All-solution OLED device and preparation method thereof

Abstract

The invention relates to the technical field of OLED device preparation, in particular to an all-solution OLED device and a preparation method thereof. The preparation method of the all-solution OLED device comprises the following steps: preparing a hole injection layer and a hole transport layer on the surface of a substrate in sequence; spin-coating a luminescent material solution on the surface of the hole transport layer and then annealing to prepare a luminescent layer; sequentially preparing an electron transport layer, an electron injection layer and a cathode on the surface of the light-emitting layer to obtain an all-solution OLED device; the luminescent material in the luminescent material solution is V-MFCz, V-HFCz or V-SAFCz. According to the invention, the film prepared from V-MFCz, V-HFCz and V-SAFCz through a solution method has excellent photophysical properties, thermal stability and solvent resistance, the preparation of a dark blue light all-solution method non-doped OLED device is realized for the first time, and four organic layers from a hole injection layer to an electron transport layer are continuously deposited through an all-solution process.

Description

Technical Field

[0001] The present invention relates to the technical field of OLED device preparation, and in particular to a full-solution OLED device and a preparation method thereof. Background Art

[0002] Ever since the study of electroluminescence from organic materials began, organic light-emitting diodes (OLEDs) have been considered a promising technology for the next generation of information display and lighting. OLEDs are typically composed of multiple layers of different materials. This multilayer structure separates charge injection, charge transport, and light-emitting functions into different layers, significantly improving efficiency and lifespan. Currently, the main preparation processes for OLEDs are vacuum evaporation and solution methods. Generally speaking, the films prepared using the vacuum evaporation process are uniform and dense, with precise control of film thickness and no mutual influence between layers, but this increases manufacturing costs and the complexity of the manufacturing process. The solution preparation process, on the other hand, has a simple manufacturing process, low cost, and can achieve large-area manufacturing. However, when preparing devices using the multilayer solution method, there is a problem of corrosion of the lower film by the upper solvent, resulting in poor film quality and low device efficiency.

[0003] As the core of OLED devices, the research of luminescent materials is crucial. Compared to green and red emitting materials, devices based on blue and deep blue emitting materials do not meet the requirements for commercial application in terms of device efficiency, stability, and color purity. Therefore, the research and development of blue and deep blue luminescent materials has always been a focus of academia and industry. Currently, most research on the use of cross-linked materials in OLED devices focuses on hole transport materials, while there is less research on their direct modification on luminescent layer materials. To date, cross-linkable blue luminescent materials have remained largely unexplored.

[0004] Therefore, providing a deep blue light-emitting device prepared by a full solution method is of great significance to the technical field of OLED device preparation. Summary of the Invention

[0005] Based on the above content, the purpose of the present invention is to provide a full solution OLED device and a preparation method thereof.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] One of the technical solutions of the present invention is a method for preparing a full solution OLED device, comprising the following steps:

[0008] A hole injection layer and a hole transport layer are sequentially prepared on the surface of the substrate;

[0009] preparing a light-emitting layer by spin-coating a light-emitting material solution on the surface of the hole transport layer and then annealing;

[0010] Sequentially preparing an electron transport layer, an electron injection layer, and a cathode on the surface of the light-emitting layer to obtain the full-solution OLED device;

[0011] The luminescent material in the luminescent material solution is V-MFCz, V-HFCz or V-SAFCz;

[0012] The V-MFCz is 9,9'-((9,9-dimethyl-9H-fluorene-2,7-diyl)bis(4,1-phenylene))bis(3-vinyl-9H-carbazole), and the structural formula is

[0013] The V-HFCz is 9,9'-((9,9-dihexyl-9H-fluorene-2,7-diyl)bis(4,1-phenylene))bis(3-vinyl-9H-carbazole), and the structural formula is

[0014] The V-SAFCz is 10-phenyl-2',7'-bis(4-(3-vinyl-9H-carbazol-9-yl)phenyl)-10H-spiro[acridine-9,9'-fluorene], and the structural formula is

[0015] In a preferred embodiment of the present invention, the hole injection layer is a PEDOT:PSS thin film with a thickness of 30 to 40 nm.

[0016] In a preferred embodiment of the present invention, the hole transport layer is a TFB thin film with a thickness of 5 to 15 nm.

[0017] In a preferred embodiment of the present invention, the electron transport layer is a 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene thin film with a thickness of 30 to 50 nm.

[0018] In a preferred embodiment of the present invention, the electron injection layer is a lithium fluoride thin film with a thickness of 0.5 to 1.5 nm.

[0019] In a preferred embodiment of the present invention, the cathode is an aluminum thin film with a thickness of 80 to 200 nm.

[0020] In a preferred embodiment of the present invention, the hole injection layer, hole transport layer and electron transport layer are all prepared by spin coating followed by annealing; the electron injection layer and cathode are prepared by physical vapor deposition.

[0021] In a preferred embodiment of the present invention, the concentration of the luminescent material solution is 10-20 mg / mL, and the solvent is chlorobenzene; after the spin coating is completed, the process further includes annealing at 180-300° C. for 30 minutes in an argon atmosphere.

[0022] In a preferred embodiment of the present invention, the thickness of the light-emitting layer is 40 nm.

[0023] The second technical solution of the present invention is a full-solution OLED device prepared according to the above preparation method.

[0024] The present invention discloses the following technical effects:

[0025] The preparation of organic light-emitting diodes (OLEDs) by the full solution method is of great significance for the application of large-area OLED displays. In order to realize the preparation of OLED devices by the full solution method, the present invention introduces ethylene as a cross-linking group, fluorene or spirofluorene as the mother core, and carbazole as the electron-donating group to design and synthesize three thermally cross-linked luminescent materials V-MFCz, V-HFCz and V-SAFCz, and study their basic properties such as photophysical properties, morphological stability and thermodynamic properties. Using the three molecules V-MFCz, V-HFCz and V-SAFCz as pure light-emitting layers, the non-doped devices all show deep blue light emission. The emission wavelength, maximum current efficiency (CE), power efficiency (PE), external quantum efficiency (EQE) and CIE coordinates of the non-doped blue light full solution processing device based on V-MFCz are 440nm, 1.20cdA -1 , 0.58lm W -1 , 0.73% and (0.16, 0.08). The emission wavelength, maximum current efficiency (CE), power efficiency (PE), external quantum efficiency (EQE) and CIE coordinates of the non-doped blue light full solution processing device based on V-HFCz are 443nm, 2.28cdA -1 , 1.17lmW -1 , 1.72% and (0.16, 0.09). The emission wavelength, maximum current efficiency (CE), power efficiency (PE), external quantum efficiency (EQE) and CIE coordinates of the non-doped blue light all-solution processing device based on V-SAFCz are 444nm, 3.13cdA -1 , 1.60lmW -1 , 1.91% and (0.17, 0.09). These results provide a basis and ideas for the multilayer solution processing of undoped deep blue light-emitting devices.

[0026] The thin films of V-MFCz, V-HFCz and V-SAFCz prepared by the solution method have excellent photophysical properties, thermal stability and solvent resistance. The present invention realizes the preparation of deep blue light non-doped OLED devices by the full solution method for the first time, in which the four organic layers from the hole injection layer to the electron transport layer are continuously deposited by the full solution process. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 Compound V-MFCz (Solvent: Chloroform-d) 1 HNMR spectrum.

[0029] Figure 2 For compound V-HFCz (solvent: chloroform-d) 1 HNMR spectrum.

[0030] Figure 3 Compound V-SAFCz (Solvent: Chloroform-d) 1 H NMR spectrum.

[0031] Figure 4 The optimized ground state configurations and frontier molecular orbitals of compounds V-MFCz, V-HFCz and V-SAFz.

[0032] Figure 5 UV-vis absorption (a) and PL spectra (b) of V-MFCz, V-HFCz and V-SAFCz films before cross-linking (the solid line in the figure refers to the film obtained by the preparation method of Example 2 without annealing) and after cross-linking (the dotted line in the figure refers to the film obtained by annealing according to the preparation method of Example 2); UV photoelectron energy spectra of V-MFCz (c) V-HFCz (d) V-SAFCz (e) cross-linked films (referring to the film obtained by annealing according to the preparation method of Example 2).

[0033] Figure 6 TGA curves of V-MFCz (a), V-HFCz (b) and V-SAFCz (c); DSC curves of V-MFCz (d), V-HFCz (e) and V-SAFCz (f).

[0034] Figure 7 Solvent resistance of V-MFCz, V-HFCz and V-SAFCz films at different temperatures.

[0035] Figure 8 FTIR spectra of V-MFCz (a), V-HFCz (b) and V-SAFCz (c) before and after cross-linking; solvent resistance of V-MFCz (d), V-HFCz (e) and V-SAFCz (f) cross-linked films to different solvents.

[0036] Figure 9 XRD patterns of V-MFCz, V-HFCz and V-SAFCz films before and after cross-linking.

[0037] Figure 10 Contact angles of V-MFCz(a), V-HFCz(b), and V-SAFCz(c) cross-linked films with toluene; contact angles of V-MFCz(d), V-HFCz(e), and V-SAFCz(f) cross-linked films with water.

[0038] Figure 11 Surface morphologies of V-MFCz film before (a) and after (b) cross-linking; surface morphologies of V-HFCz film before (c) and after (d) cross-linking; surface morphologies of V-SAFCz film before (e) and after (f) cross-linking.

[0039] Figure 12 Energy level diagram (a) of V-MFCz, V-HFCz and V-SAFCz full solution devices; EL spectrum (b); JVL curve (c); CE-L-PE curve (d); EQE-L curve (e); CIE coordinate diagram (f).

[0040] Figure 13 EL spectra of V-MFCz device (a), V-HFCz device (b), and V-SAFCz device (c) at different voltages. DETAILED DESCRIPTION

[0041] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0042] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the stated range, is also encompassed within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0043] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0044] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0045] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0046] The technical solutions described in the present invention are conventional solutions in the art unless otherwise specified. All reagents and solvents used in synthesis and measurement were purchased from commercial suppliers and used without further purification unless otherwise specified. The technical solutions provided by the present invention are described in detail below with reference to the examples, but these examples should not be construed as limiting the scope of protection of the present invention.

[0047] Example 1

[0048] This embodiment provides methods for preparing three thermally cross-linked luminescent materials: 9,9'-((9,9-dimethyl-9H-fluorene-2,7-diyl)bis(4,1-phenylene))bis(3-vinyl-9H-carbazole) (V-MFCz), 9,9'-((9,9-dihexyl-9H-fluorene-2,7-diyl)bis(4,1-phenylene))bis(3-vinyl-9H-carbazole) (V-HFCz), and 10-phenyl-2',7'-bis(4-(3-vinyl-9H-carbazol-9-yl)phenyl)-10H-spiro[acridine-9,9'-fluorene] (V-SAFCz). The steps are as follows:

[0049] 3.22 g (10.0 mmol) of 9-(4-bromophenyl)carbazole and 50 mL of anhydrous N,N-dimethylformamide were added to a 250 mL two-necked flask and cooled to 0°C in an ice-water bath. Under argon protection, 13.72 mL (150 mmol) of phosphorus oxychloride was slowly added dropwise to the flask and stirred at room temperature for 2 hours. The temperature was then raised to 90°C and stirred under reflux for 20 hours. After the reaction of 9-(4-bromophenyl)carbazole was completed, the reaction solution was poured into ice water and sodium hydroxide solution (1 mol·L) was added. -1 ) to neutral pH. Filter through a Buchner funnel, and extract the filter cake with 100 mL of dichloromethane. After the extract was evaporated to remove the solvent under reduced pressure, it was separated and purified using silica gel column chromatography (eluent: petroleum ether: dichloromethane v:v = 2:1) to obtain 2.45 g of a white solid with a yield of 69.8%. 1H NMR (400MHz, Chloroform-d) δ10.13(s,1H),8.67(s,1H),8.21(d,J=7.6Hz,1H),7.96(d,J=8.5Hz,1H),7.78(d,J=8.6Hz,2H),7.52–7.36(m,6H).

[0050] Synthesis of 9,9'-((9,9-dimethyl-9H-fluorene-2,7-diyl)bis(4,1-phenylene))bis(9H-carbazole-3-carbaldehyde): 1.1 g (3.14 mmol) of 9-(4-bromophenyl)-9H-carbazole-3-carbaldehyde, 0.61 g (1.37 mmol) of 9,9-dimethylfluorene-2,7-diboronic acid pinacol ester, and anhydrous potassium carbonate (2 mol·L) were added to a 250 mL two-necked flask. -1 ), 0.24 g (0.2 mmol) of tetrakis(triphenylphosphine)palladium, and 1,4-dioxane:water (90 mL:22.5 mL). Under argon protection, the oil bath was heated to 120°C and stirred for 48 hours. The reaction was monitored by silica gel thin-layer chromatography (developing solvent: petroleum ether: dichloromethane v:v = 1:6) to determine the complete reaction of 9,9-dimethylfluorene-2,7-diboronic acid pinacol ester. After washing with 50 mL of saturated brine to remove the palladium catalyst, the product was extracted three times with 50 mL of dichloromethane. The organic phase was dried over anhydrous sodium sulfate, filtered, and the solvent was evaporated under reduced pressure. Finally, the crude product was separated and purified by silica gel column chromatography (eluent: petroleum ether: dichloromethane v:v = 1:3) to obtain 0.565 g of a white solid with a yield of 56.5%. 1 H NMR(400MHz,Chloroform-d)δ10.15(s,2H),8.71(d,J=1.6Hz,2H),8.25(d,J=7.8Hz,2H),8.06–7.85(m,8H),7.80 (d,J=1.7Hz,2H),7.74(dd,J=7.8,1.7Hz,2H),7.70–7.48(m,10H),7.41(ddd,J=8.0,5.7,2.4Hz,2H),1.68(s,6H).

[0051] Synthesis of 9,9'-((9,9-dihexyl-9H-fluorene-2,7-diyl)bis(4,1-phenylene))bis(9H-carbazole-3-carbaldehyde): 1.4 g (4 mmol) of 9-(4-bromophenyl)-9H-carbazole-3-carbaldehyde, 0.97 g (1.67 mmol) of 2,2'-(9,9-dihexyl-9H-fluorene-2,7-diyl)bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolane), anhydrous potassium carbonate (2 mol·L) and 1,4-dimethyl-2,4-dioxaborolane were added to a 250 mL two-necked flask. -1), 0.28 g (0.25 mmol) of tetrakis(triphenylphosphine)palladium, and 1,4-dioxane:water (90 mL:22.5 mL). Under the protection of argon gas, the oil bath was heated to 120°C and stirred for 48 hours. After monitoring the completion of the reaction by silica gel thin-layer chromatography (developing solvent: petroleum ether: dichloromethane v:v = 1:2), 50 mL of saturated brine was added to wash and remove the palladium catalyst. The product was extracted three times with 50 mL of dichloromethane. The organic phase was dried over anhydrous sodium sulfate, filtered, and the solvent was evaporated under reduced pressure. Finally, the crude product was separated and purified by silica gel column chromatography (eluent: petroleum ether: dichloromethane v:v = 2:1) to obtain 1.1 g of a white solid with a yield of 75.0%. 1 H NMR (400MHz, Chloroform-d) δ10.15(s,2H),8.71(s,2H),8.25(s,2H),8.00(s,2H),7.96(d,J=8.8Hz,4H),7.89(d,J=7.6Hz,2H),7.73(dd,J=7.6,1.7Hz ,2H),7.71–7.67(m,6H),7.56(d,J=8.4Hz,2H),7.50(s,4H),7.41(td,J=5.8 ,3.0Hz,2H),2.14(d,J=7.8Hz,4H),1.26(s,4H),1.15(s,12H),0.79(s,6H).

[0052] Synthesis of 2',7'-dibromo-10-phenyl-10H-spiro[acridine-9,9'-fluorene]: 3.23 g (10 mmol) of 2-bromotriphenylamine was added to a 100 mL three-necked flask. The flask was repeatedly evacuated and filled with argon three times. 40 mL of anhydrous tetrahydrofuran was added, and the cryogenic reactor was cooled to -78°C. 4.8 mL of n-butyllithium (n-BuLi, 2.5 M in hexane, 12 mmol) was slowly added via syringe, and stirring was continued at -78°C for 1 hour. A solution of 3.70 g (11 mmol) of 2,7-dibromofluorenone dissolved in 20 mL of tetrahydrofuran was slowly added dropwise to the flask. After 1 hour, the mixture was allowed to react at room temperature overnight. After the reaction was completed by monitoring by silica gel thin layer chromatography (developing solvent: petroleum ether: dichloromethane v:v=5:1), 5 mL of deionized water was added to quench the reaction, and 30 mL of dichloromethane was extracted three times. The organic phase was dried over anhydrous sodium sulfate, filtered, and evaporated to remove the solvent under reduced pressure. The crude product was separated by silica gel column chromatography to obtain a yellow solid (eluent: petroleum ether: dichloromethane V:V =3:1). The resulting yellow solid was dissolved in 50 mL of glacial acetic acid and 5 mL of concentrated hydrochloric acid (36%) and refluxed at 120°C for 5 h. The mixture was cooled to room temperature, and the precipitated solid was filtered. The filter cake was washed with petroleum ether to obtain 3.64 g of a white solid with a yield of 64%. 1H NMR (400MHz, Chloroform-d) δ7.72(t,J=7.7Hz,2H),7.66–7.58(m,3H),7.55–7.44(m,6H),7.01–6.93(m,2H),6.66–6.58(m,2H),6.38(d,J=11.7Hz,4H).

[0053] Synthesis of the intermediate 10-phenyl-2',7'-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-10H-spiro[acridine-9,9'-fluorene]: To a 250 mL two-necked flask were added 3.50 g (6.19 mmol) of 2',7'-dibromo-10-phenyl-10H-spiro[acridine-9,9'-fluorene], 6.29 g (24.77 mmol) of bis(pinacolato)boronate, 0.68 g (0.93 mmol) of [1,1-bis(diphenylphosphino)ferrocene]palladium dichloride, 4.86 g (49.53 mmol) of potassium acetate, and 100 mL of anhydrous 1,4-dioxane. Under argon, the mixture was heated to 80°C in an oil bath and stirred for 10 h. After monitoring the reaction completion by silica gel thin-layer chromatography (developing solvent: petroleum ether: dichloromethane v:v = 1:5), 50 mL of saturated brine was added to wash and remove the palladium catalyst. The product was extracted three times with 80 mL of dichloromethane. The organic phase was dried over anhydrous sodium sulfate, filtered, and the solvent was evaporated under reduced pressure. Finally, the crude product was separated and purified by silica gel column chromatography (eluent: petroleum ether: dichloromethane v:v = 1:3) to obtain 3.95 g of a white solid in a yield of 96.8%. 1 HNMR(400MHz,Chloroform-d)δ7.89(s,2H),7.83(d,J=4.6Hz,4H),7.73(d,J=7.7Hz,2H),7. 63–7.55(m,3H),6.93(d,J=7.1Hz,2H),6.58–6.52(m,2H),6.42–6.35(m,4H),1.31(s,24H).

[0054] Synthesis of intermediate 9,9'-((10-phenyl-10H-spiro[acridine-9,9'-fluorene]-2',7'-diyl)bis(4,1-phenylene))bis(9H-carbazole-3-carbaldehyde): 1.4 g (4 mmol) of 9-(4-bromophenyl)-9H-carbazole-3-carbaldehyde, 1.1 g (1.67 mmol) of 10-phenyl-2',7'-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-10H-spiro[acridine-9,9'-fluorene], anhydrous potassium carbonate (2 mol·L) and 10-nitropropane were added in sequence. -1), 0.29 g (0.25 mmol) of [1,1-bis(diphenylphosphino)ferrocene]palladium dichloride, and toluene:water (60 mL:12 mL). Under the protection of an argon atmosphere, the oil bath was heated to 120°C and stirred for 48 hours. After monitoring the completion of the reaction by silica gel thin-layer chromatography (developing solvent: petroleum ether: dichloromethane v:v = 1:7), 50 mL of saturated brine was added to wash and remove the palladium catalyst. The product was extracted three times with 50 mL of dichloromethane, and the organic phase was dried over anhydrous sodium sulfate, filtered, and evaporated to remove the solvent under reduced pressure. Finally, the crude product was separated and purified by silica gel column chromatography (eluent: petroleum ether: dichloromethane v:v = 1:5) to obtain 0.95 g of a white solid with a yield of 60.0%. 1 HNMR(400MHz,Chloroform-d)δ10.13(s,2H),8.69(s,2H),8.22(d,J=7.7Hz,2H),8.00(d,J=5.1Hz ,2H),7.97(d,J=5.5Hz,3H),7.84(d,J=8.2Hz,4H),7.79(d,J=7.6Hz,2H),7.72(t,J=7.9Hz,3H),7 .60(d,J=8.7Hz,4H),7.54(d,J=6.8Hz,3H),7.49(d,J=3.9Hz,4H),7.44(d,J=8.1Hz,2H),7.40(d, J=7.4Hz,2H),7.00–6.98(m,2H),6.68–6.66(m,2H),6.61(d,J=9.6Hz,2H),6.44(d,J=9.7Hz,2H).

[0055] Synthesis of compound V-MFCz: 3.66 g (10.23 mmol) of methyltriphenylphosphonium bromide, 1.15 g (10.23 mmol) of potassium tert-butoxide and 50 mL of anhydrous tetrahydrofuran were added to a 100 mL two-necked flask and placed in an ice-water bath for 2 h to generate a Wittig reagent; 1.5 g (2.05 mmol) of 9,9'-((9,9-dimethyl-9H-fluorene-2,7-diyl)bis(4,1-phenylene))bis(9H-carbazole-3-carbaldehyde) and 50 mL of anhydrous tetrahydrofuran were added to a 250 mL two-necked flask. After evacuating and purging the air three times, the Wittig reagent was transferred to a 250 mL two-necked flask using a 10 mL syringe and heated to 65°C under argon protection for 20 h. After monitoring the reaction completion by silica gel thin-layer chromatography (developing solvent: petroleum ether:dichloromethane v:v = 2:1), 5 mL of deionized water was added to quench the reaction, followed by extraction three times with ethyl acetate, and the solvent was evaporated under reduced pressure. The crude product was separated and purified by alumina column chromatography (eluent: petroleum ether:dichloromethane v:v = 10:1) and recrystallized from ethyl acetate and n-hexane to obtain 0.84 g of a white powder in a 56.5% yield.1 HNMR(400MHz,Chloroform-d)δ8.18(d,J=8.4Hz,4H),7.97–7.87(m,6H),7.79(s,2H),7.70(dd,J=18.4,8.9Hz,6H),7.56(d,J=10.3Hz,2 H),7.52–7.42(m,6H),7.32(t,J=6.8Hz,2H),6.95(dd,J=17.5,10.9Hz,2H),5.82(d,J=17.5Hz,2H),5.24(d,J=11.0Hz,2H),1.67(s,6H).

[0056] Compound V-MFCz (Solvent: Chloroform-d) 1 HNMR spectrum Figure 1 shown.

[0057] Synthesis of compound V-HFCz: 3.68 g (10.31 mmol) of methyltriphenylphosphonium bromide, 1.16 g (10.31 mmol) of potassium tert-butoxide and 50 mL of anhydrous tetrahydrofuran were added to a 100 mL two-necked flask and placed in an ice-water bath for 2 h to generate a Wittig reagent; 1.8 g (2.06 mmol) of 9,9'-((9,9-hexylmethyl-9H-fluorene-2,7-diyl)bis(4,1-phenylene))bis(9H-carbazole-3-carbaldehyde) and 50 mL of anhydrous tetrahydrofuran were added to a 250 mL two-necked flask, and after evacuating and purging three times, the Wittig reagent was transferred to a 250 mL two-necked flask with a 10 mL syringe and heated to 65°C under argon protection for 20 h. After monitoring the reaction completion by silica gel thin-layer chromatography (developing solvent: petroleum ether:dichloromethane v:v = 3:1), 5 mL of deionized water was added to quench the reaction, followed by extraction three times with ethyl acetate, and the solvent was evaporated under reduced pressure. The crude product was separated and purified by alumina column chromatography (eluent: petroleum ether:dichloromethane v:v = 15:1) and recrystallized from ethyl acetate and n-hexane to obtain 1.34 g of a white powder in a yield of 74.8%. 1H NMR(400MHz,Chloroform-d)δ8.20–8.16(m,4H),7.93(d,J=6.4Hz,4H),7.88(d,J=7.6Hz ,2H),7.72(dd,J=7.6,1.7Hz,2H),7.71–7.67(m,6H),7.57–7.55(m,2H),7.51(d,J=8.1Hz ,2H),7.46(d,J=8.7Hz,4H),7.34–7.31(m,2H),6.97–6.93(m,2H),5.82(d,J=17.5Hz,2H ),5.25(d,J=10.9Hz,2H),2.15–2.12(m,4H),1.17–1.09(m,12H),0.78(t,J=7.2Hz,10H).

[0058] Compound V-HFCz (Solvent: Chloroform-d) 1 HNMR spectrum Figure 2 shown.

[0059] Synthesis of compound V-SAFCz: 1.13 g (3.17 mmol) of methyltriphenylphosphonium bromide, 0.37 g (3.17 mmol) of potassium tert-butoxide and 50 mL of anhydrous tetrahydrofuran were added to a 100 mL two-necked flask and placed in an ice-water bath for 2 h to generate a Wittig reagent; 0.6 g (0.63 mmol) of 9,9'-((10-phenyl-10H-spiro[acridine-9,9'-fluorene]-2',7'-diyl)bis(4,1-phenylene))bis(9H-carbazole-3-carbaldehyde) and 50 mL of anhydrous tetrahydrofuran were added to a 250 mL two-necked flask. After evacuation three times, the Wittig reagent was transferred to a 250 mL two-necked flask using a 10 mL syringe and the temperature was raised to 65°C under argon protection for 20 h. After monitoring the reaction completion by silica gel thin-layer chromatography (developing solvent: petroleum ether:dichloromethane v:v = 1:3), 5 mL of deionized water was added to quench the reaction, followed by extraction three times with dichloromethane, and the solvent was evaporated under reduced pressure. The crude product was separated and purified by alumina column chromatography (eluent: petroleum ether:dichloromethane v:v = 8:1) and recrystallized from dichloromethane and n-hexane to obtain 0.32 g of a white powder, with a yield of 53.0%. 1H NMR(800MHz,Chloroform-d)δ8.18–8.12(m,4H),7.98(d,J=7.7Hz,2H),7.81(d,J=7.5Hz,5H),7.78(d, J=4.5Hz,2H),7.73(s,2H),7.62–7.57(m,5H),7.56–7.52(m,4H),7.44–7.40(m,4H),7.38(d,J=8.3Hz, 2H),7.30(d,J=6.4Hz,2H),7.00–6.97(m,2H),6.93(dd,J=17.5,10.7Hz,2H),6.66(d,J=7.0Hz,2H),6. 62(d,J=8.0Hz,2H),6.44(d,J=8.5Hz,2H),5.80(d,J=17.5Hz,2H),5.30(s,1H),5.23(d,J=10.9Hz,2H).

[0060] Compound V-SAFCz (Solvent: Chloroform-d) 1 H NMR spectrum Figure 3 shown.

[0061] The synthetic routes of the intermediate 10-phenyl-2',7'-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-10H-spiro[acridine-9,9'-fluorene] and compounds V-MFCz, V-HFCz, and V-SAFCz are as follows:

[0062]

[0063] Example 2

[0064] Etched and patterned indium tin oxide (ITO) glass was used as a substrate. Prior to OLED device fabrication, the ITO glass substrate was cleaned with detergent, deionized water, acetone, isopropyl alcohol, and ethanol, boiled in ethanol, blown dry, and then treated with oxygen plasma for 10 minutes on a CIF CPC-a plasma cleaner. 40 μL of a poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) (PEDOT:PSS) 4083 solution was spin-coated on the ITO substrate at 4000 rpm for 30 seconds and then heated at 140°C in air for 20 minutes. Poly[(9,9-dioctylfluorene-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl)diphenylamine)](TFB) was dissolved in chlorobenzene to prepare a 6 mg / mL solution. 40 μL of the solution was spin-coated on the obtained PEDOT:PSS film at 4000 rpm for 30 seconds and then heated at 140°C in an air atmosphere for 20 minutes. The luminescent materials V-MFCz, V-HFCz or V-SAFCz were each dissolved in chlorobenzene at 15 mg / mL. 40 μL of the solution was spin-coated at 4000 rpm for 30 seconds and then heated at 140°C in an air atmosphere for 20 minutes. pm spin coating on the obtained TFB film for 30 seconds, and then heated at 300℃, 180℃ and 280℃ for 30 minutes respectively in an argon (Ar) atmosphere. 1,3,5-Tris(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBi) was dissolved in toluene to prepare a 20 mg / mL solution, and 40μL of the solution was spin coated on the V-MFCz, V-HFCz or V-SAFCz cross-linked film at a speed of 4000rpm for 30 seconds, and then heated at 100℃ for 20 minutes in an argon atmosphere. In a Technol Science ZHDS-400 vacuum vapor deposition system, lithium fluoride (LiF) and aluminum (Al) were respectively added at a pressure of about 6×10-4Pa at a speed of about 100℃. and Thin films were deposited at a deposition rate of 100 nm. During this process, the thickness of each deposited layer was monitored by quartz crystal oscillation. The device had an emission area of 2 mm × 3 mm, determined by the overlap area of the anode and cathode. Electroluminescence (EL) spectra were measured on a Konicaminolta CS-2000 spectrometer. Current density, luminance, voltage (JVL), and external quantum efficiency (EQE) curves were recorded on a computer-controlled Keithley 2400 source meter equipped with a silicon photodiode under an Ar atmosphere in a glove box. The resulting OLED device structure was ITO / PEDOT:PSS (30 nm) / TFB (10 nm) / V-MFCz, V-HFCz, or V-SAFCz (40 nm) / TPBi (40 nm) / lithium fluoride (LiF) (1 nm) / aluminum (Al) (100 nm). ITO, PEDOT:PSS, TFB, TPBi, LiF, and Al served as the anode, hole injection layer (HIL), hole transport layer (HTL), electron transport layer (ETL), electron injection layer (EIL), and cathode, respectively. The OLED performance is shown in Table 2. The OLED devices produced using V-MFCz, V-HFCz, and V-SAFCz are labeled V-MFCz, V-HFCz, and V-SAFCz, respectively.

[0065] Fluorene, as a blue light unit, has a high solid-state fluorescence quantum yield and good modification sites, but the carbon atom at position 9 of fluorene is easily oxidized, resulting in a fluorenone defect. The present invention introduces an alkane or a cyclized triarylamine at the carbon atom at position 9 to inhibit the fluorenone effect. Among them, the alkyl chain can increase solubility and reduce the crosslinking temperature. Spirofluorene azaanthracene has an orthogonal vertical configuration, which can increase molecular rigidity, reduce intermolecular π-π stacking in the thin film state, and weaken fluorescence quenching caused by molecular aggregation. Therefore, in the present invention, three thermally crosslinked blue light molecules V-MFCz, V-HFCz and V-SAFz were designed and synthesized using 9,9-dimethylfluorene, 9,9-dihexylfluorene and 10-phenyl-10H-spiro[acridine-9,9'-fluorene] as the parent core, carbazole as the luminescent group, and vinyl as the crosslinking group. The three molecules are synthesized through a three-step reaction: Vilsmeier-Hack formylation reaction, Suzuki coupling and Wittig reaction.

[0066] In order to study the ground state structure of the molecule, quantum chemical calculations were performed based on density functional theory (DFT). The electron cloud distribution of the frontier molecular orbital (FMO) was simulated ( Figure 4). The highest occupied molecular orbital (HOMO) distribution of V-MFCz and V-HFCz is mainly distributed on the entire molecular skeleton, while the HOMO of V-SAFCz is distributed on the cyclized triarylamine. The lowest unoccupied molecular orbital (LUMO) distribution of the three molecules is mainly distributed on the fluorenyl group and the bridged benzene ring. The theoretical HOMO of V-MFCz, V-HFCz and V-SAFCz are -5.17eV, -5.17eV and -5.10eV, respectively, and the theoretical LUMO are -1.56eV, -1.54eV and -1.51eV, respectively. The calculated band gap widths (Eg) are 3.61eV, 3.63eV and -3.59eV, respectively, which meet the requirements for blue light emission. In addition, the oscillator strengths (f) of V-MFCz, V-HFCz, and V-SAFCz are 1.0578, 1.0811, and 0.0001, respectively, indicating that among the three molecules, V-HFCz has the strongest fluorescence intensity, while the fluorescence intensity of V-SAFCz is relatively weak.

[0067] The present invention studies the UV-visible absorption properties of V-MFCz, V-HFCz and V-SAFz films before and after crosslinking. The UV-visible absorption spectra of the films are as follows: Figure 5 As shown. Figure 5 As shown in (a), the UV-vis absorption spectra of V-MFCz, V-HFCz and V-SAFCz films before and after crosslinking are basically the same. It can be seen that the absorption peak around 209nm is the π-π* transition of the benzene ring, the absorption peak around 244nm is the n-π* transition of carbazole, the absorption peak around 290nm is the π-π* transition of carbazole, and the absorption peak around 350nm is the π-π* electronic transition of the molecular skeleton. The onset wavelength λ of the UV-vis absorption spectra of crosslinked V-MFCz, V-HFCz and V-SAFCz films onset The wavelengths of the three molecules are 397 nm, 399 nm and 401 nm respectively. g They are 3.12eV, 3.11eV and 3.09eV respectively.

[0068] The present invention also analyzes the fluorescence (PL) characteristics of V-MFCz, V-HFCz and V-SAFz in thin films. Figure 5As shown in (b), the emission peaks of V-MFCz, V-HFCz and V-SAFCz films after cross-linking are 411nm, 412nm and 412nm, respectively. Since the electron donating ability of hexyl and triarylamine is stronger than that of methyl, they show a slight red shift. The half-peak widths of V-MFCz, V-HFCz and V-SAFCz cross-linked films are 56, 60, and 62nm, respectively. In addition, the photoluminescence quantum yields (PLQYs) of V-MFCz, V-HFCz and V-SAFCz cross-linked films are 20.34%, 22.35% and 22.01%, respectively. In addition, the HOMO energy levels of the three cross-linked films were tested by X-ray photoelectron spectroscopy (UPS). As shown Figure 5 As shown in (c), (d), and (e), the secondary electron cutoff edge (E cutoff ) are 16.60, 16.62 and 16.55 eV respectively, and the Fermi edge (E HOMO ) are 1.08, 1.08, and 0.97 eV, respectively. The HOMO energy levels calculated by formula (1) are -5.70, -5.68, and -5.64 eV, respectively. The LUMO energy levels calculated by formula (2) are -2.58, -2.57, and -2.55 eV, respectively. Table 1 summarizes the photophysical properties of the materials, which are beneficial for the construction of OLED devices.

[0069] HOMO=-[hν-(E cutoff -E HOMO )] (1)

[0070] LUMO=HOMO+E g (2)

[0071] Table 1 Photophysical data of V-MFCz, V-HFCz and V-SAFz films

[0072]

[0073]

[0074] According to the thermogravimetric analysis results ( Figure 6 In (a)-(c)), when the mass loss is 5%, the thermal decomposition temperatures of V-MFCz, V-HFCz and V-SAFCz reach 457.53, 442.89, and 502.74°C, respectively, indicating that all three molecules have excellent thermal stability. According to the differential scanning calorimetry curve, it can be seen that ( Figure 6In Figures (d)-(f), during the first heating process, V-MFCz, V-HFCz, and V-SAFCz exhibit distinct endothermic peaks at 291°C, 137°C, and 226°C, corresponding to the melting temperatures of the three materials, respectively. Melting before cross-linking facilitates molecular collisions and reactions. V-MFCz, V-HFCz, and V-SAFCz exhibit distinct exothermic peaks at 293°C, 149°C, and 259°C, corresponding to the cross-linking process. These experimental results demonstrate that extending the alkyl chain significantly lowers the cross-linking temperature. During the second heating process, no distinct endothermic or exothermic peaks are observed in any of the three materials, indicating that the cross-linking reaction is complete after the first heating process.

[0075] When the cross-linking reaction is complete, a network-like film insoluble in organic solvents will be formed ( Figure 7 When V-MFCz, V-HFCz, and V-SAFCz films were heated at 300, 180, and 280°C for 30 min, respectively, the solvent resistance of the cross-linked films reached 100%. To further determine whether the cross-linking reaction had completely occurred, the chemical structures of V-MFCz, V-HFCz, and V-SAFCz before and after cross-linking were determined using FT-IR ( Figure 8 (a)-(c)), after cross-linking of the film, 1623 cm -1 The C=C stretching vibration peak near the end of the reaction disappears, indicating that the cross-linking reaction has completely occurred. In addition, the UV-visible absorption intensity of the samples before and after immersion in different solvents was also tested ( Figure 8 (d)-(f)). The UV-vis spectra of the cross-linked film before and after different immersions have the same absorption intensity, indicating that the cross-linked film can resist the erosion of various solvents and avoid the interlayer solubility problem when preparing devices by solution method. According to X-ray diffraction (XRD) characterization ( Figure 9 ). No distinct diffraction peaks were observed in the V-MFCz, V-HFCz, and V-SAFCz films spin-coated on silicon wafers before and after annealing. This indicates that the solution-processed emitting layer (EML) maintains a well-defined amorphous state, preventing the occurrence of crystallization that could harm device performance.

[0076] The contact angle of the cross-linked film with toluene and water was tested ( Figure 10 ), the θ values of the cross-linked film with toluene were 5.59, 4.98, and 4.47°, respectively, indicating good wettability, which is beneficial for the subsequent spin coating of the electron transport layer; at the same time, the θ values with water were 96.03, 96.45, and 90.15°, respectively, indicating good hydrophobicity, which can avoid the adverse effects of moisture in the environment on device performance. According to the atomic force microscope (AFM) image ( Figure 11The RMS roughness of the V-MFCz film before and after cross-linking was 1.04 nm and 1.46 nm, respectively; the RMS roughness of the V-HFCz film before and after cross-linking was 0.93 nm and 1.45 nm, respectively; and the RMS roughness of the V-SAFCz film before and after cross-linking was 0.46 nm and 1.17 nm. Compared to V-MFCz and V-HFCz, the RMS of the V-SAFCz film was slightly lower. This is due to the orthorhombic configuration of the 10-phenyl-10H-spiro[acridine-9,9'-fluorene] group in V-SAFCz, which provides significant steric hindrance and prevents intermolecular aggregation. The low RMS values of the films indicate a uniform and flat surface with good morphological stability.

[0077] The performance data of the V-MFCz, V-HFCz, and V-SAFCz devices prepared in Example 2 are shown in Table 2.

[0078] Table 2 Performance data of all-solution devices

[0079]

[0080] Note: a brightness is 1cd·m -2 a) Voltage at 5 V; b) CIE coordinates measured at 5 V.

[0081] The OLED device prepared by the full solution method in Example 2 of the present invention exhibits blue EL performance, and the emission peaks of V-MFCz, V-HFCz, and V-SAFCz are 440, 443, and 444 nm, respectively. Figure 12 In (b), the half-peak widths are 43, 49, and 48 nm, respectively, indicating that the device has good color purity. In addition, the device maintains a stable EL spectrum at an operating voltage of 5-10 V, and the CIE coordinates change slightly, indicating good electrochemical stability ( Figure 13 From the curve of current density and brightness versus voltage (JVL) ( Figure 12 As can be seen in (c), the maximum brightness values of V-MFCz, V-HFCz, and V-SAFCz devices are 7735, 3369, and 4054 cd m -2 The turn-on voltages are 4.5, 3.8 and 3.5 V respectively. The low turn-on voltage indicates that the device structure is well designed. Figure 12 As can be seen in (d), the maximum current efficiencies of V-MFCz, V-HFCz, and V-SAFCz devices are 1.2, 2.18, and 3.13 cdA, respectively. -1 , the maximum power efficiency is 0.58, 1.17 and 1.6lmW respectively -1 From the curve of external quantum efficiency and brightness (EQE-L) ( Figure 12As can be seen in (e), the maximum external quantum efficiencies of V-MFCz, V-HFCz, and V-SAFCz devices are 0.73, 1.72, and 1.91%, respectively.

[0082] The present invention has designed and successfully synthesized three thermally cross-linked blue light molecules, V-MFCz, V-HFCz, and V-SAFCz. All three materials have high thermal stability and excellent solution processability, and all have achieved the preparation of all-solution blue light devices. Among them, the device based on V-MFCz achieves deep blue emission at 440nm, with CIE coordinates of (0.16, 0.08), which is consistent with the NTSC standard for blue light. The device based on V-SAFCz has excellent performance, EQE max The CIE coordinates are (0.17, 0.10) and the cross-linking strategy has great potential in the field of EL and provides an effective design strategy for the further development of all-solution OLEDs.

[0083] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing a full solution OLED device, characterized in that: The following steps are involved: A hole injection layer and a hole transport layer are sequentially prepared on the surface of the substrate; preparing a light-emitting layer by spin-coating a light-emitting material solution on the surface of the hole transport layer and then annealing; Sequentially preparing an electron transport layer, an electron injection layer, and a cathode on the surface of the light-emitting layer to obtain the full-solution OLED device; The luminescent material in the luminescent material solution is V-MFCz, V-HFCz or V-SAFCz; The V-MFCz is 9,9'-((9,9-dimethyl-9H-fluorene-2,7-diyl)bis(4,1-phenylene))bis(3-vinyl-9H-carbazole), and the structural formula is The V-HFCz is 9,9'-((9,9-dihexyl-9H-fluorene-2,7-diyl)bis(4,1-phenylene))bis(3-vinyl-9H-carbazole), and the structural formula is The V-SAFCz is 10-phenyl-2',7'-bis(4-(3-vinyl-9H-carbazol-9-yl)phenyl)-10H-spiro[acridine-9,9'-fluorene], and the structural formula is 2. The method for preparing a full solution OLED device according to claim 1, wherein: The hole injection layer is a PEDOT:PSS film with a thickness of 30 to 40 nm.

3. The method for preparing a full solution OLED device according to claim 1, wherein: The hole transport layer is a TFB thin film with a thickness of 5 to 15 nm.

4. The method for preparing a full solution OLED device according to claim 1, wherein: The electron transport layer is a 1,3,5-tris(1-phenyl-1H-benzimidazole-2-yl)benzene film with a thickness of 30 to 50 nm.

5. The method for preparing a full solution OLED device according to claim 1, wherein: The electron injection layer is a lithium fluoride film with a thickness of 0.5 to 1.5 nm.

6. The method for preparing a full solution OLED device according to claim 1, wherein: The cathode is an aluminum film with a thickness of 80 to 200 nm.

7. The method for preparing a full solution OLED device according to claim 1, wherein: The hole injection layer, hole transport layer and electron transport layer are all prepared by spin coating and then annealing; the electron injection layer and cathode are prepared by physical vapor deposition.

8. The method for preparing a full solution OLED device according to claim 1, wherein: The concentration of the luminescent material solution is 10-20 mg / mL, and the solvent is chlorobenzene. After the spin coating is completed, the method further includes annealing at 180-300° C. for 30 minutes in an argon atmosphere.

9. The method for preparing a full solution OLED device according to claim 1, wherein: The thickness of the light-emitting layer is 40 nm.

10. A full-solution OLED device prepared according to the preparation method according to any one of claims 1 to 9.

Images