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

Abstract

A light-emitting layer (3) has: a continuous film (6) which is mainly composed of sulfide of Zn and sulfide of an additive metal comprising at least one of Cd, Sn, Mn, Ga, In, Ce, or Cu and in which the mole fraction of the additive metal to Zn is at least 1 mol%; and a plurality of emissive quantum dots (7) encapsulated in the continuous film (6).

Description

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

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

[0002] To improve the efficiency of quantum dot light-emitting diodes, it is necessary to balance the amount of electrons and holes (positive holes) injected into the quantum dot light-emitting layer (carrier balance). Patent Document 1 discloses a method for improving luminous efficiency by lowering the energy barrier required for hole injection from a hole-transporting polymer material into quantum dots, thereby improving injection efficiency. Non-Patent Document 1 discloses a method for improving luminous efficiency by improving hole injection efficiency by using cadmium-doped zinc sulfide as the material for the outermost shell of quantum dots whose surfaces are modified with organic ligands.

[0003] Japanese Patent Publication No. 2019-119831

[0004] Cadmium-Doped Zinc Sulfide Shell as a Hole Injection Springboard for Red, Green, and Blue Quantum Dot Light-Emitting Diodes. Adv. Sci. 2022, 9, 2104488

[0005] Conventional quantum dots modified with organic ligands suffer from poor durability, while quantum dots coated with a continuous semiconductor instead of organic ligands are more durable but suffer from carrier imbalance and reduced luminescence efficiency.

[0006] A light-emitting element according to one aspect of the present disclosure includes an anode, a cathode, and a light-emitting layer located between the anode and the cathode. The light-emitting layer includes a continuous film mainly composed of a sulfide of Zn and a sulfide of an additive metal selected from at least one of Cd, Sn, Mn, Ga, In, Ce, and Cu, in which the molar fraction of the additive metal relative to the Zn is 1 mol % or more, and a plurality of light-emitting quantum dots encapsulated in the continuous film.

[0007] A light emitting element having high durability and high luminous efficiency can be realized.

[0008] 1 is a cross-sectional view showing a schematic configuration of a light-emitting device according to the present disclosure;

[0023] FIG. 1 shows three graphs showing the relationship between emission illuminance and driving voltage versus emission time in a comparative light-emitting device;

[0024] FIG. 2 is a graph showing the relationship between emission luminance versus emission time in a comparative light-emitting device;

[0025] FIG. 3 is a diagram explaining factors behind a decrease in emission luminance of a comparative light-emitting layer;

[0026] FIG. 4 is a band gap diagram of a hole transport layer, a comparative light-emitting layer, and an electron transport layer in a comparative light-emitting device;

[0027] FIG. 5 is a diagram showing a method for synthesizing a metal sulfide precursor according to the present disclosure;

[0028] FIG. 6 is a diagram showing the results of photoelectron yield (PYS) measurements of a metal sulfide monolayer;

[0029] FIG. 7 is a diagram showing the voltage-current characteristics of a hole-only device (HOD) showing the hole injection ability into the quantum dot layer contained in each sulfide medium;

[0029] FIG. 8 is a diagram showing the maximum EQE and the luminance reduction rate after 5 hours of operation of a light-emitting device using a quantum dot layer contained in each sulfide medium as a light-emitting layer;

[0029] FIG. 9 is a diagram showing first, second, third, and fourth examples of the ratio of the mass of a plurality of light-emitting quantum dots to the mass of the light-emitting layer;

[0029] FIG. 10 is a diagram showing a method for manufacturing a light-emitting device according to the present disclosure;

[0029] FIG. 11 is a schematic diagram showing an example of the configuration of a display device according to the present disclosure;

[0029] FIG. 12 is a cross-sectional diagram showing an example of the configuration of a display device according to the present disclosure;

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following describes an embodiment of the present disclosure. For convenience of explanation, the same reference numerals are used to designate components having the same functions as those previously described, and the description thereof may not be repeated.

[0010] 1 is a cross-sectional view showing a schematic configuration of a light-emitting element 101 according to the present disclosure. The light-emitting element 101 includes an anode 1, a hole transport layer 2, a light-emitting layer 3, an electron transport layer 4, and a cathode 5. The anode 1, the hole transport layer 2, the light-emitting layer 3, the electron transport layer 4, and the cathode 5 may be stacked in this order from the substrate (not shown) side, or may be stacked in the reverse order.

[0011] The light emitting element 101 emits light from the light emitting layer 3 in response to a current flowing between the anode 1 and the cathode 5. The light emitting element 101 may be a QLED (quantum dot light emitting diode) element.

[0012] Light-emitting layer 3 is located between anode 1 and cathode 5. Hole-transporting layer 2 is located between anode 1 and light-emitting layer 3. Electron-transporting layer 4 is located between cathode 5 and light-emitting layer 3.

[0013] The light-emitting layer 3 includes a continuous film 6 and a plurality of light-emitting quantum dots 7. An example of a material for the electron transport layer 4 is ZnMgO.

[0014] The continuous film 6 contains a plurality of quantum dots 7. Here, containing means that the continuous film 6 covers a part or all of the surface of each quantum dot 7, for example. The continuous film 6 may be a single film that is not separated by a material other than the continuous film 6. In addition, the continuous film 6 has an area of ​​1000 nm when viewed from above the light emitting element 101. ２ Alternatively, the continuous film 6 may be an integral film formed by chemical bonding of the materials constituting the continuous film 6. The continuous film 6 is formed, for example, so as to partially or completely fill the spaces formed between the quantum dots 7 contained in the continuous film 6. There may be voids in the light-emitting layer 3. The quantum dots 7 contained in the continuous film 6 may be spaced apart from one another.

[0015] The continuous film 6 is mainly composed of a sulfide of Zn (zinc) and a sulfide of an additive metal comprising at least one of Cd (cadmium), Sn (tin), Mn (manganese), Ga (gallium), In (indium), Ce (cerium), and Cu (copper). In the continuous film 6, the molar fraction of the additive metal constituting the sulfide of the additive metal relative to the Zn constituting the Zn sulfide is 1 mol % or more.

[0016] The continuous film 6 is mainly composed of a primary sulfide, which is a sulfide of Zn, and secondary sulfides. The secondary sulfides are composed of at least one of a sulfide of Cd, a sulfide of Sn, a sulfide of Mn, a sulfide of Ga, a sulfide of In, a sulfide of Ce, and a sulfide of Cu. In the continuous film 6, when the molar fraction of Zn belonging to the primary sulfides is taken as 100 mol %, the total molar fraction of Cd, Sn, Mn, Ga, In, Ce, and Cu belonging to the secondary sulfides is 1 mol % or more.

[0017] The continuous film 6 contains a metal sulfide as a main component. The difference between the first level of the electron transport layer 4 and the first level of the continuous film 6 is defined as ΔE(e), and the difference between the second level of the hole transport layer 2 and the second level of the continuous film 6 is defined as ΔE(h). In this case, the difference between ΔE(e) and ΔE(h) is 1 eV or less. When the difference between ΔE(e) and ΔE(h) is 1 eV or less, it is not essential that the metal sulfide contains at least one of Zn sulfide, Cd sulfide, Sn sulfide, Mn sulfide, Ga sulfide, In sulfide, Ce sulfide, and Cu sulfide.

[0018] The first level is CBM or LUMO. The second level is VBM or HOMO. CBM is the bottom of the conduction band. VBM is the top of the valence band. LUMO is the energy level of the lowest unoccupied molecular orbital. HOMO is the energy level of the highest occupied molecular orbital. LUMO and HOMO are negative values ​​(unit: eV) with the vacuum level as the reference (0). CBM and VBM are mainly used in inorganic materials, while LUMO and HOMO are mainly used in organic materials. It is possible to replace one of CBM and LUMO with the other. It is possible to replace one of VBM and HOMO with the other.

[0019] "Containing a certain material (herein referred to as material A) as the main component" includes (1) the case where it is made of material A, and (2) the case where it contains a small amount of impurities in addition to (1) but can achieve the same function as (1).

[0020] The quantum dots 7 are luminescent and may be formed of a group II-VI semiconductor crystal such as MgS, MgSe, MgTe, CaS, CaSe, CaTe, SrS, SrSe, SrTe, BaS, BaSe, BaTe, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, HgS, HgSe, or HgTe, a group III-V semiconductor crystal such as GaAs, GaP, InN, InAs, InP, or InSb, a group IV semiconductor crystal such as Si or Ge, or a group IV semiconductor crystal such as CsPbI ３ , CsPbBr ３ , CsPbCl ３ The perovskite structure may include at least one of crystals having a perovskite structure such as:

[0021] The bandgap of the continuous film 6 may be larger than the bandgap of the plurality of light-emitting quantum dots 7 .

[0022] By forming a light-emitting element by incorporating a plurality of quantum dots 7 into a continuous film whose main component is Zn sulfide (the molar fraction of the added metal relative to Zn is less than 1 mol %), energy transfer between the plurality of quantum dots 7 is unlikely to occur, thereby achieving high reliability, but this may result in low luminous efficiency.

[0023] From here on, we will discuss the case where a continuous film containing Zn sulfide as a main component (the molar fraction of the added metal relative to Zn is less than 1 mol%) is used instead of the continuous film 6. This continuous film will also be called a comparative continuous film. A light-emitting layer having a comparative continuous film will also be called a comparative light-emitting layer. A light-emitting element having a comparative light-emitting layer will also be called a comparative light-emitting element.

[0024] Figure 2 shows three graphs illustrating the relationship between the emission illuminance (unit: %) and the driving voltage (unit: V) versus the emission time (unit: hour) for a comparative light-emitting element. The three graphs 201 to 203 shown in Figure 2 show the cases where the molar concentrations of ZnS (zinc sulfide) in the comparative continuous film are as follows: In the comparative light-emitting element, its luminous efficiency per current (EQE) is roughly proportional to its emission illuminance.

[0025] Graph 201: 0.08M (equivalent to mol / L) Graph 202: 0.04M Graph 203: 0.02M According to Fig. 2, in the comparative light-emitting element, the maximum luminous irradiance does not differ significantly depending on the molar concentration of ZnS in the comparative continuous film. The maximum value of EQE corresponding to the maximum luminous irradiance is approximately 7.0%.

[0026] 2, in the comparative light-emitting device, the greater the molar concentration of ZnS in the comparative continuous film, the smaller the luminance, especially after the value has stabilized. According to Fig. 2, in the comparative light-emitting device, the greater the molar concentration of ZnS in the comparative continuous film, the larger the driving voltage, especially after the value has stabilized.

[0027] FIG. 3 is a graph showing the relationship between the light emission luminance (arbitrary unit) and the light emission time (arbitrary unit) in the comparative light emitting element.

[0028] 3, period 8 is the period during which the comparative light-emitting element is continuously emitting light, and timing 9 is the timing at which the continuous emission of the comparative light-emitting element is stopped and restarted. According to Fig. 3, the emission luminance of the comparative light-emitting element peaks at timing 9, then decreases with the passage of emission time within period 8, and peaks again at the next timing 9. Comparing the cases where the molar concentration of ZnS in the comparative continuous film is high and low, it can be seen that the rate of decrease in the emission luminance of the comparative light-emitting element is greater when the molar concentration of ZnS in the comparative continuous film is high.

[0029] FIG. 4 is a diagram illustrating the factors that cause the emission luminance of the comparative light-emitting layer 10 to decrease.

[0030] When the comparative light-emitting element has a good carrier balance, electrons 11 and holes 12 recombine in the center of the comparative light-emitting layer 10, enabling highly efficient light emission.

[0031] When the carrier balance in the comparative light-emitting element is poor (excess electrons), electrons 11 gradually accumulate in the comparative light-emitting layer 10, and the electrons 11 accumulated in the comparative light-emitting layer 10 are thermally deactivated through a trion state, making it difficult to achieve highly efficient light emission.

[0032] 5 is a band gap diagram of the hole transport layer 2, the comparative light-emitting layer 10, and the electron transport layer 4 in the comparative light-emitting element. Comparing the comparative continuous film 13 with a high molar concentration of ZnS and a low molar concentration of ZnS, the comparative continuous film 13 tends to suppress the injection of holes 12 into the quantum dots 7 more effectively.

[0033] Even if carriers pass through the comparative continuous film 13, if there is a sufficient energy barrier between the comparative continuous film 13 and the first level of the hole transport layer 2, and if there is also a sufficient energy barrier between the comparative continuous film 13 and the second level of the electron transport layer 4, the carriers will remain in the comparative light-emitting layer 10 and will not cause leakage, and there will be no particular problem.

[0034] From the above discussion, when comparing the cases where the molar concentration of ZnS in the comparative continuous film 13 is high and low, it can be seen that the case where the molar concentration of ZnS in the comparative continuous film 13 is high tends to exhibit the following (a) and (b). This tendency is thought to be due to a poor carrier balance (excess electrons).

[0035] (a) The EQE of the comparative light-emitting element is low (b) The amount of decrease in the luminance of the comparative light-emitting element with respect to continuous emission of the comparative light-emitting element is large Experiments were conducted to confirm the effects of the present disclosure. Findings obtained from these experiments will be described below with reference to Figures 6 to 9.

[0036] 6 is a diagram showing a method for synthesizing a metal sulfide precursor according to the present disclosure. The metal sulfide may be a sulfide that is the main component of the continuous film 6. FIG. 6 illustrates the reaction of zinc xanthate. A quantum dot layer corresponding to the light-emitting layer 3 was prepared as follows. Materials are not limited to these as long as they have the same function.

[0037] (Synthesis of Metal Sulfide Precursor) Various metal xanthate complexes were synthesized and used as metal sulfide precursors. Zinc chloride or cadmium chloride was dissolved in pure water and mixed with 2.5 times the molar amount of potassium ethylxanthate. After stirring for 12 hours, the metal xanthate precipitate was recovered and washed three times with pure water. Most of the metal xanthate was decomposed at 150°C to form metal sulfide.

[0038] (Ligand exchange of quantum dots corresponding to quantum dot 7) An octane solution containing InP / ZnS quantum dots modified with oleic acid was mixed with a DMF solution containing zinc chloride and zinc xanthate. The mixture was stirred vigorously while the two layers remained separated, and the quantum dots were transferred to the DMF layer. The quantum dots modified with xanthic acid and chloride ions were precipitated by adding ethyl acetate, and the precipitate was redispersed in a DMF solution containing a predetermined concentration of xanthogen metal.

[0039] (Formation of quantum dot layer) A DMF solution containing the quantum dots modified with xanthogenic acid and each metal xanthate was applied to a substrate and heated at 150°C for 30 minutes to thermally decompose the metal xanthate, thereby forming a quantum dot layer in which the quantum dots were encapsulated in a continuous film of metal sulfide corresponding to continuous film 6.

[0040] Figure 7 shows the results of photoelectron yield (PYS) measurements of metal sulfide monolayers. PYS measurements were performed to measure the valence band state (VBM) of the metal sulfide in the media. A DMF solution of only the xanthate metal precursor for each media was applied to ITO and then heated at 150°C to form a metal sulfide monolayer corresponding to continuous film 6. Substituting 20% ​​of the Zn in the ZnS film corresponding to comparative continuous film 13 with Cd increased the VBM. This confirmed that when used in media containing quantum dots, the energy barrier required to inject holes from the HOMO of the hole transport layer corresponding to hole transport layer 2 into the quantum dots is reduced, making hole injection easier. The energy levels vary depending on the measurement method, measurement conditions, and fitting method; however, the relative level relationships can be considered correct when measured using the same method.

[0041] Figure 8 shows the voltage-current characteristics of hole-only devices (HODs) that demonstrate the hole injection properties of quantum dot layers contained in each sulfide medium. HODs were fabricated to compare the hole injection properties of quantum dot layers in which quantum dots were dispersed in each sulfide medium. In the HODs, only holes are injected as carriers. The HODs were fabricated with a layered structure of ITO / NiO nanoparticles / poly-TPD / quantum dots / PMA / Ag. The quantum dot ligands were replaced with zinc xanthate, and a DMF solution containing 15 mg / ml of quantum dots was prepared. The molar concentration of the sulfide precursor mixed into the quantum dot solution was adjusted to a predetermined ratio. To inject only holes from the electrode, a phosphomolybdic acid (PMA) solution was applied to the quantum dot layer and baked at 110°C. By replacing 20% ​​of the Zn in the ZnS medium with Cd, the amount of current at the same voltage increases when compared with the same amount of medium, indicating that the hole injection into the quantum dot layer is improved.

[0042] FIG. 9 shows the maximum EQE and the luminance decrease rate after 5 hours of operation of the light-emitting element corresponding to light-emitting element 101, using a quantum dot layer contained in each sulfide medium as the light-emitting layer. Light-emitting elements having a quantum dot layer in which quantum dots are dispersed in each sulfide medium were fabricated to have a layered structure of ITO / NiO nanoparticles / poly-TPD / quantum dots / ZnMgO / Ag. The ligands of quantum dots with a composition of InP / ZnS and emitting red light were substituted with zinc xanthate and zinc chloride, and a DMF solution with a quantum dot concentration of 15 mg / ml was prepared. The molar concentration of the sulfide precursor mixed into the quantum dot solution was adjusted to a predetermined ratio. According to the examples and comparative examples in FIG. 9, the EQE increased by replacing 20% ​​of the Zn in the ZnS medium with Cd. Furthermore, it was confirmed that the decrease in luminance during initial operation was suppressed. This is thought to be due to the effect of improved hole injection, which makes it less likely for excess electrons to accumulate in the quantum dot layer. In the present disclosure, Cd is used as an additive to ZnS, but an appropriate amount of a metal that forms a sulfide semiconductor with a higher VBM than ZnS may be added.

[0043] FIG. 10 shows a first example 14, a second example 15, a third example 16, and a fourth example 17 regarding the ratio of the mass of the light-emitting quantum dots 7 to the mass of the light-emitting layer 3.

[0044] In Example 14, the light-emitting layer 3 has a single layer structure of a normally arranged layer 18. In Example 2 15, the light-emitting layer 3 has a laminate structure of two normally arranged layers 18. In Example 3 16, the light-emitting layer 3 has a laminate structure of a normally arranged layer 18 (on the hole transport layer 2 side) and a sparsely arranged layer 19 (on the electron transport layer 4 side). In Example 4 17, the light-emitting layer 3 has a laminate structure of a sparsely arranged layer 19 (on the hole transport layer 2 side) and a normally arranged layer 18 (on the electron transport layer 4 side).

[0045] The ratio of the mass of the plurality of luminescent quantum dots 7 contained in the normally arranged layer 18 to the mass of the normally arranged layer 18 is 88%. The ratio of the mass of the plurality of luminescent quantum dots 7 contained in the sparsely arranged layer 19 to the mass of the sparsely arranged layer 19 is 65%.

[0046] In each of the third example 16 and the fourth example 17, a higher EQE was achieved in the light-emitting device 101 compared to the first example 14. In the second example 15, no improvement in the EQE was observed in the light-emitting device 101 compared to the first example 14.

[0047] The light-emitting layer 3 has a laminated structure of multiple layers including a sparsely arranged layer 19, and the mass ratio of the multiple light-emitting quantum dots 7 contained in the sparsely arranged layer 19 to the mass of the sparsely arranged layer 19 may be 20% or more and 80% or less. Specific examples include the configuration of either Example 3 16 or Example 4 17 (wherein the ratio is 65%).

[0048] 11 is a diagram showing a method for manufacturing the light-emitting device 101. The method for manufacturing the light-emitting device 101 includes a step S1 of dispersing a first metal complex 20, a second metal complex 21, and a large number of light-emitting quantum dots 7 in a solvent 22 to prepare a quantum dot dispersion liquid 23, and a step S2 of applying and heating the quantum dot dispersion liquid 23 to form a light-emitting layer 3.

[0049] The first metal complex 20 is thermally decomposable and contains Zn. Examples of the first metal complex 20 include zinc dithiocarboxylate, zinc xanthogenate, zinc dithiocarbamate, and zinc tertiary alkylthiolate. Dithiocarboxylic acid has a structure represented by XC(=S)SH (X is a carbon substituent). Xanthogenic acid has a structure represented by ROC(=S)SH (R is hydrogen, a hydrocarbon group, etc.). Dithiocarbamic acid has a structure represented by R ２ It has a structure represented by NC(=S)SH. Tertiary alkyl thiol is R ２ It has a structure represented by C-SH.

[0050] The second metal complex 21 is thermally decomposable and contains an additive metal. The additive metal is at least one of Cd, Sn, Mn, Ga, In, Ce, and Cu. Examples of the ligand of the second metal complex 21 include dithiocarboxylic acid, xanthic acid, dithiocarbamic acid, and tertiary alkylthiol.

[0051] The solvent 22 may be a polar solvent or a non-polar solvent, and may be a polar solvent including at least one of a formamide-based solvent, an acetamide-based solvent, an ester-based solvent, a ketone-based solvent, a sulfoxide solvent, an ether-based solvent, a thioether-based solvent, and a nitrile-based solvent.

[0052] The manufacturing method of the light emitting device 101 may include a step of exposing and developing the applied quantum dot dispersion liquid 23 .

[0053] Fig. 12 is a schematic diagram showing a configuration example of a display device 401 according to the present disclosure. Fig. 13 is a cross-sectional view showing a configuration example of a display device 401 according to the present disclosure. As shown in Fig. 12, the display device 401 includes a display unit DA including a plurality of subpixels SP, a first driver X1 and a second driver X2 that drive the plurality of subpixels SP, and a display controller DC that controls the first driver X1 and the second driver X2. Each subpixel SP includes a light-emitting element 305 and a pixel circuit PC connected to the light-emitting element 305. The pixel circuit PC may be connected to a scanning signal line GL, a data signal line DL, and an emission control line EL. The scanning signal line GL and the emission control line EL may be connected to the first driver X1, and the data signal line DL may be connected to the second driver X2.

[0054] The display device 401 may include a pixel circuit substrate 313 including a substrate 311 and a pixel circuit layer 312, a light-emitting element layer 314, and a sealing layer 315. The substrate 311 may be a glass substrate, a resin substrate, or the like. The substrate 311 may be flexible. The pixel circuit layer 312 includes, for example, a plurality of pixel circuits PC arranged in an inorganic matrix. The pixel circuit PC may include a pixel capacitor to which a grayscale signal is written, a transistor that controls the current value of the light-emitting element 305 in accordance with the grayscale signal, a transistor connected to a scanning signal line GL and a data signal line DL, and a transistor connected to a light-emitting control line EL.

[0055] As shown in FIG. 13 , the display device 401 includes a pixel circuit substrate 313 and a light-emitting element layer 314. The light-emitting element layer 314 may include, in order from the pixel circuit substrate 313 side, a first electrode D1, an edge cover film JF covering the edge of the first electrode D1, a first functional layer FK, a light-emitting layer (quantum dot layer) 330, a second functional layer SK, and a second electrode D2. The first functional layer FK may have a hole injection function and a hole transport function, and the second functional layer SK may have an electron transport function. The light-emitting element layer 314 may include a light-emitting element 305R including a light-emitting layer 330R that emits red light, a light-emitting element 305G including a light-emitting layer 330G that emits green light, and a light-emitting element 305B including a light-emitting layer 330B that emits blue light. The sealing layer 315 includes an inorganic insulating film such as a silicon nitride film or a silicon oxide film, and prevents foreign substances (water, oxygen, etc.) from entering the light-emitting element layer 314.

[0056] Examples of materials that can be used for the first functional layer FK include organic materials such as poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4'-(N-4-sec-butylphenyl))diphenylamine)] (TFB), poly(4-butyltriphenylamine) (p-TPD), poly(9-vinylcarbazole) (PVK), [9,9'-[1,2-phenylenebis(methylene)]bis[N3,N3,N6,N6-tetrakis(4-methoxyphenyl)-9H-carbazole-3,6-diamine] (V886), and 7,7'-bi[1,4]benzoxazino[2,3,4-kl]phenoxazine (HN-D1), and inorganic materials such as NiO nanoparticles.

[0057] As the material for the second functional layer SK, organic materials such as (2,2',2''-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi), bathocuproine (BCP), and nanoparticles of organometallic complexes, and inorganic materials such as nanoparticles of n-type oxide semiconductors can be used. Examples of organometallic complexes include tris(8-quinolinol)aluminum complex (Alq3). Examples of n-type oxide semiconductors include metal oxides such as ZnO and ZnMgO.

[0058] In Fig. 13, the quantum dot layer is used as the light-emitting layer 330, but this is not limiting. The quantum dot layer can also be used as a wavelength conversion layer or a photosensor layer. Furthermore, a power generating element can be configured with a quantum dot layer between a pair of electrodes. For example, holes and electrons can be generated in the quantum dots from light incident on the quantum dot layer, and then transported to the electrodes to generate an electromotive force.

[0059] The light-emitting element 101 can be applied as the light-emitting element 305. To give specific examples, an anode 1 can be applied as the first electrode D1, a hole transport layer 2 can be applied as the first functional layer FK, a light-emitting layer 3 can be applied as the light-emitting layer 330, an electron transport layer 4 can be applied as the second functional layer SK, and a cathode 5 can be applied as the second electrode D2.

[0060] 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.

[0061] 1 anode 2 hole transport layer 3 light-emitting layer 4 electron transport layer 5 cathode 6 continuous film 7 quantum dots 8 period 9 timing 10 comparative light-emitting layer 11 electrons 12 holes 13 comparative continuous film 14 first example 15 second example 16 third example 17 fourth example 18 normally arranged layer 19 sparsely arranged layer 20 first metal complex 21 second metal complex 22 solvent 23 quantum dot dispersion 101, 305 light-emitting element 201, 202, 203 graph 401 display device

Claims

1. an anode; a cathode; a light-emitting layer located between the anode and the cathode, The light-emitting layer is a continuous film containing, as its main components, a sulfide of Zn and a sulfide of an additive metal consisting of at least one of Cd, Sn, Mn, Ga, In, Ce, and Cu, wherein the molar fraction of the additive metal relative to the Zn is 1 mol % or more; a plurality of luminescent quantum dots encapsulated in the continuous film; the light-emitting layer has a laminated structure of a plurality of layers including a sparsely arranged layer, a ratio of the mass of the luminescent quantum dots contained in the sparsely arranged layer to the mass of the sparsely arranged layer is 20% or more and 80% or less; Light-emitting element.

2. an anode; a cathode; a light-emitting layer located between the anode and the cathode; a hole transport layer located between the anode and the light-emitting layer; an electron transport layer located between the cathode and the light-emitting layer; The light-emitting layer is a continuous film containing a metal sulfide as a main component, wherein a first level is CBM or LUMO, a second level is VBM or HOMO, a difference between the first level of the electron transport layer and the first level of the continuous film is ΔE(e), and a difference between the second level of the hole transport layer and the second level of the continuous film is ΔE(h), and the difference between ΔE(e) and ΔE(h) is 1 eV or less; a plurality of luminescent quantum dots encapsulated in the continuous film; the light-emitting layer has a laminated structure of a plurality of layers including a sparsely arranged layer, a ratio of the mass of the luminescent quantum dots contained in the sparsely arranged layer to the mass of the sparsely arranged layer is 20% or more and 80% or less; Light-emitting element.

3. The light-emitting device according to claim 1 , wherein the band gap of the continuous film is larger than the band gap of the plurality of light-emitting quantum dots.

4. A display device comprising the light-emitting device according to claim 1 or 2.

5. A step of preparing a quantum dot dispersion by dispersing a thermally decomposable first metal complex containing Zn, a thermally decomposable second metal complex containing an additive metal consisting of at least one of Cd, Sn, Mn, Ga, In, Ce, and Cu, and a large number of luminescent quantum dots in a solvent; and applying and heating the quantum dot dispersion liquid to form a light-emitting layer.

6. The method for manufacturing a light-emitting element according to claim 5 , further comprising the step of exposing and developing the applied quantum dot dispersion liquid.