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

Abstract

The light-emitting element (2) has a light-emitting layer (23) located between an anode (21) and a cathode (25). The light-emitting layer includes a plurality of quantum dots (30) and an inorganic matrix (31) filled between the plurality of quantum dots and having a metal oxide. The inorganic matrix includes a first portion (41) having a metal oxide and a second portion (42). The ratio of oxygen atoms to metal atoms in the second portion is higher than the ratio of oxygen atoms to metal atoms in the first portion, and is equal to or less than the ratio of oxygen atoms to metal atoms in the stoichiometric metal oxide.

Description

Technical Field

[0001] This disclosure relates to a light-emitting element, a display device having the light-emitting element, and a method for manufacturing the light-emitting element. Background Technology

[0002] Non-Patent Document 1 discloses a quantum dot structure containing quantum dots (semiconductor nanoparticles) within a matrix containing silicon oxide (silicon dioxide) as a light emitter. The structure containing quantum dots within the matrix improves the reliability of the quantum dots by protecting them with the matrix.

[0003] Existing technical documents Non-patent literature Non-patent literature 1: Cong Shen, Yanqing Zhu et al. Blue-Emitting InP / GaP / ZnSQuantum Dots with Enhanced Stability by Siloxane Capping: Implication for Electroluminescent Devices. ACS Appl. Nano Mater. 2022.5.2, pp. 2801-2811. Summary of the Invention The technical problem this disclosure aims to solve In light-emitting elements having a structure as described in Non-Patent Document 1 within the light-emitting layer, there are instances where the injection of charge from each electrode into the quantum dots is hindered by the matrix, leading to increased resistance or decreased luminous efficiency of the light-emitting element. Furthermore, oxygen atoms in the matrix of the structure described in Non-Patent Document 1 can degrade the quantum dots, the material surrounding the quantum dots, or the material surrounding the structure.

[0004] Technical solutions for solving technical problems One aspect of the light-emitting element disclosed herein comprises: an anode; a cathode opposite to the anode; and a light-emitting layer located between the anode and the cathode, the light-emitting layer comprising: a plurality of quantum dots; and an inorganic matrix filled between the plurality of quantum dots and having a metal oxide, the inorganic matrix comprising: a first portion having the metal oxide; and a second portion having the metal oxide, wherein the ratio of oxygen atoms to metal atoms is higher than the ratio of oxygen atoms to metal atoms in the first portion, and is lower than the stoichiometric ratio of oxygen atoms to metal atoms in the metal oxide.

[0005] This disclosure discloses a method for manufacturing a light-emitting element, wherein the light-emitting element has an anode, a cathode opposite to the anode, and a light-emitting layer located between the anode and the cathode. The method for manufacturing the light-emitting element includes forming the light-emitting layer, the light-emitting layer comprising a plurality of quantum dots and an inorganic matrix, the inorganic matrix filling the spaces between the plurality of quantum dots and having a metal oxide, the inorganic matrix comprising: a first portion having the metal oxide; and a second portion having the metal oxide, wherein the ratio of oxygen atoms to metal atoms is higher than the ratio of oxygen atoms to metal atoms in the first portion, and is lower than the stoichiometric ratio of oxygen atoms to metal atoms in the metal oxide. Beneficial Effects According to one aspect of the present disclosure, in the light-emitting element, it is possible to achieve a design that improves the efficiency of charge vector quantum dot injection from each electrode, or to reduce the degradation of the light-emitting layer or the area surrounding the light-emitting layer. Attached Figure Description

[0006] Figure 1 This is a schematic side cross-sectional view of the display device according to the first embodiment.

[0007] Figure 2 This is a schematic diagram of the display device according to the first embodiment.

[0008] Figure 3 This is a schematic enlarged view of the cross-section of the light-emitting layer in the first embodiment.

[0009] Figure 4 This is a schematic diagram illustrating the inorganic matrix between the quantum dots in the first embodiment.

[0010] Figure 5 This is a schematic diagram illustrating an example of the structure of the inorganic matrix according to the first embodiment.

[0011] Figure 6 This is a schematic diagram illustrating another example of the structure of the inorganic matrix of the first embodiment.

[0012] Figure 7 This is a schematic diagram illustrating another example of the structure of the inorganic matrix of the first embodiment.

[0013] Figure 8 This is a flowchart illustrating a method for forming the light-emitting layer according to the first embodiment.

[0014] Figure 9 This is a schematic diagram showing the first dispersion of the first embodiment.

[0015] Figure 10 This is a cross-sectional view showing a part of the process of forming the light-emitting layer according to the first embodiment.

[0016] Figure 11 This is a flowchart illustrating a method for forming the light-emitting layer according to the second embodiment.

[0017] Figure 12 This is a cross-sectional view showing a part of the method for forming the light-emitting layer according to the second embodiment.

[0018] Figure 13 This is a schematic side sectional view of the display device according to the third embodiment.

[0019] Figure 14 This is a schematic enlarged view of the cross-section of the light-emitting layer in the third embodiment.

[0020] Figure 15 This is a flowchart illustrating a method for forming a light-emitting layer according to a third embodiment.

[0021] Figure 16 This is a process side view showing the mixing process in the method for forming the light-emitting layer according to the third embodiment.

[0022] Figure 17 This is a schematic diagram illustrating the reaction process of the precursor in the third embodiment.

[0023] Figure 18 This is a schematic diagram showing the third dispersion of the third embodiment.

[0024] Figure 19 This is a schematic diagram showing the fourth dispersion of the third embodiment.

[0025] Figure 20 This is a cross-sectional view showing a part of the process of forming the light-emitting layer according to the third embodiment.

[0026] Figure 21 This is a flowchart illustrating a method for forming a light-emitting layer according to the fourth embodiment.

[0027] Figure 22 This is a schematic side cross-sectional view of the display device according to the fifth embodiment. Detailed Implementation

[0028] [First Implementation Method] <Display Devices: Overview> Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. Furthermore, in each drawing, the same reference numerals are used to denote the same components, and their descriptions are omitted. Additionally, in this disclosure, to simplify the illustration, the scale may sometimes differ depending on the drawing for components labeled with the same reference numerals, and different cross-sectional lines may sometimes be used. However, the components shown in each drawing of this disclosure are merely illustrative, and their scale is not limited to the examples shown in the drawings. Furthermore, in this disclosure, for components labeled with different cross-sectional lines, the components labeled with the same reference numerals are components having the same structure as described above.

[0029] Figure 2 This is a schematic diagram of the 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 or a smartphone. The display device 1 includes a display section DA comprising a plurality of sub-pixels X and a drive circuit DR for driving 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 for driving the light-emitting element 2. The display device 1 displays on the display section DA by controlling the light emission of each of the plurality of light-emitting elements 2 formed from the display section DA via the drive circuit DR and the pixel circuit PC.

[0030] Reference Figure 1 The structure of the display section DA of the display device 1 will be described in more detail, especially the structure of the light-emitting element 2. Figure 1 A schematic side cross-sectional view of the display device 1 according to an embodiment of the present disclosure is shown, particularly a cross-section perpendicular to the display surface of the display device 1 and passing through the light-emitting element 2. Furthermore, the cross-sectional views of each process of the display device in this disclosure, as well as the cross-sectional views of each process described later, represent... Figure 1 The cross-section corresponding to the cross-section of the display device 1 shown.

[0031] like Figure 1 As shown, the display device 1 of this embodiment includes the aforementioned plurality of light-emitting elements 2 and substrate 3 in the display section DA, and in particular, the plurality of light-emitting elements 2 are provided on the substrate 3. The display device 1 has, for example, a structure in which layers of light-emitting elements 2 are stacked on a substrate 3 formed as a pixel circuit PC (TFT, not shown). In addition, in this specification, the direction from the light-emitting elements 2 to the substrate 3 of the display device 1 is described as the "downward direction", and the direction opposite to the downward direction is described as the "upward direction".

[0032] The light-emitting element 2 has a hole transport layer 22, a light-emitting layer 23, an electron transport layer 24, and a cathode 25 sequentially on the anode 21 from one side of the substrate 3. The anode 21 is electrically connected to the TFT of the substrate 3.

[0033] <Overview of Light Emitting Elements> The composition of each layer of the light-emitting element 2 will be explained in more detail below.

[0034] The anode 21 and cathode 25 contain conductive materials and are electrically connected to the hole transport layer 22 and the electron transport layer 24, respectively.

[0035] 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 (also known as aluminum-doped zinc oxide, ZAO), BZO (boron-doped zinc oxide), or FTO (fluorine-doped tin oxide). The transparent electrode can be deposited as a film by methods such as sputtering. Furthermore, either the anode 21 or the cathode 25 may contain a metallic material; preferably, Al, Cu, Au, Ag, or Mg, or alloys thereof, which have high visible light reflectivity.

[0036] Hole transport layer 22 is a layer containing a hole transport material that transports holes from anode 21 to light-emitting layer 23. In light-emitting elements containing quantum dots, the material of hole transport layer 22 can be conventionally used organic or inorganic materials. For example, hole transport layer 22 may also contain at least one of polyvinylcarbazole (PVK) and [N,N”-bis(4-butylphenyl)-N,N”-bis(phenyl)-benzidine] (TPD) as the hole transport material. In addition, as organic materials for the hole transport layer 22, conductive compounds such as 4,4”-bis(carbazole-9-yl)biphenyl (CBP), polyphenylene vinylidene (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 inorganic materials for the hole transport layer 22, metal oxides such as molybdenum oxide, NiO, Cr2O3, MgO, MgZnO, LaNiO3, MoO3, or WO3 can be used. In particular, materials with high electron affinity and ionization potential are preferred for the hole transport layer 22.

[0037] 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. In the electron transport layer 24, conventionally used organic or inorganic materials can be used in light-emitting elements containing quantum dots. For example, the electron transport layer 24 can contain at least one of zinc oxide (ZnO), zinc magnesium oxide (ZnMgO), titanium oxide (TiO), and tungsten oxide (WO3). Alternatively, it can contain nanoparticles of these inorganic materials, i.e., inorganic nanoparticle materials. Alternatively, the electron transport layer 24 can contain organic materials such as tris(8-hydroxyquinoline)aluminum complex (Alq3), copper hydroxide (BCP), or (2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole) (t-Bu-PBD). Furthermore, metal oxides such as ZnO, ZAO, ITO, InGaZnO, or electron-emitting compounds can also be used as inorganic materials for the electron transport layer 24. In particular, materials with low electron affinity are preferred for the electron transport layer 24.

[0038] In this embodiment, the hole transport layer 22 and the electron transport layer 24 can be formed using vacuum evaporation, sputtering, or coating with a colloidal solution, employing the materials described above. Furthermore, the light-emitting element 2 may have 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. Moreover, the light-emitting element 2 may also have an intermediate layer between the hole transport layer 22 and the light-emitting layer 23, or between the electron transport layer 24 and the light-emitting layer 23. These hole injection layers, electron injection layers, and intermediate layers can all be formed using the same methods as the hole transport layer 22 or the electron transport layer 24.

[0039] <Emitting Layer: Quantum Dots> Reference Figure 3 and Figure 1 The light-emitting layer 23 of this embodiment will be described in more detail. Figure 3 Enlarged display Figure 1 The luminescent layer 23 in the cross-section shown, especially when magnified. Figure 1 A schematic diagram of region E1 is shown.

[0040] The light-emitting layer 23 contains multiple quantum dots 30 and an inorganic matrix 31.

[0041] Quantum dot 30 can be, for example, a core / shell structure quantum dot having a core and a shell formed around the core. In this embodiment, quantum dot 30 is, for example, a luminescent semiconductor nanoparticle that emits light through excitons generated by the recombination of injected electrons and holes. For example, the recombination of electrons and holes in quantum dot 30 is mainly generated in the core. The core of quantum dot 30 has valence band energy levels and conduction band energy levels, and it is a luminescent material that emits light through positive holes in the valence band energy level and the recombination of electrons in the conduction band energy level. The light emitted from quantum dot 30 has a narrow spectrum due to the quantum confinement effect, thus enabling the emission of light with a deeper chromaticity. In addition, the shell has the function of suppressing the generation of defects or dangling bonds in the core and reducing the recombination of the carrier after the deactivation process.

[0042] The quantum dot 30 may also contain a core material having a conventionally known core / shell structure, as well as a material used in the shell material, in both the core and shell materials. For example, the quantum dot 30 may also have InP / ZnS, CdSe / ZnS, CdSe / ZnSe, CdSe / CdS, ZnSe / ZnS, or CIGS / ZnS as the core / shell structure. Furthermore, the shell may be formed from multiple layers containing various materials that are different from each other.

[0043] The quantum dot 30 has a particle size of approximately 1-100 nm. The wavelength of light emitted from the quantum dot 30 can be controlled by the particle size. In particular, the quantum dot 30 has a core / shell structure, so the wavelength of light emitted from the quantum dot 30 can be controlled by controlling the particle size of the core. Therefore, by controlling the particle size of the quantum dot 30, the wavelength of light emitted by the display device 1 can be controlled.

[0044] <Light-emitting layer: Inorganic matrix> In this embodiment, the inorganic matrix 31 is filled between a plurality of quantum dots 30. Further reference... Figure 4 A more detailed description is given of the inorganic matrix 31 filled between the multiple quantum dots 30. Figure 4 Schematic diagrams 401 and 402 are schematic diagrams illustrating the inorganic matrix 31 filled between the quantum dots 30. Specifically, schematic diagrams 401 and 402 respectively illustrate... Figure 3 The diagram shows two examples of groups P of two quantum dots 30 and the region (space) K between them. In particular, the schematic diagrams 401 and 402 are examples of groups of quantum dots 30A and quantum dots 30B, namely groups P1 and P2, respectively.

[0045] In this instruction manual, such as Figure 4As shown in schematic diagram 401 of group P1, the inorganic matrix 31 is filled between multiple quantum dots 30. It is sufficient to know the region K that is filled at least between quantum dots 30A and 30B. Region K is the area in the cross-section of the light-emitting layer 23 surrounded by two straight lines (sharing a common external tangent) that tangent to the outer peripheries of quantum dots 30A and 30B, and the outer periphery of the quantum dots 30A and 30B opposite to those in the schematic diagram. Therefore, as... Figure 4 As shown in the schematic diagram 402 of group P2, even if quantum dot 30A and quantum dot 30B are close to each other, region K may still exist. In addition, inorganic matrix 31 fills region K.

[0046] The inorganic matrix 31 filling the spaces between the multiple quantum dots 30 means that the region K between quantum dots 30A and 30B is entirely composed of the inorganic matrix 31. For example, the region K between quantum dots 30A and 30B may also contain materials such as ligands that are different from the material of the inorganic matrix 31. Specifically, for example, to improve the dispersibility of the quantum dots 30 in the dispersion formed for coating, a light-emitting layer 23 may be added. In this dispersion, the light-emitting layer 23 may contain organic ligands located on the outer peripheral surfaces of the quantum dots 30. In this case, from the viewpoint of improving the reliability of the light-emitting layer 23, for example, the weight ratio of the organic ligands to the total weight of the region K may be less than 5%.

[0047] Return to reference Figure 1 as well as Figure 3 The inorganic matrix 31 can fill the area of ​​the light-emitting layer 23 other than the multiple quantum dots 30. For example, the outer edge (upper and lower surfaces) of the light-emitting layer 23 can also be covered by the inorganic matrix 31. Alternatively, the inorganic matrix 31 can be provided from the outer edge of the light-emitting layer 23, with the quantum dots 30 located away from this outer edge. The outer edge of the light-emitting layer 23 can also be formed not only by the inorganic matrix 31, but also with a portion of the quantum dots 30 exposed from the inorganic matrix 31. The inorganic matrix 31 can represent the portion of the light-emitting layer 23 excluding the multiple quantum dots 30.

[0048] The inorganic substrate 31 can be located at any position along the thickness direction of the light-emitting layer 23, having a thickness of 1000 nm in a plane direction orthogonal to the thickness direction. 2 The above-mentioned area is a continuous film. In addition, in the light-emitting layer 23, the quantum dots 30 can be encapsulated within the continuous film of the inorganic matrix 31.

[0049] For example, if more than 80% of the quantum dots 30 constituting the light-emitting layer 23 have more than 60% of their surface in contact with the continuous film of the inorganic matrix 31, it can be said that the quantum dots 30 contained in the light-emitting layer 23 are encapsulated within the inorganic matrix 31. In this way, the light-emitting layer 23, which contains the quantum dots 30 contained within the inorganic matrix 31, improves the light-emitting properties and extends the lifetime.

[0050] The light-emitting layer 23, at any position along the film thickness direction, on a plane orthogonal to the film thickness direction, per 1000 nm... 2 It may contain more than one quantum dot 30. In this case, the light-emitting layer 23 typically contains a sufficient concentration of quantum dots 30 to function as the light-emitting layer of the light-emitting element.

[0051] The inorganic matrix 31 can, for example, extend throughout the entire surrounding area of ​​the quantum dot 30. Figure 3 As shown, in any cross-section passing through any quantum dot 30, the inorganic matrix 31 can be located entirely around the quantum dot 30. Here, "the inorganic matrix 31 is located entirely around the quantum dot 30" means that the inorganic matrix 31 is located at more than 90% of the perimeter of the quantum dot 30. Furthermore, as... Figure 3 As shown, the surface of quantum dot 30 can also be in contact with inorganic matrix 31.

[0052] The band gap of the inorganic matrix 31 can be 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 inorganic matrix 31 can be wider than the band gap of the constituent material of the shell.

[0053] In this embodiment, the inorganic matrix 31 has a metal oxide. Here, the metal oxide in this specification includes oxides having atoms as metal atoms, which are generally referred to as half-metal atoms, including silicon (Si), boron (B), germanium (Ge), arsenic (As), antimony (Sb) and tellurium (Te).

[0054] Furthermore, the term "atom" in this disclosure does not refer solely to a single atom. "Atom" in this disclosure includes atoms existing in molecular form (containing two or more atoms, including the atom itself and other different atoms), atoms existing in complex form, atoms existing in compound form, or atoms existing in ionic form. However, "atom" in this disclosure does not limit the existence of other atoms. That is, metal atoms include metal atoms existing in the form of compounds containing metal atoms, as well as metal atoms existing in the form of metal ions. Regardless of their form of existence, if the presence of metal atoms in a substance can be determined through analysis, that substance can be considered to contain metal atoms.

[0055] In particular, the inorganic matrix 31 may, for example, contain silicon oxide (SiO2) as a metal oxide. Furthermore, the inorganic matrix 31 may contain one or more compounds selected from the group consisting of titanium oxide (TiO2), aluminum oxide (Al2O3), boron oxide (B2O3), phosphorus oxide (P2O5), germanium oxide (GeO2), hafnium oxide (HfO2), zinc oxide (ZnO), zirconium oxide (ZrO2), tellurium oxide (TeO2), bismuth oxide (Bi2O3), vanadium oxide (V2O5), antimony oxide (Sb2O5), lead oxide (PbO), and copper oxide (CuO). Additionally, the chemical formulas listed in parentheses after the compound name are representative examples.

[0056] Here, the chemical formulas of the aforementioned metal oxides are described as stoichiometric proportions. However, a portion of the inorganic matrix 31 of this embodiment may also have metal oxides with compositional proportions different from those of the stoichiometric metal oxides. In particular, in the metal oxides of the inorganic matrix 31 of this embodiment, the ratio of oxygen atoms to metal atoms is stoichiometric, that is, the ratio of oxygen atoms to metal atoms in the metal oxide is less than or equal to the stoichiometric proportion.

[0057] Furthermore, the metal oxide referred to as stoichiometry in this specification refers to the metal oxide having the most stable composition ratio among the composition ratios obtained from the atomic valence ratios of the metal atoms and oxygen atoms of that metal oxide. For example, silicon oxide can be represented by the chemical formulas SiO2 and SiO, but unless otherwise specified, silicon oxide referred to as stoichiometry in this specification refers to silicon oxide having the same composition ratio as SiO2. Similarly, stoichiometric titanium oxide refers to a metal oxide with the same composition ratio as TiO2; stoichiometric aluminum oxide refers to a metal oxide with the same composition ratio as Al2O3; stoichiometric boron oxide refers to a metal oxide with the same composition ratio as B2O3; stoichiometric phosphorus oxide refers to a metal oxide with the same composition ratio as P2O5; stoichiometric germanium oxide refers to a metal oxide with the same composition ratio as GeO2; stoichiometric hafnium oxide refers to a metal oxide with the same composition ratio as HfO2; and stoichiometric zinc oxide refers to a metal oxide with the same composition ratio as ZnO. The following are stoichiometric terms for the metal oxide: zirconium oxide (ZrO2) is a metal oxide with the same composition ratio as ZrO2; tellurium oxide (TeO2) is a metal oxide with the same composition ratio as TeO2; bismuth oxide (Bi2O3) is a metal oxide with the same composition ratio as Bi2O3; vanadium oxide (V2O5) is a metal oxide with the same composition ratio as vanadium dioxide; antimony oxide (Sb2O5) is a metal oxide with the same composition ratio as Sb2O5; lead oxide (PbO) is a metal oxide with the same composition ratio as PbO; and copper oxide (CuO) is a metal oxide with the same composition ratio as CuO.

[0058] <Structure of Metal Oxides> For a specific example of the structure of the metal oxide in the inorganic matrix 31, see [reference]. Figures 5 to 7 Please provide an explanation. Figures 5 to 7 This is a schematic diagram illustrating an example of the structure of the metal oxide contained in the inorganic matrix 31 of this embodiment. Figures 5 to 7 An example of the structure of the inorganic matrix 31 is shown in the case where the inorganic matrix 31 contains silicon oxide as a metal oxide 60.

[0059] like Figure 5 As shown, the metal oxide 60 contained in the inorganic matrix 31 has a two-dimensional mesh structure with Si-O-Si bonds. Furthermore, in Figure 5 In the metal oxide 60, there is a bonding region BD in which a portion of the Si-O-Si bonds are replaced with Si-Si bonds.

[0060] like Figure 6 As shown, the metal oxide 60 contained in the inorganic matrix 31 can also be a metal oxide 64 containing SiO. For example, assuming Figure 6 In the metal oxide 64 shown, the centers of silicon atoms and oxygen atoms are in the same plane. In this case, the metal oxide 64 can have Si-Si bonds extending in directions approximately orthogonal to the extension directions of each Si-O-Si bond. Thus, the metal oxide 64 can have a two-dimensional network structure with approximately equal numbers of Si-O-Si bonds and Si-Si bonds.

[0061] Figure 6 The metal oxide 64 shown contains approximately equal numbers of silicon and oxygen atoms as metal atoms. Therefore, the ratio of oxygen atoms to metal atoms in metal oxide 64 is stoichiometric to that in silicon oxide, or in other words, to the ratio of oxygen atoms to metal atoms in SiO2 is 50%.

[0062] like Figure 7 As shown, the metal oxide 60 contained in the inorganic matrix 31 can be a metal oxide 65 containing SiO2, in other words, it can also contain silicon oxide as a stoichiometric component. In this case, the metal oxide 65 can include a two-dimensional network structure having only Si-O-Si bonds.

[0063] In this embodiment, Figure 5 The number of bonding sites BD in the shown metal oxide 60 is less than or equal to the number of Si-O-Si bonds in the metal oxide 60. Therefore, the ratio of oxygen atoms to metal atoms in the metal oxide 60 is between the ratio of oxygen atoms to metal atoms in the metal oxide 64 and the ratio of oxygen atoms to metal atoms in the metal oxide 65. In other words, the ratio of oxygen atoms to metal atoms in the metal oxide 60 is more than 50% of the stoichiometric ratio of oxygen atoms to metal atoms in the metal oxide 65.

[0064] <Distance between joints> Figure 5 The average distance L of the close bonding regions BD in the metal oxide 60 shown is longer as the number of Si-O-Si bond bonding regions BD is smaller. The length of the average distance L will be examined below.

[0065] For example, the distance between the oxygen atom and the silicon atom in the Si-O-Si bond in the metal oxide 60 is defined as distance d. In typical SiO2, distance d is approximately 0.16 nm. Furthermore, in the metal oxide 60, the ratio of the bonding portion BD to the total number of Si-O-Si bonds is r. In this case, when the metal oxide of the inorganic matrix 31 possesses SiO...x When x=2(1-r), the condition holds true.

[0066] Here, it is assumed that the silicon and oxygen atoms in the metal oxide 60 are located on a certain plane, and further, it is assumed that on this plane... Figure 5 The diagram shows a square SQ on a metal oxide 60. One side of the square SQ has a length of d, and one of its four vertices is located at the center of a silicon atom, while the other two are located at the centers of oxygen atoms adjacent to that silicon atom. In this case, the area of ​​the square SQ is d. 2 The square SQ contains 1 / 2 oxygen atoms. Therefore, the square SQ contains r / 2 bonding regions BD.

[0067] Therefore, the average area of ​​a junction BD in the metal oxide 60 is d. 2 / (r / 2)=2d 2 Therefore, the square root of this area corresponds to the average distance L, so L = d(2 / r). 1 / 2 As can be seen from this formula, the smaller the ratio r, in other words, the smaller the ratio of the bonding part BD to the Si-O-Si bond, the longer the average distance L.

[0068] <Emitting Layer: Part 1 and Part 2> When returning to the reference Figure 1 and Figure 3 In this embodiment, the inorganic matrix 31 comprises a first portion 41 and a second portion 42 having a metal oxide. In this embodiment, the ratio of oxygen atoms to metal atoms in the second portion 42 is higher than the ratio of oxygen atoms to metal atoms in the first portion 41. For example, with x and y as real numbers, the inorganic matrix 31 comprises silicon oxide as the metal oxide, and the silicon oxide contained in the first portion 41 is made of SiO₂. x The silicon dioxide contained in Part 2, Section 42 is composed of SiO y When expressed as x, then y is higher than x.

[0069] Regarding the ratio of oxygen atoms to metal atoms in the metal oxide of the inorganic matrix 31 of the luminescent layer 23 in this embodiment, Method 1: The ratio of metal atoms to oxygen atoms in the thickness direction of the luminescent layer 23 can be measured using SIMS (Secondary Ion Mass Spectrometry). Alternatively, Method 2: The ratio of metal atoms to oxygen atoms in the thickness direction of the luminescent layer 23 can be measured and confirmed by performing ion sputtering on the luminescent layer 23 and then performing XPS (X-ray photoelectron spectroscopy). Alternatively, Method 3: The ratio of metal atoms to oxygen atoms in the region of interest can be measured and confirmed by performing AES (Auger electron spectroscopy) on a cross-section of the luminescent layer 23. Alternatively, Method 4: The ratio of metal atoms to oxygen atoms in the region of interest of the cross-section of the luminescent layer 23 can be measured and confirmed using EDX (Energy Dispersive X-ray Spectroscopy) of a SEM (Scanning Electron Microscopy) or TEM (Transmission Electron Microscopy). In Method 4, when using TEM, the cross-section of the luminescent layer 23 can also be processed simultaneously using FIB (Focused Ion Beam). In addition, the methods for confirming the above proportions can be prioritized in the order of methods 1 to 4. If the confirmation can be made by the previous methods, the confirmation based on the later methods can be omitted.

[0070] In this embodiment, the first portion 41 is located closer to the anode 21 than the second portion 42. Specifically, the light-emitting layer 23 may also include: a first light-emitting layer 23A containing the first portion 41; and a second light-emitting layer 23B located closer to the cathode 25 than the first light-emitting layer 23A and containing the second portion 42. In this case, a portion of the quantum dots 30 may be located at the boundary between the first light-emitting layer 23A and the second light-emitting layer 23B; in other words, it may be contained within both the first light-emitting layer 23A and the second light-emitting layer 23B.

[0071] <Emitting Layer: Postscript> The quantum dots 30 in the light-emitting layer 23 can be regularly arranged in the light-emitting layer 23, or they can be randomly contained in the light-emitting layer 23. Furthermore, in Figure 1 In the luminescent layer 23 shown, an inorganic matrix 31, described later, is formed between two quantum dots 30, and the quantum dots 30 are not in contact with each other. However, it is not limited to this, and the luminescent layer 23 may also contain two or more quantum dots 30 in contact with each other. In addition, the film thickness of the luminescent layer 23 can be about 1 nm to 100 nm.

[0072] As will be described later, when the light-emitting layer 23 is formed from a quantum dot dispersion containing quantum dots 30, a step of heating the quantum dot dispersion is sometimes included. Therefore, in this embodiment, from the viewpoint of the heat resistance of the light-emitting element 2, all layers of the light-emitting element 2 from the anode 21 to the cathode 25 may also be formed from layers of inorganic material.

[0073] <Injection of charge into the luminescent layer> In this embodiment, the light-emitting layer 23 has a metal oxide on the inorganic matrix 31 filled between the quantum dots 30. Furthermore, the inorganic matrix 31 has a first portion 41 and a second portion 42 with a higher proportion of oxygen atoms relative to metal atoms compared to the first portion 41. Therefore, in the metal oxide contained in the inorganic matrix 31, the proportion of oxygen atoms relative to metal atoms varies depending on their position.

[0074] In the metal oxide contained in the inorganic matrix 31, when the ratio of oxygen atoms to metal atoms is close to the aforementioned ratio in the stoichiometric metal oxide, the bonding between metal atoms and oxygen atoms increases, and the structure formed by the metal oxide becomes denser. Therefore, the second part 42, where the ratio of oxygen atoms to metal atoms is closer to the aforementioned ratio in the stoichiometric metal oxide than the first part 41, further suppresses foreign matter such as moisture from reaching the quantum dot 30, thereby improving the protective effect of the quantum dot 30.

[0075] On the other hand, in the metal oxide contained in the inorganic matrix 31, when the proportion of oxygen atoms relative to metal atoms is low, the portion where metal atoms are bonded to each other increases, as in the aforementioned bonding portion BD. In the bonding portion BD, the metal oxide exhibits stronger metallic or semiconductor properties compared to the portion containing Si-O-Si bonds. Therefore, the inorganic matrix 31 with the bonding portion BD readily transfers charge via this bonding portion BD. In particular, metal oxides containing more bonding portions BD transfer charge more efficiently than metal oxides with fewer bonding portions BD.

[0076] In the metal oxide contained in the inorganic matrix 31, when the proportion of oxygen atoms relative to metal atoms is low, the distance between two adjacent bonding regions BD becomes shorter. The shorter the distance between two adjacent bonding regions BD, the higher the probability of charge tunneling between the bonding regions BD. Therefore, in the metal oxide contained in the inorganic matrix 31, when the proportion of oxygen atoms relative to metal atoms is low, charge movement is easier in the metal oxide.

[0077] Through the above, the light-emitting layer 23 can improve the movement of charge in the first part 41 while protecting the quantum dot 30 in the second part 42. Therefore, the light-emitting element 2 equipped with the light-emitting layer 23 can be designed to improve the injection efficiency of charge from each electrode to the quantum dot 30 while protecting the quantum dot 30, thus achieving both long lifespan and luminous efficiency. The display device 1 equipped with the light-emitting element 2 that balances long lifespan and luminous efficiency achieves either a long lifespan or low power consumption.

[0078] Specifically, the light-emitting layer 23 contains a metal oxide in the inorganic matrix 31 with a lower ratio of oxygen atoms to metal atoms compared to the stoichiometric ratio of metal oxides. Therefore, compared to the case where the light-emitting layer 23 contains only stoichiometric metal oxides as the inorganic matrix 31, the concentration of oxygen atoms in the light-emitting layer 23 is reduced. Thus, the light-emitting layer 23 reduces the degradation caused by oxidation of the quantum dot 30 or layers adjacent to the light-emitting layer 23 due to the reduced oxygen atoms in the inorganic matrix 31. Therefore, the light-emitting element 2 of this embodiment reduces the degradation of each layer between the anode 21 and the cathode 25, thereby extending its lifespan.

[0079] Furthermore, in the light-emitting layer 23 of this embodiment, the first portion 41 is located closer to the anode 21 than the second portion 42. Therefore, the light-emitting element 2 equipped with the light-emitting layer 23 can improve the injection efficiency of holes injected into the quantum dot 30 from the anode 21 side via the first portion 41, and can also protect the quantum dot 30 located on the cathode 25 side of the light-emitting layer 23 in the second portion 42.

[0080] Typically, due to the difference in mobility between holes and electrons, in the emitting layer of a quantum dot-based light-emitting element, there tends to be an excess of electrons relative to the injected hole concentration. This excess of electrons in the emitting layer can not only reduce the exciton generation efficiency but can also sometimes increase the generation of Auger electrons, which do not contribute to luminescence and can cause degradation of the emitting layer and surrounding layers.

[0081] The light-emitting element 2 of this embodiment increases the injection efficiency of holes into the light-emitting layer 23 and reduces excessive electrons by having a first portion 41 on the anode 21 side of the light-emitting layer 23. Furthermore, the light-emitting element 2 protects the quantum dots 30 on the cathode 25 side of the light-emitting layer 23 by having a second portion 42 on the cathode 25 side of the light-emitting layer 23. In particular, the second portion 42 effectively reduces the degradation of the quantum dots 30 located on the cathode 25 side of the light-emitting layer 23 caused by Auger electrons induced by electrons injected from the cathode 25. Therefore, the light-emitting element 2 of this embodiment effectively balances the improvement of the luminous efficiency of the light-emitting layer 23 and the protection of the quantum dots 30.

[0082] Furthermore, in this embodiment, the light-emitting layer 23 includes a first portion 41 on the anode 21 side, where the ratio of oxygen atoms to metal atoms is lower than that in the second portion 42. Therefore, the light-emitting layer 23 further reduces the degradation of the quantum dots 30 and hole transport layer 22 located on the anode 21 side of the light-emitting layer 23 caused by oxygen atoms in the inorganic matrix 31. Thus, the light-emitting element 2 of this embodiment further suppresses the decrease in hole injection efficiency from the anode 21 to the quantum dots 30 of the light-emitting layer 23, and further reduces excessive electrons in the light-emitting layer 23.

[0083] <Supplementary Notes on the Ratio of Oxygen Atoms to Metal Atoms in Inorganic Matrix> As described above, the ratio of oxygen atoms to metal atoms in the metal oxide of the inorganic matrix 31 can be 50% or more, which is the stoichiometric ratio of oxygen atoms to metal atoms in the metal oxide. With this configuration, the light-emitting element 2 can improve the protective effect of the inorganic matrix 31 on the quantum dot 30.

[0084] In particular, when the inorganic matrix 31 contains SiO x When it is a metal oxide, x can be 1 or more and 2 or less. In this case, as described above, since a two-dimensional mesh-like structure is formed in the metal oxide contained in the inorganic matrix 31, the protective effect of the quantum dot 30 can be further improved.

[0085] Here, as described above, considering that points of charge movement via the aforementioned junctions BD are easily generated in the metal oxide of the inorganic matrix 31, the shorter the average distance L between the junctions BD, the better the efficiency of charge movement in the inorganic matrix 31. In particular, if the average distance L is less than 1 nm, then the charge can tunnel between the junctions BD more efficiently.

[0086] Therefore, if we find that d = 0.16nm and L = d(2 / r)... 1 / 2 And for L≤1nm, r≥0.051. The metal oxide of inorganic matrix 31 possesses SiO... x In the case described above, x = 2(1-r) holds true. Therefore, from the viewpoint of improving charge movement in the inorganic matrix 31 by effectively generating charge tunneling between the junctions BD, the above-mentioned x can be 1.9 or less.

[0087] <Manufacturing Method of Display Device> The display device 1 of this embodiment can also be manufactured by forming multiple light-emitting elements 2 on a substrate 3 on which a driving circuit DR, pixel circuit PC, etc., are formed separately. In the manufacturing method of the light-emitting element 2 of this embodiment, the formation method of each layer other than the light-emitting layer 23 can be any method, and can be formed by general materials and general film-forming processes. For example, a solution in which the materials of each layer are dispersed can be coated by spin coating or slot coating, and the solution can be dried to form the above-mentioned layers into films. For example, by preparing a solution in which the materials of each layer are mixed with a solvent for viscosity control, and printing the solution by inkjet printing or screen printing, the above-mentioned layers can be formed into films. Since the printing method can uniformly form films of each layer over a large area, it is suitable for manufacturing light-emitting panels and display panels.

[0088] The manufacturing method of the light-emitting element 2 in this embodiment includes the method for forming the light-emitting layer 23, which will be described later. (Refer to...) Figures 8 to 10 The method for forming the light-emitting layer 23 in this embodiment will be described. Figure 8 This is a flowchart illustrating the method for forming the light-emitting layer 23 in this embodiment. Figure 9 This is a schematic diagram showing the first dispersion liquid, described later, used in the method for forming the light-emitting layer 23 in this embodiment. Figure 10 This is a cross-sectional view showing a part of the method for forming the light-emitting layer 23 in this embodiment.

[0089] In the method for forming the light-emitting layer 23 in this embodiment, firstly, a first dispersion and a second dispersion are prepared (step S1). For example, the first dispersion and the second dispersion may also be dispersions of quantum dots 30 and metal oxides of inorganic matrix 31 dispersed by microparticles.

[0090] Reference Figure 9 An example illustrating the first dispersion. In Figure 9 The diagram shows a first dispersion L1 injected into container C. The first dispersion L1 is, for example, a dispersion in which quantum dots 30 and nanoparticles 50, as first microparticles, are dispersed in a solvent 51 containing, for example, toluene. Nanoparticles 50 are nanoparticles containing metal atoms and oxygen atoms, and may be, for example, silicon oxide nanoparticles. The ratio of oxygen atoms to metal atoms in nanoparticles 50 may be approximately the same as the ratio of oxygen atoms to metal atoms in the first part 41 described above. The particle size of nanoparticles 50 may be, for example, 1 nm to 10 nm.

[0091] The second dispersion may have the same structure as the first dispersion, except that it contains nanoparticles that are second microparticles instead of nanoparticles 50, which are first microparticles, with a higher ratio of oxygen atoms to metal atoms than nanoparticles 50.

[0092] The first and second dispersions can be prepared by adding separately synthesized quantum dots 30 and metal oxide nanoparticles to a solvent 51 such as toluene. For example, the metal oxide nanoparticles can be synthesized by mixing an alkaline aqueous solution with a metal salt to obtain a precipitate, followed by centrifugation, drying, and calcination of the precipitate. The ratio of oxygen atoms to metal atoms in the synthesized nanoparticles can be adjusted according to the ratio of the mixed alkaline aqueous solution to the metal salt.

[0093] Return to reference Figure 8 After the preparation of the first dispersion and the second dispersion, a laminate comprising the substrate 3 and the layers formed on the substrate 3 before the formation of the light-emitting layer 23 is used as a substrate, and the first dispersion L1 is coated on this substrate (step S2). (Refer to...) Figure 10 The steps following step S2 will be explained in more detail.

[0094] For example, such as Figure 10 As shown in step S2-1, at the start of execution of step S2, an anode 21 and a hole transport layer 22 are sequentially formed on the substrate 3. In this case, in step S2, as... Figure 10 As shown in step S2-2, a first dispersion L1 is coated on the upper surface of the hole transport layer 22.

[0095] Next, the first dispersion L1 is dried by heating, for example, at 80°C for 10 minutes on each portion of the substrate 3 containing the coated first dispersion L1 (step S3). As a result, the solvent 51 of the coated first dispersion L1 evaporates, and both the quantum dots 30 and nanoparticles 50 aggregate on the side of the substrate 3, with the nanoparticles 50 surrounding the quantum dots 30 forming the first portion 41. Through the above, as... Figure 10 As shown in step S3, a first light-emitting layer 23A is formed, comprising quantum dots 30 and a first portion 41 filled between the quantum dots 30.

[0096] Next, a laminate comprising the substrate 3 to the first light-emitting layer 23A is used as a substrate, and a second dispersion is coated onto this substrate (step S4). Then, the second dispersion is dried by heating each portion of the substrate 3 containing the coated second dispersion (step S5). As described above, the second dispersion contains nanoparticles with a higher proportion of oxygen atoms relative to metal atoms compared to the nanoparticles 50 contained in the first dispersion L1. Therefore, in step S5, the second portion 42 is formed by the nanoparticles contained in the second dispersion. Through the above, as... Figure 10 As shown in step S5, a second light-emitting layer 23B is formed, comprising quantum dots 30 and a second portion 42 filled between the quantum dots 30, and the formation of the light-emitting layer 23 is completed.

[0097] By using the above method, a light-emitting element 2 having the light-emitting layer 23 of this embodiment can be manufactured. In particular, according to the above method, by adjusting the ratio of oxygen atoms to metal atoms in the microparticles added to the first dispersion L1 and the second dispersion respectively, the ratio of oxygen atoms to metal atoms in each part of the inorganic matrix 31 can be appropriately designed.

[0098] [Second Implementation] <Evaporation of Inorganic Substrates> The display device 1 of this embodiment has the same configuration as the display device 1 of the previous embodiment, except that the manufacturing method of the light-emitting element 2 is different. The manufacturing method of the light-emitting element 2 of this embodiment differs from that of the light-emitting element 2 of the previous embodiment only in the method of forming the light-emitting layer 23. (Refer to...) Figure 11 and Figure 12 The method for forming the light-emitting layer 23 in this embodiment will be described in detail. Figure 11 This is a flowchart illustrating the method for forming the light-emitting layer 23 in this embodiment. Figure 12 This is a cross-sectional view showing a part of the method for forming the light-emitting layer 23 in this embodiment.

[0099] In the method for forming the light-emitting layer 23 of this embodiment, firstly, a first quantum dot layer comprising quantum dots 30 is formed on the upper surface of the hole transport layer 22 (step S6). Step S6 can be performed, for example, as follows: after coating a dispersion in which a plurality of quantum dots 30 are dispersed in a solvent such as toluene onto the upper surface of the hole transport layer 22, the solvent is evaporated by heating the coated dispersion, etc. Thus, as... Figure 12 As shown in step S6, a first quantum dot layer 32 containing quantum dots 30 is formed on the upper surface of the hole transport layer 22.

[0100] Next, using a vapor deposition apparatus that includes, for example, the first metal oxide containing nanoparticles 50 described in the previous embodiment as the first vapor deposition source, microparticles of the metal oxide are vapor deposited onto the first quantum dot layer 32 (step S7). Thus, as... Figure 12 As shown in step S7, the first metal oxide in the first vapor deposition source, such as nanoparticles 50, permeates into the spaces between the quantum dots 30 of the first quantum dot layer 32 and forms a film on the upper surface of the hole transport layer 22. Therefore, in step S7, the first metal oxide is formed at a position covering the first quantum dot layer 32, and this first metal oxide is the first portion 41. Thus, a first light-emitting layer 23A comprising quantum dots 30 and the first portion 41 filling the spaces between the quantum dots 30 is formed through step S7.

[0101] Furthermore, in step S6, the first quantum dot layer 32 is formed, for example, by coating a dispersion of quantum dots 30 as described above. Therefore, the quantum dots 30 coated in step S6 may sometimes approach or contact the upper surface of the hole transport layer 22 due to their own weight. Therefore, compared to the first light-emitting layer 23A of the previous embodiment, each quantum dot 30 may also be biased towards the hole transport layer 22 side in this embodiment's first light-emitting layer 23A.

[0102] Next, a second quantum dot layer containing quantum dots 30 is formed on the upper surface of the first light-emitting layer 23A (step S8). Step S8 can be performed using the same method as step S6, except that the layer onto which the dispersion is coated is the first light-emitting layer 23A. Thus, a second quantum dot layer containing quantum dots 30 is formed on the upper surface of the first light-emitting layer 23A.

[0103] Next, microparticles of metal oxide are deposited onto the formed second quantum dot layer (step S9). Step S9, compared to step S7, can also be performed using the same method, except that a second metal oxide containing a higher ratio of oxygen atoms to metal atoms is used for deposition compared to the first metal oxide in the first deposition source. Thus, as... Figure 12 As shown in step S9, a second light-emitting layer 23B is formed, comprising quantum dots 30 and a second portion 42 filled between the quantum dots 30, thus completing the formation of the light-emitting layer 23. Furthermore, for the same reasons as described above, in this embodiment, compared to the second light-emitting layer 23B of the previous embodiment, each quantum dot 30 may be biased towards one side of the first light-emitting layer 23A.

[0104] By using the above method, a light-emitting element 2 having the light-emitting layer 23 of this embodiment can be manufactured. In particular, according to the above method, vapor deposition is used in the formation of the first portion 41 and the second portion 42, thus shortening the process of heating each portion on the substrate 3 including the quantum dots 30, or enabling the heating process to be performed at a low temperature. Therefore, according to the above method, the degradation of the quantum dots 30 or the hole transport layer 22 of the light-emitting layer 23 can be further reduced.

[0105] Furthermore, in this embodiment, the method for vapor deposition of a metal oxide microparticle in steps S7 and S9 has been described, but it is not limited thereto. For example, in steps S7 and S9, vapor deposition can be performed using a first vapor deposition source and a second vapor deposition source that contain a mixture of a first metal oxide and a second metal oxide. In this case, the second vapor deposition source used in step S9 can have a higher ratio of the second metal oxide to the first metal oxide compared to the first vapor deposition source used in step S7. According to the above method, by adjusting the ratio of the first metal oxide to the second metal oxide in each of the first and second vapor deposition sources, the ratio of oxygen atoms to metal atoms in the first portion 41 and the second portion 42 formed in each step can be easily adjusted.

[0106] In this embodiment, firstly, the first quantum dot layer 32 is formed in step S6, and then, in step S7, the first light-emitting layer 23A is formed by evaporating metal oxide microparticles. Therefore, each quantum dot 30 in both the first light-emitting layer 23A and the second light-emitting layer 23B can be biased towards the hole transport layer 22. With this configuration, since each quantum dot 30 of the light-emitting layer 23 is closer to the hole transport layer 22, the light-emitting element 2 improves the injection efficiency of holes from the hole transport layer 22 to each quantum dot 30, further reducing the electron transmittance in the light-emitting layer 23.

[0107] However, this embodiment is not limited to the above method. For example, before step S6, the process of forming a thin film containing metal oxide microparticles can be performed using the same method as in step S7. In this case, the direct contact between the quantum dots 30 contained in the first light-emitting layer 23A and the hole transport layer 22 can be reduced. This ensures sufficient distance between the quantum dots 30 and the hole transport material of the hole transport layer 22. With the above configuration, the energy of the excitons generated in the quantum dots 30 can be reduced from moving towards the hole transport material of the hole transport layer 22 that is in contact with or near the quantum dots 30, thus deactivating the quantum dots 30.

[0108] [Third Implementation Method] <Second part located inside the first part: Structure> Figure 13 This is a schematic side cross-sectional view of the display device 4 according to this embodiment. Compared with the display device 1 of the previous embodiment, the display device 4 of this embodiment has a light-emitting element 5 instead of a light-emitting element 2. Compared with the light-emitting element 2, the light-emitting element 5 has a light-emitting layer 26 instead of a light-emitting layer 23.

[0109] Reference Figure 14 More details about the light-emitting layer 26. Figure 14 Enlarged display Figure 13The luminescent layer 26 in the cross-section shown is particularly magnified. Figure 13 A schematic diagram of region E2 is shown.

[0110] The light-emitting layer 26 includes a plurality of quantum dots 30 and an inorganic matrix 31. The inorganic matrix 31 has a first portion 41 and a second portion 42. Compared with the light-emitting layer 23, the only difference between the light-emitting layer 26 and the light-emitting layer 26 is the positional relationship between the first portion 41 and the second portion 42. In addition, for reasons described later, the position of each quantum dot 30 in the light-emitting layer 26 can also be biased towards the hole transport layer 22 compared with the light-emitting layer 23.

[0111] like Figure 14 As shown, in the light-emitting layer 26, the second portion 42 is located closer to the quantum dot 30 than the first portion 41. Specifically, in the light-emitting layer 26, the second portion 42 is located around each quantum dot 30. More specifically, the second portion 42 may contain each quantum dot 30. Furthermore, the first portion 41 is located around each of the second portions 42. More specifically, the first portion 41 may contain each of the second portions 42. Therefore, the light-emitting layer 26 can be viewed as having a plurality of quantum dot structures and a first portion 41 filling the spaces between the plurality of quantum dot structures, each quantum dot structure having a quantum dot 30 and a second portion 42 surrounding the quantum dot 30.

[0112] In addition to the above, the display device 4 of this embodiment may also have the same configuration as the display device 1 of the previous embodiment.

[0113] In the light-emitting layer 26 of this embodiment, the second portion 42 is located closer to each quantum dot 30 than the first portion 41. In particular, in the light-emitting layer 26, the second portion 42 is located around each quantum dot 30, and the first portion 41, which has a lower proportion of oxygen atoms to metal atoms compared to the second portion 42, is located around the second portion 42.

[0114] Therefore, the light-emitting layer 26 can protect each quantum dot 30 by means of the second portion 42, which is closer to each quantum dot 30 than the first portion 41. Furthermore, the light-emitting layer 26 more efficiently transmits charge carriers from each charge transport layer through the first portion 41. Additionally, although the second portion 42 is located between each quantum dot 30 and the first portion 41 in the light-emitting layer 26, charge carriers transmitted from the first portion 41 to each quantum dot 30 are injected into each quantum dot 30 through tunneling through the second portion 42. Therefore, the light-emitting element 5 equipped with the light-emitting layer 26 of this embodiment can more efficiently balance the protection of the quantum dots 30 and the efficiency of charge injection from each electrode into the quantum dots 30. Moreover, as described above, when each quantum dot 30 in the light-emitting layer 26 is biased towards the hole transport layer 22, for the same reasons as above, the light-emitting element 2 further reduces the excess electrons in the light-emitting layer 26.

[0115] <Second part located inside the first part: Manufacturing method: Preparation of dispersion tablets> The manufacturing method of the light-emitting element 5 in this embodiment differs from the manufacturing method of the light-emitting element 2 described above only in that the method for forming the light-emitting layer 23 is replaced with the method for forming the light-emitting layer 26 described later. (Refer to...) Figures 15 to 20 The method for forming the light-emitting layer 26 in this embodiment will be described in detail. Figure 15 This is a flowchart illustrating the method for forming the light-emitting layer 26 in this embodiment. Figure 16 This is a process side view showing the mixing process described later in the method for forming the light-emitting layer 26 of this embodiment. Figure 17 This is a schematic diagram illustrating the reaction process of the precursor described later in this embodiment. Figure 18 and Figure 19 This is a schematic diagram showing the third and fourth dispersions, which will be described later, used in the method for forming the light-emitting layer 26 of this embodiment. Figure 20 This is a cross-sectional view showing a part of the method for forming the light-emitting layer 26 in this embodiment.

[0116] In the method for forming the light-emitting layer 26 of this embodiment, firstly, a third dispersion and a fourth dispersion are prepared (step S10). Specifically, in this embodiment, the third dispersion is prepared, for example, as described later, by a method including a mixing step, wherein the mixing step mixes a dispersion containing quantum dots 30 and a dispersion containing a metal oxide precursor. (Refer to...) Figure 16 The mixing process is described below.

[0117] In the method for preparing the third dispersion in this embodiment, before the mixing step, a preparation is performed... Figure 16 The dispersions LA and LB are shown in step S10-1. In the preparation method of the third dispersion in this embodiment, for example, commercially available blue quantum dots, which are quantum dots 30, are used as the halogen source to prepare zinc chloride (ZnCl2) powder. The core of the blue quantum dots is ZnSeTe, and the shell is ZnS. It can also be coordinated with an organic ligand different from the precursor of the inorganic matrix 31 described later. In addition, as the precursor of the inorganic matrix 31, tetramethyl orthosilicate (TMOS) as shown in formula (1) and 3-(mercaptopropyl)trimethoxysilane (MPS) as shown in formula (2) are prepared. In addition, octane (C8H) is prepared as the solvent. 18 N,N-dimethylformamide (DMF) and other precursors. However, this embodiment is not limited to these, and the precursor of the inorganic matrix 31 may also be tetraethyl silicate (TEOS).

[0118] [Chemical Formula 1] [Chemical Formula 2] In this embodiment, ZnCl2, MPS, and TMOS can also be dispersed in DMF to prepare a 10 ml dispersion LA. The dispersion LA can be a 10 ml mixture of ZnCl2 with a concentration of 0.6 mol / L, MPS with a concentration of 0.2 mol / L, and TMOS with a concentration of 0.02 mol / L.

[0119] In this embodiment, the quantum dots 30 coordinated with the organic ligands can also be dispersed in octane at a concentration of 1 mg / ml to prepare a 10 ml dispersion LB. Since octane and DMF have different polarities, when dispersions LA and LB are left to stand in a container, the liquid in the container separates into a layer of dispersion LA and a layer of dispersion LB.

[0120] In the mixing process, dispersions LA and LB are thoroughly stirred and mixed. This stirring can be performed for 1 to 48 hours, preferably for about 10 to 20 hours. During the stirring process, a portion of the ligands located at quantum dots 30 are replaced by MPS with organic ligands. Therefore, quantum dots 30 are more easily dispersed in DMF than quantum dots, such as... Figure 16 As shown in step S10-2, quantum dots 30 migrate from dispersion LB to dispersion LA. Specifically, MPS is coordinated to quantum dots 30 with thiol groups as coordinating functional groups. As described later, an inorganic matrix is ​​formed by the reaction of MPS coordinated to quantum dots 30 with TMOS, thus the MPS is more firmly coordinated to quantum dots 30 compared to the case where organic ligands are coordinated to quantum dots 30. Therefore, the luminescent layer 26 formed by the method of this embodiment can more strongly protect the quantum dots 30. Furthermore, the organic ligands may not be completely replaced by MPS, or the organic ligands may remain in a portion of the ligands coordinated to the quantum dots 30 (e.g., less than 5% by weight). Residual organic ligands prevent the aggregation of quantum dots 30 in the dispersion or suppress the formation of cracks in the luminescent layer 26.

[0121] Furthermore, in the dispersion LA, MPS and TMOS react along the reaction process described later, forming silicon oxide around the quantum dot 30. (See reference...) Figure 17 The reaction process of the precursor containing the inorganic matrix 31 containing MPS and TMOS in the mixing process of step S10 is described in detail.

[0122] For example, Figure 17 As shown in schematic diagram 1701, the two TMOS61 react with water (H2O), thereby forming, as shown in schematic diagram 1702, the methoxy groups of each TMOS61 react with the hydroxyl groups (OH groups). -The derivative 62 is substituted. This reaction is carried out using halogens such as chlorine as catalysts, producing methanol as a byproduct. Furthermore, as... Figure 17 As shown in schematic diagram 1702, the two derivatives 62 react with each other through dehydration condensation, as shown in schematic diagram 1703, to form a condensate 63 with Si-O-Si bonds.

[0123] By performing the above reactions, as described above Figure 7 As shown, a metal oxide 65 with a two-dimensional network structure of SiO2 is formed by multiple TMOS61. The above-mentioned reaction is also generated by the reaction between the methoxy groups of the multiple MPS and the methoxy groups of the TMOS and MPS respectively.

[0124] Therefore, in the mixing process of this embodiment, in the MPS located at quantum dot 30, the trimethoxysilyl group located on the side opposite to the quantum dot 30 reacts with other MPS or TMOS. The silicon oxide formed in this reaction is less prone to oxygen vacancies. Therefore, the composition of this silicon oxide is set to SiO2. x In this case, the value of x becomes approximately close to 2. Therefore, in the mixing process of this embodiment, a second portion 42 is formed around the quantum dot 30, which contains a metal oxide with a relatively high ratio of oxygen atoms to metal atoms.

[0125] Based on the above, such as Figure 16 As shown in step S10-2, a quantum dot structure 52 is formed by mixing dispersion LA and dispersion LB. This quantum dot structure 52 comprises quantum dots 30 and a second portion 42 of a metal oxide containing the quantum dots 30. Specifically, in the mixing process of this embodiment, the precursor metal oxide is converted into a precursor in a dispersion containing multiple quantum dots 30 and a metal oxide. Furthermore, in step S10-2, the quantum dot structure 52 can also be transferred to the interface between dispersion LA and dispersion LB.

[0126] Next, the quantum dot structure 52 is extracted from the dispersion LA by centrifugation at 4000 rpm for 5 minutes. During centrifugation of the dispersion LA, unsuitable solvents such as ethyl acetate or acetone can be added to the dispersion LA to precipitate the quantum dot structure 52. The precipitated quantum dot structure 52 is then extracted and dispersed in a solvent containing toluene to prepare a third dispersion.

[0127] Reference Figure 18 The third dispersion prepared through the above mixing process will be explained. Figure 18The diagram shows a third dispersion L3 injected into container C. The third dispersion L3 is, for example, a dispersion in which multiple quantum dot structures 52 are dispersed in solvent 51. As described above, the quantum dot structure 52 has a quantum dot 30 and a second portion 42 enclosing the quantum dot 30. Furthermore, the quantum dot structure 52 may also have a thiol group from MPS and a carbon chain bonded to the thiol group between the quantum dot 30 and the second portion 42. The second portion 42 is formed by the reaction of MPS located on the quantum dot 30 with TMOS, resulting in a more robust MPS configuration on the quantum dot 30 compared to the case where organic ligands are located on the quantum dot 30. Therefore, the light-emitting layer 26 formed by the method of this embodiment can more strongly protect the quantum dot 30. Furthermore, the organic ligand may not be completely replaced by MPS, or a portion of the ligands located on the quantum dot 30 may remain (e.g., less than 5% by weight). A suitable amount of residual organic ligands prevents the aggregation of quantum dots 30 in the dispersion or inhibits the generation of cracks in the luminescent layer 26.

[0128] Next, refer to Figure 19 The fourth dispersion will be described. For example... Figure 19 As shown, the fourth dispersion L4 is, for example, a dispersion in which multiple nanoparticles 50, which are metal oxide microparticles as the third microparticles, are dispersed in solvent 51. In other words, compared with the first dispersion L1, the fourth dispersion L4 can have the same structure except that it does not contain quantum dots 30. In particular, the ratio of oxygen atoms to metal atoms in the nanoparticles 50 is lower than the ratio of oxygen atoms to metal atoms in the second part 42 formed by the reaction of the metal oxide precursor.

[0129] <Second part located inside the first part: Manufacturing method: Formation of the light-emitting layer> When returning to the reference Figure 15 At that time, after the preparation of the third dispersion and the fourth dispersion, a laminate comprising the substrate 3 and the layers formed on the substrate 3 before the formation of the light-emitting layer 26 is used as a substrate, and the third dispersion L3 is coated on the substrate (step S11). (Refer to...) Figure 20 The steps following step S11 will be explained in more detail.

[0130] For example, step S11 is performed in the same way as step S2 described above, except that the third dispersion L3 is applied instead of the first dispersion L1. Therefore, as Figure 20 As shown in step S11, a third dispersion L3 is coated on the upper surface of the hole transport layer 22.

[0131] Next, the third dispersion L3 is dried by heating various portions of the substrate 3, including the coated third dispersion L3 (step S12). Step S12, compared to step S3, can be performed in the same way except that the third dispersion L3 is dried instead of the first dispersion L1. Therefore, as... Figure 20 As shown in step S12, the solvent 51 of the coated third dispersion L3 evaporates, and the quantum dot structures 52 aggregate on the substrate 3 side. Thus, a layer containing the quantum dot structures 52, namely the quantum dot structure layer 52A, is formed on the hole transport layer 22. In step S12, the quantum dot structures 52 aggregate on the hole transport layer 22 side by their own weight. Therefore, in the light-emitting layer 26 formed by the method described later, each quantum dot 30 is closer to the hole transport layer 22.

[0132] Next, the laminate containing substrate 3 and the layers formed on substrate 3 before step S12 is used as a substrate, and a fourth dispersion liquid L4 is coated on this substrate (step S13). In other words, in step S13, the fourth dispersion liquid L4 is coated from above the quantum dot structure layer 52A. Thus, as Figure 20 As shown in step S13, the fourth dispersion L4 penetrates into the space between multiple quantum dot structures 52 of the quantum dot structure layer 52A, thereby allowing the nanoparticles 50 to enter the space between the multiple quantum dot structures 52.

[0133] Next, the fourth dispersion L4 is dried by heating various portions of the substrate 3, including the coated fourth dispersion L4 (step S14). Compared to step S3, step S14 can be performed in the same way except that the fourth dispersion L4 is dried instead of the first dispersion L1. As a result, the solvent 51 of the coated fourth dispersion L4 evaporates, and the nanoparticles 50 surrounding the quantum dot structure 52 become the first part 41. Through the above, as... Figure 20 As shown in step S14, a light-emitting layer 26 is formed, comprising a quantum dot structure 52 and a first portion 41 filled between the quantum dot structure 52.

[0134] By using the above method, a light-emitting element 2 having the light-emitting layer 26 of this embodiment can be manufactured. In particular, by forming the second portion 42 through the reaction of the precursor according to the above method, a dense metal oxide containing few oxygen vacancies can be formed in the second portion 42. Therefore, by using the above method, the protective effect of the second portion 42 on the quantum dot 30 can be further improved. Furthermore, by using the above method, a light-emitting layer 26 biased towards the hole transport layer 22 side of the quantum dot 30 can be formed.

[0135] [Fourth Implementation Method] <Second section located inside the first section: combined vapor deposition> The display device 4 of this embodiment has the same configuration as the display device 4 of the previous embodiment, except that the manufacturing method of the light-emitting element 5 is different. The manufacturing method of the light-emitting element 5 of this embodiment differs from that of the light-emitting element 5 of the previous embodiment only in the method of forming the light-emitting layer 26. (Refer to...) Figure 21 The method for forming the light-emitting layer 26 in this embodiment will be described in detail. Figure 21 This is a flowchart illustrating the method for forming the light-emitting layer 26 in this embodiment.

[0136] The method for forming the light-emitting layer 26 in this embodiment can be performed by modifying some of the steps in the method for forming the light-emitting layer 26 in the previous embodiment. For example, in the method for forming the light-emitting layer 26 in this embodiment, the preparation of the third dispersion is first performed (step S15). Step S15 can also be performed by the same method as the preparation of the third dispersion L3 in the previous embodiment. Therefore, the third dispersion L3 according to this embodiment can be the same as the third dispersion L3 in the previous embodiment. In other words, except that the preparation of the fourth dispersion L4 is not performed compared to step S10 in the previous embodiment, step S15 can also be performed by the same method.

[0137] Next, steps S11 and S12 in the previous embodiment are executed sequentially. As a result, a quantum dot structure layer 52A is formed on the hole transport layer 22, as described in the previous embodiment.

[0138] Next, microparticles of metal oxide are deposited onto the quantum dot structure layer 52A (step S16). In step S16, compared to the second part 42, deposition is performed using a third deposition source of metal oxide having a low ratio of oxygen atoms to metal atoms. In particular, step S16 is performed in the same manner as step S7 described above, except that the quantum dot structure layer 52A is used instead of the first quantum dot layer 32 as the deposition target. Therefore, in step S16, deposition of metal oxide around the quantum dot structure 52 is performed. As a result, a light-emitting layer 26 is formed, comprising the quantum dot structure 52 and the first part 41 filled between the quantum dot structure 52.

[0139] By using the above method, a light-emitting element 2 having the light-emitting layer 26 of this embodiment can be manufactured. In particular, according to the above method, after forming the quantum dot structure layer 52A, the light-emitting layer 26 can be formed without performing heating processes or the like that could cause degradation of the quantum dots 30, etc., in the quantum dot structure layer 52A. Therefore, according to the above method, the degradation of the quantum dots 30 in the light-emitting layer 26 is further reduced.

[0140] [Fifth Implementation Method] <Third luminescent layer> Figure 22 This is a schematic side cross-sectional view of the display device 6 according to this embodiment. Compared with the aforementioned display device 1, the display device 6 of this embodiment has a light-emitting element 7 instead of a light-emitting element 2. Compared with the light-emitting element 2, the light-emitting element 7 has a light-emitting layer 27 instead of a light-emitting layer 23.

[0141] The light-emitting layer 27 includes a plurality of quantum dots 30 and an inorganic matrix 31. In addition, the light-emitting layer 27 includes a first light-emitting layer 27A stacked on top of each other, a second light-emitting layer 27B located on the cathode 25 side of the first light-emitting layer 27A, and a third light-emitting layer 27C located between the first light-emitting layer 27A and the second light-emitting layer 27B.

[0142] The first light-emitting layer 27A and the second light-emitting layer 27B have the same structure as the aforementioned first light-emitting layer 23A and second light-emitting layer 23B, respectively. Furthermore, compared to the first light-emitting layer 23A, the third light-emitting layer 27C has the same structure except that it has a third portion 43 replacing the first portion 41. The third portion 43 is part of the inorganic matrix 31, in other words, it contains a metal oxide. The ratio of oxygen atoms to metal atoms in the third portion 43 is higher than that in the first portion 41, but lower than that in the second portion 42.

[0143] Apart from the above, the display device 6 of this embodiment has the same configuration as the aforementioned display device 1.

[0144] The light-emitting layer 27 of this embodiment has a third portion 43, which is part of the inorganic matrix 31. The ratio of oxygen atoms to metal atoms in the third portion 43 is between the ratio in the first portion 41 and the ratio in the second portion 42. Therefore, the light-emitting element 7 equipped with the light-emitting layer 27 can more effectively achieve a configuration that balances long lifespan and luminous efficiency.

[0145] In particular, in this embodiment, the inorganic matrix 31 contained in the light-emitting layer 27 has a first portion 41, a third portion 43, and a second portion 42 sequentially from the anode 21 side to the cathode 25 side. Therefore, in this embodiment, the proportion of oxygen atoms to metal atoms in the inorganic matrix 31 gradually increases from the anode 21 side to the cathode 25 side. As a result, the light-emitting element 7 equipped with the light-emitting layer 27 more effectively balances long lifespan and luminous efficiency.

[0146] The manufacturing method of the display device 6 in this embodiment differs from the manufacturing method of the display device 1 described above only in the manufacturing method of the light-emitting element 7. The manufacturing method of the light-emitting element 7 in this embodiment differs from the manufacturing method of the light-emitting element 2 described above only in that a method for forming the light-emitting layer 27 is used instead of a method for forming the light-emitting layer 23. Specifically, the method for forming the light-emitting layer 27 is performed by changing a portion of the steps in the method for forming the light-emitting layer 23.

[0147] Specifically, in the method for forming the light-emitting layer 27, in step S1, a fifth dispersion containing a quantum dot structure is prepared. The quantum dot structure has quantum dots and a metal oxide containing the quantum dots. The fifth dispersion has the same composition as the first dispersion, except that the ratio of oxygen atoms to metal atoms in the metal oxide of the dispersed quantum dot structure is between the ratios described above in the first dispersion and the ratios described above in the second dispersion.

[0148] Furthermore, the method for forming the light-emitting layer 27 includes a step between step S3 and step S4 to form the third light-emitting layer 27C by coating with the fifth dispersion and drying in the fifth dispersion. The step of forming the third light-emitting layer 27C, in addition to forming the third portion from metal oxide microparticles in the fifth dispersion, can also be performed using the same method as steps S2 and S3, or steps S4 and S5.

[0149] This disclosure is not limited to the embodiments described above, and various modifications can be made within the scope of the claims. Embodiments obtained by appropriately combining the technical solutions disclosed in different embodiments are also included in the technical scope of this disclosure. Moreover, new technical features can be formed by combining the technical means disclosed in each embodiment.

[0150] Explanation of reference numerals in the attached figures 1: Display device; 2: Light-emitting element; 3: Substrate; 21: Anode; 23: Emissive layer; 25: Cathode; 30: Quantum dots; 31: Inorganic matrix; 41: Part One; 42: Part Two.

Claims

1. A light-emitting element, characterized in that, It possesses: anode; The cathode is opposite to the anode; as well as A light-emitting layer is located between the anode and the cathode. The light-emitting layer includes: Multiple quantum dots; as well as An inorganic matrix, which fills the spaces between the plurality of quantum dots and contains metal oxides. The inorganic matrix comprises: The first part, having the aforementioned metal oxide; and The second part has the metal oxide, wherein the ratio of oxygen atoms to metal atoms is higher than that of oxygen atoms to metal atoms in the first part, and is lower than the ratio of oxygen atoms to metal atoms in the metal oxide as a stoichiometric proportion.

2. The light-emitting element according to claim 1, characterized in that, The ratio of oxygen atoms to metal atoms in each of the first and second portions is more than 50% in terms of the ratio of oxygen atoms to metal atoms in the metal oxide, as stoichiometrically.

3. The light-emitting element according to claim 1 or 2, characterized in that, The first portion is located closer to the anode side than the second portion.

4. The light-emitting element according to claim 1 or 2, characterized in that, The second part is located closer to the quantum dot than the first part.

5. The light-emitting element according to claim 4, characterized in that, The second portion is located around the quantum dot, and the first portion is located around the second portion.

6. The light-emitting element according to any one of claims 1 to 5, characterized in that, The metal oxide comprises silicon oxide.

7. The light-emitting element according to claim 6, characterized in that, The metal oxide contains SiO x The x is greater than or equal to 1 and less than or equal to 2.

8. The light-emitting element according to claim 7, characterized in that, The x is less than 1.

9.

9. The light-emitting element according to any one of claims 1 to 8, characterized in that, The inorganic matrix comprises a third portion having the metal oxide, wherein the ratio of oxygen atoms to metal atoms is higher than that of oxygen atoms to metal atoms in the first portion and lower than that of oxygen atoms to metal atoms in the second portion.

10. The light-emitting element according to claim 9, characterized in that, The third part is located between the first part and the second part.

11. A display device, characterized in that, It includes a plurality of light-emitting elements, wherein the light-emitting elements are the light-emitting elements described in any one of claims 1 to 10.

12. A method for manufacturing a light-emitting element, the light-emitting element having an anode, a cathode opposite to the anode, and a light-emitting layer located between the anode and the cathode, the method for manufacturing the light-emitting element being characterized in that it includes forming the light-emitting layer. The light-emitting layer comprises a plurality of quantum dots and an inorganic matrix, wherein the inorganic matrix fills the spaces between the plurality of quantum dots and has a metal oxide component. The inorganic matrix comprises: The first part has the aforementioned metal oxide; The second part has the metal oxide, and the ratio of oxygen atoms to metal atoms is higher than that of oxygen atoms to metal atoms in the first part, and is lower than the ratio of oxygen atoms to metal atoms in the metal oxide as a stoichiometric measure.

13. The method for manufacturing a light-emitting element according to claim 12, characterized in that, The process of forming the light-emitting layer includes: The formation of a first light-emitting layer, the first light-emitting layer comprising a plurality of said quantum dots and the first portion; and The formation of a second light-emitting layer, the second light-emitting layer comprising a plurality of the quantum dots and the second portion.

14. The method for manufacturing a light-emitting element according to claim 13, characterized in that, The process of forming the first light-emitting layer includes coating a first dispersion onto a substrate. The first dispersion contains a plurality of quantum dots and first microparticles as microparticles of the metal oxide. The process of forming the second light-emitting layer includes a process of coating a second dispersion onto a substrate. The second dispersion contains a plurality of the quantum dots and second microparticles as microparticles of the metal oxide. Compared with the first microparticles, the second microparticles have a higher proportion of oxygen atoms relative to metal atoms.

15. The method for manufacturing a light-emitting element according to claim 13, characterized in that, The process of forming the first light-emitting layer includes: A first quantum dot layer is formed on a substrate, the first quantum dot layer comprising a plurality of said quantum dots; and The metal oxide is deposited around the quantum dots in the first quantum dot layer using a first evaporation source, the first evaporation source having the metal oxide. The process of forming the second light-emitting layer includes: A second quantum dot layer is formed on a substrate, the second quantum dot layer comprising a plurality of the said quantum dots; and The metal oxide is deposited around the quantum dots in the second quantum dot layer using a second evaporation source having the metal oxide, and having a higher proportion of oxygen atoms relative to metal atoms in the second evaporation source compared to the first evaporation source.

16. The method for manufacturing a light-emitting element according to claim 15, characterized in that, The first and second evaporation sources each have a first metal oxide and a second metal oxide, wherein the second metal oxide has a higher proportion of oxygen atoms relative to metal atoms compared to the first metal oxide. The ratio of the second metal oxide to the first metal oxide in the second vapor deposition source is higher than the ratio of the second metal oxide to the first metal oxide in the first vapor deposition source.

17. The method for manufacturing a light-emitting element according to claim 12, characterized in that, The process of forming the light-emitting layer includes: The formation of a plurality of quantum dot structures, each quantum dot structure comprising the quantum dot and a second portion surrounding the quantum dot; and The first portion is formed around each of the quantum dot structures.

18. The method for manufacturing a light-emitting element according to claim 17, characterized in that, The formation of the quantum dot structure involves converting a precursor in a dispersion into the metal oxide, the dispersion comprising a plurality of the quantum dots and the precursor of the metal oxide.

19. The method for manufacturing a light-emitting element according to claim 18, characterized in that, The process of forming the first part includes: A dispersion liquid containing a third microparticle is coated on a substrate containing the quantum dot structure. The third microparticle is a microparticle of the metal oxide and has a lower proportion of oxygen atoms relative to metal atoms compared to the metal oxide in the quantum dot structure.

20. The method for manufacturing a light-emitting element according to claim 18, characterized in that, The process of forming the first part includes depositing the metal oxide around the quantum dot structure using a third evaporation source, the third evaporation source comprising the metal oxide, and having a lower proportion of oxygen atoms relative to metal atoms compared to the metal oxide in the quantum dot structure.

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