Inorganic nanoparticle ink, electron transport thin film, and light emitting diode

Abstract

The application discloses an inorganic nanoparticle ink, an electron transport thin film and a light emitting diode. The inorganic nanoparticle ink comprises inorganic nanoparticles, an alcohol-soluble amino resin and an alcohol organic solvent. The alcohol-soluble amino resin contains a large number of polar groups such as alcohol and amine groups, has good alcohol solubility, and can form good mutual solubility with the inorganic nanoparticles. Thus, the proportion of the alcohol-soluble amino resin and the inorganic nanoparticles can be effectively adjusted, the electron transport performance of the inorganic nanoparticle ink can be effectively adjusted, and the electron transport thin film with good electron transport performance can be prepared, and then the light emitting diode with high light emitting efficiency and long service life can be prepared.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of display, in particular to an inorganic nanoparticle ink, an electron transport film prepared from the inorganic nanoparticle ink, and a light emitting diode comprising the electron transport film. BACKGROUND

[0002] Currently widely used light emitting diodes are organic light emitting diodes (OLED) and quantum dot light emitting diodes (QLED). The traditional OLED and QLED device structure generally comprises an anode, a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer and a cathode. Under the action of an electric field, the holes generated by the anode of the light emitting device and the electrons generated by the cathode move and are injected into the hole transport layer and the electron transport layer, respectively, and finally migrate to the light emitting layer. When the two meet in the light emitting layer, energy excitons are generated, thereby exciting light emitting molecules to ultimately produce visible light.

[0003] The existing light emitting diode, especially the quantum dot light emitting diode, the commonly used electron transport layer is mainly formed by inkjet printing of an electron transport material containing inorganic semiconductor particles. Such electron transport layer has excellent electron transport performance, which can make the light emitting diode comprising the same have good electron mobility and high light emitting efficiency.

[0004] However, the existing electron transport material has poor stability and is easy to agglomerate. The solvent in the electron transport material volatilizes quickly during printing, which leads to the formation of black spots during inkjet printing film formation, and the formed film is prone to have holes, thereby resulting in poor film formation uniformity and affecting the light emitting efficiency and service life of the light emitting diode. SUMMARY

[0005] Therefore, the present application provides an inorganic nanoparticle ink, which aims to improve the problem of poor film formation uniformity of the existing inorganic nanoparticle ink to some extent.

[0006] The present application is implemented in the following manner. An inorganic nanoparticle ink comprises: inorganic nanoparticles, an alcohol-soluble amino resin, and an alcohol organic solvent.

[0007] Optionally, in some embodiments of the present application, the inorganic nanoparticle ink consists of the inorganic nanoparticles, the alcohol-soluble amino resin and the alcohol organic solvent.

[0008] Optionally, in some embodiments of the present application, based on the total mass of the inorganic nanoparticle ink, the content of the inorganic nanoparticles is 0.02-30.0wt%, the content of the alcohol-soluble amino resin is 0.001-10.0wt%, and the content of the alcohol organic solvent is 60-99.8wt%.

[0009] Optionally, in some embodiments of the present application, the alcohol-soluble amino resin is selected from one or more of melamine formaldehyde resin, alkyl ether modified melamine formaldehyde resin, and carboxyl modified melamine formaldehyde resin, the alkyl ether modified melamine formaldehyde resin is selected from one or more of methyl etherified melamine formaldehyde resin and butyl etherified melamine formaldehyde resin; and / or

[0010] The molecular weight of the alcohol-soluble amino resin is 200-2000.

[0011] Optionally, in some embodiments of the present application, when the alcohol-soluble amino resin is at least one of alkyl ether modified melamine formaldehyde resin and carboxyl modified melamine formaldehyde resin, the alcohol-soluble amino resin is coordinatedly connected with the inorganic nanoparticles.

[0012] Optionally, in some embodiments of the present application, the inorganic nanoparticles are selected from one or more of metal oxide nanoparticles and doped metal oxide nanoparticles, the material of the metal oxide nanoparticles is selected from one or more of ZnO, TiO2, SnO2, Ta2O3, ZrO2, and NiO, the material of the doped metal oxide nanoparticles is selected from one or more of TiLiO, ZnAlO, ZnMgO, ZnBeO, ZnSnO, ZnLiO, and InSnO; and / or

[0013] The average particle size of the inorganic nanoparticles is 3-20 nm.

[0014] Optionally, in some embodiments of the present application, the alcohol organic solvent is at least one of methanol, ethanol, propanol, butanol, pentanol, hexanol, ethylene glycol, triethylene glycol, glycerol, butanediol, and hexanediol.

[0015] Correspondingly, the present application also provides an electron transport thin film, which is prepared by a film forming process using the inorganic nanoparticle ink.

[0016] Correspondingly, the present application also provides a light emitting diode, which comprises an anode, a light emitting layer, an electron transport layer, and a cathode which are sequentially stacked, the electron transport layer is prepared by a film forming process using the inorganic nanoparticle ink, or the electron transport layer is the electron transport thin film.

[0017] Optionally, in some embodiments of the present application, the anode is selected from a doped metal oxide electrode, a composite electrode, a graphene electrode, and a carbon nanotube electrode, wherein the material of the doped metal oxide electrode is selected from at least one of indium-doped tin oxide, fluorine-doped tin oxide, antimony-doped tin oxide, aluminum-doped zinc oxide, gallium-doped zinc oxide, indium-doped zinc oxide, magnesium-doped zinc oxide, and aluminum-doped magnesium oxide, the composite electrode is selected from 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, or ZnS / Al / ZnS; and / or

[0018] The light-emitting layer is an organic light-emitting layer or a quantum dot light-emitting layer, wherein the material of the organic light-emitting layer is selected from at least one of 4,4'-bis(N-carbazole)-1,1'-biphenyl: tris[2-(p-tolyl)pyridine-C2,N) iridium(III), 4,4',4"-tris(carbazole-9-yl) triphenylamine: tris[2-(p-tolyl)pyridine-C2,N) iridium, diaromatic anthracene derivative, stilbene aromatic derivative, pyrene derivative, fluorene derivative, TBPe fluorescent material, TTPX fluorescent material, TBRb fluorescent material, and DBP fluorescent material, the material of the quantum dot light-emitting layer is selected from at least one of a single-structure quantum dot and a core-shell structure quantum dot, the material of the single-structure quantum dot, the material of the core of the core-shell structure quantum dot, and the material of the shell of the core-shell structure quantum dot are selected from at least one of CdSe, CdS, CdTe, ZnSe, ZnS, CdTe, ZnTe, CdZnS, CdZnSe, CdZnTe, ZnSeS, ZnSeTe, ZnTeS, CdSeS, CdSeTe, CdTeS, CdZnSeTe, CdZnSTe, InP, InXs, GxP, GxXs, GxSb, XlN, XlP, InXsP, InNP, InNSb, GxXlNP, InXlNP, CuInS2, CuInSe2, and AgInS2; and / or

[0019] The material of the cathode is selected from at least one of Ag, Al, Au, Pt, Ca, and Ba.

[0020] The inorganic nanoparticle ink described in the present application contains the alcohol-soluble amino resin, the alcohol-soluble amino resin contains a large number of polar groups such as alcohol and amine groups, has good alcohol solubility, and can form good mutual solubility with the inorganic nanoparticles, so that the ratio of the alcohol-soluble amino resin to the inorganic nanoparticles can be effectively adjusted, the electron transport performance of the inorganic nanoparticle ink can be effectively adjusted, thereby being beneficial to the preparation of an electron transport film with good electron transport performance, and further being beneficial to the preparation of a light-emitting diode with high luminous efficiency and long service life. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0022] Figure 1 is a structural schematic diagram of a light-emitting diode provided by an embodiment of the present application;

[0023] Figure 2 is a structural schematic diagram of another light-emitting diode provided by an embodiment of the present application;

[0024] Figure 3 is a structural schematic diagram of still another light-emitting diode provided by an embodiment of the present application. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application. In addition, it should be understood that the specific embodiments described herein are only used to illustrate and explain the present application, and are not used to limit the present application.

[0026] In the present application, the orientation words such as "upper" and "lower" generally refer to the upper and lower in the actual use or working state of the device, and specifically refer to the direction of the drawing surface in the drawings; and "inner" and "outer" refer to the outline of the device. In addition, in the description of the present application, the term "comprising" means "including but not limited to". The terms first, second, third, etc. are only used as labels, and do not impose numerical requirements or establish sequences.

[0027] Various embodiments of the present application can exist in a range of forms; it should be understood that the description in a range form is merely for the convenience and brevity, and should not be construed as a hard limitation on the scope of the present application; therefore, it should be considered that the range description has disclosed all possible sub-ranges and single values within the range. For example, it should be considered that the range description from 1 to 6 has disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single values within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fraction or integer) within the indicated range.

[0028] The present application provides an inorganic nanoparticle ink, comprising inorganic nanoparticles, an alcohol-soluble amino resin, and an alcohol organic solvent.

[0029] In some embodiments, the content of the inorganic nanoparticles is 0.02-30.0 wt%, the content of the alcohol-soluble amino resin is 0.001-10.0 wt%, and the content of the alcohol organic solvent is 60-99.8 wt%, based on the total mass of the inorganic nanoparticle ink.

[0030] In some embodiments, the inorganic nanoparticles can be selected from, but not limited to, one or more of metal oxide nanoparticles and doped metal oxide nanoparticles. The material of the metal oxide nanoparticles can be selected from, but not limited to, one or more of ZnO, TiO2, SnO2, Ta2O3, ZrO2, and NiO. The material of the doped metal oxide nanoparticles can be selected from, but not limited to, one or more of TiLiO, ZnAlO, ZnMgO, ZnBeO, ZnSnO, ZnLiO, and InSnO.

[0031] In at least one embodiment, the inorganic nanoparticles are selected from ZnO nanoparticles or ZnMgO nanoparticles.

[0032] In some embodiments, the average particle size of the inorganic nanoparticles is 3-20 nm. Inorganic nanoparticles with the average particle size have good electron transport properties. If the average particle size of the inorganic nanoparticles is too small, the stability is poor; and if the average particle size of the inorganic nanoparticles is too large, the electron transport rate is low and the film-forming property is poor, which is not conducive to electron transport.

[0033] The alcohol-soluble amino resin can be selected from, but not limited to, one or more of melamine formaldehyde resin, alkyl ether modified melamine formaldehyde resin, and carboxyl modified melamine formaldehyde resin. The alcohol-soluble amino resin contains a large number of polar groups such as alcohol and amine groups, has good alcohol solubility, and can form good miscibility with the inorganic nanoparticles. Thus, the ratio of the alcohol-soluble amino resin to the inorganic nanoparticles can be effectively adjusted, and the electron transport performance of the inorganic nanoparticle ink can be effectively adjusted.

[0034] When the alcohol-soluble amino resin is selected from at least one of alkyl ether modified melamine formaldehyde resin and carboxyl modified melamine formaldehyde resin, the alcohol-soluble amino resin is coordinated with the inorganic nanoparticles. The alkyl ether and carboxyl groups in the alkyl ether modified melamine formaldehyde resin and carboxyl modified melamine formaldehyde resin can have good coordination with the inorganic nanoparticles, so that the inorganic nanoparticles can be better dissolved in the alcohol organic solvent, and phase separation between the inorganic nanoparticles and the alcohol solvent can be avoided. The alcohol-soluble amino resin can have a relatively wide molecular weight range, so that a relatively wide viscosity range can be obtained, and the inorganic nanoparticle ink can have a suitable viscosity and surface tension for inkjet printing. Thus, the selection range of the alcohol organic solvent is also relatively wide, and the solvent evaporation rate can be controlled to some extent by selecting the type of alcohol organic solvent, which is beneficial to preparing an electronic transport thin film with good film-forming property.

[0035] The alkyl ether modified melamine formaldehyde resin can be selected from, but not limited to, one or more of methyl etherified melamine formaldehyde resin and butyl etherified melamine formaldehyde resin. In some embodiments, the methyl etherified melamine formaldehyde resin is selected from methyl etherified high imino melamine formaldehyde resin.

[0036] In some embodiments, the molecular weight of the alcohol-soluble amino resin is 200-2000. The alcohol-soluble amino resin has suitable viscosity and reactivity in the molecular weight range. If the molecular weight is too low, the viscosity is low, and the reactivity is high, which can cause excessive reaction between the alcohol-soluble amino resin and the inorganic nanoparticles, affecting the electron transport performance of the inorganic nanoparticles. If the molecular weight is too high, the viscosity is large, which is not conducive to film formation, and the reactivity is also low, which is not conducive to the reaction between the alcohol-soluble amino resin and the inorganic nanoparticles.

[0037] The alcohol organic solvent can effectively dissolve the inorganic nanoparticles and the alcohol-soluble amino resin. In some embodiments, the alcohol organic solvent is selected from fatty alcohol organic solvents. The fatty alcohol organic solvent can be selected from, but not limited to, at least one of methanol, ethanol, propanol, butanol, pentanol, hexanol, ethylene glycol, triethylene glycol, glycerol, butanediol, and hexanediol.

[0038] In some embodiments, the inorganic nanoparticle ink is composed of the inorganic nanoparticles, the alcohol-soluble amino resin, and the alcohol organic solvent.

[0039] The inorganic nanoparticle ink has a viscosity of 0.5-50 mPa.s at 25°C. In this way, when the inorganic nanoparticle ink is used to form a film by using an inkjet printing method, the inorganic nanoparticle ink can be properly released from the nozzle of the inkjet printing head, and the nozzle can be prevented from being blocked. In at least some embodiments, the inorganic nanoparticle ink has a viscosity of 3.0-15.0 mPa.s at 25°C.

[0040] The inorganic nanoparticle ink has a surface tension of 20-55 mN / m at 25°C. In this way, the inorganic nanoparticle ink can be properly released from the nozzle of the inkjet printing head, and has good film-forming properties.

[0041] In some embodiments, the inorganic nanoparticle ink has a boiling point of 150-400°C. Within the boiling point range, the alcohol organic solvent in the inorganic nanoparticle ink can be volatilized to form a film. If the boiling point is too low, the alcohol organic solvent can volatilize too quickly, which is not conducive to controlling the film-forming morphology. If the boiling point is too high, the alcohol organic solvent can volatilize too slowly, which can make it impossible to completely remove the alcohol organic solvent by post-processing, or the processing time can be too long, which can affect film formation and cause the processing time to be extended and the economic benefits to be reduced.

[0042] The inorganic nanoparticle ink described in the present application contains the alcohol-soluble amino resin, which contains a large number of polar groups such as alcohol and amine groups, has good alcohol solubility, and can form good miscibility with the inorganic nanoparticles. In this way, the ratio of the alcohol-soluble amino resin to the inorganic nanoparticles can be effectively adjusted, and the electronic transport performance of the inorganic nanoparticle ink can be effectively adjusted.

[0043] Further, the alcohol-soluble amino resin has good film-forming properties, so that the inorganic nanoparticle ink has good film-forming properties, which is conducive to preparing a uniform and flat electronic transport film.

[0044] Further, since the alcohol-soluble amino resin has insulating property but no electron transport property, the ratio of the alcohol-soluble amino resin to the inorganic nanoparticles in the electron transport thin film can be adjusted by adjusting the ratio of the alcohol-soluble amino resin to the inorganic nanoparticles in the inorganic nanoparticle ink, so as to adjust and control the distance between adjacent inorganic nanoparticles and the distance between the light-emitting layer and the electron transport layer, and further adjust the electron transport capability of the electron transport thin film, and further promote the electron-hole transport balance of the light-emitting diode comprising the electron transport thin film, so as to avoid the phenomenon of low efficiency and fast decay of the light-emitting diode caused by excessive electrons or holes in the light-emitting layer, and thus improve the efficiency and service life of the light-emitting diode.

[0045] Further, when the inorganic nanoparticle ink is used to prepare the electron transport thin film on the quantum dot light-emitting layer, due to the presence of the alcohol-soluble amino resin, the alcohol-soluble amino resin exists between the inorganic nanoparticles and the quantum dots, and an electron blocking film formed of the alcohol-soluble amino resin is formed between the inorganic nanoparticles and the quantum dots, so as to further reduce the number of electrons entering the light-emitting layer in the light-emitting diode, and further promote the electron-hole transport balance of the light-emitting diode comprising the electron transport thin film, so as to avoid the phenomenon of low efficiency and fast decay of the light-emitting diode caused by excessive electrons or holes in the light-emitting layer, and thus improve the efficiency and service life of the light-emitting diode.

[0046] It can be understood that the inorganic nanoparticle ink can be an electron transport ink or an electron transport ink for inkjet printing.

[0047] In some embodiments, the preparation method of the inorganic nanoparticle ink comprises: dissolving inorganic nanoparticles and an alcohol-soluble amino resin in an alcohol organic solvent in a certain proportion to obtain the inorganic nanoparticle ink.

[0048] In another embodiment, the preparation method of the inorganic nanoparticle ink comprises: dissolving inorganic nanoparticles in a first alcohol organic solvent to obtain an inorganic nanoparticle solution; dissolving an alcohol-soluble amino resin in a second alcohol organic solvent to obtain an amino resin solution; and mixing the inorganic nanoparticle solution and the amino resin solution in a certain proportion to obtain the inorganic nanoparticle ink.

[0049] It can be understood that the first alcohol organic solvent and the second alcohol organic solvent can be independently selected from, but are not limited to, the above-mentioned alcohol organic solvents, i.e., the first alcohol organic solvent and the second alcohol organic solvent can be independently selected from, but are not limited to, at least one of methanol, ethanol, propanol, butanol, pentanol, hexanol, ethylene glycol, triethylene glycol, glycerol, butanediol and hexanediol.

[0050] The present application also provides an electron transport thin film prepared by a film forming process using the inorganic nanoparticle ink.

[0051] In some embodiments, the electron transport thin film can be prepared by disposing the inorganic nanoparticle ink on a substrate, and removing the solvent by post-treatment to obtain the electron transport thin film.

[0052] It can be understood that the method of disposing the inorganic nanoparticle ink on a substrate can be a solution method. The solution method can be spin coating, printing, inkjet printing, blade coating, printing, dip-coating, immersion, spraying, roll coating, casting, slot coating, stripe coating, etc.

[0053] It can be understood that the post-treatment can be at least one of heating drying, cooling drying, and reduced pressure drying.

[0054] In some embodiments, the heating drying can be pulse heating or continuous heating, and the temperature of the heating can be 60-180℃. Within the range, the solvent can be effectively removed, and the inorganic nanoparticles can be prevented from being damaged.

[0055] The temperature of the cooling drying can be 0-20℃. Within the range, the solvent can be effectively removed, and the inorganic nanoparticles can be prevented from being damaged.

[0056] The vacuum degree during the reduced pressure drying can be 1x10 -6 Torr to normal pressure. Within the range, the solvent can be effectively removed, and the inorganic nanoparticles can be prevented from being damaged.

[0057] In some embodiments, the thickness of the electron transport thin film can be 10-120nm. In at least some embodiments, the thickness of the electron transport thin film can be 20-80nm.

[0058] The electron transport thin film including the inorganic nanoparticle ink has a uniform and flat surface, and has good stability and suitable electron transport performance.

[0059] Please refer to Figure 1 The present embodiments also provide a light emitting diode 100 including an anode 10, a light emitting layer 20, an electron transport layer 30, and a cathode 40 which are sequentially stacked. The electron transport layer 30 is prepared from the inorganic nanoparticle ink described above, or the electron transport layer 30 is the electron transport thin film described above.

[0060] Please further refer to Figure 2In some embodiments, the light emitting diode 100 further comprises a hole transport layer 50 between the anode 10 and the light emitting layer 20. In other words, the light emitting diode 100 comprises the anode 10, the hole transport layer 50, the light emitting layer 20, the electron transport layer 30 and the cathode 40 in sequence.

[0061] Further reference is made to Figure 3 In some embodiments, the light emitting diode 100 further comprises a hole injection layer 60 between the anode 10 and the hole transport layer 50. In other words, the light emitting diode 100 comprises the anode 10, the hole injection layer 60, the hole transport layer 50, the light emitting layer 20, the electron transport layer 30 and the cathode 40 in sequence.

[0062] The anode 10 is an anode known in the art for use in light emitting diodes, for example, can be selected from, but not limited to, a doped metal oxide electrode, a composite electrode, a graphene electrode, a carbon nanotube electrode. The material of the doped metal oxide electrode can be selected from, but not limited to, at least one 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). The composite electrode is a composite electrode with a metal sandwiched between doped or undoped transparent metal oxides, such as 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, etc.

[0063] The light emitting layer 20 can be an organic light emitting layer or a quantum dot light emitting layer. When the light emitting layer 20 is an organic light emitting layer, the light emitting diode 100 can be an organic light emitting diode; when the light emitting layer 20 is a quantum dot light emitting layer, the light emitting diode 100 can be a quantum dot light emitting diode.

[0064] The material of the organic light emitting layer is a material known in the art for an organic light emitting layer of a light emitting diode, for example, can be selected from, but not limited to, at least one of CBP:Ir(mppy)3 (4,4'-bis(N-carbazole)-1,1'-biphenyl: tris[2-(p-tolyl)pyridine-C2,N) iridium(III)], TCTX:Ir(mmpy) (4,4',4"-tris(carbazol-9-yl)triphenylamine: tris[2-(p-tolyl)pyridine-C2,N) iridium), diaryl anthracene derivatives, stilbene aromatic derivatives, pyrene derivatives, fluorene derivatives, blue light emitting TBPe fluorescent material, green light emitting TTPX fluorescent material, orange light emitting TBRb fluorescent material, and red light emitting DBP fluorescent material.

[0065] The material of the quantum dot light emitting layer is a quantum dot material known in the art for a quantum dot light emitting layer of a light emitting diode, for example, can be selected from, but not limited to, at least one of a single structure quantum dot and a core-shell structure quantum dot. The material of the single structure quantum dot, the material of the core of the core-shell structure quantum dot, and the material of the shell of the core-shell structure quantum dot can be selected from, but not limited to, at least one of a II-VI compound, a III-V compound, and a I-III-VI compound. As an example, the II-VI compound can be selected from, but not limited to, at least one of CdSe, CdS, CdTe, ZnSe, ZnS, CdTe, ZnTe, CdZnS, CdZnSe, CdZnTe, ZnSeS, ZnSeTe, ZnTeS, CdSeS, CdSeTe, CdTeS, CdZnSeTe, and CdZnSTe; the III-V compound can be selected from, but not limited to, at least one of InP, InXs, GxP, GxXs, GxSb, XlN, XlP, InXsP, InNP, InNSb, GxXlNP, and InXlNP; the I-III-VI compound can be selected from, but not limited to, at least one of CuInS2, CuInSe2, and AgInS2.

[0066] As an example, the core-shell structure quantum dot can be selected from, but not limited to, at least one of CdSe / CdSeS / CdS, InP / ZnSeS / ZnS, CdZnSe / ZnSe / ZnS, CdSeS / ZnSeS / ZnS, CdSe / ZnS, CdSe / ZnSe / ZnS, ZnSe / ZnS, ZnSeTe / ZnS, CdSe / CdZnSeS / ZnS, and InP / ZnSe / ZnS.

[0067] The material of the cathode 40 is a cathode material known in the art for a light emitting diode, for example, can be selected from, but not limited to, at least one of Ag, Al, Au, Pt, Ca, and Ba.

[0068] The material of the hole transport layer 50 can also be a material known in the art for a hole transport layer, for example, can be selected from, but not limited to, at least one of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene (spiro-omeTAD), 4,4'-cyclohexylbis[N,N-di(4-methylphenyl)benzenamine] (TAPC), N,N'-bis(1-naphthyl)-N,N'-diphenyl-1,1'-diphenyl-4,4'-diamine (NPB), 4,4'-bis(N-carbazole)-1,1'-biphenyl (CBP), poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4'-(N-(p-butylphenyl))diphenylamine)] (TFB), poly(9-vinylcarbazole) (PVK), polytriphenylamine (Poly-TPD), and 4,4',4''-tris(carbazol-9-yl)triphenylamine (TCTA).

[0069] The material of the hole injection layer 60 can also be a material known in the art for a hole injection layer, for example, can be selected from, but not limited to, at least one of 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (HAT-CN), PEDOT:PSS, a derivative of PEDOT:PSS doped with s-MoO3 (PEDOT:PSS:s-MoO3), nickel oxide, molybdenum oxide, tungsten oxide, vanadium oxide, molybdenum sulfide, tungsten sulfide, and copper oxide.

[0070] It can be understood that the light emitting diode 100 can further add some functional layers commonly used in light emitting diodes to help improve the performance of the light emitting diode, for example, an electron blocking layer, a hole blocking layer, an electron injection layer, an interface modification layer, etc.

[0071] It can be understood that the materials of the layers of the light emitting diode 100 can be adjusted according to the light emitting requirements of the light emitting diode 100.

[0072] It can be understood that the light emitting diode 100 can be a normal light emitting diode or an inverted light emitting diode.

[0073] The inorganic nanoparticle ink described in the present application is contained in the electron transport layer 30 of the light emitting diode 100, thereby having higher light emitting efficiency and longer service life.

[0074] The present application also relates to a display device, which comprises the light emitting diode 100.

[0075] The present application will be described in detail below through specific embodiments, and the following embodiments are only part of the embodiments of the present application, and are not a limitation of the present application.

[0076] Example 1

[0077] Preparation of inorganic nanoparticle ink

[0078] In a single-neck flask with a volume of 500 mL, ZnO nanoparticles, hexanol, methyl etherified high imino melamine formaldehyde resin (brand: CYMEL 325), and butanediol were sequentially added under stirring, and after the addition was completed, the mixture was continuously stirred for 30 min to obtain an inorganic nanoparticle ink.

[0079] In the inorganic nanoparticle ink of this example, the content of ZnO nanoparticles was 3 wt%, the content of hexanol was 50 wt%, the content of methyl etherified high imino melamine formaldehyde resin was 1 wt%, and the content of butanediol was 46 wt%.

[0080] Preparation of electron transport thin film

[0081] The inorganic nanoparticle ink was printed on a pixel substrate by an inkjet printer to form a thin film with a size of 20 x 30 um and a resolution of 200 x 200 ppi;

[0082] The substrate with the thin film formed thereon was placed on a hot plate, and was volatilized and dried at 100°C and under vacuum of 1 x 10 -4 Torr for 30 min to obtain an electron transport thin film with a thickness of 50 nm.

[0083] Example 2

[0084] Preparation of inorganic nanoparticle ink

[0085] In a single-neck flask with a volume of 500 mL, ZnO nanoparticles, ethylene glycol, butyl etherified melamine formaldehyde resin (brand: CYMEL 1158), and triethylene glycol were sequentially added under stirring, and after the addition was completed, the mixture was continuously stirred for 30 min to obtain an inorganic nanoparticle ink.

[0086] In the inorganic nanoparticle ink of this example, the content of ZnO nanoparticles was 2 wt%, the content of ethylene glycol was 40 wt%, the content of butyl etherified melamine formaldehyde resin was 0.5 wt%, and the content of triethylene glycol was 57.5 wt%.

[0087] Preparation of electron transport thin film

[0088] The inorganic nanoparticle ink was printed on a pixel substrate by an inkjet printer to form a thin film with a size of 20 x 30 um and a resolution of 200 x 200 ppi;

[0089] The substrate with the thin film formed thereon is placed on a hot plate and volatilized and dried at 130°C under nitrogen flow for 30 min to obtain an electron transport thin film with a thickness of 50 nm.

[0090] Example 3

[0091] Preparation of inorganic nanoparticle ink

[0092] In a single-mouth flask with a volume of 500 mL, ZnO nanoparticles, ethylene glycol, carboxyl-modified melamine formaldehyde resin (brand: CYMEL 1141), and triethylene glycol are sequentially added under stirring, and after the addition is completed, the mixture is continuously stirred for 30 min to obtain inorganic nanoparticle ink.

[0093] In the inorganic nanoparticle ink of this example, the content of ZnO nanoparticles is 3 wt%, the content of ethylene glycol is 40 wt%, the content of carboxyl-modified melamine formaldehyde resin is 1 wt%, and the content of triethylene glycol is 56 wt%.

[0094] Preparation of electron transport thin film

[0095] The inorganic nanoparticle ink is printed on a pixel substrate by an inkjet printer to form a thin film with a size of 20 x 30 um and a resolution of 200 x 200 ppi;

[0096] The substrate with the thin film formed thereon is placed on a hot plate and volatilized and dried at 130°C under nitrogen flow for 30 min to obtain an electron transport thin film with a thickness of 50 nm.

[0097] Example 4

[0098] This example is basically the same as Example 1, except that melamine formaldehyde resin is used to replace the methyl etherified high imino melamine formaldehyde resin in Example 1.

[0099] Example 5

[0100] This example is basically the same as Example 1, except that TiO2 nanoparticles and ZnMgO nanoparticles are used to replace the ZnO nanoparticles in Example 1.

[0101] In this example, the content of TiO2 nanoparticles is 1.5 wt%, and the content of ZnMgO nanoparticles is 1.5 wt%.

[0102] Example 6

[0103] This example is basically the same as Example 1, except that butyl etherified melamine formaldehyde resin and carboxyl-modified melamine formaldehyde resin are used to replace the methyl etherified high imino melamine formaldehyde resin in Example 1.

[0104] In this embodiment, the content of the carboxyl-modified melamine formaldehyde resin is 0.5wt%, and the content of the carboxyl-modified melamine formaldehyde resin is 0.5wt%.

[0105] Example 7

[0106] This embodiment is basically the same as Example 1, except that the content of the ZnO nanoparticles in this embodiment is 0.03wt%, and the content of the hexanol is 52.97wt%.

[0107] Example 8

[0108] This embodiment is basically the same as Example 1, except that the content of the ZnO nanoparticles in this embodiment is 15wt%, and the content of the hexanol is 38wt%.

[0109] Example 9

[0110] This embodiment is basically the same as Example 1, except that the content of the ZnO nanoparticles in this embodiment is 27wt%, and the content of the hexanol is 26wt%.

[0111] Example 10

[0112] This embodiment is basically the same as Example 1, except that the content of the ZnO nanoparticles in this embodiment is 0.01wt%, and the content of the hexanol is 52.99wt%.

[0113] Example 11

[0114] This embodiment is basically the same as Example 1, except that the content of the ZnO nanoparticles in this embodiment is 40wt%, and the content of the hexanol is 13wt%.

[0115] Example 12

[0116] This embodiment is basically the same as Example 1, except that the content of the methyl etherified high imino melamine formaldehyde resin in this embodiment is 0.001wt%, and the content of the butanediol is 46.999wt%.

[0117] Example 13

[0118] This embodiment is basically the same as Example 1, except that the content of the methyl etherified high imino melamine formaldehyde resin in this embodiment is 5wt%, and the content of the butanediol is 42wt%.

[0119] Example 14

[0120] This embodiment is basically the same as Example 1, except that the content of the methyl etherified high imino melamine formaldehyde resin in this embodiment is 10wt%, and the content of the butanediol is 37wt%.

[0121] Example 15

[0122] This example is basically the same as Example 1, except that the content of the methyl etherified high imino melamine formaldehyde resin in this example is 0.0001 wt%, and the content of butanediol is 46.9999 wt%.

[0123] Example 16

[0124] This example is basically the same as Example 1, except that the content of the methyl etherified high imino melamine formaldehyde resin in this example is 20 wt%, and the content of butanediol is 27 wt%.

[0125] Comparative Example 1

[0126] Preparation of inorganic nanoparticle ink

[0127] In a single-mouth flask with a volume of 500 mL, zinc oxide, hexanol, and butanediol were sequentially added under stirring, and after the addition was completed, the mixture was continuously stirred for 30 min to obtain an inorganic nanoparticle ink.

[0128] In the inorganic nanoparticle ink of this example, the content of ZnO nanoparticles was 0.05 wt%, the content of hexanol was 50 wt%, and the content of butanediol was 49.95 wt%.

[0129] Preparation of electron transport thin film

[0130] The inorganic nanoparticle ink was printed on a pixel substrate using an inkjet printer to form a thin film with a size of 20 x 30 um and a resolution of 200 x 200 ppi;

[0131] The substrate with the thin film formed was placed on a hot plate and volatilized and dried at 100°C under a nitrogen gas stream for 30 min to obtain an electron transport thin film with a thickness of 50 nm.

[0132] Comparative Example 2

[0133] This comparative example is basically the same as Comparative Example 1, except that in the inorganic nanoparticle ink of this comparative example, the content of ZnO nanoparticles was 3 wt%, the content of hexanol was 50 wt%, and the content of butanediol was 47 wt%.

[0134] The film-forming uniformity of the inorganic nanoparticle inks of Examples 1-16 and Comparative Examples 1-2 was tested using a white light interferometer, and the film-forming uniformity in the long axis direction and the short axis direction parallel to the electron transport thin film was tested, respectively. The test results in the short axis direction in the film-forming uniformity test are shown in Table 1.

[0135] Table 1

[0136]

[0137]

[0138] From Table 1, it can be seen that:

[0139] Compared with the inorganic nanoparticle ink of Comparative Examples 1-2, the inorganic nanoparticle ink of Examples 1-10, 12-14 and 16 has better film forming uniformity.

[0140] Compared with the inorganic nanoparticle ink of Example 1, the inorganic nanoparticle ink of Example 11 has poor film forming uniformity, which may be due to the too high content of ZnO nanoparticles in the inorganic nanoparticle ink of Example 11.

[0141] Compared with the inorganic nanoparticle ink of Example 1, the inorganic nanoparticle ink of Example 15 has poor film forming uniformity, which may be due to the too low content of methyl etherified high imino melamine formaldehyde resin in the inorganic nanoparticle ink of Example 15.

[0142] Device Example 1

[0143] An ITO anode 10 with a thickness of 1 nm is provided;

[0144] A PEDOT:PSS material is spin-coated on the anode 10, annealed at 120°C for 10 min, to obtain a hole injection layer 60 with a thickness of 45 nm;

[0145] A TFB material is spin-coated on the hole injection layer 60, annealed at 230°C for 10 min, to obtain a hole transport layer 50 with a thickness of 28 nm;

[0146] A red CdSe / ZnS quantum dot material is spin-coated on the hole transport layer 50, annealed at 100°C for 15 min, to obtain a light-emitting layer 20 with a thickness of 18 nm;

[0147] The inorganic nanoparticle ink in Example 1 is printed on the light-emitting layer 20 by using an inkjet printer, and is then dried by volatilization at 100°C and under vacuum 1x10 -4 Torr for 30 min, to obtain an electron transport layer 30 with a thickness of 50 nm;

[0148] Ag is evaporated on the electron transport layer 30, to obtain a cathode 40 with a thickness of 120 nm;

[0149] Packaging is performed, to obtain a light-emitting diode 100.

[0150] Device Examples 2-16

[0151] Device Examples 2-16 are substantially the same as Device Example 1, except that the inorganic nanoparticle ink of Examples 2-16 is used to replace the inorganic nanoparticle ink of Device Example 1, respectively.

[0152] Device Comparative Examples 1-2

[0153] Device Comparative Examples 1-2 are substantially the same as Device Example 1, except that the inorganic nanoparticle ink of Comparative Examples 1-2 is used to replace the inorganic nanoparticle ink of Device Example 1, respectively.

[0154] The maximum luminous efficiency and T95 lifetime of the light emitting diodes of Device Examples 1-16 and Device Comparative Examples 1-2 are tested. The test results are shown in Table 2.

[0155] wherein,

[0156] The maximum luminous efficiency is tested by using a luminance meter PR650 and a keithley to test the luminance and current, respectively, and the current density is obtained according to the light emitting area, the maximum luminance is obtained by the luminance meter test, and the ratio of the maximum luminance to the current density is the determination of the maximum luminous efficiency;

[0157] The T95 lifetime is tested by using a 128-channel lifetime test system customized by Guangzhou New Vision Company, the system architecture is a 2 mA constant voltage and constant current source driving the light emitting diode, the change of the test voltage or current is tested, a photodiode detector and a test system test the luminance (photo current) change of the light emitting diode, a luminance meter test calibrates the luminance (photo current) of the electroluminescent device, and the time experienced by the electroluminescent device when the initial luminance decays to 95% is obtained.

[0158] Table 2

[0159]

[0160]

[0161] From Table 2, it can be seen that:

[0162] Compared with the light emitting diodes of Comparative Examples 1-2, the light emitting diodes of Examples 1-16 have higher maximum luminous efficiency.

[0163] Compared with the light emitting diodes of Comparative Examples 1-2, the light emitting diodes of Examples 1-9, 11-14 have higher maximum luminous efficiency and longer lifetime.

[0164] Compared with the light emitting diode of Example 4, the light emitting diode of Example 1 has higher maximum luminous efficiency and longer service life, which is probably because the methyl ether group contained in the methyl etherified high imino melamine formaldehyde resin contained in the inorganic nanoparticle ink of the light emitting diode of Example 1 can form coordination between the ZnO nanoparticles, which is conducive to the uniform dispersion of the inorganic nanoparticles in the solvent, so that the inorganic nanoparticle ink has viscosity and surface tension more suitable for inkjet printing, thereby effectively controlling the volatilization rate of the alcohol organic solvent, and further conducive to obtaining an electron transport layer with good film forming property.

[0165] Compared with the light emitting diode of Example 1, the light emitting diode of Example 10 has lower maximum luminous efficiency and shorter service life, which is probably because the content of ZnO nanoparticles in the inorganic nanoparticle ink of the light emitting diode of Example 10 is too low.

[0166] Compared with the light emitting diode of Example 1, the light emitting diode of Example 15 has shorter service life, which is probably because the content of methyl etherified high imino melamine formaldehyde resin in the inorganic nanoparticle ink of the light emitting diode of Example 15 is too low.

[0167] Compared with the light emitting diode of Example 1, the light emitting diode of Example 16 has lower maximum luminous efficiency and shorter service life, which is probably because the content of methyl etherified high imino melamine formaldehyde resin in the inorganic nanoparticle ink of the light emitting diode of Example 15 is too high.

[0168] The inorganic nanoparticle ink, the electron transport film and the light emitting diode provided by the embodiments of the present application are described in detail above, and specific examples are applied in this paper to describe the principles and implementation modes of the present application. The above description of the embodiments is only used to help understand the method and its core idea of the present application; at the same time, for those skilled in the art, according to the idea of the present application, the specific implementation mode and application range will be changed, and the above description of the present application should not be understood as a limitation.

Claims

1. An inorganic nanoparticle ink, characterized in that, include: Inorganic nanoparticles; An alcohol-soluble amino resin, wherein the alcohol-soluble amino resin is selected from one or more of alkyl ether modified melamine-formaldehyde resin and carboxyl modified melamine-formaldehyde resin, and the alcohol-soluble amino resin is coordinated and linked to the inorganic nanoparticles. Alcohols as organic solvents; Based on the total mass of the inorganic nanoparticle ink, the content of the inorganic nanoparticles is 0.02–30.0 wt%, the content of the alcohol-soluble amino resin is 0.001–10.0 wt%, and the content of the alcohol organic solvent is 60–99.8 wt%.

2. The inorganic nanoparticle ink as described in claim 1, characterized in that, The inorganic nanoparticle ink is composed of the inorganic nanoparticles, the alcohol-soluble amino resin, and the alcohol-based organic solvent.

3. The inorganic nanoparticle ink as described in claim 1 or 2, characterized in that, The alkyl ether modified melamine-formaldehyde resin is selected from one or more of methyl etherified melamine-formaldehyde resin and butyl etherified melamine-formaldehyde resin.

4. The inorganic nanoparticle ink as described in claim 1 or 2, characterized in that, The molecular weight of the alcohol-soluble amino resin is 200 to 2000.

5. The inorganic nanoparticle ink as described in claim 4, characterized in that, The inorganic nanoparticles possess electron transport properties; The viscosity of the inorganic nanoparticle ink at 25°C is 0.5–50 mPa·s; The surface tension of the inorganic nanoparticle ink at 25°C ranges from 20 to 55 mN / m. The boiling point of the inorganic nanoparticle ink is 150–400℃.

6. The inorganic nanoparticle ink as described in claim 1 or 2, characterized in that, The inorganic nanoparticles are selected from one or more of metal oxide nanoparticles and doped metal oxide nanoparticles; the metal oxide nanoparticles are selected from one or more of ZnO, TiO2, SnO2, Ta2O3, ZrO2, and NiO; and the doped metal oxide nanoparticles are selected from one or more of TiLiO, ZnAlO, ZnMgO, ZnBeO, ZnSnO, ZnLiO, and InSnO; and / or The inorganic nanoparticles have an average particle size of 3–20 nm.

7. The inorganic nanoparticle ink as described in claim 1 or 2, characterized in that, The alcoholic organic solvent is selected from at least one of methanol, ethanol, propanol, butanol, pentanol, hexanol, ethylene glycol, triethylene glycol, glycerol, butanediol, and hexanediol.

8. An electron transport thin film, characterized in that, The electron transport film is prepared by a film-forming process using the inorganic nanoparticle ink described in any one of claims 1 to 7.

9. A light-emitting diode, characterized in that, include: An anode, a light-emitting layer, an electron transport layer, and a cathode are sequentially stacked. The electron transport layer is prepared by a film-forming process using the inorganic nanoparticle ink described in any one of claims 1 to 7, or the electron transport layer is the electron transport thin film described in claim 8.

10. The light-emitting diode as described in claim 9, characterized in that, The anode is selected from doped metal oxide electrodes, composite electrodes, graphene electrodes, and carbon nanotube electrodes. The doped metal oxide electrode is selected from at least one of indium-doped tin oxide, fluorine-doped tin oxide, antimony-doped tin oxide, aluminum-doped zinc oxide, gallium-doped zinc oxide, indium-doped zinc oxide, magnesium-doped zinc oxide, and aluminum-doped magnesium oxide. The composite electrode is selected from 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, or ZnS / Al / ZnS; and / or The light-emitting layer is an organic light-emitting layer or a quantum dot light-emitting layer. The organic light-emitting layer is selected from at least one of the following: 4,4'-bis(N-carbazole)-1,1'-biphenyl:tris[2-(p-tolyl)pyridine-C2,N)iridium(III), 4,4',4”-tris(carbazole-9-yl)triphenylamine:tris[2-(p-tolyl)pyridine-C2,N)iridium, diaromatic anthracene derivatives, stilbene aromatic derivatives, pyrene derivatives, fluorene derivatives, TBPe fluorescent materials, TTPX fluorescent materials, TBRb fluorescent materials, and DBP fluorescent materials. The quantum dot light-emitting layer is selected from at least one of single-structure quantum dots and core-shell structure quantum dots. The materials for quantum dots, the core materials for core-shell quantum dots, and the shell materials for core-shell quantum dots are selected from at least one of CdSe, CdS, CdTe, ZnSe, ZnS, CdTe, ZnTe, CdZnS, CdZnSe, CdZnTe, ZnSeS, ZnSeTe, ZnTeS, CdSeS, CdSeTe, CdTeS, CdZnSeTe, CdZnSTe, InP, InXs, GxP, GxXs, GxSb, XlN, XlP, InXsP, InNP, InNSb, GxXlNP, InXlNP, CuInS2, CuInSe2, and AgInS2; and / or The cathode material is selected from at least one of Ag, Al, Au, Pt, Ca, and Ba.

Images