A hole transport thin film, an optoelectronic device, a preparation method and a display device

Abstract

This application discloses a hole transport thin film, an optoelectronic device, a preparation method, and a display device. The hole transport thin film is made of block copolymers and crosslinked compounds. The block copolymers include fluorene-containing groups, aniline-containing groups, and groups containing first crosslinking groups. The crosslinked compound includes a main chain and at least two second crosslinking groups connected to the main chain. All or part of the hydrogen atoms in the crosslinked compound are replaced by fluorine atoms, and the second crosslinking groups undergo a crosslinking reaction with the first crosslinking groups. The hole transport thin film of this application has a predominantly non-crosslinked structure near the hole injection layer and a predominantly crosslinked structure near the light-emitting layer. This reduces interfacial miscibility between the hole transport thin film and the light-emitting layer, thereby improving the current efficiency of the optoelectronic device.

Description

Technical Field

[0001] This application relates to the field of display technology, and in particular to a hole transport thin film, an optoelectronic device, a preparation method thereon, and a display device. Background Technology

[0002] Optoelectronic devices have wide applications in new energy, sensing, communication, display and lighting fields, such as solar cells, photodetectors, organic light-emitting devices (OLEDs) or quantum dot light-emitting devices (QLEDs).

[0003] Traditional optoelectronic devices mainly consist of an anode, a hole injection layer, a hole transport layer (i.e., a hole transport film), a light-emitting layer, an electron transport layer, an electron injection layer, and a cathode. Under the influence of an electric field, holes generated at the anode and electrons generated at the cathode move and are injected into the hole transport layer and electron transport layer, respectively, eventually migrating to the light-emitting layer. When the two meet in the light-emitting layer, they generate excitons, which excite the light-emitting molecules to ultimately produce visible light.

[0004] Since hole transport is carried out by organic materials and electron transport by inorganic materials, and the electron mobility of inorganic nanoparticles is much greater than that of holes, hole transport materials with high hole mobility are needed to match them. Theoretically, hole transport materials with high hole mobility can improve the above problems, but the actual current efficiency of the devices is not high. Summary of the Invention

[0005] In view of this, this application provides a hole transport thin film, an optoelectronic device, a preparation method, and a display device, aiming to improve the problem of low current efficiency of optoelectronic devices corresponding to hole transport thin films in related technologies.

[0006] The embodiments of this application are implemented as follows: a hole transport film, the hole transport film comprising a block copolymer and a crosslinking compound;

[0007] The block copolymer includes fluorene-containing groups, aniline-containing groups, and groups containing a first crosslinking group;

[0008] The crosslinked compound includes a main chain and at least two second crosslinking groups connected to the main chain, and all or part of the hydrogen atoms in the crosslinked compound are replaced by fluorine atoms. The second crosslinking groups undergo a crosslinking reaction with the first crosslinking groups to form a crosslinked structure in the block copolymer.

[0009] Optionally, the content of the crosslinking compound increases or decreases from one side of the hole transport film to the other.

[0010] Optionally, in some embodiments of this application, the general formula of the block copolymer is:

[0011]

[0012] Where n, m, and p are mole fractions, n + m + p = 1, 0 <n<0.95,0≤m<0.95,0<p<0.05;

[0013] R1 to R5 are the same or different groups, and R1 to R5 are C1 to C20 alkyl, aromatic or heteroaromatic groups;

[0014] R6 is the first crosslinking group.

[0015] Optionally, in some embodiments of this application, the general formula of the crosslinking compound is:

[0016] R8—R9—R 10 ,

[0017] Wherein, R9 is a C1 to C20 alkyl group, or R9 is a C1 to C20 alkyl group, and at least one carbon atom is substituted by a heteroatom. When multiple carbon atoms are substituted by heteroatoms, the heteroatom is located in a non-adjacent position.

[0018] R8 and R 10 These can be the same or different second crosslinking groups.

[0019] Optionally, in some embodiments of this application, the general formula of R6 is chemical formula 2, chemical formula 3, or chemical formula 4:

[0020]

[0021] R7 is a C1 to C20 alkyl, aromatic, or heteroaromatic group.

[0022] Optionally, in some embodiments of this application, when the general formula of R6 is the chemical formula 2, R8 and R... 10 Each group is independently selected from any of the following groups:

[0023]

[0024] Optionally, in some embodiments of this application, when the general formula of R6 is the chemical formula 3, R8 and R... 10 Each group is independently selected from any of the following groups:

[0025]

[0026] Optionally, in some embodiments of this application, when the general formula of R6 is the chemical formula 4, R8 and R... 10 Each group is independently selected from either a primary amino group or a secondary amino group.

[0027] Optionally, in some embodiments of this application, the crosslinking compound has a weight percentage greater than 0 and less than or equal to 5% in the material of the hole transport film.

[0028] This application also provides a method for fabricating an optoelectronic device, comprising the following steps:

[0029] A material solution comprising a block copolymer and a crosslinking compound is provided, wherein the block copolymer comprises fluorene-containing groups, aniline-containing groups, and groups comprising first crosslinking groups; the crosslinking compound comprises a main chain and at least two second crosslinking groups connected to the main chain, and wherein all or part of the hydrogen atoms in the crosslinking compound are replaced by fluorine atoms;

[0030] A substrate is provided, on which an anode is formed. A material solution is disposed on the anode and subjected to crosslinking treatment to obtain a hole transport film, wherein the second crosslinking group and the first crosslinking group undergo a crosslinking reaction.

[0031] A cathode is fabricated on the hole transport film.

[0032] Accordingly, this application also provides an optoelectronic device, including a cathode, a light-emitting layer, a hole transport film and an anode stacked sequentially, wherein the hole transport film includes a first side and a second side, the first side facing the anode and the second side facing the light-emitting layer, and the hole transport film includes a block copolymer and a crosslinked compound;

[0033] The block copolymer includes fluorene-containing groups, aniline-containing groups, and groups containing a first crosslinking group;

[0034] The crosslinked compound includes a main chain and at least two second crosslinking groups connected to the main chain, and all or part of the hydrogen atoms in the crosslinked compound are replaced by fluorine atoms. The second crosslinking groups undergo a crosslinking reaction with the first crosslinking groups to form a crosslinked structure in the block copolymer.

[0035] Optionally, from the first surface to the second surface, the content of the block copolymer decreases and the content of the crosslinking compound increases.

[0036] Accordingly, this application also provides a display device, which includes the above-mentioned optoelectronic device.

[0037] In the hole transport film material of this application embodiment, the fluorene-containing groups and aniline-containing groups in the block copolymer impart hole transport performance to the hole transport film. By controlling the content of the fluorene-containing groups and aniline-containing groups, the highest occupied molecular orbital (HOMO) energy level of the hole transport film can be adjusted to adapt to the HOMO energy levels of different light-emitting layer materials, achieving better hole mobility. Simultaneously, during the process of fabricating the hole transport film from the block copolymer and crosslinking compound, the second crosslinking group in the crosslinking compound and the first crosslinking group in the block copolymer can undergo a crosslinking reaction. Since the crosslinking compound contains at least two second crosslinking groups and the block copolymer contains one first crosslinking group, the crosslinking compound can connect at least two block copolymer molecules, forming a crosslinked structure in the hole transport film. Furthermore, due to the presence of fluorine atoms in the crosslinking compound, it tends to be located in the upper layer of the hole transport film, i.e., the side closer to the light-emitting layer is dominated by the crosslinked structure. Because the cross-linked structure has good solvent resistance, it can prevent the material components of the light-emitting layer from penetrating into the hole transport film, thereby reducing the interfacial missolution between the hole transport film and the light-emitting layer, and thus improving the current efficiency of optoelectronic devices. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a schematic diagram of the structure of an optoelectronic device provided in an embodiment of this application;

[0040] Figure 2 This is a schematic flowchart of a method for fabricating an optoelectronic device according to an embodiment of this application;

[0041] Figure 3 This is a current efficiency test curve of the optoelectronic device of Embodiment 1 of this application;

[0042] Figure 4 This is a current efficiency test curve of the optoelectronic device in Embodiment 2 of this application;

[0043] Figure 5 This is a current efficiency test curve of the optoelectronic device in Embodiment 3 of this application;

[0044] Figure 6 This is a current efficiency test curve of the optoelectronic device in Comparative Example 1.

[0045] Figure 7 This is a current efficiency test curve of the optoelectronic device in Comparative Example 2. Detailed Implementation

[0046] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. In addition, it should be understood that the specific embodiments described herein are only for illustration and explanation of this application and are not intended to limit this application. In this application, unless otherwise stated, directional terms such as "upper" and "lower" specifically refer to the drawing directions in the accompanying drawings. In addition, in the description of this application, the term "including" means "including but not limited to". Various embodiments of the present invention may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and conciseness and should not be construed as a hard limitation on the scope of the present invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single values ​​within that range. For example, it should be assumed that the description of a range from 1 to 6 specifically discloses subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the range referred to.

[0047] In optoelectronic devices such as QLEDs, the core of quantum dot materials is composed of inorganic nanoparticles, and electron transport is also done by inorganic materials. The electron mobility of inorganic nanoparticles is much greater than that of holes, thus requiring hole transport materials with high hole mobility to match them. Theoretically, hole transport materials with high hole mobility can improve the above problem, but the actual current efficiency of the devices is not high.

[0048] Further research by the applicant revealed that the reason why devices using hole transport materials with high hole migration efficiency have low current efficiency is mainly because ligand-modified quantum dot materials have good solubility and stability in solvents. Since the quantum dot emitting layer is typically fabricated on a hole transport film, the good solubility of quantum dot materials makes it easy for the material to seep into the hole transport film along with the solvent during fabrication, leading to interfacial dissolution between the final emitting layer and the hole transport film, thus affecting the current efficiency of the optoelectronic device. Based on this, this application provides a hole transport film as described below to improve the problem of low current efficiency in devices using hole transport materials in related technologies.

[0049] This application provides a hole transport thin film, primarily used in optoelectronic devices. Please refer to... Figure 1 , Figure 1 This is a schematic diagram of the structure of an optoelectronic device provided in an embodiment of this application. The hole transport thin film 10 includes a block copolymer and a crosslinking compound; the block copolymer includes fluorene-containing groups, aniline-containing groups, and groups containing first crosslinking groups; the crosslinking compound includes a main chain and at least two second crosslinking groups connected to the main chain, and all or part of the hydrogen atoms in the crosslinking compound are replaced by fluorine atoms, and the second crosslinking groups undergo a crosslinking reaction with the first crosslinking groups to form a crosslinked structure in the block copolymer.

[0050] It is understood that in the hole transport film 10 of this application embodiment, the fluorene-containing groups and aniline-containing groups in the block copolymer impart hole transport performance to the hole transport film 10. By controlling the content of the fluorene-containing groups and aniline-containing groups, the highest occupied molecular orbital (HOMO) energy level of the hole transport film 10 can be adjusted to adapt to the HOMO energy levels of different light-emitting layer materials, thereby achieving better hole mobility. In the process of fabricating the hole transport film 10 from the block copolymer and the crosslinking compound, the second crosslinking group in the crosslinking compound and the first crosslinking group in the block copolymer can undergo a crosslinking reaction. Since the crosslinking compound contains at least two second crosslinking groups and the block copolymer contains one first crosslinking group, the crosslinking compound can connect at least two block copolymer molecules, thereby forming a crosslinked structure in the hole transport film 10. It should be noted that due to the complexity of polymer chemical reactions, the above crosslinking reaction may not be able to proceed 100% according to the ideal crosslinking reaction model, and some crosslinking compound molecules may only connect to one block copolymer molecule, but at least a certain proportion of crosslinked structures can be formed. Meanwhile, due to the presence of fluorine atoms in the cross-linked compound, it tends to be located in the upper layer of the hole transport film 10 (with... Figure 1 (Referring to the structure of the light-emitting layer), meaning that the side near the light-emitting layer is predominantly cross-linked. Because the cross-linked structure has good solvent resistance, it can prevent the material components of the light-emitting layer from penetrating into the hole transport film 10, thereby reducing interfacial dissolution between the hole transport film 10 and the light-emitting layer, and thus improving the current efficiency of the optoelectronic device.

[0051] As an example, along the thickness direction of the hole transport film 10, from one side to the other, the content of the crosslinking compound increases or decreases. For example, with... Figure 1Taking the optoelectronic device shown as an example, the hole transport thin film 10 can be formed by a wet process. During the wet film formation process, fluorine-containing groups tend to accumulate on the surface of the hole transport thin film 10 (i.e., the side close to the light-emitting layer). Therefore, the hole transport thin film 10 can form a gradient cross-linked structure from the bottom layer (the side close to the hole injection layer) to the top layer (the side close to the light-emitting layer). The closer to the bottom layer, the more the content of the block copolymer, that is, the side close to the hole injection layer is mainly non-cross-linked structure; the closer to the top layer, the more the cross-linked compound, and the cross-linked structure formed by the cross-linked compound can prevent the material components of the light-emitting layer from penetrating into the hole transport thin film 10, thereby reducing the interfacial miscibility between the hole transport thin film 10 and the light-emitting layer, and thus improving the current efficiency of the optoelectronic device.

[0052] In one embodiment, the material of the hole transport thin film 10 is a composition of a block copolymer and a cross-linked compound. The block copolymer includes a fluorene-containing group, an aniline-containing group, and a first cross-linking group-containing group. The cross-linked compound includes a main chain and at least two second cross-linking groups connected to the main chain. The second cross-linking group undergoes a cross-linking reaction with the first cross-linking group, and all or part of the hydrogen atoms in the cross-linked compound are replaced by fluorine atoms. For example, when the cross-linked compound includes two second cross-linking groups, the cross-linked compound can be connected to two block copolymers by the two second cross-linking groups respectively, and the cross-linked compound is connected between the two block copolymers, thereby forming a cross-linked structure of the block copolymer. When the cross-linked compound includes three second cross-linking groups, one cross-linked compound molecule can connect three block copolymer molecules. Due to the complexity of the polymer chemical reaction, the above cross-linking reaction may not be able to proceed 100% according to the ideal cross-linking reaction model, and some cross-linked compound molecules may also only connect one or two block copolymer molecules, but at least a certain proportion of cross-linked structures can be formed. In this embodiment, the material of the hole transport thin film 10 can be only a block copolymer and a cross-linked compound. It can be understood that the material of the hole transport thin film 10 can also include other materials in addition to the block copolymer and the cross-linked compound, such as a high thermal conductivity material to enhance the heat dissipation of the hole transport thin film 10; or a magnetic material to enhance the magnetism of the hole transport thin film 10.

[0053] In one embodiment, the structural general formula of the block copolymer in the hole transport thin film 10 is as follows:

[0054]

[0055] Wherein, n, m, and p are mole fractions, n + m + p = 1, 0 < n < 0.95, 0 ≤ m < 0.95, 0 < p < 0.05; R1 to R5 are the same or different groups, and R1 to R5 are C1 to C20 alkyl groups, aromatic groups or heteroaromatic groups; R6 is a first cross-linking group.

[0056] It is understood that R1 to R5 can be the same substituent, for example, they can be alkyl, aromatic, or heteroaromatic groups simultaneously. R1 to R5 can also be different substituents. For ease of description, the copolymer repeating unit formed by the fluorene-containing group and the triphenylamine-containing group is named unit A, the homopolymer repeating unit formed by the fluorene-containing group is named unit B, and the homopolymer repeating unit formed by the triphenylamine-containing group is named unit C. It is understood that the block copolymer of this embodiment can be a block copolymer including only units A and C, or it can be a block copolymer including units A, B, and C simultaneously. This application does not impose any particular limitation. The molar fraction of unit C can be determined according to the required number of crosslinking structures, and then the corresponding block copolymer structure can be selected. It should be noted that the molar fraction of unit C should be less than 5% to avoid an excessively large proportion of crosslinking groups, which would reduce the current efficiency of the device.

[0057] In one embodiment, the general formula of the crosslinking compound in the material of the hole transport film 10 is:

[0058] R8—R9—R 10 ,

[0059] Wherein, R9 is a C1-C20 alkyl group, or R9 is a C1-C20 alkyl group, and at least one carbon atom is substituted by a heteroatom. When multiple carbon atoms are substituted by heteroatoms, the heteroatoms are located in non-adjacent positions. R8 and R 10 These can be the same or different second crosslinking groups.

[0060] It is understood that the crosslinking compound in this embodiment has R9 as the main chain, which is mainly composed of flexible alkyl groups and may contain heteroatoms. A second crosslinking group R8 and R9 are respectively attached to both ends of the main chain. 10 There are a total of two second crosslinking groups. It should be noted that R8 and R... 10 The second crosslinking group can be either structurally identical or structurally different. By setting a second crosslinking group at each end of the main chain of the hole transport film 10, a network crosslinking structure can be formed inside the hole transport film 10, improving the solvent resistance of the hole transport film 10 and better preventing the material components of the light-emitting layer from penetrating into the hole transport film 10.

[0061] In one embodiment, the first crosslinking group R6 in the block copolymer has the general formula of chemical formula 2, chemical formula 3, or chemical formula 4:

[0062]

[0063] R7 is a C1 to C20 alkyl, aromatic, or heteroaromatic group.

[0064] In this embodiment, the phenylcyclohexane structure of Formula 2 undergoes isomerization upon heating, resulting in the formation of two double bonds, which constitute the first crosslinking bond and react with a crosslinking compound. The isomerization reaction equation for phenylcyclohexane is as follows:

[0065]

[0066] Furthermore, the double bond of butadiene in Formula 3 and the epoxy functional group in Formula 4 can both serve as the first crosslinking bond for the crosslinking reaction. Preferably, the general formula of the first crosslinking group R6 is Formula 4, which has a smaller steric hull, making the crosslinking reaction easier, more efficient, and easier to control. When Formula 3 is used as the first crosslinking group, the crosslinking reaction requires a higher temperature, and when Formula 2 is used, a small amount of reversible reaction occurs, reducing efficiency. Therefore, Formula 4 is the preferred first crosslinking group.

[0067] It should be noted that in this embodiment, the first crosslinking group R6 of the block copolymer has low reactivity for self-crosslinking, and as a side chain of the block copolymer, the first crosslinking group R6 is constrained by the main chain and has weak mobility. Therefore, the first crosslinking group R6 rarely undergoes self-crosslinking reaction, and mainly undergoes crosslinking reaction with the second crosslinking group.

[0068] In one embodiment, when the general formula of the first crosslinking group R6 is chemical 2, the second crosslinking groups R8 and R... 10 Each group is independently selected from any of the following groups:

[0069]

[0070] It is understandable that when the general formula of the first crosslinking group R6 is chemical 2, the second crosslinking groups R8 and R... 10 They can be the same group or different groups. For example, R8 and R 10 They can all be chemical formula 21, or all be chemical formula 22, or all be chemical formula 23, or all be chemical formula 24. For example, the R8 group can be chemical formula 21, R... 10 The functional groups can be chemical formula 22 / 23 / 24, i.e., R8 and R. 10 These are different second crosslinking groups. It is understandable that when R8 and R... 10 When both are chemical formula 23, the first crosslinking group R6 and the second crosslinking groups R8 and R 10 All are phenylcyclohexane, meaning that in this embodiment, the block copolymer and the phenylcyclohexane in the crosslinking compound can undergo a self-crosslinking reaction. When the second crosslinking groups R8 and R... 10When each is independently selected from chemical formula 21 / chemical formula 22 / chemical formula 24, the first crosslinking group R6 can undergo a crosslinking reaction with the epoxy or double bond in the second crosslinking group, so that a network crosslinking structure is formed inside the hole transport film 10, which improves the solvent resistance of the hole transport film 10 and better prevents the material components of the light-emitting layer from penetrating into the hole transport film 10.

[0071] In one embodiment, when the general formula of the first crosslinking group R6 is chemical 3, the second crosslinking groups R8 and R... 10 Each group is independently selected from any of the following groups:

[0072]

[0073] It is understandable that when the general formula of the first crosslinking group R6 is chemical 3, the second crosslinking groups R8 and R... 10 They can be the same group or different groups. For example, R8 and R 10 They can all be chemical formula 31, or all be chemical formula 32, or all be chemical formula 33, or all be chemical formula 34. For example, R8 can be chemical formula 31, R... 10 It can be chemical formula 32 / chemical formula 33 / chemical formula 34, i.e., R8 and R. 10 These are different second crosslinking groups. The double bond of butadiene in chemical formula 3 acts as the first crosslinking bond and undergoes a crosslinking (addition) reaction with the second crosslinking groups (chemical formulas 31-34) to form a network crosslinking structure, which improves the solvent resistance of the hole transport film 10 and better prevents the material components of the light-emitting layer from penetrating into the hole transport film 10.

[0074] In one embodiment, when the general formula of the first crosslinking group R6 is Chemical 4, the second crosslinking groups R8 and R... 10 Each is independently selected from one of the primary amino group (Chemical Formula 41) and the secondary amino group (Chemical Formula 42):

[0075]

[0076] It is understandable that when the general formula of the first crosslinking group R6 is Chemical 4, the second crosslinking groups R8 and R... 10 They can be the same group or different groups. For example, R8 and R 10 They can all be primary amine groups, or they can all be secondary amine groups. For example, R8 is a primary amine group, R... 10 It is a secondary amino group, or R8 is a secondary amino group, R 10 It is a primary amine group, namely R8 and R 10These are different second crosslinking groups. The epoxy functional groups in Formula 4 can all act as first crosslinking bonds to crosslink with the second crosslinking groups (amino groups) to form a network crosslinking structure, which improves the solvent resistance of the hole transport film 10 and better prevents the material components of the light-emitting layer from penetrating into the hole transport film 10.

[0077] In one embodiment, the crosslinking compound has a weight percentage greater than 0 and less than or equal to 5% in the hole transport film material. Since the crosslinking compound is a non-conductive structure, it cannot function as a hole transporter. If its proportion is too high, it will affect the hole transport efficiency; for example, when the crosslinking compound accounts for 50%, the maximum current efficiency of the device is only 10 cd / A. Therefore, when the weight percentage of the crosslinking compound is less than or equal to 5%, it ensures good hole transport efficiency while forming a network crosslinked structure, improving the solvent resistance of the hole transport film 10, and better preventing the material components of the light-emitting layer from penetrating into the hole transport film 10. Simultaneously, when the crosslinking compound concentration is low, the corresponding concentration of the second crosslinking group is also relatively low, which can greatly reduce the probability of the second crosslinking group undergoing self-crosslinking reaction, making the crosslinking reaction mainly occur between the first and second crosslinking groups, resulting in a higher effective utilization rate of the second crosslinking group.

[0078] In one embodiment, the block copolymer in the hole transport film 10 has a weight-average molecular weight greater than or equal to 50,000 and less than or equal to 250,000. For example, the weight-average molecular weight of the block copolymer can be 50,000, 60,000, 70,000, 90,000, 120,000, 150,000, 180,000, 200,000, 250,000, etc. The degree of polymerization of the block copolymer has a significant impact on the interfacial miscibility of the materials. When the weight-average molecular weight of the block copolymer is low, the hole transport film 10 may become interfacially miscible with the light-emitting layer; when the weight-average molecular weight of the block copolymer is too high, it will affect its solubility and dispersibility. Therefore, when the weight-average molecular weight of the block copolymer meets the above conditions, it can better prevent the material components of the light-emitting layer from penetrating into the hole transport film 10 and has good solubility.

[0079] This application also provides a method for fabricating an optoelectronic device. Please refer to [link to relevant documentation]. Figure 2 , Figure 2 This is a schematic flowchart of a method for fabricating an optoelectronic device according to an embodiment of this application. The fabrication method includes the following steps:

[0080] Step S21: Provide a material solution comprising a block copolymer and a crosslinking compound, wherein the block copolymer comprises a fluorene-containing group, an aniline-containing group, and a group comprising a first crosslinking group; the crosslinking compound comprises a main chain and at least two second crosslinking groups connected to the main chain, and all or part of the hydrogen atoms in the crosslinking compound are replaced by fluorine atoms.

[0081] In this step, the block copolymer and crosslinking compound can first be prepared into a material solution. For example, conventional organic solvents can be used to dissolve the block copolymer and crosslinking compound, such as toluene, chlorobenzene, cyclohexylbenzene, methyl benzoate, ethyl benzoate, anisole, etc. The solvent can be a single type or a mixture of two or more different solvents.

[0082] In this embodiment, the order of addition of the block copolymer, crosslinking compound and solvent is not limited, as long as the three are fully mixed to obtain a block copolymer solution.

[0083] Step S22: Provide a substrate, on which an anode is formed. Place the above-mentioned material solution on the anode and perform cross-linking treatment to obtain a hole transport film, wherein the second cross-linking group and the first cross-linking group undergo a cross-linking reaction.

[0084] In this step, there are no restrictions on the type of substrate. The substrate can be a conventionally used substrate, such as a rigid substrate made of glass, or a flexible substrate made of polyimide. The anode 40 can be made of one or more of metals, carbon materials, and metal oxides. For example, metals can be one or more of Al, Ag, Cu, Mo, Au, Ba, Ca, and Mg. Carbon materials can be one or more of graphite, carbon nanotubes, graphene, and carbon fibers. Metal oxides can be doped or undoped metal oxides, including one or more of ITO, FTO, ATO, AZO, GZO, IZO, MZO, and AMO. Composite electrodes can also include those with metal sandwiched between doped or undoped transparent metal oxides. Composite electrodes include, but are not limited to, one or more of AZO / Ag / AZO, AZO / Al / AZO, ITO / Ag / ITO, ITO / Al / ITO, ZnO / Ag / ZnO, ZnO / Al / ZnO, TiO2 / Ag / TiO2, TiO2 / Al / TiO2, ZnS / Ag / ZnS, ZnS / Al / ZnS, TiO2 / Ag / TiO2, and TiO2 / Al / TiO2. In one embodiment, an anode 40 is formed on a substrate, and a hole transport film 10 comprising a block copolymer and a crosslinked compound is disposed on the anode 40. In another embodiment, an anode 40 and a hole injection layer 50 are formed on a substrate, and a hole transport film 10 comprising a block copolymer and a crosslinked compound is disposed on the hole injection layer 50. If the optoelectronic device further includes other functional layers, then correspondingly, other functional layers may also be formed on the substrate.

[0085] The block copolymers and crosslinking compounds in this embodiment can be referred to the relevant descriptions in the above embodiments, and will not be repeated here.

[0086] Specifically, a solution method can be used to deposit a material solution comprising block copolymers and crosslinking compounds onto a substrate. Solution methods include, but are not limited to, spin coating, drop coating, coating, inkjet printing, blade coating, dip coating, immersion coating, spray coating, roller coating, vapor deposition, or casting, etc., to obtain a wet film. Then, a crosslinking treatment is performed to form a crosslinked structure of the block copolymer, resulting in a hole transport film 10. Due to the presence of fluorine atoms, the crosslinking compound tends to be located in the upper layer of the hole transport film 10 (i.e.,...). Figure 1 (Referring to the structure of the original text), thus the hole transport film 10 forms a gradient molecular structure from the bottom layer to the top layer. The closer to the top layer, the higher the content of cross-linking compounds and the more cross-linked structures there are; the closer to the bottom layer, the lower the content of cross-linking compounds and the fewer cross-linked structures there are. That is, the content of cross-linking compounds increases from the side facing the anode to the side away from the anode.

[0087] For example, the wet film on the substrate can first undergo a first heat treatment to evaporate the organic solvent in the wet film and form a molten hole transport film. Then, the hole transport film can undergo a second heat treatment to crosslink and solidify the second crosslinking groups in the crosslinking compound with the first crosslinking groups in the block copolymer. The temperature of the second heat treatment is higher than that of the first heat treatment. For example, the temperature of the first heat treatment can be less than 100°C, such as 95°C, 80°C, 70°C, 60°C, 50°C, 40°C, etc. The higher the temperature, the faster the solvent evaporates. Vacuum drying at room temperature can also be used. The temperature of the second heat treatment can be between 100°C and 200°C, such as 100°C, 120°C, 140°C, 160°C, 180°C, 190°C, 200°C, etc.

[0088] In this embodiment, the thickness of the final hole transport film can be controlled and adjusted by controlling and adjusting conditions such as the solution concentration used in the solution method. The thickness of the hole transport film can range from 10 to 50 nm, such as 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 40 nm, and 50 nm. Taking spin coating as an example, the thickness of the hole transport film can be controlled by adjusting the solution concentration, spin coating speed, and spin coating time.

[0089] Step S23: Fabricate a cathode on a hole transport film.

[0090] The material of cathode 20 is a known cathode material in the art, and the material of anode 40 described above can be selected. This step will not be repeated. The thickness of cathode 20 is a known cathode thickness in the art, for example, it can be from 10nm to 200nm, such as 10nm, 35nm, 50nm, 80nm, 120nm, 150nm, 200nm, etc.

[0091] It should be noted that the anode 40, the light-emitting layer 30, the cathode 20, and other functional layers in this application can all be prepared using conventional techniques in the art, including but not limited to solution methods and deposition methods. Solution methods include, but are not limited to, spin coating, coating, inkjet printing, blade coating, dip-coating, immersion, spraying, roller coating, or casting. Deposition methods include chemical methods and physical methods. Chemical methods include, but are not limited to, chemical vapor deposition, continuous ion layer adsorption and reaction, anodic oxidation, electrolytic deposition, or co-precipitation. Physical methods include, but are not limited to, thermal evaporation coating, electron beam evaporation coating, magnetron sputtering, multi-arc ion plating, physical vapor deposition, atomic layer deposition, or pulsed laser deposition. When the anode 40, the light-emitting layer 30, the cathode 20, and other functional layers are prepared using solution methods, a drying process must be added.

[0092] It is understandable that the preparation method of optoelectronic devices may also include an encapsulation step. The encapsulation material may be acrylic resin or epoxy resin. The encapsulation may be machine encapsulation or manual encapsulation. Ultraviolet curing adhesive may be used. The concentration of oxygen and water in the environment where the encapsulation step is carried out is less than 0.1 ppm to ensure the stability of the optoelectronic device.

[0093] In this embodiment, a material solution containing block copolymers and crosslinking compounds is deposited on a substrate to form a hole transport film. During film formation, the second crosslinking group in the crosslinking compound and the first crosslinking group in the block copolymer can undergo a crosslinking reaction. Since the crosslinking compound contains at least two second crosslinking groups and the block copolymer contains one first crosslinking group, the crosslinking compound can connect at least two block copolymer molecules, thus forming a crosslinked structure in the hole transport film 10. Simultaneously, due to the presence of fluorine atoms in the crosslinking compound, it tends to be located in the upper layer of the hole transport film 10 (i.e.,...). Figure 1 (Referring to the structure of the original text), during the film formation process, fluorine-containing groups tend to accumulate at the interface between the hole transport film 10 and air (on the side near the light-emitting layer). Therefore, the hole transport film 10 forms a gradually cross-linked structure from the bottom layer (the side near the hole injection layer) to the top layer (the side near the light-emitting layer). The closer to the bottom layer, the higher the content of the block copolymer; that is, the side near the hole injection layer is dominated by a non-cross-linked structure. The closer to the top layer, the higher the content of cross-linked compounds, and thus the higher the content of the cross-linked structure; that is, the side near the light-emitting layer is dominated by a cross-linked structure. Because the cross-linked structure has good solvent resistance, it can prevent the material components of the light-emitting layer from penetrating into the hole transport film 10. Therefore, the hole transport film 10 prepared in this embodiment can reduce the interfacial miscibility between the hole transport film 10 and the light-emitting layer, thereby improving the current efficiency of the optoelectronic device.

[0094] Please see Figure 1 This application also provides an optoelectronic device 100, which includes a cathode 20, a light-emitting layer 30, a hole transport film 10, and an anode 40 stacked sequentially. The hole transport film 10 includes a first side and a second side, with the first side facing the anode 40 and the second side facing the light-emitting layer 30. The hole transport film 10 includes a block copolymer and a crosslinking compound. The block copolymer includes fluorene-containing groups, aniline-containing groups, and groups containing first crosslinking groups. The crosslinking compound includes a main chain and at least two second crosslinking groups connected to the main chain. All or part of the hydrogen atoms in the crosslinking compound are replaced by fluorine atoms. The second crosslinking groups undergo a crosslinking reaction with the first crosslinking groups to form a crosslinked structure in the block copolymer.

[0095] The cathode 20 is made of materials known in the art for cathodes, and the anode 40 is made of materials known in the art for anodes. Please refer to the relevant descriptions above, which will not be repeated here.

[0096] The light-emitting layer 30 can be a quantum dot light-emitting layer, and the optoelectronic device 100 can be a quantum dot optoelectronic device. The thickness of the light-emitting layer 30 can be within the range of the thickness of the light-emitting layer in quantum dot optoelectronic devices known in the art, for example, it can be 5nm to 100nm, such as 5nm, 10nm, 20nm, 50nm, 80nm, 100nm, etc.; or it can be 60-100nm.

[0097] The material of the quantum dot emitting layer is a quantum dot known in the art for use in quantum dot emitting layers, such as one of red quantum dots, green quantum dots, and blue quantum dots. The quantum dots can be selected from, but are not limited to, at least one of single-structure quantum dots and core-shell structure quantum dots. For example, quantum dots may be selected from, but are not limited to, at least one of group II-VI compounds, group III-V compounds, and group I-III-VI compounds; the group II-VI compounds are selected from at least one of CdSe, CdS, CdTe, ZnSe, ZnS, CdTe, ZnTe, CdZnS, CdZnSe, CdZnTe, ZnSeS, ZnSeTe, ZnTeS, CdSeS, CdSeTe, CdTeS, CdZnSeS, CdZnSeTe, and CdZnSTe; the group III-V compounds are selected from InP, InAs, GaP, GaAs, GaSb, AlN, AlP, InAsP, InNP, InNSb, GaAlNP, and InAlNP; and the group I-III-VI compounds are selected from at least one of CuInS2, CuInSe2, and AgInS2.

[0098] The hole transport thin film 10 can be referred to in the relevant description above, and will not be repeated here.

[0099] In this embodiment, the hole transport film 10 in the optoelectronic device 100 includes a block copolymer and a crosslinking compound. The second crosslinking group in the crosslinking compound can undergo a crosslinking reaction with the first crosslinking group in the block copolymer. Since the crosslinking compound contains at least two second crosslinking groups and the block copolymer contains one first crosslinking group, the crosslinking compound can connect at least two block copolymer molecules, thereby forming a crosslinked structure in the hole transport film 10. Simultaneously, due to the presence of fluorine atoms in the crosslinking compound, it tends to be located in the upper layer of the hole transport film 10 (i.e.,...). Figure 1 (The structure is referenced here), meaning that the side near the light-emitting layer is predominantly cross-linked. Because the cross-linked structure has good solvent resistance, it can prevent the material components of the light-emitting layer from penetrating into the hole transport film 10. Therefore, in the optoelectronic device 100 of this embodiment, the interfacial missolution between the hole transport film 10 and the light-emitting layer is less frequent, resulting in higher current efficiency for the optoelectronic device 100.

[0100] As an example, from the first side (facing the anode 40) to the second side (facing the light-emitting layer 30) of the hole transport film 10, the content of block copolymers decreases while the content of crosslinking compounds increases. Since fluorine-containing groups tend to accumulate on the surface of the hole transport film 10 (i.e., the side near the light-emitting layer), the hole transport film 10 can form a gradually changing crosslinked structure from the bottom layer (the side near the hole injection layer) to the top layer (the side near the light-emitting layer). The closer to the bottom layer, the higher the content of block copolymers; that is, the side near the hole injection layer is predominantly non-crosslinked. The closer to the top layer, the higher the content of crosslinking compounds. The crosslinked structure formed by these compounds prevents the material components of the light-emitting layer from penetrating into the hole transport film 10, thereby reducing interfacial miscibility between the hole transport film 10 and the light-emitting layer, and thus improving the current efficiency of the optoelectronic device.

[0101] Further reading Figure 1 In one embodiment, the optoelectronic device 100 may further include a hole injection layer (HIL) 50. The hole injection layer 50 is located between the hole transport film 10 and the anode 40. The material of the hole injection layer 50 may be selected from materials with hole injection capability, including but not limited to one or more of PEDOT:PSS, MCC, CuPc, F4-TCNQ, HATCN, transition metal oxides, and transition metal chalcogenides. PEDOT:PSS is a high molecular block copolymer, also known as poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid). The thickness of the hole injection layer 50 may be, for example, from 10 nm to 100 nm, such as 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 100 nm, etc.

[0102] Further reading Figure 1 In one embodiment, the optoelectronic device 100 may further include an electron transport layer 60, which is located between the cathode 20 and the light-emitting layer 30. The electron transport layer 60 may be an oxide semiconductor nanomaterial with electron transport capability, and the oxide semiconductor nanomaterial may be selected from, but is not limited to, at least one of ZnO, TiO2, SnO2, Ta2O3, ZrO2, NiO, TiLiO, ZnAlO, ZnMgO, ZnSnO, ZnLiO, and InSnO.

[0103] It is understandable that, in addition to the functional layers mentioned above, the optoelectronic device 100 may also have some conventional functional layers used in optoelectronic devices to improve their performance, such as electron blocking layers, hole blocking layers, electron injection layers, and interface modification layers. It is also understandable that the materials and thicknesses of each layer of the optoelectronic device 100 can be adjusted according to the light-emitting requirements of the optoelectronic device 100.

[0104] In some embodiments of this application, the optoelectronic device 100 is a quantum dot light-emitting diode, and its structure can be glass substrate-anode-(hole injection layer)-hole transport layer-quantum dot light-emitting layer-electron transport layer-cathode. The hole injection layer is optional; the quantum dot light-emitting diode structure may or may not include a hole injection layer.

[0105] This application also provides a display device, including the optoelectronic device provided in this application. The display device can be any electronic product with display function, including but not limited to smartphones, tablets, laptops, digital cameras, digital camcorders, smart wearable devices, smart weighing scales, in-vehicle displays, televisions, or e-book readers. Among them, smart wearable devices can be, for example, smart bracelets, smartwatches, virtual reality (VR) headsets, etc.

[0106] The technical solutions and effects of this application will be described in detail below through specific embodiments, comparative examples and experimental examples. The following embodiments are only some embodiments of this application and are not intended to limit this application.

[0107] Example 1

[0108] This embodiment provides a quantum dot light-emitting diode and its fabrication method. The structural composition of the quantum dot light-emitting diode is described in [reference]. Figure 1 The quantum dot light-emitting diode of this embodiment includes a cathode 20, an electron transport layer 60, a light-emitting layer 30, a hole transport film 10, a hole injection layer 50 and an anode 40 stacked sequentially from top to bottom.

[0109] The materials of each layer in a quantum dot light-emitting diode are:

[0110] The cathode 20 is made of Al and has a thickness of 25 nm.

[0111] The material of electron transport layer 60 is Zn 0.7 Mg 0.3 O.

[0112] The material of the light-emitting layer 30 is nano-ZnS.

[0113] The hole transport film 10 is made of a block copolymer (95% wt) and a crosslinking compound (5% wt) as described in this application. The block copolymer has the general formula described above, a weight-average molecular weight of 90,000, and a molecular weight dispersion index of 2.8. R1 to R5 are alkyl groups containing 3 carbon atoms, and R6 contains benzocyclobutane. The crosslinking compound has the general formula described above, in which some hydrogen atoms are replaced by fluorine. R9 is an alkyl backbone containing 6 carbon atoms, and R8 and R... 10They are the same crosslinking groups, and the structural formula is as follows:

[0114]

[0115] The material of the hole injection layer 50 is PEDOT:PSS.

[0116] The anode 40 is made of ITO with a thickness of 100 nm, and a glass substrate is provided on one side of the anode 40.

[0117] The method for fabricating the quantum dot light-emitting diode in this embodiment includes the following steps:

[0118] Materials for preparing hole transport film 10: Block copolymer and crosslinking compound are dissolved in ethyl benzoate to obtain hole transport material solution (12 mg / mL).

[0119] Anode 40 is prepared on a glass substrate.

[0120] PEDOT:PSS was spin-coated on the side of the anode 40 away from the glass substrate at a speed of 5000 for 30 seconds, followed by annealing at 200°C for 15 minutes to obtain the hole injection layer 50.

[0121] A hole transport material solution is spin-coated on the side of the hole injection layer 50 away from the anode 40 at a speed of 3000 rpm for 30 seconds. Then, it is dried at 90°C and annealed at 140°C to obtain the hole transport film 10.

[0122] CdZnSe quantum dots are spin-coated on the side of the hole transport film 10 away from the hole injection layer 50, and then annealed to obtain the light-emitting layer 30.

[0123] Zn is spin-coated on the side of the light-emitting layer 30 away from the hole transport film 10. 0.9 Mg 0.1 O, then undergoes annealing to obtain electron transport layer 60.

[0124] Al cathode 20 is prepared by vapor deposition on the side of electron transport layer 60 away from light-emitting layer 30.

[0125] Example 2

[0126] This embodiment provides a quantum dot light-emitting diode and its preparation method. Compared with the quantum dot light-emitting diode of Embodiment 1, the only difference is that the hole transport film 10 is made of a block copolymer (99% wt) and a crosslinking compound (1% wt) as described in this application. The block copolymer has the general formula described above, a weight-average molecular weight of 100,000, and a molecular weight dispersion index of 1.8. R1 to R5 are alkyl groups containing 10 carbon atoms, and R6 contains cyclohexane. The crosslinking compound has the general formula described above, where R9 is an alkyl backbone containing 3 carbon atoms, and R8 and R... 10 It is a primary amino group.

[0127] Example 3

[0128] This embodiment provides a quantum dot light-emitting diode and its preparation method. Compared with the quantum dot light-emitting diode of Embodiment 1, the only difference is that the hole transport film 10 is made of a block copolymer (97% wt) and a crosslinking compound (3% wt) as described in this application. The block copolymer has the general formula described above, a weight-average molecular weight of 120,000, and a molecular weight dispersion index of 2.4. R1, R2, R4, and R5 are alkyl groups containing 10 carbon atoms, R3 is an alkyl group containing 15 carbon atoms, and R6 contains cyclohexane. The crosslinking compound has the general formula described above, where R9 is an alkyl backbone containing 6 carbon atoms, and R8 and R... 10 They are the same crosslinking groups, and the structural formula is as follows:

[0129]

[0130] Comparative Example 1

[0131] Comparative Example 1 provides a quantum dot light-emitting diode and its fabrication method. The only difference between this comparative example and the quantum dot light-emitting diode of Example 1 is the material of the hole transport film 10. The hole transport film 10 of Comparative Example 1 is made of cross-linked TFB.

[0132] Comparative Example 2

[0133] Comparative Example 1 provides a quantum dot light-emitting diode and its fabrication method. Compared with the quantum dot light-emitting diode of Example 1, the only difference of the quantum dot light-emitting diode of this comparative example is that the hole transport film 10 is made of non-crosslinked TFB.

[0134] Current efficiency tests were performed on Examples 1-3 and Comparative Examples 1 and 2, and the test curves are shown below. Figures 3-7 As shown, the maximum current efficiency (cd / A) of Examples 1-3 and Comparative Examples 1 and 2 can be obtained as follows: 100, 125, 89, 61, and 32, respectively.

[0135] The test results show that the maximum current efficiency of Comparative Example 1 is higher than that of Comparative Example 2, indicating that the cross-linked TFB hole transport film can improve the current efficiency of optoelectronic devices compared to the non-cross-linked TFB hole transport film. Furthermore, the maximum current efficiency of Examples 1-3 is higher than that of Comparative Example 1, indicating that the optoelectronic devices corresponding to the graded cross-linked hole transport films of Examples 1-3 of this application have even higher current efficiency.

[0136] In summary, the hole transport film of this application comprises a block copolymer and a crosslinking compound. The block copolymer includes fluorene-containing groups, aniline-containing groups, and groups containing a first crosslinking group. The crosslinking compound includes a main chain and at least two second crosslinking groups connected to the main chain. All or part of the hydrogen atoms in the crosslinking compound are replaced by fluorine atoms. The second crosslinking groups undergo a crosslinking reaction with the first crosslinking groups to form a crosslinked structure in the block copolymer. By controlling the content of the fluorene-containing groups and the aniline-containing groups, the highest occupied molecular orbital (HOMO) energy level of the hole transport film 10 can be adjusted to adapt to the HOMO energy levels of materials in different light-emitting layers, achieving a better hole mobility. Simultaneously, during the fabrication of the hole transport film 10 from the block copolymer and the crosslinking compound, the second crosslinking groups in the crosslinking compound and the first crosslinking groups in the block copolymer can undergo a crosslinking reaction. Since the crosslinking compound contains at least two second crosslinking groups and the block copolymer contains one first crosslinking group, the crosslinking compound can connect at least two block copolymer molecules, forming a crosslinked structure in the hole transport film 10. Furthermore, due to the presence of fluorine atoms in the cross-linked compound, it tends to be located in the upper layer of the hole transport film 10 (with... Figure 1 (Referring to the structure of the light-emitting layer), meaning that the side near the light-emitting layer is predominantly cross-linked. Because the cross-linked structure has good solvent resistance, it can prevent the material components of the light-emitting layer from penetrating into the hole transport film 10, thereby reducing interfacial dissolution between the hole transport film 10 and the light-emitting layer, and thus improving the current efficiency of the optoelectronic device.

[0137] The hole transport thin film and its preparation method, optoelectronic device and its preparation method, and display device provided in the embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the methods and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A hole transport thin film, characterized in that, The hole transport film comprises block copolymers and crosslinked compounds; The block copolymer includes fluorene-containing groups, aniline-containing groups, and groups containing a first crosslinking group; The crosslinked compound includes a main chain and at least two second crosslinking groups connected to the main chain, and all or part of the hydrogen atoms in the crosslinked compound are replaced by fluorine atoms. The second crosslinking groups undergo a crosslinking reaction with the first crosslinking groups to form a crosslinked structure in the block copolymer. Along the thickness direction of the hole transport film, from one side to the other, the content of the crosslinking compound increases or decreases. The general formula of the cross-linked compound is: R8—R9—R 10 , Wherein, R9 is a C1-C20 alkyl group, or R9 is a C1-C20 alkyl group, and at least one carbon atom is substituted by a heteroatom. When multiple carbon atoms are substituted by heteroatoms, the heteroatom is located in a non-adjacent position. R8 and R 10 These can be the same or different second crosslinking groups.

2. The hole transport thin film according to claim 1, characterized in that, The general formula of the block copolymer is: ， Where n, m, and p are mole fractions, n + m + p = 1, 0 <n<0.95,0≤m<0.95,0<p<0.05; R1 to R5 are the same or different groups, and R1 to R5 are C1 to C20 alkyl, aromatic or heteroaromatic groups; R6 is the first crosslinking group.

3. The hole transport thin film according to claim 2, characterized in that, The general formula of R6 is chemical formula 2, chemical formula 3, or chemical formula 4: 、 、 ， Chemical formula 2 Chemical formula 3 Chemical formula 4 R7 is a C1-C20 alkyl, aromatic, or heteroaromatic group.

4. The hole transport thin film according to claim 3, characterized in that, When the general formula of R6 is the chemical formula 2, R8 and R 10 Each group is independently selected from any of the following groups: 、 、 、 。 5. The hole transport thin film according to claim 3, characterized in that, When the general formula of R6 is the chemical formula 3, R8 and R 10 Each group is independently selected from any of the following groups: 、 、 、 。 6. The hole transport thin film according to claim 3, characterized in that, When the general formula of R6 is the chemical formula 4, R8 and R 10 Each group is independently selected from either a primary amino group or a secondary amino group.

7. The hole transport thin film according to claim 1, characterized in that, The crosslinking compound has a weight percentage greater than 0 and less than or equal to 5% in the material of the hole transport film.

8. A method for fabricating an optoelectronic device, characterized in that, Includes the following steps: A material solution comprising a block copolymer and a crosslinking compound is provided, wherein the block copolymer comprises fluorene-containing groups, aniline-containing groups, and groups comprising first crosslinking groups; the crosslinking compound comprises a main chain and at least two second crosslinking groups connected to the main chain, and all or part of the hydrogen atoms in the crosslinking compound are replaced by fluorine atoms; A substrate is provided, on which an anode is formed. A material solution is disposed on the anode and subjected to crosslinking treatment to obtain a hole transport film, wherein the second crosslinking group and the first crosslinking group undergo a crosslinking reaction. A cathode is fabricated on the hole transport film; Along the thickness direction of the hole transport film, from one side to the other, the content of the crosslinking compound increases or decreases. The general formula of the cross-linked compound is: R8—R9—R 10 , Wherein, R9 is a C1-C20 alkyl group, or R9 is a C1-C20 alkyl group, and at least one carbon atom is substituted by a heteroatom. When multiple carbon atoms are substituted by heteroatoms, the heteroatom is located in a non-adjacent position. R8 and R 10 These can be the same or different second crosslinking groups.

9. A photoelectric device comprising a cathode, a light-emitting layer, a hole transport film, and an anode sequentially stacked, wherein the hole transport film includes a first surface and a second surface, the first surface facing the anode and the second surface facing the light-emitting layer, characterized in that... The hole transport film comprises block copolymers and crosslinked compounds; The block copolymer includes fluorene-containing groups, aniline-containing groups, and groups containing a first crosslinking group; The crosslinked compound includes a main chain and at least two second crosslinking groups connected to the main chain, and all or part of the hydrogen atoms in the crosslinked compound are replaced by fluorine atoms. The second crosslinking groups undergo a crosslinking reaction with the first crosslinking groups to form a crosslinked structure in the block copolymer. From the first surface to the second surface, the content of the block copolymer decreases, and the content of the crosslinking compound increases; The general formula of the cross-linked compound is: R8—R9—R 10 , Wherein, R9 is a C1-C20 alkyl group, or R9 is a C1-C20 alkyl group, and at least one carbon atom is substituted by a heteroatom. When multiple carbon atoms are substituted by heteroatoms, the heteroatom is located in a non-adjacent position. R8 and R 10 These can be the same or different second crosslinking groups.

10. A display device, characterized in that, The display device includes the optoelectronic device as described in claim 9.

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