Ligand for electron transport layer, ink composition comprising same, and light-emitting device comprising same

Abstract

A ligand for an electron transport layer according to an embodiment of the present invention is bound to the surface of metal oxide nanoparticles and is represented by chemical formula 1. [Chemical formula 1] In chemical formula 1, X1 is C(R1) or N, X2 is C(R2) or N, X3 is C(R3) or N, X4 is C(R4) or N, wherein R1, R2, R3, and R4 are each independently hydrogen, deuterium, or a C1-C5 alkoxy group, a C2-C10 alkenyl group, or C1-C5 carbonyl group, which are substituted with or without deuterium or a C1-C5 alkyl group, or are each bonded with R1 and R2 to form a ring, with R2 and R3 to form a ring, or with R3 and R4 to form a ring.

Description

Ligand for electron transport layer, ink composition containing same, and light-emitting device containing same

[0001] A ligand for an electron transport layer, an ink composition comprising the same, and a light-emitting device comprising the same are disclosed.

[0002] Quantum dots (QDs) are crystalline semiconductors measuring from a few to tens of nanometers in size, and can be composed of hundreds to thousands of atoms. Because of their extremely small size, QDs possess a large surface area per unit volume, allowing most atoms to reside on the crystal surface. Because these QDs possess discrete energy levels due to quantum confinement, they can exhibit optical and / or electrical properties distinct from those of bulk semiconductors, which have continuous energy bands.

[0003] A light-emitting device including such quantum dots is a device that converts electrical energy into light energy, and may generally include a first electrode, a hole transport layer, a light-emitting layer, an electron transport layer, a second electrode, etc.

[0004] Holes injected from the first electrode move to the light-emitting layer via the hole transport layer, and electrons injected from the second electrode move to the light-emitting layer via the electron transport layer. These holes and electrons recombine in the light-emitting layer to generate excitons. Light is generated when these excitons change from an excited state to a ground state.

[0005] Recently, much research and development has been conducted on electron transport layers containing inorganic nanoparticles, as well as on ligands corresponding to inorganic nanoparticles. Conventional inorganic nanoparticle ligands, such as silane [RSiX3 (X = chloride or alkoxy)] and carboxylate ligands, are commercially available and have been extensively studied to date. However, these silane and carboxylate ligands are vulnerable to moisture and can be prone to hydrolysis.

[0006] One embodiment of the present invention is to provide an ink composition for an electron transport layer having excellent dispersibility and dispersion stability even at high concentrations.

[0007] One embodiment of the present invention provides an ink composition for an electron transport layer having a size distribution of particles of which Dv(50) is less than 80 nm.

[0008] One embodiment of the present invention is to provide an ink composition for an electron transport layer having excellent long-term preservation properties.

[0009] One embodiment of the present invention is to provide an ink composition for an electron transport layer having excellent discharge characteristics in an inkjet printing process.

[0010] One embodiment of the present invention provides an ink composition for an electron transport layer including an inorganic material that implements excellent device characteristics.

[0011] In addition to the above-mentioned tasks, embodiments according to the present invention can be used to achieve other tasks not specifically mentioned.

[0012] A ligand for an electron transport layer according to one embodiment of the present invention is bonded to the surface of a metal oxide nanoparticle and is represented by the following chemical formula 1.

[0013] [Chemical Formula 1]

[0014]

[0015] In the above chemical formula 1,

[0016] X1 is C(R1) or N, X2 is C(R2) or N, X3 is C(R3) or N, X4 is C(R4) or N,

[0017] The above R1, R2, R3 and R4 are, independently of each other, hydrogen, deuterium, deuterium or a C1-C5 alkoxy group substituted or unsubstituted with a C1-C5 alkyl group, C2-C 10 An alkenyl group of, or a carbonyl group of C1-C5, or R1 and R2 combine to form a ring, or R2 and R3 combine to form a ring, or R3 and R4 combine to form a ring,

[0018] C2-C above 10 The alkenyl group of is substituted with a substituted or unsubstituted amide group, and is substituted with or not substituted with deuterium,

[0019] The above amide group is a deuterium, a C1-C5 alkyl group, or a C3-C 15 substituted or unsubstituted with a non-directional ring,

[0020] The above C1-C5 carbonyl group is substituted with an alkoxy group which is unsubstituted or substituted with deuterium or a C1-C5 alkyl group.

[0021] An ink composition for an electron transport layer according to one embodiment of the present invention comprises a solvent, metal oxide nanoparticles dispersed in the solvent, and the aforementioned ligand for an electron transport layer dispersed in the solvent and bonded to the surface of the metal oxide nanoparticles.

[0022] A light-emitting device according to one embodiment of the present invention includes a first electrode, a second electrode facing the first electrode, a light-emitting layer positioned between the first electrode and the second electrode, and an electron transport layer positioned between the second electrode and the light-emitting layer.

[0023] Here, the electron transport layer is formed using the ink composition for the electron transport layer described above.

[0024] A ligand for an electron transport layer according to one embodiment of the present invention and an ink composition including the same may have excellent dispersibility and dispersion stability even at high concentrations, may have a Dv(50) size of less than 80 nm in the size distribution of particles, may have excellent long-term preservation properties, and may have excellent discharge characteristics in an inkjet printing process.

[0025] In addition, a light-emitting device to which an ink composition for an electron transport layer according to one embodiment of the present invention is applied may have excellent device characteristics.

[0026] FIG. 1 schematically illustrates a cross-sectional view of a light-emitting device according to one embodiment of the present invention.

[0027] FIG. 2a is a graph showing the optical density according to wavelength of an ink composition manufactured according to Example 1, FIG. 2b is a graph showing the optical density according to wavelength of an ink composition manufactured according to Example 2, FIG. 2c is a graph showing the optical density according to wavelength of an ink composition manufactured according to Example 3, and FIG. 2d is a graph showing the optical density according to wavelength of an ink composition manufactured according to Comparative Example 1.

[0028] Figure 3 is a photograph taken immediately after the preparation of ink compositions prepared according to Examples 1 to 3 and Comparative Example 1.

[0029] FIG. 4a is a graph showing the transmission profile of an ink composition manufactured according to Example 1, FIG. 4b is a graph showing the transmission profile of an ink composition manufactured according to Example 3, and FIG. 4c is a graph showing the transmission profile of an ink composition manufactured according to Comparative Example 1.

[0030] FIG. 5a is a graph showing the sedimentation rate of an ink composition manufactured according to Example 1, FIG. 5b is a graph showing the sedimentation rate of an ink composition manufactured according to Example 3, and FIG. 5c is a graph showing the sedimentation rate of an ink composition manufactured according to Comparative Example 1.

[0031] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily practice the present invention. The present invention may be implemented in various different forms and is not limited to the embodiments described herein. In the drawings, parts irrelevant to the description are omitted to clearly explain the present invention, and the same reference numerals are used throughout the specification for identical or similar components. In addition, detailed descriptions of widely known and publicly known technologies are omitted.

[0032] In order to clearly represent various layers and regions in the drawings, the thicknesses are enlarged. When a layer, membrane, region, plate, etc. is said to be "over" another part, this includes not only the case where it is "directly over" that part, but also the case where there is another part in between. On the other hand, when a part is said to be "directly over" another part, it means that there is no other part in between. Conversely, when a layer, membrane, region, plate, etc. is said to be "under" another part, this includes not only the case where it is "directly under" that part, but also the case where there is another part in between. On the other hand, when a part is said to be "directly under" another part, it means that there is no other part in between.

[0033] Throughout the specification, whenever a part is said to "include" a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise stated.

[0034] Throughout the specification, “composition” means a substance in which two or more components are uniformly mixed, and is a concept that includes not only finished products but also intermediate materials for manufacturing finished products.

[0035]

[0036] A ligand for an electron transport layer according to one embodiment of the present invention can be bound to the surface of metal oxide nanoparticles.

[0037] In this specification, the electron transport layer is located between the light-emitting layer and one electrode, and electrons injected from the one electrode reach the light-emitting layer via the electron transport layer. The electron transport layer may be a single layer or may be divided into two or more layers. In addition, in this specification, the electron transport layer may also mean an electron injection layer and an electron transport auxiliary layer.

[0038] The ligand according to embodiments of the present invention can improve the moisture vulnerability of conventional silane-based or carboxylate-based ligands, thereby implementing an ink composition for an electron transport layer having an inorganic material with excellent ink preservation and dispersion stability.

[0039] In addition, the ligand according to the embodiments is a bidentate ligand type, which can form strong bonds to various surfaces and modify the surface of inorganic nanoparticles, thereby enabling the implementation of an ink composition for an electron transport layer having excellent dispersibility even at high concentrations and excellent dispersion stability and storage stability.

[0040] An electron transport layer according to an embodiment comprises metal oxide nanoparticles and a ligand bound to the surface of the metal oxide nanoparticles.

[0041] The ligand for such an electron transport layer can be represented by the following chemical formula 1.

[0042] [Chemical Formula 1]

[0043]

[0044]

[0045] In the above chemical formula 1,

[0046] X1 is C(R1) or N, X2 is C(R2) or N, X3 is C(R3) or N, X4 is C(R4) or N,

[0047] The above R1, R2, R3 and R4 are, independently of each other, hydrogen, deuterium, deuterium or a C1-C5 alkoxy group substituted or unsubstituted with a C1-C5 alkyl group, C2-C 10 An alkenyl group of, or a carbonyl group of C1-C5, or R1 and R2 combine to form a ring, or R2 and R3 combine to form a ring, or R3 and R4 combine to form a ring,

[0048] C2-C above 10 The alkenyl group of is substituted with a substituted or unsubstituted amide group, and is substituted with or not substituted with deuterium,

[0049] The above amide group is a deuterium, a C1-C5 alkyl group, or a C3-C 15 substituted or unsubstituted with a non-directional ring,

[0050] The above C1-C5 carbonyl group is substituted with an alkoxy group which is unsubstituted or substituted with deuterium or a C1-C5 alkyl group.

[0051] The ligand according to the embodiment may include two or more anchoring moieties that are bound to the surface of metal oxide nanoparticles to form a chelate structure. Here, the anchoring moieties refer to moieties that allow the ligand to be adsorbed onto the nanoparticles when the ligand is coordinated to the metal oxide nanoparticles. For example, in the compound of formula 1, the anchoring moieties may be *-OH, *=N-*', *-N=*' (* and *' are binding sites).

[0052] According to one embodiment, the ligand for the electron transport layer may include at least one of the compounds represented by the following chemical formula 2 or the following chemical formula 3.

[0053] [Chemical Formula 2]

[0054]

[0055]

[0056] [Chemical Formula 3]

[0057]

[0058]

[0059] Among the above chemical formula 2 and the above chemical formula 3,

[0060] A1 and A2 are, independently of each other, a C4-C7 ring, which is aromatic or non-aromatic, and which contains or does not contain nitrogen,

[0061] R 10 is a C1-C5 alkoxy group substituted or unsubstituted with hydrogen, deuterium, deuterium or C1-C5 alkyl group, C2-C 10 An alkenyl group of R, or a carbonyl group of C1-C5, or an adjacent R 10 Combines with and forms a ring,

[0062] C2-C above 10 The alkenyl group of is substituted with a substituted or unsubstituted amide group, and is substituted with or not substituted with deuterium,

[0063] The above amide group is a deuterium, a C1-C5 alkyl group, or a C3-C 15 substituted or unsubstituted with a non-directional ring,

[0064] The above C1-C5 carbonyl group is substituted with an alkoxy group which is unsubstituted or substituted with a deuterium or a C1-C5 alkyl group,

[0065] The above adjacent R 10 When these are combined to form a ring, the formed ring is a C4-C7 ring, is aromatic or non-aromatic, and may or may not contain nitrogen.

[0066] A ligand for an electron transport layer according to one embodiment may include at least one of compounds represented by the following chemical formula 2-1, the following chemical formula 2-2, the following chemical formula 3-1, the following chemical formula 3-2, or the following chemical formula 3-3.

[0067] [Chemical Formula 2-1]

[0068]

[0069]

[0070] [Chemical Formula 2-2]

[0071]

[0072]

[0073] [Chemical Formula 3-1]

[0074]

[0075]

[0076] [Chemical Formula 3-2]

[0077]

[0078]

[0079] [Chemical Formula 3-3]

[0080]

[0081]

[0082] Among the above chemical formula 2-1, the above chemical formula 2-2, the above chemical formula 3-1, the above chemical formula 3-2, and the above chemical formula 3-3,

[0083] Z1, Z2, Z3, Z4, Z5, Z6 and Z7 are, independently of each other, C or N,

[0084] R 11 , R 12 , R 13 , R 14 , R 15 , R 16 and R 17Silver, independently of one another, is a C1-C5 alkoxy group substituted or unsubstituted with hydrogen, deuterium, deuterium or a C1-C5 alkyl group, C2-C 10 An alkenyl group of R, or a carbonyl group of C1-C5, or R 11 and R 12 or R combine to form a ring, or 12 Wow R 13 These combine to form a ring, or R 13 and R 14 or R combine to form a ring, or 15 Wow R 16 These combine to form a ring, or R 16 and R 17 These combine to form a ring,

[0085] C2-C above 10 The alkenyl group of is substituted with a substituted or unsubstituted amide group, and is substituted with or not substituted with deuterium,

[0086] The above amide group is a deuterium, a C1-C5 alkyl group, or a C3-C 15 substituted or unsubstituted with a non-directional ring,

[0087] The above C1-C5 carbonyl group is substituted with an alkoxy group which is unsubstituted or substituted with deuterium or a C1-C5 alkyl group.

[0088] The ligand represented by the above chemical formula 2-1, the above chemical formula 2-2, the above chemical formula 3-1, the above chemical formula 3-2, and the above chemical formula 3-3 may specifically include at least one of the following compounds, but is not limited thereto.

[0089]

[0090]

[0091]

[0092]

[0093]

[0094]

[0095]

[0096]

[0097]

[0098]

[0099]

[0100] A ligand for an electron transport layer according to one embodiment may include at least one of compounds represented by the following chemical formula 2-3, the following chemical formula 2-4, the following chemical formula 3-4, or the following chemical formula 3-5.

[0101] [Chemical Formula 2-3]

[0102]

[0103]

[0104] [Chemical Formula 2-4]

[0105]

[0106]

[0107] [Chemical Formula 3-4]

[0108]

[0109]

[0110] [Chemical Formula 3-5]

[0111]

[0112]

[0113] Among the above chemical formulas 2-3, 2-4, 3-4, and 3-5,

[0114] Z1, Z2, Z3, Z4, Z5, Z6 and Z7 are, independently of each other, C or N,

[0115] R 11 , R 12 , R 13 , R 14 , R 15, R 16 and R 17 Silver, independently of one another, is a C1-C5 alkoxy group substituted or unsubstituted with hydrogen, deuterium, deuterium or a C1-C5 alkyl group, C2-C 10 An alkenyl group of R, or a carbonyl group of C1-C5, or R 11 and R 12 or R combine to form a ring, or 12 Wow R 13 These combine to form a ring, or R 13 and R 14 or R combine to form a ring, or 15 Wow R 16 These combine to form a ring, or R 16 and R 17 These combine to form a ring,

[0116] C2-C above 10 The alkenyl group of is substituted with a substituted or unsubstituted amide group, and is substituted with or not substituted with deuterium,

[0117] The above amide group is a deuterium, a C1-C5 alkyl group, or a C3-C 15 substituted or unsubstituted with a non-directional ring,

[0118] The above C1-C5 carbonyl group is substituted with an alkoxy group which is unsubstituted or substituted with deuterium or a C1-C5 alkyl group.

[0119] The ligands represented by the above chemical formulas 2-3, 2-4, 3-4, and 3-5 may specifically include one or more of the following compounds, but are not limited thereto.

[0120]

[0121]

[0122]

[0123]

[0124]

[0125]

[0126]

[0127]

[0128]

[0129]

[0130]

[0131]

[0132] The ligand for the electron transport layer according to one embodiment may include three or more ring structures, and may specifically include at least one of the following compounds, but is not limited thereto.

[0133]

[0134]

[0135]

[0136]

[0137]

[0138] A ligand for an electron transport layer according to one embodiment may include a compound represented by the following chemical formula 4.

[0139] [Chemical Formula 4]

[0140]

[0141]

[0142] In the above chemical formula 4,

[0143] R 31 and R 32 are, independently of each other, hydrogen, deuterium, a C1-C5 alkyl group substituted or unsubstituted with a deuterium or C1-C5 alkyl group, or a C3-C substituted or unsubstituted with a deuterium or C1-C5 alkyl group 15 is a non-directional ring.

[0144] The ligand represented by chemical formula 4 may specifically include at least one of the following compounds, but is not limited thereto.

[0145]

[0146]

[0147]

[0148]

[0149]

[0150]

[0151]

[0152] A ligand for an electron transport layer according to one embodiment may include a compound represented by the following chemical formula 5.

[0153] [Chemical Formula 5]

[0154]

[0155]

[0156] In the above chemical formula 5,

[0157] R 41 is a C1-C5 alkyl group which is unsubstituted or substituted with a C1-C5 alkyl group or a C1-C5 alkyl group.

[0158] The ligand represented by chemical formula 5 may specifically include at least one of the following compounds, but is not limited thereto.

[0159]

[0160]

[0161]

[0162]

[0163]

[0164] In an electron transport layer according to one embodiment, the metal oxide may be represented by the following chemical formula 6.

[0165] [Chemical Formula 6]

[0166] Zn 1-x M x O

[0167]

[0168] In the above chemical formula 6,

[0169] M is Mg, Ba, Ca, Zr, W, Li, Ti, Y, Al, Co, or a combination thereof, and 0 ≤ x ≤ 0.5.

[0170]

[0171] In general, for metal oxide nanoparticles (e.g., ZnO) used in electron transport layers, ligands were not introduced to the surface to secure a certain level of electron mobility.

[0172] This can result in reduced dispersibility of the metal oxide nanoparticles, agglomeration, and poor long-term stability. Furthermore, when preparing ink compositions containing metal oxide nanoparticles, it can be difficult to select an appropriate solvent, and ink can clog inkjet printer heads, resulting in poor discharge characteristics. Furthermore, in light-emitting devices containing quantum dots in the light-emitting layer, direct contact between the quantum dots and the metal oxide can result in a quenching phenomenon.

[0173] On the other hand, the ligand according to the embodiments forms a chelate structure with the metal oxide nanoparticles to form a strong bond, so that the agglomeration of the metal oxide nanoparticles can be prevented, the dispersibility can be greatly improved, and the long-term stability can also be greatly improved.

[0174] Furthermore, when an electron transport layer including a ligand according to the embodiments is applied to a light-emitting device, direct contact between quantum dots and metal oxide nanoparticles can be minimized, and quenching phenomena can be minimized. Furthermore, not only electron injection / transport characteristics but also electron conductivity can be improved.

[0175] In addition, by changing the surface state of the metal oxide nanoparticles due to the ligand forming the chelate structure, a variety of solvents can be selected for preparing the ink composition, and the composition of the ink composition can be diversified.

[0176] In the case of ligands represented by chemical formulae 2-1 to 2-4 and 3-1 to 3-5, the dispersibility of metal oxide nanoparticles can be further greatly improved, and long-term stability can also be significantly improved.

[0177] In addition, conventional silane-based and carboxylate-based ligands are susceptible to moisture and may experience problems of hydrolysis, but the ligands according to the embodiments may not be hydrolyzed, and thus long-term stability, long-term preservation, and storage properties may be improved.

[0178] An ink composition for an electron transport layer according to one embodiment may include a solvent, metal oxide nanoparticles, and the aforementioned ligand bonded to the surface of the metal oxide nanoparticles. Here, the metal oxide nanoparticles and the ligand may be uniformly dispersed in the solvent while forming a chelate structure.

[0179] The solvent may be, for example, one or more of an alcohol solvent, an ether solvent, an aliphatic hydrocarbon solvent, or an aromatic hydrocarbon solvent.

[0180] For example, the solvent may be methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, 2-methylheptane, 3-methylheptane, 4-methylheptane, 2,2-dimethylhexane, 2,3-dimethylhexane, 2,4-dimethylhexane, 2,5-dimethylhexane, 3,3-dimethylhexane, 3-ethylhexane, 2,2,4-trimethylpentane, 2-methyloctane, 2-methylnonane, 2-methyldecane, 2-methylundecane, 2-methyldodecane, 2-methyltridecane, methylcyclohexane, ethylcyclohexane, 1,1-dimethylcyclohexane, 1,2-dimethylcyclohexane, cycloheptane, methylcycloheptane, bicyclohexyl, decalin, Toluene, xylene, ethylbenzene, diethylbenzene, mesitylene, propylbenzene, cyclohexylbenzene, dimethoxybenzene, anisole, ethoxytoluene, phenoxytoluene, isopropylbiphenyl, dimethylanisole, propylanisole, 1-ethylnaphthalene, 2-ethylnaphthalene, 2-ethylbiphenyl, octylbenzene, 1,3-dipropoxybenzene, 4-methoxybenzaldehyde-dimethyl-acetal, 4,4'-difluorodiphenylmethane, diphenylether, 1,2-dimethoxy-4-(1-propenyl)benzene, 2-phenoxytoluene, diphenylmethane,2-phenylpyridine, dimethyl benzyl ether, 3-phenoxytoluene, 3-phenylpyridine, 2-phenylanisole, 2-phenoxytetrahydropuran, 1-propyl-4-phenyl benzene, 2-phenoxy-1,4-dimethyl benzene, ethyl-2-naphtyl-ether, dodecylbenzene, 2,2,5-tri-methyl diphenyl ether, dibenzyl-ether, 2,3,5-trimethyldiphenyl ether, N-methyldiphenylamine, 4-isopropylbiphenyl, α,α-dichlorodiphenylmethane, 4-(3-phenylpropyl)pyridine, methyl benzoate, ethyl benzoate, n-propyl benzoate, iso-propyl benzoate, t-butyl benzoate, benzyl benzoate, 1,1-bis(3,4-dimethylphenyl)ethane, ethylene glycol hexyl ether, diethylene glycol butyl ether, diethylene glycol isopropyl ether, diethylene glycol hexyl ether, tripropylene glycol Butyl ether, diethylene glycol tert-butyl ether, diethylene glycol butyl methyl ether (DEGBME), diethylene glycol monomethyl ether (DEGME), diethylene glycol ethyl methyl ether (DEGEME), diethylene glycol dibutyl ether (DEGDBE), propylene glycol methyl ether acetate (PGMEA),may include, but are not limited to, triethylene glycol monomethyl ether (TGME), diethylene glycol monobutyl ether (DGBE), cyclohexylbenzene, propylene glycol methyl ether acetate, triethylene glycol monomethyl ether, diethylene glycol monobutyl ether, or any combination thereof.

[0181] The ink composition according to the embodiment may further include known additives for the purposes of controlling energy band levels, controlling electron mobility, and improving coating uniformity.

[0182] The ink composition according to the embodiments may exhibit excellent dispersibility and dispersion stability, and excellent long-term storage properties and stability. Furthermore, when forming an electron transport layer using a solution process such as inkjet printing during the manufacture of a light-emitting device, the ink composition according to the embodiments may exhibit excellent discharge characteristics, enabling the formation of a uniform thin film and achieving uniform performance.

[0183] In the ink composition according to the embodiments, the size of Dv(50) in the size distribution of the metal oxide particles may be less than about 80 nm. Furthermore, in the ink composition according to the embodiments, the size of Dv(50) in the size distribution of the metal oxide particles may be less than about 10 nm. As a result, the dispersibility and dispersion stability may be further improved, and the long-term storage properties and long-term stability may also be further improved.

[0184] FIG. 1 is a drawing schematically showing a cross-section of a light-emitting element according to one embodiment.

[0185] Referring to FIG. 1, a light-emitting device (10) according to one embodiment includes a first electrode (110), a hole transport layer (120), a light-emitting layer (130), an electron transport layer (140), and a second electrode (150). The first electrode (110) and the second electrode (150) face each other, the light-emitting layer (130) is positioned between the first electrode (110) and the second electrode (150), and the electron transport layer (140) is positioned between the second electrode (150) and the light-emitting layer (130).

[0186] At this time, the electron transport layer (140) can be formed by a solution process using an ink composition for an electron transport layer according to embodiments. The electron transport layer (140) can have a single-layer or multi-layer structure, and can be a concept including an electron injection layer, an electron control layer, a hole blocking layer, a buffer layer, an electron transport auxiliary layer, etc.

[0187] Although not shown, a substrate may be positioned on the first electrode or the second electrode. The substrate may be a glass or plastic substrate using a known material, or may be a flexible substrate.

[0188] The first electrode (110) may be, for example, an anode and may include a high work function material that facilitates hole injection. The first electrode (110) may be, for example, a reflective electrode, a semi-transmissive electrode, or a transmissive electrode.

[0189] The hole transport layer (120) is located in the path along which holes injected from the first electrode (110) move, and may have a single-layer or multi-layer structure, and may include a hole injection layer, a hole control layer, an electron blocking layer, a buffer layer, a hole transport auxiliary layer, etc.

[0190] The light-emitting layer (130) may include a quantum dot, and for example, the quantum dot may include one or more of a group III-VI semiconductor compound, a group II-VI semiconductor compound, a group III-V semiconductor compound, a group I-III-VI semiconductor compound, a group IV-VI semiconductor compound, or a group IV element or compound.

[0191] Here, “Group I” may include elements of Group IB in the IUPAC periodic table, and Group I elements may include, for example, copper (Cu), silver (Ag), gold (Au), etc.

[0192] “Group II” may include elements of Group IIA and Group IIB in the IUPAC periodic table, and Group II elements may include, for example, magnesium (Mg), calcium (Ca), zinc (Zn), etc.

[0193] “Group III” may include elements of Group IIIA and Group IIIB in the IUPAC periodic table, and Group III elements may include, for example, aluminum (Al), gallium (Ga), indium (In), thallium (Tl), etc.

[0194] “Group IV” may include elements of Group IVA and Group IVB in the IUPAC periodic table, and Group IV elements may include, for example, carbon (C), silicon (Si), germanium (Ge), tin (Sn), etc.

[0195] “Group V” may include elements of Group VA and Group VB in the IUPAC periodic table, and Group V elements may include, for example, nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb), etc.

[0196] “Group VI” may include elements of Group VIA and Group VIB in the IUPAC periodic table, and Group VI elements may include, for example, sulfur (S), selenium (Se), and tellurium (Te).

[0197] Additionally, quantum dots may be binary, ternary, quaternary, or pentatonic compounds. Furthermore, quantum dots may have a single structure, a core-shell structure, or a multilayer shell structure.

[0198] By controlling the size of the quantum dots, the energy band gap can be adjusted, allowing light of various wavelengths to be obtained from the quantum dot light-emitting layer. By using quantum dots of different sizes, light-emitting devices that emit light of various wavelengths can be realized. The size of the quantum dots can be selected to emit red, green, and / or blue light. Furthermore, the size of the quantum dots can be configured to combine light of various colors to emit white light.

[0199] The light-emitting layer (130) may be patterned with a red light-emitting layer, a green light-emitting layer, and / or a blue light-emitting layer. Alternatively, the light-emitting layer (130) may have a structure in which two or more layers of a red light-emitting layer, a green light-emitting layer, and a blue light-emitting layer are laminated in contact with or spaced apart from each other, or may have a structure in which two or more materials of a red light-emitting material, a green light-emitting material, and a blue light-emitting material are mixed without layer distinction, thereby emitting white light.

[0200] Additionally, the light-emitting layer (130) may include a known host and dopant. The dopant may include a phosphorescent dopant, a fluorescent dopant, or any combination thereof.

[0201] The second electrode (150) may be, for example, a cathode, which is an electron injection electrode, and may include a metal, alloy, or the like having a low work function. In addition, the second electrode (150) may be a transmissive electrode, a semi-transmissive electrode, or a reflective electrode.

[0202]

[0203] Hereinafter, the present invention will be described in more detail with examples, comparative examples, and experimental examples. However, the present invention is not limited thereto.

[0204] In the following examples and comparative examples, the solvent used in the ink was a high-boiling-point alcohol with 4 or more carbon atoms to prevent excessively rapid drying in the inkjet head.

[0205] In the following experimental examples, the size (particle size) analysis of metal oxide nanoparticles was performed using a DLS (Dynamic Light Scattering) (model name: Zetasizer Lab Blue, manufacturer: Malvern Panalytical) equipment, the optical density (absorbance) analysis was performed using a UV / vis (Ultraviolet-visible spectroscopy) (model name: LAMBDA 365 UV / Vis Spectrophotometer, manufacturer: PerkinElmer) equipment, and the dispersion stability analysis was performed using a LumiSizer Dispersion Stability Analyzer (model name: LumiSizer Dispersion Analyzer, manufacturer: LUM GmbH) equipment.

[0206]

[0207] Examples and Comparative Examples

[0208] Ink compositions according to Examples 1 to 3 and Comparative Example 1 were prepared. The ink compositions according to Examples and Comparative Example include an alcohol solvent, ZnMgO nanoparticles, which are metal oxides, and a ligand. The ligands included in the ink compositions according to Examples and Comparative Example are as shown in Table 1 below.

[0209] The ink compositions according to Examples 1 to 3 and Comparative Example 1 were manufactured according to the following steps.

[0210] 1) ZnMgO nanoparticles were synthesized by dissolving Zn(OAc)2·H2O and Mg(OAc)2·4H2O in DMSO.

[0211] 2) TMAH·5H2O was dissolved in ethanol in a separate vial, then added to the DMSO solution containing Zn and Mg precursors and stirred.

[0212] 3) ZnMgO nanoparticles were obtained after centrifugation by adding ethyl acetate.

[0213] 4) Nanoparticles were dispersed in ethanol, and each ligand was added and stirred.

[0214] 5) After washing with ethyl acetate, centrifugation was performed, and finally the sediment was dispersed in the ink solvent.

[0215] Sample substance name chemical structure mass example 1 naphthalene-2,3-diol 160.05 Example 2 naphthalene-1,2-diol 160.05 Example 3 Ethyl-3,4-dihydroxybenzoate 182.17 Comparative Example 14-methylbenzene-1,2-diol 124.05

[0216]

[0217] Experimental Example 1 - Particle Size Distribution Measurement Experiment

[0218] The particle size distribution of the ink compositions according to Examples 1 to 3 and Comparative Example 1 was measured, and the measurement results are shown in Tables 2 to 5 below. Table 2 shows the results for Example 1, Table 3 shows the results for Example 2, Table 4 shows the results for Example 3, and Table 5 shows the results for Comparative Example 1.

[0219] No.Dv(10)Dv(50)Dv(98)Dv(99)16.087.9113.0427.7526.057.8812.7323.9335.537.7911.8231.6546.047.8011.7224.4655.557.9812.5026.05Average5.857.8712.3626.77

[0220] No.Dv(10)Dv(50)Dv(98)Dv(99)158.4179.33108.08144.91256.5576.28103.32152.57355.7773.2495.06138.95457.0276.2299.27141.37556.3974.44104.14153.29Average56.8375.90101.97146.22

[0221] No.Dv(10)Dv(50)Dv(98)Dv(99)14.065.7813.9615.7024.646.2312.3612.8234.405.9711.4515.1644.525.9412.8012.9054.836.5811.2815.00Average4.496.1012.3714.32

[0222] No.Dv(10)Dv(50)Dv(98)Dv(99)146.6064.2486.78123.35245.0462.54102.60143.25341.0757.7486.90132.28449.0165.3986.34122.24Average45.4362.4890.66130.28

[0223] Referring to Tables 2 to 5, in the ink composition according to Example 1, it can be confirmed that the size distribution Dv(50) of the particles has an average particle size of 7.87 nm, which is a very small value of 10 nm or less. In addition, in the ink composition according to Example 3, it can be confirmed that the size distribution Dv(50) of the particles has an average particle size of 6.10 nm, which is a very small value of 10 nm or less. From this, it can be confirmed that the ink composition according to the examples contains a large number of very small particles, and due to this characteristic, the characteristics such as dispersibility of the ink composition can be very excellent.

[0224]

[0225] Experimental Example 2 - Dispersibility Evaluation Experiment

[0226] The optical density (OD) and turbidity of the ink compositions according to Examples 1 to 3 and Comparative Example 1 were measured to evaluate the dispersibility of the compositions. Here, the higher the OD value, the higher the absorbance and the lower the light transmittance, which can be judged as a high particle concentration, and the lower the OD value, the lower the absorbance and the higher the light transmittance, which can be judged as a low particle concentration. Turbidity was measured by taking an image of the ink composition.

[0227] The measurement results are shown in Table 6 below, Figs. 2a to 2d, and Fig. 3.

[0228] Sample concentration (wt%) Turbidity Example 12.3 Low Example 26.2 Low Example 35.2 Low Comparative Example 11.9 High

[0229] Referring to Table 6, FIGS. 2A to 2D, and FIG. 3, it can be confirmed that the concentration of the ink compositions according to Examples 1 to 3 is higher than that of the ink composition according to Comparative Example 1, but the turbidity of the ink compositions according to Examples 1 to 3 is lower than that of the ink composition according to Comparative Example 1. In the case of the ink composition according to Example 2, although it exhibits a dark color due to the color of the ligand, the turbidity appears low (clear).

[0230] Specifically, for the ink composition according to Example 1, the OD of the metal oxide nanoparticles appeared in a wavelength band of about 340 nm and the concentration was analyzed to be about 2.3 wt% (see FIG. 2a), for the ink composition according to Example 2, the OD of the metal oxide nanoparticles appeared in a wavelength band of about 320 nm and the concentration was analyzed to be 6.2 wt% (see FIG. 2b), and for the ink composition according to Example 3, the OD of the metal oxide nanoparticles appeared in a wavelength band of about 320 nm and the concentration was analyzed to be about 5.2 wt% (see FIG. 2c). On the other hand, for the ink composition according to Comparative Example 1, the OD of the metal oxide nanoparticles appeared in a wavelength band of about 300 nm and the concentration was analyzed to be 1.9 wt% (see FIG. 2b), indicating a relatively low concentration, and the turbidity was also found to be relatively high.

[0231] From this, it can be confirmed that the dispersibility of the ink composition according to the examples is better.

[0232]

[0233] Experimental Example 3 - Distributed Safety Evaluation Experiment

[0234] Experiments were conducted to evaluate the dispersion stability of the ink compositions according to Examples 1 to 3 and Comparative Example 1. The evaluation was conducted by dispersion stability analysis using a LumiSizer Dispersion Analyzer. The dispersion stability of the material was analyzed by analyzing the transmission profile through continuous transmission measurements (600 measurements at 2-minute (120-second) intervals for 20 hours) by accelerating the sedimentation (or creaming) phenomenon of the material in the tube using centrifugal force. If the measurement is performed under natural gravity, it takes several weeks or months, but by measuring the degree of ink re-separation under centrifugal force, the dispersion stability analysis time can be shortened.

[0235] Specifically, the instability index and the average centrifugal acceleration (RCA, the relative acceleration applied to the sample during the centrifugation process) of some samples were measured. Here, the instability index is a value indicating the stability of the sample. Generally, the lower this value (closer to 0), the more stable the sample is considered, and the higher the instability index value (closer to 1), the more unstable the sample is considered. The RCA value indicates the acceleration applied to the sample during the centrifugation process, and is used to measure the physical changes when the sample rotates at high speed, and the higher the RCA value, the greater the force applied during the centrifugation process (the stronger the acceleration applied).

[0236] In addition, the sedimentation velocity of the ink was measured while the manufactured ink composition was left to stand, and the dispersion stability was confirmed through the sedimentation velocity of the particles under the natural gravity (1G) of the ink.

[0237] The experimental results are shown in Table 7, Table 8, Figures 4a to 4c, and Figures 5a to 5c below.

[0238] FIG. 4a is a graph showing the transmission profile of an ink composition manufactured according to Example 1, FIG. 4b is a graph showing the transmission profile of an ink composition manufactured according to Example 3, and FIG. 4c is a graph showing the transmission profile of an ink composition manufactured according to Comparative Example 1 (in the graphs, the Y-axis is transmission in %, and the x-axis is position in mm).

[0239] FIG. 5a is a graph showing the sedimentation rate of an ink composition manufactured according to Example 1, FIG. 5b is a graph showing the sedimentation rate of an ink composition manufactured according to Example 3, and FIG. 5c is a graph showing the sedimentation rate of an ink composition manufactured according to Comparative Example 1.

[0240] SampleInstability IndexMean RCA (g)1000 rpm2000 rpm3000 rpm1000 rpm2000 rpm3000 rpmComparative Example 10.2350.5580.657124.7498.81125Example 10.0110.5090.586133.6499.81125

[0241] Referring to Table 7, in the case of the instability index, when Comparative Example 1 and Example 1 were compared by RPM, a lower value was shown in Example 1, and it can be confirmed that the dispersion stability of the ink composition using the ligand of Example 1 is relatively higher.

[0242] Referring to FIGS. 4a to 4c, in the continuous transmittance measurement, it can be confirmed that the ink using the ligand according to Comparative Example 1 has a low transmittance of 5 to 70% and low dispersion stability (see FIG. 4c), the ink using the ligand according to Example 1 has a significantly high transmittance of 70 to 80% and thus the dispersion stability is also significantly high (see FIG. 4a), and the ink using the ligand according to Example 3 has a significantly high transmittance of 80 to 85% and thus the dispersion stability is also significantly high (see FIG. 4b).

[0243]

[0244] Sample1G1 Hour1 Day1 Month1 YearComparative Example 10.0006841672.4630 μm59.1120 μm1773.36 μm21575.9 μmExample 10.0005968392.14862 μm51.5669 μm1547.00 μm18821.9 μmExample 30.0000848630.305507 μm7.332163 μm219.9649 μm2676.24 μm

[0245] Referring to Table 8 and FIGS. 5a to 5c, under natural gravity, the sedimentation velocity of the particles in the ink composition using the ligand according to Comparative Example 1 is 1773.36 μm / month, and the sedimentation velocity of the particles in the ink composition using the ligand according to Example 1 is 1547.00 μm / month, and it can be confirmed that the sedimentation velocity is significantly lower than that in Comparative Example 1, and it can be confirmed that the rate of increase in the sedimentation velocity with an increase in rpm is lower than that in Comparative Example 1, and from this, it can be confirmed that the preservation stability and long-term preservation property of the ink composition are excellent. It can be confirmed that the sedimentation velocity of the particles in the ink composition using the ligand according to Example 3 is 219.9649 μm / month, which is the lowest sedimentation velocity, and it can be confirmed that the sedimentation velocity rather significantly decreases as the rpm increases (see FIG. 5b), and from this, it can be confirmed that the preservation stability and long-term preservation property of the ink composition are very excellent.

[0246]

[0247] From this, it can be confirmed that the ligands according to the embodiments of the present invention are ligands for surface modification of metal oxide nanoparticles, and that the ink composition including them exhibits excellent dispersibility even at high concentrations, and also has excellent dispersion stability and long-term storage properties.

[0248]

[0249] Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims also fall within the scope of the present invention.

[0250]

[0251] [Explanation of symbols]

[0252] 10: Light-emitting element

[0253] 110: First electrode

[0254] 120: Hole transport layer

[0255] 130: Emissive layer

[0256] 140: Electron transport layer

[0257] 150: Second electrode

Claims

1. Bonded to the surface of metal oxide nanoparticles, Represented by the following chemical formula 1 Ligands for electron transport layers: [Chemical Formula 1] In the above chemical formula 1, X1 is C(R1) or N, X2 is C(R2) or N, X3 is C(R3) or N, X4 is C(R4) or N, The above R1, R2, R3 and R4 are, independently of each other, hydrogen, deuterium, deuterium or a C1-C5 alkoxy group substituted or unsubstituted with a C1-C5 alkyl group, C2-C 10 An alkenyl group of, or a carbonyl group of C1-C5, or R1 and R2 combine to form a ring, or R2 and R3 combine to form a ring, or R3 and R4 combine to form a ring, C2-C above 10 The alkenyl group of is substituted with an amide group, and may or may not be substituted with deuterium, The above amide group is a deuterium, a C1-C5 alkyl group, or a C3-C 15 substituted or unsubstituted with a non-directional ring, The above C1-C5 carbonyl group is substituted with an alkoxy group which is unsubstituted or substituted with a deuterium or a C1-C5 alkyl group.

2. In paragraph 1, The ligand for the electron transport layer is an electron transport layer ligand comprising at least one of the compounds represented by the following chemical formula 2 or the following chemical formula 3: [Chemical Formula 2] [Chemical Formula 3] Among the above chemical formula 2 and the above chemical formula 3, A1 and A2 are, independently of each other, a C4-C7 ring, which is aromatic or non-aromatic, and which contains or does not contain nitrogen, R 10 is a C1-C5 alkoxy group substituted or unsubstituted with hydrogen, deuterium, deuterium or C1-C5 alkyl group, C2-C 10 An alkenyl group of R, or a carbonyl group of C1-C5, or an adjacent R 10 Combines with and forms a ring, C2-C above 10 The alkenyl group of is substituted with an amide group, and may or may not be substituted with deuterium, The above amide group is a deuterium, a C1-C5 alkyl group, or a C3-C 15 substituted or unsubstituted with a non-directional ring, The above C1-C5 carbonyl group is substituted with an alkoxy group substituted or unsubstituted with a deuterium or a C1-C5 alkyl group, The above adjacent R 10 When these are combined to form a ring, the formed ring is a C4-C7 ring, is aromatic or non-aromatic, and may or may not contain nitrogen.

3. In paragraph 1, The ligand for the electron transport layer is an electron transport layer ligand comprising at least one of the compounds represented by the following chemical formula 2-1, the following chemical formula 2-2, the following chemical formula 3-1, the following chemical formula 3-2, or the following chemical formula 3-3: [Chemical Formula 2-1] [Chemical Formula 2-2] [Chemical Formula 3-1] [Chemical Formula 3-2] [Chemical Formula 3-3] Among the above chemical formula 2-1, the above chemical formula 2-2, the above chemical formula 3-1, the above chemical formula 3-2, and the above chemical formula 3-3, Z1, Z2, Z3, Z4, Z5, Z6 and Z7 are, independently of each other, C or N, R 11 , R 12 , R 13 , R 14 , R 15 , R 16 and R 17 Silver, independently of one another, is a C1-C5 alkoxy group substituted or unsubstituted with hydrogen, deuterium, deuterium or a C1-C5 alkyl group, C2-C 10 An alkenyl group of R, or a carbonyl group of C1-C5, or R 11 and R 12 or R combine to form a ring, or 12 Wow R 13 These combine to form a ring, or R 13 and R 14 or R combine to form a ring, or 15 Wow R 16 These combine to form a ring, or R 16 and R 17 These combine to form a ring, C2-C above 10 The alkenyl group of is substituted with an amide group, and may or may not be substituted with deuterium, The above amide group is a deuterium, a C1-C5 alkyl group, or a C3-C 15 substituted or unsubstituted with a non-directional ring, The above C1-C5 carbonyl group is substituted with an alkoxy group which is unsubstituted or substituted with a deuterium or a C1-C5 alkyl group.

4. In paragraph 1, The ligand for the electron transport layer is an electron transport layer ligand comprising at least one of the following compounds:

5. In paragraph 1, The ligand for the electron transport layer comprises at least one of the compounds represented by the following chemical formula 2-3, the following chemical formula 2-4, the following chemical formula 3-4, or the following chemical formula 3-5: [Chemical Formula 2-3] [Chemical Formula 2-4] [Chemical Formula 3-4] [Chemical Formula 3-5] Among the above chemical formulas 2-3, 2-4, 3-4, and 3-5, Z1, Z2, Z3, Z4, Z5, Z6 and Z7 are, independently of each other, C or N, R 11 , R 12 , R 13 , R 14 , R 15 , R 16 and R 17 Silver, independently of one another, is a C1-C5 alkoxy group substituted or unsubstituted with hydrogen, deuterium, deuterium or a C1-C5 alkyl group, C2-C 10 An alkenyl group of R, or a carbonyl group of C1-C5, or R 11 and R 12 or R combine to form a ring, or 12 Wow R 13 These combine to form a ring, or R 13 and R 14 or R combine to form a ring, or 15 Wow R 16 These combine to form a ring, or R 16 and R 17 These combine to form a ring, C2-C above 10 The alkenyl group of is substituted with an amide group, and may or may not be substituted with deuterium, The above amide group is a deuterium, a C1-C5 alkyl group, or a C3-C 15 substituted or unsubstituted with a non-directional ring, The above C1-C5 carbonyl group is substituted with an alkoxy group which is unsubstituted or substituted with a deuterium or a C1-C5 alkyl group.

6. In paragraph 1, The ligand for the electron transport layer is an electron transport layer ligand comprising at least one of the following compounds:

7. In paragraph 1, The ligand for the electron transport layer is an electron transport layer ligand comprising at least one of the following compounds:

8. In paragraph 1, The ligand for the electron transport layer is an electron transport layer ligand comprising a compound represented by the following chemical formula 4: [Chemical Formula 4] In the above chemical formula 4, R 31 and R 32 are, independently of each other, hydrogen, deuterium, a C1-C5 alkyl group substituted or unsubstituted with a deuterium or C1-C5 alkyl group, or a C3-C substituted or unsubstituted with a deuterium or C1-C5 alkyl group 15 is a non-directional ring.

9. In paragraph 1, The ligand for the electron transport layer is an electron transport layer ligand comprising at least one of the following compounds:

10. In paragraph 1, The ligand for the electron transport layer is an electron transport layer ligand comprising a compound represented by the following chemical formula 5: [Chemical Formula 5] In the above chemical formula 5, R 41 is a C1-C5 alkyl group which is unsubstituted or substituted with a C1-C5 alkyl group or a C1-C5 alkyl group.

11. In paragraph 1, The ligand for the electron transport layer is an electron transport layer ligand comprising at least one of the following compounds:

12. In paragraph 1, The above metal oxide is a ligand for an electron transport layer represented by the following chemical formula 6: [Chemical Formula 6] Zn 1-x M x O In the above chemical formula 6, M is Mg, Ba, Ca, Zr, W, Li, Ti, Y, Al, Co, or a combination thereof, 0 ≤ x ≤ 0.

5.

13. Solvent, Metal oxide nanoparticles dispersed in the above solvent, A ligand for an electron transport layer according to any one of claims 1 to 12, which is dispersed in the solvent and bound to the surface of the metal oxide nanoparticles. Including Ink composition for electron transport layer.

14. In paragraph 13, An ink composition for an electron transport layer, wherein the solvent is at least one of an alcohol-based solvent, an ether-based solvent, an aliphatic hydrocarbon solvent, or an aromatic hydrocarbon solvent.

15. First electrode, A second electrode opposite to the first electrode, A light-emitting layer positioned between the first electrode and the second electrode, and An electron transport layer positioned between the second electrode and the light-emitting layer Including, The electron transport layer is formed using the ink composition for the electron transport layer according to claim 13. Light-emitting element.

16. In paragraph 15, The above light-emitting layer is a light-emitting element including quantum dots.

17. In paragraph 16, The above quantum dot is a light-emitting device comprising at least one of a III-VI group semiconductor compound, a II-VI group semiconductor compound, a III-V group semiconductor compound, a I-III-VI group semiconductor compound, a IV-VI group semiconductor compound, or a group IV element or compound.

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