CN107382908A - A kind of biphenyl compound, organic electroluminescence device and display device - Google Patents

Abstract

The invention relates to the field of display technology, in particular to a biphenyl compound, an organic electroluminescent device and a display device. Compound according to the present invention is shown in formula (1): The compound provided by the invention is used as the host material of the light-emitting layer of the organic electroluminescent device, which improves the luminous efficiency of the organic electroluminescent device and reduces the driving voltage of the organic electroluminescent device.

Description

A biphenyl compound, an organic electroluminescent device and a display device

technical field

The invention relates to the field of display technology, in particular to a biphenyl compound, an organic electroluminescent device and a display device.

Background technique

Organic Light Emitting Display (OLED) is a new type of flat-panel display. Compared with Liquid Crystal Display (LCD), it has the advantages of thinness, lightness, wide viewing angle, active luminescence, and continuously adjustable luminous color. , low cost, fast response speed, low energy consumption, low driving voltage, wide operating temperature range, simple production process, high luminous efficiency and flexible display, etc., have attracted great attention from the industrial and scientific circles.

The development of organic electroluminescent devices has promoted the research on organic electroluminescent materials. Compared with inorganic light-emitting materials, organic electroluminescent materials have the following advantages: organic materials have good processability, and can be formed into films on any substrate by evaporation or spin coating; the diversity of organic molecular structures makes it possible to design and Modification methods are used to adjust the thermal stability, mechanical properties, luminescence and electrical conductivity of organic materials, so that there is a lot of room for improvement of materials.

The generation of organic electroluminescence depends on the recombination of carriers (electrons and holes) transported in organic semiconductor materials. As we all know, the conductivity of organic materials is very poor, there is no continuous energy band in organic semiconductors, and the transport of carriers is often described by hopping theory. In order to achieve a breakthrough in the application of organic electroluminescent devices, it is necessary to overcome the difficulties of poor charge injection and transport capabilities of organic materials. Scientists have adjusted the device structure, such as increasing the number of organic material layers of the device, and making different organic layers play different device layers. For example, some functional materials can promote electron injection from the cathode, and some functional materials can promote hole injection from the cathode. For anode injection, some materials can promote the transport of charges, while others can block the transport of electrons or holes. Of course, in organic electroluminescent devices, the most important luminescent materials of various colors must also achieve the purpose of matching with adjacent functional materials. Therefore, organic electroluminescent devices with high efficiency and long life are usually the result of the optimal combination of device structure and various organic materials, which provides great opportunities and challenges for chemists to design and develop functional materials with various structures.

In the preparation process of organic electroluminescent devices, one is called evaporation method, that is, each functional material is deposited on the substrate by vacuum thermal evaporation to form a film, which is also the mainstream technology in the industry at present. However, the shortcomings of this process are also obvious. On the one hand, the characteristics of the organic material itself determine that thermal evaporation at high temperature for a long time requires high thermal stability of the material; in addition, the long-term stable control of the evaporation rate, Maintaining the uniformity of material distribution on the substrate is also a very important requirement; and high vacuum, high temperature evaporation, high energy consumption; more importantly, because the production process of the OLED material itself is relatively complicated and the technical content is high, so the price is relatively high. Expensive, and the existing process uses evaporation, and the utilization rate of OLED materials is low, generally below 10%.

In the preparation process of organic electroluminescent devices, the other is called solution method, which uses soluble OLED materials, dissolves them in solvents, and coats them on the substrate by printing, inkjet, spin coating, etc. In order to form certain functional layers, this method distributes materials evenly, saves materials, simplifies the production process of OLED devices, and reduces the production cost of OLED devices.

Contents of the invention

The invention provides a biphenyl compound, an organic electroluminescent device containing the compound and a display device having the organic electroluminescent device. The organic electroluminescent device containing the compound has a lower driving voltage and a higher luminous efficiency.

Moreover, the biphenyl compounds provided by the invention have good solubility in organic solvents and good film-forming properties. In the preparation of organic electroluminescent devices, the light-emitting layer can be formed by a solution method.

According to one aspect of the present invention, a kind of biphenyl compound is provided, as shown in formula (1):

Wherein X is selected from substituted or unsubstituted aryl groups with 6-80 carbon atoms;

wherein A is selected from the following structures:

Wherein A1, A2 and A3 are independently selected from aliphatic alkyl groups with 1-20 carbon atoms and aliphatic alkyl groups with 1-20 carbon atoms substituted by alkoxy groups.

Further, wherein the substituted or unsubstituted aryl group with 6-80 carbon atoms is characterized in that the aryl group is selected from: phenyl, biphenyl, naphthyl, anthracenyl, phenanthrenyl, Triphenylene, pyrenyl, fluorenyl, fluoranthenyl, indenofluorenyl, cyclopentaphenanthryl, spirofluorenyl, benzofluorenyl, indenanthracenyl, dibenzofluorenyl, naphthrenyl, Benzanthryl;

Wherein the substituents are selected from: alkyl groups with 1-20 carbon atoms, cycloalkyl groups with 3-20 carbon atoms, phenyl, biphenyl, naphthyl, anthracenyl, phenanthrenyl, triphenylene , pyrenyl, fluorenyl, fluoranthenyl, indenofluorenyl, cyclopentaphenanthryl, spirofluorenyl, benzofluorenyl, dibenzofluorenyl, naphthrenyl, benzanthracenyl.

Biphenyl compounds of the present invention are preferably selected from the following structures:

According to another aspect of the present invention, a solution is provided, which at least contains the biphenyl compound of the present invention and at least one solvent. The solvent is selected from one or more of toluene, xylene, chlorobenzene, dichlorobenzene, diphenyl ether, chloroform, ethyl acetate, ethanol, isopropanol, and n-butanol.

The preparation method of the solution is as follows: in a glove box, under a nitrogen atmosphere, the compound of the present invention is dissolved in the above solvent, and then filtered through a 0.1 micron filter membrane.

In the process of preparing the above solution, the fluorescent dye required in the organic electroluminescent device can be added; the weight ratio of the fluorescent dye to the biphenyl compound of the present invention is 1:100˜1:10.

According to another aspect of the present invention, an organic electroluminescent device is provided, the organic electroluminescent device comprising the biphenyl compound according to the present invention.

Optionally, the host material of the light-emitting layer of the organic electroluminescent device is the biphenyl compound according to the present invention.

Optionally, the light-emitting layer of the organic electroluminescent device is prepared by a solution method.

According to another aspect of the present invention, there is provided a display device comprising the organic electroluminescent device according to the present invention.

The beneficial effects of the present invention are as follows:

Using the compound provided by the invention as the host material of the light-emitting layer of the organic electroluminescent device improves the luminous efficiency of the organic electroluminescent device and reduces the driving voltage of the organic electroluminescent device.

Due to the introduction of the substituent A in the biphenyl compound of the present invention, the configuration of the compound is distorted and the film-forming property of the material is better; at the same time, compared with the biphenyl compound without substituent A, the material is improved. Solubility makes the compounds provided by the invention more suitable for preparing light-emitting layer by solution method.

detailed description

The specific embodiments are only an illustration of the present invention, and do not constitute a limitation to the content of the present invention. The following will further illustrate and describe the present invention in conjunction with specific embodiments.

The invention provides a biphenyl compound, an organic electroluminescent device containing the compound and a display device having the organic electroluminescent device. The organic electroluminescent device containing the compound has a lower driving voltage and a higher luminous efficiency.

Using the compound provided by the invention as the host material of the organic light-emitting layer of the organic electroluminescent device improves the luminous efficiency of the organic electroluminescent device and reduces the driving voltage of the organic electroluminescent device.

In order to illustrate the compounds of the present invention in more detail, the following will further describe the present invention by enumerating the synthesis methods of the above-mentioned specific compounds.

The synthesis of embodiment 1 intermediate M-01:

Synthesis of compound A-1:

In a 500 ml three-necked flask, under nitrogen protection, add 220 ml of dry toluene, 20.1 g (0.05 mol) of the compound shown in formula A-0, 10.2 g (0.12 mol) of cyclohexylamine, 14.4 g (0.15 mol) of tert-butyl Sodium alkoxide, 0.58 gram (0.001mol) bis(dibenzylideneacetone) palladium, 2.02 gram (0.001mol) 10% toluene solution of tri-tert-butylphosphine, heated to reflux reaction and down to room temperature after 4 hours, added dilute Hydrochloric acid, liquid separation, the organic layer was washed with water until neutral, dried with anhydrous magnesium sulfate, separated by silica gel column, the eluate was concentrated to dryness, and recrystallized with methanol to obtain 17.6 g of the compound shown in formula A-1. The rate is 85.75%.

The obtained compound A-1 was detected by mass spectrometry, and the product m/e: 410.

Synthesis of compound A-2:

Add 16 g (0.039 mol) of the compound shown in formula A-1 into a 1000 ml stainless steel hydrogenation kettle, 300 ml of ethanol, 3 g of 5% palladium carbon, after nitrogen replacement, at 60 ° C, control 0.2 MPa hydrogen reduction reaction for 6 hours , the reaction is complete. Stop reaction, after nitrogen replacement, take out material, remove catalyst by filtration, add 600 milliliters of water in filtrate, separate out solid, after filtering out obtained solid, recrystallize with methanol, obtain off-white solid 10.2 grams shown in formula A-2, Yield 74.6%,

The product represented by the obtained formula A-2 was detected by mass spectrometry, and the m/e of the product was obtained: 350.

Synthesis of intermediate M-01:

In a 1000 ml three-necked flask, add 12.86 g (0.2 mol) of 48% hydrobromic acid aqueous solution, add 7.0 g (0.02 mol) of the compound shown in formula A-2 under stirring, heat up to reflux and keep for 5 minutes, then cool down to 25°C , add 0.5 g (0.0035 mol) of cuprous bromide, then slowly add 2.76 g (0.04 mol) of NaNO2 in 10 ml of aqueous solution under control of the temperature between 25 and 35 ° C, and slowly heat up to 60 to 65 ° C for 1 hour, then raised the temperature to 85-90°C for 2 hours, lowered the temperature, filtered, and crystallized the obtained solid with a mixed solvent of methanol and chloroform to obtain 4.17 grams of off-white solid shown in formula M-01, with a yield of 43.62%.

The product represented by the obtained formula M-01 was detected by mass spectrometry, and the m/e of the product was obtained: 478.

The product shown in the obtained formula M-01 has been carried out nuclear magnetic detection, and the obtained nuclear magnetic analysis data is as follows:

¹ HNMR (500MHz, CDCl ₃ ): δ7.48(t, 2H), δ6.99(m, 4H), δ3.06(t, 8H), δ1.65(m, 8H), δ1.58(m , 4H).

The synthesis of embodiment 2 intermediate M-02～intermediate M-13

Referring to the synthesis method of intermediate M-01, only the cyclohexylamine used in the first step of synthesizing compound A-1 was replaced with the corresponding amine. The amines used in the specific reactions and the mass spectrometry and NMR data are listed as follows:

The synthesis of embodiment 3 compound P-1

Synthesis of Intermediate B-01

In a 1000 ml three-necked flask, add 400 ml of tetrahydrofuran, 23.9 g (0.05 mol) of the compound represented by formula M-01, lower the temperature to -78°C under nitrogen protection, and slowly add 75 ml (0.12 mol) of 1.6M n-butyl Lithium n-hexane solution, after adding, keep it at -70～-78°C for 30 minutes, then add 13.5 grams (0.13mol) redistilled trimethyl borate, then slowly heat up to 25°C for 2 hours, add dilute hydrochloric acid for hydrolysis, Ethyl acetate was added for extraction, the organic layer was concentrated to dryness, and recrystallized with ethanol to obtain 11.7 g of the product represented by formula B-01, with an HPLC of 97.9%, and a yield of 57.35%.

Synthesis of compound P-1:

In the 1000 milliliter three-necked flask, add 300 milliliters of toluene, 300 milliliters of ethanol, 100 milliliters of water, 20.4 grams (0.05mol) of the compound shown in formula B-01, 36.6 grams (0.011mol) of 9-bromo-10-phenylanthracene, 27.6 grams (0.2mol) of potassium carbonate, under the protection of nitrogen, add 1.16 grams (0.001mol) tetrakistriphenylphosphine palladium, slowly warm up to 70 ° C for 8 hours, cool down, separate liquids, wash the organic layer with silica gel column decolorization, wash The liquid was removed and concentrated to dryness, separated by silica gel column chromatography, and eluted with ethyl acetate:petroleum ether=1:5 to obtain 28.7 g of the product shown in formula P-1, with a yield of 69.66%.

The product shown in the obtained formula P-1 was detected by mass spectrometry, and the m/e of the product was obtained: 824

The product shown in the obtained formula P-1 has been carried out nuclear magnetic detection, and the obtained nuclear magnetic analysis data is as follows:

¹ HNMR (500MHz, CDCl ₃ ): δ8.21(m, 8H), δ7.78(d, 2H), δ7.66(m, 4H), δ7.55(m, 4H), δ7.42(m , 10H), δ7.00 (d, 2H), δ6.58 (m, 2H), δ3.06 (m, 8H), δ1.70～1.56 (m, 12H).

Example 4 Compounds P-2, P-7, P-10, P-11, P-17, P-20, P-21, P-23, P-27, P-30, P-31, P- Synthesis of 38

Referring to the synthetic method of compound P-1, according to the specific structure of the compound, replace M-01 with one of the corresponding M-02～M-13; Bromo-10-phenylanthracene was exchanged for the corresponding bromide. The types of specific compounds and the mass spectrometry and NMR data are listed as follows:

According to another aspect of the present invention, there is provided an organic electroluminescent device comprising the biphenyl compound according to the present invention.

The typical structure of an organic electroluminescent device is: substrate/anode/hole injection layer/hole transport layer (HTL)/organic light-emitting layer (EL)/electron transport layer (ETL)/electron injection layer/cathode. The organic electroluminescent device structure can be a single light emitting layer or multiple light emitting layers.

Wherein, the substrate can be a substrate in a traditional organic electroluminescent device, such as glass or plastic. The anode can be made of transparent high-conductivity materials, such as indium tin oxide (ITO), indium zinc oxide (IZO), tin dioxide (SnO ₂ ), and zinc oxide (ZnO).

The hole injection material (HIM for short) of the hole injection layer is required to have high thermal stability (high Tg), and has a small potential barrier with the anode or the hole injection material. It is prepared by evaporation method. For electroluminescent devices, it is required that the material can be vacuum evaporated to form a pinhole-free film. Commonly used HIMs are aromatic polyamine compounds, mainly triarylamine derivatives. For the preparation of organic electroluminescent devices by the solution method, the materials are required to have appropriate solubility. After the solution is coated on the substrate and the solution evaporates, a dense and uniform amorphous film can be formed on the substrate. Commonly used HIM materials mainly include PEDOT:PSS.

The hole transport material (HTM for short) of the hole transport layer is required to have high thermal stability (high Tg), high hole transport ability, and can be vacuum evaporated to form a pinhole-free film. Commonly used HTMs are aromatic polyamine compounds, mainly triarylamine derivatives.

The organic light-emitting layer includes a host material (host) and a guest material, wherein the guest material is a light-emitting material, such as a dye. In some cases, instead of using a guest material, a host material can be directly used as the organic light-emitting layer. The host material needs to have the following characteristics: reversible electrochemical redox potential, HOMO energy level and LUMO energy level matching with the adjacent hole transport layer and electron transport layer, good and matching hole and electron transport capabilities, Good high thermal stability and film-forming properties, and suitable singlet or triplet energy gap are used to control excitons in the light-emitting layer, as well as good energy transfer with corresponding fluorescent dyes or phosphorescent dyes. The light-emitting material of the organic light-emitting layer, taking the dye as an example, needs to have the following characteristics: high fluorescence or phosphorescence quantum efficiency; the absorption spectrum of the dye and the emission spectrum of the host have a good overlap, that is, the energy of the host and the dye is adapted, and the energy from the host The dye can effectively transfer energy; the emission peaks of red, green, and blue are as narrow as possible to obtain good color purity; the stability is good, and it can be evaporated. When the organic light-emitting layer is prepared by the solution method, the material is also required to have a suitable solubility. After the solution is coated on the substrate and the solution evaporates, a dense and uniform amorphous film can be formed on the substrate.

The electron transport material (Electron transport Material, referred to as ETM) of the electron transport layer requires that the ETM has a reversible and sufficiently high electrochemical reduction potential, and a suitable HOMO energy level and LUMO (Lowest Unoccupied Molecular Orbital, the lowest unoccupied molecular orbital) energy level value makes Electrons can be injected better, and it is better to have hole blocking ability; higher electron transport ability, good film formation and thermal stability. ETMs are generally aromatic compounds with conjugated planes of electron-deficient structures. When preparing organic electroluminescent devices by evaporation method, Alq3 (8-hydroxyquinoline aluminum) or TAZ (3-phenyl-4-(1'-naphthyl)-5-benzene-1,2 ,4-triazole) or TPBi (1,3,5-tris(N-phenyl-2-benzimidazole)benzene) or a combination of any two of these three materials.

According to another aspect of the present invention, there is provided a display device comprising the organic electroluminescent device according to the present invention.

In the preparation process of the organic electroluminescent device, all the functional layers can be prepared by the evaporation method, and one or more layers can be prepared by the evaporation method, and the other functional layers can be prepared by the solution method. All the functional layers can be prepared by solution method.

It can be seen that there are many optional factors for the compound, organic electroluminescent device and display device according to the present invention, and different embodiments can be combined according to the claims of the present invention. The embodiments of the present invention are only used as a specific description of the present invention, not as a limitation of the present invention. The present invention will be further described below with reference to an organic electroluminescent device containing the compound of the present invention as an example.

The concrete structure of material used in the embodiment sees below:

Example 5

The compound of the present invention was selected as the host material of the organic light-emitting layer in the blue fluorescent organic electroluminescent device; ADN was selected as the host material of the organic light-emitting layer in the blue fluorescent organic electroluminescent device in the comparative example.

The structure of the organic electroluminescent device is: ITO/NPB (40nm)/blue light host material (30nm): DPAVBi[5%]/Alq3(20nm)/LiF(0.5nm)/Al(150nm).

The preparation process of the organic electroluminescent device is as follows: the glass plate coated with the ITO transparent conductive layer is ultrasonically treated in a commercial cleaning agent, rinsed in deionized water, ultrasonically degreased in acetone and ethanol mixed solvent, and baked in a clean environment. Roasted until moisture is completely removed, cleaned under UV light and ozone conditions, and bombarded with a beam of low-energy positive ions.

Put the above-mentioned glass substrate with an anode in a vacuum chamber, evacuate to 1×10 ^-5 ~ 9×10 ^-3 Pa, vacuum evaporate NPB on the above-mentioned anode layer film as a hole transport layer, and the evaporation rate is 0.1nm/s, and the vapor-deposited film thickness is 40nm.

On the hole transport layer, the blue light host material is vacuum evaporated: DPAVBi[5%] is used as the light-emitting layer of the organic electroluminescent device, the evaporation rate is 0.1nm/s, and the total film thickness of the evaporation is 30nm; where "DPAVBi[ 5%]" refers to the doping ratio of the blue light dye, that is, the weight ratio of the blue light host material to DPAVBi is 100:5.

Vacuum-evaporate Alq3 on the light-emitting layer as the electron transport layer of the organic electroluminescent device, the evaporation rate is 0.1nm/s, and the total film thickness of the evaporation is 20nm;

0.5nm LiF was vacuum-deposited on the electron transport layer, and 150nm Al was used as the electron injection layer and cathode.

The performance of the prepared organic electroluminescent device was tested, and the test results are shown in Table 1.

Table 1

As can be seen from Table 1, the blue fluorescent organic electroluminescent device adopting the compound of the present invention has obtained higher current efficiency and lower driving efficiency relative to the blue fluorescent organic electroluminescent device adopting ADN commonly used in the industry. Voltage.

Example 6

The compound of the invention is used as the light-emitting layer material, and the organic electroluminescence device is prepared by a solution method. In the comparative example, ADN was selected as the light-emitting layer material, and an organic electroluminescent device was prepared by a solution method.

The structure of the organic electroluminescent device is: ITO/NPB (40nm)/luminescent layer material (30nm)/Alq3 (20nm)/LiF (0.5nm)/Al (150nm).

The preparation process of the organic electroluminescent device is as follows: the glass plate coated with the ITO transparent conductive layer is ultrasonically treated in a commercial cleaning agent, rinsed in deionized water, ultrasonically degreased in acetone and ethanol mixed solvent, and baked in a clean environment. Roasted until moisture is completely removed, cleaned under UV light and ozone conditions, and bombarded with a beam of low-energy positive ions.

Put the above-mentioned glass substrate with an anode in a vacuum chamber, evacuate to 1×10 ^-5 ~ 9×10 ^-3 Pa, vacuum evaporate NPB on the above-mentioned anode layer film as a hole transport layer, and the evaporation rate is 0.1nm/s, and the vapor-deposited film thickness is 40nm.

The glass substrate on which the above-mentioned vapor-deposited hole transport layer was placed in a glove box, under a nitrogen atmosphere, the solution of the compound of the present invention (0.5% chlorobenzene solution) (comparative example using AND) spin coater at 4000r/min The speed is evenly spin-coated on the glass substrate, and then the glass substrate is vacuum-dried at a temperature of 150 degrees for 60 minutes to remove the solvent, and the prepared glass substrate coated with the luminescent layer is obtained.

The above-mentioned glass substrate coated with the luminescent layer was transferred to a vacuum chamber, and Alq3 was vacuum-deposited on the luminescent layer as the electron transport layer of the organic electroluminescent device. The evaporation rate was 0.1nm/s, and the total film was evaporated 20nm thick;

0.5nm LiF was vacuum-deposited on the electron transport layer, and 150nm Al was used as the electron injection layer and cathode.

The performance of the prepared organic electroluminescent device was tested, and the test results are shown in Table 2.

Table 2

It can be seen from Table 2 that the organic electroluminescent device using the compound of the present invention has higher current efficiency and lower driving voltage than the organic electroluminescent device using ADN.

Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and equivalent technologies thereof, the present invention also intends to include these modifications and variations.

Claims (8)

1. a biphenyl compound, is characterized in that, described compound is as shown in formula (1): Wherein X is selected from substituted or unsubstituted aryl groups with 6-80 carbon atoms; wherein A is selected from the following structures: Wherein A1, A2 and A3 are independently selected from aliphatic alkyl groups with 1-20 carbon atoms and aliphatic alkyl groups with 1-20 carbon atoms substituted by alkoxy groups. 2. biphenyl compounds according to claim 1: Wherein the substituted or unsubstituted aryl group with 6-80 carbon atoms is characterized in that the aryl group with 6-80 carbon atoms is selected from: phenyl, biphenyl, naphthyl, anthracene Base, phenanthrenyl, triphenylene, pyrenyl, fluorenyl, fluoranthene, indenofluorenyl, cyclopentaphenanthryl, spirofluorenyl, benzofluorenyl, indenanthracenyl, dibenzofluorenyl, Naphthalenyl, benzanthracenyl; Wherein the substituents are selected from: alkyl groups with 1-20 carbon atoms, cycloalkyl groups with 3-20 carbon atoms, phenyl, biphenyl, naphthyl, anthracenyl, phenanthrenyl, triphenylene , pyrenyl, fluorenyl, fluoranthenyl, indenofluorenyl, cyclopentaphenanthryl, spirofluorenyl, benzofluorenyl, dibenzofluorenyl, naphthrenyl, benzanthracenyl. 3. biphenyl compound according to claim 1, is characterized in that, described compound is selected from: 4. A solution comprising at least one biphenyl compound according to claims 1-3 and at least one solvent. 5. An organic electroluminescent device, characterized in that the organic electroluminescent device comprises the biphenyl compound according to any one of claims 1-3. 6 . The organic electroluminescent device according to claim 5 , wherein the host material of the light-emitting layer of the organic electroluminescent device is the biphenyl compound according to any one of claims 1-3. 7. The organic electroluminescent device according to claim 5, wherein the light-emitting layer of the organic electroluminescent device is prepared by a solution method. 8. A display device, characterized by comprising the organic electroluminescence device as claimed in claim 5.