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

Abstract

A red light-emitting element (5R) comprises an anode (22), a cathode (25), and a red light-emitting layer (24L) that includes quantum dots (QD) and a matrix (MR) and is disposed between the anode (22) and the cathode (25), wherein an insulating surface treatment agent (ETS) is included closer to the cathode (25) side than the matrix (MR).

Description

Light-emitting element, display device, and method for manufacturing the display device

[0001] The present disclosure relates to a light-emitting element, a display device, and a method for manufacturing 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] In the case of the light-emitting element described in Patent Document 1, generally, the number of electrons in the carriers injected into the quantum dots is more than the number of holes, which is likely to cause an electron excess state, resulting in a deterioration in the light-emitting characteristics and reliability of the light-emitting element.

[0006] Furthermore, defects may also occur in the matrix contained in the light-emitting layer of the light-emitting element described in Patent Document 1. When defects occur in the matrix, there is a problem that the light-emitting characteristics and reliability of the light-emitting element are deteriorated.

[0007] An object of one aspect of the present disclosure is to provide a light-emitting element, a display device, and a method for manufacturing a display device that can reduce the possibility of deterioration in light-emitting characteristics and reliability and improve carrier balance.

[0008] 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, and includes an insulating surface treatment agent on the cathode side of the matrix.

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

[0010] In order to solve the above-mentioned problems, the manufacturing method of the display device of the present disclosure includes the steps of: forming a first light-emitting layer including quantum dots and a matrix; forming a second light-emitting layer including quantum dots and a matrix; and applying a solution including an insulating surface treatment agent onto the matrix of the first light-emitting layer in a state where the second light-emitting layer is covered with a resist.

[0011] According to one aspect of the present disclosure, it is possible to provide a light-emitting element, a display device, and a method for manufacturing a display device that can reduce the possibility of deterioration in light-emitting characteristics and reliability and improve carrier balance.

[0012] 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 light-emitting layers provided in the light-emitting element of the display device. Fig. 6 is another schematic view for explaining the matrix. Fig. 7 is a cross-sectional view showing a method for manufacturing the display device of embodiment 1.

[0013] The following describes an embodiment of the present disclosure with reference to Figures 1 to 5. For the sake of convenience, components having the same functions as those described in a specific embodiment will be denoted by the same reference numerals, and their description may be omitted.

[0014] FIG. 1 is a plan view showing a schematic configuration of a display device 1 according to the first embodiment.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] The red subpixel RSP provided in the display area DA of the display device 1 includes a red light-emitting element 5R (light-emitting element), the green subpixel GSP provided in the display area DA of the display device 1 includes a green light-emitting element 5G (light-emitting element), and the blue subpixel BSP provided in the display area DA of the display device 1 includes a blue light-emitting element 5B (light-emitting element). The red light-emitting element 5R included in the red subpixel RSP includes an anode 22, a functional layer 24R including a red light-emitting layer, and a cathode 25. The green light-emitting element 5G included in the green subpixel GSP includes an anode 22, a functional layer 24G including a green light-emitting layer, and a cathode 25. The blue light-emitting element 5B included in the blue subpixel BSP includes an anode 22, a functional layer 24B including a blue light-emitting layer, and a cathode 25.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] The planarizing film 21 can be made of a coatable organic material such as polyimide or acrylic.

[0026] The red light-emitting element 5R includes an anode 22 above the planarization film 21, a functional layer 24R including a red light-emitting layer, and a cathode 25 above the anode 22. The green light-emitting element 5G includes an anode 22 above the planarization film 21, a functional layer 24G including a green light-emitting layer, and a cathode 25 above the anode 22. The blue light-emitting element 5B includes an anode 22 above the planarization film 21, a functional layer 24B including a blue light-emitting layer, and a cathode 25 above the anode 22. The insulating bank 23 covering the edge of the anode 22 can be formed by applying an organic material such as polyimide or acrylic and then patterning it by photolithography.

[0027] The sealing layer 6 is a light-transmitting film, and can be composed of, for example, an inorganic sealing film 26 that covers the cathode 25, an organic film 27 that is above the inorganic sealing film 26, and an inorganic sealing film 28 that is above the organic film 27. The sealing layer 6 prevents foreign substances such as water and oxygen from penetrating into the red light-emitting element 5R, the green light-emitting element 5G, and the blue light-emitting element 5B.

[0028] 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.

[0029] 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.

[0030] 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 anode 22.

[0031] 3 and 4 , the red light-emitting element 5R includes an anode 22, a cathode 25, and a functional layer 24R including a red light-emitting layer 24L disposed between the anode 22 and the cathode 25. The red light-emitting layer 24L includes quantum dots QD and a matrix MR, and has a first surface S1 which is the surface on the cathode 25 side and a second surface S2 which is the surface on the anode 22 side. Note that 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.

[0032] 3 and 4 , in the red light-emitting element 5R of this embodiment, the insulating surface treatment agent ETS is distributed in at least a portion of the matrix MR located on the cathode 25 side of the red light-emitting layer 24L, i.e., on the second surface S2 side of the cathode, as an example. Note that "the insulating 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 insulating 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 insulating 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 insulating 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 insulating 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 second surface S2 side (upper surface side) refers to a portion of the matrix MR that does not include the first surface S1 but includes the second surface S2, and may be, for example, a portion of the matrix MR that is disposed farthest from the anode 22 when the matrix MR is divided into N equal parts in the thickness direction (N is a natural number equal to or greater than 2).

[0033] Thus, the red light-emitting element 5R comprises an anode 22, a cathode 25, a red light-emitting layer 24L including quantum dots QD and a matrix MR and disposed between the anode 22 and the cathode 25, and includes an insulating surface treatment agent ETS on the cathode 25 side of the matrix MR.

[0034] The cathode 25 is located above the red light-emitting layer 24L. That is, the cathode 25 is located farther from the substrate 12 than the red light-emitting layer 24L. The insulating surface treatment agent ETS is distributed on the surface of the matrix MR on the cathode 25 side.

[0035] It is desirable that this embodiment be applied to all light-emitting elements regardless of the emitted light color. The insulating surface treatment agent ETS may be contained in the green light-emitting element 5G and the blue light-emitting element 5B. However, it is not necessary for all light-emitting elements in the display device to contain the insulating surface treatment agent ETS.

[0036] 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.

[0037] 2 may be of either a top-emission type or a bottom-emission type. The red light-emitting element 5R, green light-emitting element 5G, and blue light-emitting element 5B have a forward-laid structure in which the cathode 25 is disposed above the anode 22. To form the red light-emitting element 5R, green light-emitting element 5G, and blue light-emitting element 5B as a top-emission type, the anode 22 may be formed of an electrode material that reflects visible light, and the cathode 25 may be formed of an electrode material that transmits visible light. To form the bottom-emission type, the anode 22 may be formed of an electrode material that transmits visible light, and the cathode 25 may be formed of an electrode material that reflects visible light.

[0038] 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.

[0039] 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.

[0040] 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 anode 22 side. 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).

[0041] Thus, the red light-emitting element 5R includes an electron transport layer between the cathode 25 and the surface treatment agent ETS.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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 Se ３ 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.

[0047] 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.

[0048] The matrix refers to a material that contains and holds quantum dots QDs, for example, a core structure, a core / shell structure, a core / shell / shell structure, or a shell structure with a continuously varying core / shell ratio, and can be referred to as a substrate, base material, or filler. The matrix MR may be solid at room temperature. The matrix MR may also be a material that contains and holds quantum dots QDs. Note that the matrix MR may be a material that can contain and hold quantum dots QDs. In the present disclosure, this also includes cases where quantum dots QDs are not distributed evenly within the matrix MR. Furthermore, certain regions of the matrix MR may contain no quantum dots QDs. The matrix MR may be a material that can hold quantum dots QDs, or the matrix MR may not hold quantum dots QDs. Figure 5 is a schematic diagram illustrating the matrix of the light-emitting layer. Figure 6 is another schematic diagram illustrating the matrix.

[0049] 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 straight lines (common circumstantial lines) tangent to the peripheries of the quantum dots QDA and QDB and the opposing peripheries of the quantum dots QDA and QDB in the cross section of the light-emitting layer. 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.

[0050] The matrix MR filling 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, the region K between the quantum dots QDA and QDB may contain a material, such as a ligand, different from the material of the matrix MR. Specifically, for example, the light-emitting layer 24L may contain an organic ligand that is added to improve the dispersibility of the quantum dots QD in the dispersion liquid used for coating and that coordinates to the outer surfaces of the quantum dots QD in the dispersion liquid. In this case, in the light-emitting layer 24L, from the viewpoint of improving the reliability of the 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%.

[0051] The matrix MR may fill the region of the light-emitting layer 24L other than the region where the quantum dots QDs are present. For example, the outer edge (top and bottom surfaces) of the light-emitting layer 24L may be covered with the matrix MR. Alternatively, the light-emitting layer 24L may be configured such that a portion of the matrix MR extends from the outer edge thereof, and the quantum dots QDs are positioned away from the outer edge. The outer edge of the 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 light-emitting layer 24L excluding the quantum dots QDs.

[0052] The matrix MR is formed at a position in the thickness direction of the light-emitting layer 24L, and has a thickness of 1000 nm in a plane direction perpendicular to the thickness direction. ２ In the light-emitting layer 24L, the quantum dots QD may be encapsulated in a continuous film of the matrix MR, in other words, the quantum dots QD may be encapsulated in a continuous film of the matrix MR.

[0053] For example, when 60% or more of the surface of 80% or more of the quantum dots QDs constituting the light-emitting layer 24L is in contact with the continuous film of the matrix MR, the quantum dots QDs contained in the light-emitting layer 24L can be said to be encapsulated in the matrix MR. In this way, the light-emitting layer 24L containing the quantum dots QDs encapsulated in the matrix MR improves the light-emitting properties and extends the lifetime.

[0054] The light-emitting layer 24L has a thickness of 1000 nm or more in a plane direction perpendicular to the film thickness direction at any position in the film thickness direction. ２ In this case, the light-emitting layer 24L generally contains a sufficient concentration of quantum dots QD to function as a light-emitting layer of a light-emitting element.

[0055] The matrix MR may be positioned, for example, over the entire periphery of the quantum dot QD. For example, as shown in the figure, in any cross section passing through any quantum dot QD, the matrix MR may be positioned over the entire periphery of the quantum dot QD. Here, "the matrix MR is positioned over the entire periphery of the quantum dot QD" may mean that the matrix MR is positioned over 90% or more of the periphery of the quantum dot QD. Furthermore, as shown in FIG. 3, the surface of the quantum dot QD and the matrix MR may be in contact with each other.

[0056] The band gap of the matrix MR may be wider than the band gap of the material constituting the quantum dot QD. When the quantum dot QD has 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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 intended to be limiting. The red light-emitting element 5R shown in Figures 3 and 4 is a top-emission type, so that the anode 22 is 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), thereby realizing an electrode that reflects visible light, and the cathode 25 is a thin film made of Al, thereby realizing an electrode that transmits visible light. The first charge transport layer 24H is composed of a laminate in which a hole injection layer (HIL) and a hole transport layer (HTL) are laminated in this order from the anode 22 side. The hole injection layer (HIL) is formed using nickel oxide particles to a thickness of 50 nm, and the hole transport layer (HTL) is formed using poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl))diphenylamine)] (TFB) to a thickness of 30 nm. Quantum dots QD were used, each having a core material made of InP and a shell material made of ZnS. A matrix MR was used, also made of ZnS.

[0061] The insulating surface treatment agent ETS includes an oligomer or polymer having a coordinating functional group and a crosslinkable functional group. The oligomer preferably contains 10 or more monomers. The polymer preferably contains 100 or more monomers.

[0062] The surface treatment agent ETS preferably contains a polymer having a coordinating functional group and a crosslinkable functional group.

[0063] The coordinating functional group preferably includes at least one selected from amine, carboxylic acid, thiol, phosphine, and halogen.

[0064] The crosslinkable functional group preferably includes at least one selected from the group consisting of thiol, carboxylic acid, azo, and nitrile.

[0065] The insulating surface treatment agent ETS preferably contains at least one of an epoxy-based crosslinking agent and an oxazoline-based crosslinking agent.

[0066] The insulating surface treatment agent ETS preferably has a crosslinked structure made of a thermally crosslinkable self-assembled monolayer material.

[0067] The self-assembled monolayer material is preferably a diacetylene monocarboxylic acid represented by the following formula (1).

[0068] The insulating surface treatment agent ETS preferably has a crosslinked structure represented by the following (chemical formula 2) made of a self-assembled monolayer material that is crosslinked by at least one of heat and UV and an acid.

[0069] The self-assembled monolayer material preferably contains an epoxy group represented by the following formula (3).

[0070] The insulating surface treatment agent ETS may contain a long alkyl chain self-assembled monolayer material (C=20 or more).

[0071] Thus, the red light-emitting element 5R contains an insulating surface treatment agent ETS containing an insulating polymer skeleton or a crosslinkable skeleton at the interface between the red light-emitting layer 24L and the second charge transport layer 24E.

[0072] The matrix MR preferably contains a metal sulfide, and the functional group capable of coordinating with the matrix MR preferably contains at least one selected from the group consisting of amine, carboxylic acid, thiol, phosphine, and halogen.

[0073] The matrix MR preferably contains an oxide containing a metal element or a metalloid element, and the functional group capable of coordinating to the matrix MR preferably contains at least one selected from the group consisting of phosphonic acid and disulfide.

[0074] The band gap of the matrix MR is preferably wider than the band gap of each quantum dot QD.

[0075] Here, of the red light-emitting element 5R, green light-emitting element 5G, and 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, but like the red light-emitting element 5R, the green light-emitting element 5G and blue light-emitting element 5B can also be configured to include the insulating surface treatment agent ETS.

[0076] In this embodiment, a case will be described as an example in which 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 are all configured to contain the insulating surface treatment agent ETS, but the present invention is not limited to this, and for example, 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, only the light-emitting element of a specific color may contain the insulating surface treatment agent ETS, or only the light-emitting elements of specific two colors may contain the insulating 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.

[0077] Furthermore, as shown in FIGS. 3 and 4, at least a portion of the distributed insulating 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.

[0078] 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 insulating 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.

[0079] Furthermore, in the 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 heat treatment to decompose the precursor material of the matrix MR, the precursor material of the matrix MR is generally heavier than the insulating surface treatment agent ETS, and when the precursor material of the matrix MR is decomposed by the heat treatment, changes in mass and volume occur under the influence of gravity. Therefore, a red light-emitting element can be realized in which, in the matrix MR, the insulating surface treatment agent ETS is not present in a region less than 3 nm from the first surface S1 of the red light-emitting layer 24L, but the insulating surface treatment agent ETS is present in a region 3 nm or more away from the first surface S1 of the red light-emitting layer 24L.

[0080] The insulating surface treatment agent ETS can be formed to a thickness of a single molecule to a few molecules that can impart insulating properties to the second surface S2 of the red light-emitting layer 24L. For example, it is preferable that the insulating surface treatment agent ETS be formed to a thickness of 0.01 nm or more and 10 nm or less in the direction perpendicular to the second surface S2. In the case of the above-mentioned electron transport layer (ETL), generally, when the insulating surface treatment agent ETS is formed to a thickness greater than 10 nm, it exhibits electron transport properties. However, when the insulating surface treatment agent ETS is formed to a thickness of 10 nm or less, electrons pass directly through the ETL due to the tunneling effect. Therefore, the electron transport properties of the electron transport layer (ETL) are not utilized. On the other hand, when the insulating surface treatment agent ETS modifies the matrix MR, as in this embodiment, even if the insulating surface treatment agent ETS is formed to a thickness of a single molecule to a few molecules, it is sufficient because it can reduce the barrier to electron injection into the matrix MR.

[0081] In this way, the insulating surface treatment agent ETS is preferably distributed at a position 3 nm or more away from the interface S1 on the anode 22 side of the red light-emitting layer 24L.

[0082] The insulating surface treatment agent ETS preferably has a distribution amount of 50 mol % or more at a position 3 nm or more away from the interface S1 of the red light-emitting layer 24L on the anode 22 side. 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 insulating 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 distribution amount of the insulating surface treatment agent ETS in the matrix MR in a region 3 nm or more away from the first surface S1 is X moles and the distribution amount of the insulating surface treatment agent ETS in a region 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.

[0083] In this manner, when the amount of the surface treatment agent ETS present in the matrix MR in a region of the red light-emitting layer 24L that is 3 nm or more away from the interface S1 on the anode 22 side is X moles, and the amount of the surface treatment agent ETS present in a region less than 3 nm away from the interface S1 is Y moles, it is preferable that (X / (X+Y))×100% be 50% or more.

[0084] In the matrix MR, the amount of the surface treatment agent ETS present in the region 3 nm or more away from the interface S1 of the red light-emitting layer 24L on the anode 22 side is set to Xm 3 The amount of the surface treatment agent ETS present in the region less than 3 nm from the interface S1 is Ym 3 In this case, (X / (X+Y))×100% may be 50% or more.

[0085] The thickness of the insulating surface treatment agent ETS is preferably 0.01 nm or more and 10 nm or less.

[0086] As described above, in the light-emitting element and display device of this embodiment, the insulating 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 surface of the red light-emitting layer 24L facing the cathode 25. Therefore, the insulating properties of the surface treatment agent ETS can suppress electron-rich electron injection from the cathode 25. As a result, the carrier balance of the light-emitting element can be improved.

[0087] 7A to 7C are cross-sectional views showing a manufacturing method of the display device 1 of the embodiment 1. The same components as those described above are denoted by the same reference numerals, and detailed description of these components will not be repeated.

[0088] The manufacturing method of the display device 1 includes the steps of forming a red light-emitting layer 24L (first light-emitting layer) containing quantum dots QD and a matrix MR, forming a blue light-emitting layer 24M (second light-emitting layer) containing quantum dots QD and a matrix MR, and applying a solution containing an insulating surface treatment agent ETS onto the matrix MR of the red light-emitting layer 24L (first light-emitting layer) while the blue light-emitting layer 24M (second light-emitting layer) is covered with a resist RG.

[0089] The manufacturing method of the display device 1 further includes a step of applying at least one of heat and UV (ultraviolet light) to a solution containing the insulating surface treatment agent ETS.

[0090] In this way, the banks 23 that separate the red light-emitting layer 24L and the blue light-emitting layer 24M, and the resist RG that covers the blue light-emitting layer 24M are formed. Then, with only the surface of the red light-emitting layer 24L exposed, a solution containing an insulating surface treatment agent ETS is added from above the red light-emitting layer 24L. Optionally, rinsing of the excess, crosslinking reaction treatment, etc. may be performed.

[0091] After applying a solution containing an insulating surface treatment agent ETS onto the matrix MR of the red light-emitting layer 24L using an insulating surface treatment agent, the resist RG on the blue light-emitting layer 24M is peeled off, thereby coating only the surface of any QD light-emitting layer with the insulating surface treatment agent ETS.

[0092] 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.

[0093] 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) 24M Blue 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 Insulating 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 element 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, the light-emitting layer including an insulating surface treatment agent on the cathode side of the matrix.

2. The light-emitting device according to claim 1, wherein the cathode is located above the light-emitting layer, and the surface treatment agent is distributed on the cathode-side surface of the matrix.

3. The light-emitting device according to claim 1 or 2, further comprising an electron transport layer between the cathode and the surface treatment agent.

4. The light-emitting device according to any one of claims 1 to 3, wherein the surface treatment agent contains an oligomer or a polymer having a coordinating functional group and a crosslinkable functional group.

5. The light-emitting element according to claim 4, wherein the oligomer contains 10 or more monomers, and the polymer contains 100 or more monomers.

6. The light-emitting device according to claim 4 or 5, wherein the surface treatment agent includes a polymer having a coordinating functional group and a crosslinkable functional group.

7. The light-emitting device according to claim 4 or 5, wherein the coordinating functional group includes at least one selected from the group consisting of amine, carboxylic acid, thiol, phosphine, and halogen.

8. The light-emitting element according to claim 4 or 5, wherein the crosslinkable functional group includes at least one selected from the group consisting of thiol, carboxylic acid, azo, and nitrile.

9. The light-emitting element according to claim 4 or 5, wherein the surface treatment agent includes at least one of an epoxy-based crosslinking agent and an oxazoline-based crosslinking agent.

10. The light-emitting device according to claim 4 or 5, wherein the surface treatment agent has a crosslinked structure made of a thermally crosslinkable self-assembled monolayer material.

11. The light-emitting device according to claim 10, wherein the self-assembled monolayer material is a diacetylene monocarboxylic acid.

12. The light-emitting device according to claim 4 or 5, wherein the surface treatment agent has a crosslinked structure made of a self-assembled monolayer material that is crosslinked by at least one of heat and UV light and an acid.

13. The light-emitting device according to claim 12, wherein the self-assembled monolayer material includes an epoxy group.

14. The light-emitting device according to any one of claims 1 to 13, wherein the surface treatment agent is distributed at a position 3 nm or more away from the interface of the light-emitting layer on the anode side.

15. The light-emitting element according to any one of claims 1 to 13, wherein, when the amount of the surface treatment agent present in the matrix in a region 3 nm or more away from the anode-side interface of the light-emitting layer is X moles and the amount of the surface treatment agent present in a region less than 3 nm from the anode-side interface is Y moles, (X / (X+Y)) × 100% is 50% or more.

16. In the matrix, the amount of the surface treatment agent present in a region 3 nm or more away from the interface of the light-emitting layer on the anode side is set to Xm 3 The amount of the surface treatment agent present in the region less than 3 nm from the anode-side interface is Ym 3 14. The light-emitting element according to claim 1, wherein, when (X / (X+Y))×100% is 50% or more.

17. The light-emitting device according to any one of claims 1 to 16, wherein the film thickness of the surface treatment agent is 0.01 nm or more and 10 nm or less.

18. The light-emitting element according to any one of claims 1 to 17, 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.

19. A light-emitting device according to any one of claims 1 to 17, wherein the matrix contains an oxide containing a metal element or a semi-metal element, and the functional group capable of coordinating to the matrix contains at least one selected from the group consisting of phosphonic acid and disulfide.

20. The light-emitting device according to any one of claims 1 to 19, wherein the band gap of the matrix is ​​wider than the band gap of each quantum dot.

21. A display device comprising the light-emitting element according to any one of claims 1 to 20.

22. A method for manufacturing a display device, comprising: a step of forming a first light-emitting layer containing quantum dots and a matrix; a step of forming a second light-emitting layer containing quantum dots and a matrix; and a step of applying a solution containing an insulating surface treatment agent onto the matrix of the first light-emitting layer while the second light-emitting layer is covered with a resist.

23. The method for manufacturing a display device according to claim 22, further comprising the step of applying at least one of heat and UV light to the solution containing the insulating surface treatment agent.

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