Light-emitting element and display device

Abstract

A red light-emitting element (5R) comprises an anode (22), a cathode (25), and a red light-emitting layer (24L) that is provided between the anode (22) and the cathode (25). The red light-emitting layer (24L) includes quantum dots (QD), a first additive (AD1) that surrounds the quantum dots (QD), and a second additive (AD2) that is a metal element. The second additive (AD2) is a different type of metal element from a metal element included in the quantum dots (QD).

Description

Light-emitting element and display device

[0001] The present disclosure relates to a light-emitting element and a display device.

[0002] In recent years, display devices equipped with quantum dot light-emitting diodes (QLEDs), which are light-emitting elements containing quantum dots, have attracted considerable attention because of their ability to achieve low power consumption, thinness, and high image quality.

[0003] For example, Patent Document 1 discloses that the band gap can be increased by adding hydrogen or halogen to quantum dots.

[0004] Japanese Patent Publication No. 2005-322877

[0005] However, the configuration disclosed in Patent Document 1 simply widens the band gap distribution of quantum dots to expand the optical absorption band, and is specialized for photoelectric conversion elements. In the field of light-emitting devices, if a configuration in which hydrogen or halogen is simply added to quantum dots without providing a separate component to suppress the migration of hydrogen or halogen, as in the configuration disclosed in Patent Document 1, is adopted, there is a reliability problem in that, for example, the hydrogen or halogen added to the quantum dots easily migrates during current driving, easily causing the conduction band minimum (CBM) and valence band maximum (VBM) of the quantum dots to easily shift from their optimal values. In addition, in such cases, there is also the problem of carrier imbalance, resulting in a decrease in luminous efficiency.

[0006] An object of one embodiment of the present disclosure is to provide a light-emitting element and a display device with improved luminous efficiency and reliability.

[0007] In order to solve the above-mentioned problems, the light-emitting element of the present disclosure includes an anode, a cathode, and a light-emitting layer provided between the anode and the cathode, wherein the light-emitting layer includes quantum dots, first additives located around the quantum dots, and second additives composed of metal elements, and the second additive is included at least between the quantum dots and a first portion that is a part of the first additive.

[0008] In order to solve the above-mentioned problems, the light-emitting element of the present disclosure comprises an anode, a cathode, and a light-emitting layer provided between the anode and the cathode, wherein the light-emitting layer includes quantum dots, first additives located around the quantum dots, and second additives composed of a metal element, and the second additives are different types of metal elements from the metal elements contained in the quantum dots.

[0009] In order to solve the above-mentioned problems, the display device of the present disclosure includes the light-emitting element.

[0010] According to one embodiment of the present disclosure, a light-emitting element and a display device with improved luminous efficiency and reliability can be provided.

[0011] 1 is a plan view showing a schematic configuration of a display device of Embodiment 1; FIG. 2 is a cross-sectional view showing a schematic configuration of a display region of the display device of Embodiment 1; FIG. 3 is a cross-sectional view showing a schematic configuration of a red light-emitting device provided in the display device of Embodiment 1; FIG. 4 is a cross-sectional view showing a schematic configuration of another red light-emitting device that can be provided in the display device of Embodiment 1; FIG. 5 is a partial enlarged view of portion A of FIG. 3 or 4, showing a quantum dot, a first adduct having a first portion, a second adduct, and a third adduct; FIG. 6 is a partial enlarged view of portion A of FIG. 3 or 4, showing a quantum dot, a first adduct having a first portion of another shape, a second adduct, and a third adduct; FIG. 7 is a diagram showing the band levels of a red light-emitting device of Comparative Example 1 that does not include a first adduct located around a quantum dot, and a red light-emitting device provided in the display device of Embodiment 1; FIG. 8 is a diagram showing a cross-section of a portion of a red light-emitting layer provided in the red light-emitting device shown in FIG. 3; FIG. 9 is a diagram showing a cross-section of another portion of the red light-emitting layer provided in the red light-emitting device shown in FIG. 3; 4 is a diagram showing a part of a manufacturing process of a quantum dot dispersion solution used when forming a red light-emitting layer provided in the red light-emitting element shown in Fig. 3. It is a diagram showing the remaining part of the manufacturing process of a quantum dot dispersion solution used when forming a red light-emitting layer provided in the red light-emitting element shown in Fig. 3.

[0012] The following describes an embodiment of the present disclosure with reference to Figures 1 to 12. For the sake of convenience, components having the same functions as those described in a specific embodiment will be denoted by the same reference numerals, and their description may be omitted.

[0013] First Embodiment FIG. 1 is a plan view showing a schematic configuration of a display device 1 according to a first embodiment.

[0014] As shown in Fig. 1, the display device 1 includes a frame area NDA and a display area DA. The display area DA of the display device 1 includes a plurality of pixels PIX, each of which includes a red subpixel RSP, a green subpixel GSP, and a blue subpixel BSP. In this embodiment, a case in which one pixel PIX is configured with a red subpixel RSP, a green subpixel GSP, and a blue subpixel BSP will be described as an example, but this is not limiting. For example, one pixel PIX may include subpixels of other colors in addition to the red subpixel RSP, the green subpixel GSP, and the blue subpixel BSP.

[0015] FIG. 2 is a cross-sectional view showing a schematic configuration of the display area DA of the display device 1 of the first embodiment.

[0016] As shown in Figure 2, in the display area DA of the display device 1, a barrier layer 3, a thin film transistor layer 4 including a transistor TR, a red light-emitting element 5R, a green light-emitting element 5G, a blue light-emitting element 5B and a bank 23, a sealing layer 6, and a functional film 39 are provided on a substrate 12 in this order from the substrate 12 side.

[0017] The red subpixel RSP provided in the display area DA of the display device 1 includes a red light-emitting element 5R (light-emitting element), the green subpixel GSP provided in the display area DA of the display device 1 includes a green light-emitting element 5G (light-emitting element), and the blue subpixel BSP provided in the display area DA of the display device 1 includes a blue light-emitting element 5B (light-emitting element). The red light-emitting element 5R included in the red subpixel RSP includes an anode 22, a functional layer 24R including a red light-emitting layer, and a cathode 25. The green light-emitting element 5G included in the green subpixel GSP includes an anode 22, a functional layer 24G including a green light-emitting layer, and a cathode 25. The blue light-emitting element 5B included in the blue subpixel BSP includes an anode 22, a functional layer 24B including a blue light-emitting layer, and a cathode 25.

[0018] The substrate 12 may be, for example, a resin substrate made of a resin material such as polyimide, or a glass substrate. In this embodiment, since the display device 1 is a flexible display device, a case where a resin substrate made of a resin material such as polyimide is used as the substrate 12 will be described as an example, but this is not limiting. If the display device 1 is a non-flexible display device, a glass substrate can be used as the substrate 12.

[0019] The barrier layer 3 is a layer that prevents foreign substances such as water and oxygen from penetrating into the transistor TR, the red light-emitting element 5R, the green light-emitting element 5G, and the blue light-emitting element 5B, and can be composed of, for example, a silicon oxide film, a silicon nitride film, a silicon oxynitride film, or a laminated film of these, formed by the CVD method.

[0020] The transistor TR portion of the thin film transistor layer 4 including the transistor TR includes the semiconductor film SEM and doped semiconductor films SEM′ and SEM″, an inorganic insulating film 16, a gate electrode G, an inorganic insulating film 18, an inorganic insulating film 20, a source electrode S and a drain electrode D, and a planarization film 21, and the portion of the thin film transistor layer 4 including the transistor TR other than the transistor TR portion includes the inorganic insulating film 16, the inorganic insulating film 18, the inorganic insulating film 20, and the planarization film 21.

[0021] The semiconductor films SEM, SEM', and SEM'' may be made of, for example, low-temperature polysilicon (LTPS) or an oxide semiconductor (for example, an In-Ga-Zn-O based semiconductor). In this embodiment, the case where the transistor TR has a top-gate structure will be described as an example, but the present invention is not limited to this, and the transistor TR may also have a bottom-gate structure.

[0022] The gate electrode G and the source electrode S and drain electrode D can be formed of a single layer or a multilayer film of a metal containing at least one of aluminum, tungsten, molybdenum, tantalum, chromium, titanium, and copper, for example.

[0023] The inorganic insulating films 16, 18 and 20 can be formed of, for example, a silicon oxide film, a silicon nitride film, a silicon oxynitride film, or a laminated film of these films, which are formed by the CVD method.

[0024] The planarizing film 21 can be made of a coatable organic material such as polyimide or acrylic.

[0025] The red light-emitting element 5R includes an anode 22 above the planarization film 21, a functional layer 24R including a red light-emitting layer, and a cathode 25. The green light-emitting element 5G includes an anode 22 above the planarization film 21, a functional layer 24G including a green light-emitting layer, and a cathode 25. The blue light-emitting element 5B includes an anode 22 above the planarization film 21, a functional layer 24B including a blue light-emitting layer, and a cathode 25. The insulating bank 23 covering the edge of the anode 22 can be formed by applying an organic material such as polyimide or acrylic and then patterning it by photolithography.

[0026] The sealing layer 6 is a light-transmitting film, and can be composed of, for example, an inorganic sealing film 26 that covers the cathode 25, an organic film 27 that is above the inorganic sealing film 26, and an inorganic sealing film 28 that is above the organic film 27. The sealing layer 6 prevents foreign substances such as water and oxygen from penetrating into the red light-emitting element 5R, the green light-emitting element 5G, and the blue light-emitting element 5B.

[0027] The inorganic sealing films 26 and 28 are each an inorganic film, and may be formed, for example, by a CVD method using a silicon oxide film, a silicon nitride film, a silicon oxynitride film, or a laminated film thereof. The organic film 27 is a light-transmitting organic film with a planarizing effect, and may be formed, for example, using a coatable organic material such as acrylic. The organic film 27 may also be formed, for example, by an inkjet method. In this embodiment, the sealing layer 6 is formed of two inorganic films and one organic film disposed between the two inorganic films. However, the stacking order of the two inorganic films and one organic film is not limited to this. Furthermore, the sealing layer 6 may be formed solely of an inorganic film, solely of an organic film, one inorganic film and two organic films, or two or more inorganic films and two or more organic films.

[0028] The functional film 39 is a film having at least one of an optical compensation function, a touch sensor function, and a protection function, for example.

[0029] FIG. 3 is a cross-sectional view showing a schematic configuration of a red light-emitting element 5R included in the display device 1 of Embodiment 1. FIG. 4 is a cross-sectional view showing a schematic configuration of another red light-emitting element 5R′ that can be included in the display device 1 of Embodiment 1. FIG. 5 is a partially enlarged view of portion A in FIG. 3 or 4, showing a quantum dot QD, a first adduct AD1 having a first portion PA1, a second adduct AD2, and a third adduct AD3. FIG. 6 is a partially enlarged view of portion A in FIG. 3 or 4, showing a quantum dot QD, a first adduct AD1 having a first portion PA1 of another shape, a second adduct AD2, and a third adduct AD3. The first adduct AD1 has at least the first portion PA1 and may further include, for example, a second portion PA2 described below. The first adduct AD1 is not uniformly distributed throughout the light-emitting layer, but is distributed at a high concentration in a certain region around the quantum dot QD in the red light-emitting layer 24L as shown in FIGS. 3 and 4. The "certain region" refers to, for example, a region within a predetermined distance from the surface of the quantum dot QD toward the outside of the quantum dot QD, and the predetermined distance is, for example, 2 nm. Distributing at a high concentration within a certain region means that there is a difference in the concentration of the first adduct AD1 between within the certain region and outside the certain region. The distribution within the certain region may include a first void SPA1 and a second void SPA2, as shown in FIG. 5 . Here, the "void" refers to, for example, a space filled with gas or liquid. A solid such as the second adduct AD2 or the third adduct AD3 may be present within the void, or the void may have a lower abundance, density, concentration, etc. of metal elements than the quantum dot QD or the first portion PA1 of the first adduct AD1. Furthermore, the first portion PA1 of the first adduct AD1 may have, for example, insulating properties. In the present disclosure, a void having an electrical conductivity of 10 ８ [A / (V·m)] or less, or electrical resistivity is 10 ８Materials and components having a resistivity of [Ω·m] or more may be considered to have insulating properties. Furthermore, as shown in FIG. 5, the first portion PA1 of the first appendage AD1 may include a second void SPA2. However, the first portion PA1 does not necessarily have to include the second void SPA2, and the first portion PA1 may be positioned around the entire periphery of the quantum dot QD. The first portion PA1 may have the shape of a continuous film with a uniform or non-uniform thickness.

[0030] The red light-emitting element 5R, green light-emitting element 5G, and blue light-emitting element 5B shown in FIG. 2 may be top-emission or bottom-emission. The display device 1 of embodiment 1 may include a light-emitting element having a forward stack structure in which the cathode 25 is disposed above the anode 22, as in the red light-emitting element 5R shown in FIG. 3. To make such a forward stack structure light-emitting element a top-emission type, the anode 22 may be formed from an electrode material that reflects visible light, and the cathode 25 may be formed from an electrode material that transmits visible light. To make such a forward stack structure light-emitting element a bottom-emission type light-emitting element, the anode 22 may be formed from an electrode material that transmits visible light, and the cathode 25 may be formed from an electrode material that reflects visible light. On the other hand, the display device 1 of embodiment 1 may include a light-emitting element having an inverted stack structure in which the anode 22 is disposed above the cathode 25, as in the red light-emitting element 5R′ shown in FIG. 4. In order to make such a light-emitting element with an inverted stack structure a top-emission type, the cathode 25 may be formed from an electrode material that reflects visible light, and the anode 22 may be formed from an electrode material that transmits visible light. In order to make such a light-emitting element with an inverted stack structure a bottom-emission type, the cathode 25 may be formed from an electrode material that transmits visible light, and the anode 22 may be formed from an electrode material that reflects visible light.

[0031] The electrode material that reflects visible light is not particularly limited as long as it can reflect visible light and has electrical conductivity. Examples of the electrode material that reflects visible light include metal materials such as Al, Mg, Li, and Ag, alloys of the metal materials, laminates of the metal materials and transparent metal oxides (e.g., indium tin oxide, indium zinc oxide, indium gallium zinc oxide, etc.), and laminates of the alloys and the transparent metal oxides.

[0032] On the other hand, the electrode material that transmits visible light is not particularly limited as long as it can transmit visible light and has conductivity, and examples thereof include transparent metal oxides (e.g., indium tin oxide, indium zinc oxide, indium gallium zinc oxide, etc.), thin films made of metal materials such as Al and Ag, and nanowires made of metal materials such as Al and Ag.

[0033] In the case of a light-emitting element having a forward stack structure in which the cathode 25 is arranged as an upper layer above the anode 22, such as the red light-emitting element 5R shown in Figure 3, the functional layer 24R including the red light-emitting layer 24L provided in the red light-emitting element 5R may be, for example, a laminate in which a first charge transport layer 24H, a red light-emitting layer 24L, and a second charge transport layer 24E are stacked in this order from the anode 22 side.

[0034] On the other hand, in the case of a light-emitting element having an inverted stack structure in which the anode 22 is arranged as an upper layer than the cathode 25, such as the red light-emitting element 5R' shown in Figure 4, the functional layer 24R' including the red light-emitting layer 24L provided in the red light-emitting element 5R' may be, for example, a laminate in which the second charge transport layer 24E, the red light-emitting layer 24L, and the first charge transport layer 24H are stacked in this order from the cathode 25 side.

[0035] The first charge transport layer 24H may include at least one of a hole injection layer (HIL) and a hole transport layer (HTL), and the second charge transport layer 24E may include at least one of an electron injection layer (EIL) and an electron transport layer (ETL).

[0036] The material used for the hole injection layer (HIL) is not particularly limited as long as it is a hole injection material that can stabilize the injection of holes into the light emitting layer, and for example, a composite of poly(3,4-ethylenedioxythiophene) (PEDOT) and polystyrene sulfonic acid (PSS) (PEDOT:PSS) can be used.

[0037] Examples of materials used for the hole transport layer (HTL) include organic materials such as poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl))diphenylamine)] (TFB), N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)-benzidine (poly-TPD), and polyvinylcarbazole (PVK), and nanoparticles having hole transport properties such as NiO particles.

[0038] The material used for the electron transport layer (ETL) may be, for example, an organic material such as 2,2′,2″-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi), or nanoparticles having electron transport properties such as ZnO particles or particles of an oxide containing Zn and Mg.

[0039] The material used for the electron injection layer (EIL) is not particularly limited as long as it is an electron-injecting material that can stabilize the injection of electrons into the light-emitting layer. For example, alkali metals or alkaline earth metals such as aluminum, strontium, calcium, lithium, cesium, magnesium oxide, aluminum oxide, strontium oxide, lithium oxide, lithium fluoride, magnesium fluoride, strontium fluoride, calcium fluoride, barium fluoride, cesium fluoride, polymethyl methacrylate polystyrene sodium sulfonate, oxides of alkali metals or alkaline earth metals, fluorides of alkali metals or alkaline earth metals, organic complexes of alkali metals, etc. may be used.

[0040] The red light-emitting layer 24L of the red light-emitting element 5R shown in FIG. 3 and the red light-emitting element 5R′ shown in FIG. 4 includes quantum dots (QDs). The quantum dots (QDs) may have, for example, a core structure, a core / shell structure, a core / shell / shell structure, or a shell structure with a continuously varying core / shell ratio. The shell may cover only a portion of the core, but more preferably completely. The core of the quantum dots (QDs) may include, for example, one or more selected from Si, Ge, CdSe, CdS, CdTe, InP, GaP, InN, ZnSe, ZnS, ZnTe, CdSeTe, GaInP, and ZnSeTe. The shell of the quantum dot QD may include, for example, one or more selected from CdS, ZnS, CdSSe, CdTeSe, CdSTe, ZnSSe, ZnSTe, ZnTeSe, and AgInP (AIP), and a material having a lattice constant close to that of the core and a larger band gap than the core may be selected. In this embodiment, an example is described in which InP is used as the core of the quantum dot QD and ZnS is used as the shell of the quantum dot QD, but this is not limited to this. The particle size of the quantum dot QD is, for example, approximately 1 to 100 nm. The wavelength of light emitted from the quantum dot QD can be controlled by the particle size. In particular, when the quantum dot QD has a core / shell structure, the wavelength of light emitted from the quantum dot QD can be controlled by controlling the particle size of the core. Therefore, by controlling the particle size of the quantum dot QD, the wavelength of light emitted by the red light-emitting element 5R, green light-emitting element 5G, and blue light-emitting element 5B provided in the display device 1 can be controlled. In addition, the phrase "a metal element of a different type from the metal element contained in the quantum dot QD" described below means that if the quantum dot QD does not contain a metal element, the second adduct AD2 can contain any metal element.

[0041] 3, 4, 5, and 6, the red light-emitting layer 24L provided in the red light-emitting element 5R shown in FIG. 3 and the red light-emitting element 5R′ shown in FIG. 4 includes the quantum dots QD described above, a first adduct AD1 located around the quantum dots QD, a metal element as the second adduct AD2, and a halogen element as the third adduct AD3. The second adduct AD2 and the third adduct AD3 are included at least between the quantum dots QD and a first portion PA1 that is a part of the first adduct AD1. In this embodiment, a case in which the red light-emitting layer 24L includes the third adduct AD3 in addition to the second adduct AD2 composed of a metal element will be described as an example. However, the present invention is not limited to this, and the red light-emitting layer 24L may include only the second adduct AD2 composed of a metal element. In this embodiment, a case where the metal element of the second adduct AD2 is a metal element of a different type from the metal element contained in the quantum dot QD is described as an example, but the present invention is not limited to this, and the metal element of the second adduct AD2 may be a metal element of the same type as the metal element contained in the quantum dot QD. In this embodiment, a case where the second adduct AD2 and the third adduct AD3 are included between the quantum dot QD and the first portion PA1 that is a part of the first adduct AD1 is described as an example, but the present invention is not limited to this, and the second adduct AD2 and the third adduct AD3 do not have to be present between the quantum dot QD and the first portion PA1 that is a part of the first adduct AD1. The red light-emitting layer 24L is provided with a first adduct AD1 positioned around the quantum dot QD, and if the presence of the first adduct AD1 can prevent, for example, the second adduct AD2 and the third adduct AD3 from easily moving during current driving, the second adduct AD2 and the third adduct AD3 may be present only in a first region, which is a region between the quantum dot QD and a first portion PA1, which is part of the first adduct AD1, in the red light-emitting layer 24L, or may be present only in a second region other than the first region in the red light-emitting layer 24L, or may be distributed throughout the first region and the second region in the red light-emitting layer 24L.In this embodiment, the case where the third adduct AD3 is a halogen element is described as an example, but the third adduct AD3 may be a chalcogen element, and further, some of the multiple third adducts AD3 may be halogen elements and the rest may be chalcogen elements. Furthermore, in this embodiment, the case where the red light-emitting layer 24L includes the third adduct AD3 in addition to the second adduct AD2 composed of a metal element is described as an example, but this is not limited thereto, and the red light-emitting layer 24L may include only the second adduct AD2 composed of a metal element. In this embodiment, the case where the metal element of the second adduct AD2 is a different type of metal element from the metal element contained in the quantum dots QD is described as an example, but this is not limited thereto, and the metal element of the second adduct AD2 may be the same type of metal element as the metal element contained in the quantum dots QD. In this embodiment, as shown in Figures 5 and 6, an example is given in which the first portion PA1 of the first adduct AD1 is located away from the quantum dot QD, but this is not limited to this, and the first portion PA1 of the first adduct AD1 may be in contact with the quantum dot QD.

[0042] Considering the movement of carriers such as electrons and holes between the quantum dots QDs, the shorter the distance between adjacent quantum dots QDs, the easier the carrier movement and the higher the luminous efficiency, and the shorter the distance between adjacent quantum dots QDs. The distance is preferably 5 nm or less, more preferably 4 nm or less, and even more preferably 2 nm or less. When the first portion PA1 of the first adduct AD1 is located away from the quantum dots QDs, for example, if the distance from the surface of the quantum dots QD to the surface of the first portion PA1 facing the quantum dots QD is 2 nm or less and the thickness of the first portion PA1 is 0.5 nm or less, the distance between adjacent quantum dots QDs will be 5 nm or less, thereby improving the luminous efficiency and reliability. Furthermore, the length of the second portion PA2 may correspond to the distance from the surface of the quantum dots QD to the surface of the first portion PA1 facing the quantum dots QDs. However, if the length of the second portion PA2 is 1 nm or less, the distance between adjacent quantum dots QDs can be 4 nm or less, which is preferable even if the thickness of the first portion PA1 is 1 nm or less. Furthermore, when the thickness of the first portion PA1 is significantly thinner than the length of the second portion PA2, it is preferable to set the length of the second portion PA2 to 1 nm or less, since this allows the distance between adjacent quantum dots QDs to approach 2 nm. Here, when the thickness of the first portion PA1 is thin and it is difficult to determine the position of the "surface of the first portion PA1 on the quantum dot QD side," the vicinity of the center of the first portion PA1 or the entire first portion PA1 may be considered as the "surface of the first portion PA1 on the quantum dot QD side." Note that "around the quantum dot QD" refers to the region extending around the quantum dot QD, that is, the region outside the surface of the quantum dot QD, for example, the region between adjacent quantum dots QD.

[0043] The surface of the quantum dot QD may be observed and identified, for example, from a cross-sectional image taken by a TEM. When a first void SPA1 as shown in FIG. 5 is observed near the surface of the quantum dot QD, the surface of the quantum dot QD that contacts the first void SPA1 may be regarded as the surface of the quantum dot QD. Furthermore, since the density of metal elements is considered to be lower than that of the quantum dot QD due to the formation of a void "around the quantum dot QD" where the first adjunct AD1 is arranged, even if the first void SPA1 is not clearly observed, the region surrounding the quantum dot QD where the density of metal elements changes significantly may be regarded as the surface of the quantum dot QD. However, when the quantum dot QD includes a shell, the shell may be made of a compound using a semimetal such as Si (for example, SiO ２ ). In this case, the surface of the quantum dot QD may be regarded as a region where the density of a metalloid changes significantly instead of the density of a metal element. Furthermore, when the quantum dot QD has a crystalline structure and the crystalline structure can be confirmed, the surface of the region having the crystalline structure in the cross-sectional image may be regarded as the surface of the quantum dot QD. When the first portion PA1 of the first adduct AD1 is located between two quantum dots QD and it is not clear on which quantum dot QD the first portion PA1 of the first adduct AD1 is located, the first portion PA1 of the first adduct AD1 may be regarded as the first adduct AD1 located on each quantum dot QD appearing to overlap or as the first adduct AD1 located on each quantum dot QD appearing to be in contact with each other and integrated. Furthermore, there may be a portion between the two quantum dots QD where the first adduct AD1 is not present. The surface of the quantum dot QD may be the surface of the core of the quantum dot QD or the surface of the shell of the quantum dot QD.

[0044] 5 and 6, the first portion PA1 of the first additive AD1 may be located at least partially around the quantum dot QD and may include one selected from silicon oxide, boron oxide, phosphorus oxide, germanium oxide, beryllium fluoride, arsenic sulfide, silicon selenide, germanium sulfide, titanium oxide, tellurium oxide, aluminum oxide, bismuth oxide, vanadium oxide, antimony oxide, lead oxide, copper oxide, zirconium fluoride, aluminum fluoride, indium fluoride, zinc chloride, zinc bromide, and silicon nitride. In this embodiment, a case where the first portion PA1 of the first additive AD1 is made of silicon oxide will be described as an example, but the present invention is not limited to this.

[0045] As shown in Figures 5 and 6, the first adduct AD1 includes a second portion PA2, and the second portion PA2 is coordinated to the quantum dot QD. That is, the first portion PA1, which is located at a distance from the quantum dot QD in at least a portion of the periphery of the quantum dot QD, is fixed to the quantum dot QD via the second portion PA2 coordinated to the quantum dot QD. Coordination can be said to occur if, when observing 10 adjacent quantum dots QD, the target compound (ligand), i.e., the second portion PA2, is present mixed with the quantum dot QD. If the second portion PA2 is present on the outermost surface of the quantum dot QD, for example, in the case of a quantum dot having a core-shell structure, within a range of 1 nm or less from the end where the shell material is present, or within a range of 2 nm or less from the region or point where elements other than the core material and shell material are mixed in a direction extending concentrically from the quantum dot, it can be considered that the second portion PA2 is coordinated to the quantum dot QD.

[0046] In the first adduct AD1 shown in Figures 5 and 6, the end of the second portion PA2 on the quantum dot QD side may contain any of an oxygen atom, a sulfur atom, a nitrogen atom, and a phosphorus atom, the end of the second portion PA2 on the first portion PA1 side may contain a carbon atom, and one or more carbon atoms may be included between the end of the second portion PA2 on the quantum dot QD side and the end of the second portion PA2 on the first portion PA1 side.

[0047] In the present embodiment, when the shell of the quantum dot QD is a metal sulfide such as ZnS, the end of the second portion PA2 on the quantum dot QD side preferably contains at least one functional group capable of coordinating to the shell, selected from amine, carboxylic acid, thiol, phosphine, and halogen. Therefore, in this embodiment, the case where 3-(mercaptopropyl)trimethoxysilane (MPS) shown in the following (Chemical Formula 1) is used as a material for forming the second portion PA2 will be described as an example, but the present invention is not limited to this. In this embodiment, the thiol (SH) moiety of 3-(mercaptopropyl)trimethoxysilane (MPS) and the propyl (CH ２ CH ２ CH ２ ) portion forms the second portion PA2 of the first adduct AD1, so that the end of the second portion PA2 on the quantum dot QD side contains a sulfur atom, the end of the second portion PA2 on the first portion PA1 side contains a carbon atom, and two carbon atoms are included between the sulfur atom at the end of the second portion PA2 on the quantum dot QD side and the carbon atom at the end of the second portion PA2 on the first portion PA1 side. In the case of this embodiment, the first portion PA1 of the first adduct AD1 is trimethoxysilane (Si(OCH ３ ) ３ ) portion and the methoxy group of tetramethyl orthosilicate (TMOS) shown in the following (chemical formula 2).

[0048] As shown in Fig. 5, the first portion PA1 of the first addition AD1 may include a second gap SPA2. In this case, as shown in Fig. 5, the first portion PA1 of the first addition AD1 includes, as a discontinuous film arranged around the quantum dot QD in a cross section passing through the quantum dot QD, for example, a porous silicon oxide film or a plurality of island-shaped silicon oxide films.

[0049] As shown in Fig. 6, the first portion PA1 of the first additive AD1 may not include the second void SPA2. In this case, as shown in Fig. 6, the first portion PA1 of the first additive AD1 includes a continuous film surrounding the quantum dots QDs in a cross section passing through the quantum dots QDs. That is, the first portion PA1 of the first additive AD1 includes a continuous film arranged around the quantum dots QDs. In this case, the first portion PA1 of the first additive AD1 may be single crystalline.

[0050] The first portion PA1 of the first additive AD1 may be composed of at least one of polycrystalline and amorphous.

[0051] Furthermore, the red light-emitting layer 24L shown in Figures 3 and 4 may include a plurality of quantum dots QDs, some of which may have a first portion PA1 including a second void SPA2, as shown in Figure 5, and another portion of the plurality of quantum dots QDs may have a first portion PA1 that does not include a second void SPA2, as shown in Figure 6.

[0052] Figure 7 is a diagram showing the band levels of a red light-emitting element 50R of Comparative Example 1 that does not have a first adjunct AD1 located around the quantum dot QD, and a red light-emitting element 5R provided in the display device 1 of Embodiment 1.

[0053] 7, in the case of the red light-emitting element 50R of Comparative Example 1, which does not have the first additive AD1 located around the quantum dots QD, for example, hydrogen or halogen added to the quantum dots easily migrates during current driving, resulting in a deterioration in reliability. As a result, the conduction band minimum (CBM) and valence band maximum (VBM) of the quantum dots QD easily change from their optimal values. For example, the difference (E1) between the valence band maximum (24H(VBM)) of the first charge transport layer 24H and the valence band maximum (QD(VBM)) of the quantum dots QD becomes larger than the difference between the conduction band minimum (24E(CBM)) of the second charge transport layer 24E and the conduction band minimum (QD(CBM)) of the quantum dots QD. In a light-emitting element that is inherently prone to an electron excess state, electron injection into the quantum dots QD may become more likely than hole injection. In such a case, in the red light emitting element 50R of Comparative Example 1, the carrier balance is deteriorated, which leads to a deterioration in the light emitting efficiency.

[0054] 5 and 6, the red light-emitting layer 24L of the red light-emitting element 5R included in the display device 1 of embodiment 1 includes the above-mentioned quantum dots QD, a first adduct AD1 located around the quantum dots QD, a metal element as the second adduct AD2, and a halogen element as the third adduct AD3. Therefore, the presence of the first adduct AD1, for example, the presence of the first portion PA1 of the first adduct AD1, can prevent, for example, the second adduct AD2 and the third adduct AD3 from easily moving during current driving, thereby preventing deterioration in reliability. Therefore, the optimal values ​​of the conduction band bottom (CBM) and valence band top (VBM) of the quantum dot QD can be maintained, and in the case of the red light-emitting element 5R, for example, as shown in Figure 7, the difference (E2) between the valence band top (24H(VBM)) of the first charge transport layer 24H and the valence band top (QD(VBM)) of the quantum dot QD can be maintained smaller than the difference (E1) in the case of the above-mentioned red light-emitting element 50R, and the difference between the conduction band bottom (24E(CBM)) of the second charge transport layer 24E and the conduction band bottom (QD(CBM)) of the quantum dot QD can be maintained larger than the difference between the conduction band bottom (24E(CBM)) of the second charge transport layer 24E and the conduction band bottom (QD(CBM)) of the quantum dot QD in the case of the above-mentioned red light-emitting element 50R. In the case of the red light-emitting element 5R provided in the display device 1 of embodiment 1, since the light-emitting element is originally prone to an electron excess state, injection of holes is more likely than injection of electrons into the quantum dots QDs, thereby improving the carrier balance and improving the luminous efficiency. The same effect can be obtained when the red light-emitting layer 24L contains a metal element as the second adduct AD2 and a halogen element or a chalcogen element as the third adduct AD3. The same effect can also be obtained when the red light-emitting layer 24L contains only the second adduct AD2, which is a metal element, or when the metal element of the second adduct AD2 is the same type of metal element as the metal element contained in the quantum dots QDs.

[0055] In the case of the red light-emitting element 50R of Comparative Example 1, since it does not have the first adduct AD1 located around the quantum dot QD, the metal element which is the second adduct AD2 and the halogen element or chalcogen element which is the third adduct AD3 easily move, for example, when the light-emitting element is driven with current, resulting in a reliability problem in that the conduction band bottom (QD(CBM)) and valence band top (QD(VBM)) of the quantum dot QD easily change from their optimal values.

[0056] Therefore, the red light-emitting layer 24L provided in the red light-emitting element 5R shown in FIG. 3 and the red light-emitting element 5R' shown in FIG. 4 includes quantum dots QD, a first adduct AD1 located around the quantum dots QD, a metal element as the second adduct AD2, and a halogen element as the third adduct AD3, as shown in FIGS. 5 and 6. Therefore, the light-emitting element 5R / 5R' and the display device 1 can be realized with improved luminous efficiency and reliability. In this embodiment, the second adduct AD2 and the third adduct AD3 are included between the quantum dots QD and the first portion PA1, which is part of the first adduct AD1. That is, in this embodiment, as shown in FIGS. 5 and 6, the second adduct AD2 and the third adduct AD3 are included in the first gap SPA1 formed between the quantum dots QD and the first portion PA1, which is part of the first adduct AD1. 5 and 6, the first portion PA1 of the first adduct AD1 is located away from the quantum dots QD. However, the present invention is not limited to this. The first portion PA1 of the first adduct AD1 may be in contact with the quantum dots QD. For example, when a part of the first portion PA1 is in contact with the quantum dots QD, the second adduct AD2 is not present between the first portion PA1 and the quantum dots QD. However, the second adduct AD2 may be present between the first portion PA1 and the quantum dots QD that are not in contact with each other. The second adduct AD2 and the third adduct AD3 described above adjust the conduction band lower edge (QD(CBM)) and the valence band upper edge (QD(VBM)) of the quantum dot QD to optimal values, and the first adduct AD1, for example, the first portion PA1 of the first adduct AD1 described above, inhibits the movement of the second adduct AD2 and the third adduct AD3 described above during current driving of the light-emitting element, thereby preventing the conduction band lower edge (QD(CBM)) and the valence band upper edge (QD(VBM)) of the quantum dot QD from changing from their optimal values. Therefore, it is possible to realize light-emitting elements 5R and 5R' and display devices 1 with improved luminous efficiency and reliability.In this embodiment, in order to enhance the effect of the above-mentioned first adduct AD1 in inhibiting the movement of the above-mentioned second adduct AD2 and the above-mentioned third adduct AD3, the first portion PA1 of the first adduct AD1 is formed to be positioned away from the quantum dots QD.However, as long as the effect of the above-mentioned first adduct AD1 in inhibiting the movement of the above-mentioned second adduct AD2 and the above-mentioned third adduct AD3 can be obtained, the first portion PA1 of the first adduct AD1 may be formed to be in contact with the quantum dots QD, or the first adduct AD1 may be formed in a state in which the above-mentioned second adduct AD2 and the above-mentioned third adduct AD3 are mixed in.

[0057] The second additive AD2 may be, for example, a metal ion M+ of a metal element having a shallow HOMO level. When the metal ion M+ of the metal element having a shallow HOMO level is arranged around the quantum dot QD, the top of the valence band (QD(VBM)) of the quantum dot QD becomes shallower, which increases the amount of hole injection and improves the luminous efficiency.

[0058] The second adduct AD2 may be a metal element having an electronegativity of 2.16 or less, and may be an alkali metal element, an alkaline earth metal element, or a transition metal element. As the second adduct AD2, one selected from Cr, Mo, Mn, Fe, Ni, and Zn is preferably used, and one selected from Na, K, Mg, Ca, and Ba is more preferably used.

[0059] The halogen element as the third adduct AD3 may be, for example, an ion X- of a halogen element having a shallow HOMO level. The chalcogen element as the third adduct AD3 may be, for example, an ion X- of a chalcogen element having a shallow HOMO level. When the ion X- of a halogen element having a shallow HOMO level or the ion X- of a chalcogen element having a shallow HOMO level is arranged around the quantum dot QD, the top of the valence band (QD(VBM)) of the quantum dot QD is less likely to become deep, the amount of hole injection can be increased, and the luminous efficiency can be improved.

[0060] The halogen element as the third adduct AD3 is preferably one selected from among F, Cl, Br and I, and the chalcogen element as the third adduct AD3 is preferably one selected from among S, Se and Te.

[0061] Fig. 8 is a diagram showing a cross section of a portion of the red light-emitting layer 24L provided in the red light-emitting element 5R shown in Fig. 3. Fig. 9 is a diagram showing a cross section of another portion of the red light-emitting layer 24L provided in the red light-emitting element 5R shown in Fig. 3. Fig. 10 is a diagram showing a cross section of yet another portion of the red light-emitting layer 24L provided in the red light-emitting element 5R shown in Fig. 3.

[0062] 8 , a cross section of a portion of the red light-emitting layer 24L includes quantum dots QD, first adducts AD1 located around the quantum dots QD, a metal element as the second adduct AD2, and a halogen element or a chalcogen element as the third adduct AD3. In this embodiment, the second adduct AD2 and the third adduct AD3 are included between the quantum dots QD and a first portion PA1 that is a part of the first adduct AD1. Between the quantum dots QD and the first portion PA1 in the cross section of the red light-emitting layer 24L, i.e., in region B surrounded by the dotted line in FIG. 8 , the value of ((number of metal atoms) / (number of all atoms)) × 100% is preferably 0.1% or more in terms of adjusting the band level of the quantum dots QD. Furthermore, when the red light-emitting layer 24L contains a halogen element or a chalcogen element as the third additive, the value of ((number of atoms of halogen elements and chalcogen elements) / (number of all atoms)) × 100% between the quantum dots QD and the first portion PA1 in the cross section of the red light-emitting layer 24L, i.e., in the region B surrounded by the dotted line in Figure 8, is preferably 0.1% or more in terms of adjusting the band level of the quantum dots QD. Note that, although not shown in Figure 8, an organic ligand or the like may be coordinated to the quantum dots QD, and therefore the (number of all atoms) may include the number of atoms contained in the organic ligand.

[0063] 9, a cross section of a portion of the red light-emitting layer 24L includes quantum dots QD, first adducts AD1 located around the quantum dots QD, a metal element different from the metal element contained in the quantum dots QD as a second adduct AD2, and a halogen element or a chalcogen element as a third adduct AD3. The region from the center of the quantum dot QD to the first portion PA1 in the cross section of the red light-emitting layer 24L, i.e., region C surrounded by a dotted line in FIG. 9, includes the second adduct AD2 and the third adduct AD3. The center of the quantum dot QD is the center of gravity determined from the distribution of the core material constituting the quantum dot QD or the core material and shell material, etc. The detection of the center of the quantum dot QD, i.e., the center of gravity of the quantum dot QD, and the second adduct AD2 and the third adduct AD3 in the region from the center of the quantum dot QD (the center of gravity of the quantum dot QD) to the first portion PA1, i.e., the region C surrounded by the dotted line in Fig. 9, can be performed by combining various spectroscopic methods such as cross-sectional images by TEM and energy dispersive X-ray spectroscopy (EDX), or by using each spectroscopic method alone. For example, for a cross-section of the red light-emitting layer 24L, the detection of the center of gravity of the quantum dot QD and the second adduct AD2 and the third adduct AD3 in the region C surrounded by the dotted line in Fig. 9 can be performed as follows by combining TEM and energy dispersive X-ray spectroscopy (EDX). By TEM measurement of the cross-section of the red light-emitting layer 24L, the position of the quantum dot QD in the red light-emitting layer 24L can be determined. Furthermore, by energy dispersive X-ray spectroscopy (EDX) measurement of the cross section of the red light-emitting layer 24L, it is possible to obtain from an element distribution image where in the cross section the core material or the core material and shell material, etc., constituting the quantum dots QDs are present. That is, from the outline (cross-sectional image) of the quantum dots QD obtained by TEM measurement of the cross section of the red light-emitting layer 24L and the region (element distribution image) in which the element distribution of the quantum dots QDs in the cross section is continuous, which is obtained by EDX measurement of the cross section of the red light-emitting layer 24L, coordinate information of the core material or the core material and shell material, etc. constituting the quantum dots QDs can be obtained, and the center (center of gravity of the quantum dots QDs) can be calculated.As shown in FIG. 9 , within a circle having a radius r that is the distance from the center of the quantum dot QD in the cross section of the red light-emitting layer 24L to the end of the quantum dot QD in the first portion PA1 that is far from the center, the value of ((the number of metal atoms of the metal element that is the second adduct AD2) / (the number of all atoms)) is preferably 10 ppm or more. Although not shown in FIG. 9 , the quantum dot QD may have an organic ligand or the like coordinated thereto, and therefore the (number of all atoms) may include the number of atoms contained in the organic ligand. When it is possible to identify the end of the quantum dot QD in the first portion PA1 that is far from the center from a cross-sectional image or the like, the distance from the center of the quantum dot QD to the end of the quantum dot QD in the first portion PA1 that is far from the center can be used as the radius r. On the other hand, when it is difficult to identify the end of the quantum dot QD in the first portion PA1 that is far from the center from a cross-sectional image or the like, for example, when a plurality of first adducts AD1 are in contact with each other, either the following first method or second method can be used. In the first method, the length of the shortest line segment connecting the center of the quantum dot QD (the center of gravity of the quantum dot QD) and the center of gravity of a region where Si is 1% or more within a certain range of cross-sectional observation is taken as the radius r. In the second method, the length of the shortest line segment connecting the center of the quantum dot QD (the center of gravity of the quantum dot QD) and the center of gravity of a region where oxygen (O) is 2% or more within a certain range of cross-sectional observation is taken as the radius r.

[0064] 10 , a cross section of a portion of the red light-emitting layer 24L includes quantum dots QDs, first adducts AD1 located around the quantum dots QDs, a metal element different from the metal element contained in the quantum dots QDs as the second adduct AD2, and a halogen element or a chalcogen element as the third adduct AD3. The cross section of the red light-emitting layer 24L including the plurality of quantum dots QDs, i.e., the region D surrounded by the dotted line in FIG. 10 , includes the second adduct AD2 and the third adduct AD3. In FIG. 10 , when one of two quantum dots QDs is a first quantum dot and the other is a second quantum dot, the second adduct AD2 is also included between the first quantum dot and the second quantum dot, i.e., outside the first adduct AD1 located around each quantum dot QD as viewed from each quantum dot QD. It is preferable that the value of ((the number of metal atoms of the metal element which is the second adduct AD2) / (the number of all atoms)) in the cross section of the red light-emitting layer 24L containing a plurality of quantum dots QDs is 10 ppm or more. Here, "all atoms" refers to identifiable atoms within the field of view of the cross section measured or observed with a measuring device such as a TEM. Although not shown in FIG. 10, the quantum dots QDs may be coordinated with organic ligands or the like, and therefore the "number of all atoms" may include the number of atoms contained in the organic ligands.

[0065] Fig. 11 is a diagram showing a part of the manufacturing process of the quantum dot dispersion solution used when forming the red light-emitting layer 24L provided in the red light-emitting element 5R shown in Fig. 3. Fig. 12 is a diagram showing the remaining part of the manufacturing process of the quantum dot dispersion solution used when forming the red light-emitting layer 24L provided in the red light-emitting element 5R shown in Fig. 3.

[0066] 11 and 12, a manufacturing process of a quantum dot dispersion solution used to form the red light-emitting layer 24L provided in the red light-emitting element 5R shown in FIG. 3 will be described. As the quantum dots QD, commercially available red light-emitting quantum dots were used. In this embodiment, the compound MX in ethanol (C ２ H ６O) Although the case where a metal halide is used as the compound MX in the solution will be described as an example, the present invention is not limited thereto. For example, at least one of a metal halide, a metal chalcogenide, a metal salt, and a metal complex may be used as the compound MX.

[0067] When the compound MX is a metal halide, the metal element M may be, for example, any one of Na, K, Mg, Ca, Ba, Cr, Mo, Mn, Fe, Ni, and Zn, and becomes a metal ion M+ of the metal element that is the second adduct AD2, and the halogen element X may be, for example, any one of F, Cl, Br, and I, and becomes a halogen ion X- of the halogen element that is the third adduct AD3. In this embodiment, InP is used as the core of the quantum dot QD, and ZnS is used as the shell of the quantum dot QD. Therefore, when a metal element of a different type from the metal element contained in the quantum dot QD is used as the metal element that is the second adduct AD2, for example, any one of Na, K, Mg, Ca, Ba, Cr, Mo, Mn, Fe, and Ni may be used, and when a metal element of the same type as the metal element contained in the quantum dot QD is used as the metal element that is the second adduct AD2, for example, Zn may be used. As described above, in this embodiment, the quantum dot QD includes a core and a shell as an example, but this is not limited to this, and the quantum dot QD does not have to include a shell.

[0068] When the compound MX is a metal chalcogenide, the metal element M may be, for example, any one of Na, K, Mg, Ca, Ba, Cr, Mo, Mn, Fe, Ni, and Zn, and becomes a metal ion M+ of the metal element that is the second adduct AD2, and the chalcogenide element X may be, for example, any one of S, Se, and Te, and becomes a chalcogenide ion X- of the chalcogenide element that is the third adduct AD3.

[0069] When the compound MX is a metal salt or a metal complex, the metal element M may be, for example, any one of Na, K, Mg, Ca, Ba, Cr, Mo, Mn, Fe, Ni, and Zn, and becomes a metal ion M+ of the metal element, which is the second adduct AD2, and the remaining X portion may be, for example, any one of a carboxylic acid, a thiol, an amine, a phosphine, a phosphoric acid, a thiocyanic acid, and a phenol having a carbon chain (having 20 or less carbon atoms).

[0070] Therefore, the ethanol (C ２ H ６ O) When a metal halide is used as the compound MX in the solution, a quantum dot dispersion solution containing metal ions M+ and halogen ions X− can be prepared; when a metal chalcogenide is used, a quantum dot dispersion solution containing metal ions M+ and chalcogenide ions X− can be prepared; when both a metal halide and a metal chalcogenide are used, a quantum dot dispersion solution containing metal ions M+ and halogen ions X− and chalcogenide ions X− can be prepared; and when a metal salt or metal complex is used, a quantum dot dispersion solution containing metal ions M+ can be prepared.

[0071] In this embodiment, the ethanol (C ２ H ６ 0) solution, for example, zinc chloride (ZnCl ２ ) 0.02 [mol / L] of ethanol (C ２ H ６ 0) solution was used. 3-(mercaptopropyl)trimethoxysilane (MPS) shown in the above (chemical formula 1) and tetramethyl orthosilicate (TMOS) shown in the above (chemical formula 2) were used as precursors for forming the first adduct AD1. Octane (C ８ H １８ ) and N-methylformamide (NMF) were used.

[0072] As shown in FIG. 11 , a zinc chloride ethanol solution was mixed with the first liquid L1, in which quantum dots (QDs) were dispersed in octane, and the mixture was then kept at room temperature for approximately one hour. Stirring may be performed using a stirrer or similar device. This process allows chlorine to inactivate any remaining defects (not deactivated by ligands) on the surface of the quantum dots (QDs). In FIG. 11 , active defects are indicated by crosses, and deactivated defects or chlorine that has entered the defects are indicated by circles. In the first liquid L1, chlorine is coordinated to the quantum dots (QDs) in addition to organic ligands. The first liquid L1 can be used directly in subsequent processes, or the first liquid L1 can be centrifuged to separate the quantum dots (QDs) coordinated with organic ligands and chlorine, and the quantum dots (QDs) can be re-dispersed in pure octane to form a new first liquid L1 for subsequent processes.

[0073] As shown in Figure 12, a second liquid L2 was prepared by dissolving MPS and TMOS in NMF, and then the first liquid L1 described above was poured onto the second liquid L2. The concentrations of MPS and TMOS in the second liquid L2 were, for example, 0.2 mol / L for MPS and 0.02 mol / L for TMOS. Based on the surface area of ​​the quantum dots QD, when the TMOS concentration was this high, the first portion PA1 of the first adduct AD1 was formed to include the second void SPA2, as shown in Figure 5. However, when the TMOS concentration was increased, the first portion PA1 of the first adduct AD1 could be formed to exclude the second void SPA2, as shown in Figure 6.

[0074] As shown in Figure 12, the first liquid L1 and the second liquid L2 were thoroughly stirred and mixed. During the stirring process, the ligands for the quantum dots QDs were exchanged. Specifically, the aforementioned organic ligands were released from the quantum dots QDs, and MPS coordinated to the quantum dots QDs. The thiol groups of MPS easily bond with sulfur (S) vacancies on the shell surface of the quantum dots QDs, and MPS inactivates the defects in the quantum dots QDs. At the same time, halogens also coordinated to the quantum dots QDs, inactivating the defects that MPS could not coordinate. Due to the ligand exchange, the quantum dots QDs no longer dispersed in octane, and the quantum dots QDs migrated from the first liquid L1 to the second liquid L2.

[0075] As shown in FIG. 12, the second liquid L2 becomes a solution in which quantum dots QDs containing metal ions M+, halogen ions X-, and the first adduct AD1 are dispersed. Subsequently, the solvent is replaced with alcohol. Specifically, the first liquid L1 is removed, and ethyl acetate is added to the second liquid L2 to precipitate and separate quantum dots QDs containing metal ions M+, halogen ions X-, and the first adduct AD1. Then, the quantum dots QDs containing metal ions M+, halogen ions X-, and the first adduct AD1 are dispersed in ethanol. Other alcohols such as methanol and IPA may be used instead of ethanol. The alcohol converts silicon oxide and silicic acid into water (H ２ O) to prevent water from corroding the quantum dots QDs.

[0076] The quantum dots QD containing the metal ions M+, halogen ions X-, and the first adduct AD1 were again precipitated and separated with ethyl acetate and dispersed in alcohol. This solution is the quantum dot dispersion solution. Note that silicon oxide and silicic acid tend to retain water, so it is desirable to repeat the alcohol dehydration process multiple times.

[0077] In this embodiment, an example has been described in which ethyl acetate is added to the second liquid L2 to precipitate and separate quantum dots QDs containing metal ions M+, halogen ions X−, and the first adduct AD1, and then the quantum dots QDs containing the metal ions M+, halogen ions X−, and the first adduct AD1 are dispersed in ethanol to form a quantum dot dispersion solution. However, the present invention is not limited to this example. For example, the quantum dot dispersion solution may be prepared by centrifuging the second liquid L2 to separate the quantum dots QDs containing the metal ions M+, halogen ions X−, and the first adduct AD1, and then dispersing the quantum dots QDs containing the metal ions M+, halogen ions X−, and the first adduct AD1 in toluene.

[0078] The red light-emitting layer 24L shown in FIGS. 3 and 4 can be formed by forming the quantum dot dispersion solution described above on a predetermined film using, for example, spin coating, slit coating, or an inkjet device.

[0079] [Additional Notes] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present disclosure. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment.

[0080] The present disclosure can be used in light-emitting devices and display devices.

[0081] 1 Display device 3 Barrier layer 4 Thin film transistor layer 5R Red light emitting element (light emitting element) 5G Green light emitting element (light emitting element) 5B Blue light emitting element (light emitting element) 6 Sealing layer 12 Substrate 16, 18, 20 Inorganic insulating film 21 Planarization film 22 Anode 24R, 24R' Functional layer including red light emitting layer 24L Red light emitting layer (light emitting layer) 24H First charge transport layer 24E Second charge transport layer 25 Cathode 26, 28 Inorganic sealing film 27 Organic film 39 Functional film QD Quantum dot AD1 First additive AD2 Second additive AD3 Third additive PA1 First portion PA2 Second portion SPA1 First gap SPA2 Second gap PIX Pixel RSP Red subpixel GSP Green subpixel BSP Blue subpixel DA Display area NDA Frame Area

Claims

1. A light-emitting device comprising: an anode; a cathode; and a light-emitting layer provided between the anode and the cathode, wherein the light-emitting layer includes quantum dots, first additives located around the quantum dots, and second additives composed of metal elements, and the second additive is included at least between the quantum dots and a first portion that is a part of the first additive.

2. A light-emitting device comprising: an anode; a cathode; and a light-emitting layer provided between the anode and the cathode, wherein the light-emitting layer includes quantum dots, first additives located around the quantum dots, and second additives composed of metal elements, and the second additives are metal elements of a different type from the metal elements contained in the quantum dots.

3. The light-emitting device according to claim 1, wherein the second additive is a metal element different from the metal element contained in the quantum dot.

4. The light-emitting element according to claim 2, wherein the second additive is included in a region from the center of the quantum dot to a first portion that is part of the first additive in a cross section of the light-emitting layer.

5. The light-emitting element according to any one of claims 1 to 4, wherein the light-emitting layer comprises a plurality of the quantum dots, the plurality of quantum dots comprising a first quantum dot and a second quantum dot adjacent to each other, and the second adduct is located between the first quantum dot and the second quantum dot.

6. A light-emitting device according to any one of claims 1 to 5, wherein a first portion that is part of the first additive is located away from the quantum dot.

7. The light-emitting element described in claim 1 or 2, wherein the value of ((number of metal atoms) / (number of all atoms)) × 100% between the quantum dot and the first portion that is part of the first additive in the cross section of the light-emitting layer is 0.1% or more.

8. The light-emitting element described in claim 1 or 4, wherein within a circle having a radius r that is the distance from the center of the quantum dot in the cross section of the light-emitting layer to the end of the first portion farther from the center of the quantum dot, the value of ((the number of metal atoms of the metal element that is the second additive) / (the number of all atoms)) is 10 ppm or more.

9. The light-emitting element according to claim 5, wherein the value of ((the number of metal atoms of the metal element that is the second additive) / (the number of all atoms)) in a cross section of the light-emitting layer containing a plurality of the quantum dots is 10 ppm or more.

10. The light-emitting device according to any one of claims 1 to 9, wherein the quantum dot includes a core, and the core includes one or more selected from the group consisting of Si, Ge, CdSe, CdS, CdTe, InP, GaP, InN, ZnSe, ZnS, ZnTe, CdSeTe, GaInP, and ZnSeTe.

11. The light-emitting device according to any one of claims 1 to 10, wherein the quantum dot includes a shell, and the shell includes one or more selected from CdS, ZnS, CdSSe, CdTeSe, CdSTe, ZnSSe, ZnSTe, ZnTeSe, and AgInP.

12. The light-emitting device according to any one of claims 1 to 11, wherein the second adduct is a metal element having an electronegativity of 2.16 or less.

13. The light-emitting device according to any one of claims 1 to 11, wherein the second additive is an alkali metal element or an alkaline earth metal element.

14. The light-emitting device according to any one of claims 1 to 11, wherein the second additive is one selected from the group consisting of Na, K, Mg, Ca, and Ba.

15. The light-emitting device according to any one of claims 1 to 11, wherein the second additive is a transition metal element.

16. The light-emitting device according to any one of claims 1 to 11, wherein the second additive is one selected from the group consisting of Cr, Mo, Mn, Fe, Ni, and Zn.

17. A light-emitting element according to any one of claims 1 to 16, wherein the first portion that is part of the first additive comprises one selected from silicon oxide, boron oxide, phosphorus oxide, germanium oxide, beryllium fluoride, arsenic sulfide, silicon selenide, germanium sulfide, titanium oxide, tellurium oxide, aluminum oxide, bismuth oxide, vanadium oxide, antimony oxide, lead oxide, copper oxide, zirconium fluoride, aluminum fluoride, indium fluoride, zinc chloride, zinc bromide, and silicon nitride.

18. A light-emitting element according to any one of claims 1 to 16, wherein the first portion that is part of the first additive is made of silicon oxide.

19. A light-emitting device according to any one of claims 1 to 16, wherein a first portion that is part of the first additive comprises a continuous film that surrounds the quantum dot in a cross section through the quantum dot.

20. A light-emitting device according to any one of claims 1 to 16, wherein a first portion that is part of the first additive comprises a discontinuous film disposed around the quantum dot in a cross section through the quantum dot.

21. The light-emitting element according to any one of claims 1 to 16, wherein the first portion that is part of the first additive is composed of at least one of polycrystalline and amorphous.

22. The light-emitting device according to any one of claims 1 to 21, wherein the first additive includes a second moiety, and the second moiety is coordinated to the quantum dot.

23. The light-emitting element described in claim 22, wherein the end of the second portion facing the quantum dot contains any one of an oxygen atom, a sulfur atom, a nitrogen atom, and a phosphorus atom, the end of the second portion facing the first portion contains a carbon atom, and one or more carbon atoms are present between the end of the second portion facing the quantum dot and the end of the second portion facing the first portion.

24. The light-emitting device according to any one of claims 1 to 23, which contains a third additive composed of a halogen element or a chalcogen element.

25. The light-emitting device according to claim 24, wherein the third additive is composed of the halogen element, and the halogen element is one selected from the group consisting of F, Cl, Br and I.

26. The light-emitting device according to claim 24, wherein the third additive is composed of the chalcogen element, and the chalcogen element is one selected from the group consisting of S, Se, and Te.

27. A light-emitting element described in any one of claims 24 to 26, wherein the value of ((number of atoms of halogen elements and chalcogen elements) / (number of all atoms)) x 100% between the quantum dot and the first portion that is part of the first additive in the cross section of the light-emitting layer is 0.1% or more.

28. A display device comprising a light-emitting element according to any one of claims 1 to 27.

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