Light-emitting element and display device

Abstract

A red light-emitting element (5R) comprises: a first electrode (22) that is an anode; a second electrode (25) that is a cathode; and a red light-emitting layer (24L) that is disposed between the first electrode (22) and the second electrode (25) and that includes quantum dots (QD) and a matrix (MR), wherein an electron-transporting surface treatment agent (ETS) is distributed in at least a portion of the matrix (MR) located on the side of a second surface (S2) on the side of the second electrode (25), which is the cathode of the red light-emitting layer (24L).

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 describes a light-emitting device having a light-emitting layer containing quantum dots in a matrix.

[0004] Japanese Patent Publication "Patent Publication No. 2011-502333"

[0005] Defects may also occur in the matrix contained in the light-emitting layer of the light-emitting element described in Patent Document 1, and when defects occur in the matrix, there is a problem that the light-emitting characteristics and reliability of the light-emitting element are deteriorated.

[0006] An object of one embodiment of the present disclosure is to provide a light-emitting element and a display device that can reduce the possibility of deterioration in light-emitting characteristics and reliability and can improve carrier balance.

[0007] In order to solve the above-mentioned problems, the light-emitting device of the present disclosure includes an anode, a cathode, and a light-emitting layer including quantum dots and a matrix and disposed between the anode and the cathode, wherein a hole-transporting surface treatment agent or an electron-transporting surface treatment agent is distributed in at least a part of the matrix located on either a first surface of the light-emitting layer facing the anode or a second surface of the light-emitting layer facing the cathode.

[0008] In order to solve the above-mentioned problems, the display device of the present disclosure includes the light-emitting element.

[0009] According to one embodiment of the present disclosure, it is possible to provide a light-emitting element and a display device that can reduce the possibility of deterioration in light-emitting characteristics and reliability and improve the carrier balance.

[0010] FIG. 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 element provided in the display device of embodiment 1. FIG. 4 is a cross-sectional view showing a schematic configuration of another red light-emitting element that can be provided in the display device of embodiment 1. FIG. 5 is a schematic view for explaining a matrix of a red light-emitting layer provided in the red light-emitting element shown in FIGS. 3 and 4. FIG. 6 is another schematic view for explaining a matrix of a red light-emitting layer provided in the red light-emitting element shown in FIGS. 3 and 4. FIG. 7 is a cross-sectional view showing a schematic configuration of a red light-emitting element provided in the display device of embodiment 2. FIG. 8 is a cross-sectional view showing a schematic configuration of another red light-emitting element that can be provided in the display device of embodiment 2. FIG. 9 is a cross-sectional view showing a schematic configuration of a red light-emitting element provided in the display device of embodiment 3. FIG. 10 is a cross-sectional view showing a schematic configuration of another red light-emitting element that can be provided in the display device of embodiment 3. FIG. 11 is a cross-sectional view showing a schematic configuration of a red light-emitting element provided in the display device of embodiment 4. FIG. 12 is a cross-sectional view showing a schematic configuration of another red light-emitting element that can be provided in the display device of embodiment 4.

[0011] The following describes embodiments 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 specific embodiments will be denoted by the same reference numerals, and their description may be omitted.

[0012] First Embodiment FIG. 1 is a plan view showing a schematic configuration of a display device 1 according to a first embodiment.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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 a first electrode 22, a functional layer 24R including a red light-emitting layer, and a second electrode 25. The green light-emitting element 5G included in the green subpixel GSP includes a first electrode 22, a functional layer 24G including a green light-emitting layer, and a second electrode 25. The blue light-emitting element 5B included in the blue subpixel BSP includes a first electrode 22, a functional layer 24B including a blue light-emitting layer, and a second electrode 25.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] The planarizing film 21 can be made of a coatable organic material such as polyimide or acrylic.

[0024] The red light-emitting element 5R includes a first electrode 22 above the planarization film 21, a functional layer 24R including a red light-emitting layer, and a second electrode 25. The green light-emitting element 5G includes a first electrode 22 above the planarization film 21, a functional layer 24G including a green light-emitting layer, and a second electrode 25. The blue light-emitting element 5B includes a first electrode 22 above the planarization film 21, a functional layer 24B including a blue light-emitting layer, and a second electrode 25. The insulating bank 23 covering the edge of the first electrode 22 can be formed by applying an organic material such as polyimide or acrylic and then patterning it by photolithography.

[0025] The sealing layer 6 is a light-transmitting film, and can be composed of, for example, an inorganic sealing film 26 that covers the second electrode 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.

[0026] 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.

[0027] 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.

[0028] Fig. 3 is a cross-sectional view showing a schematic configuration of the red light-emitting element 5R provided 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 provided in the display device 1 of Embodiment 1. As shown in Fig. 2, the red light-emitting element 5R is provided on the substrate 12, and therefore, although not shown in Figs. 3 and 4, it is assumed that the substrate 12 is present below the first electrode 22.

[0029] As shown in FIGS. 3 and 4 , the red light-emitting element 5R includes a first electrode 22, a second electrode 25, and a functional layer 24R including a red light-emitting layer 24L disposed between the first electrode 22 and the second electrode 25. In this embodiment, a case where the first electrode 22 is an anode and the second electrode 25 is a cathode will be described as an example. The red light-emitting layer 24L includes quantum dots QD and a matrix MR, and has a first surface S1 on the anode side, which is the first electrode 22, and a second surface S2 on the cathode side, which is the second electrode 25. In this embodiment, the first surface S1, which has no thickness, is the interface with the adjacent first charge transport layer 24H, and the second surface S2, which has no thickness, is the interface with the adjacent second charge transport layer 24E. Each of the first surface S1 and the second surface S2 may be formed of the quantum dots QD and the matrix MR, or may be formed of only the matrix MR.

[0030] 3 and 4 , in the red light-emitting element 5R of this embodiment, the electron transporting surface treatment agent ETS is distributed in at least a portion of the matrix MR located on the second electrode 25 side of the red light-emitting layer 24L, i.e., on the second surface S2 side (cathode side). The phrase "the electron transporting surface treatment agent ETS is distributed in at least a portion of the matrix MR located on the second surface S2 side" refers not only to the case where the electron transporting surface treatment agent ETS is distributed in at least a portion of the matrix MR located on the second surface S2 side, but also to the case where the electron transporting surface treatment agent ETS is formed so as to be in contact with the second surface S2 formed by the matrix MR, or the case where the electron transporting surface treatment agent ETS is formed on the second surface S2 formed by the matrix MR with a film thickness of, for example, 0.01 nm or more and 10 nm or less. In the red light-emitting element 5R, the second surface S2 is an upper surface that is disposed farther from the substrate 12 (not shown) than the first surface S1, i.e., disposed on the upper side, and the electron transporting surface treatment agent ETS is distributed in at least a portion of the matrix MR located on the upper surface side. Note that the matrix MR located on the second surface S2 side (upper surface side) here refers to a portion of the matrix MR that does not include the first surface S1 but includes the second surface S2. For example, when the matrix MR is divided into N equal parts in the thickness direction (N is a natural number of 2 or more), the portion of the matrix MR that is disposed farthest from the first electrode 22 may be the portion of the matrix MR that is disposed farthest from the first electrode 22. The red light-emitting element 5R of the present embodiment shown in FIGS. 3 and 4 described above is just one example, and is not limited to this, and may be formed by first forming the red light-emitting layer 24L including the quantum dots QD and the matrix MR, and then treating the exposed surface side of the red light-emitting layer 24L, that is, the upper surface side of the first surface S1 or the second surface S2 that is located farther from the substrate 12 (not shown), using the electron transporting surface treatment agent ETS or the hole transporting surface treatment agent HTS, as long as this can reduce the possibility of defects occurring in the matrix MR.For example, as in a red light-emitting element 5R′ of Embodiment 2 described later (see FIGS. 7 and 8 ), the electron-transporting surface treatment agent ETS may be distributed in at least a part of the matrix MR located on the second electrode 25 side of the red light-emitting layer 24L, i.e., on the first surface S1 side of the anode side; as in a red light-emitting element 5R″ of Embodiment 3 described later (see FIGS. 9 and 10 ), the hole-transporting surface treatment agent HTS may be distributed in at least a part of the matrix MR located on the second electrode 25 side of the red light-emitting layer 24L, i.e., on the second surface S2 side of the cathode side; and as in a red light-emitting element 5R′″ of Embodiment 4 described later (see FIGS. 11 and 12 ), the hole-transporting surface treatment agent HTS may be distributed in at least a part of the matrix MR located on the second electrode 25 side of the red light-emitting layer 24L, i.e., on the first surface S1 side of the anode side. Alternatively, the red-light-emitting layer 24L may be formed first, followed by heat treatment, and then treatment with the electron-transporting surface treatment agent ETS or the hole-transporting surface treatment agent HTS. Alternatively, the red-light-emitting layer 24L may be formed first, followed by treatment with the electron-transporting surface treatment agent ETS or the hole-transporting surface treatment agent HTS, followed by heat treatment. In the present disclosure, a monomer material containing a functional group having electron transport properties and a functional group capable of coordinating to the matrix MR is preferably used as the electron-transporting surface treatment agent ETS. While oligomer materials or polymer materials can also be used, it is preferable to use a monomer material because it can increase the density of the electron-transporting surface treatment agent ETS that can be coordinated to the matrix MR. Furthermore, the electron-transporting surface treatment agent ETS may contain, as necessary, polar groups, non-polar groups, water-repellent groups, etc., in addition to the functional group having electron transport properties and the functional group capable of coordinating to the matrix MR. Furthermore, the number of functional groups capable of coordinating to the matrix MR within one molecule of the electron-transporting surface treatment agent ETS is not particularly limited. Even if the number of functional groups capable of coordinating to the matrix MR in one molecule of the electron transporting surface treatment agent ETS is small, as described above, the density of the electron transporting surface treatment agent ETS that can be coordinated to the matrix MR can be increased by using a monomer material as the electron transporting surface treatment agent ETS.Therefore, as will be described later, a monomer material containing a functional group having electron transport properties and a functional group capable of coordinating to the matrix MR, such as 2-amino-5-phenylpyridine, can be suitably used as the electron transporting surface treatment agent ETS. The manufacturing process of the red-light-emitting layer 24L treated with an electron-transporting surface treatment agent ETS, such as 2-amino-5-phenylpyridine, includes the following steps: a first step of forming the red-light-emitting layer 24L containing quantum dots QD and a matrix MR; a second step of dropping the electron-transporting surface treatment agent ETS, such as 2-amino-5-phenylpyridine, onto the red-light-emitting layer 24L formed in the first step; a third step of maintaining the electron-transporting surface treatment agent ETS, such as 2-amino-5-phenylpyridine, in a dropped state on the red-light-emitting layer 24L formed in the first step for several seconds to several minutes to wait for a coordination reaction; and a fourth step of rinsing away unnecessary excess electron-transporting surface treatment agent ETS with a solvent such as ethanol. The hole-transporting surface treatment agent HTS can be preferably a monomer material containing a functional group having hole-transport properties and a functional group capable of coordinating to the matrix MR. Although oligomer materials or polymer materials can be used, it is preferable to use monomer materials because they can increase the density of the hole-transporting surface treatment agent HTS that can be coordinated to the matrix MR. Furthermore, the hole-transporting surface treatment agent HTS may contain, as necessary, polar groups, nonpolar groups, water-repellent groups, etc., in addition to the functional groups having hole-transport properties and the functional groups capable of coordinating to the matrix MR. Furthermore, the number of functional groups capable of coordinating to the matrix MR in one molecule of the hole-transporting surface treatment agent HTS is not particularly limited. Even if the number of functional groups capable of coordinating to the matrix MR in one molecule of the hole-transporting surface treatment agent HTS is small, as described above, the density of the hole-transporting surface treatment agent HTS that can be coordinated to the matrix MR can be increased by using a monomer material as the hole-transporting surface treatment agent HTS. Therefore, as described below, a monomer material containing a functional group having hole-transport properties and a functional group capable of coordinating to the matrix MR, such as 4-aminotriphenylamine, can be suitably used as the hole-transporting surface treatment agent HTS.The manufacturing process of the red light-emitting layer 24L treated with the hole-transporting surface treatment agent HTS, for example, 4-Aminotriphenylamine, includes the following steps: a first step of forming the red light-emitting layer 24L including the quantum dots QD and the matrix MR; a second step of dropping the hole-transporting surface treatment agent HTS, for example, 4-Aminotriphenylamine, onto the red light-emitting layer 24L formed in the first step; a third step of maintaining the hole-transporting surface treatment agent HTS, for example, 4-Aminotriphenylamine, in a dropped state on the red light-emitting layer 24L formed in the first step for several seconds to several minutes to wait for a coordination reaction; and a fourth step of rinsing away unnecessary excess hole-transporting surface treatment agent HTS with a solvent such as ethanol.

[0031] The second surface S2 of the red light-emitting layer 24L included in the red light-emitting element 5R shown in Fig. 3 is formed to be substantially flat, whereas the second surface S2 of the red light-emitting layer 24L included in the red light-emitting element 5R shown in Fig. 4 is formed to be uneven or curved. In a region where the amount of matrix MR is sufficiently large relative to the amount of quantum dots QD, the second surface S2 of the red light-emitting layer 24L is likely to have a shape like that shown in Fig. 3, while in a region where the amount of matrix MR is not sufficiently large relative to the amount of quantum dots QD, the second surface S2 of the red light-emitting layer 24L is likely to have a shape like that shown in Fig. 4. Therefore, the second surface S2 of the red light-emitting layer 24L included in one red light-emitting element 5R may have both the shape of the second surface S2 shown in Fig. 3 and the shape of the second surface S2 shown in Fig. 4.

[0032] 2 may be of either a top-emission type or a bottom-emission type. The red light-emitting element 5R, the green light-emitting element 5G, and the blue light-emitting element 5B have a stack structure in which the second electrode 25 serving as a cathode is disposed above the first electrode 22 serving as an anode. To form the red light-emitting element 5R, the green light-emitting element 5G, and the blue light-emitting element 5B, the first electrode 22 serving as an anode may be formed from an electrode material that reflects visible light, and the second electrode 25 serving as a cathode may be formed from an electrode material that transmits visible light. To form the bottom-emission element, the first electrode 22 serving as an anode may be formed from an electrode material that transmits visible light, and the second electrode 25 serving as a cathode may be formed from an electrode material that reflects visible light. On the other hand, in the case of an inverted stack structure in which the second electrode 25, which is an anode, is arranged as a layer above the first electrode 22, which is a cathode, as in the red light-emitting elements 5R' and 5R''', which will be described later, in order to form a top emission type, the first electrode 22, which is a cathode, may be formed from an electrode material that reflects visible light, and the second electrode 25, which is an anode, may be formed from an electrode material that transmits visible light, and in order to form a bottom emission type, the first electrode 22, which is a cathode, may be formed from an electrode material that transmits visible light, and the second electrode 25, which is an anode, may be formed from an electrode material that reflects visible light.

[0033] 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.

[0034] 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.

[0035] 2 , the functional layer 24R including the red light-emitting layer 24L included in the red light-emitting element 5R, the functional layer 24G including the green light-emitting layer included in the green light-emitting element 5G, and the functional layer 24B including the blue light-emitting layer included in the blue light-emitting element 5B may be, for example, a laminate in which a first charge transport layer 24H, a red light-emitting layer 24L, any one of a green light-emitting layer and a blue light-emitting layer, and a second charge transport layer 24E are stacked in this order from the side of the anode, the first electrode 22. 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] 2, the red light-emitting layer 24L of the red light-emitting element 5R, the green light-emitting layer of the green light-emitting element 5G, and the blue light-emitting layer of the blue light-emitting element 5B contain quantum dots QDs, and the quantum dots QDs may have, for example, a core structure, a core / shell structure, a core / shell / shell structure, or a shell structure in which the core / shell ratio is continuously changed. Note that the shell may cover only a portion of the core, but it is more preferable for the shell to completely cover the core. The core material of the quantum dot QD is, for example, a crystal of a II-VI group semiconductor such as MgS, MgSe, MgTe, CaS, CaSe, CaTe, BaS, BaSe, BaTe, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, PbS, PbSe, HgS, HgSe, HgTe, a crystal of a III-V group semiconductor such as GaAs, GaP, InN, InAs, InP, InSb, Ga ３ S ２ , Ga ２ Se ３ , In ２ S ３ , In ２ Se３ Crystals of III-VI group semiconductors such as CuInGaS, AgInGaS, CuInGaS, AgInGaZnS, CuInGaSe, AgInGaSe, etc., crystals of I-III-VI group semiconductors such as C and Si, crystals of IV group semiconductors such as CsPbI ３ , CsPbBr ３ , CsPbCl ３ The shell material can be made of a semiconductor crystal with a perovskite structure such as the above. The shell material is selected from the same material group as the core material, and is preferably one that has a lattice constant close to that of the core material and a larger band gap than the core material.

[0041] 2, the red light-emitting layer 24L of the red light-emitting element 5R, the green light-emitting layer of the green light-emitting element 5G, and the blue light-emitting layer of the blue light-emitting element 5B each include a matrix MR. The matrix MR may include, for example, a metal sulfide or an oxide containing a metal element or a metalloid element. Examples of metalloid elements include B, Si, Ge, As, Sb, and Te. The metal sulfide may include one or more metal elements selected from Zn, Mg, and Ga, and may be, for example, zinc sulfide, magnesium zinc sulfide, gallium sulfide, tellurium zinc sulfide, magnesium sulfide, or gallium zinc sulfide. Examples of oxides containing a metal element or a metalloid element include, but are not limited to, silicon oxide, beryllium oxide, boron oxide, magnesium oxide, aluminum oxide, calcium oxide, scandium oxide, titanium oxide, manganese oxide, nickel oxide, gallium oxide, germanium oxide, arsenic oxide, strontium oxide, yttrium oxide, zirconium oxide, niobium oxide, molybdenum oxide, indium oxide, tin oxide, antimony oxide, barium oxide, cerium oxide, europium oxide, hafnium oxide, tantalum oxide, and thorium oxide.

[0042] The matrix MR refers to a component that contains and holds quantum dots QDs, for example, having a core structure, a core / shell structure, a core / shell / shell structure, or a shell structure with a continuously varying core / shell ratio. It can also be referred to as a substrate, a base material, or a filler. The matrix MR may be solid at room temperature. Note that the quantum dots QDs do not necessarily have to be distributed evenly throughout the matrix MR. Furthermore, certain regions of the matrix MR may contain no quantum dots QDs. Note that even if only a portion of the quantum dots QDs are covered by the matrix MR, the matrix MR is still a component that contains and holds the quantum dots QDs. Figure 5 is a schematic diagram illustrating the matrix MR of the red light-emitting layer 24L provided in the red light-emitting element 5R shown in Figures 3 and 4. Figure 6 is another schematic diagram illustrating the matrix MR of the red light-emitting layer 24L provided in the red light-emitting element 5R shown in Figures 3 and 4. In this specification, "the matrix fills the spaces between the quantum dots QD" means that the matrix fills at least the region K between the quantum dots QDA and QDB, as shown in the set P1 in FIG. 5 . Region K is a region surrounded by two lines (common circumscribing lines) tangent to the peripheries of the quantum dots QDA and QDB in the cross section of the light-emitting layer and the opposing peripheries of the quantum dots QDA and QDB. Therefore, as shown in the set P2 in FIG. 6 , region K can exist even if the quantum dots QDA and QDB are close to each other, and the matrix fills region K. "The matrix MR fills the spaces between the quantum dots QD" does not necessarily mean that the region K between the quantum dots QDA and QDB is entirely composed of the matrix MR. For example, region K between the quantum dots QDA and QDB may contain a material such as a ligand that is different from the material of the matrix MR. Specifically, for example, the red light-emitting layer 24L may be added to improve the dispersibility of the quantum dots QD in the dispersion liquid used for coating formation, and may contain organic ligands that coordinate to the outer surfaces of the quantum dots QD in the dispersion liquid.In this case, in the red light-emitting layer 24L, from the viewpoint of improving the reliability of the red light-emitting layer 24L, for example, the weight ratio of the organic ligand to the total weight including the region K may be less than 5%. The matrix MR may fill the regions of the red light-emitting layer 24L other than the quantum dots QDs. For example, the outer edges (top and bottom surfaces) of the red light-emitting layer 24L may be covered with the matrix MR. Alternatively, a portion of the matrix MR may extend from the outer edge of the red light-emitting layer 24L, so that the quantum dots QDs are positioned away from the outer edge. The outer edge of the red light-emitting layer 24L may not be formed solely by the matrix MR, and some of the quantum dots QDs may be exposed from the matrix MR. The matrix MR may refer to the portion of the red light-emitting layer 24L excluding the quantum dots QDs. The matrix MR may extend 1000 nm in a plane perpendicular to the film thickness direction at any position in the film thickness direction of the red light-emitting layer 24L. ２ The red light-emitting layer 24L may have a continuous film with an area of ​​1000 nm or more. Furthermore, in the red light-emitting layer 24L, the quantum dots QDs may be encapsulated in the continuous film of the matrix MR. In other words, the quantum dots QDs may be encapsulated in the continuous film of the matrix MR. For example, if 60% or more of the surfaces of 80% or more of the quantum dots QDs constituting the red light-emitting layer 24L are in contact with the continuous film of the matrix MR, it can be said that the quantum dots QDs contained in the red light-emitting layer 24L are encapsulated in the matrix MR. In this way, the red light-emitting layer 24L containing the quantum dots QDs encapsulated in the matrix MR improves light-emitting characteristics and extends the lifespan. The red light-emitting layer 24L has a thickness of 1000 nm or more at any position in the film thickness direction in a plane direction perpendicular to the film thickness direction. ２The red light-emitting layer 24L may contain one or more quantum dots QDs per quantum dot QD. In this case, the red light-emitting layer 24L generally contains quantum dots QDs at a concentration sufficient to function as an emission layer of a light-emitting element. The matrix MR may be positioned, for example, around the entire periphery of the quantum dots QDs. For example, as shown in the figure, the matrix MR may be positioned around the entire periphery of any quantum dot QD in any cross section passing through the quantum dot QD. Here, "the matrix MR is positioned around the entire periphery of the quantum dot QDs" may mean that the matrix MR is positioned around 90% or more of the periphery of the quantum dot QDs. Furthermore, as shown in FIG. 3, the surface of the quantum dot QD and the matrix MR may be in contact with each other. The band gap of the matrix MR may be wider than the band gap of the material constituting the quantum dot QDs. When the quantum dot QDs have a core and a shell surrounding the core, the band gap of the matrix MR may be wider than the band gap of the material constituting the shell.

[0043] In this embodiment, as described below, a case where a matrix MR made of zinc sulfide is a component that contains and holds quantum dots QDs will be described as an example, but the present invention is not limited to this. For example, a matrix MR composed of a mixture of a first matrix (e.g., zinc sulfide) and a second matrix (e.g., silicon oxide) that are different materials may be used as a component that contains and holds quantum dots QDs. Furthermore, for example, although not shown, the first matrix and the second matrix, which are different materials, may cover different portions of the same quantum dots QDs, such as when at least some of the quantum dots QDs are only partially covered by the first matrix and the remaining portions are covered by the second matrix. Note that even when only a portion of the quantum dots QDs are covered by the first matrix or the second matrix, the first matrix or the second matrix is ​​a component that contains and holds quantum dots QDs.

[0044] A matrix MR may be filled between multiple quantum dots QDs. "A matrix MR is filled between multiple quantum dots QDs" means that a matrix MR is filled between at least two quantum dots QDs. Note that "a matrix MR is filled between two quantum dots QDs" means that a region formed between two adjacent quantum dots QDs is filled or filled with a matrix MR, or that the two adjacent quantum dots QDs are held together by the presence of a matrix MR in this region.

[0045] Unless otherwise specified or contradictory, the structure of the matrix MR may be determined as described above by observing a cross section of the light-emitting layer, for example, the red light-emitting layer 24L, with a width of about 100 nm, and it is not necessary to observe the above-described structure throughout the entire light-emitting layer, for example, the red light-emitting layer 24L. The matrix MR may contain a substance different from the main material (for example, an inorganic substance such as an inorganic semiconductor) as, for example, an additive.

[0046] In this embodiment, the red light-emitting element 5R shown in Figures 3 and 4 has the following configuration, but this is merely an example and is not limiting. Since the red light-emitting element 5R shown in Figures 3 and 4 is a top-emission type, a laminate in which an Al layer and an ITO (indium tin oxide) layer are laminated in this order from the substrate 12 side (not shown) is used as the first electrode 22 serving as the anode, thereby realizing an electrode that reflects visible light, and a thin film made of Al is used as the second electrode 25 serving as the cathode, thereby realizing an electrode that transmits visible light. The first charge transport layer 24H was composed of a laminate of a hole injection layer (HIL) and a hole transport layer (HTL) stacked in this order from the first electrode 22 side. The hole injection layer (HIL) was formed using nickel oxide particles to a thickness of 50 nm, and the hole transport layer (HTL) was formed using poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl))diphenylamine)] (TFB) to a thickness of 30 nm. The quantum dots QD used had a core material made of InP and a shell material made of ZnS. The matrix MR used a matrix made of ZnS. The electron transport surface treatment agent ETS used was 2,4,6-Tri(pyridin-4-yl)pyridine, shown in the following chemical formula 1, which is a monomer containing a functional group with electron transport properties. Note that 2,4,6-Tri(pyridin-4-yl)pyridine, shown in the following chemical formula 1, is a pyridine derivative and therefore contains a functional group with electron transport properties. The second charge transport layer 24E is composed of an electron transport layer (ETL), which is formed using zinc oxide particles to a thickness of 50 nm. Furthermore, the band gap of the matrix MR, i.e., the band gap of ZnS, is larger than the band gap of the core of the quantum dot QD, i.e., the band gap of InP.

[0047] 3 and 4 , a red light-emitting element 5R is realized by first forming a red light-emitting layer 24L containing quantum dots QD and a matrix MR, and then treating the exposed surface side of the red light-emitting layer 24L, i.e., the second surface S2 side, with an electron-transporting surface treatment agent ETS. This reduces the possibility of defects occurring in the matrix MR and reduces the possibility of deterioration in light-emitting characteristics and reliability. Furthermore, as described above, the red light-emitting element 5R contains the electron-transporting surface treatment agent ETS, which improves the transportability of electrons from the second electrode 25, which is the cathode, to the red light-emitting layer 24L. This makes it possible to realize a red light-emitting element 5R that is suitable for use in, for example, a hole-excess material configuration in which the number of holes is greater than the number of electrons in the carriers injected into the quantum dots QD, and also reduces the driving voltage. Alternatively, the red light-emitting layer 24L may be formed first, followed by a heat treatment and then a treatment using the electron transporting surface treatment agent ETS. Alternatively, the red light-emitting layer 24L may be formed first, followed by a treatment using the electron transporting surface treatment agent ETS, and then a heat treatment may be performed.

[0048] Here, of the red light-emitting element 5R, the green light-emitting element 5G, and the blue light-emitting element 5B provided in the display device 1 shown in FIG. 2 , the red light-emitting element 5R has been described as an example. However, similar to the red light-emitting element 5R, the green light-emitting element 5G and the blue light-emitting element 5B can also be configured to contain the electron-transporting surface treatment agent ETS.

[0049] In this embodiment, a case will be described as an example in which each of the red light-emitting element 5R, the green light-emitting element 5G, and the blue light-emitting element 5B included in the display device 1 shown in Fig. 2 is configured to contain the electron transporting surface treatment agent ETS, but the present invention is not limited to this. For example, only the light-emitting elements of a specific color among the red light-emitting element 5R, the green light-emitting element 5G, and the blue light-emitting element 5B included in the display device 1 shown in Fig. 2 may be configured to contain the electron transporting surface treatment agent ETS, or only the light-emitting elements of specific two colors may be configured to contain the electron transporting surface treatment agent ETS. Such a display device can reduce the possibility of defects occurring in the matrix MR and the possibility of deterioration in light-emitting characteristics and reliability.

[0050] 3 and 4 , an electron transport layer (ETL) may be provided as a second charge transport layer 24E between the red light-emitting layer 24L and the second electrode 25, which is a cathode and is located above the red light-emitting layer 24L. In such a configuration, the transportability of electrons from the second electrode 25, which is a cathode, to the red light-emitting layer 24L is improved, and therefore, in the case of a material configuration with an excess of holes, it is possible to improve the carrier balance and realize a reduction in driving voltage.

[0051] As shown in FIGS. 3 and 4, at least a portion of the distributed electron transporting surface treatment agent ETS may be in contact with both the second surface S2 and the electron transport layer (ETL), which is the second charge transport layer 24E.

[0052] Note that, for example, as shown in FIG. 4 , when the second surface S2 of the red light-emitting layer 24L is formed in an uneven or curved shape or when the matrix MR is made of a porous material, the electron transporting surface treatment agent ETS may penetrate into the inside of the matrix MR, modify the inside of the matrix MR, and reduce the possibility of defects occurring in the matrix MR.

[0053] Furthermore, in a case where the red light-emitting layer 24L is formed first, and then the treatment using the electron transporting surface treatment agent ETS is performed, followed by a heat treatment to decompose the precursor material of the matrix MR (e.g., zinc xanthogenate), the electron transporting surface treatment agent ETS is applied from above the quantum dots QD and the matrix MR contained in the red light-emitting layer 24L, so that the electron transporting surface treatment agent ETS is distributed in at least a portion of the matrix MR located on the cathode-side second surface S2 side of the red light-emitting layer 24L. Then, during the decomposition of the precursor material of the matrix MR by the heat treatment, the precursor material sinks in this state toward the first electrode 22 as it decomposes. Therefore, a red light-emitting device can be realized in which the electron transporting surface treatment agent ETS is absent in a region of the matrix MR that is less than 3 nm away from the first surface S1 in the direction toward the second surface S2 of the red light-emitting layer 24L, but is present in a region that is 3 nm or more away from the first surface S1 in the direction toward the second surface S2 of the red light-emitting layer 24L.

[0054] As described above, in the case of the red light-emitting element 5R of this embodiment, the red light-emitting layer 24L containing the quantum dots QD and the matrix MR is first formed, and then treatment is performed using the electron transporting surface treatment agent ETS from the exposed surface side of the red light-emitting layer 24L, i.e., from the second surface S2 side. Therefore, when the amount of the electron transporting surface treatment agent ETS present in the region of the matrix MR that is 3 nm or more away from the first surface S1 in the direction toward the second surface S2 is X moles, and the amount of the electron transporting surface treatment agent ETS present in the region of the matrix MR that is less than 3 nm away from the first surface S1 in the direction toward the second surface S2 is Y moles, (X / (X+Y))×100% is often 50% or more. Furthermore, when the amount of the electron transporting surface treatment agent ETS present in the region of the matrix MR that is 3 nm or more away from the first surface S1 in the direction toward the second surface S2 is X moles, 3 The amount of the electron transporting surface treatment agent ETS present in the region of less than 3 nm from the first surface S1 in the direction of the second surface S2 is defined as Ym 3 In this case, (X / (X+Y))×100% is often 50% or more.

[0055] The electron-transporting surface treatment agent ETS can be formed to a thickness of a single molecule to a few molecules that can impart electron transport properties to the second surface S2 of the red-light-emitting layer 24L. For example, it is preferable that the electron-transporting surface treatment agent ETS be formed to a thickness of 0.01 nm to 10 nm in the direction perpendicular to the second surface S2. In the case of the above-described electron-transporting layer (ETL), generally, electron transport properties are exhibited when the layer is formed to a thickness greater than 10 nm, but when the layer is formed to a thickness of 10 nm or less, electrons pass directly through the layer due to the tunneling effect, so the electron-transporting properties of the electron-transporting layer (ETL) are not utilized. On the other hand, when the electron-transporting surface treatment agent ETS modifies the matrix MR, as in this embodiment, even if the electron-transporting surface treatment agent ETS is formed to a thickness of a single molecule to a few molecules, the effect of reducing the electron injection barrier into the matrix MR is obtained, and this is sufficient.

[0056] In this embodiment, the electron transporting surface treatment agent ETS has been described using, as an example, a monomer containing a pyridine derivative as a functional group having electron transport properties, such as 2,4,6-Tri(pyridin-4-yl)pyridine shown in Chemical Formula 1 above. However, the electron transporting surface treatment agent ETS is not limited to this. Alternatively, the electron transporting surface treatment agent ETS may be a monomer containing a functional group capable of coordinating with the matrix MR and having electron transport properties, or a monomer containing a functional group capable of coordinating with the matrix MR and a functional group having electron transport properties. Furthermore, in consideration of affinity with the upper layer, the electron transporting surface treatment agent ETS may appropriately incorporate any of the following skeletons: a hydrophobic skeleton containing an alkyl chain; a hydrophilic skeleton containing, for example, an ether group, an ester group, or a polyethylene glycol (PEG)-based skeleton; or a water-repellent skeleton such as a fluorous skeleton containing many C—F groups.

[0057] When the matrix MR contains a metal sulfide such as ZnS, as in this embodiment, the electron-transporting surface treatment agent ETS preferably contains at least one functional group selected from amine, carboxylic acid, thiol, phosphine, and halogen as a functional group capable of coordinating with the matrix MR. For example, 2-Amino-5-phenylpyridine shown in the following (Chemical Formula 2) is an example of an electron-transporting surface treatment agent ETS that contains a pyridine derivative as a functional group having electron transport properties and an amine as a functional group capable of coordinating with the matrix MR. Furthermore, 2-Phenylpyridine-4-carboxylic Acid shown in the following (Chemical Formula 3) is an example of an electron-transporting surface treatment agent ETS that contains a pyridine derivative as a functional group having electron transport properties and a carboxylic acid as a functional group capable of coordinating with the matrix MR. Thus, by using an electron-transporting surface treatment agent ETS that contains both a functional group having electron transport properties and a functional group capable of coordinating with the matrix MR, electron transport properties can be more efficiently imparted to the second surface S2 of the red-light-emitting layer 24L. In this embodiment, quantum dots QDs whose shell material is made of ZnS, a metal sulfide, are used, so the electron transporting surface treatment agent ETS can be coordinated not only to the matrix MR but also to the shell of the quantum dots QDs.

[0058] As the electron transporting surface treatment agent ETS, for example, monomers shown in the following (Chemical Formulas 4 to 7) may be used. 1,4-Di[[2,2':6',2''-terpyridin]-4'-yl]benzene shown in the following (Chemical Formula 4) is a monomer containing a pyridine derivative as a functional group having electron transport properties. 5'-Phenyl-[1,1':3',1''-terphenyl]-4-amine shown in the following (Chemical Formula 5) is a monomer having electron transport properties and containing one amine as a functional group capable of coordinating to the matrix MR. 1,3,5-Tris(4-aminophenyl)benzene shown in the following (Chemical Formula 6) is a monomer having electron transport properties and containing three amines as functional groups capable of coordinating to the matrix MR. Tetraphenyl porphyrin shown in the following (Chemical Formula 7) is a monomer having electron transport properties and containing two amines as functional groups capable of coordinating to the matrix MR.

[0059] When the matrix MR contains an oxide containing a metal element or a semimetal element, such as silicon oxide or aluminum oxide, the electron transporting surface treatment agent ETS preferably contains at least one functional group selected from phosphonic acid and disulfide as a functional group capable of coordinating to the matrix MR.

[0060] The electron transporting surface treatment agent ETS may contain, as the functional group having electron transport properties, a triazole derivative or an oxadiazole derivative instead of the pyridine derivative described above, or may contain at least one selected from the group consisting of a pyridine derivative, a triazole derivative, and an oxadiazole derivative.

[0061] The electron transporting surface treatment agent ETS may be, for example, a monomer containing an oxadiazole derivative as a functional group having electron transport properties, as shown in the following chemical formulas 8 to 11. 2-Amino-5-phenyl-1,3,4-oxadiazole shown in the following chemical formula 8 is a monomer containing an oxadiazole derivative as a functional group having electron transport properties and one amine as a functional group capable of coordinating to the matrix MR. 4-(N,N-Dimethylaminosulfonyl)-7-amino-2,1,3-benzoxadiazole shown in the following chemical formula 9 is a monomer containing an oxadiazole derivative as a functional group having electron transport properties and one amine as a functional group capable of coordinating to the matrix MR. 6-[[7-(N,N-Dimethylaminosulfonyl)-2,1,3-benzoxadiazol-4-yl]amino]hexanoic acid, shown in the following chemical formula 10, is a monomer containing an oxadiazole derivative as a functional group having electron transport properties and one carboxylic acid as a functional group capable of coordinating to the matrix MR. 5-(Furan-2-yl)-1,3,4-oxadiazol-2-amine, shown in the following chemical formula 11, is a monomer containing an oxadiazole derivative as a functional group having electron transport properties and one amine as a functional group capable of coordinating to the matrix MR. Furthermore, although not shown, a monomer in which a functional group capable of coordinating to the matrix MR is incorporated into the oxadiazole derivative (2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole) (PBD) may be used as the electron-transporting surface treatment agent ETS.

[0062] The electron transporting surface treatment agent ETS may be, for example, a monomer containing a triazole derivative as a functional group having electron transport properties, as shown in the following (Chemical Formulas 12 to 16). Amicarbazone, shown in the following (Chemical Formula 12), is a monomer containing a triazole derivative as a functional group having electron transport properties and one amine as a functional group capable of coordinating to the matrix MR. 1-Aminobenzotriazole, shown in the following (Chemical Formula 13), is a monomer containing a triazole derivative as a functional group having electron transport properties and one amine as a functional group capable of coordinating to the matrix MR. 3-Amino-5-methylthio-1H-1,2,4-triazole, shown in the following (Chemical Formula 14), is a monomer containing a triazole derivative as a functional group having electron transport properties and one amine as a functional group capable of coordinating to the matrix MR. 4-Amino-1,2,4-triazole, shown in the following chemical formula 15, is a monomer containing a triazole derivative as a functional group having electron transport properties and one amine as a functional group capable of coordinating to the matrix MR. 5-Benzotriazolecarboxylic acid, shown in the following chemical formula 16, is a monomer containing a triazole derivative as a functional group having electron transport properties and one carboxylic acid as a functional group capable of coordinating to the matrix MR. Furthermore, although not shown, a monomer in which a functional group capable of coordinating to the matrix MR is incorporated into the triazole derivative 3-(biphenyl-4-yl)-5-(4-tert-butylphenyl)-4-phenyl-4H-1,2,4-triazole (TAZ) may be used as the electron-transporting surface treatment agent ETS.

[0063] As described above, in the light-emitting element and display device of this embodiment, the electron-transporting surface treatment agent ETS is distributed in at least a portion of the matrix MR located on the second surface S2 side, which is the cathode-side surface of the light-emitting layer, thereby improving the electron transport to the light-emitting layer, and in the case of a material configuration with an excess of holes, improving the carrier balance and reducing the driving voltage. Furthermore, the possibility of defects occurring in the matrix MR can be reduced, thereby reducing the possibility of deterioration in the light-emitting characteristics and reliability.

[0064] 7 and 8, a second embodiment of the present disclosure will be described. The red light-emitting element 5R′ provided in the display device of this embodiment differs from the red light-emitting element 5R described in the first embodiment in that an electron transporting surface treatment agent ETS is distributed in at least a portion of the matrix MR located on the second electrode 25 side of the red light-emitting layer 24L, i.e., on the first surface S1 side of the anode. The rest of the configuration is the same as that described in the first embodiment. For ease of explanation, components having the same functions as those shown in the drawings of the first embodiment are denoted by the same reference numerals, and their description will be omitted.

[0065] Fig. 7 is a cross-sectional view showing a schematic configuration of a red light emitting element 5R' provided in the display device of embodiment 2. Fig. 8 is a cross-sectional view showing a schematic configuration of another red light emitting element 5R' that can be provided in the display device of embodiment 2.

[0066] 7 and 8 , the red light-emitting element 5R′ includes a first electrode 22, a second electrode 25, and a functional layer 24R′ including a red light-emitting layer 24L disposed between the first electrode 22 and the second electrode 25. In this embodiment, a case will be described as an example in which the first electrode 22 is a cathode and the second electrode 25 is an anode. The red light-emitting layer 24L includes quantum dots QD and a matrix MR, and has a first surface S1 on the anode side, which is the second electrode 25, and a second surface S2 on the cathode side, which is the first electrode 22.

[0067] 7 and 8 , in the red light-emitting element 5R′ of this embodiment, a case will be described as an example in which the electron transporting surface treatment agent ETS is distributed in at least a portion of the matrix MR located on the second electrode 25 side of the red light-emitting layer 24L, i.e., on the first surface S1 side (the anode side). Note that the electron transporting surface treatment agent ETS being distributed in at least a portion of the matrix MR located on the first surface S1 side refers not only to the case in which the electron transporting surface treatment agent ETS is distributed in at least a portion of the matrix MR located on the first surface S1 side, but also to the case in which the electron transporting surface treatment agent ETS is formed so as to be in contact with the first surface S1 formed of the matrix MR, or the case in which the electron transporting surface treatment agent ETS is formed on the first surface S1 formed of the matrix MR with a film thickness of, for example, 0.01 nm or more and 10 nm or less. In the red light-emitting element 5R′, the first surface S1 is an upper surface that is disposed farther from the substrate 12 (not shown) than the second surface S2, i.e., that is disposed on the upper side, and the electron transporting surface treatment agent ETS is distributed in at least a portion of the matrix MR located on the upper surface side. Note that here, the matrix MR located on the first surface S1 side (upper surface side) refers to a portion of the matrix MR that does not include the second surface S2 but includes the first surface S1. For example, when the matrix MR is divided into N equal parts in the thickness direction (N is a natural number greater than or equal to 2), the portion of the matrix MR that is disposed farthest from the first electrode 22 may be the portion of the matrix MR that is disposed farthest from the first electrode 22. The red light-emitting element 5R′ of the present embodiment shown in the above-described FIGS. 7 and 8 is just one example, and is not limited to this, as long as the possibility of defects occurring in the matrix MR can be reduced by first forming the red light-emitting layer 24L including the quantum dots QD and the matrix MR, and then treating the exposed surface side of the red light-emitting layer 24L, that is, the upper surface side of the first surface S1 or the second surface S2 that is located farther from the substrate 12 (not shown), using the electron transporting surface treatment agent ETS or the hole transporting surface treatment agent HTS.Alternatively, the red light-emitting layer 24L may be formed first, followed by a heat treatment, and then a treatment using the electron-transporting surface treatment agent ETS or the hole-transporting surface treatment agent HTS. Alternatively, the red light-emitting layer 24L may be formed first, followed by a treatment using the electron-transporting surface treatment agent ETS or the hole-transporting surface treatment agent HTS, and then a heat treatment may be performed.

[0068] The first surface S1 of the red light-emitting layer 24L included in the red light-emitting element 5R′ shown in FIG. 7 is formed to be substantially flat, whereas the first surface S1 of the red light-emitting layer 24L included in the red light-emitting element 5R′ shown in FIG. 8 is formed to be uneven or curved. In a region where the amount of matrix MR is sufficiently large relative to the amount of quantum dots QD, the first surface S1 of the red light-emitting layer 24L is likely to have a shape like that shown in FIG. 7 , while in a region where the amount of matrix MR is not sufficiently large relative to the amount of quantum dots QD, the first surface S1 of the red light-emitting layer 24L is likely to have a shape like that shown in FIG. 8 . Therefore, the first surface S1 of the red light-emitting layer 24L included in one red light-emitting element 5R′ may have both the shape of the first surface S1 shown in FIG. 7 and the shape of the first surface S1 shown in FIG. 8 .

[0069] 7 and 8 , a red light-emitting element 5R′ can be realized by first forming a red light-emitting layer 24L containing quantum dots QD and a matrix MR, and then treating the exposed surface side of the red light-emitting layer 24L, i.e., the first surface S1 side, with an electron-transporting surface treatment agent ETS. This reduces the possibility of defects occurring in the matrix MR and reduces the possibility of deterioration in light-emitting characteristics and reliability. Furthermore, as described above, in the case of the red light-emitting element 5R′, the electron-transporting surface treatment agent ETS is contained in at least a portion of the matrix MR located on the anode-side first surface S1 side. This reduces the transportability of holes from the second electrode 25, which is the anode, to the red light-emitting layer 24L. Therefore, the red light-emitting element 5R′ can be suitably used, for example, in a hole-excess material configuration in which the number of holes is greater than the number of electrons as carriers.

[0070] As in the red light-emitting element 5R′ shown in FIGS. 7 and 8 , a hole transport layer (HTL) may be provided as the first charge transport layer 24H between the red light-emitting layer 24L and the second electrode 25, which is an anode and is located above the red light-emitting layer 24L.

[0071] Furthermore, as shown in FIGS. 7 and 8, at least a portion of the distributed electron transporting surface treatment agent ETS may be in contact with both the first surface S1 and the hole transport layer (HTL), which is the first charge transport layer 24H.

[0072] Note that, for example, as shown in FIG. 8 , when the first surface S1 of the red light-emitting layer 24L is formed in an uneven or curved shape or when the matrix MR is made of a porous material, the electron transporting surface treatment agent ETS may penetrate to the inside of the matrix MR, modify the inside of the matrix MR, and reduce the possibility of defects occurring in the matrix MR.

[0073] Furthermore, in a case where the red light-emitting layer 24L is formed first, and then a treatment using the electron transporting surface treatment agent ETS is performed, followed by a heat treatment to decompose the precursor material of the matrix MR (e.g., zinc xanthogenate), the electron transporting surface treatment agent ETS is applied from above the quantum dots QD and the matrix MR contained in the red light-emitting layer 24L. This causes the electron transporting surface treatment agent ETS to be distributed in at least a portion of the matrix MR located on the first surface S1 side of the anode side of the red light-emitting layer 24L. Then, during the decomposition of the precursor material of the matrix MR by the heat treatment, the precursor material sinks in this state toward the first electrode 22 as it decomposes. This makes it possible to realize a red light-emitting device in which the electron transporting surface treatment agent ETS is absent in a region of the matrix MR that is less than 3 nm away from the second surface S2 of the red light-emitting layer 24L in the direction toward the first surface S1, but is present in a region that is 3 nm or more away from the second surface S2 of the red light-emitting layer 24L in the direction toward the first surface S1.

[0074] As described above, in the case of the red light-emitting element 5R' of this embodiment, the red light-emitting layer 24L containing the quantum dots QD and the matrix MR is first formed, and then treatment is performed using the electron transporting surface treatment agent ETS from the exposed surface side of the red light-emitting layer 24L, i.e., from the first surface S1 side. Therefore, when the amount of the electron transporting surface treatment agent ETS present in the matrix MR in a region 3 nm or more away from the second surface S2 in the first surface S1 direction is X moles, and the amount of the electron transporting surface treatment agent ETS present in the region less than 3 nm away from the second surface S2 in the first surface S1 direction is Y moles, (X / (X+Y))×100% is often 50% or more. Furthermore, when the amount of the electron transporting surface treatment agent ETS present in the region 3 nm or more away from the second surface S2 in the first surface S1 direction in the matrix MR is X moles, 3 The amount of the electron transporting surface treatment agent ETS present in the region of less than 3 nm from the second surface S2 in the direction of the first surface S1 is defined as Ym 3 In this case, (X / (X+Y))×100% is often 50% or more.

[0075] The electron transporting surface treatment agent ETS can be formed to a thickness of a single molecule to a few molecules that can impart electron transport properties to the first surface S1 of the red light-emitting layer 24L, and is preferably formed to a thickness of, for example, 0.01 nm or more and 10 nm or less in the direction perpendicular to the first surface S1.

[0076] As described above, in the light-emitting element and display device of the present embodiment, the electron-transporting surface treatment agent ETS is distributed in at least a part of the matrix MR located on the first surface S1 side of the anode side of the light-emitting layer. This reduces the transportability of holes to the light-emitting layer, and in the case of a material configuration with an excess of holes, improves the carrier balance and reduces the possibility of defects occurring in the matrix MR, thereby reducing the possibility of deterioration in the light-emitting characteristics and reliability.

[0077] 9 and 10 , a third embodiment of the present disclosure will be described. The red light-emitting element 5R″ provided in the display device of this embodiment differs from the red light-emitting element 5R described in the first embodiment in that a hole-transporting surface treatment agent HTS is distributed in at least a portion of the matrix MR located on the second electrode 25 side of the red light-emitting layer 24L, i.e., on the second surface S2 side of the cathode. The rest of the configuration is the same as that described in the first embodiment. For ease of explanation, components having the same functions as those shown in the drawings of the first embodiment are denoted by the same reference numerals, and their description will be omitted.

[0078] FIG. 9 is a cross-sectional view showing a schematic configuration of a red light-emitting element 5R'' provided in the display device of embodiment 3. FIG. 10 is a cross-sectional view showing a schematic configuration of another red light-emitting element 5R'' that can be provided in the display device of embodiment 3.

[0079] As shown in FIGS. 9 and 10 , the red light-emitting element 5R″ includes a first electrode 22, a second electrode 25, and a functional layer 24R″ including a red light-emitting layer 24L disposed between the first electrode 22 and the second electrode 25. In this embodiment, a case will be described as an example in which the first electrode 22 is an anode and the second electrode 25 is a cathode. The red light-emitting layer 24L includes quantum dots QD and a matrix MR, and has a first surface S1 on the anode side, which is the first electrode 22, and a second surface S2 on the cathode side, which is the second electrode 25.

[0080] 9 and 10 , in the red light-emitting element 5R″ of this embodiment, a case will be described as an example in which the hole-transporting surface treatment agent HTS is distributed in at least a portion of the matrix MR located on the second electrode 25 side of the red light-emitting layer 24L, i.e., on the second surface S2 side of the cathode. Note that “the hole-transporting surface treatment agent HTS is distributed in at least a portion of the matrix MR located on the second surface S2 side” refers not only to the case in which the hole-transporting surface treatment agent HTS is distributed in at least a portion of the matrix MR located on the second surface S2 side, but also to the case in which the hole-transporting surface treatment agent HTS is formed so as to be in contact with the second surface S2 formed of the matrix MR, or the case in which the hole-transporting surface treatment agent HTS is formed on the second surface S2 formed of the matrix MR with a film thickness of, for example, 0.01 nm or more and 10 nm or less. In the red light-emitting element 5R″, the second surface S2 is an upper surface that is disposed farther from the substrate 12 (not shown) than the first surface S1, i.e., disposed on the upper side, and a hole-transporting surface treatment agent HTS is distributed in at least a part of the matrix MR located on the upper surface side.

[0081] 9 and 10 , a red light-emitting element 5R″ can be realized by first forming a red light-emitting layer 24L containing quantum dots QDs and a matrix MR, and then treating the exposed surface side of the red light-emitting layer 24L, i.e., the second surface S2 side, with a hole-transporting surface treatment agent HTS. This reduces the possibility of defects occurring in the matrix MR and reduces the possibility of deterioration in light-emitting characteristics and reliability. Furthermore, as described above, in the case of the red light-emitting element 5R″, the hole-transporting surface treatment agent HTS is contained in at least a portion of the matrix MR located on the cathode-side second surface S2 side. This reduces the transportability of electrons from the second electrode 25, which is the cathode, to the red light-emitting layer 24L. Therefore, the red light-emitting element 5R″ can be suitably used, for example, in an electron-rich material configuration in which the number of electrons is greater than the number of holes in the carriers injected into the quantum dots QDs.

[0082] As in the red light-emitting element 5R″ shown in FIGS. 9 and 10 , an electron transport layer (ETL) may be provided as a second charge transport layer 24E between the red light-emitting layer 24L and the second electrode 25, which is a cathode and is a layer above the red light-emitting layer 24L.

[0083] Furthermore, as shown in FIGS. 9 and 10 , at least a portion of the distributed hole transporting surface treatment agent HTS may be in contact with both the second surface S2 and the electron transport layer (ETL), which is the second charge transport layer 24E.

[0084] Note that, for example, as shown in FIG. 10 , when the second surface S2 of the red light-emitting layer 24L is formed in an uneven or curved shape or when the matrix MR is made of a porous material, the hole-transporting surface treatment agent HTS may penetrate to the inside of the matrix MR, modify the inside of the matrix MR, and reduce the possibility of defects occurring in the matrix MR.

[0085] Furthermore, in the case where the red light-emitting layer 24L is formed first, and then the treatment using the hole-transporting surface treatment agent HTS is performed, followed by a heat treatment for decomposing the precursor material of the matrix MR (e.g., zinc xanthogenate), the hole-transporting surface treatment agent HTS is applied from above the quantum dots QD and the matrix MR contained in the red light-emitting layer 24L, so that the hole-transporting surface treatment agent HTS is distributed in at least a part of the matrix MR located on the second surface S2 side of the red light-emitting layer 24L, which is closer to the cathode. When the precursor material of the matrix MR is decomposed by heat treatment, the decomposed precursor material remains in this state and sinks toward the first electrode 22. Therefore, a red light-emitting element can be realized in which the hole-transporting surface treatment agent HTS is not present in a region of the matrix MR that is less than 3 nm away from the first surface S1 in the direction of the second surface S2 of the red light-emitting layer 24L, but the hole-transporting surface treatment agent HTS is present in a region that is 3 nm or more away from the first surface S1 in the direction of the second surface S2 of the red light-emitting layer 24L.

[0086] As described above, in the case of the red light-emitting element 5R″ of this embodiment, the red light-emitting layer 24L including the quantum dots QD and the matrix MR is formed first, and then treatment is performed using the hole-transporting surface treatment agent HTS from the exposed surface side of the red light-emitting layer 24L, i.e., from the second surface S2 side. Therefore, when the amount of the hole-transporting surface treatment agent HTS present in the region of the matrix MR that is 3 nm or more away from the first surface S1 in the second surface S2 direction is X moles, and the amount of the hole-transporting surface treatment agent HTS present in the region of the matrix MR that is less than 3 nm away from the first surface S1 in the second surface S2 direction is Y moles, (X / (X+Y))×100% is often 50% or more. Furthermore, when the amount of the hole-transporting surface treatment agent HTS present in the region of the matrix MR that is 3 nm or more away from the first surface S1 in the second surface S2 direction is X moles, 3 The amount of the hole transporting surface treatment agent HTS present in the region of less than 3 nm from the first surface S1 in the direction of the second surface S2 is defined as Ym 3 In this case, (X / (X+Y))×100% is often 50% or more.

[0087] The film thickness of the hole-transporting surface treatment agent HTS can be formed to a film thickness of a single molecule unit to a few molecules unit that can impart hole-transporting properties to the second surface S2 of the red light-emitting layer 24L, and it is preferable that the film is formed to a film thickness of, for example, 0.01 nm or more and 10 nm or less in the direction perpendicular to the second surface S2.

[0088] In this embodiment, the hole-transporting surface treatment agent HTS is described as an example using a monomer containing a triphenylamine derivative as a functional group having hole transport properties, such as 4-Aminotriphenylamine shown in Chemical Formula 17 below, and containing one amine as a functional group capable of coordinating with the matrix MR. However, the present invention is not limited to this. For example, when the matrix MR contains an oxide containing a metal element or a metalloid element, such as silicon oxide or aluminum oxide, a monomer containing a carbazole derivative as a functional group having hole transport properties and one phosphonic acid as a functional group capable of coordinating with the matrix MR, such as [4-(3,6-Dimethyl-9H-carbazol-9-yl)butyl]phosphonic Acid shown in Chemical Formula 18 below, may be used. The hole-transporting surface treatment agent HTS is not limited to this example, and may be a monomer containing a functional group having hole transport properties, or a monomer having hole transport properties and containing a functional group capable of coordinating with the matrix MR. Furthermore, in consideration of the affinity with the upper layer, the hole-transporting surface treatment agent HTS may appropriately incorporate any of, for example, a hydrophobic skeleton containing an alkyl chain, a hydrophilic skeleton containing, for example, an ether group, an ester group, or a polyethylene glycol (PEG)-based skeleton, or a water-repellent skeleton such as a fluorous skeleton containing many C—F groups.

[0089] As described above, in the light-emitting element and display device of the present embodiment, the hole-transporting surface treatment agent HTS is distributed in at least a part of the matrix MR located on the second surface S2 side of the cathode side of the light-emitting layer. This reduces the transportability of electrons to the light-emitting layer, and in the case of a material configuration with an excess of electrons, improves the carrier balance, reduces the possibility of defects occurring in the matrix MR, and reduces the possibility of deterioration in the light-emitting characteristics and reliability.

[0090] 11 and 12 , a fourth embodiment of the present disclosure will be described. The red light-emitting element 5R′″ provided in the display device of this embodiment differs from the red light-emitting element 5R′″ described in the third embodiment in that a hole-transporting surface treatment agent HTS is distributed in at least a part of the matrix MR located on the second electrode 25 side of the red light-emitting layer 24L, i.e., on the first surface S1 side of the anode side. The rest is as described in the third embodiment. For convenience of description, components having the same functions as those shown in the drawings of the third embodiment are denoted by the same reference numerals, and their description will be omitted.

[0091] 11 is a cross-sectional view showing a schematic configuration of a red light emitting element 5R''' provided in the display device of embodiment 4. FIG. 12 is a cross-sectional view showing a schematic configuration of another red light emitting element 5R''' that can be provided in the display device of embodiment 4.

[0092] As shown in Figures 11 and 12, the red light-emitting element 5R''' includes a first electrode 22, a second electrode 25, and a functional layer 24R''' including a red light-emitting layer 24L arranged between the first electrode 22 and the second electrode 25. In this embodiment, a case will be described as an example in which the first electrode 22 is a cathode and the second electrode 25 is an anode. The red light-emitting layer 24L includes quantum dots QD and a matrix MR, and has a first surface S1 on the anode side, which is the second electrode 25, and a second surface S2 on the cathode side, which is the first electrode 22.

[0093] 11 and 12 , in the red light-emitting element 5R′″ of this embodiment, a case will be described as an example in which the hole-transporting surface treatment agent HTS is distributed in at least a part of the matrix MR located on the second electrode 25 side of the red light-emitting layer 24L, i.e., on the first surface S1 side, i.e., the anode side. Note that “the hole-transporting surface treatment agent HTS is distributed in at least a part of the matrix MR located on the first surface S1 side” refers not only to the case in which the hole-transporting surface treatment agent HTS is distributed in at least a part of the matrix MR located on the first surface S1 side, but also to the case in which the hole-transporting surface treatment agent HTS is formed so as to be in contact with the first surface S1 formed of the matrix MR, or the case in which the hole-transporting surface treatment agent HTS is formed on the first surface S1 formed of the matrix MR with a film thickness of, for example, 0.01 nm or more and 10 nm or less. In the red light-emitting element 5R''', the first surface S1 is an upper surface that is positioned farther from the substrate 12 (not shown) than the second surface S2, i.e., positioned on the upper side, and a hole-transporting surface treatment agent HTS is distributed in at least a part of the matrix MR located on the upper surface side.

[0094] 11 and 12 , a red light-emitting element 5R′″ is realized by first forming a red light-emitting layer 24L containing quantum dots QDs and a matrix MR, and then treating the exposed surface side of the red light-emitting layer 24L, i.e., the first surface S1 side, with a hole-transporting surface treatment agent HTS. This reduces the possibility of defects occurring in the matrix MR and reduces the possibility of deterioration in light-emitting characteristics and reliability. Furthermore, as described above, the red light-emitting element 5R′″ contains the hole-transporting surface treatment agent HTS in at least a portion of the matrix MR located on the anode-side first surface S1 side. This improves the transportability of holes from the second electrode 25, which is the anode, to the red light-emitting layer 24L. Therefore, the red light-emitting element 5R′″ can be suitably used, for example, in an electron-rich material configuration in which the number of electrons is greater than the number of holes in the carriers injected into the quantum dots QDs.

[0095] 11 and 12 , a hole transport layer (HTL) may be provided as the first charge transport layer 24H between the red light-emitting layer 24L and the second electrode 25, which is an anode and is located above the red light-emitting layer 24L. In such a configuration, the transportability of holes from the second electrode 25, which is an anode, to the red light-emitting layer 24L is improved, and therefore, in the case of an electron-rich material configuration, the carrier balance can be improved.

[0096] Furthermore, as shown in FIGS. 11 and 12 , at least a portion of the distributed hole-transporting surface treatment agent HTS may be in contact with both the first surface S1 and the hole-transporting layer (HTL), which is the first charge-transporting layer 24H.

[0097] Note that, for example, as shown in FIG. 12 , when the first surface S1 of the red light-emitting layer 24L is formed in an uneven or curved shape or when the matrix MR is made of a porous material, the hole-transporting surface treatment agent HTS may penetrate to the inside of the matrix MR, modify the inside of the matrix MR, and reduce the possibility of defects occurring in the matrix MR.

[0098] Furthermore, in the case where the red light-emitting layer 24L is formed first, and then the treatment using the hole-transporting surface treatment agent HTS is performed, followed by a heat treatment for decomposing the precursor material of the matrix MR (e.g., zinc xanthogenate), the hole-transporting surface treatment agent HTS is applied from above the quantum dots QD and the matrix MR contained in the red light-emitting layer 24L. As a result, the hole-transporting surface treatment agent HTS is distributed in at least a part of the matrix MR located on the first surface S1 side of the red light-emitting layer 24L, which is closer to the anode. When the precursor material of the matrix MR is decomposed by heat treatment, the decomposed precursor material remains in this state and sinks toward the first electrode 22. Therefore, a red light-emitting element can be realized in which the hole-transporting surface treatment agent HTS is not present in a region of the matrix MR that is less than 3 nm away from the second surface S2 of the red light-emitting layer 24L in the direction toward the first surface S1, but the hole-transporting surface treatment agent HTS is present in a region that is 3 nm or more away from the second surface S2 of the red light-emitting layer 24L in the direction toward the first surface S1.

[0099] As described above, in the case of the red light-emitting element 5R''' of this embodiment, the red light-emitting layer 24L including the quantum dots QD and the matrix MR is formed first, and then treatment is performed using the hole-transporting surface treatment agent HTS from the exposed surface side of the red light-emitting layer 24L, i.e., from the first surface S1 side. Therefore, when the amount of the hole-transporting surface treatment agent HTS present in the matrix MR in a region 3 nm or more away from the second surface S2 in the first surface S1 direction is X moles, and the amount of the hole-transporting surface treatment agent HTS present in the region less than 3 nm away from the second surface S2 in the first surface S1 direction is Y moles, (X / (X+Y))×100% is often 50% or more. Furthermore, when the amount of the hole-transporting surface treatment agent HTS present in the region 3 nm or more away from the second surface S2 in the first surface S1 direction in the matrix MR is X moles, 3 The amount of the hole transporting surface treatment agent HTS present in the region of less than 3 nm from the second surface S2 in the direction of the first surface S1 is defined as Ym 3 In this case, (X / (X+Y))×100% is often 50% or more.

[0100] The film thickness of the hole-transporting surface treatment agent HTS can be formed to a film thickness of a single molecule unit to a few molecules unit that can impart hole-transporting properties to the first surface S1 of the red light-emitting layer 24L, and it is preferable that the film thickness be, for example, 0.01 nm or more and 10 nm or less in the direction perpendicular to the first surface S1.

[0101] As described above, in the light-emitting element and display device of the present embodiment, the hole-transporting surface treatment agent HTS is distributed in at least a part of the matrix MR located on the first surface S1 side of the anode side of the light-emitting layer. This makes it possible to improve the transportability of holes to the light-emitting layer, and in the case of an electron-rich material configuration, it is possible to improve the carrier balance and reduce the possibility of defects occurring in the matrix MR, thereby reducing the possibility of deterioration in the light-emitting characteristics and reliability.

[0102] [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.

[0103] The present disclosure can be used in light-emitting devices and display devices.

[0104] 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 First electrode 24R, 24R', 24R'', 24R''' Functional layer including red light emitting layer 24G Functional layer including green light emitting layer 24B Functional layer including blue light emitting layer 24L Red light emitting layer (light emitting layer) 24H First charge transport layer 24E Second charge transport layer 25 Second electrode 26, 28 Inorganic sealing film 27 Organic film 39 Functional film S1 First surface S2 Second surface ETS Electron transporting surface treatment agent HTS Hole transporting surface treatment agent QD Quantum dot MR Matrix PIX Pixel RSP Red subpixel GSP Green sub-pixel BSP Blue sub-pixel DA Display area NDA Frame area

Claims

1. A light-emitting device comprising: an anode; a cathode; and a light-emitting layer including quantum dots and a matrix, the light-emitting layer being disposed between the anode and the cathode, wherein a hole-transporting surface treatment agent or an electron-transporting surface treatment agent is distributed in at least a portion of the matrix located on either a first surface of the light-emitting layer facing the anode or a second surface of the light-emitting layer facing the cathode.

2. The light-emitting element according to claim 1, wherein one of the first surface and the second surface is an upper surface that is located above the other of the first surface and the second surface, and the hole transporting surface treatment agent or the electron transporting surface treatment agent is distributed in at least a portion of the matrix located on the upper surface side.

3. The light-emitting element according to claim 1 or 2, wherein an electron transport layer is provided between the light-emitting layer and the cathode, which is a layer above the light-emitting layer, and the hole-transporting surface treatment agent is distributed in at least a portion of the matrix located on the second surface side.

4. The light-emitting device according to claim 3, wherein the hole-transporting surface treatment agent is present in a region of the matrix that is 3 nm or more away from the first surface.

5. The light-emitting element according to claim 4, wherein, when the amount of the hole-transporting surface treatment agent present in the matrix in a region 3 nm or more away from the first surface is X moles and the amount of the hole-transporting surface treatment agent present in a region less than 3 nm away from the first surface is Y moles, (X / (X+Y))×100% is 50% or more.

6. The light-emitting device according to any one of claims 3 to 5, wherein at least a portion of the distributed hole-transporting surface treatment agent is in contact with both the second surface and the electron-transporting layer.

7. The light-emitting element according to any one of claims 3 to 6, wherein the hole-transporting surface treatment agent is formed to a film thickness of 0.01 nm or more and 10 nm or less in a direction perpendicular to the second surface.

8. The light-emitting element according to claim 1 or 2, wherein a hole transport layer is provided between the light-emitting layer and the anode, which is a layer above the light-emitting layer, and the hole transporting surface treatment agent is distributed in at least a portion of the matrix located on the first surface side.

9. The light-emitting device according to claim 8, wherein the hole-transporting surface treatment agent is present in a region of the matrix that is 3 nm or more away from the second surface.

10. The light-emitting element according to claim 9, wherein, when the amount of the hole-transporting surface treatment agent present in the matrix in a region 3 nm or more away from the second surface is X moles and the amount of the hole-transporting surface treatment agent present in a region less than 3 nm away from the second surface is Y moles, (X / (X+Y))×100% is 50% or more.

11. The light-emitting device according to any one of claims 8 to 10, wherein at least a portion of the distributed hole-transporting surface treatment agent is in contact with both the first surface and the hole-transporting layer.

12. The light-emitting element according to any one of claims 8 to 11, wherein the hole-transporting surface treatment agent is formed to a film thickness of 0.01 nm or more and 10 nm or less in a direction perpendicular to the first surface.

13. The light-emitting element according to claim 1 or 2, wherein an electron transport layer is provided between the light-emitting layer and the cathode, which is a layer above the light-emitting layer, and the electron transporting surface treatment agent is distributed in at least a portion of the matrix located on the second surface side.

14. The light-emitting device according to claim 13, wherein the electron transporting surface treatment agent is present in a region of the matrix that is 3 nm or more away from the first surface.

15. The light-emitting element according to claim 13 or 14, wherein, when the amount of the electron transporting surface treatment agent present in the matrix in a region 3 nm or more away from the first surface is X moles and the amount of the electron transporting surface treatment agent present in a region less than 3 nm away from the first surface is Y moles, (X / (X+Y))×100% is 50% or more.

16. The light-emitting device according to any one of claims 13 to 15, wherein at least a portion of the distributed electron-transporting surface treatment agent is in contact with both the second surface and the electron-transporting layer.

17. The light-emitting device according to any one of claims 13 to 16, wherein the electron transporting surface treatment agent is formed to a film thickness of 0.01 nm or more and 10 nm or less in the direction perpendicular to the second surface.

18. A light-emitting element according to claim 1 or 2, wherein a hole transport layer is provided between the light-emitting layer and the anode, which is a layer above the light-emitting layer, and the electron transporting surface treatment agent is distributed in at least a portion of the matrix located on the first surface side.

19. The light-emitting device according to claim 18, wherein the electron transporting surface treatment agent is present in a region of the matrix that is 3 nm or more away from the second surface.

20. The light-emitting element according to claim 18 or 19, wherein, when the amount of the electron transporting surface treatment agent present in the matrix in a region 3 nm or more away from the second surface is X moles and the amount of the hole transporting surface treatment agent present in a region less than 3 nm away from the second surface is Y moles, (X / (X+Y))×100% is 50% or more.

21. The light-emitting device according to any one of claims 18 to 20, wherein at least a portion of the distributed electron-transporting surface treatment agent is in contact with both the first surface and the hole-transporting layer.

22. The light-emitting element according to any one of claims 18 to 21, wherein the electron transporting surface treatment agent is formed to a film thickness of 0.01 nm or more and 10 nm or less in a direction perpendicular to the first surface.

23. The light-emitting device according to any one of claims 1 to 12, wherein the hole-transporting surface treatment agent is a monomer containing a functional group having hole-transporting properties.

24. The light-emitting device according to any one of claims 1 to 12, wherein the hole-transporting surface treatment agent is a monomer that contains a functional group capable of coordinating to the matrix and has hole-transporting properties.

25. A light-emitting element described in any one of claims 1 to 12, wherein the hole-transporting surface treatment agent is a monomer containing a functional group capable of coordinating to the matrix and a functional group having hole-transporting properties.

26. The light-emitting element according to claim 23 or 25, wherein the functional group having hole transport properties is a triphenylamine derivative or a carbazole derivative.

27. The light-emitting device according to any one of claims 1, 2, and 13 to 22, wherein the electron-transporting surface treatment agent is a monomer containing a functional group having electron-transporting properties.

28. The light-emitting device according to any one of claims 1, 2, and 13 to 22, wherein the electron-transporting surface treatment agent is a monomer that contains a functional group capable of coordinating to the matrix and has electron-transporting properties.

29. A light-emitting element according to any one of claims 1, 2, and 13 to 22, wherein the electron-transporting surface treatment agent is a monomer containing a functional group capable of coordinating to the matrix and a functional group having electron-transporting properties.

30. The light-emitting element according to claim 27 or 29, wherein the functional group having electron transport properties includes at least one selected from the group consisting of pyridine derivatives, triazole derivatives, and oxadiazole derivatives.

31. The light-emitting element according to any one of claims 24, 25, 28, and 29, wherein the matrix contains a metal sulfide, and the functional group capable of coordinating with the matrix contains at least one selected from the group consisting of amine, carboxylic acid, thiol, phosphine, and halogen.

32. The light-emitting element described in any one of claims 24, 25, 28, and 29, wherein the matrix contains an oxide containing a metal element or a semimetal element, and the functional group capable of coordinating to the matrix includes at least one selected from the group consisting of phosphonic acid and disulfide.

33. A light-emitting device according to any one of claims 1 to 32, wherein the band gap of the matrix is ​​larger than the band gap of the core of the quantum dot.

34. A display device comprising a light-emitting element according to any one of claims 1 to 33.

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