WO2015000265A1 - Alcohol-soluble cathode buffer layer molecular material containing three arylphosphine oxide and azacyclo functional group, and synthesizing method and application of same - Google Patents

Abstract

Disclosed are an alcohol-soluble cathode buffer layer molecular material containing three arylphosphine oxide and azacyclo functional group, and a synthesizing method and an application of same. The cathode buffer layer material is easily synthesized and prepared (for example, vacuum sublimation and purification are not required), has desirable alcohol solublility and stable thin film appearance, and presents a good solution processing property. The electron-withdrawing phosphine oxide and the azacyclo functional group are introduced, which can effectively assist electrons in injection/transmission or collection from metal such as aluminum (Al), silver (Ag), gold (Au), and ITO or from a metal-oxide electrode, thereby avoiding using a low-work-function metal electrode unstable in the air, and further improving device stability. Moreover, because the cathode buffer layer material can interact with lithium ions, potassium ions, cesium ions, and calcium ions, the cathode buffer layer material can further be doped with inorganic salt or organic salt containing these ions, to form a doped or compounded cathode buffer layer, thereby improving the device performance.

Description

 Alcohol-soluble cathode buffer layer molecular type material containing triarylphosphine oxide and nitrogen heterocyclic functional group, synthesis method and application thereof

 The invention relates to a cathode buffer layer material, in particular to a kind of alcohol-soluble cathode buffer layer molecular type material containing a triarylphosphine oxide and a nitrogen heterocyclic functional group, and a synthesis method and application thereof. Background technique

 Efficient electron injection or collection is critical to achieving high performance organic light-emitting diodes, organic field-effect transistors and organic light-emitting field effect transistors, and optoelectronic devices such as organic photovoltaics. Compared with low work function metals such as calcium, barium, magnesium, etc., the use of metal or metal oxides with high environmental stability as cathode materials, such as Al, Ag, Au, ITO, etc., is advantageous for the preparation and application of organic optoelectronic devices. However, the latter has a higher work function, so it is particularly urgent to design and synthesize cathode buffer materials that match them to improve electron injection or collection performance.

 In the early research, the cathode interface materials such as LiF and CsF were mainly used to realize electron injection or collection of electrons from the aluminum metal cathode, but these materials were formed by vacuum evaporation. Full solution processing optoelectronic devices offer the potential to achieve low cost, large area, flexible organic optoelectronic devices. Therefore, it is important to prepare a solution-processable cathode buffer material.

 The introduction of the phosphorus oxygen group is advantageous for improving the alcohol solubility, film morphology stability and electron injection performance of the molecule. On the basis of this, the material disclosed in the present invention introduces an electron-withdrawing nitrogen heterocycle to further improve electron injection, transport properties and hole blocking properties, thereby simplifying the structure of the organic electroluminescent device and promoting device stability. In addition, the cathode buffer material can effectively assist in the injection/transportation or collection of electrons from metal or metal oxide electrodes such as Al, Ag, Au, ITO, etc.; due to lithium ion, potassium ion, barium ion, calcium ion Alternatively, the cathode buffer layer material may be doped with an inorganic or organic salt containing these ions to form a doped or composite cathode buffer layer to improve device performance.

Summary of the invention

SUMMARY OF THE INVENTION The object of the present invention is to provide a class of alcohol-soluble cathode buffer layer molecular type materials containing a triarylphosphine oxide and a nitrogen heterocyclic functional group in view of the prior art disadvantages. An alcohol-soluble cathode buffer layer molecular material containing a triarylphosphine oxide and a nitrogen heterocyclic functional group, which is characterized by having one of the following chemical structural formulas:

Wherein, R ₂ is selected from a fused ring aryl group or a substituted fused ring aryl group; and R ₂ is selected from an aromatic nitrogen heterocyclic ring or a fused ring nitrogen heterocyclic ring; n=l-2.

The above-mentioned alcohol-soluble cathode buffer layer molecular type material containing a triarylphosphine oxide and a nitrogen heterocyclic functional group, characterized in that the above is any one of the following structural units:

其中， R46和 7为碳数为 1-18的垸基链; 所述 R₂为如下结构单元的任一种： Wherein R44 and R45 are selected from an alkyl chain or an alkoxy chain having 1 to 18 carbon atoms or are any of the following structural units:

Wherein R46 and 7 are an indenyl chain having a carbon number of 1 to 18; and the R ₂ is any one of the following structural units:

其中， X为 Br或 I。

Where X is Br or I.

The synthesis method is characterized in that it comprises the following steps:

Diphenylphosphine chloride is used as a reaction raw material, and is introduced into a group by a reaction of n-butyllithium at -78 ° C to obtain an unoxidized target product containing bromine, wherein, when it contains ~1 ₄₃ , it is catalyzed by palladium. The coupling reaction introduces an aryl group or a fused ring aryl group; when R contains ₄ and R ₄₅ , the fluorenone is catalyzed to introduce an aryl group or a fused ring aryl group by methanesulfonic acid, or the ruthenium is catalyzed by potassium hydroxide. An alkyl chain or an alkoxy chain having a carbon number of 1 to 18, wherein ₆ and ₇ are catalyzed by potassium hydroxide to introduce an alkyl or alkoxy chain having a carbon number of 1 to 18; 2) using the unoxidized bromine-containing target product obtained in the step 1), by oxidation of hydrogen peroxide, to obtain an oxidized target product containing a phosphorus-oxygen group and containing bromine;

 3) reacting the bromine-containing oxidized target product obtained in the step 2) with a palladium catalyst to react with divaleryl diboron to obtain a target product containing a boronic acid ester;

4) The boronic acid ester-containing target product obtained in the step 3) is coupled with the group R ₂ by a palladium-catalyzed coupling reaction to obtain a target product, wherein when R ₂ contains R 48 or R _5Q , it is passed through t-butanol. Potassium benzotriazole is catalytically introduced into an alkyl or alkoxy chain having a carbon number of 1 to 18; for the case where ₉ is contained in R ₂ , the alkyl group having a carbon number of 1 to 18 is catalytically introduced by aluminum trichloride Base chain or alkoxy chain.

In the synthesis method, in step 3), a boronic acid ester group is introduced into the phosphoryloxy group by a palladium catalyzed reaction, and the palladium catalyzes the reaction: the reactant is under the protection of an inert gas, and the reaction temperature range is 80-100 ° C, the reaction time range is 2-12 hours, using 1,1 '-bisdiphenylphosphinoferrocene palladium dichloride as a catalyst for the reaction; Step 4) by palladium-catalyzed coupling reaction will! Coupling with R ₂ having electron-withdrawing properties, the palladium catalyzed coupling reaction: the reactant is under the protection of an inert gas, the reaction temperature is in the range of 70-110 ° C, and the reaction time is in the range of 8-36 hours, using four ( Triphenylphosphine) Palladium or a reaction using palladium acetate and a tricyclohexylphosphine system as a catalyst.

 The use of the cathode buffer material in electroluminescent display, illumination, and organic photovoltaic cell devices. Compared with the prior art, the present invention has the following advantages and benefits:

 1) The new cathode buffer layer molecular type material has good alcohol solubility.

 2) While possessing the above advantages, the new cathode buffer layer molecular material has good film morphology stability.

 3) While possessing the above advantages, the novel cathode buffer layer molecular material has better electron injection, transport and hole blocking properties, and the device performance can be improved while simplifying the structure of the organic electroluminescent device.

 4) While possessing the above advantages, the new cathode buffer layer molecular material can effectively assist the injection/transport or collection of electrons from metal or metal oxide electrodes such as Al, Ag, Au, ITO.

 5) While having the above advantages, the new cathode buffer layer molecular material can interact with lithium ions, potassium ions, strontium ions, calcium ions, etc., so the cathode buffer layer material can be combined with inorganic salts or organic salts containing these ions. Doping, forming a doped or composite cathode buffer layer, improves device performance. DRAWINGS

Figures la and lb are differential scanning calorimetry curves for the novel cathode buffer materials 1 and 2. 2 is a current density-voltage curve of an organic electroluminescent device in which the cathode is a novel cathode buffer material 1/A1, material 1: barium carbonate/Al, material 2/Α1, ion salt/Al, A1, respectively.

 Figure 3 shows the current density-voltage curves of organic photovoltaic cell devices with cathodes 1/Ag and ethanol/Ag, respectively. detailed description

 The synthesis method of a kind of alcohol-soluble cathode buffer layer molecular type material containing a triarylphosphine oxide and a nitrogen heterocyclic functional group is further described below with reference to specific examples, but the scope of the claimed invention is not limited to the implementation. The scope of the example. The sub-material structure is as follows.

Example 1, Preparation of (2-bromo-6-naphthyl)diphenylphosphine (3)

Under an atmosphere of N _2, 2,6-dibromo-naphthalene (3 g, 10.5 mmol) was dissolved in dry tetrahydrofuran (200 mL), cooled to -78 ° C. Subsequently, n-butyllithium (2.4 M n-hexane solution, 4.8 mL, 11.55 mmol) was added dropwise via a syringe. After 50 minutes, n-butyllithium C2.3 mL, 12.6 mmol)) was added by syringe. The mixture was returned to room temperature and stirring was continued overnight. After the reaction was completed, the reaction was quenched by the addition of ethanol. After the solvent was evaporated under reduced pressure, the mixture was poured into water and extracted with dichloromethane. The organic layer was dried over anhydrous magnesium sulfate, filtered, and evaporated. Example 2, Preparation of Compound (4)

 To a solution of (2-bromo-6-naphthyl)diphenylphosphine (2.7 g, 7.23 mmol) in dichloromethane (30 mL), EtOAc (EtOAc) The reaction was stirred at room temperature overnight. After the reaction was completed, an aqueous sodium sulfite solution was poured into the reaction mixture to reduce excess hydrogen peroxide and extracted with dichloromethane. The organic layer was dried over anhydrous magnesium sulfate, filtered, evaporated, evaporated, evaporated, evaporated, NMR (300 MHz, DMSO): d = 7.53-7.60 (m, 4H), 7.62-7.77 (m, 8H), 8.03-8.08 (m, 2H), 8.33 (s, 1H), 8.36 (d, 1H, J = 13.86 Hz) ppm. Example 3, 2-(9,9-bis(4-isobutoxyphenyl)-7-fluorenyl)-4,4,5,5-tetramethyl-1, Preparation of 3,2-dioxaborane (5)

1,1 '-bisdiphenylphosphinoferrocene dichloride palladium C80 mg, 0.11 mmol) was added to the compound (4) (1.35 g, 3.32 mmol), dipentyl diboron under N ₂ atmosphere. 1.26 g, 4.98 mmol), a mixture of potassium acetate (977 mg, 9.95 mmol) and 1,4-dioxane (30 mL). The reaction was heated to 80 ° C and allowed to react for 3 hours. After cooling to room temperature and removing the solvent under reduced pressure, the reaction mixture was poured into water and extracted with dichloromethane. The organic layer was dried over anhydrous magnesium sulfate, filtered, and evaporated. 1H NMR (300 MHz, DMSO): d = 1.34 (s, 12H), 7.53-7.71 (m, 11H), 7.79 (d, 1H, / = 8.16 Hz), 8.05 (d, 1H, / = 8.37 Hz) , 8.16 (d, 1H, / = 13.68 Hz), 8.39 (s, 1H) ppm. Example 4, Preparation of Cathode Cushioning Material 1

Palladium acetate (4.5 mg, 0.02 mmol), tricyclohexylphosphine (11.2 mg, 0.04 mmol) was added to compound 5 (289 mg, 0.64 mmol), 3-bromo-1,10-phenanthrene under N ₂ atmosphere. A mixture of porphyrin (150 mg, 0.58 mmol), aqueous sodium carbonate (2 M, 2 mL, 4 mmol), toluene (30 mL), and ethanol (8 mL). The reaction was heated to 100 ° C and stirred overnight. After cooling to room temperature, the reaction mixture was poured into water and extracted with dichloromethane. The organic layer was dried over anhydrous magnesium sulfate, filtered, and evaporated. 1H NMR (300 MHz, DMSO): d = 7.57-7.82 (m, 12H), 8.05-8.13 (m, 2H), 8.22-8.29 (m, 3H), 8.42 (d, 1H, / = 13.47 Hz), 8.53 (d, 1H, / = 8.1 Hz), 8.68 (s, 1H), 9.00 (s, 1H), 8.53 (d, 1H, J = 4.3 Hz), 9.63 (s, 1H) ppm. Example 5, Preparation of cathode buffer material 2

Tetrakis(triphenylphosphine)palladium (23 mg, 0.02 mmol) was added to compound 5 (331 mg, 0.73 mmol), 4,7-dibromo-2,1,3-benzothiazide under N ₂ atmosphere. A mixture of oxadiazole (93 mg, 0.32 mmol), aqueous sodium carbonate (2 M, 2 mL, 4 mmol), toluene (30 mL), and ethanol (4 mL). The reaction was heated to 90 ° C and stirred overnight. After cooling to room temperature, the reaction mixture was poured into water and extracted with dichloromethane. The organic layer was dried over anhydrous magnesium sulfate, filtered, evaporated, evaporated, 1H NMR (300 MHz, DMSO): d = 7.58-7.75 (m, 22H), 8.21-8.31 (m, 8H), 8.2 (d, 2H, / = 10.11 Hz), 8.74 (s, 2H) ppm. Example 6, Solubility Test for Novel Linear Cathode Buffer Molecular Materials

Quantitative solubility experiments were performed on the new cathode buffer materials 1 and 2. At room temperature, the solubility of Materials 1 and 2 in methanol and ethanol was greater than 10 mg mL ^_1 . Cathode buffer material ionic salt (compound 2) containing linear conjugated units reported in Liu et al., Chem. Asian J. 2012, 7, 2126-2132, heating Next, the solubility in methanol is about or less than S mg ml^ o Example 7, the thermal properties of the novel linear cathodic buffer layer molecular material

 Differential Scanning Calorimetry (DSC) was measured on a NETZSCH DSC 204 F1 thermal analyzer at a rate of 10 °C/min with nitrogen as the shielding gas.

 As shown in Figure la and Figure lb, differential scanning calorimetry shows that in the second round of heating, the new cathode buffer materials 1 and 2 exhibit significant glass transition, corresponding to glass transition temperatures of 115 ^ and 130 °, respectively. C. This indicates that the material can form a stable amorphous form. Example 8, Preparation Process and Characterization Results of Organic Electroluminescent Device Using Spin Coating Method:

In the preparation of organic electroluminescent devices, new cathode buffer materials 1 and 2 were selected as cathode buffer materials, and material 1 was doped with cesium carbonate (Cs ₂ C0 ₃ ); ionic salts were used ( Liu et al Chem. Asian J. 2012, 7, 2126-2132, Compound 2) as cathode buffer material for comparison; using laboratory existing green light molecular material (Chinese Patent Application No.: 200810218649.5) as luminescent material, device The detailed preparation process is as follows:

Indium tin oxide (ITO) conductive glass substrate with a resistance of 10-20 Ω/□ was ultrasonically cleaned by deionized water, acetone, detergent, deionized water and isopropyl alcohol. After drying in an oven, use PLASMA (oxygen). Plasma) treatment for 4 minutes. On the above treated ITO glass substrate, a PEDOT:PSS (Baytron P4083, available from Bayer AG) film having a thickness of about 40 nm was spin-coated, and the substrate was dried in a vacuum oven at 80 ° C for 8 hours to remove the solvent. A p-xylene solution of a light-emitting layer (green material, 45 nm) was spin-coated on a PEDOT:PSS layer in a nitrogen atmosphere glove box (Vacuum Atmosphere Co.) and dried at 100 ° C for 10 minutes. The new cathode buffer materials 1 and 2 of the ethanol solution are spin-coated on the light-emitting layer, dried at 80 ° C for 10 minutes; or the material 1 and Cs ₂ C0 ₃ doped (4: 1, η: η) in ethanol solution It is coated on the luminescent layer and dried at 80 ° C for 10 minutes; or a solution of the ionic salt in methanol is spin-coated on the luminescent layer. Finally, a metal Al (120 nm) cathode was vapor-deposited under a vacuum of 3 x 10 _ ⁴ Pa. The effective illuminating area of the device is 0.165 cm ² . Film thickness was measured using a Veeco Dektakl 50 step meter. The deposition rate of the metal electrode evaporation and its thickness were measured using a Sycon Instrument thickness/speed meter STM-100. Except that the spin coating process of the PEDOT:PSS film was completed in the atmosphere, all other steps were completed in a glove box in a nitrogen atmosphere.

The concentration of the new cathodic buffer material 1 and 2 for spin coating is 6 mg/mL, and the rotation speed is 2000 r/min. The concentration of material 1 in the solution for material 1 and Cs ₂ C0 ₃ doping spin coating is 6 mg/ mL, the speed is 2000 r/min; the concentration of the solution for ion salt spin coating is 2 mg/mL, and the rotation speed is 2000 r/min. And use a pure aluminum electrode device as a pair Compared to the device, the device structure is as follows:

 Device I: ITO/PEDOT: PSS/Green Light Material / Material 1/A1

Device Π: ITO/PEDOT: PSS/green material/material 1: Cs ₂ C0 ₃ /Al

 Device III: ITO/PEDOT: PSS/Green Light Material / Material 2/A1

 Device IV: ITO/PEDOT: PSS/Green Light Material / Ion Salt /A1

 Device V: ITO/PEDOT: PSS/Green Light Material / A1

As shown in Table 1, the organic electroluminescent device prepared by the spin coating method uses a cathode buffer layer material, and the ignition voltage is remarkably lowered, indicating that the electron injecting performance is good, and the current efficiency is greatly improved. The new Cathode Cushioning Materials 1 and 2 better improve the electroluminescence properties compared to the ionic salts (as shown in Table 1 and Figure 2). For example, in the organic electroluminescent device, reduce the current density, showed enhanced hole-blocking ability, respectively, so the maximum current efficiency of 4.2 cd A- ¹ B 4.5 cd A- Wo is 1.6 times when using ionic salt. After the new cathode buffer material 1 is doped with Cs ₂ C0 ₃ , the device performance is significantly improved. For example, in organic electroluminescent devices, the maximum current efficiency is 8.2 cd A- ¹ , which is 2.0 times that of material 1, indicating that material 1 is doped with cesium carbonate to form a doped or composite cathode buffer layer to improve device performance. . At the same time, the data in Table 1 shows that the use of a new cathode buffer material, with a small efficiency roll-off, is conducive to the improvement of device stability. Table 1: The cathode is a new type of cathode buffer material 1/A1, material l: Cs ₂ C0 ₃ /Al, material 2/Α1, ion salt/Al,

Preliminary characterization results of A1 organic electroluminescent devices

 Device Type Turn On Voltage Maximum Current Efficiency Current Efficiency [a]

(V) (cd A" ¹ ) (cd A" ¹ )

 Device I 4 4.2 3.9

 Device II 3.2 8.2 6.5

 Device m 2.6 4.5 4.4

 Device IV 2.8 2.7 2.1

 Device V 5.4 0.04 0.03

[a] Current efficiency at a current density of 20 mA cm ^-2 . Example 9, Preparation Process and Characterization Results of Organic Photovoltaic Cell Devices Using Spin Coating:

In the preparation process of organic photovoltaic cell devices, a new cathode buffer layer material 1 is selected as the cathode buffer layer material; DPP (TBFu) ₂ {Adv. Funct. Mater. 2009, 19, 3063-3069) is used for the organic photovoltaic cell Body Material, PC ₆₁ BM is the acceptor material of organic photovoltaic cells. The detailed preparation process of the device is as follows: Indium tin oxide (ITO) conductive glass substrate with resistance of 10-20Ω/□ is sequentially passed through deionized water, acetone, detergent Ultrasonic cleaning with deionized water and isopropanol. After drying in an oven, treat with PLASMA (oxygen plasma) for 4 minutes. On the above treated ITO glass substrate, a PEDOT:PSS (Baytron P4083, available from Bayer AG) film having a thickness of about 40 nm was spin-coated, and the substrate was dried in a vacuum oven at 80 ° C for 8 hours to remove the solvent. The active layer (DPP (TBFu) ₂ : PC ₆₁ BM, 3:2, 80 nm) in a chloroform solution was spin-coated on a PEDOT:PSS layer in a nitrogen atmosphere glove box (Vacuum Atmosphere Co.) and dried at 110 ° C. 10 minutes. The ethanol solution of the new cathode buffer material 1 was spin-coated on the active layer and dried at 80 ° C for 10 minutes. Finally, a metal Ag (60 nm) cathode was vapor-deposited under a vacuum of ³ x 10 ⁴ Pa. The effective illuminating area of the device is 0.165 cm ² . Film thickness was measured using a Veeco Dektakl 50 step meter. The deposition rate and thickness of the metal electrode evaporation were measured using a Sycon Instrument thickness/speed meter STM-100. Except that the spin coating process of the PEDOT:PSS film was completed in the atmosphere, all other steps were completed in a glove box in a nitrogen atmosphere.

 The new cathode buffer material 1 has a solution concentration of 0.5 mg/mL for spin coating and a rotational speed of 2000 r/min. A device coated with ethanol was used as a comparison device. The device structure is as follows:

Device I: ITO/PEDOT: PSS/DPP (TBFu) ₂ : PC ₆ iBM / Material 1 / Ag

Device II: ITO/PEDOT: PSS/DPP (TBFu) ₂ : PC ₆ iBM / Ethanol / Ag

As shown in Table 2 and Figure 3, the organic photovoltaic cell device fabricated by the spin coating method can significantly improve the energy conversion efficiency even after using the metal electrode silver with a high work function, using the cathode buffer layer material. For example, in an organic photovoltaic cell device, the energy conversion efficiency is 3.02%, which is 1.4 times that of ethanol, indicating that material 1 can effectively assist electron collection of the silver electrode and improve device performance. Table 2: Preliminary characterization results of organic photovoltaic cell devices with new cathode buffer materials 1/Ag, ethanol/Ag

Device Type Energy Conversion Efficiency (%) Short Circuit Current (mA cm- ² ) Open Circuit Voltage (V) Fill Factor Device 3.02 7.55 0.89 44.8 Device II 2.11 6.73 0.84 37.3

[a] Light intensity: 100 mW cm ^_2 .

Claims

claims 1. A type of alcohol-soluble cathode buffer layer molecular material containing triaryl phosphorus oxygen and nitrogen heterocyclic functional groups, which is characterized by having the following chemical structural formula: Among them, R ₃ ~ R43 are one of the following structures:

Among them, ₄ and ₅ are selected from alkyl chains or alkoxy chains with a carbon number of 1-18 or are any of the following structural units:

Among them, ₆ and ₇ are alkyl chains with carbon numbers of 1-18; The R ₂ is any one of the following structural units:

Among them, ₈ ~ 0 are selected from hydrogen atoms or from alkyl chains or alkoxy chains with a carbon number of 1-18. 3. The method for synthesizing a class of alcohol-soluble cathode buffer layer molecular materials containing triarylphosphorus oxygen and nitrogen heterocyclic functional groups according to claim 2, which is characterized in that it is synthesized using the following synthesis route:

Among them, X is Br or I. 4. The synthesis method according to claim 3, characterized in that it includes the following steps: 1) Using diphenylphosphine chloride as the reaction raw material, n-butyllithium is introduced to the group through the reaction at -78 °C to obtain the unoxidized bromine-containing target product, wherein when it contains ~1 ₄₃ , The palladium-catalyzed coupling reaction introduces an aryl group or a condensed ring aryl group; when R contains R44 and R ₄₅ , the fluorenone is catalyzed by methanesulfonic acid to introduce an aryl group or a condensed ring aryl group, or the fluorenone is introduced by potassium hydroxide. Catalytically introduce an alkyl chain or alkoxy chain with a carbon number of 1-18, wherein R46 and R47 catalyze the phenolic hydroxyl group with potassium hydroxide to introduce an alkyl chain or alkoxy chain with a carbon number of 1-18; 2) Using the unoxidized bromine-containing target product obtained in step 1), obtain an oxidized target product containing a phosphorus oxygen group and bromine through oxidation with hydrogen peroxide; 3) The bromine-containing oxidized target product obtained in step 2) is reacted with diboron divalerate through the action of a palladium catalyst to obtain the target product containing borate ester; 4) Couple the boronic acid ester-containing target product obtained in step 3) with the group R ₂ through a palladium-catalyzed coupling reaction to obtain the target product, wherein, when R ₂ contains ₈ or R _5Q , through tert-butanol Potassium is used to catalyze benzotriazole to introduce an alkyl chain or alkoxy chain with a carbon number of 1-18; when R ₂ contains R49, aluminum trichloride is used to catalyze the introduction of an alkyl chain with a carbon number of 1-18. base chain or alkoxy chain. 5. The synthetic method according to claim 3, characterized in that in step 3), the borate ester group is The palladium-catalyzed reaction is: the reactants are protected by inert gas, the reaction temperature range is 80-100 °C, the reaction time range is 2-12 hours, use 1,1 '-bisdiphenylphosphine ferrocene palladium dichloride is used as a catalyst for the reaction; Step 4) Coupling with R ₂ with electron-withdrawing properties through a palladium-catalyzed coupling reaction, the palladium-catalyzed coupling reaction is: Reactant Under the protection of inert gas, the reaction temperature range is 70-110 °C, the reaction time range is 8-36 hours, and the reaction is carried out using tetrakis (triphenylphosphine) palladium or a palladium acetate and tricyclohexylphosphine system as a catalyst. 6. Application of the cathode buffer material of claim 1 in electroluminescent display, lighting or organic photovoltaic cell devices.