Polymer containing bicarbazole unit and preparation method and application thereof

Abstract

The invention discloses a dicarbazole unit-containing polymer as well as a preparation method and application thereof. The chemical structural formula of the dicarbazole unit-containing polymer is as shown in formula (2). The carbazole unit has strong hole transport performance, and after a conjugate plane is increased to obtain a bicarbazole unit, the hole transport performance is further enhanced. The unit with better hole transport characteristic can make up the defect of hole mobility of common polymer materials, and has the advantage of high chemical stability. The dicarbazole unit-containing polymer has high potential as a hole transport layer in photoelectric devices such as a quantum dot light emitting diode and an organic light emitting diode, and different energy levels and mobility can be realized by adjusting the content of a polymerization unit. The polymer has good solubility, and can be used for preparing a large-area film through solution processing methods such as spin coating, ink-jet printing, printing and the like. # imgabs0 #

Description

Technical Field

[0001] The invention belongs to the field of optoelectronics, and in particular relates to a polymer containing bicarbazole units and a preparation method and application thereof. Background Art

[0002] In order to develop new information display technology to replace liquid crystal display (LCD), organic light emitting diode (OLED) appeared in people's field of vision. Organic light emitting diode has the characteristics of self-luminescence, low cost, wide viewing angle, low energy consumption, high efficiency, full-color display and flexible display, so it is considered to be a new generation of display technology that can replace liquid crystal display. In recent years, quantum dots have set off a wave of enthusiasm in academia and industry due to their unique properties, which is a major advancement for information technology. Quantum dot diode (QLED) is now considered to be the most promising display technology for the next generation due to its advantages such as good stability, adjustable emission color and high purity. Therefore, research and development of more complete organic light emitting diode and quantum dot light emitting diode technology is of great significance to the display and lighting fields.

[0003] Hole transport materials are important components of organic light-emitting diodes and quantum dot light-emitting diodes. High-performance hole transport materials need to meet the following conditions at the same time: (1) high optical transparency; (2) high carrier mobility; (3) appropriate energy level; and (4) good thermal stability and chemical stability.

[0004] The polymer hole transport materials represented by poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4'-(N-p-butylphenyl))] (TFB) have a large hole injection barrier and low hole mobility between the light-emitting layer materials, which limits the device performance of organic light-emitting diodes and quantum dot light-emitting diodes. Therefore, the development of units with strong hole transport properties is conducive to the synthesis of high-performance polymer hole transport materials and promotes the development of organic light-emitting diodes and quantum dot light-emitting diodes. Summary of the invention

[0005] In order to solve the shortcomings and deficiencies of the prior art, the primary purpose of the present invention is to provide a polymer containing a monomer of a bicarbazole unit. The monomer containing the bicarbazole unit has a larger conjugated plane and a stronger electron-donating ability, and can obtain a bicarbazole unit with different current transport properties. The introduction of the bicarbazole unit into the polymer has higher optical transparency and carrier mobility, and has greater potential as a hole transport polymer. Different energy levels and carrier mobility can also be achieved by adjusting the content of the polymerized unit. The polymer has good solubility and can be used to prepare large-area thin films by solution processing methods such as spin coating, inkjet printing, and printing.

[0006] Another object of the present invention is to provide a method for preparing the above polymer containing a bi-carbazole unit.

[0007] Another object of the present invention is to provide the application of the above polymer containing a bi-carbazole unit in the field of organic optoelectronics.

[0008] The object of the present invention is achieved by the following technical solutions:

[0009] A class of monomers containing a bi-carbazole unit, the chemical structural formula of which is shown in formula (1):

[0010]

[0011] In the formula, R is an alkyl group with 1 to 30 carbon atoms, a cycloalkyl group with 3 to 30 carbon atoms, an aromatic hydrocarbon group with 6 to 60 carbon atoms, or an aromatic heterocyclic group with 3 to 60 carbon atoms.

[0012] Further, the R is preferably an alkyl group with 1 to 30 carbon atoms, more preferably an alkyl group with 1 to 10 carbon atoms, and most preferably an isooctyl group.

[0013] Based on the carbazole unit, the present invention synthesizes the bi-carbazole unit through a coupling reaction to expand the conjugated length of the molecule and improve the stability of the molecule. The bi-carbazole unit has strong hole-transporting properties, and this unit with good hole-transporting characteristics can make up for the deficiency of the hole mobility of common polymer hole-transporting materials and improve the hole-transporting performance of polymer hole-transporting materials.

[0014] A class of polymers containing a bi-carbazole unit, the chemical structural formula of which is shown in formula (2):

[0015]

[0016] In the formula: x and y are the molar fractions of each unit component, satisfying: 0 < x < 1, 0 < y < 1, x + y = 1; n is the number of repeating units, n = 10 to 1000;

[0017] Ar is an aromatic hydrocarbon group with 6 to 60 carbon atoms or an aromatic heterocyclic group with 3 to 60 carbon atoms;

[0018] R is an alkyl group with 1 to 30 carbon atoms, a cycloalkyl group with 3 to 30 carbon atoms, an aromatic hydrocarbon group with 6 to 60 carbon atoms, or an aromatic heterocyclic group with 3 to 60 carbon atoms.

[0019] Further, the R is preferably an alkyl group with 1 to 30 carbon atoms, more preferably an alkyl group with 1 to 10 carbon atoms, and most preferably an isooctyl group.

[0020] Further, the Ar is preferably one or more of the following chemical structures or structural derivatives:

[0021]

[0022]

[0023] Here, R1 is an alkyl group having 1 to 30 carbon atoms, a cycloalkyl group having 3 to 30 carbon atoms, an aromatic hydrocarbon group having 6 to 60 carbon atoms, or an aromatic heterocyclic group having 3 to 60 carbon atoms.

[0024] The preparation method of the above-mentioned polymer containing bicarbazole units comprises the following steps: dissolving the monomer containing bicarbazole units described in formula (1) in an organic solvent, then adding a liquid bromine solution under light-proof conditions, stirring and reacting at room temperature, and obtaining a brominated monomer containing bicarbazole units after the reaction is completed; dissolving a compound containing an Ar structure and a brominated monomer containing bicarbazole units in an organic solvent, and then adding a tetraethylhydroxylamine aqueous solution, palladium acetate and tricyclohexylphosphine; heating to 80° C. for reaction for 24 hours, adding phenylboric acid for end-capping for 6 hours, and then adding bromobenzene for end-capping for 6 hours; after the reaction is completed, obtaining a polymer containing bicarbazole units described in formula (2);

[0025] The structural formula of the compound containing Ar structure is Ar is defined in the same manner as in formula (2).

[0026] Furthermore, the molar ratio of the compound containing an Ar structure to the brominated monomer containing a bicarbazole unit is 0-1:0-1, and the preferred molar ratio is 1:1.

[0027] Furthermore, the organic solvent is at least one of toluene and chloroform.

[0028] The above-mentioned polymer containing bicarbazole units has good solubility and can be dissolved in common organic solvents.

[0029] The above-mentioned polymer containing bicarbazole units is used in preparing the hole transport layer of organic light emitting diodes and quantum dot light emitting diodes.

[0030] Furthermore, the use of the above-mentioned polymer containing bicarbazole units to prepare the hole transport layer of the organic light-emitting diode and the quantum dot light-emitting diode comprises the following steps: dissolving the above-mentioned polymer containing bicarbazole units in an organic solvent, and then forming a film by spin coating, inkjet printing or printing to obtain the hole transport layer of the organic light-emitting diode and the quantum dot light-emitting diode; the organic solvent is xylene, tetrahydrofuran or chlorobenzene.

[0031] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0032] (1) The monomer containing bicarbazole units described in the present invention has strong hole transport performance, which can make up for the problem of low hole mobility of traditional hole transport polymers and obtain higher hole transport performance.

[0033] (2) The polymer containing bicarbazole units of the present invention has high optical transparency and carrier mobility, has great potential as a hole transport polymer, and can also achieve different energy levels by adjusting the content of the polymerized units. This type of polymer has good solubility and can be used to prepare large-area thin films by solution processing methods such as spin coating, inkjet printing, and printing. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The cyclic voltammetry curve of polymer P1 shows that the oxidation potential of polymer P1 is 1.13 V, the calibrated ferrocene oxidation potential is 0.42 V, and the calculated HOMO energy level of polymer P1 is -5.51 eV, which is between the commonly used hole injection layer and the light-emitting layer, and is suitable as a hole transport layer material.

[0035] Figure 2 The photoluminescence spectra of polymers P1 and P5 in the thin film state show that the emission peaks are both around 400nm, belonging to deep blue light emission. They have higher singlet energy levels and band gaps and can be used as hole transport layer materials for red, green and blue primary color light-emitting diodes. DETAILED DESCRIPTION

[0036] The present invention is further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0037] Unless otherwise specified, the reagents used in the examples can be purchased from the market.

[0038] Example 1: Preparation of Compound 2

[0039] (1) Preparation of 9-(2-ethylhexyl)carbazole

[0040] Under nitrogen protection, carbazole (1.67 g, 10 mmol), isooctane bromide (3.86 g, 20 mmol), potassium carbonate (4.14 g, 30 mmol) and 120 mL N, N-dimethylformamide were added to a 300 mL two-necked bottle and heated to 100 ° C for 12 hours. After the reaction was completed, the product was extracted with dichloromethane and washed five times with a saturated sodium chloride aqueous solution. After removing the organic phase solvent, the crude product was purified by column chromatography using petroleum ether as an eluent to obtain 2.53 g of a white solid with a yield of 90.7%. 1 H NMR, 13 C NMR, MS and elemental analysis results showed that the obtained compound was the target product.

[0041] (2) Preparation of Compound 1

[0042] 9-(2-ethylhexyl)carbazole (2.79 g, 10 mmol) was dissolved in 100 mL of chloroform, and then ferric chloride (4.87 g, 30 mmol) was added and reacted at room temperature for 24 hours. After the reaction was completed, the product was extracted with dichloromethane and washed five times with a saturated sodium chloride aqueous solution. After removing the organic phase solvent, the crude product was purified by column chromatography using petroleum ether: dichloromethane (3:1, v:v) as an eluent to obtain 2.45 g of a light yellow solid with a yield of 88.1%. 1 H NMR, 13 C NMR, MS and elemental analysis results showed that the obtained compound was the target product.

[0043] (3) Preparation of Compound 2

[0044] Under nitrogen protection, compound 1 (5.57 g, 10 mmol) was dissolved in 150 mL of chloroform. Under light-proof conditions, 20 mL of chloroform solution containing bromine (3.52 g, 22 mol) was added dropwise to the reaction, and the reaction was stirred at room temperature for 24 hours. Unreacted bromine was quenched with a small amount of sodium bisulfite, the product was extracted with dichloromethane, washed with saturated sodium chloride aqueous solution 3 times, and the organic phase solvent was dried by spin drying. The product was purified by silica gel chromatography, the eluent was petroleum ether: dichloromethane (4:1, v:v), and recrystallized with a mixed solvent of petroleum ether / tetrahydrofuran to obtain 5.46 g of a light yellow solid with a yield of 76.4%. 1 H NMR, 13 C NMR, MS and elemental analysis results showed that the obtained compound was the target product.

[0045] The chemical reaction equations for synthesizing compounds 1 to 2 are shown below:

[0046]

[0047] Example 2: Preparation of Compound P1

[0048] Under nitrogen protection, 2,7-bis(4,4,5,5-tetramethyl-1,3-dioxo-2-boryl)-9,9-dioctylfluorene (192.6 mg, 0.3 mmol) and compound 2 (214.4 mg, 0.3 mmol) were dissolved in 10 mL of toluene, and then tetraethylhydroxylamine aqueous solution (1 mL, wt% = 20%), palladium acetate (1 mg) and tricyclohexylphosphine (2 mg) were added; after heating to 80°C for 24 hours, the reaction mixture was added. Add phenylboronic acid (20 mg) to cap for 6 hours, then add bromobenzene (0.2 mL) to cap for 6 hours; stop the reaction, cool, precipitate the organic phase in methanol (300 mL), filter, dry, extract the crude product with methanol, acetone, and n-hexane, dissolve the polymer with toluene, and purify it by column chromatography with neutral alumina using toluene as eluent; concentrate the toluene solution of the polymer, precipitate it again in methanol solution, filter, and dry to obtain a light yellow-green fibrous polymer. 1 H NMR spectrum and elemental analysis confirmed that the target polymer was obtained. Gel permeation chromatography: Mn = 84 KDa, PDI = 2.11.

[0049] The synthetic chemical reaction equation of polymer P1 is shown below:

[0050]

[0051] Example 3: Synthesis of polymer P2

[0052] The synthesis method of polymer P2 is similar to that of P1. According to the method of Example 2, the reaction monomers are replaced with 2,7-bis(4,4,5,5-tetramethyl-1,3-dioxo-2-boryl)-N-9'-heptadecylcarbazole (197.3 mg, 0.3 mmol) and compound 2 (214.4 mg, 0.3 mmol). 1 H NMR spectrum and elemental analysis confirmed that the target polymer was obtained. Gel permeation chromatography: Mn = 91 KDa, PDI = 2.58.

[0053]

[0054] Example 4: Synthesis of polymer P3

[0055] The synthesis method of polymer P3 is similar to that of P1. According to the method of Example 2, the reaction monomers are replaced by compound 3 (189.4 mg, 0.3 mmol) and compound 2 (214.4 mg, 0.3 mmol). 1 H NMR spectrum and elemental analysis confirmed that the target polymer was obtained. Gel permeation chromatography: Mn = 50 KDa, PDI = 2.31.

[0056]

[0057] Example 5: Synthesis of polymer P4

[0058] The synthesis method of polymer P4 is similar to that of P1. According to the method of Example 2, the reaction monomers are replaced by compound 4 (188.8 mg, 0.3 mmol) and compound 2 (214.4 mg, 0.3 mmol). 1 H NMR spectrum and elemental analysis confirmed that the target polymer was obtained. Gel permeation chromatography: Mn = 49 KDa, PDI = 2.40.

[0059]

[0060] Example 6: Synthesis of polymer P5

[0061] The synthesis method of polymer P5 is similar to that of P1. According to the method of Example 2, the reaction monomers are replaced with 2,2'-[6,6,12,12-tetrahexyl-6,12-dihydroindeno[1,2-B]fluorene-2,8-bisboronic acid pinacol ester (252.9 mg, 0.3 mmol) and compound 2 (214.4 mg, 0.3 mmol). 1 H NMR spectrum and elemental analysis confirmed that the target polymer was obtained. Gel permeation chromatography: Mn = 87 KDa, PDI = 2.56.

[0062]

[0063] Example 7: Synthesis of polymer P6

[0064] The synthesis method of polymer P6 is similar to that of P1. According to the method of Example 2, the reaction monomers are replaced with 5,11-dioctyl-3,9-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolane-2-yl)-5,11-dihydroindole[3,2-B]carbazole (219.8 mg, 0.3 mmol) and compound 2 (214.4 mg, 0.3 mmol). 1 H NMR spectrum and elemental analysis confirmed that the target polymer was obtained. Gel permeation chromatography: Mn = 92 KDa, PDI = 2.61.

[0065]

[0066] Example 8: Synthesis of polymer P7

[0067] The synthesis method of polymer P7 is similar to that of P1. According to the method of Example 2, the reaction monomers were replaced with N,N-di(4-boronic acid pinesyl ester phenyl)-4-(1-methylpropyl)aniline (166.0 mg, 0.3 mmol) and compound 2 (214.4 mg, 0.3 mmol).

[0068] pass 1 H NMR spectrum and elemental analysis confirmed that the target polymer was obtained. Gel permeation chromatography: Mn = 90 KDa, PDI = 2.82.

[0069]

[0070] Example 9: Synthesis of polymer P8

[0071] The synthesis method of polymer P8 is similar to that of P1. According to the method of Example 2, the reaction monomers are replaced with 2,7-bis(4,4,5,5-tetramethyl-1,3-dioxo-2-boryl)-9,9-di-n-octylfluorene (96.3 mg, 0.15 mmol), 9-(2-ethylhexyl)-3,6-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9H-carbazole (79.70 mg, 0.15 mmol) and compound 2 (214.4 mg, 0.3 mmol). 1 H NMR spectrum and elemental analysis confirmed that the target polymer was obtained. Gel permeation chromatography: Mn = 93 KDa, PDI = 2.61.

[0072]

[0073] Example 10: Synthesis of polymer P9

[0074] The synthesis method of polymer P9 is similar to that of P1. According to the method of Example 2, the reaction monomers are replaced with compound 5 (204.2 mg, 0.3 mmol), 4-bromo-N-(4-bromophenyl)-N(4-vinylphenyl)aniline (25.7 mg, 0.06 mmol) and compound 2 (171.5 mg, 0.24 mmol). 1 H NMR spectrum and elemental analysis confirmed that the target polymer was obtained. Gel permeation chromatography: Mn = 90 KDa, PDI = 2.45.

[0075]

[0076] Example 11: Preparation of quantum dot light emitting diodes

[0077] The ITO substrate was ultrasonically cleaned with tetrahydrofuran, deionized water, and isopropanol (10 minutes each) and dried. After plasma treatment, PEDOT:PSS was spin-coated on the ITO surface. The resulting PEDOT:PSS film (~40nm) was baked at 150°C for 10min. The PEDOT:PSS-coated substrate was transferred in a glove box with oxygen and humidity <10ppm. Then, hole transport polymers (P1~P8) were spin-coated on the PEDOT:PSS layer. The resulting hole transport layer (~40nm) was baked at 100°C for 10min. Then, a 15nm red light quantum dot layer (CdSe / ZnS, octane solution) and a 40nm ZnO nanoparticle layer (ethanol solution) were prepared in turn and baked at 90°C for 10min. Finally, the device was transferred to a vacuum <1×10 -4 Aluminum electrodes were deposited in a vacuum chamber of Pa and encapsulated using epoxy resin and cover glass. The QLED devices based on polymers P1 to P8 as hole transport layers are numbered D1 to D8. At the same time, a QLED device based on poly[(9,9-dioctylfluorene-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl)diphenylamine)] (TFB, CAS: 220797-16-0) as a hole transport layer was also prepared as a control, numbered D0.

[0078] Table 1 Quantum dot light emitting device performance

[0079]

[0080]

[0081] As can be seen from Table 1, the devices based on P1 to P8 all exhibit lower turn-on voltage and higher current efficiency, and the efficiency of the prepared QLED devices is higher than that of the control hole transport polymer TFB. This shows that these polymers can be used as hole transport materials to prepare high-efficiency quantum dot light-emitting diodes.

[0082] Example 12: Preparation of organic light emitting diodes

[0083] Take the pre-made indium tin oxide (ITO) glass with a square resistance of 15Ω, clean it with acetone, detergent, deionized water and isopropanol ultrasonically, and plasma treat it for 10 minutes. Spin-coat a polyethoxythiophene (PEDOT:PSS) film doped with polystyrene sulfonic acid on ITO with a thickness of 40nm. The PEDOT:PSS film is dried in a vacuum oven at 80℃ for 8 hours. Then, spin-coat the hole transport polymer P9 on the PEDOT:PSS layer and anneal it at 200℃ for 30 minutes. Then, a xylene solution (1wt.%) of blue light emitting poly (9,9-dioctylfluorenyl-2,7-diyl) (PFO) is spin-coated on the surface of the P9 film with a thickness of 80nm as the light-emitting layer. Finally, a 1.5nm thick CsF layer and a 120nm thick metal Al layer were sequentially deposited on the light-emitting layer. The device structure was ITO / PEDOT:PSS / P9 / PFO / CsF / Al, and the device number was D9. At the same time, an OLED device without a hole transport layer was also prepared as a control. The device structure was ITO / PEDOT:PSS / PFO / CsF / Al, and it was numbered D10.

[0084] Table 2 Performance of polymer light emitting diode devices

[0085]

[0086] As can be seen from Table 2, the OLED device prepared using P9 as the hole transport layer reduces the device turn-on voltage and improves the device efficiency, indicating that the polymer can be used to prepare high-efficiency polymer light-emitting diodes.

[0087] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A polymer containing bicarbazole units, characterized in that: Its chemical structural formula is shown in Formula (2): In the formula: x and y are the molar fractions of each unit component, satisfying: 0 < x < 1, 0 < y < 1, x + y = 1; n is the number of repeating units, n = 10 - 1000; Ar is an aromatic hydrocarbon group with 6 - 60 carbon atoms or an aromatic heterocyclic group with 3 - 60 carbon atoms; R is an alkyl group with 1 - 30 carbon atoms, a cycloalkyl group with 3 - 30 carbon atoms, an aromatic hydrocarbon group with 6 - 60 carbon atoms or an aromatic heterocyclic group with 3 - 60 carbon atoms.

2. The polymer containing bicarbazole units according to claim 1, characterized in that: The said R is an alkyl group with 1 - 30 carbon atoms.

3. The polymer containing bicarbazole units according to claim 1, characterized in that: The said R is an alkyl group with 1 - 10 carbon atoms.

4. The polymer containing bicarbazole units according to claim 1, characterized in that: The said R is isooctyl.

5. A polymer containing bicarbazole units according to any one of claims 1 to 4, characterized in that: The said Ar is one or more of the following chemical structures or derivatives of the following structures: Wherein, R1 is an alkyl group with 1 - 30 carbon atoms, a cycloalkyl group with 3 - 30 carbon atoms, an aromatic hydrocarbon group with 6 - 60 carbon atoms or an aromatic heterocyclic group with 3 - 60 carbon atoms.

6. The method for preparing a polymer containing bicarbazole units according to any one of claims 1 to 5, characterized in that: Comprising the following steps: Dissolve the monomer containing a bi - carbazole unit as described in Formula (1) in an organic solvent, then add a bromine solution under light - shielding conditions, stir and react at room temperature, and after the reaction is completed, obtain a brominated monomer containing a bi - carbazole unit; Dissolve the compound containing an Ar structure and the brominated monomer containing a bi - carbazole unit in an organic solvent, then add an aqueous solution of tetraethylhydroxylamine, palladium acetate and tricyclohexylphosphine; heat to 80 °C and react for 24 hours, then add phenylboronic acid to cap for 6 hours, and then add bromobenzene to cap for 6 hours; after the reaction is completed, obtain the polymer containing a bi - carbazole unit as described in Formula (2); The structural formula of the compound containing Ar structure is The definition of Ar is the same as that of formula (2).

7. The preparation method according to claim 6, characterized in that: The molar ratio of the compound containing an Ar structure to the brominated monomer containing a bi - carbazole unit is 0 - 1:0 - 1; the organic solvent is at least one of toluene and chloroform.

8. The preparation method according to claim 6, characterized in that: The molar ratio of the compound containing an Ar structure to the brominated monomer containing a bi - carbazole unit is 1:

1.

9. Use of a polymer containing a bi - carbazole unit according to any one of claims 1 - 5 in the preparation of a hole - transporting layer of an organic light - emitting diode and a quantum dot light - emitting diode.

10. The use according to claim 9, characterized in that: The steps for using the polymer containing a bi - carbazole unit to prepare a hole - transporting layer of an organic light - emitting diode and a quantum dot light - emitting diode include: dissolving the polymer containing a bi - carbazole unit according to any one of claims 1 - 5 in an organic solvent, and then forming a film by spin - coating, ink - jet printing or printing, thereby obtaining the hole - transporting layer of the organic light - emitting diode and the quantum dot light - emitting diode; the organic solvent is xylene, tetrahydrofuran or chlorobenzene.

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