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

Abstract

A light-emitting element (2) comprises one or multiple functional layers (22, 23, 24) positioned between an anode (21) and a cathode (25). The one or multiple functional layers include: functional materials (31R, 31G, 31B); and an additive (41) and an organic polymer (51) positioned around the functional materials.

Description

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

[0001] This disclosure relates to a light-emitting element containing quantum dots (semiconductor nanoparticles), a display device equipped with the light-emitting element, and a method for manufacturing the light-emitting element.

[0002] Patent Document 1 discloses a light-emitting device in which quantum dots are used as the light-emitting material in the light-emitting layer.

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

[0004] In the light-emitting element described in Patent Document 1, deterioration of the material may occur due to the intrusion of foreign substances such as moisture or oxygen into the material such as quantum dots, or due to the conduction of heat into the material. In response to this, it is conceivable to form an adduct such as a metal oxide around the material of a specific layer in the above light-emitting element to protect the material from foreign substances or heat. However, even in this case, defects such as porosity may occur in the adduct, and consequently, the efficiency of charge transport in the layer containing the adduct may decrease due to such defects.

[0005] A light-emitting element according to one aspect of the present disclosure comprises an anode, a cathode facing the anode, and one or more functional layers located between the anode and the cathode and including a light-emitting layer containing a light-emitting material, wherein the one or more functional layers include a functional material, an adduct and an organic polymer located around the functional material.

[0006] A method for manufacturing a light-emitting element according to one aspect of the present disclosure is a method for manufacturing a light-emitting element comprising: forming an anode; forming a cathode facing the anode; and forming one or more functional layers located between the anode and the cathode and including a light-emitting layer containing a light-emitting material, wherein the formation of the one or more functional layers includes forming layers containing a functional material, an adduct located around the functional material, and an organic polymer.

[0007] This reduces the degradation of the functional material in the light-emitting element while also reducing the decrease in the mechanical strength of the layer containing the functional material.

[0008] This is a schematic side cross-sectional view of a display device according to an embodiment. This is a schematic diagram of a display device according to an embodiment. This is a schematic side cross-sectional view of a display device according to a modified example 1. This is a schematic side cross-sectional view of a display device according to a modified example 2. This is a schematic side cross-sectional view of a red light-emitting layer according to an embodiment. This is a schematic diagram showing an example of an adduct filling the space between quantum dots according to an embodiment. This is a schematic diagram showing an example of the positional relationship between quantum dots and porosity according to an embodiment. This is a flowchart of a method for manufacturing a display device according to an embodiment. This is a flowchart of a method for forming a light-emitting layer according to an embodiment. This is a step cross-sectional view of a method for forming a light-emitting layer according to an embodiment. This is another a schematic side cross-sectional view of a display device according to a comparative form. This is a schematic diagram showing how carriers are transported in the light-emitting layers according to the comparative form and the embodiment, respectively. This is a graph showing the characteristics of the light-emitting elements according to the example and the comparative example, respectively.

[0009] [Embodiments] Embodiments of the present disclosure will be described below with reference to the drawings. In each drawing, similar components are denoted by the same reference numeral and their descriptions are omitted. Also, in this disclosure, for the sake of simplicity of illustration, the scale may differ in the drawings for components denoted by the same reference numeral, and different hatching may be applied. However, the components shown in each drawing of this disclosure are merely examples, and their scale is not limited to that shown in the drawing. Furthermore, even for components denoted by different hatching in this disclosure, components denoted by the same reference numeral have the same configuration as described above. In addition, in each drawing of this disclosure, if two components have substantially the same shape but different compositions, they may be denoted by different reference numerals but have the same hatching.

[0010] <Display Device: Overview> Figure 2 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 a television or smartphone display. The display device 1 comprises a display unit DA including a plurality of subpixels and a driver circuit DR that drives the plurality of subpixels. Each of the plurality of subpixels comprises a light-emitting element 2, which will be described later, and a pixel circuit PC that drives the light-emitting element 2.

[0011] In particular, the display device 1 includes a red subpixel XR, a green subpixel XG, and a blue subpixel XB in the display unit DA. The red subpixel XR is provided with a red light-emitting element 2R that emits red light, the green subpixel XG is provided with a green light-emitting element 2G that emits green light, and the blue subpixel XB is provided with a blue light-emitting element 2B that emits blue light, each as a light-emitting element 2.

[0012] The display device 1 performs display on the display unit DA by controlling the light emitted from each of the multiple light-emitting elements 2 formed on the display unit DA via the driver circuit DR and the pixel circuit PC. In particular, the display device 1 may perform full-color display by controlling the red light from the red subpixel XR, the green light from the green subpixel XG, and the blue light from the blue subpixel XB, respectively.

[0013] <Light-emitting element: Overview> The structure of the display unit DA of the display device 1, and in particular the structure of the light-emitting element 2, will be described in more detail with reference to Figure 1. Figure 1 is a schematic side cross-sectional view of the display device 1 according to this embodiment. All schematic side cross-sectional views of the display device 1 according to this disclosure, including Figure 1, show a cross-section perpendicular to the display surface of the display device 1 and passing through the red subpixel XR, the green subpixel XG, and the blue subpixel XB.

[0014] As shown in Figure 1, the display device 1 according to this embodiment comprises a plurality of light-emitting elements 2 and a substrate 3 in the display unit DA, and in particular, a plurality of light-emitting elements 2 are provided on the substrate 3. The display device 1 has a structure in which each layer of light-emitting elements 2 is stacked on a substrate 3 on which, for example, a TFT (Thin Film Transistor) (not shown) is formed as a pixel circuit PC. In this specification, the direction from the light-emitting elements 2 to the substrate 3 of the display device 1 is described as the "downward direction," and the direction opposite to the downward direction is described as the "upward direction."

[0015] The light-emitting element 2 comprises an anode 21, a hole transport layer 22, a light-emitting layer 23, an electron transport layer 24, and a cathode 25, in this order from the substrate 3 side. In other words, the light-emitting element 2 comprises an anode 21, a cathode 25 facing the anode 21, and between the anode 21 and the cathode 25, a hole transport layer 22, a light-emitting layer 23, and an electron transport layer 24.

[0016] In particular, the light-emitting element 2 includes a light-emitting layer 23 between the anode 21 and the cathode 25, which contains at least one light-emitting material described later. As described later, the light-emitting layer 23 has the function of emitting light due to the light-emitting material it contains. Also as described later, the hole transport layer 22 has the function of transporting holes from the anode 21 to the light-emitting layer 23, and the electron transport layer 24 has the function of transporting electrons from the cathode 25 to the light-emitting layer 23. For this reason, the hole transport layer 22, the light-emitting layer 23, and the electron transport layer 24 may each be referred to as a functional layer in this disclosure.

[0017] The following describes in more detail the configuration of each layer of the light-emitting element 2.

[0018] <Light-emitting element: electrodes> The anode 21 and cathode 25 contain a conductive material and are electrically connected to the hole transport layer 22 and electron transport layer 24, respectively. The anode 21 is formed in an island shape for each subpixel, and specifically includes anode 21R located at the red subpixel XR, anode 21G located at the green subpixel XG, and anode 21B located at the blue subpixel XB. Each of the anodes 21 is electrically connected to the pixel circuit PC of each subpixel. Anodes 21R, 21G, and 21B may be partitioned by a bank BK located on the substrate 3 and containing an organic insulating material such as polyimide. On the other hand, the cathode 25 may be formed in common for multiple subpixels, for example.

[0019] At least one of the anode 21 and 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 called ZAO), BZO (boron-doped zinc oxide), or FTO (fluorine-doped tin oxide). The transparent electrode may be formed by sputtering or the like. In addition, either the anode 21 or the cathode 25 may contain a metallic material, and as the metallic material, Al, Cu, Au, Ag, or Mg alone or alloys thereof, which have high reflectivity of visible light, are preferred.

[0020] <Light-emitting element: Charge transport layer> The hole transport layer 22 has the function of transporting holes from the anode 21 to the light-emitting layer 23, and is a layer containing multiple hole transport materials as multiple functional materials. In this embodiment, the material of the hole transport layer 22 can be an organic or inorganic material that has been conventionally used in light-emitting elements including quantum dots. For example, conductive compounds such as polyvinylcarbazole (PVK), [N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)-benzidine] (TPD), 4,4'-bis(carbazole-9-yl)biphenyl (CBP), polyphenylenevinylene (PPV), a composite of poly(3,4-ethylenedioxythiophene) (PEDOT) and polystyrene sulfonic acid (PSS) (PEDOT-PSS), or poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4'-(N-4-sec-butylphenyl)diphenylamine)]) (TFB) can be used as the organic material for the hole transport layer 22. In addition, other organic materials for the hole transport layer 22 include polytrialylamine semiconductor (PTAA) or [dipyradino[2,3-f:2',3'-h]quinoxaline-2,3,6,7,10,11-hexacarbonnitrile] (HAT-CN). As an inorganic material for the hole transport layer 22, molybdenum oxide (MoO) can be used. ３ ), nickel oxide (NiO), chromium oxide (Cr ２ O ３ ), magnesium oxide (MgO), lanthanum nickel oxide (LaNiO) ３ ), or tungsten oxide (WO ３Metal oxides such as ) can be used. In particular, as the material for the hole transport layer 22, a material with a small electron affinity, which is the energy difference (absolute value) between the vacuum level and the bottom of the conductor (CBM), is preferred from the viewpoint of reducing electron outflow from the light-emitting layer 23 to the hole transport layer 22. Furthermore, as the material for the hole transport layer 22, a material whose ionization potential, which is the energy difference (absolute value) between the vacuum level and the top of the valence band (VBM), is about the same as the ionization potential of the light-emitting material of the light-emitting layer 23 is preferred. This makes it possible for the light-emitting element 2 to improve the efficiency of hole transport from the anode 21 to the hole transport layer 22 and from the hole transport layer 22 to the light-emitting layer 23. Note that the chemical formulas of the compounds in this disclosure are representative examples, and the composition ratios described in the chemical formulas may be stoichiometric or not. In this embodiment, the hole transport layer 22 may also be formed on the side and top surfaces of the bank BK.

[0021] The electron transport layer 24 has the function of transporting electrons from the cathode 25 to the light-emitting layer 23, and is a layer containing multiple electron transport materials as multiple functional materials. In particular in this embodiment, the electron transport layer 24 is in contact with the light-emitting layer 23. The material of the electron transport layer 24 can be an organic or inorganic material that has been conventionally used in light-emitting devices including quantum dots. For example, the electron transport layer 24 may use zinc oxide (ZnO), zinc magnesium oxide (ZnMgO), titanium oxide (TiO), and tungsten oxide (WO) as electron transport materials. ３ The electron transport layer 24 may contain at least one of the following, and may also contain inorganic nanoparticle materials which are nanoparticles of these inorganic materials. Alternatively, the electron transport layer 24 may contain an organic material such as tris(8-quinolinol)aluminum complex (Alq3), bathocuproin (BCP), or (2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole) (t-Bu-PBD) as the electron transport material. As the inorganic material of the electron transport layer 24, metal oxides such as ZnO, ZAO, ITO, InGaZnO, or electride may be used. In this embodiment, a part of the electron transport layer 24 may be in contact with a part of the hole transport layer 22 formed on, for example, the bank BK.

[0022] In this embodiment, the hole transport layer 22 and the electron transport layer 24 can be formed by vacuum deposition, sputtering, or a coating method using a colloidal solution, using the materials described above. The light-emitting element 2 may also have a hole injection layer as another functional layer between the anode 21 and the hole transport layer 22, and an electron injection layer as another functional layer between the cathode 25 and the electron transport layer 24. The hole injection layer and the electron injection layer may both be formed by the same method as the hole transport layer 22 or the electron transport layer 24.

[0023] In this embodiment, the charge transport layer, including the hole transport layer 22 and the electron transport layer 24, is formed in common across multiple subpixels, but is not limited to this. For example, the charge transport layer may be partitioned for each subpixel by a component containing the same organic insulating material as the bank BK. In this case, each charge transport layer may contain an appropriate material depending on the band gap of the light-emitting material contained in the light-emitting layer described later for each subpixel. In other words, each of two light-emitting elements with different emission colors may contain a charge transport layer made of a different material.

[0024] <Light-emitting element: Light-emitting layer: Overview> The light-emitting layer 23 according to this embodiment includes a light-emitting material as a functional material. In particular, the light-emitting layer 23 according to this embodiment includes light-emitting quantum dots as the light-emitting material.

[0025] The light-emitting layer 23 also includes a red light-emitting layer 23R located at the red subpixel XR, a green light-emitting layer 23G located at the green subpixel XG, and a blue light-emitting layer 23B located at the blue subpixel XB. The red light-emitting layer 23R, the green light-emitting layer 23G, and the blue light-emitting layer 23B may be partitioned into subpixels by a bank BK and a hole transport layer 22, as shown in Figure 1.

[0026] Therefore, the red light-emitting element 2R comprises an anode 21R, a hole transport layer 22, a red light-emitting layer 23R, an electron transport layer 24, and a cathode 25, located in the red subpixel XR, in that order from the substrate 3 side. Similarly, the green light-emitting element 2G comprises an anode 21G, a hole transport layer 22, a green light-emitting layer 23G, an electron transport layer 24, and a cathode 25, located in the green subpixel XG, in that order from the substrate 3 side. Furthermore, the blue light-emitting element 2B comprises an anode 21B, a hole transport layer 22, a blue light-emitting layer 23B, an electron transport layer 24, and a cathode 25, located in the blue subpixel XB, in that order from the substrate 3 side.

[0027] The structure of the light-emitting element 2 according to this embodiment is not limited to the structure shown in Figure 1. Other examples of the structure of the light-emitting element 2 according to this embodiment will be described with reference to Figures 3 and 4. Figures 3 and 4 are schematic side cross-sectional views of the display device 1 according to Modification 1 and Modification 2 of this embodiment, and in particular, they show side cross-sections at the same position as the side cross-section shown in Figure 1.

[0028] As shown in Figure 3, the display device 1 according to Modification 1 of this embodiment may include a bank BK that partitions only the anode 21 into subpixels. In Modification 1, the light-emitting layer 23 may also be partitioned into subpixels by an electron transport layer 24. In this case, the electron transport layer 24 may be in contact not only with the upper surface but also with the side surface of each light-emitting layer located at each subpixel.

[0029] Furthermore, as shown in Figure 4, the display device 1 according to Modification 1 of this embodiment may include an electron transport layer 24 and a cathode 25 having a shape that reflects the shape of the hole transport layer 22. In particular, in Modification 2, the hole transport layer 22 and the electron transport layer 24 may have portions that protrude on the side opposite to the substrate 3 at a position that overlaps with the bank BK in a plan view of the substrate 3. In other words, in Modification 2, the hole transport layer 22 and the electron transport layer 24 may have a shape that further reflects the shape of the portion of the hole transport layer 22 that protrudes on the side opposite to the substrate 3, reflecting the shape of the bank BK.

[0030] Furthermore, in this embodiment, a portion of the light-emitting layer 23 may be located on the bank BK. For example, the display device 1 according to this embodiment may include a hole transport layer 22 formed in an island shape for each subpixel, in which case a portion of the light-emitting layer 23 may be in contact with the bank BK.

[0031] The light-emitting layer 23 according to this embodiment will be described in more detail with reference to Figure 5. Figure 5 is a schematic side cross-sectional view of the red light-emitting layer 23R according to this embodiment. In particular, the schematic side cross-sectional views of the red light-emitting layer 23R in this disclosure, including Figure 5, are all schematic side cross-sectional views of the red light-emitting layer 23R in a plane along the film thickness direction DT of the light-emitting layer 23.

[0032] <Light-emitting element: Emitting layer: Quantum dots> As shown in Figures 1 and 5, the red emissive layer 23R includes a plurality of red quantum dots 31R as a plurality of emissive materials. The quantum dots in this disclosure, including the red quantum dots 31R, are luminescent semiconductor nanoparticles that emit light, for example, by the recombination of injected electrons and holes. The quantum dots in this disclosure may have a core / shell structure including, for example, a core and a shell covering the core. In this case, the recombination of electrons and holes in the quantum dot mainly occurs in the core. The core of the quantum dot has a valence band level and a conduction band level, and emits light by the recombination of holes in the valence band level and electrons in the conduction band level. Because the emission from quantum dots has a narrow spectrum due to the quantum confinement effect, it is possible to obtain emission with relatively deep chromaticity. The shell also has the function of suppressing the occurrence of defects or dangling bonds in the core and reducing the recombination of carriers that undergo a deactivation process. From the viewpoint of efficiently obtaining the quantum confinement effect in quantum dots, the particle size of the quantum dot core may be approximately twice or less the exciton Bohr radius of the core material.

[0033] Quantum dots may contain materials used for conventionally known core materials and shell materials in their respective core and shell materials. Quantum dots may have, for example, a core / shell structure including group I-III-V chalcogenide materials such as InP / ZnS, CdSe / ZnS, CdSe / ZnSe, CdSe / CdS, ZnSe / ZnS, or CuInGaS (CIGS) / ZnS, etc. In addition, quantum dots may contain InZnP, CdSeTe, or ZnSeTe. Further, the core of the quantum dots may contain CuInZnS, CuInS, CuGaS, AgInS, or ZnAgInS. Note that the shell may be formed of a plurality of layers including a plurality of different materials.

[0034] The particle size of the quantum dots is about 1 to 100 nm. The quantum dots may have a spherical shape or a non-spherical shape. In the present disclosure, the particle size of the quantum dots may be measured by performing cross-sectional observation in the film thickness direction DT of the light-emitting layer 23. In this cross-sectional observation, each particle size of the quantum dots may be regarded as the diameter of a circle having the same area as the respective cross-sectional area. The particle size of the quantum dots may be measured by measuring 20 particle sizes each in the above cross-sectional observation and calculating the average thereof. The above cross-sectional observation may be performed by analyzing an image obtained by imaging a cross-section of each layer with a transmission electron microscope image (TEM image).

[0035] The wavelength of light emission from the quantum dots can be controlled by the particle size. In particular, since the quantum dots have a core / shell structure, the wavelength of light emission from the quantum dots can be controlled by controlling the particle size of the core. Therefore, by controlling the particle size of the quantum dots, the wavelength of light emitted by each light-emitting element can be controlled.

[0036] The red light-emitting layer 23R may contain a plurality of organic ligands coordinated to the red quantum dots 31R around the red quantum dots 31R. In this case, in the red light-emitting layer 23R, from the viewpoint of improving the reliability of the red light-emitting layer 23R, for example, the weight ratio of the organic ligand to the total weight of the red light-emitting layer 23R may be less than 5%.

[0037] <Light-emitting element: Light-emitting layer: Additive and photosensitive material> As shown in Figures 1 and 5, the red light-emitting layer 23R includes an additive 41. In the red light-emitting layer 23R, the additive 41 covers the periphery of at least one of the quantum dots, as will be described in detail later. Alternatively, in the red light-emitting layer 23R, the additive 41 fills the space between at least two red quantum dots 31R. The additive 41 also has, for example, a porosity 42 that communicates with either the outer surface of the red light-emitting layer 23R, and at least one of a crack 43 located on either the upper or lower surface.

[0038] Furthermore, as shown in Figures 1 and 5, the red light-emitting layer 23R contains an organic polymer 51. In this embodiment, the organic polymer 51 fills at least a portion of at least one of the pores 42 and cracks 43 of the adduct 41. In particular, in this embodiment, the organic polymer 51 may fill more than half of all the pores 42 and cracks 43 of the adduct 41. Furthermore, in this embodiment, the organic polymer 51 may fill all of each of all the pores 42 and cracks 43 of the adduct 41. The organic polymer 51 may have a different composition from the organic ligand described above.

[0039] <Specific Configuration of Light-Emitting Element: Light-Emitting Layer: Additive> The members filling the spaces between the multiple red quantum dots 31R will be described in more detail with further reference to Figure 6. Schematic diagrams F1, F2, and F3 in Figure 6 are schematic diagrams for showing the members filling the spaces between the red quantum dots 31R. In particular, schematic diagrams F1, F2, and F3 show two examples of the pair P of two red quantum dots 31R and the region (space) K between them, as shown in Figure 5. Specifically, schematic diagrams F1, F2, and F3 show pairs P1, P2, and P3, which are examples of pairs of red quantum dots 31X and red quantum dots 31Y, respectively.

[0040] In this specification, when a member fills the space between a plurality of red quantum dots 31R, as shown in the schematic diagram F1 of the set P1 shown in FIG. 6, it suffices to know that the member fills the region K between at least the red quantum dot 31X and the red quantum dot 31Y. The region K is a region surrounded by two straight lines (common circumscribed lines) that are tangent to the outer perimeters of the red quantum dot 31X and the red quantum dot 31Y and the opposing outer perimeters of the red quantum dot 31X and the red quantum dot 31Y in the cross-section of the red light-emitting layer 23R. For this reason, as shown in the schematic diagram F2 of the set P2 shown in FIG. 6, the region K can exist even when the red quantum dot 31X and the red quantum dot 31Y are approaching each other, and the member fills the region K.

[0041] When a member fills the space between a plurality of red quantum dots 31R, it does not necessarily mean that the entire region K between the red quantum dot 31X and the red quantum dot 31Y consists only of the member. For example, as shown in the schematic diagram F1 and the schematic diagram F2, the porous 42 of the additive 41 may be included in the region K. Also, the organic polymer 51 may fill at least a part of the porous 42. Here, in a cross-section passing through two red quantum dots 31R and the region K between the two red quantum dots 31R, assume that the inner diameter of the porous 42 located in the region K is 10 nm or less and the additive 41 fills the region K excluding the porous 42. In this case, the additive 41 may be regarded as filling the region K. Also, as shown in the schematic diagram F1 of FIG. 6, the porous 42 located in the region K may cover the entire surrounding area of the region K. On the other hand, as shown in the schematic diagram F2 of FIG. 6, the porous 42 located in the region K may cover only a part of the surrounding area of the region K.

[0042] By having an inner diameter of 10 nm or less, the reduction in mechanical strength of the red light-emitting layer 23R is reduced, and the reduction in carrier injection efficiency into the red quantum dots 31R, described later, is also reduced. From the viewpoint of further improving the mechanical strength of the red light-emitting layer 23R or improving the carrier injection efficiency into the red quantum dots 31R, the inner diameter of the porous 42 may be 6 nm or less. The inner diameter of the porous 42 may be 0.5 nm or more. In this case, the adduct 41 can be easily formed by a method of forming the adduct 41 by converting the precursor of the adduct 41, described later. From the viewpoint of further simplifying the formation of the red light-emitting layer 23R, the inner diameter of the porous 42 may be 4 nm or more.

[0043] Furthermore, as shown in schematic diagram F3, region K may contain cracks 43 in the adduct 41. The organic polymer 51 may also fill at least a portion of the cracks 43. Here, in a cross-section passing through the two red quantum dots 31R and region K between the two red quantum dots 31R, the maximum width of the cracks 43 on the outermost surface of region K is 1,000 nm or less, and the adduct 41 fills the region K excluding the cracks 43. Alternatively, in the above cross-section, the maximum depth of the cracks 43 from the outermost surface of region K is 40 nm or less, and the adduct 41 fills the region K excluding the cracks 43. In this case, the adduct 41 may be considered to fill region K. Also, in the above cross-section, if it can be confirmed that the adduct 41 occupies 50% or more of the total area of ​​region K, the adduct 41 may be considered to fill region K.

[0044] By having a maximum crack width of 1,000 nm or less, the red light-emitting layer 23R can reduce the decrease in mechanical strength and the decrease in carrier injection efficiency into the red quantum dots 31R, which will be described later. From the viewpoint of further improving the mechanical strength of the red light-emitting layer 23R or improving the carrier injection efficiency into the red quantum dots 31R, the maximum crack width of 43 may be 75 nm or less. The minimum crack width of 43 may be 10 nm or more. In this case, the adduct 41 can be easily formed by a method of forming the adduct 41 by converting the precursor of the adduct 41, which will be described later. From the viewpoint of further simplifying the formation of the red light-emitting layer 23R, the minimum crack width of 43 may be 500 nm or more.

[0045] Returning to the references to Figures 1 and 5, both Figures 1 and 5 show examples of adducts 41 filling the space between two red quantum dots 31R, but this embodiment is not limited to these examples. For example, the adduct 41 may cover the periphery of at least one red quantum dot 31R. In this disclosure, if the adduct 41 is located in more than 90% of the periphery of the red quantum dot 31R in a cross-section of the red light-emitting layer 23R passing through the red quantum dot 31R, the red quantum dot 31R may be considered to be covered by the adduct 41. Furthermore, the adduct 41 may be in contact with the surface of the red quantum dot 31R. In addition, the adduct 41 may be located at any position in the film thickness direction DT of the red light-emitting layer 23R, with a distance of 1000 nm in the planar direction DP of the light-emitting layer 23. ２ It may have a continuous film with the above area.

[0046] <Functions of the adducts and photosensitive material> The red light-emitting layer 23R according to this embodiment comprises red quantum dots 31R and adducts 41 located around the red quantum dots 31R. Therefore, the red light-emitting layer 23R can reduce the degradation of the red quantum dots 31R due to the penetration of foreign substances such as oxygen or moisture into the red quantum dots 31R or the conduction of heat into the red quantum dots 31R. In particular, the adducts 41 that surround the red quantum dots 31R and the adducts 41 that fill the space between two red quantum dots 31R further reduce the degradation of the red quantum dots 31R.

[0047] Furthermore, the red light-emitting layer 23R comprises an organic polymer 51. This improves the overall density of the red light-emitting layer 23R and enhances its mechanical strength, for example, by filling the voids around the red quantum dots 31R with the organic polymer 51. In particular, since organic polymers 51 are generally more flexible than inorganic compounds, they relieve stress generated in the red light-emitting layer 23R. For this reason, the red light-emitting layer 23R equipped with the organic polymer 51 has even greater mechanical strength.

[0048] Furthermore, as will be described in more detail later, the organic polymer 51 has the function of transporting at least one of holes and electrons by hopping conduction. Therefore, compared to the case where the red light-emitting layer 23R does not have the organic polymer 51, the carrier transport efficiency in the red light-emitting layer 23R is improved. As a result, holes and electrons are more easily injected into the red quantum dots 31R contained in the red light-emitting layer 23R, and the luminescence efficiency of the red light-emitting layer 23R is improved.

[0049] In particular, improving the injection efficiency of holes and electrons into the red quantum dot 31R leads to a reduction in the probability of hole-electron recombination in areas other than the red quantum dot 31R. Therefore, with the above configuration, the red light-emitting layer 23R does not contribute to the light emission of the red light-emitting layer 23R and reduces recombination that would lead to deterioration of each part of the red light-emitting layer 23R or parts located near the red light-emitting layer 23R. Accordingly, the red light-emitting element 2R according to this embodiment reduces the deterioration of each functional layer, including the red light-emitting layer 23R, and improves reliability.

[0050] In particular, the red light-emitting layer 23R according to this embodiment includes an organic polymer 51 located in a porous 42 or crack 43 that may constrain carriers, as will be described later. This makes it easier for holes and electrons to be further injected into the red quantum dots 31R contained in the red light-emitting layer 23R, further improving the luminescence efficiency of the red light-emitting layer 23R.

[0051] Therefore, the red light-emitting element 2R according to this embodiment improves reliability by reducing the degradation of the red quantum dots 31R in the red light-emitting layer 23R while improving the mechanical strength of the red light-emitting layer 23R. In particular, the red light-emitting element 2R, which improves the reliability of the red light-emitting layer 23R among the functional layers with the above configuration, contributes to achieving further improvement in luminous efficiency and longer lifespan. The display device 1 equipped with the red light-emitting element 2R achieves a longer lifespan.

[0052] In particular, in this embodiment, the organic polymer 51 fills at least a portion of at least one of the porosity 42 and crack 43 of the adduct 41. As a result, the red light-emitting element 2R has improved mechanical strength because the organic polymer 51 more efficiently fills the voids in the red light-emitting layer 23R.

[0053] Referring to Figure 1, in this embodiment, the green light-emitting layer 23G has the same configuration as the red light-emitting layer 23R, except that it includes green quantum dots 31G that emit green light instead of red quantum dots 31R. Similarly, the blue light-emitting layer 23B has the same configuration as the red light-emitting layer 23R, except that it includes blue quantum dots 31B that emit blue light instead of red quantum dots 31R.

[0054] In other words, the green light-emitting layer 23G includes green quantum dots 31G, and adducts 41 and organic polymers 51 located around the green quantum dots 31G. The blue light-emitting layer 23B also includes blue quantum dots 31B, and adducts 41 and organic polymers 51 located around the blue quantum dots 31B.

[0055] Therefore, for the same reasons as described above, the green light-emitting element 2G and the blue light-emitting element 2B improve reliability by reducing the degradation of quantum dots in their respective light-emitting layers while improving the mechanical strength of the light-emitting layers.

[0056] Furthermore, although this embodiment describes an example in which the light-emitting layer of each light-emitting device includes an adduct 41 and an organic polymer 51 located around the quantum dot, the embodiment is not limited to this. In particular, each light-emitting device according to this embodiment includes an adduct 41 and an organic polymer 51 located around the hole transport material in at least one of its functional layers. In other words, each light-emitting device according to this embodiment comprises one or more functional layers, each including a light-emitting layer containing a light-emitting material, and each of these functional layers includes a functional material and an adduct and an organic polymer located around the functional material. In this case, the light-emitting device improves the mechanical strength of the functional layer while reducing the degradation of the functional material in the functional layer containing the adduct 41 and the organic polymer 51.

[0057] For example, each light-emitting element according to this embodiment may include an adduct 41 and an organic polymer 51 located around the hole transport material in the hole transport layer 22. In this case, the light-emitting element improves the mechanical strength of the hole transport layer 22 while reducing the degradation of the hole transport material in the hole transport layer 22. Furthermore, each light-emitting element according to this embodiment may include an adduct 41 and an organic polymer 51 located around the electron transport material in the electron transport layer 24. In this case, the light-emitting element improves the mechanical strength of the electron transport layer 24 while reducing the degradation of the electron transport material in the electron transport layer 24.

[0058] <Example of the positional relationship between quantum dots and porosity> Referring to Figure 7, an example of the positional relationship between the quantum dots contained in the light-emitting layer 23 and the porosity 42 of the adduct 41 will be explained in more detail. Figure 7 is a schematic diagram to explain an example of the positional relationship between red quantum dots 31 and porosity 42, and in particular, it is an enlarged view of the red light-emitting layer 23R in a cross-section passing through multiple red quantum dots 31R and porosity 42.

[0059] Figure 7 shows red quantum dots 31RA, 31RB, and 31RC as red quantum dots 31R. Also, porous materials 42A, 42B, and 42C are shown as porous materials 42. Note that all porous materials 42 shown in Figure 7 are filled with organic polymer 51.

[0060] In this embodiment, the quantum dots and porous 42 contained in the light-emitting layer 23 do not necessarily have to be in contact with each other, as shown in Figure 7 with the red quantum dot 31RA and porous 42A. In this case, the adduct 41 may be located between the red quantum dot 31RA and porous 42A, and the red quantum dot 31RA does not necessarily have to be in contact with the organic polymer 51 in porous 42A. As a result, the entire surface of the red quantum dot 31RA is in contact with the adduct 41, and the protective effect of the adduct 41 on the red quantum dot 31RA is further improved.

[0061] Furthermore, as shown in Figure 7, a portion of the quantum dots contained in the light-emitting layer 23 may be located inside the porous 42, such as the red quantum dot 31RB and porous 42B. In this case, a portion of the surface of the red quantum dot 31RB may be located inside the porous 42B, and this portion may be in contact with the organic polymer 51 in the porous 42B. This improves the efficiency of carrier implantation into the red quantum dot 31RB via the organic polymer 51 in contact with the red quantum dot 31RB.

[0062] Furthermore, as shown in Figure 7, the entire quantum dot contained in the light-emitting layer 23 may be located inside the porous 42, such as the red quantum dot 31RC and porous 42C. In this case, the entire surface of the red quantum dot 31RC may be in contact with the organic polymer 51 in the porous 42C. This further improves the efficiency of carrier implantation into the red quantum dot 31RC via the organic polymer 51 in contact with the red quantum dot 31RC.

[0063] <Examples of materials for the adduct> The adduct 41 may contain at least one of a metal oxide and a metal sulfide. With the above configuration, each light-emitting device has a denser adduct 41 and improves the protective effect of the adduct 41 on the quantum dots. In particular, the adduct 41 may have insulating properties. This further improves the protective effect of the adduct 41 on the quantum dots in each light-emitting device. In this disclosure, the metal atoms contained in the metal oxide of the adduct 41 may be atoms that are generally referred to as metalloid atoms, including silicon (Si), boron (B), germanium (Ge), arsenic (As), antimony (Sb), and tellurium (Te).

[0064] If the adduct 41 is insulating, for example, the adduct 41 may include at least one from the group including 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, silicon nitride, and magnesium oxide. With the above configuration, each light-emitting device has a more densely structured adduct 41 and improves the protection effect of the quantum dot by the adduct 41. However, the adduct 41 may also include a semiconductor, in which case the adduct 41 may also include zinc sulfide.

[0065] The adduct 41 may also contain halogen atoms. The adduct 41 may contain, for example, a halide or an elemental halogen. In this disclosure, “atom” does not mean only to exist as an elemental atom. In this disclosure, “atom” includes those that exist in the form of a molecule having two or more atoms, including the atom in question and another atom, those that exist in the form of a complex, those that exist in the form of a compound, or those that exist in the form of an ion. In this disclosure, “atom” does not limit the other forms of existence of an atom. That is, a halogen atom includes those that exist in the form of a compound containing a halogen atom, and those that exist in the form of a halogen ion. If a halogen atom can be identified as being present in a substance by analysis, regardless of its form of existence, the substance may be considered to contain a halogen atom.

[0066] As described later, the adduct 41 can be formed by transforming the precursor in a dispersion containing quantum dots and the precursor. When forming the adduct 41 from the precursor, gaps may form between the quantum dots, resulting in defects on the surface of the quantum dots that are not covered by the adduct 41. Therefore, by mixing a material containing halogen atoms into the dispersion, the halogen atoms can coat the surface of the quantum dots independently of the adduct 41, thereby reducing defects on the surface of the quantum dots. Consequently, the presence of halogen atoms in the adduct 41 increases the coverage of the quantum dots in the light-emitting layer of each light-emitting device, thereby improving its light-emitting properties.

[0067] <Examples of Organic Polymer Materials> The organic polymer 51 may be, for example, a polymer with 100 to 100,000 carbon atoms. Alternatively, the organic polymer 51 may be a polymer having 100 to 50,000 repeating units. By having 100 or more carbon atoms in the organic polymer 51, or by having 100 or more repeating units in the organic polymer 51, the light-emitting layer 23 containing the organic polymer 51 can be made more flexible and have improved mechanical strength. By having 100,000 or fewer carbon atoms in the organic polymer 51, or by having 50,000 or more repeating units in the organic polymer 51, the light-emitting layer 23 containing the organic polymer 51 can be formed more simply or at a lower cost.

[0068] The organic polymer 51 may be, for example, a hydrocarbon polymer. In this case, the light-emitting layer 23 containing the organic polymer 51 can be formed more simply or at a lower cost. The organic polymer 51 may also have only saturated bonds. In this case, the rotation of atoms within the molecule around the interatomic bonds becomes easier, thus improving the flexibility of the organic polymer 51. Therefore, the light-emitting layer 23 containing the organic polymer 51 having only saturated bonds has improved mechanical strength. Furthermore, since the organic polymer 51 consisting only of saturated bonds has a chemically stable structure, it is less prone to chemical changes and, consequently, less prone to degradation. For this reason, the light-emitting layer 23 containing the organic polymer 51 consisting only of saturated bonds has improved reliability.

[0069] The organic polymer 51 may include at least one of polypropylene and polyethylene represented by the following chemical formula as an organic polymer having only saturated bonds.

[0070] In this case, the light-emitting layer 23 containing the organic polymer 51 contains a more flexible organic polymer 51 to improve the mechanical strength, and can be formed more simply or at a lower cost.

[0071] Alternatively, the organic polymer 51 may include polystyrene represented by the following chemical formula as an organic polymer having an unsaturated bond.

[0072] In this case, the light-emitting layer 23 containing the organic polymer 51 contains a flexible organic polymer compared to other organic polymers to improve the mechanical strength, and can be formed more simply or at a lower cost. Further, the organic polymer 51 having a benzene ring is superior in hole transport property compared to an organic polymer having no benzene ring. Therefore, the light-emitting device 2 provided with the light-emitting layer 23 containing the organic polymer 51 having a benzene ring improves the hole injection efficiency into the quantum dots of the light-emitting layer 23.

[0073] Further, the organic polymer 51 may include at least one of polyethylene terephthalate and polyacrylonitrile as an organic polymer containing other than hydrocarbons.

[0074] In this case, the light-emitting layer 23 containing the organic polymer 51 contains a flexible and strong organic polymer 51 compared to other organic polymers to improve the mechanical strength.

[0075] The molecular weight of the organic polymer 51 may be, for example, a polymer of 10 ３ or more and 10 ６ or less. When the molecular weight of the organic polymer 51 is 10 ３ or more, the light-emitting layer 23 containing the organic polymer 51 improves the flexibility and the mechanical strength. When the molecular weight of the organic polymer 51 is 10 ６As a result of the following, the light-emitting layer 23 containing the organic polymer 51 can be formed more simply or at a lower cost. Furthermore, the molecular weight of the organic polymer 51 is 10 ３ The above 10 ６ The following conditions make it easier for the organic polymer 51 to fill the porous 42 or cracks 43.

[0076] In this embodiment, the adduct 41 and the organic polymer 51 may be made of the same material regardless of the emission color of the subpixel, but are not limited thereto. For example, the adduct 41 and the organic polymer 51 may contain appropriate materials depending on the band gap of the quantum dots contained in the emission layer of each subpixel. In other words, each of two light-emitting devices with different emission colors may contain an adduct 41 and an organic polymer 51 made of different materials.

[0077] <Manufacturing Method for Display Device: Up to the Formation of the Hole Transport Layer> The manufacturing method for the display device 1 according to this embodiment will be described with reference to Figure 8. Figure 8 is a flowchart of the manufacturing method for the display device 1 according to this embodiment.

[0078] In the manufacturing method of the display device 1 according to this embodiment, first, a substrate 3 is prepared (step S1). The substrate 3 may be formed by forming a pixel circuit and a driver for driving the light-emitting element 2 of each subpixel on a substrate such as a glass substrate or a film substrate.

[0079] Next, an anode 21 is formed on the substrate 3 (step S2). The anode 21 may be formed by forming a thin film of a conductive material common to multiple subpixels using the method described above, and then patterning the thin film for each subpixel. In step S2, regarding the patterning of the anode 21, a bank BK may be formed between each adjacent anode 21. Next, a hole transport layer 22 is formed on the anode 21 using the method described above (step S3). The hole transport layer 22 may be formed common to multiple subpixels, or it may be patterned for each subpixel. Between the formation of the anode 21 and the formation of the hole transport layer 22, a hole injection layer may be formed on the anode 21 using the same method as the formation of the hole transport layer 22, except for the material. In this case, the hole transport layer 22 may be formed on the hole injection layer.

[0080] <Manufacturing Method for Display Device: Formation of Light-Emitting Layer: Overview> Next, a light-emitting layer 23 is formed on the hole transport layer 22 (step S4). The method for forming the light-emitting layer 23 will be described in more detail with reference to Figures 9 to 19. Figure 9 is a flowchart of the method for forming the light-emitting layer 23 according to this embodiment. Figures 10 to 19 are cross-sectional views of the process side of the method for forming the light-emitting layer 23 according to this embodiment, and in particular show cross-sections corresponding to the cross-section shown in Figure 1. Hereafter, in order to simplify the explanation of the structure of the illustrated display device 1, each cross-sectional view of the process side in this disclosure will be a cross-sectional view of the process side when manufacturing the display device 1 according to the modified example 1 shown in Figure 3. However, this embodiment is not limited to this, and the display device 1 shown in Figure 1 or the display device 1 shown in Figure 4 may be manufactured by controlling the formation position of each layer as described later.

[0081] In this embodiment, step S4 is repeated as many times as the number of light-emitting colors of the subpixels of the display device 1, in other words, the number of types of light emitted by the light-emitting layer 23. In this embodiment, the display device 1 has subpixels of three light-emitting colors: red subpixel XR, green subpixel XG, and blue subpixel XB, so step S4 is repeated three times. In this embodiment, a method of forming the red light-emitting layer 23R, the green light-emitting layer 23G, and the blue light-emitting layer 23B in this order by repeating step S4 three times will be described as an example.

[0082] <Manufacturing method for display device: Formation of light-emitting layer: Formation of photosensitive layer> At the completion of step S3, as shown in step S3 of Figure 10, an anode 21, a bank BK, and a hole transport layer 22 are formed on the substrate 3. In the method for forming the red light-emitting layer 23R in step S4, first, as shown in step S41-1 of Figure 10, a photosensitive layer 61 is formed (step S41). The photosensitive layer 61 contains a photosensitive material R1. The photosensitive layer 61 may be formed by coating the photosensitive material R1 onto the hole transport layer 22 using a coating method including, for example, a conventionally known method such as a slit coating method or a spin coating method.

[0083] Next, a portion of the photosensitive material layer 61 is exposed (step S42). For example, in step S42 of the method for forming the red light-emitting layer 23R, as shown in step S42-1 of Figure 11, a photomask MR having light-transmitting portions such as openings for the red subpixels XR in a plan view of the substrate 3 is placed above the photosensitive material layer 61. Then, light such as ultraviolet light is irradiated from the side of the photomask MR on the substrate 3. As a result, a photosensitive material layer 62 is formed in which the photosensitive material R1 in the portion of the photosensitive material layer 61 that overlaps with the red subpixels XR in a plan view of the substrate 3 is transformed into the exposed photosensitive material R2.

[0084] Next, a portion of the photosensitive material layer 62 is removed (step S43). The removal of a portion of the photosensitive material layer 62 may be performed by washing the photosensitive material layer 62 containing the exposed photosensitive material R2 with a suitable developer. When the photosensitive material R1 is a positive-type photoresist, the unexposed photosensitive material R1 is poorly soluble in the developer, while the exposed photosensitive material R2 acquires solubility in the developer. Therefore, by washing the photosensitive material layer 62 with a developer, for example, in step S42 of the method for forming the red light-emitting layer 23R, only the photosensitive material R2 located in the red subpixel XR is removed, as shown in step S43-1 of Figure 11. Thus, in step S42, a photosensitive material layer 63 is formed containing the unexposed photosensitive material R1 remaining in the green subpixel XG and the blue subpixel XB.

[0085] When the photosensitive material R1 is a positive-type photoresist, the positional control of the photosensitive material R2 to be removed in step S42 becomes easier compared to when the photosensitive material R1 is a negative-type photoresist. Therefore, the photosensitive material R1 containing a positive-type photoresist simplifies the method of forming the light-emitting layer 23, or improves the accuracy of the formation position of the light-emitting layer 23.

[0086] <Manufacturing method for display device: Formation of light-emitting layer: Application of quantum dot dispersion> Next, the quantum dot dispersion is applied (step S44). In particular, in step S44 of the method for forming the red light-emitting layer 23R, as shown in step S44-1 of Figure 12, the red quantum dot dispersion 71R is applied to the remaining photosensitive layer 63 and the hole transport layer 22 exposed from the photosensitive layer 63. The red quantum dot dispersion 71R is a dispersion in which red quantum dots 31R and precursors 73 of the adduct 41 are dispersed in a solvent 72.

[0087] The precursor 73 includes a material that is converted to the adduct 41 through hydrolysis and dehydration condensation by performing a specific operation such as heating or light irradiation. The precursor 73 may have a coordinating functional group that forms a coordination bond with the surface of the red quantum dots 31R in the red quantum dot dispersion 71R. In this case, the precursor 73 may coordinate to the red quantum dots 31R in the red quantum dot dispersion 71R. For example, if the adduct 41 contains silicon oxide and the precursor 73 has a coordinating functional group, the precursor 73 may contain 3-(mercaptopropyl)trimethoxysilane (MPS) represented by the following formula.

[0088] Alternatively, for example, if the adduct 41 contains silicon oxide and the precursor 73 has a coordination functional group, the precursor 73 may contain 3-mercaptopropyl(dimethoxy)methylsilane represented by the following formula.

[0089] However, precursor 73 does not necessarily have to have a coordinating functional group. For example, if adduct 41 contains silicon oxide, precursor 73 may contain tetramethyl orthosilicate (TMOS) as shown in the following formula.

[0090] Alternatively, for example, if the adduct 41 contains silicon oxide, the precursor 73 may contain at least one silicon compound from the group represented by any of the following formulas.

[0091] Furthermore, if the adduct 41 contains zinc sulfide, the precursor 73 may contain zinc xanthogenic acid as shown in the following formula.

[0092] Alternatively, for example, if the adduct 41 contains zinc sulfide, the precursor 73 may contain ether products such as thiourea acid and dithiocarboxylic acid.

[0093] The red quantum dot dispersion 71R contains zinc chloride (ZnCl) as a halogenated halide. ２ ) may be included.

[0094] The red quantum dot dispersion 71R may be prepared, for example, by stirring a dispersion containing red quantum dots 31R and a dispersion containing precursor 73 to prepare a mixture, and then extracting the intermediate layer of the mixture. Here, the dispersion containing red quantum dots 31R may contain an organic ligand that coordinates to the red quantum dots 31R. In this case, for example, during stirring for the preparation of the mixture, the ligand that coordinates to the red quantum dots 31R may be replaced from the organic ligand with a part of the precursor 73 such as MPS. However, the mixture obtained by stirring the dispersion containing red quantum dots 31R and the dispersion containing precursor 73 does not have to have an intermediate layer. In this case, the red quantum dot dispersion 71R may be prepared by extracting the red quantum dots 31R from the liquid layer containing the red quantum dots 31R in the mixture.

[0095] <Manufacturing method for display device: Formation of light-emitting layer: Conversion of precursor> Following the application of the quantum dot dispersion, the precursor 73 is converted into an adduct 41 (step S45). In particular, in step S45 of the method for forming the red light-emitting layer 23R, the solvent 72 is volatilized by heating the applied red quantum dot dispersion 71R, and the precursor 73 is converted into an adduct 41. For example, if the precursor 73 contains TMOS and MPS, dehydration condensation occurs between TMOS molecules, between MPS molecules, and between TMOS and MPS molecules, etc., to form silicon oxide as an adduct 41. Alternatively, for example, if the precursor 73 contains zinc xanthogenic acid, in step S45, the zinc xanthogenic acid is decomposed to form zinc sulfide as an adduct 41. The conversion of the precursor 73 to an adduct 41 occurs sequentially around the red quantum dots 31R of the red quantum dot dispersion 71R.

[0096] Therefore, as shown in step S45-1 of Figure 12, a red quantum dot layer 74R is formed in step S45 of the method for forming the red light-emitting layer 23R. The red quantum dot layer 74R comprises a plurality of red quantum dots 31R and an adduct 41 that fills the spaces between the plurality of red quantum dots 31R. Of the red quantum dot layer 74R, the portion located at the red subpixel XR is located on the hole transport layer 22, and the portions located at the green subpixel XG and blue subpixel XB are located on the photosensitive material layer 63.

[0097] In the conversion from the precursor 73 to the adduct 41, multiple voids containing porous material 42 may be formed in the adduct 41 due to outgassing from the precursor 73 or volume contraction of the red quantum dot dispersion 71R. In addition, in the above conversion, cracks 43, which are not shown in step S45-1 of Figure 12, may be formed in the adduct 41 due to the generation of stress in the adduct 41 caused by volume contraction of the red quantum dot dispersion 71R.

[0098] <Manufacturing method for display device: Formation of light-emitting layer: Processing of quantum dot layer> Next, the quantum dot layer is patterned (step S46). In this embodiment, the patterning of the quantum dot layer is performed by a lift-off method by removing the photosensitive material layer remaining on the hole transport layer 22. In particular, in step S46 of the method for forming the red light-emitting layer 23R, the photosensitive material layer 63 is removed together with the red quantum dot layer 74R located on the photosensitive material layer 63 by washing the photosensitive material layer 63 with a cleaning solution that also dissolves the unexposed photosensitive material R1. As a result, as shown in step S46-1 of Figure 13, only the portion of the red quantum dot layer 74R located at the red subpixel XR remains on the hole transport layer 22.

[0099] Next, the quantum dot layer is immersed in a dispersion containing an organic polymer (step S47). In this embodiment, as a method for immersing the quantum dot layer in a dispersion containing an organic polymer, for example, as shown in step S47-1 of Figure 13, the organic polymer dispersion 81 is applied to the upper part of each section on the substrate 3. This immerses the red quantum dot layer 74R remaining on the hole transport layer 22 into the organic polymer dispersion 81.

[0100] The organic polymer dispersion 81 is a dispersion containing organic polymer 51 dispersed in a solvent. Furthermore, at least a portion of the pores 42 contained in the red quantum dot layer 74R communicates with the surface of the red quantum dot layer 74R, and cracks 43 are formed on the surface of the red quantum dot layer 74R. For this reason, the organic polymer 51 in the organic polymer dispersion 81 is introduced from the surface of the red quantum dot layer 74R into the pores 42 or cracks 43 contained in the adduct 41 of the red quantum dot layer 74R immersed in the organic polymer dispersion 81.

[0101] As a result, as shown in step S47-1 of Figure 13, at least a portion of the porosity 42 and cracks 43 contained in the red quantum dot layer 74R are filled with the organic polymer 51. Thus, the red light-emitting layer 23R located on the hole transport layer 22 and in the red subpixel XR is formed.

[0102] Next, the organic polymer dispersion is removed (step S48). The removal of the organic polymer dispersion may be performed, for example, by washing the hole transport layer 22 and the area around the red light-emitting layer 23R with a liquid containing only the solvent and no organic polymer 51 from the organic polymer dispersion 81. As a result, the formation of the red light-emitting layer 23R is completed, as shown in step S48-1 of Figure 14.

[0103] <Manufacturing method for display device: Formation of light-emitting layer: Formation of light-emitting layer of other light-emitting color> In this embodiment, following the formation of the red light-emitting layer 23R, the formation of the green light-emitting layer 23G is carried out. In forming the green light-emitting layer 23G, first, as shown in step S41-2 of Figure 14, a photosensitive material layer 64 containing the photosensitive material R1 is formed on the hole transport layer 22 and the red light-emitting layer 23R by the same method as in step S41 described above. Here, the side and top surfaces of the red light-emitting layer 23R are in contact with the photosensitive material layer 64 containing the photosensitive material R1. However, the organic polymer 51 that has penetrated the porosity 42 or crack 43 even once is strongly adsorbed to the porosity 42 or crack 43 by the capillary effect, so the organic polymer 51 is less likely to flow out to the outside of the photosensitive material layer 64, etc.

[0104] Next, a portion of the photosensitive material layer 64 is exposed using the same method as in step S42 described above. For example, in step S42 of the method for forming the green light-emitting layer 23G, as shown in step S42-2 of Figure 15, a photomask MG having light-transmitting portions such as openings for the green subpixels XG in a plan view of the substrate 3 is placed above the photosensitive material layer 64. Then, light such as ultraviolet light is irradiated from the side of the photomask MG on the substrate 3. As a result, a photosensitive material layer 65 is formed in which the photosensitive material R1 in the portion of the photosensitive material layer 64 that overlaps with the green subpixels XG in a plan view of the substrate 3 is transformed into the exposed photosensitive material R2.

[0105] Next, using the same method as in step S43 described above, in other words, the photosensitive layer 65 containing the exposed photosensitive material R2 is washed with an appropriate developer to remove a portion of the photosensitive layer 65. As a result, in step S42 of the method for forming the green light-emitting layer 23G, as shown in step S43-2 of Figure 15, only the photosensitive material R2 located in the green subpixel XG is removed. Therefore, in step S42, a photosensitive layer 66 is formed that contains the unexposed photosensitive material R1 remaining in the red subpixel XR and the blue subpixel XB.

[0106] Next, the quantum dot dispersion is applied using the same method as in step S44 described above. In particular, in step S44 of the method for forming the green light-emitting layer 23G, as shown in step S44-2 of Figure 16, the green quantum dot dispersion 71G is applied to the remaining photosensitive layer 66 and the hole transport layer 22 exposed from the photosensitive layer 65. The green quantum dot dispersion 71G may be the same as the red quantum dot dispersion 71R in that it contains green quantum dots 31G instead of red quantum dots 31R.

[0107] Next, the precursor 73 in the green quantum dot dispersion 71G is converted to the adduct 41 by the same method as in step S45 described above. As a result, as shown in step S45-2 of Figure 17, the green quantum dot layer 74G is formed in step S45 of the method for forming the green light-emitting layer 23G. The green quantum dot layer 74G comprises a plurality of green quantum dots 31G and adducts 41 located around the plurality of green quantum dots 31G. Of the green quantum dot layer 74G, the portion located at the green subpixel XG is located on the hole transport layer 22, and the portions located at the red subpixel XR and blue subpixel XB are located on the photosensitive material layer 66.

[0108] For the same reasons as described above, in step S45 of the method for forming the green light-emitting layer 23G, at least one of the porosity 42 and the crack 43 may be formed in the adduct 41 of the green quantum dot layer 74G.

[0109] Next, the green quantum dot layer 74G is patterned by removing the remaining photosensitive material layer 66 using the same method as in step S46 described above. As a result, as shown in step S46-2 of Figure 18, only the portion of the green quantum dot layer 74G located at the green subpixel XG remains on the hole transport layer 22.

[0110] Next, the green quantum dot layer 74G remaining on the hole transport layer 22 is immersed in the organic polymer dispersion 81 using the same method as in step S47. As a result, at least a portion of the pores 42 or cracks 43 contained in the green quantum dot layer 74G are filled with the organic polymer 51, as shown in step S47-2 of Figure 18. Thus, the green light-emitting layer 23G located on the hole transport layer 22 and located in the green subpixel XG is formed.

[0111] In the step of immersing the green quantum dot layer 74G in the organic polymer dispersion 81, the red light-emitting layer 23R is again immersed in the organic polymer dispersion 81. Therefore, even in this step, or in other words, even after the formation of the red light-emitting layer 23R, the pores 42 or cracks 43 in the red light-emitting layer 23R that do not contain the organic polymer 51 may be filled with the organic polymer 51.

[0112] Next, the organic polymer dispersion 81 is removed using the same method as in step S48. This completes the formation of the green light-emitting layer 23G, as shown in step S48-2 of Figure 19.

[0113] In this embodiment, following the formation of the green light-emitting layer 23G, the blue light-emitting layer 23B is formed. The formation of the blue light-emitting layer 23B may be carried out in the same manner as the formation of the red light-emitting layer 23R or the green light-emitting layer 23G, except that the quantum dots in the quantum dot dispersion are blue quantum dots 31B and the blue light-emitting layer 23B is formed on the blue subpixel XB. As a result, the blue light-emitting layer 23B located on the blue subpixel XB is formed, as shown in step S48-3 of Figure 19. With this, the formation of the red light-emitting layer 23R, the green light-emitting layer 23G, and the blue light-emitting layer 23B is completed, and the formation of the light-emitting layer 23 is completed.

[0114] <Manufacturing method for display device: After formation of electron transport layer> Referring back to Figure 8, following the formation of the light-emitting layer 23, an electron transport layer 24 is formed on the light-emitting layer 23 by the method described above (step S5). The electron transport layer 24 may be formed in common for multiple subpixels, or it may be patterned for each subpixel. Alternatively, the electron transport layer 24 may be formed so as to partition the light-emitting layer 23 for each subpixel.

[0115] Next, the cathode 25 is formed (step S6). The cathode 25 may be formed by forming a thin conductive film common to multiple subpixels using the method described above. With this, the light-emitting element 2 is formed on the substrate 3, and the manufacturing of the display device 1 is completed. According to the above method, a light-emitting element 2 with improved reliability and mechanical strength of the light-emitting layer 23 can be manufactured.

[0116] Furthermore, in the method for forming the light-emitting element 2 according to this embodiment, the formation of the light-emitting layer 23 includes immersion of the quantum dot layer in a dispersion containing an organic polymer 51. This allows the organic polymer 51 to be introduced into the pores 42 or cracks 43 contained in the quantum dot layer by a simple method. Therefore, according to the above method, the light-emitting layer 23 can be formed by a simpler method.

[0117] <Display device according to comparative form> The display device 1 according to this embodiment will be described in more detail by comparison with the display device according to the comparative form. Figure 20 is a schematic side cross-sectional view of the display device 1A according to the comparative form, and in particular, it is a side cross-section at the same position as the side cross-section of the display device 1 according to modified example 1 shown in Figure 3.

[0118] The comparative display device 1A, compared to the display device 1 according to Modification 1 of this embodiment, includes a light-emitting element 2A instead of a light-emitting element 2. Compared to the light-emitting element 2, the light-emitting element 2A includes a light-emitting layer 23A instead of a light-emitting layer 23. The light-emitting layer 23A includes a red light-emitting layer 23RA located at the red subpixel XR, a green light-emitting layer 23GA located at the green subpixel XG, and a blue light-emitting layer 23BA located at the blue subpixel XB. Therefore, the display device 1A includes a red light-emitting element 2RA with a red light-emitting layer 23RA, a green light-emitting element 2GA with a green light-emitting layer 23GA, and a blue light-emitting element 2BA with a blue light-emitting layer 23BA.

[0119] The light-emitting layer 23A does not contain the organic polymer 51 compared to the light-emitting layer 23. Therefore, the adduct 41 in the light-emitting layer 23A includes a porous 42 or a crack 43 (not shown in Figure 20), while the organic polymer 51 is not located inside the porous 42 or crack 43. Except for the above, the light-emitting layer 23A has the same configuration as the light-emitting layer 23. The display device 1A according to the comparative embodiment is manufactured by the same method as the manufacturing method of the display device 1 according to this embodiment, except that steps S47 and S48 described above are not performed.

[0120] <Carrier Transport in the Light-Emitting Layer> The carrier transport mechanism in the light-emitting layer of each light-emitting element in the display device 1 according to this embodiment and the display device 1A according to a comparative embodiment will be described in more detail with reference to Figure 21. Figure 21 is a schematic diagram showing how carriers are transported in the light-emitting layer 23A according to the comparative embodiment and the light-emitting layer 23 according to this embodiment. In particular, schematic diagram F1 in Figure 21 is an enlarged side cross-section of the red light-emitting layer 23RA according to the comparative embodiment, and schematic diagram F2 in Figure 21 is an enlarged side cross-section of the red light-emitting layer 23R according to this embodiment.

[0121] In each schematic diagram in Figure 21, the red light-emitting element of each display device is driven, and when a hole from the anode and an electron from the cathode are injected into the light-emitting layer, the transport of the hole and electron through the red light-emitting layer is shown. In particular, in Figure 21, holes are represented by h+ and electrons by e-.

[0122] In both the comparative form and this embodiment, holes and electrons are injected into the red quantum dots in the red light-emitting layer, and the red quantum dots emit light when the holes and electrons recombine. In both the comparative form and this embodiment, the holes and electrons in the red light-emitting layer are injected into the red quantum dots by propagating through the adduct 41.

[0123] In the comparative configuration, the red light-emitting layer 23RA has a porous 42 or a crack 43 (not shown in Figure 21) on at least one side of either the anode 21 side or the cathode 25 side relative to any of the red quantum dots 31R. Furthermore, in the comparative configuration, the organic polymer 51 is not located inside the porous 42 or crack 43, resulting in a void inside the porous 42 or crack 43.

[0124] Therefore, as shown in schematic diagram F1, pores 42 or cracks 43 located on the cathode 25 side of the red quantum dot 31R may trap electrons propagating through the adduct 41. Also, as shown in schematic diagram F1, pores 42 or cracks 43 located on the anode 21 side of the red quantum dot 31R may trap holes propagating through the adduct 41.

[0125] As a result, in the comparative form of the red light-emitting element 2RA, the injection efficiency of holes or electrons into the red quantum dots 31R contained in the red light-emitting layer 23RA decreases, which may lead to a decrease in luminescence efficiency. Furthermore, if both holes and electrons are trapped in the porous 42 or crack 43, recombination of holes and electrons may occur in the porous 42 or crack 43. Since the recombination of holes and electrons that occurs in the porous 42 or crack 43 does not contribute to the luminescence of the red light-emitting layer 23RA, the luminescence efficiency of the comparative form of the red light-emitting element 2RA may decrease even further.

[0126] On the other hand, the red light-emitting layer 23R according to this embodiment has a porous 42 or crack 43 in which at least a portion of the interior is filled with an organic polymer 51. Therefore, as shown in schematic diagram F2, holes and electrons injected into the porous 42 or crack 43 are conducted by hopping through the organic polymer 51 that fills the porous 42 or crack 43.

[0127] As a result, the red light-emitting layer 23R according to this embodiment reduces the trapping of holes and electrons in the porous 42 or cracks 43, thereby improving the injection efficiency of holes and electrons into the red quantum dots 31R. Furthermore, the occurrence of hole and electron recombination in the porous 42 or cracks 43 is reduced by hopping conduction of holes and electrons through the organic polymer 51.

[0128] Therefore, the red light-emitting element 2R according to this embodiment improves luminous efficiency compared to the red light-emitting element 2RA according to the comparative embodiment. For the same reason, the green light-emitting element 2G and the blue light-emitting element 2B according to this embodiment each improve luminous efficiency compared to the green light-emitting element 2GA and the blue light-emitting element 2BA according to the comparative embodiment.

[0129] <Comparative Verification of Examples and Comparative Examples> Below, the light-emitting element according to the Examples and the light-emitting element according to the Comparative Examples are manufactured, and the characteristics of each light-emitting element are measured to evaluate the light-emitting element 2 according to this embodiment and the light-emitting element 2A according to the Comparative Example.

[0130] The light-emitting element according to the example has the same configuration as the red light-emitting element 2R according to this embodiment. The light-emitting element according to the example was manufactured by performing steps S2 to S6 of the manufacturing method of the display device 1 according to this embodiment. The light-emitting element according to the comparative example has the same configuration as the red light-emitting element 2RA according to the comparative example. The light-emitting element according to the comparative example was manufactured by the same method as the light-emitting element according to the example, except that steps S47 and S48 were not performed.

[0131] The element characteristics of the light-emitting element according to the embodiment and the light-emitting element according to the comparative example were measured, and the measurement data were summarized in the graph in Figure 22. Figure 22 shows graphs representing the element characteristics of the light-emitting element according to the embodiment and the light-emitting element according to the comparative example. Graph G1 in Figure 22 is a graph representing the external quantum efficiency (EQE) as a function of the current density between the electrodes of each light-emitting element. Graph G2 in Figure 22 is a graph representing the voltage applied between the electrodes of each light-emitting element as a function of the current density between the electrodes of each light-emitting element. Graph G3 in Figure 22 is a graph representing the change in brightness of each light-emitting element over time.

[0132] In graph G1, the horizontal axis represents the current density between the electrodes of each light-emitting element (unit: mA / cm²). ２ In graph G2, the vertical axis represents the EQE (unit: %) of each light-emitting element. In graph G2, the horizontal axis represents the current density (unit: mA / cm²) between the electrodes of each light-emitting element. ２ In graph G1, the vertical axis represents the applied voltage (in V) between the electrodes of each light-emitting element. In graph G3, the horizontal axis represents the elapsed time (in h) from the start of operation of each light-emitting element, and the vertical axis represents the ratio of the brightness of each light-emitting element to the maximum brightness of each light-emitting element when the maximum brightness of each light-emitting element during operation is set to 1. The data shown in graph G3 is for the case where a voltage is applied so that the current flowing through each light-emitting element is 1.0 mA. In graphs G1, G2, and G3, the data related to the example is shown with a solid line, and the data related to the comparative example is shown with a dashed line.

[0133] As is clear from Graph G1, the light-emitting element according to the example achieves a higher EQE (Energy Quotient) than the light-emitting element according to the comparative example, regardless of the current density between the electrodes. This is thought to be because the light-emitting layer 23 of the light-emitting element according to the example has an organic polymer 51, which improves the carrier injection efficiency into each quantum dot of the light-emitting layer 23 in the light-emitting element according to the example.

[0134] As is clear from graphs G1 and G2, the light-emitting element according to the embodiment reduces the voltage applied between the electrodes, regardless of the current density between the electrodes, compared to the light-emitting element according to the comparative example. Therefore, the light-emitting element according to the embodiment can achieve the same brightness with a lower voltage application compared to the light-emitting element according to the comparative example, thereby reducing power consumption. As mentioned above, this is thought to be due to the improved carrier injection efficiency into each quantum dot of the light-emitting layer 23 in the light-emitting element according to the embodiment.

[0135] As is clear from Graph G3, the light-emitting element in the embodiment exhibits a reduced rate of brightness reduction from maximum brightness due to operating time compared to the light-emitting element in the comparative example. In particular, in the comparative example, the brightness of the light-emitting element decreases to about 40% of the maximum brightness after about 50 hours from the application of voltage. On the other hand, in the embodiment, the brightness of the light-emitting element maintains about 60% of the maximum brightness even after about 140 hours from the application of voltage.

[0136] From this, it can be said that the light-emitting element according to the example has improved reliability of the functional layer including the light-emitting layer 23 compared to the light-emitting element according to the comparative example. This is thought to be because, in the light-emitting element according to the example, the recombination of holes and electrons in the porous 42, etc., which can cause deterioration of the functional layer, is reduced, and the reliability of the functional layer is improved.

[0137] This disclosure is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the different technical means disclosed in each embodiment are also included in the technical scope of this disclosure. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment.

[0138] 1 Display device 2 Light-emitting element 3 Substrate 21 Anode 22 Hole transport layer (functional layer) 23 Light-emitting layer (functional layer) 24 Electron transport layer (functional layer) 25 Cathode 31R Red quantum dot (light-emitting material) 31G Green quantum dot (light-emitting material) 31B Blue quantum dot (light-emitting material) 41 Adductor 42 Porous 43 Crack 51 Organic polymer 73 Precursor

Claims

1. A light-emitting element comprising: an anode; a cathode facing the anode; and one or more functional layers located between the anode and the cathode, each including a light-emitting layer containing a light-emitting material, wherein the one or more functional layers include a functional material, an adduct located around the functional material, and an organic polymer.

2. The light-emitting element according to claim 1, wherein the adduct has at least one of porosity and cracks, and the organic polymer fills at least a portion of at least one of the porosity and cracks.

3. The light-emitting element according to claim 2, wherein the adduct has at least one pore having an inner diameter of 0.5 nm or more and 10 nm or less, and the organic polymer fills at least a portion of the pore.

4. The light-emitting element according to claim 2 or 3, wherein the adduct has at least one crack having a maximum width of 10 nm or more and 1,000 nm or less, and the organic polymer fills at least a portion of the crack.

5. The light-emitting element according to any one of claims 1 to 4, wherein the number of carbon atoms in the organic polymer is 100 or more and 100,000 or less.

6. The light-emitting element according to any one of claims 1 to 5, wherein the organic polymer has 100 to 50,000 repeating units.

7. The light-emitting element according to any one of claims 1 to 6, wherein the organic polymer is a hydrocarbon polymer.

8. The light-emitting element according to any one of claims 1 to 7, wherein the organic polymer has only saturated bonds.

9. The light-emitting element according to any one of claims 1 to 8, wherein the organic polymer comprises at least one of polypropylene and polyethylene.

10. The light-emitting element according to any one of claims 1 to 7, wherein the organic polymer includes polystyrene.

11. The light-emitting element according to any one of claims 1 to 6, wherein the organic polymer comprises at least one of polyethylene terephthalate and polyacrylonitrile.

12. The molecular weight of the organic polymer is 10 ３ The above 10 ６ The following is a light-emitting element according to any one of claims 1 to 11.

13. The light-emitting element according to any one of claims 1 to 12, wherein the light-emitting layer comprises a plurality of light-emitting quantum dots as the functional material, the adducts and the organic polymer located around the quantum dots.

14. The light-emitting element according to claim 13, wherein the adduct surrounds at least one quantum dot or fills the space between at least two quantum dots.

15. The light-emitting element according to any one of claims 1 to 14, wherein the adduct comprises at least one of a metal oxide and a metal sulfide.

16. The light-emitting element according to claim 15, wherein the adduct is insulating.

17. The light-emitting element according to claim 16, wherein the adduct comprises at least one 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, silicon nitride, and magnesium oxide.

18. A display device comprising a substrate and a plurality of light-emitting elements according to any one of claims 1 to 17 on the substrate.

19. A method for manufacturing a light-emitting element, comprising: forming an anode; forming a cathode opposite the anode; and forming one or more functional layers located between the anode and the cathode, and including a light-emitting layer containing a light-emitting material, wherein the formation of the one or more functional layers includes forming layers containing a functional material, an adduct located around the functional material, and an organic polymer.

20. The method for manufacturing a light-emitting element according to claim 19, wherein the formation of one or more functional layers comprises the formation of a light-emitting layer comprising a plurality of light-emitting quantum dots as a functional material, an adduct and an organic polymer located around the quantum dots, and the formation of the light-emitting layer comprises: forming a film of a quantum dot dispersion containing precursors of the quantum dots and the adduct; forming a quantum dot layer comprising the quantum dots and the adduct by converting the precursors in the quantum dot dispersion to the adduct; and introducing the organic polymer into at least one of the porosity and cracks of the adduct by immersing the quantum dot layer in a dispersion containing the organic polymer.

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