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

Abstract

The light-emitting element includes a plurality of quantum dots, each of the plurality of quantum dots (7) including: a core (9); and a shell (10) containing the core (9) and having a first dimension (S1) in a first direction (D1) and a second dimension (S2) larger than the first dimension (S1) in a second direction (D2) perpendicular to the first direction (D1). The band gap of the base material (8) is equal to or greater than the band gap of the case (10).

Description

Technical Field

[0001] This disclosure relates to light-emitting elements, display devices, and methods for manufacturing light-emitting elements. Background Technology

[0002] As disclosed in Patent Document 1, it is known that a technique is used to increase the distance between quantum dots by coating the shell of quantum dots with a metal oxide coating, thereby suppressing Foster resonance energy transfer (FRET).

[0003] Existing technical documents Patent documents Patent Document 1: U.S. Patent Application Publication No. 2017 / 0271605 Summary of the Invention The problem the invention aims to solve In Patent Document 1, when the distance between the nuclei of quantum dots is increased by means of a metal oxide coating, the resistance of the light-emitting layer increases and the luminous efficiency may decrease.

[0004] Solution for solving the problem One embodiment of the light-emitting element disclosed herein includes: an anode and a cathode; and a light-emitting layer located between the anode and the cathode, comprising a plurality of quantum dots and a matrix material filling the space between the plurality of quantum dots, wherein each of the plurality of quantum dots comprises: a core; and a shell containing the core, having a first size in a first direction and a second size larger than the first size in a second direction perpendicular to the first direction, wherein the band gap of the matrix material is greater than or equal to the band gap of the shell.

[0005] Invention Effects According to one aspect of this disclosure, a light-emitting element with high luminous efficiency can be achieved. Attached Figure Description

[0006] Figure 1 This is a cross-sectional view showing the schematic configuration of the light-emitting element according to Embodiment 1 of this disclosure.

[0007] Figure 2 It is shown Figure 1 The image shown is a 3D representation of the quantum dots.

[0008] Figure 3 This is a three-dimensional diagram of the first variant of a quantum dot.

[0009] Figure 4 This is a three-dimensional diagram of the second variant of quantum dots.

[0010] Figure 5 This is a three-dimensional diagram of the third variant of quantum dots.

[0011] Figure 6A graph illustrating the relationship between the ratio of the core volume to the shell volume and the emission and absorption spectra of the quantum dot.

[0012] Figure 7 This graph compares the cases where the shell and medium materials are the same, and the cases where the medium's CBM is higher than the shell's CBM.

[0013] Figure 8 This is a cross-sectional view showing an example of a method for forming a light-emitting layer according to Embodiment 2 of this disclosure.

[0014] Figure 9 This is a cross-sectional view of the light-emitting layer and a top view of the plurality of quantum dots involved in Embodiment 2 of this disclosure.

[0015] Figure 10 This is a cross-sectional view of the light-emitting layer according to Embodiment 3 of this disclosure.

[0016] Figure 11 This is an explanatory diagram showing the angle between a surface perpendicular to the stacking direction and the second direction.

[0017] Figure 12 This is a cross-sectional view showing an example of the general configuration of the display device according to Embodiment 4. Detailed Implementation

[0018] The manner in which this disclosure is implemented will be described. For ease of explanation, components that have the same function as those described above will be labeled with the same reference numerals and will not be described again.

[0019] [Implementation Method 1] Figure 1 This is a cross-sectional view showing the schematic configuration of the light-emitting device 101 according to Embodiment 1 of this disclosure. The light-emitting element 101 includes an anode 1, a hole injection layer 2, a hole transport layer 3, a light-emitting layer 4, an electron transport layer 5, and a cathode 6. The light-emitting layer 4 has a plurality of quantum dots 7 and a substrate material 8. The plurality of quantum dots 7 each include a core 9 and a shell 10. The shell 10 contains the core 9.

[0020] The shell 10 has a first dimension S1 in a first direction D1. The shell 10 has a second dimension S2 in a second direction D2. The second direction D2 is perpendicular to the first direction D1. The second dimension S2 is larger than the first dimension S1.

[0021] The first dimension S1 is the dimension from one outer end of the shell 10 to the other outer end of the shell 10 in the first direction D1, and is independent of the presence of the core 9. Similarly, the second dimension S2 is the dimension from one outer end of the shell 10 to the other outer end of the shell 10 in the second direction D2, and is independent of the presence of the core 9.

[0022] The matrix material 8 fills the spaces between multiple quantum dots 7. The band gap of the matrix material 8 is greater than the band gap of the shell 10.

[0023] According to the light-emitting element 101, regarding the second direction D2, since the spacing between the nuclei 9 of the multiple quantum dots 7 can be increased, concerns about low luminous efficiency caused by Foster resonance energy shift can be reduced. Furthermore, regarding the first direction D1, since the distance between the nuclei 9 is not excessive, the increase in resistance of the light-emitting layer 4 in the first direction D1 can be suppressed. According to the light-emitting element 101, the light-emitting layer 4 has a substrate material 8. By protecting the quantum dots 7 with the substrate material 8 capable of encapsulating excitons within them, exciton diffusion and leakage current can be suppressed, achieving a light-emitting element 101 with high luminous efficiency, high current resistance, and high reliability. Therefore, a light-emitting element 101 with high luminous efficiency can be achieved.

[0024] An example of a material for the anode 1 could be ITO (Indium Tin Oxide). An example of a material for the hole injection layer 2 could be a composite of poly(3,4-ethylenedioxythiophene) (PEDOT) and polystyrene sulfonic acid (PSS) (PEDOT:PSS). An example of a material for the hole transport layer 3 could be poly(p-p-dioxythiophene) (abbreviated as "Poly-TPD"). An example of a material for the electron transport layer 5 could be ZnO. An example of a material for the cathode 6 could be Ag.

[0025] The matrix material 8 may contain at least one of SiO2, MgO, ZnO, MgS, ZnS and ZnMgS. Examples of combinations of the material of the core 9 and the material of the shell 10 are as follows (1) to (5).

[0026] (1) A combination of CdSe (material of core 9) and CdS (material of shell 10).

[0027] (2) The combination of CdSe (the material of core 9) and ZnS (the material of shell 10).

[0028] (3) A combination of InP (the material of core 9) and ZnS (the material of shell 10).

[0029] (4) Combination of ZnSe (material of core 9) and ZnS (material of shell 10).

[0030] (5) Combination of ZnTeSe (material of core 9) and ZnS (material of shell 10).

[0031] The shell 10 has a first thickness T1 on one side of the core 9 and a second thickness T2 on the other side of the core 9 in the second direction D2. The first thickness T1 and the second thickness T2 can each be 7.5 nm or more. Therefore, with respect to the second direction D2, the spacing between the core 9 and other cores 9 can be increased on both sides of the core 9.

[0032] The first thickness T1 is the dimension from one end of the core 9 to one outer end of the shell 10 in the second direction D2. The second thickness T2 is the dimension from the other end of the core 9 to the other outer end of the shell 10 in the second direction D2.

[0033] Alternatively, multiple quantum dots 7 can be positioned such that the stacking direction D3 of the anode 1, the light-emitting layer 4, and the cathode 6 aligns with the first direction D1, with two quantum dots 7 positioned relative to each other in the stacking direction D3. In this case, the size of the shell 10 in the stacking direction D3 becomes the first size S1, which is smaller than the second size S2. This avoids increasing the thickness of the light-emitting layer 4 in the stacking direction D3, thus enabling the realization of a low-resistance light-emitting layer 4 and a low-driving-voltage light-emitting element 101.

[0034] Figure 2 It is shown Figure 1 The image shows a 3D view of quantum dot 7. Figure 3 This is a three-dimensional diagram of the first variant of quantum dot 7. Figure 4 This is a three-dimensional diagram of the second variant of quantum dot 7. Figure 5 This is a three-dimensional diagram of the third variant of quantum dot 7. (See diagram below.) Figures 2-4 As shown, the shell 10 can also be a column extending along the second direction D2. Figures 2-4 In all figures, shell 10 is rod-shaped. Regarding the shape of the cross-section orthogonal to the second direction D2, in... Figure 2 The center is circular, in Figure 3 and Figure 4 The two sides are polygons, in Figure 3 The middle part is a quadrilateral, in Figure 4 The center is hexagonal. For example... Figure 5 As shown, shell 10 can also be a plate with its upper surface facing the stacking direction D3 (first direction D1).

[0035] The second size S2 can be more than 2 times but less than 3 times the first size S1. The second size S2 can also be 18 nm or more. In this way, with respect to the second direction D2, the spacing between the nuclei 9 of the multiple quantum dots 7 can be increased, thereby significantly reducing the possibility of low luminous efficiency caused by Foster resonance energy shift. If the second size S2 is less than 3 times the first size S1, the density of the nuclei 9 in the light-emitting layer 4 can be increased, thus enabling a high-brightness light-emitting element 101.

[0036] Figure 6 This is a graph illustrating the relationship between the volume ratio of core 9 to shell 10 and the emission and absorption spectra of quantum dot 7. Figure 6 In the diagram, X represents the emission spectrum of quantum dot 7, and Y represents the absorption spectrum of quantum dot 7. The emission and absorption spectra of quantum dot 7 depend on the ratio of the volume of the core 9 to the volume of the shell 10. This ratio can be less than 20%. Therefore, the likelihood of quantum dot 7 absorbing most of the light emitted by quantum dot 7 can be reduced, thus enabling the realization of a high-efficiency light-emitting element 101. Compared to quantum dot 7 with a rod-shaped shell 10, the volume of the shell 10 of quantum dot 7 with a prism-shaped shell 10 is more easily increased, by the amount of increase being the corner portion excluding the rounded portion.

[0037] Considering the resistance based on the shell 10, in the light-emitting element 101, the quantum dot 7 can be oriented such that the short axis of the quantum dot 7 is parallel to the direction of current flow.

[0038] The substrate material 8 can also be an inorganic substrate material. The substrate material 8 can also contain multiple quantum dots 7. Here, "containing" means, for example, that the substrate material 8 covers part or all of the surface of each of the multiple quantum dots 7. The substrate material 8 can also be a single film that is not separated from any material other than the substrate material 8. Furthermore, when viewed from above, the area of ​​the substrate material 8 can be 1000 nm. 2 The above can also be an integral film continuously linked by chemical bonds of the materials constituting the substrate material 8. The substrate material 8 is formed, for example, by partially or completely filling the spaces formed between the multiple quantum dots 7 contained in the substrate material 8. The light-emitting layer 4 can also have voids. The multiple quantum dots 7 embedded in the substrate material 8 can also exist spaced apart from each other.

[0039] Figure 7 This diagram compares the cases where the materials of shell 10 and medium 11 are the same, and the cases where the CBM of medium 11 is higher than that of shell 10. Medium 11 is filled between multiple quantum dots 7. It can replace CBM with LUMO. CBM is the lower end of the conduction band. LUMO is the energy level of the lowest empty orbital. CBM mainly targets inorganic matter, while LUMO mainly targets organic matter.

[0040] In quantum dot 7, preferably, the band gap of shell 10 is larger than that of core 9, and the CBM of core 9 is close to that of shell 10. If the CBM of medium 11 is deeper than that of shell 10 (corresponding to a higher ionization energy or being far from the vacuum level), there is a concern that energy transfer from that quantum dot 7 to other quantum dots 7 may occur because electrons 12 are emitted outside the shell 10 of a certain quantum dot 7. Therefore, the CBM of medium 11 is the same as that of shell 10, or shallower than that of shell 10 (corresponding to a lower ionization energy or being close to the vacuum level). The matrix material 8 can be considered as medium 11 having the characteristic features of this disclosure.

[0041] For example, when the material of the shell 10 is ZnS, options for the material of the substrate material 8 include MgS and ZnMgS, which are inorganic semiconductors with a CBM shallower than ZnS. When an inorganic semiconductor is used as the material of the substrate material 8, it is possible to suppress the rise in the driving voltage of the light-emitting element 101 caused by the substrate material 8.

[0042] Alternatively, the substrate material 8 can be SiO2, which serves as an insulator. In this case, it is expected that a light-emitting element 101 with high resistance to electrical conduction and high reliability can be achieved.

[0043] The following methods can also be used to form the matrix material 8.

[0044] Quantum dots 7, which are combinations of CdSe (material of core 9) and CdS (material of shell 10), are also referred to as "CdSe / CdS quantum dots". Quantum dots 7, which are combinations of ZnSe (material of core 9) and ZnS (material of shell 10), are also referred to as "ZnSe / ZnS quantum dots". Quantum dots 7, which are combinations of Cu2Se (material of core 9) and Cu2S (material of shell 10), are also referred to as "Cu2Se / Cu2S quantum dots". Regarding the method for forming quantum dots 7 comprising a shell 10 having a first size S1 and a second size S2, a method for forming CdSe / CdS quantum dots is disclosed. On the other hand, ZnSe / ZnS quantum dots can be formed by replacing CdSe / CdS quantum dots with ZnSe / ZnS quantum dots through a cation exchange method. This is because CdSe tends to adopt a wurtzite-type structure, which is an anisotropic crystal system, while ZnSe tends to adopt a zincblende-type structure, which is an isotropic crystal system. Therefore, it is difficult to directly manufacture quantum dots with ZnSe as the core.

[0045] The formation methods of CdSe / CdS quantum dots are shown below, for example.

[0046] Quantum dots 7 were formed using a thermal inkjet printing method. First, 3 g of trioctylphosphine oxide (TOPO), 0.280 g of octadecylphosphonic acid (ODPA), and 0.0060 g of cadmium oxide (CdO) were added to a 50 mL flask and heated to 120 °C, then purged under vacuum for 1 hour. Afterward, the solution was heated to 370 °C under a nitrogen atmosphere to completely dissolve the CdO. A solution containing 0.058 g of Se and 0.360 g of trioctylphosphine (TOP) was then injected and allowed to react for 1 minute, thereby forming CdSe nanocrystals. The size of the CdSe nanocrystals could be easily controlled by adjusting the injection temperature and growth time.

[0047] Next, the obtained CdSe nanocrystals were used as seed crystals to form CdSe / CdS quantum dots. First, a mixture of 67 mg hexylphosphonic acid (HPA), 333 mg ODPA, 3 g TOPO, and 0.1 g CdO was placed in a 50 mL flask and purged under vacuum at room temperature, then heated at 120 °C for 60 minutes. Next, CdO was slowly heated under a nitrogen atmosphere to decompose it and make the solution transparent. The injection solution was prepared at 350 °C. The injection solution was prepared by dissolving sulfur (100 mg) in TOP (1.5 mL) and mixing it with the previously prepared CdSe seed solution (200 μL). CdSe and CdS were grown for 5 minutes to form the final CdSe / CdS quantum dots. The first size S1 and the second size S2 of the shell 10 can be easily adjusted according to the amount of sulfur and CdSe nanocrystals used in the above formation method.

[0048] The methods for forming ZnSe / ZnS quantum dots are described below.

[0049] ZnSe / ZnS quantum dots are formed via a two-stage cation exchange process: CdSe / CdS quantum dots → Cu2Se / Cu2S quantum dots → ZnSe / ZnS quantum dots. First, 10 mg (0.027 mmol) of [Cu(CH3CN)4]PF6 is dissolved in 1 ml of methanol to prepare Cu... + Cation solution. CdSe / CdS quantum dots were dispersed in 5 ml of toluene and mixed into a [Cu(CH3CN)4]PF6 solution. The atomic ratio of Cu to Cd was 3. The resulting mixture was kept at room temperature for 5 minutes and then centrifuged at 3200 rpm to precipitate the Cu2Se / Cu2S quantum dots. After washing with methanol and toluene respectively, the obtained Cu2Se / Cu2S quantum dots were dispersed in 2 ml of TOP to prepare the injection solution for the synthesis of ZnSe / ZnS quantum dots. Zn was prepared by dissolving 2 mmol of ZnCl2 in a solution containing 6 ml of octadecene and 4 ml of oleylamine, degassed at 250°C under a nitrogen atmosphere. 2+Cation solution. The Cu₂Se / Cu₂S quantum dots obtained in the previous process were injected into a Zn solution and reacted in a high-temperature solution for 5 minutes to perform cation exchange. The ZnSe / ZnS quantum dots obtained above were then redeprecipitated with methanol and redispersed in toluene.

[0050] [Implementation Method 2] Figure 2 This is a cross-sectional view showing an example of a method for forming a light-emitting layer according to Embodiment 2 of the present disclosure. An example of a method for forming a light-emitting layer 4 according to Embodiment 2 of the present disclosure includes steps ST1 to ST3.

[0051] To a quantum dot solution obtained by dispersing multiple quantum dots 7 in octane at a concentration of 20 mg / ml, 0.2 M (mol) of zinc ethyl xanthate is added to prepare a coating solution 16. In step ST1, the coating solution 16 is applied to the hole transport layer 3 by spin coating at 2000 rpm. In step ST2, the coating solution 16 is dried to form a zinc ethyl xanthate film 18 with multiple quantum dots 7 dispersed. Since the coating solution 16 evaporates during spin coating, steps ST1 and ST2 can also be performed continuously in one operation. In step ST3, for example, the zinc ethyl xanthate film 18 is reacted by calcining at 160°C for 30 minutes, causing zinc sulfide (ZnS) to transform into the matrix material 8. By performing steps ST1 to ST3, a light-emitting layer 4 is formed.

[0052] In step ST1, methods such as inkjet printing or slot die coating can also be used. Furthermore, step ST2 may include operations different from those in step ST1, such as heating.

[0053] Figure 9 This is a cross-sectional view of the light-emitting layer 4 and a top view of the plurality of quantum dots 7 according to Embodiment 2 of this disclosure. Figure 9 In the top view of multiple quantum dots 7, the AA section corresponds to the section of the light-emitting layer 4.

[0054] When viewed from above, multiple quantum dots 7 can be arranged irregularly in units of no more than 6 quantum dots 7. In other words, when viewed from above, multiple quantum dots 7 can also be arranged in a so-called random configuration in units of no more than 6 quantum dots 7.

[0055] For passing Figure 8The formation of the light-emitting layer 4 using the method shown will be discussed. The volume of the zinc ethyl xanthate film 18 is approximately three times the volume of the substrate material 8. During the drying of the coating solution 16, the zinc ethyl xanthate functions as a spacer to prevent aggregation between the multiple quantum dots 7, thereby hindering the orientation associated with aggregation between the multiple quantum dots 7. Therefore, the multiple quantum dots 7 within the light-emitting layer 4 maintain a random orientation. As a result, the Foster resonance energy shift between the multiple quantum dots 7 can be reduced, thus enabling the realization of a light-emitting element 101 with high luminous efficiency.

[0056] The degree to which multiple quantum dots 7 are irregularly arranged can be controlled by the material of the precursor of the matrix material 8.

[0057] For example, propyl xanthate, butyl xanthate, or combinations thereof, with a molecular weight greater than ethyl xanthate, can be used as precursors for the matrix material 8. Consequently, the thickness of the luminescent layer 4 varies considerably relative to the coating thickness of the coating liquid 16, thus further enhancing the irregularity of the arrangement of the multiple quantum dots 7.

[0058] From an overhead view, multiple quantum dots 7 can be arranged irregularly in units of no more than 6 quantum dots 7, as shown in the reference. Figure 9 As can be seen from the following.

[0059] In the cross-sectional view of the light-emitting layer 4, multiple quantum dots 7 of the same shape are observed to be adjacent to each other. These multiple quantum dots 7 are referred to as segments 17.

[0060] In the light-emitting layer 4, within a range of 100 nm or more in the horizontal direction (perpendicular to the stacking direction D3) and 20 nm or more in the stacking direction D3, every 1 nm 2 The portion of quantum dots 7 observed at a density of 0.005 or more has attracted attention. If the number of quantum dots 7 in the segment 17 contained in this portion is 6 or less, the realization of a light-emitting element 101 with high luminous efficiency can be expected. Therefore, when viewed from above, the multiple quantum dots 7 can be regarded as an irregular configuration with 6 or less units of quantum dots 7.

[0061] When viewed from above, multiple quantum dots 7 can be arranged irregularly in units of three or fewer quantum dots 7. In other words, the number of quantum dots 7 belonging to segment 17 contained in the above-mentioned part can also be three or fewer.

[0062] If precursors with large molecular weights, such as propyl xanthate and butyl xanthate, are used, the reason why the randomness of the arrangement of multiple quantum dots 7 increases is that the volume change during the transition from the zinc sulfide precursor (zinc ethyl xanthate film 18) to zinc sulfide (matrix material 8) becomes larger. For one cycle of steps ST1~ST3, the thickness of the zinc ethyl xanthate film 18, with its large molecular weight, is greater relative to the film thickness of the matrix material 8. This results in a decrease in the density of multiple quantum dots 7 in step ST2, and an increase in the degree of freedom in the orientation of the multiple quantum dots 7, thus increasing the randomness.

[0063] [Implementation Method 3] Figure 10 This is a cross-sectional view of the light-emitting layer 4 of Embodiment 3 of this disclosure. Figure 11 This is an explanatory diagram showing the angle θ between the plane perpendicular to the stacking direction D3 and the second direction D2.

[0064] In at least one of the multiple quantum dots 7, the angle θ between the plane of the anode 1, the light-emitting layer 4, and the cathode 6 perpendicular to the stacking direction D3 and the second direction D2 can also be 10° or more.

[0065] In the case of a light-emitting layer 4 with large orientation deviations of multiple quantum dots 7, the orientation of the multiple quantum dots 7 is not only deviated in the in-plane direction, but also in the direction of electric field application (stack direction D3). At this time, the orientation of the multiple quantum dots 7 may also be deviated in the direction of electric field application.

[0066] When the orientation deviation of multiple quantum dots 7 is large, compared with the case where the orientation deviation of multiple quantum dots 7 is small, the quantum dots 7 on the stacking direction D3 have a higher probability of contact with each other. Therefore, the current can easily flow in the direction of the electric field through the contacting quantum dots 7.

[0067] In particular, when a material with a higher resistance than the material of the shell 10 is used as the substrate material 8, the proportion of current flowing into the quantum dot 7 increases, which helps to achieve a light-emitting element 101 with high luminous efficiency and low driving voltage.

[0068] In the light-emitting layer 4, within a range of 100 nm or more in the horizontal direction and 20 nm or more in the stacking direction D3, every 1 nm 2 Interest has been drawn to the portion of quantum dots 7 observed at a density of 0.005 or higher. If the average angle θ of all quantum dots 7 belonging to this portion is 10° or higher, a light-emitting element 101 with high luminous efficiency can be expected.

[0069] The thickness of the light-emitting layer 4 is 30nm. The light-emitting layer 4 is a two-layer structure of quantum dot 7, with the first dimension S1 being 10nm and the second dimension S2 being 30nm. Figure 11The value of d is obtained by combining S1cosθ and S2sinθ. If d is greater than 15 nm, it can be determined that the quantum dot 7 in the upper layer of the two-layer structure is likely to be in contact with the quantum dot 7 in the lower layer. However, when d = 15 nm, the angle θ is approximately 9.88°. Therefore, an angle θ greater than 10° is effective.

[0070] In the light-emitting layer 4, more than 40% of the quantum dots 7 can have an angle θ of 10° or higher. Alternatively, more than 60% of the quantum dots 7 in the light-emitting layer 4 can have an angle θ of 10° or higher. This allows for the random configuration of multiple quantum dots 7.

[0071] [Implementation Method 4] Figure 12 This is a cross-sectional view showing an example of the schematic configuration of the display device 201 according to Embodiment 4. The display device 201 includes three light-emitting elements 101. These three light-emitting elements 101 emit red, green, and blue light, respectively.

[0072] Three light-emitting elements 101 are formed on a TFT substrate 13 on which a TFT (Thin Film Transistor) is provided, and are separated from each other by insulating partitions 14. Pixel circuits 15 corresponding to the three light-emitting elements 101 are provided on the TFT substrate 13.

[0073] This disclosure is not limited to the embodiments described above, and various modifications can be made within the scope of the claims. Embodiments obtained by appropriately combining the technical solutions disclosed in different embodiments are also included in the technical scope of this disclosure. Furthermore, new technical features can be formed by combining the technical methods disclosed in each embodiment.

[0074] Explanation of reference numerals in the attached figures 1 Anode 2. Hole injection layer 3 Hole transport layer 4. Light-emitting layer 5. Electron transport layer 6 Cathode 7 quantum dots 8. Matrix Material 9 cores 10 shells 11. Medium 12 electrons 13 TFT substrate 14 Next door 15-pixel circuit 16 Coating liquid 17 segments 18-Ethyl xanthate zinc film 101 Light-emitting element 201 Display Device D1 First Direction D2 Second Direction D3 Stacking Direction S1 First Size S2 Second Size T1 First Thickness T2 Second Thickness θ is the angle between the plane perpendicular to the stacking direction and the second direction.

Claims

1. A light-emitting element, characterized in that, include: Anode and cathode; and A light-emitting layer, located between the anode and cathode, comprises multiple quantum dots and a matrix material filling the spaces between the quantum dots. The plurality of quantum dots each comprise: nuclear; as well as A shell containing the core, having a first dimension in a first direction and a second dimension larger than the first dimension in a second direction perpendicular to the first direction. The band gap of the matrix material is greater than or equal to the band gap of the shell.

2. The light-emitting element according to claim 1, characterized in that, In the second direction, the shell has a first thickness on one side further than the core and a second thickness on the other side further than the core. The first thickness and the second thickness are both 7.5 nm or more.

3. The light-emitting element according to claim 1 or 2, characterized in that, The plurality of quantum dots are respectively located at positions such that the stacking direction of the anode, the light-emitting layer, and the cathode is aligned with the first direction. Two of the plurality of quantum dots are located relative to each other in the stacking direction.

4. The light-emitting element according to claim 3, characterized in that, The shell is cylindrical and extends along the second direction.

5. The light-emitting element according to claim 3, characterized in that, The shell is a plate-like structure with its upper surface facing the stacking direction.

6. The light-emitting element according to claim 1 or 2, characterized in that, When viewed from above, the multiple quantum dots are arranged irregularly in units of six or fewer quantum dots.

7. The light-emitting element according to claim 1 or 2, characterized in that, In at least one of the plurality of quantum dots, the angle between the surface of the anode, the light-emitting layer, and the cathode perpendicular to the stacking direction and the second direction is 10° or more.

8. The light-emitting element according to any one of claims 1 to 7, characterized in that, The second size is more than twice and less than three times the first size.

9. The light-emitting element according to any one of claims 1 to 8, characterized in that, The second size is 18nm or larger.

10. The light-emitting element according to any one of claims 1 to 9, characterized in that, The volume ratio of the core to the shell is less than 20%.

11. The light-emitting element according to any one of claims 1 to 10, characterized in that, The matrix material is an inorganic matrix material.

12. A display device, characterized in that, It comprises the light-emitting element as described in any one of claims 1 to 11.

13. A method for manufacturing a light-emitting element, the light-emitting element having a light-emitting layer having a plurality of quantum dots and a matrix material filling the spaces between the plurality of quantum dots, characterized in that, The method for manufacturing the light-emitting element includes: The process of applying a coating solution, wherein the coating solution comprises the plurality of quantum dots and the precursor of the matrix material; The process of drying the coating liquid; and The process of firing the coating liquid and making the precursor into the matrix material. The plurality of quantum dots each comprise: nucleus; and A shell containing the core, having a first dimension in a first direction and a second dimension larger than the first dimension in a second direction perpendicular to the first direction.

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