CN111574690A

CN111574690A - PLED polymer with high hole mobility and preparation method thereof

Info

Publication number: CN111574690A
Application number: CN202010544310.5A
Authority: CN
Inventors: 冯旗
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-06-15
Filing date: 2020-06-15
Publication date: 2020-08-25

Abstract

The invention belongs to the field of organic light-emitting display, and particularly relates to a PLED polymer with high hole mobility and a preparation method thereof. The invention provides a PLED polymer with high hole mobility, which has a structure shown in a formula (I). The invention also provides a preparation method of the PLED polymer with high hole mobility, which comprises the step of carrying out Suzuki coupling reaction on the compound shown in the formula (II) and 2,2' - (9, 9-dioctyl-9H-fluorene-2, 7-diyl) bis (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborane) to prepare the polymer shown in the formula (I). The PLED polymer with high hole mobility and the preparation method thereof provided by the invention solve the technical problem of low hole mobility of the existing PLED device.

Description

PLED polymer with high hole mobility and preparation method thereof

Technical Field

The invention belongs to the field of organic light-emitting display, and particularly relates to a PLED polymer with high hole mobility and a preparation method thereof.

Background

An organic electroluminescent device (PLED) is a light emitting element which is self-luminous, high-brightness, and full-color, and a phenomenon that electrons and holes are recombined to emit light in an organic light emitting layer under the action of an applied electric field to generate current light emission. The organic electroluminescent device has: the power consumption is low under low direct current voltage; the luminous brightness is high, and the efficiency is high; the luminous color is wide; the response speed is high; thin display parts and the like. Therefore, organic electroluminescence is one of the most competitive technologies in the field of flat panel displays in the future. In order to improve the stability of the PLED device and reduce power consumption, the selection of a suitable hole injection material is a key point of research. In recent years, inorganic compounds such as vanadium oxide, tungsten oxide and molybdenum oxide are tried to be used as a hole injection layer, and although the HOMO energy level of the materials is low and the open-circuit voltage of the materials can be close to 1.0V, the low hole mobility limits the short-circuit current of the device and influences the final electroluminescent efficiency of the PLED device.

Semiconductor photoelectricity, volume 25, No. 3, page 191, 2004, discloses a device in which an ITO electrode, a metal electrode, and a polymer film therebetween are sandwiched, and the polymer film adopts a blended layer of a polymer and other small molecule light-emitting materials, so as to improve the hole mobility of a PLED stacked device. However, in the process of manufacturing the device, the metal electrode film such as Al on the polymer functional layer needs to be formed by vacuum thermal evaporation. The vacuum evaporation metal electrode needs high-vacuum-degree vacuum equipment, so that the preparation method is complicated, the cost is high, and the hole mobility is low.

Therefore, the low hole mobility of the conventional PLED device is a technical problem to be solved by those skilled in the art.

Disclosure of Invention

It is an object of the present invention to provide a PLED polymer with high hole mobility.

It is another object of the present invention to provide a method for preparing a PLED polymer having high hole mobility.

The purpose of the invention is realized by the following scheme:

the invention provides a PLED polymer with high hole mobility, which has a structure shown in a formula (I):

wherein n is 500-.

The invention also provides a preparation method of the PLED polymer with high hole mobility, which comprises the following steps of carrying out Suzuki coupling reaction on a compound shown as a formula (II) and 2,2' - (9, 9-dioctyl-9H-fluorene-2, 7-diyl) bis (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborane) to prepare a polymer shown as a formula (I):

preferably, the time of the Suzuki coupling reaction is 12-48 h.

Preferably, the temperature of the Suzuki coupling reaction in the step 1 is 100 ℃.

Preferably, the compound represented by the formula (II) is prepared by the following steps:

step 1: carrying out bromination reaction on 4,4' -diiodobiphenyl to generate 2-bromo-4, 4' -diiodo-1, 1' -biphenyl;

step 2: carrying out nucleophilic substitution reaction on the 2-bromo-4, 4 '-diiodo-1, 1' -biphenyl and 3, 6-dioctylcarbazole to generate the compound shown in the formula (III)

And step 3: carrying out nucleophilic substitution reaction on the compound shown in the formula (III) and 2, 7-dibromo spiro [ fluorene-9, 2' -ethylene oxide ] to generate a compound shown in a formula (IV):

and 4, step 4: and (3) carrying out a coupling reaction on the compound shown in the formula (IV) and 1, 4-dioxane to generate a compound shown in a formula (II).

Preferably, the 2,2' - (9, 9-dioctyl-9H-fluorene-2, 7-diyl) bis (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborane) is prepared by the following steps:

step 1: 2, 7-dibromo-fluorene is subjected to electrophilic substitution reaction to generate 2, 7-dibromo-9, 9-dioctyl-fluorene;

step 2: and carrying out nucleophilic substitution reaction on the 2, 7-dibromo-9, 9-dioctyl-fluorene and bis pinacol borate to generate 2,2' - (9, 9-dioctyl-9H-fluorene-2, 7-diyl) bis (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborane).

Compared with the prior art, the invention has the following advantages and beneficial effects:

when the PLED polymer prepared by the embodiment of the invention is used as a single-hole device, the effective voltage of the PLED polymer prepared by the invention is higher than that of a PFO device along with the increase of current density, and the effective voltage of the PLED polymer is higher than that of the PFO deviceThe highest effective voltage reaches 7.56x10^-5cm²The higher the effective voltage of a single-hole device, the higher the hole transport efficiency.

In addition, the HOMO energy levels of the PLED polymer prepared by the invention are measured to be-5.38, -5.40, -5.39 and-5.39 eV respectively. And the LUMO energy levels are-3.39, -3.34, -3.35 and-3.36 eV respectively, and the low HOMO energy level and the high LUMO energy level can provide enough driving force for the effective separation of excitons in the PLED device, so that the hole mobility of the PLED device is greatly improved.

Drawings

FIG. 1 is a current density-effective voltage curve of PLED polymer having high hole mobility prepared by example of the present invention.

Detailed Description

The present invention will be described in further detail with reference to specific examples, which are not intended to limit the present invention in any manner. Reagents, methods and apparatus used in the present invention are conventional in the art unless otherwise indicated.

Example 1

Under the protection of argon, 4' -diiodobiphenyl (8.12g, 20mmol) and acetic acid (60ml) were added to a 150ml two-necked flask, and liquid bromine (2.31ml, 45mmol) dissolved in 30ml of acetic acid was added dropwise from a constant pressure dropping funnel under ice bath, and then the reaction solution was warmed to room temperature to react for 12 hours. After the reaction, excess liquid bromine was removed with aqueous sodium bisulfite solution, the product was extracted with dichloromethane (100ml), the organic phase was washed with saturated aqueous sodium chloride solution 4 times, dried, filtered, the solvent was dried by spinning, and the crude product was chromatographed on silica gel column using petroleum ether as eluent to give 2-bromo-4, 4 '-diiodo-1, 1' -biphenyl (7.56g, yield 78%) whose chemical reaction equation is:

example 2

Under the protection of nitrogen, 3, 6-dioctylcarbazole (3.91g, 10mmol), 5ml triethylamine, and trimethylamine hydrochloride (1) were added to a 100ml three-necked flask equipped with an isopiestic dropping funnel.0g, 10mmol) and 30ml dichloromethane. Cooled to 0 ℃ in an ice bath, p-toluenesulfonyl chloride (2.8g, 15mmol) was added and the reaction was continued for 2 hours in an ice bath. After the reaction, the mixture is extracted by dichloromethane, and the organic phase is washed by water and then is washed by anhydrous MgSO₄And (5) drying. The solvent was removed by rotary evaporation under reduced pressure, and the crude product was subjected to silica gel column chromatography using petroleum ether/ethyl acetate (volume ratio: 10:1) as an eluent to give the compound represented by the formula (III) (7.8g, yield 92.0%) whose chemical reaction formula is:

example 3

Under nitrogen, magnesium turnings (4.8g, 20mmol), the compound represented by the formula (III) (8.03g, 10mmol) and 50ml of THF were charged into a 250ml three-necked flask. Then 2, 7-dibromospiro [ fluorene-9, 2' -oxirane in 20ml THF was added](3.52g, 10mmol) while slowly heating to 75 ℃ to initiate the reaction, and the reaction system was reacted under reflux for 4 hours. To a further 250ml three-necked flask equipped with a constant pressure dropping funnel, ethyl formate (2.4g, 33mmol) and 100ml of THF were added under nitrogen and reacted at 25 ℃. The mixed solution after the reaction was transferred to a constant-pressure low-liquid funnel with a syringe, and 50ml of an ethyl formate solution was added dropwise. After the dropwise addition, standing the reaction solution for 12h, adding excessive methanol into the reaction solution to quench the reaction, pouring 100ml of saturated ammonium chloride aqueous solution into the reaction solution, extracting with dichloromethane, washing the organic phase with water, and then washing with anhydrous MgSO₄And (5) drying. The solvent was removed by rotary evaporation under reduced pressure, and the crude product was subjected to silica gel column chromatography using petroleum ether/ethyl acetate (20: 1 by volume) as an eluent to give the compound represented by the formula (IV) (11.1g, yield 87.0%) whose chemical reaction formula is:

example 4

To a 300ml two-necked flask, 1, 4-dioxane (8.81g, 100mmol), a compound represented by the formula (IV) (10.63g, 100mmol), sodium tert-butoxide (24.03g, 250mmol), palladium acetate (1.12g, 5mmol), tri-tert-butylphosphine (1.21g, 6mmol) and formic acid (150ml) were charged under a nitrogen atmosphere. The reaction was heated to 80 ℃ for 24 hours. After the reaction, the product was extracted with dichloromethane, washed three times with saturated aqueous sodium chloride solution, dried, filtered, and the solvent was evaporated to dryness with petroleum ether: column chromatography on silica gel with dichloromethane (volume ratio ═ 8: 1) as eluent gave the compound represented by formula (II) (85.5g, yield 70%) whose chemical reaction equation is:

example 5

2, 7-dibromo-fluorene (16.2g, 50mmol) and 200ml of dimethyl sulfoxide were sequentially added to a 500ml three-necked flask under nitrogen protection, and after stirring for 30 minutes, a 50 wt% aqueous NaOH solution was slowly added dropwise. After 2 hours, additional octyl bromide (21.25g, 110mmol) was added. After 6 reactions at room temperature, 100ml of dilute hydrochloric acid were added. The crude product is chromatographed by silica gel column with pure PE as eluent to obtain viscous liquid and is recrystallized by acetone to finally obtain the compound 2, 7-dibromo-9, 9-dioctyl-fluorene (45.62g, yield 84%), and the chemical reaction equation is as follows:

example 6

Under the protection of nitrogen, 2, 7-dibromo-9, 9-dioctyl-fluorene (32.85g, 60mmol), bis (pinacolato) borate (45.7g, 0.18mol), potassium acetate (17.67g, 0.18mol), catalyst 1,1' -bis (diphenylphosphino) ferrocene palladium chloride (4.90g, 6mmol) and 300ml dioxane were added into a three-necked flask, and the temperature was controlled at 90 ℃ for 24 hours. After the reaction was terminated, potassium acetate was filtered off, the organic phase was eluted with PE/DCM 4/1 (volume ratio) by column chromatography using 100-200 mesh and 200-300 mesh silica gel, and the purified crude product was recrystallized from hot ethanol to obtain 2,2' - (9, 9-dioctyl-9H-fluorene-2, 7-diyl) bis (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborane) (24.3g, yield 63%) having the chemical reaction equation:

example 7

A100 ml two-necked flask was charged with the compound represented by the formula (II) (0.52g, 0.5mmol), 2,2' - (9, 9-dioctyl-9H-fluorene-2, 7-diyl) bis (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborane) (0.4g, 0.5mmol), 7ml of toluene and 2ml of an aqueous potassium carbonate solution. After stirring to completely dissolve, the solution was purged with nitrogen by bubbling 8 times, and 10mg of Pd (PPh) was added₃)₄. Reacting at 100 ℃ for 48 hours under the protection of argon, cooling, pouring the reaction liquid into 200ml of methanol, extracting the collected precipitate in a Soxhlet extractor by using methanol, n-hexane and acetone respectively for 12 hours, dissolving the residual solid by using 100ml of chloroform, filtering by using a 0.45-micron polytetrafluoroethylene filter membrane, concentrating the obtained filtrate, precipitating into 300ml of methanol, filtering and drying to obtain the polymer P1(415mg, the yield is 86%) shown in the formula (I), wherein the reaction chemical formula is as follows:

example 8

This example differs from example 7 in that the reaction time was 36h, resulting in polymer P2(325 mg. yield 85%).

Example 9

This example differs from example 7 in that the reaction time was 24h, resulting in polymer P3(301mg, 86% yield).

Example 10

This example differs from example 7 in that the reaction time was 12h, resulting in polymer P4(254mg, 84% yield).

In summary, the invention prepares a single-hole device based on pure PFO and P1-P4, and the structure of the device is as follows: ITO/PEDOT PSS (40nm) Polymer (70nm)/MoO₃(10nm)/Al (120 nm). FIG. 1 is a current density-effective voltage curve of PLED polymer hole-forming devices prepared in examples 7-10 of the present invention, and it can be seen from FIG. 1 that the current density-effective voltage curves of P1-P4 are obtained after entering the ohmic regionThe relationship becomes J^1/2V and linearly increases, indicating better current stability. And with the increase of current density, the effective voltage of P1-P4 is higher than that of the PFO device, wherein P1 with the highest polymerization degree has the highest effective voltage and reaches 7.56x10^-5cm²The higher the effective voltage of a single-hole device, the higher the hole transport efficiency.

The PLED polymers prepared in examples 7-10 of the present invention were subjected to cyclic voltammetric measurements, and their electrochemical properties after correction according to the empirical formula and the oxidation potential of ferrocene (0.38V) are shown in Table 1:

TABLE 1 electrochemical Properties of the inventive Polymer P1-P4

Polymer and method of making same	Optical bandgap (eV)	HOMO(eV)	LUMO(ev)
				P1	2.08	-5.38	-3.39
P2	2.05	-5.40	-3.34
				P3	2.04	-5.39	-3.35
P4	2.04	-5.39	-3.36

As can be seen from Table 1, the HOMO levels of the PLED polymers prepared in examples 7 to 10 of the present invention were measured to be-5.38 eV, -5.40eV, -5.39eV, and-5.39 eV, respectively. And the LUMO energy levels are respectively-3.39 eV, -3.34eV, -3.35eV and-3.36 eV, and in conclusion, the low HOMO energy level and the high LUMO energy level can provide enough driving force for the effective separation of excitons in the PLED device, so that the hole mobility of the PLED device is greatly improved.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.

Claims

1. A PLED polymer with high hole mobility, characterized in that the structure is shown in formula (I):

wherein n is 500-.

2. A preparation method of a PLED polymer with high hole mobility is characterized by comprising the steps of carrying out Suzuki coupling reaction on a compound shown as a formula (II) and 2,2' - (9, 9-dioctyl-9H-fluorene-2, 7-diyl) bis (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborane) to prepare a polymer shown as a formula (I),

3. the method for preparing a PLED polymer with high hole mobility according to claim 2, wherein the time of the Suzuki coupling reaction is 12 to 48 hours.

4. The method for preparing a PLED polymer with high hole mobility according to claim 2 wherein the temperature of the Suzuki coupling reaction in step 1 is 100 ℃.

5. The method for preparing a PLED polymer with high hole mobility according to claim 2, wherein the compound represented by the formula (II) is prepared by the following steps:

step 2: carrying out nucleophilic substitution reaction on the 2-bromo-4, 4 '-diiodo-1, 1' -biphenyl and 3, 6-dioctylcarbazole to generate a compound shown as a formula (III):

and step 3: carrying out nucleophilic substitution reaction on the compound shown in the formula (III) and 2, 7-dibromo spiro [ fluorene-9, 2' -oxirane ] to generate a compound shown in a formula (IV),

6. The method for preparing a PLED polymer with high hole mobility according to claim 2 wherein the 2,2' - (9, 9-dioctyl-9H-fluorene-2, 7-diyl) bis (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborane) is prepared by the following steps: