Polyfluorene material as well as preparation method and application thereof

Abstract

The invention discloses a polyfluorene material as well as a preparation method and application thereof, and belongs to the field of organic photoelectric materials. The polyfluorene material has the following structural formula: # imgabs0 #, in the formula, R is selected from substituted or unsubstituted C1-C16 alkyl, substituted or unsubstituted C2-C16 alkenyl and substituted or unsubstituted C2-C16 alkynyl, and n is a repeating unit. The polyfluorene material prepared by the invention has excellent photoelectric properties, better blue light stability and higher luminous efficiency.

Description

Technical Field

[0001] The present invention belongs to the field of organic optoelectronic materials, and particularly relates to a polyfluorene material with good optoelectronic properties, a preparation method thereof, and applications thereof. Background Art

[0002] Since the discovery of conductive polyacetylene in 1977, polymer semiconductors have developed rapidly in the past forty-odd years and have been widely used in the fields of organic light-emitting diodes (OLEDs), organic field-effect transistors, organic photovoltaic cells, memory storage, and biological and chemical sensing. As a member of polymer semiconductors, polyfluorene materials themselves have deep blue light-emitting characteristics and relatively high fluorescence quantum efficiency, and have excellent development prospects in the field of organic electroluminescence. However, the wide bandgap of the blue light material itself limits the carrier mobility of the thin film and affects the performance of electroluminescence. Therefore, to achieve efficient and stable blue light-emitting devices, it is urgent to improve the structural design of polyfluorene materials to enhance the optoelectronic properties of the thin film. Summary of the Invention

[0003] The purpose of the present invention is to provide a polyfluorene material, a preparation method thereof, and applications thereof in view of the deficiencies of the prior art. The prepared polyfluorene material has more excellent optoelectronic properties, better blue light stability, and higher luminous efficiency.

[0004] To achieve the above purpose, the present invention adopts the following technical solutions: In the first aspect, a polyfluorene material is provided, which has a structural formula shown in Formula I: ; In the formula, R is selected from substituted or unsubstituted C1-C 16 alkyl, substituted or unsubstituted C2-C 16 alkenyl, substituted or unsubstituted C2-C 16 alkynyl, and n is a repeating unit.

[0005] In the second aspect, a preparation method of a polyfluorene material is provided, including: In the presence of an inert atmosphere and an alkaline substance, nucleophilic substitution reaction is carried out on Compound 1 and RX to generate Compound 2; , , In RX, the definition of R is the same as that in Formula I, and X is a methyl benzenesulfonate group or a trifluoromethanesulfonate group; In an inert atmosphere, Compound 2 is subjected to dehalogenative carbon-carbon coupling reaction under the action of an auxiliary agent and a catalyst to generate the polymer shown in Formula I.

[0006] The synthesis route is as follows:

[0007] Further, in the nucleophilic substitution reaction, the basic substance used is selected from potassium hydroxide, sodium hydroxide, sodium hydride or sodium tert-butoxide.

[0008] Further, in the nucleophilic substitution reaction, the organic solvent used is selected from N , N N,N'-dimethylformamide, N , N N,N'-dimethylacetamide or dimethyl sulfoxide.

[0009] Further, the temperature of the nucleophilic substitution reaction is 60 - 200 °C, and the reaction time is 24 - 48 h.

[0010] Further, the molar ratio of compound 1, RX and the basic substance is 1:(2.2 - 4):(2.5 - 4.5).

[0011] Further, in the nucleophilic substitution reaction, the inert atmosphere is nitrogen.

[0012] Further, the catalyst used in the dehalogenative carbon-carbon coupling reaction is Ni(COD)2.

[0013] Further, the auxiliary agent used in the dehalogenative carbon-carbon coupling reaction is bipyridine.

[0014] Further, in the dehalogenative carbon-carbon coupling reaction, the organic solvent used is selected from N , N one or more of N,N'-dimethylformamide, toluene and tetrahydrofuran; Further, the temperature of the dehalogenative carbon-carbon coupling reaction is 80 - 120 °C, and the reaction time is 24 - 96 h.

[0015] Further, in the dehalogenative carbon-carbon coupling reaction, the inert atmosphere is nitrogen.

[0016] Further, in the dehalogenative carbon-carbon coupling reaction, the molar ratio of compound 2, the catalyst and the auxiliary agent is 1:(1.2 - 2):(2 - 4).

[0017] Further, the preparation steps of compound 1 include: Subjecting 2,7-dibromofluorene-9-one and diphenylamine to a dehydration reaction under the action of an organic acid to form compound 1.

[0018] Among them, in the dehydration reaction of 2,7-dibromofluorene-9-one and diphenylamine, the organic acid used is methanesulfonic acid, benzenesulfonic acid or p-toluenesulfonic acid.

[0019] The reaction temperature of 2,7-dibromofluorene-9-one and diphenylamine is 100 - 180 °C, and the reaction time is 2 - 12 h; The molar ratio of 2,7-dibromofluorene-9-one to diphenylamine is 1:(4 - 6).

[0020] In a third aspect, there is provided an application of the polyfluorene material described in the first aspect in preparing a light-emitting layer of an organic electroluminescent device.

[0021] Compared with the prior art, the present invention has the following beneficial effects: By introducing a bis(diphenylamine) structure at the 9-position of the fluorene unit, the present invention improves the carrier mobility of the fluorene-based semiconductor. The prepared polyfluorene material has more excellent optoelectronic properties, better blue light stability and higher luminous efficiency. In addition, the preparation method of the present invention is simple and the raw materials are easily available. Description of the Drawings

[0022] Figure 1 is the nuclear magnetic resonance hydrogen spectrum of BDPAF in Example 1 of the present invention; Figure 2 is the nuclear magnetic resonance hydrogen spectrum of MN48 in Example 1 of the present invention; Figure 3 is the gel permeation chromatography of PN48 in Example 1 of the present invention; Figure 4 is the current-voltage-luminance (J-V-L) curve of the OLED prepared with PN48 in Example 1 of the present invention as the light-emitting layer; Figure 5 is the J-V-L curve of the OLED prepared with the commercial blue light polymer PFO as the light-emitting layer. Detailed Embodiments

[0023] The present invention will be further described below in conjunction with specific embodiments. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and cannot be used to limit the protection scope of the present invention. Embodiment

[0024] 1. Synthesis of BDPAF: The synthesis route is as follows:

[0025] Take 2 g (5.92 mmol) of 2,7-dibromofluorene ketone, 5 g (29.55 mmol) of diphenylamine, and 10 mL of methanesulfonic acid, and heat under reflux at 140 °C for 6 h. Cool to room temperature, add 100 mL of saturated sodium bicarbonate solution, extract with dichloromethane, dry and rotary evaporate. Purify with a petroleum ether:ethyl acetate mixed solvent (8:1) silica gel column to obtain 3.12 g of white solid (80% yield). Its nuclear magnetic resonance hydrogen spectrum (CDCl3, 400 MHz) is as Figure 1 shown. 11H NMR (400 MHz, Chloroform-d) δ 7.58 (d, J = 8.0Hz, 2H), 7.51 – 7.46 (m, 4H),7.27 – 7.24 (m, 4H), 7.10 – 7.03 (m, 8H), 6.94(dd, J = 14.1, 8.0 Hz, 6H); Mass spectrometry (m / z): 658.438.

[0026] The prepared fluorene-based compound BDPAF has a bis(diphenylamine) structure at the 9th position, which can significantly improve the carrier mobility of the fluorene-based semiconductor and is beneficial to the subsequent structural regulation of the fluorene-based semiconductor.

[0027] 2. Synthesis of MN48 The synthesis route is as follows: Take 1 g (1.52 mmol) of BDPAF, 1.2 g (3.52 mmol) of (2-tert-butyl octyloxy) 4-methylbenzenesulfonate, 0.25 g (4.46 mmol) of potassium hydroxide, and 20 mL of dimethyl sulfoxide. Under nitrogen protection, heat under reflux at 120 °C for 36 h. Cool to room temperature, add 100 mL of saturated brine, extract with dichloromethane, dry and rotary evaporate. Purify by silica gel column with a petroleum ether:dichloromethane mixed solvent (4:1) to obtain 1.16 g of white solid (77% yield). Its 1H nuclear magnetic resonance spectrum (CDCl3, 400 MHz) is as Figure 2 shown. 1 1H NMR (400 MHz, Chloroform-d) δ 7.55 (d, J = 8.0 Hz, 2H), 7.49(d, J = 1.6 Hz, 2H), 7.45 (dd, J = 8.1, 1.8 Hz, 2H), 7.26 (d, J = 2.2 Hz,4H), 7.05 (d, J = 7.6 Hz, 4H), 6.97 (d, J = 8.6 Hz, 6H), 6.77 (d, J = 8.9 Hz,4H), 3.55 (d, J = 7.2 Hz, 4H), 1.78 (dd, J = 12.1, 6.1 Hz, 2H), 1.33 – 1.18(m, 32H), 0.83 (dd, J = 8.2, 1.2 Hz, 12H); Mass spectrometry (m / z): 995.088.

[0028] 3. Synthesis of PN48 The synthesis route is as follows:

[0029] Take 1 g (1.00 mmol) of MN48, 0.5 g (3.31 mmol) of 2,2'-bipyridine, 0.33 g (1.20 mmol) of Ni(COD)2, N , N 5 mL of N,N'-dimethylformamide and 10 mL of toluene, heat under reflux at 85 °C for 72 h under nitrogen protection, then add 0.5 mL of bromobenzene and react for 12 h. Cool to room temperature, filter and wash 5 times with dichloromethane, and purify the filtrate with a neutral alumina column; concentrate the purified solution and add it to methanol, stir and settle, filter, and then extract and purify the solid with acetone as the extraction solvent by Soxhlet extraction to obtain 0.72 g of a pale yellow solid (86% yield). Its gel permeation chromatography (GPC) is as Figure 3 shown. GPC: Mn: 15.3 kDa, Mw: 31.6 kDa, PDI: 2.06.

[0030] Example 2 Preparation of a blue OLED with PN48 as the light-emitting layer by solution method The structure of the blue OLED prepared by the solution method is: ITO / PEDOT:PSS (30 nm) / PN48 (40 nm) / TPBi (20 nm) / LiF (1 nm) / Al (100 nm). First, ultrasonically wash the ITO glass with ethanol, dry it at 120 °C, and then treat it with an ultraviolet ozone plasma cleaner for 15 min; then spin-coat 30 nm thick PEDOT:PSS, anneal at 120 °C for 10 min, then spin-coat 40 nm thick PN48 and anneal at 80 °C for 10 min in a nitrogen atmosphere; transfer the device into the evaporation chamber, and evaporate TPBi (20 nm), LiF (1 nm), and Al (100 nm) in sequence under the condition of 5×10 -4 Pa. As shown in Table 1 and Figure 4 shown, the turn-on voltage of the fabricated device A is 4.4 V, the maximum brightness L max is 1562 cd / m 2 , and the maximum external quantum efficiency is 1.41%, and the CIE coordinates are (0.16, 0.04).

[0031] Under the same preparation conditions, for the OLED device fabricated with commercial blue polymer PFO as the light-emitting layer, the device structure is: ITO / PEDOT:PSS (30 nm) / PFO (40 nm) / TPBi (20 nm) / LiF (1 nm) / Al (100 nm). The turn-on voltage of the fabricated device B is 3.8 V, and the maximum brightness L max is 616 cd / m 2, the maximum external quantum efficiency is 0.53%, and the CIE coordinates are (0.16, 0.05), as shown in Table 1 and Figure 5 as follows.

[0032] Table 1 It can be seen that compared with the existing commercial blue-light polymer PFO, the polyfluorene material prepared by the present invention has more excellent optoelectronic properties, better blue-light stability and higher luminous efficiency.

[0033] The present invention has been disclosed in the above preferred embodiments, but it is not intended to limit the present invention. Any technical solution obtained by adopting an equivalent replacement or equivalent transformation scheme falls within the protection scope of the present invention.

Claims

1. A polyfluorene material, characterized in that, Having the structural formula shown in Formula I: ； Wherein, R is selected from substituted or unsubstituted C1-C 16 alkyl, substituted or unsubstituted C2-C 16 alkenyl, substituted or unsubstituted C2-C 16 alkynyl, and n is a repeating unit.

2. The preparation method of the polyfluorene material according to claim 1, wherein Including: In the presence of an inert atmosphere and a basic substance, subjecting Compound 1 and RX to a nucleophilic substitution reaction to form Compound 2; ， ， In RX, the definition of R is the same as in Formula I, and X is a methyl benzenesulfonate group or a trifluoromethanesulfonate group; In an inert atmosphere, subjecting Compound 2 to a dehalogenative carbon-carbon coupling reaction under the action of an auxiliary agent and a catalyst to form the polymer shown in Formula I.

3. The preparation method according to claim 2, characterized in that, The nucleophilic substitution reaction satisfies one or more of the following conditions: The basic substance used is selected from potassium hydroxide, sodium hydroxide, sodium hydride or sodium tert-butoxide; The organic solvent used is selected from N , N N,N'-dimethylformamide, N , N N,N'-dimethylacetamide or dimethyl sulfoxide; The reaction temperature is 60 - 200 °C; The reaction time is 24 - 48 h.

4. The preparation method according to claim 2, wherein In the nucleophilic substitution reaction, the molar ratio of Compound 1, RX and the basic substance is 1:(2.2 - 4):(2.5 - 4.5).

5. The preparation method according to claim 2, characterized in that, The dehalogenative carbon-carbon coupling reaction satisfies one or more of the following conditions: The catalyst used is Ni(COD)2; The auxiliary agent used is bipyridine; The organic solvent used is selected from N , N one or more of N,N'-dimethylformamide, toluene, and tetrahydrofuran; The reaction temperature is 80 - 120 °C; The reaction time is 24 - 96 h.

6. The preparation method according to claim 2, characterized in that, In the dehalogenative carbon-carbon coupling reaction, the molar ratio of Compound 2, the catalyst and the auxiliary agent is 1:(1.2 - 2):(2 - 4).

7. The preparation method according to claim 2, wherein, The preparation steps of Compound 1 include: Subjecting 2,7-dibromofluorene-9-one and diphenylamine to a dehydration reaction under the action of an organic acid to form Compound 1.

8. The preparation method according to claim 7, wherein, In the dehydration reaction of 2,7-dibromofluorene-9-one and diphenylamine, it satisfies one or more of the following conditions: The organic acid is methanesulfonic acid, benzenesulfonic acid or p-toluenesulfonic acid; The reaction temperature is 100 - 180 °C; The reaction time is 2 - 12 h.

9. The preparation method according to claim 7, characterized in that, In the dehydration reaction of 2,7-dibromofluorene-9-one and diphenylamine, the molar ratio of 2,7-dibromofluorene-9-one to diphenylamine is 1:(4 - 6).

10. Use of the polyfluorene material according to claim 1 in the preparation of a light-emitting layer of an organic electroluminescent device.

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