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

Abstract

A light emitting element (2) includes a light emitting layer (23) disposed between an anode (21) and a cathode (25). The light emitting layer includes first quantum dots (31) and an additive (40). The first quantum dots are in direct contact with a layer (22) adjacent to the light emitting layer on the anode side, or are adjacent to the layer (22) via an organic ligand (41), or are adjacent to the layer (22) via a semiconductor.

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 that serves as a light emitter for a light-emitting element, comprising a quantum dot (semiconductor nanoparticle) and an appendage containing silicon oxide (silicon dioxide) surrounding the quantum dot. The structure with the appendage surrounding the quantum dot protects the quantum dot, thereby improving the reliability of the quantum dot.

[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

[0004] The technical problem to be solved by the present invention In light-emitting elements having a structure in the light-emitting layer as described in Non-Patent Document 1, the charge injected from each electrode to the quantum dots is hindered by the additives, resulting in increased resistance or decreased luminous efficiency of the light-emitting element. In particular, in the aforementioned light-emitting element, the problem of reduced efficiency in injecting charge to each quantum dot of the light-emitting layer due to low electron mobility is especially pronounced when injecting holes into the quantum dots.

[0005] 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 first quantum dot and an additive, the first quantum dot being in direct contact with a layer of the light-emitting layer adjacent to the anode side, or adjacent to the light-emitting layer through an organic ligand, or adjacent to the light-emitting layer through a semiconductor.

[0006] One aspect of the present disclosure is a method for manufacturing a light-emitting element comprising an anode, a cathode opposite to the anode, and a light-emitting layer located between the anode and the cathode. The manufacturing method includes forming the light-emitting layer, the light-emitting layer comprising a first quantum dot and an additive, the first quantum dot being in direct contact with a layer of the light-emitting layer adjacent to the anode side, or adjacent to the light-emitting layer through an organic ligand, or adjacent to the light-emitting layer through a semiconductor.

[0007] Beneficial effects According to one aspect of the present disclosure, in a light-emitting element, while protecting at least a portion of the quantum dots with an additive, the efficiency of injecting holes into the quantum dots on the anode side of the light-emitting layer can be improved. Attached Figure Description

[0008] Figure 1 This is a schematic side cross-sectional view of the display device according to the first embodiment.

[0009] Figure 2 This is a schematic diagram of the display device according to the first embodiment.

[0010] Figure 3 This is a schematic enlarged cross-sectional view of the light-emitting layer and its vicinity according to the first embodiment.

[0011] Figure 4 This is a schematic diagram illustrating the additions between the filling quantum dots involved in the first embodiment.

[0012] Figure 5 This is a schematic side cross-sectional view of the display device involved in the comparison method.

[0013] Figure 6 This is a simplified enlarged view of the cross-section of the luminescent layer and its vicinity involved in the comparison method.

[0014] Figure 7 This is a flowchart illustrating a method for manufacturing a display device according to the first embodiment.

[0015] Figure 8 This is a flowchart illustrating the method for forming the light-emitting layer according to the first embodiment.

[0016] Figure 9 This is a schematic diagram showing the quantum dot dispersion according to the first embodiment.

[0017] Figure 10 This is a schematic diagram showing the first dispersion according to the first embodiment.

[0018] Figure 11 This is a cross-sectional view showing a part of the process of forming the light-emitting layer according to the first embodiment.

[0019] Figure 12 This is a process side view showing the mixing process in the method for forming the light-emitting layer according to the second embodiment.

[0020] Figure 13 This is a schematic diagram showing the first dispersion according to the second embodiment.

[0021] Figure 14 This is a schematic side cross-sectional view of the display device according to the third embodiment.

[0022] Figure 15 This is a schematic enlarged cross-sectional view of the light-emitting layer and its vicinity as described in the third embodiment.

[0023] Figure 16 This is a flowchart illustrating the method for forming the light-emitting layer according to the third embodiment.

[0024] Figure 17 This is a schematic diagram showing the second dispersion according to the third embodiment.

[0025] Figure 18 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 19 This is a schematic side cross-sectional view of the display device according to the fourth embodiment.

[0027] Figure 20 This is a schematic enlarged cross-sectional view of the light-emitting layer and its vicinity according to the fourth embodiment.

[0028] Figure 21 This is a flowchart illustrating a method for manufacturing a display device according to the fourth embodiment.

[0029] Figure 22 This is a flowchart illustrating the method for forming the light-emitting layer according to the fourth embodiment.

[0030] Figure 23 This is a cross-sectional view showing a part of the process of forming the light-emitting layer according to the fourth embodiment. Detailed Implementation

[0031] [First Implementation] <Display Devices: Overview> Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. In the drawings, the same reference numerals are used to denote the same components, and their descriptions are omitted. Furthermore, in this disclosure, for the sake of simplicity, even components labeled with the same reference numerals may sometimes have different scales depending on the drawings, and different cross-sectional lines may sometimes be indicated. However, the components shown in the drawings of this disclosure are merely illustrative, and their scales are not limited to those shown in the drawings. Additionally, in this disclosure, even components labeled with different cross-sectional lines, components labeled with the same reference numerals have the same configuration as described above.

[0032] 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, in the form of 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 driver 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 controls the light emission of each of the plurality of light-emitting elements 2 formed on the display section DA via the driver circuit DR and the pixel circuit PC, thereby displaying on the display section DA.

[0033] Regarding the structure of the display section DA of the display device 1, especially the structure of the light-emitting element 2, refer to... Figure 1 To provide a more detailed explanation. Figure 1 This is a schematic side cross-sectional view of the display device 1 according to the embodiments of this disclosure, particularly showing a cross-section perpendicular to the display surface of the display device 1 and passing through the light-emitting element 2. Furthermore, the schematic cross-sectional views and process cross-sectional views of the display device in this disclosure all show the cross-section perpendicular to the display surface of the display device 1 and passing through the light-emitting element 2. Figure 1 The cross section corresponding to the cross section of the display device 1 shown.

[0034] like Figure 1 As shown, the display device 1 according to 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 on which a TFT (Thin Film Transistor) as a pixel circuit PC is formed (not shown). In this specification, the direction in which the light-emitting elements 2 of the display device 1 face the substrate 3 is referred to as "downward", and the direction opposite to "downward" is referred to as "upward".

[0035] 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 arranged on the anode 21 from the substrate 3 side. The anode 21 is electrically connected to the TFT of the substrate 3.

[0036] <Overview of Light Emitting Elements> The following is a more detailed description of the structure of each layer of the light-emitting element 2.

[0037] 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.

[0038] 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), or FTO (fluorine-doped tin oxide). Alternatively, either the anode 21 or the cathode 25 may contain a metallic material; preferably, it is an element of Al, Cu, Au, Ag, or Mg, or an alloy thereof, which has high visible light reflectivity. The anode 21 and the cathode 25 can be deposited as films by sputtering or patterning by dry etching.

[0039] Hole transport layer 22 is a layer adjacent to the anode 21 side of light-emitting layer 23, and it contains a hole transport material for transporting holes from anode 21 to light-emitting layer 23. Furthermore, in this disclosure, "two components adjacent" can mean that the two components are in direct contact, or it can mean that the two components are close to each other. For example, in the case of "two components adjacent" in this disclosure, the shortest distance between the two components can be less than 4 nm, and there can also be a component with a size of less than 4 nm between the two components. In this embodiment, hole transport layer 22 can contain an organic material as the hole transport material. For example, hole transport layer 22 can contain at least one of polyvinylcarbazole (PVK) and [N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)-benzidine] (TPD).

[0040] However, this embodiment is not limited to this, and the material of the hole transport layer 22 can be any organic or inorganic material conventionally used in light-emitting elements containing quantum dots. For example, as an organic material for the hole transport layer 22, conductive compounds such as 4,4'-bis(carbazole-9-yl)biphenyl (CBP), poly(p-phenylenevinylene) (PPV), a composite of polyethylene dioxythiophene (PEDOT) and polystyrene sulfonate (PSS) (PEDOT-PSS), and poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4'-(N-4-sec-butylphenyl)diphenylamine)] (TFB) can be used. As an inorganic material 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 as the material for the hole transport layer 22.

[0041] 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 any organic or inorganic material conventionally 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) as the electron transport material, or 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), red phenanthroline (BCP), or (2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole) (t-Bu-PBD) as the electron transport material. Furthermore, as the inorganic material of the electron transport layer 24, metal oxides such as ZnO, ZAO, ITO, InGaZnO, or electron compounds can also be used. In particular, materials with low electron affinity are preferred for the electron transport layer 24.

[0042] In this embodiment, the hole transport layer 22 and the electron transport layer 24 can be formed using the aforementioned materials via vacuum evaporation, sputtering, or coating with a colloidal solution. 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 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.

[0043] <Light-emitting layer: quantum dots> Regarding the light-emitting layer 23 involved in this embodiment, refer to... Figure 3 and combined Figure 1 To provide a more detailed explanation. Figure 3 It is Figure 1 A schematic diagram showing the light-emitting layer 23 in the cross-section shown, as well as the enlarged portion near the light-emitting layer 23 in the hole transport layer 22 and electron transport layer 24, particularly showing... Figure 1 The image shows a magnified outline of region E1.

[0044] The light-emitting layer 23 of this embodiment includes a plurality of quantum dots 30 and additives 40. Furthermore, the light-emitting layer of this embodiment includes an organic ligand 41.

[0045] Quantum dots 30 can be, for example, core / shell quantum dots having a core and a shell formed around the core. In this embodiment, quantum dots 30 are, for example, luminescent semiconductor nanoparticles that emit light through excitons generated by the recombination of injected electrons and holes. For example, the recombination of electrons and holes in quantum dots 30 mainly occurs in the core. The core of quantum dot 30 is a luminescent material having valence band and conduction band energy levels, emitting light through the recombination of holes in the valence band and electrons in the conduction band. Since the light emitted by quantum dots 30 has a narrow spectrum due to the quantum confinement effect, it is possible to obtain luminescence with a deeper color intensity. In addition, the shell has the function of suppressing the generation of defects or dangling bonds in the core and reducing carrier recombination after the deactivation process.

[0046] The quantum dot 30 may contain a core material and a shell material, both of which are conventionally known for their core / shell structures, within the respective core and shell materials. For example, the quantum dot 30 may have InP / ZnS, CdSe / ZnS, CdSe / ZnSe, CdSe / CdS, ZnSe / ZnS, or CIGS / ZnS as its core / shell structure. Alternatively, the shell may be formed from multiple layers containing various different materials.

[0047] The quantum dot 30 has a particle size of approximately 1-100 nm. The wavelength of light emitted by the quantum dot 30 can be controlled by its particle size. In particular, since the quantum dot 30 has a core / shell structure, 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.

[0048] At any position along the film thickness direction, and on a plane orthogonal to the film thickness direction, the light-emitting layer 23 emits light at 1000 nm intervals. 2 It may contain more than one quantum dot 30. In this case, the light-emitting layer 23 contains a concentration of quantum dots 30 required for the light-emitting layer to function as a light-emitting element.

[0049] In this embodiment, the quantum dot 30 includes a first quantum dot 31 and a second quantum dot 32. Specifically, the second quantum dot 32 is closer to the cathode 25 than the first quantum dot 31. For example, as... Figure 1 and Figure 3As shown, the light-emitting layer 23 may have a first light-emitting layer 23A and a second light-emitting layer 23B that is closer to the cathode 25 than the first light-emitting layer 23A. In this case, the first light-emitting layer 23A may contain the first quantum dot 31 of the quantum dot 30, and the second light-emitting layer 23B may contain the second quantum dot 32 of the quantum dot 30. Furthermore, the first light-emitting layer 23A and the second light-emitting layer 23B in this disclosure are merely components provided to more clearly illustrate the configuration of the light-emitting layer 23 in this disclosure. In other words, the light-emitting layer 23 may also not contain a clearly distinguishable first light-emitting layer 23A and a second light-emitting layer 23B. Thus, in this disclosure, as long as the positional relationships of the various parts of the light-emitting layer 23, such as the appendages and organic ligands described later, can be confirmed by cross-sectional observation of the light-emitting layer 23, the specific configuration of the light-emitting layer 23 in this disclosure is not particularly limited.

[0050] <Light-emitting layer: Additive> The additive 40 is insulating. For example, the additive 40 may contain at least one 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. In particular, the additive 40 may contain at least one from silicon oxide, aluminum oxide, and silicon nitride. In this case, the additive 40 becomes denser, thus further improving the effect of protecting the quantum dot 30 (described later) from foreign matter such as moisture.

[0051] The appendage 40 is located around a portion of the quantum dot 30. In particular, the appendage 40 may be located between at least two second quantum dots 32 in the quantum dot 30, and may fill the space between the two second quantum dots 32.

[0052] For the component that fills the space between multiple quantum dots 30, please refer to further details. Figure 4 To provide a more detailed explanation. Figure 4 Schematic diagrams 401 and 402 are schematic diagrams for illustrating the components between the filled quantum dots 30. Specifically, schematic diagrams 401 and 402 respectively show… Figure 3 The diagram shows two examples of a group P of two quantum dots 30 and the region (space) K between them. In particular, schematic diagrams 401 and 402 show groups P1 and P2, respectively, as examples of groups of quantum dots 30A and 30B.

[0053] In this specification, the component is filled between multiple quantum dots 30, as long as... Figure 4As shown in schematic diagram 401 of group P1, it can be seen that the component only needs to fill the region K between at least quantum dot 30A and quantum dot 30B. Region K is the area in the cross-section of the light-emitting layer 23 surrounded by two straight lines (common external tangents) that connect to the outer peripheries of quantum dots 30A and 30B, and the opposite outer peripheries of quantum dots 30A and 30B. Therefore, as Figure 4 As shown in schematic diagram 402 of group P2, even if quantum dot 30A and quantum dot 30B are close to each other, region K can still exist, and the component fills region K.

[0054] The fact that components are filled between multiple quantum dots 30 does not necessarily mean that the region K between quantum dots 30A and 30B is entirely composed of components. For example, region K between quantum dots 30A and 30B may contain materials such as ligands that are different from the component material. Specifically, for example, the light-emitting layer 23 may contain organic ligands added to improve the dispersibility of the quantum dots 30 in the dispersion used for coating formation, and coordinated on the outer peripheral surface of the quantum dots 30 in the dispersion. In this case, from the viewpoint of improving the reliability of the light-emitting layer 23, the weight ratio of organic ligands in the light-emitting layer 23 relative to the total weight of the region K may be less than 5%.

[0055] Back Figure 1 and Figure 3 With reference to the cathode 25 side, the appendage 40 is the light-emitting layer 23 adjacent to the electron transport layer 24. Specifically, the appendage 40 can form a portion of the outer edge of the light-emitting layer 23 adjacent to the lower surface 24U of the electron transport layer 24, and a portion of the outer edge of the light-emitting layer 23 can directly contact at least a portion of the lower surface 24U of the electron transport layer 24. Therefore, the light-emitting layer 23 includes the appendage 40 between the electron transport layer 24 and the second quantum dot 32. Figure 3 The thickness T1 of the attachment 40 between the electron transport layer 24 and the second quantum dot 32 can be more than 1 nm and less than 5 nm. Furthermore, in this disclosure, "thickness" can refer to the length of the component in any direction. For example, as described later, when the attachment 40 covers the second quantum dot 32, the thickness T1 of the attachment 40 refers not only to the length in the stacking direction of the light-emitting element 2, but also to the length from the center of the second quantum dot 32 outwards in the surrounding direction. Additionally, in this disclosure, "thickness" can, for example, refer to the average thickness of the component within the observation range when observing a cross-section in the stacking direction of the light-emitting element 2. In this case, the area observed in the cross-section can be 5 nm. 2 Above and 500nm 2 the following.

[0056] The second light-emitting layer 23B may include an attachment 40. In particular, the attachment 40 may be located at any position in the thickness direction of the second light-emitting layer 23B, and may have an area of ​​1000 nm in a plane direction orthogonal to the thickness direction. 2 The above is a continuous film. In addition, in the second light-emitting layer 23B, the second quantum dot 32 can be coated in the continuous film of the additive 40. In other words, the second quantum dot 32 can be coated in the continuous film of the additive 40.

[0057] For example, if more than 80% of the second quantum dots 32 constituting the second light-emitting layer 23B have more than 60% of their surface in contact with the continuous film of the additive 40, it can be said that the second quantum dots 32 contained in the second light-emitting layer 23B are coated by the additive 40. Thus, the second light-emitting layer 23B containing the second quantum dots 32 coated by the additive 40 can improve light-emitting properties and extend lifetime.

[0058] The appendage 40 may, for example, be located entirely around the second quantum dot 32. For example, as... Figure 3 As shown, in any cross-section passing through any second quantum dot 32, the appendage 40 can be located entirely around the second quantum dot 32. Here, "the appendage 40 is located entirely around the second quantum dot 32" can mean that the appendage 40 is located over 90% of the area around the second quantum dot 32. Additionally, as... Figure 3 As shown, the surface of the second quantum dot 32 can be in contact with the attachment 40.

[0059] The band gap of the additive 40 can be wider than the band gap of the material constituting the quantum dot 30. When the quantum dot 30 has a core and a shell surrounding the core, the band gap of the additive 40 can be wider than the band gap of the material constituting the shell.

[0060] <Emitting Layer: Organic Ligands> Organic ligand 41, for example, is an organic ligand having a carbon chain and a coordinating functional group at one end of the carbon chain, and can be an organic ligand commonly used as a quantum dot ligand. Organic ligand 41 is located near the first quantum dot 31, and in particular, can be coordinated on the first quantum dot 31. In other words, the coordinating functional group of organic ligand 41 can form a coordination bond with the outermost peripheral surface of the first quantum dot 31. Furthermore, in this disclosure, "organic ligand 41 is located near the first quantum dot 31" can mean that, in cross-sectional observation of the luminescent layer 23, organic ligand 41 is located within a range of less than 3 nm around the first quantum dot 31.

[0061] Furthermore, in cross-sectional observation of the light-emitting layer 23 involved in this embodiment, if it can be confirmed that the distance between the first quantum dot 31 and the organic ligand 41 is less than 1 nm, it can be considered that the organic ligand 41 is coordinated on the first quantum dot 31. Alternatively, if it can be confirmed that the first quantum dot 31 is in contact with the organic ligand 41, it can be considered that the organic ligand 41 is coordinated on the first quantum dot 31.

[0062] In this embodiment, the light-emitting layer 23 is adjacent to the upper surface 22T of the hole transport layer 22 on the anode 21 side. Specifically, in this embodiment, the first quantum dot 31 is in direct contact with the hole transport layer 22, or is adjacent to the upper surface 22T of the hole transport layer 22 through an organic ligand 41. In other words, the first quantum dot 31 is in direct contact with the layer of the light-emitting layer 23 adjacent to it on the anode 21 side, or is adjacent through an organic ligand 41. Furthermore, in this disclosure, "the first component and the second component are adjacent through a third component" can mean that the third component is located between the first component and the second component, and the third component is adjacent to both the first and second components. In other words, in the above case, the third component can directly contact the first component, or be close to the first component. Additionally, in the above case, the third component can directly contact the second component on the side opposite to the first component, or be close to the second component on the side opposite to the first component.

[0063] Therefore, in this embodiment, the hole transport layer 22 may have a portion on its upper surface 22T that does not contact the attachment 40; specifically, the hole transport layer 22 may also not have a portion adjacent to the attachment 40. For example, as Figure 3 As shown, the attachment 40 can be formed from the outer edge of the electron transport layer 24 side of the light-emitting layer 23 to the midway point of the hole transport layer 22 side of the light-emitting layer 23. Alternatively, the attachment 40 may also be present in a portion of the first light-emitting layer 23A. In other words, the attachment 40 can contact a portion of the cathode 25 side of the outer peripheral surface of the first quantum dot 31 contained in the first light-emitting layer 23A.

[0064] <Supplementary Records> The specific structure of each layer of the light-emitting element 2 involved in this embodiment can be confirmed by confirming the composition of each layer interface and its position in the film thickness direction. This confirmation can be performed, for example, by method 1: using TEM (transmission electron microscopy) to perform EDX (energy-dispersive X-ray spectroscopy) on the cross-section of each layer of the light-emitting element 2. In particular, in method 1, FIB (focused ion beam) processing can be used. Furthermore, as a more detailed method for implementing the above confirmation, method 2 can be cited: using dynamic SIMS (secondary ion mass spectrometry) to confirm the elemental or molecular distribution of each layer of the light-emitting element 2 in the film thickness direction. Additionally, method 3: in method 2, dynamic SIMS can be replaced with TOF (Time of Flight)-SIMS (static SIMS). Furthermore, the above confirmation methods are preferably performed in the order of methods 1 to 3; if the confirmation can be achieved by the aforementioned methods, subsequent confirmation methods can be omitted.

[0065] The light-emitting element 2 involved in this embodiment is not limited to the layer structure described above. For example, the light-emitting element 2 may have 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.

[0066] Furthermore, the light-emitting element 2 may 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. Therefore, the layer adjacent to the light-emitting layer 23 on the anode 21 side may be an electron blocking layer, or the layer adjacent to the light-emitting layer 23 on the cathode 25 side may be a hole blocking layer. Additionally, the light-emitting element 2 may include a protective layer or an intermediate layer on at least one of the layers between the hole transport layer 22 and the light-emitting layer 23, and between the electron transport layer 24 and the light-emitting layer 23. Therefore, at least one of the layers adjacent to the light-emitting layer 23 on the anode 21 side and the layers adjacent to the light-emitting layer 23 on the cathode 25 side may be a protective layer or an intermediate layer.

[0067] Furthermore, the light-emitting element 2 may only have a light-emitting layer 23 between the anode 21 and the cathode 25; in other words, it may not have a charge transport layer between the anode 21 and the cathode 25. In this case, the layer adjacent to the light-emitting layer 23 on the anode 21 side may be the anode 21, or the layer adjacent to the light-emitting layer 23 on the cathode 25 side may be the cathode 25.

[0068] <Light-emitting layer involved in the comparison method> The effects of the light-emitting element and display device involved in this embodiment will be explained by comparing them with the light-emitting element and display device involved in the comparison method. Figure 5 This is a schematic side cross-sectional view of the display device 1C involved in the comparison method.

[0069] Compared to the display device 1 of this embodiment, the display device 1C involved in the comparison method has a light-emitting element 2C instead of a light-emitting element 2. Compared to the light-emitting element 2, the light-emitting element 2C has a light-emitting layer 23C instead of a light-emitting layer 23.

[0070] Figure 6 It is Figure 5 A schematic diagram showing the light-emitting layer 23C in the cross-section shown, as well as the portion near the light-emitting layer 23C in the hole transport layer 22 and the electron transport layer 24, with particular emphasis on... Figure 5 The image shows a magnified outline of region EC.

[0071] The light-emitting layer 23C comprises a plurality of quantum dots 30 and attachments 40 respectively covering the quantum dots 30. Specifically, in a comparative embodiment, the attachments 40 are adjacent to both the hole transport layer 22 and the electron transport layer 24, and none of the quantum dots 30 are adjacent to either the hole transport layer 22 or the electron transport layer 24. Furthermore, the quantum dots 30 are not adjacent to the hole transport layer 22 or the electron transport layer 24 through ligands such as organic ligands.

[0072] Except for the points mentioned above, the display device 1C involved in the comparison method has the same configuration as the display device 1 involved in this embodiment.

[0073] Here, we examine the path of charge flowing through the light-emitting layer 23C when driving the light-emitting element 2C in the comparison method. In the comparison method, the additive 40 is an insulator, while the quantum dot 30 contains a material such as a semiconductor that has at least higher conductivity than the additive 40. Therefore, it is assumed that when driving the light-emitting element 2C, if... Figure 6 As shown, the charge is mainly transported along the path R that connects the hole transport layer 22 and the electron transport layer 24 via the quantum dot 30.

[0074] Under the above premise, when driving the light-emitting element 2C, the light-emitting layer 23C on path R is considered as a circuit connecting the hole transport layer 22 and the electron transport layer 24 and transferring charge. In this case, besides the resistance between the hole transport layer 22 and the electron transport layer 24, this circuit can also be considered as a circuit where each quantum dot 30 and each first additive 40 on path R functions as a virtual diode D. Figure 6 In the example shown, the virtual circuit formed along path R can be considered to contain a total of 5 diodes D, in addition to the resistance between hole transport layer 22 and electron transport layer 24.

[0075] In particular, the virtual circuit on path R of the light-emitting layer 23C involved in the comparative method has an appendage 40 not only between the electron transport layer 24 and the quantum dot 30, but also between the hole transport layer 22 and the quantum dot 30. Therefore, when driving the light-emitting element 2C containing the light-emitting layer 23C, the appendage 40 formed between the hole transport layer 22 and the quantum dot 30 functions as a virtual diode D. Therefore, in the light-emitting element 2C involved in the comparative method, the appendage 40 between the hole transport layer 22 and the quantum dot 30, which functions as a virtual diode D, reduces the efficiency of hole injection from the hole transport layer 22 to the quantum dot 30.

[0076] Generally, in light-emitting devices where quantum dots are used as the luminescent material within the luminescent layer, due to differences in the efficiency of charge injection into the luminescent layer and differences in charge mobility, there may sometimes be an excess of electrons compared to the hole concentration. This excess of electrons in the luminescent layer not only increases the deactivation process of the quantum dots and reduces the luminous efficiency of the light-emitting device, but may also indirectly cause the generation of Auger electrons. Auger electrons do not participate in the luminescence of quantum dots and can sometimes cause degradation of the quantum dots and surrounding materials.

[0077] Therefore, the light-emitting element 2C reduces the luminous efficiency of the light-emitting layer 23C and increases the number of electrons in the light-emitting layer 23C, which exacerbates the degradation of the quantum dot 30 of the light-emitting layer 23C or the transmission materials of each transmission layer caused by Auger electrons generated by the excess electrons.

[0078] Furthermore, in light-emitting elements where quantum dots are typically used as the light-emitting material in the light-emitting layer, due to the high mobility of electrons relative to holes, recombination of holes and electrons injected into the light-emitting layer sometimes occurs more frequently on the side closer to the anode. In this case, the excitons generated through this recombination will be located closer to the anode side.

[0079] Here, in the light-emitting layer containing quantum dots, energy transfer sometimes occurs, where the energy of excitons generated by the recombination of holes and electrons in the quantum dots is transferred to other components adjacent to the quantum dots. When the exciton energy is transferred to components different from the quantum dots, such as the hole transport material of the hole transport layer 22, those components may become deactivated and stop participating in light emission. Generally, the probability of energy transfer, such as the Foster transition, from the exciton energy to other materials tends to increase as the distance between the two components undergoing the energy transfer increases.

[0080] The light-emitting element 2C facilitates the close proximity of the quantum dot 30, which generates excitons in the light-emitting layer 23C, to the hole transport layer 22. Therefore, the light-emitting element 2C readily intensifies the energy transfer process from the excitons to the hole transport material in the hole transport layer 22, further reducing luminous efficiency.

[0081] <Effects of the light-emitting element involved in the implementation> On the other hand, in the light-emitting layer 23 of the light-emitting element 2 according to this embodiment, the first quantum dot 31, located closer to the anode 21 than the second quantum dot 32, is in direct contact with the hole transport layer 22, or adjacent to it through the organic ligand 41. For example, when the first quantum dot 31 is in direct contact with the hole transport layer 22, if the contact resistance is ignored, the first quantum dot 31 and the hole transport layer 22 can be considered to be in a short-circuit state, and the contact resistance is also extremely small. In addition, when the first quantum dot 31 is adjacent to the hole transport layer 22 through the organic ligand 41, hole transport from the hole transport layer 22 to the first quantum dot 31 is mainly achieved through hopping conduction via the organic ligand 41.

[0082] Therefore, in the light-emitting layer 23, the effective resistance between the first quantum dot 31 and the hole transport layer 22 can be reduced, such as the resistance formed between the first quantum dot 31 and the hole transport layer 22 in the aforementioned virtual diode D. Thus, when the light-emitting element 2 is driven, holes injected into the light-emitting layer 23 are efficiently injected into the first quantum dot 31 and efficiently transported via the first quantum dot 31 to the central side in the thickness direction of the light-emitting layer 23.

[0083] As a result, the light-emitting element 2 improves the efficiency of injecting holes from the hole transport layer 22 into the first quantum dot 31, and reduces the luminous efficiency of the light-emitting layer 23 and the degradation of each layer between the anode 21 and the cathode 25.

[0084] Furthermore, the light-emitting element 2 transports holes to the central side of the light-emitting layer 23 in the thickness direction, thus causing recombination of holes and electrons in the light-emitting layer 23 to occur at the central side of the light-emitting layer 23 in the thickness direction. Therefore, by increasing the distance between the excitons generated by this recombination and the hole transport layer 22, the light-emitting element 2 reduces the transfer of energy from the excitons to the hole transport material of the hole transport layer 22.

[0085] Furthermore, the light-emitting layer 23 of the light-emitting element 2 according to this embodiment includes an attachment 40, which is located around a portion of the quantum dots 30 containing the second quantum dots 32. Therefore, the light-emitting layer 23 can protect a portion of the quantum dots 30 from foreign matter such as moisture through the attachment 40. Thus, the light-emitting element 2 can reduce the degradation of a portion of the quantum dots 30 in the light-emitting layer 23 through the attachment 40.

[0086] Specifically, for the reasons stated above, in the light-emitting layer 23, the recombination of holes and electrons is more likely to occur in the quantum dot 30 containing the second quantum dot 32, which is located further from the cathode 25 than the first quantum dot 31. Therefore, the light-emitting element 2 can more efficiently protect the quantum dot 30 containing the second quantum dot 32, which contains excitons that are more difficult to generate than the first quantum dot 31, thereby improving the luminous efficiency.

[0087] Therefore, while reducing some of the degradation of quantum dots 30 through the additive 40, the light-emitting element 2 improves luminous efficiency and enhances the reliability of each layer between the anode 21 and the cathode 25. The display device 1 equipped with the light-emitting element 2 achieves power saving and long lifespan.

[0088] As described above, when the first quantum dot 31 is in direct contact with the hole transport layer 22, the resistance between the first quantum dot 31 and the hole transport layer 22 is only a very small contact resistance. Therefore, the light-emitting element 2, which includes a light-emitting layer 23 containing the first quantum dot 31 in direct contact with the hole transport layer 22, reduces the overall resistance and thereby improves the luminous efficiency.

[0089] Furthermore, the light-emitting layer 23, which is adjacent to the hole transport layer 22 with the first quantum dot 31 separated from the organic ligand 41, as described later, can be formed using a dispersion in which the first quantum dot 31 coordinated with the organic ligand 41 is dispersed. In the portion of the dispersion and the light-emitting layer 23 formed by the dispersion, the aggregation of the first quantum dot 31 is reduced due to the steric hindrance of the organic ligand 41. Therefore, the light-emitting element 2, which includes the light-emitting layer 23 containing the first quantum dot 31 adjacent to the hole transport layer 22 with the organic ligand 41 separated from the light-emitting layer 22, reduces the overall resistance, reduces the aggregation of the first quantum dot 31, and lowers the probability of the inactivation process in the first quantum dot. Therefore, the light-emitting element 2 with the above configuration further improves the luminous efficiency.

[0090] Specifically, the light-emitting layer 23 includes an additive 40 between the electron transport layer 24 and the second quantum dot 32. Therefore, the light-emitting element 2 is more effectively protected from foreign matter such as moisture that seeps in from the electron transport layer 24 by the additive 40. In particular, because the additive 40 fills between at least two second quantum dots 32, the light-emitting element 2 is more effectively protected from the second quantum dots 32 by the additive 40.

[0091] Furthermore, by including an additive 40 between the electron transport layer 24 and the second quantum dot 32, the light-emitting layer 23 increases the distance between the second quantum dot 32 and the interface between the light-emitting layer 23 and the electron transport layer 24, where excess electrons easily accumulate. Therefore, the light-emitting element 2 reduces the degradation of the second quantum dot 32 caused by Auger electrons generated from excess electrons accumulating at the interface between the light-emitting layer 23 and the electron transport layer 24.

[0092] Furthermore, the light-emitting layer 23 includes an appendage 40 between the electron transport layer 24 and the second quantum dot 32, and the aforementioned virtual diode D is included between the light-emitting layer 23 and the electron transport layer 24. Therefore, the light-emitting element 2 can reduce the excess electrons in the light-emitting layer 23 by reducing the electron transport efficiency from the electron transport layer 24 to the light-emitting layer 23. Thus, the light-emitting element 2 improves the carrier balance in the light-emitting layer 23, reduces the luminous efficiency of the light-emitting layer 23, and reduces the degradation of each layer between the anode 21 and the cathode 25.

[0093] In this embodiment, the thickness of the appendage 40 between the electron transport layer 24 and the second quantum dot 32 can be 1 nm or more, or, as described above, the appendage 40 can be insulating. The insulating appendage 40 further reduces the penetration of foreign matter into the second quantum dot 32. Specifically, the insulating appendage 40 reduces the injection of excess electrons, such as Auger electrons, that may degrade the quantum dot 30 into the second quantum dot 32, or the energy propagation from these electrons. Therefore, with the above configuration, the light-emitting element 2 more efficiently protects the second quantum dot 32, further reduces the degradation of the second quantum dot 32, and further improves the carrier balance of the light-emitting layer 23.

[0094] Furthermore, since the thickness of the appendage 40 between the electron transport layer 24 and the second quantum dot 32 is less than 5 nm, electron tunneling from the electron transport layer 24 to the second quantum dot 32 occurs more efficiently. Therefore, with the above configuration, the light-emitting element 2 can suppress the excessive reduction in electron transport efficiency from the electron transport layer 24 to the second quantum dot 32 and improve the luminous efficiency of the light-emitting layer 23.

[0095] The light-emitting element 2 includes a hole transport layer 22 adjacent to the anode 21 side of the light-emitting layer 23 between the anode 21 and the light-emitting layer 23, thereby further improving the hole transport efficiency from the anode 21 to the light-emitting layer 23. In particular, the hole transport layer 22 contains at least one of organic materials, especially PVK and TPD, as the hole transport material, thus further improving the hole transport efficiency from the anode 21 to the light-emitting layer 23.

[0096] <Manufacturing method of display device: up to the formation of hole transport layer> Regarding the manufacturing method of the display device 1 involved in this embodiment, please refer to... Figure 7 Please provide an explanation. Figure 7 This is a flowchart illustrating the manufacturing method of the display device 1 according to this embodiment.

[0097] In the manufacturing method of the display device 1 according to this embodiment, a substrate 3 is first prepared (step S21). The substrate 3 can be manufactured, for example, by forming a plurality of the above-described pixel circuits PC on a glass substrate.

[0098] Next, a light-emitting element 2 is formed on the substrate 3. In the process of forming the light-emitting element 2, for example, an anode 21 is first formed on the substrate 3 by any of the methods described above (step S22). For example, when the substrate 3 has multiple pixel circuits PC, the anode 21 can be formed in an island shape for each pixel circuit PC.

[0099] Next, a hole transport layer 22 is formed on the anode 21 using any of the methods described above (step S23). The hole transport layer 22 can be formed together for multiple anodes 21, or it can be formed as an island for each anode 21. When the hole transport layer 22 is formed as an island, the material of the hole transport layer 22 can be different depending on the emission color of the sub-pixel.

[0100] <Manufacturing Method of Display Device: Formation of Emissive Layer: Preparation of Dispersion> Next, the light-emitting layer 23 is formed (step S24). For the method of forming the light-emitting layer 23, please refer to... Figure 8 To provide a more detailed explanation. Figure 8 This is a flowchart illustrating 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, a quantum dot dispersion and a first dispersion are first prepared (step S1). (Refer to...) Figure 9 and Figure 10 A more detailed description is provided of the quantum dot dispersion and the first dispersion. Figure 9 and Figure 10 The diagrams show schematic representations of the quantum dot dispersion LQ and the first dispersion L1 injected into container C, respectively.

[0102] like Figure 9 As shown, the quantum dot dispersion LQ comprises quantum dots 30 dispersed in solvent 50 and organic ligands 41 coordinated to the quantum dots 30. The quantum dot dispersion LQ can be prepared by synthesizing multiple quantum dots 30 in solvent 50 using any method including conventionally known methods, and then adding the organic ligands 41 to solvent 50. Alternatively, the quantum dot dispersion LQ can be prepared by extracting individually synthesized quantum dots 30 and the organic ligands 41 coordinated to the quantum dots 30, and adding them to solvent 50. Solvent 50 can be toluene.

[0103] like Figure 10As shown, the first dispersion L1 comprises quantum dots 30 dispersed in solvent 50, a precursor 51 serving as a first precursor, and a precursor ligand 52, also serving as a first precursor, coordinated on the quantum dots 30. Precursor 51 is a precursor to additive 40, which is converted into additive 40 through a conversion process described later. Precursor ligand 52 has at least a portion of precursor 51 and a coordinating functional group located at its end and forming a coordinate bond with the outer peripheral surface of the quantum dots 30. Therefore, precursor ligand 52 is coordinated on the quantum dots 30, and through the conversion process described later, a portion on the side opposite to the coordinating functional group is converted into additive 40.

[0104] For example, when additive 40 is silicon oxide, precursor 51 may contain tetramethyl orthosilicate (TMOS) as shown in formula (1) below. In addition, when additive 40 is silicon oxide, precursor ligand 52 may contain 3-(mercaptopropyl)trimethoxysilane (MPS) as shown in formula (2) below.

[0105] [Chemical Formula 1] [Chemical Formula 2] In this case, the first dispersion L1 may contain a halogen source 53 such as ZnCl2. This halogen source 53 can act as a catalyst for the conversion of precursor 51 and precursor ligand 52 (described later) into additive 40.

[0106] The first dispersion L1 can be prepared by synthesizing a plurality of quantum dots 30 in solvent 50 using any method including conventionally known methods, and then adding the precursor 51, precursor ligand 52, and halogen source 53 to solvent 50. Alternatively, the first dispersion L1 can be prepared by extracting individually synthesized quantum dots 30 and precursor ligand 52 coordinated to the quantum dots 30, and adding them together with the precursor 51 and halogen source 53 to solvent 50.

[0107] The quantum dot 30 coordinated to the precursor ligand 52 can be synthesized, for example, by stirring a dispersion of the quantum dot 30 coordinated to the organic ligand 41, or by dispersing an excess of the precursor ligand 52. In other words, by stirring as described above, the ligand coordinated to the quantum dot 30 can be replaced from the organic ligand 41 to the precursor ligand 52.

[0108] Furthermore, step S1 is not necessarily performed after step S23, in other words, it is not necessarily performed after the hole transport layer 22 is formed. In particular, the preparation of the quantum dot dispersion LQ and the first dispersion L1 can be completed before step S23 is completed, in other words, before the hole transport layer 22 is formed.

[0109] <Manufacturing Method of Display Device: Formation of Emissive Layer: Film Formation Process> In the manufacturing method of the display device 1 according to this embodiment, after forming the hole transport layer 22 and preparing the quantum dot dispersion LQ and the first dispersion L1, a film-forming process for the light-emitting layer 23 is performed. Except Figure 8 In addition, refer to Figure 11 The film-forming process of the light-emitting layer 23 will be described in more detail. Figure 11 This is a process cross-sectional view showing the film-forming process of the light-emitting layer 23 as part of the method for forming the light-emitting layer 23.

[0110] In the film formation process of the light-emitting layer 23, firstly, a laminate containing each layer of the substrate 3 is used as the substrate, and a quantum dot dispersion LQ is coated on the substrate (step S2). For example, as Figure 11 As shown in step S2, a quantum dot dispersion LQ is coated on the hole transport layer 22 by any method including conventionally known coating methods such as spin coating.

[0111] Here, the quantum dots 30 in the coated quantum dot dispersion LQ can aggregate towards the hole transport layer 22 due to their own weight. In this case, when step S2 is completed, the quantum dots 30 in the quantum dot dispersion LQ or the organic ligands 41 coordinated on the quantum dots 30 can come into contact with the hole transport layer 22.

[0112] Next, the quantum dot dispersion LQ is dried by heating each part of the substrate 3 containing the coated quantum dot dispersion LQ at, for example, 130°C for 5 minutes (step S3). Here, in step S3, as the solvent 50 of the coated quantum dot dispersion LQ evaporates, the quantum dots 30 in the quantum dot dispersion LQ, or the organic ligands 41 coordinated on the quantum dots 30, become adjacent to the hole transport layer 22. Alternatively, as described above, at the beginning of step S3, the quantum dots 30 in the quantum dot dispersion LQ, or the organic ligands 41 coordinated on the quantum dots 30, may be in contact with the hole transport layer 22.

[0113] Therefore, as Figure 11 As shown in step S3, at least a portion of the quantum dots 30 contained in the quantum dot dispersion LQ becomes a first quantum dot 31 that is in direct contact with the hole transport layer 22 or adjacent to it through the organic ligand 41. Therefore, by performing step S3, a first light-emitting layer 23A, which is a first quantum dot layer containing the first quantum dots 31, is formed on the hole transport layer 22.

[0114] Next, using the laminate containing each layer of substrate 3 as a substrate, a first dispersion liquid L1 is coated onto the substrate (step S4). For example, as... Figure 11 As shown in step S4, the first dispersion L1 is coated on the first light-emitting layer 23A by any method including conventionally known coating methods such as spin coating.

[0115] In step S4, as long as the first quantum dots 31 contained in the first light-emitting layer 23A are kept in contact with the hole transport layer 22 or adjacent to it via the organic ligand 41, the solvent 50 of the first dispersion L1 can also penetrate into the spaces between the first quantum dots 31 of the first light-emitting layer 23A. However, the precursor 51 of the first dispersion L1 can be located at a position higher than the first quantum dots 31.

[0116] Next, the precursor of the additive 40 containing the precursor 51 and precursor ligand 52 in the first dispersion L1 is converted into additive 40 (step S5). For example, the precursor 51 and precursor ligand 52 in the first dispersion L1 are reacted by heating each part of the substrate 3 containing the coated first dispersion L1 at 100°C for 30 minutes.

[0117] The details of the above reaction when precursor 51 contains TMOS and precursor ligand 52 contains MPS will be explained. For example, through the above heating, the methoxy groups of the TMOS in precursor 51 and the MPS in precursor ligand 52 react with water (H2O) and are replaced by hydroxyl groups (OH). - Simultaneously, methanol is generated as a byproduct. Next, dehydration condensation occurs between the two hydroxyl groups, thereby causing dehydration condensation between TMOS and MPS, between two TMOS, and between two MPS. As described above, in step S5, precursor 51 and precursor ligand 52 are converted into an additive 40 containing silicon oxide.

[0118] Furthermore, the above-described reaction between precursor 51 and precursor ligand 52 can be carried out using halogen source 53 as a catalyst. Additionally, in step S5, through the above reaction, a portion of the methoxy groups present in the TMOS of precursor 51 and the MPS of precursor ligand 52 can react; in other words, methoxy or hydroxyl groups may remain in additive 40.

[0119] Here, in step S5, the precursor 51 in the coated first dispersion L1 is located around the quantum dots 30, and the precursor ligand 52 is coordinated onto the quantum dots 30. Therefore, in step S5, the transformed precursor 51 and precursor ligand 52 are converted into an additive 40 filling the spaces between the quantum dots 30. Thus, as... Figure 11 As shown in step S5, a second light-emitting layer 23B comprising a plurality of second quantum dots 32 covered by the additive 40 is formed on the first light-emitting layer 23A. As described above, the formation of the light-emitting layer 23 is completed.

[0120] <Manufacturing method of display device: after the formation of the electron transport layer> Back Figure 7Referring to the above method, after forming the light-emitting layer 23, an electron transport layer 24 is formed on the light-emitting layer 23 using any of the methods described above (step S25). Except for the formation location and the material used, the electron transport layer 24 can be formed using the same method as the hole transport layer 22.

[0121] Next, a cathode 25 is formed on the electron transport layer 24 using the methods described above (step S26). The cathode 25 can be formed together for multiple anodes 21. As described above, a display device 1 having light-emitting elements 2 on the substrate 3 is manufactured.

[0122] According to the above method, as described above, a display device 1 having a light-emitting element 2 can be manufactured. This light-emitting element 2 improves luminous efficiency and enhances the reliability of each layer between the anode 21 and the cathode 25 while reducing some of the degradation of the quantum dots 30 through the additive 40. Specifically, in this embodiment, the second light-emitting layer 23B is formed by a method including precursor conversion of the additive 40. According to the above method, the second light-emitting layer 23B, including the additive 40 filled between the two second quantum dots 32, can be formed more easily.

[0123] In this embodiment, the light-emitting element 2 of the display device 1 has its anode 21 located closer to the substrate 3 than the light-emitting layer 23. According to this configuration, when manufacturing the light-emitting element 2 using the above method, in steps S2 and S3, the quantum dots 30 or organic ligands 41 in the quantum dot dispersion LQ can be easily brought into contact with the hole transport layer 22. Therefore, because the light-emitting element 2 of the display device 1 has its anode 21 located closer to the substrate 3 than the light-emitting layer 23, the formation of the first light-emitting layer 23A is further simplified in its manufacturing process.

[0124] Furthermore, in the manufacturing method of the display device 1 according to this embodiment, during the formation process of the electron transport layer 24 and the cathode 25, an attachment 40 is formed on the upper surface side of the light-emitting layer 23. Therefore, during the formation process of the electron transport layer 24 and the cathode 25, each quantum dot 30 included in the light-emitting layer 23 is protected by the attachment 40. Therefore, the light-emitting element 2 of the display device 1 is located closer to the substrate 3 than the light-emitting layer 23 via the anode 21, which can reduce the degradation of each quantum dot 30 included in the light-emitting layer 23 during the formation process of the electron transport layer 24 and the cathode 25.

[0125] Furthermore, in the formation process of the first light-emitting layer 23A, the quantum dot dispersion LQ coated on the hole transport layer 22 does not contain the precursor of the additive 40. Therefore, in the formation process of the first light-emitting layer 23A, it is only necessary to heat the quantum dot dispersion LQ until the solvent 50 of the quantum dot dispersion LQ coated on the hole transport layer 22 evaporates. In other words, the formation process of the first light-emitting layer 23A does not require heating to the extent necessary to convert the precursor of the additive 40. Therefore, even if the hole transport layer 22 contains an organic material with high hole transport efficiency but low heat resistance compared to inorganic materials, the light-emitting element 2 can reduce the degradation of the hole transport layer 22 in the formation process of the first light-emitting layer 23A.

[0126] [Second Implementation] <Manufacturing methods using mixed processes> The display device 1 according to this embodiment has the same configuration as the display device 1 according to the previous embodiment, except that some steps in the manufacturing method of the light-emitting element 2 are different. The manufacturing method of the light-emitting element 2 according to this embodiment differs from the manufacturing method of the light-emitting element 2 according to the previous embodiment only in the method of forming the light-emitting layer 23.

[0127] The light-emitting layer 23 in this embodiment is formed using the same method as the light-emitting layer 23 in the previous embodiment, except for the content of step S1 and the composition of the first dispersion used in steps S4 and S5. (Refer to...) Figure 12 and Figure 13 The method for forming the light-emitting layer 23 according to this embodiment will be described in detail. Figure 12 This is a process side view showing the mixing process in the method for forming the light-emitting layer 23 according to this embodiment. Figure 13 This is a schematic diagram showing the first dispersion involved in this embodiment.

[0128] In step S1 of this embodiment, the quantum dot dispersion LQ can be prepared using the same method as in the previous embodiment. On the other hand, in step S1 of this embodiment, the first dispersion is prepared through a mixing process. Figure 12 The mixing process is described below.

[0129] In the mixing process involved in this embodiment, the preparation Figure 12 The dispersions LA and LB are shown in step S1-1.

[0130] Dispersion LA is a dispersion in solvent 54 of precursor 51 and precursor ligand 52, which serve as the first precursor. Solvent 54 is a polar solvent such as N,N-dimethylformamide (DMF). Dispersion LA may further contain halogen source 53 in solvent 54. Dispersion LA can be prepared by adding separately synthesized precursor 51, precursor ligand 52, and halogen source 53 to solvent 54.

[0131] Dispersion LB is, for example, a dispersion in which multiple quantum dots 30 coordinated to organic ligand 41 are dispersed in solvent 55. Specifically, dispersion LB, except that it contains solvent 55 instead of solvent 50, can be the same dispersion as quantum dot dispersion LQ, and can be prepared by the same method as quantum dot dispersion LQ. Solvent 55 is a nonpolar solvent such as octane. Because solvent 54 and solvent 55 have different polarities, when dispersions LA and LB are left to stand in a container, as... Figure 12 As shown, the liquid in the container is separated into a layer of dispersion LA and a layer of dispersion LB.

[0132] Next, dispersions LA and LB are thoroughly mixed and stirred in the aforementioned container. During stirring, a portion of the organic ligands 41 coordinated to the quantum dot 30 is replaced by precursor ligands 52. This makes it easier for the quantum dot 30 to disperse from solvent 55 into solvent 54, as... Figure 12 As shown in steps S1-2, quantum dots 30 are transferred from dispersion LB to dispersion LA.

[0133] Furthermore, during stirring, in the dispersion LA, precursor 51 and precursor ligand 52 react along the aforementioned reaction process, transforming into byproducts around quantum dot 30. Therefore, as... Figure 12 As shown in steps S1-2, a quantum dot structure 60 containing quantum dots 30 is synthesized by mixing dispersion LA and dispersion LB. For example, the quantum dot structure 60 has an appendage 61 that coats the quantum dots 30. Additionally, in step S1-2, the quantum dot structure 60 can be transferred to the interface between dispersion LA and dispersion LB.

[0134] Here, the additive 61 formed in the mixing process may have the same composition as the additive 40 described above. Furthermore, in this specification, "the two components have the same composition" does not necessarily mean that they have completely identical compositions. For example, when both additive 40 and additive 61 contain two types of atoms, if the ratio of one atom to the other atom differs by less than 1%, they can be considered to have the same composition.

[0135] Furthermore, the term "atom" in this disclosure refers not only to the case where it exists as a single atom. The term "atom" in this disclosure also includes cases where it exists in a molecular form containing two or more atoms, in a complex form, in a compound form, or in an ionic form. However, the term "atom" in this disclosure does not limit the form in which other atoms exist. That is, metal atoms also include cases where they exist in a compound form containing metal atoms or in the form of metal ions. Regardless of the form in which metal atoms exist, as long as their presence in a substance can be determined through analysis, the substance can be considered to contain metal atoms. Next, for example, quantum dot structures 60 are extracted from dispersion LA by centrifuging at 4000 rpm for 5 minutes. During centrifugation of dispersion LA, undesirable solvents such as ethyl acetate or acetone can be added to dispersion LA to precipitate quantum dot structures 60. Then, the precipitate containing quantum dot structures 60 is dispersed in solvent 50 in another container. Here, by adding precursor 51 and halogen source 53 to this dispersion, a preparation is prepared... Figure 13 The first dispersion L1A is shown.

[0136] like Figure 13 As shown, the first dispersion L1A prepared in this embodiment contains a quantum dot structure 60, a precursor 51, and a halogen source 53 dispersed in a solvent 50. In other words, the first dispersion L1A differs from the first dispersion L1 only in that it contains an additive 61 that coats the quantum dots 30, instead of the precursor ligand 52 coordinated to the quantum dots 30.

[0137] In the formation process of the light-emitting layer 23 according to this embodiment, steps S2 to S5 are performed sequentially after step S1. Here, steps S2 to S5 of the light-emitting layer 23 according to this embodiment are implemented by the same method as steps S2 to S5 of the light-emitting layer 23 according to the previous embodiment, except for the contents of steps S4 and S5.

[0138] Specifically, in step S4 of this embodiment, the first dispersion L1A is coated onto the first light-emitting layer 23A. Next, in step S5 of this embodiment, the coated first dispersion L1A is heated to convert the precursor 51 in the first dispersion L1A into the additive 40.

[0139] Here, in the first dispersion L1A after coating, the precursor 51 is located around the quantum dot structure 60. Therefore, the additive 40 derived from the precursor 51 in step S5 forms around the additive 61 of the quantum dot structure 60. In addition, as described above, the additive 61 has the same composition as the additive 40.

[0140] As a result, based on the same reasons explained in step S5 of the previous embodiment, a second light-emitting layer 23B is also formed on the first light-emitting layer 23A in step S5 of this embodiment, and the formation process of the light-emitting layer 23 is completed.

[0141] According to the method involved in this embodiment, it is also possible to manufacture a display device 1 having a light-emitting element 2, which improves the luminous efficiency and enhances the reliability of each layer between the anode 21 and the cathode 25 while reducing some of the degradation of the quantum dot 30 by the additive 40.

[0142] [Third Implementation Method] <Light-emitting layer containing semiconductors> Figure 14 This is a schematic side cross-sectional view of the display device 4 according to this embodiment. Compared with the display device 1 according to the previous embodiment, the display device 4 according to 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. Except for the above points, the display device 4 has the same configuration as the display device 1.

[0143] Reference Figure 15 and combined Figure 14 A more detailed explanation of the light-emitting layer 26 is provided. Figure 15 yes Figure 14 The cross-section shown is a magnified schematic view of the area near the light-emitting layer 26 in the hole transport layer 22 and the electron transport layer 24, particularly showing... Figure 14 A schematic diagram of region E2 shown.

[0144] The light-emitting layer 26 includes a first light-emitting layer 26A and a second light-emitting layer 26B that are sequentially stacked from the hole transport layer 22 side.

[0145] The first light-emitting layer 26A comprises a plurality of first quantum dots 31 and a semiconductor 42. Specifically, in this embodiment, the semiconductor 42 is included between the layer adjacent to the anode 21 side of the first light-emitting layer 26A (in other words, the hole transport layer 22) and the first quantum dots 31. Therefore, the first quantum dots 31 and the layer adjacent to the anode 21 side of the light-emitting layer 26, in other words, the hole transport layer 22, are adjacent to each other via the semiconductor 42. However, some of the first quantum dots 31 may be in direct contact with the hole transport layer 22.

[0146] Semiconductor 42 may cover a plurality of first quantum dots 31 or fill between at least two first quantum dots 31. Semiconductor 42 has at least higher conductivity than addendum 40. Semiconductor 42 may contain at least one of zinc sulfide, gallium sulfide, magnesium sulfide, cadmium sulfide, tin sulfide, indium sulfide, and manganese sulfide. In particular, from the viewpoint of reducing contact resistance with the first quantum dots 31, semiconductor 42 may contain the same material as the material contained in the outermost periphery of the first quantum dots 31, such as in the shell.

[0147] The second light-emitting layer 26B includes second quantum dots 32 located closer to the cathode 25 than the first quantum dot 31, and additional material 40 filling the spaces between the plurality of second quantum dots 32. In other words, the second light-emitting layer 26B may have the same configuration as the second light-emitting layer 23B described in the previous embodiment.

[0148] In the light-emitting layer 26 of the light-emitting element 5 according to this embodiment, the first quantum dot 31 is adjacent to the semiconductor 42. Therefore, in the light-emitting element 5 according to this embodiment, the effective resistance of the virtual diode D formed between the hole transport layer 22 and the first quantum dot 31 is lower than that in the case where there is an insulator such as an additive 40 between the hole transport layer 22 and the first quantum dot 31.

[0149] Therefore, in the light-emitting element 5 according to this embodiment, hole transport from the hole transport layer 22 to the first quantum dot 31 is achieved more efficiently. Thus, when the light-emitting element 5 is driven, holes injected into the light-emitting layer 26 are efficiently injected into the first quantum dot 31 and efficiently transported to the central side of the light-emitting layer 26 in the thickness direction via the first quantum dot 31.

[0150] Furthermore, the light-emitting layer 26 in this embodiment includes a second light-emitting layer 26B having the same structure as the second light-emitting layer 23B in the previous embodiment. Therefore, the light-emitting element 2 can more efficiently protect the quantum dot 30, which contains the second quantum dot 32, which is more difficult to generate with exciton energy transfer compared to the first quantum dot 31, thereby improving the luminous efficiency.

[0151] Therefore, for the same reasons explained in the previous embodiment, the light-emitting element 5 reduces some of the degradation of the quantum dot 30 by means of the additive 40, while improving luminous efficiency and enhancing the reliability of each layer between the anode 21 and the cathode 25. The display device 4 equipped with the light-emitting element 5 achieves power saving and long lifespan. In particular, in the light-emitting layer 26, the first quantum dot 31 is adjacent to the hole transport layer 22 through the semiconductor 42. As a result, the light-emitting element 5 can protect the first quantum dot 31 from foreign matter such as moisture that seeps in from the hole transport layer 22 side through the semiconductor 42, thereby further improving the reliability of the light-emitting layer 26.

[0152] Furthermore, the light-emitting layer 26 includes a semiconductor 42 filled between at least two first quantum dots 31. Therefore, the light-emitting element 2 protects the first quantum dots 31 through the semiconductor 42 while improving the efficiency of injecting holes into the first quantum dots 31. From the viewpoint of balancing the protective effect of the semiconductor 42 on the first quantum dots 31 and the efficiency of injecting holes into the first quantum dots 31, the thickness T2 of the semiconductor 42 located between the hole transport layer 22 and the first quantum dots can be 6 nm or more and 12 nm or less.

[0153] <Method for forming a light-emitting layer containing semiconductors> The manufacturing method of the display device 4 according to this embodiment is the same as that of the aforementioned manufacturing method of the display device 1, except that the method for forming the light-emitting layer 23 is replaced with the method for forming the light-emitting layer 26. (Refer to...) Figures 16 to 18 The method for forming the light-emitting layer 26 according to this embodiment will be described in detail. Figure 16 This is a flowchart illustrating the method for forming the light-emitting layer 26 according to this embodiment. Figure 17 This is a schematic diagram showing the second dispersion liquid used in the method for forming the light-emitting layer 26 according to this embodiment, which will be described later. Figure 18 This is a cross-sectional view showing a part of the method for forming the light-emitting layer 26 according to this embodiment.

[0154] In the method for forming the light-emitting layer 26 according to this embodiment, a first dispersion and a second dispersion are first prepared (step S6). The preparation of the first dispersion can be carried out by the same method as the preparation method of the first dispersion L1 or the first dispersion L1A described above.

[0155] Reference Figure 17 The second dispersion according to this embodiment will be described in detail. The second dispersion L2 is a dispersion in solvent 56 of a plurality of quantum dots 30 and a precursor 57 serving as a second precursor. The second dispersion L2 may contain ligands 58 coordinated to the quantum dots 30. The second dispersion L2 may contain a catalyst that promotes the conversion of the precursor 57 to the semiconductor 42. Solvent 56 is a polar solvent, for example, it may contain DMF.

[0156] Precursor 57 is a precursor to semiconductor 42, which is converted into semiconductor 42 by the method described later. For example, when semiconductor 42 contains metal atoms, precursor 57 may contain a metal acetate, metal nitrate, or metal halide as a metal source. Alternatively, when semiconductor 42 contains sulfur atoms, precursor 57 may contain at least one of thiourea, N-methylthiourea, 1,3-dimethylthiourea, N,N'-dimethylthiourea, tetramethylthiourea, or thioacetamide as a sulfur source. Or, precursor 57 may contain a metal complex of a metal atom coordinated with thiourea, N-methylthiourea, 1,3-dimethylthiourea, N,N'-dimethylthiourea, tetramethylthiourea, or thioacetamide.

[0157] Ligand 58 may contain halide ions or function as a catalyst to promote the conversion of precursor 57 to semiconductor 42. From the viewpoint that the coordinated quantum dot 30 can be easily dispersed in solvent 56, which is a polar solvent, ligand 58 may be polar. On the other hand, ligand 58 may have the same structure as organic ligand 41; in other words, it may be a carbon chain with a coordinating functional group at one end.

[0158] The second dispersion L2 can be prepared by adding separately synthesized quantum dots 30, precursor 57, and ligand 58 to solvent 56. Alternatively, the second dispersion L2 can be prepared by adding precursor 57 to solvent 56 containing quantum dots 30 coordinated by ligand 58. The quantum dots 30 coordinated by ligand 58 can be obtained by stirring a dispersion containing quantum dots 30 coordinated by organic ligand 41 and a dispersion containing ligand 58, thereby replacing the ligand coordinated on the quantum dots 30 with ligand 58.

[0159] In the manufacturing method of the display device 4 according to this embodiment, after forming the hole transport layer 22 and preparing the first dispersion L1 and the second dispersion L2, a film-forming process of the light-emitting layer 26 is performed. Except Figure 16 In addition, refer to Figure 18 The film-forming process of the light-emitting layer 26 will be described in more detail.

[0160] In the film formation process of the light-emitting layer 26, firstly, a laminate containing each layer of the substrate 3 is used as a substrate, and a second dispersion liquid L2 is coated on the substrate (step S7). For example, as Figure 18 As shown in step S7, the second dispersion L2 is coated on the hole transport layer 22 by any method including conventionally known coating methods such as spin coating.

[0161] Next, the precursor of semiconductor 42 containing precursor 57 in the second dispersion L2 is converted into semiconductor 42 (step S8). For example, the precursor 57 in the second dispersion L2 is reacted by heating each part of the substrate 3 containing the coated second dispersion L2 at a temperature of 80°C to 500°C for more than 1 minute.

[0162] In step S8, the precursor 57 in the coated second dispersion L2 is located around the quantum dots 30. Therefore, in step S8, the converted precursor 57 is transformed into a semiconductor 42 filling the spaces between the quantum dots 30. Thus, as... Figure 18 As shown in step S8, a first light-emitting layer 26A comprising a plurality of first quantum dots 31 covered by semiconductor 42 is formed on the hole transport layer 22.

[0163] Next, a second light-emitting layer 26B is formed on the first light-emitting layer 26A. The second light-emitting layer 26B, except that the first dispersion L1 or the first dispersion L1A is coated on the first light-emitting layer 26A, can be formed using the same method as steps S4 and S5 described above. As described above, as... Figure 18 As shown in step S5, a light-emitting layer 26 is formed.

[0164] According to the method involved in this embodiment, a display device 4 having a light-emitting element 5 can be manufactured, which improves the light-emitting efficiency while protecting the first quantum dot 31 by the semiconductor 42 and the second quantum dot 32 by the additive 40.

[0165] Furthermore, in the above method, after the formation of the second light-emitting layer 26B, the first quantum dot 31 is protected by the semiconductor 42. Therefore, according to the above method, the degradation of the first quantum dot 31 during the manufacturing process of the display device 4 can be further reduced. Additionally, in the above method, the semiconductor 42 can be formed by the conversion of the precursor 57. Therefore, according to the above method, the first light-emitting layer 23A comprising the semiconductor 42 filled between the plurality of first quantum dots 31 can be formed in a simpler manner.

[0166] [Fourth Implementation Method] <Inverted structure light-emitting element> Figure 19 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 according to this embodiment includes a light-emitting element 7 instead of a light-emitting element 2. Compared with the light-emitting element 2, the light-emitting element 7 includes, from the substrate 3 side, a cathode 25, an electron transport layer 24, a light-emitting layer 27, a hole transport layer 22, and an anode 21 in sequence. In other words, compared with the light-emitting element 2, the light-emitting element 7 includes a light-emitting layer 27 instead of a light-emitting layer 23, and the stacking order of each layer from the anode 21 to the cathode 25 is reversed. In other words, in this embodiment, the cathode 25 is located on the side closer to the substrate 3 than the light-emitting layer 27. Except for the above points, the display device 6 has the same configuration as the display device 1.

[0167] Therefore, in this embodiment, the cathode 25 can be formed in an island shape for each sub-pixel when viewed from above, or it can be electrically connected to each pixel circuit PC of the substrate 3.

[0168] On the other hand, anode 21 can be formed for multiple sub-pixels together.

[0169] For details regarding the luminescent layer 27, please refer to [link / reference]. Figure 20 and Figure 19 To provide a more detailed explanation. Figure 20 yes Figure 19 The cross-section shown is a magnified schematic view of the area near the light-emitting layer 27 in the hole transport layer 22 and the electron transport layer 24, particularly magnified. Figure 19 A schematic diagram of region E3 is shown.

[0170] The light-emitting layer 27 includes a plurality of quantum dots 30 and an additive 40. The quantum dots 30 include a first quantum dot 31 and a second quantum dot 32 located on the side closer to the cathode 25 than the first quantum dot 31.

[0171] The light-emitting layer 27 is adjacent to the lower surface 22U of the hole transport layer 22 on the anode 21 side. Specifically, in this embodiment, at least a portion of the first quantum dot 31 is adjacent to the hole transport layer 22. In other words, the first quantum dot 31 is in direct contact with or adjacent to the layer of the light-emitting layer 27 adjacent to the anode 21 side.

[0172] The appendage 40 can form a portion of the outer edge of the light-emitting layer 27 adjacent to the upper surface 24T of the electron transport layer 24. Therefore, the light-emitting layer 27 includes the appendage 40 between the electron transport layer 24 and the second quantum dot 32.

[0173] Furthermore, in the light-emitting layer 27, the additive 40 covers a plurality of quantum dots 30. In particular, the additive 40 involved in this embodiment not only fills between at least two second quantum dots 32, but also between at least two first quantum dots 31. Therefore, as long as at least a portion of the first quantum dots 31 are adjacent to the hole transport layer 22, a portion of the first quantum dots 31 can also be covered by the additive 40; in other words, the additive 40 can also be located between the hole transport layer 22 and a portion of the first quantum dots 31.

[0174] In this embodiment, the light-emitting layer 27 includes an additive 40, and the first quantum dot 31 is adjacent to the hole transport layer 22. Therefore, for the same reasons as described above, the light-emitting element 7 reduces some of the degradation of the quantum dot 30 by the additive 40, while simultaneously improving luminous efficiency and the reliability of each layer between the anode 21 and the cathode 25. The display device 6 equipped with the light-emitting element 7 achieves power saving and long lifespan.

[0175] Specifically, in this embodiment, the appendage 40 of the light-emitting layer 27 is filled not only between at least two second quantum dots 32, but also between at least two first quantum dots 31. Therefore, the light-emitting element 7 can more efficiently protect both the first quantum dots 31 and the second quantum dots 32 through the appendage 40.

[0176] <Manufacturing Method of Inverted Light-Emitting Element> Reference Figure 21 The manufacturing method of the display device 6 according to this embodiment will be described. Figure 21 This is a flowchart illustrating the manufacturing method of the display device 6 according to this embodiment.

[0177] In the manufacturing method of the display device 6 according to this embodiment, the substrate 3 is first prepared by the same method as step S21 described above. Then, steps S26 and S25 are performed sequentially to form a cathode 25 and an electron transport layer 24 on the substrate 3.

[0178] Next, the light-emitting layer 27 is formed (step S27). For the method of forming the light-emitting layer 27, please refer to... Figure 22 , Figure 23 To provide a more detailed explanation. Figure 22 This is a flowchart illustrating the method for forming the light-emitting layer 27 according to this embodiment. Figure 23 This is a process cross-sectional view showing a part of the method for forming the light-emitting layer 27 according to this embodiment, namely the film-forming process of the light-emitting layer 27.

[0179] In the process of forming the light-emitting layer 27 according to this embodiment, the preparation of the third dispersion is first performed (step S9). The third dispersion can be prepared by the same method as the preparation of the first dispersion L1 or the first dispersion L1A described above. In other words, the third dispersion according to this embodiment can have the same structure as the first dispersion L1 or the first dispersion L1A described above. In this embodiment, an example in which the third dispersion has the same structure as the first dispersion L1 will be described.

[0180] Next, the film-forming process of the light-emitting layer 27 is performed. In the film-forming process of the light-emitting layer 23, firstly, using a laminate containing each layer of the substrate 3 as a substrate, a third dispersion liquid is coated onto this substrate (step S10). For example, as... Figure 23 As shown in step S10, the third dispersion L3 is coated on the electron transport layer 24 by any method including conventionally known coating methods such as spin coating.

[0181] Next, the precursor of the additive 40 containing precursor 51 and precursor ligand 52 in the third dispersion L3 is converted into additive 40 (step S11). For example, the precursor 51 and precursor ligand 52 in the third dispersion L3 are reacted by heating each part of the substrate 3 containing the coated third dispersion L3 at 100°C for 30 minutes.

[0182] Here, in the third dispersion L3 after coating, precursor 51 and precursor ligand 52 are located around quantum dot 30. Therefore, as Figure 23 As shown in step S11, a light-emitting layer 28 having an appendage 40 covering a plurality of quantum dots 30 is formed on the electron transport layer 24.

[0183] In the quantum dot 30 of the light-emitting layer 28, there is an attachment 40 between the quantum dot 30 located on the side of the electron transport layer 24 and the electron transport layer 24. Therefore, this quantum dot 30 becomes a second quantum dot 32. On the other hand, in the quantum dot 30 of the light-emitting layer 28, there is an attachment 40 above the first quantum dot 31 located on the side opposite to the electron transport layer 24, in other words, on the side of the upper surface 28T of the light-emitting layer 28.

[0184] Next, a portion of the appendage 40 on the light-emitting layer 28 is removed (step S12). In particular, in step S12, at least a portion of the appendage 40 that is closer to the opposite side of the substrate 3 than the first quantum dot 31, in other words, closer to the upper surface 28T of the light-emitting layer 28 than the first quantum dot 31, is removed.

[0185] In step S12, the admixture 40 can be removed, for example, by exposing the upper surface 28T of the light-emitting layer 28 to diluted ammonium fluoride. In step S12, the admixture 40 is removed, for example, until the outermost surface portion of the upper surface 28T of the light-emitting layer 28 of the first quantum dot 31 is exposed. Thus, as... Figure 23 As shown in step S12, at least a portion of the light-emitting layer 27 of the first quantum dot 31 formed at the upper surface 27T is exposed.

[0186] Back Figure 21 Referring to step S23, after forming the light-emitting layer 27, a hole transport layer 22 is formed on the light-emitting layer 27 using the same method. Here, at least a portion of the first quantum dot 31 is exposed at the upper surface 27T of the light-emitting layer 27. Therefore, through the formation of the hole transport layer 22, the first quantum dot 31 exposed at the upper surface 27T of the light-emitting layer 27 is adjacent to the hole transport layer 22.

[0187] Next, an anode 21 is formed on the hole transport layer 22 using the same method as in step S22. As described above, the display device 6 according to this embodiment is manufactured.

[0188] The method described in this embodiment enables the manufacture of a display device 6 equipped with a light-emitting element 7, which improves luminous efficiency while protecting both the first quantum dot 31 and the second quantum dot 32 with the attachment 40. Specifically, the light-emitting element 7 of this embodiment has a cathode 25 located closer to the substrate 3 than the light-emitting layer 27. Therefore, the method described above enables the manufacture of a light-emitting element 7 equipped with a light-emitting layer 23, which protects both the first quantum dot 31 and the second quantum dot 32 with the attachment 40.

[0189] However, the manufacturing method of the display device 6 according to this embodiment is not limited to the method described above. For example, in this embodiment, after step S11 is completed, the third dispersion liquid L3 may be coated again, and then the precursor 51 in the third dispersion liquid L3 may be converted into the additive 40. In this case, the reaction time of the precursor 51 in the third dispersion liquid L3 may be shortened to about one-tenth of that in step S11. As a result, a light-emitting layer 27 may be formed with a thickness of the additive 40 formed on the upper surface 27T side that is smaller than the thickness of the additive 40 formed on the electron transport layer 24 side.

[0190] 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 means disclosed in different embodiments are also included within the technical scope of this disclosure. Furthermore, by combining the technical means disclosed in each embodiment, new technical features can be formed.

[0191] Explanation of reference numerals in the attached figures 1: Display device; 2: Light-emitting element; 3: Substrate; 21: Anode; 22: Hole transport layer; 23: Emissive layer; 25: Cathode; 30: Quantum dots; 31: The First Quantum Dot; 32: The second quantum dot; 40: Add-ons; 41: Organic ligands; 42: Semiconductor; 51: Precursor (first precursor); 52: Progenitor ligand (first precursor); 57: Precursor (Second Precursor); L1: First dispersion; L2: Second dispersion; L3: Third dispersion.

Claims

1. A light-emitting element, characterized in that, It possesses: anode; Cathode, which is opposite to the anode; and A light-emitting layer is located between the anode and the cathode. The light-emitting layer comprises a first quantum dot and additives. The first quantum dot is in direct contact with the light-emitting layer on the anode side of the adjacent layer, or is adjacent to it through an organic ligand, or is adjacent to it through a semiconductor.

2. The light-emitting element according to claim 1, characterized in that, The first quantum dot is in direct contact with the light-emitting layer on the anode side of the layer adjacent to it.

3. The light-emitting element according to claim 1, characterized in that, The first quantum dot and the light-emitting layer are adjacent to each other on the anode side, separated by the organic ligand.

4. The light-emitting element according to claim 1, characterized in that, The first quantum dot and the light-emitting layer are adjacent to each other on the anode side, separated by the semiconductor.

5. The light-emitting element according to any one of claims 1 to 4, characterized in that, The light-emitting layer contains a second quantum dot that is closer to the cathode side than the first quantum dot. The light-emitting layer includes the additive between the layer adjacent to the cathode side of the light-emitting layer and the second quantum dot.

6. The light-emitting element according to claim 5, characterized in that, The thickness of the additive located between the layer adjacent to the cathode side of the light-emitting layer and the second quantum dot is greater than 1 nm and less than 5 nm.

7. The light-emitting element according to claim 5 or 6, characterized in that, The light-emitting layer contains a plurality of the second quantum dots. The additive is filled between at least two of the second quantum dots.

8. The light-emitting element according to any one of claims 1 to 7, characterized in that, The light-emitting layer contains the semiconductor between the layer adjacent to the anode side of the light-emitting layer and the first quantum dot.

9. The light-emitting element according to claim 8, characterized in that, The light-emitting layer comprises a plurality of the first quantum dots. The semiconductor is filled between at least two of the first quantum dots.

10. The light-emitting element according to claim 8 or 9, characterized in that, The semiconductor comprises at least one selected from zinc sulfide, gallium sulfide, magnesium sulfide, cadmium sulfide, tin sulfide, indium sulfide, and manganese sulfide.

11. The light-emitting element according to any one of claims 1 to 7, characterized in that, The light-emitting layer comprises a plurality of the first quantum dots. The additive is filled between at least two of the first quantum dots.

12. The light-emitting element according to any one of claims 1 to 11, characterized in that, The attachment is insulating.

13. The light-emitting element according to claim 12, characterized in that, The additive comprises at least one selected from 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.

14. The light-emitting element according to claim 13, characterized in that, The additives include at least one of silicon oxide, aluminum oxide, and silicon nitride.

15. The light-emitting element according to any one of claims 1 to 14, characterized in that, It has a hole transport layer located between the anode and the light-emitting layer, and adjacent to the anode side of the light-emitting layer.

16. The light-emitting element according to claim 15, characterized in that, The hole transport layer contains organic materials.

17. The light-emitting element according to claim 16, characterized in that, The hole transport layer includes at least one of PVK and TPD.

18. A display device, characterized in that, It has a substrate, and on the substrate are a plurality of light-emitting elements as described in any one of claims 1 to 17.

19. The display device according to claim 18, characterized in that, The anode is located closer to the substrate than the light-emitting layer.

20. The display device according to claim 18, characterized in that, The cathode is located closer to the substrate than the light-emitting layer.

21. A method for manufacturing a light-emitting element, the light-emitting element comprising an anode, a cathode opposite to the anode, and a light-emitting layer located between the anode and the cathode, characterized in that, The manufacturing method includes forming the light-emitting layer. The light-emitting layer comprises a first quantum dot and additives. The first quantum dot is in direct contact with the light-emitting layer on the anode side of the adjacent layer, or is adjacent to it through an organic ligand, or is adjacent to it through a semiconductor.

22. The method for manufacturing a light-emitting element according to claim 21, characterized in that, The formation of the light-emitting layer includes: Forming a first quantum dot layer containing the first quantum dot; A first dispersion containing the precursor of the aforementioned additive, namely the first precursor, is coated onto a substrate; and The first precursor in the coated first dispersion is converted into the additive.

23. The method for manufacturing a light-emitting element according to claim 21, characterized in that, The formation of the light-emitting layer includes: A second dispersion containing the first quantum dot and the semiconductor precursor, i.e., the second precursor, is coated onto a substrate. The second precursor in the coated second dispersion is converted into the semiconductor; A first dispersion containing the precursor of the aforementioned additive, namely the first precursor, is coated onto a substrate; and The first precursor in the coated first dispersion is converted into the additive.

24. The method for manufacturing a light-emitting element according to claim 21, characterized in that, The formation of the light-emitting layer includes: A third dispersion containing the first quantum dot and the additive, i.e., the first precursor, is coated onto a substrate. The first precursor in the coated third dispersion is converted into the additive; and Remove at least a portion of the appendage that is closer to the opposite side of the substrate than the first quantum dot.

Images