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

Abstract

The light-emitting layer (3) has: a continuous film (6) having, as main components, a sulfide of Zn and a sulfide of an additive metal comprising at least one of Cd, Sn, Mn, Ga, In, Ce and Cu, the molar fraction of the additive metal relative to Zn being 1 mol% or more; and a plurality of light-emitting quantum dots (7) wrapped by the continuous film (6).

Description

TECHNICAL FIELD

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

[0002] A problem in achieving high efficiency of a quantum dot light-emitting diode is to make the injection amounts of electrons and holes (positive holes) in a quantum dot light-emitting layer consistent (carrier balance). Patent Literature 1 discloses a method for improving the injection efficiency and improving the light-emitting efficiency by reducing the energy barrier required for injection of holes from a high-molecular-weight material having hole transportability into quantum dots. Non Patent Literature 1 discloses a method for improving the light-emitting efficiency by using cadmium-doped zinc sulfide as an outermost shell material of quantum dots modified with an organic ligand to improve the hole injection efficiency.

[0003] PRIOR ART DOCUMENTS PATENT LITERATURE Patent Literature 1: Japanese Patent Application Laid-Open No. 2019-119831 NON PATENT LITERATURE Non Patent Literature 1: 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 SUMMARY Technical problem to be solved by the present disclosure A quantum dot modified with an organic ligand formed by a conventional method has a problem of low durability. On the other hand, although a quantum dot layer in which an organic ligand is replaced with a continuous semiconductor has high durability, there is a problem that carriers are destroyed and the light-emitting efficiency is easily reduced.

[0004] Technical solution to solve the technical problem A light-emitting element according to an embodiment of the present disclosure includes: an anode; a cathode; and a light-emitting layer between the anode and the cathode, the light-emitting layer including: a continuous film including a sulfide of Zn and a sulfide of an additive metal selected from Cd, Sn, Mn, Ga, In, Ce, and Cu as a main component, wherein a mole fraction of the additive metal with respect to the Zn is 1% or more; and a plurality of quantum dots having light-emitting properties, which are surrounded by the continuous film.

[0005] Advantages A light-emitting element having high durability and high light-emitting efficiency can be achieved. BRIEF DESCRIPTION OF DRAWINGS

[0006] Figure 1 is a cross-sectional view showing a schematic configuration of a light-emitting element of the present disclosure.

[0007] Figure 2 is a graph showing three curves showing the relationship between the light-emitting luminance and the driving voltage with respect to the light-emitting time in a comparative light-emitting element.

[0008] Figure 3 is a graph showing the relationship between the light-emitting luminance and the light-emitting time in a comparative light-emitting element.

[0009] Figure 4 is a graph explaining the factor of the decrease in the light-emitting luminance of a comparative light-emitting layer.

[0010] Figure 5 is a band gap diagram of a hole-transporting layer, a comparative light-emitting layer, and an electron-transporting layer in a comparative light-emitting element.

[0011] Figure 6 is a graph showing a method for synthesizing a metal sulfide precursor of the present disclosure.

[0012] Figure 7 is a graph showing the results of photoelectron yield (PYS) measurement of a metal sulfide single film.

[0013] Figure 8 is a graph showing the voltage-current characteristics of a hole-only device (HOD) for the hole-injection property of a quantum dot layer contained in each of the sulfide media.

[0014] Figure 9 is a graph showing the maximum EQE and the luminance decrease rate after driving for 5 hours of a light-emitting element in which the quantum dot layer contained in each of the sulfide media is used as a light-emitting layer.

[0015] Figure 10 is a graph showing the first example, the second example, the third example, and the fourth example of the ratio of the mass of the quantum dots involved in the plurality of light-emitting properties with respect to the mass of the light-emitting layer.

[0016] Figure 11 is a graph showing a method for manufacturing a light-emitting element of the present disclosure.

[0017] Figure 12 is a schematic view showing a configuration example of a display device of the present disclosure.

[0018] Figure 13 is a cross-sectional view showing a configuration example of a display device according to the present disclosure. DETAILED DESCRIPTION

[0019] A description is given of a mode for carrying out the present disclosure. For ease of explanation, the same reference numerals are sometimes given to components having the same function as the components described earlier, and the description thereof is not repeated.

[0020] Figure 1 is a cross-sectional view showing the outline configuration of the light-emitting element 101 of the present disclosure. The light-emitting element 101 is provided with 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 can be stacked in this order from the side of a substrate (not shown), or can be stacked in the reverse order.

[0021] The light-emitting layer 3 emits light by the current flowing between the anode 1 and the cathode 5. The light-emitting element 101 can also be a QLED (Quantum Dot Light Emitting Diode) element.

[0022] The light-emitting layer 3 is located between the anode 1 and the cathode 5. The hole transport layer 2 is located between the anode 1 and the light-emitting layer 3. The electron transport layer 4 is located between the cathode 5 and the light-emitting layer 3.

[0023] The light-emitting layer 3 has a continuous film 6 and a plurality of light-emitting quantum dots 7. As one example of the material of the electron transport layer 4, ZnMgO can be cited.

[0024] The continuous film 6 encloses the plurality of quantum dots 7. The enclosure here means, for example, that the continuous film 6 covers part or all of the surface of each quantum dot 7. The continuous film 6 can also be a single film that is not divided by a material other than the continuous film 6. In addition, the area of the continuous film 6 can be 1000 nm 2 The above can also be a one-piece film-like substance in which the materials constituting the continuous film 6 are chemically bonded without a gap. The continuous film 6 is formed, for example, so as to locally or completely fill the spaces formed between the plurality of quantum dots 7 enclosed by the continuous film 6. A void can also be present in the light-emitting layer 3. The plurality of quantum dots 7 enclosed by the continuous film 6 can also exist at intervals from each other.

[0025] The continuous film 6 has, as a main component, a sulfide of Zn (zinc) and a sulfide of an additive metal of 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 mole fraction of the additive metal constituting the sulfide of the additive metal with respect to Zn constituting the sulfide of Zn is 1 mol% or more.

[0026] The continuous film 6 has, as a main component, a main sulfide and a sub-sulfide of a sulfide of Zn. The sub-sulfide is 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 mole fraction of Zn belonging to the main sulfide is assumed to be 100 mol%, the mole fraction of the sum of Cd, Sn, Mn, Ga, In, Ce, and Cu belonging to the sub-sulfide is 1 mol% or more.

[0027] The continuous film 6 has, as a main component, a sulfide of a metal. Let the difference between the first energy level of the electron transport layer 4 and the first energy level of the continuous film 6 be ΔE(e), and let the difference between the second energy level of the hole transport layer 2 and the second energy level of the continuous film 6 be ΔE(h). At this time, the difference between ΔE(e) and ΔE(h) is 1 eV or less. In the case where the difference between ΔE(e) and ΔE(h) is 1 eV or less, it is not necessary for the sulfide of the metal to contain at least one of a sulfide of Zn, 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.

[0028] The first energy level is a CBM or a LUMO. The second energy level is a VBM or a HOMO. The CBM is a lower end of a conduction band. The VBM is an upper end of a valence band. The LUMO is an energy level of a lowest unoccupied orbital. The HOMO is an energy level of a highest occupied orbital. The LUMO and the HOMO are negative values (unit: eV) with a vacuum level as a reference (0). The CBM and the VBM are mainly objects of inorganic substances, and the LUMO and the HOMO are mainly objects of organic substances. One of the CBM and the LUMO can be replaced by the other. One of the VBM and the HOMO can be replaced by the other.

[0029] "Having a certain material (hereinafter referred to as material A) as a main component" includes (1) a case where material A is composed of, and (2) a case where a small amount of impurities is contained in addition to (1), but a function equivalent to (1) can be achieved.

[0030] The quantum dot 7 is luminescent. The quantum dot 7 can contain at least one of crystals of II-VI group semiconductors such as MgS, MgSe, MgTe, CaS, CaSe, CaTe, SrS, SrSe, SrTe, BaS, BaSe, BaTe, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, HgS, HgSe, HgTe, crystals of III-V group semiconductors such as GaAs, GaP, InN, InAs, InP, InSb, crystals of IV group semiconductors such as Si, Ge, and crystals of perovskite structure such as CsPbI3, CsPbBr3, CsPbCl3.

[0031] The band gap of the continuous film 6 may be larger than the band gap of the plurality of luminescent quantum dots 7 .

[0032] By wrapping multiple quantum dots 7 in a continuous film with Zn sulfide as the main component (the molar fraction of the added metal relative to Zn is less than 1 mol %) to form a light-emitting element, it is difficult to generate energy transfer between the multiple quantum dots 7, so high reliability can be achieved. On the other hand, the luminous efficiency may be reduced.

[0033] This article discusses the use of a continuous film primarily composed of Zn sulfide (with the molar fraction of the added metal relative to Zn being less than 1 mol %) in place of the continuous film 6. This continuous film is also referred to as a comparative continuous film. A light-emitting layer having the comparative continuous film is also referred to as a comparative light-emitting layer. A light-emitting element having the comparative light-emitting layer is also referred to as a comparative light-emitting element.

[0034] Figure 2 3 graphs showing the relationship between the emission illuminance (unit: %) and the driving voltage (unit: V) with respect to the emission time (unit: hour) in the comparative light-emitting element are shown in FIG. Figure 2 The three graphs 201 to 203 respectively show the cases where the molar concentration of ZnS (Zn sulfide) in the comparative continuous film is as follows: In the comparative light-emitting element, the luminous efficiency (EQE) per current is substantially proportional to the luminous illuminance.

[0035] Graph 201: 0.08M (mole: equivalent to mol / l) Graph 202: 0.04M Graph 203: 0.02M according to Figure 2 In the comparative light-emitting element, the molar concentration of ZnS in the comparative continuous film has no significant effect on the maximum luminous illuminance. The maximum EQE corresponding to the maximum luminous illuminance is approximately 7.0%.

[0036] according to Figure 2 In the comparative light-emitting elements, the greater the molar concentration of ZnS in the comparative continuous film, the smaller the luminous illuminance, especially after the value stabilizes. Figure 2 , in the comparative light-emitting element, the greater the molar concentration of ZnS in the comparative continuous film, especially after the numerical value stabilizes, the greater the driving voltage.

[0037] Figure 3 This is a graph showing the relationship between the emission brightness (arbitrary unit) and the emission time (arbitrary unit) in a comparative light-emitting element.

[0038] exist Figure 3In this case, period 8 is a period in which the comparison light-emitting element is continuously emitting light, and timing 9 is a timing at which the continuous light emission of the comparison light-emitting element is stopped and restarted. According to Figure 3 the light emission luminance of the comparison light-emitting element reaches a peak at timing 9, and thereafter decreases with the passage of light emission time within period 8, and reaches a peak again at the next timing 9. Comparison of the case where the molar concentration of ZnS in the comparison continuous film is large and the case where the molar concentration of ZnS in the comparison continuous film is small reveals that the larger the molar concentration of ZnS in the comparison continuous film, the greater the decrease rate of the light emission luminance of the comparison light-emitting element.

[0039] Figure 4 is a graph that explains the main reason for the decrease in the light emission luminance of the comparison light-emitting layer 10.

[0040] In the case where the carrier balance in the comparison light-emitting element is good, since the electron 11 and the hole 12 recombine again in the central portion of the comparison light-emitting layer 10, high-efficiency light emission can be performed.

[0041] In the case where the carrier balance in the comparison light-emitting element is not good (excess of electrons), since the electron 11 gradually accumulates in the comparison light-emitting layer 10, the electron 11 accumulated in the comparison light-emitting layer 10 is deactivated thermally after the triplet state, and thus high-efficiency light emission is difficult to perform.

[0042] Figure 5 is a band gap diagram of the hole transport layer 2, the comparison light-emitting layer 10, and the electron transport layer 4 in the comparison light-emitting element. Comparison of the case where the molar concentration of ZnS in the comparison continuous film 13 is large and the case where the molar concentration of ZnS in the comparison continuous film 13 is small reveals that the larger the molar concentration of ZnS in the comparison continuous film 13, the more the hole 12 is likely to be suppressed from being injected into the quantum dot 7 by the comparison continuous film 13.

[0043] Even if the carrier passes through the comparison continuous film 13, in the case where there is a sufficient energy barrier between the first energy level of the hole transport layer 2 and the second energy level of the electron transport layer 4, and further in the case where there is a sufficient energy barrier between the first energy level of the hole transport layer 2 and the second energy level of the electron transport layer 4, since the carrier stays in the comparison light-emitting layer 10, it does not become a main cause of leakage, and there is no particular problem.

[0044] According to the above discussion, comparison of the case where the molar concentration of ZnS in the comparison continuous film 13 is large and the case where the molar concentration of ZnS in the comparison continuous film 13 is small reveals that the larger the molar concentration of ZnS in the comparison continuous film 13, the more the case where (a) and (b) below is likely to occur. It is considered that this tendency is due to the poor carrier balance (excess of electrons).

[0045] (a) the EQE in the comparison light-emitting element is low; (b) the light emission luminance of the comparison light-emitting element is large with respect to the decrease in the light emission luminance of the comparison light-emitting element during the continuous light emission.

[0046] An experiment was conducted to confirm the effect of the present disclosure. Figures 6 to 9 , the insights gained from this experiment are explained.

[0047] Figure 6 : is a diagram showing a method for synthesizing a metal sulfide precursor of the present disclosure. The metal sulfide may be a sulfide corresponding to the main component of the continuous film 6 . Figure 6 The reaction of zinc xanthate is exemplified. The quantum dot layer corresponding to the light-emitting layer 3 is prepared as follows. Materials are not limited to these as long as they have the same function.

[0048] (Synthesis of Metal Sulfide Precursors) Various xanthate metal complexes are synthesized and used as metal sulfide precursors. Zinc chloride or cadmium chloride is dissolved in pure water and mixed with 2.5 times the molar amount of potassium ethylxanthate. After stirring for 12 hours, the xanthate metal precipitate is recovered and washed three times with pure water. The xanthate metal is almost completely decomposed at 150°C to form metal sulfides.

[0049] (Ligand exchange of quantum dots corresponding to quantum dot 7) An octane solution containing oleic acid-modified InP / ZnS quantum dots and a DMF solution containing zinc chloride and zinc xanthate were mixed and vigorously stirred until the two layers separated. The quantum dots were then transferred to the DMF layer. Ethyl acetate was added to precipitate the quantum dots modified with xanthate and chloride ions, and the precipitate was redispersed in a DMF solution containing a predetermined concentration of metal xanthate.

[0050] (Formation of Quantum Dot Layer) Quantum dots modified with xanthogenic acid and a DMF solution containing each xanthogenic metal are coated on a substrate and heated at 150° C. for 30 minutes to thermally decompose the xanthogenic metal, thereby forming a quantum dot layer containing quantum dots on the continuous film of metal sulfide corresponding to the continuous film 6 .

[0051] Figure 7 This graph shows the results of photoelectron yield (PYS) measurements of metal sulfide single films. PYS measurements were performed to measure the valence band state (VBM) of the metal sulfide in the medium. A DMF solution of only the xanthate metal precursor of each medium was applied to ITO and then heated at 150°C to form a metal sulfide single film corresponding to continuous film 6. Substituting 20% ​​of the Zn in the ZnS film corresponding to comparative continuous film 13 with Cd confirmed an increase in VBM. In the case of a medium containing quantum dots, this reduces the energy barrier required for hole injection from the HOMO of the hole transport layer corresponding to hole transport layer 2 into the quantum dots, facilitating hole injection. While energy levels vary depending on the measurement method, measurement conditions, and fitting method, the relative energy level relationships can be assumed to be accurate when measured using the same method.

[0052] Figure 8 is a graph showing the voltage-current characteristics of a hole-only device (HOD) indicating the hole-injection property of the quantum dot layer contained in each of the sulfide media. In order to compare the hole-injection property of the quantum dot layer in which the quantum dots are dispersed in each of the sulfide media, a HOD was produced. In the HOD, only holes are injected as carriers. The HOD was produced in a stacked structure of ITO / NiO nanoparticle / poly-TPD / quantum dot / PMA / Ag. Zinc xanthate was used to replace the ligand of the quantum dots, a DMF solution of the quantum dots was formed at a concentration of 15 mg / ml, and the molar concentration of the sulfide precursor mixed in the quantum dot solution was adjusted to a prescribed ratio. In order to inject only holes from the electrode, a phosphomolybdic acid (PMA) solution was applied to the quantum dot layer, and firing was performed at 110°C. It was found that, by replacing 20% of Zn of the ZnS medium with Cd, the amount of current at the same voltage increased when compared at the same medium, and the hole-injection property to the quantum dot layer was improved.

[0053] Figure 9 is a graph showing the maximum EQE and the luminance reduction rate after driving for 5 hours of a light-emitting element corresponding to the light-emitting element 101, using the quantum dot layer contained in each of the sulfide media as a light-emitting layer. The light-emitting element having the quantum dot layer in which the quantum dots are dispersed in each of the sulfide media was produced in such a manner as to become a stacked structure of ITO / NiO nanoparticle / poly-TPD / quantum dot / ZnMgO / Ag. Zinc xanthate and zinc chloride were used to replace the ligand of the quantum dots having a composition of InP / ZnS and emitting red light, a DMF solution of the quantum dots was formed at a concentration of 15 mg / ml, and the molar concentration of the sulfide precursor mixed in the quantum dot solution was adjusted to a prescribed ratio. In Figure 9 , according to the examples and comparative examples, the EQE rose by replacing 20% of Zn of the ZnS medium with Cd. Also, it was confirmed that the luminance reduction at the initial stage of driving was suppressed. It is considered that this is the effect that the hole-injection property is improved and it is difficult for excess electrons to accumulate in the quantum dot layer. In the present disclosure, Cd was used as an additive material for ZnS, and a metal forming a VBM higher than that of the sulfide semiconductor of ZnS can also be added in an appropriate amount.

[0054] In Figure 10 , the first example 14, the second example 15, the third example 16, and the fourth example 17 are shown with respect to the ratio of the mass of the plurality of luminescent quantum dots 7 to the mass of the light-emitting layer 3.

[0055] In the first example 14, the light-emitting layer 3 is composed of a single layer structure of the normally configured layer 18. In the second example 15, the light-emitting layer 3 is composed of a stacked structure of two layers of the normally configured layer 18. In the third example 16, the light-emitting layer 3 is composed of a stacked structure of the normally configured layer 18 (hole-transporting layer 2 side) and the sparsely configured layer 19 (electron-transporting layer 4 side). In the fourth example 17, the light-emitting layer 3 is composed of a stacked structure of the sparsely configured layer 19 (hole-transporting layer 2 side) and the normally configured layer 18 (electron-transporting layer 4 side).

[0056] The ratio of the mass of the light-emitting quantum dots 7 contained in the normally configured layer 18 to the mass of the normally configured layer 18 is 88%. The ratio of the mass of the light-emitting quantum dots 7 contained in the sparsely configured layer 19 to the mass of the sparsely configured layer 19 is 65%.

[0057] The third example 16 and the fourth example 17 can achieve higher EQE in the light-emitting element 101, respectively, as compared with the first example 14. The second example 15 does not confirm the improvement of the EQE in the light-emitting element 101 as compared with the first example 14.

[0058] The light-emitting layer 3 is a stacked structure of a plurality of layers including the sparsely configured layer 19, and the ratio of the mass of the light-emitting quantum dots 7 contained in the sparsely configured layer 19 to the mass of the sparsely configured layer 19 can also be 20% or more and 80% or less. If a specific example is given, it can also be any one of the third example 16 and the fourth example 17 (the ratio is 65%).

[0059] Figure 11 A diagram for illustrating a manufacturing method of the light-emitting element 101. The manufacturing method of the light-emitting element 101 includes a step S1 of preparing a quantum dot dispersion liquid 23 by dispersing the first metal complex 20, the second metal complex 21, and the light-emitting quantum dots 7 in a solvent 22, and a step S2 of forming the light-emitting layer 3 by coating the quantum dot dispersion liquid 23 and heating.

[0060] The first metal complex 20 is thermally decomposable and contains Zn. As one example of the first metal complex 20, zinc dithiocarboxylate, zinc xanthate, zinc dithiocarbamate, and zinc tertiary alkyl mercaptide can be given. The dithiocarboxylic acid has a structure represented by XC(=S)SH (X is a carbon substituent). The xanthic acid has a structure represented by ROC(=S)SH (R is hydrogen, a hydrocarbon group, or the like). The dithiocarbamic acid has a structure represented by R2NC(=S)SH. The tertiary alkyl mercaptide has a structure represented by R2C-SH.

[0061] The second metal complex 21 is thermally decomposable and contains an additive metal. The additive metal is composed of at least one of Cd, Sn, Mn, Ga, In, Ce, and Cu. As an example of the ligand of the second metal complex 21, dithiocarboxylic acid, xanthic acid, dithiomicotinyl acid, and tertiary alkyl mercaptan can be given.

[0062] The solvent 22 can be either a polar solvent or a nonpolar solvent. The solvent 22 can also be a polar solvent containing 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 sulfide-based solvent, and a nitrile-based solvent.

[0063] The manufacturing method of the light emitting element 101 can also include a process of exposing and developing the applied quantum dot dispersion liquid 23.

[0064] Figure 12 is a schematic view showing a configuration example of a display device 401 of the present disclosure. Figure 13 is a cross-sectional view showing a configuration example of the display device 401 of the present disclosure. As shown in Figure 12 The display device 401 includes a display portion DA including a plurality of sub-pixels SP, a first driver X1 and a second driver X2 that drive the plurality of sub-pixels SP, and a display control portion DC that controls the first driver X1 and the second driver X2. The sub-pixel SP includes a light emitting element 305 and a pixel circuit PC connected to the light emitting element 305. The pixel circuit PC can also be connected to a scan signal line GL, a data signal line DL, and a light emission control line EL. The scan signal line GL and the light emission control line EL can be connected to the first driver X1, and the data signal line DL can be connected to the second driver X2.

[0065] The display device 401 can 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 can use a glass substrate, a resin substrate, or the like. The substrate 311 can be flexible. The pixel circuit layer 312 includes, for example, a plurality of pixel circuits PC arranged with an inorganic matrix. The pixel circuit PC can include a pixel capacitor that writes a gray scale signal, a transistor that controls a current value of the light emitting element 305 according to the gray scale signal, a transistor connected to the scan signal line GL and the data signal line DL, and a transistor connected to the light emission control line EL.

[0066] As shown in Figure 13As shown, the display device 401 includes a pixel circuit substrate 313 and a light emitting element layer 314. The light emitting element layer 314 can include, in order from the pixel circuit substrate 313 side, a first electrode D1, an edge cover film JF covering edges 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 has a hole injection function and a hole transport function, and the second functional layer SK has an electron transport function. The light emitting element layer 314 can also 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 the intrusion of foreign matter (water, oxygen, and the like) into the light emitting element layer 314.

[0067] As the material of the first functional layer FK, an organic material such as poly[(9,9-dioctylfluorene-2,7-diyl)-co-(4,4'-(N-4-sec-butyphenyl))diphenylamine)] (TFB), poly(4-butyltriphenylamine) (p-TPD), poly(9-vinylcarbazole) (PVK), [9,9'-[1,2-phenylenebis(methylene)]bis[N3,N3,N6,N6-tetra(4-methoxyphenyl)-9H-carbazole-3,6-diamine] (V886), 7,7'-bis[1,4]benzoxazino[2,3,4-kl]phenoxazine (HN-D1), or the like, an inorganic material such as NiO nanoparticles, or the like, can be used.

[0068] As the material of the second functional layer SK, an organic material such as (2,2',2"-(1,3,5-benzene triyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi), bathocuproin (BCP), nanoparticles of an organic metal complex, or the like, an inorganic material such as nanoparticles of an n-type oxide semiconductor, or the like, can be used. As the organic metal complex, for example, tris(8-hydroxyquinoline)aluminum complex (Alq3) or the like can be listed. As the n-type oxide semiconductor, for example, metal oxides such as ZnO, ZnMgO, or the like can be listed.

[0069] Figure 13 In the present embodiment, the quantum dot layer is used as the light emitting layer 330, but is not limited thereto. The quantum dot layer can also be used as a wavelength conversion layer or a light sensor layer. In addition, a power generating element including the quantum dot layer between a pair of electrodes can also be configured. For example, an electromotive force can be generated by generating holes and electrons in the quantum dot from light incident to the quantum dot layer, and transporting them to the electrodes, respectively.

[0070] As the light-emitting element 305, the light-emitting element 101 can be applied. As specific examples, the anode 1 can be applied as the first electrode D1, the hole-transporting layer 2 can be applied as the first functional layer FK, the light-emitting layer 33 can be applied as the light-emitting layer 3, the electron-transporting layer 4 can be applied as the second functional layer SK, and the cathode 5 can be applied as the second electrode D2, respectively.

[0071] The present disclosure is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and embodiments obtained by appropriately combining the technical solutions disclosed in different embodiments are also included in the technical scope of the present disclosure. Furthermore, by combining the technical means disclosed in each of the embodiments, a new technical feature can be formed.

[0072] Explanation of Reference Signs 1: anode; 2: hole-transporting layer; 3: light-emitting layer; 4: electron-transporting layer; 5: cathode; 6: continuous film; 7: quantum dot; 8: period; 9: timing; 10: comparative light-emitting layer; 11: electron; 12: hole; 13: comparative continuous film; 14: first example; 15: second example; 16: third example; 17: fourth example; 18: normally configured layer; 19: sparsely configured layer; 20: first metal complex; 21: second metal complex; 22: solvent; 23: quantum dot dispersion liquid; 101, 305: light-emitting element; 201, 202, 203: graph; 401: display device.

Claims

1. A light emitting element characterized by comprising: It comprises: an anode; a cathode; and a light-emitting layer between the anode and the cathode, the light-emitting layer has: a continuous film that is a continuous film in which a sulfide of Zn and a sulfide of an additive metal composed of at least one of Cd, Sn, Mn, Ga, In, Ce, and Cu are main components, wherein the molar fraction of the additive metal with respect to the Zn is 1 mol% or more; and a plurality of light-emitting quantum dots wrapped by the continuous film.

2. A light emitting element characterized by It comprises: an anode; a cathode; a light-emitting layer between the anode and the cathode; a hole-transporting layer between the anode and the light-emitting layer; and an electron-transporting layer between the cathode and the light-emitting layer, the light-emitting layer has: a continuous film that is a continuous film in which a sulfide of a metal is a main component, wherein, when CBM or LUMO is a first energy level, VBM or HOMO is a second energy level, the difference between the first energy level of the electron-transporting layer and the first energy level of the continuous film is ΔE(e), and the difference between the second energy level of the hole-transporting layer and the second energy level of the continuous film is ΔE(h), the difference between ΔE(e) and ΔE(h) is 1 eV or less; and a plurality of light-emitting quantum dots wrapped by the continuous film.

3. The light-emitting element according to claim 1 or 2, wherein the light-emitting layer is a stacked structure of a plurality of layers, and the stacked structure of a plurality of layers includes a sparse arrangement layer, the ratio of the mass of the quantum dots contained in the sparse arrangement layer to the mass of the sparse arrangement layer in the plurality of light-emitting quantum dots is 20% or more and 80% or less.

4. The light-emitting element according to any one of claims 1 to 3, wherein the band gap of the continuous film is larger than the band gap of the plurality of light-emitting quantum dots.

5. A display device comprising the light-emitting element according to any one of claims 1 to 4.

6. A method for manufacturing a light-emitting element, comprising the steps of: It comprises: a process of preparing a quantum dot dispersion liquid by dispersing a thermally decomposable first metal complex, a thermally decomposable second metal complex, and a plurality of light-emitting quantum dots in a solvent, the first metal complex containing Zn, and the second metal complex containing an additive metal composed of at least one of Cd, Sn, Mn, Ga, In, Ce, and Cu; and a process of forming a light-emitting layer by coating and heating the quantum dot dispersion liquid.

7. The method for manufacturing a light-emitting element according to claim 6, wherein It comprises a process of exposing and developing the coated quantum dot dispersion liquid.

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