Cross-linking agent, hole transport composition, ligand, and light-emitting device

Abstract

A cross-linking agent, comprising sulfhydryl protected by a photo-cleavable group, wherein the photo-cleavable group is removed under illumination to release sulfydryl, a sulfur radical, or a sulfur anion. Also disclosed is a hole transport composition, comprising a hole transport material and a cross-linking agent. The hole transport material comprises a backbone and a side chain connected to the backbone of the hole transport material, wherein at least one of the side chain of the hole transport material and the cross-linking agent has sulfhydryl protected by a photo-cleavable group, the photo-cleavable group is removed under illumination to release sulfydryl, a sulfur radical, or a sulfur anion, and the released sulfydryl, sulfur radical, or sulfur anion is configured such that the hole transport material is cross-linked with the cross-linking agent.

Description

Crosslinking agent, hole transport composition, ligand and light-emitting device

[0001] This application claims priority to international patent application No. PCT / CN2024 / 076770, filed on February 7, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present disclosure relates to the field of display technology, and in particular to a cross-linking agent, a hole transport composition, a ligand, and a light-emitting device. Background Art

[0003] Quantum dots (QDs), as a new type of luminescent material, offer advantages such as high light color purity, high quantum efficiency, adjustable light color, and long lifespan, making them a research hotspot for new LED (light emitting diode) luminescent materials. Consequently, quantum dot light emitting diodes (QLEDs), which use quantum dot materials as the light-emitting layer, have become a major research focus for new display devices.

[0004] Summary of the Invention

[0005] In one aspect, a cross-linking agent is provided, comprising: a thiol group protected by a photolyzable group; the photolyzable group is removed under light to release a thiol group, a thiol free radical or a thiol anion.

[0006] In some embodiments, the cross-linking agent is selected from at least one of the structures shown in the following general formula I; PPG-S-R1-S-PPGⅠ, wherein R1 is selected from any one of a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkyl group including an ester bond, and a substituted or unsubstituted alkyl group including an ethylene glycol bond; PPG is the photolyzable group.

[0007] In some embodiments, the crosslinking agent is selected from at least one of the structures shown in the following general formula II: R2-(R1-S-PPG) n1 II, wherein R2 is selected from any one of secondary carbon, tertiary carbon and quaternary carbon; n1≥2.

[0008] In some embodiments, the photolyzable group is selected from at least one of the following substituents. Wherein, each R3 is independently selected from any one of H, an alkyl group, an electron-withdrawing group, an electron-donating group and a conjugated group.

[0009] In some embodiments, the crosslinking agent is selected from at least one of the following structural formulas.

[0010] In some embodiments, the cross-linking agent further comprises: a carrier transport regulating group.

[0011] In some embodiments, the crosslinker comprises a main chain and a side chain connected to the main chain of the crosslinker, the carrier transport regulating group is located on the main chain of the crosslinker, and the thiol protected by the photolyzable group is located on the side chain of the crosslinker.

[0012] In some embodiments, the cross-linking agent is selected from at least one of the structures shown in the following general formula III: R4-(R1-S-PPG) n2 III, wherein R4 is a substituted or unsubstituted carrier transport regulating group; n2≥2.

[0013] In some embodiments, the carrier transport regulating group is a hole transporting group, and the hole transporting group includes at least one of a triphenylamine group, a carbazole group, and a vicinal triphenylamine group.

[0014] In some embodiments, the crosslinking agent is selected from at least one of the following structural formulas.

[0015] On the other hand, a hole transport composition is provided, comprising: a hole transport material and a cross-linking agent; the hole transport material comprises: a main chain and a side chain connected to the main chain of the hole transport material; wherein at least one of the side chain of the hole transport material and the cross-linking agent has a thiol group protected by a photolyzable group; the photolyzable group is removed under light to release a thiol group, a thiol radical or a thiol anion; the released thiol group, thiol radical or thiol anion is configured to cross-link the hole transport material and the cross-linking agent.

[0016] In some embodiments, the crosslinking agent is selected from the crosslinking agents described in any of the above embodiments, and the released thiol groups, thiol radicals or thiol anions on the crosslinking agent are used to react with the side chains of the hole transport material to form chemical bonds.

[0017] In some embodiments, the released thiol groups, thiol radicals or thiol anions are located on the side chains of the hole transport material, and the released thiol groups, thiol radicals or thiol anions are used to react with the cross-linking agent to form a chemical bond.

[0018] In some embodiments, when the released thiol group, thiol radical or thiol anion is located on the cross-linking agent, the side chain of the hole transport material further includes: an activating group; when the released thiol group, thiol radical or thiol anion is located on the side chain of the hole transport material, the cross-linking agent further includes: an activating group; the activating group includes: at least one of a carbon-carbon double bond and a carbon-carbon triple bond.

[0019] In some embodiments, the activating group having a carbon-carbon double bond includes at least one of a styrene group, an acrylate group, an alkylacrylate group, a maleic anhydride group, and a maleimide group.

[0020] On the other hand, a ligand is provided, which is used for coordination connection with the quantum dot body, and the ligand includes: a thiol group protected by a photolyzable group; the photolyzable group is removed under light to release a thiol group, a thiol free radical or a thiol anion.

[0021] In some embodiments, the photolyzable group is selected from at least one of the following substituents. Wherein, each R3 is independently selected from any one of H, an alkyl group, an electron-withdrawing group, an electron-donating group and a conjugated group.

[0022] In some embodiments, the ligand further includes: a coordination group for coordinating and connecting with the quantum dot body; the coordination group includes: at least one of an amino group, a carboxylic acid group, a thiol group, a phosphine group, and a phosphineoxy group.

[0023] In some embodiments, the ligand is selected from at least one of the structures shown in the following general formula IV; A-R1-S-PPGIV, wherein A is the coordinating group; R1 is selected from any one of a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkyl group including an ester bond, and a substituted or unsubstituted alkyl group including an ethylene glycol bond; and PPG is the photolyzable group.

[0024] In some embodiments, the structural formula of the ligand comprises:

[0025] In some embodiments, the ligand is selected from at least one of the structures shown in the following general formula V; A-R5-(R1-S-PPG)n3V, R5 is selected from any one of substituted or unsubstituted alkyl, substituted or unsubstituted alkyl including an ester bond, and substituted or unsubstituted alkyl including an ethylene glycol bond; n3≥2.

[0026] On the other hand, a quantum dot composition is provided, which includes: a quantum dot body, a ligand and a cross-linker, wherein the ligand is coordinated and connected to the quantum dot body; wherein at least one of the ligand and the cross-linker has a thiol group protected by a photolyzable group; the photolyzable group is removed under light to release a thiol group, a sulfhydryl radical or a sulfhydryl anion; the released thiol group, sulfhydryl radical or sulfhydryl anion is configured to cross-link at least two of the quantum dot body, the ligand and the cross-linker.

[0027] In some embodiments, the crosslinker is selected from the crosslinker described in any of the above embodiments, and the thiol, thiol radical or thiol anion released from the crosslinker is used for coordination connection with the quantum dot body or for reacting with the ligand to form a chemical bond.

[0028] In some embodiments, the ligand includes: a first ligand; the structural formula of the first ligand is A1-R1-D; wherein A1 is a coordinating group capable of coordinating with the quantum dot body; R1 is selected from any one of a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkyl group including an ester bond, and a substituted or unsubstituted alkyl group including an ethylene glycol bond; D is an activating group.

[0029] In some embodiments, the ligand further includes: a second ligand; the structural formula of the second ligand is A2-R1; wherein A2 is a coordination group capable of coordinating with the quantum dot body; R1 of the first ligand and R1 of the second ligand are the same or different.

[0030] In some embodiments, the ratio of the mass of the first ligand to the mass of the ligand is greater than or equal to 5%.

[0031] In some embodiments, the ligand is selected from the ligands described in any of the above embodiments, and the thiol group, thiol radical or thiol anion released from the ligand is used to react with the cross-linker to form a chemical bond, to coordinate with the quantum dot body, or to react with another ligand to form a chemical bond.

[0032] In some embodiments, the cross-linking agent includes an activating group; the activating group includes at least one of a carbon-carbon double bond and a carbon-carbon triple bond.

[0033] On the other hand, a light-emitting device is provided, comprising: a hole transport layer and a quantum dot light-emitting layer stacked together; a material of at least one of the hole transport layer and the quantum dot light-emitting layer comprises at least one of the following materials. Wherein, each R3 is independently selected from any one of H, an alkyl group, an electron-withdrawing group, an electron-donating group and a conjugated group.

[0034] In some embodiments, the material of the hole transport layer also includes: a first cross-linking material; wherein the first cross-linking material includes: a first group; the first group includes: a main chain and a side chain connected to the main chain of the first group; the first cross-linking material also includes: a first cross-linking group connected to the side chain of the first group, and the side chain of the first group is connected to the first cross-linking group through at least two thioether structures.

[0035] In some embodiments, the first cross-linking group further comprises at least one of a triphenylamine group, a carbazole group, and a vicinal triphenylamine group.

[0036] In some embodiments, the main chain of the first group includes at least one of polycarbazole, polybenzidine, a copolymer of substituted or unsubstituted carbazole and fluorene, and a copolymer of substituted or unsubstituted benzidine and fluorene.

[0037] In some embodiments, the side chain of the first group further comprises at least one of an ethylene glycol group and an ester group.

[0038] In some embodiments, the quantum dot light-emitting layer includes: quantum dot bodies interconnected by a second cross-linking material; wherein the second cross-linking material includes at least one of the following materials; a coordination group coordinated with the quantum dot body and a second cross-linking group connected to the coordination group, the coordination group and the second cross-linking group are connected through a thioether structure; a second cross-linking group, the second cross-linking group and the quantum dot body are connected through a thioether structure; and, a first coordination group coordinated with the quantum dot body and a second coordination group coordinated with the quantum dot body, the first coordination group and the second coordination group are connected through a thioether structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] To more clearly illustrate the technical solutions of the present disclosure, the following briefly introduces the drawings required for use in some embodiments of the present disclosure. Obviously, the drawings described below are only drawings of some embodiments of the present disclosure, and those skilled in the art can also derive other drawings based on these drawings. Furthermore, the drawings described below are schematic diagrams and are not intended to limit the actual dimensions of the products, actual processes of the methods, actual timing of signals, and the like involved in the embodiments of the present disclosure.

[0040] FIG1 is a structural diagram of a quantum dot light-emitting layer prepared on a light-emitting substrate according to some embodiments of the present disclosure;

[0041] FIG2 is a structural diagram of a light-emitting substrate according to some embodiments of the present disclosure;

[0042] FIG3 is another structural diagram of the preparation of a quantum dot light-emitting layer of a light-emitting substrate according to some embodiments of the present disclosure;

[0043] FIG4 is a structural diagram of a light emitting device according to some embodiments of the present disclosure;

[0044] FIG5 is a light emitting diagram of a light emitting device including a red quantum dot light emitting layer according to some embodiments of the present disclosure;

[0045] FIG6 is a scanning electron microscope image of a quantum dot light-emitting layer in an exposed area according to some embodiments of the present disclosure;

[0046] FIG7 is a scanning electron microscope image of a quantum dot light-emitting layer in an unexposed area according to some embodiments of the present disclosure;

[0047] FIG8 is a structural diagram of a display device according to some embodiments of the present disclosure. DETAILED DESCRIPTION

[0048] The following will be combined with the accompanying drawings to clearly and completely describe the technical solutions in some embodiments of the present disclosure. Obviously, the embodiments described are only some embodiments of the present disclosure, not all embodiments. Based on the embodiments provided by the present disclosure, all other embodiments obtained by ordinary technicians in this field are within the scope of protection of the present disclosure.

[0049] Unless the context requires otherwise, throughout the specification and claims, the term "comprise" and its other forms, such as the third person singular form "comprises" and the present participle form "comprising", are to be interpreted as open and inclusive, that is, "including, but not limited to". In the description of the specification, the terms "one embodiment", "some embodiments", "exemplary embodiments", "example", "specific example" or "some examples" are intended to indicate that the particular features, structures, materials or characteristics associated with the embodiment or example are included in at least one embodiment or example of the present disclosure. The schematic representation of the above terms does not necessarily refer to the same embodiment or example. In addition, the particular features, structures, materials or characteristics may be included in any one or more embodiments or examples in any appropriate manner.

[0050] In the following, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present disclosure, unless otherwise specified, "plurality" means two or more.

[0051] When describing some embodiments, the expressions "coupled" and "connected" and their derivatives may be used. The term "connected" should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. The term "coupled" indicates, for example, that two or more components are in direct physical or electrical contact. The term "coupled" or "communicatively coupled" may also refer to two or more components that are not in direct contact with each other, but still cooperate or interact with each other. The embodiments disclosed herein are not necessarily limited to the contents of this document.

[0052] “At least one of A, B and C” has the same meaning as “at least one of A, B or C” and both include the following combinations of A, B and C: A only, B only, C only, the combination of A and B, the combination of A and C, the combination of B and C, and the combination of A, B and C.

[0053] “A and / or B” includes the following three combinations: A only, B only, and a combination of A and B.

[0054] 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).

[0055] As used herein, "parallel", "perpendicular", and "equal" include the situations described and situations similar to the situations described, and the range of the similar situations is within an acceptable deviation range, wherein the acceptable deviation range is as determined by a person of ordinary skill in the art taking into account the measurement in question and the errors associated with the measurement of the specific quantity (i.e., the limitations of the measurement system). For example, "parallel" includes absolute parallelism and approximate parallelism, wherein the acceptable deviation range of approximate parallelism can be, for example, a deviation within 5°; "perpendicular" includes absolute perpendicularity and approximate perpendicularity, wherein the acceptable deviation range of approximate perpendicularity can also be, for example, a deviation within 5°. "Equal" includes absolute equality and approximate equality, wherein the acceptable deviation range of approximate equality can be, for example, that the difference between the two equals is less than or equal to 5% of either one.

[0056] It will be understood that when a layer or element is referred to as being on another layer or substrate, it can be directly on the other layer or substrate, or intervening layers may be present therebetween.

[0057] Exemplary embodiments are described herein with reference to cross-sectional and / or plan views that are idealized exemplary drawings. In the drawings, the thickness of layers and the area of ​​regions are exaggerated for clarity. Therefore, variations in shape relative to the drawings due to, for example, manufacturing techniques and / or tolerances are contemplated. Therefore, the exemplary embodiments should not be construed as limited to the shapes of the regions shown herein, but rather include deviations in shape due to, for example, manufacturing. For example, an etched region shown as a rectangle will typically have curved features. Therefore, the regions shown in the drawings are schematic in nature, and their shapes are not intended to illustrate the actual shape of regions of the device and are not intended to limit the scope of the exemplary embodiments.

[0058] Quantum dot light emitting diodes (QLEDs), which use quantum dots (QD) as luminescent materials, are widely used in the display field. The main preparation technologies for the light-emitting layer of quantum dot LEDs include inkjet printing technology, photolithography technology, and transfer technology. Among them, photolithography technology is a more promising method for preparing high-resolution quantum dot LEDs.

[0059] Photolithography technology refers to the technology of achieving quantum dot patterning through exposure and development.

[0060] In some examples, as shown in FIG1 , a structural diagram of the preparation of a quantum dot light-emitting layer 13 of a light-emitting substrate 100 is provided. Referring to the last sub-figure in FIG1 (i.e., the sub-figure corresponding to step S8), the light-emitting substrate 100 includes: a substrate 101, a pixel defining layer 102 located on one side of the substrate 101, and a plurality of light-emitting devices 10, each of which includes a light-emitting pattern 131. The pixel defining layer 102 has a plurality of openings K, and the plurality of light-emitting devices 10 can be arranged in a one-to-one correspondence with the plurality of openings K.

[0061] Exemplarily, the plurality of light-emitting devices 10 include a first light-emitting device 10a, a second light-emitting device 10b, and a third light-emitting device 10c. For example, the first light-emitting device 10a is one of a red light-emitting device, a green light-emitting device, and a blue light-emitting device, the second light-emitting device 10b is another of the red, green, and blue light-emitting devices, and the third light-emitting device 10c is the last of the red, green, and blue light-emitting devices. The light-emitting pattern 131a of the first light-emitting device 10a, the light-emitting pattern 131b of the second light-emitting device 10b, and the light-emitting pattern 131c of the third light-emitting device 10c form the quantum dot light-emitting layer 13.

[0062] The following describes a process for sequentially forming the light emitting pattern 131a of the first light emitting device 10a, the light emitting pattern 131b of the second light emitting device 10b, and the light emitting pattern 131c of the third light emitting device 10c. As shown in FIG1 , the process includes steps S1 to S8.

[0063] It should be noted that in order to improve the efficiency of injecting electrons and holes into the light-emitting pattern 131, a functional film layer 14 is also provided between the substrate 101 and the light-emitting pattern 131. For example, the functional film layer 14 is an electron transport layer 16 (as shown in FIG. 4 ) or a hole transport layer 141 (as shown in FIG. 4 ).

[0064] S1: coating a first quantum dot luminescent material on a side of the functional film layer 14 away from the substrate 101 to form an initial luminescent pattern 130a, exposing the initial luminescent pattern 130a, and using the area where the first light-emitting device 10a is pre-formed as the exposed area.

[0065] S2: developing the initial light emitting pattern 130a, and the initial light emitting pattern 130a in the exposed area remains, forming the light emitting pattern 131a of the first light emitting device 10a.

[0066] S3: coating a second quantum dot light-emitting material on the side of the light-emitting pattern 131 a of the first light-emitting device 10 a away from the substrate 101 to form an initial light-emitting pattern 130 b .

[0067] S4: exposing the initial light emitting pattern 130b, and the area where the second light emitting device 10b is pre-formed is the exposed area.

[0068] S5: developing the initial light emitting pattern 130b, and the initial light emitting pattern 130b in the exposed area remains, forming the light emitting pattern 131b of the second light emitting device 10b.

[0069] S6: coating a third quantum dot light-emitting material on the side of the light-emitting pattern 131 b of the second light-emitting device 10 b away from the substrate 101 to form an initial light-emitting pattern 130 c .

[0070] S7: exposing the initial light emitting pattern 130c, and the area where the third light emitting device 10c is pre-formed is the exposed area.

[0071] S8: developing the initial light emitting pattern 130c, and the initial light emitting pattern 130c in the exposed area remains, forming a light emitting pattern 131c of the third light emitting device 10c.

[0072] However, in the actual process of preparing the luminescent pattern 131 of the luminescent substrate 100, as shown in Figure 2, the patterning method has the problem of incomplete elution of the previous layer of quantum dot luminescent material (such as the first quantum dot luminescent material), which will cause the next color of quantum dot luminescent material (such as the second quantum dot luminescent material) to have residual quantum dot luminescent material of the previous layer after the patterning process.

[0073] For example, as shown in FIG2 , taking the sequential formation of the light-emitting pattern 131a of the first light-emitting device 10a, the light-emitting pattern 131b of the second light-emitting device 10b, and the light-emitting pattern 131c of the third light-emitting device 10c as an example, on the side of the light-emitting pattern 131a of the first light-emitting device 10a away from the substrate 101, there is a residual layer G0 formed by the second quantum dot light-emitting material and a residual layer B0 formed by the third quantum dot light-emitting material. On the side of the light-emitting pattern 131b of the second light-emitting device 10b closer to the substrate 101, there is a residual layer R0 formed by the first quantum dot light-emitting material. On the side of the light-emitting pattern 131b of the second light-emitting device 10b farther from the substrate 101, there is a residual layer B0 formed by the third quantum dot light-emitting material. On the side of the light-emitting pattern 131c of the third light-emitting device 10c closer to the substrate 101, there is a residual layer R0 formed by the first quantum dot light-emitting material and a residual layer G0 formed by the second quantum dot light-emitting material.

[0074] The residue formed by the quantum dot luminescent material may cause color mixing. When the light emitting device 10 is turned on, the light emitting spectrum may be impure, thereby affecting the performance of the light emitting device 10 .

[0075] Therefore, in some examples, as shown in FIG3 , quantum dot patterning can be performed by setting a sacrificial layer. Since the quantum dot luminescent material on the side of the sacrificial layer away from the substrate 101 can be removed when the sacrificial layer is removed, this method can obtain a residue-free, high-color-gamut full-color quantum dot light-emitting device 10 and a full-color actively driven quantum dot light-emitting device 10.

[0076] Exemplarily, the material of the sacrificial layer includes: a carrier transport material and a cross-linking agent. The carrier transport material and the cross-linking agent form a cross-linked material under light conditions, and the cross-linked material forms the functional film layer 14 .

[0077] The following is an example of a method for patterning quantum dots using a sacrificial layer.

[0078] Exemplarily, as shown in FIG3 , the method for preparing a light-emitting device includes steps M1 to M4 .

[0079] M1: forming a first thin film 31 on the substrate 101 . The materials of the first thin film 31 include: a carrier transport material and a cross-linking agent.

[0080] Illustratively, the first film 31 is formed by a coating process.

[0081] M2: A second thin film 32 is formed on a side of the first thin film 31 away from the substrate 101. The material of the second thin film 32 includes the first quantum dot material. The first region W1 where the first light-emitting device 10a is located is exposed to light, so that the carrier transport material and the crosslinking agent in the first region W1 are crosslinked to form a crosslinked material.

[0082] Illustratively, the second film 32 is formed by a coating process.

[0083] M3: Use the first developer to dissolve the portion of the second film 32 located in the second area W2, thereby removing the portion of the second film 32 located in the second area W2. The second area W2 is the remaining area of ​​the plurality of light-emitting devices 10 except the area where the first light-emitting device 10a is located.

[0084] For example, the first quantum dot material may remain in a portion close to the substrate 101 , and a first temporary residual layer 320 may remain in the second region W2 .

[0085] M4: Use a second developer to dissolve the portion of the first film 31 located in the second area W2. The portion of the first film 31 located in the second area W2 is removed, and the portion of the first film 31 located in the first area W1 forms the functional film layer 14. The portion of the second film 32 located in the first area W1 forms the light-emitting pattern 131a of the first light-emitting device 10a.

[0086] Exemplarily, the functional film layer 14 is an electron transport layer or a hole transport layer 141 .

[0087] When removing the portion of the first film 31 located in the second region W2, the first temporary residual layer 320 is also removed. In this step, the portion of the first film 31 located in the second region W2 can be referred to as a sacrificial layer. Therefore, using a sacrificial layer during quantum dot patterning can effectively prevent the first quantum dot material from remaining in the second region W2.

[0088] Similarly, the light emitting pattern 131 b of the second light emitting device 10 b and the light emitting pattern 131 c of the third light emitting device 10 c may be formed by the same method, which will not be described in detail here.

[0089] However, when the functional film layer 14 is formed by cross-linking a carrier transport material and a cross-linking agent, there is a problem that the carrier transport material and the cross-linking agent are cross-linked and the carrier transport path is destroyed.

[0090] For example, the functional film layer 14 is a hole transport layer 141, the carrier transport material is poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-(4,4'-(N-(4-butylphenyl)-diphenylamine)] (Poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-(4,4'-(N-(4-butylphenyl), abbreviated as TFB), and the crosslinker is an aromatic azide compound. The aromatic azide compound generates nitrogen carbene under light conditions, triggering a C-H insertion reaction, and reacting with the alkyl side chain of the fluorene repeating unit in TFB, thereby obtaining a crosslinked material, which forms the hole transport layer 141.

[0091] Illustratively, the structural formula of TFB is as follows.

[0092] However, the inventors found that during this process, due to the high activity of nitrogen carbene, nitrogen carbene may react with the conjugated repeating units of the TFB main chain, destroying the hole transport path and introducing defects into the hole transport layer 141, resulting in reduced efficiency of the light-emitting device 10.

[0093] Based on this, an embodiment of the present disclosure provides a hole transport composition, which includes: a hole transport material and a crosslinker, the hole transport material includes: a main chain and a side chain connected to the main chain of the hole transport material; the side chain of the hole transport material has a thiol group, and the thiol group is used to react with the crosslinker to form a chemical bond.

[0094] Illustratively, the main chain of the hole transport material includes at least one of polycarbazole, polybenzidine, a copolymer of substituted or unsubstituted carbazole and fluorene, and a copolymer of substituted or unsubstituted benzidine and fluorene.

[0095] The structural formula of a hole transport material including a mercapto group is exemplified below.

[0096] Where n≥1.

[0097] It should be noted that the thiol group is a photosensitive group that generates sulfhydryl radicals or sulfhydryl anions under light conditions. The generated sulfhydryl radicals or sulfhydryl anions can react with the crosslinking agent to form chemical bonds to form the hole transport layer 141 having a crosslinked material.

[0098] By setting a thiol group on the side chain of the hole transport material, the thiol group on the side chain of the hole transport material reacts with the cross-linking agent to form a cross-linked material, thereby forming a hole transport layer 141. This can effectively prevent the possibility of reaction of the conjugated repeating units of the main chain of the hole transport material, maintain the hole transport path of the hole transport layer 141, and improve the luminous efficiency of the light-emitting device 10.

[0099] In some examples, the cross-linking agent includes an activating group; the activating group includes at least one of a carbon-carbon double bond and a carbon-carbon triple bond.

[0100] It should be noted that the activating group refers to an atom or a group of atoms that can facilitate electrophilic substitution reactions; it is used to increase the chemical reaction rate and the cross-linking degree of the cross-linked material.

[0101] Exemplarily, the activated group having a carbon-carbon double bond includes at least one of a styrene group, an acrylate group, an alkylacrylate group, a maleic anhydride group, and a maleimide group.

[0102] The structural formula of a cross-linking agent including an activating group is exemplified below.

[0103] It should be noted that compared with azide compounds, the activity of sulfur radicals or sulfur anions generated by thiol groups under light conditions is lower than the activity of nitrogen carbenes generated by azide compounds under light conditions. Therefore, when the photosensitive group is a thiol group, it is necessary to add an activating group to the cross-linker to increase the reactivity of the cross-linker, thereby increasing the reaction rate and cross-linking degree of the hole transport material and the cross-linker.

[0104] In other embodiments, the crosslinking agent includes a thiol group, and the side chain of the hole transport material includes an activating group.

[0105] Since the activity of the sulfur free radicals or sulfur anions generated by the thiol group under light conditions is relatively low, the thiol group on the cross-linker is connected to the side chain of the hole transport material, which can also effectively prevent the possibility of reaction of the conjugated repeating units of the main chain of the hole transport material, maintain the hole transport path of the hole transport layer 141, and improve the luminous efficiency of the light-emitting device 10.

[0106] The structural formula of a cross-linking agent including a mercapto group is exemplified below. Where n≥1.

[0107] The structural formulas of hole transport materials including activating groups in their side chains are exemplified below. Where n≥1.

[0108] In some embodiments, when the side chain of the hole transport material includes a thiol group and the crosslinker includes an activating group, and when the crosslinker includes a thiol group and the side chain of the hole transport material includes an activating group, the hole transport composition further includes: a photoradical initiator.

[0109] It should be noted that a photoradical initiator, acting as both a light-absorbing group and a free radical-generating group, triggers a thiol-ene click reaction to connect the hole transport material and the crosslinker. The thiol-ene click reaction, also known as the thiol-ene click reaction, involves the thiol group generating a free radical under the influence of ultraviolet light or heat. This radical then undergoes an addition reaction with the ene, forming a covalent bond.

[0110] Exemplarily, the reaction formula of Thiol-ene click reaction is as follows.

[0111] Here, Ra-SH represents a material including a thiol group, for example, Ra-SH represents one of a hole transport material and a cross-linking agent. denotes a material comprising an activating group, e.g. represents the other of the hole transport material and the crosslinker. Under light conditions, the photo-induced free radical initiator generates free radicals, which initiate Ra-SH and Thiol-ene click reactions occur to form cross-linked materials.

[0112] Ra-SH and Thiol-ene click reaction occurs, the activation energy required for the reaction is low, the energy of the reactive intermediate is low, and there are few side reactions and high yield; the atom utilization rate can reach 100%, which can improve the cross-linking degree of the hole transport material and the cross-linking agent.

[0113] Exemplarily, the photoradical initiator includes at least one of 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone (represented by Irgacure 369) and bis(1-(2,4-difluorophenyl)-3-pyrrolyl)titanocene (represented by Irgacure 784).

[0114] The structural formula of Irgacure 369 is shown below.

[0115] Under the condition of exposure wavelength of 365nm, Irgacure 369 generates carbon radicals, which trigger Ra-SH and Thiol-ene click reactions occur to form cross-linked materials.

[0116] The chemical formula for carbon radicals generated by Irgacure 369 when exposed to light at a wavelength of 365 nm is as follows.

[0117] The structural formula of Irgacure 784 is shown below.

[0118] Under the condition of exposure to light with a wavelength of 405nm, Irgacure 784 generates free radicals, which trigger Ra-SH and Thiol-ene click reactions occur to form cross-linked materials.

[0119] The chemical formula for free radicals generated by Irgacure 784 when exposed to light at a wavelength of 405 nm is as follows.

[0120] The photoradical initiator can be used to change the exposure wavelength at which crosslinking occurs between the hole transport material and the crosslinking agent. Longer exposure wavelengths and lower photon energy reduce damage to the conjugated repeating units and quantum dots of the hole transport material in the light-emitting device 10, thereby improving the optical performance and lifespan of the light-emitting device 10.

[0121] The hole transport layer 141 is formed by cross-linking a hole transport material having a side chain including one of a thiol group and an activating group and a cross-linking agent including the other of the thiol group and the activating group. This effectively prevents the possibility of reaction of the conjugated repeating units in the main chain of the hole transport material, thereby maintaining the hole transport path of the hole transport layer 141. Furthermore, the provision of the activating group can increase the chemical reaction rate and the degree of cross-linking between the hole transport material and the cross-linking agent, thereby improving the luminous efficiency of the light-emitting device 10.

[0122] However, the inventors discovered that thiol groups are easily oxidized to disulfide bonds, which affects the crosslinking between the thiol groups and the activating groups, thereby affecting the degree of crosslinking between the hole transport material and the crosslinking agent. Furthermore, thiol groups often have a foul odor, making materials containing thiol groups inconvenient to use.

[0123] Based on this, an embodiment of the present disclosure provides a crosslinking agent, which includes: a thiol group protected by a photolyzable group; the photolyzable group is removed under light to release a thiol group, a thiol radical or a thiol anion.

[0124] Photoremovable Protecting Group (PPG) refers to a group that can undergo decomposition reaction under the action of light.

[0125] Protecting thiol groups with photolyzable groups not only solves the problem of thiol groups having a foul odor and being inconvenient to use, but also provides greater stability and easier control. The photolyzable groups are removed under light, releasing thiol groups, sulfhydryl radicals, or sulfhydryl anions, which can further participate in cross-linking reactions.

[0126] In some examples, the photolyzable group is selected from at least one of the following substituents. Wherein, each R3 is independently selected from any one of H, an alkyl group, an electron-withdrawing group, an electron-donating group and a conjugated group.

[0127] It should be noted that, Indicates that the bond is used to connect to a sulfhydryl group.

[0128] The photolyzable group can be connected to a thiol group to protect the thiol group. The presence of the photolyzable group can not only solve the problem that the thiol group has a bad odor and is inconvenient to use, but also improve the stability of the thiol group.

[0129] In some examples, the crosslinking agent is selected from at least one of the structures shown in the following general formula I.

[0130] PPG-S-R1-S-PPGⅠ

[0131] Wherein, R1 is selected from any one of a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkyl group including an ester bond, and a substituted or unsubstituted alkyl group including an ethylene glycol bond; and PPG is a photolyzable group.

[0132] Illustratively, the cross-linking agent is selected from at least one of the following structural formulas.

[0133] Cross-linking agents with different structures can be provided by combining photolyzable groups with different structures of R1. Moreover, R1 includes alkyl, ester and glycol bonds, which can regulate the solubility of the cross-linking agent in different solvents.

[0134] In other examples, the cross-linking agent is selected from at least one of the structures shown in the following general formula II.

[0135] R2-(R1-S-PPG) n1 Ⅱ

[0136] Wherein, R2 is selected from any one of secondary carbon, tertiary carbon and quaternary carbon; n1≥2.

[0137] For example, n1=2, and the cross-linking agent is selected from at least one of the structures shown in the following general formula.

[0138] PPG-S-R1-R2-R1-S-PPG, and in this general formula, the two PPGs can be the same or different; the two R1s can be the same or different, and there is no limitation here.

[0139] For example, R2 is a secondary carbon, and the general formula can be represented as PPG-S-R1-CH2-R1-S-PPG.

[0140] Exemplarily, n1=3, and the cross-linking agent is selected from at least one of the structures shown in the following general formula.

[0141] Furthermore, the three PPGs in the general formula may be the same or different; the three R1s may be the same or different, and there is no limitation here.

[0142] For example, R2 is a tertiary carbon, and the general formula can be expressed as

[0143] For example, R2 is -CCH3, the general formula can be expressed as

[0144] Exemplarily, n1=4, and the cross-linking agent is selected from at least one of the structures shown in the following general formula.

[0145] Furthermore, the four PPGs in the general formula may be the same or different; the four R1s may be the same or different, and there is no limitation thereto.

[0146] For example, R2 is a quaternary carbon, and the general formula can be expressed as

[0147] Illustratively, the cross-linking agent is selected from at least one of the following structural formulas.

[0148] It should be noted that “——” indicates that the end of the bond is CH3.

[0149] The following is an exemplary introduction to the preparation method of the cross-linking agent.

[0150] Example 1

[0151] The structural formula of the cross-linking agent is shown below.

[0152] The preparation method of the cross-linking agent is as follows.

[0153] 2.2 mmol of 2-nitrobenzyl bromide, 1 mmol of 1,8-octanedithiol, and 4 mmol of triethylamine were dissolved in 10 mL of methanol and reacted at room temperature for 12 hours. The methanol was then concentrated under reduced pressure to remove the residue, dissolved in 50 mL of dichloromethane, washed three times with saturated ammonium chloride solution, dried over anhydrous Na₂SO₄, concentrated, and purified by silica gel column chromatography. The yield of the crosslinker was 245 mg, with a crosslinker yield of 54.7%. 1H NMR (600 MHz, CDCl₃) δ (ppm): 7.94 (2H), 7.57-7.37 (6H), 4.05 (4H), 2.42 (4H), 1.55-1.18 (14H). NMR represents the nuclear magnetic resonance (NMR) data of the crosslinker.

[0154] Example 2

[0155] The structural formula of the cross-linking agent is shown below.

[0156] The preparation method of the cross-linking agent is as follows.

[0157] 2.2 mmol of 1-(2'-bromoethyl)-2-nitrodibenzofuran, 1 mmol of 1,8-octanedithiol, and 4 mmol of triethylamine were dissolved in 10 mL of methanol and reacted at room temperature for 12 hours. The methanol was then concentrated under reduced pressure and dissolved in 50 mL of dichloromethane. The product was washed three times with saturated ammonium chloride solution, dried over anhydrous Na₂SO₄, concentrated, and purified by silica gel column chromatography. The yield of the crosslinker was 310 mg, with a crosslinker yield of 47.3%. 1H NMR (600 MHz, CDCl₃) δ (ppm): 8.43 (2H), 8.09 (4H), 7.66-7.57 (4H), 7.48-7.44 (4H), 4.03 (2H), 2.42 (4H), 2.22 (6H), 1.55-1.18 (14H).

[0158] Example 3

[0159] The structural formula of the cross-linking agent is shown below.

[0160] The preparation method of the cross-linking agent is as follows.

[0161] 1.44 mmol of 3-bromo-2,5,6-trimethyl-pyrazolo[1,2-a]pyrazole-1,7-dione, 0.6 mmol of ethylene glycol bisthioglycolate, and 1.44 mmol of triethylamine were dissolved in 10 mL of methanol and reacted at room temperature for 12 hours. The methanol was then concentrated under reduced pressure to remove the residue, dissolved in 50 mL of dichloromethane, washed three times with saturated ammonium chloride solution, dried over anhydrous Na₂SO₄, concentrated, and purified by silica gel column chromatography. The yield of the crosslinker was 152 mg, with a crosslinker yield of 42%. 1H NMR (600 MHz, CDCl₃) δ (ppm): 3.85 (4H), 3.75 (6H), 3.27 (4H), 2.41 (4H), 1.89 (6H), 1.83 (6H). MS: m / 2: 297.08981. Here, MS represents the mass spectrometry data of the cross-linking agent.

[0162] Example 4

[0163] The structural formula of the cross-linking agent is shown below.

[0164] The preparation method of the cross-linking agent is as follows.

[0165] 1.1 mmol of 3-bromo-2,5,6-trimethyl-pyrazolo[1,2-a]pyrazole-1,7-dione, 0.31 mmol of trimethylolpropane tris(3-mercaptopropionate), and 1.10 mmol of triethylamine were dissolved in 10 mL of methanol and reacted at room temperature for 12 hours. The methanol was then concentrated under reduced pressure to remove the residue, dissolved in 50 mL of dichloromethane, washed three times with saturated ammonium chloride solution, dried over anhydrous Na₂SO₄, concentrated, and purified by silica gel column chromatography. The yield of the crosslinker was 138 mg, with a crosslinker yield of 46%. 1H NMR (600 MHz, CDCl₃) δ (ppm): 3.73 (15H), 3.27 (4H), 2.87 (6H), 2.65 (6H), 1.92 (9H), 1.85 (9H), 1.73 (2H), 0.89 (3H).

[0166] Example 5

[0167] The structural formula of the cross-linking agent is shown below.

[0168] The preparation method of the cross-linking agent is as follows.

[0169] 1.1 mmol of 3-bromo-2,5,6-trimethyl-pyrazolo[1,2-a]pyrazole-1,7-dione, 0.23 mmol of pentaerythritol tetrathioglycolate, and 1.10 mmol of triethylamine were dissolved in 10 mL of methanol and reacted at room temperature for 12 hours. The methanol was then concentrated under reduced pressure to remove the residue, and the product was dissolved in 50 mL of dichloromethane. The product was washed three times with saturated ammonium chloride solution, dried over anhydrous Na₂SO₄, concentrated, and purified by silica gel column chromatography. The yield of the crosslinker was 128 mg, with a crosslinker yield of 47.2%. 1H NMR (600 MHz, CDCl₃) δ (ppm): 4.09 (8H), 3.84 (8H), 3.41 (8H), 2.40 (12H), 1.87 (12H), 1.83 (12H).

[0170] Example 6

[0171] The structural formula of the cross-linking agent is shown below.

[0172] The preparation method of the cross-linking agent is as follows.

[0173] 1.1 mmol of 3-bromo-2,5,6-trimethyl-pyrazolo[1,2-a]pyrazole-1,7-dione, 0.15 mmol of dipentaerythritol hexa(3-mercaptopropionate), and 1.10 mmol of triethylamine were dissolved in 10 mL of methanol and reacted at room temperature for 12 hours. The methanol was then concentrated under reduced pressure to remove the residue, dissolved in 50 mL of dichloromethane, washed three times with saturated ammonium chloride solution, dried over anhydrous Na₂SO₄, concentrated, and purified by silica gel column chromatography. The crosslinker yielded 133 mg, a 45.1% yield. 1H NMR (600 MHz, CDCl₃) δ (ppm): 4.21 (4H), 3.38-3.73 (24H), 2.87 (12H), 2.66 (12H), 2.42 (18H), 1.92 (18H), 1.86 (18H).

[0174] Example 7

[0175] The structural formula of the cross-linking agent is shown below.

[0176] The preparation method of the cross-linking agent is as follows.

[0177] Intermediate 2 (0.166 g, 0.5 mmol) and 2-hydroxymethyl-1,3-propanediol (16 mg, 0.15 mmol) were dissolved in 10 mL of dichloromethane, and 50 mg of 4-dimethylaminopyridine and 150 mg of dichloroethane were added. The mixture was stirred at 25° C. for 12 hours, dried by rotary evaporation, and 50 mL of saturated sodium chloride solution was added. The mixture was extracted three times with dichloromethane and then dried by rotary evaporation. Purification by column chromatography and rotary evaporation gave a crosslinking agent, designated as product 4. The yield of the crosslinking agent was 63 g, and the yield of the crosslinking agent was 40%. 1H NMR δ (ppm): 8.57(3H), 7.98(3H), 7.67(3H), 7,54(3H), 7.31-7.40(6H), 4.31(6H), 3.92(3H), 3.40(6H), 1.58(9H), 1.21(1H).

[0178] In some examples, the cross-linking agent further includes: a carrier transport regulating group.

[0179] Introducing carrier-modifying groups into crosslinkers can improve the carrier transport properties of crosslinkers.

[0180] Exemplarily, the crosslinker includes a main chain and a side chain connected to the main chain of the crosslinker, the carrier transport regulating group is located on the main chain of the crosslinker, and the thiol group protected by the photolyzable group is located on the side chain of the crosslinker.

[0181] By arranging that the carrier transport regulating group is located in the main chain of the cross-linking agent and the thiol group protected by the photolyzable group is located in the side chain of the cross-linking agent, the cross-linking reaction of the cross-linking agent occurs in the side chain of the cross-linking agent, thereby effectively preventing the cross-linking reaction of the cross-linking agent from affecting the carrier transport performance of the carrier transport regulating group of the cross-linking agent.

[0182] In some examples, the cross-linking agent is selected from at least one of the structures shown in the following formula III.

[0183] R4-(R1-S-PPG) n2 III

[0184] Wherein, R4 is a substituted or unsubstituted carrier transport regulating group; n2≥2.

[0185] For example, n2=2, the general formula can be expressed as R4-(R1-S-PPG)2; n2=3, the general formula can be expressed as R4-(R1-S-PPG)3; n2=4, the general formula can be expressed as R4-(R1-S-PPG)4.

[0186] In some examples, the carrier transport regulating group is a hole transport group, and the hole transport group includes at least one of a triphenylamine group, a carbazole group, and a vicinal triphenylamine group.

[0187] It should be noted that the hole transport group refers to a functional group that can efficiently transport holes (ie, positive charge carriers) in an organic semiconductor material.

[0188] Illustratively, the cross-linking agent is selected from at least one of the following structural formulas.

[0189] The following is an exemplary introduction to the preparation method of the cross-linking agent including the hole transport group.

[0190] Example 8

[0191] The structural formula of the cross-linking agent is shown below.

[0192] The preparation method of the cross-linking agent is as follows.

[0193] 1) Dissolve 10 mmol of N4,N4,N4',N4'-tetrakis(4-methoxyphenyl)-[1,1'-biphenyl]-4,4'-diamine in 50 mL of anhydrous dichloromethane and cool to 0°C. Add a dichloromethane solution of boron tribromide dropwise to a volume of 60 mL and a molar concentration of 2 mol / L. The mixture is then warmed to room temperature and stirred for 12 hours. A large amount of water is then added to quench the reaction. Dilute hydrochloric acid is then added to acidify the mixture. The resulting brown-black precipitate is collected by filtration, washed with deionized water, and dried under reduced pressure to obtain product 7. The yield of product 7 is 3.9 g, with a yield of 71%. 1H NMR (600 MHz, CDCl3) δ (ppm): 9.44 (4H), 7.57 (4H), 7.37 (4H), 6.99 (8H), 6.75 (8H).

[0194] 2) 20 mmol of 2-(tritylthio)acetic acid, 5 mmol of product 7, 50 mg of DAMP (4-dimethylaminopyridine), and 150 mg of EDC (ethylene dichloride) were mixed in 50 mL of dichloromethane and stirred at room temperature for 12 hours. The product 8 was purified by silica gel column chromatography after concentration to remove the dichloromethane. The yield of product 8 was 8.47 g, with a yield of 93%. 1H NMR (600 MHz, CDCl3) δ (ppm): 7.57 (4H), 7.30-7.16 (80H), 7.06 (8H), 3.54 (8H).

[0195] 3) 4 mmol of product 8 was dissolved in anhydrous dichloromethane, cooled to 0°C, and 32 mmol of triethylsilane and 320 mmol of trifluoroacetic acid (TFA) were added. Stirring was continued at 0°C for 15 minutes, then the mixture was slowly warmed to room temperature and stirred for one hour at room temperature. A saturated NaHCO3 solution was added to quench the reaction. After extraction with water / dichloromethane, the organic phase was dried and concentrated, and then purified by silica gel column chromatography to obtain product 9. The yield of product 9 was 3.29 g, with a yield of 97%. 1H NMR (600 MHz, CDCl3) δ (ppm): 7.57 (4H), 7.37 (4H), 7.18 (8H), 7.06 (8H), 3.54 (8H), 1.48 (4H).

[0196] 4) 17 mmol of 3-bromo-2,5,6-trimethyl-pyrazolo[1,2-A]pyrazole-1,7-dione, 3.52 mmol of product 9, and 17 mmol of triethylamine were dissolved in 100 mL of methanol and reacted at room temperature for 12 hours. The methanol was then removed by concentration under reduced pressure, dissolved in 100 mL of dichloromethane, washed three times with saturated ammonium chloride solution, dried over anhydrous Na2SO4, concentrated, and purified by silica gel column chromatography to obtain a cross-linker, designated as product 10. The yield of product 10 was 2.94 g, and the yield of product 10 was 52%. 1H NMR (600MHz, CDCl3) δ (ppm): 7.57(4H), 7.37(4H), 7.18(8H), 7.06(8H), 3.73(8H), 3.54(8H), 2.42(12H), 1.92(12H), 1.86(12H).

[0197] Example 9

[0198] The structural formula of the cross-linking agent is shown below.

[0199] The preparation method of the cross-linking agent is as follows.

[0200] 1) Dissolve 10 mmol of raw material 11 in 50 mL of anhydrous dichloromethane, cool to 0°C, and then add a dichloromethane solution of boron tribromide dropwise to a volume of 60 mL at a molar concentration of 2 mol / L. The mixture is then warmed to room temperature and stirred for 12 hours. A large amount of water is then added to quench the reaction. Dilute hydrochloric acid is then added to acidify the mixture. The resulting brown-black precipitate is collected by filtration, washed with deionized water, and dried under reduced pressure to obtain product 12.

[0201] 2) Mix 20 mmol of 2-(tritylthio)acetic acid, 5 mmol of product 12, DAMP (4-dimethylaminopyridine), and EDC (ethylene dichloride) in 50 mL of dichloromethane and stir at room temperature for 12 hours. The mixture was then concentrated to remove the dichloromethane and purified by silica gel column chromatography to yield product 13.

[0202] 3) 4 mmol of product 13 was dissolved in anhydrous dichloromethane, cooled to 0°C, 32 mmol of triethylsilane and 320 mmol of trifluoroacetic acid (TFA) were added, and stirring was continued at 0°C for 15 minutes. The mixture was then slowly warmed to room temperature and stirred at room temperature for one hour. A saturated NaHCO3 solution was added to quench the reaction. After extraction with water / dichloromethane, the organic phase was dried and concentrated, and then purified by silica gel column chromatography to obtain product 14.

[0203] 4) 17 mmol of 3-bromo-2,5,6-trimethyl-pyrazolo[1,2-a]pyrazole-1,7-dione, 3.52 mmol of product 14, and 17 mmol of triethylamine were dissolved in 100 mL of methanol and reacted at room temperature for 12 hours. The methanol was then removed by concentration under reduced pressure, dissolved in 100 mL of dichloromethane, washed three times with saturated ammonium chloride solution, dried over anhydrous Na2SO4, concentrated, and purified by silica gel column chromatography to obtain a cross-linker, designated product 15.

[0204] Embodiments of the present disclosure also provide another hole transport composition, which includes: a hole transport material and a cross-linker; the hole transport material includes: a main chain and a side chain connected to the main chain of the hole transport material; wherein, at least one of the side chain of the hole transport material and the cross-linker has a thiol group protected by a photolyzable group; the photolyzable group is removed under light to release a thiol group, a thiol radical or a thiol anion; the released thiol group, thiol radical or thiol anion is configured to cross-link the hole transport material and the cross-linker.

[0205] Regarding the photolyzable groups, please refer to the above description and will not be repeated here.

[0206] In some examples, the crosslinker includes a thiol group protected by a photolyzable group. For details regarding crosslinkers with thiol groups protected by photolyzable groups, refer to the crosslinker section above and are not further elaborated here. The released thiol group, thiol radical, or thiol anion from the crosslinker reacts with the side chain of the hole transport material to form a chemical bond.

[0207] By including a thiol group protected by a photolyzable group in the crosslinker, not only can the malodorous and inconvenient nature of the thiol group be overcome, but thiol groups protected by photolyzable groups also offer greater stability and easier control. The photolyzable group is removed upon illumination, releasing a thiol group, a thiol radical, or a thiol anion. The released thiol group, thiol radical, or thiol anion can then crosslink with the side chains of the hole transport material to form the hole transport layer 141.

[0208] Moreover, since the activity of the thiol groups, sulfur radicals or sulfur anions generated by the thiol groups protected by the photolyzable groups under light conditions is relatively low, the thiol groups on the cross-linking agent are connected to the side chains of the hole transport material, which can effectively prevent the possibility of reaction of the conjugated repeating units of the main chain of the hole transport material, maintain the hole transport path of the hole transport layer 141, and improve the luminous efficiency of the light-emitting device 10.

[0209] Furthermore, if the cross-linking agent includes a hole transport group, the hole transport group can compensate for the problem that holes are weaker than electrons, which is beneficial to improving the balance of carriers.

[0210] For example, when the released thiol group, thiol radical or thiol anion is located on the crosslinking agent, the side chain of the hole transport material further comprises an activating group, which comprises at least one of a carbon-carbon double bond and a carbon-carbon triple bond.

[0211] Regarding the activation group, please refer to the introduction of the activation group in the cross-linking agent section above and will not be repeated here.

[0212] Introducing an activating group into the side chain of the hole transport material can increase the reactivity of the side chain of the hole transport material, thereby increasing the reaction rate and cross-linking degree of the hole transport material and the cross-linking agent.

[0213] In other examples, when the released thiol group, thiol radical or thiol anion is located on the side chain of the hole transport material, the released thiol group, thiol radical or thiol anion is used to react with a cross-linking agent to form a chemical bond.

[0214] The hole transport material has a thiol group protected by a photolyzable group in its side chain. This not only solves the problem of thiol groups having a foul odor and being inconvenient to use, but also provides greater stability and easier control. The photolyzable group is removed upon illumination, releasing a thiol group, a thiol radical, or a thiol anion. The released thiol group, thiol radical, or thiol anion can then crosslink with a crosslinker to form the hole transport layer 141.

[0215] Moreover, since the activity of the thiol groups, sulfur radicals or sulfur anions generated by the thiol groups protected by the photolyzable groups under light conditions is relatively low, the thiol groups on the cross-linker are connected to the cross-linker, which can effectively prevent the possibility of reaction of the conjugated repeating units of the main chain of the hole transport material, maintain the hole transport path of the hole transport layer 141, and improve the luminous efficiency of the light-emitting device 10.

[0216] Exemplarily, when the released thiol group, thiol radical or thiol anion is located on the side chain of the hole transport material, the cross-linking agent further includes an activating group.

[0217] Introducing an activating group into the crosslinking agent can improve the reactivity of the crosslinking agent with the side chain of the hole transport material, thereby increasing the reaction rate and crosslinking degree of the hole transport material and the crosslinking agent.

[0218] In some examples, the side chain of the hole transport material further includes at least one of an ethylene glycol group and an ester group.

[0219] Illustratively, the hole transport material is dissolved in propylene glycol methyl ether acetate solvent.

[0220] By providing the hole transport material with a side chain including at least one of an ethylene glycol group and an ester group, the solubility of the hole transport material can be increased.

[0221] The embodiments of the present disclosure also provide a ligand for coordination connection with the quantum dot body, and the ligand includes: a thiol group protected by a photolyzable group; the photolyzable group is removed under light to release a thiol group, a thiol free radical or a thiol anion.

[0222] Regarding the photolyzable groups, please refer to the above description and will not be repeated here.

[0223] By including a thiol group protected by a photolyzable group in the ligand, the ligand can be connected to other materials (such as a cross-linking agent) after deprotection of the thiol group protected by the photolyzable group. Protecting the thiol group with a photolyzable group can solve the problem of thiol groups having a foul odor and making the ligand inconvenient to use. Moreover, thiol groups protected by photolyzable groups have better stability and are easier to control.

[0224] In some embodiments, the ligand further includes: a coordination group, which is used to coordinate and connect with the quantum dot body; the coordination group includes: at least one of an amino group, a carboxylic acid group, a thiol group, a phosphine group, and a phosphineoxy group.

[0225] Exemplarily, the ligand is selected from at least one of the structures shown in the following general formula IV.

[0226] A-R1-S-PPG Ⅳ

[0227] Wherein, A is a coordinating group; R1 is selected from any one of a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkyl group including an ester bond, and a substituted or unsubstituted alkyl group including an ethylene glycol bond; and PPG is a photolyzable group.

[0228] R1 is a connecting group, and R1 is used to realize the connection between the thiol group protected by the photolyzable group and the coordination group.

[0229] Illustratively, the structural formula of the ligand is shown below.

[0230] The preparation method of the ligand is exemplified below.

[0231] 1) 11 mmol of 3-bromo-2,5,6-trimethyl-pyrazolo[1,2-a]pyrazole-1,7-dione (represented as starting material 1), 10 mmol of ethyl mercaptoacetate, and 11 mmol of triethylamine were dissolved in 100 mL of methanol and reacted at room temperature for 12 hours. The methanol was then removed by concentration under reduced pressure, dissolved in 100 mL of dichloromethane, washed three times with saturated ammonium chloride solution, dried over anhydrous Na₂SO₄, concentrated, and purified by silica gel column chromatography to obtain product 2. The yield of product 2 was 2.82 g, with a yield of 91%. 1H NMR (600 MHz, CDCl₃) δ (ppm): 4.17 (2H), 3.73 (2H), 3.11 (2H), 2.42 (3H), 1.92 (3H), 1.86 (3H), 1.25 (3H).

[0232] 2) In a dry three-necked flask, 24 mmol of NaH was added. After vacuum / nitrogen replacement three times, 8 mmol of product 2 and 50 mL of acetone were added and the reaction was carried out at 40°C for 12 hours under nitrogen protection. Water was then added to quench the NaH. The acetone was then removed by concentration under reduced pressure, and the product was dissolved in 100 mL of dichloromethane. The product was washed three times with saturated brine, dried over anhydrous Na2SO4, concentrated, and purified by silica gel column chromatography to obtain product 3. The yield of product 3 was 2.23 g, and the yield of product 3 was 79%. 1H NMR (600 MHz, CDCl3) δ (ppm): 3.75 (2H), 3.14 (2H), 2.42 (3H), 1.89 (3H), 1.83 (3H).

[0233] 3) 10 mmol of 2-(tritylthio)acetic acid, 10 mmol of ethylene glycol, 50 mg of 4-dimethylaminopyridine, and 150 mg of dichloroethane were dissolved in 50 mL of dichloromethane and reacted at room temperature for 12 hours. The dichloromethane was then concentrated to remove the residue, and the residue was purified by silica gel column chromatography to obtain product 4. The yield of product 4 was 1.1 g, with a yield of 29%. 1H NMR (600 MHz, CDCl3) δ (ppm): 7.30-7.18 (15H), 4.78 (1H), 4.22 (2H), 3.54 (2H), 3.34 (2H).

[0234] 4) 2 mmol of product 3, 2 mmol of product 4, 50 mg of 4-dimethylaminopyridine, and 150 mg of dichloroethane were mixed and dissolved in 10 mL of dichloromethane and reacted at room temperature for 12 hours. After concentration to remove dichloromethane, the product was purified by silica gel column chromatography to obtain product 5. The yield of product 5 was 1.18 g, and the yield of product 5 was 89%. 1H NMR (600 MHz, CDCl3) δ (ppm): 7.30-7.18 (15H), 4.31 (4H), 3.73 (2H), 3.34 (2H), 2.83 (2H), 2.58 (2H), 2.42 (3H), 1.89 (3H), 1.83 (3H).

[0235] 5) 1.5 mmol of product 5 and triethylsilane were dissolved in 10 mL of dichloromethane, cooled to 0°C, and trifluoroacetic acid was added. After 15 minutes, a saturated NaHCO₃ solution was added. After extraction, the organic phase was collected, dried over Na₂SO₄, and concentrated to remove dichloromethane. Purification by silica gel column chromatography afforded the ligand, designated product 6, with a yield of 460 mg and a yield of 74%. 1H NMR (600 MHz, CDCl₃) δ (ppm): 4.31 (4H), 3.73 (2H), 3.34 (2H), 2.83 (2H), 2.58 (2H), 2.42 (3H), 1.89 (3H), 1.83 (3H), 1.52 (1H).

[0236] Furthermore, taking red quantum dots as an example, the steps of connecting the obtained ligand to the quantum dot body include:

[0237] Ligand exchange: 100 mg of red quantum dots with oleic acid ligands and 400 mg of product 6 were dissolved in chloroform, deoxygenated with nitrogen, and then heated under reflux for 4 hours. Then, the mixture was precipitated with ethanol and dissolved with a minimum amount of chloroform. After repeated dissolution and precipitation three times, a red quantum dot material with the above-mentioned ligands was obtained, which was dissolved in octane for storage.

[0238] In some examples, the ligand is selected from at least one of the structures shown in the following formula V.

[0239] A-R5-(R1-S-PPG)n3 Ⅴ

[0240] R5 is selected from any one of a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkyl group including an ester bond, and a substituted or unsubstituted alkyl group including an ethylene glycol bond; and n3≥2.

[0241] R1 and R5 may be the same or different, and there is no limitation here.

[0242] Exemplarily, the value of n3 is 2, and the ligand is selected from at least one of the structures shown in the following general formula.

[0243] Furthermore, in the general formula, the two PPGs may be the same or different; the two R1s may be the same or different, and there is no limitation thereto.

[0244] Exemplarily, the value of n3 is 3, and the ligand is selected from at least one of the structures shown in the following general formula.

[0245] Furthermore, the three PPGs in the general formula may be the same or different; the three R1s may be the same or different, and there is no limitation here.

[0246] By setting the ligand according to the general formula V, a ligand including a plurality of thiol groups protected by photolyzable groups can be provided.

[0247] An embodiment of the present disclosure also provides a quantum dot composition, which includes: a quantum dot body, a ligand and a cross-linker, wherein the ligand is coordinated and connected to the quantum dot body; wherein one of the ligand and the cross-linker has a thiol group protected by a photolyzable group; the photolyzable group is removed under light to release a thiol group, a sulfhydryl radical or a sulfhydryl anion; the released thiol group, sulfhydryl radical or sulfhydryl anion is configured to cross-link at least two of the quantum dot body, the ligand and the cross-linker.

[0248] Exemplarily, the quantum dot body may include a II-VI semiconductor compound, a III-V semiconductor compound, a IV-VI semiconductor compound, a IV semiconductor, a I-III-VI semiconductor compound, a I-II-IV-VI semiconductor compound, a II-III-V semiconductor compound, or a combination thereof. For example, the II-VI semiconductor compound may be selected from: a binary semiconductor compound such as CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, MgSe, MgS, or a mixture thereof; a ternary semiconductor compound such as CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, Cd dZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, MgZnSe, MgZnS, or mixtures thereof; and quaternary semiconductor compounds such as HgZnTeS, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, HgZnSTe, or mixtures thereof, but are not limited thereto. For another example, the III-V semiconductor compound may be selected from: binary semiconductor compounds such as GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, or mixtures thereof; ternary semiconductor compounds such as GaNPs, GaNAs, GaNSb, GaPAs, GaPSb, AlNPs, AlNAs, AlNSb, AlPAs, AlPSb, InNPs, InNAs, InNSb, InPAs, InPSb, or mixtures thereof; and quaternary semiconductor 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. For another example, the IV-VI semiconductor compound can be selected from: binary semiconductor compounds such as SnS, SnSe, SnTe, PbS, PbSe, PbTe, or mixtures thereof; ternary semiconductor compounds such as SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, or mixtures thereof; and quaternary semiconductor compounds such as SnPbSSe, SnPbSeTe, SnPbSTe, or mixtures thereof, but are not limited thereto.The Group IV semiconductor may be, for example, selected from: elemental (mono) semiconductors such as Si, Ge, or mixtures thereof; and binary semiconductor compounds such as SiC, SiGe, and mixtures thereof, but not limited thereto. The Group I-III-VI semiconductor compound may be, for example, CuInSe2, CuInS2, CuInGaSe, CuInGaS, or mixtures thereof, but not limited thereto. The Group I-II-IV-VI semiconductor compound may be, for example, CuZnSnSe, CuZnSnS, or mixtures thereof, but not limited thereto. The Group II-III-V semiconductor compound may include, for example, InZnP, but not limited thereto.

[0249] By configuring one of the ligands and crosslinkers of the quantum dot composition to have a thiol group protected by a photolyzable group, the problem of thiol groups having a foul odor and being inconvenient to use can be effectively solved. Moreover, thiol groups protected by photolyzable groups are more stable and easier to control.

[0250] In some examples, the crosslinker has a thiol group protected by a photolyzable group, and the thiol group, thiol radical, or thiol anion released from the crosslinker is used for coordination connection with the quantum dot body or for reaction with the ligand to form a chemical bond.

[0251] For the introduction of the cross-linking agent having a thiol group protected by a photolyzable group, please refer to the above content and will not be repeated here.

[0252] Regarding the introduction of the thiol groups, sulfur radicals or sulfur anions released from the cross-linking agent for coordination connection with the quantum dot body or for reaction with the ligand to form chemical bonds, please refer to the subsequent content of the light-emitting device 10 and will not be described in detail here.

[0253] In some examples, the ligand includes: a first ligand; the structural formula of the first ligand is A1-R1-D; wherein A1 is a coordinating group capable of coordinating with the quantum dot body; R1 is selected from any one of a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkyl group including an ester bond, and a substituted or unsubstituted alkyl group including an ethylene glycol bond; and D is an activating group.

[0254] For the introduction of the activating group, please refer to the above content and will not be repeated here.

[0255] By providing the first ligand with an activation group, the reaction rate and cross-linking degree between the first ligand coordinated and connected to the quantum dot body and the cross-linking agent can be increased.

[0256] In some examples, the ligand further comprises a second ligand having the structural formula A2-R1. A2 is a coordinating group capable of coordinating with the quantum dot body; R1 is selected from any of a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkyl group including an ester bond, and a substituted or unsubstituted alkyl group including an ethylene glycol bond. R1 of the first ligand and R1 of the second ligand can be the same or different, without limitation.

[0257] That is, a part of the ligand may not be provided with an activating group.

[0258] Exemplarily, the ratio of the mass of the first ligand to the mass of the ligand is greater than or equal to 5%. For example, the ratio of the mass of the first ligand to the mass of the ligand is 5%, 8%, 15%, 20%, 30%, 50%, 70%, 80%, 90% or 100%, etc., and is not limited thereto.

[0259] In other examples, the ligand has a thiol group protected by a photolyzable group, and the released thiol group, thiol radical or thiol anion on the ligand is used to react with a cross-linker to form a chemical bond, to coordinate with the quantum dot body, or to react with another ligand to form a chemical bond.

[0260] Regarding the introduction of the ligand having a thiol group protected by a photolyzable group, please refer to the above content and will not be repeated here.

[0261] Regarding the introduction of the thiol groups, sulfur radicals or sulfur anions released from the ligands to react with crosslinkers to form chemical bonds, to coordinate with the quantum dot bodies or to react with ligands to form chemical bonds, please refer to the subsequent content of the light-emitting device 10 and will not be described in detail here.

[0262] In some examples, the ligand has a thiol group protected by a photolyzable group, and the cross-linking agent includes an activating group; the activating group includes at least one of a carbon-carbon double bond and a carbon-carbon triple bond.

[0263] For the introduction of the activating group, please refer to the above content and will not be repeated here.

[0264] By providing the cross-linking agent with an activation group, the reaction rate and cross-linking degree between the ligand coordinated with the quantum dot body and the cross-linking agent can be increased.

[0265] As shown in FIG4 , an embodiment of the present disclosure further provides a light-emitting device 10 , which includes a hole transport layer 141 and a quantum dot light-emitting layer 13 that are stacked.

[0266] In some embodiments, the material of the hole transport layer 141 is formed by crosslinking a hole transport composition under light conditions. The hole transport composition includes: a hole transport material and a crosslinker; the hole transport material includes: a main chain and side chains connected to the main chain of the hole transport material; at least one of the side chains of the hole transport material and the crosslinker has a thiol group protected by a photodegradable group; the photodegradable group is removed under light to release a thiol group, a thiol radical, or a thiol anion; the released thiol group, thiol radical, or thiol anion is configured to crosslink the hole transport material and the crosslinker to form the hole transport layer 141.

[0267] For the introduction of the hole transport composition, please refer to the above content and will not be repeated here.

[0268] Under light conditions, the photodegradable groups undergo a decomposition reaction. As shown in FIG4 , the material after the decomposition of the photodegradable groups is represented as PPG1. The material of PPG1 includes at least one of the following structural formulas. Wherein, each R3 is independently selected from any one of H, an alkyl group, an electron-withdrawing group, an electron-donating group and a conjugated group.

[0269] Illustratively, the reaction formula for generating sulfide anions and PPG1 after photolysis of the photodegradable group is shown below.

[0270] It should be noted that in FIG4 , a circle is used to represent PPG1. The circle indicates the presence of PPG1 and does not limit the shape of the material after decomposition of the photodegradable group.

[0271] It is understood that the material after the photodegradable group undergoes a decomposition reaction will remain in the hole transport layer 141. Therefore, the hole transport layer 141 includes at least one of the materials after the photodegradable group decomposes.

[0272] In some examples, the material of the hole transport layer 141 further includes a first crosslinking material. The first crosslinking material includes a first group, the first group including a main chain and a side chain connected to the main chain of the first group; and the first crosslinking material further includes a first crosslinking group connected to the side chain of the first group, wherein the side chain of the first group is connected to the first crosslinking group via at least two thioether structures.

[0273] In some examples, the main chain of the first group includes at least one of polycarbazole, polybenzidine, a copolymer of substituted or unsubstituted carbazole and fluorene, and a copolymer of substituted or unsubstituted benzidine and fluorene.

[0274] It should be noted that the hole transport material is cross-linked with the cross-linking agent to form a first group, and the main chain of the first group has hole transport properties.

[0275] Illustratively, the structural formula of the first cross-linking material is as follows.

[0276] Exemplarily, the general formula for the reaction of a cross-linking agent having a thiol group protected by a photolyzable group and a hole transport material having an activating group on its side chain is shown below.

[0277] Wherein, Ra-S-PPG represents a crosslinking agent having a thiol group protected by a photolyzable group, and Ra-S-PPG releases sulfur anions under light conditions, and the sulfur anions react with the activated groups of the side chains of the hole transport material to form a first crosslinking material.

[0278] For example, the structural formula of a cross-linking agent having a mercapto group protected by a photolyzable group is as follows.

[0279] The structural formula of the hole transport material having an activating group on the side chain is as follows.

[0280] Where n≥1.

[0281] The first cross-linked material of the above structural formula is obtained by cross-linking the cross-linking agent and the hole transport material.

[0282] In some examples, the side chain of the first group further includes at least one of an ethylene glycol group and an ester group.

[0283] Exemplarily, the side chain of the hole transport material includes at least one of an ethylene glycol group and an ester group.

[0284] For example, the hole transport material is dissolved in a propylene glycol methyl ether acetate solvent for a cross-linking reaction. By configuring the side chain of the hole transport material to include at least one of an ethylene glycol group and an ester group, the solubility of the hole transport material can be increased.

[0285] In some examples, the first cross-linking group further includes at least one of a triphenylamine group, a carbazole group, and a vicinal triphenylamine group.

[0286] The triphenylamine group, the carbazole group and the vicinal triphenylamine group are hole transport groups. By providing the hole transport groups through the first cross-linking group, the hole transport performance of the first cross-linking material can be improved, thereby improving the performance of the light-emitting device 10 .

[0287] In some embodiments, the material of the quantum dot light-emitting layer 13 is formed by cross-linking a quantum dot composition under light conditions. The quantum dot composition includes: a quantum dot body, a ligand, and a cross-linker, wherein the ligand is coordinated and linked to the quantum dot body; wherein one of the ligand and the cross-linker has a thiol group protected by a photolyzable group; the photolyzable group is removed under light to release a thiol group, a thiol radical, or a thiol anion; and the released thiol group, thiol radical, or thiol anion is configured to cross-link at least two of the quantum dot body, the ligand, and the cross-linker.

[0288] For the introduction of quantum dot compositions, please refer to the above content and will not be repeated here.

[0289] It is understandable that the material after the photodegradable groups undergo decomposition reaction will remain in the quantum dot light-emitting layer 13. Therefore, the quantum dot light-emitting layer 13 includes at least one of the materials after the photodegradable groups undergo decomposition reaction.

[0290] In some embodiments, the quantum dot light-emitting layer 13 includes: quantum dot bodies interconnected by a second cross-linking material; wherein the second cross-linking material includes: a coordination group coordinated with the quantum dot body and a second cross-linking group connected to the coordination group, and the coordination group and the second cross-linking group are connected through a thioether structure.

[0291] Illustratively, the reaction formula for cross-linking the quantum dot composition under light conditions to form the material of the quantum dot light-emitting layer 13 is as follows.

[0292] In the above reaction formula, represents the skeleton structure connected to the functional group (such as sulfhydryl, sulfhydryl, sulfhydryl radical, sulfhydryl anion, active alkenyl group, etc.) in the cross-linking agent or ligand, for example, Represents the first linking group of the cross-linking agent or represents the non-functional part of the ligand. Represents the quantum dot itself.

[0293] In this example, the structural formula of the cross-linking agent is shown below.

[0294] Figure 5 is a luminescence image of a light-emitting device 10 including a red quantum dot light-emitting layer, wherein the crosslinker is the crosslinker provided in Example 3 above, the ligand is mono-[2-[(2-methyl-acryloyl)oxy]ethyl] succinate (denoted as MMES), and the ratio of the mass of the quantum dot body to the mass of the crosslinker is 40:1. The crosslinker crosslinks with the ligands on the quantum dot body to form the red quantum dot light-emitting layer. As can be seen from Figure 5, the light-emitting device 10 emits light uniformly, indicating that this method has formed a red quantum dot light-emitting layer.

[0295] Figure 6 is a scanning electron microscope image of the quantum dot light-emitting layer in the exposed area, and Figure 7 is a scanning electron microscope image of the quantum dot light-emitting layer in the unexposed area. By comparing Figures 6 and 7, it can be seen that the quantum dot composition crosslinks under light conditions to form quantum dot light-emitting layer 13, while the quantum dot composition in the unexposed area does not undergo crosslinking, that is, it does not crosslink to form quantum dot light-emitting layer 13. Figure 7 shows the morphology of substrate 101.

[0296] Exemplarily, the ligand includes a thiol group protected by a photolyzable group, and the crosslinker includes an activating group, for example, pentaerythritol acrylate. In this example, the thiol group protected by the photolyzable group serves as a ligand for the quantum dot body, reacting with the crosslinker to form the material for quantum dot light-emitting layer 13. In the material for quantum dot light-emitting layer 13, the ligand group and the second crosslinking group are connected via a thioether structure.

[0297] By using a thiol protected by a photolyzable group as a ligand of the quantum dot body, the thiol-ene click reaction can be used for cross-linking, which can reduce the temperature of cross-linking and change from thermal cross-linking to photo-cross-linking (or a combination of light and heat), simplifying the film-forming process. The thiol-ene click reaction is a click reaction with a high yield, which can improve the degree of cross-linking and is beneficial to improving the life of the light-emitting device 10. Using a thiol protected by a photolyzable group as a ligand of the quantum dot body can effectively prevent the spontaneous cross-linking of the quantum dot body in the solution and after coating, thereby achieving the effect of light-controlled cross-linking. Suitable photolyzable groups can be selected, and the deprotection reaction rate is high, which does not affect the thiol-ene click reaction. The structural design of the photolyzable group can be used to adjust the response wavelength of exposure, increase the absorbance of the cross-linking agent at the response wavelength, reduce the exposure intensity, and cause less damage to the conjugated repeating units and quantum dots of the hole transport material of the light-emitting device 10, which is beneficial to improving the optical performance and life of the light-emitting device 10.

[0298] In other examples, the second cross-linking material includes: a second cross-linking group, and the second cross-linking group and the quantum dot body are connected through a thioether structure.

[0299] Illustratively, the reaction formula for cross-linking the quantum dot composition under light conditions to form the material of the quantum dot light-emitting layer 13 is as follows.

[0300] In this example, the thiol group has a strong binding force with the metal (such as zinc) on the shell of the quantum dot body. The thiol group is a commonly used coordination group, and the polythiol ligand can become a cross-linking agent for the quantum dot body. The use of a polythiol cross-linking agent protected by a photolyzable group can prevent the quantum dot body from spontaneously cross-linking in the solution and after coating, thereby achieving the effect of light-controlled cross-linking. Moreover, the cross-linking agent can be structurally designed with a thiol group protected by a photolyzable group to adjust the response wavelength of the exposure, increase the absorbance of the cross-linking agent at the response wavelength, reduce the exposure intensity, and cause less damage to the conjugated repeating units and quantum dots of the hole transport material of the light-emitting device 10, which is beneficial to improving the optical performance and life of the light-emitting device 10.

[0301] In this example, there are no restrictions on the ligands on the quantum dot bodies. The ligands can be polar ligands, non-polar ligands, or a mixture of polar and non-polar ligands. Alternatively, the ligands can include activating groups to increase the degree of crosslinking at the same exposure dose.

[0302] Exemplarily, the thiol protected by the photolyzable group serves as a ligand of the quantum dot body and reacts with another quantum dot body to form a second cross-linking material including a second cross-linking group, wherein the second cross-linking group and the quantum dot body are connected via a thioether structure.

[0303] After photolysis, the thiol groups protected by the photodegradable groups can be deprotected and then coordinated with the shell of another quantum dot to form a second crosslinking material, resulting in a crosslinked structure. The ligands of the quantum dot can be polar, non-polar, or a mixture of polar and non-polar ligands.

[0304] In some further examples, the second cross-linking material includes: a first coordination group coordinated with the quantum dot body and a second coordination group coordinated with the quantum dot body, and the first coordination group and the second coordination group are connected through a thioether structure.

[0305] Exemplarily, a quantum dot composition includes two ligands, one of which includes a thiol group protected by a photolyzable group; the photolyzable group is removed upon exposure to light to release a thiol group, a thiol radical, or a thiol anion. The other ligand has the same structure as the first ligand described above, i.e., the structural formula of this ligand is A1-R1-D; wherein A1 is a coordinating group capable of coordinating with the quantum dot body; R1 is selected from any of a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkyl group including an ester bond, and a substituted or unsubstituted alkyl group including an ethylene glycol bond; and D is an activating group.

[0306] That is, the thiol group protected by the photolyzable group serves as one of the ligands of the quantum dot body and reacts with the ligand having an activating group of the quantum dot body to form the quantum dot light-emitting layer 13. The coordination group on the ligand having the thiol group protected by the photolyzable group is called the first coordination group, and the coordination group on the ligand having the activating group is called the second coordination group. When the thiol group protected by the photolyzable group serves as one of the ligands of the quantum dot body and reacts with the ligand having an activating group of the quantum dot body, the thiol group protected by the photolyzable group is deprotected to form a thioether structure, thereby achieving a connection between the first coordination group and the second coordination group.

[0307] This embodiment utilizes both the coordination of thiol groups with the quantum dot shell and the thiol-ene click reaction to connect with the ligand of another quantum dot, thereby increasing the degree of crosslinking. Furthermore, the ligand can be optimized to ensure that the quantum dot meets both photolithographic requirements and high electrical performance. Furthermore, the ligand can be a combination of two or more ligands, and the selection of ligands can further optimize the performance of the light-emitting device 10.

[0308] In some examples, as shown in FIG4 , the light emitting device 10 further includes an anode 11 and a cathode 12 , wherein the anode 11 , the hole transport layer 141 , the quantum dot light emitting layer 13 and the cathode 12 are stacked.

[0309] The light-emitting principle of the light-emitting device 10 is: through a circuit connected by the anode 11 and the cathode 12, the anode 11 is used to inject holes into the quantum dot light-emitting layer 13, and the cathode 12 is used to inject electrons into the quantum dot light-emitting layer 13. The injected electrons and holes form excitons (i.e., electron-hole pairs) in the quantum dot light-emitting layer 13, and the excitons return to the ground state through radiation transition and emit photons.

[0310] For example, in order to ensure that the light-emitting device 10 can effectively emit light, the anode 11 can be made of a material with a high work function, so that the holes generated by the anode 11 can effectively migrate to the quantum dot light-emitting layer 13 under the drive of the electric field, thereby combining with the electrons generated by the cathode 12 to emit light.

[0311] In some examples, the anode 11 may be a transparent electrode, in which case the material of the anode 11 may be indium tin oxide (ITO) or fluorine-doped tin dioxide conductive glass (FTO), or the material of the anode 11 may be a conductive polymer, such as polyaniline, polycarbazole, polythiophene, or polypropiole. In yet other examples, the anode 11 may be an opaque electrode, in which case the material of the anode 11 may be a metal material, such as aluminum or silver.

[0312] For example, the cathode 12 can be made of a material with a low work function, so that the electrons of the cathode 12 can be more easily injected into the film layer adjacent to it (such as the electron transport layer 16). In this way, the electrons generated by the cathode 12 can effectively migrate to the quantum dot light-emitting layer 13 under the drive of the electric field, thereby recombining with the holes generated by the anode 11 to emit light.

[0313] In some examples, the material of cathode 12 can be a metal material, a metal oxide, or a metal alloy. The metal material can be, for example, aluminum, silver, gold, magnesium, calcium, ytterbium, indium, lithium, potassium, sodium, tin, titanium, lead, samarium, or yttrium. The metal oxide can be, for example, indium tin oxide or indium zinc oxide. The metal alloy can be, for example, magnesium-silver alloy, ytterbium-gold alloy, ytterbium-silver alloy, lithium-aluminum alloy, or lithium-calcium-magnesium alloy. Alternatively, the material of cathode 12 can be a laminated material, for example, magnesium / aluminum, magnesium / silver, aluminum / silver, aluminum / gold, ytterbium / gold, ytterbium / silver, calcium / magnesium, calcium / silver, or barium / silver.

[0314] In some embodiments, as shown in FIG4 , to improve luminous efficiency, the light-emitting device 10 further includes a hole injection layer 15, which is located on a side of the hole transport layer 141 away from the quantum dot light-emitting layer 13. The light-emitting device 10 further includes an electron blocking layer (not shown), which is located on a side of the hole transport layer 141 closer to the quantum dot light-emitting layer 13.

[0315] In some embodiments, as shown in FIG4 , to improve luminous efficiency, the light-emitting device 10 further includes an electron transport layer 16 located on the side of the quantum dot light-emitting layer 13 near the cathode 12 . The light-emitting device 10 further includes at least one of an electron injection layer (not shown) and a hole blocking layer (not shown). The electron injection layer is located on the side of the electron transport layer 16 away from the quantum dot light-emitting layer 13 , and the hole blocking layer is located on the side of the electron transport layer 16 near the quantum dot light-emitting layer 13 .

[0316] By setting the hole injection layer 15, the hole transport layer 141 and the electron blocking layer, it is equivalent to setting a transition step between the anode 11 and the quantum dot light-emitting layer 13. By setting the electron injection layer, the electron transport layer 16 and the hole blocking layer, it is equivalent to setting a transition step between the cathode 12 and the quantum dot light-emitting layer 13, thereby reducing the potential barrier height that needs to be overcome for carrier transition, thereby making the light-emitting efficiency of the light-emitting device 10 higher.

[0317] For example, the material of the hole injection layer may be an organic material, such as polyethylenedioxythiophene-polystyrene sulfonate (PEDOT:PSS for short); or, the material of the hole injection layer may be an inorganic oxide, such as molybdenum oxide.

[0318] For example, the material of the electron blocking layer may include 4,4′-cyclohexylidenebis[N,N-bis(p-tolyl)aniline] or 4,4′,4″-Tris(carbazol-9-yl)triphenylamine, etc., but is not limited thereto.

[0319] For example, the material of the hole blocking layer may be 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline.

[0320] For example, the material of the electron transport layer 141 may be zinc oxide or magnesium zinc oxide, etc. Here, zinc oxide and magnesium zinc oxide may be nanoparticles or thin films prepared by a sputtering process.

[0321] For example, the material of the electron injection layer can be a metal, such as Li, Ca or Yb, or a metal salt, such as LiF, LiQ3, etc., which is not limited here.

[0322] As shown in Figure 8, an embodiment of the present disclosure further provides a light-emitting substrate 100, which includes at least one light-emitting device 10 described in any of the above embodiments. The light-emitting substrate 100 also includes a pixel driving circuit for driving the light-emitting device 10 to emit light.

[0323] The light-emitting substrate 100 includes the light-emitting device 10 provided in any of the above embodiments. Therefore, the light-emitting substrate 100 provided in the embodiment of the present disclosure has all the beneficial effects of the light-emitting device 10 provided in any of the above embodiments, which will not be described in detail here.

[0324] As shown in Figure 8, an embodiment of the present disclosure further provides a display device 1000, which includes the light-emitting substrate 100 described in any of the above embodiments. The display device 1000 also includes a driver chip for driving the light-emitting substrate 100 to display.

[0325] Display device 1000 can be any device that displays either moving (e.g., video) or stationary (e.g., still images), and whether text or images. More specifically, it is contemplated that the embodiments described herein can be implemented in or associated with a variety of electronic devices, such as, but not limited to, mobile phones (e.g., cell phones), wireless devices, personal data assistants (PDAs), handheld or portable computers, GPS receivers / navigators, cameras, MP4 video players, video cameras, game consoles, watches, clocks, calculators, television monitors, flat-panel displays, computer monitors, automotive displays (e.g., speedometer displays), navigation systems, cockpit controls and / or displays, camera view displays (e.g., displays for rearview cameras in vehicles), electronic photographs, electronic billboards or signs, projectors, architectural structures, packaging, and aesthetic structures (e.g., displays for images of a piece of jewelry). FIG8 illustrates display device 1000 as a mobile phone.

[0326] The display device 1000 includes the light emitting substrate 100 provided in any of the above embodiments. Therefore, the display device 1000 provided in the embodiment of the present disclosure has all the beneficial effects of the light emitting substrate 100 provided in any of the above embodiments, which will not be described in detail here.

[0327] 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 a person skilled in the art can conceive within the technical scope disclosed in the present disclosure should be included within 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 cross-linking agent comprising: A thiol group protected by a photolyzable group; the photolyzable group is removed under light to release a thiol group, a thiol free radical or a thiol anion.

2. The crosslinking agent according to claim 1, selected from at least one of the structures represented by the following general formula I: PPG-S-R1-S-PPG I in, R1 is selected from any one of a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkyl group including an ester bond, and a substituted or unsubstituted alkyl group including an ethylene glycol bond; and PPG is the photolyzable group.

3. The cross-linking agent according to claim 1, selected from at least one of the structures shown in the following general formula II: R2-(R1-S-PPG) n1 Ⅱ in, R2 is selected from any one of secondary carbon, tertiary carbon and quaternary carbon; n1≥2.

4. The cross-linking agent according to any one of claims 1 to 3, wherein The photolyzable group is selected from at least one of the following substituents; Wherein, each R3 is independently selected from any one of H, an alkyl group, an electron-withdrawing group, an electron-donating group and a conjugated group.

5. The cross-linking agent according to claim 4, selected from at least one of the following structural formulas; 6. The cross-linking agent according to claim 1, further comprising: Carrier transport regulating groups.

7. The cross-linking agent according to claim 6, wherein The cross-linking agent comprises a main chain and a side chain connected to the main chain of the cross-linking agent. The carrier transport regulating group is located on the main chain of the cross-linking agent, and the thiol protected by the photolyzable group is located on the side chain of the cross-linking agent.

8. The cross-linking agent according to claim 7, selected from at least one of the structures represented by the following general formula III: R4-(R1-S-PPG) n2 III in, R4 is a substituted or unsubstituted carrier transport regulating group; n2≥2.

9. The cross-linking agent according to any one of claims 6 to 8, wherein The carrier transport regulating group is a hole transport group, and the hole transport group includes at least one of a triphenylamine group, a carbazole group and a vicinal triphenylamine group.

10. The cross-linking agent according to any one of claims 6 to 9, selected from at least one of the following structural formulas:

11. A hole transport composition comprising: hole transport materials and crosslinkers; The hole transport material includes: a main chain and a side chain connected to the main chain of the hole transport material; wherein at least one of the side chain of the hole transport material and the cross-linking agent has a thiol group protected by a photolyzable group; the photolyzable group is removed under light to release a thiol group, a thiol radical or a thiol anion; The released thiol groups, thiol radicals or thiol anions are configured to cross-link the hole transport material and the cross-linking agent.

12. The hole transport composition according to claim 11, wherein The cross-linking agent is selected from the cross-linking agent according to any one of claims 1 to 10, and the thiol group, thiol radical or thiol anion released from the cross-linking agent is used to react with the side chain of the hole transport material to form a chemical bond.

13. The hole transport composition according to claim 11, wherein The released thiol groups, thiol free radicals or thiol anions are located on the side chains of the hole transport material, and the released thiol groups, thiol free radicals or thiol anions are used to react with the cross-linking agent to form a chemical bond.

14. The hole transport composition according to any one of claims 11 to 13, wherein When the released thiol group, thiol free radical or thiol anion is located on the cross-linking agent, the side chain of the hole transport material further includes: an activation group; when the released thiol group, thiol free radical or thiol anion is located on the side chain of the hole transport material, the cross-linking agent further includes: an activation group; The activating group includes at least one of a carbon-carbon double bond and a carbon-carbon triple bond.

15. The hole transport composition according to claim 14, wherein The activated group having a carbon-carbon double bond includes at least one of a styrene group, an acrylate group, an alkylacrylate group, a maleic anhydride group and a maleimide group.

16. A ligand for coordinating with a quantum dot, comprising: A thiol group protected by a photolyzable group; the photolyzable group is removed under light to release a thiol group, a thiol free radical or a thiol anion.

17. The ligand according to claim 16, wherein The photolyzable group is selected from at least one of the following substituents; Wherein, each R3 is independently selected from any one of H, an alkyl group, an electron-withdrawing group, an electron-donating group and a conjugated group.

18. The ligand according to claim 16 or 17, further comprising: A coordination group is used for coordination connection with the quantum dot body; the coordination group includes at least one of an amino group, a carboxylic acid group, a thiol group, a phosphine group and a phosphinoyl group.

19. The ligand according to claim 18, selected from at least one of the structures represented by the following general formula IV: A-R1-S-PPG IV in, A is the coordinating group; R1 is selected from any one of a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkyl group including an ester bond, and a substituted or unsubstituted alkyl group including an ethylene glycol bond; and PPG is the photolyzable group.

20. The ligand according to claim 19, wherein The structural formula of the ligand includes:

21. The ligand according to claim 18, selected from at least one of the structures represented by the following general formula V: A-R5-(R1-S-PPG)n3 V R5 is selected from any one of a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkyl group including an ester bond, and a substituted or unsubstituted alkyl group including an ethylene glycol bond; and n3≥2.

22. A quantum dot composition comprising: A quantum dot body, a ligand and a cross-linking agent, wherein the ligand is coordinated and connected to the quantum dot body; wherein at least one of the ligand and the cross-linking agent has a thiol group protected by a photolyzable group; the photolyzable group is removed under light to release a thiol group, a thiol radical or a thiol anion; The released thiol groups, thiol radicals or thiol anions are configured to cross-link at least two of the quantum dot body, the ligand and the cross-linking agent.

23. The quantum dot composition according to claim 22, wherein The cross-linking agent is selected from the cross-linking agents according to any one of claims 1 to 10, and the thiol groups, thiol radicals or thiol anions released from the cross-linking agent are used for coordination connection with the quantum dot body or for reacting with the ligand to form a chemical bond.

24. The quantum dot composition according to claim 23, wherein The ligand includes: a first ligand; the structural formula of the first ligand is A1-R1-D; wherein A1 is a coordination group capable of coordinating with the quantum dot body; R1 is selected from any one of a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkyl group including an ester bond, and a substituted or unsubstituted alkyl group including an ethylene glycol bond; and D is an activating group.

25. The quantum dot composition according to claim 24, wherein The ligand further includes: a second ligand; the structural formula of the second ligand is A2-R1; wherein A2 is a coordination group capable of coordinating with the quantum dot body; R1 of the first ligand and R1 of the second ligand are the same or different.

26. The quantum dot composition according to claim 25, wherein The ratio of the mass of the first ligand to the mass of the ligand is greater than or equal to 5%.

27. The quantum dot composition according to claim 22, wherein The ligand is selected from the ligands described in any one of claims 16 to 21, and the thiol group, thiol radical or thiol anion released from the ligand is used to react with the cross-linker to form a chemical bond, to coordinate and connect with the quantum dot body, or to react with another ligand to form a chemical bond.

28. The quantum dot composition according to claim 27, wherein The cross-linking agent includes an activating group; the activating group includes at least one of a carbon-carbon double bond and a carbon-carbon triple bond.

29. A light emitting device comprising: A hole transport layer and a quantum dot light-emitting layer are stacked; The material of at least one of the hole transport layer and the quantum dot light-emitting layer includes at least one of the following materials; Wherein, each R3 is independently selected from any one of H, an alkyl group, an electron-withdrawing group, an electron-donating group and a conjugated group.

30. The light emitting device according to claim 29, wherein The hole transport layer material further includes: a first cross-linking material; Wherein, the first cross-linking material comprises: a first group; the first group comprises: a main chain and a side chain connected to the main chain of the first group; The first cross-linking material further includes: a first cross-linking group connected to the side chain of the first group, and the side chain of the first group is connected to the first cross-linking group through at least two thioether structures.

31. The light emitting device according to claim 30, wherein The first cross-linking group further comprises: at least one of a triphenylamine group, a carbazole group and a vicinal triphenylamine group.

32. The light emitting device according to claim 30 or 31, wherein: The main chain of the first group includes at least one of polycarbazole, polybenzidine, a copolymer of substituted or unsubstituted carbazole and fluorene, and a copolymer of substituted or unsubstituted benzidine and fluorene.

33. The light emitting device according to any one of claims 30 to 32, wherein: The side chain of the first group further comprises at least one of an ethylene glycol group and an ester group.

34. The light emitting device according to any one of claims 29 to 33, wherein: The quantum dot light-emitting layer includes: quantum dot bodies interconnected by a second cross-linking material; Wherein, the second cross-linking material comprises at least one of the following materials; A coordination group coordinated with the quantum dot body and a second cross-linking group connected to the coordination group, wherein the coordination group and the second cross-linking group are connected via a thioether structure; A second cross-linking group, wherein the second cross-linking group and the quantum dot body are connected via a thioether structure; and A first coordination group coordinated with the quantum dot body and a second coordination group coordinated with the quantum dot body, wherein the first coordination group and the second coordination group are connected via a thioether structure.

Images