Nanoparticle film, preparation method thereof and display panel

Abstract

The invention provides a nanoparticle film, a preparation method thereof and a display panel. The nanoparticle film comprises first particles and second particles, the first particle comprises a first nano particle and a first ligand combined on the surface of the first nano particle, and the first ligand comprises a first ionization group; the second particle comprises a second nano particle and a second ligand combined on the surface of the second nano particle, and the second ligand comprises a second ionization group; wherein the first nanoparticles and the second nanoparticles are selected from different functional particles, and the electrical property of the first ionization group after ionization is the same as the electrical property of the second ionization group after ionization. The movement of the nanoparticles in the film forming process is controlled by controlling the surface charges of the nanoparticles, so that the problems of aggregation, sedimentation and the like caused by random collision of the nanoparticles are avoided, and the controllability and selectivity of the density and the structure of the nanoparticle film are realized.

Description

Technical Field

[0001] The present application relates to the field of display technology, and in particular, to a nanoparticle film and a preparation method thereof, and a display panel. Background Art

[0002] Colloidal nanoparticles are a promising class of functional device materials due to their unique optical, electronic, and chemical properties. The remarkable features of colloidal nanoparticles, such as ease of synthesis and low-cost solution processing capability, make them show great potential for applications in catalysis, sensors, biotechnology, electronics, photodetectors, light-emitting devices, displays, and other fields.

[0003] Compared with single-particle systems, multi-particle systems composed of multiple nanoparticles with different materials, shapes or sizes can integrate the excellent properties of each component, or the resulting overall structure can exhibit new features. This synergistic effect between multiple particles also provides the ability to manipulate the functional properties of building blocks in practical applications. However, it is still challenging to precisely control the assembly and selective placement of multiple particles on large-area substrates to form patterned components for solid-state devices. Common patterning preparation methods, such as photolithography, etching, and inkjet printing, usually directly use mixed colloids containing multiple particles when involving multi-particle systems. Due to the Brownian motion of nanoparticles in colloidal suspensions, they may aggregate and phase separate during random collisions with particles or substrates, and may settle during the drying process, which will significantly affect the performance of related equipment and the quality of film formation. Summary of the invention

[0004] The present application provides a nanoparticle film, a preparation method thereof and a display panel. The preparation method of the nanoparticle film can avoid problems such as aggregation and sedimentation caused by random collisions of nanoparticles during the film formation process, and achieve controllable and selectivity of the density and structure of the nanoparticle film.

[0005] The present application provides a nanoparticle film, which includes a first particle and a second particle; the first particle includes a first nanoparticle and a first ligand bound to the surface of the first nanoparticle, the first ligand includes a first ionizable group; the second particle includes a second nanoparticle and a second ligand bound to the surface of the second nanoparticle, the second ligand includes a second ionizable group; wherein the first nanoparticle and the second nanoparticle are selected from different functional particles, and the electrical properties of the first ionizable group after ionization are the same as the electrical properties of the second ionizable group after ionization.

[0006] In some embodiments, the functional particles are selected from at least one of semiconductor nanocrystals, inorganic nanoparticles, noble metal nanoparticles, colloidal nanosheets, and colloidal nanorods.

[0007] In some embodiments, the first ligand further includes a first anchoring group and a first dispersed chain, the first anchoring group and the first ionized group are respectively connected to the two ends of the first dispersed chain, and the first anchoring group is connected to the first nanoparticle; the second ligand further includes a second anchoring group and a second dispersed chain, the second anchoring group and the second ionized group are respectively connected to the two ends of the second dispersed chain, and the second anchoring group is connected to the second nanoparticle.

[0008] In some embodiments, in the nanoparticle film, the first particles and the second particles are uniformly distributed.

[0009] In some embodiments, the nanoparticle film includes a first side and a second side arranged opposite to each other along the thickness direction of the nanoparticle film, and the content of the first particles on the first side is greater than the content of the first particles on the second side; and / or the content of the second particles on the second side is greater than the content of the second particles on the first side.

[0010] In some embodiments, the nanoparticle film includes a first particle layer and a second particle layer, and the first particle layer and the second particle layer are stacked and distributed along the thickness direction of the nanoparticle film, wherein the first particle layer includes the first particles and the second particle layer includes the second particles.

[0011] In some embodiments, the first ligand or the second ligand includes at least one of an amine group, a carboxyl group, a thiol group, and an organic phosphorus group; the first anchoring group or the second anchoring group includes at least one of a thiol group and a siloxane group; the first dispersed chain or the second dispersed chain includes at least one of an alkylated chain, an alkoxy chain, and a group containing a branched substituent.

[0012] The present application also provides a method for preparing a nanoparticle film, the method for preparing the nanoparticle film comprising:

[0013] Providing at least a first nanoparticle and a second nanoparticle, modifying a first ligand on the surface of the first nanoparticle to obtain a first particle, and modifying a second ligand on the surface of the second nanoparticle to obtain a second particle, wherein the first ligand includes a first ionizable group, and the second ligand includes a second ionizable group, and the electrical property of the first ionizable group is the same as the electrical property of the second ionizable group, and the first particle and the second particle are dispersed in a solution medium to form a mixed solution, and the electrical property of the first ionizable group after ionization in the solution is the same as the electrical property of the second ionizable group after ionization in the solution;

[0014] placing at least one electrode into the mixed solution;

[0015] A voltage is applied to the electrode, and the first particles and the second particles move toward the electrode and are deposited on the surface of the electrode to form a nanoparticle film.

[0016] In some embodiments, an absolute value of a difference between the electrophoretic mobility of the first particle and the electrophoretic mobility of the second particle is less than or equal to a preset value, and the first particle and the second particle are uniformly distributed in the nanoparticle film;

[0017] Alternatively, the absolute value of the difference between the electrophoretic mobility of the first particle and the electrophoretic mobility of the second particle is greater than the preset value, the nanoparticle film includes a first side and a second side relatively arranged along the thickness direction of the nanoparticle film, the content of the first particles on the first side is greater than the content of the first particles on the second side, and / or the content of the second particles on the second side is greater than the content of the second particles on the first side.

[0018] The present application also provides a display panel, the display panel comprising:

[0019] a first substrate;

[0020] The nanoparticle film as described above is located on one side of the first substrate; and

[0021] The second substrate is located at a side of the nanoparticle film away from the first substrate.

[0022] The present application provides a nanoparticle film, a preparation method thereof and a display panel. The present application utilizes electrophoretic deposition (EPD) and modifies the surface of the nanoparticles with ligands containing ionized groups to adjust the surface charges of different nanoparticles, thereby controlling the electrophoretic mobility of different nanoparticles, so that the movement of the nanoparticles during the film-forming process can be controlled, avoiding problems such as aggregation and sedimentation caused by random collisions of the nanoparticles, achieving controllable and selectivity in the density and structure of the nanoparticle film, and facilitating the preparation of a nanoparticle film with a gradient or uniform structure containing a variety of particles, and achieving efficient, uniformly distributed and high-resolution assembly patterns. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic diagram of a nanoparticle film provided in an embodiment of the present application;

[0024] Figure 2 A schematic diagram of the binding of nanoparticles and ligands of a nanoparticle film provided in an embodiment of the present application;

[0025] Figure 3 A schematic diagram of electrophoretic deposition of a nanoparticle film provided in an embodiment of the present application;

[0026] Figure 4a A schematic diagram of the structure of one of the nanoparticle films provided in the embodiments of the present application;

[0027] Figure 4b A schematic diagram of the structure of one of the nanoparticle films provided in the embodiments of the present application;

[0028] Figure 4c A schematic diagram of the structure of one of the nanoparticle films provided in the embodiments of the present application;

[0029] Figure 5a A schematic diagram of forming one of the nanoparticle films provided in the embodiments of the present application;

[0030] Figure 5b A schematic diagram of forming one of the nanoparticle films provided in the embodiments of the present application;

[0031] Figure 5c A schematic diagram of forming one of the nanoparticle films provided in the embodiments of the present application;

[0032] Figure 6 Fourier transform infrared spectra of SiO2 nanoparticles before and after modification with ligands provided in the embodiments of the present application;

[0033] Figure 7 Thermogravimetric curves of SiO2 NPs with different ligand grafting rates provided in the examples of the present application;

[0034] Figure 8 A comparison chart of zeta potential and electrophoretic mobility of SiO2 NPs with different ligand grafting rates provided in the examples of the present application;

[0035] Figure 9a Cross-sectional electron micrographs of nanoparticle films formed by SiO2 NPs and QDs with different ligand grafting rates provided in the examples of the present application;

[0036] Figure 9b A schematic diagram showing the variation of Si / Cd element count ratio of a nanoparticle film formed by SiO2 NPs and QDs with different ligand grafting rates as a function of the distance from the film surface provided in the embodiments of the present application;

[0037] Fig.10 A comparison chart of EQE of nanoparticle films formed by SiO2 NPs and QDs with different ligand grafting rates provided in the examples of the present application;

[0038] Fig.11a EQE comparison diagram of nanoparticle films of different thicknesses formed by SiO2 NPs and R QDs with different ligand grafting rates provided in the embodiments of the present application;

[0039] Fig.11b EQE comparison diagram of nanoparticle films of different thicknesses formed by SiO2 NPs and G QDs with different ligand grafting rates provided in the embodiments of the present application;

[0040] Fig.12 A schematic diagram of the variation of Si / Cd element count ratios of nanoparticle films containing TiO2 without modified ligands and TiO2 with modified ligands as a function of film surface distance provided in the embodiments of the present application;

[0041] Fig.13 PL spectra of nanoparticle films containing TiO2 without modified ligands and TiO2 after modified ligands provided in the examples of the present application;

[0042] Fig.14 The embodiment of the present application provides a curve diagram of the change of EQE of the nanoparticle film containing TiO2 without modified ligand and containing TiO2 after modified ligand with the addition amount of TiO2 after modified ligand. DETAILED DESCRIPTION

[0043] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application.

[0044] The present application may repeat reference numerals and / or reference letters in different implementations. Such repetition is for the purpose of simplicity and clarity and does not in itself indicate the relationship between the various implementations and / or settings discussed.

[0045] Electrophoretic deposition (EPD) is a directed assembly technology that can use an external electric field to drive the assembly and arrangement of charged nanoparticles on an electrode substrate, and has the potential to control the regular assembly of multiple particles. This technology is cost-effective, simple in equipment, short in molding time, can control the deposition thickness, has high deposition adhesion strength, and can be used on different materials and substrates of arbitrary shapes. The key parameters that determine the movement of nanoparticles in the EPD system are the surface charge and electrophoretic mobility of the particles. Nanoparticles suspended in a colloidal medium often acquire surface charges through ionization of surface groups, adsorption of charged substances, or chemical functionalization. Therefore, by designing the surface groups of nanoparticles or adjusting the surrounding environment, the arrangement and packing density of multiple particles in the EPD process can be regulated, thereby controlling the density and structure of nanoparticle films containing multiple particles.

[0046] The present application provides a nanoparticle film, such as Figure 1-Figure 2As shown, the nanoparticle film at least includes a first particle 10 and a second particle 20; the first particle 10 includes a first nanoparticle 11 and a first ligand 100 bound to the surface of the first nanoparticle 11, and the first ligand 100 includes a first ionized group 12; the second particle 20 includes a second nanoparticle 21 and a second ligand 200 bound to the surface of the second nanoparticle 21, and the second ligand 200 includes a second ionized group 22; wherein the first nanoparticle and the second nanoparticle are selected from different functional particles, and the electrical properties of the first ionized group 12 after ionization are the same as the electrical properties of the second ionized group 22 after ionization.

[0047] The first ligand 100 includes the first ionized group 12, which can be ionized in a solution medium to give the first nanoparticle 11 a surface charge, and the second ligand 200 includes the second ionized group 22, which can be ionized in a solution medium to give the second nanoparticle 21 a surface charge, so that the surfaces of the first particle 10 and the second particle 20 are charged. Figure 3 As shown, during the electrophoretic deposition process, since the surface charges of the first particle 10 and the second particle 20 are the same, the two move toward the same electrode 30 and are deposited on the same electrode 30 to form the nanoparticle film, as shown in FIG. Figure 1 shown.

[0048] In the present application, the surface charge of the first particle 10 and the second particle 20 can be controlled by selecting the type and quantity of the first ligand 100 on the surface of the first nanoparticle 11 and the type and quantity of the second ligand 200 on the surface of the second nanoparticle 21, thereby controlling the movement speed of the first particle 10 and the second particle 20 in the solution medium to achieve controllable and selectivity of the density and structure of the nanoparticle film, while avoiding problems such as aggregation and sedimentation caused by random collisions of particles.

[0049] In the present application, the first nanoparticles 11 and the second nanoparticles 21 can be selected from different functional particles, and the nanoparticle film can be assembled from a variety of particles with different functions to integrate the excellent properties of each component, improve or enhance the performance of the nanoparticle film, or give the nanoparticle film new features or functions.

[0050] In some embodiments, the first nanoparticle 11 or the second nanoparticle 21 includes at least one of semiconductor nanocrystals, inorganic nanoparticles, noble metal nanoparticles, colloidal nanosheets, and colloidal nanorods, but is not limited thereto. The particle size of the first nanoparticle 11 or the second nanoparticle 21 ranges from 5 nm to 200 nm.

[0051] In some embodiments, Figure 2 As shown, the first ligand 100 also includes a first anchoring group 13 and a first dispersed chain 14, the first anchoring group 13 and the first ionized group 12 are respectively connected to the two ends of the first dispersed chain 14, and the first anchoring group 13 is anchored to the surface of the first nanoparticle 11; the second ligand 200 also includes a second anchoring group 23 and a second dispersed chain 24, the second anchoring group 23 and the second ionized group 22 are respectively connected to the two ends of the second dispersed chain 24, and the second anchoring group 23 is anchored to the surface of the second nanoparticle 21.

[0052] In this embodiment, in order to ensure that the particles are co-deposited on the same electrode 30 and to regulate the distribution of these particles in the nanoparticle film, the particle surface needs to be modified, and the functional surface ligand used to modify the nanoparticles includes three basic components: anchoring groups, dispersed chains and ionized groups. Among them, the anchoring groups make the ligands firmly attached to the surface of the nanoparticles through coordination or covalent bonding, while the dispersed chains prevent the aggregation of nanoparticles and promote their stability in the solution, and the ionized groups give the nanoparticles surface charges by ionizing in the solvent.

[0053] The first ligand 100 and the second ligand 200 include organic ligands, such as ligands including an amine group, a ligand including a carboxyl group, a ligand including a thiol group, or a ligand including an organic phosphorus group, but are not limited thereto.

[0054] The selection of the first anchoring group 13 or the second anchoring group 23 needs to be selected according to the surface groups of the nanoparticles used. For example, for CdSe / ZnS core-shell structure quantum dots or Pb-based perovskite quantum dots with metal atoms on the surface, a thiol group with a strong coordination binding force can be selected as the anchoring group. For inorganic nanoparticles such as SiO2 and TiO2 with hydroxyl groups on the surface, a siloxane group can be selected to covalently bond with them, but it is not limited to this.

[0055] The first dispersed chain 14 and the second dispersed chain 24 can be selected from alkylated chains, alkoxy chains and other structures containing branched substituents according to the solvent system, but are not limited thereto.

[0056] The first ionizable group 12 and the second ionizable group 22 can be selected from carboxyl groups, amine groups, etc. as ionizable groups, wherein the carboxyl groups can be ionized in the solvent to make the particles negatively charged, and the amine groups can be ionized in the solvent to make the particles positively charged.

[0057] In the process of electrophoretic deposition, the electrophoretic mobility (μ) of the particles is a key factor, which determines the speed of the particle movement. Therefore, for different types of nanoparticles, the relative electrophoretic mobility of different nanoparticles can be adjusted to make them obtain different movement speeds in the electric field drive, thereby preparing nanoparticle films with gradient or uniform structures containing multiple particles. In a certain liquid medium, the mobility of charged particles is proportional to the zeta potential, which is related to its surface charge. The surface charge of nanoparticles comes from the ionization of ligands, so the change in its mobility can be controlled by adjusting the ligand content.

[0058] In some embodiments, mobility is related to the solvent parameters (such as dielectric constant and viscosity) used in addition to being related to zeta potential. In the same solvent system, the relative size of mobility can be regulated by limiting the zeta potential of each particle. The absolute value of the zeta potential of each particle should be greater than 30mV to ensure the dispersion stability of the particles. The absolute value of the zeta potential of the preferred particles is in the range of 40-60mV. When the zeta potential value is too high, the repulsion between the particles is large, which is not conducive to stable deposition.

[0059] This application uses electrophoretic deposition technology, and adjusts the relative electrophoretic mobility of individual nanoparticles by surface design and charge regulation of nanoparticles, so that the movement of nanoparticles in the film formation process can be controlled, avoiding problems such as aggregation and sedimentation caused by random collisions, and achieving controllable and selective density and structure of nanoparticle films, which is conducive to the preparation of nanoparticle films with gradient or uniform structures containing multiple particles. At the same time, combined with photolithography technology to prepare high-precision patterned electrodes, high-efficiency, uniformly distributed and high-resolution assembly pattern arrays can be obtained, which have good application prospects in display, biological imaging and other aspects.

[0060] In some embodiments, Figure 4a As shown, in the nanoparticle film, the first particles 10 and the second particles 20 can be uniformly distributed.

[0061] In some embodiments, Figure 4b-4c As shown, the nanoparticle film includes a first side 01 and a second side 02 which are relatively arranged along the thickness direction (X direction) of the nanoparticle film, and the content of the first particles 10 on the first side 01 is greater than the content of the first particles 10 on the second side 02; and / or the content of the second particles 20 on the second side 02 is greater than the content of the second particles 20 on the first side 01.

[0062] Specifically, Figure 4bAs shown, in the nanoparticle film, along the thickness direction of the nanoparticle film, i.e., the X direction, the content of the first particles 10 may be distributed in a gradient increasing manner, and the content of the second particles 20 may be distributed in a gradient decreasing manner. That is, in the nanoparticle film, the first particles 10 and the second particles 20 form a gradient structure.

[0063] like Figure 4c As shown, the nanoparticle film includes a first particle layer 101 and a second particle layer 201. Along the thickness direction of the nanoparticle film, the first particle layer 101 and the second particle layer 201 are stacked and distributed, wherein the first particle layer 101 includes the first particles 10, and the second particle layer 201 includes the second particles 20. That is, in the nanoparticle film, the first particles 10 and the second particles 20 are deposited in layers to form a layered structure.

[0064] In the process of forming the nanoparticle film, the first particle 10 is obtained by modifying the surface of the first nanoparticle 11 with the first ligand 100, and the second particle 20 is obtained by modifying the surface of the second nanoparticle 21 with the second ligand 200. By controlling the type or amount of the first ligand 100 and the second ligand 200, the electrophoretic mobility of the first particle 10 and the second particle 20 during the electrophoretic deposition process can be made equivalent, and the movement speed of the first particle 10 and the second particle 20 toward the same electrode can be made consistent, so that the nanoparticle film structure deposited on the electrode surface is a structure in which the first particle 10 and the second particle 20 are evenly distributed. By controlling the type or amount of the first ligand 100 and the second ligand 200, the electrophoretic mobility of the first particle 10 and the second particle 20 during the electrophoretic deposition process can also be made to have a certain size difference, and the movement speed of the first particle 10 and the second particle 20 toward the same electrode can be made different, so that the nanoparticle film structure deposited on the electrode surface is a gradient structure or a layered structure formed by the first particle 10 and the second particle 20.

[0065] It should be noted that the types of particles contained in the nanoparticle film of the present application are not limited to the two types in the above embodiments. The nanoparticle film can also contain three or more particles. The principle and structure are similar to those in the above embodiments and will not be described in detail here.

[0066] The present application also provides a method for preparing a nanoparticle film, the method for preparing the nanoparticle film comprising:

[0067] At least a first nanoparticle 11 and a second nanoparticle 21 are provided, a first ligand 100 is modified on the surface of the first nanoparticle 11 to obtain a first particle 10, and a second ligand 200 is modified on the surface of the second nanoparticle 21 to obtain a second particle 20, wherein the first ligand 100 includes a first ionized group 12, and the second ligand 200 includes a second ionized group 22, and the first particle 10 and the second particle 20 are dispersed in a solution medium to form a mixed solution, wherein the electrical properties of the first ionized group 12 after ionization in the solution are the same as the electrical properties of the second ionized group 22 after ionization in the solution;

[0068] placing at least one electrode 30 into the mixed solution;

[0069] A voltage is applied to the electrode 30 , and the first particles 10 and the second particles 20 move toward the electrode 30 and are deposited on the surface of the electrode 30 to form a nanoparticle film.

[0070] In some embodiments, Figure 2 As shown, the first ligand 100 also includes a first anchoring group 13 and a first dispersed chain 14, the first anchoring group 13 and the first ionized group 12 are respectively connected to the two ends of the first dispersed chain 14, and the first anchoring group 13 is anchored to the surface of the first nanoparticle 11; the second ligand 200 also includes a second anchoring group 23 and a second dispersed chain 24, the second anchoring group 23 and the second ionized group 22 are respectively connected to the two ends of the second dispersed chain 24, and the second anchoring group 23 is anchored to the surface of the second nanoparticle 21.

[0071] In some embodiments, Figure 3 As shown, the electrode 30 may include two electrodes 30 with opposite polarities, and the two electrodes 30 are inserted into the mixed solution in parallel. The electrode 30 may include a substrate and an electrode layer located on the substrate. The material of the electrode layer includes but is not limited to indium tin oxide (ITO), graphene, metal, etc., and the material of the substrate includes but is not limited to glass, organic glass, hard insulating film material, soft insulating film material, etc.

[0072] The method for preparing the nanoparticle film of the present application utilizes electrophoretic deposition and modifies ligands on the surface of the nanoparticles. The surface charge of the nanoparticles is regulated by adjusting the type and amount of ligands on the surface of the nanoparticles, thereby controlling the electrophoretic mobility of the nanoparticles. This allows the movement speed of the nanoparticles to be controlled, thereby achieving controllable and selectivity in the density and structure of the nanoparticle film. Therefore, the method can be used to prepare nanoparticle films containing multiple particles with a gradient or uniform structure.

[0073] In some embodiments, after applying voltage to the electrode 30, during the movement of the first particle 10 and the second particle 20 in the mixed solution, the absolute value of the difference between the electrophoretic mobility of the first particle 10 and the electrophoretic mobility of the second particle 20 can be less than or equal to a preset value, so that the first particle 10 and the second particle 20 are evenly distributed in the nanoparticle film. Further, the preset value is 0.5*10 -5 cm 2 s -1 V -1 .

[0074] In the process of preparing the nanoparticle film, the surface charge of the first particle 10 and the surface charge of the second particle 20 can be adjusted by adjusting the amount of the first ligand 100 modified on the surface of the first nanoparticle 11 and the amount of the second ligand 200 modified on the surface of the second nanoparticle 21, thereby controlling the electrophoretic mobility of the first particle 10 to be equal to or similar to the electrophoretic mobility of the second particle 20, so that the first particle 10 and the second particle 20 are evenly distributed in the formed nanoparticle film.

[0075] Specifically, Figure 5a As shown, the mobility of the second particle B is fixed and the mobility of the first particle A is regulated. When the mobility of A is equal to the mobility of B (μ A ≈μ B ), the movement speeds of A and B are consistent, and they migrate to the same electrode substrate at the same time, thereby forming a nanoparticle film with multiple particles evenly distributed. Wherein, when the absolute value of the difference between the electrophoretic mobility of the first particle 10 and the electrophoretic mobility of the second particle 20 is less than or equal to 0.5*10 -5 cm 2 s -1 V -1 When , it can be considered that the mobility of A is equivalent to the mobility of B.

[0076] In some embodiments, after applying a voltage to the electrode 30, during the movement of the first particle 10 and the second particle 20 in the mixed solution, the absolute value of the difference between the electrophoretic mobility of the first particle and the electrophoretic mobility of the second particle can be greater than the preset value, so that the nanoparticle film includes a first side 01 and a second side 02 relatively arranged along the thickness direction of the nanoparticle film, the content of the first particle 10 on the first side 01 is greater than the content of the first particle 10 on the second side 02, and / or the content of the second particle 20 on the second side 02 is greater than the content of the second particle 20 on the first side 01.

[0077] In some embodiments, during the preparation of the nanoparticle film, the surface charge of the first particle 10 and the surface charge of the second particle 20 can be adjusted by adjusting the amount of the first ligand 100 modified on the surface of the first nanoparticle 11 and the amount of the second ligand 200 modified on the surface of the second nanoparticle 21, thereby controlling the electrophoretic mobility of the first particle 10 to be greater than or less than the electrophoretic mobility of the second particle 20, so that in the formed nanoparticle film, along the thickness direction of the nanoparticle film, the first particle 10 and the second particle 20 are distributed in a gradient or layered manner.

[0078] Specifically, Figure 5b As shown, the mobility of the second particle B is fixed and the mobility of the first particle A is regulated. When the mobility of A is lower than the mobility of B (μ A <μ B ), most of B migrates quickly and reaches the electrode surface first, while A lags behind B. The mobility of different first particles A can be made different, thus forming a gradient structure in which the content of A increases and the content of B decreases in the direction from the second side 02 to the first side 01 (i.e., the thickness direction of the nanoparticle film); or the mobility of B can be made much greater than the mobility of A, thus forming a layered structure of A and B, that is, all B is preferentially deposited on the electrode surface due to its fast movement speed to form a film layer composed of B, while A is later deposited on the surface of the film layer composed of B due to its slow movement speed.

[0079] like Figure 5c As shown, Figure 5b In contrast, when the mobility of A is greater than the mobility of B (μ A >μ B ), most of A migrates quickly and reaches the electrode surface first, while B lags behind A, forming a gradient structure with decreasing content of A from the second side 02 to the first side 01; or when the mobility of A is much greater than the mobility of B, a layered structure of A and B can be formed, that is, all A is preferentially deposited on the electrode surface due to its fast movement speed to form a film layer composed of A, while B is deposited later on the surface of the film layer composed of A due to its slow movement speed.

[0080] The present application immerses two opposing electrodes in a mixed solution containing multiple particles, drives multiple charged particles to move toward the same electrode in an electric field, and controls the surface charges of different particles to obtain nanoparticle films containing multiple particles with different structures.

[0081] The preparation method of the nanoparticle film can also be extended to the development of various other materials with different functions, including uniform composite materials and gradient functional materials, such as making a double nanoparticle optical gradient structure with a gradient refractive index. For example, in a double nanoparticle system of solid SiOx and hollow SiOx, their mobility can be adjusted by modifying ligands on the surface of the particles, and they can be made into a gradient structure with a gradient refractive index using EPD. These optical gradient structures have important application potential in anti-reflective coatings, light focusing, and lenses. Therefore, by customizing the composition of multi-particle films according to specific requirements, new ways can be explored in the fields of optoelectronics, biological applications, etc.

[0082] For quantum dot (QD) particles, the use of inorganic nanoparticles and co-deposition thereof can make QDs uniformly dispersed in the matrix composed of inorganic particles, spacing quantum dots, thereby reducing self-absorption between QDs and improving the luminous efficiency of QD deposited films. Other functional materials such as scattering particles can also be introduced to increase internal reflection and optical path, etc. to improve blue light absorption efficiency and thus increase QD luminous efficiency. Using this multi-particle collaborative electrodeposition method of the present application, combined with the use of a high-precision patterned electrode substrate, a high-luminous efficiency, uniform distribution and high-resolution assembly pattern can be achieved, which has significant advantages in large-area multi-color full-color display arrays.

[0083] The nanoparticle film and preparation method thereof of the present application can be applied to quantum dot display fields such as quantum dot color filter (Quantum Dots Color Filter, QDCF), quantum dot light guide plate (Quantum Dots Light Guide Plate, QD LGP), quantum dot light emitting diode (Quantum Dot Light Emitting Diodes, QLED), quantum dot organic light emitting diode (Quantum Dot Organic Light Emitting Diodes, QD-OLED), and can also be applied to other fields involving nanoparticles, such as solar cells, spectrometers, optical structures, biological applications, etc.

[0084] The nanoparticle film and the preparation method thereof of the present application are further described below through specific examples.

[0085] Example 1

[0086] 1. Composition of Nanoparticle Film

[0087] In this embodiment, the nanoparticle film includes first particles 10 and second particles 20 . The first particles 10 include first nanoparticles 11 and first ligands 100 bound to the surface of the first nanoparticles 11 . The second particles 20 include second nanoparticles 21 and second ligands 200 bound to the surface of the second nanoparticles 21 .

[0088] Specifically, the first particle 10 is QDs, the first nanoparticle 11 is a QD nanoparticle, for example, it can be a CdSe / ZnS core-shell structure quantum dot, and the first ligand 100 is SH-PEG-COOH (where SH is the first anchoring group 13, PEG is the first dispersed chain 14, and COOH is the first ionized group 12). Among them, the particle size of the QD nanoparticle is 10-20nm, and the surface is modified with SH-PEG-COOH ligand to make it negatively charged. Since the ligand content affects the QD charge and luminescence quantum yield, considering the high photoluminescence quantum yield (PLQY), the content of the first ligand 100 is 33.4wt% of the mass of the QD nanoparticle. The zeta potential of QDs is -42.3mV, and the mobility is -2.8*10 -5 cm 2 s -1 V -1 .

[0089] The second particle 20 is SiO2 NPs, the second nanoparticle 21 is SiO2 nanoparticles, and the second ligand 200 is siloxane-PEG-COOH (wherein siloxane is the second anchoring group 23, PEG is the second dispersing chain 24, and COOH is the second ionizing group 22). The particle size of SiO2 NPs is about 15 nm, and SiO2 NPs with a particle size of about 15 nm are selected to be mixed with QDs to maintain suspension stability and prevent poor deposition morphology caused by macrocolloids.

[0090] This embodiment is a co-deposition system of QD nanoparticles and SiO2 nanoparticles. The surface charge of the particles is regulated by changing the number of ligands on the surface of SiO2 nanoparticles, thereby controlling the relative electrophoretic mobility between the particles and QDs, and obtaining a customized structure of a nanoparticle film containing multiple particles during the electrodeposition process.

[0091] 2. Preparation method of nanoparticle film

[0092] Step S1, modifying the first ligand 100 on the surface of the first nanoparticle 11 to obtain the first particle 10, modifying the second ligand 200 on the surface of the second nanoparticle 21 to obtain the second particle 20, and dispersing the first particle 10 and the second particle 20 in a solvent to form a mixed solution.

[0093] The specific step S1 includes:

[0094] S11, bonding the first ligand 100SH-PEG-COOH to the surface of QD nanoparticles to form first particle QDs;

[0095] S12, bonding the second ligand 200 siloxane-PEG-COOH to the surface of SiO2 nanoparticles to form second particles SiO2NPs;

[0096] Wherein, step S12 specifically includes:

[0097] In the first step, silane-PEG-NH2 is bonded to the surface of SiO2 nanoparticles via hydrolysis condensation;

[0098] In the second step, the NH2 groups were converted into COOH groups by reacting with anhydride. The siloxane groups acted as anchoring groups and chemically bonded to the surface of SiO2 nanoparticles, the PEG chains provided dispersion in the PGMEA solution, and the COOH groups promoted ionization. The successful modification of the ligands on the surface of SiO2 nanoparticles was confirmed by Fourier transform infrared spectroscopy (FTIR), such as Figure 6 shown.

[0099] The amount of the second ligand 200 grafted on the surface of SiO2 NPs is mainly controlled by adjusting the amount of the second ligand 200 added in the modification reaction. In this embodiment, SiO2 NPs with ligand grafting rates of 4%, 10% and 20% were prepared and characterized by thermogravimetric analyzer (TGA). Figure 7 As shown. Figure 8 As shown in the figure, as the ligand grafting rate of the surface modified SiO2 nanoparticles increases from 4% to 20%, the zeta potential and mobility of SiO2 NPs increase. Among them, the amount of ligand added refers to the mass ratio of the amount of ligand put into the synthesis reaction to the mass ratio of the unmodified SiO2 nanoparticles put into the synthesis reaction, and the ligand grafting rate refers to the ratio of the ligand content actually connected to the surface of the SiO2 nanoparticles after the reaction to the total mass of the modified particles SiO2 NPs. The ligand grafting rate of the particles can be controlled by adjusting the amount of ligand added in the synthesis reaction.

[0100] S13. Dispersing QDs and SiO2 NPs in the solvent PGMEA at the same concentration (concentration range is 5-40 mg / mL) to form a mixed solution containing first particle QDs and second particle SiO2 NPs.

[0101] Step S2: placing a pair of electrodes 30 into the mixed solution prepared in step S1.

[0102] Specifically, a first electrode and a second electrode are vertically immersed in the mixed solution, wherein the first electrode includes a first substrate and a first electrode layer located on the first substrate, and the second electrode includes a second substrate and a second electrode layer located on the second substrate. The materials of the first electrode layer and the second electrode layer can be indium tin oxide (ITO), graphene, metal, etc.

[0103] Step S3: applying a voltage to a pair of electrodes 30, the first particles 10 and the second particles 20 move to the same electrode 30 and deposit on the surface of the electrode 30 to form a nanoparticle film.

[0104] Specifically, the first electrode can be a positive electrode, and the second electrode can be a negative electrode. The SH-PEG-COOH ligand modified on the surface of QDs makes QDs negatively charged, and the siloxane-PEG-COOH ligand modified on the surface of SiO2 NPs makes SiO2 NPs negatively charged. After voltage is applied, under the action of the electric field, both QDs and SiO2 NPs move toward the positive electrode side and are deposited on the surface of the positive electrode to form a nanoparticle film containing first particles QDs and second particles SiO2 NPs.

[0105] In this example, nanoparticle films formed by co-deposition of QDs and SiO2 NPs with different mobilities were prepared. The controlled assembly of QDs and SiO2 NPs particles was confirmed by analyzing scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and calculating the Si and Cd element ratios, as shown in Figure 2. Figure 9a-9b As shown. Figure 9a-9b It can be seen that the nanoparticle film formed by co-deposition of SiO2 NPs with a ligand grafting rate of 4% (i.e., SiO2-4%) and QDs presents a gradient distribution structure of the layered cross section, among which the low mobility (-2.1*10 -5 cm 2 s -1 V -1 ) are mainly distributed on the top of the nanoparticle film; SiO2 NPs with a ligand grafting rate of 10% (i.e., SiO2-10%) have a mobility comparable to that of QDs (-3.1*10 -5 cm 2 s -1 V -1 , zeta potential is -45.8mV), achieving uniform distribution between QDs and SiO2 NPs. When the mobility of SiO2 NPs increases to -4.3*10 -5 cm 2 s -1 V -1When the ligand grafting rate is 20% (i.e., SiO2-20%), the migration speed of SiO2 NPs is faster than that of QDs, and the gradient distribution of SiO2 NPs in the nanoparticle film gradually decreases from bottom to top.

[0106] The above nanoparticle films have different luminescence properties (Photoluminescence, PL) due to their different assembly structures, such as Fig.10 As shown in the figure, compared with the single-component QD film, the layered or gradient co-deposited multi-particle nanoparticle film exhibits enhanced PL performance. This is because the QDs and SiO2NPs particles partially interpenetrate each other in the film, and the nanoparticle film containing SiO2NPs with a ligand grafting rate of 20% (SiO2-20%) exhibits a slightly higher external quantum efficiency (EQE) due to the wider gradient distribution. The uniformly co-deposited nanoparticle film containing QDs and SiO2NPs with a ligand grafting rate of 10% (SiO2-10%) shows the highest EQE. This significant enhancement of EQE is attributed to the spatial isolation provided by the SiO2 particles, which effectively suppresses the self-absorption between QDs.

[0107] like Figure 11a-Figure 11b As shown, this embodiment further adjusts the blending mass ratio of QDs and SiO2 NPs with a ligand grafting rate of 20% (SiO2-20%) (mass ratio range is 4:1-1:4) to optimize the spacing between QDs to enhance the luminescence performance of the multi-particle nanoparticle film. Figure 11a-Figure 11b It can be seen that the ideal ratios of RQDs (red quantum dots) and G QDs (green quantum dots) to SiO2 NPs are 1:1 and 1:2, respectively.

[0108] Example 2

[0109] Example 2 is based on Example 1 and further introduces a third particle, TiO2 particles, to construct a multi-particle co-deposited nanoparticle film.

[0110] The third particle includes a third nanoparticle and a third ligand bound to the surface of the third nanoparticle. The third particle is TiO2 NPs, the third nanoparticle is a TiO2 nanoparticle, and the third ligand is a titanate coupling agent containing a carboxylic acid group. The particle size of the TiO2 nanoparticle is 100nm-200nm. In order to be compatible with the QD and SiO2 systems, the titanate coupling agent containing a carboxylic acid group is used to modify the TiO2 nanoparticles so that it obtains a considerable electrophoretic mobility.

[0111] A nanoparticle film composed of QDs, SiO2 NPs and TiO2 NPs was prepared by the nanoparticle film preparation method of the present application, wherein the materials and preparation methods of QDs and SiO2 NPs are the same as those in Example 1, QDs and SiO2 NPs use the optimized ratio obtained in Example 1 (the optimized ratio of R QDs to SiO2 NPs is 1:1, and the optimized ratio of G QDs to SiO2 NPs is 1:2), and the added content of TiO2 NPs is 0.5%-5% of the total amount of QDs and SiO2 NPs. Fig.12 As shown in Figure 2, the cross-sectional Ti and Cd count ratio curves of the nanoparticle film confirm that when unmodified ligand TiO2 nanoparticles are used, the Ti element in the upper region of the formed nanoparticle film presents an increasing gradient structure due to the difference in mobility. The nanoparticle film formed using ligand-modified TiO2 nanoparticles (TiO2-OA) exhibits a uniform distribution of Ti elements throughout its depth. This allows the ligand-modified TiO2 nanoparticles in multi-particle films to exert an effective scattering effect to improve the utilization of blue light to obtain enhanced PL performance, such as Fig.13 By controlling the content of ligand-modified TiO2 nanoparticles, the scattering can be further tuned and optimized to achieve more efficient energy conversion, such as Fig.14 As shown, for the red luminescent nanoparticle film, when it contains 2% ligand-modified TiO2 nanoparticles, the EQE increases by 2.3 times compared with the case where no TiO2 nanoparticles are contained; for the green luminescent nanoparticle film, when it contains 3% ligand-modified TiO2 nanoparticles, the EQE increases by 3.1 times compared with the case where no TiO2 nanoparticles are contained, and the luminescence efficiency is significantly improved.

[0112] The present application also provides a display panel, comprising a first substrate, the nanoparticle film as described above, and a second substrate. The nanoparticle film is located on one side of the first substrate; the second substrate is located on a side of the nanoparticle film away from the first substrate, and the first substrate and the second substrate are arranged opposite to each other.

[0113] In some embodiments, the first substrate may be an array substrate, the nanoparticle film may be a luminescent film, such as a quantum dot luminescent film, and the display panel may be a quantum dot light emitting diode (QLED) or a quantum dot organic light emitting diode (QD-OLED).

[0114] In some embodiments, the first substrate may be a glass substrate or a flexible substrate, the nanoparticle film may be a quantum dot color filter, the nanoparticle film and the first substrate together constitute a color filter substrate, and the second substrate may be an array substrate. The display panel may be a light emitting diode (LED) or an organic light emitting diode (OLED), etc.

[0115] In some embodiments, the display panel further includes an anti-reflection layer, which is disposed on at least one side of the first substrate or the second substrate to reduce reflection, and the anti-reflection layer may include the nanoparticle film as described above.

[0116] The present application also provides a display device, which includes a display panel and a light guide plate located on one side of the display panel.

[0117] In some embodiments, the display panel may be the display panel described above, and the display panel includes the nanoparticle film described above.

[0118] In some embodiments, the light guide plate may be a quantum dot light guide plate (QD LGP) comprising the nanoparticle film as described above.

[0119] In summary, the present application provides a nanoparticle film, a preparation method thereof, and a display panel. The present application utilizes electrophoretic deposition (EPD) and modifies the surface of the nanoparticles with ligands containing ionized groups to adjust the surface charges of different nanoparticles, thereby controlling the electrophoretic mobility of different nanoparticles, so that the movement of the nanoparticles during the film formation process can be controlled, avoiding problems such as aggregation and sedimentation caused by random collisions of the nanoparticles, and achieving controllable and selectivity in the density and structure of the nanoparticle film, which is conducive to the preparation of nanoparticle films with gradient or uniform structures containing multiple particles, and realizing efficient, uniformly distributed and high-resolution assembly patterns.

[0120] In summary, although the present application has been disclosed as above with preferred embodiments, the above preferred embodiments are not intended to limit the present application. Ordinary technicians in this field can make various changes and modifications without departing from the spirit and scope of the present application. Therefore, the scope of protection of the present application shall be based on the scope defined in the claims.

Claims

1. A nanoparticle film, characterized in that: including a first particle and a second particle; The first particle includes a first nanoparticle and a first ligand bound to the surface of the first nanoparticle, wherein the first ligand includes a first ionizable group; The second particle includes a second nanoparticle and a second ligand bound to the surface of the second nanoparticle, wherein the second ligand includes a second ionizable group; The first nanoparticle and the second nanoparticle are selected from different functional particles, and the electrical properties of the first ionizable group after ionization are the same as the electrical properties of the second ionizable group after ionization.

2. The nanoparticle film according to claim 1, characterized in that The functional particles are selected from at least one of semiconductor nanocrystals, inorganic nanoparticles, noble metal nanoparticles, colloidal nanosheets, and colloidal nanorods.

3. The nanoparticle film according to claim 1, characterized in that: The first ligand further comprises a first anchoring group and a first dispersed chain, the first anchoring group and the first ionized group are respectively connected to two ends of the first dispersed chain, and the first anchoring group is connected to the first nanoparticle; The second ligand further includes a second anchoring group and a second dispersed chain, the second anchoring group and the second ionized group are respectively connected to two ends of the second dispersed chain, and the second anchoring group is connected to the second nanoparticle.

4. The nanoparticle film according to claim 1, characterized in that In the nanoparticle film, the first particles and the second particles are uniformly distributed.

5. The nanoparticle film according to claim 1, characterized in that: The nanoparticle film comprises a first side and a second side which are arranged opposite to each other along the thickness direction of the nanoparticle film, and the content of the first particles on the first side is greater than the content of the first particles on the second side; And / or, the content of the second particles on the second side is greater than the content of the second particles on the first side.

6. The nanoparticle film according to claim 1 or 5, characterized in that: The nanoparticle film includes a first particle layer and a second particle layer. The first particle layer and the second particle layer are stacked and distributed along the thickness direction of the nanoparticle film. The first particle layer includes the first particles, and the second particle layer includes the second particles.

7. The nanoparticle film according to claim 3, characterized in that: The first ligand or the second ligand includes at least one of an amine group, a carboxyl group, a thiol group, and an organic phosphorus group; The first anchoring group or the second anchoring group comprises at least one of a mercapto group and a siloxane group; The first dispersed chain or the second dispersed chain includes at least one of an alkylated chain, an alkoxy chain, and a group containing a branched substituent.

8. A method for preparing a nanoparticle film, characterized in that: include: Providing at least a first nanoparticle and a second nanoparticle, modifying a first ligand on the surface of the first nanoparticle to obtain a first particle, and modifying a second ligand on the surface of the second nanoparticle to obtain a second particle, wherein the first ligand includes a first ionizable group, and the second ligand includes a second ionizable group, and the first particle and the second particle are dispersed in a solution medium to form a mixed solution, wherein the electrical property of the first ionizable group after ionization in the solution is the same as the electrical property of the second ionizable group after ionization in the solution; placing at least one electrode into the mixed solution; A voltage is applied to the electrode, and the first particles and the second particles move toward the electrode and are deposited on the surface of the electrode to form a nanoparticle film.

9. The method for preparing the nanoparticle film according to claim 8, characterized in that: An absolute value of a difference between the electrophoretic mobility of the first particles and the electrophoretic mobility of the second particles is less than or equal to a preset value, and the first particles and the second particles are uniformly distributed in the nanoparticle film; Alternatively, the absolute value of the difference between the electrophoretic mobility of the first particle and the electrophoretic mobility of the second particle is greater than the preset value, the nanoparticle film includes a first side and a second side relatively arranged along the thickness direction of the nanoparticle film, the content of the first particles on the first side is greater than the content of the first particles on the second side, and / or the content of the second particles on the second side is greater than the content of the second particles on the first side.

10. A display panel, characterized in that: The display panel comprises: a first substrate; The nanoparticle film according to any one of claims 1 to 7, located on one side of the first substrate; and The second substrate is located at a side of the nanoparticle film away from the first substrate.

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