments, the first wavelength light absorbing molecule includes a diazide group, and the first wavelength light blocking layer includes a cross-linked structure formed by cross-linking the first wavelength light absorbing molecule and the polymer molecules.

[0012] In some embodiments, the first wavelength light blocking layer further includes remaining first wavelength light absorbing molecules.

[0013] In some embodiments, the quantum dot light-emitting layer includes a plurality of quantum dots, at least some of the plurality of quantum dots include a quantum dot body and a ligand coordinated to the quantum dot body, and the polymer molecule is further cross-linked with at least some of the ligands through the diazide group.

[0014] In some embodiments, the polymer molecule is made of the same material as the hole transport material.

[0015] In some embodiments, the hole transport layer further includes a remaining first cross-linking agent.

[0016] In some embodiments, the first wavelength light absorbing molecule comprises a benzophenone group or a single azide group, and the first wavelength light absorbing molecule has the same light absorbing properties as the first cross-linking agent.

[0017] In some embodiments, in the first wavelength light-blocking layer, the first wavelength light-absorbing molecules are connected to the polymer molecules through chemical bonds, and the polymer molecules are not cross-linked.

[0018] In some embodiments, the quantum dot light-emitting layer includes a plurality of quantum dots, at least some of the plurality of quantum dots include a quantum dot body and a ligand coordinated to the quantum dot body, and the first wavelength light absorbing molecule is connected to at least some of the ligands through a chemical bond.

[0019] In some embodiments, the thickness of the first wavelength light blocking layer is less than or equal to 2 nm.

[0020] In some embodiments, the quantum dot light-emitting layer has a cross-linked structure and includes quantum dots, a second cross-linking agent, and the first wavelength light-absorbing molecules, and the quantum dots are cross-linked with at least the second cross-linking agent.

[0021] In some embodiments, the first wavelength light absorbing molecule comprises a diazide group.

[0022] In some embodiments, the first wavelength light absorbing molecule comprises a benzophenone group or a single azide group.

[0023] In some embodiments, the first wavelength light absorbing molecule includes a single azide group, and the para-group of the azide group includes any one of an alkyl group, an ether, an alcohol, and a halogen; or the first wavelength light absorbing molecule includes a benzophenone group, and the benzene ring on the benzophenone group is not connected to an electron-donating group.

[0024] In some embodiments, the light-emitting device further includes: a hole injection layer located between the substrate and the hole transport layer; an electron transport layer located on the side of the quantum dot light-emitting layer away from the substrate; and a second electrode located on the side of the electron transport layer away from the substrate, and the substrate is the first electrode.

[0025] In some embodiments, the first wavelength light-blocking layer is located between the hole transport layer and the quantum dot light-emitting layer, the hole transport layer includes a cross-linked structure generated by cross-linking a first cross-linker with a hole transport material, the first wavelength light-blocking layer also includes polymer molecules, the material of the polymer molecules is the same as that of the hole transport material, the material of the first wavelength light-absorbing molecules is the same as that of the first cross-linker, the first wavelength light-blocking layer includes a cross-linked structure generated by cross-linking the first wavelength light-absorbing molecules with the polymer molecules, and the quantum dot light-emitting layer includes a cross-linked structure generated by cross-linking a second cross-linker with quantum dots.

[0026] According to another aspect of the present disclosure, a display device is provided, which includes a plurality of light-emitting devices described in any one of the above embodiments.

[0027] According to another aspect of the present disclosure, a method for preparing a light-emitting device is provided, comprising: providing a substrate; providing a first mixed solution comprising a hole transport material and a first cross-linking agent on the substrate, curing the first mixed solution to form a first cured layer, irradiating the first cured layer with a first wavelength of light to cross-link the first cross-linking agent with the hole transport material to form a hole transport layer; providing a first wavelength of light absorbing molecules on a side of the hole transport layer away from the substrate; providing a second mixed solution on a side of the hole transport layer away from the substrate, the second mixed solution comprising quantum dots and a second cross-linking agent, curing the second mixed solution to form a second cured layer; and irradiating the second cured layer with a third wavelength of light to cross-link at least the second cross-linking agent with the quantum dots, the third wavelength of light comprising the first wavelength of light, the first wavelength of light absorbing molecules absorbing a first wavelength of light in the third wavelength of light to prevent the first wavelength of light in the third wavelength of light from irradiating the hole transport layer.

[0028] In some embodiments, providing a first wavelength light absorbing molecule on a side of the hole transport layer away from the substrate comprises: providing a third mixed solution comprising polymer molecules and the first wavelength light absorbing molecule on a side of the hole transport layer away from the substrate, and applying the third mixed solution on the hole transport layer to form a first wavelength light blocking layer.

[0029] In some embodiments, the first wavelength light absorbing molecule includes a diazide group, and the third wavelength light further includes a second wavelength light. Radiating the second solidified layer with the third wavelength light to crosslink at least the second crosslinker with the quantum dots comprises: the second crosslinker absorbs the second wavelength of the third wavelength light and crosslinks with the quantum dots to form a quantum dot light-emitting layer; and the first wavelength light absorbing molecule absorbs the first wavelength of the third wavelength light and crosslinks with the polymer molecules.

[0030] In some embodiments, the quantum dots include a quantum dot body and a ligand coordinated to the quantum dot body. Irradiating the second solidified layer with light of a third wavelength to crosslink at least the second crosslinker with the quantum dots further comprises: crosslinking the polymer molecules with the ligand via the diazide groups under irradiation with light of a first wavelength within the third wavelength.

[0031] In some embodiments, the first wavelength light absorbing molecule includes a single azide group or a benzophenone group, the quantum dot includes a quantum dot body and a ligand coordinated to the quantum dot body, and the third wavelength light also includes a second wavelength light. Irradiating the second solidified layer with the third wavelength light to crosslink at least the second crosslinker with the quantum dots may include: the second crosslinker absorbs the second wavelength of light in the third wavelength light and crosslinks with the quantum dots to form a quantum dot light-emitting layer, the first wavelength light absorbing molecule absorbs the first wavelength of light in the third wavelength light and is chemically bonded to the polymer molecule; or the second crosslinker absorbs the second wavelength of light in the third wavelength light and crosslinks with the quantum dots to form a quantum dot light-emitting layer, the first wavelength light absorbing molecule absorbs the first wavelength of light in the third wavelength light and is chemically bonded to the ligand.

[0032] In some embodiments, providing a first wavelength light absorbing molecule on a side of the hole transport layer away from the substrate and providing a second mixed solution on a side of the hole transport layer away from the substrate includes: providing a second mixed solution on a side of the hole transport layer away from the substrate, the second mixed solution including the quantum dots, the second cross-linking agent, and the first wavelength light absorbing molecule, and curing the second mixed solution to form a second cured layer.

[0033] In some embodiments, the first wavelength light-absorbing molecule includes a diazide group, and the third wavelength light further includes a second wavelength light. Irradiating the second cured layer with the third wavelength light to crosslink at least the second crosslinker with the quantum dots comprises: the second crosslinker absorbs the second wavelength of the third wavelength light and crosslinks with the quantum dots, and the first wavelength light-absorbing molecule absorbs the first wavelength of the third wavelength light and crosslinks with the quantum dots, thereby forming a quantum dot light-emitting layer.

[0034] In some embodiments, the first wavelength light absorbing molecule includes a single azide group or a benzophenone group, the quantum dot includes a quantum dot body and a ligand coordinated to the quantum dot body, and the third wavelength light also includes a second wavelength light. Irradiating the second solidified layer with the third wavelength light to crosslink at least the second crosslinker with the quantum dots comprises: the second crosslinker absorbs the second wavelength of light in the third wavelength light and crosslinks the quantum dots, and the first wavelength light absorbing molecule absorbs the first wavelength of light in the third wavelength light and connects to the ligand via a chemical bond to form a quantum dot light-emitting layer.

[0035] In some embodiments, the concentration ratio of the hole transport material to the first cross-linking agent in the first mixed solution is 8 mg / ml: 0.05-0.5 mg / ml. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Hereinafter, various exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings, in which:

[0037] FIG1 shows a flow chart of a method for preparing a light-emitting device;

[0038] FIG2 shows a chemical formula of a hole transport material;

[0039] FIG3 shows the current density of a light-emitting device before and after the quantum dot light-emitting layer is exposed;

[0040] FIG4 shows the device efficiency of a light-emitting device before and after the quantum dot light-emitting layer is exposed;

[0041] FIG5 shows an arrangement of first wavelength light absorbing molecules in a light emitting device according to an embodiment of the present disclosure;

[0042] FIG6 shows a chemical formula of a first wavelength light absorbing molecule according to an embodiment of the present disclosure;

[0043] FIG7 shows another chemical formula of a first wavelength light absorbing molecule according to an embodiment of the present disclosure;

[0044] FIG8 shows another chemical formula of a first wavelength light absorbing molecule according to an embodiment of the present disclosure;

[0045] FIG9 shows another chemical formula of a first wavelength light absorbing molecule according to an embodiment of the present disclosure;

[0046] FIG10 shows another chemical formula of a first wavelength light absorbing molecule according to an embodiment of the present disclosure;

[0047] FIG11 shows another chemical formula of a first wavelength light absorbing molecule according to an embodiment of the present disclosure;

[0048] FIG12 shows another chemical formula of a first wavelength light absorbing molecule according to an embodiment of the present disclosure;

[0049] FIG13 shows another chemical formula of a first wavelength light absorbing molecule according to an embodiment of the present disclosure;

[0050] FIG14 shows another arrangement of first wavelength light absorbing molecules in a light emitting device according to an embodiment of the present disclosure;

[0051] FIG15 shows another arrangement of first wavelength light absorbing molecules in a light emitting device according to an embodiment of the present disclosure;

[0052] FIG16 shows a schematic structural diagram of a light emitting device according to an embodiment of the present disclosure;

[0053] FIG17 shows a schematic structural diagram of another light emitting device according to an embodiment of the present disclosure;

[0054] FIG18 shows a schematic structural diagram of another light emitting device according to an embodiment of the present disclosure;

[0055] FIG19 shows a block diagram of a display device according to an embodiment of the present disclosure; and

[0056] FIG20 shows a flow chart of a method for preparing a light-emitting device according to an embodiment of the present disclosure.

[0057] It should be understood that the accompanying drawings are merely schematic illustrations of exemplary embodiments of the present disclosure and are not intended to limit the present disclosure and are not necessarily drawn to scale. In addition, in the accompanying drawings, identical or similar components are indicated by identical or similar reference numerals. DETAILED DESCRIPTION

[0058] The following will clearly describe the technical solutions in the embodiments of the present disclosure in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of them. Based on the embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present disclosure.

[0059] Before formally describing the technical solutions of the embodiments of the present disclosure, the following explanations and definitions are given for the terms used in the embodiments of the present disclosure to help those skilled in the art to more clearly understand the technical solutions of the embodiments of the present disclosure.

[0060] In this article, the term "crosslinker," also known as a bridging agent, generates diradicals upon exposure. Crosslinkers are primarily used in polymer materials. Before crosslinking, polymers are linear molecules with low strength, are easily broken, and lack elasticity. Crosslinkers create chemical bonds between linear molecules, connecting them to form a network structure, which can improve the polymer's strength, elasticity, stability, and solvent resistance.

[0061] In this article, terms such as "crosslinking" or "crosslinking reaction" refer to the reaction of two or more molecules (generally linear molecules) bonding and crosslinking to form relatively stable molecules (bulk molecules) of a network structure. This reaction transforms linear or slightly branched macromolecules into a three-dimensional network structure, thereby improving properties such as strength, heat resistance, wear resistance, and solvent resistance. The crosslinking method can be chemical crosslinking or physical crosslinking. Chemical crosslinking is generally achieved through polycondensation and polyaddition reactions, and is formed by covalent bonds. For example, the vulcanization of rubber and the curing of unsaturated polyester resins are all chemical crosslinking. Physical crosslinking uses radiation such as light and heat to crosslink linear polymers, and is usually formed by physical forces such as hydrogen bonds. For example, radiation crosslinking of polyethylene is physical crosslinking. Linear polymers are improved in mechanical strength, elasticity, dimensional stability, solvent resistance, etc. after moderate crosslinking, so crosslinking reactions can be used for polymer modification.

[0062] As used herein, the term "uncrosslinked" means that the molecular structure remains substantially the same and has not been transformed from a linear molecule into a three-dimensional network structure. For example, uncrosslinked polymer molecules remain linear molecules.

[0063] As used herein, terms such as "A is chemically bonded to B" mean that A and B are bonded to each other via a chemical bond. For example, A may be chemically bonded to an atom on the surface of B or to a ligand of B; similarly, B may be chemically bonded to an atom on the surface of A or to a ligand of A.

[0064] In this article, terms such as "A is connected to B through a chemical bond but not cross-linked with B" mean that after a specific reaction, A is only connected to atoms on the surface of B or ligands of B through chemical bonds, but does not participate in the cross-linking process of B, that is, A does not cause B to change from a linear molecule to a three-dimensional network structure.

[0065] Quantum dot light-emitting diode devices include upright and inverted device structures. The upright device structure includes a stacked anode, hole injection layer, hole transport layer, quantum dot light-emitting layer, electron transport layer, and cathode. During the preparation of the upright device structure, the photolithographic patterning process involves exposing and cross-linking the hole transport layer and quantum dot light-emitting layer separately.

[0066] Figure 1 shows a flow chart for preparing some film layers in a quantum dot light-emitting diode device. As shown in Figure 1, a substrate is first provided, and then a hole injection layer is formed on the substrate. A mixed solution comprising a hole transport material and crosslinker 1 is then applied to the hole injection layer and cured to form a first intermediate film layer. The first intermediate film layer is then exposed to UV light 1. Crosslinker 1 absorbs UV light 1 and crosslinks with the hole transport material, forming a crosslinked hole transport layer. Since crosslinker 1 is typically present in excess in the mixed solution, in addition to the crosslinked hole transport layer, the hole transport layer also includes residual uncrosslinked crosslinker 1. Next, a mixed solution comprising quantum dots (QDs) and crosslinker 2 is applied to the hole transport layer (including the crosslinked hole transport layer and residual uncrosslinked crosslinker 1) and cured to form a second intermediate film layer. The second intermediate film layer is then exposed to UV light 2 in the second step. UV light 2 includes not only the primary wavelength band UV2 but also wavelengths such as UV1. Crosslinker 2 absorbs the primary wavelength band UV2 and crosslinks the quantum dots (QDs), forming a crosslinked quantum dot light-emitting layer. However, during the second exposure process, UV2 is typically not completely absorbed by the quantum dot light-emitting layer and crosslinker 2, but instead passes through the quantum dot light-emitting layer and irradiates the hole transport layer. Because UV2 also contains wavelengths such as UV1, and the hole transport layer contains residual uncrosslinked crosslinker 1, the residual uncrosslinked crosslinker 1 further absorbs the UV1 wavelength in UV2, further crosslinking the hole transport layer and forming a deeply crosslinked hole transport layer.

[0067] Research has found that crosslinking of hole transport materials reduces the hole mobility of the hole transport layer, thereby reducing the hole transport capacity of the hole transport layer. Specifically, the inventors tested quantum dot light-emitting diode devices, exposing the uncrosslinked hole transport layer only to UV1 without exposing the quantum dot light-emitting layer to UV2. The results showed that after exposure, the hole transport capacity of the hole transport layer decreased by approximately half, indicating that crosslinking of crosslinker 1 with the hole transport material leads to a decrease in the hole transport capacity of the hole transport layer.

[0068] In fact, this is understandable. Figure 2 shows the molecular structure of a commonly used hole transport material, referred to as polymer TFB. Polymer TFB forms a thin film structure with a certain degree of order through the orderly stacking of benzene rings. The degree of order of polymer semiconductor stacking is an important factor influencing the improvement of the carrier mobility (i.e., carrier transport ability) of the polymer semiconductor film layer. However, during the cross-linking process, cross-linker 1 will form bonds with the polymer TFB molecular chain, which will destroy the orderly stacked film structure, thereby reducing the hole transport ability of the hole transport layer.

[0069] Continuing with reference to FIG1 , during the second exposure process, the residual uncross-linked cross-linker 1 in the hole transport layer will further absorb the UV1 band in UV2, causing the hole transport layer to further cross-link to form a deeply cross-linked hole transport layer. Therefore, the hole transport ability of the hole transport layer will further decrease, thereby significantly reducing the efficiency of the quantum dot light-emitting diode device.

[0070] Figure 3 shows the current density of a quantum dot light-emitting diode device before the quantum dot light-emitting layer is exposed and cross-linked, and the current density of the quantum dot light-emitting layer after the quantum dot light-emitting layer is exposed and cross-linked. As shown in Figure 3, the current density of the device after exposure and cross-linking drops to about 40% of the current density of the device before exposure and cross-linking. This is because, during the process of exposing quantum dots, the residual uncross-linked cross-linking agent 1 in the hole transport layer will further absorb the UV1 band in UV2, causing the hole transport layer to further cross-link to form a deeply cross-linked hole transport layer, and the hole mobility of the hole transport layer will further decrease (for example, a decrease of more than 50%). The decrease in hole mobility will cause the current density of the quantum dot light-emitting diode device to decrease.

[0071] Figure 4 shows the external quantum efficiency (EQE) of the quantum dot light-emitting diode device in Figure 3 before the quantum dot light-emitting layer is exposed and cross-linked, and the external quantum efficiency after the quantum dot light-emitting layer is exposed and cross-linked. In a quantum dot light-emitting diode device, the hole mobility of the hole transport layer is usually significantly lower than the electron mobility of the electron transport layer. During the quantum dot exposure process, the residual uncross-linked cross-linker 1 in the hole transport layer further absorbs the UV1 band in UV2, which further reduces the hole mobility of the hole transport layer, thereby causing the electron and hole transport capabilities in the quantum dot light-emitting diode device to be more unbalanced, resulting in a significant reduction in the EQE of the quantum dot light-emitting diode device, for example, the EQE drops by about 30% to 40%. As shown in Figure 4, before exposure and cross-linking, the EQE of the quantum dot light-emitting diode device is 23.8% ± 2.5%; after exposure and cross-linking, the EQE of the quantum dot light-emitting diode device drops to 15.8% ± 0.6%, a decrease of about 33%.

[0072] In order to solve the problems existing in the prior art, some embodiments of the present disclosure provide some design solutions, which can reduce or even eliminate the amount of ultraviolet light reaching the hole transport layer when the quantum dot light-emitting layer is exposed, thereby preventing the hole transport layer from further cross-linking and thus avoiding reducing the hole mobility of the hole transport layer.

[0073] Some embodiments of the present disclosure provide a light-emitting device comprising: a substrate, a hole transport layer located on the substrate, a quantum dot light-emitting layer located on a side of the hole transport layer remote from the substrate, and first-wavelength light-absorbing molecules located on a side of the hole transport layer remote from the substrate. The first-wavelength light-absorbing molecules can absorb light of a first wavelength that can induce a cross-linking reaction in the hole transport layer.

[0074] In the preparation process of the light-emitting device, it involves exposing and cross-linking the hole transport layer and the quantum dot light-emitting layer separately. The quantum dot light-emitting layer can be exposed and cross-linked using a third wavelength of light. The third wavelength of light includes at least a first wavelength of light and a second wavelength of light. The second wavelength of light can be used to cross-link the quantum dots, while the first wavelength of light can cause the hole transport layer to cross-link. In the various disclosed embodiments, by providing a first wavelength of light absorbing molecules on the side of the hole transport layer away from the substrate, the first wavelength of light absorbing molecules can absorb the first wavelength of light. In this way, when the quantum dot light-emitting layer above the hole transport layer is exposed and cross-linked, even if the third wavelength of light passes through the quantum dot light-emitting layer, the first wavelength of light in the third wavelength of light will not reach the hole transport layer, but will be absorbed by the first wavelength of light absorbing molecules before reaching the hole transport layer. In this way, the hole transport layer will not undergo further cross-linking, thereby avoiding a decrease in the hole mobility of the hole transport layer and avoiding affecting the efficiency of the light-emitting device.

[0075] The first wavelength light absorbing molecules can be located between the hole transport layer and the quantum dot light emitting layer, or can be located in the quantum dot light emitting layer, or can be located on the side of the quantum dot light emitting layer away from the substrate, as long as it is ensured that when the quantum dot light emitting layer is exposed and cross-linked, the first wavelength light absorbing molecules can absorb the first wavelength light in the third wavelength light before it reaches the hole transport layer.

[0076] The following describes different arrangements of the first wavelength light absorbing molecules in the light emitting device using several embodiments.

[0077] Figure 5 shows a light-emitting device 100 according to an embodiment of the present disclosure, which includes: a substrate 101; a hole transport layer 102 located on the substrate 101; a first wavelength light-blocking layer 104 located on the side of the hole transport layer 102 away from the substrate 101, the first wavelength light-blocking layer 104 including the above-mentioned first wavelength light-absorbing molecules, which can absorb the first wavelength light that can cause a cross-linking reaction in the hole transport layer 102; and a quantum dot light-emitting layer 103 located on the side of the first wavelength light-blocking layer 104 away from the substrate 101.

[0078] The preparation process of the light emitting device 100 is roughly as follows.

[0079] First, a substrate 101 is provided. The substrate 101 may be, for example, an anode of the light-emitting device 100 . The material of the substrate 101 may be any appropriate material, for example, ITO.

[0080] Next, a first mixed solution comprising a hole transport material and a first crosslinking agent is provided on substrate 101. The first mixed solution is cured to form a first cured layer. A first exposure process is performed, i.e., irradiating the first cured layer with light of a first wavelength to crosslink the first crosslinking agent with the hole transport material to form hole transport layer 102.

[0081] The first wavelength of light may be ultraviolet light, and illustratively, the first wavelength of light may be 254 nm ultraviolet light. The hole transport material may be any appropriate material, including but not limited to TFB (Poly (9,9-dioctylfluorene-alt-N-(4-secbutylphenyl)-diphenylamine)), polyTPD (Poly [N, N'-bis (4-butylphenyl) -N, N'-bis (phenyl) -benzi), PVK (Polyvinylcarbazole), etc. The first cross-linking agent may be a cross-linking agent molecule such as an azide system, a diazo system, or a benzophenone system. The hole transport layer 102 includes a cross-linked structure generated by cross-linking the hole transport material and the first cross-linking agent. In some embodiments, the hole transport layer 102 is a composite system, and in addition to the cross-linked structure, the hole transport layer 102 also includes the remaining first cross-linking agent. Here, "the remaining first cross-linking agent" refers to the excess first cross-linking agent that does not participate in the cross-linking reaction. In the first mixed solution, the first crosslinking agent may be in excess. After the first exposure crosslinking step, all the hole transport materials in the first mixed solution have undergone crosslinking reaction, while part of the first crosslinking agent may remain without undergoing crosslinking.

[0082] Next, a third solution is provided on the side of the hole transport layer 102 away from the substrate 101. In some embodiments, the third solution may be a solution of first-wavelength light-absorbing molecules. In alternative embodiments, the third solution is a mixed solution comprising a polymer molecule solution and a first-wavelength light-absorbing molecule solution. In the case of a mixed solution, the mixed solution of the polymer molecule solution and the first-wavelength light-absorbing molecule solution can be applied to the hole transport layer 102 that has undergone the first step of exposure and cross-linking, and formed by spin coating or blade coating to form a first-wavelength light-blocking layer 104. The first-wavelength light-blocking layer 104 is a composite film layer composed of polymer molecules and first-wavelength light-absorbing molecules. Since first-wavelength light-absorbing molecules are typically small organic molecules, they are not suitable for solution film formation. Polymer molecules, on the other hand, are large molecules, so a mixed solution composed of polymer molecules and first-wavelength light-absorbing molecules can facilitate the application of solution film formation. The polymer molecules can be the same as the hole transport material, such as TFB, PVK, Poly-TPD, etc., or other polymer molecules that are easy to form films.

[0083] Next, a second mixed solution comprising quantum dots and a second crosslinking agent is provided on a side of the first wavelength light-blocking layer 104 facing away from the substrate 101, and the second mixed solution is cured to form a second solidified layer. The second crosslinking agent can be any suitable crosslinking agent capable of crosslinking the quantum dots, and the embodiments of the present disclosure are not limited thereto. For example, the second crosslinking agent can be a benzophenone-based crosslinking agent.

[0084] Finally, the second exposure process is performed, that is, the second cured layer is irradiated with light of a third wavelength. The third wavelength light includes not only the second wavelength light (e.g., 365 nm) that can crosslink the quantum dots, but also the first wavelength light (e.g., 254 nm, 0.047 mW / cm 2 ) and other wavelengths (e.g. 405nm, 5mW / cm 2 ). The second cross-linking agent absorbs the second wavelength of light and undergoes a cross-linking reaction with the quantum dots, forming quantum dot light-emitting layer 103. At least a first wavelength of light within the third wavelength of light passes through quantum dot light-emitting layer 103 and is absorbed by the first wavelength light-absorbing molecules in first wavelength light-blocking layer 104. Depending on the material type of the first wavelength light-absorbing molecules, after exposure to the first wavelength of light, the first wavelength light-absorbing molecules in first wavelength light-blocking layer 104 may or may not undergo a cross-linking reaction with the polymer molecules, as will be described in detail below.

[0085] It can be seen that by providing the first wavelength light-blocking layer 104 between the hole transport layer 102 and the quantum dot light-emitting layer 103, when the quantum dot light-emitting material is exposed to light, even if the first wavelength of the third wavelength light passes through the quantum dot light-emitting layer 103, the first wavelength light does not reach the hole transport layer 102. Instead, it is absorbed by the first wavelength light-absorbing molecules in the first wavelength light-blocking layer 104 before reaching the hole transport layer 102. In this way, the hole transport layer 102 is not further cross-linked, thereby preventing a decrease in the hole mobility of the hole transport layer 102 and preventing a reduction in the efficiency of the light-emitting device 100.

[0086] For example, the first wavelength light blocking layer 104 may include an azide group or a benzophenone group, both of which can absorb the first wavelength light.

[0087] Exemplarily, the thickness of the first wavelength light blocking layer 104 is less than or equal to 2 nm, for example, it can be 0.5 nm, 1.0 nm, 1.5 nm, 2.0 nm, etc.

[0088] Exemplarily, the content ratio of the first wavelength light-absorbing molecules in the first wavelength light-blocking layer 104 is greater than the content ratio of the first crosslinking agent in the hole transport layer 102. It should be noted that the first wavelength light-absorbing molecules herein include both crosslinked first wavelength light-absorbing molecules in the first wavelength light-blocking layer 104 and residual uncrosslinked first wavelength light-absorbing molecules in the first wavelength light-blocking layer 104. Similarly, the first crosslinking agent herein includes both crosslinked first crosslinking agents in the hole transport layer 102 and residual uncrosslinked first crosslinking agents in the hole transport layer 102. Exemplarily, "content ratio" may refer to a mass percentage.

[0089] The first wavelength light absorbing molecules in the first wavelength light blocking layer 104 can be various suitable materials. Some possible material choices for the first wavelength light absorbing molecules are listed below. It should be noted that the materials listed below are only a portion of the materials that can be selected for the first wavelength light absorbing molecules, and the first wavelength light absorbing molecules are not limited to these listed materials.

[0090] FIG6 shows a chemical formula of a first wavelength light absorbing molecule, which is That is, each first-wavelength light-absorbing molecule includes two azide groups, referred to as a diazide molecule. R1-R4 can be the same or different and can be selected from fluorine atoms or hydrogen atoms. The azide group N3 in the first-wavelength light-absorbing molecule can generate a highly active nitrogen carbene free radical under irradiation with the first wavelength of light. This nitrogen carbene free radical can undergo a cross-linking reaction with the polymer molecules, resulting in the first-wavelength light-blocking layer 104 comprising a cross-linked structure. When the para-, para-, or meta-position of the azide group N3 is a fluorine atom, this helps to better stabilize the nitrogen carbene free radical and promote the cross-linking reaction between the first-wavelength light-absorbing molecule and the polymer molecules.

[0091] As shown in Figure 7, when R1 to R4 are all fluorine atoms, the chemical formula in Figure 6 becomes

[0092] When the first wavelength light absorbing molecules have the molecular structure shown in FIG6 or FIG7 , in the second exposure process, the first wavelength light absorbing molecules in the first wavelength light blocking layer 104 absorb the first wavelength light in the third wavelength light and undergo a cross-linking reaction with the polymer molecules, so that the first wavelength light blocking layer 104 includes a cross-linked structure.

[0093] In some embodiments, in addition to the crosslinked structure, the first wavelength light-blocking layer 104 also includes residual first wavelength light-absorbing molecules, meaning that the first wavelength light-blocking layer 104 is a composite film. Similarly, the term "residual first wavelength light-absorbing molecules" herein refers to excess first wavelength light-absorbing molecules that have not participated in the crosslinking reaction. To ensure that the very thin first wavelength light-blocking layer 104 can fully absorb the first wavelength light during the second exposure process, the first wavelength light-blocking layer 104 typically contains an excess of first wavelength light-absorbing molecules. After the second exposure process, all polymer molecules have undergone crosslinking, but some first wavelength light-absorbing molecules may remain, uncrosslinked.

[0094] Quantum dot light-emitting layer 103 is formed by cross-linking a plurality of quantum dots with a second cross-linking agent. In some embodiments, the quantum dots include a quantum dot body and ligands coordinated to the quantum dot body. During the second exposure process, under irradiation with the first wavelength of light within the third wavelength, the polymer molecules in first wavelength light-blocking layer 104 not only cross-link with the first wavelength light-absorbing molecules but also may cross-link with the ligands of at least some of the plurality of quantum dots via the diazide groups.

[0095] In some embodiments, the material of the first wavelength light-absorbing molecules in the first wavelength light-blocking layer 104 can be the same as the material of the first crosslinker in the hole transport layer 102. For example, the first wavelength light-absorbing molecules and the first crosslinker can both be diazide molecules, such as the molecular structures shown in Figures 6 or 7. Diazide molecules can fully absorb light of the first wavelength. In other embodiments, the material of the polymer molecules in the first wavelength light-blocking layer 104 can be the same as the hole transport material in the hole transport layer 102, such as TFB, polyTPD, PVK, or the like.

[0096] In some embodiments, the polymer molecule is TFB, and the first wavelength light absorbing molecule is a diazide molecule. When preparing a third mixed solution comprising the polymer molecule and the first wavelength light absorbing molecule, in some examples, the concentration ratio of the polymer molecule solution to the first wavelength light absorbing molecule solution can be 0.8 mg / ml:0.5 mg / ml, resulting in a first wavelength light-blocking layer 104 having a thickness of approximately 2 nm. In other examples, the concentration ratio of the polymer molecule solution to the first wavelength light-absorbing molecule solution can be 0.5 mg / ml:0.5 mg / ml, resulting in a first wavelength light-blocking layer 104 having a thickness of approximately 1 nm. In yet other examples, when the thickness of the first wavelength light-blocking layer 104 is required to be less than 1 nm, the concentration of the first wavelength light-absorbing molecule in the third mixed solution is no less than the concentration of the first crosslinker in the first mixed solution (comprising the hole transport material and the first crosslinker).

[0097] The inventors conducted comparative experiments on the light-emitting device of FIG1 (referred to as QLED device 1) and the light-emitting device 100 of FIG5. The hole transport layer and quantum dot light-emitting layer of QLED device 1 were subjected to a two-step exposure process, respectively. Furthermore, the hole transport layer 102 and quantum dot light-emitting layer 103 of light-emitting device 100 were subjected to a two-step exposure process, respectively. Testing showed that the hole current density of light-emitting device 100 was approximately four times higher than that of QLED device 1. This is because the first wavelength light-blocking layer 104 in light-emitting device 100 absorbs the first wavelength light that passes through the quantum dot light-emitting layer 103 during the second exposure process, preventing the first wavelength light from irradiating the hole transport layer 102, thereby preventing further reduction in the hole transport capacity of the hole transport layer 102. This shows that providing the first wavelength light-blocking layer 104 in light-emitting device 100 can maintain the hole transport capacity of the hole transport layer 102 at a high level even after the second exposure process.

[0098] In some embodiments, the material of the first wavelength light absorbing molecule is different from that of the first crosslinker; however, the first wavelength light absorbing molecule and the first crosslinker have the same light absorption properties. It should be noted that the phrase "the first wavelength light absorbing molecule and the first crosslinker have the same light absorption properties" means that the first wavelength light absorbing molecule and the first crosslinker can both absorb light in the same wavelength band, for example, both can absorb light of the first wavelength.

[0099] For example, the first wavelength light absorbing molecule is not a diazide molecule, but a molecule including a single azide group, and the structure of this type of molecule can be, for example, a half structure of a diazide molecule.

[0100] FIG8 shows a molecular structure of a first wavelength light absorbing molecule, which is methyl 4-azidotetrafluorobenzoate. It is a monoazide molecule.

[0101] FIG9 shows another molecular structure of the first wavelength light absorbing molecule, which is 4-azidotetrafluorobenzoic acid. It is a monoazide molecule.

[0102] FIG10 shows another molecular structure of the first wavelength light absorbing molecule, which is 4-azidotetrafluorobenzaldehyde. It is a monoazide molecule.

[0103] These monoazide molecules containing a 4-azidotetrafluorophenyl group can serve as precursor molecules for synthesizing diazide molecules. When the first-wavelength light-absorbing molecule is a monoazide molecule, such as those shown in Figures 8 to 10 , it shares the same UV absorption band as the first crosslinker and can absorb light of the first wavelength, thereby absorbing the first wavelength during the second exposure step.

[0104] When the first wavelength light absorbing molecule is a monoazide molecule such as Figure 8 to Figure 10, in the second step exposure process, the first wavelength light absorbing molecule in the first wavelength light blocking layer 104 absorbs the first wavelength light in the third wavelength light to produce a nitrene radical. In some cases, the first wavelength light absorbing molecule is connected to the polymer molecule by a chemical bond, but will not undergo a cross-linking reaction with the polymer molecule, i.e., the polymer molecule will not be changed from a linear molecule to a three-dimensional network structure, and the polymer molecule is not cross-linked. Or in other cases, the first wavelength light absorbing molecule is connected to the quantum dot ligand at the interface of the first wavelength light blocking layer 104 and the quantum dot light emitting layer 103 by a chemical bond, but will not undergo a cross-linking reaction with the quantum dot ligand. This is beneficial because if the first wavelength light absorbing molecule undergoes a cross-linking reaction with the quantum dot ligand, the photoluminescence quantum efficiency (PLQY) of the quantum dot may be reduced, thereby causing problems such as insufficient brightness in the light emitting device. Using monoazide molecules as the first wavelength light absorbing molecules only absorbs the first wavelength light and produces a single nitrene free radical. The single nitrene free radical will not participate in the cross-linking process of quantum dots, thereby avoiding problems such as insufficient brightness caused by the cross-linking of the first wavelength light absorbing molecules and quantum dot ligands.

[0105] In some alternative embodiments, the material of the first wavelength light absorbing molecule is different from that of the first crosslinking agent, and the first wavelength light absorbing molecule includes a benzophenone group. Such first wavelength light absorbing molecule and the first crosslinking agent have the same light absorption properties and can absorb light of the first wavelength.

[0106] FIG11 shows a molecular structure of a first wavelength light absorbing molecule, which is benzophenone It is a benzophenone molecule.

[0107] FIG12 shows another molecular structure of the first wavelength light absorbing molecule, which is 4,4'-difluorobenzophenone. It is a benzophenone molecule.

[0108] FIG13 shows another molecular structure of the first wavelength light absorbing molecule, which is 4-chlorobenzophenone. It is a benzophenone molecule.

[0109] When the first-wavelength light-absorbing molecules are benzophenone-based molecules, such as those shown in Figures 11 to 13 , during the second exposure process, the first-wavelength light-absorbing molecules in the first-wavelength light-blocking layer 104 absorb the first wavelength of light in the third wavelength, generating carbon carbene radicals. In some cases, the first-wavelength light-absorbing molecules are chemically bonded to the polymer molecules but do not undergo a cross-linking reaction with the polymer molecules. This means that the polymer molecules do not transform from linear molecules into a three-dimensional network structure, and the polymer molecules remain uncross-linked. Alternatively, in other cases, the first-wavelength light-absorbing molecules are chemically bonded to the quantum dot ligands at the interface between the first-wavelength light-blocking layer 104 and the quantum dot light-emitting layer 103 but do not undergo a cross-linking reaction with the quantum dot ligands. This is beneficial because if the first-wavelength light-absorbing molecules cross-link with the quantum dot ligands, the photoluminescence quantum efficiency (PLQY) of the quantum dots may be reduced, thereby causing problems such as insufficient brightness in the light-emitting device. Using benzophenone-based molecules as the first-wavelength light-absorbing molecules, however, only absorbs the first wavelength of light but does not cross-link with the quantum dot ligands, thereby avoiding problems such as insufficient brightness in the light-emitting device.

[0110] The above description describes the placement of a first wavelength light-blocking layer 104 between the hole transport layer 102 and the quantum dot light-emitting layer 103. The first wavelength light-blocking layer 104 includes first wavelength light-absorbing molecules. The first wavelength light-absorbing molecules can be any suitable type of molecule, such as a diazide molecule, a monoazide molecule, or a benzophenone molecule. By placing the first wavelength light-blocking layer 104 between the hole transport layer 102 and the quantum dot light-emitting layer 103, when the quantum dot light-emitting material is exposed, even if the first wavelength of the third wavelength light passes through the quantum dot light-emitting layer 103, the first wavelength light does not reach the hole transport layer 102. Instead, it is absorbed by the first wavelength light-absorbing molecules in the first wavelength light-blocking layer 104 before reaching the hole transport layer 102. This prevents further crosslinking of the hole transport layer 102, thereby preventing a decrease in hole mobility in the hole transport layer 102 and thus preventing a reduction in the efficiency of the light-emitting device 100.

[0111] Figure 14 shows a schematic diagram of the structure of a light-emitting device 200 according to another embodiment of the present disclosure. Aside from the placement of the first wavelength light-blocking layer 104, light-emitting device 200 has substantially the same structure as light-emitting device 100, and therefore, the same reference numerals are used to designate the same components. Therefore, the detailed roles and functions of components in Figure 14 with the same reference numerals as those in Figure 5 can be found in the description of Figure 5 and will not be repeated here. For the sake of brevity, only the differences between light-emitting device 200 and light-emitting device 100 will be discussed below.

[0112] As shown in Figure 14, the light-emitting device 200 includes: a substrate 101; a hole transport layer 102 located on the substrate 101; a quantum dot light-emitting layer 103 located on the side of the hole transport layer 102 away from the substrate 101; and a first wavelength light-blocking layer 104 located on the side of the quantum dot light-emitting layer 103 away from the substrate 101, the first wavelength light-blocking layer 104 includes the aforementioned first wavelength light-absorbing molecules, and the first wavelength light-absorbing molecules can absorb the first wavelength light that can cause a cross-linking reaction in the hole transport layer 102.

[0113] The structure and function of the first wavelength light-blocking layer 104 can be seen in the description of the first wavelength-blocking layer 104 in FIG5 . The material of the first wavelength light-absorbing molecule can be the same as or different from the material of the first crosslinker. For example, the first wavelength light-absorbing molecule can be a diazide molecule, such as the diazide molecules shown in FIG6 and FIG7 ; a monoazide molecule, such as the monoazide molecules shown in FIG8 to FIG10 ; a benzophenone molecule, such as the benzophenone molecules shown in FIG11 to FIG13 ; or other suitable molecules.

[0114] During the preparation of the light-emitting device 200, a substrate 101 and a hole transport layer 102 are first prepared. Then, a second mixed solution including quantum dots and a second cross-linking agent is provided on the side of the hole transport layer 102 away from the substrate 101, and the second mixed solution is cured to form a second solidified layer. Then, the second exposure process is not performed on the second solidified layer first, but a first wavelength light blocking layer 104 is formed on the side of the second solidified layer away from the substrate 101. The method for forming the first wavelength light blocking layer 104 can refer to the description of Figure 5 above. After the first wavelength light blocking layer 104 is formed, the first wavelength light blocking layer 104 is irradiated with a third wavelength light. The third wavelength light includes a second wavelength light (for example, 365 nm) that can cause the quantum dots to cross-link, a first wavelength light (for example, 254 nm, 0.047 mW / cm 2 ), and some other wavelengths (e.g. 405nm, 5mW / cm 2 The first wavelength of the third wavelength is absorbed by the first wavelength light-absorbing molecules in the first wavelength light-blocking layer 104 and thus does not radiate to the hole transport layer 102. The second wavelength of the third wavelength passes through the first wavelength light-blocking layer 104 and is absorbed by the second cross-linking agent. The second cross-linking agent then undergoes a cross-linking reaction with the quantum dots to form the quantum dot light-emitting layer 103.

[0115] It can be seen that by providing the first wavelength light-blocking layer 104 on the side of the quantum dot light-emitting layer 103 away from the substrate 101, the first wavelength light in the second exposure process can also be prevented from irradiating the hole transport layer 102. In this way, the hole transport layer 102 will not undergo further cross-linking, thereby preventing a decrease in the hole mobility of the hole transport layer 102 and preventing a decrease in the efficiency of the light-emitting device 200.

[0116] Figure 15 shows a schematic structural diagram of a light-emitting device 300 according to another embodiment of the present disclosure. Aside from the placement of the first-wavelength light-absorbing molecules, light-emitting device 300 has substantially the same structure as light-emitting device 100, and therefore, the same reference numerals are used to designate the same components. Therefore, the detailed roles and functions of the components in Figure 15 with the same reference numerals as those in Figure 5 can be found in the description of Figure 5 and will not be repeated here. For the sake of brevity, only the differences between light-emitting device 300 and light-emitting device 100 will be described below.

[0117] As shown in FIG15 , a light-emitting device 300 includes a substrate 101; a hole transport layer 102 located on the substrate 101; and a quantum dot light-emitting layer 303 located on a side of the hole transport layer 102 away from the substrate 101. The quantum dot light-emitting layer 303 has a cross-linked structure and includes quantum dots, a second cross-linking agent, and first-wavelength light-absorbing molecules. The first-wavelength light-absorbing molecules and the first cross-linking agent can absorb ultraviolet light in the same wavelength band, for example, both can absorb light of the first wavelength. The second cross-linking agent can absorb light of a second wavelength different from the first wavelength, and the quantum dots are cross-linked with at least the second cross-linking agent.

[0118] During the preparation of the light-emitting device 300, a substrate 101 and a hole transport layer 102 are first prepared. Then, a second mixed solution including quantum dots, a second cross-linking agent, and first wavelength light absorbing molecules is provided on the side of the hole transport layer 102 away from the substrate 101, and the second mixed solution is cured to form a second cured layer. The second cross-linking agent can be any suitable cross-linking agent that can cross-link the quantum dots, and the embodiments of the present disclosure are not limited to this. For example, the second cross-linking agent can be a benzophenone cross-linking agent. In some embodiments, the concentration of the first wavelength light absorbing molecules in the second mixed solution can be 0.2 to 0.5 mg / ml, for example, 0.2 mg / ml, 0.3 mg / ml, 0.4 mg / ml, 0.5 mg / ml, etc. For example, in the second mixed solution, the concentration ratio of the first wavelength light absorbing molecules to the quantum dots can be 0.2 to 0.5 mg / ml: 20 mg / ml.

[0119] Afterwards, the second cured layer is subjected to a second exposure process, i.e., the second cured layer is irradiated with light of a third wavelength. The third wavelength light includes not only the second wavelength light (e.g., 365 nm) that can cause the quantum dots to crosslink, but also the first wavelength light (e.g., 254 nm, 0.047 mW / cm 2 ) and other wavelengths (e.g. 405nm, 5mW / cm 2 Under irradiation with light of a third wavelength, the second crosslinker absorbs the second wavelength within the third wavelength and undergoes a crosslinking reaction with the quantum dots. The first-wavelength light-absorbing molecules absorb the first wavelength within the third wavelength. Depending on the material type of the first-wavelength light-absorbing molecules, they may or may not undergo a crosslinking reaction with the quantum dots, as will be described in detail below.

[0120] It can be seen that by adding the first wavelength light-absorbing molecules to the quantum dot light-emitting layer 303, the first wavelength light-absorbing molecules can absorb the first wavelength light involved in the second exposure process in the quantum dot light-emitting layer 303, and prevent the light from irradiating the hole transport layer 102. In this way, further cross-linking of the hole transport layer 102 can be avoided, thereby preventing a decrease in the hole mobility of the hole transport layer 102, thereby helping to improve the efficiency of the light-emitting device 300.

[0121] In some embodiments, the first wavelength light-absorbing molecule in the quantum dot light-emitting layer 303 includes a diazide group. Exemplarily, the first wavelength light-absorbing molecule has the molecular structure shown in FIG6 or FIG7 . In this case, during the second exposure process, the second crosslinker absorbs the second wavelength of light in the third wavelength light and undergoes a crosslinking reaction with the quantum dots. Simultaneously, the first wavelength light-absorbing molecule absorbs the first wavelength of light in the third wavelength light and undergoes a crosslinking reaction with the quantum dots, thereby forming a crosslinked quantum dot light-emitting layer 303. Exemplarily, the first wavelength light-absorbing molecule in the quantum dot light-emitting layer 303 and the first crosslinker in the hole transport layer 102 can be the same.

[0122] In some alternative embodiments, the first wavelength light absorbing molecule in the quantum dot light emitting layer 303 is not a diazide molecule, but a molecule including a single azide group. Although this type of first wavelength light absorbing molecule is different from the first cross-linking agent, it has the same light absorption characteristics as the first cross-linking agent and can absorb the first wavelength of light. For example, this type of molecular structure can be half of the structure of a diazide molecule. For example, monoazide molecules include but are not limited to methyl 4-azidotetrafluorobenzoate shown in Figure 8, 4-azidotetrafluorobenzoic acid shown in Figure 9, 4-azidotetrafluorobenzaldehyde shown in Figure 10, etc. These monoazide molecules containing 4-azidotetrafluorophenyl can be precursor molecules for synthesizing diazide molecules. In some embodiments, in the monoazide molecule, the group opposite to the N3 of the azide group can be any one of an alkyl, ether, alcohol, or halogen.

[0123] When the first wavelength light absorbing molecule is a monoazide molecule, in the second exposure process, the second cross-linking agent absorbs the second wavelength of light in the third wavelength of light and undergoes a cross-linking reaction with the quantum dot, while the first wavelength light absorbing molecule absorbs the first wavelength of light in the third wavelength of light and generates a nitrene free radical. The first wavelength light absorbing molecule is chemically bonded to the quantum dot ligand but does not undergo a cross-linking reaction with the quantum dot ligand, thereby forming a quantum dot light-emitting layer 303. This is beneficial because if the first wavelength light absorbing molecule cross-links with the quantum dot ligand, the photoluminescence quantum efficiency (PLQY) of the quantum dot may be reduced, thereby causing the light-emitting device to have problems such as insufficient brightness. Using a monoazide molecule as the first wavelength light absorbing molecule only absorbs the first wavelength of light and produces a single nitrene free radical. The single nitrene free radical does not participate in the cross-linking process of the quantum dot, thereby avoiding problems such as insufficient brightness caused by the cross-linking of the first wavelength light absorbing molecule with the quantum dot ligand.

[0124] In some alternative embodiments, the first wavelength light absorbing molecules in the quantum dot light emitting layer 303 are not diazide molecules, but molecules including benzophenone groups. Although this type of first wavelength light absorbing molecule is different from the first cross-linking agent, it has the same light absorption characteristics as the first cross-linking agent and can absorb the first wavelength of light. For example, benzophenone molecules include but are not limited to benzophenone shown in Figure 11, 4,4' difluorobenzophenone shown in Figure 12, 4-chlorobenzophenone shown in Figure 13, etc. In some embodiments, in the benzophenone molecules, the benzene ring on the benzophenone structural unit is not connected to an electron-pushing group, and the electron-pushing group includes but is not limited to a nitrogen atom, a phosphorus atom, an oxygen atom, a sulfur atom, etc.

[0125] When the first-wavelength light-absorbing molecules are benzophenone-based molecules, in the second exposure process, the second crosslinker absorbs the second wavelength of light in the third wavelength and undergoes a crosslinking reaction with the quantum dots, while the first-wavelength light-absorbing molecules absorb the first wavelength of light in the third wavelength and generate carbon carbene radicals. The first-wavelength light-absorbing molecules are chemically bonded to the quantum dot ligands but do not undergo a crosslinking reaction with the quantum dot ligands, thereby forming the quantum dot light-emitting layer 303. This is beneficial because if the first-wavelength light-absorbing molecules crosslink with the quantum dot ligands, the photoluminescence quantum efficiency (PLQY) of the quantum dots may be reduced, resulting in problems such as insufficient brightness in the light-emitting device. However, using benzophenone-based molecules as the first-wavelength light-absorbing molecules only absorbs the first wavelength of light but does not participate in the crosslinking process of the quantum dots, thereby avoiding problems such as insufficient brightness caused by crosslinking of the first-wavelength light-absorbing molecules with the quantum dot ligands.

[0126] As previously mentioned, crosslinking of the crosslinker with the hole transport material can result in a decrease in the hole mobility of the hole transport layer. Therefore, in other embodiments of the present disclosure, the hole mobility of the hole transport layer is increased by reducing the concentration of the first crosslinker in the first mixed solution (a mixed solution of the hole transport material and the first crosslinker).

[0127] Specifically, the inventors designed three concentrations for the first mixed solution: the concentration ratios of the hole transport material and the first crosslinker in the first mixed solution were 8 mg / ml:0.5 mg / ml, 8 mg / ml:0.2 mg / ml, and 8 mg / ml:0.05 mg / ml, respectively. The three first mixed solutions were cured to form three first solidified layers. Then, a first exposure process was performed, i.e., irradiating the three first solidified layers with light of a first wavelength to crosslink the first crosslinker with the hole transport material to form three different hole transport layers. Quantum dot light-emitting layers were then formed above the three hole transport layers to form three different light-emitting devices. For simplicity, the light-emitting device corresponding to the concentration ratio of the hole transport material to the first cross-linker of 8 mg / ml:0.5 mg / ml is called light-emitting device 1, the light-emitting device corresponding to the concentration ratio of the hole transport material to the first cross-linker of 8 mg / ml:0.2 mg / ml is called light-emitting device 2, and the light-emitting device corresponding to the concentration ratio of the hole transport material to the first cross-linker of 8 mg / ml:0.05 mg / ml is called light-emitting device 3.

[0128] The current density of light-emitting devices 1, 2, and 3 before and after the first exposure process was tested. The results showed that the current density of light-emitting device 1 decreased by about 50 times (from 65 mA / cm2 to 1.5 mA / cm3) after the first exposure process compared to that before the first exposure process. 2 Down to 1.3 mA / cm 2 ), the current density of the light emitting device 2 decreased by about 15 times (from 33mA / cm 2 Down to 2.5 mA / cm 2 ), the current density of the light emitting device 3 decreased by about 3 times (from 90mA / cm 2 Down to 30mA / cm 2 ), the reduction in hole mobility will lead to a decrease in the current density of the light-emitting device. This result shows that, first, the crosslinking of the first crosslinker and the hole transport material does reduce the hole mobility of the hole transport layer. However, the lower the concentration of the first crosslinker in the first mixed solution, the less the reduction in hole mobility of the hole transport layer due to exposure crosslinking will be, and thus the smaller the impact on the reduction in the current density of the light-emitting device will be.

[0129] The inventors further tested the EQE of light-emitting devices 1, 2, and 3 that did not perform the first exposure process and the EQE of light-emitting devices 1, 2, and 3 that performed the first exposure process. The results showed that compared with before the first exposure process, after the first exposure process, the EQE of light-emitting device 1 decreased by about 30% (from 23% to 16%), the EQE of light-emitting device 2 decreased by about 20% (from 15.5% to 12%), and the EQE of light-emitting device 3 decreased by about 15% (from 21% to 18%). This shows that the lower the concentration of the first cross-linking agent in the first mixed solution, the less the hole mobility of the hole transport layer will decrease due to exposure cross-linking, and thus the smaller the impact on the imbalance of electrons and holes in the light-emitting device, thereby making the EQE of the light-emitting device decrease less.

[0130] It should be noted that reducing the concentration of the first cross-linking agent in the first mixed solution can be implemented alone or in any combination with the above embodiments. For example, instead of providing the first wavelength light-blocking layer 104 between the hole transport layer 102 and the quantum dot light-emitting layer 103 or on the side of the quantum dot light-emitting layer 103 away from the substrate 101, the concentration of the first cross-linking agent in the first mixed solution can be reduced when preparing the hole transport layer 102 to improve the hole mobility of the hole transport layer 102. Alternatively, instead of adding the first wavelength light-absorbing molecule to the quantum dot light-emitting layer 303, the concentration of the first cross-linking agent in the first mixed solution can be reduced when preparing the hole transport layer 102 to improve the hole mobility of the hole transport layer 102. Alternatively, based on the light-emitting devices 100, 200, and 300, the concentration of the first cross-linking agent in the first mixed solution can be reduced when preparing the hole transport layer 102 to further improve the hole mobility of the hole transport layer 102.

[0131] FIG16 shows a schematic structural diagram of a light-emitting device 400 according to an embodiment of the present disclosure. As shown in FIG16 , light-emitting device 400 includes a substrate 101, a hole injection layer 105, a hole transport layer 102, a first wavelength light-blocking layer 104, a quantum dot light-emitting layer 103, an electron transport layer 106, and a second electrode 107, stacked in sequence. Substrate 101 can be, for example, an anode, and second electrode 107 can be, for example, a cathode. Light-emitting device 400 is an upright light-emitting device.

[0132] In some embodiments, the material of the polymer molecules in the first wavelength light blocking layer 104 is the same as the hole transport material in the hole transport layer 102, and the material of the first wavelength light absorbing molecules in the first wavelength light blocking layer 104 is the same as the material of the first crosslinking agent in the hole transport layer 102. In one example, the material of the substrate 101 is ITO, the material of the hole injection layer 105 is poly(3,4-ethylenedioxythiophene (PEDOT), the hole transport material of the hole transport layer 102 is TFB, the first crosslinking agent of the hole transport layer 102 is a diazide molecule, the polymer molecules of the first wavelength light blocking layer 104 are TFB, the first wavelength light absorbing molecules of the first wavelength light blocking layer 104 are diazide molecules, the second crosslinking agent in the quantum dot light emitting layer 103 is a benzophenone crosslinking agent, and the electron transport layer 102 is a diazide crosslinking agent. The material of electrode 6 is molybdenum oxide, and the material of second electrode 107 is aluminum. Compared with a light-emitting device without a first wavelength light-blocking layer, the current density of light-emitting device 400 is increased by approximately 4 times. This is because the first wavelength light-blocking layer 104 in light-emitting device 400 absorbs the first wavelength light that passes through quantum dot light-emitting layer 103 during the second exposure process, preventing the first wavelength light from irradiating hole transport layer 102, thereby preventing further reduction in the hole mobility of hole transport layer 102, thereby increasing the current density of light-emitting device 400.

[0133] Figure 17 shows a schematic structural diagram of a light-emitting device 500 according to another embodiment of the present disclosure. As shown in Figure 17, light-emitting device 500 includes a substrate 101, a hole injection layer 105, a hole transport layer 102, a quantum dot light-emitting layer 103, a first wavelength light-blocking layer 104, an electron transport layer 106, and a second electrode 107, which are stacked in sequence. Substrate 101 can be, for example, an anode, and second electrode 107 can be, for example, a cathode. This light-emitting device 500 is an upright light-emitting device.

[0134] Figure 18 shows a schematic structural diagram of a light-emitting device 600 according to another embodiment of the present disclosure. As shown in Figure 18, light-emitting device 600 includes a substrate 101, a hole injection layer 105, a hole transport layer 102, a quantum dot light-emitting layer 303, an electron transport layer 106, and a second electrode 107, stacked in sequence. Substrate 101 can be, for example, an anode, and second electrode 107 can be, for example, a cathode. Light-emitting device 600 is an upright light-emitting device. The structure of quantum dot light-emitting layer 303 is the same as that of quantum dot light-emitting layer 303 in Figure 15.

[0135] Figure 19 shows a block diagram of a display device 700 according to an embodiment of the present disclosure. The display device 700 includes a plurality of sub-pixels, each of which is provided with a light-emitting device, which may be the light-emitting device described in any of the previous embodiments. At least two of the plurality of light-emitting devices emit light of different colors. For example, some of the plurality of light-emitting devices include a red quantum dot light-emitting layer and are used to emit red light; some of the plurality of light-emitting devices include a green quantum dot light-emitting layer and are used to emit green light; and some of the plurality of light-emitting devices include a blue quantum dot light-emitting layer and are used to emit blue light, thereby enabling the display device 700 to achieve full-color display. Of course, the display device 700 also includes other components not shown, such as a driving circuit for providing an electrical signal to the light-emitting device to drive the light-emitting device to emit light. The display device 700 may also include structures such as a circuit board and / or an integrated circuit (IC).

[0136] The display device 700 can be any product or component based on quantum dots for display, such as a mobile phone, a tablet computer, a television, a monitor, a laptop computer, a digital photo frame, or a navigator.

[0137] The display device 700 can have substantially the same technical effects as the light-emitting device described in the previous embodiment. Therefore, for the purpose of brevity, a repeated description will not be given here.

[0138] The quantum dots provided in various embodiments of the present disclosure may be any appropriate quantum dots, including but not limited to: any of group IIB-VIA quantum dots, group IIIA-VA quantum dots, group IVA-VIA quantum dots, core-shell quantum dots, and ABX3 type perovskite quantum dots. In ABX3 type perovskite quantum dots, A is CH3NH3 + (methylamine), NH2CH=NH2(formamidine) and Cs + One or more of, B is Pb 2+ and Sn 2+ One or two of the following, X is Cl - Br - and I - One or more of the ABX3 type perovskite quantum dots include CH3NH3PbBr3, CH3NH3PbCl3, CH3NH3PbI3, CsPbBr3, CsPbCl3 and CsPbI3.

[0139] Exemplarily, the IIB-VIA group quantum dots are selected from: binary compounds such as one or more of CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, MgSe, and MgS; ternary compounds such as CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZn Te, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, MgZnSe, MgZnS, or mixtures thereof; and quaternary compounds such as HgZnTeS, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, HgZnSTe, or mixtures thereof, but are not limited thereto.

[0140] The IIIA-VA group quantum dots are selected from: binary compounds such as GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, or mixtures thereof; ternary compounds such as GaNPs, GaNAs, GaNSb, GaPAs, GaPSb, AlNPs, AlNAs, AlNSb, AlPAs, AlPSb, InNPs, InNAs, InNSb, InPAs, InPSb, or mixtures thereof; and quaternary compounds such as GaAlNPs, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNPs, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNPs, InAlNAs, InAlNSb, InAlPAs, InAlPSb, or mixtures thereof, but are not limited thereto.

[0141] Group IVA-VIA quantum dots are selected from, but are not limited to, binary compounds such as SnS, SnSe, SnTe, PbS, PbSe, PbTe, or mixtures thereof; ternary compounds such as SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, or mixtures thereof; and quaternary compounds such as SnPbSSe, SnPbSeTe, SnPbSTe, or mixtures thereof. Group IVA-VIA quantum dots are selected, for example, from elemental (mono) semiconductors such as Si, Ge, or mixtures thereof; and binary semiconductor compounds such as SiC, SiGe, and mixtures thereof.

[0142] Core-shell quantum dots are those in which one material is the core and the other is the shell. For example, a CdS / ZnS quantum dot is one in which the core is CdS and the shell is ZnS.

[0143] In some other embodiments, the quantum dots may be other nanoscale materials, such as nanorods, nanosheets, etc. The components of other nanoscale materials may include at least one of 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, and C.

[0144] For example, quantum dots can include cadmium-free (Cd) quantum dots. Cadmium-free quantum dots are quantum dots that do not include cadmium (Cd). Cadmium (Cd) can cause serious environmental / health problems, so non-cadmium-based quantum dots can be effectively used.

[0145] FIG20 shows a flow chart of a method 800 for preparing a light emitting device. As shown in FIG20 , the method 800 includes the following steps:

[0146] S801: Provide a substrate. The substrate may be, for example, an anode of a light-emitting device, and the material of the substrate may be any appropriate material, such as ITO.

[0147] S802: A first mixed solution comprising a hole transport material and a first crosslinking agent is provided on a substrate, and the first mixed solution is cured to form a first cured layer. A first exposure process is performed, i.e., irradiating the first cured layer with light of a first wavelength to crosslink the first crosslinking agent with the hole transport material to form the hole transport layer.

[0148] The first wavelength of light may be ultraviolet light, and illustratively, the first wavelength of light may be 254 nm ultraviolet light. The hole transport material may be any appropriate material, including but not limited to TFB, polyTPD, PVK, etc. The first cross-linking agent may be a cross-linking agent molecule such as an azide system, a diazo system, or a benzophenone system. The hole transport layer 102 includes a cross-linked structure generated by cross-linking the hole transport material and the first cross-linking agent. In some embodiments, the hole transport layer 102 is a composite system, and in addition to the cross-linked structure, the hole transport layer 102 also includes the remaining first cross-linking agent. Here, "remaining first cross-linking agent" refers to the excess first cross-linking agent that does not participate in the cross-linking reaction. In the first mixed solution, the first cross-linking agent may be in excess. After the first step of exposure cross-linking, all the hole transport materials in the first mixed solution have undergone a cross-linking reaction, and some of the first cross-linking agent will remain and no cross-linking will occur.

[0149] S803: providing first wavelength light absorbing molecules on a side of the hole transport layer away from the substrate. The first wavelength light absorbing molecules can absorb light of a first wavelength.

[0150] S804: providing a second mixed solution including quantum dots and a second cross-linking agent on a side of the hole transport layer away from the substrate, and curing the second mixed solution to form a second cured layer.

[0151] S805: Execute a second exposure process, that is, use a third wavelength of light to irradiate the second cured layer to at least cross-link the second cross-linking agent and the quantum dots, the third wavelength of light includes the first wavelength of light, and the first wavelength light absorbing molecules absorb the first wavelength of light in the third wavelength of light to prevent the first wavelength of light in the third wavelength of light from irradiating the hole transport layer.

[0152] In method 800, by providing first-wavelength light-absorbing molecules on the side of the hole transport layer away from the substrate, these first-wavelength light-absorbing molecules can absorb the first-wavelength light. Thus, when the quantum dot light-emitting layer above the hole transport layer is exposed and cross-linked, even if third-wavelength light passes through the quantum dot light-emitting layer, the first wavelength of the third-wavelength light will not reach the hole transport layer. Instead, it will be absorbed by the first-wavelength light-absorbing molecules before reaching the hole transport layer. In this way, further cross-linking of the hole transport layer is prevented, thereby preventing a decrease in the hole mobility of the hole transport layer and thus preventing a decrease in the efficiency of the light-emitting device.

[0153] When the light-emitting device is the light-emitting device 100 shown in FIG. 5 , step S803 may include the following sub-steps: providing a third mixed solution comprising polymer molecules and first-wavelength light-absorbing molecules on a side of the hole transport layer 102 away from the substrate 101; applying the third mixed solution onto the hole transport layer 102; and forming a film by spin coating or blade coating to form the first-wavelength light-blocking layer 104. Exemplarily, the concentration ratio of the polymer molecules to the first-wavelength light-absorbing molecules in the third mixed solution may be 0.8 to 0.5 mg / ml:0.5 mg / ml. For example, the concentration ratio of the polymer molecules to the first-wavelength light-absorbing molecules may be 0.8 mg / ml:0.5 mg / ml, 0.7 mg / ml:0.5 mg / ml, 0.6 mg / ml:0.5 mg / ml, 0.5 mg / ml:0.5 mg / ml, etc. The solvent in the third mixed solution may be any suitable solvent, for example, chlorobenzene.

[0154] The polymer molecules can be the same as the hole transport material, such as TFB, PVK, Poly-TPD, etc., or different from the hole transport material, such as other polymer molecules that are easy to form a film. The first wavelength light absorbing molecule can be the same as the first cross-linking agent, or different from the first cross-linking agent. For example, the first wavelength light absorbing molecule can be a diazide molecule as shown in Figure 6 or Figure 7, or a monoazide molecule as shown in Figures 8 to 10, or a benzophenone molecule as shown in Figures 11 to 13, or other suitable types of molecules. In some embodiments, the material of the polymer molecules in the first wavelength light blocking layer 104 is the same as the hole transport material in the hole transport layer 102, and the material of the first wavelength light absorbing molecule in the first wavelength light blocking layer 104 is the same as the material of the first cross-linking agent in the hole transport layer 102. For example, the thickness of the first wavelength light blocking layer 104 is less than or equal to 2 nm, for example, 0.5 nm, 1 nm, 2 nm, etc. The first wavelength light blocking layer 104 and the first cross-linking agent can absorb ultraviolet light in the same wavelength band, and both can absorb the first wavelength light (ultraviolet light of 254 nm).

[0155] When the first wavelength light-absorbing molecules in the first wavelength light-blocking layer 104 are diazide molecules as shown in FIG. 6 or 7 , step S805 may include the following sub-steps: irradiating the second solidified layer with light of a third wavelength, causing the second cross-linking agent to absorb the second wavelength of light in the third wavelength and undergo a cross-linking reaction with the quantum dots to form the quantum dot light-emitting layer 103; and causing the first wavelength light-absorbing molecules to absorb the first wavelength of light in the third wavelength and undergo a cross-linking reaction with the polymer molecules to form a cross-linked first wavelength light-blocking layer 104. In some cases, step S805 may further include the following sub-steps: irradiating the second solidified layer with light of a third wavelength, causing the second cross-linking agent to absorb the second wavelength of light in the third wavelength and undergo a cross-linking reaction with the quantum dots to form the quantum dot light-emitting layer 103; and causing the first wavelength light-absorbing molecules to absorb the first wavelength of light in the third wavelength and undergo a cross-linking reaction with the polymer molecules, while the polymer molecules also undergo a cross-linking reaction with the quantum dot ligands via the diazide groups.

[0156] In some embodiments, in addition to the crosslinked structure, the first wavelength light-blocking layer 104 also includes residual first wavelength light-absorbing molecules, meaning that the first wavelength light-blocking layer 104 is a composite film. Similarly, the term "residual first wavelength light-absorbing molecules" herein refers to excess first wavelength light-absorbing molecules that have not participated in the crosslinking reaction. To ensure that the very thin first wavelength light-blocking layer 104 can fully absorb the first wavelength light during the second exposure process, the first wavelength light-blocking layer 104 typically contains an excess of first wavelength light-absorbing molecules. After the second exposure process, all polymer molecules have undergone crosslinking, but some first wavelength light-absorbing molecules may remain, uncrosslinked.

[0157] In some embodiments, the polymer molecule is TFB, and the first wavelength light absorbing molecule is a diazide molecule. When preparing a third mixed solution comprising the polymer molecule and the first wavelength light absorbing molecule, in some examples, the concentration ratio of the polymer molecule solution to the first wavelength light absorbing molecule solution can be 0.8 mg / ml:0.5 mg / ml, resulting in a first wavelength light-blocking layer 104 having a thickness of approximately 2 nm. In other examples, the concentration ratio of the polymer molecule solution to the first wavelength light-absorbing molecule solution can be 0.5 mg / ml:0.5 mg / ml, resulting in a first wavelength light-blocking layer 104 having a thickness of approximately 1 nm. In yet other examples, when the thickness of the first wavelength light-blocking layer 104 is required to be less than 1 nm, the concentration of the first wavelength light-absorbing molecule in the third mixed solution is no less than the concentration of the first crosslinker in the first mixed solution (comprising the hole transport material and the first crosslinker).

[0158] When the first wavelength light absorbing molecules in the first wavelength light blocking layer 104 are monoazide molecules as shown in FIG. 8 to FIG. 10 , step S805 may include the following sub-steps:

[0159] The second cured layer is irradiated with light of a third wavelength, and the second cross-linking agent absorbs the second wavelength of light in the third wavelength of light and cross-links with the quantum dots to form a quantum dot light-emitting layer 103. At the same time, the first wavelength light-absorbing molecules in the first wavelength light-blocking layer 104 absorb the first wavelength of light in the third wavelength of light to generate nitrene radicals. In some cases, the first wavelength light-absorbing molecules are chemically bonded to the polymer molecules, but do not undergo a cross-linking reaction with the polymer molecules, that is, the polymer molecules are not changed from linear molecules to a three-dimensional network structure, and the polymer molecules are not cross-linked. Or in other cases, the first wavelength light-absorbing molecules are chemically bonded to the quantum dot ligands at the interface of the first wavelength light-blocking layer 104 and the quantum dot light-emitting layer 103, but do not undergo a cross-linking reaction with the quantum dot ligands.

[0160] When the first wavelength light absorbing molecules in the first wavelength light blocking layer 104 are benzophenone molecules as shown in FIG. 11 to FIG. 13 , step S805 may include the following sub-steps:

[0161] The second cured layer is irradiated with light of a third wavelength. The second crosslinker absorbs the second wavelength of light within the third wavelength and crosslinks with the quantum dots to form the quantum dot light-emitting layer 103. Simultaneously, the first wavelength light-absorbing molecules within the first wavelength light-blocking layer 104 absorb the first wavelength of light within the third wavelength, generating carbon carbene radicals. In some cases, the first wavelength light-absorbing molecules are chemically bonded to the polymer molecules but do not undergo a crosslinking reaction with the polymer molecules. This means that the polymer molecules do not transform from linear molecules into a three-dimensional network structure, and the polymer molecules remain uncrosslinked. Alternatively, in other cases, the first wavelength light-absorbing molecules are chemically bonded to the quantum dot ligands at the interface between the first wavelength light-blocking layer 104 and the quantum dot light-emitting layer 103 but do not undergo a crosslinking reaction with the quantum dot ligands.

[0162] It is beneficial that the first-wavelength light-absorbing molecules in the first-wavelength light-blocking layer 104 do not undergo a cross-linking reaction with the quantum dot ligands. This is because if the first-wavelength light-absorbing molecules do cross-link with the quantum dot ligands, the photoluminescence quantum efficiency (PLQY) of the quantum dots may be reduced, resulting in problems such as insufficient brightness of the light-emitting device. Using monoazide or benzophenone molecules as the first-wavelength light-absorbing molecules, however, only absorbs light of the first wavelength and does not participate in the cross-linking process with the quantum dots. This avoids problems such as insufficient brightness caused by cross-linking of the first-wavelength light-absorbing molecules with the quantum dot ligands.

[0163] When the light-emitting device is the light-emitting device 300 shown in FIG. 15 , steps S803 and S804 may include the following sub-steps: providing a second mixed solution on a side of the hole transport layer 102 away from the substrate 101, the second mixed solution comprising quantum dots, a second crosslinker, and first wavelength light-absorbing molecules, and curing the second mixed solution to form a second cured layer. In some embodiments, the concentration of the first wavelength light-absorbing molecules in the second mixed solution is 0.2 to 0.5 mg / ml, for example, 0.2 mg / ml, 0.3 mg / ml, 0.4 mg / ml, 0.5 mg / ml, etc. For example, in the second mixed solution, the concentration ratio of the first wavelength light-absorbing molecules to the quantum dots may be 0.2 to 0.5 mg / ml: 20 mg / ml.

[0164] When the light emitting device is the light emitting device 300 shown in FIG15 , step S805 may include the following sub-steps: performing a second exposure process on the second solidified layer, that is, irradiating the second solidified layer with light of a third wavelength. The third wavelength light includes not only the second wavelength light (e.g., 365 nm) that can cause the quantum dots to crosslink, but also the first wavelength light (e.g., 254 nm, 0.047 mW / cm 2 ) and other wavelengths (e.g. 405nm, 5mW / cm 2Under irradiation with light of a third wavelength, the second crosslinker absorbs the second wavelength within the third wavelength and undergoes a crosslinking reaction with the quantum dots. The first-wavelength light-absorbing molecules absorb the first wavelength within the third wavelength. Depending on the material type of the first-wavelength light-absorbing molecules, they may or may not undergo a crosslinking reaction with the quantum dots.

[0165] When the first wavelength light-absorbing molecules in the quantum dot light-emitting layer 303 are diazide molecules as shown in FIG. 6 or FIG. 7 , step S805 may include the following sub-steps: irradiating the second cured layer with light of a third wavelength, causing the second cross-linking agent to absorb the second wavelength of light in the third wavelength and undergo a cross-linking reaction with the quantum dots, while simultaneously absorbing the first wavelength of light in the third wavelength and undergoing a cross-linking reaction with the quantum dots, thereby forming a cross-linked quantum dot light-emitting layer 303. Exemplarily, the first wavelength light-absorbing molecules in the quantum dot light-emitting layer 303 and the first cross-linking agent in the hole transport layer 102 may be the same.

[0166] When the first wavelength light absorbing molecules in the quantum dot light emitting layer 303 are the monoazide molecules shown in Figures 8 to 10 or the dibenzophenone molecules shown in Figures 11 to 13, step S805 may include the following sub-steps: using the third wavelength light to irradiate the second solidified layer, the second cross-linker absorbs the second wavelength light in the third wavelength light and undergoes a cross-linking reaction with the quantum dots, the first wavelength light absorbing molecules absorb the first wavelength light in the third wavelength light, the first wavelength light absorbing molecules are connected to the quantum dot ligands through chemical bonds but do not undergo a cross-linking reaction with the quantum dot ligands, thereby forming the quantum dot light emitting layer 303.

[0167] Although this type of first wavelength light absorbing molecule is different from the first cross-linking agent, it has the same light absorption characteristics as the first cross-linking agent and can absorb light of the first wavelength. When the first wavelength light absorbing molecule in the quantum dot light emitting layer 303 is a monoazide molecule shown in Figures 8 to 10, in some embodiments, the group opposite to the N3 of the azide group can be any one of an alkyl, ether, alcohol, and halogen. When the first wavelength light absorbing molecule in the quantum dot light emitting layer 303 is a benzophenone molecule shown in Figures 11 to 13, in some embodiments, the benzene ring on the benzophenone structural unit is not connected to an electron-donating group, and the electron-donating group includes but is not limited to a nitrogen atom, a phosphorus atom, an oxygen atom, a sulfur atom, and the like.

[0168] It is beneficial that the first wavelength light-absorbing molecules in the quantum dot light-emitting layer 303 do not undergo a cross-linking reaction with the quantum dot ligands. This is because if the first wavelength light-absorbing molecules do cross-link with the quantum dot ligands, the photoluminescence quantum efficiency (PLQY) of the quantum dots may be reduced, resulting in problems such as insufficient brightness in the light-emitting device. Using monoazide or benzophenone molecules as the first wavelength light-absorbing molecules, however, only absorbs the first wavelength and does not participate in the cross-linking process with the quantum dots. This avoids problems such as insufficient brightness caused by cross-linking of the first wavelength light-absorbing molecules with the quantum dot ligands.

[0169] In method 800, a first wavelength light-blocking layer 104 comprising first wavelength light-absorbing molecules is formed between the hole transport layer 102 and the quantum dot light-emitting layer 103, or a first wavelength light-blocking layer 104 comprising first wavelength light-absorbing molecules is formed on the side of the quantum dot light-emitting layer 103 facing away from the substrate 101, or first wavelength light-absorbing molecules are added to the quantum dot light-emitting layer 303. The first wavelength light-absorbing molecules can be any suitable type of molecule, such as a diazide molecule, a monoazide molecule, a benzophenone molecule, or the like. When the quantum dot light-emitting material is exposed to light, even if the first wavelength of light within the third wavelength passes through the quantum dot light-emitting layer, the first wavelength does not reach the hole transport layer 102. Instead, the first wavelength is absorbed by the first wavelength light-absorbing molecules before reaching the hole transport layer 102. This prevents further crosslinking of the hole transport layer 102, thereby preventing a decrease in hole mobility in the hole transport layer 102 and improving the efficiency of the light-emitting device.

[0170] In some other embodiments, when preparing the first mixed solution (a mixed solution of a hole transport material and a first cross-linking agent), the hole mobility of the hole transport layer is improved by reducing the concentration of the first cross-linking agent in the first mixed solution.

[0171] Specifically, the concentration ratios of the hole transport material and the first crosslinker in the first mixed solution can be 8 mg / ml:0.5 mg / ml, 8 mg / ml:0.2 mg / ml, and 8 mg / ml:0.05 mg / ml, respectively. The three first mixed solutions are cured to form three first cured layers. Then, a first exposure process is performed, i.e., the three first cured layers are irradiated with light of a first wavelength to cause the first crosslinker to crosslink with the hole transport material to form three different hole transport layers. Then, quantum dot light-emitting layers are formed above the three hole transport layers to form three different light-emitting devices. For simplicity, the light-emitting device corresponding to the concentration ratio of the hole transport material and the first crosslinker of 8 mg / ml:0.5 mg / ml is referred to as light-emitting device 1, the light-emitting device corresponding to the concentration ratio of the hole transport material and the first crosslinker of 8 mg / ml:0.2 mg / ml is referred to as light-emitting device 2, and the light-emitting device corresponding to the concentration ratio of the hole transport material and the first crosslinker of 8 mg / ml:0.05 mg / ml is referred to as light-emitting device 3.

[0172] The current density of light-emitting devices 1, 2, and 3 before and after the first exposure process was tested. The results showed that the current density of light-emitting device 1 decreased by about 50 times (from 65 mA / cm2 to 1.5 mA / cm3) after the first exposure process compared to that before the first exposure process. 2 Down to 1.3 mA / cm 2 ), the current density of the light emitting device 2 decreased by about 15 times (from 33mA / cm 2 Down to 2.5 mA / cm 2 ), the current density of the light emitting device 3 decreased by about 3 times (from 90mA / cm 2 Down to 30mA / cm 2 ), the reduction in hole mobility will lead to a decrease in the current density of the light-emitting device. This result shows that, first, the crosslinking of the first crosslinker and the hole transport material does reduce the hole mobility of the hole transport layer. However, the lower the concentration of the first crosslinker in the first mixed solution, the less the reduction in hole mobility of the hole transport layer due to exposure crosslinking will be, and thus the smaller the impact on the reduction in the current density of the light-emitting device will be.

[0173] The inventors further tested the EQE of light-emitting devices 1, 2, and 3 that did not perform the first exposure process and the EQE of light-emitting devices 1, 2, and 3 that performed the first exposure process. The results showed that compared with before the first exposure process, after the first exposure process, the EQE of light-emitting device 1 decreased by about 30% (from 23% to 16%), the EQE of light-emitting device 2 decreased by about 20% (from 15.5% to 12%), and the EQE of light-emitting device 3 decreased by about 15% (from 21% to 18%). This shows that the lower the concentration of the first cross-linking agent in the first mixed solution, the less the hole mobility of the hole transport layer will decrease due to exposure cross-linking, and thus the smaller the impact on the imbalance of electrons and holes in the light-emitting device, thereby making the EQE of the light-emitting device decrease less.

[0174] It should be noted that reducing the concentration of the first cross-linking agent in the first mixed solution can be implemented alone or in any combination with the above embodiments. For example, instead of providing the first wavelength light-blocking layer 104 between the hole transport layer 102 and the quantum dot light-emitting layer 103 or on the side of the quantum dot light-emitting layer 103 away from the substrate 101, the concentration of the first cross-linking agent in the first mixed solution can be reduced when preparing the hole transport layer 102 to improve the hole mobility of the hole transport layer 102. Alternatively, instead of adding the first wavelength light-absorbing molecule to the quantum dot light-emitting layer 303, the concentration of the first cross-linking agent in the first mixed solution can be reduced when preparing the hole transport layer 102 to improve the hole mobility of the hole transport layer 102. Alternatively, based on the light-emitting devices 100, 200, and 300, the concentration of the first cross-linking agent in the first mixed solution can be reduced when preparing the hole transport layer 102 to further improve the hole mobility of the hole transport layer 102.

[0175] For other technical effects of method 800 , reference may be made to the technical effects of the light-emitting device described in the previous embodiment, and for the sake of brevity, they will not be repeated here.

[0176] It will be understood that although the terms first, second, third, etc. may be used to describe various elements, components, areas, layers and / or parts in this article, these elements, components, areas, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, area, layer or part from another element, component, area, layer or part. Therefore, the first element, component, area, layer or part discussed above can be referred to as the second element, component, area, layer or part without departing from the teachings of the present disclosure.

[0177] Spatially relative terms such as "row," "column," "under," "above," "left," "right," and the like may be used herein to describe the relationship of one element or feature to another element or feature as illustrated in the figures for ease of description. It will be understood that these spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figure is flipped, the element described as "under other elements or features" will be oriented as "above other elements or features." Thus, the exemplary term "under" can encompass both orientations of above and below. The device can be oriented otherwise (rotated 90 degrees or in other orientations) and the spatially relative descriptors used herein are interpreted accordingly. In addition, it will also be understood that when a layer is referred to as "between two layers," it can be the only layer between the two layers, or one or more intermediate layers may also be present.

[0178] The terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present disclosure. As used herein, the singular forms "one", "an" and "the" are intended to also include the plural forms, unless the context clearly indicates otherwise. It will be further understood that the terms "include" and / or "comprise" when used in this specification specify the presence of the features, wholes, steps, operations, elements and / or parts, but do not exclude the presence of one or more other features, wholes, steps, operations, elements, parts and / or their groups or add one or more other features, wholes, steps, operations, elements, parts and / or their groups. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. In the description of this specification, the description of the reference terms "one embodiment", "another embodiment" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment are included in at least one embodiment of the present disclosure. In this specification, the schematic representation of the above terms does not necessarily need to be directed to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. Furthermore, those skilled in the art may combine different embodiments or examples and features of different embodiments or examples described in this specification without mutual contradiction.

[0179] It will be understood that when an element or layer is referred to as being “on,” “connected to,” “coupled to,” or “adjacent to” another element or layer, it can be directly on, directly connected to, directly coupled to, or directly adjacent to another element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly connected to,” “directly coupled to,” or “directly adjacent to” another element or layer, no intervening elements or layers are present. However, in no case should “on” or “directly on” be interpreted as requiring that one layer completely cover the underlying layer.

[0180] Embodiments of the present disclosure are described herein with reference to schematic illustrations (and intermediate structures) of idealized embodiments of the present disclosure. As such, variations in the illustrated shapes, for example as a result of manufacturing techniques and / or tolerances, should be expected. Therefore, embodiments of the present disclosure should not be construed as limited to the specific shapes of the regions illustrated herein, but should include deviations in shapes, for example, due to manufacturing. Therefore, the regions illustrated in the figures are schematic in nature, and their shapes are not intended to illustrate the actual shape of the regions of the device and are not intended to limit the scope of the present disclosure. For example, an etched area shown as a rectangle will typically have curved features. Therefore, the regions shown in the figures are schematic in nature, and their shapes are not intended to illustrate the actual shape of the regions of the device and are not intended to limit the scope of the exemplary embodiments.

[0181] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art to which the present disclosure belongs. It will be further understood that terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the relevant art and / or the context of this specification, and will not be interpreted in an idealized or overly formal sense unless explicitly defined as such herein.

[0182] As will be appreciated by those skilled in the art, although the various steps of the method of the present disclosure are described in a particular order in the accompanying drawings, this does not require or imply that the steps must be performed in that particular order unless the context clearly indicates otherwise. Additionally or alternatively, multiple steps may be combined into a single step and / or a single step may be broken down into multiple steps and performed. In addition, other method steps may be inserted between steps. An inserted step may represent an improvement to a method such as that described herein, or may be unrelated to the method. In addition, a given step may not be fully completed before the next step begins.

[0183] As used herein, "about," "substantially," or "approximately" includes the stated value and an average value that is within an acceptable range of deviation from the particular value as determined by one of ordinary skill in the art taking into account the measurements in question and the errors associated with the measurement of the particular quantity (i.e., the limitations of the measurement system).

[0184] The above description is merely a specific embodiment of the present disclosure, but the scope of protection of the present disclosure is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this disclosure should be included in the scope of protection of the present disclosure. Therefore, the scope of protection of the present disclosure should be based on the scope of protection of the claims.

Claims

1. A light-emitting device, comprising: a substrate; a hole transport layer located on the substrate; a quantum dot light-emitting layer located on a side of the hole transport layer away from the substrate; and a first wavelength light-absorbing molecule located on a side of the hole transport layer away from the substrate, wherein the first wavelength light-absorbing molecule is configured to absorb first wavelength light capable of causing a crosslinking reaction in the hole transport layer.

2. The light-emitting device according to claim 1, further comprising a first wavelength light-blocking layer, wherein the first wavelength light-blocking layer is located between the hole transport layer and the quantum dot light-emitting layer or on a side of the quantum dot light-emitting layer away from the hole transport layer, and the first wavelength light-blocking layer comprises the first wavelength light-absorbing molecule.

3. The light-emitting device according to claim 2, wherein the first wavelength light-blocking layer comprises an azide group or a benzophenone group.

4. The light-emitting device according to claim 3, wherein the first wavelength light-absorbing molecule comprises a single azide group or a bis-azide group.

5. The light-emitting device according to any one of claims 2-4, wherein the hole transport layer comprises a crosslinked structure formed by crosslinking a first crosslinking agent and a hole transport material.

6. The light-emitting device according to claim 5, wherein a content ratio of the first wavelength light-absorbing molecule in the first wavelength light-blocking layer is greater than a content ratio of the first crosslinking agent in the hole transport layer.

7. The light-emitting device according to claim 5, wherein the first wavelength light-blocking layer further comprises a polymer molecule.

8. The light-emitting device according to claim 7, wherein the first wavelength light-absorbing molecule comprises a bis-azide group, and the first wavelength light-blocking layer comprises a crosslinked structure formed by crosslinking the first wavelength light-absorbing molecule and the polymer molecule.

9. The light-emitting device according to claim 8, wherein the first wavelength light-blocking layer further comprises remaining first wavelength light-absorbing molecules.

10. The light-emitting device according to claim 8 or 9, wherein the quantum dot light-emitting layer comprises a plurality of quantum dots, at least some of the plurality of quantum dots comprise a quantum dot body and ligands coordinated on the quantum dot body, and the polymer molecule is further crosslinked with at least some of the ligands through the bis-azide group.

11. The light-emitting device according to claim 7, wherein a material of the polymer molecule is the same as that of the hole transport material.

12. The light-emitting device according to any one of claims 5-11, wherein the hole transport layer further comprises remaining first crosslinking agent.

13. The light-emitting device according to claim 7, wherein the first wavelength light-absorbing molecule comprises a benzophenone group or a single azide group, and the first wavelength light-absorbing molecule has the same light absorption characteristics as the first crosslinking agent.

14. The light-emitting device according to claim 13, wherein in the first wavelength light-blocking layer, the first wavelength light-absorbing molecule is connected to the polymer molecule through a chemical bond, and the polymer molecule is uncrosslinked.

15. The light-emitting device according to claim 13, Among them, the quantum dot light-emitting layer includes a plurality of quantum dots, at least some of the plurality of quantum dots include a quantum dot body and ligands coordinated on the quantum dot body, and the first wavelength light-absorbing molecules are connected to at least some of the ligands by chemical bonds.

16. The light-emitting device according to any one of claims 2-15, Among them, the thickness of the first wavelength light-blocking layer is less than or equal to 2 nm.

17. The light-emitting device according to claim 1, Among them, the quantum dot light-emitting layer is a crosslinked structure and includes quantum dots, a second crosslinking agent, and the first wavelength light-absorbing molecules, and the quantum dots are crosslinked with at least the second crosslinking agent.

18. The light-emitting device according to claim 17, Among them, the first wavelength light-absorbing molecules include bis-azide groups.

19. The light-emitting device according to claim 17, Among them, the first wavelength light-absorbing molecules include benzophenone groups or single azide groups.

20. The light-emitting device according to claim 19, Among them, the first wavelength light-absorbing molecules include single azide groups, and the para-group of the azide group includes any one of alkyl, ether, alcohol, and halogen; or the first wavelength light-absorbing molecules include benzophenone groups, and the benzene ring on the benzophenone group is not connected to an electron-donating group.

21. The light-emitting device according to any one of claims 2-16, further includes: a hole injection layer located between the substrate and the hole transport layer; an electron transport layer located on the side of the quantum dot light-emitting layer away from the substrate; and a second electrode located on the side of the electron transport layer away from the substrate, wherein the substrate is the first electrode.

22. The light-emitting device according to claim 21, Among them, the first wavelength light-blocking layer is located between the hole transport layer and the quantum dot light-emitting layer, the hole transport layer includes a crosslinked structure formed by crosslinking a first crosslinking agent and a hole transport material, the first wavelength light-blocking layer further includes polymer molecules, the material of the polymer molecules is the same as that of the hole transport material, the material of the first wavelength light-absorbing molecules is the same as that of the first crosslinking agent, the first wavelength light-blocking layer includes a crosslinked structure formed by crosslinking the first wavelength light-absorbing molecules and the polymer molecules, and the quantum dot light-emitting layer includes a crosslinked structure formed by crosslinking a second crosslinking agent and quantum dots.

23. A display device includes a plurality of light-emitting devices according to any one of claims 1-22.

24. A method for preparing a light-emitting device, includes: providing a substrate; providing a first mixed solution including a hole transport material and a first crosslinking agent on the substrate, curing the first mixed solution to form a first cured layer, and irradiating the first cured layer with first wavelength light to crosslink the first crosslinking agent and the hole transport material to form a hole transport layer; providing first wavelength light-absorbing molecules on the side of the hole transport layer away from the substrate; A second mixed solution is provided on a side of the hole transport layer away from the substrate, the second mixed solution including quantum dots and a second crosslinking agent, and the second mixed solution is cured to form a second cured layer; and the second cured layer is irradiated with third-wavelength light to cause at least the second crosslinking agent to crosslink with the quantum dots, the third-wavelength light including the first-wavelength light, and a first-wavelength light absorbing molecule absorbs the first-wavelength light in the third-wavelength light to prevent the first-wavelength light in the third-wavelength light from irradiating the hole transport layer.

25. The method according to claim 24, wherein, providing a first-wavelength light absorbing molecule on a side of the hole transport layer away from the substrate includes: providing a third mixed solution including polymer molecules and the first-wavelength light absorbing molecule on a side of the hole transport layer away from the substrate, and applying the third mixed solution onto the hole transport layer to form a first-wavelength light blocking layer.

26. The method according to claim 25, wherein, the first-wavelength light absorbing molecule includes a diazide group, and the third-wavelength light further includes a second-wavelength light, wherein irradiating the second cured layer with third-wavelength light to cause at least the second crosslinking agent to crosslink with the quantum dots includes: the second crosslinking agent absorbs the second-wavelength light in the third-wavelength light and crosslinks with the quantum dots to form a quantum dot light-emitting layer, and the first-wavelength light absorbing molecule absorbs the first-wavelength light in the third-wavelength light and crosslinks with the polymer molecules.

27. The method according to claim 26, wherein, the quantum dots include a quantum dot body and ligands coordinated on the quantum dot body, wherein irradiating the second cured layer with third-wavelength light to cause at least the second crosslinking agent to crosslink with the quantum dots further includes: under the irradiation of the first-wavelength light in the third-wavelength light, the polymer molecules also crosslink with the ligands through the diazide group.

28. The method according to claim 25, wherein, the first-wavelength light absorbing molecule includes a single azide group or a benzophenone group, the quantum dots include a quantum dot body and ligands coordinated on the quantum dot body, and the third-wavelength light further includes a second-wavelength light, wherein irradiating the second cured layer with third-wavelength light to cause at least the second crosslinking agent to crosslink with the quantum dots includes: the second crosslinking agent absorbs the second-wavelength light in the third-wavelength light and crosslinks with the quantum dots to form a quantum dot light-emitting layer, and the first-wavelength light absorbing molecule absorbs the first-wavelength light in the third-wavelength light and is connected to the polymer molecules through a chemical bond; or, the second crosslinking agent absorbs the second-wavelength light in the third-wavelength light and crosslinks with the quantum dots to form a quantum dot light-emitting layer, and the first-wavelength light absorbing molecule absorbs the first-wavelength light in the third-wavelength light and is connected to the ligands through a chemical bond.

29. The method according to claim 24, wherein, Providing a first wavelength light absorbing molecule on a side of the hole transport layer away from the substrate and providing a second mixed solution on a side of the hole transport layer away from the substrate, including: Providing a second mixed solution on a side of the hole transport layer away from the substrate, the second mixed solution including the quantum dots, the second crosslinking agent, and the first wavelength light absorbing molecule, and curing the second mixed solution to form the second cured layer.

30. The method according to claim 29, wherein, the first wavelength light absorbing molecule includes a diazide group, and the third wavelength light further includes a second wavelength light, wherein irradiating the second cured layer with the third wavelength light to at least crosslink the second crosslinking agent with the quantum dots includes: the second crosslinking agent absorbing the second wavelength light in the third wavelength light and crosslinking with the quantum dots, and the first wavelength light absorbing molecule absorbing the first wavelength light in the third wavelength light and crosslinking with the quantum dots to form a quantum dot light emitting layer.

31. The method according to claim 29, wherein, the first wavelength light absorbing molecule includes a single azide group or a benzophenone group, the quantum dots include a quantum dot body and ligands coordinated on the quantum dot body, and the third wavelength light further includes a second wavelength light, wherein irradiating the second cured layer with the third wavelength light to at least crosslink the second crosslinking agent with the quantum dots includes: the second crosslinking agent absorbing the second wavelength light in the third wavelength light and crosslinking with the quantum dots, and the first wavelength light absorbing molecule absorbing the first wavelength light in the third wavelength light and connecting to the ligands through chemical bonds to form a quantum dot light emitting layer.

32. The method according to any one of claims 24-31, wherein, the concentration ratio of the hole transport material to the first crosslinking agent in the first mixed solution is 8 mg / ml: 0.05-0.5 mg / ml.

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