Display device, light-emitting element manufacturing method, and display device manufacturing method

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 manufacturing method thereof. [Background technology]

[0002] Patent Document 1 discloses a light-emitting device having a light-emitting layer containing 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 containing quantum dots as the light-emitting material, 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] One possible solution to prevent the propagation of foreign matter between quantum dots is to reduce the density of quantum dots in the light-emitting layer. In this case, 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 required to apply to the light-emitting element to achieve 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, wherein the light-emitting layer has, in a stacking direction from the first electrode to the second electrode, a first region in which the 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 aspect of the present disclosure comprises a substrate and red, green, and blue light-emitting elements on the substrate, each of which is a light-emitting element according to one aspect 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 the 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 method for manufacturing a display device according to one aspect 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 aspect of the present disclosure. [Effects 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 luminous layer is reduced. [Brief explanation of the drawings]

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

[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 dots" refers to dots having a maximum width of 100 nm or less. The shape of the quantum dots 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 dots 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 an uneven surface, or a combination thereof.

[0014] Quantum dots are typically made of semiconductors. The semiconductors may have a certain band gap. The semiconductors may be any material capable of emitting light and may include at least the materials described below. The semiconductors may emit red, green, and blue light, respectively. The semiconductors may include, for example, at least one selected from the group consisting of II-VI compounds, III-V compounds, chalcogenides, and perovskite compounds. The II-VI compounds refer to compounds containing Group II and Group VI elements, while the III-V compounds refer to compounds containing Group III and Group V elements. Furthermore, Group II elements may include Group 2 and Group 12 elements, Group III elements may include Group 3 and Group 13 elements, Group V elements may include Group 5 and Group 15 elements, and Group VI 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 containing 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 CsPbX 3 , 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 groups 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 groups using Arabic numerals is based on the current IUPAC system.

[0020] The light-emitting layer 4 has a first region P1 where the first light-emitting layer 6 is provided and a second region P2 where the second light-emitting layer 8 is provided, as viewed in the stacking direction, which is the 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 cross section of the light-emitting layer 4 has the first region P1 where the first light-emitting layer 6 is provided and the second region P2 where the second light-emitting layer 8 is provided. The cut surface can be selected from any plane parallel to the stacking direction, as long as it can be confirmed that the light-emitting layer 4 has the first region P1 where the first light-emitting layer 6 is provided and the second region P2 where 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 made of an inorganic matrix. As used herein, 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 ​​preferably filled in the light-emitting layer 4. The inorganic matrix preferably fills the regions of the light-emitting layer 4 other than the quantum dots 5. The inorganic matrix preferably fills 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 this does not exclude the case where 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 the 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 with an area of ​​at least 100%. A continuous film means a region in one 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, or 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 distances 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 with 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, if the quantum dots 5 have a core / shell structure, the shell concentration may be 0% or more and 58% or less. Furthermore, if 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. Therefore, the concentration of the region combining the inorganic matrix and the shell may be within the range obtained by adding the range of the inorganic matrix concentration to the range of the shell concentration.

[0028] The inorganic matrix is ​​preferably 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 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 weaker than noise.

[0030] The inorganic material constituting the inorganic matrix preferably 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. Examples of the metal sulfide include 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). Examples of the metal oxide include zinc oxide (ZnO), titanium oxide (TiO2), tin oxide (SnO2), tungsten oxide (WO3), and zirconium oxide (ZrO2). The chemical formulas in parentheses after the compound names are representative examples. The composition ratios described in the chemical formulas are preferably stoichiometric, meaning that the actual composition of the compound is the same as the chemical formula, but are not necessarily stoichiometric.

[0031] The above-described 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, and 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 restriction on adding a material different from the main inorganic material as an additive.

[0033] In the second light-emitting layer 8, the spaces between the quantum dots 5 may be further filled with an organic compound. In the first light-emitting layer 6, the spaces between the 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, foreign matter including oxygen and water may cause pixels to become non-luminous.

[0035] When the density of quantum dots 5 is high, the effective thickness of the medium (or inorganic medium) protecting the surface defects of the quantum dots 5 is thin, making the surface of the quantum dots 5 highly active and reactive, and also increasing the number of quantum dots 5 that can fit into a given volume through which oxygen and water diffuse. Therefore, if foreign matter containing oxygen or water gets into a pixel during display manufacturing, the quantum dots 5 can be oxidized in a chain reaction, causing the entire pixel to become non-luminous. In other words, dark spots appear in the image displayed on the display. On the other hand, reducing the density of quantum dots 5 increases the thickness of the inorganic medium around the quantum dots 5, making it difficult to inject current, reducing luminous efficiency and increasing power consumption throughout the display. Therefore, it was not possible to reduce the density of quantum dots 5 across 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 substantial thickness. Therefore, in the second region P2, the QD surface activity is low and less reactive, and the number of quantum dots 5 that can enter a given volume through which oxygen and water diffuse is small. Therefore, even if a foreign substance 15 containing oxygen and water enters the light-emitting layer 4 as shown in FIG. 2, or even if oxidation of the quantum dots 5 in the first region P1 progresses as shown in FIG. 3, oxidation of the quantum dots 5 in the second region P2 is less likely to progress. The darker the hatching color of the quantum dots 5 shown in FIGS. 2 and 3, the more oxidation has progressed. This also 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 higher than that in the second region P2, which makes it easier to inject current into the first light-emitting layer 6 and reduces 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 numerals, and detailed description 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. This makes the surface of the quantum dots 5 highly active and reactive, and a large number of quantum dots 5 can fit into a given volume into which oxygen and water diffuse. Therefore, as shown in FIG. 5, when foreign matter 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 brightness 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. The vertical axis represents the brightness 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 that drives the quantum dots 5 in the first region P1 is, as shown by the curve C1, to Voltage V th1 Next door , the 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 in the first region P1, and the protection of the quantum dots 5 is strengthened, but on the other hand, current injection becomes more difficult and the voltage V becomes higher.

[0047] The voltage V that drives the quantum dots 5 in the second region P2 is V when the luminance L is zero, as shown by the curve C2. th1 voltage V th2 and the luminance L is L max When the voltage V 2max This 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 regarding 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 penetrate into 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 light-emitting element 1 when foreign matter 15 is present. Fig. 11 is a graph showing the relationship between voltage and brightness regarding the operation of light-emitting element 1 when foreign matter 15 is present. Components similar to those described above are given the same reference numerals, and detailed description of these components will not be repeated.

[0051] When the foreign matter 15 penetrates 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 electron level at least on the surface (and inside) of the quantum dots 5 in the first region P1 changes significantly, and current is less likely to be injected into the carrier transport layer that matches the electron level of the unoxidized quantum dots 5. In other words, current is less likely to flow into the first region P1. For this reason, in the above case, 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 in 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 substance 15, and the emitting pixels are determined to have no foreign substance. This determination result is then fed back to the driver of the light-emitting element 1. The driver drives the non-emitting pixels determined to have a foreign substance based on curve C2, and drives the emitting pixels determined to have no foreign substance based on curve C1.

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

[0054] Alternatively, the relationship between drive current and luminance for the first region P1 may be measured in advance, and both pixels without foreign matter 15 and pixels with foreign matter 15 may be driven with a constant drive current based on that measurement. Pixels without foreign matter 15 can emit light at a predetermined luminance. In pixels with foreign matter 15, the area of ​​the second region P2 is smaller than the area of ​​the first region P1, so the current density driving the second region P2 is correspondingly larger. This automatically compensates for the reduction in the luminance area due to only the second region emitting light, and maintains a certain level of pixel luminance. This makes dark spots 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 set to 100%. In this light-emitting element 91, the inorganic medium portion is 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 a light-emitting element 81 whose 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 a 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 foreign matter 15, and no non-light-emitting pixels are produced, as shown in FIG. 14.

[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 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 quantum dots 5 are not well protected. Therefore, only the second region P2 (area ratio 0.1) is used for driving. As a result, the current driving the pixel is large (1 / 0.1 x 2 = 20 times), but since there are far fewer pixels with foreign substances 15 than 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. In addition, the area ratio of the second region P2 is preferably 0.1 or more to ensure the luminance of the pixel where the foreign matter 15 is present.

[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 illustrating 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 illustrating the density of the quantum dots 5 formed in the second region P2 provided in the light-emitting layer 4.

[0064] The structure of the light-emitting device 1 according to embodiment 1 can be verified by cross-sectional transmission electron microscopy (TEM). The density of the quantum dots 5 can be determined by the area filling factor (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 filling rate is 91%. If the particle size of the quantum dots 5 is d (= 5 nm) and the distance between the quantum dots 5 is L, the areal filling rate is

number

[0066] From the above, it is preferable that the area filling rate of the first region P1 is 63% to 91%. Also, it is preferable that the density of the quantum dots 5 in the second region P2 is 30% to 46%.

[0067] When the quantum dots 5 are cubic in 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 device 1A according to a modification of Embodiment 1. Components similar to those described above are denoted by the same reference numerals, 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 a first light-emitting layer 6 is provided, and a second region P2A in which a 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 the intersecting direction intersecting the stacking direction in the second light-emitting layer 8A is lower than the density of the quantum dots 5 along the intersecting direction in the first light-emitting layer 6.

[0072] Thus, the second region P2A has a substantially constant QD density along the vertical direction compared to the first region P1, but a lower QD density along the horizontal direction. Water and oxygen resulting from foreign matter diffuse only into the first region P1, and do 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 device 1 A. Components similar to those described above are designated by similar 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, where the QD density is high along the crossing direction of the light-emitting layer 4A. Curve C4 shows the voltage-luminance characteristics of the quantum dots 5 in the second region P2A, where the QD density is low along the crossing 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 regions have the same 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, the light emission threshold voltage can be made the same in the first region P1 and the second region P2A, so that the drive voltage of 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 there is no foreign matter. Fig. 20 is a graph showing the relationship between voltage and brightness regarding the operation of light-emitting element 1A when there is no foreign matter. 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 1. 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 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 substance 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 this range. Since the brightness of the second region P2A is lower than that of the first region P1 at the same voltage, the brightness is compensated for by driving it at a higher 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 driven by V 1max When the brightness is L max By finding pixels that do not reach this threshold, the presence or absence of foreign matter is determined and the result is fed back to the drive.

[0082] 23 to 29 are cross-sectional views showing a method for manufacturing the light-emitting element 1 according to embodiment 1. Components similar to those described above are given the same reference numerals, 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, as shown in FIG. 25, the first resist layer 16 is removed from the hole transport layer 13.

[0086] 26, the second light-emitting layer 8 in the second region P2 is covered with a 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 less likely to deteriorate due to the 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 ink jetting, thereby completing 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 can be the following solutions.

[0091] In the case of an inorganic solution, quantum dots 5 and a ZnS precursor (such as zinc thiourea) are mixed and applied (solvent: DMF (N,N-dimethylformamide) or the like), and the ZnS precursor is reacted by heating at 250°C for 30 minutes to form ZnS. The density of 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, which is thickly formed with the 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 processes. In particular, when the ZnS of the second light-emitting layer 8 is formed by heating a solution containing a ZnS precursor, the above-described 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 denoted by the same reference numerals, 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 in the same manner as 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 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.

[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 all equal to each other.

[0098] Each light-emitting element of the display device 18 according to this embodiment is Book The display device 18 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 plurality of 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 a method for manufacturing the display device 18 according to this embodiment, a substrate 19 having a plurality of subpixel regions is prepared. On the substrate 19, a first electrode 2 is formed for each subpixel region, and a hole transport layer 13 is formed in common to the plurality of subpixel regions. Next, a first resist layer 16 is formed for each subpixel region. Next, a second light-emitting layer 8 is formed in common to the plurality of subpixel regions by the method described above. 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 subpixel regions by the method described above. 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 subpixel regions. The display device 18 may be manufactured in this manner. 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, of 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 where the density of the quantum dots 5 is high. The green light emitting element 12G has only the first region P1G where the density of the quantum dots 5 is high. And the blue light emitting element 12B has both the first region P1B where the density of the quantum dots 5 is high and the second region P2B where the density of the quantum dots 5 is low.

[0103] The reason why the second region P2B with 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 modification. 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 numerals, and detailed description 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 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 second region P2R, second region P2G, and second region P2B.

[0108] When the hole transport layer (HTL) 13 and electron transport layer (ETL) 14 are common to all colors, a shorter emission wavelength (larger band gap and shallower CBM (Conduction Band Minimum)) tends to result in electron deficiency and hole excess. Therefore, carrier balance is more likely to be achieved even in the second regions P2R, P2G, and P2B, where the density of quantum dots 5 is low (effectively, the inorganic compound is thicker, suppressing the injection of holes, which have lower mobility than electrons). Therefore, the shorter the emission wavelength, the higher the luminance of the second regions P2R, P2G, and P2B, allowing the area ratio of the second regions P2R, P2G, and P2B to be reduced. In other words, a shorter emission wavelength allows the area ratio of the first regions P1R, P1G, and P1B to be increased, reducing the display's power consumption.

[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 regions P1R and P1G of the red light-emitting element 12R and 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 denoted by the same reference numerals, 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, a first region P1R is sandwiched between second regions P2R. In any cross section along the stacking direction of the light-emitting layer 4 of the green light-emitting element 12G, a first region P1G is sandwiched between second regions P2G. In any cross section along the stacking direction of the light-emitting layer 4 of the blue light-emitting element 12B, a first region P1B is sandwiched between second regions P2B.

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

[0113] Foreign matter and impurities are likely to infiltrate the peripheries 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, which can easily deteriorate the quantum dots 5. Therefore, by forming second regions P2R, P2G, and P2B on the peripheries of the red light-emitting element 12R, the green light-emitting element 12G, and the blue light-emitting element 12B, respectively, the quantum dots 5 can be protected from deterioration. While the illustration shows a case in which all light-emitting elements have the above structure, this is not necessary; even if just one light-emitting element has the above structure, the above effect can be achieved. Furthermore, it is not necessary to confirm the structure in multiple cross-sections; it is sufficient to confirm the structure in at least one cross-section. This is because the above effect can be 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 a 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 30-nm-wide divided regions Q1 to Q20. Furthermore, for any of 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 given divided region and a second average density D2 representing the average density of quantum dots in the other divided region are determined to satisfy D2<0.7×D1. If any one of many combinations of any of 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 with a density equal to or greater than (D1 + D2) / 2 can be regarded as the first region P1, and the region with 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 equal to or greater than D3 can be regarded as the first region P1, and the region having a density less than D3 can be regarded as the second region P2. When calculated using any one of the methods, if the divided regions Q1 to Q20 of the light-emitting layer 4 satisfy the above-mentioned condition 1, 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 approximately 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. Furthermore, if one quantum dot straddles the boundary between adjacent divided regions, the area of ​​one quantum dot can be divided at the boundary line, and the divided amount can be calculated as the area of ​​the quantum dot in each region.

[0118] Furthermore, when the average density of quantum dots 5 in each of the divided regions Q1 to Q20 is divided into 10 classes from 0 to the maximum, a histogram obtained by accumulating the number of divided regions for each class satisfies condition 2, that is, 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, among the many combinations of any one of the divided regions Q1 to Q20 and any other divided region, consider the combination of divided region Q2, in which the average density of quantum dots 5 is 9, and divided region Q16, in which the average density of quantum dots 5 is 4. Since the first average density D1 = 9 and the second average density D2 = 4, 0.7 × D1 = 6.3, which satisfies condition 1 of D2 < 0.7 × D1. The histogram shown in FIG. 36 has two maximal values, density 5 and density 8, and therefore satisfies condition 2. Therefore, the light-emitting layer 4 according to this example 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 a 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 numerals, 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 as a numerical value.

[0124] For example, among the many combinations of any one of the divided regions Q1 to Q20 and any other divided region, consider the combination of divided region Q8, in which the average density of quantum dots 5 is 9, and divided region Q18, in which the average density of quantum dots 5 is 7. Since the first average density D1 = 9 and the second average density D2 = 7, 0.7 × D1 = 6.3 is obtained, which does not satisfy condition 1 of D2 < 0.7 × D1. However, the histogram shown in FIG. 38 has two maximal values, densities 7 and 9, and therefore satisfies condition 2. Therefore, the light-emitting layer 4 according to this example 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 yet another average density of quantum dots 5 in the light-emitting layer 4. Components similar to those described above are given the same reference numerals, 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 example is shown numerically.

[0127] 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 is 9, the second average density D2 is 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 example can be regarded as having a first light-emitting layer 6 and a second light-emitting layer 8. The threshold value between the first region P1 and the second region P2 is (D1+D2) / 2=7.5.

[0128] Fig. 41 is a schematic diagram showing yet another average density of quantum dots 5 in a light-emitting layer according to a comparative example. Fig. 42 is a histogram showing yet another average density of quantum dots 5 in a light-emitting layer according to a comparative example. Components similar to those described above are given the same reference numerals, and detailed description 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 numerically.

[0130] For example, among the many combinations of any one of the divided regions Q1 to Q20 and any other divided region, consider the combination of divided region Q16, in which the average density of quantum dots 5 is 9, with divided region Q2, in which the average density of quantum dots 5 is 7. Since the first average density D1=9 and the second average density D2=7, 0.7×D1=6.3, which does not satisfy condition 1 of D2<0.7×D1. Furthermore, the histogram shown in FIG. 42 has one maximum value at a density of 8, and therefore does not satisfy condition 2. Therefore, 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. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment. [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 matrix) 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 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 comprises 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; A display device, wherein the second light-emitting layer has spaces between the quantum dots filled with an inorganic matrix.

2. When any two of the red light emitting element, green light emitting element, and blue light emitting element are defined as a short wavelength element and a long wavelength element, respectively, the following is true:

2. The display device of claim 1, 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.

3. a substrate, and a red light emitting element, a green light emitting element, and a blue light emitting element on the substrate; Among the red light-emitting element, the green light-emitting element, and the blue light-emitting element, only the blue light-emitting element comprises 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; A display device, wherein the second light-emitting layer has spaces between the quantum dots filled with an inorganic matrix.

4. 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: a light-emitting layer forming step of forming the light-emitting layer having a first region where a first light-emitting layer is provided and a second region where 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; the second light-emitting layer has spaces between the quantum dots filled with an inorganic matrix; 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; Including, A method for manufacturing a light-emitting element, wherein the first light-emitting layer forming step is carried out after the second light-emitting layer forming step.

5. A method for manufacturing a light-emitting 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, comprising: a light-emitting layer forming step of forming the light-emitting layer having a first region where a first light-emitting layer is provided and a second region where 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; the second light-emitting layer has spaces between the quantum dots filled with an inorganic matrix; 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; Including, The second light-emitting layer forming step a film-forming step of forming a second light-emitting material layer containing 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; A method for manufacturing a light-emitting element, comprising:

6. a substrate preparation step of preparing a substrate having a plurality of subpixel regions; a light-emitting element manufacturing method 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 in each of the sub-pixel regions on the substrate, the method including: a light-emitting element 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; Including, 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 method for manufacturing a display device, wherein the second light-emitting layer has spaces between the quantum dots filled with an inorganic matrix.

7. The light-emitting layer forming step in the light-emitting element forming step includes: 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 containing 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 6 , comprising:

Images