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

Abstract

This light-emitting element (1) comprises a first electrode (2), a second electrode (3) and a light-emitting layer (4) having a plurality of quantum dots (5), wherein: the light-emitting layer (4) has, when viewed in a stacking direction which is the direction from the first electrode (2) toward the second electrode (3), a first region (P1) provided with a first light-emitting layer (6), and a second region (P2) provided with a second light-emitting layer (8); the density of the quantum dots (5) in the second light-emitting layer (8) is lower than the density of the quantum dots (5) in the first light-emitting layer (6); and in the second light-emitting layer (8), an inorganic compound (10) fills a space between the plurality of quantum dots (5).

Description

[Technical field]

[0001] The present disclosure relates to a light-emitting element having quantum dots, a display device having the light-emitting element as a light-emitting element, and a method for manufacturing the same. [Background technology]

[0002] Patent Document 1 discloses a light-emitting device including a light-emitting layer having semiconductor nanocrystals (quantum dots) as a light-emitting material. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2007-95685 Summary of the Invention [Problem to be solved by the invention]

[0004] When foreign matter such as moisture or air enters a light-emitting layer that contains quantum dots as light-emitting materials, the foreign matter may propagate between the quantum dots and permeate the entire light-emitting layer, causing deterioration of many of the quantum dots in the light-emitting layer and resulting in a decrease in the light-emitting efficiency of the light-emitting device.

[0005] In order to prevent the propagation of foreign matter between the quantum dots, it is possible to reduce the density of the quantum dots in the light-emitting layer, but in this case, the carriers injected into the quantum dots are less likely to be transported through the quantum dots, resulting in a decrease in the light-emitting efficiency of the light-emitting layer or an increase in the voltage applied to the light-emitting element to obtain a given brightness. [Means for solving the problem]

[0006] A light-emitting element according to one embodiment of the present disclosure includes a first electrode, a second electrode, and a light-emitting layer having a plurality of quantum dots between the first electrode and the second electrode, the light-emitting layer having, in a stacking direction from the first electrode to the second electrode, a first region in which a first light-emitting layer is provided and a second region in which a second light-emitting layer is provided, the density of the quantum dots in the second light-emitting layer being lower than the density of the quantum dots in the first light-emitting layer, and the spaces between the plurality of quantum dots in the second light-emitting layer being filled with an inorganic matrix.

[0007] A display device according to one embodiment of the present disclosure comprises a substrate and a red light-emitting element, a green light-emitting element, and a blue light-emitting element on the substrate, each of the red light-emitting element, the green light-emitting element, and the blue light-emitting element being a light-emitting element according to one embodiment of the present disclosure.

[0008] Furthermore, a method for manufacturing a light-emitting element according to one embodiment of the present disclosure is a method for manufacturing a light-emitting element including a first electrode, a second electrode, and a light-emitting layer having a plurality of quantum dots between the first electrode and the second electrode, the method including a light-emitting layer formation step of forming the light-emitting layer having, as viewed in a stacking direction from the first electrode to the second electrode, a first region in which a first light-emitting layer is provided and a second region in which a second light-emitting layer is provided, the density of the quantum dots in the second light-emitting layer being lower than the density of the quantum dots in the first light-emitting layer, and the spaces between the plurality of quantum dots in the second light-emitting layer being filled with an inorganic matrix.

[0009] In addition, a manufacturing method for a display device according to one embodiment of the present disclosure includes a substrate preparation process for preparing a substrate having a plurality of sub-pixel regions, and a light-emitting element formation process for forming the light-emitting element in each of the sub-pixel regions on the substrate by a light-emitting element manufacturing method according to one embodiment of the present disclosure. Effect of the Invention

[0010] The increase in the applied voltage required to obtain a predetermined luminance is reduced, while the decrease in the luminous efficiency of the entire light-emitting element due to the inclusion of foreign matter in the light-emitting layer is reduced. [Brief description of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view of a light-emitting element according to embodiment 1. FIG. [Diagram 2] 5A to 5C are cross-sectional views showing the operation of the light-emitting device. [Diagram 3] 5 is another cross-sectional view showing the operation of the light-emitting element. FIG. [Figure 4] FIG. 11 is a cross-sectional view of a light-emitting element according to a comparative example. [Diagram 5] 5A to 5C are cross-sectional views showing the operation of the light-emitting device. [Figure 6] 5 is another cross-sectional view showing the operation of the light-emitting element. FIG. [Figure 7] 4 is a graph showing the relationship between voltage and luminance for the operation of the light-emitting device according to the first embodiment. [Figure 8] 4 is a cross-sectional view showing the operation of the light-emitting element when no foreign object is present; FIG. [Figure 9] 4 is a graph showing the relationship between voltage and brightness for the operation of the light emitting device without a foreign object. [Figure 10] 5 is a cross-sectional view showing the operation of the light-emitting element when a foreign object is present; FIG. [Figure 11] 4 is a graph showing the relationship between voltage and brightness for operation of the light emitting device in the presence of a foreign object. [Figure 12] 10A and 10B are schematic diagrams for explaining an image displayed on a screen by a light-emitting element according to a comparative example. [Figure 13] 2 is a schematic diagram for explaining an image displayed on a screen by the light-emitting element according to the first embodiment. FIG. [Figure 14] 13A and 13B are schematic diagrams for explaining an image displayed on a screen by a light-emitting element according to another comparative example. [Figure 15] FIG. 2 is a diagram for explaining the density of quantum dots formed in a first region provided in a light emitting layer of the light emitting device according to the first embodiment. [Figure 16] FIG. 4 is a diagram for explaining the density of quantum dots formed in a second region provided in the light-emitting layer. [Figure 17]4 is a cross-sectional view of a light-emitting device according to a modified example of the first embodiment. [Figure 18] 4 is a graph showing the relationship between voltage and brightness for operation of the light emitting element. [Figure 19] 4 is a cross-sectional view showing the operation of the light-emitting element when no foreign object is present; FIG. [Figure 20] 4 is a graph showing the relationship between voltage and brightness for the operation of the light emitting device without a foreign object. [Figure 21] 5 is a cross-sectional view showing the operation of the light-emitting element when a foreign object is present; FIG. [Figure 22] 4 is a graph showing the relationship between voltage and brightness for operation of the light emitting device in the presence of a foreign object. [Diagram 23] 2A to 2C are cross-sectional views illustrating a method for manufacturing the light-emitting element according to the first embodiment. [Figure 24] 5A to 5C are cross-sectional views illustrating a method for manufacturing the light-emitting element. [Diagram 25] 5A to 5C are cross-sectional views illustrating a method for manufacturing the light-emitting element. [Figure 26] 5A to 5C are cross-sectional views illustrating a method for manufacturing the light-emitting element. [Figure 27] 5A to 5C are cross-sectional views illustrating a method for manufacturing the light-emitting element. [Figure 28] 5A to 5C are cross-sectional views illustrating a method for manufacturing the light-emitting element. [Figure 29] 5A to 5C are cross-sectional views illustrating a method for manufacturing the light-emitting element. [Diagram 30] FIG. 1 is a plan view of a display device according to a first embodiment. [Diagram 31] FIG. 11 is a plan view of a display device according to a modified example of the first embodiment. [Diagram 32] FIG. 11 is a plan view of a display device according to another modified example of the first embodiment. [Diagram 33] 4 is a graph showing energy levels of red light-emitting elements, green light-emitting elements, and blue light-emitting elements provided in the display device. [Diagram 34] FIG. 11 is a plan view of a display device according to a second embodiment. [Diagram 35]11 is a schematic diagram showing the average density of quantum dots in a plurality of divided regions of a light-emitting layer of a light-emitting device according to embodiment 3. FIG. [Diagram 36] 1 is a histogram showing the average density of the quantum dots. [Figure 37] FIG. 4 is a schematic diagram showing another average density of the quantum dots. [Figure 38] 4 is a histogram showing another average density of the quantum dots. [Figure 39] FIG. 13 is a schematic diagram showing still another average density of the quantum dots. [Diagram 40] 11 is a histogram showing yet another average density of the quantum dots. [Diagram 41] FIG. 13 is a schematic diagram showing still another average density of the quantum dots. [Diagram 42] 11 is a histogram showing yet another average density of the quantum dots. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] (Embodiment 1) 1 is a cross-sectional view of a light-emitting element 1 according to embodiment 1. The light-emitting element 1 includes a first electrode 2, a second electrode 3, and a light-emitting layer 4 having a plurality of quantum dots (QDs) 5 between the first electrode 2 and the second electrode 3. The first electrode 2 may be an anode. The second electrode 3 may be a cathode. A hole transport layer 13 may be formed between the light-emitting layer 4 and the first electrode 2. An electron transport layer 14 may be formed between the light-emitting layer 4 and the second electrode 3.

[0013] In this specification, "quantum dot" means a dot having a maximum width of 100 nm or less. The shape of the quantum dot is not particularly limited as long as it satisfies the above maximum width, and is not limited to a spherical three-dimensional shape (circular cross-sectional shape). The shape of the quantum dot may be, for example, a polygonal cross-sectional shape, a rod-like three-dimensional shape, a branch-like three-dimensional shape, a three-dimensional shape with unevenness on the surface, or a combination thereof.

[0014] The quantum dots may typically be made of a semiconductor. The semiconductor may have a certain band gap. The semiconductor may be any material capable of emitting light, and may include at least the materials described below. The semiconductor may be capable of emitting red, green, and blue light, respectively. The semiconductor may include at least one selected from the group consisting of II-VI group compounds, III-V group compounds, chalcogenides, and perovskite compounds. The II-VI group compounds refer to compounds containing II and VI elements, and the III-V group compounds refer to compounds containing III and V elements. The II group elements may include Group 2 and Group 12 elements, the III group elements may include Group 3 and Group 13 elements, the V group elements may include Group 5 and Group 15 elements, and the VI group elements may include Group 6 and Group 16 elements.

[0015] The II-VI compound includes, for example, at least one selected from the group consisting of MgS, MgSe, MgTe, CaS, CaSe, CaTe, SrS, SrSe, SrTe, BaS, BaSe, BaTe, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, HgS, HgSe, and HgTe.

[0016] The III-V compound includes, for example, at least one selected from the group consisting of GaAs, GaP, InN, InAs, InP, and InSb.

[0017] Chalcogenides are compounds that contain a Group VI A(16) element, such as CdS or CdSe. Chalcogenides may also include mixed crystals thereof.

[0018] The perovskite compound has a composition represented by the general formula CsPbX3, for example. The constituent element X includes at least one element selected from the group consisting of Cl, Br, and I.

[0019] Here, the numbering of element families using Roman numerals is based on the old IUPAC (International Union of Pure and Applied Chemistry) system or the old CAS (Chemical Abstracts Service) system, while the numbering of element families using Arabic numerals is based on the current IUPAC system.

[0020] The light-emitting layer 4 has a first region P1 in which the first light-emitting layer 6 is provided and a second region P2 in which the second light-emitting layer 8 is provided, as viewed in the stacking direction from the first electrode 2 to the second electrode 3. That is, when the light-emitting layer 4 is cut along a plane parallel to the stacking direction as shown in FIG. 1, the light-emitting layer 4 has, in the cross section, the first region P1 in which the first light-emitting layer 6 is provided and the second region P2 in which the second light-emitting layer 8 is provided. The cut surface can be selected from any plane parallel to the stacking direction, and it is sufficient that it can be confirmed that the light-emitting layer 4 has the first region P1 in which the first light-emitting layer 6 is provided and the second region P2 in which the second light-emitting layer 8 is provided in at least one cross section.

[0021] The density of the quantum dots 5 in the second light-emitting layer 8 is lower than the density of the quantum dots 5 in the first light-emitting layer 6 .

[0022] In the second light-emitting layer 8, the spaces between the quantum dots 5 are filled with an inorganic compound 10. The inorganic compound 10 is composed of an inorganic matrix. In this specification, the term "inorganic matrix" refers to a material made of an inorganic material that contains and holds other substances. In other words, the inorganic matrix referred to here refers to a material made of an inorganic material that contains and holds quantum dots 5. The inorganic matrix is ​​an element that constitutes the film in which the quantum dots are distributed.

[0023] The inorganic matrix is ​​desirably filled in the light-emitting layer 4. The inorganic matrix may fill the regions of the light-emitting layer 4 other than the quantum dots 5. The inorganic matrix may fill the regions of the light-emitting layer 4 other than the quantum dots 5. Note that the outer edge of the light-emitting layer 4 does not need to be formed only by the inorganic matrix, and it is not excluded that some of the quantum dots 5 are exposed from the inorganic matrix.

[0024] The inorganic matrix may refer to the portion of the light-emitting layer 4 excluding the quantum dots 5 .

[0025] The inorganic matrix may encapsulate a plurality of quantum dots 5. The inorganic matrix may be formed so as to fill spaces formed between the plurality of quantum dots 5. The inorganic matrix may partially or completely fill spaces between the quantum dots 5.

[0026] The inorganic matrix is ​​1000 nm in the plane direction perpendicular to the film thickness direction. 2 It is desirable for the film to have a continuous film having an area of ​​at least 100 mm. A continuous film means a region in a plane that is not separated by any material other than the material that constitutes the continuous film. The inorganic matrix may be made of the same material as the shell material of the quantum dots 5. In this case, the average distance between adjacent cores (core-to-core distance) may be 3 nm or more, and may be 5 nm or more. Alternatively, the average distance between adjacent cores may be 0.5 times or more the average core diameter. The core-to-core distance is the average of the shortest distance between 20 adjacent cores in cross-sectional observation. The core-to-core distance should be kept wider than the distance when the shell materials are in contact with each other. The average core diameter is the average of the core diameters of 20 adjacent cores in cross-sectional observation. The core diameter can be the diameter of a circle having the same area as the core area in cross-sectional observation.

[0027] The concentration of the inorganic matrix in the light-emitting layer 4 may be 9% or more and 70% or less, as measured from the area ratio in image processing of cross-sectional observation. Furthermore, when the quantum dots 5 have a core / shell structure, the concentration of the shell may be 0% or more and 58% or less. Furthermore, when the shell material and the inorganic matrix material are the same (the constituent elements are the same), it is practically difficult to distinguish between the shell and the inorganic matrix, so the concentration of the region combining the inorganic matrix and the shell may be within the numerical range obtained by adding the numerical range of the shell concentration to the above-mentioned numerical range of the inorganic matrix concentration.

[0028] The inorganic matrix may be solid at room temperature.

[0029] The light-emitting layer 4 may be composed of quantum dots 5 and an inorganic matrix. The intensity of the carbon chain structure detected when the light-emitting layer 4 is analyzed may be equal to or less than noise. If the light-emitting layer 4 does not contain an organic ligand, the intensity of the carbon chain structure detected will be weak, equal to or less than noise.

[0030] The inorganic material constituting the inorganic matrix desirably has a band gap wider than the band gap of the material constituting the quantum dots 5. The inorganic material constituting the inorganic matrix may be a semiconductor material or an insulating material. The inorganic material constituting the inorganic matrix may be a sulfide semiconductor. The inorganic material constituting the inorganic matrix includes, for example, a metal sulfide and / or a metal oxide. The metal sulfide may 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), or magnesium sulfide (MgGa2S4). The metal oxide may be zinc oxide (ZnO), titanium oxide (TiO2), tin oxide (SnO2), tungsten oxide (WO3), or zirconium oxide (ZrO2). The chemical formulas written in parentheses after the names of the compounds are representative examples. In addition, the composition ratios described in the chemical formulas are preferably stoichiometric, in which the composition of the actual compounds is as described in the chemical formula, but are not necessarily stoichiometric.

[0031] The above-mentioned structure of the inorganic matrix can be confirmed by observing a cross section of the light-emitting layer 4 with a width of about 100 nm, but it is not necessary to observe the entire light-emitting layer 4.

[0032] Furthermore, the inorganic matrix may be made mainly of an inorganic material, and there is no prohibition on the addition of a material different from the main inorganic material as an additive.

[0033] In the second light-emitting layer 8, the spaces between the multiple quantum dots 5 may be further filled with an organic compound. In the first light-emitting layer 6, the spaces between the multiple quantum dots 5 may be filled with an inorganic compound 10 and an organic compound.

[0034] In a display including an LED (Light Emitting Diode) element having quantum dots 5, a pixel may become non-emitting due to foreign matter including oxygen and water.

[0035] When the density of the quantum dots 5 is high, the effective thickness of the medium (or inorganic medium) that protects the surface defects of the quantum dots 5 is thin, so that the surface activity of the quantum dots 5 is high and the number of quantum dots 5 that enter a certain volume into which oxygen and water diffuse increases. For this reason, if foreign matter containing oxygen or water enters a pixel during the manufacture of the display, the quantum dots 5 are oxidized in a chain reaction, and the entire pixel may become non-luminous. In other words, a dark spot is generated in the image displayed on the display. On the other hand, if the density of the quantum dots 5 is reduced, the thickness of the inorganic medium around the quantum dots 5 becomes thick, making it difficult to inject current, decreasing the luminous efficiency and increasing the power consumption of the entire display, so that it was not possible to reduce the density of the quantum dots 5 in the entire pixel.

[0036] Therefore, in the first embodiment, a second region P2 having a low density of quantum dots 5 is provided in the lamination plane of the light-emitting layer 4 of each pixel in the display.

[0037] Fig. 2 is a cross-sectional view showing the operation of the light-emitting element 1. Fig. 3 is another cross-sectional view showing the operation of the light-emitting element 1.

[0038] In the second region P2 where the second light-emitting layer 8 is provided and where the QD density is low, the inorganic medium containing the inorganic compound 10 that protects the QD surface defects of the quantum dots 5 has a large effective thickness. Therefore, in the second region P2, the activity of the QD surface is low and the reaction is difficult, and the number of quantum dots 5 that enter a certain volume into which oxygen and water diffuse is small. Therefore, even if a foreign matter 15 containing oxygen and water enters the light-emitting layer 4 as shown in FIG. 2, even if the oxidation of the quantum dots 5 in the first region P1 progresses as shown in FIG. 3, the oxidation of the quantum dots 5 in the second region P2 is difficult to progress. Here, the darker the color of the hatching of the quantum dots 5 shown in FIG. 2 and FIG. 3, the more oxidation progresses. The same applies to the figures described below.

[0039] On the other hand, in the first region P1 where the first light-emitting layer 6 is provided, the density of the quantum dots 5 is greater than that in the second region P2, making it easier to inject a current into the first light-emitting layer 6 and reducing the driving voltage of the first light-emitting layer 6. Therefore, in the light-emitting element 1 according to this embodiment, the first light-emitting layer 6 reduces an increase in power consumption, while the second light-emitting layer 8 reduces the possibility of the element becoming non-emitting due to the intrusion of foreign matter.

[0040] Fig. 4 is a cross-sectional view of a light-emitting element 91 according to a comparative example. Fig. 5 is a cross-sectional view showing the operation of the light-emitting element 91. Fig. 6 is another cross-sectional view showing the operation of the light-emitting element 91. Components similar to those described above are given the same reference symbols, and detailed descriptions of these components will not be repeated.

[0041] The light-emitting element 91 includes a first electrode 2, a second electrode 3, and a light-emitting layer 94 having a plurality of quantum dots 5 between the first electrode 2 and the second electrode 3. The light-emitting layer 94 corresponds to the first light-emitting layer 6 described above with reference to FIG.

[0042] The quantum dots 5 are nano-sized and highly active and reactive. When the density of the quantum dots 5 is high, the effective thickness of the inorganic medium that protects the surface defects of the quantum dots 5 is thin. Therefore, the surface activity of the quantum dots 5 is high and they are prone to react, and a large number of quantum dots 5 enter a certain volume into which oxygen and water diffuse. Therefore, as shown in FIG. 5, when a foreign substance 15 containing oxygen or water enters the light-emitting layer 94, the quantum dots 5 are oxidized in a chain reaction, and the entire pixel of the light-emitting element 91 becomes non-luminous as shown in FIG. 6.

[0043] 7 is a graph showing the relationship between voltage and luminance regarding the operation of the light-emitting element 1. The horizontal axis represents the voltage applied between the first electrode 2 and the second electrode 3 of the light-emitting element 1 to cause the light-emitting element 1 to emit light, and the vertical axis represents the luminance of the light-emitting element 1 that emits light according to the voltage.

[0044] Curve C1 shows the voltage-luminance characteristics of the quantum dots 5 in the first region P1 where the QD density of the light-emitting layer 4 is high. Curve C2 shows the voltage-luminance characteristics of the quantum dots 5 in the second region P2 where the QD density of the light-emitting layer 4 is low.

[0045] The voltage V for driving the quantum dots 5 in the first region P1 is, as shown by the curve C1, when the luminance L is zero. To Voltage V th1 Next , luminance L is L max When To V 1max and become.

[0046] In the second region P2, the density of the quantum dots 5 is made lower than that in the first region P1, and the quantum dots 5 are more strongly protected, but on the other hand, current injection becomes more difficult and the voltage V becomes higher.

[0047] The voltage V for driving the quantum dots 5 in the second region P2 is V th1 Voltage greater than V th2 and the luminance L is L max When the voltage V 2max It becomes.

[0048] Fig. 8 is a cross-sectional view showing the operation of the light-emitting element 1 when there is no foreign matter 15. Fig. 9 is a graph showing the relationship between voltage and brightness for the operation of the light-emitting element 1 when there is no foreign matter 15. Components similar to those described above are given the same reference numerals, and detailed descriptions of these components will not be repeated.

[0049] When the foreign matter 15 does not enter the light-emitting layer 4, the voltage V th1 ~V 1max Therefore, the light emitting element 1 is driven only in the range of V th2 (>V 1max The quantum dots 5 included in the second region P2, which is the region P1, do not emit light.

[0050] Fig. 10 is a cross-sectional view showing the operation of the light-emitting element 1 when a foreign object 15 is present. Fig. 11 is a graph showing the relationship between voltage and brightness regarding the operation of the light-emitting element 1 when a foreign object 15 is present. Components similar to those described above are given the same reference numerals, and detailed descriptions of these components will not be repeated.

[0051] When the foreign matter 15 has penetrated into the light-emitting layer 4, the oxidation of the quantum dots 5 in the first region P1 is likely to proceed. As a result, the electronic level of at least the surface (and inside) of the quantum dots 5 in the first region P1 changes significantly, and a current is less likely to be injected into the carrier transport layer that matches the electronic level of the unoxidized quantum dots 5; in other words, a current is less likely to flow into the first region P1. For this reason, in the above-mentioned case, a current is injected only into the second region P2. That is, when the voltage V th2 ~V 2max By driving the light emitting element 1 within this range, the quantum dots 5 included in the second region P2 of the light emitting layer 4 are made to emit light.

[0052] As a specific driving method, after manufacturing a display including the light-emitting element 1, all pixels are driven by a voltage V 1max Then, by finding non-emitting pixels, the non-emitting pixels are determined to have a foreign matter 15, and the emitting pixels are determined to have no foreign matter. This determination result is then fed back to a drive section for the light-emitting element 1. The drive section drives the non-emitting pixels determined to have a foreign matter based on curve C2, and drives the emitting pixels determined to have no foreign matter based on curve C1.

[0053] This driving method can be implemented within the scope of inspections that are normally performed to correct luminance variations in pixels during the display manufacturing process.

[0054] Alternatively, the relationship between the drive current and the brightness for the first region P1 may be measured in advance, and both the pixels without the foreign matter 15 and the pixels with the foreign matter 15 may be driven with a constant current based on the measured relationship. The pixels without the foreign matter 15 can emit light at a predetermined brightness. In the pixel with the foreign matter 15, the area of ​​the second region P2 is smaller than the area of ​​the first region P1, so the current density for driving the second region P2 is larger accordingly, which automatically compensates for the reduction in the light-emitting area caused by only the second region emitting light, and the brightness of the pixel can be maintained to a certain degree. This makes it possible to make the dark spot 20 (FIG. 12) less noticeable to the human eye.

[0055] Fig. 12 is a schematic diagram for explaining an image displayed on a screen by a light-emitting element 91 according to a comparative example. Fig. 13 is a schematic diagram for explaining an image displayed on a screen by a light-emitting element 1 according to embodiment 1. Fig. 14 is a schematic diagram for explaining an image displayed on a screen by a light-emitting element 81 according to another comparative example. Components similar to those described above are given the same reference symbols, and detailed descriptions of these components will not be repeated.

[0056] In the light emitting element 91, the light emitting layer 94 has only the first region P1. In the light emitting element 81, the light emitting layer 84 has only the second region P2.

[0057] [Table 1] As shown in Table 1, the power consumption of a display including a light-emitting element 91 in which the light-emitting layer 94 has only the first region P1 is taken as 100%. In this light-emitting element 91, the inorganic medium portion becomes thin, and therefore non-emitting pixels occur due to QD degradation caused by foreign matter 15 as shown in FIG.

[0058] In the case of the light-emitting element 81 in which the light-emitting layer 84 has only the second region P2, the density of the quantum dots 5 is low, making it difficult to inject current, resulting in a decrease in light-emitting efficiency (which is half the light-emitting efficiency of the light-emitting element 91 having only the first region P1), and the power consumption of the display is 200%. On the other hand, the inorganic compound 10 in the inorganic medium portion is thick, providing strong protection for the quantum dots 5. As a result, the quantum dots 5 are not deteriorated by the foreign matter 15, and no non-light-emitting pixels are produced, as shown in FIG.

[0059] In the light-emitting element 1 according to the first embodiment, in a pixel without a foreign substance 15, only the first region P1 (area ratio 0.9) emits light. The second region P2 does not contribute to light emission. Therefore, the drive current of the first region P1 is increased (1 / 0.9 times) to obtain the same brightness as the light-emitting element 91 having only the first region P1, so that the power consumption of the light-emitting element 1 is higher than that of the light-emitting element 91.

[0060] In a pixel with a foreign substance 15, the first region P1 does not emit light because the protection of the quantum dots 5 is weak. Therefore, it is driven only by the second region P2 (area ratio 0.1). Therefore, the current driving the pixel becomes large (1 / 0.1 x 2 = 20 times), but since there are very few pixels with foreign substances 15 compared to pixels without foreign substances 15, they do not contribute to the power consumption of the entire display.

[0061] In order to reduce the power consumption of the display according to this embodiment to 150% or less, the area ratio of the second region P2 should be 0.33 or less. Moreover, in order to ensure the luminance of the pixel where the foreign matter 15 is present, it is desirable that the area ratio of the second region P2 be 0.1 or more.

[0062] That is, the area ratio of the second region P2 to the total area of ​​the first region P1 and the second region P2 is preferably 10% to 33%. For example, in any cross section along the stacking direction of the light-emitting layer 4, the area of ​​the second region P2 is preferably 10% to 33% of the total area of ​​the first region P1 and the second region P2.

[0063] Fig. 15 is a diagram for explaining the density of the quantum dots 5 formed in the first region P1 provided in the light-emitting layer 4 of the light-emitting element 1. Fig. 16 is a diagram for explaining the density of the quantum dots 5 formed in the second region P2 provided in the light-emitting layer 4.

[0064] The configuration of the light-emitting element 1 according to the embodiment 1 can be verified by a cross-sectional TEM (Transmission Electron Microscopy). The density of the quantum dots 5 can be determined by the area filling rate (the ratio of the cross-sectional area of ​​the quantum dots 5 to the total area) of the cross section along the stacking direction of the light-emitting layer 4.

[0065] In the case of closest packing (quantum dots 5 are spherical), the areal packing ratio is 91%. If the particle diameter of the quantum dots 5 is d (= 5 nm) and the distance between the quantum dots 5 is L, the areal packing ratio is

number

[0066] In view of the above, the area filling rate of the first region P1 is preferably 63% to 91%. Moreover, the density of the quantum dots 5 in the second region P2 is preferably 30% to 46%.

[0067] When the quantum dot 5 has a cubic shape, the diameter d (=5 nm) is taken as the length of one side of the cube, and the area filling rate in the case of closest packing is taken as 100%, resulting in the following range.

[0068] That is, the area filling rate of the first region P1 is preferably 69% to 100%. The density of the quantum dots 5 in the second region P2 is preferably 30% to 51%.

[0069] 17 is a cross-sectional view of a light-emitting element 1A according to a modified example of embodiment 1. Components similar to those described above are given the same reference characters, and detailed description of these components will not be repeated.

[0070] The light-emitting element 1A includes a first electrode 2, a second electrode 3, and a light-emitting layer 4A having a plurality of quantum dots 5 between the first electrode 2 and the second electrode 3. When viewed in the stacking direction from the first electrode 2 to the second electrode 3, the light-emitting layer 4A includes a first region P1 in which the first light-emitting layer 6 is provided, and a second region P2A in which the second light-emitting layer 8A is provided.

[0071] The density of the quantum dots 5 along the stacking direction in the second light-emitting layer 8A is similar to the density of the quantum dots 5 along the stacking direction in the first light-emitting layer 6. However, the density of the quantum dots 5 along a crossing direction intersecting the stacking direction in the second light-emitting layer 8A is lower than the density of the quantum dots 5 along the crossing direction in the first light-emitting layer 6.

[0072] Thus, the second region P2A has substantially the same QD density along the vertical direction as the first region P1, and only the QD density along the horizontal direction is smaller. Water and oxygen due to foreign matter diffuses only into the first region P1, and does not diffuse into the second region P2A.

[0073] 18 is a graph showing the relationship between voltage and luminance for the operation of light emitting element 1A. Components similar to those described above are given the same reference numerals, and detailed descriptions of these components will not be repeated.

[0074] Curve C3 shows the voltage-luminance characteristics of the quantum dots 5 in the first region P1, which has a high QD density along the intersecting direction of the light-emitting layer 4A. Curve C4 shows the voltage-luminance characteristics of the quantum dots 5 in the second region P2A, which has a low QD density along the intersecting direction of the light-emitting layer 4A.

[0075] Since the first region P1 and the second region P2A have the same QD density in the vertical direction, both have a light emission threshold voltage V th1 (=V th2 ) However, since the QD density in the lateral direction is lower in the second region P2A than in the first region P1, the luminance at the same voltage is lower for the quantum dots 5 in the second region P2A, as shown by curve C4 in FIG.

[0076] In this way, since the light emission threshold voltage can be made the same in the first region P1 and the second region P2A, the drive voltage for the pixel having the foreign matter can be reduced.

[0077] Fig. 19 is a cross-sectional view showing the operation of light-emitting element 1A when no foreign matter is present. Fig. 20 is a graph showing the relationship between voltage and brightness for the operation of light-emitting element 1A when no foreign matter is present. Components similar to those described above are given the same reference numerals, and detailed descriptions of these components will not be repeated.

[0078] When the foreign matter 15 has not penetrated into the light-emitting layer 4A, the voltage V th1 ~V 1max Both the first region P1 and the second region P2A are driven in the range of 0.1 V to 1.0 V. Then, the luminance becomes the sum of the luminance of the quantum dots 5 in the first region P1 and the luminance of the quantum dots 5 in the second region P2A, as shown by the curve C5.

[0079] Fig. 21 is a cross-sectional view showing the operation of light-emitting element 1A when a foreign object is present. Fig. 22 is a graph showing the relationship between voltage and brightness regarding the operation of light-emitting element 1A when a foreign object is present. Components similar to those described above are given the same reference numerals, and detailed descriptions of these components will not be repeated.

[0080] When a foreign object 15 has entered the light-emitting layer 4, only the second region P2A is driven. th2 ~V 2max The second region P2A is made to emit light by driving it in the range. Since the second region P2A has a lower luminance at the same voltage than the first region P1, the luminance is compensated for by driving it at a high voltage. At this time, the first region P1 does not emit light.

[0081] As a driving method, after manufacturing a display including the light-emitting element 1A, all pixels are V 1max When the brightness is L max By finding pixels that do not reach this threshold, the presence or absence of a foreign object is determined and the result is fed back to the drive.

[0082] 23 to 29 are cross-sectional views showing a manufacturing method of the light-emitting element 1 according to embodiment 1. Components similar to those described above are given the same reference characters, and detailed description of these components will not be repeated.

[0083] First, the first electrode 2 to the hole transport layer 13 are formed by a general method such as vapor deposition, sputtering, coating, or inkjet, and the portion of the hole transport layer 13 corresponding to the first region P1 is covered with a first resist layer 16 as shown in FIG. 23.

[0084] Then, as shown in FIG. 24, the second light emitting layer 8 in the second region P2 is formed by a method such as coating.

[0085] Next, the first resist layer 16 is removed from the hole transport layer 13 as shown in FIG.

[0086] 26, the second light-emitting layer 8 in the second region P2 is covered with the second resist layer 17. In the second light-emitting layer 8 in the second region P2, the density of the quantum dots 5 is low and the quantum dots 5 are strongly protected, so that the quantum dots 5 are not easily deteriorated by application and peeling of the second resist layer 17.

[0087] Then, as shown in FIG. 27, the first light-emitting layer 6 is formed in the first region P1 by a method such as coating.

[0088] Next, as shown in FIG. 28, the second resist layer 17 is removed from the second light-emitting layer 8.

[0089] Thereafter, the electron transport layer 14 and the second electrode 3 are formed by a general method such as vapor deposition, sputtering, coating, or inkjet, to complete the light emitting device 1.

[0090] The quantum dot solution for forming the first light-emitting layer 6 in the first region P1 and the quantum dot solution for forming the second light-emitting layer 8 in the second region P2 may be any of the following solutions.

[0091] In the case of an inorganic solution, the quantum dots 5 and a ZnS precursor (zinc thiourea, etc.) are mixed and applied (solvent: DMF (N,N-dimethylformamide), etc.), and the ZnS precursor is reacted by heating at 250°C for 30 minutes to form ZnS. The density of the quantum dots 5 in the ZnS can be changed by changing the ratio between the quantum dots 5 and the ZnS precursor.

[0092] In the case of an organic solution, a dispersion solution (solvent: hexane, octane, etc.) of quantum dots 5 having organic ligands is applied. After application, heating may be performed to volatilize the solvent.

[0093] In this way, by producing the second region P2 before the first region P1, the second light-emitting layer 8 having a thick layer of inorganic compound 10 having a protective function is formed before the first light-emitting layer 6. This prevents the second light-emitting layer 8 from being deteriorated by subsequent steps. In particular, when the ZnS of the second light-emitting layer 8 is formed by heating a solution containing a ZnS precursor, the above-mentioned production method makes it difficult for damage caused by the heating to propagate to the first light-emitting layer 6 and the like.

[0094] 30 is a plan view of the display device 18 according to embodiment 1. Components similar to those described above are given the same reference symbols, and detailed description of these components will not be repeated.

[0095] The display device 18 includes a substrate 19, and a red light emitting element 12R, a green light emitting element 12G, and a blue light emitting element 12B on the substrate 19. Each of the red light emitting element 12R, the green light emitting element 12G, and the blue light emitting element 12B is configured similarly to the light emitting element 1 described above.

[0096] That is, the red light emitting element 12R has a first light emitting layer 6R corresponding to the first region P1R having a high density of quantum dots 5 and a second light emitting layer 8R corresponding to the second region P2R having a low density of quantum dots 5. The green light emitting element 12G has a first light emitting layer 6G corresponding to the first region P1G having a high density of quantum dots 5 and a second light emitting layer 8G corresponding to the second region P2G having a low density of quantum dots 5. The blue light emitting element 12B has a first light emitting layer 6B corresponding to the first region P1B having a high density of quantum dots 5 and a second light emitting layer 8B corresponding to the second region P2B having a low density of quantum dots 5.

[0097] The ratio between the area of ​​the first region P1R and the area of ​​the second region P2R, the ratio between the area of ​​the first region P1G and the area of ​​the second region P2G, and the ratio between the area of ​​the first region P1B and the area of ​​the second region P2B are equal to each other.

[0098] Each light-emitting element of the display device 18 according to this embodiment is Books It may be manufactured by the same manufacturing method as the light-emitting element 1 according to the embodiment. Here, in the manufacturing method of the display device 18, the first electrode 2 and the light-emitting layer 4 of the light-emitting element 1 may be formed for each sub-pixel region of the substrate 19, and the remaining layers may be formed in common to the multiple sub-pixel regions.

[0099] In this case, for example, the light-emitting layer 4 of each light-emitting element of the display device 18 may be formed by patterning using a resist. For example, in the manufacturing method of the display device 18 according to this embodiment, a substrate 19 having a plurality of sub-pixel regions is prepared, and the first electrode 2 is formed for each sub-pixel region and the hole transport layer 13 is formed in common to the plurality of sub-pixel regions on the substrate 19. Next, a first resist layer 16 is formed for each sub-pixel region. Next, a second light-emitting layer 8 is formed in common to the plurality of sub-pixel regions by the above-mentioned method. Next, the second light-emitting layer 8 is patterned by removing the first resist layer 16. Next, a second resist layer 17 is formed at a position including the upper surface of the second light-emitting layer 8. Next, a first light-emitting layer 6 is formed in common to the plurality of sub-pixel regions by the above-mentioned method. Next, the first light-emitting layer 6 is patterned by removing the second resist layer 17. Next, the remaining electron transport layer 14 and second electrode 3 are formed in common to the plurality of sub-pixel regions. In this manner, the display device 18 may be manufactured. The patterning of the first light-emitting layer 6 and the second light-emitting layer 8 in each light-emitting element of the display device 18 may be performed for each light-emitting element having the same emission wavelength.

[0100] 31 is a plan view of a display device 18A according to a modified example. Components similar to those described above are designated by the same reference numerals, and detailed description of these components will not be repeated.

[0101] In the display device 18A, among the red light emitting element 12R, the green light emitting element 12G, and the blue light emitting element 12B, only the blue light emitting element 12B is configured in the same manner as the light emitting element 1 described above.

[0102] That is, the red light emitting element 12R has only the first region P1R having a high density of quantum dots 5. The green light emitting element 12G has only the first region P1G having a high density of quantum dots 5. And the blue light emitting element 12B has both the first region P1B having a high density of quantum dots 5 and the second region P2B having a low density of quantum dots 5.

[0103] The reason why the second region P2B having a low density of quantum dots 5 is provided only in the blue light-emitting element 12B is that the quantum dots 5 that emit blue light in the blue light-emitting element 12B are more susceptible to deterioration by oxygen, moisture, etc. than the quantum dots 5 in the red light-emitting element 12R and the green light-emitting element 12G.

[0104] Fig. 32 is a plan view of a display device 18B according to another modified example. Fig. 33 is a graph showing the energy levels of red light emitting element 12R, green light emitting element 12G, and blue light emitting element 12B provided in display device 18B. Components similar to those described above are given the same reference symbols, and detailed descriptions of these components will not be repeated.

[0105] Of the red light emitting element 12R, the green light emitting element 12G, and the blue light emitting element 12B, the light emitting element having the shorter emission wavelength is designated as a short wavelength element, and the light emitting element having the longer emission wavelength is designated as a short wavelength element. element is defined as a long wavelength element. Here, in at least one combination of the short wavelength element and the long wavelength element, a cross section of the light emitting layer 4 of the short wavelength element is compared with a cross section of the light emitting layer 4 of the long wavelength element in any cross section along the stacking direction of the short wavelength element or the long wavelength element of the display device 18B. In this case, in the cross section, the ratio of the area of ​​the second region P2R, P2G, or P2B to the total area of ​​the light emitting layer 4 of the short wavelength element is smaller than the ratio of the area of ​​the second region P2R, P2G, or P2B to the total area of ​​the light emitting layer 4 of the long wavelength element.

[0106] For example, the red light emitting element 12R has a first light emitting layer 6R corresponding to the first region P1R where the density of the quantum dots 5 is high and a second light emitting layer 8R corresponding to the second region P2R where the density of the quantum dots 5 is low. The green light emitting element 12G has a first light emitting layer 6G corresponding to the first region P1G where the density of the quantum dots 5 is high and a second light emitting layer 8G corresponding to the second region P2G where the density of the quantum dots 5 is low. The blue light emitting element 12B has a first light emitting layer 6B corresponding to the first region P1B where the density of the quantum dots 5 is high and a second light emitting layer 8B corresponding to the second region P2B where the density of the quantum dots 5 is low.

[0107] The ratio of the area of ​​the second region P2B to the total area of ​​the first region P1B and the second region P2B is smaller than the ratio of the area of ​​the second region P2G to the total area of ​​the first region P1G and the second region P2G. The ratio of the area of ​​the second region P2G to the total area of ​​the first region P1G and the second region P2G is smaller than the ratio of the area of ​​the second region P2R to the total area of ​​the first region P1R and the second region P2R. That is, the area ratios of the second regions P2R, P2G, and P2B are largest in the order of the second region P2R, the second region P2G, and the second region P2B.

[0108] In the case where the hole transport layer (HTL) 13 and the electron transport layer (ETL) 14 are common to each color, the shorter the emission wavelength (the larger the band gap and the shallower the CBM (Conduction Band Minimum)), the more likely it is that there will be a shortage of electrons and an excess of holes. For this reason, the carrier balance is more likely to be achieved even in the second regions P2R, P2G, and P2B, where the density of the quantum dots 5 is low (the inorganic compound is effectively thick, and the injection of holes, which have a lower mobility than electrons, can be suppressed). Therefore, the shorter the emission wavelength, the higher the luminance of the second regions P2R, P2G, and P2B can be, and the smaller the area ratio of the second regions P2R, P2G, and P2B can be. In other words, the shorter the emission wavelength, the larger the area ratio of the first regions P1R, P1G, and P1B can be, and the lower the power consumption of the display can be.

[0109] Therefore, the area ratio of the first region of the light emitting element having a shorter emission wavelength is larger than the area ratio of the first region of the light emitting element having a longer emission wavelength. That is, for example, the area ratio of the first region P1B of the blue light emitting element 12B having a shorter emission wavelength is larger than the area ratios of the first region P1R and the first region P1G of the red light emitting element 12R and the green light emitting element 12G having a longer emission wavelength. And, the area ratio of the first region P1G of the green light emitting element 12G having a shorter emission wavelength is larger than the area ratio of the first region P1R of the red light emitting element 12R having a longer emission wavelength.

[0110] (Embodiment 2) 34 is a plan view of a display device 18C according to embodiment 2. Components similar to those described above are given the same reference symbols, and detailed description of these components will not be repeated.

[0111] The display device 18C includes a substrate 19, and a red light emitting element 12R, a green light emitting element 12G, and a blue light emitting element 12B on the substrate 19. In any cross section along the stacking direction of the light emitting layer 4 of the red light emitting element 12R, the first region P1R is sandwiched between the second regions P2R. In any cross section along the stacking direction of the light emitting layer 4 of the green light emitting element 12G, the first region P1G is sandwiched between the second regions P2G. In any cross section along the stacking direction of the light emitting layer 4 of the blue light emitting element 12B, the first region P1B is sandwiched between the second regions P2B.

[0112] The second region P2R surrounds the first region P1R in the stacking direction of the light-emitting layer 4. The second region P2G surrounds the first region P1G in the stacking direction. The second region P2B surrounds the first region P1B in the stacking direction of the light-emitting layer 4.

[0113] Foreign matter and impurities are likely to enter the periphery of the red light emitting element 12R, the green light emitting element 12G, and the blue light emitting element 12B from the cross section of the light emitting layer 4, and the quantum dots 5 are likely to deteriorate. For this reason, the quantum dots 5 can be protected from deterioration by forming the second regions P2R, P2G, and P2B on the periphery of the red light emitting element 12R, the green light emitting element 12G, and the blue light emitting element 12B, respectively. Although the case where all the light emitting elements have the above structure is illustrated, this is not necessary, and the above effect can be achieved as long as even one light emitting element has the above structure. Furthermore, it is not necessary to confirm the structure in multiple cross sections in the cross section, and it is sufficient to confirm the above structure in at least one cross section. This is because the above effect is achieved at least in that cross section.

[0114] (Embodiment 3) Fig. 35 is a schematic diagram showing the average density of quantum dots 5 in 20 divided regions Q1 to Q20 of the light-emitting layer 4 of the light-emitting element 1 according to embodiment 3. Fig. 36 is a histogram showing the average density of quantum dots 5 in the light-emitting layer 4. Components similar to those described above are given the same reference symbols, and detailed description of these components will not be repeated.

[0115] In any cross section of the light emitting layer 4 along the stacking direction, a range of 600 nm in a direction perpendicular to the stacking direction is divided into 20 divided regions Q1 to Q20 with a width of 30 nm. Furthermore, for any divided region among the divided regions Q1 to Q20 and any other divided region, a first average density D1 representing the average density of quantum dots in the arbitrary divided region and a second average density D2 representing the average density of quantum dots in the arbitrary divided region are determined to satisfy D2<0.7×D1. If any one of many combinations of any divided region among the divided regions Q1 to Q20 and any other divided region satisfies D2<0.7×D1, the light emitting layer 4 is deemed to satisfy condition 1 of D2<0.7×D1.

[0116] In this case, among the divided regions Q1 to Q20 of the light-emitting layer 4, the region having a density of (D1+D2) / 2 or more can be regarded as the first region P1, and the region having a density less than (D1+D2) / 2 can be regarded as the second region P2. Alternatively, an arbitrarily determined density value may be designated as D3, and the region having a density of D3 or more may be regarded as the first region P1, and the region having a density less than D3 may be regarded as the second region P2. When the divided regions Q1 to Q20 of the light-emitting layer 4 satisfy the above-mentioned condition 1 when calculated by any one of the methods, the light-emitting layer 4 can be regarded as having a first light-emitting layer 6 and a second light-emitting layer 8 having a lower density of quantum dots 5 than the first light-emitting layer 6. The width of the divided regions Q1 to Q20 may be 20 nm to 40 nm, which is about two to three times the particle diameter of the quantum dots 5.

[0117] The density of the quantum dots 5 is determined by image processing of a cross-sectional TEM image, and is the ratio of the quantum dot area in a divided region of a certain area (the above-mentioned certain width × layer thickness), and is classified into about 10 classes from density 0 to maximum. In addition, when one quantum dot straddles the boundary between adjacent divided regions, the area of ​​one quantum dot is divided at the boundary line, and the divided amount is counted as the area of ​​the quantum dot in each region.

[0118] In addition, when the average density of the quantum dots 5 in each of the divided regions Q1 to Q20 is divided into 10 classes from 0 to maximum, a histogram obtained by integrating the number of divided regions for each class satisfies condition 2 that the histogram has at least two maximum values.

[0119] In this case, among the divided regions Q1 to Q20 of the light-emitting layer 4, the region equal to or greater than (D1+D2) / 2 can be regarded as the first region P1, and the region less than (D1+D2) / 2 can be regarded as the second region P2. In other words, when the divided regions Q1 to Q20 of the light-emitting layer 4 satisfy the above condition 2, the light-emitting layer 4 can be regarded as having a first light-emitting layer 6 and a second light-emitting layer 8 having a lower density of quantum dots 5 than the first light-emitting layer 6.

[0120] In FIG. 35, the average density of the quantum dots 5 in each of the divided regions Q1 to Q20 is shown as a numerical value.

[0121] For example, when considering a combination of a divided region Q2 in which the average density of quantum dots 5 is 9 and a divided region Q16 in which the average density of quantum dots 5 is 4 among many combinations of any divided region among the divided regions Q1 to Q20 and any other divided region, the first average density D1=9, the second average density D2=4, and therefore 0.7×D1=6.3, which satisfies the condition 1 of D2<0.7×D1. The histogram shown in FIG. 36 has two maximum values ​​of density 5 and density 8, and therefore satisfies the condition 2. Therefore, the light emitting layer 4 according to this embodiment can be regarded as having a first light emitting layer 6 and a second light emitting layer 8. The threshold between the first region P1 and the second region P2 is (D1+D2) / 2=6.5.

[0122] Fig. 37 is a schematic diagram showing the average density of quantum dots 5 in the light-emitting layer 4 according to another example. Fig. 38 is a histogram showing another average density of quantum dots 5 in the light-emitting layer 4. Components similar to those described above are given the same reference symbols, and detailed description of these components will not be repeated.

[0123] In FIG. 37, the average density of the quantum dots 5 in each of the divided regions Q1 to Q20 according to another example is shown numerically.

[0124] For example, when considering a combination of a divided region Q8 in which the average density of quantum dots 5 is 9 and a divided region Q18 in which the average density of quantum dots 5 is 7 among many combinations of any divided region among the divided regions Q1 to Q20 and any other divided region, the first average density D1=9, the second average density D2=7, and therefore 0.7×D1=6.3, which does not satisfy the condition 1 of D2<0.7×D1. However, the histogram shown in FIG. 38 has two maximum values ​​of density 7 and density 9, and therefore satisfies the condition 2. Therefore, the light emitting layer 4 according to this embodiment can be regarded as having a first light emitting layer 6 and a second light emitting layer 8. The threshold between the first region P1 and the second region P2 is (D1+D2) / 2=8.

[0125] Fig. 39 is a schematic diagram showing the average density of quantum dots 5 in a light-emitting layer 4 according to yet another example. Fig. 40 is a histogram showing still another average density of quantum dots 5 in the light-emitting layer 4. Components similar to those described above are given the same reference characters, and detailed description of these components will not be repeated.

[0126] In FIG. 39, the average density of the quantum dots 5 in each of the divided regions Q1 to Q20 according to yet another embodiment is shown numerically.

[0127] The histogram shown in FIG. 40 does not satisfy condition 2 because it has one maximum value of density 8. However, when considering a combination of a divided region Q5 in which the average density of quantum dots 5 is 9 and a divided region Q15 in which the average density of quantum dots 5 is 6 among many combinations of any divided region among the divided regions Q1 to Q20 and any other divided region, the first average density D1=9, the second average density D2=6, and therefore 0.7×D1=6.3, which satisfies condition 1 of D2<0.7×D1. Therefore, the light emitting layer 4 according to this embodiment can be regarded as having a first light emitting layer 6 and a second light emitting layer 8. The threshold between the first region P1 and the second region P2 is (D1+D2) / 2=7.5.

[0128] Fig. 41 is a schematic diagram showing still another average density of the quantum dots 5 in the light-emitting layer according to the comparative example. Fig. 42 is a histogram showing still another average density of the quantum dots 5 in the light-emitting layer according to the comparative example. Components similar to those described above are given the same reference symbols, and detailed descriptions of these components will not be repeated.

[0129] In FIG. 41, the average density of the quantum dots 5 in each of the divided regions Q1 to Q20 according to the comparative example is shown as a numerical value.

[0130] For example, when considering a combination of a divided region Q16 having an average density of quantum dots 5 of 9 and a divided region Q2 having an average density of quantum dots 5 of 7 among many combinations of any divided region among the divided regions Q1 to Q20 and any other divided region, the first average density D1=9, the second average density D2=7, and therefore 0.7×D1=6.3, which does not satisfy condition 1 of D2<0.7×D1. The histogram shown in FIG. 42 has one maximum value of density 8, and therefore does not satisfy condition 2. For this reason, the light emitting layer according to the comparative example cannot be regarded as having a first light emitting layer 6 and a second light emitting layer 8.

[0131] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. The technical scope of the present invention also includes embodiments obtained by appropriately combining the technical means disclosed in the different embodiments. Furthermore, new technical features can be formed by combining the technical means disclosed in the respective embodiments. [Explanation of symbols]

[0132] 1 Light emitting element 2 1st electrode 3 Second electrode 4. Light-emitting layer 5. Quantum dots 6 First light-emitting layer 8 Second light-emitting layer 10 Inorganic compounds (inorganic matrices) 12R Red light emitting element 12G Green light emitting element 12B Blue light emitting element 18 Display Devices P1 1st area P2 2nd area Q1~Q20 divided area

Claims

1. a first electrode, a second electrode, and a light emitting layer having a plurality of quantum dots between the first electrode and the second electrode; the light emitting layer has, when viewed in a stacking direction that is a direction from the first electrode to the second electrode, a first region in which a first light emitting layer is provided and a second region in which a second light emitting layer is provided, the density of the quantum dots in the second light-emitting layer is lower than the density of the quantum dots in the first light-emitting layer; The second light-emitting layer is a light-emitting element in which spaces between the quantum dots are filled with an inorganic matrix.

2. 2. The light-emitting element of claim 1, wherein when a range of 600 nm in a cross section of the light-emitting layer along the stacking direction is divided into 20 divided regions with a width of 30 nm, a first average density D1 of quantum dots in a first divided region among the divided regions and a second average density D2 of quantum dots in a second divided region that is a divided region different from the first divided region satisfy D2 < 0.7 × D1.

3. 3. The light-emitting element according to claim 1, wherein when a range of 600 nm in any cross section of the light-emitting layer along the stacking direction is divided into 20 divided regions of 30 nm width in a direction perpendicular to the stacking direction, and the average density of quantum dots in each of the divided regions is divided into 10 classes from 0 to maximum, a histogram obtained by accumulating the number of the divided regions for each class has at least two maximum values.

4. The light-emitting element according to claim 1 , wherein the first region is sandwiched between the second regions in any cross section of the light-emitting layer taken along the stacking direction.

5. The light-emitting element according to claim 1 , wherein the second region surrounds the first region when viewed in the stacking direction.

6. 3. The light-emitting element according to claim 1, wherein in any cross section of the light-emitting layer along the stacking direction, the area of ​​the second region is 10% or more and 33% or less of the total area of ​​the first region and the second region.

7. 3 . The light-emitting element according to claim 1 , wherein an area filling rate of the quantum dots in the first light-emitting layer is 63% or more and 91% or less in any cross section along the stacking direction of the first light-emitting layer.

8. 3 . The light-emitting element according to claim 1 , wherein an area filling rate of the quantum dots in the second light-emitting layer is 30% or more and 46% or less in any cross section along the stacking direction of the second light-emitting layer.

9. The light-emitting device according to claim 1 , wherein the light-emitting layer is filled with the inorganic matrix.

10. The inorganic matrix has a thickness of 1000 nm in a plane direction intersecting the lamination direction. ２ 3. The light-emitting device according to claim 1, wherein the light-emitting device has a continuous film having an area of ​​at least 100 nm.

11. A substrate and a red light emitting element, a green light emitting element, and a blue light emitting element on the substrate, A display device, wherein each of the red light emitting element, the green light emitting element, and the blue light emitting element is the light emitting element according to claim 1 .

12. Regarding any two of the red light emitting element, the green light emitting element, and the blue light emitting element, when the light emitting element having a shorter emission wavelength is defined as a short wavelength element and the light emitting element having a longer emission wavelength is defined as a long wavelength element, The display device described in claim 11, wherein in at least one combination of the short wavelength element and the long wavelength element of the display device, and in any cross section along the stacking direction of the short wavelength element or the long wavelength element, the ratio of the area of ​​the second region to the total area of ​​the light-emitting layer of the short wavelength element is smaller than the ratio of the area of ​​the second region to the total area of ​​the light-emitting layer of the long wavelength element.

13. A substrate and a red light emitting element, a green light emitting element, and a blue light emitting element on the substrate, A display device, wherein only the blue light emitting element is the light emitting element according to claim 1 , among the red light emitting element, the green light emitting element and the blue light emitting element.

14. A method for manufacturing a light-emitting device including a first electrode, a second electrode, and a light-emitting layer having a plurality of quantum dots between the first electrode and the second electrode, the method comprising the steps of: a light emitting layer forming step of forming the light emitting layer having a first region in which a first light emitting layer is provided and a second region in which a second light emitting layer is provided, as viewed in a stacking direction that is a direction from the first electrode to the second electrode; the density of the quantum dots in the second light-emitting layer is lower than the density of the quantum dots in the first light-emitting layer; A method for manufacturing a light-emitting device, wherein the second light-emitting layer has spaces between the quantum dots filled with an inorganic matrix.

15. The light emitting layer forming step includes: a first light-emitting layer forming step of forming the first light-emitting layer; a second light-emitting layer forming step of forming the second light-emitting layer; The method for producing a light-emitting device according to claim 14 , comprising:

16. The method for manufacturing a light-emitting element according to claim 15 , wherein the first light-emitting layer forming step is carried out after the second light-emitting layer forming step.

17. The second light-emitting layer forming step includes: a film formation step of forming a second light-emitting material layer including a second light-emitting material obtained by mixing a precursor of the inorganic matrix and the quantum dots; a heating step of heating the second light-emitting material layer after the film-forming step to form the inorganic matrix from the precursor and obtain the second light-emitting layer; The method for producing a light-emitting device according to claim 15 , comprising:

18. a substrate preparation step of preparing a substrate having a plurality of subpixel regions; a light-emitting element forming step of forming the light-emitting element in each of the sub-pixel regions on the substrate by the light-emitting element manufacturing method according to claim 14; A method for manufacturing a display device comprising the steps of:

19. The light emitting layer forming step in the light emitting element forming step is a resist layer forming step of forming a first resist layer on each of the sub-pixel regions; a second light-emitting material layer forming step of forming a second light-emitting material layer including a second light-emitting material obtained by mixing a precursor of the inorganic matrix and the quantum dots after the resist layer forming step; a second light emitting material layer patterning step of removing the first resist layer and patterning the second light emitting material layer for each of the sub-pixel regions to form the second light emitting layer after the second light emitting material layer forming step; a coating step of forming a second resist layer on an upper surface of the second light-emitting layer after the second light-emitting material layer patterning step; a first light-emitting layer forming step of forming the first light-emitting layer for each of the sub-pixel regions after the coating step; a coating removal step of removing the second resist layer after the first light emitting layer formation step; The method for manufacturing a display device according to claim 18 , comprising:

20. A semiconductor device comprising: a first electrode; a second electrode; and a light-emitting layer having a plurality of quantum dots between the first electrode and the second electrode; the light emitting layer has, when viewed in a stacking direction that is a direction from the first electrode to the second electrode, a first region in which a first light emitting layer is provided and a second region in which a second light emitting layer is provided, the density of the quantum dots in the second light-emitting layer is lower than the density of the quantum dots in the first light-emitting layer; The second light-emitting layer is a light-emitting element including a plurality of the quantum dots and an inorganic matrix therebetween.

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