Complex, method for preparing complex, electroluminescent device, and display device

Abstract

The application discloses a complex, a preparation method of the complex, an electroluminescent device and a display device. The complex has a structure shown in a general formula (I). The electroluminescent device comprises an electrode modification layer arranged between an electron transport layer and a cathode. The material of the electrode modification layer comprises the complex or the complex prepared by the preparation method. The electrode modification layer greatly reduces the work function of the cathode, improves the energy level matching degree of the cathode and the electron transport layer, reduces the risk of oxidation corrosion of the cathode, promotes the balance of hole-electron transport, and is beneficial to improving the photoelectric performance and service life of the electroluminescent device.

Description

Technical Field

[0001] This application relates to the field of optoelectronic technology, specifically to a coordination compound, a method for preparing the coordination compound, an electroluminescent device, and a display device. Background Technology

[0002] Electroluminescent devices belong to the category of optoelectronic devices, which are electronic devices that emit light when an electric field is applied. Electroluminescent devices include, but are not limited to, organic light-emitting diodes (OLEDs) and quantum dot light-emitting diodes (QLEDs). The light-emitting principle of electroluminescent devices is as follows: electrons are injected from the cathode into the light-emitting region, and holes are injected from the anode into the light-emitting region. Electrons and holes recombine in the light-emitting region to form excitons. These excitons then release photons through radiative transitions, thereby emitting light.

[0003] Electroluminescent devices typically employ a "sandwich" structure, comprising an anode, a functional layer, and a cathode arranged sequentially. The functional layer includes a light-emitting layer and an electron transport layer, with the light-emitting layer closer to the anode and the electron transport layer closer to the cathode. Existing electroluminescent devices often use metals with low work function as cathode materials, such as silver (Ag), aluminum (Al), and silver-magnesium alloys, to reduce the work function difference between the cathode and the electron transport layer, thereby improving the matching degree between the cathode and the electron transport layer and facilitating electron injection. However, there is still a certain difference between the low work function metal and the electron transport layer material. Taking QLEDs as an example, nano-zinc oxide is a commonly used material for the electron transport layer in QLEDs, with an work function of 3.5 eV to 4.0 eV, while silver, as a cathode material, has an work function of 4.26 eV, resulting in a work function difference of 0.26 eV to 0.76 eV between the cathode and the electron transport layer. Furthermore, metals with low work function are usually chemically reactive, making the cathode susceptible to corrosion from water and oxygen in the environment, thus negatively impacting the stability of the electroluminescent device. By setting an electrode modification layer between the electron transport layer and the cathode, the energy level matching degree between the cathode and the electron transport layer can be improved, thus enabling the use of metals with high work function as cathode materials. However, existing electrode modification materials are usually conductive polymers or conductive polymers doped with inorganic oxides, which have the disadvantage of poor oxidation resistance and limited effect on improving the energy level matching degree between the cathode and the electron transport layer.

[0004] Therefore, optimizing electrode modification materials to further improve the matching degree between the cathode and the electron transport layer, and ensuring the stability of electroluminescent devices, is of great significance to the application and development of electroluminescent devices. Summary of the Invention

[0005] This application provides a coordination compound, a method for preparing the coordination compound, an electroluminescent device, and a display device. By providing a novel coordination compound as an electrode modification material, the matching degree between the cathode and the electron transport layer is further improved, and the risk of cathode oxidation corrosion is reduced.

[0006] The technical solution of this application is as follows:

[0007] In a first aspect, this application provides a coordination compound having the structure shown in the following general formula (Ⅰ):

[0008]

[0009] In general formula (Ⅰ), A is a metallic iridium complex group, and the nitrogen atom is coordinated with the iridium atom in A, R x It includes at least one of hydrogen atom, alkyl, aromatic group, heteroaryl, alkenyl, alkoxy, acyloxy and amide group, where n is 1 or 2.

[0010] Furthermore, A has the structure shown in general formula (a) or general formula (b) below:

[0011]

[0012] In general formulas (a) and (b), R1 to R e Each of the atoms is independently selected from halogen atoms, alkyl, alkoxy, aromatic or heteroaryl groups, and R1 to R d At least two of them are aromatic or heteroaryl, R1 to R d Two or more atoms in the formula (Ⅰ) can be bonded together to form a ring, and * indicates a connecting bond to the N atom in the general formula (Ⅰ).

[0013] Furthermore, A is selected from any one of the groups shown in the following structural formulas:

[0014]

[0015]

[0016] Where * represents the bonding bond to the N atom in general formula (Ⅰ).

[0017] Furthermore, the R x Selected from hydrogen atoms, methyl, phenyl, or vinyl atoms.

[0018] Furthermore, the complex is selected from compounds represented by any one of the following structural formulas:

[0019]

[0020]

[0021] Secondly, this application provides a method for preparing a coordination compound, comprising the following steps:

[0022] A solution containing a metallic iridium complex is provided, and compound X is added to the solution containing the metallic iridium complex to obtain a mixture;

[0023] The mixture was subjected to a reflux reaction at a preset temperature to obtain the complex.

[0024] The iridium complex has the structure shown in general formula (II) below:

[0025]

[0026] In general formula (II), R1 to R6 are independently selected from halogen atoms, alkyl, alkoxy, aromatic or heteroaryl, and at least two of R1 to R6 are aromatic or heteroaryl, two or more of R1 to R6 can be bonded to form a ring, and at least one of R1 to R6 is a halogen atom.

[0027] The compound X has the structure shown in the following general formula (Ⅲ):

[0028]

[0029] In general formula (Ⅲ), R x It includes at least one of hydrogen atom, alkyl, aromatic group, heteroaryl, alkenyl, alkoxy, acyloxy and amide group.

[0030] Furthermore, the iridium metal complex is selected from one or more compounds shown in the following structural formulas:

[0031]

[0032] Furthermore, the compound X is selected from one or more compounds shown in the following structural formulas:

[0033]

[0034] Furthermore, the preparation method further includes the steps of: adding a precipitant to the complex, performing solid-liquid separation and collecting the liquid phase, removing the solvent from the liquid phase, and obtaining the purified complex; the precipitant is selected from at least one of n-hexane, n-heptane, and n-octane.

[0035] Further, in the mixture, the molar ratio of the iridium complex to the compound X is (1-10):1.

[0036] Thirdly, this application provides an electroluminescent device, the electroluminescent device comprising:

[0037] anode;

[0038] The cathode is disposed opposite to the anode;

[0039] A light-emitting layer is disposed between the anode and the cathode;

[0040] An electron transport layer is disposed between the light-emitting layer and the cathode; and

[0041] An electrode modification layer is disposed between the electron transport layer and the cathode, and the material of the electrode modification layer includes a complex as described in any one of the first aspects or a complex prepared by any one of the preparation methods described in the second aspect.

[0042] Furthermore, the electroluminescent device further includes: a hole transport layer disposed between the anode and the light-emitting layer, wherein the material of the hole transport layer is selected from nickel oxide, poly(9,9-dioctylfluorene-CO-N-(4-butylphenyl)diphenylamine), 3-hexyl-substituted polythiophene, polymeric triarylamine, poly(9-vinylcarbazole), poly[bis(4-phenyl)(4-butylphenyl)amine], 4,4',4”-tris(carbazole-9-yl)triphenylamine, 4,4'-bis(9-carbazole)biphenyl, poly(N,N'-bis(4-phenyl)biphenyl)diphenylamine, etc. (-Butylphenyl)-N,N'-bis(phenyl)benzidine), poly(9,9-dioctylfluorene-co-bis-N,N-phenyl-1,4-phenylenediamine), N,N'-diphenyl-N,N'-di(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine, and N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine; the material of the light-emitting layer is quantum dots, which are selected from group II-VI compounds, group III-V compounds, and group I-III-VI compounds. The compound is selected from at least one of the following groups: CdSe, CdS, CdTe, ZnSe, ZnS, CdTe, ZnTe, CdZnS, CdZnSe, CdZnTe, ZnSeS, ZnSeTe, ZnTeS, CdSeS, CdSeTe, CdTeS, CdZnSeS, CdZnSeTe, and CdZnSTe; and the compound is selected from at least one of the following groups: InP, InAs, GaP, GaAs, GaSb, AlN, and Al. P, InAsP, InNP, InNSb, GaAlNP, and InAlNP, wherein the I-III-VI group compounds are selected from at least one of CuInS2, CuInSe2, and AgInS2; the electron transport layer material comprises metal oxide nanoparticles selected from at least one of ZnO, TiO2, SnO2, Ta2O3, ZrO2, TiLiO, ZnGaO, ZnAlO, ZnMgO, ZnSnO, ZnLiO, and InSnO.

[0043] Furthermore, the cathode material is selected from at least one of metals, carbon materials, and metal oxides. The metal is selected from at least one of Al, Ag, Cu, Mo, Au, Ba, Ca, and Mg. The carbon material is selected from at least one of graphite, carbon nanotubes, graphene, and carbon fibers. The metal oxide is selected from at least one of ITO, FTO, ATO, AZO, GZO, IZO, MZO, and AMO. The cathode thickness is 60 nm to 100 nm.

[0044] Furthermore, the thickness of the electron transport layer is 20 nm to 60 nm, and the thickness of the electrode modification layer is 2 nm to 5 nm.

[0045] Fourthly, this application provides a display device, which includes an electroluminescent device as described in any of the third aspects.

[0046] This application provides a coordination compound, a method for preparing the coordination compound, an electroluminescent device, and a display device, which have the following technical advantages:

[0047] The complex has the structure shown in general formula (I). The complex readily forms a spatial dipole arrangement of anion-cation layers on the metal surface. Since dipoles can improve carrier transport, the work function of the metal is greatly reduced. The complex contains hydroxypyridinone groups, which have ideal antioxidant properties, giving the complex good antioxidant properties. It can be used as an electrode modification layer for electroluminescent devices to improve electron injection capability and protect the cathode.

[0048] The preparation method of the complex includes the following steps: mixing a solution containing a metallic iridium complex (having the structure shown in general formula (II)) with compound X (having the structure shown in general formula (III)) to obtain a mixture, and then placing the mixture under a preset temperature for reflux reaction to obtain the complex. It has the advantages of mild reaction conditions, simple operation, and suitability for industrial production. Because the reaction conditions are mild, only one or two halogen atoms in the metallic iridium complex (when at least two of R1 to R6 in general formula (II) are halogen atoms) are replaced by the hydroxypyridinone group of compound X, thereby reducing the steric hindrance of the complex and facilitating the formation of a large number of dipoles on the metal surface.

[0049] The electroluminescent device includes an electrode modification layer disposed between the electron transport layer and the cathode. The electrode modification layer is made of the complex or a complex prepared by the method of the complex. The complex can stably form a spatial dipole arrangement of anion-cation layers on the cathode surface. The dipoles can improve carrier transport, thereby greatly reducing the work function of the cathode, improving the energy level matching degree between the cathode and the electron transport layer, promoting hole-electron transport balance, and thus improving the photoelectric performance of the electroluminescent device. In addition, the complex contains hydroxypyridinone groups with antioxidant properties, which can reduce the risk of oxidative corrosion of the cathode, thereby extending the service life of the electroluminescent device. The electroluminescent device can be applied in display devices, which can improve the display effect and service life of the display device. Attached Figure Description

[0050] The technical solution and other beneficial effects of this application will become apparent from the following detailed description of specific embodiments in conjunction with the accompanying drawings.

[0051] Figure 1 This is a schematic flowchart of a method for preparing a coordination compound provided in an embodiment of this application.

[0052] Figure 2 This is a schematic diagram of the structure of an electroluminescent device provided in an embodiment of this application.

[0053] Figure 3 This is a schematic diagram of another electroluminescent device provided in an embodiment of this application.

[0054] Figure 4 This is a schematic diagram of the structure of an electroluminescent device provided in Example 1. Detailed Implementation

[0055] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0056] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this invention. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0057] It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of embodiments. Furthermore, in the description of this application, the term "comprising" means "including but not limited to," and the terms "a plurality of" or "multiple layers" mean two or more layers. Various embodiments of this application may exist in a range format; it should be understood that the description in a range format is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single digits within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any referenced number (fraction or integer) within the indicated range.

[0058] This application provides a coordination compound having the structure shown in the following general formula (Ⅰ):

[0059]

[0060] In general formula (Ⅰ), A is a metallic iridium complex group, and the nitrogen atom is coordinated with the iridium atom in A, R x It includes at least one of hydrogen atom, alkyl, aromatic group, heteroaryl, alkenyl, alkoxy, acyloxy and amide group, where 0 < n ≤ 2.

[0061] The complex shown in general formula (Ⅰ) can easily form a spatial dipole arrangement of anion-cation layers on the metal surface. Since the dipoles can improve carrier transport, the work function of the metal is greatly reduced. The complex contains a hydroxypyridinone group, which has ideal antioxidant properties, so the complex has good antioxidant properties and can be used as an electrode modification layer for electroluminescent devices to improve electron injection capability and protect the cathode.

[0062] It should be noted that, compared with complexes with n=2, complexes with n=1 have the advantage of low steric hindrance, which is conducive to generating more dipoles. When used as electrode modification materials, they have a better effect on improving the photoelectric performance of electroluminescent devices.

[0063] In some embodiments of this application, A has the structure shown in general formula (a) or general formula (b) below:

[0064]

[0065] In general formulas (a) and (b), R1 to R e Each of the atoms is independently selected from halogen atoms, alkyl, alkoxy, aromatic or heteroaryl groups, and R1 to R d At least two of them are aromatic or heteroaryl, R1 to R d Two or more of them can be bonded together to form a ring, and * indicates a connecting bond to the N atom in general formula (Ⅰ).

[0066] In some embodiments of this application, A is selected from any of the groups shown in the following structural formulas:

[0067]

[0068]

[0069] Where * represents the bonding bond to the N atom in general formula (Ⅰ).

[0070] In some embodiments of this application, R x Selected from hydrogen atoms, methyl, phenyl, or vinyl atoms.

[0071] In some embodiments of this application, the coordination compound is selected from compounds represented by any of the following structural formulas:

[0072]

[0073] This application also provides a method for preparing a complex, such as... Figure 1 As shown, it includes the following steps:

[0074] S10. Provide a solution containing a metallic iridium complex, and add compound X to the solution containing the metallic iridium complex to obtain a mixture;

[0075] S20. The mixture from step S10 is placed at a preset temperature for reflux reaction to obtain a complex.

[0076] The reaction mechanism of the preparation method is as follows: under high temperature conditions, the nitrogen atom on the pyridine ring in compound X acts as a nucleophile reaction site to attack the iridium ion in the metal iridium complex, forming an Ir-N bond, thereby generating the novel iridium complex of the present application.

[0077] In step S10, the solvent of the solution containing the iridium complex is an organic solvent, including but not limited to N,N-dimethylformamide and / or dimethyl sulfoxide. The iridium complex has the structure shown in the following general formula (II):

[0078]

[0079] In general formula (II), R1 to R6 are independently selected from halogen atoms, alkyl, alkoxy, aromatic or heteroaryl, and at least two of R1 to R6 are aromatic or heteroaryl, two or more of R1 to R6 can be bonded to form a ring, and at least one of R1 to R6 is a halogen atom.

[0080] In some embodiments of this application, the iridium metal complex is selected from one or more compounds shown in the following structural formulas:

[0081]

[0082]

[0083] It should be noted that the iridium complexes shown in any of the above structural formulas have a spatially symmetrical structure, and the positions of each chlorine atom in each iridium complex are equivalent. When the iridium complex reacts with compound X, the hydroxypyridinone group in compound X can replace any one or two chlorine atoms.

[0084] In some embodiments of this application, compound X has the structure shown in the following general formula (Ⅲ):

[0085]

[0086] In general formula (Ⅲ), R x It includes at least one of hydrogen atom, alkyl, aromatic group, heteroaryl, alkenyl, alkoxy, acyloxy and amide group.

[0087] In some embodiments of this application, compound X is selected from one or more compounds shown in the following structural formulas:

[0088]

[0089] In step S20, the conditions for the reflux reaction are not specifically limited, only requiring that the following conditions be met: when only one of R1 to R6 is a halogen atom, it can promote the substitution of the halogen atom in the iridium complex via the hydroxypyridinone group of compound X; when two or more of R1 to R6 are halogen atoms, it can promote the substitution of one or two halogen atoms in the iridium complex via the hydroxypyridinone group of compound X. For example, the reflux reaction temperature is 120°C, and the reaction time is 1 hour.

[0090] In some embodiments of this application, the preparation method of the complex further includes step S30: adding a precipitant to the complex, performing solid-liquid separation and collecting the liquid phase, removing the solvent from the liquid phase, and obtaining a purified complex; the precipitant is selected from at least one of n-hexane, n-heptane, and n-octane.

[0091] In some embodiments of this application, in the mixture of step S10, the molar ratio of the iridium complex to compound X is (1-10):1. If the amount of compound X added is too small, the antioxidant properties of the final complex will be limited. If the amount of compound X added is too large, multiple hydroxypyridinone groups may be substituted for the iridium complex, resulting in a significant increase in steric hindrance. Therefore, when it is used as an electrode modification material for electroluminescent devices, the number of dipoles generated on the cathode material surface is limited, thus limiting the improvement effect on the photoelectric performance of the electroluminescent device.

[0092] This application also provides an electroluminescent device, such as... Figure 2 As shown, the electroluminescent device 1 includes an anode 11, a light-emitting layer 12, an electron transport layer 13, an electrode modification layer 14, and a cathode 15. The anode 11 and the cathode 15 are disposed opposite to each other. The light-emitting layer 12 is disposed between the anode 11 and the cathode 15. The electron transport layer 13 is disposed between the light-emitting layer 12 and the cathode 15. The electrode modification layer 14 is disposed between the electron transport layer 13 and the cathode 15. The material of the electrode modification layer 14 includes any one or more of the complexes described in the embodiments of this application or the complexes prepared by any one of the preparation methods described in the embodiments of this application.

[0093] In the electroluminescent device 1, the materials of the anode 11 and the cathode 15 include, but are not limited to, at least one of metals, carbon materials, and metal oxides. For example, the metal may be at least one of Al, Ag, Cu, Mo, Au, Ba, Ca, and Mg; the carbon material may be at least one of graphite, carbon nanotubes, graphene, and carbon fibers; the metal oxide may be a doped or undoped metal oxide, including at least one of ITO, FTO, ATO, AZO, GZO, IZO, MZO, and AMO, and also includes doped metal oxides. A composite electrode comprising a metal sandwiched between doped or undoped transparent metal oxides, including but not limited to one or more of AZO / Ag / AZO, AZO / Al / AZO, ITO / Ag / ITO, ITO / Al / ITO, ZnO / Ag / ZnO, ZnO / Al / ZnO, TiO2 / Ag / TiO2, TiO2 / Al / TiO2, ZnS / Ag / ZnS, ZnS / Al / ZnS, TiO2 / Ag / TiO2, and TiO2 / Al / TiO2. The thickness of the anode can be, for example, from 60 nm to 150 nm, and the thickness of the cathode can be, for example, from 60 nm to 100 nm.

[0094] The electron transport layer 13 is made of, but is not limited to, metal oxide nanoparticles. These metal oxide nanoparticles are oxide semiconductor nanoparticles with electron transport capabilities. They can be undoped or doped. The doped metal oxide nanoparticles include a dopant element and a host metal element, which are not the same. The dopant element can be a metal or a non-metal, for example, selected from one or more of Al, Ga, Li, Cd, Cr, In, Cu, Fe, Mg, Sn, Sb, Ag, Ti, La, Nb, Mn, Zn, and Ce. The metal oxide nanoparticles can be, for example, at least one of ZnO, TiO2, SnO2, Ta2O3, ZrO2, TiLiO, ZnGaO, ZnAlO, ZnMgO, ZnSnO, ZnLiO, and InSnO. The thickness of the electron transport layer 13 can be, for example, from 20 nm to 60 nm.

[0095] Compared to existing electroluminescent devices, the electroluminescent device 1 of this application embodiment adds an electrode modification layer 14 between the electron transport layer 13 and the cathode 15. The work function of the cathode 15 is adjusted by the electrode modification layer 14. Specifically, the electrode modification layer 14 contains a complex. Since the anions of the complex are easily adsorbed on the surface of the metal (cathode material) and the cations are distributed outside the anions, a spatial dipole arrangement of an anion-cation layer can be stably formed on the metal surface. The dipoles can improve carrier transport, thereby greatly reducing the work function of the metal, improving the energy level matching degree between the cathode 15 and the electron transport layer 13, and promoting hole-electron transport balance. Furthermore, since the electron transport layer 13 is mostly made of metal oxide nanoparticles, which have surface defects that easily adsorb water and oxygen, the absence of the electrode modification layer 14 would cause the cathode 15 to be susceptible to oxidation and corrosion due to the adsorption of water and oxygen by the electron transport layer 13. This would negatively impact the photoelectric performance and lifespan of the electroluminescent device 1. The electrode modification layer 14 contains hydroxypyridinone groups with antioxidant properties, which can reduce the risk of oxidation and corrosion of the cathode 15. In other words, the electrode modification layer 14 can serve as a protective layer for the cathode 15, reducing the negative impact of water and oxygen adsorbed by the electron transport layer 13 on the cathode 15.

[0096] In some embodiments of this application, such as Figure 3 As shown, in Figure 2 Based on the electroluminescent device 1 shown, the electroluminescent device 1 further includes a hole transport layer 16, which is disposed between the anode 11 and the light-emitting layer 12.

[0097] The hole transport layer 16 is made of materials including, but not limited to, nickel oxide, poly(9,9-dioctylfluorene-CO-N-(4-butylphenyl)diphenylamine), 3-hexyl-substituted polythiophene, polymeric triarylamine, poly(9-vinylcarbazole), poly[bis(4-phenyl)(4-butylphenyl)amine], 4,4',4”-tris(carbazole-9-yl)triphenylamine, 4,4'-bis(9-carbazole)biphenyl, and poly(N,N'bis(4-butylphenyl)-N,N The hole transport layer 16 may contain at least one of the following: '-bis(phenyl)benzidine), poly(9,9-dioctylfluorene-co-bis-N,N-phenyl-1,4-phenylenediamine), N,N'-diphenyl-N,N'-di(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine, and N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine. The thickness of the hole transport layer 16 may be, for example, 20 nm to 40 nm.

[0098] It is understood that the electroluminescent device 1 may also include other film layers that facilitate hole injection from the anode 11 into the light-emitting layer 12. For example, the electroluminescent device 1 may also include a hole injection layer disposed between the hole transport layer 16 and the anode 11. The material of the hole injection layer includes, but is not limited to, 3,4-ethylenedioxythiophene monomer (PEDOT), styrene sulfonate (PSS), copper phthalocyanine (CuPc), 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone (F4-TCNQ), 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazabenzophenanthrene (HATCN), transition metal oxides, and transition metal chalcogenides, wherein the transition metal oxide may be NiO. x MoO x WO x CrO x And one or more of CuO, the metal chalcogenide compound being MoS x MoSe x WS x 、WSe x And one or more of CuS, the thickness of the hole injection layer can be, for example, 15 nm to 30 nm.

[0099] In some embodiments of this application, the material of the light-emitting layer 12 is quantum dots, corresponding to the electroluminescent device 1 being a quantum dot light-emitting diode; the electroluminescent device 1 can be a quantum dot light-emitting diode with a positive structure or a quantum dot light-emitting diode with an inverted structure. The quantum dots can be at least one of red quantum dots, green quantum dots, and blue quantum dots, and the quantum dots can be selected from, but are not limited to, at least one of single-structure quantum dots, core-shell structure quantum dots, inorganic perovskite quantum dots, and organic-inorganic hybrid perovskite quantum dots. For a single-structure quantum dot, the quantum dot includes, but is not limited to, at least one of group II-VI compounds, group III-V compounds, and group I-III-VI compounds. For example, group II-VI compounds may be at least one of CdSe, CdS, CdTe, ZnSe, ZnS, CdTe, ZnTe, CdZnS, CdZnSe, CdZnTe, ZnSeS, ZnSeTe, ZnTeS, CdSeS, CdSeTe, CdTeS, CdZnSeS, CdZnSeTe, and CdZnSTe. For example, group III-V compounds may be at least one of InP, InAs, GaP, GaAs, GaSb, AlN, AlP, InAsP, InNP, InNSb, GaAlNP, and InAlNP. For example, group I-III-VI compounds may be at least one of CuInS2, CuInSe2, and AgInS2. For core-shell quantum dots, the core and shell materials are independently selected from at least one of group II-VI, III-V, and I-III-VI compounds. Blue quantum dots can be, for example, cadmium zinc sulfide / zinc sulfide (CdZnS / ZnS) with a particle size of 2 nm to 5 nm and an emission wavelength of 450 nm; red quantum dots can be, for example, indium phosphide / zinc sulfide (InP / ZnS) with a particle size of 9 nm to 11 nm and an emission wavelength of 625 nm; green quantum dots can be, for example, indium phosphide / zinc sulfide (InP / ZnS) with a particle size of 4 nm to 6 nm and an emission wavelength of 530 nm. The general structural formula for inorganic perovskite quantum dots is AMX3, where A is Cs. + Ions, where M is a divalent metal cation, and M includes, but is not limited to, Pb. 2+ Sn 2+ Cu 2+ Ni 2+ Cd 2+ Cr 2+ Mn 2 + Co 2+ Fe 2+ 、Ge 2+ Yb 2+ Or Eu 2+X is a halide anion, including but not limited to Cl. - ,Br - Or I - The general structural formula for organic-inorganic hybrid perovskite quantum dots is BMX3, where B is an organic amine cation, including but not limited to CH3(CH2). n -2NH 3+ (n≥2) or NH3(CH2) n NH3 2+ (n≥2), M is a divalent metal cation, and M includes, but is not limited to, Pb. 2+ Sn 2+ Cu 2+ Ni 2+ Cd 2+ Cr 2+ Mn 2+ Co 2+ Fe 2+ 、Ge 2+ Yb 2+ Or Eu 2+ X is a halide anion, including but not limited to Cl. - ,Br - Or I - The particle size of the quantum dots can be, for example, 6 nm to 10 nm, and the thickness of the light-emitting layer 13 can be, for example, 20 nm to 60 nm.

[0100] It should be noted that the preparation methods for each layer in the electroluminescent device 1 include, but are not limited to, solution methods and deposition methods. Solution methods include, but are not limited to, spin coating, coating, inkjet printing, blade coating, dip-coating, immersion, spraying, roller coating, or casting. After the wet film is obtained by the solution method, a drying process is required. The drying process includes all processes that can enable the wet film to obtain higher energy and transform into a dry film. The drying process can be, for example, heat treatment, or static natural drying. Among them, "heat treatment" can be isothermal heat treatment or non-isothermal heat treatment (e.g., temperature gradient change). The preparation methods for the cathode include, but are not limited to, deposition methods and solution methods. Deposition methods include chemical methods and physical methods. Chemical methods include, but are not limited to, chemical vapor deposition, continuous ion layer adsorption and reaction, anodic oxidation, electrolytic deposition, or co-precipitation. Physical methods include, but are not limited to, thermal evaporation coating, electron beam evaporation coating, magnetron sputtering, multi-arc ion plating, physical vapor deposition, atomic layer deposition, or pulsed laser deposition.

[0101] This application also provides a display device, including any of the electroluminescent devices described in this application. The display device can be any electronic product with display functionality, including but not limited to smartphones, tablets, laptops, digital cameras, digital camcorders, smart wearable devices, smart weighing scales, in-vehicle displays, televisions, or e-book readers. Smart wearable devices can be, for example, smart bracelets, smartwatches, virtual reality (VR) headsets, etc.

[0102] The technical solutions and effects of this application will be described in detail below through specific embodiments, comparative examples and experimental examples. The following embodiments are only some embodiments of this application and are not intended to limit this application.

[0103] Example 1

[0104] This embodiment provides a coordination compound and its preparation method. The structure of the coordination compound in this embodiment is shown in formula (1.1):

[0105]

[0106] The method for preparing the complex in this embodiment includes the following steps:

[0107] S1.1. Take an appropriate amount of iridium complex A (commercially available) and add it to 30 mL of N,N-dimethylformamide, and disperse it evenly to prepare a mixed solution with a concentration of 0.2 mol / L.

[0108] S1.2 Add compound X1 (commercially available) to the mixture from step S1.1 until the molar ratio of iridium complex A to compound X1 is 4.0:1, and mix well to obtain a mixture.

[0109] S1.3. The mixture from step S1.2 is stirred and refluxed at 120°C for 1 hour to obtain a reaction product containing a complex.

[0110] S1.4 Add n-hexane dropwise to the reaction product of step S1.3 while stirring thoroughly until no precipitate is formed. Stop adding n-hexane, let it stand and settle naturally, filter to remove the precipitate and collect the liquid phase. Then centrifuge the collected liquid phase at 3000 r / min for 10 min, collect the supernatant, and dry it under reduced pressure (pressure -0.1 MPa) to remove the solvent from the supernatant to obtain the purified complex.

[0111] The structure of the metallic iridium complex A is shown in equation (1.2):

[0112]

[0113] The structure of compound X1 is shown in formula (1.3):

[0114]

[0115] Example 2

[0116] This embodiment provides a coordination compound and its preparation method. The structure of the coordination compound in this embodiment is shown in formula (2.1):

[0117]

[0118] The method for preparing the complex in this embodiment includes the following steps:

[0119] S2.1. Take an appropriate amount of iridium complex A (commercially available) and add it to 30 mL of N,N-dimethylformamide. Disperse it evenly to obtain a mixed solution with a concentration of 0.2 mol / L.

[0120] S1.2 Add compound X2 (commercially available) to the mixture from step S2.1 until the molar ratio of iridium complex A to compound X2 is 2.5:1, and mix well to obtain a mixture;

[0121] S2.3. The mixture from step S2.2 is stirred and refluxed at 120°C for 1 hour to obtain a reaction product containing a complex.

[0122] S2.4. Add n-hexane dropwise to the reaction product of step S2.3 while stirring thoroughly until no precipitate is formed. Stop adding n-hexane, let it stand and settle naturally, filter to remove the precipitate and collect the liquid phase. Then centrifuge the collected liquid phase at 3000 r / min for 10 min, collect the supernatant, and dry it under reduced pressure (pressure -0.1 MPa) to remove the solvent from the supernatant to obtain the purified complex.

[0123] The structure of the iridium complex A is shown in formula (1.2), and the structure of compound X2 is shown in formula (2.2).

[0124]

[0125] Example 3

[0126] This embodiment provides a coordination compound and its preparation method. The structural formula of the coordination compound in this embodiment is shown in formula (3.1):

[0127]

[0128] The method for preparing the complex in this embodiment includes the following steps:

[0129] S3.1. Take an appropriate amount of iridium complex B (commercially available) and add it to 30 mL of N,N-dimethylformamide. Disperse it evenly to prepare a mixed solution with a concentration of 0.2 mol / L.

[0130] S3.2 Add compound X1 to the mixture from step S3.1 until the molar ratio of iridium complex B to compound X1 is 4.0:1, and mix well to obtain a mixture.

[0131] S3.3. The mixture from step S3.2 is stirred and refluxed at 120°C for 1 hour to obtain a reaction product containing a complex.

[0132] S3.4 Add n-hexane dropwise to the reaction product of step S3.3 while stirring thoroughly until no precipitate is formed. Stop adding n-hexane, let it stand and settle naturally, filter to remove the precipitate and collect the liquid phase. Then centrifuge the collected liquid phase at 3000 r / min for 10 min, collect the supernatant, and dry it under reduced pressure (pressure -0.1 MPa) to remove the solvent from the supernatant to obtain the purified complex.

[0133] The structure of compound X1 is shown in formula (1.3), and the structure of the iridium complex B is shown in formula (3.2).

[0134]

[0135] Example 4

[0136] This embodiment provides a coordination compound and its preparation method. The structural formula of the coordination compound in this embodiment is shown in formula (4.1):

[0137]

[0138] The method for preparing the complex in this embodiment includes the following steps:

[0139] S4.1. Take an appropriate amount of iridium complex C (commercially available) and add it to 30 mL of N,N-dimethylformamide. Disperse it evenly to obtain a mixed solution with a concentration of 0.2 mol / L.

[0140] S4.2 Add compound X1 to the mixture from step S4.1 until the molar ratio of iridium complex C to compound X1 is 4.0:1, and mix well to obtain a mixture.

[0141] S4.3. Place the mixture from step S4.2 under reflux at 120°C for 1 hour to obtain a reaction product containing a complex.

[0142] S4.4 Add n-hexane dropwise to the reaction product of step S4.3 while stirring thoroughly until no precipitate is formed. Stop adding n-hexane, let it stand and settle naturally, filter to remove the precipitate and collect the liquid phase. Then centrifuge the collected liquid phase at 3000 r / min for 10 min, collect the supernatant, and dry it under reduced pressure (pressure -0.1 MPa) to remove the solvent from the supernatant to obtain the purified complex.

[0143] The structure of compound X1 is shown in formula (1.3), and the structure of the iridium complex C is shown in formula (4.2).

[0144]

[0145] Example 5

[0146] This embodiment provides a coordination compound and its preparation method. The structural formula of the coordination compound in this embodiment is shown in formula (5.1):

[0147]

[0148] The method for preparing the complex in this embodiment includes the following steps:

[0149] S5.1. Take an appropriate amount of iridium complex D (commercially available) and add it to 30 mL of N,N-dimethylformamide. Disperse it evenly to obtain a mixed solution with a concentration of 0.2 mol / L.

[0150] S5.2 Add compound X2 to the mixture from step S5.1 until the molar ratio of iridium complex D to compound X1 is 4.0:1, and mix well to obtain a mixture.

[0151] S5.3. The mixture from step S5.2 is stirred and refluxed at 120°C for 1 hour to obtain a reaction product containing a complex.

[0152] S5.4 Add n-hexane dropwise to the reaction product of step S5.3 while stirring thoroughly until no precipitate is formed. Stop adding n-hexane, let it stand and settle naturally, filter to remove the precipitate and collect the liquid phase. Then centrifuge the collected liquid phase at 3000 r / min for 10 min, collect the supernatant, and dry it under reduced pressure (pressure -0.1 MPa) to remove the solvent from the supernatant to obtain the purified complex.

[0153] The structure of compound X2 is shown in formula (2.2), and the structure of the iridium complex D is shown in formula (5.2).

[0154]

[0155] Example 6

[0156] This embodiment provides a coordination compound and its preparation method. The structure of the coordination compound in this embodiment is shown in formula (6.1):

[0157]

[0158] The method for preparing the complex in this embodiment includes the following steps:

[0159] S6.1. Take an appropriate amount of iridium complex A and add it to 30 mL of N,N-dimethylformamide. Disperse it evenly to prepare a mixed solution with a concentration of 0.2 mol / L.

[0160] S6.2 Add compound X1 to the mixture from step S6.1 until the molar ratio of iridium complex A to compound X1 is 4.0:1, and mix well to obtain a mixture.

[0161] S6.3. The mixture from step S6.2 is stirred and refluxed at 120°C for 1.5 h to obtain a reaction product containing a complex.

[0162] S6.4 Add n-hexane dropwise to the reaction product of step S6.3 while stirring thoroughly until no precipitate is formed. Stop adding n-hexane, let it stand and settle naturally, filter to remove the precipitate and collect the liquid phase. Then centrifuge the collected liquid phase at 3000 r / min for 10 min, collect the supernatant, and dry it under reduced pressure (pressure -0.1 MPa) to remove the solvent from the supernatant to obtain the purified complex.

[0163] Example 7

[0164] This embodiment provides an electroluminescent device and its fabrication method, such as Figure 4 As shown, the electroluminescent device 1 is a quantum dot light-emitting diode with an upright structure. In the direction from bottom to top, the electroluminescent device 1 includes a substrate 10, an anode 11, a hole transport layer 16, a light-emitting layer 12, an electron transport layer 13, an electrode modification layer 14, and a cathode 15 arranged sequentially.

[0165] The materials and thicknesses of each layer in the electroluminescent device of this embodiment are as follows:

[0166] The substrate 10 is made of glass and has a thickness of 2 mm.

[0167] The anode 11 is made of ITO and has a thickness of 55 nm.

[0168] The material of the light-emitting layer 12 is CdZnSe / ZnS core-shell structured blue quantum dots, and the thickness of the light-emitting layer 12 is 30nm;

[0169] The electron transport layer 13 is made of nano-ZnO with a particle size of 5 nm, and the thickness of the electron transport layer 13 is 40 nm.

[0170] The material of the electrode modification layer 14 is the complex in Example 1, and the thickness of the electrode modification layer 14 is 5 nm;

[0171] The cathode 15 is made of silver and has a thickness of 70 nm.

[0172] The hole transport layer 16 is made of TFB material and has a thickness of 40 nm.

[0173] The fabrication method of the electroluminescent device in this embodiment includes the following steps:

[0174] S7.1. Provide a substrate containing an anode (ITO). Under a nitrogen atmosphere (H2O and O2 content less than 5ppm) at room temperature and pressure, inkjet print a TFB-chlorobenzene solution with a concentration of 10mg / mL on the side of the anode away from the substrate. Then place it at 80℃ for constant temperature heat treatment for 15min and let it stand to cool for 5min to obtain a hole transport layer.

[0175] S7.2 Under a nitrogen atmosphere at normal temperature and pressure (H2O and O2 content less than 5ppm), inkjet print a CdZnSe / ZnS core-shell structure blue quantum dot-n-octane solution with a concentration of 20mg / mL on the side of the hole transport layer away from the anode in step S7.1. Then, heat-treat it at 80℃ for 15min and let it stand and cool for 5min to obtain the light-emitting layer.

[0176] S7.3 Under a nitrogen atmosphere at normal temperature and pressure (H2O and O2 content less than 5ppm), inkjet print a nano ZnO-ethanol solution with a concentration of 30mg / mL on the side of the light-emitting layer away from the hole transport layer in step S7.2. Then, heat-treat at 80℃ for 20min and let it stand and cool for 5min to obtain the electron transport layer.

[0177] S7.4 Under a nitrogen atmosphere at normal temperature and pressure (H2O and O2 content less than 5ppm), inkjet print a complex-hexane solution with a concentration of 5mg / mL on the side of the light-emitting layer away from the hole transport layer in step S7.3. Then, heat-treat at 80℃ for 20min and let it stand and cool for 5min to obtain the electrode modification layer.

[0178] S7.5, at a vacuum degree of 10 -5 In a nitrogen atmosphere at Pa, silver is vacuum-deposited on the side of the electrode modification layer away from the electron transport layer in step S7.4 to obtain a cathode, which is then encapsulated to obtain an electroluminescent device.

[0179] Example 8

[0180] This embodiment provides an electroluminescent device. Compared with the electroluminescent device of Embodiment 7, the only difference of the electroluminescent device in this embodiment is that the material of the electrode modification layer is replaced by the complex of Embodiment 1 with the complex of Embodiment 2.

[0181] Example 9

[0182] This embodiment provides an electroluminescent device. Compared with the electroluminescent device of Embodiment 7, the only difference of the electroluminescent device in this embodiment is that the material of the electrode modification layer is replaced by the complex of Embodiment 1 with the complex of Embodiment 3.

[0183] Example 10

[0184] This embodiment provides an electroluminescent device. Compared with the electroluminescent device of Embodiment 7, the only difference of the electroluminescent device in this embodiment is that the material of the electrode modification layer is replaced by the complex of Embodiment 1 with the complex of Embodiment 4.

[0185] Example 11

[0186] This embodiment provides an electroluminescent device. Compared with the electroluminescent device of Embodiment 7, the only difference of the electroluminescent device in this embodiment is that the material of the electrode modification layer is replaced by the complex of Embodiment 1 with the complex of Embodiment 5.

[0187] Example 12

[0188] This embodiment provides an electroluminescent device. Compared with the electroluminescent device of Embodiment 7, the only difference of the electroluminescent device in this embodiment is that the material of the electrode modification layer is replaced by the complex of Embodiment 1 with the complex of Embodiment 6.

[0189] Comparative Example 1

[0190] This comparative example provides an electroluminescent device. Compared with the electroluminescent device of Example 7, the only difference of the electroluminescent device in this example is that the electrode modification layer is omitted.

[0191] Comparative Example 2

[0192] This comparative example provides an electroluminescent device. Compared with the electroluminescent device of Example 7, the only difference of the electroluminescent device in this example is that the material of the electrode modification layer is replaced by "the complex of Example 1" with "the metal iridium complex A shown in Formula (1.2)".

[0193] Experimental Example

[0194] The electroluminescent devices of Examples 7 to 12, as well as the electroluminescent devices of Comparative Examples 1 and 2, were subjected to performance tests. The performance test parameters were: the maximum external quantum efficiency (EQE) of the electroluminescent devices under a constant current driving condition of 2 mA. max The performance test results for the following parameters are detailed in Table 1: %, turn-on voltage (VT,V), and the time required for the brightness of the electroluminescent device to decay from 100% to 50% at a brightness of 1000 nits (T50-1K,h).

[0195] Table 1 Performance test results of the electroluminescent devices of Examples 7 to 12, and Comparative Examples 1 and 2

[0196]

[0197] As shown in Table 1, compared with the electroluminescent devices of Comparative Examples 1 and 2, the electroluminescent devices of Examples 7 to 12 have significant advantages in photoelectric performance and lifespan. For example, the EQE of the electroluminescent device of Example 7 is significantly higher. max The EQE of the electroluminescent device in Comparative Example 1 max 3.9 times that of the electroluminescent device in Comparative Example 2, and the EQE of the electroluminescent device in Comparative Example 2. max The VT of the electroluminescent device in Example 7 is only 37% of that in Comparative Example 1 and only 54% of that in Comparative Example 2; the T50-1K of the electroluminescent device in Example 7 is 3.1 times that in Comparative Example 1 and 2.3 times that in Comparative Example 2. This indicates that providing an electrode modification layer between the electron transport layer and the cathode of the electroluminescent device, and the material of the electrode modification layer including the complexes of the embodiments of this application, is beneficial to improving the photoelectric performance and lifespan of the electroluminescent device. In addition, as can be seen from Examples 7 and 12, it is preferable that one halogen atom in the iridium complex is replaced by a hydroxypyridinone group of compound X to avoid a significant increase in steric hindrance, which would result in a limited number of dipoles generated by the complex on the cathode material surface, and is beneficial to further improve the photoelectric performance of the electroluminescent device.

[0198] The foregoing has provided a detailed description of a complex, a method for preparing the complex, an electroluminescent device, and a display device provided in the embodiments of this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are only for the purpose of helping to understand the technical solutions and core ideas of this application; those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A complex, characterized in that, The complex has the structure shown in the following general formula (Ⅰ): In general formula (Ⅰ), A is a metallic iridium complex group, and the nitrogen atom is coordinated with the iridium atom in A, R x Selected from hydrogen atoms or alkyl groups, where n is 1 or 2; The group A is selected from any one of the groups shown in the following structural formulas: Where * represents the bonding bond to the N atom in general formula (Ⅰ).

2. The complex according to claim 1, characterized in that, The complex is selected from compounds represented by any one of the following structural formulas:

3. A method for preparing a complex, characterized in that, Includes the following steps: A solution containing a metallic iridium complex is provided, and compound X is added to the solution containing the metallic iridium complex to obtain a mixture; The mixture was subjected to a reflux reaction at a preset temperature to obtain the complex. The iridium metal complex is selected from one or more compounds shown in the following structural formulas: The compound X has the structure shown in the following general formula (Ⅲ): In general formula (Ⅲ), R x Selected from hydrogen atoms or alkyl groups.

4. The preparation method according to claim 3, characterized in that, The compound X is selected from one or more compounds shown in the following structural formulas:

5. The preparation method according to claim 4, characterized in that, The preparation method further includes the steps of: adding a precipitant to the complex, performing solid-liquid separation and collecting the liquid phase, removing the solvent from the liquid phase, and obtaining the purified complex; the precipitant is selected from at least one of n-hexane, n-heptane, and n-octane.

6. The preparation method according to any one of claims 3 to 5, characterized in that, In the mixture, the molar ratio of the iridium complex to compound X is (1-10):

1.

7. An electroluminescent device, characterized in that, The electroluminescent device includes: anode; The cathode is disposed opposite to the anode; A light-emitting layer is disposed between the anode and the cathode; An electron transport layer is disposed between the light-emitting layer and the cathode; and An electrode modification layer is disposed between the electron transport layer and the cathode, wherein the material of the electrode modification layer includes the complex as described in claim 1 or 2 or the complex prepared by the preparation method described in any one of claims 3 to 6.

8. The electroluminescent device according to claim 7, characterized in that, The electroluminescent device further includes a hole transport layer disposed between the anode and the light-emitting layer. The material of the hole transport layer is selected from nickel oxide, poly(9,9-dioctylfluorene-CO-N-(4-butylphenyl)diphenylamine), 3-hexyl-substituted polythiophene, polymeric triarylamine, poly(9-vinylcarbazole), poly[bis(4-phenyl)(4-butylphenyl)amine], 4,4',4”-tris(carbazole-9-yl)triphenylamine, 4,4'-bis(9-carbazole)biphenyl, poly(N,N'bis(4-butylphenyl)-N,N'- The light-emitting layer is selected from at least one of the following: bis(phenyl)benzidine, poly(9,9-dioctylfluorene-co-bis-N,N-phenyl-1,4-phenylenediamine), N,N'-diphenyl-N,N'-di(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine, and N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine; the light-emitting layer is made of quantum dots, which are selected from at least one of group II-VI compounds, group III-V compounds, and group I-III-VI compounds. The group II-VI compounds are selected from at least one of CdSe, CdS, CdTe, ZnSe, ZnS, CdTe, ZnTe, CdZnS, CdZnSe, CdZnTe, ZnSeS, ZnSeTe, ZnTeS, CdSeS, CdSeTe, CdTeS, CdZnSeS, CdZnSeTe, and CdZnSTe; the group III-V compounds are selected from InP, InAs, GaP, GaAs, GaSb, AlN, AlP, and In. The compounds are AsP, InNP, InNSb, GaAlNP, and InAlNP, wherein the I-III-VI group compounds are selected from at least one of CuInS2, CuInSe2, and AgInS2; the electron transport layer material comprises metal oxide nanoparticles, wherein the metal oxide nanoparticles are selected from at least one of ZnO, TiO2, SnO2, Ta2O3, ZrO2, TiLiO, ZnGaO, ZnAlO, ZnMgO, ZnSnO, ZnLiO, and InSnO.

9. The electroluminescent device according to claim 7, characterized in that, The cathode material is selected from at least one of metals, carbon materials, and metal oxides. The metal is selected from at least one of Al, Ag, Cu, Mo, Au, Ba, Ca, and Mg. The carbon material is selected from at least one of graphite, carbon nanotubes, graphene, and carbon fibers. The metal oxide is selected from at least one of ITO, FTO, ATO, AZO, GZO, IZO, MZO, and AMO. The cathode thickness is 60 nm to 100 nm.

10. The electroluminescent device according to claim 7, characterized in that, The thickness of the electron transport layer is 20 nm to 60 nm, and the thickness of the electrode modification layer is 2 nm to 5 nm.

11. A display device, characterized in that, The display device includes an electroluminescent device as described in any one of claims 7 to 10.

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