Light emitting element, display device, and method for manufacturing light emitting element

Abstract

A light emitting element (2) is provided with a light emitting layer (23) disposed between a first electrode (21) and a second electrode (25). The light emitting layer includes a quantum dot structure (40) which includes quantum dots (30) and an adduct (31) positioned around the quantum dots. In a cross-section of the light emitting layer, the concentration of halogen atoms in a region which includes a second straight line is 1 atm% or more, the second straight line being parallel to a first straight line and having a distance equal to or more than a half of an average particle diameter of the quantum dots from the first straight line, the first straight line passing through a plurality of quantum dots in the light emitting layer. Alternatively, the light emitting layer includes a first light emitting layer (23A) and a second light emitting layer (23B) which include a plurality of quantum dot structures, and in a cross-section of the light emitting layer, the concentration of halogen atoms in a region which includes a fifth straight line is 1 atm% or more, the fifth straight line equally dividing the space between a third straight line and a fourth straight line, the third straight line passing through a plurality of quantum dots in the first light emitting layer, and the fourth straight line being parallel to the third straight line and passing through a plurality of quantum dots in the second light emitting layer. Alternatively, the concentration of halogen atoms in the light emitting layer is 2 atm% or more.

Description

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

[0001] The present disclosure relates to a light-emitting element, a display device including the light-emitting element, and a method for manufacturing the light-emitting element.

[0002] Non-Patent Document 1 discloses a quantum dot structure having quantum dots (semiconductor nanoparticles) and an additive containing silicon oxide (silica) located around the quantum dots as a light emitter used in a light-emitting device. The structure having the additive around the quantum dots protects the quantum dots with the additive, improving the reliability of the quantum dots.

[0003] Cong Shen, Yanqing Zhu et al. Blue-Emitting InP / GaP / ZnS Quantum Dots with Enhanced Stability by Siloxane Capping: Implication for Electroluminescent Devices. ACS Appl. Nano Mater. 2022.5.2, pp. 2801-2811.

[0004] In a light-emitting device having a structure such as that described in Non-Patent Document 1 in the light-emitting layer, the injection of charges from each electrode into the quantum dots may be hindered by the additives, resulting in an increase in the resistance of the light-emitting device or a decrease in the light-emitting efficiency of the light-emitting device.

[0005] A light-emitting element according to one aspect of the present disclosure comprises first and second electrodes facing each other, and a light-emitting layer disposed between the first and second electrodes, wherein the light-emitting layer includes quantum dot structures, each including quantum dots and an adduct located around the quantum dots, arranged in a direction intersecting a film thickness direction, and wherein, in a cross section perpendicular to an in-plane direction of the light-emitting layer, a concentration of halogen atoms is 1 atm% or more in a region including a second line that is parallel to a first line passing through a plurality of the quantum dots in the light-emitting layer and has a distance from the first line that is equal to or greater than half the average particle diameter of the quantum dots.

[0006] A light-emitting element according to another aspect of the present disclosure includes first and second electrodes opposing each other, and a light-emitting layer provided between the first and second electrodes. The light-emitting layer includes quantum dot structures, each including quantum dots and an additive located around the quantum dots, arranged in a direction intersecting a film thickness direction. The light-emitting layer includes a first light-emitting layer including a plurality of the quantum dot structures, and a second light-emitting layer including a plurality of the quantum dot structures and located on either side of the first light-emitting layer in the film thickness direction. In a cross section perpendicular to an in-plane direction of the light-emitting layer, a fifth line equally dividing a line between a third line passing through the plurality of quantum dots in the first light-emitting layer and a fourth line passing through the plurality of quantum dots in the second light-emitting layer and parallel to the third line has a concentration of halogen atoms of 1 atm % or more.

[0007] A light-emitting element according to another aspect of the present disclosure comprises opposing first and second electrodes and a light-emitting layer disposed between the first and second electrodes, the light-emitting layer including quantum dots and adducts positioned around the quantum dots, and a concentration of halogen atoms in the light-emitting layer of 2 atm % or more.

[0008] A method for manufacturing a light-emitting element according to one aspect of the present disclosure is a method for manufacturing a light-emitting element including first and second electrodes facing each other and a light-emitting layer provided between the first and second electrodes, the method including forming the light-emitting layer including quantum dot structures, each including quantum dots and an adduct located around the quantum dots, arranged in a direction intersecting a film thickness direction, the quantum dot structures including quantum dots and adducts located around the quantum dots, the concentration of halogen atoms in a region including a second line, which is parallel to a first line passing through a plurality of the quantum dots in the light-emitting layer and has a distance from the first line that is equal to or greater than half the average particle diameter of the quantum dots, in a cross section perpendicular to an in-plane direction of the light-emitting layer.

[0009] A method for manufacturing a light-emitting element according to another aspect of the present disclosure is a method for manufacturing a light-emitting element including first and second electrodes opposing each other, and a light-emitting layer provided between the first and second electrodes, the method including forming the light-emitting layer including quantum dot structures, each including quantum dots and an additive located around the quantum dots, arranged in a direction intersecting a film thickness direction, the quantum dot structures including a first light-emitting layer including a plurality of the quantum dot structures, and a second light-emitting layer including a plurality of the quantum dot structures and located on either side of the first light-emitting layer in the film thickness direction, and in a cross section perpendicular to an in-plane direction of the light-emitting layer, a concentration of halogen atoms in a region including a fifth line equally dividing a line between a third line passing through the plurality of quantum dots in the first light-emitting layer and a fourth line passing through the plurality of quantum dots in the second light-emitting layer is 1 atm % or more.

[0010] According to a configuration according to one aspect of the present disclosure, in a light-emitting element, the efficiency of hole injection into quantum dots located on the anode side in the light-emitting layer is improved while at least some of the quantum dots are protected by an additive.

[0011] 1 is a schematic side cross-sectional view of a display device according to embodiment 1. FIG. 1 is a schematic view of a display device according to embodiment 1. FIG. 2 is a schematic view showing a quantum dot structure according to embodiment 1. FIG. 3 is a schematic enlarged view of a light-emitting layer in a side cross-section of a display device according to embodiment 1. FIG. 4 is a flowchart showing a method for manufacturing a display device according to embodiment 1. FIG. 5 is a process side view showing a mixing step in a method for forming a light-emitting layer according to embodiment 1. FIG. 6 is a schematic view showing a first dispersion according to embodiment 1. FIG. 7 is a process cross-sectional view showing a part of a method for forming a light-emitting layer according to embodiment 1. FIG. 8 is a flowchart showing a method for manufacturing a display device according to embodiment 2. FIG. 9 is a process side view showing a mixing step in a method for forming a light-emitting layer according to embodiment 2. FIG. 10 is a schematic view showing a first dispersion according to embodiment 2. FIG. 11 is a schematic enlarged view of a light-emitting layer in a side cross-section of a display device according to embodiment 3. FIG. 12 is a schematic side cross-sectional view of a display device according to embodiment 4. FIG. 13 is a schematic enlarged view of a light-emitting layer in a side cross-section of a display device according to embodiment 4. FIG. 14 is a schematic view showing an addition that fills spaces between quantum dots according to embodiment 4. FIG. 15 is a flowchart showing a method for manufacturing a display device according to embodiment 4. FIG. 16 is a schematic view showing a fifth dispersion according to embodiment 4. FIG. 17 is a process cross-sectional view showing a part of a method for forming a light-emitting layer according to embodiment 4.

[0012] [Embodiment 1] <Display Device: Overview> 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 but the same hatching.

[0013] 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.

[0014] 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 perpendicular to the in-plane direction DP of the light-emitting layer 23, which will be described later. Note that each schematic cross-sectional view and each process 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.

[0015] 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 the 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."

[0016] The light-emitting element 2 includes an anode 21 as a first electrode, a hole transport layer 22, a light-emitting layer 23, an electron transport layer 24, and a cathode 25 as a second electrode, in this order from the substrate 3 side. The anode 21 is electrically connected to the TFT of the substrate 3.

[0017] <Outline of Light-Emitting Element> The structure of each layer of the light-emitting element 2 will be described in more detail below.

[0018] The anode 21 and the cathode 25 comprise conductive materials and are electrically connected to the hole transport layer 22 and the electron transport layer 24, respectively.

[0019] At least one of the anode 21 and the cathode 25 is a transparent electrode that transmits visible light. Examples of transparent electrodes include ITO (indium tin oxide), IZO (indium zinc oxide), ZnO, AZO (aluminum-doped zinc oxide, also known as ZAO), BZO (boron-doped zinc oxide), and FTO (fluorine-doped tin oxide). Either the anode 21 or the cathode 25 may contain a metal material. As the metal material, Al, Cu, Au, Ag, or Mg, or an alloy thereof, which have high visible light reflectance, are preferred. The anode 21 and the cathode 25 may be formed by sputtering or the like, or may be patterned by dry etching or the like.

[0020] 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 including quantum dots. For example, conductive compounds such as polyvinylcarbazole (PVK), [N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)-benzidine] (TPD), 4,4'-bis(carbazol-9-yl)biphenyl (CBP), polyphenylenevinylene (PPV), a composite of poly(3,4-ethylenedioxythiophene) (PEDOT) and polystyrene sulfonic acid (PSS) (PEDOT-PSS), and poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4'-(N-4-sec-butylphenyl)diphenylamine)]) (TFB) can be used as organic materials for the hole transport layer 22. Examples of inorganic materials for the hole transport layer 22 include molybdenum oxide, NiO, and Cr. ２ O ３ , MgO, MgZnO, LaNiO ３ , MoO ３ , or W.O. ３In particular, as the material for the hole transport layer 22, a material having a large electron affinity and ionization potential is suitable.

[0021] 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 material of the electron transport layer 24 can 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 can be made of zinc oxide (ZnO), zinc magnesium oxide (ZnMgO), titanium oxide (TiO), and tungsten oxide (WO ３ ), or may contain an inorganic nanoparticle material that is a nanoparticle of these inorganic materials. Alternatively, the electron transport layer 24 may contain an organic material as the electron transport 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). 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 vacuum deposition, sputtering, or a coating method using a colloidal solution using the above-mentioned materials. The light-emitting element 2 may also 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. The light-emitting element 2 may also 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. The 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.

[0023] <Light-emitting layer: quantum dot structure> The light-emitting layer 23 according to this embodiment will be described in more detail with reference to Fig. 3 in addition to Fig. 1. Fig. 3 is an enlarged schematic view of the light-emitting layer 23 in the cross section shown in Fig. 1, and in particular, an enlarged view of region E1 shown in Fig. 1.

[0024] The light-emitting layer 23 according to this embodiment includes a plurality of quantum dots 30 and an adduct 31. The light-emitting layer 23 according to this embodiment also includes a ligand 32.

[0025] In particular, the light-emitting layer 23 according to this embodiment includes a plurality of quantum dot structures 40, each including a quantum dot 30, a ligand 32 located near the outermost surface of the quantum dot 30, and an adduct 31 located close to the ligand 32 on the side opposite to the quantum dot 30. Fig. 4 is a schematic cross-sectional view of the quantum dot structure 40, and in particular shows a schematic cross-sectional view of the quantum dot structure 40 taken along a plane passing through the center of the quantum dot 30 and the adduct 31 of the quantum dot structure 40.

[0026] 3 , the plurality of quantum dot structures 40 in the light-emitting layer 23 are arranged in a direction intersecting with the thickness direction DT of the light-emitting layer 23, for example, in an in-plane direction DP that is a direction perpendicular to the thickness direction DT of the light-emitting layer 23. The light-emitting layer 23 also includes the plurality of quantum dot structures 40 at different positions in the thickness direction DT.

[0027] Therefore, the light-emitting layer 23 includes a first light-emitting layer 23A and a second light-emitting layer 23B, each including a plurality of quantum dot structures 40 arranged in the in-plane direction DP. The second light-emitting layer 23B is located on either side of the first light-emitting layer 23A in the thickness direction DT. In this embodiment, the second light-emitting layer 23B is located closer to the cathode 25 than the first light-emitting layer 23A.

[0028] In the present disclosure, "quantum dot structures 40 arranged in the in-plane direction DP" does not necessarily mean that the multiple quantum dot structures 40 are on the same plane. For example, as shown by the dotted line in FIG. 3 , in a cross section perpendicular to the in-plane direction DP of the light-emitting layer 23, a line passing through the quantum dots 30 of the multiple quantum dot structures 40 in the first light-emitting layer 23A is defined as a first line 51. In this case, if the first line 51 is parallel to the in-plane direction DP and passes through all of the quantum dots 30 of the multiple quantum dot structures 40 included in the first light-emitting layer 23A, the quantum dot structures 40 may be considered to be arranged in the in-plane direction DP. In this embodiment, a case in which the first line 51 is parallel to the in-plane direction DP will be described as an example.

[0029] <Light-Emitting Layer: Quantum Dots> The quantum dots 30 may each have a core / shell structure, including a core and a shell surrounding the core. In this embodiment, the quantum dots 30 are, for example, luminescent semiconductor nanoparticles that emit light due to excitons generated by the recombination of injected electrons and holes. For example, the recombination of electrons and holes in the quantum dots 30 occurs primarily in the core. The core of the quantum dot 30 is a luminescent material that has a valence band level and a conduction band level and emits light due to the recombination of holes in the valence band level and electrons in the conduction band level. The light emitted from the quantum dots 30 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.

[0030] The core and shell materials of the quantum dots 30 may each contain materials used for the core and shell materials of conventionally known core / shell quantum dots. The quantum dots 30 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.

[0031] The quantum dots 30 have a particle size of about 1 to 100 nm. The wavelength of light emitted from the quantum dots 30 can be controlled by the particle size. In particular, since the quantum dots 30 have a core / shell structure, the wavelength of light emitted from the quantum dots 30 can be controlled by controlling the particle size of the core. Therefore, by controlling the particle size of the quantum dots 30, the wavelength of light emitted by the display device 1 can be controlled.

[0032] The light-emitting layer 23 has a thickness of 1000 nm or less in an in-plane direction DP 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 30 per layer. In this case, the light-emitting layer 23 generally contains quantum dots 30 at a concentration sufficient to function as a light-emitting layer of a light-emitting device.

[0033] <Light-emitting layer: additive> The additive 31 has, for example, insulating properties. －８ [A / (V·m)] or less, or electrical resistivity is 10 ８ Materials and components having a resistivity of Ω·m or more may be considered to have insulating properties. The additive 31 may include, for example, silicon oxide, and in particular, silica (SiO ２ The additive 31 may contain silicon oxide, in which silicon atoms and oxygen atoms are strongly bonded. When the additive 31 contains silicon oxide, the light-emitting element 2 can improve the effect of protecting the quantum dots 30 by the additive 31. In addition, the additive 31 may contain boron oxide (B ２ O ３ ), phosphorus oxide (P ２ O ５ ), germanium oxide (GeO ２ ), beryllium fluoride (BeF ２ ), arsenic sulfide (As ２ S ３ ), silicon selenide (SiSe ２ ), germanium sulfide (GeS), titanium oxide (TiO ２ ), tellurium oxide (TeO ２ ), aluminum oxide (Al ２ O ３ ), bismuth oxide (Bi ２ O ３ ), vanadium oxide (V ２ O５ ), antimony oxide (Sb ２ O ５ ), lead oxide (PbO), silicon nitride (Si ３ N ４ ) may contain one or more selected from the group consisting of. The chemical formulas written in parentheses after the compound names are representative examples. The composition ratios written in the chemical formulas may be stoichiometric, but do not necessarily have to be stoichiometric.

[0034] The addition 31 is located around the quantum dot 30. In particular, the addition 31 may be located between at least two quantum dots 30. In the present disclosure, the term "surrounding" refers to a region extending around an object (here, the quantum dot 30), and the distance from the object is not particularly limited. However, in the present disclosure, the term "surrounding" may refer to a region extending outward from the surface of the object to a given width, or may refer to a region from the quantum dot 30 having a width approximately within the distance between adjacent quantum dots 30. In addition, in the present disclosure, "disposed around" does not necessarily mean continuously surrounding the object, but also includes cases where the object is intermittently surrounded and cases where the addition 31 is disposed in only a part of the region extending around the object.

[0035] The adduct 31 may be solid. In the present disclosure, "solid" may mean that the constituent elements of the adduct 31 are not deficient or that the deficient elements are negligibly small, and typically, the size of the deficient region is 5 nm or less.

[0036] As shown in FIG. 4 , a cross section through the quantum dot 30 may include discontinuities 31D arranged around the quantum dot 30. In the present disclosure, a "discontinuity" may be a region where one or more of the constituent elements of the additive 31 are missing, and typically has a size of more than 8 nm. The discontinuities 31D may penetrate the additive 31 three-dimensionally. Furthermore, when the additive 31 for one quantum dot 30 is composed of multiple parts that are separate and independent from each other, the discontinuities 31D may include gaps between the multiple parts. In the present disclosure, a "solid discontinuous film" may mean a film that has discontinuities 31D and is solid in regions other than the discontinuities 31D.

[0037] However, the addition 31 does not have to have the discontinuity 31D, and the addition 31 may be located all around the quantum dot 30. In the present disclosure, "the addition 31 is located all around the quantum dot 30" may mean that the addition 31 is located around 90% or more of the periphery of the quantum dot 30. Furthermore, the addition 31 may have a portion in contact with the surface of the quantum dot 30.

[0038] The additive 31 may include a continuous film having a uniform or non-uniform thickness. The maximum thickness of the additive 31, particularly the maximum thickness T1 of the additive 31 in the normal direction to the outermost surface of the quantum dot 30 shown in FIG. 4, may be 2 nm or less.

[0039] The additive 31 may be porous. The pores of the porous material may be regions lacking one or more of the constituent elements of the additive 31, and typically have a size of more than 5 nm and not more than 8 nm.

[0040] The band gap of the additive 31 is wider than the band gap of the constituent material of the quantum dot 30. When the quantum dot 30 has a core and a shell surrounding the core, the band gap of the additive 31 is wider than the band gap of the constituent material of the shell. The additive 31 may include at least one of polycrystalline and amorphous.

[0041] <Light-emitting layer: Ligand> The ligand 32 may be an organic ligand containing carbon and may further contain one or more of hydrogen, nitrogen, and oxygen. The ligand 32 may be, for example, an organic ligand having a carbon chain and a coordinating functional group located at one end of the carbon chain, which is generally used as a ligand for quantum dots. The ligand 32 may be located near the quantum dots 30, and may particularly be coordinated to the quantum dots 30. In other words, the coordinating functional group of the ligand 32 may form a coordinate bond with the outermost surface of the quantum dots 30.

[0042] When a cross-sectional observation of the light-emitting layer 23 according to this embodiment confirms that the distance between the quantum dots 30 and the ligands 32 is 1 nm or less, the ligands 32 may be considered to be coordinated to the quantum dots 30. Alternatively, when it is confirmed that the quantum dots 30 and the ligands 32 are in contact with each other, the ligands 32 may be considered to be coordinated to the quantum dots 30.

[0043] For example, the adduct 31 may be located near the side of the ligand 32 that faces the quantum dot 30, i.e., the side opposite to the side having the coordinating functional group. In particular, the ligand 32 may be located near the adduct 31, and further, the ligand 32 may be chemically bonded to the adduct 31.

[0044] In addition, when it is confirmed in cross-sectional observation of the light-emitting layer 23 according to this embodiment that the distance between the adduct 31 and the ligand 32 is 1 nm or less, the ligand 32 may be considered to be bonded to the adduct 31. Alternatively, when it is confirmed that the adduct 31 and the ligand 32 are in contact with each other, the ligand 32 may be considered to be bonded to the adduct 31.

[0045] <Light-Emitting Layer: Halogen Atoms> In this embodiment, the light-emitting layer 23 contains halogen atoms. The concentration of halogen atoms in the light-emitting layer 23 may be 2 atm % or more. The concentration of halogen atoms in the light-emitting layer 23 may be confirmed by checking the concentration of halogen atoms in a plane perpendicular to the in-plane direction DP of the light-emitting layer 23, as shown in FIG. 1 or 3, for example.

[0046] 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.

[0047] In particular, the light-emitting layer 23 may contain halogen atoms in the adducts 31 of the quantum dot structures 40. For example, when the adducts 31 contain silicon oxide, the adducts 31 may have a structure in which some of the oxygen atoms bonded to silicon atoms are substituted with halogen atoms. More specifically, at least some of the adducts 31 may have a halogen group at their terminals. Additionally, in each quantum dot structure 40, the concentration of halogen atoms may be higher on the side of the adduct 31 opposite the quantum dots 30 than on the side of the quantum dots 30. The adducts 31 may have, for example, Cl atoms as halogen atoms.

[0048] <Distribution of Halogen Atoms in the Light-Emitting Layer> The distribution of halogen atoms in the light-emitting layer 23 will be described in more detail with reference to FIG.

[0049] 3, in a cross section perpendicular to the in-plane direction DP of the light-emitting layer 23, a line that is parallel to the first line 51 and has a distance D1 from the first line 51 that is equal to or greater than half the average particle diameter of the quantum dots 30 is defined as a second line 52. As shown in FIG. 3, the second line 52 may be located closer to the anode 21 than the first line 51, or may be located closer to the cathode 25 than the first line 51.

[0050] It should be noted that the "average particle size of the quantum dots 30" in the present disclosure is not limited to the average particle size of all the quantum dots 30 contained in the light-emitting layer 23. For example, in the present disclosure, the total cross-sectional area of ​​the quantum dots 30 in the observed cross section may be divided by the number of quantum dots 30 in the cross section to calculate the average cross-sectional area per quantum dot 30. Next, the diameter of the quantum dots 30 when the average cross-sectional area is the same as the cross-sectional area of ​​the quantum dots 30 passing through their centers may be taken as the average particle size of the quantum dots 30. The average particle size of the quantum dots 30 measured by the above method may be 10 nm, and thus the distance D1 may be 5 nm.

[0051] For example, Fig. 3 shows an example in which the first straight line 51 passes through the center of each quantum dot 30 of all the quantum dot structures 40 included in the first light-emitting layer 23A. Fig. 3 also shows an example in which the distance D1 is the distance from the center of the quantum dot 30 of the quantum dot structure 40 included in the first light-emitting layer 23A to the outer peripheral surface of the appendage 31. In this case, as shown in Fig. 3, the second straight line 52 is a straight line that passes through the end of the appendage 31 of the quantum dot structure 40 included in the first light-emitting layer 23A on the anode 21 side or the end of the appendage 31 on the cathode 25 side.

[0052] In this embodiment, the first line 51A may be a line passing through the quantum dots 30 of the quantum dot structures 40 included in the second light-emitting layer 23B in a cross section perpendicular to the in-plane direction DP of the light-emitting layer 23. In this case, the second line 52A may be a line that is parallel to the first line 51A and has a distance D1 from the first line 51A that is equal to or greater than half the average particle diameter of the quantum dots 30 in a cross section perpendicular to the in-plane direction DP of the light-emitting layer 23.

[0053] 3, a region including the first straight line 51 in a cross section perpendicular to the in-plane direction DP of the light-emitting layer 23 is defined as a first region 61. In addition, a region including the second straight line 52 and having the same area as the first region 61 in the cross section is defined as a second region 62, as shown by a dashed line in FIG.

[0054] For example, the first region 61 may be a region including 4 to 100 quantum dots 30. Alternatively, the first region 61 may be a region including 30 nm ２ 4000nm or more ２ The first region 61 may be a region including a range of 1 nm to 10 nm above and below the first straight line 51 in the film thickness direction DT, and a range of 3 nm to 200 nm above the first straight line 51.

[0055] However, in the present disclosure, "the areas of the two regions are the same" does not necessarily mean that the areas of the two regions are completely the same. For example, if the difference in area of ​​the second region 62 relative to the area of ​​the first region 61 is 10% or less, the areas of the first region 61 and the second region 62 may be considered to be the same.

[0056] In the present embodiment, the concentration of halogen atoms in the second region 62 is 1 atm% or more. The concentration of halogen atoms in the second region 62 is higher than the concentration of halogen atoms in the first region 61. In particular, the difference in the concentration of halogen atoms between the first region 61 and the second region 62 is 1 atm% or more. The region in the light-emitting layer 23 including the second region 62 where the concentration of halogen atoms is 1 atm% or more may include an end portion of the adduct 31. In the present disclosure, the "end portion of the adduct 31" may include, for example, a portion of the adduct 31 in the cross section of the light-emitting layer 23 that is closer to the periphery than the center in the thickness direction of the adduct 31.

[0057] 3 , in this embodiment, in a cross section perpendicular to the in-plane direction DP of the light-emitting layer 23, a region including the first line 51A may be referred to as a first region 61A, and a region including the second line 52A and having the same area as the first region 61A may be referred to as a second region 62A. In other words, the first region 61A and the second region 62A may include a cross section of the second light-emitting layer 23B in a cross section perpendicular to the in-plane direction DP of the light-emitting layer 23.

[0058] <Method for Confirming the Structure of the Light-Emitting Layer> The specific structure of each layer of the light-emitting element 2 according to this embodiment may be realized by confirming the composition of each layer in a cross section and its position in the film thickness direction. In particular, the composition of each part of the light-emitting layer 23 may be confirmed by confirming the composition at each position in a cross section perpendicular to the in-plane direction DP of the light-emitting layer 23.

[0059] The above confirmation may be performed, for example, by EDX (energy dispersive X-ray spectroscopy) on a cross section perpendicular to the in-plane direction DP of the light-emitting layer 23 using an electron microscope such as a TEM (transmission electron microscope). More specifically, the above confirmation may involve, for example, irradiating the cross section perpendicular to the in-plane direction DP of the light-emitting layer 23 with an electron beam along a first line 51 and a second line 52 to generate respective electron images. In this case, the first region 61 and the second region 62 may include ranges actually irradiated with electrons by the above method. In other words, the first region 61 and the second region 62 may each be a region of the cross section perpendicular to the in-plane direction DP of the light-emitting layer 23 where an electron image is generated at one time by the above method.

[0060] <Additional Note> The light-emitting element 2 according to this embodiment is not limited to the layer structure described above. For example, the light-emitting element 2 may include at least one of a hole injection layer located between the anode 21 and the hole transport layer 22 and an electron injection layer located between the cathode 25 and the electron transport layer 24. The light-emitting element 2 may also include at least one of an electron blocking layer located between the hole transport layer 22 and the light-emitting layer 23 and a hole blocking layer located between the electron transport layer 24 and the light-emitting layer 23.

[0061] Furthermore, in this embodiment, the display device 1 includes the light-emitting element 2 having the 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, the cathode 25, the electron transport layer 24, the light-emitting layer 23, the hole transport layer 22, and the anode 21. In this case, the second light-emitting layer 23B may be located closer to the anode 21 than the first light-emitting layer 23A, or may be located closer to the cathode 25.

[0062] <Improving Efficiency of Charge Injection into Quantum Dots> The concentration of halogen atoms in the light-emitting layer 23 according to this embodiment is 2 atm or more. Furthermore, the light-emitting layer 23 according to this embodiment has a concentration of halogen atoms of 1 atm % or more in the second region 62, in other words, in the region away from the quantum dots 30 in a cross section perpendicular to the in-plane direction DP of the light-emitting layer 23. In other words, the light-emitting layer 23 includes a quantum dot structure 40 having a high halogen concentration on the side of the adduct 31. In this embodiment, this configuration is due to the fact that a portion of the end of the adduct 31 of the quantum dot structure 40 is replaced with a halogen atom.

[0063] When the light-emitting element 2 according to this embodiment is driven, electrons injected from the cathode 25 into the light-emitting layer 23 through the electron transport layer 24 may react with atoms located at the ends of the adduct 31, converting the atoms into anions. In this case, the electrons are trapped at the ends of the adduct 31.

[0064] In general, in a field injection light-emitting element containing quantum dots as the light-emitting material of the light-emitting layer, an excess of electrons may occur in the light-emitting layer, where the concentration of electrons is higher than the concentration of holes, due to factors such as differences in charge mobility and differences in the efficiency of charge injection from each electrode to the light-emitting layer.

[0065] An excess of electrons reduces the efficiency of exciton generation through hole-electron recombination in quantum dots, and the excess electrons may increase the efficiency of generating high-energy electrons such as Auger electrons. In particular, the excess electrons may cause unnecessary charging of quantum dots. Charged quantum dots promote the generation of high-energy electrons such as Auger electrons. The above-mentioned excess high-energy electrons such as Auger electrons not only increase the deterioration of the light-emitting layer or layers adjacent to the light-emitting layer, but also promote the occurrence of deactivation processes in materials such as quantum dots that do not contribute to light emission. Furthermore, it is difficult to inject charges, including holes and electrons, into charged quantum dots, further reducing the luminous efficiency of the light-emitting layer.

[0066] On the other hand, the light-emitting element 2 according to this embodiment contains many halogen atoms in the additive 31, and in particular, the light-emitting element 2 contains many halogen atoms near the end of the additive 31. Therefore, electron trapping by the additive 31 based on the mechanism of charge injection described above is more likely to occur. As a result, the light-emitting element 2 reduces the effective electron concentration in the light-emitting layer 23, thereby improving the luminous efficiency of the light-emitting layer 23 and improving the reliability of each layer from the anode 21 to the cathode 25. In particular, when the region in the light-emitting layer 23 where the concentration of halogen atoms is 1 atm % or more includes the end portion of the additive 31, electron trapping by the additive 31 is more likely to occur.

[0067] Furthermore, electrons injected into the light-emitting layer 23 are trapped by the addition 31, thereby reducing charge buildup of the quantum dots 30 in the light-emitting element 2. Therefore, with the above configuration, the light-emitting element 2 improves the efficiency of charge injection into each quantum dot 30 in the light-emitting layer 23, thereby improving the light-emitting efficiency of the light-emitting layer 23. Furthermore, with the above configuration, the light-emitting element 2 can reduce the generation of electrons that do not contribute to light emission, such as Auger electrons, thereby improving the light-emitting efficiency of the light-emitting layer 23 or reducing deterioration of the light-emitting layer 23 or layers located in the vicinity of the light-emitting layer 23. In particular, the addition 31 according to this embodiment has insulating properties. Therefore, the light-emitting element 2 more efficiently traps electrons in the addition 31.

[0068] In addition, the light-emitting layer 23 according to this embodiment includes an appendage 31 located around the quantum dots 30. Therefore, the appendage 31 can reduce the penetration of foreign matter such as moisture into the quantum dots 30 in the light-emitting layer 23, thereby reducing deterioration of the quantum dots 30. Furthermore, the appendage 31 according to this embodiment has insulating properties. Therefore, the light-emitting element 2 can more efficiently reduce the transfer of energy of the excess electrons to the quantum dots 30, and thus can further reduce deterioration of the quantum dots 30.

[0069] Therefore, the light-emitting element 2 according to this embodiment reduces deterioration of the quantum dots 30 in the light-emitting layer 23, while improving the efficiency of charge injection into the quantum dots 30 or reducing the generation of excess electrons and excess electrons in the light-emitting layer 23. Therefore, the light-emitting element 2 improves light-emitting efficiency while reducing deterioration of each layer between the anode 21 and the cathode 25. The display device 1 including the light-emitting element 2 achieves a longer lifespan and lower power consumption.

[0070] In particular, in the light-emitting layer 23 according to this embodiment, the concentration of halogen atoms in the second region 62 is higher than the concentration of halogen atoms in the first region 61. In particular, in this embodiment, the concentration of halogen atoms in the second region 62 is higher by 1 atm or more than the concentration of halogen atoms in the first region 61. Therefore, the light-emitting element 2 including this light-emitting layer 23 more efficiently generates the above-mentioned electron traps at the end of the appendage 31.

[0071] The maximum thickness T1 of the addition 31 is 2 nm or less. Therefore, the light-emitting element 2 can trap electrons in the addition 31 while allowing some of the holes and electrons to tunnel through the addition 31 and inject them into the quantum dots 30. Therefore, with the above configuration, the light-emitting element 2 can further improve the concentration of charges injected into the quantum dots 30, and ultimately improve the luminous efficiency of the light-emitting layer 23.

[0072] <Overview of Display Device Manufacturing Method> The display device 1 according to this embodiment may be manufactured by forming multiple light-emitting elements 2 on a substrate 3 on which a driver circuit DR, pixel circuits PC, and the like are separately formed. In the manufacturing method of the light-emitting element 2 according to this embodiment, the layers other than the light-emitting layer 23 may be formed by any method, using common materials and common film-forming processes. For example, each layer can be formed by applying a solution containing the materials for each layer by a spin coating method, a slit coating method, or the like, and then drying the solution. For example, each layer can be formed by preparing a solution in which the materials for each layer are mixed with a solvent for viscosity control, and printing the solution by an inkjet method, a screen printing method, or the like. The printing method is suitable for producing light-emitting panels and display panels because it allows each layer to be uniformly formed over a large area.

[0073] The method for manufacturing the light-emitting element 2 according to this embodiment includes a method for forming the light-emitting layer 23, which will be described later. In this embodiment, the method for forming the light-emitting layer 23 includes preparing a first dispersion liquid, which will be described later, containing quantum dots 30 and an additive 31, and applying the first dispersion liquid to a substrate to form a quantum dot material layer, which will be described later.

[0074] A method for forming the light-emitting layer 23 according to this embodiment will be described with reference to Figs. 5 to 8. Fig. 5 is a flowchart showing the method for forming the light-emitting layer 23 according to this embodiment. Fig. 6 is a side view showing a mixing step in the method for forming the light-emitting layer 23 according to this embodiment. Fig. 7 is a schematic view showing a first dispersion liquid, described below, used in the method for forming the light-emitting layer 23 according to this embodiment. Fig. 8 is a cross-sectional view showing a film-forming step, which is part of the method for forming the light-emitting layer 23 according to this embodiment.

[0075] <Method for Forming Light-Emitting Layer: Mixing Step> In the method for forming the light-emitting layer 23 according to this embodiment, first, a first dispersion is prepared. The preparation of the first dispersion includes a mixing step of mixing a second dispersion in which the quantum dots 30 are dispersed with a third dispersion in which the precursor of the adduct 31 and a halogen source (described later) are dispersed (step S1). The mixing step will be described with reference to FIG. 6 .

[0076] 6 shows a second dispersion L2 and a third dispersion L3 injected into a container. The second dispersion L2 contains a plurality of quantum dots 30, each coordinated with an organic ligand 71, dispersed in a solvent 70 containing octane or the like. The third dispersion L3 contains a precursor 73 and a precursor ligand 74, which are precursors of the adduct 31, and a halogen source 75, dispersed in a solvent 72.

[0077] In this embodiment, the case where the adduct 31 contains silicon oxide will be described. In this case, the solvent 72 contains, for example, N,N-dimethylformamide (DMF). Furthermore, for example, the precursor 73 contains tetramethyl orthosilicate (TMOS) represented by the following formula (1), and the precursor ligand 74 contains 3-(mercaptopropyl)trimethoxysilane (MPS) represented by the following formula (2). Furthermore, for example, the halogen source 75 is ZnCl２ Includes.

[0078] The solvent 70 of the second dispersion L2 and the solvent 72 of the third dispersion L3 have different polarities. Therefore, when the second dispersion L2 and the third dispersion L3 are poured into the same container and allowed to stand, the dispersion in the container separates into two layers: a liquid layer of the second dispersion L2 and a liquid layer of the third dispersion L3. Furthermore, in this embodiment, the organic ligand 71 disperses more easily in the solvent 70 than in the solvent 72. Therefore, the quantum dots 30 coordinated with the organic ligand 71 are dispersed in the solvent 70.

[0079] In the mixing step, the second dispersion L2 and the third dispersion L3 are thoroughly stirred and mixed. During the stirring process, a portion of the organic ligands 71 ​​coordinated to the quantum dots 30 are replaced with precursor ligands 74. This makes it easier for the quantum dots 30 to disperse in the solvent 72 than in the solvent 70. Therefore, in step S1 according to this embodiment, as shown in step S1-2 of FIG. 6 , a fourth dispersion L4 is prepared, which is a mixture of the second dispersion L2 and the third dispersion L3, and in which the quantum dots 30 have migrated from the second dispersion L2 to the third dispersion L3. In particular, when the precursor ligand 74 according to this embodiment contains MPS, the precursor ligand 74 may coordinate to the quantum dots 30 using a thiol group as a coordinating functional group.

[0080] In step S1, when the precursor 73 contains TMOS and the precursor ligand 74 contains MPS, silicon oxide contained in the adduct is generated by conversion of the precursor 73 and the precursor ligand 74. For example, in step S1, the methoxy groups of the precursor 73 and the precursor ligand 74 are converted to water (H ２O), resulting in substitution with a hydroxyl group (OH-), and methanol being produced as a by-product. Next, dehydration condensation occurs between the two hydroxyl groups, resulting in dehydration condensation between the precursor 73 and the precursor ligand 74, between the two precursors 73, and between the two precursor ligands 74. As a result, in step S1, at least a portion of the precursor 73 and the precursor ligand 74 is converted into silicon oxide, which is an adduct. The halogen source 75 dispersed in the third dispersion L3 may function as a catalyst for the conversion between the precursor 73 and the precursor ligand 74 described above.

[0081] As described above, in the fourth dispersion L4 in step S1, the precursor ligands 74 are coordinated to the quantum dots 30. Furthermore, the conversion of the precursor ligands 74 described above in step S1 occurs on the side of the silicon atoms toward the methoxy groups, but not on the side of the silicon atoms toward the thiol groups. Therefore, in the precursor ligands 74, some of the methoxy groups on the side opposite the quantum dots 30 are converted to silicon oxide, while the thiol groups located on the quantum dots 30 side and forming coordinate bonds with the quantum dots 30 remain intact.

[0082] 6 , the quantum dots 30 dispersed in the third dispersion liquid L3 are coordinated with ligands 32 that are coordinated to the outermost surfaces of the quantum dots 30 and are derived from the thiol groups of the precursor ligands 74. Furthermore, at the end of the ligands 32 opposite the quantum dots 30, adducts 33 containing silicon oxide formed by conversion of the methoxy groups of the precursor 73 and the precursor ligand 74 are formed. As described above, in step S1, a quantum dot structure 41 is synthesized that includes the quantum dots 30, the ligands 32 that are coordinated to the quantum dots 30, and the adducts 33 located around the quantum dots 30. Note that in the present disclosure, only the quantum dots 30 included in the quantum dot structure 41 are hatched to facilitate distinction between the dispersed quantum dots 30 coordinated with the organic ligands 71 ​​and the quantum dots 30 included in the quantum dot structure 41.

[0083] The adduct 33 may have the same structure as the adduct 31 except for some of the terminal atoms. In the above-described conversion between the precursor 73 and the precursor ligand 74, dehydration condensation between some of the hydroxyl groups may not occur. For this reason, the adduct 33 formed by the conversion between the precursor 73 and the precursor ligand 74 may have a terminal hydroxyl group.

[0084] Next, the third dispersion L3 is extracted from the container, and the third dispersion L3 is centrifuged at 4000 rpm for 5 minutes, or the like, to extract the quantum dot structures 41 from the third dispersion L3 (step S2). When centrifuging the third dispersion L3, a poor solvent such as ethyl acetate or acetone may be added to the third dispersion L3 to precipitate the quantum dot structures 41.

[0085] Next, the precipitate containing the quantum dot structure 41 produced in step S2 is added to a solvent (step S3), thereby preparing a first dispersion liquid in which the quantum dot structure 41 is dispersed in the solvent.

[0086] The first dispersion liquid prepared in step S3 will be described with reference to Fig. 7. Fig. 7 shows the first dispersion liquid L1 poured into the container C. The first dispersion liquid L1 contains a plurality of quantum dot structures 41 dispersed in a solvent 76. In other words, the first dispersion liquid L1 contains the quantum dots 30 and the adduct 33. The solvent 76 contains, for example, toluene.

[0087] Note that step S1 does not have to be started after the formation of the hole transport layer 22. In particular, in this embodiment, steps S1 to S3 only need to be completed by the time the formation of the hole transport layer 22 is completed. In other words, in this embodiment, it is only necessary that the first dispersion L1 be prepared by the time the formation of the hole transport layer 22 is completed.

[0088] <Method for forming light-emitting layer: film-forming step> Following step S3, in other words following the preparation of the first dispersion liquid L1, a film-forming step is carried out in which the first dispersion liquid L1 is used to form the light-emitting layer 23. The film-forming step will be described in more detail with reference to FIG.

[0089] In the film formation process according to this embodiment, first, a laminate including the substrate 3 and the layers formed on the substrate 3 up to step S3 is used as the substrate, and a first dispersion L1 is applied to the substrate (step S4). At the start of step S4 according to this embodiment, the anode 21 and the hole transport layer 22 are formed on the substrate 3. Therefore, in step S4, as shown in step S4 of Fig. 8, the first dispersion L1 is applied onto the hole transport layer 22. In step S4, the first dispersion L1 may be applied by various application methods including conventionally known methods such as spin coating and inkjet printing.

[0090] The quantum dot structures 41 in the applied first dispersion L1 accumulate on the side of the hole transport layer 22 due to their own weight. In this case, at the completion of step S2, the quantum dot structures 41 in the first dispersion L1 are aligned along the in-plane direction of the hole transport layer 22. Furthermore, in the first dispersion L1, a plurality of quantum dot structures 41 may be positioned along the film thickness direction of the hole transport layer 22.

[0091] Next, each portion of the substrate 3 containing the applied first dispersion L1 is heated, for example, at 100° C. for 30 minutes to dry the first dispersion L1 (step S5). This volatilizes the solvent 76 of the applied first dispersion L1. Therefore, in step S5, a quantum dot material layer 77 containing a plurality of quantum dot structures 41 is formed on the hole transport layer 22.

[0092] As described above, the quantum dot structures 41 in the first dispersion liquid L1 are aligned along the in-plane direction of the hole transport layer 22. Therefore, in the quantum dot material layer 77 formed in step S5, the quantum dot structures 41 are also aligned along the in-plane direction of the hole transport layer 22. Furthermore, the quantum dot material layer 77 may include a plurality of quantum dot structures 41 aligned along the film thickness direction of the hole transport layer 22.

[0093] Next, the halogen source 75 is dropped onto the quantum dot material layer 77 (step S6). For example, in step S6, the halogen source 75 is dropped from above the quantum dot material layer 77, as shown in step S6-1 in Fig. 8. In step S6, a dispersion liquid in which the halogen source 75 is dispersed in a suitable solvent may be dropped onto the quantum dot material layer 77.

[0094] By dropping the halogen source 75 onto the quantum dot material layer 77, at least a portion of the hydroxyl groups located at the ends of the adducts 33 of the quantum dot structures 41 contained in the quantum dot material layer 77 reacts with the halogen source 75, and the hydroxyl groups are replaced with halogen groups. Furthermore, a dehydration condensation reaction may further proceed between some of the hydroxyl groups in the adducts 33 of the quantum dot structures 41 contained in the quantum dot material layer 77, using the dropped halogen source 75 as a catalyst.

[0095] 8, the additives 33 contained in the quantum dot material layer 77 become additives 31, in other words, the quantum dot structures 41 contained in the quantum dot material layer 77 become quantum dot structures 40. In this way, the light-emitting layer 23 containing a plurality of quantum dot structures 40 is formed. In step S6, the light-emitting layer 23 after the halogen source 75 has been dropped may be heated at 100° C. for 30 minutes, for example, to dry the dropped halogen source 75.

[0096] In steps S4 and S5, since the multiple quantum dot structures 41 are arranged along the in-plane direction of the hole transport layer 22, the multiple quantum dot structures 40 included in the light-emitting layer 23 are also arranged along the in-plane direction of the hole transport layer 22. When the quantum dot material layer 77 includes multiple quantum dot structures 41 along the film thickness direction, the layer of the quantum dot material layer 77 including the quantum dot structures 41 arranged on the substrate 3 side may become the first light-emitting layer 23A. Furthermore, the layer of the quantum dot material layer 77 including the quantum dot structures 41 arranged on the side opposite to the substrate 3 may become the second light-emitting layer 23B.

[0097] The above method allows the manufacture of the light-emitting element 2 including the light-emitting layer 23 according to this embodiment. In particular, the above method allows the quantum dot structure 40 to be formed more simply than a method in which the addition 31 is grown around the quantum dots 30.

[0098] Furthermore, the above method includes a method of dropping the halogen source 75 onto the quantum dot material layer 77. This makes it possible to easily substitute halogen groups for the hydroxyl groups located at the ends of the adducts 33 of the quantum dot structures 41 contained in the quantum dot material layer 77, and thus to easily increase the concentration of halogen atoms at the ends of the adducts 31. Therefore, the quantum dot structures 40 can be formed more simply than in a method in which the adducts 31 containing halogen atoms at their ends are directly formed around the quantum dots 30.

[0099] [Embodiment 2] <Modification of Mixing Step> The display device 1 according to this embodiment has the same configuration as the display device 1 according to the previous embodiment. The manufacturing method of the display device 1 according to this embodiment is the same as the manufacturing method of the display device 1 according to the previous embodiment, except for a part of the method of forming the light-emitting layer 23 included in the light-emitting element 2.

[0100] The method for forming the light-emitting layer 23 according to this embodiment will be described with reference to Fig. 9 to Fig. 11. Fig. 9 is a flowchart showing the method for forming the light-emitting layer 23 according to this embodiment. Fig. 10 is a side view showing a mixing step in the method for forming the light-emitting layer 23 according to this embodiment. Fig. 11 is a schematic view showing a first dispersion liquid (described below) used in the method for forming the light-emitting layer 23 according to this embodiment.

[0101] In the method for forming the light-emitting layer 23 according to this embodiment, first, a mixing step is performed in which the second dispersion liquid in which the quantum dots 30 are dispersed is mixed with the third dispersion liquid in which the precursor of the additive 31 and a halogen source (described later) are dispersed (step S7). As shown in step S7-1 in Fig. 10 , the second dispersion liquid L2 and the third dispersion liquid L3 according to this embodiment each have the same configuration as the second dispersion liquid L2 and the third dispersion liquid L3 according to the previous embodiment.

[0102] Step S7 according to this embodiment differs from step S1 according to the previous embodiment in the conditions for converting the precursor 73 and the precursor ligand 74. For example, in step S7, the time for mixing the second dispersion L2 and the third dispersion L3 is shortened compared to step S1. In other words, in step S7, the time for converting the precursor 73 and the precursor ligand 74 is shortened compared to step S1. As a result, in step S7, the substitution rate of the ligands coordinated to the quantum dots 30 contained in the second dispersion L2 is lower compared to step S1.

[0103] Therefore, when the second dispersion L2 and the third dispersion L3 according to this embodiment are mixed, only a portion of the precursor 73 and the precursor ligand 74 are converted into the adduct 33. Therefore, in the fourth dispersion L4, which is a mixture of the second dispersion L2 and the third dispersion L3 according to this embodiment, the quantum dots 30 are dispersed in both the second dispersion L2 and the third dispersion L3, as shown in step S7-2 of Fig. 10. However, the second dispersion L2 contains quantum dots 30 coordinated with organic ligands 71, and the third dispersion L3 contains quantum dot structures 41 including the quantum dots 30, the ligands 32, and the adducts 33.

[0104] In this embodiment, following step S7, at least a portion of the precursor 73 and the precursor ligand 74 are removed from the fourth dispersion L4 (step S8). Step S8 is performed, for example, by removing the precursor 73, the precursor ligand 74, and the halogen source 75 together with the solvent 72 from the fourth dispersion L4. Step S8 may be performed after precipitating the quantum dot structures 41 in the third dispersion L3 in advance. As a result, as shown in step S8 of FIG. 10 , the fourth dispersion L4 becomes a dispersion containing a plurality of quantum dots 30 coordinated with organic ligands 71 ​​and a plurality of quantum dot structures 41 dispersed in the solvent 70.

[0105] Next, a halogen source 75 is added to the fourth dispersion L4 from which at least a portion of the precursor 73 and the precursor ligand 74 has been removed (step S9). For example, step S9 may be performed by adding dropwise the halogen source 75 added dropwise in step S6 according to the previous embodiment to the fourth dispersion L4.

[0106] As a result, as described in the previous embodiment, at least a part of the remaining hydroxyl groups is substituted with halogen groups in the adduct 33 of the quantum dot structure 41 in the fourth dispersion L4 to which the halogen source 75 has been added. Therefore, in step S9, the quantum dot structure 41 in the fourth dispersion L4 becomes a quantum dot structure 40 including the adduct 31, as shown in step S9 in FIG.

[0107] Next, the quantum dot structures 40 are extracted from the fourth dispersion L4 by the same method as in steps S2 and S3 of the previous embodiment, and the quantum dot structures 40 are dispersed in a solvent 76 to prepare a first dispersion. As shown in Fig. 11 , the first dispersion L1A of this embodiment may have the same configuration as the first dispersion L1A except that it contains the quantum dot structures 40 instead of the quantum dot structures 41.

[0108] Next, by the same method as in steps S4 and S5 of the previous embodiment, the first dispersion L1A is applied onto the hole transport layer 22, and the first dispersion L1A is dried to form a quantum dot material layer on the hole transport layer 22. However, since the quantum dot material layer formed in this embodiment includes an array of quantum dot structures 40, this quantum dot material layer directly becomes the light-emitting layer 23. This completes the method for forming the light-emitting layer 23 according to this embodiment.

[0109] The above method allows the manufacture of a light-emitting element 2 including the light-emitting layer 23 according to this embodiment. In particular, the above method allows the quantum dot structure 40 to be synthesized in the fourth dispersion liquid L4, thereby eliminating the need for the step of dripping the halogen source 75 onto the quantum dot material layer formed in step S5. Therefore, the above method allows the light-emitting layer 23 to be formed more simply or in a shorter time. However, the method for forming the light-emitting layer 23 according to this embodiment is not limited to the above, and dripping the halogen source 75 onto the quantum dot material layer may also be performed in this embodiment from the viewpoint of further improving the concentration of halogen atoms in the formed quantum dot material layer.

[0110] [Embodiment 3] <Modification of Halogen Atom Distribution> The display device 1 according to this embodiment has the same configuration as the display device 1 according to each of the above-described embodiments, except for the distribution of halogen atoms in the light-emitting layer 23. The light-emitting layer 23 according to this embodiment will be described in more detail with reference to Fig. 12. Fig. 12 is a schematic diagram showing an enlarged side cross section of the light-emitting layer 23 of the light-emitting element 2 according to this embodiment, particularly showing an enlarged region corresponding to region E1 shown in Fig. 1.

[0111] The light-emitting layer 23 according to this embodiment includes a plurality of quantum dot structures 40 having the same configuration as the quantum dot structures 40 according to the above-described embodiments. The light-emitting layer 23 according to this embodiment also includes a first light-emitting layer 23A and a second light-emitting layer 23B including a plurality of quantum dot structures 40 arranged in the in-plane direction DP. The second light-emitting layer 23B is located on either side of the first light-emitting layer 23A in the thickness direction DT. In this embodiment, the second light-emitting layer 23B is located closer to the cathode 25 than the first light-emitting layer 23A.

[0112] 12 , in a cross section perpendicular to the in-plane direction DP of the light-emitting layer 23, a line passing through the quantum dots 30 of the quantum dot structures 40 in the first light-emitting layer 23A is defined as a third line 53. The third line 53 may be the same as the above-mentioned first line 51. In this embodiment, a case where the third line 53 is parallel to the in-plane direction DP will be described as an example.

[0113] 12 , in the cross section perpendicular to the in-plane direction DP of the light-emitting layer 23, a line that is parallel to the third line 53 and passes through the quantum dots 30 of the quantum dot structures 40 in the second light-emitting layer 23B is defined as a fourth line 54. The fourth line 54 may be the same as the above-mentioned first line 51A.

[0114] 12 , in the cross section perpendicular to the in-plane direction DP of the light-emitting layer 23, a line equally dividing the third line 53 and the fourth line 54 is defined as a fifth line 55. Therefore, in the cross section, a distance D2 between the third line 53 and the fifth line 55 in the film thickness direction DT is the same as a distance D3 between the fourth line 54 and the fifth line 55 in the film thickness direction DT. The distance D2 or the distance D3 may be the same as the above-mentioned distance D1, and in this case, the fifth line 55 may be the same as the above-mentioned second line 52.

[0115] 12 , in a cross section perpendicular to the in-plane direction DP of the light-emitting layer 23, a region including the third straight line 53 is defined as a third region 63. When the third straight line 53 is identical to the first straight line 51, the third region 63 may be identical to the above-described first region 61. Furthermore, the area of ​​the third region 63 may be determined by the same method as the area of ​​the first region 61.

[0116] 12 , in a cross section perpendicular to the in-plane direction DP of the light-emitting layer 23, a region including the fourth straight line 54 is defined as a fourth region 64. When the fourth straight line 54 is identical to the first straight line 51A, the fourth region 64 may be identical to the above-described first region 61A.

[0117] 12 , in a cross section perpendicular to the in-plane direction DP of the light-emitting layer 23, a region that includes the fifth line 55 and has the same area as the third region 63 or the fourth region 64 is defined as a fifth region 65. When the fifth line 55 is the same as the second line 52, the fifth region 65 may be the same as the second region 62 described above.

[0118] In this embodiment, the concentration of halogen atoms in the fifth region 65 is 1 atm% or more. The concentration of halogen atoms in the fifth region 65 is higher than the concentration of halogen atoms in at least one of the third region 63 and the fourth region 64. In particular, the difference in the concentration of halogen atoms between the fifth region 65 and the third region 63 or the fourth region 64 is 1 atm% or more. Note that, in this embodiment as well, the concentration of halogen atoms in the light-emitting layer 23 may be 2 atm% or more.

[0119] In the light-emitting layer 23 according to this embodiment, the concentration of halogen atoms in the second region 62, in other words, in a region of a cross section perpendicular to the in-plane direction DP of the light-emitting layer 23 that is distant from the quantum dots 30 in the first light-emitting layer 23A as well as from the quantum dots 30 in the second light-emitting layer 23B, is 1 atm % or more. In other words, the quantum dot structure 40 included in the first light-emitting layer 23A according to this embodiment contains many halogen atoms at the end of the adduct 31 that faces the second light-emitting layer 23B. Furthermore, the quantum dot structure 40 included in the second light-emitting layer 23B according to this embodiment contains many halogen atoms at the end of the adduct 31 that faces the first light-emitting layer 23A.

[0120] Therefore, when the light-emitting element 2 according to this embodiment is driven, electrons transported from the second light-emitting layer 23B to the first light-emitting layer 23A are likely to be trapped by the additives 31 in the first light-emitting layer 23A or the second light-emitting layer 23B. This reduces the effective electron concentration in the light-emitting layer 23, thereby improving the luminous efficiency of the light-emitting layer 23 and improving the reliability of each layer from the anode 21 to the cathode 25. Furthermore, the light-emitting element 2 reduces charge-up of the quantum dots 30, improving the luminous efficiency of the light-emitting layer 23 or reducing deterioration of the light-emitting layer 23 or layers located in the vicinity of the light-emitting layer 23.

[0121] Therefore, for the same reasons as described above, the light-emitting element 2 improves luminous efficiency while reducing deterioration of each layer between the anode 21 and the cathode 25. The display device 1 including the light-emitting element 2 achieves a longer life and reduced power consumption.

[0122] In particular, in the light-emitting layer 23 according to this embodiment, the concentration of halogen atoms in the fifth region 65 is higher than the concentration of halogen atoms in at least one of the third region 63 and the fourth region 64. In particular, in this embodiment, the concentration of halogen atoms in the fifth region 65 is higher by 1 atm or more than the concentration of halogen atoms in at least one of the third region 63 and the fourth region 64. Therefore, the light-emitting element 2 including this light-emitting layer 23 more efficiently generates the above-described electron traps at the end of the appendage 31.

[0123] The display device 1 according to this embodiment may be manufactured by any of the manufacturing methods for the display device 1 described above.

[0124] 13 is a schematic side cross-sectional view of a display device 4 according to this embodiment. The display device 4 according to this embodiment differs in configuration from the display device 1 described above only in that it includes a light-emitting element 5 instead of the light-emitting element 2. The light-emitting element 5 differs in configuration from the light-emitting element 2 only in that it includes a light-emitting layer 26 instead of the light-emitting layer 23.

[0125] The light-emitting layer 26 will be described in more detail with reference to Fig. 14. Fig. 14 is an enlarged schematic view of the light-emitting layer 26 in the cross section shown in Fig. 13, and in particular of the region E2 shown in Fig. 13.

[0126] The light-emitting layer 26 according to this embodiment includes a plurality of quantum dots 30 and an additive 31. In particular, the additive 31 according to this embodiment fills the space between at least two quantum dots 30.

[0127] The material filling the spaces between the quantum dots 30 will be described in more detail with further reference to Fig. 15 . Schematic diagrams 151 and 152 in Fig. 15 are schematic diagrams showing the material filling the spaces between the quantum dots 30. In particular, schematic diagrams 151 and 152 are diagrams showing two examples of a set P of two quantum dots 30 and the region (space) K between them, as shown in Fig. 14 . In particular, schematic diagrams 151 and 152 are diagrams showing sets P1 and P2, which are examples of sets of quantum dots 30A and 30B, respectively.

[0128] In this specification, "a member filling the spaces between the quantum dots 30" means that the member fills at least the region K between the quantum dots 30A and 30B, as shown in the schematic diagram 151 of the set P1 in Fig. 15. Region K is a region surrounded by two lines (common circumscribing lines) tangent to the peripheries of the quantum dots 30A and 30B and the opposing peripheries of the quantum dots 30A and 30B in the cross section of the light-emitting layer 26. Therefore, as shown in the schematic diagram 152 of the set P2 in Fig. 15, region K can exist even if the quantum dots 30A and 30B are close to each other, and the member fills region K.

[0129] The expression "a material fills the spaces between the quantum dots 30" does not necessarily mean that the region K between the quantum dots 30A and 30B is made entirely of the material. For example, the region K between the quantum dots 30A and 30B may contain a material such as the ligand 32 described above, which is not shown in Fig. 14. In this case, in the light-emitting layer 26, from the viewpoint of improving the reliability of the light-emitting layer 26, the weight ratio of the ligand 32 to the total weight including the region K may be less than 5%, for example.

[0130] Referring back to FIG. 14 , the addition 31 is formed at a position in the thickness direction DT of the light-emitting layer 26 such that the addition 31 is 1000 nm in the in-plane direction DP of the light-emitting layer 26 . ２ In the light-emitting layer 26, the quantum dots 30 may be encapsulated in the continuous film of the additive 31. In other words, the quantum dots 30 may be encapsulated in the continuous film of the additive 31.

[0131] For example, when 60% or more of the surface of 80% or more of the quantum dots 30 constituting the light-emitting layer 26 is in contact with the continuous film of the additive 31, the quantum dots 30 contained in the light-emitting layer 26 can be said to be encapsulated in the additive 31. In this way, the light-emitting layer 26 containing the quantum dots 30 encapsulated in the additive 31 has improved luminescence properties and a longer lifespan.

[0132] The addition 31 may be located, for example, all around the quantum dot 30. For example, as shown in Fig. 14 , in any cross section passing through any quantum dot 30, the addition 31 may be located all around the quantum dot 30. Here, "the addition 31 is located all around the quantum dot 30" may mean that the addition 31 is located over 90% or more of the periphery of the quantum dot 30. Furthermore, as shown in Fig. 14 , the surface of the quantum dot 30 and the addition 31 may come into contact with each other.

[0133] 14 , one quantum dot 30 and an appendage 31 located within a predetermined distance from the center of the quantum dot 30 may be considered as a quantum dot structure 42. In this case, the light-emitting layer 26 includes a first light-emitting layer 26A and a second light-emitting layer 26B, each including a plurality of quantum dot structures 42 arranged in the in-plane direction DP. The second light-emitting layer 26B is located on either side of the first light-emitting layer 26A in the thickness direction DT. In this embodiment, the second light-emitting layer 26B is located closer to the cathode 25 than the first light-emitting layer 26A.

[0134] In this embodiment, a first line 51, a second line 52, a third line 53, a fourth line 54, and a fifth line 55 are assumed in accordance with the above definitions, as shown in Fig. 14. In this embodiment, an example is shown in which the first line 51 is parallel to the in-plane direction DP and coincides with the third line 53, as shown in Fig. 14.

[0135] Also in this embodiment, a first region 61, a second region 62, a third region 63, a fourth region 64, and a fifth region 65 are assumed in accordance with the above definitions, as shown in Fig. 14. In this embodiment, an example in which the first region 61 and the third region 63 are the same is shown, as shown in Fig. 14.

[0136] In this embodiment, the concentration of halogen atoms in the second region 62 or the fifth region 65 is 1 atm % or more. The concentration of halogen atoms in the second region 62 may be higher than the concentration of halogen atoms in the first region 61. The concentration of halogen atoms in the fifth region 65 may be higher than the concentration of halogen atoms in at least one of the third region 63 and the fourth region 64.

[0137] Therefore, for the same reason as described above, when the light-emitting element 5 according to this embodiment is driven, electrons injected into the light-emitting layer 26 are more likely to be trapped by the additives 31. This reduces the effective electron concentration in the light-emitting layer 26, thereby improving the luminous efficiency of the light-emitting layer 26 and improving the reliability of each layer from the anode 21 to the cathode 25. Furthermore, the light-emitting element 5 reduces charge-up of the quantum dots 30, improving the luminous efficiency of the light-emitting layer 26 or reducing deterioration of the light-emitting layer 26 or layers located in the vicinity of the light-emitting layer 26.

[0138] Therefore, for the same reasons as those described above, the light-emitting element 5 improves luminous efficiency while reducing deterioration of each layer between the anode 21 and the cathode 25. The display device 4 including the light-emitting element 5 achieves a longer life and reduced power consumption.

[0139] Furthermore, the light-emitting layer 26 according to this embodiment includes an additive 31 that fills the space between at least two quantum dots 30. Therefore, in the light-emitting device 5, the additive 31 further improves the protective effect of the quantum dots 30, thereby further reducing deterioration of the quantum dots 30.

[0140] <Method for forming a light-emitting layer including an additive filling spaces between quantum dots> The manufacturing methods for the display device 4 and the light-emitting element 5 are the same as those for the display device 1 and the light-emitting element 2 described above, except that they include a method for forming the light-emitting layer 26, which will be described later, instead of the method for forming the light-emitting layer 23. The method for forming the light-emitting layer 26 according to this embodiment will be described with reference to FIGS. 16 to 18. FIG. 16 is a flowchart showing the method for forming the light-emitting layer 26 according to this embodiment. FIG. 17 is a schematic diagram showing a fifth dispersion liquid, which will be described later, used in the method for forming the light-emitting layer 26 according to this embodiment. FIG. 18 is a cross-sectional view showing a film formation process, which is part of the method for forming the light-emitting layer 26 according to this embodiment.

[0141] In the method for forming the light-emitting layer 26 according to this embodiment, first, for example, the above-mentioned steps S7, S8, S9, and S2 are performed in this order. In other words, in the method for forming the light-emitting layer 26 according to this embodiment, first, the quantum dot structure 40 is synthesized in a fourth dispersion liquid L4, which is a mixture of the second dispersion liquid L2 and the third dispersion liquid L3, and then the quantum dot structure 40 is extracted from the fourth dispersion liquid L4.

[0142] Next, the quantum dot structures 40 extracted in step S2, the precursor 73, and the halogen source 75 are added to the solvent 76 (step S10). As a result, in step S10, a fifth dispersion L5 is prepared in which the quantum dot structures 40, the precursor 73, and the halogen source 75 are dispersed in the solvent 76, as shown in Fig. 17. In other words, the fifth dispersion L5 may have the same configuration as the first dispersion L1A, except that the fifth dispersion L5 further contains the precursor 73 and the halogen source 75 dispersed in the solvent 76.

[0143] Following step S8, in other words following the preparation of the fifth dispersion L5, a film-forming step is carried out in which the fifth dispersion L5 is used to form the light-emitting layer 26. This film-forming step will be described in more detail with reference to FIG.

[0144] In the film formation process according to this embodiment, first, a laminate including the substrate 3 and the layers formed on the substrate 3 up to step S10 is used as the substrate, and a fifth dispersion L5 is applied to the substrate (step S11). Step S11 may be performed in the same manner as step S4, except that the fifth dispersion L5 is applied instead of the first dispersion L1. In other words, in step S11, the fifth dispersion L5 is applied onto the hole transport layer 22, as shown in step S11 in FIG.

[0145] Next, the precursors 73 in the applied fifth dispersion L5 are converted into the adducts 31 (step S12). For example, the portions of the substrate 3 containing the applied fifth dispersion L5 are heated, for example, at 100° C. for 30 minutes, to cause a reaction of the precursors 73 in the fifth dispersion L5. As a result, in step S12, the solvent 76 of the fifth dispersion L5 is evaporated, and reactions between the precursors 73 and between the precursors 73 and hydroxyl groups of the adducts 31 of the quantum dot structure 40 occur.

[0146] The halogen source 75 in the fifth dispersion L5 may function as a catalyst for the above reaction. Therefore, in step S12, the precursor 73 may be converted directly into the adduct 31 by the above reaction. Alternatively, in step S12, the precursor 73 may be converted into the adduct 33 by the above reaction. In this case, the adduct 33 may react with the halogen source 75 to replace the hydroxyl group of the adduct 33 with a halogen group, thereby forming the adduct 31.

[0147] The reaction of the precursor 73 in step S12 occurs in a state in which the precursor 73 is located around the quantum dot structure 40. Therefore, the adducts 31 formed by converting the precursor 73 are sequentially formed between the quantum dot structures 40, particularly on the adducts 31 contained in the quantum dot structure 40. Therefore, in step S12, the adducts 31 are formed so as to fill the spaces between the quantum dot structures 40, and eventually, the adducts 31 that fill the spaces between the quantum dots 30 are formed, as shown in step S12 in FIG.

[0148] Furthermore, in step S12, the substitution of hydroxyl groups with halogeno groups in the adduct 33 generated by converting the precursor 73 also occurs in a state in which the adduct 33 is located around the quantum dot structure 40. Therefore, in step S12, not only is the concentration of halogen atoms in the adduct 31 increased, but the concentration of halogen atoms in the adduct 31 is also increased closer to the periphery of the quantum dot 30 than in the vicinity of the quantum dot 30.

[0149] As a result of the above, the light-emitting layer 26 including the plurality of quantum dots 30 and the additives 31 filling the spaces between the plurality of quantum dots 30 is formed on the hole transport layer 22 .

[0150] The above method makes it possible to manufacture a light-emitting element 5 including the light-emitting layer 26 according to this embodiment. In particular, the above method makes it possible to form the light-emitting layer 26 including the additives 31 that fill the spaces between the quantum dots 30. Therefore, the above method makes it possible to reduce deterioration of the quantum dots 30 in processes subsequent to the process of forming the light-emitting layer 26 of the light-emitting element 5.

[0151] The method for forming the light-emitting layer 26 according to this embodiment is not limited to the above. For example, in the method for forming the light-emitting layer 26, steps S1 and S2 of the method for forming the light-emitting layer 23 according to embodiment 1 may be performed to extract the quantum dot structures 41. Thereafter, a fifth dispersion liquid in which the quantum dot structures 41, the precursor 73, and the halogen source 75 are dispersed in the solvent 76 may be prepared, and the film formation step described above may be performed using the fifth dispersion liquid. In this case, the hydroxyl groups of the adducts 33 of the quantum dot structures 41 may react with the halogen source 75 in the fifth dispersion liquid before or after application and be substituted with halogen groups.

[0152] Alternatively, in the method for forming the light-emitting layer 26, in step S10, the fifth dispersion may be prepared by adding only the quantum dot structure 40 and the precursor 73 to the solvent 76. In this case, following step S11, the halogen source 75 may be added dropwise to the applied fifth dispersion.

[0153] In this embodiment, in any of the above-described steps, conversion from the precursor 73 to the adduct 31 or substitution of the hydroxyl groups of the adduct 33 with halogeno groups is carried out before the adduct 33 that fills the spaces between the quantum dots 30 is formed. Therefore, according to the above-described method, the hydroxyl groups of the adduct 33 and the halogen source 75 can be reacted more efficiently, and the adduct 31 can be formed more efficiently, compared to a case in which the adduct 33 that fills the spaces between the quantum dots 30 is formed and then the halogen source 75 is added dropwise to the adduct 33.

[0154] 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.

[0155] REFERENCE SIGNS LIST 1 display device 2 light-emitting element 3 substrate 21 anode (first electrode) 23 light-emitting layer 23A first light-emitting layer 23B second light-emitting layer 25 cathode (second electrode) 30 quantum dot 31 additive 40 quantum dot structure 51 to 55 first to fifth lines 61 to 65 first to fifth regions 73 precursor 75 halogen source 77 quantum dot material layer L1 to L4 first to fourth dispersions

Claims

1. A light-emitting device comprising a first electrode and a second electrode facing each other, and a light-emitting layer provided between the first electrode and the second electrode, wherein the light-emitting layer includes a quantum dot structure including a quantum dot and an additive located around the quantum dot, and the quantum dot structures are arranged in a direction intersecting with the film thickness direction, and in a cross-section perpendicular to the in-plane direction of the light-emitting layer, the concentration of halogen atoms in a region including a second straight line that is parallel to a first straight line passing through a plurality of the quantum dots of the light-emitting layer and has a distance of at least half of the average particle size of the quantum dots from the first straight line is 1 atm% or more.

2. The light-emitting device according to claim 1, wherein the concentration of halogen atoms in a second region that is a region including the second straight line and has the same area as the first region is higher than the concentration of halogen atoms in a first region including the first straight line.

3. The light-emitting device according to claim 2, wherein the difference in the concentration of halogen atoms between the first region and the second region is 1 atm% or more.

4. A light-emitting device comprising a first electrode and a second electrode facing each other, and a light-emitting layer provided between the first electrode and the second electrode, wherein the light-emitting layer includes a quantum dot structure including a quantum dot and an additive located around the quantum dot, and the quantum dot structures are arranged in a direction intersecting with the film thickness direction, the light-emitting layer includes a first light-emitting layer including a plurality of the quantum dot structures and a second light-emitting layer including a plurality of the quantum dot structures and located on either side of the first light-emitting layer in the film thickness direction, and in a cross-section perpendicular to the in-plane direction of the light-emitting layer, the concentration of halogen atoms in a region including a fifth straight line that bisects the space between a third straight line passing through a plurality of the quantum dots of the first light-emitting layer and a fourth straight line passing through a plurality of the quantum dots of the second light-emitting layer and parallel to the third straight line is 1 atm% or more.

5. The light-emitting device according to claim 4, wherein the concentration of halogen atoms in a fifth region that is a region including the fifth straight line and has the same area as the third region or the fourth region is higher than the concentration of halogen atoms in at least one of a third region including the third straight line and a fourth region including the fourth straight line in a cross-section perpendicular to the in-plane direction of the light-emitting layer.

6. The light-emitting device according to claim 5, wherein the difference in the concentration of halogen atoms between at least one of the third region and the fourth region and the fifth region is 1 atm% or more.

7. The light-emitting element according to any one of claims 1 to 6, wherein the additive has insulating properties.

8. The light-emitting element according to any one of claims 1 to 7, wherein the additive contains at least one kind selected from the group consisting of silicon oxide, boron oxide, phosphorus oxide, germanium oxide, beryllium fluoride, arsenic sulfide, silicon selenide, germanium sulfide, titanium oxide, tellurium oxide, aluminum oxide, bismuth oxide, vanadium oxide, antimony oxide, lead oxide, and silicon nitride.

9. The light-emitting element according to any one of claims 1 to 8, wherein the additive contains silicon oxide.

10. The light-emitting element according to any one of claims 1 to 9, wherein the maximum thickness of the additive in the normal direction of the outermost surface of the quantum dot is 2 nm or less.

11. The light-emitting element according to any one of claims 1 to 10, wherein the additive fills the space between at least two of the quantum dots.

12. The light-emitting element according to any one of claims 1 to 11, wherein the region where the concentration of the halogen atom in the light-emitting layer is 1 atm% or more includes the terminal portion of the additive.

13. A light-emitting element including a first electrode and a second electrode facing each other, and a light-emitting layer provided between the first electrode and the second electrode, wherein the light-emitting layer includes quantum dots and an additive located around the quantum dots, and the concentration of the halogen atom in the light-emitting layer is 2 atm% or more.

14. A display device including a plurality of the light-emitting elements according to any one of claims 1 to 13.

15. A method for manufacturing a light-emitting element including a first electrode and a second electrode facing each other, and a light-emitting layer provided between the first electrode and the second electrode, the method including forming the light-emitting layer including a quantum dot structure including quantum dots and an additive located around the quantum dots, and arranging the quantum dot structure in a direction intersecting the film thickness direction, wherein in a cross section perpendicular to the in-plane direction of the light-emitting layer, the concentration of the halogen atom in a region including a second straight line that is parallel to a first straight line passing through a plurality of the quantum dots in the light-emitting layer and has a distance of at least half of the average particle diameter of the quantum dots from the first straight line is 1 atm% or more.

16. A method for manufacturing a light-emitting device including a first electrode and a second electrode facing each other, and a light-emitting layer provided between the first electrode and the second electrode, the method including forming the light-emitting layer including a quantum dot structure including a quantum dot and an additive located around the quantum dot, the quantum dot structure being arranged in a direction intersecting with the film thickness direction, the light-emitting layer including a first light-emitting layer including a plurality of the quantum dot structures and a second light-emitting layer including a plurality of the quantum dot structures and located on either side in the film thickness direction with respect to the first light-emitting layer, and the concentration of halogen atoms in a region including a fifth straight line that bisects the space between a third straight line passing through a plurality of the quantum dots of the first light-emitting layer and a fourth straight line passing through a plurality of the quantum dots of the second light-emitting layer in a cross section perpendicular to the in-plane direction of the light-emitting layer being 1 atm% or more.

17. The method for manufacturing a light-emitting device according to claim 15 or 16, wherein the formation of the light-emitting layer includes preparing a first dispersion liquid including the quantum dot and the additive, and forming a quantum dot material layer by applying the first dispersion liquid onto a substrate.

18. The method for manufacturing a light-emitting device according to claim 17, wherein the formation of the light-emitting layer includes dropping a halogen source onto the quantum dot material layer.

19. The preparation of the first dispersion liquid includes mixing a second dispersion liquid including the quantum dot and a third dispersion liquid including a precursor of the additive and a halogen source, and converting at least a part of the precursor into the additive in the mixing of the second dispersion liquid and the third dispersion liquid. The method for manufacturing a light-emitting device according to claim 17 or 18.

20. In the mixing of the second dispersion liquid and the third dispersion liquid, a part of the precursor is converted into the additive, and the preparation of the first dispersion liquid includes removing at least a part of the precursor from a fourth dispersion liquid that is a mixed liquid of the second dispersion liquid and the third dispersion liquid, and adding a halogen source to the fourth dispersion liquid from which at least a part of the precursor has been removed. The method for manufacturing a light-emitting device according to claim 19.

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