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

Abstract

A light-emitting device and a preparation method therefor, and a display apparatus. The light-emitting device comprises a light-emitting layer, the light-emitting layer comprising quantum dot bodies, first ligands and second ligands, wherein the first ligands are connected to the quantum dot bodies, and are connected by means of first cross-linking structures; the second ligands are dispersed in a quantum dot light-emitting layer, and at least some of the second ligands are connected by means of second cross-linking structures; and the first ligands and the second ligands have the same polarity. The light-emitting device has less residual of the light-emitting layer in neighboring sub-pixels, thereby achieving a wider color gamut and better light-emitting performance. Moreover, the presence of the second ligands enables the first ligands to bind with quantum dots more stably, and thus the light-emitting performance of the light-emitting device is more stable.

Description

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

[0001] At least one embodiment of the present disclosure relates to a light-emitting device, a manufacturing method thereof, and a display device. Background Art

[0002] Photolithography is used to pattern the light-emitting layer in the preparation of electroluminescent or photoluminescent devices, such as quantum dot light-emitting devices. Quantum dot light-emitting layer processing is an effective method, especially for the preparation of high-resolution display panels. Generally, in the process of patterning the light-emitting layer using photolithography, the properties of the ligands on the surface of the quantum dots are utilized to cause them to change their solubility under preset conditions. After exposure and development, a patterned quantum dot light-emitting layer can be achieved.

[0003] However, during the preparation process, light-emitting layer materials of a certain color tend to remain in adjacent sub-pixel regions of other colors, thereby causing color crosstalk and affecting the color gamut and performance of the light-emitting device.

[0004] Summary of the Invention

[0005] At least one embodiment of the present disclosure provides a light-emitting device, which includes a light-emitting layer, and the light-emitting layer includes: a quantum dot body, a first ligand, and a second ligand; the first ligand is connected to the quantum dot body and is connected through a first cross-linking structure; the second ligand is dispersed in the quantum dot light-emitting layer, at least part of the second ligand is connected through a second cross-linking structure, and the first ligand and the second ligand have the same polarity. The light-emitting device provided by the embodiment of the present disclosure is a quantum dot light-emitting device (QLED), for example, including an active quantum dot light-emitting device (AMQLED) or a passive quantum dot light-emitting device, which can be used for display panels, backlight sources, etc. The light-emitting layer of the light-emitting device provided by the embodiment of the present disclosure has less residue in adjacent sub-pixels, a wider color gamut, and better luminescence performance; and the presence of the second ligand can make the combination of the first ligand and the quantum dot body more stable, and the luminescence performance of the light-emitting device is more stable.

[0006] For example, in the light-emitting device provided by at least one embodiment of the present disclosure, the total content ratio of the first ligand to the second ligand in the light-emitting layer is 10%-25%.

[0007] For example, in the light-emitting device provided in at least one embodiment of the present disclosure, the content ratio of the second ligand to the first ligand is 0.5-1.5.

[0008] For example, in the light-emitting device provided in at least one embodiment of the present disclosure, the first end of the first ligand is coordinated and connected to the quantum dot body, and the second ends of different first ligands are bonded to each other to form the first cross-linked structure; the first end of the second ligand is not connected to the quantum dot body, and the second ends of different second ligands are bonded to each other to form the second cross-linked structure.

[0009] For example, in the light-emitting device provided in at least one embodiment of the present disclosure, the first ligand and / or the second ligand include a short-chain ligand, and the number of carbon atoms in the main chain of the short-chain ligand is less than 12.

[0010] For example, in the light-emitting device provided in at least one embodiment of the present disclosure, the second ligand includes a long-chain ligand, and the number of carbon atoms in the main chain of the long-chain ligand is greater than or equal to 12.

[0011] For example, in the light-emitting device provided in at least one embodiment of the present disclosure, the second ligand and the first ligand are photosensitizing ligands, and the compositions of the second ligand and the first ligand may be the same or different.

[0012] For example, in the light-emitting device provided in at least one embodiment of the present disclosure, at least one of the first ligand initial ligand and the second supplementary ligand contains an ester group, the second ligand and the functional group at the first end include any one or more of thiol, amino, and carboxyl groups, and the functional group at the second end includes a double bond.

[0013] For example, in the light-emitting device provided in at least one embodiment of the present disclosure, the light-emitting layer includes: a first light-emitting layer emitting light of a first color, a second light-emitting layer emitting light of a second color, and a third light-emitting layer emitting light of a third color; the first light-emitting layer includes a first quantum dot body emitting light of the first color, the second light-emitting layer includes a second quantum dot body emitting light of the second color, and the third light-emitting layer includes a third quantum dot body emitting light of the third color; the content of the second ligand in the first light-emitting layer, the second light-emitting layer, and the third light-emitting layer are all different.

[0014] For example, in the light-emitting device provided in at least one embodiment of the present disclosure, the amount of the second ligand in the second light-emitting layer is greater than the amount of the second ligand in the first light-emitting layer, and the amount of the second ligand in the first light-emitting layer is greater than the amount of the second ligand in the third light-emitting layer; the first color is red, the second color is green, and the third color is blue.

[0015] For example, in the light-emitting device provided in at least one embodiment of the present disclosure, the light-emitting layer is located on a substrate, and the amount of the second ligand on the upper surface of the light-emitting layer away from the substrate is greater than the amount of the second ligand on the lower surface of the light-emitting layer close to the substrate.

[0016] For example, in the light-emitting device provided in at least one embodiment of the present disclosure, the size of the quantum dot particles in the light-emitting layer and the overall particles formed by agglomeration of multiple quantum dot particles are less than 100 nanometers.

[0017] For example, the light-emitting device provided in at least one embodiment of the present disclosure further includes an auxiliary layer, where the auxiliary layer is located on a side of the light-emitting layer close to the substrate and in contact with the light-emitting layer.

[0018] For example, in the light-emitting device provided in at least one embodiment of the present disclosure, the light-emitting layer also includes nanoparticles, at least part of the nanoparticles fill the gaps between the quantum dot bodies, and the surfaces of the nanoparticles are coordinated with filling ligands, and the filling ligands are ligands with the same composition as at least one of the first ligand and the second ligand.

[0019] For example, in the light-emitting device provided in at least one embodiment of the present disclosure, the nanoparticles are P-type semiconductor nanoparticles.

[0020] At least one embodiment of the present disclosure further provides a display device, which includes any one of the display devices provided in the embodiments of the present disclosure.

[0021] At least one embodiment of the present disclosure further provides a method for preparing a light-emitting device, which is used to prepare any one of the light-emitting devices provided in the embodiments of the present disclosure, and the method for preparing the light-emitting device includes: forming the light-emitting layer, and the forming of the light-emitting layer includes: forming a quantum dot solution, including forming a pre-quantum dot solution, wherein the pre-quantum dot solution includes an initial ligand, and ligand coordination is performed in the pre-quantum dot solution, and the initial ligand is coordinated on the quantum dot body in the pre-quantum dot solution; adding a first supplementary ligand to the pre-quantum dot solution coordinated by the ligand to form the quantum dot solution, wherein the polarity of the first supplementary ligand is the same as the polarity of the initial ligand, and at least part of the first supplementary ligand is not coordinated with the quantum dot body; forming a pre-quantum dot layer using the quantum dot solution; and performing a photolithography process on the pre-quantum dot layer to form the light-emitting layer.

[0022] For example, in the method for preparing a light-emitting device provided in at least one embodiment of the present disclosure, the first supplementary ligand and the initial ligand are ligands with the same composition or ligands with different compositions.

[0023] For example, the method for preparing a light-emitting device provided in at least one embodiment of the present disclosure further includes: cleaning the quantum dot body after the ligand coordination; and adding the first supplementary ligand to the pre-quantum dot solution after cleaning the quantum dot body.

[0024] For example, in the method for preparing a light-emitting device provided in at least one embodiment of the present disclosure, the amount of the first supplementary ligand added to the pre-quantum dot solution coordinated by the ligand accounts for 1% to 20% of the concentration of the pre-quantum dot solution.

[0025] For example, in the method for preparing a light-emitting device provided in at least one embodiment of the present disclosure, the photolithography process includes an exposure-development step, and the method for preparing the light-emitting device further includes: adding a second supplementary ligand to the developer used in the exposure-development step, wherein the initial ligand, the first supplementary ligand and the second supplementary ligand are all photosensitive ligands, and the polarity of the second supplementary ligand is the same as the polarity of the first supplementary ligand.

[0026] For example, in the preparation method of the light-emitting device provided in at least one embodiment of the present disclosure, the functional group at the first end of any one of the initial ligand, the first supplementary ligand and the second supplementary ligand includes at least one of a thiol group, an amino group and a carboxyl group, the functional group at the second end of any one of the initial ligand, the first supplementary ligand and the second supplementary ligand includes a double bond, and any one of the initial ligand, the first supplementary ligand and the second supplementary ligand contains an ester group.

[0027] For example, in the method for preparing a light-emitting device provided in at least one embodiment of the present disclosure, the amount of the second supplementary ligand added to the developer is 0.5% to 10% by mass of the developer.

[0028] For example, in the method for preparing a light-emitting device provided in at least one embodiment of the present disclosure, the first supplementary ligand and / or the second supplementary ligand include a short-chain ligand, and the number of carbon atoms in the main chain of the short-chain ligand is less than 12.

[0029] For example, in the method for preparing a light-emitting device provided in at least one embodiment of the present disclosure, the first supplementary ligand and / or the second supplementary ligand include a long-chain ligand, and the number of carbon atoms in the main chain of the long-chain ligand is greater than or equal to 12.

[0030] For example, the preparation method of the light-emitting device provided in at least one embodiment of the present disclosure also includes: providing a substrate; forming a soluble layer including an auxiliary ligand on the substrate, wherein the polarity of the auxiliary ligand is the same as the polarity of the initial ligand and the polarity of the first supplementary ligand; and forming the pre-quantum dot layer on the soluble layer.

[0031] For example, the preparation method of the light-emitting device provided in at least one embodiment of the present disclosure further includes: forming an anode, a hole injection layer and a hole transport layer in sequence on the substrate, and forming the easily soluble layer on the hole transport layer; or, forming a cathode, an electron injection layer and an electron transport layer in sequence on the substrate, and forming the easily soluble layer on the electron transport layer.

[0032] For example, in the preparation method of the light-emitting device provided in at least one embodiment of the present disclosure, the forming of the light-emitting layer includes: sequentially forming a first light-emitting layer in the first sub-pixel area, forming a second light-emitting layer in the second sub-pixel area, and forming a third light-emitting layer in the third sub-pixel area, wherein the first light-emitting layer includes a first quantum dot body that emits light of a first color, the second light-emitting layer includes a second quantum dot body that emits light of a second color, and the third light-emitting layer includes a third quantum dot body that emits light of a third color; forming each of the first light-emitting layer, the second light-emitting layer, and the third light-emitting layer includes forming the corresponding quantum dot solution, adding the first supplementary ligand, forming the corresponding pre-quantum dot layer using the corresponding quantum dot solution, and performing a photolithography process on the corresponding pre-quantum dot layer to form each corresponding light-emitting layer.

[0033] For example, the preparation method of the light-emitting device provided in at least one embodiment of the present disclosure also includes: after preparing the first light-emitting layer, eluting the first quantum dot body located in the second sub-pixel area and the third sub-pixel area; after preparing the second light-emitting layer, eluting the second quantum dot body located in the first sub-pixel area and the third sub-pixel area; and after preparing the third light-emitting layer, eluting the third quantum dot body located in the first sub-pixel area and the second sub-pixel area.

[0034] For example, in the preparation method of the light-emitting device provided in at least one embodiment of the present disclosure, the mass percentage of the first supplementary ligand added to the quantum dot solution used to form the first light-emitting layer, the mass percentage of the first supplementary ligand added to the quantum dot solution used to form the second light-emitting layer, and the mass percentage of the first supplementary ligand added to the quantum dot solution used to form the third light-emitting layer are different from each other.

[0035] For example, in the preparation method of the light-emitting device provided in at least one embodiment of the present disclosure, the first color is red, the second color is green, and the third color is blue; in the process of preparing the first light-emitting layer, the mass percentage of the first supplementary ligand added to the quantum dot solution used to form the first light-emitting layer is 5% to 15%; in the process of preparing the second light-emitting layer, the mass percentage of the first supplementary ligand added to the quantum dot solution used to form the second light-emitting layer is 10% to 20%; in the process of preparing the third light-emitting layer, the mass percentage of the first supplementary ligand added to the quantum dot solution used to form the second light-emitting layer is 1% to 10%.

[0036] For example, the method for preparing a light-emitting device provided in at least one embodiment of the present disclosure further includes: adding nanoparticles to the pre-quantum dot solution, and forming the pre-quantum dot layer using the quantum dot solution obtained after adding the nanoparticles.

[0037] For example, in the method for preparing a light-emitting device provided in at least one embodiment of the present disclosure, the nanoparticles are P-type semiconductor nanoparticles. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings of the embodiments will be briefly introduced below. Obviously, the drawings in the following description only relate to some embodiments of the present disclosure, rather than limiting the present disclosure.

[0039] FIG1A is a schematic structural diagram of a light-emitting device provided in one embodiment of the present disclosure;

[0040] FIG1B is a schematic structural diagram of another light-emitting device provided in one embodiment of the present disclosure;

[0041] FIG2 is a schematic diagram of the state before and after the cross-linking reaction between the first ligand and the second ligand in the light-emitting layer in FIG1 ;

[0042] FIG3 is a nuclear magnetic resonance spectrum of a light-emitting layer of a light-emitting device provided in one embodiment of the present disclosure;

[0043] FIG4 is a schematic block diagram of a display device provided by an embodiment of the present disclosure;

[0044] FIG5 is a flow chart of a method for preparing a light-emitting device according to an embodiment of the present disclosure;

[0045] 6A-6H are schematic diagrams of a method for manufacturing a light-emitting device according to an embodiment of the present disclosure;

[0046] FIG7 is a thermogravimetric curve of a thermogravimetric experiment performed on a sample of the first pre-quantum dot solution after ligand exchange of the first quantum dot body with the initial ligand during the three preparation processes;

[0047] FIG8 is a schematic diagram of a process of cross-linking reaction between the initial ligand and / or the first supplementary ligand;

[0048] FIG9 is a diagram showing device efficiency when different amounts of the first supplementary ligand are added to the quantum dot solution;

[0049] FIG10 is an electron microscope image of the light-emitting layer after film formation under conditions where the total mass percentage of the initial ligand and the first supplementary ligand in the quantum dot solution is different;

[0050] FIG11 is an electron microscope image of the residual state of the quantum dot body of the light-emitting device in the non-target area obtained under conditions where the amount of the second supplementary ligand added to the developer is different in mass percentage of the developer. DETAILED DESCRIPTION

[0051] To make the purpose, technical solutions, and advantages of the embodiments of the present disclosure more clear, the technical solutions of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings of the embodiments of the present disclosure. The embodiments described below are part of the embodiments of the present disclosure, not all of the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0052] Unless otherwise defined, the technical or scientific terms used herein should have the usual meanings understood by persons of ordinary skill in the field to which the invention belongs. The words "first", "second" and similar terms used in this disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, words such as "include" or "comprise" mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Words such as "connect" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0053] In a color display panel using quantum dot light-emitting devices, one pixel includes multiple sub-pixels, and the luminous colors of the quantum dot light-emitting devices of the multiple sub-pixels are different from each other. Photolithography is a commonly used and effective method for preparing the quantum dot light-emitting layer of a quantum dot light-emitting device. During the preparation of the quantum dot light-emitting layer using photolithography, due to the complex interaction between the quantum dots and the film layer below them, and due to the volatilization of the quantum dot solvent in the quantum dot solution used to prepare the quantum dot light-emitting layer, some quantum dots agglomerate into large particles, and during the development process, some quantum dots (luminescent quantum dot bodies) remain in non-target areas, such as in adjacent sub-pixel areas. These quantum dots remaining in adjacent sub-pixel areas will crosstalk the colors of adjacent sub-pixels, affecting the color gamut and performance of the quantum dot light-emitting device. Therefore, in order to solve the problem of color crosstalk in high-resolution quantum dot light-emitting devices (QLEDs) and achieve mass production of high-resolution QLEDs, it is necessary to solve the problem of quantum dot residue in the process of preparing the patterned light-emitting layer by photolithography.

[0054] At least one embodiment of the present disclosure provides a light-emitting device, which includes a light-emitting layer, and the light-emitting layer includes: a quantum dot body, a first ligand, and a second ligand; the first ligand is connected to the quantum dot body and is connected through a first cross-linking structure; the second ligand is dispersed in the quantum dot light-emitting layer, at least part of the second ligand is connected through a second cross-linking structure, and the first ligand and the second ligand have the same polarity. The light-emitting device provided by the embodiment of the present disclosure is a quantum dot light-emitting device (QLED), for example, including an active quantum dot light-emitting device (AMQLED) or a passive quantum dot light-emitting device, which can be used for display panels, backlight sources, etc. The light-emitting layer of the light-emitting device provided by the embodiment of the present disclosure has less residue in adjacent sub-pixels, a wider color gamut, and better luminescence performance; and the presence of the second ligand can make the combination of the first ligand and the quantum dot more stable, and the luminescence performance of the light-emitting device is more stable.

[0055] At least one embodiment of the present disclosure further provides a display device, which includes any one of the display devices provided in the embodiments of the present disclosure.

[0056] At least one embodiment of the present disclosure further provides a method for preparing a light-emitting device, which is used to prepare any one of the light-emitting devices provided in the embodiments of the present disclosure, and the method for preparing the light-emitting device includes: the method for preparing the light-emitting device includes: forming the light-emitting layer, and the forming of the light-emitting layer includes: forming a quantum dot solution, including forming a pre-quantum dot solution, wherein the pre-quantum dot solution includes an initial ligand, ligand coordination is performed in the pre-quantum dot solution, and the initial ligand is coordinated on the quantum dot body in the pre-quantum dot solution; adding a first supplementary ligand to the pre-quantum dot solution coordinated by the ligand to form the quantum dot solution, wherein the polarity of the first supplementary ligand is the same as that of the initial ligand, and at least part of the first supplementary ligand is a second supplementary ligand that is not coordinated with the quantum dot body; forming a pre-quantum dot layer using the quantum dot solution; and performing a photolithography process on the pre-quantum dot layer to form the light-emitting layer.

[0057] In the preparation method of the light-emitting device provided by the embodiment of the present disclosure, after the quantum dot body and the initial ligand are ligand-coordinated, a first supplementary ligand is further added to the quantum dot solution, and the polarity of the first supplementary ligand is the same as that of the initial ligand, so that at least part of the first supplementary ligand is an excess ligand, and at least part of the first supplementary ligand is used as a second ligand that is not coordinated with the quantum dot body, thereby being able to bind sufficient ligands to the sites on the surface of the quantum dot body, for example, to fill the sites, and there is an excess of the second ligand, so as to increase the dispersibility of the quantum dots in the pre-quantum dot layer after film formation formed by the quantum dot solution, form more single-particle quantum dots and small aggregates of quantum dots, reduce the agglomeration of the quantum dot body, reduce or avoid the formation of large-particle quantum dot clusters, and be able to prepare patterns by photolithography. During the process of patterning the light-emitting layer, the solubility of the quantum dot body in the developer is increased, so that large particles of the quantum dot body can be prevented from agglomerating and remaining in non-target areas during the development process, thereby affecting the color gamut and performance of the light-emitting device. During the development process, most of the non-cross-linked quantum dots located in non-target areas (for example, sub-pixels adjacent to the target sub-pixels used to form the light-emitting layer) after exposure can be removed, and the quantum dot body is kept only in the target area as much as possible, for example, only in the target sub-pixel area to prevent the problem of light-emitting color crosstalk caused by remaining in the adjacent sub-pixel area, which greatly reduces the residue of the quantum dot body in the non-target area, effectively improves the patterning accuracy of the light-emitting layer of the light-emitting device, and is of great significance to the realization of high-color gamut, high-performance, high-resolution quantum dot light-emitting devices or light-emitting panels.

[0058] For example, FIG1A is a schematic structural diagram of a light-emitting device provided by one embodiment of the present disclosure. Referring to FIG1A , for example, the light-emitting layer 5 includes: a first light-emitting layer 51 emitting light of a first color, a second light-emitting layer 52 emitting light of a second color, and a third light-emitting layer 53 emitting light of a third color. The first light-emitting layer includes a first quantum dot body emitting light of the first color, the second light-emitting layer includes a second quantum dot body emitting light of the second color, and the third light-emitting layer includes a third quantum dot body emitting light of the third color. For example, the light-emitting device 10 is applied to a display panel, which includes multiple pixels, each pixel including multiple sub-pixels, for example, each pixel including three sub-pixels, each including a first light-emitting layer 51, a second light-emitting layer 52, and a third light-emitting layer 53, respectively, to achieve color display. Ideally, the first light-emitting layer 51, the second light-emitting layer 52, and the third light-emitting layer 53 are each located in their respective sub-pixel regions, with no quantum dots remaining in other sub-pixels to avoid crosstalk between light of different colors emitted by different sub-pixels.

[0059] For example, the quantum dots disclosed herein include a quantum dot body and a ligand connected to the quantum dot body, wherein the quantum dot body includes any one of group IIB-VIA quantum dots, group IIIA-VA quantum dots, group IVA-VIA quantum dots, core-shell quantum dots, and ABX3 type perovskite quantum dots. In the ABX3 type perovskite quantum dots, A is CH3NH3 + (methylamine), NH2CH=NH2(formamidine) and Cs + One or more of, B is Pb 2+ and Sn 2+ One or two of the following, X is Cl - Br - and I - One or more of the ABX3 type perovskite quantum dots include CH3NH3PbBr3, CH3NH3PbCl3, CH3NH3PbI3, CsPbBr3, CsPbCl3 and CsPbI3.

[0060] Exemplarily, the IIB-VIA group quantum dots are selected from: binary compounds such as one or more of CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, MgSe, and MgS; ternary compounds such as CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZn Te, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, MgZnSe, MgZnS, or mixtures thereof; and quaternary compounds such as HgZnTeS, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, HgZnSTe, or mixtures thereof, but are not limited thereto.

[0061] The IIIA-VA group quantum dots are selected from: binary compounds such as GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, or mixtures thereof; ternary compounds such as GaNPs, GaNAs, GaNSb, GaPAs, GaPSb, AlNPs, AlNAs, AlNSb, AlPAs, AlPSb, InNPs, InNAs, InNSb, InPAs, InPSb, or mixtures thereof; and quaternary compounds such as GaAlNPs, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNPs, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNPs, InAlNAs, InAlNSb, InAlPAs, InAlPSb, or mixtures thereof, but are not limited thereto.

[0062] Group IVA-VIA quantum dots are selected from, but are not limited to, binary compounds such as SnS, SnSe, SnTe, PbS, PbSe, PbTe, or mixtures thereof; ternary compounds such as SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, or mixtures thereof; and quaternary compounds such as SnPbSSe, SnPbSeTe, SnPbSTe, or mixtures thereof. Group IVA-VIA quantum dots are selected, for example, from elemental (mono) semiconductors such as Si, Ge, or mixtures thereof; and binary semiconductor compounds such as SiC, SiGe, and mixtures thereof.

[0063] Core-shell quantum dots are structures where one material is the core and the other is the shell. For example, a CdS / ZnS quantum dot is a quantum dot where the core is CdS and the shell is ZnS.

[0064] In some other embodiments, the quantum dot bodies may be other nanoscale materials, such as nanorods, nanosheets, etc. The components of other nanoscale materials may include at least one of CdS, CdSe, CdTe, ZnSe, InP, PbS, CuInS2, ZnO, CsPbCl3, CsPbBr3, CsPhI3, CdS / ZnS, CdSe / ZnS, ZnSe, InP / ZnS, PbS / ZnS, InAs, InGaAs, InGaN, GaNk, ZnTe, Si, Ge, and C.

[0065] For example, the quantum dot body can include cadmium (Cd)-free quantum dots. Cadmium-free quantum dots are quantum dots that do not include cadmium (Cd). Cadmium (Cd) can cause serious environmental / health problems, so non-cadmium-based quantum dots can be effectively used.

[0066] FIG2 is a schematic diagram illustrating the states of the first and second ligands in the light-emitting layer of FIG1 before and after a cross-linking reaction. Referring to FIG1A-2 , a light-emitting device 10 provided in at least one embodiment of the present disclosure includes a light-emitting layer 5, which includes a quantum dot body 50, a first ligand 01, and a second ligand 02. The first ligand 01 is coordinated to the quantum dot body 50 to bond with the quantum dot body 50, and the plurality of first ligands 01 are cross-linked to each other via a first cross-linking structure. The second ligand 02 is not coordinated to the quantum dot and is cross-linked via a second cross-linking structure. The polarity of the second ligand is the same as that of the first ligand. As shown in FIG2 (a), during the preparation of the light-emitting layer, before the first ligand and the second ligand undergo a cross-linking reaction, there are first ligands 01 coordinated to the surface of the quantum dot body 50 and second ligands 02 not coordinated to the quantum dot body 50; the first ligands 01 coordinated to the surface of the quantum dot body 50 are cross-linked to form a first cross-linked structure 01a, and the second ligands 02 are cross-linked to form a second cross-linked structure 02a, thereby obtaining the final light-emitting layer, as shown in FIG2 (b). In addition, the final light-emitting layer also contains second ligands 02 not coordinated to the quantum dot body 50. For example, the second ligands 02 are present on the surface of the light-emitting layer 5, on the surface of the quantum dots, and in the gaps between adjacent quantum dot bodies.

[0067] In the light-emitting device 10 provided by the embodiment of the present disclosure, the second ligand 02 is an excess ligand in the ligand that can be combined with the ligand that can be combined with the quantum dot body 50. Therefore, on the one hand, in the process of preparing the light-emitting layer 5, the ligand used to combine with the quantum dot body 50 is also excessive, so that the sites on the surface of the quantum dot body can be combined with enough ligands, for example, the sites are fully occupied or substantially fully occupied, and there is an excess of the second ligand 02 to increase the dispersibility of the quantum dots in the pre-quantum dot layer after the film is formed using the quantum dot solution, to form more single-particle quantum dots and small aggregates of quantum dots, to reduce the agglomeration of quantum dots, and to reduce or avoid the formation of large particles. Quantum dot clusters can increase the solubility of quantum dots in the developer during the process of preparing a patterned light-emitting layer by photolithography, thereby avoiding large-particle quantum dot clusters from remaining in non-target areas during the development process and affecting the color gamut and performance of the light-emitting device. The prepared light-emitting layer 5 has less residue in non-target areas such as adjacent sub-pixels, a wider color gamut, and better luminescence performance. On the other hand, the second ligand 02 is an excess ligand in the ligand that can be combined with the ligand that can be combined with the quantum dot body 50. The presence of the second ligand 02 can make the combination of the first ligand 01 and the quantum dot body 50 more stable, and the luminescence performance of the light-emitting device more stable.

[0068] For example, the total content ratio of the first ligand and the second supplementary ligand in the light-emitting layer 5 is 10%-25%. For example, the content ratio of the second ligand to the first ligand is 0.5-1.5, so that the light-emitting device can achieve good luminescence performance. For example, through experiments, it has been found that to ensure the luminescence performance of the light-emitting device, the preferred range of the content ratio of the second supplementary ligand to the first ligand is 0.75-1.25 or 0.8-1.

[0069] For example, referring to FIG2(b), a continuous second cross-linked structure 02a runs through multiple quantum dot bodies 50 and cooperates with the excess second ligand 02 in the light-emitting layer to make the formed light-emitting layer more stable, increase the dispersion of quantum dots in the pre-quantum dot layer formed using the quantum dot solution after film formation, form more single-particle quantum dots and small aggregates of quantum dots, reduce quantum dot agglomeration, and increase the solubility of quantum dots in the developer. This can prevent large quantum dot clusters from remaining in non-target areas during the development process and affecting the color gamut and performance of the light-emitting device. The second cross-linked structure 02a can exist in various locations and can also exist between two quantum dots, or on the surface of one or more quantum dots.

[0070] The polarity of the second ligand is the same as that of the first ligand means that the effective functional group of the second ligand is the same as that of the first ligand, the first end of the second ligand and the first ligand can both be coordinated and bound to the quantum dot, and the second ends of different second ligands and the second ends of different first ligands can bond to each other to form a cross-linked structure.

[0071] For example, the first end of the first ligand 01 is coordinated with the quantum dot body to combine with the quantum dot body, and the second ends of different first ligands 01 are bonded to each other to form a first cross-linked structure; the first end of the second ligand 02 is not coordinated with the quantum dot body, and the second ends of different second ligands 02 are bonded to each other to form a second cross-linked structure.

[0072] For example, the second ligand 02 and the first ligand 01 are photosensitizing ligands. For example, the second ligand 02 and the first ligand 01 are ligands of the same composition or ligands of different compositions, but both contain functional groups capable of coordinating with the quantum dot body and functional groups capable of bonding to each other to cross-link with each other, and can undergo cross-linking under light (e.g., ultraviolet light) conditions, so as to form a patterned light-emitting layer using a photolithography process, and simultaneously form a first cross-linked structure and a second cross-linked structure.

[0073] For example, the functional group at the first end of the first ligand 01 and / or the second ligand 02 includes at least one of a thiol group (-SH), an amino group (-NH2), and a carboxyl group (-COOH), the functional group at the second end of the first ligand 01 and / or the second ligand 02 includes a double bond, and the first ligand 01 and / or the second ligand 02 contain an ester group, such as an acrylate. For example, the first ligand 01 and / or the second ligand 02 further contain a polyethylene glycol polymer chain structure (PEG structure). The first ligand 01 and the second ligand 02 are soluble in an ester solvent, and the solvent of the developer is an ester solvent, such as propylene glycol methyl ether acetate (PGMEA).

[0074] At least one of a thiol group (-SH), an amino group (-NH2) and a carboxyl group (-COOH), a double bond, an ester group, and a PEG structure are all the above-mentioned effective functional groups.

[0075] Taking the first ligand and / or the second ligand containing acrylate as an example, the general chemical formula of both can be: CH2=CHCOO-PEG-A (A can be selected from: thiol, amino, carboxyl), specifically, for example, it can be thiol PEG acrylate (chemical formula CH2=CHCOO-PEG-SH) or carboxyl PEG acrylate (chemical formula CH2=CHCOO-PEG-COOH).

[0076] For example, the first ligand and / or the second ligand include but are not limited to mono[2-[(2-methyl-acryloyl)oxy]ethyl]succinate (MMES), which is a commonly used ligand that can coordinate with the quantum dot body and has good solubility in the developer.

[0077] Of course, the types listed above are only exemplary, and the first ligand and the second ligand are not limited to the types listed above.

[0078] For example, in one embodiment, both the first and second ligands are MMES. Figure 3 shows an NMR spectrum of the light-emitting layer 5. As can be seen from Figure 3, characteristic chemical shift peaks ① and ② of MMES are present. Peaks ① and ② are relatively sharp, representing peaks characteristic of hydrogen on the C=C double bond. When MMES is in a free state, i.e., as the second ligand, these characteristic peaks are relatively sharp, indicating the presence of free MMES ligands. However, after MMES is coordinated with the quantum dot bulk, relatively flatter, broader peaks ③ and ④ appear. In the light-emitting layer 5, in addition to the relatively flatter, broader peaks ③ and ④, sharp MMES peaks ⑤ and ⑥ are still visible. Peaks ⑤ and ⑥ are identical to peaks ① and ②, respectively, indicating the presence of uncoordinated, free MMES ligands, i.e., the second ligand.

[0079] For example, the first ligand 01 and / or the second ligand 02 include a short-chain ligand, and the number of carbon atoms in the main chain of the short-chain ligand is less than 12, such as 3-aminobutyric acid methyl ester. For example, according to the results of experimental tests, the number of carbon atoms in the main chain is 6-10, which is better. The short-chain ligand has low steric hindrance, which is conducive to allowing more ligands to be bound to the surface of the quantum dot body, thereby improving the solubility of the non-crosslinked area of ​​the front quantum dot layer during the development process of the front quantum dot layer to form the pattern of the light-emitting layer 5 in the target area, and reducing the residue of quantum dots in non-target areas.

[0080] For example, the first ligand 01 and / or the second ligand 02 may further include a long-chain ligand, wherein the number of carbon atoms in the main chain of the long-chain ligand is greater than or equal to 12, such as mercapto PEG acrylate. The long-chain ligand not only provides an ester group for dissolution in a developer and a double bond for undergoing a cross-linking reaction under illumination, but also facilitates the provision of a PEG structure, which is beneficial for increasing the solubility of the unilluminated portion of the pre-quantum dot layer used to prepare the light-emitting layer in the developer, thereby reducing the residue of the final light-emitting layer in non-target areas.

[0081] For example, the amount of the second ligand O2 in the first light-emitting layer 51, the second light-emitting layer 52, and the third light-emitting layer 53 is different to accommodate the difference in stability between the quantum dot bodies and the ligands of different luminescent colors. The amount of the second ligand can refer to the mass percentage of the second ligand in the corresponding light-emitting layer.

[0082] For example, the amount of second ligand O2 in the second light-emitting layer 52 is greater than that in the first light-emitting layer 51, and the amount of second ligand O2 in the first light-emitting layer 51 is greater than that in the third light-emitting layer 53; the first color is red, the second color is green, and the third color is blue. That is, among the light-emitting layers that emit red, green, and blue light, respectively, the amount of second ligand O2 in the green light-emitting layer is the largest. According to previous experimental results, when forming light-emitting layers using an exposure-development process, under the same development conditions, the amount of blue-emitting quantum dots, red-emitting quantum dots, and green-emitting quantum dots remaining in non-target areas increases in descending order, meaning that green quantum dots are most likely to remain. Therefore, the green quantum dot body needs to add the most second ligand, so that the amount of free quantum dots finally formed is the largest, so as to fully increase the dispersion of quantum dots in the pre-quantum dot layer after film formation formed by using the solution to prepare quantum dots that emit green light, form more single-particle quantum dots and small aggregates of quantum dots, reduce the agglomeration of quantum dots, and increase the solubility of quantum dots in the developer, so as to avoid large-particle quantum dot clusters remaining in non-target areas during the development process and affecting the color gamut and performance of the light-emitting device.

[0083] For example, the light-emitting layer 5 is located on the substrate 1, and the amount of the second ligand O2 on the upper surface of the light-emitting layer 5 away from the substrate 1 is greater than the amount of the second ligand O2 on the lower surface of the light-emitting layer 5 close to the substrate. This is true for the first light-emitting layer 51, the second light-emitting layer 52, and the third light-emitting layer 53. During the process of forming the light-emitting layer 5, the first light-emitting layer 51, the second light-emitting layer 52, and the third light-emitting layer 53 are formed in sequence. After the first light-emitting layer 51 is formed, the pre-quantum dot layer used to form the second light-emitting layer 52 is exposed and developed. During this process, a larger amount of the second ligand O2 on the upper surface of the first light-emitting layer 51 away from the substrate 1 is beneficial for maintaining the stable binding between the quantum dot bodies and the first ligands in the first light-emitting layer 51. The same is true for the other light-emitting layers.

[0084] For example, referring to FIG1A , the light-emitting device 10 in each sub-pixel further includes a first electrode 2 , for example, the first electrode 2 is an anode, for example, the material of the anode is a transparent conductive material, such as indium tin oxide (ITO) or indium zinc oxide (IZO), etc., and the specific type of the transparent conductive material is not limited. For example, the light-emitting device 10 further includes a hole injection layer 2 and a hole transport layer 3 sequentially arranged on the first electrode 1, and the light-emitting layer 5 is located on the hole transport layer 3. For example, the material of the hole injection layer is a polymer of 3,4-ethylenedioxythiophene monomer (PEDOT), and the material of the hole transport layer is 1,2,4,5-tetrakis(trifluoromethyl)benzene (TFB). For example, the light-emitting device 10 further includes a second electrode 8 arranged opposite to the first electrode 2, the second electrode 8 is a cathode, for example, the material of the second electrode 8 is metal aluminum (Al), and it can also be a stacked structure, for example, a stacked structure composed of three layers of metals of Ti / Al / Ti as the anode. Of course, the material of the cathode is not limited to the types listed above. For example, the light emitting device 10 further includes an electron transport layer 7 located on a side of the light emitting layer 5 close to the cathode. For example, the material of the electron transport layer is zinc oxide (ZnO).

[0085] Of course, the materials for the hole injection layer, hole transport layer, and electron transport layer functional film layers are not limited to the types listed above, and those skilled in the art can select them according to conventional techniques in the art. The light-emitting device 10 is not limited to the bottom emission type shown in FIG. 1A ; it can also be a top emission type. Those skilled in the art can adapt the corresponding structural changes according to conventional techniques in the art.

[0086] For example, the light emitting device 10 further includes a pixel defining layer 6 , which is located between adjacent sub-pixels to define opening regions of a plurality of sub-pixels, and the light emitting layer 5 is located within the opening region of each sub-pixel.

[0087] For example, the quantum dot particles in the light-emitting layer, as well as the aggregated particles formed by agglomerating multiple quantum dot particles, are less than 100 nanometers in size. In the light-emitting layer of the light-emitting device provided by the embodiments of the present disclosure, the quantum dots have a high degree of dispersion, the quantum dot layer of the device is manufactured with high precision, and the color gamut is wider, enabling the realization of high-precision, high-PPI light-emitting panels (such as display panels or backlight panels), and improving the performance of the light-emitting device.

[0088] For example, the size of a single quantum dot particle in the light-emitting layer is less than 10 nanometers. For example, the average particle size of blue quantum dots emitting blue light ranges from 2.0 nm to 4.5 nm, the average particle size of green quantum dots emitting green light ranges from 3 nm to 5 nm, and the average particle size of red quantum dots emitting red light ranges from 3.5 nm to 5.5 nm.

[0089] For example, the light-emitting device 10 further includes nanoparticles, at least some of which are filled in the gaps between the quantum dot bodies, and the surface of the nanoparticles is coordinated with a filling ligand, which is the same ligand as at least one of the first ligand and the second ligand. During the manufacturing process, the above-mentioned nanoparticles are added to the quantum dot solution used to form the light-emitting layer, and some of the nanoparticles are filled in the gaps between the quantum dot bodies. At least one of the first ligand and the second ligand is coordinated on the surface of the nanoparticles and thus combined with the nanoparticles to form the filling ligands in the light-emitting device finally prepared. As a result, the filling ligand is the same ligand as at least one of the first ligand and the second ligand. Nanoparticles with smaller volumes can fill the gaps between the quantum dot bodies to reduce leakage current. At the same time, nanoparticles with larger specific surface areas can bind more ligands, thereby further increasing the solubility of the pre-quantum dot layer in the developer after film formation, thereby reducing the residue of the final light-emitting layer in non-target areas.

[0090] For example, the nanoparticles are P-type semiconductor nanoparticles. Therefore, since holes are majority carriers in the light-emitting device, adding P-type semiconductor nanoparticles can accelerate hole injection, increase electron migration rate, and thus improve the conductive performance of the light-emitting device.

[0091] For example, the diameter of the P-type semiconductor nanoparticles ranges from 2 nm to 5 nm. For example, the material of the P-type semiconductor nanoparticles is at least one of NiOx, MoOx, WOx, and Vox. Of course, the material of the P-type semiconductor nanoparticles is not limited to the aforementioned types.

[0092] For example, referring to FIG1A , the light-emitting device 10 further includes an auxiliary layer 4, which is located on the side of the light-emitting layer 5 near the substrate 1 and in contact with the light-emitting layer 5. Taking a pixel comprising first to third sub-pixels as an example, the auxiliary layer 4 includes a first auxiliary layer 41, a second auxiliary layer 42, and a third auxiliary layer 43. The first auxiliary layer 41 is located in the first sub-pixel region, on the side of the first light-emitting layer 51 near the substrate 1 and in contact with the first light-emitting layer 51; the second auxiliary layer 42 is located in the second sub-pixel region, on the side of the second light-emitting layer 52 near the substrate 1 and in contact with the second light-emitting layer 52; and the third auxiliary layer 43 is located in the third sub-pixel region, on the side of the third light-emitting layer 53 near the substrate 1 and in contact with the third light-emitting layer 53. The auxiliary layer 4 includes cross-linked auxiliary ligands, the polarity of which is the same as that of the first ligand and the second ligand (please refer to the previous description for the definition of "same polarity"). For example, the auxiliary ligand may be the same ligand as the first ligand and / or the second ligand, or may be a ligand with the same polarity but different composition. For example, the selection of the type of auxiliary ligand can refer to the above introduction to the types of the first ligand and the second ligand. Before forming the pre-quantum dot layer for forming the light-emitting layer, a soluble layer for forming the auxiliary layer is first formed, the soluble layer includes the above-mentioned auxiliary ligand, and then the pre-quantum dot layer is formed with the second soluble layer 4b as the substrate. The pre-quantum dot layer is subjected to an exposure-development process to obtain the light-emitting layer 5 and the auxiliary layer 4. The auxiliary layer 4 is generated by a cross-linking reaction of the illuminated portion of the soluble layer, and the light-emitting layer 5 is generated by a cross-linking reaction of the illuminated portion of the pre-quantum dot layer. This greatly increases the solubility of the double-layer structure of "pre-quantum dot layer / soluble layer 4b" as a whole in the developer, reducing the residue of the final light-emitting layer in non-target areas other than the target sub-pixel.

[0093] Figure 1B is a schematic diagram of the structure of another light-emitting device provided by one embodiment of the present disclosure. For example, the embodiment shown in Figure 1B differs from Figure 1A in that, based on Figure 1A, auxiliary layer 4 is removed. For example, light-emitting layer 5 is formed directly on hole transport layer 3. The other features and technical effects of the embodiment shown in Figure 1B are the same as those in Figure 1A, and can be referred to the previous description and will not be repeated here.

[0094] At least one embodiment of the present disclosure provides a display device. FIG4 is a schematic block diagram of a display device provided by at least one embodiment of the present disclosure. Referring to FIG4 , the display device 100 includes any one of the light-emitting devices 10 provided by the embodiments of the present disclosure. The display device can be, for example, a display panel, or any product or component with a display function, such as a monitor, an OLED panel, an OLED TV, electronic paper, a mobile phone, a tablet computer, a laptop computer, a digital photo frame, or a navigation system. Of course, the display devices provided by the embodiments of the present disclosure are not limited to the types listed above.

[0095] Accordingly, the display devices provided by the embodiments of the present disclosure all have the technical effects of the light-emitting devices provided by the embodiments of the present disclosure.

[0096] At least one embodiment of the present disclosure further provides a method for preparing a light-emitting device, which is used to prepare any one of the light-emitting devices provided in the embodiments of the present disclosure. FIG5 is a flow chart of a method for preparing a light-emitting device provided in at least one embodiment of the present disclosure. Referring to FIG5 , the method for preparing the light-emitting device includes forming a light-emitting layer, and forming the light-emitting layer includes steps S1 to S4.

[0097] S1: forming a quantum dot solution, including forming a pre-quantum dot solution, wherein the pre-quantum dot solution includes an initial ligand, ligand coordination is performed in the pre-quantum dot solution, and the initial ligand is coordinated on the quantum dot body in the pre-quantum dot solution.

[0098] S2: adding a first supplementary ligand to the ligand-coordinated pre-quantum dot solution to form the quantum dot solution, wherein the polarity of the first supplementary ligand is the same as that of the initial ligand, and at least part of the first supplementary ligand is not coordinated with the quantum dot body.

[0099] S3: forming a front quantum dot layer using a quantum dot solution.

[0100] S4: performing a photolithography process on the front quantum dot layer to form a light-emitting layer.

[0101] For example, after ligand coordination, the quantum dot includes the quantum dot body and the ligand coordinated on the quantum dot body. The preparation method of the light-emitting device also includes: after ligand coordination, the quantum dot body is cleaned (or the quantum dot is cleaned); and after cleaning the quantum dot body, the first supplementary ligand is added to the pre-quantum dot solution. In order to clean the interfering substances that are replaced by the initial ligand and are bound to the quantum dot body before the initial ligand is added, the adverse effects of these interfering substances are avoided, but the initial ligand remaining after the coordination with the quantum dot body will be washed away. Therefore, after the quantum dot body is cleaned after ligand coordination, the first supplementary ligand is added to the pre-quantum dot solution. The polarity of the first supplementary ligand is the same as that of the initial ligand, and the effective functional group of the first supplementary ligand is the same as that of the initial ligand. The first supplementary ligand can also be coordinated and bound to the quantum dot body, thereby providing the pre-quantum dot solution with a certain amount of light. Supplementing the liquid with an excess of ligands that can coordinate and bind to the quantum dot body is beneficial to filling the coordination sites on the surface of the quantum dot body, and the presence of excess second ligands is beneficial to enhancing the dispersibility of the quantum dots, forming more single-particle quantum dots and small aggregates of quantum dots, reducing the agglomeration of quantum dots, reducing or avoiding the formation of large-particle quantum dot clusters, and being able to increase the solubility of quantum dots in the developer in the process of preparing a patterned light-emitting layer by photolithography, thereby avoiding large-particle quantum dot clusters from remaining in non-target areas during the development process and affecting the color gamut and performance of the light-emitting device.

[0102] For example, a photolithography process includes an exposure-development step, and a method for preparing a light-emitting device further includes: adding a second supplementary ligand to a developer used in the exposure-development step, wherein the initial ligand, the first supplementary ligand, and the second supplementary ligand are all photosensitive ligands, and the polarity of the first supplementary ligand is the same as that of the initial ligand, thereby increasing the solubility of quantum dots in the developer and further reducing quantum dot agglomeration. In addition, at least a portion of the second supplementary ligand added to the developer will be retained in the final light-emitting layer, and at least a portion of the second supplementary ligand will serve as a second ligand in the final light-emitting layer to ensure the presence of the second ligand in the final light-emitting layer and increase the amount of the second ligand in the final light-emitting layer. The second ligand in the light-emitting layer of the final light-emitting device may also include at least one of the initial ligand and the first supplementary ligand.

[0103] For example, the first supplementary ligand, the second supplementary ligand and the initial ligand are the same ligand or different ligands.

[0104] The polarity of the first supplementary ligand is the same as the polarity of the initial ligand and the polarity of the second supplementary ligand, which means that the effective functional group of the first supplementary ligand is the same as the effective functional group of the initial ligand and the effective functional group of the second supplementary ligand, the first end of the first supplementary ligand, the first end of the initial ligand, and the first end of the second supplementary ligand can all be coordinated and bound to the quantum dot body, and the second ends of different first supplementary ligands, the second ends of different initial ligands, and the second ends of different second supplementary ligands can all bond to each other to form cross-links.

[0105] For example, the initial ligand, the first supplemental ligand, and the second supplemental ligand are ligands of the same composition or ligands of different compositions.

[0106] For example, the functional group at the first end of any one of the initial ligand, the first supplementary ligand, and the second supplementary ligand includes at least one of a thiol group (-SH), an amino group (-NH2), and a carboxyl group (-COOH), the functional group at the second end of the initial ligand and / or the first supplementary ligand includes a double bond, and any one of the initial ligand, the first supplementary ligand, and the second supplementary ligand contains an ester group such as an acrylate. For example, any one of the initial ligand, the first supplementary ligand, and the second supplementary ligand also contains a polymer chain structure of polyethylene glycol (PEG structure). The initial ligand and the first supplementary ligand can be dissolved in an ester solvent, and the solvent of the developer is an ester solvent, such as propylene glycol methyl ether acetate (PGMEA).

[0107] At least one of a thiol group (-SH), an amino group (-NH2) and a carboxyl group (-COOH), a double bond, an ester group, and a PEG structure are all the above-mentioned effective functional groups.

[0108] Taking the example that any one of the initial ligand, the first supplementary ligand and the second supplementary ligand contains acrylate, the general chemical formula of the initial ligand, the first supplementary ligand and the second supplementary ligand can all be: CH2=CHCOO-PEG-A (A can be selected from: thiol, amino, carboxyl). Specifically, for example, it can be thiol PEG acrylate (chemical formula CH2=CHCOO-PEG-SH) or carboxyl PEG acrylate (chemical formula CH2=CHCOO-PEG-COOH).

[0109] For example, any one of the initial ligand, the first supplementary ligand and the second supplementary ligand includes but is not limited to mono[2-[(2-methyl-acryloyl)oxy]ethyl]succinate (MMES), which is a commonly used ligand that can coordinate with the quantum dot body and has good solubility in the developer.

[0110] For example, forming the light-emitting layer 5 includes: sequentially forming a first light-emitting layer 51 in the first sub-pixel area, forming a second light-emitting layer 52 in the second sub-pixel area, and forming a third light-emitting layer 53 in the third sub-pixel area, wherein the first light-emitting layer 51 includes a first quantum dot body that emits light of a first color, the second light-emitting layer 52 includes a second quantum dot body that emits light of a second color, and the third light-emitting layer 53 includes a third quantum dot body that emits light of a third color; forming each of the first light-emitting layer 51, the second light-emitting layer 52, and the third light-emitting layer 53 includes forming a corresponding quantum dot solution, adding a first supplementary ligand, forming a corresponding pre-quantum dot layer using the corresponding quantum dot solution, and performing a photolithography process on the corresponding pre-quantum dot layer to form each corresponding light-emitting layer.

[0111] For example, the method for preparing a light-emitting device further includes: providing a substrate; forming a readily soluble layer comprising an auxiliary ligand on the substrate, wherein the polarity of the auxiliary ligand is the same as that of the initial ligand and the first supplementary ligand; and forming the pre-quantum dot layer on the readily soluble layer. This increases the solubility of the overall structure of the "pre-quantum dot layer / pre-soluble layer" in a developer solution and reduces residues of the ultimately formed light-emitting layer in non-target areas.

[0112] The following describes a method for manufacturing a light-emitting device according to an embodiment of the present disclosure through specific examples.

[0113] 6A to 6H are schematic diagrams of a method for manufacturing a light-emitting device according to an embodiment of the present disclosure. In this embodiment, the manufacturing process of the light-emitting device is as follows, where an inverted bottom emission type light-emitting device is taken as an example.

[0114] Referring to Figure 6A, a substrate 1 is provided, and a patterned first electrode 2 is prepared on the substrate 1 in advance. For example, the first electrode 2 is an anode, for example, the material of the anode is a transparent conductive material, and the transparent conductive material is, for example, indium tin oxide (ITO) or indium zinc oxide (IZO), etc., and the specific type of the transparent conductive material is not limited. For example, the structure shown in Figure 6A is washed with water, ethanol, and acetone in sequence, and the structure is blown dry with a nitrogen gun for standby use. Then, for example, a hole injection layer 2 and a hole transport layer 3 are formed in sequence on the first electrode 2, for example, by spin coating to form the hole injection layer 2 and the hole transport layer 3 in sequence. For example, the material of the hole injection layer is a polymer of 3,4-ethylenedioxythiophene monomer (PEDOT), and the material of the hole transport layer is 1,2,4,5-tetrakis(trifluoromethyl)benzene (TFB).

[0115] For example, a pixel defining layer 6 is formed to define openings in a plurality of sub-pixel regions, and subsequently, a plurality of light-emitting layers are formed in the openings in the plurality of sub-pixel regions. For example, in this embodiment, the pixel defining layer 6 is formed on the hole transport layer 3. The design of the pixel defining layer 6 is not limited to this embodiment; those skilled in the art may design it according to different needs. This is merely an example.

[0116] Then, referring to FIG6B , a first pre-quantum dot solution is formed, comprising first quantum dot bodies and initial ligands. The initial ligands undergo ligand exchange (i.e., ligand coordination) with the first quantum dot bodies, displacing the interfering substances coordinated with the first quantum dot bodies. For example, the first quantum dot bodies are red quantum dot bodies that emit red light. Then, a first supplementary ligand is added to the first pre-quantum dot solution to form a first quantum dot solution. The polarity of the first supplementary ligand is the same as that of the initial ligand. For the specific type and requirements of the first supplementary ligand, please see the above description, thereby supplementing the first pre-quantum dot solution with an excess of ligands that can coordinate with the first quantum dot body, which is beneficial to fill the coordination positions on the surface of the first quantum dot body, and the presence of excess second ligands is beneficial to enhance the dispersibility of the first quantum dot body, forming more single-particle first quantum dot bodies and small aggregates of the first quantum dot body, reducing the agglomeration of the first quantum dot body, reducing or avoiding the formation of large-particle quantum dot clusters, and being able to increase the solubility of the first quantum dot body in the developer during the process of preparing the patterned first light-emitting layer by photolithography, thereby avoiding large-particle quantum dot clusters from remaining in non-target areas other than the first sub-pixel area during the development process and affecting the color gamut and performance of the light-emitting device.

[0117] Here, it is taken as an example that the initial ligand and the first supplementary ligand used in forming the first to third light-emitting layers are both MMES.

[0118] For example, in the process of preparing the first light-emitting layer 51, the mass percentage of the first supplementary ligand added to the first quantum dot solution used to form the first light-emitting layer 51 is 5% to 15%, for example, the optimal is 10%. In the first quantum dot solution, the total ligand amount of the initial ligand and the first supplementary ligand is preferably around 20%. According to thermogravimetric testing, before the addition of the first supplementary ligand, after the initial ligand and the quantum dot body undergo ligand exchange, a maximum of about 10% of the initial ligand (MMES) is added to the surface of the first quantum dot body (and the subsequent second quantum dot body and the third quantum dot body). That is, the total MMES in the quantum dot solution is 20%, of which 10% of the MMES is coordinated with the first quantum dot body and 10% of the MMES is free. As a result, in the formed first quantum dot solution, there is a far greater excess of ligands, which allows the initial ligand and the first supplementary ligand to occupy the sites on the surface of the first quantum dot body as much as possible.

[0119] Figure 7 shows the thermogravimetric curves of the thermogravimetric experiment on the samples of the first pre-quantum dot solution after the first quantum dot body was ligand-exchanged with the initial ligand and the first supplementary ligand during the three preparation processes. A far excess of MMES ligand was used for exchange in each ligand exchange process, and only the initial ligand was allowed to volatilize during the thermogravimetric test. The RQD in Figure 7 represents the first pre-quantum dot solution including the red quantum dot body. It can be seen from Figure 7 that the final three tests obtained that the amount of initial ligand coordinated with the first quantum dot body was 10.2%, 10.5%, and 10.6%, respectively, which is basically stable at about 10%, that is, the upper limit of the maximum binding amount of the initial ligand (such as MMES) on the first quantum dot body is 10%. The amount of ligand mentioned in this embodiment refers to the mass percentage.

[0120] Then, after executing the steps shown in FIG6A , referring to FIG6B , for example, before forming the first pre-quantum dot layer a, a first easily soluble layer 4a is formed using an auxiliary ligand solution. The ligand solution contains an auxiliary ligand, and the polarity of the auxiliary ligand is the same as the polarity of the initial ligand and the polarity of the first supplementary ligand. For example, the selection of the type of auxiliary ligand can refer to the above introduction to the types of the initial ligand and the first supplementary ligand. The auxiliary ligand can be the same ligand as the initial ligand and the first supplementary ligand or a different ligand. Here, the auxiliary ligand is also MMES as an example. After forming the first easily soluble layer 4a, the first pre-quantum dot layer a is spin-coated using the first easily soluble layer 4a as a substrate, so that the first pre-quantum dot layer a / first easily soluble layer 4a double-layer structure as a whole has greatly increased solubility in the developer, thereby reducing the residue of the finally formed first light-emitting layer 51 in non-target areas other than the first sub-pixel.

[0121] After forming the first readily soluble layer 4a, a first pre-quantum dot layer a is formed on the first readily soluble layer 4a using a first quantum dot solution. Specifically, the method for preparing a light-emitting device further includes: forming a readily soluble layer comprising an initial ligand or a first supplementary ligand on a substrate; and subsequently forming the pre-quantum dot layer on the readily soluble layer. For example, the first pre-quantum dot layer a is formed by spin coating, and the first pre-quantum dot layer a is exposed using a first mask M1. During the exposure process, a cross-linking reaction occurs between the initial ligands and / or the first supplementary ligands in the portion of the first pre-quantum dot layer a not obscured by the mask. Figure 8 is a schematic diagram of the cross-linking reaction between the initial ligands and / or the first supplementary ligands. Under ultraviolet (UV) light, the double bonds of the MMES open, allowing two double bonds of the MMES to undergo an addition reaction, forming the cross-linked structure shown in Figure 8. The portion of the first pre-quantum dot layer a exposed to UV light does not dissolve in the developer solution and remains as the first light-emitting layer 51 (as shown in Figure 6C). At the same time, the portion of the first easily soluble layer 4a exposed to ultraviolet light also undergoes a cross-linking reaction and is retained in the subsequent development process as a first auxiliary layer 41. The first auxiliary layer 41 is located in the first sub-pixel area, on the side of the first light-emitting layer 51 close to the substrate 1 and in contact with the first light-emitting layer 51.

[0122] 1% of a second supplementary ligand is added to the developer. Here, for example, the second supplementary ligand is MMES and the developer solvent is PGMEA. That is, the exposed portion is developed with a PGMEA developer containing 1% MMES to form the first light-emitting layer 51 of the first sub-pixel (e.g., a red sub-pixel emitting red light) shown in FIG. 6C .

[0123] The sample of the first light-emitting layer 51 was subjected to nuclear magnetic resonance testing, and the nuclear magnetic resonance spectrum is shown in Figure 3. There are relatively flat and wide peaks ③ and ④ in the spectrum, corresponding to the initial ligands bound to the quantum dot body, and there are relatively sharp MMES peaks ⑤ and ⑥, corresponding to the second supplementary ligands dispersed in the light-emitting layer, that is, the light-emitting layer has a second ligand that is not connected to the quantum dot body.

[0124] A small amount of the second supplementary ligand in the developer will remain in the second sub-pixel region and the third sub-pixel region. After the first light-emitting layer 51 is formed, the first quantum dot bodies in the second sub-pixel region and the third sub-pixel region are washed away.

[0125] Next, a second pre-quantum dot solution is formed using a method similar to that used to form the first pre-quantum dot solution. The second pre-quantum dot solution includes a second quantum dot body and an initial ligand. The initial ligand is subjected to ligand exchange (i.e., ligand coordination) with the second quantum dot body, and the initial ligand replaces the interfering substance coordinated with the second quantum dot body, displacing the interfering substance. For example, the second quantum dot body is a green quantum dot body that emits green light. Then, a first supplementary ligand is added to the second pre-quantum dot solution to form a second quantum dot solution. The polarity of the first supplementary ligand is the same as that of the initial ligand. For the specific type and technical effect of the first supplementary ligand, please see the above description.

[0126] For example, after experimental exploration, in the process of preparing the second light-emitting layer 52, the mass percentage of the first supplementary ligand added to the second quantum dot solution used to form the second light-emitting layer 52 is 10% to 20%, for example, the optimal is 15%. After thermogravimetric testing, before the addition of the first supplementary ligand, after the initial ligand and the quantum dot body undergo ligand exchange, a maximum of about 10% of the initial ligand (MMES) is added to the surface of the second quantum dot body, that is, the total MMES in the quantum dot solution is 25%, of which about 10% of the MMES is coordinated with the first quantum dot body, and the remaining MMES is free. As a result, in the formed first quantum dot solution, there is a far greater amount of ligand, which allows the initial ligand and the first supplementary ligand to occupy the sites on the surface of the first quantum dot body as much as possible.

[0127] Referring to FIG6D , for example, before forming the second pre-quantum dot layer b, a second easily soluble layer 4b is first formed using an auxiliary ligand solution. The ligand solution contains an auxiliary ligand, and the polarity of the auxiliary ligand is the same as that of the initial ligand and the first supplementary ligand (for the definition of the same polarity, please refer to the previous description). For example, the selection of the type of auxiliary ligand can refer to the above introduction to the types of the initial ligand and the first supplementary ligand. The auxiliary ligand can be a ligand with the same composition as the initial ligand and the first supplementary ligand, or a ligand with different compositions. Here, the auxiliary ligand is also MMES as an example. After forming the second easily soluble layer 4b, the first pre-quantum dot layer a is spin-coated using the second easily soluble layer 4b as a substrate, so that the double-layer structure of "second pre-quantum dot layer b / second easily soluble layer 4b" as a whole has greatly increased solubility in the developer, thereby reducing the residue of the finally formed second light-emitting layer 52 in non-target areas other than the second sub-pixel.

[0128] After forming the second easily soluble layer 4b, a second pre-quantum dot layer b is formed using a second quantum dot solution. For example, the second pre-quantum dot layer b is formed by spin coating, and the second pre-quantum dot layer b is exposed using a second mask M2. During the exposure process, a cross-linking reaction occurs between the initial ligands and / or the first supplementary ligands in the portion of the second pre-quantum dot layer b that is not blocked by the mask. Under ultraviolet light (UV), the double bonds of MMES are opened, allowing the two double bonds of MMES to undergo an addition reaction, forming a cross-linked structure as shown in Figure 8. The portion exposed to UV light will not dissolve in the developer and will remain as the second light-emitting layer 52 (as shown in Figure 6E). At the same time, the portion of the second easily soluble layer 4b exposed to UV light also undergoes a cross-linking reaction and is retained in the subsequent development process as the second auxiliary layer 42. The second auxiliary layer 42 is located in the second sub-pixel area on the side of the second light-emitting layer 52 close to the substrate 1 and in contact with the second light-emitting layer 52.

[0129] 1% of a second supplementary ligand is added to the developer. Here, for example, the second supplementary ligand is MMES and the developer solvent is PGMEA. That is, the exposed second sub-pixel (e.g., a green sub-pixel emitting green light) is developed using a PGMEA developer containing 1% MMES to form the second light-emitting layer 52 in FIG. 6E .

[0130] The sample of the second light-emitting layer 52 was subjected to nuclear magnetic resonance testing. The results of the nuclear magnetic resonance testing were similar to those in Figure 3. There were relatively flat and wide peaks ③ and ④, and sharp MMES peaks ⑤ and ⑥ could still be seen, which proved that there were still uncoordinated free MMES ligands in the second light-emitting layer 52, that is, the second ligand was present.

[0131] The second supplementary ligand in the developer solution will have a trace amount of residue in the first sub-pixel region and the third sub-pixel region. After the second light-emitting layer 52 is formed, the second quantum dot bodies in the first sub-pixel region and the third sub-pixel region are washed away. That is, after the second light-emitting layer 52 is prepared, the second quantum dot bodies located in the second sub-pixel region and the third sub-pixel region are washed away. The surface of the previously formed light-emitting layer has the second ligand, for example, the surface of the first light-emitting layer 51 has the second ligand, and the surface sites of the first quantum dot bodies are already occupied by the bound ligand. This is more conducive to the process of forming the next light-emitting layer (for example, the second light-emitting layer 52), making the previously formed first light-emitting layer more stable and less likely to be dissolved and washed away.

[0132] Next, a third pre-quantum dot solution is formed using a method similar to that used to form the first pre-quantum dot solution. The third pre-quantum dot solution includes a third quantum dot body and an initial ligand. The initial ligand is subjected to ligand exchange (i.e., ligand coordination) with the third quantum dot body, and the initial ligand replaces the interfering substance coordinated with the third quantum dot body, displacing the interfering substance. For example, the third quantum dot body is a blue quantum dot body that emits blue light. Then, a first supplementary ligand is added to the third pre-quantum dot solution to form a third quantum dot solution. The polarity of the first supplementary ligand is the same as that of the initial ligand. For the specific type and technical effect of the first supplementary ligand, please see the above description.

[0133] For example, through experimental exploration, during the preparation of the third light-emitting layer 53, the mass percentage of the first supplementary ligand added to the third quantum dot solution used to form the third light-emitting layer 53 is 1% to 10%, for example, 3% is optimal. Thermogravimetric testing shows that before the addition of the first supplementary ligand, after the initial ligand and the quantum dot body undergo ligand exchange, a maximum of about 10% of the initial ligand (MMES) is added to the surface of the third quantum dot body. That is, the total MMES in the quantum dot solution is about 13%, about 10% of which is coordinated with the third quantum dot body, and the remaining MMES is free. As a result, the third quantum dot solution formed has a far greater excess of ligands, which allows the initial ligand and the first supplementary ligand to occupy as many sites on the surface of the third quantum dot body as possible.

[0134] Referring to Figure 6F, for example, before forming the third pre-quantum dot layer c, the third easily soluble layer 4c is first formed using an auxiliary ligand solution. The ligand solution contains an auxiliary ligand, and the polarity of the auxiliary ligand is the same as the polarity of the initial ligand and the polarity of the first supplementary ligand. For example, the selection of the type of auxiliary ligand can refer to the above introduction to the types of the initial ligand and the first supplementary ligand. The auxiliary ligand can be the same ligand as the initial ligand and the first supplementary ligand or a different ligand. Here, the auxiliary ligand is also MMES as an example. After forming the third easily soluble layer 4c, the third pre-quantum dot layer c is spin-coated using the third easily soluble layer 4c as a substrate, so that the double-layer structure of "third pre-quantum dot layer c / third easily soluble layer 4c" as a whole has greatly increased solubility in the developer, reducing the residual effect of the finally formed third light-emitting layer 53 in non-target areas other than the third sub-pixel.

[0135] After forming the third readily soluble layer 4c, a third pre-quantum dot layer c is formed using a third quantum dot solution. For example, the third pre-quantum dot layer c is formed by spin coating, and the third pre-quantum dot layer c is exposed using a third mask M3. During the exposure process, a cross-linking reaction occurs between the initial ligands and / or the first supplementary ligands in the portion of the third pre-quantum dot layer c not blocked by the mask. Under ultraviolet light (UV), the double bonds of the MMES are opened, allowing the two double bonds of the MMES to undergo an addition reaction, forming a cross-linked structure as shown in Figure 8. The portion exposed to UV light will not dissolve in the developer and will remain as the third light-emitting layer 53 (as shown in Figure 6G). At the same time, the portion of the third readily soluble layer 4c exposed to UV light also undergoes a cross-linking reaction and is retained in the subsequent development process as the third auxiliary layer 43. The third auxiliary layer 43 is located in the third sub-pixel area, on the side of the third light-emitting layer 53 close to the substrate 1, and in contact with the third light-emitting layer 53.

[0136] 1% of a second supplementary ligand is added to the developer. Here, for example, the second supplementary ligand is MMES and the developer solvent is PGMEA. That is, the exposed portion is developed with a PGMEA developer containing 1% MMES to form the third light-emitting layer 53 in the third sub-pixel (e.g., a blue sub-pixel emitting blue light) shown in FIG. 6G .

[0137] The sample of the third light-emitting layer 53 was subjected to nuclear magnetic resonance testing. The results of the nuclear magnetic resonance testing were similar to those in Figure 3. There were relatively flat and broad peaks ③ and ④, and sharp MMES peaks ⑤ and ⑥ could still be seen, which proved that there were still uncoordinated free MMES ligands in the third light-emitting layer 53, that is, the second ligand was present.

[0138] The second supplementary ligand in the developer will have a trace amount of residue in the first sub-pixel region and the second sub-pixel region. After the third light-emitting layer 53 is formed, the third quantum dot body in the first sub-pixel region and the second sub-pixel region is washed away. That is, after the third light-emitting layer 53 is prepared, the third quantum dot body located in the first sub-pixel region and the second sub-pixel region is washed away. The surface of the previously formed light-emitting layer has the second ligand, for example, the surface of the first light-emitting layer 51 and the second light-emitting layer 52 formed previously have the second ligand. The surface sites of the first quantum dot body and the second quantum dot body are already occupied by the bound ligand, which is more conducive to the process of forming the next light-emitting layer (for example, the third light-emitting layer 53). The previously formed first light-emitting layer 51 and the second light-emitting layer 52 are more stable and not easily dissolved or washed away.

[0139] 6H , an electron transport layer 7 is formed on the side of the light-emitting layer 5 close to the cathode. For example, the material of the electron transport layer is zinc oxide (ZnO), and the electron transport layer 7 is formed by spin coating, for example. Then, a second electrode 8 is formed by evaporation and arranged opposite to the first electrode 2. The second electrode 8 is a cathode. For example, the material of the second electrode 8 is metal aluminum (Al). It can also be a laminated structure, such as a laminated structure composed of three layers of metal of Ti / Al / Ti as an anode. Of course, the material of the second electrode, the material of the hole injection layer, the hole transport layer, and the materials of the functional film layers of the electron transport layer are not limited to the types listed above, and those skilled in the art can select them according to conventional techniques in the art. The light-emitting device 10 is not limited to the bottom emission type shown in FIG. 1A , but can also be a top emission type. Those skilled in the art can make adaptive changes to the corresponding structure according to conventional techniques in the art.

[0140] The light-emitting device is then packaged to form a final light-emitting device.

[0141] Adding a second supplementary ligand to the developer can increase the solubility of quantum dots in the developer, helping to solve the problem of quantum dots remaining in non-target areas. In the light-emitting device structure finally prepared, the original ligands in the target pixel will be cross-linked into a network structure, and the use of a developer to which the second supplementary ligand is added will result in uncross-linked second supplementary ligands remaining in the light-emitting layer of the target pixel. The second ligand in the light-emitting layer of the light-emitting device finally prepared includes uncross-linked second supplementary ligands, that is, the retained second supplementary ligands that are not bound to the quantum dot body and are not cross-linked serve as the second ligand in the light-emitting layer of the light-emitting device finally prepared. Of course, the second ligand in the light-emitting layer of the light-emitting device finally prepared may also include some retained initial ligands or first supplementary ligands that are not bound to the quantum dot body and are not cross-linked.

[0142] For example, during the development process of forming the light-emitting layer, the amount of the second supplementary ligand added to the developer is 0.5% to 10% by mass of the developer. In the above examples of forming the first to third light-emitting layers, the amount of the second supplementary ligand (e.g., MMES) added to the developer is 1% by mass of the developer.

[0143] The amount of the second supplementary ligand added to the developer relative to the mass percentage of the developer affects the residual quantum dots in the non-target areas of the light-emitting device. Figure 11 shows electron micrographs of the residual quantum dots in the non-target areas of the light-emitting device obtained under different conditions of the amount of the second supplementary ligand added to the developer relative to the mass percentage of the developer. Here, the solvent of the developer is PGMEA (PMA for short) as an example. Referring to FIG11(a), when the solvent is simply used as the developer, that is, under the condition of "PMA development", a large number of quantum dots remain in the non-target area in the final light-emitting device (the white granular structure in the figure represents the residual quantum dots or the residual whole particles formed by the aggregation of multiple quantum dots); referring to FIG11(b), when the amount of the second supplementary ligand added to the developer is 0.2% by mass of the developer, that is, under the condition of "0.2% MMES-PMA", the large number of quantum dots remaining in the non-target area is significantly reduced; referring to FIG11(c), when the amount of the second supplementary ligand added to the developer is increased to 1% by mass of the developer, that is, under the condition of "1% MMES-PMA", the residual quantum dots are further reduced (the residual amount is 105 / μm). 2 ); Referring to (d) of FIG11 , when the amount of the second supplementary ligand added to the developer increases to 10% by mass of the developer, that is, under the condition of "10% MMES-PMA", when the solvent of the developer is PGMEA, the residual amount of quantum dots in the non-target area no longer decreases further (the residual amount is 101 / μm 2 ). The residue of quantum dots in non-target areas will affect the final color gamut of the device, so it is necessary to further increase the second ligand in the quantum dot solution to ultimately solve the problem of quantum dot residue.

[0144] For example, the mass percentage of the added initial ligand is not less than 10%, and the amount of the first supplementary ligand added to the pre-quantum dot solution after ligand coordination accounts for 1% to 20% of the concentration of the pre-quantum dot solution. The initial ligand and the first supplementary ligand are used to ensure that there is a sufficient amount of the first supplementary ligand. In the quantum dot solution, the total ligand amount of the initial ligand and the first supplementary ligand is preferably between 11% and 30%. Too little cannot solve the problem of residue, and too much reduces the efficiency of the device. After ligand exchange, the mass percentage of the initial ligand coordinated with the quantum dot body is about 10%. Therefore, when the mass percentage of the added initial ligand is not less than 10%, the mass percentage of the first supplementary ligand is 1% to 20%.

[0145] Through experiments, it was found that in order to obtain a better effect of preventing the quantum dot layer emitting different colors of light from remaining in non-target areas, the mass percentage of the first supplementary ligand added to the quantum dot solution emitting red light is 5% to 15%, the optimal amount is 8% to 12%, and a fixed optimal amount is 10%; the mass percentage of the first supplementary ligand added to the quantum dot solution emitting green light is 10% to 20%, the optimal amount is 13% to 17%, and a fixed optimal amount is 15%; the mass percentage of the first supplementary ligand added to the quantum dot solution emitting blue light is 1% to 10%, the optimal amount is 2% to 5%, and a fixed optimal amount is 3%.

[0146] In the preparation method of the light-emitting device provided in the embodiment shown in Figures 6A-6G, the mass percentage of the first supplementary ligand added to the quantum dot solution used to form the first light-emitting layer 51, the mass percentage of the first supplementary ligand added to the quantum dot solution used to form the second light-emitting layer 52, and the mass percentage of the first supplementary ligand added to the quantum dot solution used to form the third light-emitting layer 53 are different from each other to match the different residual degrees of quantum dot layers with different luminescent colors in non-target areas during the preparation process.

[0147] For example, in the process of forming the light-emitting layer using the exposure-development process, under the same development conditions, the residues of blue-emitting quantum dots, red-emitting quantum dots, and green-emitting quantum dots in non-target areas increase in descending order. That is, the green quantum dots are the most difficult to be completely removed from the non-target areas by development. Therefore, the green quantum dots require the addition of the largest amount of first supplementary ligand, thereby maximizing the amount of free quantum dots ultimately formed. This increases the dispersion of quantum dots in the pre-quantum dot layer formed after film formation using a solution for preparing green-emitting quantum dots, forms more single-particle quantum dots and small aggregates of quantum dots, reduces quantum dot aggregation, and increases the solubility of quantum dots in the developer. This prevents large quantum dot clusters from remaining in non-target areas during the development process, thereby affecting the color gamut and performance of the light-emitting device. For example, the first light-emitting layer 51 emits red light, the second light-emitting layer 52 emits green light, and the third light-emitting layer 53 emits blue light; the mass percentage of the first supplementary ligand added to the quantum dot solution used to form the second light-emitting layer 52 is greater than the mass percentage of the first supplementary ligand added to the quantum dot solution used to form the first light-emitting layer 51, and the mass percentage of the first supplementary ligand added to the quantum dot solution used to form the first light-emitting layer 51 is greater than the mass percentage of the first supplementary ligand added to the quantum dot solution used to form the third light-emitting layer 53, so that the dispersibility of the quantum dots in the light-emitting layers emitting various colors of light and the solubility in the developer can be appropriately adjusted.

[0148] If the amount of the first supplementary ligand added to the quantum dot solution is too little, it will lead to insufficient ligands, and the effect of increasing the solubility of quantum dots in the developer is not ideal; if the amount of the first supplementary ligand added to the quantum dot solution is too much, it will lead to a decrease in efficiency.

[0149] Figure 9 is a diagram of device efficiency when different amounts of the first supplementary ligand are added to the quantum dot solution. Figure 9 takes a quantum dot solution (RQD) including a red quantum dot body as an example, and takes the initial ligand and the first supplementary ligand as MMES as an example, and presents the results under the following experimental conditions: RQDs with different ligand ratios are obtained by adding different amounts of the first supplementary ligand to the pre-quantum dot solution after ligand exchange by adding the initial ligand. The total mass percentages of the initial ligand and the first supplementary ligand in the RQD are 9.2% (RQD-MMES-9.2%), 12.7% (RQD-MMES-12.7%), 18.5% (RQD-MMES-18.5%) and 29.2% (RQD-MMES-29.2%), respectively. A control experiment is carried out on the light-emitting device prepared using this condition to explore the degree of influence of the amount of the added first supplementary ligand on the efficiency of the light-emitting device. Among them,

[0150] Under the condition RQD-MMES-9.2%, without adding the first supplementary ligand, the content of the initial ligand coordinated with the quantum dot bulk is 9.2%;

[0151] Under the condition of RQD-MMES-12.7%, the content of the initial ligand coordinated with the quantum dot body is 9.2%, and the first supplementary ligand is added as the second ligand, and the content of the second ligand is about 3.5%;

[0152] Under the condition of RQD-MMES-18.5%, the content of the initial ligand coordinated with the quantum dot body is 9.2%, and the first supplementary ligand is added as the second ligand, and the content of the second ligand is about 9.3%;

[0153] Under the condition of RQD-MMES-29.2%, the content of the initial ligand coordinated with the quantum dot body is 9.2%, and the first supplementary ligand is added as the second ligand, and the content of the second ligand is about 20%.

[0154] As can be seen from Figure 9, the total mass percentage of the initial ligand and the first supplementary ligand in the RQD increased from 9.2% to 18.5%, that is, the content of the added first supplementary ligand increased from 0% to 9.3%, and the external quantum efficiency (EQE) of the light-emitting device did not decrease, but increased slightly. This shows that increasing the content of the first supplementary ligand added to the quantum dot solution to a certain proportion does not affect the device efficiency, but greatly benefits the reduction of residuals and improves the luminous performance of the light-emitting device. However, when the total mass percentage of the initial ligand and the first supplementary ligand increased to 29.2%, that is, when the content of the first supplementary ligand added to the quantum dot solution increased to 20%, the conductivity of the light-emitting device was affected by the excessive addition of the first supplementary ligand, and the efficiency of the light-emitting device was greatly reduced to about 13%.

[0155] In a method for manufacturing a light-emitting device, the difference from the embodiment shown in Figures 6A-6H above is that, during the process of manufacturing the first to third light-emitting layers, after the initial ligands exchange with the quantum dot body, the first supplementary ligand is not added to the quantum dot solution. The other steps of this preparation method are the same as those of the embodiment shown in Figures 6A-6H above. The first to third light-emitting layers formed using this preparation method were subjected to thermogravimetric testing and nuclear magnetic resonance testing. According to the thermogravimetric testing, the initial ligand content in the first light-emitting layer, the initial ligand content in the second light-emitting layer, and the initial ligand content in the third light-emitting layer were all about 10%. This content is basically the same as the maximum content of the initial ligand that can be bound to the surface of the quantum dot body obtained in the previous test, which can prove that the second ligand is basically absent in the final light-emitting layer. In addition, nuclear magnetic resonance (NMR) tests were performed on samples of the final first light-emitting layer 51, second light-emitting layer 52, and third light-emitting layer 53. The NMR test results showed that relatively flat and broad peaks ③ and ④ were present, but there were no sharp peaks ⑤ and ⑥ representing MMES. This proves that there are no uncoordinated free MMES ligands in the first light-emitting layer 51, the second light-emitting layer 52, and the third light-emitting layer 53, that is, no second ligand is present. Compared with the preparation method of the light-emitting device provided in the embodiment of the present application, this production method cannot guarantee the formation of an excessive amount of second ligand, and thus no light-emitting layer containing the second ligand is obtained. In addition, it was detected that there was a trace amount of MMES residue in the developer in the second and third sub-pixels.

[0156] In another method for fabricating a light-emitting device, no second supplementary ligand is added to the developer during the fabrication of the first to third light-emitting layers. The remaining steps of this method are identical to those of the embodiment illustrated in Figures 6A-6H . The first to third light-emitting layers formed using this method were subjected to thermogravimetric and nuclear magnetic resonance (NMR) testing. Thermogravimetric testing revealed that the initial ligand content in the first, second, and third light-emitting layers was approximately 10%. This content is roughly equivalent to the maximum initial ligand content capable of binding to the surface of the quantum dot bulk obtained in previous tests, confirming the substantial absence of the second ligand in the final light-emitting layer. Furthermore, NMR testing was performed on samples of the final first, second, and third light-emitting layers 51, 52, and 53. The NMR test results revealed relatively flat, broad peaks ③ and ④, but absent the sharp peaks ⑤ and ⑥ characteristic of MMES. This demonstrates the absence of uncoordinated, free MMES ligands, i.e., the presence of the second ligand, in the first, second, and third light-emitting layers 51, 52, and 53. Compared to the method for preparing the light-emitting device provided in the embodiments of the present application, this method cannot guarantee the formation of an excess of the second ligand, and thus cannot produce a light-emitting layer containing the second ligand. Furthermore, it was detected that no MMES in the developer remained in the second or third sub-pixels.

[0157] In addition, FIG10 is an electron microscope image of the light-emitting layer after film formation under conditions where the total mass percentage of the initial ligand and the first supplementary ligand in the quantum dot solution is different. The inventors have found that if the quantum dot solution is obtained without adding excess first supplementary ligand to the pre-quantum dot solution, then after the pre-quantum dot layer formed by the quantum dot solution is formed, there will be large agglomerated particles in the pre-quantum dot layer, as shown in FIG10(b). It can be seen that there are many large white agglomerated particles in the pre-quantum dot layer. These agglomerated particles will cause the pre-quantum dot layer to easily remain in non-target areas during the subsequent photolithography process, such as remaining in sub-pixel areas of other colors, causing color light crosstalk. However, according to the preparation method of the above-mentioned light-emitting device provided by the embodiment of the present disclosure, the first supplementary ligand is added to the pre-quantum dot solution to obtain the quantum dot solution. After the pre-quantum dot layer formed by the quantum dot solution is formed, there are no large agglomerated particles in the pre-quantum dot layer, as shown in FIG10(a). Figure 10 (a) shows the quantum dot particles under the above-mentioned condition RQD-MMES-18.5%, and Figure 10 (b) shows the quantum dot particles under the above-mentioned condition RQD-MMES-9.2% (i.e., without adding the first supplementary ligand). This proves that after the initial ligand is added to the pre-quantum dot solution so that the quantum dot body undergoes ligand exchange and combines with the initial ligand, the first supplementary ligand is added to the pre-quantum dot solution so that there are excess ligands, thereby enhancing the dispersion of the quantum dots in the quantum dot solution, so that the quantum dot particles are basically in a monodisperse state after film formation, which is beneficial to reducing the residue of the final light-emitting layer in non-target areas, improving the lithography accuracy, avoiding cross-color and improving the luminescence performance of the device, and is conducive to the production of high PPI, high color gamut, and high-performance quantum dot light-emitting devices.

[0158] For example, in the preparation method of the light-emitting device provided in another embodiment of the present disclosure, the step of forming the easily soluble layer can also be removed, and the other steps are the same as those in the embodiment shown in Figures 6A-6H, which can also achieve the technical effect of reducing the agglomeration of quantum dots, reducing or avoiding the formation of large-particle quantum dot clusters, and increasing the solubility of quantum dots in the developer.

[0159] For example, in the embodiment shown in Figures 6A-6H above, an anode, a hole injection layer, and a hole transport layer are sequentially formed on a substrate, and a readily soluble layer is formed on the hole transport layer. In another embodiment of the present disclosure, a cathode, an electron injection layer, and an electron transport layer can be sequentially formed on a substrate, and a readily soluble layer is formed on the electron transport layer.

[0160] For example, in the method for preparing a light-emitting device provided in another embodiment of the present disclosure, the method for preparing a light-emitting device further includes: adding nanoparticles to a pre-quantum dot solution, and forming a pre-quantum dot layer using the quantum dot solution obtained after adding the nanoparticles. Some of the nanoparticles are filled in the gaps between the quantum dot bodies, and at least one of the initial ligand and the first supplementary ligand will coordinate on the surface of the nanoparticles, thereby combining with the nanoparticles to form the filling ligand in the light-emitting device finally prepared above. As a result, the filling ligand is the same ligand as at least one of the initial ligand and the first supplementary ligand. Nanoparticles with smaller volumes can fill the gaps between the quantum dot bodies to reduce leakage current. At the same time, nanoparticles with larger specific surface areas can bind more ligands, thereby further increasing the solubility of the pre-quantum dot layer in the developer after film formation, thereby reducing the residue of the final light-emitting layer in non-target areas.

[0161] For example, the nanoparticles are P-type semiconductor nanoparticles. Therefore, since holes are majority carriers in the light-emitting device, adding P-type semiconductor nanoparticles can accelerate hole injection, increase electron migration rate, and thus improve the conductive performance of the light-emitting device.

[0162] For example, the diameter of the P-type semiconductor nanoparticles ranges from 2 nm to 5 nm. For example, the material of the P-type semiconductor nanoparticles is at least one of NiOx, MoOx, WOx, and VOx. Of course, the material of the P-type semiconductor nanoparticles is not limited to the aforementioned types.

[0163] For example, the initial ligand and / or the first supplementary ligand include a short-chain ligand, and the number of carbon atoms in the main chain of the short-chain ligand is less than 12, such as methyl 3-aminobutyrate. For example, according to the results of experimental tests, a main chain carbon atom number of 6-10 has a better effect. The short-chain ligand has low steric hindrance, which is conducive to allowing more ligands to be bound to the surface of the quantum dot body, thereby improving the solubility of the non-crosslinked area of ​​the front quantum dot layer during the development process of the front quantum dot layer to form a pattern of the light-emitting layer in the target area, and reducing the residue of quantum dots in non-target areas.

[0164] For example, the initial ligand and / or the first supplemental ligand may further include a long-chain ligand having a main chain with 12 or more carbon atoms, such as mercapto PEG acrylate. Long-chain ligands not only provide ester groups for dissolution in developer and double bonds for cross-linking under illumination, but also facilitate the provision of PEG structures, which helps improve the solubility of the unilluminated portion of the pre-quantum dot layer used to prepare the light-emitting layer in the developer, thereby reducing the residue of the final light-emitting layer in non-target areas.

[0165] There are a few points to note:

[0166] (1) The drawings of the embodiments of the present disclosure only relate to the structures related to the embodiments of the present disclosure. Other structures may refer to conventional designs.

[0167] (2) For the sake of clarity, in the drawings used to describe the embodiments of the present disclosure, the thickness of layers or regions is exaggerated or reduced, that is, these drawings are not drawn according to the actual scale.

[0168] (3) In the absence of conflict, the embodiments of the present disclosure and the features therein may be combined with each other to form new embodiments.

[0169] The above description is merely an exemplary embodiment of the present disclosure and is not intended to limit the scope of protection of the present disclosure. The scope of protection of the present disclosure is determined by the scope defined in the claims.

Claims

1. A light-emitting device comprising a light-emitting layer, wherein: The light-emitting layer includes: A quantum dot body, a first ligand, and a second ligand; The first ligand is connected to the quantum dot body through a first cross-linking structure; The second ligand is dispersed in the quantum dot light-emitting layer, at least part of the second ligand is connected via a second cross-linking structure, and the first ligand and the second ligand have the same polarity.

2. The light emitting device according to claim 1, wherein The total content ratio of the first ligand and the second ligand in the light-emitting layer is 10%-25%.

3. The light emitting device according to claim 2, wherein The content ratio of the second ligand to the first ligand is 0.5-1.

5. The light emitting device according to claim 2 , wherein: The first end of the first ligand is coordinated and connected to the quantum dot body, and the second ends of different first ligands are bonded to each other to form the first cross-linked structure; The first end of the second ligand is not connected to the quantum dot body, and the second ends of different second ligands are bonded to each other to form the second cross-linking structure.

5. The light emitting device according to any one of claims 1 to 4, wherein: The first ligand and / or the second ligand include a short-chain ligand, wherein the number of carbon atoms in the main chain of the short-chain ligand is less than 12.

6. The light emitting device according to any one of claims 1 to 5, wherein: The second ligand includes a long-chain ligand, and the number of carbon atoms in the main chain of the long-chain ligand is greater than or equal to 12.

7. The light emitting device according to any one of claims 1 to 6, wherein: The second ligand and the first ligand are photosensitizing ligands, and the compositions of the second ligand and the first ligand may be the same or different.

8. The light emitting device according to any one of claims 1 to 7, wherein: At least one of the first ligand and the second ligand contains an ester group, and the functional group of the second ligand at the first end includes any one or more of a thiol group, an amino group, and a carboxyl group, and the functional group at the second end includes a double bond.

9. The light emitting device according to any one of claims 1 to 6, wherein: The light-emitting layer includes: a first light-emitting layer emitting light of a first color, a second light-emitting layer emitting light of a second color, and a third light-emitting layer emitting light of a third color; the first light-emitting layer includes a first quantum dot body emitting light of the first color, the second light-emitting layer includes a second quantum dot body emitting light of the second color, and the third light-emitting layer includes a third quantum dot body emitting light of the third color; The contents of the second ligand in the first light-emitting layer, the second light-emitting layer and the third light-emitting layer are all different.

10. The light emitting device according to claim 9, wherein The amount of the second ligand in the second light-emitting layer is greater than the amount of the second ligand in the first light-emitting layer, and the amount of the second ligand in the first light-emitting layer is greater than the amount of the second ligand in the third light-emitting layer; The first color is red, the second color is green, and the third color is blue.

11. The light emitting device according to any one of claims 1 to 10, wherein: The light-emitting layer is located on a substrate, and an amount of the second ligand on an upper surface of the light-emitting layer away from the substrate is greater than an amount of the second ligand on a lower surface of the light-emitting layer close to the substrate.

12. The light emitting device according to any one of claims 1 to 11, wherein: The size of the quantum dot particles in the light-emitting layer and the overall particles formed by agglomeration of multiple quantum dot particles is less than 100 nanometers.

13. The light emitting device according to any one of claims 1 to 12, further comprising an auxiliary layer, wherein: The auxiliary layer is located on a side of the light-emitting layer close to the substrate and in contact with the light-emitting layer.

14. The light emitting device according to any one of claims 1 to 13, wherein: The light-emitting layer further comprises nanoparticles, at least part of which fills the gaps between the quantum dot bodies. The surfaces of the nanoparticles are coordinated with filling ligands, which are ligands with the same composition as at least one of the first ligand and the second ligand.

15. The light emitting device according to claim 14, wherein The nanoparticles are P-type semiconductor nanoparticles.

16. A display device comprising the light-emitting device according to any one of claims 1 to 15.

17. A method for preparing a light-emitting device, for preparing the light-emitting device according to any one of claims 1 to 15, the method comprising: forming the light-emitting layer, wherein the forming of the light-emitting layer comprises: Forming a quantum dot solution, including forming a pre-quantum dot solution, wherein the pre-quantum dot solution includes an initial ligand, ligand coordination is performed in the pre-quantum dot solution, and the initial ligand is coordinated to the quantum dot body in the pre-quantum dot solution; A first supplementary ligand is added to the pre-quantum dot solution coordinated by the ligand to form the quantum dot solution, wherein the polarity of the first supplementary ligand is the same as the polarity of the initial ligand. At least part of the first supplementary ligand is not coordinated with the quantum dot body; forming a front quantum dot layer using the quantum dot solution; and A photolithography process is performed on the front quantum dot layer to form the light-emitting layer.

18. The method for preparing a light-emitting device according to claim 17, wherein: The first supplementary ligand and the initial ligand are ligands with the same composition or ligands with different compositions.

19. The method for preparing a light-emitting device according to claim 17 or 18, further comprising: After the ligand is coordinated, the quantum dot body is cleaned; as well as After cleaning the quantum dot body, the first supplementary ligand is added to the pre-quantum dot solution.

20. The method for preparing a light-emitting device according to any one of claims 17 to 19, wherein: The amount of the first supplementary ligand added to the pre-quantum dot solution coordinated by the ligand accounts for 1% to 20% of the concentration of the pre-quantum dot solution.

21. The method for preparing a light-emitting device according to any one of claims 17 to 20, wherein: The photolithography process includes an exposure-development process, and the method for preparing the light-emitting device further includes: A second supplementary ligand is added to the developer used in the exposure-development process, wherein the initial ligand, the first supplementary ligand and the second supplementary ligand are all photosensitive ligands, and the polarity of the second supplementary ligand is the same as that of the first supplementary ligand.

22. The method for preparing a light-emitting device according to claim 21, wherein: The functional group at the first end of any one of the initial ligand, the first supplementary ligand and the second supplementary ligand includes at least one of a thiol group, an amino group and a carboxyl group, the functional group at the second end of any one of the initial ligand, the first supplementary ligand and the second supplementary ligand includes a double bond, and any one of the initial ligand, the first supplementary ligand and the second supplementary ligand contains an ester group.

23. The method for preparing a light-emitting device according to claim 21 or 22, wherein: The amount of the second supplementary ligand added to the developer is 0.5% to 10% by mass of the developer.

24. The method for preparing a light-emitting device according to any one of claims 21 to 23, wherein: The first supplementary ligand and / or the second supplementary ligand comprises a short-chain ligand, wherein the number of carbon atoms in the main chain of the short-chain ligand is less than 12.

25. The method for preparing a light-emitting device according to any one of claims 21 to 24, wherein: The first supplementary ligand and / or the second supplementary ligand include a long-chain ligand, and the number of carbon atoms in the main chain of the long-chain ligand is greater than or equal to 12.

26. The method for preparing a light-emitting device according to any one of claims 17 to 25, further comprising: providing a substrate; forming a readily soluble layer comprising an auxiliary ligand on the substrate, wherein the polarity of the auxiliary ligand is the same as the polarity of the initial ligand and the polarity of the first supplementary ligand; as well as The front quantum dot layer is formed on the easily soluble layer.

27. The method for preparing a light-emitting device according to claim 26, further comprising: forming an anode, a hole injection layer, and a hole transport layer in sequence on the substrate, and forming the easily soluble layer on the hole transport layer; or, A cathode, an electron injection layer and an electron transport layer are sequentially formed on the substrate, and the easily soluble layer is formed on the electron transport layer.

28. The method for preparing a light-emitting device according to any one of claims 17 to 27, wherein: The forming of the light-emitting layer comprises: sequentially forming a first light-emitting layer in a first sub-pixel region, forming a second light-emitting layer in a second sub-pixel region, and forming a third light-emitting layer in a third sub-pixel region, wherein the first light-emitting layer comprises a first quantum dot body emitting light of a first color, the second light-emitting layer comprises a second quantum dot body emitting light of a second color, and the third light-emitting layer comprises a third quantum dot body emitting light of a third color; Forming each of the first light-emitting layer, the second light-emitting layer and the third light-emitting layer includes forming the corresponding quantum dot solution, adding the first supplementary ligand, using the corresponding quantum dot solution to form the corresponding pre-quantum dot layer, and performing a photolithography process on the corresponding pre-quantum dot layer to form each corresponding light-emitting layer.

29. The method for preparing a light-emitting device according to claim 28, further comprising: After preparing the first light-emitting layer, washing away the first quantum dot bodies located in the second sub-pixel region and the third sub-pixel region; After preparing the second light-emitting layer, washing away the second quantum dot bodies located in the first sub-pixel region and the third sub-pixel region; and After the third light-emitting layer is prepared, the third quantum dot bodies located in the first sub-pixel region and the second sub-pixel region are washed away.

30. The method for preparing a light-emitting device according to claim 28 or 29, wherein: The mass percentage of the first supplementary ligand added to the quantum dot solution used to form the first light-emitting layer, the mass percentage of the first supplementary ligand added to the quantum dot solution used to form the second light-emitting layer, and the mass percentage of the first supplementary ligand added to the quantum dot solution used to form the third light-emitting layer are different from each other.

31. The method for preparing a light-emitting device according to claim 30, wherein: The first color is red, the second color is green, and the third color is blue; In the process of preparing the first light-emitting layer, the mass percentage of the first supplementary ligand added to the quantum dot solution used to form the first light-emitting layer is 5% to 15%; In the process of preparing the second light-emitting layer, the mass percentage of the first supplementary ligand added to the quantum dot solution used to form the second light-emitting layer is 10% to 20%; During the preparation of the third light-emitting layer, the mass percentage of the first supplementary ligand added to the quantum dot solution for forming the second light-emitting layer is 1% to 10%.

32. The method for preparing a light-emitting device according to any one of claims 17 to 31, further comprising: Nanoparticles are added to the pre-quantum dot solution, and the pre-quantum dot layer is formed using the quantum dot solution obtained after adding the nanoparticles.

33. The method for preparing a light-emitting device according to claim 32, wherein: The nanoparticles are P-type semiconductor nanoparticles.

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