Fluorene-containing compound, hole injection material, OLED device and preparation method and application thereof
阅读说明：本技术 一种含芴的化合物、空穴注入材料、oled器件及其制备方法和应用 (Fluorene-containing compound, hole injection material, OLED device and preparation method and application thereof ) 是由 张双 张晓龙 谭奇 于 2019-04-30 设计创作，主要内容包括：本发明提供了一种含芴的化合物、空穴注入材料、OLED器件及其制备方法和应用,所述含芴的化合物的结构如式I所示；本发明提供的含芴的化合物具有良好的交叉超共轭特性和热稳定性,而且无需加入额外的物质,非常适用于作为有机电致发光器件的空穴注入材料,能够赋予材料良好的成膜性能而且还可以通过在芴环上进行改性,结合强吸电基团,赋予化合物分子较强的还原电位,进一步提高化合物的空穴注入效果,辅助器件的空穴传输层高效地进行空穴注入,应用前景良好。(The invention provides a fluorene-containing compound, a hole injection material, an OLED device, a preparation method and application thereof, wherein the structure of the fluorene-containing compound is shown as a formula I; the fluorene-containing compound provided by the invention has good cross hyperconjugation characteristics and thermal stability, does not need to add extra substances, is very suitable for being used as a hole injection material of an organic electroluminescent device, can endow the material with good film-forming performance, can also endow the compound molecule with stronger reduction potential by modifying on a fluorene ring and combining with a strong electron-absorbing group, further improves the hole injection effect of the compound, assists a hole transport layer of the device to efficiently inject holes, and has good application prospect.)
1. A fluorene-containing compound is characterized in that the structure of the fluorene-containing compound is shown as a formula I:
wherein R is1、R2、R3、R4、R5、R6、R7、R8、R9、R10、R11And R12Independently selected from any one of hydrogen, halogen atom, cyano, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted alkoxy, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl and substituted or unsubstituted aryloxy;
X1and X2Independently selected from any one of alkylene or substituted alkylene.
2. The fluorene-containing compound of claim 1, wherein R is1、R2、R3、R4、R5、R6、R7、R8、R9、R10、R11And R12Independently selected from any one of halogen atom, cyano, substituted alkyl, alkenyl, substituted alkenyl, aryl or substituted aryl;
preferably, R1、R2、R3、R4、R5、R6、R7、R8、R9、R10、R11And R12Independently selected from any one of fluorine atom, cyano, trifluoromethyl, vinyl, dicyanovinyl, phenyl, fluorenyl or trifluoromethyl substituted phenyl.
3. The fluorene-containing compound according to claim 1 or 2, wherein X is1And X2Independently selected from any one of alkylene, fluorine substituted alkylene or cyano substituted alkylene;
preferably, X1And X2Independently selected from any one of methylene, difluoromethylene or dicyanomethylene.
4. The fluorene-containing compound according to any one of claims 1 to 3, wherein the fluorene-containing compound comprises
preferably, the fluorene-containing compound is Any one of them.
5. The method for preparing a fluorene-containing compound according to any one of claims 1 to 4, wherein the method comprises a coupling reaction of a compound a and a compound b under the catalysis of a palladium catalyst to obtain the fluorene-containing compound, wherein the structure of the compound a is
6. The preparation method according to claim 5, wherein the molar ratio of the compound a to the compound b is 1: 1-1.2;
preferably, the palladium catalyst comprises tetrakis (triphenylphosphine) palladium and/or palladium acetate;
preferably, the amount of the palladium catalyst is 0.1-5% of that of the compound a calculated by molar amount;
preferably, the coupling reaction is carried out in the presence of magnesium;
preferably, the molar ratio of the compound a to magnesium is 1: 1.1-1.5.
7. The process according to claim 5 or 6, wherein the solvent for the coupling reaction is diethyl ether and/or tetrahydrofuran;
preferably, the coupling reaction is carried out under the protection of protective gas;
preferably, the protective gas comprises any one of nitrogen, neon or argon or a combination of at least two thereof;
preferably, the temperature of the coupling reaction is 30-100 ℃;
preferably, the coupling reaction time is 20-100 h.
8. A hole injection material comprising the fluorene-containing compound according to any one of claims 1 to 4.
9. An OLED device, characterized in that the hole injection layer of the OLED device comprises the hole injection material according to claim 8.
10. Use of a fluorene-containing compound according to any one of claims 1-4, a hole injection material according to claim 8, an OLED device according to claim 9 for the manufacture of a semiconductor device.
Technical Field
The invention belongs to the field of semiconductor materials, and relates to a fluorene-containing compound, a hole injection material, an OLED device, and a preparation method and application thereof.
Background
Energy level matching is crucial for organic electroluminescent devices, and a stack structure of the organic electroluminescent device, such as a classical organic electroluminescent device, includes: the cathode, the electron transport layer, the light emitting layer, the hole transport layer and the anode are made of ITO, but the work function is high, and the energy level difference from most hole transport materials is about 0.4 eV. Therefore, if a hole injection layer is added between the anode and the hole transport layer, on one hand, the injection of charges can be increased, and on the other hand, the overall efficiency and the service life of the device can be improved.
Of course, doping some strong oxidant into the hole transport layer as a hole injection layer is also another way to improve the hole injection efficiency of the organic electroluminescent device. However, this method requires energy levels of a host material and a dopant material, and generally, the HOMO level of the host material needs to be close to the LUMO level of the guest material, so that electrons in the HOMO level can jump to the LUMO level of the dopant, and a free hole is formed in the hole transport layer, thereby increasing the conductivity of the device. Meanwhile, the doping can bend the interface energy band, and holes can be injected in a tunneling mode. For the selection of the dopant, lewis acid type metal complexes, halogens, allenes and quinones are common, and the metal complexes and the halogens have the defects of instability and the like during device processing. The allyl compounds have more steps in the synthesis and higher cost.
CN106458840A discloses a fluoroalkyl fluorene derivative, and specifically discloses a structure containing 2, 7-disubstituted 9, 9-fluoroalkyl fluorene diradical, which is shown as follows:
the R groups are the same and are selected from the group consisting of: straight or branched achiral C 1-C14Alkyl radical, C1-C14Haloalkyl, C1-C14Fluoroalkyl radical, C2-C14An alkenyl group, optionally 1, 2, 3, 4 or 5 CH therein2The group is replaced by oxygen, provided that no acetal, ketal, peroxide, or vinyl ether is present in the R group; the disclosed compounds show effective electrochemical stability and reversibility and good fluorescence lifetime when used as electroluminescent devices, but do not show strong thermal stability.
At present, compounds with spirofluorene, bifluorene and bifluorene structures are also widely applied to organic electroluminescent devices, and can be used as electron transport materials, hole injection materials and the like, and compounds with different structures show different performances.
CN102442938A discloses a novel compound, which has stable properties, simple preparation process, high luminous efficiency and high carrier mobility, and can be used in the electron transport layer of electroluminescent devices. The applied device can obviously reduce the driving voltage and improve the current efficiency. The compound mother nucleus is selected from 2, 10-disubstituted-7, 7,14, 14-tetraalkyl-7, 14-dihydrofluoreno [2,1a ] fluorene, and the structure is shown as follows:
the terminal groups Ar1 and Ar2 are selected from pyridine groups, phenyl groups, biphenyl groups or naphthyl groups, A, B is a chemical bond or an aromatic ring with 6-30 carbon atoms, R is an alkyl group with 1-12 carbon atoms or an aryl group with 6-30 carbon atoms, and m and n are integers of 0-2. The pyridine groups lacking electrons are introduced to two sides of the fluoreno [2,1a ] fluorene group, so that the charge transfer capability of the compound can be improved, and the compound has good electron transfer performance. Meanwhile, the aromatic group connected with the pyridyl can improve the molecular weight of the compound so as to increase the glass transition temperature of the compound; it is also possible to reduce the coplanarity of such compounds and thus to improve their film-forming properties. Has higher stability at room temperature, and the applied device also has higher stability. However, this compound has a complicated structure and is not suitable for use in an electron transport layer as a material for a hole injection layer.
The existing hole injection material usually can be doped with metal complexes, strong oxidants and the like, has the problems of instability in processing, has higher requirements on the energy level of the material, is expensive and has higher cost, and is not beneficial to actual production and application. How to develop a material which has good stability and hole injection property during processing is of great significance for its application.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a fluorene-containing compound, a hole injection material, an OLED device, a preparation method and an application thereof, so as to solve the problems of poor hole injection capability caused by high cost and high LUMO energy level due to unstable heat during processing and additional doping of other substances in the existing material.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a fluorene-containing compound, wherein the structure of the compound is shown in formula I:
wherein R is1、R2、R3、R4、R5、R6、R7、R8、R9、R10、R11And R12Independently selected from any one of hydrogen, halogen atom, cyano, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted alkoxy, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl and substituted or unsubstituted aryloxy;
X1And X2Independently selected from any one of alkylene or substituted alkylene.
According to the fluorene-containing compound provided by the invention, the fluorenyl groups are connected at the positions 4 and 5 of the fluorenyl groups, so that the molecular weight of the compound is increased, a carbon-based framework is formed, the thermal stability of the compound is enhanced, and compared with the single fluorenyl group which has the problem of small molecular weight and thermal instability, the fluorene-containing compound has better thermal stability; meanwhile, a double bond is introduced to the 9-position of the fluorenyl group to form a large cross-conjugation system together with the two fluorenyl groups, so that the compound has good cross-hyperconjugation characteristic and lower LUMO energy level, the stability of the compound is further improved, the compound is very suitable for being used as a hole injection material of an organic electroluminescent device, and the material can be endowed with good film-forming performance.
The halogen atom in the invention includes any one of fluorine atom, chlorine atom or bromine atom.
The alkyl in the invention can be straight-chain alkyl or branched-chain alkyl, and can be alkyl with chirality or alkyl without chirality. More specifically methyl, ethyl, n-propyl, isopropyl, n-heptyl, octadecyl, eicosyl and the like, and generally, an achiral alkyl group is preferred. The alkylene group in the present invention may be a linear alkylene group or a branched alkylene group, and specifically may be a methylene group, an ethylene group, or the like; the substituted alkylene group may be substituted with any group, and may be, for example, cyanomethylene, dicyanomethylene, or the like And the dotted line indicates the position of the double bond access in formula I.
The alkoxy group in the present invention may be a linear alkoxy group or a branched alkoxy group, and may be, for example, a methoxy group, an ethoxy group, an isopropoxy group, or the like.
The alkenyl group in the present invention may be vinyl, propenyl, 1, 3-butadienyl, etc., and the substituted alkenyl group may be cyanovinyl, dicyanovinyl, etc.
The aryl groups described herein may be phenyl, naphthyl, anthryl, phenanthryl, fluorenyl, and the like; heteroaryl groups can be pyridyl, pyrrolyl, thienyl, furyl, indolyl, quinolinyl, and the like; the aryloxy group may be phenoxy, naphthoxy, or the like.
The substitution in the present invention means that alkyl, aryl and the like groups can be substituted with any substituent, wherein the substituent can be halogen atom, cyano, alkynyl, aryl, heteroaryl, aryloxy, halogenated hydrocarbon group, alkenyl or cyano-substituted alkenyl, sulfonic group, amino and the like; more preferred is a cyano group, a halogenated hydrocarbon group, a halogen atom or a cyano-substituted alkenyl group; wherein the halogenated hydrocarbon group may be a trifluoromethyl group, a chloropropyl group or the like.
Preferably, R1、R2、R3、R4、R5、R6、R7、R8、R9、R10、R11And R12Independently selected from any one of halogen atom, cyano, substituted alkyl, alkenyl, substituted alkenyl, aryl or substituted aryl.
Preferably, R1、R2、R3、R4、R5、R6、R7、R8、R9、R10、R11And R12Independently selected from any one of fluorine atom, cyano, trifluoromethyl, vinyl, dicyanovinyl, phenyl, fluorenyl or trifluoromethyl substituted phenyl.
Preferably, X1And X2Independently selected from any one of alkylene, fluoro-substituted alkylene or cyano-substituted alkylene.
Preferably, X1And X2Independently selected from any one of methylene, difluoromethylene or dicyanomethylene.
In the present invention, the substituent of the fluorene ring mainly affects the hole injection effect of the compound, and secondly, has a certain effect on the thermal stability of the compound. Substituents on the fluorene ring, i.e. in formula I, R1～R12And X1、X2Can be totally substituted, partially substituted orThe substituent groups are the same or different, and the substituent groups can be uniformly substituted or randomly substituted.
The total substitution, partial substitution and non-substitution on the fluorene ring have an influence on the properties of the compound, and the total substitution has a better hole injection effect than the partial substitution and non-substitution.
The substituent on the fluorene ring is preferably a strong electron-withdrawing group, such as a cyano group, dicyanoethylene, fluoro group, trifluoromethyl group, and the like, and due to the strong electron-withdrawing property of these groups, a strong reduction potential can be imparted to the molecule, and the hole injection effect can be further improved, thereby assisting the hole transport layer to efficiently perform hole injection.
If a substituent on the fluorene ring is a group which does not have strong electron absorption property, such as alkyl, the LUMO level of the material is increased after the compound is prepared into the material, and the hole injection performance of the material is seriously affected.
In addition, the substituents on the fluorene ring are generally not selected to be relatively reactive groups. For example, when the substituent on the fluorene ring is a chlorine atom, it is reactive and easily generates radicals, which ultimately affects the device performance.
The fluorene-containing compound includes
Preferably, the fluorene-containing compound is Any one of them.
In the present invention, the fluorene-containing compounds are preferred to have better thermal stability and hole injection effect.
In a second aspect, the present invention provides a preparation method of the fluorene-containing compound according to the first aspect, the preparation method including a coupling reaction of a compound a and a compound b under the catalysis of a palladium catalyst to obtain the fluorene-containing compound, wherein the structure of the compound a isThe structure of the compound b isR1、R2、R3、R4、R5、R6、R7、R8、R9、R10、R11And R12And X1And X2In the same manner as defined in the first aspect, i.e., R1、R2、R3、R4、R5、R6、R7、R8、R9、R10、R11And R12Independently selected from any one of hydrogen, halogen atom, cyano, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted alkoxy, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl and substituted or unsubstituted aryloxy; x 1And X2Independently selected from any one of alkylene or substituted alkylene.
Preferably, the molar ratio of the compound a to the compound b is 1: 1-1.2, and may be 1:1, 1:1.05, 1:1, 1:1.12, 1:1.15, 1:1.18 or 1:1.2, for example.
Preferably, the palladium catalyst comprises tetrakis (triphenylphosphine) palladium and/or palladium acetate.
The palladium catalyst of the present invention is not limited to the above-mentioned compounds, and any divalent palladium compound which can be catalyzed can be used in the reaction of the present invention.
Preferably, the amount of the palladium catalyst is 0.1 to 5% of the compound a, for example, 0.1%, 0.2%, 0.3%, 0.5%, 0.8%, 0.9%, 1%, 2%, 3%, 4%, 5%, etc. calculated by mole.
Preferably, the coupling reaction is carried out in the presence of magnesium.
Preferably, the molar ratio of the compound a to magnesium is 1: 1.1-1.5, and may be, for example, 1:1.1, 1:1.2, 1:1.3, 1:1.4, or 1:1.5, etc.
Preferably, the solvent of the coupling reaction is diethyl ether and/or tetrahydrofuran.
Preferably, the coupling reaction is carried out under protection of a protective gas.
Preferably, the protective gas comprises any one of nitrogen, neon or argon or a combination of at least two thereof.
Preferably, the temperature of the coupling reaction is 30 to 100 ℃, for example, 30 ℃, 40 ℃, 50 ℃, 60 ℃, 70 ℃, 80 ℃, 90 ℃ or 100 ℃.
Preferably, the coupling reaction time is 20-100 h, for example, 20h, 30h, 40h, 50h, 60h, 70h, 80h, 90h or 100 h.
In a third aspect, the present invention provides a hole injection material comprising the fluorene-containing compound according to the first aspect.
The fluorene-containing compound provided by the invention has good thermal stability and hole injection performance, so the prepared hole injection material has good hole injection efficiency,
in a fourth aspect, the present invention provides an OLED device whose hole injection layer comprises a hole injection material as described in the third aspect.
In a fifth aspect, the present invention provides the fluorene-containing compound of the first aspect, the hole injection material of the third aspect, and the use of the OLED device of the fourth aspect in the preparation of a semiconductor device.
Compared with the prior art, the invention has the following beneficial effects:
the fluorene group is connected to the 4 and 5 positions of the fluorene group, so that the molecular weight of the compound is increased, a carbon-based framework is formed, the thermal stability of the compound is enhanced, the compound is generally not affected at more than 400 ℃, the highest temperature can reach 500-600 ℃, and compared with the single fluorene group, the compound has smaller molecular weight and has the problem of thermal instability; meanwhile, a double bond is introduced to the 9 position of the fluorenyl group to form a large cross conjugation system together with the two fluorenyl groups, so that the compound has good cross super conjugation property and lower LUMO energy level, the LUMO value can reach-5.2-5.5 eV generally, the stability of the compound is further improved, no additional substance is required to be added, the compound is very suitable for being used as a hole injection material of an organic electroluminescent device, and the material can be endowed with good film-forming property.
According to the fluorene-containing compound provided by the invention, the fluorene ring is modified, and a strong electron-absorbing group is combined, so that a strong reduction potential can be given to the compound molecules, the hole injection effect of the compound is further improved, and the hole injection is efficiently carried out by a hole transport layer of an auxiliary device.
Detailed Description
The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.
The raw materials, solvents, catalysts and the like for the reactions used in the examples of the present invention can be purchased directly or synthesized according to known methods.
The thermogravimetric analyzer used in the embodiment of the present invention has the following model: TGA/DSC 1/1100SF of METTLER.
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