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

Abstract

Light-emitting elements (3R, 3G, 3B) are provided with an anode (31), a hole transport layer (32), a light-emitting layer (33), an electron transport layer (34), and a cathode (35) in this order. The light emitting layer contains a plurality of quantum dots (QDR, QDG, QDB) and an inorganic matrix material (4) filled between the plurality of quantum dots. The light emitting element further includes at least one of a first auxiliary layer (36) and a second auxiliary layer. The first auxiliary layer is in contact with the cathode side of the light-emitting layer, and the second auxiliary layer is in contact with the anode side of the light-emitting layer. The first auxiliary layer and the second auxiliary layer are configured from a material different from the inorganic matrix material.

Description

Technical Field

[0001] The present disclosure relates to a light-emitting element including quantum dots as a light-emitting material, a display device including a plurality of the light-emitting elements, and a method for manufacturing the light-emitting element. Background Art

[0002] Patent Document 1 discloses a light-emitting element including a semiconductor nanoparticle layer between electrodes. Prior art literature Patent Literature

[0003] Patent Document 1: Japanese Patent Application No. 2007-95685 Summary of the invention Problems to be solved by the invention

[0004] In a light-emitting element having a light-emitting layer containing quantum dots as a light-emitting material, a process that does not contribute to the light emission of the quantum dots, such as a quenching process caused by energy transfer of excitons generated in the quantum dots to other layers, may occur. Solutions to Solve Problems

[0005] The light-emitting element according to one embodiment of the present disclosure comprises: an anode and a cathode; a light-emitting layer located between the anode and the cathode and including a plurality of quantum dots and an inorganic matrix material filling between the plurality of quantum dots; a hole transport layer located between the anode and the light-emitting layer; an electron transport layer located between the light-emitting layer and the cathode; and at least one of a first auxiliary layer and a second auxiliary layer. The first auxiliary layer is in contact with the cathode side of the light-emitting layer and is composed of a material different from the inorganic matrix material, and the second auxiliary layer is in contact with the anode side of the light-emitting layer and is composed of a material different from the inorganic matrix material.

[0006] A method for manufacturing a light-emitting element according to one embodiment of the present disclosure includes: applying a solution of a first precursor containing a plurality of quantum dots and a first metal sulfide, and then modifying the first precursor into the first metal sulfide to thereby form a light-emitting layer; and applying a second precursor of a second metal sulfide different from the first metal sulfide, and then modifying the second precursor into a second metal sulfide to thereby form an auxiliary layer connected to the light-emitting layer. Effects of the Invention

[0007] The probability of occurrence of a process that contributes to light emission of the light-emitting layer is increased, thereby improving the light emission efficiency of the light-emitting element. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a schematic side cross-sectional view of the display device involved in Embodiment 1, and a schematic diagram for showing the inorganic matrix material filled between quantum dots. Figure 2 This is a schematic plan view of the display device according to Embodiment 1. Figure 3 This is an energy band diagram showing an example of the band gap of each part of the light-emitting element according to Embodiment 1. Figure 4 This is a flowchart showing an example of a method for manufacturing the display device according to Embodiment 1. Figure 5 This is a schematic side cross-sectional view of a display device according to Embodiment 2. Figure 6 This is an energy band diagram showing an example of the band gap of each part of the light-emitting element involved in Embodiment 2. Figure 7 FIG. 1 is an energy band diagram showing another example of the band gap of each part of the light emitting element according to Embodiment 2. FIG. Figure 8 This is a schematic side cross-sectional view of a display device according to Embodiment 3. DETAILED DESCRIPTION

[0009] [Implementation Method 1] <Overview of Display Device> Figure 2 1 is a schematic plan view of a display device 1 according to the present embodiment. The display device 1 includes a display portion DA and a frame portion NA formed on the periphery of the display portion DA. The display device 1 displays on the display portion DA by controlling the light emission from each of a plurality of light emitting elements described later formed on the display portion DA. A driver for driving each of the plurality of light emitting elements of the display portion DA may also be formed on the frame portion NA.

[0010] <Overview of substrate and light-emitting element> The display portion DA of the display device 1 involved in this embodiment includes a plurality of red sub-pixels, green sub-pixels, and blue sub-pixels. A red light-emitting element is formed in the red sub-pixel, a green light-emitting element is formed in the green sub-pixel, and a blue light-emitting element is formed in the blue sub-pixel. The red light-emitting element, the green light-emitting element, and the blue light-emitting element emit red light, green light, and blue light, respectively. Thus, the display device 1 controls the plurality of light-emitting elements of the display portion DA, for example, by a driver formed in the frame portion NA, so as to perform color display.

[0011] In addition, in this embodiment, blue light is, for example, light having a central wavelength of light emission in a band of 380 nm or more and 500 nm or less. In addition, green light is, for example, light having a central wavelength of light emission in a band of more than 500 nm and less than 600 nm. In addition, red light refers to light having a central wavelength of light emission in a band of more than 600 nm and less than 780 nm.

[0012] Reference Figure 1 The structure of the display portion DA of the display device 1 according to the present embodiment will be described in more detail. Figure 1 101 is a schematic side cross-sectional view of a display device 1 according to the present embodiment, and schematic views 102 and 103 are schematic views for illustrating an inorganic matrix material that fills spaces between quantum dots described later.

[0013] Figure 1 The schematic side cross-sectional view 101 of the display device 1 is shown in FIG. Figure 2 The II-line cross-sectional view shown in the figure is particularly a side cross-sectional view perpendicular to the upper surface of the display unit DA and passing through the red light emitting element 3R, the green light emitting element 3G and the blue light emitting element 3B described later. Figure 1 The schematic side cross-section 101 is a cross-section at the same position as the cross-section shown.

[0014] Figure 1 Schematic diagrams 102 and 103 are diagrams showing two examples of a group P of two blue quantum dots QDB and a region (space) K therebetween, as shown in the schematic side section 101. In particular, the schematic diagrams 102 and 103 are diagrams showing examples of groups of quantum dots QD1 and QD2, namely, group P1 and group P2, respectively.

[0015] The display device 1 includes a substrate 2 such as a glass substrate or a film substrate and a light-emitting element 3 on the substrate 2 in the display portion DA. The light-emitting element 3 includes an anode 31, a hole transport layer 32, a light-emitting layer 33, an electron transport layer 34, and a cathode 35 in order from the substrate 2 side toward the upper surface side of the display portion DA. In addition, the light-emitting element 3 involved in this embodiment includes a first auxiliary layer 36 between the light-emitting layer 33 and the electron transport layer 34.

[0016] When the substrate 2 is viewed from above, the light-emitting element 3 forms a red light-emitting element 3R by means of the anode 31, the hole transport layer 32, the red light-emitting layer 33R, the electron transport layer 34, the cathode 35, and the first auxiliary layer 36 overlapping with the red sub-pixel. In addition, when the substrate 2 is viewed from above, the light-emitting element 3 forms a green light-emitting element 3G by means of the anode 31, the hole transport layer 32, the green light-emitting layer 33G, the electron transport layer 34, the cathode 35, and the first auxiliary layer 36 overlapping with the green sub-pixel. In addition, when the substrate 2 is viewed from above, the light-emitting element 3 forms a blue light-emitting element 3B by means of the anode 31, the hole transport layer 32, the blue light-emitting layer 33B, the electron transport layer 34, the cathode 35, and the first auxiliary layer 36 overlapping with the blue sub-pixel.

[0017] In addition, the display device 1 includes a bank BK. The bank BK separates a plurality of light-emitting elements included in the display device 1. The bank BK is formed on the substrate 2, and is formed between a plurality of anodes 31 when the substrate 2 is viewed from above. In the present embodiment, the hole transport layer 32, the light-emitting layer 33, the electron transport layer 34, and the first auxiliary layer 36 are divided into each sub-pixel by the bank BK. In addition, the cathode 35 is formed in common to a plurality of sub-pixels.

[0018] The bank BK may be formed at a position overlapping with the end of each anode 31 when the substrate 2 is viewed from above. In this case, the bank BK can reduce the influence of electric field concentration at the end of the anode 31 in each light-emitting element on the injection of holes from the anode 31 into the light-emitting layer 33.

[0019] The anode 31 and the cathode 35 are electrodes containing a conductive material and are electrically connected to the hole transport layer 32 and the electron transport layer 34. By applying a voltage to at least one of the anode 31 and the cathode 35, holes and electrons are injected from the anode 31 and the cathode 35 into the hole transport layer 32 and the electron transport layer 34, respectively.

[0020] In this embodiment, the anode 31 may be electrically connected to a pixel circuit (not shown) formed for each sub-pixel on the substrate 2. The display device 1 may control the voltage applied to each anode 31 by driving the pixel circuit individually. For example, the display device 1 may control the light emission from each light-emitting element by driving the voltage applied to each anode 31 while applying a predetermined voltage to the cathode 35.

[0021] At least one of the anode 31 and the cathode 35 is a transparent electrode that transmits visible light. As the transparent electrode, for example, ITO, InZnO, SnO2, or FTO can be used. In addition, either the anode 31 or the cathode 35 can also be a reflective electrode. The reflective electrode can include a metal material with high reflectivity of visible light, and the metal material can be, for example, Al, Ag, Cu, or Au alone or an alloy thereof.

[0022] The hole transport layer 32 is a layer that transports holes injected from the anode 31 to the light-emitting layer 33. In a light-emitting element including quantum dots, etc., the material of the hole transport layer 32 can use an organic or inorganic material with hole transport properties that has been used in the past. The electron transport layer 34 is a layer that transports electrons injected from the cathode 35 to the light-emitting layer 33. In a light-emitting element including quantum dots, etc., the material of the electron transport layer 34 can use an organic or inorganic material with electron transport properties that has been used in the past.

[0023] <Quantum dot> The light emitting layer 33 includes a red light emitting layer 33R, a green light emitting layer 33G, and a blue light emitting layer 33B. When the substrate 2 is viewed from above, the red light emitting layer 33R, the green light emitting layer 33G, and the blue light emitting layer 33B are formed at positions overlapping with the red sub-pixels, the green sub-pixels, and the blue sub-pixels, respectively.

[0024] The red light-emitting layer 33R, the green light-emitting layer 33G, and the blue light-emitting layer 33B each include a plurality of red quantum dots QDR, green quantum dots QDG, and blue quantum dots QDB as quantum dots. By driving each light-emitting element, holes are injected into each quantum dot from the anode 31 via the hole transport layer 32, and electrons are injected into each quantum dot from the cathode 35 via the electron transport layer 34.

[0025] The red quantum dot QDR, the green quantum dot QDG, and the blue quantum dot QDB may also have a so-called core / shell structure, for example, having a core and at least a portion of a shell located around the core. In this case, the core of each quantum dot is injected with holes from the anode 31 and electrons from the cathode 35, and excitons generated by the recombination of the holes and electrons emit light. The red quantum dot QDR, the green quantum dot QDG, and the blue quantum dot QDB emit red light, green light, and blue light from each core.

[0026] It should be noted that, in the present invention, the "quantum dot" contained in the light-emitting layer 33 refers to a point with a maximum width of less than 100 nm. The shape of the quantum dot is not particularly limited as long as it satisfies the range of the above-mentioned maximum width, and is not limited to a spherical three-dimensional shape (circular cross-sectional shape). The shape of the quantum dot can be, for example, a polygonal cross-sectional shape, a rod-shaped three-dimensional shape, a branch-shaped three-dimensional shape, a three-dimensional shape with concave and convex on the surface, or a combination of these shapes.

[0027] Quantum dots are typically preferably made of semiconductors. Semiconductors may have a certain band gap. Semiconductors may be materials that can emit light, and may contain at least the following materials. Semiconductors may emit red, green, and blue light, respectively. Semiconductors may, for example, contain at least one selected from the group consisting of II-VI compounds, III-V compounds, chalcogen compounds, and perovskite compounds. It should be noted that II-VI compounds refer to compounds containing II-group elements and VI-group elements, and III-V compounds refer to compounds containing III-group elements and V-group elements. In addition, II-group elements include Group 2 elements and Group 12 elements, Group III elements include Group 3 elements and Group 13 elements, Group V elements include Group 5 elements and Group 15 elements, and Group VI elements may include Group 6 elements and Group 16 elements.

[0028] The II-VI group compound, for example, contains at least one selected from the group consisting of MgS, MgSe, MgTe, CaS, CaSe, CaTe, SrS, SrSe, SrTe, BaS, BaSe, BaTe, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, HgS, HgSe and HgTe.

[0029] The III-V group compound includes, for example, at least one selected from the group consisting of GaAs, GaP, InN, InAs, InP, and InSb.

[0030] Chalcogenides are compounds containing elements of Group VIA (16), such as CdS or CdSe. Chalcogenides may also include these mixed crystals.

[0031] The perovskite compound has a composition represented by the general formula CsPbX3, for example. The constituent element X includes at least one selected from the group consisting of Cl, Br, and I, for example.

[0032] Here, the numbering notation of element groups using Roman numerals is based on the old IUPAC (International Union of Pure and Applied Chemistry) method or the old CAS (Chemical Abstracts Service) method, and the numbering notation of element groups using Arabic numerals is based on the current IUPAC method.

[0033] <Inorganic matrix materials> In addition, the red light-emitting layer 33R, the green light-emitting layer 33G, and the blue light-emitting layer 33B each include an inorganic matrix material 4 filling between a plurality of quantum dots. The inorganic matrix material 4, for example, includes an inorganic matrix material 4R, an inorganic matrix material 4G, and an inorganic matrix material 4B formed at a position overlapping with the red sub-pixel, the green sub-pixel, and the blue sub-pixel in a top view of the substrate 2. The inorganic matrix material 4R, the inorganic matrix material 4G, and the inorganic matrix material 4B may contain different materials from each other, or may contain the same material as each other.

[0034] In addition, the inorganic matrix material 4 filling between the plurality of quantum dots refers to, for example Figure 1 As shown in the schematic diagram 102 of the group P1 shown in FIG. 1 , the region K between the quantum dots QD1 and QD2 is filled. The region K is an area surrounded by two straight lines (common external tangent lines) connected to the peripheries of the quantum dots QD1 and QD2 and the peripheries opposite to the quantum dots QD1 and QD2 in the cross section of the light-emitting layer 33. Therefore, as shown in FIG. Figure 1As shown in the schematic diagram 103 of the group P2, even if the quantum dot QD1 and the quantum dot QD2 are close to each other, the region K may exist, and the inorganic matrix material 4 fills the region K.

[0035] In addition, the so-called inorganic matrix material 4 filling between multiple quantum dots does not mean that the region K between the quantum dot QD1 and the quantum dot QD2 is entirely composed of the inorganic matrix material 4. For example, the region K between the quantum dot QD1 and the quantum dot QD2 may also contain materials such as organic materials different from the inorganic matrix material 4. Specifically, for example, the light-emitting layer 33 may contain an organic ligand, which is added to improve the dispersibility of the quantum dots in the solution used in the coating formation and is coordinated with the peripheral surface of the quantum dots in the solution. In this case, in the light-emitting layer 33, from the viewpoint of improving the reliability of the light-emitting layer 33, for example, the weight ratio of the organic ligand to the total weight of the region K may be less than 5%.

[0036] The inorganic matrix material 4 may also fill the region other than the plurality of quantum dots in the light-emitting layer 33. For example, the outer edge (upper surface and lower surface) of the light-emitting layer 33 may also be covered by the inorganic matrix material 4. In addition, it may also be configured such that part of the inorganic matrix material 4 is separated from the outer edge of the light-emitting layer 33, and the quantum dots are located at a position separated from the outer edge. The outer edge of the light-emitting layer 33 may not only be formed by the inorganic matrix material 4, but part of the quantum dots may be exposed from the inorganic matrix material 4. The inorganic matrix material 4 may also represent a portion of the light-emitting layer 33 where the plurality of quantum dots are removed.

[0037] The inorganic matrix material 4 may contain a plurality of quantum dots. The inorganic matrix material 4 may also be formed to fill the space formed between the plurality of quantum dots. The plurality of quantum dots may be embedded in the inorganic matrix material 4 at intervals. The inorganic matrix material 4 may also partially or completely fill the space between the plurality of quantum dots.

[0038] The inorganic matrix material 4 may also include a continuous film having a thickness of 1000 nm along a plane direction perpendicular to the film thickness direction. 2 The continuous film may be a film that is not separated on one plane by materials other than the material constituting the continuous film. The continuous film may also be an integrated film that is continuously connected by chemical bonds of the inorganic matrix material 4.

[0039] The inorganic matrix material 4 may also be the same material as the shell contained in each of the plurality of quantum dots. In this case, the average distance between adjacent cores in the light-emitting layer 33 (inter-core distance) may also be more than 3 nm. Alternatively, the average distance between the adjacent cores may also be more than 0.5 times the average core diameter. The inter-core distance is the distance obtained by averaging the distance between 20 adjacent cores in a space containing 20 cores. The inter-core distance may also be kept wider than the distance when the shells are in contact with each other. The average core diameter is the diameter obtained by averaging the core diameters of 20 cores under cross-sectional observation in a space containing 20 cores. The core diameter may be set to the diameter of a circle having the same area as the core area in cross-sectional observation.

[0040] The concentration of the inorganic matrix material 4 in the light-emitting layer 33 is, for example, the area ratio occupied by the inorganic matrix material 4 in the cross section of the light-emitting layer 33. In cross-sectional observation, the concentration may be greater than 10% and less than 90%, or greater than 30% and less than 70%. The concentration may be measured, for example, based on the area ratio of an image obtained by cross-sectional observation. When the quantum dot is a core-shell structure, the concentration of the shell may be greater than 1% and less than 50%. The ratio of the core of the quantum dot to the shell and the inorganic matrix material 4 may be adjusted to be less than 100% after the total. In the case where the shell and the inorganic matrix material 4 cannot be distinguished, the shell may also be regarded as a part of the inorganic matrix material 4.

[0041] The light emitting layer 33 may also be composed of a plurality of quantum dots and the inorganic matrix material 4. When analyzing the light emitting layer 33, the intensity of carbon detected by the chain structure may be lower than the noise.

[0042] From the viewpoint of reducing the outflow of holes and electrons injected into the light-emitting layer 33 to the outside of the light-emitting layer 33 or the wave function seepage in the quantum confinement effect, the constituent material of the inorganic matrix material 4 may have a wider band gap than the constituent material of the core material including the quantum dots. In particular, from the above viewpoint, the constituent material of the inorganic matrix material 4 may have a lower electron affinity and a higher ionization potential than the constituent material of the quantum dots.

[0043] As the material constituting the inorganic matrix material 4, a semiconductor or an insulator can be used. For example, the inorganic matrix material 4 can also be composed of an inorganic semiconductor material. Examples of the constituent materials of the inorganic matrix material 4 include metal sulfides and / or metal oxides. Metal sulfides can be, for example, zinc sulfide (ZnS), zinc magnesium sulfide (ZnMgS, ZnMgS2), gallium sulfide (GaS, Ga2S3), zinc tellurium sulfide (ZnTeS), magnesium sulfide (MgS), zinc gallium sulfide (ZnGa2S4), and magnesium sulfide (MgGa2S4). Metal oxides can also be zinc oxide (ZnO), titanium oxide (TiO2), tin oxide (SnO2), tungsten oxide (WO3), and zirconium oxide (ZrO2). In addition, the chemical formula recorded in brackets after the compound name is a representative example. In addition, the composition ratio recorded in the chemical formula is ideal as long as the composition of the actual compound is stoichiometric as the chemical formula, but it may not be stoichiometric.

[0044] The structure of the inorganic matrix material 4 is observed with a width of about 100 nm in the cross-sectional observation of the light-emitting layer 33. It is sufficient to know that it is the above structure, and it is not necessary to observe the above structure in the entire light-emitting layer 33. The inorganic matrix material 4 may contain a substance different from the main material of the inorganic substance such as the inorganic semiconductor, for example, as an additive.

[0045] <First auxiliary layer> The first auxiliary layer 36 is located between the light-emitting layer 33 and the cathode 35 in each light-emitting element, and is particularly connected to the cathode 35 side of the light-emitting layer 33. The first auxiliary layer 36 may be the same material as the inorganic matrix material, but is preferably composed of a different material. The first auxiliary layer 36, for example, includes a first auxiliary layer 36R, a first auxiliary layer 36G, and a first auxiliary layer 36B, which are formed at a position overlapping with the red sub-pixel, the green sub-pixel, and the blue sub-pixel when viewed from above the substrate 2. The first auxiliary layer 36R, the first auxiliary layer 36G, and the first auxiliary layer 36B may contain different materials or the same materials.

[0046] In each light-emitting element according to the present embodiment, the distance between the light-emitting layer 33 and the electron transport layer 34 is only as great as the thickness of the first auxiliary layer 36, in other words, the distance between the quantum dots and the electron transport layer 34 is separated. Thus, in each light-emitting element, the probability of occurrence of a process that does not contribute to the light emission of the quantum dots of the light-emitting layer 33, such as a quenching process in which the energy of excitons generated by the quantum dots of the light-emitting layer 33 moves to the material of the electron transport layer 34, is reduced.

[0047] Generally, the probability of energy transfer between two semiconductor materials is inversely proportional to the square of the distance between the two semiconductor materials. Therefore, the distance between the light-emitting layer 33 and the electron transport layer 34 is separated by only the thickness of the first auxiliary layer 36, so that the light-emitting element of this embodiment more effectively reduces the probability of occurrence of a process that does not contribute to the luminescence of the quantum dots of the light-emitting layer 33.

[0048] Therefore, each light-emitting element of the present embodiment has the first auxiliary layer 36, which increases the probability of occurrence of the process that contributes to the light emission of the light-emitting layer 33, thereby improving the light emission efficiency of the light-emitting layer 33. In particular, when the inorganic matrix material 4 is filled between the plurality of quantum dots as in the light-emitting layer 33 of the present embodiment, the excitons generated by the quantum dots become easy to move to other layers via the inorganic matrix material 4. Therefore, each light-emitting element of the present embodiment can more effectively reduce the probability of occurrence of the process that does not contribute to the light emission of the light-emitting layer 33 through the first auxiliary layer 36.

[0049] <Band gap of each part of the light emitting element> The first auxiliary layer 36 will be described in detail using an example of the band gap of each portion of the light emitting element of this embodiment. Figure 3 1 is an energy band diagram showing an example of the band gap of each part of the light-emitting element of this embodiment, especially the blue light-emitting element 3B. In addition, the energy band diagrams in this specification are all energy band diagrams having a vacuum level on the upper side of the paper. In addition, the left and right directions of the energy band diagrams in this specification represent the direction of the thickness in the display direction of the display device 1, and the left side of the paper is shown as the anode 31 side and the right side is shown as the cathode 35 side.

[0050] In the energy band diagrams in this specification, the Fermi levels of the anode 31 and the cathode 35 are shown. In addition, the band gaps of the hole transport layer 32, the blue light-emitting layer 33B, the electron transport layer 34, and the first auxiliary layer 36B are shown. In particular, the band gaps of the blue quantum dots QDB and the inorganic matrix material 4B are shown for the blue light-emitting layer 33B. In this case, Figure 3 As shown, the energy band diagram of the blue light-emitting layer 33B is simplified to a diagram in which the band gap of the inorganic matrix material 4B is located at both ends of the band gap of the blue quantum dots QDB.

[0051] like Figure 3As shown, the electron affinity of the first auxiliary layer 36B is less than the electron affinity of the inorganic matrix material 4B. In general, the electron injection barrier from the first layer to the second layer is equivalent to the electron affinity of the first layer minus the electron affinity of the second layer. Therefore, compared with the electron injection barrier from the electron transport layer 34 to the inorganic matrix material 4B, the electron injection barrier from the electron transport layer 34 to the first auxiliary layer 36B becomes larger. Therefore, the blue light-emitting element 3B of this embodiment has a lower injection efficiency of electrons from the electron transport layer 34 to the inorganic matrix material 4B than the case where the first auxiliary layer 36B is not provided or the case where the above-mentioned injection barrier is not provided.

[0052] Generally, in an electric field injection type light-emitting element including quantum dots in a light-emitting material, due to the height of the mobility of electrons relative to holes, sometimes there is an excess of electrons with a concentration higher than the concentration of holes injected into the quantum dot layer. Due to the excess of electrons in the quantum dot layer, an increase in deactivation processes, including the generation of Auger electrons by the transfer of energy between electrons, etc., sometimes occurs in the quantum dot layer. As a result, the excess of electrons may sometimes cause a decrease in the luminous efficiency of the light-emitting element or inactivation of the quantum dots of the light-emitting element.

[0053] The blue light-emitting element 3B of this embodiment has a first auxiliary layer 36B, thereby reducing the injection efficiency of electrons from the cathode 35 to the blue light-emitting layer 33B, and reducing the excess of electrons in the blue light-emitting layer 33B. Therefore, the blue light-emitting element 3B of this embodiment improves the carrier balance in the blue light-emitting layer 33B, and reduces the reduction in the luminous efficiency of the blue light-emitting layer 33B or the deactivation of the blue quantum dots QDB.

[0054] In addition, if Figure 3 As shown, the ionization potential of the first auxiliary layer 36B is greater than that of the inorganic matrix material 4B, while the ionization potential is smaller than that of the electron transport layer 34. Generally speaking, the injection barrier of holes from the first layer to the second layer is equivalent to the value obtained by subtracting the ionization potential of the first layer from the ionization potential of the second layer. Therefore, there are barriers in the injection of holes from the inorganic matrix material 4B to the first auxiliary layer 36B and the injection of holes from the first auxiliary layer 36B to the electron transport layer 34.

[0055] In summary, the blue light-emitting element 3B of this embodiment can reduce the outflow of holes injected into the blue light-emitting layer 33B from the inorganic matrix material 4B to the electron transport layer 34, compared with the case without the first auxiliary layer 36B. Therefore, the blue light-emitting element 3B improves the carrier balance in the blue light-emitting layer 33B by increasing the concentration of holes in the blue light-emitting layer 33B, thereby reducing the decrease in the luminous efficiency of the blue light-emitting layer 33B or the deactivation of the blue quantum dots QDB.

[0056] In addition, as described above, the first auxiliary layer 36B reduces the deactivation process such as the generation of Auger electrons in the blue light-emitting layer 33B and the electron transport layer 34. Thus, the first auxiliary layer 36B can also reduce the occurrence of the process in which the Auger electrons attack the blue quantum dots QDB or the electron transport material of the electron transport layer 34, which can generate defects in the blue light-emitting layer 33B or the electron transport layer 34. Therefore, the first auxiliary layer 36B protects the blue light-emitting layer 33B or the electron transport layer 34, and improves the reliability of the blue light-emitting layer 33B or the electron transport layer 34.

[0057] In addition, Figure 3 The relationship between the band gaps of the various parts of the blue light emitting element 3B is described in FIG. 1 , but the band gaps of the various parts of the red light emitting element 3R and the green light emitting element 3G may also have the same Figure 3 Specifically, in the red light-emitting element 3R, the electron affinity of the first auxiliary layer 36R may be smaller than that of the inorganic matrix material 4R, and the ionization potential is large, while the ionization potential may be smaller than that of the electron transport layer 34. In addition, in the green light-emitting element 3G, the electron affinity of the first auxiliary layer 36G is also smaller than that of the inorganic matrix material 4G, and the ionization potential is large, while the ionization potential may be smaller than that of the electron transport layer 34.

[0058] <Relationship between the inorganic matrix material and the material of the first auxiliary layer> The first auxiliary layer 36 may also contain the non-metallic element contained in the inorganic matrix material 4 and the first metal element that is the same as the metal element contained in the inorganic matrix material 4. In this case, the first auxiliary layer 36 may contain the same element as the inorganic matrix material 4, but only the chemical composition is different. In this case, the inorganic matrix material 4 and the first auxiliary layer 36 can be formed from at least a portion of the common raw materials.

[0059] In addition, the first auxiliary layer 36 may also contain the non-metallic element contained in the inorganic matrix material 4 and the second metal element whose period is earlier than the first metal element. In this case, the first auxiliary layer 36 can easily increase the band gap compared with the inorganic matrix material 4, and can easily achieve a band gap of Figure 3 The first auxiliary layer 36 and the inorganic matrix material 4 are in the relationship shown.

[0060] Specifically, for example, in the case where the inorganic matrix material 4 includes ZnS, the first auxiliary layer 36 may include Mg X Zn 1-X S (0<X<1) or MgS. For example, in the inorganic matrix material 4 including Mg X Zn 1-X In the case of S (0<X<1), the first auxiliary layer 36 may include Mg Y Zn 1-YS (0 < X < Y < 1) or MgS. For example, when the inorganic matrix material 4 includes ZnO 1-X S X When (0 < X < 1), the first auxiliary layer 36 may include ZnO 1-Y S Y (0 < X < Y < 1), ZnS, Mg Z Zn 1-Z S (0 < Z < 1) or MgS. When the inorganic matrix material 4 and the first auxiliary layer 36 contain the above materials, the inorganic matrix material 4 and the first auxiliary layer 36 can be realized with a simpler structure Figure 3 The relationship of the band gaps shown

[0061] The first auxiliary layer 36 may also include a mixed crystal containing the above non-metal element, first metal element, and second metal element. In this case, the first auxiliary layer 36 protects the light-emitting layer 33 or the electron transport layer 34 more strongly

[0062] In addition, from the viewpoint of sufficiently ensuring the function of protecting the light-emitting layer 33 and the electron transport layer 34 and sufficiently reducing the holes passing through the first auxiliary layer 36, the film thickness of the first auxiliary layer 36 can be 5 nm or more, or can be 10 nm or more. In addition, from the viewpoint of reducing the resistance of the entire light-emitting element, the film thickness of the first auxiliary layer 36 can be 20 nm or less. For example, it can also be thinner than the film thickness of the electron transport layer 34

[0063] By filling between the quantum dots with the inorganic matrix material 4, the inorganic matrix material 4 protects the surface of the quantum dots more strongly. As a result, the display device 1 can improve the reliability of the light-emitting elements included therein and suppress the reduction in luminance with respect to the driving time of the light-emitting elements

[0064] <Supplement of Light-Emitting Element> The structure of the light-emitting element 3 is not limited to Figure 1 the structure shown in the schematic side cross-sectional view 101. For example, the light-emitting element 3 may further include a cover layer on the cathode 35 for improving the efficiency of extracting light from each light-emitting element. In addition, the light-emitting element 3 may include a hole injection layer between each anode 31 and the hole transport layer 32

[0065] In the present embodiment, each light-emitting element can extract the light from the light-emitting layer 33 from the side of the electrode having light-transmittance among the anode 31 and the cathode 35. In this case, in order to improve the extraction efficiency of the light from the light-emitting layer 33, the electrode on the opposite side of the electrode having light-transmittance among the anode 31 and the cathode 35 may also have light reflectivity

[0066] In particular, in this embodiment, when each light-emitting element extracts light from the light-emitting layer 33 from electrodes formed on the substrate 2 side among the anode 31 and the cathode 35, in this embodiment, from the anode 31 side, the substrate 2 may also have light transparency.

[0067] The light emitting element 3 involved in this embodiment includes the anode 31 on the substrate 2 side of the anode 31 and the cathode 35, but is not limited thereto. For example, the light emitting element 3 may include the cathode 35, the electron transport layer 34, the first auxiliary layer 36, the light emitting layer 33, the hole transport layer 32, and the anode 31 in sequence on the substrate 2. In this case, the cathode 35 may be formed in an island shape for each sub-pixel, and each cathode 35 may be electrically connected to the pixel circuit of the substrate 2. In addition, the anode 31 may be formed in common in a plurality of sub-pixels.

[0068] <Method for manufacturing a display device: before forming a hole transport layer> Reference Figure 4 , a method for manufacturing the display device 1 according to this embodiment is described in detail. Figure 4 This is a flowchart for explaining the method for manufacturing the display device 1 according to the present embodiment.

[0069] Reference Figure 4 In the manufacturing method of the display device of the present embodiment, first, a substrate 2 is prepared (step S1). In the present embodiment, for example, a thin film transistor may be formed for each sub-pixel on a glass substrate or a film substrate, thereby manufacturing a substrate 2 having a pixel circuit for each sub-pixel. In addition, a frame portion NA may be formed by forming a driver or the like on the peripheral portion of the substrate 2.

[0070] Next, the anode 31 is formed on the substrate 2 (step S2). The anode 31 can be formed by, for example, forming a thin film of a metal material or the like on the substrate 2 by sputtering or the like, and then patterning the film by dry etching or the like.

[0071] Next, the bank BK is formed on the substrate 2 and the anode 31 (step S3). The bank BK can be formed by, for example, applying a photosensitive resin material to form a film on the substrate 2 and the anode 31 and then patterning the film by photolithography or the like.

[0072] Next, the hole transport layer 32 is formed on the anode 31 and the bank BK (step S4). The hole transport layer 32 can be formed by, for example, applying a material having a hole transport property to form a film on the anode 31 and the bank BK.

[0073] <Method for manufacturing display device: formation of light-emitting layer> After step S4 is completed, the process of forming the light-emitting layer 33 is performed. In the process of forming the light-emitting layer 33, for example, first, a solution containing quantum dots and a first precursor as a precursor of the inorganic matrix material 4 is applied to the hole transport layer 32 formed in the sub-pixel corresponding to any color (step S5). In this embodiment, the first precursor is a precursor of the first metal sulfide contained in the inorganic matrix material 4. For example, a solution in which blue quantum dots QDB and the first precursor as a precursor of the inorganic matrix material 4 are mixed is applied to the hole transport layer 32 formed in the blue sub-pixel.

[0074] The solution can be synthesized by, for example, dispersing the quantum dots and the first precursor in a solvent such as DMF (N,N-dimethylformamide). The synthesis of quantum dots can be synthesized, for example, by a conventionally known method for synthesizing quantum dots of a core / shell structure. In addition, in order to improve the dispersibility of the quantum dots in the solution, the solution can also contain an organic ligand coordinated to the outermost surface of the quantum dots.

[0075] The solution can be applied by, for example, using an inkjet nozzle to eject the solution onto the hole transport layer 32 overlapping with a sub-pixel of any luminescent color and between the banks BK when the display device 1 is viewed from above. Thus, a layer including quantum dots of the corresponding luminescent color and the first precursor is formed on the hole transport layer 32 corresponding to the sub-pixel of a certain luminescent color.

[0076] Next, the first precursor is heated by heating the applied solution (step S6). In step S6, for example, each layer on the substrate 2 containing the applied solution is heated in an atmosphere of 150°C for 30 minutes. As a result, the first precursor in the solution is modified into a first metal sulfide. Here, the first precursor is successively formed around the quantum dots in the solution by heating in step S6. Therefore, by step S6, the inorganic matrix material 4 is formed to fill between a plurality of quantum dots. Through the above, a light-emitting layer comprising a plurality of quantum dots and an inorganic matrix material 4 filling between the quantum dots is formed. It should be noted that, in the case where the solution includes an organic ligand, the organic ligand can be modified into a sulfide by heating in step S6, or the organic ligand can be volatilized from the solution, so that the weight ratio of the organic ligand in the light-emitting layer is less than 5%.

[0077] <Method for Manufacturing Display Device: Formation of First Auxiliary Layer> After the step of forming the light-emitting layer 33, the step of forming the first auxiliary layer 36 is performed. In the step of forming the first auxiliary layer 36, for example, first, a solution containing a second precursor as a precursor of the first auxiliary layer 36 is applied to a position on the light-emitting layer 33 formed in the immediately preceding step S6 (step S7). In the present embodiment, the second precursor is a precursor of a second metal sulfide different from the first metal sulfide contained in the inorganic matrix material 4 and contained in the first auxiliary layer 36. Application of the solution containing the second precursor can be performed by a conventionally known coating method.

[0078] Next, the second precursor is heated by heating the applied solution (step S8). Step S8 can also be performed by, for example, the same method as the heating of the solution in step S6. Thus, the second precursor in the solution is modified into a second metal sulfide, forming a first auxiliary layer 36 in contact with the light-emitting layer 33.

[0079] <Method of Manufacturing Display Device: Patterning of Quantum Dot Layer and First Auxiliary Layer> In addition, steps S5 to S8 are repeatedly performed for each sub-pixel while changing the luminescent color and the discharge position of the quantum dots in the solution discharged in step S5, and the precursor and the discharge position of the first auxiliary layer 36 discharged in step S7. Thus, the light-emitting layer 33 including the red light-emitting layer 33R, the green light-emitting layer 33G, and the blue light-emitting layer 33B, and the first auxiliary layer 36 including the first auxiliary layer 36R, the first auxiliary layer 36G, and the first auxiliary layer 36B are formed.

[0080] In addition, when step S8 is repeatedly executed from step S5, the light-emitting layer of any sub-pixel that has been formed is heated in step S6 and step S8. However, since the quantum dots in the light-emitting layer are filled with the inorganic matrix material 4, the quantum dots are protected from the influence of heat by the inorganic matrix material 4. Therefore, according to the manufacturing method of the display device 1 described above, the degradation of the quantum dots in the light-emitting layer can be reduced.

[0081] In this embodiment, a method of forming the light emitting layer 33 for each sub-pixel by applying a solution to each sub-pixel by a coating method such as an inkjet method is described, but the method of forming the light emitting layer 33 is not limited thereto. The light emitting layer 33 can be manufactured by patterning using, for example, a lift-off method.

[0082] For example, after forming a photosensitive resin layer having an opening only at a position corresponding to a certain sub-pixel by photolithography or the like, the solution is applied to a plurality of sub-pixels. Afterwards, the photosensitive resin layer is removed by using an appropriate developer, so that the solution can remain only at a position corresponding to a certain sub-pixel. Then, by heating the solution, a light-emitting layer can be formed only at a certain sub-pixel.

[0083] In this case, the light-emitting layer of any sub-pixel that has been formed is exposed to the developer when the photosensitive resin layer is peeled off. Therefore, in the above method, the solution can be heated each time the solution is patterned to form light-emitting layers one by one. In this case, since the quantum dots in the light-emitting layer are filled with the inorganic matrix material 4, the quantum dots in the light-emitting layer that has been formed are protected by the inorganic matrix material 4 and are not affected by the developer. Therefore, the above method can also reduce the degradation of the quantum dots in the light-emitting layer.

[0084] <Method for Manufacturing Display Device: After Formation of Electron Transport Layer> After the first auxiliary layer 36 is formed, the electron transport layer 34 is then formed on the first auxiliary layer 36 (step S9). The electron transport layer 34 can be formed by, for example, applying a material having an electron transport property on the first auxiliary layer 36 and forming a film.

[0085] Next, the cathode 35 is formed on the electron transport layer 34 and BK (step S10). The cathode 35 can be formed by forming a thin film of a metal material on the electron transport layer 34 and BK by sputtering or the like. Figure 1 The light emitting element 3 illustrated in the schematic side cross-sectional view 101 is formed on the substrate 2, and the manufacturing process of the display device 1 is completed.

[0086] According to the manufacturing method of the display device 1 of this embodiment, the light-emitting layer 33 and the first auxiliary layer 36 can be formed by coating a solution and modifying a precursor in the solution. Therefore, according to the manufacturing method of the display device 1 of this embodiment, the light-emitting layer 33 and the first auxiliary layer 36 can be formed more simply.

[0087] Furthermore, according to the method for manufacturing the display device 1 of the present embodiment, the electron transport layer 34 is formed on the first auxiliary layer 36. Therefore, according to the method for manufacturing the display device 1 of the present embodiment, the contact between the light-emitting layer 33 and the electron transport layer 34 can be reduced, and the degradation of the quantum dots in the light-emitting layer 33 in the step of forming the electron transport layer 34 can be reduced.

[0088] [Implementation method 2] <Second auxiliary layer> In the following, other embodiments of the present disclosure will be described. In addition, for the sake of convenience, components having the same functions as those described in the above embodiments are denoted by the same reference numerals, and their description will not be repeated.

[0089] Figure 52 is a schematic side cross-sectional view of the display device 1 of this embodiment. The display device 1 according to this embodiment has the same configuration as the display device 1 of the previous embodiment, except that the light emitting element 3 includes a second auxiliary layer 37 instead of the first auxiliary layer 36 .

[0090] The second auxiliary layer 37 is located between the anode 31 and the light-emitting layer 33 in each light-emitting element, and in particular, is in contact with the anode 31 side of the light-emitting layer 33. The second auxiliary layer 37 may be the same material as the inorganic matrix material, but is preferably composed of a different material. The second auxiliary layer 37, for example, includes a second auxiliary layer 37R, a second auxiliary layer 37G, and a second auxiliary layer 37B, which are formed at positions overlapping with the red sub-pixel, the green sub-pixel, and the blue sub-pixel when viewed from above the substrate 2. The second auxiliary layer 37R, the second auxiliary layer 37G, and the second auxiliary layer 37B may contain different materials from each other, or may contain the same material as each other.

[0091] In each light-emitting element involved in this embodiment, the distance between the light-emitting layer 33 and the hole transport layer 32 is only separated by the thickness of the second auxiliary layer 37, in other words, the distance between the quantum dot and the hole transport layer 32 is separated. Therefore, for the same reason as described in the previous embodiment, the probability of occurrence of a process that does not contribute to the light emission of the quantum dot of the light-emitting layer 33 is reduced. Therefore, each light-emitting element of this embodiment increases the probability of occurrence of a process that contributes to the light emission of the light-emitting layer 33 by including the second auxiliary layer 37, thereby improving the light emission efficiency of the light-emitting layer 33.

[0092] The second auxiliary layer 37 will be described in detail by taking an example of the band gap of each part of the light emitting element of this embodiment. Figure 6 2 is an energy band diagram for showing an example of the band gap of each part of the light-emitting element of this embodiment, particularly the blue light-emitting element 3B.

[0093] like Figure 6 As shown, the electron affinity of the second auxiliary layer 37B is smaller than that of the inorganic matrix material 4B, and the electron affinity is smaller than that of the hole transport layer 32. Therefore, there is a barrier in the electron injection from the inorganic matrix material 4B to the second auxiliary layer 37B. In addition, compared with the injection barrier of electrons from the inorganic matrix material 4B to the hole transport layer 32, the injection barrier of electrons from the inorganic matrix material 4B to the second auxiliary layer 37B becomes larger. Therefore, the blue light-emitting element 3B of this embodiment reduces the electrons injected into the blue light-emitting layer 33B and flows out to the hole transport layer 32 side to become an ineffective current compared with the case where the second auxiliary layer 37B is not provided or the case where the above-mentioned injection barrier is not provided.

[0094] In addition, the ionization potential of the second auxiliary layer 37B is equal to that of the inorganic matrix material 4B. In addition, in this specification, "the ionization potentials of two layers are equal" does not necessarily mean that the ionization potentials of the two layers are exactly the same value. For example, the ionization potentials of the above two layers may also have a difference of 0.5 eV or less. In Figure 6 it is exemplified that the ionization potential of the second auxiliary layer 37B is larger than that of the inorganic matrix material 4B, but it is not limited thereto. For example, the case where the ionization potential of the second auxiliary layer 37B is smaller than that of the inorganic matrix material 4B, but the difference is 0.5 eV or less is also included in this embodiment.

[0095] Therefore, the injection barrier of holes from the hole transport layer 32 to the second auxiliary layer 37B does not change significantly compared with the injection barrier of holes from the hole transport layer 32 to the inorganic matrix material 4B. In addition, there is almost no barrier for holes to be injected from the second auxiliary layer 37 to the inorganic matrix material 4B. Therefore, the second auxiliary layer 37B reduces the case where the injection efficiency of holes from the anode 31 to the blue light-emitting layer 33B is reduced. Therefore, the second auxiliary layer 37B reduces the deterioration of the carrier balance in the blue light-emitting layer 33B, and reduces the reduction of the light-emitting efficiency of the blue light-emitting layer 33B or the progress of the inactivation of the blue quantum dots QDB.

[0096] Figure 6 The second auxiliary layer 37B shown may also contain at least one of the non-metallic elements contained in the inorganic matrix material 4B, the first metal element the same as the metal element contained in the inorganic matrix material 4B, and the second metal element in a higher period than the first metal element, similar to the first auxiliary layer 36. Specifically, for example, when the inorganic matrix material 4B includes ZnS, the second auxiliary layer 37B may include Mg X Zn 1-X S(0 < X < 1) or MgS. When the inorganic matrix material 4B includes Mg X Zn 1-X S(0 < X < 1), the second auxiliary layer 37B may also include Mg Y Zn 1-Y S(0 < X < Y < 1) or MgS. When the inorganic matrix material 4B includes ZnO 1-X S X (0 < X < 1), the second auxiliary layer 37B may include ZnO 1-Y S Y (0 < X < Y < 1), ZnS, Mg Z Zn 1-Z S(0 < Z < 1) or MgS. When the inorganic matrix material 4B and the second auxiliary layer 37B contain the above materials, the inorganic matrix material 4B and the second auxiliary layer 37B can achieve the Figure 6 shown relationship of the band gap.

[0097] <Other examples of the second auxiliary layer> By explaining other examples of the band gaps of the respective parts of the light-emitting element of the present embodiment, other examples of the second auxiliary layer 37 will be described in more detail. Figure 7 It is a band diagram showing other examples of the band gaps of the respective parts of the light-emitting element of the present embodiment, particularly the blue light-emitting element 3B.

[0098] As Figure 7 shown, the ionization potential of the second auxiliary layer 37B is smaller than that of the inorganic matrix material 4B, and is also larger than that of the hole transport layer 32. In this case, the injection barrier of holes from the hole transport layer 32 to the second auxiliary layer 37B and the injection barrier of holes from the second auxiliary layer 37B to the inorganic matrix material 4B are both smaller than the injection barrier of holes from the hole transport layer 32 to the inorganic matrix material 4B. In other words, the efficiency of transporting holes from the anode 31 via the second auxiliary layer 37B to the inorganic matrix material 4B is higher than the efficiency of transporting holes from the hole transport layer 32 to the inorganic matrix material 4B.

[0099] Therefore, the second auxiliary layer 37B improves the injection efficiency of holes from the anode 31 to the blue light-emitting layer 33B. Therefore, the second auxiliary layer 37B improves the carrier balance in the blue light-emitting layer 33B and reduces the decrease in the light-emitting efficiency of the blue light-emitting layer 33B or the progress of inactivation of the blue quantum dots QDB.

[0100] Figure 7 The second auxiliary layer 37B shown is also the same as Figure 6 the second auxiliary layer 37B shown, and may contain at least one of a non-metal element contained in the inorganic matrix material 4B, a first metal element the same as the metal element contained in the inorganic matrix material 4B, and a second metal element in a higher period than the first metal element. Specifically, for example, when the inorganic matrix material 4B contains Mg X Zn 1-X S (0 < X < 1), the second auxiliary layer 37B may contain Mg Y Zn 1-Y S (0 < Y < X < 1). When the inorganic matrix material 4B includes ZnO 1-X S X (0 < X < 1), the second auxiliary layer 37B may include ZnO 1-Y S Y (0 < X < Y < 1). When the inorganic matrix material 4B and the second auxiliary layer 37B contain the above materials, the inorganic matrix material 4B and the second auxiliary layer 37B can achieve the relationship of the band gaps shown by a simpler structure. Figure 7 The relationship of the band gaps shown.

[0101] On the other hand, Figure 7 The second auxiliary layer 37B shown may also include an element different from the element contained in the inorganic matrix material 4B. For example, when the inorganic matrix material 4B includes ZnS, the second auxiliary layer 37B may also include CdS or In2S3. In this case, the inorganic matrix material 4B and the second auxiliary layer 37B can also be realized by a simpler structure. Figure 7 The band gap relationship is shown.

[0102] Figure 6 or Figure 7 The second auxiliary layer 37B shown may also include a mixed crystal including the above-mentioned non-metallic element, the first metal element, and the second metal element. In this case, the second auxiliary layer 37B more strongly protects the blue light emitting layer 33B or the hole transport layer 32 .

[0103] In addition, from the viewpoint of fully ensuring the function of protecting the light-emitting layer 33 and the hole transport layer 32 and sufficiently reducing the electrons passing through the second auxiliary layer 37B, the film thickness of the second auxiliary layer 37B can be 5 nm or more, or 10 nm or more. In addition, from the viewpoint of reducing the resistance of the entire light-emitting element, the film thickness of the second auxiliary layer 37B can be 20 nm or less, and for example, can be thinner than the film thickness of the hole transport layer 32.

[0104] In addition, Figure 6 and Figure 7 In the embodiment, the relationship between the band gaps of the blue light emitting element 3B is described, but the band gaps of the red light emitting element 3R and the green light emitting element 3G may also have the same Figure 6 or Figure 7 The same relationship as the band gap shown. Specifically, in the red light-emitting element 3R, the electron affinity of the second auxiliary layer 37R may also be smaller than that of the inorganic matrix material 4R and the hole transport layer 32, and have the same ionization potential as that of the inorganic matrix material 4R. Alternatively, in the red light-emitting element 3R, the ionization potential of the second auxiliary layer 37R may be smaller than that of the inorganic matrix material 4R, and the ionization potential may be greater than that of the hole transport layer 32. In the green light-emitting element 3G, the electron affinity of the second auxiliary layer 37G is also smaller than that of the inorganic matrix material 4G and the hole transport layer 32, and may also have the same ionization potential as that of the inorganic matrix material 4G. Alternatively, in the green light-emitting element 3G, the ionization potential of the second auxiliary layer 37G may be smaller than that of the inorganic matrix material 4G, and the ionization potential may be greater than that of the hole transport layer 32.

[0105] <Other examples of the method for manufacturing a display device> The display device 1 according to the present embodiment can also be manufactured by the same method as the method for manufacturing the display device 1 according to the previous embodiment, except that the order of some steps is changed and the material of the second precursor is changed.

[0106] Specifically, in the method for manufacturing the display device 1 according to the present embodiment, the following step S4 is performed: Figure 4 In the steps S7 and S8 in the steps shown in the figure, the second precursor is used as a precursor of the second metal sulfide contained in the second auxiliary layer 37 in step S7 of the present embodiment. Alternatively, in the method for manufacturing the display device 1 according to the present embodiment, after step S6 is completed, the method proceeds to step S9. Thus, the display device 1 including the second auxiliary layer 37 according to the present embodiment in the light-emitting element 3 is manufactured.

[0107] According to the manufacturing method of the display device 1 involved in this embodiment, the light-emitting layer 33 and the second auxiliary layer 37 can be formed by coating the solution and modifying the precursor in the solution. Therefore, according to the manufacturing method of the display device 1 of this embodiment, the light-emitting layer 33 and the second auxiliary layer 37 can be formed more simply.

[0108] [Implementation method 3] <Display device with two auxiliary layers> Figure 8 1 is a schematic side cross-sectional view of the display device 1 according to this embodiment. The display device 1 according to this embodiment has the same configuration as the display device 1 of each of the above embodiments, except that the light emitting element 3 includes both the first auxiliary layer 36 and the second auxiliary layer 37 .

[0109] In this embodiment, the first auxiliary layer 36 is also located between the light-emitting layer 33 and the cathode 35 in each light-emitting element, and is particularly in contact with the cathode 35 side of the light-emitting layer 33. In addition, the second auxiliary layer 37 is located between the anode 31 and the light-emitting layer 33 in each light-emitting element, and is particularly in contact with the anode 31 side of the light-emitting layer 33. Both the first auxiliary layer 36 and the second auxiliary layer 37 may be made of the same material as the inorganic matrix material, but are preferably made of different materials.

[0110] In each light-emitting element involved in this embodiment, the quantum dots of the light-emitting layer 33 can be separated from both the hole transport layer 32 and the electron transport layer 34. Therefore, each light-emitting element involved in this embodiment has the first auxiliary layer 36 and the second auxiliary layer 37, thereby further increasing the probability of occurrence of the process that contributes to the light emission of the light-emitting layer 33, and further improving the light emission efficiency of the light-emitting layer 33.

[0111] The first auxiliary layer 36 and the second auxiliary layer 37 involved in this embodiment may respectively include any one of the materials of the first auxiliary layer 36 and the second auxiliary layer 37 described above. In addition, the first auxiliary layer 36 may have Figure 3 The second auxiliary layer 37 may have a band gap of Figure 6 and Figure 7 The band gap shown in any one of them.

[0112] In this case, the first auxiliary layer 36 and the second auxiliary layer 37 further improve the carrier balance in the light emitting layer 33 and further improve the light emitting efficiency. In addition, the first auxiliary layer 36 and the second auxiliary layer 37 can protect any one of the light emitting layer 33 , the hole transport layer 32 and the electron transport layer 34 .

[0113] In this embodiment, an example is described in which the red light-emitting element 3R, the green light-emitting element 3G, and the blue light-emitting element 3B all include the first auxiliary layer 36 and the second auxiliary layer 37, but the structure of the display device 1 involved in this embodiment is not limited to this. For example, the display device 1 may include the first auxiliary layer 36 and the second auxiliary layer 37 in at least one of the red light-emitting element 3R, the green light-emitting element 3G, and the blue light-emitting element 3B. For example, the red light-emitting element 3R may include only the first auxiliary layer 36R, the green light-emitting element 3G may include both the first auxiliary layer 36G and the second auxiliary layer 37G, and the blue light-emitting element 3B may include only the second auxiliary layer 37B.

[0114] The display device 1 according to the present embodiment can also be manufactured by the same method as the method for manufacturing the display device 1 according to the previous embodiment, except that some steps are additionally performed. Specifically, in the method for manufacturing the display device 1 according to the present embodiment, the following step S4 is performed. Figure 4 Step S7 and step S8 in each process shown. In step S7 of the present embodiment, the second precursor is used as a precursor of the second metal sulfide included in the second auxiliary layer 37, similarly to step S7 in the previous embodiment. However, in the manufacturing method of the display device 1 of the present embodiment, after step S6 is completed, step S7 and thereafter are performed. Following step S6, in step S7, the second precursor is used as a precursor of the first metal sulfide included in the first auxiliary layer 36. Thus, the display device 1 having both the first auxiliary layer 36 and the second auxiliary layer 37 involved in the present embodiment in the light-emitting element 3 is manufactured.

[0115] According to the manufacturing method of the display device 1 of this embodiment, the first auxiliary layer 36, the light-emitting layer 33, and the second auxiliary layer 37 can be formed by coating a solution and modifying a precursor in the solution. Therefore, according to the manufacturing method of the display device 1 of this embodiment, the first auxiliary layer 36, the light-emitting layer 33, and the second auxiliary layer 37 can be formed more simply.

[0116] The present disclosure is not limited to the above-mentioned embodiments, and various changes can be made within the scope indicated by the claims. The embodiments obtained by appropriately combining the technical solutions disclosed in different embodiments are also included in the technical scope of the present disclosure. For example, the display device 1 only needs to include the first auxiliary layer 36 or the second auxiliary layer 37 in at least one of the red light-emitting element 3R, the green light-emitting element 3G, and the blue light-emitting element 3B. For example, the red light-emitting element 3R only includes the first auxiliary layer 36R, and the green light-emitting element 3G and the blue light-emitting element 3B may not include any of the first auxiliary layer 36 and the second auxiliary layer 37. Since the red light-emitting element 3R has the smallest band gap of the light-emitting layer, the configuration of the present disclosure mostly works effectively. In addition, new technical features can be formed by combining the technical means disclosed in each embodiment. Component Symbols

[0117] 1 Display device 3B blue light emitting element 3G green light emitting element 3R red light emitting element 4 Inorganic matrix materials 31 Anode 32Hole transport layer 33 Luminous Layer 34Electron transport layer 35 cathode 36First auxiliary layer 37 Second auxiliary layer QDR Red Quantum Dots QDG Green Quantum Dots QDB Blue Quantum Dots

Claims

1. A light emitting element, characterized in that: have: Anode and cathode; A light-emitting layer, which is located between the anode and the cathode and includes a plurality of quantum dots and an inorganic matrix material filling between the plurality of quantum dots; In addition, the light emitting element further comprises at least one of the following (i) or (ii): (i) an electron transport layer located between the light-emitting layer and the cathode; and a first auxiliary layer, which is in contact with the cathode side of the light-emitting layer and is composed of a material different from the inorganic matrix material; (ii) a hole transport layer located between the anode and the light-emitting layer; as well as A second auxiliary layer is in contact with the anode side of the light-emitting layer and is composed of a material different from the inorganic matrix material.

2. The light emitting element according to claim 1, characterized in that The weight ratio of the organic ligand contained in the light-emitting layer is less than 5%.

3. The light emitting element according to claim 1 or 2, characterized in that: The inorganic matrix material is composed of an inorganic semiconductor material.

4. The light emitting element according to any one of claims 1 to 3, characterized in that: The band gap of the inorganic matrix material is greater than or equal to the band gap of the material included in the plurality of quantum dots.

5. The light emitting element according to any one of claims 1 to 4, characterized in that: Compared with the plurality of quantum dots, the inorganic matrix material has a lower electron affinity and a higher ionization potential.

6. The light emitting element according to any one of claims 1 to 5, characterized in that: have: The electron transport layer and the first auxiliary layer, The first auxiliary layer has a lower electron affinity than the inorganic matrix material.

7. The light emitting element according to claim 6, characterized in that An ionization potential of the first auxiliary layer is lower than an ionization potential of the electron transport layer.

8. The light emitting element according to claim 6 or 7, characterized in that: The first auxiliary layer has a greater ionization potential than the inorganic matrix material.

9. The light emitting element according to any one of claims 6 to 8, characterized in that: The first auxiliary layer includes a non-metallic element contained in the inorganic matrix material; and The inorganic matrix material includes at least one of a first metal element and a second metal element in a period higher than the first metal element.

10. The light emitting element according to claim 9, characterized in that The first auxiliary layer includes a mixed crystal including the non-metal element and the first metal element and the second metal element.

11. The light emitting element according to claim 9, characterized in that The inorganic matrix material contains ZnS, The first auxiliary layer contains Mg x Zn 1-x S(0 < X < 1) or MgS.

12. The light emitting element according to claim 9, characterized in that The inorganic matrix material includes Mg x Zn 1-X S(0 <X<1), The first auxiliary layer contains Mg Y Zn 1-Y S (0 < X < Y < 1) or MgS.

13. The light emitting element according to claim 9, characterized in that The inorganic matrix material contains ZnO 1-X S X (0 <X<1), The first auxiliary layer contains ZnO 1-Y S Y (0 < X < Y < 1), ZnS, Mg Z Zn 1-Z S (0 < Z < 1) or MgS.

14. The light emitting element according to any one of claims 1 to 13, characterized in that: The hole transport layer and the second auxiliary layer are provided. The electron affinity of the second auxiliary layer is lower than that of the inorganic matrix material.

15. The light emitting element according to claim 14, characterized in that: The electron affinity of the second auxiliary layer is lower than the electron affinity of the hole transport layer.

16. The light emitting element according to claim 14, characterized in that The ionization potential of the second auxiliary layer is equal to the ionization potential of the inorganic matrix material.

17. The light emitting element according to any one of claims 14 to 16, characterized in that: The second auxiliary layer includes a non-metallic element included in the inorganic matrix material; and The inorganic matrix material includes at least one of a first metal element and a second metal element in a period higher than the first metal element.

18. The light emitting element according to claim 17, characterized in that The second auxiliary layer includes a mixed crystal including the non-metal element, the first metal element, and the second metal element.

19. The light emitting element according to claim 17, characterized in that: The inorganic matrix material contains ZnS, The second auxiliary layer contains Mg X Zn 1-X S(0 < X < 1) or MgS.

20. The light emitting element according to claim 17, wherein: The inorganic matrix material includes Mg X Zn 1-X S(0 <X<1), The second auxiliary layer contains Mg Y Zn 1-Y S (0 < X < Y < 1) or MgS.

21. The light emitting element according to claim 17, wherein: The inorganic matrix material contains ZnO 1-X S X (0 <X<1), The second auxiliary layer contains ZnO 1-Y S Y (0 < X < Y < 1), ZnS, Mg Z Zn 1-Z S (0 < Z < 1) or MgS.

22. The light emitting element according to any one of claims 1 to 13, characterized in that: The hole transport layer and the second auxiliary layer are provided. The second auxiliary layer has a lower ionization potential than the inorganic matrix material.

23. The light emitting element according to claim 22, characterized in that The second auxiliary layer has an ionization potential greater than an ionization potential of the hole transport layer.

24. The light emitting element according to claim 22, characterized in that The inorganic matrix material contains ZnS, The second auxiliary layer contains CdS or In2S3.

25. The light emitting element according to claim 22, characterized in that The second auxiliary layer comprises a non-metallic element contained in the above-mentioned inorganic matrix material; and The inorganic matrix material contains at least one of a first metal element and a second metal element that is located in a higher period than the first metal element.

26. The light emitting element according to claim 25, characterized in that The second auxiliary layer includes a mixed crystal including the non-metal element, the first metal element, and the second metal element.

27. The light emitting element according to claim 25, characterized in that The inorganic matrix material includes Mg X Zn 1-X S(0 <X<1), The second auxiliary layer includes Mg Y Zn 1-Y S(0 <Y<X<1)。 28. The light emitting element according to claim 25, characterized in that The inorganic matrix material includes ZnO 1-X S X (0 <X<1), The second auxiliary layer includes ZnO 1-Y S Y (0 <X<Y<1)。 29. The light emitting element according to any one of claims 1 to 28, characterized in that: The device includes the electron transport layer, the hole transport layer, the first auxiliary layer, and the second auxiliary layer.

30. The light emitting element according to any one of claims 1 to 29, characterized in that: The first auxiliary layer is thinner than the electron transport layer.

31. The light emitting element according to any one of claims 1 to 30, characterized in that: The second auxiliary layer is thinner than the hole transport layer.

32. A display device, characterized in that: A light-emitting element according to any one of claims 1 to 31.

33. A method for manufacturing a light emitting element, characterized in that: include: A process of applying a solution of a first precursor containing a plurality of quantum dots and a first metal sulfide, and then modifying the first precursor into the first metal sulfide to form a light-emitting layer; and A step of applying a second precursor of a second metal sulfide different from the first metal sulfide, and then modifying the second precursor into the second metal sulfide to form an auxiliary layer in contact with the light-emitting layer.

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