WO2024084617A1 - 発光素子、表示装置、発光素子の製造方法 - Google Patents

発光素子、表示装置、発光素子の製造方法 Download PDF

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Publication number
WO2024084617A1
WO2024084617A1 PCT/JP2022/038898 JP2022038898W WO2024084617A1 WO 2024084617 A1 WO2024084617 A1 WO 2024084617A1 JP 2022038898 W JP2022038898 W JP 2022038898W WO 2024084617 A1 WO2024084617 A1 WO 2024084617A1
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light
inorganic filler
emitting layer
quantum dots
anode
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French (fr)
Japanese (ja)
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一輝 丸橋
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Sharp Display Technology Corp
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Sharp Display Technology Corp
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Priority to JP2024551122A priority Critical patent/JP7818094B2/ja
Priority to CN202280101229.7A priority patent/CN120092490A/zh
Priority to PCT/JP2022/038898 priority patent/WO2024084617A1/ja
Publication of WO2024084617A1 publication Critical patent/WO2024084617A1/ja
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B33/00—Electroluminescent light sources
    • H05B33/10—Apparatus or processes specially adapted to the manufacture of electroluminescent light sources
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B33/00—Electroluminescent light sources
    • H05B33/12—Light sources with substantially two-dimensional [2D] radiating surfaces
    • H05B33/14—Light sources with substantially two-dimensional [2D] radiating surfaces characterised by the chemical or physical composition or the arrangement of the electroluminescent material, or by the simultaneous addition of the electroluminescent material in or onto the light source
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B33/00—Electroluminescent light sources
    • H05B33/12—Light sources with substantially two-dimensional [2D] radiating surfaces
    • H05B33/20—Light sources with substantially two-dimensional [2D] radiating surfaces characterised by the chemical or physical composition or the arrangement of the material in which the electroluminescent material is embedded
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00—Organic light-emitting devices
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00

Definitions

  • This disclosure relates to a light-emitting element and a display device equipped with the light-emitting element.
  • Patent Document 1 discloses a light-emitting element in which the light-emitting layer contains multiple quantum dots with shell thicknesses that differ from one another, thereby improving the confinement of carriers to the quantum dots.
  • the light-emitting device disclosed in Patent Document 1 can be said to be configured to suppress reactive current by reducing the outflow of carriers injected into the quantum dots to the outside of the quantum dots. For this reason, it is difficult to reduce the reactive current flowing between the quantum dots in the light-emitting device disclosed in Patent Document 1.
  • a light-emitting element includes an anode, a cathode, and a light-emitting layer located between the anode and the cathode, the light-emitting layer having a plurality of quantum dots and an inorganic filler, the inorganic filler filling the spaces between the plurality of quantum dots and containing at least one of a metal sulfide or a metal oxide, and the inorganic filler has a lower concentration of at least one of sulfur atoms or oxygen atoms in the direction from the anode to the cathode.
  • a light-emitting element includes an anode, a cathode, and a light-emitting layer located between the anode and the cathode, the light-emitting layer having a plurality of quantum dots and an inorganic filler, the inorganic filler filling the spaces between the plurality of quantum dots and containing at least one of a metal sulfide and a metal oxide, and the inorganic filler has a portion on the cathode side where the concentration of at least one of the sulfur atoms or oxygen atoms is lower than the concentration of the at least one of the sulfur atoms or oxygen atoms on the anode side.
  • a light-emitting element includes an anode, a cathode, and a light-emitting layer located between the anode and the cathode, the light-emitting layer having a plurality of quantum dots and an inorganic filler, the inorganic filler filling the spaces between the plurality of quantum dots and containing at least one of a metal sulfide and a metal oxide, and the density of atomic defects of at least one of sulfur atoms and oxygen atoms in the inorganic filler increases in the direction from the anode to the cathode.
  • a light-emitting element includes an anode, a cathode, and a light-emitting layer located between the anode and the cathode, the light-emitting layer having a plurality of quantum dots and an inorganic filler material containing a chalcogenide and filling the spaces between the plurality of quantum dots, and in the inorganic filler material, the concentration of chalcogen element atoms decreases in the direction from the anode to the cathode.
  • a light-emitting element includes an anode, a cathode, and a light-emitting layer located between the anode and the cathode, the light-emitting layer having a plurality of quantum dots and an inorganic filler, the inorganic filler filling the spaces between the plurality of quantum dots, including a ternary compound semiconductor having metal atoms, having a concentration gradient of the metal atoms in the direction from the anode to the cathode, and the band gap of the inorganic filler decreasing in the direction from the anode to the cathode.
  • a method for manufacturing a light-emitting element includes an anode, a cathode, and a light-emitting layer located between the anode and the cathode, the light-emitting layer having a plurality of quantum dots and an inorganic filler, the inorganic filler filling the spaces between the quantum dots and including at least one of a metal sulfide and a metal oxide, the method including applying a first solution including the plurality of quantum dots and a first inorganic precursor, forming a first portion of the light-emitting layer by heating the first solution at a first temperature to transform the first inorganic precursor into the inorganic filler, applying a second solution including a second inorganic precursor onto the first portion, and forming a second portion of the light-emitting layer onto the first portion by heating the second solution at a second temperature higher than the first temperature to transform the second inorganic precursor into the inorganic filler.
  • a method for manufacturing a light-emitting element includes an anode, a cathode, and a light-emitting layer located between the anode and the cathode, the light-emitting layer having a plurality of quantum dots and an inorganic filler, the inorganic filler filling the spaces between the quantum dots and containing a ternary compound semiconductor having metal atoms, and having a concentration gradient of the metal atoms in a direction from the anode to the cathode, the method comprising: applying a first solution containing the plurality of quantum dots and a first inorganic precursor having a plurality of metal sources; forming a first portion of the light-emitting layer by transforming the first inorganic precursor into the inorganic filler by heating the first solution; applying a second solution on the first portion, the second solution containing a second inorganic precursor having a plurality of the metal sources, the ratio of the metal sources being different from that of the first solution; and
  • FIG. 2 is a diagram showing a schematic cross-sectional side view of the display device according to the first embodiment, a schematic cross-sectional view of quantum dots, and a schematic diagram showing an inorganic filler that fills spaces between the quantum dots.
  • 1 is a schematic plan view of a display device according to a first embodiment.
  • 4 is a flowchart illustrating an example of a method for manufacturing a light-emitting element according to the first embodiment.
  • FIG. 11 is a schematic cross-sectional side view of a display device according to a second embodiment.
  • FIG. 11 is a schematic cross-sectional side view of a display device according to a third embodiment.
  • 13 is a schematic band diagram of each layer of a light-emitting device according to a modified example of the third embodiment.
  • FIG. FIG. 11 is a schematic cross-sectional side view of a display device according to a fourth embodiment.
  • FIG. 2 is a schematic plan view of a display device according to the present embodiment.
  • the display device 1 is a device that can be used, for example, as a display for a television or a smartphone.
  • the display device 1 comprises a display unit DA and a frame unit NA formed on the outer periphery of the display unit DA.
  • the display device 1 performs display on the display unit DA by controlling the emission of light from each of a number of light-emitting elements (described below) formed in the display unit DA.
  • Drivers and the like for driving each of the multiple light-emitting elements of the display unit DA may be formed in the frame unit NA.
  • the display section DA of the display device 1 may include a plurality of sub-pixels including a red sub-pixel, a green sub-pixel, and a blue sub-pixel.
  • a light-emitting element which will be described later, is formed in each sub-pixel, and each light-emitting element individually emits light. This allows the display device 1 to perform display by individually controlling the emission of light from the plurality of light-emitting elements of the display section DA using, for example, a driver formed in the frame section NA.
  • Fig. 1 is a schematic side cross-sectional view 101 of the display device 1 according to this embodiment, a schematic cross-sectional view 102 of quantum dots 50 described later, and schematic views 103 and 104 showing inorganic filler 51 filling spaces between the quantum dots 50.
  • the direction from a substrate 20 to a cathode 26 of the display device 1 described later may be described as "upper”, and the opposite direction may be described as "lower”.
  • the schematic cross-sectional side view 101 is a cross-sectional view taken along line I-I in FIG. 2, and shows a cross section passing through the light-emitting element 11 in a plan view of the substrate 20 of the display device 1 according to this embodiment. Note that all schematic cross-sectional side views of the display device in this disclosure show a cross section of the display device corresponding to the cross section shown in the schematic cross-sectional side view 101.
  • the schematic cross-sectional view 102 is a diagram showing a cross-section of the quantum dot 50 passing through approximately the center of the quantum dot 50.
  • the schematic views 103 and 104 are respectively diagrams showing two examples of a set P of two quantum dots 50 and a region (space) K between them, as shown in the schematic cross-sectional side view 101.
  • the schematic views 103 and 104 are respectively diagrams showing sets P1 and P2, which are examples of sets of quantum dots 50A and quantum dots 50B.
  • display device 1 includes light-emitting element 11.
  • light-emitting element 11 includes substrate 20.
  • substrate 20 is formed at a position overlapping display section DA and frame section NA in a plan view of display device 1, and light-emitting element 11 may be considered to include a portion of substrate 20 that overlaps display section DA in a plan view of display device 1.
  • substrate 20 may be formed across display section DA and frame section NA in a plan view of display device 1.
  • the top surface of substrate 20 may be approximately parallel to the display surface of display device 1, in other words, the plan view of substrate 20 may be approximately the same as the plan view of display device 1.
  • the light-emitting element 11 includes, in order from the substrate 20 side, an anode 21, a hole injection layer 22, a hole transport layer 23, a light-emitting layer 24, an electron transport layer 25, and a cathode 26.
  • the light-emitting element 11 may include, in order from the substrate 20 side, a cathode, an electron transport layer, a light-emitting layer, a hole transport layer, a hole injection layer, and an anode.
  • the light-emitting element 11 may include an electron injection layer between the electron transport layer 25 and the cathode 26.
  • the light-emitting element 11 may be formed individually for each of the multiple sub-pixels described above.
  • the display device 1 may also include a driver or the like (not shown) at a position overlapping with the frame portion NA of the substrate 20 in a planar view.
  • the substrate 20 may include a pixel circuit (not shown) corresponding to each sub-pixel.
  • the pixel circuit may be electrically connected to the anode 21 of the light-emitting element 11.
  • the display device 1 may control the light emission from each light-emitting element 11 by controlling the application of a voltage to the anode 21 by each pixel circuit through the control of a driver or the like.
  • At least one of the anode 21 and the cathode 26 is a transparent electrode that transmits visible light.
  • the transparent electrode for example, ITO, InZnO, SnO 2 , FTO, or the like may be used.
  • either the anode 21 or the cathode 26 may be a reflective electrode.
  • the reflective electrode may contain a metal material having a high reflectance of visible light, and the metal material may be, for example, Al, Ag, Cu, or Au alone or an alloy of these.
  • the hole injection layer 22 is a layer that injects holes from the anode 21 to the light emitting layer 24.
  • the material of the hole injection layer 22 may be an organic or inorganic material having hole transport properties that has been conventionally adopted in light emitting devices including quantum dots.
  • the hole injection layer 22 may contain nickel oxide (NiO) nanoparticles.
  • the hole injection layer 22 may also contain a self-assembled monolayer of [2-(3,6-dimethoxy-9H-carbozol-9-yl)ethyl]phosphonic acid (MeO-2PACz).
  • the material of the hole injection layer 22 include a composite of poly(3,4-ethylenedioxythiophene) (PEDOT) and polystyrene sulfonic acid (PSS) (abbreviated as "PEDOT:PSS”), CuSCN (copper thiocyanate), and the like.
  • the hole injection layer 22 may contain bulk NiO (nickel oxide) that is not a nanoparticle as a material. These materials may be used alone or in combination of two or more.
  • the hole transport layer 23 is a layer that transports holes injected from the anode 21 into the hole injection layer 22 to the light emitting layer 24.
  • the material of the hole transport layer 23 can be an organic or inorganic material having hole transport properties that has been conventionally used in light emitting devices containing quantum dots.
  • Examples of materials for the hole transport layer 23 include poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4'-(N-4-sec-butylphenyl))diphenylamine)] (abbreviated as "TFB”), poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)-benzidine] (abbreviated as "poly-TPD”), polyvinylcarbazole (abbreviated as "PVK”), etc. These materials may be used alone or in a mixture or stack of two or more types as appropriate.
  • the electron transport layer 25 is a layer that transports electrons injected from the cathode 26 to the light-emitting layer 24.
  • the electron transport layer 25 according to this embodiment has nanoparticles 30 as an electron transport material.
  • the electron transport layer 25 may also contain a ligand capable of coordinating to the nanoparticles 30.
  • the nanoparticles 30 may be nanoparticles of zinc oxide (ZnO), zinc oxide (ZnO) doped with at least one of Li, Mg, Al, Ti, Ga, and Zr, titanium oxide (TiO 2 ), or zirconium oxide (ZrO 2 ).
  • ZnO zinc oxide
  • ZnO zinc oxide
  • TiO 2 titanium oxide
  • ZrO 2 zirconium oxide
  • the chemical formulas are representative examples.
  • the composition ratios described in the chemical formulas do not necessarily have to be stoichiometric, in which the composition of the actual compound is exactly as described in the chemical formula.
  • the electron transport material contained in the electron transport layer 25 is not limited to the nanoparticles 30.
  • the electron transport layer 25 may use an organic or inorganic material having electron transport properties that has been conventionally adopted in light-emitting devices containing quantum dots as the electron transport material.
  • the electron transport material may include, for example, 2,2',2"-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (abbreviated as "TPBi"), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (abbreviated as "BCP”), 4,7-diphenyl-1,10-phenanthroline (abbreviated as "Bphen”), or the like.
  • TPBi 2,2',2"-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole)
  • BCP 2,9-dimethyl-4,7-diphenyl-1,10-phen
  • the electron transport layer 25 may include bulk zinc oxide (ZnO), zinc oxide (ZnO), titanium oxide (TiO 2 ), or zirconium oxide (ZrO 2 ), which is not a nanoparticle, as the electron transport material.
  • Bulk zinc oxide (ZnO) may be doped with at least one of Li, Mg, Al, Ti, Ga, and Zr.
  • the electron transport material may include only one of the above-mentioned materials, or may include two or more of them as appropriate.
  • the light-emitting layer 24 includes, in order from the anode 21 side, a first light-emitting layer 40 as a first part and a second light-emitting layer 41 as a second part. Both the first light-emitting layer 40 and the second light-emitting layer 41 have a plurality of quantum dots 50 as light-emitting materials.
  • the quantum dots 50 have a core/shell structure including a core 50C and at least one shell 50S covering the periphery of the core 50C, as shown in, for example, a schematic cross-sectional view 102.
  • the shell 50S may have a plurality of layers from the center of the core 50C to the periphery.
  • the first light-emitting layer 40 and the second light-emitting layer 41 may include a ligand capable of coordinating with the shell 50S of the outermost layer of the quantum dots 50.
  • the core 50C of the quantum dot 50 emits light due to excitons generated by the recombination of holes and electrons injected from the anode 21 and the recombination of the holes and electrons.
  • the shell 50S of the quantum dot 50 may have a function of protecting the core 50C, such as compensating for defects in the core 50C.
  • the quantum dot 50 may also have various other structures that are known in the art.
  • quantum dot refers to a dot with a maximum width of 100 nm or less.
  • the shape of the quantum dot 50 may be within a range that satisfies the above maximum width, and is not particularly restricted, and is not limited to a spherical three-dimensional shape (circular cross-sectional shape).
  • the shape of the quantum dot 50 may be, for example, a polygonal cross-sectional shape, a rod-like three-dimensional shape, a branch-like three-dimensional shape, a three-dimensional shape with unevenness on the surface, or a combination of these.
  • the quantum dot 50 is typically made of a semiconductor.
  • the semiconductor may have a certain band gap.
  • the semiconductor may be any material capable of emitting light, and may include at least the materials described below.
  • the semiconductor may be capable of emitting blue, green, and red light, respectively.
  • the semiconductor may include at least one selected from the group consisting of II-VI compounds, III-V compounds, chalcogenides, and perovskite compounds.
  • the II-VI compounds refer to compounds containing II and VI elements
  • the III-V compounds refer to compounds containing III and V elements.
  • the II elements may include Group 2 and Group 12 elements
  • the III elements may include Group 3 and Group 13 elements
  • the V elements may include Group 5 and Group 15 elements
  • the VI elements may include Group 6 and Group 16 elements.
  • the II-VI compound includes, for example, at least one selected from the group consisting of MgS, MgSe, MgTe, CaS, CaSe, CaTe, SrS, SrSe, SrTe, BaS, BaSe, BaTe, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, HgS, HgSe, and HgTe.
  • the III-V compound includes, for example, at least one selected from the group consisting of GaAs, GaP, GaSb, InN, InAs, InP, and InSb.
  • Chalcogenides are compounds that contain elements from group VI A(16), such as CdS or CdSe. Chalcogenides may also include mixed crystals of these.
  • the perovskite compound has a composition represented by the general formula CsPbX 3 , CsSnX 3 , CH 3 NH 3 PbX 3 , or CH 3 NH 3 SnX 3.
  • the constituent element X includes at least one element selected from the group consisting of Cl, Br, and I, for example.
  • the numbering of element groups using Roman numerals is based on the old IUPAC (International Union of Pure and Applied Chemistry) system or the old CAS (Chemical Abstracts Service) system, and the numbering of element groups using Arabic numerals is based on the current IUPAC system.
  • the concentration of the quantum dots 50 in the first light-emitting layer 40 is higher than the concentration of the quantum dots 50 in the second light-emitting layer 41. Therefore, in the light-emitting layer 24, the concentration of the quantum dots 50 may have a portion where it is lower in the direction from the anode 21 to the cathode 26, may have a portion where it is gradually lower, may be lower throughout the entire light-emitting layer 24, or may be gradually lower throughout the entire layer. In the following, as an example, a case where the concentration is gradually lower throughout the entire light-emitting layer 24 will be described, but the present invention is not necessarily limited to this configuration.
  • the concentration of the material in each part of the light-emitting layer 24 “gradually decreases” is illustrated as an example, but is not necessarily limited to this configuration.
  • concentration of the material when the concentration of the material "gradually decreases," it does not exclude cases where there are parts where the concentration is lower, where there are parts where the concentration is gradually lower, where the concentration is lower throughout the entire light-emitting layer 24, or where the concentration is gradually lower throughout the entire layer.
  • the "gradually decreasing" concentration at the boundary between the light-emitting layer 24 and an adjacent layer may indicate a change in concentration that is not related to the desired concentration configuration. In other words, since the change in concentration of sulfur atoms and oxygen atoms at the boundary is not necessarily steep, the region 1.2 nm or less from the interface may be excluded from the light-emitting layer 27.
  • the concentration of a material in each part of the light-emitting layer 24 is, for example, the area ratio occupied by the material in the cross section of the light-emitting layer 24.
  • the gradually decreasing concentration of a material in each part of the light-emitting layer 24 refers to the concentration decreasing gradually or stepwise, and does not limit the presence of parts with approximately the same concentration of the material.
  • the part with approximately the same concentration of the material refers to a part where the difference in the area ratio occupied by the material in a 200 nm2 region is within 5% when observing the cross section of the light-emitting layer 24.
  • the area ratio occupied by the quantum dots 50 may be 60% or more from the viewpoint of reducing reactive current in which carriers are not injected into the quantum dots and do not contribute to light emission.
  • the area ratio may be 90% or less from the viewpoint of enhancing the protective effect of the inorganic filler 51 on the quantum dots 50, which will be described later.
  • the area ratio occupied by the quantum dots 50 may be 5% or more, and may be 60% or less from the viewpoint of enhancing the protective effect of the inorganic filler 51 on the quantum dots 50 against foreign matter from the cathode 26 side, which will be described later.
  • the light emitting layer 24 includes an inorganic filler 51 that fills spaces between the quantum dots 50.
  • the light emitting layer 24 includes the inorganic filler 51 as an inorganic matrix material that fills spaces between the quantum dots 50.
  • the inorganic filler 51 includes a first inorganic filler 52 and a second inorganic filler 53.
  • the first light emitting layer 40 includes the first inorganic filler 52 of the inorganic filler 51
  • the second light emitting layer 41 includes the second inorganic filler 53 of the inorganic filler 51.
  • the first light emitting layer 40 includes the first inorganic filler 52 that fills spaces between the quantum dots 50
  • the second light emitting layer 41 includes the first quantum dots 50 and the second inorganic filler 53 that fills spaces between the quantum dots 50.
  • inorganic filler 51 fills the spaces between multiple quantum dots 50, it is sufficient to understand that it fills at least region K between quantum dot 50A and quantum dot 50B, as shown in schematic diagram 103 of group P1 in FIG. 1.
  • Region K is a region surrounded by two straight lines (common circumscribing lines) tangent to the peripheries of quantum dot 50A and quantum dot 50B, and the opposing peripheries of quantum dot 50A and quantum dot 50B, in the cross section of light-emitting layer 24.
  • region K can exist even if quantum dot 50A and quantum dot 50B are close to each other, and inorganic filler 51 fills region K.
  • the inorganic filler 51 filling the gaps between the quantum dots 50 does not necessarily mean that the region K between the quantum dots 50A and 50B is entirely made of the inorganic filler 51.
  • the region K between the quantum dots 50A and 50B may contain a material such as a ligand different from the material of the inorganic filler 51.
  • the light-emitting layer 24 may contain an organic ligand that is added to improve the dispersibility of the quantum dots 50 in the solution used for coating and that is coordinated to the outer surface of the quantum dots 50 in the solution.
  • the weight ratio of the organic ligand to the total weight including the region K may be less than 5% from the viewpoint of improving the reliability of the light-emitting layer 24.
  • the inorganic filler 51 may fill areas of the light-emitting layer 24 other than the multiple quantum dots 50.
  • the outer edge (top and bottom) of the light-emitting layer 24 may be covered with the inorganic filler 51.
  • a portion of the inorganic filler 51 may extend from the outer edge of the light-emitting layer 24, and the quantum dots 50 may be positioned away from the outer edge.
  • the outer edge of the light-emitting layer 24 may not be formed only by the inorganic filler 51, and some of the quantum dots 50 may be exposed from the inorganic filler 51.
  • the inorganic filler 51 may refer to the portion of the light-emitting layer 24 other than the multiple quantum dots 50.
  • the inorganic filler 51 may contain a plurality of quantum dots 50.
  • the inorganic filler 51 may be formed so as to fill spaces formed between the plurality of quantum dots 50.
  • the plurality of quantum dots 50 may be embedded in the inorganic filler 51 at intervals.
  • the inorganic filler 51 may include a continuous film having an area of 1000 nm2 or more along a plane direction perpendicular to the film thickness direction.
  • the continuous film may be a film that is not separated by a material other than the material that constitutes the continuous film in one plane.
  • the continuous film may be an integral film that is connected without interruption by chemical bonds of the inorganic filler 51.
  • the concentration of the inorganic filler 51 in the light-emitting layer 24 is, for example, the area ratio occupied by the inorganic filler 51 in the cross section of the light-emitting layer 24. This concentration may be 10% or more and 90% or less, or 30% or more and 70% or less, in cross-sectional observation. This concentration may be measured, for example, from the area ratio of an image obtained by cross-sectional observation.
  • the concentration of the shell 50S may be 1% or more and 50% or less.
  • the ratios of the core 50C, the shell 50S, and the inorganic filler 51 may be appropriately adjusted so that the sum is 100% or less.
  • the shell 50S of the outermost layer of the quantum dots 50 and the inorganic filler 51 may contain the same material.
  • the lattice mismatch at the interface between the shell 50S and the inorganic filler 51 is reduced, and defects such as dangling bonds at the interface are reduced. Therefore, the above configuration improves the efficiency of carrier injection into the quantum dots 50.
  • the above configuration also suppresses a decrease in the protective effect of the quantum dots 50 caused by defects at the interface, and also suppresses deactivation of excitons in the quantum dots 50, thereby improving the reliability of the light-emitting layer 24 and the luminous efficiency of the light-emitting element 11.
  • the shell 50S of the outermost layer of the quantum dot 50 and the inorganic filler 51 may be made of the same material.
  • the shell 50S of the outermost layer of the quantum dot 50 and the inorganic filler 51 may be distinguished by checking the difference in crystallinity. For example, when observing a cross section of the light-emitting layer 24, if there are parts that are made of the same composition but have different crystallinity, the one with the higher crystallinity may be regarded as the shell 50S and the other as the inorganic filler 51. If the shell 50S and the inorganic filler 51 cannot be distinguished, the shell 50S may be considered as part of the inorganic filler 51.
  • the light-emitting layer 24 may be composed of a plurality of quantum dots 50 and an inorganic filler 51.
  • the intensity of carbon detected by the chain structure may be equal to or less than the noise.
  • the percentage of carbon detected from the light-emitting layer 24 may be 5% or less, 1% or less, or may not be detected at all.
  • quantum dots 50 coordinated with organic ligands are used in the light-emitting layer 24 as in the known technology, the carbon chain of the organic ligand may decompose, or the organic ligand itself may come off the quantum dot, with long-term operation. In this case, the quantum dots 50 may deteriorate and the brightness may decrease.
  • the display device 1 can achieve high reliability, in other words, it can achieve suppression of brightness decrease with long-term operation of the light-emitting element 11.
  • the inorganic filler 51 includes at least one of a metal sulfide and a metal oxide.
  • the metal sulfide may be, for example, zinc sulfide (ZnS), zinc magnesium sulfide (Zn x Mg 1-x S (0 ⁇ x ⁇ 1), ZnMgS 2 ), gallium sulfide (GaS, Ga 2 S 3 ), zinc tellurium sulfide (Zn x Te 1-x S (0 ⁇ x ⁇ 1)), magnesium sulfide (MgS), zinc digallium tetrasulfide (ZnGa 2 S 4 ), or magnesium digallium tetrasulfide (MgGa 2 S 4 ).
  • the metal oxide may be zinc oxide (ZnO), titanium oxide (TiO 2 ), tin oxide (SnO 2 ), tungsten oxide (WO 3 ), or zirconium oxide (ZrO 2 ). It is desirable that the constituent material of the inorganic filler 51 has a band gap wider than that of the constituent material of the quantum dot 50 (for example, the material of the core 50C or the shell 50S).
  • inorganic filler 51 may include a chalcogenide, including a metal sulfide or a metal oxide.
  • inorganic filler 51 may include a compound that includes a Group VI A(16) element.
  • the first inorganic filler 52 and the second inorganic filler 53 may be made of inorganic materials of the same composition. This reduces the lattice mismatch between the first inorganic filler 52 and the second inorganic filler 53. Therefore, with the above configuration, the light-emitting element 11 reduces defects such as dangling bonds at the boundary between the first light-emitting layer 40 and the second light-emitting layer 41, further improving the reliability of the light-emitting layer 24 and the light-emitting efficiency of the light-emitting element 11.
  • materials of the same composition do not mean made of the exact same material, and may have, for example, 5% or less of atomic substitutions or defects.
  • a first surface is defined as connecting the quantum dots 50 located in the first light-emitting layer 40 closest to the cathode 26 and a second surface is defined as connecting the quantum dots 50 located in the second light-emitting layer 41 closest to the anode 21, at each position in the plan view of the substrate 20.
  • the interface between the first light-emitting layer 40 and the second light-emitting layer 41 may be located between the first surface and the second surface.
  • the light-emitting element 11 may have a layer between the first surface and the second surface that contains the first inorganic filler 52 and the second inorganic filler 53 and does not contain quantum dots 50.
  • the boundary between the light-emitting layer 24 and the electron transport layer 25 may be confirmed by observing a cross section passing through the light-emitting layer 24 and the electron transport layer 25 to confirm the concentration of sulfur atoms or oxygen atoms at each position of the cross section.
  • the boundary between the light-emitting layer 24 and the electron transport layer 25 may be confirmed by taking the portion in the cross section where the concentration of sulfur atoms or oxygen atoms is 25% or more as the light-emitting layer 24 and the portion where the concentration is less than 25% as the electron transport layer 25.
  • the portion in the cross section where the concentration of sulfur atoms or oxygen atoms decreases by 25% or more may be regarded as the boundary between the light-emitting layer 24 and the electron transport layer 25.
  • the portion where the concentration of the atom changes by 25% or more may be regarded as the boundary between the light-emitting layer 24 and the electron transport layer 25. Therefore, as long as the above is satisfied, a portion in the vicinity of which quantum dots 50 are not confirmed may also be regarded as part of the light-emitting layer 24.
  • the change in concentration of sulfur atoms and oxygen atoms is not necessarily steep at the interface between the light-emitting layer 24 and the electron transport layer 25. For this reason, the region 1.2 nm or less on the anode 21 side from the interface determined above may be excluded from the light-emitting layer 24, or may be included in the electron transport layer 25.
  • the concentration of sulfur atoms in the first inorganic filler 52 is higher than the concentration of sulfur atoms in the second inorganic filler 53.
  • the concentration of oxygen atoms in the first inorganic filler 52 is higher than the concentration of oxygen atoms in the second inorganic filler 53. Therefore, in the inorganic filler 51, the concentration of at least one of sulfur atoms and oxygen atoms gradually decreases in the direction from the anode 21 to the cathode 26.
  • the concentration of atoms of the chalcogen element contained in the chalcogenide gradually or stepwise decreases in the direction from the anode 21 to the cathode 26.
  • the density of atomic defects of sulfur atoms in the first inorganic filler 52 is lower than the density of atomic defects of sulfur atoms in the second inorganic filler 53.
  • the density of atomic defects of oxygen atoms in the first inorganic filler 52 is lower than the density of atomic defects of oxygen atoms in the second inorganic filler 53. Therefore, in the inorganic filler 51, the density of atomic defects of at least one of sulfur atoms or oxygen atoms gradually increases in the direction from the anode 21 to the cathode 26.
  • the difference in the concentration of sulfur atoms or oxygen atoms at each position of the inorganic filler 51 in the direction from the anode 21 to the cathode 26 may correspond to the difference in the density of defects of sulfur atoms or defects of oxygen atoms in the inorganic filler 51 at each position.
  • the concentration of atomic defects in the atoms of the chalcogen element contained in the chalcogenide in the inorganic filler 51 increases gradually or in steps in the direction from the anode 21 to the cathode 26.
  • the atomic concentration of the chalcogen element in the inorganic filler (inorganic matrix material) 51 decreases gradually or in steps in the direction from the anode 21 to the cathode 26.
  • the metal sulfide and metal oxide of the inorganic filler 51 may be read as chalcogenide, and the sulfur atoms and oxygen atoms of the inorganic filler 51 may be read as atoms of the chalcogen element.
  • the concentration of sulfur or oxygen atoms in inorganic filler 51 correlates with the density of free electrons at each position of inorganic filler 51. This is because the concentration of free electrons possessed by inorganic filler 51 changes depending on the concentration of sulfur or oxygen atoms in inorganic filler 51. In particular, when defects of sulfur or oxygen atoms occur in inorganic filler 51 and the defects are activated, two free electrons are generated per defect in the vicinity of the defect.
  • the hole density at the interface between the hole transport layer 23 and the light-emitting layer 24 is expressed by the following formula.
  • e is the elementary charge
  • ⁇ 0 is the dielectric constant of a vacuum
  • ⁇ r is the relative dielectric constant of the hole transport layer
  • J is the current density of the hole transport layer
  • L is the film thickness of the hole transport layer
  • ⁇ is the hole mobility of the hole transport layer 23.
  • the vicinity of the interface refers to a region within 1.2 nm from the interface in the film thickness direction.
  • the current density J flowing through the hole transport layer 23 is 10 mA/cm 2.
  • the relative dielectric constant ⁇ r of the hole transport layer 23 is 3.5
  • the film thickness L is 30 nm
  • the hole mobility ⁇ is 10 ⁇ 4 cm 2 /Vs.
  • the hole density p in the vicinity of the interface between the hole transport layer 23 and the light emitting layer 24 is 1.4 ⁇ 10 16 cm ⁇ 3 .
  • the density of free electrons in the inorganic filler 51 may be 1 ⁇ 10 16 cm -3 or less in a region within 1.2 nm in the film thickness direction from the end face of the light emitting layer 24 on the anode 21 side.
  • the density of free electrons in the first inorganic filler 52 in the first light emitting layer 40 may be 1 ⁇ 10 16 cm -3 or less in a region within 1.2 nm in the film thickness direction of the first light emitting layer 40 from the interface between the hole transport layer 23 and the first light emitting layer 40.
  • the activation rate of the inorganic filler 51 is not high, and is considered to be about 1%.
  • the activation rate of the inorganic filler 51 in the light-emitting layer 24 is set to 1%, in other words, one of every 100 sulfur or oxygen atom defects in the inorganic filler 51 is activated to generate two free electrons.
  • the defect density of the sulfur or oxygen atoms of the inorganic filler 51 may be 5 ⁇ 10 17 cm ⁇ 3 or less.
  • the density of the free electrons of the inorganic filler 51 in this region can be set to 1 ⁇ 10 16 cm ⁇ 3 or less, and the efficiency of injection of holes from the hole transport layer 23 to the light-emitting layer 24 can be improved.
  • the free electron density of the inorganic filler 51 is small, the resistivity of the inorganic filler 51 is high. This reduces reactive current that does not contribute to light emission, which is generated when carriers flow through the inorganic filler 51 and are not injected into the quantum dots 50. Therefore, with the above configuration, the light emission efficiency of the light emitting element 11 is improved.
  • inorganic filler 51 is made of zinc sulfide (ZnS)
  • ZnS zinc sulfide
  • the lattice constant of sulfur sulfide is about 5.87 ⁇
  • each lattice contains four sulfur atoms. Therefore, in the above case, the ratio of sulfur atom defects to zinc atoms in inorganic filler 51 is 5 ⁇ 10 17 cm -3 ⁇ (5.87 ⁇ ) 3 /4, or about 2.5 ⁇ 10 -3 %.
  • the density of free electrons on the electron transport layer 25 side of the light-emitting layer 24 will be considered. If free electrons are present near the interface between the electron transport layer 25 and the light-emitting layer 24, the free electrons will move in the light-emitting layer 24 to the anode 21 side when the light-emitting element 11 is driven. For this reason, if the density of free electrons on the electron transport layer 25 side of the light-emitting layer 24 is high, a greater proportion of free electrons will flow between the quantum dots 50 where they are injected into the quantum dots 50.
  • the electron mobility in the light-emitting layer 24 will decrease, which may result in a decrease in the electron transport ability of the light-emitting layer 24.
  • the concentration of electrons injected from the electron transport layer 25 will decrease, which may lead to an excess of holes in the light-emitting layer 24.
  • the density of free electrons near the interface between the electron transport layer 25 and the light-emitting layer 24 be within a predetermined range.
  • the density of free electrons in the light emitting layer 24 near the interface between the light emitting layer 24 and the electron transport layer 25 is preferably equal to or higher than the density of free electrons in the electron transport layer 25.
  • the density of free electrons in the electron transport layer 25 is about 1 ⁇ 10 18 cm ⁇ 3 .
  • the density of free electrons in the inorganic filler 51 may be 1 ⁇ 10 18 cm ⁇ 3 or higher in a region within 1.2 nm in the film thickness direction from the end face on the cathode 26 side of the light emitting layer 24.
  • the density of free electrons in the second inorganic filler 53 in the second light emitting layer 41 may be 1 ⁇ 10 18 cm ⁇ 3 or higher in a region within 1.2 nm in the film thickness direction of the second light emitting layer 41 from the interface between the electron transport layer 25 and the second light emitting layer 41.
  • the activation rate of inorganic filler 51 in light-emitting layer 24 is set to 1%.
  • the defect density of sulfur atoms or oxygen atoms in inorganic filler 51 may be 5 ⁇ 10 19 cm -3 or more in a region within 1.2 nm in the film thickness direction from the end face of light-emitting layer 24 on the cathode 26 side.
  • the density of free electrons in inorganic filler 51 in this region can be made 1 ⁇ 10 18 cm -3 or more, and the efficiency of injection of electrons from electron transport layer 25 to light-emitting layer 24 can be improved.
  • the atomic defects of the inorganic filler 51 of the light-emitting layer 24 near the interface between the electron transport layer 25 and the light-emitting layer 24 are about 10% or less.
  • the inorganic filler 51 is made of zinc sulfide (ZnS)
  • ZnS zinc sulfide
  • the value obtained by multiplying the density of atomic defects by (5.87 ⁇ ) 3 /4 should be 0.1 or less.
  • the density of atomic defects that satisfies the above is 0.1 ⁇ 4/(5.87 ⁇ ) 3 or less, which is approximately 2 ⁇ 10 21 cm -3 or less.
  • the defect density of sulfur atoms or oxygen atoms of the inorganic filler 51 may be 2 ⁇ 10 21 cm -3 or less in a region within 1.2 nm in the film thickness direction from the end face of the light-emitting layer 24 on the cathode 26 side.
  • the defect density of sulfur atoms or oxygen atoms of the second inorganic filler 53 in the second light-emitting layer 41 may be 2 ⁇ 10 21 cm -3 or less in a region within 1.2 nm in the film thickness direction of the second light-emitting layer 41 from the interface between the electron transport layer 25 and the second light-emitting layer 41.
  • the activation rate of inorganic filler 51 in light-emitting layer 24 is set to 1%.
  • the density of free electrons in inorganic filler 51 may be 4 ⁇ 10 19 cm -3 or less in a region within 1.2 nm in the film thickness direction from the end face of light-emitting layer 24 on the cathode 26 side.
  • the defect density of sulfur atoms or oxygen atoms in inorganic filler 51 in this region can be set to 2 ⁇ 10 21 cm -3 or less, and the decrease in the electron transport ability of light-emitting layer 24 can be reduced.
  • the density of free electrons in a region within 1.2 nm in the film thickness direction from the end face on the anode 21 side of the light-emitting layer 24 may be 1/10 or less of the density of free electrons in a region within 1.2 nm in the film thickness direction from the end face on the cathode 26 side of the light-emitting layer 24.
  • the density of free electrons in the first inorganic filler 52 of the first light-emitting layer 40 may be 1/10 or less of the density of free electrons in the second inorganic filler 53 of the second light-emitting layer 41.
  • the efficiency of hole injection and the efficiency of electron injection into the light-emitting layer 24 can be improved in both directions, so that the driving voltage of the light-emitting element 11 can be reduced and the energy efficiency of the light-emitting layer 24 can be improved. Furthermore, the carrier balance in the light-emitting layer 24 can be adjusted, and the light-emitting efficiency of the light-emitting element 11 is improved.
  • Fig. 3 is a flow chart showing the method for manufacturing the light emitting device 11 according to this embodiment.
  • a substrate 20 is prepared (step S1).
  • the substrate 20 may be a glass substrate or a film substrate, etc., on which a pixel circuit is formed for each sub-pixel.
  • the substrate 20 may also be formed with a driver in the frame portion NA and wiring between the driver and each pixel circuit, etc.
  • the anode 21 is formed on the substrate 20 (step S2).
  • the anode 21 may be formed by depositing a thin film of a metal material on the substrate 20 by a sputtering method or the like.
  • the anode 21 may be formed so as to be electrically connected to the pixel circuit, or may be patterned for each sub-pixel.
  • the anode 21 may be formed by forming an ITO film with a thickness of 30 nm on the substrate 20 by a sputtering method.
  • a hole injection layer 22 is formed on the anode 21 (step S3).
  • step S32 for example, a solution in which nickel oxide nanoparticles are dispersed at 15 mg/mL in a solvent in which water and 2-methoxyethanol are mixed in equal volumes may be applied to the anode 21 by spin coating and baked at 200 degrees. The process may be performed only once, or may be repeated about two to five times.
  • a solution in which MeO-2PACz is dispersed in an ethanol solvent may be applied to the layer of nickel oxide nanoparticles by spin coating under a nitrogen atmosphere, and the solvent may be evaporated by baking. This may form a layered structure of the layer of nickel oxide nanoparticles and the self-assembled monolayer of MeO-2PACz to form the hole injection layer 22.
  • a hole transport layer 23 is formed on the hole injection layer 22 (step S4).
  • a solution in which poly-TPD is dispersed in a chlorobenzene solvent may be applied to the self-assembled monolayer by spin coating in a nitrogen atmosphere, and the solvent may then be volatilized by baking.
  • a poly-TPD film with a thickness of 30 nm may be formed on the self-assembled monolayer to form the hole transport layer 23.
  • a TFB film or a PVK film may be formed instead of the poly-TPD film.
  • the light-emitting layer 24 is formed on the hole transport layer 23.
  • the light-emitting layer 24 is formed by forming the first light-emitting layer 40 and then forming the second light-emitting layer 41 on the first light-emitting layer 40.
  • a first solution synthesized in advance in a separate process is applied onto the hole transport layer 23 by a spin coating method or the like (step S5).
  • the first solution is a mixed solution containing a plurality of quantum dots 50 and a first inorganic precursor which is a precursor of the first inorganic filler 52.
  • the first inorganic precursor contains a metal source for the first inorganic filler 52 and a sulfur source or an oxygen source.
  • the first solution applied onto the hole transport layer 23 is heated at a first temperature (step S6).
  • the first temperature may be 150°C.
  • the first solution applied onto the hole transport layer 23 may be heated for 30 minutes in an atmosphere of 150°C.
  • the solvent of the first solution evaporates and the first inorganic precursor in the first solution is modified to form a first inorganic filler 52.
  • the first inorganic precursor in the first solution is modified by heating in step S6, and a first inorganic filler 52 is gradually formed around the quantum dots 50 in the first solution. Therefore, by step S6, the first inorganic filler 52 is formed so as to fill the spaces between the multiple quantum dots 50.
  • a first light-emitting layer 40 is formed, which includes multiple quantum dots 50 and the first inorganic filler 52 that fills the spaces between the quantum dots 50.
  • the second solution synthesized in advance in a separate process is applied onto the first light-emitting layer 40 by a spin coating method or the like (step S7).
  • the second solution is a mixed solution containing a plurality of quantum dots 50 and a second inorganic precursor which is a precursor of the second inorganic filler 53.
  • the second inorganic precursor contains a metal source of the second inorganic filler 53 and a sulfur source or an oxygen source.
  • the precursor i.e., the first inorganic precursor and the second inorganic precursor
  • the precursor may contain, for example, a zinc source containing zinc carboxylate or the like, a magnesium source containing magnesium carboxylate or the like, a selenium source containing selenourea or the like, or a sulfur source containing thiourea or the like.
  • the precursor may contain, for example, at least one of a metal acetate, a metal nitrate, or a metal halide salt as a metal source, and thiourea, N-methylthiourea, 1,3-dimethylthiourea, N,N'-dimethylthiourea, tetramethylthiourea, or thioacetamide as a sulfur source.
  • the precursor 36 may contain a metal complex in which a metal atom is coordinated with thiourea, N-methylthiourea, 1,3-dimethylthiourea, N,N'-dimethylthiourea, tetramethylthiourea, or thioacetamide.
  • the concentration of quantum dots 50 relative to the concentration of the second inorganic precursor in the second solution is lower than the concentration of quantum dots 50 relative to the concentration of the first inorganic precursor in the first solution. This makes it possible to make the concentration of quantum dots 50 in the second light-emitting layer 41 formed by the method described below lower than the quantum dots 50 in the first light-emitting layer 40, while making the amount of the second solution applied in step S8 substantially the same as the amount of the first solution applied in step S6.
  • the second solution applied onto the first light-emitting layer 40 is heated at a second temperature higher than the first temperature (step S8).
  • the second temperature may be 200°C.
  • the second solution applied onto the first light-emitting layer 40 may be heated for 30 minutes in an atmosphere at 200°C.
  • the solvent of the second solution evaporates and the second inorganic precursor in the second solution is modified to form the second inorganic filler 53.
  • the second light-emitting layer 41 is formed, which includes a plurality of quantum dots 50 and the second inorganic filler 53 filling the spaces between the quantum dots 50, similar to the first light-emitting layer 40.
  • Both steps S6 and S8 include a process of heating a solution containing a precursor having a metal source of inorganic filler 51 and a sulfur source or an oxygen source.
  • the sulfur source or oxygen source contained in the precursor in the solution may volatilize together with the solvent.
  • the amount of volatilization of the sulfur source or oxygen source tends to increase as the heating temperature of the solution increases.
  • the heating temperature of the second solution in step S8 is a second temperature, which is higher than the first temperature, which is the heating temperature of the first solution in step S6. Therefore, the proportion of the sulfur source or oxygen source that volatilizes from the second solution in step S8 is higher than the proportion of the sulfur source or oxygen source that volatilizes from the first solution in step S6.
  • the first and second solutions heated in steps S6 and S8 both contain quantum dots 50. Therefore, in order to improve the dispersibility of the quantum dots 50 in the first and second solutions, xanthogenic acid may be added to both solutions as a ligand capable of coordinating with the quantum dots 50.
  • the concentration of quantum dots 50 in the second solution is lower than the concentration of quantum dots 50 in the first solution. Therefore, when xanthogenic acid is added to the first solution and the second solution, the proportion of xanthogenic acid coordinated to the quantum dots 50 in the second solution is lower than the proportion of xanthogenic acid coordinated to the quantum dots 50 in the first solution.
  • the concentration of sulfur atoms derived from xanthogenic acid remaining in the second light-emitting layer 41 is lower than the concentration of sulfur atoms derived from xanthogenic acid remaining in the first light-emitting layer 40. Therefore, the density of atomic defects of sulfur atoms in the second inorganic filler 53 of the second light-emitting layer 41 is greater than the density of atomic defects of sulfur atoms in the first inorganic filler 52 of the first light-emitting layer 40.
  • the density of atomic defects of sulfur atoms or oxygen atoms in the second inorganic filler 53 formed in step S8 is higher than the density of atomic defects of sulfur atoms or oxygen atoms in the first inorganic filler 52 formed in step S6. Therefore, the above process forms a light-emitting layer 24 having an inorganic filler 51 in which the density of atomic defects of at least one of sulfur atoms or oxygen atoms gradually increases in the direction from the anode 21 to the cathode 26. In other words, the above process forms a light-emitting layer 24 having an inorganic filler 51 in which the concentration of at least one of sulfur atoms or oxygen atoms gradually decreases in the direction from the anode 21 to the cathode 26.
  • the electron transport layer 25 is formed on the light-emitting layer 24 (step S9).
  • a solution in which zinc oxide nanoparticles 30 are dispersed in an ethanol solvent may be applied to the light-emitting layer 24 by a spin coating method or the like under a nitrogen atmosphere, and the solution may be dried to form the electron transport layer 25 having a thickness of 60 nm.
  • the zinc oxide nanoparticles 30 may be doped with at least one of Li, Mg, Al, Ti, Ga, and Zr.
  • the nanoparticles 30 may also be titanium oxide or zirconium oxide nanoparticles.
  • the cathode 26 is formed on the electron transport layer 25 (step S10).
  • the cathode 26 may be formed by depositing a 50 nm-thick silver thin film by vacuum deposition. In this manner, the light-emitting element 11 is manufactured.
  • the manufacture of the display device 1 may be completed, or, following the manufacture of the light-emitting element 11, a sealing layer or the like may be formed to seal or protect the light-emitting element 11.
  • the light-emitting element 11 includes a light-emitting layer 24 having a plurality of quantum dots 50 and an inorganic filler 51 filling spaces between the plurality of quantum dots 50.
  • the inorganic filler 51 contains at least one of a metal sulfide and a metal oxide, and the concentration of at least one of sulfur atoms and oxygen atoms gradually decreases in the direction from the anode 21 to the cathode 26.
  • the density of defects of at least one of sulfur atoms and oxygen atoms gradually increases in the direction from the anode 21 to the cathode 26.
  • the light-emitting element 11 can improve the efficiency of hole injection and the efficiency of electron injection into the light-emitting layer 24 in both directions, so that the driving voltage of the light-emitting element 11 can be reduced and the energy efficiency of the light-emitting layer 24 can be improved. Furthermore, the carrier balance in the light-emitting layer 24 can be adjusted, improving the light-emitting efficiency of the light-emitting element 11.
  • the concentration of the quantum dots 50 in the second light-emitting layer 41 is lower than the concentration of the quantum dots 50 in the first light-emitting layer 40. Therefore, in the light-emitting layer 24, the concentration of the quantum dots 50 gradually decreases in the direction from the anode 21 to the cathode 26.
  • the mobility of electrons in a semiconductor is higher than that of holes, so that in the light-emitting layer 24 containing quantum dots 50, light is mainly emitted from the quantum dots 50 located on the anode 21 side. Therefore, with the above configuration, the free electron density of the first inorganic filler 52 on the anode 21 side in the light-emitting layer 24 is small, so the resistance is large. As a result, the light-emitting layer 24 can reduce reactive current that does not contribute to light emission, which is generated when carriers do not enter the quantum dots 50 and flow through the first inorganic filler 52. Therefore, with the above configuration, the light-emitting element 11 can more efficiently obtain light emission from the quantum dots 50.
  • defects in the inorganic filler 52 are more likely to be formed on the surface than inside. Therefore, with the above configuration, the average distance between the defects and the quantum dots 50 can be increased, and therefore deactivation of excitons due to defects can be suppressed, and the light-emitting efficiency of the light-emitting element 1 can be improved.
  • the second light-emitting layer 41 can effectively increase the thickness of the inorganic filler 51 that fills the spaces between the quantum dots 50 compared to the first light-emitting layer 40, thereby enhancing the protective effect of the inorganic filler 51 on the quantum dots 50. Therefore, the light-emitting element 11 can more efficiently protect the light-emitting layer 24 from foreign matter such as moisture and oxygen that infiltrate from the cathode 26 side, or heat that propagates from the cathode 26 side.
  • the light-emitting element 11 has an anode 21 on the substrate 20 side.
  • the infiltration of foreign matter such as moisture is less likely to progress in the substrate 20 than in the layers between the electrodes of the light-emitting element 11.
  • foreign matter is more likely to infiltrate the light-emitting element 11 from the cathode 26 side, which is the side opposite the substrate 20 side.
  • the electron transport layer 25 located on the cathode 26 side of the light-emitting layer 24 has nanoparticles 30, foreign matter that has infiltrated the light-emitting element 11 from the cathode 26 side is more likely to reach the light-emitting layer 24 through the nanoparticles 30.
  • the light-emitting element 11 can more efficiently enhance the protective effect of the quantum dots 50 by the inorganic filler 51 of the light-emitting layer 24 due to the above-mentioned configuration. Since the infiltration of foreign matter such as moisture is less likely to progress in a glass substrate than in a film substrate, it is preferable that the substrate 20 is a glass substrate.
  • the inorganic filler 51 may contain a binary compound semiconductor.
  • the difference in density of atomic defects of sulfur atoms or oxygen atoms at each position of the inorganic filler 51 can be easily realized by the difference in heating temperature in the above-mentioned steps S6 and S8.
  • the inorganic filler 51 may contain zinc sulfide from the viewpoint of increasing the efficiency of carrier injection into the quantum dots 50 while enhancing the protective effect of the quantum dots 50.
  • Fig. 4 is a schematic side cross-sectional view of the display device 2 according to the present embodiment.
  • the display device 2 according to the present embodiment has the same configuration as the display device 1 according to the previous embodiment, except that it includes a light-emitting element 12 instead of the light-emitting element 11.
  • the light-emitting element 12 has the same configuration as the light-emitting element 11 according to the previous embodiment, except that it includes a light-emitting layer 27 instead of the light-emitting layer 24.
  • the light-emitting layer 27 has, in order from the anode 21 side, a first light-emitting layer 40 and a second light-emitting layer 42.
  • the first light-emitting layer 40 of this embodiment has the same configuration as the first light-emitting layer 40 of the previous embodiment.
  • the second light-emitting layer 42 of this embodiment differs from the second light-emitting layer 41 of the previous embodiment only in that it has only a second inorganic filler 53 and does not have quantum dots 50.
  • the light-emitting layer 27 has a first light-emitting layer 40 as a quantum dot layer, which includes quantum dots 50 and a first inorganic filler 52 as an inorganic filler 51.
  • the light-emitting layer 27 also has a second light-emitting layer 42 as an inorganic filler layer, which includes a second inorganic filler 53 as an inorganic filler 51.
  • the second light-emitting layer 42 has only the inorganic filler 51 out of the quantum dots 50 and the inorganic filler 51. As long as this configuration is satisfied, the second light-emitting layer 42 may have a material different from the quantum dots 50 and the inorganic filler 51.
  • the light-emitting layer 27 has a plurality of quantum dots 50, and further has, as the inorganic filler 51, a first inorganic filler 52 and a second inorganic filler 53, in that order from the anode 21 side. Therefore, also in this embodiment, the inorganic filler 51 contains at least one of a metal sulfide or a metal oxide, and the concentration of at least one of the sulfur atoms or oxygen atoms gradually decreases in the direction from the anode 21 to the cathode 26. In particular, in the inorganic filler 51, the density of defects of at least one of the sulfur atoms or oxygen atoms gradually increases in the direction from the anode 21 to the cathode 26.
  • the light-emitting element 12 suppresses the movement of electrons injected from the electron transport layer 25 in the light-emitting layer 27 between the quantum dots 50 for the same reasons as those explained for the light-emitting element 11. Therefore, the light-emitting element 12 reduces the reactive current in the light-emitting layer 24, improving the light-emitting efficiency and reliability.
  • the light-emitting layer 27 of the light-emitting element 12 has a second light-emitting layer 42 that does not have quantum dots 50. Therefore, the light-emitting layer 27 does not have quantum dots 50 that may be deteriorated by foreign matter from the cathode 26 side in the second light-emitting layer 42 on the cathode 26 side. In addition, since the second light-emitting layer 42 does not contain quantum dots 50, the effective film thickness of the second inorganic filler 53 is increased, and the protective effect of the light-emitting layer 27 is increased.
  • the light-emitting layer 27 efficiently transports electrons, which have a higher mobility than holes, from the second light-emitting layer 42 to the first light-emitting layer 40, and light is emitted from the quantum dots 50 in the first light-emitting layer 40. Therefore, the light-emitting element 12 can improve the light-emitting efficiency while more efficiently increasing the protective effect of the quantum dots 50 by the inorganic filler 51 of the light-emitting layer 24.
  • the film thickness of the second light-emitting layer 42 may be 1.2 nm or more, or 6 nm or more. As a result, the second light-emitting layer 42 has a thickness that is approximately twice or more the unit cell of the second inorganic filler, which can efficiently enhance the protective effect of the light-emitting layer 27.
  • the density of free electrons in the inorganic filler 51 may be 1 ⁇ 10 18 cm ⁇ 3 or more in a region within 1.2 nm in the film thickness direction from the end face of the light-emitting layer 27 on the cathode 26 side.
  • the above configuration can sufficiently increase the free electron density in the region, and therefore the light-emitting layer 27 is preferable because it can reduce the resistivity of the inorganic filler 51 in the above region, thereby minimizing the increase in the driving voltage of the light-emitting element 12 and increasing the protection effect of the quantum dots 50.
  • the boundary between the light-emitting layer 27 and the electron transport layer 25 may be confirmed by observing a cross section passing through the light-emitting layer 27 and the electron transport layer 25 and confirming the composition of the material at each position of the cross section.
  • the portion where the concentration of at least one atom contained in the second inorganic filler 53 is 25% or less may be regarded as the boundary between the light-emitting layer 27 and the electron transport layer 25.
  • the portion where the concentration of at least one atom contained in the second inorganic filler 53 decreases by 25% or more may be regarded as the boundary between the light-emitting layer 27 and the electron transport layer 25.
  • the portion where the concentration of the atom changes by 25% or more may be regarded as the boundary between the light-emitting layer 27 and the electron transport layer 25.
  • the criteria for confirming the boundary are given priority in the order of description, in other words, the earlier description takes priority over the later description.
  • the portion in which the composition of the second inorganic filler 53 can be confirmed may be considered to be included in the second light-emitting layer 42, and therefore in the light-emitting layer 27.
  • the light-emitting element 12 may be manufactured by the same method as the manufacturing method of the light-emitting element 11 according to the previous embodiment according to the flowchart shown in FIG. 3, except for the material of the second solution applied onto the first light-emitting layer 40 in step S7.
  • the second solution contains only the second inorganic precursor out of the quantum dots 50 and the second inorganic precursor which is a precursor of the second inorganic filler 53.
  • the second solution may contain other materials except the quantum dots 50 and the second inorganic precursor.
  • step S8 a second light-emitting layer 42 having the second inorganic filler 53 but no quantum dots 50 is formed on the first light-emitting layer 40.
  • Fig. 5 is a schematic side cross-sectional view of the display device 3 according to the present embodiment.
  • the display device 3 according to the present embodiment has the same configuration as the display device 2 according to the previous embodiment, except that it includes a light-emitting element 13 instead of the light-emitting element 12.
  • the light-emitting element 13 has the same configuration as the light-emitting element 12 according to the previous embodiment, except that it includes a light-emitting layer 28 instead of the light-emitting layer 27.
  • the light-emitting layer 28 has, in order from the anode 21 side, a first light-emitting layer 40, a second light-emitting layer 43, a third light-emitting layer 44, and a fourth light-emitting layer 45.
  • the first light-emitting layer 40 has the same configuration as the first light-emitting layer 40 according to each of the above-mentioned embodiments.
  • the second light-emitting layer 43 includes a plurality of quantum dots 50 and a second inorganic filler 54 that fills the spaces between the plurality of quantum dots 50.
  • the third light-emitting layer 44 includes a plurality of quantum dots 50 and a third inorganic filler 55 that fills the spaces between the plurality of quantum dots 50.
  • the fourth light-emitting layer 45 has the same configuration as the second light-emitting layer 42 according to the previous embodiment, except that it includes a fourth inorganic filler 56 instead of the second inorganic filler 53.
  • the quantum dots 50 contained in the second light-emitting layer 43 and the third light-emitting layer 44 have the same configuration as the quantum dots 50 according to each of the above-mentioned embodiments.
  • the second inorganic filler 54, the third inorganic filler 55, and the fourth inorganic filler 56 have the same configuration as the first inorganic filler 52 according to each of the above-mentioned embodiments, except for the concentration of at least one of the sulfur atoms and the oxygen atoms.
  • the light-emitting layer 28 comprises quantum dots 50 and a first inorganic filler 52, a second inorganic filler 54, a third inorganic filler 55, and a fourth inorganic filler 56 as inorganic fillers 51.
  • the light-emitting layer 28 comprises a first light-emitting layer 40, a second light-emitting layer 43, and a third light-emitting layer 44 as quantum dot layers including the quantum dots 50 and the inorganic fillers 51.
  • the light-emitting layer 28 also comprises a fourth light-emitting layer 45 that comprises only the inorganic filler 51 out of the quantum dots 50 and the inorganic fillers 51.
  • the first inorganic filler 52, the second inorganic filler 54, the third inorganic filler 55, and the fourth inorganic filler 56 have progressively lower concentrations of at least one of sulfur atoms and oxygen atoms in this order.
  • the concentration of at least one of sulfur atoms and oxygen atoms in the inorganic filler 51 gradually decreases in the direction from the anode 21 toward the cathode 26.
  • the density of atomic defects of at least one of sulfur atoms and oxygen atoms increases in the order of the first inorganic filler 52, the second inorganic filler 54, the third inorganic filler 55, and the fourth inorganic filler 56.
  • the density of atomic defects of at least one of sulfur atoms and oxygen atoms increases in the inorganic filler 51 in the direction from the anode 21 toward the cathode 26.
  • the light-emitting element 13 suppresses the movement of electrons injected from the electron transport layer 25 between the quantum dots 50 in the light-emitting layer 24. Therefore, the light-emitting element 13 reduces the reactive current in the light-emitting layer 24, improving the light-emitting efficiency and reliability.
  • the concentration of quantum dots 50 in the light-emitting layer 28 decreases in the order of the first light-emitting layer 40, the second light-emitting layer 43, and the third light-emitting layer 44. Furthermore, as described above, the fourth light-emitting layer 45 does not have quantum dots 50. Therefore, for the same reasons as those described in each of the above embodiments, the light-emitting element 13 can improve the light-emitting efficiency while more efficiently enhancing the protective effect of the quantum dots 50 provided by the inorganic filler 51 in the light-emitting layer 24.
  • the light-emitting element 13 can reduce the decrease in light-emitting efficiency even when the efficiency of hole injection into the light-emitting layer 28 decreases due to the deterioration of each part.
  • the light-emitting element 13 recombination of electrons and holes in the light-emitting layer 28 occurs in the quantum dots 50 near the second light-emitting layer 43 at the time of shipment of the display device 3, and the quantum dots 50 in the second light-emitting layer 43 mainly emit light.
  • the mobility and injection efficiency of holes from the hole injection layer 22 to the light-emitting layer 28 may decrease due to the deterioration of each part of the light-emitting element 13 caused by the deterioration caused by the driving of the display device 3 or by aging.
  • recombination of electrons and holes in the light-emitting layer 28 may occur in the quantum dots 50 on the anode 21 side rather than the second light-emitting layer 43.
  • the recombination of electrons and holes in the light-emitting layer 28 occurs in the quantum dots 50 near the first light-emitting layer 40, and the quantum dots 50 in the first light-emitting layer 40 can mainly emit light, so that the light-emitting element 13 can reduce a decrease in the light-emitting efficiency.
  • the light-emitting layer 28 can improve the reliability of the light-emitting element 13.
  • the manufacturing method of the light-emitting element 13 according to this embodiment can be the same as the manufacturing method of the light-emitting element 12 according to the previous embodiment, except for the method of forming the light-emitting layer 28.
  • the first light-emitting layer 40, the second light-emitting layer 43, and the third light-emitting layer 44 of the light-emitting layer 28 may be formed by repeatedly performing the above-mentioned steps S5 and S6.
  • the concentration of the quantum dots 50 in the solution to be applied in step S5 is gradually decreased, and the heating temperature of the solution in step S6 is gradually increased, and steps S5 and S6 are repeatedly performed.
  • the concentration of the quantum dots 50 in the solution to be applied does not necessarily have to be changed, and may be approximately the same concentration.
  • the fourth light-emitting layer 45 may be formed by carrying out steps S7 and S8 according to the previous embodiment.
  • the heating temperature of the solution in step S8 is higher than the heating temperature of the solution in step S6 described above, and steps S7 and S8 are carried out. This allows the above-mentioned fourth light-emitting layer 45 to be formed, and the light-emitting layer 28 to be formed.
  • the display device according to the modification has the same configuration as the display device 3 according to the present embodiment, except for the material of the inorganic filler 51 of the light-emitting layer 28 of the light-emitting element 13.
  • the inorganic filler 51 according to this modified example includes a ternary compound semiconductor having metal atoms.
  • the first inorganic filler 52, the second inorganic filler 54, the third inorganic filler 55, and the fourth inorganic filler 56 have gradually increasing or gradually decreasing concentrations of the above-mentioned metal atoms in this order.
  • the inorganic filler 51 according to this modified example has a concentration gradient of metal atoms in the direction from the anode 21 to the cathode 26.
  • the inorganic filler 51 may contain magnesium atoms, or may contain a sulfide containing zinc atoms.
  • the inorganic filler 51 may contain zinc magnesium sulfide (ZnMgS, ZnMgS 2 ) as a sulfide containing both magnesium atoms and zinc atoms.
  • the first inorganic filler 52, the second inorganic filler 54, the third inorganic filler 55, and the fourth inorganic filler 56 may contain zinc magnesium sulfide whose composition is expressed as ZnXMg1 - XS1 -Y .
  • X and Y are real numbers satisfying 0 ⁇ X ⁇ 1 and 0 ⁇ Y ⁇ 1, and the value of X increases in the order of the first inorganic filler 52, the second inorganic filler 54, the third inorganic filler 55, and the fourth inorganic filler 56.
  • the inorganic filler 51 has a concentration gradient in which the concentration of zinc atoms gradually increases in the direction from the anode 21 to the cathode 26, while the concentration of magnesium atoms gradually decreases.
  • Y represents the proportion of sulfur atom defects in the inorganic filler 51, and may increase in the order of the first inorganic filler 52, the second inorganic filler 54, the third inorganic filler 55, and the fourth inorganic filler 56.
  • the fourth inorganic filler 56 contains zinc sulfide, which is a binary compound semiconductor.
  • the inorganic filler 51 according to this embodiment is not limited to a configuration consisting of only ternary compound semiconductors, and may also contain some binary compound semiconductors.
  • the manufacturing method of the light-emitting element 13 according to this modified example can be the same as the manufacturing method of the light-emitting element 13 according to this embodiment, except for the method of forming the light-emitting layer 28.
  • the first light-emitting layer 40, the second light-emitting layer 43, and the third light-emitting layer 44 of the light-emitting layer 28 may be formed by repeatedly performing the above-mentioned steps S5 and S6.
  • the fourth light-emitting layer 45 may be formed by performing steps S7 and S8 according to this embodiment.
  • step S5 a first solution containing a plurality of quantum dots 50 and a first inorganic precursor having a plurality of metal sources is applied onto the hole transport layer 23.
  • step S6 the applied first solution is heated to modify the first inorganic precursor into a first inorganic filler 52, thereby forming the first light-emitting layer 40.
  • step S5 a second solution containing a plurality of quantum dots 50 and a second inorganic precursor having a plurality of metal sources is applied onto the hole transport layer 23.
  • the ratio of the metal source in the second inorganic precursor is made different from that in the first inorganic precursor, so that the ratio of the metal source in the second solution is made different from that in the first solution.
  • step S6 a second light-emitting layer 43 is formed having a second inorganic filler 54 having a different concentration of metal atoms from that of the first inorganic filler 52.
  • the heating temperature of the second solution may be higher than the heating temperature of the first solution.
  • the third light-emitting layer 44 and the fourth light-emitting layer 45 are formed, so that the light-emitting layer 28 is formed.
  • Fig. 6 is a schematic band diagram for illustrating an example of the band gap of each part of the light emitting element 13 according to this modification. Note that the band diagram in Fig. 6 has a vacuum level on the upper side of the paper. The left and right directions of the band diagram in Fig. 6 represent the thickness direction in the display direction of the display device 3, with the left side of the paper being the anode 21 side and the right side being the cathode 26 side.
  • the Fermi levels of the anode 21 and the cathode 26 are shown. Also, the band gaps of the hole injection layer 22, the hole transport layer 23, and the electron transport layer 25 are shown. In particular, in the band diagram of FIG. 6, the band gap of the nanoparticles 30 is shown as the band gap of the electron transport layer 25.
  • the band gap of the first light-emitting layer 40, the second light-emitting layer 43, the third light-emitting layer 44, and the fourth light-emitting layer 45 are shown as the band gap of the light-emitting layer 28.
  • the band diagram of FIG. 6 shows the band gaps of the core 50C and the shell 50S of the quantum dot 50, and the band gaps of the first inorganic filler 52, the second inorganic filler 54, the third inorganic filler 55, and the fourth inorganic filler 56.
  • inorganic filler 51 fills the spaces between the quantum dots 50.
  • the band gaps of the first light-emitting layer 40, the second light-emitting layer 43, and the third light-emitting layer 44 can be illustrated such that the band gap of the inorganic filler 51 is located on both ends of the band gap of the quantum dots 50. Note that only the band gap of the fourth inorganic filler 56 is illustrated for the fourth light-emitting layer 45.
  • the band gaps of the first inorganic filler 52, the second inorganic filler 54, the third inorganic filler 55, and the fourth inorganic filler 56 become gradually smaller in this order.
  • the band gap of the inorganic filler 51 becomes gradually smaller in the direction from the anode 21 toward the cathode 26.
  • the gradient of the band gap of the inorganic filler 51 described above is realized by the concentration gradient of the metal atoms in the inorganic filler 51 described above.
  • the electron affinity of the inorganic filler 51 gradually increases in the direction from the anode 21 toward the cathode 26.
  • the electron affinity of each part corresponds to the distance from the vacuum level to the upper end of the band gap. Therefore, in the band diagram of FIG. 6, the lower the upper end of the band gap of a certain layer is located, the greater the electron affinity of that layer. In other words, the larger the band gap of a certain layer, the smaller the electron affinity of that layer tends to be.
  • the barrier to electron injection from the first layer to the second layer corresponds to the electron affinity of the first layer minus the electron affinity of the second layer. Therefore, in this modified example, a barrier exists for the injection of electrons from the fourth inorganic filler 56 to the third inorganic filler 55. Similarly, in this modified example, a barrier exists for the injection of electrons from the third inorganic filler 55 to the second inorganic filler 54, and for the injection of electrons from the second inorganic filler 54 to the first inorganic filler 52.
  • the light-emitting element 13 suppresses the movement of electrons through the inorganic filler 51 in the direction from the cathode 26 to the anode 21. Therefore, the light-emitting element 13 can increase the proportion of carriers injected into the quantum dots 50 relative to carriers that contribute to the reactive current flowing through the inorganic filler 51.
  • the light-emitting element 13 suppresses the movement of electrons injected from the electron transport layer 25 between the quantum dots 50 in the light-emitting layer 24, thereby reducing the reactive current in the light-emitting layer 24 and improving the light-emitting efficiency and reliability.
  • the band gap of the inorganic filler 51 can be easily designed by adjusting the concentration of magnesium atoms.
  • the efficiency of carrier injection into the quantum dots 50 can be increased while improving the protective effect of the quantum dots 50.
  • Fig. 7 is a schematic side cross-sectional view of the display device 4 according to this embodiment.
  • the display device 4 according to this embodiment includes a light-emitting element 14 instead of the light-emitting element 13.
  • the display device 4 according to this embodiment also includes a plurality of sub-pixels in a plan view, and in particular includes a red sub-pixel SPR, a green sub-pixel SPG, and a blue sub-pixel SPB.
  • the light-emitting element 14 includes a red light-emitting element 14R, a green light-emitting element 14G, and a blue light-emitting element 14B.
  • the red light-emitting element 14R is located on the red sub-pixel SPR
  • the green light-emitting element 14G is located on the green sub-pixel SPG
  • the blue light-emitting element 14B is located on the blue sub-pixel SPB.
  • the light emitting element 14 includes a bank 60 on the substrate 20.
  • the bank 60 includes an insulating resin material, for example, including polyimide, and is formed in each layer of the light emitting element 14, from the anode 21 to partway through the fourth light emitting layer 45 of the light emitting layer 28. Therefore, the bank 60 separates each layer of the light emitting element 14, from the anode 21 to the third light emitting layer 44 of the light emitting layer 28.
  • each layer from the anode 21 of the light-emitting element 14 to the third light-emitting layer 44 of the light-emitting layer 28 is partitioned into a red subpixel SPR, a green subpixel SPG, and a blue subpixel SPB in a plan view of the substrate 20.
  • the fourth light-emitting layer 45, the electron transport layer 25, and the cathode 26 of the light-emitting layer 28 may be formed in common to the multiple subpixels described above.
  • the light-emitting layer 28 is partitioned by the bank 60 into a red light-emitting layer 28R, a green light-emitting layer 28G, and a blue light-emitting layer 28B.
  • the red light-emitting layer 28R is located on the red subpixel SPR
  • the green light-emitting layer 28G is located on the green subpixel SPG
  • the blue light-emitting layer 28B is located on the blue subpixel SPB.
  • the first light-emitting layer 40 is divided into a first red light-emitting layer 40R, a first green light-emitting layer 40G, and a first blue light-emitting layer 40B.
  • the second light-emitting layer 43 is divided into a second red light-emitting layer 43R, a second green light-emitting layer 43G, and a second blue light-emitting layer 43B.
  • the third light-emitting layer 44 is divided into a third red light-emitting layer 44R, a third green light-emitting layer 44G, and a third blue light-emitting layer 44B.
  • the red light-emitting layer 28R, the green light-emitting layer 28G, and the blue light-emitting layer 28B may have a common fourth light-emitting layer 45.
  • the first red light-emitting layer 40R, the second red light-emitting layer 43R, and the third red light-emitting layer 44R include red quantum dots 57 that emit red light.
  • the first green light-emitting layer 40G, the second green light-emitting layer 43G, and the third green light-emitting layer 44G include green quantum dots 58 that emit green light.
  • the first blue light-emitting layer 40B, the second blue light-emitting layer 43B, and the third blue light-emitting layer 44B include blue quantum dots 59 that emit blue light.
  • Each of the red quantum dots 57, the green quantum dots 58, and the blue quantum dots 59 may have the same configuration as the quantum dots 50, except for the light-emitting color.
  • Red light is light that has a central emission wavelength in a wavelength band of more than 600 nm and less than 780 nm.
  • Green light is light that has a central emission wavelength in a wavelength band of more than 500 nm and less than 600 nm.
  • Blue light is light that has a central emission wavelength in a wavelength band of more than 400 nm and less than 500 nm.
  • the red light-emitting layer 28R, the green light-emitting layer 28G, and the blue light-emitting layer 28B have the same configuration as the light-emitting layer 28 according to the previous embodiment.
  • the first light-emitting layer 40, the second light-emitting layer 43, the third light-emitting layer 44, and the fourth light-emitting layer 45 each have a first inorganic filler 52, a second inorganic filler 54, a third inorganic filler 55, and a fourth inorganic filler 56.
  • the red light-emitting layer 28R, the green light-emitting layer 28G, and the blue light-emitting layer 28B each have the same inorganic filler 51 as the inorganic filler 51 according to the previous embodiment.
  • the red light-emitting element 14R includes a substrate 20, an anode 21, a hole injection layer 22, a hole transport layer 23, a red light-emitting layer 28R, an electron transport layer 25, and a cathode 26 formed in the red subpixel SPR.
  • the green light-emitting element 14G includes a substrate 20, an anode 21, a hole injection layer 22, a hole transport layer 23, a green light-emitting layer 28G, an electron transport layer 25, and a cathode 26 formed in the green subpixel SPG.
  • the blue light-emitting element 14B includes a substrate 20, an anode 21, a hole injection layer 22, a hole transport layer 23, a blue light-emitting layer 28B, an electron transport layer 25, and a cathode 26 formed in the blue subpixel SPB.
  • the anode 21, the hole injection layer 22, and the hole transport layer 23 may have the same design in the red subpixel SPR, the green subpixel SPG, and the blue subpixel SPB.
  • each anode 21 is electrically connected to a driving circuit formed in each subpixel of the substrate 20.
  • the display device 4 applies a common potential to the cathode 26 and individually controls the voltage application to each anode 21 via the pixel circuit of the substrate 20. This allows the red light from the red light emitting element 14R, the green light from the green light emitting element 14G, and the blue light from the blue light emitting element 14B to be extracted individually from each sub-pixel, thereby providing a color display.
  • the light-emitting element 14 according to this embodiment may be manufactured by the same method as the light-emitting element 13 according to the previous embodiment, except for the manufacturing process of the light-emitting layer 28.
  • a photosensitive resin is formed only in a specific subpixel by photolithography using a photosensitive resin.
  • a solution containing quantum dots is applied and formed as a film common to a plurality of subpixels.
  • the light-emitting layer 28 may be formed only in a specific subpixel by peeling off the photosensitive resin together with the applied solution.
  • the light-emitting layer 28 may be formed by applying different light-emitting layers 28 to each subpixel by an inkjet method or the like.
  • the red light-emitting element 14R, green light-emitting element 14G, and blue light-emitting element 14B of this embodiment each have the same configuration as the light-emitting element 13 of the previous embodiment, except for the light emission color of the quantum dots in the light-emitting layer 28. Therefore, for the same reasons as described above, the red light-emitting element 14R, green light-emitting element 14G, and blue light-emitting element 14B each can improve the light-emitting efficiency while more efficiently enhancing the protective effect of the quantum dots 50 by the inorganic filler 51 in the light-emitting layer 24.
  • the band gap of the material of the quantum dot core varies depending on the emission color of the core.
  • a light-emitting element having a light-emitting layer that has quantum dots as the light-emitting material has a different band gap in the charge transport layer, including the hole injection layer, hole transport layer, and electron transport layer, that is suitable for the emission color of the light-emitting layer. Therefore, if the same charge transport layer is applied to light-emitting elements having light-emitting layers that contain quantum dots with different emission colors, the carrier balance of the light-emitting layer 28 may not be optimized in any of the light-emitting elements.
  • the red light emitting element 14R, the green light emitting element 14G, and the blue light emitting element 14B each have an inorganic filler 51 with a different band gap in the stacking direction. Therefore, in the red light emitting element 14R, the green light emitting element 14G, and the blue light emitting element 14B, the light emitting position of the quantum dot differs in the stacking direction depending on the band gap of the quantum dot.
  • the light-emitting element 14 even if the charge transport layer is not optimized for the light-emitting element of each subpixel, the carrier balance of each light-emitting layer 28 can be optimized by varying the light-emitting position of the quantum dots. Therefore, the light-emitting element 14 of this embodiment can improve the carrier balance of each light-emitting layer 28 and increase the light-emitting efficiency while simplifying the manufacturing process by sharing the charge transport layer in each subpixel.
  • the red light-emitting element 14R, the green light-emitting element 14G, and the blue light-emitting element 14B each have the same layered structure as the light-emitting element 13 according to the previous embodiment, but this is not limited to the above.
  • the red light-emitting element 14R, the green light-emitting element 14G, and the blue light-emitting element 14B each may have the same layered structure as either the light-emitting element 11 or the light-emitting element 12 described above.
  • any one of the red light emitting element 14R, the green light emitting element 14G, and the blue light emitting element 14B may have the same layered structure as the light emitting element according to any of the above-mentioned embodiments.
  • some of the red light emitting element 14R, the green light emitting element 14G, and the blue light emitting element 14B may have a structure different from that of the light emitting element according to each of the above-mentioned embodiments.

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PCT/JP2022/038898 2022-10-19 2022-10-19 発光素子、表示装置、発光素子の製造方法 Ceased WO2024084617A1 (ja)

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WO2026058408A1 (ja) * 2024-09-13 2026-03-19 シャープディスプレイテクノロジー株式会社 表示装置、及び表示装置の製造方法

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