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

Abstract

According to the present invention, a matrix material (Mx) contains an inorganic semiconductor and an additive, fills space between first quantum dots QD1 (QD1) and second quantum dots (QD2), and has: a first portion located adjacent to the first quantum dots QD1 (QD1); a second portion located adjacent to the second quantum dots (QD2); and a third portion that is located between the first and second portions and in which the concentration of the additive is higher than that in the first and second portions.

Description

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

[0001] The present disclosure relates to a light-emitting element, a display device, and a method for manufacturing a light-emitting element.

[0002] US Pat. No. 6,299,499 discloses quantum dots with fluoride-containing ligands or fluoride anions bound to their surfaces.

[0003] Patent Publication No. 2020-180278 (published November 5, 2020)

[0004] The invention described in Patent Document 1 has a problem in that the durability of the light-emitting element is low.

[0005] A light-emitting element according to one aspect of the present disclosure comprises a light-emitting layer including first quantum dots and second quantum dots, and a matrix material (1) containing an inorganic semiconductor and an additive, (2) filling the space between the first quantum dots and the second quantum dots, and (3) having a first portion adjacent to the first quantum dots, a second portion adjacent to the second quantum dots, and a third portion located between the first portion and the second portion and having a higher concentration of the additive than the first portion and the second portion.

[0006] A method for manufacturing a light-emitting element according to one aspect of the present disclosure includes applying a dispersion containing a precursor of an inorganic semiconductor, an additive, a plurality of quantum dots, and a solvent, and modifying the precursor of the inorganic semiconductor into the inorganic semiconductor so that the crystal growth rate of the inorganic semiconductor is equal to or less than the thermal diffusion rate of the additive.

[0007] According to one aspect of the present disclosure, the durability of the light-emitting element can be improved.

[0008] 14 is a cross-sectional view showing an example of a configuration of a light-emitting device according to an embodiment of the present disclosure. FIG. 1 is a schematic diagram showing an example of a region between quantum dots shown in FIG. 1. FIG. 15 is a schematic diagram showing another example of a region between quantum dots shown in FIG. 1. FIG. 16 is a schematic diagram showing an example of a configuration of the light-emitting layer shown in FIG. 1. FIG. 17 is a schematic diagram showing another example of a configuration of the light-emitting layer shown in FIG. 1. FIG. 18 is a schematic diagram focusing on the first quantum dots and the second quantum dots adjacent to each other shown in FIGS. 4 and 5. FIG. 19 is a diagram showing an example of a concentration distribution of an additive along arrows BC in FIG. 5. FIG. 20 is a schematic diagram showing an example of a dotted additive in the example configuration shown in FIG. 21. FIG. 22 is a flow chart showing an example of a method for manufacturing the light-emitting device shown in FIG. 22. FIG. 23 is a schematic diagram showing an example of a dispersion liquid used in a step of forming the light-emitting layer shown in FIG. 23. FIG. 24 is a flow chart showing an example of a step of forming the light-emitting layer shown in FIG. 24. FIG. 25 is a diagram showing the light-emitting characteristics of a light-emitting device according to an example embodiment of the present disclosure and a light-emitting device of a comparative example. FIG. 26 is a schematic diagram showing an example of a configuration of the light-emitting layer of a light-emitting device according to an embodiment of the present disclosure. FIG. 27 is a schematic diagram showing an example of a dotted additive in the example configuration shown in FIG. 25. FIG. 28 is a schematic diagram focusing on the first quantum dots and the second quantum dots adjacent to each other shown in FIGS. 26 and 27. 1A and 1B are schematic diagrams illustrating modified examples of a light-emitting layer of a light-emitting element according to an embodiment of the present disclosure.

[0009] [Embodiment 1] (Cross-sectional configuration of light-emitting element) Figure 1 is a cross-sectional view showing an example configuration of a light-emitting element according to an embodiment of the present disclosure. As shown in Figure 1, a light-emitting element 10 according to this embodiment includes a first electrode E1 and a second electrode E2 facing each other, and a light-emitting layer Em located between the first electrode E1 and the second electrode E2. The light-emitting element 10 may further include a charge functional layer F1 between the first electrode E1 and the light-emitting layer Em, and may include a charge functional layer F2 between the second electrode E2 and the light-emitting layer Em.

[0010] At least one of the first electrode E1 and the second electrode E2 is a transparent electrode. One of the first electrode E1 and the second electrode E2 is an anode, and the other is a cathode. The charge functional layers F1 and F2 may include one or more of a charge injection layer, a charge transport layer, and a charge blocking layer. The light-emitting layer Em includes a plurality of quantum dots QD, including first quantum dots QD1 and second quantum dots QD2, and a matrix material Mx. The matrix material Mx (1) includes an inorganic semiconductor and an additive Ad (see FIG. 8 ), and (2) fills spaces between the first quantum dots QD1 and the second quantum dots QD2. The additive Ad may include at least one of a halogen element and an organic compound.

[0011] The matrix material Mx refers to a component that contains and holds other substances, and can be referred to as a base material, a parent material, or a filler. The matrix material Mx may be solid at room temperature. The matrix material Mx may be a component that contains and holds the first quantum dots QD1 and the second quantum dots QD2. The matrix material Mx may be a component of the light-emitting layer Em that contains the first quantum dots QD1 and the second quantum dots QD2.

[0012] 2 and 3 are schematic diagrams showing examples of regions between the quantum dots shown in FIG. 1 . A matrix material Mx may be filled in the light-emitting layer Em. As shown in FIG. 1 , the matrix material Mx may fill a region (space) B between the first and second quantum dots QD1 and QD2. As shown in FIGS. 2 and 3 , region B is a region surrounded by two lines (common circumscribing lines) tangent to the peripheries of the first and second quantum dots QD1 and QD2 and the opposing peripheries of the first and second quantum dots QD1 and QD2 in a cross-sectional view. As shown in FIG. 3 , region B may exist even if the first quantum dot QD1 is close to the second quantum dot QD2. As shown in FIG. 1 , the matrix material Mx may fill a region (space) in the light-emitting layer Em other than the multiple quantum dots including the first and second quantum dots QD1 and QD2. The matrix material Mx may fill a region (space) in the light-emitting layer Em other than the quantum dot groups. It should be noted that three or more quantum dots including the first and second quantum dots QD1 and QD2 are collectively referred to as a quantum dot group.

[0013] The matrix material Mx may fill regions (spaces) in the light-emitting layer Em other than the multiple quantum dots including the first and second quantum dots QD1 and QD2. The outer edges (top and bottom surfaces) of the light-emitting layer Em may be covered with the matrix material Mx. Alternatively, a portion of the matrix material Mx may extend from the outer edge of the light-emitting layer Em, and the quantum dots QD may be positioned away from the outer edge. The outer edge of the light-emitting layer Em may not be formed solely with the matrix material Mx, and some of the quantum dots may be exposed from the matrix material Mx. The matrix material Mx may refer to the portion of the light-emitting layer Em other than the multiple quantum dots including the first and second quantum dots QD1 and QD2.

[0014] The matrix material Mx may contain the first and second quantum dots QD1 and QD2. The matrix material Mx may contain a quantum dot group including the first and second quantum dots QD1 and QD2. The matrix material Mx may be formed to fill the space formed between the first and second quantum dots QD1 and QD2. The matrix material Mx may partially or completely fill the space between the quantum dot group including the first and second quantum dots QD1 and QD2. The light-emitting layer Em may have a quantum dot group including the first and second quantum dots QD1 and QD2, and the matrix material Mx may fill the area other than the quantum dot group. The first and second quantum dots QD1 and QD2 may be embedded in the matrix material Mx at intervals.

[0015] The matrix material Mx is formed in a thickness of 1000 nm along the surface direction perpendicular to the thickness direction of the light-emitting layer Em. ２ The matrix material Mx may include a continuous film having an area of ​​at least 1000 nm. A continuous film means a film that is not divided by a material other than the material that constitutes the continuous film in one plane. The continuous film may be an integrated film that is connected without interruption by chemical bonds of the materials that constitute the matrix material Mx.

[0016] The matrix material Mx may be the same material as the shell of the first quantum dot QD1. 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. The core-to-core distance should be kept wider than the distance when the shells are in contact with each other. The average core diameter is the average of the core diameters of 20 adjacent cores observed in cross-section. The core diameter can be the diameter of a circle having the same area as the core area in cross-section observation.

[0017] The concentration of the matrix material Mx in the light-emitting layer Em is, for example, the area ratio occupied by the matrix material Mx in the cross section of the light-emitting layer Em. This concentration may be 10% to 90% or 30% to 70% in cross-sectional observation. This concentration may be measured, for example, from the area ratio in image processing of cross-sectional observation. When the first quantum dot QD1 has a core-shell structure, the shell concentration may be 1% to 50%. When the shell material and the matrix material Mx are the same material (same composition) and the shell and matrix material Mx are indistinguishable, the concentration of the combined region of the matrix material Mx and shell may be within the numerical range obtained by adding the numerical range of the concentration of the matrix material Mx to the numerical range of the concentration of the shell. The ratio of the core, shell, and matrix material Mx of the quantum dot QD may be adjusted appropriately so that the total is 100% or less. In this way, when the shell and matrix material Mx are indistinguishable, the shell may be part of the matrix material Mx.

[0018] The light-emitting layer Em may be composed of a plurality of quantum dots including first and second quantum dots QD1 and QD2 and a matrix material Mx. When the light-emitting layer Em is analyzed, the intensity of carbon detected due to the chain structure may be equal to or less than noise.

[0019] The material constituting the matrix material Mx desirably has a wider band gap than the material constituting the first and second quantum dots QD1 and QD2. A semiconductor or an insulator can be used as the material constituting the matrix material Mx. Examples of the material constituting the matrix material Mx include metal sulfides and / or metal oxides. Metal sulfides include, for example, zinc sulfide (ZnS), zinc magnesium sulfide (ZnMgS, ZnMgS ２ ), gallium sulfide (GaS, Ga ２ S ３ ), zinc tellurium sulfide (ZnTeS), magnesium sulfide (MgS), zinc gallium sulfide (ZnGa ２ S ４ ), magnesium sulfide (MgGa ２ S ４ The metal oxide may be zinc oxide (ZnO), titanium oxide (TiO ２ ), tin oxide (SnO ２ ), tungsten oxide (WO ３ ), zirconium oxide (ZrO ２ ) The chemical formulas written in parentheses after the compound names are representative examples. The composition ratios written in the chemical formulas are preferably stoichiometric, so that the actual composition of the compounds is as shown in the chemical formulas, but they do not necessarily have to be stoichiometric.

[0020] The structure of the matrix material Mx can be determined by observing a cross section of the light-emitting layer Em with a width of about 100 nm, as long as it is clear that the matrix material Mx has the above-described configuration, and it is not necessary to observe the above-described configuration throughout the entire light-emitting layer Em. The matrix material Mx may contain a substance different from the main material (e.g., an inorganic substance such as an inorganic semiconductor) as, for example, an additive.

[0021] (Configuration of the Light-Emitting Layer) FIGS. 4 and 5 are each a schematic diagram showing an example of the configuration of the light-emitting layer shown in FIG. 1 , and correspond to an enlarged cross-sectional view of the portion indicated by the box A in FIG. 1 . As shown in FIGS. 4 and 5 , the matrix material Mx has a plurality of crystal portions CG, including a first crystal portion CG1 and a second crystal portion CG2. The matrix material Mx may be a so-called "polycrystalline body." The first crystal portion CG1 is a single crystal epitaxially grown from the surface of the first quantum dot QD1, and the second crystal portion CG2 is a single crystal epitaxially grown from the surface of the second quantum dot QD2. The arrangement and orientation of the crystal lattice G1 of the first crystal portion CG1 follows the arrangement and orientation of the crystal lattice G2 on the surface of the first quantum dot QD1. The arrangement and orientation of the crystal lattice G1 of the second crystal portion CG2 follows the arrangement and orientation of the crystal lattice G2 on the surface of the second quantum dot QD2. Note that multiple crystal portions CG may be in contact with one quantum dot QD, or one crystal portion CG may contain two or more quantum dots QD. Hereinafter, for simplicity of explanation, unless otherwise specified, a configuration example in which the first crystal portion CG1 contains the first quantum dot QD1 as shown in Figures 4 and 5 will be described.

[0022] 4 and 5, between adjacent first quantum dots QD1 and QD2, the first crystal portion CG1 growing from the surface of the first quantum dot QD1 and the second crystal portion CG2 growing from the surface of the second quantum dot QD2 come into contact with each other, forming a crystal grain boundary Bd. As shown in Fig. 4, the quantum dots QD are usually arranged randomly, and the crystal orientations of the outermost layers of the quantum dots QD are different from each other. Therefore, at the crystal grain boundary Bd, the crystal lattices G1 and crystal orientations of the first crystal portion CG1 and the second crystal portion CG2 are mismatched. 5, even if the quantum dots QD are aligned and the crystal orientations of the outermost layers of the quantum dots QD are aligned, the crystal lattices G1 of the first crystal portion CG1 and the second crystal portion CG2 are mismatched unless the distance between the first quantum dot QD1 and the second quantum dot QD2 is an integer multiple of the lattice constants of the first crystal portion CG1 and the second crystal portion CG2. At the crystal grain boundary Bd of the crystal portion CG, at least one of the crystal orientation and the crystal lattice G1 is mismatched, and therefore the crystal grain boundary Bd is also called a "crystal mismatch plane."

[0023] Fig. 6 is a schematic diagram focusing on the first quantum dot QD1 and the second quantum dot QD2 adjacent to each other shown in Fig. 4. As shown in Fig. 6, the matrix material Mx includes a first portion P1 adjacent to the first quantum dot QD1, a second portion P2 adjacent to the second quantum dot QD2, and a third portion P3 located between the first portion P1 and the second portion P2. The concentration of the additive Ad (see Fig. 8) in the third portion P3 is higher than the concentrations of the additive Ad in the first portion P1 and the second portion P2.

[0024] In the matrix material Mx, a high concentration distribution region Hp having a higher concentration of the additive Ad than the first portion P1 and the second portion P2 is formed so as to include the third portion P3. The first portion P1 and the second portion P2 may include a portion where the concentration of the additive Ad is 0. The additive Ad is scattered in the third portion P3.

[0025] The intermediate positions between the first quantum dots QD1 and the second quantum dots QD2 are located within the third portion P3. The first quantum dots QD1 and the second quantum dots QD2 are each individually surrounded by a high-concentration distribution region Hp. As a result, as shown in FIG. 4 , in a cross-sectional view of the light-emitting layer Em including the first quantum dots QD1 and the second quantum dots QD2, the high-concentration distribution region Hp has a mesh-like shape.

[0026] 7 is a diagram showing an example of the concentration distribution of the additive along the arrow BC in FIG. 5. As shown in FIG. 7, the concentration of the additive Ad (see FIG. 8) is highest at the crystal grain boundary Bd and decreases from the crystal grain boundary Bd toward the surfaces of the first quantum dot QD1 and the second quantum dot QD2. Although this concentration distribution was described using FIG. 5, other configurations (e.g., FIG. 4) may also have a similar concentration distribution. Even in a configuration example in which multiple crystal portions CG are in contact with the first quantum dot QD1, assuming a single three-dimensional region including multiple crystal portions CG in contact with the first quantum dot QD1, the concentration of the additive Ad decreases from the boundary surface of the three-dimensional region toward the surface of the first quantum dot QD1.

[0027] Therefore, the matrix material Mx has multiple crystalline portions CG, and at least a portion of the grain boundaries Bd within the matrix material Mx is included in the high-concentration distribution region Hp. The concentration of the additive Ad (see FIG. 8) decreases from the boundary surface of the three-dimensional region toward the surfaces of the first quantum dots QD1 and the second quantum dots QD2. The concentration of the additive Ad at a certain position can be calculated as the density of the additive Ad in a unit volume centered at that position.

[0028] FIG. 8 is a schematic diagram showing an example of the distribution of additives in the example configuration shown in FIG. 4 . As shown in FIG. 8 , the additive Ad is scattered at the grain boundaries Bd of the crystalline portion CG and in their vicinity (i.e., the high-concentration distribution region Hp). As a result, the additive Ad inactivates lattice defects at the grain boundaries Bd (and in their vicinity). In a configuration without the additive Ad, the grain boundaries Bd are crystal mismatch planes, and therefore dangling bonds are generated at a high density at the grain boundaries Bd (and in their vicinity). These dangling bonds act as non-radiative bond centers or carrier traps, reducing the luminous efficiency of the light-emitting layer Em. On the other hand, in the configuration according to the present disclosure, the additive Ad accepts unpaired electrons from the dangling bonds. This eliminates the dangling bonds.

[0029] For this reason, the additive Ad contains one or more halogen elements. The one or more halogen elements may include one or more of fluorine, chlorine, bromine, and iodine. The one or more halogen elements preferably belong to the same period or a higher period as at least one of the elements constituting the matrix material Mx. Furthermore, when the one or more halogen elements include two or more halogen elements, the halogen element that is most abundant in terms of the amount of substance among the two or more halogen elements preferably belongs to the same period or a higher period as at least one of the elements constituting the matrix material Mx.

[0030] Depending on the characteristics of the light emitted by the first quantum dot QD1, such as the wavelength, the core of the first quantum dot QD1 may be made of a variety of materials, including II-VI compounds, III-V compounds, perovskite compounds, and chalcopyrite compounds. On the other hand, in order to confine excitons in the core of the first quantum dot QD1, the shell of the first quantum dot QD1 often uses a compound with a larger band gap than the core material. The material constituting the shell of the first quantum dot QD1 may be the same as the material constituting the inorganic semiconductor contained in the matrix material Mx. The band gap of the inorganic semiconductor contained in the matrix material Mx may be larger than the band gap of the material constituting the core of the first quantum dot QD1.

[0031] In the present disclosure, a group III-V compound refers to an inorganic compound containing a group III element and a group V element in a composition ratio of approximately 1:1, and a group II-VI compound refers to an inorganic compound containing a group II element and a group VI element in a composition ratio of approximately 1:1. Group II elements include group 2 elements and group 12 elements. Group III elements include group 3 elements and group 13 elements. Group IV elements include group 4 elements and group 14 elements. Group VI elements include group 6 elements and group 16 elements. Here, the notation of the group numbers of elements using Roman numerals is based on the old IUPAC system or the old CAS system, and the notation of the group numbers of elements using Arabic numerals is based on the new IUPAC system.

[0032] Group 6 elements are also called chalcogen elements. Chalcogen elements include oxygen, sulfur, selenium, and tellurium. Both Group 2 and Group 12 elements are metallic elements. Therefore, II-VI compounds containing Group 6 elements are also called metal chalcogenides. Metal chalcogenides exhibit one of three crystalline forms: wurtzite, zinc blende, and rock salt. Metal chalcogenides are prone to defects where chalcogen elements are missing. The ease with which halogen elements bond to these defects depends on the ionic radius, regardless of the crystalline form. The closer the ionic radius of the halogen element is to the ionic radius of the chalcogen element, the easier it is to bond. When the ionic radius of the halogen element is equal to or smaller than the ionic radius of the chalcogen element, bonding is easier than when the ionic radius of the halogen element is larger than the ionic radius of the chalcogen element.

[0033] Therefore, when the matrix material Mx contains a metal chalcogenide, it is preferable that the one or more halogen elements belong to the same period or a higher period than at least one of the chalcogen elements constituting the metal chalcogenide of the matrix material Mx. Furthermore, when the one or more halogen elements contain two or more halogen elements, it is preferable that the halogen element that is most abundant in terms of the amount of substance among the two or more halogen elements belongs to the same period or a higher period than at least one of the chalcogen elements constituting the metal chalcogenide. The matrix material Mx may contain a metal sulfide.

[0034] It is known that the ionic radii of elements belonging to the second period of the long period table differ significantly from those of elements belonging to the third period or later due to differences in electrostatic shielding of atomic nuclei by closed shells. Therefore, when the matrix material Mx contains a chalcogen element of the second period (i.e., oxygen), it is preferable that the additive Ad also contains a halogen element of the second period (i.e., fluorine). When the matrix material Mx contains a chalcogen element of the third period or later, it is preferable that the additive Ad also contains a halogen element of the third period or later.

[0035] In the high concentration distribution region Hp (including the third portion P3) of the matrix material Mx, the concentration of the additive Ad may be approximately the same as the density of the dangling bonds in the entire matrix material Mx. Specifically, the concentration of the additive Ad in the third portion P3 is 10 １６ / cm ３ 10 above １９ / cm ３ It may be in the following range:

[0036] Additionally / alternatively, the additive Ad may include one or more organic compounds. In this case, the additive Ad accepts unpaired electrons from the dangling bonds or shares electrons with the dangling bonds, thereby eliminating the dangling bonds. The organic compound may be a ligand agent. The carbon chain of the organic compound is a short chain. In the present disclosure, "short chain" means that the number of carbon atoms is 6 or less.

[0037] In this disclosure, "organic" refers to so-called "organic compounds." Covalent bonds are broken and organic compounds are decomposed by current, heat, light, water, and oxygen. Patent Document 1 discloses quantum dots with fluoride-containing ligands or fluoride anions bound to their surfaces, where the fluoride-containing ligands or fluoride anions are organic compounds. When the organic compounds bound to the surfaces deteriorate, the distance between the quantum dots decreases, making them more susceptible to fluorescence resonance energy transfer (FRET). Alternatively / in addition, the quantum dots may aggregate or become deactivated. These factors result in reduced luminous efficiency. Therefore, the prior art disclosed in Patent Document 1 suffers from the problem of low durability of light-emitting devices.

[0038] On the other hand, "inorganic" refers to a so-called "inorganic compound." Inorganic compounds are less likely to decompose than organic compounds. The matrix material Mx according to the present disclosure is made of an inorganic semiconductor and is therefore less likely to decompose. Therefore, aspects according to the present disclosure can improve the durability of light-emitting devices. It should be noted here that the inorganic semiconductor constituting the matrix material Mx may contain impurities. For example, residues and decomposition products of organic compounds such as organic solvents, organic surfactants, organic ligand agents, and organic photoresists may be contained in the matrix material Mx. The third portion P3 of the matrix material Mx may contain a carbon element.

[0039] The inorganic semiconductor contained in the matrix material Mx may be a simple substance consisting of one type of Group 14 element, such as diamond (C), silicon (Si), or germanium (Ge). The inorganic semiconductor may be a compound consisting of two or more types of Group 14 elements, such as SiC or GeC. The inorganic semiconductor contained in the matrix material Mx may be an inorganic compound consisting of two or more elements selected from Group I elements, Group II elements, Group III elements, Group IV elements, Group V elements, Group VI elements, and Group VII elements, or a mixed crystal thereof. The inorganic semiconductor may be, for example, a II-VI group compound such as MgO, MgS, ZnO, ZnS, ZnSe, and ZnTe, or a mixed crystal thereof. The inorganic semiconductor may be, for example, a III-V group compound such as BN, AlN, GaN, InN, AlP, GaP, InP, AlAs, GaAs, and InAs, or a mixed crystal thereof. The inorganic semiconductor may be, for example, Al２ O ３ , Ga ２ O ３ , In ２ O ３ , and SiO ２ The inorganic semiconductor may be an oxide such as SnN. The inorganic semiconductor may be a nitride such as SnN. The inorganic semiconductor may be a compound consisting of one or more transition metal elements and one or more Group 6 elements excluding oxygen. The transition metal elements include Group 3 to Group 12 elements, and the Group 6 elements excluding oxygen include sulfur (S), selenium (Se), and tellurium (Te). The inorganic semiconductor contained in the matrix material Mx may further be a ternary compound such as a perovskite-type compound or a chalcopyrite-type compound, or a compound consisting of four or more elements.

[0040] The organic ligand agent included as the additive Ad is an organic compound capable of bonding to the surface of the first quantum dot QD1. In particular, an organic compound capable of bonding to a specific site such as a defect is preferable. Examples of the organic ligand agent include trioctylphosphine (TOP), trioctylphosphine oxide (TOPO), oleic acid, oleylamine, octylamine, trioctylamine, hexadecylamine, octanethiol, dodecanethiol, hexylphosphonic acid (HPA), tetradecylphosphonic acid (TDPA), and octylphosphinic acid (OPA).

[0041] The matrix material Mx is formed in a thickness of 1000 nm in a plane direction (xy plane direction) perpendicular to the thickness direction (z direction) of the light-emitting layer Em (excluding the cross section of the quantum dot QD). ２ The film may include a continuous film having an area of ​​100 μm or more.

[0042] (Manufacturing Method) Fig. 9 is a flow chart showing an example of a method for manufacturing the light-emitting element shown in Fig. 1. As shown in Fig. 9, first, a substrate is prepared (Step S1). The substrate may be a simple support substrate or an active substrate on which wiring and circuit elements are formed. Next, a first electrode E1 is formed on the substrate (Step S2), a charge functional layer F1 is formed (Step S3), and a light-emitting layer Em is formed (Step S4).

[0043] FIG. 10 is a schematic diagram illustrating an example of a dispersion liquid used in the process of forming the light-emitting layer shown in FIG. 9 . As shown in FIG. 10 , dispersion liquid L1 contains an inorganic semiconductor precursor My, an additive Ad, a plurality of quantum dots QDs, and a solvent L2. When the inorganic semiconductor constituting the matrix material Mx is a metal sulfide, precursor My may contain, for example, a metal acetate, a metal nitrate, or a metal halide salt as a metal source, and at least one of thiourea, N-methylthiourea, 1,3-dimethylthiourea, N,N'-dimethylthiourea, tetramethylthiourea, or thioacetamide as a sulfur source. Alternatively, precursor 36 may contain a metal complex in which thiourea, N-methylthiourea, 1,3-dimethylthiourea, N,N'-dimethylthiourea, tetramethylthiourea, or thioacetamide is coordinated to a metal atom. Additive Ad acts as a ligand agent to protect the quantum dots QDs. Therefore, at least a portion of additive Ad is coordinated to the surface of the quantum dots QDs.

[0044] 11 is a flow chart showing an example of the process for forming the light-emitting layer shown in FIG. 11. As shown in FIG. 11, in the process for forming the light-emitting layer (step S4), first, dispersion liquid L1 is applied onto charge functional layer F1 (step S11). Next, the applied dispersion liquid L1 is dried (step S12). In this drying, dispersion liquid L1 is heated at a temperature lower than the decomposition temperature of precursor My to volatilize solvent L2.

[0045] The dried dispersion liquid L1 is then solidified (step S13). In this solidification, the dispersion liquid L1 is heated to a high temperature equal to or higher than the decomposition temperature of the precursor My, decomposing the precursor My and forming an inorganic semiconductor. One or more of the temperature rise time, temperature retention time, and temperature fall time during this high-temperature heating are set so that the crystal growth of the inorganic semiconductor is slow. As a result, the crystal growth rate at which the inorganic semiconductor crystal portion CG epitaxially grows from the surface of the quantum dots QD is equal to or lower than the thermal diffusion rate of the additive Ad. Instead of or in addition to high-temperature heating that transforms the inorganic semiconductor precursor My into an inorganic semiconductor, the dried dispersion liquid L1 may be irradiated with visible light or near-ultraviolet light to decompose the precursor My.

[0046] Such slow crystal growth causes the additive Ad to separate and concentrate between the growing crystal portions CG. As a result of the separation and concentration, a high-concentration distribution region Hp is formed, as described above with reference to FIGS. 4 to 8. Therefore, the additive Ad is likely to bind to lattice defects at (and in the vicinity of) the grain boundaries Bd.

[0047] 9 again, following the step of forming the light-emitting layer (step S4), a charge functional layer F2 is formed (step S5), and a second electrode E2 is formed (step S6). Furthermore, a thin film sealing layer may be formed to cover the light-emitting element 10 in order to protect the light-emitting element 10 from water and oxygen.

[0048] (Examples and Comparative Examples) Fig. 12 is a diagram showing the light-emitting characteristics of a light-emitting element according to an example of the present disclosure and a light-emitting element according to a comparative example. The horizontal axis of Fig. 12 represents the current density applied to the light-emitting elements 10 and 20, and the vertical axis represents the external quantum efficiency (EQE) of the light-emitting elements 10 and 20. As shown in Fig. 12, the current density at which the EQE peaks in the light-emitting element 10 according to the example of the present disclosure is lower than the current density at which the EQE peaks in the light-emitting element 20 according to the comparative example. Furthermore, the peak value of the EQE in the light-emitting element 10 according to the example of the present disclosure is higher than the peak value of the EQE in the light-emitting element 20 according to the comparative example.

[0049] The light-emitting element 10 of the example according to the present disclosure was fabricated as described above with reference to Figures 9 to 11. Therefore, the crystal growth of the crystalline portion CG included in the matrix material Mx in the light-emitting element 10 of the example was slow. On the other hand, the light-emitting element 20 of the comparative example was fabricated so that the crystal growth was fast in step S13, and was otherwise fabricated in the same manner as the light-emitting element 10 of the example. Note that the material used in the light-emitting element 10 of the example and the material used in the light-emitting element 20 of the comparative example were the same.

[0050] In the comparative light-emitting device 20, it was estimated that the additive Ad did not bond to the lattice defects that occurred at high density at the grain boundaries Bd (and their vicinity). Therefore, the dangling bonds in the lattice defects acted as non-radiative bond centers or carrier traps, reducing the carrier injection efficiency into the quantum dots QD and the radiative recombination probability. As a result, the EQE of the light-emitting device 20 peaked at high current densities, and the peak value was low at approximately 5%.

[0051] On the other hand, in the light-emitting device 10 of the example, it was estimated that the additive Ad was bonded to the lattice defects that occurred at a high density at the grain boundary Bd (and its vicinity). As a result, the lattice defects were inactivated. As a result, compared to the light-emitting device 20 of the comparative example, the EQE of the light-emitting device 20 of the example showed a peak on the low current density side, and the peak value was improved by about 15%.

[0052] [Embodiment 2] Another embodiment of the present disclosure will be described below. For ease of explanation, the same reference numerals will be used to designate components having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

[0053] 13 is a schematic diagram showing an example of the configuration of a light-emitting layer of a light-emitting device according to an embodiment of the present disclosure. As shown in FIG. 13 , in the light-emitting layer Em according to this embodiment, the first crystal portion CG1 and the second crystal portion CG2 are separated from each other, forming a crystal grain boundary Bd. The portion of the matrix material Mx between the first crystal portion CG and the second crystal portion CG2 may be polycrystalline or amorphous, but is preferably amorphous. In other respects, the configuration of the light-emitting device 10 according to this embodiment is similar to the configuration of the light-emitting device 10 according to the first embodiment described above.

[0054] 14 is a schematic diagram showing an example of the distribution of additives in the configuration example shown in FIG. 13. As shown in FIG. 14, the additives Ad are distributed at and near the grain boundaries Bd of the crystal portion CG (i.e., high-concentration distribution regions Hp). Therefore, the configuration according to this embodiment also improves the durability and EQE of the light-emitting element 10, similar to the configuration according to the first embodiment. Furthermore, the EQE of the light-emitting element 10 peaks at a low current density.

[0055] 15 is a schematic diagram focusing on the first quantum dot QD1 and the second quantum dot QD2 adjacent to each other shown in FIGS. 13 and 14. As shown in FIG. 15, the matrix material Mx has a first portion P1, a second portion P2, and a third portion P3, as well as a fourth portion P4 located between the second portion P2 and the third portion P3 and a fifth portion P5 located between the third portion P3 and the fourth portion P4. The concentration of the additive Ad in the fourth portion P4 is higher than the concentration of the additive Ad in the first portion P1 and the second portion P2. The concentration of the additive Ad in the fifth portion P5 is lower than the concentration of the additive Ad in the third portion P3 and the fourth portion P4.

[0056] The matrix material Mx is formed with a high-concentration distribution region Hp including the third portion P3, which has a higher concentration of the additive Ad than the first portion P1 and the second portion P2, and a high-concentration distribution region Hp including the fourth portion P4, which has a higher concentration of the additive Ad than the first portion P1 and the second portion P2. The fifth portion P5 is not included in the high-concentration distribution region Hp. The first portion P1, the second portion P2, and the fifth portion P5 may include a portion where the concentration of the additive Ad is zero. The third portion P3 and the fourth portion P4 are dotted with the additive Ad. The first quantum dot QD1 is surrounded by the high-concentration distribution region Hp including the third portion P3, and the second quantum dot QD2 is surrounded by the high-concentration distribution region Hp including the fourth portion P4.

[0057] The shape of the crystal portion CG and the arrangement of the high-concentration distribution region Hp depend on the shape of the quantum dot QD and the crystal growth rate. For example, a portion of the high-concentration distribution region Hp may be along a substantially spherical surface centered on the first quantum dot QD1. For example, a portion of the high-concentration distribution region Hp may have a constant distance from the surface of the first quantum dot QD1.

[0058] (Modification) Fig. 16 is a schematic diagram showing a modification of the light-emitting layer of a light-emitting element according to an embodiment of the present disclosure. As shown in Fig. 16, the light-emitting layer Em of the light-emitting element 10 may have an intermediate configuration between the configuration according to embodiment 1 and the configuration according to embodiment 2. For example, adjacent crystal portions CG may be partially in contact with each other. For example, some adjacent crystal portions CG may be separated from each other, and some adjacent crystal portions CG may be in contact with each other.

[0059] Third Embodiment Another embodiment of the present disclosure will be described below.

[0060] 17 is a schematic diagram showing a configuration example of a display device according to an embodiment of the present disclosure. As shown in Fig. 17, a display device 30 according to the present disclosure includes one or more light-emitting elements 10 according to the present disclosure. The display device 30 includes a self-luminous display device and a display device using the light-emitting element 10 as a backlight.

[0061] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present disclosure. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment.

[0062] 10 Light-emitting element 30 Display device Ad Additive Bd Grain boundary Em Light-emitting layer Hp High concentration distribution region L1 Dispersion liquid L2 Solvent Mx Matrix material My Precursor P1 First portion P2 Second portion P3 Third portion P4 Fourth portion P5 Fifth portion QD Quantum dot QD1 First quantum dot QD2 Second quantum dot

Claims

1. A first quantum dot and a second quantum dot; (1) A light-emitting device comprising a light-emitting layer including: (1) a matrix material that contains an inorganic semiconductor and an additive; (2) that fills a space between the first quantum dot and the second quantum dot; and (3) that has a first portion adjacent to the first quantum dot, a second portion adjacent to the second quantum dot, and a third portion that is located between the first portion and the second portion and has a higher concentration of the additive than the first portion and the second portion.

2. the light emitting layer has a quantum dot group including the first quantum dot and the second quantum dot, The light-emitting device according to claim 1 , wherein the matrix material fills an area other than the quantum dots.

3. The light-emitting device according to claim 1 , wherein the additive comprises a halogen atom.

4. The light-emitting element according to claim 3 , wherein the halogen atoms are interspersed in the third portion.

5. The light-emitting device according to claim 1 , wherein an intermediate position between the first quantum dot and the second quantum dot is present within the third portion.

6. The light-emitting element according to claim 1 , wherein a high concentration distribution region in which the concentration of the additive is higher than the first portion and the second portion is formed in the matrix material so as to include the third portion.

7. The light-emitting device according to claim 6 , wherein the first quantum dot is surrounded by the high-concentration distribution region.

8. The light-emitting element according to claim 6 , wherein the high concentration distribution region has a mesh shape in a cross-sectional view of the light-emitting layer.

9. The light-emitting element according to claim 1 , wherein the matrix material has a fourth portion located between the second portion and the third portion and having a higher concentration of the additive than the first portion and the second portion.

10. The light-emitting device according to claim 9 , wherein the matrix material has a fifth portion located between the third portion and the fourth portion and having a lower concentration of the additive than the third portion and the fourth portion.

11. The light-emitting element described in claim 9, wherein the matrix material is separated into a high concentration distribution region including the third portion, in which the concentration of the additive is higher than that of the first portion and the second portion, and a high concentration distribution region including the fourth portion, in which the concentration of the additive is higher than that of the first portion and the second portion.

12. The light-emitting element according to claim 11 , wherein the first quantum dot is surrounded by the high concentration distribution area including the third portion, and the second quantum dot is surrounded by the high concentration distribution area including the fourth portion.

13. The matrix material has a plurality of crystal parts, The light-emitting device according to claim 6 , wherein at least a part of a crystal grain boundary of the matrix material is included in the high concentration distribution region.

14. The light-emitting element according to claim 6 , wherein a portion of the high-concentration distribution region is along a substantially spherical surface centered on the first quantum dot.

15. The light-emitting device according to claim 6 , wherein a part of the high-concentration distribution region has a constant distance from a surface of the first quantum dot.

16. The light-emitting device according to claim 1 , wherein the first portion of the matrix material contacts a core or a shell of the first quantum dot.

17. The light-emitting element according to claim 15 , wherein the material constituting the shell of the first quantum dot is the same as the material constituting the inorganic semiconductor.

18. The light-emitting element according to claim 1 , wherein the band gap of the inorganic semiconductor is larger than the band gap of a material constituting the core of the first quantum dot.

19. The concentration of the halogen atoms in the third portion is 10 １６ / cm ３ More than 10 １９ / cm ３ The light-emitting device according to claim 3 , wherein:

20. The light-emitting device according to claim 1 , wherein the additive comprises an organic compound.

21. The light-emitting device according to claim 20 , wherein the organic compound is a ligand agent.

22. The light-emitting device of claim 20 , wherein the third portion comprises elemental carbon.

23. The light-emitting element according to claim 20 , wherein the carbon chain of the organic compound is a short chain.

24. The light-emitting element according to claim 3 , wherein the halogen atoms include any one of fluorine, chlorine, bromine, and iodine.

25. The light-emitting element according to claim 3 , wherein the halogen atom belongs to the same period or a higher period than at least one of the elements constituting the inorganic semiconductor.

26. The additive contains two or more halogen atoms, 4. The light-emitting element according to claim 3, wherein the halogen atom having the largest amount of substance ratio among the two or more kinds of halogen atoms belongs to the same period or a higher period than at least one kind of atom constituting the inorganic semiconductor.

27. The light emitting device of claim 3 , wherein the inorganic semiconductor comprises a metal chalcogenide.

28. 28. The light-emitting element according to claim 27, wherein the halogen atom belongs to the same period or a higher period than at least one of the chalcogen elements constituting the metal chalcogenide.

29. The additive contains two or more halogen elements, 28. The light-emitting element according to claim 27, wherein the halogen element having the largest amount of substance ratio among the two or more halogen elements belongs to the same period or a higher period than at least one of the chalcogen elements constituting the metal chalcogenide.

30. The light-emitting device according to claim 1 , wherein the inorganic semiconductor comprises a metal sulfide.

31. The matrix material is formed in a thickness direction of 1000 nm in a plane direction perpendicular to the thickness direction of the light-emitting layer. ２ The light-emitting device according to claim 1 , comprising a continuous film having an area of ​​at least 100 nm.

32. A display device comprising the light-emitting element according to claim 1 .

33. applying a dispersion including an inorganic semiconductor precursor, an additive, a plurality of quantum dots, and a solvent; A method for producing a light-emitting device, comprising modifying a precursor of the inorganic semiconductor into the inorganic semiconductor such that a crystal growth rate of the inorganic semiconductor is equal to or lower than a thermal diffusion rate of the additive.