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 fabrication method, and a display device. The hole transport thin film comprises a first polymer and a second polymer. The first polymer is a conductive polymer material. The second polymer is a block polymer comprising a first block and a second block. The first block is a copolymer block formed by fluorene-containing groups and aniline-containing groups, and the second block is also a copolymer block formed by fluorene-containing groups and aniline-containing groups. Furthermore, the aniline-containing groups in the second block are connected to electron-donating groups. All or part of the hydrogen atoms in the second polymer are replaced by fluorine atoms. In this application, the second polymer, primarily located in the top layer, contains electron-donating groups, which can increase the LUMO energy level of the top layer of the hole transport thin film, increasing the difficulty for electrons to transition from the luminescent material layer to the hole transport layer, thereby reducing the aging rate of the hole transport layer.

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 while electron transport is carried out by inorganic materials, and the electron migration efficiency of inorganic nanoparticles is much greater than that of holes, this leads to a large accumulation of charge at the interface between the hole transport layer and the quantum dot emitting layer. Consequently, a small number of electrons jump to the hole transport layer under the influence of an electric field, forming excitons. This accelerates the aging of the hole transport material, affecting device efficiency and lifetime. Therefore, it is necessary to develop a hole transport layer material to reduce electron jumps to the hole transport layer, thereby reducing the aging rate of the hole transport layer. 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 accelerated aging of hole transport materials due to electron transition to the hole transport layer in related technologies.

[0006] The embodiments of this application are implemented as follows: a hole transport film, the hole transport film comprising a first polymer and a second polymer;

[0007] The first polymer is a conductive polymer material;

[0008] The second polymer is a block polymer comprising a first block and a second block, wherein the first block is a copolymer block formed by a fluorene-containing group and an aniline-containing group, the second block is a copolymer block formed by a fluorene-containing group and an aniline-containing group, and the aniline-containing group in the second block is attached to an electron-donating group.

[0009] In the second polymer, all or part of the hydrogen atoms are replaced by fluorine atoms.

[0010] Optionally, in some embodiments of the present application, along the thickness direction of the hole-transporting thin film, from one side to the other side, the content of the second polymer increases or decreases.

[0011] Optionally, in some embodiments of the present application, the molar fraction of the second block in the second polymer is greater than or equal to 0.1% and less than or equal to 15%.

[0012] Optionally, in some embodiments of the present application, the LUMO energy level of the second polymer is greater than or equal to -2.5 eV and less than or equal to -1.8 eV.

[0013] Optionally, in some embodiments of the present application, the electron-donating group is an electron-donating group with a heterocyclic structure.

[0014] Optionally, in some embodiments of the present application, the structural general formula of the second polymer is as follows:

[0015]

[0016] Wherein, the molar fraction of the first block is n, the molar fraction of the second block is m, and 0.001 ≤ m ≤ 0.15;

[0017] R1 to R3 are the same or different groups, and R1 to R3 are C1 - C20 alkyl groups, aromatic groups or heteroaromatic groups; <00,sup>[0000042]]

[0018] R4 is an electron-donating group with a heterocyclic structure.

[0019] Optionally, in some embodiments of the present application, the second polymer further includes a third block, and the third block includes a self-crosslinking group.

[0020] Optionally, in some embodiments of the present application, the structural general formula of the second polymer is as follows:

[0021]

[0022] Wherein, the molar fraction of the third block is q, and 0 < q ≤ 0.05, and R5 is a group containing a crosslinking bond.

[0023] Optionally, in some embodiments of the present application, R5 is one of the following structural formulas:

[0024]

[0025] Wherein, R6 is a C1 - C20 alkyl group, or R6 is a C1 - C20 alkyl group and at least one carbon atom is replaced by a heteroatom. When there are multiple carbon atoms replaced by heteroatoms, the heteroatoms are located at non-adjacent positions.

[0026] Optionally, in some embodiments of this application, R4 is selected from at least one of carbazole groups, triazole groups, and triazine groups.

[0027] Optionally, in some embodiments of this application, the conductive polymer material is polyaniline, polythiophene, polyfluorene, or a copolymer formed from at least two of polyaniline, polythiophene, and polyfluorene.

[0028] Optionally, in some embodiments of this application, the weight-average molecular weight of the hole transport film material is greater than or equal to 50,000 and less than or equal to 250,000.

[0029] This application also provides a method for fabricating an optoelectronic device, comprising the following steps:

[0030] A material solution comprising a first polymer and a second polymer is provided, wherein the first polymer is a conductive polymer; the second polymer is a block polymer comprising a first block and a second block, wherein the first block is a copolymer block formed by a fluorene-containing group and an aniline-containing group, and the second block is a copolymer block formed by a fluorene-containing group and an aniline-containing group, and wherein the aniline-containing group in the second block is attached to an electron-donating group; all or part of the hydrogen atoms in the second polymer are replaced by fluorine atoms;

[0031] A substrate is provided, on which an anode is formed. The material solution is placed on the anode and dried to obtain a hole transport film.

[0032] A cathode is fabricated on the hole transport film.

[0033] 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 first polymer and a second polymer.

[0034] The first polymer is a conductive polymer material;

[0035] The second polymer is a block polymer comprising a first block and a second block, wherein the first block is a copolymer block formed by a fluorene-containing group and an aniline-containing group, the second block is a copolymer block formed by a fluorene-containing group and an aniline-containing group, and the aniline-containing group in the second block is attached to an electron-donating group.

[0036] In the second polymer, all or part of the hydrogen atoms are replaced by fluorine atoms.

[0037] Optionally, in some embodiments of this application, the content of the first polymer decreases from the first surface to the second surface, while the content of the second polymer increases.

[0038] Accordingly, this application also provides a display device, which includes the above-mentioned optoelectronic device.

[0039] The hole transport film of this application includes a first polymer and a second polymer; the first polymer is a conductive polymer material; the second polymer is a block polymer including a first block and a second block, wherein the first block is a copolymer block formed by a fluorene-containing group and an aniline-containing group, and the second block is a copolymer block formed by a fluorene-containing group and an aniline-containing group, and the aniline-containing group in the second block is attached to an electron-donating group; all or part of the hydrogen atoms in the second polymer are replaced by fluorine atoms.

[0040] The hole transport film in this embodiment comprises a first polymer and a second polymer. During the fabrication of the hole transport film, the second polymer, due to the presence of fluorine atoms, tends to be located on the upper layer of the hole transport film. This is because fluorine atoms have high electronegativity, small atomic radii, short CF bonds, and bond energies as high as 500 kJ / mol. The mutual repulsion between adjacent fluorine atoms causes them to not lie in the same plane, but rather to be distributed helically along the carbon chain. In particular, in a perfluorocarbon chain, the sum of the van der Waals radii of two fluorine atoms is approximately 0.27 nm, essentially surrounding and filling the CCC bond. This almost void-free spatial barrier prevents any atom or group from entering and breaking the CCC bond. Therefore, during film formation, fluorine-containing groups tend to accumulate at the interface between the hole transport film 10 and air (on the side closer to the light-emitting layer) and extend into the air. Consequently, the closer to the top layer (on the side closer to the light-emitting layer), the higher the content of the second polymer.

[0041] Since the second polymer, which is mainly located in the top layer, contains electron-donating groups, it can increase the LUMO energy level of the top layer of the hole transport film. The increase in the LUMO energy level of the top layer of the hole transport film increases the difficulty for electrons to jump from the light-emitting material layer to the hole transport layer, thereby reducing the aging rate of the hole transport layer and thus improving the lifetime of optoelectronic devices. Attached Figure Description

[0042] 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.

[0043] Figure 1 This is a schematic diagram of the structure of an optoelectronic device provided in an embodiment of this application;

[0044] Figure 2 This is a schematic flowchart of a method for fabricating an optoelectronic device according to an embodiment of this application;

[0045] Figure 3 This is a schematic diagram of the energy levels of each functional layer of an optoelectronic device provided in Embodiment 1 of this application;

[0046] Figure 4 This is a schematic diagram of the energy levels of each functional layer of an optoelectronic device provided in Embodiment 2 of this application;

[0047] Figure 5 This is a schematic diagram of the energy levels of each functional layer of an optoelectronic device provided in Embodiment 3 of this application. Detailed Implementation

[0048] 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.

[0049] In optoelectronic devices such as QLEDs, hole transport is carried out by organic materials while electron transport is carried out by inorganic materials. The electron migration efficiency of inorganic nanoparticles is much greater than that of holes. This leads to a large accumulation of charge at the interface between the hole transport layer and the quantum dot light-emitting layer. Consequently, a small number of electrons jump to the hole transport layer under the influence of an electric field, forming excitons and accelerating the aging of the hole transport material. Based on this, this application provides a hole transport thin film as described below to improve the problem of accelerated aging of hole transport materials caused by electron migration to the hole transport material in related technologies.

[0050] This application provides a hole transport thin film 10, mainly used in optoelectronic devices 100. 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 first polymer and a second polymer; the first polymer is a conductive polymer material; the second polymer is a block polymer including a first block and a second block, wherein the first block is a copolymer block formed by a fluorene-containing group and an aniline-containing group, and the second block is a copolymer block formed by a fluorene-containing group and an aniline-containing group, and the aniline-containing group in the second block is connected to an electron-donating group; all or part of the hydrogen atoms in the second polymer are replaced by fluorine atoms.

[0051] It should be noted that the aniline-containing group in the embodiments can be a diphenylamine-containing group or a triphenylamine-containing group, and this application does not make any special limitation.

[0052] It is understood that, in the process of fabricating the hole transport film 10 in this embodiment, the second polymer, due to the presence of fluorine atoms, tends to be located in the upper layer of the hole transport film 10 (i.e.,...). Figure 1 (The structure is for reference only). This is because fluorine atoms have high electronegativity, small atomic radii, short CF bonds, and bond energies as high as 500 kJ / mol. The mutual repulsion between adjacent fluorine atoms causes them to not lie in the same plane, but rather to be distributed helically along the carbon chain. Especially in perfluorocarbon chains, the sum of the van der Waals radii of two fluorine atoms is approximately 0.27 nm, essentially surrounding and filling the CCC bond. This almost gapless spatial barrier prevents any atom or group from entering and breaking the CCC bond. Therefore, during film formation, fluorine-containing groups tend to accumulate at the interface between the hole transport film 10 and air (on the side closer to the light-emitting layer) and extend into the air. Thus, the closer to the top layer (on the side closer to the light-emitting layer), the higher the content of the second polymer.

[0053] Since the second polymer, which is mainly located in the top layer, contains electron-donating groups, it can increase the LUMO (Lowest Unoccupied Molecular Orbital) energy level of the top layer of the hole transport film 10. The increase in the LUMO energy level of the top layer of the hole transport film 10 increases the difficulty of electrons jumping from the light-emitting material layer to the hole transport layer, thereby reducing the aging rate of the hole transport layer and thus improving the lifetime of optoelectronic devices.

[0054] As an example, along the thickness direction of the hole transport film 10, from one side to the other, the content of the second polymer increases or decreases. For example, with... Figure 1 Taking the illustrated optoelectronic device as an example, a hole transport film 10 can be formed using a wet process. During the wet film formation process, fluorine-containing groups tend to accumulate on the surface of the hole transport film 10 (i.e., the side near the light-emitting layer). Therefore, the hole transport film 10 can form a gradient molecular 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 first polymer; the closer to the top layer, the higher the content of the second polymer. Since the second polymer, mainly located in the top layer, contains electron-donating groups, it can increase the LUMO energy level of the top layer of the hole transport film. Corresponding to the gradient molecular structure from the bottom layer to the top layer, the hole transport film 10 can form a gradient LUMO energy level that gradually increases from the bottom layer to the top layer. The increase in the LUMO energy level of the top layer of the hole transport film increases the difficulty for electrons to jump from the light-emitting material layer to the hole transport layer, thereby reducing the aging rate of the hole transport layer and thus improving the lifetime of the optoelectronic device.

[0055] In one embodiment, the hole transport film 10 is a composition of a first polymer and a second polymer. The first polymer is a conductive polymer. The second polymer is a block polymer comprising a first block and a second block. The first block is a copolymer block formed by a fluorene-containing group and an aniline-containing group, and the second block is also a copolymer block formed by a fluorene-containing group and an aniline-containing group. Furthermore, the aniline-containing group in the second block is attached to an electron-donating group. All or part of the hydrogen atoms in the second polymer are replaced by fluorine atoms. That is, the hole transport film 10 is made solely of the first polymer and the second polymer. It is understood that the hole transport film 10 may also include other materials besides the first and second polymers, such as a high thermal conductivity material to enhance the heat dissipation of the hole transport film 10, or a magnetic material to enhance the magnetism of the hole transport film 10.

[0056] In one embodiment, the conductive polymer material can be polyaniline, polythiophene, polyfluorene, or a copolymer formed from at least two of polyaniline, polythiophene, and polyfluorene. For example, polyaniline can be poly(N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine) (poly-TPD), polythiophene can be poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) (PEDOT:PSS), and polyfluorene can be poly(9,9-dioctylfluorene-co-bis-N,N-phenyl-1,4-phenylenediamine) (PFB), poly(9,9-dioctylfluorene-CO-N-(4-butylphenyl)diphenylamine) (TFB), etc. The conductive polymer material can be one or more of the above materials, or it can be a block copolymer including the corresponding functional groups. The embodiments of this application do not particularly limit the specific materials used.

[0057] In one embodiment, the molar fraction of the second block in the second polymer is greater than or equal to 0.1% and less than or equal to 15%. Since the aniline-containing groups in the second block are linked to electron-donating groups, if the molar fraction of the second block is too high, the content of electron-donating groups will also increase. Excessive electron-donating groups will reduce the hole transport efficiency of the hole transport film 10. Therefore, the molar fraction of the second block in the second polymer is preferably no more than 15%.

[0058] In one embodiment, the LUMO energy level of the second polymer is greater than or equal to -2.5 eV and less than or equal to -1.8 eV. For example, the LUMO energy level of the second polymer can be -2.5 eV, -2.3 eV, -2.2 eV, -2.1 eV, -2.0 eV, -1.9 eV, -1.8 eV, etc. The second polymer is mainly located on the side closer to the light-emitting layer on the hole transport film 10. When the LUMO energy level of the second polymer meets the above conditions, the LUMO energy level difference between the hole transport film 10 and the light-emitting layer can exceed 1.5 eV, which can reduce the probability of electrons transitioning from the light-emitting layer to the hole transport film 10. Furthermore, the HOMO energy level of the second polymer is preferably less than or equal to -5.2 eV, for example, it can be -5.2 eV, -5.3 eV, -5.4 eV, etc. Since the higher the molar fraction of aniline-containing groups, the higher the HOMO energy level of the second polymer, the HOMO energy level of the second polymer can be adjusted by adjusting the molar fraction of aniline-containing groups, so that the top HOMO energy level of the hole transport film 10 is closer to the light-emitting layer, thereby improving the hole mobility.

[0059] In one embodiment, the material of the hole transport film 10 has the following general structural formula for the second polymer:

[0060]

[0061] Wherein, the mole fraction of the first block is n, the mole fraction of the second block is m, and 0.001≤m≤0.15;

[0062] R1 to R3 are the same or different groups, and R1 to R3 are C1 to C20 alkyl, aromatic or heteroaromatic groups, while R4 is an electron-donating group with a heterocyclic structure.

[0063] It is understood that R1 to R3 can be the same substituent, for example, they can be alkyl, aromatic, or heteroaromatic groups simultaneously. R1 to R3 can also be different substituents. The copolymer repeating unit formed by the fluorene-containing group and the triphenylamine-containing group is the first block, and the copolymer repeating unit formed by the fluorene-containing group and the diphenylamine-containing group is the second block. The R4 group in the second block is an electron-donating group. For example, the electron-donating group can be dialkylamino (-NR2), alkylamino (-NHR), amino (-NH2), hydroxyl (-OH), alkoxy (-OR), amide (-NHCOR), acyloxy (-OCOR), etc. Preferably, the electron-donating group in this application is a heterocyclic electron-donating group. For example, the heterocyclic electron-donating group can be selected from at least one of carbazole groups, triazole groups, and triazine groups. When the heterocyclic electron-donating group is selected from two or three of the above groups, it can be understood that the second block includes two or three sub-blocks, each sub-block containing one electron-donating group. Heteroatoms can increase the electron cloud density of carbon atoms on the ring, thereby increasing the LUMO energy level of the top layer of the hole transport film 10. This can prevent electrons from jumping from the light-emitting layer to the hole transport film 10, and at the same time, it will not affect the hole transport efficiency when the content is not particularly high.

[0064] In one embodiment, the second polymer in the hole transport film 10 further includes a third block, which comprises a self-crosslinking group. As described above, the hole transport film 10 forms a gradient molecular 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 first polymer; the closer to the top layer, the higher the content of the second polymer. Simultaneously, since the second polymer also includes a self-crosslinking group, a self-crosslinking reaction occurs during the molding of the hole transport film 10, making the side of the hole transport film near the light-emitting layer primarily a crosslinked polymer. This provides better solvent resistance and prevents the material components of the light-emitting layer from penetrating into the hole transport film, thus reducing hole transport efficiency. Therefore, the hole transport film 10 of this embodiment not only increases the difficulty of electron transition from the light-emitting material layer to the hole transport film 10, thereby reducing the aging rate of the hole transport layer, but also reduces interfacial miscibility between the hole transport film 10 and the light-emitting layer, thereby improving current efficiency.

[0065] In one embodiment, the general structural formula of the second polymer is as follows:

[0066]

[0067] Among them, the molar fraction of the third block is q, and 0.001 ≤ m ≤ 0.15, 0 < q ≤ 0.05, and R5 is a self-crosslinking group containing a crosslinking bond.

[0068] It can be understood that the above group including R5 is the third block. The crosslinking bond in R5 can form a crosslinked structure inside the second polymer. R5 can be a group containing a thermal crosslinking bond and undergoes a crosslinking reaction by heating, or it can be a group containing an ultraviolet light-responsive crosslinking bond and undergoes a crosslinking reaction by ultraviolet light irradiation. It should be noted that since the self-crosslinking group does not have conductivity, the molar fraction of the third block should not be higher than 5%. An excessively high content of the self-crosslinking group will significantly reduce the electron transport efficiency.

[0069] In one embodiment, R5 in the second polymer is one of the following structural formulas:

[0070]

[0071] Among them, R6 is an alkyl group with 1 to 20 carbon atoms, or R6 is an alkyl group with 1 to 20 carbon atoms and at least one carbon atom is substituted by a heteroatom. When there are multiple carbon atoms substituted by heteroatoms, the heteroatoms are located at non-adjacent positions. In the above R5 group, the double bond in Chemical Formula 1 can undergo an addition reaction, thereby forming a crosslinked structure between the second polymers. The molecular structure of Chemical Formula 2 will undergo isomerization when heated, and the reaction equation is as follows:

[0072]

[0073] After isomerization, two double bonds are formed, which can enable crosslinking reaction between the second polymers to obtain a crosslinked polymer. The crosslinked structure has better solvent resistance and can prevent small molecules in the light-emitting layer from infiltrating into the hole-transporting thin film 10 (i.e., interfacial miscibility), thereby improving the hole migration efficiency and the stability of the optoelectronic device.

[0074] In one embodiment, the weight-average molecular weight of the material of the hole transport film 10 is greater than or equal to 50,000 and less than or equal to 250,000. For example, the weight-average molecular weight of the first polymer or the second polymer can be 50,000, 70,000, 90,000, 120,000, 150,000, 180,000, 200,000, 230,000, 250,000, etc. If the weight-average molecular weight of the first polymer or the second polymer is too small, the hole transport film 10 may become interfacially miscible with the adjacent functional layer, affecting the luminous efficiency. For example, when the weight-average molecular weight of the first polymer or the second polymer is small, the hole transport film 10 may become interfacially miscible with the hole injection layer, or the hole transport film 10 may become interfacially miscible with the light-emitting layer. If the weight-average molecular weight of the first polymer or the second polymer is too large, it will affect its solubility in the solvent and the subsequent wet film formation process.

[0075] 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:

[0076] Step S21: Provide a material solution comprising a first polymer and a second polymer, wherein the first polymer is a conductive polymer material; the second polymer is a block polymer comprising a first block and a second block, wherein the first block is a copolymer block formed by a fluorene-containing group and an aniline-containing group, and the second block is a copolymer block formed by a fluorene-containing group and an aniline-containing group, and the aniline-containing group in the second block is attached to an electron-donating group; all or part of the hydrogen atoms in the second polymer are replaced by fluorine atoms.

[0077] In this step, the first polymer and the second polymer can be first prepared into a polymer material solution. For example, conventional organic solvents can be used to dissolve the first polymer and the second polymer, 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.

[0078] In this embodiment, the order of adding the first polymer, the second polymer, and the solvent is not limited, as long as the three are fully mixed to obtain a polymer solution.

[0079] Step S22: Provide a substrate on which an anode is formed. Place the above-mentioned material solution on the anode and perform a drying process to obtain a hole transport film.

[0080] 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 first polymer and a second polymer material 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.

[0081] The first polymer and the second polymer in this embodiment can be referred to the relevant descriptions in the above embodiments, and will not be repeated here.

[0082] Specifically, a solution method can be used to deposit a material solution comprising a first polymer and a second polymer onto a substrate. Solution methods include, but are not limited to, spin coating, drop coating, coating, inkjet printing, blade coating, dip-coating, immersion, spraying, roller coating, vapor deposition, or casting, etc., to prepare a wet film. Then, a drying process is performed to obtain a hole transport film. During film formation, the second polymer, due to the presence of fluorine atoms, tends to be located on the upper layer of the hole transport film 10 (i.e., fluorine atoms). Figure 1 (Referring to the structure), thus the hole transport film 10 forms a gradient molecular structure from the bottom layer (the side near the hole injection layer) to the top layer (the side near the light-emitting layer), that is, from the side facing the anode to the side away from the anode, the content of the second polymer increases.

[0083] In one embodiment, when the second polymer does not include self-crosslinking groups, 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 hole transport film. Then, the hole transport film undergoes a second heat treatment at a temperature higher than the first heat treatment. The second heat treatment is used to eliminate residual stress within the hole transport film, thereby reducing the risk of layer deformation and cracking. 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 wet film dries. Vacuum drying at room temperature can also be used. The temperature of the second heat treatment can be between 100°C and 250°C, for example, 100°C, 130°C, 160°C, 180°C, 200°C, 220°C, 240°C, 250°C, etc. It is understandable that the second heat treatment can be an annealing process, which includes sequential heating, holding and cooling processes. For example, the dry hole transport film is heated to 220°C and held for 30 minutes, and then cooled to room temperature at a rate of 5°C / min.

[0084] In one embodiment, when the second polymer includes self-crosslinking groups, the drying process may simultaneously include a crosslinking and curing step. For example, if the self-crosslinking groups in the second polymer contain thermal crosslinking bonds, a heating method can be used for crosslinking. For instance, a first heat treatment can be performed on the wet film on the substrate to evaporate the organic solvent in the wet film and form a molten hole transport film, followed by a second heat treatment to crosslink and cure the second polymer. The temperature of the second heat treatment is higher than that of the first heat treatment, as detailed above. Alternatively, if the self-crosslinking groups in the second polymer contain UV-responsive crosslinking groups, the crosslinking reaction can be carried out by UV irradiation. For example, the first heat treatment process described above can be used to evaporate the organic solvent and form a molten hole transport film, followed by UV irradiation with a wavelength of 365 nm to crosslink and cure the hole transport film.

[0085] 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.

[0086] Step S23: Fabricate a cathode on a hole transport film.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] In this embodiment, a material solution containing a first polymer and a second polymer is deposited on a substrate to form a hole transport film. During film formation, the second polymer containing fluorine groups tends to accumulate at the interface between the hole transport film 10 and air (on the side near the light-emitting layer) and extends into the air. Therefore, the hole transport film 10 forms a gradient molecular 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 first polymer; the closer to the top layer, the higher the content of the second polymer. Since the second polymer, mainly located in the top layer, contains electron-donating groups, it can increase the LUMO energy level of the top layer of the hole transport film 10. Corresponding to the gradient molecular structure from the bottom to the top layer, the hole transport film 10 can form a gradient LUMO energy level that gradually increases from the bottom to the top layer. The increase in the LUMO energy level of the top layer of the hole transport film 10 increases the difficulty for electrons to jump from the light-emitting material layer to the hole transport layer, thereby reducing the aging rate of the hole transport layer and improving the lifetime of the optoelectronic device.

[0091] Therefore, the hole transport film 10 prepared in this embodiment can reduce the probability of electrons transitioning to the hole transport layer and reduce the aging rate of the hole transport layer while meeting the basic hole mobility requirements, thereby improving the lifespan of optoelectronic devices.

[0092] 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 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 first polymer and a second polymer. The first polymer is a conductive polymer material. The second polymer is a block polymer including a first block and a second block. The first block is a copolymer block formed by a fluorene-containing group and an aniline-containing group, and the second block is a copolymer block formed by a fluorene-containing group and an aniline-containing group. In the second block, the aniline-containing group is connected to an electron-donating group. All or part of the hydrogen atoms in the second polymer are replaced by fluorine atoms.

[0093] 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. The light-emitting layer 30 can be a quantum dot light-emitting layer, in which case 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 thicknesses of light-emitting layers 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.

[0094] 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.

[0095] The hole transport thin film 10 can be referred to in the relevant description above, and will not be repeated here.

[0096] In this embodiment, the hole transport film 10 in the optoelectronic device 100 includes a first polymer and a second polymer. The second polymer, containing fluorine groups, tends to accumulate at the interface between the hole transport film 10 and air (on the side near the light-emitting layer) and extends into the air. Therefore, the hole transport film 10 forms a gradient molecular 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 first polymer; the closer to the top layer, the higher the content of the second polymer. Furthermore, since the second polymer contains electron-donating groups, it can increase the LUMO energy level of the top layer of the hole transport film 10. The increase in the LUMO energy level of the top layer of the hole transport film 10 increases the difficulty for electrons to jump from the light-emitting material layer to the hole transport layer, thereby reducing the aging rate of the hole transport layer and thus improving the lifetime of the optoelectronic device.

[0097] 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 the first polymer decreases while the content of the second polymer increases. Since the fluorine-containing groups of the second polymer tend to accumulate on the surface of the hole transport film 10 (i.e., the side closer to the light-emitting layer), the hole transport film 10 can form a gradient molecular structure from the bottom layer (the side closer to the hole injection layer) to the top layer (the side closer to the light-emitting layer). The closer to the bottom layer, the higher the content of the first polymer; the closer to the top layer, the higher the content of the second polymer. Since the second polymer, mainly located in the top layer, contains electron-donating groups, it can increase the LUMO energy level of the top layer of the hole transport film. Corresponding to the gradient molecular structure from the bottom to the top layer, the hole transport film 10 can form a gradient LUMO energy level that gradually increases from the bottom to the top layer. The increase in the LUMO energy level of the top layer of the hole transport film increases the difficulty for electrons to jump from the light-emitting material layer to the hole transport layer, thereby reducing the aging rate of the hole transport layer and thus improving the lifetime of the optoelectronic device.

[0098] 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 polymer, and its Chinese name is 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] Example 1

[0105] 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.

[0106] The materials of each layer in a quantum dot light-emitting diode are:

[0107] The cathode 20 is made of Al.

[0108] The material of electron transport layer 60 is Zn 0.7 Mg 0.3 O.

[0109] The material of the light-emitting layer 30 is nano-ZnS.

[0110] The hole transport film 10 is made of a first polymer (60% wt) and a second polymer (40% wt) as described in this application, wherein the first polymer is TFB; the second polymer has the following general formula, wherein R1 to R3 are alkyl groups containing 5 carbon atoms, R4 is an imidazole group, and the molar fraction of the second polymer is 3%; R5 is an olefin containing 6 carbon atoms, and some H atoms are substituted.

[0111]

[0112] The material of the hole injection layer 50 is PEDOT:PSS.

[0113] 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.

[0114] The method for fabricating the quantum dot light-emitting diode in this embodiment includes the following steps:

[0115] Materials for preparing hole transport film 10: Dissolve the first polymer and the second polymer in cyclohexylbenzene to obtain a hole transport material solution (13 mg / mL).

[0116] Anode 40 is prepared on a glass substrate.

[0117] 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.

[0118] 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 40°C and annealed at 230°C to obtain the hole transport film 10.

[0119] 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.

[0120] 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.

[0121] Al cathode 20 is prepared by vapor deposition on the side of electron transport layer 60 away from light-emitting layer 30.

[0122] After heat treatment, the LUMO level of the hole transport film 10 is a graded level, and it is located closer to the light-emitting layer 30. The LUMO level of the hole transport film 10 can reach -2.1 eV. Please refer to the energy level diagram. Figure 3 .

[0123] Example 2

[0124] 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 of the quantum dot light-emitting diode of this embodiment is that the substituent R4 in the second polymer of the hole transport film 10 is different. R4 is a carbazole group and its molar fraction in the second polymer is 15%.

[0125] After heat treatment, the LUMO level of the hole transport film 10 is a graded level, and it is located closer to the light-emitting layer 30. The LUMO level of the hole transport film 10 can reach -2.0 eV. Please refer to the energy level diagram. Figure 4 .

[0126] Example 3

[0127] 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 of the quantum dot light-emitting diode of this embodiment is that the hole transport film 10 is made of a first polymer (80% wt) and a second polymer (20% wt) of this application. The first polymer is polyaniline and its derivatives. In the second polymer, R1 to R3 are methyl, R4 is triazole, and the molar fraction of the second polymer is 5%. R5 is phenylpropane containing 12 carbon atoms.

[0128] After heat treatment, the LUMO level of the hole transport film 10 is a graded level, and it is located closer to the light-emitting layer 30. The LUMO level of the hole transport film 10 can reach -2.2 eV. Please refer to the energy level diagram. Figure 5 .

[0129] As can be seen from the energy level diagrams of Examples 1-3, the LUMO energy level of the hole transport film 10 is a graded energy level. In Example 1, the LUMO energy level of the hole transport film 10 is increased from -3.4 eV to -2.1 eV, which increases the LUMO energy level difference between the hole transport film 10 and the light-emitting layer to 2.0 eV. In Example 2, the LUMO energy level of the hole transport film 10 is increased from -3.4 eV to -2.0 eV, which increases the LUMO energy level difference between the hole transport film 10 and the light-emitting layer to 2.1 eV. In Example 3, the LUMO energy level of the hole transport film 10 is increased from -3.4 eV to -2.2 eV, which increases the LUMO energy level difference between the hole transport film 10 and the light-emitting layer to 1.9 eV.

[0130] The widening of the LUMO energy level difference between the hole transport film 10 and the light-emitting layer increases the difficulty for electrons to transition from the light-emitting material layer to the hole transport layer, thereby reducing the aging rate of the hole transport layer and thus improving the lifespan of optoelectronic devices.

[0131] The hole transport thin film, optoelectronic device, 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 method 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 thin film comprises a first polymer and a second polymer; The first polymer is a conductive polymer material, and the conductive polymer material is polyaniline, polythiophene, polyfluorene or a copolymer formed by at least two of polyaniline, polythiophene and polyfluorene; The second polymer is a block polymer comprising a first block and a second block. The first block is a copolymer block formed by a fluorene-containing group and an aniline-containing group, and the second block is a copolymer block formed by a fluorene-containing group and an aniline-containing group. And the aniline-containing group in the second block is connected with an electron-donating group; All or part of the hydrogen atoms in the second polymer are substituted by fluorine atoms; Along the thickness direction of the hole transport thin film, from one side to the other side, the content of the second polymer increases or decreases.

2. The hole transport thin film according to claim 1, characterized in that, The molar fraction of the second block in the second polymer is greater than or equal to 0.1% and less than or equal to 15%.

3. The hole transport thin film according to claim 1, characterized in that, The LUMO energy level of the second polymer is greater than or equal to -2.5 eV and less than or equal to -1.8 eV.

4. The hole transport thin film according to claim 1, characterized in that, The electron-donating group is an electron-donating group with a heterocyclic structure.

5. The hole transport thin film according to claim 4, characterized in that, The second polymer comprises the following structural general formula: ， Wherein, the molar fraction of the first block is n, and the molar fraction of the second block is m, and 0.001≤m≤0.15; R1~R3 are the same or different groups, and R1~R3 are C1~C20 alkyl groups, aromatic groups or heteroaromatic groups; R4 is an electron-donating group with a heterocyclic structure.

6. The hole transport thin film according to claim 5, characterized in that, The second polymer further comprises a third block, and the third block comprises a self-crosslinking group.

7. The hole transport thin film according to claim 6, characterized in that, The structural general formula of the second polymer is as follows: ， 8. The hole transport thin film according to claim 7, characterized in that, Wherein, the molar fraction of the third block is q, and 0<q≤0.05, and R5 is a group containing a crosslinking bond. 、 ， The R5 is one of the following structural formulas:

9. The hole transport thin film according to any one of claims 5-8, characterized in that, Wherein, R6 is a C1~C20 alkyl group, or R6 is a C1~C20 alkyl group, and at least one carbon atom is substituted by a heteroatom. When there are multiple carbon atoms substituted by heteroatoms, the heteroatoms are located at non-adjacent positions.

10. The hole transport thin film according to claim 1, characterized in that, The R4 is selected from at least one of carbazole groups, triazole groups and triazine groups.

11. A method for fabricating an optoelectronic device, characterized in that, The weight-average molecular weight of the second polymer is greater than or equal to 50000 and less than or equal to 250000. Comprises the following steps: Providing a material solution comprising a first polymer and a second polymer. Wherein, the first polymer is a conductive polymer material, and the conductive polymer material is polyaniline, polythiophene, polyfluorene or a copolymer formed by at least two of polyaniline, polythiophene and polyfluorene; the second polymer is a block polymer comprising a first block and a second block. The first block is a copolymer block formed by a fluorene-containing group and an aniline-containing group, and the second block is a copolymer block formed by a fluorene-containing group and an aniline-containing group. And the aniline-containing group in the second block is connected with an electron-donating group; all or part of the hydrogen atoms in the second polymer are substituted by fluorine atoms; Providing a substrate, an anode is formed on the substrate, the material solution is disposed on the anode, and a drying treatment is performed to obtain a hole transport thin film; Fabricating a cathode on the hole transport thin film; Along the thickness direction of the hole transport film, from one side to the other, the content of the second polymer increases or decreases.

12. 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 a first polymer and a second polymer; The first polymer is a conductive polymer material, which is polyaniline, polythiophene, polyfluorene, or a copolymer formed from at least two of polyaniline, polythiophene, and polyfluorene; The second polymer is a block polymer comprising a first block and a second block, wherein the first block is a copolymer block formed by a fluorene-containing group and an aniline-containing group, the second block is a copolymer block formed by a fluorene-containing group and an aniline-containing group, and the aniline-containing group in the second block is attached to an electron-donating group. In the second polymer, all or part of the hydrogen atoms are replaced by fluorine atoms; From the first surface to the second surface, the content of the first polymer decreases, and the content of the second polymer increases.

13. A display device, characterized in that, The display device includes the optoelectronic device as described in claim 12.

Images