Light-emitting element, display device, and production method for light-emitting element

Abstract

This light-emitting element includes a light-emitting layer situated between an anode and a cathode, and an electron transport layer situated between the cathode and the light-emitting layer. The light-emitting layer has a first halogen atom and a plurality of quantum dots, and the electron transport layer has a second halogen atom.

Description

Light-emitting element, display device, and method for manufacturing the same

[0001] The present disclosure relates to a light-emitting device that includes quantum dots as a light-emitting material, a display device that includes the light-emitting device, and a method for manufacturing the light-emitting device.

[0002] Patent Document 1 discloses a light-emitting device in which a light-emitting layer contains quantum dots as a light-emitting material, each quantum dot having a core and a shell surrounding the core.

[0003] Japanese Patent Application Publication No. 2009-88276

[0004] In the light-emitting device described in Patent Document 1, which contains quantum dots as a light-emitting material, defects occurring around the quantum dots can cause the quantum dots to deteriorate, leading to deterioration of the light-emitting layer.

[0005] A light-emitting element according to one aspect of the present disclosure includes an anode, a cathode facing the anode, a light-emitting layer located between the anode and the cathode and having first halogen atoms and a plurality of quantum dots, and an electron transport layer located between the cathode and the light-emitting layer and having second halogen atoms.

[0006] A method for manufacturing a light-emitting element according to one aspect of the present disclosure includes forming an anode, forming a cathode facing the anode, forming a light-emitting layer located between the anode and the cathode and having first halogen atoms and a plurality of quantum dots, and forming an electron transport layer located between the cathode and the light-emitting layer and having second halogen atoms.

[0007] The defects occurring around the quantum dots in the light-emitting layer are reduced, and the light-emitting efficiency or reliability of the light-emitting device is improved.

[0008] FIG. 1 is a schematic cross-sectional side view of a display device according to embodiment 1. FIG. 2 is a schematic plan view of a display device according to embodiment 1. FIG. 3 is a flowchart of a method for manufacturing a display device according to embodiment 1. FIG. 4 is a schematic cross-sectional side view of a display device according to embodiment 2. FIG. 5 is a schematic view showing an example of a member that fills spaces between quantum dots according to embodiment 2. FIG. 6 is a flowchart of a method for forming a light-emitting layer according to embodiment 2. FIG. 7 is a graph showing the relationship between current density and luminance in a light-emitting element according to an example. FIG. 8 is a graph showing the relationship between current density and external quantum efficiency in a light-emitting element according to an example. FIG. 9 is a schematic cross-sectional side view of a display device according to embodiment 3.

[0009] [Embodiment 1] <Display Device> Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that in each drawing, similar configurations are assigned the same reference numerals, and their description will be omitted. Furthermore, in this disclosure, for simplicity of illustration, components assigned the same reference numerals may be drawn to different scales and may be hatched differently depending on the drawing. However, the components shown in each drawing of the present disclosure are merely examples, and the scales are not limited to those shown in the drawings. Furthermore, in this disclosure, components with different hatching have the same configuration as described above. Furthermore, in each drawing of the present disclosure, when two components have substantially the same shape but different compositions, etc., they may be assigned different reference numerals and the same hatching. Components having the same functions as components previously described in each embodiment of the present disclosure will be assigned the same reference numerals, and their description will not be repeated.

[0010] 2 is a schematic diagram of a display device 1 according to this embodiment. The display device 1 is a device that can be used, for example, as a display for a television, a smartphone, or the like. The display device 1 includes a display unit DA including a plurality of sub-pixels X, and a driver circuit DR that drives the plurality of sub-pixels X. Each of the plurality of sub-pixels X includes a light-emitting element 2 and a pixel circuit PC that drives the light-emitting element 2. The display device 1 performs display on the display unit DA by controlling light emission from each of the plurality of light-emitting elements 2 formed in the display unit DA via the driver circuit DR and the pixel circuit PC.

[0011] The structure of the display unit DA of the display device 1, particularly the structure of the light-emitting element 2, will be described in more detail with reference to Fig. 1. Fig. 1 is a schematic side cross-sectional view of the display device 1 according to an embodiment of the present disclosure, particularly showing a cross section perpendicular to the display surface of the display device 1 and passing through the light-emitting element 2. In other words, the cross section shown in Fig. 1 is a cross section parallel to the film thickness direction of the light-emitting layer 23, which will be described later, for example. Note that each schematic cross-sectional view of the display device according to the present disclosure shows a cross section corresponding to the cross section of the display device 1 shown in Fig. 1.

[0012] 1, the display device 1 according to this embodiment includes a display section DA that includes the above-described plurality of light-emitting elements 2 and a substrate 3, and in particular includes a plurality of light-emitting elements 2 on the substrate 3. The display device 1 has a structure in which the layers of the light-emitting elements 2 are stacked on the substrate 3 on which, for example, TFTs (Thin Film Transistors) (not shown) are formed as pixel circuits PC. In this specification, the direction from the light-emitting elements 2 of the display device 1 to the substrate 3 is referred to as the "downward direction," and the direction opposite to the downward direction is referred to as the "upward direction."

[0013] <Outline of Light-Emitting Element> The light-emitting element 2 includes an anode 21, a hole transport layer 22, a light-emitting layer 23, an electron transport layer 24, and a cathode 25, in this order from the substrate 3 side. In other words, the light-emitting layer 23 is located between the anode 21 and the cathode 25, and the electron transport layer 24 is located between the cathode 25 and the light-emitting layer 23. The anode 21 is electrically connected to the TFT of the substrate 3.

[0014] The structure of each layer of the light emitting element 2 will be described in more detail below.

[0015] <Electrodes> The anode 21 and the cathode 25 contain a conductive material and are electrically connected to the hole transport layer 22 and the electron transport layer 24, respectively.

[0016] At least one of the anode 21 and the cathode 25 is a transparent electrode that transmits visible light. Examples of the transparent electrode include ITO (indium tin oxide), IZO (indium zinc oxide), and SnO ２(tin oxide), FTO (fluorine-doped tin oxide), or the like is used. Either the anode 21 or the cathode 25 may contain a metal material, and the metal material is preferably Al, Ag, Cu, or Au alone or an alloy thereof, which have a high reflectivity for visible light. In the case where the display device 1 is a so-called top-emission display device in which light from the light-emitting element 2 is extracted from the light-emitting layer 23 to the side opposite the substrate 3, the anode 21 may be a reflective electrode and the cathode 25 may be a transparent electrode. In the case where the display device 1 is a so-called bottom-emission display device in which light from the light-emitting element 2 is extracted from the light-emitting layer 23 to the side of the substrate 3, the anode 21 may be a transparent electrode and the cathode 25 may be a reflective electrode. The anode 21 and the cathode 25 may be formed by a sputtering method or the like, or may be patterned by dry etching or the like.

[0017] <Hole Transport Layer> The hole transport layer 22 is a layer containing a hole transport material that transports holes from the anode 21 to the light-emitting layer 23. In this embodiment, the material of the hole transport layer 22 can be an organic or inorganic material that has been conventionally used in light-emitting devices containing quantum dots. For example, the organic material of the hole transport layer 22 can be 4,4',4''-tris(9-carbazolyl)triphenylamine (TCTA), 4,4'-bis[N-(1-naphthyl)-N-phenyl-amino]-biphenyl (NPB), zinc phthalocyanine (ZnPC), di[4-(N,N-ditolylamino)phenyl]cyclohexane (TAPC), 4,4'-bis(carbazol-9-yl)biphenyl (CBP), 2,3,6,7,10,11-hexacyano-1,4,5, 8,9,12-hexaazatriphenylene (HATCN), poly(N-vinylcarbazole) (PVK), poly(2,7-(9,9-di-n-octylfluorene)-(1,4-phenylene-((4-sec-butylphenyl)imino)-1,4-phenylene (TFB), or N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)-benzidine (Poly-TPD) can be used. Examples of inorganic materials for the hole transport layer 22 include NiO, MgNiO, and LaNiO. ３ ,CuO,Cu ２ O, MoO ３or a material in which a CN group, an SCN group, or an SeCN group is bonded to a metal, such as CuSCN. In particular, a material with a large electron affinity and ionization potential is suitable as the material for the hole transport layer 22.

[0018] <Electron Transport Layer> The electron transport layer 24 is a layer containing an electron transport material that transports electrons from the cathode 25 to the light-emitting layer 23. The electron transport layer 24 according to this embodiment contains a plurality of nanoparticles 31 as the electron transport material. The nanoparticles 31 may have a core-shell structure having, for example, a particle-shaped core and a shell surrounding the core. The shell of the nanoparticles 31 may cover the periphery of the core of the nanoparticles 31, or may be located on a part of the surface of the core of the nanoparticles 31.

[0019] The core material of the nanoparticles 31 is, for example, ZnO, MgZnO, LiZnO, TiO ２ , and SrTiO ３ The shell material of the nanoparticles 31 may be different from the core material and may include at least one of metal oxides such as MgO, ZrO, etc. ２ , Al ２ O ３ , Y ２ O ３ , SiO ２ , ZnS, ZnMgS, and SrS.

[0020] The shell of the nanoparticle 31 may have a thickness of 0.4 nm or more from the viewpoint of ensuring film-forming properties of the shell. Furthermore, the shell of the nanoparticle 31 may have a thickness of 1.0 nm or less from the viewpoint of reducing the inhibition of electron injection into the nanoparticle 31 by the shell. The shell of the nanoparticle 31 may be located over ⅙ or more of the surface of the core from the viewpoint of efficiently protecting the core of the nanoparticle 31.

[0021] However, the electron transport material of the electron transport layer 24 may be an organic or inorganic material that has been conventionally used in light emitting devices containing quantum dots. For example, the electron transport layer 24 may be made of zinc oxide (ZnO), zinc magnesium oxide (ZnMgO), titanium oxide (TiO), and tungsten oxide (WO ３ ) Alternatively, the electron transport layer 24 may contain an organic material such as tris(8-quinolinol)aluminum complex (Alq3), bathocuproine (BCP), or (2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole) (t-Bu-PBD) as the electron transport material. Note that, as the inorganic material of the electron transport layer 24, metal oxides such as ZnO, ZAO, ITO, InGaZnO, or electride may be used. In particular, a material with a small electron affinity is suitable as the material of the electron transport layer 24.

[0022] In this embodiment, the hole transport layer 22 and the electron transport layer 24 can be formed by using the above-mentioned materials by vacuum deposition, sputtering, or a coating method using a colloidal solution. In particular, when the electron transport layer 24 contains nanoparticles 31, the electron transport layer 24 may be formed by coating a nanoparticle dispersion liquid in which the nanoparticles 31 are dispersed in an appropriate solvent, and then drying the coated nanoparticle dispersion liquid.

[0023] The nanoparticles 31 may be synthesized, for example, by synthesizing a core of the nanoparticles 31, forming a shell around the core, and then washing the core. Specifically, in synthesizing the core, for example, a solution is prepared by dissolving zinc acetate dihydrate and magnesium acetate tetrahydrate in dimethyl sulfoxide at a molar ratio of 85:15. Note that, by identifying the material of the solution using an XRD (X-ray diffraction device), it was found that the solution contains a crystalline structure of ZnO.

[0024] Next, a solution of tetramethylammonium hydroxide dissolved in ethanol is added to the solution and stirred for 1 hour. Next, magnesium acetate tetrahydrate is added to the stirred solution in an amount of, for example, 30 to 50 mol % relative to the solute of the solution, and the solution is subjected to ultrasonic treatment and allowed to stand for several days. Furthermore, elemental analysis of the solution using an ICP-AES (inductively coupled plasma atomic emission spectroscopy) or an XPS (photoelectron spectroscopy) or the like revealed that the solution contained Mg.

[0025] Next, the solution is left to stand, and then washed three times by adding ethyl acetate and ethanol and centrifuging the mixture. In this manner, nanoparticles 31 having a ZnO core surrounded by a MgO shell may be synthesized.

[0026] The light-emitting element 2 may include a hole injection layer between the anode 21 and the hole transport layer 22, or an electron injection layer between the cathode 25 and the electron transport layer 24. Furthermore, the light-emitting element 2 may include an intermediate layer between the hole transport layer 22 and the light-emitting layer 23, or between the electron transport layer 24 and the light-emitting layer 23. These hole injection layer, electron injection layer, and intermediate layer may all be formed by the same method as the hole transport layer 22 or the electron transport layer 24.

[0027] <Light-Emitting Layer> The light-emitting layer 23 includes a plurality of quantum dots 41. Each of the quantum dots 41 may have a core / shell structure, including a core and a shell surrounding the core. In this embodiment, the quantum dots 41 are, for example, luminescent semiconductor nanoparticles that emit light upon recombination of injected electrons and holes. For example, the recombination of electrons and holes in the quantum dots 41 occurs primarily in the core. Light emitted from the quantum dots 41 has a narrow spectrum due to the quantum confinement effect, making it possible to obtain light with a relatively deep chromaticity. Furthermore, the shell functions to suppress the occurrence of defects or dangling bonds in the core and reduce the recombination of carriers undergoing a deactivation process.

[0028] The core and shell materials of the quantum dots 41 may each contain materials used for the core and shell materials of conventionally known core / shell quantum dots. The quantum dots 41 may have a core / shell structure such as InP / ZnS, CdSe / ZnS, CdSe / ZnSe, CdSe / CdS, ZnSe / ZnS, or CIGS / ZnS. The shell may be formed of multiple layers containing multiple different materials.

[0029] The quantum dots 41 have a particle size of about 1 to 100 nm. The wavelength of light emitted from the quantum dots 41 can be controlled by the particle size. In particular, since the quantum dots 41 have a core / shell structure, the wavelength of light emitted from the quantum dots 41 can be controlled by controlling the particle size of the core. Therefore, by controlling the particle size of the quantum dots 41, the wavelength of light emitted by the display device 1 can be controlled.

[0030] The light-emitting layer 23 has a thickness of 1000 nm or less in a plane direction perpendicular to the thickness direction at any position in the thickness direction. ２ The light-emitting layer 23 may contain one or more quantum dots 41. In this case, the light-emitting layer 23 generally contains quantum dots 41 at a concentration sufficient to function as a light-emitting layer of a light-emitting element.

[0031] <Halogen Atoms> The light-emitting element 2 according to this embodiment has halides in both the light-emitting layer 23 and the electron transport layer 24. In particular, the light-emitting layer 23 has first halides 51 located around the quantum dots 41, and the electron transport layer 24 has second halides 52 located around the nanoparticles 31.

[0032] In this embodiment, the first halide 51 has a first halogen atom, and the second halide 52 has a second halogen atom. Therefore, the light-emitting layer 23 has the first halogen atom, and the electron transport layer 24 has the second halogen atom.

[0033] In this disclosure, "atom" does not only mean that an atom exists as a single atom. In this disclosure, "atom" also includes an atom that exists in the form of a molecule having two or more atoms, including the atom and another atom, an atom that exists in the form of a complex, an atom that exists in the form of a compound, or an atom that exists in the form of an ion. However, in this disclosure, "atom" does not limit the form of existence of other atoms. In other words, a halogen atom includes an atom that exists in the form of a compound having a halogen atom, and an atom that exists in the form of a halogen ion. Regardless of the form of existence of a halogen atom, if its presence in a substance can be identified by analysis, the substance may be considered to contain a halogen atom.

[0034] The light-emitting layer 23 may have a first halide 51 located around the quantum dots 41 and as a ligand coordinated to the surface of the quantum dots 41. In this case, the first halide 51 may have, for example, a first halogen atom at the end of a carbon chain. The electron transport layer 24 may have a second halide 52 located around the nanoparticles 31 and as a ligand coordinated to the surface of the nanoparticles 31. In this case, the second halide 52 may have, for example, a second halogen atom at the end of a carbon chain. However, this embodiment is not limited to this, and the light-emitting layer 23 may have a first halogen atom that forms a direct coordinate bond with the surface of the quantum dots 41, and the electron transport layer 24 may have a second halogen atom that forms a direct coordinate bond with the surface of the nanoparticles 31.

[0035] When it is confirmed in cross-sectional observation of the light-emitting layer 23 or the electron transport layer 24 that the distance between the quantum dot 41 or nanoparticle 31 and the ligand is 2 nm or less, the ligand may be considered to be coordinated to the quantum dot 41 or nanoparticle 31. Alternatively, when it is confirmed that the quantum dot 41 or nanoparticle 31 and the ligand are in contact with each other, the ligand may be considered to be coordinated to the quantum dot 41 or nanoparticle 31.

[0036] <Compensation of defects by halogen atoms> The ligands coordinated to the electron transport material such as the quantum dots 41 or the nanoparticles 31 form coordinate bonds, which are weaker than chemical bonds, and therefore the coordinate bonds between the quantum dots 41 or the nanoparticles 31 and the ligands may be released.

[0037] The ligand has the function of compensating for defects on the surface of the quantum dots 41 or nanoparticles 31, thereby reducing deterioration of the quantum dots 41 or nanoparticles 31. Therefore, when the coordinate bond between the quantum dots 41 or nanoparticles 31 and the ligand is released, defects may occur on the surface of the quantum dots 41 or nanoparticles 31.

[0038] In particular, defects on the surface of the quantum dots 41 increase the probability of a deactivation process occurring due to the recombination of electrons and holes at the defects, or increase the probability of Auger electron generation due to the interaction between two electrons. As a result, defects on the surface of the quantum dots 41 may cause a decrease in the luminous efficiency of the light-emitting layer 23 or deterioration of the quantum dots 41. Furthermore, defects on the surface of the nanoparticles 31 may cause a decrease in the electron transport efficiency of the electron transport layer 24 due to deterioration of the nanoparticles 31, or deterioration of the nanoparticles 31 due to the increased probability of Auger electron generation described above.

[0039] In this embodiment, the light-emitting layer 23 contains a first halogen atom, and the electron transport layer 24 contains a second halogen atom. As a result, for example, if a first halogen atom serving as a ligand is removed from the surface of the quantum dot 41, causing a defect on the surface of the quantum dot 41, the second halogen atom in the electron transport layer 24 may coordinate to the defect and compensate for the defect. Furthermore, for example, if a second halogen atom serving as a ligand is removed from the surface of the nanoparticle 31, causing a defect on the surface of the nanoparticle 31, the first halogen atom in the light-emitting layer 23 may coordinate to the defect and compensate for the defect.

[0040] Therefore, the light-emitting layer 23 and the electron transport layer 24 according to this embodiment each contain halogen atoms that compensate for defects caused by ligand detachment from the other material. Therefore, the light-emitting element 2 reduces deterioration of at least one of the quantum dots 41 in the light-emitting layer 23 and the electron transport material, such as the nanoparticles 31 in the electron transport layer 24, thereby improving light-emitting efficiency or reliability. The display device 1 having the light-emitting element 2 on the substrate 3 achieves power saving and a long life.

[0041] In this embodiment, the second halogen atom may be a halogen atom of a different type from the first halogen atom. In other words, the second halogen atom may have a different electronegativity from the first halogen atom. In this case, due to the difference in electronegativity between the first halogen atom and the second halogen atom, the coordination of the other halogen atom to defects resulting from the removal of one halogen atom from the material occurs efficiently. Therefore, with the above configuration, the light-emitting element 2 further reduces deterioration of at least one of the quantum dots 41 in the light-emitting layer 23 and the nanoparticles 31 in the electron transport layer 24, thereby improving luminous efficiency or reliability.

[0042] In particular, in this embodiment, the electronegativity of the first halogen atom may be higher than the electronegativity of the second halogen atom. In this case, the first halogen atom is less likely to leave the quantum dots 41 than the second halogen atom is to leave the nanoparticles 31, thereby reducing the occurrence of defects in the quantum dots 41. Furthermore, in other words, the second halogen atom is more likely to leave the nanoparticles 31 than the first halogen atom is to leave the quantum dots 41. Therefore, the second halogen atom is more likely to leave the nanoparticles 31, and the second halogen atom that has left the nanoparticles 31 can more easily compensate for defects that have occurred in the quantum dots 41.

[0043] Compared with the reduction in degradation of the nanoparticles 31, the reduction in degradation of the quantum dots 41 contributes more significantly to improving the luminous efficiency or reliability of the light-emitting element 2. Therefore, with the above-described configuration, the light-emitting element 2 can more effectively reduce the degradation of the quantum dots 41 in the light-emitting layer 23, thereby further improving the luminous efficiency or reliability.

[0044] The total amount of the first halogen atoms in the light-emitting layer 23 may be greater than the total amount of the second halogen atoms in the electron transport layer 24. In this case, even if a first halogen atom is separated from a quantum dot 41 to cause a defect, other first halogen atoms are more likely to compensate for the defect. Therefore, with the above configuration, the light-emitting element 2 can more effectively reduce deterioration of the quantum dots 41 in the light-emitting layer 23, and further improve the light-emitting efficiency or reliability.

[0045] In this embodiment, the light-emitting layer 23 and the electron transport layer 24 may be adjacent to each other. This reduces the distance between the quantum dots 41 in the light-emitting layer 23 and the nanoparticles 31 in the electron transport layer 24. Therefore, with the above configuration, the first halogen atoms are more likely to compensate for defects in the nanoparticles 31, or the second halogen atoms are more likely to compensate for defects in the quantum dots 41. Therefore, with the above configuration, the light-emitting element 2 further reduces deterioration of at least one of the quantum dots 41 in the light-emitting layer 23 and the nanoparticles 31 in the electron transport layer 24, thereby improving luminous efficiency or reliability.

[0046] In the present disclosure, "two layers adjacent to each other" is not limited to a configuration in which the two layers are in contact with each other, but may also include a case in which a thin film of 3 nm or less is located between the two layers. For example, a thin film of a thickness that does not affect the compensation of defects in nanoparticles 31 by the first halogen atoms or the compensation of defects in quantum dots 41 by the second halogen atoms may be located between light-emitting layer 23 and electron transport layer 24.

[0047] Due to the above circumstances, the first halogen atoms may migrate to the electron transport layer 24, and the second halogen atoms may migrate to the light-emitting layer 23. For this reason, the light-emitting layer 23 may contain the second halogen atoms, and the electron transport layer 24 may contain the first halogen atoms. However, in this embodiment, the ratio of the first halogen atoms to all halogen atoms in the light-emitting layer 23 may be 30% or more, and the ratio of the second halogen atoms to all halogen atoms in the electron transport layer 24 may be 30% or more. This further improves the luminous efficiency or reliability of the light-emitting element 2 described above.

[0048] <Additional Notes> The materials of each layer of the light-emitting element 2 according to this embodiment may be confirmed by, for example, observing a cross section of each layer of the light-emitting element 2 and confirming the material of each portion of the cross section. For example, in this confirmation, Method 1: EDX (Energy Dispersive X-ray Spectroscopy) using a TEM (Transmission Electron Microscope) may be performed on the cross section of each layer of the light-emitting element 2. Furthermore, Method 2: EELS (Electron Energy Loss Spectroscopy) using a TEM may be performed on the cross section of each layer of the light-emitting element 2. Additionally, in this embodiment, Method 3: TOF (Time Of Flight)-SIMS (Secondary Ion Mass Spectroscopy), in other words, static SIMS, may be performed on the cross section of each layer of the light-emitting element 2. Note that the confirmation of the materials of each layer of the light-emitting element 2 in this embodiment is prioritized in the order of Method 1, Method 2, and Method 3 described above. If the material can be confirmed by the first method, the confirmation of the material by the second method may be omitted.

[0049] In this embodiment, the display device 1 includes a light-emitting element 2 having an anode 21 closer to the substrate 3 than the light-emitting layer 23, but is not limited to this. For example, the light-emitting element 2 may include, in order from the substrate 3 side, a cathode 25, an electron transport layer 24, the light-emitting layer 23, a hole transport layer 22, and the anode 21.

[0050] <Method of Manufacturing Display Device> An example of a method of manufacturing the display device 1 according to this embodiment will be described with reference to Fig. 3. Fig. 3 is a flowchart of the method of manufacturing the display device 1 according to this embodiment.

[0051] In the manufacturing method of the display device 1 according to this embodiment, first, a substrate 3 is prepared (step S1). The preparation of the substrate 3 may be performed, for example, by forming a driver circuit DR and a pixel circuit PC such as a TFT on a substrate such as a rigid glass substrate or a flexible film substrate.

[0052] Next, the anode 21 is formed by the above-described method (step S2), and then the hole transport layer 22 is formed (step S3). The anode 21 may be formed, for example, by depositing a thin film of the above-described material and then patterning it for each subpixel. The hole transport layer 22 may be formed in common to multiple subpixels by a method such as coating or film formation, or may be further patterned.

[0053] Next, the light-emitting layer 23 is formed (step S4). The light-emitting layer 23 may be formed, for example, by applying a quantum dot dispersion liquid, in which a plurality of quantum dots 41 and a first halide 51 are dispersed, onto the hole transport layer 22, and then heating and drying the applied quantum dot dispersion liquid. In forming the light-emitting layer 23, the deposition of a layer containing quantum dots 41 and the patterning of the layer for each subpixel may be repeatedly performed while changing the emission color of the quantum dots 41 dispersed in the quantum dot dispersion liquid.

[0054] Next, the electron transport layer 24 is formed (step S5). The electron transport layer 24 may be formed by, for example, applying a nanoparticle dispersion liquid, in which the nanoparticles 31 synthesized by the above-described method and the second halide 52 are dispersed, to the light-emitting layer 23 and drying the applied dispersion liquid.

[0055] Next, the cathode 25 is formed by the method described above. The cathode 25 may be formed, for example, by depositing a thin film of the material described above in common to a plurality of sub-pixels. This completes the manufacture of the display device 1. By the method described above, it is possible to form a light-emitting element 2 on the substrate 3 with improved luminous efficiency or reliability.

[0056] [Embodiment 2] <Addendum> Another embodiment of the present disclosure will be described below. Fig. 4 is a schematic side cross-sectional view of a display device 1 according to this embodiment. The display device 1 according to this embodiment has the same configuration as the display device 1 according to the previous embodiment, except that at least one of the light-emitting layer 23 and the electron transport layer 24 of the light-emitting element 2 has an addendum 61. In this embodiment, an example will be described in which both the light-emitting layer 23 and the electron transport layer 24 have the addendum 61.

[0057] The additives 61 are located around the quantum dots 41 in the light-emitting layer 23, and around the nanoparticles 31 in the electron transport layer 24. The additives 61 have the function of protecting the quantum dots 41 or the nanoparticles 31 from factors that may deteriorate the quantum dots 41 or the nanoparticles 31, such as moisture or oxygen that has penetrated from outside the display device 1, or heat. Therefore, the light-emitting element 2 in which at least one of the light-emitting layer 23 and the electron transport layer 24 has the additive 61 reduces deterioration of the quantum dots 41 or the nanoparticles 31 and improves luminous efficiency or reliability.

[0058] The additive 61 may include at least one of a metal oxide and a metal sulfide. In this case, the additive 61 becomes denser, thereby better protecting the quantum dots 41 or nanoparticles 31 from moisture, air, heat, and the like. In particular, the additive 61 may have insulating properties. This reduces deterioration of the additive 61 due to the passage of electricity through the additive 61, and as a result, the protective effect of the additive 61 on the quantum dots 41 or nanoparticles 31 is less likely to decrease. The metal atoms contained in the metal oxide or metal sulfide included in the additive 61 in the present disclosure may include atoms that are sometimes generally referred to as metalloid atoms. For example, the metal oxide or metal sulfide included in the additive 61 may include silicon (Si), boron (B), germanium (Ge), arsenic (As), antimony (Sb), or tellurium (Te) as metal atoms.

[0059] The additive 61 may include at least one of silicon oxide, boron oxide, phosphorus oxide, germanium oxide, beryllium fluoride, tellurium oxide, aluminum oxide, bismuth oxide, lead oxide, silicon nitride, and magnesium oxide, in which case the additive 61 becomes denser and better protects the quantum dots 41 or nanoparticles 31 from moisture, air, heat, and the like.

[0060] In particular, when the additive 61 is made of silicon oxide, silicon oxide forms a three-dimensionally dense crystal structure, which further protects the quantum dots 41 or nanoparticles 31 from moisture, air, heat, and the like. In the present disclosure, "the additive 61 is made of silicon oxide" is not limited to a configuration in which the additive 61 is completely made of silicon oxide, but may refer to a configuration in which, for example, other elements are added to silicon oxide, or in which residual organic ligands are contained. Alternatively, "the additive 61 is made of silicon oxide" may refer to a configuration in which an intermediate generated in the process of forming silicon oxide, including, for example, Si-OH, Si-Cl, etc., is contained. Furthermore, "the additive 61 is made of silicon oxide" may refer to a configuration in which, for example, Si-O-CH ３ It may also refer to a configuration containing at least a portion of a silicon oxide precursor, which will be described later, including, for example, silicon dioxide. Even in these cases, if it is confirmed that the additive 61 contains 50 mass % or more of silicon oxide, the additive 61 may be considered to be made of silicon oxide.

[0061] In this embodiment, the total volume of the adducts 61 in the light-emitting layer 23 may be larger than the total volume of the first halogen atoms. Alternatively, the total volume of the adducts 61 in the electron transport layer 24 may be larger than the total volume of the second halogen atoms. With the above configuration, the adducts 61 can more efficiently protect the quantum dots 41 or the nanoparticles 31.

[0062] In the present disclosure, the total volume of the first halogen atoms and the total volume of the second halogen atoms may be interpreted as the total volume of the first halide 51 and the total volume of the second halide 52, respectively. The total volume of a predetermined material in each layer of the light-emitting element 2 may be calculated, for example, from the ratio of the area of ​​the material to a region having a predetermined area in the cross section of each layer of the light-emitting element 2.

[0063] In this embodiment, the concentration of the first halogen atoms in the light-emitting layer 23 may be 10 ppm or more, and the concentration of the second halogen atoms in the electron transport layer 24 may be 10 ppm or more. As a result, the light-emitting element 2 protects the quantum dots 41 or nanoparticles 31 with the additive 61, while efficiently compensating for defects generated in the quantum dots 41 or nanoparticles 31 by the above-mentioned halogen atoms.

[0064] In the present embodiment, when both the light-emitting layer 23 and the electron transport layer 24 contain the additive 61, the additive 61 contained in the light-emitting layer 23 and the additive 61 contained in the electron transport layer 24 may contain the same material. This allows at least a portion of the material for forming the additive 61 between the light-emitting layer 23 and the electron transport layer 24 to be common in the present embodiment, thereby simplifying the manufacturing method of the light-emitting element 2 and reducing the manufacturing cost of the light-emitting element 2. Furthermore, with the above configuration, the light-emitting element 2 can reduce the difference in the band gap of the additive 61 between the light-emitting layer 23 and the electron transport layer 24. This improves the efficiency of electron transport from the electron transport layer 24 to the light-emitting layer 23, and ultimately improves the luminous efficiency of the light-emitting element 2.

[0065] The maximum thickness of the additive 61 may be 2 nm or less in at least one of the light-emitting layer 23 and the electron transport layer 24. In the light-emitting layer 23 or the electron transport layer 24 having the additive 61 with a maximum thickness of 2 nm or less, the probability of charge being injected into the quantum dots 41 or nanoparticles 31 by tunneling through the additive 61 increases. Therefore, the light-emitting element 2 has an improved luminous efficiency due to the above configuration.

[0066] In the present disclosure, the "thickness of the additive" may be the thickness of the additive 61 located around the quantum dot 41 or nanoparticle 31 from the surface of the quantum dot 41 or nanoparticle 31. In addition, in the present disclosure, the "maximum thickness of the additive" may be the maximum thickness of the additive 61 found by observing the cross section of the light-emitting layer 23 or the electron transport layer 24 to confirm 20 quantum dots 41 or nanoparticles 31 and their vicinity.

[0067] <Shape of Additive> In this embodiment, the additive 61 surrounds at least one quantum dot 41 in the light-emitting layer 23. Alternatively, the additive 61 fills the space between at least two quantum dots 41 in the light-emitting layer 23. Furthermore, in this embodiment, the additive 61 surrounds at least one nanoparticle 31 in the electron transport layer 24. Alternatively, the additive 61 fills the space between at least two nanoparticles 31 in the electron transport layer 24. Both the light-emitting layer 23 and the electron transport layer 24 may contain the additive 61.

[0068] In the present disclosure, "the adduct 61 surrounds the quantum dot 41 or nanoparticle 31" may mean that the adduct 61 is located around the entire quantum dot 41 or nanoparticle 31 in a cross section passing through the quantum dot 41 or nanoparticle 31. Here, "the adduct 61 is located around the entire quantum dot 41 or nanoparticle 31" may mean that the adduct 61 is located around 90% or more of the quantum dot 41 or nanoparticle 31.

[0069] Next, the material filling the spaces between the multiple quantum dots 41 or nanoparticles 31 will be described in more detail with further reference to Fig. 5. Schematic diagrams F1 and F2 in Fig. 5 are schematic diagrams showing the material filling the spaces between the quantum dots 41. In particular, schematic diagrams F1 and F2 are respectively diagrams showing two examples of a set P of two quantum dots 41 and the region (space) K between them, as shown in Fig. 4. In particular, schematic diagrams F1 and F2 are respectively diagrams showing a set P1 and a set P2 including a quantum dot 71 and a quantum dot 72, as examples of sets of two quantum dots 41.

[0070] In this specification, the expression "a member fills the spaces between the quantum dots 41" means that the member fills at least the region K between the quantum dots 71 and 72, as shown in the schematic diagram F1 of the set P1 in Fig. 5. The region K is a region surrounded by two lines (common circumscribing lines) tangent to the peripheries of the quantum dots 71 and 72 and the opposing peripheries of the quantum dots 71 and 72 in the cross section of the light-emitting layer 23. Therefore, as shown in the schematic diagram F2 of the set P2 in Fig. 5, the region K can exist even if the quantum dots 71 and 72 are close to each other, and the member fills the region K.

[0071] The expression "a material fills the spaces between the quantum dots 41" does not necessarily mean that the region K between the quantum dots 71 and 72 is made entirely of the material. For example, the region K between the quantum dots 71 and 72 may contain a material such as an organic ligand.

[0072] Note that the expression "a material fills the spaces between the plurality of nanoparticles 31" means that the material fills the region K after replacing the quantum dots 41 with the nanoparticles 31.

[0073] An additive 61 that surrounds at least one quantum dot 41 or fills the space between at least two quantum dots 41 better protects the quantum dot 41 and extends its lifetime. Furthermore, an additive 61 that surrounds at least one nanoparticle 31 or fills the space between at least two nanoparticles 31 better protects the nanoparticle 31 and extends its lifetime. In particular, an additive 61 that fills the space between two quantum dots 41 or two nanoparticles 31 extends the lifetime of the quantum dot 41 or nanoparticle 31, respectively. When both the light-emitting layer 23 and the electron transport layer 24 contain an additive 61, the additive 61 extends the lifetime of both the quantum dot 41 and the nanoparticle 31. By extending the lifetime of both the quantum dots 41 and the nanoparticle 31, the lifetime of the light-emitting element 2 is extended.

[0074] The additive 61 is formed at a position in the thickness direction of the light-emitting layer 23 or the electron transport layer 24, and has a thickness of 1000 nm in a direction perpendicular to the thickness direction.２ In the light-emitting layer 23 or the electron transport layer 24, the quantum dots 41 or the nanoparticles 31 may be encapsulated in the continuous film of the adduct 61. In other words, the quantum dots 41 or the nanoparticles 31 may be encapsulated in the continuous film of the adduct 61.

[0075] For example, when 80% or more of the quantum dots 41 constituting the light-emitting layer 23 have 60% or more of their surfaces in contact with the continuous film of the additive 61, it can be said that the quantum dots 41 contained in the light-emitting layer 23 are encapsulated in the additive 61. Similarly, when 80% or more of the nanoparticles 31 constituting the electron transport layer 24 have 60% or more of their surfaces in contact with the continuous film of the additive 61, it can be said that the nanoparticles 31 contained in the electron transport layer 24 are encapsulated in the additive 61. In this way, the additive 61 encapsulating the quantum dots 41 or nanoparticles 31 extends the life of the quantum dots 41 or nanoparticles 31.

[0076] <Method of forming the adduct> The display device 1 according to this embodiment can be manufactured by the same method as the manufacturing method of the display device 1 according to the previous embodiment, except for steps S4 and S5, in other words, the method of forming the light-emitting layer 23 and the method of forming the electron transport layer 24.

[0077] A method for forming the light-emitting layer 23 in the method for manufacturing the display device 1 according to this embodiment will be described with reference to Fig. 6. Fig. 6 is a flowchart of the method for forming the light-emitting layer 23 according to this embodiment.

[0078] For example, the formation of the light-emitting layer 23 is performed following the execution of steps S1 to S3 described with reference to Fig. 3. In the formation of the light-emitting layer 23 according to this embodiment, first, a first quantum dot dispersion liquid and a precursor dispersion liquid are prepared (step S41).

[0079] The first quantum dot dispersion may have the same composition as the quantum dot dispersion described in the previous embodiment, or the first quantum dot dispersion may not contain the first halogen atom. The precursor dispersion is prepared by dispersing a precursor of the adduct 61 in a solvent having a polarity different from that of the solvent of the first quantum dot dispersion.

[0080] The precursor of the adduct 61 in this embodiment is a material that is converted into the adduct 61 by hydrolysis, dehydration condensation, or the like, for example, by an operation such as heating in a dispersion liquid. For example, when the adduct 61 contains silicon oxide, the precursor may contain tetramethyl orthosilicate (TMOS) represented by the following formula (1):

[0081] Furthermore, for example, when the additive 61 contains silicon oxide, the precursor may contain 3-(mercaptopropyl)trimethoxysilane (MPS) represented by the following formula (2).

[0082] The precursor dispersion contains ZnCl as the halogen source of the first halogen atom. ２ may include:

[0083] Next, the first quantum dot dispersion and the precursor dispersion are stirred (step S42). For example, the prepared first quantum dot dispersion and the precursor dispersion may be placed in a container with a stirrer and stirred for 24 hours. As a result, the ligands coordinated to the first quantum dot dispersion are replaced with, for example, a precursor of the adduct 61, specifically MPS, etc., and the polarity of the solvent in which the quantum dots 41 are dispersed changes accordingly. Therefore, as a result of the stirring, a precipitate containing the quantum dots 41 and the precursor of the adduct 61 is formed in the mixed dispersion of the first quantum dot dispersion and the precursor dispersion. Note that in step S42, a layer containing the precipitate may be formed, for example, between the solvent of the first quantum dot dispersion and the solvent of the precursor dispersion.

[0084] Next, the precipitate is extracted and washed (step S43). The extraction and washing of the precipitate may be performed, for example, by adding a poor solvent such as ethyl acetate or acetone to the mixed dispersion liquid of step S42 to generate a precipitate, and then centrifuging the precipitate. The extraction and washing of the precipitate may be performed multiple times.

[0085] Next, a second quantum dot dispersion is prepared (step S44). The second quantum dot dispersion may be prepared by adding the washed precipitate to a solvent such as toluene. This prepares a second quantum dot dispersion in which the quantum dots 41, the precursor of the adduct 61, and the first halogen atoms are dispersed.

[0086] Next, a second quantum dot dispersion is applied (step S45). Step S45 may be performed by the same method as that used to apply the quantum dot dispersion described in the previous embodiment. Next, the applied second quantum dot dispersion is heated (step S46). As a result, the precursors of the adducts 61 in the applied second quantum dot dispersion are sequentially converted into the adducts 61 around the quantum dots 41. Therefore, by the above method, the adducts 61 are formed on the hole transport layer 22, filling the spaces between the multiple quantum dots 41. In this way, the light-emitting layer 23 according to this embodiment is formed.

[0087] The electron transport layer 24 according to this embodiment is formed following the formation of the light-emitting layer 23 described above. In particular, the electron transport layer 24 according to this embodiment can be formed by a method similar to the method for forming the light-emitting layer 23 described above, but with the quantum dots replaced with nanoparticles and the first halogen atoms replaced with second halogen atoms. This results in the electron transport layer 24 according to this embodiment being formed on the light-emitting layer 23. Next, step S6 described with reference to FIG. 3 is performed, thereby manufacturing the display device 1 according to this embodiment.

[0088] <Comparison of characteristics of light-emitting element> Light-emitting elements according to Examples 1, 2, 3, and 4, each having the same configuration as the light-emitting element 2 according to the previous embodiment or the light-emitting element 2 according to the present embodiment, were manufactured, and their light-emitting characteristics were measured.

[0089] The light-emitting element according to Example 1 has the same configuration as the light-emitting element 2 according to the previous embodiment. In other words, the light-emitting element according to Example 1 does not have the additive 61 in either the light-emitting layer 23 or the electron transport layer 24. The light-emitting element according to Example 2 has the same configuration as the light-emitting element 2 according to this embodiment, and in particular, only the light-emitting layer 23 has the additive 61, and the electron transport layer 24 does not have the additive 61. The light-emitting element according to Example 3 has the same configuration as the light-emitting element 2 according to this embodiment, and in particular, only the electron transport layer 24 has the additive 61, and the light-emitting layer 23 does not have the additive 61. The light-emitting element according to Example 2 has the same configuration as the light-emitting element 2 according to this embodiment, and in particular, both the light-emitting layer 23 and the electron transport layer 24 have the additive 61.

[0090] By measuring the luminance while changing the voltage applied to the light-emitting element according to each example, the luminance and external quantum efficiency versus the current density of the current flowing through each light-emitting element were measured and summarized in the graphs of Figures 7 and 8. Figure 7 is a graph showing the luminance versus the current density of the current flowing through the light-emitting element according to each example, and Figure 8 is a graph showing the external quantum efficiency versus the current density of the current flowing through the light-emitting element according to each example. In the graphs of Figures 7 and 8, the data for Example 1 is shown by a solid line, the data for Example 2 by a dotted line, the data for Example 3 by a dashed line, and the data for Example 4 by a dashed line.

[0091] As shown in the graph of FIG. 7, when the current density flowing through the light-emitting device according to each example was 30 mA / cm ２ 8, the external quantum efficiency of the light-emitting elements according to each example increases in proportion to the current density even when the current density of the flowing current is about 30 mA / cm. ２ This is thought to be because defects occurring in the quantum dots 41 or nanoparticles 31 of the light-emitting devices according to the respective examples are compensated for by the first halogen atoms or the second halogen atoms, thereby reducing the increase in the deactivation process due to an increase in current density.

[0092] 7 and 8, the light-emitting device according to Example 4 tends to have higher luminance and external quantum efficiency relative to the current density of the flowing current compared to the light-emitting devices according to the other Examples. In particular, as shown in the graph of FIG. 8, the external quantum efficiency of the light-emitting device according to Example 4 reaches a maximum of approximately 12%. This is thought to be due to the fact that both the quantum dots 41 and the nanoparticles 31 of the light-emitting device according to Example 4 are protected by the additives 61, thereby improving the luminous efficiency and reliability of the light-emitting device.

[0093] [Embodiment 3] <Relationship between particle diameter of quantum dots and total amount of halogen atoms> A further embodiment of the present disclosure will be described below. Fig. 9 is a schematic side cross-sectional view of a display device 1 according to this embodiment. Note that the schematic side cross-sectional view of the display device 1 shown in Fig. 9 is a schematic side cross-sectional view of the display device 1 taken along a cross section passing through a red subpixel SPR, a green subpixel SPG, and a blue subpixel SPB, which will be described later, of the display device 1.

[0094] The display unit DA of the display device 1 according to this embodiment has red subpixels SPR, green subpixels SPG, and blue subpixels SPB formed therein, which are arranged two-dimensionally when viewed in a plan view of the substrate 3, for example. In this embodiment, a red light-emitting element 2R serving as a first light-emitting element is located in the red subpixel SPR, a green light-emitting element 2G serving as a second light-emitting element is located in the green subpixel SPG, and a blue light-emitting element 2B serving as a third light-emitting element is located in the blue subpixel SPB. The display device 1 according to this embodiment performs full-color display using red light from the red light-emitting element 2R in the red subpixel SPR, green light from the green light-emitting element 2G in the green subpixel SPG, and blue light from the blue light-emitting element 2B in the blue subpixel SPB.

[0095] 9 , a bank BK made of a resin material such as polyimide is formed on the substrate 3. The bank BK divides at least the light-emitting layer 23 of the light-emitting element 2 into subpixels. Therefore, the light-emitting layer 23 is divided by the bank BK into a red light-emitting layer 23R located in the red subpixel SPR, a green light-emitting layer 23G located in the green subpixel SPG, and a blue light-emitting layer 23B located in the blue subpixel SPB. In this embodiment, the bank BK may divide each layer of the light-emitting element 2, from the anode 21 to the electron transport layer 24, into subpixels. On the other hand, the cathode 25 may be formed in common to multiple subpixels.

[0096] The red light-emitting element 2R includes layers from an anode 21 to a cathode 25, including a red light-emitting layer 23R, located in the red subpixel SPR. The green light-emitting element 2G includes layers from an anode 21 to a cathode 25, including a green light-emitting layer 23G, located in the green subpixel SPG. The blue light-emitting element 2B includes layers from an anode 21 to a cathode 25, including a blue light-emitting layer 23B, located in the blue subpixel SPB.

[0097] The red light-emitting layer 23R, the green light-emitting layer 23G, and the blue light-emitting layer 23B have the same configuration as the light-emitting layer 23 according to each of the above-described embodiments, except that they contain red quantum dots 41R, green quantum dots 41G, and blue quantum dots 41B, respectively, as quantum dots 41.

[0098] The red quantum dots 41R, green quantum dots 41G, and blue quantum dots 41B emit red light, green light, and blue light, respectively. Here, when the cores of the quantum dots are made of the same material, the quantum dots may emit light with a shorter wavelength as the particle diameter of the cores of the quantum dots becomes smaller. Therefore, when the cores of the red quantum dots 41R, green quantum dots 41G, and blue quantum dots 41B are made of the same material, the particle diameters of the cores of the red quantum dots 41R, green quantum dots 41G, and blue quantum dots 41B may become smaller in this order. In this embodiment, an example is described in which the cores of the red quantum dots 41R, green quantum dots 41G, and blue quantum dots 41B are made of the same material, the particle diameters of the cores become smaller in this order, and the shell thicknesses are the same. In other words, this embodiment describes a case in which the particle diameters of the red quantum dots 41R, green quantum dots 41G, and blue quantum dots 41B become smaller in this order.

[0099] In the present disclosure, the particle size of the quantum dots may be measured by performing cross-sectional observation of the light-emitting layer 23 in the film thickness direction. In this cross-sectional observation, the particle size of each quantum dot may be considered to be the same as the diameter of a circle having the same area as the cross-sectional area of ​​the quantum dot. Therefore, the shape of the quantum dots 41 is not necessarily limited to a spherical shape. The particle size of the quantum dots may be measured by measuring the particle size of 20 quantum dots and calculating the average. The cross-sectional observation may be performed by analyzing a cross-sectional image obtained by imaging using a TEM.

[0100] In this embodiment, the total amount of the first halogen atoms in the red light-emitting layer 23R of the red light-emitting element 2R is greater than the total amount of the first halogen atoms in the green light-emitting layer 23G of the green light-emitting element 2G. Furthermore, the total amount of the first halogen atoms in the green light-emitting layer 23G of the green light-emitting element 2G is greater than the total amount of the first halogen atoms in the blue light-emitting layer 23B of the blue light-emitting element 2B.

[0101] In general, the particle size of the quantum dots 41 is proportional to the surface area of ​​the quantum dots 41, in other words, the smaller the particle size of the quantum dots 41, the smaller the surface area of ​​the quantum dots 41. For this reason, the surface areas of the red quantum dots 41R, green quantum dots 41G, and blue quantum dots 41B tend to decrease in this order.

[0102] With the above configuration, in this embodiment, the larger the particle size of the quantum dots 41 included in the light-emitting layer 23 in each subpixel, the larger the total amount of first halogen atoms in the light-emitting layer 23. In other words, in this embodiment, the larger the surface area of ​​the quantum dots 41 included in the light-emitting layer 23 in each subpixel, the larger the total amount of first halogen atoms in the light-emitting layer 23.

[0103] In this embodiment, it is assumed that the number of quantum dots 41 in the light-emitting layer 23 is the same among the subpixels. In this case, in this embodiment, the difference in the number of first halogen atoms per unit area of ​​the quantum dots 41 among the subpixels, which is caused by the difference in surface area among the red quantum dots 41R, green quantum dots 41G, and blue quantum dots 41B, is reduced. Therefore, the display device 1 according to this embodiment can make the light-emitting characteristics of each light-emitting element more uniform regardless of the emission color of the subpixel, thereby improving display quality and extending the life of each light-emitting element.

[0104] Except for the above, the red light-emitting element 2R, green light-emitting element 2G, and blue light-emitting element 2B according to this embodiment each have the same configuration as the light-emitting element 2 according to the above-described embodiments. Therefore, each of the red light-emitting element 2R, green light-emitting element 2G, and blue light-emitting element 2B according to this embodiment also reduces deterioration of at least one of the quantum dots 41 in the light-emitting layer and the nanoparticles 31 in the electron transport layer 24, thereby improving luminous efficiency or reliability.

[0105] The display device 1 according to this embodiment may be manufactured by the same method as the method for manufacturing the display device 1 according to the previous embodiment, except that in forming the light-emitting layer 23, patterning of the layer containing the quantum dots 41 is repeatedly performed while changing the emission color of the quantum dots 41. Here, in forming the light-emitting layer 23, the concentration of the first halogen atoms added to the first quantum dot dispersion liquid or the precursor dispersion liquid may be changed depending on the particle size of the quantum dots 41.

[0106] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present disclosure. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment.

[0107] REFERENCE SIGNS LIST 1 Display device 2 Light-emitting element 2R Red light-emitting element (first light-emitting element) 2G Green light-emitting element (second light-emitting element) 3 Substrate 21 Anode 23 Light-emitting layer 24 Electron transport layer 25 Cathode 31 Nanoparticles 41 Quantum dots 51 First halide 52 Second halide 61 Additive

Claims

1. A light-emitting element comprising: an anode; a cathode facing the anode; a light-emitting layer located between the anode and the cathode and having first halogen atoms and a plurality of quantum dots; and an electron transport layer located between the cathode and the light-emitting layer and having second halogen atoms.

2. The light-emitting device according to claim 1, wherein the second halogen atom has a different electronegativity than the first halogen atom.

3. The light-emitting device according to claim 2, wherein the electronegativity of said first halogen atom is higher than the electronegativity of said second halogen atom.

4. The light-emitting element according to any one of claims 1 to 3, wherein the second halogen atoms are halogen atoms of a different type from the first halogen atoms.

5. The light-emitting device according to any one of claims 1 to 4, wherein the light-emitting layer and the electron transport layer are adjacent to each other.

6. The light-emitting device according to any one of claims 1 to 5, wherein at least one of the light-emitting layer and the electron-transporting layer contains an additive.

7. The light-emitting device according to claim 6, wherein the light-emitting layer contains the additive, and the additive fills a space between at least two of the quantum dots in the light-emitting layer.

8. The light-emitting device according to claim 6 or 7, wherein the electron transport layer contains the additive and a plurality of nanoparticles, and the additive fills the gap between at least two of the nanoparticles in the electron transport layer.

9. The light-emitting device according to claim 6, wherein the light-emitting layer contains the additive, and the additive surrounds at least one of the quantum dots in the light-emitting layer.

10. The light-emitting device according to claim 6 or 9, wherein the electron transport layer contains the additive and a plurality of nanoparticles, and the additive surrounds at least one of the nanoparticles in the electron transport layer.

11. The light-emitting element according to claim 6, wherein the light-emitting layer comprises the additive, and in the light-emitting layer, the additive surrounds at least one of the quantum dots or fills the space between at least two of the quantum dots, and the electron transport layer comprises the additive and a plurality of nanoparticles, and in the electron transport layer, the additive surrounds at least one of the nanoparticles or fills the space between at least two of the nanoparticles.

12. The light-emitting device according to any one of claims 6 to 11, wherein the additive includes at least one of a metal oxide and a metal sulfide.

13. The light-emitting element according to any one of claims 6 to 12, wherein the additive has insulating properties.

14. The light-emitting element according to any one of claims 6 to 13, wherein the additive comprises at least one of silicon oxide, boron oxide, phosphorus oxide, germanium oxide, beryllium fluoride, tellurium oxide, aluminum oxide, bismuth oxide, lead oxide, silicon nitride, and magnesium oxide.

15. The light-emitting device according to any one of claims 6 to 14, wherein the additive comprises silicon oxide.

16. A light-emitting device according to any one of claims 6 to 15, wherein the total volume of the adduct in the light-emitting layer is greater than the total volume of the first halogen atoms, or the total volume of the adduct in the electron transport layer is greater than the total volume of the second halogen atoms.

17. The light-emitting device according to claim 16, wherein the concentration of the first halogen atoms in the light-emitting layer is 10 ppm or more, or the concentration of the second halogen atoms in the electron transport layer is 10 ppm or more.

18. The light-emitting element according to any one of claims 6 to 17, wherein both the light-emitting layer and the electron transport layer contain the additive, and the additive contained in the light-emitting layer and the additive contained in the electron transport layer contain the same material.

19. The light-emitting device according to any one of claims 6 to 18, wherein the maximum thickness of the additive in at least one of the light-emitting layer and the electron transport layer is 2 nm or less.

20. The light-emitting device according to any one of claims 1 to 19, wherein the total amount of the first halogen atoms in the light-emitting layer is greater than the total amount of the second halogen atoms in the electron-transporting layer.

21. A display device comprising a substrate and a plurality of light-emitting elements according to any one of claims 1 to 20 positioned on said substrate.

22. The display device described in claim 21, wherein the plurality of light-emitting elements include a first light-emitting element and a second light-emitting element having a light-emitting layer with quantum dots having a particle size smaller than that of the first light-emitting element, and the total amount of the first halogen atoms in the light-emitting layer of the first light-emitting element is greater than the total amount of the first halogen atoms in the light-emitting layer of the second light-emitting element.

23. A method for manufacturing a light-emitting element, comprising: forming an anode; forming a cathode facing the anode; forming a light-emitting layer located between the anode and the cathode, the light-emitting layer having first halogen atoms and a plurality of quantum dots; and forming an electron transport layer located between the cathode and the light-emitting layer, the electron transport layer having second halogen atoms.

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