ZnS composite material and preparation method thereof, ZnS thin film, and light-emitting device

Abstract

This application belongs to the field of display technology, and in particular relates to a method for preparing a ZnS composite material, comprising the steps of: dissolving a zinc source and a sulfur source in an organic solvent, adding a precious metal salt to carry out a mixing reaction, and obtaining a mixed salt solution; and adding an alkali source to the mixed salt solution to make the solution alkaline, and carrying out a hydrothermal reaction to obtain the ZnS composite material. The method for preparing the ZnS composite material provided in the embodiments of the present application has a simple process, and the prepared ZnS composite material has few surface defects, good electrical conductivity, high electron transfer efficiency, good interfacial contact performance with adjacent functional layers, and good dispersion stability in solution.

Description

Technical Field

[0001] The present application belongs to the field of display technology, and in particular relates to a ZnS composite material and a preparation method thereof, a ZnS thin film, and a light-emitting device. Background Art

[0002] Quantum dots (QDs), as semiconductor materials for next-generation lighting and display devices, possess unique optical properties, including a wide excitation spectrum, a narrow emission spectrum, high light color purity, high luminescence quantum efficiency, adjustable luminescence color, and a long service life. Furthermore, the preparation process of quantum dots offers advantages that cannot be matched by organic synthesis, such as simplicity, low cost, and low toxicity. Semiconductor quantum dots exhibit a quantum size effect, allowing researchers to control the size of quantum dots to achieve the desired specific wavelength of light emission. For example, the wavelength of CdSe QDs can be tuned from blue to red. In traditional inorganic electroluminescent devices, electrons and holes are injected from the cathode and anode, respectively, and then recombine in the light-emitting layer to form excitons, which emit light. Conduction band electrons in wide-bandgap semiconductors can be accelerated under high electric fields to obtain high enough energy to collide with QDs, causing them to emit light.

[0003] In recent years, inorganic semiconductors as electron transport layers have become a hot topic of research. ZnS, a Group II-VI direct-gap n-type semiconductor, boasts a wide bandgap of 3.7 eV, a low work function, and excellent stability, high transparency, and safety and non-toxicity. Furthermore, ZnS possesses two distinct structural forms, zinc blende and wurtzite, and possesses stable chemical properties, abundant resources, and low cost. It holds enormous potential for applications in light-emitting diodes, flat-panel displays, fluorescent inks, and biomarkers. In the field of novel displays, ZnS could be a suitable electron transport layer material.

[0004] ZnS nanoparticles are easy to aggregate and have certain defects on their surface, resulting in obvious surface defects in the ZnS film. This makes the ZnS film have poor interface contact with the adjacent luminescent active layer, leading to serious carrier recombination and limiting its electron transport performance. Summary of the Invention

[0005] The purpose of this application is to provide a ZnS composite material and a preparation method thereof, as well as a ZnS thin film and a light-emitting device, aiming to solve the problem of poor electron transport performance of existing ZnS materials to a certain extent.

[0006] To achieve the above application objectives, the technical solutions adopted in this application are as follows:

[0007] In a first aspect, the present application provides a method for preparing a ZnS composite material, comprising the following steps:

[0008] Dissolving a zinc source and a sulfur source in an organic solvent, adding a noble metal salt to carry out a mixing reaction, and obtaining a mixed salt solution;

[0009] An alkali source is added to the mixed salt solution to make the solution alkaline, and a hydrothermal reaction is performed to obtain a ZnS composite material.

[0010] In a second aspect, the present application provides a ZnS composite material, wherein the ZnS composite material is doped with noble metal ions, and hydroxyl groups are bound to the surface of the ZnS composite material.

[0011] In a third aspect, the present application provides a ZnS thin film, which includes the ZnS composite material prepared by the above method, or contains the above ZnS composite material.

[0012] In a fourth aspect, the present application provides a light-emitting device, which includes an anode and a cathode arranged opposite to each other and a light-emitting unit combined between the anode and the cathode, the light-emitting unit including a light-emitting layer and an electron transport layer, and the electron transport layer is arranged between the light-emitting layer and the cathode; wherein the electron transport layer contains the ZnS composite material prepared by the above method, or contains the above-mentioned ZnS composite material, or contains the above-mentioned ZnS thin film.

[0013] The preparation method of the ZnS composite material provided in the first aspect of the present application is simple. In the prepared ZnS composite material, the doped noble metal ions are conducive to the subsequent hydroxyl group filling the S vacancies on the surface of the ZnS material, especially the S vacancies adjacent to the noble metal. In addition, the doped noble metal ions can enhance the electrical conductivity of the ZnS material, thereby improving the electron transfer rate of the ZnS composite material. In addition, the hydroxyl group modifies the S vacancies in the ZnS material, reduces the defect states on the surface of the ZnS material, and forms a double anion structure of -S and -OH on the surface of the ZnS composite material, thereby improving the electron transfer performance of the ZnS material, improving the interface contact between the ZnS material and the adjacent active layer, and at the same time helping to improve the dispersion stability of the ZnS material in solution.

[0014] The ZnS composite material provided in the second aspect of this application, doped with precious metal ions, enhances its electrical conductivity and increases its electron transfer rate. Furthermore, the hydroxyl groups bound to the surface of the ZnS composite material reduce surface defects, improve the interfacial contact performance between the ZnS composite material and adjacent functional layers, enhance electron transfer and carrier recombination, and improve the dispersion stability of the ZnS composite material in solution, thereby extending the storage time of the solution.

[0015] The ZnS thin film provided in the third aspect of the present application, due to its inclusion of the aforementioned ZnS composite material, exhibits few surface defects, excellent conductivity, high electron transport efficiency, good interfacial contact with adjacent functional layers, and excellent dispersion stability in solution. Consequently, the ZnS thin film is dense and flat, tightly bonded to adjacent functional layers, and exhibits excellent stability, facilitating electron transport and improving carrier recombination efficiency.

[0016] The light-emitting device provided in the fourth aspect of the present application has a high carrier recombination efficiency, stable device luminescence performance, and high luminescence efficiency, because the electron transport layer comprises the aforementioned ZnS composite material having few surface defects, good conductivity, high electron transport efficiency, good interface contact with adjacent functional layers, and good dispersion stability in solution, or comprises the aforementioned ZnS thin film having a dense and flat film layer, close bonding with adjacent functional layers, and good stability. Therefore, the light-emitting device of the present application has high carrier recombination efficiency, stable device luminescence performance, and high luminescence efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0018] Figure 1 1 is a schematic flow chart of a method for preparing a ZnS composite material provided in an embodiment of the present application;

[0019] Figure 2 A positive-type light-emitting device is provided in an embodiment of the present invention.

[0020] Figure 3 The invention provides a light-emitting device with an inverted configuration. DETAILED DESCRIPTION

[0021] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application more clearly understood, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0022] In this application, the term "and / or" describes the association relationship between associated objects, indicating that three relationships may exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural.

[0023] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0024] It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. Some or all of the steps can be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0025] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The singular forms "a", "an" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0026] The weights of the relevant components mentioned in the examples of this application may not only refer to the specific content of each component, but also represent the weight ratio between the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the examples of this application, it is within the scope disclosed in the examples of this application. Specifically, the mass in the examples of this application may be μg, mg, g, kg, etc., which are mass units known in the chemical industry.

[0027] The terms "first" and "second" are used solely for descriptive purposes to distinguish objects, such as substances, from one another and should not be understood to indicate or imply relative importance or to implicitly specify the quantity of the technical features being referred to. For example, without departing from the scope of the embodiments of this application, a first XX may also be referred to as a second XX, and similarly, a second XX may also be referred to as a first XX. Thus, features defined as "first" or "second" may explicitly or implicitly include one or more of such features.

[0028] A first aspect of the present invention provides a method for preparing a ZnS composite material, comprising the following steps:

[0029] S10. The zinc source and the sulfur source are dissolved in an organic solvent, and a noble metal salt is added to carry out a mixed reaction to obtain a mixed salt solution;

[0030] S20. Add an alkali source to the mixed salt solution to make the solution alkaline, and perform a hydrothermal reaction to obtain a ZnS composite material.

[0031] The preparation method of the ZnS composite material provided in the first aspect of the present application is to dissolve a zinc source and a sulfur source in an organic solvent so that the sulfur element and the zinc element combine to form a ZnS crystal nucleus; add a precious metal salt to carry out a mixed reaction so that while the ZnS crystal nucleus continues to grow, the precious metal ions are doped into the ZnS to form a ZnS material doped with precious metal ions. Then, an alkali source is added to adjust the solution to alkalinity to induce hydroxyl groups to modify the S vacancies on the surface of the ZnS material to obtain a ZnS composite material. The preparation method of the ZnS composite material of the embodiment of the present application, through a simple process, on the one hand, dopes the ZnS material with precious metal ions, the doped precious metal atoms have a certain affinity, and the bond energy between the precious metal and S is lower than the Zn-S bond, which makes it easier to capture hydroxyl groups, which is conducive to the subsequent hydroxyl groups filling the S vacancies on the surface of the ZnS material, especially the S vacancies adjacent to the precious metal. In addition, the doped precious metal ions can enhance the conductive properties of the ZnS material, thereby improving the electron transfer rate of the ZnS composite material. On the other hand, by modifying the S vacancies in the ZnS material with hydroxyl groups, the defect states on the ZnS material surface are reduced, so that the surface of the ZnS composite material is simultaneously bound to -S and -OH anions through adsorption or bonding, forming a double-anion structure of -S and -OH. This not only improves the electron transport performance of the ZnS material, but also the -S and -OH anions on the ZnS surface can improve the interfacial contact and reduce the recombination of excitons at the interface, thereby improving the interfacial contact between the ZnS material and the adjacent active layer, promoting more efficient electron transmission. At the same time, because the amount of hydroxyl groups on the ZnS material surface is increased, according to the principle of like dissolves like, the ZnS material has better compatibility with solvents such as alcohol, which is beneficial to improving the dispersion stability of the ZnS material in solution.

[0032] Specifically, in step S10, to ensure that the ZnS core is formed first and to avoid the direct formation of noble metal sulfides, the desired ZnS material cannot be obtained. Therefore, after dissolving the zinc source and sulfur source in an organic solvent, a noble metal salt is added for a mixing reaction. This allows the added noble metal ions to be doped into the ZnS during the ZnS growth process, forming a mixed salt solution containing a noble metal-doped ZnS composite material, which provides conditions for the subsequent replacement of sulfur vacancies by hydroxyl groups.

[0033] In some embodiments, the molar ratio of the sulfur source to the zinc source is (1-3):1. If the sulfur source content is too low, not all of the zinc source can be converted to ZnS, resulting in an incomplete reaction and hindering the doping of precious metal ions. If the sulfur source content is too high, the residual sulfur source can combine with the subsequently added precious metal salt to form precious metal sulfides, which not only affects the purity of the ZnS composite material and reduces the composite material's electron transport performance, but also affects the stability of the device. In some specific embodiments, the molar ratio of the sulfur source to the zinc source is (1-1.5):1, (1.5-2):1, (2-3):1, or (2.5-3):1.

[0034] In some embodiments, the molar ratio of the noble metal salt to the zinc source is (0.02-0.1):1. If the amount of noble metal added is too high, the ZnS material will suffer from severe lattice distortion due to the doping of a large amount of noble metal ions, forming a large number of defects and damaging the electrochemical properties of the ZnS material itself. If the amount of noble metal added is too low, it will not be conducive to inducing the modification of hydroxyl groups on the ZnS material, nor will it be conducive to improving the electron transport properties of the ZnS material. In some specific embodiments, the molar ratio of the noble metal salt to the zinc source is (0.02-0.04):1, (0.04-0.06):1, (0.06-0.08):1, or (0.08-0.1):1.

[0035] In some embodiments, the concentration of the zinc source in the mixed salt solution is 0.1 mol / L to 1 mol / L. This concentration range of zinc source has optimal reactivity with the sulfur source and subsequently added precious metal salts. If the concentration is too low, the yield is low. If the concentration is too high, large-sized ZnS crystals are easily formed within the reaction time, which is not conducive to the dissolution and dispersion of the ZnS material, and the film-forming performance is poor, resulting in poor film density. In some specific embodiments, the concentration of the zinc source in the mixed salt solution is 0.1 mol / L to 0.3 mol / L, 0.3 mol / L to 0.5 mol / L, 0.5 mol / L to 0.7 mol / L, or 0.7 mol / L to 1 mol / L.

[0036] In some embodiments, a zinc source and a sulfur source are dissolved in an organic solvent, and after adding a noble metal salt, the mixture is reacted at a temperature of 20° C. to 40° C. for 30 minutes to 1 hour to fully form a ZnS composite material doped with a noble metal.

[0037] In some embodiments, the zinc source is selected from at least one soluble inorganic zinc salt or organic zinc salt selected from zinc acetate, zinc nitrate, zinc chloride, and zinc acetate dihydrate. In some embodiments, the sulfur source is selected from at least one of thiourea, thioacetamide, and L-cysteine. These zinc and sulfur sources have good solubility in alcoholic solvents, which facilitates the reaction of zinc ions and sulfur ions to form the ZnS material.

[0038] In some embodiments, the organic solvent is selected from at least one alcohol solvent selected from methanol, ethanol, and butanol. These alcohol solvents have good solubility for zinc sources, sulfur sources, and precious metal salts, low solvent toxicity, and are environmentally friendly. At the same time, they have a low boiling point and are easily separated from the product without residue.

[0039] In some embodiments, the noble metal salt is selected from at least one of gold salts, palladium salts, rhodium salts, and platinum salts. These noble metal ions are doped into the ZnS material, and the bond energy with the S ion is lower than the Zn-S bond, forming adjacent sulfur vacancies. Under alkaline conditions, -OH is more likely to fill the S vacancies adjacent to the noble metal. The S vacancies on the surface of the ZnS material are modified by hydroxyl groups to form a ZnS material with a double anion surface layer, thereby improving the electron transport performance of the ZnS material and improving the interface contact between the ZnS material and the corresponding active layer, thereby improving the electron transport efficiency. In some specific embodiments, the noble metal salt is selected from at least one of chloroauric acid, palladium chloride, rhodium chloride, and platinum chloride. These noble metal chlorides have good solubility in alcohol solvents.

[0040] Specifically, in step S20, an alkaline source is added to the mixed salt solution to adjust the solution pH to 8 to 12. Under alkaline conditions, hydroxyl groups are induced to modify the S vacancies on the surface of the ZnS material, thereby obtaining a ZnS composite material having -S and -OH double anions modified on the surface. The alkaline environment of pH 8 to 12 allows for the stable presence of hydroxide ions, which is beneficial for modifying the surface of the ZnS material with hydroxyl groups.

[0041] In some embodiments, after adding an alkali source to the mixed salt solution to make the solution pH 8-12, the mixture is reacted at a temperature of 80-120° C. for 0.5-2 hours to allow the hydroxyl groups to fully modify the surface of the ZnS material.

[0042] In some embodiments, the alkaline source is selected from at least one of sodium hydroxide, potassium hydroxide, and tetramethylammonium hydroxide, and these alkaline sources can effectively adjust the pH of the solution.

[0043] In some embodiments, the ZnS composite material has a particle size of 10 nm to 30 nm. The ZnS composite material prepared in the embodiments of the present application has a small and uniform particle size and good dispersion stability, which results in good film-forming properties of the ZnS composite material, a dense and smooth film layer, and further improves the bonding stability between the ZnS composite material film layer and the adjacent active layer, reduces interfacial impedance, and improves electron transport performance.

[0044] A second aspect of an embodiment of the present application provides a ZnS composite material, wherein the ZnS composite material is doped with noble metal atoms, and hydroxyl groups are bonded to the surface of the ZnS composite material.

[0045] The ZnS composite material provided in the second aspect of the present application has enhanced conductivity and increased electron transfer rate due to the ZnS composite material being doped with precious metal ions. Furthermore, hydroxyl groups are bound to the surface of the ZnS composite material by adsorption or bonding, and the S vacancies on the surface of the ZnS composite material are modified by hydroxyl groups, thereby reducing surface defect states of the ZnS composite material, improving the interfacial contact performance between the ZnS composite material and the adjacent functional layer, and enhancing electron transfer and carrier recombination. Furthermore, the dispersion stability of the ZnS composite material in solution is improved, and the storage time of the solution is extended.

[0046] The ZnS composite material provided in the embodiments of the present application can be prepared by the method of any of the above embodiments.

[0047] In some embodiments, the noble metal ions are selected from at least one of gold ions, platinum ions, palladium ions, and rhodium ions. These noble metal ions are doped into the ZnS material, and the bonding energy with the S ions is lower than the Zn-S bond, which is more conducive to hydroxyl modification of S vacancies on the surface of the ZnS material, thereby improving the electron transport performance of the ZnS material, improving the interface contact between the ZnS material and the corresponding active layer, and improving the electron transport efficiency.

[0048] In some embodiments, in the ZnS composite material, the molar ratio of noble metal ions to zinc ions is (0.02-0.1):1. If the ratio of noble metal ions is too high, the ZnS material will suffer from severe lattice distortion due to the doping of a large amount of noble metal ions, forming a large number of defects and destroying the electrochemical properties of the ZnS material itself; if the ratio of noble metal ions is too low, it will be detrimental to improving the electron transport performance of the ZnS material, nor will it be conducive to inducing the modification of hydroxyl groups on the ZnS material.

[0049] In some embodiments, the ZnS composite material has a particle size of 10 nm to 30 nm, is relatively small and uniform, and has good dispersion stability, so that the ZnS composite material has good film-forming performance and a dense and smooth film layer.

[0050] A third aspect of the embodiments of the present application provides a ZnS thin film, which includes the ZnS composite material prepared by the above method, or contains the above ZnS composite material.

[0051] The ZnS thin film provided in the third aspect of the present application, due to its inclusion of the aforementioned ZnS composite material, exhibits few surface defects, excellent conductivity, high electron transport efficiency, good interfacial contact with adjacent functional layers, and excellent dispersion stability in solution. Consequently, the ZnS thin film is dense and flat, tightly bonded to adjacent functional layers, and exhibits excellent stability, facilitating electron transport and improving carrier recombination efficiency.

[0052] A fourth aspect of an embodiment of the present application provides a light-emitting device, which includes an anode and a cathode arranged opposite to each other and a light-emitting unit combined between the anode and the cathode, the light-emitting unit including a light-emitting layer and an electron transport layer, and the electron transport layer is arranged between the light-emitting layer and the cathode; wherein the electron transport layer contains the ZnS composite material prepared by the above method, or contains the above-mentioned ZnS composite material, or contains the above-mentioned ZnS thin film.

[0053] The light-emitting device provided in the fourth aspect of the present application has a high carrier recombination efficiency, stable device luminescence performance, and high luminescence efficiency, because the electron transport layer comprises the aforementioned ZnS composite material having few surface defects, good conductivity, high electron transport efficiency, good interface contact with adjacent functional layers, and good dispersion stability in solution, or comprises the aforementioned ZnS thin film having a dense and flat film layer, close bonding with adjacent functional layers, and good stability. Therefore, the light-emitting device in the embodiment of the present application has high carrier recombination efficiency, stable device luminescence performance, and high luminescence efficiency.

[0054] In the embodiment of the present application, the device is not limited by the device structure and can be a device with a positive structure or a device with an inverted structure.

[0055] In one embodiment, a positive structure light emitting device includes a stacked structure of an anode and a cathode arranged opposite to each other, a light emitting layer arranged between the anode and the cathode, and the anode is arranged on a substrate. Furthermore, a hole functional layer such as a hole injection layer, a hole transport layer, and an electron blocking layer may be arranged between the anode and the light emitting layer; an electron functional layer such as an electron transport layer, an electron injection layer, and a hole blocking layer may be arranged between the cathode and the light emitting layer. Figure 2 In some specific embodiments of positive-type devices, the light-emitting device includes a substrate, an anode disposed on a surface of the substrate, a hole transport layer disposed on a surface of the anode, a light-emitting layer disposed on a surface of the hole transport layer, an electron transport layer disposed on a surface of the light-emitting layer, and a cathode disposed on a surface of the electron transport layer.

[0056] In one embodiment, the inverted structure light emitting device includes a stacked structure of an anode and a cathode arranged opposite to each other, a light emitting layer arranged between the anode and the cathode, and the cathode is arranged on a substrate. Furthermore, a hole functional layer such as a hole injection layer, a hole transport layer, and an electron blocking layer may be arranged between the anode and the light emitting layer; an electron functional layer such as an electron transport layer, an electron injection layer, and a hole blocking layer may be arranged between the cathode and the light emitting layer, as shown in the attached figure. Figure 3 In some embodiments of inversion structure devices, the light-emitting device includes a substrate, a cathode disposed on a surface of the substrate, an electron transport layer disposed on a surface of the cathode, a light-emitting layer disposed on a surface of the electron transport layer, a hole transport layer disposed on a surface of the light-emitting layer, and an anode disposed on a surface of the hole transport layer.

[0057] In some embodiments, the choice of substrate is not limited, and a rigid substrate or a flexible substrate can be used. In some specific embodiments, the rigid substrate includes, but is not limited to, one or more of glass and metal foil. In some specific embodiments, the flexible substrate includes, but is not limited to, one or more of polyethylene terephthalate (PET), polyethylene terephthalate (PEN), polyetheretherketone (PEEK), polystyrene (PS), polyethersulfone (PES), polycarbonate (PC), polyarylate (PAT), polyarylate (PAR), polyimide (PI), polyvinyl chloride (PV), polyethylene (PE), polyvinyl pyrrolidone (PVP), and textile fiber.

[0058] In some embodiments, the anode material is not limited and can be selected from doped metal oxides, including but not limited to one or more of indium-doped tin oxide (ITO), fluorine-doped tin oxide (FTO), antimony-doped tin oxide (ATO), aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO), indium-doped zinc oxide (IZO), magnesium-doped zinc oxide (MZO), and aluminum-doped magnesium oxide (AMO). It can also be selected from composite electrodes formed by sandwiching metals between doped or undoped transparent metal oxides, including but not limited to one or more of AZO / Ag / AZO, AZO / Al / AZO, ITO / Ag / ITO, ITO / Al / ITO, ZnO / Ag / ZnO, ZnO / Al / ZnO, TiO2 / Ag / TiO2, TiO2 / Al / TiO2, ZnS / Ag / ZnS, ZnS / Al / ZnS, TiO2 / Ag / TiO2, and TiO2 / Al / TiO2.

[0059] In some embodiments, the hole injection layer includes but is not limited to one or more of an organic hole injection material, a doped or undoped transition metal oxide, and a doped or undoped metal sulfide compound. In some specific embodiments, the organic hole injection material includes but is not limited to one or more of poly(3,4-ethylenedioxythiophene)-polystyrenesulfonic acid (PEDOT:PSS), copper phthalocyanine (CuPc), 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanoquinone-dimethane (F4-TCNQ), and 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (HATCN). In some specific embodiments, the transition metal oxide includes but is not limited to one or more of MoO3, VO2, WO3, CrO3, and CuO. In some specific embodiments, the metal sulfide compound includes but is not limited to one or more of MoS2, MoSe2, WS2, WSe2, and CuS.

[0060] In some embodiments, the hole transport layer can be selected from organic materials having hole transport capability and / or inorganic materials having hole transport capability. In some specific embodiments, the organic materials having hole transport capability include, but are not limited to, poly(9,9-dioctylfluorene-co-N-(4-butylphenyl)diphenylamine) (TFB), polyvinylcarbazole (PVK), poly(N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine) (poly-TPD), poly(9,9-dioctylfluorene-co-bis-N,N-phenyl-1,4-phenylenediamine) (PFB), 4,4',4"-tris(carbazol-9-yl)triphenylamine (TCTA), 4,4'-bis(9-carbazol)biphenyl (CBP), N , N'-diphenyl-N,N'-di(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD), N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine (NPB). In some specific embodiments, the inorganic material having hole transport capability includes, but is not limited to, one or more of doped graphene, undoped graphene, C60, doped or undoped MoO3, VO2, WO3, CrO3, CuO, MoS2, MoSe2, WS2, WSe2, and CuS.

[0061] In some embodiments, the light-emitting layer includes a quantum dot material, which includes, but is not limited to, at least one semiconductor compound selected from Groups II-IV, II-VI, II-V, III-V, III-VI, IV-VI, I-III-VI, II-IV-VI, and II-IV-V of the Periodic Table, or a core-shell structure semiconductor compound composed of at least two of the foregoing semiconductor compounds. In some specific embodiments, the quantum dot functional layer material is selected from at least one semiconductor nanocrystalline compound selected from CdSe, CdS, CdTe, ZnO, ZnSe, ZnS, ZnTe, HgS, HgSe, HgTe, and CdZnSe, or a semiconductor nanocrystalline compound composed of at least two of the foregoing semiconductor compounds having a mixed, gradient mixed, core-shell, or combined structure. In other specific embodiments, the quantum dot functional layer material is selected from at least one semiconductor nanocrystalline compound selected from the group consisting of InAs, InP, InN, GaN, InSb, InAsP, InGaAs, GaAs, GaP, GaSb, AlP, AlN, AlAs, AlSb, CdSeTe, and ZnCdSe, or a semiconductor nanocrystalline compound having a mixed, gradient mixed, core-shell, or combined structure of at least two of them. In other embodiments, the quantum dot functional layer material is selected from at least one of perovskite nanoparticle materials (particularly luminescent perovskite nanoparticle materials), metal nanoparticle materials, and metal oxide nanoparticle materials. Each of these quantum dot materials possesses the characteristics of quantum dots and exhibits excellent photoelectric performance.

[0062] In some embodiments, the particle size range of the quantum dot material is 2 to 10 nm. If the particle size is too small, the film-forming property of the quantum dot material deteriorates, and the energy resonance transfer effect between the quantum dot particles is significant, which is not conducive to the application of the material. If the particle size is too large, the quantum effect of the quantum dot material is weakened, resulting in a decrease in the photoelectric performance of the material.

[0063] In some embodiments, the material of the electron transport layer includes the aforementioned ZnS composite material.

[0064] In some embodiments, the cathode material can be one or more of various conductive carbon materials, conductive metal oxide materials, and metal materials. In some specific embodiments, the conductive carbon material includes but is not limited to doped or undoped carbon nanotubes, doped or undoped graphene, doped or undoped graphene oxide, C60, graphite, carbon fiber, porous carbon, or a mixture thereof. In some specific embodiments, the conductive metal oxide material includes but is not limited to ITO, FTO, ATO, AZO, or a mixture thereof. In some specific embodiments, the metal material includes but is not limited to Al, Ag, Cu, Mo, Au, or an alloy thereof; wherein the metal material, its form includes but is not limited to dense film, nanowire, nanosphere, nanorod, nanocone, hollow nanosphere, or a mixture thereof; preferably, the cathode is Ag or Al.

[0065] In some specific embodiments, the preparation of the light-emitting device of the embodiment of the present application includes the steps of:

[0066] S30. Obtaining a substrate having an anode deposited thereon;

[0067] S40. Growing a hole transport layer on the anode surface;

[0068] S50. Then, a quantum dot light-emitting layer is deposited on the hole transport layer;

[0069] S60. Finally, an electron transport layer is deposited on the quantum dot light-emitting layer, and a cathode is evaporated on the electron transport layer to obtain a light-emitting device.

[0070] Specifically, in step S30, to obtain a high-quality zinc oxide nanomaterial film, the ITO substrate undergoes a pretreatment process. The basic and specific processing steps include: cleaning the ITO conductive glass with a detergent to initially remove surface stains, then ultrasonically cleaning it in deionized water, acetone, anhydrous ethanol, and deionized water for 20 minutes each to remove surface impurities, and finally drying it with high-purity nitrogen to obtain the ITO positive electrode.

[0071] Specifically, in step S40, the step of growing the hole transport layer includes: placing the ITO substrate on a spin coater, and spin coating a film with a prepared solution of hole transport material; controlling the film thickness by adjusting the concentration of the solution, the spin coating speed, and the spin coating time, and then thermally annealing at an appropriate temperature.

[0072] Specifically, in step S50, the step of depositing a quantum dot light-emitting layer on the hole transport layer includes: placing the substrate on which the hole transport layer has been spin-coated on a spin coater, spin-coating a light-emitting substance solution of a certain concentration into a film, and controlling the thickness of the light-emitting layer to about 20 to 60 nm by adjusting the concentration of the solution, the spin-coating speed and the spin-coating time, and drying at an appropriate temperature.

[0073] Specifically, in step S60, the step of depositing an electron transport layer on the quantum dot light-emitting layer includes: the electron transport layer is the electron transport composite material of the present application: the substrate on which the quantum dot light-emitting layer has been spin-coated is placed on a spin coater, and a solution of the electron transport composite material prepared at a certain concentration is spin-coated into a film by processes such as drop coating, spin coating, immersion, coating, printing, and evaporation. The thickness of the electron transport layer is controlled to be about 20 to 60 nm by adjusting the concentration of the solution, the spin coating speed (preferably, the rotation speed is between 3000 and 5000 rpm) and the spin coating time, and then annealed at 150°C to 200°C to form a film to fully remove the solvent.

[0074] Specifically, in step S60, the cathode preparation step includes: placing the substrate after depositing each functional layer in a vapor deposition chamber and thermally evaporating a layer of 60-100 nm of metallic silver or aluminum as a cathode through a mask.

[0075] In a further embodiment, the obtained QLED device is packaged. The packaging process can be performed using a conventional machine or manual packaging. Preferably, the oxygen content and water content in the packaging process environment are both less than 0.1 ppm to ensure device stability.

[0076] In order to make the above implementation details and operations of this application clearly understood by those skilled in the art, as well as to demonstrate the significant improvement in performance of the ZnS composite material and its preparation method, ZnS thin film, and light-emitting device in the embodiments of this application, the above technical solution is illustrated by multiple embodiments below.

[0077] Example 1

[0078] A method for preparing a ZnS composite material comprises the following steps:

[0079] 1. Add zinc chloride to 50 ml of methanol to form a solution with a total concentration of 0.5 M, and add thiourea (molar ratio, S 2- :Zn 2+ =2:1); then add chloroauric acid (molar ratio, noble metal ion: zinc ion = 0.05:1) and stir to react for 1 hour to obtain a mixed solution;

[0080] 2. Sodium hydroxide was added to the above solution to adjust the pH to 10. After hydrothermal reaction at 120°C for 1 hour, the solution was precipitated with acetone and then dispersed with ethanol to obtain a ZnS composite material with a double anion surface modification.

[0081] Example 2

[0082] A method for preparing a ZnS composite material comprises the following steps:

[0083] 1. Add zinc nitrate to 50 ml of ethanol to form a solution with a total concentration of 0.5 M, and add thioacetamide (molar ratio, S2- :Zn 2+ =2:1); then palladium chloride (molar ratio, noble metal ion: zinc ion = 0.03:1) was added and stirred for reaction for 1 hour to obtain a mixed solution;

[0084] 2. Potassium hydroxide was added to the above solution to adjust the pH to 11. After hydrothermal reaction at 110°C for 2 hours, the solution was precipitated with acetone and then dispersed with ethanol to obtain a ZnS composite material with a double anion surface modification.

[0085] Example 3

[0086] A method for preparing a ZnS composite material comprises the following steps:

[0087] 1. Add zinc acetate to 50 ml of methanol to form a solution with a total concentration of 0.5 M, and add L-cysteine ​​(molar ratio, S 2- :Zn 2+ =2:1); then add rhodium chloride (molar ratio, noble metal ion: zinc ion = 0.03:1) and stir to react for 1 hour to obtain a mixed solution;

[0088] 2. Tetramethylammonium hydroxide was added to the above solution, and the pH was adjusted to 10. After hydrothermal reaction at 120°C for 2 hours, the solution was precipitated with acetone and then dispersed with ethanol to obtain a ZnS composite material with a double anion surface modification.

[0089] Example 4

[0090] A method for preparing a ZnS composite material comprises the following steps:

[0091] 1. Add zinc chloride to 50 ml of methanol to form a solution with a total concentration of 0.5 M, and add thiourea (molar ratio, S 2- :Zn 2+ =1:1); then add chloroauric acid (molar ratio, noble metal ion: zinc ion = 0.05:1) and stir to react for 1 hour to obtain a mixed solution;

[0092] 2. Sodium hydroxide was added to the above solution to adjust the pH to 10. After hydrothermal reaction at 120°C for 1 hour, the solution was precipitated with acetone and then dispersed with ethanol to obtain a ZnS composite material with a double anion surface modification.

[0093] Example 5

[0094] A method for preparing a ZnS composite material comprises the following steps:

[0095] 1. Add zinc chloride to 50 ml of methanol to form a solution with a total concentration of 0.5 M, and add thiourea (molar ratio, S 2- :Zn 2+=3:1); then add chloroauric acid (molar ratio, noble metal ion: zinc ion = 0.05:1) and stir to react for 1 hour to obtain a mixed solution;

[0096] 2. Sodium hydroxide was added to the above solution to adjust the pH to 10. After hydrothermal reaction at 120°C for 1 hour, the solution was precipitated with acetone and then dispersed with ethanol to obtain a ZnS composite material with a double anion surface modification.

[0097] Example 6

[0098] A quantum dot light-emitting diode comprises a stacked structure of an anode and a cathode arranged opposite each other, a quantum dot light-emitting layer arranged between the anode and the cathode, an electron transport layer arranged between the cathode and the quantum dot light-emitting layer, and a hole transport layer arranged between the anode and the quantum dot light-emitting layer, wherein the anode is arranged on a substrate. The substrate is made of a glass sheet, the anode is made of an ITO substrate, the hole transport layer is made of TFB, the quantum dot light-emitting layer is made of CdSe, the electron transport layer is made of the ZnS composite material prepared in Example 1, and the cathode is made of Al.

[0099] Example 7

[0100] A quantum dot light-emitting diode comprises a stacked structure of an anode and a cathode arranged opposite each other, a quantum dot light-emitting layer arranged between the anode and the cathode, an electron transport layer arranged between the cathode and the quantum dot light-emitting layer, and a hole transport layer arranged between the anode and the quantum dot light-emitting layer, wherein the anode is arranged on a substrate. The substrate is made of a glass sheet, the anode is made of an ITO substrate, the hole transport layer is made of TFB, the quantum dot light-emitting layer is made of CdSe, the electron transport layer is made of the ZnS composite material prepared in Example 2, and the cathode is made of Al.

[0101] Example 8

[0102] A quantum dot light-emitting diode comprises a stacked structure of an anode and a cathode arranged opposite each other, a quantum dot light-emitting layer arranged between the anode and the cathode, an electron transport layer arranged between the cathode and the quantum dot light-emitting layer, and a hole transport layer arranged between the anode and the quantum dot light-emitting layer, wherein the anode is arranged on a substrate. The substrate is made of a glass sheet, the anode is made of an ITO substrate, the hole transport layer is made of TFB, the quantum dot light-emitting layer is made of CdSe, the electron transport layer is made of the ZnS composite material prepared in Example 3, and the cathode is made of Al.

[0103] Example 9

[0104] A quantum dot light-emitting diode comprises a stacked structure of an anode and a cathode arranged opposite each other, a quantum dot light-emitting layer arranged between the anode and the cathode, an electron transport layer arranged between the cathode and the quantum dot light-emitting layer, and a hole transport layer arranged between the anode and the quantum dot light-emitting layer, wherein the anode is arranged on a substrate. The substrate is made of a glass sheet, the anode is made of an ITO substrate, the hole transport layer is made of TFB, the quantum dot light-emitting layer is made of CdSe, the electron transport layer is made of the ZnS composite material prepared in Example 4, and the cathode is made of Al.

[0105] Example 10

[0106] A quantum dot light-emitting diode comprises a stacked structure of an anode and a cathode arranged opposite each other, a quantum dot light-emitting layer arranged between the anode and the cathode, an electron transport layer arranged between the cathode and the quantum dot light-emitting layer, and a hole transport layer arranged between the anode and the quantum dot light-emitting layer, wherein the anode is arranged on a substrate. The substrate is made of a glass sheet, the anode is made of an ITO substrate, the hole transport layer is made of TFB, the quantum dot light-emitting layer is made of CdSe, the electron transport layer is made of the ZnS composite material prepared in Example 5, and the cathode is made of Al.

[0107] Comparative Example 1

[0108] A method for preparing a ZnS composite material comprises the following steps:

[0109] 1. Add zinc chloride to 50 ml of methanol to form a solution with a total concentration of 0.5 M, and add thiourea (molar ratio, S 2- :Zn 2+ =2:1) ​​stirring and reacting for 1 hour to obtain a mixed solution;

[0110] 2. Sodium hydroxide was added to the above solution to adjust the pH to 10. After hydrothermal reaction at 120°C for 1 hour, the solution was precipitated with acetone and then dispersed with ethanol to obtain a ZnS composite material.

[0111] Comparative Example 2

[0112] A method for preparing a ZnS composite material comprises the following steps:

[0113] 1. Add zinc chloride to 50 ml of methanol to form a solution with a total concentration of 0.5 M, and add thiourea (molar ratio, S 2- :Zn 2+ =2:1); then add chloroauric acid (molar ratio, noble metal ion: zinc ion = 0.5:1) and stir to react for 1 hour to obtain a mixed solution;

[0114] 2. Sodium hydroxide was added to the above solution to adjust the pH to 10. After hydrothermal reaction at 120°C for 1 hour, the solution was precipitated with acetone and then dispersed with ethanol to obtain a ZnS composite material.

[0115] Comparative Example 3

[0116] A method for preparing a ZnS composite material comprises the following steps:

[0117] 1. Add zinc chloride to 50 ml of methanol to form a solution with a total concentration of 0.5 M, and add thiourea (molar ratio, S 2- :Zn 2+ =2:1); then add chloroauric acid (molar ratio, noble metal ion: zinc ion = 0.05:1) and stir to react for 1 hour to obtain a mixed solution;

[0118] 2. Sodium hydroxide was added to the above solution to adjust the pH to 7. After hydrothermal reaction at 120°C for 1 hour, the solution was precipitated with acetone and then dispersed with ethanol to obtain a ZnS composite material.

[0119] Comparative Example 4

[0120] A method for preparing a ZnS composite material comprises the following steps:

[0121] 1. Add zinc chloride to 50 ml of methanol to form a solution with a total concentration of 0.5 M, and add thiourea (molar ratio, S 2- :Zn 2+ =0.5:1); then add chloroauric acid (molar ratio, noble metal ion: zinc ion = 0.05:1) and stir to react for 1 hour to obtain a mixed solution;

[0122] 2. Sodium hydroxide was added to the above solution to adjust the pH to 10. After hydrothermal reaction at 120°C for 1 hour, the solution was precipitated with acetone and then dispersed with ethanol to obtain a ZnS composite material.

[0123] Comparative Example 5

[0124] A method for preparing a ZnS composite material comprises the following steps:

[0125] 1. Add zinc chloride to 50 ml of methanol to form a solution with a total concentration of 0.5 M, and add thiourea (molar ratio, S 2- :Zn 2+ =2:1); then add aluminum chloride (molar ratio, aluminum ion: zinc ion = 0.05:1) and stir to react for 1 hour to obtain a mixed solution;

[0126] 2. Sodium hydroxide was added to the above solution to adjust the pH to 10. After hydrothermal reaction at 120°C for 1 hour, the solution was precipitated with acetone and then dispersed with ethanol to obtain a ZnS composite material.

[0127] Comparative Example 6

[0128] A method for preparing a ZnS composite material comprises the following steps:

[0129] 1. Add zinc chloride to 50 ml of methanol to form a solution with a total concentration of 0.5 M, and add thiourea (molar ratio, S 2- :Zn 2+ =4:1); then add chloroauric acid (molar ratio, noble metal ion: zinc ion = 0.05:1) and stir to react for 1 hour to obtain a mixed solution;

[0130] 2. Sodium hydroxide was added to the above solution to adjust the pH to 10. After hydrothermal reaction at 120°C for 1 hour, the solution was precipitated with acetone and then dispersed with ethanol to obtain a ZnS composite material.

[0131] Comparative Examples 7 to 12

[0132] Comparative Examples 7 to 12 use the ZnS composite materials prepared in Comparative Examples 1 to 6 as electron transport materials, respectively, to provide quantum dot light-emitting diodes having the structure of Example 6.

[0133] Furthermore, in order to verify the advancement of the ZnS composite materials prepared in Examples 1 to 5 of the present application and the quantum dot light-emitting diodes in Examples 6 to 10 thereof, performance tests were conducted in the examples of the present invention.

[0134] Test Example 1

[0135] In the present invention, the ZnS composite materials of Examples 1 to 5 and Comparative Examples 1 to 6 were fabricated into ZnS nanofilms having a thickness of 30 nanometers. The current and voltage values ​​of the ZnS nanomaterial films of Examples 1 to 5 and Comparative Examples 1 to 6 were tested, and the resistance of the ZnS nanomaterial films (the resistance test was for a single-electron structure device, i.e., cathode / electron transport film / anode) was calculated, as shown in Table 1 below:

[0136] Test Example 2

[0137] The external quantum efficiency (EQE) of the quantum dot light-emitting diodes of Examples 6 to 10 and the quantum dot light-emitting diodes of Comparative Examples 7 to 12 was measured using an EQE optical test instrument in the embodiment of the present invention, as shown in Table 1 below:

[0138] Table 1

[0139]

[0140] From the above test results, it can be seen that the resistance of the thin films made of the double anion modified ZnS composite materials prepared in Examples 1 to 5 of the present invention is significantly lower than the resistance of the thin films of the ZnS materials in Comparative Examples 1 to 6. In addition, the external quantum efficiency of the quantum dot light-emitting diodes made from the ZnS composite materials of Examples 1 to 5 of the present invention corresponding to Examples 6 to 10 is significantly higher than the external quantum efficiency of the quantum dot light-emitting diodes of Comparative Examples 7 to 12. Specifically: Compared with Comparative Example 1 without precious metal doping, Comparative Example 2 with too high a precious metal doping ratio, Comparative Example 3 with too low a pH adjustment, Comparative Example 4 with too low a sulfur content, Comparative Example 5 with doping with non-precious metal aluminum, and Comparative Example 6 with too high a sulfur content, the thin films made of the ZnS composite materials in Example 1 have lower resistance, and the quantum dot light-emitting diodes have better external quantum efficiency. It is illustrated that in the embodiments of the present invention, under the conditions of a molar ratio of the sulfur source to the zinc source of (1-3):1, a molar ratio of the noble metal salt to the zinc source of (0.02-0.1):1, and a pH of 8-12, the conductive properties of the zinc sulfide nanomaterial modified with a double anion are significantly improved, thereby effectively improving the luminous efficiency of the quantum dot light-emitting device.

[0141] In addition, it is worth noting that the specific embodiments provided in this application are all based on blue light quantum dots Cd X Zn 1-X The use of S / ZnS as a light-emitting layer material is based on the fact that blue-light emitting systems are more commonly used (as blue quantum dot-based LEDs are more difficult to achieve high efficiency, they are therefore more valuable for reference). This does not mean that the present invention is limited to blue-light emitting systems. The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application are intended to be included within the scope of protection of this application.

Claims

1. A method for preparing a ZnS composite material, characterized in that: The following steps are involved: A zinc source and a sulfur source are dissolved in an organic solvent to combine the sulfur and zinc elements to form ZnS crystal nuclei, and a noble metal salt is added for a mixing reaction, so that the ZnS crystal nuclei continue to grow while the noble metal ions are doped into the ZnS to obtain a mixed salt solution; the molar ratio of the sulfur source to the zinc source is (1-3):1; the molar ratio of the noble metal salt to the zinc source is (0.02-0.1):1; and the concentration of the zinc source in the mixed salt solution is 0.1 mol / L to 1 mol / L; An alkali source is added to the mixed salt solution to make the solution alkaline, and a hydrothermal reaction is performed to induce hydroxyl modification of S vacancies on the surface of the material, so that -S and -OH are simultaneously combined on the surface of the material to obtain a ZnS composite material.

2. The method for preparing the ZnS composite material according to claim 1, wherein: The mixing reaction conditions include: reacting at a temperature of 20° C. to 40° C. for 30 minutes to 1 hour.

3. The method for preparing the ZnS composite material according to claim 2, wherein: Adding an alkaline source to the mixed salt solution to make the pH of the solution 8 to 12; and / or The hydrothermal reaction conditions are as follows: the reaction is carried out at a temperature of 80-120° C. for 0.5-2 hours.

4. The method for preparing the ZnS composite material according to any one of claims 1 to 3, wherein: The zinc source is selected from at least one of zinc acetate, zinc nitrate, zinc chloride, and zinc acetate dihydrate; and / or The sulfur source is selected from at least one of thiourea, thioacetamide, and L-cysteine; and / or The noble metal salt is selected from at least one of gold salt, palladium salt, rhodium salt and platinum salt; and / or The organic solvent is selected from: at least one of methanol, ethanol, and butanol; and / or The alkaline source is selected from at least one of sodium hydroxide, potassium hydroxide, and tetramethylammonium hydroxide.

5. The method for preparing the ZnS composite material according to claim 4, wherein: The noble metal salt is selected from at least one of chloroauric acid, palladium chloride, rhodium chloride and platinum chloride; and / or The particle size of the ZnS composite material is 10nm-30nm.

6. A ZnS composite material according to any one of claims 1 to 5, characterized in that The ZnS composite material is doped with noble metal ions, and the surface of the ZnS composite material is bound with hydroxyl groups.

7. The ZnS composite material according to claim 6, wherein The noble metal ions are selected from at least one of gold ions, platinum ions, palladium ions, and rhodium ions; and / or In the ZnS composite material, the molar ratio of the noble metal ions to the zinc ions is (0.02-0.1):1; and / or The particle size of the ZnS composite material is 10nm-30nm.

8. A ZnS thin film, characterized in that: The ZnS film comprises a ZnS composite material prepared by the method according to any one of claims 1 to 5, or comprises a ZnS composite material according to any one of claims 6 to 7.

9. A light emitting device, characterized in that: The light-emitting device includes an anode and a cathode arranged opposite to each other, and a light-emitting unit coupled between the anode and the cathode, wherein the light-emitting unit includes a light-emitting layer and an electron transport layer, and the electron transport layer is arranged between the light-emitting layer and the cathode; wherein the electron transport layer contains a ZnS composite material prepared by the method according to any one of claims 1 to 5, or contains a ZnS composite material according to any one of claims 6 to 7, or contains a ZnS thin film according to claim 8.

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