Ink, method for producing the same, light emitting device, and display apparatus

Abstract

This application relates to an ink comprising a solvent and an amine metal ion complex and metal nanoparticles dispersed in the solvent, wherein the amine metal ion complex is obtained by coordination of a polyaliphatic amine compound with a metal ion. The ink exhibits good stability, suitable surface tension, and suitable viscosity, resulting in excellent film-forming properties.

Description

Technical Field

[0001] This application relates to the field of display technology, and in particular to an ink and its preparation method, a light-emitting device, and a display apparatus. Background Technology

[0002] The functional layers of common optoelectronic devices are usually fabricated using inkjet printing. The quality of the ink is a key factor that determines the quality of the product. Therefore, higher requirements are placed on the various properties of the ink for each functional layer, such as ink viscosity, surface tension, and ink stability. Currently, research on ink is receiving increasing attention. Summary of the Invention

[0003] Therefore, it is necessary to provide an ink that can improve stability, a method for preparing the same, a light-emitting device, and a display device.

[0004] One embodiment of this application provides an ink comprising a solvent and an amine metal ion complex and metal nanoparticles dispersed in the solvent, wherein the amine metal ion complex is obtained by coordination of a polyaliphatic amine compound with a metal ion.

[0005] In one embodiment, the mass ratio of the amine metal ion complex to the metal nanoparticles is (3:1) to (1:5).

[0006] In one embodiment, the mass ratio of the amine metal ion complex to the metal nanoparticles is 1:2.

[0007] In one embodiment, the polyaliphatic amine compound comprises one or more of the following structures:

[0008]

[0009] Where R is H or -CH2CH2OH.

[0010] In one embodiment, the polyaliphatic amine compound includes one or more of polyvinylimide, polyethoxyethyleneimide, tetraethylenepentamine, pentaethylenehexamine, and hexamethylenetetramine.

[0011] In one embodiment, the metal ion includes Ag. + Zn 2+ Mg 2+ Cu 2+ Co 2+ and Ni 2+ One or more of them; and / or

[0012] The average particle size of the metal nanoparticles is <20 nm; and / or

[0013] The metal nanoparticles include one or more of Ag, Al, Cu, and Au; and / or

[0014] The solvent includes one or more of alcohols, ketones, and esters.

[0015] In one embodiment, the solvent includes one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, n-pentanol, n-hexanol, acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, ethyl acetate, propyl acetate, and methyl benzoate.

[0016] In one embodiment, the ink further includes a polyaliphatic amine compound dispersed in a solvent, and the mass of the polyaliphatic amine compound does not exceed 20% of the sum of the mass of the amine metal ion complex and the polyaliphatic amine compound.

[0017] An embodiment of this application also provides a method for preparing ink, comprising the following steps:

[0018] Polyaliphatic amine compounds are mixed with salt compounds containing metal ions to undergo a coordination reaction to generate amine metal ion complexes.

[0019] The amine metal ion complex and metal nanoparticles are mixed in a solvent.

[0020] In one embodiment, the mass ratio of the polyaliphatic amine compound to the metal ion-containing salt compound is 1:(10-100); and / or

[0021] The salt compounds include acetates; and / or

[0022] The reaction time for the coordination reaction is 2 h to 5 h; and / or

[0023] The mass ratio of the amine metal ion complex to the metal nanoparticles is (3:1) to (1:5); and / or

[0024] The solvent includes one or more of alcohols, ketones, and esters.

[0025] In one embodiment, the mass ratio of the amine metal ion complex to the metal nanoparticles is 1:2; and / or

[0026] The solvent includes one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, n-pentanol, n-hexanol, acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, ethyl acetate, propyl acetate, and methyl benzoate.

[0027] An embodiment of this application also provides a light-emitting device, including a plurality of light-emitting layers, wherein an electron injection layer, an electron collection layer and a hole transport layer are disposed between at least two adjacent light-emitting layers, the electron collection layer being located between the electron injection layer and the hole transport layer, and the electron injection layer being prepared by solution method using ink as described in any of the above embodiments or ink prepared by the ink preparation method as described in any of the above embodiments.

[0028] In one embodiment, the material of the light-emitting layer includes quantum dot light-emitting materials or organic light-emitting materials; the quantum dot light-emitting materials include one or more of group II-VI compound semiconductors, group III-V compound semiconductors, group I-III-VI compound semiconductors, and perovskite quantum dots; the group II-VI compound semiconductors include one or more of ZnCdSeS, CdSe / CdS, CdSeS / CdS, CdSe / CdS / ZnS, ZnCdSeS / ZnS, and ZnCdS / ZnS; the group III-V compound semiconductors include one or more of InP and InP / ZnS; and the group I-III-VI compound semiconductors include CuInS. One or more of AgInS, CuInS / ZnS, and AnInS / ZnS, wherein the perovskite quantum dots include CsPbM3, where M is Cl, Br, or I; the organic light-emitting material includes one or more of fluorescent materials, phosphorescent materials, and thermally activated delayed fluorescence materials; the fluorescent material includes one or more of TPBe, TTPA, TBRb, and DBP; the phosphorescent material includes one or more of Firpic, Ir(ppy)3, Ir(ppy)2acac, and Ir(piq)3; the thermally activated delayed fluorescence material includes one or more of ACRSA, DIC-TRZ, 2CzPN, PXZ-TRZ, and pCNBCzoCF3; and / or

[0029] The electron collecting layer is made of one or more of the following materials: PMA, MoO3, WO3, V2O5, ReO3, MnO3, CuI, NDP-9, HATCN, PEDOT:PSS, and FeCl3; and / or

[0030] The hole transport layer is made of one or more of the following materials: TFB, PVK, Poly-TPD, PFB, NPB, TAPC, TCTA, mCP, CBP, mCBP, CDBP, CuSCN, and NiO; and / or

[0031] The thickness of the electron injection layer is 10 nm to 30 nm.

[0032] One embodiment of this application also provides a display device, including a light-emitting device as described in any of the above embodiments.

[0033] The ink described above is obtained by mixing amine metal ion complexes obtained by coordinating polyaliphatic amine compounds with metal ions with metal nanoparticles. The ink has good stability, suitable surface tension and suitable viscosity, and has a good film-forming effect. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the structure of the light-emitting device in Example 5.

[0035] Figure label:

[0036] 100: Light-emitting device; 101: Anode substrate; 102: Hole injection layer; 103: First hole transport layer; 104: First light-emitting layer; 105: First electron injection layer; 106: Electron collection layer; 107: Second hole transport layer; 108: Second light-emitting layer; 109: Second electron injection layer; 110: Cathode. Detailed Implementation

[0037] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of this application.

[0038] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0039] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0040] One embodiment of this application provides an ink comprising a solvent and an amine metal ion complex and metal nanoparticles dispersed in the solvent, wherein the amine metal ion complex is obtained by coordination of a polyaliphatic amine compound with a metal ion.

[0041] The ink described above is obtained by mixing amine metal ion complexes obtained by coordinating polyaliphatic amine compounds with metal ions with metal nanoparticles. The ink has good stability, suitable surface tension and suitable viscosity, and good film-forming effect.

[0042] Furthermore, the inventors discovered through research that when the ink meets the quality standards of a viscosity of 2 mPa·s to 10 mPa·s, a surface tension of 20 mN / m to 50 mN / m, and can remain stable for more than 5 days at a constant temperature of 25°C, the functional layers of the light-emitting device prepared with this ink exhibit good functional performance after film formation. Furthermore, the ink obtained by mixing amine metal ion complexes and metal nanoparticles in the above embodiment also meets the above quality standards in terms of viscosity, surface tension, and stability. Therefore, the above ink can be used to prepare the functional layers of the light-emitting device.

[0043] In one embodiment, the ink described above can be used, for example, to fabricate an electron injection layer for a light-emitting device.

[0044] In one embodiment, the ink can be used, for example, to fabricate an electron injection layer between two adjacent light-emitting layers of a light-emitting device. In a more specific embodiment, the light-emitting device is a stacked light-emitting device. The ink comprises an amine metal ion complex and metal nanoparticles. The metal ions in the amine metal ion complex can act as connectors between molecules of polyaliphatic amine compounds, causing the electron orbitals between the molecules to fuse, reducing the insulation of the polyaliphatic amine compounds, and significantly improving their conductivity, which is more conducive to electron injection. Furthermore, after the amine metal ion complex is mixed with the metal nanoparticles, the metal nanoparticles can, on the one hand, enhance the charge generation capability of the charge generation unit, and on the other hand, reduce the energy level barrier between the charge generation unit and the lower light-emitting layer, making it easier for the electrons collected by the charge generation unit to be injected into the light-emitting layer, reducing the accumulation of charge near the charge generation unit, thereby significantly reducing the driving voltage of the light-emitting device and significantly improving the device lifetime.

[0045] The inventors discovered that when inks obtained by mixing polyaliphatic amine compounds with metal nanoparticles are used to fabricate electron injection layers, the polyaliphatic amine compounds and metal nanoparticles come into contact with each other. The polyaliphatic amine compounds alter the surface potential of the metal nanoparticles, reducing the injection barrier for electrons to enter the light-emitting layer, thus facilitating electron injection. However, because polyaliphatic amine compounds are insulators, the overall electron injection performance is still not ideal. Furthermore, by coordinating polyaliphatic amine compounds with metal ions to form amine-metal ion complexes, the metal ions act as intermolecular connectors between amine molecules. The intermolecular electronic orbitals of the polyaliphatic amine compounds are fused, the insulating properties are weakened, and the conductivity is significantly enhanced, further improving the electron injection capability.

[0046] The ink described above can be used to form an electron injection layer between two adjacent light-emitting layers of a light-emitting device using a solution method. This electron injection layer can serve as an electron extraction channel for the charge generation unit, making it easier for electrons generated by the charge generation unit to be injected into the light-emitting layer. This significantly reduces the driving voltage of the light-emitting device and significantly improves its current efficiency and lifespan.

[0047] In one embodiment, the mass ratio of the amine metal ion complex to the metal nanoparticles is (3:1) to (1:5). Using a mass ratio within this specific range ensures that the electron injection layer made using this ink not only enhances the charge generation capability of the charge generation unit but also allows electrons to be injected more smoothly into the underlying light-emitting layer, resulting in a lower driving voltage, higher current efficiency, and longer lifespan for the light-emitting device. Understandably, the mass ratio of the polyaliphatic amine compound to the metal nanoparticles can be, for example, 3:1, 3:2, 3:4, 3:5, 2:1, 2:3, 2:5, 1:1, 1:2, 1:3, 1:4, 1:5, etc., and is not limited thereto. Preferably, the mass ratio of the amine metal ion complex to the metal nanoparticles is 1:2.

[0048] In one embodiment, the polyaliphatic amine compound includes one or more of the following structures:

[0049]

[0050] Where R is H or -CH2CH2OH.

[0051] Understandably, polyaliphatic amine compounds can be polyaliphatic amine polymers or small molecule polyaliphatic amine compounds. Furthermore, polyaliphatic amine polymers may include, but are not limited to, polyvinylimide (PEI) and polyethoxyethyleneimide (PEIE), etc., and small molecule polyaliphatic amine compounds may include, but are not limited to, tetraethylenepentamine (TEPA), pentaethylenehexamine, and hexamethylenetetramine, etc. Understandably, polyaliphatic amine compounds may also include, but are not limited to, one or more of polyvinylimide, polyethoxyethyleneimide, tetraethylenepentamine, pentaethylenehexamine, and hexamethylenetetramine.

[0052] In one embodiment, the metal ion coordinating with the polyaliphatic amine compound may include, but is not limited to, Ag. + Zn 2+ Mg 2+ Cu 2+ Co 2+ and Ni 2+ One or more of these compounds. The coordination bonds formed by these metal ions and polyaliphatic amine compounds are relatively stable. After the ink film is formed, the coordination bonds are not easily detached during subsequent annealing and other post-processing processes, which can ensure stable electron injection capability.

[0053] In one embodiment, the average particle size of the metal nanoparticles is <20 nm. The smaller the particle size of the metal nanoparticles, the better they are dispersed in the solvent, resulting in a more uniform electron injection layer film formed by solution deposition of the ink. This helps ensure that the stacked light-emitting device has stable and good electron injection performance.

[0054] In one embodiment, the metal nanoparticles are dispersed in the solvent without precipitation for at least 24 hours. The fact that the metal nanoparticles do not precipitate in the solvent for a relatively long period indicates that they can be sufficiently and stably dispersed in the ink without agglomeration, which is beneficial for film formation.

[0055] In one embodiment, the metal nanoparticles may include, but are not limited to, one or more of Ag, Al, Cu, and Au. These metal nanoparticles possess excellent electrical conductivity, which facilitates charge generation. When amine metal ion complexes are mixed with metal nanoparticles, the strong electrical conductivity of the metal nanoparticles enhances the charge generation capability of the charge-generating unit. Simultaneously, with the assistance of the amine metal ion complexes, electrons can be easily injected into the light-emitting layer.

[0056] In one embodiment, the solvent is a non-aqueous solvent. Further, the solvent is preferably a non-aqueous solvent with moderate volatility. These solvents can sufficiently disperse the amine metal ion complex and metal nanoparticles to form a stable and uniform ink. After the ink is deposited as a film using a solution method, it can fully evaporate and dry within a short time to form an electron injection layer without adversely affecting the performance of the light-emitting device.

[0057] Furthermore, the solvent may include, but is not limited to, one or a mixture of alcohols, ketones, and esters.

[0058] Furthermore, the solvent may include, but is not limited to, one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, n-pentanol, n-hexanol, acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, ethyl acetate, propyl acetate, and methyl benzoate.

[0059] Furthermore, the solvent is preferably a non-aqueous solvent with a boiling point of 100°C to 200°C, such as, but not limited to, n-hexanol, n-pentanol, etc.

[0060] In one embodiment, the ink further includes a polyaliphatic amine compound dispersed in a solvent, wherein the mass of the polyaliphatic amine compound does not exceed 20% of the sum of the masses of the amine metal ion complex and the polyaliphatic amine compound. Understandably, the polyaliphatic amine compound can coordinate with metal ions to form stable coordination bonds, effectively weakening the insulating properties of amine molecules, improving their conductivity, and facilitating electron injection. Furthermore, metal nanoparticles also possess a certain ability to coordinate with polyaliphatic amine compounds. Therefore, the ink also includes a small amount of uncoordinated polyaliphatic amine compounds to bind with metal nanoparticles, thereby enhancing the ink's stability. Understandably, the uncoordinated polyaliphatic amine compounds in the ink can only be in small amounts; the ink composition still primarily consists of amine metal ion complexes to ensure that the insulating properties of the amine substances are weakened, thereby enhancing electron injection capability. Understandably, the polyaliphatic amine compounds in the ink can be added separately or are polyaliphatic amine compounds that did not undergo coordination reactions during the preparation of the amine metal ion complex.

[0061] The aforementioned ink can form an electron injection layer between two adjacent light-emitting layers in a light-emitting device using a solution method. The electron injection layer includes amine metal ion complexes and metal nanoparticles. The metal ions in the amine metal ion complexes can act as connectors between molecules of polyaliphatic amine compounds, causing the electron orbitals between the molecules to fuse, reducing the insulation of the polyaliphatic amine compounds, and significantly improving their conductivity, which is more conducive to electron injection. Furthermore, after the amine metal ion complexes are mixed with the metal nanoparticles, the metal nanoparticles can enhance the charge generation capability of the charge generation unit on the one hand, and reduce the energy level barrier between the unit and the lower light-emitting layer on the other hand, making it easier for the collected electrons to be injected into the light-emitting layer, reducing the accumulation of charge near the charge generation unit, thereby significantly reducing the driving voltage of the light-emitting device and significantly improving the device lifespan.

[0062] Understandably, the aforementioned ink can also be used to fabricate electron injection layers at other locations in light-emitting devices. Understandably, the aforementioned ink can also be used to fabricate other functional layers in light-emitting devices, not limited to electron injection layers. Understandably, the aforementioned ink is not limited to the fabrication of light-emitting devices and can also be used for other purposes.

[0063] An embodiment of this application also provides a method for preparing ink, comprising the following steps:

[0064] Polyaliphatic amine compounds are mixed with salt compounds containing metal ions to undergo a coordination reaction to generate amine metal ion complexes.

[0065] Amine metal ion complexes and metal nanoparticles are mixed in a solvent.

[0066] In one embodiment, the mass ratio of the polyaliphatic amine compound to the salt compound containing metal ions is 1:(10-100). Within this mass range, the polyaliphatic amine compound can coordinate with the metal ions to form amine-metal ion complexes, which is beneficial for improving electron injection capability.

[0067] In one embodiment, the salt compound may be, for example, an acetate, and it is understood that other salt compounds may also be used, not limited thereto, as long as the metal ions in the salt compound can readily undergo a coordination reaction with the polyaliphatic amine compound.

[0068] In one embodiment, the coordination reaction takes 2 to 5 hours. Furthermore, when the coordination reaction is complete, the liquid in the reaction system is clear.

[0069] In one embodiment, the coordination reaction can be carried out at room temperature.

[0070] In one embodiment, the mass ratio of the amine metal ion complex to the metal nanoparticles is (3:1) to (1:5). Preferably, the mass ratio of the amine metal ion complex to the metal nanoparticles is 1:2.

[0071] In one embodiment, the polyaliphatic amine compound includes one or more of the following structures:

[0072]

[0073] Where R is H or -CH2CH2OH.

[0074] Furthermore, polyaliphatic amine compounds may include, but are not limited to, one or more of polyvinylimide, polyethoxyethyleneimide, tetraethylenepentamine, pentaethylenehexamine, and hexamethylenetetramine.

[0075] In one embodiment, the metal ions may include, but are not limited to, Ag. + Zn 2+ Mg 2+ Cu 2+ Co 2+ and Ni 2+ One or more of them.

[0076] In one embodiment, the average particle size of the metal nanoparticles is <20 nm.

[0077] In one embodiment, the metal nanoparticles may include, but are not limited to, one or more of Ag, Al, Cu and Au.

[0078] In one embodiment, the solvent may include, but is not limited to, one or more of alcohols, ketones, and esters.

[0079] Furthermore, the solvent may include, but is not limited to, one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, n-pentanol, n-hexanol, acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, ethyl acetate, propyl acetate, and methyl benzoate.

[0080] In one embodiment, the ink further includes a polyaliphatic amine compound dispersed in a solvent, wherein the mass of the polyaliphatic amine compound does not exceed 20% of the sum of the mass of the amine metal ion complex and the polyaliphatic amine compound.

[0081] Understandably, metal nanoparticles can be obtained commercially or through various self-made methods, and there are no particular restrictions on the specific methods of acquisition.

[0082] In one embodiment, a method for preparing metal nanoparticles is provided, comprising the following steps:

[0083] An alcohol solution containing phenylhydrazine is mixed with metal ions and a stabilizer, and the mixture is heated until the color becomes constant.

[0084] An embodiment of this application also provides a light-emitting device, including multiple light-emitting layers. At least two adjacent light-emitting layers are provided with an electron injection layer, an electron collection layer and a hole transport layer. The electron collection layer is located between the electron injection layer and the hole transport layer. The electron injection layer is prepared by solution method using ink from any of the above embodiments or ink prepared by the preparation method of ink from any of the above embodiments.

[0085] The aforementioned light-emitting device has a simple structure and can be fabricated using a solution-based process, which does not damage the properties of other pre-fabricated functional layers, thus ensuring the stability of the device's performance. Furthermore, the electron collection layer and hole transport layer constitute the charge generation unit of the light-emitting device. The electron injection layer enhances charge generation and lowers the energy level barrier between the charge generation unit and the light-emitting layer, allowing electrons generated by the charge generation unit to be easily injected into the lower light-emitting layer. This significantly reduces the driving voltage of the light-emitting device and improves current efficiency and lifetime.

[0086] Understandably, the electron flow direction in this application is the conventional flow direction from cathode to anode, and the injection of electrons from the charge generation unit into the light-emitting layer in this application is also carried out in the direction of electron flow. Understandably, the lower light-emitting layer mentioned in this application refers to the next light-emitting layer that electrons in the light-emitting device will flow through after passing through the charge generation unit.

[0087] In one embodiment, the light-emitting device is a stacked light-emitting device.

[0088] In one embodiment, in the two adjacent light-emitting layers described above, the light-emitting layer connected to the electron injection layer is closer to the anode, and the light-emitting layer connected to the hole transport layer is closer to the cathode.

[0089] In one embodiment, the solution method may include, but is not limited to, spin coating, printing, etc.

[0090] In one embodiment, when preparing the electron injection layer using ink via solution deposition, the film can be deposited in an inert gas atmosphere. Understandably, the inert gas can be, but is not limited to, nitrogen, argon, etc. Deposition in an inert gas atmosphere prevents water and oxygen in the air from damaging the fabricated film and also prevents the metal nanoparticles in the ink from being oxidized during film deposition, thus avoiding adverse effects on the performance of the light-emitting device.

[0091] Understandably, the number of light-emitting layers can be two, three, four, or more. At least two adjacent light-emitting layers form a charge-generating unit by providing an electron-collecting layer and a hole-transporting layer, and an electron-injection layer is also provided to assist in injecting the electrons generated by the charge-generating unit into the lower light-emitting layer. Understandably, if the number of light-emitting layers exceeds two, an electron-injection layer, an electron-collecting layer, and a hole-transporting layer can be provided between each adjacent light-emitting layer, or only between some of the adjacent light-emitting layers.

[0092] In one embodiment, the light-emitting material of the light-emitting layer includes quantum dot light-emitting materials or organic light-emitting materials.

[0093] In one embodiment, the quantum dot luminescent material may include, but is not limited to, one or more of group II-VI compound semiconductors, group III-V compound semiconductors, group I-III-VI compound semiconductors, and perovskite quantum dots.

[0094] Optionally, the II-VI compound semiconductor may include, but is not limited to, one or more of ZnCdSeS, CdSe / CdS, CdSeS / CdS, CdSe / CdS / ZnS, ZnCdSeS / ZnS, and ZnCdS / ZnS.

[0095] Alternatively, III-V compound semiconductors may include, but are not limited to, one or more of InP and InP / ZnS.

[0096] Optionally, the I-III-VI group compound semiconductors may include, but are not limited to, one or more of CuInS, AgInS, CuInS / ZnS, and AnInS / ZnS.

[0097] Optionally, perovskite quantum dots may include, but are not limited to, CsPbM3, where M is Cl, Br, or I.

[0098] In one embodiment, the organic light-emitting material may include, but is not limited to, one or more of fluorescent materials, phosphorescent materials, and thermally activated delayed fluorescent materials.

[0099] Alternatively, the fluorescent material may include, but is not limited to, one or more of TPBe, TTPA, TBRb and DBP.

[0100] Alternatively, the phosphorescent material may include, but is not limited to, one or more of Firpic, Ir(ppy)3, Ir(ppy)2acac and Ir(piq)3.

[0101] Optionally, the thermally activated delayed fluorescence material may include, but is not limited to, one or more of ACRSA, DIC-TRZ, 2CzPN, PXZ-TRZ, and pCNBCzoCF3.

[0102] In one embodiment, the charge generation unit may be, but is not limited to, a bulk heterojunction or bilayer film composed of a strong electron acceptor (deep LUMO) and a strong electron donor (deep HOMO) material. The charge generation mechanism involves the transfer of electrons from the HOMO level of the electron donor material to the LUMO level of the electron acceptor material, and the HOMO level of the electron donor and the LUMO level of the electron acceptor are located close to each other. In any embodiment of this application, the electron collection layer is the electron acceptor layer. Further, the material of the electron collection layer used in solution processing may include, but is not limited to, one or more of PMA, MoO3, WO3, V2O5, ReO3, MnO3, CuI, NDP-9, HATCN, PEDOT:PSS, and FeCl3.

[0103] In one embodiment, the hole transport layer may be made of conventional materials in the art, such as, but not limited to, one or more of TFB, PVK, Poly-TPD, PFB, NPB, TAPC, TCTA, mCP, CBP, mCBP, CDBP, CuSCN, and NiO.

[0104] In one embodiment, the thickness of the electron injection layer is 10 nm to 30 nm. A thickness within this range ensures good electron injection capability without affecting other device performance characteristics.

[0105] The charge generation unit between two adjacent light-emitting layers consists of an electron collection layer and hole transport. Although this charge generation unit has a certain charge generation capability, without the electron injection layer made of ink as described in any of the above embodiments, the potential barrier for the electrons collected by the charge generation unit to be injected into the light-emitting layer is large. Electrons are difficult to inject into the lower light-emitting layer, which easily leads to charge accumulation near the electron collection layer. This will have a significant adverse impact on the driving voltage, current efficiency, and device lifetime of the stacked light-emitting device. When an electron injection layer made of ink as described in any of the above embodiments is provided between the electron collection layer and the lower light-emitting layer, electron injection is smoother, the driving voltage of the light-emitting device is significantly reduced, and the current efficiency and device lifetime are significantly improved.

[0106] One embodiment of this application also provides a display device, including the light-emitting device as described in any of the above embodiments. It will be understood that the display device may include, for example, a display screen for a mobile phone, computer, television, etc.

[0107] The ink, its preparation method, light-emitting device, and display device described herein are further explained in detail below through specific embodiments and comparative examples. The light-emitting device structures prepared in each embodiment are relatively specific. It is understood that in other embodiments, the invention is not limited to these. For example, the injection layer and transport layer between the light-emitting layer and the corresponding electrode layer may be absent, or only one of them may be present; an electron transport layer may also be provided between the light-emitting layer and the electron injection layer made using the ink in any embodiment of this invention; the light-emitting device may be a multilayer light-emitting device, or other light-emitting devices containing multiple light-emitting layers; the number of light-emitting layers is not limited to two layers, but may be three or more layers; the material selection and thickness setting of each layer may also be determined according to the specific product; the light-emitting device may be an upright device or an inverted device, and the corresponding anode may be disposed close to the substrate, or the cathode may be disposed close to the substrate.

[0108] Example 1

[0109] Step 1: Preparation of amine metal ion complexes

[0110] 15 mg of zinc acetate dihydrate powder was added to 2 mL of PEI (Mw ~ 25000, 1 wt% ethanol), and stirred at room temperature for 3 h until the solution became clear. The solution was then dried in a vacuum chamber to obtain PEI-Zn. 2+ Coordination compounds.

[0111] Step 2: Preparation of metal nanoparticles

[0112] 10 mL of 0.011 g / mL phenylhydrazine ethanol solution was slowly added dropwise to 40 mL of isopropanol solution consisting of 1 mmol silver acetate and 3 mmol tetraethylenepentamine (TEPA), and stirred at 60 °C until the color was constant. The solution was then centrifuged and vacuum dried to obtain Ag NPs.

[0113] Step 3: Preparing the Ink

[0114] Weigh 10 mg of the Ag NPs prepared in step two and disperse them evenly in 10 mL of ethanol. Then add 5 mg of the PEI-Zn prepared in step one. 2+ The complex was added to the dispersion and stirred at room temperature until completely dissolved. After centrifugation to remove insoluble matter, it was ready for use. PEI-Zn 2+ The mass ratio of the complex to Ag NPs is 1:2.

[0115] Example 2

[0116] Step 1: Same as Step 1 in Example 1.

[0117] Step 2: Same as Step 2 in Example 1.

[0118] Step 3: Preparing the Ink

[0119] Weigh 10 mg of the Ag NPs prepared in step two and disperse them evenly in 10 mL of ethanol. Then, add 10 mg of the PEI-Zn prepared in step one. 2+ The complex was added to the dispersion and stirred at room temperature until completely dissolved. After centrifugation to remove insoluble matter, it was ready for use. PEI-Zn 2+ The mass ratio of the complex to Ag NPs is 1:1.

[0120] Example 3

[0121] Step 1: Same as Step 1 in Example 1.

[0122] Step 2: Same as Step 2 in Example 1.

[0123] Step 3: Preparing the Ink

[0124] Weigh 10 mg of the Ag NPs prepared in step two and disperse them evenly in 10 mL of ethanol. Then add 30 mg of the PEI-Zn prepared in step one. 2+ The complex was added to the dispersion and stirred at room temperature until completely dissolved. After centrifugation to remove insoluble matter, it was ready for use. PEI-Zn 2+ The mass ratio of the complex to Ag NPs is 3:1.

[0125] Example 4

[0126] Step 1: Same as Step 1 in Example 1.

[0127] Step 2: Same as Step 2 in Example 1.

[0128] Step 3: Preparing the Ink

[0129] Weigh 10 mg of the Ag NPs prepared in step two and disperse them evenly in 10 mL of ethanol. Then add 2 mg of the PEI-Zn from step one. 2+ The complex was added to the dispersion and stirred at room temperature until completely dissolved. After centrifugation to remove insoluble matter, it was ready for use. PEI-Zn 2+ The mass ratio of the complex to Ag NPs is 1:5.

[0130] Comparative Example 1

[0131] Step 1: Polyaliphatic amine compounds do not coordinate with metal ions, so PEI is used directly.

[0132] Step 2: Same as Step 2 in Example 1.

[0133] Step 3: Preparing the Ink

[0134] Weigh 10 mg of Ag NPs prepared in step two and disperse them evenly in 10 mL of ethanol. Then add 5 mg of PEI from step one to the dispersion and stir at room temperature until completely dissolved. Centrifuge to remove insoluble matter and set aside. The mass ratio of PEI to Ag NPs is 1:2.

[0135] The inks prepared in Examples 1 to 4 and Comparative Example 1 were tested for properties such as viscosity, surface tension, and stability. The test results are shown in Table 1 below.

[0136] The viscosity of the ink was tested using a viscometer, and the standard range for evaluating the viscosity of the ink was 2 mPa·s to 10 mPa·s.

[0137] The viscosity of the ink was tested using a surface tension tester. The standard range for evaluating the surface tension of the ink is 20 mN / m to 50 mN / m.

[0138] Stability evaluation: Malvern laser particle size analyzer was used. Evaluation criteria: the time corresponding to the percentage of particles larger than 1 μm in a 1% mass fraction dispersion being less than 1% was measured after constant temperature at 25℃; stability after constant temperature at 25℃ for more than 5 days was considered acceptable.

[0139] Table 1. Test results of ink viscosity, surface tension, and stability.

[0140]

[0141] As can be seen from Table 1, a comparison between Examples 1 to 4 and Comparative Example 1 shows that the amine-metal ion complexes formed by the coordination of polyaliphatic amine compounds in the ink with metal ions can significantly improve the stability of the ink, and the ink has suitable viscosity and surface tension.

[0142] Example 5

[0143] Step 1: Preparation of amine metal ion complexes

[0144] 15 mg of zinc acetate dihydrate powder was poured into 2 mL of PEI (Mw ~ 25000, 1 wt% ethanol), and stirred until the solution became clear. The solution was then dried in a vacuum chamber to obtain PEI-Zn. 2+ Coordination compounds.

[0145] Step 2: Preparation of metal nanoparticles

[0146] 10 mL of 0.011 g / mL phenylhydrazine ethanol solution was slowly added dropwise to 40 mL of isopropanol solution consisting of 1 mmol silver acetate and 3 mmol tetraethylenepentamine (TEPA), and stirred at 60 °C until the color was constant. The solution was then centrifuged and vacuum dried to obtain Ag NPs.

[0147] Step 3: Preparing the Ink

[0148] Weigh 10 mg of the Ag NPs prepared in step two and disperse them evenly in 10 mL of ethanol. Then add 5 mg of the PEI-Zn prepared in step one. 2+ The complex was added to the dispersion and stirred at room temperature until completely dissolved. After centrifugation to remove insoluble matter, it was ready for use. PEI-Zn 2+ The mass ratio of the complex to Ag NPs is 1:2.

[0149] Step 4: Preparation of electron collecting layer ink

[0150] Phosphomolybdic acid (PMA) was dissolved in acetonitrile at a concentration of 1 mg / mL, then coated onto an evaporating dish and transferred to an insulated container purged with nitrogen. The mixture was then baked at 200°C for 5 hours. The baked film was scraped off and dissolved in 1-butanol.

[0151] Step 5: Fabricating the light-emitting device

[0152] Figure 1 A schematic diagram of the structure of the light-emitting device 100 is shown, and the specific manufacturing steps include:

[0153] (1) The ITO anode substrate 101 was cleaned and then treated under UV conditions for 15 min to increase its work function and wettability.

[0154] (2) On the anode substrate 101 after step (1), spin-coat a 30nm thick layer of PEDOT:PSS and bake at 150°C for 20min in an air atmosphere to form a hole injection layer 102.

[0155] (3) TFB with a thickness of 20 nm is spin-coated on the hole injection layer 102 formed in step (2), and then baked at 180°C for 60 min in a nitrogen atmosphere to form the first hole transport layer 103.

[0156] (4) A 60nm thick polymer light-emitting layer F8BT is spin-coated on the first hole transport layer 103 formed in step (3) and baked at 130°C for 10 minutes to form the first light-emitting layer 104.

[0157] (5) Spin coat the ink prepared in step three with a thickness of 15 nm on the first light-emitting layer 104 formed in step (4), and bake it at 120°C for 15 min to form the first electron injection layer 105.

[0158] (6) Spin coat a 10 nm thick electron collection layer ink prepared in step four onto the first electron injection layer 105 formed in step (5), and bake at 120°C for 20 min to form electron collection layer 106.

[0159] (7) A 20 nm thick TFB is spin-coated on the electron collection layer 106 formed in step (6) and baked at 150 °C for 30 min to form the second hole transport layer 107.

[0160] (8) Spin-coat 80nm F8BT on the second hole transport layer 107 formed in step (7) and bake at 130°C for 15min to form the second light-emitting layer 108.

[0161] (9) The second light-emitting layer 108 formed in step (8) is vacuum-deposited with 1 nm of LiF to form the second electron injection layer 109.

[0162] (10) A 100 nm thick Al layer is vacuum-deposited on the second implantation layer 109 formed in step (9), and finally encapsulated and annealed at 80 °C for 30 min to form a cathode 110.

[0163] Example 6

[0164] Step 1: Same as Step 1 in Example 5.

[0165] Step 2: Same as Step 2 in Example 5.

[0166] Step 3: Preparing the Ink

[0167] Weigh 10 mg of the Ag NPs prepared in step two and disperse them evenly in 10 mL of ethanol. Then, add 10 mg of the PEI-Zn prepared in step one. 2+ The complex was added to the dispersion and stirred at room temperature until completely dissolved. After centrifugation to remove insoluble matter, it was ready for use. PEI-Zn 2+ The mass ratio of the complex to Ag NPs is 1:1.

[0168] Step 4: Same as step 4 in Example 5.

[0169] Step 5: Same as step 5 in Example 5.

[0170] Example 7

[0171] Step 1: Same as Step 1 in Example 5.

[0172] Step 2: Same as Step 2 in Example 5.

[0173] Step 3: Preparing the Ink

[0174] Weigh 10 mg of the Ag NPs prepared in step two and disperse them evenly in 10 mL of ethanol. Then add 30 mg of the PEI-Zn prepared in step one. 2+ The complex was added to the dispersion and stirred at room temperature until completely dissolved. After centrifugation to remove insoluble matter, it was ready for use. PEI-Zn 2+The mass ratio of the complex to Ag NPs is 3:1.

[0175] Step 4: Same as step 4 in Example 5.

[0176] Step 5: Same as step 5 in Example 5.

[0177] Example 8

[0178] Step 1: Same as Step 1 in Example 5.

[0179] Step 2: Same as Step 2 in Example 5.

[0180] Step 3: Preparing the Ink

[0181] Weigh 10 mg of the Ag NPs prepared in step two and disperse them evenly in 10 mL of ethanol. Then add 2 mg of the PEI-Zn from step one. 2+ The complex was added to the dispersion and stirred at room temperature until completely dissolved. After centrifugation to remove insoluble matter, it was ready for use. PEI-Zn 2+ The mass ratio of the complex to Ag NPs is 1:5.

[0182] Step 4: Same as step 4 in Example 5.

[0183] Step 5: Same as step 5 in Example 5.

[0184] Example 9

[0185] Step 1: Same as Step 1 in Example 5.

[0186] Step 2: Same as Step 2 in Example 5.

[0187] Step 3: Same as step 3 in Example 5.

[0188] Step 4: Same as step 4 in Example 5.

[0189] Step 5: Fabricating the light-emitting device

[0190] The specific production steps include:

[0191] (1) The ITO anode substrate was cleaned and then treated under UV conditions for 15 min to increase its work function and wettability.

[0192] (2) On the anode substrate treated in step (1), spin-coat a 50 nm thick layer of PEDOT:PSS and bake at 150 °C for 20 min in an air atmosphere to form a hole injection layer.

[0193] (3) TFB is spin-coated on the hole injection layer formed in step (2) with a thickness of 30 nm, and then baked at 160 °C for 30 min in a nitrogen atmosphere to form the first hole transport layer.

[0194] (4) Spin-coat a 20nm thick green QDs ink onto the first hole transport layer formed in step (3) and bake at 100°C for 10 minutes to form the first light-emitting layer.

[0195] (5) Spin-coat a 30nm thick ZnO layer on the first light-emitting layer formed in step (4) and anneal at 100°C for 10min to form the first electron transport layer.

[0196] (6) Spin coat a 15 nm thick layer of ink prepared in step three onto the first electron transport layer formed in step (5), and bake at 120°C for 15 min to form the first electron injection layer.

[0197] (7) Spin coat a 10 nm thick electron collection layer ink prepared in step four onto the first electron injection layer formed in step (6), and bake at 120°C for 20 min to form an electron collection layer.

[0198] (8) A 30 nm thick TFB layer is spin-coated on the electron collection layer formed in step (7) and baked at 120 °C for 30 min to form a second hole transport layer.

[0199] (9) Spin-coat a 20nm thick green QDs ink onto the second hole transport layer formed in step (8) and bake at 100°C for 15 minutes to form the second light-emitting layer.

[0200] (10) Spin-coat a 30nm thick ZnO layer on the second light-emitting layer formed in step (9) and anneal at 100°C for 10min to form a second electron transport layer.

[0201] (11) A 100 nm thick Al layer is vacuum-deposited on the second electron transport layer formed in step (10), and finally encapsulated and annealed at 100 °C for 30 min to form a cathode.

[0202] Comparative Example 2

[0203] Step 1: Same as Step 1 in Example 5.

[0204] Step 2: No step 2, no metal nanoparticles added.

[0205] Step 3: Making Ink

[0206] Weigh 5 mg of the PEI-Zn prepared in step one. 2+ The complex was uniformly dispersed in 10 mL of ethanol, stirred at room temperature until completely dissolved, and centrifuged to remove insoluble matter before use.

[0207] Step 4: Same as step 4 in Example 5.

[0208] Step 5: Same as step 5 in Example 5.

[0209] Comparative Example 3

[0210] Step 1: Same as Step 1 in Example 5.

[0211] Step 2: No step 2, no metal nanoparticles added.

[0212] Step 3: Making Ink

[0213] Weigh 5 mg of the PEI-Zn prepared in step one. 2+ The complex was uniformly dispersed in 10 mL of ethanol, stirred at room temperature until completely dissolved, and centrifuged to remove insoluble matter before use.

[0214] Step 4: Same as step 4 in Example 5.

[0215] Step 5: Same as step 5 in Example 9.

[0216] Comparative Example 4

[0217] Step 1: Same as Step 1 in Example 5.

[0218] Step 2: Same as Step 2 in Example 5.

[0219] Step 3: Preparing the Ink

[0220] Weigh 10 mg of the Ag NPs prepared in step two and disperse them evenly in 10 mL of ethanol. Then add 40 mg of the PEI-Zn prepared in step one. 2+ The complex was added to the dispersion and stirred at room temperature until completely dissolved. After centrifugation to remove insoluble matter, it was ready for use. PEI-Zn 2+ The mass ratio of the complex to Ag NPs is 4:1.

[0221] Step 4: Same as step 4 in Example 5.

[0222] Step 5: Same as step 5 in Example 5.

[0223] Comparative Example 5

[0224] Step 1: Same as Step 1 in Example 5.

[0225] Step 2: Same as Step 2 in Example 5.

[0226] Step 3: Preparing the Ink

[0227] Weigh 10 mg of the Ag NPs prepared in step two and disperse them evenly in 10 mL of ethanol. Then add 1.67 mg of the PEI-Zn prepared in step one. 2+ The complex was added to the dispersion and stirred at room temperature until completely dissolved. After centrifugation to remove insoluble matter, it was ready for use. PEI-Zn 2 + The mass ratio of the complex to Ag NPs is 1:6.

[0228] Step 4: Same as step 4 in Example 5.

[0229] Step 5: Same as step 5 in Example 5.

[0230] Comparative Example 6

[0231] Step 1: Polyaliphatic amine compounds do not coordinate with metal ions, so PEI is used directly.

[0232] Step 2: Same as Step 2 in Example 5.

[0233] Step 3: Preparing the Ink

[0234] Weigh 10 mg of Ag NPs prepared in step two and disperse them evenly in 10 mL of ethanol. Then add 5 mg of PEI from step one to the dispersion and stir at room temperature until completely dissolved. Centrifuge to remove insoluble matter and set aside. The mass ratio of PEI to Ag NPs is 1:2.

[0235] Step 4: Same as step 4 in Example 5.

[0236] Step 5: Same as step 5 in Example 5.

[0237] The light-emitting devices prepared in Examples 5 to 9 and Comparative Examples 2 to 6 were tested for driving voltage, current efficiency, and LT95 lifetime. The driving voltage and current efficiency were tested using an IVL device, and the LT95 lifetime was tested using a lifetime aging device. The test results are shown in Table 2 below.

[0238] Table 2 Performance test results of light-emitting devices

[0239]

[0240] As shown in Table 2, compared with Comparative Example 6, Example 5 demonstrates that when the ink composition includes amine metal ion complexes and metal nanoparticles, compared with the use of polyaliphatic amine compounds that do not contain metal ion coordination, the driving voltage of the light-emitting device is significantly reduced, the current efficiency is significantly improved, and the device lifespan is significantly increased.

[0241] Compared with Comparative Examples 4-5, Examples 5-9 demonstrate that when the mass ratio of amine metal ion complex to metal nanoparticles is between (3:1) and (1:5), the driving voltage of the light-emitting device is significantly reduced, the current efficiency is significantly improved, and the device lifespan is significantly increased.

[0242] Compared with Comparative Example 2 and Comparative Example 3, Example 5 shows that when the ink composition contains metal nanoparticles, the driving voltage of the light-emitting device is significantly reduced, the current efficiency is significantly improved, and the device lifespan is significantly increased compared with the ink composition without metal nanoparticles.

[0243] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0244] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A light-emitting device, characterized in that, The device comprises multiple light-emitting layers, with an electron injection layer, an electron collection layer, and a hole transport layer disposed between at least two adjacent light-emitting layers. The electron collection layer is located between the electron injection layer and the hole transport layer. The electron injection layer is prepared using an ink via a solution method. The ink comprises a solvent and amine metal ion complexes and metal nanoparticles dispersed in the solvent. The amine metal ion complexes are obtained by coordinating polyaliphatic amine compounds with metal ions. The polyaliphatic amine compounds include one or more of the following structures: Wherein, R is H or -CH2CH2OH; The metal ions include Ag. + Zn 2+ Mg 2+ Cu 2+ Co 2+ and Ni 2+ One or more of the following; The metal nanoparticles include one or more of Ag, Al, Cu, and Au; The mass ratio of the amine metal ion complex to the metal nanoparticles is (3:1) to (1:5).

2. The light-emitting device according to claim 1, characterized in that, The average particle size of the metal nanoparticles is <20 nm.

3. The light-emitting device according to claim 1, characterized in that, The mass ratio of the amine metal ion complex to the metal nanoparticles is 1:

2.

4. The light-emitting device according to any one of claims 1 to 3, characterized in that, The ink further includes a polyaliphatic amine compound dispersed in the solvent, and the mass of the polyaliphatic amine compound does not exceed 20% of the sum of the mass of the amine metal ion complex and the polyaliphatic amine compound.

5. The light-emitting device according to claim 1, characterized in that, The polyaliphatic amine compounds include one or more of polyvinylimide, polyethoxyethyleneimide, tetraethylenepentamine, pentaethylenehexamine, and hexamethylenetetramine.

6. The light-emitting device according to any one of claims 1 to 3 and 5, characterized in that, The solvent includes one or more of alcohols, ketones, and esters.

7. The light-emitting device according to claim 6, characterized in that, The solvent includes one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, n-pentanol, n-hexanol, acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, ethyl acetate, propyl acetate, and methyl benzoate.

8. The light-emitting device according to any one of claims 1 to 3, 5, and 7, characterized in that, The ink also includes a polyaliphatic amine compound dispersed in a solvent, and the mass of the polyaliphatic amine compound does not exceed 20% of the sum of the mass of the amine metal ion complex and the polyaliphatic amine compound.

9. The light-emitting device according to claim 1, characterized in that, The material of the light-emitting layer includes quantum dot light-emitting materials or organic light-emitting materials; the quantum dot light-emitting materials include one or more of group II-VI compound semiconductors, group III-V compound semiconductors, group I-III-VI compound semiconductors, and perovskite quantum dots; the group II-VI compound semiconductors include one or more of ZnCdSeS, CdSe / CdS, CdSeS / CdS, CdSe / CdS / ZnS, ZnCdSeS / ZnS, and ZnCdS / ZnS; the group III-V compound semiconductors include one or more of InP and InP / ZnS; and the group I-III-VI compound semiconductors include CuInS and AgInS. One or more of CuInS / ZnS and AnInS / ZnS, wherein the perovskite quantum dots include CsPbM3, where M is Cl, Br, or I; the organic light-emitting material includes one or more of fluorescent materials, phosphorescent materials, and thermally activated delayed fluorescence materials; the fluorescent material includes one or more of TPBe, TTPA, TBRb, and DBP; the phosphorescent material includes one or more of Firpic, Ir(ppy)3, Ir(ppy)2acac, and Ir(piq)3; the thermally activated delayed fluorescence material includes one or more of ACRSA, DIC-TRZ, 2CzPN, PXZ-TRZ, and pCNBCzoCF3; and / or The electron collection layer is made of one or more of the following materials: PMA, MoO3, WO3, V2O5, ReO3, MnO3, CuI, NDP-9, HATCN, PEDOT:PSS, and FeCl3; and / or The hole transport layer is made of one or more of the following materials: TFB, PVK, Poly-TPD, PFB, NPB, TAPC, TCTA, mCP, CBP, mCBP, CDBP, CuSCN, and NiO; and / or The thickness of the electron injection layer is 10 nm to 30 nm.

10. A method for preparing the ink according to any one of claims 1 to 9, characterized in that, Includes the following steps: Polyaliphatic amine compounds are mixed with salt compounds containing metal ions to undergo a coordination reaction to generate amine metal ion complexes. The amine metal ion complex and metal nanoparticles are mixed in a solvent.

11. The method for preparing ink according to claim 10, characterized in that, The mass ratio of the polyaliphatic amine compound to the metal ion-containing salt compound is 1:(10-100); and / or The salt compounds include acetates; and / or The reaction time for the coordination reaction is 2 h to 5 h; and / or The mass ratio of the amine metal ion complex to the metal nanoparticles is (3:1) to (1:5); and / or The solvent includes one or more of alcohols, ketones, and esters.

12. The method for preparing ink according to claim 11, characterized in that, The mass ratio of the amine metal ion complex to the metal nanoparticles is 1:2; and / or The solvent includes one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, n-pentanol, n-hexanol, acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, ethyl acetate, propyl acetate, and methyl benzoate.

13. A display device, characterized in that, Includes the light-emitting device as described in any one of claims 1 to 9.

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